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Sample records for advancing tidewater glacier

  1. 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.

  2. Modelling the behaviour of tidewater glaciers

    NASA Astrophysics Data System (ADS)

    Nick, Faezeh Maghami

    2006-09-01

    More than half of the annual mass transfer from whole cryosphere to the world's oceans occurs through calving. Uncertainties in predicting future sea level are partly caused by a lack of knowledge of the behaviour of calving glaciers. A better understanding of the factors that control the response of calving glaciers to climate change is needed to interpret the past or predict the future behaviour of these glaciers in a warmer climate. Over the past years, interest in the response of calving glaciers to climate change has increased considarably. Many bservational and modelling studies have been carried out to investigate the dynamics of the calving process and the associated response of the glacier terminus. It has been suggested that calving glaciers are inherently unstable showing a periodic advance and retreat that may be nearly independent of climate. The cycle of slow advance and rapid retreat of calving glaciers is mainly a function of fjord geometry, water depth at the glacier terminus, and sedimentation at the glacier front. Some other studies show that climate acts as a first-order control on the advance/retreat. Hence, the diverse behaviour of calving glaciers is a result of both internal dynamics and climate. In this thesis the dynamics of tidewater glaciers (temperate grounded calving glaciers) and the involved processes such as iceberg calving, basal sliding, and proglacial moraine bank are investigated. A numerical ice-flow model is developed, which simulates the rapid retreat and slow advance of tidewater glaciers very well. To construct a time-evolving numerical model that simulates the behaviour of calving glaciers, it is necessary to formulate realistic calving boundary conditions. Empirical studies provide two different calving schemes, the flotation and the water-depth model. We introduce two numerical ice-flow models using the water-depth and the flotation scheme. The results show that any model in which the loss of ice at the glacier front

  3. 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

  4. 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.

  5. 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.

  6. Bathymetric Controls On Observed Tidewater Glacier Retreat In Northwest Greenland

    NASA Astrophysics Data System (ADS)

    Porter, D. F.; Tinto, K. J.; Boghosian, A.; Cochran, J. R.; Bell, R. E.

    2013-12-01

    Although many of the largest glaciers in Greenland are losing mass, the large variability in observed mass wastage of the remaining glaciers clouds interpretation of the proposed external forcings, such as warming of the ocean or atmosphere. Some glaciers are accelerating and thinning while other nearby glaciers advance and gain mass. Recent efforts suggest that increased ocean temperatures may be responsible for the observed glacial retreat in Greenland and Antarctica through increased basal melting beneath floating ice tongues and vertical ice faces of tidewater glaciers. Basal melting may contribute significantly to calving and thinning, and to an eventual speeding up of the glacier, resulting in thinning further inland. Knowledge of fjord geometry is crucial for ice-ocean interaction because the availability of ocean heat to the ice will be restricted by narrow sills and shallow grounding lines. We investigate whether the variability in observed changes among Greenland glaciers can be partially explained by variation in fjord geometry. Some features of a fjord that could influence the ice-ocean system include the depth of the grounding line, the presence of sills, sloping bed, and the water cavity shape beneath floating ice. New estimates of fjord bathymetries in northwest Greenland, using airborne gravimetry measurements from NASA Operation IceBridge flights, are compared to estimates of ice acceleration and mass wastage of neighboring glaciers. We investigate the correlation between fjord geometry features and several glacier parameters, such as surface velocity and elevation changes. We determine that the geometry of glacial fjords play a large role in determining the stability of outlet glaciers. Deep sills and deep terminus grounding lines will allow greater interaction with the deep and warm Atlantic water off the shelf break. For two neighboring glaciers in northwest Greenland, we find that the glacier with a deeper grounding line, and presumably in

  7. 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.

  8. Calving rates at tidewater glaciers vary strongly with ocean temperature

    PubMed Central

    Luckman, Adrian; Benn, Douglas I.; Cottier, Finlo; Bevan, Suzanne; Nilsen, Frank; Inall, Mark

    2015-01-01

    Rates of ice mass loss at the calving margins of tidewater glaciers (frontal ablation rates) are a key uncertainty in sea level rise projections. Measurements are difficult because mass lost is replaced by ice flow at variable rates, and frontal ablation incorporates sub-aerial calving, and submarine melt and calving. Here we derive frontal ablation rates for three dynamically contrasting glaciers in Svalbard from an unusually dense series of satellite images. We combine ocean data, ice-front position and terminus velocity to investigate controls on frontal ablation. We find that frontal ablation is not dependent on ice dynamics, nor reduced by glacier surface freeze-up, but varies strongly with sub-surface water temperature. We conclude that calving proceeds by melt undercutting and ice-front collapse, a process that may dominate frontal ablation where submarine melt can outpace ice flow. Our findings illustrate the potential for deriving simple models of tidewater glacier response to oceanographic forcing. PMID:26450063

  9. Calving rates at tidewater glaciers vary strongly with ocean temperature

    NASA Astrophysics Data System (ADS)

    Luckman, Adrian; Benn, Douglas I.; Cottier, Finlo; Bevan, Suzanne; Nilsen, Frank; Inall, Mark

    2015-10-01

    Rates of ice mass loss at the calving margins of tidewater glaciers (frontal ablation rates) are a key uncertainty in sea level rise projections. Measurements are difficult because mass lost is replaced by ice flow at variable rates, and frontal ablation incorporates sub-aerial calving, and submarine melt and calving. Here we derive frontal ablation rates for three dynamically contrasting glaciers in Svalbard from an unusually dense series of satellite images. We combine ocean data, ice-front position and terminus velocity to investigate controls on frontal ablation. We find that frontal ablation is not dependent on ice dynamics, nor reduced by glacier surface freeze-up, but varies strongly with sub-surface water temperature. We conclude that calving proceeds by melt undercutting and ice-front collapse, a process that may dominate frontal ablation where submarine melt can outpace ice flow. Our findings illustrate the potential for deriving simple models of tidewater glacier response to oceanographic forcing.

  10. Calving rates at tidewater glaciers vary strongly with ocean temperature.

    PubMed

    Luckman, Adrian; Benn, Douglas I; Cottier, Finlo; Bevan, Suzanne; Nilsen, Frank; Inall, Mark

    2015-01-01

    Rates of ice mass loss at the calving margins of tidewater glaciers (frontal ablation rates) are a key uncertainty in sea level rise projections. Measurements are difficult because mass lost is replaced by ice flow at variable rates, and frontal ablation incorporates sub-aerial calving, and submarine melt and calving. Here we derive frontal ablation rates for three dynamically contrasting glaciers in Svalbard from an unusually dense series of satellite images. We combine ocean data, ice-front position and terminus velocity to investigate controls on frontal ablation. We find that frontal ablation is not dependent on ice dynamics, nor reduced by glacier surface freeze-up, but varies strongly with sub-surface water temperature. We conclude that calving proceeds by melt undercutting and ice-front collapse, a process that may dominate frontal ablation where submarine melt can outpace ice flow. Our findings illustrate the potential for deriving simple models of tidewater glacier response to oceanographic forcing. PMID:26450063

  11. Seismic Tremor Reveals Subglacial Discharge at Tidewater Glaciers

    NASA Astrophysics Data System (ADS)

    Bartholomaus, T. C.; Larsen, C. F.; O'Neel, S.; West, M. E.; Amundson, J. M.; Walter, J. I.; Catania, G. A.; Stearns, L. A.; Walker, R. T.; Sutherland, D.; Shroyer, E.; Nash, J. D.

    2014-12-01

    Subglacial discharge from the termini of tidewater glaciers drives submarine terminus melting, influences fjord circulation, erodes and redeposits subglacial sediment, and is a central component of proglacial marine ecosystems. The timing and variability of subglacial discharge can also exert a strong influence on the upstream flow of tidewater glaciers through hydrology-mediated changes in basal motion. However, a lack of observations of subglacial discharge at the ice-ocean interface hinders progress in understanding these processes and contributes to some of the largest uncertainties in sea level rise projections. Here we demonstrate that passive seismic observations collected adjacent to glaciers can meet this observational need. At tidewater and lake-terminating glaciers in Alaska and Greenland, we observe hourly to seasonal variations in low-amplitude, background seismic noise, termed glacio-hydraulic tremor. Variations in tremor amplitude correlate with discharge during the drainage of a glacially-dammed lake and reveal increases in discharge efficiency over the course of the melt season. Recordings of glacio-hydraulic tremor across a range of settings suggest widespread utility for our method. Reliable prediction of future sea level rise requires observations of subglacial discharge that elicit physical insight and can validate models. Our findings provide a platform for new understanding of ice-ocean interactions and related oceanographic, geologic, and ecological disciplines.

  12. Dendrochronology to the Beat of a Different Drummer: Lakes Dammed by a Tidewater Glacier Out of Phase with Climate

    NASA Astrophysics Data System (ADS)

    Capps, D.; Wiles, G.; Clague, J.

    2009-04-01

    Glacier-dammed lakes typically form during glacier advance or retreat that is in phase with climate change. Most glacier-dammed lakes that have formed in the past century are located in closed basins created by glacier retreat and downwasting. However, tidewater glaciers can be relatively insensitive to climate and can advance when adjacent land-based glaciers are in retreat. The regimen of tidewater glaciers is strongly controlled by the nature of the terminus. When a morainal shoal or fjord constriction limits mass loss due to calving, the glacier may remain stable or advance even in a warming climate. However, a small perturbation in climate can cause the terminus to retreat off a shoal or beyond a constriction into deeper, open water. Once this happens, more mass is lost through calving than is replenished and the glacier may catastrophically retreat. Because many tidewater glaciers are large, this cycle can be several hundred years in length, thereby lagging climatic perturbations that affect other glaciers. Many tidewater glaciers have dammed lakes as they advanced over the past century. Brady Glacier, at the head of Taylor Bay in southeast Alaska, advanced through most of the 20th century. When George Vancouver's party mapped Taylor Bay in 1794, the glacier terminus was a steep calving front. In 1880 John Muir visited the glacier and commented that it was advancing onto an outwash plain that it had built. It continued to advance until the 1960s and has remained at almost the same position since then, despite thinning many tens of meters. As Brady Glacier advanced, it buried trees along the walls of the fjord and impounded large lakes in tributary valleys. At least two of these lakes formed on opposite sides of the glacier in areas occupied by mature forest. We collected incremental cores and discs of trees killed by overriding ice and rising lake waters in order to establish a dendrochronological history of the last glacier advance and the filling of the

  13. Reconstructing the behaviour of a major SW Greenland tidewater glacier over the last millennium.

    NASA Astrophysics Data System (ADS)

    Pearce, Danni; Mair, Doug W. F.; Rea, Brice R.; Schofield, J. Ed; Lea, James M.; Kamenos, Nick; Schoenrock, Kate; Stachnik, Lukasz

    2016-04-01

    Greenlandic tidewater glaciers have experienced widespread retreat over the last century. However, information on their dynamics prior to this are poorly constrained due to a lack of observations and paucity, in many cases of mapped or mappable deglacial evidence. Especially lacking is evidence for tidewater glacier advance during the Little Ice Age (LIA). This severely restricts our understanding of the long-term (centennial-millennial timescale) relationships between climate and calving at marine terminating margins in Greenland and elsewhere. Kangiata Nunaata Sermia (KNS) is the most dynamic tidewater glacier in southwest Greenland having retreated >22 km since its LIA-maximum (c. 1761). This project takes advantage of the site's unique combination of terrestrial evidence of glacier change (glacial geomorphology, sedimentology, and Norse archaeology) and novel marine evidence (coralline algae) to reconstruct both its advance and retreat over the last millennium. We present glacial geomorphological mapping, which followed a morphstratigraphic approach, using a combination of aerial photos, a DEM and field mapping. Radiocarbon dating from peat sequences were used to determine the timing and rates of advance of KNS to the LIAmax. This has provided evidence for pre-LIA moraines, deglacial and neoglacial, and rapid changes in meltwater routing that may have contributed to the abandonment of nearby Norse settlements. Isotopic analysis of annually banded coralline algae (Lithothamnion glaciale), collected during summer 2015, will provide proxy evidence for changes in fjord water conditions. This data will contribute towards a millennial timescale record of tidewater glacier dynamics that will help to validate models linking calving to climate.

  14. High Sensitivity of Tidewater Glacier Dynamics to Shape

    NASA Astrophysics Data System (ADS)

    Enderlin, E. M.; Howat, I. M.; Vieli, A.

    2012-12-01

    Tidewater outlet glaciers in close proximity to each other, and therefore likely exposed to similar external forcing, display contrasting dynamic behavior. This variability has been attributed to differences in outlet shape (i.e., bed elevation and width), but this dependence has not been investigated in detail. We apply a one-dimensional (depth-integrated, flow-line) numerical ice flow model to glaciers of varying width and bed topography, based on observations from Greenland, and compare their response to perturbation at the calving front, designed to simulate a reduction in buttressing. Each glacier is initially grounded on a shoal, immediately seaward of a basal depression, and perturbed from steady state by increasing the strain rate across the calving front. Following this perturbation, all glaciers undergo initial retreat and thinning as the glacier geometry adjusts to the new stress balance. Narrower glaciers and those with higher shoals tend to reach a new steady state before they become ungrounded from the shoal, resulting in little total retreat and thinning. On the other hand, wider glaciers and those with deeper shoals are initially closer to flotation, so that thinning results in ungrounding over the basal depression and rapid, unstable retreat. Once triggered, along-flow differences in outlet shape influence both the timing and magnitude of this retreat. The difference in initial thickness between several glaciers that remain stable and those that undergo unstable retreat is on the order of 10's of meters, and small (< 35 m) changes in bed height can result in switching from stable to unstable retreat. Since these differences are similar to the resolution of ice thickness measurements, it is unclear whether observations can adequately constrain prognostic models of glacier dynamics.

  15. Debris entrainment and landform genesis during tidewater glacier surges

    NASA Astrophysics Data System (ADS)

    Lovell, Harold; Fleming, Edward J.; Benn, Douglas I.; Hubbard, Bryn; Lukas, Sven; Rea, Brice R.; Noormets, Riko; Flink, Anne E.

    2015-08-01

    The englacial entrainment of basal debris during surges presents an opportunity to investigate processes acting at the glacier bed. The subsequent melt-out of debris-rich englacial structures during the quiescent phase produces geometrical ridge networks on glacier forelands that are diagnostic of surge activity. We investigate the link between debris entrainment and proglacial geomorphology by analyzing basal ice, englacial structures, and ridge networks exposed at the margins of Tunabreen, a tidewater surge-type glacier in Svalbard. The basal ice facies display clear evidence for brittle and ductile tectonic deformation, resulting in overall thickening of the basal ice sequence. The formation of debris-poor dispersed facies ice is the result of strain-induced metamorphism of meteoric ice near the bed. Debris-rich englacial structures display a variety of characteristics and morphologies and are interpreted to represent the incorporation and elevation of subglacial till via the squeezing of till into basal crevasses and hydrofracture exploitation of thrust faults, reoriented crevasse squeezes, and preexisting fractures. These structures are observed to melt-out and form embryonic geometrical ridge networks at the base of a terrestrially grounded ice cliff. Ridge networks are also located at the terrestrial margins of Tunabreen, neighboring Von Postbreen, and in a submarine position within Tempelfjorden. Analysis of network characteristics allows these ridges to be linked to different formational mechanisms of their parent debris-rich englacial structures. This in turn provides an insight into variations in the dominant tectonic stress regimes acting across the glacier during surges.

  16. Rapid Changes of Large Tidewater Glaciers in SE Greenland

    NASA Astrophysics Data System (ADS)

    Stearns, L. A.; Hamilton, G. S.

    2005-12-01

    New field and satellite remote sensing measurements show that Kangerdlugssuaq Glacier and Helheim Glacier, two fast-flowing tidewater glaciers in South-East Greenland, accelerated 40-300% between 2001 and 2005 and retreated 3-5 km since July 2003. Together, the catchment basins of these two glaciers encompass ~10% of the area of the Greenland ice sheet. Previous studies observed rates of surface lowering on the main trunks of both glaciers that were too large to be caused by enhanced surface melting or decreased snow fall alone. One hypothesis to explain the thinning rates is a change in ice dynamics. We use repeat satellite imagery and published reports to reconstruct the last ~decade of flow histories for both glaciers and compare the results with velocities derived from field GPS surveys in the summer 2005. Helheim Glacier was flowing at ~8 km/yr in 1995 and 2001. In 2005, flow speeds were ~11.7 km/yr, a ~40% increase. The acceleration of Kangerdlugssuaq Glacier was more substantial. Portions of the main trunk that were flowing at ~5 km/yr in 1988, 1996 and 2001 were flowing at ~14 km/yr in summer 2005, an almost threefold increase. The accelerations in flow speeds were accompanied by other changes, including the rapid retreat of calving fronts that had maintained quasi-stable positions for the previous ~40 years, and a lowering of the ice surface by about 100 m, leaving stranded ice on adjacent ridges. The rapid thinning, acceleration and retreat of these two relatively nearby glaciers suggests a common triggering mechanism, such as enhanced surface melting due to regional climate warming. The current flow speeds, ~11 - 14 km/yr at the terminus, are too fast to be caused solely by internal deformation of the ice, implying that an increase in basal sliding forced by additional meltwater production is the probable cause of the velocity increases. The new observations and the hypothesized cause highlight the sensitivity of large outlet glaciers to local climate

  17. Submarine melting at tidewater glaciers: comparison of numerical modelling, buoyant plume theory and hydrographic data.

    NASA Astrophysics Data System (ADS)

    Slater, D. A.; Nienow, P. W.; Goldberg, D. N.; Cowton, T. R.; Sole, A. J.

    2014-12-01

    Observations of the mass balance of the Greenland ice sheet in recent decades have shown significant losses at the coastal margins through the thinning, speed-up and retreat of tidewater glaciers. Ocean forcing, via melting of submerged ice at the calving fronts of tidewater glaciers, has been identified as a possible driver of this behaviour. Such submarine melting may provide a significant direct contribution to the negative mass balance of the glacier and could also amplify calving rates. Quantification of submarine melting remains uncertain however since modelling of fjord circulation and submarine melting is challenging, hydrographic data from pro-glacial fjords are sparse and direct observation of submarine melting at a tidewater glacier has so far proved impossible. Here, we compare submarine melt rates obtained using buoyant plume theory to those from a numerical model (MITgcm), finding reasonable agreement between the two methods. We then use buoyant plume theory, due to its faster computational speed, to investigate the dependence of melt rate on subglacial discharge, subglacial channel size (and thus emerging flow velocity) and fjord-water temperature. Finally we apply the theory to real tidewater glaciers, finding significant gaps between modelled melt rates and those estimated from hydrographic data. We discuss possible reasons for such disagreements and their implications for constraining the importance of submarine melting to tidewater glacier mass balance.

  18. Spatio-temporal Variation in Glacier Ice as Habitat for Harbor Seals in an Alaskan Tidewater Glacier Fjord

    NASA Astrophysics Data System (ADS)

    Womble, J. N.; McNabb, R. W.; Gens, R.; Prakash, A.

    2015-12-01

    Some of the largest aggregations of harbor seals (Phoca vitulina richardii) in Alaska occur in tidewater glacier fjords where seals rest upon icebergs that are calved from tidewater glaciers into the marine environment. The distribution, amount, and size of floating ice in fjords are likely important factors influencing the spatial distribution and abundance of harbor seals; however, fine-scale characteristics of ice habitat that are used by seals have not been quantified using automated methods. We quantified the seasonal changes in ice habitat for harbor seals in Johns Hopkins Inlet, a tidewater glacier fjord in Glacier Bay National Park, Alaska, using aerial photography, object-based image analysis, and spatial models. Aerial photographic surveys (n = 53) were conducted of seals and ice during the whelping (June) and molting (August) seasons from 2007-2014. Surveys were flown along a grid of 12 transects and high-resolution digital photos were taken directly under the plane using a vertically aimed camera. Seal abundance and spatial distribution was consistently higher during June (range: 1,672-4,340) than August (range: 1,075-2,582) and corresponded to the spatial distribution and amount of ice. Preliminary analyses from 2007 suggest that the average percent of icebergs (ice ≥ than 1.6m2) and brash ice (ice < 1.6m2) per scene were greater in June (icebergs: 1.8% ± 1.6%; brash ice: 43.8% ± 38.9%) than August (icebergs: 0.2% ± 0.7%; brash ice; 15.8% ± 26.4%). Iceberg angularity (an index of iceberg shape) was also greater in June (1.7 ± 0.9) than August (0.9 ± 0.9). Potential factors that may influence the spatio-temporal variation in ice habitat for harbor seals in tidewater glacier fjords include frontal ablation rates of glaciers, fjord circulation, and local winds. Harbor seals exhibit high seasonal fidelity to tidewater glacier fjords, thus understanding the relationships between glacier dynamics and harbor seal distribution will be critical for

  19. 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).

  20. Quantification of Seasonal and Interannual Variability of Proglacial Meltwater from a Tidewater Glacier

    NASA Astrophysics Data System (ADS)

    Darlington, E. F.; Hodgkins, R.; Jenkins, A.

    2014-12-01

    Ice - ocean interactions of tidewater glaciers remain poorly understood; yet 39% of the global glaciated area drains directly into the ocean via tidewater glaciers. As the Arctic cryosphere continues to lose mass in response to a warming climate, more detailed observations are needed to increase our understanding of ice - ocean processes, enabling improved model predictions of Arctic change. Svalbard hosts a high proportion of tidewater glaciers, including Kronebreen, the fastest flowing glacier on the archipelago. The proglacial meltwater exiting the base of Kronebreen transports fine grained sediment to Kongsfjorden, entrained in a buoyant plume which spreads laterally and is visible at the surface. In-situ measurements of the concentration and spectral reflectance of these surface sediments were used to calibrate spectral data from the MODIS instruments on the Terra and Aqua satellites. Temperature and salinity in front of the calving face, and throughout the meltwater plume, have been measured using a hand held CTD. The spatial surface pattern of total suspended sediment (TSS; g l-1) and plume area, has been quantified for every cloud free day between 1st June - 30th September from 2002 - 2013. High TSS sediment during the early melt season indicates flushing, whilst sediment exhaustion is apparent at the end. We show that the areal extent of these proglacial plumes responds to atmospheric temperature, with a 12 day lag. An underlying seasonal evolution of plume extent is apparent; plume area is small at the beginning and end of the melt season, peaking mid-July. Wind speed and direction also play a role in dictating the length of plume formation, with katabatic winds originating from the glacier, lengthening plumes. However, the overall extent of the sediment plume is dependent on meltwater inputs. As such, this method enables the daily to interannual quantification of proglacial meltwater release from tidewater glaciers, utilizing remote sensing.

  1. 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.

  2. The landform and sediment assemblage produced by multiple surges of a large tidewater glacier system in Van Keulenfjorden, Svalbard

    NASA Astrophysics Data System (ADS)

    Lovell, Harold; Lukas, Sven; Benn, Douglas

    2013-04-01

    The geomorphology produced during tidewater glacier surges in Svalbard is often well-preserved on fjord floors, and recent studies utilising swath bathymetry data have helped to characterise these submarine landsystems at various locations. However, in order to capture the full geomorphological record of surging in glaciomarine environments, it is also important to assess the landforms and sediments deposited at the terrestrial margins of such systems. We present mapping and sedimentological data from Nathorstbreen, a large tidewater glacier system at the head of Van Keulenfjorden which is currently surging and has advanced approximately 12.5 km since 2008. The active glacier margin is bordered by a saturated mud apron which has encroached onto the older moraine areas and contains a number of large stranded icebergs. This is interpreted as a low-gradient mobile push moraine composed of soft fjord-floor sediments which have been bulldozed in front of the glacier as it advances, resulting in a significant shallowing of the fjord. The lateral moraine areas are thought to be associated with a previous surge in ca. 1870. They are characterised by sharp-crested ridges and hummocky, ice-cored topography composed of poorly-sorted diamict, interspersed with a large number of pools. At the distal margin of the ice-cored topography there are smoother, more-rounded ridges composed primarily of deformed sands and marine clays. These are interpreted as proglacially-pushed shallow marine and fjord-floor sediments which have been elevated into a terrestrial position. The detailed analysis of coastal sections reveals two transitions from subglacial (poorly-sorted diamict) to proglacial (sands and clays) sediment sequences within the moraine area, indicating that there were at least two separate advances prior to the ongoing surge. This interpretation appears to be supported by initial re-analysis of historic maps and swath bathymetry data. This work demonstrates that detailed

  3. Variability of subglacial discharge recorded with thermal infrared timelapse of a tidewater glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Byers, L. C.; Stearns, L. A.; Brunsell, N. A.; Catania, G. A.; Fried, M.; Bartholomaus, T.; Felikson, D.; Sutherland, D.; Carroll, D.; Shroyer, E.; Nash, J. D.; Walker, R. T.; Finnegan, D. C.; LeWinter, A.

    2015-12-01

    Subglacial hydrology and the dynamics therein are important modulators of ice flow in the Greenland Ice Sheet. At tidewater outlet glaciers the characteristics of proglacial discharge affect fjord circulation, sediment deposition, submarine melt rates, and iceberg calving. Information about the spatio-temporal variability of discharge is limited by the challenges of in situ data collection at tidewater glaciers. Here, we present summertime measurements of subglacial discharge variability using a thermal infrared (7.5μm to 13μm) camera and intervalometer at Kangerlussuup Sermia (KS), a ~4km wide outlet glacier in the Uummannaq Bay region of West Greenland (71.46 N, 51.43 W). KS has an advantageous geometry for this investigation because of its shallow grounding zone and well-entrenched subglacial hydrologic system. In tandem, these characteristics promote buoyant freshwater to rise to the fjord surface from discrete outlets at the glacier's base. We investigate the timing of plume activity at these outlets and discuss potential controls on outlet switching. Raw camera measurements cannot be accurately converted to surface temperature without correcting for environmental variables and scene geometry, both of which are time-evolving during data acquisition. Our processing methodology relies on a variety of existing techniques -- image segmentation, ray casting, atmospheric radiative transfer modeling, Monte Carlo simulations -- and a variety of ancillary data products -- satellite imagery, atmospheric reanalysis, meteorologic and hydrologic measurements -- to produce the final results. What is gained is an unprecedented view into interactions between the cryosphere, hydrosphere, and atmosphere that control the dynamic and sensitive terminus region of a tidewater outlet glacier.

  4. Ice dynamics of Bowdoin tidewater glacier, Northwest Greenland, from borehole measurements and numerical modelling

    NASA Astrophysics Data System (ADS)

    Seguinot, Julien; Funk, Martin; Ryser, Claudia; Jouvet, Guillaume; Bauder, Andreas; Sugiyama, Shin

    2016-04-01

    The observed rapid retreat of ocean-terminating glaciers in southern Greenland in the last two decades has now propagated to the northwest. Hence, tidewater glaciers in this area, some of which have remain stable for decades, have started retreating rapidly through iceberg calving in recent years, thus allowing a monitoring and investigation of ice dynamical changes starting from the early stages of retreat. Here, we present an ice dynamical study from Bowdoin Glacier, a tidewater outlet glacier located at the northwestern margin of the Greenland Ice Sheet. The glacier surface experiences lowering at a rate of 1.5 m/a since 2007. A rapid calving front retreat of 260 m/a was also observed since 2008, while no significant changes occurred during the previous 20 years. From July 2014 to July 2015, we monitored, 2 km upstream from the calving front, subglacial water pressure changes in boreholes, internal ice deformation through tilt sensors at different depths, englacial ice temperature profiles from the glacier bed to the surface, and high resolution surface motion from GPS records. These measurement show that the glacier is temperate-based, yet internal deformation accounts for about 10 % of the annual surface motion. A seasonal increase in both deformation and sliding at the onset of the melt season is associated with a drop in water pressure in part of the subglacial system. These observations are used to calibrate the Parallel Ice Sheet Model (PISM) for numerical simulations of ice flow in the Bowdoin Glacier catchment, aiming for a better understanding of iceberg calving processes in relation to changes in internal and basal ice dynamics.

  5. Modeling of submarine melting of Greenland tidewater glaciers using an ocean general circulation model

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Rignot, E. J.; Menemenlis, D.; Koppes, M.

    2010-12-01

    The acceleration of Greenland tidewater glaciers has increased the mass loss from the Greenland Ice Sheet. Submarine melting is one of the possible drivers for glacier acceleration. Enhanced submarine melting could result from ocean warming, changes in ocean current, and increase in sub-glacial runoff. We use a combination of numerical modeling and field data to understand the mechanism of submarine melting in Greenland. Specifically, oceanographic data (temperature, salinity, and current velocity) were collected in August 2008 and 2010 near the calving fronts of the Lille Gletscher, Store Gletscher, Eqip Sermia, Kangilerngata Sermia, Sermeq Kujatdleq and Sermeq Avangnardleq glaciers in central West Greenland. These data are compared to high-resolution regional ocean simulations carried out using the Massachusetts Institute of Technology general circulation model (MITgcm). MITgcm includes submarine melting at the base of an ice shelf and we have added a new module to simulate the melting process along the vertical calving face of Greenland tidewater glaciers. We integrate the MITgcm with JRA25 atmospheric and ECCO2 oceanic boundary conditions and compare the simulation results with the West Greenland data. We also conduct model sensitivity studies for ocean temperature, sub-glacial runoff, and fjord. The preliminary results show a quadratic increase in submarine melting with warmer ocean temperature and a role of sub-glacial runoff in changing ocean circulation. This study could help us evaluate the impact of ocean warming and enhanced runoff on submarine melting and in turn on glacier mass balance. This work is performed at UCI under a contact with NASA Cryosphere Science Program.

  6. Object-Based Image Classification of Floating Ice Used as Habitat for Harbor Seals in a Tidewater Glacier Fjord in Alaska

    NASA Astrophysics Data System (ADS)

    McNabb, R. W.; Womble, J. N.; Prakash, A.; Gens, R.; Ver Hoef, J.

    2014-12-01

    Tidewater glaciers play an important role in many landscape and ecosystem processes in fjords, terminating in the sea and calving icebergs and discharging meltwater directly into the ocean. Tidewater glaciers provide floating ice for use as habitat for harbor seals (Phoca vitulina richardii) for resting, pupping, nursing, molting, and avoiding predators. Tidewater glaciers are found in high concentrations in Southeast and Southcentral Alaska; currently, many of these glaciers are retreating or have stabilized in a retracted state, raising questions about the future availability of ice in these fjords as habitat for seals. Our primary objective is to investigate the relationship between harbor seal distribution and ice availability at an advancing tidewater glacier in Johns Hopkins Inlet, Glacier Bay National Park, Alaska. To this end, we use a combination of visible and infrared aerial photographs, object-based image analysis (OBIA), and statistical modeling techniques. We have developed a workflow to automate the processing of the imagery and the classification of the fjordscape (e.g., individual icebergs, brash ice, and open water), providing quantitative information on ice coverage as well as properties not typically found in traditional pixel-based classification techniques, such as block angularity and seal density across the fjord. Reflectance variation in the red channel of the optical images has proven to be the most important first-level criterion to separate open water from floating ice. This first-level criterion works well in areas without dense brash ice, but tends to misclassify dense brash ice as single icebergs. Isolating these large misclassified regions and applying a higher reflectance threshold as a second-level criterion helps to isolate individual ice blocks surrounded by dense brash ice. We present classification results from surveys taken during June and August, 2007-2013, as well as preliminary results from statistical modeling of the

  7. Rainstorm-induced event sedimentation at the tidewater front of a temperate glacier

    SciTech Connect

    Cowan, E.A.; Powell, R.D.; Smith, N.D.

    1988-05-01

    Runoff from a late summer storm drained rapidly to a subglacial stream of McBride Glacier, southeast Alaska. The stream transported large volumes of sediment that discharged from the glacier's tidewater front directly into fjord water at 40 m depth. Measurements of salinity, temperature, and suspended-sediment concentration indicate that the sediment was transported by interflows within brackish fjord water. Sedimentation rates were exceptionally high (up to five times normal). Laminated fine sand accumulated in proximal sediment traps, and silty mud accumulated in distal traps. The low frequency of large storms late in the melt season indicates that the sedimentary products would be rare but significant marker horizons in temperate glaciomarine sequences.

  8. Co-evolution of tidewater glacier calving front morphology and submarine melt rates in a high resolution ocean model

    NASA Astrophysics Data System (ADS)

    Slater, D. A.; Nienow, P. W.; Goldberg, D. N.; Cowton, T. R.; Sole, A. J.

    2015-12-01

    Rapid dynamic changes at the margins of the Greenland Ice Sheet, synchronous with ocean warming, have raised concern that tidewater glaciers can respond rapidly and sensitively to ocean forcing. One way in which ocean forcing would manifest is through the melting of the submerged parts of tidewater glacier calving fronts, with the spatial distribution of submarine melt a control on their morphology. Calving front morphology has thus far received little attention and yet has the potential to significantly impact calving rates and therefore tidewater glacier dynamics. Here we present a model which allows us to study the evolution of calving front morphology in two dimensions. We outline a new routine for calculating submarine melt rates from ocean models at calving fronts of arbitrary geometry, and for adjusting this geometry according to the calculated melt rates. This routine is applied to a high resolution (~1m) non-hydrostatic ocean model (MITgcm) with a glacier boundary (calving front) which evolves in time according to the simulated submarine melt rates. The model shows, consistent with recent observations, that submarine melting leads to undercutting of tidewater glacier calving fronts. We examine how undercut magnitude, undercut depth and potential steady states respond to variation in subglacial discharge, ice velocity, and fjord depth, temperature and stratification. In addition to this analysis we use a diagnostic full-Stokes flow-line ice model to examine how these geometries affect ice internal stress and potential for calving. In undertaking this work we aim to elucidate a process which - supposing tidewater glaciers are sensitive to ocean forcing - must provide a fundamental link between the ocean and the ice.

  9. Bluefin 9M AUV Survey of the Hubbard Glacier Morainal Bank: Proof-of-Concept Study of Autonomous Underwater Vehicle Investigations Proximal to a Tidewater Glacier

    NASA Astrophysics Data System (ADS)

    Goff, J. A.; Gulick, S. P. S.; Lawson, D. E.; O'Halloran, W.

    2014-12-01

    Hubbard Glacier is one of the few advancing tidewater glaciers in the world, offering a premier opportunity for studying ice/sediment/seawater interactions at a tidewater glacier front that is in contact with the stabilizing submarine morainal bank. However, the seafloor and water column proximal to the ice face of a marine-terminating glacier is one of the most challenging and extreme environments imaginable for marine survey work. Frequently choked with constantly-shifting mélange ice at the sea surface and at risk from calving, surface vessels cannot operate safely proximal to the ice face. AUV (Autonomous Underwater Vehicle) technology provides an opportunity to survey in areas where surface vessels cannot. Operating well below the sea surface the AUV can operate without hindrance or danger to human operators. In addition, the AUV can be programmed to operate close to the seafloor at a constant altitude, enabling the finest-detail currently possible for acoustic seafloor mapping and consistent resolution irrespective of water depth. With these considerations in mind, we conducted a proof-of-concept survey of the Hubbard Glacier morainal bank in June, 2014. We utilized the Bluefin 9M, the smallest of their line of AUVs. Its size enabled deployment and recovery from a small charter fishing vessel well-suited to navigating through mélange-choked waters. The AUV's payload included a Klein UUV-3500 interferometric sonar (455/900 kHz), which enables acquisition of sidescan backscatter and swath bathymetry up to ~75 m to each side of the instrument from ~10 m altitude over the seabed, and sensors for measuring conductivity, temperature, depth (CTD) and optical backscatter (OBS). Although our operations were shortened due to an unfortunate failure in the sonar electronics, sufficient data were collected along the morainal bank to clearly prove the viability of AUV operations in this harsh environment. The data provide centimeter-scale seafloor detail close to the

  10. Fluctuations of a Greenlandic tidewater glacier driven by changes in atmospheric forcing: observations and modelling of Kangiata Nunaata Sermia, 1859-present

    NASA Astrophysics Data System (ADS)

    Lea, J. M.; Mair, D. W. F.; Nick, F. M.; Rea, B. R.; van As, D.; Morlighem, M.; Nienow, P. W.; Weidick, A.

    2014-11-01

    Many tidewater glaciers in Greenland are known to have undergone significant retreat during the last century following their Little Ice Age maxima. Where it is possible to reconstruct glacier change over this period, they provide excellent records for comparison to climate records, as well as calibration/validation for numerical models. These glacier change records therefore allow for tests of numerical models that seek to simulate tidewater glacier behaviour over multi-decadal to centennial timescales. Here we present a detailed record of behaviour from Kangiata Nunaata Sermia (KNS), SW Greenland, between 1859 and 2012, and compare it against available oceanographic and atmospheric temperature data between 1871 and 2012. We also use these records to evaluate the ability of a well-established one-dimensional flow-band model to replicate behaviour for the observation period. The record of terminus change demonstrates that KNS has advanced/retreated in phase with atmosphere and ocean climate anomalies averaged over multi-annual to decadal timescales. Results from an ensemble of model runs demonstrate that observed dynamics can be replicated. Model runs that provide a reasonable match to observations always require a significant atmospheric forcing component, but do not necessarily require an oceanic forcing component. Although the importance of oceanic forcing cannot be discounted, these results demonstrate that changes in atmospheric forcing are likely to be a primary driver of the terminus fluctuations of KNS from 1859 to 2012. We propose that the detail and length of the record presented makes KNS an ideal site for model validation exercises investigating links between climate, calving rates, and tidewater glacier dynamics.

  11. Tidewater Dynamics at Store Glacier, West Greenland from Daily Repeat UAV Survey

    NASA Astrophysics Data System (ADS)

    Hubbard, A., II; Ryan, J.; Toberg, N.; Todd, J.; Christoffersen, P.; Snooke, N.; Box, J. E.

    2015-12-01

    A significant component of the Greenland ice sheet's mass wasteage to sea level rise is attributed to the acceleration and dynamic thinning at its tidewater margins. To improve understanding of the rapid mass loss processes occurring at large tidewater glaciers, we conducted a suite of daily repeat aerial surveys across the terminus of Store Glacier, a large outlet draining the western Greenland Ice Sheet, from May to July 2014 (https://www.youtube.com/watch?v=-y8kauAVAfE). A suite flock of Unmanned Aerial Vehicles (UAVs) were equipped with digital cameras, which, in combination with onboard GPS, enabled production of high spatial resolution orthophotos and digital elevation models (DEMs) using standard structure-from-motion techniques. These data provide insight into the short-term dynamics of Store Glacier surrounding the break-up of the sea-ice mélange that occurred between 4 and 7 June. Feature tracking of the orthophotos reveals that mean speed of the terminus is 16 - 18 md-1, which was independently verified against a high temporal resolution time-series derived from an expendable/telemetric GPS deployed at the terminus. Differencing the surface area of successive orthophotos enable quantification of daily calving rates, which significantly increase just after melange break-up. Likewise, by differencing bulk freeboard volume of icebergs through time we could also constrain the magnitude and variation of submarine melt. We calculate a mean submarine melt rate of 0.18 md-1 throughout the spring period with relatively little supraglacial runoff and no active meltwater plumes to stimulate fjord circulation and upwelling of deeper, warmer water masses. Finally, we relate calving rates to the zonation and depth of water-filled crevasses, which were prominent across parts of the terminus from June onwards.

  12. Tidewater Glacier Velocities from Repeat Ground-Based Terrestrial LiDAR Scanning; Helheim Glacier, Southeast Greenland

    NASA Astrophysics Data System (ADS)

    Finnegan, D. C.; Hamilton, G. S.; Stearns, L. A.; LeWinter, A. L.; Farid, H.; Renedo, H.

    2014-12-01

    Tidewater glaciers exhibit dynamic behaviors across a range of spatial and temporal scales, posing a challenge to both in situ and remote sensing observations. In situ measurements capture variability over very short time intervals, but with limited spatial coverage, and at significant cost and risk to deploy. Conversely, airborne and satellite remote sensing is capable of measuring changes over large spatial extents but at limited temporal resolution. Here we use a near-situ approach to observing dynamic glacier behavior. Terrestrial LiDAR Scanning (TLS) combines the rapid acquisition capabilities of in situ measurements with the broad spatial coverage of traditional remote sensing, and can be carried out from a safe off-ice location. Repeat (30 min) high-resolution, long-range (6-10km) TLS surveys were conducted at Helheim Glacier, southeast Greenland, during July 9-14, 2014, and coincident in situ global positioning system (GPS) observations were acquired close to the glacier terminus. Analysis of these data allows for independent estimates of flow displacement and verification of 3D analytic techniques for quantifying vector motion. These techniques will enable the automated processing of large volumes of repeat scanning data to be collected during planned the deployment of an autonomous version of our LiDAR scanning system.

  13. Reconstructing Fjord Circulation Near a Greenland Tidewater Glacier with Physical Modeling and in Situ Mooring Data

    NASA Astrophysics Data System (ADS)

    Schild, K. M.; Hawley, R. L.; Straneo, F.; Cenedese, C.

    2014-12-01

    The rapid speedup of Greenland tidewater glaciers over the last decade, and subsequent mass loss, has been attributed to an increase in air temperature and a synchronous increase in ocean temperatures. The warming subtropical waters previously thought to only exist offshore of Greenland, have been observed throughout most Greenland fjords, and have been suggested to play a large role in submarine melting of the floating glacier terminus and subsequent calving. Warm subtropical water can become entrained by subglacial meltwater as it exits from beneath the glacier. As the buoyant subglacial meltwater moves along the glacier terminus to the surface, the entrained subtropical water contributes to terminus melting and subsequent iceberg melting. However, the impact of a meltwater plume on fjord stratification has been difficult to study due to the limited accessibility of the proglacial environment. We collected a mooring record of salinity and temperature from 2010-2013 at 14 m depth in Sermilik fjord, East Greenland (~25-30 km from the terminus of Helheim Glacier). This record shows a temperature deviation from a sinusoidal seasonal trend between June and October each year; temperatures steadily decrease between June and August and warm again over the subsequent two months. We hypothesize there are three factors driving temperature and salinity changes in the surface waters: (1) subglacial meltwater release, (2) glacier calving, and (3) proglacial circulation. In this study we construct a physical model of the proglacial fjord environment. We modify the quantity, duration and depth of subglacial meltwater release to reconstruct the mooring temperature and salinity records. Results of this study illuminate the influence of subglacial discharge and iceberg melt on proglacial fjord dynamics, an important component in understanding ice sheet- ocean interactions in a warming climate.

  14. The importance of tidewater glaciers for marine mammals and seabirds in Svalbard, Norway

    NASA Astrophysics Data System (ADS)

    Lydersen, Christian; Assmy, Philipp; Falk-Petersen, Stig; Kohler, Jack; Kovacs, Kit M.; Reigstad, Marit; Steen, Harald; Strøm, Hallvard; Sundfjord, Arild; Varpe, Øystein; Walczowski, Waldek; Weslawski, Jan Marcin; Zajaczkowski, Marek

    2014-01-01

    Approximately 60% of Svalbard's land areas are glaciated at the present time. The Archipelago has more than 1100 glaciers (> 1 km2) and 163 of these are “tidewater glaciers” - that is glaciers that terminate (with their calving front) at the sea. It has been known for a long time that these glacier front areas are important feeding areas for seabirds and marine mammals. Herein, we review current knowledge regarding the importance of these areas for these animals and reflect upon the processes that create these apparent “hotspots”. Kittiwakes Rissa tridactyla, routinely dominate avian assemblages in front of glaciers in Svalbard, but fulmars Fulmarus glacialis, ivory gulls Pagophila eburnea and glaucous gulls Larus hyperboreus also contribute to aggregations, which can sometimes comprise many thousands of individuals. The birds are often found in the so-called “brown zone”, which is an area in front of tidewater glaciers that is ice-free due to currents and muddy due to suspended sediments. Animals at these sites typically have their stomachs full of large zooplankton or fish. These brown zones are also foraging hotspots for Svalbard's ringed seals (Pusa hispida) and white whales (Delphinapterus leucas). Prime breeding habitat for ringed seals in Svalbard occurs deep in the fjords where ice pieces calved from the glacier fronts become frozen into land-fast sea-ice, promoting the accumulation of snow to a depth suitable for ringed seal females to dig out birth lairs above breathing holes in the ice. These pupping areas are important hunting areas for polar bears (Ursus maritimus) in spring, especially female bears with cubs of the year during the period following emergence from the winter/birthing den. Glacier-ice pieces floating in coastal areas are also important for all seal species in the region as dry platforms during moulting and also as general resting platforms for both birds and seals. During the last decade there have been several years with a

  15. Submarine melting at the grounding line of Greenland's tidewater glaciers: Observations and Implications. (Invited)

    NASA Astrophysics Data System (ADS)

    Rignot, E. J.; Xu, Y.; Koppes, M. N.; Menemenlis, D.; Schodlok, M.; Spreen, G.

    2010-12-01

    The traditional view on the mass balance of the Greenland Ice Sheet is that interior snowfall accumulation is balanced by discharge of surface runoff and icebergs at the periphery. Most Greenland glaciers however terminate in the ocean, and melt in contact with the warm ocean waters to produce glacial melt before detaching into icebergs. Underneath floating ice shelves, the melting process is governed by the buoyancy associated with the melting of glacier ice at the seawater-ice interface. Under tidewater glaciers, the melting process is also forced by the strongly buoyant influx of subglacial freshwater near the grounding line. In August 2008, we collected bathymetry, temperature, salinity and current velocity data in front of 4 west Greenland glaciers (Eqip Sermia, Kangilerngata Sermia, Sermeq Kujatdleq and Sermeq Avangnardleq) to calculate the rates of submarine melting of the calving faces. The results revealed large rates of melting (meters per day), and large spatial variations from fjord to fjord as well as across the calving faces. In August 2010, we returned to Eqip Sermia, Sermeq Avangnardleq and visited Store and Little glaciers to conduct similar measurements. Strong outflows of subglacial water were detected on Avangnardleq, Lille and Store glaciers, and high rates of submarine melting were deduced from the data. We find that the sea bed in front of the calving faces (100 to 500 m) are much shallower than in the bulk of the glacial fjords (800 to 900 m), and the sill depth at the fjord entrance (~300 m ) is confirmed to be the major control on the access of warm ocean waters to the submerged calving faces. In the presence of heavy brash ice, our data suggest a conceivably weakened submarine circulation. Finally, we combine our summer data with long-term records of temperature and salinity, at the depth relevant to submarine melting, from the ECCO2 ocean state estimation project to examine seasonal to long-term trends in thermal forcing from the ocean

  16. The importance of tidewater glaciers for marine mammals and seabirds in Svalbard, Norway

    NASA Astrophysics Data System (ADS)

    Lydersen, Christian; Assmy, Philipp; Falk-Petersen, Stig; Kohler, Jack; Kovacs, Kit M.; Reigstad, Marit; Steen, Harald; Strøm, Hallvard; Sundfjord, Arild; Varpe, Øystein; Walczowski, Waldek; Weslawski, Jan Marcin; Zajaczkowski, Marek

    2014-01-01

    Approximately 60% of Svalbard's land areas are glaciated at the present time. The Archipelago has more than 1100 glaciers (> 1 km2) and 163 of these are “tidewater glaciers” - that is glaciers that terminate (with their calving front) at the sea. It has been known for a long time that these glacier front areas are important feeding areas for seabirds and marine mammals. Herein, we review current knowledge regarding the importance of these areas for these animals and reflect upon the processes that create these apparent “hotspots”. Kittiwakes Rissa tridactyla, routinely dominate avian assemblages in front of glaciers in Svalbard, but fulmars Fulmarus glacialis, ivory gulls Pagophila eburnea and glaucous gulls Larus hyperboreus also contribute to aggregations, which can sometimes comprise many thousands of individuals. The birds are often found in the so-called “brown zone”, which is an area in front of tidewater glaciers that is ice-free due to currents and muddy due to suspended sediments. Animals at these sites typically have their stomachs full of large zooplankton or fish. These brown zones are also foraging hotspots for Svalbard's ringed seals (Pusa hispida) and white whales (Delphinapterus leucas). Prime breeding habitat for ringed seals in Svalbard occurs deep in the fjords where ice pieces calved from the glacier fronts become frozen into land-fast sea-ice, promoting the accumulation of snow to a depth suitable for ringed seal females to dig out birth lairs above breathing holes in the ice. These pupping areas are important hunting areas for polar bears (Ursus maritimus) in spring, especially female bears with cubs of the year during the period following emergence from the winter/birthing den. Glacier-ice pieces floating in coastal areas are also important for all seal species in the region as dry platforms during moulting and also as general resting platforms for both birds and seals. During the last decade there have been several years with a

  17. Investigating the flow and stress regime at the front of a tidewater outlet glacier

    NASA Astrophysics Data System (ADS)

    Mercenier, Rémy; Luethi, Martin; Vieli, Andreas; Rohner, Christoph; Small, David

    2016-04-01

    Dynamic changes in ocean-terminating glaciers are responsible for approximately half of the current high rate of mass loss of the Greenland ice sheet. The related calving process, which occurs when the stresses at the calving front exceed the fracture toughness of ice, is still not well understood and poorly represented in current generation ice-sheet models, but is a crucial requisite to understand and model dynamics and future mass loss of the ice sheet. Here, we use a two-dimensional finite-element model to compute the stress and flow fields near the front of a tidewater outlet glacier. First, we perform a sensitivity analysis for an idealized glacier exploring the effects of variable calving front slope, water depth and basal sliding. We then apply the model to two flowlines of Eqip Sermia, an ocean terminating outlet glacier in West Greenland. Detailed velocity and geometry measurements obtained from terrestrial radar interferometry serve as constraints to the model. These flowline geometries and velocities strongly differ. One flowline ends with a ˜ 50 meter vertical cliff, close to floatation, while the other has a 150-200 meter high grounded front with a ˜ 45° slope and for which extrusion flow is observed. These different geometry settings lead to substantial difference in stress and flow regimes. This stress analysis improves our understanding of how and where the ice is susceptible to failure and crevasse formation for different idealized as well as real conditions. In further work, we aim to use this information as a constraint to investigate the short-term and long-term processes related to outlet glacier calving.

  18. Jakobshavn Isbrae: Velocity variations from hourly to decadal time scales at Greenland's fastest tidewater glacier

    NASA Astrophysics Data System (ADS)

    Podrasky, David Bryan

    Outlet glaciers in Greenland, and elsewhere, have recently shown large variations in terminus position and ice flux. One example is the tidewater retreat of Jakobshavn Isbrae, which began in the late 1990s with high thinning rates, acceleration and collapse of the floating glacier tongue. The retreat has continued to the present, with glacier speeds more than doubling in two decades' time. A campaign of in-situ measurements was initiated in 2006 with the aim of determining the importance of short-term forcing as a control on the continuing evolution of the glacier. Three years of continuous GPS measurements along the centerline of Jakobshavn Isbrae reveal seasonal velocity variations due to seasonally varying terminus position. The relationship between glacier speed and surface melt is complex, with both speed-up and slowdown events in response to variations in the rate of surface melt. During a particularly long and intense melt season in 2007, a series of melt-driven slowdowns effectively reduced the mean ice flow over the whole year. On shorter timescales, the response to surface meltwater input is more predictable with diurnal velocity variations of 1--2 % that closely match changes in meltwater input. The influence of iceberg calving and tidal forcing is restricted to the lower 10 km of the glacier, imposing an upper limit on longitudinal stress coupling length of a few ice thicknesses. The response to these forcings does not exceed 5 % of mean flow. This is consistent with a glacier operating under high driving stresses. Ice sheet velocities as far as 120 km inland of the margin have responded to the continuing retreat with increases in speed. The flow has also rotated toward the centerline of the main channel. This speedup and channelization of flow are the result of evolving ice surface gradients as the glacier continues to respond to changes initiated at the periphery. This shows that ocean driven changes have led to increased ice flux far inland on the

  19. Directivity of Underwater Sounds Generated in the Vicinity of Tidewater Glaciers

    NASA Astrophysics Data System (ADS)

    Glowacki, O.; Deane, G. B.; Moskalik, M.; Tegowski, J.; Blondel, P.

    2014-12-01

    Progressive climate shifts are particularly pronounced in the Polar Regions, including glacial fjords and bays. Many different tools are now widely used to investigate the rate of glaciers' movement, intensity of calving events and subglacial freshwater outflows or changes in an ice concentration at the sea surface. However, harsh polar conditions make the most of them difficult to conduct and temporal and spatial resolution is often unsatisfactory. Therefore, there is a growing need to develop new methods for quantifying glacier processes. Recently, the application of passive marine acoustics has proved to be promising in this field. Here measurements of ambient noise field directionality made during summer 2013 and spring 2014 in different locations in the Hornsund Fjord, Spitsbergen are presented and discussed. Field data were collected from an inflatable boat using floating buoy equipped with two omnidirectional broadband hydrophones mounted on a horizontal axis, tilt sensor and magnetic compass. A few hours of recordings were analyzed and time differences of arrivals were calculated to obtain directions to the sound sources. The results not only confirm previous observations that underwater sounds in the Hornsund fjord propagates from various directions in distinct spectral bands. They primarily reveal that determined arrival angles together with calculated noise spectral intensity may provide valuable information about the activity of individual glaciers and the distribution of melting glacial ice across the Arctic fjord. Thereby, the applicability of ambient noise oceanography in the study of tidewater glaciers is clearly shown. This work has been supported by the Polish National Science Center grants nos. 2011/03/B/ST10/04275 and 2013/11/N/ST10/01729, Office of Naval Research, Ocean Acoustics Division, grant no. N00014-1410213, and the statutory activity of the Institute of Geophysics Polish Academy of Sciences.

  20. Latitudinal variation of sedimentation and erosion rates from Patagonia and Antarctic Peninsula tidewater glaciers (46°-65° S)

    NASA Astrophysics Data System (ADS)

    Fernandez-Vasquez, R. A.; Anderson, J. B.; Wellner, J. S.; Minzoni, R. L.

    2012-12-01

    We present the results of the study of tidewater glacier depositional basins, across a broad latitudinal transect from central Patagonia (46°S) to the Antarctic Peninsula (65°S). Based on sediment cores and seismic records, we estimate accumulation rates at several timescales as well as sediment-volume derived erosion rates (Er) for millennial time scales. In the Antarctic Peninsula, accumulation rates are ~100 mm/yr for centennial and millennial timescales. In Patagonia, proximal basins are in general well isolated and have short timescale (decadal-centennial) sedimentary records and high accumulation rates, whereas medial (more distal) basins have millennial scale sedimentary records and low accumulation rates. We hypothesize that the "Saddler effect" in the accumulation rates of the Patagonian study areas exists because Neoglacial advance and recent post-Little Ice Age retreat has left well isolated proximal basins that effectively trap sediments. This, along with high sediment yields, produces high decadal accumulation rates. There is no such organization of basins in the Antarctic Peninsula fjords and bays and no such clear manifestation of Neoglacial advances or morphologies. Erosion rates span two orders of magnitude from 0.03 mm/yr for Lapeyrère Bay at Anvers Island, Antarctica (~64.5°S), to 1.09 mm/yr for San Rafael Glacier in northern Patagonia (~46.5°S). Rates for Antarctic Peninsula glaciers are in general lower than those of temperate Patagonian glaciers. A good correlation of erosion rates and modern sea level annual temperature was found. A latitudinal decrease in millennial erosion rates is interpreted as a result of decreasing annual temperature although decreasing annual precipitation may also be a factor. However, local variability within each region might be influenced by differences in bedrock geology (e.g. Herbert Sound versus Lapeyrère and Andvord bays ) and drainage basin morphology (hypsometry, number of glaciers and length of overall

  1. Changing tidewater glacier extent and response to climate from Little Ice Age to present: observations and modelling of Kangiata Nunaata Sermia, SW Greenland

    NASA Astrophysics Data System (ADS)

    Mair, D.; Lea, J. M.; Nick, F. M.; Rea, B. R.; Nienow, P. W.

    2013-12-01

    Records of Greenlandic tidewater glacier (TWG) change are primarily restricted to the period covered by satellite observation. This study extends the record of terminus change of the tidewater outlet glacier Kangiata Nunaata Sermia (KNS), SW Greenland to its Little Ice Age maximum (LIAmax). This is achieved using a combination of geomorphology, written observations, and historical and satellite imagery. We explore likely marine and atmospheric controls on terminus change by comparison with existing records of local air and ocean temperatures and, for earlier periods, by modelling glacier response to systematic changes in marine and oceanic forcings at the terminus. Results from the glacier reconstruction show that retreat began in the late 18th century, with the terminus retreating at least 12 km from its LIAmax by 1859. KNS then experienced a period of relative stability before advancing to its 20th century maximum by ~1920. Significant retreat occurred from 1921-1965, before periods of advance and retreat up until 1997. Subsequent to this, KNS has retreated by 2 km up to the end of the 2012 melt season. The LIAmax to present retreat of KNS totals 22.6 km. Comparison of terminus fluctuations to local air temperature (1866-present) and sea surface temperature (1870-present) anomalies demonstrate that air temperature exerts a significant modulating control on terminus stability for the duration of the record. A state-of-the-art 1-dimensional flow-band model driven by submarine melt (SM) and crevasse water depth (CWD; Nick et al, 2010) is capable of reconstructing observed terminus fluctuations during earlier periods for realistic values of SM using a range of CWD. This provides confidence that such models are capable of predicting TWG terminus variability over centennial timescales.

  2. Long-term Autonomous Tidewater Glacier Monitoring Using a Long-Range Terrestrial LiDAR Scanner; Helheim Glacier, Southeast Greenland

    NASA Astrophysics Data System (ADS)

    Finnegan, D. C.; LeWinter, A.; Hamilton, G. S.; Gadomski, P. J.; Stearns, L. A.

    2015-12-01

    Tidewater glaciers exhibit dynamic behaviors across a range of spatial and temporal scales, posing a challenge to both in situ and remote sensing observational strategies. In situ measurements can capture variability over very short time intervals, but with limited spatial coverage and at significant cost and risk to deploy. Conversely, airborne and satellite remote sensing is capable of measuring changes over large spatial extents but at limited temporal sampling. In recent work, we have shown that long-range Terrestrial LiDAR Scanning (TLS) from fixed near-situ locations is capable of combining the rapid acquisition capabilities of in situ measurements with the broad spatial coverage of traditional remote sensing. LiDAR scanners have typically operated for short-duration campaigns (days to weeks) due to the technical complexity of the instrumentation, which has limited their contribution to tidewater glacier studies to "snapshot" observational datasets. This paper describes the development and deployment an autonomous full-waveform, long range (6-10 km) TLS system for extended operation (> 1 year) in a remote Arctic environment. The instrument uses a 1064μm wavelength laser which has been optimized for snow and ice, and allows us to acquire multi-dimensional point-cloud measurements of the lower reaches of the glacier, its terminus and the mélange to distances in excess of 10 km every few hours. The system was deployed at Helheim Glacier, southeast Greenland in late July, 2015. Helheim Glacier is a large tidewater outlet glacier of the Greenland Ice Sheet and the focus of a coordinated interdisciplinary program to study of its dynamics and interaction with the ocean. Results from our year-round scanning instrument will provide new insights into short and long-term ice motion and terminus behavior at temporal and spatial resolutions previously not possible.

  3. A synthesis of the ongoing seasonal work in a west Greenland tidewater outlet glacier fjord, Godthåbsfjord

    NASA Astrophysics Data System (ADS)

    Mortensen, J.; Bendtsen, J.; Rysgaard, S.

    2015-12-01

    The coastal waters off west Greenland is subjected to significant temperature fluctuations which might affect the mass loss from local tidewater outlet glaciers from the Greenland Ice Sheet in different ways. We present a comprehensive hydrographic data set from a west Greenland fjord, Godthåbsfjord, a fjord in contact with the Greenland Ice Sheet through tidewater outlet glaciers. We analyze with respect to water masses, dynamics, seasonal and interannual hydrographic variability. Through seasonal observations of hydrographic and moored observations we recognize a seasonal pattern in the fjords circulation system, where an intermediate baroclinic circulation mode driven by tidal currents at the fjord entrance is associated as an important local heat source for the fjord. Four distinct circulation modes are observed in the fjord of which all can contribute to glacial ice melt. In water observation of a subglacial plume core will be presented and discussed with respect to vertical distribution of water masses and local heat budget in the fjord. The example of the extreme case of subglacial plume will be discussed (ice-dammed lake drainage).

  4. On the role of submarine melting of tidewater glaciers in driving the Greenland ice sheet out of balance (Invited)

    NASA Astrophysics Data System (ADS)

    Rignot, E. J.; Koppes, M. N.; Velicogna, I.

    2009-12-01

    The Greenland ice sheet is losing mass and the rate of mass loss has been increasing with time. A recent comparison of the components contributing to the mass balance of the ice sheet suggests that half of the signal is caused by an increase in runoff and half by ice dynamics, i.e. the acceleration of outlet glaciers. The root cause of the glacier acceleration is a de-stabilization of the glacier frontal regions, i.e. an un-grounding of the frontal parts which reduces buttressing and allows faster rates of ice sliding to sea. While the role of surface melt water on the lubrication of the glacier bed has been highly publicized, detailed study of the effect of melt water on glacier flow suggest that it can only account for a moderate acceleration of glaciers. De-stabilization of glaciers from vertical thinning is key, yet the increase in runoff is not large enough to explain the observations. We propose instead that submarine melting of the glacier submerged faces has been the main trigger and control. In August 2008, we collected CTD and current measurements in the front of 4 glaciers, 100 km north of Jakobshavn Isbrae, in West Greenland. Calculation of heat and mass flow reveal submarine melt rates ranging from 1 to 3 meters per day, or 100 times larger than the rates of surface melt. Large variations exist from one glacier to the next, but the results suggest that submarine melting is a large contributor to glacier thinning, capable of explaining glacier un-grounding and de-stabilization. Submarine melting removes from 20% to 90% of the ice that reaches the ocean, the rest being discharged as icebergs. Prior studies totally ignored the role of submarine melting in Greenland and only considered iceberg calving. We conclude than more detailed studies of ice-ocean interactions in tidewater glacier environments are absolutely critical to better understand present-day and future evolutions of the Greenland ice sheet in a warming climate.

  5. SedBerg and SedPlume Models: Simulating Sediment Delivery from Tidewater Glaciers to the Marine Environment

    NASA Astrophysics Data System (ADS)

    Mugford, R. I.; Dowdeswell, J. A.

    2009-12-01

    Glaciated fjords are dynamic sedimentary environments with high deposition rates, thus providing high-resolution sedimentary records of deglaciation and Holocene environmental change. Two numerical models, SedBerg and SedPlume, have been developed to simulate marine sedimentation from tidewater glaciers for the dominant transport processes of iceberg-rafting and glacial meltwater plumes. Icebergs calved from tidewater glaciers contain sediment, which is released as the icebergs melt. SedBerg utilises Monte Carlo based techniques to simulate the formation, drift and melt of a population of icebergs, and the subsequent deposition. Subaqueous and subaerial melt of the icebergs result in a continuous rainout of sediment with occasional sediment dumping from overturning events. Underlying the model are parametric probability distributions to describe the stochastic behaviour of iceberg production and dynamics. Turbid meltwater emerging from beneath a glacier into a fjord rises as a buoyant forced plume due to salinity and temperature contrasts with the ambient fjord water. SedPlume utilises an integral model formulation for the conservation of volume, momentum, buoyancy and sediment mass along the path of a turbulent, entraining plume injected into stably stratified ambient fluid. The resulting non-linear ordinary differential equations are solved numerically. When the plume reaches the surface, it is treated as a radially spreading surface gravity current, for which exact solutions exist for the mass flux of sediment deposited. A case study is examined for each model. SedBerg is applied to Kangerdlugssuaq Fjord, East Greenland, as an example of an iceberg-dominated depositional environment. The sedimentation rate due to iceberg rafting is simulated for Kangerdlugssuaq Fjord over the last 1500 years, with climatic, oceanographic and glacial conditions estimated from a mixture of present day measurements and inferences from the sedimentary record. SedPlume is applied to

  6. Salinity and water temperature observations from the inaccessible waters beneath the dense ice mélange and tidewater glacier margins in Greenland obtained using instrumented ringed seals

    NASA Astrophysics Data System (ADS)

    Mernild, Sebastian H.; Holland, David M.; Holland, Denise; Rosing-Asvid, Aqqalu

    2015-04-01

    Observations obtained by ringed seals (Pusa hispida) near tidewater glacier margins in Ilulissat Icefjord and Sermilik Fjord provide a novel platform to examine the otherwise inaccessible waters beneath the dense ice melangé within the first 0-10 km of the calving front - to advance our understanding of the hydrographic conditions of the waters near the outlet glaciers. CTD (Conductivity, Temperature, and Depth) Oceanography SRDL (Satellite Relay Data Logger) instruments were mounted on ringed seals with the aim of continuously measuring water salinity, depth, and the location (coordinates) of the seals. Instruments were mounted in August and September to illustrate the non-summer month's variability. A clear link, for example, in the north and south arms of Ilulissat Icefjord is shown after spikes in ice sheet melt water runoff on salinity changes in the upper water column. Small-amplitude runoff variability during the recession of runoff in late-summer did not create a clear signal in fjord salinity variability. The effect of runoff spikes on fjord salinity is less pronounced near the ice-margin of Jakobshavn Glacier than in the north and south arms. The vertically uneven change in salinity in days after a runoff peak indicate uneven vertical distribution of runoff draining through the glacier margin, where most runoff entered the fjord in the upper 50 m (the amount of englacial runoff decreased from the water surface and downwards). The seal-dive salinity profiles did not capture any signal of englacial freshwater entering the fjord across the grounding line. Even though, the seal observations seems to advance our understanding of hydrographic changes in the inaccessible waters beneath the dense ice mélange at the tide water margins.

  7. Spring bloom dynamics in a subarctic fjord influenced by tidewater outlet glaciers (Godthåbsfjord, SW Greenland)

    NASA Astrophysics Data System (ADS)

    Meire, Lorenz; Mortensen, John; Rysgaard, Søren; Bendtsen, Jørgen; Boone, Wieter; Meire, Patrick; Meysman, Filip J. R.

    2016-06-01

    In high-latitude fjord ecosystems, the spring bloom accounts for a major part of the annual primary production and thus provides a crucial energy supply to the marine food web. However, the environmental factors that control the timing and intensity of these spring blooms remain uncertain. In 2013, we studied the spring bloom dynamics in Godthåbsfjord, a large fjord system adjacent to the Greenland Ice Sheet. Our surveys revealed that the spring bloom did not initiate in the inner stratified part of the fjord system but only started farther away from tidewater outlet glaciers. A combination of out-fjord winds and coastal inflows drove an upwelling in the inner part of the fjord during spring (April-May), which supplied nutrient-rich water to the surface layer. This surface water was subsequently transported out-fjord, and due to this circulation regime, the biomass accumulation of phytoplankton was displaced away from the glaciers. In late May, the upwelling weakened and the dominant wind direction changed, thus reversing the direction of the surface water transport. Warmer water was now transported toward the inner fjord, and a bloom was observed close to the glacier terminus. Overall, our findings imply that the timing, intensity, and location of the spring blooms in Godthåbsfjord are controlled by a combination of upwelling strength and wind forcing. Together with sea ice cover, the hydrodynamic regime hence plays a crucial role in structuring food web dynamics of the fjord ecosystem.

  8. Long-term dynamics of a tidewater outlet glacier in West Greenland and its relation to external forcing

    NASA Astrophysics Data System (ADS)

    Vieli, Andreas; Luethi, Martin; Moreau, Luc; Reisser, Moritz; Ian, Joughin

    2015-04-01

    Dynamic changes of ocean-terminating outlet glaciers such as terminus retreat and flow acceleration are responsible for about half of the current mass loss of the Greenland ice sheet. Although these changes seem related to the general warming in recent decades, the detailed link between external forcing from the atmosphere and/or ocean and glacier response is not well understood. Further, existing observations of tidewater outlet glacier change also show strong temporal fluctuations and are mostly limited to the last two decades of satellite observations. It is therefore difficult to derive and interpret long-term trends in outlet glacier change which is relevant in the context of century scale predictions. Here we present and analyse a detailed long-term record of flow and geometry evolution of Eqi Sermia, a ocean terminating outlet glacier in West Greenland. This record starts in 1912 and has, due to its proximity to the main access route for early expeditions to the ice sheet, a decadal and smaller resolution. This historic record is supplemented by data from satellites and ground based radar interferometry for deriving front positions and flow velocities in the two recent decades. The front and flow speed of Eqi Sermia was more or less stable between 1912 with aslow retreat phase between 1920 to the 1960, followed by a slight readvance in the 1980s. In 2007 the terminus started to retreat very rapidly, retreated 3 km since and in a step wise fashion and almost quadrupled its flow speed at the terminus. A comparison with surface mass balance and temperature records suggests a close relation of the long-term evolution of Egi Sermia to atmospheric forcing rather than oceanic, perhaps reflecting the relatively shallow fjord depths. In contrast, the recent rapid retreat and acceleration may be due to a changing regime in the calving process and geometric effects.

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

    USGS Publications Warehouse

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

    2015-01-01

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

  10. Unusually loud ambient noise in tidewater glacier fjords: A signal of ice melt

    NASA Astrophysics Data System (ADS)

    Pettit, Erin Christine; Lee, Kevin Michael; Brann, Joel Palmer; Nystuen, Jeffrey Aaron; Wilson, Preston Scot; O'Neel, Shad

    2015-04-01

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

  11. Processes of deposition of interlaminated sand-and-mud at a temperate tidewater glacier

    SciTech Connect

    Cowan, E.A.; Duncker, J.D.; Powell, R.D.

    1985-01-01

    Interlaminated sand-and-mud is the most common lithofacies deposited proximal (<1km) to McBride Glacier, Glacier Bay, Alaska. Two main sediment sources are a subglacial melt-water stream discharging at 100m depth that rises to form turbid overflow plumes and subaqueous sediment gravity flows. Traps collected sediment settling from turbid overflows within 300m of the glacier face at an average rate of 780mg dry sediment cm/sup -2/ day/sup -1/ (about. 06 cm/sup -2/ day /sup -1/). Very-fine sand or silt laminae (0.5mm to a few grains thick) trapped over several days, have sharp basal contacts and grade into thicker mud laminae. These couplets, termed cyclopels, are produced about twice daily, and result from plume interaction with diurnal tidal currents, fluctuations in melt water discharge and variations in spatial distribution of the overflow. Short cores from McBride Inlet include: sediment gravity flow deposits, cyclopels, ice-rafted debris, and homogeneous mud. Sediment gravity flow deposits predominate in cores from ice-proximal locations, and cyclopels are observed primarily in cores from distal locations (>1km) where they are not obscured by sediment gravity flow deposits. Ice-rafted debris is found as laminae in cores throughout the inlet because of high calving rates of debris-rich ice and the wide areal dispersal of bergs.

  12. Evaluations of new and existing methods for the quantification of tidewater glacier terminus change, and their comparability to numerical model output.

    NASA Astrophysics Data System (ADS)

    Lea, James M.; Mair, Douglas WF; Rea, Brice R.

    2014-05-01

    Several different methodologies have previously been employed in the tracking of glacier terminus change, though a systematic comparison of these has not been undertaken. Similarly, the suitability of using the resulting data for the calibration/validation of numerical models has not been evaluated. This could be especially significant for flowline modelling of tidewater glaciers, where discrepancies between the different terminus tracking methods could potentially introduce bias into model calibrations. The choice of method for quantifying terminus change of tidewater glaciers is therefore significant from both glacier monitoring, and numerical modelling viewpoints. In this study we evaluate three existing methodologies that have been widely used to track terminus change (the centreline, bow and box methods) against a full range of idealised glaciological scenarios, and examples of 6 real glaciers in Greenland. We also evaluate two new methodologies that aim to reduce measurement error compared to the existing methodologies, and allow direct comparison of results to those of flowline models. These are (1) a modification to the box method, that can account for termini retreating through fjords that change orientation (termed the curvilinear box method [CBM]), and (2) a method that determines the average terminus position relative to the glacier centreline using an inverse distance weighting extrapolation (termed the extrapolated centreline method [ECM]). No single method achieved complete accuracy for all scenarios though the ECM was best, being able to successfully account for variable fjord orientation, width and terminus geometry. Only results from the centreline, CBM and ECM will be directly comparable to flowline model output, though the CBM and ECM are likely to be the most accurate when applied to real world scenarios.

  13. Investing the role of buoyancy in iceberg calving dynamics from tidewater glaciers

    NASA Astrophysics Data System (ADS)

    Trevers, Matt; Payne, Tony; Cornford, Stephen

    2016-04-01

    The Greenland Ice Sheet (GIS) currently makes a major and accelerating contribution to sea level rise (SLR), with its contribution split roughly evenly between surface mass balance changes due to increased melting and dynamic ice loss through calving. In recent decades, many of Greenland's major outlet glaciers have retreated dramatically due to increased iceberg calving, associated with an increase in velocity and inland thinning. The potential contribution to SLR of a complete collapse of the GIS is ~7m. Iceberg calving is an important process not only as a major source of mass loss from the GIS, but also for the controlling influence it has on the dynamics of the grounding line and over the ice sheet as a whole. Despite plenty of scientific attention and a diverse body of literature, the processes involved in calving, their controlling factors and how it feeds back into glacier and ice sheet dynamics are still not fully understood. This presents a major uncertainty into projections of SLR over the coming decades and centuries. Using Elmer/Ice, a state-of-the-art full-Stokes finite-element model, we are able to resolve the stress distributions in high resolution at the calving front. Buoyancy forces have been proposed as a major influencing factor in inducing calving. By investigating the stress distributions induced in a buoyant calving front, we hope to gain an understanding of how environmental influences such as surface thinning and waterline notch-cutting influence the calving rate, and compare this to observations from calving glaciers in Greenland.

  14. Tidewater Margin Dynamics in Central East Greenland Over two Decades

    NASA Astrophysics Data System (ADS)

    Jiskoot, H.; Juhlin, D.; St. Pierre, H.; Citterio, M.

    2010-12-01

    Sheet. About 90% of Geikie Plateau’s area drains through tidewater glaciers. It is the first time that this magnitude of calving in this region has been recognised. Our glacier inventory data will be available through GLIMS. Differencing the new glacier inventory tidewater margins from those derived from GEUS map database ice polygons (from early-mid 1980s photogrammetric maps) suggests that the total number of tidewater fronts was 131 in the 1980s and 113 in the 2000s. The corresponding calving margin length decreased from 197 to 186 km and results in an areal loss of 31 km2 over two decades. The net retreat of 77 glaciers in 1980s-2000 (-20 km2) and 2000-2005 (-27 km2) show an increase in tidewater margin retreat rate from about 1.5 to 4.5 km2 a-1. Tidewater advances are negligible, apart from two surges: we attempt to account for this behaviour and for the subjective confidence of the 1980s ice polygons in our data analysis. Neither a correlation between calving width and terminus retreat nor between glacier size/type/latitude and retreat could be established. Central and northern Blosseville Kyst glaciers appear more dynamic, which may be due to a combination of sea ice dynamics and fjord temperature/morphology.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Factors Affecting Haul-Out Behavior of Harbor Seals (Phoca vitulina) in Tidewater Glacier Inlets in Alaska: Can Tourism Vessels and Seals Coexist?

    PubMed Central

    2015-01-01

    Large numbers of harbor seals (Phoca vitulina) use habitat in tidewater glaciers in Alaska for pupping, breeding, and molting. Glacial fjords are also popular tourist destinations; however, visitation by numerous vessels can result in disturbance of seals during critical life-history phases. We explored factors affecting haul-out behavior of harbor seals at a glacial site frequented by tourism vessels. In 2008-10, we deployed VHF transmitters on 107 seals in Endicott Arm, Alaska. We remotely monitored presence and haul-out behavior of tagged seals and documented vessel presence with time-lapse cameras. We evaluated the influence of environmental and physical factors on the probability of being hauled out, duration of haul-out bouts, and as factors associated with the start and end of a haulout. Location, season, hour, and interactions of location by year, season, hour, and sex significantly influenced haul-out probability, as did ice, weather, and vessels. Seals were more likely to be hauled out with greater ice availability during the middle of the day, and less likely to be hauled out if vessels were present. Cruise ships had the strongest negative effect; however, most vessel types negatively affected haul-out probability. Haul-out duration was longest in association with starting on incoming tides, clear skies, no precipitation, occurring in the middle of the day, and ending in the late afternoon or evening. End of haulouts was associated with increasing cloud cover, low ice availability, and vessel presence; large-sized tourism vessels or all-vessel-types combined were significant predictors of ending a haul-out bout. Probability of being hauled out was highest in June, during pupping season. Potential disturbances of harbor seals could be reduced, enabling longer resting times for seals and fewer interruptions for nursing pups, if vessels focused the majority of visits to glacial habitat to before or after the hours of 08:00-17:00 or, less optimally, 09

  20. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 1. Borehole-based englacial and subglacial measurements from a rapidly-moving tidewater glacier: Store Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Hubbard, Bryn; Doyle, Samuel; Christoffersen, Poul; Young, Tun Jan; Hofstede, Coen; Hubbard, Alun; Box, Jason; Todd, Joe; Bougamont, Marion

    2016-04-01

    As part of the Subglacial Access and Fast Ice Research Experiment (SAFIRE) pressurised hot water was used to drill four 603-616 m-long boreholes to the bed of the Greenland Ice Sheet at a site located 30 km from the calving front of fast-flowing, marine-terminating Store Glacier (70 degrees N, ~1000 m elevation). Four wired sensor strings were successfully installed in three of the boreholes. These included a thermistor string to obtain the englacial temperature profile installed in the same borehole as a string of tilt sensors to measure borehole deformation, and two sets of combined water pressure, electrical conductivity and turbidity sensors installed just above the bed in separate, adjacent boreholes. The boreholes made a strong hydrological connection to the bed during drilling, draining rapidly to ~80 m below the ice surface. The connection of subsequent boreholes was observed as a perturbation in water pressure and temperature recorded in neighbouring boreholes, indicating an effective hydrological connection between them. The sensors, which were wired to data-loggers at the surface, operated for between ~30 and >80 days from late summer into autumn before the cables stretched and snapped, with the lowermost sensors failing first. The records obtained from these sensors reveal (i) subglacial water pressures that were close to overburden but which generally increased through the period of measurement and varied diurnally by ~0.3 m, (ii) a minimum englacial temperature of -21 degrees C underlain by a zone of temperate ice, some tens of m thick, located immediately above the bed, and (iii) high rates of internal deformation and strain that increased towards the bed. These borehole observations are complemented by GPS measurements of ice motion, meteorological data, and seismic and radar surveys.

  1. Glacier-terminus fluctuations in the Wrangell and Chugach mountains resulting from non-climate controls

    SciTech Connect

    Sturm, M.; Hall, D.K.; Benson, C.S.; Field, W.O.

    1992-03-01

    Non-climatically controlled fluctuations of glacier termini were studied in two regions in Alaska. In the Wrangell Mountains, eight glaciers on Mt. Wrangell, an active volcano, have been monitored over the past 30 years using terrestrial surveys, aerial photogrammetry and digitally registered satellite images. Results, which are consistent between different methods of measurement, indicate that the termini of most glaciers were stationary or had retreated slightly. However, the termini of the 30-km-long Ahtna Glacier and the smaller Center and South MacKeith glaciers began to advance in the early 1960s and have advanced steadily at rates between 5 and 18 m yr-1 since then. These three glaciers flow from the summit caldera of ML Wrangell near the active North Crater, where increased volcanic heating since 1964 has melted over 7 x 107 M3 of ice. The authors suspect that volcanic meltwater has changed the basal conditions for the glaciers, resulting in their advance. In College Fjord, Prince William Sound, the terminus fluctuations of two tidewater glaciers have been monitored since 1931 by terrestrial surveying, photogrammetry, and most recently, from satellite imagery. Harvard Glacier, a 40-kmlong tidewater glacier, has been advancing steadily at nearly 20 m yr-1 since 1931, while the adjacent Yale Glacier has retreated at approximately 50 m yr-1 during the same period, though for short periods, both rates have been much higher.

  2. Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise

    USGS Publications Warehouse

    Larsen, C.F.; Motyka, R.J.; Arendt, A.A.; Echelmeyer, K.A.; Geissler, P.E.

    2007-01-01

    The digital elevation model (DEM) from the 2000 Shuttle Radar Topography Mission (SRTM) was differenced from a composite DEM based on air photos dating from 1948 to 1987 to detennine glacier volume changes in southeast Alaska and adjoining Canada. SRTM accuracy was assessed at ??5 in through comparison with airborne laser altimetry and control locations measured with GPS. Glacier surface elevations lowered over 95% of the 14,580 km2 glacier-covered area analyzed, with some glaciers thinning as much as 640 in. A combination of factors have contributed to this wastage, including calving retreats of tidewater and lacustrine glaciers and climate change. Many glaciers in this region are particularly sensitive to climate change, as they have large areas at low elevations. However, several tidewater glaciers that had historically undergone calving retreats are now expanding and appear to be in the advancing stage of the tidewater glacier cycle. The net average rate of ice loss is estimated at 16.7 ?? 4.4 km3/yr, equivalent to a global sea level rise contribution of 0.04 ?? 0.01 mm/yr. Copyright 2007 by the American Geophysical Union.

  3. Early Holocene glacier advance, southern Coast Mountains, British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Menounos, Brian; Koch, Johannes; Osborn, Gerald; Clague, John J.; Mazzucchi, David

    2004-07-01

    Terrestrial and lake sediment records from several sites in the southern Coast Mountains, British Columbia, provide evidence for an advance of alpine glaciers during the early Holocene. Silty intervals within organic sediments recovered from two proglacial lakes are bracketed by AMS 14C-dated terrestrial macrofossils and Mazama tephra to 8780-6730 and 7940- 6730 14C yr BP [10,150-7510 and 8990- 7510 cal yr BP]. Radiocarbon ages ranging from 7720 to 7380 14C yr BP [8630- 8020 cal yr BP] were obtained from detrital wood in recently deglaciated forefields of Sphinx and Sentinel glaciers. These data, together with previously published data from proglacial lakes in the Canadian Rockies, imply that glaciers in western Canada advanced during the early Holocene. The advance coincides with the well-documented 8200-yr cold event identified in climate proxy data sets in the North Atlantic region and elsewhere.

  4. Initial AUV Investigation of the Dynamic Morainal Bank Environment of the Advancing Hubbard Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Lawson, D. E.; Gulick, S. P. S.; Goff, J. A.

    2015-12-01

    Hubbard Glacier has been steadily advancing into tidewater > 200 years; advance over last 40 years has averaged ~34 m/yr, although at spatially variable rates across the terminus (14-80 m/yr) and with a seasonal advance and retreat cycle of ~100 m to 300 m, but as much as 600 m. The advance of the terminus is synchronous with the movement of the morainal bank that underlies it. The mechanics of this motion and the related sedimentological processes responsible for this coordinated advance of the grounding line are based largely on inferences from geophysical surveys of remnant morainal banks. In situ and repeated observations of the submarine margin are required to improve our understanding of how the terminus advances into deep fjords. We conducted initial submarine observations using a Bluefin 9M AUV (Autonomous Underwater Vehicle) and acquired high-resolution swath bathymetry and sidescan backscatter along a ~2 km long section of the ice face of the glacier. Onboard oceanographic measurements and surface CTD casts were obtained during AUV deployment. Decimeter-scale imagery of the seabed reveals numerous erosional and depositional bedforms and gravitational features next to the ice face and down the morainal bank's proximal slope. The moraine surface adjacent to the ice face is coarse, apparently swept clear of finer materials, exhibits gravel stripes and boulder lags. The slope into the fjord displays a sequence of bedforms from barchan-shaped dunes up to 15 m on a side to barchanoid transverse ridges >50 m long to transverse ridges >100 m long. This transition implies increased sand supply to the bed downslope. Channels, erosional gullies and scours cross the upper slope, while localized slump and flow failures occur sporadically across the face. We speculate that high concentration bottom flows originating from turbulent subglacial discharge are likely processes creating the barchan forms and that the flow velocity reduces with distance from the grounding

  5. Bursts of calving activity and controls on the terminus position of Yahtse Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Bartholomaus, T. C.; Larsen, C. F.; West, M. E.; Oneel, S.

    2011-12-01

    The tidewater glacier terminus is the interface that links oceanic and glaciological processes. Tidewater glaciers contribute large amounts of cold, fresh water to their fjords. Ocean heat exerts a significant control on glacier mass balance. On the Gulf of Alaska, the terminus of tidewater Yahtse Glacier has advanced slowly since its 1990 post-Little Ice Age minimum. At Yahtse's terminus, ice flowing at 18 m/d encounters water with temperatures of up to 10.5°C (measured 1.5 km from the terminus). Profiles of temperature and salinity in Icy Bay, in which Yahtse Glacier terminates, have revealed a strongly stratified, single-cell circulation pattern. Fresh, glacier outflow exits the bay atop warm, saline Gulf of Alaska water. The Alaska Coastal Current, a major source of Icy Bay water, has warmed by 1°C over the last 40 years. These observations prompt the question of how a tidewater advance may be sustained in spite of warming ocean and atmosphere temperatures. Superimposed on Yahtse Glacier's longer-term advance have been smaller-scale summer retreats and winter-spring re-advances. These smaller fluctuations indicate that factors that change on short timescales, such as ocean conditions and weather, also have an important control on terminus position. Observed bursts in calving frequency are a further reflection of the unsteady conditions at the glacier terminus. In the present study, we use seismograms recorded on bedrock within 500 m of the glacier terminus as a calving counter. The epicenters of a significant majority of glacier-generated seismic events within the St. Elias Mountains have been located to within 15 km of the terminus of Yahtse Glacier. Previous study at Yahtse Glacier has revealed that at least 75% of these seismic events originate from calving processes, most notably through the interactions between iceberg and water. Calving frequency is characterized by a relatively steady rate of background events, punctuated by bursts of calving activity

  6. Effect of glacial drainage water on the CO2 system and ocean acidification state in an Arctic tidewater-glacier fjord during two contrasting years

    NASA Astrophysics Data System (ADS)

    Fransson, Agneta; Chierici, Melissa; Nomura, Daiki; Granskog, Mats A.; Kristiansen, Svein; Martma, Tõnu; Nehrke, Gernot

    2015-04-01

    In order to investigate the effect of glacial water on the CO2 system in the fjord, we studied the variability of the total alkalinity (AT), total dissolved inorganic carbon (CT), dissolved inorganic nutrients, oxygen isotopic ratio (δ18O), and freshwater fractions from the glacier front to the outer Tempelfjorden on Spitsbergen in winter 2012 (January, March, and April) and 2013 (April) and summer/fall 2013 (September). The two contrasting years clearly showed that the influence of freshwater, mixing, and haline convection affected the chemical and physical characteristics of the fjord. The seasonal variability showed the lowest calcium carbonate saturation state (Ω) and pH values in March 2012 coinciding with the highest freshwater fractions. The highest Ω and pH were found in September 2013, mostly due to CO2 uptake during primary production. Overall, we found that increased freshwater supply decreased Ω, pH, and AT. On the other hand, we observed higher AT relative to salinity in the freshwater end-member in the mild and rainy winter of 2012 (1142 μmol kg-1) compared to AT in 2013 (526 μmol kg-1). Observations of calcite and dolomite crystals in the glacial ice suggested supply of carbonate-rich glacial drainage water to the fjord. This implies that winters with a large amount of glacial drainage water partly provide a lessening of further ocean acidification, which will also affect the air-sea CO2 exchange.

  7. Peak water from glaciers: advances and challenges in a global perspective (Arne Richter Award for Outstanding Young Scientists Lecture)

    NASA Astrophysics Data System (ADS)

    Huss, Matthias; Hock, Regine

    2014-05-01

    Mountain glaciers show a high sensitivity to changes in climate forcing. In a global perspective, their anticipated retreat will pose far-reaching challenges to the manage- ment of fresh water resources and will raise sea levels significantly within only a few decades. Different model frameworks have been applied to simulate melt water con- tributions of glaciers outside the two ice sheets for the recent IPCC report. However, these models depend on strongly simplified, and often empirical descriptions of the driving processes hampering the reliability of the results. For example, glacier retreat is parameterized with volume-area scaling thus neglecting the glacier's actual geome- try and the surface elevation feedback. Frontal ablation of tidewater and lake-calving glaciers, an important mass loss component for a third of the world's glacier area, is not accounted for. Thus, a transition from the physically-based mass balance-ice flow models developed for single glaciers to the application at the global scale is urgently needed. The chal- lenges are manifold but can be tackled with the new data sets, methods and process- understanding that have emerged during the last years. Here, we present a novel glacier model for calculating the response of surface mass balance and 3D glacier geometry for each individual glacier around the globe. Our approach accounts for feedbacks due to glacier retreat and includes models for mass loss due to frontal ablation and the refreezing of water in the snow/firn. The current surface geometry and thickness distribution for each of the world's roughly 200'000 glaciers is extracted from the Randolph Glacier Inventory v3.2 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. Regionally specified cumulative global sea level rise due to glacier mass loss until 2100 is discussed in the light of model uncertainties and the advantages of using a

  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. 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.

  10. Modelling the impact of submarine frontal melting and ice melange on glacier dynamics

    NASA Astrophysics Data System (ADS)

    Krug, J.; Durand, G.; Gagliardini, O.; Weiss, J.

    2015-05-01

    Submarine melting of the calving face of tidewater glaciers and the mechanical back force applied by the ice melange layer are two mechanisms generally proposed to explain seasonal variations at the calving front of tidewater glaciers. However, the way these processes affect the calving rate and glacier dynamics remains uncertain. In this study, we used a finite element-based model that solves the full Stokes equations to simulate the impact of these forcings on two-dimensional theoretical flow line glacier configurations. The model, which includes calving processes, suggests that frontal melting affects the position of the terminus only slightly (less than a few hundred metres) and does not affect the multiannual glacier mass balance at all. However, the ice melange has a greater impact on the advance and retreat cycles of the glacier front (more than several kilometres) and its consequences for the mass balance are not completely negligible, stressing the need for better characterization of forcing properties. We also show that ice melange forcing against the calving face can mechanically prevent crevasse propagation at sea level and hence prevent calving. Results also reveal different behaviours in grounded and floating glaciers: in the case of a floating extension, the strongest forcings can disrupt the glacier equilibrium by modifying its buttressing and ice flux at the grounding line.

  11. Patagonian Glacier Advances in Concert with those in Western North America

    NASA Astrophysics Data System (ADS)

    Maurer, M. K.; Menounos, B.; Clague, J. J.; osborn, G.

    2012-12-01

    The question of whether Holocene glacier advances in the Northern and Southern hemispheres are synchronous remains open. Here we report on the evidence for late Holocene advances at Stoppani Glacier (54.78° S, 68.98° W), 50 km west of Ushuaia, Argentina, and compare this record to glacier fluctuations in western North America. The glacier is an outlet glacier of the Darwin Cordillera icefield, has an area of 92 km2 and descends to 80 m asl. Wood mats containing stumps in growth position are separated by units of till in a 100-m-high section through the northeast lateral moraine. Radiocarbon ages on the wood mats and stumps decrease up-section, demonstrating that Stoppani Glacier advanced successively farther over the past 3800 years. The earliest of the advances is recorded by a till overlying peat containing wood that returned a calibrated radiocarbon age of 3.83-3.64 ka (kilo calendar years BP). This advance coincides with a well documented glacier advance in western Canada, the so-called '4.2 ka event' [4.2-3.8 ka]. Stoppani Glacier further thickened and overran stumps in growth position at 3.16-2.95 and at 2.86-2.76 ka; both of these events are contemporaneous with widespread advances of alpine glaciers in British Columbia and Alberta. A fourth advance of Stoppani Glacier at about 2.30-2.01 ka coincides with advances of Deming Glacier on Mount Baker, Washington, USA [2.35-2.15 ka], and several glaciers in the Coast Mountains of British Columbia, Canada. The final advance of Stoppani Glacier began about 0.29 ka when the glacier thickened, overran a vegetated surface, and deposited till that forms the crest of the moraine. This advance coincides with the maximum, classical, Little Ice Age advance of nearly all glaciers in western North America. Collectively, our data indicate that Stoppani Glacier advanced in step with glaciers in western North America during the late Holocene. The most parsimonious explanation is that century-scale climate forcing

  12. Rapid advance of two mountain glaciers in response to mine-related debris loading

    NASA Astrophysics Data System (ADS)

    Jamieson, Stewart S. R.; Ewertowski, Marek W.; Evans, David J. A.

    2015-07-01

    Rapid glacier advance is known to occur by a range of mechanisms. However, although large-scale debris loading has been proposed as a process for causing rapid terminus advance, it has rarely been observed. We use satellite remote sensing data to observe accelerated glacier terminus advance in response to massive supraglacial loading on two glaciers in Kyrgyzstan. Over a 15 year period, mining activity has led to the dumping of spoil of up to 180 m thick on large parts of these valley glaciers. We find that the termini of these glaciers advance by 1.2 and 3.2 km, respectively, at a rate of up to 350 m yr-1. Our analysis suggests that although enhanced basal sliding could be an important process, massive supraglacial loads have also caused enhanced internal ice deformation that would account for most, or all, of the glacier terminus advance. In addition, narrowing of the glacier valley and mining and dumping of ice alter the mass balance and flow regime of the glaciers. Although the scale of supraglacial loading is massive, this full-scale experiment provides insight into glacier flow acceleration response where small valley glaciers are impacted by very large volumes of landslide debris.

  13. Alaskan glaciers: Recent observations in respect to the earthquake-advance theory

    USGS Publications Warehouse

    Post, A.S.

    1965-01-01

    Preliminary aerial photographic studies indicate that the Alaskan earthquake produced some rockfalls but no significant snow and ice avalanches on glaciers. No rapid, short-lived glacier advances (surges) are conclusively associated with this earthquake. Recent evidence fails to support the earthquake-advance theory of Tarr and Martin.

  14. 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.

  15. Marine Geophysical Surveying Along the Hubbard Glacier Terminus, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Goff, J. A.; Davis, M.; Gulick, S. P.; Lawson, D. E.; Willems, B. A.

    2010-12-01

    Tidewater glaciers are a challenging environment for marine investigations, owing to the dangers associated with calving and restrictions on operations due to dense floating ice. We report here on recent efforts to conduct marine geophysical surveys proximal to the ice face of Hubbard Glacier, in Disenchantment Bay, Alaska. Hubbard is an advancing tidewater glacier that has twice recently (1986 and 2002) impinged on Gilbert Point, which separates Russell Fiord from Disenchantment Bay, thereby temporarily creating a glacially-dammed Russell Lake. Continued advance will likely form a more permanent dam, rerouting brackish outflow waters into the Situk River, near Yakutat, Alaska. Our primary interest is in studying the development and motion of the morainal bank which, for an advancing tidewater glacier, stabilizes it against rapid retreat. For survey work, we operated with a small, fast, aluminum-hulled vessel and a captain experienced in operating in ice-bound conditions, providing a high margin of safety and maneuverability. Differencing of multibeam bathymetric data acquired in different years can identify and quantify areas of deposition and erosion on the morainal bank front and in Disenchantment Bay proper, where accumulation rates are typically > 1 m/yr within 1 km of the glacier terminus. The advance or retreat rate of the morainal bank can be determined by changes in the bed elevation through time; we document advance rates that average > 30 m/yr in Disenchantment Bay, but which vary substantially over different time periods and at different positions along the ice face. Georeferencing of available satellite imagery allows us to directly compare the position of the glacial terminus with the position of the morainal bank. From 1978 to 1999, and then to 2006, the advances in terminus and morainal bank positions were closely synchronized along the length of the glacier face. In the shallower Russell Fiord side of the terminus, a sediment ridge was mapped both

  16. Surface melt dominates Alaska glacier mass balance

    USGS Publications Warehouse

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

    2015-01-01

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

  17. Mechanisms that Amplify, Attenuate and Deviate Glacier Response to Climate Change in Central East Greenland. (Invited)

    NASA Astrophysics Data System (ADS)

    Jiskoot, H.

    2013-12-01

    only pose problems for the direct interpretation of climate change from length and volume changes due to their dynamically-driven advance and retreat regimes, but also for the reconstruction of LIA extents from trimlines and moraines, and the reconstruction of surface mass balance due to crevasses, potholes or debris-cover. This presentation will address a range of MAAD, including thermal regime transitions; ocean influences on tidewater-terminating glaciers; glacier fragmentation and tributary-trunk interaction; glacier surging and tidewater behaviour; seasonal variations; glacier hypsometry and morphology; terrain and substrate; melt-albedo and melt-ice flow feedbacks; and ice marginal lakes.

  18. An Initial AUV Investigation of the Morainal Bank and Ice-Proximal Submarine Processes of the Advancing Hubbard Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Lawson, D. E.; Gulick, S. P. S.; Goff, J. A.; O'Halloran, W.

    2014-12-01

    The movement of an advancing tidewater glacier occurs in concert with the morainal bank that underlies its terminus. The mechanics of motion and sedimentological processes responsible for this advance of the morainal bank with the calving terminus are not well-defined and based largely on inferences from geophysical analyses of remnant morainal banks on fjord floors. There is a general absence of in situ or direct observation of the submarine margin because it is nearly impossible to access the immediate area of the ice face by boat safely. In order to obtain such data, in June 2014 we tested the ability of a Bluefin 9M AUV (autonomous underwater vehicle) to acquire high resolution swath bathymetry and sidescan backscatter across a ~2 km long section of the ice face of Hubbard Glacier (see also Goff et al., this meeting). Additionally onboard oceanographic measurements were taken that can be compared with surface cast CTD profiles obtained during AUV deployment, including locations with subglacial discharges. The AUV test provides details on the geometry of the morainal bank and nature of the fjord wall surfaces. The decimeter-scale imagery of the seabed reveals numerous erosional and depositional bedforms and gravitational features on the morainal bank's proximal slope. Closer to the ice face, the morainal bank surface appears much coarser, with textural patterns of unknown origin, and gravel lags including boulder fields. Comparing the water depth from the AUV survey with that of NOAA bathymetric data from 2004/2006 shows the morainal bank continued to advance in pace with ice advance into fjord waters over 200m deep, water depths shoaling up to 100m near the present ice margin. The glimpse of the morainal bank afforded by the AUV test clearly demonstrated the value of this technology to ice marginal submarine investigations.

  19. Climate- vs. Earthquake-induced Rock-Glacier Advances in the Tien Shan: Insights from Lichenometry

    NASA Astrophysics Data System (ADS)

    Rosenwinkel, Swenja; Landgraf, Angela; Korup, Oliver; Sorg, Annina

    2014-05-01

    Rock glaciers have been traditionally used as landform proxies of the distribution of sporadic alpine permafrost. In the northern Tien Shan mountains of Kyrgyzstan, most distinct lobes of >200 rock glaciers that we mapped from satellite imagery occur at two major elevation levels. However, a number of particularly low-lying lobes seem difficult to reconcile with palaeoclimatic fluctuations and commensurate changes of permafrost patterns: The minimum elevation of the majority of rock-glacier snouts lies between ~2500 up to ~3700 m a.s.l., but some 10% of rock-glaciers extend down to well below 3000 m a.s.l. We hypothesize that some of the rock glaciers in this area may have formed following strong earthquakes that could have triggered massive supraglacial rock-slope failures, which would have subsequently created sediment-rich rock glaciers from clear-ice glaciers. Our hypothesis is based on the observation that the tectonically active northern Tien Shan of Kyrgyzstan and Kazakhstan was affected by a series of major earthquakes in the late 19th and earliest 20th centuries, e.g. in 1885 (Ms 6.9), 1887 (Ms 7.3), 1889 (Ms 8.3), and 1911 (Ms 8.1). All of these earthquakes had triggered numerous landslides in the northern Tien Shan. It is also likely that similarly strong earthquakes had happened before, but their recurrence intervals are long and more palaeoseismological work is in progress. We test whether lichenometry of rock-glacier surfaces together with morphometric analysis are suitable methods to testing our hypothesis. We focus on assessing the possibility of earthquake-triggered rock-glacier advances, and use lichenometry to resolve age patterns of different rock-glacier lobes. We use a dataset of several thousand lichen diameter measurements encompassing seven different species calibrated by gravestones and dated mass-movement deposits. Data on four single and two merging rock glaciers in four selected valleys in Kyrgyzstan and Kazakhstan support the notion

  20. Moraine formation during an advance/retreat cycle at a temperate alpine glacier

    NASA Astrophysics Data System (ADS)

    Brook, M.; Quincey, D.; Winkler, S.

    2012-04-01

    Mountain glaciers are highly sensitive to variations in temperature and precipitation, and so moraine records from such systems are strong indicators of climate change. Due to the prevailing trend of retreat of the majority of mountain glaciers globally over the last few decades, there are limited opportunities to observe moraine formation, especially at temperate alpine glaciers. In the Southern Alps of New Zealand, while glaciers have all experienced a major retreat since the late 19th century, within this loss of ice mass, there has been a distinct variance in individual glacier response. Indeed, while Tasman Glacier, the longest glacier in the Southern Alps has thinned and entered into the current phase of calving retreat in the early 1990s, the steeper, more responsive glaciers to the west of the Main Divide, such as Franz Josef and Fox Glacier have experienced more elaborate advance/retreat phases. We focus on moraine formation at Fox Glacier, a c. 12.5 km long valley glacier terminating at 300 m above sea level. Fox Glacier retreated substantially since the 1930s, before advancing 800 m between the mid-1980s and 1999. A minor retreat then followed until 2005, succeeded by a 300 m re-advance until 2007-8. Continued retreat and down-wasting has since followed. Superimposed on this alternating advance/retreat cycle, have been minor winter re-advances. Sedimentological and morphological information were combined with detailed observations, historical photos and recent time-lapse photography of the terminus. Characteristics of several modes of moraine formation have been observed: (1) the late 20th century advance culminated in a broad <5 m high terminal moraine, formed by an admixture of "bulldozed" proglacial sediments and dumping of supraglacial material; (2) the 21st century short-lived advances were characterized by 1-2 m high (often multi-crested) ridges with a "saw-tooth" plan-form controlled by longitudinal crevasses outcropping at the terminus; (3) time

  1. Glaciological and marine geological controls on terminus dynamics of Hubbard Glacier, southeast Alaska

    USGS Publications Warehouse

    Stearns, Leigh A.; Hamilton, Gordon S.; van der Veen, C. J.; Finnegan, D. C.; O'Neel, Shad; Scheick, J. B.; Lawson, D. E.

    2015-01-01

    Hubbard Glacier, located in southeast Alaska, is the world's largest non-polar tidewater glacier. It has been steadily advancing since it was first mapped in 1895; occasionally, the advance creates an ice or sediment dam that blocks a tributary fjord (Russell Fiord). The sustained advance raises the probability of long-term closure in the near-future, which will strongly impact the ecosystem of Russell Fiord and the nearby community of Yakutat. Here, we examine a 43-year record of flow speeds and terminus position to understand the large-scale dynamics of Hubbard Glacier. Our long-term record shows that the rate of terminus advance has increased slightly since 1895, with the exception of a slowed advance between approximately 1972 and 1984. The short-lived closure events in 1986 and 2002 were not initiated by perturbations in ice velocity or environmental forcings, but were likely due to fluctuations in sedimentation patterns at the terminus. This study points to the significance of a coupled system where short-term velocity fluctuations and morainal shoal development control tidewater glacier terminus position.

  2. Glaciological and marine geological controls on terminus dynamics of Hubbard Glacier, southeast Alaska

    NASA Astrophysics Data System (ADS)

    Stearns, L. A.; Hamilton, G. S.; van der Veen, C. J.; Finnegan, D. C.; O'Neel, S.; Scheick, J. B.; Lawson, D. E.

    2015-06-01

    Hubbard Glacier, located in southeast Alaska, is the world's largest nonpolar tidewater glacier. It has been steadily advancing since it was first mapped in 1895; occasionally, the advance creates an ice or sediment dam that blocks a tributary fjord (Russell Fiord). The sustained advance raises the probability of long-term closure in the near future, which will strongly impact the ecosystem of Russell Fiord and the nearby community of Yakutat. Here, we examine a 43 year record of flow speeds and terminus position to understand the large-scale dynamics of Hubbard Glacier. Our long-term record shows that the rate of terminus advance has increased slightly since 1895, with the exception of a slowed advance between approximately 1972 and 1984. The short-lived closure events in 1986 and 2002 were not initiated by perturbations in ice velocity or environmental forcings but were likely due to fluctuations in sedimentation patterns at the terminus. This study points to the significance of a coupled system where short-term velocity fluctuations and morainal shoal development control tidewater glacier terminus position.

  3. Seasonal and short term fluctuations of iceberg flux from Hans Glacier Spitsbergen

    NASA Astrophysics Data System (ADS)

    Jania, Jacek; Blaszczyk, Malgorzata; Cieply, Michal; Grabiec, Mariusz; Budzik, Tomasz; Ignatiuk, Dariusz; Uszczyk, Aleksander; Tymrowska, Patrycja; Majchrowska, Elzbieta; Prominska, Agnieszka; Walczowski, Waldemar; Pastusiak, Tadeusz; Petlicki, Michal; Puczko, Dariusz

    2016-04-01

    Glacier iceberg flux due to calving might be an important source of freshwater deliver to Arctic fjords. Mass loss due to calving gives also significant contribution of glacier mass budget. Seasonal changes of dynamics of tidewater glaciers is generally known. After advance of glacier front during winter, summer recession occurs thanks to higher calving in the warmer period of the year. Nevertheless, annual course of iceberg flux intensity is not calculated frequently. Observations and survey of glacier dynamics were conducted on Hans Glacier a polythermal glacier ending down into Hornsund Fiord in Southern Spitsbergen. They provide information for discernment of seasonal calving intensity and iceberg supply to the fiord as a source of freshwater seasonally and in shorter periods of time. Source data on glacier front geometry, bathymetry of the fore bay, seasonal fluctuation of ice-cliff position and glacier velocity were obtained by different field survey and remote sensing methods. Time lapse photos, repeated terrestrial laser scanning and measurements of sea water temperature, salinity and dynamics as well, together with record from meteorological stations were used to determine factors of calving intensity. Calving flux from the glacier to Hornsund Fjord was calculated for short-period events and selected summer seasons between 2007 and 2015. Interannual differences in calving flux were also estimated. Ratios of meltwater to iceberg freshwater supply to the fiord was preliminarily estimated as well.

  4. Estimating ice-melange properties with repeat UAV surveys over Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Toberg, Nick; Ryan, Johnny; Christoffersen, Poul; Snooke, Neal; Todd, Joe; Hubbard, Alun

    2016-04-01

    observed melange height with the model of hydrostatic equilibrium, we estimate the mean thickness to be 126 m. Whereas the mean melange elevation did not change appreciably in our study area, from the date observations started on 13 May until it disintegrated 4-8 June, we found daily melange elevation change up to 140 % of the observed mean value when tabular icebergs were added to it. Observations showed this increase in melange thickness halted calving and that calving did not resume until the melange had thinned and returned to the observed mean value. We found the mean daily speed of the melange to be 46 m/day, from 13 May to 4 June, whereas the terminus of the glacier flowed with a mean daily velocity of 16 m/day while the melange was present. The higher mean speed of the melange is explained by the motion of large tabular icebergs, which travelled hundreds of metres into the fjord over the course of a single day. The imagery collected over Store Glacier provide evidence that large tidewater glaciers are stabilized by proglacial ice mélange forming in winter. When melange was present, large calving events strengthened melange by adding to its overall thickness distribution, stopping calving altogether for up to several days following a large calving event, and slowing the flow of the glacier to half of the speed observed the previous day. When the melange was advected suddenly down the fjord, with no apparent weakening, the glacier responded by increasing both flow speed and calving rate simultaneously. The data produced from repeat UAV surveys clearly demonstrates the potential of this new and rapidly advancing method of data collection.

  5. Laboratory investigations of granular and hydrodynamic processes in tidewater glacial fjords

    NASA Astrophysics Data System (ADS)

    Cathles, Mac; Thompson, Oluwatoyin; Burton, Justin

    Accelerated warming in the past few decades has led to a dramatic increase in glacial activity. This is perhaps most apparent in tidewater glacial fjords, where gravitational flows from ice sheets are focused into narrow channels of thick, fast-flowing ice which terminate into the ocean. The result is a complex system involving both melting and iceberg calving which has a direct impact on the Earth's climate and sea level rise. However, there are numerous inherent difficulties in collecting field data from remote, ice-choked fjords. To address this, we use a laboratory scale model to measure aspects of tidewater glaciers which are not observable in nature. Our model has helped to uncover the source of glacial earthquakes, where floating, cubic-kilometer scaled icebergs capsize due to gravitational instability, and temporarily reverse the velocity of the glacier. In addition, we use our model to address two other important components of tidewater glaciers involving a granular ice mélange which applies stresses on the glacier, and the role of iceberg capsize in disrupting the stratified heat transport at the glacier's terminus. We acknowledge support from NSF DMR-1506446.

  6. Glacialmorphological reconstruction of glacier advances and glacial lake outburst floods at the Cachapoal glacier in the Dry Central Andes of Chile (34°S)

    NASA Astrophysics Data System (ADS)

    Iturrizaga, Lasafam; Charrier, Reynaldo

    2013-04-01

    Throughout the Andes Mountain range of South America a general trend of glacier shrinkage has taken place in the last century. Only a few glaciers have shown a rather non-continuous trend of glacier retreat and temporally advanced or even surged during the mid-19th to 20th century. One of the earliest assumed glacier surges has occurred in the upper Cachapoal catchment area at the homonymous glacier. In climatic respect the Cachapoal glacier is located in the transition zone from the most southern part of the Dry Central Andes of Chile to the more humid zone of the Wet Andes. The region is affected mainly by winter precipitation deriving from the Westerlies. The debris-covered, 12 km-long Cachapoal glacier represents one of the largest valley glaciers in the Central Andes. It is an avalanche-fed glacier with an almost 1500 m-high head wall in its upper catchment area flowing down from Picos del Barroso (5180 m) and terminates at an elevation of 2630 m a.s.l. with a bifurcated glacier tongue. A large moraine complex, almost 2 km in length and 500 m in width, separates the two glacier lobes. During times of advanced glacier tongue positions the Ríos Molina and Cachapoal may be have blocked independently at two distinct localities which are situated about 2300 m apart from each other. A blockage with temporal lake formation has occurred at least in the years 1848, 1955 and 1981 (cf. Plagemann 1887, Peña 1981), from which the rupture of the earliest glacier barrier has been the most devastating. This event is locally reminded as "la gran avenida en seco" in the historical record. Geomorphological evidence of the past historical and modern glacier expansions is given in the proglacial area by a fresh dead-ice hummocky topography and glacial trimlines at the valley flanks. More down valley broad outwash plains and boulder clusters indicate past high energy floods produced by glacier lake outbursts. Regarding the small size of the catchment area of the Río Molina

  7. Complex patterns of glacier advances during the Lateglacial in the Chagan-Uzun Valley, Russian Altai

    NASA Astrophysics Data System (ADS)

    Gribenski, Natacha; Lukas, Sven; Jansson, Krister N.; Stroeven, Arjen P.; Preusser, Frank; Harbor, Jonathan M.; Blomdin, Robin; Ivanov, Mikhail N.; Heyman, Jakob; Petrakov, Dmitry; Rudoy, Alexei; Clifton, Tom; Lifton, Nathaniel A.; Caffee, Marc W.

    2016-04-01

    Over the last decades, numerous paleoglacial reconstructions have been carried out in Central Asian mountain ranges because glaciers in this region are sensitive to climate change, and thus their associated glacial deposits can be used as proxies for paleoclimate inference. However, non-climatic factors can complicate the relationship between glacier fluctuation and climate change. Careful investigations of the geomorphological and sedimentological context are therefore required to understand the mechanisms behind glacier retreat and expansion. In this study we present the first detailed paleoglacial reconstruction of the Chagan Uzun valley, located in the Russian Altai. This reconstruction is based on detailed geomorphological mapping, sedimentological logging, in situ cosmogenic 10Be and 26Al surface exposure dating of glacially transported boulders, and Optically Stimulated Luminescence (OSL) dating. The Chagan Uzun valley includes extensive lobate moraine belts (>100 km2) deposited in the intramontane Chuja basin, reflecting a series of pronounced former glacial advances. Observation of "hillside-scale" folding and extensive faulting of pre-existing soft sediments within the outer moraine belts, together with the geomorphology, indicate that these moraine belts were formed during glacier-surge like events. In contrast, the inner (up-valley) glacial landforms of the Chagan Uzun valley indicate that they were deposited by retreat of temperate valley glaciers and do not include features indicative of surging. Cosmogenic ages associated with the outermost, innermost and intermediary stages, all indicate deposition times clustered around 19.5 ka, although the 10Be ages of the outermost margin are likely slightly underestimated due to brief episode of glacial lake water coverage. Such close deposition timings are consistent with periods of fast or surge advances, followed by active glacier retreat. OSL dating yields significantly older ages of thick lacustrine

  8. 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

  9. 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.

  10. 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.

  11. Accelerating frontal retreat and seasonal variability in North West Svalbard glaciers

    NASA Astrophysics Data System (ADS)

    Mansell, D.; Luckman, A.; Murray, T.

    2009-04-01

    Calving flux is a significant mass balance component for Svalbard glaciers. Calving processes in relation to fjord conditions, glacier velocity and frontal positions are currently poorly understood despite their importance. We present an unprecedented series of data showing ice-front behaviour and surface velocities for NW Svalbard glaciers and discuss the fundamental controls on the calving processes between 1991 and 2008. Glacier flow speeds, ice marginal position, and the presence and absence of fjord ice were derived from ERS, ENVISAT, ALOS and Landsat scenes, and melt modelling was used to investigate seasonal forcing. During this period many tidewater terminating glaciers in the region have shown accelerating rates of retreat, a few show steady retreat, and some remain stable. Superimposed on the long-term retreat of some glacier fronts, including Kronebreen, the fastest flowing glacier in Svalbard, is a seasonal signal which shows advance of the ice-front in the summer. By monitoring the terminus velocity and frontal position of outlet glaciers at high temporal resolution, both the magnitude and seasonality of the controlling processes are investigated and used to provide a better understanding of the impact of climate warming on Arctic ice loss.

  12. A major advance of tropical Andean glaciers during the Antarctic cold reversal.

    PubMed

    Jomelli, V; Favier, V; Vuille, M; Braucher, R; Martin, L; Blard, P-H; Colose, C; Brunstein, D; He, F; Khodri, M; Bourlès, D L; Leanni, L; Rinterknecht, V; Grancher, D; Francou, B; Ceballos, J L; Fonseca, H; Liu, Z; Otto-Bliesner, B L

    2014-09-11

    The Younger Dryas stadial, a cold event spanning 12,800 to 11,500 years ago, during the last deglaciation, is thought to coincide with the last major glacial re-advance in the tropical Andes. This interpretation relies mainly on cosmic-ray exposure dating of glacial deposits. Recent studies, however, have established new production rates for cosmogenic (10)Be and (3)He, which make it necessary to update all chronologies in this region and revise our understanding of cryospheric responses to climate variability. Here we present a new (10)Be moraine chronology in Colombia showing that glaciers in the northern tropical Andes expanded to a larger extent during the Antarctic cold reversal (14,500 to 12,900 years ago) than during the Younger Dryas. On the basis of a homogenized chronology of all (10)Be and (3)He moraine ages across the tropical Andes, we show that this behaviour was common to the northern and southern tropical Andes. Transient simulations with a coupled global climate model suggest that the common glacier behaviour was the result of Atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration. During the Antarctic cold reversal, glaciers advanced primarily in response to cold sea surface temperatures over much of the Southern Hemisphere. During the Younger Dryas, however, northern tropical Andes glaciers retreated owing to abrupt regional warming in response to reduced precipitation and land-surface feedbacks triggered by a weakened Atlantic meridional overturning circulation. Conversely, glacier retreat during the Younger Dryas in the southern tropical Andes occurred as a result of progressive warming, probably influenced by an increase in atmospheric carbon dioxide. Considered with evidence from mid-latitude Andean glaciers, our results argue for a common glacier response to cold conditions in the Antarctic cold reversal exceeding that of the Younger Dryas. PMID:25156258

  13. 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

  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. PMID:23857302

  15. Mountain glacier velocity variation during a retreat-advance cycle quantified using high-precision analysis of ASTER images

    NASA Astrophysics Data System (ADS)

    Anderson, B.; Herman, F.; Leprince, S.

    2009-12-01

    Analysis of optical satellite imagery (ASTER) has revealed the contrasting response of mountain glaciers to similar climatic forcing. High-resolution and near-complete coverage of ice velocities in the central part of the Southern Alps, New Zealand, has been obtained from feature tracking using repeat imagery in 2002 and 2006. Precise orthorectification, co-registration and correlation is carried out using the freely available software COSI-corr. This analysis, combined with short time windows, has enabled velocities to be captured even in the accumulation areas, where velocities are lowest and surface features ephemeral. The results indicate large dynamic changes in some glaciers have occurred between 2002 and 2006. The steep and more responsive Fox and Franz Josef Glaciers increased speed by factors of as much as three during the period, while the low-angled and debris covered Tasman Glacier showed no measurable velocity change. Velocity increases on the steeper glaciers are the result of an observed thickening and steepening of the glacier tongues as the glaciers moved from a retreat phase in 2002 to an advance phase in 2006. This contrasting behaviour is consistent with observed terminus position changes - the steeper glaciers have undergone several advance/retreat cycles during the period of observation (1894 - present) while the low-angled glacier showed little terminus response until retreat resulting from the accelerating growth of a pro-glacial lake in 1983.

  16. Dendrochronology and late Holocene history of Bering piedmont glacier, Alaska

    USGS Publications Warehouse

    Wiles, G.C.; Post, A.; Muller, E.H.; Molnia, B.F.

    1999-01-01

    Fluctuations of the piedmont lobe of Bering Glacier and its sublobe Steller Glacier over the past two millennia are reconstructed using 34 radiocarbon dates and tree-ring data from 16 sites across the glaciers' forelands. The general sequence of glacial activity is consistent with well-dated fluctuations of tidewater and land-terminating glaciers elsewhere along the Gulf of Alaska. Extensive forested areas along 25 km of the Bering ice margin were inundated by glacio-lacustrine and glacio-fluvial sediments during a probable ice advance shortly before 500 cal yr A.D. Regrowth of forests followed the retreating ice as early as the 7th century A.D., with frequent interruptions of tree growth due to outwash aggradation. Forests overrun by ice and buried in outwash indicate readvance about 1080 cal yr A.D. Retreat followed, with ice-free conditions maintained along the distal portions of the forefield until the early 17th century after which the ice advanced to within a few kilometers of its outer Neoglacial moraine. Ice reached this position after the mid-17th century and prior to 200 yr ago. Since the early 20th century, glacial retreat has been punctuated by periodic surges. The record from forests overrun by the nonsurging Steller Lobe shows that this western ice margin was advancing by 1250 A.D., reaching near its outer moraine after 1420 cal yr A.D. Since the late 19th century, the lobe has dominantly retreated.

  17. Modelling the impact of submarine frontal melting and ice mélange on glacier dynamics

    NASA Astrophysics Data System (ADS)

    Krug, J.; Durand, G.; Gagliardini, O.; Weiss, J.

    2015-01-01

    Two mechanisms are generally proposed to explain seasonal variations in the calving front of tidewater glaciers: submarine melting of the calving face and the mechanical back-force applied by the ice mélange. However, the way these processes affect the calving rate and the glacier dynamics remains uncertain. In this study, we used the finite element model Elmer/Ice to simulate the impact of these forcings on more than 200 two dimensional theoretical flowline glacier configurations. The model, which includes calving processes, suggests that frontal melting affects the position of the terminus only slightly (< a few hundred meters) and does not affect the pluriannual glacier mass balance at all. However, the ice mélange has a greater impact on the advance and retreat cycles of the glacier front (more than several 1000 m) and its consequences for the mass balance are not completely negligible, stressing the need for better characterization of forcing properties. We also show that ice mélange forcing against the calving face can mechanically prevent crevasse propagation at sea level and hence prevent calving. Results also revealed different behaviors in grounded and floating glaciers: in the case of a floating extension, the heaviest forcings can disrupt the glacier equilibrium by modifying its buttressing and ice flux at the grounding line.

  18. 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.

  19. 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

  20. Geomorphological consequences of a glacier advance across a paraglacial rock avalanche deposit

    NASA Astrophysics Data System (ADS)

    Cook, Simon J.; Porter, Philip R.; Bendall, Charles A.

    2013-05-01

    Glacial reworking of paraglacial rock slope sediment has been inferred from long-deglaciated terrains to contribute significantly to glacial sediment transfer. At Feegletscher, Switzerland, we provide the first description of the geomorphological consequences of glacier advance across paraglacial rock avalanche sediment. This produced a small arcuate end moraine that encloses a zone of hummocky debris. The sedimentology of these landforms is conditioned by rock avalanche sediment and can be differentiated from purely glacial sediments, indicating that the contribution of glacially reworked rock avalanche debris may be recognisable in deglaciated terrain. Remarkably, much of the overridden rock avalanche debris has maintained its angularity and delicate brecciation features, despite up to 40 years of glacial action. We suggest that the surface 'carapace facies' of the rock avalanche deposit, comprising large openwork blocks, limited the effectiveness of glacial erosion processes. The carapace facies will have resisted significant erosion by the relatively thin glacier because of its high shear strength and because it was able to transmit subglacial meltwater efficiently. Thus, enhanced debris transfer associated with reworking of paraglacial rock avalanche sediment should not necessarily be expected during the initial stages of glacier advance.

  1. Ocean-Glacier Interactions in Alaska and Comparison to Greenland

    NASA Astrophysics Data System (ADS)

    Motyka, R. J.; Truffer, M.

    2011-12-01

    Meltwater from Alaska's coastal glaciers and icefields accounts for nearly half of the total freshwater discharged into the Gulf of Alaska (GOA), with 10% coming from glacier volume loss associated with rapid thinning and retreat of glaciers (Neal et al, 2010). This glacier freshwater discharge contributes to maintaining the Alaska Coastal Current (ACC), which eventually reaches the Arctic Ocean (Royer and Grosch, 2006), thereby linking changes of glaciers along the coast of Alaska to the whole Arctic system. Water column temperatures on the shelf of northern GOA, monitored at buoy GAK1 near Seward, have increased by about 1 deg C since 1970 throughout the 250 m depth and vertical density stratification has also increased. Roughly half of the glacier contribution to ACC is derived from the ~ 50 tidewater glaciers (TWG) that drain from Alaska's coastal mountains into the Gulf of Alaska (GOA). Fjord systems link these TWGs to the GOA, with fjord circulation patterns driven in part by buoyancy-driven convection of subglacial freshwater discharge at the head of the fjord. Neoglacial shallow sills (< 50 m deep) modulate the influx of warm ocean waters (up to 10 deg C) into these fjords. Convection of these warm waters melts icebergs and submerged faces of TWGs. The study of interactions between glaciers, fjords, and the ocean in coastal Alaska has had a long but very sporadic history. We examine this record starting with the "TWG cycle" hypothesis. We next examine recent hydrographic data from several different TWG fjords, representative of advancing and retreating TWGs (Columbia, Yahtse, Hubbard, and LeConte Glaciers), evaluate similarities and differences, and estimate the relative contributions of submarine glacier melting and subglacial discharge to fjord circulation. Circulation of warm ocean waters in fjords has also been hypothesized to play an important role in destabilizing and modulating glacier discharge from outlet glaciers in Greenland. We therefore compare

  2. A new glacier inventory for 2009 reveals spatial and temporal variability in glacier response to atmospheric warming in the Northern Antarctic Peninsula, 1988-2009

    NASA Astrophysics Data System (ADS)

    Davies, B. J.; Carrivick, J. L.; Glasser, N. F.; Hambrey, M. J.; Smellie, J. L.

    2011-12-01

    The Northern Antarctic Peninsula has recently exhibited ice-shelf disintegration, glacier recession and acceleration. However, the dynamic response of land-terminating, ice-shelf tributary and tidewater glaciers has not yet been quantified or assessed for variability, and there are sparse published data for glacier classification, morphology, area, length or altitude. This paper firstly uses ASTER images from 2009 and a SPIRIT DEM from 2006 to classify the area, length, altitude, slope, aspect, geomorphology, type and hypsometry of 194 glaciers on Trinity Peninsula, Vega Island and James Ross Island. Secondly, this paper uses LANDSAT-4 and ASTER images from 1988 and 2001 and data from the Antarctic Digital Database (ADD) from 1997 to document glacier change 1988-2009. From 1988-2001, 90 % of glaciers receded, and from 2001-2009, 79 % receded. Glaciers on the western side of Trinity Peninsula retreated relatively little. On the eastern side of Trinity Peninsula, the rate of recession of ice-shelf tributary glaciers has slowed from 12.9 km2 a-1 (1988-2001) to 2.4 km2 a-1 (2001-2009). Tidewater glaciers on the drier, cooler Eastern Trinity Peninsula experienced fastest recession from 1988-2001, with limited frontal retreat after 2001. Land-terminating glaciers on James Ross Island also retreated fastest in the period 1988-2001. Large tidewater glaciers on James Ross Island are now declining in areal extent at rates of up to 0.04 km2 a-1. This east-west difference is largely a result of orographic temperature and precipitation gradients across the Antarctic Peninsula. Strong variability in tidewater glacier recession rates may result from the influence of glacier length, altitude, slope and hypsometry on glacier mass balance. High snowfall means that the glaciers on the Western Peninsula are not currently rapidly receding. Recession rates on the eastern side of Trinity Peninsula are slowing as the floating ice tongues retreat into the fjords and the glaciers reach a

  3. 10Be exposure dating of onset and timing of Neoglacial glacier advances in the Ecrins massif, French Alps

    NASA Astrophysics Data System (ADS)

    Le Roy, Melaine; Deline, Philip; Carcaillet, Julien

    2013-04-01

    Alpine glaciers are known to be highly sensitive to change in temperature and precipitation on decadal to centennial time scales. For two decades, numerous studies on Holocene climate revealed a period marked by abrupt cold reversals (e.g. 8.2 ka event) with increasing frequency and magnitude after the Holocene Climatic Optimum, during the so-called Neoglacial period (roughly the last 4 ka). State-of-the-art studies indicate that largest alpine glaciers failed to exceed their Little Ice Age (LIA) extent during these LIA Type-Events, unlike certain smaller glaciers. In the French Alps, very few investigations were conducted to date on Holocene glacier variability. Almost all studies focused on the most glacierized area: the Mont Blanc massif, where suitable organic remains to apply radiocarbon dating and dendrochronology are available. Other glacierized massifs are poorly studied, without any Holocene/Neoglacial glacier chronology up to now. Here, we present the results of a study focusing on six glacier forefields distributed in the Ecrins massif. Detailed geomorphological mapping and in-situ produced 10Be dating were carried on multi-crested so-called "LIA composite moraines". The targeted ridges are located in distal position with respect to late LIA drift in order to identify Holocene cold pulses that have led to (or slightly exceeded) LIA-like glacier extent. The 35 10Be ages obtained revealed that the onset of Neoglacial occurred at ~4.2 ka, and that at least two other advances were recorded at ~3.3 ka and ~0.85 ka. One site has yielded a nearly complete Neoglacial record as four discrete events have been dated. These results highlight the potential of lateral moraine ridge stratigraphy which could yield accurate record when sufficiently preserved, but also the different preservation of landforms along the glacier margin which could censor the record.

  4. Quantifying the Availability of Tidewater Glacial Ice as Habitat for Harbor Seals in a Tidewater Glacial Fjord in Alaska Using Object-Based Image Analysis of Airborne Visible Imagery

    NASA Astrophysics Data System (ADS)

    Prakash, A.; Haselwimmer, C. E.; Gens, R.; Womble, J. N.; Ver Hoef, J.

    2013-12-01

    Tidewater glaciers are prominent landscape features that play a significant role in landscape and ecosystem processes along the southeastern and southcentral coasts of Alaska. Tidewater glaciers calve large icebergs that serve as an important substrate for harbor seals (Phoca vitulina richardii) for resting, pupping, nursing young, molting, and avoiding predators. Many of the tidewater glaciers in Alaska are retreating, which may influence harbor seal populations. Our objectives are to investigate the relationship between ice conditions and harbor seal distributions, which are poorly understood, in John's Hopkins Inlet, Glacier Bay National Park, Alaska, using a combination of airborne remote sensing and statistical modeling techniques. We present an overview of some results from Object-Based Image Analysis (OBIA) for classification of a time series of very high spatial resolution (4 cm pixels) airborne imagery acquired over John's Hopkins Inlet during the harbor seal pupping season in June and during the molting season in August from 2007 - 2012. Using OBIA we have developed a workflow to automate processing of the large volumes (~1250 images/survey) of airborne visible imagery for 1) classification of ice products (e.g. percent ice cover, percent brash ice, percent ice bergs) at a range of scales, and 2) quantitative determination of ice morphological properties such as iceberg size, roundness, and texture that are not found in traditional per-pixel classification approaches. These ice classifications and morphological variables are then used in statistical models to assess relationships with harbor seal abundance and distribution. Ultimately, understanding these relationships may provide novel perspectives on the spatial and temporal variation of harbor seals in tidewater glacial fjords.

  5. 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.

  6. Advances in ice radar studies of a temperate alpine glacier, South Cascade Glacier, Washington, U.S.A.

    USGS Publications Warehouse

    Fountain, A.G.; Jacobel, R.W.

    1997-01-01

    South Cascade Glacier, Washington, U.S.A., is one of the most extensively studied glaciers in the Western Hemisphere. In addition to mass-balance measurements, which date to 1958, numerous hydrological investigations have been carried out during the last three decades, and repeated ice-thickness determinations have been made using a variety of techniques. In the late 1960s, the basal topography was initially determined by gravitimetric methods. In the mid-1970s some of the first depth measurements using radar on temperate ice were made. The basal topography was remapped soon after from a series of point radar measurements and boreholes drilled to the glacier bottom. During the 1990s, the ice thickness was remapped using digital recording of continuous profiles that obtained over 5000 ice-thickness measurements. Profiles have been corrected for the finite beamwidth of the antenna radiation pattern and reflections in steep terrain, resulting in a significantly improved depiction of the basal surface and internal structures. The map based on our recent radar profiles confirms the large-scale features of the basal topography previously depicted and reveals more structural detail. A bright reflector was detected at the base of the glacier and could be traced in adjacent profiles. Comparison with results from water-level measurements in boreholes drilled to the bed indicates that the reflector is a subglacial conduit.

  7. Tidewater Community College 2000 Graduate Survey Study.

    ERIC Educational Resources Information Center

    Kleiman, Lisa S.

    The 2000 Tidewater Community College (TCC) Graduate Survey Study is a measure of student satisfaction with the college educational experience. The study gives demographic data pertaining to all 2000 graduates, as well as enrollment, attendance, employment, educational, and attitudinal data generated from survey respondents. Highlights of the…

  8. Tidewater Community College 1998 Graduate Survey Study.

    ERIC Educational Resources Information Center

    Kleiman, Lisa

    This report presents Tidewater Community College's (TCC's) (Virginia) 1998 graduate survey study. Approximately half of the graduates attended another college or university prior to enrolling at TCC. A small portion enrolled directly from high school. Almost three-fourths of the graduates were working either full- or part-time while enrolled, and…

  9. Tidewater Community College Distance Learning Report.

    ERIC Educational Resources Information Center

    Tidewater Community Coll., Norfolk, VA.

    This study of distance learning at Tidewater Community College (TCC) was conducted to determine enrollment patterns, retention, and success in distance learning courses and student perceptions. Distance learning was defined as students enrolled in one of three modes of course delivery: telecourse, online, and compressed video. The time frame for…

  10. Uniform summer cooling drove glacier re-advance across New Zealand during the late-glacial climate reversal

    NASA Astrophysics Data System (ADS)

    Eaves, S.; Mackintosh, A. N.; Winckler, G.; Schaefer, J. M.; Anderson, B.; Townsend, D.

    2014-12-01

    Rapid, millennial-scale climate events characterised the last global glacial-interglacial transition (18-11 ka). In New Zealand, the timing and magnitude of climatic events during this period are poorly understood. Improving our understanding of these events will help to identify the mechanisms via which rapid shifts in climate occur. In this study, we report results from geomorphological mapping, cosmogenic 3He exposure dating and numerical glacier modelling, which show evidence for re-advance of mountain glaciers on Mt Ruapehu in central North Island, New Zealand (39°S) during the late glacial chron (15-11 ka). Using a distributed energy balance model, coupled with a 2D ice flow model, we perform a range of experiments and sensitivity analyses to constrain estimates of past temperature associated with the mapped and dated former ice limits. We find that glaciers in North Island re-advanced early in the late glacial period in response to a likely temperature cooling of 2.5 - 3.4 °C relative to present day, assuming precipitation remained within ± 20% of present. This reconstructed cooling is greater than recorded in nearby pollen archives, which may reflect a seasonal bias between climate proxies. Using our glacier model, we quantify the length sensitivity of glaciers on Mt. Ruapehu to seasonal climate changes. We find that a 3 °C cooling relative to present causes a c. 80% increase in glacier length when applied to the austral summer months (Dec-Feb), compared to c. 20% in winter (June-August). Thus, glaciers in North Island, New Zealand are most sensitive to temperature changes during summer. Strong agreement between our late-glacial reconstructions and other summer temperature proxy records (e.g. mountain glaciers, chironomids) from the Southern Alps, suggest New Zealand experienced uniform summertime cooling during the late-glacial climate reversal.

  11. a Younger Dryas Advance of Cirque Glaciers Near the 60TH Parallel, Westernmost Canada

    NASA Astrophysics Data System (ADS)

    Osborn, G.; Menounos, B.; Goehring, B. M.

    2013-12-01

    Our previous work demonstrates that following the decay of the Cordilleran Ice Sheet which commenced at 16 ka (kilo calendar yrs BP), alpine glaciers in southern and central latitudes of British Columbia advanced during the Younger Dryas Chronozone (YD) [12.9-11.7 ka]. The magnitude of this advance, however, markedly differs throughout this region; this difference likely arises from the complexity of a decaying ice sheet in mountainous terrain instead of climatic factors. In an attempt to constrain the timing of the YD and the timing and style of Cordilleran Ice Sheet decay near its northern limit (northwest British Columbia and southern Yukon), we used satellite imagery and aerial photography to identify probable late Pleistocene moraines in regions which would have been major accumulation centers for the ice sheet. Based on that analysis, we studied cirques which lie in the headwaters of Kusawa and Bennett lakes, northernmost British Columbia and cirques 20 km to the south of Kaskawulsh Glacier, Kluane National Park. Yukon. Moraines believed to predate the Little Ice Age [1.0-0.15 ka] are present in less than 10% of the cirques studied in both regions. The subdued, vegetated moraines lie 150-500 m beyond those ascribed to the Little Ice Age. We sampled multiple boulders for 10Be dating from four of these moraines, in addition to moraines interpreted to be Little Ice Age deposits. Two of these pre-LIA moraines yielded statistically equivalent median ages of 11.21 × 0.91 [n=4] and 11.35 × 0.96 ka [n=2]. We await analyses from the other moraines. These results imply that: 1) high-elevation cirques were deglaciated prior to the YD; 2) cirque glaciers advanced at the same time a retreating northerly lobe of the Cordilleran Ice Sheet constructed moraines of YD age in valleys near Whitehorse, 500 m lower in elevation. The implication would be a complex pattern of late Pleistocene advances in the northern part of the Cordilleran Ice Sheet, similar to the observed

  12. Termini of calving glaciers as self-organized critical systems

    NASA Astrophysics Data System (ADS)

    Åström, J. A.; Vallot, D.; Schäfer, M.; Welty, E. Z.; O'Neel, S.; Bartholomaus, T. C.; Liu, Yan; Riikilä, T. I.; Zwinger, T.; Timonen, J.; Moore, J. C.

    2014-12-01

    Over the next century, one of the largest contributions to sea level rise will come from ice sheets and glaciers calving ice into the ocean. Factors controlling the rapid and nonlinear variations in calving fluxes are poorly understood, and therefore difficult to include in prognostic climate-forced land-ice models. Here we analyse globally distributed calving data sets from Svalbard, Alaska (USA), Greenland and Antarctica in combination with simulations from a first-principles, particle-based numerical calving model to investigate the size and inter-event time of calving events. We find that calving events triggered by the brittle fracture of glacier ice are governed by the same power-law distributions as avalanches in the canonical Abelian sandpile model. This similarity suggests that calving termini behave as self-organized critical systems that readily flip between states of sub-critical advance and super-critical retreat in response to changes in climate and geometric conditions. Observations of sudden ice-shelf collapse and tidewater glacier retreat in response to gradual warming of their environment are consistent with a system fluctuating around its critical point in response to changing external forcing. We propose that self-organized criticality provides a yet unexplored framework for investigations into calving and projections of sea level rise.

  13. Distribution and spawning dynamics of capelin (Mallotus villosus) in Glacier Bay, Alaska: A cold water refugium

    USGS Publications Warehouse

    Arimitsu, M.L.; Piatt, J.F.; Litzow, M.A.; Abookire, A.A.; Romano, Marc D.; Robards, M.D.

    2008-01-01

    Pacific capelin (Mallotus villosus) populations declined dramatically in the Northeastern Pacific following ocean warming after the regime shift of 1977, but little is known about the cause of the decline or the functional relationships between capelin and their environment. We assessed the distribution and abundance of spawning, non-spawning adult and larval capelin in Glacier Bay, an estuarine fjord system in southeastern Alaska. We used principal components analysis to analyze midwater trawl and beach seine data collected between 1999 and 2004 with respect to oceanographic data and other measures of physical habitat including proximity to tidewater glaciers and potential spawning habitat. Both spawning and non-spawning adult Pacific capelin were more likely to occur in areas closest to tidewater glaciers, and those areas were distinguished by lower temperature, higher turbidity, higher dissolved oxygen and lower chlorophyll a levels when compared with other areas of the bay. The distribution of larval Pacific capelin was not sensitive to glacial influence. Pre-spawning females collected farther from tidewater glaciers were at a lower maturity state than those sampled closer to tidewater glaciers, and the geographic variation in the onset of spawning is likely the result of differences in the marine habitat among sub-areas of Glacier Bay. Proximity to cold water in Glacier Bay may have provided a refuge for capelin during the recent warm years in the Gulf of Alaska.

  14. Repeated large-scale retreat and advance of Totten Glacier indicated by inland bed erosion

    NASA Astrophysics Data System (ADS)

    Aitken, A. R. A.; Roberts, J. L.; Ommen, T. D. Van; Young, D. A.; Golledge, N. R.; Greenbaum, J. S.; Blankenship, D. D.; Siegert, M. J.

    2016-05-01

    Climate variations cause ice sheets to retreat and advance, raising or lowering sea level by metres to decametres. The basic relationship is unambiguous, but the timing, magnitude and sources of sea-level change remain unclear; in particular, the contribution of the East Antarctic Ice Sheet (EAIS) is ill defined, restricting our appreciation of potential future change. Several lines of evidence suggest possible collapse of the Totten Glacier into interior basins during past warm periods, most notably the Pliocene epoch, causing several metres of sea-level rise. However, the structure and long-term evolution of the ice sheet in this region have been understood insufficiently to constrain past ice-sheet extents. Here we show that deep ice-sheet erosion—enough to expose basement rocks—has occurred in two regions: the head of the Totten Glacier, within 150 kilometres of today’s grounding line; and deep within the Sabrina Subglacial Basin, 350–550 kilometres from this grounding line. Our results, based on ICECAP aerogeophysical data, demarcate the marginal zones of two distinct quasi-stable EAIS configurations, corresponding to the ‘modern-scale’ ice sheet (with a marginal zone near the present ice-sheet margin) and the retreated ice sheet (with the marginal zone located far inland). The transitional region of 200–250 kilometres in width is less eroded, suggesting shorter-lived exposure to eroding conditions during repeated retreat–advance events, which are probably driven by ocean-forced instabilities. Representative ice-sheet models indicate that the global sea-level increase resulting from retreat in this sector can be up to 0.9 metres in the modern-scale configuration, and exceeds 2 metres in the retreated configuration.

  15. Repeated large-scale retreat and advance of Totten Glacier indicated by inland bed erosion.

    PubMed

    Aitken, A R A; Roberts, J L; van Ommen, T D; Young, D A; Golledge, N R; Greenbaum, J S; Blankenship, D D; Siegert, M J

    2016-05-19

    Climate variations cause ice sheets to retreat and advance, raising or lowering sea level by metres to decametres. The basic relationship is unambiguous, but the timing, magnitude and sources of sea-level change remain unclear; in particular, the contribution of the East Antarctic Ice Sheet (EAIS) is ill defined, restricting our appreciation of potential future change. Several lines of evidence suggest possible collapse of the Totten Glacier into interior basins during past warm periods, most notably the Pliocene epoch, causing several metres of sea-level rise. However, the structure and long-term evolution of the ice sheet in this region have been understood insufficiently to constrain past ice-sheet extents. Here we show that deep ice-sheet erosion-enough to expose basement rocks-has occurred in two regions: the head of the Totten Glacier, within 150 kilometres of today's grounding line; and deep within the Sabrina Subglacial Basin, 350-550 kilometres from this grounding line. Our results, based on ICECAP aerogeophysical data, demarcate the marginal zones of two distinct quasi-stable EAIS configurations, corresponding to the 'modern-scale' ice sheet (with a marginal zone near the present ice-sheet margin) and the retreated ice sheet (with the marginal zone located far inland). The transitional region of 200-250 kilometres in width is less eroded, suggesting shorter-lived exposure to eroding conditions during repeated retreat-advance events, which are probably driven by ocean-forced instabilities. Representative ice-sheet models indicate that the global sea-level increase resulting from retreat in this sector can be up to 0.9 metres in the modern-scale configuration, and exceeds 2 metres in the retreated configuration. PMID:27193684

  16. 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

  17. Thermal structure of Svalbard glaciers and implications for thermal switch models of glacier surging

    NASA Astrophysics Data System (ADS)

    Sevestre, Heïdi; Benn, Douglas I.; Hulton, Nicholas R. J.; Bælum, Karoline

    2015-10-01

    Switches between cold- and warm-based conditions have long been invoked to explain surges of High Arctic glaciers. Here we compile existing and new data on the thermal regime of six glaciers in Svalbard to test the applicability of thermal switch models. Two of the large glaciers of our sample are water terminating while one is land terminating. All three have a well-known surge history. They have a thick basal layer of temperate ice, superimposed by cold ice. A cold terminus forms during quiescence but is mechanically removed by calving on tidewater glaciers. The other three glaciers are relatively small and are either entirely cold or have a diminishing warm core. All three bear evidence of former warm-based thermal regimes and, in two cases, surge-like behavior during the Little Ice Age. In Svalbard, therefore, three types of glaciers have switched from slow to fast flow: (1) small glaciers that underwent thermal cycles during and following the Little Ice Age (switches between cold- and warm-based conditions), (2) large terrestrial glaciers which remain warm based throughout the entire surge cycle but develop cold termini during quiescence, and (3) large tidewater glaciers that remain warm based throughout the surge cycle. Our results demonstrate that thermal switching cannot explain the surges of large glaciers in Svalbard. We apply the concept of enthalpy cycling to the spectrum of surge and surge-like behavior displayed by these glaciers and demonstrate that all Svalbard surge-type glaciers can be understood within a single conceptual framework.

  18. Synchoronous inter-hemispheric alpine glacier advances during the Late Glacial?

    NASA Astrophysics Data System (ADS)

    Bakke, Jostein; Paasche, Øyvind

    2016-04-01

    The termination of the last glaciation in both hemispheres was a period of rapid climate swings superimposed on the overall warming trend, resulting from large-scale reorganizations of the atmospheric and oceanic circulation patterns in both hemispheres. Environmental changes during the deglaciation have been inferred from proxy records, as well as by model simulations. Several oscillations took place both in northern and southern hemispheres caused by melt water releases such as during the Younger Dryas in north and the Antarctic Cold Reversal in south. However, a consensus on the hemispheric linkages through ocean and atmosphere are yet to be reached. Here we present a new multi-proxy reconstruction from a sub-annually resolved lake sediment record from Lake Lusvatnet in Arctic Norway compared with a new reconstruction from the same time interval at South Georgia, Southern Ocean, suggesting inter-hemispheric climate linkages during the Bølling/Allerød time period. Our reconstruction of the alpine glacier in the lake Lusvatnet catchment show a synchronous glacier advance with the Birch-hill moraine complex in the Southern Alps, New Zealand during the Intra Allerød Cooling period. We propose these inter hemispheric climate swings to be forced by the northward migration of the southern Subtropical Front during the Antarctic Cold Reversal. Such a northward migration of the Subtropical Front is shown in model simulation and in palaeorecords to reduce the Agulhas leakage impacting the strength of the Atlantic meridional overturning circulation. We simply ask if this can be the carrier of rapid climate swings from one hemisphere to another? Our high-resolution reconstructions provide the basis for an enhanced understanding of the tiny balance between migration of the Subtropical Front in the Southern Ocean and the teleconnection to northern hemisphere.

  19. Investigating the Response of Greenland Outlet Glaciers to Perturbations Using a 1D Flowline Model

    NASA Astrophysics Data System (ADS)

    Petrakopoulos, K.; Stearns, L. A.; van der Veen, C. J.

    2015-12-01

    Over the past two decades, the behavior of many Greenland tidewater outlet glaciers has been characterized by dramatic acceleration, thinning, and retreat. In some cases this behavior is followed by re-advance, thickening and deceleration. The mechanisms that control glacier stability are not fully understood, and hinder ice sheet mass balance projections. Many studies suggest that accelerations are caused exclusively by processes at the terminus, namely by mechanisms that result in increases in iceberg calving rates. In this study we investigate whether comparable accelerations can initiate at different places along the glacier trunk due to changes in subglacial processes or shear margin evolution. We begin our experiments using a prognostic depth integrated (1-D) flowline model applied to Helheim Glacier, and investigate its flow response to perturbations at the terminus and up-flow. Our work shows that large-scale accelerations could have initiated up-flow far from the terminus. The results of this study will contribute to the long-lasting debate about the role of terminus dynamics, and thus ocean conditions, in modulating ice sheet mass balance.

  20. 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.

  1. Development of Ideas About Holocene and Latest Pleistocene Glacier Advances in the North American Cordillera

    NASA Astrophysics Data System (ADS)

    Osborn, G.

    2014-12-01

    It all started when Francois Matthes coined the phrase "little ice age" (LIA) in 1939 to explain cirque moraines in the Sierra Nevada. Porter and Denton in the late 60's promoted the concept that the LIA was part of a multi-millennium regrowth of glaciers called "Neoglaciation."A second set of small moraines found in a few cirques short distances downvalley of LIA moraines in the American Rockies began attracting some attention in the 1940s-50s. By the 1960s-70s there was much argument over the age(s) of these moraines. A proliferation of ages appeared in the literature in the 1970s-80s, but Thom Davis and Jerry Osborn in 1987 proposed that most or all these outer cirque moraines are actually Younger Dryas (YD) in age.In Alberta in the 1970s, Brian Luckman began studying LIA deposits and Osborn began mapping outer cirque moraines (Crowfoot moraines). The two joined forces for an overview of Holocene glacial history in the Canadian Rockies in 1979.Eric Leonard and Mel Reasoner began lake-sediment studies in the Canadian Rockies in the 1980s-90s. Reasoner and Osborn concluded using lake sediments that the type Crowfoot moraine is YD in age, and in Colorado and Wyoming, Davis, Reasoner, and Brian Menounos established YD ages of outer cirque moraines. Lateral-moraine stratigraphy, begun in the 1980s by June Ryder and Osborn in British Columbia, corroborated the evidence from lake sediments that minor advances and retreats punctuated a gradual Neoglacial expansion of glaciers that began 7 or 8 ka.The era of cosmogenic dating began in the 1990s, with John Gosse's work in the Wind River Range. Most, but not all, cosmogenic ages on outer cirque moraines, including those yielded by Shaun Marcott's broad survey, are in support of the concept that such moraines are YD or pre-YD in age, although uncertainties resulting from production-rate questions remain. There have been various claims of early Holocene advances greater in magnitude than the LIA, but these have been

  2. Peak water from glaciers: advances and challenges in a global perspective

    NASA Astrophysics Data System (ADS)

    Huss, M.; Hock, R.

    2014-12-01

    Mountain glaciers show a high sensitivity to changes in climate forcing. In a global perspective, their anticipated retreat will pose far-reaching challenges to the management of fresh water resources and will raise sea levels significantly within only a few decades. Different model frameworks have been applied to simulate melt water contributions of glaciers outside the two ice sheets for the recent IPCC report. However, these models depend on strongly simplified, and often empirical descriptions of the driving processes hampering the reliability of the results. Thus, a transition from the physically-based mass balance-ice flow models developed for single glaciers to the application at the global scale is urgently needed. The challenges are manifold but can be tackled with the new data sets, methods and process-understanding that have emerged during the last years. Here, we present a novel glacier model for calculating the response of surface mass balance and 3D glacier geometry for each individual glacier around the globe. Our approach accounts for feedbacks due to glacier retreat and includes models for mass loss due to frontal ablation and refreezing of water in the snow/firn. This allows the calculation of the components of proglacial runoff for each individual glacier in a process-based way. The current surface geometry and thickness distribution for each of the world's roughly 200'000 glaciers is extracted from the Randolph Glacier Inventory v3.3 and terrain models. Our simulations are driven with 14 Global Circulation Models from the CMIP5 project using the RCP4.5, RCP8.5 and RCP2.6 scenarios. We focus on the timing of peak water from glacierized catchments in all climatic regions of the earth and the corresponding importance of these regime changes on hydrological stress. Peak water represents a crucial tipping point for sustained water supply even for regions with only a minor glacier coverage, and is relevant to the dynamics of sea level rise. The

  3. Preliminary bathymetry of Shoup Basin and late Holocene changes of Shoup Glacier, Alaska

    USGS Publications Warehouse

    Post, Austin; Viens, R.J.

    2000-01-01

    Shoup Glacier is a retreating, tidewater-calving glacier in northeast Prince William Sound, Alaska. Historical records, vegetation distribution, and sediment depth in Shoup Bay indicate that the glacier reached a late Holocene maximum at the mouth of Shoup Bay prior to 1750. When first observed around 1900, the terminus was stable on a series of shallow, bedrock obstructions between Shoup Bay and Shoup Basin, 2 miles from the late Holocene maximum. Shoup Glacier receded into tidewater in 1957 and in the following 33 years retreated 1.3 miles to expose Shoup Basin, a deep (more than 350 feet) basin with virtually no sediment accumulation. Shoup Glacier is expected to stabilize at the head of Shoup Basin shortly after the year 2000 and will not readvance if present climatic conditions continue.

  4. 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.

  5. Postflood persistence and recolonization of endangered tidewater goby populations

    USGS Publications Warehouse

    Lafferty, K.D.; Swift, C.C.; Ambrose, R.F.

    1999-01-01

    Before-and-after surveys at several southern California sites indicated that populations of endangered tidewater goby Eucyclogobius newberryi persisted through heavy flooding in 1995. This was contrary to our expectations that flooding might have led to extirpation in some smaller wetlands. There was also no significant change in tidewater goby density before and after the flooding. Several apparent recolonization events coincided with the flood, suggesting that flooding may be important for the long-term persistence of the species.

  6. Multi-decadal elevation changes on Bagley Ice Valley and Malaspina Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Muskett, Reginald R.; Lingle, Craig S.; Tangborn, Wendell V.; Rabus, Bernhard T.

    2003-08-01

    Digital elevation models (DEMs) of Bagley Ice Valley and Malaspina Glacier produced by (i) Intermap Technologies, Inc. (ITI) from airborne interferometric synthetic aperture radar (InSAR) data acquired 4-13 September 2000, (ii) the German Aerospace Center (DRL) from spaceborne InSAR data acquired by the Shuttle Radar Topography Mission (SRTM) 11-22 February 2000, and (iii) the US Geological Survey (USGS) from aerial photographs acquired in 1972/73, were differenced to estimate glacier surface elevation changes from 1972 to 2000. Spatially non-uniform thickening, 10 +/- 7 m on average, is observed on Bagley Ice Valley (accumulation area) while non-uniform thinning, 47 +/- 5 m on average, is observed on the glaciers of the Malaspina complex (mostly ablation area). Even larger thinning is observed on the retreating tidewater Tyndall Glacier. These changes have resulted from increased temperature and precipitation associated with climate warming, and rapid tidewater retreat.

  7. 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.

  8. Continued rapid glacier recession following the 1995 collapse of the Prince Gustav Ice Shelf on the Antarctic Peninsula (Invited)

    NASA Astrophysics Data System (ADS)

    Glasser, N. F.; Scambos, T. A.

    2009-12-01

    We use optical satellite imagery (ASTER and Landsat) to document changes in the Prince Gustav Ice Shelf (PGIS) and its tributary glaciers before and after its 1995 collapse. Interpretation of a pre-collapse Landsat 4-5 TM image acquired in February 1988 shows that the ice shelf was fed primarily by Sjogren Glacier from the Antarctic Peninsula and by Rhoss Glacier from James Ross Island (JRI). In 1988, the PGIS contained numerous structural discontinuities (rifts and crevasses), which collectively indicate that ice-shelf break-up had commenced at least seven years before collapse. Meltwater ponds and streams were also common across its surface. After the ice shelf collapsed, Rhoss Glacier became a tidewater glacier and has since experienced rapid and continued recession. Between January 2001 and December 2006 (six to eleven years after the collapse of the PGIS), the front of Rhoss Glacier receded a total of 13.6 km. We conclude that where tributary glaciers become tidewater glaciers they react to ice-shelf removal by rapid and continued recession and that the response time of glaciers on the Antarctic Peninsula to ice-shelf removal is measured on annual to decadal timescales. This rapid recession, coupled with previously documented tributary glacier thinning and acceleration, indicates that Antarctic Peninsula glaciers are extremely sensitive to ice-shelf collapse.

  9. 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.

  10. The Impacts of Advancing Glaciers and Jökulhlaups on the 19th Century Farming Community in the Suðursveit District South of Vatnajökull Glacier, Iceland.

    NASA Astrophysics Data System (ADS)

    Sigurmundsson, F. S.; Gísladóttir, G.; Erlendsson, E.

    2014-12-01

    Few areas in Iceland were as vulnerable to climate changes during the 19th century as the region south of Vatnajökull glacier. The region was repeatedly affected by glacier advance and jökulhlaups (glacier outburst floods) during the Little Ice Age AD 1300-1900 (LIA). The land area between the glacier and the coast was occupied by farming community. The aim of this research is to quantify and map the size of lost vegetated area in the 19th century during the glacial advance in the climax of the LIA and the impact these events had on the community, land-use, ownership, value of estates and livelihood. This research employs historical written sources to investigate changes in the cultural and natural landscape. Historical data and field observations will be collected and stored in a GIS database designed for the research, allowing data to be analyzed and presented on maps. The first recorded impact on the settlement is from 1794 when the Breiðármerkurjökull outlet glacier advanced and devastated pastures and crofts belonging in west of the district. Seventy five years later, in 1868, the largest estate was completely destroyed by a jökulhlaup. In 1829 a farm site in the middle of the district was moved due to repeated jökulhlaup. The outlet glacier Brókarjökull initiated annual jökulhlaups during 1820 -1870, devastating pastures and hayfields and woodlands of a total of 3 prominent estates in the area (by 1200 ha), causing devaluation of 33-66% on these estates. In the eastern part extensive jökulhlaups changed the glacial river channel causing the river to flow over vast area devastating 80 % of the eastern most estate causing its abandonment in 1892. The climate change and accompanied hazards during the 19th century changed the landscape of the Suðursveit district significantly. By the turn of the 20thcentury the vegetated land in the district had been reduced by 35% and areas of sediments increased by 25% and glaciated area increased by 10%. These

  11. Advance of alpine glaciers during final retreat of the Cordilleran ice sheet in the Finlay River area, northern British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Lakeman, Thomas R.; Clague, John J.; Menounos, Brian

    2008-03-01

    Sharp-crested moraines, up to 120 m high and 9 km beyond Little Ice Age glacier limits, record a late Pleistocene advance of alpine glaciers in the Finlay River area in northern British Columbia. The moraines are regional in extent and record climatic deterioration near the end of the last glaciation. Several lateral moraines are crosscut by meltwater channels that record downwasting of trunk valley ice of the northern Cordilleran ice sheet. Other lateral moraines merge with ice-stagnation deposits in trunk valleys. These relationships confirm the interaction of advancing alpine glaciers with the regionally decaying Cordilleran ice sheet and verify a late-glacial age for the moraines. Sediment cores were collected from eight lakes dammed by the moraines. Two tephras occur in basal sediments of five lakes, demonstrating that the moraines are the same age. Plant macrofossils from sediment cores provide a minimum limiting age of 10,550-10,250 cal yr BP (9230 ± 50 14C yr BP) for abandonment of the moraines. The advance that left the moraines may date to the Younger Dryas period. The Finlay moraines demonstrate that the timing and style of regional deglaciation was important in determining the magnitude of late-glacial glacier advances.

  12. Bearings on the Future: The Tidewater Community College Strategic Plan.

    ERIC Educational Resources Information Center

    Tidewater Community Coll., Norfolk, VA.

    This document describes strategic planning at Tidewater Community College (TCC) (Virginia). The TCC strategic plan is the culmination of two years of intensive discussions among the college faculty, students, and board members, as well as the members of the South Hampton Roads community at large. This plan comprises three sections. The first…

  13. Jakobshavn Glacier

    Atmospheric Science Data Center

    2013-04-17

    ... Icebergs released from the glacier drift slowly with the ocean currents and pose hazards for shipping along the coast. The Multi-angle Imaging ... Glacier location:  Greenland Arctic Ocean thumbnail:  ...

  14. 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)

  15. Microbial community development on the surface of Hans and Werenskiold Glaciers (Svalbard, Arctic): a comparison.

    PubMed

    Grzesiak, Jakub; Górniak, Dorota; Świątecki, Aleksander; Aleksandrzak-Piekarczyk, Tamara; Szatraj, Katarzyna; Zdanowski, Marek K

    2015-09-01

    Surface ice and cryoconite holes of two types of polythermal Svalbard Glaciers (Hans Glacier--grounded tidewater glacier and Werenskiold Glacier-land-based valley glacier) were investigated in terms of chemical composition, microbial abundance and diversity. Gathered data served to describe supraglacial habitats and to compare microbe-environment interactions on those different type glaciers. Hans Glacier samples displayed elevated nutrient levels (DOC, nitrogen and seston) compared to Werenskiold Glacier. Adjacent tundra formations, bird nesting sites and marine aerosol were candidates for allochtonic enrichment sources. Microbial numbers were comparable on both glaciers, with surface ice containing cells in the range of 10(4) mL(-1) and cryoconite sediment 10(8) g(-1) dry weight. Denaturating gradient gel electrophoresis band-based clustering revealed differences between glaciers in terms of dominant bacterial taxa structure. Microbial community on Werenskiold Glacier benefited from the snow-released substances. On Hans Glacier, this effect was not as pronounced, affecting mainly the photoautotrophs. Over-fertilization of Hans Glacier surface was proposed as the major factor, desensitizing the microbial community to the snow melt event. Nitrogen emerged as a limiting factor in surface ice habitats, especially to Eukaryotic algae. PMID:26104673

  16. Iceberg Calving and Flow Dynamics at Helheim Glacier, East Greenland, from Time-Lapse Photography

    NASA Astrophysics Data System (ADS)

    Hamilton, G. S.; Khan, S. A.; Schild, K. M.; Stearns, L. A.; Nettles, M.; Ahlstrøm, A. P.; Andersen, M. L.; Davis, J. L.; Ekström, G.; Elósegui, P.; Forsberg, R.; de Juan, J.; Larsen, T. B.; Stenseng, L.

    2008-12-01

    Helheim Glacier in East Greenland is the focus of coordinated studies aimed at understanding tidewater outlet-glacier dynamics and kinematics, and their link to glacial earthquakes. As part of this effort, we installed three time-lapse cameras overlooking the calving terminus of the glacier during the Arctic summer of 2008. Images were captured every five minutes during the mostly unattended period of operation. Several interesting aspects of the glacier's behavior are observed in the image sequences, including vertical displacement of the glacier terminus by ocean tides, and very large calving events. These observations, in combination with simultaneous measurements of ice flow, ocean tides (including tsunamis) and seismic activity, contribute to our understanding of the dynamics of Helheim Glacier and the source mechanism of glacial earthquakes.

  17. 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.

  18. Holocene and latest Pleistocene climate and glacier fluctuations in Iceland

    NASA Astrophysics Data System (ADS)

    Geirsdóttir, Áslaug; Miller, Gifford H.; Axford, Yarrow; Ólafsdóttir, Sædís

    2009-10-01

    Multiproxy climate records from Iceland document complex changes in terrestrial climate and glacier fluctuations through the Holocene, revealing some coherent patterns of change as well as significant spatial variability. Most studies on the Last Glacial Maximum and subsequent deglaciation reveal a dynamic Iceland Ice Sheet (IIS) that responded abruptly to changes in ocean currents and sea level. The IIS broke up catastrophically around 15 ka as the Polar Front migrated northward and sea level rose. Indications of regional advance or halt of the glaciers are seen in late Alleröd/early Younger Dryas time and again in PreBoreal time. Due to the apparent rise of relative sea level in Iceland during this time, most sites contain evidence for fluctuating, tidewater glacier termini occupying paleo fjords and bays. The time between the end of the Younger Dryas and the Preboreal was characterized by repeated jökulhlaups that eroded glacial deposits. By 10.3 ka, the main ice sheet was in rapid retreat across the highlands of Iceland. The Holocene thermal maximum (HTM) was reached after 8 ka with land temperatures estimated to be 3 °C higher than the 1961-1990 reference, and net precipitation similar to modern. Such temperatures imply largely ice-free conditions across Iceland in the early to mid-Holocene. Several marine and lacustrine sediment climate proxies record substantial summer temperature depression between 8.5 and 8 ka, but no moraines have been detected from that time. Termination of the HTM and onset of Neoglacial cooling took place sometime after 6 ka with increased glacier activity between 4.5 and 4.0 ka, intensifying between 3.0 and 2.5 ka. Although a distinct warming during the Medieval Warm Period is not dramatically apparent in Icelandic records, the interval from ca AD 0 to 1200 is commonly characterized by relative stability with slow rates of change. The literature most commonly describes Little Ice Age moraines (ca AD 1250-1900) as representing the

  19. Bruggen Glacier, Chile

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Expedition 3 crew of the International Space Station caught a rare glimpse of the massive ice fields and glaciers of Patagonia early in the afternoon on September 25, 2001. This part of the South American coast sees frequent storms and is often obscured from view by cloud cover. Bruggen Glacier in southern Chile is the largest western outflow from the Southern Patagonian Ice Field and, unlike most glaciers worldwide, advanced significantly since 1945. From 1945 to 1976, Bruggen surged 5 km across the Eyre Fjord, reaching the western shore by 1962 and cutting off Lake Greve from the sea. The glacier continued advancing both northward and southward in the fjord to near its present position before stabilizing. The growth covers a distance of more than 10 km north to south, adding nearly 60 square km of ice. Additional information on this and other Patagonian glaciers may be found at the following link: USGS - Historic Fluctuations of Outlet Glaciers from the Patagonian Ice Fields. Image ISS003-E-6061 was provided by the Earth Sciences and Image Analysis Laboratory at Johnson Space Center. Additional images taken by astronauts and cosmonauts can be viewed at the NASA-JSC Gateway to Astronaut Photography of Earth.

  20. Submarine landforms characteristic of glacier surges in two Spitsbergen fjords

    NASA Astrophysics Data System (ADS)

    Ottesen, D.; Dowdeswell, J. A.; Benn, D. I.; Kristensen, L.; Christiansen, H. H.; Christensen, O.; Hansen, L.; Lebesbye, E.; Forwick, M.; Vorren, T. O.

    2008-08-01

    Well-preserved submarine landforms, all less than 100 years old, are imaged on high-resolution swath bathymetry obtained from Van Keulenfjorden and Rindersbukta (inner Van Mijenfjorden), Spitsbergen, Svalbard. Several tidewater glaciers in these fjords have surged in the last few hundred years. Streamlined landforms, found within the limits of known surges, are interpreted as mega-scale glacial lineations (MSGL) formed subglacially beneath actively surging ice. Large transverse ridges are terminal moraines formed by thrusting at the maximum position of glacier surges. Sediment lobes at the distal margins of terminal moraines are interpreted as glacigenic debris flows, formed either by failure of the frontal slopes of thrust moraines or from deforming sediment extruded from beneath the glacier. Sinuous ridges are eskers, formed after surge termination by the sedimentary infilling of subglacial conduits. Concordant ridges, parallel to former ice margins, are interpreted as minor push moraines, probably formed annually during winter glacier readvance. Discordant ridges, oblique to former ice margins, are interpreted as crevasse-squeeze ridges, forming when soft subglacial sediments are injected into basal crevasses. These submarine landforms have been deposited in the following sequence based on cross-cutting relationships between them, linked to stages of the surge cycle: (1) MSGL; (2a) terminal moraines and (2b) lobe-shaped debris flows; (3) isolated areas of crevasse-fill ridges; (4) eskers and (5) annual retreat ridges. A descriptive landsystem model for tidewater surge-type glaciers has been developed, whose wider applicability is emphasised by comparison with two areas in Isfjorden, Spitsbergen. The model also has a number of features in common with landsystem models for terrestrial surge-type glaciers, but is likely to be more complete since submarine landforms are particularly well preserved. The landforms discussed here may be produced and preserved in

  1. 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

  2. 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

  3. Ongoing calving-frontal dynamics of glaciers in the Northern Patagonia Icefield, Chile

    NASA Astrophysics Data System (ADS)

    Bown, F.; Rivera, A.; Burger, F.; Carrión, D.; Cisternas, S.; Gacitúa, G.; Pena, M.; Oberreuter, J.; Silva, R.; Uribe, J. A.; Wendt, A.; Zamora, R.

    2013-05-01

    Patagonian glaciers are increasingly contributing to the global-sea level rise due to negative mass balances in recent decades, in spite of moderated temperature and precipitation changes taking place in the region. The Austral Chilean glaciers retreat and thinning are strongly influenced by local topography and frontal characteristics, both playing a key role in disrupting glacier responses. One of the main ice bodies in this region is the Northern Patagonian Icefield ( NPI, 46S/73W, 3953 km2), a plateau from where tens of outlet glaciers have been inventoried. Many of these glaciers are ending at sea or freshwater lakes where they are calving. This calving feature is typically associated to non-climatic fluctuations characterized by abnormally-high and sudden retreat and other exacerbated behaviors such as ice flow acceleration and dynamical thinning. The main aim of this work is the study of recent calving dynamics of three glaciers of the NPI, in order to analyze similarities versus differences associated to their location, topographical constraints and bathymetry, among other features. With this aim, airborne LIDAR and radar surveys, as well as field trips were conducted to the area in year 2012 where several instruments and sensors were installed. The selected study sites were the NPI eastern side freshwater calving glaciers Colonia (47.19S/73.29W) and Nef (47.03S/73.27W), and the NPI western margin tidewater calving San Rafael glacier (46.70S/73.76W). With all the collected data, calving fluxes of 0.03 km3 a-1 and 0.08 km3 a-1 were detected at Glaciares Colonia and Nef respectively. At San Rafael, the calving flux was much higher (0.94 km3 a-1) mainly due to a deeper bathymetry near the glacier front, and very high velocities (10m d-1) compared to the eastern side glaciers. At Glaciar San Rafael the calving flux is very likely modulated by tidal components and local buoyancy conditions, while at the eastern glaciers, calving is a near marginal feature

  4. Polar versus temperate grounding-line sedimentary systems and marine glacier stability during sea level rise by global warming

    SciTech Connect

    Powell, R.D. . Geology Dept.); Pyne, A.R. . Antarctic Research Center); Hunter, L.E.; Rynes, N.R.

    1992-01-01

    Marine-ending glaciers may retreat with global warming as sea level rises by ocean thermal expansion. If the sea floor rises by sediment accumulation, then glaciers may not feel the effect of sea level rise. A submersible ROV and other techniques have been used to collect data from temperate and polar glaciers to compare sediment production and mass balance of their grounding-line systems. Temperature Alaskan valley glaciers flow at about 0.2--2 km/a and have high volumes of supraglacial, englacial and subglacial debris. However, most sediment contributed to the base of their tidewater cliffs comes from subglacial streams or squeezing out subglacial sediment and pushing it with other marine sediment into a morainal bank. Blue Glacier, a thin, locally fed polar glacier in Antarctica, flows slowly and has minimal glacial debris. The grounding-line system at the tidewater cliff is a morainal bank that forms solely by pushing of marine sediment. An Antarctic polar outlet glacier, Mackay Glacier, terminating as a floating glacier-tongue, has similar volumes of basal debris to Alaskan temperature glaciers and flows at 250 m/a. However, no subglacial streams issued from Mackay's grounding line and all sedimentation was by rockfall and grainfall rainout from seawater undermelt of the tongue. A grounding-line wedge of glacimarine diamicton is deposited over subglacial (lodgement ) till. Although Antarctic grounding-line accumulation rates are three orders of magnitude smaller than Alaskan rates, both are capable of compensating for predicted rises in sea level by thermal heating from global warming.

  5. 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.

  6. OMEGA - an operational glacier monitoring system

    NASA Astrophysics Data System (ADS)

    Pellikka, P. K. E.

    2003-04-01

    Glacier changes reflect local climate changes and are one of the most important direct indicators of global climate change. In general, the glaciers are retreating in Europe, but some glaciers are advancing. However, even in small areas glacier responses can be different. The application of glaciers as indicators requires sufficient amount of glaciers, which is possible only with remote sensing methods. Remote sensing data have been used for glacier monitoring from the late 19th century, first as terrestrial photographs, but later as aerial photographs. A new era began in the 1970’s as optical satellite data became available. Since late 1990’s the glacier monitoring could be performed with numerous satellite and airborne sensors ranging from satellite radar data to airborne laser scanner data. All together, the development of new remote sensing technologies and methods provides many possibilities for studies of glacier features and parameters. The glacier parameters of interest in operational monitoring are the changes of glacier area and volume, and the variation of glacier zones, such as snow, firn and ice. These parameters enable the estimation of relative volume change, AAR and equilibrium line, for example. Operational monitoring involves that the remote sensing data to be used is available continuously, the image processing methods are accurate and the processing chain is developed so that the derivation of the aimed parameters works fluently. The OMEGA project aims at the development of an operational glacier monitoring system applying all the potential remote sensing data. The objectives are to develop workflows and semi-automatic image processing methodologies for different data types in order to retrieve glacier parameters, to construct databases of the study glaciers and to develop the prototype of an operational monitoring system. The test glaciers are Hintereisferner in Austria and Engabreen in Norway. The deliverable of the project is the OMEGA

  7. Continuous Monitoring of Greenland Outlet Glaciers Using an Autonomous Terrestrial LiDAR Scanning System: Design, Development and Testing at Helheim Glacier

    NASA Astrophysics Data System (ADS)

    LeWinter, A. L.; Finnegan, D. C.; Hamilton, G. S.; Stearns, L. A.; Gadomski, P. J.

    2014-12-01

    Greenland's fast-flowing tidewater outlet glaciers play a critical role in modulating the ice sheet's contribution to sea level rise. Increasing evidence points to the importance of ocean forcing at the marine margins as a control on outlet glacier behavior, but a process-based understanding of glacier-ocean interactions remains elusive in part because our current capabilities for observing and quantifying system behavior at the appropriate spatial and temporal scales are limited. A recent international workshop on Greenland's marine terminating glaciers (US CLIVAR, Beverly, MA, June 2013) recommended the establishment of a comprehensive monitoring network covering Greenland's largest outlet glacier-fjord systems to collect long-term time series of critical in situ glaciological, oceanographic and atmospheric parameters needed to understand evolving relationships between different climate forcings and glacier flow. Given the remote locations and harsh environments of Greenland's glacial fjords, the development of robust autonomous instrumentation is a key step in making the observing networks a reality. This presentation discusses the design and development of a fully-autonomous ground-based Light Detection and Ranging (LiDAR) system for monitoring outlet glacier behavior. Initial deployment of the system is planned for spring 2015 at Helheim Glacier in southeast Greenland. The instrument will acquire multi-dimensional point-cloud measurements of the mélange, terminus, and lower-reaches of the glacier. The heart of the system is a long-range, 1064 nm wavelength Terrestrial Laser Scanner (TLS) that we have previously used in campaign-style surveys at Helheim Glacier and at Hubbard Glacier in Alaska. We draw on this experience to design and fabricate the power and enclosure components of the new system, and use previously acquired data from the instrument, collected August 2013 and July 2014 at Helheim, to optimize our data collection strategy and design the data

  8. 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.

  9. 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.

  10. LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from 10Be surface exposure dating

    NASA Astrophysics Data System (ADS)

    Zech, R.; Kull, Ch.; Kubik, P. W.; Veit, H.

    2007-06-01

    Surface exposure dating (SED) is an innovative tool being already widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22-25 ka and thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11-13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been substantially overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions further west and south.

  11. LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from 10Be surface exposure dating

    NASA Astrophysics Data System (ADS)

    Zech, R.; Kull, Ch.; Kubik, P. W.; Veit, H.

    2007-10-01

    Surface exposure dating (SED) is an innovative tool already being widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22-25 ka and was thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11-13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions farther west and south.

  12. Glaciers in the Rupal Valley (Nanga Parbat)

    NASA Astrophysics Data System (ADS)

    Schmidt, Susanne; Nüsser, Marcus

    2014-05-01

    The widely discussed controversy about Himalayan glacier changes instigated a current boom in studies on a regional scale. In contrast to often simplified assumptions of general and mostly rapid glacier retreat, recent studies show a more complex pattern with stable, advancing and retreating glaciers. Furthermore, changes of debris covered glaciers are discussed controversial. Due to the great vertical span and steep relief, large ice streams in the Himalaya and Karakoram are often primarily fed by avalanches. Their impact on glacier mass balances is often unconsidered in present studies. However, Hewitt (2014) highlighted the crucial role of snow and ice re-distribution by avalanches for Karakoram glaciers. He used a concept of glacier typology based on different nourishment processes introduced at the beginning of the 20th century. By using this concept, Hewitt classified large glaciers in order to identify the effect of avalanches on the mass balance, because many Karakoram glaciers show low down-wasting or even thickening processes described as the "Karakoram anomaly" (Hewitt 2005). Also in the Nanga Parbat region, the western corner of the High Himalaya, the topography is characterized by steep rock walls with vertical distances up to 4700 m. The debris covered glaciers reach down to 2920 m a.s.l. and are regularly fed by small and large avalanches. Our field based investigations show that the glaciers are characterized by small retreating rates since 1857, when Adolph Schlagintweit has mapped them for the first time; others such as the Raikot Glacier are fluctuating since 1934. Furthermore, the extent of down-wasting varies between different glaciers. By using multi-temporal satellite data, topographical maps, sketches and terrestrial photographs changes of glacier lengths were measured. In order to calculate the down-wasting rates, a digital elevation model (DEM) with a spatial resolution of 30x30 m² was derived from the digitized contour lines of the

  13. Hasty retreat of glaciers in northern Patagonia

    NASA Astrophysics Data System (ADS)

    Paul, Frank; Mölg, Nico

    2014-05-01

    decline (area and thickness loss). Some glaciers retreated more than 3 km over this time period or even disappeared completely. Typically, these glaciers lost contact to the accumulation areas of tributaries and melted away as dead ice. Furthermore, numerous proglacial lakes formed or expanded rapidly, increasing the local hazard potential. On the other hand, some glaciers located on or near to (still active) volcanoes have also slightly advanced over the same time period. Observed trends in temperature (decreasing) are in contrast to the observed strong glacier shrinkage, indicating that also other factors must play a role.

  14. Glacier area and length changes in Norway from repeat inventories

    NASA Astrophysics Data System (ADS)

    Winsvold, S. H.; Andreassen, L. M.; Kienholz, C.

    2014-10-01

    In this study, we assess glacier area and length changes in mainland Norway from repeat Landsat TM/ETM+-derived inventories and digitized topographic maps. The multi-temporal glacier inventory consists of glacier outlines from three time ranges: 1947 to 1985 (GIn50), 1988 to 1997 (GI1990), and 1999 to 2006 (GI2000). For the northernmost regions, we include an additional inventory (GI1900) based on historic maps surveyed between 1895 and 1907. Area and length changes are assessed per glacier unit, 36 subregions, and for three main parts of Norway: southern, central, and northern. The results show a decrease in the glacierized area from 2994 km2 in GIn50 to 2668 km2 in GI2000 (total 2722 glacier units), corresponding to an area reduction of -326 km2, or -11% of the initial GIn50 area. The average length change for the full epoch (within GIn50 and GI2000) is -240 m. Overall, the comparison reveals both area and length reductions as general patterns, even though some glaciers have advanced. The three northernmost subregions show the highest retreat rates, whereas the central part of Norway shows the lowest change rates. Glacier area and length changes indicate that glaciers in maritime areas in southern Norway have retreated more than glaciers in the interior, and glaciers in the north have retreated more than southern glaciers. These observed spatial trends in glacier change are related to a combination of several factors such as glacier geometry, elevation, and continentality, especially in southern Norway.

  15. 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

  16. Glacier Sensitivity Across the Andes

    NASA Astrophysics Data System (ADS)

    Sagredo, E. A.; Lowell, T. V.; Rupper, S.

    2010-12-01

    Most of the research on causes driving former glacial fluctuations, and the climatic signals involved, has focused on the comparisons of sequences of glacial events in separate regions of the world and their temporal-phasing relationship with terrestrial or extraterrestrial climate-forcing mechanisms. Nevertheless the climatic signals related with these glacial advances are still under debate. This impossibility to resolve these questions satisfactorily have been generally attributed to the insufficiently precise chronologies and unevenly distributed records. However, behind these ideas lies the implicit assumption that glaciers situated in different climate regimes respond uniformly to similar climatic perturbations. This ongoing research is aimed to explore the climate-glacier relationship at regional scale, through the analysis of the spatial variability of glacier sensitivity to climatic change. By applying a Surface Energy Mass Balance model (SEMB) developed by Rupper and Roe (2008) to glaciers located in different climatic regimes, we analyzed the spatial variability of mass balance changes under different baseline conditions and under different scenarios of climatic change. For the sake of this research, the analysis is being focused on the Andes, which in its 9,000 km along the western margin of South America offers an unparalleled climatic diversity. Preliminary results suggest that above some threshold of climate change (a hypothetical uniform perturbation), all the glaciers across the Andes would respond in the “same direction” (advancing or retreating). Below that threshold, glaciers located in some climatic regimes may be insensitive to the specific perturbation. On the other hand, glaciers located in different climatic regimes may exhibit a “different magnitude” of change under a uniform climatic perturbation. Thus, glaciers located in the dry Andes of Perú, Chile and Argentina are more sensitive to precipitation changes than variations in

  17. 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.

  18. 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.

  19. Linking morphology across the glaciofluvial interface: A 10Be supported chronology of glacier advances and terrace formation in the Garonne River, northern Pyrenees, France

    NASA Astrophysics Data System (ADS)

    Stange, K. M.; van Balen, R. T.; Kasse, C.; Vandenberghe, J.; Carcaillet, J.

    2014-02-01

    The Garonne River drains an important part of the northern Pyrenees and its northern foreland. We investigated the middle reaches of the Garonne River establishing a detailed morphogenetic profile of its foreland terrace staircase and the preserved palaeoglacier margins. We particularly focussed on the glaciofluvial interface, linking (also genetically) the fluvial sediment archives in the foreland with the terminal glacial basin upstream of the Pyrenees mountain front. Using cosmogenic nuclide 10Be analyses, two terrace exposures have been dated, including a prominent fluvioglacial outwash fan at the foreland transition. We identified three terminal margins of late Pleistocene glacier advances. The prominent Garonne staircase consists of three major terrace complexes, comprising eight individual terrace levels. Results indicate a young age of the lower terrace complex of the Garonne staircase (MIS 4-2). The morphogenetic relationships and the new 10Be exposure age constraints suggest that during the last glaciation (Würmian) the Garonne glacier reached its maximum extent at the north Pyrenean mountain front, apparently already during MIS 4. Two different ice margins were associated with MIS 2, indicating close to maximum ice-extent during early MIS 2 (LGM) and relatively stationary ice-recession in the late MIS 2. The extensive Garonne terrace complexes formed under cold-climate conditions and were abandoned by incision during major glacial-interglacial transitions. During warm-cold climate transitions lateral erosion caused the reworking of previously abandoned palaeofloodplains. The long-term (Quaternary) incision of the Garonne and other north Pyrenean rivers indicates that the proximal Aquitaine foreland basin experienced uplift. However, non-uniform lateral course migrations and valley asymmetries of the north Pyrenean piedmont rivers indicate that uplift magnitude is variable, with maximum amounts in the centre of the molasse-fan of Lannemezan: Rivers on

  20. Alaska: Glaciers of Kenai Fjords National Park and Katmai and Lake Clark National Parks and Preserve

    NASA Technical Reports Server (NTRS)

    Giffen, bruce A.; Hall, Dorothy K.; Chien, Janet Y. L.

    2011-01-01

    There are hundreds of glaciers in Kenai Fjords National Park (KEFJ) and Katmai National Park and Preserve (KATM) covering over 2276 sq km of park land (circa 2000). There are two primary glacierized areas in KEFJ -- the Harding Icefield and the Grewingk-Yalik Glacier Complex, and three primary glacierized areas in KATM - the Mt. Douglas area, the Kukak Volcano to Mt. Katmai area and the Mt. Martin area. Most glaciers in these parks terminate on land, though a few terminate in lakes. Only KEFJ has tidewater glaciers, which terminate in the ocean. Glacier mapping and analysis of the change in glacier extent has been accomplished on a decadal scale using satellite imagery, primarily Landsat data from the 1970s, 1980s, and from 2000. Landsat Multispectral Scanner (MSS), Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) imagery was used to map glacier extent on a park-wide basis. Classification of glacier ice using image processing software, along with extensive manual editing, was employed to create Geographic Information System (GIS) outlines of the glacier extent for each park. Many glaciers that originate in KEFJ but terminate outside the park boundaries were also mapped. Results of the analysis show that there has been a reduction in the amount of glacier ice cover in the two parks over the study period. Our measurements show a reduction of approximately 21 sq km, or -1.5% (from 1986 to 2000), and 76 sq km, or -7.7% (from 1986/87 to 2000), in KEFJ and KATM, respectively. This work represents the first comprehensive study of glaciers of KATM. Issues that complicate the mapping of glacier extent include: debris-cover (moraine and volcanic ash), shadows, clouds, fresh snow, lingering snow from the previous season, and differences in spatial resolution between the MSS and TM or ETM+ sensors. Similar glacier mapping efforts in western Canada estimate mapping errors of 3-4%. Measurements were also collected from a suite of glaciers in KEFJ and KATM detailing

  1. Alaska: Glaciers of Kenai Fjords National Park and Katmai National Park and Preserve

    NASA Technical Reports Server (NTRS)

    Giffens, Bruce A.; Hall, Dorothy K.; Chien, Janet Y. L.

    2014-01-01

    There are hundreds of glaciers in Kenai Fjords National Park (KEFJ) and Katmai National Park and Preserve (KATM) covering over 2,276 sq km of park land (ca. 2000). There are two primary glacierized areas in KEFJ (the Harding Icefield and the Grewingk-Yalik Glacier Complex) and three primary glacierized areas in KATM (the Mt. Douglas area, the Kukak Volcano to Mt. Katmai area, and the Mt. Martin area). Most glaciers in these parks terminate on land, though a few terminate in lakes. Only KEFJ has tidewater glaciers, which terminate in the ocean. Glacier mapping and analysis of the change in glacier extent has been accomplished on a decadal scale using satellite imagery, primarily Landsat data from the 1970s, 1980s, and from2000. Landsat Multispectral Scanner (MSS),Thematic Mapper (TM), and Enhanced Thematic Mapper Plus (ETM) imagery was used to map glacier extent on a park-wide basis. Classification of glacier ice using image-processing software, along with extensive manual editing, was employed to create Geographic Information System (GIS)outlines of the glacier extent for each park. Many glaciers that originate in KEFJ but terminate outside the park boundaries were also mapped. Results of the analysis show that there has been a reduction in the amount of glacier ice cover in the two parks over the study period. Our measurements show a reduction of approximately 21 sq km, or 1.5(from 1986 to 2000), and 76 sq km, or 7.7 (from19861987 to 2000), in KEFJ and KATM, respectively. This work represents the first comprehensive study of glaciers of KATM. Issues that complicate the mapping of glacier extent include debris cover(moraine and volcanic ash), shadows, clouds, fresh snow, lingering snow from the previous season, and differences in spatial resolution between the MSS,TM, or ETM sensors. Similar glacier mapping efforts in western Canada estimate mapping errors of 34. Measurements were also collected from a suite of glaciers in KEFJ and KATM detailing terminus positions

  2. Attribution of glacier fluctuations to climate change

    NASA Astrophysics Data System (ADS)

    Oerlemans, J.

    2012-04-01

    Glacier retreat is a worlwide phenomenon, which started around the middle of the 19th century. During the period 1800-1850 the number of retreating and advancing glaciers was roughly equal (based on 42 records from different continents). During the period 1850-1900 about 92% of all mountain glaciers became shorter (based on 65 records). After this, the percentage of shrinking glaciers has been around 90% until the present time. The glacier signal is rather coherent over the globe, especially when surging and calving glaciers are not considered (for such glaciers the response to climate change is often masked by length changes related to internal dynamics). From theoretical studies as well as extensive meteorological work on glaciers, the processes that control the response of glaciers to climate change are now basically understood. It is useful to make a difference between geometric factors (e.g. slope, altitudinal range, hypsometry) and climatic setting (e.g. seasonal cycle, precipitation). The most sensitive glaciers appear to be flat glaciers in a maritime climate. Characterizing the dynamic properties of a glacier requires at least two quantities: the climate sensitivity, expressing how the equilibrium glacier state depends on the climatic conditions, and the response time, indicating how fast a glacier approaches a new equilibrium state after a stepwise change in the climatic forcing. These quantities can be estimated from relatively simple theory, showing that differences among glaciers are substantial. For larger glaciers, climate sensitivities (in terms of glacier length) vary from 1 to 8 km per 100 m change in the equilibrium-line altitude. Response times are mainly in the range of 20 to 200 years, with most values between 30 and 80 years. Changes in the equilibrium-line altitude or net mass balance of a glacier are mainly driven by fluctuations in air temperature, precipitation, and global radiation. Energy-balance modelling for many glaciers shows that

  3. South Cascade Glacier bibliography

    SciTech Connect

    Fountain, A.G.; Fulk, M.A.

    1984-01-01

    South Cascade Glacier, in Washington State, resides in a well-defined basin with mainly unglacierized divides making it ideal for most glaciological and hydrological studies. This bibliography is divided into three cateogories: (1) studies done about South Cascade Glacier specifically; (2) studies that use data from South Cascade Glacier but do not focus on or give insight to the glacier itself; and (3) instrumentation studies and non-glacier projects including snow studies done in the basin. (ACR)

  4. Ice-proximal sediment dynamics and their effect on the stability of Muir Glacier, Alaska: A case study of non-climatic glacier response

    SciTech Connect

    Hunter, L.E.; Powell, R.D. . Dept. of Geology)

    1992-01-01

    Recent studies have shown that water depth at tidewater termini affect calving rates and, therefore, glacier mass balance and terminus stability. Grounding-line water depths are themselves governed by glacial and marine processes that interact during the formation of morainal bank depocenters. These morainal banks can fluctuate 10s of meters in height within an interval of a few weeks. Recent investigations in Glacier Bay have focused on quantitatively assessing sediment budgets in the ice-proximal environment. The monitoring of morainal banks in upper Muir Inlet has included repeated bathymetric mapping, sediment trap studies, bottom grab sampling, glacier and iceberg sampling, and submersible ROV investigations within 1 km of the terminus. Such relationships are important in interpreting recent changes in the dynamics of Muir Glacier where a century of retreat has been succeeded by quasi stability. The new glacier regime has accompanied basin infilling from approximately 100 m depth to a maximum of 52 m at the grounding line. Two large grounding-line fans have aggraded to deltas and reduced the length of the calving margin from 900 m to 290 m wide. These effects have reduced the ice flow velocities by 45%. Annual morainal bank growth ranged from 10[sup 6] to 10[sup 7] m[sup 3] and is the result of glacifluvial dumping, suspension settling from turbid overflow plumes, debris dumping from ice-cliff and iceberg melting, glacier squeezing and pushing of morainal bank sediment, and sediment gravity flow processes. Each of these processes are an integral facet of the morainal bank dynamics and glacier response. These studies of Muir Glacier indicate that glacier response to sediment dynamics need to be addresses before climatic implications are made.

  5. 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.

  6. 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

  7. Glaciers of Europe

    USGS Publications Warehouse

    Williams, Richard S., Jr.; 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

  8. 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

  9. Tidewater Community College Biennial Transfer Student Report, 1996-97 and 1997-98 Academic Years.

    ERIC Educational Resources Information Center

    Janicki, Heidi

    This report provides an analysis of Tidewater Community College (TCC) (Virginia) students who transferred to a four-year institution in Virginia beginning in fall 1996 or 1997. The following topics are discussed: overview of the transfer process; acceptance and enrollment rates for each of the four-year institutions; performance of TCC graduates…

  10. REPRODUCTIVE ECOLOGY OF THE TIDEWATER SILVERSIDE, 'MENIDIA PENINSULAE' (PISCES: ATHERINIDAE) FROM SANTA ROSA ISLAND, FLORIDA

    EPA Science Inventory

    The reproductive ecology of the tidewater silverside, Menidia peninsulae, was studied during February 1982 through February 1983 along the shoreline of Santa Rosa Island, Florida. Adult Menidia were observed at low tide spawning on a red alga, Ceramium byssoideum, which was growi...

  11. 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.

  12. Linking the spatial variability of glacier mass loss to fjord geometry

    NASA Astrophysics Data System (ADS)

    Porter, D. F.; Tinto, K. J.; Boghosian, A.; Cochran, J. R.; Csatho, B. M.; Bell, R. E.

    2015-12-01

    There is compelling evidence of increasing mass loss of the ice sheets using a diverse set of observations, including increased thinning rates measured from both airborne and satellite altimeters, elevated mass fluxes resulting from the acceleration of outlet glaciers, and mass changes measured directly from satellite gravimetry. A dominant characteristic of observed change in Greenland outlet glaciers is that it is locally random. Numerous studies have revealed a high degree of spatial and temporal variability of outlet glacier mass change. Modeling studies suggest that increased ocean temperatures may be responsible for the observed glacial retreat in Greenland through increased basal melting, leading to increased calving rates, terminus retreat, glacier speedup, and eventually thinning of inland ice. Knowledge of fjord geometry is crucial for ice-ocean interaction because the availability of ocean heat to the ice will be restricted by narrow sills and shallow grounding lines. We investigate whether the variability in observed changes among Greenland glaciers can be partially explained by variation in fjord geometry. Using statistical techniques commonly employed to detect patterns in complex spatial data, we objectively show that mass change in Greenland tidewater glaciers between 2003 and 2009 is indeed mostly spatially incoherent. Except for a few clusters of similar change in the NW and Scoresby Sund regions, there is significant glacier-scale variability in mass loss rates. To understand the drivers of this local variability, we compare fjord bathymetries from all regions of Greenland, modeled using airborne gravimetry measurements from NASA Operation IceBridge flights, to estimates of glaciological change. Specifically, we investigate the correlation between water depths at the grounding line and the dynamic mass loss of tidewater glaciers. In theory, a deep grounding line will allow greater interaction with the warm Atlantic Water observed in most fjords

  13. Glaciers: A water resource

    USGS Publications Warehouse

    Meier, Mark; Post, Austin

    1995-01-01

    Most Americans have never seen a glacier, and most would say that glaciers are rare features found only in inaccessible, isolated wilderness mountains. Are they really so rare? Or are they really potentially important sources of water supply?

  14. Glacier area and length changes in Norway from repeat inventories

    NASA Astrophysics Data System (ADS)

    Winsvold, S. H.; Andreassen, L. M.; Kienholz, C.

    2014-06-01

    In this study, we assess glacier area and length changes in mainland Norway from repeat Landsat TM/ETM+ derived inventories and digitized topographic maps. The multi-temporal glacier inventory consists of glacier outlines from within three time ranges: 1947 to 1985 (GIn50), 1988 to 1997 (GI1990), and 1999 to 2006 (GI2000). For the northernmost regions, we include an additional inventory (GI1900), based on historic maps surveyed between 1895 to 1907. Area and length changes are assessed per glacier unit, for 36 subregions, and for three main parts of Norway: southern, central and northern Norway. The results show a decrease of the glacierized area from 2994 km2 in GIn50, to 2668 km2 in GI2000 (totally 2722 glacier units), corresponding to an area reduction of -326 km2, or -11% of the initial GIn50 area. This is equivalent to an average change rate of -11 km2 a-1 over the past 30 years. The average length change for the full epoch (within GIn50 and GI2000) is -240 m, corresponding to an average length change rate of -8 m a-1. Overall, the comparison reveals both area and length reduction as a general pattern, even though some glaciers have advanced. The three northernmost glacier regions show the strongest retreat rates, whereas the central part of Norway shows the lowest change rates. Glacier area and length changes indicate that glaciers in maritime areas in southern Norway have retreated more than glaciers in the interior, and glaciers in the north have retreated more than southern glaciers. These observed spatial trends in glacier change are related to a combination of several geographical factors like glacier geometry and elevation, and other climatic aspects, such as continentality and the North Atlantic Oscillation.

  15. Investigating the Cause of the 2012 Acceleration of Jakobshavn Isbræ, Greenland Using High Resolution Observations of the Glacier Terminus

    NASA Astrophysics Data System (ADS)

    Cassotto, R.; Fahnestock, M. A.; Boettcher, M. S.; Amundson, J. M.; Truffer, M.

    2014-12-01

    After decades of relative stability, Jakobshavn Isbræ, a tidewater glacier in West Greenland, started to destabilize at the turn of the century. The glacier thinned, the perennial tongue disintegrated, velocities doubled, and the terminus retreated. The glacier evolved over the next several years as it showed large seasonal variations in speed and a progressive kilometer-scale retreat of its calving front. Then, during the 2012 summer, Jakobshavn set a new record when its speed increased to rates more than four times the 1990s values, and consequently became the fastest glacier recorded by satellite yet. A 2-week field study was conducted along the terminus at that time; ground portable radar interferometers (GPRI), time-lapse cameras, GPS, and a tide gauge were deployed to characterize glacier dynamics along the ice-ocean boundary. We use >10,000 interferograms recorded with the terrestrial interferometers to probe the cause of this acceleration. We observe a 33% increase in glacier speed and a 250% increase in the amplitude of response to tidal forcing during our study period. We explore how the location of the terminus along the reverse bed slope contributed to the observed speedup, and we compare our findings with the long-term record of satellite observations. Our data show that understanding tidewater glacier dynamics requires knowledge of short-term variations along glacier termini that is currently not available from satellites. This study provides insight into such short-term dynamics on spatial scales comparable to satellite InSAR but with temporal resolution similar to GPS.

  16. 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.

  17. Upper and Lower Bounds on the Stability of Calving Glaciers

    NASA Astrophysics Data System (ADS)

    Ma, Y.; Bassis, J. N.

    2015-12-01

    Iceberg calving is responsible for nearly half of the mass lost from ice sheets to the oceans. However, a lack of a well-parameterized calving model leaves most numerical ice sheet models incomplete. Previous studies have sought to parameterize iceberg calving assuming that calving occurs when a surface crevasse intersects with a basal one. Although a variety of models have successfully reproduced patterns of glacier retreat, they are frequently tuned by adding melt water into surface crevasses until glacier behavior matches observations, which is puzzling because calving also occurs during winter when no melt water is available. Here we examine crevasse propagation using a 2D full-Stokes finite element model along the center flow of an idealized glacier terminating in ocean to see when water-free surface crevasses intersect with water-filled basal crevasses on a lubricated bed. Crevasse propagation is computed using the Nye zero-stress-model, assuming they have a negligible effect on the stress field of the glacier. We find that for a given water depth, simulated glaciers evolve to a state where either basal and surface crevasses intersect or the glacier begins to float. This allows us to map out a stability threshold that predicts for a given water depth if certain ice thicknesses will result in full thickness failure. Assuming seeds for crevasses are present everywhere, this threshold poses an upper limit on ice thickness: as the thickness decreases full thickness penetration is increasingly likely. Comparing our theoretical stability threshold with observational data deduced from Operation IceBridge, we find that most tidewater glaciers have water depth and ice thickness combinations fall in a narrow region above our predicted threshold and below buoyancy. The agreement between observations and our simulations suggests that glaciers evolve until they approach a critical stability threshold where small perturbations can trigger calving events. The stability

  18. 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

  19. 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.

  20. The break-up of a lacustrine floating ice tongue, Yakutat Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Yakutat Glacier has been exposed to calving retreat for more than a century with a total terminus retreat of over 15 km since 1903. This temperate glacier in Southeast Alaska calves into over 300 m deep Harlequin Lake. Cold, non-stratified lake water with uniform temperatures of around 1 °C combined with the large lake depth allowed this glacier to form a 17.2 km2 floating tongue. This floating tongue existed for over a decade between 2000 and 2010. Thinning in this terminus area exceeds 6 m during the summer. Digital elevation model differencing shows annual thinning rates of around 9 m yr-1 in the terminus area with a glacier wide mean of 4.07±0.03 m yr-1 (2007-2010). Calving rates are highly variable with periods of rapid retreat followed by periods of relative stability. The most recent period of rapid retreat began in 2010, when the floating tongue disintegrated into large tabular ice bergs. Those ice bergs calve as crevasses transform into rifts, a process supported by rapid thinning. Once the rifts intersect, large tabular icebergs are able to disconnect from the tongue and float away, generally without rolling over. This episodic style of calving also produces a large number of small ice bergs. Tidewater glaciers in the vicinity of Yakutat Glacier are exposed to a similar climate, but they neither form nor maintain a stable floating tongue, nor do they calve large tabular icebergs, even when retreating into over-deepened basins. We hypothesize that the different calving behavior is caused by the presence or absence of submarine melt as the glacier retreats into an over-deepening. In the case of a tidewater glacier, submarine melt can be large leading to instability and retreat. In a lacustrine system, subaquatic melt is negligible, allowing floating tongues to form. The recent break-up of this floating tongue shows certain similarities to the disintegration of ice shelves in Antarctica, but on a much smaller scale and in temperate ice. To better

  1. Fuzzy Cognitive Maps for Glacier Hazards Assessment: Application to Predicting the Potential for Glacier Lake Outbursts

    NASA Astrophysics Data System (ADS)

    Furfaro, R.; Kargel, J. S.; Fink, W.; Bishop, M. P.

    2010-12-01

    Glaciers and ice sheets are among the largest unstable parts of the solid Earth. Generally, glaciers are devoid of resources (other than water), are dangerous, are unstable and no infrastructure is normally built directly on their surfaces. Areas down valley from large alpine glaciers are also commonly unstable due to landslide potential of moraines, debris flows, snow avalanches, outburst floods from glacier lakes, and other dynamical alpine processes; yet there exists much development and human occupation of some disaster-prone areas. Satellite remote sensing can be extremely effective in providing cost-effective and time- critical information. Space-based imagery can be used to monitor glacier outlines and their lakes, including processes such as iceberg calving and debris accumulation, as well as changing thicknesses and flow speeds. Such images can also be used to make preliminary identifications of specific hazardous spots and allows preliminary assessment of possible modes of future disaster occurrence. Autonomous assessment of glacier conditions and their potential for hazards would present a major advance and permit systematized analysis of more data than humans can assess. This technical leap will require the design and implementation of Artificial Intelligence (AI) algorithms specifically designed to mimic glacier experts’ reasoning. Here, we introduce the theory of Fuzzy Cognitive Maps (FCM) as an AI tool for predicting and assessing natural hazards in alpine glacier environments. FCM techniques are employed to represent expert knowledge of glaciers physical processes. A cognitive model embedded in a fuzzy logic framework is constructed via the synergistic interaction between glaciologists and AI experts. To verify the effectiveness of the proposed AI methodology as applied to predicting hazards in glacier environments, we designed and implemented a FCM that addresses the challenging problem of autonomously assessing the Glacier Lake Outburst Flow

  2. Remote Sensing Characterization of Glaciers in the N. Himachal Pradesh

    NASA Astrophysics Data System (ADS)

    Le, D.; Catania, G. A.

    2012-12-01

    Glaciers in high mountain Asia represent the largest volume of ice outside of the polar regions. They play an important role in the water resources of communities downstream and there has been recent dispute over the total amount of ice present how it is changing. The immense quantity of glaciers and variability of glacier types in the Himalayas coupled with the sparse amount of suitable satellite data limits the capability of conducting detailed and efficient remote sensing observations on a regional scale. This study aims to develop a semi-automated characterization of approximately 5,000 glaciers in the N. Himachal Pradesh region of India using multi-spectral data. We use an August 2002 Landsat 7 Enhanced Thematic Mapper Plus (ETM+) image because of its small percentage of snow and cloud cover, and because it is acquired late in the summer allowing for delineation of ablation and accumulation zones. Glacier outlines from the GLIMS glacier database for this region comprise total glacier area including debris covered ice regions. We outline the accumulation (snow-covered) region for each glacier exploiting the high reflectance value of snow compared to ice and debris. We further outline debris-free, bare-ice using a threshold on a ratio image of ETM+ bands 4 and 5. Subtracting this region from the GLIMS outlines leaves us with the debris-covered ice region. Using our resulting ablation and accumulation areas, we compute the area-accumulation ratio (AAR) for the many glaciers in our region. These data are compared to mean aspect, mean elevation, glacier size, percentage of debris cover, and mean equilibrium line altitude (ELA) for each glacier. This study hopes to contribute to and improve on glacier databases for the Himalayan region and to advance glacier analyses using remote sensing data. A possible future aim is to identify benchmark glaciers which can be used for detailed future study.

  3. Glacier changes in the Karakoram region mapped by multimission satellite imagery

    NASA Astrophysics Data System (ADS)

    Rankl, M.; Kienholz, C.; Braun, M.

    2014-05-01

    Positive glacier-mass balances in the Karakoram region during the last decade have fostered stable and advancing glacier termini positions, while glaciers in the adjacent mountain ranges have been affected by glacier recession and thinning. In addition to fluctuations induced solely by climate, the Karakoram is known for a large number of surge-type glaciers. The present study provides an updated and extended inventory on advancing, stable, retreating, and surge-type glaciers using Landsat imagery from 1976 to 2012. Out of 1219 glaciers the vast majority showed a stable terminus (969) during the observation period. Sixty-five glaciers advanced, 93 glaciers retreated, and 101 surge-type glaciers were identified, of which 10 are new observations. The dimensional and topographic characteristics of each glacier class were calculated and analyzed. Ninety percent of nonsurge-type glaciers are shorter than 10 km, whereas surge-type glaciers are, in general, longer. We report short response times of glaciers in the Karakoram and suggest a shift from negative to balanced/positive mass budgets in the 1980s or 1990s. Additionally, we present glacier surface velocities derived from different SAR (synthetic aperture radar) sensors and different years for a Karakoram-wide coverage. High-resolution SAR data enables the investigation of small and relatively fast-flowing glaciers (e.g., up to 1.8 m day-1 during an active phase of a surge). The combination of multitemporal optical imagery and SAR-based surface velocities enables an improved, Karakoram-wide glacier inventory and hence, provides relevant new observational information on the current state of glaciers in the Karakoram.

  4. Temporal genetic analysis of the endangered tidewater goby: extinction-colonization dynamics or drift in isolation?

    PubMed

    Kinziger, Andrew P; Hellmair, Michael; McCraney, W Tyler; Jacobs, David K; Goldsmith, Greg

    2015-11-01

    Extinction and colonization dynamics are critical to understanding the evolution and conservation of metapopulations. However, traditional field studies of extinction-colonization are potentially fraught with detection bias and have rarely been validated. Here, we provide a comparison of molecular and field-based approaches for assessment of the extinction-colonization dynamics of tidewater goby (Eucyclogobius newberryi) in northern California. Our analysis of temporal genetic variation across 14 northern California tidewater goby populations failed to recover genetic change expected with extinction-colonization cycles. Similarly, analysis of site occupancy data from field studies (94 sites) indicated that extinction and colonization are very infrequent for our study populations. Comparison of the approaches indicated field data were subject to imperfect detection, and falsely implied extinction-colonization cycles in several instances. For northern California populations of tidewater goby, we interpret the strong genetic differentiation between populations and high degree of within-site temporal stability as consistent with a model of drift in the absence of migration, at least over the past 20-30 years. Our findings show that tidewater goby exhibit different population structures across their geographic range (extinction-colonization dynamics in the south vs. drift in isolation in the north). For northern populations, natural dispersal is too infrequent to be considered a viable approach for recolonizing extirpated populations, suggesting that species recovery will likely depend on artificial translocation in this region. More broadly, this work illustrates that temporal genetic analysis can be used in combination with field data to strengthen inference of extinction-colonization dynamics or as a stand-alone tool when field data are lacking. PMID:26460923

  5. Tidewater and Weather-exposure Tests on Metals Used in Aircraft

    NASA Technical Reports Server (NTRS)

    Mutchler, Willard; Galvin, W G

    1939-01-01

    Tidewater and weather-exposure tests on various aluminum alloys, magnesium alloys, and stainless steels are now being conducted by the National Bureau of Standards. Exposures were begun in June 1938 and, according to present plans, are to continue over a 3-year period. The methods of exposure and the materials being investigated are described and the more important results obtained up to the conclusion of the first year's exposure are reported.

  6. Norwegian mountain glaciers in the past, present and future

    NASA Astrophysics Data System (ADS)

    Nesje, Atle; Bakke, Jostein; Dahl, Svein Olaf; Lie, Øyvind; Matthews, John A.

    2008-01-01

    Documentation of glacier changes is a key element for reconstruction of past climate variability and early detection of global climate change. In this paper, records of Holocene glacier variations in different regions in Norway have been synthesised. During the period from approximately 8000 to 4000 cal. yr BP, most glaciers in Norway were completely melted away at least once due to high summer temperatures and/or reduced winter precipitation. Lichenometrically and historically dated moraines at Jostedalsbreen, in Jotunheimen, at Hardangerjøkulen, and at Folgefonna were used to extend records of glacier length variations back to their maximum position during the 'Little Ice Age'. The timing of the maximum 'Little Ice Age' glacial advance in different parts of southern Norway varied considerably, ranging from the early 18th century to the late 19th century. Cumulative glacier length variations of glaciers in southern Norway show an overall retreat from ˜ AD 1750 to the 1930s-40s. Thereafter, most Norwegian glaciers retreated significantly. Short maritime outlet glaciers with a short response time (< 10-15 yr) started to advance in the mid-1950s, whereas long outlet glaciers with longer frontal time lag (> 15-20 yr) continued their retreat to the 1980s. In the 1990s, however, several of the maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s. Since 2000 most of the observed glaciers have retreated remarkably fast (annual frontal retreat > 100 m) mainly due to high summer temperatures. The last glacier inventory in Norway published in 1988 shows that there were 1627 glaciers covering a total area of 2609 km 2 with an estimated volume of 164 km 3. Modern climate-glacier relationships from mass balance data in Scandinavia have been used to present possible effects on the Norwegian glaciers of climate scenarios between 1961-1990 and 2070-2100 presented by the 'RegClim' project. This long-term weather

  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. Glacier Change and Biologic Succession: a new Alaska Summer Research Academy (ASRA) Science Camp Module for Grades 8-12 in Glacier Bay National Park, Alaska

    NASA Astrophysics Data System (ADS)

    Connor, C. L.; Drake, J.; Good, C.; Fatland, R.; Hakala, M.; Woodford, R.; Donohoe, R.; Brenner, R.; Moriarty, T.

    2008-12-01

    During the summer of 2008, university faculty and instructors from southeast Alaska joined the University Alaska Fairbanks(UAF)Alaska Summer Research Academy(ASRA)to initiate a 12-day module on glacier change and biologic succession in Glacier Bay National Park. Nine students from Alaska, Colorado, Massachusetts, and Texas, made field observations and collected data while learning about tidewater glacier dynamics, plant succession, post-glacial uplift, and habitat use of terrestrial and marine vertebrates and invertebrates in this dynamic landscape that was covered by 6,000 km2 of ice just 250 years ago. ASRA students located their study sites using GPS and created maps in GIS and GOOGLE Earth. They deployed salinometers and temperature sensors to collect vertical profiles of seawater characteristics up-bay near active tidewater glacier termini and down-bay in completely deglaciated coves. ASRA student data was then compared with data collected during the same time period by Juneau undergraduates working on the SEAMONSTER project in Mendenhall Lake. ASRA students traversed actively forming, up-bay recessional moraines devoid of vegetation, and the fully reforested Little Ice Age terminal moraine near Park Headquarters in the lower bay region. Students surveyed marine organisms living between supratidal and subtidal zones near glaciers and far from glaciers, and compared up-bay and down-bay communities. Students made observations and logged sightings of bird populations and terrestrial mammals in a linear traverse from the bay's northwestern most fjord near Mt. Fairweather for 120 km to the bay's entrance, south of Park Headquarters at Bartlett Cove. One student constructed an ROV and was able to deploy a video camera and capture changing silt concentrations in the water column as well as marine life on the fjord bottom. Students also observed exhumed Neoglacial spruce forests and visited outcrops of Silurian reef faunas, now fossilized in Alexander terrane

  9. 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.

  10. 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)

  11. Partitioning of Submarine Melt and Calving across the front of Store Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Hubbard, A., II; Chauche, N.

    2015-12-01

    Processes unique to the marine-termini of fast-flowing tidewater outlet glaciers can potentially drive extreme rates of mass wastage thereby providing a rapid link between the terrestrial ice reservoir and the oceanic sink. Here we attempt to directly quantify the pattern and magnitude of calving and melt at the front of Store Glacier, a major outlet draining the western sector of the Greenland ice sheet. Integration of range-survey technologies on a robust, heavy displacement marine platform coupled with high-resolution photogrammetry allowed the production of accurate, ~m resolution 3d digital terrain models (DTMs) of the glacier front. A swath-interferometric sonar system calibrated via an inertial motion unit stabilized with RTK GPS and vector-compass data-streams was combined with photogrammetric processing of repeat UAV surveys. The results of three repeat surveys across the front of Store Glaciers in 2012 is presented during which significant ice flow, melt and calving events were imaged, complimented with AWS, on-ice GPS stations and time-lapse/video camera sequences. The residual of successive DTMs yield the 3d pattern of frontal change allowing the processes calving and melt to be quantified and constrained in unprecedented detail. The pattern of submarine melt is further validated against indirect estimates of submarine melt derived from oceanographic circulation measurements within the fjord.

  12. Mass changes of outlet glaciers along the Nordensjköld Coast, northern Antarctic Peninsula, based on TanDEM-X satellite measurements

    NASA Astrophysics Data System (ADS)

    Rott, Helmut; Floricioiu, Dana; Wuite, Jan; Scheiblauer, Stefan; Nagler, Thomas; Kern, Michael

    2014-11-01

    We analyzed volume change and mass balance of outlet glaciers of the northern Antarctic Peninsula over the period 2011 to 2013, using topographic data of high vertical accuracy and great spatial detail, acquired by bistatic radar interferometry of the TanDEM-X/TerraSAR-X satellite formation. The study area includes glaciers draining into the Larsen-A, Larsen Inlet, and Prince-Gustav-Channel embayments. After collapse of buttressing ice shelves in 1995 the glaciers became tidewater calving glaciers and accelerated, resulting in increased ice export. Downwasting of most glaciers is going on, but at reduced rates compared to previous years in accordance with deceleration of ice flow. The rate of mass depletion is 4.2 ± 0.4 Gt a-1, with the largest contribution by Drygalski Glacier amounting to 2.2 ± 0.2 Gt a-1. On the technological side, the investigations demonstrate the capability of satellite-borne single-pass radar interferometry as a new tool for accurate and detailed monitoring of glacier volume change.

  13. 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

  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. 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

  16. 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.

  17. Calving processes and the dynamics of calving glaciers

    NASA Astrophysics Data System (ADS)

    Benn, Douglas I.; Warren, Charles R.; Mottram, Ruth H.

    2007-06-01

    and velocity distribution. Realistic solutions to the problem of modelling ice flow therefore depend critically on an appropriate choice of sliding law. Models that assume that basal velocities are controlled by basal drag can replicate much of the observed behaviour of calving glaciers with grounded termini, but an important limitation is that they cannot be used to model floating glacier termini or ice shelves. Alternative sliding laws that parameterise drag from the glacier margins provide more flexible and robust ways of representing calving in ice sheet models. Such models can explain a remarkable range of observed phenomena within a simple, unifying framework, including: downglacier increases in velocity and strain rates where basal and/or lateral drag diminishes; flow acceleration in response to thinning through time; the tendency for glaciers to stabilise at 'pinning points' in relatively shallow water or fjord narrowings; the constraints on ice shelf stability; and the contrasts in calving rates between tidewater and freshwater calving glaciers. Many unresolved issues remain, however, including the role played by the removal of backstress in the acceleration of retreating calving glaciers, and the controls on melting at and below the waterline.

  18. Climatic Significance of Holocene Glacier Fluctuations in New Zealand

    NASA Astrophysics Data System (ADS)

    Doughty, A. M.; Mackintosh, A. N.; Anderson, B. A.; Putnam, A. E.; Barrell, D.; Denton, G.; Schaefer, J. M.

    2012-12-01

    Holocene glacier fluctuations in New Zealand are represented by well-preserved moraine complexes in the Southern Alps. Recent cosmogenic dating of Holocene moraine sequences has allowed for interhemispheric comparisons of glacier advances and hence climate change. However, Balco (2009, Science, v 324, p 599-600) and others have asked "Can the timing and magnitude of observed past glacier changes in a particular region be explained by stochastic variability inherent in a steady climate, or is a change in the mean climate required?" To understand better the link between glaciers and climate during the Holocene, we evaluate possible past climate parameters by simulating ice extent at several well-preserved moraines deposited by the Cameron Glacier in the Arrowsmith Range, Southern Alps, New Zealand. We use a coupled 2-D ice-flow and distributed energy balance model with a snow transport component, the latter of which is necessary because, in its present-day configuration, this glacier receives a component of its accumulation from frequent snow avalanches. In our first experiment, we use steady-state simulations to identify the temperature and precipitation forcing required to fit the modelled Cameron Glacier to each of the geomorphically-defined moraine ridges. In our second experiment, we forced the glacier model with a time series of stochastic climate forcing that excludes a background temperature change. We discuss results of these tests, which permit assessment of the sensitivity and response of the Cameron Glacier to different modes of climate variability.

  19. Do Glaciers on Cascade Volcanoes Behave Differently Than Other Glaciers in the Region?

    NASA Astrophysics Data System (ADS)

    Riedel, J. L.; Ryane, C.; Osborn, J.; Davis, T.; Menounos, B.; Clague, J. J.; Koch, J.; Scott, K. M.; Reasoner, M.

    2006-12-01

    It has been suggested that glaciers on two stratovolcanoes in the Cascade Range of Washington state, Mt. Baker and Glacier Peak, achieved their maximum extent of the past 10,000 years during the early Holocene. These findings differ from most evidence in western North America, which indicates that Little Ice Age moraines represent the most extensive glacier advances of the Holocene. Significant early Holocene advances are difficult to reconcile with the documented warm, dry conditions at this time in western North America. Our data indicate that glaciers on these volcanoes responded similarly to Holocene climatic events as glaciers in other areas in Washington and British Columbia. Heavy winter accumulation and favorable hypsometry have been proposed as the explanations for the unusual behavior of glaciers on volcanoes compared to similar-sized glaciers elsewhere in the Cascade Range. However, glacier mass balance on the volcanoes is controlled by not only these factors, but also by glacier geometry, snow erosion and ablation. Accumulation zones of glaciers on isolated Cascade stratovolcanoes are high, but are narrow at the top. For example, the accumulation zone of Deming Glacier on the southwest side of Mt. Baker extends above 3000 m asl, but due to its wedge shape lies largely below 2500 m asl. Furthermore, glaciers on Mt. Baker and other symmetrical volcanoes have high ablation rates because they are not shaded, and south-southwest aspects are subject to erosion of snow by prevailing southwesterly winds. Modern glacier observations in the North Cascades quantify the important influence of aspect and snow erosion on glacier mass balance. For example, average equilibrium line altitude (ELA) of Easton Glacier on the south flank of Mt. Baker is 2160 m, whereas the ELA of a north-facing cirque glacier 25km to the east is 2040m. Our research at Mt. Baker contradicts the claim of extensive early Holocene advances on the south flank of the volcano. Tephra set SC, which

  20. Tidewater and Weather-exposure Tests on Metals Used in Aircraft II.

    NASA Technical Reports Server (NTRS)

    Mutchler, Willard; Galvin, W G

    1942-01-01

    This report is an addendum to NACA Technical Note No. 736, which dealt with tidewater and weather-exposure tests being conducted by the National Bureau of Standards on various aluminum alloys, magnesium alloys, and stainless steels used in aircraft. The exposures were begun in June 1938 and were terminated, for this particular series, in June 1941. The methods of exposure and the materials being investigated are described, and the more important results obtained up to the conclusion of the second year's exposure are reported.

  1. 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

  2. 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

  3. Modeling debris-covered glaciers: extension due to steady debris input

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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, mass balance gradients can be 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 advection. We ran 120 simulations in which a 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. Our model and parameter selections produce two-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. 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). The model reproduces first-order relationships between debris cover, AARs, and glacier surface velocities from glaciers in High Asia. 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.

  4. Combined Datasets From GPS, Raised Shorelines, Tide Gauges and Glacier Volume Changes Used to Differentiate Between GIA, Elastic Rebound and Tectonics in Glacier Bay, Alaska.

    NASA Astrophysics Data System (ADS)

    Larsen, C. F.; Motyka, R.; Elliott, J. L.; Freymuller, J. T.; Echelmeyer, K. A.; Ivins, E. R.

    2006-12-01

    Eight years of GPS observations show uplift rates of 10 to 32 mm/yr over a large area of southeast Alaska, with the fastest rates observed in upper Glacier Bay and to the east of Yakutat. Rates of relative sea level (RSL) change at several tide gauges in the region are among the fastest anywhere and indicate steady sea level fall over the past 100 yrs. Studies of raised shorelines at 32 sites throughout the region also show rapid RSL changes of up to 5.7 m over the last 250 yrs. Both the RSL and the GPS data show the greatest uplift surrounding areas of post-Little Ice Age (LIA) deglaciation. Following the LIA, a tidewater retreat unloaded over 3000 Gt of ice from Glacier Bay. Ongoing ice loss from mountain glacier wastage is constrained with laser altimetry and the SRTM DEM. A narrow range of viscoelastic rebound models is capable of completely accounting for the rapid uplift observed by these three data types when the load models are constrained by the observed and modeled ice loss of the region. If, however, only the GPS data were available, a much wider range of earth models would be able to reproduce the observations. This clearly illustrates the advantage of multiple datasets. In addition to new observations from our continuing GPS surveys, we will present new modeling results which examine the combined tectonic and GIA signatures in the horizontal GPS velocity field across this rapidly deforming plate boundary.

  5. 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.

  6. 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.

  7. 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.

  8. A High-Resolution Sensor Network for Monitoring Glacier Dynamics

    NASA Astrophysics Data System (ADS)

    Edwards, S.; Murray, T.; O'Farrell, T.; Rutt, I. C.; Loskot, P.; Martin, I.; Selmes, N.; Aspey, R.; James, T.; Bevan, S. L.; Baugé, T.

    2013-12-01

    adoption of beacon based time division multiple access (tdma). In-house single-epoch GNSS processing software provides 1-2 cm coordinate time-series capable of detecting a major calving event during the 2012 pilot study. These data can be synthesised with other remotely sensed data e.g. airborne lidar, oblique photogrammetry and TanDEM-X satellite imagery derived DEMs giving an opportunity to fine-tune glacial models delivering a deeper understanding of the contribution to sea-level rise made by tidewater glaciers such as Helheim. The flexibility of our network would make it suitable for deployment in other extreme environments such as areas at risk from earthquakes and landslides.

  9. 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.

  10. Evaluating glacier volume changes since the Little Ice Age maximum and consequences for stream flow by integrating models of glacier flow and hydrology in the Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Huh, K. I.; Mark, B. G.; Baraer, M.; Ahn, Y.

    2014-12-01

    Assessing the historical contribution of glacier ice volume loss to stream flow based on reconstructed volume changes through Little Ice Age (LIA) can be directly related to the understanding of glacier-hydrology in the current epoch of rapid glacier ice loss that has disquieting implications for water resources in the Cordillera Blanca of the Peruvian Andes. However, the accurate prediction of the future glacial meltwater availability for the increasing regional Andean society needs more extensive quantitative estimation from long-term glacial meltwater of reconstructed glacial volume. Modeling LIA paleoglaciers using a cellular automata glacier flow model in different catchments of the Cordillera Blanca allows us to reconstruct glacier volume and its change from likely combinations of climatic control variables and time. We compute the rate and magnitude of glacier volume changes for Yanamarey and Queshque glaciers between the LIA and modern defined by 2011 Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model Version 2 (GDEM V2) from the Cordillera Blanca. Also, we employ a recently demonstrated hydrological stream model (Baraer et al., 2012) for integrating the reconstructed glacier volume and its change to calculate glacier contribution to meltwater runoff as a function of glacier loss rate in the Yanamarey and the Queshque catchments, and reconstruct long-term glacier significance to stream flow.

  11. Glacier response to North Atlantic climate variability during the Holocene

    NASA Astrophysics Data System (ADS)

    Balascio, N. L.; D'Andrea, W. J.; Bradley, R. S.

    2015-12-01

    Small glaciers and ice caps respond rapidly to climate variations, and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation. However, there is only sparse and fragmentary evidence for higher-frequency variations in glacier size because in many Northern Hemisphere regions glacier advances of the past few hundred years were the most extensive and destroyed the geomorphic evidence of ice growth and retreat during the past several thousand years. Thus, most glacier records have been of limited use for investigating centennial-scale climate forcing and feedback mechanisms. Here we report a continuous record of glacier activity for the last 9.5 ka from southeast Greenland derived from high-resolution measurements on a proglacial lake sediment sequence. Physical and geochemical parameters show that the glaciers responded to previously documented Northern Hemisphere climatic excursions, including the "8.2 ka" cooling event, the Holocene Thermal Maximum, Neoglacial cooling, and 20th century warming. In addition, the sediments indicate centennial-scale oscillations in glacier size during the late Holocene. Beginning at 4.1 ka, a series of abrupt glacier advances occurred, each lasting ~100 years and followed by a period of retreat, that were superimposed on a gradual trend toward larger glacier size. Thus, while declining summer insolation caused long-term cooling and glacier expansion during the late Holocene, climate system dynamics resulted in repeated episodes of glacier expansion and retreat on multi-decadal to centennial timescales. These episodes coincided with ice rafting events in the North Atlantic Ocean and periods of regional ice cap expansion, which confirms their regional significance and indicates that considerable glacier activity on these timescales is a normal feature of

  12. From valley to marginal glaciation in alpine-type relief: Lateglacial glacier advances in the Pięć Stawów Polskich/Roztoka Valley, High Tatra Mountains, Poland

    NASA Astrophysics Data System (ADS)

    Zasadni, Jerzy; Kłapyta, Piotr

    2016-01-01

    The Pięć Stawów Polskich-Roztoka Valley in the High Tatras (Western Carpathians) features typical alpine-type relief with a deeply incised glacial trough and large, compound trough head cirque. The prominent hypsographic maximum in the valley (1680-2000 m) along with a broad cirque bottom had provided a vast space for recording glacial and periglacial landforms, specifically the most recent Lateglacial advances. The valley has been intensively studied before in the context of glacial chronology. In this paper, we re-establish the post-Last Glacial Maximum (LGM) glacial chronology of the valley via detailed geomorphologic mapping, equilibrium line altitude (ELA) reconstruction, and Schmidt hammer (SH) dating, along with a critical review of previously published cosmogenic exposure age data (36Cl) and lacustrine sediment chronology. Our results indicate that the first four of the five distinguished Lateglacial stages (Roztoka I-III, Pusta I) occurred before the Bølling/Allerød (B/A) interstadial; thus, virtually the entire valley became deglaciated in course of the Oldest Dryas cold phase. A distinct reorganization of deglacial patterns from valley-type to marginal-type occurred before B/A warming when the ELA increased above the valley hypsographic maximum concentrated at the cirque bottom elevation. It shows that noticeable deglaciation step can be caused due to topographic reason with a minimal climate forcing. This points also to an important role of glaciated valley hypsography in regulating the distribution of moraines which is rarely taken into account in paleoglaciological reconstructions. We infer that glaciers vanished in the Tatra Mountains during the B/A interstadial. Later, a renewed advance during the Younger Dryas (Pusta II) formed a nearly continuous, festoon shaped pattern of moraines and rock glaciers in close distance to cirque backwalls. Furthermore, we discus some paleoenvironmental significance of the geomorphological record in the valley

  13. The Status of Glaciers in the Hindu Kush-Himalayas from satellite data

    NASA Astrophysics Data System (ADS)

    Bajracharya, S. R.; Maharjan, S.; Shrestha, F.; Shrestha, B.; Wanqin, G.; Shiyin, L.; Xiaojun, Y.; Khattak, G. A.

    2011-12-01

    In contrary to general glacier retreat in this vast Hindu Kush-Himalayan (HKH) region, some of the glaciers are advancing in the Karakorum (Hewitt, 1985). To understand the climate change impacts on glaciers, it is crucial to update the glacier status. The bigger concern in the HKH region, however, is the lack of long-term information on glaciers at the regional level for any kind of credible baseline or assessment of change. Hence to provide the up to date glacier information the glacier inventory was carried out using a single source satellite images of latest date so far possible. The present mapping of glaciers is the first effort of homogeneous glacier inventory of entire Hindu Kush-Himalayan region, which made the first time reporting of glaciers from Myanmar and first generation of glacier mapping and inventory of Afghanistan and Jammu & Kashmir and Arunachal states of India for ICIMOD. For Nepal, Bhutan, Pakistan, some states of India (Himachal, Uttarakhand and Sikkim) and Ganges basin in China will be the second generation glacier mapping and inventory of ICIMOD. The inventory is based on Landsat 7 ETM+ satellite images from 2005±3 years and SRTM DEM. The methodology of semi-automatic mapping and inventory is developed and implemented in the present study for quick delivery of glacier database. A first attempt is also made to map and deliver the Clean Ice and Debris Cover glaciers data separately. The glacier parameters like Glacier ID (Watershed and GLIMS), Area (Debris Cover and Clean Ice), Elevation, Slope, Aspect, Thickness, Ice reserve and 100m Glacier Area-Altitude bins are generated. The glaciers with sizes larger than 0.02 km2 are mapped. From the entire HKH region about 54,800 glaciers are mapped with about 60,400 km2 glacier area and 6,100 km3 estimated ice reserves. It was found that the average glacier area of the HKH region is 1.10 km2 per glacier (Bajracharya and others 2011).

  14. Chronology of a Small Glacier in Eastern British Columbia, Canada.

    PubMed

    Bray, J R

    1964-04-17

    The age of trees growing on the moraines of a small, high-altitude glacier in the Canadian Rockies suggests that the date of the maximum post-Pleistocene ice advance was around A.D. 1714, with another later advance about 1832. These two dates are synchronous with the two major periods of recent ice advance in the area. PMID:17752569

  15. Identifying surging glaciers in the Central Karakoram for improved climate change impact assessment

    NASA Astrophysics Data System (ADS)

    Paul, Frank; Bolch, Tobias; Mölg, Nico; Rastner, Philipp

    2015-04-01

    Several recent studies have investigated glacier changes in the Karakoram mountain range, a region where glaciers behave differently (mass gain and advancing tongues) compared to most other regions in the world. Attribution of this behaviour to climate change is challenging, as many glaciers in the Karakoram are of surge type and have actively surged in the recent past. The measured changes in length, area, volume or velocity in this region are thus depending on the time-period analysed and include non-climatic components. Hence, a proper analysis of climate change impacts on glaciers in this region requires a separation of the surging from the non-surging glaciers. This is challenging as the former often lack the typical surface characteristics such as looped moraines (e.g. when they are steep and small) and/or they merge (during a surge) with a larger non-surging glacier and create looped moraines on its surface. By analysing time series of satellite images that are available since 1961, the heterogeneous behaviour of glaciers in the Karakoram can be revealed. In this study, we have analysed changes in glacier terminus positions in the Karakoram over different time periods from 1961 to 2014 for several hundred glaciers using Corona KH-4 and KH-4B, Hexagon KH-9, Terra ASTER, and Landsat MSS, TM, ETM+ and OLI satellite data. For the last 15 years, high-speed animations of image time-series reveal details of glacier flow and surge dynamics that are otherwise difficult to detect. For example, several of the larger glaciers with surging tributaries (e.g. Panmah, Sarpo Laggo, Skamri, K2 glacier) are stationary and downwasting despite the mass contributions from the surging glaciers. The analysis of the entire time series reveals a complex pattern of changes through time with retreating, advancing, surging and stationary glaciers that are partly regionally clustered. While most of the non-surging glaciers show only small changes in terminus position (±100 m or less

  16. 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

  17. 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

  18. 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

  19. Timescale dependence of glacial erosion rates: A case study of Marinelli Glacier, Cordillera Darwin, southern Patagonia

    NASA Astrophysics Data System (ADS)

    Fernandez, Rodrigo A.; Anderson, John B.; Wellner, Julia S.; Hallet, Bernard

    2011-03-01

    Erosion rates have been estimated for a number of glaciated basins around the world, mostly based on modern observations (last few decades) of sediment fluxes to fjords. We use time-constrained sediment volumes delivered by Marinelli Glacier (55°S), an outlet glacier of the Cordillera Darwin ice cap, southern Patagonian Andes, Tierra del Fuego, to determine erosion rates across different timescales. Sediment volumes are derived using a dense grid of high- and low-frequency single channel seismic data and swath bathymetry data along with piston and Kasten cores. Our results show dramatic differences in erosion rates over different timescales. Erosion rates at Marinelli Glacier diminish about 80% (or by factor of ˜5) with each ten-fold increase in the time span over which erosion rates are averaged: 29.3 mm/yr for the last 45 years, 5.3 mm/yr for the last 364 years, and 0.5 mm/yr for the last 12,500 years. These results indicate that modern sediment yields and erosion rates from temperate tidewater glaciers can exceed long-term values over the time of deglaciation after the Last Glacial Maximum (centennial and millennial timescales) by up to 2 orders of magnitude. In view of the low exhumation rates of Cordillera Darwin (˜0.07 mm/yr average for the last 30 Myr), modern erosion rates could be up to 3 orders of magnitude higher than rates over geological time. We conclude that the pattern of erosion rate variation with time reflects the sensitivity of glaciers to climate variability.

  20. 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

  1. The response of debris-covered glaciers to climate change: A numerical modeling approach

    NASA Astrophysics Data System (ADS)

    Anderson, Leif S.; Anderson, Robert S.

    2016-04-01

    Debris-covered glaciers are common in rapidly-eroding alpine landscapes. When thicker than a few centimeters, surface debris suppresses melt rates. Continuous debris cover can therefore reduce the mass balance gradient in the ablation zone, leading to increases in glacier length. In order to quantify feedbacks in the debris-glacier-climate system, we developed a 2D long-valley numerical glacier model that includes deposition of debris on the glacier surface, and both englacial and supraglacial debris advection. We ran 120 simulations in which a steady state debris-free glacier responds to a step increase of surface debris deposition. Simulated glaciers advance to new steady states in which ice accumulation equals ice ablation, and debris input equals debris loss from the glacier. The debris flux onto the glacier surface, and the details of 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. Continuous debris cover reduces ice discharge gradients, ice thickness gradients, and velocity gradients relative to debris-free glaciers forced by the same climate. Debris-forced glacier extension decreases the ratio of accumulation zone to total glacier area (AAR). The model reproduces first-order relationships between debris cover, AARs, and glacier surface velocities reported from glaciers in High Asia. We also explore the response of debris-covered glaciers to increases in the equilibrium-line altitude (climate warming). We highlight the conditions required to generate a low surface velocity 'dead' ice terminal reach during a warming climate, and the associated increase of fractional glacier surface debris. We also compare our debris-covered glacier climate response results with data from glaciers in High Asia. Our model provides a quantitative, theoretical

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 4300-Year Old 'Glacier Forests', Southern Coast Mountains, British Columbia and their Global Context

    NASA Astrophysics Data System (ADS)

    Koch, J.

    2014-12-01

    Dendrochronology and radiocarbon dating of in situ and detrital wood have been utilized to date Holocene glacier fluctuations in Garibaldi Provincial Park and at the Pemberton Icefield in the southern Coast Mountains of British Columbia. Fieldwork at over 30 glaciers has been carried out since 2002. The focus of this paper is on wood that has been radiocarbon dated between 4500 and 4000 years ago, which has been found at six glaciers. At four glaciers the wood was washing out from beneath present-day glacier snouts. At Helm Glacier in Garibaldi Park thirteen detrital branches and stumps were recovered, and at West Squamish Glacier at the Pemberton Icefield seven detrital branches, stems, and stumps were sampled. Some of these samples had diameters of up to 40 cm and were up to 250 cm long, and thus are much larger than any living trees near the present treeline. Tree-ring analysis shows that these glaciers advanced into and over mature forests that had grown near present-day glacier margins for at least 135 years (Helm) and 357 years (W Squamish). Evidence for permanent snow and ice patches forming, as well as glaciers advancing beyond present-day extents at this time is found in the central Coast Mountains, Yukon Territory, Arctic Canada, Norway, and the Swiss Alps. Glacier advances of similar age have been reconstructed not only in western Canada, but also in Europe, Asia, South America, New Zealand, and Antarctica indicating the global nature of this event. A peak in ice-rafted debris in the North Atlantic about 4200 years ago may have been the result of reduced solar output, and based on Earth's position in the obliquity cycle glaciers should have started to expand 4000 years ago. These 'glacier forests' thus could provide a probable start date for Neoglaciation.

  7. 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.

  8. Ocean properties, ice-ocean interactions, and calving front morphology at two major west Greenland glaciers

    NASA Astrophysics Data System (ADS)

    Chauché, N.; Hubbard, A.; Gascard, J.-C.; Box, J. E.; Bates, R.; Koppes, M.; Sole, A.; Patton, H.

    2013-11-01

    Warm sub-polar mode water (SPMW) has been identified as a primary driver of mass loss of marine terminating glaciers draining the Greenland Ice Sheet (GrIS) yet, the specific mechanisms by which SPMW interacts with these tidewater termini remain uncertain. We present oceanographic data from Rink Glacier (RG) and Store Glacier (SG) fjords, two major marine outlets draining the western sector of the GrIS into Baffin Bay over the contrasting melt-seasons of 2009 and 2010. Submarine melting occurs wherever ice is in direct contact with warmer water and the consistent presence of 2.8 °C SPMW adjacent to both ice fronts below 400 m throughout all surveys indicates that melting is maintained by a combination of molecular diffusion and large scale, weak convection, diffusional (hereafter called ubiquitous) melting. At shallower depths (50-200 m), cold, brine-enriched water (BEW) formed over winter appears to persist into the summer thereby buffering this melt by thermal insulation. Our surveys reveal four main modes of glacier-ocean interaction, governed by water depth and the rate of glacier runoff water (GRW) injected into the fjord. Deeper than 200 m, submarine melt is the only process observed, regardless of the intensity of GRW or the depth of injection. However, between the surface and 200 m depth, three further distinct modes are observed governed by the GRW discharge. When GRW is weak (≲1000 m3 s-1), upward motion of the water adjacent to the glacier front is subdued, weak forced or free convection plus diffusional submarine melting dominates at depth, and seaward outflow of melt water occurs from the glacier toe to the base of the insulating BEW. During medium intensity GRW (∼1500 m3 s-1), mixing with SPMW yields deep mixed runoff water (DMRW), which rises as a buoyant plume and intensifies local submarine melting (enhanced buoyancy-driven melting). In this case, DMRW typically attains hydrostatic equilibrium and flows seaward at an intermediate depth of

  9. Multiple Glacial Advance and Retreat Cycles Preserved in Yakutat Bay, Southern Alaska: Potential for Constraining Cordilleran Ice Sheet and Southern Alaskan Climate Histories

    NASA Astrophysics Data System (ADS)

    Willems, B. A.; Gulick, S. P.; Powell, R. D.; Jaeger, J. M.; Cowan, E. A.

    2005-12-01

    Determining the timing and extent of past advances of temperate tidewater glaciers can be difficult. However, identifying and constraining such advances in the sedimentary record is necessary for understanding local, regional or global climate change. Disenchantment and Yakutat Bays fronting the Hubbard Glacier, southern Alaska, were the focus of two geophysical surveys in 2004. These studies aimed to more accurately determine the history of sediment fluxes, advances and retreats of Hubbard Glacier, and how these processes may relate to climatic oscillations. One survey collected high-resolution, deep-tow boomer (Huntec) sub-bottom profiles and piston cores, whereas the other survey recorded a high-resolution, deeper penetrating (ca.3600ms vs. ca.100ms TWT with boomer), single GI-gun profile up Yakutat and Disenchantment Bays as well as swath maps with associated Chirp profiles, and jumbo piston cores. Together, the data provide a better understanding of Late Quaternary to Holocene sedimentation of the area. The Huntec record is valuable when evaluating Holocene sedimentary fluxes and processes. Several facies occur within the record, which have been interpreted as representing sediment debris flows and turbidity currents. This record also demonstrates the extent and frequency of large scale flooding events within the bay, such as those recorded in 1986 and 2002. Multiple glacial advance/retreat sequences have been interpreted from the GI-gun profile. Each sequence is primarily recognized by an unconformity (Glacial Erosion Surface) that is commonly overlain by 3 seismic facies. The basal ice-contact facies, which also commonly include morainal bank forms, has low-amplitude, chaotic reflections. The middle facies has slightly stratified to hummocky reflections interpreted as ice-proximal facies. The upper facies has highly stratified, continuous, high frequency reflections representing ice-distal conditions. Two or more retrogressive retreat sequences occur up

  10. Area and Elevation Changes of a Debris-Covered Glacier and a Clean-Ice Glacier Between 1952-2013 Using Aerial Images and Structure-from-Motion

    NASA Astrophysics Data System (ADS)

    Lardeux, P.; Glasser, N. F.; Holt, T.; Irvine-Fynn, T. D.; Hubbard, B. P.

    2015-12-01

    Since 1952, the clean-ice Glacier Blanc has retreated twice as fast as the adjacent debris-covered Glacier Noir. Located in the French Alps and separated by only 1 km, both glaciers experience the same climatic conditions, making them ideal to evaluate the impact of debris cover on glacier evolution. We used aerial photographs from 16 acquisitions from 1952 to 2013 to reconstruct and analyze glacier elevation changes using Structure-from-Motion (SfM) techniques. Here, we present the process of developing sub-metric resolution digital elevation models (DEMs) from these aerial photographs. By combining 16 DEMs, we produced a dataset of elevation changes of Glacier Noir and Glacier Blanc, including time-series analysis of lateral and longitudinal profiles, glacier hypsometry and mass balance variation. Our preliminary results indicate that Glacier Noir and Glacier Blanc have both thinned to a similar magnitude, ≤ 20 m, despite a 1 km retreat for Glacier Blanc and only 500 m for Glacier Noir. However, these elevation change reconstructions are hampered by large uncertainties, principally due to the lack of independent camera calibration on the historical imagery. Initial attempts using posteriori correction grids have proven to significantly increase the accuracy of these data. We will present some of the uncertainties and solutions linked to the use of SfM on such a large scale and on such an old dataset. This study demonstrates how SfM can be used to investigate long-term trends in environmental change, allowing glacier monitoring to be up-scaled. It also highlights the need for on-going validation of methods to increase the accuracy and precision of SfM in glaciology. This work is not only advancing our understanding of the role of the debris layer, but will also aid glacial geology more generally with, for example, detailed geomorphological analysis of proglacial terrain and Quaternary sciences with quick and accurate reconstruction of a glacial paleo-environment.

  11. Multitemporal Landsat multispectral scanner and thematic mapper data of the Hubbard Glacier region, southeast Alaska

    USGS Publications Warehouse

    Walker, K.-M.; Zenone, C.

    1988-01-01

    In late May 1986, the advancing Hubbard Glacier blocked the entrance to Russell Fiord near Yakutat, Alaska, creating a large ice-dammed lake. Runoff from the surrounding glaciated mountains raised the level of the lake to about 25 m above sea level by 8 October, when the ice dam failed. Remote sensing offers one method to monitor this large tidal glacier system, particularly the glacier activity that would portend the re-closure of Russell Fiord. -Authors

  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. Pine Island Glacier

    Atmospheric Science Data Center

    2013-04-16

    ... 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 ...

  14. 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.

  15. Seabed corrugations beneath an Antarctic ice shelf revealed by autonomous underwater vehicle survey: Origin and implications for the history of Pine Island Glacier

    NASA Astrophysics Data System (ADS)

    Graham, Alastair G. C.; Dutrieux, Pierre; Vaughan, David G.; Nitsche, Frank O.; Gyllencreutz, Richard; Greenwood, Sarah L.; Larter, Robert D.; Jenkins, Adrian

    2013-09-01

    Ice shelves are critical features in the debate about West Antarctic ice sheet change and sea level rise, both because they limit ice discharge and because they are sensitive to change in the surrounding ocean. The Pine Island Glacier ice shelf has been thinning rapidly since at least the early 1990s, which has caused its trunk to accelerate and retreat. Although the ice shelf front has remained stable for the past six decades, past periods of ice shelf collapse have been inferred from relict seabed "corrugations" (corrugated ridges), preserved 340 km from the glacier in Pine Island Trough. Here we present high-resolution bathymetry gathered by an autonomous underwater vehicle operating beneath an Antarctic ice shelf, which provides evidence of long-term change in Pine Island Glacier. Corrugations and ploughmarks on a sub-ice shelf ridge that was a former grounding line closely resemble those observed offshore, interpreted previously as the result of iceberg grounding. The same interpretation here would indicate a significantly reduced ice shelf extent within the last 11 kyr, implying Holocene glacier retreat beyond present limits, or a past tidewater glacier regime different from today. The alternative, that corrugations were not formed in open water, would question ice shelf collapse events interpreted from the geological record, revealing detail of another bed-shaping process occurring at glacier margins. We assess hypotheses for corrugation formation and suggest periodic grounding of ice shelf keels during glacier unpinning as a viable origin. This interpretation requires neither loss of the ice shelf nor glacier retreat and is consistent with a "stable" grounding-line configuration throughout the Holocene.

  16. Climatic Slow-down of the Pamir-Karakoram-Himalaya Glaciers Over the Last 25 Years

    NASA Astrophysics Data System (ADS)

    Dehecq, A.; Gourmelen, N.; Trouvé, E.

    2015-12-01

    Climate warming over the 20th century has caused drastic changes in mountain glaciers globally, and of the Himalayan glaciers in particular. The stakes are high; glaciers and ice caps are the largest contributor to the increase in the mass of the world's oceans, and the Himalayas play a key role in the hydrology of the region, impacting on the economy, food safety and flood risk. Partial monitoring of the Himalayan glaciers has revealed a contrasted picture; while many of the Himalayan glaciers are retreating, in some cases locally stable or advancing glaciers in this region have also been observed. Several studies based on field measurements or remote sensing have shown a dominant slow-down of mountain glaciers globally in response to these changes. But they are restricted to a few glaciers or small regions and none has analysed the dynamic response of glaciers to climate changes at regional scales. Here we present a region-wide analysis of annual glacier flow velocity covering the Pamir-Karakoram-Himalaya region obtained from the analysis of the entire archive of Landsat data. Over 90% of the ice-covered regions, as defined by the Randolph Glacier Inventory, are measured, with precision on the retrieved velocity of the order of 4 m/yr. The change in velocities over the last 25 years will be analysed with reference to regional glacier mass balance and topographic caracteristics. We show that the first order temporal evolution of glacier flow mirrors the pattern of glacier mass balance. We observe a general decrease of ice velocity in regions of known ice mass loss, and a more complex patterns consisting of mixed acceleration and decrease of ice velocity in regions that are known to be affected by stable mass balance and surge-like behavior.

  17. Glacier change in Garibaldi Provincial Park, southern Coast Mountains, British Columbia, since the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Koch, Johannes; Menounos, Brian; Clague, John J.

    2009-04-01

    Fluctuations of glaciers during the 20th century in Garibaldi Provincial Park, in the southern Coast Mountains of British Columbia, were reconstructed from historical documents, aerial photographs, and fieldwork. Over 505 km 2, or 26%, of the park, was covered by glacier ice at the beginning of the 18th century. Ice cover decreased to 297 km 2 by 1987-1988 and to 245 km 2 (49% of the early 18th century value) by 2005. Glacier recession was greatest between the 1920s and 1950s, with typical frontal retreat rates of 30 m/a. Many glaciers advanced between the 1960s and 1970s, but all glaciers retreated over the last 20 years. Times of glacier recession coincide with warm and relatively dry periods, whereas advances occurred during relatively cold periods. Rapid recession between 1925 and 1946, and since 1977, coincided with the positive phase of the Pacific Decadal Oscillation (PDO), whereas glaciers advanced during its negative phase (1890-1924 and 1947-1976). The record of 20th century glacier fluctuations in Garibaldi Park is similar to that in southern Europe, South America, and New Zealand, suggesting a common, global climatic cause. We conclude that global temperature change in the 20th century explains much of the behaviour of glaciers in Garibaldi Park and elsewhere.

  18. Tropical glaciers and climate dynamics: Resolving the linkages

    NASA Astrophysics Data System (ADS)

    Mölg, Thomas

    2013-04-01

    Large-scale atmosphere/ocean circulation and mountain glaciers represent two entirely different scales in the climate system. Therefore, statistical linkages between the two mask a cascade of processes that act on different temporal and spatial dimensions. Low-latitude glaciers are particularly well suited for studying such processes, since these glaciers are situated in the "heart" of the global climate system (the tropics). This presentation gives an overview of a decade of research on tropical climate and glaciers on Kilimanjaro (East Africa), which is, to our knowledge, the only case where space/time linkages between high-altitude glaciers and climate dynamics have been investigated systematically throughout the main scales. This includes the complex modification of atmospheric flow when air masses impinge on high mountains, an aspect that has been widely neglected from a cryospheric viewpoint. The case of Kilimanjaro demonstrates (1) the great potential of learning about climate system processes and their connections, (2) advances in our understanding of the importance of moisture for glaciers that lie far above the mean freezing level, and (3) methodological advances in combining atmospheric and cryospheric modelling.

  19. 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.

  20. ADVANCED COMPOSITES TECHNOLOGY CASE STUDY AT NASA LANGLEY RESEARCH CENTER

    EPA Science Inventory

    Under the Chesapeake Bay Agreement, NASA-LaRC is a member of the Tidewater Interagency Pollution Prevention Program (TIPPP). t NASA-LaRC, a technique for producing advanced composite materials without the use of solvents has been developed. his assessment was focused on the produ...

  1. 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

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Yasunari, Teppei J.

    2011-12-01

    The subject of climate change in the Tibetan Plateau (TP) and Himalayas has taken on increasing importance because of the availability of water resources from their mountain glaciers (Immerzeel et al 2010). Many of the glaciers over these regions have been retreating, while some are advancing and stable (Yao et al 2004, Scherler et al 2011). Other studies report that some glaciers in the Himalayas show acceleration of their shrinkage (e.g., Fujita and Nuimura 2011). However, the causes of glacier melting are still difficult to grasp because of the complexity of climatic change and its influence on glacier issues. Despite this, it is vital that we pursue further study to enable future predictions of glacier changes. The paper entitled 'Climate and glacier change in southwestern China during the past several decades' by Li et al (2011) provided carefully analyzed, quality controlled, long-term data on atmospheric temperature and precipitation during the period 1961-2008. The data were obtained from 111 Chinese stations. The researchers performed systematic analyses of temperature and precipitation over the whole southwestern Chinese domain. They discussed those changes in terms of other meteorological components such as atmospheric circulation patterns, radiation and altitude difference, and then showed how these factors could contribute to climate and glacier changes in the region. Air temperature and precipitation are strongly associated with glacier mass balance because of heat balance and the addition of mass when it snows. Temperature warming trends over many places in southwestern China were unequivocally dominant in all seasons and at higher altitudes. This indicates that the heat contribution to the glaciers has been increasing. On the other hand, precipitation has a wider variability in time and space. It is more difficult to clearly understand the effect of precipitation on the climate and glacier melting characteristics in the whole of southwestern China

  4. Calving dynamics at Helheim Glacier from a high-resolution observational network.

    NASA Astrophysics Data System (ADS)

    Selmes, Nick; Aspey, Robin; Baugé, Tim; Bevan, Suzanne; Edwards, Stuart; Everett, Alistair; James, Timothy; Loskot, Pavel; Luckman, Adrian; Martin, Ian; Murray, Tavi; O'Farrell, Tim; Rutt, Ian

    2014-05-01

    Calving glaciers play a crucial role in the mass balance of the Greenland Ice Sheet; acceleration of these glaciers results in increased mass loss from the ice sheet interior and a corresponding rise in sea level. Understanding the controls on calving is crucial for predicting the dynamic response of tidewater glaciers to environmental change, but understanding of calving is hindered by the difficulty of obtaining appropriate field measurements, and by the complexity of the system being observed. We designed and deployed a wireless network of GPS nodes which transmit to off-glacier base stations every few seconds, allowing observations right up to node loss through calving. We ran a network of 20 sensors over the period July - September 2013 on the highly crevassed surface of Helheim Glacier, one of the largest and fastest flowing of the Greenland outlets. Topographic change, additional velocities, and calving flux were provided by two sets of stereo time-lapse cameras, TanDEM-X satellite imagery, repeat airborne lidar, and airborne and spaceborne optical remotely-sensed imagery. At the start of our field season we observed the expression on the fjord surface of a point-source subglacial meltwater plume. We monitored the evolution of the plume and its effect on the exposed calving face and ice mélange from time-lapse cameras, optical remotely-sensed imagery and lidar data. We compare these observations to our record of frontal positions to study the plume's role in controlling the spatial extent of iceberg calving. Our 53 day study period contained several large calving events which resulted in frontal retreat of ~1.5 km. We present the glacier's dynamic and topographic response to these calving events through this very large and rich dataset. Typically the glacier ice flows down slope and speeds up as ice progresses towards the calving front, with notable acceleration after each calving event. Intriguingly we see periods where sensors behave in unexpected ways

  5. Global-scale analysis of satellite-derived debris distribution on glacier

    NASA Astrophysics Data System (ADS)

    Sasaki, O.; Noguchi, O.; Zhang, Y.; Hirabayashi, Y.; Kanae, S.

    2015-12-01

    In high relief mountain regions, many glaciers have supraglacial debris in their ablation area, which affects the response of these glaciers to climate change through altering ice melting rates. The thin debris accelerates ice melting and the thick one suppresses it. In order to understand the changes of glacier mass balance and runoff patterns under climate change, it is important to assess the effect of debris-cover on these glaciers. However, the assessment of the debris effect is difficult because it is difficult to measure debris thickness at large scale only from field measurements. Here, we attempted to estimate a global distribution of debris thickness on glaciers by using a thermal resistance of supraglacial debris derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite stereo imageries and radiometer products of Clouds and the Earth's Radiant Energy System (CERES). The obtained distribution map covers approximately 88% of total glacier area recorded in a global glacier outline of the Randorf Glacier Inventory (RGI). Investigations on several glaciers showed that the ASTER-derived thermal resistances correlated reasonably well with ground-surveyed debris thickness. The results indicate that 11% of total global glaciers are covered by supraglacial debris cover and the regional differences in debris distribution are apparent from region to region. Debris cover is relatively thin and accelerates ice melting in western Himalaya, North America, Canada, and Scandinavia, whereas debris cover is relatively thick and inhibits ice melting in eastern Himalaya, Alps, Caucasus and Andes region.

  6. Knik Glacier, Alaska; summary of 1979, 1980, and 1981 data and introduction of new surveying techniques

    USGS Publications Warehouse

    Mayo, L.R.; Trabant, D.C.

    1982-01-01

    Knik Glacier in south-central Alaska has the potential to reform Lake George, Alaska 's largest glacier-dammed lake. Measurements of surface altitude, snow depth, terminus position, glacier speed, and ice depth are being made in an attempt to determine the mechanisms that could cause a significant re-advance of the glacier. New surveying and data reduction techniques were developed by the authors and employed successfully at Knik Glacier. These include precise geodetic surveying by the ' trisection ' technique, calculation of surface altitude at a specially-fixed ' index point ' from three point measurements on a rough, moving glacier surface, and calculation of ice thickness from low frequency radar measurements. In addition, this report summarizes the data collected from 1979 to 1981 in support of this goal. (USGS)

  7. Glacier Shrinkage In The East Pamir Plateau In China During The Last 50 Years As Revealed By Two Times' Inventories

    NASA Astrophysics Data System (ADS)

    Wang, N.; Liu, S.; Xu, J.; Guo, W.

    2013-05-01

    The east Pamir Plateau located in China is the source area of the Kaxigar River, one of the tributary of the Tarim River in southern Xinjiang and a vital river to the social and economic development of Kaxigar City. Glaciers in the region play an important role as for the melting water nourishment and seasonal and decadal regulation to the runoff of the Kaxigar River. Early results indicate that glaciers in the region were in a slight retreat during the early 1960s and 2001 with area reduction by 6.2%. To understand their most recent dynamics of glaciers in the region, we have compiled a new inventory of these glaciers based on Landsat TM/ETM+ images acquired in 2009 without clouds and snow cover in the glacierized mountains. At the same time, we have updated the first glacier inventory by digitizing glacier outlines from topographical maps with modification and verification mostly based on aerial photographs. Our results indicate the total glacier area of 2564km2 in 1962 has become decreased to 2038km2 in 2009, 20.5% smaller than their original total. Small glaciers have experienced higher area reduction rate than that of large glaciers, the 11188 glaciers smaller than 10km2 have lost 27.8% of the total area while those 48 glaciers larger than 10km2 have decreased by 11.3% in area. However, there are 7 glaciers of which 6 glaciers with debris cover showing an advancing trend during the same period with average advance by 470m during 1963 and 2009. Compared with early observation, glacier retreat in the region seems accelerated which may be attributed to regional climate warming.

  8. Glacier winds in the Rongbuk Valley, north of Mount Everest: 1. Meteorological modeling with remote sensing data

    NASA Astrophysics Data System (ADS)

    Song, Yu; Zhu, Tong; Cai, Xuhui; Lin, Weili; Kang, Ling

    2007-06-01

    Persistent glacier winds blowing from noon to midnight in summer are present in the Rongbuk Valley, north of Mount Everest, with a maximum speed of 10 m s-1 and a vertical thickness as high as 1 km. These glacier winds may bring upper level atmosphere ozone to the surface, having a significant impact on the atmospheric environment. Such phenomena may be typical of the Tibetan Plateau, where most high mountains are covered by snow or glacier ice throughout the year. The Advanced Regional Prediction Model was used to simulate the down-valley flows, using realistic topography but neglecting synoptic winds. The modeling results agree well with the observations obtained in June 2002, revealing that the glacier winds are thermal flows primarily driven by the along-valley temperature gradient between the colder air over the glacier surface and the warmer air over surface areas covered by rock debris, which maintains air advection along the Rongbuk Valley. Downslope winds over the glacier slopes, especially from the western valley side, and the West Rongbuk Glacier, were forced by their inertia farther down into the valley and would intensify the glacier winds. The narrowing of the Rongbuk Valley could also speed up the glacier winds. Sensitivity tests showed that the detailed distribution of the Rongbuk Glacier, delineated by data from the Enhanced Thematic Mapper Plus on Landsat 7, plays an important role in glacier winds development. The glacier winds could be much weaker in winter when the area is completely snow covered.

  9. Comparison of multiple glacier inventories with a new inventory derived from high-resolution ALOS imagery in the Bhutan Himalaya

    NASA Astrophysics Data System (ADS)

    Nagai, H.; Fujita, K.; Sakai, A.; Nuimura, T.; Tadono, T.

    2016-01-01

    Digital glacier inventories are invaluable data sets for revealing the characteristics of glacier distribution and for upscaling measurements from selected locations to entire mountain ranges. Here, we present a new inventory of Advanced Land Observing Satellite (ALOS) imagery and compare it with existing inventories for the Bhutan Himalaya. The new inventory contains 1583 glaciers (1487 ± 235 km2), thereof 219 debris-covered glaciers (951 ± 193 km2) and 1364 debris-free glaciers (536 ± 42 km2). Moreover, we propose an index for quantifying consistency between two glacier outlines. Comparison of the overlap ratio demonstrates that the ALOS-derived glacier inventory contains delineation uncertainties of 10-20 % which depend on glacier size, that the shapes and geographical locations of glacier outlines derived from the fourth version of the Randolph Glacier Inventory have been improved in the fifth version, and that the latter is consistent with other inventories. In terms of whole glacier distribution, each data set is dominated by glaciers of 1.0-5.0 km2 area (31-34 % of the total area), situated at approximately 5400 m elevation (nearly 10 % in 100 m bin) with either north or south aspects (22 and 15 %). However, individual glacier outlines and their area exhibit clear differences among inventories. Furthermore, consistent separation of glaciers with inconspicuous termini remains difficult, which, in some cases, results in different values for glacier number. High-resolution imagery from Google Earth can be used to improve the interpretation of glacier outlines, particularly for debris-covered areas and steep adjacent slopes.

  10. Debris-Covered Glaciers in the Sierra Nevada, California, and Their Implications for Snowline Reconstructions

    USGS Publications Warehouse

    Clark, D.H.; Clark, M.M.; Gillespie, A.R.

    1994-01-01

    Ice-walled melt ponds on the surfaces of active valley-floor rock glaciers and Matthes (Little Ice Age) moraines in the southern Sierra Nevada indicate that most of these landforms consist of glacier ice under thin (ca. 1 - 10 m) but continuous covers of rock-fall-generated debris. These debris blankets effectively insulate the underlying ice and greatly reduce rates of ablation relative to that of uncovered ice. Such insulation explains the observations that ice-cored rock glaciers in the Sierra, actually debris-covered glaciers, are apparently less sensitive to climatic warming and commonly advance to lower altitudes than do adjacent bare-ice glaciers. Accumulation-area ratios and toe-to-headwall-altitude ratios used to estimate equilibrium-line altitudes (ELAs) of former glaciers may therefore yield incorrect results for cirque glaciers subject to abundant rockfall. Inadvertent lumping of deposits from former debris-covered and bare-ice glaciers partially explains an apparently anomalous regional ELA gradient reported for the pre-Matthes Recess Peak Neoglacial advance. Distinguishing such deposits may be important to studies that rely on paleo-ELA estimates. Moreover, Matthes and Recess Peak ELA gradients along the crest evidently depend strongly on local orographic effects rather than latitudinal climatic trends, indicating that simple linear projections and regional climatic interpretations of ELA gradients of small glaciers may be unreliable.

  11. Optical Remote Sensing of Glacier Characteristics: A Review with Focus on the Himalaya

    PubMed Central

    Racoviteanu, Adina E.; Williams, Mark W.; Barry, Roger G.

    2008-01-01

    The increased availability of remote sensing platforms with appropriate spatial and temporal resolution, global coverage and low financial costs allows for fast, semi-automated, and cost-effective estimates of changes in glacier parameters over large areas. Remote sensing approaches allow for regular monitoring of the properties of alpine glaciers such as ice extent, terminus position, volume and surface elevation, from which glacier mass balance can be inferred. Such methods are particularly useful in remote areas with limited field-based glaciological measurements. This paper reviews advances in the use of visible and infrared remote sensing combined with field methods for estimating glacier parameters, with emphasis on volume/area changes and glacier mass balance. The focus is on the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor and its applicability for monitoring Himalayan glaciers. The methods reviewed are: volumetric changes inferred from digital elevation models (DEMs), glacier delineation algorithms from multi-spectral analysis, changes in glacier area at decadal time scales, and AAR/ELA methods used to calculate yearly mass balances. The current limitations and on-going challenges in using remote sensing for mapping characteristics of mountain glaciers also discussed, specifically in the context of the Himalaya.

  12. Latest Pleistocene and Holocene Glacier Fluctuations in southernmost Patagonia

    NASA Astrophysics Data System (ADS)

    Menounos, B.; Maurer, M.; Clague, J. J.; osborn, G.; Ponce, F.; Davis, P. T.; Rabassa, J.; Coronato, A.; Marr, R.

    2011-12-01

    Summer insolation has been proposed to explain long-term glacier fluctuations during the Holocene. If correct, the record of glacier fluctuations at high latitudes in the Southern Hemisphere should differ from that in the Northern Hemisphere. Testing this insolation hypothesis has been hampered by dating uncertainties of many Holocene glacier chronologies from Patagonia. We report on our ongoing research aimed at developing a regional glacier chronology at the southern end of the Andes north and west of Ushuaia, Argentina. We have found evidence for an advance of cirque glaciers at the end of the Pleistocene; one or locally two closely spaced moraines extend up to 2 km beyond Little Ice Age moraines. Radiocarbon dating of terrestrial macrofossils recovered from basal sediments behind two of these moraines yielded ages of 10,320 ± 25 and 10,330 ± 30 14C yr BP. These moraines may record glacier advances coeval with the Antarctic Cold Reversal; surface exposure dating of these moraines is currently in progress to test this hypothesis. We find no evidence of Holocene moraines older than 6800 14C yr BP, based on the distribution of Hudson tephra of that age. At some sites, there is evidence for an early Neoglacial advance of glaciers slightly beyond (< 0.5 km) Little Ice Age limits. Terrestrial macrofossils at the upper contact of basal till from one site yielded an age of 4505 ± 30 14C yr BP; this age overlaps the most probable age range of early Neoglacial ice expansion in southern Patagonia reported by Porter (2000) and the age of plants killed by expansion of the Quelccaya Ice Cap in Peru. We have documented multiple wood mats with stumps in growth position separated by till units in a 100 m section of the northeast lateral moraine at Stoppani Glacier (54.78 S, 68.98 W), 50 km west of Ushuaia. Ten radiocarbon ages on these wood mats range in age from 3510 ± 15 to 135 ± 15 14C yr BP. The mats decrease in age up-section; many overlap with published age ranges for

  13. Austrian glaciers in historical documents of the last 400 years: implications for historical hydrology

    NASA Astrophysics Data System (ADS)

    Fischer, Andrea; Seiser, Bernd

    2014-05-01

    First documentations of Austrian glaciers date from as early as 1601. Early documentations were triggered by glacier advances that created glacier-dammed lakes that caused floods whenever the dam collapsed . Since then, Austrian glaciers have been documented in drawings, descriptions and later on in maps and photography. These data are stored in historical archives but today only partly exploited for historical glaciology. They are of special interest for historical hydrology in glacier-covered basins, as the extent of the snow, firn and ice cover and its elevation affect the hydrological response of the basin to precipitation events in several ways: - Firn cover: the more area is covered by firn, the higher is the capacity for retention or even refreezing of liquid precipitation and melt water. - Ice cover: the area covered by glaciers can be affected by melt and contributes to a peak discharge on summer afternoons. - Surface elevation and temperatures: in case of precipitation events, the lower surface temperatures and higher surface elevation of the glaciers compared to ice-free ground have some impact on the capacity to store precipitation. - Glacier floods: for the LIA maximum around 1850, a number of advancing glaciers dammed lakes which emptied during floods. These parameters show different variability with time: glacier area varies only by about 60% to 70% between the LIA maximum and today. The variability of the maximum meltwater peak changes much more than the area. Even during the LIA maximum, several years were extremely warm, so that more than twice the size of today's glacier area was subject to glacier melt. The minimum elevations of large glaciers were several hundred meters lower than today, so that in terms of today's summer mean temperatures, the melt water production from ice ablation would have been much higher than today. A comparison of historical glacier images and description with today's makes it clear that the extent of the snow cover and

  14. Bed Topography of Store Glacier and Fjord, Greenland from High-Resolution Gravity Data and Multi-Beam Echo Sounding

    NASA Astrophysics Data System (ADS)

    An, L.; Rignot, E. J.; Muto, A.; Morlighem, M.; Kemp, C.

    2014-12-01

    Store Glacier is a major west Greenland outlet tidewater glacier draining an area of 30,000 square km into Uummannaq Fjord, and flowing at a speed of 4.8 km per year at its terminus. The bed topography of the glacier is poorly known and the fjord bathymetry was partially surveyed for the first time in August 2012. In this study, we present a new approach for the inference of the glacier bed topography, ice thickness and sea floor bathymetry using high-resolution airborne gravity data combined with other data. In August 2012, we acquired a 250 m spacing grid of free-air gravity data at a speed of 50 knots with accuracy at sub-milligal level much higher accuracy than NASA Operation IceBridge (OIB) gravity campaign with approximate 5.2 km resolution at 290 knots flying speed. In August 2012 and 2013, we used multi-beam echo sounding to survey the sea floor bathymetry in front of the glacier, extending to the calving face of the glacier. Inland, we combined radar-derived ice thickness with ice motion vectors to reconstruct the bed topography at a high resolution. Using a 3D inversion of the gravity data, we reconstruct seamless bed topography across the ice front boundary that matches interior data and sea floor bathymetry, and provides information about sediment thickness beneath and in front of the glacier. Comparison of the results with prior maps reveals vast differences. IBCAO3 bathymetry suggests an ice front grounded at sea level while the measured ice front is grounded 550 m below sea level. The seamless topography obtained across the grounding line reveals the presence of a previously unknown sill, which explains why the glacier has been so stable in the last 50 years. The results have important impacts on the interpretation of the glacier stability, and sensitivity to thermal forcing from the ocean and surface melt. This work was conducted at UCI under a contract with the Gordon and Betty More Foundation and with NASA.

  15. Modeling seasonal velocity variability and assessing the influence of glacial hydrology and sea-ice buttressing at the Belcher Glacier, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Pimentel, S.; Flowers, G. E.; Boon, S.; Clavano, W.; Copland, L.; Danielson, B.; Duncan, A.; Kavanaugh, J. L.; Sharp, M. J.; van Wychen, W. D.

    2011-12-01

    Seasonal ice dynamics on marine outlet glaciers can be influenced by the effects of both glacial hydrology and sea-ice buttressing. In summer surface meltwater finds its way through crevasses and moulins into the subglacial drainage system thereby modulating the extent of glacier sliding. Whereas in winter sea-ice build-up in front of the glacier terminus provides a buttressing effect exerting a back stress on the glacier ice. In this study we seek to distinguish between contributions from these two processes at a large fast-flowing tidewater-terminating Arctic glacier. The Belcher Glacier is the largest outlet glacier of the Devon Island Ice Cap in the Canadian high-Arctic. We employ the use of a hydrologically coupled higher-order ice-flow model together with field data collected in 2008 and 2009. Model output is compared against surface GPS observations as well as remotely sensed velocities derived using speckle tracking methods on Radarsat-2 imagery. Five major drainage sub-catchments have been identified on the Belcher and a melt model is used to generate daily surface runoff for each sub-catchment. The observed timing of lake drainage and moulin openings in each sub-catchment allow a seasonal timeseries of meltwater inputs to the subglacial drainage system to be constructed. Model simulations for 2008 and 2009 forced with this meltwater input timeseries are presented. Model responses to tidal forcing and changes in sea-ice back stress at the terminus are examined and compared alongside hydrologically driven accelerations.

  16. Extirpation and recolonization in a metapopulation of an endangered fish, the tidewater goby

    USGS Publications Warehouse

    Lafferty, K.D.; Swift, C.C.; Ambrose, R.F.

    1999-01-01

    The tidewater goby (Eucyclogobius newberryi), an endangered species in the United States, occurs in a series of isolated coastal wetlands in California. Using historical presence-absence data and our own surveys, we estimated annual rates of extirpation and recolonization for several populations of the goby in southern California. As predicted, large wetlands had lower rates of extirpation than small wetlands. There was a negative but statistically nonsignificant correlation between recolonization rate and distance to the nearest northerly source population. Populations at small sites were sensitive to drought, presumably because droughts can eliminate suitable habitat at small wetlands. Populations in small wetlands have declined over time, even after accounting for variation in stream flow, supporting the species' endangered status. Our study emphasizes the need to understand metapopulation dynamics for conserving species where the unit of conservation is a local population. It is also emphasizes the importance of not treating metapopulations as identical units. Finally, our results provide a means for describing the decline of a species that is complex in time and space and provide insight into how to target protection measures among metapopulations.

  17. Assessment of the photoenhanced toxicity of a weathered oil to the tidewater silverside

    USGS Publications Warehouse

    Little, E.E.; Cleveland, L.; Calfee, R.; Barron, M.G.

    2000-01-01

    Studies were conducted to determine the interactive toxicity of a water- accommodated fraction (WAF) of a weathered middle distillate petroleum and solar radiation to an estuarine organism, the tidewater silverside (Menidia beryllina). Juvenile silversides were monitored for survival and growth during a 7-d static renewal exposure to dilutions of WAFs of an environmentally weathered oil collected in the vicinity of an abandoned oil field in California. Ultraviolet (UV) treatments were based on incident sunlight intensity and spectra measured at this site. Exposure to UV alone was not lethal to the fish, and WAF in the absence of UV was toxic at the highest total petroleum hydrocarbon (TPH) concentration (3.03 mg/L) after 96 h of exposure. Water-accommodated fractions toxicity increased significantly with increasing UV irradiance and duration of exposure. The 7-d LC50 concentrations for the control, low, medium, and high irradiance were 2.84, 1.27, 0.93, and 0.51 mg/L TPH, respectively. Significant mortality occurred among fish previously exposed to WAF in the absence of irradiance, whereas WAF toxicity was unaffected by UV exposure prior to the toxicity test. Thus, the mode of action is a photosensitization of the accumulated petroleum residue rather than a photoactivation of WAF. Chemical analysis indicates that the WAF contains limited amounts of polycyclic aromatic hydrocarbons (PAHS) known to be photoenhanced, suggesting that other constituents may be responsible for the observed photoenhanced toxicity.

  18. Evolving force balance at Columbia Glacier, Alaska, during its rapid retreat

    USGS Publications Warehouse

    O'Neel, S.; Pfeffer, W.T.; Krimmel, R.; Meier, M.

    2005-01-01

    Changes in driving and resistive stresses play an essential role in governing the buoyancy forces that are important controls on the speed and irreversibility of tidewater glacier retreats. We describe changes in geometry, velocity, and strain rate and present a top-down force balance analysis performed over the lower reach of Columbia Glacier. Our analysis uses new measurements and estimates of basal topography and photogrammetric surface velocity measurements made between 1977 and 2001, while assuming depth-independent strain. Sensitivity tests show that the method is robust and insensitive to small changes in the calculation parameters. Spatial distributions of ice speed show little correspondence with driving stress. Instead, spatial patterns of ice speed exhibit a nonlinear correspondence with basal drag. Primary resistance to flow comes from basal drag, but lateral drag becomes increasingly more important throughout the retreat, which may account for observed increases in speed. Maximum basal drag is always located in a prominent constriction located ~12 km upstream from the preretreat terminus. Once the terminus retreated into deep water off the terminal moraine marking the modern maximum extent, the upstream location of this maximum basal drag helped to promote thinning and decrease effective pressure in the lower region by limiting replenishing ice flow from upstream. An increase in both ice velocity and calving resulted, initiating what appears to be an irreversible retreat. Copyright 2005 by the American Geophysical Union.

  19. Mass balance investigation of alpine glaciers through LANDSAT TM data

    NASA Technical Reports Server (NTRS)

    Bayr, Klaus J.

    1989-01-01

    An analysis of LANDSAT Thematic Mapper (TM) data of the Pasterze Glacier and the Kleines Fleisskees in the Austrian Alps was undertaken and compared with meteorological data of nearby weather stations. Alpine or valley glaciers can be used to study regional and worldwide climate changes. Alpine glaciers respond relatively fast to a warming or cooling trend in temperature through an advance or a retreat of the terminus. In addition, the mass balance of the glacier is being affected. Last year two TM scenes of the Pasterze Glacier of Aug. 1984 and Aug. 1986 were used to study the difference in reflectance. This year, in addition to the scenes from last year, one MSS scene of Aug. 1976 and a TM scene from 1988 were examined for both the Pasterze Glacier and the Kleines Fleisskees. During the overpass of the LANDSAT on 6 Aug. 1988 ground truthing on the Pasterze Glacier was undertaken. The results indicate that there was considerable more reflectance in 1976 and 1984 than in 1986 and 1988. The climatological data of the weather stations Sonnblick and Rudolfshuette were examined and compared with the results found through the LANDSAT data. There were relations between the meteorological and LANDSAT data: the average temperature over the last 100 years showed an increase of .4 C, the snowfall was declining during the same time period but the overall precipitation did not reveal any significant change over the same period. With the use of an interactive image analysis computer, the LANDSAT scenes were studied. The terminus of the Pasterze Glacier retreated 348 m and the terminus of the Kleines Fleisskees 121 m since 1965. This approach using LANDSAT MSS and TM digital data in conjunction with meteorological data can be effectively used to monitor regional and worldwide climate changes.

  20. Revealing glacier flow and surge dynamics from animated satellite image sequences: examples from the Karakoram

    NASA Astrophysics Data System (ADS)

    Paul, F.

    2015-04-01

    Although animated images are very popular on the Internet, they have so far found only limited use for glaciological applications. With long time-series of satellite images becoming increasingly available and glaciers being well recognized for their rapid changes and variable flow dynamics, animated sequences of multiple satellite images reveal glacier dynamics in a time-lapse mode, making the otherwise slow changes of glacier movement visible and understandable for a wide public. For this study animated image sequences were created from freely available image quick-looks of orthorectified Landsat scenes for four regions in the central Karakoram mountain range. The animations play automatically in a web-browser and might help to demonstrate glacier flow dynamics for educational purposes. The animations revealed highly complex patterns of glacier flow and surge dynamics over a 15-year time period (1998-2013). In contrast to other regions, surging glaciers in the Karakoram are often small (around 10 km2), steep, debris free, and advance for several years at comparably low annual rates (a few hundred m a-1). The advance periods of individual glaciers are generally out of phase, indicating a limited climatic control on their dynamics. On the other hand, nearly all other glaciers in the region are either stable or slightly advancing, indicating balanced or even positive mass budgets over the past few years to decades.

  1. Microbial Energetics Beneath the Taylor Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Mikucki, J. A.; Turchyn, A. V.; Farquhar, J.; Priscu, J. C.; Schrag, D. P.; Pearson, A.

    2007-12-01

    Subglacial microbiology is controlled by glacier hydrology, bedrock lithology, and the preglacial ecosystem. These factors can all affect metabolic function by influencing electron acceptor and donor availability in the subglacial setting leaving biogeochemical signatures that can be used to determine ecosystem processes. Blood Falls, an iron-rich, episodic subglacial outflow from the Taylor Glacier in the McMurdo Dry Valleys Antarctica provides an example of how microbial community structure and function can provide insight into subglacial hydrology. This subglacial outflow contains cryoconcentrated, Pliocene-age seawater salts that pooled in the upper Taylor Valley and was subsequently covered by the advance of the Taylor Glacier. Biogeochemical measurements, culture-based techniques, and genomic analysis were used to characterize microbes and chemistry associated with the subglacial outflow. The isotopic composition of important geochemical substrates (i.e., δ34Ssulfate, Δ33Ssulfate, δ18Osulfate, δ18Owater, Δ14SDIC) were also measured to provide more detail on subglacial microbial energetics. Typically, subglacial systems, when driven to anoxia by the hydrolysis of organic matter, will follow a continuum of redox chemistries utilizing electron acceptors with decreasing reduction potential (e.g., Fe (III), sulfate, CO2). Our data provide no evidence for sulfate reduction below the Taylor Glacier despite high dissolved organic carbon (450 μM C) and measurable metabolic activity. We contend that, in the case of the Taylor Glacier, the in situ bioenergetic reduction potential has been 'short-circuited' at Fe(III)-reduction and excludes sulfate reduction and methanogenesis. Given the length of time that this marine system has been isolated from phototrophic production (~2 Mya) the ability to degrade and consume increasingly recalcitrant organic carbon is likely an important component to the observed redox chemistry. Our work indicates that glacier hydrology

  2. 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

  3. 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.

  4. Analysis of Environmental Forcing and Melange Fluctuation in Asynchronous Retreat of Ocean Terminating Glaciers in Greenland's Sermilik Fjord

    NASA Astrophysics Data System (ADS)

    Seifert, F.; Galey, C. E.; Bassis, J. N.

    2014-12-01

    Widespread near synchronous retreat of marine terminating outlet glaciers has been observed across wide swaths of the Greenland Ice Sheet. However, despite large-scale patterns of retreat, there is considerable variability in the timing and retreat patterns of individual glaciers with geographically adjacent glaciers that experience similar climate and meteorological forcing displaying markedly different behavior. Here we applied an automated identification algorithm that we developed to track the terminus and melange in order better understand the complex dynamics and varying drivers of glacier retreat. The algorithm was applied to three major glaciers (Helheim Glacier, Fenris Glacier and Midgard Glacier) that terminate in Greenland's Sermilik Fjord over the period of 2000- 2014. The terminus position and the percentage of the fjord filled with melange or sea ice from 2001 to present was determined. Since these glaciers exist within the same fjord system, they should experience comparable environmental forcing conditions, but appear to respond to these conditions differently causing them to have varying patterns of retreat. Helheim Glacier and Fenris Glacier have terminus locations closely spaced in the fjord but Helheim Glacier's terminus retreated over 7 km before advancing to stabilize at a 5 km retreat over the observation period and Fenris Glacier's terminus has stayed in roughly the same place. Midgard Glacier is located across the fjord from Helheim Glacier and its terminus has continuously retreated with a retreat of approximately 8 km. This asynchronous retreat shows that proximity alone cannot determine retreat behavior, and a more complex interaction between internal variability and external forcing must be taking place. To better understand the variability within the system and the cause of asynchronous retreat, ocean and air temperature datasets, in conjunction with the fjord geometry, were compared with our derived melange/sea ice and terminus

  5. Spatial features of glacier changes in the Barents-Kara Sector

    NASA Astrophysics Data System (ADS)

    Sharov, A. I.; Schöner, W.; Pail, R.

    2009-04-01

    steepened. Significant positive height changes of 25 to 50 m were also registered at several insular ice caps smaller than 300 km² with top heights of about 300 m. At sub-regional scale the horizontal distribution of glacier changes was not uniform and correlated astonishingly well with the geopotential field represented in existing gravity anomaly maps of the Arctic. The locations of positive glacier changes systematically neighbored with the locations of strong positive gravity anomalies. Conversely, the largest negative changes were situated in the close vicinity of negative anomalies. Hence we supposed that significant lateral variations of geopotential might influence the local intensity of solid precipitation, snow accumulation rate and glacier regime in the High Arctic. A basic set of simple differential equations describing glacioclimatic settings in the heterogeneous field of gravity was compiled and critically compared with the relevant knowledge obtained by some other investigators. As a result, a new working hypothesis about gravity driven fluctuations in the long-term regime of cryospheric resources was devised and argued. First numerical simulations, statistical analyses of meteorological and tidal data rows, error balance estimates and specific glaciological surveys in 2001, 2006 and 2008 demonstrated major spatiotemporal singularities, principal methodological advantages and a higher feasibility of the proposed hypothesis compared to similar empirical-theoretical concepts developed by "lunarists" and "astro-meteorologists". New remote sensing data to be obtained from GOCE and CryoSat-2 satellites over the Barents-Kara Sector, which represents the largest cluster of tidewater glaciers and gravity anomalies in the Old World, might essentially contribute to the verification of this still conjectural theory.

  6. Interpreting Terminus Fluctuations at Helheim Glacier, Southeast Greenland, through Modeling and Observations

    NASA Astrophysics Data System (ADS)

    Kehrl, L. M.; Joughin, I. R.; Shapero, D.

    2014-12-01

    Marine-terminating outlet glaciers are highly sensitive to changes at the ice-ocean boundary. Changes at the ice-ocean boundary (calving events, submarine melting) can alter the terminus position and thereby the stress balance. If the terminus retreats into deeper water, more of the driving stress must then be balanced by longitudinal stress gradients, which cause the glacier to speed up. This study combines satellite observations and modeling (Elmer/Ice) to investigate the relationship between glacier dynamics and terminus position at Helheim Glacier, southeast Greenland, from 2000-2014. Helheim Glacier retreated about 7 km from 2001-2005 as warm ocean water entered the nearby fjord. From 2005-2006, the glacier re-advanced by 3 km as a floating or near-floating ice tongue formed over the basal overdeepening in front of the glacier terminus. Since then, Helheim's terminus position has remained relatively stable, with terminus fluctuations of < 2 km. Our model experiments consider both large terminus fluctuations (> 2 km) associated with rapid retreat and small terminus fluctuations (< 500 m) associated with individual calving events. We run the model simulations with both a flowline and three-dimensional model to better constrain our uncertainties. Our results show that Helheim Glacier responds rapidly to changes in terminus position of more than a few hundred meters. Small terminus fluctuations can cause velocity variations that extend up to 30 km inland, which roughly corresponds with the spatial extent of the weak bed (20-40 kPa) underneath Helheim Glacier.

  7. Spatial debris-cover effect on the maritime glaciers of Mount Gongga, south-eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Hirabayashi, Y.; Fujita, K.; Liu, S.; Liu, Q.

    2013-06-01

    The Tibetan Plateau and surroundings contain a large number of debris-covered glaciers, on which debris cover affects glacier response to climate change by altering ice melting rates and spatial patterns of mass loss. Insufficient spatial distribution of debris thickness data makes it difficult to analyze regional debris-cover effects. Mount Gongga glaciers, maritime glaciers in the south-eastern Tibetan Plateau, are characterized by a substantial reduction in glacier length and ice mass in recent decades. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)-derived thermal property of the debris layer reveals that 68% of the glaciers have extensive mantles of supraglacial debris in their ablation zones, in which the proportion of debris cover to total glacier area varies from 1.74% to 53.0%. Using a surface energy-mass balance model accounting for the debris-cover effect applied at a regional scale, we find that although the presence of supraglacial debris has a significant insulating effect on heavily debris-covered glaciers, it accelerates ice melting on ~ 10.2% of the total ablation area and produces rapid wastage of ~ 25% of the debris-covered glaciers, resulting in the similar mass losses between debris-covered and debris-free glaciers. Widespread debris cover also facilitates the development of active terminus regions. Regional differences in the debris-cover effect are apparent, highlighting the importance of debris cover for understanding glacier status and hydrology in both the Tibetan Plateau and other mountain ranges around the world.

  8. Reconstructing Glaciers on Mars

    NASA Astrophysics Data System (ADS)

    Hubbard, A., II; Brough, S.; Hubbard, B. P.

    2015-12-01

    Mars' mid-latitudes host a substantial volume of ice, equivalent to a ~1 - 2.5 m-thick global layer or the sum of Earth's glaciers and ice caps outside of Antarctica and Greenland. These deposits are the remnants of what is believed to have been a once far larger 'ice age', culminating in a last martian glacial maximum. Despite the identification of >1,300 glacier-like forms (GLFs) - the first order component of Mars' glacial landsystem - in Mars' mid-latitudes, little is known about their composition, dynamics or former extent. Here, we reconstruct the former 3D extent of a well-studied GLF located in eastern Hellas Planitia. We combine high-resolution geomorphic and topographic data, obtained from the High-Resolution Imaging Science Experiment (HiRISE) camera, to reconstruct the GLF's former limits. We then apply a perfect plasticity rheological model, to generate multiple flow-parallel ice-surface transects. These are combined with the GLF's boundary to guide interpolation using ArcGIS' 'Topo to Raster' function to produce a continuous 3D surface for the reconstructed former GLF. Our results indicate that, since its reconstructed 'recent maximum' extent, the GLF's volume has reduced by 0.31 km3 and its area by 6.85 km2, or 70%. On-going research is addressing the degree to which this change is typical of Mars' full GLF population.

  9. 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

  10. Survival, growth and stress response of juvenile tidewater goby, Eucyclogobius newberryi, to interspecific competition for food

    PubMed Central

    Chase, Daniel A.; Flynn, Erin E.; Todgham, Anne E.

    2016-01-01

    Reintroduction of endangered fishes to historic habitat has been used as a recovery tool; however, these fish may face competition from other fishes that established in their native habitat since extirpation. This study investigated the physiological response of tidewater goby, Eucyclogobius newberryi, an endangered California fish, when competing for food with threespine stickleback, Gasterosteus aculeatus, a native species, and rainwater killifish, Lucania parva, a non-native species. Survival, growth and physiological indicators of stress (i.e. cortisol, glucose and lactate concentrations) were assessed for juvenile fish held for 28 days in two food-limited conditions. When fed a 75% ration, survival of E. newberryi was significantly lower when held with G. aculeatus. In all fish assemblages, weight and relative condition decreased then stabilized over the 28 day experiment, while length remained unchanged. Whole-body cortisol in E. newberryi was not affected by fish assemblage; however, glucose and lactate concentrations were significantly higher with conspecifics than with other fish assemblages. When fed a 50% ration, survival of E. newberryi decreased during the second half of the experiment, while weight and relative condition decreased and length remained unchanged in all three fish assemblages. Cortisol concentrations were significantly higher for all fish assemblages compared with concentrations at the start of the experiment, whereas glucose and lactate concentrations were depressed relative to concentrations at the start of the experiment, with the magnitude of decrease dependent on the species assemblage. Our findings indicate that E. newberryi exhibited reduced growth and an elevated generalized stress response during low food availability. In response to reduced food availability, competition with G. aculeatus had the greatest physiological effect on E. newberryi, with minimal effects from the non-native L. parva. This study presents the first

  11. Survival, growth and stress response of juvenile tidewater goby, Eucyclogobius newberryi, to interspecific competition for food.

    PubMed

    Chase, Daniel A; Flynn, Erin E; Todgham, Anne E

    2016-01-01

    Reintroduction of endangered fishes to historic habitat has been used as a recovery tool; however, these fish may face competition from other fishes that established in their native habitat since extirpation. This study investigated the physiological response of tidewater goby, Eucyclogobius newberryi, an endangered California fish, when competing for food with threespine stickleback, Gasterosteus aculeatus, a native species, and rainwater killifish, Lucania parva, a non-native species. Survival, growth and physiological indicators of stress (i.e. cortisol, glucose and lactate concentrations) were assessed for juvenile fish held for 28 days in two food-limited conditions. When fed a 75% ration, survival of E. newberryi was significantly lower when held with G. aculeatus. In all fish assemblages, weight and relative condition decreased then stabilized over the 28 day experiment, while length remained unchanged. Whole-body cortisol in E. newberryi was not affected by fish assemblage; however, glucose and lactate concentrations were significantly higher with conspecifics than with other fish assemblages. When fed a 50% ration, survival of E. newberryi decreased during the second half of the experiment, while weight and relative condition decreased and length remained unchanged in all three fish assemblages. Cortisol concentrations were significantly higher for all fish assemblages compared with concentrations at the start of the experiment, whereas glucose and lactate concentrations were depressed relative to concentrations at the start of the experiment, with the magnitude of decrease dependent on the species assemblage. Our findings indicate that E. newberryi exhibited reduced growth and an elevated generalized stress response during low food availability. In response to reduced food availability, competition with G. aculeatus had the greatest physiological effect on E. newberryi, with minimal effects from the non-native L. parva. This study presents the first

  12. Preliminary bathymetry of McCarty Fiord and Neoglacial changes of McCarty Glacier, Alaska

    USGS Publications Warehouse

    Post, Austin

    1980-01-01

    Preliminary bathymetry (at 1:20,000 scale) and other scientific studies of McCarty Fiord, Alaska, Conducted by the Research Vessel Growler in 1978, showed this 15 mile-long waterway to be a narrow, deeply scoured basin enclosed by a terminal-moraine shoal. This valley was formerly filled by McCarty Glacier, which began a drastic retreat shortly after 1909; the glacier reached shallow water at the head of the fiord around 1960. The relative rate of retreat in deep water and on land is disclosed by the slower melting of stagnent ice left in a side valley. Soundings and profiles show the main channel to extend to a depth as great as 957 feet and to have the typical ' U ' shape of a glacier-eroded valley; since the glacier 's retreat, sediments have formed a nearly level deposit in the deepest part of the fiord. Old forest debris dated by carbon-14 indicates that a neoglacial advance of the glacier began before 3,395 years B.P. (before present); by 1,500 B.P. the glacier filled most of the fiord, and before the glacier culminated its advance around 1860 , two glacier-dammed lakes were formed in side valleys. (USGS)

  13. Advance of East Antarctic outlet glaciers during the Hypsithermal: Implications for the volume state of the Antarctic ice sheet under global warming

    SciTech Connect

    Domack, E.W. ); Jull, A.J.T. ); Nakao, Seizo )

    1991-11-01

    The authors present the first circum-East Antarctic chronology for the Holocene, based on 17 radiocarbon dates generated by the accelerator method. Marine sediments form around East Antarctica contain a consistent, high-resolution record of terrigenous (ice-proximal) and biogenic (open-marine) sedimentation during Holocene time. This record demonstrates that biogenic sedimentation beneath the open-marine environment on the continental shelf has been restricted to approximately the past 4 ka, whereas a period of terrigenous sedimentation related to grounding line advance of ice tongues and ice shelves took place between 7 and 4 ka. An earlier period of open-marine (biogenic sedimentation) conditions following the late Pleistocene glacial maximum is recognized from the Prydz Bay (Ocean Drilling Program) record between 10.7 and 7.3 ka. Clearly, the response of outlet systems along the periphery of the East Antarctic ice sheet during the mid-Holocene was expansion. This may have been a direct consequence of climate warming during an Antarctic Hypsithermal. Temperature-accumulation relations for the Antarctic indicate that warming will cause a significant increase in accumulation rather than in ablation. Models that predict a positive mass balance (growth) of the Antarctic ice sheet under global warming are supported by the mid-Holocene data presented herein.

  14. Holocene glacier activity in the British Columbia Coast Mountains, Canada

    NASA Astrophysics Data System (ADS)

    Mood, Bryan J.; Smith, Dan J.

    2015-11-01

    The Coast Mountains flank the Pacific Ocean in western British Columbia, Canada. Subdivided into the southern Pacific Ranges, central Kitimat Ranges and northern Boundary Ranges, the majority of large glaciers and icefields are located in the Boundary and Pacific ranges. Prior descriptions of the Holocene glacial history of this region indicate the Holocene was characterized by repeated episodes of ice expansion and retreat. Recent site-specific investigations augment our understanding of the regional character and duration of these events. In this paper, previously reported and new radiocarbon evidence is integrated to provide an updated regional assessment. The earliest evidence of glacier expansion in the Coast Mountains comes from the Boundary Ranges at 8.9 and 7.8 ka and in the Pacific Ranges at 8.5-8.2 ka, with the latter advance corresponding to an interval of rapid, global climate deterioration. Although generally warm and dry climates from 7.3 to 5.3 ka likely limited the size of glaciers in the region, there is radiocarbon evidence for advances over the interval from 7.3 to 6.0 and at 5.4-5.3 ka in the Pacific Ranges. Following these advances, glaciers in the Pacific Ranges expanded down valley at 4.8-4.6, 4.4-4.0, 3.5-2.6, 1.4-1.2, and 0.8-0.4 ka, while glaciers in Boundary Ranges were advancing at 4.1-4.0, 3.7-3.4, 3.1-2.8, 2.3, 1.7-1.1, and 0.8-0.4 ka. After 0.4 ka, it appears that most glaciers in the Coast Mountains continued to expand to attain their maximum Holocene extents by the early 18th to late 19th centuries. This enhanced record of Holocene glacier activity highlights the temporal synchrony in the Coast Mountains. Individual expansion events in the mid-to late Holocene broadly correspond to intervals of regional glacier activity reported in the Canadian Rocky Mountains, in Alaska, and on high-elevation volcanic peaks in Washington State.

  15. Rapid Holocene glacier fluctuations in arctic Norway in concert with the strength and spatial pattern of the westerlies

    NASA Astrophysics Data System (ADS)

    Bakke, J.; Dahl, S.

    2011-12-01

    Alpine glaciers are often located in remote regions of the world, areas that only rarely are covered by instrumental records or biological proxy data. Reconstructions of glaciers have therefore proven useful for understanding past climate dynamics on both shorter and longer time-scales. Because of selective preservation of moraine ridges, such records do not exclude the possibility of multiple Holocene glacier advances. This problem is true regardless whether cosmogenic isotopes or lichenometry have been used to date the moraines, or based on radiocarbon dating of mega-fossils buried in till or underneath the moraines themselves. To overcome this problem Karlén (1976) initially suggested that glacial erosion and the associated production of rock-flour deposited in downstream distal glacier-fed lakes could provide continuous records of glacial fluctuations, hence overcoming the problem of selective moraine preservation. In recent years, new collaborative research efforts have developed the methods used to reconstruct past glacier activity based on sediments deposited in distal glacier-fed lakes. Records of glacier fluctuations as preserved in lake sediments now includes the application of various methods such as measuring the amount of minerogenic versus biologic matter (typically inferred from Loss-on-ignition (LOI)), grain size analysis (GSA), magnetic properties (MP), geochemical elements (GE), Rare-Earth Elements (REE), Bulk Sediment Density (BSD), but also other techniques such as XRF analyses. Several glaciers along the coast of Arctic Norway have been reconstructed based on multi-proxy approaches. Here we present data on Holocene glacier fluctuations from three geographical areas; the ice cap Folgefonna, the Okstindan glacier massif and from a small alpine glacier in Lyngen. In Scandinavia, the overall pattern of glacier growth and the onset of the Neoglacial previously have been attributed to the gradual weakening of summer insolation at high northern

  16. 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.

  17. Investigating Long-term Behavior of Outlet Glaciers in Greenland

    NASA Technical Reports Server (NTRS)

    Csatho, Beata; vanderVeen, Kees; Schenk, Toni

    2005-01-01

    Repeat surveys by airborne laser altimetry in the 1990s have revealed significant thinning of outlet glaciers draining the interior of the Greenland Ice Sheet, with thinning rates up to several meters per year. To fully appreciate the significance of these recent glacier changes, the magnitude of retreat and surface lowering must be placed within the broader context of the retreat since the Last Glacial Maximum and, more significantly, of the retreat following the temporary glacier advance during the Little Ice Age (LIA). The LIA maximum stand is marked by trimlines, sharp boundaries between recently deglacifated unvegetated rocks, and vegetated surfaces at higher elevations. The objective of this project was to demonstrate the use of remote sensing data to map these trimlines and other glacial geomorphologic features.

  18. Rapid, climate-driven changes in outlet glaciers on the Pacific coast of East Antarctica.

    PubMed

    Miles, B W J; Stokes, C R; Vieli, A; Cox, N J

    2013-08-29

    Observations of ocean-terminating outlet glaciers in Greenland and West Antarctica indicate that their contribution to sea level is accelerating as a result of increased velocity, thinning and retreat. Thinning has also been reported along the margin of the much larger East Antarctic ice sheet, but whether glaciers are advancing or retreating there is largely unknown, and there has been no attempt to place such changes in the context of localized mass loss or climatic or oceanic forcing. Here we present multidecadal trends in the terminus position of 175 ocean-terminating outlet glaciers along 5,400 kilometres of the margin of the East Antarctic ice sheet, and reveal widespread and synchronous changes. Despite large fluctuations between glaciers--linked to their size--three epochal patterns emerged: 63 per cent of glaciers retreated from 1974 to 1990, 72 per cent advanced from 1990 to 2000, and 58 per cent advanced from 2000 to 2010. These trends were most pronounced along the warmer western South Pacific coast, whereas glaciers along the cooler Ross Sea coast experienced no significant changes. We find that glacier change along the Pacific coast is consistent with a rapid and coherent response to air temperature and sea-ice trends, linked through the dominant mode of atmospheric variability (the Southern Annular Mode). We conclude that parts of the world's largest ice sheet may be more vulnerable to external forcing than recognized previously. PMID:23985874

  19. Revealing glacier flow and surge dynamics from animated satellite image sequences: examples from the Karakoram

    NASA Astrophysics Data System (ADS)

    Paul, F.

    2015-11-01

    Although animated images are very popular on the internet, they have so far found only limited use for glaciological applications. With long time series of satellite images becoming increasingly available and glaciers being well recognized for their rapid changes and variable flow dynamics, animated sequences of multiple satellite images reveal glacier dynamics in a time-lapse mode, making the otherwise slow changes of glacier movement visible and understandable to the wider public. For this study, animated image sequences were created for four regions in the central Karakoram mountain range over a 25-year time period (1990-2015) from freely available image quick-looks of orthorectified Landsat scenes. The animations play automatically in a web browser and reveal highly complex patterns of glacier flow and surge dynamics that are difficult to obtain by other methods. In contrast to other regions, surging glaciers in the Karakoram are often small (10 km2 or less), steep, debris-free, and advance for several years to decades at relatively low annual rates (about 100 m a-1). These characteristics overlap with those of non-surge-type glaciers, making a clear identification difficult. However, as in other regions, the surging glaciers in the central Karakoram also show sudden increases of flow velocity and mass waves travelling down glacier. The surges of individual glaciers are generally out of phase, indicating a limited climatic control on their dynamics. On the other hand, nearly all other glaciers in the region are either stable or slightly advancing, indicating balanced or even positive mass budgets over the past few decades.

  20. From WAC to CCCAC: Writing across the Curriculum Becomes Communication, Collaboration, and Critical Thinking (and Computers) across the Curriculum at Tidewater Community College.

    ERIC Educational Resources Information Center

    Reiss, Donna

    Even without a formal program for writing across the curriculum, Tidewater Community College in Virginia has sustained communication-across-the-curriculum activities for nearly 20 years. Faculty groups have routinely gathered both formally and informally to discuss ways to improve student writing, to incorporate communication and collaboration…

  1. Collaborating with the local community of Kullorsuaq, Greenland to obtain high-quality hydrographic measurements near Alison Glacier

    NASA Astrophysics Data System (ADS)

    Porter, D. F.; Turrin, M.; Tinto, K. J.; Giulivi, C. F.; Cochran, J. R.; Bell, R. E.

    2014-12-01

    Warming ocean waters around Greenland have been implicated, along with warmer air temperatures, in the rapid increase of melt of the tidewater glaciers that drain the ice sheet. Most available regional oceanographic measurements have been collected during the summer seasons and are concentrated near the largest and most accessible glaciers. In order to gain a more comprehensive picture of the changing environment around the entirety of Greenland, more fjords, especially in the north, must be sampled. In July 2014, we travelled to Kullorsuaq in Northwest Greenland in order to foster a partnership with the local community to obtain new hydrographic data from CTD casts near Alison Glacier (74.6N, 57W). The terminus of this glacier abruptly retreated 10 km between 2000 and 2006. Although adequate observations from that time period are unavailable, our recently collected temperature and salinity data suggests that the deep water near Alison is similar to the waters further south, where near-synchronous ocean warming and glacial acceleration has been documented. Over the course of two sampling days, a hand-operated winch from a small boat was used to make standard CTD casts in front of Alison Glacier. We find evidence of glacial and mélange melt and the signature of both Polar and Atlantic Water masses at depth. Along-fjord casts illustrate how the ocean waters are modified as they circulate in and out of the fjord and the interaction of this water with the melting glacial front. At 500m depths, ocean temperatures are about 3°C above the in-situ freezing point of seawater, suggesting a possible influence of warm ocean waters on the mass loss of Alison Glacier. Using NASA Operation IceBridge and satellite altimetry data, we relate our new hydrographic data to the observed recent changes in Alison Glacier. An additional important result is that this short field campaign uncovered the possibility of working with local Greenlandic communities to aid scientists in both

  2. Constraining calving front processes on W Greenland outlet glaciers using inertial-corrected laser scanning & swath-bathymetry

    NASA Astrophysics Data System (ADS)

    Bates, R.; Hubbard, A.; Neale, M.; Woodward, J.; Box, J. E.; Nick, F.

    2010-12-01

    Calving and submarine melt account for the majority of loss from the Antarctic and over 50% of that from the Greenland Ice Sheet. These ice-ocean processes are highly efficient mass-loss mechanisms, providing a rapid link between terrestrial ice (storage) and the oceanic sink (sea level/freshwater flux) which renders the ocean-outlet-ice sheet system potentially highly non-linear. Despite this, the controls on tidewater processes are poorly understood and a process based description of them is lacking from the present generation of coupled ice sheet models. We present details from an innovative study where two survey techniques are integrated to enable the construction of accurate, ~m resolution 3d digital terrain models (DTMs) of the aerial and submarine ice front of calving outlet glaciers. A 2km range terrestrial laser scanner was combined with a 416KHz swath-interferometric system and corrected via an inertial motion unit stabilized by RTK GPS and gyro-compass data. The system was mounted aboard a heavy displacement (20,000kg) yacht in addition to a light displacement (100kg) semi-autonomous boat and used to image the aerial and submarine calving fronts of two large outlet glaciers in W Greenland. Six daily surveys, each 2.5km long were repeated across Lille Glacier during which significant ice flow, melt and calving events were observed and captured from on-ice GPS stations and time-lapse sequences. A curtain of CTD and velocity casts were also conducted to constrain the fresh and oceanic mass and energy fluxes within the fjord. The residual of successive DTMs yield the spatial pattern of frontal change enabling the processes of aerial and submarine calving and melt to be quantified and constrained in unprecedented detail. These observed frontal changes are tentatively related to local dynamic, atmospheric and oceanographic processes that drive them. A partial survey of Store Glacier (~7km calving front & W Greenland 2nd largest outlet after Jakobshavn Isbrae

  3. 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

  4. Glacier dynamics of the Pamir-Karakoram-Himalaya region over the last 40 years

    NASA Astrophysics Data System (ADS)

    Gourmelen, N.; Dehecq, A.; Trouvé, E.

    2014-12-01

    Climate warming over the 20th century has caused drastic changes in mountain glaciers globally, and of the Himalayan glaciers in particular. The stakes are high; glaciers and ice caps are the largest contributor to the increase in the mass of the world's oceans, and the Himalayas play a key role in the hydrology of the region, impacting on the economy, food safety and flood risk. Partial monitoring of the Himalayan glaciers has revealed a mixed picture; while many of the Himalayan glaciers are retreating, in some cases locally stable or advancing glaciers in this region have also been observed. But recent controversies have highlighted the need to understand the glaciers dynamic and its relationship with climate change in the region. Earth Observation provides a mean for global and long-term monitoring of mountain glaciers' dynamics. In the frame of the Dragon program, a partnership between the European Space Agency (ESA) and the Chinese Center for Earth Observation (NRSCC), we begun a monitoring program aimed at quantifying multidecadal changes in glaciers' flow at the scale of the entire Himalayas and Karakoram from a 40 years' archive of Earth Observation. Ultimately, the provision of a global and time-sensitive glaciers velocity product will help to understand the evolution of the Himalayan glaciers in lights of glaciological (e.g. presence of debris-cover, surges, proglacial lakes) and climatic conditions. Here we present a region-wide analysis of annual and seasonnal glacier flow velocity covering the Pamir-Karakoram-Himalaya region obtained from the analysis of the entire archive of Landsat data. Over 90% of the ice-covered regions, as defined by the Randolph Glacier Inventory, are measured, with precision on the retrieved velocity of the order of 2 m/yr. We show that the first order temporal evolution of glacier flow mirrors the pattern of glacier mass balance. We observe a general decrease of ice velocity in regions of known ice mass loss, and a more

  5. Cosmogenic 36Cl exposure ages reveal a 9.3 ka BP glacier advance and the Late Weichselian-Early Holocene glacial history of the Drangajökull region, northwest Iceland

    NASA Astrophysics Data System (ADS)

    Brynjólfsson, Skafti; Schomacker, Anders; Ingólfsson, Ólafur; Keiding, Jakob K.

    2015-10-01

    We present twenty-four new cosmogenic isotope (36Cl) surface exposure ages from erratic boulders, moraine boulders and glacially eroded bedrock that constrain the late Weichselian to Holocene glacial history of the Drangajökull region, northwest Iceland. The results suggest a topographically controlled ice sheet over the Vestfirðir (Westfjords) peninsula during the last glaciation. Cold based non-erosive sectors of the ice sheet covered most of the mountains while fjords and valleys were occupied with erosive, warm-based ice. Old36Cl exposure ages from highlands and mountain plateaux (L8; 76.5 ka and H1; 41.6 ka) in combination with younger erratic boulders (L7; 26.2 and K1-K4; 15.0-13.8 ka) superimposed on such surfaces suggest the presence of non-erosive ice over uplands and plateaux in the Vestfirðir peninsula during the last glaciation. Glacially scoured terrain and erratic boulders yielding younger exposure ages (L1-L6; 11.3-9.1 ka and R1, R6-R7; 10.6-9.4 ka) in the lowland areas indicate that the valleys and fjords of the Vestfirðir peninsula were occupied by warm-based, dynamic ice during the last glaciation. The deglaciation of mountain Leirufjall by 26.2 ka BP suggests that ice thinning and deglaciation of some mountains and plateaux preceded any significant lateral retreat of the ice sheet. Subsequently this initial ice thinning was followed by break-up of the shelf based ice sheet off Vestfirðir about 15 ka BP. Hence, the new exposure ages suggest a stepwise asynchronous deglaciation on land, following the shelf break-up with some valleys and most of the highlands, ice free by 14-15 ka BP. The outermost moraine at the mouth of Leirufjörður is dated to 9.3 ka BP, and we suggest the moraine to be formed by a glacier re-advance in response to a cooler climate forced by the reduced Atlantic Meridional Overturning Circulation at around 9.3 ka BP. A system of moraines proximal to the 9.3 ka moraine in Leirufjörður as well as a 9.4 ka deglaciation age

  6. 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

  7. 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

  8. Monitoring Popocatepetl volcano's glaciers (Mexico): case study of glacier extinction

    NASA Astrophysics Data System (ADS)

    Delgado, H.; Julio, P.; Huggel, C.; Brugman, M.

    2003-04-01

    Popocatépetl volcano is located 60 km southeast of Mexico City and is one of the three ice-clad volcanoes in Mexico. The two glaciers of Popocatépetl became extinct after a strong retreat due to the combination of at least three causes: global change, change in regional meteorological conditions (induced by the vicinity to highly polluted areas) and local enforcement (namely volcanic eruption). Glacier dimensions of Popocatépetl glaciers have been measured by photogrammetric means, and even though continuous monitoring was not feasible for decades, in recent years availability of aerial photographs allowed a better documentation of glacier areal changes. The first inventory made in 1958 threw an areal extent of 0.89 km2. A second inventory of the areal extent of the two small glaciers of Popocatépetl in 1982 reported 0.56 km2. Average retreat rate resulted nearly 14,000 m2/year. An areal measurement for 1996 resulted in an-order-of-magnitude smaller retreat rate (more than 1,500 m2/year). In early 1997, the retreat rate was nearly 12,500 m2/year, an order of magnitude similar as that of the 1958-1982 period. This scheme changed strongly in the following years when retreat rate was twice in 1998 and more than 7 times greater in 1999. By the end of the year 2000, the retreat rate remained in the same order of magnitude as in early 1999. Since the year 2000 and up to the present, the glaciers are just a series of independent ice masses (seracs) and the bedrock is seen in between them. GPR determinations made in 1995 showed a 40 m average ice thickness. During ice drilling in the year 2000 at nearly the same spot where GPR determinations were made in 1995, a thickness of 4 m was found. Therefore, glacier shrinkage has been documented not only by areal restriction but also by strong changes in thickness. The strong retreat experienced by Popocatépetl’s glaciers along the last decades, were possibly due to global climatic enforcement and proximity to industrial

  9. Pattern and forcing of Northern Hemisphere glacier variations during the last millennium

    NASA Astrophysics Data System (ADS)

    Porter, Stephen C.

    1986-07-01

    Time series depicting mountain glacier fluctuations in the Alps display generally similar patterns over the last two centuries, as do chronologies of glacier variations for the same interval from elsewhere in the Northern Hemisphere. Episodes of glacier advance consistently are associated with intervals of high average volcanic aerosol production, as inferred from acidity variations in a Greenland ice core. Advances occur whenever acidity levels rise sharply from background values to reach concentrations ≥1.2 μequiv H +/kg above background. A phase lag of about 10-15 yr, equivalent to reported response lags of Alpine glacier termini, separates the beginning of acidity increases from the beginning of subsequent ice advances. A similar relationship, but based on limited and less-reliable historical data and on lichenometric ages, is found for the preceding 2 centuries. Calibrated radiocarbon dates related to advances of non-calving and non-surging glaciers during the earlier part of the Little Ice Age display a comparable consistent pattern. An interval of reduced acidity values between about 1090 and 1230 A.D. correlates with a time of inferred glacier contraction during the Medieval Optimum. The observed close relation between Noothern Hemisphere glacier fluctuations and variations in Greenland ice-core acidity suggests that sulfur-rich aerosols generated by volcanic eruptions are a primary forcing mechanism of glacier fluctuations, and therefore of climate, on a decadal scale. The amount of surface cooling attributable to individual large eruptions or to episodes of eruptions is simlar to the probable average temperature reduction during culminations of Little Ice Age alacier advances (ca. 0.5°-1.2°C), as inferred from depression of equilibrium-line altitudes.

  10. Spatial patterns in glacier characteristics and area changes from 1962 to 2006 in the Kanchenjunga-Sikkim area, eastern Himalaya

    NASA Astrophysics Data System (ADS)

    Racoviteanu, A. E.; Arnaud, Y.; Williams, M. W.; Manley, W. F.

    2015-03-01

    This study investigates spatial patterns in glacier characteristics and area changes at decadal scales in the eastern Himalaya - Nepal (Arun and Tamor basins), India (Teesta basin in Sikkim) and parts of China and Bhutan - based on various satellite imagery: Corona KH4 imagery, Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Advanced Spaceborne Thermal Emission Radiometer (ASTER), QuickBird (QB) and WorldView-2 (WV2). We compare and contrast glacier surface area changes over the period of 1962-2000/2006 and their dependency on glacier topography (elevation, slope, aspect, percent debris cover) and climate (solar radiation, precipitation) on the eastern side of the topographic barrier (Sikkim) versus the western side (Nepal). Glacier mapping from 2000 Landsat ASTER yielded 1463 ± 88 km2 total glacierized area, of which 569 ± 34 km2 was located in Sikkim and 488 ± 29 km2 in eastern Nepal. Supraglacial debris covered 11% of the total glacierized area, and supraglacial lakes covered about 5.8% of the debris-covered glacier area alone. Glacier area loss (1962 to 2000) was 0.50 ± 0.2% yr-1, with little difference between Nepal (0.53 ± 0.2% yr-1) and Sikkim (0.44 ± 0.2% yr-1. Glacier area change was controlled mostly by glacier area, elevation, altitudinal range and, to a smaller extent, slope and aspect. In the Kanchenjunga-Sikkim area, we estimated a glacier area loss of 0.23 ± 0.08% yr-1 from 1962 to 2006 based on high-resolution imagery. On a glacier-by-glacier basis, clean glaciers exhibit more area loss on average from 1962 to 2006 (34%) compared to debris-covered glaciers (22%). Glaciers in this region of the Himalaya are shrinking at similar rates to those reported for the last decades in other parts of the Himalaya, but individual glacier rates of change vary across the study area with respect to local topography, percent debris cover or glacier elevations.

  11. Recent Elevation Changes on Bagley Ice Valley, Guyot and Yahtse Glaciers, Alaska, from ICESat Altimetry, Star-3i Airborne, and SRTM Spaceborne DEMs

    NASA Astrophysics Data System (ADS)

    Muskett, R. R.; Sauber, J. M.; Lingle, C. S.; Rabus, B. T.; Tangborn, W. V.; Echelmeyer, K. A.

    2005-12-01

    Three- to 5-year surface elevation changes on Bagley Ice Valley, Guyot and Yahtse Glaciers, in the eastern Chugach and St. Elias Mtns of south-central Alaska, are estimated using ICESat-derived data and digital elevation models (DEMs) derived from interferometric synthetic aperture radar (InSAR) data. The surface elevations of these glaciers are influenced by climatic warming superimposed on surge dynamics (in the case of Bagley Ice Valley) and tidewater glacier dynamics (in the cases of Guyot and Yahtse Glaciers) in this coastal high-precipitation regime. Bagley Ice Valley / Bering Glacier last surged in 1993-95. Guyot and Yahtse Glaciers, as well as the nearby Tyndell Glacier, have experienced massive tidewater retreat during the past century, as well as during recent decades. The ICESat-derived elevation data we employ were acquired in early autumn in both 2003 and 2004. The NASA/NIMA Shuttle Radar Topography Mission (SRTM) DEM that we employ was derived from X-band InSAR data acquired during this 11-22 Feb. 2000 mission and processed by the German Aerospace Center. This DEM was corrected for estimated systematic error, and a mass balance model was employed to account for seasonal snow accumulation. The Star-3i airborne, X-band, InSAR-derived DEM that we employ was acquired 4-13 Sept. 2000 by Intermap Technologies, Inc., and was also processed by them. The ICESat-derived profiles crossing Bagley Ice Valley, differenced with Star-3i DEM elevations, indicate preliminary mean along-profile elevation increases of 5.6 ± 3.4 m at 1315 m altitude, 7.4 ± 2.7 m at 1448 m altitude, 4.7 ± 1.9 m at 1557 m altitude, 1.3 ± 1.4 m at 1774 m altitude, and 2.5 ± 1.5 m at 1781 m altitude. This is qualitatively consistent with the rising surface on Bagley Ice Valley observed by Muskett et al. [2003]. The ICESat-derived profiles crossing Yahtse Glacier, differenced with the SRTM DEM elevations, indicate preliminary mean elevation changes (negative implies decrease) of -0.9 ± 3

  12. 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.

  13. Maximum extent of Late Pleistocene glaciers and last deglaciation of La Cerdanya mountains, Southeastern Pyrenees

    NASA Astrophysics Data System (ADS)

    Palacios, David; Gómez-Ortiz, Antonio; Andrés, Nuria; Vázquez-Selem, Lorenzo; Salvador-Franch, Ferran; Oliva, Marc

    2015-02-01

    This paper examines glacial evolution in the La Pera and Malniu cirques, and Arànser, La Llosa and Duran valleys, in the Cerdanya massifs on the south-facing slopes of the eastern Pyrenees. A geomorphologic analysis and dating of moraine boulders, glacially polished bedrock and rock glacier blocks were carried out by means of cosmogenic 36Cl surface exposure dating. The maximum ice advance was contemporary with the Last Glacial Maximum at 23 ka ago, and it was of greater or only slightly lesser magnitude than for previous Quaternary advances. The termini of glaciers remained close to maximum positions, with minor advances and retreats until 18-17 ka when the glacial tongues disappeared from the valleys. Depending on the previous topography, these glaciers left behind a single polygenic moraine, in the case of confined valleys, or multiple moraines next to each other in the case of flat, more open areas. A final glacial advance is detected during the Oldest Dryas close to the cirque headwalls, and the glaciers finally disappeared during the Bølling interstadial. The glaciers were then replaced by rock glaciers, whose front immediately became inactive, although their activity continued near their source area until the early Holocene.

  14. Helicopter-borne and ground-towed radar surveys of the Fourcade Glacier on King George Island, Antarctica

    NASA Astrophysics Data System (ADS)

    Kim, K. Y.; Lee, J.; Hong, M. H.; Hong, J. K.; Shon, H.

    2010-02-01

    To determine subglacial topography and internal features of the Fourcade Glacier on King George Island in Antarctica, helicopter-borne and ground-towed ground-penetrating radar (GPR) data were recorded along four profiles in November 2006. Signature deconvolution, f-k migration velocity analysis, and finite-difference depth migration applied to the mixed-phase, single-channel, ground-towed data, were effective in increasing vertical resolution, obtaining the velocity function, and yielding clear depth images, respectively. For the helicopter-borne GPR, migration velocities were obtained as root-mean-squared velocities in a two-layer model of air and ice. The radar sections show rugged subglacial topography, englacial sliding surfaces, and localised scattering noise. The maximum depth to the basement is over 79m in the subglacial valley adjacent to the south-eastern slope of the divide ridge between Fourcade and Moczydlowski Glaciers. In the ground-towed profile, we interpret a complicated conduit above possible basal water and other isolated cavities, which are a few metres wide. Near the terminus, the GPR profiles image sliding surfaces, fractures, and faults that will contribute to the tidewater calving mechanism forming icebergs in Potter Cove.

  15. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 3. Englacial and subglacial conditions revealed by seismic reflection data on Store Glacier, West Greenland.

    NASA Astrophysics Data System (ADS)

    Hofstede, Coen; Eisen, Olaf; Young, Tun Jan; Doyle, Samuel; Hubbard, Bryn; Christoffersen, Poul; Hubbard, Alun

    2015-04-01

    Basal conditions have a profound influence on the dynamics of outlet glaciers. As part of the SAFIRE research programme, we carried out a seismic survey on Store Glacier, a tidewater glacier terminating in Uummanaq Fjord in West Greenland (see joint abstracts by Christoffersen et al. and Doyle et al. for details). At the survey site the ice moves 700m/a making the terrain crevassed and bumpy. Despite the rough terrain we collected two 1.5 km long survey lines parallel and perpendicular to the ice flow direction using a 300m snow streamer and explosives as a source. The seismic data reveal an ice thickness of about 620m and 20 to 30m of subglacial sediment on the upstream side of the area thinning in the downstream direction. From polarity reversals seen along the ice-bed contact we speculate that the sediments have varying degrees of water content. The ice itself has several englacial reflections parallel and close to the bed. At approximately 475m depth, a clear single englacial reflection is observed in the parallel survey line. Thermistor data installed at this location show a clear increase in ice temperature starting at this depth. We speculate that the observed englacial reflection is caused by a change in crystal orientation fabric allowing greater ice deformation below this depth causing increased strain heating.

  16. 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 ...

  17. 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

  18. Recent evolution and mass balance of Cordón Martial glaciers, Cordillera Fueguina Oriental

    NASA Astrophysics Data System (ADS)

    Strelin, Jorge; Iturraspe, Rodolfo

    2007-10-01

    Past and present glacier changes have been studied at Cordón Martial, Cordillera Fueguina Oriental, Tierra del Fuego, providing novel data for the Holocene deglaciation history of southern South America and extrapolating as well its future behavior based on predicted climatic changes. Regional geomorphologic and stratigraphic correlations indicate that the last glacier advance deposited the ice-proximal ("internal") moraines of Cordón Martial, around 330 14C yr BP, during the Late Little Ice Age (LLIA). Since then glaciers have receded slowly, until 60 years ago, when major glacier retreat started. There is a good correspondence for the past 100 years between the surface area variation of four small cirque glaciers at Cordón Martial and the annual temperature and precipitation data of Ushuaia. Between 1984 and 1998, Martial Este Glacier lost 0.64 ± 0.02 × 10 6 m 3 of ice mass (0.59 ± 0.02 × 10 6 m 3 w.e.), corresponding to an average ice thinning of 7.0 ± 0.2 m (6.4 ± 0.2 m w.e), according to repeated topographic mapping. More detailed climatic data have been obtained since 1998 at the Martial Este Glacier, including air temperature, humidity and solar radiation. These records, together with the monthly mass balance measured since March 2000, document the annual response of the Martial Este Glacier to the climate variation. Mass balances during hydrological years were positive in 2000, negative in 2001 and near equilibrium in 2002. Finally, using these data and the regional temperature trend projections, modeled for different future scenarios by the Atmosphere-Ocean Model (GISS-NASA/GSFC), potential climatic-change effects on this mountain glacier were extrapolated. The analysis shows that only the Martial Este Glacier may survive this century.

  19. On the 'real' mass loss of some surging glaciers in the central Karakoram

    NASA Astrophysics Data System (ADS)

    Paul, Frank

    2016-04-01

    Several assessments of the mass changes of surging glaciers in the central Karakoram (and elsewhere) have shown near-zero changes over the typically decadal-long observation periods. This is in line with the theory that during a surge mass from a reservoir area is moved down-glacier to a receiving area with limited overall change. The resulting elevation changes of the glacier surface as determined by differencing DEMs from two points in time show a typical pattern (decreasing at higher, increasing at lower elevations) with a possible strong frontal advance (km scale) of the terminus. However, this is only half of the story as the observed mass gain at lower elevations is ultimately also a loss. This loss can only be determined when it is calculated separately and when sufficiently precise DEMs from the beginning and the end of a surge are available for each individual glacier. As the latter are hard to obtain, this study presents a simplified geomorphometric approach to approximate a potential maximum surge volume for 20 glaciers with a channel-like glacier fore field. By assuming a semi-elliptical cross-section of the channels, simple measurements of their average width, height and length in Google Earth provide the volume. Further glacier-specific parameters are taken from a recently compiled glacier inventory (area, slope) and Google Earth (minimum length and highest/lowest elevations) to obtain characteristics such as elevation ranges and volume. The average annual specific volume loss for each glacier is then determined by dividing the calculated surge volumes by the respective glacier area and the duration of a full surge cycle (obtained in a previous study). Which glacier area (minimum?) and surge duration (only the active phase?) have to be taken for this calculation is likely a matter of debate. With surge distances between about 1 and 5 km and channel widths (heights) between 300 and 700 (50 and 125) m, the surge volumes vary between 15 and 250 (mean 80

  20. 10Be dating of the end of low-altitude rock glacier activity in the Alps - evidence for cold conditions during the early Preboreal.

    NASA Astrophysics Data System (ADS)

    Kerschner, Hanns; Ivy-Ochs, Susan

    2010-05-01

    Large relict rock glacier complexes are conspicious features in the Alps. Their occurence can roughly be subdivided into a "lower rock glacier belt", which reaches down to about 1900 m a.s.l., an "intermediate rock glacier belt" with rock glacier snouts at around present-day timberline (approx. 2200 m a.s.l) in the central Alps and an "upper rock glacier belt" at similar altitudes as presently active rock glaciers. All these rock glaciers indicate the former presence of discontinuous permafrost at their respective altitudes and are good indicators for the mean annual air temperature during their active period. The end of rock glacier activity at a given altitude marks also the end of the existence of permafrost conditions. Experience from the Alps shows that it may take about a century until the surface of a rock glacier is stabilized, Hence, if it is possible to date the surface of a relict rock glacier with 10Be, we get a close date for the end of permafrost activity at the altitude of the rock glacier. From the difference between the altitude of the relict rock glacier and presently active rock glaciers, the rise of mean annual air temperature can be calculated. Relict rock glaciers at present-day timberline at Julierpass (Swiss Alps) and at Larstigtal (Austrian Alps) gave ages in the order of 10.5 ka BP for surface stabilization. Both rock glaciers, which belong to the "intermediate rock glacier belt", developed from lateral moraines and scree slopes. They started to move into former glacier beds after ice recession from the Younger Dryas "Egesen" advance. Their age indicates that climatic conditions favouring permafrost existence about 300 - 400 m below 20th century permafrost occurence prevailed during most of the Preboreal. Taken together with the Kartell glacier advance (10.8 ka) they show that rapid climatic warming at the Younger Dryas / Holocene boundary was followed by more unstable climatic conditions and and somewhat slower warming until full Holocene

  1. Glacier Mass Balance measurements in Bhutan

    NASA Astrophysics Data System (ADS)

    Jackson, Miriam; Tenzin, Sangay; Tashi, Tshering

    2014-05-01

    Long-term glacier measurements are scarce in the Himalayas, partly due to lack of resources as well as inaccessibility of most of the glaciers. There are over 600 glaciers in Bhutan in the Eastern Himalayas, but no long-term measurements. However, such studies are an important component of hydrological modelling, and especially relevant to the proposed expansion of hydropower resources in this area. Glaciological studies are also critical to understanding the risk of jøkulhlaups or GLOFS (glacier lake outburst floods) from glaciers in this region. Glacier mass balance measurements have been initiated on a glacier in the Chamkhar Chu region in central Bhutan by the Department of Hydro-Met Services in co-operation with the Norwegian Water Resources and Energy Directorate. Chamkhar Chu is the site of two proposed hydropower plants that will each generate over 700 MW, although the present and future hydrological regimes in this basin, and especially the contribution from glaciers, are not well-understood at present. There are about 94 glaciers in the Chamkhar Chhu basin and total glacier area is about 75 sq. km. The glaciers are relatively accessible for the Himalayas, most of them can be reached after only 4-5 days walk from the nearest road. One of the largest, Thana glacier, has been chosen as a mass balance glacier and measurements were initiated in 2013. The glacier area is almost 5 sq. km. and the elevation range is 500 m (5071 m a.s.l. to 5725 m a.s.l.) making it suitable as a benchmark glacier. Preliminary measurements on a smaller, nearby glacier that was visited in 2012 and 2013 showed 1 m of firn loss (about 0.6 m w.eq.) over 12 months.

  2. Holocene glacier history of the Lago Argentino basin, Southern Patagonian Icefield

    NASA Astrophysics Data System (ADS)

    Strelin, Jorge A.; Kaplan, Michael R.; Vandergoes, Marcus J.; Denton, George H.; Schaefer, Joerg M.

    2014-10-01

    We present new geomorphic, stratigraphic, and chronologic data for Holocene glacier fluctuations in the Lago Argentino basin on the eastern side of the southern Patagonian Andes. Chronologic control is based on 14C and surface-exposure 10Be dating. After the Lateglacial maximum at 13,000 cal yrs BP, the large ice lobes that filled the eastern reaches of Lago Argentino retreated and separated into individual outlet glaciers; this recession was interrupted only by a stillstand or minor readvance at 12,200 cal yrs BP. The eight largest of these individual outlet glaciers are, from north to south: Upsala, Agassiz, Onelli, Spegazzini, Mayo, Ameghino, Perito Moreno, and Grande (formerly Frías). Holocene recession of Upsala Glacier exposed Brazo Cristina more than 10,115 ± 100 cal yrs BP, and reached inboard of the Holocene moraines in Agassiz Este Valley by 9205 ± 85 cal yrs BP; ice remained in an inboard position until 7730 ± 50 cal yrs BP. Several subsequent glacier readvances are well documented for the Upsala and Frías glaciers. The Upsala Glacier readvanced at least seven times, the first being a relatively minor expansion - documented only in stratigraphic sections - between 7730 ± 50 and 7210 ± 45 cal yrs BP. The most extensive Holocene advances of Upsala Glacier resulted in the deposition of the Pearson 1 moraines and related landforms, which are divided into three systems. The Pearson 1a advance occurred about 6000-5000 cal yrs BP and was followed by the slightly less-extensive Pearson 1b and 1c advances dated to 2500-2000 and 1500-1100 cal yrs BP, respectively. Subsequent advances of Upsala Glacier resulted in deposition of the Pearson 2 moraines and corresponding landforms, also separated into three systems, Pearson 2a, 2b, and 2c, constructed respectively at ˜700, >400, and <300 cal yrs BP to the early 20th century. Similar advances are also recorded by moraine systems in front of Grande Glacier and herein separated into the Frías 1 and Frías 2a, 2b

  3. Longitudinal surface structures (flowstripes) on Antarctic glaciers

    NASA Astrophysics Data System (ADS)

    Glasser, N. F.; Gudmundsson, G. H.

    2012-03-01

    Longitudinal surface structures ("flowstripes") are common on many glaciers but their origin and significance are poorly understood. In this paper we present observations of the development of these longitudinal structures from four different Antarctic glacier systems; the Lambert Glacier/Amery Ice Shelf area, the Taylor and Ferrar Glaciers in the Ross Sea sector, Crane and Jorum Glaciers (ice-shelf tributary glaciers) on the Antarctic Peninsula, and the onset zone of a tributary to the Recovery Glacier Ice Stream in the Filchner Ice Shelf area. Mapping from optical satellite images demonstrates that longitudinal surface structures develop in two main situations: (1) as relatively wide flow stripes within glacier flow units and (2) as relatively narrow flow stripes where there is convergent flow around nunataks or at glacier confluence zones. Our observations indicate that the confluence features are narrower, sharper, and more clearly defined features. They are characterised by linear troughs or depressions on the ice surface and are much more common than the former type. Longitudinal surface structures within glacier flow units have previously been explained as the surface expression of localised bed perturbations but a universal explanation for those forming at glacier confluences is lacking. Here we propose that these features are formed at zones of ice acceleration and extensional flow at glacier confluences. We provide a schematic model for the development of longitudinal surface structures based on extensional flow that can explain their ridge and trough morphology as well as their down-ice persistence.

  4. 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)

  5. 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. PMID:26450208

  6. Constraining Paleo-Glacier Dynamics Using Optically Stimulated Luminescence (OSL) Bedrock Exposure Dating

    NASA Astrophysics Data System (ADS)

    Brun, F.; Valla, P.; King, G. E.; Herman, F.

    2014-12-01

    Quantifying glacier dynamics over the late-Pleistocene remains an important challenge for understanding glacial response to climate change. Historical glacier reconstructions are spatially limited (e.g. the European Alps) and cover only the last ~100 yrs, restricting their use as paleoclimatic proxies. Bedrock dating methods such as Terrestrial Cosmogenic Nuclides (TCN) dating or lichenometry allows glacier fluctuations to be reconstructed over longer timescales. However, these methods have limited temporal resolution, and therefore do not enable accurate dating of recent glacier fluctuations (e.g. short glacier re-advances). Here, we use a novel in situ dating method based on Optically Stimulated Luminescence (OSL) to fill this temporal/spatial gap. OSL dating is based on the time-accumulation of trapped electrons in the lattice defects of minerals. OSL-exposure dating is based on the bleaching (i.e. resetting) of the minerals' luminescence signal when they are exposed to light (Sohbati et al., 2012 JGR-Solid Earth), which depends on exposure time, effective photon flux and light attenuation by minerals. We analyzed 10 samples in the Val d'Hérens (Swiss Alps) where post-LGM glacier dynamics remain poorly constrained and short glacier re-advances are thought to occur during the Holocene. Bedrock samples were drilled and small cores were sliced into 1-mm thick discs from which natural luminescence profiles were measured. We calibrated the luminescence model parameters using historically-exposed bedrock samples (~100 yr) near the Mont-Miné glacier, and used this on-site calibration to date surface exposure of glacial bedrock at various elevations along the valley; initial relative dating results are promising. Although OSL-exposure dating appears an efficient tool for historical glacier reconstructions, OSL bleaching over longer timescales (i.e. late-Pleistocene to Holocene) requires more investigation before use as a chronometer.

  7. 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.

  8. Southern Alaska Glaciers: Spatial and Temporal Variations in Ice Volume

    NASA Technical Reports Server (NTRS)

    Sauber, J.; Molnia, B. F.; Lutchke, S.; Rowlands, D.; Harding, D.; Carabajal, C.; Hurtado, J. M.; Spade, G.

    2004-01-01

    Although temperate mountain glaciers comprise less than 1% of the glacier-covered area on Earth, they are important because they appear to be melting rapidly under present climatic conditions and, therefore, make significant contributions to rising sea level. In this study, we use ICESat observations made in the last 1.5 years of southern Alaska glaciers to estimate ice elevation profiles, ice surface slopes and roughness, and bi-annual and/or annual ice elevation changes. We report initial results from the near coastal region between Yakutat Bay and Cape Suckling that includes the Malaspina and Bering Glaciers. We show and interpret ice elevations changes across the lower reaches of the Bagley Ice Valley for the period between October 2003 and May 2004. In addition, we use off-nadir pointing observations to reference tracks over the Bering and Malaspina Glaciers in order to estimate annual ice elevation change. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Shuttle Radar Topography Mission (SRTM) derived DEMs are used to estimate across track regional slopes between ICESat data acquisitions. Although the distribution and quantity of ICESat elevation profiles with multiple, exact repeat data is currently limited in Alaska, individual ICESat data tracks, provide an accurate reference surface for comparison to other elevation data (e.g. ASTER and SRTM X- and C-band derived DEMs). Specifically we report the elevation change over the Malaspina Glacier's piedmont lobe between a DEM derived from SRTM C-band data acquired in Feb. 2000 and ICESat Laser #2b data from Feb.-March 2004. We also report use of ICESat elevation data to enhance ASTER derived absolute DEMs. Mountain glaciers generally have rougher surfaces and steeper regional slopes than the ice sheets for which the ICESat design was optimized. Therefore, rather than averaging ICESat observations over large regions or relying on crossovers, we are working with well-located ICESat

  9. Holocene glacier fluctuations inferred from lacustrine sediment, Emerald Lake, Kenai Peninsula, Alaska

    NASA Astrophysics Data System (ADS)

    LaBrecque, Taylor S.; Kaufman, Darrell S.

    2016-01-01

    Physical and biological characteristics of lacustrine sediment from Emerald Lake were used to reconstruct the Holocene glacier history of Grewingk Glacier, southern Alaska. Emerald Lake is an ice-marginal threshold lake, receiving glaciofluvial sediment when Grewingk Glacier overtops the topographic divide that separates it from the lake. Sub-bottom acoustical profiles were used to locate core sites to maximize both the length and resolution of the sedimentary sequence recovered in the 4-m-long cores. The age model for the composite sequence is based on 13 14C ages and a 210Pb profile. A sharp transition from the basal inorganic mud to organic-rich mud at 11.4 ± 0.2 ka marks the initial retreat of Grewingk Glacier below the divide of Emerald Lake. The overlaying organic-rich mud is interrupted by stony mud that records a re-advance between 10.7 ± 0.2 and 9.8 ± 0.2 ka. The glacier did not spill meltwater into the lake again until the Little Ice Age, consistent with previously documented Little Ice Ages advances on the Kenai Peninsula. The retreat of Grewingk Glacier at 11.4 ka took place as temperature increased following the Younger Dryas, and the subsequent re-advance corresponds with a climate reversal beginning around 11 ka across southern Alaska.

  10. Late Pleistocene oscillations of the Drau Glacier (southern Austria)

    NASA Astrophysics Data System (ADS)

    Karnitschar, Christina; Reitner, Jürgen; Draganits, Erich

    2016-04-01

    The Drau Glacier was the largest Pleistocene glacier in the southeastern part of the Alps and significantly shaped the landscape in this region. The study area is located at the termination of the Drau Glacier in the southern part of Austria (Carinthia). The investigation aims to decipher glacial dynamics during the Late Pleistocene glacial advance, stabilisation and final recession of this glacier based on geological/geomorphological mapping, interpretation of airborne laser scan (ALS) topographic data and lithostratigraphic investigations of glacial and periglacial sediments. Special emphasis is laid on the reconstruction of the maximum extent of the glaciation (LGM). Based on previous mapping by Bobek (1959) and Ucik (1996-1998) more details have been gained for the paleogeographic reconstruction based on glacial and non-glacial erosion and accumulation features. These include traces of pre-Upper Pleistocene glaciation, drumlins, terminal moraines and kettle holes. Paleogeographic reconstruction was done with correlation of different outcrops based on lithostratigraphy and ALS topography. Sequences of gravel related to glacial advance covered by till, followed by periglacial sediments allowed detailed reconstruction of the glacial sequence in this area and the complex succession of various extents of the Drau Glacier. References Bobek, Hans. 1959: Der Eisrückgang im östlichen Klagenfurter Becken. In: Mitteilungen der österreichischen geographischen Gesellschaft, Wien. Ucik, Friedrich Hans. 1996: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 141, S. 340, Wien. Ucik, Friedrich Hans. 1997: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 141, S. 325-326, Wien. Ucik, Friedrich Hans. 1998: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 142, S. 333-334, Wien.

  11. Comparison of the responses of two temperate Alpine valley glaciers to climate change at the decadal scale

    NASA Astrophysics Data System (ADS)

    Gabbud, Chrystelle; Tahir, Adnan Ahmad; Micheletti, Natan; Lane, Stuart

    2015-04-01

    Glacier advance and recession are considered as key indicators of climate change by the Intergovernmental Panel on Climate Change. Understanding the relationship between climatic variations and glacial responses is crucial. Here, we use archival photogrammetric methods to generate high resolution and precise Digital Elevation Models (DEMs) of two Alpine valley glaciers that have shown a contrasting response to recent climatic variability. Digital photogrammetry is well-established for glacier monitoring, mass balance determination and computation of the volumes of ice mass change. Reconstructions of the recent history of glaciers have been performed through and since the Little Ice Age and also more recently in relation to recent global warming. This study uses aerial imagery available from the early 1960s. Archival digital photogrammetry is applied to reconstruct the decadal scale glacial history of the Haut Glacier d'Arolla and the Glacier de Tsijiore Nouve in south western Switzerland. The data generated are used to explore the linkages between glacier changes and climate forcing. While both of the glaciers were subject to exactly the same climatic settings (they are only a few km apart), the responses to climatic variability have been markedly different. The data show continual recession of the Haut Glacier d'Arolla since 1967, associated with long-term climatic amelioration but only a weak response to shorter-term climatic deterioration. Glacier surface velocity estimates obtained using surface particle tracking showed that, unlike for most Swiss glaciers during the late 1970s and early 1980s, ice mass flux from the accumulation zone was too low to compensate for the effects of glacier thinning. Associated with glacier response time, that means that whilst there may have been a reduction in the ablation rate during the colder period, the flux did still not exceed the ablation rate, and hence snout advance was prevented. By contrast, the Tsijiore Nouve Glacier

  12. Mesoscale Icefield Breezes over Athbasca Glacier.

    NASA Astrophysics Data System (ADS)

    Conway, J. P.; Helgason, W.; Pomeroy, J. W.; Sicart, J. E.

    2015-12-01

    Atmospheric boundary layer (ABL) dynamics over glaciers are of great interest as they can modify the response of glacier mass balance to large scale climate forcing. A key feature of the glacier ABL is formation of katabatic winds driven by turbulent sensible heat exchange with a cooler underlying ice surface. These winds can markedly alter the spatio-temporal distribution of air temperature over glacier surfaces from the environmental lapse rate, which in turn affects the distribution of melt. An intensive field campaign was conducted over 13 days in June 2015 at Athabasca Glacier, an outlet of Columbia Icefield in the Rocky Mountains of Canada. Multiple automatic weather stations, eddy covariance systems, distributed temperature sensors, SODAR and kite profiling systems were used to characterise how the glacier ABL evolved spatially and temporally, how the differences in glacier ABL properties were related to valley and regional circulation and what effect these differences had on surface lapse rates. In general strong daytime down-glacier winds were observed over the glacier. These winds extended well beyond the glacier into the proglacial area and through the depth of lower ice-free valley. On most days wind speed was consistent or increasing through to the top of the above-glacier profiles (100 to 200 m), indicating a quite well mixed surface boundary layer. A wind speed maximum in the lowest few metres above the glacier surface, characteristic of a katabatic wind, was only observed on one day. The dominant circulation within the valley appears to be what could be termed an 'icefield breeze'; strong down-glacier winds driven by mesoscale pressure gradients that are set up by differential suface heating over the non-glaciated valleys and much the larger Columbia Icefield upstream of the glacier. The effect of the different circulations on lapse rates will be explored with a view to developing variable lapse rates for modelling glacier mass balance.

  13. Changes of glaciers in the Andes of Chile and priorities for future work.

    PubMed

    Pellicciotti, F; Ragettli, S; Carenzo, M; McPhee, J

    2014-09-15

    Glaciers in the Andes of Chile seem to be shrinking and possibly loosing mass, but the number and types of studies conducted, constrained mainly by data availability, are not sufficient to provide a synopsis of glacier changes for the past or future or explain in an explicit way causes of the observed changes. In this paper, we provide a systematic review of changes in glaciers for the entire country, followed by a discussion of the studies that have provided evidence of such changes. We identify a missing type of work in distributed, physically-oriented modelling studies that are needed to bridge the gap between the numerous remote sensing studies and the specific, point scale works focused on process understanding. We use an advanced mass balance model applied to one of the best monitored glaciers in the region to investigate four main research issues that should be addressed in modelling studies for a sound assessment of glacier changes: 1) the use of physically-based models of glacier ablation (energy balance models) versus more empirical models (enhanced temperature index approaches); 2) the importance of the correct extrapolation of air temperature forcing on glaciers and in high elevation areas and the large uncertainty in model outputs associated with it; 3) the role played by snow gravitational redistribution; and 4) the uncertainty associated with future climate scenarios. We quantify differences in model outputs associated with each of these choices, and conclude with suggestions for future work directions. PMID:24300481

  14. 125 years of glacier survey of the Austrian Alpine Club: results and future challenges

    NASA Astrophysics Data System (ADS)

    Fischer, Andrea

    2016-04-01

    One of the aims of the German and Austrian Alpine Club was the scientific investigation of the Alps. In 1891, several years after Swiss initiatives, Richter put out a call to contribute to regular glacier length surveys in the Eastern Alps. Since then more than 100 glaciers have been surveyed on a first biannual and later annual basis. The database includes measured data showing a general glacier retreat since 1891, with two periods of glacier advances in the 1920s and 1980s. Less well known are the sketches and reports which illustrate, for instance, changes in surface texture. The interpretation of length change data requires a larger sample of data for a reasonable interpretation on a regional scale. Nearly every time series in the long history of investigation includes gaps, e.g. in cases of problematic snout positions on steep rock walls or in lakes, or of debris-covered tongues. Current climate change adds the problem of glaciers splitting up into several smaller glaciers which behave differently. Several basic questions need to be addressed to arrive at a most accurate prolongated time series: How should measurements on disintegrating or debris-covered (and thus more or less stagnating) glaciers be documented, and how can we homogenize length change time series? Despite of uncertainties, length change data are amongst the longest available records, bridging the gap to moraine datings of the early holocene.

  15. Glacier dynamics and lake development on South Georgia during the late-glacial and early Holocene.

    NASA Astrophysics Data System (ADS)

    Rosqvist, Gunhild; Davies, Sarah; Leng, Melanie

    2014-05-01

    Geochemical records from lakes on South Georgia provide data on glacier variation and lake development since 18.6 ka. Glaciers retreated and lakes had developed already by 18.6 ka BP. The retreat was probably a response to the increased insolation combined with sea-ice decline that also have been suggested to be the key factors responsible for the pre-18 ka BP warming registered on the Antarctic peninsula. South Georgia glaciers responded earlier compared to glaciers located in southernmost South America and in the New Zealand Alps. The lake records show a terrestrial response to the Antarctic Cold Reversal (ACR) confirming, together with marine evidence, the extent to which an Antarctic climate pattern is registered in the Southern Ocean at this time. The timing of glacier retreat after 12 ka BP on South Georgia coincides with major glacier recession in Southern South America and New Zealand. Our data indicate that the glaciers on South Georgia kept a relatively advanced position until ca 8 ka BP after which they retreated rapidly to above 200 m a sl. The South Georiga lake records reveal a terrestrial response, but of opposite sign, to changes in the North Atlantic during the late glacial indicating that a link exist between terrestrial sub-Antarctic and the Northern Hemisphere during deglaciation.

  16. Late Holocene glacial history of the Copper River Delta, coastal south-central Alaska, and controls on valley glacier fluctuations

    NASA Astrophysics Data System (ADS)

    Barclay, David J.; Yager, Elowyn M.; Graves, Jason; Kloczko, Michael; Calkin, Parker E.

    2013-12-01

    Fluctuations of four valley glaciers in coastal south-central Alaska are reconstructed for the past two millennia. Tree-ring crossdates on 216 glacially killed stumps and logs provide the primary age control, and are integrated with glacial stratigraphy, ages of living trees on extant landforms, and historic forefield photographs to constrain former ice margin positions. Sheridan Glacier shows four distinct phases of advance: in the 530s to c.640s in the First Millennium A.D., and the 1240s to 1280s, 1510s to 1700s, and c.1810s to 1860s during the Little Ice Age (LIA). The latter two LIA advances are also recorded on the forefields of nearby Scott, Sherman and Saddlebag glaciers. Comparison of the Sheridan record with other two-millennia long tree-ring constrained valley glacier histories from south-central Alaska and Switzerland shows the same four intervals of advance. These expansions were coeval with decreases in insolation, supporting solar irradiance as the primary pacemaker for centennial-scale fluctuations of mid-latitude valley glaciers prior to the 20th century. Volcanic aerosols, coupled atmospheric-oceanic systems, and local glacier-specific effects may be important to glacier fluctuations as supplemental forcing factors, for causing decadal-scale differences between regions, and as a climatic filter affecting the magnitude of advances.

  17. Seasonal variabilty of surface velocities and ice discharge of Columbia Glacier, Alaska using high-resolution TanDEM-X satellite time series and NASA IceBridge data

    NASA Astrophysics Data System (ADS)

    Vijay, Saurabh; Braun, Matthias

    2014-05-01

    Columbia Glacier is a grounded tidewater glacier located on the south coast of Alaska. It has lost half of its volume during 1957-2007, more rapidly after 1980. It is now split into two branches, known as Main/East and West branch due to the dramatic retreat of ~ 23 km and calving of iceberg from its terminus in past few decades. In Alaska, a majority of the mass loss from glaciers is due to rapid ice flow and calving icebergs into tidewater and lacustrine environments. In addition, submarine melting and change in the frontal position can accelerate the ice flow and calving rate. We use time series of high-resolution TanDEM-X stripmap satellite imagery during 2011-2013. The active image of the bistatic TanDEM-X acquisitions, acquired over 11 or 22 day repeat intervals, are utilized to derive surface velocity fields using SAR intensity offset tracking. Due to the short temporal baselines, the precise orbit control and the high-resolution of the data, the accuracies of the velocity products are high. We observe a pronounce seasonal signal in flow velocities close to the glacier front of East/Main branch of Columbia Glacier. Maximum values at the glacier front reach up to 14 m/day were recorded in May 2012 and 12 m/day in June 2013. Minimum velocities at the glacier front are generally observed in September and October with lowest values below 2 m/day in October 2012. Months in between those dates show corresponding increase or deceleration resulting a kind of sinusoidal annual course of the surface velocity at the glacier front. The seasonal signal is consistently decreasing with the distance from the glacier front. At a distance of 17.5 km from the ice front, velocities are reduced to 2 m/day and almost no seasonal variability can be observed. We attribute these temporal and spatial variability to changes in the basal hydrology and lubrification of the glacier bed. Closure of the basal drainage system in early winter leads to maximum speeds while during a fully

  18. 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.

  19. Spatially heterogeneous wastage of Himalayan glaciers

    PubMed Central

    Fujita, Koji; Nuimura, Takayuki

    2011-01-01

    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. PMID:21808042

  20. Historical and future hydrologic response to glacier recession in the Cordillera Real, Bolivia

    NASA Astrophysics Data System (ADS)

    Frans, C. D.; Istanbulluoglu, E.; Naz, B.; Lettenmaier, D. P.; Condom, T.; Clarke, G. K.; Burns, P. J.; Nolin, A. W.

    2013-12-01

    In many partially glaciated watersheds climate-forced glacier recession has altered and will continue to alter seasonal water availability, leading to profound implications for water supply systems. The tropical glaciers of the Cordillera Real, Bolivia, whose melt water significantly contributes to water supply and energy production for the densely populated La Paz area, have retreated at unprecedented rates since the 1970's. This glacier recession will continue with ongoing increasing temperatures projected for the subtropical Andes. We use a recently developed glacio-hydrological model to evaluate the contribution of glacier melt to watershed discharge, and track this contribution in time with changing glacier area. A glacier model, solving time-evolving and spatially-distributed balance equations for glacier mass and momentum, is integrated within the Distributed Hydrology Soil Vegetation Model (DHSVM). The glacio-hydrologic behavior of Cordillera Real watersheds is simulated during the historical period of 1987-2010. This model application is validated through comparisons with satellite derived glacier extent estimates and in-situ mass balance, surface energy flux, and stream discharge measurements. The retrospective analysis indicates that glacier melt contributed, on average, 31% (63%) of total annual (dry season-JJA) watershed discharge. Further, the modeling approach is used to predict the transitioning contribution of glacier melt and watershed hydrology through the 21st century. Multiple realizations of the 21st century meteorological data, used to force the glacier-hydrological model, are produced using a stochastic statistical downscaling technique. In this technique a weather generator (Advanced Weather Generator, AWE-GEN) is employed with statistical parameters of the future climate obtained from predictions of 11 CMIP5 general circulation models (GCMs). Future simulations indicate a 17% (23%) decrease in annual (JJA) runoff by the end of the 21st

  1. 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.

  2. UV - GLACIER NATIONAL PARK MT

    EPA Science Inventory

    Brewer 134 is located in Glacier NP, measuring ultraviolet solar radiation. Irradiance and column ozone are derived from this data. Ultraviolet solar radiation is measured with a Brewer Mark IV, single-monochrometer, spectrophotometer manufactured by SCI-TEC Instruments, Inc. of ...

  3. 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.

  4. Reconstruction of late Holocene glacier retreat and relevant climatic and topographic patterns in southeastern Tibet by glacier mapping and equilibrium line altitude calculation

    NASA Astrophysics Data System (ADS)

    Loibl, David; Lehmkuhl, Frank

    2014-05-01

    Temperate glaciers in the eastern Nyainqêntanglha range, southeastern Tibet, are highly sensitive to climate change and are therefore of particular high interest for research on late Holocene changes of the monsoonal climate in High Asia. However, due to the remoteness of the area, the scarcity of empirical data, and the challenges to remote sensing work posed by cloud and snow cover, knowledge about the glacier dynamics and changes is still very limited. We applied a remote sensing approach that allowed a comprehensive regional glacier survey despite the few available data. Geomorphologic characteristics, distribution and late Holocene changes of 1964 glaciers were mapped from one of the few appropriate late summer satellite images: a Landsat ETM+ scene from September 23, 1999. The glacier dataset was subsequently parameterized by DEM supported measurements. Complex climate-relief-glacier interactions were studied in detail for three large glaciers in neighboring valleys. Despite their spatial proximity, these display strong heterogeneity in terms of catchment morphology, debris cover, and glacier characteristics. The results of this case study then provided the conceptual basis to use geomorphological evidence, i.e. trimlines and latero-frontal moraines, to obtain quantitative data on the changes since the Little Ice Age (LIA) maximum glacier advance. Statistical analysis of glacier length change revealed an average retreat of ~ 40 % and a trend towards stronger retreat for smaller glaciers. An evaluation of different methods to calculate equilibrium line altitudes (ELAs) indicates that an optimized toe-to-ridge altitude method (TRAM) outperforms other methods in settings with complex topography and a lack of mass-balance measurements. However, a large number of glacier measurements is crucial for high quality TRAM results and special attention has to be paid to different morphological glacier characteristics: debris-cover, reconstitution, valley floor

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

    NASA Astrophysics Data System (ADS)

    Yasunari, Teppei J.

    2011-12-01

    The subject of climate change in the Tibetan Plateau (TP) and Himalayas has taken on increasing importance because of the availability of water resources from their mountain glaciers (Immerzeel et al 2010). Many of the glaciers over these regions have been retreating, while some are advancing and stable (Yao et al 2004, Scherler et al 2011). Other studies report that some glaciers in the Himalayas show acceleration of their shrinkage (e.g., Fujita and Nuimura 2011). However, the causes of glacier melting are still difficult to grasp because of the complexity of climatic change and its influence on glacier issues. Despite this, it is vital that we pursue further study to enable future predictions of glacier changes. The paper entitled 'Climate and glacier change in southwestern China during the past several decades' by Li et al (2011) provided carefully analyzed, quality controlled, long-term data on atmospheric temperature and precipitation during the period 1961-2008. The data were obtained from 111 Chinese stations. The researchers performed systematic analyses of temperature and precipitation over the whole southwestern Chinese domain. They discussed those changes in terms of other meteorological components such as atmospheric circulation patterns, radiation and altitude difference, and then showed how these factors could contribute to climate and glacier changes in the region. Air temperature and precipitation are strongly associated with glacier mass balance because of heat balance and the addition of mass when it snows. Temperature warming trends over many places in southwestern China were unequivocally dominant in all seasons and at higher altitudes. This indicates that the heat contribution to the glaciers has been increasing. On the other hand, precipitation has a wider variability in time and space. It is more difficult to clearly understand the effect of precipitation on the climate and glacier melting characteristics in the whole of southwestern China

  6. A new model for global glacier change and sea-level rise

    NASA Astrophysics Data System (ADS)

    Huss, Matthias; Hock, Regine

    2015-09-01

    The anticipated retreat of glaciers around the globe will pose far-reaching challenges to the management of fresh water resources and significantly contribute to sea-level rise within the coming decades. Here, we present a new model for calculating the 21st century mass changes of all glaciers on Earth outside the ice sheets. The Global Glacier Evolution Model (GloGEM) includes mass loss due to frontal ablation at marine-terminating glacier fronts and accounts for glacier advance/retreat and surface Elevation changes. Simulations are driven with monthly near-surface air temperature and precipitation from 14 Global Circulation Models forced by the RCP2.6, RCP4.5 and RCP8.5 emission scenarios. Depending on the scenario, the model yields a global glacier volume loss of 25-48% between 2010 and 2100. For calculating glacier contribution to sea-level rise, we account for ice located below sea-level presently displacing ocean water. This effect reduces glacier contribution by 11-14%, so that our model predicts a sea-level equivalent (multi-model mean +-1 standard deviation) of 79+-24 mm (RCP2.6), 108+-28 mm (RCP4.5) and 157+-31 mm (RCP8.5). Mass losses by frontal ablation account for 10% of total ablation globally, and up to 30% regionally. Regional equilibrium line altitudes are projected to rise by 100-800 m until 2100, but the effect on ice wastage depends on initial glacier hypsometries.

  7. Transient Meltwater in Mullins Valley Glacier, McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Grimm, R. E.; Stillman, D. E.; Kowalewski, D. E.

    2014-12-01

    Mullins Glacier is a cold-based debris-covered glacier feeding into Beacon Valley, at high altitude in the McMurdo Dry Valleys of Antarctica. Ice is exposed at the headwall in Mullins Valley but the majority of the glacier is buried beneath a sublimation till (lag deposit composed of englacial and supraglacial debris). This till is initially ~10 cm thick but gradually thickens to ~60 cm at the glacier terminus (~8 km distant). Mullins Glacier has been postulated to be one of the world's oldest alpine glaciers: tephrachronology places a minimum age of the overlying sublimation till near the terminus at 7.9 Ma. Our measurements of the complex resistivity (aka spectral induced polarization or dielectric spectroscopy) of massive Mullins Glacier ice reveal two distinct origins. The electrical properties of clean ice or ice with rock fragments are typical of meteoric polar ice (Stillman et al., JGR, 2013). However, "dirty" ice is electrically distinct, indicating soluble impurity content near lattice saturation. This behavior, which we also observed for Lake Vostok accretion ice, is consistent with freezing from saline, draining water. Therefore one hypothesis it that the dirty ice formed by infiltration in former clement environments. However, very efficient segregation is subsequently required, and not all dirty ice is at the top of the ice column. Dirty ice likely samples debris bands, which are more commonly observed in cores where Mullins Glacier has advanced onto the main (Beacon) valley floor and is nearly stagnant. If debris bands are correlated to lattice impurity saturation via the dirty ice, then they may have been transiently at or near melting. This may be a primary feature of the environment during debris accumulation or simply due to the high thermal inertia of debris. Alternatively, debris bands and associated salts may be carried below the annual thermal wave where they experience near-constant, supereutectic temperatures. Elevated temperatures may be

  8. Glacier terminus fluctuations on Mt. Baker, Washington, USA, 1940-1990, and climatic variations

    SciTech Connect

    Harper, J.T. )

    1993-11-01

    The terminus positions of six glaciers located on Mount Baker, Washington, were mapped by photogrammetric techniques at 2- to 7-yr intervals for the period 1940-1990. Although the timing varied slightly, each of the glaciers experienced a similar fluctuation sequence consisting of three phases: (1) rapid retreat, beginning prior to 1940 and lasting through the late 1940s to early 1950s; (2) approximately 30 yr of advance, ending in the late 1970s to early 1980s; (3) retreat though 1990. Terminus positions changed by up to 750 m during phases, with the advance phase increasing the lengths of glaciers by 13 to 24%. These fluctuations are well explained by variations in a smoothed time-series of accumulation-season precipitation and ablation-season mean temperature. The study glaciers appear to respond to interannual scale changes in climate within 20 yr or less. The glaciers on Mount Baker have a maritime location and a large percentage of area at high elevation, which may make their termini undergo greater fluctuations in response to climatic changes, especially precipitation variations, than most other glaciers in the North Cascades region. 40 refs., 6 figs., 2 tabs.

  9. Brief Communication: Global reconstructions of glacier mass change during the 20th century are consistent

    NASA Astrophysics Data System (ADS)

    Marzeion, B.; Leclercq, P. W.; Cogley, J. G.; Jarosch, A. H.

    2015-12-01

    Recent estimates of the contribution of glaciers to sea-level rise during the 20th century are strongly divergent. Advances in data availability have allowed revisions of some of these published estimates. Here we show that outside of Antarctica, the global estimates of glacier mass change obtained from glacier-length-based reconstructions and from a glacier model driven by gridded climate observations are now consistent with each other, and also with an estimate for the years 2003-2009 that is mostly based on remotely sensed data. This consistency is found throughout the entire common periods of the respective data sets. Inconsistencies of reconstructions and observations persist in estimates on regional scales.

  10. Brief Communication: Global glacier mass loss reconstructions during the 20th century are consistent

    NASA Astrophysics Data System (ADS)

    Marzeion, B.; Leclercq, P. W.; Cogley, J. G.; Jarosch, A. H.

    2015-07-01

    Estimates of the contribution of glaciers to sea-level rise during the 20th century that were published in recent years are strongly divergent. Advances in data availability have allowed revisions of some of these published estimates. Here we show that outside of Antarctica, the global estimates of glacier mass loss obtained from glacier-length-based reconstructions and from a glacier model driven by gridded climate observations are now consistent with each other, and also with an estimate for the years 2003-2009 that is mostly based on remotely sensed data. This consistency is found throughout the entire common periods of the respective data sets. Inconsistencies of reconstructions and observations persist in estimates on regional scales.

  11. Marine record of surge-induced outburst floods from the Bering Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Jaeger, John M.; Nittrouer, Charles A.

    1999-09-01

    The Bering Glacier, Alaska, is the largest temperate glacier in the world. It episodically surges with rapid advances of the glacier terminus followed by large outburst floods delivering freshwater and sediment to the adjacent Gulf of Alaska. We describe the marine record of the 1993 1995 surge and document a 100 yr history of surges recorded in marine sedimentary deposits seaward of the Bering Glacier. In 1994 and 1995, we collected box cores that contained high-porosity laminated sediments at the seabed surface. Profiles of 234Th and chlorophyll-a indicate that these sediments were deposited very rapidly (0.1 cm · day-1) in association with the surge. A 250-cm-long kasten core extended this record, in which 7 laminated beds, 10 30 cm thick, alternated with bioturbated sediments. On the basis of 210Pb chronology, 6 of these beds accumulated in the past 100 yr and can be correlated with historical surges.

  12. Glacier area changes in Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Khromova, Tatiana; Nosenko, Gennady; Kutuzov, Stanislav; Muraviev, Anton; Chernova, Ludmila

    2014-01-01

    Glaciers are widely recognized as key indicators of climate change. Recent evidence suggests an acceleration of glacier mass loss in several key mountain regions. Glacier recession implies landscape changes in the glacial zone, the origin of new lakes and activation of natural disaster processes, catastrophic mudflows, ice avalanches, outburst floods, etc. The absence or inadequacy of such information results in financial and human losses. A more comprehensive evaluation of glacier changes is imperative to assess ice contributions to global sea level rise and the future of water resources from glacial basins. One of the urgent steps is a full inventory of all ice bodies and their changes. The first estimation of glacier state and glacier distribution on the territory of the former Soviet Union has been done in the USSR Glacier Inventory (UGI) published in 1965-1982. The UGI is based on topographic maps and air photos and reflects the status of the glaciers in the 1940s-1970s. There is information about 28 884 glaciers with an area of 7830.75 km2 in the inventory. It covers 25 glacier systems in Northern Eurasia. In the 1980s the UGI has been transformed into digital form as a part of the World Glacier Inventory (WGI). Recent satellite data provide a unique opportunity to look again at these glaciers and to evaluate changes in glacier extent for the second part of the 20th century. About 15 000 glacier outlines for the Caucasus, Polar Urals, Pamir Alay, Tien Shan, Altai, Kamchatka and Russian Arctic have been derived from ASTER and Landsat imagery and can be used for glacier change evaluation. Results of the analysis indicate the steady trend in glacier shrinkage in all mountain regions for the second part of the 20th century. Glacier area loss for the studied regions varies from 13% (Tien Shan) to 22.3% (Polar Urals). The common driver, most likely, is an increase in summer air temperature. There is also a very large variability in the degree of individual

  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. 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.

  15. 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.

  16. 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.

  17. Modeling ice front Dynamics of Greenland outlet glaciers using ISSM

    NASA Astrophysics Data System (ADS)

    Morlighem, M.; Bondzio, J. H.; Seroussi, H. L.; Rignot, E. J.

    2015-12-01

    The recent increase in the rate of mass loss from the Greenland Ice Sheet is primarily due to the acceleration and thinning of outlet glaciers along the coast. This acceleration is a dynamic response to the retreat of calving fronts, which leads to a loss in resistive stresses. These processes need to be included in ice sheet models in order to be able to accurately reproduce current trends in mass loss, and in the long term reduce the uncertainty in the contribution of ice sheets to sea level rise. Today, the vast majority of ice sheet models that include moving boundaries are one dimensional flow line and vertical flow band models, that are not adapted to the complex geometries of Greenland outlet glaciers, as they do not accurately capture changes in lateral stresses. Here, we use the level set method to track moving boundaries within a 2D plane view model of the Ice Sheet System Model (ISSM), and investigate the sensitivity of Store Glacier, in western Greenland, to the amount of melting occurring at its calving front. We explore different calving laws and obtain the best results with a new simple calving law adapted from von Mises yield criterion. We show that the ocean circulation near the front and the amount of runoff are able to trigger ice front advance and retreat depending on the amount of melting that they produce at the calving face, but the bed topography controls the stable positions of the ice front. The modeled calving front of Store Glacier, for which we have quality bed topography and sea floor bathymetry data, is particularly stable because of the presence of a large sill at the glacier terminus. If the ice front detaches from this stabilizing sill due to larger amounts of melting at the front or due to large calving events, the glacier front starts to retreat as the bed deepens inland, until it finds another stabilizing feature in the bed topography. The new bed topography maps based on mass conservation make it possible to model more

  18. Pan-ice-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes.

    PubMed

    Miles, Bertie W J; Stokes, Chris R; Jamieson, Stewart S R

    2016-05-01

    The dynamics of ocean-terminating outlet glaciers are an important component of ice-sheet mass balance. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic Ice Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974-1990, before switching to advance in every drainage basin during the two most recent periods, 1990-2000 and 2000-2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea ice and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica. PMID:27386519

  19. Pan–ice-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes

    PubMed Central

    Miles, Bertie W. J.; Stokes, Chris R.; Jamieson, Stewart S. R.

    2016-01-01

    The dynamics of ocean-terminating outlet glaciers are an important component of ice-sheet mass balance. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic Ice Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974–1990, before switching to advance in every drainage basin during the two most recent periods, 1990–2000 and 2000–2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea ice and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica. PMID:27386519

  20. 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

  1. Characteristics of recessional moraines at a temperate glacier in SE Iceland: Insights into patterns, rates and drivers of glacier retreat

    NASA Astrophysics Data System (ADS)

    Chandler, Benjamin M. P.; Evans, David J. A.; Roberts, David H.

    2016-03-01

    Icelandic glaciers are sensitive to climate variability on short-term timescales owing to their North Atlantic maritime setting, and have been undergoing ice-marginal retreat since the mid-1990s. Recent patterns, rates and drivers of ice-frontal retreat at Skálafellsjökull, SE Iceland, are examined using small-scale recessional moraines as a geomorphological proxy. These small-scale recessional moraines exhibit distinctive sawtooth planform geometries, and are constructed by a range of genetic processes associated with minor ice-margin re-advance, including (i) combined push/squeeze mechanisms, (ii) bulldozing of pre-existing proglacial material, and (iii) submarginal freeze-on. Remote-sensing investigations and lichenometric dating highlight sequences of annually-formed recessional moraines on the northern and central parts of the foreland. Conversely, moraines are forming on a sub-annual timescale at the southeastern Skálafellsjökull margin. Using annual moraine spacing as a proxy for annual ice-margin retreat rates (IMRRs), we demonstrate that prominent periods of glacier retreat at Skálafellsjökull are coincident with those at other Icelandic outlet glaciers, as well as those identified at Greenlandic outlet glaciers. Analysis of IMRRs and climate data suggests summer air temperature, sea surface temperature and the North Atlantic Oscillation have an influence on IMRRs at Skálafellsjökull, with the glacier appearing to be most sensitive to summer air temperature. On the basis of further climate data analyses, we hypothesise that sea surface temperature may drive air temperature changes in the North Atlantic region, which in turn forces IMRRs. The increase in sea surface temperature over recent decades may link to atmospheric-driven variations in North Atlantic subpolar gyre dynamics.

  2. From 'true' glaciers to rock glaciers? The case of the Llanos la Liebre rock glacier, dry Andes of Chile.

    NASA Astrophysics Data System (ADS)

    Monnier, S.; Kinnard, C.

    2012-04-01

    In the dry Andes of Chile, rock glaciers are the most widespread and remarkable superficial landforms, and may constitute important solid water reservoirs. The existence of huge (up to 2-3 kilometres of length) rock glaciers located in deep cirques questions possible derivation from former 'true' glaciers. The issue is of importance (i) for understanding the mechanisms of the landscape evolution from glacial realm to periglacial realm, and (ii) because it may determine the ice content of the concerned rock glaciers. In the Colorado Río valley, in the upper part of the Elqui catchment (~30.15 deg. S and 70.80 deg. W), we investigated the internal structure of the Llanos la Liebre rock glacier using ground-penetrating radar (GPR). With 50 MHz antennas and a constant offset of 2 m between antennas, we performed various GPR profiles, especially a ~2.2 km-long one almost covering the entire length of the rock glacier. The processing and the subsequent interpretation of the GPR data were mainly based on the modelling of the radar wave velocity. Hence, the final representation of the internal structure of the rock glacier integrates the reconstructed stratigraphy, the 2-D velocity model, and first attempts for estimating the ice/water contents. The most striking results are: the neat identification of the base of the superficial blocky layer and of the rock glacier floor; the occurrence of stratigraphic patterns reminiscent of 'true' glaciers; the supremacy of high radar wave velocities in the upper part of the rock glacier. On the latter bases and taking into account the whole geomorphology of the site, the derivation of the Llanos la Liebre rock glacier from a former, buried glacier is debated.

  3. Recent Observations and Structural Analysis of Surge-Type Glaciers in the Glacier Bay Area

    NASA Astrophysics Data System (ADS)

    Mayer, H.; Herzfeld, U. C.

    2003-12-01

    The Chugach-St.-Elias Mountains in North America hold the largest non-polar connected glaciated area of the world. Most of its larger glaciers are surge-type glaciers. In the summer of 2003, we collected aerial photographic and GPS data over numerous glaciers in the eastern St. Elias Mountains, including the Glacier Bay area. Observed glaciers include Davidson, Casement, McBride, Riggs, Cushing, Carroll, Rendu, Tsirku, Grand Pacific, Melbern, Ferris, Margerie, Johns Hopkins, Lamplugh, Reid, Burroughs, Morse, Muir and Willard Glaciers, of which Carroll, Rendu, Ferris, Grand Pacific, Johns Hopkins and Margerie Glaciers are surge-type glaciers. Our approach utilizes a quantitative analysis of surface patterns, following the principles of structural geology for the analysis of brittle-deformation patterns (manifested in crevasses) and ductile deformation patterns (visible in folded moraines). First results will be presented.

  4. Himalayan Glacier Disasters: Changing Geomorphological Process Landscape, or a Changing Human Landscape?

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.; Leonard, G. J.

    2012-12-01

    Recent deadly glacier-related disasters in the Himalayan-Karakoram region—the Attabad landslide and formation of glacier meltwater-fed Lake Gojal, the Gayari ice avalanche/landslide and burial of a Pakistani Army base, and the Seti River outburst disaster—beg the question of whether disasters may be on the rise. Science is not yet ready to offer a full answer, but it is an important one to resolve, because future land-use planning and mitigative measures may be affected. Natural disasters have been commonplace throughout the long human history of the Himalaya-Karakoram region. The broad outlines of the changing natural process, natural hazard, and risk environment may be established. The risk is rising rapidly primarily due to increased human presence in these once-forbidding mountains. Risk is shifting also because climate change is modifying the land surface process system. Rapidly changing glaciers cause a destabilization of the landscape. Glaciers are fundamentally a mestastable phenomenon put in motion by the high gravitational potential energies of the components of glacial systems: snow, ice, water, and debris. Any change in the climate-land-glacier system MUST result in a change in the land process system, with hazards and risks rising or falling or changing location or type. Most commonly, glacier-related disasters include a natural process cascade; as the factors affecting land surface processes and the frequency or magnitude of any one of the elements of the process cascade changes, the net hazard and risk to people changes. Otherwise similar glaciers and glacierized basins have differing sets of hazardous conditions and processes depending on whether the glacier is stable, advancing or retreating. The consequences for the overall risk to people will depend on the details of a specific glacier near a particular village or bridge or railroad. One size does not fit all. Generalizations about trends in natural hazards as related to climate change

  5. Active seismoelectric exploration of glaciers

    NASA Astrophysics Data System (ADS)

    Kulessa, B.; Murray, T.; Rippin, D.

    2006-04-01

    Repeatable and strong seismoelectric signals were recorded on Glacier de Tsanfleuron, Switzerland, using a vertical sounding geometry. Electromagnetic waves are inferred to be generated by electrokinetic conversion of seismic energy within the snow pack and near the dry-wet ice and ice-bed interfaces. A simple gradient-based scheme allows such electrokinetic interface responses (EIRs) to be isolated from noise. EIRs depend sensitively on the azimuthal orientation of the receiving array of electrical dipoles. Seismoelectric techniques promise to allow mapping even of thin water-bearing strata within or beneath glaciers or frozen ground, estimation of hydraulic or fluid properties of such strata, as well as monitoring of ice fracturing or basal properties and processes at improved spatial resolution.

  6. Monitoring of time and space evolution of glaciers' flow at the scale of the Karakoram and Himalayas

    NASA Astrophysics Data System (ADS)

    Dehecq, Amaury; Gourmelen, Noel; Trouvé, Emmanuel; Wegmuller, Urs; Cheng, Xiao

    2014-05-01

    Climate warming over the 20th century has caused drastic changes in mountain glaciers globally, and of the Himalayan glaciers in particular. The stakes are high; glaciers and ice caps are the largest contributor to the increase in the mass of the world's oceans, and the Himalayas play a key role in the hydrology of the region, impacting on the economy, food safety and flood risk to a large population. Partial monitoring of the Himalayan glaciers has revealed a mixed picture; while many of the Himalayan glaciers are retreating, in some cases locally stable or advancing glaciers in this region have also been observed. But recent controversies have highlighted the need to understand the glaciers dynamic and its relationship with climate change in this region. Earth Observation provides a mean for global and long-term monitoring of mountain glaciers' dynamics. In the frame of the Dragon program, a partnership between the European Space Agency (ESA) and the Chinese Center for Earth Observation (NRSCC), we begun a monitoring program aimed at quantifying multidecadal changes in glaciers' flow at the scale of the entire Himalayas and Karakoram from a 40 years' archive of Earth Observation. Ultimately, the provision of a global and time-sensitive glaciers velocity product will help to understand the evolution of the Himalayan glaciers in lights of glaciological (e.g. presence of debris-cover, surges, proglacial lakes) and climatic conditions. In this presentation, we focus on the analysis of the Landsat archive spanning the 1972 to 2012 period, which is global and provide multidecadal and continuous observation. We present the processing strategy including preprocessing of the images, image-matching and merging of the various results obtained from the repetitivity of the acquisitions in order to obtain a more robust, precise and complete glaciers velocity fields. We show that the recent archive (Landsat 4, 5 and 7, from 1982 to 2013) allows an estimate of the velocity for

  7. Processes on a glacier-dominated coast, Alaska

    USGS Publications Warehouse

    Molnia, Bruce F.

    1985-01-01

    The 500 km long Gulf of Alaska coastline between Cape Suckling and Cape Spencer can be characterized by constant rapid change in an environment of glaciers, stormy climate, high relief, and extreme oceanographic parameters. During a more than 200-year history of observation, bays have completely filled with sediment, new bays have appeared, glaciers have advanced and retreated as much as 40 km, streams have been captured, and spits have grown as much as 10 km in length, earthquakes have uplifted the coast as much as 15 m, and in general, few features have been static. More than 250 km of coastline have undergone erosion and retreat, with maximum retreat exceeding 4 km at Icy Bay.

  8. 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

  9. 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

  10. The GAMDAM Glacier Inventory: a quality controlled inventory of Asian glaciers

    NASA Astrophysics Data System (ADS)

    Nuimura, T.; Sakai, A.; Taniguchi, K.; Nagai, H.; Lamsal, D.; Tsutaki, S.; Kozawa, A.; Hoshina, Y.; Takenaka, S.; Omiya, S.; Tsunematsu, K.; Tshering, P.; Fujita, K.

    2014-06-01

    We present a new glacier inventory for the high mountain Asia named "Glacier Area Mapping for Discharge from the Asian Mountains" (GAMDAM). Glacier outlines were delineated manually using more than 226 Landsat ETM+ scenes from the period 1999-2003, in conjunction with a digital elevation model (DEM) and high-resolution Google Earth imagery. Geolocations are consistent between the Landsat imagery and DEM due to systematic radiometric and geometric corrections made by the United States Geological Survey. We performed repeated delineation tests and rigorous peer review of all scenes used in order to maintain the consistency and quality of the inventory. Our GAMDAM Glacier Inventory (GGI) includes 82776 glaciers covering a total area of 87507 ± 13126 km2 in the high mountain Asia. Thus, our inventory represents a greater number (+4%) of glaciers but significantly less surface area (-31%) than a recent global glacier inventory (Randolph Glacier Inventory, RGI). The employed definition of the upper boundaries of glaciers, glacier recession since the 1970s, and misinterpretation of seasonal snow cover are likely causes of discrepancies between the inventories, though it is difficult to evaluate these effects quantitatively. The GGI will help improve the temporal consistency of the RGI, which incorporated glacier outlines from the 1970s for the Tibetan Plateau, and will provide new opportunities to study Asian glaciers.

  11. 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.

  12. 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.

  13. 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

  14. Latest Pleistocene and Holocene glacier fluctuations in southernmost Tierra del Fuego, Argentina

    NASA Astrophysics Data System (ADS)

    Menounos, Brian; Clague, John J.; Osborn, Gerald; Davis, P. Thompson; Ponce, Federico; Goehring, Brent; Maurer, Malyssa; Rabassa, Jorge; Coronato, Andrea; Marr, Rob

    2013-10-01

    Some researchers propose that summer insolation controls long-term changes in glacier extent during the Holocene. If this hypothesis is correct, the record of glacier fluctuations at high latitudes in the Southern Hemisphere should differ from that in the Northern Hemisphere. Although the chronology of Holocene glacier fluctuations in the Northern Hemisphere is well established, much uncertainty remains in the ages of Holocene glacier fluctuations in the Southern Hemisphere, especially South America. Here we report on latest Pleistocene and Holocene glacier fluctuations at the southern end of the Andes north and west of Ushuaia, Argentina. Surface exposure ages (10Be) from glaciated bedrock beyond cirque moraines indicate that alpine areas were free of ice by ca 16.9 ka. One, and in some cases two, closely spaced moraines extend up to 2 km beyond Little Ice Age moraines within many of the cirques in the region. The mean age of five 10Be ages from two pre-Little Ice Age moraines is 14.27-12.67 ka, whereas a minimum limiting radiocarbon age for a smaller, recessional moraine in one cirque is 12.38-12.01 ka. Our ages imply that, following glacier retreat beginning about 18.52-17.17 ka, cirque glaciers first advanced during the Antarctic Cold Reversal (14.5-12.9 ka) and may have later advanced or stabilized in the Younger Dryas Chronozone (12.9-11.7 ka). Based on the distribution of thick, geochemically distinct, and well-dated Hudson tephra, no Holocene moraines appear to be older than 7.96-7.34 ka. At some sites, there is evidence for one or more advances of glaciers sometime between 7.96-7.34 ka and 5.29-5.05 ka to limits only tens of meters beyond Little Ice Age maximum positions. Taken together, the data: 1) do not support the summer insolation hypothesis to explain Holocene glacier fluctuations in southernmost Patagonia; 2) confirm paleobotanical evidence for a warm, dry early Holocene; and 3) suggest that some glaciers in the region reached extents comparable to

  15. Perturbation of dynamic response at short outlets glaciers of Jostedalsbreen, maritime South Norway?

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan

    2010-05-01

    Mountain glaciers are key indicators of global climate change. Changes in glacier volume, area, and length are determined by the climate and related mass flux/glacier flow. For several aspects of sustainable development in high-mountain regions (hydro-electric energy, water supply, tourism, etc.) it is crucial to estimate future glacier variations. Therefore, the interactions and relationships between individual meteorological and glaciological parameters need to be known before any model can be applied. Due to their steep mass balance gradient and high mass turnover, maritime mountain glaciers might respond very sensitively to changes of predominant weather or climate conditions. The steep outlet glaciers of Jostedalsbreen, western South Norway, underwent two fairly contrasting periods during the past 20 years. Interpretation of this ‘extreme' behaviour presented here deserved special attention. Detailed analysis of mass-balance, length variation, and climate data from maritime Southern Norway reveals their variations are not entirely determined by air temperature changes. A considerable increase in ice mass and related frontal advance during the AD 1990s was caused by increased winter precipitation. By contrast, a frontal retreat starting around AD 2000 continued and accelerated in recent years. Although above-average summer air temperatures unambiguously were responsible for this retreat, its proportion significantly exceeded the slight contemporary glacier mass loss. Since 2000, length variations at the short outlets of Jostedalsbreen seem to be decoupled from the net mass-balance data series. Additionally, the dynamic response of the glacier front to net balance and mass flux variations has been disturbed. Previously applicable terminus reaction times of 3 to 4 years have been replaced by an immediate response to higher summer air temperatures. The correlation of net balance to length variation dropped significant since AD 2000. Comparable changes between

  16. High-Resolution Monitoring of Himalayan Glacier Dynamics Using Unmanned Aerial Vehicles

    NASA Astrophysics Data System (ADS)

    Immerzeel, W.; Kraaijenbrink, P. D. A.; Shea, J.; Shrestha, A. B.; Pellicciotti, F.; Bierkens, M. F.; de Jong, S. M.

    2014-12-01

    Himalayan glacier tongues are commonly debris covered and play an important role in modulating the glacier response to climate . However, they remain relatively unstudied because of the inaccessibility of the terrain and the difficulties in field work caused by the thick debris mantles. Observations of debris-covered glaciers are therefore limited to point locations and airborne remote sensing may bridge the gap between scarce, point field observations and coarse resolution space-borne remote sensing. In this study we deploy an Unmanned Airborne Vehicle (UAV) on two debris covered glaciers in the Nepalese Himalayas: the Lirung and Langtang glacier during four field campaigns in 2013 and 2014. Based on stereo-imaging and the structure for motion algorithm we derive highly detailed ortho-mosaics and digital elevation models (DEMs), which we geometrically correct using differential GPS observations collected in the field. Based on DEM differencing and manual feature tracking we derive the mass loss and the surface velocity of the glacier at a high spatial resolution and accuracy. We also assess spatiotemporal changes in supra-glacial lakes and ice cliffs based on the imagery. On average, mass loss is limited and the surface velocity is very small. However, the spatial variability of melt rates is very high, and ice cliffs and supra-glacial ponds show mass losses that can be an order of magnitude higher than the average. We suggest that future research should focus on the interaction between supra-glacial ponds, ice cliffs and englacial hydrology to further understand the dynamics of debris-covered glaciers. Finally, we conclude that UAV deployment has large potential in glaciology and it represents a substantial advancement over methods currently applied in studying glacier surface features.

  17. Global Land Ice Measurements from Space: Documenting the Demise of Earth's Glaciers Using ASTER.

    NASA Astrophysics Data System (ADS)

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

    2001-05-01

    GLIMS (Global Land Ice Measurements from Space) is a global consortium whose purpose is to determine the extent of the world's glaciers and the rate at which they are changing. GLIMS has requested more than 2000 ASTER (Advanced Spaceborne Thermal Emission and reflection Radiometer) images over the Earth's glaciers and ice sheets where the instrument gain is set to compliment the requested latitude and time of year. We've recently received hundreds of cloud-free, stereo images with 15-meter spatial resolution in visible-near infrared (VNIR) that can resolve ogives, crevasses, and small bodies of water on the surface of glaciers. The first ASTER GLIMS images specially acquired to enhance details of snow and ice of glaciers have also been received and given preliminary analysis. The variable gain has provided a wider dynamic range over snow and ice compared to Landsat data. The relatively high spatial resolution of ASTER VNIR produces a glacier classification that effectively separates water and snow from glacier ice and medial moraines. We are currently assessing the effects of including the 30-meter short wave infrared (SWIR) and 90-meter thermal infrared (TIR) in our analysis. We will highlight our study that uses ASTER images to detect and monitor supraglacial lakes on glaciers in the Mount Everest region (Tibet and Nepal). We have found that ASTER offers powerful capabilities to monitor supraglacial lakes in terms of (1) surface area, growth, and disappearance (spatial resolution = 15 m), (2) net translation on the glacier with respect to immobile points, (3) inorganic turbidity (15-m resolution), and (4) temperature (90-m resolution). Still lacking is a suite of field observations tied in time and space to ASTER observations to help validate/verify and fine-tune the algorithms used for terrain classification and other analysis. Thus, we consider our new results as a demonstration of capability rather than as definitive new results.

  18. 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).

  19. GLIMS: Progress in Mapping the World's glaciers

    NASA Astrophysics Data System (ADS)

    Raup, B. H.; Khalsa, S. J. S.; Armstrong, R.; Racoviteanu, A.

    2009-04-01

    The Global Land Ice Measurements from Space (GLIMS) initiative has built a database of glacier outlines and related attributes, 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. The database currently contains outlines for approximately 83,000 glaciers. Of these, 549 glaciers have outlines from more than one time, which can be studied for change. The glacier-by-glacier area-change signal over large areas tends to be noisy, but the mode of the distribution of area change for these 549 glaciers is -5%. 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 creates interactive maps on our Web site, www.glims.org, and can also supply glacier layers to other servers over the Internet. As a service to the GLIMS community, the database contains metadata on all ASTER imagery (approximately 200,000 images) acquired over glacierized terrain. Reduced-resolution images can be viewed either as a layer in the MapServer application, or overlaid on the virtual globe within Google Earth. 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), MapInfo, GML (Geography Markup Language) and GMT (Generic Mapping Tools). This "clip-and-ship" function allows users to download only the data they are interested in. In this presentation we describe our flexible Web interfaces to the database, which includes various ancillary layers, facilitates enhanced analysis of glacier systems, their distribution, and their impacts on other Earth systems.

  20. Global Monitoring of Mountain Glaciers Using High-Resolution Spotlight Imaging from the International Space Station

    NASA Astrophysics Data System (ADS)

    Donnellan, A.; Green, J. J.; Bills, B. G.; Goguen, J.; Ansar, A.; Knight, R. L.; Hallet, B.; Scambos, T. A.; Thompson, L. G.; Morin, P. J.

    2013-12-01

    Mountain glaciers around the world are retreating rapidly, contributing about 20% to present-day sea level rise. Numerous studies have shown that mountain glaciers are sensitive to global environmental change. Temperate-latitude glaciers and snowpack provide water for over 1 billion people. Glaciers are a resource for irrigation and hydroelectric power, but also pose flood and avalanche hazards. Accurate mass balance assessments have been made for only 280 glaciers, yet there are over 130,000 in the World Glacier Inventory. The rate of glacier retreat or advance can be highly variable, is poorly sampled, and inadequately understood. Liquid water from ice front lakes, rain, melt, or sea water and debris from rocks, dust, or pollution interact with glacier ice often leading to an amplification of warming and further melting. Many mountain glaciers undergo rapid and episodic events that greatly change their mass balance or extent but are sparsely documented. Events include calving, outburst floods, opening of crevasses, or iceberg motion. Spaceborne high-resolution spotlight optical imaging provides a means of clarifying the relationship between the health of mountain glaciers and global environmental change. Digital elevation models (DEMs) can be constructed from a series of images from a range of perspectives collected by staring at a target during a satellite overpass. It is possible to collect imagery for 1800 targets per month in the ×56° latitude range, construct high-resolution DEMs, and monitor changes in high detail over time with a high-resolution optical telescope mounted on the International Space Station (ISS). Snow and ice type, age, and maturity can be inferred from different color bands as well as distribution of liquid water. Texture, roughness, albedo, and debris distribution can be estimated by measuring bidirectional reflectance distribution functions (BRDF) and reflectance intensity as a function of viewing angle. The non-sun-synchronous orbit

  1. 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%. PMID:25123485

  2. Surging glaciers in Iceland - research status and future challenges

    NASA Astrophysics Data System (ADS)

    Ingolfsson, Olafur

    2013-04-01

    Twenty six Icelandic outlet glaciers, ranging from 0.5-1.500 km2, are known to surge, with terminal advances ranging from of few tens of meters to about 10 km. The geomorphic signatures of surges vary, from large-scale folded and thrusted end moraine systems, extensive dead-ice fields and drumlinized forefields to drift sheets where fast ice-flow indicators are largely missing. Case studies from the forefields of Brúarjökull, Eyjabakkajökull and Múlajökull surging glaciers will be presented. At Brúarjökull, extremely rapid ice flow during surge was sustained by overpressurized water causing decoupling beneath a thick sediment sequence that was coupled to the glacier. The ice-marginal position of the 1890 surge is marked by a sedimentary wedge formed within five days and a large moraine ridge that formed in about one day ("instantaneous end-moraine"). Three different qualitative and conceptual models are required to explain the genesis of the Eyjabakkajökull moraines: a narrow, single-crested moraine ridge at the distal end of a marginal sediment wedge formed in response to decoupling of the subglacial sediment from the bedrock and associated downglacier sediment transport; large lobate end moraine ridges with multiple, closely spaced, asymmetric crests formed by proglacial piggy-back thrusting; moraine ridges with different morphologies may reflect different members of an end moraine continuum. A parallel study highlighting the surge history of Eyjabakkajökull over the last 4400 years suggests climate control on surge frequencies. The Múlajökull studies concern an active drumlin field (>100 drumlins) that is being exposed as the glacier retreats. The drumlins form through repeated surges, where each surge causes deposition of till bed onto the drumlin while similtaneously eroding the sides. Finally, a new landsystem model for surging North Iceland cirque glaciers will be introduced. References Benediktsson,I. Ö., Schomacker, A., Lokrantz, H. & Ing

  3. 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…

  4. 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. PMID:23486246

  5. GIS-based glacier inventory of China

    NASA Astrophysics Data System (ADS)

    Li, X.; Wu, L.-Z.

    2003-04-01

    The project of the Glacier Inventory of China initialized in 1979 was just accomplished in 2000. This inventory was complied based on numerous LandSat TM images, aerial photographs, and topographic maps. More than 40 Chinese glaciologists made their great efforts in this work. With the newest statistics from the inventory, there are total 46,928 glaciers in China; the total area is 59,406 km2 and the ice volume is 5,598 km3. We launched a new project to digitize the 11 volumes of published glacier data and all the distribution maps of glaciers in China. Large-scale topographic maps were also used as reference to reconstruct a more accurate geographic coordinate system of the inventory. We paid particularly attention to the data quality control. The properties of both the spatial and attribute data were carefully examined with a few operations by manual and computerized checks. Since the digital inventory lays a baseline for the monitoring of glacier change, we are going to release the database on the Internet and with CD-ROMs. In additions, the second glacier inventory in some glaciered drainages were carried out. Chinese glaciologist are using new generation remote sensors such as ASTER and LandSat ETM+ to identify glacier change in many areas. Preliminary results showed that the change is significant.

  6. 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.

  7. 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

  8. Englacial Hydrology of Temperate Glaciers

    NASA Astrophysics Data System (ADS)

    Fountain, A. G.; Creyts, T. T.

    2015-12-01

    The englacial region of temperate glaciers is generally treated as a passive conveyor of water from the surface to the bed. Consequently, few studies have examined this region and relatively little is known. This is an important issue because englacial processes probably exert a first order control on the distribution of water to the subglacial hydraulic system. Controlling the water distribution probably controls the type of subglacial hydraulic features present and therefore sliding behavior. Certainly, englacial conduits play a major, if not primary, role in conveying water in the ablation zone. In regions of over-deepenings, areas highly crevassed, or in the accumulation zone, the importance of englacial conduits is less clear. Field studies have shown that intersecting englacial passageways in these regions are relatively common, implying that large water fluxes can drain efficiently through a network of fractures. Hypothetically, efficient drainage systems composed of englacial conduits develop in response to point input of large surface water fluxes. Where input is small and distributed, common to highly crevassed areas or the accumulation zone, water is probably routed through a network of englacial fractures. Glacier geometry may also play a role. Conduits may not develop in the over-deepened (closed basins) regions of a glacier requiring another flow pathway. That englacial fractures exist and can convey water presents a promising alternative. Measured rates of flow in fractures strongly suggest laminar conditions and a sufficient fracture density exists to accommodate the estimated water flux generated upstream by surface melt. The slow flow rates do not generate sufficient viscous heat to compensate expected rates of closure by freezing, however field observations and seismic evidence point to spontaneous fracture formation at depth that must regenerate the fracture network. It is unfortunate that englacial investigations are ignored in favor of

  9. Accelerating thinning of Kenai Peninsula glaciers, Alaska

    NASA Astrophysics Data System (ADS)

    VanLooy, J.; Forster, R.; Ford, A.

    2006-11-01

    Temperate mountain glaciers are thinning at high rates and significantly contributing to sea level rise. Due to these glaciers' remote locations, remote sensing and digital elevation models (DEMs) are an effective way to calculate their thinning rates and contribution to sea level rise. Comparisons of 1950s United States Geological Survey (USGS) and 2000 Shuttle Radar Topographic Mission (SRTM) DEMs with DEMs produced from Lidar profiles of glacier center-lines indicate thinning rates from the mid-1990s to 1999 (-0.72 +/- 0.13 m y-1) accelerated by a factor of 1.5 as compared with 1950 to mid-1990s (-0.47 +/- 0.01 m y-1) for glaciers on the Harding Icefield. Overall, comparison of USGS and SRTM DEMs indicate the Harding Icefield and Grewingk-Yalik Glacier Complex, Alaska, are thinning -0.61 +/- 0.12 m y-1 from 1950 to 1999.

  10. 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

  11. Spatial and Temporal Variability of Winter Accumulation on Taku Glacier, Southeast Alaska, between 2012 and 2015

    NASA Astrophysics Data System (ADS)

    Smith, B.; Campbell, S. W.; Hollander, J.; Slavin, B. V.; Wolf, J.; Wilner, J.; Moore, T.

    2015-12-01

    Glacier mass balance is an integral part of understanding a glacier's health and dynamics. A key component of determining mass balance is winter accumulation which is traditionally estimated by digging and measuring snow densities from within snow pits. However, this method represents a labor-intensive point measurement which may not fully capture spatial variability of accumulation. To more efficiently estimate spatial variability of winter accumulation across Taku Glacier and its main tributaries in southeastern Alaska in 2015, we used a 400 MHz Ground Penetrating Radar (GPR) Common Offset (CO) surveys along centerline transects which were also collected during a 2012 study. We used common midpoint (CMP) surveys, migration, snow pits, and probing to improve depth estimates and provide ground truth of winter accumulation depth measurements from CO surveys. We determined that the winter accumulation was significantly lower in 2015 than in 2012. However, gradients in accumulation versus elevation were consistent from year to year along centerline transects. We suggest that this low accumulation may be influencing the recent two year stall of Taku Glacier which has exhibited an advancing terminus for nearly a century. We recommend that further studies be conducted to extend the reach of this dataset beyond 2 years. This data would be invaluable to future models and mass balance studies on the Icefield and may capture key components that suggest a tipping point from advance to retreat of Taku Glacier.

  12. The length of the glaciers in the world - a straightforward method for the automated calculation of glacier center lines

    NASA Astrophysics Data System (ADS)

    Machguth, H.; Huss, M.

    2014-05-01

    Glacier length is an important measure of glacier geometry but global glacier inventories are mostly lacking length data. Only recently semi-automated approaches to measure glacier length have been developed and applied regionally. Here we present a first global assessment of glacier length using a fully automated method based on glacier surface slope, distance to the glacier margins and a set of trade-off functions. The method is developed for East Greenland, evaluated for the same area as well as for Alaska, and eventually applied to all ∼200 000 glaciers around the globe. The evaluation highlights accurately calculated glacier length where DEM quality is good (East Greenland) and limited precision on low quality DEMs (parts of Alaska). Measured length of very small glaciers is subject to a certain level of ambiguity. The global calculation shows that only about 1.5% of all glaciers are longer than 10 km with Bering Glacier (Alaska/Canada) being the longest glacier in the world at a length of 196 km. Based on model output we derive global and regional area-length scaling laws. Differences among regional scaling parameters appear to be related to characteristics of topography and glacier mass balance. The present study adds glacier length as a central parameter to global glacier inventories. Global and regional scaling laws might proof beneficial in conceptual glacier models.

  13. Spatial Pattern of the Glacier Shrinkages over the Tibetan Plateau since the Little Ice Age and the Role of the Summer Freezing Level

    NASA Astrophysics Data System (ADS)

    Wang, N.; Yao, T.; Thompson, L. G.; Mosley-Thompson, E.

    2015-12-01

    Many Asian large rivers originate from glaciers over the Tibetan Plateau. The changes of glaciers in this region have a significant impact on water supply. In recent years, the Karakoram Anomaly, i.e., the glaciers in Karakoram remained stable and even expanded in contrast to the receding of the glaciers nearby and worldwide, has attracted much attention. There have been many attempts to explain this phenomenon. In order to better understand the causes of this phenomenon, the spatial pattern of the variations of the glaciers in the whole Tibetan Plateau should be explored on a longer time scale. During the Little Ice Age (LIA), the glaciers over the Tibetan Plateau advanced and formed easily recognizable end and lateral moraines, which could be used to identify the extents of glaciers. Using remote sensing images and aerial photos, along with field works, we recognized the distributions of the LIA's moraines of about 2000 glaciers over the Tibetan Plateau. It was found that the glacier areas have reduced by larger than 25% in the southeast Tibetan Plateau and the northeast margin of the Tibetan Plateau while less than 10% in the northwest Tibetan Plateau (including the Karakoram) since the LIA. A similar spatial pattern of the shrinkages of the glaciers was also revealed over the past decades. It's noted that the summer freezing level is much higher than the glacier median elevation in the southeast Tibetan Plateau while much lower in the northwest Tibetan Plateau, and the summer freezing level showed a decreasing trend in the northwest Tibetan Plateau (including the Karakoram) while increasing in the southeast Tibetan Plateau over the past decades. These imply that the summer freezing level play an important role in the spatial variations of the glaciers over the Tibetan Plateau.

  14. Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources

    NASA Astrophysics Data System (ADS)

    Spencer, Robert G. M.; Vermilyea, Andrew; Fellman, Jason; Raymond, Peter; Stubbins, Aron; Scott, Durelle; Hood, Eran

    2014-05-01

    Glacier ecosystems are a significant source of bioavailable, yet ancient dissolved organic carbon (DOC). Characterizing DOC in Mendenhall Glacier outflow (southeast Alaska) we document a seasonal persistence to the radiocarbon-depleted signature of DOC, highlighting ancient DOC as a ubiquitous feature of glacier outflow. We observed no systematic depletion in Δ 14C-DOC with increasing discharge during the melt season that would suggest mobilization of an aged subglacial carbon store. However, DOC concentration, δ 13C-DOC, Δ 14C-DOC and fluorescence signatures appear to have been influenced by runoff from vegetated hillslopes above the glacier during onset and senescence of melt. In the peak glacier melt period, the Δ 14C-DOC of stream samples at the outflow (-181.7 to -355.3‰) was comparable to the Δ 14C-DOC for snow samples from the accumulation zone (-207.2 to -390.9‰), suggesting that ancient DOC from the glacier surface is exported in glacier runoff. The pre-aged DOC in glacier snow and runoff is consistent with contributions from fossil fuel combustion sources similar to those documented previously in ice cores and thus provides evidence for anthropogenic perturbation of the carbon cycle. Overall, our results emphasize the need to further characterize DOC inputs to glacier ecosystems, particularly in light of predicted changes in glacier mass and runoff in the coming century.

  15. The GAMDAM glacier inventory: a quality-controlled inventory of Asian glaciers

    NASA Astrophysics Data System (ADS)

    Nuimura, T.; Sakai, A.; Taniguchi, K.; Nagai, H.; Lamsal, D.; Tsutaki, S.; Kozawa, A.; Hoshina, Y.; Takenaka, S.; Omiya, S.; Tsunematsu, K.; Tshering, P.; Fujita, K.

    2015-05-01

    We present a new glacier inventory for high-mountain Asia named "Glacier Area Mapping for Discharge from the Asian Mountains" (GAMDAM). Glacier outlines were delineated manually using 356 Landsat ETM+ scenes in 226 path-row sets from the period 1999-2003, in conjunction with a digital elevation model (DEM) and high-resolution Google EarthTM imagery. Geolocations are largely consistent between the Landsat imagery and DEM due to systematic radiometric and geometric corrections made by the United States Geological Survey. We performed repeated delineation tests and peer review of glacier outlines in order to maintain the consistency and quality of the inventory. Our GAMDAM glacier inventory (GGI) includes 87 084 glaciers covering a total area of 91 263 ± 13 689 km2 throughout high-mountain Asia. In the Hindu Kush-Himalaya range, the total glacier area in our inventory is 93% that of the ICIMOD (International Centre for Integrated Mountain Development) inventory. Discrepancies between the two regional data sets are due mainly to the effects of glacier shading. In contrast, our inventory represents significantly less surface area (-24%) than the recent global Randolph Glacier Inventory, version 4.0 (RGI), which includes 119 863 ± 9201 km2 for the entirety of high Asian mountains. Likely causes of this disparity include headwall definition, effects of exclusion of shaded glacier areas, glacier recession since the 1970s, and inclusion of seasonal snow cover in the source data of the RGI, although it is difficult to evaluate such effects quantitatively. Further rigorous peer review of GGI will both improve the quality of glacier inventory in high-mountain Asia and provide new opportunities to study Asian glaciers.

  16. Black soot and the survival of Tibetan glaciers.

    PubMed

    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

    2009-12-29

    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

  17. 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

  18. Fjord - Glacier Ice Interactions: Nuup Kangerlua (Godthåbsfjord) Southwest Greenland

    NASA Astrophysics Data System (ADS)

    Motyka, R. J.; Truffer, M.; Dryer, W. P.; Fahnestock, M. A.; Cassotto, R. K.; Mortensen, J.; Rysgaard, S.

    2012-12-01

    The study of interactions between glaciers, fjords, and the ocean in coastal Greenland is still in its infancy. Circulation of warm ocean waters into fjords has been hypothesized to play an important role in destabilizing and modulating glacier discharge from outlet glaciers in Greenland, but details on the dynamics of this interaction remain sparse. To help fill this gap, we conducted a series of hydrographic measurements over a six-day period in late August 2011 in the proglacial fjord Kangersuneq at the head of Nuup Kangerlua (Godthåbsfjord) near Nuuk in southwest Greenland. Because of iceberg conditions, we were unable to approach any closer than 12 km to the tidewater glacier Kangiata Nunaata Sermia (KNS) at the head of the fjord. We conducted the majority of our measurements over the KNS Little Ice Age (LIA) moraine, a sill which forms a barrier between the inner and outer fjord. The LIA sill lies about 22 km from KNS, spans the 4-km-wide fjord and has a maximum water depth of 170 m. Water depths fall to over 300 m on either side of this sill and all water entering or leaving the inner basin must flow over it. For comparison, we also conducted transects at a second location inside the inner basin, 12 km from the KNS terminus and in much deeper water (> 300 m). Our transects included shipboard CTD (conductivity, temperature, density) and current measurements, the latter using rail-mounted 150 kHz and 600 kHz RDI ADCPs (Acoustic Doppler Current Profilers). Iceberg conditions in the fjord prevented measurements while underway. The CTD measurements showed a highly stratified water column capped by a 5 m freshwater layer. The warmest (3 deg. C) and most saline water (32) lies directly over the sill, near the bottom of the water column. The freshwater fraction at 20 m water depth is 7.6% with 6.0% from subglacial freshwater discharge and 1.6% derived from submarine melting of ice. We timed our survey to bracket the neap tide to reduce complexities related to tidal

  19. Seismic stratigraphy of the Bering Trough, Gulf of Alaska: Late Quaternary history of Bering Glacier dynamics

    NASA Astrophysics Data System (ADS)

    Montelli, A.; Gulick, S. P. S.; Worthington, L. L.; Mix, A. C.; Zellers, S.; Jaeger, J. M.

    2014-12-01

    Sedimentary architecture of the cross-shelf Bering Trough is studied using 5 high resolution seismic profiles integrated with the drilling data acquired during Integrated Ocean Drilling Program (IODP) Expedition 341. The objectives of this work are to constrain the number of advance-retreat cycles that have occurred through the Late Quaternary, examine the impact of the Bering Glacier on the continental shelf and slope, and reconstruct Bering Glacier dynamics. By tying these sequences with δ18O stratigraphy, we can test the Bering Glacier's relation to global ice sheet evolution and better understand the degree to which the glacial advance-retreat cycles were in phase with global events. Our results show that: (1) Identification of erosional surfaces and glacigenic landforms that record positions of stillstand events and diagnose the style of retreat allow us to distinguish nine phases of glacial advances and subsequent retreats. (2) Mapping shows that glacier pathways and flow directions through time are influenced by the occurrence of thick grounding-zone deposits and shifting foci of erosion. (3) Continuous buildup of glacigenic sediment fills tectonically created accommodation space and allows the glacier to advance seaward for the last three advances. Discovery of systematic, prominent deposition of glacial diamict and ice-rafted debris (IRD) during phases of glacial retreat is supported by the drilling data and suggests reconsideration of IRD impact on slope sedimentation. (4) The trough mouth fan started its development during marine isotope stage (MIS) 6, progressively advancing to the position of present shelf edge during the subsequent MIS 4 and MIS 2 and is recognized by evidence of extensive deposition of glacigenic debris flows on the slope. (5) Sedimentation rates in the depocenter are exceptionally high and are estimated to be 1-2 m/k.y. through the middle Pleistocene on the shelf and 4-5 m/k.y. average through MIS 6 on the slope.

  20. 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.

  1. Spatial patterns in glacier area and elevation changes from 1962 to 2006 in the monsoon-influenced eastern Himalaya

    NASA Astrophysics Data System (ADS)

    Racoviteanu, A.; Arnaud, Y.; Williams, M.; Manley, W. F.

    2014-07-01

    This study presents spatial patterns in glacier area and elevation changes in the monsoon-influenced part of the Himalaya (eastern Nepal and Sikkim) at multiple spatial scales. We combined Corona KH4 and topographic data with more recent remote-sensing data from Landsat 7 Enhanced Thematic Mapper Plus (ETM+), the Advanced Spaceborne Thermal Emission Radiometer (ASTER), QuickBird (QB) and WorldView-2 (WV2) sensors. We present: (1) spatial patterns of glacier parameters based on a new "reference" geospatial Landsat/ASTER glacier inventory from ~ 2000; (2) changes in glacier area (1962-2006) and their dependence on topographic variables (elevation, slope, aspect, percent debris cover) as well as climate variables (solar radiation and precipitation), extracted on a glacier-by-glacier basis and (3) changes in glacier elevations for debris-covered tongues and their relationship to surface temperature extracted from ASTER data. Glacier mapping from 2000 Landsat/ASTER yielded 1463 km2 ± 88 km2 total glacierized area in Nepal (Tamor basin) and Sikkim (Zemu basin), parts of Bhutan and China, of which we estimated 569 km2 ± 34 km2 to be located in Sikkim. Supraglacial debris covered 11% of the total glacierized area, and supraglacial lakes covered about 5.8% of the debris-covered area. Based on analysis of high-resolution imagery, we estimated an area loss of -0.24% ± 0.08% yr-1 from the 1960's to the 2010's, with a higher rate of retreat in the last decade (-0.43% yr-1 ± 0.9 % from 2000 to 2006) compared to the previous decades (-0.20% yr-1 ± 0.16% from 1962 to 2000). Retreat rates of clean glaciers were -0.7% yr-1, almost double than those of debris-covered glaciers (-0.3% yr-1). Debris-covered tongues experienced an average lowering of -30.8 m ± 39 m from 1960's to 2000's (-0.8 m ± 0.9 m yr-1), with enhanced thinning rates in the upper part of the debris covered area, and overall thickening at the glacier termini.

  2. 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.

  3. 10Be surface exposure dating of rock glaciers in Larstigtal, Tyrol, Austria

    NASA Astrophysics Data System (ADS)

    Ivy-Ochs, S.; Kerschner, H.; Maisch, M.; Christl, M.; Kubik, P. W.; Schluchter, C.

    2009-04-01

    In the context of Lateglacial and Holocene climate change research, rock glaciers (creeping mountain permafrost) also play an important role. They are phenomena of discontinuous alpine permafrost and as such good indicators for the mean annual air temperature for the period they are active. We have 10Be surface exposure dated boulders from two relict rock glaciers in Larstigtal, Austria. This is the type area for a postulated mid-Holocene cold period called the Larstig oscillation. The period of activity was suggested to be of similar age as the mid-Holocene Frosnitz advance of glaciers in the Venediger Mountains farther to the east (Patzelt and Bortenschlager, 1973). For rock glaciers of this size to be active at 2200 m a.s.l. in Larstig valley would have required a significant drop in temperatures, thus a marked mid-Holocene cold pulse, for at least several centuries at around 7.0 ka. In contrast, our exposure dates show that the rock glaciers stabilized during the early Preboreal (Ivy-Ochs et al., submitted). We see no distinct pattern with respect to exposure age and boulder location on the rock glaciers. This implies that for our site the blocks did not acquire inherited 10Be during exposure in the free rock face, in the talus at the base of the slope, or during transport on the rock glaciers. Our data point to final stabilization of the Larstigtal rock glaciers in the earliest Holocene and not in the middle Holocene. Combined with data from other archives (Nicolussi et al., 2005), there appears to have been no time window in the middle Holocene long enough for rock glaciers of the size and at the elevation of the Larstig site to have formed. Ivy-Ochs, S., Kerschner, H., Maisch, M., Christl, M., Kubik, P.W., Schlüchter, C., Latest Pleistocene and Holocene glacier variations in the European Alps. Quaternary Science Reviews (submitted). Nicolussi, K., Kaufmann, M., Patzelt, G., van der Plicht, J., Thurner, A., 2005. Holocene tree-line variability in the Kauner

  4. ASTER image based assessment of glacier mass balance of Nanga Parbat massif, Pakistan

    NASA Astrophysics Data System (ADS)

    Kargel, Jeffrey; Leonard, Gregory; Haritashya, Umesh

    2014-05-01

    Starting with the analytical approach given in detail by Nuth and Kääb (2011; henceforth NK2011), we have further developed an approach toward analysis of repeat stereo ASTER-derived DEMs to extract specific and net annual mass balance of glaciers of Nanga Parbat, Pakistan. We used the approach of NK2011 to coregister DEMs obtained from ASTER stereo images acquired in September 2004 and October 2010, and the glacier outlines produced by Haritashya et al. (2014 in prep) as a mask to isolate glacier from stable (nonglacier) areas. We then devised a protocol to remove DEM data deemed to be the pits, cones, and bulges that are common artifacts with ASTER DEM data. We developed an approach similar to that given by NK2011 to make corrections for cross- and along-track errors of elevation differences and to zero out the mean elevation difference bias for stable (non-glacier points). The largest sources of correctable error were cross-track and along-track slope-dependent artifacts, which we corrected using an approach modified from that of NK2011. Several small systematic errors, such as that related to elevation, became even smaller when cross- and along-track errors were corrected. We then proceeded to analyze the statistics for the cumulative ice area and for individual glaciers. Also using the DEM-change spread function for stable areas, we deconvolved the random error from the actual change signal present in the glacier areas. Ten glaciers of Nanga Parbat thinned by an average of 6 m, i.e., 1 m/year over the 6-year period. Ice in the highest elevations remained fairly stable or even thickened by a few meters, whereas that in lower elevations thinned. Bazhin Glacier apparently was undergoing a surge-like phenomenon of rapid mass transfer from higher elevations (where thinning occurred) to lower elevations (where it thickened), though the terminus advanced by only ~182 m (Haritashya et al. 2014). Hence, our results indicate fluctuations of glaciers in Nanga Parbat

  5. 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.

  6. 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

  7. 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.

  8. Step-wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Nettles, M.; Larsen, T. B.; Elósegui, P.; Hamilton, G. S.; Stearns, L. A.; Ahlstrøm, A. P.; Davis, J. L.; Andersen, M. L.; de Juan, J.; Khan, S. A.; Stenseng, L.; Ekström, G.; Forsberg, R.

    2008-12-01

    Geodetic observations show several large, sudden increases in flow speed at Helheim Glacier, one of Greenland's largest outlet glaciers, during summer, 2007. These step-like accelerations, detected along the length of the glacier, coincide with teleseismically detected glacial earthquakes and major iceberg calving events. No coseismic offset in the position of the glacier surface is observed; instead, modest tsunamis associated with the glacial earthquakes implicate glacier calving in the seismogenic process. Our results link changes in glacier velocity directly to calving-front behavior at Greenland's largest outlet glaciers, on timescales as short as minutes to hours, and clarify the mechanism by which glacial earthquakes occur.

  9. Interaction between glacier and glacial lake in the Bhutan, Himalaya

    NASA Astrophysics Data System (ADS)

    Tsutaki, S.; Fujita, K.; Yamaguchi, S.; Sakai, A.; Nuimura, T.; Sugiyama, S.; Komori, J.; Takenaka, S.; Tshering, P.

    2012-12-01

    Recession of mountain glaciers in the Himalayas has been reported in the context of global warming. Associated with the glacier retreat, supraglacial lakes have been formed on the termini of debris-covered glaciers. Although it has been said that lake-terminating glaciers flow faster than land-terminating glaciers, observational evidence was scarce. We observationally investigated the influence of the presence/absence of glacial lakes on changes in surface elevation through glacier dynamics in two debris-covered glaciers, Thorthormi Glacier (land-terminating) and Lugge Glacier (lake-terminating), in the Lunana region, the Bhutan Himalaya. We surveyed the surface elevation of debris-covered areas of the two glaciers in 2004 and 2011 by a differential GPS. Change in surface elevation of the lake-terminating Lugge Glacier was much more negative than that of the land-terminating Thorthormi Glacier. Considering almost flat slope and location at lower elevation, however, larger ice thinning rate of the Thorthormi Glacier should have been expected than the Lugge Glacier. We measured surface flow speed of the two glaciers during 2009-2010 by multitemporal orthorectified The Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) images of ALOS. Surface flow speed of the Thorthormi Glacier was faster in the upper reaches and reduced toward the downstream. In contrast, the flow speed at the Lugge Glacier measured in the same periods was greatest at the lower most part. Observed spatial distribution of surface flow speed at both glaciers are evaluated by a two-dimensional numerical flow model. The model shows that contribution of basal sliding to surface flow velocity is large in the lower part of both glaciers. Particularly in the Thorthormi Glacier, approximately 100% of surface flow velocity attribute to basal sliding. Calculated emergence velocity at the Thorthormi Glacier is larger than that at the Lugge Glacier. This result suggests that decreasing in flow

  10. Glacier Instability, Rapid Glacier Lake Growth and Related Hazards at Belvedere Glacier, Macugnaga, Italy

    NASA Astrophysics Data System (ADS)

    Huggel, C.; Kaeaeb, A.; Haeberli, W.; Mortara, G.; Chiarle, M.; Epifani, F.

    2002-12-01

    Starting in summer 2000, Belvedere Glacier, near Macugnaga, Italian Alps, developed an extraordinary change in flow, geometry and surface appearance. A surge-type flow acceleration started in the lower parts of the Monte-Rosa east face, leading to strong crevassing and deformation of Belvedere Glacier, accompanied by bulging of its orographic right margin. In September 2001, a small supraglacial lake developed on the glacier. High water pressure and accelerated movement lasted into winter 2001/2002. The ice, in places, started to override moraines from the Little Ice Age. In late spring and early summer 2002, the supraglacial lake grew at extraordinary rates reaching a maximum area of more than 150'000 m2 by end of June. The evolution of such a large supraglacial lake, a rather unique feature in the Alps, was probably enabled by changes in the subglacial drainage system in the course of the surge-like developments with high water pressure in the glacier. At the end of June, an enhanced growth of the lake level with a rise of about 1 m per day was observed such that the supraglacial lake became a urgent hazard problem for the community of Macugnaga. Emergency measures had to be taken by the Italian Civil Protection. The authors thereby acted as the official expert advisers. Temporal evacuations were ordered and a permanent monitoring and alarm system was installed. Pumps with a maximum output of 1 m3/s were brought to the lake. Bathymetric studies yielded a maximum lake depth of 55 m and a volume of 3.3 millions of cubic meters of water. Aerial photography of 1995, 1999, September 2001 and October 2001 was used to calculate ice flow velocities and changes in surface altitude. Compared to the period of 1995 to 1999, the flow accelerated by about five times in 2001 (max. speeds up to 200 m/yr). Surface uplift measured was about 10-15 m/yr. The results of the photogrammetric studies were used to evaluate different possible lake-outburst scenarios, in particular

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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 produces the correct Little Ice Age maximum glacier length and simulates the observed magnitude of the 1978-surge. Abrahamsenbreen is strongly out of balance with the current climate. If climatic conditions will 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 yr-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 to increase the ablation area, thereby causing a negative perturbation of the mass budget. We found that the occurrence of surges leads to a somewhat stronger 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 E. For a decrease of E of only 160 m, the glacier would steadily grow into the Woodfjorddalen until after 2000 years it would reach the Woodfjord and calving could slow down the advance.

  12. Glacier length fluctuations in southern Norway back to the 17th century based on historical data: opposite behaviour compared to the Alps?

    NASA Astrophysics Data System (ADS)

    Nussbaumer, S. U.; Luterbacher, J.; Nesje, A.; Wanner, H.; Zumbühl, H. J.

    2009-04-01

    The understanding of past and present glacier variations is a key task for evaluating current climate change. Historical and proxy-records have documented a partly asynchronous evolution in temperature, precipitation and glacial variations between European regions during the Little Ice Age (LIA), with the causes of these temporal anomalies yet being poorly understood. The comparison between the Alps and Scandinavia allows an assessment of the spatial distribution of glacier fluctuations in the studied areas during the last few centuries. Here we present temporally high-resolved glacier reconstructions for southern Norway covering the period back to the 17th century, based on newly discovered historical material. Length changes were determined by the interpretation of high-quality historical documents such as drawings, paintings, prints, photographs, maps and written sources that are abundant for selected glaciers in the area (Folgefonna, Jostedalsbreen). Historical material is only available in adequate quantity for those glaciers which drew the attention of travellers, scientists and artists through their reputation and scenic attraction, reflecting also the glacier perception at that time. A critical quality check of the documentary data was necessary in order to get reliable information on past glacier extents. The glacier extents obtained were finally compared with existing moraine findings in the glacier forefield. Results from outlet glaciers from Folgefonna (Bondhusbreen, Buerbreen) and Jostedalsbreen (Briksdalsbreen, Bøyabreen, Suphellebreen, Bergsetbreen, Nigardsbreen, Lodalsbreen) indicate a highly different glacier evolution compared to the Alps. According to the historical record, the maximum glacier extent occurred at Folgefonna at around 1890, and at Jostedalsbreen at around 1750, respectively. In the Alps, existing glacier length records (e.g. for Unterer Grindelwaldgletscher, Switzerland, or Mer de Glace, France) show glacier advances around 1600

  13. Peeking Under the Ice… Literally: Records of Arctic Climate Change from Radiocarbon Dating Moss Emerging from Beneath Retreating Glaciers

    NASA Astrophysics Data System (ADS)

    Briner, J. P.; Schweinsberg, A.; Miller, G. H.; Lifton, N. A.; Beel, C. R.; Bennike, O.

    2014-12-01

    Dramatic changes are taking place throughout the Arctic. Many glaciers have already melted away completely, and most others are well on their way as rising snowline elevations promise continued glacier retreat. Emerging from beneath retreating glacier margins is a landscape rich in information about past climate and glacier changes. Within newly exposed bedrock is an inventory of cosmogenic nuclides that archive past ice cover timing and duration. Lake basins re-appearing due to retreating ice preserve sediment archives that tell of cooling climate and advancing ice. And ancient surfaces vegetated with tundra communities that have long been entombed beneath frozen-bedded ice caps are now being revealed for the first time in millennia. This presentation will focus on the climate and glacier record derived from radiocarbon dating of in situ moss recently exhumed from retreating local ice cap margins on western Greenland. Dozens of radiocarbon ages from moss group into several distinct modes, which are interpreted as discrete times of persistent summer cooling and resultant glacier expansion. The data reveal a pattern of glacier expansion beginning ~5000 years ago, followed by periods of glacier growth around 3500 and 1500 years ago. Because these times of glacier expansion are recorded at many sites in western Greenland and elsewhere in the Arctic, they are interpreted as times of step-wise summer cooling events during the Holocene. These non-linear climate changes may be a result of feedbacks that amplify linear insolation forcing of Holocene climate. In addition to these insights into the Arctic climate system, the antiquity of many radiocarbon ages of ice-killed moss indicate that many arctic surfaces are being re-exposed for the first time in millennia due to retreating ice, emphasizing the unprecedented nature of current summer warming.

  14. Ice-front variations and speed changes of calving glaciers in the Southern Patagonia Icefield from 1984 to 2013

    NASA Astrophysics Data System (ADS)

    Sakakibara, D.; Sugiyama, S.

    2014-12-01

    Southern Patagonia Icefield (SPI) is losing volume, and the loss is due partly to rapid changes in outlet glaciers that terminate in lakes or the ocean. Despite their key influence, relatively few of these calving glaciers have had high-frequency measurements on their frontal variations and ice speed changes. We present frontal variations and ice speed changes of all glaciers having a surface area exceeding 100 km2 in the SPI from 1984 to 2013. The analysis is based on satellite images acquired using Landsat 4, 5, 7, and 8. From 1984 to 2011, only the two termini of Glaciar Pío XI advanced. Of the remaining glacial fronts, 12 changed less than ±0.5 km, but 17 retreated at least 0.5 km. In the latter group, three (Glaciar Jorge Montt, HPS12, and Upsala) retreated over 6 km. Averaged over all 31 glacial fronts of the calving glaciers, the front positions retreated 1.56 km (median: 0.71 km). Along the centerline within 20-km of the front, the ice speeds ranged from 50±40 to 5900±200 m a-1. Except for regions showing large acceleration or deceleration, the mean speed over the measured area decreased by 30 m a-1 from 1984 to 2011. The three most rapidly retreating glaciers showed much larger acceleration near the calving front. Except for Pío XI, the glaciers fall into one of three categories: stable front position without significant ice speed change, gradual retreat with deceleration, and rapid retreat with large acceleration. The overall retreat trend was probably due to the long-term warming trend. Nevertheless, our data demonstrated that the extraordinary large retreats in the three glaciers were not directly controlled by the warming trend, but instead driven by glacier dynamics. Such dynamically controlled rapid recession of several calving glaciers plays a key role in the recent volume decrease of the SPI.

  15. 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

  16. Climatology of Andean glaciers: A framework to understand glacier response to climate change

    NASA Astrophysics Data System (ADS)

    Sagredo, E. A.; Lowell, T. V.

    2012-04-01

    Recent glacial and climate models suggest that glaciers located in contrasting climates could respond with different magnitudes to identical climatic perturbations. This implies that to understand the response of glaciers to a particular climate perturbation or to compare glacial fluctuations between different regions, climate conditions that permit glaciers to exist must be taken into account. In this study we systematize, classify, and identify the spatial distribution of the climates that permit the occurrence of present-day glaciers in the climatically diverse Andes. A first approximation suggests that a sample of 234 Andean glaciers exist under three distinctive combinations of temperature and precipitation conditions: i) cold and dry, ii) intermediate, and iii) warm and wet conditions. Cluster analysis (CA) and Principal Component analysis (PCA) of temperature, precipitation, and humidity reveal seven climatic configurations that support present-day Andean glaciers and suggest that these configurations have a distinctive geographical distribution. The groups are: 1) inner tropics and Tierra del Fuego, 2) wetter outer tropics, 3) drier outer tropics, 4) subtropics, 5) central Chile-Argentina (semi-arid), 6) northern and central Patagonia, and 7) southern Patagonia. This classification provides a basis to examine the spatial variability of glacier sensitivity to climate change, to unravel the causes of past glacial fluctuations, to understand the climatic signals driving present-day glacier fluctuations, and perhaps to predict the response of glaciers to future climate changes.

  17. 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

  18. Biogeochemistry of glacier and rock glacier outflow in the western United States

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Glaciers are melting at unprecedented rates worldwide, releasing bioavailable minerals and nutrients and altering downstream biogeochemistry. Though much research has focused on the recession of ice-glaciers in alpine environments, far less is known about the melt dynamics and biogeochemistry of rock glaciers. Rock glaciers, which are mixtures of ice and rocks that flow like a glacier, are far more abundant in mountainous regions of the western United States than ice glaciers. Little is known about their influence on downstream hydrology and water quality. We report here preliminary results of a west-wide survey of the influence of glaciers and rock glaciers on headwater properties. Measurements of specific conductance, nitrate (NO3-), ammonium (NH4+), dissolved silica, and dissolved organic matter were compared between glaciers, rock glaciers, and snow-fed reference streams from three basins in the Colorado Front Range. Samples were collected from ice, where possible, and downstream at 500m intervals from the first flowing water to tree line. UV and fluorescence data were analyzed using excitation emission matrices (EEMs) and PARAFAC modeling. High concentrations of NH4+ were only found in ice and the most upstream locations; NH4+ was below detection at all lower elevation sites, whereas NO3- concentrations were low in the headwaters and higher downstream. The fluorescence spectrum of DOC from both ice and the highest elevations had a strong autochthonous (microbial or algal) signal that was replaced by a more allochtonous, terrestrially-derived DOC as it approached tree line. Rock glacier stream chemistry was intermediate between glacier-fed streams and strictly snow fed drainages. DOC levels for ice glaciers ranged 2-3mg/L with increasing values downstream, while rock glaciers ranged from 1-2.5 mg/L with attenuation downstream. Snowfed only streams had DOC values at detection <0.5mg/L, with the exception at Lake Husted outflow, with an upland wetland, unlike the

  19. GCM Simulations of Tropical Ice Accumulations: Implications for Cold-based Glaciers

    NASA Technical Reports Server (NTRS)

    Haberle, R. M.; Montmessin, F.; Forget, F.; Levrard, B.; Head, J. W., III; Laskar, J.

    2004-01-01

    Each of the three Tharsis Montes shield volcanoes on Mars has fan-shaped deposits on their flanks. A detailed analysis of the multiple facies of the Arsia Mons deposits, coupled with field observations of polar glaciers in Antarctica, shows that they are consistent with deposition from cold-based mountain glaciers. Key features of these glaciers are: (1) they formed only on the western flank of each volcano, (2) enough ice accumulated to cause them to flow but without basal melting, (3) there were multiple advances and retreats, (4) the last major glaciation was more than several million years ago, (5) the areal extent of the deposits they left behind decreases northward, (6) together the deposits range in elevation from a low of 1.5 to a high of 8.5 km, and (7) there are no signs that significant accumulation is occurring today.

  20. Reconstruction of mass balance variations for Franz Josef Glacier, New Zealand, 1913 to 1989

    SciTech Connect

    Woo, Mingko Woo ); Fitzharris, B.B. )

    1992-11-01

    A model of mass balance is constructed for the Franz Josef Glacier on the west coast of New Zealand. It uses daily data from a nearby, but short-record climate station. The model is extended back to 1913 by creating hybrid climate data from a long-record, but more distant, climate station. Its monthly data provide long-term temperature and precipitation trends, and daily fluctuations are simulated using a stochastic approach that is tuned to the characteristics of the short-record station. The glacier model provides estimates of equilibrium-line altitudes which are in reasonable agreement with those observed, and variations of cumulative mass balance that correspond with patterns of advance and retreat of the glacier terminus.

  1. Heterogeneous Status of Glacial Terminal-Contacted Lakes in Himalayas Due to Different Geomorphology and Glacier Characters

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Nie, Y.; Liu, S.

    2014-12-01

    Widespread expanding of glacial lakes around the Himalayas, which has led (or will lead) to hazard risks in their downstream valleys due to the potential glacial outburst flood (GLOF), has been widely reported during the past decades. Among all type of glacial lakes, those lakes contacted with the terminals of modern glaciers are generally found experienced most remarkable area increases. That is mostly due to the coupled processes, such as calving, between the lake growths and ice tongue retreats. Thermal absorption and convection of lake water are important for calving at the ice cliff or sub-marine melting under the supra-ponded water bodies. Currently, many larger moraine dammed lakes, e. g., Imja Tsho (Nepal) and Longbasaba Lake (China), are observed undergoing remarkable growths and synchronically with the rapid ice margin collapses due to calving. Some newly formed and rapidly growing supraglacial lakes are also identified on the debris-covered region of Himalayan glaciers, e. g., the Rongbuk Glacier (China), Ngozumpa Glacier (Nepal) and Thorthormi Glacier (Butan), which are speculated to experience accelerated expanding in the near future and finally developing as bigger terminal-calving lakes. However, not all such lake-glacier systems present the same scenes. After experienced the phases of rapid lake growth and terminal retreat, despite the contacting and calving still existing, the positions of the calving lines may be balanced by the positive advances of the ice tongue. We have observed several lakes with stagnation of growth or even shrinkage in lake area as the advance of the calving ice margin. The heterogeneous status of these ice-contacted glacial lakes are mainly due to the different local geomorphology (e. g., slope, lake-basin shape and valley aspect) and glacier characters (e. g., debris cover, velocity and mass balance). These related factors are important for both the prediction of lake and glacier changes and the evaluation of GLOF hazards

  2. Airborne LiDAR DEMs as a tool for deriving information on past glacier extent and ice flow

    NASA Astrophysics Data System (ADS)

    Seiser, Bernd; Fischer, Andrea

    2014-05-01

    The quantification of ice volumes and the identification of ice flow regimes within historical glacier systems are important steps towards understanding historical phases of glacier advance and disintegration in the context of Holocene climate fluctuation. Topographic LiDAR DEMs provide an excellent tool for gaining various kinds of spatially distributed information. Several case studies have been performed in the Austrian Alps, where LiDAR DEMs are available for almost the entire glacier area. LiDAR DEMs achieve vertical accuracies of few decimetres and can be used to calculate hillshade images with flat incidence angles, so that the surface structures of moraines and other glacial deposits can be identified. These hillshade images were used together with aerial photographs to identify the LIA (Little Ice Age) moraines and the elevation of the lateral moraines, so that, together with information on today's ice volume, a lower limit for the LIA ice volume could be calculated. The resulting LIA glacier areas showed good coincidence with former reconstructions based on field mapping and airborne photogrammetry. In addition to that, historical ice flow directions could be derived from the structure of basal moraines. These data allow an interpretation of the changing contribution of specific tributary glaciers to a joint glacier tongue, which may result in an important switch in ice dynamics leading to fast glacier advances recorded by frontal moraines. The combination of terrestrial long-term observations and LiDAR data documents the genesis of specific geomorphological features in the periglacial area by recording the processes occurring during the disintegration of glacier tongues. For example, the deposition of the material from former medial moraines in the newly formed periglacial area can be identified and quantified from the LiDAR data as well as debris flows or rock falls from the LIA moraines.

  3. Distinct patterns of seasonal Greenland glacier velocity

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  4. 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

  5. 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.

  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. PMID:12917679

  7. 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

  8. Towards a complete World Glacier Inventory

    NASA Astrophysics Data System (ADS)

    Zemp, Michael

    2013-04-01

    The need for an inventory of the world's glaciers evolved during the International Hydrological Decade (1965-74). As a result, guidelines were established in the mid 1970s to compile a worldwide detailed inventory of existing perennial snow and ice masses. Following these international guidelines, several countries started compiling national glacier inventories based primarily on aerial photographs and maps. In the 1980s, the World Glacier Inventory (WGI) database was launched together with a status report about global and regional glacierised surface areas for the second half of the 20th century. These estimates were based on the detailed inventory data together with preliminary estimates of the remaining glacierised regions derived from early satellite imagery. In the late 1990s, the Global Land Ice Measurements from Space (GLIMS) database was initiated to continue the inventory task with space-borne sensors. In the WGI, glaciers are represented by geographical point coordinates. The GLIMS database includes digital outlines. Both include exact time stamps and tabular information on glacier classifications, length, area, orientation, and altitude range. Both are regularly updated with newly available data: the WGI stores point information for the second half of the 20th century whereas the GLIMS includes digital outlines for the 21st century. Since these detailed glacier inventories are not (yet) globally complete, there have been several efforts towards preliminary estimates of the overall global glacier coverage. A first, well elaborated one was included in the original status report of the WGI, published in 1989, and was refined in 2005 with information from other sources by Dyurgerov and Meier. Other studies used the detailed WGI, or an extended format by Cogley, for regional or global up-scaling of glacier extents. In 2003, Cogley published a global map of percentage glacier coverage per 1°x1° grid box (GGHydro) that is widely used for modeling at global

  9. Glacier variations in the Northern Caucasus compared to climatic reconstructions over the past millennium

    NASA Astrophysics Data System (ADS)

    Solomina, Olga; Bushueva, Irina; Dolgova, Ekaterina; Jomelli, Vincent; Alexandrin, Mikhail; Mikhalenko, Vladimir; Matskovsky, Vladimir

    2016-05-01

    resolution of the data available and ambiguous interpretation of the evidence. The first LIA maximum glacier extent in the past millennium is poorly constrained. According to our data, it occurred prior to the year 1598 CE (tree-ring-based minimum age). Two other major phases of advances occurred in the second half of the 17th century CE and the first half of 19th century CE. General glacier retreat in the Northern Caucasus started in the late 1840s CE, with four to five minor readvances in the 1860s-1880s CE and three readvances or steady states in the 20th century CE (1910s, 1920s and 1970s-1980s). Since the last LIA maximum in the middle of the 19th century CE, most glaciers have decreased in length by more than 1000 m, and the rise in the elevation of the glacier fronts has exceeded 200 m. The glacier advances correspond to summer temperature minima and are generally coherent with the reconstructed mass balance of the Garabashi Glacier. A comparison of a tree-ring-based summer temperature reconstruction in the Northern Caucasus with detailed reconstructions of summer temperature and glacier fluctuations in the Alps shows a pronounced agreement between the records and supports the similarity between the patterns of climatic and glacier variations in the two regions.

  10. Winter speed-up of ice flow at quiescent surge-type glaciers in Yukon, Canada

    NASA Astrophysics Data System (ADS)

    Furuya, M.; Abe, T.

    2013-12-01

    Glacier surge exhibits order-of-magnitude faster velocity and km-scale terminus advance during its short active phase after a long quiescent period. The observations of glacier surge are still limited, and the mechanisms of glacier surge cycle remain elusive. Moreover, with the exception of several well-examined glaciers, the glacier dynamics during their quiescent periods remains even more uncertain due to the paucity of surface velocity measurement data. Here we examined spatial-temporal changes in the ice surface velocity of surge-type glaciers in the St. Elias Mountains near the border of Alaska and Yukon during the period from December 2006 to March 2011. We applied the offset-tracking (feature-tracking) technique to the L-band synthetic aperture radar (SAR) images derived from the Japanese Advanced Land Observation Satellite (ALOS). The Chitina, Anderson, Walsh, and Logan Glaciers, the major subpolar surge-type glaciers of the Chitina River valley system, could be examined with the highest temporal resolution because of the overlap of multiple satellite tracks. We have found significant upstream accelerations from fall to winter at a number of glaciers during their quiescence. Moreover, whereas the upstream propagating summer speed-up was observed, the winter speed-up propagated from upstream to downglacier. Although the winter speed-up seems to be at odds with the well-known summer speed-up, these observations are consistent with the fragmentary but well-known fact of glacier surge that often initiates in winter, suggesting that some of the mechanisms would be valid even during quiescent phases. Ice surface velocity at mountain glaciers and ice sheets typically exhibits the greatest acceleration from spring to early summer, followed by deceleration in mid-summer to fall, and is slowest in winter. These short-term velocity changes are attributed to subglacial slip associated with water pressure changes that occur because of the seasonal variability of

  11. Reconstructing the annual mass balance of the Echaurren Norte glacier (Central Andes, 33.5° S) using local and regional hydroclimatic data

    NASA Astrophysics Data System (ADS)

    Masiokas, Mariano H.; Christie, Duncan A.; Le Quesne, Carlos; Pitte, Pierre; Ruiz, Lucas; Villalba, Ricardo; Luckman, Brian H.; Berthier, Etienne; Nussbaumer, Samuel U.; González-Reyes, Álvaro; McPhee, James; Barcaza, Gonzalo

    2016-04-01

    Despite the great number and variety of glaciers in southern South America, in situ glacier mass-balance records are extremely scarce and glacier-climate relationships are still poorly understood in this region. Here we use the longest (> 35 years) and most complete in situ mass-balance record, available for the Echaurren Norte glacier (ECH) in the Andes at ˜ 33.5° S, to develop a minimal glacier surface mass-balance model that relies on nearby monthly precipitation and air temperature data as forcing. This basic model is able to explain 78 % of the variance in the annual glacier mass-balance record over the 1978-2013 calibration period. An attribution assessment identified precipitation variability as the dominant forcing modulating annual mass balances at ECH, with temperature variations likely playing a secondary role. A regionally averaged series of mean annual streamflow records from both sides of the Andes between ˜ 30 and 37° S is then used to estimate, through simple linear regression, this glacier's annual mass-balance variations since 1909. The reconstruction model captures 68 % of the observed glacier mass-balance variability and shows three periods of sustained positive mass balances embedded in an overall negative trend over the past 105 years. The three periods of sustained positive mass balances (centered in the 1920s-1930s, in the 1980s and in the first decade of the 21st century) coincide with several documented glacier advances in this region. Similar trends observed in other shorter glacier mass-balance series suggest that the Echaurren Norte glacier reconstruction is representative of larger-scale conditions and could be useful for more detailed glaciological, hydrological and climatological assessments in this portion of the Andes.

  12. International Symposium on Fast Glacier Flow

    NASA Technical Reports Server (NTRS)

    Lingle, Craig S.

    1990-01-01

    Cryospheric Sciences Program "International Symposium on Fast Glacier Flow" (PI, C. Lingle) provided partial support for publication of Annals of Glaciology 36 by the International Glaciological Society. Annals of Glaciology is a peer-reviewed journal. Annals 36, which was published in 2003, contains 39 peer-reviewed and edited papers from the International Symposium on Fast Glacier Flow, which was held in Yakutat, Alaska, 10-14 June 2002.

  13. 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.

  14. 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.

  15. Glacier speed-up events and water inputs on the lower Franz Josef Glacier, New Zealand

    NASA Astrophysics Data System (ADS)

    Kehrl, L. M.; Horgan, H.; Mackintosh, A. N.; Anderson, B. A.; Dadic, R.

    2012-12-01

    A glacier speed-up event occurs when a water input exceeds the capacity of the subglacial drainage system, and the subglacial water pressure increases. Several studies have suggested that glacier speed-up events do not affect overall glacier motion, as high ice-flow velocities during the event are offset by lower ice-flow velocities after the event due to a more efficient subglacial drainage system. In this study, we combine in-situ velocity measurements with a full Stokes glacier flowline model to explore the temporal and spatial variability in glacier flow on the lower Franz Josef Glacier, Southern Alps, New Zealand. Significant volumes of water enter the Franz Josef Glacier throughout the year due to high rainfall rates and year-round ablation. As a result, we infer that the subglacial drainage system is generally well-developed. In late summer (March) 2011, measured ice-flow velocities increased by up to 75% above background values because of rain events and by up to 32% above background values because of diurnal melt cycles. The observed speed-up events occurred at all survey locations within 4 ± 1 hours after the peak water input. We use a flowline model to show that a spatially-uniform subglacial water pressure, which increased during periods of heavy rain and glacier melt, can reproduce the measured ice-flow velocities across the lower glacier. From our results, we suggest that the variability in water inputs, rather than the mean water input to the system, is the primary driver in glacier speed-up events. If this is the case and the variability in water inputs is maintained, then glacier speed-up events can occur even if the subglacial drainage system is well-developed.

  16. 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.

  17. Creating improved ASTER DEMs over glacierized terrain

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    Digital elevation models (DEMs) produced from ASTER stereo imagery over glacierized terrain frequently contain data voids, which some software packages fill by interpolation. Even when interpolation is applied, the results are often not accurate enough for studies of glacier thickness changes. DEMs are created by automatic cross-correlation between the image pairs, and rely on spatial variability in the digital number (DN) values for this process. Voids occur in radiometrically homogeneous regions, such as glacier accumulation areas covered with uniform snow, due to lack of correlation. The same property that leads to lack of correlation makes possible the derivation of elevation information from photoclinometry, also known as shape-from-shading. We demonstrate a technique to produce improved DEMs from ASTER data by combining the results from conventional cross-correlation DEM-generation software with elevation information produced from shape-from-shading in the accumulation areas of glacierized terrain. The resulting DEMs incorporate more information from the imagery, and the filled voids more accurately represent the glacier surface. This will allow for more accurate determination of glacier hypsometry and thickness changes, leading to better predictions of response to climate change.

  18. Glacier crevasses: Observations, models, and mass balance implications

    NASA Astrophysics Data System (ADS)

    Colgan, William; Rajaram, Harihar; Abdalati, Waleed; McCutchan, Cheryl; Mottram, Ruth; Moussavi, Mahsa S.; Grigsby, Shane

    2016-03-01

    We review the findings of approximately 60 years of in situ and remote sensing studies of glacier crevasses, as well as the three broad classes of numerical models now employed to simulate crevasse fracture. The relatively new insight that mixed-mode fracture in local stress equilibrium, rather than downstream advection alone, can introduce nontrivial curvature to crevasse geometry may merit the reinterpretation of some key historical observation studies. In the past three decades, there have been tremendous advances in the spatial resolution of satellite imagery, as well as fully automated algorithms capable of tracking crevasse displacements between repeat images. Despite considerable advances in developing fully transient three-dimensional ice flow models over the past two decades, both the zero stress and linear elastic fracture mechanics crevasse models have remained fundamentally unchanged over this time. In the past decade, however, multidimensional and transient formulations of the continuum damage mechanics approach to simulating ice fracture have emerged. The combination of employing damage mechanics to represent slow upstream deterioration of ice strength and fracture mechanics to represent rapid failure at downstream termini holds promise for implementation in large-scale ice sheet models. Finally, given the broad interest in the sea level rise implications of recent and future cryospheric change, we provide a synthesis of 10 mechanisms by which crevasses can influence glacier mass balance.

  19. Modelling the hydrological response of debris-free and debris-covered glaciers to present climatic conditions in the semiarid Andes of central Chile

    NASA Astrophysics Data System (ADS)

    Ayala, Alvaro; Pellicciotti, Francesca; MacDonell, Shelley; McPhee, James; Vivero, Sebastián; Campos, Cristián; Egli, Pascal

    2016-04-01

    We investigate the main contributors to runoff of a 62 km2 glacierized catchment in the semiarid Andes of central Chile, where both debris-free and debris-covered glaciers are present, combining an extensive set of field measurements, remote sensing products and an advanced glacio-hydrological model (TOPKAPI-ETH). The catchment contains two debris-free glaciers reaching down to 3900 m asl (Bello and Yeso Glaciers) and one debris-covered avalanche-fed glacier reaching to 3200 m asl (Piramide Glacier). A unique dataset of field measurements collected in the ablation seasons 2013-14 and 2014-15 included four automatic weather stations, manual measurements of snow depth and debris cover thickness, discharge measurements at glaciers outlets, photographic monitoring of surface albedo as well as ablation stakes measurements and snow pits. TOPKAPI-ETH combines physically-oriented parameterizations of snow and ice ablation, gravitational distribution of snow, snow albedo evolution, glacier dynamics, runoff routing and the ablation of debris-covered ice.We obtained the first detailed estimation of mass balance and runoff contribution of debris-covered glaciers in this mountainous region. Results show that while the mass balance of Bello and Yeso Glaciers is mostly controlled by air temperature lapse rates, the mass balance of Piramide Glacier is governed by debris thickness and avalanches. In fact, gravitational distribution by avalanching on wet years plays a key role and modulates the mass balance gradient of all glaciers in the catchment and can turn local mass balance from negative to positive. This is especially the case for Piramide Glacier, which shows large amounts of snow accumulation below the steep walls surrounding its upper area. Despite the thermal insulation effect of the debris cover, the contribution to runoff from debris-free and debris-covered glaciers is similar, mainly due to elevation differences. At the catchment scale, snowmelt represents more than 60

  20. Bed topography under Antarctic outlet glaciers revealed by mass conservation and radar data

    NASA Astrophysics Data System (ADS)

    Morlighem, M.; Rignot, E. J.; Mouginot, J.; Seroussi, H. L.

    2015-12-01

    Bed topography, together with ice thickness, is an essential characteristic of glaciers and ice sheets for many glaciological applications. Despite significant technical advances, it remains challenging to measure ice thickness remotely, especially in deep troughs occupied by outlet glaciers. The method of mass conservation, that combines radar-derived ice thickness data with high-resolution InSAR-derived ice velocity vectors, provides an effective method for generating a high-resolution bed from sparse radar sounding profiles, and has been successfully applied along the coast of the Greenland Ice Sheet. Applying the same technique to the coast of the Antarctic Ice Sheet presents a number of challenges. The coverage of ice thickness data collected in Antarctica, for example, is much less comprehensive compared to Greenland, especially in the wake of NASA's Operation IceBridge (OIB) Mission in 2010-2015. Here, we combine radar sounder data collected by various centers (OIB/Center for Remote Sensing of Ice Sheets, the British Antarctic Survey and University of Texas) acquired between 1998 and 2011, with high-resolution ice motion data from interferometric SAR (ALOS PALSAR, RADARSAT-2 and Envisat ASAR) to reconstruct bed topography beneath major Antarctic outlet glaciers at an unprecedented level of detail. The results reveal some important features not known previously at that level of detail and shed light on the vulnerability of these glaciers in a warming climate. We find for example that Recovery glacier is deeper than in previous mappings and has long grooves parallel to the flow direction. Denman Glacier, East Antarctica, flow along a deep, narrow trough more than 2,000 m below sea level that extends more than 100 km inland. We find ridges and bumps in the vicinity of the grounding line of Thwaites Glacier, in the Amundsen Sea sector, that are consistent with the pattern of grounding line retreat. We have also a new mapping of the trough upstream of David

  1. Connecting hydrology and evolving properties of subglacial sediment beneath Russell Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Bougamont, M. H.; Christoffersen, P.; Hubbard, A.; Fitzpatrick, A.; Doyle, S. H.; Carter, S. P.; Fricker, H. A.; Pettersson, R.

    2012-12-01

    Seasonal flow variations have been observed on a large number of glaciers in Greenland. Typical for many glaciers is a speed up during spring, a slow down during summer, and a return to the winter velocity during fall. The drainage of supra-glacial lakes, which has been observed together with transient changes in ice flow, is another common characteristic of the Greenland Ice Sheet. The subsequent processes taking place at the bed of the ice sheet is, however, hindered by a paucity of data and observations. Recent advances in numerical modeling suggest that the hydrological system of glaciers overriding a hard bed responds to changes in discharge and that slowdown occurs when there is a switch from distributed to channelized drainage, yet the possible role of subglacial sediment in storing water and modulating ice flow remains unknown. This is problematic because large areas of the Greenland Ice Sheet could be underlain by such sediment. Here, we study the potential mechanisms responsible for seasonal flow changes for glaciers overriding soft sediments with a particular focus on sediment properties evolving from changing hydrological conditions. Our chosen site of investigation is the land-terminating Russell Glacier on the West Coast of Greenland where geophysical surveys have revealed the presence of subglacial sediment with a typical porosity of 30-35% and a thickness of about 20m. We have estimated the current distribution of basal stress beneath Russell glacier from an inversion of the observed surface velocity with the Glimmer-CISM higher order ice flow model. This inversion showed production of meltwater at a rate of 0.1 m/yr, which is consistent with the presence of weak subglacial sediment. To develop an understanding of the implication of the presence of weak subglacial sediment, we used forward simulations with the Glimmer-CISM model with basal conditions prescribed according to sedimentary processes and a regional hydrology system fed by supraglacial

  2. 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.

  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. 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 change