Sample records for radiation-induced glacier melt

  1. Increased ocean-induced melting triggers glacier retreat in northwest and southeast Greenland

    NASA Astrophysics Data System (ADS)

    Wood, M.; Rignot, E. J.; Fenty, I. G.; Menemenlis, D.; Millan, R.; Morlighem, M.; Mouginot, J.

    2017-12-01

    Over the past 30 years, the tidewater glaciers of northwest, central west, and southeast Greenland have exhibited widespread retreat, yet we observe different behaviors from one glacier to the next, sometimes within the same fjord. This retreat has been synchronous with oceanic warming in Baffin Bay and the Irminger Sea. Here, we estimate the ocean-induced melt rate of marine-terminating glaciers in these sectors of the Greenland Ice Sheet using simulations from the MITgcm ocean model for various water depths, ocean thermal forcing (TF) and subglacial water fluxes (SG). We use water depth from Ocean Melting Greenland (OMG) bathymetry and inverted airborne gravity, ocean thermal forcing from the Estimating the Circulation and Climate of the Ocean (Phase II, ECCO2) combined with CTD data from 2012 and 2015, and time series of subglacial water flux combining runoff production from the 1-km Regional Atmospheric Climate Model (RACMO2.3) with basal melt beneath land ice from the JPL/UCI ISSM model. Time series of melt rates are formed as a function of grounding line depth, SG flux and TF. We compare the results with the history of ice velocity and ice front retreat to quantify the impact of ice melt by the ocean over past three decades. We find that the timing of ice front retreat coincides with enhanced ocean-induced melt and that abrupt retreat is induced when additional ablation exceeds the magnitude of natural seasonal variations of the glacier front. Sverdrup Gletscher, Umiamako Isbrae, and the northern branch Puisortoq Gletscher in northwest, central west, and southwest Greenland, respectively, began multi-kilometer retreats coincident with ocean warming and enhanced melt. Limited retreat is observed where the bathymetry is shallow, on a prograde slope or glacier is stuck on a sill, e.g. Ussing Braeer in the northwest, Sermeq Avannarleq in central west, and Skinfaxe Gletscher in the southeast. These results illustrate the sensitivity of glaciers to changes in

  2. Extended T-index models for glacier surface melting: a case study from Chorabari Glacier, Central Himalaya, India

    NASA Astrophysics Data System (ADS)

    Karakoti, Indira; Kesarwani, Kapil; Mehta, Manish; Dobhal, D. P.

    2016-10-01

    Two enhanced temperature-index (T-index) models are proposed by incorporating meteorological parameters viz. relative humidity, wind speed and net radiation. The models are an attempt to explore different climatic variables other than temperature affecting glacier surface melting. Weather data were recorded at Chorabari Glacier using an automatic weather station during the summers of 2010 (July 10 to September 10) and 2012 (June 10 to October 25). The modelled surface melt is validated against the measured point surface melting at the snout. Performance of the developed models is evaluated by comparing with basic temperature-index model and is quantified through different efficiency criteria. The results suggest that proposed models yield considerable improvement in surface melt simulation . Consequently, the study reveals that glacier surface melt depends not only on temperature but also on weather parameters viz. relative humidity, wind speed and net radiation play a significant role in glacier surface melting. This approach provides a major improvement on basic temperature-index method and offers an alternative to energy balance model.

  3. The contribution of glacier melt to streamflow

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schaner, Neil; Voisin, Nathalie; Nijssen, Bart

    2012-09-13

    Ongoing and projected future changes in glacier extent and water storage globally have lead to concerns about the implications for water supplies. However, the current magnitude of glacier contributions to river runoff is not well known, nor is the population at risk to future glacier changes. We estimate an upper bound on glacier melt contribution to seasonal streamflow by computing the energy balance of glaciers globally. Melt water quantities are computed as a fraction of total streamflow simulated using a hydrology model and the melt fraction is tracked down the stream network. In general, our estimates of the glacier meltmore » contribution to streamflow are lower than previously published values. Nonetheless, we find that globally an estimated 225 (36) million people live in river basins where maximum seasonal glacier melt contributes at least 10% (25%) of streamflow, mostly in the High Asia region.« less

  4. Light-absorbing impurities accelerate glacier melt in the Central Tibetan Plateau.

    PubMed

    Li, Xiaofei; Kang, Shichang; He, Xiaobo; Qu, Bin; Tripathee, Lekhendra; Jing, Zhefan; Paudyal, Rukumesh; Li, Yang; Zhang, Yulan; Yan, Fangping; Li, Gang; Li, Chaoliu

    2017-06-01

    Light-absorbing impurities (LAIs), such as organic carbon (OC), black carbon (BC), and mineral dust (MD) deposited on the glacier surface can reduce albedo, thus accelerating the glacier melt. Surface fresh snow, aged snow, granular ice, and snowpits samples were collected between August 2014 and October 2015 on the Xiao Dongkemadi (XDKMD) glacier (33°04'N, 92°04'E) in the central Tibetan Plateau (TP). The spatiotemporal variations of LAIs concentrations in the surface snow/ice were observed to be consistent, differing mainly in magnitudes. LAIs concentrations were found to be in the order: granular ice>snowpit>aged snow>fresh snow, which must be because of post-depositional effects and enrichment. In addition, more intense melting led to higher LAIs concentrations exposed to the surface at a lower elevation, suggesting a strong negative relationship between LAIs concentrations and elevation. The scavenging efficiencies of OC and BC were same (0.07±0.02 for OC, 0.07±0.01 for BC), and the highest enrichments was observed in late September and August for surface snow and granular ice, respectively. Meanwhile, as revealed by the changes in the OC/BC ratios, intense glacier melt mainly occurred between August and October. Based on the SNow ICe Aerosol Radiative (SNICAR) model simulations, BC and MD in the surface snow/ice were responsible for about 52%±19% and 25%±14% of the albedo reduction, while the radiative forcing (RF) were estimated to be 42.74±40.96Wm -2 and 21.23±22.08Wm -2 , respectively. Meanwhile, the highest RF was observed in the granular ice, suggesting that the exposed glaciers melt and retreat more easily than the snow distributed glaciers. Furthermore, our results suggest that BC was the main forcing factor compared with MD in accelerating glacier melt during the melt season in the Central TP. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Melting beneath Greenland outlet glaciers and ice streams

    NASA Astrophysics Data System (ADS)

    Alexander, David; Perrette, Mahé; Beckmann, Johanna

    2015-04-01

    Basal melting of fast-flowing Greenland outlet glaciers and ice streams due to frictional heating at the ice-bed interface contributes significantly to total glacier mass balance and subglacial meltwater flux, yet modelling this basal melt process in Greenland has received minimal research attention. A one-dimensional dynamic ice-flow model is calibrated to the present day longitudinal profiles of 10 major Greenland outlet glaciers and ice streams (including the Jakobshavn Isbrae, Petermann Glacier and Helheim Glacier) and is validated against published ice flow and surface elevation measurements. Along each longitudinal profile, basal melt is calculated as a function of ice flow velocity and basal shear stress. The basal shear stress is dependent on the effective pressure (difference between ice overburden pressure and water pressure), basal roughness and a sliding parametrization. Model output indicates that where outlet glaciers and ice streams terminate into the ocean with either a small floating ice tongue or no floating tongue whatsoever, the proportion of basal melt to total melt (surface, basal and submarine melt) is 5-10% (e.g. Jakobshavn Isbrae; Daugaard-Jensen Glacier). This proportion is, however, negligible where larger ice tongues lose mass mostly by submarine melt (~1%; e.g. Nioghalvfjerdsfjorden Glacier). Modelled basal melt is highest immediately upvalley of the grounding line, with contributions typically up to 20-40% of the total melt for slippery beds and up to 30-70% for resistant beds. Additionally, modelled grounding line and calving front migration inland for all outlet glaciers and ice streams of hundreds of metres to several kilometres occurs. Including basal melt due to frictional heating in outlet glacier and ice stream models is important for more accurately modelling mass balance and subglacial meltwater flux, and therefore, more accurately modelling outlet glacier and ice stream dynamics and responses to future climate change.

  6. Where glaciers meet water: Subaqueous melt and its relevance to glaciers in various settings

    NASA Astrophysics Data System (ADS)

    Truffer, Martin; Motyka, Roman J.

    2016-03-01

    Glacier change is ubiquitous, but the fastest and largest magnitude changes occur in glaciers that terminate in water. This includes the most rapidly retreating glaciers, and also several advancing ones, often in similar regional climate settings. Furthermore, water-terminating glaciers show a large range in morphology, particularly when ice flow into ocean water is compared to that into freshwater lakes. All water-terminating glaciers share the ability to lose significant volume of ice at the front, either through mechanical calving or direct melt from the water in contact. Here we present a review of the subaqueous melt process. We discuss the relevant physics and show how different physical settings can lead to different glacial responses. We find that subaqueous melt can be an important trigger for glacier change. It can explain many of the morphological differences, such as the existence or absence of floating tongues. Subaqueous melting is influenced by glacial runoff, which is largely a function of atmospheric conditions. This shows a tight connection between atmosphere, oceans and lakes, and glaciers. Subaqueous melt rates, even if shown to be large, should always be discussed in the context of ice supply to the glacier front to assess its overall relevance. We find that melt is often relevant to explain seasonal evolution, can be instrumental in shifting a glacier into a different dynamical regime, and often forms a large part of a glacier's mass loss. On the other hand, in some cases, melt is a small component of mass loss and does not significantly affect glacier response.

  7. The impact of glacier geometry on meltwater plume structure and submarine melt in Greenland fjords

    NASA Astrophysics Data System (ADS)

    Carroll, D.; Sutherland, D. A.; Hudson, B.; Moon, T.; Catania, G. A.; Shroyer, E. L.; Nash, J. D.; Bartholomaus, T. C.; Felikson, D.; Stearns, L. A.; Noël, B. P. Y.; Broeke, M. R.

    2016-09-01

    Meltwater from the Greenland Ice Sheet often drains subglacially into fjords, driving upwelling plumes at glacier termini. Ocean models and observations of submarine termini suggest that plumes enhance melt and undercutting, leading to calving and potential glacier destabilization. Here we systematically evaluate how simulated plume structure and submarine melt during summer months depends on realistic ranges of subglacial discharge, glacier depth, and ocean stratification from 12 Greenland fjords. Our results show that grounding line depth is a strong control on plume-induced submarine melt: deep glaciers produce warm, salty subsurface plumes that undercut termini, and shallow glaciers produce cold, fresh surface-trapped plumes that can overcut termini. Due to sustained upwelling velocities, plumes in cold, shallow fjords can induce equivalent depth-averaged melt rates compared to warm, deep fjords. These results detail a direct ocean-ice feedback that can affect the Greenland Ice Sheet.

  8. Assessing glacier melt contribution to streamflow at Universidad Glacier, central Andes of Chile

    NASA Astrophysics Data System (ADS)

    Bravo, Claudio; Loriaux, Thomas; Rivera, Andrés; Brock, Ben W.

    2017-07-01

    Glacier melt is an important source of water for high Andean rivers in central Chile, especially in dry years, when it can be an important contributor to flows during late summer and autumn. However, few studies have quantified glacier melt contribution to streamflow in this region. To address this shortcoming, we present an analysis of meteorological conditions and ablation for Universidad Glacier, one of the largest valley glaciers in the central Andes of Chile at the head of the Tinguiririca River, for the 2009-2010 ablation season. We used meteorological measurements from two automatic weather stations installed on the glacier to drive a distributed temperature-index and runoff routing model. The temperature-index model was calibrated at the lower weather station site and showed good agreement with melt estimates from an ablation stake and sonic ranger, and with a physically based energy balance model. Total modelled glacier melt is compared with river flow measurements at three sites located between 0.5 and 50 km downstream. Universidad Glacier shows extremely high melt rates over the ablation season which may exceed 10 m water equivalent in the lower ablation area, representing between 10 and 13 % of the mean monthly streamflow at the outlet of the Tinguiririca River Basin between December 2009 and March 2010. This contribution rises to a monthly maximum of almost 20 % in March 2010, demonstrating the importance of glacier runoff to streamflow, particularly in dry years such as 2009-2010. The temperature-index approach benefits from the availability of on-glacier meteorological data, enabling the calculation of the local hourly variable lapse rate, and is suited to high melt regimes, but would not be easily applicable to glaciers further north in Chile where sublimation is more significant.

  9. Modeled climate-induced glacier change in Glacier National Park, 1850-2100

    USGS Publications Warehouse

    Hall, M.H.P.; Fagre, D.B.

    2003-01-01

    The glaciers in the Blackfoot-Jackson Glacier Basin of Glacier National Park, Montana, decreased in area from 21.6 square kilometers (km2) in 1850 to 7.4 km2 in 1979. Over this same period global temperatures increased by 0.45??C (?? 0. 15??C). We analyzed the climatic causes and ecological consequences of glacier retreat by creating spatially explicit models of the creation and ablation of glaciers and of the response of vegetation to climate change. We determined the melt rate and spatial distribution of glaciers under two possible future climate scenarios, one based on carbon dioxide-induced global warming and the other on a linear temperature extrapolation. Under the former scenario, all glaciers in the basin will disappear by the year 2030, despite predicted increases in precipitation; under the latter, melting is slower. Using a second model, we analyzed vegetation responses to variations in soil moisture and increasing temperature in a complex alpine landscape and predicted where plant communities are likely to be located as conditions change.

  10. Combining a Distributed Melt Model and Meteorological Data of Shackleton Glacier, Canadian Rockies

    NASA Astrophysics Data System (ADS)

    Mueller, M.; Jiskoot, H.

    2010-12-01

    Runoff from the Canadian Rocky Mountains into the Upper Columbia and Kootenay basins is strongly dominated by winter snow accumulation and spring melt, and it has been suggested that future reductions in snowpack will create increased competition for water between spring and early fall (Hamlet & Lettenmaier, 1999). Although the glacierised area is substantial for affecting summer flows in these basins, there are no measurements or quantified estimates of glacier runoff contribution. In an effort to provide an estimate of glacier runoff for the region, we measured ablation over 5 years, set up weather stations and temperature sensors in Summers 2009 and 2010 and developed a melt model for Shackleton Glacier (42.5 km2), the largest outlet of the Clemenceau Icefield Group (271 km2), which is the major local ice mass feeding into the Upper Columbia basin. Two HOBO weather stations (WS) were installed on the glacier for two weeks in Summer 2010, one near the left lateral moraine on very dirty ice, and one mid-glacier on relatively clean ice. Instrumentation included pyranometers (solar radiation and albedo), and temperature, wind speed and direction, relative humidity and barometric pressure sensors. A weather station off ice provided additional temperature and precipitation data. Other data included daily ablation stake measurements, surface roughness measurements, temperature data from Tidbit loggers on and off ice, and daily manual weather observations. Yearly ablation stake measurements and summer weather observations have been made by our team since 2005. A BC River Forecast Centre automatic snow pillow station provides additional temperature and precipitation data. Using these meteorological and ablation data for parameterisation and optimisation, a distributed GIS melt model was constructed from a simple energy balance model. The model is driven by hourly direct and diffuse radiation and DEM hillshading, an albedo parameterisation based on four ice/snow zones

  11. Causes of Glacier Melt Extremes in the Alps Since 1949

    NASA Astrophysics Data System (ADS)

    Thibert, E.; Dkengne Sielenou, P.; Vionnet, V.; Eckert, N.; Vincent, C.

    2018-01-01

    Recent record-breaking glacier melt values are attributable to peculiar extreme events and long-term warming trends that shift averages upward. Analyzing one of the world's longest mass balance series with extreme value statistics, we show that detrending melt anomalies makes it possible to disentangle these effects, leading to a fairer evaluation of the return period of melt extreme values such as 2003, and to characterize them by a more realistic bounded behavior. Using surface energy balance simulations, we show that three independent drivers control melt: global radiation, latent heat, and the amount of snow at the beginning of the melting season. Extremes are governed by large deviations in global radiation combined with sensible heat. Long-term trends are driven by the lengthening of melt duration due to earlier and longer-lasting melting of ice along with melt intensification caused by trends in long-wave irradiance and latent heat due to higher air moisture.

  12. Spatio-temporal Variability of Albedo and its Impact on Glacier Melt Modelling

    NASA Astrophysics Data System (ADS)

    Kinnard, C.; Mendoza, C.; Abermann, J.; Petlicki, M.; MacDonell, S.; Urrutia, R.

    2017-12-01

    Albedo is an important variable for the surface energy balance of glaciers, yet its representation within distributed glacier mass-balance models is often greatly simplified. Here we study the spatio-temporal evolution of albedo on Glacier Universidad, central Chile (34°S, 70°W), using time-lapse terrestrial photography, and investigate its effect on the shortwave radiation balance and modelled melt rates. A 12 megapixel digital single-lens reflex camera was setup overlooking the glacier and programmed to take three daily images of the glacier during a two-year period (2012-2014). One image was chosen for each day with no cloud shading on the glacier. The RAW images were projected onto a 10m resolution digital elevation model (DEM), using the IMGRAFT software (Messerli and Grinsted, 2015). A six-parameter camera model was calibrated using a single image and a set of 17 ground control points (GCPs), yielding a georeferencing accuracy of <1 pixel in image coordinates. The camera rotation was recalibrated for new images based on a set of common tie points over stable terrain, thus accounting for possible camera movement over time. The reflectance values from the projected image were corrected for topographic and atmospheric influences using a parametric solar irradiation model, following a modified algorithm based on Corripio (2004), and then converted to albedo using reference albedo measurements from an on-glacier automatic weather station (AWS). The image-based albedo was found to compare well with independent albedo observations from a second AWS in the glacier accumulation area. Analysis of the albedo maps showed that the albedo is more spatially-variable than the incoming solar radiation, making albedo a more important factor of energy balance spatial variability. The incorporation of albedo maps within an enhanced temperature index melt model revealed that the spatio-temporal variability of albedo is an important factor for the calculation of glacier

  13. Effect of Topography on Subglacial Discharge and Submarine Melting During Tidewater Glacier Retreat

    NASA Astrophysics Data System (ADS)

    Amundson, J. M.; Carroll, D.

    2018-01-01

    To first order, subglacial discharge depends on climate, which determines precipitation fluxes and glacier mass balance, and the rate of glacier volume change. For tidewater glaciers, large and rapid changes in glacier volume can occur independent of climate change due to strong glacier dynamic feedbacks. Using an idealized tidewater glacier model, we show that these feedbacks produce secular variations in subglacial discharge that are influenced by subglacial topography. Retreat along retrograde bed slopes (into deep water) results in rapid surface lowering and coincident increases in subglacial discharge. Consequently, submarine melting of glacier termini, which depends on subglacial discharge and ocean thermal forcing, also increases during retreat into deep water. Both subglacial discharge and submarine melting subsequently decrease as glacier termini retreat out of deep water and approach new steady state equilibria. In our simulations, subglacial discharge reached peaks that were 6-17% higher than preretreat values, with the highest values occurring during retreat from narrow sills, and submarine melting increased by 14% for unstratified fjords and 51% for highly stratified fjords. Our results therefore indicate that submarine melting acts in concert with iceberg calving to cause tidewater glacier termini to be unstable on retrograde beds. The full impact of submarine melting on tidewater glacier stability remains uncertain, however, due to poor understanding of the coupling between submarine melting and iceberg calving.

  14. Directly measuring melt at a vertical face tidewater glacier: is it possible?

    NASA Astrophysics Data System (ADS)

    Sutherland, D.; Amundson, J. M.; Duncan, D.; Jackson, R. H.; Kienholz, C.; Motyka, R. J.; Nash, J. D.

    2017-12-01

    Direct observations of melt on the underwater portion of tidewater glaciers have proved elusive, mostly due to the inherent dangers of making measurements next to a calving ice front. Additionally, the melting process itself is often masked by large ice speeds, variable calving across the glacier front, and enhanced melting due to rising subglacial discharge plumes. Here, we use repeat multibeam sonar images of LeConte Glacier to assess the possibility of measuring terminus melt in situ. LeConte Glacier is a fast-moving tidewater system in southeast Alaska with ice speeds of 25 m d-1 and previously estimated submarine melting that accounts for 50% of ice loss at the front. In August 2016, May 2017, and September 2017, we conducted intensive fieldwork at the 1.5 km long, 250 m deep glacier front, collecting dozens of repeat multibeam images of the underwater terminus. Combined with coincident time-lapse photography and surface radar measurements, we attempt to disentangle the ambient melt at the glacier face from ice motion and calving. We use a suite of oceanographic observations of the emerging subglacial discharge plume to separate portions of the glacier front that show evidence of enhanced melting versus portions outside of the affected plume areas. We find a complex, time-varying geometry, with regions of undercutting, overcutting, and large discharge channels. Measurements like these are critical to i) improving numerical model parameterizations of coupled glacier-ocean interactions and ii) developing a process-based understanding of how the literal ice-ocean boundary evolves in time and space.

  15. Ablation from calving and surface melt at lake-terminating Bridge Glacier, British Columbia, 1984-2013

    NASA Astrophysics Data System (ADS)

    Chernos, M.; Koppes, M.; Moore, R. D.

    2016-01-01

    Bridge Glacier is a lake-calving glacier in the Coast Mountains of British Columbia and has retreated over 3.55 km since 1972. The majority of this retreat has occurred since 1991. This retreat is substantially greater than what has been inferred from regional climate indices, suggesting that it has been driven primarily by calving as the glacier retreated across an overdeepened basin. In order to better understand the primary drivers of ablation, surface melt (below the equilibrium line altitude, ELA) and calving were quantified during the 2013 melt season using a distributed energy balance model (DEBM) and time-lapse imagery. Calving, estimated using areal change, velocity measurements, and assuming flotation were responsible for 23 % of the glacier's ablation below the ELA during the 2013 melt season and were limited by modest flow speeds and a small terminus cross-section. Calving and surface melt estimates from 1984 to 2013 suggest that calving was consistently a smaller contributor of ablation. Although calving was estimated to be responsible for up to 49 % of the glacier's ablation for individual seasons, averaged over multiple summers it accounted between 10 and 25 %. Calving was enhanced primarily by buoyancy and water depths, and fluxes were greatest between 2005 and 2010 as the glacier retreated over the deepest part of Bridge Lake. The recent rapid rate of calving is part of a transient stage in the glacier's retreat and is expected to diminish within 10 years as the terminus recedes into shallower water at the proximal end of the lake. These findings are in line with observations from other lake-calving glacier studies across the globe and suggest a common large-scale pattern in calving-induced retreat in lake-terminating alpine glaciers. Despite enhancing glacial retreat, calving remains a relatively small component of ablation and is expected to decrease in importance in the future. Hence, surface melt remains the primary driver of ablation at Bridge

  16. Observed Melt Season Seismicity of Taylor Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Carmichael, J. D.; Pettit, E. C.; Creager, K. C.

    2006-12-01

    Sufficient evidence exists to suggest that interaction of crevasses and meltwater accelerates ice cliff disintegration of tidewater glaciers. It is not clear what role meltwater plays in calving characteristics from dry- based polar glaciers. We have obtained seismic data from a six-sensor seismic array deployed in October of 2004 near the terminus cliffs of Taylor Glacier, West Antarctica, to analyze near-cliff seismicity throughout a melt season. Discharge data from the adjacent Lawson stream suggests that dramatic increases in meltwater volume temporally correlate with changes in seismic character near ice cliffs. We calculated source-locations for ice-quake during hours of melting and re-freezing and found most large energy events to be located near the ice cliffs. The associated spectra and waveform characteristics are indicative of literature descriptions of crevassing events.

  17. What color should snow algae be and what does it mean for glacier melt?

    NASA Astrophysics Data System (ADS)

    Dial, R. J.; Ganey, G. Q.; Loso, M.; Burgess, A. B.; Skiles, M.

    2017-12-01

    Specialized microbes colonize glaciers and ice sheets worldwide and, like all organisms, they are unable to metabolize water in its solid form. It is well understood that net solar radiation controls melt in almost all snow and ice covered environments, and theoretical and empirical studies have documented the substantial reduction of albedo by these microbes both on ice and on snow, implicating a microbial role in glacier melt. If glacial microbiomes are limited by liquid water, and the albedo-reducing properties of individual cells enhance melt rates, then natural selection should favor those microbes that melt ice and snow crystals most efficiently. Here we: (1) argue that natural selection favors a red color on snow and a near-black color on ice based on instantaneous radiative forcing. (2) Review results of the first replicated, controlled field experiment to both quantify the impact of microbes on snowmelt in "red-snow" communities and demonstrate their water-limitation and (3) show the extent of snow-algae's spatial distribution and estimate their contribution to snowmelt across a large Alaskan icefield using remote sensing. On the 700 km2 of a 2,000 km2 maritime icefield in Alaska where red-snow was present, microbes increased snowmelt over 20% by volume, a percentage likely to increase as the climate warms and particulate pollution intensifies with important implications for models of sea level rise.

  18. Seismic multiplet response triggered by melt at Blood Falls, Taylor Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Carmichael, Joshua D.; Pettit, Erin C.; Hoffman, Matt; Fountain, Andrew; Hallet, Bernard

    2012-09-01

    Meltwater input often triggers a seismic response from glaciers and ice sheets. It is difficult, however, to measure melt production on glaciers directly, while subglacial water storage is not directly observable. Therefore, we document temporal changes in seismicity from a dry-based polar glacier (Taylor Glacier, Antarctica) during a melt season using a synthesis of seismic observation and melt modeling. We record icequakes using a dense six-receiver network of three-component geophones and compare this with melt input generated from a calibrated surface energy balance model. In the absence of modeled surface melt, we find that seismicity is well-described by a diurnal signal composed of microseismic events in lake and glacial ice. During melt events, the diurnal signal is suppressed and seismicity is instead characterized by large glacial icequakes. We perform network-based correlation and clustering analyses of seismic record sections and determine that 18% of melt-season icequakes are repetitive (multiplets). The epicentral locations for these multiplets suggest that they are triggered by meltwater produced near a brine seep known as Blood Falls. Our observations of the correspondingp-wave first motions are consistent with volumetric source mechanisms. We suggest that surface melt enables a persistent pathway through this cold ice to an englacial fracture system that is responsible for brine release episodes from the Blood Falls seep. The scalar moments for these events suggest that the volumetric increase at the source region can be explained by melt input.

  19. Estimating spring terminus submarine melt rates at a Greenlandic tidewater glacier using satellite imagery

    NASA Astrophysics Data System (ADS)

    Moyer, Alexis N.; Nienow, Peter W.; Gourmelen, Noel; Sole, Andrew J.; Slater, Donald A.

    2017-12-01

    Oceanic forcing of the Greenland Ice Sheet is believed to promote widespread thinning at tidewater glaciers, with submarine melting proposed as a potential trigger of increased glacier calving, retreat, and subsequent acceleration. The precise mechanism(s) driving glacier instability, however, remain poorly understood, and while increasing evidence points to the importance of submarine melting, estimates of melt rates are uncertain. Here we estimate submarine melt rate by examining freeboard changes in the seasonal ice tongue of Kangiata Nunaata Sermia at the head of Kangersuneq Fjord, southwest Greenland. We calculate melt rates for March and May 2013 by differencing along-fjord surface elevation, derived from high-resolution TanDEM-X digital elevation models, in combination with ice velocities derived from offset tracking applied to TerraSAR-X imagery. Estimated steady state melt rates reach up to 1.4 ± 0.5 m d^-1 near the glacier grounding line, with mean values of up to 0.8 ± 0.3 and 0.7 ± 0.3 m d^1 for the eastern and western parts of the ice tongue, respectively. Melt rates decrease with distance from the ice front and vary across the fjord. This methodology reveals spatio-temporal variations in submarine melt rates at tidewater glaciers which develop floating termini, and can be used to improve our understanding of ice-ocean interactions and submarine melting in glacial fjords.

  20. In-situ measurements of light-absorbing impurities in snow of glacier on Mt. Yulong and implications for radiative forcing estimates.

    PubMed

    Niu, Hewen; Kang, Shichang; Shi, Xiaofei; Paudyal, Rukumesh; He, Yuanqing; Li, Gang; Wang, Shijin; Pu, Tao; Shi, Xiaoyi

    2017-03-01

    The Tibetan Plateau (TP) or the third polar cryosphere borders geographical hotspots for discharges of black carbon (BC). BC and dust play important roles in climate system and Earth's energy budget, particularly after they are deposited on snow and glacial surfaces. BC and dust are two kinds of main light-absorbing impurities (LAIs) in snow and glaciers. Estimating concentrations and distribution of LAIs in snow and glacier ice in the TP is of great interest because this region is a global hotspot in geophysical research. Various snow samples, including surface aged-snow, superimposed ice and snow meltwater samples were collected from a typical temperate glacier on Mt. Yulong in the snow melt season in 2015. The samples were determined for BC, Organic Carbon (OC) concentrations using an improved thermal/optical reflectance (DRI Model 2001) method and gravimetric method for dust concentrations. Results indicated that the LAIs concentrations were highly elevation-dependent in the study area. Higher contents and probably greater deposition at relative lower elevations (generally <5000masl) of the glacier was observed. Temporal difference of LAIs contents demonstrated that LAIs in snow of glacier gradually increased as snow melting progressed. Evaluations of the relative absorption of BC and dust displayed that the impact of dust on snow albedo and radiative forcing (RF) is substantially larger than BC, particularly when dust contents are higher. This was verified by the absorption factor, which was <1.0. In addition, we found the BC-induced albedo reduction to be in the range of 2% to nearly 10% during the snow melting season, and the mean snow albedo reduction was 4.63%, hence for BC contents ranging from 281 to 894ngg -1 in snow of a typical temperate glacier on Mt. Yulong, the associated instantaneous RF will be 76.38-146.96Wm -2 . Further research is needed to partition LAIs induced glacial melt, modeling researches in combination with long-term in

  1. Direct Measurements of Iceberg Melt in Greenland Tidewater Glacier Fjords

    NASA Astrophysics Data System (ADS)

    Schild, K. M.; Sutherland, D.; Straneo, F.; Elosegui, P.

    2017-12-01

    The increasing input of freshwater to the subpolar North Atlantic, both through glacier meltwater runoff and the melting of calved icebergs, has significant implications for the Atlantic meridional overturning circulation and regional scale circulation. However, the magnitude and timing of this meltwater input has been challenging to quantify because iceberg melt rates are largely unknown. Here we use data from a simultaneous glaciological and oceanographic field campaign conducted in Sermilik Fjord, southeast Greenland, during July 2017 to map the surface and submarine geometry of large icebergs and use repeat surveys to directly measure iceberg melt rates. We use a combination of coincident ship-based multibeam submarine scans, ocean hydrography measurements, aerial drone mapping, and high precision iceberg-mounted GPS measurements to construct a detailed picture of iceberg geometry and melt. This synthesis of in situ iceberg melt measurements is amongst the first of its kind. Here, we will discuss the results of the 2017 field campaign, the implications of variable iceberg meltwater input throughout the water column, and comparisons to standard melt rate parameterizations and tidewater glacier submarine melt rate calculations.

  2. Increased Melting of Glaciers during Cotopaxi volcano awakening in 2015

    NASA Astrophysics Data System (ADS)

    Ramon, Patricio; Vallejo, Silvia; Almeida, Marco; Gomez, Juan Pablo; Caceres, Bolivar

    2016-04-01

    Cotopaxi (5897 m), located about 50 km south of Quito (Ecuador), is one of the most active volcanoes in the Andes and its historical eruptions have caused a great impact on the population by the generation of lahars along its three main drainages (N, S, E). Starting on April 2015 the seismic monitoring networks and the SO2 gas detection network in May 2015 showed a significant increase from their background values, in June a geodetic instrument located in the NE flank started to record inflation; all this indicated the beginning of a new period of unrest. On August 14, five small phreatic explosions occurred, accompanied by large gas and ash emissions, ash falls were reported to the W of the volcano and to the S of Quito capital city. Three new episodes of ash and gas emissions occurred afterwards and towards the end of November 2015, the different monitoring parameters indicated a progressive reduction in the activity of the volcano. Since August 18 almost weekly overflights were made in order to conduct thermal (FLIR camera), visual and SO2 gas monitoring. Towards the end of August thermal measurements showed for the first time the presence of new thermal anomalies (13.5 to 16.3 °C) located in the crevices of the N glaciers, at the same time fumarolic gases were observed coming out from those fractures. On a flight made on September 3, the presence of water coming out from the basal fronts of the northern glaciers was clearly observed and the formation of narrow streams of water running downslope, while it was evident the appearance of countless new crevices in the majority of glacier ends, but also new cracks and rockslides on the upper flanks. All this led to the conclusion that an abnormal process was producing the melting of the glaciers around the volcano. Starting on September it was possible to observe the presence of small secondary lahars descending several streams and we estimated that many of them are due to increased glacier melting. Later

  3. The role of melting alpine glaciers in mercury export and transport: An intensive sampling campaign in the Qugaqie Basin, inland Tibetan Plateau.

    PubMed

    Sun, Xuejun; Wang, Kang; Kang, Shichang; Guo, Junming; Zhang, Guoshuai; Huang, Jie; Cong, Zhiyuan; Sun, Shiwei; Zhang, Qianggong

    2017-01-01

    Glaciers, particularly alpine glaciers, have been receding globally at an accelerated rate in recent decades. The glacial melt-induced release of pollutants (e.g., mercury) and its potential impact on the atmosphere and glacier-fed ecosystems has drawn increasing concerns. During 15th-20th August, 2011, an intensive sampling campaign was conducted in Qugaqie Basin (QB), a typical high mountain glacierized catchment in the inland Tibetan Plateau, to investigate the export and transport of mercury from glacier to runoff. The total mercury (THg) level in Zhadang (ZD) glacier ranged from <1 to 20.8 ng L -1 , and was slightly higher than levels measured in glacier melt water and the glacier-fed river. Particulate Hg (PHg) was the predominant form of Hg in all sampled environmental matrices. Mercury concentration in Qugaqie River (QR) was characterized by a clear diurnal variation which is linked to glacier melt. The estimated annual Hg exports by ZD glacier, the upper river basin and the entire QB were 8.76, 7.3 and 157.85 g, respectively, with respective yields of 4.61, 0.99 and 2.74 μg m -2  yr -1 . Unique landforms and significant gradients from the glacier terminus to QB estuary might promote weathering and erosion, thereby controlling the transport of total suspended particulates (TSP) and PHg. In comparison with other glacier-fed rivers, QB has a small Hg export yet remarkably high Hg yield, underlining the significant impact of melting alpine glaciers on regional Hg biogeochemical cycles. Such impacts are expected to be enhanced in high altitude regions under the changing climate. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. The role of melting alpine glaciers in mercury export and transport: an intensive sampling campaign in the Qugaqie Basin, inland Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Sun, X.; Zhang, Q.

    2016-12-01

    Glaciers, particularly alpine glaciers, have been receding globally at an accelerated rate in recent decades. The glacial melt-induced release of pollutants (e.g., mercury) and its potential impact on the atmosphere and glacier-fed ecosystems has drawn increasing concerns. During 15th to 20th August, 2011, an intensive sampling campaign was conducted in Qugaqie Basin (QB), a typical high mountain glacierized catchment in the inland Tibetan Plateau, to investigate the export and transport of mercury from glacier to runoff. The total mercury (THg) level in Zhadang (ZD) glacier ranged from < 1 to 20.8 ng L-1, and was slightly higher than levels measured in glacier melt water and the glacier-fed river. Particulate Hg (PHg) was the predominant form of Hg in all sampled environmental matrices. Mercury concentration in Qugaqie River (QR) was characterized by a clear diurnal variation which is linked to glacier melt. The estimated annual Hg exports by ZD glacier, the upper river basin and the entire QB were 8.76, 7.3 and 157.85 g, respectively, with respective yields of 4.61, 0.99 and 2.74 μg m-2 yr-1. Unique landforms and significant gradients from the glacier terminus to QB estuary might promote weathering and erosion, thereby controlling the transport of total suspended particulates (TSP) and PHg. In comparison with other glacier-fed rivers, QB has a small Hg export yet remarkably high Hg yield, underlining the significant impact of melting alpine glaciers on regional Hg biogeochemical cycles. Such impacts are expected to be enhanced in high altitude regions under the changing climate.

  5. Evidence for persistent organic pollutants released from melting glacier in the central Tibetan Plateau, China.

    PubMed

    Li, Jun; Yuan, Guo-Li; Wu, Ming-Zhe; Sun, Yong; Han, Peng; Wang, Gen-Hou

    2017-01-01

    Glacier alluvial deposits record persistent organic pollutants (POPs) not only derived from the atmospheric deposition but also from the release of glacial melting. The evidence for melting glacier in the Tibetan Plateau (TP) as a secondary source of pollutants is introduced through investigating the concentration of organochlorine pesticides (OCPs) in four deposited profiles collected at the edge of the Changwengluozha glacier. Two concentration peaks were observed for dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs) in the past century. The first peak was observed in the 1970s, corresponding with the heavy usage of HCHs and DDTs in the surrounding countries and regions. The second one was in 2000 when the production and usage of DDTs and HCHs were strictly limited, which possibly indicated a significant release from melting glacier. This result was further supported by the enantiomeric fraction values for α-HCH and o,p'-DDT. On the other hand, the dramatic increase of polycyclic aromatic hydrocarbons (PAHs) from atmospheric deposition, which was associated with the socioeconomic development in Tibet, shaded the release of PAHs from melting glacier. This study reveals not only the air deposition history of legacy POPs but also a substantial release of OCPs from glacier to the adjacent environment. Our research supports the hypothesis that the melting glacier in the TP represents a secondary source of OCPs, which is consistent with the findings in the Alps glaciers. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Role of sub-regional variations on melting Response of Indian-Himalayan Glaciers

    NASA Astrophysics Data System (ADS)

    Tayal, S.; Hasnain, S. I.

    2010-12-01

    Glaciers play a crucial role in maintaining ecosystem stability as they act as buffers and regulate the runoff water supply from high mountains to the plains during both dry and wet spells. Retreat of Hindu Kush-Himalaya-Tibetan glaciers is one of the major environmental problems facing the south Asian and south-east Asian region. The Himalayan mountain range spans 2500 km east to west and includes diverse cultures of five countries (Afghanistan, Pakistan, India, Tibet (China), Nepal, Bhutan) and a range of weather patterns, which has been strongly affected by regional climate change. The glaciers of Indian Himalayan ranges covers an area of 19000 km2 contains over 9500 glaciers and feed major perennial river systems like Indus, Ganges, Brahmaputra, and sustain the livelihood of over 0.5 billion south Asians. Glaciers are melting fast but their response time varies from westerly nourished Kashmir Himalaya glaciers to south-west monsoon nourished Sikkim Himalaya glaciers based on regional climatic variations. Changes in mass balance of a glacier are considered as the most direct representative of the impacts of meteorological parameters on the glacier dynamic responses. A comparative study of mass balance, based on field measurements techniques is being conducted on two benchmark glaciers in the Indian Himalaya. The glaciers currently being monitored are Kolahoi glacier (340 07 - 340 12 N: 750 16 - 750 23E), Kashmir Himalaya and E.Rathong glacier (270 33 - 480 36 N: 880 06 - 880 08 E), Sikkim Himalaya. One year mass balance results (2008-2009) for both the benchmark glaciers are now available and are being presented. Mass balance for Kolahoi glacier located in sub-tropical to temperate setting and nourished by westerly system show range from -2.0 m.w.e. to -3.5 m.w.e. per annum. Whereas, the E. Rathong glacier located in tropical climatic settings and nourished by SW monsoon system show range from -2.0 m.w.e. to -5.0 m.w.e. per annum. The (2009/2010) mass balance

  7. When glaciers and ice sheets melt: consequences for planktonic organisms

    PubMed Central

    SOMMARUGA, RUBEN

    2016-01-01

    The current melting of glaciers and ice sheets is a consequence of climatic change and their turbid meltwaters are filling and enlarging many new proglacial and ice-contact lakes around the world, as well as affecting coastal areas. Paradoxically, very little is known on the ecology of turbid glacier-fed aquatic ecosystems even though they are at the origin of the most common type of lakes on Earth. Here, I discuss the consequences of those meltwaters for planktonic organisms. A remarkable characteristic of aquatic ecosystems receiving the discharge of meltwaters is their high content of mineral suspensoids, so-called glacial flour that poses a real challenge for filter-feeding planktonic taxa such as Daphnia and phagotrophic groups such as heterotrophic nanoflagellates. The planktonic food-web structure in highly turbid meltwater lakes seems to be truncated and microbially dominated. Low underwater light levels leads to unfavorable conditions for primary producers, but at the same time, cause less stress by UV radiation. Meltwaters are also a source of inorganic and organic nutrients that could stimulate secondary prokaryotic production and in some cases (e.g. in distal proglacial lakes) also phytoplankton primary production. How changes in turbidity and in other related environmental factors influence diversity, community composition and adaptation have only recently begun to be studied. Knowledge of the consequences of glacier retreat for glacier-fed lakes and coasts will be crucial to predict ecosystem trajectories regarding changes in biodiversity, biogeochemical cycles and function. PMID:26869738

  8. Spatiotemporal tracer variability in glacier melt and its influence on hydrograph separation

    NASA Astrophysics Data System (ADS)

    Schmieder, Jan; Marke, Thomas; Strasser, Ulrich

    2017-04-01

    Glaciers are important seasonal water contributors in many mountainous regions. Knowledge on the timing and amount of glacier melt water is crucial for water resources management, especially in downstream regions where the water is needed (hydropower, drinking water) or where it represents a potential risk (drought, flood). This becomes even more relevant in a changing climate. Environmental tracers are a useful tool in the assessment of ice water resources, because they provide information about the sources, flow paths and traveling times of water contributing to streamflow at the catchment scale. Hydrometric and meteorological measurements combined with tracer analyses help to unravel streamflow composition and improve the understanding of hydroclimatological processes. Empirical studies on runoff composition are necessary to parameterize and validate hydrological models in a process-oriented manner, rather than comparing total measured and simulated runoff only. In the present study three approaches of hydrograph separation are compared to decide which sampling frequency is required to capture the spatiotemporal variability of glacier melt, and to draw implications for future studies of streamflow partitioning. Therefore glacier melt contributions to a proglacial stream at the sub-daily, daily, and seasonal scale were estimated using electrical conductivity and oxygen-18 as tracers. The field work was conducted during December 2015 and September 2016 in the glaciated (34%) high-elevation catchment of the Hochjochbach, a small sub-basin (17 km2) of the Oetztaler Ache river in the Austrian Alps, ranging from 2400 to 3500 m a.s.l. in elevation. Hydroclimatological data was provided by an automatic weather station and a streamflow gauging station equipped with a pressure transducer. Water samples of streamflow, glacier melt, and rain were collected throughout the winter period (December to March) and the ablation season (July to September). In the proposed

  9. Human activities and its Responses to Glacier Melt Water Over Tarim River Basin

    NASA Astrophysics Data System (ADS)

    He, Hai; Zhou, Shenbei; Bai, Minghao

    2017-04-01

    Tarim River Basin lies in the south area of Xinjiang Uygur Autonomous Region, the north-west area of China. It is the longest inland river of China. Being far away from ocean and embraced by high mountains, Tarim River Basin is the typical arid region in the world. The intensity of human activities increased rapidly in Tarim River Basin since 1980's and water resources lacking is the major issue restricting the development of social economy. The glacier melt water plays an important role for the regional social and economic development, and it accounts for 40% of mountain-pass runoff. It is a fragile mutual-dependent relationship between local sustainable development and runoff. Under the background of global change glacier melt water process has also changed especially in the arid and semi-arid region. Due to climate change, glacier in Tarim River Basin has melted in an observed way since 1980s, together with increasing trend of annual rainfall and virgin flow in mountain basins. Correspondingly, human activity gets more frequent since 1970s, resulting into the obvious fragile mutual-dependent relationship between basin runoff and water use amount. Through an analysis of meteorological, hydrological and geographical observation data from 1985 to 2015, this thesis make a multi-factor variance analysis of population, cultivation area, industrial development and runoff in upstream and mid-stream of Tarim River under changing conditions. Furthermore, the regulation function of natural factors and water demand management factors on relationship between runoff and water using amount are discussed, including temperature, rainfall, and evaporation, water conservation technology and soil-water exploitation administrative institutions. It concludes that: first, increase in glacier runoff, rainfall amount, and virgin flow haven't notably relieved ecological issue in Tarim River Basin, and even has promoted water use behaviour in different flowing areas and noticeably reduced

  10. Laboratory Experiments Investigating Glacier Submarine Melt Rates and Circulation in an East Greenland Fjord

    NASA Astrophysics Data System (ADS)

    Cenedese, C.

    2014-12-01

    Idealized laboratory experiments investigate the glacier-ocean boundary dynamics near a vertical 'glacier' (i.e. no floating ice tongue) in a two-layer stratified fluid, similar to Sermilik Fjord where Helheim Glacier terminates. In summer, the discharge of surface runoff at the base of the glacier (subglacial discharge) intensifies the circulation near the glacier and increases the melt rate with respect to that in winter. In the laboratory, the effect of subglacial discharge is simulated by introducing fresh water at melting temperatures from either point or line sources at the base of an ice block representing the glacier. The circulation pattern observed both with and without subglacial discharge resembles those observed in previous studies. The buoyant plume of cold meltwater and subglacial discharge water entrains ambient water and rises vertically until it finds either the interface between the two layers or the free surface. The results suggest that the meltwater deposits within the interior of the water column and not entirely at the free surface, as confirmed by field observations. The submarine melt rate increases with the subglacial discharge rate. Furthermore, the same subglacial discharge causes greater submarine melting if it exits from a point source rather than from a line source. When the subglacial discharge exits from two point sources, two buoyant plumes are formed which rise vertically and interact. The results suggest that the distance between the two subglacial discharges influences the entrainment in the plumes and consequently the amount of submarine melting and the final location of the meltwater within the water column. Hence, the distribution and number of sources of subglacial discharge may play an important role in glacial melt rates and fjord stratification and circulation. Support was given by NSF project OCE-113008.

  11. Air temperature thresholds to evaluate snow melting at the surface of Alpine glaciers by T-index models: the case study of Forni Glacier (Italy)

    NASA Astrophysics Data System (ADS)

    Senese, A.; Maugeri, M.; Vuillermoz, E.; Smiraglia, C.; Diolaiuti, G.

    2014-03-01

    The glacier melt conditions (i.e.: null surface temperature and positive energy budget) can be assessed by analyzing meteorological and energy data acquired by a supraglacial Automatic Weather Station (AWS). In the case this latter is not present the assessment of actual melting conditions and the evaluation of the melt amount is difficult and simple methods based on T-index (or degree days) models are generally applied. These models require the choice of a correct temperature threshold. In fact, melt does not necessarily occur at daily air temperatures higher than 273.15 K. In this paper, to detect the most indicative threshold witnessing melt conditions in the April-June period, we have analyzed air temperature data recorded from 2006 to 2012 by a supraglacial AWS set up at 2631 m a.s.l. on the ablation tongue of the Forni Glacier (Italian Alps), and by a weather station located outside the studied glacier (at Bormio, a village at 1225 m a.s.l.). Moreover we have evaluated the glacier energy budget and the Snow Water Equivalent (SWE) values during this time-frame. Then the snow ablation amount was estimated both from the surface energy balance (from supraglacial AWS data) and from T-index method (from Bormio data, applying the mean tropospheric lapse rate and varying the air temperature threshold) and the results were compared. We found that the mean tropospheric lapse rate permits a good and reliable reconstruction of glacier air temperatures and the major uncertainty in the computation of snow melt is driven by the choice of an appropriate temperature threshold. From our study using a 5.0 K lower threshold value (with respect to the largely applied 273.15 K) permits the most reliable reconstruction of glacier melt.

  12. Hydrologically-induced slow-down as a mechanism for tidewater glacier retreat

    NASA Astrophysics Data System (ADS)

    Hewitt, Ian

    2017-04-01

    Outlet glaciers flowing into the ocean often terminate at a calving front, whose position is sensitively determined by the balance between ice discharge and calving/terminus-melting. Rapid retreat of tidewater glaciers can be initiated when the front is perturbed from a preferred pinning point, particularly when the glacier sits in an overdeepened trough. This is believed to make certain areas of ice sheets particularly vulnerable to ice loss. A number of factors may cause a previously stable front position to become unstable, including changes in buttressing provided by an ice shelf, and changes in ocean temperature. Another possibility is that initial retreat is induced by a reduction in the supply of ice from the interior of the ice sheet. Such a reduction can naturally arise from an increase in surface melting and runoff (in the absence of accumulation changes), and this may be amplified if more efficient meltwater routing reduces basal lubrication, as has been observed in some areas of the Greenland ice sheet. Since the initiation of rapid retreat often results in an increase of ice discharge at the front (due to increased ice thickness), such a process may not be easy to detect. In this study, I employ a simplified model of an outlet glacier and its frontal behaviour to examine the extent to which hydrologically induced slow-down of the feeding ice sheet may induce (or help to induce) calving front retreat. The model builds on earlier parameterisations of grounding line fluxes, and assumes that calving occurs according to a criterion that keeps the front close to the flotation thickness. The glacier bed is assumed to be plastic. This allows for a transparent identification of the different forcing terms affecting margin position. We conclude that hydrologically-induced slow-down of ice sheets is likely to have a more significant effect on mass loss than hydrologically-induced speed-up.

  13. Morphological evidence and direct estimates of rapid melting beneath Totten Glacier Ice Shelf, East Antarctica

    NASA Astrophysics Data System (ADS)

    Greenbaum, Jamin; Schroeder, Dustin; Grima, Cyril; Habbal, Feras; Dow, Christine; Roberts, Jason; Gwyther, David; van Ommen, Tas; Siegert, Martin; Blankenship, Donald

    2017-04-01

    Totten Glacier drains at least 3.5 meters of eustatic sea level potential from marine-based ice in the Aurora Subglacial Basin (ASB) in East Antarctica, more than the combined total of all glaciers in West Antarctica. Totten Glacier has been the most rapidly thinning glacier in East Antarctica since satellite altimetry time series began and the nature of the thinning suggests that it is driven by enhanced basal melting due to ocean processes. While grounded ice thinning rates have been steady, recent work has shown that Totten's floating ice shelf may not have the same thinning behavior; as a result, it is critical to observe ice shelf and cavity boundary conditions and basal processes to understand this apparent discrepancy. Warm Modified Circumpolar Deep Water (MCDW), which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the nearby Sabrina Coast continental shelf and deep depressions in the seafloor provide access for MCDW to reach the ice shelf cavity. Given its northern latitude, numerical ice sheet modeling indicates that Totten Glacier may be prone to retreat caused by hydrofracture in a warming climate, so it is important to understand how intruding MCDW is affecting thinning of Totten Glacier's ice shelf. Here we use post-processed, focused airborne radar observations of the Totten Glacier Ice Shelf to delineate multi-km wide basal channels and flat basal terraces associated with high basal reflectivity and specularity (flatness) anomalies and correspondingly large ice surface depressions that indicate active basal melting. Using a simple temperature-attenuation model, and basal roughness corrections, we present basal melt rates associated with the radar reflection and specularity anomalies and compare them to those derived from numerical ocean circulation modeling and an ice flow divergence calculation. Sub-ice shelf ocean circulation modeling and under-ice robotic observations of Pine Island Glacier Ice

  14. Quantifying present and future glacier melt-water contribution to runoff in a Central Himalayan river basin

    NASA Astrophysics Data System (ADS)

    Prasch, M.; Mauser, W.; Weber, M.

    2012-10-01

    Water supply of most lowland cultures heavily depends on rain and melt-water from the upstream mountains. Especially melt-water release of alpine mountain ranges is usually attributed a pivotal role for the water supply of large downstream regions. Water scarcity is assumed as consequence of glacier shrinkage and possible disappearance due to Global Climate Change, particular for large parts of Central and South East Asia. In this paper, the application and validation of a coupled modeling approach with Regional Climate Model outputs and a process-oriented glacier and hydrological model is presented for a Central Himalayan river basin despite scarce data availability. Current and possible future contributions of ice-melt to runoff along the river network are spatially explicitly shown. Its role among the other water balance components is presented. Although glaciers have retreated and will continue to retreat according to the chosen climate scenarios, water availability is and will be primarily determined by monsoon precipitation and snow-melt. Ice-melt from glaciers is and will be a minor runoff component in summer monsoon-dominated Himalayan river basins.

  15. Evaluation of the most suitable threshold value for modelling snow glacier melt through T- index approach: the case study of Forni Glacier (Italian Alps)

    NASA Astrophysics Data System (ADS)

    Senese, Antonella; Maugeri, Maurizio; Vuillermoz, Elisa; Smiraglia, Claudio; Diolaiuti, Guglielmina

    2014-05-01

    Glacier melt occurs whenever the surface temperature is null (273.15 K) and the net energy budget is positive. These conditions can be assessed by analyzing meteorological and energy data acquired by a supraglacial Automatic Weather Station (AWS). In the case this latter is not present at the glacier surface the assessment of actual melting conditions and the evaluation of melt amount is difficult and degree-day (also named T-index) models are applied. These approaches require the choice of a correct temperature threshold. In fact, melt does not necessarily occur at daily air temperatures higher than 273.15 K, since it is determined by the energy budget which in turn is only indirectly affected by air temperature. This is the case of the late spring period when ablation processes start at the glacier surface thus progressively reducing snow thickness. In this study, to detect the most indicative air temperature threshold witnessing melt conditions in the April-June period, we analyzed air temperature data recorded from 2006 to 2012 by a supraglacial AWS (at 2631 m a.s.l.) on the ablation tongue of the Forni Glacier (Italy), and by a weather station located nearby the studied glacier (at Bormio, 1225 m a.s.l.). Moreover we evaluated the glacier energy budget (which gives the actual melt, Senese et al., 2012) and the snow water equivalent values during this time-frame. Then the ablation amount was estimated both from the surface energy balance (MEB from supraglacial AWS data) and from degree-day method (MT-INDEX, in this latter case applying the mean tropospheric lapse rate to temperature data acquired at Bormio changing the air temperature threshold) and the results were compared. We found that the mean tropospheric lapse rate permits a good and reliable reconstruction of daily glacier air temperature conditions and the major uncertainty in the computation of snow melt from degree-day models is driven by the choice of an appropriate air temperature threshold. Then

  16. Polychlorinated Biphenyls in a Temperate Alpine Glacier: 1. Effect of Percolating Meltwater on their Distribution in Glacier Ice.

    PubMed

    Pavlova, Pavlina Aneva; Jenk, Theo Manuel; Schmid, Peter; Bogdal, Christian; Steinlin, Christine; Schwikowski, Margit

    2015-12-15

    In Alpine regions, glaciers act as environmental archives and can accumulate significant amounts of atmospherically derived pollutants. Due to the current climate-warming-induced accelerated melting, these pollutants are being released at correspondingly higher rates. To examine the effect of melting on the redistribution of legacy pollutants in Alpine glaciers, we analyzed polychlorinated biphenyls in an ice core from the temperate Silvretta glacier, located in eastern Switzerland. This glacier is affected by surface melting in summer. As a result, liquid water percolates down and particles are enriched in the current annual surface layer. Dating the ice core was a challenge because meltwater percolation also affects the traditionally used parameters. Instead, we counted annual layers of particulate black carbon in the ice core, adding the years with negative glacier mass balance, that is, years with melting and subsequent loss of the entire annual snow accumulation. The analyzed samples cover the time period 1930-2011. The concentration of indicator PCBs (iPCBs) in the Silvretta ice core follows the emission history, peaking in the 1970s (2.5 ng/L). High PCB values in the 1990s and 1930s are attributed to meltwater-induced relocation within the glacier. The total iPCB load at the Silvretta ice core site is 5 ng/cm(2). A significant amount of the total PCB burden in the Silvretta glacier has been released to the environment.

  17. Air temperature, radiation budget and area changes of Quisoquipina glacier in the Cordillera Vilcanota (Peru)

    NASA Astrophysics Data System (ADS)

    Suarez, Wilson; Macedo, Nicolás; Montoya, Nilton; Arias, Sandro; Schauwecker, Simone; Huggel, Christian; Rohrer, Mario; Condom, Thomas

    2015-04-01

    The Peruvian Andes host about 71% of all tropical glaciers. Although several studies have focused on glaciers of the largest glaciered mountain range (Cordillera Blanca), other regions have received little attention to date. In 2011, a new program has been initiated with the aim of monitoring glaciers in the centre and south of Peru. The monitoring program is managed by the Servicio Nacional de Meteorología e Hidrología del Perú (SENAMHI) and it is a joint project together with the Universidad San Antonio Abad de Cusco (UNSAAC) and the Autoridad Nacional del Agua (ANA). In Southern Peru, the Quisoquipina glacier has been selected due to its representativeness for glaciers in the Cordillera Vilcanota considering area, length and orientation. The Cordillera Vilcanota is the second largest mountain range in Peru with a glaciated area of approximately 279 km2 in 2009. Melt water from glaciers in this region is partly used for hydropower in the dry season and for animal breeding during the entire year. Using Landsat 5 images, we could estimate that the area of Quisoquipina glacier has decreased by approximately 11% from 3.66 km2 in 1990 to 3.26 km2 in 2010. This strong decrease is comparable to observations of other tropical glaciers. In 2011, a meteorological station has been installed on the glacier at 5180 m asl., measuring air temperature, wind speed, relative humidity, net short and longwave radiation and atmospheric pressure. Here, we present a first analysis of air temperature and the radiation budget at the Quisoquipina glacier for the first three years of measurements. Additionally, we compare the results from Quisoquipina glacier to results obtained by the Institut de recherche pour le développement (IRD) for Zongo glacier (Bolivia) and Antizana glacier (Ecuador). For both, Quisoquipina and Zongo glacier, net shortwave radiation may be the most important energy source, thus indicating the important role of albedo in the energy balance of the glacier

  18. Channelized ice melting in the ocean boundary layer beneath Pine Island Glacier, Antarctica.

    PubMed

    Stanton, T P; Shaw, W J; Truffer, M; Corr, H F J; Peters, L E; Riverman, K L; Bindschadler, R; Holland, D M; Anandakrishnan, S

    2013-09-13

    Ice shelves play a key role in the mass balance of the Antarctic ice sheets by buttressing their seaward-flowing outlet glaciers; however, they are exposed to the underlying ocean and may weaken if ocean thermal forcing increases. An expedition to the ice shelf of the remote Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet that has rapidly thinned and accelerated in recent decades, has been completed. Observations from geophysical surveys and long-term oceanographic instruments deployed down bore holes into the ocean cavity reveal a buoyancy-driven boundary layer within a basal channel that melts the channel apex by 0.06 meter per day, with near-zero melt rates along the flanks of the channel. A complex pattern of such channels is visible throughout the Pine Island Glacier shelf.

  19. Ice-Shelf Melt Response to Changing Winds and Glacier Dynamics in the Amundsen Sea Sector, Antarctica

    NASA Astrophysics Data System (ADS)

    Donat-Magnin, Marion; Jourdain, Nicolas C.; Spence, Paul; Le Sommer, Julien; Gallée, Hubert; Durand, Gaël.

    2017-12-01

    It has been suggested that the coastal Southern Ocean subsurface may warm over the 21st century in response to strengthening and poleward shifting winds, with potential adverse effects on West Antarctic glaciers. However, using a 1/12° ocean regional model that includes ice-shelf cavities, we find a more complex response to changing winds in the Amundsen Sea. Simulated offshore subsurface waters get colder under strengthened and poleward shifted winds representative of the SAM projected trend. The buoyancy-driven circulation induced by ice-shelf melt transports this cold offshore anomaly onto the continental shelf, leading to cooling and decreased melt below 450 m. In the vicinity of ice-shelf fronts, Ekman pumping contributes to raise the isotherms in response to changing winds. This effect overwhelms the horizontal transport of colder offshore waters at intermediate depths (between 200 and 450 m), and therefore increases melt rates in the upper part of the ice-shelf cavities, which reinforces the buoyancy-driven circulation and further contributes to raise the isotherms. Then, prescribing an extreme grounding line retreat projected for 2100, the total melt rates simulated underneath Thwaites and Pine Island are multiplied by 2.5. Such increase is explained by a larger ocean/ice interface exposed to CDW, which is then amplified by a stronger melt-induced circulation along the ice draft. Our main conclusions are that (1) outputs from ocean models that do not represent ice shelf cavities (e.g., CMIP5 models) should not be directly used to predict the thermal forcing of future ice shelf cavities; (2) coupled ocean/ice sheet models with a velocity-dependent melt formulation are needed for future projections of glaciers experiencing a significant grounding line retreat.

  20. Groundwater resources vulnerability due to melting glaciers in the Talgar alluvian fan, northern Tien-Shan

    NASA Astrophysics Data System (ADS)

    Saks, Tomas; Timuhins, Andrejs; Sennikovs, Juris; Ibraimov, Vitaliy; Sotnikov, Evgeniy; Salybekova, Valentina; Rahimov, Timur; Popovs, Konrads

    2017-04-01

    Alluvial fans on the mountain slopes in Central Asia are an important source of the groundwater, due to there capacity of storing large quantities of the fresh groundwater and due to the fact that most urban centres are situated in the mountainous terrain or along mountain slopes. The groundwater resources in the alluvial fans are replenished by the infiltration from the rivers, which drain the mountain catchments and by infiltration from the precipitation, and released on there lower reaches as a series of seasonal springs or infiltrated into the lower lying aquifers. The rivers with there catchments in the mountainous terrain are fed by the precipitation (with the peak in May-June due to snow melt) and glacier melt. The glacier meltwater constitutes up to 90% of the river runoff in July-August, due to peak in glacier melt and low precipitation, providing much needed freshwater for agriculture in the dry season. In this study an attempt to quantify the importance of the glacier meltwater on the groundwater resources through groundwater modelling in the Talgar alluvial fan, Ili-Alatau mountain range has been performed. The results suggest that glacier meltwater is a substantial portion of the groundwater resources in the Talgar alluvial fan, with up to 30m drop of the groundwater level, if the glaciers disappear, endangering existing groundwater supply. The transient simulations suggest that disappearance of the glaciers and highly variable annual precipitation would result in highly fluctuating groundwater levels, as well as disappearance of most of the springs at the foot of the alluvial fan. These results are especially relevant for the northern Tien-Shan, where glaciers have been rapidly retreating over last 50 years, and some of the glaciers could disappear in next decades.

  1. Observations and modeling of ocean-induced melt beneath Petermann Glacier Ice Shelf in northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Cai, Cilan; Rignot, Eric; Menemenlis, Dimitris; Nakayama, Yoshihiro

    2017-08-01

    We update observationally based estimates of subaqueous melt, Qm, beneath Petermann Glacier Ice Shelf (PGIS), Greenland, and model its sensitivity to oceanic thermal forcing, TF, and subglacial runoff, Qsg, using the Massachusetts Institute of Technology general circulation model (MITgcm), in a two-dimensional domain, with 20 m vertical and 40 m horizontal resolution at the grounding line. We adjust the drag coefficient to match the observationally based Qm. With the inclusion of Qsg, the maximum melt rate (Qmmax) is 2 times larger in summer and 1/3 larger annually than in winter. Qmmax increases above linear with TF and below linear with Qsg. We estimate that Qmmax increased by 24% (+8.1 m/yr) beneath PGIS from the 1990s to the 2000s from a 0.21°C warming in ocean temperature and a doubling in Qsg, hence contributing to its thinning. If the PGIS is removed, we estimate that the modeled melt rate near the grounding line will increase 13-16 times.

  2. Sea ice breakup and marine melt of a retreating tidewater outlet glacier in northeast Greenland (81°N).

    PubMed

    Bendtsen, Jørgen; Mortensen, John; Lennert, Kunuk; K Ehn, Jens; Boone, Wieter; Galindo, Virginie; Hu, Yu-Bin; Dmitrenko, Igor A; Kirillov, Sergei A; Kjeldsen, Kristian K; Kristoffersen, Yngve; G Barber, David; Rysgaard, Søren

    2017-07-10

    Rising temperatures in the Arctic cause accelerated mass loss from the Greenland Ice Sheet and reduced sea ice cover. Tidewater outlet glaciers represent direct connections between glaciers and the ocean where melt rates at the ice-ocean interface are influenced by ocean temperature and circulation. However, few measurements exist near outlet glaciers from the northern coast towards the Arctic Ocean that has remained nearly permanently ice covered. Here we present hydrographic measurements along the terminus of a major retreating tidewater outlet glacier from Flade Isblink Ice Cap. We show that the region is characterized by a relatively large change of the seasonal freshwater content, corresponding to ~2 m of freshwater, and that solar heating during the short open water period results in surface layer temperatures above 1 °C. Observations of temperature and salinity supported that the outlet glacier is a floating ice shelf with near-glacial subsurface temperatures at the freezing point. Melting from the surface layer significantly influenced the ice foot morphology of the glacier terminus. Hence, melting of the tidewater outlet glacier was found to be critically dependent on the retreat of sea ice adjacent to the terminus and the duration of open water.

  3. Hydro-chemical Characterization of Glacier Melt Water of Ponkar Glacier, Manang, Nepal.

    NASA Astrophysics Data System (ADS)

    Shrestha, R.; Sandeep, S.

    2017-12-01

    The study was carried out in Ponkar Glacier, representing Himalayan glacier of Nepal. The study aims in determining the physical-chemical properties of the glacier melt water. The sampling sites included moraine dammed, Ponkar Lake at 4100 m a.s.l to the downstream glaciated stream at 3580 m a.s.l. The water samples were collected from the seven different sites. Temperature was recorded by digital multi-thermometer on site. The samples were brought to the laboratory and the parameters were analyzed according to the APHA, AWWA and WEF standards. The glacier meltwater was slightly basic with pH 7.44 (±0.307). The meltwater was found to be in the range 30-60 which implies the water is moderately soft resulting value of concentration 36.429±8.664 mg CaCO3 L-1 and the electrical conductivity was found to be 47.14 (±11.18) µS/cm. The concentration of anion was in the order of HCO3 - > Cl- > SO42- > NO3- > TP-PO43- with the concentration 194.286±40.677, 55.707±30.265, 11.533±1.132 mgL-1, 1.00±0.7 mgL-1 and 0.514±0.32 mgL-1 respectively. Calcium carbonate weathering was found out to be the major source of dissolved ions in the region. The heavy metals were found in the order Al>Fe>Mn>Zn with concentration 1.34±0.648, 1.103±0.917, 0.08±0.028 and 0.023±0.004 mgL-1 respectively. The concentration of iron, manganese and zinc in some sites were below the detection limit. These results represent baseline data for the physical-chemical properties of the glacier meltwater

  4. Climate-induced glacier and snow loss imperils alpine stream insects.

    PubMed

    Giersch, J Joseph; Hotaling, Scott; Kovach, Ryan P; Jones, Leslie A; Muhlfeld, Clint C

    2017-07-01

    Climate warming is causing rapid loss of glaciers and snowpack in mountainous regions worldwide. These changes are predicted to negatively impact the habitats of many range-restricted species, particularly endemic, mountaintop species dependent on the unique thermal and hydrologic conditions found only in glacier-fed and snow melt-driven alpine streams. Although progress has been made, existing understanding of the status, distribution, and ecology of alpine aquatic species, particularly in North America, is lacking, thereby hindering conservation and management programs. Two aquatic insects - the meltwater stonefly (Lednia tumana) and the glacier stonefly (Zapada glacier) - were recently proposed for listing under the U.S. Endangered Species Act due to climate-change-induced habitat loss. Using a large dataset (272 streams, 482 total sites) with high-resolution climate and habitat information, we describe the distribution, status, and key environmental features that limit L. tumana and Z. glacier across the northern Rocky Mountains. Lednia tumana was detected in 113 streams (175 sites) within Glacier National Park (GNP) and surrounding areas. The probability of L. tumana occurrence increased with cold stream temperatures and close proximity to glaciers and permanent snowfields. Similarly, densities of L. tumana declined with increasing distance from stream source. Zapada glacier was only detected in 10 streams (24 sites), six in GNP and four in mountain ranges up to ~600 km southwest. Our results show that both L. tumana and Z. glacier inhabit an extremely narrow distribution, restricted to short sections of cold, alpine streams often below glaciers predicted to disappear over the next two decades. Climate warming-induced glacier and snow loss clearly imperils the persistence of L. tumana and Z. glacier throughout their ranges, highlighting the role of mountaintop aquatic invertebrates as sentinels of climate change in mid-latitude regions. © 2016

  5. Bathymetry and retreat of Southeast Greenland glaciers from Operation IceBridge and Ocean Melting Greenland data

    NASA Astrophysics Data System (ADS)

    Millan, R.; Rignot, E. J.; Morlighem, M.; Bjork, A. A.; Mouginot, J.; Wood, M.

    2017-12-01

    Southeast Greenland has been one of the largest contributors to ice mass loss in Greenland in part because of significant changes in glacier dynamics. The leading hypothesis for the changes in glacier dynamics is that enhanced thermal forcing from the ocean has dislodged a number of glaciers from their anchoring positions and some of them retreated rapidly along a reverse bed. The glaciers response has been observed to vary significantly from one fjord to the next, but until now there was not enough data to understand or interpret these changes. In particular, there was no data on glacier bed topography and seafloor bathymetry in the fjords. Here we present the results of new fjord mapping by the NASA Ocean Melting Greenland mission combined with a recent high-resolution airborne gravity survey by NASA Operation IceBridge. We combine these data with a reconstruction of the bed using a mass conservation approach upstream extending into the glacial fjords for the first time. In the fjord and along the ice-ocean transition, we employ a 3D inversion of gravity data to infer the bed elevation along a set of 9 survey boxes spanning south of Helheim Glacier to the southern tip of Southeast Greenland. We combine the results with an analysis of the glacier front history since the 1930's and Conductivity Temperature Depth data obtained in the fjord by OMG in 2016. The data reveals bed elevations several 100-m deeper than previously thought, for almost all the glaciers, up to 500 m for some of them. For many glaciers, the bed profiles help to completely understand the history of retreat of the glaciers. For instance, glaciers stranded on sills have been stable; glaciers on a reverse slope have retreated rapidly; and glaciers with a normal slope have retreated slowly. The mapping also helps document the extent of the marine portion of the glacier basins. In many of the fjords, we document the presence of warm, salty Atlantic Water which fuels large melt rates. We employ

  6. Quantifying changes in the contribution of upstream snow and glacier melt to downstream low flows in the River Rhine

    NASA Astrophysics Data System (ADS)

    Stahl, K.; Kohn, I.; Boehm, M.; Seibert, J.; Freudiger, D.; Gerlinger, K.; Weiler, M.

    2016-12-01

    Low flows impact river ecosystems and impair water use. In the mid- and downstream reaches of one of the largest rivers in Europe, the River Rhine, low flows can threaten a variety of ecosystem services and direct uses. Low flows in summer and fall are sustained by the snow and ice melt contribution from the glacierized mountain headwaters upstream. This study explores changes in the discharge components of rain, snowmelt and ice melt during extreme low flow events from a downstream perspective. Quantification of the discharge components is based on a novel method of runoff component tracking that was implemented into a model chain, consisting of the HBV model, which includes a glacier mass balance model allowing for areal glacier changes, for the headwaters and the distributed hydrological model LARSIM for the remaining Rhine basin. A transient model run at daily resolution was calibrated to glacier volume change, basin-wide snow cover and snow water equivalent and discharge variability at many gauging stations over the period 1901-2006. The analysis of the resulting discharge components revealed that over the course of the 20th Century, the loss of glacier volume and glacier area in the headwaters appears to have compensated an increasingly negative glacier mass balance, resulting in little long-term change to the ice melt component in summer streamflow - thus showing no clear `peak-water' trend. While the glacier ice melt component was less than two percent of the average annual discharge of the mid and lower reaches of the River Rhine, models suggest its fraction was much higher during extreme low flow events. The low flows of the summers of 1921, 1947, and 2003 were comprised of record daily ice melt fractions of more than one fifth of the daily discharge along the mid and lower reaches from Basel to the mouth. A scenario model run with suppressed glacier area change suggests that the ice melt discharge component would have doubled if the same meteorological

  7. Multiscale radar mapping of surface melt over mountain glaciers in High Mountain Asia

    NASA Astrophysics Data System (ADS)

    Steiner, N.; McDonald, K. C.

    2017-12-01

    Glacier melt dominates input for many hydrologic systems in the Himalayan Hindukush region that feed rivers that are critical for downstream ecosystems and hydropower generation in this highly populated area. Deviation in seasonal surface melt timing and duration with a changing climate has the potential to affect up to a billion people on the Indian Subcontinent. Satellite-borne microwave remote sensing has unique capabilities that allow monitoring of numerous landscape processes associated with snowmelt and freeze/thaw state, without many of the limitations in optical-infrared sensors such as solar illumination or atmospheric conditions. The onset of regional freeze/thaw and surface melting transitions determine important surface hydrologic variables like river discharge. Theses regional events are abrupt therefore difficult to observe with low-frequency observation sensors. Recently launched synthetic aperture radar (SAR) onboard the Sentinel-1 A and B satellites from the European Space Agency (ESA) provide wide-swath and high spatial resolution (50-100 m) C-Band SAR observations with observations frequencies not previously available, on the order of 8 to 16 days. The Sentinel SARs provide unique opportunity to study freeze/thaw and mountain glacier melt dynamics at process level scales, spatial and temporal. The melt process of individual glaciers, being fully resolved by imaging radar, will inform on the radiometric scattering physics associated with surface hydrology during the transition from melted to thawed state and during refreeze. Backscatter observations, along with structural information about the surface will be compared with complimentary coarse spatial resolution C-Band radar scatterometers, Advanced Scatterometer (ASCAT Met Op A+B), to understand the sub-pixel contribution of surface melting and freeze/thaw signals. This information will inform on longer-scale records of backscatter from ASCAT, 2006-2017. We present a comparison of polarimetric C

  8. Dust, Elemental Carbon and Other Impurities on Central Asian Glaciers: Origin and Radiative Forcing

    NASA Astrophysics Data System (ADS)

    Schmale, J.; Flanner, M.; Kang, S.; Sprenger, M.; Zhang, Q.; Li, Y.; Guo, J.; Schwikowski, M.

    2015-12-01

    In Central Asia, more than 60 % of the population depends on water stored in glaciers and mountain snow. While temperature, precipitation and dynamic processes are key drivers of glacial change, deposition of light absorbing impurities such as mineral dust and black carbon can lead to accelerated melting through surface albedo reduction. Here, we discuss the origin of deposited mineral dust and black carbon and their impacts on albedo change and radiative forcing (RF). 218 snow samples were taken from 13 snow pits on 4 glaciers, Abramov (Pamir), Suek, Glacier No. 354 and Golubin (Tien Shan), representing deposition between summer 2012 and 2014. They were analyzed for elemental and organic carbon by a thermo-optical method, mineral dust by gravimetry, and iron by ICP-MS. Back trajectory ensembles were released every 6 hours with the Lagranto model for the covered period at all sites. Boundary layer "footprints" were calculated to estimate general source regions and combined with MODIS fire counts for potential fire contributions. Albedo reduction due to black carbon and mineral dust was calculated with the Snow-Ice-Aerosol-Radiative model (SNICAR), and surface spectral irradiances were derived from atmospheric radiative transfer calculations to determine the RF under clear-sky and all sky conditions using local radiation measurements. Dust contributions came from Central Asia, the Arabian Peninsula, the Sahara and partly the Taklimakan. Fire contributions were higher in 2014 and generally came from the West and North. We find that EC exerts roughly 3 times more RF than mineral dust in fresh and relatively fresh snow (~5 W/m2) and up to 6 times more in snow that experienced melting (> 10 W/m2) even though EC concentrations (average per snow pit from 90 to 700 ng/g) were up to two orders of magnitude lower than mineral dust (10 to 140 μg/g).

  9. Estimation of snow and glacier melt contribution to Liddar stream in a mountainous catchment, western Himalaya: an isotopic approach.

    PubMed

    Jeelani, Gh; Shah, Rouf A; Jacob, Noble; Deshpande, Rajendrakumar D

    2017-03-01

    Snow- and glacier-dominated catchments in the Himalayas are important sources of fresh water to more than one billion people. However, the contribution of snowmelt and glacier melt to stream flow remains largely unquantified in most parts of the Himalayas. We used environmental isotopes and geochemical tracers to determine the source water and flow paths of stream flow draining the snow- and glacier-dominated mountainous catchment of the western Himalaya. The study suggested that the stream flow in the spring season is dominated by the snowmelt released from low altitudes and becomes isotopically depleted as the melt season progressed. The tracer-based mixing models suggested that snowmelt contributed a significant proportion (5-66 %) to stream flow throughout the year with the maximum contribution in spring and summer seasons (from March to July). In 2013 a large and persistent snowpack contributed significantly (∼51 %) to stream flow in autumn (September and October) as well. The average annual contribution of glacier melt to stream flow is little (5 %). However, the monthly contribution of glacier melt to stream flow reaches up to 19 % in September during years of less persistent snow pack.

  10. Geenland Glacier Albedo Variability

    NASA Astrophysics Data System (ADS)

    2004-01-01

    The program for Arctic Regional Climate Assessment (PARCA) is a NASA-funded project with the prime goal of addressing the mass balance of the Greenland ice sheet. Since the formal initiation of the program in 1995, there has been a significant improvement in the estimates of the mass balance of the ice sheet. Results from this program reveal that the high-elevation regions of the ice sheet are approximately in balance, but the margins are thinning. Laser surveys reveal significant thinning along 70 percent of the ice sheet periphery below 2000 m elevations, and in at least one outlet glacier, Kangerdlugssuaq in southeast Greenland, thinning has been as much as 10 m/yr. This study examines the albedo variability in four outlet glaciers to help separate out the relative contributions of surface melting versus ice dynamics to the recent mass balance changes. Analysis of AVHRR Polar Pathfinder albedo shows that at the Petermann and Jakobshavn glaciers, there has been a negative trend in albedo at the glacier terminus from 1981 to 2000, whereas the Stor+strommen and Kangerdlugssuaq glaciers show slightly positive trends in albedo. These findings are consistent with recent observations of melt extent from passive microwave data which show more melt on the western side of Greenland and slightly less on the eastern side. Significance of albedo trends will depend on where and when the albedo changes occur. Since the majority of surface melt occurs in the shallow sloping western margin of the ice sheet where the shortwave radiation dominates the energy balance in summer (e.g. Jakobshavn region) this region will be more sensitive to changes in albedo than in regions where this is not the case. Near the Jakobshavn glacier, even larger changes in albedo have been observed, with decreases as much as 20 percent per decade.

  11. Greenland Glacier Albedo Variability

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The program for Arctic Regional Climate Assessment (PARCA) is a NASA-funded project with the prime goal of addressing the mass balance of the Greenland ice sheet. Since the formal initiation of the program in 1995, there has been a significant improvement in the estimates of the mass balance of the ice sheet. Results from this program reveal that the high-elevation regions of the ice sheet are approximately in balance, but the margins are thinning. Laser surveys reveal significant thinning along 70 percent of the ice sheet periphery below 2000 m elevations, and in at least one outlet glacier, Kangerdlugssuaq in southeast Greenland, thinning has been as much as 10 m/yr. This study examines the albedo variability in four outlet glaciers to help separate out the relative contributions of surface melting versus ice dynamics to the recent mass balance changes. Analysis of AVHRR Polar Pathfinder albedo shows that at the Petermann and Jakobshavn glaciers, there has been a negative trend in albedo at the glacier terminus from 1981 to 2000, whereas the Stor+strommen and Kangerdlugssuaq glaciers show slightly positive trends in albedo. These findings are consistent with recent observations of melt extent from passive microwave data which show more melt on the western side of Greenland and slightly less on the eastern side. Significance of albedo trends will depend on where and when the albedo changes occur. Since the majority of surface melt occurs in the shallow sloping western margin of the ice sheet where the shortwave radiation dominates the energy balance in summer (e.g. Jakobshavn region) this region will be more sensitive to changes in albedo than in regions where this is not the case. Near the Jakobshavn glacier, even larger changes in albedo have been observed, with decreases as much as 20 percent per decade.

  12. Rapid melting dynamics of the Morteratsch glacier (Swiss Alps) from UAV photogrammetry and field spectroscopy data

    NASA Astrophysics Data System (ADS)

    Di Mauro, Biagio; Garzonio, Roberto; Rossini, Micol; Baccolo, Giovanni; Julitta, Tommaso; Cavallini, Giuseppe; Mattavelli, Matteo; Colombo, Roberto

    2017-04-01

    The impact of atmospheric impurities on the optical properties of snow and ice has been largely acknowledged in the scientific literature. Beyond this, the evaluation of the effect of specific organic and inorganic particles on melting dynamics remains a major challenge. In this contribution, we examine the annual melting dynamics of a large valley glacier of the Swiss Alps using UAV photogrammetry. We then compare the melting patterns to the presence of surface impurities on the glacier surface. Two surveys (in July and September 2016) with a lightweight Unmanned Aerial Vehicle (UAV) were organized on the ablation zone of the Morteratsch glacier (Swiss Alps). The UAV (DJI, Phantom 4) was equipped with a high resolution digital camera, and flew at a constant altitude of 150 from the glacier surface. 30 ground control points were placed on the glacier, and their coordinates were determined with a differential GPS (dGPS) for georeferencing UAV images. Contemporary to the UAV surveys, field spectroscopy data were collected on the glacier surface with an Analytical Spectral Device (ASD Field spec.) spectrometer covering the visible and near infrared spectral ranges, and ice samples were collected to determine the abundance of microorganism and algae. From the UAV RGB data, two point clouds were created using Structure from Motion (SfM) algorithms. The point clouds (each consisting of about 15M points) were then converted in Digital Surface Models (DSM) and orthomosaics by interpolation. The difference between the two DSM was calculated and converted in Snow Water Equivalent (SWE), in order to assess the ice lost by the glacier during the ablation season. The point clouds were compared and the displacement vectors were estimated using different algorithms. The elevation changes estimated from UAV data were compared with the abundance of microorganisms and algae. The reflectance spectra of ice with microorganisms and algae show a chlorophyll absorption feature at 680 nm

  13. Energy Balance and Hydrological Modelling of Zongo Glacier, Bolivia, Using ERA-40 Reanalysis Data

    NASA Astrophysics Data System (ADS)

    Duguay, M.; Hock, R.; Sicart, J.; Coudrain, A.

    2008-12-01

    In the Andes several regions profit significantly from glacial melt water for drink water supply and electricity production. During the dry season, glacier melt is significant source of water in the semi-arid region of La Paz, Bolivia. The Andean glaciers are retreating and water resources after reaching a culmination, will decrease. This implicates serious environmental and socio-economical consequences. For an effective attenuation, it is crucial to furnish quantitative predictions of the glacier mass loss and its effects on the water resources in these regions. A distributed energy balance model has been developed to model mass balance and melt induced discharge of tropical glaciers. We want to predict the changes in glacier melt discharge in response to future climate change for the region of La Paz, Bolivia and later regionalize the model to a larger area. The model operates on daily steps, has a 20 m grid resolution, and is forced by daily data of air temperature, humidity, wind speed, global radiation and precipitation. As a test basin, we calibrate the model at Glaciar Zongo, Bolivia, 16°15'S , 68°°10'W which is monitored by the French Institute for Research for the Development (IRD) . Zongo Glacier is a 1,8 km2 large and the catchment is 63% glacierized. Mass balance, weather station and discharge data are available on daily basis from 1991 onward. The measurements have gaps and only two years (1994-95 and 1999-00) with continuous data are available. In order to allow for multi-year simulations we force the model by daily ERA-40 reanalysis data from the European Center for Weather Forecast (ECMWF). To downscale the data we compare the daily data 1991-2002 to the observations at the glacier. Results indicate a fair agreement for air temperature, but a rather poor correlation between the ERA-40 data and the observations for wind speed, global radiation and precipitation. The correlation is improved using monthly values. So far, test runs of the model

  14. Afghanistan Glacier Diminution

    NASA Astrophysics Data System (ADS)

    Shroder, J. F.; Bishop, M.; Haritashya, U.; Olsenholler, J.

    2008-12-01

    Glaciers in Afghanistan represent a late summer - early fall source of melt water for late season crop irrigation in a chronically drought-torn region. Precise river discharge figures associated with glacierized drainage basins are generally unavailable because of the destruction of hydrological gauging stations built in pre-war times although historic discharge data and prior (1960s) mapped glacier regions offer some analytical possibilities. The best satellite data sets for glacier-change detection are declassified Cornona and Keyhole satellite data sets, standard Landsat sources, and new ASTER images assessed in our GLIMS (Global Land Ice Measurements from Space) Regional Center for Southwest Asia (Afghanistan and Pakistan). The new hyperspectral remote sensing survey of Afghanistan completed by the US Geological Survey and the Afghanistan Ministry of Mines offers potential for future detailed assessments. Long-term climate change in southwest Asia has decreased precipitation for millennia so that glaciers, rivers and lakes have all declined from prehistoric and historic highs. As many glaciers declined in ice volume, they increased in debris cover until they were entirely debris-covered or became rock glaciers, and the ice was protected thereby from direct solar radiation, to presumably reduce ablation rates. We have made a preliminary assessment of glacier location and extent for the country, with selected, more-detailed, higher-resolution studies underway. In the Great Pamir of the Wakhan Corridor where the largest glaciers occur, we assessed fluctuations of a randomly selected 30 glaciers from 1976 to 2003. Results indicate that 28 glacier-terminus positions have retreated, and the largest average retreat rate was 36 m/yr. High albedo, non-vegetated glacier forefields formed prior to 1976, and geomorphological evidence shows apparent glacier-surface downwasting after 1976. Climatic conditions and glacier retreat have resulted in disconnection of tributary

  15. Arctic warming: nonlinear impacts of sea-ice and glacier melt on seabird foraging.

    PubMed

    Grémillet, David; Fort, Jérôme; Amélineau, Françoise; Zakharova, Elena; Le Bot, Tangi; Sala, Enric; Gavrilo, Maria

    2015-03-01

    Arctic climate change has profound impacts on the cryosphere, notably via shrinking sea-ice cover and retreating glaciers, and it is essential to evaluate and forecast the ecological consequences of such changes. We studied zooplankton-feeding little auks (Alle alle), a key sentinel species of the Arctic, at their northernmost breeding site in Franz-Josef Land (80°N), Russian Arctic. We tested the hypothesis that little auks still benefit from pristine arctic environmental conditions in this remote area. To this end, we analysed remote sensing data on sea-ice and coastal glacier dynamics collected in our study area across 1979-2013. Further, we recorded little auk foraging behaviour using miniature electronic tags attached to the birds in the summer of 2013, and compared it with similar data collected at three localities across the Atlantic Arctic. We also compared current and historical data on Franz-Josef Land little auk diet, morphometrics and chick growth curves. Our analyses reveal that summer sea-ice retreated markedly during the last decade, leaving the Franz-Josef Land archipelago virtually sea-ice free each summer since 2005. This had a profound impact on little auk foraging, which lost their sea-ice-associated prey. Concomitantly, large coastal glaciers retreated rapidly, releasing large volumes of melt water. Zooplankton is stunned by cold and osmotic shock at the boundary between glacier melt and coastal waters, creating new foraging hotspots for little auks. Birds therefore switched from foraging at distant ice-edge localities, to highly profitable feeding at glacier melt-water fronts within <5 km of their breeding site. Through this behavioural plasticity, little auks maintained their chick growth rates, but showed a 4% decrease in adult body mass. Our study demonstrates that arctic cryosphere changes may have antagonistic ecological consequences on coastal trophic flow. Such nonlinear responses complicate modelling exercises of current and future

  16. Unusually loud ambient noise in tidewater glacier fjords: a signal of ice melt

    USGS Publications Warehouse

    Pettit, Erin C.; Lee, Kevin M.; Brann, Joel P.; Nystuen, Jeffrey A.; Wilson, Preston S.; O'Neel, Shad

    2015-01-01

    In glacierized fjords, the ice-ocean boundary is a physically and biologically dynamic environment that is sensitive to both glacier flow and ocean circulation. Ocean ambient noise offers insight into processes and change at the ice-ocean boundary. Here we characterize fjord ambient noise and show that the average noise levels are louder than nearly all measured natural oceanic environments (significantly louder than sea ice and non-glacierized fjords). Icy Bay, Alaska has an annual average sound pressure level of 120 dB (re 1 μPa) with a broad peak between 1000 and 3000 Hz. Bubble formation in the water column as glacier ice melts is the noise source, with variability driven by fjord circulation patterns. Measurements from two additional fjords, in Alaska and Antarctica, support that this unusually loud ambient noise in Icy Bay is representative of glacierized fjords. These high noise levels likely alter the behavior of marine mammals.

  17. Vulnerability of Southeast Greenland Glaciers to Warm Atlantic Water From Operation IceBridge and Ocean Melting Greenland Data

    NASA Astrophysics Data System (ADS)

    Millan, R.; Rignot, E.; Mouginot, J.; Wood, M.; Bjørk, A. A.; Morlighem, M.

    2018-03-01

    We employ National Aeronautics and Space Administration (NASA)'s Operation IceBridge high-resolution airborne gravity from 2016, NASA's Ocean Melting Greenland bathymetry from 2015, ice thickness from Operation IceBridge from 2010 to 2015, and BedMachine v3 to analyze 20 major southeast Greenland glaciers. The results reveal glacial fjords several hundreds of meters deeper than previously thought; the full extent of the marine-based portions of the glaciers; deep troughs enabling warm, salty Atlantic Water (AW) to reach the glacier fronts and melt them from below; and few shallow sills that limit the access of AW. The new oceanographic and topographic data help to fully resolve the complex pattern of historical ice front positions from the 1930s to 2017: glaciers exposed to AW and resting on retrograde beds have retreated rapidly, while glaciers perched on shallow sills or standing in colder waters or with major sills in the fjords have remained stable.

  18. Glaciation of alpine valleys: The glacier - debris-covered glacier - rock glacier continuum

    NASA Astrophysics Data System (ADS)

    Anderson, Robert S.; Anderson, Leif S.; Armstrong, William H.; Rossi, Matthew W.; Crump, Sarah E.

    2018-06-01

    Alpine ice varies from pure ice glaciers to partially debris-covered glaciers to rock glaciers, as defined by the degree of debris cover. In many low- to mid-latitude mountain ranges, the few bare ice glaciers that do exist in the present climate are small and are found where snow is focused by avalanches and where direct exposure to radiation is minimized. Instead, valley heads are more likely to be populated by rock glaciers, which can number in the hundreds. These rock-cloaked glaciers represent some of the most identifiable components of the cryosphere today in low- to mid-latitude settings, and the over-steepened snouts pose an often overlooked hazard to travel in alpine terrain. Geomorphically, rock glaciers serve as conveyor belts atop which rock is pulled away from the base of cliffs. In this work, we show how rock glaciers can be treated as an end-member case that is captured in numerical models of glaciers that include ice dynamics, debris dynamics, and the feedbacks between them. Specifically, we focus on the transition from debris-covered glaciers, where the modern equilibrium line altitude (ELA) intersects the topography, to rock glaciers, where the modern ELA lies above the topography. On debris-covered glaciers (i.e., glaciers with a partial rock mantle), rock delivered to the glacier from its headwall, or from sidewall debris swept into the glacier at tributary junctions, travels englacially to emerge below the ELA. There it accumulates on the surface and damps the rate of melt of underlying ice. This allows the termini of debris-covered glaciers to extend beyond debris-free counterparts, thereby decreasing the ratio of accumulation area to total area of the glacier (AAR). In contrast, rock glaciers (i.e., glaciers with a full rock mantle) occur where and when the environmental ELA rises above the topography. They require avalanches and rockfall from steep headwalls. The occurrence of rock glaciers reflects this dependence on avalanche sources

  19. Dissolved and particulate organic carbon in the melt water of Icelandic glaciers

    NASA Astrophysics Data System (ADS)

    Chifflard, Peter; Reiss, Martin

    2017-04-01

    Recently, glaciers have been recognized as unique ecosystems with potential effects on the global carbon cycle. Among other transport processes organic carbon stored in glacier ecosystems is released from the glaciers through melt at the glaciers surface that discharges into proglacial streams and finally into the ocean. Nevertheless, the potential role of glaciers in the carbon cycle remains poorly understood (Hood et al. 2015). One particular problem in this respect is that there is a lack in regional and global analysis of the total amount of organic carbon released from glaciers. Although, the release of organic carbon has been investigated in proglacial streams in Alaska, the European Alps and Greenland, to our knowledge, there is no information available for Icelandic proglacial streams. Thus, the aims of this study are: 1) to develop a first base information about the concentration of dissolved and particulate organic carbon (DOC and POC) in several Icelandic proglacial streams and 2) to detect the variability of DOC and POC along a proglacial stream from the glacier source to the mouth into the Atlantic Ocean. Therefore, a field trip was conducted between 23 and 31 July 2016, whereby, 25 water samples were taken. The sampling points cover melt water from the following Icelandic glaciers Vatnajökull, Langjökull, Hofsjökull, Myrdalsjökull and Tungnafellsjökull. Further water samples were taken along the river Hvitá starting at the glacier Langjökull and ending at the mouth into the Atlantic ocean in the southwest of Iceland. At every sample point electrical conductivity, water temperate and the pH-value were measured in situ using a calibrated portable water quality meter (Hanna Combo HI98129). The water samples (130 ml) were filtered using pre-combusted GF/F filters (Whatman, pore sizes 0.7 µm) and stored in a cooling box until the shipment to the laboratory of the Department for Geography, Philipps-University of Marburg. The DOC concentrations in

  20. Comparison of the meteorology and surface energy fluxes of debris-free and debris-covered glaciers in the southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Yang, W.

    2017-12-01

    Knowledge of the meteorology and energy fluxes of debris-free and debris-covered glaciers is important for understanding the varying response of glaciers to climate change. Field measurements at the debris-free Parlung No. 4 Glacier and the debris-covered 24K Glacier in the southeastern Tibetan Plateau were carried out to compare the meteorology and surface energy fluxes and to understand the factors controlling the melting process. The meteorological comparisons displayed temporally synchronous fluctuations in air temperature, relative humidity, incoming longwave radiation (Lin), but notable differences in precipitation, incoming shortwave radiation (Sin) and wind speed. Under the prevailing regional precipitation and debris conditions, more Lin (42 W/m2) was supplied from warmer and more humid air and more Sin (58 W/m2) was absorbed at the 24K Glacier. The relatively high energy supply led mainly to an increased energy output via turbulent heat fluxes and outgoing longwave radiation, rather than glacier melting beneath the thick debris. The sensitivity experiment showed that melting rates were sensitive to variations in energy supply with debris thicknesses of less than 10 cm. In contrast, energy supply to the ablation zone of the Parlung No. 4 Glacier mainly resulted in snow/ice melting, the magnitude of which was significantly influenced by the energy supplied by Sin and the sensible heat flux.

  1. Snow Melt Chemistry: Major and Trace Cation Contributions to Downstream Systems from the Llewellyn and Matthes Glaciers, Juneau Icefield

    NASA Astrophysics Data System (ADS)

    Huston, K.; Gianotti, Z.; Fortner, S. K.; John, C.; Kehrwald, N. M.; Kennedy, J.

    2017-12-01

    Previous work has revealed very little information on melt chemistry of the temperate Juneau Icefield. Improving this understanding is central to evaluating how current changes in climate will impact nutrient delivery to downstream ecosystems. The study focused on evaluating late melt season concentrations of major and trace cations on the Juneau Icefield. During the 2016 season, 30 supraglacial stream samples from the Llewellyn Glacier had K, Mg, Ca, and Na concentrations that varied across two to three orders of magnitude. For example, Ca ranged from 2-2023 ug/L. We collected surface snow from a transect across the Matthes and Llewellyn glaciers in late July and early August 2017 to retrieve data on actively melting snow of the Juneau Icefield. We collected these samples across a glacial flow divide to assess spatial variation in surface chemistry. We have used physical observations and chemical signatures (e.g. sea salt, eolian deposits) to identify the source and post-depositional fate of glacier chemistry. Additionally, we have compared our chemical results with existing datasets for greater understanding of chemical cycling through glacier systems.

  2. Annually-layered lake sediments reveal strongly increased release of persistent chemicals due to accelerated glacier melting

    NASA Astrophysics Data System (ADS)

    Anselmetti, Flavio S.; Blüthgen, Nancy; Bogdal, Christian; Schmid, Peter

    2010-05-01

    Melting glaciers may represent a secondary source of chemical pollutants that have previously been incorporated and stored in the ice. Of particular concern are persistent organic pollutants (POPs), such as the insecticide dichlorodiphenyl trichloroethane (DDT) and industrial chemicals like polychlorinated biphenyls (PCBs), which are hazardous environmental contaminants due to their persistent, bioaccumulative and toxic properties. They were introduced in the 1930s and eventually banned in the 1970s. After release into the environment these chemicals were atmospherically transported to even remote areas such as the Alps and were deposited and stored in glaciers. Ongoing drastic glacier melting due to global warming, which is expected to further accelerate, implies the significance of studying the fate of these 'legacy pollutants'. Proglacial lake sediments provide well-dated and high-resolution archives to reconstruct timing and quantities of such a potentially hazardous remobilization. The goal of this study is to reconstruct the historical inputs of POPs into remote alpine lakes and to investigate the accelerated release of POPs from melting glaciers. Due to their lipophilic character, these chemicals exhibit a high tendency to adsorb to particles whereas concentrations in water are expected to be low. Therefore, quantitative determination in annually-layered lake sediment provides an excellent way to investigate the temporal trend of inputs into lakes that act as particle sinks. For this purpose, sediment cores were sampled from proglacial lakes in the Bernese Alps (Switzerland), which are exclusively fed by glacial melt waters. For comparison, cores were also taken from nearby high-alpine lakes located in non-glaciated catchments, which only should record the initial atmospheric fall-out. Sediment layers were dated by annual varve counting and radionuclide measurements; they cover the time period from the mid 20th century to today. The measured time series of

  3. Tropical Glaciers

    NASA Astrophysics Data System (ADS)

    Fountain, Andrew

    The term "tropical glacier" calls to mind balmy nights and palm trees on one hand and cold, blue ice on the other. Certainly author Gabriel Garcia Marqez exploited this contrast in One Hundred Years of Solitude. We know that tropical fish live in warm, Sun-kissed waters and tropical plants provide lush, dense foliage populated by colorful tropical birds. So how do tropical glaciers fit into this scene? Like glaciers everywhere, tropical glaciers form where mass accumulation—usually winter snow—exceeds mass loss, which is generally summer melt. Thus, tropical glaciers exist at high elevations where precipitation can occur as snowfall exceeds melt and sublimation losses, such as the Rwenzori Mountains in east Africa and the Maoke Range of Irian Jaya.

  4. Rapid melting dynamics of an alpine glacier with repeated UAV photogrammetry

    NASA Astrophysics Data System (ADS)

    Rossini, Micol; Di Mauro, Biagio; Garzonio, Roberto; Baccolo, Giovanni; Cavallini, Giuseppe; Mattavelli, Matteo; De Amicis, Mattia; Colombo, Roberto

    2018-03-01

    Glacial retreat is a major problem in the Alps, especially over the past 40 years. Unmanned aerial vehicles (UAVs) can provide an unparalleled opportunity to track the spatiotemporal variations in rapidly changing glacial morphological features related to glacial dynamics. The objective of this study is to evaluate the potential of commercial UAV platforms to detect the evolution of the surface topography and morphology of an alpine glacier over a short time scale through the repeated acquisition of high-resolution photogrammetric data. Two high-resolution UAV surveys were performed on the ablation region of the Morteratsch Glacier (Swiss Alps) in July and September 2016. First, structure-from-motion (SfM) techniques were applied to create orthophotos and digital surface models (DSMs) of the glacial surface from multi-view UAV acquisitions. The geometric accuracy of DSMs and orthophotos was checked using differential global navigation satellite system (dGNSS) ground measurements, and an accuracy of approximately 17 cm was achieved for both models. High-resolution orthophotos and DSMs made it possible to provide a detailed characterization of rapidly changing glacial environments. Comparing the data from the first and the second campaigns, the evolution of the lower part of the glacier in response to summer ablation was evaluated. Two distinct processes were revealed and accurately quantified: an average lowering of the surface, with a mean ice thinning of 4 m, and an average horizontal displacement of 3 m due to flowing ice. These data were validated through a comparison of different algorithms and approaches, which clearly showed the consistency of the results. The melt rate spatial patterns were then compared to the glacial brightness and roughness maps derived from the September UAV acquisition. The results showed that the DSM differences describing the glacial melt rates were inversely related to the glacial brightness. In contrast, a positive but weaker

  5. Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt

    NASA Astrophysics Data System (ADS)

    Dunse, T.; Schellenberger, T.; Hagen, J. O.; Kääb, A.; Schuler, T. V.; Reijmer, C. H.

    2015-02-01

    Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the polar regions. Here we present continuous GPS measurements and satellite synthetic-aperture-radar-based velocity maps from Basin-3, the largest drainage basin of the Austfonna ice cap, Svalbard. Our observations demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of Basin-3. The resulting iceberg discharge of 4.2±1.6 Gt a-1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. With the seawater displacement by the terminus advance accounted for, the related sea-level rise contribution amounts to 7.2±2.6 Gt a-1. This rate matches the annual ice-mass loss from the entire Svalbard archipelago over the period 2003-2008, highlighting the importance of dynamic mass loss for glacier mass balance and sea-level rise. The active role of surface melt, i.e. external forcing, contrasts with previous views of glacier surges as purely internal dynamic instabilities. Given sustained climatic warming and rising significance of surface melt, we propose a potential impact of the hydro-thermodynamic feedback on the future stability of ice-sheet regions, namely at the presence of a cold-based marginal ice plug that restricts fast drainage of inland ice. The possibility of large-scale dynamic instabilities such as the partial disintegration of ice sheets is acknowledged but not quantified in global projections of sea-level rise.

  6. [Chemical composition and daily variation of melt water during ablation season in monsoonal temperate Glacier region: a case study of Baishui Glacier No. 1].

    PubMed

    Zhu, Guo-Feng; Pu, Tao; He, Yuan-Qing; Wang, Pei-Zhen; Kong, Jian-Long; Zhang, Ning-Ning; Xin, Hui-Juan

    2012-12-01

    Melt water samples collected continuously from 29 August to 3 September 2009 in the Baishui Glacier No. 1 at elevation of 4750 m were analyzed for pH, conductivity, delta18O and inorganic ions. The results showed that the pH had obvious diurnal variations and was increased slightly by the influence of precipitation. The dissolution of alkaline soluble salts in the dust was the main reason for the increase of melt water conductivity; the value of delta18O was relatively low in strong ablation period and high in slight ablation period. Different from other research areas, the concentrations of Na+, K+, which were influenced by lithological and marine water vapor, were higher than that of Mg2+ in the study area; HCO3- and Ca2+ accounted for more than 80% of total ions in snow and ice melt water, indicating that the ions mainly came from limestone and the melt water was a typical carbonate solution; The content of melt water had an obvious daily change with temperature change, but the response amplitudes were different; Monsoon transport, local rock lithology, human industrial and agricultural activities were the main sources of inorganic ions and the deciding factors of the ion composition in the Baishui Glacier No. 1.

  7. Melt-induced speed-up of Greenland ice sheet offset by efficient subglacial drainage.

    PubMed

    Sundal, Aud Venke; Shepherd, Andrew; Nienow, Peter; Hanna, Edward; Palmer, Steven; Huybrechts, Philippe

    2011-01-27

    Fluctuations in surface melting are known to affect the speed of glaciers and ice sheets, but their impact on the Greenland ice sheet in a warming climate remains uncertain. Although some studies suggest that greater melting produces greater ice-sheet acceleration, others have identified a long-term decrease in Greenland's flow despite increased melting. Here we use satellite observations of ice motion recorded in a land-terminating sector of southwest Greenland to investigate the manner in which ice flow develops during years of markedly different melting. Although peak rates of ice speed-up are positively correlated with the degree of melting, mean summer flow rates are not, because glacier slowdown occurs, on average, when a critical run-off threshold of about 1.4 centimetres a day is exceeded. In contrast to the first half of summer, when flow is similar in all years, speed-up during the latter half is 62 ± 16 per cent less in warmer years. Consequently, in warmer years, the period of fast ice flow is three times shorter and, overall, summer ice flow is slower. This behaviour is at odds with that expected from basal lubrication alone. Instead, it mirrors that of mountain glaciers, where melt-induced acceleration of flow ceases during years of high melting once subglacial drainage becomes efficient. A model of ice-sheet flow that captures switching between cavity and channel drainage modes is consistent with the run-off threshold, fast-flow periods, and later-summer speeds we have observed. Simulations of the Greenland ice-sheet flow under climate warming scenarios should account for the dynamic evolution of subglacial drainage; a simple model of basal lubrication alone misses key aspects of the ice sheet's response to climate warming.

  8. Effects of ice shelf basal melt variability on evolution of Thwaites Glacier

    NASA Astrophysics Data System (ADS)

    Hoffman, M. J.; Fyke, J. G.; Price, S. F.; Asay-Davis, X.; Perego, M.

    2017-12-01

    Theory, modeling, and observations indicate that marine ice sheets on a retrograde bed, including Thwaites Glacier, Antarctica, are only conditionally stable. Previous modeling studies have shown that rapid, unstable retreat can occur when steady ice-shelf basal melting causes the grounding line to retreat past restraining bedrock bumps. Here we explore the initiation and evolution of unstable retreat of Thwaites Glacier when the ice-shelf basal melt forcing includes temporal variability mimicking realistic climate variability. We use the three-dimensional, higher-order Model for Prediction Across Scales-Land Ice (MPASLI) model forced with an ice shelf basal melt parameterization derived from previous coupled ice sheet/ocean simulations. We add sinusoidal temporal variability to the melt parameterization that represents shoaling and deepening of Circumpolar Deep Water. We perform an ensemble of 250 year duration simulations with different values for the amplitude, period, and phase of the variability. Preliminary results suggest that, overall, variability leads to slower grounding line retreat and less mass loss than steady simulations. Short period (2 yr) variability leads to similar results as steady forcing, whereas decadal variability can result in up to one-third less mass loss. Differences in phase lead to a large range in mass loss/grounding line retreat, but it is always less than the steady forcing. The timing of ungrounding from each restraining bedrock bump, which is strongly affected by the melt variability, is the rate limiting factor, and variability-driven delays in ungrounding at each bump accumulate. Grounding line retreat in the regions between bedrock bumps is relatively unaffected by ice shelf melt variability. While the results are sensitive to the form of the melt parameterization and its variability, we conclude that decadal period ice shelf melt variability could potentially delay marine ice sheet instability by up to many decades. However

  9. Light-absorbing impurities enhance glacier albedo reduction in the southeastern Tibetan plateau

    NASA Astrophysics Data System (ADS)

    Zhang, Yulan; Kang, Shichang; Cong, Zhiyuan; Schmale, Julia; Sprenger, Michael; Li, Chaoliu; Yang, Wei; Gao, Tanguang; Sillanpää, Mika; Li, Xiaofei; Liu, Yajun; Chen, Pengfei; Zhang, Xuelei

    2017-07-01

    Light-absorbing impurities (LAIs) in snow of the southeastern Tibetan Plateau (TP) and their climatic impacts are of interest not only because this region borders areas affected by the South Asian atmospheric brown clouds but also because the seasonal snow and glacier melt from this region form important headwaters of large rivers. In this study, we collected surface snow and snowpit samples from four glaciers in the southeastern TP in June 2015 to investigate the comprehensive observational data set of LAIs. Results showed that the LAI concentrations were much higher in the aged snow and granular ice than in the fresh snow and snowpits due to postdepositional processes. Impurity concentrations fluctuated across snowpits, with maximum LAI concentrations frequently occurring toward the bottom of snowpits. Based on the SNow ICe Aerosol Radiative model, the albedo simulation indicated that black carbon and dust account for approximately 20% of the albedo reduction relative to clean snow. The radiative forcing caused by black carbon and dust deposition on the glaciers were between 1.0-141 W m-2 and 1.5-120 W m-2, respectively. Black carbon (BC) played a larger role in albedo reduction and radiative forcing than dust in the study area, enhancing approximately 15% of glacier melt. Analysis based on the Fire INventory from NCAR indicated that nonbiomass-burning sources of BC played an important role in the total BC deposition, especially during the monsoon season. This study suggests that eliminating anthropogenic BC could mitigate glacier melt in the future of the southeastern TP.

  10. The dynamic bacterial communities of a melting High Arctic glacier snowpack

    PubMed Central

    Hell, Katherina; Edwards, Arwyn; Zarsky, Jakub; Podmirseg, Sabine M; Girdwood, Susan; Pachebat, Justin A; Insam, Heribert; Sattler, Birgit

    2013-01-01

    Snow environments can occupy over a third of land surface area, but little is known about the dynamics of snowpack bacteria. The effect of snow melt on bacterial community structure and diversity of surface environments of a Svalbard glacier was examined using analyses of 16S rRNA genes via T-RFLP, qPCR and 454 pyrosequencing. Distinct community structures were found in different habitat types, with changes over 1 week apparent, in particular for the dominant bacterial class present, Betaproteobacteria. The differences observed were consistent with influences from depositional mode (snowfall vs aeolian dusts), contrasting snow with dust-rich snow layers and near-surface ice. Contrary to that, slush as the decompositional product of snow harboured distinct lineages of bacteria, further implying post-depositional changes in community structure. Taxa affiliated to the betaproteobacterial genus Polaromonas were particularly dynamic, and evidence for the presence of betaproteobacterial ammonia-oxidizing bacteria was uncovered, inviting the prospect that the dynamic bacterial communities associated with snowpacks may be active in supraglacial nitrogen cycling and capable of rapid responses to changes induced by snowmelt. Furthermore the potential of supraglacial snowpack ecosystems to respond to transient yet spatially extensive melting episodes such as that observed across most of Greenland's ice sheet in 2012 merits further investigation. PMID:23552623

  11. The dynamic bacterial communities of a melting High Arctic glacier snowpack.

    PubMed

    Hell, Katherina; Edwards, Arwyn; Zarsky, Jakub; Podmirseg, Sabine M; Girdwood, Susan; Pachebat, Justin A; Insam, Heribert; Sattler, Birgit

    2013-09-01

    Snow environments can occupy over a third of land surface area, but little is known about the dynamics of snowpack bacteria. The effect of snow melt on bacterial community structure and diversity of surface environments of a Svalbard glacier was examined using analyses of 16S rRNA genes via T-RFLP, qPCR and 454 pyrosequencing. Distinct community structures were found in different habitat types, with changes over 1 week apparent, in particular for the dominant bacterial class present, Betaproteobacteria. The differences observed were consistent with influences from depositional mode (snowfall vs aeolian dusts), contrasting snow with dust-rich snow layers and near-surface ice. Contrary to that, slush as the decompositional product of snow harboured distinct lineages of bacteria, further implying post-depositional changes in community structure. Taxa affiliated to the betaproteobacterial genus Polaromonas were particularly dynamic, and evidence for the presence of betaproteobacterial ammonia-oxidizing bacteria was uncovered, inviting the prospect that the dynamic bacterial communities associated with snowpacks may be active in supraglacial nitrogen cycling and capable of rapid responses to changes induced by snowmelt. Furthermore the potential of supraglacial snowpack ecosystems to respond to transient yet spatially extensive melting episodes such as that observed across most of Greenland's ice sheet in 2012 merits further investigation.

  12. Hydrochemical Signatures of Glacier Melt and Groundwater Storage on Volcán Chimborazo, Ecuador

    NASA Astrophysics Data System (ADS)

    McLaughlin, R.; Ng, G. H. C.; La Frenierre, J.; Wickert, A. D.; Baraer, M.

    2016-12-01

    With ever-growing water demands for hydroelectricity, agriculture, and domestic use, the accelerated retreat of tropical glaciers is raising concerns about future water supply sustainability. In the tropical Andes, where precipitation is seasonal and spatially heterogeneous, glaciers are particularly important as their storage and slow release of water helps to modulate stream discharge on daily to yearly time scales. Predicting the effect their shrinkage will have on water resources is not straightforward as little is known about the connections in these glaciated volcanic catchments between meltwater, groundwater, precipitation and surficial discharge. Here, stable isotope and major ion analyses inform a hydrochemical mixing model in order to identify water sources and their relative contributions to stream and spring discharge on Volcán Chimborazo, a stratovolcano located in the Ecuadorian Andes. Moisture in this region generally arrives from the Amazon basin to the east, resulting in a steep northeast-southwest precipitation gradient that produces wet and dry sides of the mountain. Dry season water samples were collected on both sides from major streams and springs at varying elevations and distances from the glacier tongues, along with samples of precipitation (when possible) and glacier ice. Data on specific conductivity, pH, and temperature were collected in situ for each sample. The paired catchment study allows us to isolate a primarily glacial melt signature on the dry side and compare it to data on the wet side, where glacial melt and precipitation both contribute to groundwater and surface-water discharge.

  13. The Intensity, Directionality, and Statistics of Underwater Noise From Melting Icebergs

    NASA Astrophysics Data System (ADS)

    Glowacki, Oskar; Deane, Grant B.; Moskalik, Mateusz

    2018-05-01

    Freshwater fluxes from melting icebergs and glaciers are important contributors to both sea level rise and anomalies of seawater salinity in polar regions. However, the hazards encountered close to icebergs and glaciers make it difficult to quantify their melt rates directly, motivating the development of cryoacoustics as a remote sensing technique. Recent studies have shown a qualitative link between ice melting and the accompanying underwater noise, but the properties of this signal remain poorly understood. Here we examine the intensity, directionality, and temporal statistics of the underwater noise radiated by melting icebergs in Hornsund Fjord, Svalbard, using a three-element acoustic array. We present the first estimate of noise energy per unit area associated with iceberg melt and demonstrate its qualitative dependence on exposure to surface current. Finally, we show that the analysis of noise directionality and statistics makes it possible to distinguish iceberg melt from the glacier terminus melt.

  14. Polychlorinated Biphenyls in a Temperate Alpine Glacier: 2. Model Results of Chemical Fate Processes.

    PubMed

    Steinlin, Christine; Bogdal, Christian; Pavlova, Pavlina A; Schwikowski, Margit; Lüthi, Martin P; Scheringer, Martin; Schmid, Peter; Hungerbühler, Konrad

    2015-12-15

    We present results from a chemical fate model quantifying incorporation of polychlorinated biphenyls (PCBs) into the Silvretta glacier, a temperate Alpine glacier located in Switzerland. Temperate glaciers, in contrast to cold glaciers, are glaciers where melt processes are prevalent. Incorporation of PCBs into cold glaciers has been quantified in previous studies. However, the fate of PCBs in temperate glaciers has never been investigated. In the model, we include melt processes, inducing elution of water-soluble substances and, conversely, enrichment of particles and particle-bound chemicals. The model is validated by comparing modeled and measured PCB concentrations in an ice core collected in the Silvretta accumulation area. We quantify PCB incorporation between 1900 and 2010, and discuss the fate of six PCB congeners. PCB concentrations in the ice core peak in the period of high PCB emissions, as well as in years with strong melt. While for lower-chlorinated PCB congeners revolatilization is important, for higher-chlorinated congeners, the main processes are storage in glacier ice and removal by particle runoff. This study gives insight into PCB fate and dynamics and reveals the effect of snow accumulation and melt processes on the fate of semivolatile organic chemicals in a temperate Alpine glacier.

  15. Widespread albedo decreasing and induced melting of Himalayan snow and ice in the early 21st century.

    PubMed

    Ming, Jing; Wang, Yaqiang; Du, Zhencai; Zhang, Tong; Guo, Wanqin; Xiao, Cunde; Xu, Xiaobin; Ding, Minghu; Zhang, Dongqi; Yang, Wen

    2015-01-01

    The widely distributed glaciers in the greater Himalayan region have generally experienced rapid shrinkage since the 1850s. As invaluable sources of water and because of their scarcity, these glaciers are extremely important. Beginning in the twenty-first century, new methods have been applied to measure the mass budget of these glaciers. Investigations have shown that the albedo is an important parameter that affects the melting of Himalayan glaciers. The surface albedo based on the Moderate Resolution Imaging Spectroradiometer (MODIS) data over the Hindu Kush, Karakoram and Himalaya (HKH) glaciers is surveyed in this study for the period 2000-2011. The general albedo trend shows that the glaciers have been darkening since 2000. The most rapid decrease in the surface albedo has occurred in the glacial area above 6000 m, which implies that melting will likely extend to snow accumulation areas. The mass-loss equivalent (MLE) of the HKH glacial area caused by surface shortwave radiation absorption is estimated to be 10.4 Gt yr-1, which may contribute to 1.2% of the global sea level rise on annual average (2003-2009). This work probably presents a first scene depicting the albedo variations over the whole HKH glacial area during the period 2000-2011. Most rapidly decreasing in albedo has been detected in the highest area, which deserves to be especially concerned.

  16. Surface melt dominates Alaska glacier mass balance

    USGS Publications Warehouse

    Larsen Chris F,; Burgess, E; Arendt, A.A.; O'Neel, Shad; Johnson, A.J.; Kienholz, C.

    2015-01-01

    Mountain glaciers comprise a small and widely distributed fraction of the world's terrestrial ice, yet their rapid losses presently drive a large percentage of the cryosphere's contribution to sea level rise. Regional mass balance assessments are challenging over large glacier populations due to remote and rugged geography, variable response of individual glaciers to climate change, and episodic calving losses from tidewater glaciers. In Alaska, we use airborne altimetry from 116 glaciers to estimate a regional mass balance of −75 ± 11 Gt yr−1 (1994–2013). Our glacier sample is spatially well distributed, yet pervasive variability in mass balances obscures geospatial and climatic relationships. However, for the first time, these data allow the partitioning of regional mass balance by glacier type. We find that tidewater glaciers are losing mass at substantially slower rates than other glaciers in Alaska and collectively contribute to only 6% of the regional mass loss.

  17. Solar Radiation Patterns and Glaciers in the Western Himalaya

    NASA Astrophysics Data System (ADS)

    Dobreva, I. D.; Bishop, M. P.

    2013-12-01

    Glacier dynamics in the Himalaya are poorly understood, in part due to variations in topography and climate. It is well known that solar radiation is the dominant surface-energy component governing ablation, although the spatio-temporal patterns of surface irradiance have not been thoroughly investigated given modeling limitations and topographic variations including altitude, relief, and topographic shielding. Glaciation and topographic conditions may greatly influence supraglacial characteristics and glacial dynamics. Consequently, our research objectives were to develop a GIS-based solar radiation model that accounts for Earth's orbital, spectral, atmospheric and topographic dependencies, in order to examine the spatio-temporal surface irradiance patterns on glaciers in the western Himalaya. We specifically compared irradiance patterns to supraglacial characteristics and ice-flow velocity fields. Shuttle Radar Mapping Mission (SRTM) 90 m data were used to compute geomorphometric parameters that were input into the solar radiation model. Simulations results for 2013 were produced for the summer ablation season. Direct irradiance, diffuse-skylight, and total irradiance variations were compared and related to glacier altitude profiles of ice velocity and land-surface topographic parameters. Velocity and surface information were derived from analyses of ASTER satellite data. Results indicate that the direct irradiance significantly varies across the surface of glaciers given local topography and meso-scale relief conditions. Furthermore, the magnitude of the diffuse-skylight irradiance varies with altitude and as a result, glaciers in different topographic settings receive different amounts of surface irradiance. Spatio-temporal irradiance patterns appear to be related to glacier surface conditions including supraglacial lakes, and are spatially coincident with ice-flow velocity conditions on some glaciers. Collectively, our results demonstrate that glacier

  18. Controls on Seasonal Terminus Positions at Central West Greenland Tidewater Glaciers

    NASA Astrophysics Data System (ADS)

    Fried, M.; Catania, G. A.; Bartholomaus, T. C.; Stearns, L. A.; Sutherland, D.; Shroyer, E.; Nash, J. D.; Carroll, D.

    2016-12-01

    Each year, tidewater glaciers in Greenland undergo seasonal terminus position cycles, characterized by wintertime advance and summertime retreat. In many cases, this seasonal cycle is superimposed on top of long-term terminus retreat. Understanding the mechanisms that control the seasonal cycle - and how such controls differ between glaciers - might elucidate how tidewater glaciers regulate dynamic ice loss on these longer timescales. However, the controls on terminus position are numerous and complex, making it difficult to identify the dominant process controlling terminus position. To address this, we examine satellite-derived terminus position time series for a suite of glaciers in central west Greenland in conjunction with observations of environmental forcings. In particular, we focus on estimated runoff at the glacier grounding line, mélange conditions in the proglacial fjord and (where possible) in-situ measurements of ocean temperature. We find that seasonal terminus advance and retreat more closely follow the presence or absence of runoff than mélange conditions and, where studied, ocean forcing. At the majority of glaciers studied, localized terminus ablation occurs where runoff-driven submarine melt emerges at the grounding line. This often induces heterogeneous rates of retreat across the glacier front and leads to the formation of local terminus embayments. Calving accelerates in these embayments allowing for local runoff to influence the magnitude and timing of mean seasonal retreat. At glaciers with grounding line depths in excess of 500 m, localized retreat due to submarine melt can be outstripped by large slab rotation calving events, likely initiated by different forcing mechanisms. Our observations emphasize that across-flow heterogeneities in terminus position are diagnostic of how runoff-induced melt helps control seasonal terminus cycles.

  19. Passive microwave (SSM/I) satellite predictions of valley glacier hydrology, Matanuska Glacier, Alaska

    USGS Publications Warehouse

    Kopczynski, S.E.; Ramage, J.; Lawson, D.; Goetz, S.; Evenson, E.; Denner, J.; Larson, G.

    2008-01-01

    We advance an approach to use satellite passive microwave observations to track valley glacier snowmelt and predict timing of spring snowmelt-induced floods at the terminus. Using 37 V GHz brightness temperatures (Tb) from the Special Sensor Microwave hnager (SSM/I), we monitor snowmelt onset when both Tb and the difference between the ascending and descending overpasses exceed fixed thresholds established for Matanuska Glacier. Melt is confirmed by ground-measured air temperature and snow-wetness, while glacier hydrologic responses are monitored by a stream gauge, suspended-sediment sensors and terminus ice velocity measurements. Accumulation area snowmelt timing is correlated (R2 = 0.61) to timing of the annual snowmelt flood peak and can be predicted within ??5 days. Copyright 2008 by the American Geophysical Union.

  20. Widespread Albedo Decreasing and Induced Melting of Himalayan Snow and Ice in the Early 21st Century

    PubMed Central

    Ming, Jing; Wang, Yaqiang; Du, Zhencai; Zhang, Tong; Guo, Wanqin; Xiao, Cunde; Xu, Xiaobin; Ding, Minghu; Zhang, Dongqi; Yang, Wen

    2015-01-01

    Background The widely distributed glaciers in the greater Himalayan region have generally experienced rapid shrinkage since the 1850s. As invaluable sources of water and because of their scarcity, these glaciers are extremely important. Beginning in the twenty-first century, new methods have been applied to measure the mass budget of these glaciers. Investigations have shown that the albedo is an important parameter that affects the melting of Himalayan glaciers. Methodology/Principal Findings The surface albedo based on the Moderate Resolution Imaging Spectroradiometer (MODIS) data over the Hindu Kush, Karakoram and Himalaya (HKH) glaciers is surveyed in this study for the period 2000–2011. The general albedo trend shows that the glaciers have been darkening since 2000. The most rapid decrease in the surface albedo has occurred in the glacial area above 6000 m, which implies that melting will likely extend to snow accumulation areas. The mass-loss equivalent (MLE) of the HKH glacial area caused by surface shortwave radiation absorption is estimated to be 10.4 Gt yr-1, which may contribute to 1.2% of the global sea level rise on annual average (2003–2009). Conclusions/Significance This work probably presents a first scene depicting the albedo variations over the whole HKH glacial area during the period 2000–2011. Most rapidly decreasing in albedo has been detected in the highest area, which deserves to be especially concerned. PMID:26039088

  1. Tracer-based identification of rock glacier thawing in a glacierized Alpine catchment

    NASA Astrophysics Data System (ADS)

    Engel, Michael; Penna, Daniele; Tirler, Werner; Comiti, Francesco

    2017-04-01

    Current warming in high mountains leads to increased melting of snow, glacier ice and permafrost. In particular rock glaciers, as a creeping form of mountain permafrost, may release contaminants such as heavy metals into the stream during intense melting periods in summer. This may have strong impacts on both water quantity and quality of fresh water resources but might also harm the aquatic fauna in mountain regions. In this context, the present study used stable isotopes of water and electrical conductivity (EC) combined with trace, major and minor elements to identify the influence of permafrost thawing on the water quality in the glacierized Solda catchment (130 km2) in South Tyrol (Italy). We carried out a monthly sampling of two springs fed by an active rock glacier at about 2600 m a.s.l. from July to October 2015. Furthermore, we took monthly water samples from different stream sections of the Solda River (1110 to m a.s.l.) from March to November 2015. Meteorological data were measured by an Automatic Weather Station at 2825 m a.s.l. of the Hydrographic Office (Autonomous Province of Bozen-Bolzano). First results show that water from the rock glacier springs and stream water fell along the global meteoric water line. Spring water was slightly more variable in isotopic ratio (δ2H: -91 to - 105 ) and less variable in dissolved solutes (EC: 380 to 611 μS/cm) than stream water (δ2H: -96 to - 107 ‰ and EC: 212 to 927 μS/cm). Both spring water and stream water showed a pronounced drop in EC during July and August, very likely induced by increased melt water dilution. In both water types, element concentrations of Ca and Mg were highest (up to 160 and 20 mg/l, respectively). In September, spring water showed higher concentrations in Cu, As, and Pb than stream water, indicating that these elements partly exceeded the concentration limit for drinking water. These observations highlight the important control, which rock glacier thawing may have on water quality

  2. Contributions to Jarvis Creek Watershed, Alaska, from Winter Accumulation and Glacier Melt Inferred Through Airborne and Ground-Penetrating Radar

    NASA Astrophysics Data System (ADS)

    Campbell, S. W.; Liljedahl, A. K.; Douglas, T. A.; Bernsen, S.; Gatesman, T.; Gerbi, C. C.

    2017-12-01

    Glacier meltwater contributions to river discharge has been increasing in much of the Arctic, likely because of higher air temperatures. For small glaciers that provide a large portion of meltwater to downstream discharge, a sustained negative mass balance is concerning to surrounding ecosystems because the water budget will ultimately decline when glacier ice disappears. Separating components of the hydrological budget is important for predicting future discharge, particularly when major inputs such as glacier ice melt are at risk of total loss. Jarvis Glacier in Eastern Alaska offers an example of this potential scenario. It is a 6-km long glacier that has been in retreat since the 1950's, yet it accounts for 15% of the annual downstream discharge into Jarvis Creek (Liljedahl et al., 2017). In March 2012 through April 2017 we completed yearly airborne and ground-penetrating radar surveys over Jarvis Glacier and its surrounding non-glaciated watershed. These surveys were conducted to assess winter snow accumulation and its potential contribution to the hydrological budget of Jarvis Creek. We also surveyed glacier ice thicknesses to estimate ice volume and potential long term future meltwater contributions to Jarvis Creek based on its sustained negative mass balance. High-frequency radar collected across Jarvis Glacier reveal winter accumulation rates between 1.1-1.9 m SWE. Thickness of winter snow in the surrounding glacier-free valleys is highly variable but it tended to accumulate as drifts near ridge tops or low in the valleys. Low-frequency GPR reveals ice thickness reaching 250 m, mid-glacier, tapering to less than 100 m near the debris-rich terminus. Several over-deepened basins exist and an obvious polythermal structure with 20-30 m of cold ice overlaying temperate ice is also evident. Our presentation will summarize further details of these results in relation to current and potential future contributions of glacier ice and winter snowpack melt to Jarvis

  3. The energy balance on the surface of a tropical glacier tongue. Investigations on glacier Artesonraju, Cordillera Blanca, Perú.

    NASA Astrophysics Data System (ADS)

    Juen, I.; Mölg, T.; Wagnon, P.; Cullen, N. J.; Kaser, G.

    2006-12-01

    The Cordillera Blanca in Perú is situated in the Outer Tropics spanning from 8 to 10 ° South. Solar incidence and air temperature show only minor seasonal variations whereas precipitation occurs mainly from October to April. An energy balance station was installed on the tongue of glacier Artesonraju (4850 m a.s.l.) in March 2004. In this study each component of the energy balance on the glacier surface is analysed separately over a full year, covering one dry and one wet season. During the dry season glacier melt at the glacier tongue is app. 0.5 m we per month. In the wet season glacier melt is twice as much with 1 m we per month. This is due to higher energy fluxes and decreased sublimation during the wet season. With an energy balance model that has already been proved under tropical climate conditions (Mölg and Hardy, 2004) each energy flux is changed individually to evaluate the change in the amount of glacier melt. First results indicate that a change in humidity related variables affects glacier melt very differently in the dry and wet season, whereas a change in air temperature changes glacier melt more constantly throughout the year.

  4. Bacterial diversity and bioprospecting for cold-active enzymes from culturable bacteria associated with sediment from a melt water stream of Midtre Lovenbreen glacier, an Arctic glacier.

    PubMed

    Vardhan Reddy, Puram Vishnu; Shiva Nageswara Rao, Singireesu Soma; Pratibha, Mambatta Shankaranarayanan; Sailaja, Buddhi; Kavya, Bakka; Manorama, Ravoori Ruth; Singh, Shiv Mohan; Radha Srinivas, Tanuku Naga; Shivaji, Sisinthy

    2009-10-01

    Culturable bacterial diversity of Midtre Lovenbreen glacier, an Arctic glacier, was studied using 12 sediment samples collected from different points, along a transect, from the snout of Midtre Lovenbreen glacier up to the convergence point of the melt water stream with the sea. Bacterial abundance appeared to be closer to the convergence point of the glacial melt water stream with the sea than at the snout of the glacier. A total of 117 bacterial strains were isolated from the sediment samples. Based on 16S rRNA gene sequence analyses, the isolates (n=117) could be categorised in to 32 groups, with each group representing a different taxa belonging to 4 phyla (Actinobacteria, Bacilli, Flavobacteria and Proteobacteria). Representatives of the 32 groups varied in their growth temperature range (4-37 degrees C), in their tolerance to NaCl (0.1-1M NaCl) and in the growth pH range (2-13). Only 14 of 32 representative strains exhibited amylase, lipase and (or) protease activity and only one isolate (AsdM4-6) showed all three enzyme activities at 5 and 20 degrees C respectively. More than half of the isolates were pigmented. Fatty acid profile studies indicated that short-chain fatty acids, unsaturated fatty acids, branched fatty acids, cyclic and cis fatty acids are predominant in the psychrophilic bacteria.

  5. Calving Geometry of Thwaites Glacier Linked to Semi-brittle Ice Dynamics

    NASA Astrophysics Data System (ADS)

    Logan, L. C.; Lavier, L.; Choi, E.; Tan, E.; Catania, G. A.; Holt, J.

    2016-12-01

    In the coming decades the linkage between ice dynamics, basal melt, and calving will play a central role in the flow of Thwaites Glacier, which has undergone vast and recent retreat. We explore this connection using a 3D, transient, thermomechanical ice flow model under different basal melt scenarios. Our use of a semi-brittle ice rheology enables the time-dependent development and tracking of surface and basal crevasses that determine the calving rate at this location. With the use of adaptive re-meshing, we are able to simulate the glacier's retreat response to different boundary forcings. We show that the resulting characteristic pinch-and-swell model geometries in the floating tongue compare well with airborne radar data acquired across the grounding line and floating tongue of Thwaites Glacier. These geometric features may be reproduced using this semi-brittle rheology, and further, are linked directly to the calving rate of Thwaites Glacier (and others). The use of semi-brittle rheology on decadal time scales may help provide constraints on the near-term future behavior of glaciers vulnerable to ocean-induced retreat, as this rheology targets the complex interaction of ice failure, basal melt, and flow.

  6. Solar radiation, cloudiness and longwave radiation over low-latitude glaciers: implications for mass-balance modelling

    NASA Astrophysics Data System (ADS)

    Mölg, Thomas; Cullen, Nicolas J.; Kaser, Georg

    Broadband radiation schemes (parameterizations) are commonly used tools in glacier mass-balance modelling, but their performance at high altitude in the tropics has not been evaluated in detail. Here we take advantage of a high-quality 2 year record of global radiation (G) and incoming longwave radiation (L↓) measured on Kersten Glacier, Kilimanjaro, East Africa, at 5873 m a.s.l., to optimize parameterizations of G and L↓. We show that the two radiation terms can be related by an effective cloud-cover fraction neff, so G or L↓ can be modelled based on neff derived from measured L↓ or G, respectively. At neff = 1, G is reduced to 35% of clear-sky G, and L↓ increases by 45-65% (depending on altitude) relative to clear-sky L↓. Validation for a 1 year dataset of G and L↓ obtained at 4850 m on Glaciar Artesonraju, Peruvian Andes, yields a satisfactory performance of the radiation scheme. Whether this performance is acceptable for mass-balance studies of tropical glaciers is explored by applying the data from Glaciar Artesonraju to a physically based mass-balance model, which requires, among others, G and L↓ as forcing variables. Uncertainties in modelled mass balance introduced by the radiation parameterizations do not exceed those that can be caused by errors in the radiation measurements. Hence, this paper provides a tool for inclusion in spatially distributed mass-balance modelling of tropical glaciers and/or extension of radiation data when only G or L↓ is measured.

  7. Thermal Properties and Energy Fluxes in Pre-monsoon Season of 2016 at the Ponkar Debris-Covered Glacier, Manang, Nepal Himalaya

    NASA Astrophysics Data System (ADS)

    Chand, M. B.; Kayastha, R. B.; Armstrong, R. L.

    2016-12-01

    Himalayan glaciers are characterized by the presence of extensive debris cover in ablation areas. It is essential to understand the thermal properties and assess the effect of debris in glacier ice melt rate in debris-covered glaciers. Meteorological conditions are recorded on the lower ablation zone of the debris-covered Ponkar Glacier, Bhimthang, Manang, Nepal during pre-monsoon season of 2016. Debris temperature at different depths is monitored for winter and pre-monsoon season to estimate the effective heat conduction. Similarly, melt under the debris is also measured for pre-monsoon season. The incoming and outgoing shortwave radiations are measured at 2 m above the surface and other variables including air temperature, humidity, wind speed, and precipitation are used to estimate surface energy balance. Energy flux is dominated by net shortwave radiation as the foremost source of melting, where contribution of net longwave radiation, sensible, latent, and conductive heat flux is low. The daily average temperature gradients of the debris layer from surface to 30 cm below for winter and pre-monsoon seasons are 0.04 oC cm-1 and 0.23 oC cm-1, respectively. Debris thermal conductivities are 0.30 W m-1 K-1 and 1.69 W m-1 K-1 for the winter and pre-monsoon season, respectively. The higher value of conductivity during pre-monsoon season is due to the higher air temperature and increased precipitation compared to the winter months. The daily mean measured ice melt under a debris layer of 11-20 cm ranges from 0.6 to 1.1 cm. Estimation of melt at a few points can be used to estimate the general melting pattern for the glacier surface, which can be improved by using the spatial distribution of debris thickness and surface temperature.

  8. Topography and Radiative Forcing Patterns on Glaciers in the Karakoram Himalaya

    NASA Astrophysics Data System (ADS)

    Dobreva, I. D.; Bishop, M. P.; Liu, J. C.; Liang, D.

    2015-12-01

    Glaciers in the western Himalaya exhibit significant spatial variations in morphology and dynamics. Climate, topography and debris cover variations are thought to significantly affect glacier fluctuations and glacier sensitivity to climate change, although the role of topography and radiative forcing have not been adequately characterized and related to glacier fluctuations and dynamics. Consequently, we examined the glaciers in the Karakoram Himalaya, as they exhibit high spatial variability in glacier fluctuation rates and ice dynamics including flow velocity and surging. Specifically, we wanted to examine the relationships between these glacier characteristics and temporal patterns of surface irradiance over the ablation season. To accomplish this, we developed and used a rigorous GIS-based solar radiative transfer model that accounts for the direct and diffuse-skylight irradiance components. The model accounts for multiple topographic effects on the magnitude of irradiance reaching glacier surfaces. We specifically used the ASTER GDEM digital elevation model for irradiance simulations. We then examined temporal patterns of irradiance at the grid-cell level to identify the dominant patterns that were used to train a 3-layer artificial neural network. Our results demonstrate that there are unique spatial and temporal patterns associated with downwasting and surging glaciers, and that these patterns partially account for the spatial distribution of advancing and retreating glaciers. Lower-altitude terminus regions of surging glaciers exhibited relatively low surface irradiance values that decreased in magnitude with time, demonstrating that high-velocity surging glaciers facilitate relief production and exhibit steeper surface irradiance gradients with altitude. Collectively, these results demonstrate the important role that local and regional topography play in governing climate-glacier dynamics in the Himalaya.

  9. An Integrated Modeling System for Estimating Glacier and Snow Melt Driven Streamflow from Remote Sensing and Earth System Data Products in the Himalayas

    NASA Technical Reports Server (NTRS)

    Brown, M. E.; Racoviteanu, A. E.; Tarboton, D. G.; Sen Gupta, A.; Nigro, J.; Policelli, F.; Habib, S.; Tokay, M.; Shrestha, M. S.; Bajracharya, S.

    2014-01-01

    Quantification of the contribution of the hydrologic components (snow, ice and rain) to river discharge in the Hindu Kush Himalayan (HKH) region is important for decision-making in water sensitive sectors, and for water resources management and flood risk reduction. In this area, access to and monitoring of the glaciers and their melt outflow is challenging due to difficult access, thus modeling based on remote sensing offers the potential for providing information to improve water resources management and decision making. This paper describes an integrated modeling system developed using downscaled NASA satellite based and earth system data products coupled with in-situ hydrologic data to assess the contribution of snow and glaciers to the flows of the rivers in the HKH region. Snow and glacier melt was estimated using the Utah Energy Balance (UEB) model, further enhanced to accommodate glacier ice melt over clean and debris-covered tongues, then meltwater was input into the USGS Geospatial Stream Flow Model (Geo- SFM). The two model components were integrated into Better Assessment Science Integrating point and Nonpoint Sources modeling framework (BASINS) as a user-friendly open source system and was made available to countries in high Asia. Here we present a case study from the Langtang Khola watershed in the monsoon-influenced Nepal Himalaya, used to validate our energy balance approach and to test the applicability of our modeling system. The snow and glacier melt model predicts that for the eight years used for model evaluation (October 2003-September 2010), the total surface water input over the basin was 9.43 m, originating as 62% from glacier melt, 30% from snowmelt and 8% from rainfall. Measured streamflow for those years were 5.02 m, reflecting a runoff coefficient of 0.53. GeoSFM simulated streamflow was 5.31 m indicating reasonable correspondence between measured and model confirming the capability of the integrated system to provide a quantification

  10. What do We Know the Snow Darkening Effect Over Himalayan Glaciers?

    NASA Technical Reports Server (NTRS)

    Yasunari, T. J.; Lau, K.-U.; Koster, R. D.; Suarez, M.; Mahanama, S. P.; Gautam, R.; Kim, K. M.; Dasilva, A. M.; Colarco, P. R.

    2011-01-01

    The atmospheric absorbing aerosols such as dust, black carbon (BC), organic carbon (OC) are now well known warming factors in the atmosphere. However, when these aerosols deposit onto the snow surface, it causes darkening of snow and thereby absorbing more energy at the snow surface leading to the accelerated melting of snow. If this happens over Himalayan glacier surface, the glacier meltings are expected and may contribute the mass balance changes though the mass balance itself is more complicated issue. Glacier has mainly two parts: ablation and accumulation zones. Those are separated by the Equilibrium Line Altitude (ELA). Above and below ELA, snow accumulation and melting are dominant, respectively. The change of ELA will influence the glacier disappearance in future. In the Himalayan region, many glacier are debris covered glacier at the terminus (i.e., in the ablation zone). Debris is pieces of rock from local land and the debris covered parts are probably not affected by any deposition of the absorbing aerosols because the snow surface is already covered by debris (the debris covered parts have different mechanism of melting). Hence, the contribution of the snow darkening effect is considered to be most important "over non debris covered part" of the Himalayan glacier (i.e., over the snow or ice surface area). To discuss the whole glacier retreat, mass balance of each glacier is most important including the discussion on glacier flow, vertical compaction of glacier, melting amount, etc. The contribution of the snow darkening is mostly associated with "the snow/ice surface melting". Note that the surface melting itself is not always directly related to glacier retreats because sometimes melt water refreezes inside of the glacier. We should discuss glacier retreats in terms of not only the snow darkening but also other contributions to the mass balance.

  11. Hydro-glaciological modeling in the Upper Maipo River basin, extratropical Andes Cordillera, with explicit representation of debris-covered glaciers.

    NASA Astrophysics Data System (ADS)

    McPhee, J. P.; Castillo, Y.; Escobar, M.; Pellicciotti, F.

    2014-12-01

    In this work we improve and calibrate a hydro-glaciological model based on a simplified energy balance approach using the WEAP modeling platform for two catchments in the headwaters of the Maipo River Basin, in the Andes Mountains of Central Chile. The Morales Creek catchment includes the San Francisco glacier, a clean glacier occupying 7% of the catchment area. The Pirámide catchment holds the debris-covered Pirámide Glacier, which covers 20% of the catchment area. Detailed field measurements have been carried out on both glaciers to characterize their melt and meteorological regimes. We calibrate an Enhanced Temperature Index melt model against ablation stakes and runoff measurements, and obtain clear differences between the optimal parameters for the clean and debris-covered glaciers. Calibrate melt threshold temperatures are 0,25 and 0,5ºC for the clean and debris-covered glaciers, respectively, while the fraction of net shortwave radiation employed for melting is 90 and 83% for clean and debris-covered glaciers, respectively. These results are coherent with an insulating effect of the debris cover at the Pirámide glacier. The hydrologic contribution of ice melt for the clean, San Francisco glacier is equivalent to 32% of total runoff measured at the Morales Creek outlet during the simulation period; on the other hand, ice melt accounts for 83% of total runoff estimated at the outlet of the Pirámide catchment over the same period. These results are part on an ongoing effort aimed at quantifying cryospheric contribution to the hydrology of the Maipo River basin, one of the key river basins in Chile, on the face of accelerated climate change, and is the first documented work to explicitly include debris-covered glaciers in a context of basin-wide hydrological modeling.

  12. Summer energy balance and ablation of high elevation glaciers in the central Chilean Andes

    NASA Astrophysics Data System (ADS)

    Brock, Benjamin; Rivera, Andres; Burger, Flavia; Bravo, Claudio

    2014-05-01

    Glaciers of the semi-arid central Chilean Andes are an important freshwater source for the populous Central Valley region of Chile, but have been shrinking in recent decades. The surface energy balance of these glaciers is of high scientific interest as summer ablation occurs through both sublimation and melt. During the 2012-13 Austral Summer a glacio-meteorological monitoring programme was established on Olivares Alfa (3.9 km2, 4130-4800 m elevation) and Beta (8.3 km2, 3620-4850 m elevation) Glaciers and their forelands in the Upper Olivares Valley, 33°00'-33°11' S, 70°05'-70°15' W, approximately 50 km north-east of Santiago. This included complete automatic weather stations (AWSs) with sonic rangers to record surface ablation on the ablation zones of the two glaciers, and one AWS in the proglacial area of Olivares Alfa Glacier including precipitation gauge. To complement these point data, daily images of the glaciers were captured with fixed cameras in order to calculate snow cover and albedo distributions. To calculate the surface energy balance and rates of melt and sublimation, a model was developed which uses direct AWS measurements of the radiative fluxes and calculates the turbulent fluxes of sensible and latent heat using the bulk aerodynamic approach. The model also calculates the subsurface heat flux and includes a simple scheme to estimate refreezing of melt water within surface snow or ice. Meteorological data and model results for the December to May period will be presented in this paper. Model calculations match closely the cumulative ablation curve of the sonic ranger at Olivares Alfa, with a slight overestimation, and overestimate cumulative ablation recorded by the sonic ranger at Olivares Beta, possibly due, at least in part, to uncertain snow density values. Modelled cumulative ablation in the December-April period is 2.2 m water equivalent (w.e.) at Olivares Alfa (0.10 m sublimation, 2.10 m melt) and 2.34 m w.e. at Olivares Beta (0.18 m

  13. Greenland outlet glacier dynamics from Extreme Ice Survey (EIS) photogrammetry

    NASA Astrophysics Data System (ADS)

    Hawbecker, P.; Box, J. E.; Balog, J. D.; Ahn, Y.; Benson, R. J.

    2010-12-01

    Time Lapse cameras fill gaps in our observational capabilities: 1. By providing much higher temporal resolution than offered by conventional airborne or satellite remote sensing. 2. While GPS or auto-theodolite observations can provide higher time resolution data than from photogrammetry, survival of these instruments on the hazardous glacier surface is limited, plus, the maintenance of such systems can be more expensive than the maintenance of a terrestrial photogrammetry installation. 3. Imagery provide a high spatial density of observations across the glacier surface, higher than is realistically available from GPS or other in-situ observations. 4. time lapse cameras provide observational capabilities in Eulerian and Lagrangian frames while GPS or theodolite targets, going along for a ride on the glacier, provide only Lagrangian data. Photogrammetry techniques are applied to a year-plus of images from multiple west Greenland glaciers to determine the glacier front horizontal velocity variations at hourly to seasonal time scales. The presentation includes comparisons between glacier front velocities and: 1. surface melt rates inferred from surface air temperature and solar radiation observations; 2. major calving events identified from camera images; 3. surface and near-surface ocean temperature; 4. land-fast sea ice breakup; 5. tidal variations; 6. supra-glacial melt lake drainage events observed in daily optical satellite imagery; and 7.) GPS data. Extreme Ice Survey (EIS) time lapse camera overlooking the Petermann glacier, installed to image glacier dynamics and to capture the predicted ice "island" detachment.

  14. Testing geographical and climatic controls on glacier retreat

    NASA Astrophysics Data System (ADS)

    Freudiger, Daphné; Stahl, Kerstin; Weiler, Markus

    2015-04-01

    Glacier melt provides an important part of the summer discharge in many mountainous basins. The understanding of the processes behind the glacier mass losses and glacier retreats observed during the last century is therefore relevant for a sustainable management of the water resources and reliable models for the prediction of future changes. The changes in glacier area of 49 sub-basins of the Rhine River in the Alps were analyzed for the time period 1900-2010 by comparing the glacier areas of Siegfried maps for the years 1900 and 1940 with satellite derived glacier areas for the years 1973, 2003 and 2010. The aim was to empirically investigate the controls of glacier retreat and its regional differences. All glaciers in the glacierized basins retreated over the last 110 years with some variations in the sub-periods. However, the relative changes in glacier area compared to 1900 differed for every sub-basin and some glaciers decreased much faster than others. These observed differences were related to a variety of different potential controls derived from different sources, including mean annual solar radiation on the glacier surface, average slope, mean glacier elevation, initial glacier area, average precipitation (summer and winter), and the precipitation catchment area of the glacier. We fitted a generalized linear model (GLM) and selected predictors that were significant to assess the individual effects of the potential controls. The fitted model explains more than 60% of the observed variance of the relative change in glacier area with the initial area alone only explaining a small proportion. Some interesting patterns emerge with higher average elevation resulting in higher area changes, but steeper slopes or solar radiation resulting in lower relative glacier area changes. Further controls that will be tested include snow transport by wind or avalanches as they play an important role for the glacier mass balance and potentially reduce the changes in glacier

  15. Hydro-Chemical Characterization of Melt Waters of Ponkar Glacier, Manang, Nepal

    NASA Astrophysics Data System (ADS)

    Shrestha, R.; Sandeep, S.

    2016-12-01

    The study was carried out in Ponkar Glacier, representing Himalayan glacier of Nepal. The study aims in determining the hydrochemistry of the glacier melt water. The sampling sites included moraine dammed, Ponkar Lake at 4120 m a.s.l to the downstream glaciated river at 3580 m a.s.l. The water samples were collected from the seven different sites according to the geological features. On site measurements of the parameters like pH, temperature, electrical conductivity was done by digital multi-probes. The samples were brought to the laboratory and the parameters were analyzed according to the standard guidelines and protocols. The glacier meltwater was slightly basic with pH 7.44 (±0.32). The water was slightly hard 36.43 (±9.15) mg CaCO3/L and the electrical conductivity was found to be 47.14 (±11.18) µS/cm. The concentration of anion was in the order of HCO3 - > Cl- > SO42- > NO3- > PO43-. Calcium carbonate weathering was found out to be the major source of dissolved ions in the region. The parameters like chloride, total silica and iron were found to be 55.71 (±32.03) mg/L, 1.13 (±0.76) mg/L and 1.1 (±0.97) mg/L which is in the significant range. Whereas the concentration of manganese (<0.05 mg/L) and zinc (<0.02 mg/L) were not in detectable levels in few stations. The results of this study can be helpful in preliminary assessment of hydrochemistry and its linkage with climate change impacts in this region.

  16. Ocean forcing drives glacier retreat sometimes

    NASA Astrophysics Data System (ADS)

    Bassis, J. N.; Ultee, E.; Ma, Y.

    2015-12-01

    Observations show that marine-terminating glaciers respond to climate forcing nonlinearly, with periods of slow or negligible glacier advance punctuated by abrupt, rapid retreat. Once glacier retreat has initiated, glaciers can quickly stabilize with a new terminus position. Alternatively, retreat can be sustained for decades (or longer), as is the case for Columbia Glacier, Alaska where retreat initiated ~1984 and continues to this day. Surprisingly, patterns of glacier retreat show ambiguous or even contradictory correlations with atmospheric temperature and glacier surface mass balance. Despite these puzzles, observations increasingly show that intrusion of warm subsurface ocean water into fjords can lead to glacier erosion rates that can account for a substantial portion of the total mass lost from glaciers. Here we use a simplified flowline model to show that even relatively modest submarine melt rates (~100 m/a) near the terminus of grounded glaciers can trigger large increases in iceberg calving leading to rapid glacier retreat. However, the strength of the coupling between submarine melt and calving is a strong function of the geometry of the glacier (bed topography, ice thickness and glacier width). This can lead to irreversible retreat when the terminus is thick and grounded deeply beneath sea level or result in little change when the glacier is relatively thin, grounded in shallow water or pinned in a narrow fjord. Because of the strong dependence on glacier geometry, small perturbations in submarine melting can trigger glaciers in their most advanced—and geometrically precarious—state to undergo sudden retreat followed by much slower re-advance. Although many details remain speculative, our model hints that some glaciers are more sensitive than others to ocean forcing and that some of the nonlinearities of glacier response to climate change may be attributable to variations in difficult-to-detect subsurface water temperatures that need to be better

  17. Spatio-temporal variation in microclimate, the surface energy balance and ablation over a cirque glacier

    NASA Astrophysics Data System (ADS)

    Hannah, David M.; Gurnell, Angela M.; McGregor, Glenn R.

    2000-06-01

    Climatic processes, operating at a range of scales, drive energy fluxes at the glacier surface which control meltwater generation and ultimately runoff. Nevertheless, to date, most glacier microclimate research has been both temporally (short-term) and spatially (single station) restricted. This paper addresses this knowledge gap by reporting on a detailed, empirical study which characterizes spatio-temporal variations in and linkages between glacier microclimate, surface energy and mass exchanges within a small glacierized cirque (Taillon Glacier, French Pyrénées) over two melt seasons. Data collected at five automatic weather stations (AWSs) and over ablation stake networks suggest that topoclimates, altitude and transient snowline position primarily determine the distribution of glacier energy receipt and, in turn, snow- and ice-melt patterns. Generally net radiation is the dominant energy source, followed by sensible heat, while latent heat is an energy sink. However, the magnitude and partitioning of energy balance terms, and consequently ablation, vary across the glacier both seasonally and with prevailing weather conditions. Importantly, this paper demonstrates that such monitoring programmes are required to truly represent and provide a sound basis for modelling glacier energy and mass-balances in both space and time.

  18. Influence of spatial discretization, underground water storage and glacier melt on a physically-based hydrological model of the Upper Durance River basin

    NASA Astrophysics Data System (ADS)

    Lafaysse, M.; Hingray, B.; Etchevers, P.; Martin, E.; Obled, C.

    2011-06-01

    SummaryThe SAFRAN-ISBA-MODCOU hydrological model ( Habets et al., 2008) presents severe limitations for alpine catchments. Here we propose possible model adaptations. For the catchment discretization, Relatively Homogeneous Hydrological Units (RHHUs) are used instead of the classical 8 km square grid. They are defined from the dilineation of hydrological subbasins, elevation bands, and aspect classes. Glacierized and non-glacierized areas are also treated separately. In addition, new modules are included in the model for the simulation of glacier melt, and retention of underground water. The improvement resulting from each model modification is analysed for the Upper Durance basin. RHHUs allow the model to better account for the high spatial variability of the hydrological processes (e.g. snow cover). The timing and the intensity of the spring snowmelt floods are significantly improved owing to the representation of water retention by aquifers. Despite the relatively small area covered by glaciers, accounting for glacier melt is necessary for simulating the late summer low flows. The modified model is robust over a long simulation period and it produces a good reproduction of the intra and interannual variability of discharge, which is a necessary condition for its application in a modified climate context.

  19. Variability of Basal Melt Beneath the Pine Island Glacier Ice Shelf, West Antarctica

    NASA Technical Reports Server (NTRS)

    Bindschadler, Robert; Vaughan, David G.; Vornberger, Patricia

    2011-01-01

    Observations from satellite and airborne platforms are combined with model calculations to infer the nature and efficiency of basal melting of the Pine Island Glacier ice shelf, West Antarctica, by ocean waters. Satellite imagery shows surface features that suggest ice-shelf-wide changes to the ocean s influence on the ice shelf as the grounding line retreated. Longitudinal profiles of ice surface and bottom elevations are analyzed to reveal a spatially dependent pattern of basal melt with an annual melt flux of 40.5 Gt/a. One profile captures a persistent set of surface waves that correlates with quasi-annual variations of atmospheric forcing of Amundsen Sea circulation patterns, establishing a direct connection between atmospheric variability and sub-ice-shelf melting. Ice surface troughs are hydrostatically compensated by ice-bottom voids up to 150m deep. Voids form dynamically at the grounding line, triggered by enhanced melting when warmer-than-average water arrives. Subsequent enlargement of the voids is thermally inefficient (4% or less) compared with an overall melting efficiency beneath the ice shelf of 22%. Residual warm water is believed to cause three persistent polynyas at the ice-shelf front seen in Landsat imagery. Landsat thermal imagery confirms the occurrence of warm water at the same locations.

  20. Characterization of meltwater 'ingredients' at the Haig Glacier, Canadian Rockies: the importance of glaciers to regional water resources

    NASA Astrophysics Data System (ADS)

    Miller, K.; Marshall, S.

    2017-12-01

    With rising temperatures, Alberta's glaciers are under stresses which change and alter the timing, amount, and composition of meltwater contributions to rivers that flow from the Rocky Mountains. Meltwater can be stored within a glacier or it can drain through the groundwater system, reducing and delaying meltwater delivery to glacier-fed streams. This study tests whether the glacier meltwater is chemically distinct from rain or snow melt, and thus whether meltwater contributions to higher-order streams that flow from the mountains can be determined through stream chemistry. Rivers like the Bow, North Saskatchewan, and Athabasca are vital waterways for much of Alberta's population. Assessing the extent of glacier meltwater is vital to future water resource planning. Glacier snow/ice and meltwater stream samples were collected during the 2017 summer melt season (May- September) and analyzed for isotope and ion chemistry. The results are being used to model water chemistry evolution in the melt stream through the summer season. A chemical mixing model will be constructed to determine the fractional contributions to the Haig meltwater stream from precipitation, surface melt, and subglacial meltwaters. Distinct chemical water signatures have not been used to partition water sources and understand glacier contributions to rivers in the Rockies. The goal of this work is to use chemical signatures of glacial meltwater to help assess the extent of glacier meltwater in Alberta rivers and how this varies through the summer season.

  1. A fjord-glacier coupled system model

    NASA Astrophysics Data System (ADS)

    de Andrés, Eva; Otero, Jaime; Navarro, Francisco; Prominska, Agnieszka; Lapazaran, Javier; Walczowski, Waldemar

    2017-04-01

    With the aim of studying the processes occurring at the front of marine-terminating glaciers, we couple a fjord circulation model with a flowline glacier dynamics model, with subglacial discharge and calving, which allows the calculation of submarine melt and its influence on calving processes. For ocean modelling, we use a general circulation model, MITgcm, to simulate water circulation driven by both fjord conditions and subglacial discharge, and for calculating submarine melt rates at the glacier front. To constrain freshwater input to the fjord, we use estimations from European Arctic Reanalysis (EAR). To determine the optimal values for each run period, we perform a sensitivity analysis of the model to subglacial discharge variability, aimed to get the best fit of model results to observed temperature and salinity profiles in the fjord for each of these periods. Then, we establish initial and boundary fjord conditions, which we vary weekly-fortnightly, and calculate the submarine melt rate as a function of depth at the calving front. These data are entered into the glacier-flow model, Elmer/Ice, which has been added a crevasse-depth calving model, to estimate the glacier terminus position at a weekly time resolution. We focus our study on the Hansbreen Glacier-Hansbukta Fjord system, in Southern Spitsbergen, Svalbard, where a large set of data are available for both glacier and fjord. The bathymetry of the entire system has been determined from ground penetrating radar and sonar data. In the fjord we have got temperature and salinity data from CTDs (May to September, 2010-2014) and from a mooring (September to May, 2011-2012). For Hansbreen, we use glacier surface topography data from the SPIRIT DEM, surface mass balance from EAR, centre line glacier velocities from stake measurements (May 2005-April 2011), weekly terminus positions from time-lapse photos (Sept. 2009-Sept. 2011), and sea-ice concentrations from time-lapse photos and Nimbus-7 SMMR and DMSP SSM

  2. Glacier-derived August runoff in northwest Montana

    USGS Publications Warehouse

    Clark, Adam; Harper, Joel T.; Fagre, Daniel B.

    2015-01-01

    The second largest concentration of glaciers in the U.S. Rocky Mountains is located in Glacier National Park (GNP), Montana. The total glacier-covered area in this region decreased by ∼35% over the past 50 years, which has raised substantial concern about the loss of the water derived from glaciers during the summer. We used an innovative weather station design to collect in situ measurements on five remote glaciers, which are used to parameterize a regional glacier melt model. This model offered a first-order estimate of the summer meltwater production by glaciers. We find, during the normally dry month of August, glaciers in the region produce approximately 25 × 106 m3 of potential runoff. We then estimated the glacier runoff component in five gaged streams sourced from GNP basins containing glaciers. Glacier-melt contributions range from 5% in a basin only 0.12% glacierized to >90% in a basin 28.5% glacierized. Glacier loss would likely lead to lower discharges and warmer temperatures in streams draining basins >20% glacier-covered. Lower flows could even be expected in streams draining basins as little as 1.4% glacierized if glaciers were to disappear.

  3. Improving Understanding of Glacier Melt Contribution to High Asian River Discharge through Collaboration and Capacity Building with High Asian CHARIS Partner Institutions

    NASA Astrophysics Data System (ADS)

    Armstrong, Richard; Brodzik, Mary Jo; Armstrong, Betsy; Barrett, Andrew; Fetterer, Florence; Hill, Alice; Jodha Khalsa, Siri; Racoviteanu, Adina; Raup, Bruce; Rittger, Karl; Williams, Mark; Wilson, Alana; Ye, Qinghua

    2017-04-01

    The Contribution to High Asia Runoff from Ice & Snow (CHARIS) project uses remote sensing data combined with modeling from 2000 to the present to improve proportional estimates of melt from glaciers and seasonal snow surfaces. Based at the National Snow and Ice Data Center (NSIDC), University of Colorado, Boulder, USA, the CHARIS project objectives are twofold: 1) capacity-building efforts with CHARIS partners from eight High Asian countries to better forecast future availability and vulnerability of water resources in the region, and 2) improving our ability to systematically assess the role of glaciers and seasonal snow in the freshwater resources of High Asia. Capacity-building efforts include working with CHARIS partners from Bhutan, Nepal, India, Pakistan, Afghanistan, Kazakhstan, Kyrgyzstan and Tajikistan. Our capacity-building activities include training, data sharing, supporting fieldwork, graduate student education and infrastructure development. Because of the scarcity of in situ data in this High Asian region, we are using the wealth of available remote sensing data to characterize digital elevation, daily maps of fractional snow-cover, annual maps of glacier and permanent snow cover area and downscaled reanalysis temperature data in snow melt models to estimate the relative proportions of river runoff from glacierized and seasonally snow-covered surfaces. Current collaboration with Qinghua Ye, visiting scientist at NSIDC from the Institute of Tibetan Plateau Research, CAS, focuses on remote sensing methods to detect changes in the mountain cryosphere. Collaboration with our Asian partners supports the systematic analysis of the annual cycle of seasonal snow and glacier ice melt across the High Mountain Asia region. With our Asian partners, we have derived reciprocal benefits, learning from their specialized local knowledge and obtaining access to their in situ data. We expect that the improved understanding of runoff from snow and glacier surfaces will

  4. Submarine melting from repeat UAV surveys of icebergs

    NASA Astrophysics Data System (ADS)

    Hubbard, A., II; Ryan, J.; Smith, L. C.; Hamilton, G. S.

    2017-12-01

    Greenland's tidewater glaciers are a primary contributor to global sea-level rise, yet their future trajectory remains uncertain due to their non-linear response to oceanic forcing: particularly with respect to rapid submarine melting and under-cutting of their calving fronts. To improve understanding of ice-ocean interactions, we conducted repeat unmanned aerial vehicle (UAV) surveys across the terminus of Store Glacier and its adjacent fjord between May and June 2014. The derived imagery provides insight into frontal plume dynamics and the changing freeboard volume of icebergs in the fjord as they ablate. Following the methodology of Enderlin and Hamilton (2014), by differencing iceberg freeboard volume, we constrain submarine melt rates adjacent to the calving front. We find that plume and submarine melt rates are critical to mass loss variability across the calving front. Although the frontal ablation of Store Glacier is dominated by large mechanical calving events, the undercutting induced by the meltwater plume increases the frequency of calving and initiates frontal retreat. We conclude that even small increases in submarine melting due to changes in the meltwater plume duration and/or circulation patterns can have important consequences for frontal mass loss from large outlet glaciers draining the Greenland ice sheet.

  5. GPS-derived estimates of surface mass balance and ocean-induced basal melt for Pine Island Glacier ice shelf, Antarctica

    NASA Astrophysics Data System (ADS)

    Shean, David E.; Christianson, Knut; Larson, Kristine M.; Ligtenberg, Stefan R. M.; Joughin, Ian R.; Smith, Ben E.; Stevens, C. Max; Bushuk, Mitchell; Holland, David M.

    2017-11-01

    In the last 2 decades, Pine Island Glacier (PIG) experienced marked speedup, thinning, and grounding-line retreat, likely due to marine ice-sheet instability and ice-shelf basal melt. To better understand these processes, we combined 2008-2010 and 2012-2014 GPS records with dynamic firn model output to constrain local surface and basal mass balance for PIG. We used GPS interferometric reflectometry to precisely measure absolute surface elevation (zsurf) and Lagrangian surface elevation change (Dzsurf/ Dt). Observed surface elevation relative to a firn layer tracer for the initial surface (zsurf - zsurf0') is consistent with model estimates of surface mass balance (SMB, primarily snow accumulation). A relatively abrupt ˜ 0.2-0.3 m surface elevation decrease, likely due to surface melt and increased compaction rates, is observed during a period of warm atmospheric temperatures from December 2012 to January 2013. Observed Dzsurf/ Dt trends (-1 to -4 m yr-1) for the PIG shelf sites are all highly linear. Corresponding basal melt rate estimates range from ˜ 10 to 40 m yr-1, in good agreement with those derived from ice-bottom acoustic ranging, phase-sensitive ice-penetrating radar, and high-resolution stereo digital elevation model (DEM) records. The GPS and DEM records document higher melt rates within and near features associated with longitudinal extension (i.e., transverse surface depressions, rifts). Basal melt rates for the 2012-2014 period show limited temporal variability despite large changes in ocean temperature recorded by moorings in Pine Island Bay. Our results demonstrate the value of long-term GPS records for ice-shelf mass balance studies, with implications for the sensitivity of ice-ocean interaction at PIG.

  6. Small-Scale Variations in Melt of the Debris-Covered Emmons Glacier, Mount Rainier, USA

    NASA Astrophysics Data System (ADS)

    Dits, T. M.; Nelson, L. I.; Moore, P. L.; Pasternak, J. H.

    2014-12-01

    In a warming climate the vitality of mid-latitude glaciers is an important measure of local response to global climate change. However, debris-covered glaciers can respond to climate change in a nonlinear manner. Supraglacial debris alters the energy balance at the atmosphere-glacier interface compared with debris-free glaciers, and can result in both accelerated and reduced ablation through complex processes that occur on a variety of scales. Emmons Glacier, on the northeast slope of Mount Rainier (Washington, USA), offers an opportunity to study these processes in supraglacial debris that are otherwise difficult to study in situ (e.g. Himalayan glaciers). Emmons Glacier underwent a steady advance in the late 20th century despite a warming climate, in part due to increased surface debris cover. Key energy balance variables were measured in August of 2013 and 2014 using a temporary weather station installed directly on the debris-covered terminus of Emmons Glacier. Ablation of debris-covered ice was monitored in situ with ablation stakes drilled into the debris-covered ice in a 3600 m2 grid, a size comparable to a single pixel in leading thermal remote-sensing platforms. Debris thickness at the study site ranged from 3-50 cm at the ablation stakes, and textures varied from sand and gravel to large boulders with open pore space. Daily ablation rates varied by a factor of 5 in this small area and were affected by debris thickness, texture, and moisture as well as local surface slope and aspect. On this scale, ablation rates correlated better with debris surface temperature than air temperature. Spatial gradients in ablation rate may strongly influence long-term melt rates through evolving surface topography and consequent redistribution of supraglacial debris, but cannot be resolved using thermal imagery from most current satellite platforms. A preliminary field experiment with a ground-based thermal infrared camera yielded temperature measurements with fine spatial

  7. Reduced melt on debris-covered glaciers: investigations from Changri Nup Glacier, Nepal

    NASA Astrophysics Data System (ADS)

    Wagnon, Patrick; Vincent, Christian; Shea, Joseph M.; Immerzeel, Walter W.; Kraaijenbrink, Philip; Shrestha, Dibas; Soruco, Alvaro; Arnaud, Yves; Brun, Fanny; Berthier, Etienne; Futi Sherpa, Sonam

    2017-04-01

    Approximately 25% of the glacierized area in the Everest region is covered by debris, yet the surface mass balance of debris-covered portions of these glaciers has not been measured directly. In this study, ground-based measurements of surface elevation and ice depth are combined with terrestrial photogrammetry, unmanned aerial vehicle (UAV) and satellite elevation models to derive the surface mass balance of the debris-covered tongue of Changri Nup Glacier, located in the Everest region. Over the debris-covered tongue, the mean elevation change between 2011 and 2015 is -0.93 m year-1 or -0.84 m water equivalent per year (w.e. a-1). The mean emergence velocity over this region, estimated from the total ice flux through a cross section immediately above the debris-covered zone, is +0.37mw.e. a-1. The debris-covered portion of the glacier thus has an area averaged mass balance of -1.21+/-0.2mw.e. a-1 between 5240 and 5525 m above sea level (m a.s.l.). Surface mass balances observed on nearby debris-free glaciers suggest that the ablation is strongly reduced (by ca. 1.8mw.e. a-1) by the debris cover. The insulating effect of the debris cover has a larger effect on total mass loss than the enhanced ice ablation due to supraglacial ponds and exposed ice cliffs. This finding contradicts earlier geodetic studies and should be considered for modelling the future evolution of debris-covered glaciers.

  8. Mapping surface temperature variability on a debris-covered glacier with an unmanned aerial vehicle

    NASA Astrophysics Data System (ADS)

    Kraaijenbrink, P. D. A.; Litt, M.; Shea, J. M.; Treichler, D.; Koch, I.; Immerzeel, W.

    2016-12-01

    Debris-covered glacier tongues cover about 12% of the glacier surface in high mountain Asia and much of the melt water is generated from those glaciers. A thin layer of supraglacial debris enhances ice melt by lowering the albedo, while thicker debris insulates the ice and reduces melt. Data on debris thickness is therefore an important input for energy balance modelling of these glaciers. Thermal infrared remote sensing can be used to estimate the debris thickness by using an inverse relation between debris surface temperature and thickness. To date this has only been performed using coarse spaceborne thermal imagery, which cannot reveal small scale variation in debris thickness and its influence on the heterogeneous melt patterns on debris-covered glaciers. We deployed an unmanned aerial vehicle mounted with a thermal infrared sensor over the debris-covered Lirung Glacier in Nepal three times in May 2016 to reveal the spatial and temporal variability of surface temperature in high detail. The UAV survey matched a Landsat 8 overpass to be able to make a comparison with spaceborne thermal imagery. The UAV-acquired data is processed using Structure from Motion photogrammetry and georeferenced using DGPS-measured ground control points. Different surface types were distinguished by using data acquired by an additional optical UAV survey in order to correct for differences in surface emissivity. In situ temperature measurements and incoming solar radiation data are used to calibrate the temperature calculations. Debris thicknesses derived are validated by thickness measurements of a ground penetrating radar. Preliminary analysis reveals a spatially highly heterogeneous pattern of surface temperature over Lirung Glacier with a range in temperature of over 40 K. At dawn the debris is relatively cold and its temperature is influenced strongly by the ice underneath. Exposed to the high solar radiation at the high altitude the debris layer heats up very rapidly as sunrise

  9. [Isolation and characterization of a lytic bacteriophage from Mingyong glacier melt water].

    PubMed

    Li, Mingyuan; Ji, Xiuling; Wang, Baoqiang; Zhang, Qi; Lin, Lianbing; Zhang, Bing; Wei, Yunlin

    2012-02-04

    Glacier is a unique ecological system. This study focused on the isolation and characterization of a cold-active bateriophage from Mingyong glacier area in northwest Yunnan. Bacterial strains isolated from glacial melt water were used as host cells to isolate and purify bacteriophages by double-layer plate method. The morphology of the isolated phages and their host strains were observed by electron microscope. Restriction fragment length polymorphism (RFLP) analysis of genomic DNA, constituent proteins and physiological analysis of the bacteriophages were further carried out to characterize the phages. A lytic cold-active bacteriophage, designated as MYSP03, was isolated from Mingyong glacier. Its host strain MYB03 was identified as a member of genus Flavobacterium, based on the 16S rRNA sequence analysis. The bacteriophage MYSP03 has a isometric head (about 72 nm in diameter) and a long tail (about 240 nm in length and 10 nm in width), but no envelope was detected. Physiological analysis results showed that MYSP03 had infection activity at 4 degrees C, and clear and transparent plaques were formed on double-layer plates between 4 and 20 degrees C. Its optimum infection temperature was 10 degrees C and optimal pH 9.4, respectively. It is insensitive to chloroform. Furthermore, the genome of MYSP03 consists of double-stranded DNA and is approximately 66 kb.

  10. Glacier meltwater flow paths and storage in a geomorphologically complex glacial foreland: the case of the Tapado glacier, dry Andes of Chile (30°S)

    NASA Astrophysics Data System (ADS)

    Pourrier, J.; Jourde, H.; Kinnard, C.; Gascoin, S.; Monnier, S.

    2013-12-01

    In the Dry Andes, high altitude glacierized catchments are important contributor to streamflow and aquifer recharge. In this study we focused on the Tapado catchment, (30°S, 9 km2, elevation range: 4000m - 5550m) located in the upper Elqui river basin in northern Chile. This catchment encompasses the Tapado glacial complex, composed of an assemblage of the Tapado glacier and the glacial foreland (debris-covered glacier, rock glacier and moraines). Here we present the results of intensive hydrometeorological observations conducted over the 2011 glacier melt season (February to April). Weather, discharge and water electrical conductivity were monitored near the glacier snout and at the outlet of the glacial foreland. GPR observations realized on the glacial foreland are used to verify or complete interpretations of underground transfer modalities. The results show that the water production from the Tapado glacier is highly correlated with weather conditions, in particular incoming shortwave radiation and air temperature. Resulting daily and seasonal streamflow variability is buffered by the glacial foreland, where underground transfers occur through complex flow paths. However, the development of a thermokarst drainage network in a part of the glacial foreland, allows fast and concentrated water transfers, which reduces this buffering effect. The glacial foreland is shown to act as a reservoir, storing water during period of strong ice melt and providing water to downstream areas during periods of low melt. The internal structure of the glacial foreland revealed by GPR observations corroborates these analyses. The south-western part is composed by massive ice, covered by rock debris. The north-eastern part is composed by mixed ice and rock debris, presenting spatially variable ice content. Finally, the computation of the catchment water balance shows that the Tapado catchment presents a particularly high specific discharge in summer under a dry hydro

  11. Relationship between glacier melting and atmospheric circulation in the southeast Siberia

    NASA Astrophysics Data System (ADS)

    Osipova, O. P.; Osipov, E. Y.

    2018-01-01

    The interaction between climate and cryosphere is a key issue in recent years. Changes in surface mass balance of mountain glaciers closely correspond to differential changes in atmospheric circulation. Mountain glaciers in southeast Siberia located on East Sayan, Baikalsky and Kodar ridges have been continuously shrinking since the end of the Little Ice Age. In this study we used daily synoptic weather maps (Irkutsk Center of Hydrometeorology and Environmental Monitoring), 500 hPa, 700 hPa and 850 hPa geopotential height and air temperature data of NCEP/NCAR reanalysis to assess relationships between atmospheric circulation patterns and the sum of positive temperature (SPT), a predictor of summer ice/snow ablation. Results show that increased SPT (ablation) is generally associated with anticyclones and anticyclonic pressure fields (with cloudless weather conditions) and warm atmospheric fronts. Decreased SPT (ablation) is strongly correlated with cyclones and cyclonic type pressure fields, cold atmospheric fronts and air advections. Significant correlations have been found between ablation and cyclonic/anticyclonic activity. Revealed decreasing trends in the SPT in three glaciarized ridges at the beginning of the 21st century led to changes of air temperature and snow/ice melt climates.

  12. Melting Himalayan glaciers contaminated by legacy atmospheric depositions are important sources of PCBs and high-molecular-weight PAHs for the Ganges floodplain during dry periods.

    PubMed

    Sharma, Brij Mohan; Nizzetto, Luca; Bharat, Girija K; Tayal, Shresth; Melymuk, Lisa; Sáňka, Ondřej; Přibylová, Petra; Audy, Ondřej; Larssen, Thorjørn

    2015-11-01

    Melting glaciers are natural redistributors of legacy airborne pollutants, affecting exposure of pristine proglacial environments. Our data shows that melting Himalayan glaciers can be major contributors of polychlorinated biphenyls (PCBs) and high-molecular-weight polycyclic aromatic hydrocarbons (PAHs) for surface water in the Gangetic Plain during the dry season. Glacial emissions can exceed in some cases inputs from diffuse sources within the catchment. We analyzed air, deposition and river water in several sections along the Ganges River and its major headwaters. The predominant glacial origin of these contaminants in the Himalayan reach was demonstrated using air-water fugacity ratios and mass balance analysis. The proportion of meltwater emissions compared to pollutant discharge at downstream sections in the central part of the Gangetic Plain was between 2 and 200%. By remobilizing legacy pollutants from melting glaciers, climate change can enhance exposure levels over large and already heavily impacted regions of Northern India. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Bathymetry of Torssukatak fjord and one century of glacier stability

    NASA Astrophysics Data System (ADS)

    An, L.; Rignot, E. J.; Morlighem, M.

    2017-12-01

    Marine-terminating glaciers dominate the evolution of the Greenland Ice Sheet(GrIS) mass balance as they control 90% of the ice discharge into the ocean. Warm air temperatures thin the glaciers from the top to unground ice fronts from the bed. Warm oceans erode the submerged grounded ice, causing the grounding line to retreat. To interpret the recent and future evolution of two outlet glaciers, Sermeq Avangnardleq (AVA) and Sermeq Kujatdleq (KUJ) in central West Greenland, flowing into the ice-choked Torssukatak fjord (TOR), we need to know their ice thickness and bed topography and the fjord bathymetry. Here, we present a novel mapping of the glacier bed topography, ice thickness and sea floor bathymetry near the grounding line using high resolution airborne gravity data from AIRGrav collected in August 2012 with a helicopter platform, at 500 m spacing grid, 50 knots ground speed, 80 m ground clearance, with submilligal accuracy, i.e. higher than NASA Operation IceBridge (OIB)'s 5.2 km resolution, 290 knots, and 450 m clearance. We also employ MultiBeam Echo Sounding data (MBES) collected in the fjord since 2009. We had to wait until the summer of 2016, during Ocean Melting Greenland (OMG), to map the fjord bathymetry near the ice fronts for the first time. We constrain the 3D inversion of the gravity data with MBES in the fjord and a reconstruction of the glacier bed topography using mass conservation (MC) on land ice. The seamless topography obtained across the grounding line reveal the presence of a 300-m sill for AVA, which explains why this glacier has been stable for a century, despite changes in surface melt and ocean-induced melt and the presence of a deep fjord (800 m) in front of the glacier. For KUJ, we also reveal the presence of a wide sill (300 m depth) near the current ice front which explains its stability and the stranding of iceberg debris in front of the glacier. The results shed new light on the evolution of these glaciers and explain their

  14. Radiation, Aerosol Joint Observation-Modeling Exploration over Glaciers in Himalayan Asia (RAJO-MEGHA)

    NASA Astrophysics Data System (ADS)

    Tsay, S. C.; Holben, B. N.

    2016-12-01

    All major rivers that run through densely populated Asia (i.e., Yangtze, Yellow in China; Mekong in Southeast Asian peninsula; Brahmaputra, Ganges, Indus in Indian subcontinent) originate in High Mountain Asia (HMA) and are fed by the seasonal melt of snowpack and glaciers. Although varying greatly in space and time, the overall snowpack/ glaciers in the HMA are losing mass and retreating at an accelerated rate (e.g., Kulkarni et al., 2007; Kehrwald et al., 2008), as revealed from recent observations. This situation poses an imminent danger to the water supply and environmental hazards (e.g., soil erosion, glacial-lake-outburst flood) not only to regional inhabitants, but also to the global ecosystem through feedback mechanisms. Comprehensive regional-to-global assimilation models, advancing in lockstep with the advent of satellite observations (e.g., MODIS-/CERES-like sensors) and complementary surface measurements (e.g., AERONET), are playing an ever-increasing role in developing mitigation strategies. However, the complex characteristics of HMA, such as its ragged terrain, atmospheric inhomogeneity, snow susceptibility, and ground-truth accessibility, introduces difficulties for the aforementioned research tools to retrieve/assess radiative forcing on snow/ice melting with a high degree of fidelity. In terms of quantifying radiative forcing, the key components are transport/evolution of light-absorbing aerosols (e.g., dust, black carbon) aloft, the surface solar/terrestrial irradiance budget, and snow reflectivity/absorptivity with/without impurities. The RAJO-MEGHA (Sanskrit for Dust-Cloud) project is an initiative on the integrated (aerosols, clouds, and precipitation) measurements in the vicinity of HMA (e.g., Indo-Gangetic Plain, Himalaya-Tibetan Plateau). We will discuss an array of ground-based (e.g., AERONET, MPLNET, SMARTLabs, etc.) and satellite (e.g., Terra, A-Train, etc.) sensors utilized to acquire aerosol characteristics, sources/sinks, and

  15. Mass balance model parameter transferability on a tropical glacier

    NASA Astrophysics Data System (ADS)

    Gurgiser, Wolfgang; Mölg, Thomas; Nicholson, Lindsey; Kaser, Georg

    2013-04-01

    The mass balance and melt water production of glaciers is of particular interest in the Peruvian Andes where glacier melt water has markedly increased water supply during the pronounced dry seasons in recent decades. However, the melt water contribution from glaciers is projected to decrease with appreciable negative impacts on the local society within the coming decades. Understanding mass balance processes on tropical glaciers is a prerequisite for modeling present and future glacier runoff. As a first step towards this aim we applied a process-based surface mass balance model in order to calculate observed ablation at two stakes in the ablation zone of Shallap Glacier (4800 m a.s.l., 9°S) in the Cordillera Blanca, Peru. Under the tropical climate, the snow line migrates very frequently across most of the ablation zone all year round causing large temporal and spatial variations of glacier surface conditions and related ablation. Consequently, pronounced differences between the two chosen stakes and the two years were observed. Hourly records of temperature, humidity, wind speed, short wave incoming radiation, and precipitation are available from an automatic weather station (AWS) on the moraine near the glacier for the hydrological years 2006/07 and 2007/08 while stake readings are available at intervals of between 14 to 64 days. To optimize model parameters, we used 1000 model simulations in which the most sensitive model parameters were varied randomly within their physically meaningful ranges. The modeled surface height change was evaluated against the two stake locations in the lower ablation zone (SH11, 4760m) and in the upper ablation zone (SH22, 4816m), respectively. The optimal parameter set for each point achieved good model skill but if we transfer the best parameter combination from one stake site to the other stake site model errors increases significantly. The same happens if we optimize the model parameters for each year individually and transfer

  16. Energy balance-based distributed modeling of snow and glacier melt runoff for the Hunza river basin in the Pakistan Karakoram Himalayan region

    NASA Astrophysics Data System (ADS)

    Shrestha, M.; Wang, L.; Koike, T.; Xue, Y.; Hirabayashi, Y.; Ahmad, S.

    2012-12-01

    A spatially distributed biosphere hydrological model with energy balance-based multilayer snow physics and multilayer glacier model, including debris free and debris covered surface (enhanced WEB-DHM-S) has been developed and applied to the Hunza river basin in the Pakistan Karakoram Himalayan region, where about 34% of the basin area is covered by glaciers. The spatial distribution of seasonal snow and glacier cover, snow and glacier melt runoff along with rainfall-contributed runoff, and glacier mass balances are simulated. The simulations are carried out at hourly time steps and at 1-km spatial resolution for the two hydrological years (2002-2003) with the use of APHRODITE precipitation dataset, observed temperature, and other atmospheric forcing variables from the Global Land Data Assimilation System (GLDAS). The pixel-to-pixel comparisons for the snow-free and snow-covered grids over the region reveal that the simulation agrees well with the Moderate Resolution Imaging Spectroradiometer (MODIS) eight-day maximum snow-cover extent data (MOD10A2) with an accuracy of 83% and a positive bias of 2.8 %. The quantitative evaluation also shows that the model is able to reproduce the river discharge satisfactorily with Nash efficiency of 0.92. It is found that the contribution of rainfall to total streamflow is small (about 10-12%) while the contribution of snow and glacier is considerably large (35-40% for snowmelt and 50-53% for glaciermelt, respectively). The model simulates the state of snow and glaciers at each model grid prognostically and thus can estimate the net annual mass balance. The net mass balance varies from -2 m to +2 m water equivalent. Additionally, the hypsography analysis for the equilibrium line altitude (ELA) suggests that the average ELA in this region is about 5700 m with substantial variation from glacier to glacier and region to region. This study is the first to adopt a distributed biosphere hydrological model with the energy balance- based

  17. Recent Activity of Glaciers of Mount Rainier, Washington

    USGS Publications Warehouse

    Sigafoos, Robert S.; Hendricks, E.L.

    1972-01-01

    Knowing the ages of trees growing on recent moraines at Mount Rainier, Wash., permits the moraines to be dated. Moraines which are ridges of boulders, gravel, sand, and dust deposited at the margins of a glacier, mark former limits of a receding glacier. Knowing past glacial activity aids our understanding of past climatic variations. The report documents the ages of moraines deposited by eight glaciers. Aerial photographs and planimetric maps show areas where detailed field studies were made below seven glaciers. Moraines, past ice positions, and sample areas are plotted on the photographs and maps, along with trails, roads, streams, and landforms, to permit critical areas to be identified in the future. Ground photographs are included so that sample sites and easily accessible moraines can be found along trails. Tables present data about trees sampled in areas near the glaciers of Mount Rainier, Wash. The data in the tables show there are modern moraines of different age around the mountain; some valleys contain only one modern moraiine; others contain as many as nine. The evidence indicates a sequence of modern glacial advances terminating at about the following A.D. dates: 1525, 1550, 1625-60, 1715, 1730-65, 1820-60, 1875, and 1910. Nisqually River valley near Nisqually Glacier contains one moraine formed before A.D. 1842; Tahoma Creek valley near South Tahoma Glacier contains three moraines formed before A.D. 1528; 1843, and 1864; South Puyallup River valley near Tahoma Glacier, six moraines A.D. 1544, 1761, 1841, 1851, 1863, 1898; Puyallup Glacier, one moraine, A.D. 1846; Carbon Glacier, four moraines, 1519, 1763, 1847, 1876; Winthrop Glacier, four moraines, 1655, 1716, 1760, amid 1822; Emmons Glacier, nine moraines, 1596, 1613, 1661, 1738, 1825, 1850, 1865, 1870, 1901; and Ohanapecosh Glacier, three moraines, 1741, 1846, and 1878. Abandoned melt-water and flood channels were identified within moraine complexes below three glaciers, and their time of

  18. Energy and mass balance observations on La Mare Glacier (Ortles-Cevedale, European Alps)

    NASA Astrophysics Data System (ADS)

    Carturan, L.; Cazorzi, F.; Dalla Fontana, G.

    2009-04-01

    An experimental site was setup in 2005 on the ablation area of La Mare Glacier, at 2990 m a.s.l., to study the energy and mass balance exchanges between the glacier surface and the atmosphere and to investigate the climatic sensitivity of this particular glacier. An Automatic Weather Station was operated, in the framework of a monitoring network which has been implemented in the Upper Val de La Mare experimental watershed (Trentino, Italy). This basin was selected for a study of climate change effects on cryosphere and hydrology at high-altitude catchments. The 36.2 km2 wide basin has an average altitude of 2906 m a.s.l. and at present the 25% of its surface is glacierized; the annual runoff regime is dominated by snow and ice melt. Direct mass balance measurements have been performed since 1967 on Careser glacier (2.83 km2) and since 2003 on La Mare glacier (3.97 km2). The AWS is mounted on a tripod which stands freely on the glacier surface and is solar-powered. The variables measured are: air temperature and relative humidity, wind speed and direction, shortwave and longwave incoming and outgoing radiation, precipitation and surface height. All the data are sampled at five-minute intervals as average values, with the exception of surface height which is sampled at hourly intervals, as instantaneous values. The collected data were used to calculate the point energy and mass balance and to compare the results with similar investigations carried out on glaciers and available in literature. In particular, our attention has been focussed on some processes which regulate the response to climate changes. The relative importance of the energy balance components was examined and a clear predominance of shortwave radiation inputs was found to exist during melt conditions. Given the relevance of the shortwave net balance, the ice albedo temporal variability (values ranging from 0.1 to 0.5) has been investigated and correlated with meteorological variables. Furthermore, a

  19. Climate-induced glacier and snow loss imperils alpine stream insects

    USGS Publications Warehouse

    Giersch, J. Joseph; Hotaling, Scott; Kovach, Ryan; Jones, Leslie A.; Muhlfeld, Clint C.

    2017-01-01

    Climate warming is causing rapid loss of glaciers and snowpack in mountainous regions worldwide. These changes are predicted to negatively impact the habitats of many range-restricted species, particularly endemic, mountaintop species dependent on the unique thermal and hydrologic conditions found only in glacier-fed and snowmelt-driven alpine streams. Though progress has been made, existing understanding of the status, distribution, and ecology of alpine aquatic species, particularly in North America, is lacking, thereby hindering conservation and management programs. Two aquatic insects – the meltwater stonefly Lednia tumana and the glacier stonefly Zapada glacier – were recently proposed for listing under the U.S. Endangered Species Act due to climate-change-induced habitat loss. Using a large dataset (272 streams, 482 total sites) with high-resolution climate and habitat information, we describe the distribution, status, and key environmental features that limit L. tumana and Z. glacier across the northern Rocky Mountains. Lednia tumana was detected in 113 streams (175 sites) within Glacier National Park (GNP) and surrounding areas. The probability of L. tumana occurrence increased with cold stream temperatures and close proximity to glaciers and permanent snowfields. Similarly, densities of L. tumana declined with increasing distance from stream source. Zapada glacier was only detected in 10 streams (20 sites), six in GNP and four in mountain ranges up to ~600 km southwest. Our results show that both L. tumana and Z. glacier inhabit an extremely narrow distribution, restricted to short sections of cold, alpine streams often below glaciers predicted to disappear over the next two decades. Climate warming-induced glacier and snow loss clearly imperils the persistence of L. tumana and Z. glacier throughout their ranges, highlighting the role of mountaintop aquatic invertebrates as sentinels of climate change in mid-latitude regions.

  20. Glaciers. Attribution of global glacier mass loss to anthropogenic and natural causes.

    PubMed

    Marzeion, Ben; Cogley, J Graham; Richter, Kristin; Parkes, David

    2014-08-22

    The ongoing global glacier retreat is affecting human societies by causing sea-level rise, changing seasonal water availability, and increasing geohazards. Melting glaciers are an icon of anthropogenic climate change. However, glacier response times are typically decades or longer, which implies that the present-day glacier retreat is a mixed response to past and current natural climate variability and current anthropogenic forcing. Here we show that only 25 ± 35% of the global glacier mass loss during the period from 1851 to 2010 is attributable to anthropogenic causes. Nevertheless, the anthropogenic signal is detectable with high confidence in glacier mass balance observations during 1991 to 2010, and the anthropogenic fraction of global glacier mass loss during that period has increased to 69 ± 24%. Copyright © 2014, American Association for the Advancement of Science.

  1. Dynamic Response of a High Arctic Glacier to Melt and Runoff Variations

    NASA Astrophysics Data System (ADS)

    van Pelt, Ward J. J.; Pohjola, Veijo A.; Pettersson, Rickard; Ehwald, Lena E.; Reijmer, Carleen H.; Boot, Wim; Jakobs, Constantijn L.

    2018-05-01

    The dynamic response of High Arctic glaciers to increased runoff in a warming climate remains poorly understood. We analyze a 10-year record of continuous velocity data collected at multiple sites on Nordenskiöldbreen, Svalbard, and study the connection between ice flow and runoff within and between seasons. During the melt season, the sensitivity of ice motion to runoff at sites in the ablation and lower accumulation zone drops by a factor of 3 when cumulative runoff exceeds a local threshold, which is likely associated with a transition from inefficient (distributed) to efficient (channelized) drainage. Average summer (June-August) velocities are found to increase with summer ablation, while subsequent fall (September-November) velocities decrease. Spring (March-May) velocities are largely insensitive to summer ablation, which suggests a short-lived impact of summer melt on ice flow during the cold season. The net impact of summer ablation on annual velocities is found to be insignificant.

  2. Contribution potential of glaciers to water availability in different climate regimes

    PubMed Central

    Kaser, Georg; Großhauser, Martin; Marzeion, Ben

    2010-01-01

    Although reliable figures are often missing, considerable detrimental changes due to shrinking glaciers are universally expected for water availability in river systems under the influence of ongoing global climate change. We estimate the contribution potential of seasonally delayed glacier melt water to total water availability in large river systems. We find that the seasonally delayed glacier contribution is largest where rivers enter seasonally arid regions and negligible in the lowlands of river basins governed by monsoon climates. By comparing monthly glacier melt contributions with population densities in different altitude bands within each river basin, we demonstrate that strong human dependence on glacier melt is not collocated with highest population densities in most basins. PMID:21059938

  3. Crystallographic effects during radiative melting of semitransparent materials

    NASA Astrophysics Data System (ADS)

    Webb, B. W.; Viskanta, R.

    1987-10-01

    Experiments have been performed to illustrate crystallogrpahic effects during radiative melting of unconfined vertical layers of semitransparent material. Radiative melting of a polycrystalline paraffin was performed and the instantaneous layer weight and transmittance were measured using a cantilever beam technique and thermopile radiation detector, respectively. The effects of radiative flux, initial solid subcooling, spectral distribution of the irradiation, and crystal structure of the solid as determined qualitatively by the sample solidification rate were studied. Experimental results show conclusively the dominant influence of cystallographic effects in the form of multiple internal scattering of radiation during the melting process. A theoretical model is formulated to predict the melting rate of the material. Radiation transfer is treated by solving the one-dimensional radiative transfer equation for an absorbing-scattering medium using the discrete ordinates method. Melting rate and global layer reflectance as predicted by the model agree well with experimental data. Parametric studies conducted with the model illustrate the sensitivity of the melting behavior to such variables as incident radiative flux, initial layer opacity (material extinction coefficient), and scattering asymmetry factor.

  4. Modelling The Energy And Mass Balance Of A Black Glacier

    NASA Astrophysics Data System (ADS)

    Grossi, G.; Taschner, S.; Ranzi, R.

    A distributed energy balance hydrologic model has been implemented to simulate the melting season of the Belvedere glacier, situated in the Anza river basin (North- Western Italy) for a few years. The Belvedere Glacier is an example of SblackS glacier, ´ since the ablation zone is covered by a significant debris layer. The glacierSs termi- nus has an altitude of 1785 m asl which is very unusual for the Southern side of the European Alps. The model accounts for the energy exchange processes at the inter- face between the atmospheric boundary layer and the snow/ice/debris layer. To run the model hydrometeorological and physiographic data were collected, including the depth of the debris cover and the tritium (3H) concentration in the glacial river. Mea- surements of the soil thermal conductivity were carried out during a field campaign organised within the glaciers monitoring GLIMS project, at the time of the passage of the Landsat and the Terra satellites last 15 August 2001. A comparison of the different energy terms simulated by the model assigns a dominant role to the shortwave radia- tion, which provides the highest positive contribution to the energy available for snow- and ice-melt, while the sensible heat turns out to be the second major source of heat. Longwave radiation balance and latent heat seem to be less relevant and often nega- tive. The role of the debris cover is not negligible, since its thermal insulation causes, on average, a decrease in the ice melt volume. One of the model variables is the tem- perature of the debris cover, which can be a useful information when a black glacier is to be monitored through remote sensing techniques. The visible and near infrared radi- ation data do not always provide sufficient information to detect the glaciers' margins beneath the debris layer. For this reason the information of the different thermal sur- face characteristics (pure ice, debris covered ice, rock), proved by the energy balance model results was

  5. Runoff generation from neighboring headwater basins with differing glacier coverage using the distributed hydrological model WaSiM, Eklutna, Alaska

    NASA Astrophysics Data System (ADS)

    Ostman, J. S.; Loso, M.; Liljedahl, A. K.; Gaedeke, A.; Geck, J. E.

    2017-12-01

    Many Alaska glaciers are thinning and retreating, and glacier wastage is projected to affect runoff processes from glacierized basins. Accordingly, effective resource management in glacierized watersheds requires quantification of a glacier's role on streamflow generation. The Eklutna catchment (311 km2) supplies water and electricity for Anchorage, Alaska (pop. 300,000) via Eklutna Lake. The Eklutna headwaters include the West Fork (64 km2, 46% glacier), and the East Fork (101 km2, 12% glacier). Total average annual discharge (2009-2015) is similar from the West (42,100 m3) and East (42,200 m3) forks, while specific annual runoff from the West Fork (2940 mm) exceeds that of the East Fork (1500 mm). To better understand what controls runoff, we are simulating the Eklutna annual water budget using a distributed watershed-level hydrological model. We force the Water Flow and Balance Simulation Model (WaSiM) using continuous air temperature, precipitation, wind speed, shortwave incoming radiation, and relative humidity primarily measured in the West Fork basin. We use Eklutna Glacier snow accumulation and ablation to calibrate the snowmelt and glacier sub-modules. Melt season discharge from the West and East forks is used for runoff comparison. Preliminary results show 2013-2015 simulated glacier point balances (accumulation and melt) are within 15% of glacier stake observations. Runoff was effectively modeled in the West Fork (NSE=0.80), while being over-predicted in the East Fork , which we attribute to a lack of forcing data in the less-glacierized basin. The simulations suggest that 78% of West Fork total runoff is from glacier melt, compared with <40% in the East Fork where glacier runoff contribution is higher during low-snow years.

  6. Basal terraces on melting ice shelves

    NASA Astrophysics Data System (ADS)

    Dutrieux, Pierre; Stewart, Craig; Jenkins, Adrian; Nicholls, Keith W.; Corr, Hugh F. J.; Rignot, Eric; Steffen, Konrad

    2014-08-01

    Ocean waters melt the margins of Antarctic and Greenland glaciers, and individual glaciers' responses and the integrity of their ice shelves are expected to depend on the spatial distribution of melt. The bases of the ice shelves associated with Pine Island Glacier (West Antarctica) and Petermann Glacier (Greenland) have similar geometries, including kilometer-wide, hundreds-of-meter high channels oriented along and across the direction of ice flow. The channels are enhanced by, and constrain, oceanic melt. New meter-scale observations of basal topography reveal peculiar glaciated landscapes. Channel flanks are not smooth, but are instead stepped, with hundreds-of-meters-wide flat terraces separated by 5-50 m high walls. Melting is shown to be modulated by the geometry: constant across each terrace, changing from one terrace to the next, and greatly enhanced on the ~45° inclined walls. Melting is therefore fundamentally heterogeneous and likely associated with stratification in the ice-ocean boundary layer, challenging current models of ice shelf-ocean interactions.

  7. What influences climate and glacier change in southwestern China?

    NASA Astrophysics Data System (ADS)

    Yasunari, Teppei J.

    2011-12-01

    the atmospheric effects on snow albedo with a multiple scattering radiative transfer model for the atmosphere-snow system J. Meteorol. Soc. Japan 77 595-614 Aoki Te, Kuchiki K, Niwano M, Kodama Y, Hosaka M and Tanaka T 2011 Physically based snow albedo model for calculating broadband albedos and the solar heating profile in snowpack for general circulation models J. Geophys. Res. 116 D11114 Flanner M G and Zender C S 2006 Linking snowpack microphysics and albedo evolution J. Geophys. Res. 111 D12208 Flanner M G, Zender C S, Randerson J T and Rasch P J 2007 Present-day climate forcing and response from black carbon in snow J. Geophys. Res. 112 D11202 Flanner M G, Zender C S, Hess P G, Mahowald N M, Painter T H, Ramanathan V and Rasch P J 2009 Springtime warming and reduced snow cover from carbonaceous particles Atmos. Chem. Phys. 9 2481-97 Fujita K 2008 Effect of precipitation seasonality on climatic sensitivity of glacier mass balance Earth Planet. Sci. Lett. 276 14-9 Fujita K, Sakai A, Nuimura T, Yamaguchi S and Sharma R 2009 Recent changes in Imja Glacial Lake and its damming moraine in the Nepal Himalaya revealed by in situ surveys and multi-temporal ASTER imagery Environ. Res. Lett. 4 045205 Fujita K and Nuimura T 2011 Spatially heterogeneous wastage of Himalayan glaciers Proc. Natl Acad. Sci. USA at press doi: 10.1073/pnas.1106242108 Gautam R, Hsu N C and Lau K M 2010 Premonsoon aerosol characterization and radiative effects over the Indo-Gangetic Plains: Implications for regional climate warming J. Geophys. Res. 115 D17208 Immerzeel W W, van Beek L P H and Bjerkens M F P 2010 Climate change will affect the Asian water towers Science 328 1382-5 Lau K M, Kim M K and Kim K M 2006 Asian monsoon anomalies induced by aerosol direct effects Clim. Dyn. 26 855-64 Lau K M, Kim M K, Kim K M and Lee W S 2010 Enhanced surface warming and accelerated snow melt in the Himalayas and Tibetan Plateau induced by absorbing aerosols Environ. Res. Lett. 5 025204 Li Z, He Y, An W

  8. Mass-balance modelling of Ak-Shyirak massif Glaciers, Inner Tian Shan

    NASA Astrophysics Data System (ADS)

    Rets, Ekaterina; Barandun, Martina; Belozerov, Egor; Petrakov, Dmitry; Shpuntova, Alena

    2017-04-01

    Tian Shan is a water tower of Central Asia. Rapid and accelerating glacier downwasting is typical for this region. Study sites - Sary-Tor glacier and Glacier No.354 are located in Ak-Shyirak massif, Naryn headwaters. Sary-Tor was chosen as representative for Ak-Shyirak (Ushnurtsev, 1991; Oledeneniye TianShanya, 1995) for direct mass-balance measurements in 1985-1991. Glacier No.354 was an object of direct mass-balance measurements for 2011-2016. An energy-balance distributed A-Melt model (Rets et al, 2010) was used to reconstruct mass-balance for the glaciers for 2003-2015. Verification of modelingresults showed a good reproduction of direct melting measurements data on ablation stakes and mass loss according to geodetic method. Modeling results for Glacier No. 354 were compared to different modeling approach: distributed accumulation and temperature-index melt (Kronenberg et al, 2016)

  9. Disruption of Drift glacier and origin of floods during the 1989-1990 eruptions of Redoubt Volcano, Alaska

    USGS Publications Warehouse

    Trabant, D.C.; Waitt, R.B.; Major, J.J.

    1994-01-01

    Melting of snow and glacier ice during the 1989-1990 eruption of Redoubt Volcano caused winter flooding of the Drift River. Drift glacier was beheaded when 113 to 121 ?? 106 m3 of perennial snow and ice were mechanically entrained in hot-rock avalanches and pyroclastic flows initiated by the four largest eruptions between 14 December 1989 and 14 March 1990. The disruption of Drift glacier was dominated by mechanical disaggregation and entrainment of snow and glacier ice. Hot-rock avalanches, debris flows, and pyroclastic flows incised deep canyons in the glacier ice thereby maintaining a large ice-surface area available for scour by subsequent flows. Downvalley flow rheologies were transformed by the melting of snow and ice entrained along the upper and middle reaches of the glacier and by seasonal snowpack incorporated from the surface of the lower glacier and from the river valley. The seasonal snowpack in the Drift River valley contributed to lahars and floods a cumulative volume equivalent to about 35 ?? 106 m3 of water, which amounts to nearly 30% of the cumulative flow volume 22 km downstream from the volcano. The absence of high-water marks in depressions and of ice-collapse features in the glacier indicated that no large quantities of meltwater that could potentially generate lahars were stored on or under the glacier; the water that generated the lahars that swept Drift River valley was produced from the proximal, eruption-induced volcaniclastic flows by melting of snow and ice. ?? 1994.

  10. Mountain glaciers caught on camera

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2011-12-01

    Many glaciers around the world are melting, and new research is showing some of the dramatic details. Ulyana Horodyskyj, a graduate student at the Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado at Boulder, set up cameras to take time-lapse photographs of three lakes on a glacier in Nepal. This allowed her and her colleagues to see the supraglacial lake drain in real time for the first time, making it possible to estimate how much water was involved and how long it took for the lake to drain and refill. Horodyskyj said in a press conference at the AGU Fall Meeting that such observations of supraglacial lakes are valuable because in a warming climate, melting glaciers can lead to formation of supraglacial lakes.

  11. Submarine melt rates under Greenland's ice tongues

    NASA Astrophysics Data System (ADS)

    Wilson, Nat; Straneo, Fiametta; Heimbach, Patrick; Cenedese, Claudia

    2017-04-01

    The few remaining ice tongues (ice-shelf like extensions) of Greenland's glaciers are undergoing rapid changes with potential implications for the stability of the ice sheet. Submarine melting is recognized as a major contributor to mass loss, yet the magnitude and spatial distribution of melt are poorly known or understood. Here, we use high resolution satellite imagery to infer the magnitude and spatial variability of melt rates under Greenland's largest remaining ice tongues: Ryder Glacier, Petermann Glacier and Nioghalvfjerdsbræ (79 North Glacier). We find that submarine plus aerial melt approximately balance the ice flux from the grounded ice sheet for the first two while at Nioghalvfjerdsbræ the total melt flux exceeds the inflow of ice indicating thinning of the ice tongue. We also show that melt rates under the ice tongues vary considerably, exceeding 60 m yr-1 near the grounding zone and decaying rapidly downstream. Channels, likely originating from upstream subglacial channels, give rise to large melt variations across the ice tongues. Using derived melt rates, we test simplified melt parameterizations appropriate for ice sheet models and find the best agreement with those that incorporate ice tongue geometry in the form of depth and slope.

  12. Influence of Glacier Melting and River Discharges on the Nutrient Distribution and DIC Recycling in the Southern Chilean Patagonia

    NASA Astrophysics Data System (ADS)

    Vargas, Cristian A.; Cuevas, L. Antonio; Silva, Nelson; González, Humberto E.; De Pol-Holz, Ricardo; Narváez, Diego A.

    2018-01-01

    The Chilean Patagonia constitutes one of the most important and extensive fjord systems worldwide, therefore can be used as a natural laboratory to elucidate the pathway of both organic and inorganic matter in the receiving environment. In this study we use data collected during an intensive oceanographic cruise along the Magellan Strait into the Almirantazgo Fjord in southern Patagonia to evaluate how different sources of dissolved inorganic carbon (DIC) and recycling may impact particulate organic carbon (POC) δ13C and influence the nutrients and carbonate system spatial distribution. The carbonate system presented large spatial heterogeneity. The lowest total alkalinity and DIC were associated to freshwater dilution observed near melting glaciers. The δ13CDIC analysis suggests that most DIC in the upper 50 m depth was not derived from terrestrial organic matter remineralization. 13C-depleted riverine and ice-melting DIC influence the DIC pool along the study area, but due to that DIC concentration from rivers and glaciers is relatively low, atmospheric carbon contribution or biological processes seem to be more relevant. Intense undersaturation of CO2 was observed in high chlorophyll waters. Respired DIC coming from the bottom waters seems to be almost insignificant for the inorganic carbon pool and therefore do not impact significantly the stable carbon isotopic composition of dissolved organic carbon and POC in the upper 50 m depth. Considering the combined effect of cold and low alkalinity waters due to ice melting, our results highlight the importance of these processes in determining corrosive waters for CaCO3 and local acidification processes associated to calving glacier in fjord ecosystems.

  13. On the impact of ice-ocean interaction on Greenland glaciers versus calving speed.

    NASA Astrophysics Data System (ADS)

    Rignot, E. J.; Menemenlis, D.; Morlighem, M.; Wood, M.; Millan, R.; Mouginot, J.; An, L.

    2016-12-01

    Glacier retreat from frontal ablation is a delicate balance between subaqueous melt, calving processes and bed geometry. Here, we model subaqueous melt from a large number of Greenland tidewater glaciers using generalized 3D, high resolution simulations of ice melt from the MITgcm ocean model constrained by subglacial melt from RACMO2.3 and ISSM, ocean temperature from ECCO2-4km Arctic, and bed topography from OMG and MC for 1992-2015. The results are analyzed in combination with ice-front retreat and glacier speed from Landsat and imaging radar data since the 1990s. We find that subaqueous melt is 2-3 times greater in summer than in winter and doubled in magnitude since the 1990s because of enhanced ice sheet runoff and warmer ocean temperature. Glaciers that retreated rapidly are characterized by subaqueous melt rates comparable to their calving speed and favorable bed geometry. Glaciers dominated by calving processes are in contrast more resilient to thermal forcing from the ocean, especially in the presence of stabilizing geometry. The study highlights the fundamental importance of calving processes in controlling glacier retreat in Greenland.

  14. Modeling the Rock Glacier Cycle

    NASA Astrophysics Data System (ADS)

    Anderson, R. S.; Anderson, L. S.

    2016-12-01

    Rock glaciers are common in many mountain ranges in which the ELA lies above the peaks. They represent some of the most identifiable components of today's cryosphere in these settings. Their oversteepened snouts pose often-overlooked hazards to travel in alpine terrain. Rock glaciers are supported by avalanches and by rockfall from steep headwalls. The winter's avalanche cone must be sufficiently thick not to melt entirely in the summer. The spatial distribution of rock glaciers reflects this dependence on avalanche sources; they are most common on lee sides of ridges where wind-blown snow augments the avalanche source. In the absence of rockfall, this would support a short, cirque glacier. Depending on the relationship between rockfall and avalanche patterns, "talus-derived" and "glacier-derived" rock glaciers are possible. Talus-derived: If the spatial distribution of rock delivery is similar to the avalanche pattern, the rock-ice mixture will travel an englacial path that is downward through the short accumulation zone before turning upward in the ablation zone. Advected debris is then delivered to the base of a growing surface debris layer that reduces the ice melt rate. The physics is identical to the debris-covered glacier case. Glacier-derived: If on the other hand rockfall from the headwall rolls beyond the avalanche cone, it is added directly to the ablation zone of the glacier. The avalanche accumulation zone then supports a pure ice core to the rock glacier. We have developed numerical models designed to capture the full range of glacier to debris-covered glacier to rock glacier behavior. The hundreds of meter lengths, tens of meters thicknesses, and meter per year speeds of rock glaciers are well described by the models. The model can capture both "talus-derived" and "glacier-derived" rock glaciers. We explore the dependence of glacier behavior on climate histories. As climate warms, a pure ice debris-covered glacier can transform to a much shorter rock

  15. Release of PCBs from Silvretta glacier (Switzerland) investigated in lake sediments and meltwater.

    PubMed

    Pavlova, P A; Zennegg, M; Anselmetti, F S; Schmid, P; Bogdal, C; Steinlin, C; Jäggi, M; Schwikowski, M

    2016-06-01

    This study is part of our investigations about the release of persistent organic pollutants from melting Alpine glaciers and the relevance of the glaciers as secondary sources of legacy pollutants. Here, we studied the melt-related release of polychlorinated biphenyls (PCBs) in proglacial lakes and glacier streams of the catchment of the Silvretta glacier, located in the Swiss Alps. To explore a spatial and temporal distribution of chemicals in glacier melt, we combined two approaches: (1) analysing a sediment record as an archive of past remobilization and (2) passive water sampling to capture the current release of PCBs during melt period. In addition, we determined PCBs in a non-glacier-fed stream as a reference for the background pollutant level in the area. The PCBs in the sediment core from the Silvretta lake generally complied with trends of PCB emissions into the environment. Elevated concentrations during the most recent ten years, comparable in level with times of the highest atmospheric input, were attributed to accelerated melting of the glacier. This interpretation is supported by the detected PCB fractionation pattern towards heavier, less volatile congeners, and by increased activity concentrations of the radioactive tracer (137)Cs in this part of the sediment core. In contrast, PCB concentrations were not elevated in the stream water, since no significant difference between pollutant concentrations in the glacier-fed and the non-glacier-fed streams was detected. In stream water, no current decrease of the PCBs with distance from the glacier was observed. Thus, according to our data, an influence of PCBs release due to accelerated glacier melt was only detected in the proglacial lake, but not in the other compartments of the Silvretta catchment.

  16. A calving law for ice sheet models; Investigating the role of surface melt on dynamics of Greenland outlet glaciers

    NASA Astrophysics Data System (ADS)

    Nick, F. M.; van der Veen, C. J.; Vieli, A.

    2008-12-01

    alving of icebergs accounts for perhaps as much as half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. We have formulated a calving model that can be readily incorporated into time-evolving numerical ice-flow models. Our model is based on downward penetration of water-filled surface crevasses and upward propagation of basal crevasses. A calving event occurs when the depth of the surface crevasse (which increases as melting progresses through the summer) reaches the height of the basal crevasse. Our numerical ice sheet model is able to reproduce observed seasonal changes of Greenland outlet glaciers, such as fluctuations in flow speed and terminus positions. We have applied the model to Helheim Glacier on the east coast, and Petermann Glacier in the northwest. Our model suggests that rapid retreat of the claving front is highly affected by the amplified calving rate due to increasing water level in surface crevasses during warmer summers. Our results show little response to seasonally enhanced basal lubrication from surface melt. This modeling study provides insights into the role of surface and basal hydrology to ice sheet dynamics and on how to incorporate calving in ice sheet models and therefore advances our ability to predict future ice sheet change.

  17. Exploring the mobility of cryoconite on High-Arctic glaciers

    NASA Astrophysics Data System (ADS)

    Irvine-Fynn, T. D.; Hodson, A. J.; Bridge, J. W.; Langford, H.; Anesio, A.; Ohlanders, N.; Newton, S.

    2010-12-01

    There has been a growing awareness of the significance of biologically active dust (cryoconite) on the energy balance of, and nutrient cycling at glacier surfaces. Moreover, researchers have estimated the mass of biological material released from glacier ice to downstream environments and ecosystems, including the melt-out of cells from emergent ice in the ablation area. However, the processes, rates and mechanisms of cryoconite mobility and transport have not been fully explored. For many smaller valley glaciers in the High-Arctic, the climate dictates only a thin (~ 1m) layer of ice at the glacier surface is at the melting point during the summer months. This surface ice is commonly characterized by an increased porosity in response to incident energy and hydraulic conditions, and has been termed the “weathering crust”. The presence of cryoconite, with its higher radiation absorption, exacerbates the weathering crust development. Thus, crucially, the transport of cryoconite is not confined to simply a ‘smooth’ ice surface, but rather also includes mobility in the near-surface ice matrix. Here, we present initial results from investigations of cryoconite transport at Midtre Lovénbreen and Longyearbreen, two north-facing valley glaciers in Svalbard (Norway). Using time-lapse imagery, we explore the transport rates of cryoconite on a glacier surface and consider the associations between mobility and meteorological conditions. Results suggest some disparity between micro-, local- and plot-scale observations of cryoconite transport: the differences imply controlling influences of cryoconite volume, ice surface topography and ice structure. While to examine the relative volumes of cryoconite exported from the glacier surface by supraglacial streams we employ flow cytometry, using SYBR-Green-II staining to identify the biological component of the suspended load. Preliminary comparisons between shallow (1m) ice cores and in-stream concentrations suggest

  18. Isotopic composition of ice cores and meltwater from upper fremont glacier and Galena Creek rock glacier, Wyoming

    USGS Publications Warehouse

    DeWayne, Cecil L.; Green, J.R.; Vogt, S.; Michel, R.; Cottrell, G.

    1998-01-01

    Meltwater runoff from glaciers can result from various sources, including recent precipitation and melted glacial ice. Determining the origin of the meltwater from glaciers through isotopic analysis can provide information about such things as the character and distribution of ablation on glaciers. A 9.4 m ice core and meltwater were collected in 1995 and 1996 at the glacigenic Galena Creek rock glacier in Wyoming's Absaroka Mountains. Measurements of chlorine-36 (36Cl), tritium (3H), sulphur-35 (35S), and delta oxygen-18 (??18O) were compared to similar measurements from an ice core taken from the Upper Fremont Glacier in the Wind River Range of Wyoming collected in 1991-95. Meltwater samples from three sites on the rock glacier yielded 36Cl concentrations that ranged from 2.1 ?? 1.0 X 106 to 5.8??0.3 X 106 atoms/l. The ice-core 36Cl concentrations from Galena Creek ranged from 3.4??0.3 X 105 to 1.0??0.1 X 106 atoms/l. Analysis of an ice core from the Upper Fremont Glacier yielded 36Cl concentrations of 1.2??0.2 X 106 and 5.2??0.2 X 106 atoms/l for pre- 1940 ice and between 2 X 106 and 3 X 106 atoms/l for post-1980 ice. Purdue's PRIME Lab analyzed the ice from the Upper Fremont Glacier. The highest concentration of 36Cl in the ice was 77 ?? 2 X 106 atoms/l and was deposited during the peak of atmospheric nuclear weapons testing in the late 1950s. This is an order of magnitude greater than the largest measured concentration from both the Upper Fremont Glacier ice core that was not affected by weapons testing fallout and the ice core collected from the Galena Creek rock glacier. Tritium concentrations from the rock glacier ranged from 9.2??0.6 to 13.2??0.8 tritium units (TU) in the meltwater to -1.3??1.3 TU in the ice core. Concentrations of 3H in the Upper Fremont Glacier ice core ranged from 0 TU in the ice older than 50 years to 6-12 TU in the ice deposited in the last 10 years. The maximum 3H concentration in ice from the Upper Fremont Glacier deposited in the

  19. Glacier melt buffers river runoff in the Pamir Mountains

    NASA Astrophysics Data System (ADS)

    Pohl, Eric; Gloaguen, Richard; Andermann, Christoff; Knoche, Malte

    2017-03-01

    Newly developed approaches based on satellite altimetry and gravity measurements provide promising results on glacier dynamics in the Pamir-Himalaya but cannot resolve short-term natural variability at regional and finer scale. We contribute to the ongoing debate by upscaling a hydrological model that we calibrated for the central Pamir. The model resolves the spatiotemporal variability in runoff over the entire catchment domain with high efficiency. We provide relevant information about individual components of the hydrological cycle and quantify short-term hydrological variability. For validation, we compare the modeled total water storages (TWS) with GRACE (Gravity Recovery and Climate Experiment) data with a very good agreement where GRACE uncertainties are low. The approach exemplifies the potential of GRACE for validating even regional scale hydrological applications in remote and hard to access mountain regions. We use modeled time series of individual hydrological components to characterize the effect of climate variability on the hydrological cycle. We demonstrate that glaciers play a twofold role by providing roughly 35% of the annual runoff of the Panj River basin and by effectively buffering runoff both during very wet and very dry years. The modeled glacier mass balance (GMB) of -0.52 m w.e. yr-1 (2002-2013) for the entire catchment suggests significant reduction of most Pamiri glaciers by the end of this century. The loss of glaciers and their buffer functionality in wet and dry years could not only result in reduced water availability and increase the regional instability, but also increase flood and drought hazards.Plain Language Summary<span class="hlt">Glaciers</span> store large amounts of water in the form of ice. They grow and shrink dominantly in response to climatic conditions. In Central Asia, where rivers originate in the high mountains, <span class="hlt">glaciers</span> are an important source for sustainable water availability. Thus</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B54B..05H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B54B..05H"><span>Differences in dissolved organic matter lability between alpine <span class="hlt">glaciers</span> and alpine rock <span class="hlt">glaciers</span> of the American West</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hall, E.; Fegel, T. S., II; Baron, J.; Boot, C. M.</p> <p>2015-12-01</p> <p>While alpine <span class="hlt">glaciers</span> in montane regions represent the largest flux of dissolved organic matter (DOM) from global ice <span class="hlt">melt</span> no research has examined the bioavailability of DOM <span class="hlt">melted</span> out of glacial ice in the western continental United States. Furthermore, rock <span class="hlt">glaciers</span> are an order of magnitude more abundant than ice <span class="hlt">glaciers</span> in U.S., yet are not included in budgets for perennial ice carbon stores. Our research aims to understand differences in the bioavailability of carbon from ice <span class="hlt">glaciers</span> and rock <span class="hlt">glaciers</span> along the Central Rocky Mountains of Colorado. Identical microbial communities were fed standardized amounts of DOM from four different ice <span class="hlt">glacier</span>-rock <span class="hlt">glaciers</span> pairs. Using laboratory incubations, paired with mass spectrometry based metabolomics and 16S gene sequencing; we were able to examine functional definitions of DOM lability in glacial ice. We hypothesized that even though DOM quantities are similar in the outputs of both glacial types in our study area, ice glacial DOM would be more bioavailable than DOM from rock <span class="hlt">glaciers</span> due to higher proportions of byproducts from microbial metabolism than rock <span class="hlt">glacier</span> DOM, which has higher amounts of "recalcitrant" plant material. Our results show that DOM from ice <span class="hlt">glaciers</span> is more labile than DOM from geologically and geographically similar paired rock <span class="hlt">glaciers</span>. Ice <span class="hlt">glacier</span> DOM represents an important pool of labile carbon to headwater ecosystems of the Rocky Mountains. Metabolomic analysis shows numerous compounds from varying metabolite pathways, including byproducts of nitrification before and after incubation, meaning that, similar to large maritime <span class="hlt">glaciers</span> in Alaska and Europe, subglacial environments in the mountain ranges of the United States are hotspots for biological activity and processing of organic carbon.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28163355','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28163355"><span>An enhanced temperature index model for debris-covered <span class="hlt">glaciers</span> accounting for thickness effect.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Carenzo, M; Pellicciotti, F; Mabillard, J; Reid, T; Brock, B W</p> <p>2016-08-01</p> <p>Debris-covered <span class="hlt">glaciers</span> are increasingly studied because it is assumed that debris cover extent and thickness could increase in a warming climate, with more regular rockfalls from the surrounding slopes and more englacial <span class="hlt">melt</span>-out material. Debris energy-balance models have been developed to account for the <span class="hlt">melt</span> rate enhancement/reduction due to a thin/thick debris layer, respectively. However, such models require a large amount of input data that are not often available, especially in remote mountain areas such as the Himalaya, and can be difficult to extrapolate. Due to their lower data requirements, empirical models have been used extensively in clean <span class="hlt">glacier</span> <span class="hlt">melt</span> modelling. For debris-covered <span class="hlt">glaciers</span>, however, they generally simplify the debris effect by using a single <span class="hlt">melt</span>-reduction factor which does not account for the influence of varying debris thickness on <span class="hlt">melt</span> and prescribe a constant reduction for the entire <span class="hlt">melt</span> across a <span class="hlt">glacier</span>. In this paper, we present a new temperature-index model that accounts for debris thickness in the computation of <span class="hlt">melt</span> rates at the debris-ice interface. The model empirical parameters are optimized at the point scale for varying debris thicknesses against <span class="hlt">melt</span> rates simulated by a physically-based debris energy balance model. The latter is validated against ablation stake readings and surface temperature measurements. Each parameter is then related to a plausible set of debris thickness values to provide a general and transferable parameterization. We develop the model on Miage <span class="hlt">Glacier</span>, Italy, and then test its transferability on Haut <span class="hlt">Glacier</span> d'Arolla, Switzerland. The performance of the new debris temperature-index (DETI) model in simulating the <span class="hlt">glacier</span> <span class="hlt">melt</span> rate at the point scale is comparable to the one of the physically based approach, and the definition of model parameters as a function of debris thickness allows the simulation of the nonlinear relationship of <span class="hlt">melt</span> rate to debris thickness, summarised by the </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AdWR...94..457C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AdWR...94..457C"><span>An enhanced temperature index model for debris-covered <span class="hlt">glaciers</span> accounting for thickness effect</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carenzo, M.; Pellicciotti, F.; Mabillard, J.; Reid, T.; Brock, B. W.</p> <p>2016-08-01</p> <p>Debris-covered <span class="hlt">glaciers</span> are increasingly studied because it is assumed that debris cover extent and thickness could increase in a warming climate, with more regular rockfalls from the surrounding slopes and more englacial <span class="hlt">melt</span>-out material. Debris energy-balance models have been developed to account for the <span class="hlt">melt</span> rate enhancement/reduction due to a thin/thick debris layer, respectively. However, such models require a large amount of input data that are not often available, especially in remote mountain areas such as the Himalaya, and can be difficult to extrapolate. Due to their lower data requirements, empirical models have been used extensively in clean <span class="hlt">glacier</span> <span class="hlt">melt</span> modelling. For debris-covered <span class="hlt">glaciers</span>, however, they generally simplify the debris effect by using a single <span class="hlt">melt</span>-reduction factor which does not account for the influence of varying debris thickness on <span class="hlt">melt</span> and prescribe a constant reduction for the entire <span class="hlt">melt</span> across a <span class="hlt">glacier</span>. In this paper, we present a new temperature-index model that accounts for debris thickness in the computation of <span class="hlt">melt</span> rates at the debris-ice interface. The model empirical parameters are optimized at the point scale for varying debris thicknesses against <span class="hlt">melt</span> rates simulated by a physically-based debris energy balance model. The latter is validated against ablation stake readings and surface temperature measurements. Each parameter is then related to a plausible set of debris thickness values to provide a general and transferable parameterization. We develop the model on Miage <span class="hlt">Glacier</span>, Italy, and then test its transferability on Haut <span class="hlt">Glacier</span> d'Arolla, Switzerland. The performance of the new debris temperature-index (DETI) model in simulating the <span class="hlt">glacier</span> <span class="hlt">melt</span> rate at the point scale is comparable to the one of the physically based approach, and the definition of model parameters as a function of debris thickness allows the simulation of the nonlinear relationship of <span class="hlt">melt</span> rate to debris thickness, summarised by the </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9654D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9654D"><span>Mountain <span class="hlt">glaciers</span> darkening: geochemical characterizazion of cryoconites and their <span class="hlt">radiative</span> impact on the Vadret da Morteratsch (Swiss Alps)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di Mauro, Biagio; Baccolo, Giovanni; Garzonio, Roberto; Piazzalunga, Andrea; Massabò, Dario; Colombo, Roberto</p> <p>2016-04-01</p> <p>Mountain <span class="hlt">glaciers</span> represent an important source of fresh water across the globe. It is well known that these reservoirs are seriously threatened by global climate change, and a widespread reduction of <span class="hlt">glacier</span> extension has been observed in recent years. Surface processes that promote ice <span class="hlt">melting</span> are driven both by air temperature/precipitation and surface albedo. This latter is mainly influenced by the growth of snow grains and by the impurities content (such as mineral dust, soot, ash etc.). The origin of these light-absorbing impurities can be local or distal, and often, as a consequence of <span class="hlt">melting</span> processes, they can aggregate on the <span class="hlt">glacier</span> tongue, forming characteristics cryoconites, that decrease ice albedo and hence promote the <span class="hlt">melting</span>. In this contribution, we coupled satellite images (EO1 - Hyperion and Landsat 8 - OLI) and ground hyperspectral data (ASD field spectrometer) for characterizing ice and snow surface reflectance of the Vadret da Morteratsch <span class="hlt">glacier</span> (Swiss Alps). On the <span class="hlt">glacier</span> ablation zone, we sampled ice, snow, surface dust and cryoconite material. To evaluate the possible impact of anthropogenic and natural emissions on cryoconites formation, we determined their geochemical composition (through the Neutron Activation Analysis, NAA) and the concentration of Black Carbon (BC), Organic Carbon (OC), Elemental Carbon (EC) and Levoglucosan. From satellite data, we computed the Snow Darkening Index (SDI), which is non-linearly correlated with dust content in snow. Results showed that, during 2015 summer season, ice albedo in the ablation zone reached very low values of about 0.1-0.2. The darkening of the <span class="hlt">glacier</span> can be attributed to the impact of surface dust (from lateral moraine and Saharan desert) and cryoconites, coupled with grain growth driven by the extremely warm 2015 summer. The geochemical characterization of non-ice material contained in the cryoconites can provide important information regarding their source and the possible impact of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915651L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915651L"><span>Algal communities in cryoconite holes on the Russell <span class="hlt">glacier</span>, Southwest Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lamsters, Kristaps; Stivrins, Normunds; Karušs, Jānis; Krievāns, Māris; Rečs, Agnis</p> <p>2017-04-01</p> <p>The surface of the Greenland Ice Sheet in ablation zone has considerably darkened in the last decades, thus absorbing more solar <span class="hlt">radiation</span> and accelerating ice <span class="hlt">melting</span>. Darkening of <span class="hlt">glacier</span> is made of different impurities that reduce surface albedo. These impurities are represented as cryoconite - combination of dust, soot and microorganisms. While mineral dust composes the greatest part of cryoconite, the black carbon is the most solar <span class="hlt">radiation</span> absorbing constituent. Microorganisms on the ice are concentrated in cryoconite holes, which have long been of scientific interest, but still remain poorly understood. In order to investigate the microbial communities in cryoconite holes, we collected 12 samples from cryoconite holes at 6 sites located on a 2.5 km long transect line on Russell <span class="hlt">glacier</span>, Southwest Greenland. The first sampling site was set 3 km from <span class="hlt">glacier</span> margin at 552 m a.s.l. and the last sampling site was 500 m from the <span class="hlt">glacier</span> margin at 423 m a.s.l. Depth and diameter of each cryoconite hole, as well as pH, temperature and electrical conductivity was measured in situ on July 29, 2017. During microscopic analysis all microcharcoal (10-100 µm), spheroidal carbonaceous particles (soot), pollen, spores and algae were recorded. Principal Component Analysis reveal two clusters of cryoconite holes (located at 423-465 m a.s.l. and 465-552 m a.s.l.) indicating altitudinal differences. Further, our results show that the biomass of green algae Mesotaeniaceae is correlated with temperature. Meanwhile green algae Chlamydomonadaceae correlates with temperature, microcharcoal and soot particle abundance. Our results show that green algae are dominant type of microorganisms inhabiting cryconite holes on the Russell's <span class="hlt">glacier</span> at least up to distance of 3 km from ice margin. It is contrary to the previous study of Uetake et al. (2010), who found that cyanobacterial (Oscillatoriaceae) community dominated at 510-635 m altitude of the ablation area of Russell <span class="hlt">glacier</span> in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12..565E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12..565E"><span>Greenland iceberg <span class="hlt">melt</span> variability from high-resolution satellite observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Enderlin, Ellyn M.; Carrigan, Caroline J.; Kochtitzky, William H.; Cuadros, Alexandra; Moon, Twila; Hamilton, Gordon S.</p> <p>2018-02-01</p> <p>Iceberg discharge from the Greenland Ice Sheet accounts for up to half of the freshwater flux to surrounding fjords and ocean basins, yet the spatial distribution of iceberg meltwater fluxes is poorly understood. One of the primary limitations for mapping iceberg meltwater fluxes, and changes over time, is the dearth of iceberg submarine <span class="hlt">melt</span> rate estimates. Here we use a remote sensing approach to estimate submarine <span class="hlt">melt</span> rates during 2011-2016 for 637 icebergs discharged from seven marine-terminating <span class="hlt">glaciers</span> fringing the Greenland Ice Sheet. We find that spatial variations in iceberg <span class="hlt">melt</span> rates generally follow expected patterns based on hydrographic observations, including a decrease in <span class="hlt">melt</span> rate with latitude and an increase in <span class="hlt">melt</span> rate with iceberg draft. However, we find no longitudinal variations in <span class="hlt">melt</span> rates within individual fjords. We do not resolve coherent seasonal to interannual patterns in <span class="hlt">melt</span> rates across all study sites, though we attribute a 4-fold <span class="hlt">melt</span> rate increase from March to April 2011 near Jakobshavn Isbræ to fjord circulation changes <span class="hlt">induced</span> by the seasonal onset of iceberg calving. Overall, our results suggest that remotely sensed iceberg <span class="hlt">melt</span> rates can be used to characterize spatial and temporal variations in oceanic forcing near often inaccessible marine-terminating <span class="hlt">glaciers</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C12B..02N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C12B..02N"><span>Investigating role of ice-ocean interaction on <span class="hlt">glacier</span> dynamic: Results from numerical modeling applied to Petermann <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nick, F. M.; van der Veen, C. J.; Vieli, A.; Pattyn, F.; Hubbard, A.; Box, J. E.</p> <p>2010-12-01</p> <p>Calving of icebergs and bottom <span class="hlt">melting</span> from ice shelves accounts for roughly half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. Petermann <span class="hlt">Glacier</span> (north Greenland) with its ~17 km wide and ~ 60 km long floating ice-shelf is experiencing high rates of bottom <span class="hlt">melting</span>. The recent partial disintegration of its shelf (in August 2010) presents a natural experiment to investigate the dynamic response of the ice sheet to its shelf retreat. We apply a numerical ice flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as shelf disintegration, bottom <span class="hlt">melting</span>, sea ice or sikkusak disintegration and surface run off to the mass balance of Petermann <span class="hlt">Glacier</span> and assess its stability. Our modeling study provides insights into the role of ice-ocean interaction, and on response of Petermann <span class="hlt">Glacier</span> to its recent massive ice loss.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B41E0115M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B41E0115M"><span>Experimental evidence that microbial activity lowers the albedo of <span class="hlt">glacier</span> surfaces: the cryoconite casserole experiment.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Musilova, M.; Tranter, M.; Takeuchi, N.; Anesio, A. M.</p> <p>2014-12-01</p> <p>Darkened <span class="hlt">glacier</span> and ice sheet surfaces have lower albedos, absorb more solar <span class="hlt">radiation</span> and consequently <span class="hlt">melt</span> more rapidly. The increase in <span class="hlt">glacier</span> surface darkening is an important positive feedback to warming global temperatures, leading to ever growing world-wide ice mass loss. Most studies focus primarily on glacial albedo darkening caused by the physical properties of snow and ice surfaces, and the deposition of dark impurities on <span class="hlt">glaciers</span>. To date, however, the important effects of biological activity have not been included in most albedo reduction models. This study provides the first experimental evidence that microbial activity can significantly decrease the albedo of <span class="hlt">glacier</span> surfaces. An original laboratory experiment, the cryoconite casserole, was designed to test the microbial darkening of <span class="hlt">glacier</span> surface debris (cryoconite) under simulated Greenlandic summer conditions. It was found that minor fertilisation of the cryoconite (at nutrient concentrations typical of glacial ice <span class="hlt">melt</span>) stimulated extensive microbial activity. Microbes intensified their organic carbon fixation and even mined phosphorous out of the <span class="hlt">glacier</span> surface sediment. Furthermore, the microbial organic carbon production, accumulation and transformation caused the glacial debris to darken further by 17.3% reflectivity (albedo analogue). These experiments are consistent with the hypothesis that enhanced fertilisation by anthropogenic inputs results in substantial amounts of organic carbon fixation, debris darkening and ultimately to a considerable decrease in the ice albedo of <span class="hlt">glacier</span> surfaces on global scales. The sizeable amounts of microbially produced <span class="hlt">glacier</span> surface organic matter and nutrients can thus be a vital source of bioavailable nutrients for subglacial and downstream environments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT........62Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT........62Z"><span>Recent <span class="hlt">glacier</span> surface snowpack <span class="hlt">melt</span> in Novaya Zemlya and Severnaya Zemlya derived from active and passive microwave remote sensing data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Meng</p> <p></p> <p>The warming rate in the Russian High Arctic (RHA) (36˜158°E, 73˜82°N) is outpacing the pan-Arctic average, and its effect on the small <span class="hlt">glaciers</span> across this region needs further examination. The temporal variation and spatial distribution of surface <span class="hlt">melt</span> onset date (MOD) and total <span class="hlt">melt</span> days (TMD) throughout the Novaya Zemlya (NovZ) and Severnaya Zemlya (SevZ) archipelagoes serve as good indicators of ice mass ablation and <span class="hlt">glacier</span> response to regional climate change in the RHA. However, due to the harsh environment, long-term glaciological observations are limited, necessitating the application of remotely sensed data to study the surface <span class="hlt">melt</span> dynamics. The high sensitivity to liquid water and the ability to work without solar illumination and penetrate non-precipitating clouds make microwave remote sensing an ideal tool to detect <span class="hlt">melt</span> in this region. This work extracts resolution-enhanced passive and active microwave data from different periods and retrieves a decadal <span class="hlt">melt</span> record for NovZ and SevZ. The high correlation among passive and active data sets instills confidence in the results. The mean MOD is June 20th on SevZ and June 10th on NovZ during the period of 1992-2012. The average TMDs are 47 and 67 days on SevZ and NovZ from 1995 to 2011, respectively. NovZ had large interannual variability in the MOD, but its TMD generally increased. SevZ MOD is found to be positively correlated to local June reanalysis air temperature at 850hPa geopotential height and occurs significantly earlier (˜0.73 days/year, p-value < 0.01) from 1992 to 2011. SevZ also experienced a longer TMD trend (˜0.75 days/year, p-value < 0.05) from 1995 to 2011. Annual mean TMD on both islands are positively correlated with regional summer mean reanalysis air temperature and negatively correlated to local sea ice extent. These strong correlations might suggest that the Russian High Arctic <span class="hlt">glaciers</span> are vulnerable to the continuously diminishing sea ice extent, the associated air temperature</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70020269','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70020269"><span>The geochemical record in rock <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Steig, E.J.; Fitzpatrick, J.J.; Potter, N.; Clark, D.H.</p> <p>1998-01-01</p> <p>A 9.5 m ice core was extracted from beneath the surficial debris cover of a rock <span class="hlt">glacier</span> at Galena Creek, northwestern Wyoming. The core contains clean, bubble-rich ice with silty debris layers spaced at roughly 20 cm intervals. The debris layers are similar in appearance to those in typical alpine <span class="hlt">glaciers</span>, reflecting concentration of debris by <span class="hlt">melting</span> at the surface during the summer ablation season. Profiles of stable isotope concentrations and electrical conductivity measurements provide independent evidence for <span class="hlt">melting</span> in association with debris layers. These observations are consistent with a glacial origin for the ice, substantiating the glacigenic model for rock <span class="hlt">glacier</span> formation. The deuterium excess profile in the ice indicates that the total depth of meltwater infiltration is less than the thickness of one annual layer, suggesting that isotope values and other geochemical signatures are preserved at annual resolution. This finding demonstrates the potential for obtaining useful paleoclimate information from rock <span class="hlt">glacier</span> ice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C13D0859R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C13D0859R"><span><span class="hlt">Glacier</span> <span class="hlt">Melt</span> Detection in Complex Terrain Using New AMSR-E Calibrated Enhanced Daily EASE-Grid 2.0 Brightness Temperature (CETB) Earth System Data Record</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramage, J. M.; Brodzik, M. J.; Hardman, M.</p> <p>2016-12-01</p> <p>Passive microwave (PM) 18 GHz and 36 GHz horizontally- and vertically-polarized brightness temperatures (Tb) channels from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) have been important sources of information about snow <span class="hlt">melt</span> status in glacial environments, particularly at high latitudes. PM data are sensitive to the changes in near-surface liquid water that accompany <span class="hlt">melt</span> onset, <span class="hlt">melt</span> intensification, and refreezing. Overpasses are frequent enough that in most areas multiple (2-8) observations per day are possible, yielding the potential for determining the dynamic state of the snow pack during transition seasons. AMSR-E Tb data have been used effectively to determine <span class="hlt">melt</span> onset and <span class="hlt">melt</span> intensification using daily Tb and diurnal amplitude variation (DAV) thresholds. Due to mixed pixels in historically coarse spatial resolution Tb data, <span class="hlt">melt</span> analysis has been impractical in ice-marginal zones where pixels may be only fractionally snow/ice covered, and in areas where the <span class="hlt">glacier</span> is near large bodies of water: even small regions of open water in a pixel severely impact the microwave signal. We use the new enhanced-resolution Calibrated Passive Microwave Daily EASE-Grid 2.0 Brightness Temperature (CETB) Earth System Data Record product's twice daily obserations to test and update existing snow <span class="hlt">melt</span> algorithms by determining appropriate <span class="hlt">melt</span> thresholds for both Tb and DAV for the CETB 18 and 36 GHz channels. We use the enhanced resolution data to evaluate <span class="hlt">melt</span> characteristics along <span class="hlt">glacier</span> margins and <span class="hlt">melt</span> transition zones during the <span class="hlt">melt</span> seasons in locations spanning a wide range of <span class="hlt">melt</span> scenarios, including the Patagonian Andes, the Alaskan Coast Range, and the Russian High Arctic icecaps. We quantify how improvement of spatial resolution from the original 12.5 - 25 km-scale pixels to the enhanced resolution of 3.125 - 6.25 km improves the ability to evaluate <span class="hlt">melt</span> timing across boundaries and transition zones in diverse glacial environments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33D1226P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33D1226P"><span>What controls the survival of ice cliffs on debris-covered <span class="hlt">glaciers</span>? An investigation into the aspect-dependent evolution of supraglacial cliffs in the Nepalese Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pellicciotti, F.; Buri, P.</p> <p>2017-12-01</p> <p>Supraglacial ice cliffs exist on debris-covered <span class="hlt">glaciers</span> worldwide, but despite increasing evidence of their important role in the surface <span class="hlt">melt</span> of debris-covered <span class="hlt">glaciers</span>, their role and importance at the <span class="hlt">glacier</span> scale is still little understood. Acting as windows of energy transfer through the debris, they can contribute to very large <span class="hlt">glacier</span> mass losses. Their abundance and life cycle might thus explain the anomalous behavior of much higher than expected mass losses of the debris-covered <span class="hlt">glaciers</span> of High Mountain Asia, a controversial finding of recent research in a region where <span class="hlt">glaciers</span> are highly relevant as water sources for millions of people downstream. Cliffs' evolution in time and distribution in space will determine their total contribution to the mass balance of <span class="hlt">glaciers</span>, but while spatial distribution has been recently inferred from remote sensing studies, their temporal evolution is largely unknown. Here, we make use of recent advancements in our ability to model these complex features and use a novel 3D numerical model of cliff backwasting and very high resolution topographic data to show that supraglacial ice cliffs existence is controlled by aspect. Because of lack of observed south-facing cliffs, we rotate north-facing cliff systems observed in high detail over the debris-covered Lirung <span class="hlt">glacier</span>, in the Nepalese Himalaya, towards southerly aspects and use the model coupled to the very high resolution topography to simulate the continuous evolution of selected cliffs over one <span class="hlt">melt</span> season. Cliffs facing south (in the Northern Hemisphere) do not survive the duration of an ablation season and disappear within few weeks to few months due to very strong solar <span class="hlt">radiation</span> receipts. Our model shows a progressive, continuous flattening of southerly facing cliffs, which is a result of their vertical gradient of incoming solar <span class="hlt">radiation</span>. We also show that there is a clear range of aspects (northwest to northeast) that allows cliff survival because of energy and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2840S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2840S"><span>Tracer and hydrometric techniques to determine the contribution of <span class="hlt">glacier</span> <span class="hlt">melt</span> to a proglacial stream in the Ötztal Alps (Tyrol, Austria)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmieder, Jan; Marke, Thomas; Strasser, Ulrich</p> <p>2016-04-01</p> <p><span class="hlt">Glaciers</span> are important seasonal water contributors in many mountainous landscapes. For water resources management it is important to know about the timing and amount of released <span class="hlt">glacier</span> <span class="hlt">melt</span> water, especially in downstream regions where the water is needed (hydropower, drinking water) or where it represents a potential risk (drought, flood). Seasonal availability of <span class="hlt">melt</span> water is strongly dependent on boundary layer atmospheric processes and becomes even more relevant in a changing climate. Environmental tracers are a useful tool in the assessment of snow and ice water resources, because they provide information about the sources, flow paths and traveling times of water contributing to streamflow at the catchment scale. Previously, high-elevation tracer studies throughout the Alps have been scarce as they require intense field work in remote areas. However, hydrometric and meteorological measurements combined with tracer analyses help to unravel streamflow composition and improve the understanding of hydroclimatological processes. On top of that, empirical studies are necessary to parameterize and validate hydrological models in more process-oriented ways, rather than comparing total measured and simulated runoff only. In the present study three approaches are applied to derive <span class="hlt">glacier</span> <span class="hlt">melt</span> contributions to a proglacial stream at the seasonal scale and to identify their individual advances and limitations. Tracers used for each approach are (1) electrical conductivity, (2) stable isotopes of water and (3) heavy metals. The field work was conducted during the summer of 2015 in the glaciated (35%) high-elevation catchment of the Hochjochbach, a small sub-basin (17 km²) of the Ötztaler Ache river in the Austrian Alps, ranging from 2400 to 3500 m.a.s.l. in elevation. Hydroclimatological data was provided by an automatic weather station and a gauging station equipped with a pressure transducer. Water samples from shallow groundwater, streamflow, <span class="hlt">glacier</span> and snow <span class="hlt">melt</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27363134','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27363134"><span>[Mercury Transport from <span class="hlt">Glacier</span> to Runoff in Typical Inland Glacial Area in the Tibetan Plateau].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Xue-jun; Wang, Kang; Guo, Jun-ming; Kang, Shi-chang; Zhang, Guo-shuai; Huang, Jie; Cong, Zhi-yuan; Zhang, Qiang-gong</p> <p>2016-02-15</p> <p>To investigate the transport of mercury from <span class="hlt">glacier</span> to runoff in typical inland glacial area in the Tibetan Plateau, we selected Zhadang <span class="hlt">glacier</span> and Qugaqie river Basin located in the Nyainqentanglha Range region and collected samples from snow pit, <span class="hlt">glacier</span> <span class="hlt">melt</span>-water and Qugaqie river water during 15th August to 9'h September 2011. Mercury speciation and concentrations were determined and their distribution and controlling factors in different environmental compartments were analyzed. The results showed that the average THg concentrations were (3.79 +/- 5.12) ng x L(-1), (1.06 +/- 0.77) ng x L(-1) and (1.02 +/- 0.24) ng x L(-1) for <span class="hlt">glacier</span> snow, <span class="hlt">glacier</span> <span class="hlt">melt</span>-water and Qugaqie river water, respectively, all of which were at the global background levels. Particulate-bound mercury accounted for large proportion of mercury in all environmental matrices, while mercury in glacial <span class="hlt">melt</span>-water was controlled by total suspended particle, and mercury in Qugaqie river water co-varied with runoff. With the increase of temperature, <span class="hlt">glacier</span> <span class="hlt">melted</span> and released water as well as mercury into <span class="hlt">glacier</span>-fed river. Total mercury concentrations in <span class="hlt">glacier</span> <span class="hlt">melt</span> water, upstream and downstream peaked at 14:00, 16:00 and after 20:00, respectively, reflecting the process of mercury release from <span class="hlt">glacier</span> and its subsequent transport in the <span class="hlt">glacier</span> fed river. The transport of riverine mercury was controlled by multiple factors. Under the context of climate change, <span class="hlt">glacier</span> ablation and the increasing runoff will play increasingly important roles in mercury release and transport.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-GSFC_20171208_Archive_e001479.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-GSFC_20171208_Archive_e001479.html"><span><span class="hlt">Glaciers</span> and Sea Level Rise</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-08</p> <p>This ice cave in Belcher <span class="hlt">Glacier</span> (Devon Island, Canada) was formed by <span class="hlt">melt</span> water flowing within the <span class="hlt">glacier</span> ice. To learn about the contributions of <span class="hlt">glaciers</span> to sea level rise, visit: www.nasa.gov/topics/earth/features/<span class="hlt">glacier</span>-sea-rise.html Credit: Angus Duncan, University of Saskatchewan NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC53C0912D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC53C0912D"><span>Fate of <span class="hlt">Glaciers</span> in the Tibetan Plateau by 2100</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duan, K.</p> <p>2017-12-01</p> <p>As the third polar on the Earth, the Tibetan plateau holds more than 40,000 <span class="hlt">glaciers</span> which have experienced a rapid retreat in recent decades. The variability of equilibrium line altitude (ELA) indicates expansion and wastage of <span class="hlt">glacier</span> directly. Here we simulated the ELA variability in the Tibetan Plateau based on a full surface energy and mass balance model. The simulation results are agreement with the observations. The ELAs have risen at a rate of 2-8m/a since 1970 throughout the Plateau, especially in the eastern Plateau where the ELAs have risen to or over the top altitude of <span class="hlt">glacier</span>, indicating the <span class="hlt">glaciers</span> are accelerating to <span class="hlt">melting</span> over there. Two <span class="hlt">glaciers</span>, XD <span class="hlt">glacier</span> in the center of the Plateau and Qiyi <span class="hlt">glacier</span> in the Qilian Mountain, are chosen to simulate its future ELA variability in the scenarios of RCP2.6, RCP4.5 and RCP 8.5 given by IPCC. The results show the ELAs will arrive to its maximum in around 2040 in RCP2.6, while the ELAs will be over the top altitude of <span class="hlt">glaciers</span> in 2035-2045 in RCP4.5 and RCP8.5, suggesting the <span class="hlt">glaciers</span> in the eastern Plateau will be <span class="hlt">melting</span> until the disappear of the <span class="hlt">glaciers</span> by the end of 2100.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992AIPC..277...61P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992AIPC..277...61P"><span>Changes in water supply in Alpine regions due to <span class="hlt">glacier</span> retreat</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pelto, Mauri S.</p> <p>1992-06-01</p> <p>In the late 1970s global temperature rose abruptly, and between 1977 and 1990 has averaged 0.4 °C above the 1940-76 mean. In 1980, 50% of the the alpine <span class="hlt">glaciers</span> observed in the Swiss Alps, Peruvian Andes, Norwegian Coast Range, Northern Caucasus and Washington's North Cascades were advancing. By 1990 in response to the warming only 15% were still advancing. During the peak non-<span class="hlt">glacier</span> snow <span class="hlt">melt</span> period <span class="hlt">glaciers</span> are unsaturated aquifers soaking up and holding meltwater for the first two-six weeks of the <span class="hlt">melt</span> season. This storage acts as a buffer for spring snow <span class="hlt">melt</span> flooding, and spreads the peak spring flow over a longer period. In the late summer <span class="hlt">glaciers</span> buffer low flow periods by providing large volumes of meltwater. As <span class="hlt">glaciers</span> retreat the amount of water they can store decreases raising spring flood danger and the areal extend exposed for late summer meltwater generation decreases, thus reducing late summer flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/circ/1981/0850d/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/circ/1981/0850d/report.pdf"><span>Effects of volcanism on the <span class="hlt">glaciers</span> of Mount St. Helens</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Brugman, Melinda M.; Post, Austin</p> <p>1981-01-01</p> <p>The cataclysmic eruption of Mount St. Helens May 18, 1980, removed 2.9 km2 (about 0.13 km3) of <span class="hlt">glacier</span> snow and ice including a large part of Shoestring, Forsyth, Wishbone, Ape, Nelson, and all of Loowit and Leschi <span class="hlt">Glaciers</span>. Minor eruptions and bulging of the volcano from March 27 to May 17 shattered <span class="hlt">glaciers</span> which were on the deforming rock and deposited ash on other <span class="hlt">glaciers</span>. Thick ash layers persisted after the May 18 eruption through the summer on most of the remaining snow and ice, and protected winter snow from <span class="hlt">melting</span> on Swift and Dryer <span class="hlt">Glaciers</span>. <span class="hlt">Melting</span> and recrystalization of snow and ice surviving on Mount St. Helens could cause and lubricate mudflows and generate outburst floods. Study of <span class="hlt">glaciers</span> that remain on this active volcano may assist in recognizing potential hazards on other volcanoes and lead to new contributions to knowledge of the transient response of <span class="hlt">glaciers</span> to changes in mass balance or geometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C23A0399S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C23A0399S"><span>Using Icebergs to Constrain Fjord Circulation and Link to <span class="hlt">Glacier</span> Dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sutherland, D.; Straneo, F.; Hamilton, G. S.; Stearns, L. A.; Roth, G.</p> <p>2014-12-01</p> <p>The importance of icebergs is increasingly being recognized in the ocean-<span class="hlt">glacier</span> interactions community. Icebergs are ubiquitous in Greenland's outlet glacial fjords and provide a physical link between the <span class="hlt">glacier</span> and the ocean into which they <span class="hlt">melt</span>. The iceberg shape is influenced by <span class="hlt">glacier</span> size and calving mechanics, while the amount of <span class="hlt">melt</span> produced depends on ambient water properties and the residence time of the iceberg in the fjord. Here, we use hourly positions of icebergs tracked with helicopter deployed GPS sensors to calculate velocities in the Sermilik Fjord/Helheim <span class="hlt">Glacier</span> system. Data comes from three summertime deployments in 2012-2014, where icebergs were tagged in the ice mélange and moved through the fjord and onto the continental shelf. The iceberg-derived velocities provide information on ice mélange movement, fjord variability, and coastal currents on the shelf. Using simple <span class="hlt">melt</span> rate parameterizations, we estimate the total freshwater input due to iceberg <span class="hlt">melt</span> in Sermilik Fjord based on the observed residence times and satellite-derived iceberg distributions. These observations complement conventional oceanographic and glaciological data, and can quickly, and relatively inexpensively, characterize circulation throughout any given <span class="hlt">glacier</span>-ocean system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C32B..06D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C32B..06D"><span>Basal Terraces on <span class="hlt">Melting</span> Ice Shelves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dutrieux, P.; Stewart, C.; Jenkins, A.; Nicholls, K. W.; Corr, H. F. J.; Rignot, E. J.; Steffen, K.</p> <p>2014-12-01</p> <p>Ocean waters <span class="hlt">melt</span> the margins of Antarctic and Greenland <span class="hlt">glaciers</span> and individualglaciers' responses and the integrity of their ice shelves are expected to depend on thespatial distribution of <span class="hlt">melt</span>. The bases of the ice shelves associated with Pine Island<span class="hlt">Glacier</span> (West Antarctica) and Petermann <span class="hlt">Glacier</span> (Greenland) have similar geometries,including kilometers-wide, hundreds-of-meter-high channels oriented along and acrossthe direction of ice flow. The channels are enhanced by, and constrain, oceanic <span class="hlt">melt</span>.New, meter-scale observations of basal topography reveal peculiar glaciated landscapes.Channel flanks are not smooth, but are instead stepped, with hundreds-of-meters-wideflat terraces separated by 5-50 m-high walls. <span class="hlt">Melting</span> is shown to be modulated by thegeometry: constant across each terrace, changing from one terrace to the next, and greatlyenhanced on the ~45°-inclined walls. <span class="hlt">Melting</span> is therefore fundamentally heterogeneousand likely associated with stratification in the ice-ocean boundary layer, challengingcurrent models of ice shelf-ocean interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JHyd..519.1068P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JHyd..519.1068P"><span><span class="hlt">Glacier</span> meltwater flow paths and storage in a geomorphologically complex glacial foreland: The case of the Tapado <span class="hlt">glacier</span>, dry Andes of Chile (30°S)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pourrier, J.; Jourde, H.; Kinnard, C.; Gascoin, S.; Monnier, S.</p> <p>2014-11-01</p> <p>The Tapado catchment is located in the upper Elqui river basin (4000-5550 m) in northern Chile. It comprises the Tapado glacial complex, which is an assemblage of the Tapado <span class="hlt">glacier</span> and the glacial foreland (debris-covered <span class="hlt">glacier</span>, rock <span class="hlt">glacier</span>, and moraines). Although the hydrological functioning of this catchment is poorly known, it is assumed to actively supply water to the lower semi-arid areas of the Elqui river basin. To improve our knowledge of the interactions and water transfers between the cryospheric compartment (<span class="hlt">glacier</span>, debris-covered <span class="hlt">glacier</span>, and rock <span class="hlt">glacier</span>) and the hydrological compartment (aquifers, streams), the results of monitoring of meteorological conditions, as well as discharge, conductivity and temperature of streams and springs located in the Tapado catchment were analyzed. The hydrological results are compared to results inferred from a ground penetrating radar (GPR) survey of the underground structure of the glacial foreland. Water production from the Tapado <span class="hlt">glacier</span> was shown to be highly correlated with daily and monthly weather conditions, particularly solar <span class="hlt">radiation</span> and temperature. The resulting daily and monthly streamflow cycles were buffered by the glacial foreland, where underground transfers took place through complex flow paths. However, the development of a thermokarst drainage network in a portion of the glacial foreland enabled rapid concentrated water transfers that reduced the buffer effect. The glacial foreland was shown to act as a reservoir, storing water during high <span class="hlt">melt</span> periods and supplying water to downstream compartments during low <span class="hlt">melt</span> periods. GPR observations revealed the heterogeneity of the internal structure of the glacial foreland, which is composed of a mixture of ice and rock debris mixture, with variable spatial ice content, including massive ice lenses. This heterogeneity may explain the abovementioned hydrological behaviors. Finally, calculation of a partial hydrological budget confirmed the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AtmRe.200...77L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AtmRe.200...77L"><span>Light-absorbing impurities in a southern Tibetan Plateau <span class="hlt">glacier</span>: Variations and potential impact on snow albedo and <span class="hlt">radiative</span> forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Xiaofei; Kang, Shichang; Zhang, Guoshuai; Qu, Bin; Tripathee, Lekhendra; Paudyal, Rukumesh; Jing, Zhefan; Zhang, Yulan; Yan, Fangping; Li, Gang; Cui, Xiaoqing; Xu, Rui; Hu, Zhaofu; Li, Chaoliu</p> <p>2018-02-01</p> <p>Light-absorbing impurities (LAIs), such as organic carbon (OC), black carbon (BC), and mineral dust (MD), deposited on the surface snow of <span class="hlt">glacier</span> can reduce the surface albedo. As there exists insufficient knowledge to completely characterize LAIs variations and difference in LAIs distributions, it is essential to investigate the behaviors of LAIs and their influence on the <span class="hlt">glaciers</span> across the Tibetan Plateau (TP). Therefore, surface snow and snowpit samples were collected during September 2014 to September 2015 from Zhadang (ZD) <span class="hlt">glacier</span> in the southern TP to investigate the role of LAIs in the <span class="hlt">glacier</span>. LAIs concentrations were observed to be higher in surface aged snow than in the fresh snow possibly due to post-depositional processes such as <span class="hlt">melting</span> or sublimation. The LAIs concentrations showed a significant spatial distribution and marked negative relationship with elevation. Impurity concentrations varied significantly with depth in the vertical profile of the snowpit, with maximum LAIs concentrations frequently occurred in the distinct dust layers which were deposited in non-monsoon, and the bottom of snowpit due to the eluviation in monsoon. Major ions in snowpit and backward trajectory analysis indicated that regional activities and South Asian emissions were the major sources. According to the SNow ICe Aerosol <span class="hlt">Radiative</span> (SNICAR) model, the average simulated albedo caused by MD and BC in aged snow collected on 31 May 2015 accounts for about 13% ± 3% and 46% ± 2% of the albedo reduction. Furthermore, we also found that instantaneous RF caused by MD and BC in aged snow collected on 31 May 2015 varied between 4-16 W m- 2 and 7-64 W m- 2, respectively. The effect of BC exceeds that of MD on albedo reduction and instantaneous RF in the study area, indicating that BC played a major role on the surface of the ZD <span class="hlt">glacier</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C53A0296A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C53A0296A"><span>Methane seeps along boundaries of arctic permafrost thaw and <span class="hlt">melting</span> <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anthony, P.; Walter Anthony, K. M.; Grosse, G.; Chanton, J.</p> <p>2014-12-01</p> <p>Methane, a potent greenhouse gas, accumulates in subsurface hydrocarbon reservoirs. In the Arctic, impermeable icy permafrost and glacial overburden form a 'cryosphere cap' that traps gas leaking from these reservoirs, restricting flow to the atmosphere. We document the release of geologic methane to the atmosphere from abundant gas seeps concentrated along boundaries of permafrost thaw and receding <span class="hlt">glaciers</span> in Alaska. Through aerial and ground surveys we mapped >150,000 seeps identified as bubbling-<span class="hlt">induced</span> open holes in lake ice. Subcap methane seeps had anomalously high fluxes, 14C-depletion, and stable isotope values matching known coalbed and thermogenic methane accumulations in Alaska. Additionally, we observed younger subcap methane seeps in Greenland that were associated with ice-sheet retreat since the Little Ice Age. These correlations suggest that in a warming climate, continued disintegration of permafrost, <span class="hlt">glaciers</span>, and parts of the polar ice sheets will relax pressure on subsurface seals and further open conduits, allowing a transient expulsion of geologic methane currently trapped by the cryosphere cap.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018NatCC...8..135H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018NatCC...8..135H"><span>Global-scale hydrological response to future <span class="hlt">glacier</span> mass loss</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huss, Matthias; Hock, Regine</p> <p>2018-01-01</p> <p>Worldwide <span class="hlt">glacier</span> retreat and associated future runoff changes raise major concerns over the sustainability of global water resources1-4, but global-scale assessments of <span class="hlt">glacier</span> decline and the resulting hydrological consequences are scarce5,6. Here we compute global <span class="hlt">glacier</span> runoff changes for 56 large-scale <span class="hlt">glacierized</span> drainage basins to 2100 and analyse the glacial impact on streamflow. In roughly half of the investigated basins, the modelled annual <span class="hlt">glacier</span> runoff continues to rise until a maximum (`peak water') is reached, beyond which runoff steadily declines. In the remaining basins, this tipping point has already been passed. Peak water occurs later in basins with larger <span class="hlt">glaciers</span> and higher ice-cover fractions. Typically, future <span class="hlt">glacier</span> runoff increases in early summer but decreases in late summer. Although most of the 56 basins have less than 2% ice coverage, by 2100 one-third of them might experience runoff decreases greater than 10% due to <span class="hlt">glacier</span> mass loss in at least one month of the <span class="hlt">melt</span> season, with the largest reductions in central Asia and the Andes. We conclude that, even in large-scale basins with minimal ice-cover fraction, the downstream hydrological effects of continued <span class="hlt">glacier</span> wastage can be substantial, but the magnitudes vary greatly among basins and throughout the <span class="hlt">melt</span> season.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005EOSTr..86..415F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005EOSTr..86..415F"><span><span class="hlt">Glacier</span> shrinkage and water resources in the Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Francou, Bernard; Coudrain, Anne</p> <p></p> <p>For more than a century <span class="hlt">glaciers</span> around the world have been <span class="hlt">melting</span> as air temperatures rise due to a combination of natural processes and human activity. The disappearance of these <span class="hlt">glaciers</span> can have wide-ranging effects, such as the creation of new natural hazards or changes in stream flow that could threaten water suppliesSome of the most dramatic <span class="hlt">melting</span> has occurred in the Andes mountain range in South America. To highlight the climatic and glacial change in the Andes and to encourage the scientific community to strengthen the <span class="hlt">glacier</span> observation network that stretches from Colombia to the Patagonian ice fields, the Instituto Nacional de Recursos Naturales (INRENA), Perú, and the Institute of Research and Development (IRD), France, recently organized the second Symposium on Mass Balance of Andean <span class="hlt">Glaciers</span> in Huaráz,Perú.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.6261D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.6261D"><span><span class="hlt">Glacier</span> discharge and climate variations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dominguez, M. Carmen; Rodriguez-Puebla, Concepcion; Encinas, Ascension H.; Visus, Isabel; Eraso, Adolfo</p> <p>2010-05-01</p> <p>Different studies account for the warming in the polar regions that consequently would affect <span class="hlt">Glacier</span> Discharge (GD). Since changes in GD may cause large changes in sensible and latent heat fluxes, we ask about the relationships between GD and climate anomalies, which have not been quantified yet. In this study we apply different statistical methods such as correlation, Singular Spectral Analysis and Wavelet to compare the behaviour of GD data in two Experimental Pilot Catchments (CPE), one (CPE-KG-62°S) in the Antarctica and the other (CPE-KVIA-64°N) in the Arctic regions. Both CPE's are measuring sub- and endo-<span class="hlt">glacier</span> drainage for recording of <span class="hlt">glacier</span> <span class="hlt">melt</span> water run-off. The CPE-KG-62°S is providing hourly GD time series since January 2002 in Collins <span class="hlt">glacier</span> of the Maxwell Bay in King George Island (62°S, 58°W). The second one, CPE-KVIA-64°N, is providing hourly GD time series since September 2003 in the Kviarjökull <span class="hlt">glacier</span> of the Vatnajökull ice cap in Iceland (64°N, 16°W). The soundings for these measurements are pressure sensors installed in the river of the selected catchments for the ice cap (CPE-KG-62°S) and in the river of the <span class="hlt">glacier</span> for (CPE-KVIA-64°N). In each CPE, the calibration function between level and discharge has been adjusted, getting a very high correlation coefficient (0.99 for the first one and 0.95 for the second one), which let us devise a precise discharge law for the <span class="hlt">glacier</span>. We obtained relationships between GD with atmospheric variables such as <span class="hlt">radiation</span>, temperature, relative humidity, atmospheric pressure and precipitation. We also found a negative response of GD to El Niño teleconnection index. The results are of great interest due to the GD impact on the climate system and in particular for sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..433S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..433S"><span>The response of surface mass and energy balance of a continental <span class="hlt">glacier</span> to climate variability, western Qilian Mountains, China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Weijun; Qin, Xiang; Wang, Yetang; Chen, Jizu; Du, Wentao; Zhang, Tong; Huai, Baojuan</p> <p>2017-08-01</p> <p>To understand how a continental <span class="hlt">glacier</span> responds to climate change, it is imperative to quantify the surface energy fluxes and identify factors controlling <span class="hlt">glacier</span> mass balance using surface energy balance (SEB) model. Light absorbing impurities (LAIs) at the glacial surface can greatly decrease surface albedo and increase glacial <span class="hlt">melt</span>. An automatic weather station was set up and generated a unique 6-year meteorological dataset for the ablation zone of Laohugou <span class="hlt">Glacier</span> No. 12. Based on these data, the surface energy budget was calculated and an experiment on the glacial <span class="hlt">melt</span> process was carried out. The effect of reduced albedo on glacial <span class="hlt">melting</span> was analyzed. Owing to continuous accumulation of LAIs, the ablation zone had been darkening since 2010. The mean value of surface albedo in <span class="hlt">melt</span> period (June through September) dropped from 0.52 to 0.43, and the minimum of daily mean value was as small as 0.1. From the records of 2010-2015, keeping the clean ice albedo fixed in the range of 0.3-0.4, LAIs caused an increase of +7.1 to +16 W m-2 of net shortwave <span class="hlt">radiation</span> and an removal of 1101-2663 mm water equivalent. Calculation with the SEB model showed equivalent increases in glacial <span class="hlt">melt</span> were obtained by increasing air temperature by 1.3 and 3.2 K, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1818019S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1818019S"><span><span class="hlt">Glacier-induced</span> Hazards in the Trans-Himalaya of Ladakh (NW-India)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmidt, Susanne; Dame, Juliane; Nüsser, Marcus</p> <p>2016-04-01</p> <p><span class="hlt">Glaciers</span> are important water resources for irrigated crop cultivation in the semi-arid Trans-Himalaya of Ladakh (NW-India). Due to global warming, many <span class="hlt">glaciers</span> of South Asia have retreated over the last century and further ice loss will threaten local livelihoods in the long run. In the short term, an increase of flood events caused by <span class="hlt">melting</span> <span class="hlt">glaciers</span> and permafrost is expected for the Himalayan region. Beside large catastrophic events, small outburst floods are 'more' regularly reported for various parts of the region. This also holds true for the Trans-Himalayan region of Ladakh, where small <span class="hlt">glaciers</span> exist at high altitudes. Caused by <span class="hlt">glacier</span> retreat, a number of proglacial lakes have been formed, most of them dammed by ice filled moraines. The potential risk of these lakes is shown by recent reports on glacial lake outburst flood in the villages Nidder in October 2010 and Gya in August 2014. The 2014 flood destroyed several agricultural terraces, a new concrete bridge and two houses. Own remote sensing analyses shows the increase of a moraine dammed proglacial lake in the upper catchment area, which grew from about 0.03 to 0.08 km2 between 1969 and 2014. Because of the relatively stable altitude of the lake level, one can assume that the flood was caused by a piping process, initiated by <span class="hlt">melted</span> ice bodies in the moraine. Already in the 1990s a small GLOF was observed in the village, which destroyed some fields. As in 2014, the lake was not completely spilled and a short-term decrease of the lake area is detectable in remote sensing data. Thus, further GLOF-events can be expected for the future. Beside physical risk factors, population growth and new infrastructure development along the streams and valleys increases potential damages of floods. Therefore, investigations are required to estimate the risks of these small glacial lakes and the potential flood effected area for the case study of Gya as well as for the whole region of Ladakh. Remote sensing data are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC31C1007B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC31C1007B"><span>Changes of <span class="hlt">glacier</span>, <span class="hlt">glacier</span>-fed rivers and lakes in Altai Tavan Bogd National Park, Western Mongolia, based on multispectral satellite data from 1990 to 2017</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Batsaikhan, B.; Lkhamjav, O.; Batsaikhan, N.</p> <p>2017-12-01</p> <p>Impacts on <span class="hlt">glaciers</span> and water resource management have been altering through climate changes in Mongolia territory characterized by dry and semi-arid climate with low precipitation. <span class="hlt">Melting</span> <span class="hlt">glaciers</span> are early indicators of climate change unlike the response of the forests which is slower and takes place over a long period of time. Mountain <span class="hlt">glaciers</span> are important environmental components of local, regional, and global hydrological cycles. The study calculates an overview of changes for <span class="hlt">glacier</span>, <span class="hlt">glacier</span>-fed rivers and lakes in Altai Tavan Bogd mountain, the Western Mongolia, based on the indexes of multispectral data and the methods typically applied in <span class="hlt">glacier</span> studies. Were utilized an integrated approach of Normalized Difference Snow Index (NDSI) and Normalized Difference Water Index (NDWI) to combine Landsat, MODIS imagery and digital elevation model, to identify <span class="hlt">glacier</span> cover are and quantify water storage change in lakes, and compared that with and climate parameters including precipitation, land surface temperature, evaporation, moisture. Our results show that <span class="hlt">melts</span> of <span class="hlt">glacier</span> at the study area has contributed to significantly increase of water storage of lakes in valley of The Altai Tavan Bogd mountain. There is hydrologic connection that lake basin is directly fed by <span class="hlt">glacier</span> meltwater.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C23A1199B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C23A1199B"><span>Modeling of Greenland outlet <span class="hlt">glaciers</span> response to future climate change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beckmann, J.</p> <p>2017-12-01</p> <p>Over the past two decades net mass loss from the Greenland ice sheet (GIS) quadrupled, resulting in 25% of the global mean sea level (GMSL) rise. Increased mass loss of the GIS is caused by enhanced surface <span class="hlt">melting</span> and speedup of the marine-terminating outlet <span class="hlt">glaciers</span>. This speedup has been related, among other factors, to enhanced submarine <span class="hlt">melting</span>, which in turn is caused by warming of the surrounding ocean and by increased subglacial, meltwater discharge. Yet, ice-ocean processes are not properly represented in contemporary Greenland Ice Sheet models used to project future changes in the GIS. In this work, we performed numerical experiments with a one-dimensional plume model coupled to a one-dimensional (depth- and width- integrated) ice flow model for several representative outlet <span class="hlt">glaciers</span> in Greenland. We investigate the dynamic response of the coupled ice-flow plume model to scenarios of future climate change. In particular, we examine the transient response of the outlet <span class="hlt">glaciers</span> to projected changes in surface <span class="hlt">melting</span>, ocean temperature and subglacial discharge. With our modeling approach we quantify the amount of the surface and submarine <span class="hlt">melting</span> and the resulting retreat and mass loss for each individual <span class="hlt">glacier</span> for the next 100 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRE..122.2445B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRE..122.2445B"><span>Recent Basal <span class="hlt">Melting</span> of a Mid-Latitude <span class="hlt">Glacier</span> on Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Butcher, Frances E. G.; Balme, M. R.; Gallagher, C.; Arnold, N. S.; Conway, S. J.; Hagermann, A.; Lewis, S. R.</p> <p>2017-12-01</p> <p>Evidence for past basal <span class="hlt">melting</span> of young (late Amazonian-aged), debris-covered <span class="hlt">glaciers</span> in Mars' mid-latitudes is extremely rare. Thus, it is widely thought that these viscous flow features (VFFs) have been perennially frozen to their beds. We identify an instance of recent, localized wet-based mid-latitude glaciation, evidenced by a candidate esker emerging from a VFF in a tectonic rift in Tempe Terra. Eskers are sedimentary ridges deposited in ice-walled meltwater conduits and are indicative of glacial <span class="hlt">melting</span>. We compare the candidate esker to terrestrial analogues, present a geomorphic map of landforms in the rift, and develop a landsystem model to explain their formation. We propose that the candidate esker formed during a transient phase of wet-based glaciation. We then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid-latitude VFF; both are within tectonic graben/rifts proximal to volcanic provinces. Finally, we calculate potential basal temperatures for a range of VFF thicknesses, driving stresses, mean annual surface temperatures, and geothermal heat fluxes, which unlike previous studies, include the possible role of internal strain heating. Strain heating can form an important additional heat source, especially in flow convergence zones, or where ice is warmer due to elevated surface temperatures or geothermal heat flux. Elevated geothermal heat flux within rifts, perhaps combined with locally-elevated strain heating, may have permitted wet-based glaciation during the late Amazonian, when cold climates precluded more extensive wet-based glaciation on Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1211533N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1211533N"><span>Role of ice-ocean interaction on <span class="hlt">glacier</span> instability: Results from numerical modelling applied to Petermann <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nick, Faezeh M.; Hubbard, Alun; van der Veen, Kees; Vieli, Andreas</p> <p>2010-05-01</p> <p>Calving of icebergs and bottom <span class="hlt">melting</span> from ice shelves accounts for roughly half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. Petermann <span class="hlt">Glacier</span> (north Greenland) with its 16 km wide and 80 km long floating tongue, experiences massive bottom <span class="hlt">melting</span>. We apply a numerical ice flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as bottom <span class="hlt">melting</span>, sea ice or sikkusak disintegration, surface run off and iceberg calving to the mass balance and instability of Petermann <span class="hlt">Glacier</span> and its ice shelf. Our modelling study provides insights into the role of ice-ocean interaction, and on how to incorporate calving in ice sheet models, improving our ability to predict future ice sheet change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1910394W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1910394W"><span>Geoengineering Outlet <span class="hlt">Glaciers</span> and Ice Streams</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wolovick, Michael</p> <p>2017-04-01</p> <p>Mass loss from Greenland and Antarctica is highly sensitive to the presence of warm ocean water that drives <span class="hlt">melting</span> of ice shelves and marine terminated <span class="hlt">glaciers</span>. This warm water resides offshore at depth and accesses the grounding line through deep but narrow troughs and fjords. Here, we investigate the possibility of blocking warm water transport through these choke points with an artificial sill. Using a simple width-averaged model of ice stream flow coupled to a buoyant-plume model of submarine <span class="hlt">melt</span>, we find that grounding line retreat and sea level rise can be delayed or reversed for hundreds of years if warm water is prevented from accessing outlet <span class="hlt">glaciers</span> and ice-shelf cavities. <span class="hlt">Glaciers</span> with a floating shelf exhibit a strong response to the presence of the artificial sill regardless of our choice of calving law, while tidewater <span class="hlt">glaciers</span> require a strong linkage between submarine <span class="hlt">melt</span> and iceberg calving for the artificial sill to have an effect. As a result of this difference and as a result of differing degrees of overdeepening in the basal topography, Antarctica and Greenland present very different societal cost-benefit analyses. Intervention in Greenland would be low-cost and low-reward: the volume of the artificial sill is comparable to existing large public works projects such as the Dubai Islands or the Suez Canal, but the magnitude of averted sea-level rise is small, the success of the intervention depends on the choice of calving law, and the <span class="hlt">glaciers</span> return to their non-geoengineered trajectories within one to two centuries. Intervention in Antarctica, on the other hand, would be high-cost and high-reward: the volume of the artificial sill is one to two orders of magnitude greater, but the averted sea level rise is much larger, the intervention is successful regardless of the choice of calving law, and the ice streams remain far from their non-geoengineered trajectories throughout the 1000 year duration of our model runs. In both cases, an</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5020593','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5020593"><span>Subglacial discharge at tidewater <span class="hlt">glaciers</span> revealed by seismic tremor</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Amundson, Jason M.; Walter, Jacob I.; O'Neel, Shad; West, Michael E.; Larsen, Christopher F.</p> <p>2015-01-01</p> <p>Abstract Subglacial discharge influences <span class="hlt">glacier</span> basal motion and erodes and redeposits sediment. At tidewater <span class="hlt">glacier</span> termini, discharge drives submarine terminus <span class="hlt">melting</span>, affects fjord circulation, and is a central component of proglacial marine ecosystems. However, our present inability to track subglacial discharge and its variability significantly hinders our understanding of these processes. Here we report observations of hourly to seasonal variations in 1.5–10 Hz seismic tremor that strongly correlate with subglacial discharge but not with basal motion, weather, or discrete icequakes. Our data demonstrate that vigorous discharge occurs from tidewater <span class="hlt">glaciers</span> during summer, in spite of fast basal motion that could limit the formation of subglacial conduits, and then abates during winter. Furthermore, tremor observations and a <span class="hlt">melt</span> model demonstrate that drainage efficiency of tidewater <span class="hlt">glaciers</span> evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured <span class="hlt">glacierized</span> environments. PMID:27667869</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70157091','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70157091"><span>Subglacial discharge at tidewater <span class="hlt">glaciers</span> revealed by seismic tremor</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bartholomaus, Timothy C.; Amundson, Jason M.; Walter, Jacob I.; O'Neel, Shad; West, Michael E.; Larsen, Christopher F.</p> <p>2015-01-01</p> <p>Subglacial discharge influences <span class="hlt">glacier</span> basal motion and erodes and redeposits sediment. At tidewater <span class="hlt">glacier</span> termini, discharge drives submarine terminus <span class="hlt">melting</span>, affects fjord circulation, and is a central component of proglacial marine ecosystems. However, our present inability to track subglacial discharge and its variability significantly hinders our understanding of these processes. Here we report observations of hourly to seasonal variations in 1.5–10 Hz seismic tremor that strongly correlate with subglacial discharge but not with basal motion, weather, or discrete icequakes. Our data demonstrate that vigorous discharge occurs from tidewater <span class="hlt">glaciers</span> during summer, in spite of fast basal motion that could limit the formation of subglacial conduits, and then abates during winter. Furthermore, tremor observations and a <span class="hlt">melt</span> model demonstrate that drainage efficiency of tidewater <span class="hlt">glaciers</span> evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured <span class="hlt">glacierized</span> environments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016FrEaS...4..102V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016FrEaS...4..102V"><span>The changing impact of snow conditions and refreezing on the mass balance of an idealized Svalbard <span class="hlt">glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Van Pelt, Ward; Pohjola, Veijo; Reijmer, Carleen</p> <p>2016-11-01</p> <p><span class="hlt">Glacier</span> surface <span class="hlt">melt</span> and runoff depend strongly on seasonal and perennial snow (firn) conditions. Not only does the presence of snow and firn directly affect <span class="hlt">melt</span> rates by reflecting solar <span class="hlt">radiation</span>, it may also act as a buffer against mass loss by storing <span class="hlt">melt</span> water in refrozen or liquid form. In Svalbard, ongoing and projected amplified climate change with respect to the global mean change has severe implications for the state of snow and firn and its impact on <span class="hlt">glacier</span> mass loss. Model experiments with a coupled surface energy balance - firn model were done to investigate the surface mass balance and the changing role of snow and firn conditions for an idealized Svalbard <span class="hlt">glacier</span>. A climate forcing for the past, present and future (1984-2104) is constructed, based on observational data from Svalbard Airport and a seasonally dependent projection scenario. Results illustrate ongoing and future firn degradation in response to an elevational retreat of the equilibrium line altitude (ELA) of 31 m decade-1. The temperate firn zone is found to retreat and expand, while cold ice in the ablation zone warms considerably. In response to pronounced winter warming and an associated increase in winter rainfall, the current prevalence of refreezing during the <span class="hlt">melt</span> season gradually shifts to the winter season in a future climate. Sensitivity tests reveal that in a present and future climate the density and thermodynamic structure of Svalbard <span class="hlt">glaciers</span> are heavily influenced by refreezing. Refreezing acts as a net buffer against mass loss. However, the net mass balance change after refreezing is substantially smaller than the amount of refreezing itself, which can be ascribed to <span class="hlt">melt</span>-enhancing effects after refreezing, which partly offset the primary mass-retaining effect of refreezing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.water.usgs.gov/wri024165','USGSPUBS'); return false;" href="http://pubs.water.usgs.gov/wri024165"><span>Water, ice, and meteorological measurements at South Cascade <span class="hlt">Glacier</span>, Washington, 2000-01 balance years</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Krimmel, Robert M.</p> <p>2002-01-01</p> <p>Winter snow accumulation and summer snow, firn, and ice <span class="hlt">melt</span> were measured at South Cascade <span class="hlt">Glacier</span>, Washington, to determine the winter and net balances for the 2000 and 2001 balance years. In 2000, the winter balance, averaged over the <span class="hlt">glacier</span>, was 3.32 meters, and the net balance was 0.38 meters. The winter balance was the ninth highest since the record began in 1959. The net balance was greater than 33 of the 41 years since 1959. In 2001, the winter balance was 1.90 meters, and net balance was -1.57 meters. The winter balance was lower than all but 4 years since 1959, and the net balance was more negative than all but 5 other years. Runoff was measured from the <span class="hlt">glacier</span> basin and an adjacent non-<span class="hlt">glacierized</span> basin. Air temperature, precipitation, humidity, wind speed and solar <span class="hlt">radiation</span> were measured nearby. Ice displacements were measured for the 1998-2001 period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.U13B..09K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.U13B..09K"><span>Accessing the inaccessible: making (successful) field observations at tidewater <span class="hlt">glacier</span> termini</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kienholz, C.; Amundson, J. M.; Jackson, R. H.; Motyka, R. J.; Nash, J. D.; Sutherland, D.</p> <p>2017-12-01</p> <p><span class="hlt">Glaciers</span> terminating in ocean water (tidewater <span class="hlt">glaciers</span>) show complex dynamic behavior driven predominantly by processes at the ice-ocean interface (sedimentation, erosion, iceberg calving, submarine <span class="hlt">melting</span>). A quantitative understanding of these processes is required, for example, to better assess tidewater <span class="hlt">glaciers</span>' fate in our rapidly warming environment. Lacking observations close to <span class="hlt">glacier</span> termini, due to unpredictable risks from calving, hamper this understanding. In an effort to remedy this lack of knowledge, we initiated a large field-based effort at LeConte <span class="hlt">Glacier</span>, southeast Alaska, in 2016. LeConte <span class="hlt">Glacier</span> is a regional analog for many tidewater <span class="hlt">glaciers</span>, but better accessible and observable and thus an ideal target for our multi-disciplinary effort. Our ongoing campaigns comprise measurements from novel autonomous vessels (temperature, salinity and current) in the immediate proximity of the <span class="hlt">glacier</span> terminus and additional surveys (including multibeam bathymetry) from boats and moorings in the proglacial fjord. These measurements are complemented by iceberg and <span class="hlt">glacier</span> velocity measurements from time lapse cameras and a portable radar interferometer situated above LeConte Bay. GPS-based velocity observations and <span class="hlt">melt</span> measurements are conducted on the <span class="hlt">glacier</span>. These measurements provide necessary input for process-based understanding and numerical modeling of the <span class="hlt">glacier</span> and fjord systems. In the presentation, we discuss promising initial results and lessons learned from the campaign.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918586S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918586S"><span>Ocean impact on Nioghalvfjerdsfjorden <span class="hlt">Glacier</span>, Northeast Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schaffer, Janin; Kanzow, Torsten; von Appen, Wilken-Jon; Mayer, Christoph</p> <p>2017-04-01</p> <p>The ocean plays an important role in modulating the mass balance of the Greenland Ice Sheet by delivering heat to the marine-terminating outlet <span class="hlt">glaciers</span> around Greenland. The largest of three outlet <span class="hlt">glaciers</span> draining the Northeast Greenland Ice Stream is Nioghalvfjerdsfjorden <span class="hlt">Glacier</span> (also referred to as 79 North <span class="hlt">Glacier</span>). Historic observations showed that warm waters of Atlantic origin are present in the subglacial cavity below the 80 km long floating ice tongue of the Nioghalvfjerdsfjorden <span class="hlt">Glacier</span> and cause strong basal <span class="hlt">melt</span> at the grounding line, but to date it has been unknown how those warm water enter the cavity. In order to understand how Atlantic origin waters carry heat into the subglacial cavity beneath Nioghalvfjerdsfjorden <span class="hlt">Glacier</span>, we performed bathymetric, hydrographic, and velocity observations in the vicinity of the main <span class="hlt">glacier</span> calving front aboard RV Polarstern in summer 2016. The bathymetric multibeam data shows a 500 m deep and 2 km narrow passage downstream of a 310 m deep sill. This turned out to be the only location deep enough for an exchange of Atlantic waters between the <span class="hlt">glacier</span> cavity and the continental shelf. Hydrographic and velocity measurements revealed a density driven plume in the vicinity of the <span class="hlt">glacier</span> calving front causing a rapid flow of waters of Atlantic origin warmer 1°C into the subglacial cavity through the 500 m deep passage. In addition, glacially modified waters flow out of the <span class="hlt">glacier</span> cavity below the 80 m deep ice base. In the vicinity of the <span class="hlt">glacier</span>, the glacially modified waters form a distinct mixed layer situated above the Atlantic waters and below the ambient Polar water. At greater distances from the <span class="hlt">glacier</span> this layer is eroded by lateral mixing with ambient water. Based on our observations we will present an estimate of the ocean heat transport into the subglacial cavity. In comparison with historic observations we find an increase in Atlantic water temperatures throughout the last 20 years. The resulting</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1246355','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1246355"><span>Distributed modeling of ablation (1996–2011) and climate sensitivity on the <span class="hlt">glaciers</span> of Taylor Valley, Antarctica</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Hoffman, Matthew J.; Fountain, Andrew G.; Liston, Glen E.</p> <p></p> <p>Here, the McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the <span class="hlt">glacier</span> ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where <span class="hlt">melt</span>, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated <span class="hlt">melt</span> rates up to ten times higher than overmore » smooth <span class="hlt">glacier</span> surfaces. In contrast, the vertical terminal cliffs on the <span class="hlt">glaciers</span> can have higher or lower <span class="hlt">melt</span> rates than the horizontal surfaces due to differences in incoming solar <span class="hlt">radiation</span>. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~–0.02 m w.e. K –1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1246355-distributed-modeling-ablation-climate-sensitivity-glaciers-taylor-valley-antarctica','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1246355-distributed-modeling-ablation-climate-sensitivity-glaciers-taylor-valley-antarctica"><span>Distributed modeling of ablation (1996–2011) and climate sensitivity on the <span class="hlt">glaciers</span> of Taylor Valley, Antarctica</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Hoffman, Matthew J.; Fountain, Andrew G.; Liston, Glen E.</p> <p>2016-02-24</p> <p>Here, the McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the <span class="hlt">glacier</span> ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where <span class="hlt">melt</span>, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated <span class="hlt">melt</span> rates up to ten times higher than overmore » smooth <span class="hlt">glacier</span> surfaces. In contrast, the vertical terminal cliffs on the <span class="hlt">glaciers</span> can have higher or lower <span class="hlt">melt</span> rates than the horizontal surfaces due to differences in incoming solar <span class="hlt">radiation</span>. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~–0.02 m w.e. K –1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.C31F..07N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.C31F..07N"><span>Role of ice-ocean interaction on <span class="hlt">glacier</span> instability: Results from numerical modeling applied to Petermann <span class="hlt">Glacier</span> (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nick, F.; Hubbard, A.; Vieli, A.; van der Veen, C. J.; Box, J. E.; Bates, R.; Luckman, A. J.</p> <p>2009-12-01</p> <p>Calving of icebergs and bottom <span class="hlt">melting</span> from ice shelves accounts for roughly half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. Petermann <span class="hlt">Glacier</span> (north Greenland) with its 16 km wide and 80 km long floating tongue, experiences massive bottom <span class="hlt">melting</span>. We apply a numerical ice flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as bottom <span class="hlt">melting</span>, sea ice or sikkusak disintegration, surface run off and iceberg calving to the mass balance and instability of Petermann <span class="hlt">Glacier</span> and its ice shelf. Our modeling study provides insights into the role of ice-ocean interaction, and on how to incorporate calving in ice sheet models, improving our ability to predict future ice sheet change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1610408F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1610408F"><span>Austrian <span class="hlt">glaciers</span> in historical documents of the last 400 years: implications for historical hydrology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischer, Andrea; Seiser, Bernd</p> <p>2014-05-01</p> <p>First documentations of Austrian <span class="hlt">glaciers</span> date from as early as 1601. Early documentations were triggered by <span class="hlt">glacier</span> advances that created <span class="hlt">glacier</span>-dammed lakes that caused floods whenever the dam collapsed . Since then, Austrian <span class="hlt">glaciers</span> have been documented in drawings, descriptions and later on in maps and photography. These data are stored in historical archives but today only partly exploited for historical glaciology. They are of special interest for historical hydrology in <span class="hlt">glacier</span>-covered basins, as the extent of the snow, firn and ice cover and its elevation affect the hydrological response of the basin to precipitation events in several ways: - Firn cover: the more area is covered by firn, the higher is the capacity for retention or even refreezing of liquid precipitation and <span class="hlt">melt</span> water. - Ice cover: the area covered by <span class="hlt">glaciers</span> can be affected by <span class="hlt">melt</span> and contributes to a peak discharge on summer afternoons. - Surface elevation and temperatures: in case of precipitation events, the lower surface temperatures and higher surface elevation of the <span class="hlt">glaciers</span> compared to ice-free ground have some impact on the capacity to store precipitation. - <span class="hlt">Glacier</span> floods: for the LIA maximum around 1850, a number of advancing <span class="hlt">glaciers</span> dammed lakes which emptied during floods. These parameters show different variability with time: <span class="hlt">glacier</span> area varies only by about 60% to 70% between the LIA maximum and today. The variability of the maximum meltwater peak changes much more than the area. Even during the LIA maximum, several years were extremely warm, so that more than twice the size of today's <span class="hlt">glacier</span> area was subject to <span class="hlt">glacier</span> <span class="hlt">melt</span>. The minimum elevations of large <span class="hlt">glaciers</span> were several hundred meters lower than today, so that in terms of today's summer mean temperatures, the <span class="hlt">melt</span> water production from ice ablation would have been much higher than today. A comparison of historical <span class="hlt">glacier</span> images and description with today's makes it clear that the extent of the snow cover and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.G53A..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.G53A..01S"><span>Asia High Mountain <span class="hlt">Glacier</span> Mass Balance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shum, C. K.; Su, X.; Shang, K.; Cogley, J. G.; Zhang, G.; Howat, I. M.; Braun, A.; Kuo, C. Y.</p> <p>2015-12-01</p> <p>The Asian High Mountain encompassing the Qinghai-Tibetan Plateau has the largest glaciated regions in the world outside of Greenland and Antarctica. The Tibetan Plateau is the source or headwater of many major river systems, which provide water resources to more than a billion people downstream. The impact of climate change on the Tibetan Plateau physical processes, including mountain <span class="hlt">glacier</span> wastage, permafrost active layer thickening, the timing and the quantity of the perennial snowpack <span class="hlt">melt</span> affecting upstream catchments, river runoffs, land-use, have significant effects on downstream water resources. Exact quantification of the Asian High Mountain <span class="hlt">glacier</span> wastage or its mass balance on how much of the <span class="hlt">melt</span> water contributes to early 21st century global sea-level rise, remain illusive or the published results are arguably controversial. The recent observed significant increase of freshwater storage within the Tibetan Plateaus remains a limitation to exactly quantify mountain <span class="hlt">glacier</span> wastage. Here, we provide an updated estimate of Asia high mountain <span class="hlt">glacier</span> mass balance using satellite geodetic observations during the last decade, accounting for the hydrologic and other processes, and validated against available in situ mass balance data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC21H1188S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC21H1188S"><span>Glacial-hydrogeomorphic process of proglacial lake expansion and exploring its amplification effect on <span class="hlt">glacier</span> recession in the Himalayas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Song, C.; Sheng, Y.; Wang, J.; Ke, L.; Nie, Y.</p> <p>2016-12-01</p> <p>Glacial lakes, as a key component of the cryosphere in the Himalayas in response to climate change, pose significant threats to the downstream lives and properties and eco-environment via outburst floods, yet our understanding of their evolution and reaction mechanism with connected <span class="hlt">glaciers</span> is limited. Here, a regional investigation of glacial lake evolution and glacial-hydrogeomorphic process was conducted by integrating optical imagery, satellite altimetry and DEM. A classification scheme was first used to group glacial lakes of similar glacial and geo-morphology. Our studies show that debris-contact proglacial lakes experienced much more rapid expansions than ice cliff-contact and non-<span class="hlt">glacier</span>-contact lakes. We further estimate the mass balance of parent <span class="hlt">glaciers</span> and elevation changes in lake surfaces and debris-covered <span class="hlt">glacier</span> tongues. Results reveal that the upstream expansion of debris-contact proglacial lakes was not directly related to rising water levels but with a geomorphological alternation of upstream lake basins caused by ice <span class="hlt">melt-induced</span> debris subsidence at <span class="hlt">glacier</span> termini. It suggests that the hydrogeomorphic process of <span class="hlt">glacier</span> thinning and retreat, in comparison with direct meltwater supply alone, may have governed primarily the recent glacial lake expansion across the Himalayas. The mechanism of proglacial lake expansion provides an indirect way to estimate the lowering rates of <span class="hlt">glacier</span> terminus. The debris-covered <span class="hlt">glacier</span> fronts show considerable ice <span class="hlt">melts</span>, with the lowering rate ranging from 1.0 to 9.7 m/yr. The rates exhibit obvious correlations with contacted lake sizes, centerline length and area of <span class="hlt">glaciers</span>, suggesting that the <span class="hlt">glacier</span> termini thinning is the combined effect of interplays between glacial lakes and ice flux from parent <span class="hlt">glaciers</span>. Our study implies that substantial mass loss occurred at lake-contact <span class="hlt">glacier</span> fronts, which cannot be ignored in assessing the overall mass balance of Himalayan <span class="hlt">glaciers</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C14B..02A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C14B..02A"><span>Competing roles of air temperature and summer precipitation events on proglacial stream discharges in Chhota Shigri <span class="hlt">Glacier</span> catchment, Indian Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>AL, R.</p> <p>2016-12-01</p> <p>It has been widely recognized that western Himalayan region depends heavily on <span class="hlt">glacier</span> and snow <span class="hlt">melt</span> for its water needs. This is true especially for the Chenab sub-basin and more generally for other sub-catchments of the mighty Indus catering to the water demands of millions of stake holders who depend on this water resource. However, there are very few studies available to understand high altitude glaciated catchments, the climatic controls over their flow regimes, and their dependency on <span class="hlt">glacier</span> mass balances, mainly because of poor access. Hence, the proglacial stream discharges from Chhota Shigri <span class="hlt">Glacier</span>, a representative <span class="hlt">glacier</span> of western Himalayan region has been analyzed for understanding the impact of rising air temperatures and highly variable summer precipitation events on discharges that are sourced majorly from snow <span class="hlt">melt</span> and <span class="hlt">glacier</span> wastage. This study, for the first time attempts to understand the factors influencing the interannual, subseasonal, and the diurnal variability observed in this representative catchment over four ablation seasons (2010-2013), by monitoring solar <span class="hlt">radiation</span>, air temperature, summer precipitation, albedo and transient snow cover. The proglacial discharge is governed by air temperatures and albedo-enhancing summer precipitation events, which also enhances transient snow cover. While, the positive mass balance years gave rise to lesser proglacial discharges in comparison to negative mass balance years, lesser winter accumulation was compensated by the lower ablation resulting summer snowfall events in some years. While rising summer air temperatures give rise to <span class="hlt">glacier</span> wastage, the role of <span class="hlt">melting</span> transient snow cover on stream discharge is highly significant, especially for positive mass balance years. The pronounced interannual variations and the decreased proglacial discharge in comparison to 1980s suggest that Chhota Shigri <span class="hlt">Glacier</span> is possibly wasting its way to reach equilibrium to the changed climatic conditions of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C22A..02N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C22A..02N"><span>Response of major Greenland outlet <span class="hlt">glaciers</span> to oceanic and atmospheric forcing: Results from numerical modeling on Petermann, Jakobshavn and Helheim <span class="hlt">Glacier</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nick, F. M.; Vieli, A.; Pattyn, F.; Van de Wal, R.</p> <p>2011-12-01</p> <p>Oceanic forcing has been suggested as a major trigger for dynamic changes of Greenland outlet <span class="hlt">glaciers</span>. Significant <span class="hlt">melting</span> near their calving front or beneath the floating tongue and reduced support from sea ice or ice melange in front of their calving front can result in retreat of the terminus or the grounding line, and an increase in calving activities. Depending on the geometry and basal topography of the <span class="hlt">glacier</span>, these oceanic forcing can affect the <span class="hlt">glacier</span> dynamic differently. Here, we carry out a comparison study between three major outlet <span class="hlt">glaciers</span> in Greenland and investigate the impact of a warmer ocean on <span class="hlt">glacier</span> dynamics and ice discharge. We present results from a numerical ice-flow model applied to Petermann <span class="hlt">Glacier</span> in the north, Jakobshavn <span class="hlt">Glacier</span> in the west, and Helheim <span class="hlt">Glacier</span> in the southeast of Greenland.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012NatGe...5..419W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012NatGe...5..419W"><span>Geologic methane seeps along boundaries of Arctic permafrost thaw and <span class="hlt">melting</span> <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walter Anthony, Katey M.; Anthony, Peter; Grosse, Guido; Chanton, Jeffrey</p> <p>2012-06-01</p> <p>Methane, a potent greenhouse gas, accumulates in subsurface hydrocarbon reservoirs, such as coal beds and natural gas deposits. In the Arctic, permafrost and <span class="hlt">glaciers</span> form a `cryosphere cap' that traps gas leaking from these reservoirs, restricting flow to the atmosphere. With a carbon store of over 1,200Pg, the Arctic geologic methane reservoir is large when compared with the global atmospheric methane pool of around 5Pg. As such, the Earth's climate is sensitive to the escape of even a small fraction of this methane. Here, we document the release of 14C-depleted methane to the atmosphere from abundant gas seeps concentrated along boundaries of permafrost thaw and receding <span class="hlt">glaciers</span> in Alaska and Greenland, using aerial and ground surface survey data and in situ measurements of methane isotopes and flux. We mapped over 150,000 seeps, which we identified as bubble-<span class="hlt">induced</span> open holes in lake ice. These seeps were characterized by anomalously high methane fluxes, and in Alaska by ancient radiocarbon ages and stable isotope values that matched those of coal bed and thermogenic methane accumulations. Younger seeps in Greenland were associated with zones of ice-sheet retreat since the Little Ice Age. Our findings imply that in a warming climate, disintegration of permafrost, <span class="hlt">glaciers</span> and parts of the polar ice sheets could facilitate the transient expulsion of 14C-depleted methane trapped by the cryosphere cap.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1121805-modeling-effect-glacier-recession-streamflow-response-using-coupled-glacio-hydrological-model','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1121805-modeling-effect-glacier-recession-streamflow-response-using-coupled-glacio-hydrological-model"><span>Modeling the effect of <span class="hlt">glacier</span> recession on streamflow response using a coupled glacio-hydrological model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Frans, Chris D.; Clarke, Garry K. C.; Burns, P.; ...</p> <p>2014-02-27</p> <p>Here, we describe an integrated spatially distributed hydrologic and <span class="hlt">glacier</span> dynamic model, and use it to investigate the effect of <span class="hlt">glacier</span> recession on streamflow variations for the Upper Bow River basin, a tributary of the South Saskatchewan River. Several recent studies have suggested that observed decreases in summer flows in the South Saskatchewan River are partly due to the retreat of <span class="hlt">glaciers</span> in the river's headwaters. Modeling the effect of <span class="hlt">glacier</span> changes on streamflow response in river basins such as the South Saskatchewan is complicated due to the inability of most existing physically-based distributed hydrologic models to represent <span class="hlt">glacier</span> dynamics.more » We compare predicted variations in <span class="hlt">glacier</span> extent, snow water equivalent and streamflow discharge made with the integrated model with satellite estimates of <span class="hlt">glacier</span> area and terminus position, observed streamflow and snow water equivalent measurements over the period of 1980 2007. Simulations with the coupled hydrology-<span class="hlt">glacier</span> model reduce the uncertainty in streamflow predictions. Our results suggested that on average, the <span class="hlt">glacier</span> <span class="hlt">melt</span> contribution to the Bow River flow upstream of Lake Louise is about 30% in summer. For warm and dry years, however, the <span class="hlt">glacier</span> <span class="hlt">melt</span> contribution can be as large as 50% in August, whereas for cold years, it can be as small as 20% and the timing of <span class="hlt">glacier</span> <span class="hlt">melt</span> signature can be delayed by a month.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-GSFC_20171208_Archive_e001480.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-GSFC_20171208_Archive_e001480.html"><span><span class="hlt">Glaciers</span> and Sea Level Rise</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-08</p> <p><span class="hlt">Melt</span> water ponded at surface in the accumulation zone of Columbia <span class="hlt">Glacier</span>, Alaska, in July 2008. To learn about the contributions of <span class="hlt">glaciers</span> to sea level rise, visit: www.nasa.gov/topics/earth/features/<span class="hlt">glacier</span>-sea-rise.html Credit: W. Tad Pfeffer, University of Colorado at Boulder NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013HESSD..10.2743F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013HESSD..10.2743F"><span>Identification of glacial <span class="hlt">melt</span> water runoff in a karstic environment and its implication for present and future water availability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Finger, D.; Hugentobler, A.; Huss, M.; Voinesco, A.; Wernli, H.; Fischer, D.; Weber, E.; Jeannin, P.-Y.; Kauzlaric, M.; Wirz, A.; Vennemann, T.; Hüsler, F.; Schädler, B.; Weingartner, R.</p> <p>2013-03-01</p> <p><span class="hlt">Glaciers</span> all over the world are expected to continue to retreat due to the global warming throughout the 21st century. Consequently, future seasonal water availability might become scarce once <span class="hlt">glacier</span> areas have declined below a certain threshold affecting future water management strategies. Particular attention should be paid to <span class="hlt">glaciers</span> located in a karstic environment, as parts of the <span class="hlt">melt</span> water can be drained by souterrain karst systems. In this study tracer experiments, karst modeling and <span class="hlt">glacier</span> <span class="hlt">melt</span> modeling are combined in order to identify flow paths in a high alpine, <span class="hlt">glacierized</span>, karstic environment (<span class="hlt">Glacier</span> de la Plaine Morte, Switzerland) and to investigate current and predict future downstream water availability. Flow paths through the karst underground were determined with natural and fluorescent tracers. Subsequently, tracer results and geologic information were assembled in a karst model. Finally, <span class="hlt">glacier</span> <span class="hlt">melt</span> projections driven with a climate scenario were performed to discuss future water availability in the area surrounding the <span class="hlt">glacier</span>. The results suggest that during late summer <span class="hlt">glacier</span> <span class="hlt">melt</span> water is rapidly drained through well-developed channels at the <span class="hlt">glacier</span> bottom to the north of the <span class="hlt">glacier</span>, while during low flow season <span class="hlt">melt</span> water enters into the karst and is drained to the south. Climate change projections reveal that by the end of the century <span class="hlt">glacier</span> <span class="hlt">melt</span> will be significantly reduced in the summer, jeopardizing water availability in <span class="hlt">glacier</span>-fed karst springs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C14A..07J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C14A..07J"><span>Investigating plume dynamics at the ocean-<span class="hlt">glacier</span> interface with turbulence profiling and autonomous vessels</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jackson, R. H.; Nash, J. D.; Sutherland, D. A.; Amundson, J. M.; Kienholz, C.; Skyllingstad, E. D.; Motyka, R. J.</p> <p>2017-12-01</p> <p>The exchanges of heat and freshwater at tidewater <span class="hlt">glacier</span> termini are modulated by small-scale turbulent processes. However, few observations have been obtained near the ocean-<span class="hlt">glacier</span> interface, limiting our ability to quantify turbulent fluxes or test <span class="hlt">melt</span> parameterizations in ocean-<span class="hlt">glacier</span> models. Here, we explore the turbulent plume dynamics at LeConte <span class="hlt">Glacier</span>, Alaska with three extensive field campaigns in May, August and September (2016-17). Two autonomous vessels collected repeat transects of velocity and water properties near the <span class="hlt">glacier</span>, often within 20 m of the terminus. Concurrent shipboard surveying measured turbulence with a vertical microstructure profiler, along with water properties and velocity. These high-resolution surveys provide a 3D view of the circulation and allow us to quantify turbulent fluxes in the near-<span class="hlt">glacier</span> region. We observe two regimes at the terminus: an energetic upwelling plume driven by subglacial discharge at a persistent location, and submarine <span class="hlt">melt</span>-driven convection along other parts of the terminus. We trace the evolution of the subglacial discharge plume as it flows away from the <span class="hlt">glacier</span>, from an initial stage of vigorous mixing to a more quiescent outflow downstream. Resolving these spatial patterns of upwelling and mixing near <span class="hlt">glaciers</span> is a key step towards understanding submarine <span class="hlt">melt</span> rates and glacial fjord circulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28733603','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28733603"><span>Sediment transport drives tidewater <span class="hlt">glacier</span> periodicity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brinkerhoff, Douglas; Truffer, Martin; Aschwanden, Andy</p> <p>2017-07-21</p> <p>Most of Earth's <span class="hlt">glaciers</span> are retreating, but some tidewater <span class="hlt">glaciers</span> are advancing despite increasing temperatures and contrary to their neighbors. This can be explained by the coupling of ice and sediment dynamics: a shoal forms at the <span class="hlt">glacier</span> terminus, reducing ice discharge and causing advance towards an unstable configuration followed by abrupt retreat, in a process known as the tidewater <span class="hlt">glacier</span> cycle. Here we use a numerical model calibrated with observations to show that interactions between ice flow, glacial erosion, and sediment transport drive these cycles, which occur independent of climate variations. Water availability controls cycle period and amplitude, and enhanced <span class="hlt">melt</span> from future warming could trigger advance even in <span class="hlt">glaciers</span> that are steady or retreating, complicating interpretations of <span class="hlt">glacier</span> response to climate change. The resulting shifts in sediment and meltwater delivery from changes in <span class="hlt">glacier</span> configuration may impact interpretations of marine sediments, fjord geochemistry, and marine ecosystems.The reason some of the Earth's tidewater <span class="hlt">glaciers</span> are advancing despite increasing temperatures is not entirely clear. Here, using a numerical model that simulates both ice and sediment dynamics, the authors show that internal dynamics drive <span class="hlt">glacier</span> variability independent of climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.1411M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.1411M"><span>Estimation of Sub Hourly <span class="hlt">Glacier</span> Albedo Values Using Artificial Intelligence Techniques</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moya Quiroga, Vladimir; Mano, Akira; Asaoka, Yoshihiro; Udo, Keiko; Kure, Shuichi; Mendoza, Javier</p> <p>2013-04-01</p> <p><span class="hlt">Glaciers</span> are the most important fresh water reservoirs storing about 67% of total fresh water. Unfortunately, they are retreating and some small <span class="hlt">glaciers</span> have already disappeared. Thus, snow <span class="hlt">glacier</span> <span class="hlt">melt</span> (SGM) estimation plays an important role in water resources management. Whether SGM is estimated by complete energy balance or a simplified method, albedo is an important data present in most of the methods. However, this is a variable value depending on the ground surface and local conditions. The present research presents a new approach for estimating sub hourly albedo values using different artificial intelligence techniques such as artificial neural networks and decision trees along with measured and easy to obtain data. . The models were developed using measured data from the Zongo-Ore station located in the Bolivian tropical <span class="hlt">glacier</span> Zongo (68°10' W, 16°15' S). This station automatically records every 30 minutes several meteorological parameters such as incoming short wave <span class="hlt">radiation</span>, outgoing short wave <span class="hlt">radiation</span>, temperature or relative humidity. The ANN model used was the Multi Layer Perceptron, while the decision tree used was the M5 model. Both models were trained using the WEKA software and validated using the cross validation method. After analysing the model performances, it was concluded that the decision tree models have a better performance. The model with the best performance was then validated with measured data from the Equatorian tropical <span class="hlt">glacier</span> Antizana (78°09'W, 0°28'S). The model predicts the sub hourly albedo with an overall mean absolute error of 0.103. The highest errors occur for albedo measured values higher than 0.9. Considering that this is an extreme value coincident with low measured values of incoming short wave <span class="hlt">radiation</span>, it is reasonable to assume that such values include errors due to censored data. Assuming a maximum albedo of 0.9 improved the accuracy of the model reducing the MAE to less than 0.1. Considering that the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C23C0671S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C23C0671S"><span>Seasonal Subglacial Hydrological Evolution of a Greenland Tidewater <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schild, K. M.; Hawley, R. L.; Morriss, B. F.; Hoffman, M. J.; Catania, G. A.; Neumann, T.</p> <p>2012-12-01</p> <p>The contribution to sea level rise from <span class="hlt">melting</span> ice sheets has doubled in the last decade. The rapid acceleration of Greenland's outlet <span class="hlt">glaciers</span> has been one of the dominant factors in this contribution. Also in this last decade, Greenland has experienced an increase in average summer atmospheric temperature and associated increases in summer surface <span class="hlt">melt</span> duration and extent. These increases in surface <span class="hlt">melt</span> have been strongly linked with increased <span class="hlt">glacier</span> sliding at the base through changes in the sublgacial hydrological system. Previous research has looked at conduit evolution of land-terminating and alpine <span class="hlt">glaciers</span>, but marine-terminating <span class="hlt">glaciers</span>, although more sensitive to environmental change, have not been thoroughly studied. The goal of this project is to investigate the timing between rapid supra-glacial lake drainages (delivering a pulse of water to the base) and the appearance of a meltwater sediment plume at the terminus. We constructed a high-temporal resolution (sub-daily) time series of lake evolution, drainage and sediment plume appearance at Rink Isbræ (west Greenland) using MODIS satellite imagery from 2000-2012. We compare the time of year and the rate of travel of the pulse to establish a better understanding of seasonal conduit development for tidewater outlet <span class="hlt">glaciers</span>. Additionally, in comparing these variables between years, we plan to examine how the subglacial system changes when <span class="hlt">melt</span> season duration and intensity increase. With a clearer understanding of the mechanisms controlling fluctuations in ice flow, specifically those acting in the subglacial environment, scientists can more accurately predict the future of the Greenland Ice Sheet and its effect on global sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120012430','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120012430"><span>What Influences Climate and <span class="hlt">Glacier</span> Change in the Southwestern China?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yasunari, Teppei J.</p> <p>2012-01-01</p> <p>The subject of climate change in the areas of the Tibetan Plateau (TP) and the Himalayas has taken on increasing importance because of available water resources from their mountain <span class="hlt">glaciers</span>. Many of these <span class="hlt">glaciers</span> over the region have been retreating, while some are advancing and stable. Other studies report that some <span class="hlt">glaciers</span> in the Himalayas show acceleration on their shrinkage. However, the causes of the <span class="hlt">glacier</span> <span class="hlt">meltings</span> are still difficult to grasp because of the complexity of climatic change and its influence on <span class="hlt">glacier</span> issues. However, it is vital that we pursue further study to enable the future prediction on <span class="hlt">glacier</span> changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013TCD.....7.5579C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013TCD.....7.5579C"><span>Ocean properties, ice-ocean interactions, and calving front morphology at two major west Greenland <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chauché, N.; Hubbard, A.; Gascard, J.-C.; Box, J. E.; Bates, R.; Koppes, M.; Sole, A.; Patton, H.</p> <p>2013-11-01</p> <p>Warm sub-polar mode water (SPMW) has been identified as a primary driver of mass loss of marine terminating <span class="hlt">glaciers</span> draining the Greenland Ice Sheet (GrIS) yet, the specific mechanisms by which SPMW interacts with these tidewater termini remain uncertain. We present oceanographic data from Rink <span class="hlt">Glacier</span> (RG) and Store <span class="hlt">Glacier</span> (SG) fjords, two major marine outlets draining the western sector of the GrIS into Baffin Bay over the contrasting <span class="hlt">melt</span>-seasons of 2009 and 2010. Submarine <span class="hlt">melting</span> occurs wherever ice is in direct contact with warmer water and the consistent presence of 2.8 °C SPMW adjacent to both ice fronts below 400 m throughout all surveys indicates that <span class="hlt">melting</span> is maintained by a combination of molecular diffusion and large scale, weak convection, diffusional (hereafter called ubiquitous) <span class="hlt">melting</span>. At shallower depths (50-200 m), cold, brine-enriched water (BEW) formed over winter appears to persist into the summer thereby buffering this <span class="hlt">melt</span> by thermal insulation. Our surveys reveal four main modes of <span class="hlt">glacier</span>-ocean interaction, governed by water depth and the rate of <span class="hlt">glacier</span> runoff water (GRW) injected into the fjord. Deeper than 200 m, submarine <span class="hlt">melt</span> is the only process observed, regardless of the intensity of GRW or the depth of injection. However, between the surface and 200 m depth, three further distinct modes are observed governed by the GRW discharge. When GRW is weak (≲1000 m3 s-1), upward motion of the water adjacent to the <span class="hlt">glacier</span> front is subdued, weak forced or free convection plus diffusional submarine <span class="hlt">melting</span> dominates at depth, and seaward outflow of <span class="hlt">melt</span> water occurs from the <span class="hlt">glacier</span> toe to the base of the insulating BEW. During medium intensity GRW (∼1500 m3 s-1), mixing with SPMW yields deep mixed runoff water (DMRW), which rises as a buoyant plume and intensifies local submarine <span class="hlt">melting</span> (enhanced buoyancy-driven <span class="hlt">melting</span>). In this case, DMRW typically attains hydrostatic equilibrium and flows seaward at an intermediate depth of </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/pp/p1386k/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/pp/p1386k/"><span><span class="hlt">Glaciers</span> of North America - <span class="hlt">Glaciers</span> of Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Molnia, Bruce F.</p> <p>2008-01-01</p> <p> literature for each of the 11 mountain ranges, the large island, the island chain, and the archipelago was conducted to determine both the individual and the regional status of Alaskan <span class="hlt">glaciers</span> and to characterize changes in thickness and terminus position of representative <span class="hlt">glaciers</span> in each mountain range or island group. In many areas, observations used for determining changes date from the late 18th or early 19th century. Temperature records at all Alaskan meteorological recording stations document a 20th century warming trend. Therefore, characterizing the response of Alaska's <span class="hlt">glaciers</span> to changing climate helps to quantify potential sea-level rise from past, present, and future <span class="hlt">melting</span> of <span class="hlt">glacier</span> ice (deglaciation of the 14 <span class="hlt">glacierized</span> regions of Alaska), understand present and future hydrological changes, and define impacts on ecosystems that are responding to deglacierization. Many different types of data were scrutinized to determine baselines and to assess the magnitude of <span class="hlt">glacier</span> change. These data include the following: published descriptions of <span class="hlt">glaciers</span> (1794-2000), especially the comprehensive research by Field (1975a) and his colleagues in the Alaska part of Mountain <span class="hlt">Glaciers</span> of the Northern Hemisphere, aerial photography (since 1926), ground photography (since 1884), airborne radar (1981-91), satellite radar (1978-98), space photography (1984-94), multispectral satellite imagery (since 1972), aerial reconnaissance and field observations made by many scientists during the past several decades, and various types of proxy data. The published and unpublished data available for each <span class="hlt">glacierized</span> region and individual <span class="hlt">glacier</span> varied significantly. Geospatial analysis of digitized U.S. Geological Survey (USGS) topographic maps is used to statistically define selected glaciological parameters in the eastern part of the Alaska Range. The analysis determined that every mountain range and island group investigated can be characterized by significant glac</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C44B..04T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C44B..04T"><span>When ice meets water: Sub-aqueous <span class="hlt">melt</span> and its relevance in various settings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Truffer, M.; Motyka, R. J.</p> <p>2014-12-01</p> <p>The largest <span class="hlt">glacier</span> changes are primarily observed in settings where ice flows into a proglacial water body. However, the responses to this interaction are not uniform. Rapidly retreating <span class="hlt">glaciers</span> can occur in close vicinity to advancing ones. Calving styles and <span class="hlt">glacier</span> morphologies vary greatly as well. Temperate lake-calving <span class="hlt">glaciers</span> frequently exhibit floating tongues; but this is rarely observed on temperate tidewater <span class="hlt">glaciers</span>. Calving styles range from mostly sub-aerial calving to full-thickness calving to slow detachment of large ice bergs. In addition to the more obvious mechanical calving, <span class="hlt">glaciers</span> lose mass at their termini through sub-aqueous <span class="hlt">melting</span>. <span class="hlt">Melt</span> rates of submerged ice have been shown to vary over several orders of magnitudes, and can range up to several meters per day. This large range is a consequence of different proglacial water temperatures, and of different modes of water transport. Water convection in proglacial water bodies can be driven by winds and tides, but subglacial water discharge is commonly the strongest and most variable driver. Here we attempt to relate the variability of forcings and <span class="hlt">melt</span> rates to the various morphologies and calving styles of different water-terminating <span class="hlt">glaciers</span>. The highest <span class="hlt">melt</span> rates are observed at low-latitude tidewater <span class="hlt">glaciers</span>, where ocean water can be warm (7 - 10 deg C) and subglacial discharge high. In such settings, sub-aqueous <span class="hlt">melt</span> can reach the same magnitude as ice flux delivered to the terminus and it can control ice terminus position. Polar tidewater <span class="hlt">glaciers</span>, such as those in Greenland, often exhibit floating tongues. Although <span class="hlt">melt</span> rates are likely much lower, they can have a large effect under a floating tongue because of the much larger exposure of ice to water. Changes in <span class="hlt">melt</span> rates can therefore affect the stability of such floating tongues. Low <span class="hlt">melt</span> rates occur at some ice shelves at high latitudes, where the temperature and freshwater forcings are small. This situation can also occur at</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33A1174O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33A1174O"><span>Partitioning the Water Budget in a <span class="hlt">Glacierized</span> Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Neel, S.; Sass, L.; McGrath, D.; McNeil, C.; Myers, K. F.; Bergstrom, A.; Koch, J. C.; Ostman, J. S.; Arendt, A. A.; LeWinter, A.; Larsen, C. F.; Marshall, H. P.</p> <p>2017-12-01</p> <p><span class="hlt">Glaciers</span> couple to the ecosystems in which they reside through their mass balance and subsequent runoff. The unique timing and composition of <span class="hlt">glacier</span> runoff notably impacts ecological and socio-economically important processes, including thermal modulation of streams, nearshore primary production, and groundwater exchange. Predicting how these linkages will evolve as <span class="hlt">glaciers</span> continue to retreat requires a better understanding of basin- to region-scale water budgets. Here we develop a partitioned water balance for Alaska's Wolverine <span class="hlt">Glacier</span> basin for 2016. Our presentation will highlight mass-balance forcing and sensitivity, as well as analyses of hydrometric and geochemical partitioning. These observations provide constraints for hypsometry-based regional projections of <span class="hlt">glacier</span> change, which form the basis of future biogeochemical scenarios. Local climate records show relatively minor warming and drying over the 1967 -2016 interval, yet the impact on the <span class="hlt">glacier</span> was substantial; the average annual balance rate over the study interval is -0.5 m/yr. We performed a sensitivity experiment that suggests that elevation-independent processes drive first-order variability in <span class="hlt">glacier</span>-wide mass balance solutions Analysis of runoff and precipitation data suggest that previously ignored components of the hydrologic cycle (groundwater, evapotranspiration, off-<span class="hlt">glacier</span> snowpack storage, and snow redistribution) may substantially contribute to the basin wide water budget. Initial geochemical assessments (carbon, water isotopes, major ions) highlight unique source signatures (<span class="hlt">glacier</span>-derived, snow-<span class="hlt">melt</span>, groundwater), which will be further explored using a mixing model approach. Applying a range of climate forcings over centennial time-scales suggests the regional equilibrium line altitude is likely to increase by more than 100 m, which will result in extensive <span class="hlt">glacier</span> area losses. Such changes will likely modify the runoff from this basin by increasing inter-annual streamflow</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03386&hterms=Glacier+retreat+global&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DGlacier%2Bretreat%2Bglobal','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03386&hterms=Glacier+retreat+global&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DGlacier%2Bretreat%2Bglobal"><span>Malaspina <span class="hlt">Glacier</span>, Alaska, Perspective with Landsat Overlay</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2003-01-01</p> <p><p/>Malaspina <span class="hlt">Glacier</span> in southeastern Alaska is considered the classic example of a piedmont <span class="hlt">glacier</span>. Piedmont <span class="hlt">glaciers</span> occur where valley <span class="hlt">glaciers</span> exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes. Malaspina <span class="hlt">Glacier</span> is actually a compound <span class="hlt">glacier</span>, formed by the merger of several valley <span class="hlt">glaciers</span>, the most prominent of which seen here are Agassiz <span class="hlt">Glacier</span> (left) and Seward <span class="hlt">Glacier</span> (right). In total, Malaspina <span class="hlt">Glacier</span> is up to 65 kilometers (40 miles) wide and extends up to 45 kilometers (28 miles) from the mountain front nearly to the sea. <p/>This perspective view was created from a Landsat satellite image and an elevation model generated by the Shuttle Radar Topography Mission (SRTM). Landsat views both visible and infrared light, which have been combined here into a color composite that generally shows glacial ice in light blue, snow in white, vegetation in green, bare rock in grays and tans, and the ocean (foreground) in dark blue. The back (northern) edge of the data set forms a false horizon that meets a false sky. <p/><span class="hlt">Glaciers</span> erode rocks, carry them down slope, and deposit them at the edge of the <span class="hlt">melting</span> ice, typically in elongated piles called moraines. The moraine patterns at Malaspina <span class="hlt">Glacier</span> are quite spectacular in that they have huge contortions that result from the <span class="hlt">glacier</span> crinkling as it gets pushed from behind by the faster-moving valley <span class="hlt">glaciers</span>. <p/><span class="hlt">Glaciers</span> are sensitive indicators of climatic change. They can grow and thicken with increasing snowfall and/or decreased <span class="hlt">melting</span>. Conversely, they can retreat and thin if snowfall decreases and/or atmospheric temperatures rise and cause increased <span class="hlt">melting</span>. Landsat imaging has been an excellent tool for mapping the changing geographic extent of <span class="hlt">glaciers</span> since 1972. The elevation measurements taken by SRTM in February 2000 now provide a near-global baseline against which future non-polar region glacial thinning or thickening can be assessed. <p</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMGC41A0866G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMGC41A0866G"><span>Snow and <span class="hlt">glacier</span> change in koshi Basin Himalaya and its response to global warming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gao, Y.; Yang, X.; Yao, T.; Yufeng, D.</p> <p>2010-12-01</p> <p>Recently, the argument that Himalayan <span class="hlt">glaciers</span> will completely <span class="hlt">melt</span> is rather controversial and the U.N.'s leading panel on climate change has apologized for misleading data published in a 2007 report that warned Himalayan <span class="hlt">glaciers</span> could <span class="hlt">melt</span> by 2035. Why the gradual <span class="hlt">melting</span> of Himalayan <span class="hlt">glaciers</span> makes most of the major media headlines? This is because Himalayan <span class="hlt">glacier</span> is the headstream of major rivers in South Asia and Southeast Asia and more than 1/6 people live there. If mass of the <span class="hlt">glaciers</span> <span class="hlt">melt</span> or even disappear, people who rely on those rivers will be at risk. After this dispute, we need to realize that:”Although the <span class="hlt">melting</span> rate still need to further study, the Himalayan <span class="hlt">glaciers</span> are indeed <span class="hlt">melting</span>. And in these areas, there are more uncertainties to affect water resource, such as snow fall, precipitation, regional temperature changes and so on”. Koshi Basin Himalaya, located in the boundary between China and Nepal, consist of three rivers i.e. Sun Koshi, Arun river (the headwaters of arun river in China called Pengqu) and Tamur. All of them converge to India Ganga River. The total area of Koshi Basin is about ~57,870 km2 and elevation ranges from 21 m (plain) to 8825m (Mountain <span class="hlt">glacier</span>). This basin has the typical vertical zonation of Himalaya, so we choose it as the study area. Based on the snow cover data observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Terra spacecraft from 2000-2010, the spatial-temporal distribution and variation of snow cover over the koshi basin are statistical analyzed. <span class="hlt">Glacier</span> changes are also detected from Landsat images in 2000, 2005 and 2010. It is found that snow cover areas are mainly concentrated in the Ridge of Himalaya Mountain. And there are more persistently snow covered areas and <span class="hlt">glaciers</span> in the South Slope of Himalaya Mountain with aspect to the North Slope, although the mean elevation of the North Slope is higher than south slope. During the decade of 2000-2010, a slight decreasing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.C51B0477B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.C51B0477B"><span>Surface mass balance of Greenland mountain <span class="hlt">glaciers</span> and ice caps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Benson, R. J.; Box, J. E.; Bromwich, D. H.; Wahr, J. M.</p> <p>2009-12-01</p> <p>Mountain <span class="hlt">glaciers</span> and ice caps contribute roughly half of eustatic sea-level rise. Greenland has thousands of small mountain <span class="hlt">glaciers</span> and several ice caps > 1000 sq. km that have not been included in previous mass balance calculations. To include small <span class="hlt">glaciers</span> and ice caps in our study, we use Polar WRF, a next-generation regional climate data assimilation model is run at grid resolution less than 10 km. WRF provides surface mass balance data at sufficiently high resolution to resolve not only the narrow ice sheet ablation zone, but provides information useful in downscaling <span class="hlt">melt</span> and accumulation rates on mountain <span class="hlt">glaciers</span> and ice caps. In this study, we refine Polar WRF to simulate a realistic surface energy budget. Surface <span class="hlt">melting</span> is calculated in-line from surface energy budget closure. Blowing snow sublimation is computed in-line. <span class="hlt">Melt</span> water re-freeze is calculated using a revised scheme. Our results are compared with NASA's Gravity Recovery and Climate Experiment (GRACE) and associated error is calculated on a regional and local scale with validation from automated weather stations (AWS), snow pits and ice core data from various regions along the Greenland ice sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....3741S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....3741S"><span>Assessment of Greenland Outlet <span class="hlt">Glacier</span> Albedo Variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stroeve, J.</p> <p>2003-04-01</p> <p>Recent studies have shown that the coastal regions of the Greenland ice sheet are thinning rapidly. Analysis of passive microwave satellite data since 1979 have revealed a corresponding positive trend in the areal extent of <span class="hlt">melt</span>. This trend was emphasized in 2002, when the total area of surface <span class="hlt">melt</span> on the Greenland ice sheet surpased the maximum <span class="hlt">melt</span> extent from the past 24 years by more than 9%. Increases in coastal temperatures have certainly contributed to <span class="hlt">melting</span> near the margins. However, the high rate of thinning in the coastal regions, up to several m/yr, cannot be explained by increases in temperatures alone. Some of the thinning is likely creep thinning resulting from discharge velocities that exceed balance velocities. In order to better understand the role of ablation in the recent thinning rates, the variability in the surface albedo at four outlet <span class="hlt">glaciers</span> is analyzed from 1981 to 2000 using the AVHRR Polar Pathfinder data set. The four <span class="hlt">glaciers</span> analyzed are the following: Storstrommen (77N, 23W), Kangerdlugssuaq (68N, 33W), Petermann (81N, 62W) and Jakobshavn (69N, 50W). Clear sky albedo changes over time from May through September for the period 1981-2000 are presented. These months are chosen in order to capture the full cycle of <span class="hlt">melt</span> onset and refreeze. The albedo record at the <span class="hlt">glaciers</span> shows large seasonal and interannual variability. Resuls indicate a steady decrease in surface albedo during the summer months from 1981 to 2000, particularly in the Jakobshavn drainage basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.H43G1524M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.H43G1524M"><span>Streamflow response to <span class="hlt">glacier</span> <span class="hlt">melt</span> and related fluvial sediment transport in a proglacial Alpine river system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morche, D.; Schuchardt, A.; Baewert, H.; Weber, M.; Faust, M.</p> <p>2016-12-01</p> <p><span class="hlt">Glaciers</span> in the European Alps are retreating since the end of the Little Ice Age around 1850. Where the <span class="hlt">glaciers</span> shrink, they leave unconsolidated sediment stores (moraines, till, glacifluvial deposits). These sediment stores are highly vulnerable for being subsequently eroded and are thus a key variable (source) in the fluvial sediment budget of proglacial areas. The fluvial system in proglacial areas is more or less continuously fed with (fine) sediment by glacial <span class="hlt">melt</span> water (glacial milk) during the ablation period and infrequently (e.g. during rainstorm events) supplied with sediment by landslides, debris flows, rock fall or fluvial transport from the slopes. A part of the sediment input is temporary stored in intermitted sinks, such as the river bed, bars or braid plains. These storages can be reworked and then become sources for fluvial sediment transport mainly during floods. These sediment transporting processes are highly variable in both, the temporal and spatial scale. A research project has been set up in the Kaunertal valley, Austrian Alps. The presented part of this joint project is focussed on the quantification of recent fluvial sediment dynamics in the proglacial Fagge River below the <span class="hlt">glacier</span> Gepatschferner. The <span class="hlt">glacier</span> is located in the Eastern European Alps at the south end of the Kaunertal valley covering an area of 15.7 km² (2012) and is drained by the Fagge River. During the years 2012 to 2015 the Gepatschferner has shown an accelerated glacial retreat leading to the exposure of unconsolidated sediments as well as bedrock areas. The main aim of the presented part of the joint project is the investigation of the fluvial sediment transport rates in the proglacial Fagge River in the Kaunertal valley. Sediment output of the glacial meltwater stream was measured during the ablation periods at a gauging station installed in front of the <span class="hlt">glacier</span> outlet. Water level was recorded every 15 minutes and discharge measurements were made at different</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C53A0828B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C53A0828B"><span>Fluctuations of a Temperate Mountain <span class="hlt">Glacier</span> in Response to Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bachmann, M.; Bidlake, W.</p> <p>2012-12-01</p> <p><span class="hlt">Glacier</span> mass balance is a fundamental parameter for understanding and predicting the evolution of <span class="hlt">glaciers</span> on the landscape in response to climate change. The USGS Ice and Climate Project (ICP) continues to extend the longest-running USGS benchmark <span class="hlt">glacier</span> mass-balance record at South Cascade <span class="hlt">Glacier</span>, Washington. Due to the importance of South Cascade <span class="hlt">Glacier</span> data sets for glaciological and climate research, ICP is releasing decades-old previously unpublished <span class="hlt">glacier</span> surface and bed maps, mass balance data at individual sites, ice velocity data, and an updated ice inventory for the surrounding basin. The complete record includes a pre-Industrial Revolution reconstruction of the <span class="hlt">glacier</span> and seasonal mass balance measurements for the past 54 years (1958-2012). Since 2000, the <span class="hlt">glacier</span> has experienced four of the five most negative summer balances and two of the largest positive accumulation years, indicating that the <span class="hlt">glacier</span> is continuing to respond to recent warming and precipitation changes. Recently, ICP has developed a temperature-index <span class="hlt">glacier</span> <span class="hlt">melt</span> model that extrapolates daily accumulation and <span class="hlt">melt</span> rates from intermittent field observations based on regional meteorological data, and an expert system for mass balance that captures the strengths of both measurement and modeling for assessing mass balance. The models have been successfully calibrated at South Cascade <span class="hlt">Glacier</span>, where ample observations are available, but are designed to be used with as few or as many glaciological field data as are available for a given ice mass.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.2773W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.2773W"><span>Satellite-derived submarine <span class="hlt">melt</span> rates and mass balance (2011-2015) for Greenland's largest remaining ice tongues</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilson, Nat; Straneo, Fiammetta; Heimbach, Patrick</p> <p>2017-12-01</p> <p>Ice-shelf-like floating extensions at the termini of Greenland <span class="hlt">glaciers</span> are undergoing rapid changes with potential implications for the stability of upstream <span class="hlt">glaciers</span> and the ice sheet as a whole. While submarine <span class="hlt">melting</span> is recognized as a major contributor to mass loss, the spatial distribution of submarine <span class="hlt">melting</span> and its contribution to the total mass balance of these floating extensions is incompletely known and understood. Here, we use high-resolution WorldView satellite imagery collected between 2011 and 2015 to infer the magnitude and spatial variability of <span class="hlt">melt</span> rates under Greenland's largest remaining ice tongues - Nioghalvfjerdsbræ (79 North <span class="hlt">Glacier</span>, 79N), Ryder <span class="hlt">Glacier</span> (RG), and Petermann <span class="hlt">Glacier</span> (PG). Submarine <span class="hlt">melt</span> rates under the ice tongues vary considerably, exceeding 50 m a-1 near the grounding zone and decaying rapidly downstream. Channels, likely originating from upstream subglacial channels, give rise to large <span class="hlt">melt</span> variations across the ice tongues. We compare the total <span class="hlt">melt</span> rates to the influx of ice to the ice tongue to assess their contribution to the current mass balance. At Petermann <span class="hlt">Glacier</span> and Ryder <span class="hlt">Glacier</span>, we find that the combined submarine and aerial <span class="hlt">melt</span> approximately balances the ice flux from the grounded ice sheet. At Nioghalvfjerdsbræ the total <span class="hlt">melt</span> flux (14.2 ± 0.96 km3 a-1 w.e., water equivalent) exceeds the inflow of ice (10.2 ± 0.59 km3 a-1 w.e.), indicating present thinning of the ice tongue.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12..701M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12..701M"><span>Spatiotemporal variability of Canadian High Arctic <span class="hlt">glacier</span> surface albedo from MODIS data, 2001-2016</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mortimer, Colleen A.; Sharp, Martin</p> <p>2018-02-01</p> <p>Inter-annual variations and longer-term trends in the annual mass balance of <span class="hlt">glaciers</span> in Canada's Queen Elizabeth Islands (QEI) are largely attributable to changes in summer <span class="hlt">melt</span>. The largest source of <span class="hlt">melt</span> energy in the QEI in summer is net shortwave <span class="hlt">radiation</span>, which is modulated by changes in <span class="hlt">glacier</span> surface albedo. We used measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors to investigate large-scale spatial patterns, temporal trends, and variability in the summer surface albedo of QEI <span class="hlt">glaciers</span> from 2001 to 2016. Mean summer black-sky shortwave broadband albedo (BSA) decreased at a rate of 0.029±0.025 decade-1 over that period. Larger reductions in BSA occurred in July (-0.050±0.031 decade-1). No change in BSA was observed in either June or August. Most of the decrease in BSA, which was greatest at lower elevations around the margins of the ice masses, occurred between 2007 and 2012, when mean summer BSA was anomalously low. The first principal component of the 16-year record of mean summer BSA was well correlated with the mean summer North Atlantic Oscillation index, except in 2006, 2010, and 2016, when the mean summer BSA appears to have been dominated by the August BSA. During the period 2001-2016, the mean summer land surface temperature (LST) over the QEI <span class="hlt">glaciers</span> and ice caps increased by 0.049±0.038 °C yr-1, and the BSA record was negatively correlated (r: -0.86) with the LST record, indicative of a positive ice-albedo feedback that would increase rates of mass loss from the QEI <span class="hlt">glaciers</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41C0676G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41C0676G"><span>A Comparison of the Seasonal Change of Albedo across <span class="hlt">Glaciers</span> and Ice-Covered Lakes of the Taylor Valley, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gooseff, M. N.; Bergstrom, A.</p> <p>2016-12-01</p> <p>The Dry Valleys of Antarctica are a polar desert ecosystem consisting of piedmont and alpine <span class="hlt">glaciers</span>, ice-covered lakes, and vast expanses of bare soil. The ecosystem is highly dependent on glacial <span class="hlt">melt</span> a water source. Because average summer temperatures are close to freezing, <span class="hlt">glacier</span> ice and lake ice are very closely linked to the energy balance. A slight increase in incoming <span class="hlt">radiation</span> or decrease in albedo can have large effects on the timing and volume of available liquid water. However, we have yet to fully characterize the seasonal evolution of albedo in the valleys. In this study, we used a camera, gps, and short wave radiometer to characterize the albedo within and across landscape types in the Taylor Valley. These instruments were attached to a helicopter and flown on a prescribed path along the valley at approximately 300 feet above the ground surface five different times throughout the season from mid-November to mid-January, 2015-2016. We used these data to calculate the albedo of each <span class="hlt">glacier</span>, lake, and the soil surface of the lake basins in the valley for each flight. As expected, we found that all landscape types had significantly different albedo, with the <span class="hlt">glaciers</span> consistently the highest throughout the season and the bare soils the lowest (p-value < 0.05). We hypothesized that albedo would decrease throughout the season with snow <span class="hlt">melt</span> and increasing sediment exposure on the <span class="hlt">glacier</span> and lake surfaces. However, small snow events (< 3 cm) caused somewhat persistent high albedo on the lakes and <span class="hlt">glaciers</span>. Furthermore, there was a range in albedo across <span class="hlt">glaciers</span> and each responded to seasonal snow and <span class="hlt">melt</span> differently. These findings highlight the importance of understanding the spatial and temporal variability in albedo and the close coupling of climate and landscape response. We can use this new understanding of landscape albedo to better predict how the Dry Valley ecosystems will respond to changing climate at the basin scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70020677','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70020677"><span>Water flow through temperate <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Fountain, A.G.; Walder, J.S.</p> <p>1998-01-01</p> <p>Understanding water movement through a <span class="hlt">glacier</span> is fundamental to several critical issues in glaciology, including <span class="hlt">glacier</span> dynamics, <span class="hlt">glacier-induced</span> floods, and the prediction of runoff from <span class="hlt">glacierized</span> drainage basins. to this end we have synthesized a conceptual model os water movement through a temperate <span class="hlt">glacier</span> from the surface to the outlet stream. Processes that regulate the rate and distribution of water input at the <span class="hlt">glacier</span> surface and that regulate water movement from the surface to the bed play important but commonly neglected roles in <span class="hlt">glacier</span> hydrology. Where a <span class="hlt">glacier</span> is covered by a layer of porous, permeable firn (the accumulation zone), the flux of water to the <span class="hlt">glacier</span> interior varies slowly because the firn temporarily stores water and thereby smooths out variations in the supply rate. In the firn-free ablation zone, in contrast, the flux of water into the <span class="hlt">glacier</span> depends directly on the rate of surface <span class="hlt">melt</span> or rainfall and therefore varies greatly in time. Water moves from the surface to the bed through an upward branching arborescent network consisting of both steeply inclined conduits, formed by the enlargement of intergranular veins, and gently inclined conduits, sprqwned by water flow along the bottoms of near-surface fractures (crevasses). Englacial drainage conduits deliver water to the <span class="hlt">glacier</span> bed at a linited number of points, probably a long distance downglacier of where water enters the <span class="hlt">glacier</span>. Englacial conduits supplied from the accumulation zone are quasi steady state features that convey the slowly varying water flux delivered via the firn. their size adjusts so that they are usually full of water and flow is pressurized. In contrast, water flow in englacial conduits supplied from the ablation area is pressurized only near times of peak daily flow or during rainstorms; flow is otherwise in an open-channel configuration. The subglacial drainage system typically consists of several elements that are distinct both morpphologically and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998Geomo..21..207A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998Geomo..21..207A"><span>Topographic context of <span class="hlt">glaciers</span> and perennial snowfields, <span class="hlt">Glacier</span> National Park, Montana</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Allen, Thomas R.</p> <p>1998-01-01</p> <p>Equilibrium-line altitudes (ELAs) of modem <span class="hlt">glaciers</span> in the northern Rocky Mountains are known to correspond with regional climate, but strong subregional gradients such as across the Continental Divide in <span class="hlt">Glacier</span> National Park, Montana, also exert topoclimatic influences on the ELA. This study analyzed the relationships between <span class="hlt">glacier</span> and snowfield morphology, ELA, and surrounding topography. <span class="hlt">Glaciers</span> and perennial snowfields were mapped using multitemporal satellite data from the Landsat Thematic Mapper and aerial photography within an integrated Geographic Information System (GIS). Relationships between <span class="hlt">glacier</span> morphology and ELA were investigated using discriminant analysis. Four morphological categories of perennial snow and ice patches were identified: cirque <span class="hlt">glacier</span>, niche <span class="hlt">glacier</span>, ice cap, and snowfield. ELA was derived from overlaid <span class="hlt">glacier</span> boundaries and Digital Elevation Models (DEMs) within the GIs. DEMs provided topographic variables and models of solar <span class="hlt">radiation</span> and wind exposure/shelteredness. Regression analysis showed the effects of exposure; on snow accumulation, the strong influence of local topography through upslope zone morphology such as cirque backwalls, and the tendency for <span class="hlt">glaciers</span> with high ELAs to exhibit compactness in morphology. Results highlight the relatively compact shape and larger area of <span class="hlt">glaciers</span> adjacent to the Continental Divide. Discriminant analysis correctly predicted the type of <span class="hlt">glacier</span> morphology in more than half the observations using factored variables of <span class="hlt">glacier</span> shape, elevation range, and upslope area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1919320L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1919320L"><span>River conferences under temperate valley <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lane, Stuart; Egli, Pascal; Irving, James</p> <p>2017-04-01</p> <p>Both geophysical measurements (ground penetrating radar) and hydrological inference has shown that subglacial drainage networks are dendritic and that means that they must have confluences. In general, there are very few studies of rivers under <span class="hlt">glaciers</span> and almost no consideration at all of confluences, despite the fact that they could be a critical parameter in understanding coupling at the ice-sediment bed interface. Subglacial channels, normally known as conduits, are typically associated with the combined effect of hydraulic pressure driven ice <span class="hlt">melt</span> (which opens them) and ice overburden pressure (which closes them). Inferences from dye break out curves shows that has the efficiency of ice <span class="hlt">melt</span> increases progressively during the summer ablation season, <span class="hlt">melt</span> rates closure rates and a channelized system becomes progressively more effective. Most recently, measurements at the Upper Arolla <span class="hlt">Glacier</span> show that the effects of this growing efficiency is an evolution in the subglacial hydrological system towards higher peak flows and lower base flows later in the <span class="hlt">melt</span> season. This increases the probability that late in the <span class="hlt">melt</span> season, sediment transport becomes discontinuous, with overnight deposition and daytime erosion. This would in turn produce the rapid reductions in sediment transport capacity overnight needed to deposit sediment and to block conduits, increase basal water pressure and explain the hydraulic jacking observed in snout marginal zones at a time when it should not be expected. The question that follows is what effects do confluences have on this process? The geometry of subglacial channels is such that when they join they lead to rapid changes in hydraulic geometry. Crucially, these are likely to have a non-linear impact upon sediment transport capacity, which should reduce disproportionally in the conduits downstream of the junction. Thus, it is possible that confluence zones under <span class="hlt">glaciers</span> become sites of very rapid sediment accumulation and blockage</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C43D..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C43D..07S"><span>Supraglacial lakes on Himalayan debris-covered <span class="hlt">glacier</span> (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sakai, A.; Fujita, K.</p> <p>2013-12-01</p> <p>Debris-covered <span class="hlt">glaciers</span> are common in many of the world's mountain ranges, including in the Himalayas. Himalayan debris-covered <span class="hlt">glacier</span> also contain abundant glacial lakes, including both proglacial and supraglacial types. We have revealed that heat absorption through supraglacial lakes was about 7 times greater than that averaged over the whole debris-covered zone. The heat budget analysis elucidated that at least half of the heat absorbed through the water surface was released with water outflow from the lakes, indicating that the warm water enlarge englacial conduits and produce internal ablation. We observed some portions at debris-covered area has caved at the end of <span class="hlt">melting</span> season, and ice cliff has exposed at the side of depression. Those depression has suggested that roof of expanded water channels has collapsed, leading to the formation of ice cliffs and new lakes, which would accelerate the ablation of debris-covered <span class="hlt">glaciers</span>. Almost glacial lakes on the debris-covered <span class="hlt">glacier</span> are partially surrounded by ice cliffs. We observed that relatively small lakes had non-calving, whereas, calving has occurred at supraglacial lakes with fetch larger than 80 m, and those lakes expand rapidly. In the Himalayas, thick sediments at the lake bottom insulates <span class="hlt">glacier</span> ice and lake water, then the lake water tends to have higher temperature (2-4 degrees C). Therefore, thermal undercutting at ice cliff is important for calving processes in the glacial lake expansion. We estimated and subaqueous ice <span class="hlt">melt</span> rates during the <span class="hlt">melt</span> and freeze seasons under simple geomorphologic conditions. In particular, we focused on valley wind-driven water currents in various fetches during the <span class="hlt">melt</span> season. Our results demonstrate that the subaqueous ice <span class="hlt">melt</span> rate exceeds the ice-cliff <span class="hlt">melt</span> rate above the water surface when the fetch is larger than 20 m with the water temperature of 2-4 degrees C. Calculations suggest that onset of calving due to thermal undercutting is controlled by water</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApPhL.104z3106H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApPhL.104z3106H"><span>Internal stress-<span class="hlt">induced</span> <span class="hlt">melting</span> below <span class="hlt">melting</span> temperature at high-rate laser heating</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hwang, Yong Seok; Levitas, Valery I.</p> <p>2014-06-01</p> <p>In this Letter, continuum thermodynamic and phase field approaches (PFAs) predicted internal stress-<span class="hlt">induced</span> reduction in <span class="hlt">melting</span> temperature for laser-irradiated heating of a nanolayer. Internal stresses appear due to thermal strain under constrained conditions and completely relax during <span class="hlt">melting</span>, producing an additional thermodynamic driving force for <span class="hlt">melting</span>. Thermodynamic <span class="hlt">melting</span> temperature for Al reduces from 933.67 K for a stress-free condition down to 898.1 K for uniaxial strain and to 920.8 K for plane strain. Our PFA simulations demonstrated barrierless surface-<span class="hlt">induced</span> <span class="hlt">melt</span> nucleation below these temperatures and propagation of two solid-<span class="hlt">melt</span> interfaces toward each other at the temperatures very close to the corresponding predicted thermodynamic equilibrium temperatures for the heating rate Q ≤1.51×1010K/s. At higher heating rates, kinetic superheating competes with a reduction in <span class="hlt">melting</span> temperature and <span class="hlt">melting</span> under uniaxial strain occurs at 902.1 K for Q = 1.51 × 1011 K/s and 936.9 K for Q = 1.46 × 1012 K/s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT.......137S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT.......137S"><span>The Influence of Subglacial Hydrology on Arctic Tidewater <span class="hlt">Glaciers</span> and Fjords</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schild, Kristin M.</p> <p></p> <p>Mass loss from the Greenland Ice Sheet has accelerated throughout the last decade, predominantly due to a quadrupling of ice discharge by iceberg calving, submarine <span class="hlt">melting</span>, and meltwater runoff at marine-terminating outlet <span class="hlt">glaciers</span>. The recent acceleration has been linked to the transport of increasing amounts of meltwater, fuelled by warming temperatures. These processes include enhanced basal sliding, inefficient subglacial drainage networks, and a warming of ocean waters in contact with the <span class="hlt">glacier</span> terminus. Understanding the impact of meltwater on tidewater <span class="hlt">glacier</span> dynamics, both subglacially and proglacially, is a key component in predicting <span class="hlt">glacier</span> health and future sea level rise. However, the spatial and temporal magnitude of this meltwater impact is poorly understood. The goals of this dissertation are to identify how meltwater travels subglacially through a tidewater <span class="hlt">glacier</span> system, establish a method to monitor tidewater <span class="hlt">glacier</span> discharge remotely, and calculate the impact of subglacial discharge on terminus stability.. The inaccessibility of subglacial and terminus environments prohibits direct hydrological observations. We use combinations of remote sensing, reanalysis models, and in situ fjord data to accomplish these research goals by measuring indicators of subglacial meltwater discharge and fjord circulation (sediment plumes exiting the terminus and the movement of small icebergs in the fjord). By monitoring the timing and duration of plumes exiting a fast-flowing Greenland tidewater <span class="hlt">glacier</span>, we found short-term variability in meltwater discharge, persistent subglacial pathways, and evidence of over-winter subglacial storage. Using <span class="hlt">glaciers</span> in Svalbard, we established a new method to determine sediment concentration from Landsat-8 spectral reflectance, and used this sediment concentration to quantify relative seasonal meltwater discharge at tidewater <span class="hlt">glaciers</span>. Finally, we used the movement of icebergs and ocean temperatures to establish a terminus</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018FrEaS...6...31F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018FrEaS...6...31F"><span>Dissolved trace and minor elements in cryoconite holes and supraglacial streams, Canada <span class="hlt">Glacier</span>, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fortner, Sarah K.; Lyons, W. Berry</p> <p>2018-04-01</p> <p>Here we present a synthesis of the trace element chemistry in <span class="hlt">melt</span> on the surface Canada <span class="hlt">Glacier</span>, Taylor Valley, McMurdo Dry Valleys (MDV), Antarctica ( 78°S). The MDV is largely ice-free. Low accumulation rates, strong winds, and proximity to the valley floor make these <span class="hlt">glaciers</span> dusty in comparison to their inland counterparts. This study examines both supraglacial <span class="hlt">melt</span> streams and cryoconite holes. Supraglacial streams on the lower Canada <span class="hlt">Glacier</span> have median dissolved (<0.4 µm) concentrations of Fe, Mn, As, Cu, and V of 71.5, 75.5, 3.7, 4.6, and 4.3 nM. All dissolved Cd concentrations and the vast majority of Pb values are below our analytical detection (i.e. 0.4 and 0.06 nM). Chemical behavior did not follow similar trends for eastern and western draining waters. Heterogeneity likely reflects distinctions eolian deposition, rock:water ratios, and hydrologic connectivity. Future increases in wind-delivered sediment will likely drive dynamic responses in <span class="hlt">melt</span> chemistry. For elements above detection limits, dissolved concentrations in <span class="hlt">glacier</span> surface <span class="hlt">melt</span> are within an order of magnitude of concentrations observed in proglacial streams (i.e. flowing on the valley floor). This suggests that <span class="hlt">glacier</span> surfaces are an important source of downstream chemistry. The Fe enrichment of cryoconite water relative to N, P, or Si exceeds enrichment observed in marine phytoplankton. This suggests that the <span class="hlt">glacier</span> surface is an important source of Fe to downstream ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1512341E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1512341E"><span>Arctic polynya and <span class="hlt">glacier</span> interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edwards, Laura</p> <p>2013-04-01</p> <p>Major uncertainties surround future estimates of sea level rise attributable to mass loss from the polar ice sheets and ice caps. Understanding changes across the Arctic is vital as major potential contributors to sea level, the Greenland Ice Sheet and the ice caps and <span class="hlt">glaciers</span> of the Canadian Arctic archipelago, have experienced dramatic changes in recent times. Most ice mass loss is currently focused at a relatively small number of <span class="hlt">glacier</span> catchments where ice acceleration, thinning and calving occurs at ocean margins. Research suggests that these tidewater <span class="hlt">glaciers</span> accelerate and iceberg calving rates increase when warming ocean currents increase <span class="hlt">melt</span> on the underside of floating <span class="hlt">glacier</span> ice and when adjacent sea ice is removed causing a reduction in 'buttressing' back stress. Thus localised changes in ocean temperatures and in sea ice (extent and thickness) adjacent to major glacial catchments can impact hugely on the dynamics of, and hence mass lost from, terrestrial ice sheets and ice caps. Polynyas are areas of open water within sea ice which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~50,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas play a vital role in the heat balance of the polar oceans and strongly impact regional oceanography. Where polynyas develop adjacent to tidewater <span class="hlt">glaciers</span> their influence on ocean circulation and water temperatures may play a major part in controlling subsurface ice <span class="hlt">melt</span> rates by impacting on the water masses reaching the calving front. Areas of open water also play a significant role in controlling the potential of the atmosphere to carry moisture, as well as allowing heat exchange between the atmosphere and ocean, and so can influence accumulation on (and hence thickness of) <span class="hlt">glaciers</span> and ice caps. Polynya presence and size also has implications for sea ice extent and therefore potentially the buttressing effect on neighbouring</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28558426','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28558426"><span>Insights into mercury deposition and spatiotemporal variation in the <span class="hlt">glacier</span> and <span class="hlt">melt</span> water from the central Tibetan Plateau.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Paudyal, Rukumesh; Kang, Shichang; Huang, Jie; Tripathee, Lekhendra; Zhang, Qianggong; Li, Xiaofei; Guo, Junming; Sun, Shiwei; He, Xiaobo; Sillanpää, Mika</p> <p>2017-12-01</p> <p>Long-term monitoring of global pollutant such as Mercury (Hg) in the cryosphere is very essential for understanding its bio-geochemical cycling and impacts in the pristine environment with limited emission sources. Therefore, from May 2015 to Oct 2015, surface snow and snow-pits from Xiao Dongkemadi <span class="hlt">Glacier</span> and <span class="hlt">glacier</span> <span class="hlt">melt</span> water were sampled along an elevation transect from 5410 to 5678m a.s.l. in the central Tibetan Plateau (TP). The concentration of Hg in surface snow was observed to be higher than that from other parts of the TP. Unlike the southern parts of the TP, no clear altitudinal variation was observed in the central TP. The peak Total Hg (Hg T ) concentration over the vertical profile on the snow pits corresponded with a distinct yellowish-brown dust layer supporting the fact that most of the Hg was associated with particulate matter. It was observed that only 34% of Hg in snow was lost when the surface snow was exposed to sunlight indicating that the surface snow is less influenced by the post-depositional process. Significant diurnal variation of Hg T concentration was observed in the river water, with highest concentration observed at 7pm when the discharge was highest and lowest concentration during 7-8am when the discharge was lowest. Such results suggest that the rate of discharge was influential in the concentration of Hg T in the <span class="hlt">glacier</span> fed rivers of the TP. The estimated export of Hg T from Dongkemadi river basin is 747.43gyr -1 , which is quite high compared to other <span class="hlt">glaciers</span> in the TP. Therefore, the export of global contaminant Hg might play enhanced role in the Alpine regions as these <span class="hlt">glaciers</span> are retreating at an alarming rate under global warming which may have adverse impact on the ecosystem and the human health of the region. Copyright © 2017 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41C1237P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41C1237P"><span>Sensitivity of Totten <span class="hlt">Glacier</span> Ice Shelf extent and grounding line to oceanic forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pelle, T.; Morlighem, M.; Choi, Y.</p> <p>2017-12-01</p> <p>Totten <span class="hlt">Glacier</span> is a major outlet <span class="hlt">glacier</span> of the East Antarctic Ice Sheet and has been shown to be vulnerable to ocean-<span class="hlt">induced</span> <span class="hlt">melt</span> in both its past and present states. The intrusion of warm, circumpolar deep water beneath the Totten <span class="hlt">Glacier</span> Ice Shelf (TGIS) has been observed to accelerate ice shelf thinning and promote iceberg calving, a primary mechanism of mass discharge from Totten. As such, accurately simulating TGIS's ice front dynamics is crucial to the predictive capabilities of ice sheet models in this region. Here, we study the TGIS using the Ice Sheet System Model (ISSM) and test the applicability of three calving laws: Crevasse Formation calving, Eigen calving, and Tensile Stress calving. We simulate the evolution of Totten <span class="hlt">Glacier</span> through 2100 under enhanced oceanic forcing in order to investigate both future changes in ice front dynamics and possible thresholds of instability. In addition, we artificially retreat Totten's ice front position and allow the model to proceed dynamically in order to analyze the response of the <span class="hlt">glacier</span> to calving events. Our analyses show that Tensile Stress calving most accurately reproduces Totten <span class="hlt">Glacier</span>'s observed ice front position. Furthermore, unstable grounding line retreat is projected when Totten is simulated under stronger oceanic thermal forcing scenarios and when the calving front is significantly retreated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.5501L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.5501L"><span>Mechanisms and Simulation of accelerated shrinkage of continental <span class="hlt">glaciers</span>: a case study of Urumqi <span class="hlt">Glacier</span> No. 1 Eastern Tianshan, Central Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Zhongqin; Ren, Jiawen; Li, Huilin; Wang, Puyu; Wang, Feiteng</p> <p>2016-04-01</p> <p>Similar to most mountain <span class="hlt">glaciers</span> in the world, Urumqi <span class="hlt">Glacier</span> No. 1 (UG1), the best observed <span class="hlt">glacier</span> in China with continued glaciological and climatological monitoring records of longer than 50 years has experienced an accelerated recession during the past several decades. The purpose of this study is to investigate the acceleration of recession. By taking UG1 as an example, we analyze the generic mechanisms of acceleration of shrinkage of continental mountain <span class="hlt">glaciers</span>. The results indicate that the acceleration of mass loss of UG1 commenced first in 1985 and second in 1996 and that the latter was more vigorous. The air temperature rises during <span class="hlt">melting</span> season, the ice temperature augment of the <span class="hlt">glacier</span> and the albedo reduction on the <span class="hlt">glacier</span> surface are considered responsible for the accelerated recession. In addition, the simulations of the accelerated shrinkage of UG1 are introduced.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611108L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611108L"><span><span class="hlt">Glaciers</span> and small ice caps in the macro-scale hydrological cycle - an assessment of present conditions and future changes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lammers, Richard; Hock, Regine; Prusevich, Alexander; Bliss, Andrew; Radic, Valentina; Glidden, Stanley; Grogan, Danielle; Frolking, Steve</p> <p>2014-05-01</p> <p><span class="hlt">Glacier</span> and small ice cap <span class="hlt">melt</span> water contributions to the global hydrologic cycle are an important component of human water supply and for sea level rise. This <span class="hlt">melt</span> water is used in many arid and semi-arid parts of the world for direct human consumption as well as indirect consumption by irrigation for crops, serving as frozen reservoirs of water that supplement runoff during warm and dry periods of summer when it is needed the most. Additionally, this <span class="hlt">melt</span> water reaching the oceans represents a direct input to sea level rise and therefore accurate estimates of this contribution have profound economic and geopolitical implications. It has been demonstrated that, on the scale of <span class="hlt">glacierized</span> river catchments, land surface hydrological models can successfully simulate <span class="hlt">glacier</span> contribution to streamflow. However, at global scales, the implementation of <span class="hlt">glacier</span> <span class="hlt">melt</span> in hydrological models has been rudimentary or non-existent. In this study, a global <span class="hlt">glacier</span> mass balance model is coupled with the University of New Hampshire Water Balance/Transport Model (WBM) to assess recent and projected future <span class="hlt">glacier</span> contributions to the hydrological cycle over the global land surface (excluding the ice sheets of Greenland and Antarctica). For instance, results of WBM simulations indicate that seasonal <span class="hlt">glacier</span> <span class="hlt">melt</span> water in many arid climate watersheds comprises 40 % or more of their discharge. Implicitly coupled <span class="hlt">glacier</span> and WBM models compute monthly <span class="hlt">glacier</span> mass changes and resulting runoff at the <span class="hlt">glacier</span> terminus for each individual <span class="hlt">glacier</span> from the globally complete Randolph <span class="hlt">Glacier</span> Inventory including over 200 000 <span class="hlt">glaciers</span>. The time series of <span class="hlt">glacier</span> runoff is aggregated over each hydrological modeling unit and delivered to the hydrological model for routing downstream and mixing with non-glacial contribution of runoff to each drainage basin outlet. WBM tracks and uses glacial and non-glacial components of the in-stream water for filling reservoirs, transfers of water between</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29791884','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29791884"><span>Rainfall as primary driver of discharge and solute export from rock <span class="hlt">glaciers</span>: The Col d'Olen Rock <span class="hlt">Glacier</span> in the NW Italian Alps.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Colombo, Nicola; Gruber, Stephan; Martin, Maria; Malandrino, Mery; Magnani, Andrea; Godone, Danilo; Freppaz, Michele; Fratianni, Simona; Salerno, Franco</p> <p>2018-10-15</p> <p>Three hypotheses exist to explain how meteorological variables drive the amount and concentration of solute-enriched water from rock <span class="hlt">glaciers</span>: (1) Warm periods cause increased subsurface ice <span class="hlt">melt</span>, which releases solutes; (2) rain periods and the <span class="hlt">melt</span> of long-lasting snow enhance dilution of rock-<span class="hlt">glacier</span> outflows; and (3) percolation of rain through rock <span class="hlt">glaciers</span> facilitates the export of solutes, causing an opposite effect as that described in hypothesis (2). This lack of detailed understanding likely exists because suitable studies of meteorological variables, hydrologic processes and chemical characteristics of water bodies downstream from rock <span class="hlt">glaciers</span> are unavailable. In this study, a rock-<span class="hlt">glacier</span> pond in the North-Western Italian Alps was studied on a weekly basis for the ice-free seasons 2014 and 2015 by observing the meteorological variables (air temperature, snowmelt, rainfall) assumed to drive the export of solute-enriched waters from the rock <span class="hlt">glacier</span> and the hydrochemical response of the pond (water temperature as a proxy of rock-<span class="hlt">glacier</span> discharge, stable water isotopes, major ions and selected trace elements). An intra-seasonal pattern of increasing solute export associated with higher rock-<span class="hlt">glacier</span> discharge was found. Specifically, rainfall, after the winter snowpack depletion and prolonged periods of atmospheric temperature above 0 °C, was found to be the primary driver of solute export from the rock <span class="hlt">glacier</span> during the ice-free season. This occurs likely through the flushing of isotopically- and geochemically-enriched icemelt, causing concomitant increases in the rock-<span class="hlt">glacier</span> discharge and the solute export (SO 4 2- , Mg 2+ , Ca 2+ , Ni, Mn, Co). Moreover, flushing of microbially-active sediments can cause increases in NO 3 - export. Copyright © 2018 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C13D0872J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C13D0872J"><span>Monitoring Jakobshavn <span class="hlt">Glacier</span> using Sequential Landsat Images</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jian, Z.; Zhuoqi, C.; Cheng, X.</p> <p>2016-12-01</p> <p>Jakobshavn <span class="hlt">Glacier</span> is the fastest (19 m per day) and one of the most active <span class="hlt">glaciers</span> around the world. Discharging more than 35km3 of ice every year, its mass loss surpasses anyone else outside the Antarctic. From Landsat 8 OLI Images on August 14, 2015, we find a huge iceberg about 5 km2 calved from resulting in the front shrinking for 1060.8m. NSIDC ice velocity data and weather station data on Jakobshavn <span class="hlt">glacier</span> are used to analyze the cause of calving. On one hand, upstream <span class="hlt">glacier</span> push forward the Jakobshavn <span class="hlt">glacier</span> westward continually, many cracks were formed over the <span class="hlt">glacier</span> surface. Surface <span class="hlt">melting</span> water flow into the interior of <span class="hlt">glaciers</span> to accelerate calving. On the other hand with the gradually rising temperature, the bottom of <span class="hlt">glaciers</span> accelerate ablation. When <span class="hlt">glaciers</span> move into the ocean and the thin bottom can not provide strong enough support, calving occurs. Before this incident, we trace sequential Landsat data during 1986 to 2015. In 2010, it had another large-scale calving. We draw from our data that Jakobshavn retreated intensely in the past 30 years although in the last 10 years it appears more stable. The speed of <span class="hlt">glacier</span> shrinking during 1996 to 2006 is three times as fast as past 10 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22303905-internal-stress-induced-melting-below-melting-temperature-high-rate-laser-heating','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22303905-internal-stress-induced-melting-below-melting-temperature-high-rate-laser-heating"><span>Internal stress-<span class="hlt">induced</span> <span class="hlt">melting</span> below <span class="hlt">melting</span> temperature at high-rate laser heating</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Hwang, Yong Seok, E-mail: yshwang@iastate.edu; Levitas, Valery I., E-mail: vlevitas@iastate.edu</p> <p></p> <p>In this Letter, continuum thermodynamic and phase field approaches (PFAs) predicted internal stress-<span class="hlt">induced</span> reduction in <span class="hlt">melting</span> temperature for laser-irradiated heating of a nanolayer. Internal stresses appear due to thermal strain under constrained conditions and completely relax during <span class="hlt">melting</span>, producing an additional thermodynamic driving force for <span class="hlt">melting</span>. Thermodynamic <span class="hlt">melting</span> temperature for Al reduces from 933.67 K for a stress-free condition down to 898.1 K for uniaxial strain and to 920.8 K for plane strain. Our PFA simulations demonstrated barrierless surface-<span class="hlt">induced</span> <span class="hlt">melt</span> nucleation below these temperatures and propagation of two solid-<span class="hlt">melt</span> interfaces toward each other at the temperatures very close to the corresponding predicted thermodynamicmore » equilibrium temperatures for the heating rate Q≤1.51×10{sup 10}K/s. At higher heating rates, kinetic superheating competes with a reduction in <span class="hlt">melting</span> temperature and <span class="hlt">melting</span> under uniaxial strain occurs at 902.1 K for Q = 1.51 × 10{sup 11 }K/s and 936.9 K for Q = 1.46 × 10{sup 12 }K/s.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Geomo.311....1A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Geomo.311....1A"><span>Debris thickness patterns on debris-covered <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, Leif S.; Anderson, Robert S.</p> <p>2018-06-01</p> <p>Many debris-covered <span class="hlt">glaciers</span> have broadly similar debris thickness patterns: surface debris thickens and tends to transition from convex- to concave-up-down <span class="hlt">glacier</span>. We explain this pattern using theory (analytical and numerical models) paired with empirical observations. Down <span class="hlt">glacier</span> debris thickening results from the conveyor-belt-like nature of the <span class="hlt">glacier</span> surface in the ablation zone (debris can typically only be added but not removed) and from the inevitable decline in ice surface velocity toward the terminus. Down-<span class="hlt">glacier</span> thickening of debris leads to the reduction of sub-debris <span class="hlt">melt</span> and debris emergence toward the terminus. Convex-up debris thickness patterns occur near the up-<span class="hlt">glacier</span> end of debris covers where debris emergence dominates (ablation controlled). Concave-up debris thickness patterns occur toward <span class="hlt">glacier</span> termini where declining surface velocities dominate (velocity controlled). A convex-concave debris thickness profile inevitably results from the transition between ablation-control and velocity-control down-<span class="hlt">glacier</span>. Debris thickness patterns deviating from this longitudinal shape are most likely caused by changes in hillslope debris supply through time. By establishing this expected debris thickness pattern, the effects of climate change on debris cover can be better identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C41G..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C41G..07S"><span>Measurements of Velocity and Ablation from Bering <span class="hlt">Glacier</span> During the Recent Surge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shuchman, R. A.; Roussi, C.; Endsley, K. A.; Josberger, E. G.; Hart, B. E.</p> <p>2011-12-01</p> <p>Bering <span class="hlt">Glacier</span>, in south central Alaska, the largest and longest <span class="hlt">glacier</span> in continental North America, is once again surging. The last surge occurred in the 1993-1995 time period; the current surge was first documented by satellite observations in January 2011. In mid-May 2011 we deployed <span class="hlt">Glacier</span> Ablation Sensing System (GASS) units at six sites from the terminus (sea level) to the Bagley Ice field (1200m). At each GASS site the date, time, GPS WAAS enabled location, air temperature, <span class="hlt">melt</span>, wind speed, upward and downward looking light intensity are measured and recorded on an hourly basis. The <span class="hlt">melt</span> is determined by measuring acoustically the distance between the sensor's housing which is mounted on an aluminum pole stream drilled approximately 10 m in to the ice or snow surface. Two of the GASS sites nearest the terminus transmit data back via the iridium network and are reported on the web (www.beringglacier.org - click on 2011 ablation monitoring). As of late July 2011, the <span class="hlt">glacier</span> had moved approximately 785m at the terminus (B1) and 858m at B2 approximately 15 km up <span class="hlt">glacier</span> at an altitude of approximately 340m. B1 total <span class="hlt">melt</span> from mid-May was 494 cm, while B2 <span class="hlt">melted</span> 383 cm. From previous observations, the average daily <span class="hlt">melt</span> at Bering in the summer is approximately 5cm/day, and the velocity at B2 was 4.5 m/day, with a total displacement in 2010 of approximately 280m. B2 is presently moving 12m/day down from its peak observed displacement of 18m/day in late May. In late July, B1 at the terminus is moving approximately 7m/day, slower than its maximum daily displacement of over 15m/day observed in late May. In contrast, the 2010 GASS unit measurement at the <span class="hlt">glacier</span> terminus observed a daily movement of only .14m/day with a total displacement of only approximately 10 meters. The hourly observations for all six GASS units will be presented along with interpretation as to why the <span class="hlt">melts</span> and displacements vary over the observation period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912518P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912518P"><span>Influencing factors on the cooling effect of coarse blocky top-layers on relict rock <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pauritsch, Marcus; Wagner, Thomas; Mayaud, Cyril; Thalheim, Felix; Kellerer-Pirklbauer, Andreas; Winkler, Gerfried</p> <p>2017-04-01</p> <p> impact on the thermal regime of the Schöneben Rock <span class="hlt">Glacier</span> and, as the major wind direction, especially for higher wind speeds, is from west towards east, it is suspected that wind-forced convection is even more important at the Dürrtal Rock <span class="hlt">Glacier</span>. The limited incident solar <span class="hlt">radiation</span> at the Schöneben Rock <span class="hlt">Glacier</span> results in a longer seasonal snow cover that appears earlier in autumn and can persist longer during the <span class="hlt">melting</span> season. Moreover, with the predominant westerly wind, snow is supposedly transported from neighboring catchments (i.a. the Dürrtal Rock <span class="hlt">Glacier</span> catchment) towards the Schöneben Rock <span class="hlt">Glacier</span> catchment. Thus, in times with relatively cold air temperatures the coarse blocky surface at the Dürrtal Rock <span class="hlt">Glacier</span> is better connected to the atmosphere than the more northern exposed Schöneben rock <span class="hlt">glacier</span> because of the missing or only partial snow cover, which results in an enhanced cooling effect. It can be concluded that the cooling effect of coarse blocky debris is highly variable in alpine environments and can show considerable variations, depending on the heterogeneous structure of the layer itself and a complex interplay of slope aspect-related microclimatic effects such as incident solar <span class="hlt">radiation</span>, predominant wind direction and snow cover dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C11C0797A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C11C0797A"><span>In-Situ Mass Balance Measurements and Morphology Study of Patsio <span class="hlt">Glacier</span>, Himachal Pradesh, Western Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Angchuk, T.; AL, R.; Mandal, A.; Soheb, M.; Bahuguna, I. M.; Singh, V.; Linda, A.</p> <p>2016-12-01</p> <p>The present ongoing study is oriented to do the detailed study of the Patsio <span class="hlt">glacier</span> which is in the Bhaga Basin, Lahaul, Himachal Pradesh. Patsio <span class="hlt">glacier</span> is a compound valley <span class="hlt">glacier</span> survived by two prominent tributaries namely Eastern and Western. The two tributaries are facing opposite to each other. The Western tributary facing almost eastward shows higher <span class="hlt">melting</span> as compared to Eastern tributary facing northwest. This is probably due to solar <span class="hlt">radiation</span> and sunshine hour, as Western tributary receives high solar <span class="hlt">radiation</span> and for longer duration. A series of supraglacial lakes which were connected to each other through supra channels were observed on the upper part of the ablation zone at an altitude range of 5100 m and 5300 m amsl. A dead ice covered with thick debris was observed below the current terminus. Despite the large variability of the mass balance in the different seasons Patsio <span class="hlt">glacier</span> annual balance for the year 2012-2013 was found to be 0.04 ± 0.40 m w.e. the low values signifies that <span class="hlt">glacier</span> has lost significant amount of mass in recent past and now it is near to the equilibrium state. Seasonal mass balance of Patsio <span class="hlt">glacier</span> has shown wide range of variability in the mass balances. Patsio <span class="hlt">glacier</span> receives most of the accumulation during the winter months and duration is long whereas, ablation season is short but quite significant. Monthly and daily variation has depicted that peak ablation months are July and August. The daily ablation in the month of August 2013 was found to be around 5 cm per day, probably due to air temperature. To have a clear picture of the meteorological parameters and its relation with <span class="hlt">glacier</span> an AWS has set up on the Patsio <span class="hlt">glacier</span> at an altitude of 5050 m amsl in June 2014. Seasonal mass balance gradients show that gradient was high during the early and late ablation seasons as compared to peak ablation season. The mass balance for the year 2010-2011 was slightly positive.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70048144','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70048144"><span>Does calving matter? Evidence for significant submarine <span class="hlt">melt</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bartholomaus, Timothy C.; Larsen, Christopher F.; O’Neel, Shad</p> <p>2013-01-01</p> <p>During the summer in the northeast Pacific Ocean, the Alaska Coastal Current sweeps water with temperatures in excess of 12 °C past the mouths of <span class="hlt">glacierized</span> fjords and bays. The extent to which these warm waters affect the mass balance of Alaskan tidewater <span class="hlt">glaciers</span> is uncertain. Here we report hydrographic measurements made within Icy Bay, Alaska, and calculate rates of submarine <span class="hlt">melt</span> at Yahtse <span class="hlt">Glacier</span>, a tidewater <span class="hlt">glacier</span> terminating in Icy Bay. We find strongly stratified water properties consistent with estuarine circulation and evidence that warm Gulf of Alaska water reaches the head of 40 km-long Icy Bay, largely unaltered. A 10–20 m layer of cold, fresh, glacially-modified water overlies warm, saline water. The saline water is observed to reach up to 10.4 °C within 1.5 km of the terminus of Yahtse <span class="hlt">Glacier</span>. By quantifying the heat and salt deficit within the glacially-modified water, we place bounds on the rate of submarine <span class="hlt">melt</span>. The submarine <span class="hlt">melt</span> rate is estimated at >9 m d−1, at least half the rate at which ice flows into the terminus region, and can plausibly account for all of the submarine terminus mass loss. Our measurements suggest that summer and fall subaerial calving is a direct response to thermal undercutting of the terminus, further demonstrating the critical role of the ocean in modulating tidewater <span class="hlt">glacier</span> dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33D1227B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33D1227B"><span>Modelling the contribution of supraglacial ice cliffs to the mass-balance of <span class="hlt">glaciers</span> in the Langtang catchment, Nepalese Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buri, P.; Steiner, J. F.; Miles, E.; Ragettli, S.; Pellicciotti, F.</p> <p>2017-12-01</p> <p>Supraglacial cliffs are typical surface features of debris-covered <span class="hlt">glaciers</span> worldwide, affecting surface evolution, and mass balance by providing a direct ice-atmosphere interface where <span class="hlt">melt</span> rates can be very high. As a result, ice cliffs act as windows of energy transfer from the atmosphere to the ice, and enhance <span class="hlt">melt</span> and mass losses of otherwise insulated ice. However, their contribution to <span class="hlt">glacier</span> mass balance has never been quantified at the <span class="hlt">glacier</span> scale, and all inference has been obtained from upscaling results of point-scale models or observations at select individual cliffs. Here we use a 3D, physically-based backwasting model to estimate the volume losses associated with the <span class="hlt">melting</span> and backwasting of supraglacial ice cliffs for the entire debris-covered <span class="hlt">glacier</span> area of the Langtang catchment. We estimate mass losses for the 2014 <span class="hlt">melt</span> season and compare them to recent values of <span class="hlt">glacier</span> mass balance determined from geodetic and numerical modelling approached. Cliff outlines and topography are derived from high-resolution stereo SPOT6-imagery from April 2014. Meteorological data to force the model are provided by automatic weather stations on- and off-<span class="hlt">glacier</span> within the valley. The model simulates ice cliff backwasting by considering the cliff-atmosphere energy-balance, reburial by debris and the effects of adjacent ponds. In the <span class="hlt">melt</span> season of 2014, cliffs' distribution and patterns of mass losses vary considerably from <span class="hlt">glacier</span> to <span class="hlt">glacier</span>, and we relate rates of volume loss to both <span class="hlt">glaciers</span>' and cliffs' characteristics. Only cliffs with a northerly aspect account for substantial losses. Uncertainty in our estimates is due to the quality of the stereo DEM, uncertainties in the cliff delineation and the fact that we use a conservative approach to cliff delineation and discard very small cliffs and those for which uncertainty in topography is high. Despite these uncertainties, our work presents the first estimate of the importance of supraglacial ice</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-GSFC_20171208_Archive_e002000.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-GSFC_20171208_Archive_e002000.html"><span>Susitna <span class="hlt">Glacier</span>, Alaska</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-08</p> <p>NASA image acquired August 27, 2009 Like rivers of liquid water, <span class="hlt">glaciers</span> flow downhill, with tributaries joining to form larger rivers. But where water rushes, ice crawls. As a result, <span class="hlt">glaciers</span> gather dust and dirt, and bear long-lasting evidence of past movements. Alaska’s Susitna <span class="hlt">Glacier</span> revealed some of its long, grinding journey when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite passed overhead on August 27, 2009. This satellite image combines infrared, red, and green wavelengths to form a false-color image. Vegetation is red and the glacier’s surface is marbled with dirt-free blue ice and dirt-coated brown ice. Infusions of relatively clean ice push in from tributaries in the north. The <span class="hlt">glacier</span> surface appears especially complex near the center of the image, where a tributary has pushed the ice in the main <span class="hlt">glacier</span> slightly southward. A photograph taken by researchers from the U.S. Geological Survey (archived by the National Snow and Ice Data Center) shows an equally complicated Susitna <span class="hlt">Glacier</span> in 1970, with dirt-free and dirt-encrusted surfaces forming stripes, curves, and U-turns. Susitna flows over a seismically active area. In fact, a 7.9-magnitude quake struck the region in November 2002, along a previously unknown fault. Geologists surmised that earthquakes had created the steep cliffs and slopes in the <span class="hlt">glacier</span> surface, but in fact most of the jumble is the result of surges in tributary <span class="hlt">glaciers</span>. <span class="hlt">Glacier</span> surges—typically short-lived events where a <span class="hlt">glacier</span> moves many times its normal rate—can occur when <span class="hlt">melt</span> water accumulates at the base and lubricates the flow. This water may be supplied by meltwater lakes that accumulate on top of the <span class="hlt">glacier</span>; some are visible in the lower left corner of this image. The underlying bedrock can also contribute to <span class="hlt">glacier</span> surges, with soft, easily deformed rock leading to more frequent surges. NASA Earth Observatory image created by Jesse Allen and Robert</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.2047D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.2047D"><span>Irrigation as a Potential Driver for Anomalous <span class="hlt">Glacier</span> Behavior in High Mountain Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Kok, Remco J.; Tuinenburg, Obbe A.; Bonekamp, Pleun N. J.; Immerzeel, Walter W.</p> <p>2018-02-01</p> <p>Many <span class="hlt">glaciers</span> in the northwest of High Mountain Asia (HMA) show an almost zero or positive mass balance, despite the global trend of <span class="hlt">melting</span> <span class="hlt">glaciers</span>. This phenomenon is often referred to as the "Karakoram anomaly," although strongest positive mass balances can be found in the Kunlun Shan mountain range, northeast of the Karakoram. Using a regional climate model, in combination with a moisture-tracking model, we show that the increase in irrigation intensity in the lowlands surrounding HMA, particularly in the Tarim basin, can locally counter the effects of global warming on <span class="hlt">glaciers</span> in Kunlun Shan, and parts of Pamir and northern Tibet, through an increase in summer snowfall and decrease in net radiance. Irrigation can thus affect the regional climate in a way that favors <span class="hlt">glacier</span> growth, and future projections of <span class="hlt">glacier</span> <span class="hlt">melt</span>, which may impact millions of inhabitants surrounding HMA, will need to take into account predicted changes in irrigation intensity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1715554K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1715554K"><span><span class="hlt">Glacier</span> Dynamics and Outburst Flood Potential from the Imja and Thulagi <span class="hlt">Glacier</span>-Lake Systems (Nepal)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kargel, Jeffrey; Leonard, Gregory; Regmi, Dhananjay; Haritashya, Umesh; Chand, Mohan; Pradhan, Suresh; Sapkota, Nawaraj; Byers, Alton; Joshi, Sharad; McKinney, Daene; Mool, Pradeep; Somos-Valenzuela, Marcelo; Huggel, Christian</p> <p>2015-04-01</p> <p>Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous <span class="hlt">glacier</span> lakes, i.e., most likely to cause death and destruction in case of a <span class="hlt">glacier</span> lake outburst flood (GLOF). Imja Lake and the associated Imja and Lhoste-Shar <span class="hlt">glaciers</span> have been intensively studied; Thulagi <span class="hlt">Glacier</span> and its lake are much less studied. Collectively, we have undertaken a series of increasingly thorough bathymetric and land surveys and satellite remote sensing analyses of Imja Lake and its <span class="hlt">glacier</span> setting. We are analyzing several expeditions' data to build a detailed assessment of the <span class="hlt">glacier</span> and lake to better establish the dynamical evolution of the system and its future GLOF potential. Our most recent, most complete bathymetric survey of Imja Lake has revealed a much greater volume (75,200,000 cubic meters) and maximum depth (149.8 m) than found before. Our analysis suggests that not all possible Imja GLOF scenarios would result in devastation. Some moraine <span class="hlt">melt</span>-through or down-cutting mechanisms -- perhaps <span class="hlt">induced</span> by extreme monsoon precipitation or an earthquake -- could generate outbursts lasting from 10,000-100,000 seconds ("slow GLOFs"), thus limiting peak flows and downstream damage. The potential damage from a slow GLOF from Imja Lake -- even if there is a large total volume -- is lessened by the relatively low peak discharge and because the major villages downstream from Imja Lake are situated just outside of and above a deep, broad outwash and debris-flow channel system. Imja and other <span class="hlt">glaciers</span> in the area have built a large fan, now deeply trenched, which is able to accommodate the peak discharges of potential slow GLOFs, such that Dingboche and other villages would be spared. However, local geomorphology also bears evidence of "fast GLOFs," such as may be issued by a tsunami, which could be initiated by a large mass movement into Imja Lake and which might override and damage the end moraine in <100 seconds. Dingboche and other villages are vulnerable to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C51A0627G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C51A0627G"><span>Field Investigation of the Turbulent Flux Parameterization and Scalar Turbulence Structure over a <span class="hlt">Melting</span> Valley <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guo, X.; Yang, K.; Yang, W.; Li, S.; Long, Z.</p> <p>2011-12-01</p> <p>We present a field investigation over a <span class="hlt">melting</span> valley <span class="hlt">glacier</span> on the Tibetan Plateau. One particular aspect lies in that three <span class="hlt">melt</span> phases are distinguished during the <span class="hlt">glacier</span>'s ablation season, which enables us to compare results over snow, bare-ice, and hummocky surfaces [with aerodynamic roughness lengths (z0M) varying on the order of 10-4-10-2 m]. We address two issues of common concern in the study of glacio-meteorology and micrometeorology. First, we study turbulent energy flux estimation through a critical evaluation of three parameterizations of the scalar roughness lengths (z0T for temperature and z0q for humidity), viz. key factors for the accurate estimation of sensible heat and latent heat fluxes using the bulk aerodynamic method. The first approach (Andreas 1987, Boundary-Layer Meteorol 38:159-184) is based on surface-renewal models and has been very widely applied in glaciated areas; the second (Yang et al. 2002, Q J Roy Meteorol Soc 128:2073-2087) has never received application over an ice/snow surface, despite its validity in arid regions; the third approach (Smeets and van den Broeke 2008, Boundary-Layer Meteorol 128:339-355) is proposed for use specifically over rough ice defined as z0M > 10-3 m or so. This empirical z0M threshold value is deemed of general relevance to glaciated areas (e.g. ice sheet/cap and valley/outlet <span class="hlt">glaciers</span>), above which the first approach gives underestimated z0T and z0q. The first and the third approaches tend to underestimate and overestimate turbulent heat/moisture exchange, respectively (relative errors often > 30%). Overall, the second approach produces fairly low errors in energy flux estimates; it thus emerges as a practically useful choice to parameterize z0T and z0q over an ice/snow surface. Our evaluation of z0T and z0q parameterizations hopefully serves as a useful source of reference for physically based modeling of land-ice surface energy budget and mass balance. Second, we explore how scalar turbulence</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19..795D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19..795D"><span>Response of Antarctic ice shelf <span class="hlt">melt</span> to SAM trend and possible feedbacks with the ice-dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Donat-Magnin, Marion; Jourdain, Nicolas C.; Gallée, Hubert; Spence, Paul; Cornford, Stephen L.; Le Sommer, Julien; Durand, Gaël</p> <p>2017-04-01</p> <p>The observed positive trend in the Southern Annular Mode (SAM) may warm the Southern Ocean sub-surface through decreased Ekman downward pumping. Subsequent change in ice-shelves <span class="hlt">melt</span> has been suggested to trigger <span class="hlt">glacier</span> acceleration in West Antarctica. Here we use a regional ocean model configuration of the Amundsen Sea that includes interactive ice-shelf cavities. Our results show that the inclusion of ice-shelves changes the ocean response to the projected SAM trend, i.e. it typically inhibits a part of the SAM-<span class="hlt">induced</span> subsurface warming. Heat budget analysis has been used to propose responsible mechanisms. Regarding Thwaites and Pine Island, sub ice-shelf <span class="hlt">melt</span> increases above 400m by approximately 40% for Thwaites and 10% for Pine Island and decreases by up to 10% below in response to ocean temperature changes driven by the projected SAM trend. The <span class="hlt">melt</span> sensitivity to poleward shifting winds is nonetheless small compared to the sensitivity to an ice-sheet instability, i.e. to a projected change in the shape of ice-shelf cavities. For instance, the sub ice-shelf <span class="hlt">melt</span> are doubled near the grounding line of some <span class="hlt">glaciers</span> in response to the largest grounding line retreat projected for 2100. Large increase in basal <span class="hlt">melt</span> close to the grounding line could largely impact instability and <span class="hlt">glacier</span> acceleration. Our work suggests the need for including ice shelves into ocean models, and to couple ocean models to ice-sheet models in climate projections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70031151','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70031151"><span>Geochemistry and source waters of rock <span class="hlt">glacier</span> outflow, Colorado Front Range</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Williams, M.W.; Knauf, M.; Caine, N.; Liu, F.; Verplanck, P.L.</p> <p>2006-01-01</p> <p>We characterize the seasonal variation in the geochemical and isotopic content of the outflow of the Green Lake 5 rock <span class="hlt">glacier</span> (RG5), located in the Green Lakes Valley of the Colorado Front Range, USA. Between June and August, the geochemical content of rock <span class="hlt">glacier</span> outflow does not appear to differ substantially from that of other surface waters in the Green Lakes Valley. Thus, for this alpine ecosystem at this time of year there does not appear to be large differences in water quality among rock <span class="hlt">glacier</span> outflow, <span class="hlt">glacier</span> and blockslope discharge, and discharge from small alpine catchments. However, in September concentrations of Mg2+ in the outflow of the rock <span class="hlt">glacier</span> increased to more than 900 ??eq L-1 compared to values of less than 40 ??eq L-1 at all the other sites, concentrations of Ca2+ were greater than 4,000 ??eq L-1 compared to maximum values of less than 200 ??eq L-1 at all other sites, and concentrations of SO42- reached 7,000 ??eq L-1, compared to maximum concentrations below 120 ??eq L-1 at the other sites. Inverse geochemical modelling suggests that dissolution of pyrite, epidote, chlorite and minor calcite as well as the precipitation of silica and goethite best explain these elevated concentrations of solutes in the outflow of the rock <span class="hlt">glacier</span>. Three component hydrograph separation using end-member mixing analysis shows that <span class="hlt">melted</span> snow comprised an average of 30% of RG5 outflow, soil water 32%, and base flow 38%. Snow was the dominant source water in June, soil water was the dominant water source in July, and base flow was the dominant source in September. Enrichment of ?? 18O from - 10??? in the outflow of the rock <span class="hlt">glacier</span> compared to -20??? in snow and enrichment of deuterium excess from +17.5??? in rock <span class="hlt">glacier</span> outflow compared to +11??? in snow, suggests that <span class="hlt">melt</span> of internal ice that had undergone multiple <span class="hlt">melt</span>/freeze episodes was the dominant source of base flow. Copyright ?? 2005 John Wiley & Sons, Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMED41A0255B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMED41A0255B"><span>Various Particulate Matter Effects on Glacial <span class="hlt">Melting</span> Rates in the Himalayan Mountain Range</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barwegen, S.</p> <p>2017-12-01</p> <p>Due to increased human activity and the impact of global warming in the Himalayas, <span class="hlt">glaciers</span> are <span class="hlt">melting</span> at alarming rates. It is hypothesized that by the year 2100, about 5,500 <span class="hlt">glaciers</span> located in the Hindu-Kush will <span class="hlt">melt</span> by up to 70%-90%. This will be severely detrimental to farmers as well as lessen the potential to harness hydropower, which requires the <span class="hlt">glaciers</span> to be fully present (Vidal 2015). The <span class="hlt">melting</span> of these <span class="hlt">glaciers</span> is accelerating, in part, due to the deposition of particulate matter onto the snow, which lowers the albedo and causes the <span class="hlt">glaciers</span> to absorb more heat. The Himalayan <span class="hlt">glaciers</span>, specifically, are <span class="hlt">melting</span> due to intense human movement over the snow, movement of particulate matter from storms, the increase in temperatures due to global warming, and soot deposited from forest fires (Dimmick 2014). This whole mountain range needs to retain <span class="hlt">glaciers</span> in order to support the population of people living there by providing water. This project investigated the effect of both different types and amounts of particulate matter (PM) on ice <span class="hlt">melting</span> rates. It was a model simulating the impact of PM of varying sizes and sources on glacial <span class="hlt">melting</span> rates in the Himalayan <span class="hlt">glaciers</span>. The impact of eight different types of PM (charcoal, pumice, sand/organic soil mixture, peat moss/soil, gravel/soil, soot, and soil), at two different masses (0.1g and 0.3g) on the <span class="hlt">melting</span> rate of ice was assessed. Ice cubes were covered in PM and placed 5 cm away from a 50W incandescent bulb, with mass measured at regular intervals as they <span class="hlt">melted</span>. Mass loss was recorded at 3, 6, 9, and 15 minutes and each sample type was repeated in triplicate. Over the course of the experiment, the ice cubes with 0.1 gram of PM were observed to be <span class="hlt">melting</span> at a slower rate. Of the ice cubes with .3 g of PM on top, the ice covered in the sand and organic soil mixture had the lowest mass loss (3.4 g over 15 minutes), while the gravel and potting soil (4.9 g over 15 minutes) resulted in the highest (4</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C51B0985C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C51B0985C"><span>Grounding line processes on the Totten <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cook, S.; Watson, C. S.; Galton-Fenzi, B.; Peters, L. E.; Coleman, R.</p> <p>2017-12-01</p> <p>The Totten <span class="hlt">Glacier</span> has been an area of recent interest due to its large drainage basin, much of which is grounded below sea level and has a history of large scale grounding line movement. Reports that warm water reaches the sub-ice shelf cavity have led to speculation that it could be vulnerable to future grounding line retreat. Over the Antarctic summer 2016/17 an array of 6 GPS and autonomous phase-sensitive radar (ApRES) units were deployed in the grounding zone of the Totten <span class="hlt">Glacier</span>. These instruments measure changes in ice velocity and thickness which can be used to investigate both ice dynamics across the grounding line, and the interaction between ice and ocean in the subglacial cavity. Basal <span class="hlt">melt</span> rates calculated from the ApRES units on floating ice range from 1 to 17 m/a. These values are significantly lower than previous estimates of basal <span class="hlt">melt</span> rate produced by ocean modelling of the subglacial cavity. Meanwhile, GPS-derived velocity and elevation on the surface of the ice show a strong tidal signal, as does the vertical strain rate within the ice derived from internal layering from the ApRES instruments. These results demonstrate the significance of the complex grounding pattern of the Totten <span class="hlt">Glacier</span>. The presence of re-grounding points has significant implications for the dynamics of the <span class="hlt">glacier</span> and the ocean circulation within the subglacial cavity. We discuss what can be learned from our in situ measurements, and how they can be used to improve models of the <span class="hlt">glacier</span>'s future behaviour.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24999726','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24999726"><span>Polychlorinated biphenyls in <span class="hlt">glaciers</span>. 2. Model results of deposition and incorporation processes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Steinlin, Christine; Bogdal, Christian; Scheringer, Martin; Pavlova, Pavlina A; Schwikowski, Margit; Schmid, Peter; Hungerbühler, Konrad</p> <p>2014-07-15</p> <p>In previous work, Alpine <span class="hlt">glaciers</span> have been identified as a secondary source of persistent organic pollutants (POPs). However, detailed understanding of the processes organic chemicals undergo in a glacial system was missing. Here, we present results from a chemical fate model describing deposition and incorporation of polychlorinated biphenyls (PCBs) into an Alpine <span class="hlt">glacier</span> (Fiescherhorn, Switzerland) and an Arctic <span class="hlt">glacier</span> (Lomonosovfonna, Norway). To understand PCB fate and dynamics, we investigate the interaction of deposition, sorption to ice and particles in the atmosphere and within the <span class="hlt">glacier</span>, revolatilization, diffusion and degradation, and discuss the effects of these processes on the fate of individual PCB congeners. The model is able to reproduce measured absolute concentrations in the two <span class="hlt">glaciers</span> for most PCB congeners. While the model generally predicts concentration profiles peaking in the 1970s, in the measurements, this behavior can only be seen for higher-chlorinated PCB congeners on Fiescherhorn <span class="hlt">glacier</span>. We suspect seasonal <span class="hlt">melt</span> processes are disturbing the concentration profiles of the lower-chlorinated PCB congeners. While a lower-chlorinated PCB congener is mainly deposited by dry deposition and almost completely revolatilized after deposition, a higher-chlorinated PCB congener is predominantly transferred to the <span class="hlt">glacier</span> surface by wet deposition and then is incorporated into the <span class="hlt">glacier</span> ice. The incorporated amounts of PCBs are higher on the Alpine <span class="hlt">glacier</span> than on the Arctic <span class="hlt">glacier</span> due to the higher precipitation rate and aerosol particle concentration on the former. Future studies should include the effects of seasonal <span class="hlt">melt</span> processes, calculate the quantities of PCBs incorporated into the entire <span class="hlt">glacier</span> surface, and estimate the quantity of chemicals released from <span class="hlt">glaciers</span> to determine the importance of <span class="hlt">glaciers</span> as a secondary source of organic chemicals to remote aquatic ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16054693','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16054693"><span>Organochlorine compounds in ice <span class="hlt">melt</span> water from Italian Alpine rivers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Villa, Sara; Negrelli, Christian; Finizio, Antonio; Flora, Onelio; Vighi, Marco</p> <p>2006-01-01</p> <p>Organochlorine chemicals (OCs) (dichlorodiphenyltrichloroethanes, hexachlorocyclohexanes, and hexachlorobenzene) were measured in ice <span class="hlt">melt</span> water from five <span class="hlt">glaciers</span> in the Italian Alps. Even though the data collected may not be sufficient for a precise description of persistent organic pollutant release patterns from <span class="hlt">glacier</span> <span class="hlt">melting</span>, they have, however, highlighted the potential for surface water contamination. Concentrations were of the same order of magnitude in all glacial streams, indicating comparable contamination levels in different <span class="hlt">glaciers</span> of the alpine region. OC levels in nonglacial springs sampled in the same areas are usually lower. Even if differences during the <span class="hlt">melting</span> season (from spring to autumn) have been identified, a regular seasonal pattern in OC concentrations was not observed. Risk for the aquatic environment is excluded through direct water exposure, but it is likely to occur through biomagnification and secondary poisoning exposure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=10532&hterms=glacier+melt&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dglacier%2Bmelt','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=10532&hterms=glacier+melt&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dglacier%2Bmelt"><span>Alaska <span class="hlt">Glaciers</span> and Rivers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2007-01-01</p> <p>The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image on October 7, 2007, showing the Alaska Mountains of south-central Alaska already coated with snow. Purple shadows hang in the lee of the peaks, giving the snow-clad land a crumpled appearance. White gives way to brown on the right side of the image where the mountains yield to the lower-elevation Susitna River Valley. The river itself cuts a silver, winding path through deep green forests and brown wetlands and tundra. Extending from the river valley, are smaller rivers that originated in the Alaska Mountains. The source of these rivers is evident in the image. Smooth white tongues of ice extend into the river valleys, the remnants of the <span class="hlt">glaciers</span> that carved the valleys into the land. Most of the water flowing into the Gulf of Alaska from the Susitna River comes from these mountain <span class="hlt">glaciers</span>. <span class="hlt">Glacier</span> <span class="hlt">melt</span> also feeds <span class="hlt">glacier</span> lakes, only one of which is large enough to be visible in this image. Immediately left of the Kahiltna River, the aquamarine waters of Chelatna Lake stand out starkly against the brown and white landscape.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRC..122.6611C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRC..122.6611C"><span>Subglacial discharge-driven renewal of tidewater <span class="hlt">glacier</span> fjords</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carroll, Dustin; Sutherland, David A.; Shroyer, Emily L.; Nash, Jonathan D.; Catania, Ginny A.; Stearns, Leigh A.</p> <p>2017-08-01</p> <p>The classic model of fjord renewal is complicated by tidewater <span class="hlt">glacier</span> fjords, where submarine <span class="hlt">melt</span> and subglacial discharge provide substantial buoyancy forcing at depth. Here we use a suite of idealized, high-resolution numerical ocean simulations to investigate how fjord circulation driven by subglacial plumes, tides, and wind stress depends on fjord width, grounding line depth, and sill height. We find that the depth of the grounding line compared to the sill is a primary control on plume-driven renewal of basin waters. In wide fjords the plume exhibits strong lateral recirculation, increasing the dilution and residence time of glacially-modified waters. Rapid drawdown of basin waters by the subglacial plume in narrow fjords allows for shelf waters to cascade deep into the basin; wide fjords result in a thin, boundary current of shelf waters that flow toward the terminus slightly below sill depth. Wind forcing amplifies the plume-driven exchange flow; however, wind-<span class="hlt">induced</span> vertical mixing is limited to near-surface waters. Tidal mixing over the sill increases in-fjord transport of deep shelf waters and erodes basin stratification above the sill depth. These results underscore the first-order importances of fjord-<span class="hlt">glacier</span> geometry in controlling circulation in tidewater <span class="hlt">glacier</span> fjords and, thus, ocean heat transport to the ice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://wa.water.usgs.gov/projects/glacier/data/bidlake_AGU_2010.pdf','USGSPUBS'); return false;" href="http://wa.water.usgs.gov/projects/glacier/data/bidlake_AGU_2010.pdf"><span><span class="hlt">Glacier</span> modeling in support of field observations of mass balance at South Cascade <span class="hlt">Glacier</span>, Washington, USA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Josberger, Edward G.; Bidlake, William R.</p> <p>2010-01-01</p> <p>The long-term USGS measurement and reporting of mass balance at South Cascade <span class="hlt">Glacier</span> was assisted in balance years 2006 and 2007 by a new mass balance model. The model incorporates a temperature-index <span class="hlt">melt</span> computation and accumulation is modeled from <span class="hlt">glacier</span> air temperature and gaged precipitation at a remote site. Mass balance modeling was used with glaciological measurements to estimate dates and magnitudes of critical mass balance phenomena. In support of the modeling, a detailed analysis was made of the "<span class="hlt">glacier</span> cooling effect" that reduces summer air temperature near the ice surface as compared to that predicted on the basis of a spatially uniform temperature lapse rate. The analysis was based on several years of data from measurements of near-surface air temperature on the <span class="hlt">glacier</span>. The 2006 and 2007 winter balances of South Cascade <span class="hlt">Glacier</span>, computed with this new, model-augmented methodology, were 2.61 and 3.41 mWE, respectively. The 2006 and 2007 summer balances were -4.20 and -3.63 mWE, respectively, and the 2006 and 2007 net balances were -1.59 and -0.22 mWE. PDF version of a presentation on the mass balance of South Cascade <span class="hlt">Glacier</span> in Washington state. Presented at the American Geophysical Union Fall Meeting 2010.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C41D0696C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C41D0696C"><span>Hydrological response in catchments whit debris covered <span class="hlt">glaciers</span> in the semi-arid Andes, Chile</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caro, A.; McPhee, J.; MacDonell, S.; Pellicciotti, F.; Ayala, A.</p> <p>2016-12-01</p> <p><span class="hlt">Glaciers</span> in the semi-arid Andes Cordillera in Chile have shrank rapidly during the 20th century. Negative mass balance contributes to increase the surface area of debris-covered <span class="hlt">glaciers</span>. Recent research in Chile suggests that contributions from <span class="hlt">glaciers</span> to summer season river flow in dry years is very important, however hydrological processes determining the <span class="hlt">glacier</span> contribution are still poorly understood in the region. This work seeks to determine appropriate parameters for the simulation of <span class="hlt">melt</span> volume in two watersheds dominated by debris-covered <span class="hlt">glaciers</span>, in order to understand its variability in time and space, in the area with the largest population in Chile. The hydrological simulation is performed for the Tapado (30°S) and Pirámide (33ºS) <span class="hlt">glaciers</span>, which can be defined as cold and temperate respectively. To simulate the hydrological behaviour we adopt the physically-based TOPographic Kinematic wave APproximation model (TOPKAPI-ETH). The hydrometeorological records necessary model runs have been collected through fieldwork from 2013 to 2015. Regarding the calibration of the model parameters <span class="hlt">melting</span> ETI, its observed that the value for TF in Pirámide is a third of the value for Tapado <span class="hlt">glacier</span>, while SRF is half in Tapado regarding to Pirámide. The runoff in the <span class="hlt">glaciers</span>, the constant snow and ice storage are higher in Tapado regarding Pirámide. Results show a contribution of glacial outflow to runoff during 2015 of 55% in Tapado and 77% in Pirámide, with maximum contributions between January and March in Tapado and Pirámide between November and March, presenting the relevance of the permanence of snow cover during spring and shelter that provides debris-covered in reducing the <span class="hlt">melting</span> <span class="hlt">glacier</span>. The results have allowed to know the relevance of the <span class="hlt">glacier</span> contribution to mountain streams, allowing to know the calibration parameters most relevant in the hydrology balance of <span class="hlt">glacier</span> basins in the Andes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7743D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7743D"><span>Simulation and prediction of equilibrium line altitude of <span class="hlt">glaciers</span> in the eastern Tibetan plateau</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duan, Keqin</p> <p>2017-04-01</p> <p>As the third polar on the Earth, the Tibetan plateau holds more than 40,000 <span class="hlt">glaciers</span> which have experienced a rapid retreat in recent decades. <span class="hlt">Glacier</span> loss has increased concern for water resources around the Tibetan plateau. The variability of equilibrium line altitude (ELA) indicates expansion and wastage of <span class="hlt">glacier</span> directly. Here we simulated the ELA variability in the eastern Tibetan Plateau based on a full surface energy and mass balance model. The simulation results are agreement with the observations. The ELAs have risen at a rate of 2-8m/a since 1970 throughout the eastern Plateau, especially in the Qilian Mountain and the southeastern Plateau where the ELAs have risen to or over the top altitude of <span class="hlt">glacier</span>, indicating the <span class="hlt">glaciers</span> are accelerating to <span class="hlt">melting</span> over there. Two typical <span class="hlt">glacier</span>, Xiaodongkemadi <span class="hlt">glacier</span> in the center of the Plateau and Qiyi <span class="hlt">glacier</span> in the Qilian Mountain, are chosen to simulate its future ELA variability in the scenarios of RCP2.6, RCP4.5 and RCP 8.5 given by IPCC. The results show the ELAs will arrive to its maximum in around 2040 in the scenario of RCP2.6, while the ELAs will be over the top altitude of <span class="hlt">glaciers</span> in 2035-2045 in the scenarios of RCP4.5 and RCP8.5, suggesting the <span class="hlt">glaciers</span> in the eastern plateau will be <span class="hlt">melting</span> until the disappear of the <span class="hlt">glaciers</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IJT....36.1848V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJT....36.1848V"><span>Laser-<span class="hlt">Induced</span> <span class="hlt">Melting</span> of Co-C Eutectic Cells as a New Research Tool</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van der Ham, E.; Ballico, M.; Jahan, F.</p> <p>2015-08-01</p> <p>A new laser-based technique to examine heat transfer and energetics of phase transitions in metal-carbon fixed points and potentially to improve the quality of phase transitions in furnaces with poor uniformity is reported. Being reproducible below 0.1 K, metal-carbon fixed points are increasingly used as reference standards for the calibration of thermocouples and <span class="hlt">radiation</span> thermometers. At NMIA, the Co-C eutectic point is used for the calibration of thermocouples, with the fixed point traceable to the International Temperature Scale (ITS-90) using <span class="hlt">radiation</span> thermometry. For thermocouple use, these cells are deep inside a high-uniformity furnace, easily obtaining excellent <span class="hlt">melting</span> plateaus. However, when used with <span class="hlt">radiation</span> thermometers, the essential large viewing cone to the crucible restricts the furnace depth and introduces large heat losses from the front furnace zone, affecting the quality of the phase transition. Short laser bursts have been used to illuminate the cavity of a conventional Co-C fixed-point cell during various points in its <span class="hlt">melting</span> phase transition. The laser is employed to partially <span class="hlt">melt</span> the metal at the rear of the crucible providing a liquid-solid interface close to the region being observed by the reference pyrometer. As the laser power is known, a quantitative estimate of can be made for the Co-C latent heat of fusion. Using a single laser pulse during a furnace-<span class="hlt">induced</span> <span class="hlt">melt</span>, a plateau up to 8 min is observed before the crucible resumes a characteristic conventional <span class="hlt">melt</span> curve. Although this plateau is satisfyingly flat, well within 100 mK, it is observed that the plateau is laser energy dependent and elevates from the conventional <span class="hlt">melt</span> "inflection-point" value.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4740423','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4740423"><span>Complex Greenland outlet <span class="hlt">glacier</span> flow captured</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Aschwanden, Andy; Fahnestock, Mark A.; Truffer, Martin</p> <p>2016-01-01</p> <p>The Greenland Ice Sheet is losing mass at an accelerating rate due to increased surface <span class="hlt">melt</span> and flow acceleration in outlet <span class="hlt">glaciers</span>. Quantifying future dynamic contributions to sea level requires accurate portrayal of outlet <span class="hlt">glaciers</span> in ice sheet simulations, but to date poor knowledge of subglacial topography and limited model resolution have prevented reproduction of complex spatial patterns of outlet flow. Here we combine a high-resolution ice-sheet model coupled to uniformly applied models of subglacial hydrology and basal sliding, and a new subglacial topography data set to simulate the flow of the Greenland Ice Sheet. Flow patterns of many outlet <span class="hlt">glaciers</span> are well captured, illustrating fundamental commonalities in outlet <span class="hlt">glacier</span> flow and highlighting the importance of efforts to map subglacial topography. Success in reproducing present day flow patterns shows the potential for prognostic modelling of ice sheets without the need for spatially varying parameters with uncertain time evolution. PMID:26830316</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1914648T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1914648T"><span>A 3D Full-Stokes Calving Model Applied to a West Greenland Outlet <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Todd, Joe; Christoffersen, Poul; Zwinger, Thomas; Råback, Peter; Chauché, Nolwenn; Hubbard, Alun; Toberg, Nick; Luckman, Adrian; Benn, Doug; Slater, Donald; Cowton, Tom</p> <p>2017-04-01</p> <p>Iceberg calving from outlet <span class="hlt">glaciers</span> accounts for around half of all mass loss from both the Greenland and Antarctic ice sheets. The diverse nature of calving and its complex links to both internal dynamics and external climate make it challenging to incorporate into models of <span class="hlt">glaciers</span> and ice sheets. Consequently, calving represents one of the most significant uncertainties in predictions of future sea level rise. Here, we present results from a new 3D full-Stokes calving model developed in Elmer/Ice and applied to Store <span class="hlt">Glacier</span>, the second largest outlet <span class="hlt">glacier</span> in West Greenland. The calving model implements the crevasse depth criterion, which states that calving occurs when surface and basal crevasses penetrate the full thickness of the <span class="hlt">glacier</span>. The model also implements a new 3D rediscretization approach and a time-evolution scheme which allow the calving front to evolve realistically through time. We use the model to test Store's sensitivity to two seasonal environmental processes believed to significantly influence calving: submarine <span class="hlt">melt</span> undercutting and ice mélange buttressing. Store <span class="hlt">Glacier</span> discharges 13.9 km3 of ice annually, and this calving rate shows a strong seasonal trend. We aim to reproduce this seasonal trend by forcing the model with present day levels of submarine <span class="hlt">melting</span> and ice mélange buttressing. Sensitivity to changes in these frontal processes was also investigated, by forcing the model with a) increased submarine <span class="hlt">melt</span> rates acting over longer periods of time and b) decreased mélange buttressing force acting over a reduced period. The model displays a range of observed calving behaviour and provides a good match to the observed seasonal evolution of the Store's terminus. The results indicate that ice mélange is the primary driver of the observed seasonal advance of the terminus and the associated seasonal variation in calving rate. The model also demonstrates a significant influence from submarine <span class="hlt">melting</span> on calving rate. The results</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018WRR....54.2336H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018WRR....54.2336H"><span>The Value of Hydrograph Partitioning Curves for Calibrating Hydrological Models in <span class="hlt">Glacierized</span> Basins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, Zhihua; Vorogushyn, Sergiy; Unger-Shayesteh, Katy; Gafurov, Abror; Kalashnikova, Olga; Omorova, Elvira; Merz, Bruno</p> <p>2018-03-01</p> <p>This study refines the method for calibrating a glacio-hydrological model based on Hydrograph Partitioning Curves (HPCs), and evaluates its value in comparison to multidata set optimization approaches which use <span class="hlt">glacier</span> mass balance, satellite snow cover images, and discharge. The HPCs are extracted from the observed flow hydrograph using catchment precipitation and temperature gradients. They indicate the periods when the various runoff processes, such as <span class="hlt">glacier</span> <span class="hlt">melt</span> or snow <span class="hlt">melt</span>, dominate the basin hydrograph. The annual cumulative curve of the difference between average daily temperature and <span class="hlt">melt</span> threshold temperature over the basin, as well as the annual cumulative curve of average daily snowfall on the <span class="hlt">glacierized</span> areas are used to identify the starting and end dates of snow and <span class="hlt">glacier</span> ablation periods. Model parameters characterizing different runoff processes are calibrated on different HPCs in a stepwise and iterative way. Results show that the HPC-based method (1) delivers model-internal consistency comparably to the tri-data set calibration method; (2) improves the stability of calibrated parameter values across various calibration periods; and (3) estimates the contributions of runoff components similarly to the tri-data set calibration method. Our findings indicate the potential of the HPC-based approach as an alternative for hydrological model calibration in <span class="hlt">glacierized</span> basins where other calibration data sets than discharge are often not available or very costly to obtain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1622S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1622S"><span>The role of <span class="hlt">glaciers</span> for Swiss hydropower production</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schaefli, Bettina; Manso, Pedro; Fischer, Mauro; Huss, Matthias</p> <p>2016-04-01</p> <p>In Switzerland, hydropower represents over 50% of the total annual electricity production. Given the Alpine setting of the country, this hydropower production (HPP) strongly relies on the natural storage of discharge in form of ice and snow over months to decades. The sensitivity of <span class="hlt">glacier</span>-fed HPP systems with respect to climate change depends on how the today's production and the infrastructure design relies on the seasonal streamflow delay expected from the natural storage effect of snow and ice. For low-head run-of-river HPP plants built on large lowland rivers, the ongoing <span class="hlt">glacier</span> retreat (resulting in strong summer <span class="hlt">melt</span>) currently sustains higher flows during summer months, an effect that will certainly be reduced once the <span class="hlt">glaciers</span> will have reached a critical size. This effect will also modify the inflow to the large storage HPP plants that have been designed to shift large amounts of meltwater inflows from summer to winter. The management of these reservoirs will certainly have to be adapted to future inflow patterns. An interesting case are high-head run-of-river plants (with heads from 100 to 1100 m) that short-circuit a given river reach. Future regime shifts with less sustained summer flow and more concentrated spring <span class="hlt">melt</span> flows might critically reduce the annual production due to intake overflow during spring and reduced flow during summer. In this work, we discuss the role of <span class="hlt">glaciers</span> for these different HPP types in detail, including an overview of how <span class="hlt">glacier</span> retreat might influence their production. This comprehensive study synthesizes up-to-date estimations of <span class="hlt">glacier</span> mass change since the 1980s and its influence on high Alpine discharge regimes and state-of-the art simulations of potential future <span class="hlt">glacier</span> discharge regimes. We also attempt an extrapolation to the country level based on a hydropower GIS database that has been developed for economic purposes. Ongoing Swiss research on sediment production and management might complete this picture</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813160S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813160S"><span>Snow and <span class="hlt">glaciers</span> in the tropics: the importance of snowfall level and snow line altitude in the Peruvian Cordilleras</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schauwecker, Simone; Rohrer, Mario; Huggel, Christian; Salzmann, Nadine; Montoya, Nilton; Endries, Jason; Perry, Baker</p> <p>2016-04-01</p> <p>The snow line altitude, defined as the line separating snow from ice or firn surfaces, is among the most important parameters in the <span class="hlt">glacier</span> mass and energy balance of tropical <span class="hlt">glaciers</span>, since it determines net shortwave <span class="hlt">radiation</span> via surface albedo. Therefore, hydroglaciological models require estimations of the <span class="hlt">melting</span> layer during precipitation events, as well as parameterisations of the transient snow line. Typically, the height of the <span class="hlt">melting</span> layer is implemented by simple air temperature extrapolation techniques, using data from nearby meteorological stations and constant lapse rates. Nonetheless, in the Peruvian mountain ranges, stations at the height of <span class="hlt">glacier</span> tongues (>5000 m asl.) are scarce and the extrapolation techniques must use data from distant and much lower elevated stations, which need prior careful validation. Thus, reliable snowfall level and snow line altitude estimates from multiple data sets are necessary. Here, we assemble and analyse data from multiple sources (remote sensing, in-situ station data, reanalysis data) in order to assess their applicability in estimating both, the <span class="hlt">melting</span> layer and snow line altitude. We especially focus on the potential of radar bright band data from TRMM and CloudSat satellite data for its use as a proxy for the snow/rain transition height. As expected for tropical regions, the seasonal and regional variability in the snow line altitude is comparatively low. During the course of the dry season, Landsat satellite as well as webcam images show that the transient snow line is generally increasing, interrupted by light snowfall or graupel events with low precipitation amounts and fast decay rates. We show limitations and possibilities of different data sources as well as their applicability to validate temperature extrapolation methods. Further on, we analyse the implications of the relatively low variability in seasonal snow line altitude on local <span class="hlt">glacier</span> mass balance gradients. We show that the snow line</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP23E..03W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP23E..03W"><span>A 400-year ice core <span class="hlt">melt</span> layer record of summertime warming in the Alaska Range</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Winski, D.; Osterberg, E. C.; Kreutz, K. J.; Wake, C. P.; Ferris, D. G.; Campbell, S. W.; Baum, M.; Raudzens Bailey, A.; Birkel, S. D.; Introne, D.; Handley, M.</p> <p>2017-12-01</p> <p>Warming in high-elevation regions has socially relevant impacts on <span class="hlt">glacier</span> mass balance, water resources, and sensitive alpine ecosystems, yet very few high-elevation temperature records exist from the middle or high latitudes. While many terrestrial paleoclimate records provide critical temperature records from low elevations over recent centuries, <span class="hlt">melt</span> layers preserved in alpine <span class="hlt">glaciers</span> present an opportunity to develop calibrated, annually-resolved temperature records from high elevations. We present a 400-year temperature record based on the <span class="hlt">melt</span>-layer stratigraphy in two ice cores collected from Mt. Hunter in the Central Alaska Range. The ice core record shows a 60-fold increase in <span class="hlt">melt</span> frequency and water equivalent <span class="hlt">melt</span> thickness between the pre-industrial period (before 1850) and present day. We calibrate the <span class="hlt">melt</span> record to summer temperatures based on local and regional weather station analyses, and find that the increase in <span class="hlt">melt</span> production represents a summer warming of at least 2° C, exceeding rates of temperature increase at most low elevation sites in Alaska. The Mt. Hunter <span class="hlt">melt</span> layer record is significantly (p<0.05) correlated with surface temperatures in the central tropical Pacific through a Rossby-wave like pattern that <span class="hlt">induces</span> high temperatures over Alaska. Our results show that rapid alpine warming has taken place in the Alaska Range for at least a century, and that conditions in the tropical oceans contribute to this warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.2286S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.2286S"><span>Geomorphic feedbacks between hillslopes and valley <span class="hlt">glaciers</span> - implications for climate reconstructions and landscape evolution (GM Division Outstanding ECS Award Lecture and Penck Lecture)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scherler, Dirk</p> <p>2017-04-01</p> <p> heat transport and thus ice <span class="hlt">melt</span> rates, heavily debris-covered <span class="hlt">glaciers</span> are longer and extent to lower and warmer elevations compared to debris-free <span class="hlt">glaciers</span>, all other things being equal. Therefore, if warming <span class="hlt">induces</span> an increase in headwall erosion rates, the increased supply of rocks should lead to an increase in supraglacial debris cover, which would reduce ice <span class="hlt">melting</span> and slow down <span class="hlt">glacier</span> retreat. Theoretically this effect could offset part of the warming-<span class="hlt">induced</span> <span class="hlt">glacier</span> shrinking. Large slope failures that result in a sudden increase in debris cover may even trigger <span class="hlt">glacier</span> advances, as has been proposed for a few <span class="hlt">glaciers</span> already. Such geomorphic feedbacks between headwalls and valley <span class="hlt">glaciers</span> ought to be most pronounced in steep landscapes like the Himalaya, where existing glacial chronologies often lack spatial coherence. Some heavily debris-covered valley <span class="hlt">glaciers</span> can be found to lie entirely below the regional climatic snowline where they are sustained by snow avalanches. Such <span class="hlt">glaciers</span> typically flow at low velocities and their key role in glacial landscape evolution may lie in keeping the base of headwalls free from talus deposits and thereby sustain a steep and retreating headwall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70174306','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70174306"><span><span class="hlt">Glaciers</span> dominate eustatic sea-level rise in the 21st century</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Meier, Mark Frederick; Dyurgerov, M.B.; Rick, Ursula K.; Pfeffer, William Tad; Anderson, Suzanne P.; Glazovsky, Andrey F.</p> <p>2007-01-01</p> <p>Ice loss to the sea currently accounts for virtually all of the sea-level rise that is not attributable to ocean warming, and about 60% of the ice loss is from <span class="hlt">glaciers</span> and ice caps rather than from the two ice sheets. The contribution of these smaller <span class="hlt">glaciers</span> has accelerated over the past decade, in part due to marked thinning and retreat of marine-terminating <span class="hlt">glaciers</span> associated with a dynamic instability that is generally not considered in mass-balance and climate modeling. This acceleration of <span class="hlt">glacier</span> <span class="hlt">melt</span> may cause 0.1 to 0.25 meter of additional sea-level rise by 2100.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P43C2901U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P43C2901U"><span>Analysis of crevasse patterns on Helheim and Kangerdlugssuaq <span class="hlt">Glaciers</span> in Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Udell, K.; Walker, C. C.; Schmidt, B. E.</p> <p>2017-12-01</p> <p>As a tidewater <span class="hlt">glacier</span> flows through a valley, it accumulates fractures that provide qualitative information on how <span class="hlt">glacier</span> thickness, climate forcing, and areas of compression and extension conspire within the ice. These fracture patterns remain and evolve on the <span class="hlt">glacier</span>, and rapid changes in the pattern can be indicative of a transition in the movement of the <span class="hlt">glacier</span>. Not only can the fractures provide qualitative information about a <span class="hlt">glacier</span>, they can also provide quantitative information that allows for the calculation of the stress field and dynamics that the ice experiences. Helheim and Kangerdlugssuaq both terminate in the ocean, potentially providing information on the transition from solid <span class="hlt">glacier</span> to mélange, which is an important but not well understood process. Using satellite imagery, we traced surface crevasses present along each <span class="hlt">glacier</span> for available images between 2001-2016 using geospatial software QGIS. We also qualitatively tracked any surface <span class="hlt">melt</span> ponds present, and monitored for large fractures or regions of the terminus that appeared to be susceptible to or currently calving. With the trace maps, we will use spatial analysis techniques to allow us to quantify the visible patterns and compare the information from year to year and <span class="hlt">glacier</span> to <span class="hlt">glacier</span>. Once we can quantitatively describe fracture density in different areas of the <span class="hlt">glacier</span>, we will also be able to better describe the transition within the <span class="hlt">glacier</span> from solid mass to highly-fractured and collapsing. Having this data for each <span class="hlt">glacier</span> allows for comparisons to be made within regions of individual <span class="hlt">glaciers</span> as well as between <span class="hlt">glaciers</span>. Using this information, we can answer questions about the relationship between density and pattern of fractures to the stability of the terminus, the stresses that drive glacial fractures, and what effects climate has on <span class="hlt">glacier</span> dynamics and calving. Preliminary observations include the increasing prevalence of <span class="hlt">melt</span> ponds beginning in 2004 as well as the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.3156A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.3156A"><span>A Century of Stability of Avannarleq and Kujalleq <span class="hlt">Glaciers</span>, West Greenland, Explained Using High-Resolution Airborne Gravity and Other Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>An, L.; Rignot, E.; Mouginot, J.; Millan, R.</p> <p>2018-04-01</p> <p>The evolution of Greenland <span class="hlt">glaciers</span> in a warming climate depends on their depth below sea level, flow speed, surface <span class="hlt">melt</span>, and ocean-<span class="hlt">induced</span> undercutting at the calving front. We present an innovative mapping of bed topography in the frontal regions of Sermeq Avannarleq and Kujalleq, two major <span class="hlt">glaciers</span> flowing into the ice-choked Torssukatak Fjord, central west Greenland. The mapping combines a mass conservation algorithm inland, multibeam echo sounding data in the fjord, and high-resolution airborne gravity data at the ice-ocean transition where other approaches have traditionally failed. We obtain a reliable, precision (±40 m) solution for bed topography across the ice-ocean boundary. The results reveal a 700 m deep fjord that abruptly ends on a 100-300 m deep sill along the calving fronts. The shallow sills explain the presence of stranded icebergs, the resilience of the <span class="hlt">glaciers</span> to ocean-<span class="hlt">induced</span> undercutting by warm Atlantic water, and their remarkable stability over the past century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.H23D1147S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.H23D1147S"><span><span class="hlt">Glacier</span> Change Detection in the Hindu Kush of Afghanistan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shroder, J. F.; Bishop, M. P.</p> <p>2004-12-01</p> <p>A half century of intermittently collected cryospheric and hydrologic data in Afghanistan has involved diverse field surveys, aerial photography, and satellite imagery that enable change detection in the war-torn, drought-stricken region. Afghanistan relies heavily upon snow-and ice-<span class="hlt">melt</span> for vital irrigation and ground-water recharge, yet the past two decades of war have only exacerbated the originally already deficient information collection and analysis of such data. <span class="hlt">Glacier</span> field studies and base-line inventory work initiated in the pre-war 1960-1970 period are now providing limited change detection information for the vital physical analysis necessary in the reconstruction of the country. Five case study areas were selected for renewed assessment over the intervening half century, from the western-most ice masses of the Koh-i-Foladi region in central Afghanistan, through the Mir Samir and Sakhi regions of the central Hindu Kush, to the Keshnikhan and Pamir areas of the Wakhan Corridor. Certain incompatibilities or ambiguities exist between Soviet-era and Western-derived data sets. In general, however, <span class="hlt">glaciers</span> of Afghanistan are continuing to downwaste and retreat, with smaller ice masses disappearing altogether, presumably as the climatic snowline continues to rise above the peaks, a trend first noticed in the 1960s. <span class="hlt">Glacier</span> survival in the lower central areas is now in part determined by topographic shielding from solar <span class="hlt">radiation</span> high in shadowed cirques, or being preserved beneath increasing debris covers, whereas in the higher regions to the northeast, fewer changes to the larger, higher altitude <span class="hlt">glaciers</span> are apparent. Renewed assessment of all Afghanistan <span class="hlt">glaciers</span> is now underway as a part of the USGS- and NASA-supported GLIMS (Global Land-Ice Measurements from Space) project, and is viewed as an important element in the primary geodata collection and hazard assessment necessary for aiding in rebuilding the infrastructure of the beleaguered nation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012WRR....4812508J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012WRR....4812508J"><span>Role of snow and <span class="hlt">glacier</span> <span class="hlt">melt</span> in controlling river hydrology in Liddar watershed (western Himalaya) under current and future climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jeelani, G.; Feddema, Johannes J.; van der Veen, Cornelis J.; Stearns, Leigh</p> <p>2012-12-01</p> <p>Snowmelt and icemelt are believed to be important regulators of seasonal discharge of Himalayan rivers. To analyze the long term contribution of snowmelt and <span class="hlt">glacier</span>/icemelt to river hydrology we apply a water budget model to simulate hydrology of the Liddar watershed in the western Himalaya, India for the 20th century (1901-2010) and future IPCC A1B climate change scenario. Long term (1901-2010) temperature and precipitation data in this region show a warming trend (0.08°C yr-1) and an increase in precipitation (0.28 mm yr-1), with a significant variability in seasonal trends. In particular, winter months have undergone the most warming, along with a decrease in precipitation rates; precipitation has increased throughout the spring. These trends have accelerated the <span class="hlt">melting</span> and rapid disappearance of snow, causing a seasonal redistribution in the availability of water. Our model results show that about 60% of the annual runoff of the Liddar watershed is contributed from the snowmelt, while only 2% is contributed from <span class="hlt">glacier</span> ice. The climate trend observed from the 1901 to 2010 time period and its impact on the availability of water will become significantly worse under the IPCC climate change scenarios. Our results suggest that there is a significant shift in the timing and quantity of water runoff in this region of the Himalayas due to snow distribution and <span class="hlt">melt</span>. With greatly increased spring runoff and its reductions in summer potentially leading to reduced water availability for irrigation agriculture in summer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918509L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918509L"><span>An eddy covariance system to characterize the atmospheric surface layer and turbulent latent heat fluxes over a debris-covered Himalayan <span class="hlt">glacier</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Litt, Maxime; Steiner, Jakob F.; Stigter, Emmy E.; Immerzeel, Walter; Shea, Joseph Michael</p> <p>2017-04-01</p> <p>Over debris-covered <span class="hlt">glaciers</span>, water content variations in the debris layer can drive significant changes in its thermal conductivity and significantly impact <span class="hlt">melt</span> rates. Since sublimation and evaporation are favoured in high-altitude conditions, e.g., low atmospheric pressure and high wind speeds, they are expected to strongly influence the water balance of the debris-layer. Dedicated latent heat fluxes measurements at the debris surface are essential to characterize the debris heat conductivity in order to assess underlying ice <span class="hlt">melt</span>. Furthermore, the contribution of the turbulent fluxes in the surface energy balance over debris covered <span class="hlt">glacier</span> remains uncertain since they are generally evaluated through similarity methods which might not be valid in complex terrain. We present the first results of a 15-day eddy-covariance experiment installed at the end of the monsoon (September-October) on a 3-m tower above the debris-covered Lirung <span class="hlt">glacier</span> in Nepal. The tower also included measurements of the 4 <span class="hlt">radiation</span> components. The eddy covariance measurements allowed for the characterization of the turbulence in the atmospheric surface layer, as well as the direct measurements of evaporation, sublimation and turbulent sensible heat fluxes. The experiment helps us to evaluate the contribution of turbulent fluxes to the surface energy balance over this debris-covered <span class="hlt">glacier</span>, through a precise characterization of the overlying turbulent atmospheric surface layer. It also helps to study the role of the debris-layer water content changes through evaporation and sublimation and its feedback on heat conduction in this layer. The large observed turbulent fluxes play a significant role in the energy balance at the debris surface and significantly influence debris moisture, conductivity and subsequently underlying ice <span class="hlt">melt</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....10580S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....10580S"><span>Dry calving processes at the ice cliff of an antarctic local <span class="hlt">glacier</span>: the study case of Strandline <span class="hlt">Glacier</span> (Northern Victoria Land, Antarctica)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smiraglia, C.; Motta, M.; Vassena, G.; Diolaiuti, G.</p> <p>2003-04-01</p> <p>In Antartic coastal area, where the ice sheet and the large outlet <span class="hlt">glaciers</span> do not reach the sea and where some rugged mountain chains are often present, many small <span class="hlt">glaciers</span> can be found. They are the so called local or alpine type <span class="hlt">glaciers</span>, which have their terminus ground-based such as the real alpine <span class="hlt">glaciers</span> and rarely reach the main valley floors. They are practically isolated and independent from the supply flowing down from the plateau and their mass balance is mainly controlled by sublimation and aeolic erosion and accumulation. The <span class="hlt">glaciers</span> closer to the coast are submitted to the <span class="hlt">melting</span> as well, and when the terminus is cliff-shaped they are also affected by dry calving. The most known and studied Antarctic local <span class="hlt">glaciers</span> are placed in the Dry Valleys region (Chinn, 1985), but this kind of <span class="hlt">glaciers</span> is also diffused all along the Northern Victoria Land coastal region (Chinn and others, 1989). Since the first Italian Antarctic expedition (1985), many studies have been carried out on this type of <span class="hlt">glaciers</span>, which can be usefull for detailed mass balance evaluations and for obtaining information about the effects of the present climatic dynamics on the Antarctic coastal environment (Baroni and Orombelli, 1987; Baroni and others, 1995; Meneghel, 1999; Vassena and others., 2001). The Strandline <span class="hlt">Glacier</span> (74 41 S; 164 07 E), in particular is a small alpine <span class="hlt">glacier</span> (0,79 kmq) on the coast of Terra Nova Bay, Northern Victoria Land; it is a cold <span class="hlt">glacier</span> where accumulation and ablation basins are mainly controlled by wind processes. Its terminus forms in the central part a grounded ice cliff about 30 m high, about 130 m far from the sea. On that <span class="hlt">glacier</span> mass balance, surface velocity and calving rate were measured. During the southern summer season 2000-2001 many topographycal profiles of the ice cliff were surveyed by using both classical topographical and glaciological methods (total station and stakes) and GPS technique. It was so possible to detect the short term</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT.......234B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT.......234B"><span>Three Dimensional <span class="hlt">Glacier</span> Flow of Bylot Island Derived Using Sentinel 1A and 1B</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bobeck, J. M.</p> <p></p> <p>With the rise of temperatures in the Arctic, Sentinel 1A and 1B data are used to examine the current state of Bylot Island's <span class="hlt">glaciers</span>. This will provide valuable data for future sea-level and climate models to accurately predict the contribution the High Canadian Arctic has to sea-level rise. Bylot Island is in a unique location in the High Canadian Arctic, as it sits on a transition zone between warming in the north and historical cooling to the south. By using Interferometric Synthetic Aperture Radar (InSAR), the three dimensional velocity vectors are calculated and used to produce horizontal velocity and <span class="hlt">melt</span> loss maps for Bylot Island. Optical Feature Tracking is employed using Landsat 7 and Landsat 8 data to validate results and calculate Bylot Island's ice cap extent. Results show a decrease in overall <span class="hlt">glacier</span> velocity, but increased <span class="hlt">glacier</span> thinning from surface <span class="hlt">melt</span>. Increased glacial thinning can be contributed to a <span class="hlt">Melt</span>-Albedo positive feedback cycle. With <span class="hlt">melting</span> beginning earlier each season, the overall extent of Bylot Island is rapidly decreasing and contributing more <span class="hlt">melt</span> to sea-level than previously thought.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26ES...74a2022F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26ES...74a2022F"><span><span class="hlt">Glacier</span> retreat of the Tian Shan and its impact on the urban growth and environment evaluated from satellite remote sensing data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fu, B. H.; Guo, Q.; Yan, F.; Zhang, J.; Shi, P. L.; Ayinuer, M.; Xue, G. L.</p> <p>2017-07-01</p> <p>The retreat of mountain <span class="hlt">glaciers</span>, notably in high Asia, provides evidence for the rise of global temperature. The mass balance is vital for the health of a <span class="hlt">glacier</span>. If the amount of frozen precipitation in the accumulation zone exceeds the quantity of glacial ice loss due to <span class="hlt">melting</span> or lies in the ablation zone, the <span class="hlt">glacier</span> will advance. Conversely, if the accumulation is less than the ablation, the <span class="hlt">glacier</span> will retreat. <span class="hlt">Glaciers</span> in retreat will have negative mass balances, and if they do not reach an equilibrium between accumulation and ablation, will eventually disappear. Long-term changes of the mountain <span class="hlt">glaciers</span> in the Tian Shan, Central Asia, are not well constrained. Analyses of satellite remote sensing data combined with the ground observations reveal a 37.5% decline of <span class="hlt">glaciered</span> area from 1989 to 2014 in No.1 <span class="hlt">Glacier</span>, the headwaters of the Urumqi River basin, Chinese Tian Shan, which could be linked to increased summer <span class="hlt">melting</span>. The results show that the area of <span class="hlt">glaciers</span> was reduced from 31.55 km2 in 18 August 1989 to 28.66 km2 in 24 August 1994 and 19.74 km2 in 31 August 2014. The <span class="hlt">glacier</span> area was reduced by 0.47 km2/per year in recent 25 years since 1989, and the annual reduction was 1.5%. Meanwhile, the urban area of Urumqi, the biggest city of Xinjiang Uygur Autonomous Region, increased from 156 km2 in 1989 to 555 km2 in 2014. Correspondingly, the population of permanent residents increased from 1.06 million in 1989 to 3.53 million in 2014. We suggest that the decline of <span class="hlt">glacier</span> area is driven primarily by summer <span class="hlt">melting</span> and, possibly, linked to the combined effects of the global rise in temperatures and black carbon/CO2 emission from coal-fired power plants, cement plants and petroleum chemical plants from the nearby Urumqi and surrounding regions. The continuing retreat of <span class="hlt">glaciers</span> will have a number of different quantitative impacts. Populations in the arid Central Asia regions are heavily dependent on snow and <span class="hlt">glacier</span> <span class="hlt">melt</span> for their irrigation and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130014410','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130014410"><span>Sensitivity and Response of Bhutanese <span class="hlt">Glaciers</span> to Atmospheric Warming</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rupper, Summer; Schaefer, Joerg M.; Burgener, Landon K.; Koenig, Lora S.; Tsering, Karma; Cook, Edward</p> <p>2013-01-01</p> <p><span class="hlt">Glacierized</span> change in the Himalayas affects river-discharge, hydro-energy and agricultural production, and Glacial Lake Outburst Flood potential, but its quantification and extent of impacts remains highly uncertain. Here we present conservative, comprehensive and quantitative predictions for <span class="hlt">glacier</span> area and meltwater flux changes in Bhutan, monsoonal Himalayas. In particular, we quantify the uncertainties associated with the <span class="hlt">glacier</span> area and meltwater flux changes due to uncertainty in climate data, a critical problem for much of High Asia. Based on a suite of gridded climate data and a robust <span class="hlt">glacier</span> <span class="hlt">melt</span> model, our results show that <span class="hlt">glacier</span> area and meltwater change projections can vary by an order of magnitude for different climate datasets. However, the most conservative results indicate that, even if climate were to remain at the present-day mean values, almost 10% of Bhutan s <span class="hlt">glacierized</span> area would vanish and the meltwater flux would drop by as much as 30%. Under the conservative scenario of an additional 1 C regional warming, <span class="hlt">glacier</span> retreat is going to continue until about 25% of Bhutan s <span class="hlt">glacierized</span> area will have disappeared and the annual meltwater flux, after an initial spike, would drop by as much as 65%. Citation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27266318','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27266318"><span>Distribution and transportation of mercury from <span class="hlt">glacier</span> to lake in the Qiangyong <span class="hlt">Glacier</span> Basin, southern Tibetan Plateau, China.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sun, Shiwei; Kang, Shichang; Huang, Jie; Li, Chengding; Guo, Junming; Zhang, Qianggong; Sun, Xuejun; Tripathee, Lekhendra</p> <p>2016-06-01</p> <p>The Tibetan Plateau is home to the largest aggregate of <span class="hlt">glaciers</span> outside the Polar Regions and is a source of fresh water to 1.4 billion people. Yet little is known about the transportation and cycling of Hg in high-elevation <span class="hlt">glacier</span> basins on Tibetan Plateau. In this study, surface snow, <span class="hlt">glacier</span> <span class="hlt">melting</span> stream water and lake water samples were collected from the Qiangyong <span class="hlt">Glacier</span> Basin. The spatiotemporal distribution and transportation of Hg from <span class="hlt">glacier</span> to lake were investigated. Significant diurnal variations of dissolved Hg (DHg) concentrations were observed in the river water, with low concentrations in the morning (8:00am-14:00pm) and high concentrations in the afternoon (16:00pm-20:00pm). The DHg concentrations were exponentially correlated with runoff, which indicated that runoff was the dominant factor affecting DHg concentrations in the river water. Moreover, significant decreases of Hg were observed during transportation from <span class="hlt">glacier</span> to lake. DHg adsorption onto particulates followed by the sedimentation of particulate-bound Hg (PHg) could be possible as an important Hg removal mechanism during the transportation process. Significant decreases in Hg concentrations were observed downstream of Xiao Qiangyong Lake, which indicated that the high-elevation lake system could significantly affect the distribution and transportation of Hg in the Qiangyong <span class="hlt">Glacier</span> Basin. Copyright © 2016. Published by Elsevier B.V.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.6251B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.6251B"><span>Quantifying ice cliff contribution to debris-covered <span class="hlt">glacier</span> mass balance from multiple sensors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brun, Fanny; Wagnon, Patrick; Berthier, Etienne; Kraaijenbrink, Philip; Immerzeel, Walter; Shea, Joseph; Vincent, Christian</p> <p>2017-04-01</p> <p>Ice cliffs on debris-covered <span class="hlt">glaciers</span> have been recognized as a hot spot for <span class="hlt">glacier</span> <span class="hlt">melt</span>. Ice cliffs are steep (even sometimes overhanging) and fast evolving surface features, which make them challenging to monitor. We surveyed the topography of Changri Nup <span class="hlt">Glacier</span> (Nepalese Himalayas, Everest region) in November 2015 and 2016 using multiple sensors: terrestrial photogrammetry, Unmanned Aerial Vehicle (UAV) photogrammetry, Pléiades stereo images and ASTER stereo images. We derived 3D point clouds and digital elevation models (DEMs) following a Structure-from-Motion (SfM) workflow for the first two sets of data to monitor surface elevation changes and calculate the associated volume loss. We derived only DEMs for the two last data sets. The derived DEMs had resolutions ranging from < 5 cm to 30 m. The derived point clouds and DEMs are used to quantify the ice <span class="hlt">melt</span> of the cliffs at different scales. The very high resolution SfM point clouds, together with the surface velocity field, will be used to calculate the volume losses of 14 individual cliffs, depending on their size, aspect or the presence of supra glacial lake. Then we will extend this analysis to the whole <span class="hlt">glacier</span> to quantify the contribution of ice cliff <span class="hlt">melt</span> to the overall <span class="hlt">glacier</span> mass balance, calculated with the UAV and Pléiades DEMs. This research will provide important tools to evaluate the role of ice cliffs in regional mass loss.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3286865','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3286865"><span><span class="hlt">Radiation-induced</span> <span class="hlt">melting</span> in coherent X-ray diffractive imaging at the nanoscale</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ponomarenko, O.; Nikulin, A. Y.; Moser, H. O.; Yang, P.; Sakata, O.</p> <p>2011-01-01</p> <p>Coherent X-ray diffraction techniques play an increasingly significant role in the imaging of nanoscale structures, ranging from metallic and semiconductor to biological objects. In material science, X-rays are usually considered to be of a low-destructive nature, but under certain conditions they can cause significant <span class="hlt">radiation</span> damage and heat loading on the samples. The qualitative literature data concerning the tolerance of nanostructured samples to synchrotron <span class="hlt">radiation</span> in coherent diffraction imaging experiments are scarce. In this work the experimental evidence of a complete destruction of polymer and gold nanosamples by the synchrotron beam is reported in the case of imaging at 1–10 nm spatial resolution. Numerical simulations based on a heat-transfer model demonstrate the high sensitivity of temperature distribution in samples to macroscopic experimental parameters such as the conduction properties of materials, <span class="hlt">radiation</span> heat transfer and convection. However, for realistic experimental conditions the calculated rates of temperature rise alone cannot explain the <span class="hlt">melting</span> transitions observed in the nanosamples. Comparison of these results with the literature data allows a specific scenario of the sample destruction in each particular case to be presented, and a strategy for damage reduction to be proposed. PMID:21685675</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9407L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9407L"><span>Remotely-sensed and field-based observations of <span class="hlt">glacier</span> change in the Annapurna-Manaslu region, Nepal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lovell, Arminel; Carr, Rachel; Stokes, Chris</p> <p>2017-04-01</p> <p>Himalayan <span class="hlt">glaciers</span> have shrunk rapidly during the past twenty years. Understanding the factors controlling these losses is vital for forecasting changes in water resources, as the Himalaya houses the headwaters of major river systems, with densely populated catchments downstream. However, our knowledge of Himalayan <span class="hlt">glaciers</span> is comparatively limited, due to their high-altitude, remote location. This is particularly the case in the Annapurna-Manaslu region, which has received relatively little scientific attention to date. Here, we present initial findings from remotely sensed data analysis, and our first field campaign in October 2016. Feature tracking of Band 8 Landsat imagery demonstrates that velocities in the region reach a maximum of 70-100 m a-1 , which is somewhat faster than those reported in the Khumbu region (e.g. Quincey et al 2009). A number of <span class="hlt">glaciers</span> have substantial stagnant ice tongues, and most are flowing faster in the upper ablation zone than in the lower sections. The most rapidly flowing <span class="hlt">glaciers</span> are located in the south-east of the Annapurna-Manaslu region and tend to also be the largest. Interestingly, initial observations suggest that the debris-covered ablation zones in the south-east are flowing more rapidly than the smaller, clean-ice <span class="hlt">glaciers</span> in the north of the region. Comparison of velocities between 2000-2001 and 2014-2015 suggests deceleration on some <span class="hlt">glacier</span> tongues. In October 2016, we conducted fieldwork on Annapurna South <span class="hlt">Glacier</span>, located at the foot of Annapurna I. Here, we collected a number of datasets, with the aim of assessing the relationship between surface elevation change, ice velocities and debris cover. These included: i) installing ablation stakes in areas with varying debris cover; ii) quantifying debris characteristics, using Wolman counting and by measuring thickness; iii) surveying the <span class="hlt">glacier</span> surface, using a differential GPS; iv) monitoring ice cliff <span class="hlt">melting</span>, using Structure from Motion and; v) measuring surface</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.7687T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.7687T"><span>Dynamic interactions between <span class="hlt">glacier</span> and glacial lake in the Bhutan Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsutaki, S.; Fujita, K.; Yamaguchi, S.; Sakai, A.; Nuimura, T.; Komori, J.; Takenaka, S.; Tshering, P.</p> <p>2012-04-01</p> <p>.9-18.8 m yr-1 at the Thorthormi <span class="hlt">Glacier</span> while -12.0-2.7 m yr-1 at the Lugge <span class="hlt">Glacier</span>. This result suggests that decreasing in flow velocity towards the terminus in the Thorthormi <span class="hlt">Glacier</span> causes compressive flow. It suggests that the compressive flow of the Thorthormi <span class="hlt">Glacier</span> counterbalanced surface <span class="hlt">melting</span>, resulting in inhibition of the surface lowering. In contrast, the extensional flow of the Lugge <span class="hlt">Glacier</span> accelerated the surface lowering. Speed up of <span class="hlt">glacier</span> terminus <span class="hlt">induced</span> extensional flow regime causes the thinning of ice and increase in basal motion, which will lead to further flow acceleration. Such positive feedbacks have been found over the ice streams in the polar ice sheets. In this study we showed the observational evidences, in which the similar feedbacks make contrast the terminus behaviors of <span class="hlt">glaciers</span> in the Bhutan Himalaya. If the supraglacial lake on Thorthormi <span class="hlt">Glacier</span> expanded, the surface lowering may be accelerated in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000074257&hterms=Antarctic+icebergs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DAntarctic%2Bicebergs','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000074257&hterms=Antarctic+icebergs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DAntarctic%2Bicebergs"><span><span class="hlt">Glacier</span> and Ice Shelves Studies Using Satellite SAR Interferometry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rignot, Eric</p> <p>1999-01-01</p> <p>Satellite radar interferometry is a powerful technique to measure the surface velocity and topography of <span class="hlt">glacier</span> ice. On ice shelves, a quadruple difference technique separates tidal motion from the steady creep flow deformation of ice. The results provide a wealth of information about <span class="hlt">glacier</span> grounding lines , mass fluxes, stability, elastic properties of ice, and tidal regime. The grounding line, which is where the <span class="hlt">glacier</span> detaches from its bed and becomes afloat, is detected with a precision of a few tens of meters. Combining this information with satellite radar altimetry makes it possible to measure <span class="hlt">glacier</span> discharge into the ocean and state of mass balance with greater precision than ever before, and in turn provide a significant revision of past estimates of mass balance of the Greenland and Antarctic Ice Sheets. Analysis of creep rates on floating ice permits an estimation of basal <span class="hlt">melting</span> at the ice shelf underside. The results reveal that the action of ocean water in sub-ice-shelf cavities has been largely underestimated by oceanographic models and is the dominant mode of mass release to the ocean from an ice shelf. Precise mapping of grounding line positions also permits the detection of grounding line migration, which is a fine indicator of <span class="hlt">glacier</span> change, independent of our knowledge of snow accumulation and ice <span class="hlt">melting</span>. This technique has been successfully used to detect the rapid retreat of Pine Island <span class="hlt">Glacier</span>, the largest ice stream in West Antarctica. Finally, tidal motion of ice shelves measured interferometrically provides a modern, synoptic view of the physical processes which govern the formation of tabular icebergs in the Antarctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016WRR....52.3888B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016WRR....52.3888B"><span>High-resolution modeling of coastal freshwater discharge and <span class="hlt">glacier</span> mass balance in the Gulf of Alaska watershed</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beamer, J. P.; Hill, D. F.; Arendt, A.; Liston, G. E.</p> <p>2016-05-01</p> <p>A comprehensive study of the Gulf of Alaska (GOA) drainage basin was carried out to improve understanding of the coastal freshwater discharge (FWD) and <span class="hlt">glacier</span> volume loss (GVL). Hydrologic processes during the period 1980-2014 were modeled using a suite of physically based, spatially distributed weather, energy-balance snow/ice <span class="hlt">melt</span>, soil water balance, and runoff routing models at a high-resolution (1 km horizontal grid; daily time step). Meteorological forcing was provided by the North American Regional Reanalysis (NARR), Modern Era Retrospective Analysis for Research and Applications (MERRA), and Climate Forecast System Reanalysis (CFSR) data sets. Streamflow and <span class="hlt">glacier</span> mass balance modeled using MERRA and CFSR compared well with observations in four watersheds used for calibration in the study domain. However, only CFSR produced regional seasonal and long-term trends in water balance that compared favorably with independent Gravity Recovery and Climate Experiment (GRACE) and airborne altimetry data. Mean annual runoff using CFSR was 760 km3 yr-1, 8% of which was derived from the long-term removal of stored water from <span class="hlt">glaciers</span> (<span class="hlt">glacier</span> volume loss). The annual runoff from CFSR was partitioned into 63% snowmelt, 17% <span class="hlt">glacier</span> ice <span class="hlt">melt</span>, and 20% rainfall. <span class="hlt">Glacier</span> runoff, taken as the sum of rainfall, snow, and ice <span class="hlt">melt</span> occurring each season on <span class="hlt">glacier</span> surfaces, was 38% of the total seasonal runoff, with the remaining runoff sourced from nonglacier surfaces. Our simulations suggests that existing GRACE solutions, previously reported to represent <span class="hlt">glacier</span> mass balance alone, are actually measuring the full water budget of land and ice surfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12..301B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12..301B"><span>Simple models for the simulation of submarine <span class="hlt">melt</span> for a Greenland glacial system model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beckmann, Johanna; Perrette, Mahé; Ganopolski, Andrey</p> <p>2018-01-01</p> <p>Two hundred marine-terminating Greenland outlet <span class="hlt">glaciers</span> deliver more than half of the annually accumulated ice into the ocean and have played an important role in the Greenland ice sheet mass loss observed since the mid-1990s. Submarine <span class="hlt">melt</span> may play a crucial role in the mass balance and position of the grounding line of these outlet <span class="hlt">glaciers</span>. As the ocean warms, it is expected that submarine <span class="hlt">melt</span> will increase, potentially driving outlet <span class="hlt">glaciers</span> retreat and contributing to sea level rise. Projections of the future contribution of outlet <span class="hlt">glaciers</span> to sea level rise are hampered by the necessity to use models with extremely high resolution of the order of a few hundred meters. That requirement in not only demanded when modeling outlet <span class="hlt">glaciers</span> as a stand alone model but also when coupling them with high-resolution 3-D ocean models. In addition, fjord bathymetry data are mostly missing or inaccurate (errors of several hundreds of meters), which questions the benefit of using computationally expensive 3-D models for future predictions. Here we propose an alternative approach built on the use of a computationally efficient simple model of submarine <span class="hlt">melt</span> based on turbulent plume theory. We show that such a simple model is in reasonable agreement with several available modeling studies. We performed a suite of experiments to analyze sensitivity of these simple models to model parameters and climate characteristics. We found that the computationally cheap plume model demonstrates qualitatively similar behavior as 3-D general circulation models. To match results of the 3-D models in a quantitative manner, a scaling factor of the order of 1 is needed for the plume models. We applied this approach to model submarine <span class="hlt">melt</span> for six representative Greenland <span class="hlt">glaciers</span> and found that the application of a line plume can produce submarine <span class="hlt">melt</span> compatible with observational data. Our results show that the line plume model is more appropriate than the cone plume model for simulating</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740004942','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740004942"><span>Evaluation of <span class="hlt">glacier</span> mass balance by observing variations in transient snowline positions. [Jostedalsbreen ice cap, Norway</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oestrem, G. (Principal Investigator)</p> <p>1973-01-01</p> <p>The author has identified the following significant results. The transient snowline on five outlet <span class="hlt">glaciers</span> from the Jostedalsbreen ice-cap in Southwestern Norway could be determined from ERTS-1 image 1336-10260, when bands MSS 5, 6, and 7 were combined in an additive color viewer. The snowline was situated at a very low altitude at the time of imagery (24 June 1973) indicating that <span class="hlt">glacier</span> <span class="hlt">melt</span> was behind normal schedule, a fact that has a hydrologic bearing: one could expect less <span class="hlt">melt</span> water in the streams. The idea to use ERTS-1 imagery in snowline determinations proved realistic and relatively easy to apply in practice. The method will be useful to estimate the <span class="hlt">glaciers</span>' mass balance for large areas, provided some ground truth observations are made. Images from the end of the <span class="hlt">melt</span> season are of course vital in this work.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C24A..08P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C24A..08P"><span>Global mountain snow and ice loss driven by dust and black carbon <span class="hlt">radiative</span> forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Painter, T. H.</p> <p>2014-12-01</p> <p>Changes in mountain snow and <span class="hlt">glaciers</span> have been our strongest indicators of the effects of changing climate. Earlier <span class="hlt">melt</span> of snow and losses of <span class="hlt">glacier</span> mass have perturbed regional water cycling, regional climate, and ecosystem dynamics, and contributed strongly to sea level rise. Recent studies however have revealed that in some regions, the reduction of albedo by light absorbing impurities in snow and ice such as dust and black carbon can be distinctly more powerful than regional warming at <span class="hlt">melting</span> snow and ice. In the Rocky Mountains, dust deposition has increased 5 to 7 fold in the last 150 years, leading to ~3 weeks earlier loss of snow cover from forced <span class="hlt">melt</span>. In absolute terms, in some years dust <span class="hlt">radiative</span> forcing there can shorten snow cover duration by nearly two months. Remote sensing retrievals are beginning to reveal powerful dust and black carbon <span class="hlt">radiative</span> forcing in the Hindu Kush through Himalaya. In light of recent ice cores that show pronounced increases in loading of dust and BC during the Anthropocene, these forcings may have contributed far more to <span class="hlt">glacier</span> retreat than previously thought. For example, we have shown that the paradoxical end of the Little Ice Age in the European Alps beginning around 1850 (when <span class="hlt">glaciers</span> began to retreat but temperatures continued to decline and precipitation was unchanged) very likely was driven by the massive increases in deposition to snow and ice of black carbon from industrialization in surrounding nations. A more robust understanding of changes in mountain snow and ice during the Anthropocene requires that we move past simplistic treatments (e.g. temperature-index modeling) to energy balance approaches that assess changes in the individual forcings such as the most powerful component for <span class="hlt">melt</span> - net solar <span class="hlt">radiation</span>. Remote sensing retrievals from imaging spectrometers and multispectral sensors are giving us more powerful insights into the time-space variation of snow and ice albedo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..390H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..390H"><span>Pathways of Petermann <span class="hlt">Glacier</span> meltwater, Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heuzé, Céline; Wåhlin, Anna; Johnson, Helen; Münchow, Andreas</p> <p>2016-04-01</p> <p>Radar and satellite observations suggest that the floating ice shelf of Petermann <span class="hlt">Glacier</span> loses up to 80% of its mass through basal <span class="hlt">melting</span>, caused by the intrusion of warm Atlantic Water into the fjord and under the ice shelf. The fate of Petermann's glacial meltwater is still largely unknown. It is investigated here, using hydrographic observations collected during a research cruise on board I/B Oden in August 2015. Two methods are used to detect the meltwater from Petermann: a mathematical one that provides the concentration of ice shelf meltwater, and a geometrical one to distinguish the meltwater from Petermann and the meltwater from other ice shelves. The meltwater from Petermann mostly circulates on the north side of the fjord. At the sill, 0.5 mSv of meltwater leave the fjord, mostly on the northeastern side between 100 and 350 m depth, but also in the central channel, albeit with a lesser concentration. Meltwater from Petermann is found in all the casts in Hall Basin, notably north of the sill by Greenland coast. The geometrical method reveals that the casts closest to the Canadian side mostly contain meltwater from other, unidentified <span class="hlt">glaciers</span>. As Atlantic Water warms up, it is key to monitor Greenland <span class="hlt">melting</span> <span class="hlt">glaciers</span> and track their meltwater to properly assess their impact on the ocean circulation and sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSHE12A..07H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSHE12A..07H"><span>Pathways of Petermann <span class="hlt">Glacier</span>'s Meltwaters, Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heuzé, C.; Wahlin, A.; Johnson, H. L.; Muenchow, A.</p> <p>2016-02-01</p> <p>Radar and satellite observations suggest that the floating ice shelf of Petermann <span class="hlt">glacier</span>, north Greenland, loses up to 80% of its mass through basal <span class="hlt">melting</span>, caused by the intrusion of warm Atlantic water into the fjord and under the ice shelf. Although Greenland meltwaters are key to sea level rise projections and can potentially disrupt the whole ocean circulation, the fate of Petermann's glacial meltwater is still largely unknown. It is investigated here, using hydrographic observations collected during a research cruise onboard I/B Oden in August 2015. Two layers are found: one at 200 m (i.e. terminus depth) mostly on the eastern side of the fjord where a calving event occurred this summer, and one around 500 m depth (i.e. the grounding line) on the western side. At the sill, approximately 3 mSv of freshwater leave the fjord around 150 m on the eastern side. On the western side, a more complex circulation occurs as waters intrude in. Outside of the fjord in Hall Basin, only one layer is found, around 300 m, but its oxygen content and T-S properties suggests it is a mixture between Petermann's meltwater, meltwater from the neighbouring <span class="hlt">glaciers</span>, surface run-off and sea ice. As Atlantic water warms up, it is key to monitor Greenland <span class="hlt">melting</span> <span class="hlt">glaciers</span> to properly assess sea level rise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC11A0958C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC11A0958C"><span>Emerging Glacial Lakes in the Cordillera Blanca, Peru: A Case Study at Arteson <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chisolm, R. E.; Mckinney, D. C.; Gomez, J.; Voss, K.</p> <p>2012-12-01</p> <p>Tropical <span class="hlt">glaciers</span> are an essential component of the water resources systems in the mountainous regions where they are located, and a warming climate has resulted in the accelerated retreat of Andean <span class="hlt">glaciers</span> in recent decades. The shrinkage of Andean <span class="hlt">glaciers</span> influences the flood risk for communities living downstream as new glacial lakes have begun to form at the termini of some <span class="hlt">glaciers</span>. As these lakes continue to grow in area and volume, they pose an increasing risk of glacial lake outburst floods (GLOFs). Ice thickness measurements have been a key missing link in studying the tropical <span class="hlt">glaciers</span> in Peru and how climate change is likely to impact glacial <span class="hlt">melt</span> and the growth of glacial lakes. Ground penetrating radar (GPR) has rarely been applied to <span class="hlt">glaciers</span> in Peru to measure ice thickness, and these measurements can tell us a lot about how a warming climate will affect <span class="hlt">glacier</span> mass balance. This study presents GPR data taken in July 2012 at the Arteson <span class="hlt">glacier</span> in the Cordillera Blanca, Peru. A new lake has begun to form at the terminus of the Arteson <span class="hlt">glacier</span>, and this lake has key features, including overhanging ice and loose rock likely to create landslides, that could trigger a catastrophic GLOF if the lake continues to grow. This new lake is part of a series of three lakes that have formed below the Arteson <span class="hlt">glacier</span>. The two lower lakes, Artesonraju and Paron, are much larger so that if there were an avalanche or landslide into the new lake below Arteson <span class="hlt">glacier</span>, the impact could potentially be more catastrophic than a GLOF from one single lake. Estimates of how the lake mass balance is likely to evolve due to the retreating <span class="hlt">glacier</span> are key to assessing the flood risk from this dynamic three-lake system. Because the <span class="hlt">glacier</span> mass balance and lake mass balance are closely linked, the ice thickness measurements and measurements of the bed slope of the Arteson <span class="hlt">glacier</span> and underlying bedrock give us a clue to how the lake is likely to evolve. GPR measurements of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C44A..07K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C44A..07K"><span>Seasonal and Elevational Variations of Black Carbon and Dust in Snow and Ice in the Solu-Khumbu, Nepal and Estimated <span class="hlt">Radiative</span> Forcings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kaspari, S.; Painter, T. H.; Gysel, M.; Skiles, M.; Schwikowski, M.</p> <p>2014-12-01</p> <p>Black carbon (BC) and dust deposited on snow and <span class="hlt">glacier</span> surfaces can reduce the surface albedo, accelerate <span class="hlt">melt</span>, and trigger albedo feedback. Assessing BC and dust concentrations in snow and ice in the Himalaya is of interest because this region borders large BC and dust sources, and seasonal snow and <span class="hlt">glacier</span> ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snowpits at elevations between 5400 and 6400 m asl from Mera <span class="hlt">glacier</span> located in the Solu-Khumbu region of Nepal. The samples were measured for Fe concentrations (used as a dust proxy) via ICP-MS, total impurity content gravimetrically, and BC concentrations using a Single Particle Soot Photometer (SP2). BC and Fe concentrations are substantially higher at elevations < 6000 m due to post-depositional processes including <span class="hlt">melt</span> and sublimation and greater loading in the lower troposphere. Because the largest areal extent of snow and ice resides at elevations < 6000 m, the higher BC and dust concentrations at these elevations can reduce the snow and <span class="hlt">glacier</span> albedo over large areas, accelerating <span class="hlt">melt</span>, affecting <span class="hlt">glacier</span> mass-balance and water resources, and contributing to a positive climate forcing. <span class="hlt">Radiative</span> transfer modeling constrained by measurements at 5400 m at Mera La indicates that BC concentrations in the winter-spring snow/ice horizons are sufficient to reduce albedo by 6-10% relative to clean snow, corresponding to localized instantaneous <span class="hlt">radiative</span> forcings of 75-120 W m-2. The other bulk impurity concentrations, when treated separately as dust, reduce albedo by 40-42% relative to clean snow and give localized instantaneous <span class="hlt">radiative</span> forcings of 488 to 525 W m-2. Adding the BC absorption to the other impurities results in additional <span class="hlt">radiative</span> forcings of 3 W m-2. While these results suggest that the snow albedo and <span class="hlt">radiative</span> forcing effect of dust is considerably greater than BC, there are several sources of uncertainty.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CG....105..103M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CG....105..103M"><span>A geophone wireless sensor network for investigating <span class="hlt">glacier</span> stick-slip motion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martinez, Kirk; Hart, Jane K.; Basford, Philip J.; Bragg, Graeme M.; Ward, Tyler; Young, David S.</p> <p>2017-08-01</p> <p>We have developed an innovative passive borehole geophone system, as part of a wireless environmental sensor network to investigate <span class="hlt">glacier</span> stick-slip motion. The new geophone nodes use an ARM Cortex-M3 processor with a low power design capable of running on battery power while embedded in the ice. Only data from seismic events was stored, held temporarily on a micro-SD card until they were retrieved by systems on the <span class="hlt">glacier</span> surface which are connected to the internet. The sampling rates, detection and filtering levels were determined from a field trial using a standard commercial passive seismic system. The new system was installed on the Skalafellsjökull <span class="hlt">glacier</span> in Iceland and provided encouraging results. The results showed that there was a relationship between surface <span class="hlt">melt</span> water production and seismic event (ice quakes), and these occurred on a pattern related to the <span class="hlt">glacier</span> surface <span class="hlt">melt</span>-water controlled velocity changes (stick-slip motion). Three types of seismic events were identified, which were interpreted to reflect a pattern of till deformation (Type A), basal sliding (Type B) and hydraulic transience (Type C) associated with stick-slip motion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.H53E1573K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.H53E1573K"><span>Heat Exchange Processes and Thermal Dynamics of a <span class="hlt">Glacier</span>-Fed Stream</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khamis, K.; Hannah, D. M.; Brown, L. E.; Milner, A. M.</p> <p>2012-12-01</p> <p><span class="hlt">Glacier</span>-fed river thermal regimes vary markedly in space and time. However, knowledge is limited of fundamental processes controlling alpine stream temperature dynamics. The few studies have not sufficiently characterised above-stream micro-climate and have been limited to single <span class="hlt">melt</span> seasons. To address the research gap, this study quantified heat exchanges at the water surface and bed of a <span class="hlt">glacier</span> fed stream over two summers to improve understanding of factors and processes driving thermal dynamics. An automatic weather station and river gauge were set up on a stream 1.5 km from the Taillon <span class="hlt">Glacier</span>, French Pyrénées. Hydro-meteorological observations were recorded at 15-min intervals between 16 June-2 September 2010 and 2011. Energy balance components were measured [net <span class="hlt">radiation</span> (Q*); bed heat flux (Qbhf)] or estimated based on site-specific data [sensible heat transfer (Qh); latent heat (Qe); fluid friction (Qf)]. During 2010, snowline altitude was lower and <span class="hlt">glacier</span> ablation occurred in late season. During 2010, the mean snowline altitude was lower and ablation of <span class="hlt">glacier</span> ice occurred later in the season Mean water temperature was lower (-0.8°C), precipitation greater (+87mm) and daily discharge variation lower (-0.03 m3s-1) than 2011. The net heat budget was strongly positive in both summers, with the majority of energy exchanged at the air-water interface. Averaged over the seasons, Q* was the largest heat source (~80% of total flux); Qh (~13%) and Qf (~3%) were also sources. Qe displayed inter-annual variability; during 2010 (2011) it contributed 5.2% (0.03%) of the total heat budget due to windier, drier conditions that offset early season condensation gains with late season evaporative losses. Energy exchanges at the channel - river bed interface comprised <1% of the heat budget; Qbhf was a sink (source) during 2010 (2011). Daily flux totals were used to characterize sub-seasonal dynamics. Declines in net <span class="hlt">radiation</span> receipt and total energy available to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33A1167K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33A1167K"><span>Rapid downwasting of lower portion of Ponkar <span class="hlt">Glacier</span> and its impacts in Manang, Nepal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kayastha, R. B.; Armstrong, R. L.; Sherpa, T. C.; Bajracharya, S. R.; Maharjan, S. B.; Joshi, S.; Shrestha, F.</p> <p>2017-12-01</p> <p>Quantifying and understanding the dynamics of <span class="hlt">melting</span> of the underlying ice has always been a challenge especially in the rough terrains of the Himalayas. This study incorporates the use of Unmanned Aerial Vehicle (UAV) to analyze the downwasting of Ponkar <span class="hlt">Glacier</span>, Manang, Nepal Himalayas. Four repeat aerial surveys have been conducted using a Quad Copter and a fixed wing UAVs on the lower part of the <span class="hlt">glacier</span>. The surveys have been conducted in March and July 2016 (quad copter) and in November 2016 and May 2017 (fixed wing). Three ablation stakes are also installed on the survey region of the <span class="hlt">glacier</span> so as to compare the ice <span class="hlt">melt</span>. Comparing the high resolution DEMs (2 and 10 cm) generated from those aerial surveys, downwasting of the <span class="hlt">glacier</span> is found to be ranging from 0.68 m to 0.94 m under the debris thickness of 11 and 20 cm, respectively from 20 March to 5 July 2016. Similarly, average downwasting of the lower part of the <span class="hlt">glacier</span> is found to be 0.47 m since 14 November 2016 to 5 May 2017. The downwasting follows a heterogeneous pattern across the <span class="hlt">glacier</span>. The net ablation of 2.04 and 2.21 m are found at debris thickness of 11 and 20 cm from March 2016 to May 2017, respectively. Alongside that, a 16 MHZ Multi Low frequency Ground Penetrating Radar (GPR) has also been used to estimate the underlying ice thickness. The result indicates thickness of 80 m near the terminus of the <span class="hlt">glacier</span>. To address the change in the <span class="hlt">glacier</span> to the changing climate, the meteorological conditions prevailing in the valley also needs to be properly understood. Hence, six precipitation gauges and temperature sensors have been installed along the downstream valley of the <span class="hlt">glacier</span> at different elevations ranging from 1926 to 3780 m asl. Based on the observed data, average vertical and longitudinal precipitation gradients of the valley have been found to be 2.9 % m-1 and -0.45 % m-1, respectively. Likewise, the temperature lapse rate has been found to be -0.0088 °C m-1. These preliminary</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22538614','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22538614"><span>Antarctic ice-sheet loss driven by basal <span class="hlt">melting</span> of ice shelves.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pritchard, H D; Ligtenberg, S R M; Fricker, H A; Vaughan, D G; van den Broeke, M R; Padman, L</p> <p>2012-04-25</p> <p>Accurate prediction of global sea-level rise requires that we understand the cause of recent, widespread and intensifying <span class="hlt">glacier</span> acceleration along Antarctic ice-sheet coastal margins. Atmospheric and oceanic forcing have the potential to reduce the thickness and extent of floating ice shelves, potentially limiting their ability to buttress the flow of grounded tributary <span class="hlt">glaciers</span>. Indeed, recent ice-shelf collapse led to retreat and acceleration of several <span class="hlt">glaciers</span> on the Antarctic Peninsula. But the extent and magnitude of ice-shelf thickness change, the underlying causes of such change, and its link to <span class="hlt">glacier</span> flow rate are so poorly understood that its future impact on the ice sheets cannot yet be predicted. Here we use satellite laser altimetry and modelling of the surface firn layer to reveal the circum-Antarctic pattern of ice-shelf thinning through increased basal <span class="hlt">melt</span>. We deduce that this increased <span class="hlt">melt</span> is the primary control of Antarctic ice-sheet loss, through a reduction in buttressing of the adjacent ice sheet leading to accelerated <span class="hlt">glacier</span> flow. The highest thinning rates occur where warm water at depth can access thick ice shelves via submarine troughs crossing the continental shelf. Wind forcing could explain the dominant patterns of both basal <span class="hlt">melting</span> and the surface <span class="hlt">melting</span> and collapse of Antarctic ice shelves, through ocean upwelling in the Amundsen and Bellingshausen seas, and atmospheric warming on the Antarctic Peninsula. This implies that climate forcing through changing winds influences Antarctic ice-sheet mass balance, and hence global sea level, on annual to decadal timescales.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUSM.U31A..04K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUSM.U31A..04K"><span>A World of Changing <span class="hlt">Glaciers</span>: Hazards, Opportunities, and Measures of Global Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kargel, J. S.; Wessels, R.; Kieffer, H. H.</p> <p>2002-05-01</p> <p><span class="hlt">Glaciers</span> around the world are, with rare exceptions, stagnating or in hasty retreat. Whether growing or shrinking, significant changes in the extent of <span class="hlt">glaciers</span> have major impacts on nature and humanity in their immediate vicinity, because land uses are utterly different depending on whether the land is covered by ice. Upon <span class="hlt">glacier</span> retreat, new land uses may become possible: (1) Transportation corridors may become feasible where previously there were barriers. (2) Exposure of the lithosphere may yield mineral riches that previously were inaccessible. (3) New wildlife habitat and migration routes may develop, thus promoting genetic diffusion/interbreeding of previously isolated populations. <span class="hlt">Glacier</span> impacts go well beyond the locality where they occur. Many <span class="hlt">glaciers</span> regulate water flow, and contribute to annual water availability and hydropower production. In some regions, such in the Hindu Kush-Himlaya (HKH), especially the western provinces of China, the carrying capacity of the land and further economic development and well-being of the populace is partly dependent on <span class="hlt">melting</span> <span class="hlt">glaciers</span>. In India, \\8 billion worth of hydroelectric power (at U.S. electric rates) is generated each year; 50% of that is attributable to runoff from Himalayan <span class="hlt">glaciers</span> and high-altitude snow fields. Nearly \\1 billion worth of hydroelectric power is due to the current negative mass balance of <span class="hlt">glaciers</span>. In Nepal, glaciogenic hydropower is even more crucial. Although it may be many decades in coming, the ongoing sharp reduction in <span class="hlt">glacier</span> area in the HKH will eventually be reflected in heightened water shortages in a region where water already is in short supply. Other <span class="hlt">glaciers</span> store large amounts of meltwater and release it suddenly, causing havoc and taking lives downstream. This is a major problem in the HKH region and is significant locally in other heavily glaciated regions, such as Alaska. Sea level is a global issue impacted significantly by <span class="hlt">melting</span> <span class="hlt">glaciers</span> wherever they occur</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.9354M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.9354M"><span>Physically-based distributed mass balance modeling of a tropical <span class="hlt">glacier</span>: An application to backward modeling of past climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moelg, T.; Cullen, N. J.; Hardy, D. R.; Winkler, M.; Kaser, G.</p> <p>2009-04-01</p> <p>The use of spatially distributed (2-D) mass balance models has increased in recent years, but mostly focuses on extratropical <span class="hlt">glacier</span> surfaces. Here we present the first application of a process-based 2-D model to an African <span class="hlt">glacier</span>: Kersten <span class="hlt">Glacier</span> on Kilimanjaro. Multi-year data from an automatic weather station (AWS) at 5873 m a.s.l. (500 hPa) serve to force the model. Validation variables comprise surface temperature, surface height change, snow depth, and incoming <span class="hlt">radiation</span> - all of which indicate a good model performance. Analyses of the interannual variability in the most significant total mass budget terms (surface accumulation, <span class="hlt">melt</span>, and sublimation), as well as in the related energy fluxes, exhibit a strong link to atmospheric moisture of a particular year. This is because net shortwave <span class="hlt">radiation</span> (a result of both cloudiness and surface albedo) is the most variable energy flux on monthly to annual time scales. Internal accumulation (refreezing of <span class="hlt">melt</span> water), however, shows a time lag and is strongest after a very wet year. Due to the limited validation data at lower elevations, we also perform a detailed sensitivity study by varying 17 model parameters - which yields a total mass loss estimate of 522 +/- 105 kg/m2/year under present climate conditions. Moreover, the verified model allows us to perform backward modeling of the last maximum extent of Kersten <span class="hlt">Glacier</span> in the 1880s, which is indicated by a well preserved terminal moraine. This step reveals decreases in precipitation (30-45%), water vapor pressure (0.1-0.3 hPa) and cloud cover (2-4 percentage units) as the most likely local climate change between late 19th century and present. Thus, the study also demonstrates how 2-D modeling can help reconstruct past climate for a remote place prior to the availability of measurements. In our case these findings have great relevance for the debate of surface versus mid-tropospheric climate change in the tropics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C13G..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C13G..04M"><span>2017 Rapid Retreat Of Thwaites <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Milillo, P.; Rignot, E. J.; Mouginot, J.; Scheuchl, B.</p> <p>2017-12-01</p> <p>We employ data from the second generation of SAR systems e.g. the Italian COSMO- SkyMed (CSK) constellation and the German TanDEM-X (TDX) formation to monitor grounding line retreat using short repeat-time interferometry and accurate InSAR DEM on Thwaites <span class="hlt">glacier</span> in the Amundsen Sea Embayment (ASE), West Antarctica. The ASE is a marine-based ice sheet with a retrograde bed containing enough ice to raise global sea level by 120 cm. Several studies have inferred the mechanical properties of portions of ASE using observationally constrained numerical models, but these studies offer only temporal snapshots of basal mechanics owing to a dearth of observational time series. Prior attempts of grounding lines mapping have been limited because few space-borne SAR missions offer the short-term repeat pass capability required to map the differential vertical displacement of floating ice at tidal frequencies with sufficient detail to resolve grounding line boundaries in areas of fast ice deformation. Using 1-day CSK repeat pass data and TDX DEMs, we collected frequent, high-resolution grounding line measurements of Thwaites <span class="hlt">glaciers</span> spanning 2015-2017. We compare the results with ERS data spanning 1996-2011, and Sentinel-1a 2014-2015 data. Between 2011 and 2017 we observe a maximum retreat of 5-7 km across the main Thwaites <span class="hlt">glacier</span> tongue and Thwaites Eastern ice shelf (TEIS) corresponding to an increased retreat rate of 0.5 km/yr. Grounding line retreat has been fueled by the enhanced intrusion of warm, salty, subsurface ocean water of circumpolar deep water origin onto the continental shelf, beneath the floating ice shelf, to reach the <span class="hlt">glacier</span> grounding zone and <span class="hlt">melt</span> it from below at rates varying from 50 to 150 m/yr. The retreat rate varies depending on the magnitude of ice <span class="hlt">melt</span> by the ocean, the rate of ice thinning and the shape of the <span class="hlt">glacier</span> surface and bed topography.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C33B0796S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C33B0796S"><span>Quantifying Suspended Sediment Concentration from Subglacial Sediment Plumes Discharging from Two Svalbard Tidewater <span class="hlt">Glaciers</span> using Landsat 8 and In Situ Measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schild, K. M.; Hawley, R. L.; Chipman, J. W.; Benn, D.</p> <p>2016-12-01</p> <p>Marine-terminating outlet <span class="hlt">glaciers</span> discharge most of an ice sheet's mass loss through iceberg calving, submarine <span class="hlt">melting</span>, and meltwater runoff. While calving can be quantified by in situ and remote sensing observations, meltwater runoff, submarine <span class="hlt">melting</span>, and the subglacial transport of meltwater are not well constrained due to inherent difficulties measuring the subglacial and proglacial environments. Previous studies have used sediment plumes and suspended sediment concentration (SSC) as a proxy for <span class="hlt">glacier</span> meltwater runoff at land-terminating <span class="hlt">glaciers</span>. However, the relationship between satellite reflectacne and SSC, established predominantly from land-terminating <span class="hlt">glacier</span> data, does not relate well for tidewater <span class="hlt">glaciers</span>. Additionally, the difficulties in sampling the near terminus region of large tidewater <span class="hlt">glaciers</span> makes it challenging to accurately constrain or identify the relationship between sediment plumes and satellite reflectance. In this study we use simultaneous Landsat 8 imagery and in situ fjord measurements at two Svalbard tidewater <span class="hlt">glaciers</span> to establish a relationship between SSC and Landsat 8 surface reflectacne in a tidewater <span class="hlt">glacier</span> Setting. Results from fieldwork conducted during low and peak meltwater runoff periods at Kronebreen and Tunabreen <span class="hlt">glaciers</span> will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24920320','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24920320"><span>Variations of algal communities cause darkening of a Greenland <span class="hlt">glacier</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lutz, Stefanie; Anesio, Alexandre M; Jorge Villar, Susana E; Benning, Liane G</p> <p>2014-08-01</p> <p>We have assessed the microbial ecology on the surface of Mittivakkat <span class="hlt">glacier</span> in SE-Greenland during the exceptional high <span class="hlt">melting</span> season in July 2012 when the so far most extreme <span class="hlt">melting</span> rate for the Greenland Ice Sheet has been recorded. By employing a complementary and multi-disciplinary field sampling and analytical approach, we quantified the dramatic changes in the different microbial surface habitats (green snow, red snow, biofilms, grey ice, cryoconite holes). The observed clear change in dominant algal community and their rapidly changing cryo-organic adaptation inventory was linked to the high <span class="hlt">melting</span> rate. The changes in carbon and nutrient fluxes between different microbial pools (from snow to ice, cryoconite holes and glacial forefronts) revealed that snow and ice algae dominate the net primary production at the onset of <span class="hlt">melting</span>, and that they have the potential to support the cryoconite hole communities as carbon and nutrient sources. A large proportion of algal cells is retained on the glacial surface and temporal and spatial changes in pigmentation contribute to the darkening of the snow and ice surfaces. This implies that the fast, <span class="hlt">melt-induced</span> algal growth has a high albedo reduction potential, and this may lead to a positive feedback speeding up <span class="hlt">melting</span> processes. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.5330K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.5330K"><span>Climatic controls on the pace of <span class="hlt">glacier</span> erosion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koppes, Michele; Hallet, Bernard; Rignot, Eric; Mouginot, Jeremie; Wellner, Julia; Love, Katherine</p> <p>2016-04-01</p> <p> decrease in long-term relative to modern erosion rates may in part reflect the temporal averaging of warm and cold-based conditions over the lifecycle of these <span class="hlt">glaciers</span>. Higher temperatures and precipitation rates at the end of glaciations favor the production of water from rainfall, surface <span class="hlt">melting</span> and internal <span class="hlt">melting</span>, which promotes sliding, erosion and sediment production and evacuation from under the ice. Hence, climatic variation, more than the extent of ice cover or ice volume, controls the pace at which <span class="hlt">glaciers</span> shape mountains.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFMIP52A0750K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFMIP52A0750K"><span>Five 'Supercool' Icelandic <span class="hlt">Glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Knudsen, O.; Roberts, M. J.; Roberts, M. J.; Tweed, F. S.; Russell, A. J.; Lawson, D. E.; Larson, G. J.; Evenson, E. B.; Bjornsson, H.</p> <p>2001-12-01</p> <p>Sediment entrainment by glaciohydraulic supercooling has recently been demonstrated as an effective process at Matanuska <span class="hlt">glacier</span>, Alaska. Although subfreezing meltwater temperatures have been recorded at several Alaskan <span class="hlt">glaciers</span>, the link between supercooling and sediment accretion remains confined to Matanuska. This study presents evidence of glaciohydraulic supercooling and associated basal ice formation from five Icelandic <span class="hlt">glaciers</span>: Skeidarárjökull, Skaftafellsjökull, Kvíárjökull, Flaájökull, and Hoffellsjökull. These observations provide the best example to-date of glaciohydraulic supercooling and related sediment accretion outside Alaska. Fieldwork undertaken in March, July and August 2001 confirmed that giant terraces of frazil ice, diagnostic of the presence of supercooled water, are forming around subglacial artesian vents. Frazil flocs retrieved from these vents contained localised sandy nodules at ice crystal boundaries. During periods of high discharge, sediment-laden frazil flocs adhere to the inner walls of vents, and continue to trap suspended sediment. Bands of debris-rich frazil ice, representing former vents, are texturally similar to basal ice exposures at the <span class="hlt">glacier</span> margins, implying a process-form relationship between glaciohydraulic freeze-on and basal ice formation. It is hypothesised that glaciohydraulic supercooling is generating thick sequences of basal ice. Observations also confirm that in situ <span class="hlt">melting</span> of basal ice creates thick sedimentary sequences, as sediment structures present in the basal ice can be clearly traced into ice-marginal ridges. Glaciohydraulic supercooling is an effective sediment entrainment mechanism at Icelandic <span class="hlt">glaciers</span>. Supercooling has the capacity to generate thick sequences of basal ice and the sediments present in basal ice can be preserved. These findings are incompatible with established theories of intraglacial sediment entrainment and basal ice formation; instead, they concur with, and extend, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11..723R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11..723R"><span>Surge dynamics and lake outbursts of Kyagar <span class="hlt">Glacier</span>, Karakoram</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Round, Vanessa; Leinss, Silvan; Huss, Matthias; Haemmig, Christoph; Hajnsek, Irena</p> <p>2017-03-01</p> <p>The recent surge cycle of Kyagar <span class="hlt">Glacier</span>, in the Chinese Karakoram, caused formation of an ice-dammed lake and subsequent glacial lake outburst floods (GLOFs) exceeding 40 million m3 in 2015 and 2016. GLOFs from Kyagar <span class="hlt">Glacier</span> reached double this size in 2002 and earlier, but the role of <span class="hlt">glacier</span> surging in GLOF formation was previously unrecognised. We present an integrative analysis of the <span class="hlt">glacier</span> surge dynamics from 2011 to 2016, assessing surge mechanisms and evaluating the surge cycle impact on GLOFs. Over 80 <span class="hlt">glacier</span> surface velocity fields were created from TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement), Sentinel-1A, and Landsat satellite data. Changes in ice thickness distribution were revealed by a time series of TanDEM-X elevation models. The analysis shows that, during a quiescence phase lasting at least 14 years, ice mass built up in a reservoir area at the top of the <span class="hlt">glacier</span> tongue, and the terminus thinned by up to 100 m, but in the 2 years preceding the surge onset this pattern reversed. The surge initiated with the onset of the 2014 <span class="hlt">melt</span> season, and in the following 15 months velocity evolved in a manner consistent with a hydrologically controlled surge mechanism. Dramatic accelerations coincided with <span class="hlt">melt</span> seasons, winter deceleration was accompanied by subglacial drainage, and rapid surge termination occurred following the 2015 GLOF. Rapid basal motion during the surge is seemingly controlled by high water pressure, caused by input of surface water into either an inefficient subglacial drainage system or unstable subglacial till. The potential lake volume increased to more than 70 million m3 by late 2016, as a result of over 60 m of thickening at the terminus. Lake formation and the evolution of the ice dam height should be carefully monitored through remote sensing to anticipate large GLOFs in the near future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750018397','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750018397"><span>Evaluation of <span class="hlt">glacier</span> mass balance by observing variations in transient snowline positions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oestrem, G. (Principal Investigator)</p> <p>1974-01-01</p> <p>The author has identified the following significant results. The transient snowline on five outlet <span class="hlt">glaciers</span> from the Jostedalsbreen ice cap in southwestern Norway could be determined from ERTS image no. 1336-102060, when bands MSS 5, 6, and 7 were combined in an additive color viewer. The snowline was situated at a very low altitude at the time of imagery (24 June 1973) indicating that <span class="hlt">glacier</span> <span class="hlt">melt</span> was behind normal schedule, a fact that has a hydrologic bearing: less <span class="hlt">melt</span> water in the streams could be expected. The use of ERTS imagery in snowline determinations proved realistic and relatively easy to apply in practice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.2667R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.2667R"><span>Bathymetry data reveal <span class="hlt">glaciers</span> vulnerable to ice-ocean interaction in Uummannaq and Vaigat glacial fjords, west Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rignot, E.; Fenty, I.; Xu, Y.; Cai, C.; Velicogna, I.; Cofaigh, C. Ó.; Dowdeswell, J. A.; Weinrebe, W.; Catania, G.; Duncan, D.</p> <p>2016-03-01</p> <p>Marine-terminating <span class="hlt">glaciers</span> play a critical role in controlling Greenland's ice sheet mass balance. Their frontal margins interact vigorously with the ocean, but our understanding of this interaction is limited, in part, by a lack of bathymetry data. Here we present a multibeam echo sounding survey of 14 glacial fjords in the Uummannaq and Vaigat fjords, west Greenland, which extends from the continental shelf to the <span class="hlt">glacier</span> fronts. The data reveal valleys with shallow sills, overdeepenings (>1300 m) from glacial erosion, and seafloor depths 100-1000 m deeper than in existing charts. Where fjords are deep enough, we detect the pervasive presence of warm, salty Atlantic Water (AW) (>2.5°C) with high <span class="hlt">melt</span> potential, but we also find numerous <span class="hlt">glaciers</span> grounded on shallow (<200 m) sills, standing in cold (<1°C) waters in otherwise deep fjords, i.e., with reduced <span class="hlt">melt</span> potential. Bathymetric observations extending to the <span class="hlt">glacier</span> fronts are critical to understand the <span class="hlt">glacier</span> evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.1644O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.1644O"><span>Attribution of <span class="hlt">glacier</span> fluctuations to climate change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oerlemans, J.</p> <p>2012-04-01</p> <p><span class="hlt">Glacier</span> retreat is a worlwide phenomenon, which started around the middle of the 19th century. During the period 1800-1850 the number of retreating and advancing <span class="hlt">glaciers</span> was roughly equal (based on 42 records from different continents). During the period 1850-1900 about 92% of all mountain <span class="hlt">glaciers</span> became shorter (based on 65 records). After this, the percentage of shrinking <span class="hlt">glaciers</span> has been around 90% until the present time. The <span class="hlt">glacier</span> signal is rather coherent over the globe, especially when surging and calving <span class="hlt">glaciers</span> are not considered (for such <span class="hlt">glaciers</span> the response to climate change is often masked by length changes related to internal dynamics). From theoretical studies as well as extensive meteorological work on <span class="hlt">glaciers</span>, the processes that control the response of <span class="hlt">glaciers</span> to climate change are now basically understood. It is useful to make a difference between geometric factors (e.g. slope, altitudinal range, hypsometry) and climatic setting (e.g. seasonal cycle, precipitation). The most sensitive <span class="hlt">glaciers</span> appear to be flat <span class="hlt">glaciers</span> in a maritime climate. Characterizing the dynamic properties of a <span class="hlt">glacier</span> requires at least two quantities: the climate sensitivity, expressing how the equilibrium <span class="hlt">glacier</span> state depends on the climatic conditions, and the response time, indicating how fast a <span class="hlt">glacier</span> approaches a new equilibrium state after a stepwise change in the climatic forcing. These quantities can be estimated from relatively simple theory, showing that differences among <span class="hlt">glaciers</span> are substantial. For larger <span class="hlt">glaciers</span>, climate sensitivities (in terms of <span class="hlt">glacier</span> length) vary from 1 to 8 km per 100 m change in the equilibrium-line altitude. Response times are mainly in the range of 20 to 200 years, with most values between 30 and 80 years. Changes in the equilibrium-line altitude or net mass balance of a <span class="hlt">glacier</span> are mainly driven by fluctuations in air temperature, precipitation, and global <span class="hlt">radiation</span>. Energy-balance modelling for many <span class="hlt">glaciers</span> shows that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014TCry....8.1457C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014TCry....8.1457C"><span>Ice-ocean interaction and calving front morphology at two west Greenland tidewater outlet <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chauché, N.; Hubbard, A.; Gascard, J.-C.; Box, J. E.; Bates, R.; Koppes, M.; Sole, A.; Christoffersen, P.; Patton, H.</p> <p>2014-08-01</p> <p>Warm, subtropical-originating Atlantic water (AW) has been identified as a primary driver of mass loss across the marine sectors of the Greenland Ice Sheet (GrIS), yet the specific processes by which this water mass interacts with and erodes the calving front of tidewater <span class="hlt">glaciers</span> is frequently modelled and much speculated upon but remains largely unobserved. We present a suite of fjord salinity, temperature, turbidity versus depth casts along with glacial runoff estimation from Rink and Store <span class="hlt">glaciers</span>, two major marine outlets draining the western sector of the GrIS during 2009 and 2010. We characterise the main water bodies present and interpret their interaction with their respective calving fronts. We identify two distinct processes of ice-ocean interaction which have distinct spatial and temporal footprints: (1) homogenous free convective <span class="hlt">melting</span> which occurs across the calving front where AW is in direct contact with the ice mass, and (2) localised upwelling-driven <span class="hlt">melt</span> by turbulent subglacial runoff mixing with fjord water which occurs at distinct injection points across the calving front. Throughout the study, AW at 2.8 ± 0.2 °C was consistently observed in contact with both <span class="hlt">glaciers</span> below 450 m depth, yielding homogenous, free convective submarine <span class="hlt">melting</span> up to ~200 m depth. Above this bottom layer, multiple interactions are identified, primarily controlled by the rate of subglacial fresh-water discharge which results in localised and discrete upwelling plumes. In the record <span class="hlt">melt</span> year of 2010, the Store <span class="hlt">Glacier</span> calving face was dominated by these runoff-driven plumes which led to a highly crenulated frontal geometry characterised by large embayments at the subglacial portals separated by headlands which are dominated by calving. Rink <span class="hlt">Glacier</span>, which is significantly deeper than Store has a larger proportion of its submerged calving face exposed to AW, which results in a uniform, relatively flat overall frontal geometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-JPL-20171130-EARTHf-0001-DIY+Glacier+Modeling+with+Virtual+Earth+System+Laboratory.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-JPL-20171130-EARTHf-0001-DIY+Glacier+Modeling+with+Virtual+Earth+System+Laboratory.html"><span>JPL-20171130-EARTHf-0001-DIY <span class="hlt">Glacier</span> Modeling with Virtual Earth System Laboratory</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-11-30</p> <p>Eric Larour, JPL Climate Scientist, explains the NASA research tool "VESL" -- Virtual Earth System Laboratory -- that allows anyone to run their own climate experiment. The user can use a slider to simulate and increase or decrease in the amount of snowfall on a particular <span class="hlt">glacier</span> then see a video of the results, including the <span class="hlt">glacier</span> <span class="hlt">melting</span>'s effect on sea level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC22C..06H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC22C..06H"><span>The potential for retreating alpine <span class="hlt">glaciers</span> to alter alpine ecosystems in the Colorado Front Range</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hall, E.; Baron, J.</p> <p>2013-12-01</p> <p><span class="hlt">Glaciers</span> are retreating at an unprecedented rate. In mid-latitude alpine ecosystems the presence of <span class="hlt">glaciers</span> and rock <span class="hlt">glaciers</span> govern rates and ecology of alpine and sub-alpine ecosystems. Changes in the thermal environment due to the loss of isothermal habitat and inputs from <span class="hlt">glacier</span> <span class="hlt">melt</span> chemistry are altering alpine ecosystems in unpredictable ways. In particular, <span class="hlt">glacier</span> may be a source of nitrogen that is altering alpine ecosystem dynamics. Loch Vale Watershed (LVWS) located within Rocky Mountain National Park. LVWS contains a surface <span class="hlt">glacier</span> (Andrew's <span class="hlt">glacier</span>) and a rock <span class="hlt">glacier</span> (Taylor's <span class="hlt">glacier</span>) at the headwater of each of the two drainages within the watershed. We collected precipitation from a National Atmospheric Deposition Site and surface water from multiple alpine lakes and streams during a particularly high and low snow year in the Colorado Front Range. We also sampled stream and lake sediments at each site to analyze the associated microbial community. Concentrations of nitrate and ammonium, relative abundance of amoA (the gene responsible for a key step in the microbial nitrification pathway), and the dual isotope signal to nitrate all point to snow <span class="hlt">melt</span> as a key deliverer of nitrogen to ecosystems along the Colorado Front Range. However, late summer surface water chemistry is isotopically similar to the chemistry of glacial ice. This suggests that retreating <span class="hlt">glacier</span> may be an additional source of N to alpine ecosystems and have the potential to alter microbial community composition, biogeochemical rate processes, and ecosystem function. These dynamics are most likely not unique to the Colorado Front Range and should be globally distributed as <span class="hlt">glaciers</span> continue to retreat in high altitude ecosystems around the world.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.9903K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.9903K"><span>Airborne laser scanning based quantification of dead-ice <span class="hlt">melting</span> in recently deglaciated terrain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klug, C.; Sailer, R.; Schümberg, M.; Stötter, J.</p> <p>2012-04-01</p> <p>Dead-ice is explained as stagnant glacial ice, not influenced by <span class="hlt">glacier</span> flow anymore. Whenever <span class="hlt">glaciers</span> have negative mass balances and an accumulation of debris-cover on the surface, dead-ice may form. Although, there are numerous conceptual process-sediment-landform models for the <span class="hlt">melt</span>-out of dead-ice bodies and areas of dead-ice environments at <span class="hlt">glacier</span> margins are easily accessible, just a few quantitative studies of dead-ice <span class="hlt">melting</span> have been carried out so far. Processes and rates of dead-ice <span class="hlt">melting</span> are commonly believed to be controlled by climate and debris-cover properties, but there is still a lack of knowledge about this fact. This study has a focus on the quantification of process <span class="hlt">induced</span> volumetric changes caused by dead-ice <span class="hlt">melting</span>. The research for this project was conducted at Hintereisferner (Ötztal Alps, Austria), Gepatschferner (Ötztal Alps, Austria) and Schrankar (Stubai Alps, Austria), areas for which a good data basis of ALS (Airborne Laser Scanning) measurements is available. 'Hintereisferner' can be characterized as a typical high alpine environment in mid-latitudes, which ranges between approximately 2250 m and 3740 m a.s.l.. The Hintereisferner region has been investigated intensively since many decades. Two dead ice bodies at the orographic right side and one at the orographic left side of the Hintereisferner <span class="hlt">glacier</span> terminus (approx. at 2500 m to 2550 m a.s.l.) were identified. Since 2001, ALS measurements have been carried out regularly at Hintereisferner resulting in a unique data record of 21 ALS flight campaigns, allowing long-term explorations of the two dead-ice areas. The second study area of 'Gepatschferner' in the Kaunertal ranges between 2060 m and 3520 m a.s.l. and is the second largest <span class="hlt">glacier</span> of Austria. Near the <span class="hlt">glacier</span> tongue at the orographic right side a significant dead ice body has formed. The ALS data used for quantification include a period of time of 4 years (2006 - 2010). 'Schrankar' is located in the Western</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA206992','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA206992"><span><span class="hlt">Glacier</span> and Climate Studies West Gulkana <span class="hlt">Glacier</span> and Environs, Alaska</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1988-09-01</p> <p>Sauberer and Dirmhirn 1952; Hoinkes 1970; Holiagren 1971; Ambach 1974) have shown that under cloudy conditions, the longwave incoming <span class="hlt">radiation</span> component...Rapids <span class="hlt">Glacier</span>, Alaska. Transactions of the American Geophysical Union 34:345. 60 Sauberer , F., and I. Dirmhirn. 1952. Der strahlungshaushalt horizontaler</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://geology.geoscienceworld.org/content/38/4/319','USGSPUBS'); return false;" href="http://geology.geoscienceworld.org/content/38/4/319"><span><span class="hlt">Glacier</span> microseismicity</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>West, Michael E.; Larsen, Christopher F.; Truffer, Martin; O'Neel, Shad; LeBlanc, Laura</p> <p>2010-01-01</p> <p>We present a framework for interpreting small <span class="hlt">glacier</span> seismic events based on data collected near the center of Bering <span class="hlt">Glacier</span>, Alaska, in spring 2007. We find extremely high microseismicity rates (as many as tens of events per minute) occurring largely within a few kilometers of the receivers. A high-frequency class of seismicity is distinguished by dominant frequencies of 20–35 Hz and impulsive arrivals. A low-frequency class has dominant frequencies of 6–15 Hz, emergent onsets, and longer, more monotonic codas. A bimodal distribution of 160,000 seismic events over two months demonstrates that the classes represent two distinct populations. This is further supported by the presence of hybrid waveforms that contain elements of both event types. The high-low-hybrid paradigm is well established in volcano seismology and is demonstrated by a comparison to earthquakes from Augustine Volcano. We build on these parallels to suggest that fluid-<span class="hlt">induced</span> resonance is likely responsible for the low-frequency <span class="hlt">glacier</span> events and that the hybrid <span class="hlt">glacier</span> events may be caused by the rush of water into newly opening pathways.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C33B0814C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C33B0814C"><span>Estimating stream discharge from a Himalayan <span class="hlt">Glacier</span> using coupled satellite sensor data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Child, S. F.; Stearns, L. A.; van der Veen, C. J.; Haritashya, U. K.; Tarpanelli, A.</p> <p>2015-12-01</p> <p>The 4th IPCC report highlighted our limited understanding of Himalayan <span class="hlt">glacier</span> behavior and contribution to the region's hydrology. Seasonal snow and <span class="hlt">glacier</span> <span class="hlt">melt</span> in the Himalayas are important sources of water, but estimates greatly differ about the actual contribution of <span class="hlt">melted</span> <span class="hlt">glacier</span> ice to stream discharge. A more comprehensive understanding of the contribution of <span class="hlt">glaciers</span> to stream discharge is needed because streams being fed by <span class="hlt">glaciers</span> affect the livelihoods of a large part of the world's population. Most of the streams in the Himalayas are unmonitored because in situ measurements are logistically difficult and costly. This necessitates the use of remote sensing platforms to obtain estimates of river discharge for validating hydrological models. In this study, we estimate stream discharge using cost-effective methods via repeat satellite imagery from Landsat-8 and SENTINEL-1A sensors. The methodology is based on previous studies, which show that ratio values from optical satellite bands correlate well with measured stream discharge. While similar, our methodology relies on significantly higher resolution imagery (30 m) and utilizes bands that are in the blue and near-infrared spectrum as opposed to previous studies using 250 m resolution imagery and spectral bands only in the near-infrared. Higher resolution imagery is necessary for streams where the source is a <span class="hlt">glacier</span>'s terminus because the width of the stream is often only 10s of meters. We validate our methodology using two rivers in the state of Kansas, where stream gauges are plentiful. We then apply our method to the Bhagirathi River, in the North-Central Himalayas, which is fed by the Gangotri <span class="hlt">Glacier</span> and has a well monitored stream gauge. The analysis will later be used to couple river discharge and <span class="hlt">glacier</span> flow and mass balance through an integrated hydrologic model in the Bhagirathi Basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.V12B..01G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.V12B..01G"><span>Ice Thickness, <span class="hlt">Melting</span> Rates and Styles of Activity in Ice-Volcano Interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gudmundsson, M. T.</p> <p>2005-12-01</p> <p>In most cases when eruptions occur within <span class="hlt">glaciers</span> they lead to rapid ice <span class="hlt">melting</span>, jokulhlaups and/or lahars. Many parameters influence the style of activity and its impact on the environment. These include ice thickness (size of <span class="hlt">glacier</span>), bedrock geometry, magma flow rate and magma composition. The eruptions that have been observed can roughly be divided into: (1) eruptions under several hundred meters thick ice on a relatively flat bedrock, (2) eruptions on flat or sloping bed through relatively thin ice, and (3) volcanism where effects are limitied to confinement of lava flows or <span class="hlt">melting</span> of ice by pyroclastic flows or surges. This last category (ice-contact volcanism) need not cause much ice <span class="hlt">melting</span>. Many of the deposits formed by Pleistocene volcanism in Iceland, British Columbia and Antarctica belong to the first category. An important difference between this type of activity and submarine activity (where pressure is hydrostatic) is that pressure at vents may in many cases be much lower than glaciostatic due to partial support of ice cover over vents by the surrounding <span class="hlt">glacier</span>. Reduced pressure favours explosive activity. Thus the effusive/explosive transition may occur several hundred metres underneath the ice surface. Explosive fragmentation of magma leads to much higher rates of heat transfer than does effusive eruption of pillow lavas, and hence much higher <span class="hlt">melting</span> rates. This effect of reduced pressure at vents will be less pronounced in a large ice sheet than in a smaller <span class="hlt">glacier</span> or ice cap, since the hydraulic gradient that drives water away from an eruption site will be lower in the large <span class="hlt">glacier</span>. This may have implications for form and type of eruption deposits and their relationship with ice thickness and <span class="hlt">glacier</span> size.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912069K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912069K"><span>Sudden disintegration of ice in the glacial-proglacial transition zone of the largest <span class="hlt">glacier</span> in Austria</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kellerer-Pirklbauer, Andreas; Avian, Michael; Hirschmann, Simon; Lieb, Gerhard Karl; Seier, Gernot; Sulzer, Wolfgang; Wakonigg, Herwig</p> <p>2017-04-01</p> <p>Rapid deglaciation does not only reveal a landscape which is prone to rapid geomorphic changes and sediment reworking but also the <span class="hlt">glacier</span> ice itself might be in a state of disintegration by ice <span class="hlt">melting</span>, pressure relief, crevasse formation, ice collapse or changes in the <span class="hlt">glacier</span>'s hydrology. In this study we considered the sudden disintegration of <span class="hlt">glacier</span> ice in the glacial-proglacial transition zone of Pasterze <span class="hlt">Glacier</span>. Pasterze <span class="hlt">Glacier</span> is a typical alpine valley <span class="hlt">glacier</span> and covers currently some 16.5 km2 making it to the largest <span class="hlt">glacier</span> in Austria. This <span class="hlt">glacier</span> is an important site for alpine mass tourism in Austria related to a public high alpine road and a cable car which enable access to the <span class="hlt">glacier</span> rather easily also for unexperienced mountaineers. Spatial focus in our research is given on two particular study areas where several ice-mass movement events occurred during the 2015- and 2016-<span class="hlt">melting</span> seasons. The first study area is a crevasse field at the lower third of the <span class="hlt">glacier</span> tongue. This lateral crevasse field has been substantially modified during the last two <span class="hlt">melting</span> seasons particularly because of thermo-erosional effects of a glacial stream which changed at this site from subglacial (until 2015) to <span class="hlt">glacier</span>-lateral revealing a several tens of meters high unstable ice cliff prone to ice falls of different magnitudes. The second study area is located at the proglacial area. At Pasterze <span class="hlt">Glacier</span> the proglacial area is widely influenced by dead-ice bodies of various dimensions making this area prone to slow to sudden geomorphic changes caused by ice mass changes. A particular ice-mass movement event took place on 20.09.2016. Within less than one hour the surface of the proglacial area changed substantially by tilting, lateral shifting, and subsidence of the ground accompanied by complete ice disintegration of once-debris covered ice. To understand acting processes at both areas of interest and to quantify mass changes we used field observations, terrain</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..575B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..575B"><span>Investigating ice cliff evolution and contribution to <span class="hlt">glacier</span> mass-balance using a physically-based dynamic model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buri, Pascal; Miles, Evan; Ragettli, Silvan; Brun, Fanny; Steiner, Jakob; Pellicciotti, Francesca</p> <p>2016-04-01</p> <p>Supraglacial cliffs are a surface feature typical of debris-covered <span class="hlt">glaciers</span>, affecting surface evolution, <span class="hlt">glacier</span> downwasting and mass balance by providing a direct ice-atmosphere interface. As a result, <span class="hlt">melt</span> rates can be very high and ice cliffs may account for a significant portion of the total <span class="hlt">glacier</span> mass loss. However, their contribution to <span class="hlt">glacier</span> mass balance has rarely been quantified through physically-based models. Most cliff energy balance models are point scale models which calculate energy fluxes at individual cliff locations. Results from the only grid based model to date accurately reflect energy fluxes and cliff <span class="hlt">melt</span>, but modelled backwasting patterns are in some cases unrealistic, as the distribution of <span class="hlt">melt</span> rates would lead to progressive shallowing and disappearance of cliffs. Based on a unique multitemporal dataset of cliff topography and backwasting obtained from high-resolution terrestrial and aerial Structure-from-Motion analysis on Lirung <span class="hlt">Glacier</span> in Nepal, it is apparent that cliffs exhibit a range of behaviours but most do not rapidly disappear. The patterns of evolution cannot be explained satisfactorily by atmospheric <span class="hlt">melt</span> alone, and are moderated by the presence of supraglacial ponds at the base of cliffs and by cliff reburial with debris. Here, we document the distinct patterns of evolution including disappearance, growth and stability. We then use these observations to improve the grid-based energy balance model, implementing periodic updates of the cliff geometry resulting from modelled <span class="hlt">melt</span> perpendicular to the ice surface. Based on a slope threshold, pixels can be reburied by debris or become debris-free. The effect of ponds are taken into account through enhanced <span class="hlt">melt</span> rates in horizontal direction on pixels selected based on an algorithm considering distance to the water surface, slope and lake level. We use the dynamic model to first study the evolution of selected cliffs for which accurate, high resolution DEMs are available</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41F..07P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41F..07P"><span>Opportunities and Challenges in Enhancing Value of Annual <span class="hlt">Glacier</span> Mass Balance Monitoring Examples from Western North America</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pelto, M. S.</p> <p>2017-12-01</p> <p>Alpine <span class="hlt">glacier</span> mass balance is the most accurate indicator of <span class="hlt">glacier</span> response to climate and with retreat of alpine <span class="hlt">glaciers</span> is one of the clearest signals of global climate change. Completion of long term, representative and homogenous mass balance field measurement of mass balance, compiled by WGMS, is a key climate data record. To ensure a monitoring program remains vital and funded local collaboration and connecting the research to local societal impacts is crucial. Working with local partners in collecting and providing the right data is critical whether their interest is in hydropower, irrigation, municipal supply, hazard reduction and/or aquatic ecosystems. The expansion of remote sensing and modeling capability provides both a challenge to continued relevance and an opportunity for field mass balance programs to expand relevance. In modelling studies of both <span class="hlt">glacier</span> mass balance and <span class="hlt">glacier</span> runoff transient balance data has equivalent value with annual balance data, for both calibration runs and as an input variable. This increases the utility of mid-season field observations. Remote sensing provides repeat imagery that often identifies the AAR and transient snowline of a <span class="hlt">glacier</span>. For runoff assessment understanding the specific percent of <span class="hlt">glacier</span> surface area that is <span class="hlt">glacier</span> ice, older firn, and retained snowpack from the previous winter at frequent intervals during the <span class="hlt">melt</span> season is vital since each region has a different <span class="hlt">melt</span> factor. A denser field observation network combined with this imagery can provide additional point balance values of ablation that complement the mass balance record. Periodic measurement of mass balance at a denser network using GPR, LIDAR, TLS or probing is required to better understand long term point balance locations and is important at end of the <span class="hlt">melt</span> season not just beginning, and has value mid-season for modelling. Applications of each of utility of field mass balance observations will be illustrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMGC31B..03F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMGC31B..03F"><span>Adapting to climate change at <span class="hlt">Glacier</span> National Park, Montana, USA (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fagre, D. B.</p> <p>2009-12-01</p> <p>The impact of climate change on mountain watersheds has been studied at <span class="hlt">Glacier</span> National Park, Montana since 1991. Despite a 14% increase in annual precipitation, <span class="hlt">glaciers</span> have receded, snow packs have diminished, and late season stream discharge has declined. Snow <span class="hlt">melts</span> one month earlier in the spring, leading to earlier hydrologic peaks and tree invasions of subalpine meadows. This has been largely driven by annual temperature increases that are 2-3 times greater than the global average for the past century. How do scientists and park managers adapt? Although stopping the <span class="hlt">glaciers</span> from disappearing is not a management option, park staff have embarked on an aggressive education and interpretation effort to use <span class="hlt">melting</span> <span class="hlt">glaciers</span> as the segue into dialog about climate change. Media such as podcasts, handouts, posters, visitor center displays and roadside signage complement interpretive ranger-led talks about climate change and incorporate the latest glacial data from ongoing research. With few historic data on most animal populations, <span class="hlt">Glacier</span> Park staff and other scientists are unable to assess the impacts of climate change to resources that the public cares about. They have recently initiated alpine wildlife monitoring programs to track populations of potentially climate-sensitive organisms such as the American pika (Ochotona princeps). Recognizing that climate change increases the frequency and severity of extreme weather events, design specifications for reconstruction of an alpine highway were adjusted to include larger culverts and hardened rock walls. Species that are dependent on cold water will be at risk as <span class="hlt">glaciers</span> and snowfields disappear but managers cannot control these processes. However, they are proactively reducing other stressors to sensitive native fish species by removing exotic, introduced species that are competitors. In addition to these adaptation measures, <span class="hlt">Glacier</span> Park has implemented shuttles, fleet conversions and enhanced building</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.nps.gov/glba/learn/nature/upload/Madison_Etherington_2005_Ocean2004AnnualReport-2.pdf','USGSPUBS'); return false;" href="https://www.nps.gov/glba/learn/nature/upload/Madison_Etherington_2005_Ocean2004AnnualReport-2.pdf"><span>Monitoring of oceanographic properties of <span class="hlt">Glacier</span> Bay, Alaska 2004</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Madison, Erica N.; Etherington, Lisa L.</p> <p>2005-01-01</p> <p><span class="hlt">Glacier</span> Bay is a recently (300 years ago) deglaciated fjord estuarine system that has multiple sills, very deep basins, tidewater <span class="hlt">glaciers</span>, and many streams. <span class="hlt">Glacier</span> Bay experiences a large amount of runoff, high sedimentation, and large tidal variations. High freshwater discharge due to snow and ice <span class="hlt">melt</span> and the presence of the tidewater <span class="hlt">glaciers</span> makes the bay extremely cold. There are many small- and large-scale mixing and upwelling zones at sills, glacial faces, and streams. The complex topography and strong currents lead to highly variable salinity, temperature, sediment, primary productivity, light penetration, stratification levels, and current patterns within a small area. The oceanographic patterns within <span class="hlt">Glacier</span> Bay drive a large portion of the spatial and temporal variability of the ecosystem. It has been widely recognized by scientists and resource managers in <span class="hlt">Glacier</span> Bay that a program to monitor oceanographic patterns is essential for understanding the marine ecosystem and to differentiate between anthropogenic disturbance and natural variation. This year’s sampling marks the 12th continuous year of monitoring the oceanographic conditions at 23 stations along the primary axes within <span class="hlt">Glacier</span> Bay, AK, making this a very unique and valuable data set in terms of its spatial and temporal coverage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24305146','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24305146"><span>North Atlantic warming and the retreat of Greenland's outlet <span class="hlt">glaciers</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Straneo, Fiammetta; Heimbach, Patrick</p> <p>2013-12-05</p> <p>Mass loss from the Greenland ice sheet quadrupled over the past two decades, contributing a quarter of the observed global sea-level rise. Increased submarine <span class="hlt">melting</span> is thought to have triggered the retreat of Greenland's outlet <span class="hlt">glaciers</span>, which is partly responsible for the ice loss. However, the chain of events and physical processes remain elusive. Recent evidence suggests that an anomalous inflow of subtropical waters driven by atmospheric changes, multidecadal natural ocean variability and a long-term increase in the North Atlantic's upper ocean heat content since the 1950s all contributed to a warming of the subpolar North Atlantic. This led, in conjunction with increased runoff, to enhanced submarine <span class="hlt">glacier</span> <span class="hlt">melting</span>. Future climate projections raise the potential for continued increases in warming and ice-mass loss, with implications for sea level and climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.C31A1247M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.C31A1247M"><span>Meltwater <span class="hlt">Induced</span> <span class="hlt">Glacier</span> Landslides - Waxell Ridge, AK</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Molnia, B. F.; Angeli, K. M.; Bratton, D. A.; Keeler, R. H.; Noyles, C.</p> <p>2006-12-01</p> <p>Within the past year, two large landslides have originated from south-facing peaks on Waxell Ridge, the bedrock massif that separates the Bagley Icefield from Bering <span class="hlt">Glacier</span>, Alaska. Each involves a near-summit hanging <span class="hlt">glacier</span>. In each instance, the presence of meltwater appears to be a triggering factor. The largest of the two, which occurred on September 14, 2005, originated from just below the summit of 3,236-m-high Mt Steller and landed on the surface of Bering <span class="hlt">Glacier</span>, nearly 2,500 m below. The Alaska Volcano Observatory estimated the volume of this landslide, which consisted of rock, <span class="hlt">glacier</span> ice, and snow, to be approximately 50 million cubic meters. Unlike most large Alaskan <span class="hlt">glacier</span>-related landslides, this one was not triggered by an earthquake. However, the energy that the slide released was intense enough to generate a seismic signal that was recorded around the world with magnitudes of 3.8 to greater than 5. The slide extended ~10 km down the Bering <span class="hlt">Glacier</span> from the point of impact. Much of the surface on which the slide occurred had a slope >50 degrees. The second landslide, located ~6 km to the west of Mt Steller, originated from a secondary summit of a 2,500- m-high unnamed peak. The date of its occurrence is unknown, but its toe sits on winter 2005-2006 snow. Both slides have been examined from helicopter and fixed-wing overflights, and with a variety of vertical and oblique aerial photographs. Oblique aerial photographs obtained of the Mt Steller slide on September 15, 2005 depict a 10-15-m-diameter moulin or englacial stream channel in the truncated 30-m-thick <span class="hlt">glacier</span> ice that comprises the east wall of the landslide scarp. The presence of this unusual glacial-hydrologic feature at an elevation above 3,000 m, suggests that a large volume of water had recently been flowing on Mt Steller's east ridge and that the water might have had a role in triggering the landslide. Similarly, there is evidence of an englacial channel on the west flank of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27435236','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27435236"><span>Contributions of natural and anthropogenic <span class="hlt">radiative</span> forcing to mass loss of Northern Hemisphere mountain <span class="hlt">glaciers</span> and quantifying their uncertainties.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hirabayashi, Yukiko; Nakano, Kazunari; Zhang, Yong; Watanabe, Satoshi; Tanoue, Masahiro; Kanae, Shinjiro</p> <p>2016-07-20</p> <p>Observational evidence indicates that a number of <span class="hlt">glaciers</span> have lost mass in the past. Given that <span class="hlt">glaciers</span> are highly impacted by the surrounding climate, human-influenced global warming may be partly responsible for mass loss. However, previous research studies have been limited to analyzing the past several decades, and it remains unclear whether past <span class="hlt">glacier</span> mass losses are within the range of natural internal climate variability. Here, we apply an optimal fingerprinting technique to observed and reconstructed mass losses as well as multi-model general circulation model (GCM) simulations of mountain <span class="hlt">glacier</span> mass to detect and attribute past <span class="hlt">glacier</span> mass changes. An 8,800-year control simulation of <span class="hlt">glaciers</span> enabled us to evaluate detectability. The results indicate that human-<span class="hlt">induced</span> increases in greenhouse gases have contributed to the decreased area-weighted average masses of 85 analyzed <span class="hlt">glaciers</span>. The effect was larger than the mass increase caused by natural forcing, although the contributions of natural and anthropogenic forcing to decreases in mass varied at the local scale. We also showed that the detection of anthropogenic or natural influences could not be fully attributed when natural internal climate variability was taken into account.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...629723H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...629723H"><span>Contributions of natural and anthropogenic <span class="hlt">radiative</span> forcing to mass loss of Northern Hemisphere mountain <span class="hlt">glaciers</span> and quantifying their uncertainties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hirabayashi, Yukiko; Nakano, Kazunari; Zhang, Yong; Watanabe, Satoshi; Tanoue, Masahiro; Kanae, Shinjiro</p> <p>2016-07-01</p> <p>Observational evidence indicates that a number of <span class="hlt">glaciers</span> have lost mass in the past. Given that <span class="hlt">glaciers</span> are highly impacted by the surrounding climate, human-influenced global warming may be partly responsible for mass loss. However, previous research studies have been limited to analyzing the past several decades, and it remains unclear whether past <span class="hlt">glacier</span> mass losses are within the range of natural internal climate variability. Here, we apply an optimal fingerprinting technique to observed and reconstructed mass losses as well as multi-model general circulation model (GCM) simulations of mountain <span class="hlt">glacier</span> mass to detect and attribute past <span class="hlt">glacier</span> mass changes. An 8,800-year control simulation of <span class="hlt">glaciers</span> enabled us to evaluate detectability. The results indicate that human-<span class="hlt">induced</span> increases in greenhouse gases have contributed to the decreased area-weighted average masses of 85 analyzed <span class="hlt">glaciers</span>. The effect was larger than the mass increase caused by natural forcing, although the contributions of natural and anthropogenic forcing to decreases in mass varied at the local scale. We also showed that the detection of anthropogenic or natural influences could not be fully attributed when natural internal climate variability was taken into account.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C53D..02M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C53D..02M"><span>Remote Sensing Observations of Advancing and Surging Tidewater <span class="hlt">Glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McNabb, R. W.; Kääb, A.; Nuth, C.; Girod, L.; Truffer, M.; Fahnestock, M. A.</p> <p>2017-12-01</p> <p>Progress has been made in understanding the glaciological frontiers of tidewater <span class="hlt">glacier</span> dynamics and surge dynamics, though many aspects of these topics are not well-understood. Advances in the processing of digital elevation models (DEMs) from ASTER imagery, as well as the increased availability and temporal density of satellite images such as Landsat and the Sentinel missions, provide an unprecedented wealth of satellite data over <span class="hlt">glaciers</span>, providing new opportunities to learn about these topics. As one of the largest glaciated regions in the world outside of the Greenland and Antarctic ice sheets, <span class="hlt">glaciers</span> in Alaska and adjacent regions in Canada have been highlighted for their elevated contributions to global sea level rise, through both high levels of <span class="hlt">melt</span> and frontal ablation/calving from a large number of tidewater <span class="hlt">glaciers</span>. The region is also home to a number of surging <span class="hlt">glaciers</span>. We focus on several tidewater <span class="hlt">glaciers</span> in the region, including Turner, Tsaa, Harvard, and Meares <span class="hlt">Glaciers</span>. Turner <span class="hlt">Glacier</span> is a surge-type tidewater <span class="hlt">glacier</span> with a surge period of approximately eight years, while Tsaa <span class="hlt">Glacier</span> is a tidwewater <span class="hlt">glacier</span> that has shown rapid swings in terminus position on the order of a year. Harvard and Meares <span class="hlt">Glaciers</span> have been steadily advancing since at least the mid-20th century, in contrast with neighboring <span class="hlt">glaciers</span> that are retreating. Using a combination of ASTER, Landsat, and Sentinel data, we present and examine high-resolution time series of elevation, velocity, and terminus position for these <span class="hlt">glaciers</span>, as well as updated estimates of volume change and frontal ablation rates, including on sub-annual time scales. Preliminary investigations of elevation change on Turner <span class="hlt">Glacier</span> show that changes are most pronounced in the lower reaches of the <span class="hlt">glacier</span>, below a prominent icefall approximately 15km from the head of the <span class="hlt">glacier</span>. On Harvard and Meares <span class="hlt">Glaciers</span>, elevation changes in the upper reaches of both <span class="hlt">glaciers</span> have been generally small or</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.C23A0594C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.C23A0594C"><span>Reconstructing the history of major Greenland <span class="hlt">glaciers</span> since the Little Ice Age</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Csatho, B. M.; Schenk, A. F.; van der Veen, C. J.; Stearns, L.; Babonis, G. S.</p> <p>2008-12-01</p> <p>The Greenland Ice Sheet may have been responsible for rapid sea level rise during the last interglacial period and recent studies indicate that it is likely to make a faster contribution to sea-level rise than previously believed. Rapid thinning and velocity increase has been observed on most major outlet <span class="hlt">glaciers</span> with terminus retreat that might lead to increased discharge from the interior and consequent further thinning and retreat. Potentially, such behavior could have serious implications for global sea level. However, the current thinning may simply be a manifestation of longer-term behavior of the ice sheet as it responds to the general warming following the Little Ice Age (LIA). Although Greenland outlet <span class="hlt">glaciers</span> have been comprehensively monitored since the 1980s, studies of long-term changes mostly rely on records of the calving front position. Such records can be misleading because the <span class="hlt">glacier</span> terminus, particularly if it is afloat, can either advance or retreat as ice further upstream thins and accelerates. To assess whether recent trends deviate from longer-term behavior, we examined three rapidly thinning and retreating outlet <span class="hlt">glaciers</span>, Jakobshavn Isbrae in west, Kangerdlussuaq <span class="hlt">Glacier</span> in east and Petermann <span class="hlt">Glacier</span> in northwest Greenland. <span class="hlt">Glacier</span> surface and trimline elevations, as well as terminus positions were measured using historical photographs and declassified satellite imagery acquired between the 1940s and 1985. These results were combined with data from historical records, ground surveys, airborne laser altimetry, satellite observations and field mapping of lateral moraines and trimlines, to reconstruct the history of changes since the (LIA) up to the present. We identified several episodes of rapid thinning and ice shelf break-up, including thinning episodes that occurred when the calving front was stationary. Coastal weather station data are used to assess the influence of air temperatures and intensity of surface <span class="hlt">melting</span>, and to isolate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41B1211H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41B1211H"><span>Rapid changes in <span class="hlt">glacier</span> surface processes and downstream river basin in the Central Himalayan region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haritashya, U. K.; Strattman, K.; Kargel, J. S.</p> <p>2017-12-01</p> <p>A high altitude <span class="hlt">glacierized</span> region in the central Himalaya hosts thousands of <span class="hlt">glaciers</span> and originates major rivers like the Ganges and Yamuna. This region has seen significant changes in last few decades due to climate system coupling involving the westerlies and the monsoon, high seismic activities, complex topography, extensive <span class="hlt">glacier</span> debris cover, and widespread mass movement. Consequently, we analyzed regional variability in hundreds of <span class="hlt">glacier</span> surface processes and downstream river basins of varying geomorphology using a variety of satellite imagery from the early 1990s to 2017. Our results indicate a massive increase in supraglacial ponds in south facing <span class="hlt">glaciers</span>. Several of these ponds are either seasonal and forms exactly at the same location every year or forms at the beginning of the <span class="hlt">melt</span> season and drains out as the season progresses from April to July/August. We also observed evolution in size of these ponds in the last two decades to the point where some of them now seem to be stationary and might increase in size and develop large lake in the future. To understand our result and <span class="hlt">melting</span> pattern in the region, we also analyzed ice velocity and surface temperature; both of which reveals a temporal shift in the pattern. <span class="hlt">Glacier</span> surface temperatures, especially show a warming pattern in recent years and strong correlation with debris cover. Additionally, we also observed changes in the downstream region both around the river bed and steep slopes where massive erosion of Himalayan <span class="hlt">glaciers</span> are depositing and transporting excessive amount of sediments. Overall, our results are discussed in the context of better landscape evolution modeling from the top of the <span class="hlt">glacier</span> to the several km downstream from the <span class="hlt">glacier</span> terminus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C11E..08R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C11E..08R"><span>Himalayan <span class="hlt">glaciers</span>: understanding contrasting patterns of <span class="hlt">glacier</span> behavior using multi-temporal satellite imagery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Racoviteanu, A.</p> <p>2014-12-01</p> <p>High rates of <span class="hlt">glacier</span> retreat for the last decades are often reported, and believed to be <span class="hlt">induced</span> by 20th century climate changes. However, regional <span class="hlt">glacier</span> fluctuations are complex, and depend on a combination of climate and local topography. Furthermore, in ares such as the Hindu-Kush Himalaya, there are concerns about warming, decreasing monsoon precipitation and their impact on local <span class="hlt">glacier</span> regimes. Currently, the challenge is in understanding the magnitude of feedbacks between large-scale climate forcing and small-scale <span class="hlt">glacier</span> behavior. Spatio-temporal patterns of <span class="hlt">glacier</span> distribution are still llimited in some areas of the high Hindu-Kush Himalaya, but multi-temporal satellite imagery has helped fill spatial and temporal gaps in regional <span class="hlt">glacier</span> parameters in the last decade. Here I present a synopsis of the behavior of <span class="hlt">glaciers</span> across the Himalaya, following a west to east gradient. In particular, I focus on spatial patterns of <span class="hlt">glacier</span> parameters in the eastern Himalaya, which I investigate at multi-spatial scales using remote sensing data from declassified Corona, ASTER, Landsat ETM+, Quickbird and Worldview2 sensors. I also present the use of high-resolution imagery, including texture and thermal analysis for mapping <span class="hlt">glacier</span> features at small scale, which are particularly useful in understanding surface trends of debris-covered <span class="hlt">glaciers</span>, which are prevalent in the Himalaya. I compare and contrast spatial patterns of <span class="hlt">glacier</span> area and élévation changes in the monsoon-influenced eastern Himalaya (the Everest region in the Nepal Himalaya and Sikkim in the Indian Himalaya) with other observations from the dry western Indian Himalaya (Ladakh and Lahul-Spiti), both field measurements and remote sensing-based. In the eastern Himalaya, results point to <span class="hlt">glacier</span> area change of -0.24 % ± 0.08% per year from the 1960's to the 2006's, with a higher rate of retreat in the last decade (-0.43% /yr). Debris-covered <span class="hlt">glacier</span> tongues show thinning trends of -30.8 m± 39 m</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18...73R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18...73R"><span>Debris-covered Himalayan <span class="hlt">glaciers</span> under a changing climate: observations and modelling of Khumbu <span class="hlt">Glacier</span>, Nepal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rowan, Ann; Quincey, Duncan; Egholm, David; Gibson, Morgan; Irvine-Fynn, Tristram; Porter, Philip; Glasser, Neil</p> <p>2016-04-01</p> <p>Many mountain <span class="hlt">glaciers</span> are characterised in their lower reaches by thick layers of rock debris that insulate the <span class="hlt">glacier</span> surface from solar <span class="hlt">radiation</span> and atmospheric warming. Supraglacial debris modifies the response of these <span class="hlt">glaciers</span> to climate change compared to <span class="hlt">glaciers</span> with clean-ice surfaces. However, existing modelling approaches to predicting variations in the extent and mass balance of debris-covered <span class="hlt">glaciers</span> have relied on numerical models that represent the processes governing <span class="hlt">glaciers</span> with clean-ice surfaces, and yield conflicting results. Moreover, few data exist describing the mass balance of debris-covered <span class="hlt">glaciers</span> and many observations are only made over short periods of time, but these data are needed to constrain and validate numerical modelling experiments. To investigate the impact of supraglacial debris on the response of a <span class="hlt">glacier</span> to climate change, we developed a numerical model that couples the flow of ice and debris to include important feedbacks between mass balance, ice flow and debris accumulation. We applied this model to a large debris-covered Himalayan <span class="hlt">glacier</span> - Khumbu <span class="hlt">Glacier</span> in the Everest region of Nepal. Our results demonstrate that supraglacial debris prolongs the response of the <span class="hlt">glacier</span> to warming air temperatures and causes lowering of the <span class="hlt">glacier</span> surface in situ, concealing the magnitude of mass loss when compared with estimates based on glacierised area. Since the Little Ice Age, the volume of Khumbu <span class="hlt">Glacier</span> has reduced by 34%, while <span class="hlt">glacier</span> area has reduced by only 6%. We predict a further decrease in <span class="hlt">glacier</span> volume of 8-10% by AD2100 accompanied by dynamic and physical detachment of the debris-covered tongue from the active <span class="hlt">glacier</span> within the next 150 years. For five months during the 2014 summer monsoon, we measured temperature profiles through supraglacial debris and proglacial discharge on Khumbu <span class="hlt">Glacier</span>. We found that temperatures at the ice surface beneath 0.4-0.7 m of debris were sufficient to promote considerable</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060040185&hterms=glacier+melt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dglacier%2Bmelt','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060040185&hterms=glacier+melt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dglacier%2Bmelt"><span>Rapid bottom <span class="hlt">melting</span> widespread near Antarctic ice sheet grounding lines</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rignot, E.; Jacobs, S.</p> <p>2002-01-01</p> <p>As continental ice from Antartica reaches the grounding line and begins to float, its underside <span class="hlt">melts</span> into the ocean. Results obtained with satellite radar interferometry reveal that bottom <span class="hlt">melt</span> rates experienced by large outlet <span class="hlt">glaciers</span> near their grounding lines are far higher than generally assumed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22391780-flow-induced-migration-polymer-melts-theory-simulation','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22391780-flow-induced-migration-polymer-melts-theory-simulation"><span>Flow <span class="hlt">induced</span> migration in polymer <span class="hlt">melts</span> – Theory and simulation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Dorgan, John Robert, E-mail: jdorgan@mines.edu; Rorrer, Nicholas Andrew, E-mail: nrorrer@mines.edu</p> <p>2015-04-28</p> <p>Flow <span class="hlt">induced</span> migration, whereby polymer <span class="hlt">melts</span> are fractionated by molecular weight across a flow field, represents a significant complication in the processing of polymer <span class="hlt">melts</span>. Despite its long history, such phenomena remain relatively poorly understood. Here a simple analytical theory is presented which predicts the phenomena based on well-established principles of non-equilibrium thermodynamics. It is unambiguously shown that for purely viscous materials, a gradient in shear rate is needed to drive migration; for purely viscometric flows no migration is expected. Molecular scale simulations of flow migration effects in dense polymer <span class="hlt">melts</span> are also presented. In shear flow the <span class="hlt">melts</span> exhibitmore » similar behavior as the quiescent case; a constant shear rate across the gap does not <span class="hlt">induce</span> chain length based migration. In comparison, parabolic flow causes profound migration for both unentangled and entangled <span class="hlt">melts</span>. These findings are consistent with the analytical theory. The picture that emerges is consistent with flow <span class="hlt">induced</span> migration mechanisms predominating over competing chain degradation mechanisms.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03387&hterms=glacier+melt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dglacier%2Bmelt','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03387&hterms=glacier+melt&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dglacier%2Bmelt"><span>Malaspina <span class="hlt">Glacier</span>, Alaska, Anaglyph with Landsat Overlay</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2003-01-01</p> <p><p/>This anaglyph view of Malaspina <span class="hlt">Glacier</span> in southeastern Alaska was created from a Landsat satellite image and an elevation model generated by the Shuttle Radar Topography Mission (SRTM). Malaspina <span class="hlt">Glacier</span> is considered the classic example of a piedmont <span class="hlt">glacier</span>. Piedmont <span class="hlt">glaciers</span> occur where valley <span class="hlt">glaciers</span> exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes. Malaspina <span class="hlt">Glacier</span> is actually a compound <span class="hlt">glacier</span>, formed by the merger of several valley <span class="hlt">glaciers</span>, the most prominent of which seen here are Agassiz <span class="hlt">Glacier</span> (left) and Seward <span class="hlt">Glacier</span> (right). In total, Malaspina <span class="hlt">Glacier</span> is up to 65 kilometers (40 miles) wide and extends up to 45 kilometers (28 miles) from the mountain front nearly to the sea. <p/><span class="hlt">Glaciers</span> erode rocks, carry them down slope, and deposit them at the edge of the <span class="hlt">melting</span> ice, typically in elongated piles called moraines. The moraine patterns at Malaspina <span class="hlt">Glacier</span> are quite spectacular in that they have huge contortions that result from the <span class="hlt">glacier</span> crinkling as it gets pushed from behind by the faster-moving valley <span class="hlt">glaciers</span>. <p/>Numerous other features of the <span class="hlt">glaciers</span> and the adjacent terrain are clearly seen when viewing this image at full resolution. The series of tonal arcs on Agassiz <span class="hlt">Glacier</span>'s extension onto the piedmont are called 'ogives.' These arcs are believed to be seasonal features created by deformation of the <span class="hlt">glacier</span> as it passes over bedrock irregularities at differing speeds through the year. Assuming one light-and-dark ogive pair per year, the rate of motion of the glacial ice can be estimated (in this case, about 200 meters per year where the ogives are most prominent). Just to the west, moraine deposits abut the eroded bedrock terrain, forming a natural dam that has created a lake. Near the northwest corner of the scene, a recent landslide has deposited rock debris atop a small <span class="hlt">glacier</span>. Sinkholes are common in many areas of the moraine deposits. The sinkholes form when</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015TCD.....9.4865M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015TCD.....9.4865M"><span><span class="hlt">Glacier</span> dynamics over the last quarter of a century at Jakobshavn Isbræ</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muresan, I. S.; Khan, S. A.; Aschwanden, A.; Khroulev, C.; Van Dam, T.; Bamber, J.; van den Broeke, M. R.; Wouters, B.; Kuipers Munneke, P.; Kjær, K. H.</p> <p>2015-09-01</p> <p>Observations over the past two decades show substantial ice loss associated with the speedup of marine terminating <span class="hlt">glaciers</span> in Greenland. Here we use a regional 3-D outlet <span class="hlt">glacier</span> model to simulate the behaviour of Jakobshavn Isbræ (JI) located in west Greenland. Using atmospheric and oceanic forcing we tune our model to reproduce the observed frontal changes of JI during 1990-2014. We identify two major accelerations. The first occurs in 1998, and is triggered by moderate thinning prior to 1998. The second acceleration, which starts in 2003 and peaks in summer 2004, is triggered by the final breakup of the floating tongue, which generates a reduction in buttressing at the JI terminus. This results in further thinning, and as the slope steepens inland, sustained high velocities have been observed at JI over the last decade. As opposed to other regions on the Greenland Ice Sheet (GrIS), where dynamically <span class="hlt">induced</span> mass loss has slowed down over recent years, both modelled and observed results for JI suggest a continuation of the acceleration in mass loss. Further, we find that our model is not able to capture the 2012 peak in the observed velocities. Our analysis suggests that the 2012 acceleration of JI is likely the result of an exceptionally long <span class="hlt">melt</span> season dominated by extreme <span class="hlt">melt</span> events. Considering that such extreme surface <span class="hlt">melt</span> events are expected to intensify in the future, our findings suggest that the 21st century projections of the GrIS mass loss and the future sea level rise may be larger than predicted by existing modelling results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22304437','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22304437"><span>Isolation of oligotrophic yeasts from supraglacial environments of different altitude on the Gulkana <span class="hlt">Glacier</span> (Alaska).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Uetake, Jun; Yoshimura, Yoshitaka; Nagatsuka, Naoko; Kanda, Hiroshi</p> <p>2012-11-01</p> <p>Psychrophilic yeasts have been isolated from supra- and subglacial ice at many sites worldwide. To understand the ecology of psychrophilic yeasts on <span class="hlt">glaciers</span>, we focused on their adaptation to wide range of nutrient concentrations and their distribution with altitude on the Gulkana <span class="hlt">Glacier</span> in Alaska. We found various culturable psychrophilic yeasts on the ice surfaces of the <span class="hlt">glacier</span>, and 11 species were isolated with incubation at 4 °C in four different dilutions of agar medium. Some of our isolated species (Rhodotorula psychrophenolica, Rhodotorula aff. psychrophenolica, Rhodotorula glacialis, and Basidiomycota sp. 1) can grow on the low dissolved organic matter (DOC) concentrations medium (7.6 mg L(-1)) which is close to the typical level of supraglacial <span class="hlt">melt</span> water, suggesting that these species can inhabit in any supraglacial meltwater. Otherwise, most of other species were isolated only from higher DOC concentration medium (183 mg L(-1) -18.3 g L(-1)), suggesting that these are inhabitant around the cryoconite, because DOC concentrations in <span class="hlt">melted</span> surface-ice contained cryoconite is much higher than in <span class="hlt">melted</span> water. Similarity of altitudinal distribution between culturable yeast and algal biomass suggests that the ecological role played by the cold-adapted yeasts is as organic matter decomposers and nutrient cyclers in <span class="hlt">glacier</span> ecosystem. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..495S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..495S"><span>Controls of air temperature variability over an Alpine <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shaw, Thomas; Brock, Ben; Ayala, Álvaro; Rutter, Nick</p> <p>2016-04-01</p> <p>Near surface air temperature (Ta) is one of the most important controls on energy exchange between a <span class="hlt">glacier</span> surface and the overlying atmosphere. However, not enough detail is known about the controls on Ta across a <span class="hlt">glacier</span> due to sparse data availability. Recent work has provided insights into variability of Ta along <span class="hlt">glacier</span> centre-lines in different parts of the world, yet there is still a limited understanding of off-centreline variability in Ta and how best to estimate it from distant off-<span class="hlt">glacier</span> locations. We present a new dataset of distributed 2m Ta records for the Tsanteleina <span class="hlt">Glacier</span> in Northwest Italy from July-September, 2015. Data provide detailed information of lateral (across-<span class="hlt">glacier</span>) and centre-line variations in Ta, with ~20,000 hourly observations from 17 locations. The suitability of different vertical temperature gradients (VTGs) in estimating air temperature is considered under a range of meteorological conditions and from different forcing locations. A key finding is that local VTGs account for a lot of Ta variability under a broad range of climatic conditions. However, across-<span class="hlt">glacier</span> variability is found to be significant, particularly for high ambient temperatures and for localised topographic depressions. The relationship of spatial Ta patterns with regional-scale reanalysis data and alternative Ta estimation methodologies are also presented. This work improves the knowledge of local scale Ta variations and their importance to <span class="hlt">melt</span> modelling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.5267S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.5267S"><span>Formation of <span class="hlt">melt</span> channels on ice shelves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sergienko, Olga</p> <p>2013-04-01</p> <p><span class="hlt">Melt</span> channels have been observed on ice shelves experiencing strong <span class="hlt">melting</span> in both Greenland (Petermann <span class="hlt">Glacier</span>) and Antarctica (Pine Island <span class="hlt">Glacier</span>). Using a fully-couple ice-shelf/sub-ice-shelf-ocean flow model, it is demonstrated that these channels can form spontaneously in laterally confined ice shelves. These channels have transverse extent of a few kilometers and a vertical relief of about a few hundred meters. Meltrates and sea-water transport in the channels are significantly higher than in between the channels on the smooth flat ice bottom. In circumstances where an ice shelf has no-slip conditions at its lateral boundaries, the ice-shelf/sub-ice-shelf-cavity system exhibits equilibrium periodic states, where the same configurations repetitively appear with a periodicity of about 30-35 years. This peculiar dynamics of the system has strong implications on the interpretation of the remote and in-situ observations and inferences of the system parameters (e.g., <span class="hlt">melt</span> rates) based on these observations. For instance, the persistent temporal changes in the ice-shelf thickness are caused by internal dynamics of the <span class="hlt">melt</span> channels, and, in contrast to traditional interpretation, can be independent of the oceanic forcings.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C23A1200W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C23A1200W"><span>Ocean-<span class="hlt">Glaciers</span> Interactions in the Southern Svalbard Fjord, Hornsund.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walczowski, W.; Beszczynska-Moeller, A.; Prominska, A.; Kruss, A.</p> <p>2017-12-01</p> <p>The Arctic fjords constitute a link between the ocean and land, therefore there are highly vulnerable to warming and are expected to exhibit the earliest environmental changes resulting from anthropogenic impacts on climate. In the Arctic, the inshore boundary of a fjord system is usually dominated by tidewater <span class="hlt">glaciers</span> while its offshore boundary is strongly influenced by warm oceanic waters. Improved understanding of the fjord-ocean exchange and processes within Arctic fjords is of a highest importance because their response to atmospheric, oceanic and glacial variability provides a key to understand the past and to forecast the future of the high latitude <span class="hlt">glaciers</span> and Arctic climate. The results of field measurements in the Hornsund fjord (southern Svalbard), collected under the Polish-Norwegian projects GLAERE and AWAKE-2, will be presented. Interannual variability of warm Atlantic water entering the fjord, seasonal changes of ocean properties in the <span class="hlt">glacier</span> bays and the structure of the water column in the vicinity of the <span class="hlt">glacier</span> termination will be addressed. Direct contact of warm oceanic water with a <span class="hlt">glacier</span>'s wall causes submarine <span class="hlt">melting</span>, undercutting and <span class="hlt">glacier</span> calving. Turbulent plumes of subglacial meltwater constitute an important mechanism of heat transfer and also influence a <span class="hlt">glacier</span> retreat. However our understanding of these processes is limited due to problems with obtaining in situ data close to the <span class="hlt">glacier</span> wall. Therefore special attention will be paid to observations of the underwater parts of Hornsund <span class="hlt">glaciers</span> and new measurements of water column fine structure and mixing in the turbulent meltwater plumes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AGUFMIP41A..03M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AGUFMIP41A..03M"><span>Assessing the Response of Alaska's <span class="hlt">Glaciers</span> to Post-Little Ice Age Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Molnia, B. F.</p> <p>2001-12-01</p> <p> below an elevation of 1,500 m are retreating, thinning, and/or stagnating. Some advancing <span class="hlt">glaciers</span> have tidewater termini. The two largest <span class="hlt">glaciers</span>, Bering and Malaspina <span class="hlt">Glaciers</span>, are thinning and retreating, losing several cubic kilometers of ice each year to <span class="hlt">melting</span> and calving; TALKEETNA MOUNTAINS, AHKLUN-WOOD RIVER MOUNTAINS, KIGLUAIK MOUNTAINS, AND THE BROOKS RANGE: every <span class="hlt">glacier</span> examined is retreating. Some disappeared during the twentieth century. <span class="hlt">Glaciers</span> at higher elevations show little or no change. Perhaps, at these locations, regional climate change has not resulted in temperatures being elevated to a level where they impact existing <span class="hlt">glacier</span> ice. Increases in precipitation may also be compensating for increases in <span class="hlt">melting</span>. Throughout Alaska, in response to post-Little Ice Age climate change, all but a few <span class="hlt">glaciers</span> that descent below an elevation of 1,500 m have thinned, stagnated, and/or retreated. Of the nearly 700 named Alaskan <span class="hlt">glaciers</span>, less than a dozen are currently advancing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26104673','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26104673"><span>Microbial community development on the surface of Hans and Werenskiold <span class="hlt">Glaciers</span> (Svalbard, Arctic): a comparison.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grzesiak, Jakub; Górniak, Dorota; Świątecki, Aleksander; Aleksandrzak-Piekarczyk, Tamara; Szatraj, Katarzyna; Zdanowski, Marek K</p> <p>2015-09-01</p> <p>Surface ice and cryoconite holes of two types of polythermal Svalbard <span class="hlt">Glaciers</span> (Hans <span class="hlt">Glacier</span>--grounded tidewater <span class="hlt">glacier</span> and Werenskiold <span class="hlt">Glacier</span>-land-based valley <span class="hlt">glacier</span>) were investigated in terms of chemical composition, microbial abundance and diversity. Gathered data served to describe supraglacial habitats and to compare microbe-environment interactions on those different type <span class="hlt">glaciers</span>. Hans <span class="hlt">Glacier</span> samples displayed elevated nutrient levels (DOC, nitrogen and seston) compared to Werenskiold <span class="hlt">Glacier</span>. Adjacent tundra formations, bird nesting sites and marine aerosol were candidates for allochtonic enrichment sources. Microbial numbers were comparable on both <span class="hlt">glaciers</span>, with surface ice containing cells in the range of 10(4) mL(-1) and cryoconite sediment 10(8) g(-1) dry weight. Denaturating gradient gel electrophoresis band-based clustering revealed differences between <span class="hlt">glaciers</span> in terms of dominant bacterial taxa structure. Microbial community on Werenskiold <span class="hlt">Glacier</span> benefited from the snow-released substances. On Hans <span class="hlt">Glacier</span>, this effect was not as pronounced, affecting mainly the photoautotrophs. Over-fertilization of Hans <span class="hlt">Glacier</span> surface was proposed as the major factor, desensitizing the microbial community to the snow <span class="hlt">melt</span> event. Nitrogen emerged as a limiting factor in surface ice habitats, especially to Eukaryotic algae.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRB..119.2504Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRB..119.2504Y"><span>Evaluation of <span class="hlt">glacier</span> changes in high-mountain Asia based on 10 year GRACE RL05 models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yi, Shuang; Sun, Wenke</p> <p>2014-03-01</p> <p>In this paper, 10 years of time-variable gravity data from the Gravity Recovery and Climate Experiment Release 05 have been used to evaluate the <span class="hlt">glacier</span> <span class="hlt">melting</span> rate in high-mountain Asia (HMA) using a new computing scheme, i.e., the Space Domain Inverse method. We find that in HMA area, there are three different kinds of signal sources that should be treated together. The two generally accepted sources, <span class="hlt">glacier</span> <span class="hlt">melting</span> and India underground water depletion, are estimated to change at the rate of -35.0 ± 5.8 Gt/yr (0.09 mm/yr sea level rising) and -30.6 ± 5.0 Gt/yr, respectively. The third source is the remarkable positive signal (+30 Gt/yr) in the inner Tibetan Plateau, which is challenging to explain. Further, we have found that there is a 5 year undulation in Pamir and Karakoram, which can explain the controversies of the previous studies on the <span class="hlt">glacier</span> <span class="hlt">melting</span> rate here. This 5 year signal can be explained by the influence of Arctic Oscillation and El Niño-Southern Oscillation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1513236H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1513236H"><span>Climate sensitivity of Tibetan Plateau <span class="hlt">glaciers</span> - past and future implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heyman, Jakob; Hubbard, Alun; Stroeven, Arjen P.; Harbor, Jonathan M.</p> <p>2013-04-01</p> <p>The Tibetan Plateau is one of the most extensively glaciated, non-Polar regions of the world, and its mountain <span class="hlt">glaciers</span> are the primary source of <span class="hlt">melt</span> water for several of the largest Asian rivers. During glacial cycles, Tibetan Plateau <span class="hlt">glaciers</span> advanced and retreated multiple times, but remained restricted to the highest mountain areas as valley <span class="hlt">glaciers</span> and ice caps. Because <span class="hlt">glacier</span> extent is dominantly controlled by climate, the past extent of Tibetan <span class="hlt">glaciers</span> provide information on regional climate. Here we present a study analyzing the past maximum extents of <span class="hlt">glaciers</span> on the Tibetan Plateau with the output of a 3D <span class="hlt">glacier</span> model, in an effort to quantify Tibetan Plateau climate. We have mapped present-day <span class="hlt">glaciers</span> and glacial landforms deposited by formerly more extensive <span class="hlt">glaciers</span> in eight mountain regions across the Tibetan Plateau, allowing us to define present-day and past maximum <span class="hlt">glacier</span> outlines. Using a high-resolution (250 m) higher-order <span class="hlt">glacier</span> model calibrated against present-day <span class="hlt">glacier</span> extents, we have quantified the climate perturbations required to expand present-day <span class="hlt">glaciers</span> to their past maximum extents. We find that a modest cooling of at most 6°C for a few thousand years is enough to attain past maximum extents, even with 25-75% precipitation reduction. This evidence for limited cooling indicates that the temperature of the Tibetan Plateau remained relatively stable over Quaternary glacial cycles. Given the significant sensitivity to temperature change, the expectation is perhaps that a future warmer climate might result in intense <span class="hlt">glacier</span> reduction. We have tested this hypothesis and modeled the future <span class="hlt">glacier</span> development for the three mountain regions with the largest present-day <span class="hlt">glacier</span> cover using a projected warming of 2.8 to 6.2°C within 100 years (envelope limits from IPCC). These scenarios result in dramatic <span class="hlt">glacier</span> reductions, including 24-100% ice volume loss after 100 years and 77-100% ice volume loss after 300 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A43M..04Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A43M..04Y"><span><span class="hlt">Glaciers</span> bring more precipitation over south slope of the Himalayas and less moisture to the Tibetan Plateau</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, K.; Lin, C.; Chen, D.</p> <p>2017-12-01</p> <p>Due to the warming climate, significant retreat of <span class="hlt">glaciers</span> in the Himalayan region is observed. Thus, it is crucial to understand whether and how the <span class="hlt">glaciers</span> impact (feedback to) regional climate. Due to lack of observational data, most processes with <span class="hlt">glaciers</span> are however not well documented. For instance, convergence takes place when summertime upslope flows of warm and moist air masses meet cool and dry katabatic winds over a <span class="hlt">glacier</span> slope, which may <span class="hlt">induce</span> local convections and precipitations. This work intends to test this hypothesis according to an experiment conducted with the Weather Research and Forecasting (WRF) Model focusing on the Himalayan region. Three cases are designed for the experiment: a) a normal run as the control case; b) a sensitive run with land use ice/snow replaced by bare ground tundra and the maximum snow albedo set to 0.25; and c) a sensitive run with land use ice/snow replaced by bare ground tundra and no new snowing. According to differences between the control case and both the two sensitive cases, here we found that <span class="hlt">glaciers</span> overall leads to less precipitation over <span class="hlt">glacier</span>-covered areas and north of the Himalayas, which can be attributed to the suppressing of cooling <span class="hlt">glacier</span> surfaces to upslope moist flows. By contrast, a zone of extra more precipitation (that can be up to 200 mm for JJA) is clearly found over the south slope of the Himalayas at elevation of 4-5 km where it meets the <span class="hlt">glacier</span> terminus, accompanied with the convergence of upslope air masses and katabatic winds. Case b) reflects a smaller such effect when compared to case c), possibly because it takes a portion of energy for ice/snow <span class="hlt">melting</span>. When it comes to impacts on water vapor transport, <span class="hlt">glaciers</span> will result approximately 2% less moisture flowing into the Tibetan Plateau.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A43M..04Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A43M..04Y"><span><span class="hlt">Glaciers</span> bring more precipitation over south slope of the Himalayas and less moisture to the Tibetan Plateau</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yee, L.; Isaacman-VanWertz, G. A.; Wernis, R. A.; Kreisberg, N. M.; Upshur, M. A.; Thomson, R. J.; Geiger, F.; Bering, M. S.; Glasius, M.; Offenberg, J. H.; Lewandowski, M.; Liu, Y.; McKinney, K. A.; de Sá, S. S.; Martin, S. T.; Alexander, M. L. L.; Palm, B. B.; Jimenez, J. L.; Brito, J.; Artaxo, P.; Hu, W.; Campuzano-Jost, P.; Day, D.; Viegas, J.; Manzi, A. O.; Oliveira, M. B.; de Souza, R.; Machado, L.; Longo, K.; Hering, S. V.; Goldstein, A. H.</p> <p>2016-12-01</p> <p>Due to the warming climate, significant retreat of <span class="hlt">glaciers</span> in the Himalayan region is observed. Thus, it is crucial to understand whether and how the <span class="hlt">glaciers</span> impact (feedback to) regional climate. Due to lack of observational data, most processes with <span class="hlt">glaciers</span> are however not well documented. For instance, convergence takes place when summertime upslope flows of warm and moist air masses meet cool and dry katabatic winds over a <span class="hlt">glacier</span> slope, which may <span class="hlt">induce</span> local convections and precipitations. This work intends to test this hypothesis according to an experiment conducted with the Weather Research and Forecasting (WRF) Model focusing on the Himalayan region. Three cases are designed for the experiment: a) a normal run as the control case; b) a sensitive run with land use ice/snow replaced by bare ground tundra and the maximum snow albedo set to 0.25; and c) a sensitive run with land use ice/snow replaced by bare ground tundra and no new snowing. According to differences between the control case and both the two sensitive cases, here we found that <span class="hlt">glaciers</span> overall leads to less precipitation over <span class="hlt">glacier</span>-covered areas and north of the Himalayas, which can be attributed to the suppressing of cooling <span class="hlt">glacier</span> surfaces to upslope moist flows. By contrast, a zone of extra more precipitation (that can be up to 200 mm for JJA) is clearly found over the south slope of the Himalayas at elevation of 4-5 km where it meets the <span class="hlt">glacier</span> terminus, accompanied with the convergence of upslope air masses and katabatic winds. Case b) reflects a smaller such effect when compared to case c), possibly because it takes a portion of energy for ice/snow <span class="hlt">melting</span>. When it comes to impacts on water vapor transport, <span class="hlt">glaciers</span> will result approximately 2% less moisture flowing into the Tibetan Plateau.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28925251','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28925251"><span>Understanding and Predicting the Fate of Semivolatile Organic Pesticides in a <span class="hlt">Glacier</span>-Fed Lake Using a Multimedia Chemical Fate Model.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wu, Xiaolin; Davie-Martin, Cleo L; Steinlin, Christine; Hageman, Kimberly J; Cullen, Nicolas J; Bogdal, Christian</p> <p>2017-10-17</p> <p><span class="hlt">Melting</span> <span class="hlt">glaciers</span> release previously ice-entrapped chemicals to the surrounding environment. As <span class="hlt">glacier</span> <span class="hlt">melting</span> accelerates under future climate warming, chemical release may also increase. This study investigated the behavior of semivolatile pesticides over the course of one year and predicted their behavior under two future climate change scenarios. Pesticides were quantified in air, lake water, glacial meltwater, and streamwater in the catchment of Lake Brewster, an alpine <span class="hlt">glacier</span>-fed lake located in the Southern Alps of New Zealand. Two historic-use pesticides (endosulfan I and hexachlorobenzene) and three current-use pesticides (dacthal, triallate, and chlorpyrifos) were frequently found in both air and water samples from the catchment. Regression analysis indicated that the pesticide concentrations in glacial meltwater and lake water were strongly correlated. A multimedia environmental fate model was developed for these five chemicals in Brewster Lake. Modeling results indicated that seasonal lake ice cover <span class="hlt">melt</span>, and varying contributions of input from glacial <span class="hlt">melt</span> and streamwater, created pulses in pesticide concentrations in lake water. Under future climate scenarios, the concentration pulse was altered and glacial <span class="hlt">melt</span> made a greater contribution (as mass flux) to pesticide input in the lake water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A53I..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A53I..05S"><span>The role of turbulent fluxes in the atmospheric boundary layer above a debris-covered <span class="hlt">glacier</span> in the Himalayas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steiner, J. F.; Stigter, E.; Litt, M.; Shea, J.; Bierkens, M. F.; Immerzeel, W. W.</p> <p>2017-12-01</p> <p>Debris-covered <span class="hlt">glaciers</span> play an important role in the water cycle in high altitude catchments in the Himalaya. The <span class="hlt">melt</span> dynamics of these <span class="hlt">glaciers</span> are complex as a result of the debris. A thin debris layer (up to a few cm) may act as a facilitator of <span class="hlt">melt</span>, whereas a thick layer serves primarily as an insulator. The debris cover itself shows a strong diurnal variation in temperature and humidity resulting in a complex interaction with the atmospheric boundary layer (ABL). Energy balance models are a common way to quantify sub-debris <span class="hlt">melt</span>, but the importance of turbulent fluxes in this energy balance have so far been poorly investigated. We hypothesize that they may play a substantial role during phases of wetting and drying. In this study, ABL characteristics and surface turbulent fluxes are measured using an automatic weather station including an eddy-correlation (EC) system on the debris-covered Lirung <span class="hlt">glacier</span> in Nepal over a 10 day period in late 2016, during the transition period from monsoon to the drier post-monsoon. The measurements are combined with surface temperature measurements and thermal UAV flights covering the footprint area of the EC tower to quantify the surface fluxes over a larger area. Our results show that turbulent fluxes do play a substantial role in the energy balance of debris-covered <span class="hlt">glaciers</span>, and need to be accounted for to accurately simulate <span class="hlt">glacier</span> <span class="hlt">melt</span>. The EC tower results are subsequently evaluated against a number of different bulk approaches to quantify sensible and latent heat fluxes and are evaluated against turbulence characteristics. If found accurate enough, these approaches require less advanced measurement set-ups and can be applied on a wider scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C31C..04J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C31C..04J"><span>Mechanisms that Amplify, Attenuate and Deviate <span class="hlt">Glacier</span> Response to Climate Change in Central East Greenland. (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiskoot, H.</p> <p>2013-12-01</p> <p> only pose problems for the direct interpretation of climate change from length and volume changes due to their dynamically-driven advance and retreat regimes, but also for the reconstruction of LIA extents from trimlines and moraines, and the reconstruction of surface mass balance due to crevasses, potholes or debris-cover. This presentation will address a range of MAAD, including thermal regime transitions; ocean influences on tidewater-terminating <span class="hlt">glaciers</span>; <span class="hlt">glacier</span> fragmentation and tributary-trunk interaction; <span class="hlt">glacier</span> surging and tidewater behaviour; seasonal variations; <span class="hlt">glacier</span> hypsometry and morphology; terrain and substrate; <span class="hlt">melt</span>-albedo and <span class="hlt">melt</span>-ice flow feedbacks; and ice marginal lakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27638795','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27638795"><span>Do morphometric parameters and geological conditions determine chemistry of <span class="hlt">glacier</span> surface ice? Spatial distribution of contaminants present in the surface ice of Spitsbergen <span class="hlt">glaciers</span> (European Arctic).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lehmann, Sara; Gajek, Grzegorz; Chmiel, Stanisław; Polkowska, Żaneta</p> <p>2016-12-01</p> <p>The chemism of the <span class="hlt">glaciers</span> is strongly determined by long-distance transport of chemical substances and their wet and dry deposition on the <span class="hlt">glacier</span> surface. This paper concerns spatial distribution of metals, ions, and dissolved organic carbon, as well as the differentiation of physicochemical parameters (pH, electrical conductivity) determined in ice surface samples collected from four Arctic <span class="hlt">glaciers</span> during the summer season in 2012. The studied <span class="hlt">glaciers</span> represent three different morphological types: ground based (Blomlibreen and Scottbreen), tidewater which evolved to ground based (Renardbreen), and typical tidewater <span class="hlt">glacier</span> (Recherchebreen). All of the <span class="hlt">glaciers</span> are functioning as a glacial system and hence are subject to the same physical processes (<span class="hlt">melting</span>, freezing) and the process of ice flowing resulting from the cross-impact force of gravity and topographic conditions. According to this hypothesis, the article discusses the correlation between morphometric parameters, changes in mass balance, geological characteristics of the <span class="hlt">glaciers</span> and the spatial distribution of analytes on the surface of ice. A strong correlation (r = 0.63) is recorded between the aspect of <span class="hlt">glaciers</span> and values of pH and ions, whereas dissolved organic carbon (DOC) depends on the minimum elevation of <span class="hlt">glaciers</span> (r = 0.55) and most probably also on the development of the accumulation area. The obtained results suggest that although certain morphometric parameters largely determine the spatial distribution of analytes, also the geology of the bed of <span class="hlt">glaciers</span> strongly affects the chemism of the surface ice of <span class="hlt">glaciers</span> in the phase of strong recession.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41A1171B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41A1171B"><span>Evolution of Pine Island <span class="hlt">Glacier</span> subglacial conditions in response to 18 years of ice flow acceleration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brisbourne, A.; Bougamont, M. H.; Christoffersen, P.; Cornford, S. L.; Nias, I.; Vaughan, D.; Smith, A.</p> <p>2017-12-01</p> <p>Antarctica's main contribution to sea-level rise originates from the Amundsen Coast, when warm ocean water intrudes onto the continental shelf. As a result, strong <span class="hlt">melting</span> beneath the ice shelves <span class="hlt">induces</span> thinning near the grounding line of <span class="hlt">glaciers</span>, which is ensued by large ice flow speed up diffusing rapidly inland. In particular, ice loss from Pine Island <span class="hlt">Glacier</span> (PIG) accounts for 20% of the total ice loss in West Antarctica, amounting to 0.12 mm yr-1 of global sea-level rise. Forecasting the future flow of Amundsen Coast <span class="hlt">glaciers</span> is however hindered by large uncertainties regarding how the thinning initiated at the grounding line is transmitted upstream, and how the grounded flow will ultimately respond. This work aims at elucidating the role of subglacial processes beneath PIG tributaries in modulating the ice flow response to frontal perturbations. We used the Community Ice Sheet Model (CISM 2.0) to perform numerical inversions of PIG surface velocity as observed in 1996 and 2014. Over that time period, ice flow acceleration has been widespread over PIG's basin, and the inversions provide insights into the related evolution of the basal thermal and stress conditions. We assume the latter to be directly related to changes in the properties of a soft sediment (till) layer known to exist beneath PIG. We find that the overall bed strength has weakened by 18% in the region of enhanced flow, and that the annual <span class="hlt">melt</span> production for PIG catchment increased by 25% between 1996 and 2014. Specifically, regions of high <span class="hlt">melt</span> production are located in the southern tributaries, where the overall stronger bed allows for more frictional <span class="hlt">melting</span>. However, we find no significant and widespread change in the basal strength of that region, and we infer that the water produced is transported away in a concentrated hydrological system, without much interaction with the till layer. In contrast, we find that relatively less basal <span class="hlt">melting</span> occurs elsewhere in the catchment, where the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140006603','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140006603"><span>Rift in Antarctic <span class="hlt">Glacier</span>: a Unique Chance to Study Ice Shelf Retreat</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Howat, Ian M.; Jezek, Ken; Studinger, Michael; Macgregor, Joseph A.; Paden, John; Floricioiu, Dana; Russell, Rob; Linkswiler, Matt; Dominguez, Roseanne T.</p> <p>2012-01-01</p> <p>It happened again, but this time it was caught in the act. During the last week of September 2011 a large transverse rift developed across thefloating terminus of West Antarcticas PineIsland <span class="hlt">Glacier</span>, less than 5 years after its lastlarge calving event, in 2007 (Figure 1). PineIsland <span class="hlt">Glaciers</span> retreat has accelerated substantiallyin the past 2 decades, and it is nowlosing 50 gigatons of ice per year, or roughly 25 of Antarcticas total annual contributionto sea level rise [Rignot et al., 2008]. The <span class="hlt">glaciers</span> recent accelerated retreat is likely triggered by ocean warming and increased submarine <span class="hlt">melting</span>. As such, it is of significant interest to glaciologists and of heightened societal relevance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AtmEn.138..114D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AtmEn.138..114D"><span>Individual particles of cryoconite deposited on the mountain <span class="hlt">glaciers</span> of the Tibetan Plateau: Insights into chemical composition and sources</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dong, Zhiwen; Qin, Dahe; Kang, Shichang; Liu, Yajun; Li, Yang; Huang, Jie; Qin, Xiang</p> <p>2016-08-01</p> <p> influenced by large deserts in central Asia. Therefore, the transport and deposition of cryoconite is of great significance for understanding regional atmospheric environment and circulation. Large amounts of biological, NaCl and MCS particles were observed in the cryoconite, implying that in addition to dust and BC, many types of light absorbing impurities (LAI) together could influence the <span class="hlt">glacier</span> albedo change and <span class="hlt">induce</span> ice <span class="hlt">melting</span> in the mountain <span class="hlt">glaciers</span> of the Tibetan Plateau. Moreover, a high BC concentration in the south (e.g., YL and ZD) could significantly change the albedo of snow and ice, at a greater rate than dust, causing significant <span class="hlt">melting</span> of the <span class="hlt">glaciers</span> under global warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.C44A..01D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.C44A..01D"><span>WCRP's Climate and Cryosphere (CliC) Project: Climate Change and Middle and Low Latitude <span class="hlt">Glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dick, C. A.; Clic Project, W.</p> <p>2004-12-01</p> <p>The newest World Climate Research Programme (WCRP) Core Project, the Climate and Cryosphere (CliC) Project, is concerned with all aspects of the interactions between the cryosphere and climate. The cryosphere, defined as those portions of the Earth's surface where water exists in solid form, is an integral part of the climate system, both responding to, and influencing climate change. The cryosphere also provides many of the best indicators of climate variability and change. In addition to a range of direct physical indicators (e.g., snow/sea ice/<span class="hlt">glacier</span> extent and thickness, river and lake freeze-up/break-up dates, etc.), ice cores from <span class="hlt">glaciers</span>, ice caps and ice sheets have been shown to contain a wealth of information about past climate and environmental conditions. Ice cores are of particular value, since they often come from areas that are remote and poorly observed, yet have a major effect on the climate of the rest of the globe. General Circulation Models (GCMs) usually predict that the Earth's polar regions will warm fastest with the increasing levels of atmospheric greenhouse gases. However, models also indicate that continental interiors should warm more quickly than marine areas at non-polar latitudes. In fact, while some areas in the Arctic and Antarctic have warmed rapidly over the last few decades, it has generally been in the middle and low latitudes that the greatest effects of climate change have been observed. Particularly obvious has been the widespread retreat of <span class="hlt">glaciers</span>. This retreat, and the warming which it implies, will have not only important scientific consequences but also socio-economic consequences in areas where <span class="hlt">glacier</span> <span class="hlt">melt</span>-water is an important component of the water supply. <span class="hlt">Glaciers</span> preserve records of climate and the environment through both the isotopic composition of the water molecules, and through the chemicals 'trapped' in the snow, firn and ice layers. In polythermal (i.e., cold) <span class="hlt">glaciers</span> where only limited <span class="hlt">melt</span> occurs, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/wri/1998/4090/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/wri/1998/4090/report.pdf"><span>Water, ice, and meteorological measurements at South Cascade <span class="hlt">Glacier</span>, Washington, 1997 balance year</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Krimmel, Robert M.</p> <p>1998-01-01</p> <p>Winter snow accumulation and summer snow, firn, and ice <span class="hlt">melt</span> were measured at South Cascade <span class="hlt">Glacier</span>, Washington to determine the winter and net balances for the 1997 balance year. The 1997 winter balance, averaged over the <span class="hlt">glacier</span>, was 3.71 meters, and the net balance was 0.63 meter. The winter balance was the greatest since 1972 (4.27 meters), and the second largest since the record began in 1959. The net balance, which was positive for the second year in a row, was 1.57 meters greater than the 1977-96 average (-0.94 meter). Runoff was measured from the <span class="hlt">glacier</span> and an adjacent non-<span class="hlt">glacierized</span> basin. Air temperature and precipitation were measured nearby. This report makes these data available to the glaciological and climatological community.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915639P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915639P"><span>Chronological constraints on the Holocene <span class="hlt">glacier</span> dynamics of the Argentière <span class="hlt">Glacier</span> (Mont Blanc massif, France) based on cosmogenic nuclide dating</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Protin, Marie; Schimmelpfennig, Irene; Mugnier, Jean-Louis; Ravanel, Ludovic; Deline, Philip; Le Roy, Melaine; Moreau, Luc; Aster Team</p> <p>2017-04-01</p> <p>While reconstruction of <span class="hlt">glacier</span> fluctuations during the Holocene provides important information about the <span class="hlt">glacier</span> response to natural climate change, it is still a challenge to accurately constrain chronologies of past <span class="hlt">glacier</span> advances and retreats. Moraine deposits and roches moutonnées represent valuable geomorphic markers of advanced <span class="hlt">glacier</span> extensions, while the currently ongoing <span class="hlt">glacier</span> <span class="hlt">melt</span> uncovers proglacial bedrock that can be used as a new archive to investigate the durations when a <span class="hlt">glacier</span> was in retreated position during the Holocene. Our study focuses on the Mont-Blanc massif (MBM), located in the Western Alps and hosting some of the largest <span class="hlt">glaciers</span> of Europe. Chronologies of Holocene <span class="hlt">glacier</span> fluctuations in this area are still sparse, even if recent studies considerably improved the temporal reconstruction of Holocene advances of some <span class="hlt">glaciers</span> in the MBM and locations near-by (e.g. Le Roy et al., 2015). Here we present preliminary 10Be exposure ages obtained from moraine boulders, roches moutonnées and pro- and subglacial bedrock in the area of the Argentière <span class="hlt">Glacier</span>, located on the north-western flank of the MBM. The ages of moraine boulders and roche moutonnée surfaces outboard of the investigated moraines suggest that the Early Holocene deglaciation of this area started around 11 ka ago. Also, 10Be measurements of recently deglaciated bedrock surfaces indicate that the <span class="hlt">glacier</span> was at a position at least as retracted as today for a minimum duration of 7 ka throughout the Holocene. The 10Be measurement of one sample from a surface that is currently still covered by 60 m of ice suggests that the <span class="hlt">glacier</span> was shorter than today for at least a duration of 3 ka. These first results will soon be completed with in situ 14C measurements, which will allow us to quantify and take into account subglacial erosion rates and thus to more accurately determine the cumulative duration of pro- and subglacial bedrock exposure during the Holocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8585V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8585V"><span>Future streamflow droughts in <span class="hlt">glacierized</span> catchments: the impact of dynamic <span class="hlt">glacier</span> modelling and changing thresholds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Van Tiel, Marit; Van Loon, Anne; Wanders, Niko; Vis, Marc; Teuling, Ryan; Stahl, Kerstin</p> <p>2017-04-01</p> <p>In <span class="hlt">glacierized</span> catchments, snowpack and <span class="hlt">glaciers</span> function as an important storage of water and hydrographs of highly <span class="hlt">glacierized</span> catchments in mid- and high latitudes thus show a clear seasonality with low flows in winter and high flows in summer. Due to the ongoing climate change we expect this type of storage capacity to decrease with resultant consequences for the discharge regime. In this study we focus on streamflow droughts, here defined as below average water availability specifically in the high flow season, and which methods are most suitable to characterize future streamflow droughts as regimes change. Two <span class="hlt">glacierized</span> catchments, Nigardsbreen (Norway) and Wolverine (Alaska), are used as case study and streamflow droughts are compared between two periods, 1975-2004 and 2071-2100. Streamflow is simulated with the HBV light model, calibrated on observed discharge and seasonal <span class="hlt">glacier</span> mass balances, for two climate change scenarios (RCP 4.5 & RCP 8.5). In studies on future streamflow drought often the same variable threshold of the past has been applied to the future, but in regions where a regime shift is expected this method gives severe "droughts" in the historic high-flow period. We applied the new alternative transient variable threshold, a threshold that adapts to the changing hydrological regime and is thus better able to cope with this issue, but has never been thoroughly tested in <span class="hlt">glacierized</span> catchments. As the <span class="hlt">glacier</span> area representation in the hydrological modelling can also influence the modelled discharge and the derived streamflow droughts, we evaluated in this study both the difference between the historical variable threshold (HVT) and transient variable threshold (TVT) and two different <span class="hlt">glacier</span> area conceptualisations (constant area (C) and dynamical area (D)), resulting in four scenarios: HVT-C, HVT-D, TVT-C and TVT-D. Results show a drastic decrease in the number of droughts in the HVT-C scenario due to increased <span class="hlt">glacier</span> <span class="hlt">melt</span>. The deficit</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Geomo.287..116M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Geomo.287..116M"><span>Temporal dynamics of suspended sediment transport in a <span class="hlt">glacierized</span> Andean basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mao, Luca; Carrillo, Ricardo</p> <p>2017-06-01</p> <p>Suspended sediment transport can affect water quality and aquatic ecosystems, and its quantification is of the highest importance for river and watershed management. Suspended sediment concentration (SSC) and discharge were measured at two locations in the Estero Morales, a Chilean Andean stream draining a small basin (27 km2) hosting <span class="hlt">glacierized</span> areas of about 1.8 km2. Approximately half of the suspended sediment yield (470 t year- 1 km- 2) was transported during the snowmelt period and half during <span class="hlt">glacier</span> <span class="hlt">melting</span>. The hysteresis patterns between discharge and SSC were calculated for each daily hydrograph and were analysed to shed light on the location and activity of different sediment sources at the basin scale. During snowmelt, an unlimited supply of fine sediments is provided in the lower and middle part of the basin and hysteresis patterns tend to be clockwise as the peaks in SSC precede the peak of discharge in daily hydrographs. Instead, during <span class="hlt">glacier</span> <span class="hlt">melting</span> the source of fine sediments is the proglacial area, producing counterclockwise hysteresis. It is suggested that the analysis of hysteretic patterns over time provides a simple concept for interpreting variability of location and activity of sediment sources at the basin scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/120940-glacier-fluctuations-kenai-fjords-alaska-evaluation-controls-iceberg-calving-glaciers','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/120940-glacier-fluctuations-kenai-fjords-alaska-evaluation-controls-iceberg-calving-glaciers"><span><span class="hlt">Glacier</span> fluctuations in the Kenai Fjords, Alaska, U.S.A.: An evaluation of controls on Iceberg-calving <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Wiles, G.C.; Calkin, P.E.; Post, A.</p> <p></p> <p>The histories of four iceberg-calving outlet-<span class="hlt">glacier</span> systems in the Kenai Fjords National Park underscore the importance of fiord depth, sediment supply, and fiord geometry on <span class="hlt">glacier</span> stability. These parameters, in turn, limit the reliability of calving <span class="hlt">glacier</span> chronologies as records of climatic change. Tree-ring analysis together with radiocarbon dating show that the Northwestern and McCarty <span class="hlt">glaciers</span>, with large drainage basins, were advancing in concert with nearby land-terminating <span class="hlt">glaciers</span> about A.D. 600. After an interval of retreat and possible nonclimatically <span class="hlt">induced</span> extension during the Medieval Warm Period, these ice margins advanced again through the Little Ice Age and then retreated synchronouslymore » with the surrounding land-terminating <span class="hlt">glaciers</span> about A.D. 1900. In contrast, Holgate and Aialik <span class="hlt">glaciers</span>, with deeper fiords and smaller basins, retreated about 300 yr earlier. Reconstructions of Little Ice Age <span class="hlt">glaciers</span> suggest that equilibrium-line altitudes of Northwestern and McCarty <span class="hlt">glaciers</span> were, respectively, 270 and 500 m lower than now. Furthermore, the reconstructions show that these two <span class="hlt">glaciers</span> were climatically sensitive when at their terminal moranies. However, with ice margins at their present recessional positions and accumulation area ratios between 0.8 and 0.9, only McCarty <span class="hlt">Glacier</span> shows evidence of advance. Aialik and Holgate <span class="hlt">glaciers</span> were climatically insensitive during the Little Ice Age maxima and remain insensitive to climate. 40 refs., 7 figs., 2 tabs.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814340V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814340V"><span>Holocene record of <span class="hlt">glacier</span> variability from lake sediments reveals tripartite climate history for Svalbard</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van der Bilt, Willem; Bakke, Jostein; Vasskog, Kristian; D`Andrea, William; Bradley, Raymond; Olafsdottir, Sædis</p> <p>2016-04-01</p> <p>The Arctic is responding sensitively to ongoing global climate change, warming and moistening faster than any other region on the planet. Holocene proxy paleoclimate time series are increasingly used to put this amplified response in perspective by understanding Arctic climate processes beyond the instrumental period. <span class="hlt">Glaciers</span> rapidly respond to climate shifts as demonstrated by their current demise around the world. This response has a composite climate signature, marked by shifts in hydroclimate (winter precipitation) as well as (summer) temperature. Attendant changes in <span class="hlt">glacier</span> size are recorded by variations in glacigenic rock flour that may be deposited in downstream lakes. Here, we present a Holocene reconstruction of <span class="hlt">glacier</span> activity, based on sediments from Hajeren, a <span class="hlt">glacier</span>-fed lake on northwest Spitsbergen in the High Arctic Svalbard archipelago. Owing to undisturbed sediments and robust age control, we could resolve variability on a sub-centennial scale. To ensure the accurate detection of <span class="hlt">glacier</span> activity, we applied a toolbox of physical, magnetic and geochemical proxies in conjunction with multivariate statistics. Our findings indicate a three-stage Holocene climate history for Svalbard, driving by <span class="hlt">melt</span> water pulses, episodic Atlantic cooling and a decline in orbitally driven summer insolation. Correspondence between inferred advances, including a Holocene <span class="hlt">glacier</span> maximum around 9.5 ka BP, suggests forcing by the <span class="hlt">melting</span> LIS during the Early Holocene. Following a late Holocene Thermal Maximum around 7.4 ka BP, <span class="hlt">glaciers</span> disappeared from the catchment. <span class="hlt">Glaciers</span> reformed around 4.2 ka BP during the regional onset of the Neoglacial, supporting previous findings. This transition did, however, not mark the onset of persistent <span class="hlt">glacier</span> activity in the catchment, but a series of centennial-scale cycles of growth and decay, including events around 3.3 and 1.1 ka BP. As orbitally driven insolation declined towards the present, the glaciation threshold</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-GSFC_20171208_Archive_e000099.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-GSFC_20171208_Archive_e000099.html"><span>NASA-funded study says <span class="hlt">glacier</span> shape matters and influences vulnerability to <span class="hlt">melting</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-12-08</p> <p>A new NASA-funded study has identified which <span class="hlt">glaciers</span> in West Greenland are most susceptible to thinning in the coming decades by analyzing how they’re shaped. The research could help predict how much the Greenland Ice Sheet will contribute to future sea level rise in the next century, a number that currently ranges from inches to feet. “There are <span class="hlt">glaciers</span> that popped up in our study that flew under the radar until now,” said lead author Denis Felikson, a graduate research assistant at The University of Texas Institute for Geophysics (UTIG) and a Ph.D. student in The University of Texas Department of Aerospace Engineering and Engineering Mechanics. Felikson’s study was published in Nature Geoscience on April 17. Read more: go.nasa.gov/2pJJwNA Caption: Terminus of Kangerlugssuup Sermerssua <span class="hlt">glacier</span> in west Greenland Photo credit: Denis Felikson, Univ. of Texas NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2003/ofr-03-100/ofr-03-100.html','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2003/ofr-03-100/ofr-03-100.html"><span>Preliminary assessment of landslide-<span class="hlt">induced</span> wave hazards, Tidal Inlet, <span class="hlt">Glacier</span> Bay National Park, Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Wieczorek, Gerald F.; Jakob, Matthias; Motyka, Roman J.; Zirnheld, Sandra L.; Craw, Patricia</p> <p>2003-01-01</p> <p>A large potential rock avalanche above the northern shore of Tidal Inlet, <span class="hlt">Glacier</span> Bay National Park, Alaska, was investigated to determine hazards and risks of landslide-<span class="hlt">induced</span> waves to cruise ships and other park visitors. Field and photographic examination revealed that the 5 to 10 million cubic meter landslide moved between AD 1892 and 1919 after the retreat of Little Ice Age <span class="hlt">glaciers</span> from Tidal Inlet by AD 1890. The timing of landslide movement and the glacial history suggest that glacial debuttressing caused weakening of the slope and that the landslide could have been triggered by large earthquakes of 1899-1900 in Yakutat Bay. Evidence of recent movement includes fresh scarps, back-rotated blocks, and smaller secondary landslide movements. However, until there is evidence of current movement, the mass is classified as a dormant rock slump. An earthquake on the nearby active Fairweather fault system could reactivate the landslide and trigger a massive rock slump and debris avalanche into Tidal Inlet. Preliminary analyses show that waves <span class="hlt">induced</span> by such a landslide could travel at speeds of 45 to 50 m/s and reach heights up to 76 m with wave runups of 200 m on the opposite shore of Tidal Inlet. Such waves would not only threaten vessels in Tidal Inlet, but would also travel into the western arm of <span class="hlt">Glacier</span> Bay endangering large cruise ships and their passengers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9409F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9409F"><span>Sensitivity of <span class="hlt">glacier</span> mass balance and equilibrium line altitude to climatic change on King George Island, Antarctic Peninsula.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Falk, Ulrike; Lopez, Damian; Silva-Busso, Adrian</p> <p>2017-04-01</p> <p>The South Shetland Islands are located at the northern tip of the Antarctic Peninsula which is among the fastest warming regions on Earth. Surface air temperature increases (ca. 3 K in 50 years) are concurrent with retreating <span class="hlt">glacier</span> fronts, an increase in <span class="hlt">melt</span> areas, ice surface lowering and rapid break-up and disintegration of ice shelves. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to ±1.0 K/100 m), and a distinct spatial heterogeneity reflecting the impact of synoptic weather patterns especially during winter glacial mass accumulation periods. The increased mesocyclonic activity during the winter time in the study area results in intensified advection of warm, moist air with high temperatures and rain, and leads to <span class="hlt">melt</span> conditions on the ice cap, fixating surface air temperatures to the <span class="hlt">melting</span> point. The impact on winter accumulation results in even more negative mass balance estimates. Six years of glaciological measurements on mass balance stake transects are used with a <span class="hlt">glacier</span> <span class="hlt">melt</span> model to assess changes in <span class="hlt">melt</span> water input to the coastal waters, <span class="hlt">glacier</span> surface mass balance and the equilibrium line altitude. The average equilibrium line altitude (ELA) calculated from own glaciological observations for KGI over the time period 2010 - 2015 amounts to ELA=330±100 m. Published studies suggest rather stable condition slightly negative <span class="hlt">glacier</span> mass balance until the mid 80's with an ELA of approx. 150 m. The calculated accumulation area ratio suggests rather dramatic changes in extension of the inland ice cap for the South Shetland Islands until an equilibrium with concurrent climate conditions is reached.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22519575','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22519575"><span>Mercury distribution and deposition in <span class="hlt">glacier</span> snow over western China.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Qianggong; Huang, Jie; Wang, Feiyue; Mark, Loewen; Xu, Jianzhong; Armstrong, Debbie; Li, Chaoliu; Zhang, Yulan; Kang, Shichang</p> <p>2012-05-15</p> <p>Western China is home to the largest aggregate of <span class="hlt">glaciers</span> outside the polar regions, yet little is known about how the <span class="hlt">glaciers</span> in this area affect the transport and cycling of mercury (Hg) regionally and globally. From 2005 to 2010, extensive <span class="hlt">glacier</span> snow sampling campaigns were carried out in 14 snowpits from 9 <span class="hlt">glaciers</span> over western China, and the vertical distribution profiles of Hg were obtained. The Total Hg (THg) concentrations in the <span class="hlt">glacier</span> snow ranged from <1 to 43.6 ng L(-1), and exhibited clear seasonal variations with lower values in summer than in winter. Spatially, higher THg concentrations were typically observed in <span class="hlt">glacier</span> snows from the northern region where atmospheric particulate loading is comparably high. <span class="hlt">Glacier</span> snowpit Hg was largely dependent on particulate matters and was associated with particulate Hg, which is less prone to postdepositional changes, thus providing a valuable record of atmospheric Hg deposition. Estimated atmospheric Hg depositional fluxes ranged from 0.74 to 7.89 μg m(-2) yr(-1), agreeing very well with the global natural values, but are one to two orders of magnitude lower than that of the neighboring East Asia. Elevated Hg concentrations were observed in refrozen ice layers in several snowpits subjected to intense <span class="hlt">melt</span>, indicating that Hg can be potentially released to meltwater.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70026311','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70026311"><span>An integrated geospatial approach to monitoring the Bering <span class="hlt">Glacier</span> system, Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Josberger, E.G.; Payne, J.; Savage, S.; Shuchman, R.; Meadows, G.</p> <p>2004-01-01</p> <p>The Bering <span class="hlt">Glacier</span> is the largest and longest <span class="hlt">glacier</span> in continental North America, with an area of approximately 5,175 km2, and a length of 190 km. It is also the largest surging <span class="hlt">glacier</span> in America, having surged at least five times during the twentieth century. The last surge of the Bering <span class="hlt">Glacier</span> occurred in 1993-1995, since then, the <span class="hlt">glacier</span> has undergone constant and significant retreat thereby expanding the boundaries of Vitus Lake and creating a highly dynamic system, both ecologically and hydrologically. This study utilized GIS to integrate remote sensing observations, with detailed bathymetric, hydrographic and in situ water quality measurements of the rapidly expanding Vitus Lake. Vitus Lake has nearly doubled in surface area from 58.4 km2 to 108.8 km2, with a corresponding increase in water volume from 6.1 km3 to 10.5 km3 over the same period. The remote sensing observations were used to direct a systematic bathymetric, hydrographic and water quality measurement survey in Vitus Lake which revealed a complex three dimensional structure that is the result of sea water inflow, convection generated by ice <span class="hlt">melting</span> and the injection of fresh water from beneath the <span class="hlt">glacier</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMNG33A0192G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMNG33A0192G"><span>Inferring Ice Thickness from a <span class="hlt">Glacier</span> Dynamics Model and Multiple Surface Datasets.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guan, Y.; Haran, M.; Pollard, D.</p> <p>2017-12-01</p> <p>The future behavior of the West Antarctic Ice Sheet (WAIS) may have a major impact on future climate. For instance, ice sheet <span class="hlt">melt</span> may contribute significantly to global sea level rise. Understanding the current state of WAIS is therefore of great interest. WAIS is drained by fast-flowing <span class="hlt">glaciers</span> which are major contributors to ice loss. Hence, understanding the stability and dynamics of <span class="hlt">glaciers</span> is critical for predicting the future of the ice sheet. <span class="hlt">Glacier</span> dynamics are driven by the interplay between the topography, temperature and basal conditions beneath the ice. A <span class="hlt">glacier</span> dynamics model describes the interactions between these processes. We develop a hierarchical Bayesian model that integrates multiple ice sheet surface data sets with a <span class="hlt">glacier</span> dynamics model. Our approach allows us to (1) infer important parameters describing the <span class="hlt">glacier</span> dynamics, (2) learn about ice sheet thickness, and (3) account for errors in the observations and the model. Because we have relatively dense and accurate ice thickness data from the Thwaites <span class="hlt">Glacier</span> in West Antarctica, we use these data to validate the proposed approach. The long-term goal of this work is to have a general model that may be used to study multiple <span class="hlt">glaciers</span> in the Antarctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSM.B23B..06X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSM.B23B..06X"><span>Molecular Characterization of Cryoconite Organic Matter from the Athabasca <span class="hlt">Glacier</span>, Canadian Rocky Mountains</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Y.; Simpson, M. J.; Eyles, N.; Simpson, A.; Baer, A. J.</p> <p>2009-05-01</p> <p>Cryoconite is a dark-colored, dust-like material found on the surfaces of <span class="hlt">glaciers</span>. Cryoconite holes, which are produced by accelerated ice <span class="hlt">melt</span> due to more solar <span class="hlt">radiation</span> absorption by cryoconite than bare ice, act as habitats for microbial life and biologically mediated chemical reactions on otherwise relatively inert <span class="hlt">glacier</span> surfaces. Cryoconite holes may behave as bacterial shelters during "Snowball Earth" events postulated for the Neoproterozoic Earth. In this study organic matter (OM) biomarkers and a host of one- and two-dimensional NMR techniques were used to characterize cryoconite organic matter (COM) collected from the Athabasca <span class="hlt">Glacier</span> in the Canadian Rocky Mountains. Solvent extracts contain large quantities of fatty acids, n-alkanols, n- alkanes, wax esters and sterols. A large contribution of C23 and C25 relative to C29 and C31 n-alkanes ([C23/(C23+C29)] = 0.51) suggests that allochthonous COM is derived mainly from lower order plants such as mosses and lichens. This is confirmed by the absence of lignin-derived phenols, a biomarker of terrestrial vascular plants, after copper (II) oxidation in extracts and NMR analyses of COM. Solution-state 1H NMR reveals prominent peptide/protein structures which are characteristic of microbial inputs, while solid-state 13C CP/MAS NMR analysis shows a very high alkyl/O-alkyl ratio (2.16), suggesting that COM is unique compared to organic matter found in nearby soils which have alkyl/O-alkyl ratio of ~0.39. Our NMR results suggest that COM is dominated by microbial-derived compounds, which is also confirmed by phospholipid fatty acid results (6,950µg/gOC) which show significant microbial contributions to COM primarily from bacteria and minor microeukaryotes. Both biomarker and NMR data suggest that COM likely supports active microbial communities on the Athabasca <span class="hlt">Glacier</span>. Given that such material is incorporated within the <span class="hlt">glacier</span> in the accumulation zone or flushed by meltwaters into subglacial environments</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.4086J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.4086J"><span>Field experiments to assess the effect of lithology and grain size on the ablation of debris covered <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Juen, M.; Mayer, C.; Lambrecht, A.; Wirbel, A.; Kueppers, U.</p> <p>2012-04-01</p> <p>Currently many <span class="hlt">glaciers</span> all over the world show negative mass balances. Because of the retreating ice masses, there is an increase of deglaciated slopes. In combination with increased <span class="hlt">melting</span> of permafrost these areas can become unstable and account for an additional supply of weathered bedrock and sediments onto the <span class="hlt">glacier</span> surface. Furthermore increasing ablation rates advance the <span class="hlt">melting</span> out and accumulation of englacial till on the <span class="hlt">glacier</span> surface. The experiment was performed during summer season 2010 at the middle tongue of Vernagtferner, a temperate <span class="hlt">glacier</span> in the Oetztal Alps, Austria. The experimental setup was designed in a way to monitor the parameters which are most crucial for controlling sub-debris ice <span class="hlt">melt</span> with regards to lithology, grain size and moisture content. Ten test plots were established with different debris grain sizes and debris thicknesses consisting of sieved natural material. The local metamorphic mica schist and volcanic debris were used for the experiment. Ablation was measured at stakes. Bare ice <span class="hlt">melt</span> was observed continuously with a sonic ranger. Three automatic weather stations were installed to record meteorological data. To obtain information concerning the internal temperature distribution of the debris cover, thermistors were installed at various depths. For each individual plot thermal conductivity and thermal diffusivity have been estimated. The observations during the season revealed a clear dependence of the sub-debris ice <span class="hlt">melt</span> on the layer thickness and the grain size. For the fine sand fraction the moisture content plays an important role, as these test fields were always water saturated. Highly porous volcanic material protects the ice much more effectively from <span class="hlt">melting</span> than similar layer thicknesses of the local mica schist. Also the albedo plays an important role, where <span class="hlt">melt</span> rates under dark debris are about 1.75 times higher than underneath brighter material. The analysis of thermal diffusivities indicates that lower</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5806186-ice-proximal-sediment-dynamics-effect-stability-muir-glacier-alaska-case-study-non-climatic-glacier-response','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5806186-ice-proximal-sediment-dynamics-effect-stability-muir-glacier-alaska-case-study-non-climatic-glacier-response"><span>Ice-proximal sediment dynamics and their effect on the stability of Muir <span class="hlt">Glacier</span>, Alaska: A case study of non-climatic <span class="hlt">glacier</span> response</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Hunter, L.E.; Powell, R.D.</p> <p>1992-01-01</p> <p>Recent studies have shown that water depth at tidewater termini affect calving rates and, therefore, <span class="hlt">glacier</span> mass balance and terminus stability. Grounding-line water depths are themselves governed by glacial and marine processes that interact during the formation of morainal bank depocenters. These morainal banks can fluctuate 10s of meters in height within an interval of a few weeks. Recent investigations in <span class="hlt">Glacier</span> Bay have focused on quantitatively assessing sediment budgets in the ice-proximal environment. The monitoring of morainal banks in upper Muir Inlet has included repeated bathymetric mapping, sediment trap studies, bottom grab sampling, <span class="hlt">glacier</span> and iceberg sampling, and submersiblemore » ROV investigations within 1 km of the terminus. Such relationships are important in interpreting recent changes in the dynamics of Muir <span class="hlt">Glacier</span> where a century of retreat has been succeeded by quasi stability. The new <span class="hlt">glacier</span> regime has accompanied basin infilling from approximately 100 m depth to a maximum of 52 m at the grounding line. Two large grounding-line fans have aggraded to deltas and reduced the length of the calving margin from 900 m to 290 m wide. These effects have reduced the ice flow velocities by 45%. Annual morainal bank growth ranged from 10[sup 6] to 10[sup 7] m[sup 3] and is the result of glacifluvial dumping, suspension settling from turbid overflow plumes, debris dumping from ice-cliff and iceberg <span class="hlt">melting</span>, <span class="hlt">glacier</span> squeezing and pushing of morainal bank sediment, and sediment gravity flow processes. Each of these processes are an integral facet of the morainal bank dynamics and <span class="hlt">glacier</span> response. These studies of Muir <span class="hlt">Glacier</span> indicate that <span class="hlt">glacier</span> response to sediment dynamics need to be addresses before climatic implications are made.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011aogs...22...91S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011aogs...22...91S"><span>Pattern of <span class="hlt">Glacier</span> Recession in Indian Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singh, Ajay; Patwardhan, Anand</p> <p></p> <p>All currently available climate models predict a near-surface warming trend under the influence of rising levels of greenhouse gases in the atmosphere. In addition to the direct effects on climate — for example, on the frequency of heat waves — this increase in surface temperatures has important consequences for the cryosphere subsequently hydrological cycle, particularly in regions where water supply is currently dominated by <span class="hlt">melting</span> snow or ice. The Indian Himalayan region occupies a special place in the mountain ecosystems of the world. These geodynamically young mountains are not only important from the standpoint of climate and as a provider of life, giving water to a large part of the Indian subcontinent, but they also harbor a rich variety of flora, fauna, human communities and cultural diversity. <span class="hlt">Glaciers</span> in this region are changing in area as well as in volume like those in other parts of the world. Studies have been carried out for recession in some of these <span class="hlt">glaciers</span> using remote sensing as well as field observation techniques. Spatiotemporal pattern in the recession rate of the studied <span class="hlt">glaciers</span> has been presented in this paper. Plausible causes for the recession have been also discussed. Finally, future scopes for observation and analysis in <span class="hlt">glaciers</span> recession have been suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171402','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171402"><span><span class="hlt">Glacier</span> Acceleration and Thinning after Ice Shelf Collapse in the Larsen B Embayment, Antarctica</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scambos, T. A.; Bohlander, J. A.; Shuman, C. A.; Skvarca, P.</p> <p>2004-01-01</p> <p>Ice velocities derived from five Landsat 7 images acquired between January 2000 and February 2003 show a two- to six-fold increase in centerline speed of four <span class="hlt">glaciers</span> flowing into the now-collapsed section of the Larsen B Ice Shelf. Satellite laser altimetry from ICEsat indicates the surface of Hektoria <span class="hlt">Glacier</span> lowered by up to 38 +/- 6 m a six-month period beginning one year after the break-up in March 2002. Smaller elevation losses are observed for Crane and Jorum <span class="hlt">glaciers</span> over a later 5-month period. Two <span class="hlt">glaciers</span> south of the collapse area, Flask and Leppard, show little change in speed or elevation. Seasonal variations in speed preceding the large post-collapse velocity increases suggest that both summer <span class="hlt">melt</span> percolation and changes in the stress field due to shelf removal play a major role in <span class="hlt">glacier</span> dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C44B..02G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C44B..02G"><span>Global <span class="hlt">glacier</span> and ice sheet surface velocities derived from 31 years of Landsat imagery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gardner, A. S.; Scambos, T. A.; Fahnestock, M. A.</p> <p>2016-12-01</p> <p><span class="hlt">Glaciers</span> and ice sheets are contributing substantial volumes of water to the world's oceans due to enhanced <span class="hlt">melt</span> resulting from changes in ocean and atmospheric conditions and respective feedbacks. Improving understanding of the processes leading to accelerated rates of ice loss is necessary for reducing uncertainties sea level projections. One key to doing this is to assemble and analyze long records of <span class="hlt">glacier</span> change that characterize grounded ice response to changes in driving stress, buttressing, and basal conditions. As part of the NASA funded GO_LIVE project we exploit 31 years of Landsat imagery to construct detailed time histories of global <span class="hlt">glacier</span> velocities. Early exploration of the dataset reveals the diversity of information to be gleaned: sudden tidewater <span class="hlt">glacier</span> speedups in the Antarctic Peninsula, rifting of Antarctic ice shelves, high variability in velocities near <span class="hlt">glacier</span> grounding lines, frequent surge activity in the mountainous regions of Alaska and High Mountain Asia, and the slowdown of land-terminating valley <span class="hlt">glaciers</span> in Arctic Canada and elsewhere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C34B..05N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C34B..05N"><span>Modeling the Spreading of Glacial <span class="hlt">Melt</span> Water from the Amundsen and Bellingshausen Seas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakayama, Y.; Timmermann, R.; Rodehacke, C. B.; Schröder, M.; Hellmer, H. H.</p> <p>2014-12-01</p> <p>The ice shelves and <span class="hlt">glaciers</span> of the West Antarctic Ice Sheet (WAIS) are rapidly thinning, especially in the Amundsen Sea (AS) and Bellingshausen Sea (BS). The high basal <span class="hlt">melting</span> of these small ice shelves is caused by relatively warm Circumpolar Deep Water (CDW) that, based on observations, mainly intrudes via two submarine glacial troughs located at the eastern and central AS continental shelf break. When CDW reaches the grounding line of the fringing <span class="hlt">glaciers</span>, it <span class="hlt">melts</span> the <span class="hlt">glaciers</span> and forms buoyant <span class="hlt">melt</span> water plumes. As the glacial <span class="hlt">melt</span> becomes part of the AS shelf circulation, it may cause a freshening of the shelf water locally as well as remotely in the Ross Sea (RS). To test whether the observed freshening of the RS is a consequence of the enhanced basal <span class="hlt">melting</span> of AS ice shelves, we use Finite-Element Sea-ice/ice-shelf/Ocean Model (FESOM) with a horizontal resolution of 2-10 km on the AS and BS continental shelves. The model is forced with 6-hourly atmospheric data from the National Centers for Environmental Prediction Climate Forecast System Reanalysis (NCEP-CFSR) for the period 1979-1988. The model results show bottom temperatures in the AS and BS close to observations, and basal <span class="hlt">melt</span> rates of AS and BS ice shelves consistent with other observation-based estimates. Using several independent virtual passive tracers to identify pathways of the glacial <span class="hlt">melt</span>, we find that the <span class="hlt">melt</span> water from the ice shelves in the AS flows towards the Ross Ice Shelf front. After 10 years of simulation, about half of the <span class="hlt">melt</span> water in the Ross Sea originates from the Getz Ice Shelf. Further, we investigate the sensitivity of the <span class="hlt">melt</span> water transport into the RS associated with the strength of the basal <span class="hlt">melt</span> water flux. When this flux is increased by 30%, the transport of glacial <span class="hlt">melt</span> into the RS more than doubles, supporting the idea that the basal <span class="hlt">melting</span> of AS and BS ice shelves is one of the main reasons for the freshening of the RS continental shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930022704&hterms=Antarctic+icebergs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DAntarctic%2Bicebergs','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930022704&hterms=Antarctic+icebergs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DAntarctic%2Bicebergs"><span>Recent acceleration of Thwaites <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ferrigno, J. G.</p> <p>1993-01-01</p> <p>The first velocity measurements for Thwaites <span class="hlt">Glacier</span> were made by R. J. Allen in 1977. He compared features of Thwaites <span class="hlt">Glacier</span> and Iceberg Tongue on aerial photography from 1947 and 1967 with 1972 Landsat images, and measured average annual displacements of 3.7 and 2.3 km/a. Using his photogrammetric experience and taking into consideration the lack of definable features and the poor control in the area, he estimated an average velocity of 2.0 to 2.9 km/a to be more accurate. In 1985, Lindstrom and Tyler also made velocity estimates for Thwaites <span class="hlt">Glacier</span>. Using Landsat imagery from 1972 and 1983, their estimates of the velocities of 33 points ranged from 2.99 to 4.02 km/a, with an average of 3.6 km/a. The accuracy of their estimates is uncertain, however, because in the absence of fixed control points, they assumed that the velocities of icebergs in the fast ice were uniform. Using additional Landsat imagery in 1984 and 1990, accurate coregistration with the 1972 image was achieved based on fixed rock points. For the period 1972 to 1984, 25 points on the <span class="hlt">glacier</span> surface ranged in average velocity from 2.47 to 2.76 km/a, with an overall average velocity of 2.62 +/- 0.02 km/a. For the period 1984 to 1990, 101 points ranged in velocity from 2.54 to 3.15 km/a, with an overall average of 2.84 km/a. During both time periods, the velocity pattern showed the same spatial relationship for three longitudinal paths. The 8-percent acceleration in a decade is significant. This recent acceleration may be associated with changes observed in this region since 1986. Fast ice <span class="hlt">melted</span> and several icebergs calved from the base of the Iceberg Tongue and the terminus of Thwaites <span class="hlt">Glacier</span>. However, as early as 1972, the Iceberg Tongue had very little contact with the <span class="hlt">glacier</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H11E1232K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H11E1232K"><span>Application of Temperature Index Model to Assess the Future Hydrological Regime of the <span class="hlt">Glacierized</span> Catchments in Nepal.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kayastha, R.; Kayastha, R. B.</p> <p>2017-12-01</p> <p>Unavailability of hydro meteorological data in the Himalayan regions is challenging on understanding the flow regimes. Temperature index model is simple yet the powerful glacio-hydrological model to simulate the discharge in the <span class="hlt">glacierized</span> basin. Modified Positive Degree Day (MPDD) Model Version 2.0 is a grid-ded based semi distributed model with baseflow module is a robust <span class="hlt">melt</span> modelling tools to estimate the discharge. MPDD model uses temperature and precipitation as a forcing datasets to simulate the discharge and also to obtain the snowmelt, icemelt, rain and baseflow contribution on total discharge. In this study two <span class="hlt">glacierized</span>, Marsyangdi and Langtang catchment were investigated for the future hydrological regimes. Marsyangdi encompasses an area of 4026.19 sq. km with 20% glaciated area, whereas Langtang catchment with area of 354.64 sq. km with 36% glaciated area is studied to examine for the future climatic scenarios. The model simulates discharge well for the observed period; (1992-1998) in Marsyangdi and from (2007-2013) in Langtang catchment. The Nash-Sutcliffe Efficiency (NSE) for the both catchment were above 0.75 with the volume difference less than - 8 %. The snow and ice <span class="hlt">melts</span> contribution in Marsyangdi were 4.7% and 10.2% whereas in Langtang the contribution is 15.3% and 23.4%, respectively. Rain contribution ( 40%) is higher than the baseflow contribution in total discharge in both basins. The future river discharge is also predicted using the future climate data from the regional climate models (RCMs) of CORDEX South Asia experiments for the medium stabilization scenario RCP4.5 and very high <span class="hlt">radiative</span> forcing scenario RCP8.5 after bias correction. The projected future discharge of both catchment shows slightly increase in both scenarios with increase of snow and ice <span class="hlt">melt</span> contribution on discharge. The result generated from the model can be utilized to understand the future hydrological regimes of the <span class="hlt">glacierized</span> catchment also the impact of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.water.usgs.gov/wri004265','USGSPUBS'); return false;" href="http://pubs.water.usgs.gov/wri004265"><span>Water, ice, meteorological, and speed measurements at South Cascade <span class="hlt">Glacier</span>, Washington, 1999 balance year</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Krimmel, Robert M.</p> <p>2001-01-01</p> <p>Winter snow accumulation and summer snow, firn, and ice <span class="hlt">melt</span> were measured at South Cascade <span class="hlt">Glacier</span>, Washington, to determine the winter and net balances for the 1999 balance year. The 1999 winter snow balance, averaged over the <span class="hlt">glacier</span>, was 3.59 meters, and the net balance was 1.02 meters. Since the winter balance record began in 1959, only three winters have had a higher winter balance. Since the net balance record began in 1953, only 2 years have had a greater positive net balance than 1999. Runoff was measured from the <span class="hlt">glacier</span> and an adjacent non-<span class="hlt">glacierized</span> basin. Air temperature, precipitation, and humidity were measured nearby, and ice speed was measured. This report makes these data available to the glaciological and climatological community.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.V31A3003S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.V31A3003S"><span>Using mineral geochemistry to decipher slab, mantle, and crustal inputs to the generation of high-Mg andesites from Mount Baker and <span class="hlt">Glacier</span> Peak, northern Cascade arc</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sas, M.; DeBari, S. M.; Clynne, M. A.; Rusk, B. G.</p> <p>2015-12-01</p> <p>A fundamental question in geology is whether subducting plates get hot enough to generate <span class="hlt">melt</span> that contributes to magmatic output in volcanic arcs. Because the subducting plate beneath the Cascade arc is relatively young and hot, slab <span class="hlt">melt</span> generation is considered possible. To better understand the role of slab <span class="hlt">melt</span> in north Cascades magmas, this study focused on petrogenesis of high-Mg andesites (HMA) and basaltic andesites (HMBA) from Mt. Baker and <span class="hlt">Glacier</span> Peak, Washington. HMA have unusually high Mg# relative to their SiO2 contents, as well as elevated La/Yb and Dy/Yb ratios that are interpreted to result from separation of <span class="hlt">melt</span> from a garnet-bearing residuum. Debate centers on the garnet's origin as it could be present in mineral assemblages from the subducting slab, deep mantle, thick lower crust, or basalt fractionated at high pressure. Whole rock analyses were combined with major, minor, and trace element analyses to understand the origin of these HMA. In the Tarn Plateau (Mt. Baker) flow unit (51.8-54.0 wt.% SiO2, Mg# 68-70) Mg#s correlate positively with high La/Yb in clinopyroxene equilibrium liquids, suggesting an origin similar to that of Aleutian adakites, where slab-derived <span class="hlt">melts</span> interact with the overlying mantle to become Mg-rich and subsequently mix with mantle-derived basalts. The source for high La/Yb in the <span class="hlt">Glacier</span> Creek (Mt. Baker) flow unit (58.3-58.7 wt.% SiO2, Mg# 63-64) is more ambiguous. High whole rock Sr/P imply origin from a mantle that was hydrated by an enriched slab component (fluid ± <span class="hlt">melt</span>). In the Lightning Creek (<span class="hlt">Glacier</span> Peak) flow unit (54.8-57.9 SiO2, Mg# 69-72) Cr and Mg contents in Cr-spinel and olivine pairs suggest a depleted mantle source, and high whole rock Sr/P indicate hydration-<span class="hlt">induced</span> mantle <span class="hlt">melting</span>. Hence Lightning Creek is interpreted have originated from a refractory mantle source that interacted with a hydrous slab component (fluid ± <span class="hlt">melt</span>). Our results indicate that in addition to slab-derived fluids, slab</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARR21012Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARR21012Z"><span>Effects of porosity on shock-<span class="hlt">induced</span> <span class="hlt">melting</span> of honeycomb-shaped Cu nanofoams</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Fengpeng</p> <p></p> <p>Metallic foams are of fundamental and applied interests in various areas, including structure engineering (e.g., lightweight structural members and energy absorbers), and shock physics (e.g., as laser ablators involving shock-<span class="hlt">induced</span> <span class="hlt">melting</span> and vaporization).Honeycomb-shaped metallic foams consist of regular array of hexagonal cells in two dimensions and have extensive applications and represent a unique, simple yet useful model structure for exploring mechanisms and making quantitative assessment. We investigate shock-<span class="hlt">induced</span> <span class="hlt">melting</span> in honeycomb-shaped Cu nanofoams with extensive molecular dynamics simulations. A total of ten porosities (phi) are explored, ranging from 0 to 0.9 at an increment of 0.1. Upon shock compression, void collapse <span class="hlt">induces</span> local <span class="hlt">melting</span> followed by supercooling for sufficiently high porosity at low shock strengths. While superheating of solid remnants occurs for sufficiently strong shocks at phi<0.1. Both supercooling of <span class="hlt">melts</span> and superheating of solid remnants are transient, and the equilibrated shock states eventually fall on the equilibrium <span class="hlt">melting</span> curve for partial <span class="hlt">melting</span>. However, phase equilibrium has not been achieved on the time scale of simulations in supercooled Cu liquid (from completely <span class="hlt">melted</span> nanofoams). The temperatures for incipient and complete <span class="hlt">melting</span> are related to porosity via a power law and approach the <span class="hlt">melting</span> temperature at zero pressure as phi tends to 1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B43B2115K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B43B2115K"><span>Compositionally heterogeneous dissolved organic matter reflects changing flowpaths in a large ice sheet catchment over the course of the <span class="hlt">melt</span> season at Leverett <span class="hlt">Glacier</span>, southwest Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kellerman, A.; Hawkings, J.; Marshall, M.; Spencer, R.; Wadham, J.</p> <p>2017-12-01</p> <p>The Greenland Ice Sheet (GrIS) is losing mass at a remarkable rate. This loss of mass coincides with the export of dissolved organic matter (DOM) and other nutrients from the ice sheet and exerts a primary control on secondary production in downstream ecosystems. However, little is known about the source and composition of DOM exported from these dilute, yet immense, systems. Samples were collected from May 11, 2015 to July 29, 2015 from the outflow of Leverett <span class="hlt">Glacier</span>, a large, land-terminating <span class="hlt">glacier</span> of the southwest GrIS. Dissolved organic carbon (DOC) concentrations were measured and the optical properties of DOM were characterized using absorbance and fluorescence spectroscopy. At the beginning of the season, when discharge is <5 m3 sec-1, red-shifted fluorescence suggests terrestrial inputs from either overridden soils or proglacial inputs dominate the DOM pool. With the onset of <span class="hlt">melt</span>, after an initial pulse in both DOC quantity and red-shifted fluorescence intensity, the DOC concentration and fluorescence intensity is diluted, with little change in DOM composition. The terrestrial signal is lost with the first outburst event in late June, and a single protein-like fluorophore is exhibited for three weeks. On July 10th, a fourth outburst event introduces a second protein-like fluorophore, indicative of production on the ice sheet, and this signature is maintained until the end of the July. These results suggest that subglaical drainage flowpaths and water source influence the exported DOC concentration and DOM composition over a summer <span class="hlt">melt</span> season. As glacial outflow shifts from higher DOC concentrations early in the season to low DOC concentrations later in the summer, these results impact estimates of carbon export from <span class="hlt">glaciers</span>. Furthermore, as composition is related to reactivity, the compositional changes observed may indicate shifts in the bioavailability of the DOM upon delivery to coastal systems, a result of changing DOM sources over the course of</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.C22A..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.C22A..03S"><span>Southern Alaska <span class="hlt">Glaciers</span>: Spatial and Temporal Variations in Ice Volume</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sauber, J.; Molnia, B. F.; Luthcke, S.; Rowlands, D.; Harding, D.; Carabajal, C.; Hurtado, J. M.; Spada, G.</p> <p>2004-12-01</p> <p>Although temperate mountain <span class="hlt">glaciers</span> comprise less than 1% of the <span class="hlt">glacier</span>-covered area on Earth, they are important because they appear to be <span class="hlt">melting</span> rapidly under present climatic conditions and, therefore, make significant contributions to rising sea level. In this study, we use ICESat observations made in the last 1.5 years of southern Alaska <span class="hlt">glaciers</span> to estimate ice elevation profiles, ice surface slopes and roughness, and bi-annual and/or annual ice elevation changes. We report initial results from the near coastal region between Yakutat Bay and Cape Suckling that includes the Malaspina and Bering <span class="hlt">Glaciers</span>. We show and interpret ice elevations changes across the lower reaches of the Bagley Ice Valley for the period between October 2003 and May 2004. In addition, we use off-nadir pointing observations to reference tracks over the Bering and Malaspina <span class="hlt">Glaciers</span> in order to estimate annual ice elevation change. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Shuttle Radar Topography Mission (SRTM) derived DEMs are used to estimate across track regional slopes between ICESat data acquisitions. Although the distribution and quantity of ICESat elevation profiles with multiple, exact repeat data is currently limited in Alaska, individual ICESat data tracks, provide an accurate reference surface for comparison to other elevation data (e.g. ASTER and SRTM X- and C-band derived DEMs). Specifically we report the elevation change over the Malaspina <span class="hlt">Glacier</span>'s piedmont lobe between a DEM derived from SRTM C-band data acquired in Feb. 2000 and ICESat Laser #2b data from Feb.-March 2004. We also report use of ICESat elevation data to enhance ASTER derived absolute DEMs. Mountain <span class="hlt">glaciers</span> generally have rougher surfaces and steeper regional slopes than the ice sheets for which the ICESat design was optimized. Therefore, rather than averaging ICESat observations over large regions or relying on crossovers, we are working with well-located ICESat</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41B1201N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41B1201N"><span>Features of the recovery process of the Kolka <span class="hlt">glacier</span> after the disaster of 2002</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nosenko, G.; Rototaeva, O.; Nikitin, S.</p> <p>2017-12-01</p> <p>There were events that attracted attention by the grand scale of the glacial catastrophe and its consequences in the North Ossetia (Caucasus Mountains) in 2002. The Kolka <span class="hlt">Glacier</span> was completely thrown out of its bed and formed a giant water-ice-stone flow, caused destruction and human deaths along the valley of the Genaldon River. The volcanic impact of Mount Kazbek was one of the key factors in this process. The recovery of a new <span class="hlt">glacier</span> in the empty circus of the Kolka <span class="hlt">glacier</span> began almost immediately. Currently, three streams of ice have closed in the rear zone of the circus, forming a joint ice massif on the bed. The dimensions of the <span class="hlt">glacier</span> vary under the influence of both new conditions for the accumulation and <span class="hlt">melting</span> of ice, and the features of the dynamics of the ice masses filling the vacated bed. This report describes the next stage of the state of the new Kolka <span class="hlt">glacier</span> - relative stabilization - and analyzes the features of the process of its recovery based on the field observations data, modern space images and the data of changes in summer air temperatures and winter precipitation on the <span class="hlt">glacier</span> area at the beginning of the 21st century. In recent years, the rate of increase in the area of the <span class="hlt">glacier</span> does not exceed 0.015 km2 per year. By September 2016, its area reached 1.11 km2, the volume - about 0.044 km3. The conditions for the formation of a new <span class="hlt">glacier</span> on the empty bottom of the circus differ significantly from the previous ones - when Kolka was restored in after a pulsation on the 1970s. In addition to increase in the summer air temperatures, the thermal balance in the circus has changed due to the increase of the open surface area of the bed and the lateral moraine. At the same time, the growth of the debris cover on the <span class="hlt">glacier</span> restrains the <span class="hlt">melting</span> process. Rockfalls and avalanches supply moraine material to the surface of the <span class="hlt">glacier</span> more intensively than in the 1970s. The conditions of accumulation also changed - the volume of food</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.G33A0983D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.G33A0983D"><span>Global Monitoring of Mountain <span class="hlt">Glaciers</span> Using High-Resolution Spotlight Imaging from the International Space Station</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Donnellan, A.; Green, J. J.; Bills, B. G.; Goguen, J.; Ansar, A.; Knight, R. L.; Hallet, B.; Scambos, T. A.; Thompson, L. G.; Morin, P. J.</p> <p>2013-12-01</p> <p>Mountain <span class="hlt">glaciers</span> around the world are retreating rapidly, contributing about 20% to present-day sea level rise. Numerous studies have shown that mountain <span class="hlt">glaciers</span> are sensitive to global environmental change. Temperate-latitude <span class="hlt">glaciers</span> and snowpack provide water for over 1 billion people. <span class="hlt">Glaciers</span> are a resource for irrigation and hydroelectric power, but also pose flood and avalanche hazards. Accurate mass balance assessments have been made for only 280 <span class="hlt">glaciers</span>, yet there are over 130,000 in the World <span class="hlt">Glacier</span> Inventory. The rate of <span class="hlt">glacier</span> retreat or advance can be highly variable, is poorly sampled, and inadequately understood. Liquid water from ice front lakes, rain, <span class="hlt">melt</span>, or sea water and debris from rocks, dust, or pollution interact with <span class="hlt">glacier</span> ice often leading to an amplification of warming and further <span class="hlt">melting</span>. Many mountain <span class="hlt">glaciers</span> undergo rapid and episodic events that greatly change their mass balance or extent but are sparsely documented. Events include calving, outburst floods, opening of crevasses, or iceberg motion. Spaceborne high-resolution spotlight optical imaging provides a means of clarifying the relationship between the health of mountain <span class="hlt">glaciers</span> and global environmental change. Digital elevation models (DEMs) can be constructed from a series of images from a range of perspectives collected by staring at a target during a satellite overpass. It is possible to collect imagery for 1800 targets per month in the ×56° latitude range, construct high-resolution DEMs, and monitor changes in high detail over time with a high-resolution optical telescope mounted on the International Space Station (ISS). Snow and ice type, age, and maturity can be inferred from different color bands as well as distribution of liquid water. Texture, roughness, albedo, and debris distribution can be estimated by measuring bidirectional reflectance distribution functions (BRDF) and reflectance intensity as a function of viewing angle. The non-sun-synchronous orbit</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.H21G1152G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.H21G1152G"><span>Changing Precipitation Patterns or Waning <span class="hlt">Glaciers</span>? Identifying Water Supply Vulnerabilities to Climate Change in the Bolivian Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guido, Z. S.; McIntosh, J. C.; Papuga, S. A.</p> <p>2010-12-01</p> <p>The Bolivian Andes have become an iconic example for the impacts of climate change. <span class="hlt">Glaciers</span> are rapidly <span class="hlt">melting</span> and some have already completely disappeared. More than 75 percent of the water consumed by 2 million people living on the flanks of the Bolivian Andes comes from mountains and it is often cited that the dwindling ice threatens the water supply of the expanding and destitute population living in the twin cities of La Paz and El Alto. However, the wet and the warm seasons and the cold and dry seasons coincide, causing high precipitation and ice melt—and therefore high streamflows—to occur only in the austral summer (October-March); during the austral winter, cold conditions limit <span class="hlt">glacier</span> <span class="hlt">melt</span>. This suggests that reductions in the water supply could be influenced more by changing precipitation amounts than continued glacial mass-wasting. We hypothesize that precipitation is the principal component of groundwater recharge for the aquifers at the base of the central Cordillera Real. Oxygen and hydrogen isotopes from rivers partially fed by <span class="hlt">glaciers</span>, groundwater, and glacial <span class="hlt">melt</span> water can help determine the relative contribution of precipitation and glacial <span class="hlt">melt</span> to important water supplies. During the dry season in August 2010, we sampled 23 sites that follow the flow path of water in the Condiriri watershed, beginning in the glacial headwaters and ending several kilometers upriver from Lake Titicaca. We collected five samples at the toe of the Pequeño Alpamayo <span class="hlt">glacier</span> and four samples from three tributary rivers that drain glaciated headwaters, which include meltwater from the Pequeño Alpamayo <span class="hlt">glacier</span>. W also collected 14 water samples from shallow and deep wells in rural communities within 40 kilometers of the <span class="hlt">glaciers</span>. If the isotopic values of groundwater are similar to rain values, as we suspect, precipitation is likely the largest contributor to groundwater resources in the region and will suggest that changing precipitation patterns present the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5179958','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5179958"><span>Temperature dependence of ice-on-rock friction at realistic <span class="hlt">glacier</span> conditions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Savage, H.; Nettles, M.</p> <p>2017-01-01</p> <p>Using a new biaxial friction apparatus, we conducted experiments of ice-on-rock friction in order to better understand basal sliding of <span class="hlt">glaciers</span> and ice streams. A series of velocity-stepping and slide–hold–slide tests were conducted to measure friction and healing at temperatures between −20°C and <span class="hlt">melting</span>. Experimental conditions in this study are comparable to subglacial temperatures, sliding rates and effective pressures of Antarctic ice streams and other <span class="hlt">glaciers</span>, with load-point velocities ranging from 0.5 to 100 µm s−1 and normal stress σn = 100 kPa. In this range of conditions, temperature dependences of both steady-state friction and frictional healing are considerable. The friction increases linearly with decreasing temperature (temperature weakening) from μ = 0.52 at −20°C to μ = 0.02 at <span class="hlt">melting</span>. Frictional healing increases and velocity dependence shifts from velocity-strengthening to velocity-weakening behaviour with decreasing temperature. Our results indicate that the strength and stability of <span class="hlt">glaciers</span> and ice streams may change considerably over the range of temperatures typically found at the ice–bed interface. This article is part of the themed issue ‘Microdynamics of ice’. PMID:28025297</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714078M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714078M"><span>Annual and seasonal mass balances of Chhota Shigri <span class="hlt">Glacier</span> (benchmark <span class="hlt">glacier</span>, Western Himalaya), India</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mandal, Arindan; Ramanathan, Alagappan; Farooq Azam, Mohd; Wagnon, Patrick; Vincent, Christian; Linda, Anurag; Sharma, Parmanand; Angchuk, Thupstan; Bahadur Singh, Virendra; Pottakkal, Jose George; Kumar, Naveen; Soheb, Mohd</p> <p>2015-04-01</p> <p>-2013 observation period. The negative gradients can be explained by the thickness of debris cover that increases with decrease in altitude, thus protecting the <span class="hlt">glacier</span> more efficiently at lower altitudes. Mass balance is strongly dependent on debris cover, exposure (solar <span class="hlt">radiation</span>) and the shading effect of surrounding steep slopes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29599537','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29599537"><span>The Multitrophic Effects of Climate Change and <span class="hlt">Glacier</span> Retreat in Mountain Rivers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fell, Sarah C; Carrivick, Jonathan L; Brown, Lee E</p> <p>2017-10-01</p> <p>Climate change is driving the thinning and retreat of many <span class="hlt">glaciers</span> globally. Reductions of ice-<span class="hlt">melt</span> inputs to mountain rivers are changing their physicochemical characteristics and, in turn, aquatic communities. <span class="hlt">Glacier</span>-fed rivers can serve as model systems for investigations of climate-change effects on ecosystems because of their strong atmospheric-cryospheric links, high biodiversity of multiple taxonomic groups, and significant conservation interest concerning endemic species. From a synthesis of existing knowledge, we develop a new conceptual understanding of how reducing <span class="hlt">glacier</span> cover affects organisms spanning multiple trophic groups. Although the response of macroinvertebrates to <span class="hlt">glacier</span> retreat has been well described, we show that there remains a relative paucity of information for biofilm, microinvertebrate, and vertebrate taxa. Enhanced understanding of whole river food webs will improve the prediction of river-ecosystem responses to deglaciation while offering the potential to identify and protect a wider range of sensitive and threatened species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.G33C..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.G33C..06S"><span>InSAR Constraints on the Deformation of Debris-Covered <span class="hlt">Glaciers</span> in the Khumbu Region of Nepal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmidt, D. A.; Hallet, B.; Barker, A. D.; Shean, D. E.; Conway, H.</p> <p>2016-12-01</p> <p>We present InSAR results for the Khumbu region of Nepal that document the downslope displacement and subsidence of the <span class="hlt">glacier</span>'s terminus. Meltwater from <span class="hlt">glaciers</span> in the Himalaya is an important water resource to the region during the dry season. Climate change is negatively impacting this frozen reservoir by increasing the <span class="hlt">melt</span> rates, causing the <span class="hlt">glaciers</span> to thin and recede. Documenting the response of these <span class="hlt">glaciers</span> is critical to forecasting the future impacts of climate change on this system. To constrain the thinning rates of <span class="hlt">glaciers</span> in the Khumbu region, we exploit SAR data from the ALOS-1 satellite, which exhibits good coherence on the debris-covered <span class="hlt">glaciers</span>. We also explore the use of SAR data from more recent satellite missions (i.e TerraSAR-X, Sentinel, ALOS-2). The ALOS-1 interferograms reveal the slow, down-slope movement of the debris-covered terminus ( mm/yr), as well as anomalous subsidence along the northwestern edge of Khumbu <span class="hlt">glacier</span>, which may indicate local thinning. Deformation rates are generally consistent with campaign GPS observations, which also help to differentiate vertical from horizontal deformation. Elsewhere within the SAR scene, active movement is detected on the <span class="hlt">glacier</span>-moraine dam of Imja Tsho, which has implications for the stability of the terminal moraine and for assessing the risk of a glacial lake outburst flood. Elsewhere, localized subsidence signals may indicate the <span class="hlt">melting</span> of entrained ice in debris-covered landforms. The significant vertical relief in the Himalaya region poses a challenge for doing differential radar interferometry, as artifacts in the digital elevation model (DEM) can propagate into the differential interferograms. We explore the impacts of using different DEMs in our analysis, in an attempt to separate the topographic artifacts from the real deformation signals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-145_NoTurningBack.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-145_NoTurningBack.html"><span>ScienceCast 145: No Turning Back: West Antarctic <span class="hlt">Glaciers</span> in Irreversible Decline</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2014-05-12</p> <p>A new study led by NASA researchers shows that half-a-dozen key <span class="hlt">glaciers</span> in the West Antarctic Ice Sheet are in irreversible decline. The <span class="hlt">melting</span> of these sprawling icy giants will affect global sea levels in the centuries ahead.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C24A..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C24A..06S"><span>Measurements of Light Absorbing Particles on Tropical South American <span class="hlt">Glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmitt, C. G.; All, J.; Schwarz, J. P.; Arnott, W. P.; Warthon, J.; Andrade, M.; Celestian, A. J.; Hoffmann, D.; Cole, R. J.; Lapham, E.; Horodyskyj, U. N.; Froyd, K. D.; Liao, J.</p> <p>2014-12-01</p> <p><span class="hlt">Glaciers</span> in the tropical Andes have been losing mass rapidly in recent decades. In addition to the documented increase in temperature, increases in light absorbing particulates deposited on <span class="hlt">glaciers</span> could be contributing to the observed <span class="hlt">glacier</span> loss. Here we present results of measurements of light absorbing particles from <span class="hlt">glaciers</span> in Peru and Bolivia. Samples have been collected by American Climber Science Program volunteers and scientists at altitudes up to 6770 meters. Collected snow samples were <span class="hlt">melted</span> and filtered in the field. A new inexpensive technique, the Light Absorption Heating Method (LAHM) has been developed for analysis of light absorbing particles collected on filters. Results from LAHM analysis are calibrated using filters with known amounts of fullerene soot, a common industrial surrogate for black carbon (BC). For snow samples collected at the same field location LAHM analysis and measurements from the Single Particle Soot Photometer (SP2) instrument are well correlated (r2 = 0.92). Co-located SP2 and LAHM filter analysis suggest that BC could be the dominant absorbing component of the light absorbing particles in some areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5309835','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5309835"><span>Obliquity-paced climate change recorded in Antarctic debris-covered <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mackay, Sean L.; Marchant, David R.</p> <p>2017-01-01</p> <p>The degree to which debris-covered <span class="hlt">glaciers</span> record past environmental conditions is debated. Here we describe a novel palaeoclimate archive derived from the surface morphology and internal debris within cold-based debris-covered <span class="hlt">glaciers</span> in Antarctica. Results show that subtle changes in mass balance impart major changes in the concentration of englacial debris and corresponding surface topography, and that over the past ∼220 ka, at least, the changes are related to obliquity-paced solar <span class="hlt">radiation</span>, manifest as variations in total summer energy. Our findings emphasize solar <span class="hlt">radiation</span> as a significant driver of mass balance changes in high-latitude mountain systems, and demonstrate that debris-covered <span class="hlt">glaciers</span> are among the most sensitive recorders of obliquity-paced climate variability in interior Antarctica, in contrast to most other Antarctic archives that favour eccentricity-paced forcing over the same time period. Furthermore, our results open the possibility that similar-appearing debris-covered <span class="hlt">glaciers</span> on Mars may likewise hold clues to environmental change. PMID:28186094</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8308R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8308R"><span>Antarctic sub-shelf <span class="hlt">melt</span> rates via SIMPEL</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reese, Ronja; Albrecht, Torsten; Winkelmann, Ricarda</p> <p>2017-04-01</p> <p>Ocean-<span class="hlt">induced</span> <span class="hlt">melting</span> below ice-shelves is currently suspected to be the dominant cause of mass loss from the Antarctic Ice Sheet (e.g. Depoorter et al. 2013). Although thinning of ice shelves does not directly contribute to sea-level rise, it may have a significant indirect impact through the potential of ice shelves to buttress their adjacent ice sheet. Hence, an appropriate representation of sub-shelf <span class="hlt">melt</span> rates is essential for modelling the evolution of ice sheets with marine terminating outlet <span class="hlt">glaciers</span>. Due to computational limits of fully-coupled ice and ocean models, sub-shelf <span class="hlt">melt</span> rates are often parametrized in large-scale or long-term simulations (e.g. Matin et al. 2011, Pollard & DeConto 2012). These parametrizations usually depend on the depth of the ice shelf base or its local slope but do not include the physical processes in ice shelf cavities. Here, we present the Sub Ice shelf <span class="hlt">Melt</span> Potsdam modEL (SIMPEL) which mimics the first-order large-scale circulation in ice shelf cavities based on an ocean box model (Olbers & Hellmer, 2010), implemented in the Parallel Ice Sheet Model (Bueler & Brown 2009, Winkelmann et al. 2011, www.pism-docs.org). In SIMPEL, ocean water is transported at depth towards the grounding line where sub-shelf <span class="hlt">melt</span> rates are highest, and then rises along the shelf base towards the calving front where refreezing can occur. <span class="hlt">Melt</span> rates are computed by a description of ice-ocean interaction commonly used in high-resolution models (McPhee 1992, Holland & Jenkins 1999). This enables the model to capture a wide-range of <span class="hlt">melt</span> rates, comparable to the observed range for Antarctic ice shelves (Rignot et al. 2013).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C12B..01F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C12B..01F"><span>Interactions of the Greenland Petermann <span class="hlt">Glacier</span> with the ocean: An initial perspective (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Falkner, K. K.; Johnson, H. L.; Melling, H.; Muenchow, A.; Samelson, R. M.; Friends Of Petermann</p> <p>2010-12-01</p> <p>Petermann <span class="hlt">Glacier</span> is major outlet <span class="hlt">glacier</span> that drains 6% of the area of the Greenland Ice Sheet in western North Greenland. It is one of four major outlet <span class="hlt">glaciers</span> on Greenland with a grounding line substantially below sea level (about 500m) and one of two such <span class="hlt">glaciers</span> to retain a substantial floating tongue. The floating ice tongue of Petermann <span class="hlt">glacier</span> is thought to lose at least 80% of its mass through ocean interaction. Based on three opportunistic ocean surveys in Petermann Fjord, we present an overview of circulation at the fjord mouth, hydrographic structure beneath the ice tongue, oceanic heat delivered to the under-ice cavity and the fate of the resulting <span class="hlt">melt</span> water. We also present an historical perspective on the August 2010 major calving event. The 1100m-deep fjord is separated from neighboring Hall Basin by a sill that is inferred to lie between 350m and 450m deep. Hall Basin is a section of Nares Strait that connects the Arctic Ocean (at the Lincoln Sea proceeding southward through Robeson Channel, Hall Basin, Kennedy Channel, Kane Basin and Smith Sound) to Baffin Bay. Sills in the Lincoln Sea (290m) and in Kane Basin (220m) restrict communication with the Arctic Ocean and Baffin Bay. The net flux of seawater through Nares Strait is southward and relatively fresh, conditioned by sources and processes within the Arctic Ocean and locally. Within Petermann Fjord, glacial <span class="hlt">melt</span> water appears on the northeast side at 200-600m. A cyclonic gyre occurs within the fjord mouth, with outflow on the northeast side. Oceanic heat fluxes into the fjord are sufficient to account for the observed rate of basal <span class="hlt">melting</span>. Cold, low salinity water intrudes far under the ice and likely limits basal <span class="hlt">melting</span> to the inland half of the tongue. The recent major calving event resulted in a loss of 300 km2 or about 20% of the total area of the floating tongue, most of which remained intact as an ice island that garnered much media attention. Available observations show calving to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C53D0768S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C53D0768S"><span>Retreat and stagnation of Little Ice Age <span class="hlt">glaciers</span> in Yosemite National Park</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stock, G. M.; Anderson, R. S.; Painter, T. H.</p> <p>2016-12-01</p> <p>The high peaks of Yosemite National Park in the Sierra Nevada, California, retain several small (<1 km2) <span class="hlt">glaciers</span> formed during the Little Ice Age. The largest of these, the Lyell and Maclure <span class="hlt">glaciers</span>, occupy the headwaters of the Tuolumne River and have been the subject of detailed scientific study since the late 19th century. We repeated historical photographs, field surveys, and velocity measurements on these <span class="hlt">glaciers</span> to document their response to climate change. Field surveys and remote sensing data indicate that <span class="hlt">glacier</span> surface areas have diminished by 67-78% since 1883, with 10% of that loss coinciding with the 2012-2015 California drought. The naturalist John Muir first measured the velocity of the Maclure <span class="hlt">Glacier</span> in 1872, finding that the <span class="hlt">glacier</span> moved about 2.6 cm/day during the late summer and early autumn. We reproduced Muir's measurements over the same seasonal period and found the <span class="hlt">glacier</span> to be moving at the same rate, despite the marked reduction in surface area. Time-averaged velocities measured over a four-year period show strong seasonality, with rates near zero in winter. Much of the present movement of the Maclure <span class="hlt">Glacier</span> must therefore occur as sliding at the bed, which is apparently enhanced by greater <span class="hlt">melt</span>. The adjacent Lyell <span class="hlt">Glacier</span> displayed virtually no movement over the same four-year time period, likely because it has thinned below a critical threshold; both <span class="hlt">glaciers</span> have thinned by more than 40 m since 1932, with thinning up to 3 m/yr during the 2012-2015 drought. New remote sensing data collected as part of NASA's Airborne Snow Observatory project offer opportunities to measure <span class="hlt">glacier</span> volume and mass balance changes from 2012 onward. Numerical modeling of <span class="hlt">glacier</span> mass balance will help to predict the timing of complete <span class="hlt">glacier</span> loss and to assess the associated hydrological impacts on downstream ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5253640','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5253640"><span>Nanoparticle-<span class="hlt">induced</span> unusual <span class="hlt">melting</span> and solidification behaviours of metals</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ma, Chao; Chen, Lianyi; Cao, Chezheng; Li, Xiaochun</p> <p>2017-01-01</p> <p>Effective control of <span class="hlt">melting</span> and solidification behaviours of materials is significant for numerous applications. It has been a long-standing challenge to increase the <span class="hlt">melted</span> zone (MZ) depth while shrinking the heat-affected zone (HAZ) size during local <span class="hlt">melting</span> and solidification of materials. In this paper, nanoparticle-<span class="hlt">induced</span> unusual <span class="hlt">melting</span> and solidification behaviours of metals are reported that effectively solve this long-time dilemma. By introduction of Al2O3 nanoparticles, the MZ depth of Ni is increased by 68%, while the corresponding HAZ size is decreased by 67% in laser <span class="hlt">melting</span> at a pulse energy of 0.18 mJ. The addition of SiC nanoparticles shows similar results. The discovery of the unusual <span class="hlt">melting</span> and solidification of materials that contain nanoparticles will not only have impacts on existing <span class="hlt">melting</span> and solidification manufacturing processes, such as laser welding and additive manufacturing, but also on other applications such as pharmaceutical processing and energy storage. PMID:28098147</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25941518','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25941518"><span>Microbial diversity on Icelandic <span class="hlt">glaciers</span> and ice caps.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lutz, Stefanie; Anesio, Alexandre M; Edwards, Arwyn; Benning, Liane G</p> <p>2015-01-01</p> <p>Algae are important primary colonizers of snow and glacial ice, but hitherto little is known about their ecology on Iceland's <span class="hlt">glaciers</span> and ice caps. Due do the close proximity of active volcanoes delivering large amounts of ash and dust, they are special ecosystems. This study provides the first investigation of the presence and diversity of microbial communities on all major Icelandic <span class="hlt">glaciers</span> and ice caps over a 3 year period. Using high-throughput sequencing of the small subunit ribosomal RNA genes (16S and 18S), we assessed the snow community structure and complemented these analyses with a comprehensive suite of physical-, geo-, and biochemical characterizations of the aqueous and solid components contained in snow and ice samples. Our data reveal that a limited number of snow algal taxa (Chloromonas polyptera, Raphidonema sempervirens and two uncultured Chlamydomonadaceae) support a rich community comprising of other micro-eukaryotes, bacteria and archaea. Proteobacteria and Bacteroidetes were the dominant bacterial phyla. Archaea were also detected in sites where snow algae dominated and they mainly belong to the Nitrososphaerales, which are known as important ammonia oxidizers. Multivariate analyses indicated no relationships between nutrient data and microbial community structure. However, the aqueous geochemical simulations suggest that the microbial communities were not nutrient limited because of the equilibrium of snow with the nutrient-rich and fast dissolving volcanic ash. Increasing algal secondary carotenoid contents in the last stages of the <span class="hlt">melt</span> seasons have previously been associated with a decrease in surface albedo, which in turn could potentially have an impact on the <span class="hlt">melt</span> rates of Icelandic <span class="hlt">glaciers</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4403510','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4403510"><span>Microbial diversity on Icelandic <span class="hlt">glaciers</span> and ice caps</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lutz, Stefanie; Anesio, Alexandre M.; Edwards, Arwyn; Benning, Liane G.</p> <p>2015-01-01</p> <p>Algae are important primary colonizers of snow and glacial ice, but hitherto little is known about their ecology on Iceland's <span class="hlt">glaciers</span> and ice caps. Due do the close proximity of active volcanoes delivering large amounts of ash and dust, they are special ecosystems. This study provides the first investigation of the presence and diversity of microbial communities on all major Icelandic <span class="hlt">glaciers</span> and ice caps over a 3 year period. Using high-throughput sequencing of the small subunit ribosomal RNA genes (16S and 18S), we assessed the snow community structure and complemented these analyses with a comprehensive suite of physical-, geo-, and biochemical characterizations of the aqueous and solid components contained in snow and ice samples. Our data reveal that a limited number of snow algal taxa (Chloromonas polyptera, Raphidonema sempervirens and two uncultured Chlamydomonadaceae) support a rich community comprising of other micro-eukaryotes, bacteria and archaea. Proteobacteria and Bacteroidetes were the dominant bacterial phyla. Archaea were also detected in sites where snow algae dominated and they mainly belong to the Nitrososphaerales, which are known as important ammonia oxidizers. Multivariate analyses indicated no relationships between nutrient data and microbial community structure. However, the aqueous geochemical simulations suggest that the microbial communities were not nutrient limited because of the equilibrium of snow with the nutrient-rich and fast dissolving volcanic ash. Increasing algal secondary carotenoid contents in the last stages of the <span class="hlt">melt</span> seasons have previously been associated with a decrease in surface albedo, which in turn could potentially have an impact on the <span class="hlt">melt</span> rates of Icelandic <span class="hlt">glaciers</span>. PMID:25941518</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1914850S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1914850S"><span>Coupling a <span class="hlt">glacier</span> evolution model and a hydrological model to simulate future runoff scenarios in the Oetztal Alps, Austria</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stoll, Elena; Oesterle, Felix; Hanzer, Florian; Nemec, Johanna; Berlin, Stefan; Schöber, Johannes; Huttenlau, Matthias; Strasser, Ulrich; Achleitner, Stefan; Förster, Kristian</p> <p>2017-04-01</p> <p>Fluctuations of <span class="hlt">glacier</span> and snow runoff play a key role in water management of alpine catchments. Consequently, the catchment water balance is strongly influenced by the variability of the seasonal snow cover and the <span class="hlt">glacier</span> <span class="hlt">melt</span>. The huge water storages enable a shift of the hydrological response of <span class="hlt">glaciers</span> across time scales, leading to response times in the range of decades. In the future, an initial increase of water availability connected to higher temperatures and respective <span class="hlt">melt</span> rates is expected to turn into a decrease as the <span class="hlt">glaciers</span> dwindle. One key question is to predict the "moment of peak discharge" when water availability will start to decrease as a consequence of the reduction of <span class="hlt">glacierized</span> areas. To assess the influence of a warming climate on runoff regimes of glaciated catchments, we couple a simple <span class="hlt">glacier</span> evolution model (GEM), based on a statistical approach, with a semi-distributed hydrological model (HQsim). Climate scenarios are taken from downscaled EURO-CORDEX data for the scenarios RCP2.6, RCP4.5, and RCP8.5, respectively. The results indicate that the impact of the <span class="hlt">glaciers</span> on runoff regimes will very likely change towards the second half of the 21st century. Given the scenarios in which most <span class="hlt">glaciers</span> will attain their minimum extent and sustain only at high elevation levels, the resulting runoff regime is dominated by precipitation and seasonal snow cover, since the "moment of peak discharge" is assumed to occur in the first half of the 21st century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C33B0731S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C33B0731S"><span>What sediment plumes at tide water <span class="hlt">glaciers</span> can tell us about fjord circulation and subglacial hydrology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schild, K. M.; Hawley, R. L.</p> <p>2013-12-01</p> <p>Marine-terminating outlet <span class="hlt">glaciers</span> discharge most of Greenland's mass, but the subglacial transport of meltwater is not well understood. The coincident rise in both ice velocity and surface <span class="hlt">melt</span> during the last decade points to a possible link between the amount of surface <span class="hlt">melt</span>, <span class="hlt">glacier</span> velocities, and discharge rates through processes including basal lubrication and/or an increase in <span class="hlt">melt</span> at the terminus due to discharge plume enhanced entrainment of warm ocean waters. Characterizing the response of the Greenland Ice Sheet to increasing <span class="hlt">melt</span> is limited in part by the lack of direct observation of the subglacial system. We use ground-based observations (time lapse cameras, DMI weather stations) and satellite remote sensing (MODIS) to infer the subglacial hydrological evolution of a tidewater <span class="hlt">glacier</span> by identifying the lag between meltwater availability, inferred from warm temperatures and supraglacial lake drainage, and the appearance of a sediment plume at the terminus. The detection of sediment plumes is constrained by melange presence in the spring and decreasing solar illumination in the fall. At Rink Isbræ, West Greenland, we find the appearance of sediment plumes lagging the onset of positive temperatures from 2007-2011 by approximately 44 days, but the plumes are present as the melange clears suggesting this lag may be much shorter but is undetectable. We also observe an abundance of sediment plumes each season (11-25 individual events), which indicates supraglacial drainage events are not the sole source for all sediment plumes. These findings suggest multiple passageways exist from the surface to the subglacial system and the presence of a well-established drainage network early in the <span class="hlt">melt</span> season. In this poster, we will discuss potential mechanisms for the episodic nature of the recorded plume events; whether they are the product of variable subglacial water supply (suggesting the presence of pulse drainages from subglacial storage basins), highly</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C22A..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C22A..08W"><span>Heat transfer in <span class="hlt">melt</span> ponds with convection and <span class="hlt">radiative</span> heating: observationally-inspired modelling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wells, A.; Langton, T.; Rees Jones, D. W.; Moon, W.; Kim, J. H.; Wilkinson, J.</p> <p>2016-12-01</p> <p><span class="hlt">Melt</span> ponds have key impacts on the evolution of Arctic sea ice and summer ice <span class="hlt">melt</span>. Small changes to the energy budget can have significant consequences, with a net heat-flux perturbation of only a few Watts per square metre sufficient to explain the thinning of sea ice over recent decades. Whilst parameterisations of <span class="hlt">melt</span>-pond thermodynamics often assume that pond temperatures remain close to the freezing point, recent in-situ observations show more complex thermal structure with significant diurnal and synoptic variability. We here consider the energy budget of <span class="hlt">melt</span> ponds and explore the role of internal convective heat transfer in determining the thermal structure within the pond in relatively calm conditions with low winds. We quantify the energy fluxes and temperature variability using two-dimensional direct numerical simulations of convective turbulence within a <span class="hlt">melt</span> pond, driven by internal <span class="hlt">radiative</span> heating and surface fluxes. Our results show that the convective flow dynamics are modulated by changes to the incoming <span class="hlt">radiative</span> flux and sensible heat flux at the pond surface. The evolving pond surface temperature controls the outgoing longwave emissions from the pond. Hence the convective flow modifies the net energy balance of a <span class="hlt">melt</span> pond, modulating the relative fractions of the incoming heat flux that is re-emitted to the atmosphere or transferred downward into the sea ice to drive <span class="hlt">melt</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050180465&hterms=sauber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsauber','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050180465&hterms=sauber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsauber"><span>Elevation change (2000-2004) on the Malaspina <span class="hlt">Glacier</span>, Alaska</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sauber, J.; Molnia, B.; Carabajal, C.; Luthcke, S.; Muskett, R.</p> <p>2005-01-01</p> <p>The <span class="hlt">glaciers</span> of the southeastern Alaska coastal region are the largest temperate <span class="hlt">glacier</span> meltwater source on Earth and may contribute one third of the total <span class="hlt">glacier</span> meltwater entering the global ocean. Since <span class="hlt">melt</span> onset and refreeeze timing in this region show a tendency toward earlier onset and longer ablation seasons, accelerated <span class="hlt">glacier</span> wastage may be occurring. In this study we focus on one of the largest temperate <span class="hlt">glacier</span> systems on Earth, the Malaspina <span class="hlt">Glacier</span>. This <span class="hlt">glacier</span>, with a length of approximately 110 km and an area of approximately square 5,000 km, has the largest piedmont lobe of any temperate <span class="hlt">glacier</span>. The entire lobe, which lies at elevations below 600 m, is within the ablation zone. We report and interpret ice elevation change between a digital elevation model (DEM) derived from the Shuttle Radar Topography Mission (SRTM C band) observations in Feb. 2000 and ICESat Laser 1-3 observations between Feb. 2003 and Nov. 2004. We use these elevation change results, along with earlier studies, to address the spatial and temporal variability in wastage of the piedmont lobe. Between 2000 and 2004 ice elevation changes of 10-30 meters occurred across the central Malaspina piedmont lobe. From 1972/73 (USGS DEM) to 1999 (SRTM corrected for estimated winter snow accumulation) Malaspina's (Agassiz, Seward Lobe, and Marvine) mean ice thinning was estimated at -47 m with maximum thinning on parts of the lobes to -160 m. The Malaspina's accumulation area is only slightly larger than its ablation area (2,575 km2 vs. 2,433 km2); unfortunately few glaciological observations are available from this source region. Snow accumulation rates have been largely inferred from low-altitude precipitation and temperature data. Comparing sequential ICESat observations in the Malaspina source region, we estimated short-term elevation increases of up to 5 meters during the winter of 2003/04.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C31B0282P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C31B0282P"><span><span class="hlt">Glacier</span> Changes in the Russian High Arctic.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pritchard, M. E.; Willis, M. J.; Melkonian, A. K.; Golos, E. M.; Stewart, A.; Ornelas, G.; Ramage, J. M.</p> <p>2014-12-01</p> <p> <span class="hlt">glacier</span> compared to rates found using ERS data in the mid-90s. Speeds have at least doubled at some of the smaller <span class="hlt">glaciers</span> that feed the Matusevich from the south. We investigate the causes of acceleration at both archipelagoes by comparing sea surface temperatures and passive microwave observations of the timing and duration of ice surface <span class="hlt">melting</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.1556S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.1556S"><span>Is organic matter found in <span class="hlt">glaciers</span> similar to soil organic matter? A detailed molecular-level investigation of organic matter found in cryoconite holes on the Athabasca <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simpson, M. J.; Xu, Y.; Eyles, N.; Simpson, A. J.; Baer, A.</p> <p>2009-04-01</p> <p>Cryoconite is a dark-coloured, dust-like material found on the surfaces of <span class="hlt">glaciers</span>. Cryoconite has received much interest recently because cryoconite holes, which are produced by accelerated ice <span class="hlt">melt</span>, act as habitats for microbes on <span class="hlt">glacier</span> surfaces and accelerate ice <span class="hlt">melt</span>. To the best of our knowledge, cyroconite organic matter (COM) has not yet been chemically characterized at the molecular level. In this study, organic matter biomarkers and a host of Nuclear Magnetic Resonance (NMR) techniques were used to characterize COM from the Athabasca <span class="hlt">Glacier</span> in the Canadian Rocky Mountains. The research questions that were targeted by this study include: 1) what are the sources of COM on the Athabasca <span class="hlt">Glacier</span>; 2) are there any biomarker and/or NMR evidence for microbial community activity in the cryoconite holes; and 3) is the COM structurally similar to terrestrial OM? Solvent extracts contained large quantities of fatty acids, n-alkanols, n-alkanes, wax esters and sterols. A large contribution of C23, C25 and C27 relative to C29 and C31 n-alkanes suggests that allochthonous COM is mainly from lower order plants (mosses, lichens). This is confirmed by the absence of lignin phenols (after copper (II) oxidation) in extracts and NMR analyses of COM. Solution-state 1H NMR reveals prominent signals from microbial components, while solid-state 13C Cross Polarization Magic Angle Spinning NMR analysis shows an atypically high alkyl/O-alkyl ratio, suggesting that COM is unique compared to organic matter found in nearby soils. The NMR results suggest that COM is dominated by microbial-derived compounds which were confirmed by phospholipid fatty acid analysis, which showed a significant microbial contribution, primarily from bacteria and minor microeukaryotes. Both biomarker and NMR data suggest that COM likely supports active microbial communities on the Athabasca <span class="hlt">Glacier</span> and that COM composition is uniquely different than that found in terrestrial environments. Our data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11..971L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11..971L"><span>Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain <span class="hlt">glacier</span> in the French Alps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Litt, Maxime; Sicart, Jean-Emmanuel; Six, Delphine; Wagnon, Patrick; Helgason, Warren D.</p> <p>2017-04-01</p> <p>Over Saint-Sorlin <span class="hlt">Glacier</span> in the French Alps (45° N, 6.1° E; ˜ 3 km2) in summer, we study the atmospheric surface-layer dynamics, turbulent fluxes, their uncertainties and their impact on surface energy balance (SEB) <span class="hlt">melt</span> estimates. Results are classified with regard to large-scale forcing. We use high-frequency eddy-covariance data and mean air-temperature and wind-speed vertical profiles, collected in 2006 and 2009 in the <span class="hlt">glacier</span>'s atmospheric surface layer. We evaluate the turbulent fluxes with the eddy-covariance (sonic) and the profile method, and random errors and parametric uncertainties are evaluated by including different stability corrections and assuming different values for surface roughness lengths. For weak synoptic forcing, local thermal effects dominate the wind circulation. On the <span class="hlt">glacier</span>, weak katabatic flows with a wind-speed maximum at low height (2-3 m) are detected 71 % of the time and are generally associated with small turbulent kinetic energy (TKE) and small net turbulent fluxes. <span class="hlt">Radiative</span> fluxes dominate the SEB. When the large-scale forcing is strong, the wind in the valley aligns with the <span class="hlt">glacier</span> flow, intense downslope flows are observed, no wind-speed maximum is visible below 5 m, and TKE and net turbulent fluxes are often intense. The net turbulent fluxes contribute significantly to the SEB. The surface-layer turbulence production is probably not at equilibrium with dissipation because of interactions of large-scale orographic disturbances with the flow when the forcing is strong or low-frequency oscillations of the katabatic flow when the forcing is weak. In weak forcing when TKE is low, all turbulent fluxes calculation methods provide similar fluxes. In strong forcing when TKE is large, the choice of roughness lengths impacts strongly the net turbulent fluxes from the profile method fluxes and their uncertainties. However, the uncertainty on the total SEB remains too high with regard to the net observed <span class="hlt">melt</span> to be able to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011TCD.....5..169J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011TCD.....5..169J"><span>Petermann <span class="hlt">Glacier</span>, North Greenland: massive calving in 2010 and the past half century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johannessen, O. M.; Babiker, M.; Miles, M. W.</p> <p>2011-01-01</p> <p>Greenland's marine-terminating <span class="hlt">glaciers</span> drain large amounts of solid ice through calving of icebergs, as well as <span class="hlt">melting</span> of floating glacial ice. Petermann <span class="hlt">Glacier</span>, North Greenland, has the Northern Hemisphere's long floating ice shelf. A massive (~270 km2) calving event was observed from satellite sensors in August 2010. In order to understand this in perspective, here we perform a comprehensive retrospective data analysis of Petermann <span class="hlt">Glacier</span> calving-front variability spanning half a century. Here we establish that there have been at least four massive (100+ km2) calving events over the past 50 years: (1) 1959-1961 (~153 km2), (2) 1991 (~168 km2), (3) 2001 (~71 km2) and (4) 2010 (~270 km2), as well as ~31 km2 calved in 2008. The terminus position in 2010 has retreated ~15 km beyond the envelope of previous observations. Whether the massive calving in 2010 represents natural episodic variability or a response to global and/or ocean warming in the fjord remains speculative, although this event supports the contention that the ice shelf recently has become vulnerable due to extensive fracturing and channelized basal <span class="hlt">melting</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814920E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814920E"><span>Tracing the spatial and temporal variability of different water sources in a <span class="hlt">glacierized</span> Alpine catchment (Eastern Italian Alps)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Engel, Michael; Penna, Daniele; Comiti, Francesco; Vignoli, Gianluca; Simoni, Silvia; Dinale, Roberto</p> <p>2016-04-01</p> <p><span class="hlt">Glacierized</span> catchments are important sources of fresh water. Although recent tracer-based studies have been carried out in these environments, more investigations are needed to understand more in detail the complex dynamics of snowmelt, <span class="hlt">glacier</span> <span class="hlt">melt</span> and groundwater contributions to stream water, the spatial and temporal variability of these sources of runoff and suspended sediment. In this study we used stable isotopes of water and electrical conductivity (EC) as tracers to identify the origin of different waters in the <span class="hlt">glacierized</span> Sulden/Solda catchment (130 km², Eastern Italian Alps). The site ranges in elevation between 1112 and 3905 m a.s.l. and includes two major sub-catchments. Rainfall samples were taken from bulk collectors placed along an elevation gradient (905-2585 m a.s.l.). Winter-integrated snowmelt samples were collected from passive capillary samplers installed at different elevations (1600-2825 m a.s.l.), whereas snowmelt was sampled from dripping snow patches. <span class="hlt">Glacier</span> <span class="hlt">melt</span> samples were taken in summer from small rivulets on the <span class="hlt">glacier</span> surface. Samples from the two main streams were collected monthly in 2014 and 2015 at different stream sections, major tributaries and springs. At the outlet, stream water was sampled daily by an automatic sampler, and EC, turbidity and water stage were measured every 5 minutes. Meteorological data were measured by two weather stations at 1600 and 2825 m a.s.l.. Manual samples were taken from February 2014 to November 2015 while the automatic sampling at the outlet was carried out from May to October 2014 and 2015. Results indicate that precipitation originated from air masses coming from the Atlantic Ocean, with limited influence of Mediterrean air masses. Snowmelt showed a pronounced isotopic enrichment during summer, which was also found for <span class="hlt">glacier</span> <span class="hlt">melt</span>, but less strong. Spring water from both sub-catchments seemed to be affected by infiltrating snowmelt during summer and represented the major stream component</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT........60D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT........60D"><span>Evaluating <span class="hlt">glacier</span> movement fluctuations using remote sensing: A case study of the Baird, Patterson, LeConte, and Shakes <span class="hlt">glaciers</span> in central Southeastern Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davidson, Robert Howard</p> <p></p> <p>. <span class="hlt">Glacier</span> movement rates were greatest for <span class="hlt">glaciers</span> whose terminuses were in fresh water (Patterson and Shakes <span class="hlt">Glaciers</span>), less for those with terminuses in salt water (LeConte <span class="hlt">Glacier</span>), and least for <span class="hlt">glaciers</span> with terminuses on dry land (Baird <span class="hlt">Glacier</span>).Based upon these findings, the presence of water, especially fresh water, at the terminal end of the Patterson and Shakes <span class="hlt">Glaciers</span> had a greater effect on <span class="hlt">glacier</span> movement than slope. Possible explanations for this effect might include a heat sink effect or tidal motions that hasten <span class="hlt">glacier</span> disintegration in the ablation zone. In a heat sink scenario, the water bodies in which the Patterson and Shakes <span class="hlt">Glaciers</span> terminus are located could act as a thermal energy transfer medium that increases <span class="hlt">glacier</span> <span class="hlt">melting</span> and subsequent retreat. On the other hand, tidal motions could act as horizontal and vertical push/pull forces, which increase the fracturing rate, calving, and subsequent retreat of <span class="hlt">glaciers</span> terminus that are is salt water like the LeConte <span class="hlt">Glacier</span>. Over the length of the study period, 1975 through 2010, there has been a 0.85°C increase in annual air temperatures that, although may seem low, may prove important when determining glacial mass balance rates. Further studies are necessary to test these hypotheses to determine if a heat sink effect and tidal motions significantly affected the movement rates for the <span class="hlt">glaciers</span> in this study area. An additional significant result of this study was the creation of shapefiles delineating the positions of the Shakes <span class="hlt">Glaciers</span> that are being submitted to the Global Land Ice Measurements from Space (GLIMS) program for inclusion in their master worldwide <span class="hlt">glacier</span> database.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C13A0425S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C13A0425S"><span>Snow Impurities on Central Asian <span class="hlt">Glaciers</span>: Mineral Dust, Organic & Elemental Carbon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmale, J.; Kang, S.; Peltier, R.; Sprenger, M.; Guo, J.; Li, Y.; Zhang, Q.</p> <p>2014-12-01</p> <p>In Central Asia, 90 % of the population depend on water stored in <span class="hlt">glaciers</span> and mountain snow cover. Accelerated <span class="hlt">melting</span> can be <span class="hlt">induced</span> by the deposition of e.g., mineral dust and black carbon that reduce the surface albedo. Data on source regions and chemical characteristics of snow impurities are however scarce in Central Asia. We studied aerosol deposited between summers of 2012 and 2013on three different <span class="hlt">glaciers</span> in the Kyrgyz Republic. Samples were taken from two snow pits on the <span class="hlt">glacier</span> Abramov in the northern Pamir and from one snow pit on Ak-Shiirak and Suek in the central Tien Shan. The snow was analyzed for elemental and total organic carbon, major ions and mineral dust. In addition, dissolved organic carbon was speciated by using the Aerodyne high-resolution time-of-flight aerosol spectrometer. Elevated mineral dust concentrations were found on all <span class="hlt">glaciers</span> during summer and winter with lower annual average concentrations (20 mg l-1)in the northern Pamir (factor 5 to 6). Correlations between dust tracers varied, indicating different source regions. Average EC concentrations showed seasonal variation in the northern Pamir (> 100 μg l-1 in summer, < 30 μg l-1 in winter) while there was little variation throughout the year in the central Tien Shan (~ 200 μg l-1). Similarly, OC:EC ratios showed no seasonal cycle in that region averaging around 3. On Abramov, the ratio was significantly higher in winter (> 12) than in summer (< 4). The average O:C ratios across all <span class="hlt">glaciers</span> ranged between 0.65 and 1.09, indicating a high degree of oxygenation which suggests long-range transport of the organic snow impurities. Marker substances such as potassium and mercury and their correlations suggest contribution from biomass burning emissions. Atmospheric measurements in August 2013 were conducted to obtain information on background aerosol characteristics in the remote high mountain areas. The average black carbon concentration was 0.26 μg/m³ (± 0.24 μg/m³).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70027337','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70027337"><span>Debris-bed friction of hard-bedded <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Cohen, D.; Iverson, N.R.; Hooyer, T.S.; Fischer, U.H.; Jackson, M.; Moore, P.L.</p> <p>2005-01-01</p> <p>[1] Field measurements of debris-bed friction on a smooth rock tablet at the bed of Engabreen, a hard-bedded, temperate <span class="hlt">glacier</span> in northern Norway, indicated that basal ice containing 10% debris by volume exerted local shear traction of up to 500 kPa. The corresponding bulk friction coefficient between the dirty basal ice and the tablet was between 0.05 and 0.08. A model of friction in which nonrotating spherical rock particles are held in frictional contact with the bed by bed-normal ice flow can account for these measurements if the power law exponent for ice flowing past large clasts is 1. A small exponent (n < 2) is likely because stresses in ice are small and flow is transient. Numerical calculations of the bed-normal drag force on a sphere in contact with a flat bed using n = 1 show that this force can reach values several hundred times that on a sphere isolated from the bed, thus drastically increasing frictional resistance. Various estimates of basal friction are obtained from this model. For example, the shear traction at the bed of a <span class="hlt">glacier</span> sliding at 20 m a-1 with a geothermally <span class="hlt">induced</span> <span class="hlt">melt</span> rate of 0.006 m a-1 and an effective pressure of 300 kPa can exceed 100 kPa. Debris-bed friction can therefore be a major component of sliding resistance, contradicting the common assumption that debris-bed friction is negligible. Copyright 2005 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/7270916-glacier-terminus-fluctuations-wrangell-chugach-mountains-resulting-from-non-climate-controls','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/7270916-glacier-terminus-fluctuations-wrangell-chugach-mountains-resulting-from-non-climate-controls"><span><span class="hlt">Glacier</span>-terminus fluctuations in the Wrangell and Chugach mountains resulting from non-climate controls</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Sturm, M.; Hall, D.K.; Benson, C.S.</p> <p></p> <p>Non-climatically controlled fluctuations of <span class="hlt">glacier</span> termini were studied in two regions in Alaska. In the Wrangell Mountains, eight <span class="hlt">glaciers</span> on Mt. Wrangell, an active volcano, have been monitored over the past 30 years using terrestrial surveys, aerial photogrammetry and digitally registered satellite images. Results, which are consistent between different methods of measurement, indicate that the termini of most <span class="hlt">glaciers</span> were stationary or had retreated slightly. However, the termini of the 30-km-long Ahtna <span class="hlt">Glacier</span> and the smaller Center and South MacKeith <span class="hlt">glaciers</span> began to advance in the early 1960s and have advanced steadily at rates between 5 and 18 m yr-1more » since then. These three <span class="hlt">glaciers</span> flow from the summit caldera of ML Wrangell near the active North Crater, where increased volcanic heating since 1964 has <span class="hlt">melted</span> over 7 x 107 M3 of ice. The authors suspect that volcanic meltwater has changed the basal conditions for the <span class="hlt">glaciers</span>, resulting in their advance. In College Fjord, Prince William Sound, the terminus fluctuations of two tidewater <span class="hlt">glaciers</span> have been monitored since 1931 by terrestrial surveying, photogrammetry, and most recently, from satellite imagery. Harvard <span class="hlt">Glacier</span>, a 40-kmlong tidewater <span class="hlt">glacier</span>, has been advancing steadily at nearly 20 m yr-1 since 1931, while the adjacent Yale <span class="hlt">Glacier</span> has retreated at approximately 50 m yr-1 during the same period, though for short periods, both rates have been much higher.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5862337','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5862337"><span>The Multitrophic Effects of Climate Change and <span class="hlt">Glacier</span> Retreat in Mountain Rivers</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2017-01-01</p> <p>Abstract Climate change is driving the thinning and retreat of many <span class="hlt">glaciers</span> globally. Reductions of ice-<span class="hlt">melt</span> inputs to mountain rivers are changing their physicochemical characteristics and, in turn, aquatic communities. <span class="hlt">Glacier</span>-fed rivers can serve as model systems for investigations of climate-change effects on ecosystems because of their strong atmospheric–cryospheric links, high biodiversity of multiple taxonomic groups, and significant conservation interest concerning endemic species. From a synthesis of existing knowledge, we develop a new conceptual understanding of how reducing <span class="hlt">glacier</span> cover affects organisms spanning multiple trophic groups. Although the response of macroinvertebrates to <span class="hlt">glacier</span> retreat has been well described, we show that there remains a relative paucity of information for biofilm, microinvertebrate, and vertebrate taxa. Enhanced understanding of whole river food webs will improve the prediction of river-ecosystem responses to deglaciation while offering the potential to identify and protect a wider range of sensitive and threatened species. PMID:29599537</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C13C0844M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C13C0844M"><span>Understanding changes in ice dynamics of southeast Greenland <span class="hlt">glaciers</span> from high resolution gravimetry data and satellite remote sensing observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Millan, R.; Rignot, E. J.; Mouginot, J.; Menemenlis, D.; Morlighem, M.; Wood, M.</p> <p>2016-12-01</p> <p>Southeast Greenland has been one of the largest contributors to ice mass losses in Greenland in the last few decades mostly as a result of changes in ice dynamics, and to a lesser extent due to the steady increase in runoff. In 1996, the region was thinning up to the ice divide (Krabill et al., 1999) and the change were clearly of ice dynamics nature. Ice-ocean interactions played a central role in triggering a faster, systematic retreat around year 2002-2005 as water of Atlantic origin started to intrude the fjords in larger amounts due to a change in oceanic circulation in the Irminger sea. The <span class="hlt">glacier</span> response varied significantly from one <span class="hlt">glacier</span> to the next in response to the oceanic change, which we attribute to variatioins in fjord bathymetry, geometry control on the <span class="hlt">glaciers</span> and calving speed of the <span class="hlt">glaciers</span>. This region is however characterized by a dearth of topography data: the fjords have never been mapped and bed topography is challenging to obtain with radio echo sounding techniques. Here, we employ a combination of Operation IceBridge (OIB) high-resolution airborne gravity from 2016, Ocean <span class="hlt">Melting</span> Greenland (OMG) EVS-2 mission low resolution gravity from 2016, and OMG bathymetry data from 2016 to map the bed elevation of the <span class="hlt">glaciers</span> and fjords over the entire southeast Greenland combining gravity, thickness, and bathymetry. The data reveal the true depth of the fjords and the <span class="hlt">glacier</span> thickness at the ice front, in a seamless fashion. We combine these data with a history of ice discharge combining estimates of ice thickness with a time series of ice velocity going back to the early 1990s. We form a time series of ice discharge, <span class="hlt">glacier</span> per <span class="hlt">glacier</span>, which is compared with surface mass balance from the RACMO 1-km downscaled model. We compare the results with simulations of ice <span class="hlt">melt</span> along the calving faces of the <span class="hlt">glaciers</span> to draw conclusions about the sensitivity of each <span class="hlt">glacier</span> to climate forcing and re-interpret their pattern of retreat in the last</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/41293','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/41293"><span>Preliminary bathymetry of McCarty Fiord and Neoglacial changes of McCarty <span class="hlt">Glacier</span>, Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Post, Austin</p> <p>1980-01-01</p> <p>Preliminary bathymetry (at 1:20,000 scale) and other scientific studies of McCarty Fiord, Alaska, Conducted by the Research Vessel Growler in 1978, showed this 15 mile-long waterway to be a narrow, deeply scoured basin enclosed by a terminal-moraine shoal. This valley was formerly filled by McCarty <span class="hlt">Glacier</span>, which began a drastic retreat shortly after 1909; the <span class="hlt">glacier</span> reached shallow water at the head of the fiord around 1960. The relative rate of retreat in deep water and on land is disclosed by the slower <span class="hlt">melting</span> of stagnent ice left in a side valley. Soundings and profiles show the main channel to extend to a depth as great as 957 feet and to have the typical ' U ' shape of a <span class="hlt">glacier</span>-eroded valley; since the <span class="hlt">glacier</span> 's retreat, sediments have formed a nearly level deposit in the deepest part of the fiord. Old forest debris dated by carbon-14 indicates that a neoglacial advance of the <span class="hlt">glacier</span> began before 3,395 years B.P. (before present); by 1,500 B.P. the <span class="hlt">glacier</span> filled most of the fiord, and before the <span class="hlt">glacier</span> culminated its advance around 1860 , two <span class="hlt">glacier</span>-dammed lakes were formed in side valleys. (USGS)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.2691H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.2691H"><span>Rapidly changing subglacial hydrological pathways at a tidewater <span class="hlt">glacier</span> revealed through simultaneous observations of water pressure, supraglacial lakes, meltwater plumes and surface velocities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>How, Penelope; Benn, Douglas I.; Hulton, Nicholas R. J.; Hubbard, Bryn; Luckman, Adrian; Sevestre, Heïdi; van Pelt, Ward J. J.; Lindbäck, Katrin; Kohler, Jack; Boot, Wim</p> <p>2017-11-01</p> <p>Subglacial hydrological processes at tidewater <span class="hlt">glaciers</span> remain poorly understood due to the difficulty in obtaining direct measurements and lack of empirical verification for modelling approaches. Here, we investigate the subglacial hydrology of Kronebreen, a fast-flowing tidewater <span class="hlt">glacier</span> in Svalbard during the 2014 <span class="hlt">melt</span> season. We combine observations of borehole water pressure, supraglacial lake drainage, surface velocities and plume activity with modelled run-off and water routing to develop a conceptual model that thoroughly encapsulates subglacial drainage at a tidewater <span class="hlt">glacier</span>. Simultaneous measurements suggest that an early-season episode of subglacial flushing took place during our observation period, and a stable efficient drainage system effectively transported subglacial water through the northern region of the <span class="hlt">glacier</span> tongue. Drainage pathways through the central and southern regions of the <span class="hlt">glacier</span> tongue were disrupted throughout the following <span class="hlt">melt</span> season. Periodic plume activity at the terminus appears to be a signal for modulated subglacial pulsing, i.e. an internally driven storage and release of subglacial meltwater that operates independently of marine influences. This storage is a key control on ice flow in the 2014 <span class="hlt">melt</span> season. Evidence from this work and previous studies strongly suggests that long-term changes in ice flow at Kronebreen are controlled by the location of efficient/inefficient drainage and the position of regions where water is stored and released.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C12B..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C12B..07S"><span>In-situ GPS records of surface mass balance, firn compaction rates, and ice-shelf basal <span class="hlt">melt</span> rates for Pine Island <span class="hlt">Glacier</span>, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shean, D. E.; Christianson, K.; Larson, K. M.; Ligtenberg, S.; Joughin, I. R.; Smith, B.; Stevens, C.</p> <p>2016-12-01</p> <p>In recent decades, Pine Island <span class="hlt">Glacier</span> (PIG) has experienced marked retreat, speedup and thinning due to ice-shelf basal <span class="hlt">melt</span>, internal ice-stream instability and feedbacks between these processes. In an effort to constrain recent ice-stream dynamics and evaluate potential causes of retreat, we analyzed 2008-2010 and 2012-2014 GPS records for PIG. We computed time series of horizontal velocity, strain rate, multipath-based antenna height, surface elevation, and Lagrangian elevation change (Dh/Dt). These data provide validation for complementary high-resolution WorldView stereo digital elevation model (DEM) records, with sampled DEM vertical error of 0.7 m. The GPS antenna height time series document a relative surface elevation increase of 0.7-1.0 m/yr, which is consistent with estimated surface mass balance (SMB) of 0.7-0.9 m.w.e./yr from RACMO2.3 and firn compaction rates from the IMAU-FDM dynamic firn model. An abrupt 0.2-0.3 m surface elevation decrease due to surface <span class="hlt">melt</span> and/or greater near-surface firn compaction is observed during a period of warm atmospheric temperatures from December 2012 to January 2013. Observed surface Dh/Dt for all PIG shelf sites is highly linear with trends of -1 to -4 m/yr and <0.4 m residuals. Similar Dh/Dt estimates with reduced variability are obtained after removing expected downward GPS pole base velocity from observed GPS antenna Dh/Dt. Estimated Dh/Dt basal <span class="hlt">melt</span> rates are 10 to 40 m/yr for the outer PIG shelf and 4 m/yr for the South shelf. These <span class="hlt">melt</span> rates are similar to those derived from ice-bottom acoustic ranging, phase-sensitive ice-penetrating radar, and high-resolution stereo DEM records. The GPS/DEM records document higher <span class="hlt">melt</span> rates within and near transverse surface depressions and rifts associated with longitudinal extension. Basal <span class="hlt">melt</span> rates for the 2012-2014 period show limited temporal variability, despite significant change in ocean heat content. This suggests that sub-shelf <span class="hlt">melt</span> rates are less sensitive to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018FrEaS...6...64K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018FrEaS...6...64K"><span>Mapping Surface Temperatures on a Debris-Covered <span class="hlt">Glacier</span> with an Unmanned Aerial Vehicle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kraaijenbrink, Philip D. A.; Shea, Joseph M.; Litt, Maxime; Steiner, Jakob F.; Treichler, Désirée; Koch, Inka; Immerzeel, Walter W.</p> <p>2018-05-01</p> <p>A mantel of debris cover often accumulates across the surface of <span class="hlt">glaciers</span> in active mountain ranges with exceptionally steep terrain, such as the Andes, Himalaya and New Zealand Alps. Such a supraglacial debris layer has a major influence on a <span class="hlt">glacier</span>'s surface energy budget, enhancing <span class="hlt">radiation</span> absorption and <span class="hlt">melt</span> when the layer is thin, but insulating the ice when thicker than a few cm. Information on spatially distributed debris surface temperature has the potential to provide insight into the properties of the debris, its effects on the ice below and its influence on the near-surface boundary layer. Here, we deploy an unmanned aerial vehicle (UAV) equipped with a thermal infrared sensor on three separate missions over one day to map changing surface temperatures across the debris-covered Lirung <span class="hlt">Glacier</span> in the Central Himalaya. We present a methodology to georeference and process the acquired thermal imagery, and correct for emissivity and sensor bias. Derived UAV surface temperatures are compared with distributed simultaneous in situ temperature measurements as well as with Landsat 8 thermal satellite imagery. Results show that the UAV-derived surface temperatures vary greatly both spatially and temporally, with -1.4±1.8, 11.0 ±5.2 and 15.3±4.7 °C for the three flights (mean±sd), respectively. The range in surface temperatures over the <span class="hlt">glacier</span> during the morning is very large with almost 50 °C. Ground-based measurements are generally in agreement with the UAV imagery, but considerable deviations are present that are likely due to differences in measurement technique and approach, and validation is difficult as a result. The difference in spatial and temporal variability captured by the UAV as compared with much coarser satellite imagery is striking and it shows that satellite derived temperature maps should be interpreted with care. We conclude that UAVs provide a suitable means to acquire surface temperature maps of debris-covered <span class="hlt">glacier</span> surfaces at</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4852812','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4852812"><span>Shifts in diversity and function of lake bacterial communities upon <span class="hlt">glacier</span> retreat</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Peter, Hannes; Sommaruga, Ruben</p> <p>2016-01-01</p> <p>Global climate change is causing a wastage of <span class="hlt">glaciers</span> and threatening biodiversity in <span class="hlt">glacier</span>-fed ecosystems. The high turbidity typically found in those ecosystems, which is caused by inorganic particles and result of the erosive activity of <span class="hlt">glaciers</span> is a key environmental factor influencing temperature and light availability, as well as other factors in the water column. Once these lakes loose hydrological connectivity to <span class="hlt">glaciers</span> and turn clear, the accompanying environmental changes could represent a potential bottleneck for the established local diversity with yet unknown functional consequences. Here, we study three lakes situated along a turbidity gradient as well as one clear unconnected lake and evaluate seasonal changes in their bacterial community composition and diversity. Further, we assess potential consequences for community functioning. <span class="hlt">Glacier</span> runoff represented a diverse source community for the lakes and several taxa were able to colonize downstream turbid habitats, although they were not found in the clear lake. Operational taxonomic unit-based alpha diversity and phylogenetic diversity decreased along the turbidity gradient, but metabolic functional diversity was negatively related to turbidity. No evidence for multifunctional redundancy, which may allow communities to maintain functioning upon alterations in diversity, was found. Our study gives a first view on how <span class="hlt">glacier</span>-fed lake bacterial communities are affected by the <span class="hlt">melting</span> of <span class="hlt">glaciers</span> and indicates that diversity and community composition significantly change when hydrological connectivity to the <span class="hlt">glacier</span> is lost and lakes turn clear. PMID:26771929</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26771929','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26771929"><span>Shifts in diversity and function of lake bacterial communities upon <span class="hlt">glacier</span> retreat.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Peter, Hannes; Sommaruga, Ruben</p> <p>2016-07-01</p> <p>Global climate change is causing a wastage of <span class="hlt">glaciers</span> and threatening biodiversity in <span class="hlt">glacier</span>-fed ecosystems. The high turbidity typically found in those ecosystems, which is caused by inorganic particles and result of the erosive activity of <span class="hlt">glaciers</span> is a key environmental factor influencing temperature and light availability, as well as other factors in the water column. Once these lakes loose hydrological connectivity to <span class="hlt">glaciers</span> and turn clear, the accompanying environmental changes could represent a potential bottleneck for the established local diversity with yet unknown functional consequences. Here, we study three lakes situated along a turbidity gradient as well as one clear unconnected lake and evaluate seasonal changes in their bacterial community composition and diversity. Further, we assess potential consequences for community functioning. <span class="hlt">Glacier</span> runoff represented a diverse source community for the lakes and several taxa were able to colonize downstream turbid habitats, although they were not found in the clear lake. Operational taxonomic unit-based alpha diversity and phylogenetic diversity decreased along the turbidity gradient, but metabolic functional diversity was negatively related to turbidity. No evidence for multifunctional redundancy, which may allow communities to maintain functioning upon alterations in diversity, was found. Our study gives a first view on how <span class="hlt">glacier</span>-fed lake bacterial communities are affected by the <span class="hlt">melting</span> of <span class="hlt">glaciers</span> and indicates that diversity and community composition significantly change when hydrological connectivity to the <span class="hlt">glacier</span> is lost and lakes turn clear.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70016963','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70016963"><span>Debris-Covered <span class="hlt">Glaciers</span> in the Sierra Nevada, California, and Their Implications for Snowline Reconstructions</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Clark, D.H.; Clark, M.M.; Gillespie, A.R.</p> <p>1994-01-01</p> <p>Ice-walled <span class="hlt">melt</span> ponds on the surfaces of active valley-floor rock <span class="hlt">glaciers</span> and Matthes (Little Ice Age) moraines in the southern Sierra Nevada indicate that most of these landforms consist of <span class="hlt">glacier</span> ice under thin (ca. 1 - 10 m) but continuous covers of rock-fall-generated debris. These debris blankets effectively insulate the underlying ice and greatly reduce rates of ablation relative to that of uncovered ice. Such insulation explains the observations that ice-cored rock <span class="hlt">glaciers</span> in the Sierra, actually debris-covered <span class="hlt">glaciers</span>, are apparently less sensitive to climatic warming and commonly advance to lower altitudes than do adjacent bare-ice <span class="hlt">glaciers</span>. Accumulation-area ratios and toe-to-headwall-altitude ratios used to estimate equilibrium-line altitudes (ELAs) of former <span class="hlt">glaciers</span> may therefore yield incorrect results for cirque <span class="hlt">glaciers</span> subject to abundant rockfall. Inadvertent lumping of deposits from former debris-covered and bare-ice <span class="hlt">glaciers</span> partially explains an apparently anomalous regional ELA gradient reported for the pre-Matthes Recess Peak Neoglacial advance. Distinguishing such deposits may be important to studies that rely on paleo-ELA estimates. Moreover, Matthes and Recess Peak ELA gradients along the crest evidently depend strongly on local orographic effects rather than latitudinal climatic trends, indicating that simple linear projections and regional climatic interpretations of ELA gradients of small <span class="hlt">glaciers</span> may be unreliable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3721114','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3721114"><span>Microbial biodiversity in <span class="hlt">glacier</span>-fed streams</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wilhelm, Linda; Singer, Gabriel A; Fasching, Christina; Battin, Tom J; Besemer, Katharina</p> <p>2013-01-01</p> <p>While <span class="hlt">glaciers</span> become increasingly recognised as a habitat for diverse and active microbial communities, effects of their climate change-<span class="hlt">induced</span> retreat on the microbial ecology of <span class="hlt">glacier</span>-fed streams remain elusive. Understanding the effect of climate change on microorganisms in these ecosystems is crucial given that microbial biofilms control numerous stream ecosystem processes with potential implications for downstream biodiversity and biogeochemistry. Here, using a space-for-time substitution approach across 26 Alpine <span class="hlt">glaciers</span>, we show how microbial community composition and diversity, based on 454-pyrosequencing of the 16S rRNA gene, in biofilms of <span class="hlt">glacier</span>-fed streams may change as <span class="hlt">glaciers</span> recede. Variations in streamwater geochemistry correlated with biofilm community composition, even at the phylum level. The most dominant phyla detected in glacial habitats were Proteobacteria, Bacteroidetes, Actinobacteria and Cyanobacteria/chloroplasts. Microorganisms from ice had the lowest α diversity and contributed marginally to biofilm and streamwater community composition. Rather, streamwater apparently collected microorganisms from various glacial and non-glacial sources forming the upstream metacommunity, thereby achieving the highest α diversity. Biofilms in the <span class="hlt">glacier</span>-fed streams had intermediate α diversity and species sorting by local environmental conditions likely shaped their community composition. α diversity of streamwater and biofilm communities decreased with elevation, possibly reflecting less diverse sources of microorganisms upstream in the catchment. In contrast, β diversity of biofilms decreased with increasing streamwater temperature, suggesting that <span class="hlt">glacier</span> retreat may contribute to the homogenisation of microbial communities among <span class="hlt">glacier</span>-fed streams. PMID:23486246</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C51A0640Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C51A0640Y"><span>3D full-Stokes modeling of the grounding line dynamics of Thwaites <span class="hlt">Glacier</span>, West Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, H.; Rignot, E. J.; Morlighem, M.; Seroussi, H. L.</p> <p>2016-12-01</p> <p>Thwaites <span class="hlt">Glacier</span> (TG) is the broadest and second largest ice stream in the West Antarctica. Satellite observations have revealed rapid grounding line retreat and mass loss of this <span class="hlt">glacier</span> in the past few decades, which has been attributed to the enhanced basal <span class="hlt">melting</span> in the Amundsen Sea Embayment. With a retrograde bed configuration, TG is on the verge of collapse according to the marine ice sheet instability theory. Here, we use the UCI/JPL Ice Sheet System Model (ISSM) to simulate the grounding line position of TG to determine its stability, rate of retreat and sensitivity to enhanced basal <span class="hlt">melting</span> using a three-dimensional full-Stokes numerical model. Simulations with simplified models (Higher Order (HO), and Shelfy-Stream Approximation (SSA)) are also conducted for comparison. We first validate our full Stokes model by conducting MISMIP3D experiments. Then we applied the model to TG using new bed elevation dataset combining IceBridge (OIB) gravity data, OIB ice thickness, ice flow vectors from interferometry and a mass conservation method at 450 m spacing. Basal friction coefficient and ice rheology of floating ice are inferred to match observed surface velocity. We find that the grounding line is capable of retreating at rate of 1km/yr under current forcing and that the <span class="hlt">glacier</span>'s sensitivity to <span class="hlt">melt</span> is higher in the Stokes model than HO or SSA, which means that projections using SSA or HO might underestimate the future rate of retreat of the <span class="hlt">glacier</span>. This work has been performed at UC Irvine and Caltech's Jet Propulsion Laboratory under a contract with NASA's Cryospheric Science Program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70043154','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70043154"><span>HIMALA: climate impacts on <span class="hlt">glaciers</span>, snow, and hydrology in the Himalayan region</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Brown, Molly Elizabeth; Ouyang, Hua; Habib, Shahid; Shrestha, Basanta; Shrestha, Mandira; Panday, Prajjwal; Tzortziou, Maria; Policelli, Frederick; Artan, Guleid; Giriraj, Amarnath; Bajracharya, Sagar R.; Racoviteanu, Adina</p> <p>2010-01-01</p> <p><span class="hlt">Glaciers</span> are the largest reservoir of freshwater on Earth, supporting one third of the world's population. The Himalaya possess one of the largest resources of snow and ice, which act as a freshwater reservoir for more than 1.3 billion people. This article describes a new project called HIMALA, which focuses on utilizing satellite-based products for better understanding of hydrological processes of the river basins of the region. With support from the US Agency for International Development (USAID), the International Centre for Integrated Mountain Development (ICIMOD), together with its partners and member countries, has been working on the application of satellite-based rainfall estimates for flood prediction. The US National Aeronautics and Space Administration (NASA) partners are working with ICIMOD to incorporate snowmelt and <span class="hlt">glacier</span> <span class="hlt">melt</span> into a widely used hydrological model. Thus, through improved modeling of the contribution of snow and ice meltwater to river flow in the region, the HIMALA project will improve the ability of ICIMOD and its partners to understand the impact of weather and climate on floods, droughts, and other water- and climate-<span class="hlt">induced</span> natural hazards in the Himalayan region in Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, and Pakistan.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110015312','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110015312"><span>HIMALA: Climate Impacts on <span class="hlt">Glaciers</span>, Snow, and Hydrology in the Himalayan Region</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brown, Molly Elizabeth; Ouyang, Hua; Habib, Shahid; Shrestha, Basanta; Shrestha, Mandira; Panday, Prajjwal; Tzortziou, Maria; Policelli, Frederick; Artan, Guleid; Giriraj, Amarnath; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20110015312'); toggleEditAbsImage('author_20110015312_show'); toggleEditAbsImage('author_20110015312_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20110015312_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20110015312_hide"></p> <p>2010-01-01</p> <p><span class="hlt">Glaciers</span> are the largest reservoir of freshwater on Earth, supporting one third of the world s population. The Himalaya possess one of the largest resources of snow and ice, which act as a freshwater reservoir for more than 1.3 billion people. This article describes a new project called HIMALA, which focuses on utilizing satellite-based products for better understanding of hydrological processes of the river basins of the region. With support from the US Agency for International Development (USAID), the International Centre for Integrated Mountain Development (ICIMOD), together with its partners and member countries, has been working on the application of satellite-based rainfall estimates for flood prediction. The US National Aeronautics and Space Administration (NASA) partners are working with ICIMOD to incorporate snowmelt and <span class="hlt">glacier</span> <span class="hlt">melt</span> into a widely used hydrological model. Thus, through improved modeling of the contribution of snow and ice meltwater to river flow in the region, the HIMALA project will improve the ability of ICIMOD and its partners to understand the impact of weather and climate on floods, droughts, and other water- and climate-<span class="hlt">induced</span> natural hazards in the Himalayan region in Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, and Pakistan.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1182930-carbonaceous-aerosols-recorded-southeastern-tibetan-glacier-analysis-temporal-variations-model-estimates-sources-radiative-forcing','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1182930-carbonaceous-aerosols-recorded-southeastern-tibetan-glacier-analysis-temporal-variations-model-estimates-sources-radiative-forcing"><span>Carbonaceous aerosols recorded in a southeastern Tibetan <span class="hlt">glacier</span>: analysis of temporal variations and model estimates of sources and <span class="hlt">radiative</span> forcing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Wang, Mo; Xu, B.; Cao, J.; ...</p> <p>2015-02-02</p> <p>High temporal resolution measurements of black carbon (BC) and organic carbon (OC) covering the time period of 1956–2006 in an ice core over the southeastern Tibetan Plateau show a distinct seasonal dependence of BC and OC with higher respective concentrations but a lower OC / BC ratio in the non-monsoon season than during the summer monsoon. We use a global aerosol-climate model, in which BC emitted from different source regions can be explicitly tracked, to quantify BC source–receptor relationships between four Asian source regions and the southeastern Tibetan Plateau as a receptor. The model results show that South Asia hasmore » the largest contribution to the present-day (1996–2005) mean BC deposition at the ice-core drilling site during the non-monsoon season (October to May) (81%) and all year round (74%), followed by East Asia (14% to the non-monsoon mean and 21% to the annual mean). The ice-core record also indicates stable and relatively low BC and OC deposition fluxes from the late 1950s to 1980, followed by an overall increase to recent years. This trend is consistent with the BC and OC emission inventories and the fuel consumption of South Asia (as the primary contributor to annual mean BC deposition). Moreover, the increasing trend of the OC / BC ratio since the early 1990s indicates a growing contribution of coal combustion and/or biomass burning to the emissions. The estimated <span class="hlt">radiative</span> forcing <span class="hlt">induced</span> by BC and OC impurities in snow has increased since 1980, suggesting an increasing potential influence of carbonaceous aerosols on the Tibetan <span class="hlt">glacier</span> <span class="hlt">melting</span> and the availability of water resources in the surrounding regions. Our study indicates that more attention to OC is merited because of its non-negligible light absorption and the recent rapid increases evident in the ice-core record.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C23A0389P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C23A0389P"><span>Collaborating with the local community of Kullorsuaq, Greenland to obtain high-quality hydrographic measurements near Alison <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Porter, D. F.; Turrin, M.; Tinto, K. J.; Giulivi, C. F.; Cochran, J. R.; Bell, R. E.</p> <p>2014-12-01</p> <p>Warming ocean waters around Greenland have been implicated, along with warmer air temperatures, in the rapid increase of <span class="hlt">melt</span> of the tidewater <span class="hlt">glaciers</span> that drain the ice sheet. Most available regional oceanographic measurements have been collected during the summer seasons and are concentrated near the largest and most accessible <span class="hlt">glaciers</span>. In order to gain a more comprehensive picture of the changing environment around the entirety of Greenland, more fjords, especially in the north, must be sampled. In July 2014, we travelled to Kullorsuaq in Northwest Greenland in order to foster a partnership with the local community to obtain new hydrographic data from CTD casts near Alison <span class="hlt">Glacier</span> (74.6N, 57W). The terminus of this <span class="hlt">glacier</span> abruptly retreated 10 km between 2000 and 2006. Although adequate observations from that time period are unavailable, our recently collected temperature and salinity data suggests that the deep water near Alison is similar to the waters further south, where near-synchronous ocean warming and glacial acceleration has been documented. Over the course of two sampling days, a hand-operated winch from a small boat was used to make standard CTD casts in front of Alison <span class="hlt">Glacier</span>. We find evidence of glacial and mélange <span class="hlt">melt</span> and the signature of both Polar and Atlantic Water masses at depth. Along-fjord casts illustrate how the ocean waters are modified as they circulate in and out of the fjord and the interaction of this water with the <span class="hlt">melting</span> glacial front. At 500m depths, ocean temperatures are about 3°C above the in-situ freezing point of seawater, suggesting a possible influence of warm ocean waters on the mass loss of Alison <span class="hlt">Glacier</span>. Using NASA Operation IceBridge and satellite altimetry data, we relate our new hydrographic data to the observed recent changes in Alison <span class="hlt">Glacier</span>. An additional important result is that this short field campaign uncovered the possibility of working with local Greenlandic communities to aid scientists in both</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C53D0773K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C53D0773K"><span>Energy balance and runoff modelling of <span class="hlt">glaciers</span> in the Kongsfjord basin in northwestern Svalbard</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kohler, J.; Pramanik, A.; van Pelt, W.</p> <p>2016-12-01</p> <p><span class="hlt">Glaciers</span> and ice caps cover 36,000 Km2 or 60% of the land area of the Svalbard archipelago. Roughly 60% of the glaciated area drains to the ocean through tidewater <span class="hlt">glacier</span> fronts. Runoff from tidewater <span class="hlt">glaciers</span> is posited to have a significant impact on fjord circulation and thereby on fjord ecosystems. Ocean circulation modelling underway in the Kongsfjord system requires specification of the freshwater amounts contributed by both tidewater and land-terminating <span class="hlt">glaciers</span> in its basin. The total basin area of Kongsfjord is 1850 km2. We use a coupled surface energy-balance and firn model (Van Pelt et al. 2015) to calculate mass balance and runoff from the Kongsfjord <span class="hlt">glaciers</span> for the period 1969-2015. Meteorological data from the nearby station at Ny-Ålesund is used for climate forcing in the model domain, with mass balance data at four <span class="hlt">glaciers</span> in the Kongsfjord watershed used to calibrate model parameters. Precipitation and temperature lapse rates are adjusted on the study <span class="hlt">glaciers</span> through repeated model runs at mass balance stake locations to match observed and modelled surface mass balance. Long-term discharge measurement at two sites in this region are used to validate the modelled runoff. Spatial and temporal evolution of <span class="hlt">melt</span>, refreezing and runoff are analyzed, along with the vertical evolution of subsurface conditions. Reference: Van Pelt, W.J.J. & J. Kohler. 2015. Modelling the long-term mass balance and firn evolution of <span class="hlt">glaciers</span> around Kongsfjorden, Svalbard. J. Glaciol, 61(228), 731-744. <span class="hlt">Glaciers</span> and ice caps cover 36,000 Km2 or 60% of the land area of the Svalbard archipelago. Roughly 60% of the glaciated area drains to the ocean through tidewater <span class="hlt">glacier</span> fronts. Runoff from tidewater <span class="hlt">glaciers</span> is posited to have a significant impact on fjord circulation and thereby on fjord ecosystems. Ocean circulation modelling underway in the Kongsfjord system requires specification of the freshwater amounts contributed by both tidewater and land-terminating <span class="hlt">glaciers</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814210B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814210B"><span>Aerosol deposition (trace elements and black carbon) over the highest <span class="hlt">glacier</span> of the Eastern European Alps during the last centuries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bertò, Michele; Barbante, Carlo; Gabrieli, Jacopo; Gabrielli, Paolo; Spolaor, Andrea; Dreossi, Giuliano; Laj, Paolo; Zanatta, Marco; Ginot, Patrick; Fain, Xavier</p> <p>2016-04-01</p> <p>Ice cores are an archive of a wide variety of climatic and environmental information from the past, retaining them for hundreds of thousands of years. Anthropogenic pollutants, trace elements, heavy metals and major ions, are preserved as well providing insights on the past atmospheric circulations and allowing evaluating the human impact on the environment. Several ice cores were drilled in <span class="hlt">glaciers</span> at mid and low latitudes, as in the European Alps. The first ice cores drilled to bedrock in the Eastern Alps were retrieved during autumn 2011 on the "Alto dell`Ortles <span class="hlt">glacier</span>", the uppermost <span class="hlt">glacier</span> of the Ortles massif (3905m, South Tirol, Italy), in the frame of the "Ortles Project". A preliminary dating of the core suggests that it should cover at least 300-400 years. Despite the summer temperature increase of the last decades this <span class="hlt">glacier</span> still contain cold ice. Indeed, O and H isotopes profiles well describe the atmospheric warming as well as the low temperatures recorded during the Little Ice Age (LIA). Moreover, this <span class="hlt">glacier</span> is located close to densely populated and industrialized areas and can be used for reconstructing for the first time past and recent air pollution and the human impact in the Eastern European Alps. The innermost part of the core is under analysis by means of a "Continuous Flow Analysis" system. This kind of analysis offers a high resolution in data profiles. The separation between the internal and the external parts of the core avoid any kind of contamination. An aluminum <span class="hlt">melting</span> head <span class="hlt">melts</span> the core at about 2.5 cm min-1. Simultaneous analyses of conductivity, dust concentration and size distribution (from 0.8 to 80 μm), trace elements with Inductive Coupled Plasma Mass Spectrometer (ICP-MS, Agilent 7500) and refractory black carbon (rBC) with the Single Particle Soot Photometer (SP2, Droplet Measurement Technologies) are performed. A fraction of the <span class="hlt">melt</span> water is collected by an auto-sampler for further analysis. The analyzed elements</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP14A..02D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP14A..02D"><span>Inferring Past Climate in Equatorial East Africa using <span class="hlt">Glacier</span> Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Doughty, A. M.; Kelly, M. A.; Anderson, B.; Russell, J. M.; Jackson, M. S.</p> <p>2016-12-01</p> <p>Mountain <span class="hlt">glaciers</span> in the northern and southern middle latitudes advanced nearly synchronously during the Last Glacial Maximum (LGM), but the timing and magnitude of cooling is less certain for the tropics. Knowing the degree of cooling in high altitude, low latitude regions advances our understanding of the cryosphere in understudied areas and contributes to our understanding of what causes ice ages. Here we use a 2-D ice flow and mass balance model to simulate <span class="hlt">glacier</span> extents in the Rwenzori Mountains of Uganda and the Democratic Republic of the Congo during the Last Glacial Maximum. In particular, we model steady-state ice extent that matches the dated moraines in the Rwenzori Mountains to infer past climate. Steady-state simulations of LGM <span class="hlt">glacier</span> extents, which match moraines dated to 20,000 years ago, can be obtained with a 20% reduction in precipitation and a 7°C cooling to match the associated moraines. A 0-50% reduction in precipitation combined with a 5-8°C cooling, respectively, agrees well with paleoclimate estimates from independent proxy records. As expected in a high precipitation environment, these <span class="hlt">glaciers</span> are very sensitive to decreases in temperature, converting large volumes of precipitation from rain to snow as well as decreasing <span class="hlt">melting</span>. <span class="hlt">Glaciers</span> in equatorial Africa appear to have been waxing and waning synchronously and by the same magnitude as <span class="hlt">glaciers</span> in the middle latitudes, suggesting a common, global forcing mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PEPI..143..369L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PEPI..143..369L"><span>Shock-<span class="hlt">induced</span> superheating and <span class="hlt">melting</span> curves of geophysically important minerals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luo, Sheng-Nian; Ahrens, Thomas J.</p> <p>2004-06-01</p> <p>Shock-state temperature and sound-speed measurements on crystalline materials, demonstrate superheating-<span class="hlt">melting</span> behavior distinct from equilibrium <span class="hlt">melting</span>. Shocked solid can be superheated to the maximum temperature, Tc'. At slightly higher pressure, Pc, shock <span class="hlt">melting</span> occurs, and <span class="hlt">induces</span> a lower shock temperature, Tc. The Hugoniot state, ( Pc, Tc), is inferred to lie along the equilibrium <span class="hlt">melting</span> curve. The amount of superheating achieved on Hugoniot is, ΘH+= Tc'/ Tc-1. Shock-<span class="hlt">induced</span> superheating for a number of silicates, alkali halides and metals agrees closely with the predictions of a systematic framework describing superheating at various heating rates [Appl. Phys. Lett. 82 (12) (2003) 1836]. High-pressure <span class="hlt">melting</span> curves are constructed by integration from ( Pc, Tc) based on the Lindemann law. We calculate the volume and entropy changes upon <span class="hlt">melting</span> at ( Pc, Tc) assuming the R ln 2 rule ( R is the gas constant) for the disordering entropy of <span class="hlt">melting</span> [J. Chem. Phys. 19 (1951) 93; Sov. Phys. Usp. 117 (1975) 625; Poirier, J.P., 1991. Introduction to the Physics of the Earth's Interior. Cambridge University Press, Cambridge, 102 pp.]. ( Pc, Tc) and the Lindemann <span class="hlt">melting</span> curves are in excellent accord with diamond-anvil cell (DAC) results for NaCl, KBr and stishovite. But significant discrepancies exist for transition metals. If we extrapolate the DAC <span class="hlt">melting</span> data [Phys. Rev. B 63 (2001) 132104] for transition metals (Fe, V, Mo, W and Ta) to 200-400 GPa where shock <span class="hlt">melting</span> occurs, shock temperature measurement and calculation would indicate ΘH+˜0.7-2.0. These large values of superheating are not consistent with the superheating systematics. The discrepancies could be reconciled by possible solid-solid phase transitions at high pressures. In particular, this work suggests that Fe undergoes a possible solid-solid phase transition at ˜200 GPa and <span class="hlt">melts</span> at ˜270 GPa upon shock wave loading, and the <span class="hlt">melting</span> temperature is ˜6300 K at 330 GPa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7948G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7948G"><span>The 2016 gigantic twin <span class="hlt">glacier</span> collapses in Tibet: towards an improved understanding of large <span class="hlt">glacier</span> instabilities and their potential links to climate change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gilbert, Adrien; Leinss, Silvan; Evans, Steve; Tian, Lide; Kääb, Andreas; Kargel, Jeffrey; Gimbert, Florent; Chao, Wei-An; Gascoin, Simon; Bueler, Yves; Berthier, Etienne; Yao, Tandong; Huggel, Christian; Farinotti, Daniel; Brun, Fanny; Guo, Wanqin; Leonard, Gregory</p> <p>2017-04-01</p> <p>In northwestern Tibet (34.0°N, 82.2°E) near lake Aru Co, the entire ablation area of an unnamed <span class="hlt">glacier</span> (Aru-1) suddenly collapsed on 17 July 2016 and transformed into a mass flow that ran out over a distance of over 8 km, killing nine people and hundreds of cattle. Remarkably, a second <span class="hlt">glacier</span> detachment with similar characteristics (Aru-2) took place 2.6 km south of the July event on 21 September 2016. These two events are unique in several aspects: their massive volumes (66 and 83 Mm3 respectively), the low slope angles (<13°) of the failed <span class="hlt">glacier</span> sections, the maximum avalanche speeds (> 200 km h-1) and their close timing within two months. The only similar event currently documented is the 2002 Kolka <span class="hlt">Glacier</span> mass flow (Caucasus Mountains). The uncommon occurrence of such large <span class="hlt">glacier</span> failures suggest that such events require very specific conditions that could be linked to <span class="hlt">glacier</span> thermal regime, bedrock lithology and morphology, geothermal activity or a particular climate setting. Using field and remote sensing observations, retrospective climate analysis, mass balance and thermo-mechanical modeling of the two <span class="hlt">glaciers</span> in Tibet, we investigate the processes involved in the twin collapses. It appears that both, mostly cold-based <span class="hlt">glaciers</span>, started to surge about 7-8 years ago, possibly in response to a long period of positive mass balance (1995-2005) followed by a sustained increase of <span class="hlt">melt</span> water delivery to the <span class="hlt">glacier</span> bed in the polythermal lower accumulation zone (1995-2016). Inversion of friction conditions at the base of the <span class="hlt">glacier</span> constrained by surface elevation change rate for both <span class="hlt">glaciers</span> shows a zone of very low basal friction progressively migrating downward until the final collapse. We interpret this to be the signature of the presence of high-pressure water dammed at the bed by the <span class="hlt">glacier</span>'s frozen periphery and toe. Large areas of low friction at the bed led to high shear stresses along the frozen side walls as evident in surface ice</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.7162I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.7162I"><span>Geomorphic consequences of two large <span class="hlt">glacier</span> and rock <span class="hlt">glacier</span> destabilizations in the Central and northern Chilean Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iribarren Anacona, Pablo; Bodin, Xavier</p> <p>2010-05-01</p> <p> <span class="hlt">glacier</span> covered 0.12km², nevertheless part of the material mobilized was channelised in a 200m-wide ravine generating an hyper-concentrated flow of snow, ice, water and debris, which traveled for 3 km downslope. The event of the Tinguiririca Volcano South flank occurred between the 29th of December 2006 and the 14th of January 2007 and affected a mountain <span class="hlt">glacier</span> of 0.46 km². The destabilization of this later led to a quasi complete detachment of the <span class="hlt">glacier</span> mass, which flowed to the bottom of the valley and, incorporating rock debris, snow and water, traveled downslope for more than 7 km. The destabilization and collapse of both studied landforms occurred during exceptionnaly warm periods of spring and summer and the climatic conditions produced intense <span class="hlt">glacier</span> downwasting in Chile. This situation might have favoured the destabilization, either by reducing the basal friction of the <span class="hlt">glacier</span> or by saturating the detritic sole of the rock <span class="hlt">glacier</span>, both mechanisms being related to large quantity of <span class="hlt">melt</span> water in the system. Although further research is needed, this temporal concordance suggests that those extreme geomorphologic phenomenons could be partly related to warming air temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/pp/p1386f/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/pp/p1386f/"><span><span class="hlt">Glaciers</span> of Asia</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Williams, Richard S.; Ferrigno, Jane G.</p> <p>2010-01-01</p> <p>This chapter is the ninth to be released in U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of <span class="hlt">Glaciers</span> of the World, a series of 11 chapters. In each of the geographic area chapters, remotely sensed images, primarily from the Landsat 1, 2, and 3 series of spacecraft, are used to analyze the specific <span class="hlt">glacierized</span> region of our planet under consideration and to monitor <span class="hlt">glacier</span> changes. Landsat images, acquired primarily during the middle to late 1970s and early 1980s, were used by an international team of glaciologists and other scientists to study various geographic regions and (or) to discuss related glaciological topics. In each <span class="hlt">glacierized</span> geographic region, the present areal distribution of <span class="hlt">glaciers</span> is compared, wherever possible, with historical information about their past extent. The atlas provides an accurate regional inventory of the areal extent of <span class="hlt">glacier</span> ice on our planet during the 1970s as part of a growing international scientific effort to measure global environmental change on the Earth?s surface. The chapter is divided into seven geographic parts and one topical part: <span class="hlt">Glaciers</span> of the Former Soviet Union (F-1), <span class="hlt">Glaciers</span> of China (F-2), <span class="hlt">Glaciers</span> of Afghanistan (F?3), <span class="hlt">Glaciers</span> of Pakistan (F-4), <span class="hlt">Glaciers</span> of India (F-5), <span class="hlt">Glaciers</span> of Nepal (F?6), <span class="hlt">Glaciers</span> of Bhutan (F-7), and the Paleoenvironmental Record Preserved in Middle-Latitude, High-Mountain <span class="hlt">Glaciers</span> (F-8). Each geographic section describes the <span class="hlt">glacier</span> extent during the 1970s and 1980s, the benchmark time period (1972-1981) of this volume, but has been updated to include more recent information. <span class="hlt">Glaciers</span> of the Former Soviet Union are located in the Russian Arctic and various mountain ranges of Russia and the Republics of Georgia, Kyrgyzstan, Tajikistan, and Kazakstun. The <span class="hlt">Glacier</span> Inventory of the USSR and the World Atlas of Ice and Snow Resources recorded a total of 28,881 <span class="hlt">glaciers</span> covering an area of 78,938 square kilometers (km2). China includes many of the mountain-<span class="hlt">glacier</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011TCry....5.1099G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011TCry....5.1099G"><span><span class="hlt">Glacier</span> contribution to streamflow in two headwaters of the Huasco River, Dry Andes of Chile</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gascoin, S.; Kinnard, C.; Ponce, R.; Lhermitte, S.; MacDonell, S.; Rabatel, A.</p> <p>2011-12-01</p> <p>Quantitative assessment of <span class="hlt">glacier</span> contribution to present-day streamflow is a prerequisite to the anticipation of climate change impact on water resources in the Dry Andes. In this paper we focus on two glaciated headwater catchments of the Huasco Basin (Chile, 29° S). The combination of <span class="hlt">glacier</span> monitoring data for five <span class="hlt">glaciers</span> (Toro 1, Toro 2, Esperanza, Guanaco, Estrecho and Ortigas) with five automatic streamflow records at sites with <span class="hlt">glacier</span> coverage of 0.4 to 11 % allows the estimation of the mean annual <span class="hlt">glacier</span> contribution to discharge between 2003/2004 and 2007/2008 hydrological years. In addition, direct manual measurements of <span class="hlt">glacier</span> runoff were conducted in summer at the snouts of four <span class="hlt">glaciers</span>, which provide the instantaneous contribution of <span class="hlt">glacier</span> meltwater to stream runoff during summer. The results show that the mean annual <span class="hlt">glacier</span> contribution to streamflow ranges between 3.3 and 23 %, which is greater than the glaciated fraction of the catchments. We argue that <span class="hlt">glacier</span> contribution is partly enhanced by the effect of snowdrift from the non-<span class="hlt">glacier</span> area to the <span class="hlt">glacier</span> surface. <span class="hlt">Glacier</span> mass loss is evident over the study period, with a mean of -0.84 m w.e. yr-1 for the period 2003/2004-2007/2008, and also contributes to increase <span class="hlt">glacier</span> runoff. An El Niño episode in 2002 resulted in high snow accumulation, modifying the hydrological regime and probably reducing the <span class="hlt">glacier</span> contribution in favor of seasonal snowmelt during the subsequent 2002/2003 hydrological year. At the hourly timescale, summertime <span class="hlt">glacier</span> contributions are highly variable in space and time, revealing large differences in effective <span class="hlt">melting</span> rates between <span class="hlt">glaciers</span> and glacierets (from 1 mm w.e. h-1 to 6 mm w.e. h-1).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4619K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4619K"><span>Glacial lakes amplify <span class="hlt">glacier</span> recession in the central Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>King, Owen; Quincey, Duncan; Carrivick, Jonathan; Rowan, Ann</p> <p>2016-04-01</p> <p>The high altitude and high latitude regions of the world are amongst those which react most intensely to climatic change. Across the Himalaya <span class="hlt">glacier</span> mass balance is predominantly negative. The spatial and temporal complexity associated with this ice loss across different <span class="hlt">glacier</span> clusters is poorly documented however, and our understanding of the processes driving change is limited. Here, we look at the spatial variability of <span class="hlt">glacier</span> hypsometry and glacial mass loss from three catchments in the central Himalaya; the Dudh Koshi basin, Tama Koshi basin and an adjoining section of the Tibetan Plateau. ASTER and SETSM digital elevation models (2014/15), corrected for elevation dependant biases, co-registration errors and along or cross track tilts, are differenced from Shuttle Radar Topographic Mission (SRTM) data (2000) to yield surface lowering estimates. Landsat data and a hypsometric index (HI), a classification scheme used to group <span class="hlt">glaciers</span> of similar hypsometry, are used to examine the distribution of <span class="hlt">glacier</span> area with altitude in each catchment. Surface lowering rates of >3 m/yr can be detected on some <span class="hlt">glaciers</span>, generally around the clean-ice/debris-cover boundary, where dark but thin surface deposits are likely to enhance ablation. More generally, surface lowering rates of around 1 m/yr are more pervasive, except around the terminus areas of most <span class="hlt">glaciers</span>, emphasising the influence of a thick debris cover on ice <span class="hlt">melt</span>. Surface lowering is only concentrated at <span class="hlt">glacier</span> termini where glacial lakes have developed, where surface lowering rates are commonly greater than 2.5 m/yr. The three catchments show contrasting hypsometric distributions, which is likely to impact their future response to climatic changes. <span class="hlt">Glaciers</span> of the Dudh Koshi basin store large volumes of ice at low elevation (HI > 1.5) in long, debris covered tongues, although their altitudinal range is greatest given the height of mountain peaks in the catchment. In contrast, <span class="hlt">glaciers</span> of the Tama Koshi</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28874558','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28874558"><span><span class="hlt">Glacier</span> shrinkage driving global changes in downstream systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Milner, Alexander M; Khamis, Kieran; Battin, Tom J; Brittain, John E; Barrand, Nicholas E; Füreder, Leopold; Cauvy-Fraunié, Sophie; Gíslason, Gísli Már; Jacobsen, Dean; Hannah, David M; Hodson, Andrew J; Hood, Eran; Lencioni, Valeria; Ólafsson, Jón S; Robinson, Christopher T; Tranter, Martyn; Brown, Lee E</p> <p>2017-09-12</p> <p><span class="hlt">Glaciers</span> cover ∼10% of the Earth's land surface, but they are shrinking rapidly across most parts of the world, leading to cascading impacts on downstream systems. <span class="hlt">Glaciers</span> impart unique footprints on river flow at times when other water sources are low. Changes in river hydrology and morphology caused by climate-<span class="hlt">induced</span> <span class="hlt">glacier</span> loss are projected to be the greatest of any hydrological system, with major implications for riverine and near-shore marine environments. Here, we synthesize current evidence of how <span class="hlt">glacier</span> shrinkage will alter hydrological regimes, sediment transport, and biogeochemical and contaminant fluxes from rivers to oceans. This will profoundly influence the natural environment, including many facets of biodiversity, and the ecosystem services that <span class="hlt">glacier</span>-fed rivers provide to humans, particularly provision of water for agriculture, hydropower, and consumption. We conclude that human society must plan adaptation and mitigation measures for the full breadth of impacts in all affected regions caused by <span class="hlt">glacier</span> shrinkage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5603989','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5603989"><span><span class="hlt">Glacier</span> shrinkage driving global changes in downstream systems</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Khamis, Kieran; Battin, Tom J.; Brittain, John E.; Barrand, Nicholas E.; Füreder, Leopold; Cauvy-Fraunié, Sophie; Gíslason, Gísli Már; Jacobsen, Dean; Hannah, David M.; Hodson, Andrew J.; Hood, Eran; Lencioni, Valeria; Ólafsson, Jón S.; Robinson, Christopher T.; Tranter, Martyn; Brown, Lee E.</p> <p>2017-01-01</p> <p><span class="hlt">Glaciers</span> cover ∼10% of the Earth’s land surface, but they are shrinking rapidly across most parts of the world, leading to cascading impacts on downstream systems. <span class="hlt">Glaciers</span> impart unique footprints on river flow at times when other water sources are low. Changes in river hydrology and morphology caused by climate-<span class="hlt">induced</span> <span class="hlt">glacier</span> loss are projected to be the greatest of any hydrological system, with major implications for riverine and near-shore marine environments. Here, we synthesize current evidence of how <span class="hlt">glacier</span> shrinkage will alter hydrological regimes, sediment transport, and biogeochemical and contaminant fluxes from rivers to oceans. This will profoundly influence the natural environment, including many facets of biodiversity, and the ecosystem services that <span class="hlt">glacier</span>-fed rivers provide to humans, particularly provision of water for agriculture, hydropower, and consumption. We conclude that human society must plan adaptation and mitigation measures for the full breadth of impacts in all affected regions caused by <span class="hlt">glacier</span> shrinkage. PMID:28874558</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C23A0386K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C23A0386K"><span>Turbulence-enhanced bottom <span class="hlt">melting</span> of a horizontal <span class="hlt">glacier</span>--lake interface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keitzl, T.; Mellado, J. P.; Notz, D.</p> <p>2014-12-01</p> <p>We use laboratory tank experiments and direct numerical simulations to investigate the meltrates of a horizontal bottom <span class="hlt">glacier</span>--lake interface as a function of lake temperature. Existing parameterisations of such meltrates are usually based on empirical fits to field observations. To understand the meltrates of an ice--water interface more systematically we study an idealised system in terms of its temperature-driven buoyancy forcing. In such systems, the meltrate can be expressed analytically for a stable stratification. Here we investigate the unstable case and present how the meltrate depends on the lake temperature when the water beneath the ice is overturning and turbulent. We use laboratory tank experiments and direct numerical simulations to study an idealised ice--water boundary. The laboratory tank experiments provide robust observation-based mean-temperature profiles. The numerical simulations provide the full three-dimensional structure of the turbulent flow down to scales not accessible in the laboratory, with a minimum 0.2mm gridspacing. Our laboratory mean-temperature profiles agree well with the numerical simulations and lend credibility to our numerical setup. The structure of the turbulent flow in our simulations is well described by two self-similar subregions, a diffusion-dominated inner layer close to the ice and a turbulence-dominated outer layer far from the ice. We provide an explicit expression for the parameterisation of the meltrate of a horizontal <span class="hlt">glacier</span>--lake interface as a function of lake temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22005957','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22005957"><span>Evaluation of the physicochemical properties and compaction behavior of <span class="hlt">melt</span> granules produced in microwave-<span class="hlt">induced</span> and conventional <span class="hlt">melt</span> granulation in a single pot high shear processor.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Loh, Z H; Sia, B Y; Heng, Paul W S; Lee, C C; Liew, Celine V</p> <p>2011-12-01</p> <p>Recently, microwave-<span class="hlt">induced</span> <span class="hlt">melt</span> granulation was shown to be a promising alternative to conventional <span class="hlt">melt</span> granulation with improved process monitoring capabilities. This study aimed to compare the physicochemical and compaction properties of granules produced from microwave-<span class="hlt">induced</span> and conventional <span class="hlt">melt</span> granulation. Powder admixtures comprising equivalent proportions by weight of lactose 200 M and anhydrous dicalcium phosphate were granulated with polyethylene glycol 3350 under the influence of microwave-<span class="hlt">induced</span> and conventional heating in a 10-L single pot high shear processor. The properties of the granules and compacts produced from the two processes were compared. Relative to conventional <span class="hlt">melt</span> granulation, the rates at which the irradiated powders heated up in microwave-<span class="hlt">induced</span> <span class="hlt">melt</span> granulation were lower. Agglomerate growth proceeded at a slower rate, and this necessitated longer massing durations for growth induction. These factors prompted greater evaporative moisture losses from the <span class="hlt">melt</span> granules. Additionally, nonuniform heating of the powders under the influence of microwaves led to increased inter-batch variations in the binder contents of resultant <span class="hlt">melt</span> granules and a reliance of content homogeneity on massing duration. Agglomerate growth proceeded more rapidly under the influence of conventional heating due to the enhanced heating capabilities of the powders. <span class="hlt">Melt</span> granules produced using the conventional method possessed higher moisture contents and improved content homogeneity. The compaction behavior of <span class="hlt">melt</span> granules were affected by their mean sizes, porosities, flow properties, binder, and moisture contents. The last two factors were responsible for the disparities in compaction behavior of <span class="hlt">melt</span> granules produced from microwave-<span class="hlt">induced</span> and conventional <span class="hlt">melt</span> granulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27993037','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27993037"><span>Chemical Composition of Microbe-Derived Dissolved Organic Matter in Cryoconite in Tibetan Plateau <span class="hlt">Glaciers</span>: Insights from Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Analysis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Feng, Lin; Xu, Jianzhong; Kang, Shichang; Li, Xiaofei; Li, Yang; Jiang, Bin; Shi, Quan</p> <p>2016-12-20</p> <p>Cryoconite in mountain <span class="hlt">glaciers</span> plays important roles in glacial ablation and biogeochemical cycles. In this study, the composition and sources of dissolved organic matter (DOM) in cryoconite from the ablation regions of two Tibetan Plateau <span class="hlt">glaciers</span> were determined using electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and fluorescence spectrometry. A marked absorbance between 300 and 350 nm in the DOM absorption spectra was observed which was consistent with microbe-derived mycosporine-like amino acids. Fluorescence excitation-emission matrices showed that DOM had intense signals at protein-like substance peaks and weak signals at humic-like substance peaks. The high-resolution mass spectra of FT-ICR-MS showed cryoconite DOM from both <span class="hlt">glaciers</span> contained diverse lignins, lipids, proteins, and unsaturated hydrocarbons. The lipids and proteins were consistent with material from microbial sources, and the lignins and unsaturated hydrocarbons were probably from vascular plant material supplied in atmospheric aerosols and debris from around the <span class="hlt">glaciers</span>. Almost one-third of the identified DOM molecules had low C/N ratios (≤20), indicating their high bioavailability. Using a conservative cryoconite distribution on Chinese mountain <span class="hlt">glacier</span> surfaces (6%) and an average debris mass per square meter of cryoconite (292 ± 196 g m -2 ), we found that the amount of DOC produced in cryoconite on Chinese <span class="hlt">glaciers</span> as much as 0.23 ± 0.1 Gg per cryoconite formation process. This dissolved organic carbon may absorb solar <span class="hlt">radiation</span>, accelerate glacial <span class="hlt">melting</span>, and be an important source of bioavailable DOM to proglacial and downstream aquatic ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.C41E0469B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.C41E0469B"><span>IceBridge Provides Novel Evidence for Thick Units of Basal Freeze-on Ice Along Petermann <span class="hlt">Glacier</span>, Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bell, R. E.; Tinto, K. J.; Wolovick, M.; Block, A. E.; Frearson, N.; Das, I.; Abdi, A.; Creyts, T. T.; Cochran, J. R.; Csatho, B. M.; Babonis, G. S.</p> <p>2011-12-01</p> <p>The Petermann <span class="hlt">Glacier</span>, one of the major outlet <span class="hlt">glaciers</span> in Greenland, drains six percent of the Greenland ice from a basin largely below sea level. Petermann <span class="hlt">Glacier</span> and its large ice shelf may be susceptible to increased change as the waters along the Greenland margin warm. The 2010 and 2011 Operation IceBridge mission, acquired a comprehensive aerogeophysical data set over the Petermann <span class="hlt">Glacier</span> that provides insights into the ice sheet structure. This analysis employs most of the data streams acquired by the Icebridge platform including ice-penetrating radar, laser altimetry, gravity and magnetics. An orthogonal 10 km grid extends from 60 km upstream of the grounding line to 240 km inland. The ice velocities in the region range from <50m/yr to >200m/yr. On the interior lines the internal layers are pulled down over 2-3 km wide regions. Up to 400m of ice from the base of the ice sheet appears to be absent in these regions. We interpret these pulled down regions as basal <span class="hlt">melt</span>. These <span class="hlt">melt</span> regions are mainly located along the upstream side of a 80 km wide east-west trending topographic ridge that separates the interior ice from the Petermann Fjord. The IceBridge magnetic data indicates that this broad flat ridge is the boundary between the Franklinian Basins and the Ellsmerian Foldbelt to the north. Downstream of these pull-down layers we have identified 4 distinct packages of ice that thicken downstream and are characterized by a strong upper reflector. These packages develop at the base of the ice sheet and reach thicknesses of 500-700m over distances of 10-20 km. These basal packages can be traced for 30-100 km following the direction of flow, and may be present close to the grounding line. These basal reflectors deflect the overlying internal layers upward indicating the addition of ice to the base of the ice sheet. The IceBridge gravity data indicates that these features are probably not off-nadir topography since these would show up as around 30mGal anomalies</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70025461','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70025461"><span>The health of <span class="hlt">glaciers</span>: Recent changes in <span class="hlt">glacier</span> regime</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Meier, M.F.; Dyurgerov, M.B.; McCabe, G.J.</p> <p>2003-01-01</p> <p><span class="hlt">Glacier</span> wastage has been pervasive during the last century; small <span class="hlt">glaciers</span> and those in marginal environments are disappearing, large mid-latitude <span class="hlt">glaciers</span> are shrinking slightly, and arctic <span class="hlt">glaciers</span> are warming. Net mass balances during the last 40 years are predominately negative and both winter and summer balances (accumulation and ablation) and mass turnover are increasing, especially after 1988. Two principal components of winter balance time-series explain about 50% of the variability in the data. <span class="hlt">Glacier</span> winter balances in north and central Europe correlate with the Arctic Oscillation, and <span class="hlt">glaciers</span> in western North America correlate with the Southern Oscillation and Northern Hemisphere air temperature. The degree of synchronization for distant <span class="hlt">glaciers</span> relates to changes in time of atmospheric circulation patterns as well as differing dynamic responses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010TCD.....4.2593B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010TCD.....4.2593B"><span>Longest time series of <span class="hlt">glacier</span> mass changes in the Himalaya based on stereo imagery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bolch, T.; Pieczonka, T.; Benn, D. I.</p> <p>2010-12-01</p> <p>Mass loss of Himalayan <span class="hlt">glaciers</span> has wide-ranging consequences such as declining water resources, sea level rise and an increasing risk of glacial lake outburst floods (GLOFs). The assessment of the regional and global impact of <span class="hlt">glacier</span> changes in the Himalaya is, however, hampered by a lack of mass balance data for most of the range. Multi-temporal digital terrain models (DTMs) allow <span class="hlt">glacier</span> mass balance to be calculated since the availability of stereo imagery. Here we present the longest time series of mass changes in the Himalaya and show the high value of early stereo spy imagery such as Corona (years 1962 and 1970) aerial images and recent high resolution satellite data (Cartosat-1) to calculate a time series of <span class="hlt">glacier</span> changes south of Mt. Everest, Nepal. We reveal that the <span class="hlt">glaciers</span> are significantly losing mass with an increasing rate since at least ~1970, despite thick debris cover. The specific mass loss is 0.32 ± 0.08 m w.e. a-1, however, not higher than the global average. The spatial patterns of surface lowering can be explained by variations in debris-cover thickness, <span class="hlt">glacier</span> velocity, and ice <span class="hlt">melt</span> due to exposed ice cliffs and ponds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150004434','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150004434"><span>Theoretical Foundations of Remote Sensing for <span class="hlt">Glacier</span> Assessment and Mapping</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bishop, Michael P.; Bush, Andrew B. G.; Furfaro, Roberto; Gillespie, Alan R.; Hall, Dorothy K.; Haritashya, Umesh K.; Shroder, John F., Jr.</p> <p>2014-01-01</p> <p>The international scientific community is actively engaged in assessing ice sheet and alpine <span class="hlt">glacier</span> fluctuations at a variety of scales. The availability of stereoscopic, multitemporal, and multispectral satellite imagery from the optical wavelength regions of the electromagnetic spectrum has greatly increased our ability to assess glaciological conditions and map the cryosphere. There are, however, important issues and limitations associated with accurate satellite information extraction and mapping, as well as new opportunities for assessment and mapping that are all rooted in understanding the fundamentals of the <span class="hlt">radiation</span> transfer cascade. We address the primary <span class="hlt">radiation</span> transfer components, relate them to <span class="hlt">glacier</span> dynamics and mapping, and summarize the analytical approaches that permit transformation of spectral variation into thematic and quantitative parameters. We also discuss the integration of satellite-derived information into numerical modeling approaches to facilitate understandings of <span class="hlt">glacier</span> dynamics and causal mechanisms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004glac.book.....H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004glac.book.....H"><span><span class="hlt">Glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hambrey, Michael; Alean, Jürg</p> <p>2004-12-01</p> <p><span class="hlt">Glaciers</span> are among the most beautiful natural wonders on Earth, as well as the least known and understood, for most of us. Michael Hambrey describes how <span class="hlt">glaciers</span> grow and decay, move and influence human civilization. Currently covering a tenth of the Earth's surface, <span class="hlt">glacier</span> ice has shaped the landscape over millions of years by scouring away rocks and transporting and depositing debris far from its source. <span class="hlt">Glacier</span> meltwater drives turbines and irrigates deserts, and yields mineral-rich soils as well as a wealth of valuable sand and gravel. However, <span class="hlt">glaciers</span> also threaten human property and life. Our future is indirectly connected with the fate of <span class="hlt">glaciers</span> and their influence on global climate and sea level. Including over 200 stunning photographs, the book takes the reader from the High-Arctic through North America, Europe, Asia, Africa, New Zealand and South America to the Antarctic. Michael Hambrey is Director of the Centre for Glaciology at the University of Wales, Aberystwyth. A past recipient of the Polar Medal, he was also given the Earth Science Editors' Outstanding Publication Award for the first edition of <span class="hlt">Glaciers</span> (Cambridge, 1995). Hambrey is also the author of Glacial Environments (British Columbia, 1994). JÜrg Alean is Professor of Geography at the Kantonsschule ZÜrcher Unterland in BÜlach, Switzerland.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000091536','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000091536"><span>Outlet <span class="hlt">Glacier</span> and Margin Elevation Changes: Near - Coastal Thinning of The Greenland Ice Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abdalati, W.; Krabill, W.; Frederick, E.; Manizade, S.; Martin, C.; Sonntag, J.; Swift, R.; Thomas, R.; Wright, W.; Yungel, J.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20000091536'); toggleEditAbsImage('author_20000091536_show'); toggleEditAbsImage('author_20000091536_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20000091536_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20000091536_hide"></p> <p>2000-01-01</p> <p>Repeat surveys by aircraft laser altimeter in 1993/4 and 1998/9 reveal significant thinning along 70% of the coastal parts of the Greenland ice sheet at elevations below about 2000 m. Thinning rates of more than 1 m/yr are common along many outlet <span class="hlt">glaciers</span>, at all latitudes and, in some cases, at elevations up to 1500 m. Warmer summers along parts of the coast may have caused a few tens of cm/yr additional <span class="hlt">melting</span>, but most of the observed thinning probably results from increased <span class="hlt">glacier</span> velocities and associated creep rates. Three <span class="hlt">glaciers</span> in the northeast all show patterns of thickness change indicative of surging behavior, and one has been independently documented as a surging <span class="hlt">glacier</span>. There are a few areas of significant thickening (over 1 m/yr), and these are probably related to higher than normal accumulation rates during the observation period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110013536&hterms=absorbing+carbon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dabsorbing%2Bcarbon','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110013536&hterms=absorbing+carbon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dabsorbing%2Bcarbon"><span>Enhanced Surface Warming and Accelerated Snow <span class="hlt">Melt</span> in the Himalayas and Tibetan Plateau <span class="hlt">Induced</span> by Absorbing Aerosols</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lau, William K.; Kim, Maeng-Ki; Kim, Kyu-Myong; Lee, Woo-Seop</p> <p>2010-01-01</p> <p>Numerical experiments with the NASA finite-volume general circulation model show that heating of the atmosphere by dust and black carbon can lead to widespread enhanced warming over the Tibetan Plateau (TP) and accelerated snow <span class="hlt">melt</span> in the western TP and Himalayas. During the boreal spring, a thick aerosol layer, composed mainly of dust transported from adjacent deserts and black carbon from local emissions, builds up over the Indo-Gangetic Plain, against the foothills of the Himalaya and the TP. The aerosol layer, which extends from the surface to high elevation (approx.5 km), heats the mid-troposphere by absorbing solar <span class="hlt">radiation</span>. The heating produces an atmospheric dynamical feedback the so-called elevated-heat-pump (EHP) effect, which increases moisture, cloudiness, and deep convection over northern India, as well as enhancing the rate of snow <span class="hlt">melt</span> in the Himalayas and TP. The accelerated <span class="hlt">melting</span> of snow is mostly confined to the western TP, first slowly in early April and then rapidly from early to mid-May. The snow cover remains reduced from mid-May through early June. The accelerated snow <span class="hlt">melt</span> is accompanied by similar phases of enhanced warming of the atmosphere-land system of the TP, with the atmospheric warming leading the surface warming by several days. Surface energy balance analysis shows that the short-wave and long-wave surface <span class="hlt">radiative</span> fluxes strongly offset each other, and are largely regulated by the changes in cloudiness and moisture over the TP. The slow <span class="hlt">melting</span> phase in April is initiated by an effective transfer of sensible heat from a warmer atmosphere to land. The rapid <span class="hlt">melting</span> phase in May is due to an evaporation-snow-land feedback coupled to an increase in atmospheric moisture over the TP <span class="hlt">induced</span> by the EHP effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/pp/1386e/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/pp/1386e/report.pdf"><span><span class="hlt">Glaciers</span> of Europe</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Williams, Richard S.; Ferrigno, Jane G.</p> <p>1993-01-01</p> <p>ALPS: AUSTRIAN: An overview is provided on the occurrence of the <span class="hlt">glaciers</span> in the Eastern Alps of Austria and on the climatic conditions in this area, Historical documents on the <span class="hlt">glaciers</span> have been available since the Middle Ages. Special glaciological observations and topographic surveys of individual <span class="hlt">glaciers</span> were initiated as early as 1846. Recent data in an inventory based on aerial photographs taken in 1969 show 925 <span class="hlt">glaciers</span> in the Austrian Alps with a total area of 542 square kilometers. Present research topics include studies of mass and energy balance, relations of <span class="hlt">glaciers</span> and climate, physical glaciology, a complete inventory of the <span class="hlt">glaciers</span>, and testing of remote sensing methods. The location of the <span class="hlt">glacier</span> areas is shown on Landsat multispectral scanner images; the improved capabilities of the Landsat thematic mapper are illustrated with an example from the Oztaler Alpen group. ALPS: SWISS: According to a <span class="hlt">glacier</span> inventory published in 1976, which is based on aerial photography of 1973, there are 1,828 <span class="hlt">glacier</span> units in the Swiss Alps that cover a total area of 1fl42 square kilometers. The Rhonegletscher, currently the ninth largest in the country, was one of the first to be studied in detail. Its surface has been surveyed repeatedly; velocity profiles were measured, and the fluctuations of its terminus were mapped and recorded from 1874 to 1914. Recent research on the <span class="hlt">glacier</span> has included climatological, hydrological, and massbalance studies. Glaciological research has been conducted on various other <span class="hlt">glaciers</span> in Switzerland concerning <span class="hlt">glacier</span> hydrology, <span class="hlt">glacier</span> hazards, fluctuations of <span class="hlt">glacier</span> termini, ice mechanics, ice cores, and mass balance. Good maps are available showing the extent of <span class="hlt">glaciers</span> from the latter decades of the 19th century. More recently, the entire country has been mapped at scales of 1:25,000, 1:50,000, 1:100,000, 1:200,000, and 1:500,000. The 1:25,000-scale series very accurately represents the <span class="hlt">glaciers</span> as well as locates</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C53D0774O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C53D0774O"><span>Impacts of Topographic Shading on Surface Energy Balance of High Mountain Asia <span class="hlt">Glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olson, M.; Rupper, S.</p> <p>2016-12-01</p> <p>Topographic shading plays an important role in the energy balance of valley <span class="hlt">glaciers</span>. While previous studies incorporate shading of varying complexity in surface energy balance models, to date, no large-scale studies have explored in depth the effects of topographic shading on <span class="hlt">glacier</span> surface energy balance, and how these vary geographically within High Mountain Asia (HMA). Here we develop a model to examine the variability in potential insolation during the summer <span class="hlt">melt</span> season using the ASTER GDEM and multi-hour solar geometry to simulate topographic shading on an idealized <span class="hlt">glacier</span>. Shading is calculated in simulations utilizing a range of slopes, aspects, and latitudes. We test <span class="hlt">glacier</span> mass balance sensitivity to these parameters for a suite of <span class="hlt">glaciers</span> throughout HMA. Our results show that shading impacts on <span class="hlt">glaciers</span> in HMA are highly variable across different geographic regions, but that they are largely predictable based on topographic characteristics such as slope and aspect. For example, we find in regions with steep topography and high relief that shading frequently dominates in the ablation zone rather than the accumulation zone, contrary to the findings of some previous studies. In these regions, topographic shading may play a more significant role in <span class="hlt">glacier</span> energy balance. These results will better define the effects of topographic shading on surface energy balance, and improve model accuracy within HMA. Additionally, this topographic shading model provides a framework to quantify how shading effects vary for advancing or retreating <span class="hlt">glaciers</span> as they respond to fluctuations in climate across HMA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.2322V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.2322V"><span>Under the <span class="hlt">glacier</span>, the groundwater - the case of Skálafell area, Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vincent, Aude; Hart, Jane</p> <p>2017-04-01</p> <p>The research addressing <span class="hlt">glaciers</span> evolution under climate change is well developed, and is now looking not only at their mass balance, but also at the associated subsurface hydrology and downstream hydrology. However, the groundwater component is rarely considered, even though it will be required to forecast the evolution of water resources and of water linked hazards under climate change. The few available studies demonstrate the existence of sub-or pro-glacial aquifers. Some of them suggest strong coupling between rivers and the aquifer, observe the flooding due to water table rising following enhanced <span class="hlt">glacier</span> <span class="hlt">melting</span>, or expect stronger recharge in the future due to <span class="hlt">glacier</span> <span class="hlt">melting</span>. The present study is the first step of a wider project, GlacAq, aiming at filling this knowledge gap, by characterizing the particular hydrogeology encountered under and downstream of <span class="hlt">glaciers</span> of alpine type, i.e. sub-, pro- and periglacial hydrogeology, and its sensibility to climate change, in order to provide operational management directions. Skálafell <span class="hlt">glacier</span> area (Iceland) has been chosen as it has already been followed for climatic, glaciological, and surface hydrology data (Hart et al. (2015), Young et al. (2015)). The present work will use those data, as well as topographic and surface data from the National Land Survey of Iceland, and geological data, to run a comprehensive numerical modelling. The work conducted on the Skálafell site will lead both to the achievement of an operational understanding of a poorly known underground system, and to the anticipation of its hydrodynamic response to climate change. The foreseen mechanisms include an enhanced sub-glacial aquifer recharge, intense surface water bodies-aquifer exchanges, and the aquifer discharge either through springs, or to an offshore system. Those offshore stocks are being increasingly recognised, but their origins are still only guessed at. Skálafell site allows the exploration of the potential role of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011TCD.....5.3423D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011TCD.....5.3423D"><span>Seasonal speed-up of two outlet <span class="hlt">glaciers</span> of Austfonna, Svalbard, inferred from continuous GPS measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dunse, T.; Schuler, T. V.; Hagen, J. O.; Reijmer, C. H.</p> <p>2011-12-01</p> <p>A large part of the ice discharge from ice caps and ice sheets occurs through spatially limited flow units that may operate in a mode of steady flow or cyclic surge behaviour. Changes in the dynamics of distinct flow units play a key role in the mass balance of Austfonna, the largest ice cap on Svalbard. The recent net mass loss of Austfonna was dominated by calving from marine terminating outlet <span class="hlt">glaciers</span>. Previous ice-surface velocity maps of the ice cap were derived by satellite radar interferometry (InSAR) and rely on data acquired in the mid-1990s with limited information concerning the temporal variability. Here, we present continuous Global Positioning System (GPS) observations along the central flowlines of two fast flowing outlet <span class="hlt">glaciers</span> over 2008-2010. The data show prominent summer speed-ups with ice-surface velocities as high as 240 % of the pre-summer mean. Acceleration follows the onset of the summer <span class="hlt">melt</span> period, indicating enhanced basal motion due to input of surface meltwater into the subglacial drainage system. In 2008, multiple velocity peaks coincide with successive <span class="hlt">melt</span> periods. In 2009, the principle <span class="hlt">melt</span> was of higher amplitude than in 2008. Flow velocities appear unaffected by subsequent <span class="hlt">melt</span> periods, suggesting a transition towards a hydraulically more efficient drainage system. The observed annual mean velocities of Duvebreen and Basin-3 exceed those from the mid-1990s by factors two and four, respectively, implying increased ice discharge at the calving front. Measured summer velocities up to 2 m d-1 for Basin-3 are close to that of Kronebreen, often referred to as the fastest <span class="hlt">glacier</span> on Svalbard.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4981079','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4981079"><span>Dynamics of <span class="hlt">glacier</span> calving at the ungrounded margin of Helheim <span class="hlt">Glacier</span>, southeast Greenland</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Selmes, Nick; James, Timothy D.; Edwards, Stuart; Martin, Ian; O'Farrell, Timothy; Aspey, Robin; Rutt, Ian; Nettles, Meredith; Baugé, Tim</p> <p>2015-01-01</p> <p>Abstract During summer 2013 we installed a network of 19 GPS nodes at the ungrounded margin of Helheim <span class="hlt">Glacier</span> in southeast Greenland together with three cameras to study iceberg calving mechanisms. The network collected data at rates up to every 7 s and was designed to be robust to loss of nodes as the <span class="hlt">glacier</span> calved. Data collection covered 55 days, and many nodes survived in locations right at the <span class="hlt">glacier</span> front to the time of iceberg calving. The observations included a number of significant calving events, and as a consequence the <span class="hlt">glacier</span> retreated ~1.5 km. The data provide real‐time, high‐frequency observations in unprecedented proximity to the calving front. The <span class="hlt">glacier</span> calved by a process of buoyancy‐force‐<span class="hlt">induced</span> crevassing in which the ice downglacier of flexion zones rotates upward because it is out of buoyant equilibrium. Calving then occurs back to the flexion zone. This calving process provides a compelling and complete explanation for the data. Tracking of oblique camera images allows identification and characterisation of the flexion zones and their propagation downglacier. Interpretation of the GPS data and camera data in combination allows us to place constraints on the height of the basal cavity that forms beneath the rotating ice downglacier of the flexion zone before calving. The flexion zones are probably formed by the exploitation of basal crevasses, and theoretical considerations suggest that their propagation is strongly enhanced when the <span class="hlt">glacier</span> base is deeper than buoyant equilibrium. Thus, this calving mechanism is likely to dominate whenever such geometry occurs and is of increasing importance in Greenland. PMID:27570721</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H42B..07H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H42B..07H"><span>Peak water from <span class="hlt">glaciers</span>: advances and challenges in a global perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huss, M.; Hock, R.</p> <p>2014-12-01</p> <p>Mountain <span class="hlt">glaciers</span> show a high sensitivity to changes in climate forcing. In a global perspective, their anticipated retreat will pose far-reaching challenges to the management of fresh water resources and will raise sea levels significantly within only a few decades. Different model frameworks have been applied to simulate <span class="hlt">melt</span> water contributions of <span class="hlt">glaciers</span> outside the two ice sheets for the recent IPCC report. However, these models depend on strongly simplified, and often empirical descriptions of the driving processes hampering the reliability of the results. Thus, a transition from the physically-based mass balance-ice flow models developed for single <span class="hlt">glaciers</span> to the application at the global scale is urgently needed. The challenges are manifold but can be tackled with the new data sets, methods and process-understanding that have emerged during the last years. Here, we present a novel <span class="hlt">glacier</span> model for calculating the response of surface mass balance and 3D <span class="hlt">glacier</span> geometry for each individual <span class="hlt">glacier</span> around the globe. Our approach accounts for feedbacks due to <span class="hlt">glacier</span> retreat and includes models for mass loss due to frontal ablation and refreezing of water in the snow/firn. This allows the calculation of the components of proglacial runoff for each individual <span class="hlt">glacier</span> in a process-based way. The current surface geometry and thickness distribution for each of the world's roughly 200'000 <span class="hlt">glaciers</span> is extracted from the Randolph <span class="hlt">Glacier</span> Inventory v3.3 and terrain models. Our simulations are driven with 14 Global Circulation Models from the CMIP5 project using the RCP4.5, RCP8.5 and RCP2.6 scenarios. We focus on the timing of peak water from <span class="hlt">glacierized</span> catchments in all climatic regions of the earth and the corresponding importance of these regime changes on hydrological stress. Peak water represents a crucial tipping point for sustained water supply even for regions with only a minor <span class="hlt">glacier</span> coverage, and is relevant to the dynamics of sea level rise. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120003525','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120003525"><span>Effects of Absorbing Aerosols on Accelerated <span class="hlt">Melting</span> of Snowpack in the Hindu-Kush-Himalayas-Tibetan Plateau Region</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lau, William K.; Kyu-Myong, Kim; Yasunari, Teppei; Gautam, Ritesh; Hsu, Christina</p> <p>2011-01-01</p> <p>The impacts of absorbing aerosol on <span class="hlt">melting</span> of snowpack in the Hindu-Kush-Himalayas-Tibetan Plateau (HKHT) region are studied using in-situ, satellite observations, and GEOS-5 GCM. Based on atmospheric black carbon measurements from the Pyramid observation ( 5 km elevation) in Mt. Everest, we estimate that deposition of black carbon on snow surface will give rise to a reduction in snow surface albedo of 2- 5 %, and an increased annual runoff of 12-34% for a typical Tibetan <span class="hlt">glacier</span>. Examination of satellite reflectivity and re-analysis data reveals signals of possible impacts of dust and black carbon in darkening the snow surface, and accelerating spring <span class="hlt">melting</span> of snowpack in the HKHT, following a build-up of absorbing aerosols in the Indo-Gangetic Plain. Results from GCM experiments show that 8-10% increase in the rate of <span class="hlt">melting</span> of snowpack over the western Himalayas and Tibetan Plateau can be attributed to the elevated-heat-pump (EHP) feedback effect, initiated from the absorption of solar <span class="hlt">radiation</span> by dust and black carbon accumulated to great height ( 5 km) over the Indo-Gangetic Plain and Himalayas foothills in the pre-monsoon season (April-May). The accelerated <span class="hlt">melting</span> of the snowpack is enabled by an EHP-<span class="hlt">induced</span> atmosphere-land-snowpack positive feedback involving a) orographic forcing of the monsoon flow by the complex terrain, and thermal forcing of the HKHT region, leading to increased moisture, cloudiness and rainfall over the Himalayas foothills and northern India, b) warming of the upper troposphere over the Tibetan Plateau, and c) an snow albedo-temperature feedback initiated by a transfer of latent and sensible heat from a warmer atmosphere over the HKHT to the underlying snow surface. Results from ongoing modeling work to assess the relative roles of EHP vs. snow-darkening effects on accelerated <span class="hlt">melting</span> of snowpack in HKHT region will also be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRF..121.1834D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRF..121.1834D"><span>A modeling study of the effect of runoff variability on the effective pressure beneath Russell <span class="hlt">Glacier</span>, West Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Fleurian, Basile; Morlighem, Mathieu; Seroussi, Helene; Rignot, Eric; van den Broeke, Michiel R.; Kuipers Munneke, Peter; Mouginot, Jeremie; Smeets, Paul C. J. P.; Tedstone, Andrew J.</p> <p>2016-10-01</p> <p>Basal sliding is a main control on <span class="hlt">glacier</span> flow primarily driven by water pressure at the <span class="hlt">glacier</span> base. The ongoing increase in surface <span class="hlt">melting</span> of the Greenland Ice Sheet warrants an examination of its impact on basal water pressure and in turn on basal sliding. Here we examine the case of Russell <span class="hlt">Glacier</span>, in West Greenland, where an extensive set of observations has been collected. These observations suggest that the recent increase in <span class="hlt">melt</span> has had an equivocal impact on the annual velocity, with stable flow on the lower part of the drainage basin but accelerated flow above the Equilibrium Line Altitude (ELA). These distinct behaviors have been attributed to different evolutions of the subglacial draining system during and after the <span class="hlt">melt</span> season. Here we use a high-resolution subglacial hydrological model forced by reconstructed surface runoff for the period 2008 to 2012 to investigate the cause of these distinct behaviors. We find that the increase in meltwater production at low elevation yields a more efficient drainage system compatible with the observed stagnation of the mean annual flow below the ELA. At higher elevation, the model indicates that the drainage system is mostly inefficient and is therefore strongly sensitive to an increase in meltwater availability, which is consistent with the observed increase in ice velocity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PhDT.......224K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PhDT.......224K"><span>The response of <span class="hlt">glaciers</span> to climate change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klok, Elisabeth Jantina</p> <p>2003-12-01</p> <p>The research described in this thesis addresses two aspects of the response of <span class="hlt">glaciers</span> to climate change. The first aspect deals with the physical processes that govern the interaction between <span class="hlt">glaciers</span> and climate change and was treated by (1) studying the spatial and temporal variation of the <span class="hlt">glacier</span> albedo from satellite images, (2) investigating the spatial distribution of the surface energy and mass balance of a <span class="hlt">glacier</span>, and (3) investigating the sensitivity of the mass balance to climate change. All of these studies are focused on Morteratschgletscher in Switzerland. The second aspect is the climatic interpretation of <span class="hlt">glacier</span> length fluctuations. This was studied by developing a model that calculates historical mass balance records from global <span class="hlt">glacier</span> length fluctuations. To increase our understanding of the variations in <span class="hlt">glacier</span> albedo, we derived surface albedos from 12 Landsat images. This constituted a stringent test for the retrieval methodology applied because Morteratschgletscher is very steep and rugged, which strongly influences the satellite signal. We aimed to retrieve surface albedos while taking into account all important processes that influence the relationship between the satellite signal and the surface albedo, e.g. the topographic effects on incoming solar <span class="hlt">radiation</span>, and the anisotropic nature of the reflection pattern of ice and snow surfaces. We then analysed the spatial and temporal pattern of the surface albedo. We developed a two-dimensional mass balance model based on the surface energy balance to study the spatial distribution of the energy and mass balance fluxes of Morteratschgletscher. Meteorological data from weather stations in the vicinity of Morteratschgletscher serve as input for the model. We corrected incoming solar <span class="hlt">radiation</span> for shading, aspect, slope, reflection from surrounding slopes, and obstruction of the sky. Ignoring these effects results in an increase in solar <span class="hlt">radiation</span> of 37%, causing a decrease in the mass</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890052291&hterms=Glasses+SiO2&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DGlasses%2BSiO2','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890052291&hterms=Glasses+SiO2&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DGlasses%2BSiO2"><span>Shock temperatures in silica glass - Implications for modes of shock-<span class="hlt">induced</span> deformation, phase transformation, and <span class="hlt">melting</span> with pressure</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schmitt, Douglas R.; Ahrens, Thomas J.</p> <p>1989-01-01</p> <p>Observations of shock-<span class="hlt">induced</span> <span class="hlt">radiative</span> thermal emissions are used to determine the gray body temperatures and emittances of silica glass under shock compression between 10 and 30 GPa. The results suggest that fused quartz deforms heterogeneously in this shock pressure range. It is shown that the 10-16 GPa range coincides with the permanent densification region, while the 16-30 GPa range coincides with the inferred mixed phase region along the silica glass Hugoniot. Low emittances in the mixed phase region are thought to represent the <span class="hlt">melting</span> temperature of the high-pressure phase, stishovite. Also, consideration is given to the effects of pressure on <span class="hlt">melting</span> relations for the system SiO2-Mg2SiO4.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.H12F..06I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.H12F..06I"><span>Bed-Deformation Experiments Beneath a Temperate <span class="hlt">Glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iverson, N. R.; Hooyer, T. S.; Fischer, U. H.; Cohen, D.; Jackson, M.; Moore, P. L.; Lappegard, G.; Kohler, J.</p> <p>2002-12-01</p> <p>Fast flow of <span class="hlt">glaciers</span> and genesis of glacial landforms are commonly attributed to shear deformation of subglacial sediment. Although models of this process abound, data gathered subglacially on the kinematics and mechanics of such deformation are difficult to interpret. Major difficulties stem from the necessity of either measuring deformation near <span class="hlt">glacier</span> margins, where conditions may be abnormal, or at the bottoms of boreholes, where the scope of instrumentation is limited, drilling disturbs sediment, and local boundary conditions are poorly known. A different approach is possible at the Svartisen Subglacial Laboratory, where tunnels <span class="hlt">melted</span> in the ice provide temporary human access to the bed of Engabreen, a temperate outlet <span class="hlt">glacier</span> of the Svartisen Ice Cap in Norway. A trough (2 m x 1.5 m x 0.5 m deep) was blasted in the rock bed, where the <span class="hlt">glacier</span> is 220 m thick and sliding at 0.1-0.2 m/d. During two spring field seasons, this trough was filled with 2.5 tons of simulated till. Instruments in the till recorded shear (tiltmeters), volume change, total normal stress, and pore-water pressure as ice moved across the till surface. Pore pressure was brought to near the total normal stress by feeding water to the base of the till with a high-pressure pump, operated in a rock tunnel 4 m below the bed surface. Results illustrate some fundamental aspects of bed deformation. Permanent shear deformation requires low effective normal stress and hence high pore-water pressure, owing to the frictional nature of till. Shear strain generally increases upward in the bed toward the <span class="hlt">glacier</span> sole, consistent with previous measurements beneath thinner ice at <span class="hlt">glacier</span> margins. At low effective normal stresses, ice sometimes decouples from underlying till. Overall, bed deformation accounts for 10-35 % of basal motion, although this range excludes shear in the uppermost 0.05 m of till where shear was not measured. Pump tests with durations ranging from seconds to hours highlight the need</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDG10003W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDG10003W"><span>Turbulent convection driven by internal <span class="hlt">radiative</span> heating of <span class="hlt">melt</span> ponds on sea ice</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wells, Andrew; Langton, Tom; Rees Jones, David; Moon, Woosok</p> <p>2016-11-01</p> <p>The <span class="hlt">melting</span> of Arctic sea ice is strongly influenced by heat transfer through <span class="hlt">melt</span> ponds which form on the ice surface. <span class="hlt">Melt</span> ponds are internally heated by the absorption of incoming <span class="hlt">radiation</span> and cooled by surface heat fluxes, resulting in vigorous buoyancy-driven convection in the pond interior. Motivated by this setting, we conduct two-dimensional direct-numerical simulations of the turbulent convective flow of a Boussinesq fluid between two horizontal boundaries, with internal heating predicted from a two-stream <span class="hlt">radiation</span> model. A linearised thermal boundary condition describes heat exchange with the overlying atmosphere, whilst the lower boundary is isothermal. Vertically asymmetric convective flow modifies the upper surface temperature, and hence controls the partitioning of the incoming heat flux between emission at the upper and lower boundaries. We determine how the downward heat flux into the ice varies with a Rayleigh number based on the internal heating rate, the flux ratio of background surface cooling compared to internal heating, and a Biot number characterising the sensitivity of surface fluxes to surface temperature. Thus we elucidate the physical controls on heat transfer through Arctic <span class="hlt">melt</span> ponds which determine the fate of sea ice in the summer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP12C..01M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP12C..01M"><span>The Petermann <span class="hlt">Glacier</span> Experiment, NW Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mix, A. C.; Jakobsson, M.; Andrews, J. T.; Jennings, A. E.; Mayer, L. A.; Marcott, S. A.; Muenchow, A.; Stoner, J. S.; Andresen, C. S.; Nicholls, K. W.; Anderson, S. T.; Brook, E.; Ceperley, E. G.; Cheseby, M.; Clark, J.; Dalerum, F.; Dyke, L. M.; Einarsson, D.; Eriksson, B.; Frojd, C.; Glueder, A.; Hedman, U.; Heirman, K.; Heuzé, C.; Hogan, K.; Holden, R.; Holm, C.; Jerram, K.; Krutzfeldt, J.; Nicolas, L.; Par, L.; Lomac-MacNair, K.; Madlener, S.; McKay, J. L.; Meijer, T.; Meiton, A.; Brian, M.; Mohammed, R.; Molin, M.; Moser, C.; Normark, E.; Padman, J.; Pecnerova, P.; Reilly, B.; Reusche, M.; Ross, A.; Stranne, C.; Trinhammer, P.; Walczak, M. H.; Walczak, P.; Washam, P.; Karasti, M.; Anker, P.</p> <p>2016-12-01</p> <p>The Petermann <span class="hlt">Glacier</span> Experiment is a comprehensive study on land, ocean, and ice in Northwest Greenland, staged from Swedish Icebreaker Oden in 2015 as a collaboration between the US, Sweden, UK, and Denmark. This talk introduces the strategic goals of the experiment and connects the various scientific results. Petermann <span class="hlt">Glacier</span> drains a significant marine-based sector of the northern Greenland Ice Sheet and terminates in a floating ice tongue, one of the largest remaining systems of its kind in the northern hemisphere. Records of the modern state of Petermann <span class="hlt">Glacier</span> and its past variations are of interest to understand the sensitivity of marine terminating outlet <span class="hlt">glaciers</span> to change, and to constrain the rates and extent of changes that have actually occurred. With this case study we are learning the rules of large scale dynamics that cannot be understood from modern observations alone. Although past behavior is not an simple analog for the future, and no single system captures all possible behaviors, insights from these case studies can be applied through models to better project how similar systems may change in the future. The Petermann Expedition developed the first comprehensive bathymetric maps of the region, drilled through the floating ice tongue to obtain sub-shelf sediment cores near the grounding line and to monitor sub-ice conditions, recovered a broad array of sediment cores documenting changing oceanic conditions in Petermann Fjord, Hall Basin, and Nares Strait, measured watercolumn properties to trace subsurface watermasses that bring heat from the Arctic Ocean into deep Petermann Fjord to <span class="hlt">melt</span> the base of the floating ice tongue, developed a detailed record of relative sealevel change on land to constrain past ice loads, and recovered pristine boulders for cosmogenic exposure dating of areal ice retreat on land. Together, these studies are shedding new light on the dynamics of past glaciation in Northwest Greenland, and contributing to fundamental</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMNS21A1919W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNS21A1919W"><span>Estimating Temporal Redistribution of Surface <span class="hlt">Melt</span> Water into Upper Stratigraphy of the Juneau Icefield, Alaska</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wilner, J.; Smith, B.; Moore, T.; Campbell, S. W.; Slavin, B. V.; Hollander, J.; Wolf, J.</p> <p>2015-12-01</p> <p>The redistribution of winter accumulation from surface <span class="hlt">melt</span> into firn or deeper layers (i.e. internal accumulation) remains a poorly understood component of <span class="hlt">glacier</span> mass balance. Winter accumulation is usually quantified prior to summer <span class="hlt">melt</span>, however the time window between accumulation and the onset of <span class="hlt">melt</span> is minimal so this is not always possible. Studies which are initiated following the onset of summer <span class="hlt">melt</span> either neglect sources of internal accumulation or attempt to estimate <span class="hlt">melt</span> (and therefore winter accumulation uncertainty) through a variety of modeling methods. Here, we used ground-penetrating radar (GPR) repeat common midpoint (CMP) surveys with supporting common offset surveys, mass balance snow pits, and probing to estimate temporal changes in water content within the winter accumulation and firn layers of the southern Juneau Icefield, Alaska. In temperate <span class="hlt">glaciers</span>, radio-wave velocity is primarily dependent on water content and snow or firn density. We assume density changes are temporally slow relative to water flow through the snow and firn pack, and therefore infer that changing radio-wave velocities measured by successive CMP surveys result from flux in surface <span class="hlt">melt</span> through deeper layers. Preliminary CMP data yield radio-wave velocities of 0.15 to 0.2 m/ns in snowpack densities averaging 0.56 g cm-3, indicating partially to fully saturated snowpack (4-9% water content). Further spatial-temporal analysis of CMP surveys is being conducted. We recommend that repeat CMP surveys be conducted over a longer time frame to estimate stratigraphic water redistribution between the end of winter accumulation and maximum <span class="hlt">melt</span> season. This information could be incorporated into surface energy balance models to further understanding of the influence of internal accumulation on <span class="hlt">glacier</span> mass balance.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.4160R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.4160R"><span>Mass balance of Djankuat <span class="hlt">Glacier</span>, Central Caucasus: observations, modeling and prediction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rybak, Oleg; Mariia, Kaminskaia; Stanislav, Kutuzov; Ivan, Lavrentiev; Polina, Morozova; Victor, Popovnin; Elena, Rybak</p> <p>2017-04-01</p> <p>Djankuat is a typical valley <span class="hlt">glacier</span> on the northern slope of the main Caucasus chain. Its present day area is approximately 2.5 square km with the characteristic ice thickness of several tens of meters. As well as other <span class="hlt">glaciers</span> in the region, Djankuat has been shrinking during the last several decades, its cumulative mass balance in 1968-2016 was equal to -13.6 m w.e. In general, Caucasus' <span class="hlt">glaciers</span> lost approximately one-third of their area and half of the volume. Prediction of further deradation of <span class="hlt">glaciers</span> in changing environment is a challenging task because rivers fed by <span class="hlt">glacier</span> <span class="hlt">melt</span> water provide from 40 to 70% of the total river run-off in the adjacent piedmont territories. Growing demand in fresh water is rather critical for the local economy development and for growing population, motivating elaboration of an effitient instrument for evaluation and forecasting of the glaciation in the Greater Caucasus. Unfortunately, systematic observations are sparse limiting possibilities for proper model development for the most of the <span class="hlt">glaciers</span>. Under these circumstances, we have to rely on the models developed for the few well-studied ones, like Djankuat, which is probably one of the most explored <span class="hlt">glaciers</span> in the world. Accumulation and ablation rates have been observed here systematically and uninterruptedly since mid 60-ies using dense stake network. Together with the mass balance components, changes in flow velocity, ice thickness and geometry were regularly evaluated. During the last several ablation seasons, direct meteorological observations were carried out using an AMS. Long series of meteorological observations at the nearest weather station allow making assessment of the <span class="hlt">glacier</span> response to climate change in the second half of the 20th century. Abundant observation data gave us the opportunity to elaborate, calibrate and validate an efficient mathematical model of surface mass balance of a typical <span class="hlt">glacier</span> in the region. Since many <span class="hlt">glaciers</span> in the Caucasus</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1614786A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1614786A"><span>Bacteria at <span class="hlt">glacier</span> surfaces: microbial community structures in debris covered <span class="hlt">glaciers</span> and cryoconites in the Italian Alps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Azzoni, Roberto; Franzetti, Andrea; Ambrosini, Roberto; D'Agata, Carlo; Senese, Antonella; Minora, Umberto; Tagliaferri, Ilario; Diolaiuti, Guglielmina</p> <p>2014-05-01</p> <p>Supraglacial debris has an important role in the <span class="hlt">glacier</span> energy budget and has strong influence on the glacial ecosystem. Sediment derives generally from rock inputs from nesting rockwalls and are abundant and continuous at the surface of debris-covered <span class="hlt">glaciers</span> (i.e. DCGs; <span class="hlt">glaciers</span> where the ablation area is mainly covered by rock debris) and sparse and fine on debris-free <span class="hlt">glaciers</span> (DFGs). Recently, evidence for significant tongue darkening on retreating debris-free <span class="hlt">glaciers</span> has been drawing increasing attention. Fine particles, the cryoconite, are locally abundant and may form cryoconite holes that are water-filled depressions on the surface of DFGs that form when a thin layer of cryoconite is heated by the sun and <span class="hlt">melts</span> the underlying ice. There is increasing evidence that cryoconite holes also host highly diverse microbial communities and can significantly contribute to global carbon cycle. However, there is almost no study on microbial communities of the debris cover of DCGs and there is a lack of data from the temporal evolution of the microbial communities in the cryoconites. To fill these gaps in our knowledge we characterized the supraglacial debris of two Italian DCGs and we investigated the temporal evolution of microbial communities on cryoconite holes in DFG. We used the Illumina technology to analyse the V5 and V6 hypervariable regions of the bacterial 16S rRNA gene amplified from samples collected distances from the terminus of two DCGs (Miage and Belvedere <span class="hlt">Glaciers</span> - Western Italian Alps). Heterotrophic taxa dominated bacterial communities, whose structure changed during downwards debris transport. Organic carbon of these recently exposed substrates therefore is probably provided more by allochthonous deposition of organic matter than by primary production by autotrophic organisms. We used ARISA fingerprinting and quantitative PCR to describe the structure and the evolution of the microbial communities and to estimate the number of the total</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.loc.gov/pictures/collection/hh/item/ca1656.photos.190898p/','SCIGOV-HHH'); return false;" href="https://www.loc.gov/pictures/collection/hh/item/ca1656.photos.190898p/"><span>2. HORSESHOE CURVE IN <span class="hlt">GLACIER</span> POINT ROAD NEAR <span class="hlt">GLACIER</span> POINT. ...</span></a></p> <p><a target="_blank" href="http://www.loc.gov/pictures/collection/hh/">Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey</a></p> <p></p> <p></p> <p>2. HORSESHOE CURVE IN <span class="hlt">GLACIER</span> POINT ROAD NEAR <span class="hlt">GLACIER</span> POINT. HALF DOME AT CENTER REAR. LOOKING NNE. GIS N-37 43 44.3 / W-119 34 14.1 - <span class="hlt">Glacier</span> Point Road, Between Chinquapin Flat & <span class="hlt">Glacier</span> Point, Yosemite Village, Mariposa County, CA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1910457M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1910457M"><span>Application of a hybrid method for downscaling of the global climate model fields for evaluation of future surface mass balance of mountain <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morozova, Polina; Rybak, Oleg; Kaminskaia, Mariia</p> <p>2017-04-01</p> <p> significant, less than 10%. Absorbed shortwave <span class="hlt">radiation</span> will increase by approximately 5%. These changes yield in dramatic shifting of the ELAs to the positions much higher than at present. This will inevitably cause degradation of the <span class="hlt">glaciers</span> and their gradual disappearance. The main contribution to <span class="hlt">glacier</span> shrinking will be made by increase of air surface temperature via enhanced ablation and extension of the <span class="hlt">melting</span> season duration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010081592','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010081592"><span>Mineralogy and Microstructures of Shock-<span class="hlt">Induced</span> <span class="hlt">Melt</span> Veins in Chondrites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sharp, Thomas G.</p> <p>2000-01-01</p> <p>The applicability of phase equilibrium data to the interpretation of shock-<span class="hlt">induced</span> <span class="hlt">melt</span> veins can only be tested by a detailed study of <span class="hlt">melt</span>- vein mineralogy to see how high-pressure assemblages vary as a function of shock conditions inferred from other indicators. We have used transmission electron microscopy (TEM), analytical electron microscopy (AEM), scanning electron microscopy (SEM), electron microprobe analysis (EMA) and optical petrography to characterize the mineralogy, microstructures, and compositions of <span class="hlt">melt</span> veins and associated high-pressure minerals in shocked chondrites and SNC meteorites. In the processes, we have gained a better understanding of what <span class="hlt">melt</span> veining can tell us about shock conditions and we have discovered new mineral phases in chondritic and SNC meteorites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1211F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1211F"><span>Multi-year analysis of distributed <span class="hlt">glacier</span> mass balance modelling and equilibrium line altitude on King George Island, Antarctic Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Falk, Ulrike; López, Damián A.; Silva-Busso, Adrián</p> <p>2018-04-01</p> <p>The South Shetland Islands are located at the northern tip of the Antarctic Peninsula (AP). This region was subject to strong warming trends in the atmospheric surface layer. Surface air temperature increased about 3 K in 50 years, concurrent with retreating <span class="hlt">glacier</span> fronts, an increase in <span class="hlt">melt</span> areas, ice surface lowering and rapid break-up and disintegration of ice shelves. The positive trend in surface air temperature has currently come to a halt. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to ±1.0 K (100 m)-1) and a distinct spatial heterogeneity reflecting the impact of synoptic weather patterns. The increased mesocyclonic activity during the wintertime over the past decades in the study area results in intensified advection of warm, moist air with high temperatures and rain and leads to <span class="hlt">melt</span> conditions on the ice cap, fixating surface air temperatures to the <span class="hlt">melting</span> point. Its impact on winter accumulation results in the observed negative mass balance estimates. Six years of continuous glaciological measurements on mass balance stake transects as well as 5 years of climatological data time series are presented and a spatially distributed <span class="hlt">glacier</span> energy balance <span class="hlt">melt</span> model adapted and run based on these multi-year data sets. The glaciological surface mass balance model is generally in good agreement with observations, except for atmospheric conditions promoting snow drift by high wind speeds, turbulence-driven snow deposition and snow layer erosion by rain. No drift in the difference between simulated mass balance and mass balance measurements can be seen over the course of the 5-year model run period. The winter accumulation does not suffice to compensate for the high variability in summer ablation. The results are analysed to assess changes in meltwater input to the coastal waters, specific <span class="hlt">glacier</span> mass balance and the equilibrium line altitude (ELA). The Fourcade <span class="hlt">Glacier</span> catchment drains</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C44A..06I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C44A..06I"><span>High-Resolution Monitoring of Himalayan <span class="hlt">Glacier</span> Dynamics Using Unmanned Aerial Vehicles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Immerzeel, W.; Kraaijenbrink, P. D. A.; Shea, J.; Shrestha, A. B.; Pellicciotti, F.; Bierkens, M. F.; de Jong, S. M.</p> <p>2014-12-01</p> <p>Himalayan <span class="hlt">glacier</span> tongues are commonly debris covered and play an important role in modulating the <span class="hlt">glacier</span> response to climate . However, they remain relatively unstudied because of the inaccessibility of the terrain and the difficulties in field work caused by the thick debris mantles. Observations of debris-covered <span class="hlt">glaciers</span> are therefore limited to point locations and airborne remote sensing may bridge the gap between scarce, point field observations and coarse resolution space-borne remote sensing. In this study we deploy an Unmanned Airborne Vehicle (UAV) on two debris covered <span class="hlt">glaciers</span> in the Nepalese Himalayas: the Lirung and Langtang <span class="hlt">glacier</span> during four field campaigns in 2013 and 2014. Based on stereo-imaging and the structure for motion algorithm we derive highly detailed ortho-mosaics and digital elevation models (DEMs), which we geometrically correct using differential GPS observations collected in the field. Based on DEM differencing and manual feature tracking we derive the mass loss and the surface velocity of the <span class="hlt">glacier</span> at a high spatial resolution and accuracy. We also assess spatiotemporal changes in supra-glacial lakes and ice cliffs based on the imagery. On average, mass loss is limited and the surface velocity is very small. However, the spatial variability of <span class="hlt">melt</span> rates is very high, and ice cliffs and supra-glacial ponds show mass losses that can be an order of magnitude higher than the average. We suggest that future research should focus on the interaction between supra-glacial ponds, ice cliffs and englacial hydrology to further understand the dynamics of debris-covered <span class="hlt">glaciers</span>. Finally, we conclude that UAV deployment has large potential in glaciology and it represents a substantial advancement over methods currently applied in studying <span class="hlt">glacier</span> surface features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C11E..02W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C11E..02W"><span>Regional <span class="hlt">Glacier</span> Mapping by Combination of Dense Optical and SAR Satellite Image Time-Series</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Winsvold, S. H.; Kääb, A.; Andreassen, L. M.; Nuth, C.; Schellenberger, T.; van Pelt, W.</p> <p>2016-12-01</p> <p>Near-future dense time series from both SAR (Sentinel-1A and B) and optical satellite sensors (Landsat 8, Sentinel-2A and B) will promote new multisensory time series applications for <span class="hlt">glacier</span> mapping. We assess such combinations of optical and SAR data among others by 1) using SAR data to supplement optical time series that suffer from heavy cloud cover (chronological gap-filling), 2) merging the two data types based on stack statistics (Std.dev, Mean, Max. etc.), or 3) better explaining <span class="hlt">glacier</span> facies patterns in SAR data using optical satellite images. As one example, summer SAR backscatter time series have been largely unexplored and even neglected in many glaciological studies due to the high content of liquid <span class="hlt">melt</span> water on the ice surface and its intrusion in the upper part of the snow and firn. This water content causes strong specular scattering and absorption of the radar signal, and little energy is scattered back to the SAR sensor. We find in many scenes of a Sentinel-1 time series a significant temporal backscatter difference between the <span class="hlt">glacier</span> ice surface and the seasonal snow as it <span class="hlt">melts</span> up <span class="hlt">glacier</span>. Even though both surfaces have typically wet conditions, we suggest that the backscatter difference is due to different roughness lengths of the two surfaces. Higher backscatter is found on the ice surface in the ablation area compared to the firn/seasonal snow surface. We find and present also other backscatter patterns in the Sentinel-1 time series related to <span class="hlt">glacier</span> facies and weather events. For the Ny Ålesund area, Svalbard we use Radarsat-2 time series to explore the <span class="hlt">glacier</span> backscatter conditions in a > 5 year period, discussing distinct temporal signals from among others refreezing of the firn in late autumn, or temporal lakes. All these examples are analyzed using the above 3 methods. By this multi-temporal and multi-sensor approach we also explore and describe the possible connection between combined SAR/optical time series and surface mass</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70197221','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70197221"><span>Enhancement of a parsimonious water balance model to simulate surface hydrology in a <span class="hlt">glacierized</span> watershed</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Valentin, Melissa M.; Viger, Roland J.; Van Beusekom, Ashley E.; Hay, Lauren E.; Hogue, Terri S.; Foks, Nathan Leon</p> <p>2018-01-01</p> <p>The U.S. Geological Survey monthly water balance model (MWBM) was enhanced with the capability to simulate <span class="hlt">glaciers</span> in order to make it more suitable for simulating cold region hydrology. The new model, MWBMglacier, is demonstrated in the heavily <span class="hlt">glacierized</span> and ecologically important Copper River watershed in Southcentral Alaska. Simulated water budget components compared well to satellite‐based observations and ground measurements of streamflow, evapotranspiration, snow extent, and total water storage, with differences ranging from 0.2% to 7% of the precipitation flux. Nash Sutcliffe efficiency for simulated and observed streamflow was greater than 0.8 for six of eight stream gages. Snow extent matched satellite‐based observations with Nash Sutcliffe efficiency values of greater than 0.89 in the four Copper River ecoregions represented. During the simulation period 1949 to 2009, <span class="hlt">glacier</span> ice <span class="hlt">melt</span> contributed 25% of total runoff, ranging from 12% to 45% in different tributaries, and <span class="hlt">glacierized</span> area was reduced by 6%. Statistically significant (p < 0.05) decreasing and increasing trends in annual <span class="hlt">glacier</span> mass balance occurred during the multidecade cool and warm phases of the Pacific Decadal Oscillation, respectively, reinforcing the link between climate perturbations and <span class="hlt">glacier</span> mass balance change. The simulations of <span class="hlt">glaciers</span> and total runoff for a large, remote region of Alaska provide useful data to evaluate hydrologic, cryospheric, ecologic, and climatic trends. MWBM <span class="hlt">glacier</span> is a valuable tool to understand when, and to what extent, streamflow may increase or decrease as <span class="hlt">glaciers</span> respond to a changing climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GPC...165..137V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GPC...165..137V"><span>Early 21st century spatially detailed elevation changes of Jammu and Kashmir <span class="hlt">glaciers</span> (Karakoram-Himalaya)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vijay, Saurabh; Braun, Matthias</p> <p>2018-06-01</p> <p>Although a number of studies indicate the regional heterogeneity of the <span class="hlt">glacier</span> elevation and mass changes in high-mountain Asia in the early 21st century, little is known about these changes with high spatial detail for some of the regions. In this study we present respective <span class="hlt">glacier</span> elevation and mass change estimates in the Indian state of Jammu and Kashmir (JK) for the period 2000-2012. Our estimates are based on the interferometric analysis of SRTM DEM and the bistatic TanDEM-X data. On an average the JK East (Karakoram) <span class="hlt">glaciers</span> showed less negative elevation changes (- 0.19 ± 0.22 m yr-1) compared to the JK West (Himalaya) <span class="hlt">glaciers</span> (- 0.50 ± 0.28 m yr-1). This agrees very well with previous studies that show a transition from larger changes in the western Himalaya to a steady-state situation in the Karakoram. We observe distinct elevation change patterns on a <span class="hlt">glacier</span> scale that is most likely linked to debris insulation and the enhanced ice <span class="hlt">melting</span> due to supraglacial lakes, ponds and ice cliffs. We also found 16 surge-type <span class="hlt">glaciers</span> in the JK East which were not documented before. In total, 25 <span class="hlt">glaciers</span> surged and 4 others appeared to be in a quiescent phase in the observation period. Our results also reveal that the <span class="hlt">glacier</span>-averaged elevation change rates of surge-type and non surge-type <span class="hlt">glaciers</span> in the JK East region are not significantly different.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.loc.gov/pictures/collection/hh/item/ca1656.color.218148c/','SCIGOV-HHH'); return false;" href="https://www.loc.gov/pictures/collection/hh/item/ca1656.color.218148c/"><span>HORSESHOE CURVE IN <span class="hlt">GLACIER</span> POINT ROAD NEAR <span class="hlt">GLACIER</span> POINT. HALF ...</span></a></p> <p><a target="_blank" href="http://www.loc.gov/pictures/collection/hh/">Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey</a></p> <p></p> <p></p> <p>HORSESHOE CURVE IN <span class="hlt">GLACIER</span> POINT ROAD NEAR <span class="hlt">GLACIER</span> POINT. HALF DOME AT CENTER REAR. SAME VIEW AT CA-157-2. LOOKING NNE. GIS: N-37' 43 44.3 / W-119 34 14.1 - <span class="hlt">Glacier</span> Point Road, Between Chinquapin Flat & <span class="hlt">Glacier</span> Point, Yosemite Village, Mariposa County, CA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.6095E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.6095E"><span>Determination of sub-daily <span class="hlt">glacier</span> uplift and horizontal flow velocity with time-lapse images using ImGRAFT</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Egli, Pascal; Mankoff, Ken; Mettra, François; Lane, Stuart</p> <p>2017-04-01</p> <p>This study investigates the application of feature tracking algorithms to monitoring of <span class="hlt">glacier</span> uplift. Several publications have confirmed the occurrence of an uplift of the <span class="hlt">glacier</span> surface in the late morning hours of the mid to late ablation season. This uplift is thought to be caused by high sub-glacial water pressures at the onset of <span class="hlt">melt</span> caused by overnight-deposited sediment that blocks subglacial channels. We use time-lapse images from a camera mounted in front of the <span class="hlt">glacier</span> tongue of Haut <span class="hlt">Glacier</span> d'Arolla during August 2016 in combination with a Digital Elevation Model and GPS measurements in order to investigate the phenomenon of <span class="hlt">glacier</span> uplift using the feature tracking toolbox ImGRAFT. Camera position is corrected for all images and the images are geo-rectified using Ground Control Points visible in every image. Changing lighting conditions due to different sun angles create substantial noise and complicate the image analysis. A small <span class="hlt">glacier</span> uplift of the order of 5 cm over a time span of 3 hours may be observed on certain days, confirming previous research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990QuEle..20..973U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990QuEle..20..973U"><span>EFFECTS OF LASER <span class="hlt">RADIATION</span> ON MATTER: <span class="hlt">Melting</span> and thermocapillary convection under the action of pulsed laser <span class="hlt">radiation</span> with an inhomogeneous spatial distribution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Uglov, A. A.; Smurov, I. Yu; Gus'kov, A. G.; Aksenov, L. V.</p> <p>1990-08-01</p> <p>A theoretical study is reported of <span class="hlt">melting</span> and thermocapillary convection under the action of laser <span class="hlt">radiation</span> with a nonmonotonic spatial distribution of the power density. An analysis is made of changes in the geometry of the molten bath with time. The transition from a nonmonotonic boundary of a <span class="hlt">melt</span>, corresponding to the spatial distribution of the <span class="hlt">radiation</span>, to a monotonic one occurs in a time of the order of 1 ms when the power density of laser <span class="hlt">radiation</span> is 105 W/cm2. The vortex structure of the flow in the molten bath is governed by the spatial distribution of the laser <span class="hlt">radiation</span> in such a way that each local power density maximum corresponds to two vortices with oppositely directed velocity components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/wri/2000/4006/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/wri/2000/4006/report.pdf"><span>Water, ice, and meteorological measurements at South Cascade <span class="hlt">Glacier</span>, Washington, 1986-1991 balance years</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Krimmel, Robert M.</p> <p>2000-01-01</p> <p>Mass balance and climate variables are reported for South Cascade <span class="hlt">Glacier</span>, Washington, for the years 1986-91. These variables include air temperature, precipitation, water runoff, snow accumulation, snow and ice <span class="hlt">melt</span> terminus position, surface level, and ice speed. Data are reduced to daily and monthly values where appropriate. The <span class="hlt">glacier</span>-averaged values of spring snow accumulation and fall net balance given in this report differ from previous results because amore complete analysis is made. Snow accumulation values for the1986-91 period ranged from 3.54 (water equivalent) meters in 1991 to2.04 meters in 1987. Net balance values ranged from 0.07 meters in1991 to -2.06 meters in 1987. The <span class="hlt">glacier</span> became much smaller during the 1986-91 period and retreated a cumulative 50 meters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018TCry...12.1347F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018TCry...12.1347F"><span>Recent dynamic changes on Fleming <span class="hlt">Glacier</span> after the disintegration of Wordie Ice Shelf, Antarctic Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Friedl, Peter; Seehaus, Thorsten C.; Wendt, Anja; Braun, Matthias H.; Höppner, Kathrin</p> <p>2018-04-01</p> <p>The Antarctic Peninsula is one of the world's regions most affected by climate change. Several ice shelves have retreated, thinned or completely disintegrated during recent decades, leading to acceleration and increased calving of their tributary <span class="hlt">glaciers</span>. Wordie Ice Shelf, located in Marguerite Bay at the south-western side of the Antarctic Peninsula, completely disintegrated in a series of events between the 1960s and the late 1990s. We investigate the long-term dynamics (1994-2016) of Fleming <span class="hlt">Glacier</span> after the disintegration of Wordie Ice Shelf by analysing various multi-sensor remote sensing data sets. We present a dense time series of synthetic aperture radar (SAR) surface velocities that reveals a rapid acceleration of Fleming <span class="hlt">Glacier</span> in 2008 and a phase of further gradual acceleration and upstream propagation of high velocities in 2010-2011.The timing in acceleration correlates with strong upwelling events of warm circumpolar deep water (CDW) into Wordie Bay, most likely leading to increased submarine <span class="hlt">melt</span>. This, together with continuous dynamic thinning and a deep subglacial trough with a retrograde bed slope close to the terminus probably, has <span class="hlt">induced</span> unpinning of the <span class="hlt">glacier</span> tongue in 2008 and gradual grounding line retreat between 2010 and 2011. Our data suggest that the <span class="hlt">glacier</span>'s grounding line had retreated by ˜ 6-9 km between 1996 and 2011, which caused ˜ 56 km2 of the <span class="hlt">glacier</span> tongue to go afloat. The resulting reduction in buttressing explains a median speedup of ˜ 1.3 m d-1 ( ˜ 27 %) between 2008 and 2011, which we observed along a centre line extending between the grounding line in 1996 and ˜ 16 km upstream. Current median ice thinning rates (2011-2014) along profiles in areas below 1000 m altitude range between ˜ 2.6 to 3.2 m a-1 and are ˜ 70 % higher than between 2004 and 2008. Our study shows that Fleming <span class="hlt">Glacier</span> is far away from approaching a new equilibrium and that the <span class="hlt">glacier</span> dynamics are not primarily controlled by the loss of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ISPAnIV-3..173N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ISPAnIV-3..173N"><span>Ikh Turgen Mountain <span class="hlt">Glacier</span> Change and 3d Surface Extents Prediction Using Long Term Landsat Image and Climate Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nasanbat, Elbegjargal; Erdenebat, Erdenetogtokh; Chogsom, Bolorchuluun; Lkhamjav, Ochirkhuyag; Nanzad, Lkhagvadorj</p> <p>2018-04-01</p> <p>The <span class="hlt">glacier</span> is most important the freshwater resources and indicator of the climate change. The researchers noted that during last decades the <span class="hlt">glacier</span> is <span class="hlt">melting</span> due to global warming. The study calculates a spatial distribution of protentional change of <span class="hlt">glacier</span> coverage in the Ikh Turgen mountain of Western Mongolia, and it integrates long-term climate data and satellite datasets. Therefore, in this experiment has tried to estimation three-dimensional surface area of the <span class="hlt">glacier</span>. For this purpose, Normalized difference snow index (NDSI) was applied to decision tree approach, using Landsat MSS, TM, ETM+ and LC8 imagery for 1975-2016, a surface and slope for digital elevation model, precipitation and air temperature historical data of meteorological station. The potential volume area significantly changed <span class="hlt">glacier</span> cover of the Ikh Turgen Mountain, and the area affected by highly variable precipitation and air temperature regimes. Between 1972 and 2016, a potential area of <span class="hlt">glacier</span> area has been decreased in Ikh Turgen mountain region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRG..116.1019U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRG..116.1019U"><span>Evidence for propagation of cold-adapted yeast in an ice core from a Siberian Altai <span class="hlt">glacier</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Uetake, Jun; Kohshima, Shiro; Nakazawa, Fumio; Takeuchi, Nozomu; Fujita, Koji; Miyake, Takayuki; Narita, Hideki; Aizen, Vladimir; Nakawo, Masayoshi</p> <p>2011-03-01</p> <p>Cold environments, including <span class="hlt">glacier</span> ice and snow, are known habitats for cold-adapted microorganisms. We investigated the potential for cold-adapted yeast to have propagated in the snow of the high-altitude Belukha <span class="hlt">glacier</span>. We detected the presence of highly concentrated yeast (over 104 cells mL-1) in samples of both an ice core and firn snow. Increasing yeast cell concentrations in the same snow layer from July 2002 to July 2003 suggests that the yeast cells propagated in the <span class="hlt">glacier</span> snow. A cold-adapted Rhodotorula sp. was isolated from the snow layer and found to be related to psychrophilic yeast previously found in other glacial environments (based on the D1/D2 26S rRNA domains). 26S rRNA clonal analysis directly amplified from meltwater within the ice core also revealed the presence of genus Rhodotorula. Analyses of the ice core showed that all peaks in yeast concentration corresponded to the peaks in indices of surface <span class="hlt">melting</span>. These results support the hypothesis that occasional surface <span class="hlt">melting</span> in an accumulation area is one of the major factors influencing cold-adapted yeast propagation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70026130','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70026130"><span>Bedload component of glacially discharged sediment: Insights from the Matanuska <span class="hlt">Glacier</span>, Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Pearce, J.T.; Pazzaglia, F.J.; Evenson, E.B.; Lawson, D.E.; Alley, R.B.; Germanoski, D.; Denner, J.D.</p> <p>2003-01-01</p> <p>The flux of glacially derived bedload and the proportions of the suspended and bedload components carried by proglacial streams are highly debated. Published data indicate a large range-from 75%-in the bedload percentage of the total load. Two "vents," where supercooled subglacial meltwater and sediment are discharged, were sampled over the course of an entire <span class="hlt">melt</span> season in order to quantify the flux of glacially delivered bedload at the Matanuska <span class="hlt">Glacier</span>, Alaska. The bedload component contributed by these vents, for the one <span class="hlt">melt</span> season monitored, is negligible. Furthermore, the bedload fluxes appear to be strongly supply limited, as shown by the poorly correlated discharge, bedload-flux magnitude, and grain-size caliber. Thus, in this case, any attempt to employ a predictive quantitative expression for coarse-sediment production based on discharge alone would be inaccurate. A nonglaciated basin proximal to the Matanuska <span class="hlt">Glacier</span> terminus yielded higher bedload sediment fluxes and larger clast sizes than delivered by the two monitored vents. Such nonglaciated basins should not be overlooked as potentially major sources of coarse bedload that is reworked and incorporated into valley outwash.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41C1252C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41C1252C"><span>Understanding calving dynamics of Greenland outlet <span class="hlt">glaciers</span> by comparing calving laws in a 3D ice sheet model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Choi, Y.; Morlighem, M.; Wood, M.; Bondzio, J. H.; Mouginot, J.</p> <p>2017-12-01</p> <p>Mass loss from marine terminating <span class="hlt">glaciers</span> along coastal Greenland is a significant contributor to global sea-level rise. Calving is one of the important processes that control the dynamics, and therefore the discharge, of these <span class="hlt">glaciers</span>. As <span class="hlt">glacier</span> termini are exposed to warmer ocean currents, ocean-<span class="hlt">induced</span> <span class="hlt">melt</span> at the calving front increases, which may lead to <span class="hlt">glacier</span> retreat and ice flow acceleration. It is therefore important to accurately parameterize calving in ice sheet models in order to improve the projections of ice sheet change. Several calving laws have been proposed, but most of them have been applied only to a specific region and have not been tested on other <span class="hlt">glaciers</span>, while some others have only been implemented in one-dimensional flowline or vertical flowband models. Here, we test and compare several calving laws recently proposed in the literature using a 3D ice sheet model. Namely: the height-above-buoyancy criterion (Vieli et al., 2002), the crevasse-depth calving law (Benn et al., 2007), the eigencalving law (Levermann et al., 2012) and von Mises tensile stress calving law (Morlighem et al., 2016). We test these calving laws on Zachariae Isstrøm (Northeast), Upernavik (Central West) and Helheim (East) <span class="hlt">glaciers</span> of Greenland. We compare the modeled ice front evolution to the observed retreat from Landsat data, and assess which calving law has the best predictive skills for each <span class="hlt">glacier</span>. Overall, von Mises tensile stress calving laws is more satisfactory than others for most regions. This study shows that calving dynamics needs to be 3D in ice sheet models to account for the complex geometry and narrow fjords along the coast of Greenland. Comparing calving laws in a 3D model makes it possible to find missing mechanisms in each criterion and to improve existing calving laws in numerical ice sheet models, which could reduce uncertainties in future sea level rise projections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C33C0838L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C33C0838L"><span>Deglaciation-<span class="hlt">induced</span> uplift of the Petermann <span class="hlt">glacier</span> ice margin observed with InSAR</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lu, Q.; Amelung, F.; Wdowinski, S.</p> <p>2016-12-01</p> <p>The Greenland ice sheet is rapidly shrinking with the fastest retreat and thinning occurring at the ice sheet margin and near the outlet <span class="hlt">glaciers</span>. The changes of the ice mass cause an elastic response of the bedrock. Ice mass loss during the summer months is associated with uplift, whereas ice mass increase during the winter months is associated with subsidence.The German TerraSAR-X and TanDEM-X satellites have systematically observed selected sites along the Greenland Petermann ice sheet margin since summer 2012. Here we present ground deformation observations obtained using an InSAR time-series approach based on small baseline interferograms. We observed rapid deglaciation-<span class="hlt">induced</span> uplift on naked bedrock near the Petermann <span class="hlt">glacier</span> ice margin Deformation observed by InSAR is consistent with GPS vertical observations. The time series displacement data reveal not only net uplift but also the seasonal variations. There is no strong relative between displacement changes and SMB ice mass change. The seasonal variations in local area may caused by both nearby SMB changes and ice dynamic changes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA03386.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA03386.html"><span>Malaspina <span class="hlt">Glacier</span>, Alaska</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2003-05-01</p> <p>Malaspina <span class="hlt">Glacier</span> in southeastern Alaska is considered the classic example of a piedmont <span class="hlt">glacier</span>. Piedmont <span class="hlt">glaciers</span> occur where valley <span class="hlt">glaciers</span> exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3790533','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3790533"><span>Community patterns of the small riverine benthos within and between two contrasting <span class="hlt">glacier</span> catchments</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Eisendle-Flöckner, Ursula; Jersabek, Christian D; Kirchmair, Martin; Hashold, Kerstin; Traunspurger, Walter</p> <p>2013-01-01</p> <p>Ongoing glacial retreat is expected to lead to numerous changes in <span class="hlt">glacier</span>-fed rivers. This study documents the development of community composition of the hitherto widely neglected micro- and meiobenthos (MMB: bacteria, fungi, algae, protists, and meiofauna) in <span class="hlt">glacier</span> rivers in response to the distinct habitat conditions driven by different stages of (de)<span class="hlt">glacierization</span>. Our model is based on the <span class="hlt">glacier</span> catchments of the Möll River (MC) and Kleinelendbach stream (KC), in the Austrian Alps, with 60% and 25% <span class="hlt">glacierization</span> and <span class="hlt">glacier</span> retreats of 403 and 26 m, respectively, since 1998. Analyses of overall catchment diversity and resemblance patterns showed that neither intense <span class="hlt">glacierization</span> nor rapid deglacierization were predominant MMB determinants. This was ascribed to the specific environmental conditions at the MC, where the rapidly retreating Pasterze <span class="hlt">glacier</span> has formed a harsh unstable proglacial, but also a benign floodplain area, with the former suppressing and the latter supporting the structural development of the MMB. Comparisons of similarly aged riverine habitats of the MC proglacial and the KC main channel further evidenced developmental suppression of the MMB (64 taxa) by the rapidly retreating MC <span class="hlt">glacier</span>, unlike the moderate glacial retreat in the KC (130 taxa). Habitat conditions interacting with <span class="hlt">melt</span> periods explained the differences in MMB resemblance patterns, which themselves differentially reflected the spatiotemporal habitat settings imposed by the different <span class="hlt">glacier</span> activities. The varying glacial influences were represented by a glaciality index (GIm) based on water temperature, electrical conductivity, and stream bed stability. The taxonomic richness of nematodes, rotifers, algae, and diatoms was distinctly related to this index, as were most MMB abundances. However, the strongest relationships to the GIm were those of nematode abundances and maturity. Our observations highlight the intense response of the MMB to ongoing <span class="hlt">glacier</span> retreat</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28266602','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28266602"><span>Subglacial discharges create fluctuating foraging hotspots for sea birds in tidewater <span class="hlt">glacier</span> bays.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Urbanski, Jacek Andrzej; Stempniewicz, Lech; Węsławski, Jan Marcin; Dragańska-Deja, Katarzyna; Wochna, Agnieszka; Goc, Michał; Iliszko, Lech</p> <p>2017-03-07</p> <p>Although the processes occurring at the front of an ice face in tidewater <span class="hlt">glacier</span> bays still await thorough investigation, their importance to the rapidly changing polar environment is spurring a considerable research effort. <span class="hlt">Glacier</span> <span class="hlt">melting</span>, sediment delivery and the formation of seabird foraging hotspots are governed by subglacial discharges of meltwater. We have combined the results of tracking black-legged kittiwakes Rissa tridactyla equipped with GPS loggers, analyses of satellite images and in situ measurements of water temperature, salinity and turbidity in order to examine the magnitude and variability of such hotspots in the context of <span class="hlt">glacier</span> bay hydrology. Small though these hotspots are in size, foraging in them appears to be highly intensive. They come into existence only if the subglacial discharge reaches the surface, if the entrainment velocity at a conduit is high and if there is sufficient macroplankton in the entrainment layer. The position and type of subglacial discharges may fluctuate in time and space, thereby influencing <span class="hlt">glacier</span> bay hydrology and the occurrence of foraging hotspots.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5339806','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5339806"><span>Subglacial discharges create fluctuating foraging hotspots for sea birds in tidewater <span class="hlt">glacier</span> bays</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Urbanski, Jacek Andrzej; Stempniewicz, Lech; Węsławski, Jan Marcin; Dragańska-Deja, Katarzyna; Wochna, Agnieszka; Goc, Michał; Iliszko, Lech</p> <p>2017-01-01</p> <p>Although the processes occurring at the front of an ice face in tidewater <span class="hlt">glacier</span> bays still await thorough investigation, their importance to the rapidly changing polar environment is spurring a considerable research effort. <span class="hlt">Glacier</span> <span class="hlt">melting</span>, sediment delivery and the formation of seabird foraging hotspots are governed by subglacial discharges of meltwater. We have combined the results of tracking black-legged kittiwakes Rissa tridactyla equipped with GPS loggers, analyses of satellite images and in situ measurements of water temperature, salinity and turbidity in order to examine the magnitude and variability of such hotspots in the context of <span class="hlt">glacier</span> bay hydrology. Small though these hotspots are in size, foraging in them appears to be highly intensive. They come into existence only if the subglacial discharge reaches the surface, if the entrainment velocity at a conduit is high and if there is sufficient macroplankton in the entrainment layer. The position and type of subglacial discharges may fluctuate in time and space, thereby influencing <span class="hlt">glacier</span> bay hydrology and the occurrence of foraging hotspots. PMID:28266602</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C51A0654S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C51A0654S"><span>Insights into ice-ocean interactions and fjord circulation from fjord sea surface temperatures at the Petermann <span class="hlt">Glacier</span>, Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Snow, T.; Shepherd, B.; Abdalati, W.; Scambos, T. A.</p> <p>2016-12-01</p> <p>Dynamic processes at marine-terminating outlet <span class="hlt">glaciers</span> are responsible for over one-third of Greenland Ice Sheet (GIS) mass loss. Enhanced intrusion of warm ocean waters at the termini of these <span class="hlt">glaciers</span> has contributed to elevated rates of ice thinning and terminus retreat over the last two decades. In situ oceanographic measurements and modeling studies show that basal <span class="hlt">melting</span> of <span class="hlt">glaciers</span> and subglacial discharge can cause buoyant plumes of water to rise to the fjord surface and influence fjord circulation characteristics. The temperature of these surface waters holds clues about ice-ocean interactions and small-scale circulation features along the <span class="hlt">glacier</span> terminus that could contribute to outlet <span class="hlt">glacier</span> mass loss, but the magnitude and duration of temperature variability remains uncertain. Satellite remote sensing has proven very effectiver for acquiring sea surface temperatuer (SST) data from these remote regions on a long-term, consistent basis and shows promise for identifying temperature anomalies at the ice front. However, these data sets have not been widely utilized to date. Here, we use satellite-derived sea surface temperatures to identify fjord surface outflow characteristics from 2000 to present at the Petermann <span class="hlt">Glacier</span>, which drains 4% of the GIS and is experiencing 80% of its mass loss from basal <span class="hlt">melt</span>. We find a general SST warming trend that coincides with early sea ice breakup and precedes two major calving events and ice speedup that began in 2010. Persistent SST anomalies along the terminus provide evidence of warm outflow that is consistent with buoyant plume model predictions. However, the anomalies are not evident early in the time series, suggesting that ocean inflow and ice-ocean interactions have experienced a regime shift since 2000. Our results provide valuable insight into fjord circulation patterns and the forcing mechanisms that contribute to terminus retreat. Comparing our results to ongoing modeling experiments, time series from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050071088&hterms=sauber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsauber','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050071088&hterms=sauber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsauber"><span>Southern Alaska <span class="hlt">Glaciers</span>: Spatial and Temporal Variations in Ice Volume</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sauber, J.; Molnia, B. F.; Lutchke, S.; Rowlands, D.; Harding, D.; Carabajal, C.; Hurtado, J. M.; Spade, G.</p> <p>2004-01-01</p> <p>Although temperate mountain <span class="hlt">glaciers</span> comprise less than 1% of the <span class="hlt">glacier</span>-covered area on Earth, they are important because they appear to be <span class="hlt">melting</span> rapidly under present climatic conditions and, therefore, make significant contributions to rising sea level. In this study, we use ICESat observations made in the last 1.5 years of southern Alaska <span class="hlt">glaciers</span> to estimate ice elevation profiles, ice surface slopes and roughness, and bi-annual and/or annual ice elevation changes. We report initial results from the near coastal region between Yakutat Bay and Cape Suckling that includes the Malaspina and Bering <span class="hlt">Glaciers</span>. We show and interpret ice elevations changes across the lower reaches of the Bagley Ice Valley for the period between October 2003 and May 2004. In addition, we use off-nadir pointing observations to reference tracks over the Bering and Malaspina <span class="hlt">Glaciers</span> in order to estimate annual ice elevation change. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Shuttle Radar Topography Mission (SRTM) derived DEMs are used to estimate across track regional slopes between ICESat data acquisitions. Although the distribution and quantity of ICESat elevation profiles with multiple, exact repeat data is currently limited in Alaska, individual ICESat data tracks, provide an accurate reference surface for comparison to other elevation data (e.g. ASTER and SRTM X- and C-band derived DEMs). Specifically we report the elevation change over the Malaspina <span class="hlt">Glacier</span>'s piedmont lobe between a DEM derived from SRTM C-band data acquired in Feb. 2000 and ICESat Laser #2b data from Feb.-March 2004. We also report use of ICESat elevation data to enhance ASTER derived absolute DEMs. Mountain <span class="hlt">glaciers</span> generally have rougher surfaces and steeper regional slopes than the ice sheets for which the ICESat design was optimized. Therefore, rather than averaging ICESat observations over large regions or relying on crossovers, we are working with well-located ICESat</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C51D..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C51D..01H"><span>How do <span class="hlt">glacier</span> inventory data aid global <span class="hlt">glacier</span> assessments and projections?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hock, R.</p> <p>2017-12-01</p> <p>Large-scale <span class="hlt">glacier</span> modeling relies heavily on datasets that are collected by many individuals across the globe, but managed and maintained in a coordinated fashion by international data centers. The Global Terrestrial Network for <span class="hlt">Glaciers</span> (GTN-G) provides the framework for coordinating and making available a suite of data sets such as the Randolph <span class="hlt">Glacier</span> Inventory (RGI), the <span class="hlt">Glacier</span> Thickness Dataset or the World <span class="hlt">Glacier</span> Inventory (WGI). These datasets have greatly increased our ability to assess global-scale <span class="hlt">glacier</span> mass changes. These data have also been vital for projecting the <span class="hlt">glacier</span> mass changes of all mountain <span class="hlt">glaciers</span> in the world outside the Greenland and Antarctic ice sheet, a total >200,000 <span class="hlt">glaciers</span> covering an area of more than 700,000 km2. Using forcing from 8 to 15 GCMs and 4 different emission scenarios, global-scale <span class="hlt">glacier</span> evolution models project multi-model mean net mass losses of all <span class="hlt">glaciers</span> between 7 cm and 24 cm sea-level equivalent by the end of the 21st century. Projected mass losses vary greatly depending on the choice of the forcing climate and emission scenario. Insufficiently constrained model parameters likely are an important reason for large differences found among these studies even when forced by the same emission scenario, especially on regional scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70041040','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70041040"><span>Listening to <span class="hlt">Glaciers</span>: Passive hydroacoustics near marine-terminating <span class="hlt">glaciers</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Pettit, E.C.; Nystuen, J.A.; O'Neel, Shad</p> <p>2012-01-01</p> <p>The catastrophic breakup of the Larsen B Ice Shelf in the Weddell Sea in 2002 paints a vivid portrait of the effects of <span class="hlt">glacier</span>-climate interactions. This event, along with other unexpected episodes of rapid mass loss from marine-terminating <span class="hlt">glaciers</span> (i.e., tidewater <span class="hlt">glaciers</span>, outlet <span class="hlt">glaciers</span>, ice streams, ice shelves) sparked intensified study of the boundaries where marine-terminating <span class="hlt">glaciers</span> interact with the ocean. These dynamic and dangerous boundaries require creative methods of observation and measurement. Toward this effort, we take advantage of the exceptional sound-propagating properties of seawater to record and interpret sounds generated at these glacial ice-ocean boundaries from distances safe for instrument deployment and operation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29346532','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29346532"><span>What color should <span class="hlt">glacier</span> algae be? An ecological role for red carbon in the cryosphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dial, Roman J; Ganey, Gerard Q; Skiles, S McKenzie</p> <p>2018-03-01</p> <p>Red-colored secondary pigments in <span class="hlt">glacier</span> algae play an adaptive role in <span class="hlt">melting</span> snow and ice. We advance this hypothesis using a model of color-based absorption of irradiance, an experiment with colored particles in snow, and the natural history of <span class="hlt">glacier</span> algae. Carotenoids and phenols-astaxanthin in snow-algae and purpurogallin in ice-algae-shield photosynthetic apparatus by absorbing overabundant visible wavelengths, then dissipating the excess radiant energy as heat. This heat <span class="hlt">melts</span> proximal ice crystals, providing liquid-water in a 0°C environment and freeing up nutrients bound in frozen water. We show that purple-colored particles transfer 87%-89% of solar energy absorbed by black particles. However, red-colored particles transfer nearly as much (85%-87%) by absorbing peak solar wavelengths and reflecting the visible wavelengths most absorbed by nearby ice and snow crystals; this latter process may reduce potential cellular overheating when snow insulates cells. Blue and green particles transfer only 80%-82% of black particle absorption. In the experiment, red-colored particles <span class="hlt">melted</span> 87% as much snow as black particles, while blue particles <span class="hlt">melted</span> 77%. Green-colored snow-algae naturally occupy saturated snow where water is non-limiting; red-colored snow-algae occupy drier, water-limited snow. In addition to increasing <span class="hlt">melt</span>, we suggest that esterified astaxanthin in snow-alga cells increases hydrophobicity to remain surficial. © FEMS 2018. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRC..121.8496K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRC..121.8496K"><span>Ocean mixing beneath Pine Island <span class="hlt">Glacier</span> ice shelf, West Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kimura, Satoshi; Jenkins, Adrian; Dutrieux, Pierre; Forryan, Alexander; Naveira Garabato, Alberto C.; Firing, Yvonne</p> <p>2016-12-01</p> <p>Ice shelves around Antarctica are vulnerable to an increase in ocean-driven <span class="hlt">melting</span>, with the <span class="hlt">melt</span> rate depending on ocean temperature and the strength of flow inside the ice-shelf cavities. We present measurements of velocity, temperature, salinity, turbulent kinetic energy dissipation rate, and thermal variance dissipation rate beneath Pine Island <span class="hlt">Glacier</span> ice shelf, West Antarctica. These measurements were obtained by CTD, ADCP, and turbulence sensors mounted on an Autonomous Underwater Vehicle (AUV). The highest turbulent kinetic energy dissipation rate is found near the grounding line. The thermal variance dissipation rate increases closer to the ice-shelf base, with a maximum value found ˜0.5 m away from the ice. The measurements of turbulent kinetic energy dissipation rate near the ice are used to estimate basal <span class="hlt">melting</span> of the ice shelf. The dissipation-rate-based <span class="hlt">melt</span> rate estimates is sensitive to the stability correction parameter in the linear approximation of universal function of the Monin-Obukhov similarity theory for stratified boundary layers. We argue that our estimates of basal <span class="hlt">melting</span> from dissipation rates are within a range of previous estimates of basal <span class="hlt">melting</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C12B..04B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C12B..04B"><span>Constraining calving front processes on W Greenland outlet <span class="hlt">glaciers</span> using inertial-corrected laser scanning & swath-bathymetry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bates, R.; Hubbard, A.; Neale, M.; Woodward, J.; Box, J. E.; Nick, F.</p> <p>2010-12-01</p> <p>Calving and submarine <span class="hlt">melt</span> account for the majority of loss from the Antarctic and over 50% of that from the Greenland Ice Sheet. These ice-ocean processes are highly efficient mass-loss mechanisms, providing a rapid link between terrestrial ice (storage) and the oceanic sink (sea level/freshwater flux) which renders the ocean-outlet-ice sheet system potentially highly non-linear. Despite this, the controls on tidewater processes are poorly understood and a process based description of them is lacking from the present generation of coupled ice sheet models. We present details from an innovative study where two survey techniques are integrated to enable the construction of accurate, ~m resolution 3d digital terrain models (DTMs) of the aerial and submarine ice front of calving outlet <span class="hlt">glaciers</span>. A 2km range terrestrial laser scanner was combined with a 416KHz swath-interferometric system and corrected via an inertial motion unit stabilized by RTK GPS and gyro-compass data. The system was mounted aboard a heavy displacement (20,000kg) yacht in addition to a light displacement (100kg) semi-autonomous boat and used to image the aerial and submarine calving fronts of two large outlet <span class="hlt">glaciers</span> in W Greenland. Six daily surveys, each 2.5km long were repeated across Lille <span class="hlt">Glacier</span> during which significant ice flow, <span class="hlt">melt</span> and calving events were observed and captured from on-ice GPS stations and time-lapse sequences. A curtain of CTD and velocity casts were also conducted to constrain the fresh and oceanic mass and energy fluxes within the fjord. The residual of successive DTMs yield the spatial pattern of frontal change enabling the processes of aerial and submarine calving and <span class="hlt">melt</span> to be quantified and constrained in unprecedented detail. These observed frontal changes are tentatively related to local dynamic, atmospheric and oceanographic processes that drive them. A partial survey of Store <span class="hlt">Glacier</span> (~7km calving front & W Greenland 2nd largest outlet after Jakobshavn Isbrae</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27262982','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27262982"><span>Future hydrological regimes and <span class="hlt">glacier</span> cover in the Everest region: The case study of the upper Dudh Koshi basin.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Soncini, Andrea; Bocchiola, Daniele; Confortola, Gabriele; Minora, Umberto; Vuillermoz, Elisa; Salerno, Franco; Viviano, Gaetano; Shrestha, Dibas; Senese, Antonella; Smiraglia, Claudio; Diolaiuti, Guglielmina</p> <p>2016-09-15</p> <p>Assessment of future water resources under climate change is required in the Himalayas, where hydrological cycle is poorly studied and little understood. This study focuses on the upper Dudh Koshi river of Nepal (151km(2), 4200-8848ma.s.l.) at the toe of Mt. Everest, nesting the debris covered Khumbu, and Khangri Nup <span class="hlt">glaciers</span> (62km(2)). New data gathered during three years of field campaigns (2012-2014) were used to set up a glacio-hydrological model describing stream flows, snow and ice <span class="hlt">melt</span>, ice cover thickness and <span class="hlt">glaciers</span>' flow dynamics. The model was validated, and used to assess changes of the hydrological cycle until 2100. Climate projections are used from three Global Climate Models used in the recent IPCC AR5 under RCP2.6, RCP4.5 and RCP8.5. Flow statistics are estimated for two reference decades 2045-2054, and 2090-2099, and compared against control run CR, 2012-2014. During CR we found a contribution of ice <span class="hlt">melt</span> to stream flows of 55% yearly, with snow <span class="hlt">melt</span> contributing for 19%. Future flows are predicted to increase in monsoon season, but to decrease yearly (-4% vs CR on average) at 2045-2054. At the end of century large reduction would occur in all seasons, i.e. -26% vs CR on average at 2090-2099. At half century yearly contribution of ice <span class="hlt">melt</span> would be on average 45%, and snow <span class="hlt">melt</span> 28%. At the end of century ice <span class="hlt">melt</span> would be 31%, and snow contribution 39%. <span class="hlt">Glaciers</span> in the area are projected to thin largely up to 6500ma.s.l. until 2100, reducing their volume by -50% or more, and their ice covered area by -30% or more. According to our results, in the future water resources in the upper Dudh Koshi would decrease, and depend largely upon snow <span class="hlt">melt</span> and rainfall, so that adaptation measures to modified water availability will be required. Copyright © 2016 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TCry...11.2463W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TCry...11.2463W"><span>Monitoring tropical debris-covered <span class="hlt">glacier</span> dynamics from high-resolution unmanned aerial vehicle photogrammetry, Cordillera Blanca, Peru</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wigmore, Oliver; Mark, Bryan</p> <p>2017-11-01</p> <p>The <span class="hlt">glaciers</span> of the Cordillera Blanca, Peru, are rapidly retreating and thinning as a result of climate change, altering the timing, quantity and quality of water available to downstream users. Furthermore, increases in the number and size of proglacial lakes associated with these <span class="hlt">melting</span> <span class="hlt">glaciers</span> is increasing potential exposure to <span class="hlt">glacier</span> lake outburst floods (GLOFs). Understanding how these <span class="hlt">glaciers</span> are changing and their connection to proglacial lake systems is thus of critical importance. Most satellite data are too coarse for studying small mountain <span class="hlt">glaciers</span> and are often affected by cloud cover, while traditional airborne photogrammetry and lidar are costly. Recent developments have made unmanned aerial vehicles (UAVs) a viable and potentially transformative method for studying <span class="hlt">glacier</span> change at high spatial resolution, on demand and at relatively low cost.Using a custom designed hexacopter built for high-altitude (4000-6000 m a. s. l. ) operation, we completed repeat aerial surveys (2014 and 2015) of the debris-covered Llaca <span class="hlt">Glacier</span> tongue and proglacial lake system. High-resolution orthomosaics (5 cm) and digital elevation models (DEMs) (10 cm) were produced and their accuracy assessed. Analysis of these datasets reveals highly heterogeneous patterns of <span class="hlt">glacier</span> change. The most rapid areas of ice loss were associated with exposed ice cliffs and meltwater ponds on the <span class="hlt">glacier</span> surface. Considerable subsidence and low surface velocities were also measured on the sediments within the pro-glacial lake, indicating the presence of extensive regions of buried ice and continued connection to the <span class="hlt">glacier</span> tongue. Only limited horizontal retreat of the <span class="hlt">glacier</span> tongue was observed, indicating that measurements of changes in aerial extent alone are inadequate for monitoring changes in <span class="hlt">glacier</span> ice quantity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016HESS...20.1197Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016HESS...20.1197Y"><span>Stable oxygen isotope variability in two contrasting <span class="hlt">glacier</span> river catchments in Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yde, Jacob C.; Knudsen, Niels T.; Steffensen, Jørgen P.; Carrivick, Jonathan L.; Hasholt, Bent; Ingeman-Nielsen, Thomas; Kronborg, Christian; Larsen, Nicolaj K.; Mernild, Sebastian H.; Oerter, Hans; Roberts, David H.; Russell, Andrew J.</p> <p>2016-03-01</p> <p>Analysis of stable oxygen isotope (δ18O) characteristics is a useful tool to investigate water provenance in <span class="hlt">glacier</span> river systems. In order to attain knowledge on the diversity of δ18O variations in Greenlandic rivers, we examined two contrasting glacierised catchments disconnected from the Greenland Ice Sheet (GrIS). At the Mittivakkat Gletscher river, a small river draining a local temperate <span class="hlt">glacier</span> in southeast Greenland, diurnal oscillations in δ18O occurred with a 3 h time lag to the diurnal oscillations in run-off. The mean annual δ18O was -14.68 ± 0.18 ‰ during the peak flow period. A hydrograph separation analysis revealed that the ice <span class="hlt">melt</span> component constituted 82 ± 5 % of the total run-off and dominated the observed variations during peak flow in August 2004. The snowmelt component peaked between 10:00 and 13:00 local time, reflecting the long travel time and an inefficient distributed subglacial drainage network in the upper part of the <span class="hlt">glacier</span>. At the Kuannersuit <span class="hlt">Glacier</span> river on the island Qeqertarsuaq in west Greenland, the δ18O characteristics were examined after the major 1995-1998 <span class="hlt">glacier</span> surge event. The mean annual δ18O was -19.47 ± 0.55 ‰. Despite large spatial variations in the δ18O values of <span class="hlt">glacier</span> ice on the newly formed <span class="hlt">glacier</span> tongue, there were no diurnal oscillations in the bulk meltwater emanating from the <span class="hlt">glacier</span> in the post-surge years. This is likely a consequence of a tortuous subglacial drainage system consisting of linked cavities, which formed during the surge event. Overall, a comparison of the δ18O compositions from glacial river water in Greenland shows distinct differences between water draining local <span class="hlt">glaciers</span> and ice caps (between -23.0 and -13.7 ‰) and the GrIS (between -29.9 and -23.2 ‰). This study demonstrates that water isotope analyses can be used to obtain important information on water sources and the subglacial drainage system structure that is highly desired for understanding <span class="hlt">glacier</span> hydrology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C41C1225L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C41C1225L"><span>Physical Limits on Hmax, the Maximum Height of <span class="hlt">Glaciers</span> and Ice Sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lipovsky, B. P.</p> <p>2017-12-01</p> <p>The longest <span class="hlt">glaciers</span> and ice sheets on Earth never achieve a topographic relief, or height, greater than about Hmax = 4 km. What laws govern this apparent maximum height to which a <span class="hlt">glacier</span> or ice sheet may rise? Two types of answer appear possible: one relating to geological process and the other to ice dynamics. In the first type of answer, one might suppose that if Earth had 100 km tall mountains then there would be many 20 km tall <span class="hlt">glaciers</span>. The counterpoint to this argument is that recent evidence suggests that <span class="hlt">glaciers</span> themselves limit the maximum height of mountain ranges. We turn, then, to ice dynamical explanations for Hmax. The classical ice dynamical theory of Nye (1951), however, does not predict any break in scaling to give rise to a maximum height, Hmax. I present a simple model for the height of <span class="hlt">glaciers</span> and ice sheets. The expression is derived from a simplified representation of a thermomechanically coupled ice sheet that experiences a basal shear stress governed by Coulomb friction (i.e., a stress proportional to the overburden pressure minus the water pressure). I compare this model to satellite-derived digital elevation map measurements of <span class="hlt">glacier</span> surface height profiles for the 200,000 <span class="hlt">glaciers</span> in the Randolph <span class="hlt">Glacier</span> Inventory (Pfeffer et al., 2014) as well as flowlines from the Greenland and Antarctic Ice Sheets. The simplified model provides a surprisingly good fit to these global observations. Small <span class="hlt">glaciers</span> less than 1 km in length are characterized by having negligible influence of basal <span class="hlt">melt</span> water, cold ( -15C) beds, and high surface slopes ( 30 deg). <span class="hlt">Glaciers</span> longer than a critical distance 30km are characterized by having an ice-bed interface that is weakened by the presence of meltwater and is therefore not capable of supporting steep surface slopes. The simplified model makes predictions of ice volume change as a function of surface temperature, accumulation rate, and geothermal heat flux. For this reason, it provides insights into</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.C23C0508L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.C23C0508L"><span>Airborne Laser Altimetry Measurements of <span class="hlt">Glacier</span> Wastage in Alaska and NW Canada</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Larsen, C. F.; Hock, R. M.; Arendt, A. A.; Zirnheld, S. L.</p> <p>2009-12-01</p> <p>Laser altimetry elevation profiles of <span class="hlt">glaciers</span> in NW North America (Alaska, Yukon, and NW British Columbia) have been collected by the University of Alaska Geophysical Institute (UAF-GI) beginning in 1993. Since then, more than 200 <span class="hlt">glaciers</span> throughout NW North America have been measured, many of them multiple times with typical repeat intervals of 3 to 5 years. All of the largest <span class="hlt">glaciers</span> here have been profiled, including at least some representative <span class="hlt">glaciers</span> from every major icefield in NW North America. Over 40 <span class="hlt">glaciers</span> were surveyed again in the summer of 2009, a significant and unusually large annual addition to our database of surface elevation changes. Beginning in August 2009 we flew the surveys using the new UAF-GI swath mapping LiDAR system which records a 0.5 km wide 3-d map of survey points on an approximately 1 m x 1 m grid along the <span class="hlt">glacier</span> centerlines. Over 40 <span class="hlt">glaciers</span> and icefields have now been surveyed 3 or more times over the past 15 years, and these regions have been analyzed for changes in their rates of wastage. These regions include the Stikine Icefield of southeast Alaska, the Columbia <span class="hlt">Glacier</span>, the Bering-Bagley and Seward-Malaspina systems, the Yakutat Icefield, <span class="hlt">Glacier</span> Bay, the Harding Icefield, and the Alaska Range. Increased <span class="hlt">melt</span> rates are generally observed over the most recent 3 to 5 year interval when compared to the previous 5 to 10 years, with many <span class="hlt">glaciers</span> experiencing a factor of two or greater in their recent area-averaged thinning rates. Hypsometry appears to be a significant factor, with those areas that have relatively low average elevation and low accumulation areas showing stronger effects of the accelerated thinning. In particular, those icefields near the Gulf of Alaska coast, such as the Yakutat, Harding and Brady Icefields, are now rapidly wasting. A few areas that have relatively high elevation accumulation areas appear to have steady rates of thinning, such as within the St. Elias Mountains.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.C21C0458P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.C21C0458P"><span>Outlet <span class="hlt">Glacier</span>-Ice Shelf-Ocean Interactions: Is the Tail Wagging the Dog?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parizek, B. R.; Walker, R. T.; Rinehart, S. K.</p> <p>2009-12-01</p> <p>While the massive interior regions of the Antarctic and Greenland Ice Sheets are presently ``resting quietly", the lower elevations of many outlet <span class="hlt">glaciers</span> are experiencing dramatic adjustments due to changes in ice dynamics and/or surface mass balance. Oceanic and/or atmospheric forcing in these marginal regions often leads to mass deficits for entire outlet basins. Therefore, coupling the wagging tail of ice-ocean interactions with the vast ice-sheet reservoirs is imperative for accurate assessments of future sea-level rise. To study ice-ocean dynamic processes, we couple an ocean-plume model that simulates ice-shelf basal <span class="hlt">melting</span> rates based on temperature and salinity profiles combined with plume dynamics associated with the geometry of the ice-shelf cavity (following Jenkins, 1991 and Holland and Jenkins, 1999) with a two-dimensional, isothermal model of outlet <span class="hlt">glacier</span>-ice shelf flow (as used in Alley et al., 2007; Walker et al., 2008; Parizek et al., in review). Depending on the assigned temperature and salinity profiles, the ocean model can simulate both water-mass end-members: either cold High Salinity Shelf Water (HSSW) or relatively warm Circumpolar Deep Water (CDW), as well as between-member conditions. Notably, the coupled system exhibits sensitivity to the initial conditions. In particular, <span class="hlt">melting</span> concentrated near the grounding line has the greatest effect in forcing grounding-line retreat. Retreat is further enhanced by a positive feedback between the ocean and ice, as the focused <span class="hlt">melt</span> near the grounding line leads to an increase in the local slope of the basal ice, thereby enhancing buoyancy-driven plume flow and subsequent <span class="hlt">melt</span> rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/971305','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/971305"><span>The influence of air temperature inversions on snowmelt and <span class="hlt">glacier</span> mass-balance simulations, Ammassalik island, SE Greenland</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Mernild, Sebastian Haugard; Liston, Glen</p> <p>2009-01-01</p> <p>In many applications, a realistic description of air temperature inversions is essential for accurate snow and <span class="hlt">glacier</span> ice <span class="hlt">melt</span>, and <span class="hlt">glacier</span> mass-balance simulations. A physically based snow-evolution modeling system (SnowModel) was used to simulate eight years (1998/99 to 2005/06) of snow accumulation and snow and <span class="hlt">glacier</span> ice ablation from numerous small coastal marginal <span class="hlt">glaciers</span> on the SW-part of Ammassalik Island in SE Greenland. These <span class="hlt">glaciers</span> are regularly influenced by inversions and sea breezes associated with the adjacent relatively low temperature and frequently ice-choked fjords and ocean. To account for the influence of these inversions on the spatiotemporal variation of airmore » temperature and snow and <span class="hlt">glacier</span> <span class="hlt">melt</span> rates, temperature inversion routines were added to MircoMet, the meteorological distribution sub-model used in SnowModel. The inversions were observed and modeled to occur during 84% of the simulation period. Modeled inversions were defined not to occur during days with strong winds and high precipitation rates due to the potential of inversion break-up. Field observations showed inversions to extend from sea level to approximately 300 m a.s.l., and this inversion level was prescribed in the model simulations. Simulations with and without the inversion routines were compared. The inversion model produced air temperature distributions with warmer lower elevation areas and cooler higher elevation areas than without inversion routines due to the use of cold sea-breeze base temperature data from underneath the inversion. This yielded an up to 2 weeks earlier snowmelt in the lower areas and up to 1 to 3 weeks later snowmelt in the higher elevation areas of the simulation domain. Averaged mean annual modeled surface mass-balance for all <span class="hlt">glaciers</span> (mainly located above the inversion layer) was -720 {+-} 620 mm w.eq. y{sup -1} for inversion simulations, and -880 {+-} 620 mm w.eq. y{sup -1} without the inversion routines, a difference of 160 mm w</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70174313','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70174313"><span>Seismic detection and analysis of icequakes at Columbia <span class="hlt">Glacier</span>, Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>O'Neel, Shad; Marshall, Hans P.; McNamara, Daniel E.; Pfeffer, William Tad</p> <p>2007-01-01</p> <p>Contributions to sea level rise from rapidly retreating marine-terminating <span class="hlt">glaciers</span> are large and increasing. Strong increases in iceberg calving occur during retreat, which allows mass transfer to the ocean at a much higher rate than possible through surface <span class="hlt">melt</span> alone. To study this process, we deployed an 11-sensor passive seismic network at Columbia <span class="hlt">Glacier</span>, Alaska, during 2004–2005. We show that calving events generate narrow-band seismic signals, allowing frequency domain detections. Detection parameters were determined using direct observations of calving and validated using three statistical methods and hypocenter locations. The 1–3 Hz detections provide a good measure of the temporal distribution and size of calving events. Possible source mechanisms for the unique waveforms are discussed, and we analyze potential forcings for the observed seismicity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..MAR.R0002T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..MAR.R0002T"><span>Earth's Climate History from <span class="hlt">Glaciers</span> and Ice Cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, Lonnie</p> <p>2013-03-01</p> <p><span class="hlt">Glaciers</span> serve both as recorders and early indicators of climate change. Over the past 35 years our research team has recovered climatic and environmental histories from ice cores drilled in both Polar Regions and from low to mid-latitude, high-elevation ice fields. Those ice core -derived proxy records extending back 25,000 years have made it possible to compare glacial stage conditions in the Tropics with those in the Polar Regions. High-resolution records of δ18O (in part a temperature proxy) demonstrate that the current warming at high elevations in the mid- to lower latitudes is unprecedented for the last two millennia, although at many sites the early Holocene was warmer than today. Remarkable similarities between changes in the highland and coastal cultures of Peru and regional climate variability, especially precipitation, imply a strong connection between prehistoric human activities and regional climate. Ice cores retrieved from shrinking <span class="hlt">glaciers</span> around the world confirm their continuous existence for periods ranging from hundreds to thousands of years, suggesting that current climatological conditions in those regions today are different from those under which these ice fields originated and have been sustained. The ongoing widespread <span class="hlt">melting</span> of high-elevation <span class="hlt">glaciers</span> and ice caps, particularly in low to middle latitudes, provides strong evidence that a large-scale, pervasive and, in some cases, rapid change in Earth's climate system is underway. Observations of <span class="hlt">glacier</span> shrinkage during the 20th and 21st century girdle the globe from the South American Andes, the Himalayas, Kilimanjaro (Tanzania, Africa) and <span class="hlt">glaciers</span> near Puncak Jaya, Indonesia (New Guinea). The history and fate of these ice caps, told through the adventure, beauty and the scientific evidence from some of world's most remote mountain tops, provide a global perspective for contemporary climate. NSF Paleoclimate Program</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.H33R..02L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.H33R..02L"><span>Decrease in <span class="hlt">glacier</span> coverage contributes to increased winter baseflow of Arctic rivers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liljedahl, A. K.; Gaedeke, A.; Baraer, M.; Chesnokova, A.; Lebedeva, L.; Makarieva, O.; O'Neel, S.</p> <p>2016-12-01</p> <p>Rising minimum daily flows in northern Eurasian and North American rivers suggest a growing influence of groundwater in the Arctic hydrological cycle, while the impact of a warmer high-latitude climate system is evident in decreased <span class="hlt">glacier</span> coverage and increasing permafrost temperatures. Multiple mechanisms have been proposed to explain the increased discharge, which is well documented but relatively poorly understood. Here we assess the long-term (up to 88 yrs) linkages between climate, <span class="hlt">glaciers</span> and hydrology in Alaska, Canadian and Russian <span class="hlt">glacierized</span> (from 0.3 to 60% <span class="hlt">glacier</span> cover) and non-<span class="hlt">glacierized</span> watersheds (31 to 186 000 km2). We are specifically interested in analyzing trends in late winter discharge from larger watersheds to refine our understanding of the regional aquifer status and annual discharge from smaller headwater basins. Field measurements of differential runoff in Interior Alaska show that glaciated headwater streams can lose significant amounts of water in summer to the underlying aquifer. The aquifer is in turn feeding the larger lowland river system throughout the year. Groundwater storage status in Arctic regions is especially prominent through winter river discharge as it is typically the only source of water to the river system for at least 6 months of the year. Our analyses aim to explore the hypothesis that the documented increase in later winter river discharge of larger watersheds can be explained at least partly, by increased <span class="hlt">glacier</span> <span class="hlt">melt</span> in summer as observed by long-term decreases in <span class="hlt">glacier</span> coverage. If true, a decrease in winter freshwater exports to the Arctic Ocean could potentially follow as <span class="hlt">glaciers</span> retreat to higher (cooler) elevations. Increased Arctic river baseflow can favor sea ice growth and fish habitats, while negatively impacting local communities in their river ice travel.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Geomo.296..142J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Geomo.296..142J"><span>An inventory and estimate of water stored in firn fields, <span class="hlt">glaciers</span>, debris-covered <span class="hlt">glaciers</span>, and rock <span class="hlt">glaciers</span> in the Aconcagua River Basin, Chile</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Janke, Jason R.; Ng, Sam; Bellisario, Antonio</p> <p>2017-11-01</p> <p>An inventory of firn fields, <span class="hlt">glaciers</span>, debris-covered <span class="hlt">glaciers</span>, and rock <span class="hlt">glaciers</span> was conducted in the Aconcagua River Basin of the semiarid Andes of central Chile. A total of 916 landforms were identified, of which rock <span class="hlt">glaciers</span> were the most abundant (669) and occupied the most total area. <span class="hlt">Glaciers</span> and debris-covered <span class="hlt">glaciers</span> were less numerous, but were about five times larger in comparison. The total area occupied by <span class="hlt">glaciers</span> and debris-covered <span class="hlt">glaciers</span> was roughly equivalent to the total area of rock <span class="hlt">glaciers</span>. Debris-covered <span class="hlt">glaciers</span> and rock <span class="hlt">glaciers</span> were subcategorized into six ice-content classes based on interpretation of surface morphology with high-resolution satellite imagery. Over 50% of rock <span class="hlt">glaciers</span> fell within a transitional stage; 85% of debris-covered <span class="hlt">glaciers</span> were either fully covered or buried. Most landforms occupied elevations between 3500 and 4500 m. <span class="hlt">Glaciers</span> and firn occurred at higher elevations compared to rock <span class="hlt">glaciers</span> and debris-covered <span class="hlt">glaciers</span>. Rock <span class="hlt">glaciers</span> had a greater frequency in the northern part of the study area where arid climate conditions exist. Firn and <span class="hlt">glaciers</span> were oriented south, debris-covered <span class="hlt">glaciers</span> west, and rock <span class="hlt">glaciers</span> southwest. An analysis of water contribution of each landform in the upper Andes of the Aconcagua River Basin was conducted using formulas that associate the size of the landforms to estimates of water stored. Minimum and maximum water storage was calculated based on a range of debris to ice content ratios for debris-covered <span class="hlt">glaciers</span> and rock <span class="hlt">glaciers</span>. In the Aconcagua River Basin, rock <span class="hlt">glaciers</span> accounted for 48 to 64% of the water stored within the landforms analyzed; <span class="hlt">glaciers</span> accounted for 15 to 25%; debris-covered <span class="hlt">glaciers</span> were estimated at 15 to 19%; firn fields contained only about 5 to 8% of the water stored. Expansion of agriculture, prolonged drought, and removal of ice-rich landforms for mining have put additional pressure on already scarce water resources. To develop long</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE10003E..0FC','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE10003E..0FC"><span>A multitemporal probabilistic error correction approach to SVM classification of alpine <span class="hlt">glacier</span> exploiting sentinel-1 images (Conference Presentation)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Callegari, Mattia; Marin, Carlo; Notarnicola, Claudia; Carturan, Luca; Covi, Federico; Galos, Stephan; Seppi, Roberto</p> <p>2016-10-01</p> <p>In mountain regions and their forelands, <span class="hlt">glaciers</span> are key source of <span class="hlt">melt</span> water during the middle and late ablation season, when most of the winter snow has already <span class="hlt">melted</span>. Furthermore, alpine <span class="hlt">glaciers</span> are recognized as sensitive indicators of climatic fluctuations. Monitoring <span class="hlt">glacier</span> extent changes and <span class="hlt">glacier</span> surface characteristics (i.e. snow, firn and bare ice coverage) is therefore important for both hydrological applications and climate change studies. Satellite remote sensing data have been widely employed for <span class="hlt">glacier</span> surface classification. Many approaches exploit optical data, such as from Landsat. Despite the intuitive visual interpretation of optical images and the demonstrated capability to discriminate glacial surface thanks to the combination of different bands, one of the main disadvantages of available high-resolution optical sensors is their dependence on cloud conditions and low revisit time frequency. Therefore, operational monitoring strategies relying only on optical data have serious limitations. Since SAR data are insensitive to clouds, they are potentially a valid alternative to optical data for <span class="hlt">glacier</span> monitoring. Compared to past SAR missions, the new Sentinel-1 mission provides much higher revisit time frequency (two acquisitions each 12 days) over the entire European Alps, and this number will be doubled once the Sentinel1-b will be in orbit (April 2016). In this work we present a method for <span class="hlt">glacier</span> surface classification by exploiting dual polarimetric Sentinel-1 data. The method consists of a supervised approach based on Support Vector Machine (SVM). In addition to the VV and VH signals, we tested the contribution of local incidence angle, extracted from a digital elevation model and orbital information, as auxiliary input feature in order to account for the topographic effects. By exploiting impossible temporal transition between different classes (e.g. if at a given date one pixel is classified as rock it cannot be classified as</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.water.usgs.gov/sir20045089/','USGSPUBS'); return false;" href="http://pubs.water.usgs.gov/sir20045089/"><span>Water, ice, and meteorological measurements at South Cascade <span class="hlt">Glacier</span>, Washington, balance year 2002</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.</p> <p>2004-01-01</p> <p>Winter snow accumulation and summer snow and ice ablation were measured at South Cascade <span class="hlt">Glacier</span>, Washington, to estimate <span class="hlt">glacier</span> mass balance quantities for balance year 2002. The 2002 <span class="hlt">glacier</span>-average maximum winter snow balance was 4.02 meters, the second largest since 1959. The 2002 <span class="hlt">glacier</span> summer, net, and annual (water year) balances were -3.47, 0.55, and 0.54 meters, respectively. The area of the <span class="hlt">glacier</span> near the end of the balance year was 1.92 square kilometers, and the equilibrium-line altitude and the accumulation area ratio were 1,820 meters and 0.84, respectively. During September 20, 2001 to September 13, 2002, the terminus retreated 4 meters, and computed average ice speeds in the ablation area ranged from 7.8 to 20.7 meters per year. Runoff from the subbasin containing the <span class="hlt">glacier</span> and from an adjacent non-<span class="hlt">glacierized</span> basin were measured during part of the 2002 water year. Air temperature, precipitation, atmospheric water-vapor pressure, wind speed and incoming solar <span class="hlt">radiation</span> were measured at selected locations near the <span class="hlt">glacier</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70135865','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70135865"><span>Velocity measurements and changes in position of Thwaites <span class="hlt">Glacier</span>/iceberg tongue from aerial photography, Landsat images and NOAA AVHRR data</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Ferrigno, Jane G.; Lucchitta, Baerbel K.; Mullinsallison, A. L.; Allen, Robert J.; Gould, W. G.</p> <p>1993-01-01</p> <p>The Thwaites <span class="hlt">Glacier</span>/iceberg tongue complex has been a significant feature of the Antarctic coastline for at least 50 years. In 1986, major changes began to occur in this area. Fast ice <span class="hlt">melted</span> and several icebergs calved from the base of the iceberg tongue and the terminus of Thwaites <span class="hlt">Glacier</span>. The iceberg tongue rotated to an east-west orientation and drifted westward. Between 1986 and 1992, a total of 140 km of drift has occurred. Remote digital velocity measurements were made on Thwaites <span class="hlt">Glacier</span> using sequential Landsat images to try to determine if changes in velocity had occurred in conjunction with the changes in ice position. Examination of the morphology of the <span class="hlt">glacier</span>/iceberg tongue showed no evidence of surge activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C44B..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C44B..08W"><span>Landsat Time-Series Analysis Opens New Approaches for Regional <span class="hlt">Glacier</span> Mapping</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Winsvold, S. H.; Kääb, A.; Nuth, C.; Altena, B.</p> <p>2016-12-01</p> <p>The archive of Landsat satellite scenes is important for mapping of <span class="hlt">glaciers</span>, especially as it represents the longest running and continuous satellite record of sufficient resolution to track <span class="hlt">glacier</span> changes over time. Contributing optical sensors newly launched (Landsat 8 and Sentinel-2A) or upcoming in the near future (Sentinel-2B), will promote very high temporal resolution of optical satellite images especially in high-latitude regions. Because of the potential that lies within such near-future dense time series, methods for mapping <span class="hlt">glaciers</span> from space should be revisited. We present application scenarios that utilize and explore dense time series of optical data for automatic mapping of <span class="hlt">glacier</span> outlines and <span class="hlt">glacier</span> facies. Throughout the season, <span class="hlt">glaciers</span> display a temporal sequence of properties in optical reflection as the seasonal snow <span class="hlt">melts</span> away, and <span class="hlt">glacier</span> ice appears in the ablation area and firn in the accumulation area. In one application scenario presented we simulated potential future seasonal resolution using several years of Landsat 5TM/7ETM+ data, and found a sinusoidal evolution of the spectral reflectance for on-<span class="hlt">glacier</span> pixels throughout a year. We believe this is because of the short wave infrared band and its sensitivity to snow grain size. The parameters retrieved from the fitting sinus curve can be used for <span class="hlt">glacier</span> mapping purposes, thus we also found similar results using e.g. the mean of summer band ratio images. In individual optical mapping scenes, conditions will vary (e.g., snow, ice, and clouds) and will not be equally optimal over the entire scene. Using robust statistics on stacked pixels reveals a potential for synthesizing optimal mapping scenes from a temporal stack, as we present in a further application scenario. The dense time series available from satellite imagery will also promote multi-temporal and multi-sensor based analyses. The seasonal pattern of snow and ice on a <span class="hlt">glacier</span> seen in the optical time series can in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150023403','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150023403"><span>Analysis of a GRACE Global Mascon Solution for Gulf of Alaska <span class="hlt">Glaciers</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Arendt, Anthony; Luthcke, Scott B.; Gardner, Alex; O'Neel, Shad; Hill, David; Moholdt, Geir; Abdalati, Waleed</p> <p>2013-01-01</p> <p>We present a high-resolution Gravity Recovery and Climate Experiment (GRACE) mascon solution for Gulf of Alaska (GOA) <span class="hlt">glaciers</span> and compare this with in situ glaciological, climate and other remote-sensing observations. Our GRACE solution yields a GOA <span class="hlt">glacier</span> mass balance of -6511 Gt a(exp.-1) for the period December 2003 to December 2010, with summer balances driving the interannual variability. Between October/November 2003 and October 2009 we obtain a mass balance of -6111 Gt a(exp. -1) from GRACE, which compares well with -6512 Gt a(exp. -1) from ICESat based on hypsometric extrapolation of <span class="hlt">glacier</span> elevation changes. We find that mean summer (June-August) air temperatures derived from both ground and lower-troposphere temperature records were good predictors of GRACE-derived summer mass balances, capturing 59% and 72% of the summer balance variability respectively. Large mass losses during 2009 were likely due to low early <span class="hlt">melt</span> season surface albedos, measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) and likely associated with the 31 March 2009 eruption of Mount Redoubt, southwestern Alaska. GRACE data compared well with in situ measurements atWolverine <span class="hlt">Glacier</span> (maritime Alaska), but poorly with those at Gulkana <span class="hlt">Glacier</span> (interior Alaska). We conclude that, although GOA mass estimates from GRACE are robust over the entire domain, further constraints on subregional and seasonal estimates are necessary to improve fidelity to ground observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005HyPr...19.2375P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005HyPr...19.2375P"><span>Snow and <span class="hlt">glacier</span> cover assessment in the high mountains of Sikkim Himalaya</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pramod Krishna, Akhouri</p> <p>2005-08-01</p> <p>This study highlights the assessment of snow and <span class="hlt">glacier</span> cover for possible inferences of global climate change impacts in high mountains like the Himalaya. The test catchment of the River Tista lies in the Sikkim state of the Indian Himalayan region, with steep mountains crossing nearly all ecozones, from subtropical to glacial. River flows are highly fluctuating, especially during the peak rainy season and snowmelt periods. Annual rainfall patterns are non-uniform and can cause large floods. Runoff and discharge downstream are highly dependent upon snow and <span class="hlt">glacier</span> extent. The temporary storage of frozen water brings about a delay in seasonal runoff. Snow cover built up in the higher regions during the winter months <span class="hlt">melts</span> in the spring-summer-autumn cycles and contributes to groundwater recharge. A spatial baseline inventory of snow cover/<span class="hlt">glacier</span>, the permanent snowline and its short-term temporal changes in the remote high-mountain areas have been analysed using multidate Indian Remote Sensing Satellite data of 1992 to 1997. A geographic information system-based overlay has led to inferences on snow cover characteristics and the alignment, dimension, slope disposition, heights of the snout and associated features of each of the <span class="hlt">glaciers</span>. Snow and <span class="hlt">glacier</span> recession are to be monitored in future on a long-term basis to derive correlations with climate-change parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C43A0530G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C43A0530G"><span>A preliminary analysis of icequakes at the Ruiz volcano <span class="hlt">glacier</span> - Colombia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Garcia Cano, L. C.; Lopez, C. M.; Muñoz Maya, J. A.; Maturana Banquez, M.; Giraldo, G. A.; Giraldo Garcia, J.</p> <p>2010-12-01</p> <p>The Ruiz volcano <span class="hlt">glacier</span> is located in the central region of Colombia at the equatorial zone but by its height it has perpetual snow. In 1985 this volcano had a catastrophic eruption that produced a lahar by <span class="hlt">glacier</span> <span class="hlt">melting</span>; this lahar buried the Armero town. From this event a seismological network was installed. Since the beginning of the seismological network of Ruiz volcano, the icequakes have been registering by the nearest station to <span class="hlt">glacier</span>. It is clear the relationship between this kind of seismicity and the meteorological conditions; the most quantity of the icequakes is registered very early at the morning and during the dry seasons. The origin and the location of these icequakes were not possible to determine because of the geometric network and of its instrumentation (short period sensor of vertical component). Since 2007 the network has been using broad band sensors and 3-component short period seismometers. We characterized the source of the icequakes from the new database in order to understand the main origin of this seismicity. This study consisted in both spectral and polarization analysis. The results show a near relation between this seismicity and shallow process related to the cryogenic phenomena, the natural motion of the <span class="hlt">glacier</span> and the volcanic heat release.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23657350','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23657350"><span>Future sea-level rise from Greenland's main outlet <span class="hlt">glaciers</span> in a warming climate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nick, Faezeh M; Vieli, Andreas; Andersen, Morten Langer; Joughin, Ian; Payne, Antony; Edwards, Tamsin L; Pattyn, Frank; van de Wal, Roderik S W</p> <p>2013-05-09</p> <p>Over the past decade, ice loss from the Greenland Ice Sheet increased as a result of both increased surface <span class="hlt">melting</span> and ice discharge to the ocean. The latter is controlled by the acceleration of ice flow and subsequent thinning of fast-flowing marine-terminating outlet <span class="hlt">glaciers</span>. Quantifying the future dynamic contribution of such <span class="hlt">glaciers</span> to sea-level rise (SLR) remains a major challenge because outlet <span class="hlt">glacier</span> dynamics are poorly understood. Here we present a <span class="hlt">glacier</span> flow model that includes a fully dynamic treatment of marine termini. We use this model to simulate behaviour of four major marine-terminating outlet <span class="hlt">glaciers</span>, which collectively drain about 22 per cent of the Greenland Ice Sheet. Using atmospheric and oceanic forcing from a mid-range future warming scenario that predicts warming by 2.8 degrees Celsius by 2100, we project a contribution of 19 to 30 millimetres to SLR from these <span class="hlt">glaciers</span> by 2200. This contribution is largely (80 per cent) dynamic in origin and is caused by several episodic retreats past overdeepenings in outlet <span class="hlt">glacier</span> troughs. After initial increases, however, dynamic losses from these four outlets remain relatively constant and contribute to SLR individually at rates of about 0.01 to 0.06 millimetres per year. These rates correspond to ice fluxes that are less than twice those of the late 1990s, well below previous upper bounds. For a more extreme future warming scenario (warming by 4.5 degrees Celsius by 2100), the projected losses increase by more than 50 per cent, producing a cumulative SLR of 29 to 49 millimetres by 2200.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/pp/1386i/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/pp/1386i/report.pdf"><span><span class="hlt">Glaciers</span> of South America</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Williams, Richard S.; Ferrigno, Jane G.</p> <p>1998-01-01</p> <p>Landsat images, together with maps and aerial photographs, have been used to produce <span class="hlt">glacier</span> inventories, define <span class="hlt">glacier</span> locations, and study <span class="hlt">glacier</span> dynamics in the countries of South America, along with the Andes Mountains. In Venezuela, Colombia, Ecuador, and Bolivia, the small <span class="hlt">glaciers</span> have been undergoing extensive <span class="hlt">glacier</span> recession since the late 1800's. <span class="hlt">Glacier</span>-related hazards (outburst floods, mud flows, and debris avalanches) occur in Colombia, in Ecuador, and associated with the more extensive (2,600 km2) <span class="hlt">glaciers</span> of Peru. The largest area of <span class="hlt">glacier</span> ice is found in Argentina and Chile, including the northern Patagonian ice field (about 4,200 km2) and the southern Patagonian ice field (about 13,000 km2), the largest <span class="hlt">glacier</span> in the Southern Hemisphere outside Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015QSRv..126..201V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015QSRv..126..201V"><span>Reconstruction of <span class="hlt">glacier</span> variability from lake sediments reveals dynamic Holocene climate in Svalbard</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van der Bilt, Willem G. M.; Bakke, Jostein; Vasskog, Kristian; D'Andrea, William J.; Bradley, Raymond S.; Ólafsdóttir, Sædis</p> <p>2015-10-01</p> <p>The Arctic is warming faster than anywhere else on Earth. Holocene proxy time-series are increasingly used to put this amplified response in perspective by understanding Arctic climate processes beyond the instrumental period. However, available datasets are scarce, unevenly distributed and often of coarse resolution. <span class="hlt">Glaciers</span> are sensitive recorders of climate shifts and variations in rock-flour production transfer this signal to the lacustrine sediment archives of downstream lakes. Here, we present the first full Holocene record of continuous <span class="hlt">glacier</span> variability on Svalbard from <span class="hlt">glacier</span>-fed Lake Hajeren. This reconstruction is based on an undisturbed lake sediment core that covers the entire Holocene and resolves variability on centennial scales owing to 26 dating points. A toolbox of physical, geochemical (XRF) and magnetic proxies in combination with multivariate statistics has allowed us to fingerprint <span class="hlt">glacier</span> activity in addition to other processes affecting the sediment record. Evidence from variations in sediment density, validated by changes in Ti concentrations, reveal <span class="hlt">glaciers</span> remained present in the catchment following deglaciation prior to 11,300 cal BP, culminating in a Holocene maximum between 9.6 and 9.5 ka cal BP. Correspondence with freshwater pulses from Hudson Strait suggests that Early Holocene <span class="hlt">glacier</span> advances were driven by the <span class="hlt">melting</span> Laurentide Ice Sheet (LIS). We find that <span class="hlt">glaciers</span> disappeared from the catchment between 7.4 and 6.7 ka cal BP, following a late Hypsithermal. <span class="hlt">Glacier</span> reformation around 4250 cal BP marks the onset of the Neoglacial, supporting previous findings. Between 3380 and 3230 cal BP, we find evidence for a previously unreported centennial-scale <span class="hlt">glacier</span> advance. Both events are concurrent with well-documented episodes of North Atlantic cooling. We argue that this brief forcing created suitable conditions for <span class="hlt">glaciers</span> to reform in the catchment against a background of gradual orbital cooling. These findings highlight the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012TCD.....6.2247S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012TCD.....6.2247S"><span>Retention and <span class="hlt">radiative</span> forcing of black carbon in Eastern Sierra Nevada snow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sterle, K. M.; McConnell, J. R.; Dozier, J.; Edwards, R.; Flanner, M. G.</p> <p>2012-06-01</p> <p>Snow and <span class="hlt">glacier</span> <span class="hlt">melt</span> water contribute water resources to a fifth of Earth's population. Snow <span class="hlt">melt</span> processes are sensitive not only to temperature changes, but also changes in albedo caused by deposition of particles such as refractory black carbon (rBC) and continental dust. The concentrations, sources, and fate of rBC particles in seasonal snow and its surface layers are uncertain, and thus an understanding of rBC's effect on snow albedo, <span class="hlt">melt</span> processes, and <span class="hlt">radiation</span> balance is critical for water management in a changing climate. Measurements of rBC in a sequence of snow pits and surface snow samples in the Eastern Sierra Nevada of California during the snow accumulation and <span class="hlt">melt</span> seasons of 2009 show that concentrations of rBC were enhanced seven fold in surface snow (~25 ng g-1) compared to bulk values in the snow pack (~3 ng g-1). Unlike major ions which are preferentially released during initial <span class="hlt">melt</span>, rBC and continental dust are retained in the snow, enhancing concentrations late into spring, until a final flush well into the <span class="hlt">melt</span> period. We estimate a combined rBC and continental dust surface <span class="hlt">radiative</span> forcing of 20 to 40 W m-2 during April and May, with dust likely contributing a greater share of the forcing than rBC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C13C0830H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C13C0830H"><span>A new <span class="hlt">Glacier</span> Inventory of the Antarctic Peninsula as compiled from pre-existing Datasets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huber, J.; Cook, A. J.; Paul, F.; Zemp, M.</p> <p>2016-12-01</p> <p>The <span class="hlt">glaciers</span> on the Antarctic Peninsula (AP) potentially make a large contribution to sea level rise. However, this contribution was difficult to estimate, as no complete <span class="hlt">glacier</span> inventory (outlines, attributes, separation from the ice sheet) was available so far. This work fills the gap and presents a new <span class="hlt">glacier</span> inventory of the AP north of 70° S based on digitally combining pre-existing datasets with GIS techniques. Rock outcrops are removed from the <span class="hlt">glacier</span> basin outlines of Cook et al. (2014) by digital intersection with the latest layer of the Antarctic Digital Database (Burton-Johnson et al. 2016). <span class="hlt">Glacier</span>-specific topographic parameters (e.g. mean elevation, slope and aspect) as well as hypsometry have been calculated from the DEM of Cook et al. (2012). We also assigned connectivity levels to all <span class="hlt">glaciers</span> following the concept by Rastner et al. (2012). Moreover, the bedrock dataset of Huss and Farinotti (2014) enabled us to add ice thickness and volume for each <span class="hlt">glacier</span>. The new inventory is available from the GLIMS database and consists of 1589 <span class="hlt">glaciers</span> covering an area of 95273 km2, slightly more than the 90000 km2 covered by <span class="hlt">glaciers</span> surrounding the Greenland Ice Sheet. The total ice volume is 34590 km3 of which 1/3 is below sea level. The hypsometric curve has a bimodal shape due to the special topography of the AP consisting mainly of ice caps with outlet <span class="hlt">glaciers</span>. Most of the <span class="hlt">glacierized</span> area is located at 200-500 m a.s.l. with a secondary maximum at 1500-1900 m. About 63% of the area is drained by marine-terminating <span class="hlt">glaciers</span> and ice shelf tributary <span class="hlt">glaciers</span> cover 35% of the area. This combination results in a high sensitivity of the <span class="hlt">glaciers</span> to climate change for several reasons: (1) only slightly rising equilibrium line altitudes would expose huge additional areas to ablation, (2) rising ocean temperatures increase <span class="hlt">melting</span> of marine terminating <span class="hlt">glaciers</span>, and (3) ice shelves have a buttressing effect on their feeding <span class="hlt">glaciers</span> and their collapse would</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016TCry...10..665A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016TCry...10..665A"><span>Estimating ice albedo from fine debris cover quantified by a semi-automatic method: the case study of Forni <span class="hlt">Glacier</span>, Italian Alps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Azzoni, Roberto Sergio; Senese, Antonella; Zerboni, Andrea; Maugeri, Maurizio; Smiraglia, Claudio; Diolaiuti, Guglielmina Adele</p> <p>2016-03-01</p> <p>In spite of the quite abundant literature focusing on fine debris deposition over <span class="hlt">glacier</span> accumulation areas, less attention has been paid to the <span class="hlt">glacier</span> <span class="hlt">melting</span> surface. Accordingly, we proposed a novel method based on semi-automatic image analysis to estimate ice albedo from fine debris coverage (d). Our procedure was tested on the surface of a wide Alpine valley <span class="hlt">glacier</span> (the Forni <span class="hlt">Glacier</span>, Italy), in summer 2011, 2012 and 2013, acquiring parallel data sets of in situ measurements of ice albedo and high-resolution surface images. Analysis of 51 images yielded d values ranging from 0.01 to 0.63 and albedo was found to vary from 0.06 to 0.32. The estimated d values are in a linear relation with the natural logarithm of measured ice albedo (R = -0.84). The robustness of our approach in evaluating d was analyzed through five sensitivity tests, and we found that it is largely replicable. On the Forni <span class="hlt">Glacier</span>, we also quantified a mean debris coverage rate (Cr) equal to 6 g m-2 per day during the ablation season of 2013, thus supporting previous studies that describe ongoing darkening phenomena at Alpine debris-free <span class="hlt">glaciers</span> surface. In addition to debris coverage, we also considered the impact of water (both from <span class="hlt">melt</span> and rainfall) as a factor that tunes albedo: meltwater occurs during the central hours of the day, decreasing the albedo due to its lower reflectivity; instead, rainfall causes a subsequent mean daily albedo increase slightly higher than 20 %, although it is short-lasting (from 1 to 4 days).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=61080&Lab=NERL&keyword=biosensors&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=61080&Lab=NERL&keyword=biosensors&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>DETECTION OF DNA DAMAGE USING <span class="hlt">MELTING</span> ANALYSIS TECHNIQUES</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>A rapid and simple fluorescence screening assay for UV <span class="hlt">radiation</span>-, chemical-, and enzyme-<span class="hlt">induced</span> DNA damage is reported. This assay is based on a <span class="hlt">melting</span>/annealing analysis technique and has been used with both calf thymus DNA and plasmid DNA (puc 19 plasmid from E. coli). DN...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPA13B0233L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPA13B0233L"><span>Threatened by: An audiovisual experience inspired by scientific data about <span class="hlt">glaciers</span> and climate change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, J.; Jeong, S.</p> <p>2017-12-01</p> <p><span class="hlt">Glaciers</span> often have been considered as a symbol of climate change, also its mass change is a major contributor to sea level rise. Dynamic discharge is one of the mechanisms that marine-terminating outlet <span class="hlt">glaciers</span> loses its mass, whose trend consists of seasonal, annual and secular patterns. These patterns, along with the other climate parameters, can be inspirational to music composition, thereby it can be expressed and transferred by musical media. Here we present `Threatened by,' a piece of electronic music accompanied by animation of <span class="hlt">glaciers</span>' movement which represent an attempt to frame the sound of the <span class="hlt">glacier</span> in freer ways vis-à-vis acoustic music. To give expression to the sound, musical production tools such as Pro Tools, Sound Forge Pro, Logic Pro X, Max/MSP, etc. are utilized to modify and combine a variety of sounds generated by a <span class="hlt">melting</span> <span class="hlt">glacier</span>. After adding impact by the way of EQ, reverberation, distortion, delay, reverse, etc., we created a two-channel stereo piece in approximately 7 minutes. Along with the musical media, we also present a video clip whose visual features corresponds to glacial properties or events. We expect this work will raise awareness of <span class="hlt">glaciers</span>' behaviour to general public, also presenting one of the examples that scientists and artists work collaboratively to come up with an artwork that has social implications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Geomo.210...59C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Geomo.210...59C"><span>Evolution of <span class="hlt">glacier</span>-dammed lakes through space and time; Brady <span class="hlt">Glacier</span>, Alaska, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Capps, Denny M.; Clague, John J.</p> <p>2014-04-01</p> <p><span class="hlt">Glacier</span>-dammed lakes and their associated jökulhlaups cause severe flooding in downstream areas and substantially influence <span class="hlt">glacier</span> dynamics. Brady <span class="hlt">Glacier</span> in southeast Alaska is well suited for a study of these phenomena because it presently dams 10 large (> 1 km2) lakes. Our objectives are to demonstrate how Brady <span class="hlt">Glacier</span> and its lakes have co-evolved in the past and to apply this knowledge to predict how the <span class="hlt">glacier</span> and its lakes will likely evolve in the future. To accomplish these objectives, we georeferenced a variety of maps, airphotos, and optical satellite imagery to characterize the evolution of the <span class="hlt">glacier</span> and lakes. We also collected bathymetry data and created bathymetric maps of select lakes. Despite small advances and retreats, the main terminus of Brady <span class="hlt">Glacier</span> has changed little since 1880. However, it downwasted at rates of 2-3 m/y between 1948 and 2000, more than the regional average. The most dramatic retreat (2 km) and downwasting (120 m) have occurred adjacent to <span class="hlt">glacier</span>-dammed lakes and are primarily the result of calving. Brady <span class="hlt">Glacier</span> is a former tidewater <span class="hlt">glacier</span>. With continued downwasting, Brady <span class="hlt">Glacier</span> may return to a tidewater regime and enter into a phase of catastrophic retreat. The situation at Brady <span class="hlt">Glacier</span> is not unique, and the lessons learned here can be applied elsewhere to identify future <span class="hlt">glacier</span>-dammed lakes, jökulhlaups, and <span class="hlt">glacier</span> instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GPC...159...61M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GPC...159...61M"><span><span class="hlt">Glacier</span> loss and hydro-social risks in the Peruvian Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mark, Bryan G.; French, Adam; Baraer, Michel; Carey, Mark; Bury, Jeffrey; Young, Kenneth R.; Polk, Molly H.; Wigmore, Oliver; Lagos, Pablo; Crumley, Ryan; McKenzie, Jeffrey M.; Lautz, Laura</p> <p>2017-12-01</p> <p>Accelerating <span class="hlt">glacier</span> recession in tropical highlands and in the Peruvian Andes specifically is a manifestation of global climate change that is influencing the hydrologic cycle and impacting water resources across a range of socio-environmental systems. Despite predictions regarding the negative effects of long-term <span class="hlt">glacier</span> decline on water availability, many uncertainties remain regarding the timing and variability of hydrologic changes and their impacts. To improve context-specific understandings of the effects of climate change and glacial <span class="hlt">melt</span> on water resources in the tropical Andes, this article synthesizes results from long-term transdisciplinary research with new findings from two <span class="hlt">glacierized</span> Peruvian watersheds to develop and apply a multi-level conceptual framework focused on the coupled biophysical and social determinants of water access and hydro-social risks in these settings. The framework identifies several interacting variables-hydrologic transformation, land cover change, perceptions of water availability, water use and infrastructure in local and regional economies, and water rights and governance-to broadly assess how <span class="hlt">glacier</span> change is embedded with social risks and vulnerability across diverse water uses and sectors. The primary focus is on the Santa River watershed draining the Cordillera Blanca to the Pacific. Additional analysis of hydrologic change and water access in the geographically distinct Shullcas River watershed draining the Huaytapallana massif towards the city of Huancayo further illuminates the heterogeneous character of hydrologic risk and vulnerability in the Andes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5746843','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5746843"><span>Pressure-<span class="hlt">Induced</span> <span class="hlt">Melting</span> of Confined Ice</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2017-01-01</p> <p>The classic regelation experiment of Thomson in the 1850s deals with cutting an ice cube, followed by refreezing. The cutting was attributed to pressure-<span class="hlt">induced</span> <span class="hlt">melting</span> but has been challenged continuously, and only lately consensus emerged by understanding that compression shortens the O:H nonbond and lengthens the H–O bond simultaneously. This H–O elongation leads to energy loss and lowers the <span class="hlt">melting</span> point. The hot debate survived well over 150 years, mainly due to a poorly defined heat exchange with the environment in the experiment. In our current experiment, we achieved thermal isolation from the environment and studied the fully reversible ice–liquid water transition for water confined between graphene and muscovite mica. We observe a transition from two-dimensional (2D) ice into a quasi-liquid phase by applying a pressure exerted by an atomic force microscopy tip. At room temperature, the critical pressure amounts to about 6 GPa. The transition is completely reversible: refreezing occurs when the applied pressure is lifted. The critical pressure to <span class="hlt">melt</span> the 2D ice decreases with temperature, and we measured the phase coexistence line between 293 and 333 K. From a Clausius–Clapeyron analysis, we determine the latent heat of fusion of two-dimensional ice at 0.15 eV/molecule, being twice as large as that of bulk ice. PMID:29112376</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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