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Sample records for island glacier faster

  1. Pine Island Glacier

    Atmospheric Science Data Center

    2013-04-16

    article title:  Pine Island Glacier, Antarctica     View ... Imaging SpectroRadiometer (MISR) images of the Pine Island Glacier in western Antarctica was acquired on December 12, 2000 during ... sea ice between the glacier and the open water in Pine Island Bay. To the left of the "icebergs" label are chunks of floating ice. ...

  2. Pine Island Glacier, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This pair of MISR images of the Pine Island Glacier in western Antarctica was acquired on December 12, 2000 during Terra orbit 5246. At left is a conventional, true-color image from the downward-looking (nadir) camera. The false-color image at right is a composite of red band data taken by the MISR forward 60-degree, nadir, and aftward 60-degree cameras, displayed in red, green, and blue colors, respectively. Color variations in the left (true-color) image highlight spectral differences. In the multi-angle composite, on the other hand, color variations act as a proxy for differences in the angular reflectance properties of the scene. In this representation, clouds show up as light purple. Blue to orange gradations on the surface indicate a transition in ice texture from smooth to rough. For example, the bright orange 'carrot-like' features are rough crevasses on the glacier's tongue. In the conventional nadir view, the blue ice labeled 'rough crevasses' and 'smooth blue ice' exhibit similar coloration, but the multi-angle composite reveals their different textures, with the smoother ice appearing dark purple instead of orange. This could be an indicator of different mechanisms by which this ice is exposed. The multi-angle view also reveals subtle roughness variations on the frozen sea ice between the glacier and the open water in Pine Island Bay.

    To the left of the 'icebergs' label are chunks of floating ice. Additionally, smaller icebergs embedded in the frozen sea ice are visible below and to the right of the label. These small icebergs are associated with dark streaks. Analysis of the illumination geometry suggests that these streaks are surface features, not shadows. Wind-driven motion and thinning of the sea ice in the vicinity of the icebergs is one possible explanation.

    Recently, Robert Bindschadler, a glaciologist at the NASA Goddard Space Flight Center discovered in Landsat 7 imagery a newly-formed crack traversing the Pine Island Glacier. This crack

  3. Pine Island Glacier, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This ASTER image was acquired on December 12, 2000, and covers an area of 38 x 48 km. Pine Island Glacier has undergone a steady loss of elevation with retreat of the grounding line in recent decades. Now, space imagery has revealed a wide new crack that some scientists think will soon result in a calving event. Glaciologist Robert Bindschadler of NASA's Goddard Space Flight Center predicts this crack will result in the calving of a major iceberg, probably in less than 18 months. Discovery of the crack was possible due to multi-year image archives and high resolution imagery. This image is located at 74.1 degrees south latitude and 105.1 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  4. Rock glaciers in the South Shetland Islands, Western Antarctica

    NASA Astrophysics Data System (ADS)

    Serrano, Enrique; López-Martínez, Jerónimo

    2000-10-01

    Rock glaciers are found in the peripheral regions of Antarctica particularly in the Antarctic Peninsula region. Study of these features is relevant for the palaeoenvironmental reconstruction of maritime Antarctica because they are indicators of permafrost and periglacial conditions. This paper reports and analyzes the results of an inventory of rock glaciers and protalus lobes in the South Shetland Islands. Nine rock glaciers and eleven protalus lobes have been identified. All of them are located in recently deglaciated zones between 300 m a.s.l. and sea level and they cover an area of 497×103 m 2. Tongue-shaped rock glaciers are more common than lobate types, being in general of medium and small sizes. They are talus rock glaciers (55%) and debris rock glaciers (45%), according to the genetic classification. The lack of a preferred orientation suggests that there is no significant microclimate control on their distribution. They are related to particular morphodynamic situations. Estimated annual velocities, based on relationships with raised beaches and transported debris volumes, range between 2.4 and 97 cm year -1, within the ranges reported for other rock glaciers. Three groups of rock glaciers can be recognised: (a) those immediate postdating the last major ice recession, (b) rock glaciers younger than 2000 years BP but pre-dating the Little Ice Age (LIA), and (c) rock glaciers formed during the LIA.

  5. Interferometric SAR observations of the Pine Island Glacier catchment area

    NASA Astrophysics Data System (ADS)

    Stenoien, Mark Daniel

    The catchment area of Pine Island Glacier, in West Antarctica, is mapped using satellite-radar interferometry and satellite-radar altimetery. The synthetic-aperture radar signal-processing algorithm implemented for this task uses precise (post-processed) orbit-ephemerides and a radar-altimeter digital-elevation-model to generate terrain-corrected and geolocated complex-imagery. The interferometric signal-processing algorithm implemented uses the same precise orbit-ephemerides and digital-elevation-model, together with synthetic-aperture-radar data collected from ascending- and descending-orbit passes to generate geometrically-corrected maps of true ice-surface motion. Satellite radar-altimeter data are used to create a digital elevation-model of the Pine Island Glacier catchment area via a unique algorithm that slope-corrects and grids the topographic estimates in a single step. The application of these tools reveals a system of tributaries channeling ice from the basin-like catchment area into the fast-flowing outlet glacier. None of the 7 tributaries mapped show a clear "onset" region, where sliding begins suddenly to dominate internal deformation as the predominant mode of ice motion; rather there is a gradual increase in ice speed, along with a gradual decrease in driving stress, along the axis of each tributary. Overall, however, regions of high (low) driving stress are closely associated with regions of large (small) surface slope, but show little correlation with the configuration of the tributaries. Furthermore, an estimate of the mass-balance of the observed portions of the Pine Island Glacier catchment area suggests that the northern and eastern slopes of the catchment area are gaining mass, while the southern slope is losing mass, making the net-balance for the observed area not distinguishable from zero.

  6. Timing of recent accelerations of Pine Island Glacier, Antarctica

    USGS Publications Warehouse

    Joughin, I.; Rignot, E.; Rosanova, C.E.; Lucchitta, B.K.; Bohlander, J.

    2003-01-01

    We have used Interferometric Synthetic Aperture Radar (InSAR) data and sequential Landsat imagery to identify and temporally constrain two acceleration events on Pine Island Glacier (PIG). These two events are separated by a period of at least seven years (1987 - 1994). The change in discharge between two flux gates indicates that the majority of the increase in discharge associated with the second acceleration originates well inland (>80 km) from the grounding line. An analysis indicates that changes in driving stress consistent with observed thinning rates are sufficient in magnitude to explain much of the acceleration.

  7. Ocean mixing beneath Pine Island Glacier Ice Shelf

    NASA Astrophysics Data System (ADS)

    Kimura, Satoshi; Dutrieux, Pierre; Jenkins, Adrian; Forryan, Alexander; Naveira Garabato, Alberto; Firing, Yvonne

    2016-04-01

    Ice shelves around Antarctica are vulnerable to increase in ocean-driven melting, with the melt rate depending on ocean temperature and strength of sub-ice-shelf-cavity circulations. We present repeated measurements of velocity, temperature, salinity, turbulent kinetic energy dissipation rate and thermal variance dissipation rate beneath Pine Island Glacier Ice Shelf, collected by CTD, ADCP and turbulence sensors mounted on an Autonomous Underwater Vehicle (AUV). The turbulence quantities measured by the AUV outside the ice shelf are in good agreement with ship-based measurements. The highest rate of turbulent kinetic energy dissipation is found near the grounding line, while its temporal fluctuation over seabed ridge within the cavity corresponds to the tidal fluctuation predicted in the Pine Island Bay to the west. The highest thermal variance dissipation rate is found when the AUV was 0.5 m away from the ice, and the thermal variance dissipation generally increases with decreasing distance between the AUV and ice.

  8. Earth system consequences of a Pine Island Glacier collapse

    NASA Astrophysics Data System (ADS)

    Green, Mattias; Schmittner, Andreas

    2016-04-01

    An intermediate complexity climate model is used to simulate the impact of an accelerated Pine Island Glacier mass loss on the large-scale ocean circulation and climate. Simulations are performed for pre-industrial conditions using hosing levels consistent with present day observation of 3,000 m3 s-1, at an accelerated rate of 6,000 m3 s-1, and at a total collapse rate of 100,000 m3 s-1, and in all experiments the hosing lasted 100 years. It is shown that even a modest input of meltwater from the glacier can introduce an initial cooling over the upper part of the Southern Ocean due to increased stratification and ice cover leading to a reduced upward heat flux from Circumpolar Deep Water. This causes global ocean heat content to increase and global surface air temperatures to decrease. The Atlantic Meridional Overturning Circulation (AMOC) increases, presumably due to changes in the density difference between Antarctic Intermediate Water and North Atlantic Deep Water. Simulations with a simultaneous hosing and increases of atmospheric CO2 concentrations show smaller effects of the hosing on global surface air temperature and ocean heat content, which we attribute to the melting of Southern Ocean sea ice. The sensitivity of the AMOC to the hosing is also reduced as the warming by the atmosphere completely dominates the perturbations. Further consequences for oceanic biogeochemical cycles in realistic future warming scenarios are discussed.

  9. Operation IceBridge: Fly Through of Pine Island Glacier Crack

    NASA Video Gallery

    This animation provides a fly through of the major rift in the Pine Island Glacier in western Antarctica. This crack, which extends at least 18 miles and is 50 meters deep, could produce an iceberg...

  10. Velocities of Pine Island and Thwaites Glaciers, West Antarctica, from ERS-1 SAR images

    USGS Publications Warehouse

    Lucchitta, B.K.; Rosanova, C.E.

    1997-01-01

    Average velocities of Pine Island and Thwaites Glaciers were measured for the time periods between 1992 and 1994 by tracking ice-surface patterns. Velocities of the central flow of the Pine Island Glacier range from 1.5 km/yr above the grounding line (separating the grounded from the floating parts of a glacier) to 2.8 km/yr near the terminus; velocities of the central Thwaites Glacier range from 2.2 km/yr above the grounding line to 3.4 km/yr at the limit of measurements on the tongue. Both glaciers show an increase in velocity of about 1 km/yr where they cross their grounding lines. The velocities derived from ERS-1 images are higher than those previously derived from Landsat images, perhaps reflecting acceleration of the glaciers. Both glaciers are exceptionally fast. The high velocities may be due to high precipitation rates over West Antarctica and the lack of a major buttressing ice shelf.

  11. Glaciers

    NASA Astrophysics Data System (ADS)

    Hambrey, Michael; Alean, Jürg

    2004-12-01

    Glaciers 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 glaciers grow and decay, move and influence human civilization. Currently covering a tenth of the Earth's surface, glacier ice has shaped the landscape over millions of years by scouring away rocks and transporting and depositing debris far from its source. Glacier meltwater drives turbines and irrigates deserts, and yields mineral-rich soils as well as a wealth of valuable sand and gravel. However, glaciers also threaten human property and life. Our future is indirectly connected with the fate of glaciers 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 Glaciers (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.

  12. Basal debris entrainment and transport in glaciers of southwestern Bylot Island, Canadian Arctic

    USGS Publications Warehouse

    Zdanowicz, C.M.; Michel, F.A.; Shilts, W.W.

    1996-01-01

    Glaciers on southwestern Bylot Island in the Canadian Arctic flow from an alpine setting in high-grade crystalline Archean terrane, on to coastal lowlands underlain by clastic sedimentary strata of Cretaceous to Tertiary age. We have used the contrasting mineralogy of the substrate as a tool to study subglacial entrainment and transport of debris in two large piedmont glaciers on Bylot Island. High chlorite/ and mica-illite/smectite ratios indicate that most basal debris is derived from crystalline rocks underlying the upper reaches of the glaciers. The subglacial accretion of Cretaceous-Tertiary sediments appears restricted to the lowermost part of the basal zone and is most noticeable near the glaciers' termini. Ice associated with discrete silty-sandy debris layers is characterized by an isotopic signature indicative of refreezing of meltwater at the glacier sole. The compositional, textural and isotopic characteristics of basal sediment and ice lead us to conclude that subglacial entrainment through basal ice accretion occurs in both the upper and marginal parts of the glaciers.

  13. Holocene glacier activity on Kerguelen Island: preliminary results from a novel proglacial lake sediment record

    NASA Astrophysics Data System (ADS)

    Støren, Eivind; Bakke, Jostein; Arnaud, Fabien; Poulenard, Jérôme; Fanget, Bernard; Malet, Emmanuel; Sabatier, Pierre

    2016-04-01

    The Polar-regions are changing rapidly as greenhouse warming is continuing with huge impact on e.g. sea ice extent and snow cover. This change triggers teleconnections to low latitude areas challenging societies and human activity. We have, however, very little quantitative information of past climate in the Polar-regions that can be used to evaluate the potential responses and the response patterns to forcing changes and changes in boundary conditions. Whatever anthropogenic changes may occur in the future, they will be superimposed on, and interact with, natural climate variations due to all the forcing we are aware of. This means we need to better document past climate/environmental variability of the Polar-regions. Especially in the Southern Ocean there are few time series recording past climate due to few suitable land areas and the few Sub-Antarctic Islands is remote and has cumbersome logistics. Continuous terrestrial records from this region are therefore urgently needed for constraining future scenarios from earth system models. Glaciers and ice caps are still ubiquitous in the Polar-regions, although they are rapidly shrinking due to the on-going warming. The continuous sedimentary records produced by glaciers, which are stored in downstream lakes, represent supreme archives of past variability wherefrom quantitative information of key climate system components can be extracted. Kerguelen Island is located within the Antarctic Circumpolar Current and the Southern Westerly wind belt and contains several glaciers and smaller ice caps. Terrestrial archives recording past history of the glaciers at Kerguelen thus have a unique potential to record past changes in oceanic and atmospheric circulation patterns from southern mid-latitudes. Here we present preliminary results from the first distal glacier-fed lake that is sampled from Kerguelen Island. A 2.8 m long sediment core was obtained from Lac Guynemer (121masl.) located at the Peninsule Loranchet at the

  14. Observations beneath Pine Island Glacier in West Antarctica and implications for its retreat

    NASA Astrophysics Data System (ADS)

    Jenkins, Adrian; Dutrieux, Pierre; Jacobs, Stanley S.; McPhail, Stephen D.; Perrett, James R.; Webb, Andrew T.; White, David

    2010-07-01

    Thinning ice in West Antarctica, resulting from acceleration in the flow of outlet glaciers, is at present contributing about 10% of the observed rise in global sea level. Pine Island Glacier in particular has shown nearly continuous acceleration and thinning, throughout the short observational record. The floating ice shelf that forms where the glacier reaches the coast has been thinning rapidly, driven by changes in ocean heat transport beneath it. As a result, the line that separates grounded and floating ice has retreated inland. These events have been postulated as the cause for the inland thinning and acceleration. Here we report evidence gathered by an autonomous underwater vehicle operating beneath the ice shelf that Pine Island Glacier was recently grounded on a transverse ridge in the sea floor. Warm sea water now flows through a widening gap above the submarine ridge, rapidly melting the thick ice of the newly formed upstream half of the ice shelf. The present evolution of Pine Island Glacier is thus part of a longer-term trend that has moved the downstream limit of grounded ice inland by 30km, into water that is 300m deeper than over the ridge crest. The pace and ultimate extent of such potentially unstable retreat are central to the debate over the possibility of widespread ice-sheet collapse triggered by climate change.

  15. 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. PMID:24031016

  16. 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.

  17. Pine Island Glacier, Antarctica, MISR Multi-angle Composite

    Atmospheric Science Data Center

    2013-12-17

    ... backward direction, which tend to be rough surfaces, appear orange, while smooth surfaces, which tend to scatter light in the forward ... quite clearly the location of the glacier itself with bright orange bands delineating the extent of the moving ice. The large crack appears ...

  18. Recent changes detected on two glaciers at the northern part of James Ross Island, Antarctica

    NASA Astrophysics Data System (ADS)

    Nývlt, Daniel; Kopačková, Veronika; Láska, Kamil; Engel, Zbyněk.

    2010-05-01

    Antarctic Peninsula is one of the regions, which have been exposed to the most rapid warming of the Earth since 1950. Consequences of climate changes are clearly documented by recent disintegration of ice shelves on both sides of the Antarctic Peninsula as well as by the retreat of land-based glaciers. James Ross Island, located close to the northernmost tip of the Antarctic Peninsula, represents an excellent place to study changes in the glacier mass-balance and their sensitivity to a regional warming trend. Two different types of glaciers of the Ulu Peninsula, the Whisky Glacier and the Davies Dome have been studied. Multi-temporal remote sensing data (aerial photographs, Landsat MSS, TM and ETM+ and Aster satellite optical and thermal multispectral data) and field survey allowed detecting changes in extent (2-D) as well as calculating glacier mass-balance changes (3-D) for these two glaciers from 1977 to 2009. The Whisky Glacier is a well-delimited valley glacier located mostly below the local Equilibrium line altitude (ELA). The glacier with high-flow velocities is fed by an intensive snow accumulation caused by prevailing southwestern winds. The Whisky Glacier covers an area of 2.3 km2 and its altitude varies from 215 to 475 m a.s.l. The Davies Dome is a flat-bottom dome glacier. Significant parts of its surface are located above the ELA and limited flow velocities are characteristic for the most parts of its body. However, the Davies Dome has a single 500-700 m wide southwestern outlet flowing towards the Whisky Bay. The Davies Dome extends an area of 6.7 km2 and its altitude ranges from 0 to 514 m a.s.l. Both glaciers experienced massive extension of their ice tongues towards the Brandy Bay during the mid Holocene. Lateral moraines located in front of the both glaciers heading down to the left coast of the Brandy Bay document this event. According to the remote sensing data and field investigations both glaciers have retreated since 1977. Between 2006 and

  19. Monitoring of land-based glaciers on James Ross Island, Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Laska, Kamil; Nyvlt, Daniel; Engel, Zbynek; Stachon, Zdenek

    2015-04-01

    Antarctic Peninsula has been considered one of the most rapidly warming parts of our planet during the second half of the 20th century. Therefore, James Ross Island located near the northern tip of the Antarctic Peninsula, represents a unique place to study the sensitivity of glacier systems to regional atmospheric warming. Since 2006, an integrated multidisciplinary study of glaciers and terrestrial ecosystems has been carried out in the northern part of Ulu Peninsula, James Ross Island. In this contribution, glacier monitoring network consisting of four dominant land-based glaciers at the Ulu Peninsula is presented. Davies Dome (DD) is an ice dome, which originates on the surface of a flat volcanic mesa at >400 m a.s.l. and terminates as a single 700 m wide outlet in Whisky Bay. In 2006, Davies Dome had an area of 6.5 km2 and lay in the altitude range 0-514 m a.s.l. Whisky Glacier (WG) is a cold-based land-terminating valley glacier, which is surrounded by an extensive area of debris-covered ice. WG covered an area of 2.4 km2 and ranged from 215 to 520 m a.s.l. Triangular Glacier (TG) is a southwest-facing land-terminating glacier with an area of 0.6 km2 ranging from 302 to 107 m a.s.l. with well-developed ice-cored terminal moraine. San Jose Glacier (SJG) is a south-facing land-terminating piedmont glacier rejuvenated from the above lying Lachman Crags Dome (~640 m a.s.l.). SJG covers an area of 0.6 km2 and extends between 138 and 310 m a.s.l. Moreover, monitoring network consists of five automatic weather stations (AWS) placed in the central and marginal parts of the selected glaciers. Each AWS was equipped with the EMS33 air temperature and humidity probes placed inside the radiation shields. Apart from that, additional instruments, e.g. albedometer, propeller anemometer, snow depth sensors were installed on the central part of DD and WG. Since 2009, annual mass balance measurements have been realized on the DD, WG and TG glaciers. In 2010, ice thickness and

  20. Buried glacier ice in permafrost, a window to the past: examples from Bylot Island, Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Fortier, D.; Coulombe, S.; Kanevskiy, M. Z.; Paquette, M.; Shur, Y.; Stephani, E.

    2011-12-01

    Bylot Island is located north of Baffin Island (73°N, 80°W) and is extensively covered by an ice cap and its outlet glaciers flowing towards the arctic lowland of the Lancaster formation. During summers of 2009 and 2011 several active-layer detachment slides exposed large massive ice bodies and other types of debris-rich ice that were interpreted as buried glacier ice. The upper part of the massive ice and debris-rich ice were usually in contact with various types of ice-contact or glacio-fluvial sediments and in some cases they were covered by mass wasting/colluvial deposits. This suggests that their preservation was likely related to burial of the ice and refreezing of the overlying sediments following permafrost aggradation. A preliminary analysis of the ice facies and ice crystals revealed the presence of four distinct types of ice: 1) clear-ice bodies with very few sediment and no organic inclusions. The ice crystals were large (cm), randomly oriented and air bubbles were observed at the junction of crystals. These characteristics could potentially indicate an englacial (snow-neve metamorphism) origin for these clear ice bodies; 2) large, meter thick, clear ice layers with no sediment, nor organics. The ice crystals were large (cm), several cm long, oriented in the same direction, and vertically aligned. These characteristics could potentially point to water that refroze in a tunnel incised in englacial ice; 3) Successive, mm to cm thick, ice layers, separated by undulating sand and gravel bands also containing cobles to boulder size rock fragments. These characteristics could potentially represent regelation ice formed at the base of glaciers and incorporated to the glacier sole; 4) mm to cm suspended aggregate of fine-grained sediments in clear ice. These micro-suspended and suspended cryostructures were sometimes deformed and aligned in the form of thin (mm) undulating layers. These micro-structures were very similar to basal ice facies, presumably

  1. Deception island, Antarctica: a terrestrial analogue for the study and understanding of the martian permafrost and subsurface glaciers

    NASA Astrophysics Data System (ADS)

    Hernandez de Pablo, M. A.; Ramos, M.; Vieira, G.; Gilichinsky, D.; Gómez, F.; Molina, A.; Segovia, R.

    2009-04-01

    The existence of permafrost on Mars was widely studied since Viking era and its presence is fundamental in the understanding of the water-cycle, the geological history of Mars, and the evolution of the martian hydrosphere. Viking, MOC, THEMIS, HRSC and HiRISE images allowed increase our knowledge about the role of ice on the martian landscapes. Polygonal terrains, glacial-like features, "basketball terrain" or pingos are some of the landforms that reveal the existence of frozen ice near the surface and in the ground forming the martian permafrost on present, recent or ancient times. The field observations and analyses done by Phoenix mission seem to confirm the existence of the martian permafrost hypothesized by the analyses of the images acquired by the previous missions to Mars. Moreover, the recent interpretations of the (RADAR) sensor on board of MRO mission also revealed that the surface of Mars seems to cover an important volume of ice forming glaciers covered by different materials. Here we propose the study of the glaciers and permafrost of Deception Island (Antarctica) such as a terrestrial analogue of the glaciers and permafrost of Mars. This active volcanic island is an exceptional site to study the permafrost since the climatic conditions maintain the surface covered by the ice and snow during the main part of the year. This characteristic allows the existence of an important permafrost layer also during the summer, and permanent glaciers in the higher part of the island. In addition, Deception Island is an active volcano. Some of the glaciers are covered by the ash and tephra what made difficult to distinguish between the covered glacier and the permafrost. The eruptive volcanic materials could have similar characteristics than some martian regolith by lithology, granulometry and texture. In this way, the study of the permafrost and glaciers in Deception Island could help to understand the martian permafrost and glaciers at present. On the other hand

  2. A new glacier inventory on southern Baffin Island, Canada, from ASTER data: I. Methods, challenges and solutions

    NASA Astrophysics Data System (ADS)

    Svoboda, F.; Paul, F.

    2009-04-01

    According to recent climate scenarios, the Arctic regions will experience a particular strong increase in temperature in the coming decades. Thus, the strongly glacierized Canadian Arctic could then greatly contribute to global sea level rise. For a quantitative assessment of overall changes a glacier inventory based on vector outlines is required. This is lacking in many remote areas, or, in the case of Baffin Island, it has been made but the data have not been forwarded to the world data centres. Within the framework of the GLIMS initiative and the GlobGlacier project we used multispectral satellite data in combination with DEM information to map and inventory glaciers and icecaps for the southern part of Cumberland Peninsula, Baffin Island (Canada), with automated techniques. In this study two ASTER scenes from August 2000 are used for DEM generation and mapping of recent glacier outlines and LIA trimlines to generate detailed glacier inventory data. Additionally a change assessment with the freely available Landsat MSS (1975) and TM (1990) scenes from the GLCF has been made. The study is separated in two parts: In the first part the applied methods and the encountered challenges are described and discussed. The results of the new inventory, the change assessment and application of the obtained data are presented in part II. A major aim of both contributions is also to discuss common standards for glacier mapping and inventory data creation. In part I the extraction of the DEM from ASTER, its accuracy, regions of error, fields of application and possible corrections are discussed. We further describe the mapping of glacier outlines from MSS, TM and ASTER which have varying resolution and spectral bands. The required manual correction of the generated glacier outlines (debris, water, snow and shadow) and the challenges that have to be considered in this region are presented as well. A major and at the same time critical part is the delineation of glacier basins

  3. Thermal structure and basal sliding parametrisation at Pine Island Glacier - a 3-D full-Stokes model study

    NASA Astrophysics Data System (ADS)

    Wilkens, N.; Behrens, J.; Kleiner, T.; Rippin, D.; Rückamp, M.; Humbert, A.

    2015-04-01

    Pine Island Glacier is one of the fastest changing glaciers of the Antarctic Ice Sheet and therefore of scientific interest. The glacier holds enough ice to raise the global sea level significantly (~ 0.5 m) when fully melted. The question addressed by numerous modelling studies of the glacier focuses on whether the observed changes are a start of an uncontrolled and accelerating retreat. The movement of the glacier is, in the fast-flowing areas, dominated by basal motion. In modelling studies the parametrisation of the basal motion is therefore crucial. Inversion methods are commonly applied to reproduce the complex surface flow structure of Pine Island Glacier by using information of the observed surface velocity field to constrain, among other things, basal sliding. We introduce two different approaches of combining a physical parameter, the basal roughness, with basal sliding parametrisations. This way basal sliding is again connected closer to its original formulation. We show that the basal roughness is an important and helpful parameter to consider and that many features of the flow structure can be reproduced with these approaches.

  4. The influence of air temperature inversions on snowmelt and glacier mass-balance simulations, Ammassalik island, SE Greenland

    SciTech Connect

    Mernild, Sebastian Haugard; Liston, Glen

    2009-01-01

    In many applications, a realistic description of air temperature inversions is essential for accurate snow and glacier ice melt, and glacier 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 glacier ice ablation from numerous small coastal marginal glaciers on the SW-part of Ammassalik Island in SE Greenland. These glaciers 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 air temperature and snow and glacier melt 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 glaciers (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.eq. y

  5. Mounting evidence for intense ocean interaction with the Pine Island Glacier Ice Shelf

    NASA Astrophysics Data System (ADS)

    Bindschadler, R.; Holland, D.; Vaughan, D.; Vornberger, P.

    2008-12-01

    The spatial signature of thinning and acceleration of the Pine Island Glacier has led to the inference that these changes originate at the seaward end of the glacier, possibly within or under the ice shelf (Payne et al., 2004; Shepherd et al., 2004). We present new analyses resulting from both new and archived satellite imagery of the ice shelf that supports this inference and provides new insights into strong seasonal and intra- annual characters of ocean-ice shelf interaction. Strong longitudinal variations in both thickness and surface elevation measured by British Antarctic Survey airborne radars (Vaughan et al., 2006) have wavelengths that correspond roughly to the annual motion of the ice shelf. These could be caused by seasonal variations in flow speed, but such variations of flow speed have never been reported and are not seen in the most recent continuous GPS observations of the ice shelf. We suggest that these strong variations in ice thickness, as large as 200 meters in an average thickness of 600 meters, are caused by seasonal variations in the properties of the water circulating underneath the ice shelf. One likely explanation is that the dominant water mass reaching the deepest parts of the ice shelf alternates between cold High Salinity Shelf Water in the winter and warm Circumpolar Deep Water in the summer. Evidence for recent strengthening of the sub- shelf circulation is the sudden occurrence of three persistent polynyas immediately adjacent to the ice front. These are located in precisely the locations expected from modeled sub-shelf circulation (Payne et al., 2007). This mode was never observed in any satellite imagery prior to the 1999-2000 austral summer (data of 7 summers since 1973 were available), but has occurred in 7 of the 9 summers since and persists throughout the summer. Payne, A.J., A. Vieli, A.P. Shepherd, D.J. Wingham and E. Rignot, 2004. Recent dramatic thinning of largest West Antarctic ice stream triggered by oceans, Geophysical

  6. Dropping aircraft-deployable GPS stations on Scar Inlet and Pine Island Glacier.

    NASA Astrophysics Data System (ADS)

    Hilmar Gudmundsson, G.; Jones, David

    2013-04-01

    There remains areas of scientific interest that heavy crevassing makes difficult or impossible to reach by ground via overland treks or an aircraft landing. We have developed an alternative strategy for instrumenting these regions: a sensor probe that can be dropped from an aircraft, partially bury itself in the snow whilst keeping its antennas protruding high above the surface to ensure a long operating life. Our probe has a 2.5m, 10kg missile-shaped design and can be deployed through a standard sonar-buoy launch tube. In order to achieve a consistent impact depth in different snow densities the case is fitted with fold-out fins one metre from the nose cone. This ensures a large step-change in impact surface area when the device is embedded to the correct depth. A small disk-gap-band parachute improves the angle of impact while damping any probe oscillations. We are now able to achieve near-vertical impact angles and a consistent snow penetration depth of one metre. The sensor is cheap to make (approximately £1000) and has a minimal environmental impact. This year we have used a large network of these sensors to instrument previously inaccessible parts of Scar Inlet and Pine Island Glacier.

  7. 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.

  8. Coupled ice shelf-ocean modeling and complex grounding line retreat for Pine Island Glacier

    NASA Astrophysics Data System (ADS)

    De Rydt, Jan; Gudmundsson, Hilmar

    2016-04-01

    Recent observations and modeling work have shown a complex mechanical coupling between Antarctica's floating ice shelves and the adjacent grounded ice sheet. A prime example is Pine Island Glacier, West Antarctica, which has a strong negative mass balance caused by a recent increase in ocean-induced melting of its ice shelf. The mass loss coincides with the retreat of the grounding line from a seabed ridge, on which it was at least partly grounded until the 1970s. At present, it is unclear what has caused the onset of this retreat, and how feedback mechanisms between the ocean and iceshelf geometry have influenced the ice dynamics. To address these questions, we present results from an offline coupling between a state-of-the-art shallow-ice flow model with grounding line resolving capabilities, and a three-dimensional ocean general circulation model with a static implementation of the ice shelf. A series of idealized experiments simulate the retreat from a seabed ridge in response to changes in the ocean forcing, and we show that the retreat becomes irreversible after 20 years of warm ocean conditions. A comparison to experiments with a simple depth-dependent meltrate parameterisation demonstrates that such parameterizations are unable to capture the details of the retreat process, and they overestimate mass loss by more than 40% over a 50-year timescale.

  9. Age and significance of former low-altitude corrie glaciers on Hoy, Orkney Islands

    USGS Publications Warehouse

    Ballantyne, C.K.; Hall, A.M.; Phillips, W.; Binnie, S.; Kubik, P.W.

    2007-01-01

    Geomorphological mapping provides evidence for two former low-level corrie glaciers on Hoy, both defined by end moraines. Five 10Be exposure ages obtained from sandstone boulders on moraine crests fall within the range 12.4??1.5 ka to 10.4??1.7 ka (weighted mean 11.7??0.6 ka), confirming that these glaciers developed during the Loch Lomond (Younger Dryas) Stade (LLS) of 12.9-11.5 cal. ka BP, and demonstrate the feasibility of using this approach to establish the age of LLS glacier limits. The equilibrium line altitude (ELA) of one of the glaciers (99 m) is the lowest recorded for any LLS glacier, and the area-weighted mean ELA for both (141 m) is consistent with a general northward ELA decrease along the west coast of Britain. The size of moraines fronting these small (???0.75 km2) glaciers implies that glacier termini remained at or close to their limits for a prolonged period. The apparent restriction of LLS glaciers to only two sites on Hoy probably reflects topographic favourability, and particularly the extent of snow-contributing areas.

  10. Autonomous ocean observations beneath Pine Island Glacier Ice Shelf, West Antarctica

    NASA Astrophysics Data System (ADS)

    Dutrieux, P.; Jenkins, A.; Jacobs, S.; Heywood, K. J.

    2015-12-01

    Warm circumpolar deep water reaching 3.5ºC above the in situ freezing point pervasively fills a network of glacially carved troughs in the Amundsen sea, West Antarctica, and melts and thins neighbouring ice shelves, including Pine Island glacier Ice Shelf (PIIS). Hydrographic, current, and microstructure observations obtained in austral summer 2009 and 2014 by an autonomous underwater vehicle beneath the PIIS are used here to detail the complex ice-ocean interaction and resulting ocean circulation. The theoretical schematic of deeply incoming warm and saline water melting the grounding line and generating a buoyant plume upwelling along the ice draft is generally consistent with observations. The cavity beneath PIIS is clearly divided in two by a seabed ridge, constraining the oceanic circulation and water masses distribution. On the seaward side of the ridge, a thick warm deep water layer circulates cyclonically and is overlaid by a thin meltwater layer. Only intermediate depth waters are allowed to overflow from the ridge top into the inner cavity, where a much thinner warm water layer is now overlaid by a thicker meltwater layer. At the ice/ocean interface, melt induced freshening is forcing an upwelling which in turn injects cyclonic vorticity and participates in creating a vigorous cyclonic recirculation in the inner cavity. The top of the ridge, where warm waters overflow in the inner cavity, is a dynamical boundary characterized by northward along-ridge currents up to 0.2 m/s and enhanced shear, thermal gradient, and mixing. Observations at two points at the ice interface indicate that the ocean remains stratified within 2 meters of the ice.

  11. A cosmogenic 3He chronology of late Quaternary glacier fluctuations in North Island, New Zealand (39°S)

    NASA Astrophysics Data System (ADS)

    Eaves, Shaun R.; N. Mackintosh, Andrew; Winckler, Gisela; Schaefer, Joerg M.; Alloway, Brent V.; Townsend, Dougal B.

    2016-01-01

    Mountain glaciers advance and retreat primarily in response to changes in climate. Establishing the timing and magnitude of mountain glacier fluctuations from geological records can thus help to identify the drivers and mechanisms of past climate change. In this study, we use cosmogenic 3He surface exposure dating and tephrochronology to constrain the timing of past glaciation on Tongariro massif in central North Island, New Zealand (39°S). Exposure ages from moraine boulders show that valley glaciation persisted between c. 30-18 ka, which coincides with the global Last Glacial Maximum. Reinterpretation of moraine tephrostratigraphy, using major element geochemistry analysis, shows that ice retreat and climatic amelioration at the last glacial termination was well underway prior to 14 ka. The equilibrium line altitude in central North Island, during the Last Glacial Maximum, was c. 1400-1550 m above sea level, which is c. 930-1080 m lower than present. Considering the uncertainties in the glacial reconstruction and temperature lapse rates, we estimate that this equilibrium line altitude lowering equates to a temperature depression of 5.6 ± 1.1 °C, relative to present. Our mapping and surface exposure dating also show evidence for an earlier period of glaciation, of similar magnitude to the Last Glacial Maximum, which culminated prior to 57 ka, probably during Marine Isotope Stage 4. Good agreement between the timing and magnitude of glacier fluctuations in central North Island and the Southern Alps indicate a response to a common climatic forcing during the last glacial cycle.

  12. Glaciers of North America - Glaciers of Alaska

    USGS Publications Warehouse

    Molnia, Bruce F.

    2008-01-01

    Glaciers cover about 75,000 km2 of Alaska, about 5 percent of the State. The glaciers are situated on 11 mountain ranges, 1 large island, an island chain, and 1 archipelago and range in elevation from more than 6,000 m to below sea level. Alaska's glaciers extend geographically from the far southeast at lat 55 deg 19'N., long 130 deg 05'W., about 100 kilometers east of Ketchikan, to the far southwest at Kiska Island at lat 52 deg 05'N., long 177 deg 35'E., in the Aleutian Islands, and as far north as lat 69 deg 20'N., long 143 deg 45'W., in the Brooks Range. During the 'Little Ice Age', Alaska's glaciers expanded significantly. The total area and volume of glaciers in Alaska continue to decrease, as they have been doing since the 18th century. Of the 153 1:250,000-scale topographic maps that cover the State of Alaska, 63 sheets show glaciers. Although the number of extant glaciers has never been systematically counted and is thus unknown, the total probably is greater than 100,000. Only about 600 glaciers (about 1 percent) have been officially named by the U.S. Board on Geographic Names (BGN). There are about 60 active and former tidewater glaciers in Alaska. Within the glacierized mountain ranges of southeastern Alaska and western Canada, 205 glaciers (75 percent in Alaska) have a history of surging. In the same region, at least 53 present and 7 former large ice-dammed lakes have produced jokulhlaups (glacier-outburst floods). Ice-capped volcanoes on mainland Alaska and in the Aleutian Islands have a potential for jokulhlaups caused by subglacier volcanic and geothermal activity. Because of the size of the area covered by glaciers and the lack of large-scale maps of the glacierized areas, satellite imagery and other satellite remote-sensing data are the only practical means of monitoring regional changes in the area and volume of Alaska's glaciers in response to short- and long-term changes in the maritime and continental climates of the State. A review of the

  13. Glacier fluctuations during the last 400 years at Mount San Lorenzo and Santa Ines Island, southern Chile

    NASA Astrophysics Data System (ADS)

    Aravena, J.; Luckman, B. H.

    2007-12-01

    We examine the local glacier fluctuations for the last 400 years in two mountain areas of the western coast of southernmost South America, Mount San Lorenzo and Santa Ines Island, using dendroglaciologic, geomorphologic and historical evidence. Mount San Lorenzo moraines span between 1636 and 1927 with periods of more frequent occurrence of glacial advances for the years 1670, 1770, 1870 and 1910. Santa Ines glacial advances are less numerous than in Mount San Lorenzo with well defined, clearly separated frontal moraines. The moraines were colonized by Nothofagus betuloides and Nothofagus antarctica two species with clear and well-preserved tree rings and the total age of the sampled trees was more precisely estimated. Dated moraines cover the last 300 years with evidence for advances during late 1600s, around 1800, 1860, 1910, 1930 and 1960. Further work is needed in dendroglaciological dating, geomorphologic surveying, and better understanding of local glacial dynamics for several glaciers to obtain a regional history of the glacier fluctuations of the southern Andes.

  14. The influence of shear bands on the grounding line retreat in Pine Island Glacier

    NASA Astrophysics Data System (ADS)

    Favier, Lionel; Durand, Gaël; Cornford, Stephen; Gagliardini, Olivier; Zwinger, Thomas

    2013-04-01

    Pine Island Glacier (PIG), West Antarctica, is known as the weak underbelly of the West Antarctic Ice Sheet. During the last 30 years, it has undergone a dramatic acceleration along with a retreat of its grounding line. The main ice stream draining PIG is laterally bounded by two thin bands of damaged ice. These shear bands may play a key role in the dynamics of the grounding line since they likely decrease the ice-shelf buttressing. The traditional approach is generally to infer the viscosity from surface velocity using data assimilation methods. However, in that case the inverse problem is under-constrained when it is coupled to the inversion of basal drag: different set of basal drag and viscosity pattern solution can lead to a good match between modelled and observed surface velocities, but would lead to different prognostic solutions associated to different grounding line migrations. Here, we follow a simpler approach and perform a sensitivity study on the shear bands effective viscosity, and its consequences for the ice dynamics. The areas of fractured ice at PIG are located using a recent SPOT satellite image. The non-fractured ice viscosity depends on ice temperatures while the fractured ice viscosity is decreased through a sensitivity study to reproduce the damaged ice of the shear bands. Using two different higher-order models (Elmer/Ice and BISICLES), we investigate the influence of the shear bands' damage on the grounding line dynamics. Each experiment in the sensitivity study gathers successively (i) the determination of basal drag through assimilation methods, (ii) a geometry relaxation over 15 years and (iii) transient perturbation experiments driven by different calving sizes. The initial geometry of the ice sheet arises from the ALBMAP data set on a 1 km grid resolution, velocities were acquired during the last International polar Year, and non-fractured ice viscosities are deduced from prescribed temperatures computed with a higher order model. We

  15. Mass budget of Queen Elizabeth Islands glaciers and ice caps, Canada, from 1992 to present

    NASA Astrophysics Data System (ADS)

    Millan, R.; Rignot, E. J.; Mouginot, J.

    2015-12-01

    Recent studies indicate to say that the Canadian Artic Archipelago's mass loss has increased in recent years. However the role of ice dynamics changes in this area is not well known. In this study, we present a comprehensive velocity mapping of the CAA using ALOS/PALSAR, RADARSAT-1, ERS1 and Landsat data between 1992 and 2015. Glaciers speed are calculated using a speckle and feature tracking algorithm.The results reveals that three large marine-terminating glaciers have accelerated significantly after 2010, while most others have slowed down or retreated to a sill to become similar to land-terminating glaciers. By combining the velocities of these glaciers with ice thickness measurements from NASA's Operation IceBridge, we calculate their ice discharge. The fluxes of these glaciers increased significantly since 2000 with a marked increase after 2011. The comparison of ice discharge with the surface mass balance from RACMO-2, shows that these glaciers came out of balance after 2011, which is also a time period where their discharge almost doubled. The analysis of RACMO-2 reveals an increase in runoff between 1970's and today and a precipitation with no significant trend. We digitalize the calving front positions of the glaciers and show an increasing rate retreat since 1976. We conclude that global pattern of velocity changes shows that the mass losses due to surface mass balance will likely going to raise in the coming years and that ice discharge will have a smaller part in the contribution of the CAA to sea level rise.

  16. Influence of Subglacial Conditions on Ice Stream Dynamics: Seismic and Potential Field Data from Pine Island Glacier, West Antarctica

    NASA Astrophysics Data System (ADS)

    Smith, A. M.; Jordan, T. A.; Ferraccioli, F.; Bingham, R. G.

    2012-12-01

    A synthesis of geophysical and glaciological data sets are used to investigate the relationship between ice dynamics and the underlying geology on Pine Island Glacier, West Antarctica. We find correlations between subglacial geology and the variability in the flow of the overlying ice. Seismic reflection amplitude analysis shows a layer of soft water-saturated sediment immediately beneath the ice. Beneath this, gravity and magnetic data indicate harder rocks containing a significant geological boundary, aligned in the ice-flow direction. Crossing this boundary, the ice velocity decreases whilst bed roughness and modeled basal drag both increase. The acoustic impedance of the soft sediments at the ice-bed interface shows no significant change across the boundary. The smoother glacier bed, overlying thicker sediments, appears to facilitate the fastest flow. Where the bed is rougher, the soft sediment layer beneath the ice is very thin and overlies basement rocks. We propose that the rough surface of the basement rocks beneath this thin sediment increases the basal drag on the ice, through the intervening soft sediment, without a detectable influence on the sediment's acoustic properties. Changes in the sub-bed (i.e. deeper than the ice-bed interface) lithology appear to account for the contrasting basal drag and ice velocity patterns over the glacier. Subglacial erosion could soon remove the thin sediment layer leading to increased basal drag and reduced ice flow in the future. We conclude that the subglacial geology plays a significant role in controlling the spatial pattern of present-day ice flow and that the consequences of subglacial erosion may be reflected in temporal changes to the ice dynamics in the past and perhaps also in the near future. Schematic of synthesized subglacial interpretation from the area of the seismic surveys. Arrow lengths for ice velocity and basal drag indicate relative magnitudes.

  17. Sulphate reducing activity detected in soil samples from Antarctica, Ecology Glacier Forefield, King George Island.

    PubMed

    Wolicka, Dorota; Zdanowski, Marek K; Żmuda-Baranowska, Magdalena J; Poszytek, Anna; Grzesiak, Jakub

    2014-01-01

    We determined sulphate-reducing activities in media inoculated with soils and with kettle lake sediments in order to investigate their potential in geomicrobiological processes in low-temperature, terrestrial maritime Antarctic habitats. Soil and sediment samples were collected in a glacier valley abandoned by Ecology Glacier during the last 30 years: from a new formed kettle lake sediment and forefield soil derived from ground moraine. Inoculated with these samples, liquid Postgate C and minimal media supplemented with various carbon sources as electron donors were incubated for 8 weeks at 4°C. High rates of sulphate reduction were observed only in media inoculated with soil. No sulphate reduction was detected in media inoculated with kettle lake sediments. In soil samples culture media calcite and elemental sulphur deposits were observed, demonstrating that sulphate-reducing activity is associated with a potential to mineral formation in cold environments. Cells observed on scanning microscopy (SEM) micrographs of post-culture-soil deposits could be responsible for sulphate-reducing activity. PMID:25804064

  18. Sulphate reducing activity detected in soil samples from Antarctica, Ecology Glacier Forefield, King George Island.

    PubMed

    Wolicka, Dorota; Zdanowski, Marek K; Żmuda-Baranowska, Magdalena J; Poszytek, Anna; Grzesiak, Jakub

    2014-01-01

    We determined sulphate-reducing activities in media inoculated with soils and with kettle lake sediments in order to investigate their potential in geomicrobiological processes in low-temperature, terrestrial maritime Antarctic habitats. Soil and sediment samples were collected in a glacier valley abandoned by Ecology Glacier during the last 30 years: from a new formed kettle lake sediment and forefield soil derived from ground moraine. Inoculated with these samples, liquid Postgate C and minimal media supplemented with various carbon sources as electron donors were incubated for 8 weeks at 4°C. High rates of sulphate reduction were observed only in media inoculated with soil. No sulphate reduction was detected in media inoculated with kettle lake sediments. In soil samples culture media calcite and elemental sulphur deposits were observed, demonstrating that sulphate-reducing activity is associated with a potential to mineral formation in cold environments. Cells observed on scanning microscopy (SEM) micrographs of post-culture-soil deposits could be responsible for sulphate-reducing activity.

  19. Ice marginal dynamics during surge activity, Kuannersuit Glacier, Disko Island, West Greenland

    NASA Astrophysics Data System (ADS)

    Roberts, David H.; Yde, Jacob C.; Knudsen, N. Tvis; Long, Antony J.; Lloyd, Jerry M.

    2009-02-01

    The Kuannersuit Glacier surged 11 km between 1995 and 1998. The surge resulted in the formation of an ice cored thrust moraine complex constructed by subglacial and proglacial glaciotectonic processes. Four main thrust zones are evident in the glacier snout area with phases of compressional folding and thrusting followed by hydrofracture in response to the build-up of compressional stresses and the aquicludal nature of submarginal permafrost and naled. Various types of stratified debris-rich ice facies occur within the marginal zone: The first (Facies I) comprises laterally continuous strata of ice with sorted sediment accumulations, and is reworked and thrust naled ice. The second is laterally discontinuous stratified debris-rich ice with distinct tectonic structures, and is derived through subglacial extensional deformation and localised regelation (Facies II), whilst the third type is characterised by reworked and brecciated ice associated with the reworking and entrainment of meteoric ice (Facies III). Hydrofracture dykes and sills (Facies IV) cross-cut the marginal ice cored thrust moraines, with their sub-vertically frozen internal contact boundaries and sedimentary structures, suggesting supercooling operated as high-pressure evacuation of water occurred during thrusting, but this is not related to the formation of basal stratified debris-rich ice. Linear distributions of sorted fines transverse to ice flow, and small stratified sediment ridges that vertically cross-cut the ice surface up-ice of the thrust zone relate to sediment migration along crevasse traces and fluvial infilling of crevasses. From a palaeoglaciological viewpoint, marginal glacier tectonics, ice sediment content and sediment delivery mechanisms combine to control the development of this polythermal surge valley landsystem. The bulldozing of proglacial sediments and the folding and thrusting of naled leads to the initial development of the outer zone of the moraine complex. This becomes

  20. Seasonal variation of meteorological variables and recent surface ablation / accumulation rates on Davies Dome and Whisky Glacier, James Ross Island, Antarctica

    NASA Astrophysics Data System (ADS)

    Láska, K.; Nývlt, D.; Engel, Z.; Budík, L.

    2012-04-01

    In this study, surface mass balance data of two glaciers on James Ross Island, Antarctica, and its spatial and temporal variations are evaluated using snow ablation stakes, ground-penetrating radar, and dGPS measurements. The investigated glaciers are located on the Ulu Peninsula, northern part of James Ross Island. Davies Dome is an ice dome, which originates on the surface of a flat volcanic mesa at elevations >400 m a.s.l. and terminates with a single 700 m wide outlet in the Whisky Bay. Davies Dome has an area of ~6.5 km2 and lies in the altitude range of 0-514 m a.s.l. Whisky Glacier is a cold-based land-terminating valley glacier surrounded by an extensive moraine ridges made of debris-covered ice. The glacier has an area of ~2.4 km2 and lies in the altitude range of 215-520 m a.s.l. Within several summer austral summers, extensive field programme were carried out on both glaciers including the operation of two automatic weather stations, field mapping and mass balance measurements. Each station was equipped with albedometer CM7B (Kipp-Zonen, Netherlands), air temperature and humidity sensor EMS33 (EMS, Czech Republic), propeller anemometer 05103 (Young, USA), and snow depth sensors (Judd, USA). In the period 2009-2011, high seasonal and interdiurnal variability of incoming solar radiation and near-surface air temperature was found as a result of changes in the circulation patterns and synoptic-scale weather systems moving in the Circumpolar Trough. High ablation and accumulation rates were recorded mainly in the spring and summer seasons (October-February), while negligible changes were found in winter (May-September). The effects of positive degree-day temperatures on the surface ablation rates were examined using a linear regression model. In this approach, near-surface air temperature maps on the glacier surfaces were derived from digital elevation model according to actual temperature lapse rates. Mass balance investigations started in 2006 on Davies

  1. Constraining the recent mass balance of Pine Island and Thwaites glaciers, West Antarctica with airborne observations of snow accumulation (Invited)

    NASA Astrophysics Data System (ADS)

    Medley, B.; Joughin, I. R.; Smith, B. E.; Das, S. B.; Steig, E. J.; Conway, H.; Gogineni, P. S.; Criscitiello, A. S.; McConnell, J. R.; van den Broeke, M. R.; Lenaerts, J.; Bromwich, D. H.; Nicolas, J. P.

    2013-12-01

    an ice core depth-age scale. From these measurements we investigate both the spatial and temporal variability in accumulation in this sector of West Antarctica as well as evaluate global and regional atmospheric model accumulation rate equivalents (i.e., precipitation minus sublimation, P-S; surface mass balance, SMB). First, we generate a spatially complete map of the 1985-2009 average annual accumulation over both Pine Island and Thwaites glaciers, which is used to precisely determine their recent mass balance. Next, we investigate the temporal variability and trend in annual accumulation rate, which is limited to Thwaites glacier. Finally, we assess the ability of three global reanalysis P-S products and a regional climate model (RACMO2) SMB product to reproduce the spatiotemporal accumulation variability over these glaciers. Accumulation rate measurements derived from airborne radar systems not only reduce the uncertainty in mass balance measurements but also provide the means with which to evaluate the skill of and discriminate between atmospheric models. New measurements from both Greenland and Antarctica as part of NASA's Operation IceBridge will further reduce our overall uncertainty in the glacial contribution to sea-level rise.

  2. Grounding line variability and subglacial lake drainage on Pine Island Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Joughin, Ian; Shean, David E.; Smith, Ben E.; Dutrieux, P.

    2016-09-01

    We produced a 6 year time series of differential tidal displacement for Pine Island Ice Shelf, Antarctica, using speckle-tracking methods applied to fine-resolution TerraSAR-X data. These results reveal that the main grounding line has maintained a relatively steady position over the last 6 years, following the speedup that terminated in ~2009. In the middle of the shelf, there are grounded spots that migrate downstream over the 6 year record. Examination of high-resolution digital elevation models reveals that these grounded spots form where deep keels (thickness anomalies) advect over an approximately flow-parallel bathymetric high, maintaining intermittent contact with the bed. These data sets also reveal several subsidence and uplift events associated with subglacial lake drainages in the fast-flowing region above the grounding line. Although these drainages approximately double the rate of subglacial water flow over periods of a few weeks, they have no discernible effect on horizontal flow speed.

  3. The Friction Law Stress Exponent under Pine Island Glacier from 15 Years of Surface Elevation and Velocity Measurements

    NASA Astrophysics Data System (ADS)

    Gillet-chaulet, F.; Durand, G.; Gagliardini, O.; Mosbeux, C.; Mouginot, J.; Remy, F.; Ritz, C.

    2015-12-01

    Polar the ice-sheets mass balance largely depends on the flow of ice-streams. Rapid basal motion generally accounts for most of the velocities. In flow models, the conditions at the base of the ice in contact with the bedrock are generally parameterised using a friction law that relates the sliding velocity to the basal shear stress. The most common law has two poorly constrained parameters, the basal slipperiness c and the stress exponent m. The basal slipperiness is expected to depend on local unobservable quantities and is routinely tuned from observed surface velocities using inverse methods. Different values for m are expected depending on the processes, from hard-bed sliding to soft bed deformation, and no consensus has emerged so far for its value that range from 1 to infinity. However, several studies have shown that the transient response of the ice-sheet models to external forcing is highly sensitive to m. Therefore, the uncertainty attached to the friction law is an important limit to our ability to evaluate future dynamical evolution of coastal regions. Calibrating m can be done only if either basal stresses and/or velocities have changed significantly while c can be assumed constant in time. Here, we use Elmer/Ice to model the flow of Pine Island Glacier (PIG), Antarctica, sufficiently far upstream of the grounding line so that we can assume no change in c. Observations show an increase of surface velocities by up to 50% between 1996 and 2010, associated with an important dynamical thinning. Using a control inverse method and different values of m, we tune a spatially varying basal slipperiness field that best fit, in the same time, observed surface velocities for years 1996, 2007, 2008, 2009 and 2010. These years correspond to the MeaSUREs project velocity datasets that have the best spatial coverage for our model domain. Surface elevations for the corresponding years are constructed using ERS and Envisat radar altimetry data. We show that the

  4. Glaciers of Greenland

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1995-01-01

    Landsat imagery, combined with aerial photography, sketch maps, and diagrams, is used as the basis for a description of the geography, climatology, and glaciology, including mass balance, variation, and hazards, of the Greenland ice sheet and local ice caps and glaciers. The Greenland ice sheet, with an estimated area of 1,736,095+/-100 km2 and volume of 2,600,000 km3, is the second largest glacier on the planet and the largest relict of the Ice Age in the Northern Hemisphere. Greenland also has 48,599+/-100 km2 of local ice caps and other types of glaciers in coastal areas and islands beyond the margin of the ice sheet.

  5. Columbia Glacier in 1984: disintegration underway

    SciTech Connect

    Meier, M.F.; Rasmussen, L.A.; Miller, D.S.

    1985-01-01

    Columbia Glacier is a large, iceberg-calving glacier near Valdez, Alaska. The terminus of this glacier was relatively stable from the time of the first scientific studies in 1899 until 1978. During this period the glacier terminated partly on Heather Island and partly on a submerged moraine shoal. In December, 1978, the glacier terminus retreated from Heather Island, and retreat has accelerated each year since then, except during a period of anomalously low calving in 1980. Although the glacier has not terminated on Heather Island since 1978, a portion of the terminus remained on the crest of the moraine shoal until the fall of 1983. By December 8, 1983, that feature had receded more than 300 m from the crest of the shoal, and by December 14, 1984, had disappeared completely, leaving most of the terminus more than 2000 meters behind the crest of the shoal. Recession of the glacier from the shoal has placed the terminus in deeper water, although the glacier does not float. The active calving face of the glacier now terminates in seawater that is about 300 meters deep at the glacier centerline. Rapid calving appears to be associated with buoyancy effects due to deep water at the terminus and subglacial runoff. 12 refs., 10 figs.

  6. A novel multispectral glacier mapping method and its performance in Greenland

    NASA Astrophysics Data System (ADS)

    Citterio, M.; Fausto, R. S.; Ahlstrom, A. P.; Andersen, S. B.

    2014-12-01

    Multispectral land surface classification methods are widely used for mapping glacier outlines. Significant post-classification manual editing is typically required, and mapping glacier outlines over larger regions remains a rather labour intensive task. In this contribution we introduce a novel method for mapping glacier outlines from multispectral satellite imagery, requiring only minor manual editing.Over the last decade GLIMS (Global Land Ice Measurements from Space) improved the availability of glacier outlines, and in 2012 the Randolph Glacier Inventory (RGI) attained global coverage by compiling existing and new data sources in the wake of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5). With the launch of Landsat 8 in 2013 and the upcoming ESA (European Space Agency) Sentinel 2 missions, the availability of multispectral imagery may grow faster than our ability to process it into timely and reliable glacier outline products. Improved automatic classification methods would enable a full exploitation of these new data sources.We outline the theoretical basis of the proposed classification algorithm, provide a step by step walk-through from raw imagery to finished ice cover grids and vector glacier outlines, and evaluate the performance of the new method in mapping the outlines of glaciers, ice caps and the Greenland Ice Sheet from Landsat 8 OLI imagery. The classification output is compared against manually digitized ice margin positions, the RGI vectors, and the PROMICE (Programme for Monitoring of the Greenland Ice Sheet) aerophotogrammetric map of Greenland ice masses over a sector of the Disko Island surge cluster in West Greenland, the Qassimiut ice sheet lobe in South Greenland, and the A.P. Olsen ice cap in NE Greenland.

  7. Characterizing interannual variability of glacier dynamics and dynamic discharge (1999-2015) for the ice masses of Ellesmere and Axel Heiberg Islands, Nunavut, Canada

    NASA Astrophysics Data System (ADS)

    Van Wychen, Wesley; Davis, Jamie; Burgess, David O.; Copland, Luke; Gray, Laurence; Sharp, Martin; Mortimer, Colleen

    2016-01-01

    Landsat 7 and RADARSAT-1/RADARSAT-2 satellite images are used to produce the most comprehensive record of glacier motion in the Canadian High Arctic to date and to characterize spatial and temporal variability in ice flow over the past ~15 years. This allows us to assess whether dynamically driven glacier change can be attributed to "surging" or "pulsing," or whether other mechanisms are involved. RADAR velocity mapping allows annual regional dynamic discharge (iceberg calving) to be calculated for 2000 and the period 2011-2015 (yielding a mean regional discharge of 2.21 ± 0.68 Gt a-1), and velocities derived from feature tracking of optical imagery allow for annual dynamic discharge to be calculated for select glaciers from 1999 to 2010. Since ~2011, several of the major tidewater-terminating glaciers within the region have decelerated and their dynamic discharge has decreased. Trinity and Wykeham Glaciers (Prince of Wales Icefield) represent a notable departure from this pattern as they have generally accelerated over the study period. The resulting increase in dynamic discharge from these glaciers entirely compensates (within error limits) for the decrease in discharge from the other tidewater glaciers across the study region. These two glaciers accounted for ~62% of total regional dynamic discharge in winter 2015 (compared to ~22% in 2000), demonstrating that total ice discharge from the Canadian High Arctic can be sensitive to variations in flow of just a few tidewater glaciers.

  8. Geomorphologic mapping in the Ny Ålesund area (Svalbard Island, Norway) for the analysis of geomorphologic effects on rock slopes induced by glacier retreat in climate sensitive High Arctic regions

    NASA Astrophysics Data System (ADS)

    Miccadei, Enrico; Piacentini, Tommaso; Casacchia, Ruggero; Sparapani, Roberto

    2014-05-01

    The geomorphological effects of glacial retreat, rapidly changing Arctic environments and consequent local temporary permafrost melting are several types of glacial and periglacial landforms (pingos, solifluction, drumlins, etc.) but also debris and rock falls, alluvial fan and glacial outwash development and scarp/slopes retreat and evolution. In this work we have realized a geomorphologic map of rockfalls, landslides, alluvial fans and the slopes and scarps of steep mountainsides in the Ny Ålesund area (Svalbard Island, Norway) focused on the analysis of rock falls as geomorphological effects of glacier retreat, permafrost degradation and higher temperatures on slope processes. The investigation is based on geological and geomorphological field survey, and remote sensing and aerial photo interpretation, The Ny Ålesund area landscape is characterized by rugged non-vegetated mountains only partially covered by glaciers, with steep flanks and rock scarps; the scarps are formed by different types of rocks (intrusive and effusive igneous rocks, marine sedimentary rocks); this landscape is highly affected by debris and rock falls (from scarps and slopes) forming wide talus slopes and by alluvial fan and fluvial outwash (from glaciers), which make the surface sedimentary cover of the island together with rock glaciers and moraine deposits and locally fluvial deposits. The work is focused on the comprehension of the role of different factors in inducing rock falls, alluvial fans, slope/scarps evolution in high geomorphological sensitivity environments (i.e. glacial, periglacial or mountain) including: orography, lithology, rock fracturation, morphostructural setting, meteorological context. The conclusions focus on the possible geomorphological hazards affecting the Ny Ålesund area.

  9. Geomatic methods applied to the study of the front position changes of Johnsons and Hurd Glaciers, Livingston Island, Antarctica, between 1957 and 2013

    NASA Astrophysics Data System (ADS)

    Rodríguez Cielos, Ricardo; Aguirre de Mata, Julián; Díez Galilea, Andrés; Álvarez Alonso, Marina; Rodríguez Cielos, Pedro; Navarro Valero, Francisco

    2016-08-01

    Various geomatic measurement techniques can be efficiently combined for surveying glacier fronts. Aerial photographs and satellite images can be used to determine the position of the glacier terminus. If the glacier front is easily accessible, the classic surveys using theodolite or total station, GNSS (Global Navigation Satellite System) techniques, laser-scanner or close-range photogrammetry are possible. When the accessibility to the glacier front is difficult or impossible, close-range photogrammetry proves to be useful, inexpensive and fast. In this paper, a methodology combining photogrammetric methods and other techniques is applied to determine the calving front position of Johnsons Glacier. Images taken in 2013 with an inexpensive nonmetric digital camera are georeferenced to a global coordinate system by measuring, using GNSS techniques, support points in accessible areas close to the glacier front, from which control points in inaccessible points on the glacier surface near its calving front are determined with theodolite using the direct intersection method. The front position changes of Johnsons Glacier during the period 1957-2013, as well as those of the land-terminating fronts of Argentina, Las Palmas and Sally Rocks lobes of Hurd glacier, are determined from different geomatic techniques such as surface-based GNSS measurements, aerial photogrammetry and satellite optical imagery. This provides a set of frontal positions useful, e.g., for glacier dynamics modeling and mass balance studies.Link to the data repository: https://doi.pangaea.de/10.1594/PANGAEA.845379.

  10. Prognostic simulations of Pine Island Glacier using a 3D full-Stokes model and an inverse method to infer basal drag

    NASA Astrophysics Data System (ADS)

    Favier, L.; Zwinger, T.; Gillet-Chaulet, F.; Durand, G.; Gagliardini, O.

    2012-04-01

    Ice discharge and grounding line retreat in West Antarctica have been accelerated during the last decades. One of the most striking example is Pine Island Glacier (PIG) which accelerated dramatically over the last 30 years. Such rapid changes in this part of Antarctica are due to large modifications of ice dynamics which are nevertheless poorly understood, and badly represented in numerical models, as pointed out by the IPCC fourth assessment report. Here, a 3D full-Stokes model of a marine ice sheet is used to carry out prognostic simulations of PIG over the next two centuries. The flow problem is coupled with the evolution of the upper and lower free surfaces, and the position of the grounding line is determined by solving the contact problem between the ice-shelf/ice-sheet lower surface and the bedrock. The upper and lower surfaces, and the bathymetry provided on a 1 km grid (courtesy of A. Le Brocq) are used to produce the initial geometry of the entire PIG basin. The mesh refinement is a function of the surface velocities (also provided on a 1 km grid by A. Le Brocq) Hessian matrix and the distance to the grounding line. Surface velocities are also used to infer the basal drag through the resolution of an inverse Robin problem. The initial surface is first relaxed and the results are compared to the observed current surface elevation, surface velocity and change in surface elevation. A perturbation experiment is then performed for which the whole ice-shelf is instantaneously removed. This test can be seen as a worst case scenario as all the buttressing induced by the ice shelf is lost instantaneously. The effect of the ice-shelf disintegration for the following two centuries is discussed in terms of grounding line retreat and increase in sea level.

  11. Subglacial bathymetry and sediment distribution beneath Pine Island Glacier ice shelf modeled using aerogravity and in situ geophysical data: New results

    NASA Astrophysics Data System (ADS)

    Muto, Atsuhiro; Peters, Leo E.; Gohl, Karsten; Sasgen, Ingo; Alley, Richard B.; Anandakrishnan, Sridhar; Riverman, Kiya L.

    2016-01-01

    Pine Island Glacier (PIG) in the Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS) is losing mass and contributing to global sea-level rise at an accelerating rate. Although recent observations and modeling have identified the incursion of relatively warm Circumpolar Deep Water (CDW) beneath the PIG ice shelf (PIGIS) as the main driver of this ice-mass loss, the lack of precise bathymetry limits furthering our understanding of the ice-ocean interactions and improving the accuracy of modeling. Here we present updated bathymetry and sediment distribution beneath the PIGIS, modeled by the inversion of aerogravity data with constraints from active-source seismic data, observations from an autonomous underwater vehicle, and the regional gravity-anomaly field derived from satellite gravity observations. Modeled bathymetry shows a submarine ridge beneath the middle of PIGIS that rises ∼350 to 400 m above the surrounding sea floor, with a minimum water-column thickness of ∼200 m above it. This submarine ridge continues across the whole width of the 45-km wide ice shelf, with no deep troughs crossing it, confirming the general features of the previously predicted sub-ice-shelf ocean circulation. However, the relatively low resolution of the aerogravity data and limitations in our inversion method leave a possibility that there is an undetected, few-kilometers-wide or narrower trough that may alter the predicted sub-ice-shelf ocean circulation. Modeled sediment distribution indicates a sedimentary basin of up to ∼800 m thick near the current grounding zone of the main PIG trunk and extending farther inland, and a region seaward of the submarine ridge where sediments are thin or absent with exposed crystalline basement that extends seaward into Pine Island Bay. Therefore, the submarine ridge marks the transition from a thick sedimentary basin providing a smooth interface over which ice could flow easily by sliding or sediment deformation, to a region with no to

  12. Glacier microseismicity

    USGS Publications Warehouse

    West, Michael E.; Larsen, Christopher F.; Truffer, Martin; O'Neel, Shad; LeBlanc, Laura

    2010-01-01

    We present a framework for interpreting small glacier seismic events based on data collected near the center of Bering Glacier, 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-induced resonance is likely responsible for the low-frequency glacier events and that the hybrid glacier events may be caused by the rush of water into newly opening pathways.

  13. Jakobshavn Glacier

    Atmospheric Science Data Center

    2013-04-17

    article title:  Greenland's Coast in Holiday Colors     View ... the area surrounding the Jakobshavn Glacier on the western coast of Greenland. The image is a false-color (near-infrared, green, blue) ... the ocean currents and pose hazards for shipping along the coast. The Multi-angle Imaging SpectroRadiometer (MISR) views the daylit ...

  14. Alpine Glaciers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 27 August 2003

    This image shows part of the western flank of Arsia Mons, the southernmost of the three great Tharsis Montes. The surface shows parallel ridges more reminiscent of a Zen garden than any typical geological feature. These ridges are not typical of lava flow fronts, so a different explanation has been proposed by Mars scientists. These ridges may instead be ancient signs of previously existing glaciers that formed high on the volcano's flank. As glaciers retreat with the seasons and shifting climate, they leave behind a mound of debris along their receding edge. Successive retreats can produce a series of parallel ridges similar to those seen here.

    Image information: VIS instrument. Latitude -6.9, Longitude 230.5 East (129.5 West). 19 meter/pixel resolution.

  15. Glaciers of Antarctica

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1988-01-01

    have been included. Again, these represent only a small fraction of the large number of aerial photographs now available in various national collections. The chapter is divided into five geographic sections. The first is the Transantarctic Mountains in the Ross Sea area. Some very large outlet glaciers flow from the East Antarctic ice sheet through the Transantarctic Mountains to the Ross Ice Shelf. Byrd Glacier, one of the largest in the world, drains an area of more than 1,000,000 km2. Next, images from the Indian Ocean sector are discussed. These include the Lambert Glacier- Amery Ice Shelf system, so large that about 25 images must be mosaicked to cover its complex system of tributary glaciers. Shirase Glacier, a tidal outlet glacier in the sector, flows at a speed of 2.5 km a-l. About 200 km inland and 200 km west of Shirase Glacier lie the Queen Fabiola (?Yamato?) Mountains, whose extensive exposures of `blue ice? lay claim to being the world?s most important meteorite-collecting locality, with more than 4,700 meteorite fragments discovered since 1969. The Atlantic Ocean sector is fringed by ice shelves into which flow large ice streams like Jutulstraumen, Stancomb-Wills, Slessor, and Recovery Glaciers. Filchner and Ronne Ice Shelves together cover an area two-thirds the size of Texas. From the western margin of the Ronne Ice Shelf, the north-trending arc of the Antarctic Peninsula, with its fjord and alpine landscape and fringing ice shelves, stretches towards South America. The Pacific Ocean sector begins with the Ellsworth Mountains, which include the highest peaks (Vinson Massif at 4,897 m) in Antarctica. The area between the Ellsworth Mountains and the eastern margin of the Ross Ice Shelf is fringed with small ice shelves and some major outlet glaciers. One of these, Pine Island Glacier, was found from comparing 1973 and 1975 images to have an average ice-front velocity of 2.4 km a-l. This part of Antarctica

  16. Principles of Glacier Mechanics

    NASA Astrophysics Data System (ADS)

    Waddington, Edwin D.

    Glaciers are awesome in size and move at a majestic pace, and they frequently occupy spectacular mountainous terrain. Naturally, many Earth scientists are attracted to glaciers. Some of us are even fortunate enough to make a career of studying glacier flow. Many others work on the large, flat polar ice sheets where there is no scenery. As a leader of one of the foremost research projects now studying the flow of mountain glaciers (Storglaciaren, Norway), Roger Hooke is well qualified to describe the principles of glacier mechanics. Principles of Glacier Mechanics is written for upper-level undergraduate students and graduate students with an interest in glaciers and the landforms that glaciers produce. While most of the examples in the text are drawn from valley glacier studies, much of the material is also relevant to “glacier flatland” on the polar ice sheets.

  17. Beardmore Glacier proposals wanted

    NASA Astrophysics Data System (ADS)

    Proposals for research projects to be conducted in the upper Beardmore Glacier area of Antarctica during the 1985-1986 field season are being accepted by t h e National Science Foundation (NSF) through August 15. Later proposal submissions should be discussed with the appropriate program managers (see below).A temporary camp with helicopter support will be established in the region. Occupation by scientific parties will likely be between mid-November 1985 and mid-January 1986. Transportation in the field will be by UH1-N twin-engine Huey helicopters (with a range of approximately 185 km) and by motor toboggans. Satellite tent camps will be established within the range of the helicopters. The exact position of the main camp will be determined in November. Likely candidates, however, are Buckley Island Quadrangle, in the area of the Walcott Névé or the Bowden Névé, near Coalsack Bluff or Mount Sirius.

  18. Ecology of Great Salt Pond, Block Island

    EPA Science Inventory

    Great Salt Pond is an island of estuarine water on Block Island, which sits in the middle of the Northwest Atlantic Continental Shelf. When the last continental glaciers retreated, they left a high spot on a terminal moraine. The rising sea from melting glaciers formed two island...

  19. Glaciers of South America

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1998-01-01

    Landsat images, together with maps and aerial photographs, have been used to produce glacier inventories, define glacier locations, and study glacier dynamics in the countries of South America, along with the Andes Mountains. In Venezuela, Colombia, Ecuador, and Bolivia, the small glaciers have been undergoing extensive glacier recession since the late 1800's. Glacier-related hazards (outburst floods, mud flows, and debris avalanches) occur in Colombia, in Ecuador, and associated with the more extensive (2,600 km2) glaciers of Peru. The largest area of glacier 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 glacier in the Southern Hemisphere outside Antarctica.

  20. Glaciers of Europe

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1993-01-01

    ALPS: AUSTRIAN: An overview is provided on the occurrence of the glaciers in the Eastern Alps of Austria and on the climatic conditions in this area, Historical documents on the glaciers have been available since the Middle Ages. Special glaciological observations and topographic surveys of individual glaciers were initiated as early as 1846. Recent data in an inventory based on aerial photographs taken in 1969 show 925 glaciers in the Austrian Alps with a total area of 542 square kilometers. Present research topics include studies of mass and energy balance, relations of glaciers and climate, physical glaciology, a complete inventory of the glaciers, and testing of remote sensing methods. The location of the glacier 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 glacier inventory published in 1976, which is based on aerial photography of 1973, there are 1,828 glacier 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 glacier has included climatological, hydrological, and massbalance studies. Glaciological research has been conducted on various other glaciers in Switzerland concerning glacier hydrology, glacier hazards, fluctuations of glacier termini, ice mechanics, ice cores, and mass balance. Good maps are available showing the extent of glaciers 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 glaciers as well as locates

  1. Faster simulation plots

    NASA Technical Reports Server (NTRS)

    Fowell, Richard A.

    1989-01-01

    Most simulation plots are heavily oversampled. Ignoring unnecessary data points dramatically reduces plot time with imperceptible effect on quality. The technique is suited to most plot devices. The departments laser printer's speed was tripled for large simulation plots by data thinning. This reduced printer delays without the expense of a faster laser printer. Surpisingly, it saved computer time as well. All plot data are now thinned, including PostScript and terminal plots. The problem, solution, and conclusions are described. The thinning algorithm is described and performance studies are presented. To obtain FORTRAN 77 or C source listings, mail a SASE to the author.

  2. A Faster Triphosphorylation Ribozyme

    PubMed Central

    Dolan, Gregory F.; Akoopie, Arvin; Müller, Ulrich F.

    2015-01-01

    In support of the RNA world hypothesis, previous studies identified trimetaphosphate (Tmp) as a plausible energy source for RNA world organisms. In one of these studies, catalytic RNAs (ribozymes) that catalyze the triphosphorylation of RNA 5'-hydroxyl groups using Tmp were obtained by in vitro selection. One ribozyme (TPR1) was analyzed in more detail. TPR1 catalyzes the triphosphorylation reaction to a rate of 0.013 min-1 under selection conditions (50 mM Tmp, 100 mM MgCl2, 22°C). To identify a triphosphorylation ribozyme that catalyzes faster triphosphorylation, and possibly learn about its secondary structure TPR1 was subjected to a doped selection. The resulting ribozyme, TPR1e, contains seven mutations relative to TPR1, displays a previously unidentified duplex that constrains the ribozyme's structure, and reacts at a 24-fold faster rate than the parent ribozyme. Under optimal conditions (150 mM Tmp, 650 mM MgCl2, 40°C), the triphosphorylation rate of TRP1e reaches 6.8 min-1. PMID:26545116

  3. Glacier discharge and climate variations

    NASA Astrophysics Data System (ADS)

    Dominguez, M. Carmen; Rodriguez-Puebla, Concepcion; Encinas, Ascension H.; Visus, Isabel; Eraso, Adolfo

    2010-05-01

    Different studies account for the warming in the polar regions that consequently would affect Glacier 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-glacier drainage for recording of glacier melt water run-off. The CPE-KG-62°S is providing hourly GD time series since January 2002 in Collins glacier 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 glacier 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 glacier 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 glacier. We obtained relationships between GD with atmospheric variables such as radiation, 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.

  4. Glacier Ecosystems of Himalaya

    NASA Astrophysics Data System (ADS)

    Kohshima, S.; Yoshimura, Y.; Takeuchi, N.; Segawa, T.; Uetake, J.

    2012-12-01

    Biological activity on glaciers has been believed to be extremely limited. However, we found various biotic communities specialized to the glacier environment in various part of the world, such as Himalaya, Patagonia and Alaska. Some of these glacier hosted biotic communities including various cold-tolerant insects, annelids and copepods that were living in the glacier by feeding on algae and bacteria growing in the snow and ice. Thus, the glaciers are simple and relatively closed ecosystems sustained by the primary production in the snow and ice. In this presentation, we will briefly introduce glacier ecosystems in Himalaya; ecology and behavior of glacier animals, altitudinal zonation of snow algal communities, and the structure of their habitats in the glacier. Since the microorganisms growing on the glacier surface are stored in the glacial strata every year, ice-core samples contain many layers with these microorganisms. We showed that the snow algae in the ice-core are useful for ice core dating and could be new environmental signals for the studies on past environment using ice cores. These microorganisms in the ice core will be important especially in the studies of ice core from the glaciers of warmer regions, in which chemical and isotopic contents are often heavily disturbed by melt water percolation. Blooms of algae and bacteria on the glacier can reduce the surface albedo and significantly affect the glacier melting. For example, the surface albedo of some Himalayan glaciers was significantly reduced by a large amount of dark-colored biogenic material (cryoconite) derived from snow algae and bacteria. It increased the melting rates of the surfaces by as much as three-fold. Thus, it was suggested that the microbial activity on the glacier could affect the mass balance and fluctuation of the glaciers.

  5. Fast-flowing outlet glaciers on Svalbard ice caps

    SciTech Connect

    Dowdeswell, J.A. ); Collin, R.L. )

    1990-08-01

    Four well-defined outlet glaciers are present on the 2510 km{sup 2} cap of Vestfonna in Nordaustlandet, Svalbard. Airborne radio echo sounding and aerial-photograph and satellite-image analysis methods are used to analyze the morphology and dynamics of the ice cap and its component outlet glaciers. The heavily crevassed outlets form linear depressions in the ice-cap surface and flow an order of magnitude faster than the ridges of uncrevassed ice between them. Ice flow on the ridges is accounted for by internal deformation alone, whereas rates of outlet glacier flow require basal motion. One outlet has recently switched into and out of a faster mode of flow. Rapid terminal advance, a change from longitudinal compression to tension, and thinning in the upper basin indicate surge behavior. Observed outlet glacier discharge is significantly greater than current inputs of mass of the ice cap, indicating that present rates of flow cannot be sustained under the contemporary climate.

  6. Malaspina Glacier, Alaska, Perspective with Landsat Overlay

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Malaspina Glacier in southeastern Alaska is considered the classic example of a piedmont glacier. Piedmont glaciers occur where valley glaciers exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes. Malaspina Glacier is actually a compound glacier, formed by the merger of several valley glaciers, the most prominent of which seen here are Agassiz Glacier (left) and Seward Glacier (right). In total, Malaspina Glacier is up to 65 kilometers (40 miles) wide and extends up to 45 kilometers (28 miles) from the mountain front nearly to the sea.

    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.

    Glaciers erode rocks, carry them down slope, and deposit them at the edge of the melting ice, typically in elongated piles called moraines. The moraine patterns at Malaspina Glacier are quite spectacular in that they have huge contortions that result from the glacier crinkling as it gets pushed from behind by the faster-moving valley glaciers.

    Glaciers are sensitive indicators of climatic change. They can grow and thicken with increasing snowfall and/or decreased melting. Conversely, they can retreat and thin if snowfall decreases and/or atmospheric temperatures rise and cause increased melting. Landsat imaging has been an excellent tool for mapping the changing geographic extent of glaciers 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.

  7. Glaciers of Asia

    USGS Publications Warehouse

    Williams, Richard S., Jr.; Ferrigno, Jane G.

    2010-01-01

    This chapter is the ninth to be released in U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of Glaciers 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 glacierized region of our planet under consideration and to monitor glacier 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 glacierized geographic region, the present areal distribution of glaciers is compared, wherever possible, with historical information about their past extent. The atlas provides an accurate regional inventory of the areal extent of glacier 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: Glaciers of the Former Soviet Union (F-1), Glaciers of China (F-2), Glaciers of Afghanistan (F?3), Glaciers of Pakistan (F-4), Glaciers of India (F-5), Glaciers of Nepal (F?6), Glaciers of Bhutan (F-7), and the Paleoenvironmental Record Preserved in Middle-Latitude, High-Mountain Glaciers (F-8). Each geographic section describes the glacier extent during the 1970s and 1980s, the benchmark time period (1972-1981) of this volume, but has been updated to include more recent information. Glaciers 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 Glacier Inventory of the USSR and the World Atlas of Ice and Snow Resources recorded a total of 28,881 glaciers covering an area of 78,938 square kilometers (km2). China includes many of the mountain-glacier

  8. 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

  9. Pine Island Bay

    Atmospheric Science Data Center

    2013-04-16

    ... article title:  Birth of a Large Iceberg in Pine Island Bay, Antarctica     View ... iceberg (42 kilometers x 17 kilometers) broke off Pine Island Glacier, West Antarctica (75°S latitude, 102°W longitude) sometime ...

  10. The thermophysics of glaciers

    SciTech Connect

    Zotikov, I.A.

    1986-01-01

    This volume presents the results of experimental and theoretical work on the thermodynamics of ice sheets and glaciers. The author has carried out extensive field work in both the Soviet Union and Antarctica over the last 25 years and has contributed to the understanding of the thermophysics of glaciers. The topics covered in this volume embrace heat flow measurement and temperature distributions in glaciers, the thermal drilling of glaciers, the melting and freezing of ice sheets, and other thermophysical problems. Also included are topics of relevance to glacial engineering.

  11. Malaspina Glacier: a modern analog to the Laurentide Glacier in New England

    SciTech Connect

    Gustavson, T.C.; Boothroyd, J.C.

    1985-01-01

    The land-based temperate Malaspina Glacier is a partial analog to the late Wisconsinan Laurentide Ice Sheet that occupied New England and adjacent areas. The Malaspina occupies a bedrock basin similar to basins occupied by the margin of the Laurentide Ice Sheet. Ice lobes of the Malaspina are similar in size to end moraine lobes in southern New England and Long Island,New York. Estimated ice temperature, ablation rates, surface slopes and meltwater discharge per unit of surface area for the Laurentide Ice Sheet are similar to those for the Malaspina Glacier. In a simple hydrologic-fluvial model for the Malaspina Glacier meltwater moves towards the glacier bed and down-glacier along intercrystalline pathways, crevasses and moulins, and a series of tunnels. Regolith and bedrock at the glacier floor, which are eroded and transported by subglacial and englacial streams, are the sources of essentially all fluvio-lacustrine sediment on the Malaspina Foreland. Supraglacial eskers containing coarse gravels occur as much as 100 m above the glacier bed and are evidence that bedload can be lifted hydraulically. Subordinant amounts of sediment are contributed to outwash by small surface streams draining the ice margin. By analogy a similar hydrologic-fluvial system existed along the southeastern margin of the Laurentide Ice Sheet. Subglacial regolith and bedrock eroded from beneath the Laurentide Ice Sheet by meltwater was also the source of most glaciofluvial and glaciolacustrine deposits in southern New England, not sediment carried to the surface of the ice sheet along shear planes and washed off the glacier by meltwater.

  12. The thickness of glaciers

    NASA Astrophysics Data System (ADS)

    Faraoni, Valerio; Vokey, Marshall W.

    2015-09-01

    Basic formulae and results of glacier physics appearing in glaciology textbooks can be derived from first principles introduced in algebra-based first year physics courses. We discuss the maximum thickness of alpine glaciers and ice sheets and the relation between maximum thickness and length of an ice sheet. Knowledge of ordinary differential equations allows one to derive also the local ice thickness.

  13. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER 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 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  14. 2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF DOME AT CENTER REAR. LOOKING NNE. GIS N-37 43 44.3 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  15. Quantifying Glacier Runoff Contribution to Nooksack River, WA in 2013-15

    NASA Astrophysics Data System (ADS)

    Pelto, M. S.

    2015-12-01

    The 2015 hydrologic year has been posited in terms of temperature as an analog for the future for the Pacific Northwest (PNW), with record warm air temperatures, warm stream temperatures and low summer streamflow. The high stream temperatures and low flows are both threats to salmon in the watershed and are offset in part by glacier runoff. Freezing levels were the highest relative to the median in the key winter months of January through May, 2015. The snowline on glaciers across the region in early July is typically at levels observed 1-2 months later in the melt season. This increases ablation since glacier ice melts faster than glacier snowcover. Very high 2015 ablation rates are occurring because glacier runoff in the PNW is primarily controlled by ablation season temperatures. In July, 2015 streamflow in the North Fork Nooksack River has been at a record low for the 77 years of record, which would increase the role of glacier runoff in stream discharge. We have measured both glacier runoff and ablation on glaciers in the North Fork Nooksack River basin during the summers of 2013-15 that allows determination of the percent of total stream discharge contributed by glaciers. In 2014 the glacier contribution exceeded 40% of total streamflow on 21 days all occurring in Aug. and Sept. Here we will present the results of 2013-2015 glacier runoff observations and the 1984-2015 mass balance observations to put in context 2015 results from our ongoing field work this summer.

  16. Glacier changes on South Georgia since the late-19th century documented in historical photographs

    NASA Astrophysics Data System (ADS)

    Gordon, John; Haynes, Valerie

    2014-05-01

    South Georgia is one of the few landmasses in the Southern Ocean. It provides a crucial geographical datapoint for glacier responses to climate change over different timescales. As part of an ongoing glacier inventory of the island, we are compiling a database of historical glacier photographs. Since the late 19th century, the island has been visited by numerous scientific and survey expeditions, as well as being the land-base for a major whaling industry. Historical photographs of the island are available from the late-19th century, beginning with the 1882-83 German International Polar Year Expedition. Many more exist from the 20th century, notably from the South Georgia Surveys in the 1950s. An assessment of the value of the photographs indicates that spatial coverage is variable, many lack reference features to pinpoint glacier positions and, in the case of smaller glaciers, the presence of snowcover makes it difficult to define the ice edge. Nevertheless, the photographs provide useful corroboration of more advanced glacier positions during the late-19th century and recession of smaller mountain and valley glaciers during the mid-20th century, while larger tidewater and sea-calving glaciers generally remained in relatively advanced positions until the 1980s. Since then, nearly all the glaciers have retreated; some of these retreats have been dramatic and a number of small mountain glaciers have fragmented or disappeared. The response of the glaciers can be related to synoptic-scale warming, particularly since the 1950s, moderated by individual glacier geometry and topography.

  17. Ablation of Martian glaciers

    NASA Technical Reports Server (NTRS)

    Moore, Henry J.; Davis, Philip A.

    1987-01-01

    Glacier like landforms are observed in the fretted terrain of Mars in the latitude belts near + or - 42 deg. It was suggested that sublimation or accumulation-ablation rates could be estimated for these glaciers if their shapes were known. To this end, photoclinometric profiles were obtained of a number of these landforms. On the basis of analyses of these profiles, it was concluded that ice is chiefly ablating from these landforms that either are inactive rock-glaciers or have materials within them that are moving exceedingly slowly at this time. These conclusions are consistent with other geologic information. The analyses were performed using a two-dimensional model of an isothermal glacier.

  18. Islands uncovered by melting polar ice

    NASA Astrophysics Data System (ADS)

    Kumar, Mohi

    Thawing glaciers north of Norway's Svalbard archipelago have revealed at least two unmapped and unclaimed islands, one roughly the size of a basketball court, according to a 20 August Reuters report. In addition, information released in August by the U.S. National Snow and Ice Data Center indicated that with one month left in the melting season, Arctic sea ice is already below the record minimum. "Reductions of snow and ice are happening at an alarming rate," said Norwegian Environment Minister Helen Bjoernoy. She suggested that these observations may indicate that the loss of sea ice is perhaps accelerating faster than predicted by the Intergovernmental Panel on Climate Change, which warned in February that summer sea ice could almost vanish by the end of this century.

  19. A strategy for monitoring glaciers

    USGS Publications Warehouse

    Fountain, Andrew G.; Krimmel, Robert M.; Trabant, Dennis C.

    1997-01-01

    Glaciers are important features in the hydrologic cycle and affect the volume, variability, and water quality of runoff. Assessing and predicting the effect of glaciers on water resources require a monitoring program to provide basic data for this understanding. The monitoring program of the U.S. Geological Survey employs a nested approach whereby an intensively studied glacier is surrounded by less intensively studied glaciers and those monitored solely by remote sensing. Ideally, each glacierized region of the United States would have such a network of glaciers. The intensively studied glacier provides a detailed understanding of the physical processes and their temporal changes that control the mass exchange of the glaciers in that region. The less intensively studied glaciers are used to assess the variability of such processes within the region.

  20. Malaspina Glacier, Alaska, Anaglyph with Landsat Overlay

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This anaglyph view of Malaspina Glacier in southeastern Alaska was created from a Landsat satellite image and an elevation model generated by the Shuttle Radar Topography Mission (SRTM). Malaspina Glacier is considered the classic example of a piedmont glacier. Piedmont glaciers occur where valley glaciers exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes. Malaspina Glacier is actually a compound glacier, formed by the merger of several valley glaciers, the most prominent of which seen here are Agassiz Glacier (left) and Seward Glacier (right). In total, Malaspina Glacier is up to 65 kilometers (40 miles) wide and extends up to 45 kilometers (28 miles) from the mountain front nearly to the sea.

    Glaciers erode rocks, carry them down slope, and deposit them at the edge of the melting ice, typically in elongated piles called moraines. The moraine patterns at Malaspina Glacier are quite spectacular in that they have huge contortions that result from the glacier crinkling as it gets pushed from behind by the faster-moving valley glaciers.

    Numerous other features of the glaciers and the adjacent terrain are clearly seen when viewing this image at full resolution. The series of tonal arcs on Agassiz Glacier's extension onto the piedmont are called 'ogives.' These arcs are believed to be seasonal features created by deformation of the glacier 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 glacier. Sinkholes are common in many areas of the moraine deposits. The sinkholes form when

  1. Rift in Antarctic Glacier: a Unique Chance to Study Ice Shelf Retreat

    NASA Technical Reports Server (NTRS)

    Howat, Ian M.; Jezek, Ken; Studinger, Michael; Macgregor, Joseph A.; Paden, John; Floricioiu, Dana; Russell, Rob; Linkswiler, Matt; Dominguez, Roseanne T.

    2012-01-01

    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 Glacier, less than 5 years after its lastlarge calving event, in 2007 (Figure 1). PineIsland Glaciers 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 glaciers recent accelerated retreat is likely triggered by ocean warming and increased submarine melting. As such, it is of significant interest to glaciologists and of heightened societal relevance.

  2. The Glaciers of HARMONIE

    NASA Astrophysics Data System (ADS)

    Mottram, Ruth; Gleeson, Emily; Pagh Nielsen, Kristian

    2016-04-01

    Developed by the large ALADIN-HIRLAM consortium, the numerical weather prediction (NWP) model system HARMONIE is run by a large number of national weather services and research institutions in Europe, the Middle East and North Africa for weather forecasting. It is now being adopted for climate research purposes as a limited area model in a form known as HCLIM. It is currently run for a number of domains, mostly in Europe but also including Greenland, at a very high resolution (~2.5 km). HARMONIE is a convection permitting non-hydrostatic model that includes the multi-purpose SURFEX surface model. By improving the characterization of glacier surfaces within SURFEX we show that weather forecast errors over both the Greenland ice sheet and over Icelandic glaciers can be significantly reduced. The improvements also facilitate increasingly accurate ice melt and runoff computations, which are important both for ice surface mass balance estimations and hydropower forecasting. These improvements will also benefit the operational HARMONIE domains that cover the Svalbard archipelago, the Alps and the Scandinavian mountain glaciers. Future uses of HCLIM for these regions, where accurately characterizing glacial terrain will be crucial for climate and glaciological applications, are also expected to benefit from this improvement. Here, we report the first results with a new glacier surface scheme in the HARMONIE model, validated with observations from the PROMICE network of automatic weather stations in Greenland. The scheme upgrades the existing surface energy balance over glaciers by including a new albedo parameterization for bare glacier ice and appropriate coefficients for calculating the turbulent fluxes. In addition the snow scheme from the SURFEX land surface module has been upgraded to allow the retention and refreezing of meltwater in the snowpack. These changes allow us to estimate surface mass balance over glaciers at a range of model resolutions that can take full

  3. Accelerating retreat and high-elevation thinning of glaciers in central Spitsbergen

    NASA Astrophysics Data System (ADS)

    Małecki, Jakub

    2016-06-01

    Svalbard is a heavily glacier-covered archipelago in the Arctic. Dickson Land (DL), in the central part of the largest island, Spitsbergen, is relatively arid and, as a result, glaciers there are relatively small and restricted mostly to valleys and cirques. This study presents a comprehensive analysis of glacier changes in DL based on inventories compiled from topographic maps and digital elevation models for the Little Ice Age (LIA) maximum, the 1960s, 1990, and 2009/2011. Total glacier area has decreased by ˜ 38 % since the LIA maximum, and front retreat increased over the study period. Recently, most of the local glaciers have been consistently thinning in all elevation bands, in contrast to larger Svalbard ice masses which remain closer to balance. The mean 1990-2009/2011 geodetic mass balance of glaciers in DL is among the most negative from the Svalbard regional means known from the literature.

  4. The GLIMS Glacier Database

    NASA Astrophysics Data System (ADS)

    Raup, B. H.; Khalsa, S. S.; Armstrong, R.

    2007-12-01

    The Global Land Ice Measurements from Space (GLIMS) project has built a geospatial and temporal database of glacier data, composed of glacier outlines and various scalar attributes. These data are being derived primarily from satellite imagery, such as from ASTER and Landsat. Each "snapshot" of a glacier is from a specific time, and the database is designed to store multiple snapshots representative of different times. We have implemented two web-based interfaces to the database; one enables exploration of the data via interactive maps (web map server), while the other allows searches based on text-field constraints. The web map server is an Open Geospatial Consortium (OGC) compliant Web Map Server (WMS) and Web Feature Server (WFS). This means that other web sites can display glacier layers from our site over the Internet, or retrieve glacier features in vector format. All components of the system are implemented using Open Source software: Linux, PostgreSQL, PostGIS (geospatial extensions to the database), MapServer (WMS and WFS), and several supporting components such as Proj.4 (a geographic projection library) and PHP. These tools are robust and provide a flexible and powerful framework for web mapping applications. As a service to the GLIMS community, the database contains metadata on all ASTER imagery acquired over glacierized terrain. Reduced-resolution of the images (browse imagery) can be viewed either as a layer in the MapServer application, or overlaid on the virtual globe within Google Earth. The interactive map application allows the user to constrain by time what data appear on the map. For example, ASTER or glacier outlines from 2002 only, or from Autumn in any year, can be displayed. The system allows users to download their selected glacier data in a choice of formats. The results of a query based on spatial selection (using a mouse) or text-field constraints can be downloaded in any of these formats: ESRI shapefiles, KML (Google Earth), Map

  5. Karakoram glacier surge dynamics

    NASA Astrophysics Data System (ADS)

    Quincey, D. J.; Braun, M.; Glasser, N. F.; Bishop, M. P.; Hewitt, K.; Luckman, A.

    2011-09-01

    We examine the surges of five glaciers in the Pakistan Karakoram using satellite remote sensing to investigate the dynamic nature of surges in this region and how they may be affected by climate. Surface velocity maps derived by feature-tracking quantify the surge development spatially in relation to the terminus position, and temporally with reference to seasonal weather. We find that the season of surge initiation varies, that each surge develops gradually over several years, and that maximum velocities are recorded within the lowermost 10 km of the glacier. Measured peak surge velocities are between one and two orders of magnitude greater than during quiescence. We also note that two of the glaciers are of a type not previously reported to surge. The evidence points towards recent Karakoram surges being controlled by thermal rather than hydrological conditions, coinciding with high-altitude warming from long-term precipitation and accumulation patterns.

  6. 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.

  7. Climate regime of Asian glaciers revealed by GAMDAM glacier inventory

    NASA Astrophysics Data System (ADS)

    Sakai, A.; Nuimura, T.; Fujita, K.; Takenaka, S.; Nagai, H.; Lamsal, D.

    2015-05-01

    Among meteorological elements, precipitation has a large spatial variability and less observation, particularly in high-mountain Asia, although precipitation in mountains is an important parameter for hydrological circulation. We estimated precipitation contributing to glacier mass at the median elevation of glaciers, which is presumed to be at equilibrium-line altitude (ELA) such that mass balance is zero at that elevation, by tuning adjustment parameters of precipitation. We also made comparisons between the median elevation of glaciers, including the effect of drifting snow and avalanche, and eliminated those local effects. Then, we could obtain the median elevation of glaciers depending only on climate to estimate glacier surface precipitation. The calculated precipitation contributing to glacier mass can elucidate that glaciers in arid high-mountain Asia receive less precipitation, while much precipitation makes a greater contribution to glacier mass in the Hindu Kush, the Himalayas, and the Hengduan Shan due to not only direct precipitation amount but also avalanche nourishment. We classified glaciers in high-mountain Asia into summer-accumulation type and winter-accumulation type using the summer-accumulation ratio and confirmed that summer-accumulation-type glaciers have a higher sensitivity than winter-accumulation-type glaciers.

  8. Climate regime of Asian glaciers revealed by GAMDAM Glacier Inventory

    NASA Astrophysics Data System (ADS)

    Sakai, A.; Nuimura, T.; Fujita, K.; Takenaka, S.; Nagai, H.; Lamsal, D.

    2014-07-01

    Among meteorological elements, precipitation has a large spatial variability and less observation, particularly in High Mountain Asia, although precipitation in mountains is an important parameter for hydrological circulation. We estimated precipitation contributing to glacier mass at median elevation of glaciers, which is presumed to be at equilibrium-line altitude (ELA) so that mass balance is zero at that elevation, by tuning adjustment parameters of precipitation. We also made comparisons between median elevation of glaciers, including the effect of drifting snow and avalanche, and eliminated those local effects. Then, we could obtain median elevation of glaciers depending only on climate to estimate glacier surface precipitation. The calculated precipitation contributing to glacier mass can elucidate that glaciers in the arid High Mountain Asia have very less precipitation, while much precipitation contribute to glacier mass in the Hindu Kush, the Himalayas, and the Hengduan Shan due to not only direct precipitation amount but also avalanche nourishment. We classified glaciers in High Mountain Asia into summer-accumulation type and winter-accumulation type using the summer accumulation ratio, and confirmed that summer-accumulation type glaciers have a higher sensitivity than winter-accumulation type glaciers.

  9. Mapping the World's glaciers from space: Results from the ESA project GlobGlacier

    NASA Astrophysics Data System (ADS)

    Paul, Frank

    2010-05-01

    The ESA project GlobGlacier aims at making a substantial contribution to current efforts of mapping the World's glaciers from satellite data using (semi-)automated techniques. For this purpose a number of key regions have been identified in close cooperation with the user group of the project and based on a set of criteria (e.g. filling the gaps in current inventories, or their potential contribution to sea-level rise). Apart from glacier outlines and terminus positions, a couple of further data products are created by the project: late summer snowlines (LSSL), topographic information, elevation changes and velocity fields. While most of the products are created from optical sensors like Landsat TM/ETM+ as available from the glovis.usgs.gov website, some of them will also utilize radar sensors and LIDAR data. The inventory data are mainly created for the year 2000 (+/- a few years) to have a good temporal match with the SRTM DEM. In selected regions, multi-temporal data sets will be used for change assessment. The new data sets will be integrated in the existing databases of GLIMS and WGMS. With this contribution we provide an overview of the current status of the project as well as its major achievements. Outlines for several thousand glaciers have already been created in many of the key regions. This includes parts of Alaska (Chigmit Mts., Kenai Peninsula, Chugach Mts.), Arctic Canada (Devon, Bylot, Baffin Island), West Greenland (Disko Island, Nuussuaq, Svartenhuk), Norway (Svartisen, Jostedalsbreen), India (Kashmir) and the European Alps. The products LSSL, topography and elevation changes were also produced for several hundred glaciers and surface velocity fields have been derived for more than 50 glaciers from radar and optical sensors. Topographic information for each glacier is obtained from freely available DEMs (e.g. SRTM, ASTER GDEM) and elevation changes are derived from DEM differencing as well as repeat track altimetry using the GLAS and RA-2

  10. Svalbard surging glacier landsystems

    NASA Astrophysics Data System (ADS)

    Lovell, Harold; Benn, Douglas; Lukas, Sven; Flink, Anne

    2014-05-01

    The percentage of Svalbard glaciers thought to be of surge-type is somewhere between 13-90% according to different sources variously based on statistical analysis and observations of diagnostic glaciological and geomorphological features, e.g. looped moraines. Developing a better understanding of which of these figures, if either, is most realistic is important in the context of glacier dynamics and related contributions of small glaciers and ice caps to sea level change in the immediate future. We present detailed geomorphological assessments of the margins of several known surge-type glaciers in Svalbard in order to update and improve the existing framework by which they are identified, and to provide a foundation for future reassessments of the surge-type glacier population based on distinct landform-sediment assemblages. Three landsystems are proposed: (1) Surges of small valley glaciers produce a prominent ice-cored latero-frontal moraine at their surge maximum and are characterised by an inner zone of ice stagnation terrain (hummocky topography, kettle lakes, debris flows) with no or only very few poorly-defined bedforms (crevasse squeeze ridges, eskers and flutes) and no recessional moraines. Many of these glaciers may have surged in the past but show no signs that they have the capability to do so again in the future. (2) Larger land-terminating glaciers, often with several tributaries, typically produce a push moraine complex which contains evidence for multiple advances, as identified from ridge-meltwater channel relationships. The inner zone often contains a large lagoon, partly dammed by the push moraine complex, and widespread ice stagnation terrain. Crevasse squeeze ridges, eskers and flutes are well-defined but small and limited in number and distribution. (3) Surges of large tidewater glaciers produce distinctive, often multi-generational, landform assemblages both in submarine and lateral terrestrial positions. The well-preserved submarine record

  11. Alaska Glaciers and Rivers

    NASA Technical Reports Server (NTRS)

    2007-01-01

    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 glaciers 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 glaciers. Glacier melt also feeds glacier 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.

  12. Glacier generated floods

    USGS Publications Warehouse

    Walder, J.S.; Fountain, A.G.; ,

    1997-01-01

    Destructive floods result from drainage of glacier-dammed lakes and sudden release of water stored within glaciers. There is a good basis - both empirical and theoretical - for predicting the magnitude of floods from ice-dammed lakes, although some aspects of flood initiation need to be better understood. In contrast, an understanding of floods resulting from release of internally stored water remains elusive, owing to lack of knowledge of how and where water is stored and to inadequate understanding of the complex physics of the temporally and spatially variable subglacial drainage system.Destructive floods result from drainage of glacier-dammed lakes and sudden release of water stored within glaciers. There is a good basis - both empirical and theoretical - for predicting the magnitude of floods from ice-dammed lakes, although some aspects of flood initiation need to be better understood. In contrast, an understanding of floods resulting from release of internally stored water remains elusive, owing to lack of knowledge of how and where water is stored and to inadequate understanding of the complex physics of the temporally and spatially variable subglacial drainage system.

  13. Late nineteenth to early twenty-first century behavior of Alaskan glaciers as indicators of changing regional climate

    USGS Publications Warehouse

    Molnia, B.F.

    2007-01-01

    Alaska's climate is changing and one of the most significant indications of this change has been the late 19th to early 21st century behavior of Alaskan glaciers. Weather station temperature data document that air temperatures throughout Alaska have been increasing for many decades. Since the mid-20th century, the average change is an increase of ?????2.0????C. In order to determine the magnitude and pattern of response of glaciers to this regional climate change, a comprehensive analysis was made of the recent behavior of hundreds of glaciers located in the eleven Alaskan mountain ranges and three island areas that currently support glaciers. Data analyzed included maps, historical observations, thousands of ground-and-aerial photographs and satellite images, and vegetation proxy data. Results were synthesized to determine changes in length and area of individual glaciers. Alaskan ground photography dates from 1883, aerial photography dates from 1926, and satellite photography and imagery dates from the early 1960s. Unfortunately, very few Alaskan glaciers have any mass balance observations. In most areas analyzed, every glacier that descends below an elevation of ?????1500??m is currently thinning and/or retreating. Many glaciers have an uninterrupted history of continuous post-Little-Ice-Age retreat that spans more than 250??years. Others are characterized by multiple late 19th to early 21st century fluctuations. Today, retreating and/or thinning glaciers represent more than 98% of the glaciers examined. However, in the Coast Mountains, St. Elias Mountains, Chugach Mountains, and the Aleutian Range more than a dozen glaciers are currently advancing and thickening. Many currently advancing glaciers are or were formerly tidewater glaciers. Some of these glaciers have been expanding for more than two centuries. This presentation documents the post-Little-Ice-Age behavior and variability of the response of many Alaskan glaciers to changing regional climate. ?? 2006.

  14. Characteristics of Glacier Ecosystem and Glaciological Importance of Glacier Microorganisms

    NASA Astrophysics Data System (ADS)

    Kohshima, S.; Yoshimura, Y.; Takeuchi, N.; Segawa, T.; Uetake, J.

    2004-12-01

    Biological activity on glaciers has been believed to be extremely limited. However, we found various biotic communities specialized to the glacier environment in various part of the world, such as Himalaya, Patagonia and Alaska. Some of these glacier hosted biotic communities including various cold-tolerant insects, annelids and copepods that were living in the glacier by feeding on algae and bacteria growing in the snow and ice. Thus, the glaciers are simple and relatively closed ecosystems sustained by the primary production in the snow and ice. Since these microorganisms growing on the glacier surface are stored in the glacial strata every year, ice-core samples contain many layers with these microorganisms. Recently, it was shown that the snow algae in the ice-core are useful for ice core dating and could be new environmental signals for the studies on past_@environment using ice cores. These microorganisms in the ice core will be important especially in the studies of ice core from the glaciers of warmer regions, in which chemical and isotopic contents are often heavily disturbed by melt water percolation. Blooms of algae and bacteria on the glacier can reduce the surface albedo and significantly affect the glacier melting. For example, the surface albedo of some Himalayan glaciers was significantly reduced by a large amount of dark-colored biogenic material (cryoconite) derived from snow algae and bacteria. It increased the melting rates of the surfaces by as much as three-fold. Thus, it was suggested that the microbial activity on the glacier could affect the mass balance and fluctuation of the glaciers.

  15. Snow and Glacier Hydrology

    NASA Astrophysics Data System (ADS)

    Brubaker, Kaye

    The study of snow and ice is rich in both fundamental science and practical applications. Snow and Glacier Hydrology offers something for everyone, from resource practitioners in regions where water supply depends on seasonal snow pack or glaciers, to research scientists seeking to understand the role of the solid phase in the water cycle and climate. The book is aimed at the advanced undergraduate or graduate-level student. A perusal of online documentation for snow hydrology classes suggests that there is currently no single text or reference book on this topic in general use. Instructors rely on chapters from general hydrology texts or operational manuals, collections of journal papers, or their own notes. This variety reflects the fact that snow and ice regions differ in climate, topography, language, water law, hazards, and resource use (hydropower, irrigation, recreation). Given this diversity, producing a universally applicable book is a challenge.

  16. Modeling Ocean-Forced Changes in Smith Glacier

    NASA Astrophysics Data System (ADS)

    Lilien, D.; Joughin, I. R.; Smith, B. E.

    2014-12-01

    Glaciers along the Amundsen Coast are changing rapidly, which has drawn substantial scientific and public attention. Modeling and observation suggest warm-water intrusion and consequent melting as the cause of observed changes, and that unstoppable retreat may have already been triggered in some drainages. While Pine Island and Thwaites Glaciers are losing the most mass and have been the predominant objects study, other systems, particularly Smith, Pope and Kohler Glaciers and the corresponding Dotson and Crosson Shelves, are changing more rapidly relative to their size. Though smaller, these glaciers still have potentially large implications for overall regional dynamics as their beds connect below sea level to surrounding basins. In particular, the long, deep trough of Smith Glacier nearly links to the large eastern tributary of Thwaites, potentially causing rapid changes of Smith to have significant impact on the continuing retreat of Thwaites.We implemented a numerical model in Elmer/Ice, an open-source, full-Stokes, finite-element software package, to investigate the response of the Smith/Pope/Kohler system to different initial conditions. We use various parameterizations of sub-shelf melting with constant magnitude to examine the sensitivity of overall dynamics to melt distribution. Because melt distribution affects lateral buttressing and upstream grounded areas, it is potentially an important control on ice shelf and outlet glacier dynamics. Through comparison to the most recent velocity data, we evaluate the ability of differing melt parameterizations to reproduce the behavior currently seen in Smith/Pope/Kohler glaciers. In addition, we investigate the effect of using different years of velocity data with constant elevation input when initiating model runs. By comparing results over the satellite record to initiation with synchronous observations, we assess the accuracy of the often necessary practice of using differently timestamped datasets.

  17. Listening to Glaciers: Passive hydroacoustics near marine-terminating glaciers

    USGS Publications Warehouse

    Pettit, E.C.; Nystuen, J.A.; O'Neel, Shad

    2012-01-01

    The catastrophic breakup of the Larsen B Ice Shelf in the Weddell Sea in 2002 paints a vivid portrait of the effects of glacier-climate interactions. This event, along with other unexpected episodes of rapid mass loss from marine-terminating glaciers (i.e., tidewater glaciers, outlet glaciers, ice streams, ice shelves) sparked intensified study of the boundaries where marine-terminating glaciers 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.

  18. Surge-like behavior at the non-surge type Matanuska Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Furuya, M.; Abe, T.

    2014-12-01

    Seasonal glacier velocity changes are attributed to subglacial slip associated with water pressure changes that occur because of the seasonal variability of meltwater input. Abe and Furuya (2014) reported winter speed-up signals and their downglacier propagation at a number of glaciers near the border of Alaska and Yukon, based on ALOS/PALSAR radar image analyses. Here we perform the similar analyses at the Chugach mountain range of South Central Alaska, and report the spatial-temporal evolution of the Matanuska Glacier. Matanuska Glacier is the largest accessible glacier in Alaska with its nearly 40 km length and 5 km width near the terminus. Comparing the winter velocity images in 2007, 2008 and 2010, those in 2010 were about 1.5-2 times faster than those during the previous two years. In addition, comparing the fall and winter velocities, winter velocities were apparently faster at every 2007-2008, 2009-2010, and 2010-2011 season. These data indicate winter speed-up or mini-surge signals even at a temperate and non-surgetype Matanuska Glacier. We also examine the spatial-temporal elevation changes, using data from the LiDAR altimeter in the Icebridge mission, and found significant elevation increase near the terminus. Winter speed-up may not be uncommon at Alaskan/Yukon glaciers. Lingle and Fatland (2003) detected faster speed in winter than in fall at non-surging Seward Glacier in the St. Elias Mountains; this is the only published and unambiguous report of winter speed-up, to our knowledge. Combined with earlier glacier hydrological studies, Lingle and Fatland proposed englacial water storage and gravity-driven water flow toward the bed in winter regardless of whether a given glacier is surge-type or not, and considered that the capacity of englacial water storage would control if a given glacier was surge-type or not. We consider that our measurements are complementary to Lingle and Fatland's observations and lend further support for their hypothesis. Basal

  19. Malaspina Glacier, Alaska

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra satellite covers an area of 55 by 40 kilometers (34 by 25 miles) over the southwest part of the Malaspina Glacier and Icy Bay in Alaska. The composite of infrared and visible bands results in the snow and ice appearing light blue, dense vegetation is yellow-orange and green, and less vegetated, gravelly areas are in orange. According to Dr. Dennis Trabant (U.S. Geological Survey, Fairbanks, Alaska), the Malaspina Glacier is thinning. Its terminal moraine protects it from contact with the open ocean; without the moraine, or if sea level rises sufficiently to reconnect the glacier with the ocean, the glacier would start calving and retreat significantly. ASTER data are being used to help monitor the size and movement of some 15,000 tidal and piedmont glaciers in Alaska. Evidence derived from ASTER and many other satellite and ground-based measurements suggests that only a few dozen Alaskan glaciers are advancing. The overwhelming majority of them are retreating.

    This ASTER image was acquired on June 8, 2001. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next six years to map and monitor the changing surface of our planet.

    ASTER is one of five Earth-observing instruments launched December 18,1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. science team leader; Bjorn Eng of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The Terra mission is part of NASA's Earth Science Enterprise, along-term research and

  20. Chernobyl fallout on Alpine glaciers

    SciTech Connect

    Ambach, W.; Rehwald, W.; Blumthaler, M.; Eisner, H.; Brunner, P.

    1989-01-01

    Measurements of the gross beta activity of snow samples from four Alpine glaciers contaminated by radioactive fallout from the Chernobyl nuclear accident and a gamma-spectrum analysis of selected samples are reported. The results are discussed with respect to possible risks to the population from using meltwater from these glaciers as drinking water.

  1. Islands of the Arctic

    NASA Astrophysics Data System (ADS)

    Dowdeswell, Julian; Hambrey, Michael

    2002-11-01

    The Arctic islands are characterized by beautiful mountains and glaciers, in which the wildlife lives in delicate balance with its environment. It is a fragile region with a long history of exploration and exploitation that is now experiencing rapid environmental change. All of these themes are explored in Islands of the Arctic, a richly illustrated volume with superb photographs from the Canadian Arctic archipelago, Greenland, Svalbard and the Russian Arctic. It begins with the various processes shaping the landscape: glaciers, rivers and coastal processes, the role of ice in the oceans and the weather and climate. Julian Dowdeswell and Michael Hambrey describe the flora and fauna in addition to the human influences on the environment, from the sustainable approach of the Inuit, to the devastating damage inflicted by hunters and issues arising from the presence of military security installations. Finally, they consider the future prospects of the Arctic islands Julian Dowdeswell is Director of the Scott Polar Research Institute and Professor of Physical Geography at 0he University of Cambridge. He received the Polar Medal from Queen Elizabeth for his contributions to the study of glacier geophysics and the Gill Memorial Award from the Royal Geographical Society. He is chair of the Publications Committee of the International Glaciological Society and head of the Glaciers and Ice Sheets Division of the International Commission for Snow and Ice. 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 Glaciers (Cambridge University Press). Hambrey is also the author of Glacial Environments (British Columbia, 1994).

  2. Patagonia Glacier, Chile

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This ASTER images was acquired on May 2, 2000 over the North Patagonia Ice Sheet, Chile near latitude 47 degrees south, longitude 73 degrees west. The image covers 36 x 30 km. The false color composite displays vegetation in red. The image dramatically shows a single large glacier, covered with crevasses. A semi-circular terminal moraine indicates that the glacier was once more extensive than at present. ASTER data are being acquired over hundreds of glaciers worldwide to measure their changes over time. Since glaciers are sensitive indicators of warming or cooling, this program can provide global data set critical to understand climate change.

    This image is located at 46.5 degrees south latitude and 73.9 degrees west longitude.

    Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud

  3. Polythermal Glacier Hydrology: A Review

    NASA Astrophysics Data System (ADS)

    Irvine-Fynn, Tristram D. L.; Hodson, Andrew J.; Moorman, Brian J.; Vatne, Geir; Hubbard, Alun L.

    2011-11-01

    The manner by which meltwater drains through a glacier is critical to ice dynamics, runoff characteristics, and water quality. However, much of the contemporary knowledge relating to glacier hydrology has been based upon, and conditioned by, understanding gleaned from temperate valley glaciers. Globally, a significant proportion of glaciers and ice sheets exhibit nontemperate thermal regimes. The recent, growing concern over the future response of polar glaciers and ice sheets to forecasts of a warming climate and lengthening summer melt season necessitates recognition of the hydrological processes in these nontemperate ice masses. It is therefore timely to present an accessible review of the scientific progress in glacial hydrology where nontemperate conditions are dominant. This review provides an appraisal of the glaciological literature from nontemperate glaciers, examining supraglacial, englacial, and subglacial environments in sequence and their role in hydrological processes within glacierized catchments. In particular, the variability and complexity in glacier thermal regimes are discussed, illustrating how a unified model of drainage architecture is likely to remain elusive due to structural controls on the presence of water. Cold ice near glacier surfaces may reduce meltwater flux into the glacier interior, but observations suggest that the transient thermal layer of near surface ice holds a hydrological role as a depth-limited aquifer. Englacial flowpaths may arise from the deep incision of supraglacial streams or the propagation of hydrofractures, forms which are readily able to handle varied meltwater discharge or act as locations for water storage, and result in spatially discrete delivery of water to the subglacial environment. The influence of such drainage routes on seasonal meltwater release is explored, with reference to summer season upwellings and winter icing formation. Moreover, clear analogies emerge between nontemperate valley glacier and

  4. Glacier Velocities and Elevation Change of the Juneau Icefield, Alaska

    NASA Astrophysics Data System (ADS)

    Melkonian, A. K.; Willis, M. J.; Pritchard, M. E.; Bernstein, S.

    2009-12-01

    Mass-loss from small icefields is the greatest contributor from the cryosphere to sea level rise at present. The Juneau Icefield is a small low-latitude glacier system in southeast Alaska. Remote-sensing data from SAR and optical instruments is examined for inter-annual and seasonal changes in glacier elevation and velocity. We use subpixel offset tracking of satellite SAR and optical images to construct a time-series of average horizontal velocities for the outlet glaciers of the icefield. Optical imagery is available from the ASTER instrument between 2000 and 2009. Eighty ASTER scene-pairs are used to generate pixel-offsets for the region. SAR imagery is available for pixel tracking between 1992-2000, although rapid decorrelation means that only repeat track images separated by 1-2 months are useful. The combined radar and optically derived time-series are compared with sparse GPS measurements made by the Juneau Icefield Research Program (JIRP). JIRP measurements and ASTER-derived velocities at the same points show a velocity of up to 1.1 m/day with differences between the two ranging from 0 to 20 cm/day over coherent areas of the ASTER pixel-offsets. Initial findings over Taku Glacier (the largest outlet glacier in the icefield) indicate that velocities from several ERS tandem-pairs, with short duration repeat passes, taken during the mid-1990s reveal velocities in the middle of Taku glacier of 1 m/day to 1.5 m/day over the faster-moving sections of the glacier. These results are within +/- 25 cm/day of velocities derived from the more recent ASTER scenes, which show a maximum average velocity of around 1.25 m/day. However, Taku Glacier is the only glacier in the icefield still advancing and is therefore not representative of the entire icefield. Data covering other outlet glaciers will be processed to determine overall trends in velocity. Several components of the ASTER processing-chain are tested. Output from two independent pixel-tracking software packages

  5. Water flow through temperate glaciers

    USGS Publications Warehouse

    Fountain, A.G.; Walder, J.S.

    1998-01-01

    Understanding water movement through a glacier is fundamental to several critical issues in glaciology, including glacier dynamics, glacier-induced floods, and the prediction of runoff from glacierized drainage basins. to this end we have synthesized a conceptual model os water movement through a temperate glacier from the surface to the outlet stream. Processes that regulate the rate and distribution of water input at the glacier surface and that regulate water movement from the surface to the bed play important but commonly neglected roles in glacier hydrology. Where a glacier is covered by a layer of porous, permeable firn (the accumulation zone), the flux of water to the glacier 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 glacier depends directly on the rate of surface melt 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 glacier bed at a linited number of points, probably a long distance downglacier of where water enters the glacier. 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

  6. Holocene record of glacier variability from lake sediments reveals tripartite climate history for Svalbard

    NASA Astrophysics Data System (ADS)

    van der Bilt, Willem; Bakke, Jostein; Vasskog, Kristian; D`Andrea, William; Bradley, Raymond; Olafsdottir, Sædis

    2016-04-01

    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. Glaciers 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 glacier size are recorded by variations in glacigenic rock flour that may be deposited in downstream lakes. Here, we present a Holocene reconstruction of glacier activity, based on sediments from Hajeren, a glacier-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 glacier 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 melt water pulses, episodic Atlantic cooling and a decline in orbitally driven summer insolation. Correspondence between inferred advances, including a Holocene glacier maximum around 9.5 ka BP, suggests forcing by the melting LIS during the Early Holocene. Following a late Holocene Thermal Maximum around 7.4 ka BP, glaciers disappeared from the catchment. Glaciers 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 glacier 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

  7. Rapid Late Holocene glacier fluctuations reconstructed from South Georgia lake sediments using novel analytical and numerical techniques

    NASA Astrophysics Data System (ADS)

    van der Bilt, Willem; Bakke, Jostein; Werner, Johannes; Paasche, Øyvind; Rosqvist, Gunhild

    2016-04-01

    The collapse of ice shelves, rapidly retreating glaciers and a dramatic recent temperature increase show that Southern Ocean climate is rapidly shifting. Also, instrumental and modelling data demonstrate transient interactions between oceanic and atmospheric forcings as well as climatic teleconnections with lower-latitude regions. Yet beyond the instrumental period, a lack of proxy climate timeseries impedes our understanding of Southern Ocean climate. Also, available records often lack the resolution and chronological control required to resolve rapid climate shifts like those observed at present. Alpine glaciers are found on most Southern Ocean islands and quickly respond to shifts in climate through changes in mass balance. Attendant changes in glacier size drive variations in the production of rock flour, the suspended product of glacial erosion. This climate response may be captured by downstream distal glacier-fed lakes, continuously recording glacier history. Sediment records from such lakes are considered prime sources for paleoclimate reconstructions. Here, we present the first reconstruction of Late Holocene glacier variability from the island of South Georgia. Using a toolbox of advanced physical, geochemical (XRF) and magnetic proxies, in combination with state-of-the-art numerical techniques, we fingerprinted a glacier signal from glacier-fed lake sediments. This lacustrine sediment signal was subsequently calibrated against mapped glacier extent with the help of geomorphological moraine evidence and remote sensing techniques. The outlined approach enabled us to robustly resolve variations of a complex glacier at sub-centennial timescales, while constraining the sedimentological imprint of other geomorphic catchment processes. From a paleoclimate perspective, our reconstruction reveals a dynamic Late Holocene climate, modulated by long-term shifts in regional circulation patterns. We also find evidence for rapid medieval glacier retreat as well as a

  8. Outlet glacier response to the 2012 collapse of the Matusevich Ice Shelf, Severnaya Zemlya, Russian Arctic

    NASA Astrophysics Data System (ADS)

    Willis, Michael J.; Melkonian, Andrew K.; Pritchard, Matthew E.

    2015-10-01

    The Matusevich Ice Shelf (MIS), located within the Severnaya Zemlya Archipelago in the Russian Arctic, rapidly broke apart between 10 August and 7 September 2012. We examine the response of the outlet glaciers that fed the MIS from local ice caps to the removal of the ice shelf. We use spaceborne laser altimetry and multiple optically derived digital elevation models to track ice surface elevation change rates (dh/dt) between 1984 and 2014. Glacier speeds are measured by pixel-tracking from optical and RADAR imagery between 2010 and 2014 and interferometric synthetic aperture radar in 1995 to compare precollapse and postcollapse velocities. We find that the three main outlet glaciers that fed the MIS are thinning an order of magnitude more rapidly than most of the rest of Severnaya Zemyla, based upon ICESat data from 2003 to 2009. Recent, 2012 to 2014 thinning rates are three to four times faster than the 30 year average thinning rate, calculated between 1984 and 2014. The springtime speeds of the largest outlet glacier (Issledovateley) have increased more than 200% at the terminus between April 2010 and April 2014. To date, changes in surface elevation (dh/dt) and velocity at the outlet glaciers near MIS are smaller than glacier responses to ice shelf collapse in Antarctica. It is possible that the MIS was already very weak prior to the 2012 collapse and unable to support back stress. Further observations are required to assess whether the thinning and nonmelt season glacier speeds are continuing to accelerate.

  9. UAVs for Glacier Mapping: Lessons Learned

    NASA Astrophysics Data System (ADS)

    McKinnon, T.; McKinnon, K. A.; Anderson, B.

    2014-12-01

    Using two different unmanned aerial vehicles (UAVs) mounted with cameras, we created a digital elevation model (DEM) of the lower 12 km^2 of Tasman Glacier, South Island, New Zealand in March 2014. The project served primarily as a proof-of-concept, and here we discuss the lessons learned, emphasizing the practical, logistical, and flight issues. We tested two different fixed-wing airframes -- a twin-boom tradition and flying wing; two different camera types, both consumer-grade RGB; and various combinations of RC and telemetry radios. We used both commercial and open-source photogrammetry software to create the mosaic and DEM imagery. Some of the most critical UAV-specific issues are: access to a launch/landing site, adequate landing zones, range, airspace contention with manned aircraft, and hardware reliability. While UAVs provide a lower-cost method for photogrammetry access, it also comes with a unique set of challenges.

  10. Accelerating Ice Loss from the Fastest Greenland and Antarctic Glaciers

    NASA Technical Reports Server (NTRS)

    Thomas, R.; Frederick, E.; Li, J.; Krabill, W.; Manizade, S.; Paden, J.; Sonntag, J.; Swift, R.; Yungel, J.

    2011-01-01

    Ice discharge from the fastest glaciers draining the Greenland and Antarctic ice sheets . Jakobshavn Isbrae (JI) and Pine Island Glacier (PIG). continues to increase, and is now more than double that needed to balance snowfall in their catchment basins. Velocity increase probably resulted from decreased buttressing from thinning (and, for JI, breakup) of their floating ice tongues, and from reduced basal drag as grounding lines on both glaciers retreat. JI flows directly into the ocean as it becomes afloat, and here creep rates are proportional to the cube of bed depth. Rapid thinning of the PIG ice shelf increases the likelihood of its breakup, and subsequent rapid increase in discharge velocity. Results from a simple model indicate that JI velocities should almost double to >20 km/a by 2015, with velocities on PIG increasing to >10 km/a after breakup of its ice shelf. These high velocities would probably be sustained over many decades as the glaciers retreat within their long, very deep troughs. Resulting sea ]level rise would average about 1.5 mm/a.

  11. Flow instabilities of Alaskan glaciers

    NASA Astrophysics Data System (ADS)

    Turrin, James Bradley

    Over 300 of the largest glaciers in southern Alaska have been identified as either surge-type or pulse-type, making glaciers with flow instabilities the norm among large glaciers in that region. Consequently, the bulk of mass loss due to climate change will come from these unstable glaciers in the future, yet their response to future climate warming is unknown because their dynamics are still poorly understood. To help broaden our understanding of unstable glacier flow, the decadal-scale ice dynamics of 1 surging and 9 pulsing glaciers are investigated. Bering Glacier had a kinematic wave moving down its ablation zone at 4.4 +/- 2.0 km/yr from 2002 to 2009, which then accelerated to 13.9 +/- 2.0 km/yr as it traversed the piedmont lobe. The wave first appeared in 2001 near the confluence with Bagley Ice Valley and it took 10 years to travel ~64 km. A surge was triggered in 2008 after the wave activated an ice reservoir in the midablation zone, and it climaxed in 2011 while the terminus advanced several km into Vitus Lake. Ruth Glacier pulsed five times between 1973 and 2012, with peak velocities in 1981, 1989, 1997, 2003, and 2010; approximately every 7 years. A typical pulse increased ice velocity 300%, from roughly 40 m/yr to 160 m/yr in the midablation zone, and involved acceleration and deceleration of the ice en masse; no kinematic wave was evident. The pulses are theorized to be due to deformation of a subglacial till causing enhanced basal motion. Eight additional pulsing glaciers are identified based on the spatiotemporal pattern of their velocity fields. These glaciers pulsed where they were either constricted laterally or joined by a tributary, and their surface slopes are 1-2°. These traits are consistent with an overdeepening. This observation leads to a theory of ice motion in overdeepenings that explains the cyclical behavior of pulsing glaciers. It is based on the concept of glaciohydraulic supercooling, and includes sediment transport and erosion

  12. Antarctic Peninsula Tidewater Glacier Dynamics

    NASA Astrophysics Data System (ADS)

    Pettit, E. C.; Scambos, T. A.; Haran, T. M.; Wellner, J. S.; Domack, E. W.; Vernet, M.

    2015-12-01

    The northern Antarctic Peninsula (nAP, north of 66°S) is a north-south trending mountain range extending transverse across the prevailing westerly winds of the Southern Ocean resulting in an extreme west-to-east precipitation gradient. Snowfall on the west side of the AP is one to two orders of magnitude higher than the east side. This gradient drives short, steep, fast-flowing glaciers into narrow fjords on the west side, while longer lower-sloping glaciers flow down the east side into broader fjord valleys. This pattern in ice dynamics affects ice-ocean interaction on timescales of decades to centuries, and shapes the subglacial topography and submarine bathymetry on timescales of glacial cycles. In our study, we calculate ice flux for the western and eastern nAP using a drainage model that incorporates the modern ice surface topography, the RACMO-2 precipitation estimate, and recent estimates of ice thinning. Our results, coupled with observed rates of ice velocity from InSAR (I. Joughin, personal communication) and Landsat 8 -derived flow rates (this study), provide an estimate of ice thickness and fjord depth in grounded-ice areas for the largest outlet glaciers. East-side glaciers either still terminate in or have recently terminated in ice shelves. Sedimentary evidence from the inner fjords of the western glaciers indicates they had ice shelves during LIA time, and may still have transient floating ice tongues (tabular berg calvings are observed). Although direct oceanographic evidence is limited, the high accumulation rate and rapid ice flux implies cold basal ice for the western nAP glaciers and therefore weak subglacial discharge relative to eastern nAP glaciers and or other tidewater fjord systems such as in Alaska. Finally, despite lower accumulation rates on the east side, the large elongate drainage basins result in a greater ice flux funneled through fewer deeper glaciers. Due to the relation between ice flux and erosion, these east-side glaciers

  13. 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.

  14. Reconstruction of glacier variability from lake sediments reveals dynamic Holocene climate in Svalbard

    NASA Astrophysics Data System (ADS)

    van der Bilt, Willem G. M.; Bakke, Jostein; Vasskog, Kristian; D'Andrea, William J.; Bradley, Raymond S.; Ólafsdóttir, Sædis

    2015-10-01

    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. Glaciers 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 glacier variability on Svalbard from glacier-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 glacier activity in addition to other processes affecting the sediment record. Evidence from variations in sediment density, validated by changes in Ti concentrations, reveal glaciers 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 glacier advances were driven by the melting Laurentide Ice Sheet (LIS). We find that glaciers disappeared from the catchment between 7.4 and 6.7 ka cal BP, following a late Hypsithermal. Glacier 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 glacier advance. Both events are concurrent with well-documented episodes of North Atlantic cooling. We argue that this brief forcing created suitable conditions for glaciers to reform in the catchment against a background of gradual orbital cooling. These findings highlight the

  15. 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

  16. Low-latitude mountain glacier evidence for abrupt climate changes

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Mosley-Thompson, E. S.; Lin, P.; Davis, M. E.; Mashiotta, T. A.; Brecher, H. H.

    2004-12-01

    Clear evidence that a widespread warming of Earth's climate system is now underway comes from low latitude mountain glaciers. Proxy temperature histories reconstructed from ice cores, and the rapidly accelerating loss of both the total ice area and ice volume on a near global scale suggest that these glaciers responding to increasing rates of melting. In situ observations reveal the startling rates at which many tropical glaciers are disappearing. For example, the retreat of the terminus of the Qori Kalis Glacier in Peru is roughly 200 meters per year, 40 times faster than its retreat rate in 1978. Similarly, in 1912 the ice on Mount Kilimanjaro covered 12.1 km2, but today it covers only 2.6 km2. If the current rate of retreat continues, the perennial ice fields may disappear within the next few decades, making this the first time in the past 11,700 years that Kilimanjaro will be devoid of the ice that shrouds its summit. Tropical glaciers may be considered ``the canaries in the coal mine'' for the global climate system as they integrate and respond to key climatological variables, such as temperature, precipitation, cloudiness, humidity, and incident solar radiation. A composite of the decadally-averaged oxygen isotopic records from three Andean and three Tibetan ice cores extending back over the last two millennia shows an isotopic enrichment in the 20th century that suggests a large-scale warming is underway at lower latitudes. Multiple lines of evidence from Africa, the Middle East, Europe and South America indicate an abrupt mid-Holocene climate event in the low latitudes. If such an event were to occur now with a global human population of 6.3 billion people, the consequences could be severe. Clearly, we need to understand the nature and cause of abrupt climate events.

  17. Modelling Greenland Outlet Glaciers

    NASA Technical Reports Server (NTRS)

    vanderVeen, Cornelis; Abdalati, Waleed (Technical Monitor)

    2001-01-01

    The objective of this project was to develop simple yet realistic models of Greenland outlet glaciers to better understand ongoing changes and to identify possible causes for these changes. Several approaches can be taken to evaluate the interaction between climate forcing and ice dynamics, and the consequent ice-sheet response, which may involve changes in flow style. To evaluate the icesheet response to mass-balance forcing, Van der Veen (Journal of Geophysical Research, in press) makes the assumption that this response can be considered a perturbation on the reference state and may be evaluated separately from how this reference state evolves over time. Mass-balance forcing has an immediate effect on the ice sheet. Initially, the rate of thickness change as compared to the reference state equals the perturbation in snowfall or ablation. If the forcing persists, the ice sheet responds dynamically, adjusting the rate at which ice is evacuated from the interior to the margins, to achieve a new equilibrium. For large ice sheets, this dynamic adjustment may last for thousands of years, with the magnitude of change decreasing steadily over time as a new equilibrium is approached. This response can be described using kinematic wave theory. This theory, modified to pertain to Greenland drainage basins, was used to evaluate possible ice-sheet responses to perturbations in surface mass balance. The reference state is defined based on measurements along the central flowline of Petermann Glacier in north-west Greenland, and perturbations on this state considered. The advantage of this approach is that the particulars of the dynamical flow regime need not be explicitly known but are incorporated through the parameterization of the reference ice flux or longitudinal velocity profile. The results of the kinematic wave model indicate that significant rates of thickness change can occur immediately after the prescribed change in surface mass balance but adjustments in flow

  18. Aletsch Glacier, Switzerland

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Aletsch Glacier, the largest glacier of Europe, covers more than 120 square kilometers (more than 45 square miles)in southern Switzerland. At its eastern extremity lies a glacierlake, Mdrjelensee (2,350 meters/7,711 feet above sea level). To the west rises Aletschhorn (4,195 meters/13,763 feet), which was first climbed in 1859. The Rhone River flows along the southern flank of the mountains.

    This image was acquired on July 23, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

    Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. The Terra mission is part of NASA's Earth Science Enterprise, a long-term research and technology program designed to examine Earth's land, oceans, atmosphere, ice and life as

  19. Mapping of debris-covered glaciers in parts of the Greater Himalaya Range, Ladakh, western Himalaya, using remote sensing and GIS

    NASA Astrophysics Data System (ADS)

    Ghosh, Swagata; Pandey, Arvind C.; Nathawat, Mahendra S.

    2014-01-01

    Glacier inventories based on visual interpretation and manual delineation of glacier boundaries are time consuming. Supraglacial debris (debris accumulated on glacier terrain) of Himalayan glaciers creates difficulty with automated glacier mapping when using satellite images. In the present study, a combination of band ratio using the TM image and slope parameter was proven to be useful for delineating glaciers' debris-covered areas. Compared to original TM bands, supervised classification using a combination of principal components two, three, and six of debris and nonglacierized areas facilitated identification of various types of supraglacial debris. Use of principal components four, three, and two of snow- and ice-covered areas as input bands for supervised classification was helpful in classifying different types of snow and ice. Results corresponded well with manually delineated glacier outlines and field observations. Error matrix revealed that the accuracy of classification of the snow- and ice-covered parts of glaciers was 86.29%. Although manual editing was required to differentiate supraglacial debris from periglacial debris (debris outside the glacier boundary), the approach using the ability of morphometric parameter combined with band ratio for delineation of debris-covered parts of glaciers and supervised classification with principal component analysis for mapping of supraglacial covers is observed to be faster than manual delineation.

  20. From Glaciers to Icebergs

    NASA Astrophysics Data System (ADS)

    Zhang, Wendy

    I will describe works from a collaboration between physics and glaciology that grew out of interactions at the Computations in Science seminar Leo Kadanoff organized at the University of Chicago. The first project considers the interaction between ocean waves and Antarctic ice shelves, large floating portions of ice formed by glacial outflows. Back-of-envelop calculation and seismic sensor data suggest that crevasses may be distributed within an ice shelf to shield it from wave energy. We also examine numerical scenarios in which changes in environmental forcing causes the ice shelf to fail catastrophically. The second project investigates the aftermath of iceberg calving off glacier terminus in Greenland using data recorded via time-lapse camera and terrestrial radar. Our observations indicate that the mélange of icebergs within the fjord experiences widespread jamming during a calving event and therefore is always close to being in a jammed state during periods of terminus quiescence. Joint work with Jason Amundson, Ivo R. Peters, Julian Freed Brown, Nicholas Guttenberg, Justin C Burton, L. Mac Cathles, Ryan Cassotto, Mark Fahnestock, Kristopher Darnell, Martin Truffer, Dorian S. Abbot and Douglas MacAyeal. Kadanoff Session DCMP.

  1. 73X Faster Than a Speeding Bullet

    NASA Video Gallery

    On Nov. 17, 2011, a NASA camera in Tullahoma, Tenn., saw a Leonid meteor -- moving 73 times faster than a bullet fired from an M-16 rifle -- as it burned up 71 miles above Nolensville, Tenn., at an...

  2. New faster CHARMM molecular dynamics engine

    PubMed Central

    Hynninen, Antti-Pekka; Crowley, Michael F

    2014-01-01

    We introduce a new faster molecular dynamics (MD) engine into the CHARMM software package. The new MD engine is faster both in serial (i.e., single CPU core) and parallel execution. Serial performance is approximately two times higher than in the previous version of CHARMM. The newly programmed parallelization method allows the MD engine to parallelize up to hundreds of CPU cores. PMID:24302199

  3. Arctic polynya and glacier interactions

    NASA Astrophysics Data System (ADS)

    Edwards, Laura

    2013-04-01

    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 glaciers 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 glacier catchments where ice acceleration, thinning and calving occurs at ocean margins. Research suggests that these tidewater glaciers accelerate and iceberg calving rates increase when warming ocean currents increase melt on the underside of floating glacier 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 glaciers their influence on ocean circulation and water temperatures may play a major part in controlling subsurface ice melt 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) glaciers and ice caps. Polynya presence and size also has implications for sea ice extent and therefore potentially the buttressing effect on neighbouring

  4. Erosion by an Alpine glacier

    NASA Astrophysics Data System (ADS)

    Herman, Frédéric; Beyssac, Olivier; Lane, Stuart; Brughelli, Mattia; Leprince, Sebastien; Brun, Fanny

    2015-04-01

    Most mountain ranges on Earth owe their morphology to the action of glaciers and icecaps over the last few million years. Our current understanding of how glaciers have modified mountainous landforms has mainly been driven through landscape evolution models. These have included an array of erosion laws and mainly progressed through the implementation of various levels of sophistication regarding ice dynamics, subglacial hydrology or thermodynamics of water flow. However, the complex nature of the erosion processes involved and the difficulty of directly examining the ice-bedrock interface of contemporary glaciers has precluded the establishment of a prevailing erosion theory. Here we quantify the spatial variations in ice sliding velocity and erosion rate of a fast-flowing Alpine glacier in New Zealand during a 5-month period. By combining high resolution 3D measurements of surface velocity from optical satellite imagery with the quantification of both the production and provenance of sediments by the glacier, we show that erosion rates are proportional to sliding velocity raised to a power of about two. This result is consistent with abrasion theory. Given that the ice sliding velocity is a nonlinear function of ice thickness and ice surface slope, the response of glacial erosion to precipitation changes is highly nonlinear. Finally, our ability to constrain the glacial abrasion law present opportunities to further examine the interaction between glaciation and mountain evolution.

  5. Columbia Glacier, Alaska, 1986-2011

    NASA Video Gallery

    The Columbia Glacier in Alaska is one of many vanishing around the world. Glacier retreat is one of the most direct and understandable effects of climate change. The consequences of the decline in ...

  6. Analysis of time series of glacier speed: Columbia Glacier, Alaska

    USGS Publications Warehouse

    Walters, R.A.; Dunlap, W.W.

    1987-01-01

    During the summer of 1984 and 1985, laser measurements were made of the distance from a reference location to markers on the surface of the lower reach of Columbia Glacier, Alaska. The speed varies from 7 to 15 m/d and has three noteworthy components: 1) a low-frequency perturbation in speed with a time scale of days related to increased precipitation, 2) semidiurnal and diurnal variations related to sea tides, and 3) diurnal variations related to glacier surface melt. -from Authors

  7. Thinning of the Monte Perdido Glacier in the Spanish Pyrenees since 1981

    NASA Astrophysics Data System (ADS)

    López-Moreno, Juan Ignacio; Revuelto, Jesús; Rico, Ibai; Chueca-Cía, Javier; Julián, Asunción; Serreta, Alfredo; Serrano, Enrique; Martín Vicente-Serrano, Sergio; Azorin-Molina, Cesar; Alonso-González, Esteban; María García-Ruiz, José

    2016-03-01

    This paper analyzes the evolution of the Monte Perdido Glacier, the third largest glacier in the Pyrenees, from 1981 to the present. We assessed the evolution of the glacier's surface area by analysis of aerial photographs from 1981, 1999, and 2006, and changes in ice volume by geodetic methods with digital elevation models (DEMs) generated from topographic maps (1981 and 1999), airborne lidar (2010) and terrestrial laser scanning (TLS, 2011, 2012, 2013, and 2014) data. We interpreted the changes in the glacier based on climate data from nearby meteorological stations. The results indicate that the degradation of this glacier accelerated after 1999. The rate of ice surface loss was almost three times greater during 1999-2006 than during earlier periods. Moreover, the rate of glacier thinning was 1.85 times faster during 1999-2010 (rate of surface elevation change = -8.98 ± 1.80 m, glacier-wide mass balance = -0.73 ± 0.14 m w.e. yr-1) than during 1981-1999 (rate of surface elevation change = -8.35 ± 2.12 m, glacier-wide mass balance = -0.42 ± 0.10 m w.e. yr-1). From 2011 to 2014, ice thinning continued at a slower rate (rate of surface elevation change = -1.93 ± 0.4 m yr-1, glacier-wide mass balance = -0.58 ± 0.36 m w.e. yr-1). This deceleration in ice thinning compared to the previous 17 years can be attributed, at least in part, to two consecutive anomalously wet winters and cool summers (2012-2013 and 2013-2014), counteracted to some degree by the intense thinning that occurred during the dry and warm 2011-2012 period. However, local climatic changes observed during the study period do not seem sufficient to explain the acceleration of ice thinning of this glacier, because precipitation and air temperature did not exhibit statistically significant trends during the study period. Rather, the accelerated degradation of this glacier in recent years can be explained by a strong disequilibrium between the glacier and the current climate, and likely by other

  8. Surface Velocities of Himalayan Glaciers: Implications for Glacial Erosion Potential During Climatic Change

    NASA Astrophysics Data System (ADS)

    Scherler, D.; Bookhagen, B.; Strecker, M. R.

    2007-12-01

    Mountain glaciers in the high elevations (> 3.5 km) of the Himalaya are very efficient erosion agents. Glacier size and thus the area affected by glacial erosion are controlled by climatic conditions. Understanding the impact of climate change and variability on glacial budgets and erosion requires knowledge of the erosive potential of glaciers, which is inferred to scale with ice flux. Here, we use ASTER satellite imagery in combination with the orthorectification and correlation tool COSI-Corr to derive horizontal surface velocities of glaciers from several regions across the Himalayan-Karakoram domain. Our results show that glaciers in the Eastern and Central Himalaya, where precipitation is mainly supplied by the Indian Summer Monsoon, are relatively slow, with velocities usually below 50-60 m/a. In contrast, glaciers in the Western Himalaya and Karakoram, receive a significant amount of precipitation during the winter months and are considerably faster with velocities often exceeding 80-100 m/a. This discrepancy is visible among glaciers of different size and orientation although local slope and catchment area effects may cause velocity excursions. A relatively sharp gradient appears to exist in the catchment area of the Sutlej River in the NW Himalaya of India at approximately 79°E. To the east, glaciers in the Garhwal Himalaya - among them Gangotri glacier, the largest in the Indian Himalaya - have mean velocities of around 20-40 m/a, whereas glaciers in the much drier Lahul region to the west attain mean velocities of around 30-60 m/a. Importantly, the Sutlej River valley marks a climatic transition zone from an annual summer-rainfall maximum (more than 75% of annual rainfall during the summer) to the east to a winter-rainfall maximum (more than 60% of annual rainfall during the winter) to the west. These observations corroborate the notion of a significant climatic boundary in this part of the Himalaya, which may have shifted west- and northward during

  9. Glacier albedo decrease in the European Alps: potential causes and links with mass balances

    NASA Astrophysics Data System (ADS)

    Di Mauro, Biagio; Julitta, Tommaso; Colombo, Roberto

    2016-04-01

    Both mountain glaciers and polar ice sheets are losing mass all over the Earth. They are highly sensitive to climate variation, and the widespread reduction of glaciers has been ascribed to the atmospheric temperature increase. Beside this driver, also ice albedo plays a fundamental role in defining mass balance of glaciers. In fact, dark ice absorbs more energy causing faster glacier melting, and this can drive to more negative balances. Previous studies showed that the albedo of Himalayan glaciers and the Greenland Ice Sheet is decreasing with important rates. In this contribution, we tested the hypothesis that also glaciers in the European Alps are getting darker. We analyzed 16-year time series of MODIS (MODerate resolution Imaging Spectrometer) snow albedo from Terra (MOD13A1, 2000-2015) and Aqua (MYD13A1, 2002-2015) satellites. These data feature a spatial resolution of 500m and a daily temporal resolution. We evaluated the existence of a negative linear and nonlinear trend of the summer albedo values both at pixel and at glacier level. We also calculated the correlation between MODIS summer albedo and glacier mass balances (from the World Glaciological Monitoring Service, WGMS database), for all the glaciers with available mass balance during the considered period. In order to estimate the percentage of the summer albedo that can be explained by atmospheric temperature, we correlated MODIS albedo and monthly air temperature extracted from the ERA-Interim reanalysis dataset. Results show that decreasing trends exist with a strong spatial variability in the whole Alpine chain. In large glaciers, such as the Aletch (Swiss Alps), the trend varies significantly also within the glacier, showing that the trend is higher in the area across the accumulation and ablation zone. Over the 17 glaciers with mass balance available in the WGMS data set, 11 gave significant relationship with the MODIS summer albedo. Moreover, the comparison between ERA-Interim temperature

  10. Fast shrinkage of tropical glaciers in Colombia

    NASA Astrophysics Data System (ADS)

    Ceballos, Jorge Luis; Euscátegui, Christian; Ramírez, Jair; Cañon, Marcela; Huggel, Christian; Haeberli, Wilfried; Machguth, Horst

    As a consequence of ongoing atmospheric temperature rise, tropical glaciers belong to the unique and threatened ecosystems on Earth, as defined by the Intergovernmental Panel on Climate Change (Houghton and others, 2001). Worldwide glacier monitoring, especially as part of the Global Climate Observing System (GCOS), includes the systematic collection of data on such perennial surface ice masses. Several peaks in the sierras of Colombia have lost their glacier cover during recent decades. Today, high-altitude glaciers still exist in Sierra Nevada de Santa Marta, in Sierra Nevada del Cocuy and on the volcanoes of Nevados del Ruiz, de Santa Isabel, del Tolima and del Huila. Comparison of reconstructions of maximum glacier area extent during the Little Ice Age with more recent information from aerial photographs and satellite images clearly documents a fast-shrinking tendency and potential disappearance of the remaining glaciers within the next few decades. In the past 50 years, Colombian glaciers have lost 50% or more of their area. Glacier shrinkage has continued to be strong in the last 15 years, with a loss of 10-50% of the glacier area. The relationship between fast glacier retreat and local, regional and global climate change is now being investigated. Preliminary analyses indicate that the temperature rise of roughly 1° C in the last 30 years recorded at high-altitude meteorological stations exerts a primary control on glacier retreat. The investigations on the Colombian glaciers thus corroborate earlier findings concerning the high sensitivity of glaciers in the wet inner tropics to temperature rise. To improve understanding of fast glacier retreat in Colombia, a modern monitoring network has been established according to the multilevel strategy of the Global Terrestrial Network for Glaciers (GTN-G) within GCOS. The observations are also contributions to continued assessments of hazards from the glacier-covered volcanoes and to integrated global change

  11. Rapid thinning and collapse of lake calving Yakutat Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Trussel, Barbara Lea

    Glaciers around the globe are experiencing a notable retreat and thinning, triggered by atmospheric warming. Tidewater glaciers in particular have received much attention, because they have been recognized to contribute substantially to global sea level rise. However, lake calving glaciers in Alaska show increasingly high thinning and retreat rates and are therefore contributors to sea level rise. The number of such lake calving systems is increasing worldwide as land-terminating glaciers retreat into overdeepened basins and form proglacial lakes. Yakutat Glacier in Southeast Alaska is a low elevation lake calving glacier with an accumulation to total area ratio of 0.03. It experienced rapid thinning of 4.43 +/- 0.06 m w.e. yr-1 between 2000-2010 and terminus retreat of over 15 km since the beginning of the 20th century. Simultaneously, adjacent Yakutat Icefield land-terminating glaciers thinned at lower but still substantial rates (3.54 +/- 0.06 m w.e. yr -1 for the same time period), indicating lake calving dynamics help drive increased mass loss. Yakutat Glacier sustained a ˜3 km long floating tongue for over a decade, which started to disintegrate into large tabular icebergs in 2010. Such floating tongues are rarely seen on temperate tidewater glaciers. The floating ice was weakened by surface ablation, which then allowed rifts to form and intersect. Ice velocity from GPS measurements showed that the ice on the floating tongue was moving substantially faster than grounded ice, which was attributed to rift opening between the floating and grounded ice. Temporal variations of rift opening were determined from time-lapse imagery, and correlated well with variations in ice speeds. Larger rift opening rates occurred during and after precipitation or increased melt episodes. Both of these events increased subglacial discharge and could potentially increase the subaqueous currents towards the open lake and thus increase drag on the ice underside. Simultaneously

  12. Erosion by an Alpine glacier.

    PubMed

    Herman, Frédéric; Beyssac, Olivier; Brughelli, Mattia; Lane, Stuart N; Leprince, Sébastien; Adatte, Thierry; Lin, Jiao Y Y; Avouac, Jean-Philippe; Cox, Simon C

    2015-10-01

    Assessing the impact of glaciation on Earth's surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years.

  13. Erosion by an Alpine glacier

    NASA Astrophysics Data System (ADS)

    Herman, Frédéric; Beyssac, Olivier; Brughelli, Mattia; Lane, Stuart N.; Leprince, Sébastien; Adatte, Thierry; Lin, Jiao Y. Y.; Avouac, Jean-Philippe; Cox, Simon C.

    2015-10-01

    Assessing the impact of glaciation on Earth’s surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years.

  14. Flow velocities of Alaskan glaciers.

    PubMed

    Burgess, Evan W; Forster, Richard R; Larsen, Christopher F

    2013-01-01

    Our poor understanding of tidewater glacier dynamics remains the primary source of uncertainty in sea level rise projections. On the ice sheets, mass lost from tidewater calving exceeds the amount lost from surface melting. In Alaska, the magnitude of calving mass loss remains unconstrained, yet immense calving losses have been observed. With 20% of the global new-water sea level rise coming from Alaska, partitioning of mass loss sources in Alaska is needed to improve sea level rise projections. Here we present the first regionally comprehensive map of glacier flow velocities in Central Alaska. These data reveal that the majority of the regional downstream flux is constrained to only a few coastal glaciers. We find regional calving losses are 17.1 Gt a(-1), which is equivalent to 36% of the total annual mass change throughout Central Alaska.

  15. Get Close to Glaciers with Satellite Imagery.

    ERIC Educational Resources Information Center

    Hall, Dorothy K.

    1986-01-01

    Discusses the use of remote sensing from satellites to monitor glaciers. Discusses efforts to use remote sensing satellites of the Landsat series for examining the global distribution, mass, balance, movements, and dynamics of the world's glaciers. Includes several Landsat images of various glaciers. (TW)

  16. Assessing streamflow sensitivity to variations in glacier mass balance

    USGS Publications Warehouse

    O'Neel, Shad; Hood, Eran; Arendt, Anthony; Sass, Louis

    2014-01-01

    The purpose of this paper is to evaluate relationships among seasonal and annual glacier mass balances, glacier runoff and streamflow in two glacierized basins in different climate settings. We use long-term glacier mass balance and streamflow datasets from the United States Geological Survey (USGS) Alaska Benchmark Glacier Program to compare and contrast glacier-streamflow interactions in a maritime climate (Wolverine Glacier) with those in a continental climate (Gulkana Glacier). Our overall goal is to improve our understanding of how glacier mass balance processes impact streamflow, ultimately improving our conceptual understanding of the future evolution of glacier runoff in continental and maritime climates.

  17. Geodetic Glacier Mass Balance of Norway

    NASA Astrophysics Data System (ADS)

    Andreassen, L. M.; Elvehøy, H.; Kjøllmoen, B.

    2014-12-01

    Glaciers in mainland Norway cover 2692 km2and span a large range from south to north. Glacier surface mass balance is monitored by the direct (also called glaciological, traditional or conventional) method and indirectly assessed by the geodetic (or cartographic) method. The current glacier monitoring programme includes direct surface mass-balance investigations on 14 glaciers. Since measurements started at Storbreen in 1949, mass balance has been measured on a total of 43 glaciers. The accuracy of the direct measurements depends on both the accuracy of the point observations and inter- and extrapolation of point values to spatially distributed values. Long series of measurements can be inhomogeneous because of changes in personnel, methods, and glacier topography. Reanalysing glacier mass balance series is recommended as standard procedure for every mass balance monitoring programme with increasing importance for long time series. Repeated, detailed glacier mapping by aerial photography and photogrammetric methods, and recently by laser scanning (LIDAR), have been performed to calculate geodetic mass balance. The geodetic results are used as an independent check of the direct method as well as to monitor volume, area and mass changes of glaciers that lack direct measurements. Since 2007, LIDAR campaigns have been conducted on a 1/3 of the glacier area in Norway including all current mass balance glaciers. The objectives of the surveys are to produce high quality digital elevation models (DEMs) and orthophotos to document the present state of the glaciers and assess glacier changes since previous surveys. Furthermore, the DEMs and orthophotos provide an accurate baseline for future repeated mapping and glacier change detection. Here we present geodetic mass balance results for Norway over the last 50 years and compare the results with the direct in-situ measurements where available. We also show examples of how glacier mass balance data are being reanalyzed

  18. Organic Carbon Dynamics in Glacier Systems

    NASA Astrophysics Data System (ADS)

    Barker, J.; Sharp, M.; Klassen, J.; Foght, J.; Turner, R.

    2004-12-01

    The biogeochemical cycling of organic carbon (OC) has important implications for aquatic system ecology because the abundance and molecular characteristics of OC influence contaminant transport and bioavailability, and determine its suitability as a substrate for microbial metabolism. There have been few studies of OC cycling in glacier systems, and questions remain regarding the abundance, provenance, and biogeochemical transformations of OC in these environments. To address these questions, the abundance and molecular characteristics of OC is investigated in three glacier systems. These systems are characterized by different thermal and hydrological regimes and have different potential OC sources. John Evans Glacier is a polythermal glacier in arctic Canada. Outre Glacier is a temperate glacier in the Coast Mountains of British Columbia, Canada. Victoria Upper Glacier is a cold-based glacier in the McMurdo Dry Valleys of Antarctica. To provide an indication of the extent to which glacier system OC dynamics are microbially mediated, microbial culturing and identification is performed and organic acid abundance and speciation is determined. Where possible, samples of supraglacial runoff, glacier ice and basal ice and subglacial meltwater were collected. The dissolved organic carbon (DOC) concentration in each sample was measured by combustion/non-dispersive infrared gas analysis. Emission and synchronous fluorescence spectroscopy were used to characterize the molecular properties of the DOC from each environment. When possible, microbial culturing and identification was performed and organic acid identification and quantification was measured by ion chromatography. DOC exists in detectable quantities (0.06-46.6 ppm) in all of the glacier systems that were investigated. The molecular characteristics of DOC vary between glaciers, between environments at the same glacier, and over time within a single environment. Viable microbes are recoverable in significant (ca

  19. Glacier recession in Iceland and Austria

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.; Williams, Richard S., Jr.; Bayr, Klaus J.

    1992-01-01

    It has been possible to measure glacier recession on the basis of Landsat data, in conjunction with comparisons of the magnitude of recession of a glacier margin with in situ measurements at fixed points along the same margin. Attention is presently given to the cases of Vatnajokull ice cap, in Iceland, and the Pasterze Glacier, in Austria, on the basis of satellite data from 1973-1987 and 1984-1990, respectively. Indications of a trend toward negative mass balance are noted. Nevertheless, while most of the world's small glaciers have been receding, some are advancing either due to local climate or the tidewater glacier cycle.

  20. Glacier fluctuations during the past 2000 years

    NASA Astrophysics Data System (ADS)

    Solomina, Olga N.; Bradley, Raymond S.; Jomelli, Vincent; Geirsdottir, Aslaug; Kaufman, Darrell S.; Koch, Johannes; McKay, Nicholas P.; Masiokas, Mariano; Miller, Gifford; Nesje, Atle; Nicolussi, Kurt; Owen, Lewis A.; Putnam, Aaron E.; Wanner, Heinz; Wiles, Gregory; Yang, Bao

    2016-10-01

    A global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions (excluding Antarctica) highlights the nature of glacier fluctuations during the late Holocene. The dataset includes 275 time series of glacier fluctuations based on historical, tree ring, lake sediment, radiocarbon and terrestrial cosmogenic nuclide data. The most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and, when available, winter precipitation reconstructions, the most important parameters for glacier mass balance. In many cases major glacier advances correlate with multi-decadal periods of decreased summer temperature. In a few cases, such as in Arctic Alaska and western Canada, some glacier advances occurred during relatively warm wet times. The timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region. However, the number of glacier advances shows a clear pattern for the high, mid and low latitudes and, hence, points to common forcing factors acting at the global scale. Globally, during the first millennium CE glaciers were smaller than between the advances in 13th to early 20th centuries CE. The precise extent of glacier retreat in the first millennium is not well defined; however, the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th/early 21st centuries. Other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the European Alps, in the 3rd-6th and 9th centuries in Norway, during the 10th-13th centuries in southern Alaska, and in the 18th century in Spitsbergen. However, no single period of common global glacier retreat of centennial duration, except for the past century, has yet been identified. In contrast, the view that the Little Ice Age was a period of global glacier expansion beginning in the 13th century

  1. Glacier recession in Iceland and Austria

    SciTech Connect

    Hall, D.K.; Williams, R.S. Jr.; Bayr, K.J. USGS, Reston, VA Keene State College, NH )

    1992-03-01

    It has been possible to measure glacier recession on the basis of Landsat data, in conjunction with comparisons of the magnitude of recession of a glacier margin with in situ measurements at fixed points along the same margin. Attention is presently given to the cases of Vatnajokull ice cap, in Iceland, and the Pasterze Glacier, in Austria, on the basis of satellite data from 1973-1987 and 1984-1990, respectively. Indications of a trend toward negative mass balance are noted. Nevertheless, while most of the world's small glaciers have been receding, some are advancing either due to local climate or the tidewater glacier cycle. 21 refs.

  2. Reconstruction of Equilibrium Line Altitudes of Nevado Coropuna Glaciers (Southern Peru) from the Late Pleistocene to the present

    NASA Astrophysics Data System (ADS)

    Úbeda, J.; Palacios, D.; Vázquez, L.

    2009-04-01

    also higher for all periods in the Northern section (5968, 5930, 5923, 5886 and 5186 m) than in the Southern section (5862, 5806, 5787 and 4951 m). The depression in ELAs during the LIA was similar in the NE (~82 m) and in the SE (~86 m). However, the 2007 ELA shows a depression of 106 m in the Southern direction. The magnitude of this depression has shown a marked tendency towards reduction in recent decades (136 m in 1955 and 124 m in 1986). Furthermore, the decrease in ELA depression seems to occur faster, with ↓Z ~12 m between 1955 and 1986 and ↓Z ~18 m between 1986 and 2007. However, during the Little Ice Age (~110 m) that value was closer to the current value (106 m). Depression in ELAs during the last maximum glacier advance has been estimated at ~782 m (NE) and ~847 m (SE). During that period, the N-S depression reached a maximum value of 235 m. These results agree with those obtained for the eastern range of the Central Andes (Smith et al. 2005 a and b) and are also within the depression intervals and trends proposed in regional-scale studies (Kelin et al. 1999). Analyses performed on a sample from a block situated on a lateral moraine in the Queñua Ranra Quebrada (NE group of the complex) suggest a chronology of ~17 Cl36 ky. for the last maximum ice mass advance. This date is in agreement with the depression in SST temperature during the same period, deduced from analyzing Mg/Ca ratios in marine foraminifera shells from the Galapagos Islands (Lea, 2006). Using surfaces and ELAs as geoindicators, deglaciation rates and the Horizon without glaciers (H0) have been calculated globally, for the complete glacier system in scenarios 1 and 2, and for glaciers in the pilot group in scenarios 1, 2 and 3. Results show that the deglaciation process is occurring differentially. Whereas several masses could disappear in a few decades, others could be preserved for centuries. Regarding the last phase of volcanic activity, a lava sample has been dated at only ~2

  3. Spatially heterogeneous wastage of Himalayan glaciers.

    PubMed

    Fujita, Koji; Nuimura, Takayuki

    2011-08-23

    We describe volumetric changes in three benchmark glaciers in the Nepal Himalayas on which observations have been made since the 1970s. Compared with the global mean of glacier mass balance, the Himalayan glaciers showed rapid wastage in the 1970s-1990s, but similar wastage in the last decade. In the last decade, a glacier in an arid climate showed negative but suppressed mass balance compared with the period 1970s-1990s, whereas two glaciers in a humid climate showed accelerated wastage. A mass balance model with downscaled gridded datasets depicts the fate of the observed glaciers. We also show a spatially heterogeneous distribution of glacier wastage in the Asian highlands, even under the present-day climate warming.

  4. The contribution of glacier melt to streamflow

    SciTech Connect

    Schaner, Neil; Voisin, Nathalie; Nijssen, Bart; Lettenmaier, D. P.

    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 melt 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.

  5. Microbial Habitat on Kilimanjaro's Glaciers

    NASA Astrophysics Data System (ADS)

    Ponce, A.; Beaty, S. M.; Lee, C.; Lee, C.; Noell, A. C.; Stam, C. N.; Connon, S. A.

    2011-03-01

    Kilimanjaro glaciers captured a history of microbial diversity and abundance of supraglacial habitats. We show that a majority of bacterial clones, as determined by bacterial 16S rRNA gene sequencing, are most closely related to those isolated from cold-water environments.

  6. Mountain Glaciers and Ice Caps

    USGS Publications Warehouse

    Ananichheva, Maria; Arendt, Anthony; Hagen, Jon-Ove; Hock, Regine; Josberger, Edward G.; Moore, R. Dan; Pfeffer, William Tad; Wolken, Gabriel J.

    2011-01-01

    Projections of future rates of mass loss from mountain glaciers and ice caps in the Arctic focus primarily on projections of changes in the surface mass balance. Current models are not yet capable of making realistic forecasts of changes in losses by calving. Surface mass balance models are forced with downscaled output from climate models driven by forcing scenarios that make assumptions about the future rate of growth of atmospheric greenhouse gas concentrations. Thus, mass loss projections vary considerably, depending on the forcing scenario used and the climate model from which climate projections are derived. A new study in which a surface mass balance model is driven by output from ten general circulation models (GCMs) forced by the IPCC (Intergovernmental Panel on Climate Change) A1B emissions scenario yields estimates of total mass loss of between 51 and 136 mm sea-level equivalent (SLE) (or 13% to 36% of current glacier volume) by 2100. This implies that there will still be substantial glacier mass in the Arctic in 2100 and that Arctic mountain glaciers and ice caps will continue to influence global sea-level change well into the 22nd century.

  7. Younger Dryas Age advance of Franz Josef Glacier in the Southern Alps of New Zealand

    SciTech Connect

    Denton, G.H. ); Hendy, C.H. )

    1994-06-03

    A corrected radiocarbon age of 11,050 [+-] 14 years before present for an advance of the Franz Josef Glacier to the Waiho Loop terminal moraine on the western flank of New Zealand's Southern Alps shows that glacier advance on a South Pacific island was synchronous with initiation of the Younger Dryas in the North Atlantic region. Hence, cooling at the beginning of the Younger Dryas probably reflects global rather than regional forcing. The source for Younger Dryas climatic cooling may thus lie in the atmosphere rather than in a North Atlantic thermohaline switch. 36 refs., 2 figs., 1 tab.

  8. The current disequilibrium of North Cascade glaciers

    NASA Astrophysics Data System (ADS)

    Pelto, Mauri S.

    2006-03-01

    Three lines of evidence indicate that North Cascade (Washington, USA) glaciers are currently in a state of disequilibrium. First, annual balance measured on nine glaciers yields a mean cumulative balance for the 1984-2004 period of -8.58 m water equivalent (w.e.), a net loss of ice thickness exceeding 9.5 m. This is a significant loss for glaciers that average 30-50 m in thickness, representing 18-32% of their entire volume.Second, longitudinal profiles completed in 1984 and 2002 on 12 North Cascade glaciers confirm this volume change indicating a loss of -5.7 to -6.3 m in thickness (5.0-5.6 m w.e.) between 1984 and 2002, agreeing well with the measured cumulative balance of -5.52 m w.e. for the same period. The change in thickness on several glaciers has been equally substantial in the accumulation zone and the ablation zone, indicating that there is no point to which the glacier can retreat to achieve equilibrium. Substantial thinning along the entire length of a glacier is the key indicator that a glacier is in disequilibrium.Third, North Cascade glacier retreat is rapid and ubiquitous. All 47 glaciers monitored are currently undergoing significant retreat or, in the case of four, have disappeared. Two of the glaciers where mass balance observations were begun, Spider Glacier and Lewis Glacier, have disappeared. The retreat since 1984 of eight Mount Baker glaciers that were all advancing in 1975 has averaged 297 m. These observations indicate broad regional continuity in glacial response to climate.

  9. Imaging evidence for Hubbard Glacier advances and retreats since the last glacial maximum in Yakutat and Disenchantment Bays, Alaska

    NASA Astrophysics Data System (ADS)

    Zurbuchen, Julie M.; Gulick, Sean P. S.; Walton, Maureen A. L.; Goff, John A.

    2015-06-01

    High-resolution 2-D multichannel seismic data, collected during the 2012 UTIG-USGS National Earthquake Hazards Reduction Program survey of Disenchantment and Yakutat Bays in southeast Alaska, provide insight into their glacial history. These data show evidence of two unconformities, appearing in the form of channels, and are interpreted to be advance pathways for Hubbard Glacier. The youngest observable channel, thought to have culminated near the main phase of the Little Ice Age (LIA), is imaged in Disenchantment Bay and ends at a terminal moraine near Blizhni Point. An older channel, thought to be from an advance that culminated in the early phase of the LIA, extends from Disenchantment Bay into the northeastern edge of Yakutat Bay, turning southward at Knight Island and terminating on the southeastern edge of Yakutat Bay. Our interpretation is that Hubbard Glacier has repeatedly advanced around the east side of Yakutat Bay in Knight Island Channel, possibly due to the presence of Malaspina Glacier cutting off access to central Yakutat Bay during times of mutual advance. We observe two distinct erosional surfaces and retreat sequences of Hubbard Glacier in Yakutat Bay, supporting the hypothesis that minor glacial advances in fjords do not erode all prior sediment accumulations. Interpretation of chaotic seismic facies between these two unconformities suggests that Hubbard Glacier exhibits rapid retreats and that Disenchantment Bay is subject to numerous episodes of outburst flooding and morainal bank collapse. These findings also suggest that tidewater glaciers preferentially reoccupy the same channels in bay and marine settings during advances.

  10. Iron from melting glaciers fuels phytoplankton blooms in the Amundsen Sea (Southern Ocean): Phytoplankton characteristics and productivity

    NASA Astrophysics Data System (ADS)

    Alderkamp, Anne-Carlijn; Mills, Matthew M.; van Dijken, Gert L.; Laan, Patrick; Thuróczy, Charles-Edouard; Gerringa, Loes J. A.; de Baar, Hein J. W.; Payne, Christopher D.; Visser, Ronald J. W.; Buma, Anita G. J.; Arrigo, Kevin R.

    2012-09-01

    The phytoplankton community composition and productivity in waters of the Amundsen Sea and surrounding sea ice zone were characterized with respect to iron (Fe) input from melting glaciers. High Fe input from glaciers such as the Pine Island Glacier, and the Dotson and Crosson ice shelves resulted in dense phytoplankton blooms in surface waters of Pine Island Bay, Pine Island Polynya, and Amundsen Polynya. Phytoplankton biomass distribution was the opposite of the distribution of dissolved Fe (DFe), confirming the uptake of glacial DFe in surface waters by phytoplankton. Phytoplankton biomass in the polynyas ranged from 0.6 to 14 μg Chl a L-1, with lower biomass at glacier sites where strong upwelling of Modified Circumpolar Deep Water from beneath glacier tongues was observed. Phytoplankton blooms in the polynyas were dominated by the haptophyte Phaeocystis antarctica, whereas the phytoplankton community in the sea ice zone was a mix of P. antarctica and diatoms, resembling the species distribution in the Ross Sea. Water column productivity based on photosynthesis versus irradiance characteristics averaged 3.00 g C m-2 d-1 in polynya sites, which was approximately twice as high as in the sea ice zone. The highest water column productivity was observed in the Pine Island Polynya, where both thermally and salinity stratified waters resulted in a shallow surface mixed layer with high phytoplankton biomass. In contrast, new production based on NO3 uptake was similar between different polynya sites, where a deeper UML in the weakly, thermally stratified Pine Island Bay resulted in deeper NO3 removal, thereby offsetting the lower productivity at the surface. These are the first in situ observations that confirm satellite observations of high phytoplankton biomass and productivity in the Amundsen Sea. Moreover, the high phytoplankton productivity as a result of glacial input of DFe is the first evidence that melting glaciers have the potential to increase phytoplankton

  11. A model study of Abrahamsenbreen, a surging glacier in northern Spitsbergen

    NASA Astrophysics Data System (ADS)

    Oerlemans, J.; van Pelt, W. J. J.

    2015-04-01

    The climate sensitivity of Abrahamsenbreen, a 20 km long surge-type glacier in northern Spitsbergen, is studied with a simple glacier model. A scheme to describe the surges is included, which makes it possible to account for the effect of surges on the total mass budget of the glacier. A climate reconstruction back to AD 1300, based on ice-core data from Lomonosovfonna and climate records from Longyearbyen, is used to drive the model. The model is calibrated by requesting that it produce the correct Little Ice Age maximum glacier length and simulate the observed magnitude of the 1978 surge. Abrahamsenbreen is strongly out of balance with the current climate. If climatic conditions remain as they were for the period 1989-2010, the glacier will ultimately shrink to a length of about 4 km (but this will take hundreds of years). For a climate change scenario involving a 2 m year-1 rise of the equilibrium line from now onwards, we predict that in the year 2100 Abrahamsenbreen will be about 12 km long. The main effect of a surge is to lower the mean surface elevation and thereby to increase the ablation area, causing a negative perturbation of the mass budget. We found that the occurrence of surges leads to a faster retreat of the glacier in a warming climate. Because of the very small bed slope, Abrahamsenbreen is sensitive to small perturbations in the equilibrium-line altitude. If the equilibrium line were lowered by only 160 m, the glacier would steadily grow into Woodfjorddalen until, after 2000 years, it would reach Woodfjord and calving would slow down the advance. The bed topography of Abrahamsenbreen is not known and was therefore inferred from the slope and length of the glacier. The value of the plasticity parameter needed to do this was varied by +20 and -20%. After recalibration the same climate change experiments were performed, showing that a thinner glacier (higher bedrock in this case) in a warming climate retreats somewhat faster.

  12. Using Metaphorical Models for Describing Glaciers

    NASA Astrophysics Data System (ADS)

    Felzmann, Dirk

    2014-11-01

    To date, there has only been little conceptual change research regarding conceptions about glaciers. This study used the theoretical background of embodied cognition to reconstruct different metaphorical concepts with respect to the structure of a glacier. Applying the Model of Educational Reconstruction, the conceptions of students and scientists regarding glaciers were analysed. Students' conceptions were the result of teaching experiments whereby students received instruction about glaciers and ice ages and were then interviewed about their understandings. Scientists' conceptions were based on analyses of textbooks. Accordingly, four conceptual metaphors regarding the concept of a glacier were reconstructed: a glacier is a body of ice; a glacier is a container; a glacier is a reflexive body and a glacier is a flow. Students and scientists differ with respect to in which context they apply each conceptual metaphor. It was observed, however, that students vacillate among the various conceptual metaphors as they solve tasks. While the subject context of the task activates a specific conceptual metaphor, within the discussion about the solution, the students were able to adapt their conception by changing the conceptual metaphor. Educational strategies for teaching students about glaciers require specific language to activate the appropriate conceptual metaphors and explicit reflection regarding the various conceptual metaphors.

  13. Generation of the relationship between glacier area and volume for a tropical glacier in Bolivian Andes

    NASA Astrophysics Data System (ADS)

    Liu, T.; Kinouchi, T.; Hasegawa, A.; Tsuda, M.; Iwami, Y.; Asaoka, Y.; Mendoza, J.

    2015-12-01

    In Andes, retreat of tropical glaciers is rapid, thus water resources currently available from glacierized catchments would be changed in its volume and temporal variations due to climate change and glacier shrinkage. The relationship between glacier area and volume is difficult to define however which is important to monitor glaciers especially those are remote or inaccessible. Water resources in La Paz and El Alto in Bolivia, strongly depend on the runoff from glacierized headwater catchments in the Cordillera Real, Andes, which is therefore selected as our study region.To predict annual glacier mass balances, PWRI-Distributed Hydrological Model (PWRI-DHM) was applied to simulate runoff from the partially glacierized catchments in high mountains (i.e. Condoriri-Huayna West headwater catchment located in the Cordillera Real, Bolivian Andes). PWRI-DHM is based on tank model concept in a distributed and 4-tank configuration including surface, unsaturated, aquifer, and river course tanks. The model was calibrated and validated with observed meteorological and hydrological data from 2011 to 2014 by considering different phases of precipitation, various runoff components from glacierized and non-glacierized areas, and the retarding effect by glacial lakes and wetlands. The model is then applied with MRI-AGCM outputs from 1987 to 2003 considering the shrinkage of glacier outlines since 1980s derived from Landsat data. Annual glacier mass balance in each 100m-grid was reproduced, with which the glacier area-volume relationship was generated with reasonable initial volume setting. Out study established a method to define the relationship between glacier area and volume by remote sensing information and glacier mass balances simulated by distributed hydrological model. Our results demonstrated that the changing trend of local glacier had a consistency the previous observed glacier area-volume relationship in the Cordillera Real.

  14. Numerical modelling of the effect of changing surface geometry on mountain glacier mass balance

    NASA Astrophysics Data System (ADS)

    Williams, Chris; Carrivick, Jonathan; Evans, Andrew; Carver, Steve

    2013-04-01

    Mountain glaciers and ice caps are extremely useful indicators of environmental change. Due to their small size, they have much faster response times to climate changes than the large ice masses of Greenland and Antarctica. Mountain glaciers are important for society as sources of water for energy production and irrigation and the meltwater cycles significantly impact local ecology. We have applied a spatially distributed surface energy balance model to a glacier record spanning 100 years. Our study encompasses (i) the creation of a GIS enabling quantitative analysis of changing glacier geometry; absolute length, area, surface lowering and volume change, over the 20th and early 21st Centuries and (ii) the development and testing of a novel user-friendly distributed-surface energy balance model that is designed specifically to consider the effect that these geometrical changes have on mountain glacier mass balance. Our study site is Kårsaglaciären in Arctic Sweden for which there is a variety of data for the past 100 years, sourced from historical surveys, satellite imagery and recent field work. This contrasts with other Arctic mountain glaciers where long-term records are rare, making model development and evaluation very difficult. Kårsaglaciären has been in a state of negative balance throughout the 20th century. Disintegration of the glacier occurred during the 1920s, breaking the glacier into two separate bodies. Between 1926 and 2008, the glacier retreated 1.3 km and reduced in area by 3.41km2. In 2008 the glacier had an estimated surface area of 0.89km2 and a length of approximately 1.0km. Firstly, we present the GIS based construction of robust three-dimensional glacier surface reconstructions for Kårsaglaciären from 1926 to 2010 using a decadal interval. We highlight the kriging interpolation methods used for surface development and the importance of inter-model sensitivity analyses as well as the use of Monte Carlo simulations used to assess the

  15. Future glacier runoff at the global scale

    NASA Astrophysics Data System (ADS)

    Huss, Matthias; Hock, Regine

    2016-04-01

    Water resources in mountain areas worldwide importantly depend on the runoff contribution by glaciers. Glacial water storage acts as an equilibrating element in the global hydrological cycle on various temporal scales. With ongoing and future glacier retreat a growing concern regarding water supply security in glacier-fed basins arises. However, glacier runoff projections at the regional or global scale are still rare and better models are urgently needed for planning and adaptation measures to cope with a changing seasonal distribution of water yields. Moreover, it is still an open debate in which region "peak water" - the maximum contribution of melting glaciers to runoff - has already been reached, i.e. whether increasing or declining annual runoff volumes must be expected. Here, we present results of a novel global glacier model for calculating the 21st century response of surface mass balance, three-dimensional glacier geometry and monthly water discharge for each individual glacier around the globe. The current surface geometry and thickness distribution for each of the world's roughly 200'000 glaciers is extracted from the Randolph Glacier Inventory 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 glacierized catchments in all climatic regions of the earth and the corresponding importance of changes in the runoff regime on hydrological stress. The maximum rate of water release from glacial storage is subject to a high spatio-temporal variability depending on glacier characteristics and the transient response to climatic change. Furthermore, we discuss the significance of projected variations in glacier runoff in relation to the hydrology of the world's large-scale drainage basins and population distribution, and highlight 'hot spot' regions where the wastage of current ice volume is particularly relevant.

  16. Relativistic kinematics for motion faster than light

    NASA Technical Reports Server (NTRS)

    Jones, R. T.

    1982-01-01

    The use of conformal coordinates in relativistic kinematics is illustrated and a simple extension of the theory of motions faster than light is provided. An object traveling at a speed greater than light discloses its presence by appearing suddenly at a point, splitting into two apparent objects which then recede from each other at sublight velocities. According to the present theory motion at speeds faster than light would not benefit a space traveler, since the twin paradox becomes inverted at such speeds. In Einstein's theory travel at the velocity of light in an intertial system is equivalent to infinite velocity for the traveler. In the present theory the converse is also true; travel at infinite velocity is equivalent to the velocity of light for the traveler.

  17. Compressing bitmap indexes for faster search operations

    SciTech Connect

    Wu, Kesheng; Otoo, Ekow J.; Shoshani, Arie

    2002-04-25

    In this paper, we study the effects of compression on bitmap indexes. The main operations on the bitmaps during query processing are bitwise logical operations such as AND, OR, NOT, etc. Using the general purpose compression schemes, such as gzip, the logical operations on the compressed bitmaps are much slower than on the uncompressed bitmaps. Specialized compression schemes, like the byte-aligned bitmap code(BBC), are usually faster in performing logical operations than the general purpose schemes, but in many cases they are still orders of magnitude slower than the uncompressed scheme. To make the compressed bitmap indexes operate more efficiently, we designed a CPU-friendly scheme which we refer to as the word-aligned hybrid code (WAH). Tests on both synthetic and real application data show that the new scheme significantly outperforms well-known compression schemes at a modest increase in storage space. Compared to BBC, a scheme well-known for its operational efficiency, WAH performs logical operations about 12 times faster and uses only 60 percent more space. Compared to the uncompressed scheme, in most test cases WAH is faster while still using less space. We further verified with additional tests that the improvement in logical operation speed translates to similar improvement in query processing speed.

  18. Benthic Trophic Interactions in an Antarctic Shallow Water Ecosystem Affected by Recent Glacier Retreat.

    PubMed

    Pasotti, Francesca; Saravia, Leonardo Ariel; De Troch, Marleen; Tarantelli, Maria Soledad; Sahade, Ricardo; Vanreusel, Ann

    2015-01-01

    The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands), a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (δ13C and δ15N stable isotope analysis) at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring) species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more compact trophic structure with increased

  19. Benthic Trophic Interactions in an Antarctic Shallow Water Ecosystem Affected by Recent Glacier Retreat

    PubMed Central

    Pasotti, Francesca; Saravia, Leonardo Ariel; De Troch, Marleen; Tarantelli, Maria Soledad; Sahade, Ricardo; Vanreusel, Ann

    2015-01-01

    The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands), a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (δ13C and δ15N stable isotope analysis) at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring) species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more compact trophic structure with increased

  20. 5. GLACIER POINT ROAD VIEW AT SENTINEL DOME PARKING AREA. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. GLACIER POINT ROAD VIEW AT SENTINEL DOME PARKING AREA. LOOKING E. GIS: N-37 42 43.8 / W-119 35 12.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  1. 1. PARKING LOT AT GLACIER POINT. HALF DOME AT CENTER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. PARKING LOT AT GLACIER POINT. HALF DOME AT CENTER REAR. LOOKING NE. GIS: N-36 43 45.8 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  2. Antarctica: Measuring glacier velocity from satellite images

    USGS Publications Warehouse

    Lucchitta, B.K.; Ferguson, H.M.

    1986-01-01

    Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

  3. Antarctica: measuring glacier velocity from satellite images

    SciTech Connect

    Lucchitta, B.K.; Ferguson, H.M.

    1986-11-28

    Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

  4. Internationally coordinated glacier monitoring: strategy and datasets

    NASA Astrophysics Data System (ADS)

    Hoelzle, Martin; Armstrong, Richard; Fetterer, Florence; Gärtner-Roer, Isabelle; Haeberli, Wilfried; Kääb, Andreas; Kargel, Jeff; Nussbaumer, Samuel; Paul, Frank; Raup, Bruce; Zemp, Michael

    2014-05-01

    Internationally coordinated monitoring of long-term glacier changes provide key indicator data about global climate change and began in the year 1894 as an internationally coordinated effort to establish standardized observations. Today, world-wide monitoring of glaciers and ice caps is embedded within the Global Climate Observing System (GCOS) in support of the United Nations Framework Convention on Climate Change (UNFCCC) as an important Essential Climate Variable (ECV). The Global Terrestrial Network for Glaciers (GTN-G) was established in 1999 with the task of coordinating measurements and to ensure the continuous development and adaptation of the international strategies to the long-term needs of users in science and policy. The basic monitoring principles must be relevant, feasible, comprehensive and understandable to a wider scientific community as well as to policy makers and the general public. Data access has to be free and unrestricted, the quality of the standardized and calibrated data must be high and a combination of detailed process studies at selected field sites with global coverage by satellite remote sensing is envisaged. Recently a GTN-G Steering Committee was established to guide and advise the operational bodies responsible for the international glacier monitoring, which are the World Glacier Monitoring Service (WGMS), the US National Snow and Ice Data Center (NSIDC), and the Global Land Ice Measurements from Space (GLIMS) initiative. Several online databases containing a wealth of diverse data types having different levels of detail and global coverage provide fast access to continuously updated information on glacier fluctuation and inventory data. For world-wide inventories, data are now available through (a) the World Glacier Inventory containing tabular information of about 130,000 glaciers covering an area of around 240,000 km2, (b) the GLIMS-database containing digital outlines of around 118,000 glaciers with different time stamps and

  5. Modelled glacier equilibrium line altitudes during the mid-Holocene in the southern mid-latitudes

    NASA Astrophysics Data System (ADS)

    Bravo, C.; Rojas, M.; Anderson, B. M.; Mackintosh, A. N.; Sagredo, E.; Moreno, P. I.

    2015-03-01

    Glacier behaviour during the mid-Holocene (MH, 6000 year BP) in the Southern Hemisphere provides observational data to constrain our understanding of the origin and propagation of palaeo-climatic signals. We examine the climatic forcing of glacier expansion in the MH by evaluating modelled glacier equilibrium line altitude (ELA) and climate conditions during the MH compared with pre-industrial time (PI, year 1750) in the mid latitudes of the Southern Hemisphere, specifically in Patagonia and the South Island of New Zealand. Climate conditions for the MH are obtained from PMIP2 models simulations, which in turn force a simple glacier mass balance model to simulate changes in equilibrium-line altitude during this period. Climate conditions during the MH show significantly (p ≤ 0.05) colder temperatures in summer, autumn and winter, and significantly (p ≤ 0.05) warmer temperatures in spring. These changes are a consequence of insolation differences between the two periods. Precipitation does not show significant changes, but exhibits a temporal pattern with less precipitation from August to September and more precipitation from October to April during the MH. In response to these climatic changes, glaciers in both analysed regions have an ELA that is 15-33 m lower than PI during the MH. The main causes of this difference are the colder temperature during the MH, reinforcing previous results that mid-latitude glaciers are more sensitive to temperature change compared to precipitation changes. Differences in temperature have a dual effect on mass balance. First, during summer and early autumn less energy is available for melting. Second in late autumn and winter, lower temperatures cause more precipitation to fall as snow rather than rain, resulting in more accumulation and higher surface albedo. For these reasons, we postulate that the modelled ELA changes, although small, may help to explain larger glacier extents observed in the mid Holocene in both South America

  6. Molecular analysis of bacterial communities from a Canadian high Arctic polythermal glacier

    NASA Astrophysics Data System (ADS)

    Bhatia, M.; Sharp, M.; Foght, J.

    2003-04-01

    The goal of this study is to characterize the bacterial communities beneath, on, and adjacent to a high Arctic polythermal glacier, with a view to understanding the origins of the subglacial microbial population. The study site is John Evans Glacier (JEG), Ellesmere Island, Canada. JEG is a polythermal glacier consisting of a core of ice at the pressure melting point, surrounded by an outer layer of cold ice. Basal melting and seasonal inputs of meltwater from the glacier surface provide liquid water for subglacial microbial life. Samples were collected from the subglacial, supraglacial, and proglacial environments at JEG. Subglacial samples included basal ice and water that had been stored beneath the glacier. Dry snow, wet snow, and water from supraglacial streams were collected as representatives of the supraglacial environment, which changes in character through the melt season. Sediments and algal mats were collected from an area directly in front of the glacier terminus and along a transect adjacent to the glacier to reflect the developing proglacial environment. Hydrochemical analyses were conducted to assess the role of microbial activity in biogeochemical processes. To compare the bacterial communities, molecular techniques were applied to total community DNA that was released from the samples by a physical cell disruption technique. The polymerase chain reaction (PCR) was used with bacterial-specific primers, one of which was fluorescently labeled, to amplify community 16S rDNA genes. Single digestions with the restriction enzymes HaeIII and HhaI were performed to conduct inter- and intra-community comparisons of the terminal restriction fragment length polymorphisms (tRFLPs) of the fluorescently tagged amplified 16S rDNA genes. Preliminary results indicate that although some species are present throughout the different environments, several species are unique to each particular habitat. Further study of replicate tRFLP data and statistical analyses will

  7. Maintenance of biodiversity on islands.

    PubMed

    Chisholm, Ryan A; Fung, Tak; Chimalakonda, Deepthi; O'Dwyer, James P

    2016-04-27

    MacArthur and Wilson's theory of island biogeography predicts that island species richness should increase with island area. This prediction generally holds among large islands, but among small islands species richness often varies independently of island area, producing the so-called 'small-island effect' and an overall biphasic species-area relationship (SAR). Here, we develop a unified theory that explains the biphasic island SAR. Our theory's key postulate is that as island area increases, the total number of immigrants increases faster than niche diversity. A parsimonious mechanistic model approximating these processes reproduces a biphasic SAR and provides excellent fits to 100 archipelago datasets. In the light of our theory, the biphasic island SAR can be interpreted as arising from a transition from a niche-structured regime on small islands to a colonization-extinction balance regime on large islands. The first regime is characteristic of classic deterministic niche theories; the second regime is characteristic of stochastic theories including the theory of island biogeography and neutral theory. The data furthermore confirm our theory's key prediction that the transition between the two SAR regimes should occur at smaller areas, where immigration is stronger (i.e. for taxa that are better dispersers and for archipelagos that are less isolated).

  8. Maintenance of biodiversity on islands.

    PubMed

    Chisholm, Ryan A; Fung, Tak; Chimalakonda, Deepthi; O'Dwyer, James P

    2016-04-27

    MacArthur and Wilson's theory of island biogeography predicts that island species richness should increase with island area. This prediction generally holds among large islands, but among small islands species richness often varies independently of island area, producing the so-called 'small-island effect' and an overall biphasic species-area relationship (SAR). Here, we develop a unified theory that explains the biphasic island SAR. Our theory's key postulate is that as island area increases, the total number of immigrants increases faster than niche diversity. A parsimonious mechanistic model approximating these processes reproduces a biphasic SAR and provides excellent fits to 100 archipelago datasets. In the light of our theory, the biphasic island SAR can be interpreted as arising from a transition from a niche-structured regime on small islands to a colonization-extinction balance regime on large islands. The first regime is characteristic of classic deterministic niche theories; the second regime is characteristic of stochastic theories including the theory of island biogeography and neutral theory. The data furthermore confirm our theory's key prediction that the transition between the two SAR regimes should occur at smaller areas, where immigration is stronger (i.e. for taxa that are better dispersers and for archipelagos that are less isolated). PMID:27122558

  9. The 24 July 2008 outburst flood of Zyndan glacier lake, Ysyk-Köl region, Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Narama, C.; Duishonakonov, M.; Kääb, A.; Abdrakhmatov, K.

    2009-04-01

    On 24 July 2008, a glacial lake outburst flood (GLOF) occurred in the Zyndan River, the Ysyk-Köl region, Kyrgyzstan. The flood killed three people and many livestock (horse, sheep, fish), and caused heavy damage destroying a bridge, road, two homes, and crops of agriculture fields. We researched the damege after two days of the GLOF. Using kinematic GPS we measured the decrease of the glacier lake area, and the according drop of the water level through the outburst. Glacier lake area of about 0.03 km2 reduced after the collapse, more than 400,000 m3 of water were discharged. While the initial flood discharge was relatively small, it increased substantially and was carrying large boulders after 30 minutes. When spreading further downstream, the dirty waters trapped eight people on islands between the stream branches. The flood discharge continued to rise until midnight and began to decrease again around 3 AM the next morning. The lake at 3771 m asl is located in front of the west Zyndan glacier at the head of the Zyndan River basin. The glacier lake had developed rapidly due to glacier shrinkage caused by recent atmospheric warming. Reasons for the outburst included melting of dead ice inside the moraine that dammed the lake. The villages downstream escaped heavy damage, because the main flood changed its direction, away from the water reservoir along the village and towards another river.

  10. Atmospheric drying as the main driver of dramatic glacier wastage in the southern Indian Ocean

    PubMed Central

    Favier, V.; Verfaillie, D.; Berthier, E.; Menegoz, M.; Jomelli, V.; Kay, J. E.; Ducret, L.; Malbéteau, Y.; Brunstein, D.; Gallée, H.; Park, Y.-H.; Rinterknecht, V.

    2016-01-01

    The ongoing retreat of glaciers at southern sub-polar latitudes is particularly rapid and widespread. Akin to northern sub-polar latitudes, this retreat is generally assumed to be linked to warming. However, no long-term and well-constrained glacier modeling has ever been performed to confirm this hypothesis. Here, we model the Cook Ice Cap mass balance on the Kerguelen Islands (Southern Indian Ocean, 49°S) since the 1850s. We show that glacier wastage during the 2000s in the Kerguelen was among the most dramatic on Earth. We attribute 77% of the increasingly negative mass balance since the 1960s to atmospheric drying associated with a poleward shift of the mid-latitude storm track. Because precipitation modeling is very challenging for the current generation of climate models over the study area, models incorrectly simulate the climate drivers behind the recent glacier wastage in the Kerguelen. This suggests that future glacier wastage projections should be considered cautiously where changes in atmospheric circulation are expected. PMID:27580801

  11. Atmospheric drying as the main driver of dramatic glacier wastage in the southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Favier, V.; Verfaillie, D.; Berthier, E.; Menegoz, M.; Jomelli, V.; Kay, J. E.; Ducret, L.; Malbéteau, Y.; Brunstein, D.; Gallée, H.; Park, Y.-H.; Rinterknecht, V.

    2016-09-01

    The ongoing retreat of glaciers at southern sub-polar latitudes is particularly rapid and widespread. Akin to northern sub-polar latitudes, this retreat is generally assumed to be linked to warming. However, no long-term and well-constrained glacier modeling has ever been performed to confirm this hypothesis. Here, we model the Cook Ice Cap mass balance on the Kerguelen Islands (Southern Indian Ocean, 49°S) since the 1850s. We show that glacier wastage during the 2000s in the Kerguelen was among the most dramatic on Earth. We attribute 77% of the increasingly negative mass balance since the 1960s to atmospheric drying associated with a poleward shift of the mid-latitude storm track. Because precipitation modeling is very challenging for the current generation of climate models over the study area, models incorrectly simulate the climate drivers behind the recent glacier wastage in the Kerguelen. This suggests that future glacier wastage projections should be considered cautiously where changes in atmospheric circulation are expected.

  12. Union Glacier: a new exploration gateway for the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Rivera, A.; Zamora, R.; Uribe, J. A.; Jaña, R.; Oberreuter, J.

    2014-02-01

    Union Glacier (79°46' S/83°24' W) in the West Antarctic Ice Sheet (WAIS), has been used by the private company Antarctic Logistic and Expeditions (ALE) since 2007 for their landing and commercial operations, providing a unique logistic opportunity to perform glaciological research in a vast region, including the Ice divide between Institute and Pine Island glaciers and the Subglacial Lake Ellsworth. Union glacier is flowing into the Ronne Ice Shelf, where future migrations of the grounding line zone (GLZ) in response to continuing climate and oceanographic changes have been modelled. In order to analyse the potential impacts on Union glacier of this scenario, we installed an array of stakes, where ice elevation, mass balance and ice velocities have been measured since 2007, resulting in near equilibrium conditions with horizontal displacements between 10 and 33 m yr-1. GPS receivers and three radar systems have been also used to map the subglacial topography, the internal structure of the ice and the presence of crevasses along surveyed tracks. The resulting radar data showed a subglacial topography with a minimum of 858 m below sea level, much deeper than estimated before. The below sea level subglacial topography confirms the potential instability of the glacier in foreseen scenarios of GLZ upstream migration during the second half of the XXI century.

  13. Preliminary bathymetry of Blackstone Bay and Neoglacial changes of Blackstone Glaciers, Alaska

    USGS Publications Warehouse

    Post, Austin

    1980-01-01

    Preliminary bathymetry (at 1:20,000 scale) and scientific studies of Blackstone Bay Alaska, by the Research Vessel Growler in 1978 disclose that the head of the bay consists of two basins separated by Willard Island and a submarine ridge. Both basins are closed on the north by terminal-moraine bars where Blackstone Glacier and its tributaries terminated as recently as about A.D. 1350; a carbon-14 date of 580 years before present on Badger Point, and old trees farther up the bay, disclose that the glaciers retreated to two narrow inlets at the head of the bay before 1400. The inlets were still glacier-covered until at least 1909. Glaciers in both inlets have continued to retreat; at present they terminate at the head of tidewater, where they discharge small icebergs. Only relatively thin sediments have accumulated in the eastern basin south of the terminal-moraine bar, and most of the bottom is hard and irregular as disclosed by soundings and profiles. The northern part of Blackstone Bay is very deep; at more than 1,100 feet below sea level a large, level accumulation of sediment is present which is presumably as much as 1,000 feet deep and has been accumulating since late Pleistocene glaciers retreated. (USGS)

  14. Atmospheric drying as the main driver of dramatic glacier wastage in the southern Indian Ocean.

    PubMed

    Favier, V; Verfaillie, D; Berthier, E; Menegoz, M; Jomelli, V; Kay, J E; Ducret, L; Malbéteau, Y; Brunstein, D; Gallée, H; Park, Y-H; Rinterknecht, V

    2016-01-01

    The ongoing retreat of glaciers at southern sub-polar latitudes is particularly rapid and widespread. Akin to northern sub-polar latitudes, this retreat is generally assumed to be linked to warming. However, no long-term and well-constrained glacier modeling has ever been performed to confirm this hypothesis. Here, we model the Cook Ice Cap mass balance on the Kerguelen Islands (Southern Indian Ocean, 49°S) since the 1850s. We show that glacier wastage during the 2000s in the Kerguelen was among the most dramatic on Earth. We attribute 77% of the increasingly negative mass balance since the 1960s to atmospheric drying associated with a poleward shift of the mid-latitude storm track. Because precipitation modeling is very challenging for the current generation of climate models over the study area, models incorrectly simulate the climate drivers behind the recent glacier wastage in the Kerguelen. This suggests that future glacier wastage projections should be considered cautiously where changes in atmospheric circulation are expected. PMID:27580801

  15. Stable oxygen isotope variability in two contrasting glacier river catchments in Greenland

    NASA Astrophysics Data System (ADS)

    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.

    2016-03-01

    Analysis of stable oxygen isotope (δ18O) characteristics is a useful tool to investigate water provenance in glacier 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 glacier 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 melt 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 glacier. At the Kuannersuit Glacier river on the island Qeqertarsuaq in west Greenland, the δ18O characteristics were examined after the major 1995-1998 glacier surge event. The mean annual δ18O was -19.47 ± 0.55 ‰. Despite large spatial variations in the δ18O values of glacier ice on the newly formed glacier tongue, there were no diurnal oscillations in the bulk meltwater emanating from the glacier 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 glaciers 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 glacier hydrology.

  16. Harnessing Light for Faster Data Processing

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Looking for a faster computer? How about an optical computer that processes data streams simultaneously and works with the speed of light? In space, NASA researchers have formed optical thin-film. By turning these thin-films into very fast optical computer components, scientists could improve computer tasks, such as pattern recognition. Dr. Hossin Abdeldayem, physicist at NASA/Marshall Space Flight Center (MSFC) in Huntsville, Al, is working with lasers as part of an optical system for pattern recognition. These systems can be used for automated fingerprinting, photographic scarning and the development of sophisticated artificial intelligence systems that can learn and evolve. Photo credit: NASA/Marshall Space Flight Center (MSFC)

  17. Columbia Glacier, Alaska recent ice loss and its relationship to seasonal terminal embayments, thinning and glacial flow

    USGS Publications Warehouse

    Sikonia, W.G.; Post, Austin

    1980-01-01

    In 1974 the U.S. Geological Survey began an intensive investigation of the stability of Columbia Glacier, a calving tidewater galcier terminating in Columbia Bay, near Valdez, Alaska. Aerial photographs taken in 1957 and a sequence of photographs taken at about 2-month intervals since 1976, when analyzed photogrammetrically, provided detailed data on changes in Columbia Glacier 's thickness, flow rate, and terminal position. Annual embayments in the glacier 's terminus form during the summer-autumn season in most years; the size of embayments appears to be related to (1) the thickness of the glacier, and (2) the position and nature of subglacial freshwater discharge. Embayments have apparently increased in size in recent years; the largest embayments yet observed formed in 1975, 1976, 1977, and 1978. From April 1, 1977, to April 1, 1978, the total volume of ice calved was about 1.0 cubic kilometer. By January 1979 the glacier front had retreated from Heather Island. Glacier flow varies seasonally and synchronously in the lower 17 kilometers of the glacier; large accelerations occur near the terminus in response to embayment formation. Daily speed within 5 kilometers of the terminus increased from about 1.9 meters per day between 1963 and 1968 to about 2.7 meters per day between 1977 and 1978. In the lowest 15 kilometers, the glacier surface was lowered about 9 meters between 1957 and 1974, and about 13 meters between 1974 and 1978. Columbia Glacier is being reduced in mass due, in part, to recent losses caused by large embayments forming annually. If such reduction continues it will result in a drastic retreat. (USGS)

  18. LOUISIANA BARRIER ISLAND EROSION STUDY.

    USGS Publications Warehouse

    Sallenger,, Asbury H.; Penland, Shea; Williams, S. Jeffress; Suter, John R.

    1987-01-01

    During 1986, the U. S. Geological Survey and the Louisiana Geological Survey began a five-year cooperative study focused on the processes which cause erosion of barrier islands. These processes must be understood in order to predict future erosion and to better manage our coastal resources. The study area includes the Louisiana barrier islands which serve to protect 41% of the nation's wetlands. These islands are eroding faster than any other barrier islands in the United States, in places greater than 20 m/yr. The study is divided into three parts: geological development of barrier islands, quantitative processes of barrier island erosion and applications of results. The study focuses on barrier islands in Louisiana although many of the results are applicable nationwide.

  19. Integration of glacier databases within the Global Terrestrial Network for Glaciers (GTN-G)

    NASA Astrophysics Data System (ADS)

    Zemp, M.; Raup, B. H.; Armstrong, R.; Ballagh, L.; Gärtner-Roer, I.; Haeberli, W.; Hoelzle, M.; Kääb, A.; Kargel, J.; Paul, F.

    2009-04-01

    Changes in glaciers and ice caps provide some of the clearest evidence of climate change and have impacts on global sea level fluctuations, regional hydrological cycles and local natural hazard situations. Internationally coordinated collection and distribution of standardized information about glaciers and ice caps was initiated in 1894 and is today coordinated within the Global Terrestrial Network for Glaciers (GTN-G). A recently established GTN-G Steering Committee coordinates, supports and advices the operational bodies responsible for the international glacier monitoring, which are the World Glacier Monitoring Service (WGMS), the US National Snow and Ice Data Center (NSIDC) and the Global Land Ice Measurements from Space (GLIMS) initiative. In this presentation, we provide an overview of (i) the integration of the various operational databases, (ii) the development of a one-stop web-interface to these databases, and (iii) the available datasets. By joint efforts consistency and interoperability of the different glacier databases is elaborated. Thereby, the lack of a complete worldwide, detailed glacier inventory as well as different historical developments and methodological contexts of the datasets are major challenges for linking individual glaciers throughout the databases. A map-based web-interface, implemented based on OpenLayer 2.0 and Web Map/Feature Services, is elaborated to spatially link the available data and to provide data users a fast overview of all available data. With this new online service, GTN-G provides fast access to information on glacier inventory data from 100,000 glaciers mainly based on aerial photographs and from 80,000 glaciers mainly based on satellite images, length change series from 1,800 glaciers, mass balance series from 230 glaciers, special events (e.g., hazards, surges, calving instabilities) from 130 glaciers, as well as 10,000 photographs from some 470 glaciers.

  20. Brief communication: Getting Greenland's glaciers right - a new data set of all official Greenlandic glacier names

    NASA Astrophysics Data System (ADS)

    Bjørk, A. A.; Kruse, L. M.; Michaelsen, P. B.

    2015-12-01

    Place names in Greenland can be difficult to get right, as they are a mix of Greenlandic, Danish, and other foreign languages. In addition, orthographies have changed over time. With this new data set, we give the researcher working with Greenlandic glaciers the proper tool to find the correct name for glaciers and ice caps in Greenland and to locate glaciers described in the historic literature with the old Greenlandic orthography. The data set contains information on the names of 733 glaciers, 285 originating from the Greenland Ice Sheet (GrIS) and 448 from local glaciers and ice caps (LGICs).

  1. Advances in Modelling of Valley Glaciers

    NASA Astrophysics Data System (ADS)

    Adhikari, Surendra

    For glaciological conditions typical of valley glaciers, the central idea of this research lies in understanding the effects of high-order mechanics and parameterizing these for simpler dynamical and statistical methods in glaciology. As an effective tool for this, I formulate a new brand of dynamical models that describes distinct physical processes of deformational flow. Through numerical simulations of idealized glacier domains, I calculate empirical correction factors to capture the effects of longitudinal stress gradients and lateral drag for simplified dynamical models in the plane-strain regime. To get some insights into real glacier dynamics, I simulate Haig Glacier in the Canadian Rocky Mountains. As geometric effects overshadow dynamical effects in glacier retreat scenarios, it appears that high-order physics are not very important for Haig Glacier, particularly for evaluating its fate. Indeed, high-order and reduced models all predict that Haig Glacier ceases to exist by about AD2080 under ongoing climate warming. This finding regarding the minimal role of high-order physics may not be broadly valid, as it is not true in advance scenarios at Haig Glacier and it may not be representative of other glaciological settings. Through a 'bulk' parameterization of high-order physics, geometric and climatic settings, sliding conditions, and transient effects, I also provide new insights into the volume-area relation, a widely used statistical method for estimating glacier volume. I find a steady-state power-law exponent of 1:46, which declines systematically to 1:38 after 100 years of sustained retreat, in good accord with the observations. I recommend more accurate scaling relations through characterization of individual glacier morphology and degree of climatic disequilibrium. This motivates a revision of global glacier volume estimates, of some urgency in sea level rise assessments.

  2. Tracking glaciers with the Alaska seismic network

    NASA Astrophysics Data System (ADS)

    West, M. E.

    2015-12-01

    More than 40 years ago it was known that calving glaciers in Alaska created unmistakable seismic signals that could be recorded tens and hundreds of kilometers away. Their long monochromatic signals invited studies that foreshadowed the more recent surge in glacier seismology. Beyond a handful of targeted studies, these signals have remained a seismic novelty. No systematic attempt has been made to catalog and track glacier seismicity across the years. Recent advances in understanding glacier sources, combined with the climate significance of tidewater glaciers, have renewed calls for comprehensive tracking of glacier seismicity in coastal Alaska. The Alaska Earthquake Center has included glacier events in its production earthquake catalog for decades. Until recently, these were best thought of as bycatch—accidental finds in the process of tracking earthquakes. Processing improvements a decade ago, combined with network improvements in the past five years, have turned this into a rich data stream capturing hundreds of events per year across 600 km of the coastal mountain range. Though the source of these signals is generally found to be iceberg calving, there are vast differences in behavior between different glacier termini. Some glaciers have strong peaks in activity during the spring, while others peak in the late summer or fall. These patterns are consistent over years pointing to fundamental differences in calving behavior. In several cases, changes in seismic activity correspond to specific process changes observed through other means at particular glacier. These observations demonstrate that the current network is providing a faithful record of the dynamic behavior of several glaciers in coastal Alaska. With this as a starting point, we examine what is possible (and not possible) going forward with dedicated detection schemes.

  3. Development of the FASTER Wheeled Bevameter

    NASA Astrophysics Data System (ADS)

    Richter, L.; Eder, V.; Hoheneder, W.; Imhof, B.; Lewinger, W.; Ransom, S.; Saaj, C.; Weclewski, P.; Waclavicek, R.,

    2014-04-01

    This paper describes the development of a Wheeled Bevameter (WB) within the FASTER project (Forward Acquisition of Soil and Terrain Data for Exploration Rovers), funded by the European Union's FP7 programme. In FASTER, novel and innovative concepts for in situ forward sensing of soil properties and terrain conditions in the planned path of a planetary rover are developed. Terrain strength measurements for assessment of the mobility of crosscountry vehicles have decades of heritage on Earth, but typically trafficability of terrains is only gauged by human operators ahead of vehicle operations rather than in-line by probes deployed from the vehicle itself, as is intended for FASTER. For FASTER, a Wheeled Bevameter (WB) has been selected as the terrain sensing instrument for the vehicle. Wheeled Bevameters are suitable for terrain measurements while driving but traditionally have mostly been employed on terrestrial vehicles to evaluate particular wheel designs. The WB as conceived in FASTER uses a dedicated, passive-rolling test wheel (‚test wheel') placed on the terrain as the loading device to enable to determine bearing strength, compressive strength and shear strength of the terrain immediately ahead of the vehicle, as well as rover-terrain interaction parameters used in semi-empirical vehicle-terrain traction models. The WB includes a placement mechanism for the test wheel. The test wheel would remain lowered onto the ground during nominal rover motion, including when climbing and descending slopes. During normal operations, the placement mechanism assumes the function of a passive suspension of the wheel, allowing it to follow the terrain contour. Quantities measured with the WB are: test wheel sinkage (through a laser sensor), test wheel vertical load, test wheel horizontal reaction force, and test wheel rotation rate. Measurements are performed while the rover is in motion. Measured test wheel rotation rate (with appropriate corrections for slight skid) can

  4. 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%.

  5. Microbial biodiversity in glacier-fed streams

    PubMed Central

    Wilhelm, Linda; Singer, Gabriel A; Fasching, Christina; Battin, Tom J; Besemer, Katharina

    2013-01-01

    While glaciers become increasingly recognised as a habitat for diverse and active microbial communities, effects of their climate change-induced retreat on the microbial ecology of glacier-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 glaciers, we show how microbial community composition and diversity, based on 454-pyrosequencing of the 16S rRNA gene, in biofilms of glacier-fed streams may change as glaciers 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 glacier-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 glacier retreat may contribute to the homogenisation of microbial communities among glacier-fed streams. PMID:23486246

  6. Microbial biodiversity in glacier-fed streams.

    PubMed

    Wilhelm, Linda; Singer, Gabriel A; Fasching, Christina; Battin, Tom J; Besemer, Katharina

    2013-08-01

    While glaciers become increasingly recognised as a habitat for diverse and active microbial communities, effects of their climate change-induced retreat on the microbial ecology of glacier-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 glaciers, we show how microbial community composition and diversity, based on 454-pyrosequencing of the 16S rRNA gene, in biofilms of glacier-fed streams may change as glaciers 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 glacier-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 glacier retreat may contribute to the homogenisation of microbial communities among glacier-fed streams.

  7. Using Metaphorical Models for Describing Glaciers

    ERIC Educational Resources Information Center

    Felzmann, Dirk

    2014-01-01

    To date, there has only been little conceptual change research regarding conceptions about glaciers. This study used the theoretical background of embodied cognition to reconstruct different metaphorical concepts with respect to the structure of a glacier. Applying the Model of Educational Reconstruction, the conceptions of students and scientists…

  8. Debris-covered Himalayan glaciers under a changing climate: observations and modelling of Khumbu Glacier, Nepal

    NASA Astrophysics Data System (ADS)

    Rowan, Ann; Quincey, Duncan; Egholm, David; Gibson, Morgan; Irvine-Fynn, Tristram; Porter, Philip; Glasser, Neil

    2016-04-01

    Many mountain glaciers are characterised in their lower reaches by thick layers of rock debris that insulate the glacier surface from solar radiation and atmospheric warming. Supraglacial debris modifies the response of these glaciers to climate change compared to glaciers with clean-ice surfaces. However, existing modelling approaches to predicting variations in the extent and mass balance of debris-covered glaciers have relied on numerical models that represent the processes governing glaciers with clean-ice surfaces, and yield conflicting results. Moreover, few data exist describing the mass balance of debris-covered glaciers 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 glacier 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 glacier - Khumbu Glacier in the Everest region of Nepal. Our results demonstrate that supraglacial debris prolongs the response of the glacier to warming air temperatures and causes lowering of the glacier 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 Glacier has reduced by 34%, while glacier area has reduced by only 6%. We predict a further decrease in glacier volume of 8-10% by AD2100 accompanied by dynamic and physical detachment of the debris-covered tongue from the active glacier 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 Glacier. We found that temperatures at the ice surface beneath 0.4-0.7 m of debris were sufficient to promote considerable

  9. 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.

  10. Reconstructing the history of major Greenland glaciers since the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Csatho, B. M.; Schenk, A. F.; van der Veen, C. J.; Stearns, L.; Babonis, G. S.

    2008-12-01

    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 glaciers 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 glaciers 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 glacier 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 glaciers, Jakobshavn Isbrae in west, Kangerdlussuaq Glacier in east and Petermann Glacier in northwest Greenland. Glacier 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 melting, and to isolate

  11. Pigeons home faster through polluted air

    PubMed Central

    Li, Zhongqiu; Courchamp, Franck; Blumstein, Daniel T.

    2016-01-01

    Air pollution, especially haze pollution, is creating health issues for both humans and other animals. However, remarkably little is known about how animals behaviourally respond to air pollution. We used multiple linear regression to analyse 415 pigeon races in the North China Plain, an area with considerable air pollution, and found that while the proportion of pigeons successfully homed was not influenced by air pollution, pigeons homed faster when the air was especially polluted. Our results may be explained by an enhanced homing motivation and possibly an enriched olfactory environment that facilitates homing. Our study provides a unique example of animals’ response to haze pollution; future studies are needed to identify proposed mechanisms underlying this effect. PMID:26728113

  12. Darks are processed faster than lights.

    PubMed

    Komban, Stanley Jose; Alonso, Jose-Manuel; Zaidi, Qasim

    2011-06-01

    Recent physiological studies claim that dark stimuli have access to greater neuronal resources than light stimuli in early visual pathway. We used two sets of novel stimuli to examine the functional consequences of this dark dominance in human observers. We show that increment and decrement thresholds are equal when controlled for adaptation and eye movements. However, measurements for salience differences at high contrasts show that darks are detected pronouncedly faster and more accurately than lights when presented against uniform binary noise. In addition, the salience advantage for darks is abolished when the background distribution is adjusted to control for the irradiation illusion. The threshold equality suggests that the highest sensitivities of neurons in the ON and OFF channels are similar, whereas the salience difference is consistent with a population advantage for the OFF system. PMID:21653869

  13. Pigeons home faster through polluted air

    NASA Astrophysics Data System (ADS)

    Li, Zhongqiu; Courchamp, Franck; Blumstein, Daniel T.

    2016-01-01

    Air pollution, especially haze pollution, is creating health issues for both humans and other animals. However, remarkably little is known about how animals behaviourally respond to air pollution. We used multiple linear regression to analyse 415 pigeon races in the North China Plain, an area with considerable air pollution, and found that while the proportion of pigeons successfully homed was not influenced by air pollution, pigeons homed faster when the air was especially polluted. Our results may be explained by an enhanced homing motivation and possibly an enriched olfactory environment that facilitates homing. Our study provides a unique example of animals’ response to haze pollution; future studies are needed to identify proposed mechanisms underlying this effect.

  14. Microbial communities evolve faster in extreme environments

    PubMed Central

    Li, Sheng-Jin; Hua, Zheng-Shuang; Huang, Li-Nan; Li, Jie; Shi, Su-Hua; Chen, Lin-Xing; Kuang, Jia-Liang; Liu, Jun; Hu, Min; Shu, Wen-Sheng

    2014-01-01

    Evolutionary analysis of microbes at the community level represents a new research avenue linking ecological patterns to evolutionary processes, but remains insufficiently studied. Here we report a relative evolutionary rates (rERs) analysis of microbial communities from six diverse natural environments based on 40 metagenomic samples. We show that the rERs of microbial communities are mainly shaped by environmental conditions, and the microbes inhabiting extreme habitats (acid mine drainage, saline lake and hot spring) evolve faster than those populating benign environments (surface ocean, fresh water and soil). These findings were supported by the observation of more relaxed purifying selection and potentially frequent horizontal gene transfers in communities from extreme habitats. The mechanism of high rERs was proposed as high mutation rates imposed by stressful conditions during the evolutionary processes. This study brings us one stage closer to an understanding of the evolutionary mechanisms underlying the adaptation of microbes to extreme environments. PMID:25158668

  15. Glaciers in 21st Century Himalayan Geopolitics

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.; Wessels, R.; Kieffer, H. H.

    2002-05-01

    Glaciers are ablating rapidly the world over. Nowhere are the rates of retreat and downwasting greater than in the Hindu Kush-Himalaya (HKH) region. It is estimated that over the next century, 40,000 square kilometers of present glacier area in the HKH region will become ice free. Most of this area is in major valleys and the lowest glaciated mountain passes. The existence and characteristics of glaciers have security impacts, and rapidly changing HKH glaciers have broad strategic implications: (1) Glaciers supply much of the fresh water and hydroelectric power in South and Central Asia, and so glaciers are valuable resources. (2) Shared economic interests in water, hydroelectricity, flood hazards, and habitat preservation are a force for common cause and reasoned international relations. (3) Glaciers and their high mountains generally pose a natural barrier tending to isolate people. Historically, they have hindered trade and intercultural exchanges and have protected against aggression. This has further promoted an independent spirit of the region's many ethnic groups. (4) Although glaciers are generally incompatible with human development and habitation, many of the HKH region's glaciers and their mountains have become sanctuaries and transit routes for militants. Siachen Glacier in Kashmir has for 17 years been "the world's highest battlefield," with tens of thousands of troops deployed on both sides of the India/Pakistan line of control. In 1999, that conflict threatened to trigger all-out warfare, and perhaps nuclear warfare. Other recent terrorist and military action has taken place on glaciers in Kyrgyzstan and Tajikistan. As terrorists are forced from easily controlled territories, many may tend to migrate toward the highest ground, where definitive encounters may take place in severe alpine glacial environments. This should be a major concern in Nepali security planning, where an Army offensive is attempting to reign in an increasingly robust and brutal

  16. Recent fluctuations of the Argentinian glaciers

    NASA Astrophysics Data System (ADS)

    Leiva, Juan Carlos

    1999-10-01

    Some of the results obtained in the glaciological research carried out since 1979 at the Argentinian Andes are shown in this paper. The research covers a wide latitudinal gap extending from the Agua Negra glacier in the province of San Juan to the Frı´as glacier situated at Mount Tronador. Agua Negra and Piloto glaciers show a very similar behavior of almost continuous retreat since 1965 while at the Plomo region a small advance period, starting in 1982, is observed in five of the 10 glaciers studied. Finally, the Frı´as glacier fluctuations record shows a very strong recession since 1850 only interrupted by the 1976 advance that continued in 1977.

  17. ICESat laser altimetry over small mountain glaciers

    NASA Astrophysics Data System (ADS)

    Treichler, Désirée; Kääb, Andreas

    2016-09-01

    Using sparsely glaciated southern Norway as a case study, we assess the potential and limitations of ICESat laser altimetry for analysing regional glacier elevation change in rough mountain terrain. Differences between ICESat GLAS elevations and reference elevation data are plotted over time to derive a glacier surface elevation trend for the ICESat acquisition period 2003-2008. We find spatially varying biases between ICESat and three tested digital elevation models (DEMs): the Norwegian national DEM, SRTM DEM, and a high-resolution lidar DEM. For regional glacier elevation change, the spatial inconsistency of reference DEMs - a result of spatio-temporal merging - has the potential to significantly affect or dilute trends. Elevation uncertainties of all three tested DEMs exceed ICESat elevation uncertainty by an order of magnitude, and are thus limiting the accuracy of the method, rather than ICESat uncertainty. ICESat matches glacier size distribution of the study area well and measures small ice patches not commonly monitored in situ. The sample is large enough for spatial and thematic subsetting. Vertical offsets to ICESat elevations vary for different glaciers in southern Norway due to spatially inconsistent reference DEM age. We introduce a per-glacier correction that removes these spatially varying offsets, and considerably increases trend significance. Only after application of this correction do individual campaigns fit observed in situ glacier mass balance. Our correction also has the potential to improve glacier trend significance for other causes of spatially varying vertical offsets, for instance due to radar penetration into ice and snow for the SRTM DEM or as a consequence of mosaicking and merging that is common for national or global DEMs. After correction of reference elevation bias, we find that ICESat provides a robust and realistic estimate of a moderately negative glacier mass balance of around -0.36 ± 0.07 m ice per year. This regional

  18. Ice flow and mass continuity of Shumsky Glacier in the Djungarski Alatau Range of Kazakhstan, Central Asia

    NASA Astrophysics Data System (ADS)

    Cherkasov, Piotr A.; Ahmetova, Galia S.; Hastenrath, Stefan

    1996-05-01

    The glaciological monitoring program on the Shumsky Glacier in the Djungarski Alatau Range of southeastern Kazakhstan has included measurements of horizontal surface ice flow velocity, net balance, and emergence velocity at a network of more than 200 stakes during 1967-1991, as well as mappings of the ice surface topography by double-theodolite triangulation and determination of ice thickness and of bedrock topography by radio echo sounding in 1984. These observations are here evaluated together to deduce the long-term average dynamic behavior of Shumsky Glacier. The glacier extends between 3100 and 4400 m with a total area of 3 km2 and length of nearly 4 km. Maximum surface velocity is 20 m yr-1 and maximum volume flux 9 × 105 m3 yr-1, located near the equilibrium line altitude around 3680 m. The ice-volume-equivalent net balance is +0.5 m yr-1 in the average over the accumulation area, changing to about -1.5 m yr-1 near the terminus. The submergent flow in the accumulation area changes to emergence of 1 m yr-1 in the lower glacier. The rate of ice thinning is less than 0.1 m yr-1 in the middle glacier, increases to 2.5 m yr-1 near the terminus, and averages 0.12 m yr-1 for the glacier as whole. In fact, the Shumsky glacier differs little from equilibrium, being in a more favorable location that the other glaciers of the Djungarski Alatau. However, trends toward slower ice flow, more negative net balance, and faster rate of ice thinning indicate response to a progressively adverse climatic environment.

  19. Erosion and transport by Byrd Glacier, Antarctica during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Licht, K. J.; Palmer, E. F.

    2013-02-01

    Glacial till samples from seven, modern-Holocene Byrd Glacier moraines were characterized using particle size analysis, sand petrography and detrital zircon geochronology and compared to Ross Sea tills deposited during the Last Glacial Maximum. The goal was to identify the paleoflow path for Byrd Glacier and assess the use of multiple provenance techniques. The coarse sand fraction of Byrd Glacier tills is dominated by lithic fragments of adjacent bedrock outcrops, except samples from the Lonewolf Nunataks, which have a higher proportion of mineral to lithic fragments, as well as a recognizable exotic component. Cluster analysis shows that Byrd Glacier tills, with the exception of the two Lonewolf Nunataks sites, do not cluster strongly with Ross Sea samples because they have a higher proportion of lithic fragments. This indicates that comminution must be an active subglacial process beneath East Antarctic outlet glaciers. Byrd Glacier tills are also typically coarser grained that Ross Sea tills and their maturity is a reflection of both glacial processes and rock type. Measured U/Pb ages of detrital zircons from Byrd Glacier tills range from Triassic to Archean (240-3540 Ma) with a dominance of grains 530-600 Ma. Ross Sea till samples show spatial variability in U/Pb age distributions, with the core sites west of the 180° longitude line showing similarity to most Byrd Glacier tills, whereas core NBP9407-39, east of 180° long., is dominated by ˜100 Ma grains. Ross Sea tills also contain a recognizable detrital zircon fraction eroded inland of the Transantarctic Mountains. Both provenance methods indicate that the ice flow line for Byrd Glacier during the LGM was to the east of Ross Island and extended on either side of Ross Bank, with the majority of ice flowing to the Ross Sea's Central Basin. Our analysis shows that sand petrography and detrital zircon U/Pb age spectra provide complementary datasets that produce similar ice flow reconstructions and reveal

  20. Black soot and the survival of Tibetan glaciers

    PubMed Central

    Xu, Baiqing; Cao, Junji; Hansen, James; Yao, Tandong; Joswia, Daniel R.; Wang, Ninglian; Wu, Guangjian; Wang, Mo; Zhao, Huabiao; Yang, Wei; Liu, Xianqin; He, Jianqiao

    2009-01-01

    We find evidence that black soot aerosols deposited on Tibetan glaciers have been a significant contributing factor to observed rapid glacier retreat. Reduced black soot emissions, in addition to reduced greenhouse gases, may be required to avoid demise of Himalayan glaciers and retain the benefits of glaciers for seasonal fresh water supplies. PMID:19996173

  1. Numerical modelling of the effect of changing surface geometry on mountain glacier mass balance

    NASA Astrophysics Data System (ADS)

    Williams, C.; Carrivick, J.; Evans, A.; Carver, S.

    2012-12-01

    Mountain glaciers and ice caps are extremely useful indicators of environmental change. Due to their small size, they have much faster response times to climate changes than the large ice masses of Greenland and Antarctica. Mountain glaciers are important for society as sources of water for energy production and irrigation. The meltwater cycles significantly impact local ecology. Consequently, models assessing the effect of complicated glacier surface geometry on glacier mass balance are becoming increasingly popular. Here we apply such a model to a glacier record spanning 100 years. Our study encompasses the creation of a GIS enabling analysis of changing glacier geometry over the 20th and early 21st Centuries and the development and testing of a novel user-friendly distributed-surface energy balance model that is designed specifically to consider the effect that these changes have on mountain glacier mass balance. Long-term records of mass balance are rare for arctic Mountain glaciers, making model development and evaluation difficult. One exception is Kårsaglaciären in arctic Sweden for which there is a variety of data for the past 100 years, sourced from historical surveys, satellite imagery and recent field work. Firstly, we present the construction of robust three-dimensional glacier surface reconstructions for Kårsaglaciären within a GIS, specifically discussing the methods of interpolation used to create the surfaces. We highlight the methods and importance of inter-model sensitivity analyses as well as Monte Carlo simulations used to assess the effect of the input data utilised in the kriging algorithms. Analyses integral to the modelling stage of the project, such as the geometries of the resultant surfaces as well as the interrelationships between them, will be discussed. Secondly, we present the melt model which has been constructed in order to test the effect of changing geometry on mass balance. Our melt model can carry out systematic testing of

  2. Quantifying global warming from the retreat of glaciers

    SciTech Connect

    Oerlemans, J. )

    1994-04-08

    Records of glacier fluctuations compiled by the World Glacier Monitoring Service can be used to derive an independent estimate of global warming during the last 100 years. Records of different glaciers are made comparable by a two-step scaling procedure; one allowing for differences in glacier geometry, the other for differences in climate sensitivity. The retreat of glaciers during the last 100 years appears to be coherent over the globe. On the basis of modeling of the climate sensitivity of glaciers, the observed glacier retreat can be explained by a linear warming trend of 0.66 kelvin per century.

  3. Why are halo coronal mass ejections faster?

    NASA Astrophysics Data System (ADS)

    Zhang, Qing-Min; Guo, Yang; Chen, Peng-Fei; Ding, Ming-De; Fang, Cheng

    2010-05-01

    Halo coronal mass ejections (CMEs) have been to be significantly faster than normal CMEs, which is a long-standing puzzle. In order to solve the puzzle, we first investigate the observed properties of 31 limb CMEs that clearly display loop-shaped frontal loops. The observational results show a strong tendency that slower CMEs are weaker in white-light intensity. Then, we perform a Monte Carlo simulation of 20000 artificial limb CMEs that have an average velocity of ~523 km s-1. The Thomson scattering of these events is calculated when they are assumed to be observed as limb and halo events, respectively. It is found that the white-light intensity of many slow CMEs becomes remarkably reduced when they turn from being viewed as a limb event to being viewed as a halo event. When the intensity is below the background solar wind fluctuation, it is assumed that they would be missed by coronagraphs. The average velocity of “detectable" halo CMEs is ~922 km s-1 very close to the observed value. This also indicates that wider events are more likely to be recorded. The results soundly suggest that the higher average velocity of halo CMEs is due to that a majority of slow events and some of narrow fast events carrying less material are so faint that they are blended with the solar wind fluctuations, and therefore are not observed.

  4. How to drill horizontal sections faster

    SciTech Connect

    Chaffin, M. )

    1991-12-01

    This paper reports that fewer trips, reduced slide time and lower drag during sliding have resulted from the application of downhole-adjustable stabilizers to horizontal drilling. Faster drilling times mean lower measurement while drilling (MWD) cost, and less wear on downhole equipment, motors and bits. These advantages combined with reduced drilling shocks have increased drilling rates and efficiency. Applying existing technology in new situations is an important way of reducing the cost of finding, exploring for and developing reserves. Engineers are responsible for using current technology to its fullest and developing new technology to reduce drilling expenses. Horizontal drilling was used in its early stages to develop the Austin chalk formation in Pearsall oil field more effectively. As procedures were generated to drill horizontal wells, Oryx drilling engineers began to develop new technology and investigate ways for existing technology to be used or altered to fit horizontal drilling programs. The new technology of downhole-adjustable stabilizers has been used successfully to further improve horizontal drilling efficiency.

  5. Fast Physics Testbed for the FASTER Project

    SciTech Connect

    Lin, W.; Liu, Y.; Hogan, R.; Neggers, R.; Jensen, M.; Fridlind, A.; Lin, Y.; Wolf, A.

    2010-03-15

    This poster describes the Fast Physics Testbed for the new FAst-physics System Testbed and Research (FASTER) project. The overall objective is to provide a convenient and comprehensive platform for fast turn-around model evaluation against ARM observations and to facilitate development of parameterizations for cloud-related fast processes represented in global climate models. The testbed features three major components: a single column model (SCM) testbed, an NWP-Testbed, and high-resolution modeling (HRM). The web-based SCM-Testbed features multiple SCMs from major climate modeling centers and aims to maximize the potential of SCM approach to enhance and accelerate the evaluation and improvement of fast physics parameterizations through continuous evaluation of existing and evolving models against historical as well as new/improved ARM and other complementary measurements. The NWP-Testbed aims to capitalize on the large pool of operational numerical weather prediction products. Continuous evaluations of NWP forecasts against observations at ARM sites are carried out to systematically identify the biases and skills of physical parameterizations under all weather conditions. The highresolution modeling (HRM) activities aim to simulate the fast processes at high resolution to aid in the understanding of the fast processes and their parameterizations. A four-tier HRM framework is established to augment the SCM- and NWP-Testbeds towards eventual improvement of the parameterizations.

  6. Glaciers in Patagonia: Controversy and prospects

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.; Alho, P.; Buytaert, W.; Célleri, R.; Cogley, J. G.; Dussaillant, A.; Guido, Z.; Haeberli, W.; Harrison, S.; Leonard, G.; Maxwell, A.; Meier, C.; Poveda, G.; Reid, B.; Reynolds, J.; Rodríguez, C. A. Portocarrero; Romero, H.; Schneider, J.

    2012-05-01

    Lately, glaciers have been subjects of unceasing controversy. Current debate about planned hydroelectric facilities—a US7- to 10-billion megaproject—in a pristine glacierized area of Patagonia, Chile [Romero Toledo et al., 2009; Vince, 2010], has raised anew the matter of how glaciologists and global change experts can contribute their knowledge to civic debates on important issues. There has been greater respect for science in this controversy than in some previous debates over projects that pertain to glaciers, although valid economic motivations again could trump science and drive a solution to the energy supply problem before the associated safety and environmental problems are understood. The connection between glaciers and climate change—both anthropogenic and natural—is fundamental to glaciology and to glaciers' practical importance for water and hydropower resources, agriculture, tourism, mining, natural hazards, ecosystem conservation, and sea level [Buytaert et al., 2010; Glasser et al., 2011]. The conflict between conservation and development can be sharper in glacierized regions than almost anywhere else. Glaciers occur in spectacular natural landscapes, but they also supply prodigious exploitable meltwater.

  7. Glacier Monitoring: Opportunities, Accomplishments, and Limitations.

    NASA Astrophysics Data System (ADS)

    Meier, M. F.; Dyurgerov, M. B.

    2001-12-01

    Glaciers and ice caps, exclusive of the two major ice sheets, have been monitored for more than a century. Initially sparked by interest in the effect of glaciers on the landscape and their sensitive response to changes of climate, glacier study is now additionally motivated because of impacts on cold-regions ecology and hydrology as well as global sea-level rise. Glacier observations in many areas provide the only real data on climate change in the mountains. A substantial number of mass balance programs were initiated during the 1960s that improved our understanding of spatial and temporal changes in climate, and provided a basis for projecting future changes to glaciers and sea level. These results show a general increase in both snow accumulation and ice melting during the last 40 years (but with net wastage predominating), and a marked increase in the sensitivity of ice wastage to air temperature since the late 1980s. The World Data Center system provided unrestricted exchange of data among glaciologists during the `cold war.' The World Glacier Monitoring Service together with the National Snow and Ice Data Center and several individuals now provide ready access to glacier data. Remaining problems include inadequate access to digital data, a size bias to small glaciers, some traditional methodologies which limit the usefulness of the results, slow incorporation of new technologies, complexity of incorporating glacier dynamics in mass balance analysis, and insufficient attention by some investigators to reporting observational error. Perhaps the most difficult problems are the extension of limited data to the synthesis of broad regional or global conclusions, and a general dwindling of support for monitoring activities.

  8. Recent Ice Loss from the Fleming and Other Glaciers, Wordie Bay, West Antarctic Peninsula

    NASA Technical Reports Server (NTRS)

    Rignot, E.; Casassa, G.; Gogineni, S.; Kanagaratnam, P.; Krabill, W.; Pritchard, H.; Rivera, A.; Thomas, R.; Turner, J.; Vaughan, D.

    2005-01-01

    Satellite radar interferometry data from 1995 to 2004, and airborne ice thickness data from 2002, reveal that the glaciers flowing into former Wordie Ice Shelf, West Antarctic Peninsula, discharge 6.8 +/- 0.3 km(exp 3)/yr of ice, which is 84 +/- 30 percent larger than a snow accumulation of 3.7 +/- 0.8 km(exp 3)/yr over a 6,300 km(exp 2) drainage basin. Airborne and ICESat laser altimetry elevation data reveal glacier thinning at rates up to 2 m/yr. Fifty km from its ice front, Fleming Glacier flows 50 percent faster than it did in 1974 prior to the main collapse of Wordie Ice Shelf. We conclude that the glaciers accelerated following ice shelf removal, and have been thinning and losing mass to the ocean over the last decade. This and other observations suggest that the mass loss from the northern part of the Peninsula is not negligible at present.

  9. Central Himalayan Glaciers and Climate Change- Pinder Glacier- A preliminary study

    NASA Astrophysics Data System (ADS)

    Pillai, J.; Patel, L. K.

    2011-12-01

    Glaciers in the Indian Himalayan Region (IHR) are the prime lifeline of Indian Subcontinent. There are about nine thousand glaciers of different size in this region. It is located within the latitudes 270N to 360N and longitude 720E to 960E. The second largest glacier, outside the polar and sub polar regions, Siachen glacier of length 74 km, is located in IHR. Many rivers in this continent originated from these glaciers. Study on the fluctuations especially of the snow cover and related parameters are important for the proper management of these rivers. Annual balance, fluctuations of glaciers, hydrological behaviour and the assessment of the winter snow pack are also critical for the proper flow and control of Himalayan Rivers. There are many hydroelectric and irrigation facilities in these snow fed rivers. Glacial melt is important as far as the river flow is concerned. Researchers had observed that the glacial mass balance has been found to show an inverse relationship with the monsoon. Glacial hydrometry and glacial melt are important aspects as far the studies of glaciers in this region. Himalayan glaciers are also important for ecosystem stability. In this perspective attempts had been made to examine the various environmental parameters of Pindari glacier and the upper reaches of the Pindari river. Pindari glacier is located in the Central Himalayan region. It is of length 8 Km. A few records available with Geological Survey of India for a period of hundred years reveals that Pindari glacial have an annual retreat of 8-10 M. Pindrai glacier had retreated about 425 M with in a period of fifty seven years. Pindari river originates from the buffer zone of Nanda Devi Biosphere Reserve (NDBR) and is located in the lower regime of Pindari glacier. It is one of the prominent tributaries of Alaknanda. Tributaries of Pindari river are from Maktoli glacier, Kafani glacier and Sunderdhunga glacier. The changes in the Pindiari catchment area had been examined from the

  10. Classification of debris-covered glaciers and rock glaciers in the Andes of central Chile

    NASA Astrophysics Data System (ADS)

    Janke, Jason R.; Bellisario, Antonio C.; Ferrando, Francisco A.

    2015-07-01

    In the Dry Andes of Chile (17 to 35° S), debris-covered glaciers and rock glaciers are differentiated from true glaciers based on the percentage of surface debris cover, thickness of surface debris, and ice content. Internal ice is preserved by an insulating cover of thick debris, which acts as a storage reservoir to release water during the summer and early fall. These landforms are more numerous than glaciers in the central Andes; however, the existing legislation only recognizes uncovered or semicovered glaciers as a water resource. Glaciers, debris-covered glaciers, and rock glaciers are being altered or removed by mining operations to extract valuable minerals from the mountains. In addition, agricultural expansion and population growth in this region have placed additional demands on water resources. In a warmer climate, as glaciers recede and seasonal water availability becomes condensed over the course of a snowmelt season, rock glaciers and debris-covered glaciers contribute a larger component of base flow to rivers and streams. As a result, identifying and locating these features to implement sustainable regional planning for water resources is important. The objective of this study is to develop a classification system to identify debris-covered glaciers and rock glaciers based on the interpretation of satellite imagery and aerial photographs. The classification system is linked to field observations and measurements of ice content. Debris-covered glaciers have three subclasses: surface coverage of semi (class 1) and fully covered (class 2) glaciers differentiates the first two forms, whereas debris thickness is critical for class 3 when glaciers become buried with more than 3 m of surface debris. Based on field observations, the amount of ice decreases from more than 85%, to 65-85%, to 45-65% for semi, fully, and buried debris-covered glaciers, respectively. Rock glaciers are characterized by three stages. Class 4 rock glaciers have pronounced

  11. A graph-based approach to glacier flowline extraction: An application to glaciers in Switzerland

    NASA Astrophysics Data System (ADS)

    Le Moine, Nicolas; Gsell, Pierre-Stéphane

    2015-12-01

    In this paper we propose a new, graph-based approach to glacier segmentation and flowline extraction. The method, which requires a set of glacier contours and a Digital Elevation Model (DEM), consists in finding an optimum branching that connects a set of vertices belonging to the topological skeleton of each glacier. First, the challenges associated with glacier flowline extraction are presented. Then, the three main steps of the method are described: the skeleton extraction and pruning algorithm, the definition and computation of a travel cost between all pairs of skeleton vertices, and the identification of the directed minimum spanning tree in the resulting directed graph. The method, which is mainly designed for valley glaciers, is applied to glaciers in Switzerland.

  12. Sea otter studies in Glacier Bay National Park and Preserve

    USGS Publications Warehouse

    Bodkin, J.L.; Kloecker, K.A.; Esslinger, G.G.; Monson, D.H.; DeGroot, J.D.; Doherty, J.

    2002-01-01

    Following translocations to the outer coast of Southeast Alaska in 1965, sea otters have been expanding their range and increasing in abundance. We began conducting surveys for sea otters in Cross Sound, Icy Strait, and Glacier Bay, Alaska in 1994, following initial reports (in 1993) of their presence in Glacier Bay. Since 1995, the number of sea otters in Glacier Bay proper has increased from around 5 to more than 1500. Between 1993 and 1997 sea otters were apparently only occasional visitors to Glacier Bay, but in 1998 long-term residence was established as indicated by the presence of adult females and their dependent pups. Sea otter distribution is limited to the Lower Bay, south of Sandy Cove, and is not continuous within that area. Concentrations occur in the vicinity of Sita Reef and Boulder Island and between Pt. Carolus and Rush Pt. on the west side of the Bay (Figure 1). We describe the diet of sea otters during 2001 in Glacier Bay based on visual observations of prey during 456 successful forage dives. In Glacier Bay, diet consisted of 62% clam, 15% mussel, 9% crab, 7% unidentified, 4& urchins, and 4% other. Most prey recovered by sea otters are commercially, socially, or ecologically important species. Species of clam include Saxidomus gigantea, Protothaca staminea, and Mya truncata. Urchins are primarily Strongylocentrotus droebachiensis and the mussel is Modiolus modiolus. Crabs include species of three genera: Cancer, Chinoecetes, and Telmessus. Although we characterize diet at broad geographic scales, we found diet to vary between sites separated by as little as several hundred meters. Dietary variation among and within sites can reflect differences in prey availability and individual specialization. We estimated species composition, density, biomass, and sizes of subtidal clams, urchins, and mussels at 9 sites in lower Glacier Bay. All sites were selected based on the presence of abundant clam siphons. Sites were not selected to allow inference to

  13. Himalayan glaciers: understanding contrasting patterns of glacier behavior using multi-temporal satellite imagery

    NASA Astrophysics Data System (ADS)

    Racoviteanu, A.

    2014-12-01

    High rates of glacier retreat for the last decades are often reported, and believed to be induced by 20th century climate changes. However, regional glacier 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 glacier regimes. Currently, the challenge is in understanding the magnitude of feedbacks between large-scale climate forcing and small-scale glacier behavior. Spatio-temporal patterns of glacier 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 glacier parameters in the last decade. Here I present a synopsis of the behavior of glaciers across the Himalaya, following a west to east gradient. In particular, I focus on spatial patterns of glacier 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 glacier features at small scale, which are particularly useful in understanding surface trends of debris-covered glaciers, which are prevalent in the Himalaya. I compare and contrast spatial patterns of glacier 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 glacier 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 glacier tongues show thinning trends of -30.8 m± 39 m

  14. A Revised Glacier Inventory of Bhaga Basin Himachal Pradesh, India : Current Status and Recent Glacier Variations

    NASA Astrophysics Data System (ADS)

    Birajdar, F.; Venkataraman, G.; Bahuguna, I.; Samant, H.

    2014-11-01

    Himalayan glaciers show large uncertainty regarding their present and future state due to their sensitive reaction towards change in climatic condition. Himalayan glaciers are unique as they are located in tropical, high altitude regions, predominantly valley type and many are covered with debris. The great northern plains of India sustain on the perennial melt of glaciers meeting the water requirements of agriculture, industries, domestic sector even in the months of summer when large tracts of the country go dry. Therefore, it is important to monitor and assess the state of snow and glaciers and to know the sustainability of glaciers in view of changing global scenarios of climate and water security of the nation. Any information pertaining to Himalayan glaciers is normally difficult to be obtained by conventional means due to its harsh weather and rugged terrains. Due to the ecological diversity and geographical vividness, major part of the Indian Himalaya is largely un-investigated. Considering the fact that Himalayan glaciers are situated in a harsh environment, conventional techniques of their study is challenging and difficult both in terms of logistics and finances whereas the satellite remote sensing offers a potential mode for monitoring glaciers in long term. In order to gain an updated overview of the present state of the glacier cover and its changes since the previous inventories, an attempt has been made to generate a new remotesensing- derived glacier inventory on 1:50,000 scale for Bhaga basin (N32°28'19.7'' - N33°0'9.9'' ; E76°56'16.3'' - E77°25'23.7'' ) Western Himalaya covering an area of 1695.63 km2. having 231 glaciers and occupying glacierized area of 385.17 ±3.71 km2. ranging from 0.03 km2. to 29.28 km2. Glacier inventory has been carried out using high resolution IRS P6 LISS III data of 2011, ASTER DEM and other ancillary data. Specific measurements of mapped glacier features are the inputs for generating the glacier inventory data

  15. Arctic Warming and Sea Ice Diminution Herald Changing Glacier and Cryospheric Hazard Regimes

    NASA Astrophysics Data System (ADS)

    Kargel, Jeffrey; Bush, Andrew; Leonard, Gregory

    2013-04-01

    The recent expansion of summertime melt zones in both Greenland and some Arctic ice caps, and the clearing of perennial sea ice from much of the Arctic, may presage more rapid shifts in mass balances of land ice than glaciologists had generally expected. The summer openings of vast stretches of open water in the Arctic, particularly in straits and the Arctic Ocean shores of the Queen Elizabeth Islands and along some Greenland coastal zones, must have a large impact on summer and early autumn temperatures and precipitation now that the surface boundary condition is no longer limited by the triple-point temperature and water-vapor pressure of H2O. This state change in the Arctic probably is part of the explanation for the expanded melt zones high in the Greenland ice sheet. However, Greenland and the Canadian Arctic are vast regions subject to climatic influences of multiple marine bodies, and the situation with sea ice and climate change remains heterogeneous, and so the local climate feedbacks from sea ice diminution remain patchy. Projected forward just a few decades, it is likely that sea ice will play a significant role in the Queen Elizabeth Islands and around Greenland only in the winter months. The region is in the midst of a dramatic climate change that is affecting the mass balances of the Arctic's ice bodies; some polar-type glaciers must be transforming to polythermal, and polythermal ones to maritime-temperate types. Attendant with these shifts, glacier response times will shorten, the distribution and sizes of glacier lakes will change, unconsolidated debris will be debuttressed, and hazards-related dynamics will shift. Besides changes to outburst flood, debris flow, and rock avalanche occurrences, the tsunami hazard (with ice and debris landslide/avalanche triggers) in glacierized fjords and the surge behaviors of many glaciers is apt to increase or shift locations. For any given location, the past is no longer the key to the present, and the present

  16. Insights into the Thwaites Glacier grounding zone from Operation IceBridge aerogravity

    NASA Astrophysics Data System (ADS)

    Tinto, K. J.; Bell, R. E.; Cochran, J. R.; Elieff, S.; Frearson, N.

    2010-12-01

    Operation IceBridge acquired 1500 km of geophysical data, at 10 km spacing, in front of the Thwaites Glacier grounding line during the 2009 season. The gravity anomalies recorded by the survey have been used to model the bathymetry of the sea floor in front of the glacier, an area inaccessible to previous surveys. The resulting map reveals previously unseen detail of the Thwaites grounding zone, as well as the spatial extent of features that were formerly only known as points affecting the ice surface. The modeled bathymetry in front of Thwaites Glacier is marked by an undulating ridge running sub-parallel to the grounding line, 40 km seaward. The highest peak on the ridge is in contact with the overlying ice shelf, hindering its flow. Ridge elevation decreases to the west, with a maximum ridge depth of 850 m and an average relief of 350 m. This is comparable in scale to the recently identified ridge crossing the channel of nearby Pine Island Glacier (Jenkins et al., 2010). The present-day grounding line of Thwaites appears to be marked by a more subdued ridge, in which we have identified a 20 km wide hollow, to a water depth of 1200 m. Our model shows that this hollow corresponds to a landward bight in the grounding line, in the region through which the fast ice flow of Thwaites Glacier is focused. This correlation was not visible on previous, coarser scale maps of the grounding line, and shows a clear relationship between the bathymetry and ice flow. Gravity inversions have been constrained by nearby marine surveys, satellite images of the ice rise at the peak of the ridge and radar and laser data from the IceBridge survey to constrain ice thickness. The absolute values of predicted bathymetry are dependent on the density of the rocks in the subsurface, for example the presence or absence of volcanic material or loose sediments. Some models of the geology of the survey area are also proposed. Uncertainty of underlying geology may account for ~100 m errors in the

  17. Birth of a Large Iceberg in Pine Island Bay, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

    A large tabular iceberg (42 kilometers x 17 kilometers) broke off Pine Island Glacier, West Antarctica (75oS latitude, 102oW longitude) sometime between November 4 and 12, 2001. Images of the glacier were acquired by the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard NASA's Terra spacecraft. This event was preceded by the formation of a large crack across the glacier in mid 2000. Data gathered by other imaging instruments revealed the crack to be propagating through the shelf ice at a rate averaging 15 meters per day, accompanied by a slight rotation of about one percent per year at the seaward margin of the rift.

    The image set shows three views of Pine Island Glacier acquired by MISR's vertical-viewing (nadir) camera. The first was captured in late 2000, early in the development of the crack. The second and third views were acquired in November 2001, just before and just after the new iceberg broke off. The existence of the crack took the glaciological community by surprise, and the rapid rate at which the crack propagated was also not anticipated. Glaciologists predicted that the rift would reach the other side of the glacier sometime in 2002. However, the iceberg detached much sooner than anticipated, and the last 10-kilometer segment that was still attached to the ice shelf snapped off in a matter of days.

    The animated sequence consists of 11 snapshots acquired by MISR's nadir camera between September 16, 2000 and November 12, 2001. Due to frequent cloud cover, the time interval between successive frames is not uniform. The flow of the glacier, widening of the rift, and subsequent break-off of the iceberg are evident. A 'jump' in the position of the rift near the middle of the sequence is due to a gap in image acquisition during Antarctic winter, when the glacier was in continuous darkness.

    Pine Island Glacier is the largest discharger of ice in Antarctica and the continent's fastest moving glacier. This area of the West

  18. Global Warming and Glaciers Melting at Fjords in Greenland

    NASA Astrophysics Data System (ADS)

    Coelho, Pablo

    2015-04-01

    This paper presents a discussion on the validation or not of a likely paradigm about the melting of polar glaciers and their direct impact on increasing ocean levels. Physico-chemical properties of ocean waters, as well as anomalies in the thermal behavior of water are used as providers of this discussion using fjords of Greenland as study area. This text seeks to infer the relationship between the most recent developments in global warming, specifically dealing with the melting of glaciers located in fjords in the eastern part of Greenland, increasing the water temperature in ocean currents and changes in sea levels. We emphasize the importance of the correlation of the water physico-chemical characteristics in these changes perceived in the studied environment. Greenland is defined by convention as the widest oceanic island in the world. In its fjords formed in the last glaciation of the Quaternary period, basically made of ice mountains with entries to the sea, there has been melts that are discussed in this work. At first, global warming and the melting of glaciers with a consequent rise in sea levels are presented almost as an axiom. This paper seeks to address the conclusions arising from this type of research according the basic laws of physics and chemistry, related to the behavior of water in their states (typically solid and liquid). The ultimate goal of this work glimpsed through some inferences and validation of water behavior in the ice condition and in its liquid state, a broader view with regard to the findings applied to the relationship between global warming and ice melting processes. Will be observed some water anomalies in the variation between its liquid and solid states to attempt a better understanding of the phenomena occurring in this area of interest as well as their possible impacts. It is noteworthy the fact that the water does not behave thermally as most liquids, with very specific consequences in relation to the variation between its

  19. Integrated firn elevation change model for glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Saß, Björn; Sauter, Tobias; Braun, Matthias

    2016-04-01

    We present the development of a firn compaction model in order to improve the volume to mass conversion of geodetic glacier mass balance measurements. The model is applied on the Arctic ice cap Vestfonna. Vestfonna is located on the island Nordaustlandet in the north east of Svalbard. Vestfonna covers about 2400 km² and has a dome like shape with well-defined outlet glaciers. Elevation and volume changes measured by e.g. satellite techniques are becoming more and more popular. They are carried out over observation periods of variable length and often covering different meteorological and snow hydrological regimes. The elevation change measurements compose of various components including dynamic adjustments, firn compaction and mass loss by downwasting. Currently, geodetic glacier mass balances are frequently converted from elevation change measurements using a constant conversion factor of 850 kg m-³ or the density of ice (917 kg m-³) for entire glacier basins. However, the natural conditions are rarely that static. Other studies used constant densities for the ablation (900 kg m-³) and accumulation (600 kg m-³) areas, whereby density variations with varying meteorological and climate conditions are not considered. Hence, each approach bears additional uncertainties from the volume to mass conversion that are strongly affected by the type and timing of the repeat measurements. We link and adapt existing models of surface energy balance, accumulation and snow and firn processes in order to improve the volume to mass conversion by considering the firn compaction component. Energy exchange at the surface is computed by a surface energy balance approach and driven by meteorological variables like incoming short-wave radiation, air temperature, relative humidity, air pressure, wind speed, all-phase precipitation, and cloud cover fraction. Snow and firn processes are addressed by a coupled subsurface model, implemented with a non-equidistant layer discretisation. On

  20. Faster Reading--One Hundred Years after Javal.

    ERIC Educational Resources Information Center

    Williams, Ray

    1979-01-01

    Discusses the origins of the interest in faster reading, oculomotor activity in reading in relation to eye movement and eye span, misapplication of eye movement data in courses designed to promote faster reading, and objections to some of the more common mechanical devices used in faster reading courses. (GT)

  1. Geocryological Structure and Glaciers Novaya Zemlya archipelago in the context of global climate processes

    NASA Astrophysics Data System (ADS)

    Kholmiansky, Mikhail; Anokhin, Vladimir

    2015-04-01

    New Earth glaciation due to the Quaternary glaciation .epohami and modern climate. We distinguish four types of ice sheets: small glaciers and snowfields - a capacity of up to 100 m .; mountain-valley glaciation - up to 200 m .; net (transition to the coverslip) - up to 300 m. and glaciation (ice sheet) - up to 500 m. The archipelago is characterized by continuous permafrost raprosraneniem, which is located under the roof of the seasonally thawed layer at a depth of 0.1 to 3.2 m . The depth is increased by its lakes and man-made Taliko up to 35 m. The temperature of the permafrost Paleozoic sandstones and shales at a depth of 15 m. Reaches -3,5°; limestones and shales containing cryopeg it reaches -2,8° at a depth of 130 m. Power Cryolithozone on drilling data and calculations 265-280 m. The average temperature of ice sheets are formed depending on the type of ice, its cut and the power supply type and morphology of the surface. It differs from the temperature of the surrounding glacier rocks on 3-7° and is at a depth from the surface of the glacier 13-15 m .: -3 - -4,5°; at a depth of 30 m .: -2°. In the age of the Quaternary glaciation entire archipelago was covered with continental ice. Global warming has resulted in a reduction of its area by 25% In the northern part of the South Island there are snowfields and small lednichki. In the area of Matochkin Shar and further north to South Bay Sulmenova, found mainly hanging and cirque glaciers, severely degraded, and in most cases do not reach the sea. At the same time, in the South Bay and Sulmenova and a number of other areas there are powerful lobes were associated with the ice sheet interior of the North Island, and reaching the sea. In the west of the archipelago to reach the sea only a few branches of the Central ice sheet; in the eastern part of the North Island ice sheet breaks in the sea in the form of ice walls up to 400 meters. This part is called the Nordenskiöld glacier. The maximum ice thickness

  2. Preliminary bathymetry of Aialik Bay and Neoglacial changes of Aialik and Pederson glaciers, Alaska

    USGS Publications Warehouse

    Post, Austin

    1980-01-01

    Preliminary bathymetry (at 1:20,000 scale) and scientific studies of Aialik Bay, Alaska, by the Research Vessel Growler in 1978 disclose that the head of the bay consists of a deep basin enclosed by a terminal-moraine shoal. A much smaller basin, into which Aialik Glacier discharges icebergs, is located west of two islands and a submarine ridge. Comparison of 1978 soundings with U.S. Coast and Geodetic Survey (now National Oceanic and Atmospheric Administration) data obtained in 1912 shows shoaling of about 64 feet in the deepest part of the small basin nearest the glacier and of about 40 feet in the large basin. The time of retreat of Aialik Glacier from the moraine bar is unknown; a faint ' trimline ' is still visible in the forest on the east side of the fiord, and a carbon-14 date suggests the retreat could have taken place as recently as 1800. The time of Aialik Glcier 's neoglacial advance to the moraine is unknown. Pederson Glacier, which terminates in part in a tidal lagoon or lake, has retreated about 0.90 mile from a moraine judged by Grant and Higgins to have been in contact with the ice about 1896. (USGS)

  3. The geochemical record in rock glaciers

    USGS Publications Warehouse

    Steig, E.J.; Fitzpatrick, J.J.; Potter, N.; Clark, D.H.

    1998-01-01

    A 9.5 m ice core was extracted from beneath the surficial debris cover of a rock glacier 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 glaciers, reflecting concentration of debris by melting at the surface during the summer ablation season. Profiles of stable isotope concentrations and electrical conductivity measurements provide independent evidence for melting in association with debris layers. These observations are consistent with a glacial origin for the ice, substantiating the glacigenic model for rock glacier 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 glacier ice.

  4. Complex Greenland outlet glacier flow captured.

    PubMed

    Aschwanden, Andy; Fahnestock, Mark A; Truffer, Martin

    2016-01-01

    The Greenland Ice Sheet is losing mass at an accelerating rate due to increased surface melt and flow acceleration in outlet glaciers. Quantifying future dynamic contributions to sea level requires accurate portrayal of outlet glaciers 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 glaciers are well captured, illustrating fundamental commonalities in outlet glacier 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

  5. Complex Greenland outlet glacier flow captured

    PubMed Central

    Aschwanden, Andy; Fahnestock, Mark A.; Truffer, Martin

    2016-01-01

    The Greenland Ice Sheet is losing mass at an accelerating rate due to increased surface melt and flow acceleration in outlet glaciers. Quantifying future dynamic contributions to sea level requires accurate portrayal of outlet glaciers 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 glaciers are well captured, illustrating fundamental commonalities in outlet glacier 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

  6. Stabilizing feedbacks in glacier-bed erosion.

    PubMed

    Alley, R B; Lawson, D E; Larson, G J; Evenson, E B; Baker, G S

    2003-08-14

    Glaciers often erode, transport and deposit sediment much more rapidly than nonglacial environments, with implications for the evolution of glaciated mountain belts and their associated sedimentary basins. But modelling such glacial processes is difficult, partly because stabilizing feedbacks similar to those operating in rivers have not been identified for glacial landscapes. Here we combine new and existing data of glacier morphology and the processes governing glacier evolution from diverse settings to reveal such stabilizing feedbacks. We find that the long profiles of beds of highly erosive glaciers tend towards steady-state angles opposed to and slightly more than 50 per cent steeper than the overlying ice-air surface slopes, and that additional subglacial deepening must be enabled by non-glacial processes. Climatic or glaciological perturbations of the ice-air surface slope can have large transient effects on glaciofluvial sediment flux and apparent glacial erosion rate.

  7. The fleeting glaciers of the Arctic

    NASA Astrophysics Data System (ADS)

    Bakke, Jostein; Røthe, Torgeir; van der Bilt, Willem; Paasche, Øyvind

    2015-04-01

    Glaciers and snow are the very symbol of the Arctic, covering large parts of its terrestrial surface throughout the year. The cool temperatures that have allowed for the widespread coverage of glaciers are now trending towards a warmer climate, and with this gradual shift we observe a non-linear response in the cryosphere of which glaciers are a key component. This change is manifested in retreating fronts and an overall thinning. Because the typology of Arctic glaciers is rich and varied, the response pattern to the on-going warming is not unison. Instead we observe large spatial variations due to the critical balance between summer temperature and winter precipitation, but also other factors such as aspect, altitude, geographical location, debris cover and so forth. Even so, minor variations is superimposed on a larger trends which suggests that in a not so distant future, glaciers will probably be less abundant than what has been common for the last 100 years. In the context of the last 10 000 years it is evident that arctic glaciers have changed significantly and they have even been smaller than they are today, which was the case 9000 to 5000 years ago. On Svalbard, three glacier lake sediment records foretell of large past variations, indicating a more articulated sensitivity to climate change than what is commonly perceived for the Arctic cryosphere. Based on the lake sediment studies we will discuss Arctic glaciers sensitivity to decadal to millenium scale climate fluctuations and discuss possible forcing mechanims behind suitable for explaining what we see.

  8. Regional Observations of Alaska Glacier Dynamics

    NASA Astrophysics Data System (ADS)

    Burgess, E. W.; Forster, R. R.; Hall, D. K.

    2010-12-01

    Alaska glaciers contribute more to sea level rise than any other glacierized mountain region in the world. Alaska is loosing ~84 Gt of ice annually, which accounts for ~0.23 mm/yr of SLR (Luthcke et al., 2008). Complex glacier flow dynamics, frequently related to tidewater environments, is the primary cause of such rapid mass loss (Larsen et al., 2007). Indirect observations indicate these complex flow dynamics occur on many glaciers throughout Alaska, but no comprehensive velocity measurements exist. We are working to measure glacier surface velocities throughout Alaska using synthetic aperture radar (SAR) offset tracking. This work focuses on the Seward/Malaspina, Bering, Columbia, Kaskawulsh, and Hubbard Glaciers and uses a MODIS land surface temperature "melt-day" product (Hall et al., 2006, 2008) to identify potential links between velocity variability and summertime temperature fluctuations. Hall, D., R. Williams Jr., K. Casey, N. DiGirolamo, and Z. Wan (2006), Satellite-derived, melt-season surface temperature of the Greenland Ice Sheet (2000-2005) and its relationship to mass balance, Geophysical Research Letters, 33(11). Hall, D., J. Box, K. Casey, S. Hook, C. Shuman, and K. Steffen (2008), Comparison of satellite-derived and in-situ observations of ice and snow surface temperatures over Greenland, Remote Sensing of Environment, 112(10), 3739-3749. Larsen, C. F., R. J. Motyka, A. A. Arendt, K. A. Echelmeyer, and P. E. Geissler (2007), Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise, J. Geophys. Res. Luthcke, S., A. Arendt, D. Rowlands, J. McCarthy, and C. Larsen (2008), Recent glacier mass changes in the Gulf of Alaska region from GRACE mascon solutions, Journal of Glaciology, 54(188), 767-777.

  9. Hubbard Glacier, Alaska: growing and advancing in spite of global climate change and the 1986 and 2002 Russell Lake outburst floods

    USGS Publications Warehouse

    Trabant, Dennis C.; March, Rod S.; Thomas, Donald S.

    2003-01-01

    Hubbard Glacier, the largest calving glacier on the North American Continent (25 percent larger than Rhode Island), advanced across the entrance to 35-mile-long Russell Fiord during June 2002, temporarily turning it into a lake. Hubbard Glacier has been advancing for more than 100 years and has twice closed the entrance to Russell Fiord during the last 16 years by squeezing and pushing submarine glacial sediments across the mouth of the fiord. Water flowing into the cutoff fiord from mountain streams and glacier melt causes the level of Russell Lake to rise. However, both the 1986 and 2002 dams failed before the lake altitude rose enough for water to spill over a low pass at the far end of the fiord and enter the Situk River drainage, a world-class sport and commercial fishery near Yakutat, Alaska.

  10. Modelled trends in oceanic conditions of Pine Island Bay between 1991 and 2014

    NASA Astrophysics Data System (ADS)

    Kimuras, Satoshi; Holland, Paul; Regan, Heather; Jenkins, Adrian; Van Wessem, Melchior

    2016-04-01

    Two ice shelves in Pine Island Bay, Pine Island Glacier and its neighbour Thwaites Glacier, have been highlighted as major drainage pathways for the West Antarctic Ice Sheet. We quantify the melting of these ice shelves and oceanic conditions between 1991 and 2014 using a general circulation model. Two different atmospheric forcing scenarios (RACMO2.3 and ERA-Interim) are used as a surface boundary. The ocean heat content of the Pine Island Bay from the simulations shows periodic decrease in the late 1990s and 2012-2014, but the magnitude of cooling is different between RACMO2.3 and ERA-Interim forced simulations. The brine rejection of the sea ice production causes enhanced overturning and cools the water north of Pine Island Glacier Ice Shelf. This cold water flows southward along the coastline, resulting in lower melt rate in the late 1990s and 2012-2014.

  11. Integrated glacier and snow hydrological modelling in the Urumqi No.1 Glacier catchment

    NASA Astrophysics Data System (ADS)

    Gao, Hongkai; Hrachowitz, Markus; Savenije, Hubert

    2015-04-01

    The glacier and snow melt water from mountainous area is an essential water resource in Northwest China, where the climate is arid. Therefore a hydrologic model including glacier and snow melt simulation is in an urgent need for water resources management and prediction under climate change in this region. In this study, the Urumqi No.1 Glacier catchment in Northwest China, with 51% area covered by glacier, was selected as the study site. An integrated daily hydrological model was developed to systematically simulate the hydrograph, runoff separation (glacier and non-glacier runoff), the glacier mass balance (GMB), the equilibrium line altitude (ELA), and the snow water equivalent (SWE). Only precipitation, temperature and sunshine hour data is required as forcing input. A combination method, which applies degree-day approach during dry periods and empirical energy balance formulation during wet seasons, was implemented to simulate snow and glacier melt. Detailed snow melt processes were included in the model, including the water holding capacity of snow pack, the liquid water refreezing process in snow pack, and the change of albedo with time. A traditional rainfall-runoff model (Xinanjiang) was applied to simulate the rainfall(snowmelt)-runoff process in non-glacierized area. Additionally, the influence of elevation on temperature and precipitation distribution, and the impact of different aspect on snow and glacier melting were considered. The model was validated, not only by long-term observed daily runoff data, but also by measured snow (SWE) and glacier data (GMB, ELA) of over 50 years. Furthermore, the calibrated model can be upscaled into a larger catchment, which further supports our proposed model and optimized parameter sets.

  12. 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.

  13. Identifying climatic drivers of glacier mass balance variability of Lewis glacier, Mt. Kenya

    NASA Astrophysics Data System (ADS)

    Nicholson, Lindsey; Prinz, Rainer; Kaser, Georg

    2013-04-01

    Lewis Glacier (Kenya, 0°09' S; 37°18' E) has a 20 year historical annual mass balance record, spanning 1979-1996 and 2010-2012. This offers an opportunity to investigate the glacier-climate interactions at ~4800m a.s.l. in the equatorial zone, which in turn allows investigation of the possible tropical mid-tropospheric conditions that must have prevailed in order to permit formerly larger glacier extents on the mountain. Here we use field data of glacier annual mass balance, seasonal glacier surface height changes and monthly precipitation records to test the impact of potential drivers on the glacier variability. We examine relationships between these glaciological data and ERA-interim atmospheric fields, satellite measurements of outgoing long wave radiation and sea surface temperatures. In all years except the mass balance year of 1989 Lewis glacier experiences a negative mass balance. Strongly negative annual mass balances occur only if one or both of the wet seasons fail to bring snowfall to the summit and both annual mass balance and rainy season surface change is well correlated with measured precipitation and enhanced convection within the equatorial rain belt in East Africa and the western Indian Ocean. Seasonal glacier surface height change is correlated with air temperature throughout the whole tropical African zone during the dry months of January and February, but the only positive mass balance year experienced seasonal cold temperature anomalies over equatorial Africa in all seasons. No single season emerges as the dominant driver of the inter-annual mass balance variability, and the climate sensitivity of the glacier surface change differs between seasons. However Lewis Glacier mass balance over the study period can be explained by moisture variability as the primary driver and temperature variability as an additional driver of glacier mass change.

  14. The slow advance of a calving glacier: Hubbard Glacier, Alaska, U.S.A

    USGS Publications Warehouse

    Trabant, D.C.; Krimmel, R.M.; Echelmeyer, K.A.; Zirnheld, S.L.; Elsberg, D.H.

    2003-01-01

    Hubbard Glacier is the largest tidewater glacier in North America. In contrast to most glaciers in Alaska and northwestern Canada, Hubbard Glacier thickened and advanced during the 20th century. This atypical behavior is an important example of how insensitive to climate a glacier can become during parts of the calving glacier cycle. As this glacier continues to advance, it will close the seaward entrance to 50 km long Russell Fjord and create a glacier-dammed, brackish-water lake. This paper describes measured changes in ice thickness, ice speed, terminus advance and fjord bathymetry of Hubbard Glacier, as determined from airborne laser altimetry, aerial photogrammetry, satellite imagery and bathymetric measurements. The data show that the lower regions of the glacier have thickened by as much as 83 m in the last 41 years, while the entire glacier increased in volume by 14.1 km3. Ice speeds are generally decreasing near the calving face from a high of 16.5 m d-1 in 1948 to 11.5 m d-1 in 2001. The calving terminus advanced at an average rate of about 16 m a-1 between 1895 and 1948 and accelerated to 32 m a-1 since 1948. However, since 1986, the advance of the part of the terminus in Disenchantment Bay has slowed to 28 m a-1. Bathymetric data from the lee slope of the submarine terminal moraine show that between 1978 and 1999 the moraine advanced at an average rate of 32 m a-1, which is the same as that of the calving face.

  15. Comparative metagenome analysis of an Alaskan glacier.

    PubMed

    Choudhari, Sulbha; Lohia, Ruchi; Grigoriev, Andrey

    2014-04-01

    The temperature in the Arctic region has been increasing in the recent past accompanied by melting of its glaciers. We took a snapshot of the current microbial inhabitation of an Alaskan glacier (which can be considered as one of the simplest possible ecosystems) by using metagenomic sequencing of 16S rRNA recovered from ice/snow samples. Somewhat contrary to our expectations and earlier estimates, a rich and diverse microbial population of more than 2,500 species was revealed including several species of Archaea that has been identified for the first time in the glaciers of the Northern hemisphere. The most prominent bacterial groups found were Proteobacteria, Bacteroidetes, and Firmicutes. Firmicutes were not reported in large numbers in a previously studied Alpine glacier but were dominant in an Antarctic subglacial lake. Representatives of Cyanobacteria, Actinobacteria and Planctomycetes were among the most numerous, likely reflecting the dependence of the ecosystem on the energy obtained through photosynthesis and close links with the microbial community of the soil. Principal component analysis (PCA) of nucleotide word frequency revealed distinct sequence clusters for different taxonomic groups in the Alaskan glacier community and separate clusters for the glacial communities from other regions of the world. Comparative analysis of the community composition and bacterial diversity present in the Byron glacier in Alaska with other environments showed larger overlap with an Arctic soil than with a high Arctic lake, indicating patterns of community exchange and suggesting that these bacteria may play an important role in soil development during glacial retreat.

  16. Glacier mass budget measurements by hydrologic means

    USGS Publications Warehouse

    Tangborn, Wendell V.

    1966-01-01

    Ice storage changes for the South Cascade Glacier drainage basin were determined for the 1957–1964 period using basin runoff and precipitation measurements. Measurements indicate that evaporation and condensation are negligible compared with the large runoff and precipitation values. Runoff, measured by a stream discharge station, averaged 4.04 m/yr; precipitation, determined by snow accumulation measurements at a central point on the glacier and by storage gages, averaged 3.82 m/yr, resulting in a basin net loss of about 0.22 m/yr. During the same period, South Cascade Glacier net budgets were determined by ablation stakes, snow density-depth profiles, and maps. The average glacier net budget for the period was −0.61sol;yr of water. This amount is equivalent to −0.26 m of water when averaged over the drainage basin (43% glacier-covered), which is in fair agreement with the net storage change measured by hydrologic methods. Agreement between the two methods for individual years is slightly less perfect. (Key words: Glaciers; water balance.)

  17. Rheology of rock glaciers: a preliminary assessment

    SciTech Connect

    Giardino, J.R.; Vitek, J.D.; Hoskins, E.R.

    1985-01-01

    Movement of rock debris under the influence of gravity, i.e., mass movement, generates a range of phenomena from soil creep, through solifluction,debris flows and rock glaciers to rock falls. Whereas the resultant forms of these phenomena are different, common elements in the mechanics of movement are utilized in the basic interpretation of the processes of formation. Measurements of morphologic variables provide data for deductive analyses of processes that operate too slowly to observe or for processes that generated relict phenomena. External and internal characteristics or rock glacier morphometry and measured rates of motion serve as the basis for the development of a rheological model to explain phenomena classified as rock glaciers. A rock glacier in the Sangre de Cristo Mountains of Southern Colorado, which exhibits a large number of ridges and furrows and lichen bare fronts of lobes, suggests present day movement. A strain-net established on the surface provides evidence of movement characteristics. These data plus morphologic and fabric data suggest two rheological models to explain the flow of this rock glacier. Model one is based upon perfect plastic flow and model two is based upon stratified fluid movement with viscosity changing with depth. These models permit a better understanding of the movement mechanics and demonstrate that catastrophic events and slow creep contribute to the morphologic characteristics of this rock glacier.

  18. Modeling debris-covered glaciers: response to steady debris deposition

    NASA Astrophysics Data System (ADS)

    Anderson, Leif S.; Anderson, Robert S.

    2016-05-01

    Debris-covered glaciers are common in rapidly eroding alpine landscapes. When thicker than a few centimeters, surface debris suppresses melt rates. If continuous debris cover is present, ablation rates can be significantly reduced leading to increases in glacier length. In order to quantify feedbacks in the debris-glacier-climate system, we developed a 2-D long-valley numerical glacier model that includes englacial and supraglacial debris advection. We ran 120 simulations on a linear bed profile in which a hypothetical steady state debris-free glacier responds to a step increase of surface debris deposition. Simulated glaciers advance to steady states in which ice accumulation equals ice ablation, and debris input equals debris loss from the glacier terminus. Our model and parameter selections can produce 2-fold increases in glacier length. Debris flux onto the glacier and the relationship between debris thickness and melt rate strongly control glacier length. Debris deposited near the equilibrium-line altitude, where ice discharge is high, results in the greatest glacier extension when other debris-related variables are held constant. Debris deposited near the equilibrium-line altitude re-emerges high in the ablation zone and therefore impacts melt rate over a greater fraction of the glacier surface. Continuous debris cover reduces ice discharge gradients, ice thickness gradients, and velocity gradients relative to initial debris-free glaciers. Debris-forced glacier extension decreases the ratio of accumulation zone to total glacier area (AAR). Our simulations reproduce the "general trends" between debris cover, AARs, and glacier surface velocity patterns from modern debris-covered glaciers. We provide a quantitative, theoretical foundation to interpret the effect of debris cover on the moraine record, and to assess the effects of climate change on debris-covered glaciers.

  19. The Glacial Buzzsaw in the Northern Basin and Range: the Importance of Glacier Size and Uplift Rates

    NASA Astrophysics Data System (ADS)

    Foster, D.; Brocklehurst, S. H.; Gawthorpe, R. L.

    2007-12-01

    The role of glaciers in limiting mountain range elevations is an important component of studies linking tectonic uplift and climate-driven erosion. Recent investigations suggesting that a glacial buzzsaw effect can efficiently offset rock uplift in tectonically active settings have concentrated on regions that have held large glaciers (10s km long at Last Glacial Maximum, LGM). However, little work has addressed the role small glaciers may play in controlling range topography. This study looks at the effectiveness of smaller (<10 km) glaciers at limiting peak and ridge elevations in both slow and relatively rapid rock uplift settings. The Lost River and Lemhi Ranges, Idaho, and the Beaverhead-Bitterroot Mountains, Idaho-Montana all experience slow rock uplift, with slip rates <0.3 mm/yr on the range-bounding normal faults. Here, swath-elevation profiles show that maximum elevations correlate well to estimates of both LGM and mean Quaternary equilibrium line altitudes (ELAs). Furthermore, peaks in hypsometry and minima in slope-elevation profiles correspond to ELAs, suggesting that small glaciers can efficiently limit range elevations where rock uplift is slow. The Teton Range, Wyoming, experiences 5-10 times faster rock uplift. In general, elevations, slope profiles, and hypsometry all correlate to both LGM and mean Quaternary ELA estimates, although supra-elevated peaks do penetrate through this zone. Comparisons of valley long-profiles show that glacier size is important in controlling valley form under more rapid rock uplift. Small (<5km) glacial valleys perched high on the range front have profiles that have steepened in response to the rapid rock uplift. In contrast, larger (>8km) valleys extend back beyond the high peaks of the range front, and have housed glaciers that have eroded deep into the range, maintaining shallow gradients. Feedback mechanisms are important in snow accumulation on the larger glaciers, which receive extra inputs of snow from the

  20. Application of artificial neural networks in hydrological modeling: A case study of runoff simulation of a Himalayan glacier basin

    NASA Technical Reports Server (NTRS)

    Buch, A. M.; Narain, A.; Pandey, P. C.

    1994-01-01

    The simulation of runoff from a Himalayan Glacier basin using an Artificial Neural Network (ANN) is presented. The performance of the ANN model is found to be superior to the Energy Balance Model and the Multiple Regression model. The RMS Error is used as the figure of merit for judging the performance of the three models, and the RMS Error for the ANN model is the latest of the three models. The ANN is faster in learning and exhibits excellent system generalization characteristics.

  1. Velocities of Thwaites Glacier and smaller glaciers along the Marie Byrd Land coast, West Antarctica

    USGS Publications Warehouse

    Rosanova, C.E.; Lucchitta, B.K.; Ferrigno, J.G.

    1998-01-01

    Average velocities for time intervals ranging from <1 to 15 years were measured by tracking ice-surface patterns on sequential Landsat and European Remote-sensing Satellite synthetic aperture radar images. Velocities of Thwaites Glacier range from 2.2 km a-1 above the grounding line to 3.4 km a-1 at the limit of measurements on Thwaites Glacier ice tongue. The glacier increases in velocity by about 1 km a-1 where it crosses the grounding line. Over the period 1984-93, Thwaites Glacier ice tongue accelerated by about 0.6 km a-1. Velocities of the floating part of several minor glaciers and some ice shelves are also determined: Land Glacier, 1.7-1.9 km a-1; DeVicq Glacier, 0.7-1.1 km a-1; Dotson Ice Shelf, 0.2-0.5 km a-1; Getz Ice Shelf, 0.2-0.8 km a-1; and Sulzberger Ice Shelf, 0.01-0.02 km a-1. The high velocities along the Marie Byrd Land coast are consistent with the high precipitation rates over West Antarctica and, for some of the glaciers, the lack of buttressing ice shelves.

  2. Multi-decadal retreat of Novaya Zemlya outlet glaciers, in response to climatic forcing

    NASA Astrophysics Data System (ADS)

    Carr, Rachel; Bell, Heather

    2016-04-01

    Arctic ice masses have rapidly lost ice from the mid-1990s, through a combination of negative surface mass balance and accelerated ice discharge from marine-terminating outlet glaciers. In the past decade, substantial mass deficits have been identified on Novaya Zemlya (NVZ), Russian High Arctic, and its outlet glaciers have retreated dramatically, likely due to declining sea ice concentrations. However, little is known about longer-term glacier behaviour on NVZ, and its potential impact on overall mass balance. Here we greatly extend the available record of retreat and assess multi-decadal glacier response to forcing between 1976 and 2014 using remotely sensed data. Following at least 25 years of gradual recession, retreat rates accelerated substantially from circa. 2000 and again from 2011 onwards. The rate and temporal pattern of retreat were strongly dependant on terminus type: marine-terminating outlets receded an order of magnitude faster than land- or lagoon-terminating glaciers and land-based termini showed limited change in retreat rate over time. Furthermore, retreat was markedly higher on the Barents Sea coast than the Kara Sea. Comparison with forcing data shows that accelerated retreat from 2011 onwards coincided with exceptionally low sea ice concentration and duration between 2011 and 2013. This suggests that sea ice is an important controlling factor, which agrees with shorter-term studies on NVZ. Although air temperature information is more limited on NVZ, data from both meteorological stations and reanalysis highlight 2011 and 2012 as two of the warmest years during the period 1950 to 2014. The limited response of land-terminating outlets suggests that air temperatures do not cause retreat directly, via melting or enhanced basal lubrication, but may have an indirect influence through melting of sea ice or hydro fracture.

  3. Glacier Changes in the Russian High Arctic.

    NASA Astrophysics Data System (ADS)

    Pritchard, M. E.; Willis, M. J.; Melkonian, A. K.; Golos, E. M.; Stewart, A.; Ornelas, G.; Ramage, J. M.

    2014-12-01

    We provide new surveys of ice speeds and surface elevation changes for ~40,000 km2 of glaciers and ice caps at the Novaya Zemlya (NovZ) and Severnaya Zemlya (SevZ) Archipelagoes in the Russian High Arctic. The contribution to sea level rise from this ice is expected to increase as the region continues to warm at above average rates. We derive ice speeds using pixel-tracking on radar and optical imagery, with additional information from InSAR. Ice speeds have generally increased at outlet glaciers compared to those measured using interferometry from the mid-1990s'. The most pronounced acceleration is at Inostrantseva Glacier, one of the northernmost glaciers draining into the Barents Sea on NovZ. Thinning rates over the last few decades are derived by regressing stacked elevations from multiple Digital Elevations Models (DEMs) sourced from ASTER and Worldview stereo-imagery and cartographically derived DEMs. DEMs are calibrated and co-registered using ICESat returns over bedrock. On NovZ thinning of between 60 and 100 meters since the 1950s' is common. Similar rates between the late 1980s' and the present are seen at SevZ. We examine in detail the response of the outlet glaciers of the Karpinsky and Russanov Ice Caps on SevZ to the rapid collapse of the Matusevich Ice Shelf in the late summer of 2012. We do not see a dynamic thinning response at the largest feeder glaciers. This may be due to the slow response of the cold polar glaciers to changing boundary conditions, or the glaciers may be grounded well above sea level. Speed increases in the interior are difficult to assess with optical imagery as there are few trackable features. We therefore use pixel tracking on Terra SARX acquisitions before and after the collapse of the ice shelf to compute rates of flow inland, at slow moving ice. Interior ice flow has not accelerated in response to the collapse of the ice shelf but interior rates at the Karpinsky Ice Cap have increased by about 50% on the largest outlet

  4. What Influences Climate and Glacier Change in the Southwestern China?

    NASA Technical Reports Server (NTRS)

    Yasunari, Teppei J.

    2012-01-01

    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 glaciers. Many of these glaciers over the region have been retreating, while some are advancing and stable. Other studies report that some glaciers in the Himalayas show acceleration on their shrinkage. However, the causes of the glacier meltings are still difficult to grasp because of the complexity of climatic change and its influence on glacier issues. However, it is vital that we pursue further study to enable the future prediction on glacier changes.

  5. Evaluating the performance of a glacier erosion model applied to Peyto Glacier, Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Vogt, R.; Mlynowski, T. J.; Menounos, B.

    2013-12-01

    Glaciers are effective agents of erosion for many mountainous regions, but primary rates of erosion are difficult to quantify due to unknown conditions at the glacier bed. We develop a numerical model of subglacial erosion and passively couple it to a vertically integrated ice flow model (UBC regional glaciation model). The model accounts for seasonal changes in water pressure at the glacier bed which affect rates of abrasion and quarrying. We apply our erosion model to Peyto Glacier, and compare estimates of glacier erosion to the mass of fine sediment contained in a lake immediately down valley from the glacier. A series of experiments with our model and ones based on subglacial sliding rates are run to explore model sensitivity to bedrock hardness, seasonal hydrology, changes in mass balance, and longer-term dimensional changes of the glacier. Our experiments show that, as expected, erosion rates are most sensitive to bedrock hardness and changes in glacier mass balance. Silt and clay contained in Peyto Lake primarily originate from the glacier, and represent sediments derived from abrasion and comminution of material produced by quarrying. Average specific sediment yield during the period AD1917-1970 from the lake is 467×190 Mg km-2yr-1 and reaches a maximum of 928 Mg km-2yr-1 in AD1941. Converting to a specific sediment yield, modelled average abrasion and quarrying rates during the comparative period are 142×44 Mg km-2yr-1 and 1167×213 Mg km-2yr-1 respectively. Modelled quarrying accounts for approximately 85-95% of the erosion occurring beneath the glacier. The basal sliding model estimates combined abrasion and quarrying. During the comparative period, estimated yields average 427×136 Mg km-2yr-1, lower than the combined abrasion and quarrying models. Both models predict maximum sediment yield when Peyto Glacier reached its maximum extent. The simplistic erosion model shows higher sensitivity to climate, as seen by accentuated sediment yield peaks

  6. Climate sensitivity of Tibetan Plateau glaciers - past and future implications

    NASA Astrophysics Data System (ADS)

    Heyman, Jakob; Hubbard, Alun; Stroeven, Arjen P.; Harbor, Jonathan M.

    2013-04-01

    The Tibetan Plateau is one of the most extensively glaciated, non-Polar regions of the world, and its mountain glaciers are the primary source of melt water for several of the largest Asian rivers. During glacial cycles, Tibetan Plateau glaciers advanced and retreated multiple times, but remained restricted to the highest mountain areas as valley glaciers and ice caps. Because glacier extent is dominantly controlled by climate, the past extent of Tibetan glaciers provide information on regional climate. Here we present a study analyzing the past maximum extents of glaciers on the Tibetan Plateau with the output of a 3D glacier model, in an effort to quantify Tibetan Plateau climate. We have mapped present-day glaciers and glacial landforms deposited by formerly more extensive glaciers in eight mountain regions across the Tibetan Plateau, allowing us to define present-day and past maximum glacier outlines. Using a high-resolution (250 m) higher-order glacier model calibrated against present-day glacier extents, we have quantified the climate perturbations required to expand present-day glaciers 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 glacier reduction. We have tested this hypothesis and modeled the future glacier development for the three mountain regions with the largest present-day glacier cover using a projected warming of 2.8 to 6.2°C within 100 years (envelope limits from IPCC). These scenarios result in dramatic glacier reductions, including 24-100% ice volume loss after 100 years and 77-100% ice volume loss after 300 years.

  7. Stationary monitoring of glacier response to climate change in China

    NASA Astrophysics Data System (ADS)

    Ren, Jiawen; Li, Zhongqin; Qin, Xiang; He, Yuanqing; He, Xiaobo; Li, Huilin

    2016-04-01

    At present, there are about 48571 glaciers with a total area of about 51.8×103 km2 and a volume of about 5.6×103 km3 in China. They are distributed widely in the high mountains in and surrounding the Tibetan Plateau and other high mountains such as Tianshan, Altay and Pamir. In view of differences in climatic conditions and glacier types, stationary monitoring of the glacier variations has been ongoing in different regions in order to investigate the glacier response to climate change. The monitoring results show that all the monitoring glaciers have been in retreat during the past decades and especially since 1990's the retreat rate has an accelerating trend. The accumulative mass balance is much negative and has a large annual variability for the monsoonal maritime glaciers in comparison with the continental and sub-continental glaciers. Under climate warming background, the acceleration of glacier melting is mainly attributed to rise in air temperature, ice temperature augment and albedo reduction of glacier surface. Particularly, the albedo reduction has a positive feedback effect on the glacier melting. Based on long term observation of glacier variations and physical properties, a simple dynamics model is coupled with mass balance modeling to make a projection of a typical glacier change in future. The primary modeling results suggest that the glacier will continue in shrinkage until vanishing within 50-90 years.

  8. Rock glaciers and the sediment dynamics in arid mountain belts

    NASA Astrophysics Data System (ADS)

    Blöthe, Jan Henrik; Höser, Thorsten; Rosenwinkel, Swenja; Korup, Oliver

    2016-04-01

    Rock glaciers are common periglacial features in highest elevations of semiarid to arid mountain ranges. Rock glaciers predominate in realms where precipitation values fall below thresholds that allow for ice glacier formation, then even outranging ice glaciers in size and number. The influence of ice glaciers on high-mountain's sediment dynamics is manifold: ice-glacier-driven erosion produces large amounts of clastic material; ice glaciers act as a conveyor belt for sediments, delivering material from their source regions to their terminus; ice glaciers entering trunk valleys form efficient dams that interrupt sediment delivery. While these mechanisms have been addressed in numerous earlier studies, the role of rock glaciers for the sediment dynamics of arid mountain belts remains elusive. We address this shortcoming by analysing a rock glacier inventory that we compiled for the Himalaya-Karakoram ranges and the Tien Shan ranges in Central Asia. Our inventory comprises more than 1000 specimen, a large number of which form dams of large trunk rivers and minor tributaries, disconnecting the sediment fluxes from upstream. In certain regions that are nearly devoid of ice-glaciers, like the Gamugah surface of NW Pakistan, rock glaciers of >10^4-m length occupy valley bottoms entirely, constituting the only mode of transport for sediments produced in headwaters. In conclusion, we call for a better understanding of the role that rock glaciers take in the sediment dynamics of arid mountain belts.

  9. Canary Islands

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This easterly looking view shows the seven major volcanic islands of the Canary Island chain (28.0N, 16.5W) and offers a unique view of the islands that have become a frequent vacation spot for Europeans. The northwest coastline of Africa, (Morocco and Western Sahara), is visible in the background. Frequently, these islands create an impact on local weather (cloud formations) and ocean currents (island wakes) as seen in this photo.

  10. Measured Climate Induced Volume Changes of Three Glaciers and Current Glacier-Climate Response Prediction

    NASA Astrophysics Data System (ADS)

    Trabant, D. C.; March, R. S.; Cox, L. H.; Josberger, E. G.

    2003-12-01

    Small but hydrologically significant shifts in climate have affected the rates of glacier volume change at the three U.S. Geological Survey Benchmark glaciers. Rate changes are detected as inflections in the cumulative conventional and reference-surface mass-balances of Wolverine and Gulkana Glaciers in Alaska and South Cascade Glacier in Washington. The cumulative mass balances are robust and have recently been corroborated by geodetic determinations of glacier volume change. Furthermore, the four-decade length of record is unique for the western hemisphere. Balance trends at South Cascade Glacier in Washington are generally in the opposite sense compared with Wolverine Glacier in Alaska; NCEP correlation of winter balance with local winter temperatures is positive at 0.59 for Wolverine and -0.64 for South Cascade Glacier. At Wolverine Glacier, the negative trend of cumulative mass balances, since measurements began in 1965, was replaced by a growth trend \\(positive mass balances\\) during the late 1970s and 1980s. The positive mass-balance trend was driven by increased precipitation during the 1976/77 to 1989 period. At Gulkana Glacier, the cumulative mass-balance trend has been negative throughout its measurement history, but with rate-change inflection points that coincide with the interdecadal climate-regime shifts in the North Pacific indices. At South Cascade Glacier, the mass-loss trend, observed since measurements began in 1953, was replaced by a positive trend between 1970 and 1976 then became strongly and continuously negative until 1997 when the rate of loss generally decreased. Since 1989, the trends of the glaciers in Alaska have also been strongly negative. These loss rates are the highest rates in the entire record. The strongly negative trends during the 1990s agree with climate studies that suggest that the period since the 1989 regime shift has been unusual. Volume response time and reference surface balance are the current suggested methods for

  11. Annual and seasonal mass balances of Chhota Shigri Glacier (benchmark glacier, Western Himalaya), India

    NASA Astrophysics Data System (ADS)

    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

    2015-04-01

    Several studies on Himalayan glaciers have been recently initiated as they are of particular interest in terms of future water supply, regional climate change and sea-level rise. In 2002, a long-term monitoring program was initiated on Chhota Shigri Glacier (15.7 square km, 9 km long, 6263-4050 m a.s.l.) located in Lahaul and Spiti Valley, Himachal Pradesh, India. This glacier lies in the monsoon-arid transition zone (western Himalaya) and is a representative glacier in Lahaul and Spiti Valley. While annual mass balances have been measured continuously since 2002 using the glaciological method, seasonal scale observations began in 2009. The annual and seasonal mass balances were then analyzed along with meteorological conditions in order to understand the role of winter and summer balances on annual glacier-wide mass balance of Chhota Shigri glacier. During the period 2002-2013, the glacier experienced a negative glacier-wide mass balance of -0.59±0.40 m w.e. a-1 with a cumulative glaciological mass balance of -6.45 m w.e. Annual glacier-wide mass balances were negative except for four years (2004/05, 2008/09, 2009/10 and 2010/11) where it was generally close to balanced conditions. Equilibrium line altitude (ELA) for steady state condition is calculated as 4950 m a.s.l. corresponding to an accumulation area ratio (AAR) of 62% using annual glacier-wide mass balance, ELA and AAR data between 2002 and 2013. The winter glacier-wide mass balance between 2009 and 2013 ranges from a maximum value of 1.38 m w.e. in 2009/10 to a minimum value of 0.89 in 2012/13 year whereas the summer glacier-wide mass balance varies from the highest value of -0.95 m w.e. in 2010/11 to the lowest value of -1.72 m w.e. in 2011/12 year. The mean vertical mass balance gradient between 2002 and 2013 was 0.66 m w.e. (100 m)-1 quite similar to Alps, Nepalese Himalayas etc. Over debris covered area, the gradients are highly variable with a negative mean value of -2.15 m w.e. (100 m)-1 over 2002

  12. Rapid Thinning of a Lake Calving Glacier: Yakutat Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Truessel, B.; Motyka, R. J.; Larsen, C. F.; Truffer, M.

    2010-12-01

    Calving glaciers around the world have recently undergone a rapid retreat and are important contributors to global sea level rise. Due to their greatly increased mass loss, tidewater glaciers in particular have long received much attention, whereas lake calving glaciers have just been identified as significant contributors. In southeast Alaska, numerous glaciers have experienced rapid retreat and significant thinning during the last several decades. To better understand the causes for these rapid changes we have focused on Yakutat Glacier, a lake calving glacier in southeast Alaska. Yakutat Glacier is part of the Yakutat Ice field and drains into Harlequin Lake, which has depths of over 300 m at the calving face. The ice field covers an area of 668 sq km and lies in a maritime area off the coast of the Gulf of Alaska. The average precipitation in the nearby town of Yakutat is over 3800 mm per year. However, the ice field divide is essentially at or below the current equilibrium line altitude (ELA) of 800 - 900 m for this region, thereby ensuring the glacier will continue to thin, provided the current trend of regional warming does not reverse. The ongoing thinning continues to lower the glaciers average elevation, increasing its average ablation, even under constant climate. This forms a positive feedback loop that is known as the Bovardsson effect. In addition, radio echo sounding shows much of the glacier base near or below sea level, indicating that lake calving will remain playing a role in the retreat. We obtained a 40 m-grid digital elevation model (DEM) derived from September 3, 2007 SPOT imagery and obtained under the IPY SPIRIT program. We used August 26, 2007 laser altimetry profiles to check the accuracy of the DEM and found a mean difference of 2 m (DEM greater) with a standard deviation of 2.3 m. We differenced this DEM from a DEM from the February 2000 Shuttle Radar Topography Mission to determine the extent of the volume change and thinning. During

  13. Distinct patterns of seasonal Greenland glacier velocity

    PubMed Central

    Moon, Twila; Joughin, Ian; Smith, Ben; van den Broeke, Michiel R; van de Berg, Willem Jan; Noël, Brice; Usher, Mika

    2014-01-01

    Predicting Greenland Ice Sheet mass loss due to ice dynamics requires a complete understanding of spatiotemporal velocity fluctuations and related control mechanisms. We present a 5 year record of seasonal velocity measurements for 55 marine-terminating glaciers distributed around the ice sheet margin, along with ice-front position and runoff data sets for each glacier. Among glaciers with substantial speed variations, we find three distinct seasonal velocity patterns. One pattern indicates relatively high glacier sensitivity to ice-front position. The other two patterns are more prevalent and appear to be meltwater controlled. These patterns reveal differences in which some subglacial systems likely transition seasonally from inefficient, distributed hydrologic networks to efficient, channelized drainage, while others do not. The difference may be determined by meltwater availability, which in some regions may be influenced by perennial firn aquifers. Our results highlight the need to understand subglacial meltwater availability on an ice sheet-wide scale to predict future dynamic changes. Key Points First multi-region seasonal velocity measurements show regional differences Seasonal velocity fluctuations on most glaciers appear meltwater controlled Seasonal development of efficient subglacial drainage geographically divided PMID:25821275

  14. ICESat Observations of Southern Alaska Glaciers

    NASA Technical Reports Server (NTRS)

    Sauber, Jeanne; Molnia, Bruce F.; Mitchell, Darius

    2003-01-01

    In late February and March, 2003, the Ice, Cloud, and land Elevation Satellite (ICESat) measured ice and land elevations along profiles across southern Alaska. During this initial data acquisition stage ICESat observations were made on 8-day repeat tracks to enable calibration and validation of the ICESat data products. Each profile consists of a series of single point values derived from centroid elevations of an $\\approx$70 m diameter laser footprint. The points are s4pakated by $\\approx$172 m along track. Data siets of 8-day observations (an ascending and descending ground track) crossed the Bering and Malaspina Glacier. Following its 1993--1995 surge; the Bering Glacier has undergone major terminus retreat as well as ike thinning in the abtation zone. During the later part of the 20th century, parts of the Malaspina thinned by about 1 m/yr. The multiple observation profiles across the Bering and Malaspina piedmont lobes obtained in February/March are being geolocated on Landsat images and the elevation profiles will be used for a number o scientific objectives. Based on our simulations of ICESat performance over the varied ice surface of the Jakobshavn Glacier of GReenland, 2003, we expect to measure annual, and possibly seasonal, ice elevation changes on the large Alaskan glaciers. Using elevation data obtained from a second laser, we plan to estimate ice elevation changes on the Bering Glacier between March and October 2003.

  15. Exploration of Uncertainty in Glacier Modelling

    NASA Technical Reports Server (NTRS)

    Thompson, David E.

    1999-01-01

    There are procedures and methods for verification of coding algebra and for validations of models and calculations that are in use in the aerospace computational fluid dynamics (CFD) community. These methods would be efficacious if used by the glacier dynamics modelling community. This paper is a presentation of some of those methods, and how they might be applied to uncertainty management supporting code verification and model validation for glacier dynamics. The similarities and differences between their use in CFD analysis and the proposed application of these methods to glacier modelling are discussed. After establishing sources of uncertainty and methods for code verification, the paper looks at a representative sampling of verification and validation efforts that are underway in the glacier modelling community, and establishes a context for these within overall solution quality assessment. Finally, an information architecture and interactive interface is introduced and advocated. This Integrated Cryospheric Exploration (ICE) Environment is proposed for exploring and managing sources of uncertainty in glacier modelling codes and methods, and for supporting scientific numerical exploration and verification. The details and functionality of this Environment are described based on modifications of a system already developed for CFD modelling and analysis.

  16. Improving Mass Balance Modeling of Benchmark Glaciers

    NASA Astrophysics Data System (ADS)

    van Beusekom, A. E.; March, R. S.; O'Neel, S.

    2009-12-01

    The USGS monitors long-term glacier mass balance at three benchmark glaciers in different climate regimes. The coastal and continental glaciers are represented by Wolverine and Gulkana Glaciers in Alaska, respectively. Field measurements began in 1966 and continue. We have reanalyzed the published balance time series with more modern methods and recomputed reference surface and conventional balances. Addition of the most recent data shows a continuing trend of mass loss. We compare the updated balances to the previously accepted balances and discuss differences. Not all balance quantities can be determined from the field measurements. For surface processes, we model missing information with an improved degree-day model. Degree-day models predict ablation from the sum of daily mean temperatures and an empirical degree-day factor. We modernize the traditional degree-day model as well as derive new degree-day factors in an effort to closer match the balance time series and thus better predict the future state of the benchmark glaciers. For subsurface processes, we model the refreezing of meltwater for internal accumulation. We examine the sensitivity of the balance time series to the subsurface process of internal accumulation, with the goal of determining the best way to include internal accumulation into balance estimates.

  17. Mathematical challenges in glacier modeling (Invited)

    NASA Astrophysics Data System (ADS)

    jouvet, G.

    2013-12-01

    Many of Earth's glaciers are currently shrinking and it is expected that this trend will continue as global warming progresses. To virtually reproduce the evolution of glaciers and finally to predict their future, one needs to couple models of different disciplines and scales. Indeed, the slow motion of ice is described by fluid mechanics equations while the daily snow precipitations and melting are described by hydrological and climatic models. Less visible, applied mathematics are essential to run such a coupling at two different levels: by solving numerically the underlying equations and by seeking parameters using optimisation methods. This talk aims to make visible the role of mathematics in this area. I will first present a short educational film I have made for the "Mathematics of Planet Earth 2013", which is an introduction to the topic. To go further, solving the mechanical model of ice poses several mathematical challenges due to the complexity of the equations and geometries of glaciers. Then, I will describe some strategies to deal with such difficulties and design robust simulation tools. Finally, I will present some simulations of the largest glacier of the European Alps, the Aletsch glacier. As a less unexpected application, I will show how these results allowed us to make a major advance in a police investigation started in 1926.

  18. The differing biogeochemical and microbial signatures of glaciers and rock glaciers

    USGS Publications Warehouse

    Fegel, Timothy S.; Baron, Jill S.; Fountain, Andrew G.; Johnson, Gunnar F.; Hall, Edward K.

    2016-01-01

    Glaciers and rock glaciers supply water and bioavailable nutrients to headwater mountain lakes and streams across all regions of the American West. Here we present a comparative study of the metal, nutrient, and microbial characteristics of glacial and rock glacial influence on headwater ecosystems in three mountain ranges of the contiguous U.S.: The Cascade Mountains, Rocky Mountains, and Sierra Nevada. Several meltwater characteristics (water temperature, conductivity, pH, heavy metals, nutrients, complexity of dissolved organic matter (DOM), and bacterial richness and diversity) differed significantly between glacier and rock glacier meltwaters, while other characteristics (Ca2+, Fe3+, SiO2 concentrations, reactive nitrogen, and microbial processing of DOM) showed distinct trends between mountain ranges regardless of meltwater source. Some characteristics were affected both by glacier type and mountain range (e.g. temperature, ammonium (NH4+) and nitrate (NO3- ) concentrations, bacterial diversity). Due to the ubiquity of rock glaciers and the accelerating loss of the low latitude glaciers our results point to the important and changing influence that these frozen features place on headwater ecosystems.

  19. The differing biogeochemical and microbial signatures of glaciers and rock glaciers

    NASA Astrophysics Data System (ADS)

    Fegel, Timothy S.; Baron, Jill S.; Fountain, Andrew G.; Johnson, Gunnar F.; Hall, Ed K.

    2016-03-01

    Glaciers and rock glaciers supply water and bioavailable nutrients to headwater mountain lakes and streams across all regions of the American West. Here we present a comparative study of the metal, nutrient, and microbial characteristics of glacial and rock glacial influence on headwater ecosystems in three mountain ranges of the contiguous U.S.: the Cascade Mountains, Rocky Mountains, and Sierra Nevada. Several meltwater characteristics (water temperature, conductivity, pH, metals, nutrients, complexity of dissolved organic matter (DOM), and bacterial richness and diversity) differed significantly between glacier and rock glacier meltwaters, while other characteristics (Ca2+, Fe3+, SiO2 concentrations, reactive nitrogen, and microbial processing of DOM) showed distinct trends between mountain ranges regardless of meltwater source. Some characteristics were affected both by glacier type and mountain range (e.g., temperature, ammonium (NH4+) and nitrate (NO3-) concentrations, and bacterial diversity). Due to the ubiquity of rock glaciers and the accelerating loss of the low-latitude glaciers, our results point to the important and changing influence that these frozen features place on headwater ecosystems.

  20. 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.

  1. Comparison of energy balance on Gangotri and Chhota Shigri Glaciers

    NASA Astrophysics Data System (ADS)

    Rastogi, G.; Ajai

    2014-11-01

    Surface energy balance of a glacier governs the physical processes taking place at the surface-atmosphere interface and connects ice ablation/accumulation to climate variability. To understand the response of Himalayan glaciers to climatic variability, a study was taken to formulate energy balance equation on two of the Indian Himalayan glaciers, one each from Indus and Ganga basins, which have different climatic and physiographic conditions. Study was carried out over Gangotri glacier (Ganga basin) and Chhota Shigri(CS) glacier from Chandra sub-basin (Indus basin). Gangotri glacier is one of the largest glaciers in the central Himalaya located in Uttarkashi District, Uttarakhand, India. Chhota Shigri glacier of Chandra sub-basin lies in Lahaul and Spiti valley of Himachal Pradesh. Energy balance components have been computed using inputs derived from satellite data, AWS (Automatic Weather Station) data and field measurements. Different components of energy balance computed are net radiation (includes net shortwave and net longwave radiation), sensible heat flux and latent heat flux. In this study comparison has been made for each of the above energy balance components as well as total energy for the above glaciers for the months of November and December, 2011. It is observed that net radiation in Gangotri glacier is higher by approximately 43 % in comparison to Chhota Shigri glacier; Sensible heat flux is lesser by 77 %; Latent heat flux is higher by 66 % in the month of November 2011. Comparison in the month of December shows that net radiation in Gangotri glacier is higher by approximately 22 % from Chhota Shigri glacier; Sensible heat flux is lesser by 90 %; Latent heat flux is higher by 3 %.Total energy received at the glacier surface and contributes for melting is estimated to be around 32 % higher in Gangotri than Chhota Shigri glacier in November, 2011 and 1.25 % higher in December, 2011. The overall results contribute towards higher melting rate in

  2. Earthshots: Satellite images of environmental change – Petermann Glacier, Greenland

    USGS Publications Warehouse

    Adamson, Thomas

    2016-01-01

    This calving is normal, but it’s worth watching Petermann and other Greenland glaciers closely. Petermann is one of the major marine-terminating glaciers of Greenland. Ice loss from the Greenland Ice Sheet has increased recently. An article in Nature concluded that climate change may cause Petermann and other Greenland glaciers to contribute to sea level rise. Landsat helps glaciologists keep a close eye on this remote but significant glacier.

  3. Columbia Glacier, Alaska: changes in velocity 1977-1986

    USGS Publications Warehouse

    Krimmel, R.M.; Vaughn, B.H.

    1987-01-01

    The Columbia Glacier, a grounded, iceberg-calving tidewater glacier near Valdez, Alaska, began to retreat about 1977. Drastic retreat occurred in 1984, and by early 1986, retreat amounted to 2km. The glacier has thinned more than 100m since 1974 at a point 4km behind the 1974 terminus position. Between 1977 and 1985 the lower glacier ice velocity increased from 3-8m/d to 10-15m/d. -from Authors

  4. Determining the maximum contribution of glacier ice to streamflow

    NASA Astrophysics Data System (ADS)

    Schaner, N. A.; Voisin, N.; Lettenmaier, D. P.

    2010-12-01

    The importance of mountain glaciers as reservoirs of water is well known. With the receding of many mountain glaciers over recent decades, concerns have been voiced about the implications for water supply systems. Previous efforts to estimate the contribution of glacier melt to streamflow have used a variety of approaches, many of which are either for very small areas or include the contribution of seasonal snowmelt in addition to glacier melt. Over larger areas, the extent of glaciers remains somewhat uncertain - the primary source is satellite observations, but estimates of glacier extent can be confounded both by the possible presence of seasonal snow cover, and glacier debris cover. We attempt a slightly different approach, and apply a simple energy balance model globally at one-quarter degree spatial and monthly temporal resolutions to provide a basis for estimating an upper bound on the contribution of glacier melt to seasonal runoff. We assume that at the time of maximum glacier melt contribution, all available energy is converted to glacier melt. Melt water quantities are then compared to monthly total runoff simulated using the Variable Infiltration Capacity (VIC) macroscale hydrology model on grid cell basis. Melt water runoff and total runoff are routed downstream to track the signature of glacier melt. Drainage basins meeting a threshold ratio of glacier melt to total runoff are used to estimate populations at risk of lowered water resources. In general, our estimates of the population at risk are lower than other, published values. When applied to USGS Benchmark glaciers, we generally underestimate glacier melt as compared to drainage basin discharge records, but we overestimate the loss of mass for the same Benchmark glaciers. Despite uncertainties in the specific quantity of melt water, our model serves to highlight areas dependent on glacier water resources at a time of climatic uncertainty.

  5. Sea otter studies in Glacier Bay National Park and Preserve: annual report 2002

    USGS Publications Warehouse

    Bodkin, James L.; Kloecker, Kimberly A.; Esslinger, George G.; Monson, Daniel H.; Coletti, Heather A.; Doherty, Janet

    2003-01-01

    Since 1995, the number of sea otters in Glacier Bay proper has increased from around 5 to more than 1200. Sea otter distribution is mostly limited to the Lower Bay, south of Sandy Cove, and is not continuous within that area. Concentrations occur in the vicinity of Sita Reef and Boulder Island and between Pt. Carolus and Rush Pt. on the west side of the Bay, although there have been occasional sightings north of Sandy Cove (Figure 1). Large portions of the Bay remain unoccupied by sea otters, but recolonization is occurring rapidly. Most prey recovered by sea otters in Glacier Bay are ecologically, commercially, or socially important species. In 2002 sea otter diet consisted of 35% clam, 26% mussel, 3% crab, 3.0% snail, 2% starfish, 11% urchins, 2% other, and 20% unidentified. Dominant clam species include the butter clam, Saxidomus gigantea, the Greenland cockle, Serripes groenlandicus, and the littleneck clam, Protothaca staminea. Urchins are primarily green urchins, Strongylocentrotus droebachiensis, and the mussel is Modiolus modiolus. Crabs observed in 2002 include the Dungeness, Cancer magister, the kelp crab Pugettia gracilis, and the helmet crab, Telmessus cherigonus. Although we characterize diet at broad geographic scales, we have previously found diet to vary between sites separated by as little as several hundred meters. Dietary variation among and within sites can reflect differences in prey availability as well as individual specialization. We estimated species composition, density, biomass, and sizes of subtidal clams, urchins, and mussels at 13 sites in Glacier Bay and 5 sites in nearby Port Althorp, where sea otters have been present for at least 20 years. All sites were selected based on the presence of abundant clam siphons and the absence of sea otters (Glacier Bay) or abundant shell litter and the presence of sea otters (Port Althorp). Glacier Bay sites were selected to achieve a broad geographic sample of dense subtidal clam beds within

  6. Late Quaternary climate change shapes island biodiversity.

    PubMed

    Weigelt, Patrick; Steinbauer, Manuel Jonas; Cabral, Juliano Sarmento; Kreft, Holger

    2016-04-01

    Island biogeographical models consider islands either as geologically static with biodiversity resulting from ecologically neutral immigration-extinction dynamics, or as geologically dynamic with biodiversity resulting from immigration-speciation-extinction dynamics influenced by changes in island characteristics over millions of years. Present climate and spatial arrangement of islands, however, are rather exceptional compared to most of the Late Quaternary, which is characterized by recurrent cooler and drier glacial periods. These climatic oscillations over short geological timescales strongly affected sea levels and caused massive changes in island area, isolation and connectivity, orders of magnitude faster than the geological processes of island formation, subsidence and erosion considered in island theory. Consequences of these oscillations for present biodiversity remain unassessed. Here we analyse the effects of present and Last Glacial Maximum (LGM) island area, isolation, elevation and climate on key components of angiosperm diversity on islands worldwide. We find that post-LGM changes in island characteristics, especially in area, have left a strong imprint on present diversity of endemic species. Specifically, the number and proportion of endemic species today is significantly higher on islands that were larger during the LGM. Native species richness, in turn, is mostly determined by present island characteristics. We conclude that an appreciation of Late Quaternary environmental change is essential to understand patterns of island endemism and its underlying evolutionary dynamics. PMID:27027291

  7. Late Quaternary climate change shapes island biodiversity.

    PubMed

    Weigelt, Patrick; Steinbauer, Manuel Jonas; Cabral, Juliano Sarmento; Kreft, Holger

    2016-04-01

    Island biogeographical models consider islands either as geologically static with biodiversity resulting from ecologically neutral immigration-extinction dynamics, or as geologically dynamic with biodiversity resulting from immigration-speciation-extinction dynamics influenced by changes in island characteristics over millions of years. Present climate and spatial arrangement of islands, however, are rather exceptional compared to most of the Late Quaternary, which is characterized by recurrent cooler and drier glacial periods. These climatic oscillations over short geological timescales strongly affected sea levels and caused massive changes in island area, isolation and connectivity, orders of magnitude faster than the geological processes of island formation, subsidence and erosion considered in island theory. Consequences of these oscillations for present biodiversity remain unassessed. Here we analyse the effects of present and Last Glacial Maximum (LGM) island area, isolation, elevation and climate on key components of angiosperm diversity on islands worldwide. We find that post-LGM changes in island characteristics, especially in area, have left a strong imprint on present diversity of endemic species. Specifically, the number and proportion of endemic species today is significantly higher on islands that were larger during the LGM. Native species richness, in turn, is mostly determined by present island characteristics. We conclude that an appreciation of Late Quaternary environmental change is essential to understand patterns of island endemism and its underlying evolutionary dynamics.

  8. Faster-X evolution of gene expression in Drosophila.

    PubMed

    Meisel, Richard P; Malone, John H; Clark, Andrew G

    2012-01-01

    DNA sequences on X chromosomes often have a faster rate of evolution when compared to similar loci on the autosomes, and well articulated models provide reasons why the X-linked mode of inheritance may be responsible for the faster evolution of X-linked genes. We analyzed microarray and RNA-seq data collected from females and males of six Drosophila species and found that the expression levels of X-linked genes also diverge faster than autosomal gene expression, similar to the "faster-X" effect often observed in DNA sequence evolution. Faster-X evolution of gene expression was recently described in mammals, but it was limited to the evolutionary lineages shortly following the creation of the therian X chromosome. In contrast, we detect a faster-X effect along both deep lineages and those on the tips of the Drosophila phylogeny. In Drosophila males, the dosage compensation complex (DCC) binds the X chromosome, creating a unique chromatin environment that promotes the hyper-expression of X-linked genes. We find that DCC binding, chromatin environment, and breadth of expression are all predictive of the rate of gene expression evolution. In addition, estimates of the intraspecific genetic polymorphism underlying gene expression variation suggest that X-linked expression levels are not under relaxed selective constraints. We therefore hypothesize that the faster-X evolution of gene expression is the result of the adaptive fixation of beneficial mutations at X-linked loci that change expression level in cis. This adaptive faster-X evolution of gene expression is limited to genes that are narrowly expressed in a single tissue, suggesting that relaxed pleiotropic constraints permit a faster response to selection. Finally, we present a conceptional framework to explain faster-X expression evolution, and we use this framework to examine differences in the faster-X effect between Drosophila and mammals.

  9. Snow and glacier mapping with polarimetric SAR

    NASA Technical Reports Server (NTRS)

    Shi, Jiancheng; Dozier, Jeff; Rott, Helmut; Davis, Robert E.

    1991-01-01

    The objective of this study was to examine the capability of mapping snow and glaciers in alpine regions using synthetic aperture radar (SAR) imagery when topographic information is not available. The topographic effects on the received power for a resolution cell can be explained by the change in illumination area and incidence angle in a slant-rante representation of SAR imagery. The specific polarization signatures and phase difference between HH and VV components are relatively independent of the illuminated are, and the incidence angle has only a small effect on these parameters. They provide a suitable measurement data set for snow and glacier mapping in a high-relief area. The results show that the C-band images of the enhancement factor, the phase difference between HH and VV scattering components, and the normalized cross product of VV scattering elements provide the capability to discriminate among snow with different wetnesses, glaciers, and rocky regions.

  10. More Data and Better Tools for the GLIMS Glacier Database

    NASA Astrophysics Data System (ADS)

    Raup, B. H.; Armstrong, R. L.; Cogley, J. G.; Hock, R.

    2015-12-01

    Earth's glaciers are changing rapidly in response to a changing climate, and this has implications for people in numerous ways, such as increased hazards from glacial lake outburst floods, changes to water resources, and increasing sea level. To understand these changes, it is vitally important to monitor glaciers through time, measuring their areal extent, changes in volume, flow velocities, snow lines, elevation distribution, and changes to associated water bodies. The glacier database of the Global Land Ice Measurements from Space (GLIMS) initiative is the only multi-temporal glacier database capable of tracking all these glacier measurements and providing them to the scientific community and broader public.This contribution presents recent results in 1) expansion of the GLIMS Glacier Database in geographic coverage by drawing on the Randolph Glacier Inventory (RGI) and other new data sets; 2) new tools for visualizing and downloading GLIMS data in a choice of formats and data models; 3) a new data model for handling multiple glacier records through time while avoiding double-counting of glacier number or area; and 4) a new system of collaboration between all members of the glacier mapping community to streamline the process of meeting various community needs. The result of this work promises to be an improved glacier data repository that will be useful for tracking changes in water resources, hazards, and mass budgets of the world's glaciers.

  11. Contrasting responses of Central Asian rock glaciers to global warming.

    PubMed

    Sorg, Annina; Kääb, Andreas; Roesch, Andrea; Bigler, Christof; Stoffel, Markus

    2015-02-06

    While the responses of Tien Shan glaciers--and glaciers elsewhere--to climatic changes are becoming increasingly well understood, this is less the case for permafrost in general and for rock glaciers in particular. We use a novel approach to describe the climate sensitivity of rock glaciers and to reconstruct periods of high and low rock glacier activity in the Tien Shan since 1895. Using more than 1500 growth anomalies from 280 trees growing on rock glacier bodies, repeat aerial photography from Soviet archives and high-resolution satellite imagery, we present here the world's longest record of rock glacier movements. We also demonstrate that the rock glaciers exhibit synchronous periods of activity at decadal timescales. Despite the complex energy-balance processes on rock glaciers, periods of enhanced activity coincide with warm summers, and the annual mass balance of Tuyuksu glacier fluctuates asynchronously with rock glacier activity. At multi-decadal timescales, however, the investigated rock glaciers exhibit site-specific trends reflecting different stages of inactivation, seemingly in response to the strong increase in air temperature since the 1970s.

  12. Contrasting responses of Central Asian rock glaciers to global warming

    PubMed Central

    Sorg, Annina; Kääb, Andreas; Roesch, Andrea; Bigler, Christof; Stoffel, Markus

    2015-01-01

    While the responses of Tien Shan glaciers – and glaciers elsewhere – to climatic changes are becoming increasingly well understood, this is less the case for permafrost in general and for rock glaciers in particular. We use a novel approach to describe the climate sensitivity of rock glaciers and to reconstruct periods of high and low rock glacier activity in the Tien Shan since 1895. Using more than 1500 growth anomalies from 280 trees growing on rock glacier bodies, repeat aerial photography from Soviet archives and high-resolution satellite imagery, we present here the world's longest record of rock glacier movements. We also demonstrate that the rock glaciers exhibit synchronous periods of activity at decadal timescales. Despite the complex energy-balance processes on rock glaciers, periods of enhanced activity coincide with warm summers, and the annual mass balance of Tuyuksu glacier fluctuates asynchronously with rock glacier activity. At multi-decadal timescales, however, the investigated rock glaciers exhibit site-specific trends reflecting different stages of inactivation, seemingly in response to the strong increase in air temperature since the 1970s. PMID:25657095

  13. 36 CFR 7.3 - Glacier National Park.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 1 2013-07-01 2013-07-01 false Glacier National Park. 7.3... REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.3 Glacier National Park. (a) Fishing. (1) Fishing... food, drink, or lodging for sale may be operated on any privately owned lands within Glacier...

  14. ASTER Imaging and Analysis of Glacier Hazards

    NASA Astrophysics Data System (ADS)

    Kargel, Jeffrey; Furfaro, Roberto; Kaser, Georg; Leonard, Gregory; Fink, Wolfgang; Huggel, Christian; Kääb, Andreas; Raup, Bruce; Reynolds, John; Wolfe, David; Zapata, Marco

    Most scientific attention to glaciers, including ASTER and other satellite-derived applications in glacier science, pertains to their roles in the following seven functions: (1) as signposts of climate change (Kaser et al. 1990; Williams and Ferrigno 1999, 2002; Williams et al. 2008; Kargel et al. 2005; Oerlemans 2005), (2) as natural reservoirs of fresh water (Yamada and Motoyama 1988; Yang and Hu 1992; Shiyin et al. 2003; Juen et al. 2007), (3) as contributors to sea-level change (Arendt et al. 2002), (4) as sources of hydropower (Reynolds 1993); much work also relates to the basic science of glaciology, especially (5) the physical phenomeno­logy of glacier flow processes and glacier change (DeAngelis and Skvarca 2003; Berthier et al. 2007; Rivera et al. 2007), (6) glacial geomorphology (Bishop et al. 1999, 2003), and (7) the technology required to acquire and analyze satellite images of glaciers (Bishop et al. 1999, 2000, 2003, 2004; Quincey et al. 2005, 2007; Raup et al. 2000, 2006ab; Khalsa et al. 2004; Paul et al. 2004a, b). These seven functions define the important areas of glaciological science and technology, yet a more pressing issue in parts of the world is the direct danger to people and infrastructure posed by some glaciers (Trask 2005; Morales 1969; Lliboutry et al. 1977; Evans and Clague 1988; Xu and Feng 1989; Reynolds 1993, 1998, 1999; Yamada and Sharma 1993; Hastenrath and Ames 1995; Mool 1995; Ames 1998; Chikita et al. 1999; Williams and Ferrigno 1999; Richardson and Reynolds 2000a, b; Zapata 2002; Huggel et al. 2002, 2004; Xiangsong 1992; Kääb et al. 2003, 2005, 2005c; Salzmann et al. 2004; Noetzli et al. 2006).

  15. Ocean and glaciers interactions in Svalbard area

    NASA Astrophysics Data System (ADS)

    Walczowski, Waldemar; Błaszczyk, Małgorzata; Wawrzyniak, Tomasz; Beszczyńska-Möller, Agnieszka

    2016-04-01

    Arctic fjords are a link between land and ocean. The inshore boundary of the fjords system is usually dominated by the tidewater glaciers and seasonal freshwater input while its offshore boundary is strongly influenced by oceanic waters. Improved understanding of the fjords-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 glaciers and Arctic climate. Rapidly changed Arctic climate requires multidisciplinary and complex investigations of the basic climate components and interactions between them. The aim of the Polish-Norwegian project 'Arctic climate system study of ocean, sea ice and glaciers interactions in Svalbard area' (AWAKE-2) is to understand the interactions between the ocean, atmosphere and cryosphere. The main oceanic heat source in Svalbard region is the West Spitsbergen Current consisting of multi-branch, northward flow of warm, Atlantic origin water (AW). During its transit through the Nordic Seas, AW releases a large amount of heat to the atmosphere. When entering the Western Svalbard fjords, AW modifies hydrographic conditions, reduces winter ice cover and directly influences tidewater glaciers. An impact of the AW variability on atmosphere and sea ice is clearly visible with strong correlations between AW properties and air temperature or sea ice coverage. For tidewater glaciers these effects can be recognized, but correlations are weaker due to different processes that influence the intensity of glaciers melting and calving. The dedicated, multidisciplinary approach was adopted to achieve the AWAKE-2 project's aims by carrying out the coordinated meteorological, oceanographic, glaciological and geophysical observations in the Hornsund fjord, the adjacent shelf and ocean.

  16. Columbia Glacier in 1986; 800 meters retreat

    USGS Publications Warehouse

    Krimmel, R.M.

    1987-01-01

    Columbia Glacier, in Prince William Sound, Alaska, continued its rapid retreat in 1986, with a retreat of 800 m. Average velocity of the lower portion of the glacier, 10 September 1986 to 26 January 1987, was three km/yr, or about one-half of the velocity during similar periods for the previous three years. This reduced velocity is a new development in the progression of the retreat, and if the calving rate follows the pattern of previous years, will result in continued retreat. (Author 's abstract)

  17. Use of terrestrial laser scanning to characterize rock glacier surface morphology and deformation, Handcart Gulch, Colorado

    NASA Astrophysics Data System (ADS)

    Cuddus, Y.; Caine, J. S.

    2012-12-01

    While there has been extensive, recent research on the kinematics of rock glaciers, few studies have been able to examine surface deformation and strain utilizing terrestrial laser scanning (TLS). TLS captures a high precision, three-dimensional point cloud of X, Y, Z data. We scanned a portion of the Handcart Gulch Rock Glacier (HRG) surface at centimeter scale resolution (standard deviation of 0.64 cm). Although the origins of rock glacier formation and subsequent kinematics are poorly understood, the general consensus is that periglacial rock glaciers are a type of mass-driven permafrost that moves on the order of tens of cm per year. Velocity near the surface is thought to be faster than at depth, producing ridge- or moraine-like structures possibly formed by near-surface, compressional buckling. The HRG, located in Pike National Forest just below the Continental Divide, is multi-lobed and composed of hydrothermally altered Proterozoic metamorphic rock. In addition to commonly observed "compressional ridges", the rock glacier surface shows a number of scarp-like discontinuities that may be indicative of extension. The rock glacier surface has limited vegetative cover and a thin, but laterally extensive, layer of unidentified black lichen and lesser amounts of green Rhizocarpon lichen. The curviplanar scarps are up to about 4 m in height and are marked by discrete discontinuities that cut the lichen-covered rock glacier surface, revealing steeply dipping (> 35°) faces that are not covered with lichen. The lichen-covered surface appears to have been displaced, top-down in the direction of the maximum topographic gradient, and along the relatively lichen-free scarps thus resembling normal faults. Lichenometry is a useful method for providing a relative dating of rock glacial movement. Rhizocarpon is commonly used for dating due to its well documented, slow growth rate and ease of identification. After a century of growth the maximum diameter of Front Range

  18. Soil processes in recently deglaciated environments in Maritime Antarctica: a study case from Elephant Point (Livingston Island, South Shetland Islands)

    NASA Astrophysics Data System (ADS)

    Oliva, Marc; Ruiz-Fernández, Jesús; Quijano, Laura; Palazón, Leticia; Navas, Ana

    2016-04-01

    Many ice-free environments in the northern Antarctic Peninsula are undergoing rapid and substantial environmental changes in response to reent climate trends. This is the case of Elephant Point (Livingston Island, South Shetland Islands), where the glacier retreat recorded during the second half of the XX century, has exposed 17% of this small peninsula (1.16 km2). Glacier retreat has exposed new ice-free land surface in the northern part of Elephant Point: a moraine extending from the western to the eastern coastlines and a relatively flat proglacial surface. Besides, a sequence of present-day beach, Holocece marine terraces and bedrock plateaus are also distributed in the southern margin of the peninsula. Periglacial processes are widespread in all the peninsula, but the type and characteristics of soils depen on the timing of glacier retreat. In this research we aim to assess how the glacier retreat affects the recently formed soils. Ten sites were sampled along a transect crossing different geomorphological units (beach, raised beaches, moraine, proglacial environment), following the direction of glacier retreat. To this purpose the upper part of selected soil profiles was sectioned in 3 cm depth interval increments to examine main soil properties, grain size distribution, soil organic carbon and pH. Besides, elemental composition and patterns of fallout (FRNs) and environmental radionuclides (ERNs) were analysed to assess if soil profile characteristics within the active layer are affected by glacier retreat. The results obtained confirm the potential for using geomorphological, edaphic and geochemical data to derive information for assessing the influence of different stages of glacier retreat in the study soils.

  19. Glacier fluctuations in the Kenai Fjords, Alaska, U.S.A.: An evaluation of controls on Iceberg-calving glaciers

    SciTech Connect

    Wiles, G.C.; Calkin, P.E.; Post, A.

    1995-08-01

    The histories of four iceberg-calving outlet-glacier systems in the Kenai Fjords National Park underscore the importance of fiord depth, sediment supply, and fiord geometry on glacier stability. These parameters, in turn, limit the reliability of calving glacier chronologies as records of climatic change. Tree-ring analysis together with radiocarbon dating show that the Northwestern and McCarty glaciers, with large drainage basins, were advancing in concert with nearby land-terminating glaciers about A.D. 600. After an interval of retreat and possible nonclimatically induced extension during the Medieval Warm Period, these ice margins advanced again through the Little Ice Age and then retreated synchronously with the surrounding land-terminating glaciers about A.D. 1900. In contrast, Holgate and Aialik glaciers, with deeper fiords and smaller basins, retreated about 300 yr earlier. Reconstructions of Little Ice Age glaciers suggest that equilibrium-line altitudes of Northwestern and McCarty glaciers were, respectively, 270 and 500 m lower than now. Furthermore, the reconstructions show that these two glaciers 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 Glacier shows evidence of advance. Aialik and Holgate glaciers were climatically insensitive during the Little Ice Age maxima and remain insensitive to climate. 40 refs., 7 figs., 2 tabs.

  20. Surface characteristics and evolution of debris covered glaciers

    NASA Astrophysics Data System (ADS)

    Mölg, Nico; Vieli, Andreas; Bolch, Tobias; Bauder, Andreas; Bhattacharya, Atanu

    2016-04-01

    Global climate change has led to increasing glacier retreat in most parts of the world. However, many heavily debris-covered glaciers have shown much smaller recession rates than their clean-ice neighbours. This can be attributed to the insulation effect of the supraglacial debris. Remote-sensing based investigations revealed that recent mass balances of debris-covered glaciers are equally negative. This fact is partly due to enhanced melting at supra-glacial lakes and ice cliffs but can also be caused by reduced mass flux. In this context, insufficient process understanding constitutes a major challenge for large scale glacier change assessment and modelling. In this project, we aim at better understanding the evolution of glaciers in connection with changes in supra-glacial debris coverage. It is performed on Zmutt Glacier in Matter valley in Switzerland and on Gangotri Glacier in Garwhal Himalaya in India. Changes in glacier length, area, debris coverage, and surface elevation were compiled based on topographic maps, oblique photos, aerial and satellite orthoimages, digital terrain models (DTMs), and glacier monitoring data for a 50 (Gangotri) and 120 (Zmutt) year period, respectively. The subsequent analysis revealed that Zmutt Glacier has been in a slow but almost continuous retreating state since the end of the 19th century and showed a clear reduction in glacier area and volume. Similarly, Gangotri Glacier has retreated and, to a smaller degree, lost volume. However, the change in glacier length and area is clearly smaller than for other nearby, less debris-covered or debris-free glaciers. This fact is attributed to the larger debris-covered area that has steadily increased. Further in the project, this data will serve as an important input and validation for the envisaged 3D flow modelling and, hence, will contribute to the understanding of the development of glaciers and debris-covered ice in a period of fast climatic changes.

  1. Malaspina Glacier, Alaska as seen from STS-66 Atlantis

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Malaspina Glacier can be seen in this north-northeastern photograph taken in November, 1994. The glacier, located in the south shore of Alaska is a classic example of a piedmont glacier lying along the foot of a mountain range. The principal source of ice for the glacier is provided by the Seward Ice Field to the north (top portion of the view) which flows through three narrow outlets onto the coastal plain. The glacier moves in surges that rush earlier-formed moraines outward into the expanding concentric patterns along the flanks of the ice mass.

  2. Sensitivity of glaciers and small ice caps to greenhouse warming

    SciTech Connect

    Oerlemans, J.; Fortuin, J.P.F. )

    1992-10-02

    Recent field programs on glaciers have supplied information that makes simulation of glacier mass balance with meteorological models meaningful. An estimate of world-wide glacier sensitivity based on a modeling study of 12 selected glaciers situated in widely differing climatic regimes shows that for a uniform 1 K warming the area-weighted glacier mass balance will decrease by 0.40 meter per year. This corresponds to a sea-level rise of 0.58 millimeter per year, a value significantly less than earlier estimates.

  3. Contrasting response of South Greenland glaciers to recent climatic change

    SciTech Connect

    Warren, C.R.; Glasser, N.F. )

    1992-05-01

    A unique geographical configuration of glaciers exists in the Narsarsuaq district of South Greenland. Two large outlet glaciers divide into seven distributaries, such that each glacier system has land-terminating, tidewater-calving, and fresh-water-calving termini. Despite a similar climatic regime, these seven glaciers have exhibited strongly contrasting terminal behavior in historical time, as shown by historical records, aerial photographs, and fieldwork in 1989. The behavior of the calving glaciers cannot be accounted for with reference solely to climatic parameters. The combination of iceberg calving dynamics and topographic control has partially decoupled them from climatic forcing such that their oscillations relate more closely to glaciodynamic than glacioclimatic factors.

  4. Monitoring and Modelling Glacier Melt and Runoff on Juncal Norte Glacier, Aconcagua River Basin, Central Chile

    NASA Astrophysics Data System (ADS)

    Pellicciotti, F.; Helbing, J. F.; Araos, J.; Favier, V.; Rivera, A.; Corripio, J.; Sicart, J. M.

    2006-12-01

    Results from a recent glacio-meteorological experiment on the Juncal Norte glacier, in central Chile, are presented. Melt water is a crucial resource in the Central Andes, as it provides drinking water, water for agriculture and for industrial uses. There is also increasing competition for water use and allocation, as water demands from mining and industry are rising. Assessing water availability in this region and its relation with climatic variations is therefore crucial. The Dry Central Andes are characterised by a climatic setting different from that of the Alps and the subtropical Andes of Bolivia and Peru. Summers are very dry and stable, with precipitation close to zero and low relative humidity. Solar radiation is very intense, and plays a key role in the energy balance of snow covers and glaciers. The main aim of this study is to investigate the glacier-climate interaction in this area, with particular attention devoted to advanced modelling techniques for the spatial redistribution of meteorological variables, in order to gain an accurate picture of the ablation processes typical of these latitudes. During the ablation season 2005/2006, an extensive field campaign was conducted on the Juncal Norte glacier, aimed at monitoring the melt and runoff generation processes on this remote glacier in the dry Andes. Melt rates, runoff at the snout, meteorological variables over and near the glacier, GPS data and glacier topography were recorded over the entire ablation season. Using this extensive and accurate data set, the spatial and temporal variability of the meteorological variables that drive the melt process on the glacier is investigated, together with the process of runoff generation. An energy balance model is used to simulate melt across the glacier, and special attention is devoted to the modelling of the solar radiation energy flux. The components of the energy balance are compared with those of Alpine basins. The validity of parameterisations of the

  5. Long-term linkages between glaciers, permafrost and hydrology at two glacierized watersheds in Alaska

    NASA Astrophysics Data System (ADS)

    Gaedeke, A.; Liljedahl, A. K.; Gatesman, T.; Campbell, S. W.; Hock, R.; Oneel, S.

    2015-12-01

    Climate warming is expected to have considerable impact on the regional water balance of high latitude Arctic and sub-Arctic glacerized watersheds. In this study we combine field observations and the physically based Water Balance Simulation Model WaSiM to refine our understanding of the linkages between glaciers, permafrost and hydrology at two nearby basins with contrasting precipitation regimes: Jarvis Cr. watershed (630 km2) on the north (rain-shadow) side of Eastern Alaska Range and the south facing Phelan Cr. (32 km2), which include the US Geological Survey benchmark site Gulkana Glacier. Both are characterized by a semi-arid climate and are sub-watersheds of the Tanana River basin (12,000 km2). Our research questions include: How has glacier water storage and release varied in the past and how are they expected to change in the future? And what are the subsequent effects on lowland runoff and regional groundwater recharge? Our analyses show i) an increase in air temperature and summer warmth index (the sum of all mean monthly air temperature above 0 °C) in recent decades and ii) a continued negative glacier mass balance. Our findings suggest that, on the larger spatial scale (Tanana River basin), the reduced glacier coverage and increased glacier wastage has, in combination with limited changes in precipitation, lead to (i) increased mean annual and (ii) late winter (March) runoff. We postulate that this is due to increased groundwater recharge, which has been fueled by the 20% reduction in glacier coverage of the Tanana River basin. Here we aim to assess the combined effect of climate change, glacier shrinkage and thawing permafrost on the regional sub-arctic mountain- to lowland hydrologic system, which may transition into a regime with less surface and more subsurface water availability.

  6. Exploiting SENTINEL-1 Amplitude Data for Glacier Surface Velocity Field Measurements: Feasibility Demonstration on Baltoro Glacier

    NASA Astrophysics Data System (ADS)

    Nascetti, A.; Nocchi, F.; Camplani, A.; Di Rico, C.; Crespi, M.

    2016-06-01

    The leading idea of this work is to continuously retrieve glaciers surface velocity through SAR imagery, in particular using the amplitude data from the new ESA satellite sensor Sentinel-1 imagery. These imagery key aspects are the free access policy, the very short revisit time (down to 6 days with the launch of the Sentinel-1B satellite) and the high amplitude resolution (up to 5 m). In order to verify the reliability of the proposed approach, a first experiment has been performed using Sentinel-1 imagery acquired over the Karakoram mountain range (North Pakistan) and Baltoro and other three glaciers have been investigated. During this study, a stack of 11 images acquired in the period from October 2014 to September 2015 has been used in order to investigate the potentialities of the Sentinel-1 SAR sensor to retrieve the glacier surface velocity every month. The aim of this test was to measure the glacier surface velocity between each subsequent pair, in order to produce a time series of the surface velocity fields along the investigated period. The necessary coregistration procedure between the images has been performed and subsequently the glaciers areas have been sampled using a regular grid with a 250 × 250 meters posting. Finally the surface velocity field has been estimated, for each image pair, using a template matching procedure, and an outlier filtering procedure based on the signal to noise ratio values has been applied, in order to exclude from the analysis unreliable points. The achieved velocity values range from 10 to 25 meters/month and they are coherent to those obtained in previous studies carried out on the same glaciers and the results highlight that it is possible to have a continuous update of the glacier surface velocity field through free Sentinel-1 imagery, that could be very useful to investigate the seasonal effects on the glaciers fluid-dynamics.

  7. Glaciers and Global Climate: Field and Remote-Sensing Studies of the Arctic

    NASA Technical Reports Server (NTRS)

    Hall, D. K.

    1998-01-01

    Glaciers are important indicators of global climate. Glacier recession, as observed from space and in the field, has been occurring for about 100 years. The present extent of glaciers and glaciers in the last Ice Age will be discussed. I will show slides of field work on glaciers and show instruments used to measure ice and snow. I will discuss reasons for studying glaciers and why remote sensing is important for glacier studies.

  8. A complex relationship between calving glaciers and climate

    USGS Publications Warehouse

    Post, A.; O'Neel, S.; Motyka, R.J.; Streveler, G.

    2011-01-01

    Many terrestrial glaciers are sensitive indicators of past and present climate change as atmospheric temperature and snowfall modulate glacier volume. However, climate interpretations based on glacier behavior require careful selection of representative glaciers, as was recently pointed out for surging and debris-covered glaciers, whose behavior often defies regional glacier response to climate [Yde and Paasche, 2010]. Tidewater calving glaciers (TWGs)mountain glaciers whose termini reach the sea and are generally grounded on the seaflooralso fall into the category of non-representative glaciers because the regional-scale asynchronous behavior of these glaciers clouds their complex relationship with climate. TWGs span the globe; they can be found both fringing ice sheets and in high-latitude regions of each hemisphere. TWGs are known to exhibit cyclic behavior, characterized by slow advance and rapid, unstable retreat, largely independent of short-term climate forcing. This so-called TWG cycle, first described by Post [1975], provides a solid foundation upon which modern investigations of TWG stability are built. Scientific understanding has developed rapidly as a result of the initial recognition of their asynchronous cyclicity, rendering greater insight into the hierarchy of processes controlling regional behavior. This has improved the descriptions of the strong dynamic feedbacks present during retreat, the role of the ocean in TWG dynamics, and the similarities and differences between TWG and ice sheet outlet glaciers that can often support floating tongues.

  9. Satellite-Based Study of Glaciers Retreat in Northern Pakistan

    NASA Astrophysics Data System (ADS)

    Munir, Siraj

    Glaciers serve as a natural regulator of regional water supplies. About 16933 Km 2 area of glaciers is covered by Pakistan. These glaciers are enormous reservoirs of fresh water and their meltwater is an important resource which feed rivers in Pakistan. Glacier depletion, especially recent melting can affect agriculture, drinking water supplies, hydro-electric power, and ecological habitats. This can also have a more immediate impact on Pakistan's economy that depends mainly on water from glacier melt. Melting of seasonal snowfall and permanent glaciers has resulted not only in reduction of water resources but also caused flash floods in many areas of Pakistan. With the advent of satellite technology, using optical and SAR data the study of glaciers, has become possible. Using temporal data, based on calculation of snow index, band ratios and texture reflectance it has been revealed that the rate of glacier melting has increased as a consequent of global warming. Comparison of Landsat images of Batura glacier for October 1992 and October 2000 has revealed that there is a decrease of about 17 sq km in Batura glaciers. Although accurate changes in glacier extent cannot be assessed without baseline information, these efforts have been made to analyze future changes in glaciated area.

  10. Implications of Glacier Volume Change for Ice-Ocean Interactions

    NASA Astrophysics Data System (ADS)

    Hood, E. W.; O'Neel, S.; Fellman, J.; Bidlack, A.; Arendt, A. A.; Arimitsu, M.; Spencer, R. G.

    2015-12-01

    Changes in climate are forcing complex glaciological responses that can be transmitted to downstream ecosystems via glacier runoff. Along the Gulf of Alaska, rates of glacier mass loss are among the highest measured on Earth. Changes in glacier volume in this region are altering the amount of glacier runoff delivered to the coastal ocean. Moreover, shifts in glacier extent are changing the location of the ice-ocean interface and, in cases where tidewater glaciers become grounded, fundamentally altering circulation in glacierized fjords. The runoff from glacier ecosystems is unique in terms of its physical and chemical properties when compared to runoff from non-glacial ecosystems. For example, the silt and chemical constituents in glacier discharge alter light penetration and the nutrient regime in near-shore marine ecosystems, which, in turn, influence levels of marine primary productivity. Future changes in the magnitude, timing, and location of glacier runoff have important implications for biogeochemical and ecological processes in glacially-dominated fjords and estuaries. This talk will highlight research from glacierized watersheds and fjords to synthesize what is known about the physical, chemical, and biological linkages that characterize icefield-ocean ecosystems along the Gulf of Alaska.

  11. Glacier modeling in support of field observations of mass balance at South Cascade Glacier, Washington, USA

    USGS Publications Warehouse

    Josberger, Edward G.; Bidlake, William R.

    2010-01-01

    The long-term USGS measurement and reporting of mass balance at South Cascade Glacier was assisted in balance years 2006 and 2007 by a new mass balance model. The model incorporates a temperature-index melt computation and accumulation is modeled from glacier 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 "glacier 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 glacier. The 2006 and 2007 winter balances of South Cascade Glacier, 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 Glacier in Washington state. Presented at the American Geophysical Union Fall Meeting 2010.

  12. Effects of volcanism on the glaciers of Mount St. Helens

    USGS Publications Warehouse

    Brugman, Melinda M.; Post, Austin

    1981-01-01

    The cataclysmic eruption of Mount St. Helens May 18, 1980, removed 2.9 km2 (about 0.13 km3) of glacier snow and ice including a large part of Shoestring, Forsyth, Wishbone, Ape, Nelson, and all of Loowit and Leschi Glaciers. Minor eruptions and bulging of the volcano from March 27 to May 17 shattered glaciers which were on the deforming rock and deposited ash on other glaciers. 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 melting on Swift and Dryer Glaciers. Melting and recrystalization of snow and ice surviving on Mount St. Helens could cause and lubricate mudflows and generate outburst floods. Study of glaciers 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 glaciers to changes in mass balance or geometry.

  13. SAR investigations of glaciers in northwestern North America

    NASA Technical Reports Server (NTRS)

    Lingle, Craig S.; Harrison, William D.

    1995-01-01

    The objective of this project was to investigate the utility of satellite synthetic aperture radar (SAR) imagery for measurement of geophysical parameters on Alaskan glaciers relevant to their mass balance and dynamics, including: (1) the positions of firn lines (late-summer snow lines); (2) surface velocities on fast-flowing (surging) glaciers, and also on slower steady-flow glaciers; and (3) the positions and changes in the positions of glacier termini. Preliminary studies of topography and glacier surface velocity with SAR interferometry have also been carried out. This project was motivated by the relationships of multi-year to decadal changes in glacier geometry to changing climate, and the probable significant contribution of Alaskan glaciers to rising sea level.

  14. Subglacial till: the deforming glacier bed

    NASA Astrophysics Data System (ADS)

    van der Meer, Jaap J. M.; Menzies, John; Rose, James

    2003-07-01

    "Till is a sediment and is perhaps more variable than any sediment known by a single name." R.F. Flint 1957 Glacial and Pleistocene Geology Tills are commonly classified according to the perceived process of deposition. However, it is increasingly recognised that this classification, which is mainly based on macroscopic field data, has severe limitations. At the same time the concept of the deforming glacier bed has become more realistic as a framework for discussing tills and their properties, and this (tectonic) concept is irreconcilable with the existing (depositional) till classification scheme. Over the last 20 years large thin sections have been used to study tills, which has provided new insights into the textural and structural properties of tills. These results have revolutionised till sedimentology as they show that, in the main, subglacial tills possess deformational characteristics. Depositional properties are rare. Based on this new insight the process of subglacial till formation is discussed in terms of glacier/ice sheet basal velocity, clay, water and carbonate content and the variability of these properties in space and time. The end result of this discussion is: till, the deforming glacier bed. To distinguish subglacial till from depositional sediments the term 'tectomict' is proposed. Within the single framework of subglacial till as the deforming glacier bed, many textural, structural and geomorphological features of till beds can be more clearly and coherently explained and understood.

  15. Stream temperature response to glacier retreat (Invited)

    NASA Astrophysics Data System (ADS)

    Moore, R. D.

    2013-12-01

    Stream temperature is a fundamental aspect of aquatic habitat, and there has been increasing concern in recent years that climatic change and glacier retreat will result in increased water temperatures, with potentially negative influences on cold and cool water species such as salmonids. A statistical model was developed to predict the maximum weekly average stream temperature based on data from 418 sites located throughout British Columbia, Canada. Catchment-scale glacier coverage was a significant predictor in the model, and example calculations indicate that plausible decreases in glacier coverage over the next few decades have the potential to result in warming that would be sufficient to cause shifts in fish species assemblages. However, this space-for-time substitution rests on assumptions that may not be valid, especially in the context of a changing climate, leading to a need to develop and apply physically based models. Reach-scale energy budget analyses indicate that parameterizations of energy fluxes used in current stream temperature models are not appropriate for steep channels with cascading flow. In particular, the sensible and latent heat fluxes are more efficient than in lower-gradient channels, and the albedo is enhanced by aeration. Over longer time scales, development of riparian forest has the potential to mitigate the effect of glacier retreat in alpine areas by shading the stream, but it may take centuries for functional riparian forest to develop at higher elevation sites.

  16. Asia High Mountain Glacier Mass Balance

    NASA Astrophysics Data System (ADS)

    Shum, C. K.; Su, X.; Shang, K.; Cogley, J. G.; Zhang, G.; Howat, I. M.; Braun, A.; Kuo, C. Y.

    2015-12-01

    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 glacier wastage, permafrost active layer thickening, the timing and the quantity of the perennial snowpack melt affecting upstream catchments, river runoffs, land-use, have significant effects on downstream water resources. Exact quantification of the Asian High Mountain glacier wastage or its mass balance on how much of the melt 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 glacier wastage. Here, we provide an updated estimate of Asia high mountain glacier 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.

  17. A Facies Model for Temperate Continental Glaciers.

    ERIC Educational Resources Information Center

    Ashley, Gail Mowry

    1987-01-01

    Discusses the presence and dynamics of continental glaciers in the domination of the physical processes of erosion and deposition in the mid-latitudes during the Pleistocene period. Describes the use of a sedimentary facies model as a guide to recognizing ancient temperate continental glacial deposits. (TW)

  18. The Bay in Place of a Glacier.

    ERIC Educational Resources Information Center

    Howell, Wayne

    1997-01-01

    The cultural resource specialist at Glacier Bay National Park (Alaska) explains the collaborative efforts of park staff and the Hoonah Tlingit to overcome language and cultural barriers in documenting park place names and clan oral history and traditions. The new park-community relationship, which follows decades of conflict, includes training…

  19. Noble Gas Signatures in Athabasca Glacier - Tracing Glacial Meltwater Sources

    NASA Astrophysics Data System (ADS)

    Niu, Y.; Hall, C. M.; Castro, M. C.; Aciego, S.; Arendt, C. A.

    2015-12-01

    We present a noble gas study in glacial meltwater (GMW) from the Athabasca Glacier (AG) in the Columbia Icefield, Canada. It constrains the relative contributions of GMW sources, water residence times, and spatial locations where the GMW originates in the alpine glacier. This is possible due to the conservative nature of noble gases and temperature dependency of their concentrations in water in equilibrium with the atmosphere (ASW) which allows for estimation of the altitude at which GMW originated. In addition, crustal He accumulates in water over time, allowing for estimation of water residence times. Water samples were collected in the morning on selected dates in May and July 2011 at two locations about 200 m apart near the terminus area at altitudes between 2000 m and 2100 m. Eight samples were collected in six different days. Results show that the major source of subglacial meltwater is ASW rather than old, compressed glacial ice, which has a distinct noble gas signature not seen in our samples. Given that, GMW samples from the AG do deviate to a certain extent from the ASW values corresponding to measured water temperature and altitude at collection points. Two patterns are observed in the concentrations of the AG samples. The first one presents a relative Ar enrichment with respect to Ne, Kr, and Xe, first observed in high-altitude springs in the Galápagos Islands (Warrier et al., 2012). The second one displays a mass-dependent pattern, first observed in Michigan rainwater (Warrier et al., 2013). A preliminary Xe analysis indicates equilibration altitudes between 2500 m and 3400 m, values compatible with local topography. Samples present He excess of 4% to 91%, and suggest an average residence time of ~400 yrs. References:Warrier, R. B., Castro, M. C., and Hall, C. M. (2012), Recharge and source-water insights from the Galapagos Islands using noble gases and stable isotopes, Water Resour. Res., 48, W03508, doi:10.1029/2011WR010954. Warrier, R. B., Castro

  20. The first glacier inventory for entire Greenland

    NASA Astrophysics Data System (ADS)

    Rastner, P.; Bolch, T.; Mölg, N.; Le Bris, R.; Paul, F.

    2012-04-01

    Detailed glacier data is becoming more and more important in the last decades to solve several research issues. One of the most prominent questions in this regard is the potential contribution of glaciers and icecaps (GIC) to global sea-level rise. Primarily, estimates are uncertain due to the globally still incomplete information about glacier location and size, as well as large uncertainties in future climate scenarios. Recent studies that calculate global sea-level rise from GIC have developed simplified approaches using information from glacier inventories or gridded data sets and a range of different global climate models and emission scenarios. However, for several strongly glacierized regions very rough assumptions about the ice distribution have to be made and an urgent demand for a globally complete glacier inventory is expressed. The GIC on Greenland are one of the regions with lacking information. Within the EU FP7 project ice2sea we mapped the GIC on Greenland using Landsat TM/ETM+ imagery acquired around the year 2000, along with an additional dataset in the North (DCW - Digital Chart of the World). A digital elevation model (DEM) with 90 m resolution (GIMP DEM) was used to derive drainage divides and henceforth topographic parameters for each entity. A major challenge in this regard is the application of a consistent strategy to separate the local GIC from the ice sheet. For this purpose we have defined different levels of connectivity (CL) of the local GIC with the ice sheet: CL0: Not connected. CL1: Connected but separable (either with drainage divides in the accumulation region or in touch only - and thus separable - in the ablation region). CL2: Connected but non-separable (the local GIC contribute to the flow of an ice sheet outlet in the ablation area). Up to now close to 12'000 GIC (only CL0 and CL1) with a total area of about 129'000 km2 have been mapped considering only entities larger than 0.1 km2. The area of the ice sheet itself is

  1. Glaciers along proposed routes extending the Copper River Highway, Alaska

    USGS Publications Warehouse

    Glass, R.L.

    1996-01-01

    Three inland highway routes are being considered by the Alaska Department of Transportation and Public Facilities to connect the community of Cordova in southcentral Alaska to a statewide road system. The routes use part of a Copper River and Northwest Railway alignment along the Copper River through mountainous terrain having numerous glaciers. An advance of any of several glaciers could block and destroy the roadway, whereas retreating glaciers expose large quantities of unconsolidated, unvegetated, and commonly ice-rich sediments. The purpose of this study was to map historical locations of glacier termini near these routes and to describe hazards associated with glaciers and seasonal snow. Historical and recent locations of glacier termini along the proposed Copper River Highway routes were determined by reviewing reports and maps and by interpreting aerial photographs. The termini of Childs, Grinnell, Tasnuna, and Woodworth Glaciers were 1 mile or less from a proposed route in the most recently available aerial photography (1978-91); the termini of Allen, Heney, and Schwan Glaciers were 1.5 miles or less from a proposed route. In general, since 1911, most glaciers have slowly retreated, but many glaciers have had occasional advances. Deserted Glacier and one of its tributary glaciers have surge-type medial moraines, indicating potential rapid advances. The terminus of Deserted Glacier was about 2.1 miles from a proposed route in 1978, but showed no evidence of surging. Snow and rock avalanches and snowdrifts are common along the proposed routes and will periodically obstruct the roadway. Floods from ice-dammed lakes also pose a threat. For example, Van Cleve Lake, adjacent to Miles Glacier, is as large as 4.4 square miles and empties about every 6 years. Floods from drainages of Van Cleve Lake have caused the Copper River to rise on the order of 20 feet at Million Dollar Bridge.

  2. Glacier and hydrology changes in future climate over western Canada

    NASA Astrophysics Data System (ADS)

    Winger, Katja; Sushama, Laxmi; Marshall, Shawn

    2016-04-01

    Glaciers are frozen fresh water reservoirs that respond to changes in temperature and snowfall. Concern is growing about the impact that changes in glaciers may have on water resources in regions such as western Canada that derive a lot of their summer streamflow from glacier melt. Given that RCM projections are an important tool and are increasingly being used in assessing projected changes to water resources, particularly due to its high resolution compared with GCMs, realistic representation of glaciers in RCMs is very important. Currently, glaciers are only represented in an extremely simplified way in the fifth generation Canadian Regional Climate Model (CRCM5). This simple approach of representing glaciers as static glacier masks is appropriate for short-term integrations, where the response of glacier to changing atmospheric conditions might still be small due to glacier response times and therefore the feedback of changing glacier extent on large-scale atmospheric flow conditions might be negligible. A new dynamic glacier scheme has been developed for use within CRCM5, based on volume-area relationships. Simulations have been performed with this glacier model and Land Surface Scheme CLASS for the 2000-2100 period over a domain covering western Canada. These simulations were driven by outputs from a CRCM5 transient climate change simulation driven by CanESM2 at the lateral boundaries, for RCPs 4.5 and 8.5. Preliminary results suggest significant decreases to glacier fractions in future climate. Though the glacier contribution to streamflows is found to dramatically decrease in future climate, the total streamflows did not show any dramatic decreases due to the increase in precipitation for these regions.

  3. Hypsometric control on glacier mass balance sensitivity in Alaska

    NASA Astrophysics Data System (ADS)

    McGrath, D.; Sass, L.; Arendt, A. A.; O'Neel, S.; Kienholz, C.; Larsen, C.; Burgess, E. W.

    2015-12-01

    Mass loss from glaciers in Alaska is dominated by strongly negative surface balances, particularly on small, continental glaciers but can be highly variable from glacier to glacier. Glacier hypsometry can exert significant control on mass balance sensitivity, particularly if the equilibrium line altitude (ELA) is in a broad area of low surface slope. In this study, we explore the spatial variability in glacier response to future climate forcings on the basis of hypsometry. We first derive mass balance sensitivities (30-70 m ELA / 1° C and 40-90 m ELA / 50% decrease in snow accumulation) from the ~50-year USGS Benchmark glaciers mass balance record. We subsequently assess mean climate fields in 2090-2100 derived from the IPCC AR5/CMIP5 RCP 6.0 5-model mean. Over glaciers in Alaska, we find 2-4° C warming and 10-20% increase in precipitation relative to 2006-2015, but a corresponding 0-50% decrease in snow accumulation due to rising temperatures. We assess changes in accumulation area ratios (AAR) to a rising ELA using binned individual glacier hypsometries. For an ELA increase of 150 m, the mean statewide AAR drops by 0.45, representing a 70% reduction in accumulation area on an individual glacier basis. Small, interior glaciers are the primary drivers of this reduction and for nearly 25% of all glaciers, the new ELA exceeds the glacier's maximum elevation, portending eventual loss. The loss of small glaciers, particularly in the drier interior of Alaska will significantly modify streamflow properties (flashy hydrographs, earlier and reduced peak flows, increased interannual variability, warmer temperatures) with poorly understood downstream ecosystem and oceanographic impacts.

  4. Distinct composition signatures of archaeal and bacterial phylotypes in the Wanda Glacier forefield, Antarctic Peninsula.

    PubMed

    Pessi, Igor S; Osorio-Forero, César; Gálvez, Eric J C; Simões, Felipe L; Simões, Jefferson C; Junca, Howard; Macedo, Alexandre J

    2015-01-01

    Several studies have shown that microbial communities in Antarctic environments are highly diverse. However, considering that the Antarctic Peninsula is among the regions with the fastest warming rates, and that regional climate change has been linked to an increase in the mean rate of glacier retreat, the microbial diversity in Antarctic soil is still poorly understood. In this study, we analysed more than 40 000 sequences of the V5-V6 hypervariable region of the 16S rRNA gene obtained by 454 pyrosequencing from four soil samples from the Wanda Glacier forefield, King George Island, Antarctic Peninsula. Phylotype diversity and richness were surprisingly high, and taxonomic assignment of sequences revealed that communities are dominated by Proteobacteria, Bacteroidetes and Euryarchaeota, with a high frequency of archaeal and bacterial phylotypes unclassified at the genus level and without cultured representative strains, representing a distinct microbial community signature. Several phylotypes were related to marine microorganisms, indicating the importance of the marine environment as a source of colonizers for this recently deglaciated environment. Finally, dominant phylotypes were related to different microorganisms possessing a large array of metabolic strategies, indicating that early successional communities in Antarctic glacier forefield can be also functionally diverse.

  5. Climate change and glacier retreat drive shifts in an Antarctic benthic ecosystem.

    PubMed

    Sahade, Ricardo; Lagger, Cristian; Torre, Luciana; Momo, Fernando; Monien, Patrick; Schloss, Irene; Barnes, David K A; Servetto, Natalia; Tarantelli, Soledad; Tatián, Marcos; Zamboni, Nadia; Abele, Doris

    2015-11-01

    The Antarctic Peninsula (AP) is one of the three places on Earth that registered the most intense warming in the last 50 years, almost five times the global mean. This warming has strongly affected the cryosphere, causing the largest ice-shelf collapses ever observed and the retreat of 87% of glaciers. Ecosystem responses, although increasingly predicted, have been mainly reported for pelagic systems. However, and despite most Antarctic species being benthic, responses in the Antarctic benthos have been detected in only a few species, and major effects at assemblage level are unknown. This is probably due to the scarcity of baselines against which to assess change. We performed repeat surveys of coastal benthos in 1994, 1998, and 2010, analyzing community structure and environmental variables at King George Island, Antarctica. We report a marked shift in an Antarctic benthic community that can be linked to ongoing climate change. However, rather than temperature as the primary factor, we highlight the resulting increased sediment runoff, triggered by glacier retreat, as the potential causal factor. The sudden shift from a "filter feeders-ascidian domination" to a "mixed assemblage" suggests that thresholds (for example, of tolerable sedimentation) and alternative equilibrium states, depending on the reversibility of the changes, could be possible traits of this ecosystem. Sedimentation processes will be increasing under the current scenario of glacier retreat, and attention needs to be paid to its effects along the AP. PMID:26702429

  6. Climate change and glacier retreat drive shifts in an Antarctic benthic ecosystem.

    PubMed

    Sahade, Ricardo; Lagger, Cristian; Torre, Luciana; Momo, Fernando; Monien, Patrick; Schloss, Irene; Barnes, David K A; Servetto, Natalia; Tarantelli, Soledad; Tatián, Marcos; Zamboni, Nadia; Abele, Doris

    2015-11-01

    The Antarctic Peninsula (AP) is one of the three places on Earth that registered the most intense warming in the last 50 years, almost five times the global mean. This warming has strongly affected the cryosphere, causing the largest ice-shelf collapses ever observed and the retreat of 87% of glaciers. Ecosystem responses, although increasingly predicted, have been mainly reported for pelagic systems. However, and despite most Antarctic species being benthic, responses in the Antarctic benthos have been detected in only a few species, and major effects at assemblage level are unknown. This is probably due to the scarcity of baselines against which to assess change. We performed repeat surveys of coastal benthos in 1994, 1998, and 2010, analyzing community structure and environmental variables at King George Island, Antarctica. We report a marked shift in an Antarctic benthic community that can be linked to ongoing climate change. However, rather than temperature as the primary factor, we highlight the resulting increased sediment runoff, triggered by glacier retreat, as the potential causal factor. The sudden shift from a "filter feeders-ascidian domination" to a "mixed assemblage" suggests that thresholds (for example, of tolerable sedimentation) and alternative equilibrium states, depending on the reversibility of the changes, could be possible traits of this ecosystem. Sedimentation processes will be increasing under the current scenario of glacier retreat, and attention needs to be paid to its effects along the AP.

  7. Climate change and glacier retreat drive shifts in an Antarctic benthic ecosystem

    PubMed Central

    Sahade, Ricardo; Lagger, Cristian; Torre, Luciana; Momo, Fernando; Monien, Patrick; Schloss, Irene; Barnes, David K. A.; Servetto, Natalia; Tarantelli, Soledad; Tatián, Marcos; Zamboni, Nadia; Abele, Doris

    2015-01-01

    The Antarctic Peninsula (AP) is one of the three places on Earth that registered the most intense warming in the last 50 years, almost five times the global mean. This warming has strongly affected the cryosphere, causing the largest ice-shelf collapses ever observed and the retreat of 87% of glaciers. Ecosystem responses, although increasingly predicted, have been mainly reported for pelagic systems. However, and despite most Antarctic species being benthic, responses in the Antarctic benthos have been detected in only a few species, and major effects at assemblage level are unknown. This is probably due to the scarcity of baselines against which to assess change. We performed repeat surveys of coastal benthos in 1994, 1998, and 2010, analyzing community structure and environmental variables at King George Island, Antarctica. We report a marked shift in an Antarctic benthic community that can be linked to ongoing climate change. However, rather than temperature as the primary factor, we highlight the resulting increased sediment runoff, triggered by glacier retreat, as the potential causal factor. The sudden shift from a “filter feeders–ascidian domination” to a “mixed assemblage” suggests that thresholds (for example, of tolerable sedimentation) and alternative equilibrium states, depending on the reversibility of the changes, could be possible traits of this ecosystem. Sedimentation processes will be increasing under the current scenario of glacier retreat, and attention needs to be paid to its effects along the AP. PMID:26702429

  8. Model based historical runoff contribution from an Alpine glacier

    NASA Astrophysics Data System (ADS)

    Zoccatelli, Davide; Bonato, Paola; Carturan, Luca; Dalla Fontana, Giancarlo; De Blasi, Fabrizio; Borga, Marco

    2016-04-01

    The aim of this work is to analyze how climatic variability and glacier retreat impact the water balance of a small (8.5 km2) glaciarised catchment in the Eastern Italia Alps over a 30 year (1983-2013) period. The analysis is carried out by coupling local high quality data and a glacio-hydrological model able to simulate both the glacier and hydrology dynamics. Runoff contribution from glacier ice is related with trends in climatic variables and with glacier retreat. The area analyzed is the headwater of Noce Bianco river basin, lying in the Ortles-Cevedale group and including the La Mare glacier. During the study period the glacier area decreased from 4.7 km2 (50% basin area) to 3.47 km2 (40% basin area). In this area the following observations are available: 30 years of daily meteorological data at high elevation close to the catchment; three DTMs of the glacier, covering the entire period, which enable the calculation of the volume change and geodetic mass balance; direct glaciological mass balance observations over the period 2003-2013; discharge measurement at the catchment outlet over the period 2007-2013. The data availability and the significant shrinking of the glacier during the analyzed period make this catchment ideal for studying the hydrological impacts of glacier retreat. The semi-distributed conceptual model includes a snow and glacier accumulation and ablation module, based on temperature-radiation index and a glacier retreat model. The glacier retreat model allows to use the annual simulated glacier mass balance to update the glacier area (Huss et al., 2010). The model simulations are carried out from 1983 to 2013. We show that the model is able to capture adequately the measured daily discharge, the observed changes in glacier area and their spatial distribution. The contribution of glacier ice meltwater to annual runoff is below 10% in the first decade of simulation. This variable however showed a clear increasing trend, with peaks for single

  9. Snowline observations to remotely derive glacier-wide mass balance on four Kyrgyz glaciers from 2003 to 2015

    NASA Astrophysics Data System (ADS)

    Barandun, Martina; Huss, Matthias; Sold, Leo; Kienholz, Christian; Usubaliev, Ryskul; Bolch, Tobias; Hoelzle, Martin

    2016-04-01

    The monitoring of glacier mass balance in remote regions is challenging but vital for understanding the response of glaciers to climate change. Direct mass balance observations are sparse and discontinuous in the Kyrgyz Tien Shan and Pamir. The under-sampling problem of glacier change assessments limits change predictions and impact projections. In this study, we elaborate on novel approaches to derive sub-seasonal glacier mass balance based on remote snowline monitoring on four Kyrgyz glaciers for a period from 2003 to 2015. The proposed methodology is based on the information content of short-term changes in snowline elevation detected with repeated remote sensing imagery for both the quantities of winter accumulation and summer ablation. By backward modelling the observed snowline position and the glacier geometry are related to the glacier-wide mass balance. Snowline position over the glacier area is detected with a semi-automatic procedure on remote sensing images (Landsat, ASTER) and automatically on terrestrial photographs. We apply the methodology to four glaciers on which direct mass balance measurements have been (re)-initiated recently and use reanalysed and partly reconstructed mass balance series as a first source to validate our approach to remotely determine the seasonal glacier mass budget. In a second step, the derived glacier-wide mass balance is compared to geodetic mass balance calculations for the first decade of the 21st century.

  10. A GRASS GIS module to obtain an estimation of glacier behavior under climate change: A pilot study on Italian glacier

    NASA Astrophysics Data System (ADS)

    Strigaro, Daniele; Moretti, Massimiliano; Mattavelli, Matteo; Frigerio, Ivan; Amicis, Mattia De; Maggi, Valter

    2016-09-01

    The aim of this work is to integrate the Minimal Glacier Model in a Geographic Information System Python module in order to obtain spatial simulations of glacier retreat and to assess the future scenarios with a spatial representation. The Minimal Glacier Models are a simple yet effective way of estimating glacier response to climate fluctuations. This module can be useful for the scientific and glaciological community in order to evaluate glacier behavior, driven by climate forcing. The module, called r.glacio.model, is developed in a GRASS GIS (GRASS Development Team, 2016) environment using Python programming language combined with different libraries as GDAL, OGR, CSV, math, etc. The module is applied and validated on the Rutor glacier, a glacier in the south-western region of the Italian Alps. This glacier is very large in size and features rather regular and lively dynamics. The simulation is calibrated by reconstructing the 3-dimensional dynamics flow line and analyzing the difference between the simulated flow line length variations and the observed glacier fronts coming from ortophotos and DEMs. These simulations are driven by the past mass balance record. Afterwards, the future assessment is estimated by using climatic drivers provided by a set of General Circulation Models participating in the Climate Model Inter-comparison Project 5 effort. The approach devised in r.glacio.model can be applied to most alpine glaciers to obtain a first-order spatial representation of glacier behavior under climate change.

  11. FASTER THALAMOCORTICAL PROCESSING FOR DARK THAN LIGHT VISUAL TARGETS

    PubMed Central

    Jin, Jianzhong; Wang, Yushi; Lashgari, Reza; Swadlow, Harvey A.; Alonso, Jose M.

    2012-01-01

    ON and OFF visual pathways originate in the retina at the synapse between photoreceptor and bipolar cells. OFF bipolar cells are shorter in length and use receptors with faster kinetics than ON bipolar cells and, therefore, process information faster. Here, we demonstrate that this temporal advantage is maintained through thalamocortical processing, with OFF visual responses reaching cortex ~ 3–6 milliseconds before ON visual responses. Faster OFF visual responses could be demonstrated in recordings from large populations of cat thalamic neurons representing the center of vision (both X and Y) and from subpopulations making connection with the same cortical orientation column. While the OFF temporal advantage diminished as visual responses reached their peak, the integral of the impulse response was greater in OFF than ON neurons. Given the stimulus preferences from OFF and ON channels, our results indicate that darks are processed faster than lights in the thalamocortical pathway. PMID:22131408

  12. Cortex Matures Faster in Youths With Highest IQ

    MedlinePlus

    ... Research News From NIH Cortex Matures Faster in Youths With Highest IQ Past Issues / Summer 2006 Table ... please turn Javascript on. Photo: Getty image (StockDisc) Youths with superior IQ are distinguished by how fast ...

  13. 52 glaciers and one lake: how to reconstruct past regional glacier variability

    NASA Astrophysics Data System (ADS)

    Vasskog, Kristian; Paasche, Øyvind; Nesje, Atle; Boyle, John F.; Birks, H. John B.

    2014-05-01

    Sediment records from distal glacier-fed lakes have been used in numerous reconstructions of past glacier activity, where the basic assumption is that the amount of minerogenic material deposited in the lake is directly proportional to the amount of upstream glacier erosion. However, the minerogenic component of the sediments in a distal glacier-fed lake is commonly derived from several different sources, not only subglacial erosion. Furthermore, glacier reconstructions tend to focus on individual mountain glaciers, which due to local effects might not always reflect regional scale glacier variability. Presently, certain high-resolution analysis techniques allow for fast multi-proxy analyses of sediment cores, which improve the basis for inferring the provenance of lake sediments; however, the only way of actually testing such inferences is to identify the different sediment sources in the adjacent catchment and characterize them using the same proxy measurements as in the lake core. Multi-proxy sedimentary fingerprinting techniques are labor-intensive, however, and proxies such as bulk geochemistry may prove of little use in differentiating between source areas if the bedrock lithology is uniform across the catchment. Here we present a simple method based on environmental magnetism that allow for tracking lake sediments to their sources in catchments where the bedrock lithology is uniform. Unlike ferro- and ferrimagnetic minerals, the magnetic susceptibility of paramagnetic minerals is inversely proportional to temperature. Thus, by measuring the bulk magnetic susceptibility (chi-Bulk) of a sediment sample both at room temperature (293K) and after freezing in liquid nitrogen (77K), the relative contribution from paramagnetic minerals to the total chi-Bulk can be inferred from the ratio of chi-Bulk77K over chi-Bulk293K. Theoretically, a ratio of 3.8 will indicate a purely paramagnetic sample, whereas progressively lower values reflect an increasing contribution

  14. Faster-X effects in two Drosophila lineages.

    PubMed

    Avila, Victoria; Marion de Procé, Sophie; Campos, José L; Borthwick, Helen; Charlesworth, Brian; Betancourt, Andrea J

    2014-10-01

    Under certain circumstances, X-linked loci are expected to experience more adaptive substitutions than similar autosomal loci. To look for evidence of faster-X evolution, we analyzed the evolutionary rates of coding sequences in two sets of Drosophila species, the melanogaster and pseudoobscura clades, using whole-genome sequences. One of these, the pseudoobscura clade, contains a centric fusion between the ancestral X chromosome and the autosomal arm homologous to 3L in D. melanogaster. This offers an opportunity to study the same loci in both an X-linked and an autosomal context, and to compare these loci with those that are only X-linked or only autosomal. We therefore investigated these clades for evidence of faster-X evolution with respect to nonsynonymous substitutions, finding mixed results. Overall, there was consistent evidence for a faster-X effect in the melanogaster clade, but not in the pseudoobscura clade, except for the comparison between D. pseudoobscura and its close relative, Drosophila persimilis. An analysis of polymorphism data on a set of genes from D. pseudoobscura that evolve rapidly with respect to their protein sequences revealed no evidence for a faster-X effect with respect to adaptive protein sequence evolution; their rapid evolution is instead largely attributable to lower selective constraints. Faster-X evolution in the melanogaster clade was not related to male-biased gene expression; surprisingly, however, female-biased genes showed evidence for faster-X effects, perhaps due to their sexually antagonistic effects in males.

  15. Positive selection drives faster-Z evolution in silkmoths.

    PubMed

    Sackton, Timothy B; Corbett-Detig, Russell B; Nagaraju, Javaregowda; Vaishna, Lakshmi; Arunkumar, Kallare P; Hartl, Daniel L

    2014-08-01

    Genes linked to X or Z chromosomes, which are hemizygous in the heterogametic sex, are predicted to evolve at different rates than those on autosomes. This "faster-X effect" can arise either as a consequence of hemizygosity, which leads to more efficient selection for recessive beneficial mutations in the heterogametic sex, or as a consequence of reduced effective population size of the hemizygous chromosome, which leads to increased fixation of weakly deleterious mutations due to genetic drift. Empirical results to date suggest that, while the overall pattern across taxa is complicated, systems with male heterogamy show a faster-X effect attributable to more efficient selection, whereas the faster-Z effect in female-heterogametic taxa is attributable to increased drift. To test the generality of the faster-Z pattern seen in birds and snakes, we sequenced the genome of the lepidopteran silkmoth Bombyx huttoni. We show that silkmoths experience faster-Z evolution, but unlike in birds and snakes, the faster-Z effect appears to be attributable to more efficient positive selection. These results suggest that female heterogamy alone is unlikely to explain the reduced efficacy of selection on vertebrate Z chromosomes. It is likely that many factors, including differences in overall effective population size, influence Z chromosome evolution.

  16. Faster-X Effects in Two Drosophila Lineages

    PubMed Central

    Ávila, Victoria; Marion de Procé, Sophie; Campos, José L.; Borthwick, Helen; Charlesworth, Brian; Betancourt, Andrea J.

    2014-01-01

    Under certain circumstances, X-linked loci are expected to experience more adaptive substitutions than similar autosomal loci. To look for evidence of faster-X evolution, we analyzed the evolutionary rates of coding sequences in two sets of Drosophila species, the melanogaster and pseudoobscura clades, using whole-genome sequences. One of these, the pseudoobscura clade, contains a centric fusion between the ancestral X chromosome and the autosomal arm homologous to 3L in D. melanogaster. This offers an opportunity to study the same loci in both an X-linked and an autosomal context, and to compare these loci with those that are only X-linked or only autosomal. We therefore investigated these clades for evidence of faster-X evolution with respect to nonsynonymous substitutions, finding mixed results. Overall, there was consistent evidence for a faster-X effect in the melanogaster clade, but not in the pseudoobscura clade, except for the comparison between D. pseudoobscura and its close relative, Drosophila persimilis. An analysis of polymorphism data on a set of genes from D. pseudoobscura that evolve rapidly with respect to their protein sequences revealed no evidence for a faster-X effect with respect to adaptive protein sequence evolution; their rapid evolution is instead largely attributable to lower selective constraints. Faster-X evolution in the melanogaster clade was not related to male-biased gene expression; surprisingly, however, female-biased genes showed evidence for faster-X effects, perhaps due to their sexually antagonistic effects in males. PMID:25323954

  17. Modelled glacier equilibrium line altitudes during the mid-Holocene in the southern mid-latitudes

    NASA Astrophysics Data System (ADS)

    Bravo, C.; Rojas, M.; Anderson, B. M.; Mackintosh, A. N.; Sagredo, E.; Moreno, P. I.

    2015-11-01

    Glacier behaviour during the mid-Holocene (MH, 6000 years BP) in the Southern Hemisphere provides observational data to constrain our understanding of the origin and propagation of palaeoclimate signals. In this study we examine the climatic forcing of glacier response in the MH by evaluating modelled glacier equilibrium line altitudes (ELAs) and climatic conditions during the MH compared with pre-industrial time (PI, year 1750). We focus on the middle latitudes of the Southern Hemisphere, specifically Patagonia and the South Island of New Zealand. Climate conditions for the MH were obtained from PMIP2 model simulations, which in turn were used to force a simple glacier mass balance model to simulate changes in ELA. In Patagonia, the models simulate colder conditions during the MH in austral summer (-0.2 °C), autumn (-0.5 °C), and winter (-0.4), and warmer temperatures (0.2 °C) during spring. In the Southern Alps the models show colder MH conditions in autumn (-0.7 °C) and winter (-0.4 °C), warmer conditions in spring (0.3 °C), and no significant change in summer temperature. Precipitation does not show significant changes but exhibits a seasonal shift, with less precipitation from April to September and more precipitation from October to April during the MH in both regions. The mass balance model simulates a climatic ELA that is 15-33 m lower during the MH compared with PI conditions. We suggest that the main causes of this difference are driven mainly by colder temperatures associated with the MH simulation. Differences in temperature have a dual effect on glacier mass balance: (i) less energy is available for ablation during summer and early autumn and (ii) lower temperatures cause more precipitation to fall as snow rather than rain in late autumn and winter, resulting in more accumulation and higher surface albedo. For these reasons, we postulate that the modelled ELA changes, although small, may help to explain larger glacier extents observed by 6000

  18. Internationally coordinated glacier monitoring - a timeline since 1894

    NASA Astrophysics Data System (ADS)

    Nussbaumer, Samuel U.; Armstrong, Richard; Fetterer, Florence; Gärtner-Roer, Isabelle; Hoelzle, Martin; Machguth, Horst; Mölg, Nico; Paul, Frank; Raup, Bruce H.; Zemp, Michael

    2016-04-01

    Changes in glaciers and ice caps provide some of the clearest evidence of climate change, with impacts on sea-level variations, regional hydrological cycles, and natural hazard situations. Therefore, glaciers have been recognized as an Essential Climate Variable (ECV). Internationally coordinated collection and distribution of standardized information about the state and change of glaciers and ice caps was initiated in 1894 and is today organized within the Global Terrestrial Network for Glaciers (GTN-G). GTN-G ensures the continuous development and adaptation of the international strategies to the long-term needs of users in science and policy. A GTN-G Steering Committee coordinates, supports and advices the operational bodies responsible for the international glacier monitoring, which are the World Glacier Monitoring Service (WGMS), the US National Snow and Ice Data Center (NSIDC), and the Global Land Ice Measurements from Space (GLIMS) initiative. In this presentation, we trace the development of the internationally coordinated glacier monitoring since its beginning in the 19th century. Today, several online databases containing a wealth of diverse data types with different levels of detail and global coverage provide fast access to continuously updated information on glacier fluctuation and inventory data. All glacier datasets are made freely available through the respective operational bodies within GTN-G, and can be accessed through the GTN-G Global Glacier Browser (http://www.gtn-g.org/data_browser.html). Glacier inventory data (e.g., digital outlines) are available for about 180,000 glaciers (GLIMS database, RGI - Randolph Glacier Inventory, WGI - World Glacier Inventory). Glacier front variations with about 45,000 entries since the 17th century and about 6,200 glaciological and geodetic mass (volume) change observations dating back to the 19th century are available in the Fluctuations of Glaciers (FoG) database. These datasets reveal clear evidence that

  19. A study of discrete glacier motion

    NASA Astrophysics Data System (ADS)

    Zoet, Lucas K.

    Knowledge of process which control glacial dynamics are imperative in quantifying the response of a glacier or ice sheet to external forcing. This dissertation focuses mainly upon the characterization of sliding ice over a bed in an unstable fashion. I investigate unstable sliding through instances where it is observed in passive seismology as well as a focused laboratory study. The laboratory study attempts to isolate specific aspects of the sliding interface, which could lead to unstable sliding. Implications of unstable sliding with regards to erosion are also dealt with. Initially the TAMSEIS array is used to observe a unique set of seismicity originating at the base of David Glacier Antarctica in which ˜ 20,000 events were located over a ˜300 day period as the ice slid over an asperity. Tidal effects at the terminus modulated the interevent spacing and magnitude of events allowing for a basic analysis of healing process between a glacier and its bed. The 300 day period of repeat seismicity is hypothesized to arise from advection of debris rich ice over the asperity. Next the erosion implications of stick slip sliding are investigated. Sudden advancement associated with seismic energy generation is hypothesized to rapidly expand water filled cavities, which form in lee of bedrock highs. The rapid expansion creates a drop in water pressure within the cavity resulting in a pressure gradient leading to rapid fracture of bedrock. During the interseismic period of a stick slipping glacier the static coefficient of friction transfers a larger shear stress to the bed than the dynamic coefficient of friction from stably sliding glacier would. Next laboratory experimentation is conducted using a biaxial shearing apparatus in order to test the hypothesis that debris rich ice can affect the stability regime of a sliding glacier. This is preformed on a suite of ice-debris samples with range entrained debris percentages and temperatures. Both synthetic ice constructed in

  20. Galapagos Islands

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color image of the Galapagos Islands was acquired on March 12, 2002, by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra satellite. The Galapagos Islands, which are part of Ecuador, sit in the Pacific Ocean about 1000 km (620 miles) west of South America. As the three craters on the largest island (Isabela Island) suggest, the archipelago was created by volcanic eruptions, which took place millions of years ago. Unlike most remote islands in the Pacific, the Galapagos have gone relatively untouched by humans over the past few millennia. As a result, many unique species have continued to thrive on the islands. Over 95 percent of the islands' reptile species and nearly three quarters of its land bird species cannot be found anywhere else in the world. Two of the more well known are the Galapagos giant tortoise and marine iguanas. The unhindered evolutionary development of the islands' species inspired Charles Darwin to begin The Origin of Species eight years after his visit there. To preserve the unique wildlife on the islands, the Ecuadorian government made the entire archipelago a national park in 1959. Each year roughly 60,000 tourists visit these islands to experience what Darwin did over a century and a half ago. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  1. Seismic reflection constraints on the glacial dynamics of Johnsons Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Benjumea, Beatriz; Teixidó, Teresa

    2001-01-01

    During two Antarctic summers (1996-1997 and 1997-1998), five seismic refraction and two reflection profiles were acquired on the Johnsons Glacier (Livingston Island, Antarctica) in order to obtain information about the structure of the ice, characteristics of the ice-bed contact and basement topography. An innovative technique has been used for the acquisition of reflection data to optimise the field survey schedule. Different shallow seismic sources were used during each field season: Seismic Impulse Source System (SISSY) for the first field survey and low-energy explosives (pyrotechnic noisemakers) during the second one. A comparison between these two shallow seismic sources has been performed, showing that the use of the explosives is a better seismic source in this ice environment. This is one of the first studies where this type of source has been used. The analysis of seismic data corresponding to one of the reflection profiles (L3) allows us to delineate sectors with different glacier structure (accumulation and ablation zones) without using glaciological data. Moreover, vertical discontinuities were detected by the presence of back-scattered energy and the abrupt change in frequency content of first arrivals shown in shot records. After the raw data analysis, standard processing led us to a clear seismic image of the underlying bed topography, which can be correlated with the ice flow velocity anomalies. The information obtained from seismic data on the internal structure of the glacier, location of fracture zones and the topography of the ice-bed interface constrains the glacial dynamics of Johnsons Glacier.

  2. Biogeochemistry differences along lineal transect from glacier to Elephant Point coast in Antarctic environment

    NASA Astrophysics Data System (ADS)

    González-Guzman, Adrián; Otero, Xosé Luis; Oliva, Marc; Ruiz-Fernández, Jesús; Pérez-Alberti, Augusto

    2015-04-01

    The main aim of this work is studying the biogeochemistry changes occurred in the soil since glacier front until Elephant Point coast, at Shetland Islands, in Antarctic. For that, it picked up 20 samples from 10 different points. Sampling has followed a lineal transect since coast to glacier, going across 5 marine terraces, the morrenic area and going through col to reach glacier front. The terrace samples 2, 3, 4 and 5 show bryophyte vegetation forms covering a wide part of the surface however vegetation is almost nonexistent in the rest of the sampling points. The particle size, pH (pHw and pHKCl), electrical conductivity, total organic carbon (TOC), total nitrogen (TN), total Fe (TFe), Fe and Al associated with organic matter (soluble in sodium pyrophosphate, Cp), amorphous oxyhydroxides-Fe (extracted with ammonium oxalate, FeO), crystalline oxyhydroxides-Fe (extracted with sodium dithionite, FeD), bioavailable plant nutrients (soluble in Mehlich 3 extractant) and clay mineralogy were analyzed. Results obtained show the importance of the alive organism in the weathering of minerals and the contribution of these to form a more evolved soil. There are also important differences at the different zones of the lineal transect due to predominant geomorphologic forces performing in each type of area. On the third hand, current global climate change is causing glacier backward movement; this allows increasing vegetal cover and growing superior vegetation forms. In this way edaphic processes will increase and with them a leaching of nutrients which able to participate positively on closest seas, rivers and lakes.

  3. Franz Josef and Fox Glaciers, New Zealand: Historic length records

    NASA Astrophysics Data System (ADS)

    Purdie, Heather; Anderson, Brian; Chinn, Trevor; Owens, Ian; Mackintosh, Andrew; Lawson, Wendy

    2014-10-01

    Compilation of modern and historical length change records for Franz Josef and Fox Glaciers demonstrates that these glaciers have lost ~ 3 km in length and at least 3-4 km2 in area since the 1800s, with the greatest overall loss occurring between 1934 and 1983. Within this dramatic and ongoing retreat, both glaciers have experienced periods of re-advance. The record from Franz Josef Glacier is the most detailed, and shows major advances from 1946 to 1951 (340 m), 1965-1967 (400 m), 1983-1999 (1420 m) and 2004-2008 (280 m). At Fox Glacier the record is similar, with advances recorded during 1964-1968 (60 m), 1985-1999 (710 m) and 2004-2008 (290 m). Apart from the latest advance event, the magnitude of advance has been greater at Franz Josef Glacier, suggesting a higher length sensitivity. Analysis of the relationship between glacier length and a reconstructed annual equilibrium line altitude (ELA) record shows that the glaciers react very quickly to ELA variations - with the greatest correlation at 3-4 years' lag. The present (2014) retreat is the fastest retreat in the records of both glaciers. While decadal length fluctuations have been linked to hemispheric ocean-atmosphere variability, the overall reduction in length is a clear sign of twentieth century warming. However, documenting glacier length changes can be challenging; especially when increased surface debris-cover makes identification of the 'true' terminus a convoluted process.

  4. Assessing streamflow sensitivity to variations in glacier mass balance

    NASA Astrophysics Data System (ADS)

    Oneel, S.; Hood, E. W.; Arendt, A. A.; Sass, L. C.; March, R. S.

    2013-12-01

    We examine long-term streamflow and mass balance data from two Alaskan glaciers located in climatically distinct basins: Gulkana Glacier, a continental glacier located in the Alaska Range, and Wolverine Glacier, a maritime glacier located in the Kenai Mountains. Both glaciers lost mass, primarily as a result of summer warming, and both basins exhibit increasing streamflow over the 1966-2011 study interval. We estimated total glacier runoff via summer mass balance, and separated the fraction related to annual mass imbalances. In both climates, the fraction of streamflow related to annual mass balance averages less than 20%, substantially smaller than the fraction related to total summer mass loss (>50%), which occurs even in years of glacier growth. The streamflow fraction related to changes in annual mass balance has increased only in the continental environment. In the maritime climate, where deep winter snowpacks and frequent rain events drive consistently high runoff, the magnitude of this streamflow fraction is small and highly variable, precluding detection of any existing trend. Changes in streamflow related to annual balance are often masked by interannual variability of maritime glacier mass balance, such that predicted scenarios of continued glacier recession are more likely to impact the quality and timing of runoff than the total basin water yield.

  5. Glacier Changes in the Bhutanese Himalaya - Present and Future

    NASA Astrophysics Data System (ADS)

    Rupper, S.; Schaefer, J. M.; Burgener, L. K.; Maurer, J.; Smith, R.; Cook, E.; Putnam, A. E.; Krusic, P.; Tsering, K.; Koenig, L.

    2012-12-01

    Glacierized 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 glacier area and meltwater flux changes in Bhutan, monsoonal Himalayas. In particular, we quantify the uncertainties associated with the glacier 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 glacier melt model, our results show that glacier area and meltwater change projections can vary by an order of magnitude for different climate datasets. The most conservative results indicate that, even if climate were to remain at the present-day mean values (1980-2000), almost 10% of Bhutan's glacierized area would vanish and the meltwater flux would drop by as much as 30%. New mapping of glacierized area from 2000-2010 shows a significant change in glacierized area of 4-6%. Thus the conservative steady-state area changes predicted by the model are already being realized. Under the conservative scenario of an additional 1°C regional warming, glacier retreat is predicted to continue until about 25% of Bhutan's glacierized area will have disappeared and the annual meltwater flux, after an initial spike, would drop by as much as 65%.

  6. Modelling glacier change in the Everest region, Nepal Himalaya

    NASA Astrophysics Data System (ADS)

    Shea, J. M.; Immerzeel, W. W.; Wagnon, P.; Vincent, C.; Bajracharya, S.

    2014-10-01

    In this study, we apply a glacier mass balance and ice redistribution model to simulate historical and future glacier change in the Everest region of Nepal. High-resolution temperature and precipitation fields derived from gridded APHRODITE data, and validated against independent station observations from the EVK2CNR network, are used to drive the historical model from 1961 to 2007. The model is calibrated against geodetically derived estimates of net glacier mass change from 1992 to 2008, termini position of four large glaciers at the end of the calibration period, average velocities observed on selected debris-covered glaciers, and total glacierized area. We integrate field-based observations of glacier mass balance and ice thickness with remotely-sensed observations of decadal glacier change to validate the model. Between 1961 and 2007, the mean modelled volume change over the Dudh Kosi basin is -6.4 ± 1.5 km3, a decrease of 15.6% from the original estimated ice volume in 1961. Modelled glacier area change between 1961 and 2007 is -101.0 ± 11.4 km2, a decrease of approximately 20% from the initial extent. Scenarios of future climate change, based on CMIP5 RCP4.5 and RCP8.5 end members, suggest that glaciers in the Everest region will continue to lose mass through the 21st century. Glaciers in the basin are concentrated between 5000 and 6000 m of elevation, and are thus expected to be sensitive to changes in temperature and equilibrium line altitude (ELA). Glacier volume reductions between -35 to -62% are possible by 2050, and sustained temperature increases to 2100 may result in total glacier volume losses of between -73 and -96%.

  7. Controlling mechanisms of Thwaites Glacier, West Antarctica

    NASA Astrophysics Data System (ADS)

    Seroussi, H. L.; Morlighem, M.; Rignot, E. J.; Larour, E. Y.; Mouginot, J.; Khazendar, A.

    2013-12-01

    Ice shelves play a major role in the stability of fast flowing ice streams in Antarctica, by exerting buttressing on inland ice and controlling the discharge of ice into the ocean. However, the mechanisms at work remain poorly understood and interactions between floating and grounded ice need to be better characterized in order to estimate the impact of climate change on the ice sheets. Thwaites glacier, in West Antarctica, features a small and heavily fractured ice shelf that provides limited back stress pressure on inland ice but is pinned on the eastern part on a prominent ridge. Thwaites glacier has maintained a consistently high velocity and negative mass balance for at least 20 years. Recent observations show a widening of its fast flowing area as well as a sustained acceleration since 2006 and a rapid retreat of its grounding line in the center of the glacier. The objective of this work is to characterize the dynamic response of Thwaites glacier to changes in its floating tongue on decadal to centennial time scales. To achieve this objective, we rely on high resolution ice flow modeling and grounding line dynamics using the Ice Sheet System Model (ISSM). We will focus on the complex interplay between the main floating tongue of Thwaites Glacier and its eastern, slow moving ice shelf, which is pinned down by an ice rumple. The speed of the eastern ice shelf is strongly affected by the coupling with the main floating ice tongue, which results in significant fluctuations in speed of the eastern ice shelf the formation of ice shelf cracks at the grounding line during acceleration phases. Our results show that ice rigidity at the junction between the eastern and western part of the shelf controls the dynamic regime of the ice shelf and suggest that Thwaites Glacier is likely to undergo substantial changes in the coming decades. This work was performed at the California Institute of Technology's Jet Propulsion Laboratory and the University of California Irvine

  8. Climatic Teleconnections Recorded By Tropical Mountain Glaciers

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Permana, D.; Mosley-Thompson, E.; Davis, M. E.

    2014-12-01

    Information from ice cores from the world's highest mountains in the Tropics demonstrates both local climate variability and a high degree of teleconnectivity across the Pacific basin. Here we examine recently recovered ice core records from glaciers near Puncak Jaya in Papua, Indonesia, which lie on the highest peak between the Himalayas and the South American Andes. These glaciers are located on the western side of the Tropical Pacific warm pool, which is the "center of action" for interannual climate variability dominated by El Niño-Southern Oscillation (ENSO). ENSO either directly or indirectly affects most regions of Earth and their populations. In 2010, two ice cores measuring 32.13 m and 31.25 m were recovered to bedrock from the East Northwall Firn ice field. Both have been analyzed in high resolution (~3 cm sample length, 1156 and 1606 samples, respectively) for stable isotopes, dust, major ions and tritium concentrations. To better understand the controls on the oxygen isotopic (δ18 O) signal for this region, daily rainfall samples were collected between January 2013 and February 2014 at five weather stations over a distance of ~90 km ranging from 9 meters above sea level (masl) on the southern coast up to 3945 masl. The calculated isotopic lapse rate for this region is 0.24 ‰/100m. Papua, Indonesian ice core records are compared to ice core records from Dasuopu Glacier in the central Himalayas and from Quelccaya, Huascarán, Hualcán and Coropuna ice fields in the tropical Andes of Peru on the eastern side of the Pacific Ocean. The composite of the annual isotopic time series from these cores is significantly (R2 =0.53) related to tropical Pacific sea surface temperatures (SSTs), reflecting the strong linkage between tropical Pacific SSTs associated with ENSO and tropospheric temperatures in the low latitudes. New data on the already well-documented concomitant loss of ice on Quelccaya, Kilimanjaro in eastern Africa and the ice fields near Puncak

  9. Glacier melt on the Third Pole

    NASA Astrophysics Data System (ADS)

    Yao, T.

    2015-12-01

    With an average elevation above 4,000 metres, the Third Pole (TP) is a unique region with many high mountains centered on the Tibetan Plateau stretching over 5 million square kilometers. Major environmental changes are taking place on the TP characterized by complex interactions of atmospheric, cryospheric, hydrological, geological and environmental processes. These processes are critical for the well-being of the three billion people inhabiting the plateau and the surrounding regions. Glacier melt is one of the most significant environmental changes observed on the TP. Over the past decade, most of the glaciers on the TP have undergone considerable melt. The Third Pole Environment (TPE) has focused on the causes of the glacier melt by conducting large-scale ground in-situ observation and monitoring, analyzing satellite images and remote sensing data, and applying numerical modeling to environmental research on the TP. The studies of long-term record of water stable isotopes in precipitation and ice core throughout the TP have revealed different features with regions, thus proposing significant influence of atmospheric circulations on spatial precipitation pattern over the TP. Validation of the result by isotope-equipped general circulation models confirms the spatial distribution of different atmospheric circulation dominances on the TP, with northern part dominated by the westerlies, southern part by the summer monsoon, and central part featuring the influences of both circulation systems. Such unique circulation patterns also bear directly on the status of glaciers and lakes over the TP and its surroundings. The studies therefore found the largest glacier melt in the monsoon-dominated southern part, moderate melt in the central part of transition, and the least melt, or even slight advance in the westerlies-dominated northern TP. It is clear that some mountains on the TP are undergoing rapid melt and the consequence of without ice and snow will be very soon. The

  10. Glacier Dynamics and Outburst Flood Potential from the Imja and Thulagi Glacier-Lake Systems (Nepal)

    NASA Astrophysics Data System (ADS)

    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

    2015-04-01

    Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, i.e., most likely to cause death and destruction in case of a glacier lake outburst flood (GLOF). Imja Lake and the associated Imja and Lhoste-Shar glaciers have been intensively studied; Thulagi Glacier 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 glacier setting. We are analyzing several expeditions' data to build a detailed assessment of the glacier 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 melt-through or down-cutting mechanisms -- perhaps induced 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 glaciers 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

  11. Surge-type glaciers in the Tien Shan (Central Asia)

    NASA Astrophysics Data System (ADS)

    Mukherjee, Kriti; Bolch, Tobias

    2016-04-01

    Surge-type glaciers in High Mountain Asia are mostly observed in Karakoram and Pamir. However, few surge-type glaciers also exist in the Tien Shan, but have not comprehensively studied in detail in the recent literature. We identified surge-type glaciers in the Tien Shan either from available literature or by manual interpretation using available satellite images (such as Corona, Hexagon, Landsat, SPOT, IRS) for the period 1960 to 2014. We identified 39 possible surge-type glaciers, showing typical characteristics like looped moraines. Twenty-two of them rapidly advanced during different periods or a surge was clearly described in the literature. For the remaining possible surge-type glaciers either the advance, in terms of time and length, were not mentioned in detail in the literature, or the glaciers have remained either stable or retreated during the entire period of our study. Most of the surge-type glaciers cluster in the Inner Tien Shan (especially in the Ak-Shiirak rage) and the Central Tien Shan, are in size and are facing North, West or North West. Pronounced surge events were observed for North Inylchek and Samoilowitsch glaciers, both of which are located in the Central Tien Shan. Samoilowitsch Glacier retreated by more than 3 km between 1960 (length ~8.9 km) and 1992 (~5.8 km), advanced by almost 3 km until 2006 and slightly retreated thereafter. The most pronounced advance occurred between 2000 and 2002. DEM differencing (based on SRTM3 data and stereo Hexagon and Cartosat-1 data) revealed a significant thickening in the middle reaches (reservoir area) of the glacier between 1973 and 2000 while the surface significantly lowered in the middle and upper parts of the glacier between 2000 and 2006. Hence, the ice mass was transferred to the lower reaches (receiving area) and caused the advance with a maximum thickening of more than 80 m. The ~30 km long North Inylchek Glacier retreated since 1943 and showed a very rapid advance of ~3.5 km especially in

  12. 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

  13. Glacier and climate change in Pakistan and Afghanistan

    NASA Astrophysics Data System (ADS)

    Shroder, J.; Bishop, M.; Burgett, A.

    2012-04-01

    Climate change predictions and water resource related issuesin Afghanistan and Pakistan have led to the need for detailed assessments and understanding of glacier fluctuations, and the determination of the dominant controlling factors governing glacier sensitivity to climate change. Consequently, we studied glacier fluctuations and the role of topography in an attempt to understand glacier fluctuations.Specifically we used ASTER imagery, Landsat ETM data, and an SRTM digital elevation model, together with Google Earth™ high-resolution imagery to examine terminus fluctuations, ice velocity variations, and local- and meso-scale topographic parameters that are related to irradiance variations, ablation, and glacial geomorphology.Multispectral satellite imagery were utilized to estimate advance and retreat rates, along with glacier profile velocities. Geomorphometric analysis was utilized to generateglacier altitude profiles of hypsometry, slope, curvature, and topographic shielding. Our results reveal that glacier response to climate change is highly variable in Pakistan, as many glaciers are advancing as well as retreating, while others exhibit a stationary terminus. It is important to note that advances in the Karakoram do not appear to be restricted to glaciers at high elevations, suggesting climate forcing. Glaciers in the Hindu Raj and Hindu Kush are retreating, with fewer glaciers advancing, indicating the possibility of a spatial trend from West to East in Pakistan. There is a dramatic diminution of Hindu Kush ice in Afghanistan. In the Karakoram, many new surging glaciers have been identified with flow velocities ranging from 200-1000 m/yr. Non- surging glaciers also exhibit relative high velocities there. Spatial patternsof relief appear to be associated with glacier debris cover, as snow/ice avalanchescontribute debris and ice mass. In addition, patterns of topographic shielding are highly variable, revealing variations in the diffuse-skylight irradiance

  14. Akpatok Island

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Akpatok Island lies in Ungava Bay in northern Quebec, Canada. Accessible only by air, Akpatok Island rises out of the water as sheer cliffs that soar 500 to 800 feet (150 to 243 m) above the sea surface. The island is an important sanctuary for cliff-nesting seabirds. Numerous ice floes around the island attract walrus and whales, making Akpatok a traditional hunting ground for native Inuit people. This image was acquired by Landsat 7's Enhanced Thematic Mapper plus (ETM+) sensor on January 22, 2001. Image provided by the USGS EROS Data Center Satellite Systems Branch

  15. Twentieth century thinning of Mendenhall Glacier, Alaska, and its relationship to climate, lake calving, and glacier run-off

    NASA Astrophysics Data System (ADS)

    Motyka, Roman J.; O'Neel, Shad; Connor, Cathy L.; Echelmeyer, Keith A.

    2003-01-01

    Mendenhall Glacier is a dynamic maritime glacier in southeast Alaska that is undergoing substantial recession and thinning. The terminus has retreated 3 km during the 20th century and the lower part of the glacier has thinned 200 m or more since 1909. Glacier-wide volume loss between 1948 and 2000 is estimated at 5.5 km 3. Wastage has been the strongest in the glacier's lower reaches, but the glacier has also thinned at higher elevations. The shrinkage of Mendenhall Glacier appears to be due primarily to surface melting and secondarily to lake calving. The change in the average rate of thinning on the lower glacier, <1 m a -1 between 1948 and 1982 and >2 m a -1 since 1982, agrees qualitatively with observed warming trends in the region. Mean annual temperatures in Juneau decreased slightly from 1947 to 1976; they then began to increase, leading to an overall warming of ˜1.6 °C since 1943. Lake calving losses have periodically been a small but significant fraction of glacier ablation. The portion of the terminus that ends in the lake is becoming increasingly vulnerable to calving because of a deep pro-glacial lake basin. If current climatic trends persist, the glacier will continue to shrink and the terminus will recede onto land at a position about 500 m inland within one to two decades. The glacier and the meltwaters that flow from it are integral components of the Mendenhall Valley hydrologic system. Approximately 13% of the recent average annual discharge of the Mendenhall River is attributable to glacier shrinkage. Glacier melt contributes 50% of the total river discharge in summer.

  16. Differences in dissolved organic matter lability between alpine glaciers and alpine rock glaciers of the American West

    NASA Astrophysics Data System (ADS)

    Hall, E.; Fegel, T. S., II; Baron, J.; Boot, C. M.

    2015-12-01

    While alpine glaciers in montane regions represent the largest flux of dissolved organic matter (DOM) from global ice melt no research has examined the bioavailability of DOM melted out of glacial ice in the western continental United States. Furthermore, rock glaciers are an order of magnitude more abundant than ice glaciers 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 glaciers and rock glaciers along the Central Rocky Mountains of Colorado. Identical microbial communities were fed standardized amounts of DOM from four different ice glacier-rock glaciers 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 glaciers due to higher proportions of byproducts from microbial metabolism than rock glacier DOM, which has higher amounts of "recalcitrant" plant material. Our results show that DOM from ice glaciers is more labile than DOM from geologically and geographically similar paired rock glaciers. Ice glacier 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 glaciers in Alaska and Europe, subglacial environments in the mountain ranges of the United States are hotspots for biological activity and processing of organic carbon.

  17. Modeling Runoff from Partially Glacierized Catchments in the Tropical Andes with Different Glacier Coverage and Land Cover Conditions

    NASA Astrophysics Data System (ADS)

    Kinouchi, T.; Mendoza, J.; Luna, J.; Asaoka, Y.

    2014-12-01

    In Bolivian Andes, retreats of tropical glaciers are rapid, thus water resources currently available from glacierized catchments for drinking, agriculture, industry and hydropower would be changed in its volume and variations due to changing climate. Water resources in La Paz and El Alto, the capital city areas of Bolivia, strongly depend on the runoff from partially glacierized catchments located in the Cordillera Real, which is a combined contribution of surface and subsurface flow from glacierized and non-glacierized areas due to rainfall, snow melt and glacier melt. To predict the long-term availability of water resources for the capital city areas, we developed a semi-distributed conceptual glacio-hydrological model that considers various runoff pathways from partially glacierized high-altitudinal catchments located in the outer tropics. In the model, the retarding effect of lakes and wetlands was considered, based on the observed hydraulic functions and distribution of wetlands. The model was applied to three sub-catchments of the Tuni Lake watershed (98km2), from which the water resources for La Paz and El Alto are supplied. With calibrated parameters, the model reproduced well the observed seasonal variations of daily runoff during recent two years. Simulated results of water balance suggested that for the catchment with a larger glacier cover, more than 40% of the annual total runoff is contributed from glacierized areas due to glacier melt and snowmelt. The contribution from glacierized areas in other two sub-catchments, with relatively smaller areas covered by glacier ice, was calculated to be between 10-15%. We found that the role of wetlands and lakes are essential in retarding and regulating the runoff from partially glacierized high-mountain catchments.

  18. Glaciers and ice caps outside Greenland

    USGS Publications Warehouse

    Sharp, Marin; Wolken, G.; Burgess, D.; Cogley, J.G.; Copland, L.; Thomson, L.; Arendt, A.; Wouters, B.; Kohler, J.; Andreassen, L.M.; O'Neel, Shad; Pelto, M.

    2015-01-01

    Mountain glaciers and ice caps cover an area of over 400 000 km2 in the Arctic, and are a major influence on global sea level (Gardner et al. 2011, 2013; Jacob et al. 2012). They gain mass by snow accumulation and lose mass by meltwater runoff. Where they terminate in water (ocean or lake), they also lose mass by iceberg calving. The climatic mass balance (Bclim, the difference between annual snow accumulation and annual meltwater runoff) is a widely used index of how glaciers respond to climate variability and change. The total mass balance (ΔM) is defined as the difference between annual snow accumulation and annual mass losses (by iceberg calving plus runoff).

  19. Mass loss on Himalayan glacier endangers water resources

    NASA Astrophysics Data System (ADS)

    Kehrwald, Natalie M.; Thompson, Lonnie G.; Tandong, Yao; Mosley-Thompson, Ellen; Schotterer, Ulrich; Alfimov, Vasily; Beer, Jürg; Eikenberg, Jost; Davis, Mary E.

    2008-11-01

    Ice cores drilled from glaciers around the world generally contain horizons with elevated levels of beta radioactivity including 36Cl and 3H associated with atmospheric thermonuclear bomb testing in the 1950s and 1960s. Ice cores collected in 2006 from Naimona'nyi Glacier in the Himalaya (Tibet) lack these distinctive marker horizons suggesting no net accumulation of mass (ice) since at least 1950. Naimona'nyi is the highest glacier (6050 masl) documented to be losing mass annually suggesting the possibility of similar mass loss on other high-elevation glaciers in low and mid-latitudes under a warmer Earth scenario. If climatic conditions dominating the mass balance of Naimona'nyi extend to other glaciers in the region, the implications for water resources could be serious as these glaciers feed the headwaters of the Indus, Ganges, and Brahmaputra Rivers that sustain one of the world's most populous regions.

  20. A macroscopic approach to glacier dynamics

    USGS Publications Warehouse

    Harrison, W.D.; Raymond, C.F.; Echelmeyer, K.A.; Krimmel, R.M.

    2003-01-01

    A simple approach to glacier dynamics is explored in which there is postulated to be a relationship between area and volume with three parameters: the time for area to respond to changes in volume, a thickness scale, and an area characterizing the condition of the initial state. This approach gives a good fit to the measurements of cumulative balance and area on South Cascade Glacier from 1970-97; the area time-scale is roughly 8 years, the thickness scale about 123 m, and the 1970 area roughly 4% larger than required for adjustment with volume. Combining this relationship with a version of mass continuity expressed in terms of area and volume produces a theory of glacier area and volume response to climate in which another time constant, the volume time-scale, appears. Area and volume both respond like a damped spring and mass system. The damping of the South Cascade response is approximately critical, and the volume time-scale is roughly 48 years, six times the area time-scale. The critically damped spring and mass analogy reproduces the time dependence predicted by the more complicated traditional theory of Nye.

  1. Pathways of Petermann Glacier meltwater, Greenland

    NASA Astrophysics Data System (ADS)

    Heuzé, Céline; Wåhlin, Anna; Johnson, Helen; Münchow, Andreas

    2016-04-01

    Radar and satellite observations suggest that the floating ice shelf of Petermann Glacier loses up to 80% of its mass through basal melting, 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 glaciers. As Atlantic Water warms up, it is key to monitor Greenland melting glaciers and track their meltwater to properly assess their impact on the ocean circulation and sea level rise.

  2. Dielectric Signatures of Annealing in Glacier Ice

    NASA Astrophysics Data System (ADS)

    Grimm, R. E.; Stillman, D. E.; MacGregor, J. A.

    2015-12-01

    We analyzed the dielectric spectra of 49 firn and ice samples from ice sheets and glaciers to better understand how differing ice formation and evolution affect electrical properties. The dielectric relaxation of ice is well known and its characteristic frequency increases with the concentration of soluble impurities in the ice lattice. We found that meteoric ice and firn generally possess two such relaxations, indicating distinct crystal populations or zonation. Typically, one population is consistent with that of relatively pure ice, and the other is significantly more impure. However, high temperatures (e.g., temperate ice), long residence times (e.g., ancient ice from Mullins Glacier, Antarctica), or anomalously high impurity concentrations favor the development of a single relaxation. These relationships suggest that annealing causes two dielectrically distinct populations to merge into one population. The dielectric response of temperate ice samples indicates increasing purity with increasing depth, suggesting final rejection of impurities from the lattice. Separately, subglacially frozen samples from the Vostok 5G ice core possess a single relaxation whose variable characteristic frequency likely reflects the composition of the source water. Multi-frequency electrical measurements on cores and in the field can track annealing of glacier ice.

  3. GLACIER PEAK WILDERNESS STUDY AREA, WASHINGTON.

    USGS Publications Warehouse

    Church, S.E.; Stotelmeyer, R.B.

    1984-01-01

    Geologic, geochemical, gravity, aeromagnetic, and mine and prospect surveys were conducted to evaluate the mineral-resource potential of the Glacier Peak Wilderness study area and proposed additions in Washington. In the study area, six areas containing several base and precious metals have been identified that have substantiated mineral-resource potential, two of which are in areas recommended for wilderness addition. An additional 10 areas have probable mineral-resource potential. The most important demonstrated resource identified is the porphyry copper-molybdenum deposit at Glacier Peak mine near the center of the wilderness study area, where a deposit totaling 1. 9 billion tons of mineralized rock has been delineated by drilling. A possible geothermal potential exists on the east side of the Glacier Peak volcano, and a possible 24-million-cu-yd cinder resource is identified at the White Chuck Cinder Cone in the wilderness study area, but both are remote and no resources were identified. No other energy resource potential was identified in this study.

  4. Glacier Bay, Alaska, from the Ground, Air, and Space

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.

    1997-01-01

    This tape uses a combination of video, three-dimensional computer imaging, and still photographs to provide a descriptive overview of the life-cycle and environmental effects of glaciers. An historical prospective of researchers and the contribution that they have made to the understanding of glaciers and Glacier Bay is presented. The data collected from these scientists have been documented and used by means of scientific visualization in the hope of learning how glacial activity relates to climate changes.

  5. Holocene cirque glacier activity in Rondane, southern Norway

    NASA Astrophysics Data System (ADS)

    Kvisvik, Bjørn Christian; Paasche, Øyvind; Dahl, Svein Olaf

    2015-10-01

    Skriufonnen is a small cirque glacier (0.03 km2) in the continental mountains of Rondane in southern Norway. At present, it is the only glacier in Rondane, and very little is known about Holocene glacier fluctuations in this region. Direct observations of the glacier began in 2002, since which time Skriufonnen has been in a state of strong decline. In order to provide a temporal context, past glacier fluctuations were reconstructed based on a series of short HTH gravity cores (n = 8) and long piston cores (n = 6) retrieved from three downstream lakes of Skriufonnen. The cores were analysed for selected magnetic properties (χbulk, ARM, SIRM, 77 K/293 K), organic content (LOI), and geochemical trace elements. Soil catchment samples (n = 6) were collected along a transect running from the three lakes up to the present glacier terminus. Bulk susceptibility (χbulk) measurements show that the finest fractions systematically return the highest values and that ferromagnetic minerals are depleted with distance to the glacier front. This means that periods dominated by paramagnetic minerals indicate very little or no glacier activity, whereas intervals with more ferromagnetic minerals suggest increased glacier activity. The quantitative core analyses indicate that Skriufonnen existed prior to 10,200 b2k (years before A.D. 2000) and disappeared ~ 10,000 b2k. No glacier activity is recorded from c. 10,000 b2k until the glacier reoccurred at the onset of the local Neoglacial period, c. 4000 b2k. The glacier attained its maximum extent between 3200 and 2400 b2k and during the end of the 'Little Ice Age' (LIA) c. A.D. 1800. Neoglacial fluctuations of Skriufonnen are in line with shifts in local summer temperatures and show a delayed Neoglacial inception compared to western Norway.

  6. Inventory of glaciers in the Sierra Nevada, California

    USGS Publications Warehouse

    Raub, William; Brown, C. Suzanne; Post, Austin

    2006-01-01

    All perennial bodies of ice in the Sierra Nevada are listed and classified. The inventory includes 497 glaciers covering a total area of 50 square kilometers and 788 small ice bodies which do not meet the definition of a glacier, covering a total of 13 square kilometers. The listings include each ice body's drainage basin, location, orientation, altitude, area, and length the glaciers are also classified as to form, source, surface condition, and nature and activity of the terminus.

  7. Response of debris-covered glaciers to climate change

    NASA Astrophysics Data System (ADS)

    Benn, D. I.; Lindsey, N.; Kathryn, H.

    2004-12-01

    The presence of supraglacial debris strongly influences glacier ablation, and the mass balance of debris-covered glaciers differs significantly from that of clean glaciers in similar climatic settings. Predicting the response of debris-covered glaciers to climate change is important for hazard mitigation strategies in many high mountain environments, especially where temporary lakes are likely to form on stagnating glacier tongues. Accurate prediction of glacier evolution requires a robust mass balance function which incorporates the effect of debris cover. We present a new model for calculating ablation beneath supraglacial debris layer from meteorological data, based on coupling the surface energy balance and conductive heat flux through the debris layer. The model performs well in a wide range of climatic settings, and results correlate well with measured melt rates in the European Alps and Svalbard. The ablation model is used to construct theoretical mass balance curves for debris covered glaciers, providing surface boundary conditions for glacier flow models. Modelled mass balance curves display reverse gradients on glacier termini where the effect of thickening debris cover with decreasing altitude outweighs that of higher air temperatures. This explains the widely-noted tendency for debris-covered glaciers to stagnate under warming climates. When the mass balance of the glacier as a whole is negative, increasing ablation with altitude causes the lower tongue to decrease in gradient. As gradients and ice thicknesses decline, the process is reinforced by a positive feedback with velocity, so less ice is delivered to the terminal zone. Low surface gradients encourage the formation of supraglacial ponds which can grow rapidly, significantly increasing mass loss from the glacier and potentially posing flood hazards.

  8. Modelling mass balance and temperature sensitivity on Shallap glacier, Peru

    NASA Astrophysics Data System (ADS)

    Gurgiser, W.; Marzeion, B.; Nicholson, L. I.; Ortner, M.; Kaser, G.

    2013-12-01

    Due to pronounced dry seasons in the tropical Andes of Peru glacier melt water is an important factor for year-round water availability for the local society. Andean glaciers have been shrinking during the last decades but present day's magnitudes of glacier mass balance and sensitivities to changes in atmospheric drivers are not well known. Therefore we have calculated spatial distributed glacier mass and energy balance of Shallap glacier (4700 m - 5700 m, 9°S), Cordillera Blanca, Peru, on hourly time steps for the period Sept. 2006 to Aug. 2008 with records from an AWS close to the glacier as model input. Our model evaluation against measured surface height change in the ablation zone of the glacier yields our model results to be reasonable and within an expectable error range. For the mass balance characteristics we found similar vertical gradients and accumulation area ratios but markedly differences in specific mass balance from year to year. The differences were mainly caused by large differences in annual ablation in the glacier area below 5000m. By comparing the meteorological conditions in both years we found for the year with more negative mass balance that total precipitation was only slightly lower but mean annual temperature was higher, thus the fraction of liquid precipitation and the snow line altitude too. As shortwave net energy turned out to be the key driver of ablation in all seasons the deviations in snow line altitude and surface albedo explain most of the deviations in available melt energy. Hence, mass balance of tropical Shallap glacier was not only sensitive to precipitation but also to temperature which has not been expected for glaciers in the Peruvian Andes before. We furthermore have investigated impacts of increasing temperature due to its multiple effects on glacier mass and energy balance (fraction of liquid precipitation, long wave incoming radiation, sensible and latent heat flux). Presenting these results should allow for better

  9. Glaciers in Southern Andes seen from STS-63 Discovery

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Glaciers in the Andes Mountains jut into two lakes in the Patagoinian lowlands. Lago Viedman appears at center in the top portion of the 70mm frame. Lago Argentina barely appears in the frame at far right. The glaciers descend from the very high and wet mountains of southern Chile (peaks reach 3,600 meters) in a range locally known as Cordillera Darwin. The lakes in the picture were carved out by the glaciers during advances of the ice.

  10. Delivering Faster Congestion Feedback with the Mark-Front Strategy

    NASA Technical Reports Server (NTRS)

    Liu, Chunlei; Jain, Raj

    2001-01-01

    Computer networks use congestion feedback from the routers and destinations to control the transmission load. Delivering timely congestion feedback is essential to the performance of networks. Reaction to the congestion can be more effective if faster feedback is provided. Current TCP/IP networks use timeout, duplicate Acknowledgement Packets (ACKs) and explicit congestion notification (ECN) to deliver the congestion feedback, each provides a faster feedback than the previous method. In this paper, we propose a markfront strategy that delivers an even faster congestion feedback. With analytical and simulation results, we show that mark-front strategy reduces buffer size requirement, improves link efficiency and provides better fairness among users. Keywords: Explicit Congestion Notification, mark-front, congestion control, buffer size requirement, fairness.

  11. Faster-than-natural spacecraft circumnavigation via way points

    NASA Astrophysics Data System (ADS)

    Bennett, Trevor; Schaub, Hanspeter; Roscoe, Christopher W. T.

    2016-06-01

    Circumnavigation relative motion is considered for applications such as inspecting a space object for damage, or characterizing space debris before engaging a remediation operation. Faster-than-natural circumnavigation is a guidance method in which the deputy spacecraft is advanced ahead of the natural Keplerian relative motion. A state transition matrix method of generating a discrete way point guidance solution is proposed for faster-than natural circumnavigation. The state transition matrix methodology is applied to both circular and elliptical chief orbits. For the circular chief case, natural relative trajectories are planar in nature. With the faster-than-natural circumnavigation, this work illustrates how the required relative trajectories become three-dimensional curves. This methodology allows for closed-form impulsive control solutions and the associated fuel cost. Numerical simulations illustrate and validate the proposed method.

  12. Columbia Glacier stake location, mass balance, glacier surface altitude, and ice radar data, 1978 measurement year

    USGS Publications Warehouse

    Mayo, L.R.; Trabant, D.C.; March, Rod; Haeberli, Wilfried

    1979-01-01

    A 1 year data-collection program on Columbia Glacier, Alaska has produced a data set consisting of near-surface ice kinematics, mass balance, and altitude change at 57 points and 34 ice radar soundings. These data presented in two tables, are part of the basic data required for glacier dynamic analysis, computer models, and predictions of the number and size of icebergs which Columbia Glacier will calve into shipping lanes of eastern Prince William Sound. A metric, sea-level coordinate system was developed for use in surveying throughout the basin. Its use is explained and monument coordinates listed. A series of seven integrated programs for calculators were used in both the field and office to reduce the surveying data. These programs are thoroughly documented and explained in the report. (Kosco-USGS)

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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 +0.37 m w.e. a-1. The debris-covered portion of the glacier thus has an area-averaged mass balance of -1.21 ± 0.2 m w.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. 1.8 m w.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.

  15. Dynamics of glacier calving at the ungrounded margin of Helheim Glacier, southeast Greenland

    PubMed Central

    Selmes, Nick; James, Timothy D.; Edwards, Stuart; Martin, Ian; O'Farrell, Timothy; Aspey, Robin; Rutt, Ian; Nettles, Meredith; Baugé, Tim

    2015-01-01

    Abstract During summer 2013 we installed a network of 19 GPS nodes at the ungrounded margin of Helheim Glacier 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 glacier calved. Data collection covered 55 days, and many nodes survived in locations right at the glacier front to the time of iceberg calving. The observations included a number of significant calving events, and as a consequence the glacier retreated ~1.5 km. The data provide real‐time, high‐frequency observations in unprecedented proximity to the calving front. The glacier calved by a process of buoyancy‐force‐induced 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 glacier 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

  16. Observations of Dynamic Changes at an Advancing Tidewater Glacier: Hubbard Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Elliott, J.; Stearns, L. A.; Pritchard, M. E.; Bartholomaus, T.

    2015-12-01

    Hubbard Glacier, located in southeast Alaska, is the largest non-polar tidewater glacier in the world and one of a small number of glaciers that is steadily advancing. These attributes make it an intriguing target for observations of variations in ice dynamics over time. We use synthetic aperture radar data (ALOS and TerraSAR-X) and high-resolution optical imagery (WorldView and Quickbird) with a pixel tracking technique to map surface velocities from 2008 to the present, lengthening and broadening the time series of ice velocities presented in previous studies. A key result from our analysis is that Hubbard displays peak speeds of up to 12 m/day during the winter months (December - February) and minimum speeds during late summer (August - September). The times of peak and minimum speeds is quite different from those found in previous studies of Hubbard surface velocities derived from Landsat imagery, GPS, and photogrammetric methods. Those studies found peak speeds during late spring (May - June) and minimum speeds in fall (October-November), a pattern observed generally at tidewater glaciers. A second major feature we observe in our time series is the dramatic seasonal variation in surface speeds. The minimum speeds we find along the terminal lobe of the glacier are much lower than those found in previous studies, with values decreasing to near zero. Such a dramatic slow down of a tidewater glacier has not been widely observed. This result, along with the recent pattern of seasonal velocity peaks and minimas, suggests that Hubbard has undergone a change in ice dynamics.

  17. Dynamics of glacier calving at the ungrounded margin of Helheim Glacier, southeast Greenland

    PubMed Central

    Selmes, Nick; James, Timothy D.; Edwards, Stuart; Martin, Ian; O'Farrell, Timothy; Aspey, Robin; Rutt, Ian; Nettles, Meredith; Baugé, Tim

    2015-01-01

    Abstract During summer 2013 we installed a network of 19 GPS nodes at the ungrounded margin of Helheim Glacier 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 glacier calved. Data collection covered 55 days, and many nodes survived in locations right at the glacier front to the time of iceberg calving. The observations included a number of significant calving events, and as a consequence the glacier retreated ~1.5 km. The data provide real‐time, high‐frequency observations in unprecedented proximity to the calving front. The glacier calved by a process of buoyancy‐force‐induced 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 glacier 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.

  18. Glacier ice-volume modeling and glacier volumes on Redoubt Volcano, Alaska

    USGS Publications Warehouse

    Trabant, Dennis C.; Hawkins, Daniel B.

    1997-01-01

    Assessment of ice volumes and hydrologic hazards on Redoubt Volcano began four months before the 1989-90 eruptions removed 0.29 cubic kilometer of perennial snow and ice from Drift glacier. A volume model was developed for evaluating glacier volumes on Redoubt Volcano. The volume model is based on third-order polynomial simulations of valley cross sections. The third-order polynomial is an interpolation from the valley walls exposed above glacier surfaces and takes advantage of ice-thickness measurements. The fortuitous 1989-90 eruptions removed the ice from a 4.5-kilometer length of Drift glacier, providing a unique opportunity for verification of the volume model. A 2.5-kilometer length was chosen in the denuded glacier valley and the ice volume was measured by digitally comparing two new maps: one derived from the most recent pre-eruption 1979 aerial photographs and the other from post-eruption 1990 aerial photographs. The measured volume in the reference reach was 99 x 106 cubic meters, about 1 percent less than was estimated by the volume model. The volume estimate produced by this volume model was much closer to the measured volume than was the volume estimated by other techniques. The verified volume model was used to evaluate the total volume of perennial snow and glacier ice on Redoubt Volcano, which was estimated to be 4.1?0.8 cubic kilometers. Substantial snow and ice covers on volcanoes exacerbate the hydrologic hazards associated with eruptions. The volume on Redoubt Volcano is about 23 times the volume that was present on Mount St. Helens before its 1980 eruption, which generated lahars and floods.

  19. Ice loss and sea level rise contribution from Alaskan glaciers

    NASA Astrophysics Data System (ADS)

    Berthier, E.; Schiefer, E.; Clarke, G. K.; Menounos, B.; Rémy, F.; Cazenave, A. A.

    2009-12-01

    Over the last 50 years, retreating glaciers and ice caps (GIC) contributed 0.5 mm/yr to SLR, and one third is believed to originate from ice masses bordering the Gulf of Alaska. However, these estimates of ice wastage in Alaska are based on methods that directly measure mass changes from a limited number of glaciers and extrapolate the results to estimate ice loss for the many thousands of others. Here, using a new glacier inventory with elevation changes derived from sequential digital elevation models (DEMs), we found that, between 1962 and 2006, Alaskan glaciers lost 41.9 ± 8.6 km**3/yr water equivalent (w.e.) and contributed 0.12 ± 0.02 mm/yr to SLR. Our ice loss is 34% lower than previous estimates. Reasons for our lower values include the higher spatial resolution of the glacier inventory used in our study and the complex pattern of ice elevation changes at the scale of individual glaciers and mountain ranges which was not resolved in earlier work. Our ice elevation changes reveal that glacier dynamics (surges, phase of the tidewater cycle, etc...) have a profound effect on the wastage of Alaska glaciers. 3D satellite view of Columbia glacier, Chugach Mountains, Alaska. (Copyright CNES 2007, Distribution Spot Image, processing E. Berthier CNRS)

  20. Inventory of Glaciers in the North Cascades, Washington

    USGS Publications Warehouse

    Post, Austin; Richardson, Don; Tangborn, Wendell V.; Rosselot, F.L.

    1971-01-01

    Perennial bodies of ice in the North Cascades having areas of at least 0.1 km2 (square kilometer) are tabulated and classified. The inventory, a contribution to the International Hydrological Decade, includes 756 glaciers, covering 267 km2, about half of the glacier area in the United States south of Alaska. Listings include each glacier's location, drainage basin, area, length, orientation, altitude, and classification as to form, source, surface, nature of terminus, and activity. These glaciers contribute annually about 800 million cubic meters of water to streamflow in the State of Washington.

  1. Little Ice Age glaciers in the Mediterranean mountains

    NASA Astrophysics Data System (ADS)

    Hughes, Philip

    2014-05-01

    Only a few small glaciers survive today in the Mountains of the Mediterranean. Notable examples are found in the Pyrenees, Maritime Alps, Italian Apennines, the Dinaric and Albanian Alps and the mountains of Turkey. Many glaciers disappeared during the 20th Century. Glaciers were much larger and more numerous during the Little Ice Age (Hughes, 2014). Small glaciers even existed as far south as the High Atlas of Morocco and the Sierra Nevada of southern Spain. In more northerly areas, such as the western Balkans, glaciers and permanent snow patches occupied hundreds of cirques on relatively low-lying mountains. In the High Atlas and the Sierra Nevada no glaciers exist today, whilst in the Balkans only a few modern glaciers have been reported. A similar situation is apparent throughout the mountains of the Mediterranean region. New evidence for glacier change since the Little Ice Age will be published soon in Hughes (2014) and this paper reviews the extent, timing and climatic significance of Little Ice Age glaciation in the Mediterranean region. Reference: Hughes, P.D. (2014) Little Ice Age glaciers in the Mediterranean mountains. In: Carozza, J.-M., Devillers, B., Morhange, C. (eds) Little Ice Age in the Mediterranean, Méditerranée, volume 123.

  2. Effect of fjord geometry on tidewater glacier stability

    NASA Astrophysics Data System (ADS)

    Åkesson, Henning; Nisancioglu, Kerim H.; Nick, Faezeh M.

    2016-04-01

    Many marine-terminating glaciers have thinned, accelerated and retreated during the last two decades, broadly consistent with warmer atmospheric and oceanic conditions. However, these patterns involve considerable spatial and temporal variability, with diverse glacier behavior within the same regions. Similarly, reconstructions of marine-terminating glaciers indicate highly asynchronous retreat histories. While it is well known that retrograde slopes can cause marine ice sheet instabilities, the effect of lateral drag and fjord width has received less attention. Here, we test the hypothesis that marine outlet glacier stability is largely controlled by fjord width, and to a less extent by regional climate forcing. We employ a dynamic flowline model on idealized glacier geometries (representative of different outlet glaciers) to investigate geometric controls on decadal and longer times scales. The model accounts for driving and resistive stresses of glacier flow as well as along-flow stress transfer. It has a physical treatment of iceberg calving and a time-adaptive grid allowing for continuous tracking of grounding-line migration. We apply changes in atmospheric and oceanic forcing and show how wide and narrow fjord sections foster glacier (in)stabilities. We also evaluate the effect of including a surface mass balance - elevation feedback in such a setting. Finally, the relevance of these results to past and future marine-terminating glacier stability is discussed.

  3. Spatial-temporal variation of glacier over koshi basin, Himalaya

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Yang, X.; Yao, T.

    2011-12-01

    Glacial change is a sensitive indicator of climate change and glacier meltwaters are vital water resource for more than 1/6 people in South and Central Asia. Due to the large extent and difficult accessibility of high mountainous terrain, there are few ground-based glacial observations. In the last decade, multi-temporal satellite imagery and older aerial photography have been used extensively to quantify glacier parameters such as glacier area, length, elevation, hypsography, and ice volume in mountainous areas throughout the world. In this study, a glacier inventory for Koshi Basin was generated for the year 1976, 1992, 2000 and 2009 using automated interpretation with remote sensing, GIS techniques and manual adjustments based on topographic maps, Landsat TM/ETM+, and SRTM DEM data. The area change of about ~3,407km2 was identified. During the past two decades, the average retreat rate of these glaciers was ~5.8% while the retreat rate from 2000 to 2009 was ~14.23%. Moreover, heavily debris-covered glaciers exist in this region. Some of them even extend several kilometers upstream from their terminus such as Kong Bu Re Bu Sang glacier. From 1992 to 2000, the decrease in total glacier area is ~30km2 while the debris coverage increased ~20km2. These increases generally occur near the boundary between clean ice and debris-covered glacier, while the glacial fronts are remarkably stable. In order to identify the effect of debris-covered glaciers, the variations of glacier area, length and elevation were calculated with and without debris-covered glaciers, respectively. Results show although the terminuses of glacial front were stagnant, the increase in debris-covered glacier contributes to the clean ice's length decrease and elevation increase, and thereby affects glacier's response to climate change. So we suggest that in the area where debris-covered glaciers are common, the clean ice and debris-covered area should be separated and the debris-covered part should

  4. Short term dynamics of the debris-covered Miage Glacier

    NASA Astrophysics Data System (ADS)

    Fyffe, Catriona; Brock, Ben; Kirkbride, Martin; Mair, Doug; Smiraglia, Claudio; Diolaiuti, Guglielmina

    2016-04-01

    Due to the often inaccessible nature of debris-covered glaciers, studies of their dynamics tend to be restricted to those using remotely sensed data. This paper presents data on the short-term glacier dynamics of the debris-covered Miage Glacier, Western Italian Alps. The glacier velocity was calculated from repeat occupation of up to 22 points using a differential GPS system over two melt seasons. Meteorological, hydrological and water chemistry data were collected over the same time periods, and the nature of the hydrological system was studied using dye tracing, to allow the short term variations in glacier dynamics to be understood in terms of the likely glacial drainage system and its evolution. The highest glacier velocities and the greatest velocity variability was found near to where a cluster of moulins enter the glacier, close to the limit of continuous debris cover. The melt from the clean and dirty ice occasionally led to inputs overcoming the channelized system (both in spring and mid-summer), leading to increased velocities. On the debris-covered lower glacier however velocities were lower and less variable, and significant speed-up was confined to a period when subglacial water was thought to have been transferred subglacially from higher upglacier. The subdued sub-debris melt signal is thought to be the cause of the reduced velocity variability, in spite of the hydrological system beneath this part of the glacier remaining inefficient.

  5. Global Terrestrial Network for Glaciers: Databases and Web interfaces

    NASA Astrophysics Data System (ADS)

    Raup, B.; Armstrong, R.; Fetterer, F.; Gartner-Roer, I.; Haeberli, W.; Hoelzle, M.; Khalsa, S. J. S.; Nussbaumer, S.; Weaver, R.; Zemp, M.

    2012-04-01

    The Global Terrestrial Network for Glaciers (GTN-G) is an umbrella organization with links to the Global Climate Observing System (GCOS), Global Terrestrial Observing System (GTOS), and UNESCO (all organizations under the United Nations), for the curation of several glacier-related databases. It is composed of the World Glacier Monitoring Service (WGMS), the U.S. National Snow and Ice Data Center (NSIDC), and the Global Land Ice Measurements from Space (GLIMS) initiative. The glacier databases include the World Glacier Inventory (WGI), the GLIMS Glacier Database, the Glacier Photograph Collection at NSIDC, and the Fluctuations of Glaciers (FoG) and Mass Balance databases at WGMS. We are working toward increased interoperability between these related databases. For example, the Web interface to the GLIMS Glacier Database has also included queryable layers for the WGI and FoG databases since 2008. To improve this further, we have produced a new GTN-G web portal (http://www.gtn-g.org/), which includes a glacier metadata browsing application. This web application allows the browsing of the metadata behind the main GTN-G databases, as well as querying the metadata in order to get to the source, no matter which database holds the data in question. A new glacier inventory, called the Randolph Glacier Inventory 1.0, has recently been compiled. This compilation, which includes glacier outlines that do not have the attributes or IDs or links to other data like the GLIMS data do, was motivated by the tight deadline schedule of the sea level chapter of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Now served from the GLIMS website (http://glims.org/), it is designed to serve that narrowly focused research goal in the near term, and in the longer term will be incorporated into the multi-temporal glacier database of GLIMS. For the required merging of large sets of glacier outlines and association of proper IDs that tie together outlines

  6. Colonization of maritime glacier ice by bdelloid Rotifera.

    PubMed

    Shain, Daniel H; Halldórsdóttir, Katrín; Pálsson, Finnur; Aðalgeirsdóttir, Guðfinna; Gunnarsson, Andri; Jónsson, Þorsteinn; Lang, Shirley A; Pálsson, Hlynur Skagfjörð; Steinþórssson, Sveinbjörn; Arnason, Einar

    2016-05-01

    Very few animal taxa are known to reside permanently in glacier ice/snow. Here we report the widespread colonization of Icelandic glaciers and ice fields by species of bdelloid Rotifera. Specimens were collected within the accumulation zones of Langjökull and Vatnajökull ice caps, among the largest European ice masses. Rotifers reached densities up to ∼100 individuals per liter-equivalent of glacier ice/snow, and were freeze-tolerant. Phylogenetic analyses indicate that glacier rotifers are polyphyletic, with independent ancestries occurring within the Pleistocene. Collectively, these data identify a previously undescribed environmental niche for bdelloid rotifers and suggest their presence in comparable habitats worldwide.

  7. How important are glaciers for Indus water resources?

    NASA Astrophysics Data System (ADS)

    Sorteberg, A.

    2013-12-01

    How important are glaciers for Indus water resources? Looking into the literature reveals a wide range of estimates to this question. They partly diverge because of different definitions of a 'water resource' and partly due to the different estimates of the contribution from the glaciers. Defining the Indus water resources as precipitation (rain and snowfall) minus the loss of water due to evapotranspiration and sublimation for non-glaciated regions and the total runoff from the glaciated regions (sum of seasonal snowmelt on top of the glacier, percolating rainfall and loss of glacier ice), we have attempted to estimate the fraction of the total water resource that is coming from the glaciated regions and the fraction due to loss of glacier ice alone (which is the part that may be lost if a glacier disappears). Here we present estimates of water resources from non-glaciated regions using a wide range of estimates from observationally based, reanalysis and land data assimilation systems. Our results indicate large differences between the different estimates even for the annual values averaged over the whole basin. The implication of this finding is that the large uncertainties in the water resources of the non-glaciated regions will prevent us from making narrow estimates of the importance of the glaciers. For estimating the contribution from the glaciers we use an energy balance model with snow metamorphosis forced with 3 hourly reanalysis data (including perturbed precipitation and temperature runs based on the uncertainties in temperature and precipitation found from 10 different datasets). As there is over 10 000 glaciers in Indus it is not possible to model individual glaciers. Instead we model ';representative' glaciers where we get the average elevation of terminus and top, avg. glacier depth etc. from the Extended World Glacier Inventory in a given sub basin (using the FAO HydroSHEDS dataset to divide the Indus basin into subbasins). The mass balance and

  8. Island Hopping

    ERIC Educational Resources Information Center

    Bennett, Gayle

    2009-01-01

    At some institutions, it may feel as though faculty live on one island and advancement staff on another. The islands form part of an archipelago, and they exchange ambassadors and send emissaries occasionally, but interactions are limited. It may even seem as though the two groups speak different languages, deal in different currencies, and abide…

  9. Anatahan Island

    Atmospheric Science Data Center

    2013-04-19

    ... of the Mariana Islands in 1914 (the first year of World War l) and Germany released the islands to Japan in 1919. Japan received a ... States by the United Nations. The wreckage of a World War II B-29 Superfortress, a four-engine propeller-driven bomber, lies on the north ...

  10. Serologic surveillance of pathogens in a declining harbor seal (Phoca vitulina) population in Glacier Bay National Park, Alaska, USA and a reference site.

    PubMed

    Hueffer, Karsten; Holcomb, Darce; Ballweber, Lora R; Gende, Scott M; Blundell, Gail; O'Hara, Todd M

    2011-10-01

    The harbor seal population in Glacier Bay National Park, Alaska, has declined by over 70% since 1992. The reasons for this decline are not known. We examined serum antibodies and feces for evidence of exposure to multiple pathogens in this population. We also studied harbor seals from a reference site on Kodiak Island. In 2007, we found antibodies against Leptospira spp. in 31% of specimens from harbor seals in Glacier Bay, but no detectable serum antibodies in samples from Kodiak. In 2008, no samples had detectable antibodies against Leptospira spp. No serum antibodies against Toxoplasma gondii, morbilliviruses, or presence of Cryptosporidium in fecal samples were detected. However, Giardia was found in 6% of the fecal samples from Glacier Bay. Our results indicate that the harbor seal population in Glacier Bay National Park could be immunologically naïve to distemper viruses and therefore vulnerable to these pathogens. Given the relatively low prevalence of antibodies and low titers, pathogens likely are not the reason for the harbor seal decline in Glacier Bay. PMID:22102671

  11. Serologic surveillance of pathogens in a declining harbor seal (Phoca vitulina) population in Glacier Bay National Park, Alaska, USA and a reference site.

    PubMed

    Hueffer, Karsten; Holcomb, Darce; Ballweber, Lora R; Gende, Scott M; Blundell, Gail; O'Hara, Todd M

    2011-10-01

    The harbor seal population in Glacier Bay National Park, Alaska, has declined by over 70% since 1992. The reasons for this decline are not known. We examined serum antibodies and feces for evidence of exposure to multiple pathogens in this population. We also studied harbor seals from a reference site on Kodiak Island. In 2007, we found antibodies against Leptospira spp. in 31% of specimens from harbor seals in Glacier Bay, but no detectable serum antibodies in samples from Kodiak. In 2008, no samples had detectable antibodies against Leptospira spp. No serum antibodies against Toxoplasma gondii, morbilliviruses, or presence of Cryptosporidium in fecal samples were detected. However, Giardia was found in 6% of the fecal samples from Glacier Bay. Our results indicate that the harbor seal population in Glacier Bay National Park could be immunologically naïve to distemper viruses and therefore vulnerable to these pathogens. Given the relatively low prevalence of antibodies and low titers, pathogens likely are not the reason for the harbor seal decline in Glacier Bay.

  12. Detecting glacier-bed overdeepenings for glaciers in the Western Italian Alps using the GlabTop2 model: the test site of the Rutor Glacier, Aosta Valley

    NASA Astrophysics Data System (ADS)

    Viani, Cristina; Machguth, Horst; Huggel, Christian; Perotti, Luigi; Giardino, Marco

    2016-04-01

    It is expected that the rapid retreat of glaciers, observed in the European Alps and other mountain regions of the world, will continue in the future. One of the most evident and relevant consequences of this phenomenon is the formation of new glacier lakes in recently deglaciated areas. During glacier retreat overdeepened parts of the glacier bed become exposed and, in some cases, filled with water. It is important to understand where these new lakes can appear because of the associated potential risks (i.e. lake outburst and consequent flood) and opportunities (tourism, hydroelectricity, water reservoir, etc.) especially in densely populated areas such as the European Alps. GlabTop2 (Glacier Bed Topography model version 2) allows to model glacier bed topography over large glaciated areas combining digital terrain information and slope-related estimates of glacier thickness. The model requires a minimum set of input data: glaciers outlines and a surface digital elevation model (DEM). In this work we tested the model on the Rutor Glacier (8,1 km2) located in the Aosta Valley. The glacier has a well-known history of a series of glacier lake outburst floods between 1430 AD and 1864 AD due to front fluctuations. After the last advance occurred during the 70s of the previous century, glacier shrinkage has been continuous and new lakes have formed in newly exposed overdeepenings. We applied GlabTop2 to DEMs derived from historical data (topographic maps and aerial photos pair) representing conditions before the proglacial lake formation. The results obtained have been compared with the present situation and existing lakes. Successively we used the model also on present-day DEMs, which are of higher resolution than the historical derived ones, and compared the modeled bed topography with an existing bedrock map obtained by in-situ geophysical investigations (GPR surveys). Preliminary results, obtained with the 1991 surface model, confirm the robustness of GlabTop2 in

  13. Global response of glacier runoff to twenty-first century climate change

    NASA Astrophysics Data System (ADS)

    Bliss, Andrew; Hock, Regine; Radić, Valentina

    2014-04-01

    The hydrology of many important river systems in the world is influenced by the presence of glaciers in their upper reaches. We assess the global-scale response of glacier runoff to climate change, where glacier runoff is defined as all melt and rain water that runs off the glacierized area without refreezing. With an elevation-dependent glacier mass balance model, we project monthly glacier runoff for all mountain glaciers and ice caps outside Antarctica until 2100 using temperature and precipitation scenarios from 14 global climate models. We aggregate results for 18 glacierized regions. Despite continuous glacier net mass loss in all regions, trends in annual glacier runoff differ significantly among regions depending on the balance between increased glacier melt and reduction in glacier storage as glaciers shrink. While most regions show significant negative runoff trends, some regions exhibit steady increases in runoff (Canadian and Russian Arctic), or increases followed by decreases (Svalbard and Iceland). Annual glacier runoff is dominated by melt in most regions, but rain is a major contributor in the monsoon-affected regions of Asia and maritime regions such as New Zealand and Iceland. Annual net glacier mass loss dominates total glacier melt especially in some high-latitude regions, while seasonal melt is dominant in wetter climate regimes. Our results highlight the variety of glacier runoff responses to climate change and the need to include glacier net mass loss in assessments of future hydrological change.

  14. Hidden Covariation Detection Produces Faster, Not Slower, Social Judgments

    ERIC Educational Resources Information Center

    Barker, Lynne A.; Andrade, Jackie

    2006-01-01

    In P. Lewicki's (1986b) demonstration of hidden covariation detection (HCD), responses of participants were slower to faces that corresponded with a covariation encountered previously than to faces with novel covariations. This slowing contrasts with the typical finding that priming leads to faster responding and suggests that HCD is a unique type…

  15. Dust transport from glacierized rivers of southern Alaska to the Gulf of Alaska: Interannual variability in magnitude and sources

    NASA Astrophysics Data System (ADS)

    Crusius, J.; Schroth, A. W.; Campbell, R. W.; Resing, J.; Gasso, S.

    2014-12-01

    Dust from high latitudes is underappreciated and little studied. We recently identified new sites of dust formation, and a new dust generation mechanism, from the southern AK coastline, in Crusius et al, 2011. Dust is generated each autumn from glacierized river valleys as river levels and discharge decrease following summer peak glacier melt. The most prominent such river is the Copper River, the single largest freshwater source to the Gulf of Alaska. Each autumn the exposed river floodplains contain abundant, fine glacial flour and represent a large dust source region, prior to significant snowfall. Strong katabatic winds channeled down mountain river valleys generate dust from the fine glacial flour, which is transported as much as several hundred kilometers into the ocean. This dust is an important source of Fe to the Gulf of Alaska, where phytoplankton growth is limited by available Fe (a micronutrient). Glaciers are rapidly losing mass in this region, so there is an increasing supply of fine glacial flour during the summer melt season, and possibly increased deposition of fine glacial flour in the dust source regions. We initiated continuous, year-round time-series measurements of dust concentration, and its geochemical composition, in August of 2011 on Middleton Island, AK, which lies in the path of the dust plume extending from the Copper River valley. Dust is clearly generated from other glacierized river valleys along the southern coast of AK, as well. We will discuss results from our continuous record spanning three dust seasons, which prominently shows these events each autumn, and displays substantial interannual variability. Dust appears to remain in the boundary layer, but is transported hundreds of kilometers into the ocean, into Fe-limited waters. It is also possible that some of this dust is redeposited on snow or glacier surfaces, enhancing melting. This dust source is not accounted for in typical global dust models.

  16. Patterns of Glacier Change in the American West

    NASA Astrophysics Data System (ADS)

    Fountain, A. G.; Basagic, H. J.; Hoffman, M. J.

    2008-12-01

    We examine a century of glacier area change in the American West, exclusive of Alaska, using historic photography, historic maps, and recent aerial photos. Of the approximately 3200 glaciers and permanent snow masses, we track about 400 glaciers across a region that spans from Washington to California and Colorado to Montana. All glaciers have retreated since 1900 with the greatest change in Montana (Lewis Range) and the Sierra Nevada of California, and the least change in Washington including the North Cascades and the Olympic Peninsula. The pattern since 1970s is more complex, with the majority of glaciers having retreated since the 1970s, some vastly more than others. The glaciers that exhibit relatively little retreat are largely restricted to the high stratovolcanoes >3500m in elevation. In these cases we infer elevated snow accumulation at higher elevations compensates for increased ablation (melt) at lower elevations. In addition, many of the most stable glaciers are debris covered in their lower elevations, due to rock fall from the relatively weak volcanic edifice. Small glaciers, <1 km2, show great variability in their behavior, with a few glaciers at equilibrium or slightly advancing, to the majority retreating, with some losing 67% of their area. These differences are more difficult to explain. We infer that local climatic/topographic influences play a dominant role in the magnitude of change while regional climate patterns control the sign of the change. Temporal patterns of glacier change are very similar across broad regions while the magnitude of that change is particular to individual glaciers.

  17. Holocene glacier history from alpine speleothems, Milchbach cave, Switzerland

    NASA Astrophysics Data System (ADS)

    Luetscher, M.; Hoffmann, D. L.; Frisia, S.; Spötl, C.

    2011-02-01

    Mountain glaciers and their sediments are prominent witnesses of climate change, responding sensitively to even small modifications in meteorological parameters. Even in such a classical and thoroughly studied area as the European Alps the record of Holocene glacier mass-balance is only incompletely known. Here we explore a novel and continuous archive of glacier fluctuations in a cave system adjacent to the Upper Grindelwald Glacier in the Swiss Alps. Milchbach cave became partly ice-free only recently and hosts Holocene speleothems. Four coeval stalagmites show consistent petrographic and stable isotopic changes between 9.2 and 2.0 ka which can be tied to abrupt modifications in the cave environment as a result of the closing and opening of multiple cave entrances by the waxing and waning of the nearby glacier. During periods of Holocene glacier advances, columnar calcite fabric is characterized by δ18O values of about -8.0‰ indicative of speleothem growth under quasi-equilibrium conditions, i.e. little affected by kinetic effect related to forced degassing or biological processes. In contrast, fabrics formed during periods of glacier minima are typical of bacterially mediated calcite precipitation within caves overlain by an alpine soil cover. Moreover, δ18O values of the bacterially mediated calcite fabrics are consistent with a ventilated cave system fostering kinetic fractionation. These data suggest that glacier retreats occurred repeatedly before 5.8 ka, and that the amplitudes of glacier retreats became substantially smaller afterwards. Our reconstruction of the Upper Grindelwald Glacier fluctuations agrees well with paleoglaciological studies from other sites in the Alps and provides a higher temporal resolution compared to traditional analyses of peat and wood remains found in glacier forefields.

  18. Imaging Evidence for Hubbard Glacier Advances and Retreats since the Last Glacial Maximum in Disenchantment and Yakutat Bays, Alaska

    NASA Astrophysics Data System (ADS)

    Zurbuchen, J.; Gulick, S. P.; Levoir, M. A.; Goff, J. A.; Haeussler, P. J.

    2013-12-01

    As glaciers advance and retreat, they leave erosional surfaces, retreat sequences, morainal banks, and terminal moraines. These features can be imaged and interpreted in seismic reflection data to gain insight into ice routing, ice-sediment processes, and preserved glacial history. High-resolution 2-D multichannel seismic data gathered on the August 2012 UTIG-USGS National Earthquake Hazards Reduction Program survey of Disenchantment and Yakutat Bays have provided understanding of the advance pathways of the Hubbard Glacier and the glacial history of the bays. These data show evidence of three unconformities appearing in the form of channels and interpreted to be glacial advance and retreat paths. The youngest observable channel in Disenchantment Bay is ~2 km wide, forming morainal banks along the edges of the bay. The depth below modern sea level in two-way travel time (twtt) shallows from 510 ms in the middle of the bay to 400 ms ~4 km north of the entrance to Yakutat Bay. The sediment contained within the youngest channel measured from the seafloor thins southward from a twtt thickness of 260 ms to 115 ms. Beneath the youngest channel lies an older, 2.2 km-wide channel which is observed at ~580 ms below sea level, and is filled with sediments ranging in thickness from 480 ms to 180 ms at the terminus. This older channel extends from Disenchantment Bay into Yakutat Bay, staying to the northeast of Yakutat Bay, then turns southward at Knight Island and shallows to 450 ms twtt before forming a terminal moraine ~10 km north of the mouth of Yakutat Bay. Evidence for the third and oldest unconformity can only be seen within a very small number of short seismic lines in Disenchantment Bay. It is the largest of the channels, at ~3 km wide and 720 ms below modern sea level. The evidence of three nested unconformities suggests that the Hubbard Glacier has had at least three major advances in recent history. Radiocarbon dating of wooden branches in moraine deposits

  19. Climate change and size evolution in an island rodent species: new perspectives on the island rule.

    PubMed

    Millien, Virginie; Damuth, John

    2004-06-01

    As stated by the island rule, small mammals evolve toward gigantism on islands. In addition they are known to evolve faster than their mainland counterparts. Body size in island mammals may also be influenced by geographical climatic gradients or climatic change through time. We tested the relative effects of climate change and isolation on the size of the Japanese rodent Apodemus speciosus and calculated evolutionary rates of body size change since the last glacial maximum (LGM). Currently A. speciosus populations conform both to Bergmann's rule, with an increase in body size with latitude, and to the island rule, with larger body sizes on small islands. We also found that fossil representatives of A. speciosus are larger than their extant relatives. Our estimated evolutionary rates since the LGM show that body size evolution on the smaller islands has been less than half as rapid as on Honshu, the mainland-type large island of Japan. We conclude that island populations exhibit larger body sizes today not because they have evolved toward gigantism, but because their evolution toward a smaller size, due to climate warming since the LGM, has been decelerated by the island effect. These combined results suggest that evolution in Quaternary island small mammals may not have been as fast as expected by the island effect because of the counteracting effect of climate change during this period.

  20. Climate change and size evolution in an island rodent species: new perspectives on the island rule.

    PubMed

    Millien, Virginie; Damuth, John

    2004-06-01

    As stated by the island rule, small mammals evolve toward gigantism on islands. In addition they are known to evolve faster than their mainland counterparts. Body size in island mammals may also be influenced by geographical climatic gradients or climatic change through time. We tested the relative effects of climate change and isolation on the size of the Japanese rodent Apodemus speciosus and calculated evolutionary rates of body size change since the last glacial maximum (LGM). Currently A. speciosus populations conform both to Bergmann's rule, with an increase in body size with latitude, and to the island rule, with larger body sizes on small islands. We also found that fossil representatives of A. speciosus are larger than their extant relatives. Our estimated evolutionary rates since the LGM show that body size evolution on the smaller islands has been less than half as rapid as on Honshu, the mainland-type large island of Japan. We conclude that island populations exhibit larger body sizes today not because they have evolved toward gigantism, but because their evolution toward a smaller size, due to climate warming since the LGM, has been decelerated by the island effect. These combined results suggest that evolution in Quaternary island small mammals may not have been as fast as expected by the island effect because of the counteracting effect of climate change during this period. PMID:15266983

  1. Evolution of Glacier Snowline Since the End of the Last Ice Age in New Zealand

    NASA Astrophysics Data System (ADS)

    Kaplan, M. R.; Putnam, A. E.; Schaefer, J. M.; Denton, G. H.; Chinn, T. J.; Barrell, D.; Doughty, A. M.; Mackintosh, A. N.; Andersen, B. G.

    2012-12-01

    An important problem in paleoclimatology is how Southern Hemisphere climate changed since the end of the last ice age. The terrestrial glacier record reflects past snowline (=equilibrium line altitude) variability and is one of the few direct proxies available, in the middle latitudes, of former atmospheric properties. We reconstruct changes in snowline since ~15 ka on the South Island of New Zealand using geomorphologic mapping, 10Be surface-exposure dating, accumulation-area ratio (AAR) methods and numerical modeling. The snowline data are a proxy for the 0°C atmospheric isotherm, which occurs above 1500 m asl in the central Southern Alps, and trends in temperature since ~15 ka. Our findings show that snowline was depressed during the Antarctic Cold Reversal. Subsequently, snowline rose ~100 m during the Younger Dryas stadial in Europe. These late glacial changes appear coherent across the southern middle latitudes. In the early Holocene, snowline was depressed >200 m relative to modern in the Southern Alps. Between 11 ka and 600 years ago, short-term oscillations punctuated a multi-millennia trend of decreasing glacier extent as snowline rose ~100 m. Since ~600 yrs ago, net snowline has continued progressively to rise. The record implies long-term warming in New Zealand since the Late Glacial period. During the Holocene, the lowest snowlines and most extensive glaciers occurred in the early part of the epoch. Snowline reconstruction and numerical modeling allow us to estimate that temperature depression during the Late Glacial was ~2.1±0.4°C (relative to modern) and increased about 0.6 to 1°C between the early and late Holocene. Our terrestrial glacier and snowline records show coherence and also they are consistent with marine records in the Australian sector, documenting a regional climate pattern. However, the climate of the southwest Pacific region was fundamentally different from that observed in the Northern Hemisphere, where the most extensive

  2. Iceberg calving at Rapidly Retreating Tidewater Glacier: Columbia Glacier, AK, USA.

    NASA Astrophysics Data System (ADS)

    McNamara, D. E.; O'Neel, S.; Marshall, H.; Pfeffer, T.

    2005-12-01

    An array of eleven seismometers including one broadband instrument was deployed around the lower Columbia Glacier margin during June 2004 for a period one year. This network recorded small local seismic events (icequakes) and four explosions detonated in boreholes on the glacier. Additionally, we documented changes in glacier geometry with a single time lapse camera. For 25 days we made detailed observations of iceberg calving, noting the time of calving events along with the location and size of the event. Ice motion was measured with GPS 7 km upstream from the terminus for 60 days and within 1 km of the terminus for 25 days using optical methods. Waveforms from the broadband sensor are used to characterize seismic signals originating from calving events. Calving events produce seismic signals which have a 1-3 Hz characteristic frequency, and non-impulsive onsets. Submarine events often contain an additional low frequency component that is not present during sub-aerial events. We use motion and photogrammetric measurements to explore the relationship between calving and ice motion and also between calving and near-terminus glacier geometry.

  3. Yeast and yeast-like diversity in the southernmost glacier of Europe (Calderone Glacier, Apennines, Italy).

    PubMed

    Branda, Eva; Turchetti, Benedetta; Diolaiuti, Guglielmina; Pecci, Massimo; Smiraglia, Claudio; Buzzini, Pietro

    2010-06-01

    The present study reports the characterization of psychrophilic yeast and yeast-like diversity in cold habitats (superficial and deep sediments, ice cores and meltwaters) of the Calderone Glacier (Italy), which is the southernmost glacier in Europe. After incubation at 4 and 20 degrees C, sediments contained about 10(2)-10(3) CFU of yeasts g(-1). The number of viable yeast cells in ice and meltwaters was several orders of magnitude lower. The concomitant presence of viable bacteria and filamentous fungi has also been observed. In all, 257 yeast strains were isolated and identified by 26S rRNA gene D1/D2 and internal transcribed spacers (1 and 2) sequencing as belonging to 28 ascomycetous and basidiomycetous species of 11 genera (Candida, Cystofilobasidium, Cryptococcus, Dioszegia, Erythrobasidium, Guehomyces, Mastigobasidium, Mrakia, Mrakiella, Rhodotorula and Sporobolomyces). Among them, the species Cryptococcus gastricus accounted for almost 40% of the total isolates. In addition, 12 strains were identified as belonging to the yeast-like species Aureobasidium pullulans and Exophiala dermatitidis, whereas 15 strains, presumably belonging to new species, yet to be described, were also isolated. Results herein reported indicate that the Calderone Glacier, although currently considered a vanishing ice body due to the ongoing global-warming phenomenon, still harbors viable psychrophilic yeast populations. Differences of yeast and yeast-like diversity between the glacier under study and other worldwide cold habitats are also discussed.

  4. Estimating the risk of glacier cavity collapse during artificial drainage: The case of Tête Rousse Glacier

    NASA Astrophysics Data System (ADS)

    Gagliardini, O.; Gillet-Chaulet, F.; Durand, G.; Vincent, C.; Duval, P.

    2011-05-01

    During the summer of 2010, the presence of a pressurized water-filled subglacial-cavity of at least 50,000 m3 was detected within the Tête Rousse Glacier (French Alps). Artificial drainage was started to avoid an uncontrolled rupture of the ice dam, but was interrupted soon after to evaluate the capacity of the cavity-roof to bear itself. The risk was that the release of pressure within the cavity during the artificial drainage would precipitate the collapse of the cavity roof and potentially flush out the remaining water flooding the valley below. An unprecedented modeling effort was deployed to answer the question of the cavity roof stability. We set up a model of the glacier with its water cavity, solved the three-dimensional full-Stokes problem, predicted the upper surface and cavity surface displacements for various drainage scenarios, and quantified the risk of the cavity failure during artificial drainage. We found that the maximum tensile stress in the cavity roof was below the rupture value, indicating a low risk of collapse. A post drainage survey of the glacier surface displacements has confirmed the accuracy of the model prediction. This practical application demonstrates that ice flow models have reached sufficient maturity to become operational and assist policy-makers when faced with glaciological hazards, thus opening new perspectives in risk management of glacier hazards in high mountain regions.

  5. Evaluating different methods for glacier mass balance interpolation on a tropical glacier

    NASA Astrophysics Data System (ADS)

    Mölg, Nico; Ceballos, Jorge Luis

    2016-04-01

    Glaciers in the inner tropics receive precipitation throughout the year while the annual temperature amplitude is small. Therefore, a seasonal distinction in accumulation and ablation season as for mid-latitude glaciers is hardly applicable. In order to better understand the sub-annual glacier development and its relation to meteorological conditions, a mass balance programme with monthly resolution was established on Conejeras Glacier in the Cordillera Central in Colombia in 2006. After almost ten years of measurements the time series has been reanalysed. The results show a mass balance of around -25 m w.e. during this period and a strong correlation to several warm and cold phases of ENSO. Reanalysis of the monthly mass balance data reveal an often low correlation between ablation/accumulation and elevation. Quality and density of the measurement network allow for the application of several different interpolation methods, recommended ones as well as "outlawed" GIS methods like Kriging. In this study we show the advantages and disadvantages of a number of possibilities and try to rank their usability according to different conditions and purposes. The application of multiple methods can also be of advantage for the estimation of uncertainty ranges.

  6. Tsivat Basin conduit system persists through two surges, Bering Piedmont Glacier, Alaska

    USGS Publications Warehouse

    Fleisher, P.J.; Cadwell, D.H.; Muller, E.H.

    1998-01-01

    The 1993-1995 surge of Bering Glacier, Alaska, occurred in two distinct phases. Phase 1 of the surge began on the eastern sector in July, 1993 and ended in July, 1994 after a powerful outburst of subglacial meltwater into Tsivat Lake basin on the north side of Weeping Peat Island. Within days, jokulhlaup discharge built a 1.5 km2 delta of ice blocks (25-30 m) buried in outwash. By late October 1994, discharge temporarily shifted to a vent on Weeping Peat Island, where a second smaller outburst dissected the island and built two new sandar. During phase 2, which began in spring 1995 and ended within five months, continuous discharge issued from several vents along the ice front on Weeping Peat Island before returining to the Tsivat Basin. Surge related changes include a five- to six-fold increase in meltwater turbidity; the redirection of supercooled water in two ice-contact lakes; and an increase in the rate of glaciolacustrine sedimentation. US Geological Survey aerial photos by Austin Post show large ice blocks in braided channels indicating excessive subglacial discharge in a similar position adjacent to Weeping Peat Island during the 1966-1967 surge. During the subsequent three decades of retreat, the location of ice-marginal, subglacial discharge vents remained aligned on a linear trend that describes the position of a persistent subglacial conduit system. The presence of a major conduit system, possibly stabilized by subglacial bedrock topography, is suggested by: 1) high-level subglacial meltwater venting along the northern side of Weeping Peat Island during the 1966-1967 surge, 2) persistent low-level discharge between surges, and 3) the recurrence of localizing meltwater outbursts associated with both phases of the 1993-1005 surge.

  7. A century of glacier change in the American West

    NASA Astrophysics Data System (ADS)

    Fountain, A. G.

    2007-12-01

    Over the past 100 years glaciers in the American West (exclusive of Alaska) have largely receded. The magnitude of the recession varies across the west, with the greatest loss in Montana and California (>50% area loss) and the least loss on the stratovolcanoes (>35%) of the Pacific Northwest. The variations can be broadly characterized by elevation. Our results suggest that increased mass loss caused by increased summer temperatures affect all glaciers, whereas increasing winter temperatures, that change the phase of precipitation from snow to rain adversely affect those glaciers less than 3000m in elevation. The high glaciers (>3000m) of California and Colorado appear to be immune to variations in snowfall making them sensitive to variations in temperature alone. We infer that these very small, steep glaciers can only hold a given amount of snow beyond which extra snow avalanches or is blown off. Conversely, during winters of little direct snowfall, additional snow may be added through win drift from the surrounding terrain. The relatively little glacier shrinkage on the stratovolcanoes is due to the high altitude of the glacier accumulation zones. An east to west decrease in glacier shrinkage from Montana through Washington is due to enhanced winter precipitation along the west coast that somewhat buffers ice loss due to summer temperatures and winter precipitation phase changes.

  8. Over 400 previously undocumented Svalbard surge-type glaciers identified

    NASA Astrophysics Data System (ADS)

    Farnsworth, Wesley R.; Ingólfsson, Ólafur; Retelle, Michael; Schomacker, Anders

    2016-07-01

    Identifying glaciers that exhibit surge-type behavior is important when using evidence of ice front fluctuations as a proxy for reconstructing past climate oscillations. This study identifies previously undocumented surge-type glaciers in Svalbard, based on the presence of crevasse squeeze ridges in glacier forelands. Crevasse squeeze ridges are landforms suggested to be unique to surging glacier land systems. Estimates vary greatly as to the actual percentage of surge-type glaciers in Svalbard, and consequently their distribution pattern is poorly understood. A detailed survey of recent (2008-2012), high-resolution aerial imagery from TopoSvalbard, provided by the Norwegian Polar Institute, allowed for a survey of all the glacier forelands in Svalbard. Before our study, 277 individual glaciers in Svalbard have been documented to exhibit surge behavior. By using crevasse squeeze ridges as indicators of surge behavior, we have identified 431 additional glaciers that have surged. We suggest that this is a modest value as the unique surge landforms were not visible in approximately one-third of the forelands with documented surge histories. Limits to the crevasse squeeze ridge technique are presented and potential controlling factors for crevasse squeeze ridge formation/preservation are discussed.

  9. Reanalysis of the USGS Alaskan benchmark glacier dataset

    NASA Astrophysics Data System (ADS)

    van Beusekom, A. E.; O'Neel, S.; March, R. S.; Sass, L. C.

    2010-12-01

    Resolving the relationship between glacier surface-forcing (climate) and glacier geometry changes is accomplished through mass-balance estimates which can be made with remote sensing methods or field-based observations. The small scale of Alaskan glaciers has prevented remote sensing methods until recently, and field data are essential for validating new techniques. Field data provide the only long duration record that can be studied with respect to climate. The United States Geological Survey has maintained a 44-year mass-balance program at Alaska’s Gulkana Glacier and Wolverine Glacier. We have reanalyzed the Alaskan benchmark glaciers mass balance time series so that all data are treated similarly and systematically. Both glaciers are undergoing sustained mass loss with an increasing rate in recent years. However, the magnitude of the calculated loss depends on the number and location of the data collection sites. We explore the sensitivity of the glacier-wide balance estimates to the method of integration used on the necessarily point data. The robustness of the balance is strengthened with use of independent photogrammetric measurements.

  10. Sensitivity and Response of Bhutanese Glaciers to Atmospheric Warming

    NASA Technical Reports Server (NTRS)

    Rupper, Summer; Schaefer, Joerg M.; Burgener, Landon K.; Koenig, Lora S.; Tsering, Karma; Cook, Edward

    2013-01-01

    Glacierized 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 glacier area and meltwater flux changes in Bhutan, monsoonal Himalayas. In particular, we quantify the uncertainties associated with the glacier 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 glacier melt model, our results show that glacier 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 glacierized 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, glacier retreat is going to continue until about 25% of Bhutan s glacierized area will have disappeared and the annual meltwater flux, after an initial spike, would drop by as much as 65%. Citation

  11. Exploring tidewater glacier retreat using past and current observations at Columbia Glacier, Alaska. (Invited)

    NASA Astrophysics Data System (ADS)

    O'Neel, S.; Pfeffer, W. T.; Howat, I. M.; Conway, H.; Columbia Glacier Consortium

    2010-12-01

    Since fulfilling Austin Post’s prediction of impending retreat in the late 1970s, Columbia Glacier has repeatedly surprised both casual and careful observers with its ability for rapid change. Over the last three decades, Columbia Glacier has lost approximately 18 km of its original 66 km length, while thinning by approximately 50% at the present terminus. The total ice volume lost to the Gulf of Alaska Estimates upwards of 120 km3 constrain the total ice volume lost to the Gulf of Alaska. Recently, the terminus supported a ~1.5 km long floating tongue for over than a year, contradicting the common assumption that the mechanical properties of temperate ice prohibit flotation over sustained time intervals. The rich history of study offers an opportunity to better understand tidewater glacier retreat, and a valuable analog to the dynamic instability underway at several ice sheet outlet glaciers. Current research aims to improve processing resolution of existing aerial photographic data, while complimenting the 30-year photogrammetric record with a suite of field observations. Recent instrumentation includes: oblique time lapse and still imagery, semi-permanent GPS, airborne radar, mass balance, passive seismology and LiDAR. This presentation will focus on innovative methods developed in recent field seasons, sharing insight each has provided into the retreat process . 1The Columbia Glacier Consortium consists of: Fabian Walter (SIO), Kenichi Matsuoka (NPI), Ben Smith (UW), Ethan Welty (CU-Boulder), Chris Larsen (UAF), Dave Finnegan (CRREL), Dan McNamara (USGS), Yushin Ahn (OSU), Julie Markus (OSU), Adam LeWinter (EIS).

  12. Devon Island

    Atmospheric Science Data Center

    2013-04-17

    article title:  Mars Researchers Rendezvous on Remote Arctic Island   ... each summer since 1999, researchers from NASA's Haughton-Mars Project and the Mars Society reside at this "polar desert" location to study the geologic and ...

  13. Examining a Half Century of Northwestern North American Glacier Behavior

    NASA Astrophysics Data System (ADS)

    Molnia, B. F.; Fahey, M. J.; Friesen, B.; Josberger, E. G.

    2015-12-01

    In 1957, as part of the United States' contribution to the International Geophysical Year (IGY), the American Geographical Society (AGS) initiated a multi-institutional mapping project to produce 1:10,000-scale topographic maps of nine northwestern North American glaciers. The project's goal was to prepare precise maps at large scales of selected small glaciers to form a permanent record of the condition of these glaciers so that at a future date they could be resurveyed and compared. Continued surveys would give the history of wastage and accumulation, and more accurate interpretation of the response of these glaciers to meteorological and other factors. The resulting maps and a descriptive summary brochure were published in 1960 by the American Geographical Society. The USGS Global Fiducials Program (GFP) began to systematically image the same nine glaciers approximately half-century after its IGY mapping. The results of the GFP analyses would permit the types of comparisons that were envisioned by the IGY project. Imagery of each of these nine glaciers has been collected from multiple sources, including Next View licensed commercial imagery, vertical and oblique aerial photography, Landsat, and US National Imagery Systems. Exploitation of the imagery has resulted in the production of new 21st century maps that can be compared and contrasted with the vintage AGS map set. Comparison will permit the calculation of a number of parameters which will provide a direct insight into the changes that northwestern North American glaciers have been experiencing during the past half century. Specifically, these comparisons will permit the calculation of changes in glacier length, area, thickness, and volume; computation of rates of glacier advance and/or retreat, rates of glacier thickening and/or thinning, and rates of volume change; production of digital elevation models (DEMs); and generation of velocity fields from crevasse migration. The subsequent re-mapping and

  14. Glacial lakes amplify glacier recession in the central Himalaya

    NASA Astrophysics Data System (ADS)

    King, Owen; Quincey, Duncan; Carrivick, Jonathan; Rowan, Ann

    2016-04-01

    The high altitude and high latitude regions of the world are amongst those which react most intensely to climatic change. Across the Himalaya glacier mass balance is predominantly negative. The spatial and temporal complexity associated with this ice loss across different glacier clusters is poorly documented however, and our understanding of the processes driving change is limited. Here, we look at the spatial variability of glacier 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 glaciers of similar hypsometry, are used to examine the distribution of glacier area with altitude in each catchment. Surface lowering rates of >3 m/yr can be detected on some glaciers, 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 glaciers, emphasising the influence of a thick debris cover on ice melt. Surface lowering is only concentrated at glacier 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. Glaciers 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, glaciers of the Tama Koshi

  15. Microbial food web dynamics along a soil chronosequence of a glacier forefield

    NASA Astrophysics Data System (ADS)

    Esperschütz, J.; Pérez-de-Mora, A.; Schreiner, K.; Welzl, G.; Buegger, F.; Zeyer, J.; Hagedorn, F.; Munch, J. C.; Schloter, M.

    2011-11-01

    Microbial food webs are critical for efficient nutrient turnover providing the basis for functional and stable ecosystems. However, the successional development of such microbial food webs and their role in "young" ecosystems is unclear. Due to a continuous glacier retreat since the middle of the 19th century, glacier forefields have expanded offering an excellent opportunity to study food web dynamics in soils at different developmental stages. In the present study, litter degradation and the corresponding C fluxes into microbial communities were investigated along the forefield of the Damma glacier (Switzerland). 13C-enriched litter of the pioneering plant Leucanthemopsis alpina (L.) Heywood was incorporated into the soil at sites that have been free from ice for approximately 10, 60, 100 and more than 700 years. The structure and function of microbial communities were identified by 13C analysis of phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL). Results showed increasing microbial diversity and biomass, and enhanced proliferation of bacterial groups as ecosystem development progressed. Initially, litter decomposition proceeded faster at the more developed sites, but at the end of the experiment loss of litter mass was similar at all sites, once the more easily-degradable litter fraction was processed. As a result incorporation of 13C into microbial biomass was more evident during the first weeks of litter decomposition. 13C enrichments of both PLEL and PLFA biomarkers following litter incorporation were observed at all sites, suggesting similar microbial foodwebs at all stages of soil development. Nonetheless, the contribution of bacteria, especially actinomycetes to litter turnover became more pronounced as soil age increased in detriment of archaea, fungi and protozoa, more prominent in recently deglaciated terrain.

  16. Microbial food web dynamics along a soil chronosequence of a glacier forefield

    NASA Astrophysics Data System (ADS)

    Esperschütz, J.; Pérez-de-Mora, A.; Schreiner, K.; Welzl, G.; Buegger, F.; Zeyer, J.; Hagedorn, F.; Munch, J. C.; Schloter, M.

    2011-02-01

    Microbial food webs are critical for efficient nutrient turnover providing the basis for functional and stable ecosystems. However, the successional development of such microbial food webs and their role in "young" ecosystems is unclear. Due to a continuous glacier retreat since the middle of the 19th century, glacier forefields have expanded offering an excellent opportunity to study food web development at differently developed soils. In the present study, litter degradation and the corresponding C fluxes into microbial communities were investigated along the forefield of the Damma glacier (Switzerland). 13C-enriched litter of the pioneering plant Leucanthemopsis alpina (L.) Heywood was incorporated into the soil at sites that have been free from ice for approximately 10, 60, 100 and more than 700 years. The structure and function of microbial communities were identified by 13C analysis of phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL). Results showed increasing microbial diversity and biomass, and enhanced proliferation of bacterial groups as ecosystem development progressed. Initially, litter decomposition proceeded faster at the more developed sites, but at the end of the experiment loss of litter mass was similar at all sites, once the more easily-degradable litter fraction was processed. As a result incorporation of 13C into microbial biomass was more evident during the first weeks of litter decomposition. 13C enrichments of both PLEL and PUFA biomarkers following litter incorporation were observed at all sites, suggesting similar microbial foodwebs at all stages of soil development. Nonetheless, the contribution of bacteria and actinomycetes to litter turnover became more pronounced as soil age increased in detriment of archaea, fungi and protozoa, more prominent in recently deglaciated terrain.

  17. 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

  18. Assessing streamflow sensitivity to variations in glacier mass balance

    USGS Publications Warehouse

    O'Neel, Shad; Hood, Eran; Arendt, Anthony; Sass, Louis

    2014-01-01

    Quantifying the impacts of changing glacier geometries (annual balance) on glacier runoff is essential for predicting future changes in streamflow in glacierized basins. However, determining the role that this component plays in total glacier runoff (Definition 5) requires consistent measurements of seasonal (or shorter period) mass balances, measurements of precipitation at multiple locations within a basin, and streamflow measurements in close proximity to a glacier’s terminus. Practical and logistical challenges associated with assembling such data sets typically preclude such partitioning. As a result, most analyses of the relationship between annual mass balance and streamflow rely on some component of model output to compute glacier runoff (e.g. Huss et al. 2008; Kaser et al. 2010). Ultimately, developing an understanding of how total gl

  19. Ocean forcing of glacier retreat in the western Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Cook, A. J.; Holland, P. R.; Meredith, M. P.; Murray, T.; Luckman, A.; Vaughan, D. G.

    2016-07-01

    In recent decades, hundreds of glaciers draining the Antarctic Peninsula (63° to 70°S) have undergone systematic and progressive change. These changes are widely attributed to rapid increases in regional surface air temperature, but it is now clear that this cannot be the sole driver. Here, we identify a strong correspondence between mid-depth ocean temperatures and glacier-front changes along the ~1000-kilometer western coastline. In the south, glaciers that terminate in warm Circumpolar Deep Water have undergone considerable retreat, whereas those in the far northwest, which terminate in cooler waters, have not. Furthermore, a mid-ocean warming since the 1990s in the south is coincident with widespread acceleration of glacier retreat. We conclude that changes in ocean-induced melting are the primary cause of retreat for glaciers in this region.

  20. Subglacial discharge at tidewater glaciers revealed by seismic tremor

    PubMed Central

    Amundson, Jason M.; Walter, Jacob I.; O'Neel, Shad; West, Michael E.; Larsen, Christopher F.

    2015-01-01

    Abstract Subglacial discharge influences glacier basal motion and erodes and redeposits sediment. At tidewater glacier termini, discharge drives submarine terminus melting, 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 glaciers 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 melt model demonstrate that drainage efficiency of tidewater glaciers evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured glacierized environments. PMID:27667869

  1. Subglacial discharge at tidewater glaciers revealed by seismic tremor

    NASA Astrophysics Data System (ADS)

    Bartholomaus, Timothy C.; Amundson, Jason M.; Walter, Jacob I.; O'Neel, Shad; West, Michael E.; Larsen, Christopher F.

    2015-08-01

    Subglacial discharge influences glacier basal motion and erodes and redeposits sediment. At tidewater glacier termini, discharge drives submarine terminus melting, 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 glaciers 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 melt model demonstrate that drainage efficiency of tidewater glaciers evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured glacierized environments.

  2. The physical basis of glacier volume-area scaling

    USGS Publications Warehouse

    Bahr, D.B.; Meier, M.F.; Peckham, S.D.

    1997-01-01

    Ice volumes are known for only a few of the roughly 160,000 glaciers worldwide but are important components of many climate and sea level studies which require water flux estimates. A scaling analysis of the mass and momentum conservation equations shows that glacier volumes can be related by a power law to more easily observed glacier surface areas. The relationship requires four closure choices for the scaling behavior of glacier widths, slopes, side drag and mass balance. Reasonable closures predict a volume-area scaling exponent which is consistent with observations, giving a physical and practical basis for estimating ice volumes. Glacier volume is insensitive to perturbations in the mass balance scaling, but changes in average accumulation area ratios reflect significant changes in the scaling of both mass balance and ice volume. Copyright 1997 by the American Geophysical Union.

  3. Subglacial discharge at tidewater glaciers revealed by seismic tremor

    USGS Publications Warehouse

    Bartholomaus, Timothy C.; Amundson, Jason M.; Walter, Jacob I.; O'Neel, Shad; West, Michael E.; Larsen, Christopher F.

    2015-01-01

    Subglacial discharge influences glacier basal motion and erodes and redeposits sediment. At tidewater glacier termini, discharge drives submarine terminus melting, 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 glaciers 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 melt model demonstrate that drainage efficiency of tidewater glaciers evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured glacierized environments.

  4. Ocean forcing of glacier retreat in the western Antarctic Peninsula.

    PubMed

    Cook, A J; Holland, P R; Meredith, M P; Murray, T; Luckman, A; Vaughan, D G

    2016-07-15

    In recent decades, hundreds of glaciers draining the Antarctic Peninsula (63° to 70°S) have undergone systematic and progressive change. These changes are widely attributed to rapid increases in regional surface air temperature, but it is now clear that this cannot be the sole driver. Here, we identify a strong correspondence between mid-depth ocean temperatures and glacier-front changes along the ~1000-kilometer western coastline. In the south, glaciers that terminate in warm Circumpolar Deep Water have undergone considerable retreat, whereas those in the far northwest, which terminate in cooler waters, have not. Furthermore, a mid-ocean warming since the 1990s in the south is coincident with widespread acceleration of glacier retreat. We conclude that changes in ocean-induced melting are the primary cause of retreat for glaciers in this region. PMID:27418507

  5. Subglacial discharge at tidewater glaciers revealed by seismic tremor

    PubMed Central

    Amundson, Jason M.; Walter, Jacob I.; O'Neel, Shad; West, Michael E.; Larsen, Christopher F.

    2015-01-01

    Abstract Subglacial discharge influences glacier basal motion and erodes and redeposits sediment. At tidewater glacier termini, discharge drives submarine terminus melting, 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 glaciers 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 melt model demonstrate that drainage efficiency of tidewater glaciers evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured glacierized environments.

  6. Faster and cleaner real-time pure shift NMR experiments

    NASA Astrophysics Data System (ADS)

    Mauhart, Johannes; Glanzer, Simon; Sakhaii, Peyman; Bermel, Wolfgang; Zangger, Klaus

    2015-10-01

    Real-time pure shift experiments provide highly resolved proton NMR spectra which do not require any special processing. Although being more sensitive than their pseudo 2D counterparts, their signal intensities per unit time are still far below regular NMR spectra. In addition, scalar coupling evolution during the individual data chunks produces decoupling sidebands. Here we show that faster and cleaner real-time pure shift spectra can be obtained through the implementation of two parameter alterations. Variation of the FID chunk lengths between individual transients significantly suppresses decoupling sidebands for any kind of real-time pure shift spectra and thus allows for example the analysis of minor components in compound mixtures. Shifting the excitation frequency between individual scans of real-time slice-selective pure shift spectra increases their sensitivity obtainable in unit time by allowing faster repetitions of acquisitions.

  7. Faster than g, revisited with high-speed imaging

    NASA Astrophysics Data System (ADS)

    Vollmer, Michael; Möllmann, Klaus-Peter

    2012-09-01

    The introduction of modern high-speed cameras in physics teaching provides a tool not only for easy visualization, but also for quantitative analysis of many simple though fast occurring phenomena. As an example, we present a very well-known demonstration experiment—sometimes also discussed in the context of falling chimneys—which is commonly described as faster than gravity, faster than g, free fall paradox or simply falling stick. So far, only a few experimental investigations have utilized photography with a maximum of 41 frames s-1. In this work, high-speed imaging with 1000 fps was used to verify theoretical predictions for the classical experiment. In addition, a modified experiment was performed to better distinguish various theoretical outcomes and also visualize the underlying physics. The topic is well suited for student projects in undergraduate courses which combine experimental laboratory work with computer modelling.

  8. Multiple object tracking using the shortest path faster association algorithm.

    PubMed

    Xi, Zhenghao; Liu, Heping; Liu, Huaping; Yang, Bin

    2014-01-01

    To solve the persistently multiple object tracking in cluttered environments, this paper presents a novel tracking association approach based on the shortest path faster algorithm. First, the multiple object tracking is formulated as an integer programming problem of the flow network. Then we relax the integer programming to a standard linear programming problem. Therefore, the global optimum can be quickly obtained using the shortest path faster algorithm. The proposed method avoids the difficulties of integer programming, and it has a lower worst-case complexity than competing methods but better robustness and tracking accuracy in complex environments. Simulation results show that the proposed algorithm takes less time than other state-of-the-art methods and can operate in real time.

  9. Island of Okinawa, Japan

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The island of Okinawa, (26.5N, 128.0E) largest of the Ryukyu Islands, Japan. The Ryukyu island group lies south of the main home islands of Japan in an arc towards the Chinese island Republic of Taiwan. As is typical throughout the Japanese home islands, intense urban development can be observed all over the island in this near vertical view.

  10. Faster Hall-Effect Current-Measuring Circuit

    NASA Technical Reports Server (NTRS)

    Sullender, Craig C.; Johnson, Daniel D.; Walker, Daniel D.

    1993-01-01

    Current-measuring circuit operates on Hall-effect-sensing and magnetic-field-nulling principles similar to those described in article, "Nulling Hall-Effect Current-Measuring Circuit" (LEW-15023), but simpler and responds faster. Designed without feedback loop, and analog pulse-width-modulated output indicates measured current. Circuit measures current at frequency higher than bandwidth of its Hall-effect sensor.

  11. Boundary conditions on faster-than-light transportation systems

    NASA Technical Reports Server (NTRS)

    Bennett, Gary L.; Knowles, H. B.

    1993-01-01

    In order to be consistent with current physical theories, any proposal of a faster-than light (FTL) transportation system must satisfy several critical conditions. It must predict the mass, space, and time dimensional changes predicted by relativity physics when velocity falls below the speed of light. It must also not violate causality, and remain consistent with quantum physics in the limit of microscopic systems. It is also essential that the proposal conserve energy.

  12. Worldwide dataset of glacier thickness observations compiled by literature review

    NASA Astrophysics Data System (ADS)

    Naegeli, Kathrin; Gärtner-Roer, Isabelle; Hagg, Wilfried; Huss, Matthias; Machguth, Horst; Zemp, Michael

    2013-04-01

    The volume of glaciers and ice caps is still poorly known, although it is expected to contribute significantly to changes in the hydrological cycle and global sea level rise over the next decades. Studies presenting worldwide estimations are mostly based on modelling and scaling approaches and are usually calibrated with only few measurements. Direct investigations of glacier thickness, a crucial parameter for ice volume calculations, are rather sparse but nevertheless available from all around the globe. This study presents a worldwide compilation of glacier thickness observation data. Literature review revealed mean and/or maximum thickness values from 442 glaciers and ice caps, elevation band information and point measurements for 10 and 14 glaciers, respectively. Resulting in a dataset containing glaciers and ice caps with areas ranging from smaller than 0.1 km2 (e.g. Pizolgletscher, Switzerland) to larger than 10'000 km2 (e.g. Agassiz Ice Cap, Canada), mean ice thicknesses between 4 m (Blaueis, Germany) and 550 m (Aletschgletscher, Switzerland) and 64 values for ice masses with entries from different years. Thickness values are derived from various observation methods and cover a survey period between 1923 and 2011. A major advantage of the database is the included metadata, giving information about specific fields, such as the mean thickness value of Aletschgletscher, which is only valid for the investigation area Konkordiaplatz and not over the entire glacier. The relatively small collection of records in the two more detailed database levels reflects the poor availability of such data. For modelling purposes, where ice thicknesses are implemented to derive ice volumes, this database provides essential information about glacier and ice cap characteristics and enables the comparison between various approaches. However, the dataset offers a great variety of locations, thicknesses and surface areas of glaciers and ice caps and can therefore help to compare

  13. Botanical Evidence of the Modern History of Nisqually Glacier, Washington

    USGS Publications Warehouse

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

    1961-01-01

    A knowledge of the areas once occupied by mountain glaciers reveals at least part of the past behavior of these glaciers. From this behavior, inferences of past climate can be drawn. The maximum advance of Nisqually Glacier in the last thousand years was located, and retreat from this point is believed to have started about 1840. The maximum downvalley position of the glacier is marked by either a prominent moraine or by a line of difference between stands of trees of strikingly different size and significantly different age. The thousand-year age of the forest beyond the moraine or line between abutting stands represents the minimum time since the surface was glaciated. This age is based on the age of the oldest trees, plus an estimated interval required for the formation of humus, plus evidence of an ancient fire, plus an interval of deposition of pyroclastics. The estimate of the date when Nisqually Glacier began to retreat from its maximum advance is based upon the ages of the oldest trees plus an interval of 5 years estimated as the time required for the establishment of trees on stable moraines. This interval was derived from a study of the ages of trees growing at locations of known past positions of the glacier. Reconnaissance studies were made on moraines formed by Emmons and Tahoma Glaciers. Preliminary analyses of these data suggest that Emmons Glacier started to recede from its maximum advance in about 1745. Two other upvalley moraines mark positions from which recession started about 1849 and 1896. Ages of trees near Tahoma Glacier indicate that it started to recede from its position of maximum advance in about 1635. About 1835 Tahoma Glacier started to recede again from another moraine formed by a readvance that ter minated near the 1635 position.

  14. The polar spirals of Mars may be due to glacier surges deflected by Coriolis forces

    NASA Astrophysics Data System (ADS)

    Weijermars, R.

    1986-01-01

    It is argued that the spiral patterns observed by the Mariner spacecraft in the layered ice deposits of the Martian polar regions are fractures which are formed perpendicularly to the gravitionally directed flow lines deflected by Coriolis forces. The minimum effective kinematic viscosity which is consistent with this hypothesis is 7 million sq m/s. It is shown that an occasional kinematic viscosity of 7 million sq m/s is sufficient to cause flow rates of 0.2 m/s along the slopes of the topographic highs. This flow rate would imply that glacier surges on the Martian poles are two orders of magnitude faster than those observed on earth.

  15. Geographic Names of Iceland's Glaciers: Historic and Modern

    USGS Publications Warehouse

    Sigurdsson, Oddur; Williams, Richard S.

    2008-01-01

    Climatic changes and resulting glacier fluctuations alter landscapes. In the past, such changes were noted by local residents who often documented them in historic annals; eventually, glacier variations were recorded on maps and scientific reports. In Iceland, 10 glacier place-names are to be found in Icelandic sagas, and one of Iceland's ice caps, Snaefellsjokull, appeared on maps of Iceland published in the 16th century. In the late 17th century, the first description of eight of Iceland's glaciers was written. Therefore, Iceland distinguishes itself in having a more than 300-year history of observations by Icelanders on its glaciers. A long-term collaboration between Oddur Sigurdsson and Richard S. Williams, Jr., led to the authorship of three books on the glaciers of Iceland. Much effort has been devoted to documenting historical glacier research and related nomenclature and to physical descriptions of Icelandic glaciers by Icelanders and other scientists from as far back as the Saga Age to recent (2008) times. The first book, Icelandic Ice Mountains, was published by the Icelandic Literary Society in 2004 in cooperation with the Icelandic Glaciological Society and the International Glaciological Society. Icelandic Ice Mountains was a glacier treatise written by Sveinn Palsson in 1795 and is the first English translation of this important scientific document. Icelandic Ice Mountains includes a Preface, including a summary of the history and facsimiles of page(s) from the original manuscript, a handwritten copy, and an 1815 manuscript (without maps and drawings) by Sveinn Palsson on the same subject which he wrote for Rev. Ebenezer Henderson; an Editor's Introduction; 82 figures, including facsimiles of Sveinn Palsson's original maps and perspective drawings, maps, and photographs to illustrate the text; a comprehensive Index of Geographic Place-Names and Other Names in the treatise; References, and 415 Endnotes. Professional Paper 1746 (this book) is the second

  16. Models for polythermal ice sheets and glaciers

    NASA Astrophysics Data System (ADS)

    Hewitt, Ian; Schoof, Christian

    2016-04-01

    The dynamics of ice-sheets and glaciers depend sensitively on their thermal structure. Many ice masses are polythermal, containing both cold ice, with temperature below the melting point, and temperate ice, with temperature at the melting point. The temperate ice is really an ice-water mixture, with water produced at grain boundaries by dissipative heating. Although the water content is typically small, it can have an important effect on ice dynamics; water content controls ice viscosity, and internal meltwater percolation affects hydrology. Locations where this may be important are in the enhanced shear layer at the base of fast-flowing outlet glaciers, and in the shear margins of ice streams. In this study, we present a simplified model to describe the temperature and water-content of polythermal ice masses, accounting for the possibility of gravity- and pressure-driven water drainage according to Darcy's law. The model is based on the principle of energy conservation and the theory of viscous compaction. Numerical solutions are described and a number of illustrative test problems presented. The model is compared with existing methods in the literature, including enthalpy gradient methods, to which it reduces under certain conditions. Based on the results of our analysis, we suggest a modified enthalpy method that allows for drainage under gravity but that can be relatively easily implemented in ice-sheet models.

  17. The Physics of Glaciers, 3rd Edition

    NASA Astrophysics Data System (ADS)

    Bahr, David

    At one time or another, who among us has not marveled at the beauty of the snow and ice-covered Alps, or admired the tenacity of polar explorers and the adventurous spirits of climbers on the glacier-clad summits of the high Himalaya? The fascination of distant ice covered expanses has enlisted more than a few recruits into the ranks of glaciologists, but many, if not most, of today's students of glaciology are a slightly less romantic and more mathematical lot, attracted by the quantitative world of physics and the applied sciences of polar climatology, ice mechanics, and snow hydrology.Once a relatively quiet branch of geophysics filled with venturesome climbers capable of reaching the objects of their study, glaciology is now a field that is fueled by a rapid influx of talent, technology, and new ideas due to the increasingly acknowledged relationships between global climate, sea level, and ice sheets. While the understanding of glacier processes has seen significant progress, as a result there is also a sense of being overwhelmed by the voluminous and sometimes speculative theories and field observations associated with an expanding discipline.

  18. Instrument for Analysis of Greenland's Glacier Mills

    NASA Technical Reports Server (NTRS)

    Behar, Alberto E.; Matthews, Jaret B.; Tran, Hung B.; Steffen, Konrad; McGrath, Dan; Phillips, Thomas; Elliot, Andrew; OHern, Sean; Lutz, Colin; Martin, Sujita; Wang, Henry

    2010-01-01

    A new instrument is used to study the inner workings of Greenland s glacier mills by riding the currents inside a glacier s moulin. The West Greenland Moulin Explorer instrument was deployed into a tubular shaft to autonomously record temperature, pressure, 3D acceleration, and location. It is built with a slightly positive buoyancy in order to assist in recovery. The unit is made up of several components. A 3-axis MEMS (microelectromechanical systems) accelerometer with 0.001-g resolution forms the base of the unit. A pressure transducer is added that is capable of withstanding 500 psi (=3.4 MPa), and surviving down to -40 C. An Iridium modem sends out data every 10 minutes. The location is traced by a GPS (Global Positioning System) unit. This GPS unit is also used for recovery after the mission. Power is provided by a high-capacity lithium thionyl chloride D-sized battery. The accelerometer is housed inside a cylindrical, foot-long (=30 cm) polyvinyl chloride (PVC) shell sealed at each end with acrylic. The pressure transducer is attached to one of these lids and a MEMS accelerometer to the other, recording 100 samples per second per axis.

  19. Combined Ice and Water Balances of Maclure Glacier, California, South Cascade Glacier, Washington, and Wolverine and Gulkana Glaciers, Alaska, 1967 Hydrologic Year

    USGS Publications Warehouse

    Tangborn, Wendell V.; Mayo, Lawrence R.; Scully, David R.; Krimmel, Robert M.

    1977-01-01

    Combined ice and water balances were measured in the 1967 hydrologic year (October 1-September 30) on four glaciers in western North America ranging in latitude from 37 deg to 63 deg N. This hydrologic year was characterized by heavier than normal winter precipitation in California and Washington and abnormally dry winter conditions in coastal Alaska. In summer the western conterminous states were abnormally dry and central and southern Alaska experienced very wet conditions. Maclure Glacier (lat 37 deg 45' N., 3,650-m (metres) mean equilibrium line altitude) had an above normal winter balance of 3.46 m and a positive annual balance of 1.05 m (metres of water equivalent). South Cascade Glacier (lat 48 deg 22' N., 1900-m mean equilibrium line altitude) had a winter balance of 3.28 m, slightly above average. Above normal summer ablation resulted in a final annual balance of -0.58 m, slightly more negative than has been the case for the past decade. Wolverine Glacier's (lat 60 deg 24' N., 1,200-m mean equilibrium line altitude) winter balance was 1.17 m, considerably below normal; the annual balance was -2.04 m. Gulkana Glacier (lat 63 deg 15' N., 1,700-m mean equilibrium line altitude) had a winter balance of 1.05 m, approximately normal for this glacier; the final annual balance was -0.30 m.

  20. Scale effects impeding palaeoclimate reconstructions from mountain glaciers

    NASA Astrophysics Data System (ADS)

    Prinz, Rainer; Nicholson, Lindsey; Mölg, Thomas; Kaser, Georg

    2016-04-01

    Lewis Glacier on Mt. Kenya lost more than 80% of its area since its last stadial in the late 19th century (L19). Can we reconstruct climate conditions sustaining Lewis Glacier in its L19 extent? First, we optimized a physical based energy and mass balance model to the modern-day glacier extent with in situ observed climate observations. Second, from this record we constructed synthetic climate scenarios (based on coupled parameter perturbation applying a simple weather generator concept) as input for the mass balance model. These scenarios reflect the observed variability in precipitation and air temperature over recent decades, reproduce the observed mass balance variability for the modern-day glacier extent, and quantify the glacier's sensitivity to climate. Using the mass balance model as optimized for the modern-day glacier on the L19 extent, driven by climate perturbations most favourable to glaciation, results in negative mass balances. This would traditionally be interpreted to mean that even the extremes of the present-day climate are incapable of reproducing the L19 conditions. Alternatively or additionally, the modelling suggests that the L19 Lewis Glacier could be sustained if a favourable climate perturbation is applied in conjunction with a modification of the gradients used to extrapolate the climate observations over the glacier surface from those optimized for the very small modern-day glacier. Such a modification might be justifiable, where the modern-day glacier is so small that it is unlikely to generate significant microclimatological effects that would be expected for the larger L19 extent, when e.g. the glacier filled its cirque reducing long-wave emissions from surrounding terrain drastically. In a general sense this finding indicates that extracting proxy climate conditions from a particular glacier geometry, using a modelling system optimized on a dramatically different geometry, may invalidate the approach, particularly if changes in

  1. Latest Pleistocene and Holocene glacier fluctuations on Mount Baker, Washington

    NASA Astrophysics Data System (ADS)

    Osborn, Gerald; Menounos, Brian; Ryane, Chanone; Riedel, Jon; Clague, John J.; Koch, Johannes; Clark, Douglas; Scott, Kevin; Davis, P. Thompson

    2012-08-01

    Glaciers on stratovolcanoes of the Pacific Northwest of North America offer opportunities for dating late Pleistocene and Holocene glacier advances because tephra and fossil wood are common in lateral moraines and in glacier forefields. We capitalize on this opportunity by examining the Holocene glacial record at Mount Baker, an active stratovolcano in northwest Washington. Earlier workers concluded that glaciers on Mount Baker during the early Holocene were more extensive than during the Little Ice Age and hypothesized that the explanation lay in unusual climatic or hypsometric effects peculiar to large volcanoes. We show that the main argument for an early Holocene glacier advance on Mount Baker, namely the absence of ca 10,000-year-old tephra on part of the south flank of the mountain, is incorrect. Moreover, a lake-sediment core indicates that a small cirque moraine previously thought be of early Holocene age is also likely older than the tephra and consequently of late Pleistocene age. Lateral and end moraines and wood mats ca 2 km downvalley of the present snout of Deming Glacier indicate that an advance during the Younger Dryas interval was little more extensive than the climactic Little Ice Age advance. Tephra and wood between tills in the left lateral moraine of Easton Glacier suggest that ice on Mount Baker was restricted in the early Holocene and that Neoglaciation began ca 6 ka. A series of progressively more extensive Neoglacial advances, dated to about 2.2, 1.6, 0.9, and 0.4 ka, are recorded by stacked tills in the right lateral moraine of Deming Glacier. Intervening retreats were long enough to allow establishment of forests on the moraine. Wood mats in moraines of Coleman and Easton glaciers indicate that Little Ice Age expansion began before 0.7 ka and was followed by retreat and a readvance ca 0.5 ka. Tree-ring and lichen data indicate glaciers on the south side of the mountain reached their maximum extents in the mid-1800s. The similarity between

  2. 36 CFR 13.1132 - What types of commercial fishing are authorized in Glacier Bay?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... fishing are authorized in Glacier Bay? 13.1132 Section 13.1132 Parks, Forests, and Public Property...-Glacier Bay National Park and Preserve Commercial Fishing § 13.1132 What types of commercial fishing are authorized in Glacier Bay? Three types of commercial fishing are authorized in Glacier Bay...

  3. 36 CFR 13.1132 - What types of commercial fishing are authorized in Glacier Bay?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... fishing are authorized in Glacier Bay? 13.1132 Section 13.1132 Parks, Forests, and Public Property...-Glacier Bay National Park and Preserve Commercial Fishing § 13.1132 What types of commercial fishing are authorized in Glacier Bay? Three types of commercial fishing are authorized in Glacier Bay...

  4. 36 CFR 13.1132 - What types of commercial fishing are authorized in Glacier Bay?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... fishing are authorized in Glacier Bay? 13.1132 Section 13.1132 Parks, Forests, and Public Property...-Glacier Bay National Park and Preserve Commercial Fishing § 13.1132 What types of commercial fishing are authorized in Glacier Bay? Three types of commercial fishing are authorized in Glacier Bay...

  5. 36 CFR 13.1132 - What types of commercial fishing are authorized in Glacier Bay?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... fishing are authorized in Glacier Bay? 13.1132 Section 13.1132 Parks, Forests, and Public Property...-Glacier Bay National Park and Preserve Commercial Fishing § 13.1132 What types of commercial fishing are authorized in Glacier Bay? Three types of commercial fishing are authorized in Glacier Bay...

  6. 36 CFR 13.1132 - What types of commercial fishing are authorized in Glacier Bay?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... fishing are authorized in Glacier Bay? 13.1132 Section 13.1132 Parks, Forests, and Public Property...-Glacier Bay National Park and Preserve Commercial Fishing § 13.1132 What types of commercial fishing are authorized in Glacier Bay? Three types of commercial fishing are authorized in Glacier Bay...

  7. Status and distribution of the Kittlitz's Murrelet Brachyramphus brevirostris along the Alaska Peninsula and Kodiak and Aleutian Islands, Alaska

    USGS Publications Warehouse

    Madison, Erica N.; Piatt, John F.; Arimitsu, Mayumi L.; Romano, Marc D.; van Pelt, Thomas I.; Nelson, S. Kim; Williams, Jeffrey C.; DeGange, Anthony R.

    2011-01-01

    The Kittlitz's Murrelet Brachyramphus brevirostris is adapted for life in glacial-marine ecosystems, being concentrated in the belt of glaciated fjords in the northern Gulf of Alaska from Glacier Bay to Cook Inlet. Most of the remaining birds are scattered along coasts of the Alaska Peninsula and Aleutian Islands, where they reside in protected bays and inlets, often in proximity to remnant glaciers or recently deglaciated landscapes. We summarize existing information on Kittlitz's Murrelet in this mainly unglaciated region, extending from Kodiak Island in the east to the Near Islands in the west. From recent surveys, we estimated that ~2400 Kittlitz's Murrelets were found in several large embayments along the Alaska Peninsula, where adjacent ice fields feed silt-laden water into the bays. On Kodiak Island, where only remnants of ice remain today, observations of Kittlitz's Murrelets at sea were uncommon. The species has been observed historically around the entire Kodiak Archipelago, however, and dozens of nest sites were found in recent years. We found Kittlitz's Murrelets at only a few islands in the Aleutian chain, notably those with long complex shorelines, high mountains and remnant glaciers. The largest population (~1600 birds) of Kittlitz's Murrelet outside the Gulf of Alaska was found at Unalaska Island, which also supports the greatest concentration of glacial ice in the Aleutian Islands. Significant populations were found at Atka (~1100 birds), Attu (~800) and Adak (~200) islands. Smaller numbers have been reported from Unimak, Umnak, Amlia, Kanaga, Tanaga, Kiska islands, and Agattu Island, where dozens of nest sites have been located in recent years. Most of those islands have not been thoroughly surveyed, and significant pockets of Kittlitz's Murrelets may yet be discovered. Our estimate of ~6000 Kittlitz's Murrelets along the Alaska Peninsula and Aleutian Islands is also likely to be conservative because of the survey protocols we employed (i.e. early

  8. Pine Island Bay movie

    Atmospheric Science Data Center

    2014-08-01

    ... between successive frames is not uniform. The flow of the glacier, widening of the rift, and subsequent break-off of the iceberg are ... a gap in image acquisition during Antarctic winter, when the glacier was in continuous darkness. MISR was built and is managed by NASA's ...

  9. High diversity and distinctive community structure of bacteria on glaciers in China revealed by 454 pyrosequencing.

    PubMed

    Liu, Qing; Zhou, Yu-Guang; Xin, Yu-Hua

    2015-12-01

    The bacterial diversity, community structure and preliminary microbial biogeographic pattern were assessed on glacier surfaces, including three northern glaciers (cold glaciers) and three southern glaciers (temperate glaciers) in China that experienced distinct climatic conditions. Pyrosequencing revealed that bacterial diversities were surprisingly high. With respect to operational taxonomic units (OTUs), Proteobacteria was the most dominant phylum on the glacier surfaces, especially Betaproteobacteria. Significant differences of the bacterial communities were observed between northern and southern glacier surfaces. The rare and abundant populations showed similar clustering patterns to the whole community. The analysis of the culturable bacterial compositions from four glaciers supported this conclusion. Redundancy analysis (RDA) and partial Mantel tests indicated that annual mean temperature, as well as geographical distance, was significantly correlated with the bacterial communities on the glaciers. It was inferred that bacterial communities on northern and southern glacier surfaces experienced different climate, water and nutrient patterns, and consequently evolved different lifestyles.

  10. Variations in Alaska tidewater glacier frontal ablation, 1985-2013

    NASA Astrophysics Data System (ADS)

    McNabb, R. W.; Hock, R.; Huss, M.

    2015-01-01

    Our incomplete knowledge of the proportion of mass loss due to frontal ablation (the sum of ice loss through calving and submarine melt) from tidewater glaciers outside of the Greenland and Antarctic ice sheets has been cited as a major hindrance to accurate predictions of global sea level rise. We present a 28 year record (1985-2013) of frontal ablation for 27 Alaska tidewater glaciers (representing 96% of the total tidewater glacier area in the region), calculated from satellite-derived ice velocities and modeled estimates of glacier ice thickness. We account for cross-sectional ice thickness variation, long-term thickness changes, mass lost between an upstream fluxgate and the terminus, and mass change due to changes in terminus position. The total mean rate of frontal ablation for these 27 glaciers over the period 1985-2013 is 15.11 ± 3.63Gta-1. Two glaciers, Hubbard and Columbia, account for approximately 50% of these losses. The regional total ablation has decreased at a rate of 0.14Gta-1 over this time period, likely due to the slowing and thinning of many of the glaciers in the study area. Frontal ablation constitutes only ˜4% of the total annual regional ablation, but roughly 20% of net mass loss. Comparing several commonly used approximations in the calculation of frontal ablation, we find that neglecting cross-sectional thickness variations severely underestimates frontal ablation.

  11. Controls of air temperature variability over an Alpine Glacier

    NASA Astrophysics Data System (ADS)

    Shaw, Thomas; Brock, Ben; Ayala, Álvaro; Rutter, Nick

    2016-04-01

    Near surface air temperature (Ta) is one of the most important controls on energy exchange between a glacier surface and the overlying atmosphere. However, not enough detail is known about the controls on Ta across a glacier due to sparse data availability. Recent work has provided insights into variability of Ta along glacier 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-glacier locations. We present a new dataset of distributed 2m Ta records for the Tsanteleina Glacier in Northwest Italy from July-September, 2015. Data provide detailed information of lateral (across-glacier) 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-glacier 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 melt modelling.

  12. Surge dynamics in the Nathorstbreen glacier system, Svalbard

    NASA Astrophysics Data System (ADS)

    Sund, M.; Lauknes, T. R.; Eiken, T.

    2014-04-01

    Nathorstbreen glacier system (NGS) recently experienced the largest surge in Svalbard since 1936, and this was examined using spatial and temporal observations from DEM differencing, time series of surface velocities from satellite synthetic aperture radar (SAR) and other sources. The upper basins with maximum accumulation during quiescence corresponded to regions of initial lowering. Initial speed-up exceeded quiescent velocities by a factor of several tens. This suggests that polythermal glacier surges are initiated in the temperate area before mass is displaced downglacier. Subsequent downglacier mass displacement coincided with areas where glacier velocity increased by a factor of 100-200 times (stage 2). After more than 5 years, the joint NGS terminus advanced abruptly into the fjord during winter, increasing velocities even more. The advance was followed by up-glacier propagation of crevasses, indicating the middle and subsequently the upper part of the glaciers reacting to the mass displacement. NGS advanced ~15 km, while another ~3 km length was lost due to calving. Surface lowering of ~50 m was observed in some up-glacier areas, and in 5 years the total glacier area increased by 20%. Maximum measured flow rates were at least 25 m d-1, 2500 times quiescent velocity, while average velocities were about 10 m d-1. The surges of Zawadzkibreen cycle with ca. 70-year periods.

  13. Levoglucosan evidence for biomass burning records over Tibetan glaciers.

    PubMed

    You, Chao; Xu, Chao; Xu, Baiqing; Zhao, Huabiao; Song, Lili

    2016-09-01

    Intense biomass burning (BB) events are widespread in tropical and subtropical Asia. However, the impact of BB aerosols on the Tibetan Plateau (TP), especially on Tibetan glaciers, is poorly understood. In this study, BB signals are revealed using the specific molecular tracer levoglucosan in snow and ice samples from different Tibetan glaciers. Tibetan glaciers mainly act as receptors of BB emissions from surrounding regions. Significant differences in levoglucosan concentrations in glacier samples collected from two slopes on the same mountain range indicate that high mountains can act as natural barriers to block the transport of smoke aerosols to the TP. Levoglucosan concentrations show a decreasing trend from west to east on glaciers impacted by the Indian summer monsoon on the southern edge of the TP, while the opposite pattern was observed on glaciers under the prevailing westerlies along the northern edge. The emission sources, the controlling climate system, as well as deposition and degradation during transport determined the spatial distribution regimes of levoglucosan concentration on Tibetan glaciers. PMID:27262131

  14. Levoglucosan evidence for biomass burning records over Tibetan glaciers.

    PubMed

    You, Chao; Xu, Chao; Xu, Baiqing; Zhao, Huabiao; Song, Lili

    2016-09-01

    Intense biomass burning (BB) events are widespread in tropical and subtropical Asia. However, the impact of BB aerosols on the Tibetan Plateau (TP), especially on Tibetan glaciers, is poorly understood. In this study, BB signals are revealed using the specific molecular tracer levoglucosan in snow and ice samples from different Tibetan glaciers. Tibetan glaciers mainly act as receptors of BB emissions from surrounding regions. Significant differences in levoglucosan concentrations in glacier samples collected from two slopes on the same mountain range indicate that high mountains can act as natural barriers to block the transport of smoke aerosols to the TP. Levoglucosan concentrations show a decreasing trend from west to east on glaciers impacted by the Indian summer monsoon on the southern edge of the TP, while the opposite pattern was observed on glaciers under the prevailing westerlies along the northern edge. The emission sources, the controlling climate system, as well as deposition and degradation during transport determined the spatial distribution regimes of levoglucosan concentration on Tibetan glaciers.

  15. Glacier calving, dynamics, and sea-level rise. Final report

    SciTech Connect

    Meier, M.F.; Pfeffer, W.T.; Amadei, B.

    1998-08-01

    The present-day calving flux from Greenland and Antarctica is poorly known, and this accounts for a significant portion of the uncertainty in the current mass balance of these ice sheets. Similarly, the lack of knowledge about the role of calving in glacier dynamics constitutes a major uncertainty in predicting the response of glaciers and ice sheets to changes in climate and thus sea level. Another fundamental problem has to do with incomplete knowledge of glacier areas and volumes, needed for analyses of sea-level change due to changing climate. The authors proposed to develop an improved ability to predict the future contributions of glaciers to sea level by combining work from four research areas: remote sensing observations of calving activity and iceberg flux, numerical modeling of glacier dynamics, theoretical analysis of the calving process, and numerical techniques for modeling flow with large deformations and fracture. These four areas have never been combined into a single research effort on this subject; in particular, calving dynamics have never before been included explicitly in a model of glacier dynamics. A crucial issue that they proposed to address was the general question of how calving dynamics and glacier flow dynamics interact.

  16. Monitoring of oceanographic properties of Glacier Bay, Alaska 2004

    USGS Publications Warehouse

    2005-01-01

    Glacier Bay is a recently (300 years ago) deglaciated fjord estuarine system that has multiple sills, very deep basins, tidewater glaciers, and many streams. Glacier Bay experiences a large amount of runoff, high sedimentation, and large tidal variations. High freshwater discharge due to snow and ice melt and the presence of the tidewater glaciers 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 Glacier 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 Glacier 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 Glacier Bay, AK, making this a very unique and valuable data set in terms of its spatial and temporal coverage.

  17. Biodiversity under threat in glacier-fed river systems

    NASA Astrophysics Data System (ADS)

    Jacobsen, Dean; Milner, Alexander M.; Brown, Lee E.; Dangles, Olivier

    2012-05-01

    Freshwater biodiversity is under threat across the globe, with climate change being a significant contributor. One impact of climate change is the rapid shrinking of glaciers, resulting in a reduction in glacial meltwater contribution to river flow in many glacierized catchments. These changes potentially affect the biodiversity of specialized glacier-fed river communities. Perhaps surprisingly then, although freshwater biodiversity is a major conservation priority, the effects of shrinkage and disappearance of glaciers on river biodiversity have hitherto been poorly quantified. Here we focus on macroinvertebrates (mainly insect larvae) and demonstrate that local (α) and regional (γ) diversity, as well as turnover among reaches (β-diversity), will be consistently reduced by the shrinkage of glaciers. We show that 11-38% of the regional species pools, including endemics, can be expected to be lost following complete disappearance of glaciers in a catchment, and steady shrinkage is likely to reduce taxon turnover in proglacial river systems and local richness at downstream reaches where glacial cover in the catchment is less than 5-30%. Our analysis demonstrates not only the vulnerability of local biodiversity hotspots but also that extinction will probably greatly exceed the few known endemic species in glacier-fed rivers.

  18. Exploring the links between transient water inputs and glacier velocity in a small temperate glacier in southeastern Alaska

    NASA Astrophysics Data System (ADS)

    Heavner, M.; Habermann, M.; Hood, E. W.; Fatland, D. R.

    2009-12-01

    Glaciers along the Gulf of Alaska are thinning and retreating rapidly. An important control on the rate at which ice is being lost is basal motion because higher glacier velocities increase the rate at which ice is delivered to ablation zones. Recent research has focused on understanding the effects of sub-glacial water storage on glacier basal motion. In this study, we examined two seasons of the effect of hydrologic controls (from large rainfall events as well as a glacier lake outburst floods) on the velocity of the Lemon Creek Glacier in southeastern Alaska. Lemon Creek Glacier is a moderately sized (~16~km2) temperate glacier at the margin of the Juneau Icefield. An ice-marginal lake forms at the head of the glacier and catastrophically drains once or twice every melt season. We have instrumented the glacier with two meteorological stations: one at the head of the glacier near the ice-marginal lake and another several kilometers below the terminus. These stations measure temperature, relative humidity, precipitation, incoming solar radiation and wind speed and direction. Lake stage in the ice-marginal lake was monitored with a pressure transducer. In addition, Lemon Creek was instrumented with a water quality sonde at the location of a US Geological Survey gaging station approximately 3 km downstream from the glacier terminus. The sonde provides continuous measurements of water temperature, dissolved oxygen, turbidity and conductivity. Finally, multiple Trimble NetRS dual frequency, differential GPS units were deployed on the glacier along the centerline of the glacier. All of the instruments were run continuously from May-September 2008 and May-September 2009 and captured threee outburst floods associated with the ice-marginal lake drainage as well as several large (>3~cm) rainfall events associated with frontal storms off of the Gulf of Alaska in late summer. Taken together, these data allow us to test the hypothesis that water inputs which overwhelm

  19. Glacier maxima in Baffin Bay during the Medieval Warm Period coeval with Norse settlement

    PubMed Central

    Young, Nicolás E.; Schweinsberg, Avriel D.; Briner, Jason P.; Schaefer, Joerg M.

    2015-01-01

    The climatic mechanisms driving the shift from the Medieval Warm Period (MWP) to the Little Ice Age (LIA) in the North Atlantic region are debated. We use cosmogenic beryllium-10 dating to develop a moraine chronology with century-scale resolution over the last millennium and show that alpine glaciers in Baffin Island and western Greenland were at or near their maximum LIA configurations during the proposed general timing of the MWP. Complimentary paleoclimate proxy data suggest that the western North Atlantic region remained cool, whereas the eastern North Atlantic region was comparatively warmer during the MWP—a dipole pattern compatible with a persistent positive phase of the North Atlantic Oscillation. These results demonstrate that over the last millennium, glaciers approached their eventual LIA maxima before what is considered the classic LIA in the Northern Hemisphere. Furthermore, a relatively cool western North Atlantic region during the MWP has implications for understanding Norse migration patterns during the MWP. Our results, paired with other regional climate records, point to nonclimatic factors as contributing to the Norse exodus from the western North Atlantic region. PMID:26665173

  20. Glacier maxima in Baffin Bay during the Medieval Warm Period coeval with Norse settlement.

    PubMed

    Young, Nicolás E; Schweinsberg, Avriel D; Briner, Jason P; Schaefer, Joerg M

    2015-12-01

    The climatic mechanisms driving the shift from the Medieval Warm Period (MWP) to the Little Ice Age (LIA) in the North Atlantic region are debated. We use cosmogenic beryllium-10 dating to develop a moraine chronology with century-scale resolution over the last millennium and show that alpine glaciers in Baffin Island and western Greenland were at or near their maximum LIA configurations during the proposed general timing of the MWP. Complimentary paleoclimate proxy data suggest that the western North Atlantic region remained cool, whereas the eastern North Atlantic region was comparatively warmer during the MWP-a dipole pattern compatible with a persistent positive phase of the North Atlantic Oscillation. These results demonstrate that over the last millennium, glaciers approached their eventual LIA maxima before what is considered the classic LIA in the Northern Hemisphere. Furthermore, a relatively cool western North Atlantic region during the MWP has implications for understanding Norse migration patterns during the MWP. Our results, paired with other regional climate records, point to nonclimatic factors as contributing to the Norse exodus from the western North Atlantic region.

  1. Glacier maxima in Baffin Bay during the Medieval Warm Period coeval with Norse settlement.

    PubMed

    Young, Nicolás E; Schweinsberg, Avriel D; Briner, Jason P; Schaefer, Joerg M

    2015-12-01

    The climatic mechanisms driving the shift from the Medieval Warm Period (MWP) to the Little Ice Age (LIA) in the North Atlantic region are debated. We use cosmogenic beryllium-10 dating to develop a moraine chronology with century-scale resolution over the last millennium and show that alpine glaciers in Baffin Island and western Greenland were at or near their maximum LIA configurations during the proposed general timing of the MWP. Complimentary paleoclimate proxy data suggest that the western North Atlantic region remained cool, whereas the eastern North Atlantic region was comparatively warmer during the MWP-a dipole pattern compatible with a persistent positive phase of the North Atlantic Oscillation. These results demonstrate that over the last millennium, glaciers approached their eventual LIA maxima before what is considered the classic LIA in the Northern Hemisphere. Furthermore, a relatively cool western North Atlantic region during the MWP has implications for understanding Norse migration patterns during the MWP. Our results, paired with other regional climate records, point to nonclimatic factors as contributing to the Norse exodus from the western North Atlantic region. PMID:26665173

  2. Glacier loss and emerging hydrologic vulnerabilities in the Peruvian Andes

    NASA Astrophysics Data System (ADS)

    Mark, B. G.; McKenzie, J. M.; Baraer, M.; Lagos, P.; Lautz, L.; Carey, M.; Bury, J.; Crumley, R.; Wigmore, O.; Somers, L. D.

    2015-12-01

    Accelerating glacier recession in the tropical Andes is transforming downstream hydrology, while increasing demands for water by end-users (even beyond the watershed limits) is complicating the assessment of vulnerability. Future scenarios of hydro-climatic vulnerability require a better understanding of coupled hydrologic and human systems, involving both multiscale process studies and more robust models of glacier-climate interactions. We synthesize research in two proglacial valleys of glacierized mountain ranges in different regions of Peru that are both in proximity to growing water usage from urban sectors, agriculture, hydroelectric generation, and mining. In both the Santa River watershed draining the Cordillera Blanca and the Shullcas River watershed below Hyuatapallana Mountain in Junin, glaciers have receded over 25% since the 1980s. Historical runoff and glacier data, combined with glacier-climate modeling, show a long-term decrease in discharge resulting from a net loss of stored water. We find evidence that this altered hydrology is transforming proglacial wetland ecology and water quality, even while water resource use has intensified. Beyond glaciers, our results show that over 60% of the dry season base flow in each watershed is groundwater sourced from heterogeneous aquifers. Municipal water supply in Huancayo already relies on 18 groundwater wells. Perceptions of water availability and actual water use practices remain relatively divorced from the actual water resources provided from each mountain range. Critical changes in glacier volume and water supply are not perceived or acknowledged consistently amongst different water users, nor reflected in water management decisions. In order to identify, understand, model, and adapt to climate-glacier-water changes, it is vital to integrate the analysis of water availability and groundwater processes (the domain of hydrologists) with that of water use (the focus for social scientists). Attention must be

  3. New glacier inventory of Salzburg 2007/09

    NASA Astrophysics Data System (ADS)

    Stocker-Waldhuber, M.; Wiesenegger, H.; Fischer, A.

    2012-04-01

    Glacier inventories are an important data basis for several investigations such as length-, area- and volume changes in the course of climate change. The new glacier inventory of Salzburg is part of the third Austrian glacier inventory (GI3) and is valid for the years 2007 and 2009 depending on each mountain range. The first inventory (GI1) was compiled in 1969 and the second one (GI2) represents the glacier state from 1998 to 2002. In Salzburg, 150 glaciers are located in the six mountain ranges: Ankogel, Glockner, Granatspitz, Sonnblick (Goldberg), Hochkönig and Venediger. The basis for the new mapping were orthophotos of 2007 and 2009 and the DEM of the southern part of Salzburg. On the basis of former inventories area-, height- and volume changes have been calculated. The biggest loss of glacier area per mountain range was found in the Ankogel range and on Hochkönig because of the disrupted structure of the thin glaciers. Referring to the absolute values, the largest changes took place in the Glockner- and Venediger mountain range with -10.11 km2 and -9.72 km2 during the period between GI1 (1969) and GI3 (2007/2009) respectively. Due to the lack of DEMs (only the southern part was available) volume changes have been calculated for about half of all glaciers in Salzburg. These are located at the Glockner, Granatspitz and Sonnblick mountain range and showed -0.335 km3 on average changes in height of 9.3 m. An extrapolation of these changes to all of the 150 glaciers in Salzburg results in a loss of about 0.7 km3 between GI1 and GI3.

  4. 2011 the first complete glacier inventory for Eastern Greenland

    NASA Astrophysics Data System (ADS)

    Rastner, P.; Bolch, T.; Paul, F.

    2011-12-01

    Meltwater from glaciers and icecaps (GIC) provide a significant contribution to global sea-level rise, but estimates are uncertain due to the globally still incomplete information about glacier location and size, as well as large uncertainties in current Global Climate Models (GCMs). Recent studies that calculate global sea-level rise from GIC have developed simplified approaches using information from glacier inventories or gridded data sets and different GCMs. However, for several strongly glacierized regions very rough assumptions about the ice distribution have to be made and an urgent demand for a globally complete glacier inventory data is expressed. The GIC on Greenland are one of these regions. Within the "EU-funded" project ice2sea we map the Eastern part of Greenland using Landsat ETM imagery acquired around the year 2000 and the ASTER GDEM to derive topographic parameters and drainage divides. Up to now more than 5500 GIC with a total area of about 26.000 square km have been mapped between 62 degrees and 80 degrees N considering only glaciers with an area larger than 0.1 square km that have no direct connection to the ice sheet. The largest valley glaciers are often debris covered, whereas smaller and mountain glaciers are often shaded due to the steep topography. Seasonal snow hiding the real glacier perimeter is a problem in some of the scenes that can only be solved by using scenes with better snow conditions. The artifacts in the GDEM are locally rather severe, but for the GIC considered for this inventory they were manageable. A comparison with the outline of the Greenland ice sheet as used in current models revealed that along the eastern coast a considerable amount of the local GIC is included in the extent of the ice sheet.

  5. On the accuracy of glacier outlines derived from satellite data

    NASA Astrophysics Data System (ADS)

    Paul, F.

    2012-04-01

    The determination of the accuracy of glacier outlines as mapped from satellite data is a mandatory task, in particular when change assessment is performed. However, this is often not correctly done as a direct comparison with a reference data set can give misleading results. Though it is widely accepted that glacier outlines as derived from a higher-resolution data set (e.g. aerial photography) can be used to determine the accuracy of outlines derived from a lower resolution data set (e.g. Landsat TM), this is not generally true and several details have to be considered. At first, changing glacier extents require to compare images acquired in the same year and rapidly changing snow conditions require to use images from the same week or at least with identical snow conditions (i.e. no snow outside of glaciers). Secondly, differences in interpretation result from the higher-spatial resolution itself and the missing shortwave infrared band in high-resolution data. In particular, the determination of the glacier boundary on panchromatic imagery can locally be impossible (when the ice and the surrounding rock have the same reflectance). Thirdly, for natural objects like glaciers the change of the resolution alone results in a change of the area covered by the respective outline. Finally, the required manual correction of debris-covered glacier parts is done differently by different analysts and also by the same analyst when digitized several times. To overcome these challenges and provide an accuracy assessment for a larger data set, we will perform a combined round robin and validation experiment in the framework of the ESA project Glaciers_cci. This will include the manual and automated digitization of glacier outlines on high and low resolution satellite data (e.g. Quickbird / Ikonos vs. Landsat TM / ETM+) in different parts of the world (Alaska, Alps, Himalaya), as well as multiple digitizations of the same set of glaciers (with and without debris cover) by

  6. Small Glacier Area Studies: A New Approach for Turkey

    NASA Technical Reports Server (NTRS)

    Yavasli, Dogukan D.; Tucker, Compton J.

    2012-01-01

    Many regions of Earth have glaciers that have been neglected for study because they are small. We report on a new approach to overcome the problem of studying small glaciers, using Turkey as an example. Prior to our study, no reliable estimates of Turkish glaciers existed because of a lack of systematic mapping, difficulty in using Landsat data collected before 1982, snowpack vs. glacier ice differentiation using existing satellite data and aerial photography, the previous high cost of Landsat images, and a lack of high-resolution imagery of small Turkish glaciers. Since 2008, a large number of < 1 m satellite images have become available at no cost to the research community. In addition, Landsat data are now free of charge from the U.S. Geological Survey, enabling the use of multiple images. We used 174 Landsat and eight high-resolution satellite images to document the areal extent of Turkish glaciers from the 1970s to 2007-2011. Multiple Landsat images, primarily Thematic Mapper (TM) data from 1984 to 2011, enabled us to minimize differentiation problems between snow and glacier ice, a potential source of error. In addition, we used Ikonos, Quickbird, and World View-1 & -2 very high-resolution imagery to evaluate our TM accuracies and determine the area of nine smaller glaciers in Turkey. We also used five Landsat-3 Return Beam Videcon (RBV) 30 m pixel resolution images, all from 1980, for six glaciers. The total area of Turkish glaciers decreased from 23 km2 in the 1970s to 10.1 km2 in 2007-2011. By 2007-2011, six Turkish glaciers disappeared, four were < 0.3 km2, and only three were 1.0 km2 or larger. No trends in precipitation from 1970 to 2006 and cloud cover from 1980 to 2010 were found, while surface temperatures increased, with summer minimum temperatures showing the greatest increase. We conclude that increased surface temperatures during the summer were responsible for the 56% recession of Turkish glaciers from the 1970s to 2006-2011.

  7. Postglacial vegetation history of Mitkof Island, Alexander Archipelago, southeastern Alaska

    USGS Publications Warehouse

    Ager, T.A.; Carrara, P.E.; Smith, Jody L.; Anne, V.; Johnson, J.

    2010-01-01

    An AMS radiocarbon-dated pollen record from a peat deposit on Mitkof Island, southeastern Alaska provides a vegetation history spanning ???12,900??cal yr BP to the present. Late Wisconsin glaciers covered the entire island; deglaciation occurred > 15,400??cal yr BP. The earliest known vegetation to develop on the island (???12,900??cal yr BP) was pine woodland (Pinus contorta) with alder (Alnus), sedges (Cyperaceae) and ferns (Polypodiaceae type). By ???12,240??cal yr BP, Sitka spruce (Picea sitchensis) began to colonize the island while pine woodland declined. By ???11,200??cal yr BP, mountain hemlock (Tsuga mertensiana) began to spread across the island. Sitka spruce-mountain hemlock forests dominated the lowland landscapes of the island until ???10,180??cal yr BP, when western hemlock (Tsuga heterophylla) began to colonize, and soon became the dominant tree species. Rising percentages of pine, sedge, and sphagnum after ???7100??cal yr BP may reflect an expansion of peat bog habitats as regional climate began to shift to cooler, wetter conditions. A decline in alders at that time suggests that coastal forests had spread into the island's uplands, replacing large areas of alder thickets. Cedars (Chamaecyparis nootkatensis, Thuja plicata) appeared on Mitkof Island during the late Holocene.

  8. Postglacial vegetation history of Mitkof Island, Alexander Archipelago, southeastern Alaska

    NASA Astrophysics Data System (ADS)

    Ager, Thomas A.; Carrara, Paul E.; Smith, Jane L.; Anne, Victoria; Johnson, Joni

    2010-03-01

    An AMS radiocarbon-dated pollen record from a peat deposit on Mitkof Island, southeastern Alaska provides a vegetation history spanning ˜12,900 cal yr BP to the present. Late Wisconsin glaciers covered the entire island; deglaciation occurred > 15,400 cal yr BP. The earliest known vegetation to develop on the island (˜12,900 cal yr BP) was pine woodland ( Pinus contorta) with alder ( Alnus), sedges (Cyperaceae) and ferns (Polypodiaceae type). By ˜12,240 cal yr BP, Sitka spruce ( Picea sitchensis) began to colonize the island while pine woodland declined. By ˜11,200 cal yr BP, mountain hemlock ( Tsuga mertensiana) began to spread across the island. Sitka spruce-mountain hemlock forests dominated the lowland landscapes of the island until ˜10,180 cal yr BP, when western hemlock ( Tsuga heterophylla) began to colonize, and soon became the dominant tree species. Rising percentages of pine, sedge, and sphagnum after ˜7100 cal yr BP may reflect an expansion of peat bog habitats as regional climate began to shift to cooler, wetter conditions. A decline in alders at that time suggests that coastal forests had spread into the island's uplands, replacing large areas of alder thickets. Cedars ( Chamaecyparis nootkatensis, Thuja plicata) appeared on Mitkof Island during the late Holocene.

  9. Glacier Sensitivity to Climate Change in the Monsoonal Himalaya: Past, Present, and Future

    NASA Astrophysics Data System (ADS)

    Rupper, S.; Maurer, J.; Schaefer, J. M.; Cook, E. R.; Putnam, A. E.; Krusic, P.; Smith, R. G.

    2013-12-01

    Glaciers are particularly sensitive to climate change, making them vulnerable elements of the environment. Of potential concern for societies is the rapid glacier retreat of Himalayan glaciers. However, the temporally short and spatially sparse instrumental records of climate, and arguably shorter and sparser glacier records, make it extremely difficult to quantify glacier sensitivity to climatic change or to place recent glacier changes into a longer, historical context. Here we address many of these issues by quantifying the glacier-climate sensitivity in the Bhutanese Himalaya over the past 800 years using a combination of remote sensing data, paleoclimate data, glacier modeling, and glacial geochronology. Bhutan is chosen for two key reasons. First, Bhutan exemplifies an area where little data on glacier changes are available and where it is logistically difficult to obtain field-based studies, a common problem for many regions of the Himalayas. Thus the methods developed here will be directly applicable to other regions. Second, glaciers in Bhutan, just as neighboring glaciers in India, Nepal, and Southwest China, sit in the bulls-eye of high snow accumulation glaciers. Sensitivity tests using a surface energy- and mass-balance model show that high accumulation regions are extremely temperature-sensitive. Therefore, Bhutan's glaciers form a highly suitable natural laboratory to investigate glacier sensitivity and response to temperature change in the monsoonal Himalaya. In this study, we map Bhutan glacierized area and volume changes over the past forty years, and show significant changes and rapid retreat of these glaciers over this period of time. In addition, we map the former glacier extents for key glacierized regions of Bhutan, and produce a 10Be chronology for glacier fluctuations for one region. Finally, we model the glacierized changes over the past 800 years using Bhutan tree-ring temperature reconstructions as climate input. Our results show that

  10. Analysis of the glacier retreat in the French Alps since the 1960s based on the new glacier inventory

    NASA Astrophysics Data System (ADS)

    Gardent, M.; Rabatel, A.; Dedieu, J. P.; Deline, P.; Schoeneich, P.

    2012-04-01

    One of the most obvious impacts of climate change in high mountain areas is the glacial retreat. Since the French glacier inventory carried out by R. Vivian in the late 1960s within the context of the WGI, there was no updated data from the overall French alpine glaciers. We present here the first results of a new diachronic inventory of the French alpine glaciers based on different sources. Glacier outlines were manually delineated using 1/25,000 topographic maps of the french National Geographical Institute (IGN) from the end of the 1960s, and IGN 50-cm-pixel orthophotographs from 2006 to 2009. For Landsat 5 TM images (30 m resolution) dating from 1985-1986, and Landsat 5 TM and Landsat 7 ETM+ images (30 and 15 m resolutions) dating from 2003, an automatic delineation with the common NDSI method was used to determine glacier limits. Each glacier has been individually checked, with a special care for debris covered and shadowed areas to adjust the delineation, using a 542 spectral bands combination. For compounded glaciers, the same limits were manually adjusted for each period. Data were integrated into a GIS and a database including all the common items (surface area, minimal and maximal elevations, aspect, debris covered area, slope…) was generated. Topographic parameters were extracted from the IGN DEM (resolution of 25 m) for the topographic maps and Landsat images from the mid-80s, and the ASTER GDEM (resolution of 30 m) for the Landsat images of the early 2000s and the orthophotographs. . Current extension of the 593 French alpine glaciers is about 275 km2. It is ~20 % less than in 1985-1986 (end of the last glacial advance period), when glacier extension was 340 km2, and ~26 % less than at the end of the 1960s, when glacier coverage was about 375 km2. Different trends are observed across the French Alps, with a stronger glacial retreat in the southern massifs: for instance, glacier shrinkage in the Ecrins massif is more than three times stronger than in

  11. 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. PMID:26632967

  12. Distribution and transportation of mercury from glacier to lake in the Qiangyong Glacier Basin, southern Tibetan Plateau, China.

    PubMed

    Sun, Shiwei; Kang, Shichang; Huang, Jie; Li, Chengding; Guo, Junming; Zhang, Qianggong; Sun, Xuejun; Tripathee, Lekhendra

    2016-06-01

    The Tibetan Plateau is home to the largest aggregate of glaciers 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 glacier basins on Tibetan Plateau. In this study, surface snow, glacier melting stream water and lake water samples were collected from the Qiangyong Glacier Basin. The spatiotemporal distribution and transportation of Hg from glacier 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 glacier 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 Glacier Basin. PMID:27266318

  13. 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.

  14. Climate downscaling for estimating glacier mass balances in northwestern North America: Validation with a USGS benchmark glacier

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Bhatt, Uma S.; Tangborn, Wendell V.; Lingle, Craig S.

    2007-11-01

    An atmosphere/glacier modeling system is described for estimating the mass balances of glaciers in both current and future climate in order to estimate their probable future contributions to rising sea level. Dynamically downscaled output from a regional atmospheric model, driven by global atmospheric reanalysis, is used to force a precipitation-temperature-area-altitude (PTAA) glacier mass balance model with daily maximum and minimum temperatures and precipitation. The modeling system is verified by hindcasting the mass balances of Gulkana Glacier, a U.S. Geological Survey (USGS) benchmark glacier in the Alaska Range, U.S.A., during a ten-year period from October 1994 to September 2004. The mass balances simulated with the atmosphere/glacier modeling system are comparable to the USGS measurements, and are also in good agreement with the meteorological station observation-forced PTAA simulations. The results suggest this is a promising approach for realistic estimation of the future mass balances of the glaciers of northwestern North America.

  15. Glacier-specific elevation changes in western Alaska

    NASA Astrophysics Data System (ADS)

    Paul, Frank; Le Bris, Raymond

    2013-04-01

    Deriving glacier-specific elevation changes from DEM differencing and digital glacier outlines is rather straight-forward if the required datasets are available. Calculating such changes over large regions and including glaciers selected for mass balance measurements in the field, provides a possibility to determine the representativeness of the changes observed at these glaciers for the entire region. The related comparison of DEM-derived values for these glaciers with the overall mean avoids the rather error-prone conversion of volume to mass changes (e.g. due to unknown densities) and gives unit-less correction factors for upscaling the field measurements to a larger region. However, several issues have to be carefully considered, such as proper co-registration of the two DEMs, date and accuracy of the datasets compared, as well as source data used for DEM creation and potential artefacts (e.g. voids). In this contribution we present an assessment of the representativeness of the two mass balance glaciers Gulkana and Wolverine for the overall changes of nearly 3200 glaciers in western Alaska over a ca. 50-year time period. We use an elevation change dataset from a study by Berthier et al. (2010) that was derived from the USGS DEM of the 1960s (NED) and a more recent DEM derived from SPOT5 data for the SPIRIT project. Additionally, the ASTER GDEM was used as a more recent DEM. Historic glacier outlines were taken from the USGS digital line graph (DLG) dataset, corrected with the digital raster graph (DRG) maps from USGS. Mean glacier specific elevation changes were derived based on drainage divides from a recently created inventory. Land-terminating, lake-calving and tidewater glaciers were marked in the attribute table to determine their changes separately. We also investigated the impact of handling potential DEM artifacts in three different ways and compared elevation changes with altitude. The mean elevation changes of Gulkana and Wolverine glaciers (about -0

  16. Faster and More Accurate Transport Procedures for HZETRN

    NASA Technical Reports Server (NTRS)

    Slaba, Tony C.; Blattnig, Steve R.; Badavi, Francis F.

    2010-01-01

    Several aspects of code verification are examined for HZETRN. First, a detailed derivation of the numerical marching algorithms is given. Next, a new numerical method for light particle transport is presented, and improvements to the heavy ion transport algorithm are discussed. A summary of various coding errors is also given, and the impact of these errors on exposure quantities is shown. Finally, a coupled convergence study is conducted. From this study, it is shown that past efforts in quantifying the numerical error in HZETRN were hindered by single precision calculations and computational resources. It is also determined that almost all of the discretization error in HZETRN is caused by charged target fragments below 50 AMeV. Total discretization errors are given for the old and new algorithms, and the improved accuracy of the new numerical methods is demonstrated. Run time comparisons are given for three applications in which HZETRN is commonly used. The new algorithms are found to be almost 100 times faster for solar particle event simulations and almost 10 times faster for galactic cosmic ray simulations.

  17. Electronic Structure Engineering of Elpasolites for Brighter and Faster Scintillators

    NASA Astrophysics Data System (ADS)

    Du, Mao-Hua; Biswas, Koushik

    2013-03-01

    Utilization of scintillator materials is one of the primary methods for radiation detection. Elpasolites are a large family of quaternary halides that have attracted considerable interest for their potential applications as γ-ray and neutron scintillators. However, many elpasolite scintillator materials currently under development suffer from low light yield and long scintillation decay time. The low light yield is partially due to a large band gap while the long scintillation decay time is a result of slow carrier transport to Ce dopants, where electrons and holes recombine to emit photons. We suggest that these problems may be mitigated by optimizing the band gap and carrier mobility by selecting constituent elements of proper electronegativity. For example, cations with lower electronegativity may lower the conduction band and increase the conduction band dispersion simultaneously, resulting in higher light yield and faster scintillation. First-principles calculations of electronic structure, small polarons, and Ce dopants in Cs2LiYCl6 and Cs2AgYCl6 compounds show that the strategy of manipulating electronegativity can lead to brighter and faster elpasolite-based scintillators. This work was supported by the U.S. DOE Office of Nonproliferation Research and Development NA22.

  18. Faster SEQUEST Searching for Peptide Identification from Tandem Mass Spectra

    PubMed Central

    Diament, Benjamin; Noble, William Stafford

    2011-01-01

    Computational analysis of mass spectra remains the bottleneck in many proteomics experiments. SEQUEST was one of the earliest software packages to identify peptides from mass spectra by searching a database of known peptides. Though still popular, SEQUEST performs slowly. Crux and TurboSEQUEST have successfully sped up SEQUEST by adding a precomputed index to the search, but the demand for ever-faster peptide identification software continues to grow. Tide, introduced here, is a software program that implements the SEQUEST algorithm for peptide identification and that achieves a dramatic speedup over Crux and SEQUEST. The optimization strategies detailed here employ a combination of algorithmic and software engineering techniques to achieve speeds up to 170 times faster than a recent version of SEQUEST that uses indexing. For example, on a single Xeon CPU, Tide searches 10,000 spectra against a tryptic database of 27,499 C. elegans proteins at a rate of 1,550 spectra per second, which compares favorably with a rate of 8.8 spectra per second for a recent version of SEQUEST with index running on the same hardware. PMID:21761931

  19. Neuromuscular strategies contributing to faster multidirectional agility performance.

    PubMed

    Spiteri, Tania; Newton, Robert U; Nimphius, Sophia

    2015-08-01

    The aim of this study was to first determine differences in neuromuscular strategy between a faster and slower agility performance, and second compare differences in muscle activation strategy employed when performing two closely executed agility movements. Participants recruited from an elite female basketball team completed an ultrasound to determine quadriceps muscle-cross sectional area; reactive isometric mid-thigh pull to determine the rate of muscle activation, rate of force development, pre-motor time and motor time; and multidirectional agility tests completing two directional changes in response to a visual stimulus. Peak and average relative muscle activation of the rectus femoris, vastus medialis, vastus lateralis, biceps femoris, semitendinosus and gastrocnemius were measured 100ms prior to heel strike (pre-heel strike) and across stance phase for both directional changes. Faster agility performance was characterized by greater pre-heel strike muscle activity and greater anterior muscle activation during stance phase resulting in greater hip and knee extension increasing propulsive impulse. Differences between directional changes appear to result from processing speed, where a greater delay in refractory times during the second directional change resulted in greater anterior muscle activation, decelerating the body while movement direction was determined.

  20. Airborne geophysical survey of ice caps in the Queen Elizabeth Islands, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Palmer, S. J.; Dowdeswell, J. A.; Christoffersen, P.; Benham, T. J.; Young, D. A.; Blankenship, D. D.; Richter, T.; Ng, G.; Grima, C.; Habbal, F.; Sharp, M. J.; Rutishauser, A.

    2014-12-01

    Previous studies have shown that between 2003 and 2009, 60 ± 6 Gt of ice was lost each year from the Canadian Arctic (Gardner et al., 2013), making the region the largest cryospheric contributor to global sea level rise outside of the great ice sheets. Glacier ice in the Queen Elizabeth Islands (QEI) currently covers more than 100,000 km2, representing 20% of Earth's ice-covered land area outside of Greenland and Antarctica. The vast majority of this ice is stored within six ice caps located on Ellesmere, Devon and Axel Heiberg islands. Recent satellite observations of the outlet glaciers draining these ice caps have revealed significant velocity variability on inter-annual and multi-year timescales (Van Wychen et al., 2014), though the drivers of these dynamics are not yet understood. Here we present results obtained in May 2014 during an airborne geophysical survey of the ice caps of Axel Heiberg, Ellesmere and Devon islands, including Agassiz Ice Cap (17,300 km2), Prince of Wales Icefield (19,300 km2) and Devon Ice Cap (14,000 km2). We used a Basler BT-67 aircraft equipped with a suite of geophysical instruments, including a phase-coherent VHF ice-penetrating radar, to measure ice thickness and investigate ice basal conditions along outlet glacier flow lines and in the interior of the ice caps. We reveal that the glaciers draining the ice caps of the QEI exhibit diverse characteristics over short spatial scales, and that fast-flowing tidewater glaciers are located adjacent to previously fast-flowing areas that have subsequently stagnated. Our results show that many ice cap outlet glaciers on Ellesmere and Devon islands are between 700 and 1000 m thick and flow through deep bedrock troughs whose beds lie below sea-level. Some of the outlet glaciers also have floating tongues of ice which extend into the adjacent fjord waters. We intend to use our results to characterize the substrate beneath the ice, and to reveal any variations in conditions at the ice