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Sample records for glacier equilibrium line

  1. From Doktor Kurowski's Schneegrenze to our modern glacier equilibrium line altitude (ELA)

    NASA Astrophysics Data System (ADS)

    Braithwaite, R. J.

    2015-06-01

    Translated into modern terminology, Kurowski suggested in 1891 that the equilibrium line altitude (ELA) of a glacier is equal to the mean altitude of the glacier when the whole glacier is in balance between accumulation and ablation. Kurowski's method has been widely misunderstood, partly due to inappropriate use of statistical terminology by later workers, and has been little tested except by Braithwaite and Müller in a 1980 paper (for 32 glaciers). I now compare Kurowski's mean altitude with balanced-budget ELA calculated for 103 modern glaciers with measured surface mass balance data. Kurowski's mean altitude is significantly higher (at 95% level) than balanced-budget ELA for 19 outlet and 42 valley glaciers, but not significantly higher for 34 mountain glaciers. The error in Kurowski mean altitude as a predictor of balanced-budget ELA might be due to generally lower balance gradients in accumulation area compared with ablation areas for many glaciers, as suggested by several workers, but some glaciers have higher gradients, presumably due to precipitation increase with altitude. The relatively close agreement between balanced-budget ELA and mean altitude for mountain glaciers (mean error -8 m with standard deviation 59 m) may reflect smaller altitude ranges for these glaciers such that there is less room for effects of different balance gradients to manifest themselves.

  2. From Doktor Kurowski's Schneegrenze to our modern glacier equilibrium line altitude (ELA)

    NASA Astrophysics Data System (ADS)

    Braithwaite, R. J.

    2015-11-01

    Translated into modern terminology, Kurowski suggested in 1891 that the equilibrium line altitude (ELA) of a glacier is equal to the mean altitude of the glacier when the whole glacier is in balance between accumulation and ablation. Kurowski's method has been widely misunderstood, partly due to inappropriate use of statistical terminology by later workers, and has only been tested by Braithwaite and Müller in a 1980 paper (for 32 glaciers). I now compare Kurowski's mean altitude with balanced-budget ELA calculated for 103 present-day glaciers with measured surface mass-balance data. Kurowski's mean altitude is significantly higher (at 95 % level) than balanced-budget ELA for 19 outlet and 42 valley glaciers, but not significantly higher for 34 mountain glaciers. The error in Kurowski mean altitude as a predictor of balanced-budget ELA might be due to generally lower balance gradients in accumulation areas compared with ablation areas for many glaciers, as suggested by several workers, but some glaciers have higher gradients, presumably due to precipitation increase with altitude. The relatively close agreement between balanced-budget ELA and mean altitude for mountain glaciers (mean error - 8 m with standard deviation 59 m) may reflect smaller altitude ranges for these glaciers such that there is less room for effects of different balance gradients to manifest themselves.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  5. Determining the Current and Future Health of Low-Latitude Andean Glaciers Using an Equilibrium Line Altitude Model and Hypsometric Data from the Randolph Glacier Inventory

    NASA Astrophysics Data System (ADS)

    Malone, A.; MacAyeal, D. R.

    2015-12-01

    Mountain glaciers have been described as the water towers of world, and for many populations in the low-latitude South American Andes, glacial runoff is vital for agricultural, industrial, and basic water needs. Previous studies of low-latitude Andean glaciers suggest a precarious future due to contemporary warming. These studies have looked at trends in freezing level heights or observations of contemporary retreat. However, regional-scale understanding of low-latitude glacial responses to present and future climate change is limited, in part due to incomplete information about the extent and elevation distribution of low-latitude glaciers. The recently published Randolph Glacier Inventory (RGI) (5.0) provides the necessary information about the size and elevation distribution of low-latitude glaciers to begin such studies. We determine the contemporary equilibrium line altitudes (ELAs) for low-latitude Andean glaciers in the RGI, using a numerical energy balance ablation model driven with reanalysis and gridded data products. Contemporary ELAs tend to fall around the peak of the elevation histogram, with an exception being the southern-most outer tropical glaciers whose modeled ELAs tend to be higher than the elevation histogram for that region (see below figure). Also, we use the linear tends in temperature and precipitation from the contemporary climatology to extrapolate 21stcentury climate forcings. Modeled ELAs by the middle on the century are universally predicted to rise, with outer tropical ELAs rising more than the inner tropical glaciers. These trends continue through the end of the century. Finally, we explore how climate variables and parameters in our numerical model may vary for different warming scenarios from United Nation's IPCC AR5 report. We quantify the impacts of these changes on ELAs for various climate change trajectories. These results support previous work on the precarious future of low latitude Andean glaciers, while providing a richer

  6. Younger Dryas and Holocene glacier fluctuations and equilibrium-line altitude variations in the Jostedalsbre region, western Norway

    SciTech Connect

    Nesje, A.

    1992-01-01

    Reconstructed Younger Dryas (11000-10000 y BP) valley- and cirque glaciers west of the Jostedalsbre ice cap suggest an equilibrium-line altitude (ELA) depression of (450{+-}200 y BP) deglaciation was characterized by vertical wastage, indicating that the LA was above the summit plateaus. During the Erdalen event (9100{+-}200 y BP) marginal moraines were formed up to 1 km beyond the Little Ice Age (LIA) moraines which lie in front of the present valley outlet glaciers of the Jostedalsbre ice cap. The average ELA lowering during this event is calculated to 325 m below the modern level. Lithostratigraphic and paleobotanical studies show that the Hypsithermal (ca. 8000-6000 y BP) ELA was about 450 m higher than at present. As a result, Jostedalsbreen probably disappeared entirely during that period. The glacier reformed about 5300 y BP. The ELA intersected the modern mean equilibrium line altitude five times from ca. 2600 y BP to the present. The outlet valley glaciers reached their maximum Neoglacial extent during the LIA in the mid-18th century, when the ELA was depressed 100-150 m below the present level. 25 refs., 9 figs.

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    The Nevado Coropuna (15°31'S-72°39'W) is a volcanic complex located 200 km NE of the city of Arequipa, in the Southern Peruvian Andes. The summit area in the complex is covered with a glacier system formed by dozens of branches descending in all directions totaling many km2 in surface area. The study of the volcanic complex and its glaciers is of great interest because it is the main water reserve for tens of thousands of people, because of the risk scenario created by the presence of ice masses on a volcano with relatively recent activity, and because it constitutes an excellent geoindicator of the effects of climate change on ice masses in the western mountain chain of the Central Andes. This research aims to analyze glacier evolution using as geoindicators variations in glacier surface and equilibrium line altitudes (ELAs), defining deglaciation rates based on those variations and preparing forecasts with them on when the ice masses might disappear if the same rates were to occur in the future. In addition, a first estimation is attempted of the chronologies of the last phase of volcanic activity and the last phase of maximum glacier advance that can be attributed to the Late Glacial or Last Glacial Maximum periods. To achieve these aims, digital topography with 50m contour interval, two orthophotos of the central section of the Coropuna complex (15-6-1955 and 21-10-1986), an ASTER satellite image (12-11-2007) and geomorphological mapping of the volcanic complex created in a previous phase of the research (Ubeda, 2007) were integrated into a Geographical Information System (GIS). The GIS was used to determine the global extent of the glacier system, and in more detail, that of two groups (NE and SE) in 1955, 1986 and 2007. Using the geomorphological cartography as a basis, the extent of the glaciers during their last advance in the Little Ice Age (LIA) and their last maximum advance were calculated. Next, surface areas for all phases were calculated using

  8. Equilibrium-line altitude during the Antarctic Cold Reversal at Río Tranquilo glacier (47°S), Central Patagonia

    NASA Astrophysics Data System (ADS)

    Sagredo, E. A.; Ward, D.; Gonzalez, M. A.; Lowell, T. V.; Kelly, M. A.; Aravena, J. C.

    2013-12-01

    Documenting the magnitude of former glacial fluctuations is critical for understanding the mechanisms and climate signals underlying these glacial events. Here, we estimate the equilibrium line altitudes (ELA) associated with the most prominent glacial advance occurred during the Last Glacial Termination (T1) at Tranquilo glacier (47°S). Geomorphic evidence suggest that, following the Last Glacial Maximum, several small glaciers, which today occupy the headwalls of Río Tranquilo valley, expanded and coalesced, forming the extended version of the Tranquilo glacier at least three different times. 10Be ages suggest that the most prominent of these glacial advances occurred ~13 kyr BP, at the end of the Antarctic Cold Reversal (ACR). Based on glacial geomorphic mapping and the application of a glaciological model (GC2D), we reconstruct the former glacial surface at Tranquilo glacier and estimate the ELA for this major glacial advance. Preliminary data show that the equilibrium line altitude at Tranquilo glacier during the ACR could have been up to 500 m lower than the present. This study represents the first effort to quantify the ELA during the Antarctic Cold Reversal in Patagonia, and provides a baseline to decipher the climatic signals driving this glacial event.

  9. Climate Reconstructions for the Younger Dryas in Graubünden, Swiss Alps: Using Glacier Geometry and Hypsometry to Estimate Equilibrium Line Altitude

    NASA Astrophysics Data System (ADS)

    Keeler, D. G.; Rupper, S.; Schaefer, J. M.; Finkel, R. C.

    2014-12-01

    Mountain glaciers serve as important paleoclimate records due to the direct physical link between glacier extent and climate. The high sensitivity of mountain glaciers to even small perturbations in the climate has the potential to provide very detailed records of regional glacier and climate histories. Recent progress in age determination techniques such as surface exposure dating has greatly improved the temporal precision of glacial records. The conversion of changes in glacier geometries to a climate signal, however, remains a significant challenge. A particular need exists for a versatile method easily applicable to diverse regions and conditions around the globe. Because the equilibrium line altitude (ELA) provides a more explicit comparison of climate than properties such as glacier length or area, ELA methods lend themselves well to such a need, and allow for a more direct investigation of the primary drivers of mountain glaciations during specific events. Here we present a new, robust ELA model for quantifying changes in climate directly from glacier geometry. The model derives from a linear flow model based on Glen's Flow law while fully accounting for glacier hypsometry. As a preliminary application, we combined our modeled ELA reconstructions with a new 10Be chronology of late glacial culminations in Graubünden in the Swiss Alps. These glacier culminations occurred during the Egesen Stadial, which has been correlated to the Younger Dryas (YD) interval. Results for two related glacier systems in Graubünden reveal an ELA depression of 365-401 m (depending on the moraines chosen) during the Egesen stage/YD compared to the modern ELA. This agrees well both with established estimates for ELA depressions in the region and an additional application performed using our model and previously determined ages on the nearby Lagrev Glacier (a 370 m ELA depression). We then reconstruct the temperature and precipitation changes required to explain the ELA changes for

  10. Modern and Little Ice Age equilibrium-line altitudes on Outlet Valley glaciers from Jostedalsbreen, western Norway: An evaluation of different approaches to their calculation

    SciTech Connect

    Torsnes, I.; Rye, N. ); Nesje, A. )

    1993-05-01

    The modern and Little Ice Age (LIA) equilibrium-line altitude (ELA) of 20 outlet valley glacier from Jostedalsbreen, western Norway, has been calculated using different approaches. Using an accumulation area ratio (AAR) of 0.6 [+-] 0.05 gave a mean little Ice Age ELA depression of 70 m. A method developed by M. Kuhle, taking the influence by topography into account gave a mean ELA depression of 35-255 m, the median elevation of glaciers 115 m, and the toe-to-headwall altitude ration 140 m. Differences in the ELA estimates can be attributed to the differences in topography and morphology of the glaciers. The AAR method appears to provide the most reliable results. This will aid in determining mean global temperatures during the LIA. 34 refs., 9 figs., 5 tabs.

  11. Reconstructed glacier geometry and inferred Equilibrium Line Altitude changes during the Late Pleistocene deglaciation in the Retezat Mountains, Southern Carpathians

    NASA Astrophysics Data System (ADS)

    Madarász, Balázs; Ruszkiczay-Rüdiger, Zsófia; Kern, Zoltán; Urdea, Petru

    2016-04-01

    Quaternary glaciations had a major imprint on the landscape and topography of the Southern Carpathians. Their transitional position between continental and Mediterranean climate zones arouses special interest concerning the timing and pattern of glaciations in this area. Probably the Retezat Mts hosted the most extended glaciation during the Late Pleistocene within this range. The peak elevations of the study area reach 2500 m asl, and the most extended glaciers descended to 1040 m in the northern and to 1130 m on the southern valleys. Major cirque floors are typically situated at 2000-2100 m asl. Glacial landforms have been mapped in order to reconstruct the past ice bodies and the elevation shifts of the paleo equilibrium line altitudes (ELA) during several deglaciation phases of the Last Glacial Maximum (LGM) and Lateglacial in the Retezat Mts. On the basis of published 10Be exposure age data on the northern valleys of the study area, deglaciation of the Retezat Mts occurred at least in five phases between ~21.0 ka and 13.5 ka [1]. Various methods (THAR, AAR, AABR) have been tested using a GIS tool to estimate the ELA of the reconstructed paleoglaciers [2] and paleo ELAs were calculated for each of the deglaciation phases. Preliminary estimates of regional LGM paleoELA employing the simplest THAR method (with a ratio of 0.5) ranged from ~1670 m during the LGM to ~2210 m for the smallest cirque glacier at 13.5 ka, respectively. The AAR and AABR methods provide somewhat higher ELAs for each phase. The obtained paleoELAs were compared to ELA reconstructions available from other Carpathian ranges and also to the Alps and Dinarides. Our data will contribute to a more accurate ELA distribution during the LGM, which may be indicative of the past state of the climate system (moisture gradient, circulation regimes). Thanks to OTKA PD83610, PD104899; NKM-96/2014, NKM-31/2015; OMAA 90öu17; LP2012-27/2012. References: [1] Ruszkiczay-Rüdiger et al. 2016 Quat. Int. (in

  12. The glaciers of Sierra Segundera (Zamora, NW Spain) during their Maximum Ice Extent: area, volume, Glacial Equilibrium Line Altitude and paleo-climatic implications

    NASA Astrophysics Data System (ADS)

    María Fernández, Jose; Ubeda, Jose; Palacios, David

    2015-04-01

    The aim of this paper is to reconstruct the Quaternary glaciers which formed the eastern sector of the Sierra Segundera ice-cap (NW Iberian Peninsula) during its Maximum Ice Extent (MIE) local phase (33 ka) in a surface area of 165 km2, to estimate the ice volumes and Equilibrium Line Altitudes (ELAs). The study area presents a wide altimetric range of approx. 1200 m, from the Tera glacier front to the Peña Trevinca (42°14'33'' N, 6°47'46'' W; 2127 m) and Peña Negra (42°14'58'' N, 6°47'39'' W; 2121 m) horns, covering a wide plateau at an altitude of over 1700 m. The reconstruction of the MIE paleoglaciers used a combination of various tools: a rheological numerical model which describes the ice flow, GIS and geomorphological field work to validate the results. The model used here allowed the reconstruction of the surface topography of the paleoglacial ice, even though there is no existing geomorphologic evidence to reveal the thickness of the ice at that time. The GIS enabled the creation of Digital Elevation Models (DEMs) and the estimation of thicknesses and volumes. The reconstructed topography and the delimitation of the geomorphologic features were used to estimate the ELA using the following methods: Area x Altitude Balance Ratio (AABR), Accumulation Area Ratio (AAR), Terminus Headwall Altitude Ratio (THAR) and Maximum Elevation of Lateral Moraines (MELM). The DEM reconstructed for the surface of the paleoglaciers obtained an estimated maximum ice thickness of over 450 m during the MIE, and a total ice volume of 2.63 x 10(10)m3 for the eastern half of the ice-cap. When estimating the paleo-ELAs, the AABR and AAR methods obtain more logical values. The AABR method obtains BR=1, which questions the BR=2 assumed as representative for medium latitude glaciers with oceanic influence; the paleo-ELA AABR was 1739 m. Applying the AAR method with the ratio 0.65 gives the result 1735 m. The THAR and MELM methods give values of 1637 m and 1651 m respectively for

  13. Mapping the Snow Line Altitude for Large Glacier Samples from Multitemporal Landsat Imagery

    NASA Astrophysics Data System (ADS)

    Rastner, P.; Nicholson, L. I.; Notarnicola, C.; Prinz, R.; Sailer, R.

    2015-12-01

    The cryosphere of mountain regions is fastly changing in response to climate change. This is particularly evident in global-scale glacier retreat. Trends in snow cover, however, are more difficult to determine, as annual fluctuations can be very large. Snow is an important parameter in the energy and mass balance of glaciers and the snow line altitude (SLA) at the end of the melting period can be considered as a proxy for the equilibrium line altitude (ELA). By frequently observing the SLA from satellite, region-wide monitoring of glaciers and improved calibration and validation of transient glacier (mass balance) models is possible. In the near future, frequent mapping of the SLA will be strongly facilitated by satellite missions like Sentinel 2A/B, where the same region will be covered every 5 days with 10 m spatial resolution. For this study we have developed an automated tool to derive the SLA for large glacier samples from remote sensing data. The method is first applied in the Ötztal Alps (Austria) where reliable in-situ data of mass balance and ELA are available for several glaciers over a 30-years period. The algorithm currently works with multi-temporal Landsat imagery (1972-2015), digital glacier outlines and a high-quality national DEM. All input datasets are atmospherically and topographically pre-processed before the SLA is automatically retrieved for each glacier. The remote-sensing derived SLA is generally about 200 m lower than the ELA, however, a clear trend in the altitude of the end of summer snow line is detectable (~ 200 m), which is in agreement with the ELA trend observed in the field. After bias correction and conversion to mass balance, the variability in observed mass balance can be well reproduced from the satellite-derived SLA time series. This is promising for application of the approach in other regions.

  14. Estimates of Regional Equilibrium Line Altitudes and Net Mass Balance from MODIS Imagery

    NASA Astrophysics Data System (ADS)

    Shea, J. M.; Menounos, B.; Moore, R. D.

    2011-12-01

    Glacier mass balance is a key variable used to assess the health of glaciers and ice sheets. Estimates of glacier mass balance are required to model the dynamic response of glaciers and ice sheets to climate change, estimate sea-level contribution from surface melt, and document the response of glaciers to climate forcing. Annually resolved estimates of regional mass balance for mountain ranges is often inferred from a sparse network of ground-based measurements of mass balance for individual glaciers. Given that net mass balance is highly correlated with the annual equilibrium line altitude (ELA), we develop an automated approach to estimate the ELA, and by inference net mass balance, on large glaciers and icefields using MODIS 250 m imagery (MOD02QKM). We discriminate areas of bare ice and snow/firn using the product of MODIS' red (0.620 - 0.670 μ m) and near infrared (0.841 - 0.876 μ m) bands. To assess the skill in estimating glacier ELAs, we compare ELAs derived from (1) manual delineation and (2) unsupervised classification of the band product to ground-based observations of ELA and net mass balance at seven long term mass-balance monitoring sites in western North America (Gulkana, Wolverine, Lemon Creek, Taku, Place, Peyto, and South Cascade). Spatial and temporal variations in MODIS-derived ELAs provide an opportunity to validate regional mass-balance models, estimate surface melt contributions to sea-level rise, and examine the cryospheric response to climate change.

  15. 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.

  16. Present and former equilibrium-line altitudes near Mount Everest, Nepal and Tibet.

    USGS Publications Warehouse

    Williams, V.S.

    1983-01-01

    New information on equilibrium-line altitudes (ELAs) of present and former glaciers in the Mount Everest area of eastern Nepal and southern Tibet has been derived from field mapping and interpretation of topographic maps and Landsat imagery. Present ELAs rise from south to north across the Himalayan Range from 5200 to 5800 m, as indicated by the altitudes of lowest cirque glaciers and highest lateral and medial moraines on valley glaciers. In contrast, ELAs during maximum late Pleistocene glaciation rose in altitude from 4300 to 5500m across the range, as indicated by altitudes of lowest cirque floors and maximum extent of glacial deposits. Highest ELAs occurred on previously unrecognized ice caps that formerly covered extensive highland areas in Tibet north of the range crest. Depression of ELAs during the late Pleistocene glaciation was about twice as great south of the range crest (950m) as north of it (400m).-from Author

  17. Evaluation of conditions along the grounding line of temperate marine glaciers: An example from Muir Inlet, Glacier Bay, Alaska

    USGS Publications Warehouse

    Seramur, K.C.; Powell, R.D.; Carlson, P.R.

    1997-01-01

    In the marine environment, stability of the glacier terminus and the location of subglacial streams are the dominant controls on the distribution of grounding-line deposits within morainal banks. A morainal bank complex in Muir Inlet, Glacier Bay, SE Alaska, is used to develop a model of terminus stability and location of subglacial streams along the grounding line of temperate marine glaciers. This model can be used to interpret former grounding-line conditions in other glacimarine settings from the facies architecture within morainal bank deposits. The Muir Inlet morainal bank complex was deposited between 1860 A.D. and 1899 A.D., and historical observations provide a record of terminus positions, glacial retreat rates and sedimentary sources. These data are used to reconstruct the depositional environment and to develop a correlation between sedimentary facies and conditions along the grounding line. Four seismic facies identified on the high-resolution seismic-reflection profiles are used to interpret sedimentary facies within the morainal bank complex. Terminus stability is interpreted from the distribution of sedimentary facies within three distinct submarine geomorphic features, a grounding-line fan; stratified ridges, and a field of push ridges. The grounding-line fan was deposited along a stable terminus and is represented on seismic-reflection profiles by two distinct seismic facies, a proximal and a distal fan facies. The proximal fan facies was deposited at the efflux of subglacial streams and indicates the location of former glacifluvial discharges into the sea. Stratified ridges formed as a result of the influence of a quasi-stable terminus on the distribution of sedimentary facies along the grounding line. A field of push ridges formed along the grounding line of an unstable terminus that completely reworked the grounding-line deposits through glacitectonic deformation. Between 1860 A.D. and 1899 A.D. (39 years), 8.96 x 108 m3 of sediment were

  18. 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.

  19. 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.

  20. 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.

  1. Younger Dryas equilibrium line altitudes and precipitation patterns in the Alps

    NASA Astrophysics Data System (ADS)

    Kerschner, Hanns; Moran, Andrew; Ivy-Ochs, Susan

    2016-04-01

    Moraine systems of the "Egesen Stadial" are widespread and easily identifiable features in the Alps. Absolute dating with terrestrial cosmogenic radionuclides shows that the maximum extent was reached during the early Younger Dryas (YD), probably as a reaction to the intense climatic downturn subsequent to Lateglacial Interstadial. In recent years, several new studies and the availability of high-quality laser-scan hillshades and orthophotos allowed a significant extension of the database of YD glaciers as "palaeoprecipitation gauges" to large hitherto unmapped regions in the Austrian and Swiss Alps. The equilibrium line altitude (ELA) of the glaciers and its lowering relative to the Little Ice Age ELA (dELA) shows a distinct and systematic spatial pattern. Along the northern slope of the Alps, dELAs are usually large (around 400 m and perhaps even more), while dELAs range around 200 m in the well sheltered areas of the central Alps, e.g. in the Engadine and in western Tyrol. Both stochastic glacier-climate models (e.g. Ohmura et al. 1992) and the heat- and mass balance equation (Kuhn 1981) allow the reconstruction of precipitation change under the assumption of a spatially constant summer temperature depression, which in turn can be estimated from biological proxies. This allows to draw the spatial pattern of precipitation change with considerable detail. Precipitation change is clearly controlled by the local relief like high mountain chains, deeply incised and long valleys and mountain passes. Generally the contrast between the northern fringe of the Alps and the interior was more pronounced than today. Climate in the Northern and and Northwestern Alps was rather wet with precipitation totals eventually exceeding modern annual sums. The central Alps received 20 - 30% less precipitation than today, mainly due to reduced winter precipitation. In the southern Alps, still scarce spatial information points to precipitation sums which were approximately similar to

  2. 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.

  3. Climatic implications of reconstructed early - Mid Pliocene equilibrium-line altitudes in the McMurdo Dry Valleys, Antarctica

    USGS Publications Warehouse

    Krusic, A.G.; Prentice, M.L.; Licciardi, J.M.

    2009-01-01

    Early-mid Pliocene moraines in the McMurdo Dry Valleys, Antarctica, are more extensive than the present alpine glaciers in this region, indicating substantial climatic differences between the early-mid Pliocene and the present. To quantify this difference in the glacier-climate regime, we estimated the equilibrium-line altitude (ELA) change since the early-mid Pliocene by calculating the modern ELA and reconstructing the ELAs of four alpine glaciers in Wright and Taylor Valleys at their early-mid Pliocene maxima. The area-altitude balance ratio method was used on modern and reconstructed early-mid Pliocene hypsometry. In Wright and Victoria Valleys, mass-balance data identify present-day ELAs of 800-1600 m a.s.l. and an average balance ratio of 1.1. The estimated ELAs of the much larger early-mid Pliocene glaciers in Wright and Taylor Valleys range from 600 to 950 ?? 170 m a.s.l., and thus are 250-600 ??170 m lower than modern ELAs in these valleys. The depressed ELAs during the early-mid-Pliocene most likely indicate a wetter and therefore warmer climate in the Dry Valleys during this period than previous studies have recognized.

  4. A simple parameterisation of melting near the grounding lines of ice shelves and tidewater glaciers

    NASA Astrophysics Data System (ADS)

    Jenkins, A.

    2012-04-01

    Both the Antarctic and Greenland ice sheets are experiencing rapid change, at least in part as a result of acceleration of some of their larger, marine-terminating outlet glaciers. It is generally assumed that the accelerations have been driven by the ocean, probably through changes in the submarine melt rate. However, the processes that drive melting, particularly in the region close to the grounding line are difficult to observer and quantify. The rapid flow of the outlet glaciers is almost always associated with an active sub-glacial hydrological system, so in the key regions where the glaciers either discharge into ice shelves or terminate in fjords there will be a flow of freshwater draining across the grounding line from the glacier bed. The input of freshwater to the ocean provides a source of buoyancy and drives convective motion alongside the ice-ocean interface. This process is modelled using the theory of buoyant plumes that has previously been applied to the study of the larger-scale circulation beneath ice shelves. The plume grows through entrainment of ocean waters, and the heat brought into the plume as a result drives melting at the ice-ocean interface. The equations are non-dimensionalised using scales appropriate for the region where the sub-glacial drainage, rather than the subsequent addition of meltwater, supplies the majority of the buoyancy forcing. It is found that the melt rate within this region can be approximated reasonably well by a simple expression that is linear in ocean temperature, has a cube root dependence on the flux of sub-glacial meltwater, and a more complex dependency on the slope of the ice-ocean interface. The model is used to investigate variability in melting induced by changes in both ocean temperature and sub-glacial discharge for a number of realistic examples of ice shelves and tidewater glaciers. The results show how warming ocean waters and increasing sub-glacial drainage both generate increases in melting near the

  5. Climate Change in the Russian Altai Mountains and its Influence on Tree Line and Glacier Dynamics

    NASA Astrophysics Data System (ADS)

    Syromyatina, M.; Moskalenko, I.; Ganushkin, D.; Chistyakov, K.

    2011-12-01

    the average for the period 1986-2004 - about 1,3°C. As tree line against the other belt borders strongly limited by summer temperature its eventual dynamics since the end of the LIA over the Altai were estimated and tree line position at different stages of modern regional warming was reconstructed. Theoretical evaluation shows that mean summer temperature increase of 1.3°C from the end of the LIA causes tree line to rise maximum by 180-280 m in different localities of the Altai. Glacial complexes of mountain massifs Mongun-Taiga, Tavan-Boghd-Ola, Turgeni-Nuru and Harhira-Nuru located in the South-Eastern Altai are represented by small glaciers mostly on northern and eastern leeward slopes. Being situated in region with dry climatic conditions (250-400 mm/year) glaciers survive only in negative forms of relief with high concentration of snow. Accumulation coefficient is mainly from 2 to 3, and on cirque glaciers is from 6 to 8. Now glaciers retreat rapidly (17% of area loss for the period of 1995-2010 for Mongun-Taiga, 12% in 2002-2009 for Tavan-Boghd-Ola), especially valley glaciers (2-10 m/yr), the number of glaciers increase due to disintegration of larger glaciers. Small forms of glaciation disappear or transform into snow patches and rock glaciers.

  6. 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.

  7. Field line mapping and equilibrium reconstructions in new CNT Configuration

    NASA Astrophysics Data System (ADS)

    Traverso, Peter; Pedersen, Thomas; Brenner, Paul; Sarasola, Xabier; Durand de Gevigney, Benoit

    2010-11-01

    The Columbia Non-neutral Torus (CNT) has the useful feature of having adjustable coil geometry, creating up to three different stellarators each having a completely new shape to its magnetic surfaces and a different Iota profile. Recently the tilt angle between the two interlocking coils has been changed for the first time on CNT, allowing a study of the new magnetic geometry. In the new configuration field line mapping has been accomplished for multiple current ratios and magnetic fields to confirm the existence of good nested magnetic surfaces. At a specific current ratio a large one-three island chain is created. Plasma parameters have been measured with the new coil configuration, both in cases of a large internal island chain, and in cases without. Full 3D equilibrium reconstructions of potential and density are being performed using a modified version of the existing Poisson-Boltzmann solver. Field line mapping in this configuration will be presented, and a progress report on the equilibrium reconstructions will also be given.

  8. Equilibrium Line Altitude fluctuations at HualcaHualca volcano (southern Peru).

    NASA Astrophysics Data System (ADS)

    Alcalá, Jesus; Palacios, David; Juan Zamorano, Jose

    2015-04-01

    Interest in Andean glaciers has substantially increased during the last decades, due to its high sensitivity to climate fluctuations. In this sense, Equilibrium Line Altitude (ELA) is a reliable indicator of climate variability that has been frequently used to reconstruct palaeoenvironmental conditions at different temporal and spatial scales. However, the number of sites with ELA reconstructions is still insufficient to determine patterns in tropical climate or estimations of atmospheric cooling since the Last Glacial Maximum. The main purpose of this study is to contribute in resolving tropical climate evolution through ELA calculations on HualcaHualca (15° 43' S; 71° 52' W; 6,025 masl), a large andesitic stratovolcano located in the south-western Peruvian Andes approximately 70 km north-west of Arequipa. We applied Terminus Headwall Altitude Ratio (THAR) with 0.2; 0.4; 0.5; 0.57 ratios, Accumulation Area Ratio (AAR) and Accumulation Area Balance Ratio (AABR) methods in four valleys of HualcaHualca volcano: Huayuray (north side), Pujro Huayjo (southwest side), Mollebaya (east side) and Mucurca (west side). To estimate ELA depression, we calculated the difference between the ELA on 1955 with its position in the Maximum Glacier Extent (MGE), Tardiglacial phases, little Ice Age (LIA) and 2000. Paleotemperature reconstructions derived from vertical temperature gradient 6.5° C / 1 km, based on GODDARD global observation system considered the most appropriate model for arid Andes. During MGE, the ELA was located between 5,005 (AABR) and 5,215 (AAR 0.67) masl. But in 1955, ELA rose to 5,685 (AABR) - 5,775 (AAR 0.67) masl. The ELA depression between those two phases is 560 - 680 m that implies a temperature decrease of 3.5° - 4.4° C. The experimental process based in the use and contrast of different ELA reconstruction techniques applied in this study suggests that THAR (0.57), AAR (0.67) or AABR are the most consistent procedures for HualcaHualca glaciers, while

  9. 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.

  10. Snow and glaciers in the tropics: the importance of snowfall level and snow line altitude in the Peruvian Cordilleras

    NASA Astrophysics Data System (ADS)

    Schauwecker, Simone; Rohrer, Mario; Huggel, Christian; Salzmann, Nadine; Montoya, Nilton; Endries, Jason; Perry, Baker

    2016-04-01

    The snow line altitude, defined as the line separating snow from ice or firn surfaces, is among the most important parameters in the glacier mass and energy balance of tropical glaciers, since it determines net shortwave radiation via surface albedo. Therefore, hydroglaciological models require estimations of the melting layer during precipitation events, as well as parameterisations of the transient snow line. Typically, the height of the melting layer is implemented by simple air temperature extrapolation techniques, using data from nearby meteorological stations and constant lapse rates. Nonetheless, in the Peruvian mountain ranges, stations at the height of glacier tongues (>5000 m asl.) are scarce and the extrapolation techniques must use data from distant and much lower elevated stations, which need prior careful validation. Thus, reliable snowfall level and snow line altitude estimates from multiple data sets are necessary. Here, we assemble and analyse data from multiple sources (remote sensing, in-situ station data, reanalysis data) in order to assess their applicability in estimating both, the melting layer and snow line altitude. We especially focus on the potential of radar bright band data from TRMM and CloudSat satellite data for its use as a proxy for the snow/rain transition height. As expected for tropical regions, the seasonal and regional variability in the snow line altitude is comparatively low. During the course of the dry season, Landsat satellite as well as webcam images show that the transient snow line is generally increasing, interrupted by light snowfall or graupel events with low precipitation amounts and fast decay rates. We show limitations and possibilities of different data sources as well as their applicability to validate temperature extrapolation methods. Further on, we analyse the implications of the relatively low variability in seasonal snow line altitude on local glacier mass balance gradients. We show that the snow line

  11. Combined Ice and Water Balances of Maclure Glacier, California, South Cascade Glacier, Washington, and Wolverine and Gulkana Glaciers, Alaska, 1967 Hydrologic Year

    USGS Publications Warehouse

    Tangborn, Wendell V.; Mayo, Lawrence R.; Scully, David R.; Krimmel, Robert M.

    1977-01-01

    Combined ice and water balances were measured in the 1967 hydrologic year (October 1-September 30) on four glaciers in western North America ranging in latitude from 37 deg to 63 deg N. This hydrologic year was characterized by heavier than normal winter precipitation in California and Washington and abnormally dry winter conditions in coastal Alaska. In summer the western conterminous states were abnormally dry and central and southern Alaska experienced very wet conditions. Maclure Glacier (lat 37 deg 45' N., 3,650-m (metres) mean equilibrium line altitude) had an above normal winter balance of 3.46 m and a positive annual balance of 1.05 m (metres of water equivalent). South Cascade Glacier (lat 48 deg 22' N., 1900-m mean equilibrium line altitude) had a winter balance of 3.28 m, slightly above average. Above normal summer ablation resulted in a final annual balance of -0.58 m, slightly more negative than has been the case for the past decade. Wolverine Glacier's (lat 60 deg 24' N., 1,200-m mean equilibrium line altitude) winter balance was 1.17 m, considerably below normal; the annual balance was -2.04 m. Gulkana Glacier (lat 63 deg 15' N., 1,700-m mean equilibrium line altitude) had a winter balance of 1.05 m, approximately normal for this glacier; the final annual balance was -0.30 m.

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

    NASA Astrophysics Data System (ADS)

    Pillai, J.; Patel, L. K.

    2011-12-01

    year 1990. Remote Sensing data of different years were used to analyze the changes in aerial extent of the pindari glacier. Pindari landscap is formed by the combined geomorphological process of fluvial and glacial. These processes are also maintaining the ecosystem balance of the catchment area. Snow covers area of this higher landscapet had been reduced considerably. The timberline of this region is shifting upper side of the glaciers, whereas the equilibrium line is also retreating. The spatial invasion in timber line and the retreat of the equilibrium line will further establish the negative mass balance of this glacier. However, the climatic variation may exacerbate the ecosystem balance of the region. All the reports on the glaciers in IHR regions review a negative mass balance and annual retreat up the glaciers. The observation records of these glaciers in IHR are about a period of hundred years this is quite in sufficient it establishes the relation between climate change and the glaciers retreat. However it is a known fact that the impact of rise in temperature due to anthropogenic effect may overstretch the rate the natural process of glacier retreat. The present study also discusses the unique phenomena of glacier melt due to climatic variations and its catastrophe.

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

    NASA Astrophysics Data System (ADS)

    De Rydt, Jan; Gudmundsson, Hilmar

    2016-04-01

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

  14. Sensitivity of very small glaciers in the Swiss Alps to future climate change

    NASA Astrophysics Data System (ADS)

    Huss, Matthias; Fischer, Mauro

    2016-04-01

    Very small glaciers (<0.5km2) currently account for up to 80% of the total number of glaciers in mountain ranges around the globe. Although their total area and volume is small compared to larger glaciers, they are a relevant component of the cryosphere contributing to landscape formation, local hydrology and sea-level rise. Very small glaciers have generally shorter response times than valley glaciers and their mass balance is strongly dependent on snow redistribution processes. Worldwide glacier monitoring has focused on medium-sized to large glaciers leaving us with a relatively limited understanding of the behavior of very small glaciers. With warming climate there is an increasing concern that very small glaciers might be the first to disappear. Already in the next decades this might result in the complete deglaciation of mountain ranges with glacier equilibrium lines close to the highest peaks. Here, we present a comprehensive modeling framework to assess past and future changes of very small glaciers at the mountain-range scale. Among other processes our model accounts for snow redistribution, changes in glacier geometry and the time-varying effect of supraglacial debris. It computes the mass balance distribution, the englacial temperature regime and proglacial runoff. The past evolution of 1'133 glaciers in the Swiss Alps is individually constrained based on geodetic ice volume changes, and the model is validated against an extensive data base of in-situ measurements on very small glaciers. Our results indicate that 52% of all very small glaciers in Switzerland will completely disappear within the next 25 years. However, a few avalanche-fed glaciers at low elevation might be able to survive even substantial atmospheric warming. We find highly variable sensitivities of very small glaciers to air temperature change, gently-sloping, low-elevation, and debris-covered glaciers being most sensitive.

  15. Hypsometric control on glacier mass balance sensitivity in Alaska

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  16. 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.

  17. Modeling mountain pine beetle disturbance in Glacier National Park using multiple lines of evidence

    USGS Publications Warehouse

    Assal, Timothy; Sibold, Jason

    2013-01-01

    Temperate forest ecosystems are subject to various disturbances which contribute to ecological legacies that can have profound effects on the structure of the ecosystem. Impacts of disturbance can vary widely in extent, duration and severity over space and time. Given that global climate change is expected to increase rates of forest disturbance, an understanding of these events are critical in the interpretation of contemporary forest patterns and those of the near future. We seek to understand the impact of the 1970s mountain pine beetle outbreak on the landscape of Glacier National Park and investigate any connection between this event and subsequent decades of extensive wildfire. The lack of spatially explicit data on the mountain pine beetle disturbance represents a major data gap and inhibits our ability to test for correlations between outbreak severity and fire severity. To overcome this challenge, we utilized multiple lines of evidence to model forest canopy mortality as a proxy for outbreak severity. We used historical aerial and landscape photos, reports, aerial survey data, a six year collection of Landsat imagery and abiotic data in combination with regression analysis. The use of remotely sensed data is critical in large areas where subsequent disturbance (fire) has erased some of the evidence from the landscape. Results indicate that this method is successful in capturing the spatial heterogeneity of the outbreak in a topographically complex landscape. Furthermore, this study provides an example on the use of existing data to reduce levels of uncertainty associated with an historic disturbance.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  20. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  2. Grounding line retreat of Pope, Smith, and Kohler Glaciers, West Antarctica, measured with Sentinel-1a radar interferometry data

    NASA Astrophysics Data System (ADS)

    Scheuchl, B.; Mouginot, J.; Rignot, E.; Morlighem, M.; Khazendar, A.

    2016-08-01

    We employ Sentinel-1a C band satellite radar interferometry data in Terrain Observation with Progressive Scans mode to map the grounding line and ice velocity of Pope, Smith, and Kohler glaciers, in West Antarctica, for the years 2014-2016 and compare the results with those obtained using Earth Remote Sensing Satellites (ERS-1/2) in 1992, 1996, and 2011. We observe an ongoing, rapid grounding line retreat of Smith at 2 km/yr (40 km since 1996), an 11 km retreat of Pope (0.5 km/yr), and a 2 km readvance of Kohler since 2011. The variability in glacier retreat is consistent with the distribution of basal slopes, i.e., fast along retrograde beds and slow along prograde beds. We find that several pinning points holding Dotson and Crosson ice shelves disappeared since 1996 due to ice shelf thinning, which signal the ongoing weakening of these ice shelves. Overall, the results indicate that ice shelf and glacier retreat in this sector remain unabated.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  4. An improved technique for the reconstruction of former glacier mass-balance and dynamics

    NASA Astrophysics Data System (ADS)

    Carr, Simon; Coleman, Christopher

    2007-11-01

    The recognition of past glacier extent and dynamics is a fundamental aspect of investigations of the climatic sensitivity of glaciers, especially when examining short-lived climate events such as the Younger Dryas or Little Ice Age. Existing approaches to the reconstruction of glacier form and dynamics depend on speculative reasoning of key glacier dynamic parameters, including the role of basal slip and subglacial deformation in glacier mass-transfer. This study reviews approaches to glacier reconstruction, derivation of former glacier equilibrium line altitudes (ELA's) and estimation of mass-balance and dynamics, concluding that most reconstructions of glacier mass-balance are compromised by a lack of glaciological considerations. An alternative approach to glacier reconstruction is presented, demonstrated and discussed, by which an empirical relationship between ablation gradient and mass loss at the ELA is used to derive mass-balance, mass-flux through the ELA and average balance velocity at the ELA. This 'glaciological' approach is applied to four reconstructed glaciers to test previous interpretations that each reflects Younger Dryas glaciation in the UK. The study concludes that this approach provides a more robust technique for reconstructing former glacier dynamics, and may be applied to test geomorphological interpretations of former mountain glaciation.

  5. Water, ice, and meteorological measurements at South Cascade glacier, Washington, balance year 2003

    USGS Publications Warehouse

    Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.

    2005-01-01

    Winter snow accumulation and summer snow and ice ablation were measured at South Cascade Glacier, Washington, to estimate glacier mass-balance quantities for balance year 2003. The 2003 glacier-average maximum winter snow balance was 2.66 meters water equivalent, which was about equal to the average of such balances for the glacier since balance year 1959. The 2003 glacier summer balance (-4.76 meters water equivalent) was the most negative reported for the glacier, and the 2003 net balance (-2.10 meters water equivalent), was the second-most negative reported. The glacier 2003 annual (water year) balance was -1.89 meters water equivalent. The area of the glacier near the end of the balance year was 1.89 square kilometers, a decrease of 0.03 square kilometer from the previous year. The equilibrium-line altitude was higher than any part of the glacier; however, because snow remained along part of one side of the upper glacier, the accumulation-area ratio was 0.07. During September 13, 2002-September 13, 2003, the glacier terminus retreated at a rate of about 15 meters per year. Average speed of surface ice, computed using a series of vertical aerial photographs dating back to 2001, ranged from 2.2 to 21.8 meters per year. Runoff from the subbasin containing the glacier and from an adjacent non-glacierized basin was gaged during part of water year 2003. Air temperature, precipitation, atmospheric water-vapor pressure, wind speed, and incoming solar radiation were measured at selected locations on and near the glacier. Summer 2003 at the glacier was among the warmest for which data are available.

  6. Time Lapse Camera Images for Observation and Visualization of Snow Lines on two Benchmark Glaciers in High Asia - Zhadang and Halji

    NASA Astrophysics Data System (ADS)

    Schröter, B.; Buchroithner, M. F.; Pieczonka, T.

    2015-12-01

    Glaciers are characteristic elements of high mountain environments and represent key indicators for the ongoing climate change. The covering snowpack considerably affects the glacier-ice surface temperature and thus the meltdown of the glaciers which in recent decades has been accelerating worldwide. Therefore, the detailed investigation of the transient snow is of high importance. Zhadang Glacier is located in the Nyainqentanglha Mountain Range on the central part of the Tibetan Plateau (30°28.24' N, 90°38.69' E). The glacier is debris-free and flows from 6,090 to 5,515 m a.s.l. Recent measurements have shown that the whole glacier is below the ELA and experiences significant glacier volume loss. In May 2010 two terrestrial cameras had been installed there and were continuously operating until September 2012 generating 6,225 images of the glacier with a frequency of three resp. six images per day. In order to use this dataset for snow line mapping all images had to be georeferenced and orthorectified. The biggest challenge was the problem of shifting camera positions due to deformations of the ground and hence the offset in the image coordinates. This was resolved by combining the manual orthorectification of one image per week with a subsequent spline interpolation to determine the changed image coordinates. The actual orthorectification was finally realized by applying a fully automated batch processing of all images. The most favorable image of each day was chosen for the manual snow line mapping process. The final aim was the calculation of the mean elevation of the snow line for every day of the data collecting period materialized by intersecting the mapped snow lines with resampled SRTM 3 data. Considering the fact that there were several weeks either with full snow cover or without any snow this aim could be achieved. The findings have been used for the evaluation of a glacier mass balance model developed at RWTH Aachen, Germany, showing a high level of

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

    NASA Astrophysics Data System (ADS)

    Mandal, Arindan; Ramanathan, Alagappan; Farooq Azam, Mohd; Wagnon, Patrick; Vincent, Christian; Linda, Anurag; Sharma, Parmanand; Angchuk, Thupstan; Bahadur Singh, Virendra; Pottakkal, Jose George; Kumar, Naveen; Soheb, Mohd

    2015-04-01

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

  8. Gulkana Glacier, Alaska-Mass balance, meteorology, and water measurements, 1997-2001

    USGS Publications Warehouse

    March, Rod S.; O'Neel, Shad

    2011-01-01

    The measured winter snow, maximum winter snow, net, and annual balances for 1997-2001 in the Gulkana Glacier basin are determined at specific points and over the entire glacier area using the meteorological, hydrological, and glaciological data. We provide descriptions of glacier geometry to aid in estimation of conventional and reference surface mass balances and descriptions of ice motion to aid in the understanding of the glacier's response to its changing geometry. These data provide annual estimates for area altitude distribution, equilibrium line altitude, and accumulation area ratio during the study interval. New determinations of historical area altitude distributions are given for 1900 and annually from 1966 to 2001. As original weather instrumentation is nearing the end of its deployment lifespan, we provide new estimates of overlap comparisons and precipitation catch efficiency. During 1997-2001, Gulkana Glacier showed a continued and accelerated negative mass balance trend, especially below the equilibrium line altitude where thinning was pronounced. Ice motion also slowed, which combined with the negative mass balance, resulted in glacier retreat under a warming climate. Average annual runoff augmentation by glacier shrinkage for 1997-2001 was 25 percent compared to the previous average of 13 percent, in accordance with the measured glacier volume reductions.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  10. Electron Broadening of Isolated Lines with Stationary Non-Equilibrium Level Populations

    SciTech Connect

    Iglesias, C A

    2005-01-12

    It is shown that a quantum kinetic theory approach to line broadening, extended to stationary non-equilibrium states, yields corrections to the standard electron impact widths of isolated lines that depend on the population of the radiator internal levels. A consistent classical limit from a general quantum treatment of the perturbing electrons also introduces corrections to the isolated line widths. Both effects are essential in preserving detailed-balance relations. Preliminary analysis indicates that these corrections may resolve existing discrepancies between theoretical and experimental widths of isolated lines. An experimental test of the results is proposed.

  11. Impact Assessment of Glacier Retreat on Catchment Water Resources in the Tropical Andes, Bolivia

    NASA Astrophysics Data System (ADS)

    Asaoka, Y.; Yoshizawa, K.; Kinouchi, T.; Umeda, M.

    2014-12-01

    Meltwater from glacier is one of the main water resources in the capital area of Bolivia. However, Andean tropical glaciers are rapidly shrinking during past some decades. We projected the response of glacier melt water, runoff and water temperature in reservoir to climate change. Objective area is Tuni reservoir catchment (90km2) with Condoriri, Tuni and HuaynaPotosi West glacier. This reservoir supplies approximately 30% of water consumption to urban area. A glacier mass balance model was applied to Condoriri, Tuni and Huayna Potosi West glacier. Simulation period is 30 years from July, 2011. We produced four types of meteorological dataset for model input with observation data and output of general circulation model: one dataset assumes that current climate persists during 30 years and the others assume that temperature increase at the ratio of 0.02 to 0.04oC/year. Furthermore, distributed runoff model and water quality model were also applied to understand the role of glacier meltwater in the Tuni reservoir catchment. Projection shows that three glaciers decrease and reach equilibrium states of mass balance by the next three decades under current climate condition. Glacial area and meltwater are projected to be 40 to 60% and 60 to 80% of present by the end of 2030's. HuaynaPotosi West glacier has higher uncertainty about the response of temperature rise than Tuni and Condoriri glacier. This is because the peak in altitudinal distribution of glacial area is higher than equilibrium line altitude for current climate condition. Projection of river discharge shows that meltwater from glacier dominates river discharge in early wet season, but meltwater from snow and rainfall dominates in mid wet season. Annual total inflow to reservoir decreases to about 40% of present condition without meltwater from glacier. Water temperature in reservoir is projected to be about 2oC higher than present.

  12. Balance Mass Flux and Velocity Across the Equilibrium Line in Ice Drainage Systems of Greenland

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Giovinetto, Mario B.; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    Estimates of balance mass flux and the depth-averaged ice velocity through the cross-section aligned with the equilibrium line are produced for each of six drainage systems in Greenland. (The equilibrium line, which lies at approximately 1200 m elevation on the ice sheet, is the boundary between the area of net snow accumulation at higher elevations and the areas of net melting at lower elevations around the ice sheet.) Ice drainage divides and six major drainage systems are delineated using surface topography from ERS (European Remote Sensing) radar altimeter data. The net accumulation rate in the accumulation zone bounded by the equilibrium line is 399 Gt/yr and net ablation rate in the remaining area is 231 Gt/yr. (1 GigaTon of ice is 1090 kM(exp 3). The mean balance mass flux and depth-averaged ice velocity at the cross-section aligned with the modeled equilibrium line are 0.1011 Gt kM(exp -2)/yr and 0.111 km/yr, respectively, with little variation in these values from system to system. The ratio of the ice mass above the equilibrium line to the rate of mass output implies an effective exchange time of approximately 6000 years for total mass exchange. The range of exchange times, from a low of 3 ka in the SE drainage system to 14 ka in the NE, suggests a rank as to which regions of the ice sheet may respond more rapidly to climate fluctuations.

  13. Glacier volume and area change by 2050 in high mountain Asia

    NASA Astrophysics Data System (ADS)

    Zhao, Liyun; Ding, Ran; Moore, John C.

    2014-11-01

    We estimate individual area and volume change by 2050 of all 67,028 glaciers, with a total area of 122,969 km2, delineated in the Randolph Glacier Inventory 2.0 of high mountain Asia (HMA). We used the 25 km resolution regional climate model RegCM 3.0 temperature and precipitation change projections forced by the IPCC A1B scenario. Glacier simulations were based on a novel surface mass balance-altitude parameterization fitted to observational data, and various volume-area scaling approaches using Shuttle Radar Topography Mission surface topography of each individual glacier. We generate mass balance-altitude relations for all the glaciers by region using nearest available glacier measurements. Equilibrium line altitude (ELA) sensitivities to temperature and precipitation change vary by region based on the relative importance of sublimation and melting processes. We also made simulations with mass balance tuned to match satellite observations of glacier thickness changes in HMA from 2003 to 2009. Net mass loss is half as much using the tuned model than using just glaciological calibration data, suggesting the representativity of benchmark glaciers is a larger source of uncertainty in future HMA contributions to sea level rise than errors in glacier inventories or volume-area scaling. Both models predict that about 35% of the glaciers in Karakoram and the northwestern Himalaya are advancing, which is consistent with the observed slight mass gain of glaciers in these regions in recent years. However, we find that 76% of all the glaciers will retreat, most of which are of the maritime type. We project total glacier area loss in high mountain Asia in 2050 to be 22% (in the tuned model) or 35% (un-tuned) of their extent in 2000, and they will contribute 5 mm (tuned model) to global sea level rise.

  14. Departure of High-temperature Iron Lines from the Equilibrium State in Flaring Solar Plasmas

    NASA Astrophysics Data System (ADS)

    Kawate, T.; Keenan, F. P.; Jess, D. B.

    2016-07-01

    The aim of this study is to clarify if the assumption of ionization equilibrium and a Maxwellian electron energy distribution is valid in flaring solar plasmas. We analyze the 2014 December 20 X1.8 flare, in which the Fe xxi 187 Å, Fe xxii 253 Å, Fe xxiii 263 Å, and Fe xxiv 255 Å emission lines were simultaneously observed by the EUV Imaging Spectrometer on board the Hinode satellite. Intensity ratios among these high-temperature Fe lines are compared and departures from isothermal conditions and ionization equilibrium examined. Temperatures derived from intensity ratios involving these four lines show significant discrepancies at the flare footpoints in the impulsive phase, and at the looptop in the gradual phase. Among these, the temperature derived from the Fe xxii/Fe xxiv intensity ratio is the lowest, which cannot be explained if we assume a Maxwellian electron distribution and ionization equilibrium, even in the case of a multithermal structure. This result suggests that the assumption of ionization equilibrium and/or a Maxwellian electron energy distribution can be violated in evaporating solar plasma around 10 MK.

  15. Glacial lakes amplify glacier recession in the central Himalaya

    NASA Astrophysics Data System (ADS)

    King, Owen; Quincey, Duncan; Carrivick, Jonathan; Rowan, Ann

    2016-04-01

    store large amounts of ice in broad accumulation zones and are more equidimensional (HI -1.2 to 1.2). Glaciers flowing onto the Tibetan Plateau have a similar hypsometric distribution to glaciers of the Dudh Koshi, but terminate at a higher altitude overall, approximately 500 m higher than glaciers of the Dudh Koshi or Tama Koshi. We estimate the approximate Equilibrium Line Altitudes (ELA) of the last 15 years to be above a substantial portion (66%- Dudh Koshi; 87%- Tama Koshi; 83% Tibetan Plateau) of the glacierised area for all three catchments. Future ice recession may therefore be governed primarily by glacier hypsometry, but is likely to be amplified by the continued development of new, or growth of current glacial lakes.

  16. 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.

  17. Hydrodynamic Models of Line-Driven Accretion Disk Winds III: Local Ionization Equilibrium

    NASA Technical Reports Server (NTRS)

    Pereyra, Nicolas Antonio; Kallman, Timothy R.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We present time-dependent numerical hydrodynamic models of line-driven accretion disk winds in cataclysmic variable systems and calculate wind mass-loss rates and terminal velocities. The models are 2.5-dimensional, include an energy balance condition with radiative heating and cooling processes, and includes local ionization equilibrium introducing time dependence and spatial dependence on the line radiation force parameters. The radiation field is assumed to originate in an optically thick accretion disk. Wind ion populations are calculated under the assumption that local ionization equilibrium is determined by photoionization and radiative recombination, similar to a photoionized nebula. We find a steady wind flowing from the accretion disk. Radiative heating tends to maintain the temperature in the higher density wind regions near the disk surface, rather than cooling adiabatically. For a disk luminosity L (sub disk) = solar luminosity, white dwarf mass M(sub wd) = 0.6 solar mass, and white dwarf radii R(sub wd) = 0.01 solar radius, we obtain a wind mass-loss rate of M(sub wind) = 4 x 10(exp -12) solar mass yr(exp -1) and a terminal velocity of approximately 3000 km per second. These results confirm the general velocity and density structures found in our earlier constant ionization equilibrium adiabatic CV wind models. Further we establish here 2.5D numerical models that can be extended to QSO/AGN winds where the local ionization equilibrium will play a crucial role in the overall dynamics.

  18. Modeled and measured glacier change and related glaciological, hydrological, and meteorological conditions at South Cascade Glacier, Washington, balance and water years 2006 and 2007

    USGS Publications Warehouse

    Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.

    2010-01-01

    Winter snow accumulation and summer snow and ice ablation were measured at South Cascade Glacier, Washington, to estimate glacier mass balance quantities for balance years 2006 and 2007. Mass balances were computed with assistance from a new model that was based on the works of other glacier researchers. The model, which was developed for mass balance practitioners, coupled selected meteorological and glaciological data to systematically estimate daily mass balance at selected glacier sites. The North Cascade Range in the vicinity of South Cascade Glacier accumulated approximately average to above average winter snow packs during 2006 and 2007. Correspondingly, the balance years 2006 and 2007 maximum winter snow mass balances of South Cascade Glacier, 2.61 and 3.41 meters water equivalent, respectively, were approximately equal to or more positive (larger) than the average of such balances since 1959. The 2006 glacier summer balance, -4.20 meters water equivalent, was among the four most negative since 1959. The 2007 glacier summer balance, -3.63 meters water equivalent, was among the 14 most negative since 1959. The glacier continued to lose mass during 2006 and 2007, as it commonly has since 1953, but the loss was much smaller during 2007 than during 2006. The 2006 glacier net balance, -1.59 meters water equivalent, was 1.02 meters water equivalent more negative (smaller) than the average during 1953-2005. The 2007 glacier net balance, -0.22 meters water equivalent, was 0.37 meters water equivalent less negative (larger) than the average during 1953-2006. The 2006 accumulation area ratio was less than 0.10, owing to isolated patches of accumulated snow that endured the 2006 summer season. The 2006 equilibrium line altitude was higher than the glacier. The 2007 accumulation area ratio and equilibrium line altitude were 0.60 and 1,880 meters, respectively. Accompanying the glacier mass losses were retreat of the terminus and reduction of total glacier area. The

  19. Seasonal changes in surface albedo of Himalayan glaciers from MODIS data and links with the annual mass balance

    NASA Astrophysics Data System (ADS)

    Brun, F.; Dumont, M.; Wagnon, P.; Berthier, E.; Azam, M. F.; Shea, J. M.; Sirguey, P.; Rabatel, A.; Ramanathan, Al.

    2015-02-01

    Few glaciological field data are available on glaciers in the Hindu Kush-Karakoram-Himalayan (HKH) region, and remote sensing data are thus critical for glacier studies in this region. The main objectives of this study are to document, using satellite images, the seasonal changes of surface albedo for two Himalayan glaciers, Chhota Shigri Glacier (Himachal Pradesh, India) and Mera Glacier (Everest region, Nepal), and to reconstruct the annual mass balance of these glaciers based on the albedo data. Albedo is retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS) images, and evaluated using ground based measurements. At both sites, we find high coefficients of determination between annual minimum albedo averaged over the glacier (AMAAG) and glacier-wide annual mass balance (Ba) measured with the glaciological method (R2 = 0.75). At Chhota Shigri Glacier, the relation between AMAAG found at the end of the ablation season and Ba suggests that AMAAG can be used as a proxy for the maximum snow line altitude or equilibrium line altitude (ELA) on winter-accumulation-type glaciers in the Himalayas. However, for the summer-accumulation-type Mera Glacier, our approach relied on the hypothesis that ELA information is preserved during the monsoon. At Mera Glacier, cloud obscuration and snow accumulation limits the detection of albedo during the monsoon, but snow redistribution and sublimation in the post-monsoon period allows for the calculation of AMAAG. Reconstructed Ba at Chhota Shigri Glacier agrees with mass balances previously reconstructed using a positive degree-day method. Reconstructed Ba at Mera Glacier is affected by heavy cloud cover during the monsoon, which systematically limited our ability to observe AMAAG at the end of the melting period. In addition, the relation between AMAAG and Ba is constrained over a shorter time period for Mera Glacier (6 years) than for Chhota Shigri Glacier (11 years). Thus the mass balance reconstruction is less robust

  20. Impact of glacio-morphological parameters in the glacier change: A case study of parts of Western Himalaya, India.

    NASA Astrophysics Data System (ADS)

    Brahmbhatt, R.; Bahuguna, I. M.; Rathore, B. P.; Kulkarni, A. V.; Shah, R.

    2014-12-01

    The Himalayas possess one of the largest resources of snow and ice, which act as a huge freshwater reservoir. Monitoring the glaciers is important to assess the overall reservoir health. In last few decades the most of the mountainous glaciers have undergone negative mass balance and terminal recessions, unlike the advancing glaciers. In this investigation, glaciers of Western Himalaya have been monitored since 1962 and variability in retreat was identified within the region. Thus, further analysis about significant parameters was taken into account to understand the relationship between glacio-morphological factors and change in glacial area. Initially change in areal extent of glaciers was derived for two time frames (1962-2001/02 and 2001/02-2010/11). The study comprised of 324 glaciers for the monitoring period of 1962-2001/02. A loss in glacial area was observed as 11% for this period. Many of these glaciers (238) were further monitored between 2001/02 and 2010/11. These glaciers showed a loss of 1.1%. The annual deglaciation has been found higher during the period of 1962-2001/02, which means rate of melting is less in this region in latest decade. Another observation in deglaciation was found spatial and temporal variability in glaciers which was addressed using glacio-morphic parameters. Areal extent of glaciers was observed to be having significant role on rate of glacial shrinkage. The another important parameter is equilibrium line altitude, i.e. the glaciers located below ELA have experienced 4.6% of deglaciation for the time frame 2001/02 - 2010/11 where as it was found to be 1.1% for the glaciers occurring above ELA. Moreover, glaciers located at lower altitude and having gentle slope show more area retreat. The results of area retreat in debris covered and debris free glaciers supports that the glaciers covered by debris retard ice melting at some extent. 158 glaciers were observed having no debris cover which shows 14% of loss in surface area. In

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  2. Strong ELA increase causes fast mass loss of glaciers in central Spitsbergen

    NASA Astrophysics Data System (ADS)

    Małecki, J.

    2015-11-01

    Svalbard is a heavily glacier covered archipelago in the Arctic. Its central regions, including Dickson Land (DL), are occupied by small alpine glaciers, which post-Little Ice Age (LIA) changes remain only sporadically investigated. This study presents a comprehensive analysis of glacier changes in DL based on inventories compiled from topographic maps and digital elevation models (DEMs) for LIA, 1960's, 1990 and 2009/11. The 37.9 ± 12.1 % glacier area decrease in DL (i.e. from 334.1 ± 38.4 km2 during LIA to 207.4 ± 4.6 km2 in 2009/11) has been primarily caused by accelerating termini retreat. The mean 1990-2009/11 geodetic mass balance of glaciers was -0.70 ± 0.06 m a-1 (-0.63 ± 0.05 m w.e. a-1), being one of the most negative from Svalbard regional means known from the literature. If the same figure was to be applied for other similar regions of central Spitsbergen, that would result in a considerable contribution to total Svalbard mass balance despite negligible proportion to total glacier area. Glacier changes in Dickson Land were linked to dramatic equilibrium line altitude (ELA) shift, which in the period 1990-2009/11 has been located ca. 500 m higher than required for steady-state. The mass balance of central Spitsbergen glaciers seems to be therefore more sensitive to climate change than previously thought.

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

    USGS Publications Warehouse

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

    2007-01-01

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

  4. Rock glacier development in the Northern Calcareous Alps at the Pleistocene-Holocene boundary

    NASA Astrophysics Data System (ADS)

    Moran, Andrew P.; Ivy Ochs, Susan; Vockenhuber, Christof; Kerschner, Hanns

    2016-11-01

    Relict rock glaciers provide information on past discontinuous permafrost and former mean annual air temperatures. A lack of records showing former permafrost distribution along the northern Alpine fringe prompted the investigation and numerical dating of a belt of relict rock glaciers in the Karwendel Mountains of the Northern Calcareous Austrian Alps. In two neighbouring cirques that were still glaciated during the early Younger Dryas, eleven 36Cl exposure ages from boulder surfaces were obtained. The ages imply the onset of rock glacier activity around ~ 12.3 ka with subsequent stabilization and permafrost melt out no later than ~ 10.1 ka. Hence, rock glacier formation coincided with glacier retreat in the cirques around the mid-Younger Dryas and continued into the early Holocene. As permafrost induced features, the rock glacier termini indicate the local past lower limit of discontinuous permafrost in open cirque floors at ~ 2000 m asl, which is around 400 m lower than during the mid-twentieth century at comparable locations in the Karwendel Mountains. Thus, a mean annual air temperature reduction of ~- 2.6 to - 3.8 °C relative to the mid-twentieth century is inferred. Based on a minimum glacier equilibrium line altitude in the cirques, a summer temperature reduction of less than - 2.6 to - 1.8 °C is shown, suggesting an increased seasonality at the time of rock glacier activity.

  5. Water, ice, and meteorological measurements at South Cascade Glacier, Washington, balance year 2002

    USGS Publications Warehouse

    Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.

    2004-01-01

    Winter snow accumulation and summer snow and ice ablation were measured at South Cascade Glacier, Washington, to estimate glacier mass balance quantities for balance year 2002. The 2002 glacier-average maximum winter snow balance was 4.02 meters, the second largest since 1959. The 2002 glacier summer, net, and annual (water year) balances were -3.47, 0.55, and 0.54 meters, respectively. The area of the glacier near the end of the balance year was 1.92 square kilometers, and the equilibrium-line altitude and the accumulation area ratio were 1,820 meters and 0.84, respectively. During September 20, 2001 to September 13, 2002, the terminus retreated 4 meters, and computed average ice speeds in the ablation area ranged from 7.8 to 20.7 meters per year. Runoff from the subbasin containing the glacier and from an adjacent non-glacierized basin were measured during part of the 2002 water year. Air temperature, precipitation, atmospheric water-vapor pressure, wind speed and incoming solar radiation were measured at selected locations near the glacier.

  6. Younger Dryas glaciers in the High Atlas, Morocco

    NASA Astrophysics Data System (ADS)

    Hughes, Philip; Fink, David

    2016-04-01

    Twelve cirque glaciers formed during the Younger Dryas on the mountains of Aksoual (3912 m a.s.l.) and Adrar el Hajj (3129 m a.s.l.) in the Marrakesh High Atlas. Moraines in two separate cirques on these mountains have been dated using 10Be and 36Cl exposure dating. In both cirques the age scatter is relatively small (13.8-10.1 ka) and all ages overlap within error with the Younger Dryas (12.9-11.7 ka). The glaciers were small and covered <2 km2 and formed on north-facing slopes. However, the altitudinal range of the glaciers was very large, with equilibrium line altitudes (ELAs) ranging from 2470 and 3560 m. This large range is attributed to local topoclimatic factors with the lowest glacier (confirmed as Younger Dryas in age by 3 exposure ages) occupying a very steep cirque floor where a combination of steep glacier gradient and a large potential avalanche catchment enabled its low-lying position. This indicates that caution should be taken when using single glacier sites for reconstructing regional palaeoclimate, especially those formed in steep catchments that have strong topoclimatic controls. The average ELA of the twelve Younger Dryas glaciers was c. 3109 m a.s.l. (St Dev = 325 m) and this represents an ELA depression of > 1000 m from the modern theoretical regional ELA. Under precipitation values similar to today this would require a mean annual temperature depression of 9°C. Moreover, the glacier-climate modelling indicates that it is very unlikely that climate was drier than today during the Younger Dryas in the Marrakesh High Atlas.

  7. Carihuayrazo S-W a little Ecuadorian glacier in the way to extinction

    NASA Astrophysics Data System (ADS)

    Cáceres, B. E.

    2015-12-01

    Carihuayrazo S-W glacier is located on the western cordillera in the Ecuadorian Andes. During the last 60 years it has been a dramatical reduction in its ice coverage corresponding to 67%. During the last 15 years an accelerated ice coverage lost has been observed with a value of 37%.The values on the reduction of ice coverage were correlated with the equilibrium line altitude (ELA) location for the Ecuadorian Andes, corresponding to 5100 meters above sea level (m.a.s.l.). This value was determined over the last 20 years using different measurements over the Antisana 15 glacier (1994-2014). This place is used as a reference to locate the coverage lost for the glaciers in the Ecuadorian Andes. At the moment the Glacier under study doesn't have accumulation area since the more higher altitude was located at 5020 meters above sea level (m.a.s.l), value that is below the equilibrium line altitude. Values for mass balance have been measured during short periods of time with high negative values. According to the observations carried out on this glacier since 2003 there is a high probability that it will disappear in the next ten years . At the moment this glacier is monitoring with special attention in order to document with detail its disappearance.

  8. Water, Ice, and Meteorological Measurements at South Cascade Glacier, Washington, Balance Years 2004 and 2005

    USGS Publications Warehouse

    Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.

    2007-01-01

    Winter snow accumulation and summer snow and ice ablation were measured at South Cascade Glacier, Washington, to estimate glacier mass-balance quantities for balance years 2004 and 2005. The North Cascade Range in the vicinity of South Cascade Glacier accumulated smaller than normal winter snowpacks during water years 2004 and 2005. Correspondingly, the balance years 2004 and 2005 maximum winter snow balances of South Cascade Glacier, 2.08 and 1.97 meters water equivalent, respectively, were smaller than the average of such balances since 1959. The 2004 glacier summer balance (-3.73 meters water equivalent) was the eleventh most negative during 1959 to 2005 and the 2005 glacier summer balance (-4.42 meters water equivalent) was the third most negative. The relatively small winter snow balances and unusually negative summer balances of 2004 and 2005 led to an overall loss of glacier mass. The 2004 and 2005 glacier net balances, -1.65 and -2.45 meters water equivalent, respectively, were the seventh and second most negative during 1953 to 2005. For both balance years, the accumulation area ratio was less than 0.05 and the equilibrium line altitude was higher than the glacier. The unusually negative 2004 and 2005 glacier net balances, combined with a negative balance previously reported for 2003, resulted in a cumulative 3-year net balance of -6.20 meters water equivalent. No equal or greater 3-year mass loss has occurred previously during the more than 4 decades of U.S. Geological Survey mass-balance measurements at South Cascade Glacier. Accompanying the glacier mass losses were retreat of the terminus and reduction of total glacier area. The terminus retreated at a rate of about 17 meters per year during balance year 2004 and 15 meters per year during balance year 2005. Glacier area near the end of balance years 2004 and 2005 was 1.82 and 1.75 square kilometers, respectively. Runoff from the basin containing the glacier and from an adjacent nonglacierized basin was

  9. Glacier fluctuations in the Southern Alps of New Zealand determined from snowline elevations

    SciTech Connect

    Chinn, T.J.H.

    1995-05-01

    Preliminary analysis of 452 determinations of end-of-summer glacier snowline altitudes (ELAs) made over 17 yr on up to 47 glaciers show good correlation with major climatic events, and conform well with fluctuations of glacier termini when reaction times are taken into consideration. With snowline altitudes used as surrogates for annual mass balance values, there is a recent trend to increased mass balances, i.e. a climate {open_quotes}cooling,{close_quotes} which follows a long period of predominantly glacial recession. Snowline trend surfaces plotted for the Southern Alps of New Zealand show considerable warping with variable departures from the steady-state equilibrium-line altitude each year. The current resurgence of the more active glaciers should continue in the near future. 39 refs., 10 figs., 1 tab.

  10. Debris-covered glaciers extend the lifespan of water supplies in the European Alps

    NASA Astrophysics Data System (ADS)

    Lardeux, Pierre; Glasser, Neil; Holt, Tom; Hubbard, Bryn

    2016-04-01

    Debris-covered glaciers have a slower melting rate than clean-ice glaciers due to the insulating effect of their debris layer. In the European Alps, debris-covered glaciers have received little attention due to their small contribution to sea-level rise. However, glaciers provide water supplies for the five main watersheds draining the European Alps (Danube, Rhine, Rhone, Po and Adige, in order of size), an area inhabited by more than 145 million people (20% of Europe's population). It is unclear what volume of ice (and so quantity of potential meltwater) is affected by a debris layer, and what the effect of this layer is for water resources in the Alps. Combining the Randolph Glacier Inventory (RGI) and online imagery services, we calculated that more than 40% of ice volume in the Alps is influenced by debris cover. In this presentation, we will show the different elements leading to this number, including our evaluation of the RGI, the volume calculation method and what percentage of ice is actually covered (0.6 to 99% of glacier surface area). Our analysis has allowed a comprehensive understanding of the debris-covered glaciers in each watershed by revealing their distribution (i.e. where they will extend water supply lifespan), and hypsometry and equilibrium line altitude (how sensitive they are to climate change). The prolonged lifespan of water supply is visible at the scale of an individual debris-covered glacier: comparing the evolution of Glacier Noir and Glacier Blanc (France) over the last 150 years indicates that Glacier Noir (debris covered) has retained 2.5 times more ice than Glacier Blanc (clean-ice) under the same climatic conditions. The number of debris-covered glaciers will increase as the >1°C rise in temperature in the European Alps since the start of the 20th Century increases the instability of rock faces and scree slopes. The evolution of these glaciers is therefore likely to have a major impact on human populations. This work shows that

  11. Quantifying the change in equilibrium-line altitude during the Last Glacial Maximum in the Subtropical Andes using a mass-balance model

    NASA Astrophysics Data System (ADS)

    Vargo, L.; Galewsky, J.

    2014-12-01

    Quantifying changes in equilibrium-line altitude (ELA) can be used to better understand past regional climates. We use a glacial mass-balance model in conjunction with global climate model (GCM) output data to calculate the change in ELA between modern and Last Glacial Maximum (LGM; 21 ka) climates in the presently hyper-arid subtropical Andes. The region is currently unglaciated, despite cold enough temperatures, as there is too little moisture to sustain glaciers. Previous studies suggest this area was glaciated during the LGM, however, little is known about the extent of the glaciation or the climate required to sustain it. The mass-balance model used in this study calculates the change in ELA using the positive degree-day (PDD) sum, the sum of daily mean air temperatures that are above zero. The PDD sum is used to calculate ablation, which is then assumed to be proportional to temperature, in order to calculate the change in ELA. Using output from several GCM simulations, we compare the change in ELA between LGM and modern climates across the different models for the subtropical Andes. These simulations suggest that the changes in climate resulted in a lowering of ELAs to the extent that parts of the subtropical Andes were glaciated during the LGM.

  12. Low beta equilibrium and stability for anisotropic pressure closed field line plasma confinement systems

    SciTech Connect

    Pastukhov, V.P.; Ilgisonis, V.I.; Subbotin, A.A.

    1994-05-01

    General formalism is developed to analyze the equilibrium and stability of low beta anisotropic pressure plasmas confined in closed field line magnetic systems. The formalism allows one to consider rather general magnetic systems with nonuniform axis curvature and longitudinal profiles of toroidal and multipole poloidal field. It also allows having a strong pressure anisotropy corresponding to enhanced plasma pressure in mirror cells of the system. As an example of such a system the authors consider the recently proposed linked mirror neutron source (LMNS). Application of the above formalism to the LMNS analysis confirms most of the preliminary results, however, they obtain a considerable reduction of mirror cell axis curvature and an appreciable ellipticity of plasma cross-section in the mirror cell midplane. They have also optimized the longitudinal pressure and magnetic field distribution.

  13. Combined Ice and Water Balances of Gulkana and Wolverine Glaciers, Alaska, and South Cascade Glacier, Washington, 1965 and 1966 Hydrologic Years

    USGS Publications Warehouse

    Meier, Mark Frederick; Tangborn, Wendell V.; Mayo, Lawrence R.; Post, Austin

    1971-01-01

    Glaciers occur in northwestern North America between lat 37 deg and 69 deg N. in two major mountain systems. The Pacific Mountain System, near the west coast, receives large amounts of precipitation, has very mild temperatures, and contains perhaps 90 percent of the glacier ice. The Rocky Mountain or Eastern System, on the other hand, receives nearly an order of magnitude less precipitation, has temperatures that range from subpolar to subtropic, and contains glaciers that are much smaller in both size and total area. As a contribution to the International Hydrological Decade program on combined balances at selected glaciers, the U.S. Geological Survey is conducting studies of ice and water balance on four glaciers in the Pacific Mountain System: Wolverine and Gulkana Glaciers in Alaska, South Cascade Glacier in Washington, and Maclure Glacier in California. Similar data are being collected by other organizations at five glaciers in western Canada, including two in the Rocky Mountain System, and at one glacier in the Rocky Mountain System in northern Alaska. Gulkana, Wolverine, South Cascade, and Maclure Glaciers have dissimilar mass balances, and each is fairly representative of the glaciers for its particular region. Gulkana Glacier (lat 63 deg 15' N., Alaska Range, Alaska) normally has an equilibrium line at an altitude of 1,800 m (meters), an activity index of about 6 mm/m (millimeters per meter), a winter balance of about 1.0 m, and an annual exchange of about 2.2 m. (Balance values are given in terms of water-equivalent measure; the winter balance of 1 m, for example, indicates a volume of ice equal in mass to a volume of water 1 m in depth covering the area of the glacier.) The normal approximate parameters for the other glaciers studied are as follows: Wolverine Glacier (lat 60 deg 24' N., Kenai Mountains, Alaska) - equilibrium-line altitude 1,200 m, activity index 9 mm/m, winter balance 2.5 m, and annual exchange 5.5 m; South Cascade Glacier (lat 48 deg 22

  14. Sedimentology and architecture of De Geer moraines in the western Scottish Highlands, and implications for grounding-line glacier dynamics

    NASA Astrophysics Data System (ADS)

    Golledge, Nicholas R.; Phillips, Emrys

    2008-07-01

    Sedimentary exposures in moraines in a Scottish Highland valley (Glen Chaorach), reveal stacked sequences of bedded and laminated silt, sand and gravel, interspersed or capped with diamicton units. In four examples, faults and folds indicate deformation by glaciotectonism and syndepositional loading. We propose that these sediments were laid down in an ice-dammed lake, close to the last ice margin to occupy this glen. Individual units within cross-valley De Geer moraine ridges are interpreted by comparison with examples from similar environments elsewhere: stratified diamictons containing laminated or bedded lenses are interpreted as subaqueous ice-marginal debris-flow deposits; massive fine-grained deposits as hyperconcentrated flow deposits, and massive gravel units as high-density debris-flow deposits. Using an allostratigraphic approach we argue that glaciotectonically deformed coarsening-upward sand and gravel sequences that culminate in deposition of subglacial diamicton represent glacier advances into the ice-marginal lake, whereas undisturbed cross-bedded sand and gravel reflects channel or fan deposits laid down during glacier retreat. A flat terrace of bedded sand and gravel at the northern end of Glen Chaorach is interpreted as subaerial glaciofluvial outwash. On the basis of these inferences we propose the following three stage deglacial event chronology for Glen Chaorach. During glacier recession, ice separation and intra-lobe ponding first led to subaquaeous deposition of sorted and unsorted facies. Subsequent glacier stabilisation and ice-marginal oscillation produced glaciotectonic structures in the ice-marginal sediment pile and formed De Geer moraines. Finally, drainage of the ice-dammed lake allowed a subaerial ice-marginal drainage system to become established. Throughout deglaciation, deposition within the lake was characterized by abrupt changes in grain size and in the architecture of individual sediment bodies, reflecting changing delivery

  15. Equilibrium of magnetic fields with arbitrary interweaving of the lines of force. I - Discontinuities in the torsion

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1986-01-01

    Consideration is given to the static force-free equilibrium of a magnetic field in which all of the lines of force connect without knotting between parallel planes. The field is formed by continuous deformation from an initial uniform field, and is conventiently described in terms of the scalar function psi, which is the stream function for the incompressible wrapping and interweaving of the lines of force. Local compression and expansion of the lines of force is described in terms of the scalar function Phi. Equilibrium in the field requires satisfaction of two independent equations which cannot be accomplished without the full freedom of both psi and Phi. It is shown that discontinuities in the torsional characteristics of the lines occur when psi is predetermined by an arbitrary pattern. Discontinuities in the winding pattern of the lines can lead to discontinuities in the associated current sheets.

  16. Size specific steady-state accumulation-area ratio: an improvement for equilibrium-line estimation of small palaeoglaciers

    NASA Astrophysics Data System (ADS)

    Kern, Zoltán; László, Péter

    2010-09-01

    Characteristic distribution of the steady-state accumulation-area ratio (AAR 0) of valley and corrie glaciers was investigated in a global dataset comprised of 46 glaciers. There is a positive relationship between AAR 0 and glacier area with smaller glaciers having lower values of AAR 0 compared with larger glaciers. The relationship between glacier area (S) and steady-state AAR of studied glaciers can be optimally described by a logarithmic regression equation. This relationship is thought to be a globally valid approximation if the size of the glacier is not smaller than 10 -1 km 2. In the case of palaeoglaciers an AAR 0 value of 0.44 ± 0.07 is best applied on glaciers with areas in the range 0.1-1 km 2, 0.54 ± 0.07 for glaciers covering areas between 1 and 4 km 2 and 0.64 ± 0.04 for glaciers larger than 4 km 2. This assumes insignificant debris cover for the investigated palaeoglaciers. The proposed size-specific AAR 0 values take into account the geometric/hypsometric properties of (palaeo)glaciers. The results have major importance for palaeoglaciological reconstructions in many regions of former marginal/niche glaciation characterized by small former glaciers.

  17. Climatic controls of western U.S. glaciers at the last glacial maximum

    USGS Publications Warehouse

    Hostetler, S.W.; Clark, P.U.

    1997-01-01

    We use a nested atmospheric modeling strategy to simulate precipitation and temperature of the western United States 18,000 years ago (18 ka). The high resolution of the nested model allows us to isolate the regional structure of summer temperature and winter precipitation that is crucial to determination of the net mass balance of late-Pleistocene mountain glaciers in this region of diverse topography and climate. Modeling results suggest that climatic controls of these glaciers varied significantly over the western U.S. Glaciers in the northern Rocky Mountains existed under relatively cold July temperatures and low winter accumulation, reflecting anticyclonic, easterly wind flow off the Laurentide Ice Sheet. In contrast, glaciers that existed under relatively warmer and wetter conditions are located along the Pacific coast south of Oregon, where enhanced westerlies delivered higher precipitation than at present. Between these two groupings lie glaciers that were controlled by a mix of cold and wet conditions attributed to the convergence of cold air from the ice sheet and moisture derived from the westerlies. Sensitivity tests suggest that, for our simulated 18 ka climate, many of the glaciers exhibit a variable response to climate but were generally more sensitive to changes in temperature than to changes in precipitation, particularly those glaciers in central Idaho and the Yellowstone Plateau. Our results support arguments that temperature depression generally played a larger role in lowering equilibrium line altitudes in the western U.S. during the last glacial maximum than did increased precipitation, although the magnitude of temperature depression required for steady-state mass balance varied from 8-18??C. Only the Sierra Nevada glaciers required a substantial increase in precipitation to achieve steady-state mass balance, while glaciers in the Cascade Range existed with decreased precipitation.

  18. 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.

  19. Climatic controls of Western U.S. Glaciers at the last glacial maximum

    NASA Astrophysics Data System (ADS)

    Hostetler, Steven W.; Clark, Peter U.

    We use a nested atmospheric modeling strategy to simulate precipitation and temperature of the western United States 18,000 years ago (18 ka). The high resolution of the nested model allows us to isolate the regional structure of summer temperature and winter precipitation that is crucial to determination of the net mass balance of late-Pleistocene mountain glaciers in this region of diverse topography and climate. Modeling results suggest that climatic controls of these glaciers varied significantly over the western U.S. Glaciers in the northern Rocky Mountains existed under relatively cold July temperatures and low winter accumulation, reflecting anticyclonic, easterly wind flow off the Laurentide Ice Sheet. In contrast, glaciers that existed under relatively warmer and wetter conditions are located along the Pacific coast south of Oregon, where enhanced westerlies delivered higher precipitation than at present. Between these two groupings lie glaciers that were controlled by a mix of cold and wet conditions attributed to the convergence of cold air from the ice sheet and moisture derived from the westerlies. Sensitivity tests suggest that, for our simulated 18 ka climate, many of the glaciers exhibit a variable response to climate but were generally more sensitive to changes in temperature than to changes in precipitation, particularly those glaciers in central Idaho and the Yellowstone Plateau. Our results support arguments that temperature depression generally played a larger role in lowering equilibrium line altitudes in the western U.S. during the last glacial maximum than did increased precipitation, although the magnitude of temperature depression required for steady-state mass balance varied from 8-18°C. Only the Sierra Nevada glaciers required a substantial increase in precipitation to achieve steady-state mass balance, while glaciers in the Cascade Range existed with decreased precipitation.

  20. 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.

  1. Past and future evolution of Himalayan glaciers: a regional climate model study

    NASA Astrophysics Data System (ADS)

    Kumar, Pankaj; Kotlarski, Sven; Moseley, Christopher; Sieck, Kevin; Frey, Holger; Stoffel, Markus; Jacob, Daniela

    2013-04-01

    Over 800 million people depend on glacier melt water runoff throughout the Hindu-Kush and Himalaya (HKH) region. The region, also called as "Water tower of Asia", is the location of several major rivers basins, like Ganges, Brahmaputra, and Indus etc. Glaciers in the HKH region are the primary source of water for the perennial rivers. Previous studies have assessed glacier areas and volumes in the HKH region by remote sensing techniques and slope-dependent thickness estimations. We here present a study in which, for the first time a glacier parameterization scheme is dynamically coupled to a regional climate model and applied over the South Asian Himalayan mountain range. The glacier scheme interactively simulates the mass balance as well as changes of the areal extent of glaciers on a sub-grid scale. Various observational data sets, in particular a regional glacier inventory, have been compiled and were used to initialize glacier area and volume in the year 1989. A simulation for the period 1989-2008 using the ECMWF ERA-Interim reanalysis as atmospheric boundary forcing was carried out. Preliminary results show a simulated decrease of glacier area of about 20% between 1989 and 2008. The spatial patterns of glacier area change show a remarkable decrease, but do show some regions of increase especially over the Karakoram (western Himalaya), a region for which available observations-based estimates also indicate a positive mass balance anomaly. The positive relation between altitude and mass balance is qualitatively reproduced by the model. The model is able to approximately represent the equilibrium line altitude (ELA) for selected sub-region when compared to observed values but simulated ELA's seem to have a systematic negative bias which, in turn, suggests an overestimation of the mean regional mass balance. Our results indicate that observed glacier changes can be approximately reproduced within a regional climate model based on simplified concepts of glacier

  2. Thoughts on some outstanding issues in the physics of equilibrium wetting and conceptual understanding of contact lines

    NASA Astrophysics Data System (ADS)

    Sefiane, K.

    2011-08-01

    Equilibrium wetting is a fundamental phenomenon, relevant to many scientific areas. Since the pioneering work on equilibrium wetting of Thomas Young (1805) [1], researchers strived to advance our understanding of this fundamental problem. Despite its apparent simplicity, equilibrium wetting phenomenon still holds many unanswered questions and represents a challenge to modern physicists and engineers. The relationship between quantities amenable to measurements, like macroscopic wetting contact angle, and other surface ener- gies and physical properties remains to be fully elucidated. Wetting is a physical problem which spans over two length scales, inner region ("microscopic") length scale and outer region ("macroscopic"). The three-phase contact line, where the macroscopic region meets the micro- scopic one, and underlying surface forces, represents a challenge to fully understand and model. In this paper, a brief review of the basics of wetting and existing concepts is first presented. Then two important questions are discussed in the light of the latest experimental findings: first the relevance of the continuum concept when describing interfaces near the three-phase contact line, and second the effect of adsorption on interfacial energies and its use to explain some interesting observations like the dependence of equilibrium contact angle on pressure and size of droplets. These recent observations raise some fundamental questions about how the three-phase contact line is conceptualised.

  3. Sensitivity of annual mass balance gradient and Hypsometry to the changing climate: the case of Dokriani Glacier, central Himalaya, India

    NASA Astrophysics Data System (ADS)

    Pratap, B.

    2015-12-01

    The glacier mass balance is undelayed, unfiltered and direct method to assess the impact of climate change on the glaciers. Many studies suggest that some of the Himalayan glaciers have lost their mass at an increased rate during the past few decades. Furthermore, the mass balance gradient and hypsometric analysis are important to understand the glacier response towards climatic perturbations. Our long term in-situ monitoring on the Dokriani Glacier provides great insights to understand the variability in central Himalayan glaciers. We report the relationship between glacier hypsometry and annual mass balance gradient (12 years) to understand the glacier's response towards climate change. Dokriani Glacier in the Bhagirathi basin is a small (7 km2) NNW exposed glacier in the western part of central Himalaya, India. The study analysed the annual balance, mass balance gradient and length changes observed during first decade of 21st century (2007-2013) and compare with the previous observations of 1990s (1992-2000). A large spatial variability in the mass balance gradients of two different periods has been observed. The equilibrium-line altitude (ELA) was fluctuated between 5000 and 5100 m a.s.l. and the derived time averaged ELA (ELAn) and balance budget ELA (ELA0) were 5075 and 4965 m a.s.l respectively during 1992-2013. The observed time-averaged accumulation-area ratio (AARn) and balance budget AAR (AAR0) were 0.67 and 0.72 respectively during 1992-2013. The higher value of AAR comprises due to flat and broader accumulation area (4.50 km2) of the glacier. Although, having larger accumulation area, the glacier has faced strong mass wasting with average annual ablation of -1.82 m w.e. a-1 in the ablation zone as compare to residual average annual accumulation of 0.41 m w.e. a-1. Based on the annual mass balance series (12 years) Dokriani Glacier has continuous negative annual balances with monotonically negative cumulative mass loss of -3.86 m w.e with the average

  4. Photographic Snow-cover Monitoring on St Sorlin Glacier, France.

    NASA Astrophysics Data System (ADS)

    Gerbaux, M.; Genthon, C.; Dedieu, J.; Balestrieri, J.

    2004-12-01

    Like most other glaciers in the Alps, the St Sorlin glacier (french Alps, 45.16°N, 6.16°E, 2900 m asl mean elevation and 3km2 of surface area) has been retreating fast in the last 20 years. To understand the meteorological factors responsible for this retreat, and to tentatively predict glaciers evolution in a changing (warming) climate, we use a distributed snow/ice mass and energy balance model derived from the CROCUS snow model (Météo-France). There is no direct meteorological observation on or near St Sorlin glacier yet, and hourly meteorology to force the snow/ice model is obtained from disaggregated meteorological analyses. The model is found to reproduce the St Sorlin mass balance of the last 20 years as obtained from field glaciological measurements and stereophotographic reconstructions. The model is also found to reproduce the interannual variations of the equilibrium line as determined from optical satellite imagery. Because of the albedo feedback involved, it is also important to verify that the summer snow/ice transition on the glacier is correctly simulated. Thus, an automated photographic system was set up facing St Sorlin glacier to monitor the evolution of the snow cover. The system was installed on the 13th of July 2004 and is still in operation at time of abstract writing. Digital photographies are taken every 4 hours, permitting so far at least one non-obstructed (rain, fog) picture per day. The first pictures in the series show an almost fully snow-covered glacier while the latest ones show bare ice up to the highest parts of the glacier. Snow is occasionally deposited during precipitation events but hardly last more than 3 days. Snow line position is deduced from pictures using a DEM with georeferenced points visible on pictures. It should then be compared with the modelled one. The automated photographic system provides not only snow cover to check snow/ice model results at seasonal time-scales, but also qualitative meteorological

  5. Glacier microseismicity

    USGS Publications Warehouse

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

    2010-01-01

    We present a framework for interpreting small glacier seismic events based on data collected near the center of Bering Glacier, Alaska, in spring 2007. We find extremely high microseismicity rates (as many as tens of events per minute) occurring largely within a few kilometers of the receivers. A high-frequency class of seismicity is distinguished by dominant frequencies of 20–35 Hz and impulsive arrivals. A low-frequency class has dominant frequencies of 6–15 Hz, emergent onsets, and longer, more monotonic codas. A bimodal distribution of 160,000 seismic events over two months demonstrates that the classes represent two distinct populations. This is further supported by the presence of hybrid waveforms that contain elements of both event types. The high-low-hybrid paradigm is well established in volcano seismology and is demonstrated by a comparison to earthquakes from Augustine Volcano. We build on these parallels to suggest that fluid-induced resonance is likely responsible for the low-frequency glacier events and that the hybrid glacier events may be caused by the rush of water into newly opening pathways.

  6. Jakobshavn Glacier

    Atmospheric Science Data Center

    2013-04-17

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

  7. 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.

  8. 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.

  9. Surges of outlet glaciers from the Drangajökull ice cap, northwest Iceland

    NASA Astrophysics Data System (ADS)

    Brynjólfsson, Skafti; Schomacker, Anders; Korsgaard, Niels J.; Ingólfsson, Ólafur

    2016-09-01

    Surface elevation and volume changes of the Drangajökull surge-type glaciers, Reykjarfjarðarjökull and Leirufjarðarjökull, were studied by comparing digital elevation models that pre-date and post-date their most recent surges. Annual glacier-frontal measurements were used to estimate average ice velocities during the last surge of the glaciers. The observations show a distinct ice discharge, most of which was from the upper reservoir areas, down to the receiving areas during the surges. The surface draw-down in the reservoir areas was usually 10-30 m during the surges, while the thickening of the receiving areas was significantly more variable, on the order of 10-120 m. Despite a negative geodetic net mass balance derived from the digital elevation models, the reservoir areas have been gaining mass since the surge terminations. This surface thickening along with considerable ablation of the receiving areas will most likely return the glacier surface profiles to the pre-surge stage. Our results indicate that (a) greatest surface thinning in the upper reservoir areas of Drangajökull rather than proximal to the equilibrium line during Vatnajökull surges and (b) development of Drangajökull surges that resembles Svalbard surge-type glaciers rather than Vatnajökull surge-type glaciers. The contrasting surge characteristics could be explained by differences in glacier geometry, topography and substratum of the Drangajökull and Vatnajökull surge-type glaciers.

  10. Recent ice dynamic and surface mass balance of Union Glacier in the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    Here we present the results of a comprehensive glaciological investigation of Union Glacier (79°46' S/83°24' W) in the West Antarctic Ice Sheet (WAIS), a major outlet glacier within the Ellsworth Mountains. Union Glacier flows into the Ronne Ice Shelf, where recent models have indicated the potential for significant grounding line zone (GLZ) migrations in response to changing climate and ocean conditions. To elaborate a glaciological base line that can help to evaluate the potential impact of this GLZ change scenario, we installed an array of stakes on Union Glacier in 2007. The stake network has been surveyed repeatedly for elevation, velocity, and net surface mass balance. The region of the stake measurements is in near-equilibrium, and ice speeds are 10 to 33 m a-1. Ground-penetrating radars (GPR) have been used to map the subglacial topography, internal structure, and crevasse frequency and depth along surveyed tracks in the stake site area. The bedrock in this area has a minimum elevation of -858 m a.s.l., significantly deeper than shown by BEDMAP2 data. However, between this deeper area and the local GLZ, there is a threshold where the subglacial topography shows a maximum altitude of 190 m. This subglacial condition implies that an upstream migration of the GLZ will not have strong effects on Union Glacier until it passes beyond this shallow ice pinning point.

  11. The Moving Lines on Electron Spectra as Charge Reflexes on Non-equilibrium States of Nanostructured Surfaces.

    PubMed

    Mishchuk, Oleg A

    2016-12-01

    The experimental results present the phenomenon of moving lines on electron spectra which are linked spatially and in time with the localization and durability of the processes of new surface producing in folds and grain boundaries. This effect was also realized for a thin-layer composite "organic on metal films on dielectric substrate" in modeling non-equilibrium conditions which are created by the intensive electron beam pulse impact. It was found that the nature of the inceptive adsorption layer, in addition to the metal film, determines the initial positions of moving lines on the spectra. The main accents in these investigations were in observations of appearance of the moving lines, dynamics of their displacements on the spectra, final stages when these lines vanished, and finding the general regularities between the spontaneous and induced events.

  12. The Moving Lines on Electron Spectra as Charge Reflexes on Non-equilibrium States of Nanostructured Surfaces

    NASA Astrophysics Data System (ADS)

    Mishchuk, Oleg A.

    2016-04-01

    The experimental results present the phenomenon of moving lines on electron spectra which are linked spatially and in time with the localization and durability of the processes of new surface producing in folds and grain boundaries. This effect was also realized for a thin-layer composite "organic on metal films on dielectric substrate" in modeling non-equilibrium conditions which are created by the intensive electron beam pulse impact. It was found that the nature of the inceptive adsorption layer, in addition to the metal film, determines the initial positions of moving lines on the spectra. The main accents in these investigations were in observations of appearance of the moving lines, dynamics of their displacements on the spectra, final stages when these lines vanished, and finding the general regularities between the spontaneous and induced events.

  13. The Moving Lines on Electron Spectra as Charge Reflexes on Non-equilibrium States of Nanostructured Surfaces.

    PubMed

    Mishchuk, Oleg A

    2016-12-01

    The experimental results present the phenomenon of moving lines on electron spectra which are linked spatially and in time with the localization and durability of the processes of new surface producing in folds and grain boundaries. This effect was also realized for a thin-layer composite "organic on metal films on dielectric substrate" in modeling non-equilibrium conditions which are created by the intensive electron beam pulse impact. It was found that the nature of the inceptive adsorption layer, in addition to the metal film, determines the initial positions of moving lines on the spectra. The main accents in these investigations were in observations of appearance of the moving lines, dynamics of their displacements on the spectra, final stages when these lines vanished, and finding the general regularities between the spontaneous and induced events. PMID:27083583

  14. Alpine Glaciers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 27 August 2003

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

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

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

    NASA Astrophysics Data System (ADS)

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

    1996-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  17. Spatial and Temporal Variations of the Firn Line Altitudes in the Asian High Mountains over the Past Decade

    NASA Astrophysics Data System (ADS)

    Wang, N.; Guo, Z.; Wu, H.

    2014-12-01

    The Variations of the equilibrium line altitude (ELA) of one glacier could determine the glacier's behaviors, i.e., advance, stable, retreat, or disappeared. In the Asian High Mountains, there exist a huge number of glaciers, but only few monitoring glaciers. This means that we could only obtain the ELA data sets from these few monitoring glaciers in the region, which restrained our understanding for the spatial distribution pattern of the ELA. Considering that the firn line altitude can indicate the equilibrium line altitude, we may investigate the variations of the firn line altitudes on many glaciers to understand the spatial and temporal variation characteristics of the ELA in the Asian High Mountains. Albedo of the firn is usually larger than that of the glacier ice. This phenomenon can be used to discern the location of the firn line on a glacier in remote sensing image. By using the Landsat TM/ETM+ data, HJ-1A/B data and DEM data, we obtained the firn line altitudes on more than 3000 glaciers in the Asian High Mountains, and found that the highest firn line altitude, over 6000 m a.s.l., was located in the Qiangtang area, which imply that the Indian monsoon moisture cause the firn line altitudes lower to the south of the Qiangtang area, in other words, the Qiangtang area is the northern boundary of the Indian monsoon. The firn line altitude was lower than 5200 m a.s.l. in the southeast Tibetan Plateau while lower than 3500 m a.s.l. in the Altai Mountains in 2010. Over the past decade, the firn line altitudes increased by about 30 to 300 m in different areas of the Tibetan Plateau, but decreased by about 80 m in the Altai Mountains.

  18. Equilibrium Line Altitudes and paleotemperature reconstructions from Nevado Hualcán (9°S) and Nevado Coropuna (15°S), Tropical Andes (Peru).

    NASA Astrophysics Data System (ADS)

    Úbeda, J.; Giráldez, C.; Palacios, D.

    2012-04-01

    system which in 13-1136Cl ka had a surface of >400 km2 (Ubeda, 2011). Glasser, N.F., Clemmens, S., Schnabel, C., Fenton, C.R. and McHargue, L., 2009. Tropical glacier fluctuations in the Cordillera Blanca, Peru between 12.5 and 7.6 ka from cosmogenic 10Be dating. Quaternary Science Reviews, 28: 3448-3458. IPCC, 2007: Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, Pachauri, R.K and Reisinger, A. (eds.)]. IPCC, Geneva, Switzerland, 104 pp. Kaser, G. and Osmaston, H., 2002. Tropical Glaciers. International Hydrology Series. Cambridge University Press, Cambridge (U.K.), 207 pp. Osmaston, H., 2005. Estimates of glacier equilibrium line altitudes by the Area x Altitude, the Area x Altitude Balance Ratio and the Area x Altitude Balance Index methods and their validation. Quaternary International, 22-31: 138-139. Úbeda, J., 2011. El impacto del cambio climático en los glaciares del complejo volcánico Nevado Coropuna (cordillera occidental de los Andes, Sur del Perú). PhD Thesis. Universidad Complutense de Madrid, (Spain), 558 pp. Available online: http://eprints.ucm.es/12076/ Research funded by CGL2009-7343 project, Government of Spain.

  19. Fluctuating snow line altitudes in the Hunza basin (Karakoram) using Landsat OLI imagery

    NASA Astrophysics Data System (ADS)

    Racoviteanu, Adina; Rittger, Karl; Brodzik, Mary J.; Painter, Thomas H.; Armstrong, Richard

    2016-04-01

    Snowline altitudes (SLAs) on glacier surfaces are needed for separating snow and ice as input for melt models. When measured at the end of the ablation season, SLAs are used for inferring stable-state glacier equilibrium line altitudes (ELAs). Direct measurements of snowlines are rarely possible particularly in remote, high altitude glacierized terrain, but remote sensing data can be used to separate these snow and ice surfaces. Snow lines are commonly visible on optical satellite images acquired at the end of the ablation season if the images are contrasted enough, and are manually digitized on screen using various satellite band combinations for visual interpretation, which is a time-consuming, subjective process. Here we use Landsat OLI imagery at 30 m resolution to estimate glacier SLAs for a subset of the Hunza basin in the Upper Indus in the Karakoram. Clean glacier ice surfaces are delineated using a standardized semi-automated band ratio algorithm with image segmentation. Within the glacier surface, snow and ice are separated using supervised classification schemes based on regions of interest, and glacier SLAs are extracted on the basis of these areas. SLAs are compared with estimates from a new automated method that relies on fractional snow covered area rather than on band ratio algorithms for delineating clean glacier ice surfaces, and on grain size (instead of supervised classification) for separating snow from glacier ice on the glacier surface. The two methods produce comparable snow/ice outputs. The fSCA-derived glacierized areas are slightly larger than the band ratio estimates. Some of the additional area is the result of better detection in shadows from spectral mixture analysis (true positive) while the rest is shallow water, which is spectrally similar to snow/ice (false positive). On the glacier surface, a thresholding the snow grain size image (grain size > 500μm) results in similar glacier ice areas derived from the supervised

  20. Estimating Glacier Retreat through Satellite Based Observation In the Beas Basin, Himachal Pradesh, India

    NASA Astrophysics Data System (ADS)

    Dutta, Shruti; Ramanathan, Al.; Linda, Anurag

    2010-05-01

    Glaciers are now well recognized as the most reliable indicators of climate (IPCC, 2007), more particularly in the regions where there is an acute paucity in the availability of meteorological database. Subsequently it can be said that monitoring the glaciers is important to assess the overall reservoir health (Kulkarni et al., 2007). Almost negligible studies have been conducted to investigate the deglaciation status in the Indian Himalaya. A change detection analysis of the areal cover of glaciers in the Beas basin, India with the aid of remote sensing techniques in the present study concludes that the Beas basin has witnessed a loss of about 22.49 km2in the last four decades which is about 22% of the area. Another major aspect of this study is the noticeable retreat of the glaciers in the period 1972-1989. The glaciers in the Beas basin show larger area loss in this period as compared to the loss in area during the 1990s and later. Thus, it can be said that in spite of the alarming scenario of a continued recession of the glaciated terrain in the Beas basin, the pace of retreat has been observed to slow down after the 1990s. The loss has been more significant in the glaciers comprising of the area of 2-5 km2range as compared to the other categories. Glaciers in the area range more than 5 km2and less than 2 km2show less variation reflecting not much of significant loss. The total number of glaciers increased in the period of last four decades although not very significantly, indicating fragmentation. The glaciers in the range 0.5-2 km2 show a higher tendency towards fragmentation. The average elevation of the glaciers in the basin underwent an upward shift from 4565 m in the year 1972 to 4629 m in the year 2006 which is a reason for concern. The gradual upward shifting of contours over a period of almost four decades can be a consequence of a shift in Equilibrium Line Altitude (ELA) which has been constantly moving upwards showing a retreat of glaciers in the

  1. Pine Island Glacier, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

    is visible as an off-vertical dark line in the MISR nadir view. In the multi-angle composite, the crack and other stress fractures show up very clearly in bright orange. Radar observations of Pine Island Glacier in the 1990's showed the glacier to be shrinking, and the newly discovered crack is expected to eventually lead to the calving of a major iceberg.

    MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

  2. 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

    have longer and deeper fjords than the west-side glaciers. These distinct differences between the glaciers of the west and east side of the AP exert a primary control on the differing ice-ocean interactions, grounding-line retreat, and subglacial erosion rates, and provide context to understand rates of nAP ice mass loss.

  3. A non-local thermodynamic equilibrium, line-blanketed synthetic spectrum of Iota Herculis - C, Al, and Si lines

    NASA Technical Reports Server (NTRS)

    Grigsby, James A.

    1991-01-01

    A non-LTE line-blanketed model stellar atmosphere is used to compute a model of I Herculis (B3 IV) with a Teff of 17,500 K and a log g of 3.75, following the conclusions of Peters and Polidan (1985). Detailed profiles of a number of lines of C, Al, and Si in the 1200-2000-A region are computed, including the resonance lines of C II, Al II, and Al III. These profiles are compared to observations obtained from the coaddition of eight IUE SWP images, using a technique developed by Leckrone and Adelman (1989). Comparison of carbon lines with a model that is underabundant in carbon by a factor of 2 relative to the sun indicates that the C abundance of Iota Her is at most one-half solar. Non-LTE effects are examined by comparing an LTE model possessing identical atmospheric parameters with the non-LTE model. Substantial differences in the populations of the model atomic states are found, but differences in the temperature structure of the two models often mask the non-LTE effects in the synthetic spectra.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  5. Estimation of glacier mass balance: An approach based on satellite-derived transient snowlines and a temperature index driven by meteorological observations

    NASA Astrophysics Data System (ADS)

    Tawde, S. A.; Kulkarni, A. V.; Bala, G.

    2015-12-01

    In the Himalaya, large area is comprised of glaciers and seasonal snow, mainly due to its high elevated mountain ranges. Long term and continuous assessment of glaciers in this region is important for climatological and hydrological applications. However, rugged terrains and severe weather conditions in the Himalaya lead to paucity in field observations. Therefore, in recent decades, glacier dynamics are extensively monitored using remote sensing in inaccessible terrain like Himalaya. Estimation of glacier mass balance using empirical relationship between mass balance and area accumulation ratio (AAR) requires an accurate estimate of equilibrium-line altitude (ELA). ELA is defined as the snowline at the end of the hydrological year. However, identification of ELA, using remote sensing is difficult because of temporal gaps, cloud cover and intermediate snowfall on glaciers. This leads to large uncertainty in glacier mass-balance estimates by the conventional AAR method that uses satellite-derived highest snowline in ablation season as an ELA. The present study suggests a new approach to improve estimates of ELA location. First, positions of modelled snowlines are optimized using satellite-derived snowlines in the early melt season. Secondly, ELA at the end of the glaciological year is estimated by the melt and accumulation models driven using in situ temperature and precipitation records. From the modelled ELA, mass balance is estimated using the empirical relationship between AAR and mass balance. The modelled mass balance is validated using field measurements on Chhota Shigri and Hamtah glaciers, Himachal Pradesh, India. The new approach shows a substantial improvement in glacier mass-balance estimation, reducing bias by 46% and 108% for Chhota Shigiri and Hamtah glaciers respectively. The cumulative mass loss reconstructed from our approach is 0.85 Gt for nine glaciers in the Chandra basin from 2001 to 2009. The result of the present study is in agreement with

  6. Principles of Glacier Mechanics

    NASA Astrophysics Data System (ADS)

    Waddington, Edwin D.

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

  7. Glacier-derived climate for the Younger Dryas in Europe

    NASA Astrophysics Data System (ADS)

    Pellitero, Ramon; Rea, Brice R.; Spagnolo, Matteo; Hughes, Philip; Braithwaite, Roger; Renssen, Hans; Ivy-Ochs, Susan; Ribolini, Adriano; Bakke, Jostein; Lukas, Sven

    2016-04-01

    We have reconstructed and calculated the glacier equilibrium line altitudes (ELA) for 120 Younger Dryas palaeoglaciers from Morocco in the south to Svalbard in the north and from Ireland in the west to Turkey in the east. The chronology of these landform were checked and, when derived from cosmogenic dates, these were recalculated based on newer production rates. Frontal moraines/limits for the palaeoglaciers were used to reconstruct palaeoglacier extent by using a GIS tool which implements a discretised solution for the assumption of perfect-plasticity ice rheology for a single flowline and extents this out to a 3D ice surface. From the resulting equilibrium profile, palaeoglaciers palaeo-ELAs were calculated using another GIS tool. Where several glaciers were reconstructed in a region, a single ELA value was generated following the methodology of Osmaston (2005). In order to utilise these ELAs for quantitative palaeo-precipitation reconstructions an independent regional temperature analysis was undertaken. A database of 121 sites was compiled where the temperature was determined from palaeoproxies other than glaciers (e.g. pollen, diatoms, choleoptera, chironimids…) in both terrestrial and offshore environments. These proxy data provides estimates of average annual, summer and winter temperatures. These data were merged and interpolated to generate maps of average temperature for the warmest and coldest months and annual average temperature. From these maps the temperature at the ELA was obtained using a lapse rate of 0.65°C/100m. Using the ELA temperature range and summer maximum in a degree-day model allows determination of the potential melt which can be taken as equivalent to precipitation given the assumption a glacier is in equilibrium with climate. Results show that during the coldest part of the Younger Dryas precipitation was high in the British Isles, the NW of the Iberian Peninsula and the Vosges. There is a general trend for declining precipitation

  8. Laboratory study of the equilibrium and eruption of line-tied magnetic flux ropes in the solar corona

    NASA Astrophysics Data System (ADS)

    Myers, Clayton Edward

    2015-03-01

    Ideal magnetohydrodynamic (MHD) instabilities such as the kink instability and the torus instability are leading candidates to explain the sudden onset of eruptive events in the solar corona. These instabilities act on line-tied magnetic flux ropes--long-lived arched structures anchored to the solar surface. In spite of substantial observational and numerical research, however, the role of these instabilities in the corona remains a subject of intense debate. For this thesis, we have constructed and operated a new line-tied flux rope experiment that permits for the first time the study of both the kink and torus instabilities in the laboratory. This experiment has the following key features: (1) the arched flux rope is line-tied to two conducting footpoints; (2) the system is magnetically dominated (low-beta) with significant stored energy; (3) the system is driven quasi-statically, producing a long-lived equilibrium; and (4) the flux rope is generated within a potential (vacuum) magnetic field arcade whose decay index---the predicted torus instability control parameter---can be externally controlled. The flux ropes are diagnosed using a two-dimensional in situ magnetic probe array whose cross-section covers a substantial portion of the plasma. The central result of this thesis is that toroidal field forces, which are traditionally neglected in the analysis of coronal flux ropes, are identified for the first time as an essential contributor to both the equilibrium and the stability of line-tied flux ropes. Most importantly, experimental measurements show that a tension force derived from a self-generated paramagnetic toroidal field exerts a restoring force on the line-tied plasma and suppresses eruptive behavior in a significant portion of the parameter space. This suppression extends to regimes that are both kink and torus unstable. We find that, in order to explain the measured tension force, low aspect ratio and line-tying effects must be considered. Finally

  9. Stark broadening for diagnostics of the electron density in non-equilibrium plasma utilizing isotope hydrogen alpha lines

    SciTech Connect

    Yang, Lin; Tan, Xiaohua; Wan, Xiang; Chen, Lei; Jin, Dazhi; Qian, Muyang; Li, Gongping

    2014-04-28

    Two Stark broadening parameters including FWHM (full width at half maximum) and FWHA (full width at half area) of isotope hydrogen alpha lines are simultaneously introduced to determine the electron density of a pulsed vacuum arc jet. To estimate the gas temperature, the rotational temperature of the C{sub 2} Swan system is fit to 2500 ± 100 K. A modified Boltzmann-plot method with b{sub i}-factor is introduced to determine the modified electron temperature. The comparison between results of atomic and ionic lines indicates the jet is in partial local thermodynamic equilibrium and the electron temperature is close to 13 000 ± 400 K. Based on the computational results of Gig-Card calculation, a simple and precise interpolation algorithm for the discrete-points tables can be constructed to obtain the traditional n{sub e}-T{sub e} diagnostic maps of two Stark broadening parameters. The results from FWHA formula by the direct use of FWHM = FWHA and these from the diagnostic map are different. It can be attributed to the imprecise FWHA formula form and the deviation between FWHM and FWHA. The variation of the reduced mass pair due to the non-equilibrium effect contributes to the difference of the results derived from two hydrogen isotope alpha lines. Based on the Stark broadening analysis in this work, a corrected method is set up to determine n{sub e} of (1.10 ± 0.08) × 10{sup 21} m{sup −3}, the reference reduced mass μ{sub 0} pair of (3.30 ± 0.82 and 1.65 ± 0.41), and the ion kinetic temperature of 7900 ± 1800 K.

  10. SAR investigations of glaciers in northwestern North America

    NASA Technical Reports Server (NTRS)

    Lingle, Craig S.; Harrison, William D.

    1995-01-01

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

  11. Glaciers of North America - Glaciers of Alaska

    USGS Publications Warehouse

    Molnia, Bruce F.

    2008-01-01

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

  12. Glaciers of South America

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1998-01-01

    Landsat images, together with maps and aerial photographs, have been used to produce glacier inventories, define glacier locations, and study glacier dynamics in the countries of South America, along with the Andes Mountains. In Venezuela, Colombia, Ecuador, and Bolivia, the small glaciers have been undergoing extensive glacier recession since the late 1800's. Glacier-related hazards (outburst floods, mud flows, and debris avalanches) occur in Colombia, in Ecuador, and associated with the more extensive (2,600 km2) glaciers of Peru. The largest area of glacier ice is found in Argentina and Chile, including the northern Patagonian ice field (about 4,200 km2) and the southern Patagonian ice field (about 13,000 km2), the largest glacier in the Southern Hemisphere outside Antarctica.

  13. Glaciers of Europe

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1993-01-01

    ALPS: AUSTRIAN: An overview is provided on the occurrence of the glaciers in the Eastern Alps of Austria and on the climatic conditions in this area, Historical documents on the glaciers have been available since the Middle Ages. Special glaciological observations and topographic surveys of individual glaciers were initiated as early as 1846. Recent data in an inventory based on aerial photographs taken in 1969 show 925 glaciers in the Austrian Alps with a total area of 542 square kilometers. Present research topics include studies of mass and energy balance, relations of glaciers and climate, physical glaciology, a complete inventory of the glaciers, and testing of remote sensing methods. The location of the glacier areas is shown on Landsat multispectral scanner images; the improved capabilities of the Landsat thematic mapper are illustrated with an example from the Oztaler Alpen group. ALPS: SWISS: According to a glacier inventory published in 1976, which is based on aerial photography of 1973, there are 1,828 glacier units in the Swiss Alps that cover a total area of 1fl42 square kilometers. The Rhonegletscher, currently the ninth largest in the country, was one of the first to be studied in detail. Its surface has been surveyed repeatedly; velocity profiles were measured, and the fluctuations of its terminus were mapped and recorded from 1874 to 1914. Recent research on the glacier has included climatological, hydrological, and massbalance studies. Glaciological research has been conducted on various other glaciers in Switzerland concerning glacier hydrology, glacier hazards, fluctuations of glacier termini, ice mechanics, ice cores, and mass balance. Good maps are available showing the extent of glaciers from the latter decades of the 19th century. More recently, the entire country has been mapped at scales of 1:25,000, 1:50,000, 1:100,000, 1:200,000, and 1:500,000. The 1:25,000-scale series very accurately represents the glaciers as well as locates

  14. Freezing Level Height in the Western Equatorial Pacific over the Last 200 Years: Glacier Evidence from Mt. Jayawijaya, Papua Province, Indonesia

    NASA Astrophysics Data System (ADS)

    Prentice, M. L.; Hope, G.; Susanto, R. D.

    2012-12-01

    The temperature and moisture history of the equatorial lower free troposphere over the last few hundred years is important for evaluating and predicting global warming. New evidence constrains the freezing level height (FLH) in the western equatorial Pacific over the last 200 years using the snow-line altitude (ELA) on glaciers at elevations of 4000 to 5000 m (600 hPa) on Mt. Jayawijaya, Papua Province, Indonesia (4oS, 136oE). The ELA of these wet tropical glaciers is closely coupled to the mean annual 0oC isotherm. The areal recession of the Jayawijaya glaciers continued to May 2011 by which time 95 percent of the ice cover that existed between 1936 and 1942 disappeared; 1 km2 remained. For the periods 2000-2006 and 2006-2011, the ELA was above 4950 m above sea level (asl). Revised reconstructions of the glaciers from 1936 to 1942 based on aerial photographs indicate that the concurrent ELA was at 4610 ± 10 m asl. The glaciers were interpreted to be in mass balance equilibrium between 1936 and 1942 because no appreciable areal change was detected and the glacier fronts had steep profiles. We assumed an accumulation area ratio of 0.8, typical of tropical glaciers. Extensive, fresh moraines downvalley from the 1936 ice margin indicate that the glaciers were more extensive and had lower ELAs in recent centuries. We define the most extensive, fresh moraine system of the Jayawijaya glaciers as representing the local Little Ice Age (LLIA) maximum and, following previous work, assign its age as ~1850. Our reconstruction of the Jayawijaya glaciers at the LLIA maximum based on moraines and current topographic divides indicates that they covered an area of 30 km2, considerably more than previous estimates. A concurrent ELA at ~4450 m asl was calculated assuming an accumulation area ratio of 0.8. The moraines indicate that the glaciers were in equilibrium. Taken together, glacier ELAs on Mt. Jayawijaya, approximating the FLH, have risen 500 m since the LLIA maximum. The

  15. Heterogeneous response of debris-covered and debris-free glaciers to climate change in Langtang Himal determined by geodetic mass balance measurements

    NASA Astrophysics Data System (ADS)

    Ragettli, Silvan; Bolch, Tobias; Pellicciotti, Francesca

    2016-04-01

    thinning mostly accelerated in recent years, while the nearly stagnant areas near the terminus show constant or decreasing thinning rates. The highest thinning rates and the strongest increase in thinning rates can be associated to areas with a large presence of supraglacial cliffs and lakes. However, the mean thinning rates per altitudinal band of such areas of maximal thinning are still 20-40% lower than thinning rates of debris-free glacier area at the same elevation. A strong melt reducing effect of supraglacial debris seems therefore indisputable. The mass balance of all glaciers during all studied periods is negative (on average 2006-2015: -0.60±0.34 m/a), but while for some glaciers the mean annual mass loss between 2006 and 2015 doubled with respect to to the period 1974-2006, for others we do not identify accelerated mass loss. The response of debris-free glaciers seems to strongly depend on glacier hypsometry: almost balanced mass budgets in recent years can be associated to high accumulation area ratios, although thinning of debris-free glacier area below the equilibrium line altitude is accelerating rapidly. We conclude that trends of glacier mass loss rates in this part of the Himalaya cannot be generalized, neither for debris-covered nor for debris-free glaciers.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  17. Terrestrial Laser Scanning as a Tool to Evaluate the Quality of Interpolated Ablation Stakes Data and the Uncertainty of an Arctic Glacier Mass Balance

    NASA Astrophysics Data System (ADS)

    Tolle, F.; Prokop, A.; Bernard, É.; Friedt, J. M.; Griselin, M.

    2015-12-01

    A network of ablation stakes has been maintained on the Austre Lovén glacier (Svalbard) over the last 8 years. Data collected thanks to this in-situ equipment served as a basis to obtain annual mass balance values. Interpolation methods were used to generalize the values measured at the stakes to the entire surface of the glacier (4.5km²). This allows for a precise quantification of the glacier's dynamics including areas where data are not easy to collect directly on the field such as the glacier snout or steep accumulation zones. Over the last 4 years, repeat terrestrial laser scanning (TLS) surveys have been undertaken twice a year. Scans were acquired at the end of the expected annual snow maximum (April) and near the end of the melting season (August). Even though these scans do not cover the entire glacier, they yield high density point clouds of the glacier surface in crucial areas. The glacier terminus, the equilibrium line area and accumulation cirques were among the zones specifically scanned. The comparison of mass balance results derived from ablation stakes data and digital elevation models (DEMs) derived from TLS measurements allowed for an assessment of the quality and uncertainty of these methods. Local variability proves higher than initially expected, especially in key areas of the glacier having the greatest impact on the global balance. Even though the Austre Lovén glacier displays a seemingly smooth and homogeneous surface, local variations have to be taken into consideration. The potential consequences of this variability on the annual mass balance will be explored.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  19. The complex behavior of the Cordilleran Ice Sheet and mountain glaciers to abrupt climate change during the latest Pleistocene

    NASA Astrophysics Data System (ADS)

    Menounos, Brian; Goehring, Brent; Osborn, Gerald; Clarke, Garry K. C.; Ward, Brent; Margold, Martin; Bond, Jeff; Clague, John J.; Lakeman, Tom; Schaefer, Joerg; Koch, Joe; Gosse, John; Stroeven, Arjen P.; Seguinot, Julien; Heyman, Jakob; Fulton, Robert

    2014-05-01

    Surficial mapping and more than 70 radiometric ages 10Be, 14C] constrain the evolution of the Cordilleran Ice Sheet (CIS) and associated mountain glaciers in western Canada during the latest Pleistocene. Our data suggest that: i) there is widespread evidence for the Younger Dryas (YD) throughout the mountains of western Canada; ii) late Pleistocene climate reconstructions based solely on alpine moraines may be misleading in regions with decaying ice sheets; iii) extensive interfluves in some mountain regions were ice-free between 16 ka and 13 ka (kilo calibrated yrs BP). Initial decay of the CIS from its maximum extent around 16 ka was likely due to a combination of climatic (surface melting) and dynamical factors. Climate amelioration during the Bølling-Allerød Warm Period [14.7-12.9 ka], likely the cause for the major phase of CIS decay, resulted in ice sheet equilibrium line altitudes (ELAs) ranging from 2500 m asl in southern BC to around 2000 m asl along the BC-Yukon border. Hence, before the onset of the Younger Dryas (YD) Cold Period [12.9-11.7 ka], the ice sheet shrank and became a labyrinth of individual and coalescing valley glaciers fed by major accumulation zones centered on the Coast Mountains and other high ranges of NW Canada. The response of remnant ice and cirque glaciers to the YD climate deterioration was highly variable. In some cases, small glaciers (0.5-2 km2) built YD moraines that were only hundreds of meters beyond those constructed during the Little Ice Age (LIA) [0.30-0.15 ka]. Our dating also reveals that much larger glaciers persisted in nearby valleys that lie hundreds of meters below the cirques. Hence, we infer that many cirques were completely deglaciated prior the YD, in contrast to low-lying valleys where ice sheet remnants persisted. Glaciers also advanced in north-central British Columbia during the YD, but here glaciers constructed large terminal and lateral moraines. In the Cassiar and northern Coast mountains, for example

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

    USGS Publications Warehouse

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

    1998-01-01

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

  1. Pine Island Glacier

    Atmospheric Science Data Center

    2013-04-16

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  3. Changes in ice dynamics of Totten Glacier, East Antarctica in the past two decades

    NASA Astrophysics Data System (ADS)

    Li, X.; Rignot, E. J.; Mouginot, J.; Morlighem, M.; Scheuchl, B.

    2015-12-01

    Totten Glacier, East Antarctica, a glacier that holds a 3.9 m sea level change equivalent, has thinned and lost mass for decades. Observed thinning by satellite altimeters is concentrated in areas of fast flow, hence is probably of dynamic origin. In this study, we derive time series of ice velocity from Landsat and interferometric (InSAR) data (ERS-1/2, RADARSAT-1, ALOS PALSAR, TanDEM/TerraSAR-X and COSMO-Skymed) for the past two decades. We find significant speed-up in ice velocity, especially in 2002-2007, followed by a period of slow decrease in 2010-2014. Comparing the results with RACMO2 surface mass balance suggests that the glacier mass balance was already negative in 1996 and became more negative into the 2000s. To examine the stability of the glacier, we develop high-resolution topographies of the ice surface and ice bottom using NASA Operation IceBridge data, TanDEM-X data, InSAR ice velocities and a mass conservation method. The results reveal a 1,500-2,300 m deep grounding zone that extends 15 km inland along two prominent side lobes grounded only 15-50 m above hydrostatic equilibrium, or ice plain. At the glacier center, we detect a 1-3±0.12 km retreat of the grounding line by comparing differential InSAR data acquired 17 years apart. The retreat is asymmetrical along the two lobes, but consistently indicates a total thinning of 12 m from 1996 to 2013. On the ice plain, the glacier is prone to rapid retreat around a region about 7 km long, but inland the bed elevation rises. Sustained thinning will cause further retreat and probably speed up, but will not be conducive to a marine- instability. The ultimate cause of the changes is not known, but probably of oceanic origin, with most changes taking place in 2002-2007.

  4. THE DIAGNOSTIC O VI ABSORPTION LINE IN DIFFUSE PLASMAS: COMPARISON OF NON-EQUILIBRIUM IONIZATION STRUCTURE SIMULATIONS TO FUSE DATA

    SciTech Connect

    De Avillez, Miguel A.; Breitschwerdt, Dieter

    2012-12-20

    The nature of the interstellar O VI in the Galactic disk is studied by means of a multi-fluid hydrodynamical approximation, tracing the detailed time-dependent evolution of the ionization structure of the plasma. Our focus is to explore the signature of any non-equilibrium ionization condition present in the interstellar medium using the diagnostic O VI ion. A detailed comparison between the simulations and FUSE data is carried out by taking lines of sight (LOS) measurements through the simulated Galactic disk, covering an extent of 4 kpc from different vantage points. The simulation results bear a striking resemblance with the observations: (1) the N(O VI) distribution with distance and angle fall within the minimum and maximum values of the FUSE data; (2) the column density dispersion with distance is constant for all the LOS, showing a mild decrease at large distances; (3) O VI has a clumpy distribution along the LOS; and (4) the time-averaged midplane density for distances >400 pc has a value of (1.3-1.4) Multiplication-Sign 10{sup -8} cm{sup -3}. The highest concentration of O VI by mass occurs in the thermally stable (10{sup 3.9} K < T {<=} 10{sup 4.2} K; 20%) and unstable (10{sup 4.2} K < T < 10{sup 5} K; 50%) regimes, both well below its peak temperature in collisional ionization equilibrium, with the corresponding volume filling factors oscillating with time between 8%-20% and 4%-5%, respectively. These results may also be relevant for intergalactic metal absorption systems at high redshifts.

  5. 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.

  6. 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

  7. North Cascade Glacier Annual Mass Balance Record Analysis 1984-2013

    NASA Astrophysics Data System (ADS)

    Pelto, M. S.

    2014-12-01

    The North Cascade Glacier Climate Project (NCGCP) was founded in 1983 to monitor 10 glaciers throughout the range and identify their response to climate change. The annual observations include mass balance, terminus behavior, glacier surface area and accumulation area ratio (AAR). Annual mass balance (Ba) measurements have been continued on the 8 original glaciers that still exist. Two glaciers have disappeared: the Lewis Glacier and Spider Glacier. In 1990, Easton Glacier and Sholes Glacier were added to the annual balance program to offset the loss. One other glacier Foss Glacier has declined to the extent that continued measurement will likely not be possible. Here we examine the 30 year long Ba time series from this project. All of the data have been reported to the World Glacier Monitoring Service (WGMS). This comparatively long record from glaciers in one region conducted by the same research program using the same methods offers some useful comparative data. Degree day factors for melt of 4.3 mm w.e.°C-1d-1 for snow and 6.6 mm w.e.°C-1d-1 for ice has been determined from 412 days of ablation observation. The variation in the AAR for equilibrium Ba is small ranging from 60 to 67. The mean annual balance of the glaciers from 1984-2013 is -0.45 ma-1, ranging from -0.31 to -0.57 ma-1 for individual glacier's. The correlation coefficient of Ba is above 0.80 between all glaciers including the USGS benchmark glacier, South Cascade Glacier. This indicates that the response is to regional climate change, not local factors. The mean annual balance of -0.45 ma-1 is close to the WGMS global average for this period -0.50 ma-1. The cumulative loss of 13.5 m w.e. and 15 m of ice thickness represents more than 20% of the volume of the glaciers.

  8. Holocene dynamics of the Rhone Glacier, Switzerland, deduced from ice flow models and cosmogenic nuclides

    NASA Astrophysics Data System (ADS)

    Goehring, Brent M.; Vacco, David A.; Alley, Richard B.; Schaefer, Joerg M.

    2012-10-01

    We describe efforts to model the Holocene extent of the Rhone Glacier, Switzerland, using four paleoclimate records as templates for paleo-equilibrium line altitude to identify candidate driving mechanisms of glaciers in the Alps. We evaluate the success of each paleoclimate template by comparing cosmogenic 10Be and 14C concentrations in pro-glacial bedrock derived from modeled glacier configurations to measured values. An adequate fit can be obtained using mean summer insolation for 46.5°N. However, use of the Dongee Cave, China, speleothem record yields the best fit by accounting for both sub-millennial (e.g. Little Ice Age and Medieval Warm Period) and multi-millennial climate variations (summer insolation). Our result indicates that glaciers in the Alps primarily responded to changes in insolation during the Holocene were smaller than today during the early Holocene when insolation was relatively high, and became larger during the mid to late Holocene. Superimposed on the first-order insolation response were shorter, sometimes large amplitude, length changes in response to short-lived climate events such as the Medieval Warm Period and the LIA.

  9. Shifting westerlies and precipitation patterns during the Late Pleistocene in southern Africa determined using glacier reconstruction and mass balance modelling

    NASA Astrophysics Data System (ADS)

    Mills, Stephanie C.; Grab, Stefan W.; Rea, Brice R.; Carr, Simon J.; Farrow, Aidan

    2012-11-01

    South Africa experiences a range of different climatic regimes and is thus an ideal region to investigate Late Pleistocene environmental and climate change. However, detailed quantifiable palaeoclimate data are sparse in the region. In particular, reliable palaeoclimatic data are essential to resolve ongoing controversies regarding temperature depression and moisture availability during glacial periods in the sub-continent. Small glaciers close to the glaciation threshold are highly sensitive to changes in temperature and precipitation and are therefore ideal indicators of past climatic conditions during their existence. This paper derives some of the first quantitative data on Last Glacial Maximum (LGM) palaeoprecipitation in southern Africa, based on glacier reconstruction and mass balance modelling for the Lesotho Highlands. The reconstruction of former glaciers and their dynamics enables the determination of glacier viability under specific climatic envelopes. Glacier reconstructions at five sites in the Lesotho Highlands yield palaeoglaciers with Equilibrium Line Altitudes (ELAs) ranging from 3095 to 3298 m a.s.l., and reconstructed steady-state mass balance and flow dynamics are comparable with modern analogues. Topoclimatic factors are investigated, with temperature-radiation-index modelling indicating that topographic shading was an important factor determining the existence of small glaciers in this region. The occurrence of glaciation in the Drakensberg during the LGM suggests a potential increase in precipitation and change in its seasonality. Such trends are likely associated with an increased frequency of westerly wave (cold front) disturbances due to the northward shift of pressure belts, which would also increase precipitation as snow at higher altitudes. The application of a high resolution climate model (HadAM3h) to test this, displays a change in the seasonal timing of precipitation during the Last Glacial cycle, with a decrease in precipitation

  10. Pine Island Glacier, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

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

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

  11. 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

  12. Global Trends in Glacial Cirque Floor Altitudes and Their Relationships with Climate, Equilibrium Line Altitudes, and Mountain Range Heights

    NASA Astrophysics Data System (ADS)

    Mitchell, S. G.; Humphries, E.

    2013-12-01

    Glacial erosion at the base of cirque headwalls and the creation of threshold slopes above cirque floors may contribute to the 'glacial buzzsaw' effect in limiting the altitude of some mountain ranges. Since glacial extent and therefore glacial erosion rate depends on the equilibrium line altitude (ELA) of a region, the altitude of cirque formation should be a function of the ELA. Several regional studies have shown that cirque floors form at an altitude approximating average Quaternary ELAs in some mountain ranges, but a global correlation has not yet been demonstrated. We examined the correlation between cirque altitudes and global ELA trends by compiling existing and new cirque altitude and morphometry data from > 30 mountain ranges at a wide range of latitudes. Where available, we calculate or present the average cirque altitude, relief, and latitude. We compared these altitudes to both the global East Pacific ELA and local ELAs where available. For the locations analyzed, the majority of average cirque altitudes fall between the Eastern Pacific modern and LGM ELAs, and mountain range height is typically limited to < 600 m above that altitude. This evidence supports the hypothesis that cirque formation is dependent upon the ELA, and that cirques likely form as a result of average, rather than extreme, glacial conditions. Furthermore, the correlation between cirque altitude and ELA, along with the restricted window of relief, implies that cirque formation is a factor in limiting peak altitude in ranges that rise above the ELA.

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

    SciTech Connect

    Mernild, Sebastian Haugard; Liston, Glen

    2009-01-01

    {sup -1}. The annual glacier loss for the two simulations was 50.7 x 10{sup 6} m{sup 3} y{sup -1} and 64.4 x 10{sup 6} m{sup 3} y{sup -1} for all glaciers - a difference of {approx}21%. The average equilibrium line altitude (ELA) for all glaciers in the simulation domain was located at 875 m a.s.l. and at 900 m a.s.l. for simulations with or without inversion routines, respectively.

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

  15. 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

  16. Afghanistan Glacier Diminution

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  19. Analysis of meteorological data and the surface energy balance of Keqicar Glacier, Tien Shan, China

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Liu, S.; Fujita, K.; Han, H.; Li, J.

    2009-04-01

    Northwestern China currently experiences a climate change with fundamental consequences for the hydrological cycle. In the strongly arid region where water resources are essential for agriculture and food production, glaciers represent important water resources, contributing significantly to streamflow. The debris is an important glaciological feature of the region and has major impact on melt rates. It is essential to understand and quantify the interaction of climate and sub-debris melt in order to assess the current situation and to predict future water yield. Note that the surface energy balance determines glacier melt. However, little is known about the variability characteristics of the surface energy fluxes in this region. For this reason, we set up two automatic weather stuation (AWSs) in the ablation area of Keqicar Glacier. Keqicar Glacier is located in the Tarim River basin (largest inland river basin in China), southwestern Tien Shan, China. It is a representative debris-covered glacier with a length of 26.0 km and a total surface area of 83.6 km2. The thickness of the debris layer varies from 0.0 to 2.50 m in general. In some places large rocks are piled up to several meters. In this study, we report on analysis of meteorological data for the period 1 July-13 September 2003, from two automatic weather stations, aimed at studying the relationship between climate and ablation. One station is located on the lower part of the ablation area where the glacier is covered by debris layer, and the other near the equilibrium line altitude (ELA). All sensors were sampled every 10 seconds, and data were stored as hourly averages. The stations were visited regularly for maintenance at two weeks intervals depending on the weather conditions and location of the AWS. A total of 17 ablation stakes were drilled into the glacier at different elevations to monitor glacier melt during the study period. Readings were taken regularly in connection with AWS maintenance. The

  20. Temperature index modeling of the Kahiltna Glacier: Comparison to multiple field and geodetic mass balance datasets

    NASA Astrophysics Data System (ADS)

    Young, Joanna C.

    Glaciers of Alaska, USA, and Northwestern Canada are shedding mass at one of the highest rates of any mountain glacier system, with significant impact at the global and local scales. Despite advances in satellite and airborne technologies, fully characterizing the temporal evolution of glacier mass change in individual watersheds remains a challenge. Temperature index modeling is an approach that can be used to expand on sparse ground observations, and that can help bridge the gap between regional and individual watershed estimates of the time series of glacier mass change. Here we present a study on temperature index modeling of glacier-wide mass balance for the large Kahiltna Glacier (502 km2, 270 to 6100 m in elevation) in the Central Alaska Range, using a combination of ground observations and past climate data products. We reproduce mass changes from 1991 to 2011, and assess model performance by comparing our results to several field and remote sensing datasets. First, we compare our results to a 20-year record of mass balance measurements at a National Park Service index site at the glacier's equilibrium line altitude. We find low correlation between index site measurements and modeled glacier-wide balances (R2 = 0.24), indicating that the index site may not be representative of the glacier-wide mass balance regime. We compare next to glacier-wide mass balances derived from airborne laser altimetry, to assess the model's long-term mass change estimates. We find disagreement between the mean annual balances for 1995 to 2010 (-0.95 +/-0.49 m w.e. yr --1 from the model versus -0.69 +0.07/-0.08 m w.e. yr --1 from laser altimetry). To validate the laser altimetry methods, we then compare estimates from 1951 to 2011 from laser altimetry and digital elevation model differencing, finding close agreement (-0.48 +0.08/-0.09 m w.e. yr--1 and -0.41 +/-0.26 m w.e. yr--1 , respectively), and lending strength to the laser altimetry centerline extrapolation techniques. We

  1. 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.

  2. Holocene glacier history from alpine speleothems, Milchbach cave, Switzerland

    NASA Astrophysics Data System (ADS)

    Luetscher, M.; Hoffmann, D. L.; Frisia, S.; Spötl, C.

    2011-02-01

    Mountain glaciers and their sediments are prominent witnesses of climate change, responding sensitively to even small modifications in meteorological parameters. Even in such a classical and thoroughly studied area as the European Alps the record of Holocene glacier mass-balance is only incompletely known. Here we explore a novel and continuous archive of glacier fluctuations in a cave system adjacent to the Upper Grindelwald Glacier in the Swiss Alps. Milchbach cave became partly ice-free only recently and hosts Holocene speleothems. Four coeval stalagmites show consistent petrographic and stable isotopic changes between 9.2 and 2.0 ka which can be tied to abrupt modifications in the cave environment as a result of the closing and opening of multiple cave entrances by the waxing and waning of the nearby glacier. During periods of Holocene glacier advances, columnar calcite fabric is characterized by δ18O values of about -8.0‰ indicative of speleothem growth under quasi-equilibrium conditions, i.e. little affected by kinetic effect related to forced degassing or biological processes. In contrast, fabrics formed during periods of glacier minima are typical of bacterially mediated calcite precipitation within caves overlain by an alpine soil cover. Moreover, δ18O values of the bacterially mediated calcite fabrics are consistent with a ventilated cave system fostering kinetic fractionation. These data suggest that glacier retreats occurred repeatedly before 5.8 ka, and that the amplitudes of glacier retreats became substantially smaller afterwards. Our reconstruction of the Upper Grindelwald Glacier fluctuations agrees well with paleoglaciological studies from other sites in the Alps and provides a higher temporal resolution compared to traditional analyses of peat and wood remains found in glacier forefields.

  3. The thickness of glaciers

    NASA Astrophysics Data System (ADS)

    Faraoni, Valerio; Vokey, Marshall W.

    2015-09-01

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

  4. Climates during Late Quaternary glacier advances: glacier-climate modeling in the Yingpu Valley, eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Xu, Xiangke

    2014-10-01

    The Last Glacial Maximum (LGM) featured a major cooling of Earth's climate, after which the climate evolved in the largest reconfiguration of the past 100 ka. Despite its significance, full understanding of the climate history during and since the LGM is still lacking on the eastern Tibetan Plateau. Recent improvements in understanding glacial extents and chronologies in the Yingpu Valley, eastern Tibetan Plateau present an opportunity to estimate the glacial climatic conditions during and since the LGM. Using a relatively new glacier-climate model, this study reconstructs glacier advances in the Yingpu Valley and quantifies the related climate conditions during the LGM, Lateglacial, and Late Holocene glacial stages. The model results show that the Yingpu Valley contained ice volumes of ˜1.65 km3, 1.03 km3, and 0.29 km3 with equilibrium line altitude (ELA) lowering values of ˜500 m, ˜410 m, and ˜150 m in the three successive glacial stages, respectively. By examining other independent paleoclimatic reconstructions, it is concluded that the temperature decreased by 4.0-5.9 °C, 3.4-3.7 °C, 0.3-0.6 °C with the precipitation amounts being 40-80%, 80-100%, and 100-110% of modern values during the LGM, Lateglacial, and Late Holocene glacial stages, respectively. The climate estimates for the three glacial stages are generally in agreement with other climatic proxy records on the Tibetan Plateau and atmospheric circulation modeling results.

  5. 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

  6. 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

  7. 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.

  8. Quantitative Evaluation of Landsat 7 ETM+ SLC-off Images for Surface Velocity Estimation of Mountain Glaciers

    NASA Astrophysics Data System (ADS)

    Jiang, L.; Sun, Y.; Liu, L.; Wang, S.; Wang, H.

    2014-12-01

    In many cases the Landsat mission series (Landsat 1-5, 7 and 8) provide our only detailed and consistent data source for mapping the global glacier changes over the last 40 years. However, the scan-line corrector (SLC) of the ETM+ sensor on board Landsat 7 permanently failed, resulting in wedge-shaped data gaps in SLC-off images that caused roughly 22% of the pixels to be missed. The SLC failure has left a serious problem for the glacial applications of ETM+ data, particularly for monitoring long-term glacier dynamics in High Asian Mountain where has few available data due to the frequently cloudy covers. This study aims to evaluate the potential of the Landsat 7 SLC-off images in deriving surface velocities of mountain glaciers. A pair of SLC-off images over the Siachen glacier acquired in Aug 2009 and 2010 was used for this purpose. Firstly, two typical filling-gap methods, the localized linear histogram match (LLHM) and the weighted liner regression (WLR), were utilized to recover the mentioned SLC-off images. Subsequently these recovered pairs were applied for deriving glacier-surface velocities with the COSI-Corr feature tracking procedure. Finally, the glacier velocity results were quantitatively compared with that of a pair of Landsat-5 TM images acquired nearly at the same time with the SLC-off pair. Our results show that (1) the WLR method achieves a better performance of gap recovering than the LLHM method, (2) the surface velocities estimated with the recovered SLC-off images are highly agreement with those of the TM images, and (3) the annual mean velocity of the Siachen glacier is approximately 70 m/yr between 2009 and 2010 with a maximum of 280 m/yr close to the glacial equilibrium line that are similar with the results in previous studies. Therefore, if a suitable filling-gap method is adopted, e.g. the WLR method, it is highly feasible that the ETM+ SLC-off data can be utilized to estimate the surface velocities of mountain glaciers.

  9. Holocene cirque glacier activity in Rondane, southern Norway

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  10. Holocene glacier variability and Neoglacial hydroclimate at Ålfotbreen, western Norway

    NASA Astrophysics Data System (ADS)

    Gjerde, Marthe; Bakke, Jostein; Vasskog, Kristian; Nesje, Atle; Hormes, Anne

    2016-02-01

    Glaciers and small ice caps respond rapidly to climate perturbations (mainly winter precipitation, and summer temperature), and the mass-balance of glaciers located in western Norway is governed mainly by winter precipitation (Pw). Records of past Pw can offer important insight into long-term changes in atmospheric circulation, but few proxies are able to accurately capture winter climate variations in Scandinavia. Reconstructions of equilibrium-line-altitude (ELA) variations from glaciers that are sensitive to changes in Pw therefore provide a unique opportunity to quantify past winter climate in this region. Here we present a new, Holocene glacier activity reconstruction for the maritime ice cap Ålfotbreen in western Norway, based on investigations of distal glacier-fed lake sediments and modern mass balance measurements (1963-2010). Several lake sediment cores have been subject to a suite of laboratory analyses, including measurements of physical parameters such as dry bulk density (DBD) and loss-on-ignition (LOI), geochemistry (XRF), surface magnetic susceptibility (MS), and grain size distribution, to identify glacial sedimentation in the lake. Both radiocarbon (AMS 14C) and 210Pb dating were applied to establish age-depth relationships in the sediment cores. A novel approach was used to calibrate the sedimentary record against a simple ELA model, which allowed reconstruction of continuous ELA changes for Ålfotbreen during the Neoglacial (when Ålfotbreen was present, i.e. the last ∼1400 years). Furthermore, the resulting ELA variations were combined with an independent summer temperature record to calculate Neoglacial Pw using the 'Liestøl equation'. The resulting Pw record is of higher resolution than previous reconstructions from glaciers in Norway and shows the potential of glacier records to provide high-resolution data reflecting past variations in hydroclimate. Complete deglaciation of the Ålfotbreen occurred ∼9700 cal yr BP, and the ice cap was

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

    PubMed Central

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

    2015-01-01

    Abstract During summer 2013 we installed a network of 19 GPS nodes at the ungrounded margin of Helheim Glacier in southeast Greenland together with three cameras to study iceberg calving mechanisms. The network collected data at rates up to every 7 s and was designed to be robust to loss of nodes as the glacier calved. Data collection covered 55 days, and many nodes survived in locations right at the glacier front to the time of iceberg calving. The observations included a number of significant calving events, and as a consequence the glacier retreated ~1.5 km. The data provide real‐time, high‐frequency observations in unprecedented proximity to the calving front. The glacier calved by a process of buoyancy‐force‐induced crevassing in which the ice downglacier of flexion zones rotates upward because it is out of buoyant equilibrium. Calving then occurs back to the flexion zone. This calving process provides a compelling and complete explanation for the data. Tracking of oblique camera images allows identification and characterisation of the flexion zones and their propagation downglacier. Interpretation of the GPS data and camera data in combination allows us to place constraints on the height of the basal cavity that forms beneath the rotating ice downglacier of the flexion zone before calving. The flexion zones are probably formed by the exploitation of basal crevasses, and theoretical considerations suggest that their propagation is strongly enhanced when the glacier base is deeper than buoyant equilibrium. Thus, this calving mechanism is likely to dominate whenever such geometry occurs and is of increasing importance in Greenland. PMID:27570721

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

    PubMed Central

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

    2015-01-01

    Abstract During summer 2013 we installed a network of 19 GPS nodes at the ungrounded margin of Helheim Glacier in southeast Greenland together with three cameras to study iceberg calving mechanisms. The network collected data at rates up to every 7 s and was designed to be robust to loss of nodes as the glacier calved. Data collection covered 55 days, and many nodes survived in locations right at the glacier front to the time of iceberg calving. The observations included a number of significant calving events, and as a consequence the glacier retreated ~1.5 km. The data provide real‐time, high‐frequency observations in unprecedented proximity to the calving front. The glacier calved by a process of buoyancy‐force‐induced crevassing in which the ice downglacier of flexion zones rotates upward because it is out of buoyant equilibrium. Calving then occurs back to the flexion zone. This calving process provides a compelling and complete explanation for the data. Tracking of oblique camera images allows identification and characterisation of the flexion zones and their propagation downglacier. Interpretation of the GPS data and camera data in combination allows us to place constraints on the height of the basal cavity that forms beneath the rotating ice downglacier of the flexion zone before calving. The flexion zones are probably formed by the exploitation of basal crevasses, and theoretical considerations suggest that their propagation is strongly enhanced when the glacier base is deeper than buoyant equilibrium. Thus, this calving mechanism is likely to dominate whenever such geometry occurs and is of increasing importance in Greenland.

  13. Ablation of Martian glaciers

    NASA Technical Reports Server (NTRS)

    Moore, Henry J.; Davis, Philip A.

    1987-01-01

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

  14. Investigation of thermodynamic equilibrium in laser-induced aluminum plasma using the H{sub α} line profiles and Thomson scattering spectra

    SciTech Connect

    Cvejić, M. E-mail: krzysztof.dzierzega@uj.edu.pl; Dzierżęga, K. E-mail: krzysztof.dzierzega@uj.edu.pl; Pięta, T.

    2015-07-13

    We have studied isothermal equilibrium in the laser-induced plasma from aluminum pellets in argon at pressure of 200 mbar by using a method which combines the standard laser Thomson scattering and analysis of the H{sub α}, Stark-broadened, line profiles. Plasma was created using 4.5 ns, 4 mJ pulses from a Nd:YAG laser at 1064 nm. While electron density and temperature were determined from the electron feature of Thomson scattering spectra, the heavy particle temperature was obtained from the H{sub α} full profile applying computer simulation including ion-dynamical effects. We have found strong imbalance between these two temperatures during entire plasma evolution which indicates its non-isothermal character. At the same time, according to the McWhirter criterion, the electron density was high enough to establish plasma in local thermodynamic equilibrium.

  15. 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.

  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. 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

  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. Controls of air temperature variability over an Alpine Glacier

    NASA Astrophysics Data System (ADS)

    Shaw, Thomas; Brock, Ben; Ayala, Álvaro; Rutter, Nick

    2016-04-01

    Near surface air temperature (Ta) is one of the most important controls on energy exchange between a glacier surface and the overlying atmosphere. However, not enough detail is known about the controls on Ta across a glacier due to sparse data availability. Recent work has provided insights into variability of Ta along glacier centre-lines in different parts of the world, yet there is still a limited understanding of off-centreline variability in Ta and how best to estimate it from distant off-glacier locations. We present a new dataset of distributed 2m Ta records for the Tsanteleina Glacier in Northwest Italy from July-September, 2015. Data provide detailed information of lateral (across-glacier) and centre-line variations in Ta, with ~20,000 hourly observations from 17 locations. The suitability of different vertical temperature gradients (VTGs) in estimating air temperature is considered under a range of meteorological conditions and from different forcing locations. A key finding is that local VTGs account for a lot of Ta variability under a broad range of climatic conditions. However, across-glacier variability is found to be significant, particularly for high ambient temperatures and for localised topographic depressions. The relationship of spatial Ta patterns with regional-scale reanalysis data and alternative Ta estimation methodologies are also presented. This work improves the knowledge of local scale Ta variations and their importance to melt modelling.

  20. Timing and paleoclimatic significance of Holocene glacier fluctuations in the Cordillera Vilcabamba of southern Peru

    NASA Astrophysics Data System (ADS)

    Licciardi, J. M.; Taggart, J. R.; Schaefer, J. M.; Lund, D. C.

    2009-12-01

    Past fluctuations in climatically sensitive tropical glaciers provide important insight into regional paleoclimatic trends and forcings, but well-dated chronologies are scarce, particularly during the Holocene. We have established precise cosmogenic 10Be surface exposure ages of moraine sequences in the Cordillera Vilcabamba (13°20’S latitude), located in the outer tropics of southern Peru. Results indicate the dominance of two major glacial culminations and associated climatic shifts in the Vilcabamba, including an early Holocene glacial interval and a somewhat less extensive glaciation late in the ‘Little Ice Age’ (LIA) period. Lichenometric measurements on the youngest moraines support the 10Be ages, but uncertainties in the lichen ages arise from the lack of a local lichen growth curve. The Peruvian glacier chronologies differ from a recently-developed New Zealand record but are broadly correlative with well-dated glacial records in Europe, suggesting climate linkages between the tropics and the North Atlantic region. For the latest Holocene, our leading hypothesis is that climate forcings involving southward migration of the Atlantic Intertropical Convergence Zone can explain concurrent glaciations in tropical South America and northern high latitudes, but the influence of other climate drivers such as the El Niño/Southern Oscillation may have also played a role. Estimated differences between equilibrium-line altitudes (ELAs) on modern glaciers and those inferred for expanded latest Holocene glaciers reveal an ELA rise of 165-200 m since the LIA, suggesting that temperatures 1.1-1.3°C cooler than present could have sustained glaciers at their LIA maximum positions if temperature was the only control, and thus providing an upper bound on temperature depression during the LIA. However, further work is required to constrain the likely role of precipitation changes. These new Peruvian glacier chronologies and ELA reconstructions complement ice core and

  1. A non-local thermodynamical equilibrium line formation for neutral and singly ionized titanium in model atmospheres of reference A-K stars

    NASA Astrophysics Data System (ADS)

    Sitnova, T. M.; Mashonkina, L. I.; Ryabchikova, T. A.

    2016-09-01

    We construct a model atom for Ti I-II using more than 3600 measured and predicted energy levels of Ti I and 1800 energy levels of Ti II, and quantum mechanical photoionization cross-sections. Non-local thermodynamical equilibrium (NLTE) line formation for Ti I and Ti II is treated through a wide range of spectral types from A to K, including metal-poor stars with [Fe/H] down to -2.6 dex. NLTE leads to weakened Ti I lines and positive abundance corrections. The magnitude of NLTE corrections is smaller compared to the literature data for FGK atmospheres. NLTE leads to strengthened Ti II lines and negative NLTE abundance corrections. For the first time, we have performed NLTE calculations for Ti I-II in the 6500 ≤ Teff ≤ 13 000 K range. For four A-type stars, we derived in LTE an abundance discrepancy of up to 0.22 dex between Ti I and Ti II, which vanishes in NLTE. For four other A-B stars, with only Ti II lines observed, NLTE leads to a decrease of line-to-line scatter. An efficiency of inelastic Ti I + H I collisions was estimated from an analysis of Ti I and Ti II lines in 17 cool stars with -2.6 ≤ [Fe/H] ≤ 0.0. Consistent NLTE abundances from Ti I and Ti II were obtained by applying classical Drawinian rates for the stars with log g ≥ 4.1, and neglecting inelastic collisions with H I for the very metal-poor (VMP) giant HD 122563. For the VMP turn-off stars ([Fe/H] ≤ -2 and log g ≤ 4.1), we obtained the positive abundance difference Ti I-II already in LTE, which increases in NLTE. Accurate collisional data for Ti I and Ti II are necessary to help solve this problem.

  2. Glaciers of Greenland

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1995-01-01

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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. Influences of Climate Warming and Facility Management on Continuous Permafrost at Matterhorn Glacier Paradise, Zermatt, Swiss Alps.

    NASA Astrophysics Data System (ADS)

    King, Lorenz; Duishonakunov, Murataly; Imbery, Stephan

    2014-05-01

    In many parts of the Alps, hazardous bedrock instabilities occur more often during the past 30 years. In many cases, permafrost degradation played a central role for instability (e.g. in 1987 the Val Pola rockslide, Italy). At other events, the role of permafrost degradation is more complex or unpredictable (e.g. in 1991 the Randa rockfall, Wallis, Swiss Alps). However, instabilities in perennially frozen bedrock may also be provoked by human influence. This is exemplarily shown at touristic facilities in the Alps. Human impact on permafrost is often underestimated, or even carelessly taken into account. The tourist resort Zermatt with more than 1.8 million overnight stays per year is located at 1600 m a.s.l. and is surrounded by high mountain ranges that often reach above 4000 m. The dry and sunny climate results in a high glacier equilibrium line thus leaving space for vast non-glaciated permafrost terrain. Numerous tourist facilities provide excellent logistics and easy access to permafrost sites, and the region is thus especially suitable for permafrost research. The infrastructure erected on permafrost consists of hotels, restaurants and mountain huts, station buildings of railways, funiculars, ski lifts and installations for artificial snowing the ski-runs. Some problems at these constructions due to permafrost degradation are shown. At the Matterhorn Glacier Paradise station at an altitude of 3820 meters, todays MAAT ranges between -6 °C and -8°C. During the construction of a tunnel in 1981 bedrock temperatures were at -12°C. Over the past 30 years, these bedrock temperatures have risen to -3 to -2°C, due to the heat brought into the tunnel by facilities and more than 490,000 visitors per year. In an elevator shaft, the temperature temporarily even rose above freezing point. Several new construction sites in continuous permafrost are described and new research data is presented. Another interesting site for permafrost and ice studies at Matterhorn

  9. Timing of glacier advances and climate in the High Tatra Mountains (Western Carpathians) during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Makos, Michał; Dzierżek, Jan; Nitychoruk, Jerzy; Zreda, Marek

    2014-07-01

    During the Last Glacial Maximum (LGM), long valley glaciers developed on the northern and southern sides of the High Tatra Mountains, Poland and Slovakia. Chlorine-36 exposure dating of moraine boulders suggests two major phases of moraine stabilization, at 26-21 ka (LGM I - maximum) and at 18 ka (LGM II). The dates suggest a significantly earlier maximum advance on the southern side of the range. Reconstructing the geometry of four glaciers in the Sucha Woda, Pańszczyca, Mlynicka and Velicka valleys allowed determining their equilibrium-line altitudes (ELAs) at 1460, 1460, 1650 and 1700 m asl, respectively. Based on a positive degree-day model, the mass balance and climatic parameter anomaly (temperature and precipitation) has been constrained for LGM I advance. Modeling results indicate slightly different conditions between northern and southern slopes. The N-S ELA gradient finds confirmation in slightly higher temperature (at least 1 °C) or lower precipitation (15%) on the south-facing glaciers during LGM I. The precipitation distribution over the High Tatra Mountains indicates potentially different LGM atmospheric circulation than at the present day, with reduced northwesterly inflow and increased southerly and westerly inflows of moist air masses.

  10. Controlling mechanisms of Thwaites Glacier, West Antarctica

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  12. 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.

  13. Snow and Glacier Hydrology

    NASA Astrophysics Data System (ADS)

    Brubaker, Kaye

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

  14. Glaciers of Antarctica

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1988-01-01

    Of all the world?s continents Antarctica is the coldest, the highest, and the least known. It is one and a half times the size of the United States, and on it lies 91 percent (30,109,800 km3) of the estimated volume of all the ice on Earth. Because so little is known about Antarctic glaciers compared with what is known about glaciers in populated countries, satellite imagery represents a great leap forward in the provision of basic data. From the coast of Antarctica to about 81?south latitude, there are 2,514 Landsat nominal scene centers (the fixed geographic position of the intersection of orbital paths and latitudinal rows). If there were cloud-free images for all these geographic centers, only about 520 Landsat images would be needed to provide complete coverage. Because of cloud cover, however, only about 70 percent of the Landsat imaging area, or 55 percent of the continent, is covered by good quality Landsat images. To date, only about 20 percent of Antarctica has been mapped at scales of 1:250,000 or larger, but these maps do include about half of the coastline. The area of Antarctica that could be planimetrically mapped at a scale of 1:250,000 would be tripled if the available Landsat images were used in image map production. This chapter contains brief descriptions and interpretations of features seen in 62 carefully selected Landsat images or image mosaics. Images were chosen on the basis of quality and interest; for this reason they are far from evenly spaced around the continent. Space limitations allow less than 15 percent of the Landsat imaging area of Antarctica to be shown in the illustrations reproduced in this chapter. Unfortunately, a wealth of glaciological and other features of compelling interest is present in the many hundreds of images that could not be included. To help show some important features beyond the limit of Landsat coverage, and as an aid to the interpretation of certain features seen in the images, 38 oblique aerial photographs

  15. Basal conditions and flow dynamics of the Rhine glacier, Alps, at the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Cohen, Denis; Gillet-Chaulet, Fabien; Zwinger, Thomas; Machguth, Horst; Haeberli, Wilfried; Fischer, Urs H.

    2016-04-01

    The safe disposal of radioactive wastes in deep geological repositories requires their containment and isolation for up to one million years. In Switzerland, repositories are planned in the northern Swiss lowlands near the marginal zone of the former Rhine glacier that repeatedly formed two extensive piedmont lobes (the Rhine and Linth lobes) over the Swiss Plateau. Future ice-age conditions may thus impact the repositories due to erosion by glaciers, permafrost conditions, and changes in groundwater fluxes. We use the Last Glacial Maximum (LGM) as a representative future ice-age scenario over northern Switzerland and model the Rhine glacier at the LGM using a full three-dimensional, thermo-mechanical model that solves Stokes flow in ice and the heat equation in both ice and rock. Permafrost in rocks and sediments is implemented using an effective heat capacity formulation. The Rhine glacier at the LGM is one of the best studied paleo-glacier with geomorphic reconstructions of terminal moraines, equilibrium lines, provenance of erratics, till extent and provenance, and evidences of cold vs warm subglacial environments. These data are compared with modeled ice ice thickness, cold vs warm basal condition, and flow paths. Numerical results indicate that LGM modeled ice extent and ice thickness are not fully consistent with geomorphic reconstructions and known climate proxies: ice is either too thick in the accumulation zone or summer temperatures are too cold at the terminus. Simulations with different climate parameters all indicate, however, that the beds of the Rhine and Linth lobes were at the melting temperature except above local topographic highs and along a thin marginal zone. Sliding speed was highest along topographic lows with ice moving at 20 to 80 m a‑1 depending on mass balance gradients. Basal shear stress was low (< 30 kPa). Melt water was probably abundant due to above-freezing temperatures in summer. Thus, melt water was likely routed over large

  16. Basal conditions and flow dynamics of the Rhine glacier, Alps, at the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Cohen, Denis; Gillet-Chaulet, Fabien; Zwinger, Thomas; Machguth, Horst; Haeberli, Wilfried; Fischer, Urs H.

    2016-04-01

    The safe disposal of radioactive wastes in deep geological repositories requires their containment and isolation for up to one million years. In Switzerland, repositories are planned in the northern Swiss lowlands near the marginal zone of the former Rhine glacier that repeatedly formed two extensive piedmont lobes (the Rhine and Linth lobes) over the Swiss Plateau. Future ice-age conditions may thus impact the repositories due to erosion by glaciers, permafrost conditions, and changes in groundwater fluxes. We use the Last Glacial Maximum (LGM) as a representative future ice-age scenario over northern Switzerland and model the Rhine glacier at the LGM using a full three-dimensional, thermo-mechanical model that solves Stokes flow in ice and the heat equation in both ice and rock. Permafrost in rocks and sediments is implemented using an effective heat capacity formulation. The Rhine glacier at the LGM is one of the best studied paleo-glacier with geomorphic reconstructions of terminal moraines, equilibrium lines, provenance of erratics, till extent and provenance, and evidences of cold vs warm subglacial environments. These data are compared with modeled ice ice thickness, cold vs warm basal condition, and flow paths. Numerical results indicate that LGM modeled ice extent and ice thickness are not fully consistent with geomorphic reconstructions and known climate proxies: ice is either too thick in the accumulation zone or summer temperatures are too cold at the terminus. Simulations with different climate parameters all indicate, however, that the beds of the Rhine and Linth lobes were at the melting temperature except above local topographic highs and along a thin marginal zone. Sliding speed was highest along topographic lows with ice moving at 20 to 80 m a-1 depending on mass balance gradients. Basal shear stress was low (< 30 kPa). Melt water was probably abundant due to above-freezing temperatures in summer. Thus, melt water was likely routed over large

  17. Evolution of Glacier Snowline Since the End of the Last Ice Age in New Zealand

    NASA Astrophysics Data System (ADS)

    Kaplan, M. R.; Putnam, A. E.; Schaefer, J. M.; Denton, G. H.; Chinn, T. J.; Barrell, D.; Doughty, A. M.; Mackintosh, A. N.; Andersen, B. G.

    2012-12-01

    An important problem in paleoclimatology is how Southern Hemisphere climate changed since the end of the last ice age. The terrestrial glacier record reflects past snowline (=equilibrium line altitude) variability and is one of the few direct proxies available, in the middle latitudes, of former atmospheric properties. We reconstruct changes in snowline since ~15 ka on the South Island of New Zealand using geomorphologic mapping, 10Be surface-exposure dating, accumulation-area ratio (AAR) methods and numerical modeling. The snowline data are a proxy for the 0°C atmospheric isotherm, which occurs above 1500 m asl in the central Southern Alps, and trends in temperature since ~15 ka. Our findings show that snowline was depressed during the Antarctic Cold Reversal. Subsequently, snowline rose ~100 m during the Younger Dryas stadial in Europe. These late glacial changes appear coherent across the southern middle latitudes. In the early Holocene, snowline was depressed >200 m relative to modern in the Southern Alps. Between 11 ka and 600 years ago, short-term oscillations punctuated a multi-millennia trend of decreasing glacier extent as snowline rose ~100 m. Since ~600 yrs ago, net snowline has continued progressively to rise. The record implies long-term warming in New Zealand since the Late Glacial period. During the Holocene, the lowest snowlines and most extensive glaciers occurred in the early part of the epoch. Snowline reconstruction and numerical modeling allow us to estimate that temperature depression during the Late Glacial was ~2.1±0.4°C (relative to modern) and increased about 0.6 to 1°C between the early and late Holocene. Our terrestrial glacier and snowline records show coherence and also they are consistent with marine records in the Australian sector, documenting a regional climate pattern. However, the climate of the southwest Pacific region was fundamentally different from that observed in the Northern Hemisphere, where the most extensive

  18. How Key GEOSS Datasets Contribute to the Global Monitoring and Assessment of Glaciers

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    An early and dramatic indicator of global climate change has been the recession of mountain glaciers. The potential impacts on water resources and global sea level rise has led to an increased interest in accurate monitoring and assessment of glaciers worldwide. Past glacier inventories recorded scalar information such as area and terminus location for glaciers in easily accessible regions of the Earth. A modern glacier inventory must be truly global, attempting to assess all of the Earth's estimated 160,000 glaciers, and contain actual glacier extents with area distribution by elevation. These data are required in order to begin modeling the response of this portion of the cryosphere to future climate change. Fortunately, the two key data sets required to produce this global inventory of glaciers were recently made available as contributions to GEOSS by GEO Member nations. These are the multispectral imagery in the Landsat archive, contributed by the U.S.A., and the Global Digital Elevation Model (GDEM) jointly contributed by the Ministry of Economy, Trade, and Industry (METI) of Japan and the United States National Aeronautics and Space Administration (NASA). This talk will describe how the Global Land Ice Monitoring from Space (GLIMS) project is utilizing these GEOSS resources by enabling GLIMS collaborators to derive detailed glacier outlines, transient snow lines, area-elevation distributions, and other pertinent information that will enhance our understanding of the current state, recent evolution, and future fate of the glaciers worldwide.

  19. Tropical climate at the last glacial maximum inferred from glacier mass-balance modeling

    USGS Publications Warehouse

    Hostetler, S.W.; Clark, P.U.

    2000-01-01

    Model-derived equilibrium line altitudes (ELAs) of former tropical glaciers support arguments, based on other paleoclimate data, for both the magnitude and spatial pattern of terrestrial cooling in the tropics at the last glacial maximum (LGM). Relative to the present, LGM ELAs were maintained by air temperatures that were 3.5??to 6.6 ??C lower and precipitation that ranged from 63% wetter in Hawaii to 25% drier on Mt. Kenya, Africa. Our results imply the need for a ~3 ??C cooling of LGM sea surface temperatures in the western Pacific warm pool. Sensitivity tests suggest that LGM ELAs could have persisted until 16,000 years before the present in the Peruvian Andes and on Papua, New Guinea.

  20. Morphology, sedimentology and stratigraphic implication of debris-covered glacier deposits from the LGM and Lateglacial (Eastern Alps, Austria)

    NASA Astrophysics Data System (ADS)

    Reitner, Jürgen M.; Seidl, Sabrina; Wagreich, Michael

    2013-04-01

    Understanding the genesis of Quaternary sediments is crucial for establishing a climato-stratigraphy and, further on, to infer paleoclimatic conditions, if possible. Especially diamictons in the high-mountain environment may be formed by variety of processes, i.e. glacial, periglacial and gravitational. On the other hand, the interpretation of morphological features might be ambiguous as for example ridges may document latero-frontal dump moraines, flow of a rock avalanche event or constituents of a rock-glacier. In addition, equilibrium line altitudes (ELAs) of paleo-glaciers are mostly based on calculations using the reconstructed glacier size and applying a more or less fixed accumulation area ration (e.g. AAR - method). However, such ELAs are of no use for stratigraphic correlations and climatic considerations, if the former glacial system was strongly influenced by supraglacial debris deriving from steep back walls of cirques. We present two examples of reconstructed debris-covered or more specifically debris-mantled paleo-glaciers, their geological and morphological setting as well as their documented sedimentology and morphology. The first example is from the easternmost part of the European Alps (Northern Calcareous Alps / Schneeberg mountains / Puchberg) where an up to 60 m high moraine systems of LGM age shows some striking morphological similarities with relict rock glacier. However, based especially on lithofacies analyses as well as on the lithology of the matrix a glacial genesis could be proven. Lateglacial glacier deposits from the interior of the Alps (Lienz Dolomites / area of Karlsbader Hütte) display a quite similar glacial system. The geometry of the deposits in relation to proglacial sturzstrom sediments, showing typical indications of dynamic fragmentation, and the amount of angular, passively transported clasts in the till point to a rock avalanche event which had hit the glacier surface during a glacier advance. As the glacial system shows

  1. New climate change scenarios reveal uncertain future for Central Asian glaciers

    NASA Astrophysics Data System (ADS)

    Lutz, A. F.; Immerzeel, W. W.; Gobiet, A.; Pellicciotti, F.; Bierkens, M. F. P.

    2012-11-01

    Central Asian water resources largely depend on (glacier) melt water generated in the Pamir and Tien Shan mountain ranges, located in the basins of the Amu and Syr Darya rivers, important life lines in Central Asia and the prominent water source of the Aral Sea. To estimate future water availability in the region, it is thus necessary to project the future glacier extent and volume in the Amu and Syr Darya river basins. The aim of this study is to quantify the impact of uncertainty in climate change projections on the future glacier extent in the Amu and Syr Darya river basins. The latest climate change projections provided by the fifth Coupled Model Intercomparison Project (CMIP5) generated for the upcoming fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC) are used to model future glacier extent in the Central Asian region for the two large river basins. The outcomes are compared to model results obtained with the climate change projections used for the fourth IPCC assessment (CMIP3). We use a regionalized glacier mass balance model to estimate changes in glacier extent as a function of glacier size and projections of temperature and precipitation. The model is developed for implementation in (large scale) hydrological models, when the spatial model resolution does not allow for modelling of individual glaciers and data scarcity is an issue. Both CMIP3 and CMIP5 model simulations point towards a strong decline in glacier extent in Central Asia. However, compared to the CMIP3 projections, the CMIP5 projections of future glacier extent in Central Asia provide a wider range of outcomes, mostly owing to greater variability in precipitation projections among the latest suite of climate models. These findings have great impact on projections of the timing and quantity of water availability in glacier melt dominated rivers in the region. Uncertainty about the size of the decline in glacier extent remains large, making estimates of future

  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. Dramatic mass loss in extreme high-elevation areas of a western Himalayan glacier: observations and modeling.

    PubMed

    Zhao, Huabiao; Yang, Wei; Yao, Tandong; Tian, Lide; Xu, Baiqing

    2016-01-01

    Rapid climate change at high elevations has accelerated glacier retreat in the Himalayas and Tibetan Plateau. However, due to the lack of long-term glaciological measurements, there are still uncertainties regarding when the mass loss began and what the magnitude of mass loss is at such high elevations. Based on in situ glaciological observations during the past 9 years and a temperature-index mass balance model, this study investigates recent mass loss of the Naimona'nyi Glacier in the western Himalayas and reconstructs a 41-year (1973/74-2013/14) equilibrium line altitude (ELA) and glacier-wide mass loss. The result indicates that even at 6000 m above sea level (a.s.l.), the annual mass loss reaches ~0.73 m water equivalent (w.e.) during the past 9 years. Concordant with the abrupt climate shift in the end of 1980s, the ELA has dramatically risen from ~5969 ± 73 m a.s.l. during 1973/74-1988/89 to ~6193 ± 75 m a.s.l. during 1989/90-2013/14, suggesting that future ice cores containing uninterrupted climate records could only be recovered at least above 6200 m a.s.l. in the Naimona'nyi region. The glacier-wide mass balance over the past 41 years is averaged to be approximately -0.40 ± 0.17 m w.e., exhibiting a significant increase in the decadal average from -0.01 ± 0.15 to -0.69 ± 0.21 m w.e. PMID:27561411

  4. Dramatic mass loss in extreme high-elevation areas of a western Himalayan glacier: observations and modeling

    PubMed Central

    Zhao, Huabiao; Yang, Wei; Yao, Tandong; Tian, Lide; Xu, Baiqing

    2016-01-01

    Rapid climate change at high elevations has accelerated glacier retreat in the Himalayas and Tibetan Plateau. However, due to the lack of long-term glaciological measurements, there are still uncertainties regarding when the mass loss began and what the magnitude of mass loss is at such high elevations. Based on in situ glaciological observations during the past 9 years and a temperature-index mass balance model, this study investigates recent mass loss of the Naimona’nyi Glacier in the western Himalayas and reconstructs a 41-year (1973/74–2013/14) equilibrium line altitude (ELA) and glacier-wide mass loss. The result indicates that even at 6000 m above sea level (a.s.l.), the annual mass loss reaches ~0.73 m water equivalent (w.e.) during the past 9 years. Concordant with the abrupt climate shift in the end of 1980s, the ELA has dramatically risen from ~5969 ± 73 m a.s.l. during 1973/74–1988/89 to ~6193 ± 75 m a.s.l. during 1989/90–2013/14, suggesting that future ice cores containing uninterrupted climate records could only be recovered at least above 6200 m a.s.l. in the Naimona’nyi region. The glacier-wide mass balance over the past 41 years is averaged to be approximately −0.40 ± 0.17 m w.e., exhibiting a significant increase in the decadal average from −0.01 ± 0.15 to −0.69 ± 0.21 m w.e. PMID:27561411

  5. Dramatic mass loss in extreme high-elevation areas of a western Himalayan glacier: observations and modeling

    NASA Astrophysics Data System (ADS)

    Zhao, Huabiao; Yang, Wei; Yao, Tandong; Tian, Lide; Xu, Baiqing

    2016-08-01

    Rapid climate change at high elevations has accelerated glacier retreat in the Himalayas and Tibetan Plateau. However, due to the lack of long-term glaciological measurements, there are still uncertainties regarding when the mass loss began and what the magnitude of mass loss is at such high elevations. Based on in situ glaciological observations during the past 9 years and a temperature-index mass balance model, this study investigates recent mass loss of the Naimona’nyi Glacier in the western Himalayas and reconstructs a 41-year (1973/74–2013/14) equilibrium line altitude (ELA) and glacier-wide mass loss. The result indicates that even at 6000 m above sea level (a.s.l.), the annual mass loss reaches ~0.73 m water equivalent (w.e.) during the past 9 years. Concordant with the abrupt climate shift in the end of 1980s, the ELA has dramatically risen from ~5969 ± 73 m a.s.l. during 1973/74–1988/89 to ~6193 ± 75 m a.s.l. during 1989/90–2013/14, suggesting that future ice cores containing uninterrupted climate records could only be recovered at least above 6200 m a.s.l. in the Naimona’nyi region. The glacier-wide mass balance over the past 41 years is averaged to be approximately ‑0.40 ± 0.17 m w.e., exhibiting a significant increase in the decadal average from ‑0.01 ± 0.15 to ‑0.69 ± 0.21 m w.e.

  6. Assessment of bed topography and debris thickness of five Nepalese glaciers

    NASA Astrophysics Data System (ADS)

    Kayastha, R. B.; Dahal, R.

    2015-12-01

    This study assesses the bed topography and debris thickness of five Nepalese glaciers using satellite image and models. The GlabTop model coupled with ArcGIS using Digital Elevation Model (DEM), glacier outline and branch lines relating with surface slope, elevation difference, shape factor and basal stress to estimate spatial ice thickness distribution, volume and approximation of bed topography on Mera Glacier in Hinku Valley, Solukhumbu district. The estimated ice thickness value is then compared with field data measured by ground penetrating radar which shows ± 25 % uncertainty in estimated ice thickness. The model is applied on three large glaciers in Khumbu region viz. Ngozumpa, Khumbu and Imja Glaciers. The ice thickness spatially distributed in three glaciers ranges from ~ 0 m at the glacier outline or moraine to ~ 360 m in the lower flat region of glacier valley at an elevation range of 4500 - 5500 m a.s.l. The bed topography reveals that there is no large deepening or possible sites for the formation of large lakes after glacier retreats except in Ngozumpa Glacier, whereas in Imja Glacier, existing glacier lake can further expand up to ~ 4 km in the Lhotse-Sar Glacier and ~ 2.5 km in the Imja Glacier. Sensitivity analysis is performed by modifying the two scaling parameters, shape factor and basal stress. The model performed very well when shape factor is 0.8 and basal stress is 150 kPa (1.5 bar) while comparing with field investigated ice thickness data. In an another attempt thermal band of Landsat 8 satellite data and debris energy balance model are used to estimate debris thickness distribution on Lirung Glacier in Langtang Valley. With this new technique it is found that the debris thickness of Lirung Glacier varies from around 93 cm in the terminus and about 27 cm in the upper part of the glacier. Based on the debris thickness estimations, average daily melt is found 5.3 mm w.e. d-1 in the upper part and 1.2 mm w.e. d-1 near terminus of the glacier

  7. 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.

  8. Influence of ENSO and PDO on mountain glaciers in the outer tropics: case studies in Bolivia

    NASA Astrophysics Data System (ADS)

    Veettil, Bijeesh Kozhikkodan; Bremer, Ulisses Franz; de Souza, Sergio Florêncio; Maier, Éder Leandro Bayer; Simões, Jefferson Cardia

    2016-08-01

    This paper emphasize on the observational investigation of an ice-covered volcano and two glaciated mountains in the Central Andes from 1984 to 2011. Annual snowlines of the Nevado Sajama in the Cordillera Occidental and the Nevado Cololo and the Nevado Huanacuni in the Cordillera Apolobamba in Bolivia were calculated using remote sensing data. Landsat TM, Landsat ETM+, and LISS-III images taken during the end of dry season were used in this study. Changes in the highest annual snowline during May-September is used an indirect measure of the changes in the equilibrium line altitude of the glaciers in the outer tropics. We tried to understand the combined influence of the El Niño-Southern Oscillation and the Pacific Decadal Oscillation on the variations in the annual snowline altitude of the selected glaciers. Meteorological data in the form of gridded datasets were used for calculating the anomalies in precipitation and temperature during the study period. It is found that the glaciated areas were fluctuated with the occurrence of warm and cold phase of ENSO but the magnitude of the influence of ENSO is observed to be controlled by the phase changes of PDO. Snowline of the Nevado Sajama fluctuated heavily when cold and warm phases of ENSO occur during the cold and warm regimes of PDO, respectively. Nevado Cololo and Nevado Huanacuni are showing a continuous retreating trend during the same period. This clearly indicates that the changes in the Pacific SST patterns have more influence on glaciers in the Cordillera Occidental compared with those in the Cordillera Oriental of the Bolivian Andes.

  9. 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

  10. 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.

  11. Seasonal and altitudinal variations in snow algal communities on an Alaskan glacier (Gulkana glacier in the Alaska range)

    NASA Astrophysics Data System (ADS)

    Takeuchi, Nozomu

    2013-09-01

    Snow and ice algae are cold tolerant algae growing on the surface of snow and ice, and they play an important role in the carbon cycles for glaciers and snowfields in the world. Seasonal and altitudinal variations in seven major taxa of algae (green algae and cyanobacteria) were investigated on the Gulkana glacier in Alaska at six different elevations from May to September in 2001. The snow algal communities and their biomasses changed over time and elevation. Snow algae were rarely observed on the glacier in May although air temperature had been above 0 ° C since the middle of the month and surface snow had melted. In June, algae appeared in the lower areas of the glacier, where the ablation ice surface was exposed. In August, the distribution of algae was extended to the upper parts of the glacier as the snow line was elevated. In September, the glacier surface was finally covered with new winter snow, which terminated algal growth in the season. Mean algal biomass of the study sites continuously increased and reached 6.3 × 10 μl m-2 in cell volume or 13 mg carbon m-2 in September. The algal community was dominated by Chlamydomonas nivalis on the snow surface, and by Ancylonema nordenskiöldii and Mesotaenium berggrenii on the ice surface throughout the melting season. Other algae were less abundant and appeared in only a limited area of the glacier. Results in this study suggest that algae on both snow and ice surfaces significantly contribute to the net production of organic carbon on the glacier and substantially affect surface albedo of the snow and ice during the melting season.

  12. Patagonia Glacier, Chile

    NASA Technical Reports Server (NTRS)

    2000-01-01

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

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

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

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

  13. 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

  14. Contribution of SAR interferometry (InSAR) to the study of alpine glaciers. The example of Forni Glacier (Central Alps, Italy): preliminary results

    NASA Astrophysics Data System (ADS)

    Sterzai, P.; Mancini, F.; Corazzato, C.; D Agata, C.; Diolaiuti, G.

    2003-04-01

    computed and velocity map obtained. The validation of interferometric data was possible comparing them with the field glaciological data obtained by GPS velocity surveys in the years 1992-1993 (Vittuari and Smiraglia, unpublished) and 1996-1997, which resulted of about 20m/y. The InSAR results give further contributions in the estimation of the velocity field of Forni Glacier for a deeper understanding of the different flow lines of the glacier. Problems related to relief effect, loss of coherence, geometry of satellite imagery and geocoding, are also discussed.

  15. Water flow through temperate glaciers

    USGS Publications Warehouse

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

    1998-01-01

    Understanding water movement through a glacier is fundamental to several critical issues in glaciology, including glacier dynamics, glacier-induced floods, and the prediction of runoff from glacierized drainage basins. to this end we have synthesized a conceptual model os water movement through a temperate glacier from the surface to the outlet stream. Processes that regulate the rate and distribution of water input at the glacier surface and that regulate water movement from the surface to the bed play important but commonly neglected roles in glacier hydrology. Where a glacier is covered by a layer of porous, permeable firn (the accumulation zone), the flux of water to the glacier interior varies slowly because the firn temporarily stores water and thereby smooths out variations in the supply rate. In the firn-free ablation zone, in contrast, the flux of water into the glacier depends directly on the rate of surface melt or rainfall and therefore varies greatly in time. Water moves from the surface to the bed through an upward branching arborescent network consisting of both steeply inclined conduits, formed by the enlargement of intergranular veins, and gently inclined conduits, sprqwned by water flow along the bottoms of near-surface fractures (crevasses). Englacial drainage conduits deliver water to the glacier bed at a linited number of points, probably a long distance downglacier of where water enters the glacier. Englacial conduits supplied from the accumulation zone are quasi steady state features that convey the slowly varying water flux delivered via the firn. their size adjusts so that they are usually full of water and flow is pressurized. In contrast, water flow in englacial conduits supplied from the ablation area is pressurized only near times of peak daily flow or during rainstorms; flow is otherwise in an open-channel configuration. The subglacial drainage system typically consists of several elements that are distinct both morpphologically and

  16. Scaling the Teflon Peaks: Granite, Glaciers, and the Highest Relief in North America

    NASA Astrophysics Data System (ADS)

    Ward, D.; Anderson, R. S.; Haeussler, P. J.

    2010-12-01

    We use a combination of field observations, remote sensing, and digital elevation data to demonstrate how the topographic character of the Alaska Range (Alaska, USA) has been influenced by the exhumation of Tertiary granitic plutons among more erodible sedimentary and metamorphic rocks. Observations that the mean elevations of many tectonically active mountain ranges follow closely the elevation of the mean Cenozoic snowline or glacial equilibrium line (ELA), rather than rates of tectonic rock uplift, have led to the “glacial buzzsaw hypothesis” - that terrain raised above the ELA is rapidly denuded by glaciers. The Alaska Range stands in prominent exception to this observation. Much of the range is developed on pervasively fractured sedimentary and metamorphic rocks and has local relief of 1000-1500 m. In contrast, early and mid-Tertiary plutons of relatively intact granite support most of the range's impressive mountains (including Mt. McKinley, or Denali, the highest mountain in North America at 6194 m), with 2500-5000 m of local relief. Moreover, these plutons are where the range's modern glaciers originate, as the high peaks protrude in some cases kilometers above modern snowlines. These glaciers flow off of the plutons onto the surrounding, softer rocks, where mean summit elevations are similar to modern snowline elevations. We exploit the Denali massif and the Kichatna Mountains to its west to illustrate the direct ways in which exhumation of granite plutons affects glacial erosion, glacier long profiles, the glacial drainage network, and the effectiveness of periglacial processes. We use simple scaling calculations to explore the potential feedbacks of relief enhancement - specifically, that of avalanching from steep valley walls - on the health of the glaciers occupying the valleys, and describe ways in which peaks can be preserved and allowed to grow to great heights. Our work indicates that most of the Alaska Range has developed in accordance with

  17. Mass balance model parameter transferability on a tropical glacier

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  18. 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.

  19. 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.

  20. Modeling of subglacial water pressure on Russell glacier, toward a better understanding of the relation between meltwater availability and ice dynamics.

    NASA Astrophysics Data System (ADS)

    de Fleurian, Basile; Morlighem, Mathieu; Seroussi, Helene; Rignot, Eric

    2016-04-01

    Basal sliding is the main control on outlet glaciers velocity. This sliding is mainly driven by the water pressure at the base of the glaciers. The ongoing increase in surface melt of the Greenland Ice Sheet warrants an examination of its impact on basal water pressure and in turn on basal sliding. Here, we examine the case of Russell glacier, West Greenland, where a remarkably extensive set of observations have been gathered. These observations suggest that the increase in runoff has no impact on the annual velocity on the lower part of the drainage basin, but yield an acceleration of ice flow above the Equilibrium Line Altitude (ELA). It is believed that this two distinct behaviours are due to different evolutions of the subglacial draining system during and after the melt season. We use here a high-resolution new generation subglacial hydrological model forced by reconstructed surface runoff for the period 2008 to 2012 to investigate the possible causes of these distinct behaviours. The model results confirm the existence of two distinct behaviours of the subglacial water pressure, an increase in the mean annual water pressure at high elevation and a stagnation of these same mean annual pressures below the ELA. The increase in meltwater at the lower elevation leads to a more developed efficient drainage system and the overall steadiness of the annual velocities, but, at higher elevation the drainage system remains mainly inefficient and is therefore strongly sensitive to the increase in meltwater availability.

  1. Dynamic behavior of the Bering Glacier-Bagley icefield system during a surge, and other measurements of Alaskan glaciers with ERS SAR imagery

    NASA Technical Reports Server (NTRS)

    Lingle, Craig S.; Fatland, Dennis R.; Voronina, Vera A.; Ahlnaes, Kristina; Troshina, Elena N.

    1997-01-01

    ERS-1 synthetic aperture radar (SAR) imagery was employed for the measurement of the dynamics of the Bagley icefield during a major surge in 1993-1994, the measurement of ice velocities on the Malaspina piedmont glacier during a quiescent phase between surges, and for mapping the snow lines and the position of the terminus of Nabesna glacier on Mount Wrangell (a 4317 m andesitic shield volcano) in the heavily glacierized Saint Elias and Wrangell Mountains of Alaska. An overview and summary of results is given. The methods used include interferometry, cross-correlation of sequential images, and digitization of boundaries using terrain-corrected SAR imagery.

  2. Debris-covered glaciers during the LGM and Lateglacial at the eastern margin of the Alps

    NASA Astrophysics Data System (ADS)

    Seidl, Sabrina; Reitner, Jürgen M.; Wagreich, Michael

    2013-04-01

    We present the reconstruction of paleo-glaciers in the easternmost part of the Alps (Schneeberg mountain) with the main focus on sedimentology, chronology and glacial dynamics. The area is dominantly made up of limestone bedrock and hence characterized by steep slopes and cirques. Two juvenile moraine-systems can be deciphered based on geological mapping. The major system is characterized by an up to 60 m high latero-frontal dump moraine with a prominent breach-lobe moraine in a lateral position. It is regarded to represent the Last Glacial Maximum (LGM; Würm Pleniglacial). The other system is much smaller and was formed most probably during the Würm Lateglacial. The angular to subangular shape of the clasts and the abundant boulders on top of the ridges indicate a high portion of passive (Boulton, 1978) i.e. supraglacial and englacial transport of debris before deposition.Thus the model of a debris-covered glacier is favored to explain both landforms and as well the corresponding sediment facies. For the pleniglacial moraine such an assumption is backed by a low accumulation/ablation area ratio (AAR) of around 1:1 based on the reconstruction of the equilibrium line altitude (ELA) using the maximum elevation of lateral moraines (MELM; Lichtenecker, 1938). Furthermore as there is no indication of a former glacier snout glacio-fluvial processes should have played a limited role in sediment transport into the forefield. Such setting pinpoints to very cold-arid conditions, which are as well found in paleo-climate reconstructions of the eastern foreland (Frenzel et al. 1992). Boulton, G.S., 1978: Boulder shapes and grain-size distribution of debris as indicators of transport paths through a glacier and till genesis.- Sedimentology, 25, 773-799. Lichtenecker, N.,1938. Die gegenwärtige und die eiszeitliche Schneegrenze in den Ostalpen. In: Verhandlungen der III. Internationalen Quartär - Konferenz, Vienna, 1936, 141-147. Frenzel, B., Pecsi, M. & Velichko, A. A., 1992

  3. 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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  6. Rapid Holocene thinning of an East Antarctic outlet glacier driven by marine ice sheet instability

    PubMed Central

    Jones, R. S.; Mackintosh, A. N.; Norton, K. P.; Golledge, N. R.; Fogwill, C. J.; Kubik, P. W.; Christl, M.; Greenwood, S. L.

    2015-01-01

    Outlet glaciers grounded on a bed that deepens inland and extends below sea level are potentially vulnerable to ‘marine ice sheet instability'. This instability, which may lead to runaway ice loss, has been simulated in models, but its consequences have not been directly observed in geological records. Here we provide new surface-exposure ages from an outlet of the East Antarctic Ice Sheet that reveal rapid glacier thinning occurred approximately 7,000 years ago, in the absence of large environmental changes. Glacier thinning persisted for more than two and a half centuries, resulting in hundreds of metres of ice loss. Numerical simulations indicate that ice surface drawdown accelerated when the otherwise steadily retreating glacier encountered a bedrock trough. Together, the geological reconstruction and numerical simulations suggest that centennial-scale glacier thinning arose from unstable grounding line retreat. Capturing these instability processes in ice sheet models is important for predicting Antarctica's future contribution to sea level change. PMID:26608558

  7. Modeling the instantaneous response of glaciers after the collapse of the Larsen B Ice Shelf

    NASA Astrophysics Data System (ADS)

    De Rydt, J.; Gudmundsson, G. H.; Rott, H.; Bamber, J. L.

    2015-07-01

    Following the disintegration of the Larsen B Ice Shelf, Antarctic Peninsula, in 2002, regular surveillance of its ˜20 tributary glaciers has revealed a response which is varied and complex in both space and time. The major outlets have accelerated and thinned, smaller glaciers have shown little or no change, and glaciers flowing into the remnant Scar Inlet Ice Shelf have responded with delay. In this study we present the first areawide numerical analysis of glacier dynamics before and immediately after the collapse of the ice shelf, combining new data sets and a state-of-the-art numerical ice flow model. We simulate the loss of buttressing at the grounding line and find a good qualitative agreement between modeled changes in glacier flow and observations. Through this study, we seek to improve confidence in our numerical models and their ability to capture the complex mechanical coupling between floating ice shelves and grounded ice.

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

    USGS Publications Warehouse

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

    1997-01-01

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

  9. 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

  10. 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

  11. A new 3-D thin-skinned rock glacier model based on helicopter GPR results from the Swiss Alps

    NASA Astrophysics Data System (ADS)

    Merz, Kaspar; Green, Alan G.; Buchli, Thomas; Springman, Sarah M.; Maurer, Hansruedi

    2015-06-01

    Mountainous locations and steep rugged surfaces covered by boulders and other loose debris are the main reasons why rock glaciers are among the most challenging geological features to investigate using ground-based geophysical methods. Consequently, geophysical surveys of rock glaciers have only ever involved recording data along sparse lines. To address this issue, we acquired quasi-3-D ground-penetrating radar (GPR) data across a rock glacier in the Swiss Alps using a helicopter-mounted system. Our interpretation of the derived GPR images constrained by borehole information results in a novel "thin-skinned" rock glacier model that explains a concentration of deformation across a principal shear zone (décollement) and faults across which rock glacier lobes are juxtaposed. The new model may be applicable to many rock glaciers worldwide. We suggest that the helicopter GPR method may be useful for 3-D surveying numerous other difficult-to-access mountainous terrains.

  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. Modeling glacier beds in the Austrian Alps: How many lakes will form in future?

    NASA Astrophysics Data System (ADS)

    Koehler, Dominik; Geilhausen, Martin; Linsbauer, Andreas

    2014-05-01

    Glacial retreat exposes landscapes with relief characteristics greatly differing from the former ice covered surfaces. If glacial retreat exposes natural basins capable of forming proglacial lakes, then the downstream hydrologic and geomorphic systems in such catchments will be significantly altered due to discharge modifications, sediment trapping, decoupling effects and long term sediment storage (e.g. Geilhausen et al. 2013). Further implications are related to hydropower management, tourism and natural hazards. Consequently, sound knowledge of present day glacier beds ("proglacial zones of tomorrow") and in particular the total number, locations and characteristics of overdeepenings are of importance. For Austria, however, this important information about significant future changes of high alpine regions is yet missing. An interdisciplinary research project is currently in preparation to close this gap. This paper presents results of a pilot study. We used a novel GIS-based approach (GlabTop, cf. Linsbauer et al. 2012) to compute approximate glacier beds in the Austrian Alps. GlabTop ('Glacier bed Topography') is based on an empirical relation between average basal shear stress and elevation range of individual glaciers and makes use of digital elevation models (DEM), glacier outlines and branch lines (i.e. a set of lines covering all important glacier branches). DEMs and glacier outlines were derived from the Austrian glacier inventory (1998) and branch lines were manually digitized. The inventory includes 911 glaciers of which 876 (96%) were considered and 35 were excluded due to size restrictions (< 0.01 km²) or insufficient DEM coverage. We found 165 overdeepenings (> 0.01 km²) with the potential of forming proglacial lakes when glacier retreat reveals the bed. The total area and volume of all overdeepenings is approx. 10 km² and 236 Mio m³ respectively and 33 lakes will be larger than 1 km³. A total glacier volume of 16 ± 5 km³ with an average ice

  14. Analysis of glacier facies using satellite techniques

    USGS Publications Warehouse

    Williams, R.S., Jr.; Hall, D.K.; Benson, C.S.

    1991-01-01

    Landsat-derived reflectance is lowest for exposed ice and increases markedly at the transient snow line. Above the slush zone is a gradual increase in near-infrared reflectance as a result of decreasing grain-size of the snow, which characterizes drier snow. Landsat data are useful in measuring the areal extent of the ice facies, the slush zone within the wet-snow facies, the snow facies (combined wet-snow, percolation and dry-snow facies), and the respective position of the transient snow line and the slush limit. In addition, fresh snowfall and/or airborne contaminants, such as soot and tephra, can limit the utility of Landsat data for delineation of the glacier facies in some cases. -from Authors

  15. Surface mass balance of Greenland mountain glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Benson, R. J.; Box, J. E.; Bromwich, D. H.; Wahr, J. M.

    2009-12-01

    Mountain glaciers and ice caps contribute roughly half of eustatic sea-level rise. Greenland has thousands of small mountain glaciers and several ice caps > 1000 sq. km that have not been included in previous mass balance calculations. To include small glaciers and ice caps in our study, we use Polar WRF, a next-generation regional climate data assimilation model is run at grid resolution less than 10 km. WRF provides surface mass balance data at sufficiently high resolution to resolve not only the narrow ice sheet ablation zone, but provides information useful in downscaling melt and accumulation rates on mountain glaciers and ice caps. In this study, we refine Polar WRF to simulate a realistic surface energy budget. Surface melting is calculated in-line from surface energy budget closure. Blowing snow sublimation is computed in-line. Melt water re-freeze is calculated using a revised scheme. Our results are compared with NASA's Gravity Recovery and Climate Experiment (GRACE) and associated error is calculated on a regional and local scale with validation from automated weather stations (AWS), snow pits and ice core data from various regions along the Greenland ice sheet.

  16. 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

  17. Erosion by an Alpine glacier

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  18. 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 ...

  19. 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

  20. Recent Changes in Arctic Glaciers, Ice Caps, and the Greenland Ice Sheet: Cold Facts About Warm Ice

    NASA Astrophysics Data System (ADS)

    Abdalati, W.

    2005-12-01

    One of the major manifestations of Arctic change can be observed in the state of balance of Arctic glaciers and ice caps and the Greenland ice sheet. These ice masses are estimated to contain nearly 3 million cubic kilometers of ice, which is more than six times greater than all the water stored in the Earth's lakes, rivers, and snow combined and is the equivalent of over 7 meters of sea level. Most of these ice masses have been shrinking in recent in years, but their mass balance is highly variable on a wide range of spatial and temporal scales. On the Greenland ice sheet most of the coastal regions have thinned substantially as melt has increased and some of its outlet glaciers have accelerated. Near the equilibrium line in West Greenland, we have seen evidence of summer acceleration that is linked to surface meltwater production, suggesting a relatively rapid response mechanism of the ice sheet change to a warming climate. At the same time, however, the vast interior regions of the Greenland ice sheet have shown little change or slight growth, as accumulation in these areas may have increased. Throughout much of the rest of the Arctic, many glaciers and ice caps have been shrinking in the past few decades, and in Canada and Alaska, the rate of ice loss seems to have accelerated during the late 1990s. These recent observations offer only a snapshot in time of the long-term behavior, but they are providing crucial information about the current state of ice mass balance and the mechanisms that control it in one of the most climatically sensitive regions on Earth. As we continue to learn more through a combination of remote sensing observations, in situ measurements and improved modeling capabilities, it is important that we coordinate and integrate these approaches effectively in order to predict future changes and their impact on sea level, freshwater discharge, and ocean circulation.

  1. Fast shrinkage of tropical glaciers in Colombia

    NASA Astrophysics Data System (ADS)

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

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

  2. 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.

  3. Erosion by an Alpine glacier

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  4. 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.

  5. 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)

  6. 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

  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. Glacier Evolution in the Altai Mountains, South-West Siberia, for the Last Half Century (with use of Geo-Informational Catalogue)

    NASA Astrophysics Data System (ADS)

    Surazakov, A. B.; Narojniy, Y. K.; Nikitin, S. A.; Aizen, V. B.

    2003-12-01

    To systemize and analyze the information for the period from 1835 to present on altitudinal distributions of glaciers, exposition, their numbers and surface areas in basins, volumes, genetic classification, location of lower and upper level of glaciers, average firn line position and main morphometric characteristics, DataBase on glacier dynamics in the Altai Mountains (AGDB) has been developed in ArcGIS Format [Tomsk State University, Russia]. Data from Glacier Catalogue [1962], topographic maps with the scale of 1:25000 and 1:50000 and air photos, which fixed glaciers' state on 1952, were digitized. Instrumental observational data on glacier tongue retreat from twenty glaciers since 1835, and radio-echo sounding measurements of 120 glacier volumes were also digitized in the AGDB. Modern state of Altai glaciers and their changes since 1952 were assessed from Resurs space images and partially from instrumental observations. Based on estimation from Resurs for the period from 1952 to 1998, the value of Altai glacier retreating was about 56.9 km2, i.e. 7.1 % of total area, varied from 4 % for valley glaciers to 16 % for glaciers of flat mountain tops. Retreat of 2-8 m per year was accompanied by their 10% mass loss. The slightest degradation occurred in inner (central) part of the glacier system, in the heads of river basins with large-scale glaciation, e.g., in the Katunski, Nothern-Chuiski and Southern-Chuiski ranges, amounting to 6.3%. These are the highest regions, reaching up to 4506 m., and 80% of Altai's glaciers are located there. In the river basins with relatively small-glacierized areas, at the peripheral regions, e.g., Kurai, Chihacheva ranges, the degradation reached its maximum values up to 22%.

  9. Geodetic Glacier Mass Balance of Norway

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  10. Lines

    ERIC Educational Resources Information Center

    Mires, Peter B.

    2006-01-01

    National Geography Standards for the middle school years generally stress the teaching of latitude and longitude. There are many creative ways to explain the great grid that encircles our planet, but the author has found that students in his college-level geography courses especially enjoy human-interest stories associated with lines of latitude…

  11. Monsoon-influenced glacier retreat in the Ladakh Range, Jammu and Kashmir

    NASA Astrophysics Data System (ADS)

    Chudley, Tom; Miles, Evan; Willis, Ian

    2016-04-01

    While the majority of glaciers in the Himalaya-Karakoram mountain chain are receding in response to climate change, stability and even growth is observed in the Karakoram, where glaciers also exhibit widespread surge-type behaviour. Changes in the accumulation regime driven by mid-latitude westerlies could explain such stability relative to the monsoon-fed glaciers of the Himalaya, but a lack of detailed meteorological records presents a challenge for climatological analyses. We therefore analyse glacier changes for an intermediate zone of the HKH to characterise the transition between the substantial retreat of Himalayan glaciers and the surging stability of Karakoram glaciers. Using Landsat imagery, we assess changes in glacier area and length from 1991-2014 across a ˜140 km section of the Ladakh Range, Jammu and Kashmir. Bordering the surging, stable portion of the Karakoram to the north and the Western Himalaya to the southeast, the Ladakh Range represents an important transitional zone to identify the potential role of climatic forcing in explaining differing glacier behaviour across the region. A total of 878 glaciers are semi-automatically identified in 1991, 2002, and 2014 using NDSI (thresholds chosen between 0.30 and 0.45) before being manually corrected. Ice divides and centrelines are automatically derived using an established routine. Total glacier area for the study region is in line with that Randolph Glacier Inventory (RGI) and ˜25% larger than the GLIMS Glacier Database, which is apparently more conservative in assigning ice cover in the accumulation zone. However, the RGI appears notably less successful in identifying glacier termini. Preliminary analysis of glaciers in our study area suggest an overall areal decline of -17.21±7.50% between 1991-2014., a figure more similar to the Zanskar ranges to the south than the Karakoram to the north. No evidence of surge-type behaviour is observed in the study area over this period. Glaciers tend to be

  12. Organic Carbon Dynamics in Glacier Systems

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  13. 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.

  14. Glacier fluctuations during the past 2000 years

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  15. 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.

  16. The role of snowmelt and glacier melt on runoff in a glacierized catchment: a multi-tracer experiment

    NASA Astrophysics Data System (ADS)

    Penna, Daniele; Engel, Michael; Mao, Luca; Dell'Agnese, Andrea; Bertoldi, Giacomo; Comiti, Francesco

    2013-04-01

    The release of water as snowmelt and ice melt in high elevation catchments has significant social and economic impacts for population living in mountain areas. This is even more critical under the current conditions of glacier retreat as a consequence of global warming. Therefore, it is important to understand the role of ice and snow meltwater on runoff dynamics and groundwater recharge in glacierized environments. This task can be effectively accomplished by integrating isotopic and other tracers that are widely recognized as useful tools for the identification of the main water sources contributing to streamflow. In this work, we collected water samples from different sources in the Saldur catchment (Eastern Italian Alps). The catchment (area: 62 km², elevation range: 1600-3700 m a.s.l.) hosts a small glacier (2.8 km²) in its upper portion. Samples of rainfall, snow, snowmelt, glacier melt, stream water (main stream and tributaries) and spring water have been manually collected between April-October 2011 and April-November 2012 approximately on a monthly basis. Furthermore, 24-hour samplings with hourly collection frequency were performed at two cross sections during five melt-runoff events. The composition in stable water isotopes was determined by laser spectroscopy and mass spectrometry. Electrical conductivity (EC) and water temperature were measured in the field. Additionally, deuterium excess (DE) was computed for all samples based on the relationship between deuterium and 18-oxygen. The isotopic composition of rainfall and snow shows marked altitudinal and seasonal variations. A strong positive correlation is also evident in the relationship between DE of spring waters and elevation. Rainfall and snow samples fall perfectly on the Global Meteoric Water Line, revealing a predominant Atlantic origin of air masses producing precipitation in the study area. EC and water temperature linearly increase with the distance from the glacier snout, suggesting a

  17. Equilibrium Shaping

    NASA Astrophysics Data System (ADS)

    Izzo, Dario; Petazzi, Lorenzo

    2006-08-01

    We present a satellite path planning technique able to make identical spacecraft aquire a given configuration. The technique exploits a behaviour-based approach to achieve an autonomous and distributed control over the relative geometry making use of limited sensorial information. A desired velocity is defined for each satellite as a sum of different contributions coming from generic high level behaviours: forcing the final desired configuration the behaviours are further defined by an inverse dynamic calculation dubbed Equilibrium Shaping. We show how considering only three different kind of behaviours it is possible to acquire a number of interesting formations and we set down the theoretical framework to find the entire set. We find that allowing a limited amount of communication the technique may be used also to form complex lattice structures. Several control feedbacks able to track the desired velocities are introduced and discussed. Our results suggest that sliding mode control is particularly appropriate in connection with the developed technique.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  19. Spatially heterogeneous wastage of Himalayan glaciers.

    PubMed

    Fujita, Koji; Nuimura, Takayuki

    2011-08-23

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

  20. 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.

  1. 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.

  2. 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.

  3. Glacier discharge and climate variations

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    Different studies account for the warming in the polar regions that consequently would affect Glacier Discharge (GD). Since changes in GD may cause large changes in sensible and latent heat fluxes, we ask about the relationships between GD and climate anomalies, which have not been quantified yet. In this study we apply different statistical methods such as correlation, Singular Spectral Analysis and Wavelet to compare the behaviour of GD data in two Experimental Pilot Catchments (CPE), one (CPE-KG-62°S) in the Antarctica and the other (CPE-KVIA-64°N) in the Arctic regions. Both CPE's are measuring sub- and endo-glacier drainage for recording of glacier melt water run-off. The CPE-KG-62°S is providing hourly GD time series since January 2002 in Collins glacier of the Maxwell Bay in King George Island (62°S, 58°W). The second one, CPE-KVIA-64°N, is providing hourly GD time series since September 2003 in the Kviarjökull glacier of the Vatnajökull ice cap in Iceland (64°N, 16°W). The soundings for these measurements are pressure sensors installed in the river of the selected catchments for the ice cap (CPE-KG-62°S) and in the river of the glacier for (CPE-KVIA-64°N). In each CPE, the calibration function between level and discharge has been adjusted, getting a very high correlation coefficient (0.99 for the first one and 0.95 for the second one), which let us devise a precise discharge law for the glacier. We obtained relationships between GD with atmospheric variables such as radiation, temperature, relative humidity, atmospheric pressure and precipitation. We also found a negative response of GD to El Niño teleconnection index. The results are of great interest due to the GD impact on the climate system and in particular for sea level rise.

  4. Edge equilibrium code for tokamaks

    SciTech Connect

    Li, Xujing; Drozdov, Vladimir V.

    2014-01-15

    The edge equilibrium code (EEC) described in this paper is developed for simulations of the near edge plasma using the finite element method. It solves the Grad-Shafranov equation in toroidal coordinate and uses adaptive grids aligned with magnetic field lines. Hermite finite elements are chosen for the numerical scheme. A fast Newton scheme which is the same as implemented in the equilibrium and stability code (ESC) is applied here to adjust the grids.

  5. A Europe-wide perspective on Younger Dryas glacier-climate

    NASA Astrophysics Data System (ADS)

    Pellitero, Ramon; Rea, Brice; Spagnolo, Matteo; Bakke, Jostein; Hughes, Philip; Ivy-Ochs, Susan; Lukas, Sven; Renssen, Hans; Ribolini, Adriano

    2015-04-01

    Equilibrium Line Altitudes have been calculated for over one hundred reconstructed palaeoglaciers stretching from North Africa in the south to Svalbard in the north and the Cantabrian Mountains in the west to the Balkans in the east. Palaeoglaciers were reconstructed based on landforms dated to the Younger Dryas and published in the academic literature. Strict quality control checks were applied to the chronology and, where necessary, dates have been recalibrated using modern calculators. 3D palaeoglaciers were reconstructed using a semi-automated GIS tool, based on Benn and Hulton (2010), which calculates ice thickness using the bed topography and assumes perfect-plasticity ice rheology. From the 3D reconstructed surfaces ELAs were calculated using another GIS tool (Pellitero et al., 2015). Where data has been generated for several glaciers in a region a single value is determined for both the AAR and AABR methods following Osmaston (2005). Preliminary results show a smooth S to N decline in ELA along the western seaboard of Europe, as far north as 60°, where it increases sharply in elevation before declining towards the north again. Along the west-east transect the ELA is located between 2000 and 3000 masl, without any consistent large-scale pattern. Locally gradients are present, for example, across the Cantabrian Range and Eastern Pyrenees, and across the west Balkans. Modern day ELA gradients are determined, where possible, along the same transects. This is achieved by determining the zero net balance ELAs from mass balance time series obtained from the World Glacier Monitoring Service. The modern-day ELA gradients are compared to those determined for the YD and are used to interpret large scale atmospheric circulation patterns. For example, the sharp rise in the ELA at approximately 60°N is assumed to be related to the location of the Polar Front. North of this temperatures would be expected to reduce significantly, but in terms of glacier mass balance

  6. Response of Different Antarctic Outlet Glacier Types to Perturbations at Their Boundaries

    NASA Astrophysics Data System (ADS)

    Weitz, N. A.; Stearns, L. A.; van der Veen, C. J.

    2015-12-01

    Ice sheets are primarily drained by outlet glaciers and ice streams that transport mass from the inland to the ocean. Determining mass loss from the ice sheets is particularly important for calculating future sea level rise. Currently, dynamic ice loss is not included in the prediction of future sea levels, due to the uncertain response of outlet glaciers to climatic perturbations. It is therefore crucial to understand how different types of glaciers respond to changes at their boundaries.Outlet glaciers can be categorized based on their geometry and the mechanisms that drive fast flow. Ice streams are wide with a small surface slope, flow fast despite low driving stress and have little basal drag. Isbrae on the other hand are narrow with a steep surface slope and large driving stress. Between these two end members fall a variety of mixed-type glaciers.We investigate the response of different types of Antarctic outlet glaciers to perturbation scenarios with a flow line model. The effect of reduction in basal drag due to increased sliding, changes in surface accumulation, an increase in submarine melting around the grounding zone, a lower back force at the terminus, and a decrease in lateral drag on glacier stability are explored. Preliminary results indicate that a short-term increase in basal sliding (e.g. from lake discharge events), or increased surface accumulation rates have little impact on the ice flow and the glacier's stability, whereas ice shelf thinning or a reduction in back force result in an immediate response of the outlet glacier. In these cases, a new stable position with an increased but constant ice discharge is obtained soon.

  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

    accumulation along the Chagan Uzun River, which confirms the presence of lacustrine sediments in the Chagan Uzun glacier foreland before the glacier advances. Such sediments could have acted as a soft bed over which fast or unstable glacier flow occurred. This is the first study reporting surge-like behaviour of former glaciers in the Altai mountain range, supported by detailed geomorphological and sedimentological evidences. Such findings are crucial for paleoclimate inference, as the surge-related features cannot be attributed to a glacier system in equilibrium with the contemporary climate, and cannot be interpreted with traditional ELA reconstructions. This study also highlights the complexity of establishing robust paleoglacial chronologies in highly dynamic environments, with interactions between glacial events and the formation and drainage of lakes.

  8. 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.

  9. 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.

  10. 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.

  11. Small valley glaciers and the effectiveness of the glacial buzzsaw in the northern Basin and Range, USA

    NASA Astrophysics Data System (ADS)

    Foster, David; Brocklehurst, Simon H.; Gawthorpe, Rob L.

    2008-12-01

    The glacial buzzsaw hypothesis suggests that efficient erosion limits topographic elevations in extensively glaciated orogens. Studies to date have largely focussed on regions where large glaciers (tens of kilometres long) have been active. In light of recent studies emphasising the importance of lateral glacial erosion in lowering peaks and ridgelines, we examine the effectiveness of small glaciers in limiting topography under both relatively slow and rapid rock uplift conditions. Four ranges in the northern Basin and Range, Idaho, Montana, and Wyoming, USA, were chosen for this analysis. Estimates of maximum Pleistocene slip rates along normal faults bounding the Beaverhead-Bitterroot Mountains (~ 0.14 mm y - 1 ), Lemhi Range (~ 0.3 mm y - 1 ) and Lost River Range (~ 0.3 mm y - 1 ) are an order of magnitude lower than those on the Teton Fault (~ 2 mm y - 1 ). We compare the distribution of glacial erosion (estimated from cirque floor elevations and last glacial maximum (LGM) equilibrium line altitude (ELA) reconstructions) and fault slip rate with three metrics of topography in each range: the along-strike maximum elevation swath profile, hypsometry, and slope-elevation profiles. In the slowly uplifting Beaverhead-Bitterroot Mountains, and Lemhi and Lost River Ranges, trends in maximum elevation parallel ELAs, independent of variations in fault slip rate. Maximum elevations are offset ~ 500 m from LGM ELAs in the Lost River Range, Lemhi Range, and northern Beaverhead-Bitterroot Mountains, and by ~ 350 m in the southern Beaverhead-Bitterroot Mountains, where glacial extents were less. The offset between maximum topography and mean Quaternary ELAs, inferred from cirque floor elevations, is ~ 350 m in the Lost River and Lemhi Ranges, and 200-250 m in the Beaverhead-Bitterroot Mountains. Additionally, slope-elevation profiles are flattened and hypsometry profiles show a peak in surface areas close to the ELA in the Lemhi Range and Beaverhead-Bitterroot Mountains

  12. 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.

  13. Implementation of a new atomic basis for the He I equilibrium line ratio technique for electron temperature and density diagnostic in the SOL for H-mode plasmas in DIII-D

    NASA Astrophysics Data System (ADS)

    Muñoz Burgos, J. M.; Schmitz, O.; Unterberg, E. A.; Loch, S. D.; Ballance, C. P.

    2011-08-01

    Evaluating the ratio of selected helium lines allows for measurement of electron densities and temperatures. This technique is applied for L-mode plasmas at TEXTOR (O. Schmitz et al., Plasma Phys. Control. Fusion 50 (2008) 115004). We report our first efforts to extend it to H-mode plasma diagnostics in DIII-D. This technique depends on the accuracy of the atomic data used in the collisional radiative model (CRM). We present predictions for the electron temperatures and densities by using recently calculated R-Matrix With Pseudostates (RMPS) and Convergent Close-Coupling (CCC) electron-impact excitation and ionization data. We include contributions from higher Rydberg states by means of the projection matrix. These effects become significant for high electron density conditions, which are typical in H-mode. We apply a non-equilibrium model for the time propagation of the ionization balance to predict line emission profiles from experimental H-mode data from DIII-D.

  14. Food Web Structure in a Harsh Glacier-Fed River

    PubMed Central

    Clitherow, Leonie R.; Carrivick, Jonathan L.; Brown, Lee E.

    2013-01-01

    Glacier retreat is occurring across the world, and associated river ecosystems are expected to respond more rapidly than those in flowing waters in other regions. The river environment directly downstream of a glacier snout is characterised by extreme low water temperature and unstable channel sediments but these habitats may become rarer with widespread glacier retreat. In these extreme environments food web dynamics have been little studied, yet they could offer opportunities to test food web theories using highly resolved food webs owing to their low taxonomic richness. This study examined the interactions of macroinvertebrate and diatom taxa in the Ödenwinkelkees river, Austrian central Alps between 2006 and 2011. The webs were characterised by low taxon richness (13–22), highly connected individuals (directed connectance up to 0.19) and short mean food chain length (2.00–2.36). The dominant macroinvertebrates were members of the Chironomidae genus Diamesa and had an omnivorous diet rich in detritus and diatoms as well as other Chironomidae. Simuliidae (typically detritivorous filterers) had a diet rich in diatoms but also showed evidence of predation on Chironomidae larvae. Food webs showed strong species-averaged and individual size structuring but mass-abundance scaling coefficients were larger than those predicted by metabolic theory, perhaps due to a combination of spatial averaging effects of patchily distributed consumers and resources, and/or consumers deriving unquantified resources from microorganisms attached to the large amounts of ingested rock fragments. Comparison of food web structural metrics with those from 62 published river webs suggest these glacier-fed river food web properties were extreme but in line with general food web scaling predictions, a finding which could prove useful to forecast the effects of anticipated future glacier retreat on the structure of aquatic food webs. PMID:23613751

  15. Glacier Change Detection in the Hindu Kush of Afghanistan

    NASA Astrophysics Data System (ADS)

    Shroder, J. F.; Bishop, M. P.

    2004-12-01

    A half century of intermittently collected cryospheric and hydrologic data in Afghanistan has involved diverse field surveys, aerial photography, and satellite imagery that enable change detection in the war-torn, drought-stricken region. Afghanistan relies heavily upon snow-and ice-melt for vital irrigation and ground-water recharge, yet the past two decades of war have only exacerbated the originally already deficient information collection and analysis of such data. Glacier field studies and base-line inventory work initiated in the pre-war 1960-1970 period are now providing limited change detection information for the vital physical analysis necessary in the reconstruction of the country. Five case study areas were selected for renewed assessment over the intervening half century, from the western-most ice masses of the Koh-i-Foladi region in central Afghanistan, through the Mir Samir and Sakhi regions of the central Hindu Kush, to the Keshnikhan and Pamir areas of the Wakhan Corridor. Certain incompatibilities or ambiguities exist between Soviet-era and Western-derived data sets. In general, however, glaciers of Afghanistan are continuing to downwaste and retreat, with smaller ice masses disappearing altogether, presumably as the climatic snowline continues to rise above the peaks, a trend first noticed in the 1960s. Glacier survival in the lower central areas is now in part determined by topographic shielding from solar radiation high in shadowed cirques, or being preserved beneath increasing debris covers, whereas in the higher regions to the northeast, fewer changes to the larger, higher altitude glaciers are apparent. Renewed assessment of all Afghanistan glaciers is now underway as a part of the USGS- and NASA-supported GLIMS (Global Land-Ice Measurements from Space) project, and is viewed as an important element in the primary geodata collection and hazard assessment necessary for aiding in rebuilding the infrastructure of the beleaguered nation.

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

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  17. Southern Alaska as an Example of the Long-Term Consequences of Mountain Building Under the Influence of Glaciers

    NASA Technical Reports Server (NTRS)

    Meigs, Andrew; Sauber, Jeanne

    2000-01-01

    Southern Alaska is a continent-scale region of ongoing crustal deformation within the Pacific-North American plate boundary zone. Glaciers and glacial erosion have dictated patterns of denudation in the orogen over the last approx. 5 My. The orogen comprises three discrete topographic domains from south to north, respectively: (1) the Chugach/St. Elias Range; (2) the Wrangell Mountains; and (3) the eastern Alaska Range. Although present deformation is distributed across the orogen, much of the shortening and uplift are concentrated in the Chugach/St. Elias Range. A systematic increase in topographic wavelength of the range from east to west reflects east-to-west increases in the width of a shallowly-dipping segment of the plate interface, separation of major upper plate structures, and a decrease in the obliquity of plate motion relative to the plate boundary. Mean elevation decays exponentially from approx. 2500 m to approx. 1100 m from east to west, respectively. Topographic control on the present and past distribution of glaciers is indicated by close correspondence along the range between mean elevation and the modern equilibrium line altitude of glaciers (ELA) and differences in the modern ELA, mean annual precipitation and temperature across the range between the windward, southern and leeward, northern flanks. Net, range- scale erosion is the sum of: (1) primary bedrock erosion by glaciers and (2) erosion in areas of the landscape that are ice-marginal and are deglaciated at glacial minima. Oscillations between glacial and interglacial climates controls ice height and distribution, which, in turn, modulates the locus and mode of erosion in the landscape. Mean topography and the mean position of the ELA are coupled because of the competition between rock uplift, which tends to raise the ELA, and enhanced orographic precipitation accompanying mountain building, which tends to lower the ELA. Mean topography is controlled both by the 60 deg latitude and maritime

  18. 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

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

    NASA Astrophysics Data System (ADS)

    Trussel, Barbara Lea

    , increased water input may cause lake level in rifts to rise resulting in faster rift propagation and spreading. Similar formation and disintegration of floating tongues are expected to occur in the glacier's future, as the ice divide lies below the current lake level. In addition to calving retreat, Yakutat Glacier is rapidly thinning, which lowers its surface and therefore exposes the ice to warmer air temperatures causing increased thinning. Even under a constant climate, this positive feedback mechanism would force Yakutat Glacier to quickly retreat and mostly disappear. Simulations of future mass loss were run for two scenarios, keeping the current climate and forcing it with a projected warming climate. Results showed that over 95% of the glacier ice will have disappeared by 2120 or 2070 under a constant vs projected climate, respectively. For the first few decades, the glacier will be able to maintain its current thinning rate by retreating and thus losing areas of lowest elevation. However, once higher elevations have thinned substantially, the glacier cannot compensate any more to maintain a constant thinning rate and transfers into an unstable run-away situation. To stop this collapse and transform Yakutat Glacier into equilibrium in its current geometry, air temperatures would have to drop by 1.5 K or precipitation would have to increase by more than 50%. An increase in precipitation alone is unlikely to lead to a stable configuration, due to the very small current accumulation area.

  20. Mass balance and hydrological contribution of glaciers in northern and central Chile

    NASA Astrophysics Data System (ADS)

    MacDonell, Shelley; Vivero, Sebastian; McPhee, James; Ayala, Alvaro; Pellicciotti, Francesca; Campos, Cristian; Caro, Dennys; Ponce, Rodrigo

    2016-04-01

    Water is a critical resource in the northern and central regions of Chile, as the area supports more than 40% of the country's population, and the regional economy depends on agricultural production and mining, which are two industries that rely heavily on a consistent water supply. Due to relatively low rates of rainfall, meltwater from snow and ice bodies in the highland areas provides a key component of the annual water supply in these areas. Consequently, accurate estimates of the rates of ablation of the cryosphere (i.e. snow and ice) are crucial for predicting current supply rates, and future projections. Whilst snow is generally a larger contributor of freshwater, during periods of drought, glaciers provide a significant source. This study aims to determine the contribution of glaciers to two catchments in northern and central Chile during a 2.5 year period, which largely consisted of extreme dry periods, but also included the recent El Niño event. This study combined field and modelling studies to understand glacier and rock glacier contributions in the Tapado (30°S), Yeso (33°S) catchments. In the field we undertook glaciological mass balance monitoring of three glaciers, monitored albedo and snow line changes using automatic cameras for three glaciers, measured discharge continuously at several points, installed six automatic weather stations and used thermistors to monitor thermal regime changes of two rock glaciers. The combination of these datasets where used to drive energy balance and hydrological models to estimate the contribution of ice bodies to streamflow in the two studied catchments. Over the course of the study all glaciers maintained a negative mass balance, however glaciers in central Chile lost more mass, which is due to the higher melt rates experienced due to lower elevations and higher temperatures. Areas free of debris generally contributed more to streamflow than sediment covered regions, and snow generally contributed more over

  1. 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

  2. 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

  3. Evaluation of Lateglacial temperatures in the Southern Alps of New Zealand based on glacier modelling at Irishman Stream, Ben Ohau Range

    NASA Astrophysics Data System (ADS)

    Doughty, Alice M.; Anderson, Brian M.; Mackintosh, Andrew N.; Kaplan, Michael R.; Vandergoes, Marcus J.; Barrell, David J. A.; Denton, George H.; Schaefer, Joerg M.; Chinn, Trevor J. H.; Putnam, Aaron E.

    2013-08-01

    Climate proxy records from the middle to high latitude Southern Hemisphere indicate that a Lateglacial (15,000-11,500 years ago) climate reversal, approximately coeval with the Antarctic Cold Reversal (ACR), interrupted a warming trend during deglaciation. In New Zealand, some palaeoclimate proxy records indicate a cool episode during the ACR (ca 14,500-12,500 years ago), while others do not express a significant change in climate. Recently published moraine maps and ages present an opportunity to improve the palaeoclimate interpretation through numerical modelling of glaciers. We use a coupled energy-balance and ice-flow model to quantify palaeoclimate from past glacier extent constrained by mapped and dated moraines in the headwaters of Irishman Stream, a high-elevation catchment in the Southern Alps. First, a suite of steady-state model runs is used to identify the temperature and precipitation forcing required to fit the modelled glacier to well-dated Lateglacial moraine crests. Second, time-dependent glacier simulations forced by a nearby proxy temperature record derived from chironomids are used to assess the fit with the glacial geomorphic record. Steady-state experiments using an optimal parameter set demonstrate that the conditions under which the 13,000 year old moraine formed were 2.3-3.2 °C colder than present with the range in temperature corresponding to a ±20% variance in precipitation relative to the present-day. This reconstructed climate change relative to the present-day corresponds to an equilibrium-line altitude of ca 2000 ± 40 m above sea level (asl), which is ca 400 m lower than present. Time-dependent simulations of glacier length produce ice advance to within 100 m of the 13,000 year old terminal moraine, indicating that the chironomid-based temperature forcing and moraine record provide consistent information about past climate. Our results, together with other climate proxy reconstructions from pollen records and marine sediment cores

  4. 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.

  5. 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.

  6. 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

  7. Surface Mass Balance of the Columbia Glacier, Alaska, 1978 and 2010 Balance Years

    USGS Publications Warehouse

    O'Neel, Shad

    2012-01-01

    Although Columbia Glacier is one of the largest sources of glacier mass loss in Alaska, surface mass balance measurements are sparse, with only a single data set available from 1978. The dearth of surface mass-balance data prohibits partitioning of the total mass losses between dynamics and surface forcing; however, the accurate inclusion of calving glaciers into predictive models requires both dynamic and climatic forcing of total mass balance. During 2010, the U.S. Geological Survey collected surface balance data at several locations distributed over the surface of Columbia Glacier to estimate the glacier-wide annual balance for balance year 2010 using the 2007 area-altitude distribution. This report also summarizes data collected in 1978, calculates the 1978 annual surface balance, and uses these observations to constrain the 2010 values, particularly the shape of the balance profile. Both years exhibit balances indicative of near-equilibrium surface mass-balance conditions, and demonstrate the importance of dynamic processes during the rapid retreat.

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  9. Insight into glacier climate interaction: reconstruction of the mass balance field using ice extent data

    NASA Astrophysics Data System (ADS)

    Visnjevic, Vjeran; Herman, Frédéric; Licul, Aleksandar

    2016-04-01

    With the end of the Last Glacial Maximum (LGM), about 20 000 years ago, ended the most recent long-lasting cold phase in Earth's history. We recently developed a model that describes large-scale erosion and its response to climate and dynamical changes with the application to the Alps for the LGM period. Here we will present an inverse approach we have recently developed to infer the LGM mass balance from known ice extent data, focusing on a glacier or ice cap. The ice flow model is developed using the shallow ice approximation and the developed codes are accelerated using GPUs capabilities. The mass balance field is the constrained variable defined by the balance rate β and the equilibrium line altitude (ELA), where c is the cutoff value: b = max(βṡ(S(z) - ELA), c) We show that such a mass balance can be constrained from the observed past ice extent and ice thickness. We are also investigating several different geostatistical methods to constrain spatially variable mass balance, and derive uncertainties on each of the mass balance parameters.

  10. 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).

  11. 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.

  12. 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.

  13. Tide-modulated seismicity in the vicinity of a calving front (Bowdoin Glacier, Greenland)

    NASA Astrophysics Data System (ADS)

    Podolskiy, Evgeny A.; Sugiyama, Shin; Funk, Martin; Walter, Fabian; Genco, Riccardo; Tsutaki, Shun; Minowa, Masahiro; Ripepe, Maurizio

    2016-04-01

    For cryogenic microseismicity to be used as an indicator of climate-induced dynamic change, it must have a clear connection with glacier dynamics (including calving, basal sliding, strain, and melt). There is currently much speculation and disagreement about these connections, particularly, with respect to the relationship between tide-modulated seismicity and dynamics of calving glaciers. Here we analyze records from an on-ice seismometer placed 250 m from the calving front of Bowdoin Glacier, northwestern Greenland. We find that the overall microseismic activity of this glacier is at least an order of magnitude larger than previously reported (more than 100,000 events within 2 weeks and up to 600 events per hour) and that it is positively correlated with falling tide velocity. Using high-resolution surface displacement measurements, we show for the first time that the correlation is relayed through strain-rate variations. The strain-rate corresponds with longitudinal stretching of the glacial surface, in response to higher melt rates and falling tide, both of which accelerate glacier movement and enhance the stretching flow regime. Previous proposals to use icequakes as a proxy for grounding line migration need to be reconsidered because Bowdoin Glacier is grounded, with no tide-induced vertical bending of the near-floating tongue, which always exhibits microseismic activity due to continuous longitudinal stretching.

  14. Two methods for firn-area and mass-balance monitoring of Svalbard glaciers with SAR satellite images

    NASA Astrophysics Data System (ADS)

    König, Max; Winther, Jan-Gunnar; Kohler, Jack; König, Florian

    This paper presents two methods for glacier monitoring on Svalbard using synthetic aperture radar (SAR) satellite images. Both methods were developed on glaciers in the Kongsfjorden area. The first method monitors the firn area extent and the firn line over time by thresholding and filtering the SAR image. Manual detection of the threshold is preferable, but using a constant threshold for all images also gives adequate results. A retreat of the firn-line position is visible, especially on Kongsvegen, corresponding to consecutive years of negative mass balance. The second method applies a k-means classification to three clusters on the glacier surface. The areal extent of the resulting class on the upper part of the glacier correlates remarkably well with the independently measured mass balance of Kongsvegen, having a correlation coefficient of around 0.89 for the various glaciers. This is because the snow from the accumulation area influences the k-means classification. Thus, on glaciers where mass-balance values are available, new mass-balance values can be predicted solely from SAR images. For glaciers where no mass balance is available, the area change cannot be calibrated to absolute mass-balance values, but relative changes can be predicted.

  15. 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%.

  16. Microbial biodiversity in glacier-fed streams

    PubMed Central

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

    2013-01-01

    While glaciers become increasingly recognised as a habitat for diverse and active microbial communities, effects of their climate change-induced retreat on the microbial ecology of glacier-fed streams remain elusive. Understanding the effect of climate change on microorganisms in these ecosystems is crucial given that microbial biofilms control numerous stream ecosystem processes with potential implications for downstream biodiversity and biogeochemistry. Here, using a space-for-time substitution approach across 26 Alpine glaciers, we show how microbial community composition and diversity, based on 454-pyrosequencing of the 16S rRNA gene, in biofilms of glacier-fed streams may change as glaciers recede. Variations in streamwater geochemistry correlated with biofilm community composition, even at the phylum level. The most dominant phyla detected in glacial habitats were Proteobacteria, Bacteroidetes, Actinobacteria and Cyanobacteria/chloroplasts. Microorganisms from ice had the lowest α diversity and contributed marginally to biofilm and streamwater community composition. Rather, streamwater apparently collected microorganisms from various glacial and non-glacial sources forming the upstream metacommunity, thereby achieving the highest α diversity. Biofilms in the glacier-fed streams had intermediate α diversity and species sorting by local environmental conditions likely shaped their community composition. α diversity of streamwater and biofilm communities decreased with elevation, possibly reflecting less diverse sources of microorganisms upstream in the catchment. In contrast, β diversity of biofilms decreased with increasing streamwater temperature, suggesting that glacier retreat may contribute to the homogenisation of microbial communities among glacier-fed streams. PMID:23486246

  17. 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.

  18. 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…

  19. 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

  20. 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.

  1. 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

  2. Recent fluctuations of the Argentinian glaciers

    NASA Astrophysics Data System (ADS)

    Leiva, Juan Carlos

    1999-10-01

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

  3. ICESat laser altimetry over small mountain glaciers

    NASA Astrophysics Data System (ADS)

    Treichler, Désirée; Kääb, Andreas

    2016-09-01

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

  4. The unfolding instability of the remnant Larsen B Ice Shelf and its tributary glaciers

    NASA Astrophysics Data System (ADS)

    Khazendar, A.; Borstad, C. P.; Scheuchl, B.; Rignot, E. J.; Seroussi, H.

    2014-12-01

    The disintegration of the northern and central parts of the Larsen B Ice Shelf in 2002 demonstrated the strong interaction between ice shelves and their tributary glaciers. The surviving southern part of the ice shelf and its glaciers have hitherto received less attention, based on the assumption that the remnant ice shelf continued to provide the glaciers with sufficient buttressing. Our findings here contradict this view, revealing significant changes since 2002 or earlier from IceBridge altimetry measurements and InSAR-derived flow speeds. The surfaces of Leppard and Flask glaciers directly upstream of their grounding lines lowered persistently by 15 to 20 m in the period 2002-2011. The thinning appears to be dynamic as the flow of both glaciers and the remnant ice shelf accelerated in the same period. Flask in particular started accelerating as early as 2000 almost doubling its flow speed by 2012. These changes are associated with a reduction in the buttressing afforded by the remnant ice shelf and an increase in its fracture as shown by our numerical modeling. One large rift in particular, only 12 km downstream of the grounding line, is revealed by the observations and modeling to be rapidly extending across the ice shelf, defining the likely front of the next large calving event. The increased fracture and continued flow acceleration of the remnant Larsen B Ice Shelf presage its approaching demise.

  5. Adiabatic evolution of plasma equilibrium

    PubMed Central

    Grad, H.; Hu, P. N.; Stevens, D. C.

    1975-01-01

    A new theory of plasma equilibrium is introduced in which adiabatic constraints are specified. This leads to a mathematically nonstandard structure, as compared to the usual equilibrium theory, in which prescription of pressure and current profiles leads to an elliptic partial differential equation. Topologically complex configurations require further generalization of the concept of adiabaticity to allow irreversible mixing of plasma and magnetic flux among islands. Matching conditions across a boundary layer at the separatrix are obtained from appropriate conservation laws. Applications are made to configurations with planned islands (as in Doublet) and accidental islands (as in Tokamaks). Two-dimensional, axially symmetric, helically symmetric, and closed line equilibria are included. PMID:16578729

  6. Points of Equilibrium in Electrostatic Fields.

    ERIC Educational Resources Information Center

    Rogers, Peter J.

    1979-01-01

    Discusses the electric field line pattern for four equal charges of the same sign placed at the corners of a square. The electric field intensity and the point of equilibrium are interpreted, taking into account three dimensions. (HM)

  7. 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

  8. Microbial diversity on Icelandic glaciers and ice caps

    PubMed Central

    Lutz, Stefanie; Anesio, Alexandre M.; Edwards, Arwyn; Benning, Liane G.

    2015-01-01

    Algae are important primary colonizers of snow and glacial ice, but hitherto little is known about their ecology on Iceland's glaciers and ice caps. Due do the close proximity of active volcanoes delivering large amounts of ash and dust, they are special ecosystems. This study provides the first investigation of the presence and diversity of microbial communities on all major Icelandic glaciers and ice caps over a 3 year period. Using high-throughput sequencing of the small subunit ribosomal RNA genes (16S and 18S), we assessed the snow community structure and complemented these analyses with a comprehensive suite of physical-, geo-, and biochemical characterizations of the aqueous and solid components contained in snow and ice samples. Our data reveal that a limited number of snow algal taxa (Chloromonas polyptera, Raphidonema sempervirens and two uncultured Chlamydomonadaceae) support a rich community comprising of other micro-eukaryotes, bacteria and archaea. Proteobacteria and Bacteroidetes were the dominant bacterial phyla. Archaea were also detected in sites where snow algae dominated and they mainly belong to the Nitrososphaerales, which are known as important ammonia oxidizers. Multivariate analyses indicated no relationships between nutrient data and microbial community structure. However, the aqueous geochemical simulations suggest that the microbial communities were not nutrient limited because of the equilibrium of snow with the nutrient-rich and fast dissolving volcanic ash. Increasing algal secondary carotenoid contents in the last stages of the melt seasons have previously been associated with a decrease in surface albedo, which in turn could potentially have an impact on the melt rates of Icelandic glaciers. PMID:25941518

  9. Microbial diversity on Icelandic glaciers and ice caps.

    PubMed

    Lutz, Stefanie; Anesio, Alexandre M; Edwards, Arwyn; Benning, Liane G

    2015-01-01

    Algae are important primary colonizers of snow and glacial ice, but hitherto little is known about their ecology on Iceland's glaciers and ice caps. Due do the close proximity of active volcanoes delivering large amounts of ash and dust, they are special ecosystems. This study provides the first investigation of the presence and diversity of microbial communities on all major Icelandic glaciers and ice caps over a 3 year period. Using high-throughput sequencing of the small subunit ribosomal RNA genes (16S and 18S), we assessed the snow community structure and complemented these analyses with a comprehensive suite of physical-, geo-, and biochemical characterizations of the aqueous and solid components contained in snow and ice samples. Our data reveal that a limited number of snow algal taxa (Chloromonas polyptera, Raphidonema sempervirens and two uncultured Chlamydomonadaceae) support a rich community comprising of other micro-eukaryotes, bacteria and archaea. Proteobacteria and Bacteroidetes were the dominant bacterial phyla. Archaea were also detected in sites where snow algae dominated and they mainly belong to the Nitrososphaerales, which are known as important ammonia oxidizers. Multivariate analyses indicated no relationships between nutrient data and microbial community structure. However, the aqueous geochemical simulations suggest that the microbial communities were not nutrient limited because of the equilibrium of snow with the nutrient-rich and fast dissolving volcanic ash. Increasing algal secondary carotenoid contents in the last stages of the melt seasons have previously been associated with a decrease in surface albedo, which in turn could potentially have an impact on the melt rates of Icelandic glaciers. PMID:25941518

  10. Microbial diversity on Icelandic glaciers and ice caps.

    PubMed

    Lutz, Stefanie; Anesio, Alexandre M; Edwards, Arwyn; Benning, Liane G

    2015-01-01

    Algae are important primary colonizers of snow and glacial ice, but hitherto little is known about their ecology on Iceland's glaciers and ice caps. Due do the close proximity of active volcanoes delivering large amounts of ash and dust, they are special ecosystems. This study provides the first investigation of the presence and diversity of microbial communities on all major Icelandic glaciers and ice caps over a 3 year period. Using high-throughput sequencing of the small subunit ribosomal RNA genes (16S and 18S), we assessed the snow community structure and complemented these analyses with a comprehensive suite of physical-, geo-, and biochemical characterizations of the aqueous and solid components contained in snow and ice samples. Our data reveal that a limited number of snow algal taxa (Chloromonas polyptera, Raphidonema sempervirens and two uncultured Chlamydomonadaceae) support a rich community comprising of other micro-eukaryotes, bacteria and archaea. Proteobacteria and Bacteroidetes were the dominant bacterial phyla. Archaea were also detected in sites where snow algae dominated and they mainly belong to the Nitrososphaerales, which are known as important ammonia oxidizers. Multivariate analyses indicated no relationships between nutrient data and microbial community structure. However, the aqueous geochemical simulations suggest that the microbial communities were not nutrient limited because of the equilibrium of snow with the nutrient-rich and fast dissolving volcanic ash. Increasing algal secondary carotenoid contents in the last stages of the melt seasons have previously been associated with a decrease in surface albedo, which in turn could potentially have an impact on the melt rates of Icelandic glaciers.

  11. 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.

  12. Implementation of a new atomic basis for the He I equilibrium line ratio technique for electron temperature and density diagnostic in the SOL for H-mode plasmas in DIII-D

    SciTech Connect

    Burgos, JMM; Schmitz, O.; Unterberg, Ezekial A; Loch, S. D.; Ballance, C. P.

    2011-01-01

    Evaluating the ratio of selected helium lines allows for measurement of electron densities and temperatures. This technique is applied for L-mode plasmas at TEXTOR (O. Schmitz et al., Plasma Phys. Control. Fusion 50 (2008) 115004). We report our first efforts to extend it to H-mode plasma diagnostics in DIII-D. This technique depends on the accuracy of the atomic data used in the collisional radiative model (CRM). We present predictions for the electron temperatures and densities by using recently calculated R-Matrix With Pseudostates (RMPS) and Convergent Close-Coupling (CCC) electron-impact excitation and ionization data. We include contributions from higher Rydberg states by means of the projection matrix. These effects become significant for high electron density conditions, which are typical in H-mode. We apply a non-equilibrium model for the time propagation of the ionization balance to predict line emission profiles from experimental H-mode data from DIII-D. (C) 2010 Elsevier B.V. All rights reserved.

  13. 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.

  14. 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.

  15. Slow geomorphologic evolution of rock glaciers in marginal periglacial environment of Southern Carpathians (Romania)

    NASA Astrophysics Data System (ADS)

    Necsoiu, M.; Onaca, A.; Ardelean, F.; Sirbu, F.; Magori, B.

    2015-12-01

    The development of remote sensing techniques in the last several decades now permits surveying areas that are difficult to access and allows capturing geomorphological processes that operate at low deformation rates. In marginal periglacial environments, where the kinematics of the rock glaciers are defined by slow flow, specific remote sensing techniques (e.g., optical image cross-correlation techniques or multitemporal interferometry) are preferred because they are capable of providing ground displacement accuracies on the order of a few mm. Recent multi-temporal image analysis of high-resolution optical and radar satellite imagery of the Retezat Mountains (in the southern Carpathian Mountains of Romania) rock glaciers revealed very low rates of deformation and confirmed that active rock glaciers still exist here. These findings were supported by geophysical investigations (electrical resistivity tomography and ground penetrating radar) and thermal monitoring, which confirmed the patchy distribution of permafrost within the investigated rock glaciers. Given the high depth of the active layer (between 5 and 10 m) and the limited thickness of the ground ice bodies, the permafrost in the Retezat Mountains was assumed to exist in marginal conditions. The sporadic permafrost from the alpine zone of the southern Carpathians is extremely sensitive to environmental changes and responds directly to air temperature fluctuations. As an example, geophysical investigations between 2007 and 2014 revealed significant ground ice disappearance from one of the studied rock glaciers (i.e., Pietrele) as a result of rising air temperature. Optical satellite data revealed that the disappearance of ground ice led to accelerated movement of this rock glacier after 2007. The variability of horizontal movement is strongly controlled by the ground thermal regime. The results confirm the hypothesis that permafrost is not in equilibrium with the present-day climate in the Romanian

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

    USGS Publications Warehouse

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

    2003-01-01

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

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. 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

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  4. 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

  5. Magnetospheric equilibrium with anisotropic pressure

    SciTech Connect

    Cheng, C.Z.

    1991-07-01

    Self-consistent magnetospheric equilibrium with anisotropic pressure is obtained by employing an iterative metric method for solving the inverse equilibrium equation in an optimal flux coordinate system. A method of determining plasma parallel and perpendicular pressures from either analytic particle distribution or particle distribution measured along the satellite's path is presented. The numerical results of axisymmetric magnetospheric equilibrium including the effects of finite beta, pressure anisotropy, and boundary conditions are presented for a bi-Maxwellian particle distribution. For the isotropic pressure cases, the finite beta effect produces an outward expansion of the constant magnetic flux surfaces in relation to the dipole field lines, and along the magnetic field the toroidal ring current is maximum at the magnetic equator. The effect of pressure anisotropy is found to further expand the flux surfaces outward. Along the magnetic field lines the westward ring current can be peak away from the equator due to an eastward current contribution resulting from pressure anisotropy. As pressure anisotropy increases, the peak westward current can become more singular. The outer boundary flux surface has significant effect on the magnetospheric equilibrium. For the outer flux boundary resembling dayside compressed flux surface due to solar wind pressure, the deformation of the magnetic field can be quite different from that for the outer flux boundary resembling the tail-like surface. 23 refs., 17 figs.

  6. Malaspina Glacier, Alaska, Perspective with Landsat Overlay

    NASA Technical Reports Server (NTRS)

    2003-01-01

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

    This perspective view was created from a Landsat satellite image and an elevation model generated by the Shuttle Radar Topography Mission (SRTM). Landsat views both visible and infrared light, which have been combined here into a color composite that generally shows glacial ice in light blue, snow in white, vegetation in green, bare rock in grays and tans, and the ocean (foreground) in dark blue. The back (northern) edge of the data set forms a false horizon that meets a false sky.

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

    Glaciers are sensitive indicators of climatic change. They can grow and thicken with increasing snowfall and/or decreased melting. Conversely, they can retreat and thin if snowfall decreases and/or atmospheric temperatures rise and cause increased melting. Landsat imaging has been an excellent tool for mapping the changing geographic extent of glaciers since 1972. The elevation measurements taken by SRTM in February 2000 now provide a near-global baseline against which future non-polar region glacial thinning or thickening can be assessed.

  7. The geochemical record in rock glaciers

    USGS Publications Warehouse

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

    1998-01-01

    A 9.5 m ice core was extracted from beneath the surficial debris cover of a rock glacier at Galena Creek, northwestern Wyoming. The core contains clean, bubble-rich ice with silty debris layers spaced at roughly 20 cm intervals. The debris layers are similar in appearance to those in typical alpine glaciers, reflecting concentration of debris by melting at the surface during the summer ablation season. Profiles of stable isotope concentrations and electrical conductivity measurements provide independent evidence for melting in association with debris layers. These observations are consistent with a glacial origin for the ice, substantiating the glacigenic model for rock glacier formation. The deuterium excess profile in the ice indicates that the total depth of meltwater infiltration is less than the thickness of one annual layer, suggesting that isotope values and other geochemical signatures are preserved at annual resolution. This finding demonstrates the potential for obtaining useful paleoclimate information from rock glacier ice.

  8. 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

  9. 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

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

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

  13. Status and trend of the Kittlitz's Murrelet Brachyramphus brevirostris in Glacier Bay, Alaska

    USGS Publications Warehouse

    Piatt, J.F.; Arimitsu, M.; Drew, G.; Madison, E.N.; Bodkin, J.; Romano, Marc D.

    2011-01-01

    We conducted standardized surveys for marine birds in Glacier Bay in seven years between 1991 and 2008. From our most recent survey, a combination of line- and strip-transect methods completed in 2008, we estimated that 4981 (95% CI 1293-8670) Kittlitz's Murrelets Brachyramphus brevirostris resided in Glacier Bay during the month of June, together with 12 195 (5607-18 783) Marbled Murrelets B. marmoratus. When counts were prorated to assign unidentified Brachyramphus murrelets to species, population estimates increased to 5641 Kittlitz's Murrelets and 13 810 Marbled Murrelets. Our surveys of bird numbers in Glacier Bay between 1991 and 2008 revealed that Kittlitz's Murrelet declined by ???85% during this period. Trend analysis suggested a rate of decline between -10.7% and -14.4% per year. No direct human impacts (e.g., bycatch, oil pollution, vessel disturbance) in our study area could fully account for a decline of this magnitude. Widespread declines of Brachyramphus murrelets and Harbor Seals Phoca vitulina in the Gulf of Alaska during the 1980s-1990s suggest large-scale influences on these marine predators, perhaps related to climate-mediated cycles in food supply. Other natural factors that may impact Glacier Bay populations include predation by avian and terrestrial predators, widespread glacial retreat and its effect on nesting and foraging habitats, and competition for food with marine predators whose abundance in Glacier Bay has increased markedly in recent years (Humpback Whales Megaptera novaeangliae and Steller Sea Lions Eumetopias jubatus).

  14. Increased flow speed on a large East Antarctic outlet glacier caused by subglacial floods

    NASA Astrophysics Data System (ADS)

    Stearns, Leigh A.; Smith, Benjamin E.; Hamilton, Gordon S.

    2008-12-01

    Changes in the velocity of large outlet glaciers and ice streams in Greenland and Antarctica are important for ice-sheet mass balance and hence sea level. Mass loss in large parts of both ice sheets is being driven by the recent accelerations of outlet glaciers in response to unknown or poorly constrained climatic or internal perturbations in their boundary conditions. Surprisingly active networks of subglacial lake drainage have recently been found beneath the Antarctic ice sheet and tentatively linked to the onset of fast ice flow. Here we report an observed acceleration of ice velocity on Byrd Glacier, East Antarctica, of about 10% of the original speed between December 2005 and February 2007. The acceleration extended along the entire 75km glacier trunk and its onset coincided with the discharge of about 1.7km3 of water from two large subglacial lakes located about 200km upstream of the grounding line. Deceleration coincided with the termination of the flood. Our findings provide direct evidence that an active lake drainage system can cause large and rapid changes in glacier dynamics.

  15. Calving processes and lake evolution at Miage glacier, Mont Blanc, Italian Alps

    NASA Astrophysics Data System (ADS)

    Diolaiuti, G.; Kirkbride, M. P.; Smiraglia, C.; Benn, D. I.; D'Agata, C.; Nicholson, L.

    A marginal ice-contact lake at Miage glacier, Mont Blanc, Italian Alps, has been studied to reconstruct changes in lake area. Historical sources, comprising sketches, maps, photographs and scientific surveys, have been supplemented by recent field surveys. These include surveys of glacier surface velocity (which varied along the glacier tongue from 70 m a-1 in the upper part to about 6 m a-1 close to the snout, consistent with data in the literature, showing that velocity rates have remained constant during the last 40 years), volumetric ice-cliff loss (-92 000 ± 180 m3 in 2002 03), lake temperature and bathymetry, and qualitative observation of calving events, crevassing, and meltwater production. Results indicate that the lake has been stable for the last half-century following a period of enlargement due to ice-marginal retreat. The lake hydrology is complex, with possible reversals of englacial water flow causing infrequent emptying episodes. The debris cover on the glacier and ice-cliff surfaces seems to have played an important role in the ice-cliff evolution and the calving phenomena; calving is driven by undercutting at the water-line aided by the opening of water- and debris-filled crevasses in the glacier surface.

  16. Geostatistical evaluation of satellite radar altimetry for high-resolution mapping of Lambert Glacier, Antarctica

    NASA Technical Reports Server (NTRS)

    Herzfeld, Ute C.; Lingle, Craig S.; Lee, Li-Her

    1993-01-01

    The potential of satellite radar altimetry for high-resolution mapping of Antarctic ice streams is evaluated, using retracked and slope-corrected data from the Lambert Glacier and Amery Ice Shelf area, East Antarctica, acquired by Geosat during the Exact Repeat Mission (ERM), 1986-89. The map area includes lower Lambert Glacier north of 72.18 deg S, the southern Amery Ice Shelf, and the grounded inland ice sheet on both sides. The Geosat ERM altimetry is found to provide substantially more complete coverage than the 1978 Seasat altimetry, due to improved tracking. Variogram methods are used to estimate the noise levels in the data as a function of position throughout the map area. The spatial structure in the data is quantified by constructing experimental variograms using altimetry from the area of the grounding zone of Lambert Glacier, which is the area chiefly of interest in this topographically complex region. Kriging is employed to invert the along-track height measurements onto a fine-scale 3 km grid. The unsmoothed along-track Geosat ERM altimetry yields spatially continuous maps showing the main topographic features of lower Lambert Glacier, upper Amery Ice Shelf and the adjacent inland ice sheet. The probable position of the grounding line of Lambert Glacier is identified from a break in slope at the grounded ice/floating ice transition. The approximate standard error of the kriged map is inferred from the data noise levels.

  17. 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.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Nicholson, Lindsey; Prinz, Rainer; Kaser, Georg

    2013-04-01

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

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

    USGS Publications Warehouse

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

    2003-01-01

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

  2. Comparative metagenome analysis of an Alaskan glacier.

    PubMed

    Choudhari, Sulbha; Lohia, Ruchi; Grigoriev, Andrey

    2014-04-01

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

  3. Glacier mass budget measurements by hydrologic means

    USGS Publications Warehouse

    Tangborn, Wendell V.

    1966-01-01

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

  4. 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.

  5. 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

  6. The evolving instability of the remnant Larsen B Ice Shelf and its tributary glaciers

    NASA Astrophysics Data System (ADS)

    Khazendar, Ala; Borstad, Christopher P.; Scheuchl, Bernd; Rignot, Eric; Seroussi, Helene

    2015-06-01

    Following the 2002 disintegration of the northern and central parts of the Larsen B Ice Shelf, the tributary glaciers of the southern surviving part initially appeared relatively unchanged and hence assumed to be buttressed sufficiently by the remnant ice shelf. Here, we modify this perception with observations from IceBridge altimetry and InSAR-inferred ice flow speeds. Our analyses show that the surfaces of Leppard and Flask glaciers directly upstream from their grounding lines lowered by 15 to 20 m in the period 2002-2011. The thinning appears to be dynamic as the flow of both glaciers and the remnant ice shelf accelerated in the same period. Flask Glacier started accelerating even before the 2002 disintegration, increasing its flow speed by ∼55% between 1997 and 2012. Starbuck Glacier meanwhile did not change much. We hypothesize that the different evolutions of the three glaciers are related to their dissimilar bed topographies and degrees of grounding. We apply numerical modeling and data assimilation that show these changes to be accompanied by a reduction in the buttressing afforded by the remnant ice shelf, a weakening of the shear zones between its flow units and an increase in its fracture. The fast flowing northwestern part of the remnant ice shelf exhibits increasing fragmentation, while the stagnant southeastern part seems to be prone to the formation of large rifts, some of which we show have delimited successive calving events. A large rift only 12 km downstream from the grounding line is currently traversing the stagnant part of the ice shelf, defining the likely front of the next large calving event. We propose that the flow acceleration, ice front retreat and enhanced fracture of the remnant Larsen B Ice Shelf presage its approaching demise.

  7. 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.

  8. 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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  11. Schmidt-hammer exposure-age dating (SHD) of Lateglacial rock glacier systems near the eastern margin of the European Alps

    NASA Astrophysics Data System (ADS)

    Kellerer-Pirklbauer, Andreas

    2016-04-01

    Rock glaciers are widespread permafrost landforms in Austria. Various rock glacier inventories list more than 4500 rock glaciers in the country; some 30-40% of them are intact. Relict (permafrost free) and pseudo-relict rock glaciers (sporadic and isolated permafrost particularly near the root zone) prevail in number. Rock glaciers are commonly formed over a period of several ka. Dating such landforms helps to understand palaeoclimatic conditions. In this study three rock glaciers consisting of gneiss were dated applying the Schmidt-hammer exposure-age dating (SHD) method. The rock glaciers are located at three neighbouring cirques in the Seckauer Tauern Range named Reichart Rock Glacier (RRG, area 1.26 km², length 1800 m, elevation range 1520-1940 m a.s.l.), Schöneben Rock Glacier (SRG, 0.11 km², 750 m, 1715-1905 m a.s.l.), and Dürrtal Rock Glacier (DRG, 0.08 km², 850 m, 1750-1980 m a.s.l.). RRG is one of the largest rock glaciers in Austria. All three landforms are influenced by lenses of permafrost at present (as indicated by ERT). During the LGM the Seckauer Tauern were covered by valley glaciers and deglaciation occurred presumably already early in the Alpine Lateglacial period. An analogue N-type Schmidt-hammer (proceq) was used for measuring the surface strength of stable blocks at the rock glacier surface by recording a rebound value (R-value) of a spring-loaded bolt. The R-value gives a relative measure of the surface hardness and hence time since exposure to weathering. Eight (RRG) or six (SRG, DRG) Schmidt-hammer measurement sites (with 50-100 individual readings) aligned along longitudinal transects (=former central flow line) between a talus slope (with relatively fresh boulders) in the root zone and the frontal ridge were measured. Mean R-value differences of 30.5 at RRG, 25.1 at SRG, and 20.7 at DRG were revealed along the three transects. The differences between the lowest and the highest R-value at the rock glaciers itself were 19.0 at RRG, 15

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    The Tibetan Plateau is one of the most extensively glaciated, non-Polar regions of the world, and its mountain glaciers are the primary source of melt water for several of the largest Asian rivers. During glacial cycles, Tibetan Plateau glaciers advanced and retreated multiple times, but remained restricted to the highest mountain areas as valley glaciers and ice caps. Because glacier extent is dominantly controlled by climate, the past extent of Tibetan glaciers provide information on regional climate. Here we present a study analyzing the past maximum extents of glaciers on the Tibetan Plateau with the output of a 3D glacier model, in an effort to quantify Tibetan Plateau climate. We have mapped present-day glaciers and glacial landforms deposited by formerly more extensive glaciers in eight mountain regions across the Tibetan Plateau, allowing us to define present-day and past maximum glacier outlines. Using a high-resolution (250 m) higher-order glacier model calibrated against present-day glacier extents, we have quantified the climate perturbations required to expand present-day glaciers to their past maximum extents. We find that a modest cooling of at most 6°C for a few thousand years is enough to attain past maximum extents, even with 25-75% precipitation reduction. This evidence for limited cooling indicates that the temperature of the Tibetan Plateau remained relatively stable over Quaternary glacial cycles. Given the significant sensitivity to temperature change, the expectation is perhaps that a future warmer climate might result in intense glacier reduction. We have tested this hypothesis and modeled the future glacier development for the three mountain regions with the largest present-day glacier cover using a projected warming of 2.8 to 6.2°C within 100 years (envelope limits from IPCC). These scenarios result in dramatic glacier reductions, including 24-100% ice volume loss after 100 years and 77-100% ice volume loss after 300 years.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  15. Calibration of a distributed ablation model for Zhadang Glacier, Tibetan Plateau,using a time lapse camera system

    NASA Astrophysics Data System (ADS)

    Schneider, C.; Huintjes, E.; Bhattacharya, A.; Sauter, T.; Yang, W.; Bolch, T.; Pieczonka, T.; Maussion, F.; Kang, S.; Buchroithner, M.; Scherer, D.; Yao, T.

    2011-12-01

    A 1-dimensional energy balance model for calculation of snow melt including sub-surface refreezing has been applied in a simplified version for distributed ablation modeling on Zhadang Glacier, Nyainqentanglha Range, Tibetan Plateau. The model includes a distributed computation of short-wave radiation on a digital elevation model. Reduction of short-wave radiation due to cloud cover has been accounted for by comparing calculated radiation against measurements at an automatic weather station (AWS) on the glacier. Air temperature was distributed using the lapse rate as derived from AWS measurements in different altitudes along the Zhadang Valley. Specific humidity and wind speed were assumed to be spatially invariant. Also, ice temperature in spring at 10 m depth was assumed to be equal all over the glacier. In the same way, accumulation as measured at the AWS using an ultra-sonic ranging system was assumed to be the same for the whole glacier surface. Snow accumulation was corrected using daily imagery obtained from an automatic time lapse camera system installed outside the glacier. The same time series of pictures allows for detailed spatial and temporal observation of the transient snow line. Gaps in AWS data are filled by downscaling of the output of WRF numerical atmospheric model output to the AWS location on the glacier. The runs of the ablation model are initialized using spatially distributed snow depth measured at a series of ablation stakes on the glacier. From the model results the location of the transient snow line can be precisely located. The findings are compared to the transient snow line as derived from the picture series. Besides the possibility of post-calibrating the spatially distributed ablation model, the results of this approach also allow for identifying further relevant spatial processes that are not yet considered.

  16. 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

    In the Northern Caucasus, glacier and climatic variations over the past centuries remain insufficiently documented. In this review, we summarized the high-resolution information on glacier and climate fluctuations in the region for the past millennium and provided a synthesis of these two lines of evidence with respect to regional climate change. The key areas considered in the paper are the Elbrus area, the Teberda and Arkhyz valleys in the Western Caucasus and the Cherek Bezengiisky and Tsey valleys in the Eastern Caucasus, where the most paleoclimatic evidence has been retrieved. We focused on the fluctuation records of the ten glaciers that are best documented. To reconstruct changes in glacier length in the past, we used aerial photos, optical space images, repeated photographs and old maps. The ages of moraines were defined with the help of instrumental records, historical images, old maps, and tree-ring dating. Lichenometry was used as a supplementary tool to determine the relative ages of glacial landforms. We reviewed the collection of control points used for the lichenometric curves and determined the time limit of potential use of this method in the Caucasus to be up to one millennium. High-resolution tree-ring-based hydroclimatic reconstructions in the Northern Caucasus are presented based on the reconstruction of June-September temperature (1595-2012 CE), the mass balance reconstruction of the Garabashi Glacier (1800-2008 CE) and the runoff of the Teberda River (low-frequency variations) for May, July and August for 1850-2005 CE. The synthesis of all the available paleoclimatic records revealed several distinct climatic periods. Evidence of a warm interval (traditionally referred to as the "Arkhyz break in glaciation") preceding the Little Ice Age (LIA) in the Caucasus is based on archeological, palynological, geochemical and pedological data. However, the conclusions concerning the duration and magnitude of this warming are still vague due to the low

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

  18. Glacier retreat in New Zealand during the Younger Dryas stadial.

    PubMed

    Kaplan, Michael R; Schaefer, Joerg M; Denton, George H; Barrell, David J A; Chinn, Trevor J H; Putnam, Aaron E; Andersen, Bjørn G; Finkel, Robert C; Schwartz, Roseanne; Doughty, Alice M

    2010-09-01

    Millennial-scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions. The presence of the Younger Dryas stadial (approximately 12.9 to approximately 11.7 kyr ago) is established throughout much of the Northern Hemisphere, but the global timing, nature and extent of the event are not well established. Evidence in mid to low latitudes of the Southern Hemisphere, in particular, has remained perplexing. The debate has in part focused on the behaviour of mountain glaciers in New Zealand, where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent. The interhemispheric behaviour of the climate system during the Younger Dryas thus remains an open question, fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period. Here we show that New Zealand's glaciers retreated after approximately 13 kyr bp, at the onset of the Younger Dryas, and in general over the subsequent approximately 1.5-kyr period. Our evidence is based on detailed landform mapping, a high-precision (10)Be chronology and reconstruction of former ice extents and snow lines from well-preserved cirque moraines. Our late-glacial glacier chronology matches climatic trends in Antarctica, Southern Ocean behaviour and variations in atmospheric CO(2). The evidence points to a distinct warming of the southern mid-latitude atmosphere during the Younger Dryas and a close coupling between New Zealand's cryosphere and southern high-latitude climate. These findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the North Atlantic led to a strong interhemispheric thermal gradient during late-glacial times, in turn leading to increased upwelling and CO(2) release from the Southern Ocean, thereby triggering Southern Hemisphere warming during the northern Younger Dryas.

  19. Glacier retreat in New Zealand during the Younger Dryas stadial.

    PubMed

    Kaplan, Michael R; Schaefer, Joerg M; Denton, George H; Barrell, David J A; Chinn, Trevor J H; Putnam, Aaron E; Andersen, Bjørn G; Finkel, Robert C; Schwartz, Roseanne; Doughty, Alice M

    2010-09-01

    Millennial-scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions. The presence of the Younger Dryas stadial (approximately 12.9 to approximately 11.7 kyr ago) is established throughout much of the Northern Hemisphere, but the global timing, nature and extent of the event are not well established. Evidence in mid to low latitudes of the Southern Hemisphere, in particular, has remained perplexing. The debate has in part focused on the behaviour of mountain glaciers in New Zealand, where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent. The interhemispheric behaviour of the climate system during the Younger Dryas thus remains an open question, fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period. Here we show that New Zealand's glaciers retreated after approximately 13 kyr bp, at the onset of the Younger Dryas, and in general over the subsequent approximately 1.5-kyr period. Our evidence is based on detailed landform mapping, a high-precision (10)Be chronology and reconstruction of former ice extents and snow lines from well-preserved cirque moraines. Our late-glacial glacier chronology matches climatic trends in Antarctica, Southern Ocean behaviour and variations in atmospheric CO(2). The evidence points to a distinct warming of the southern mid-latitude atmosphere during the Younger Dryas and a close coupling between New Zealand's cryosphere and southern high-latitude climate. These findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the North Atlantic led to a strong interhemispheric thermal gradient during late-glacial times, in turn leading to increased upwelling and CO(2) release from the Southern Ocean, thereby triggering Southern Hemisphere warming during the northern Younger Dryas. PMID

  20. Distinct patterns of seasonal Greenland glacier velocity

    PubMed Central

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

    2014-01-01

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

  1. ICESat Observations of Southern Alaska Glaciers

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  2. Exploration of Uncertainty in Glacier Modelling

    NASA Technical Reports Server (NTRS)

    Thompson, David E.

    1999-01-01

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

  3. Improving Mass Balance Modeling of Benchmark Glaciers

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  4. 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.

  5. Community interactive webtool to retrieve Greenland glacier data for 1-D geometry

    NASA Astrophysics Data System (ADS)

    Perrette, Mahé

    2015-04-01

    Marine-terminating, outlet glaciers are challenging to include in conventional Greenland-wide ice sheet models because of the large variation in scale between model grid size (typically 10 km) and outlet glacier width (typically 1-5km), making it a subgrid scale feature. A possible approach to tackle this problem is to use one-dimensional flowline models for the individual glaciers (e.g. Nick et al., 2013, Nature; Enderlin et al 2013a,b, The Cryosphere). Here we present a python- and javascript- based webtool to prepare data required to feed in or validate a flowline model. It is designed primarily to outline the glacier geometry and returns relevant data averaged over cross-sections. The tool currently allows to: visualize 2-D ice sheet data (zoom/pan), quickly switch between datasets (e.g. ice thickness, bedrock elevation, surface velocity) interpolated / transformed on a common grid. draw flowlines from user-input seeds on the map, calculated from a vector field of surface velocity, as an helpful guide for point 3 interactively draw glacier outline (side and middle lines) on top of the data mesh the outlined glacier domain in the horizontal plane extract relevant data into a 1-D longitudinal profile download the result as a netCDF file The project is hosted on github to encourage collaboration, under the open-source MIT Licence. The server-side is written in python (open-source) using the web-framework flask, and the client-side (javascript) makes use of the d3 library for interactive figures. For now it only works locally in a web browser (start server: "python runserver.py"). Data need to be downloaded separately from the original sources. See the README file in the project for information how to use it. Github projects: https://github.com/perrette/webglacier1d (main) https://github.com/perrette/dimarray (dependency)

  6. Edge Equilibrium Code (EEC) For Tokamaks

    SciTech Connect

    Li, Xujling

    2014-02-24

    The edge equilibrium code (EEC) described in this paper is developed for simulations of the near edge plasma using the finite element method. It solves the Grad-Shafranov equation in toroidal coordinate and uses adaptive grids aligned with magnetic field lines. Hermite finite elements are chosen for the numerical scheme. A fast Newton scheme which is the same as implemented in the equilibrium and stability code (ESC) is applied here to adjust the grids

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

    USGS Publications Warehouse

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

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

    USGS Publications Warehouse

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

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Rastogi, G.; Ajai

    2014-11-01

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

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

    USGS Publications Warehouse

    Adamson, Thomas

    2016-01-01

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

  12. 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

  13. Determining the maximum contribution of glacier ice to streamflow

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  14. Malaspina Glacier, Alaska, Anaglyph with Landsat Overlay

    NASA Technical Reports Server (NTRS)

    2003-01-01

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

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

    Numerous other features of the glaciers and the adjacent terrain are clearly seen when viewing this image at full resolution. The series of tonal arcs on Agassiz Glacier's extension onto the piedmont are called 'ogives.' These arcs are believed to be seasonal features created by deformation of the glacier as it passes over bedrock irregularities at differing speeds through the year. Assuming one light-and-dark ogive pair per year, the rate of motion of the glacial ice can be estimated (in this case, about 200 meters per year where the ogives are most prominent). Just to the west, moraine deposits abut the eroded bedrock terrain, forming a natural dam that has created a lake. Near the northwest corner of the scene, a recent landslide has deposited rock debris atop a small glacier. Sinkholes are common in many areas of the moraine deposits. The sinkholes form when

  15. Approaches to the Treatment of Equilibrium Perturbations

    NASA Astrophysics Data System (ADS)

    Canagaratna, Sebastian G.

    2003-10-01

    Perturbations from equilibrium are treated in the textbooks by a combination of Le Châtelier's principle, the comparison of the equilibrium constant K with the reaction quotient Q,and the kinetic approach. Each of these methods is briefly reviewed. This is followed by derivations of the variation of the equilibrium value of the extent of reaction, ξeq, with various parameters on which it depends. Near equilibrium this relationship can be represented by a straight line. The equilibrium system can be regarded as moving on this line as the parameter is varied. The slope of the line depends on quantities like enthalpy of reaction, volume of reaction and so forth. The derivation shows that these quantities pertain to the equilibrium system, not the standard state. Also, the derivation makes clear what kind of assumptions underlie our conclusions. The derivation of these relations involves knowledge of thermodynamics that is well within the grasp of junior level physical chemistry students. The conclusions that follow from the derived relations are given as subsidiary rules in the form of the slope of ξeq, with T, p, et cetera. The rules are used to develop a visual way of predicting the direction of shift of a perturbed system. This method can be used to supplement one of the other methods even at the introductory level.

  16. Snow and glacier mapping with polarimetric SAR

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    PubMed

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

    2015-02-06

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

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

    PubMed Central

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

    2015-01-01

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

  19. 36 CFR 7.3 - Glacier National Park.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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

  20. ASTER Imaging and Analysis of Glacier Hazards

    NASA Astrophysics Data System (ADS)

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

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

  1. 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.

  2. Columbia Glacier in 1986; 800 meters retreat

    USGS Publications Warehouse

    Krimmel, R.M.

    1987-01-01

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

  3. Investigating connections between local-remote atmospheric variability and Greenland outlet glacier behavior

    NASA Astrophysics Data System (ADS)

    Sobolowski, Stefan; Chen, Linling; Miles, Victoria

    2016-04-01

    /climate dynamics in glacier behavior. Our study suggests a strong relationship between large-scale tropospheric circulation patterns, such as the so-called Greenland Blocking Index (GBI), and glacier front position. This relationship is seen in the wintertime (summertime) circulation influence on spring (fall) front position. Dynamically, a physical pathway is illustrated via canonical correlation analyses and composites of low-mid level winds, which show strong southerly advection into the region when the GBI is positive. There are also potential links between local and remote diabatic heating in the atmospheric column, SSTs, sea-ice concentration and front position. Whether there are physical pathways connecting remote surface processes, such as heating along western Greenland is not yet clear. Causality is always difficult to infer in reanalysis-based studies but physical intuition and theory provide multiple lines of evidence, which suggest a substantial influence of large-scale atmospheric dynamics at the margins of the GrIS. Improving our understanding of these physical connections will be crucial, as we know the outlet glaciers will respond under rapidly changing climate conditions.

  4. Surface characteristics and evolution of debris covered glaciers

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  5. Getting Freshman in Equilibrium.

    ERIC Educational Resources Information Center

    Journal of Chemical Education, 1983

    1983-01-01

    Various aspects of chemical equilibrium were discussed in six papers presented at the Seventh Biennial Conference on Chemical Education (Stillwater, Oklahoma 1982). These include student problems in understanding hydrolysis, helping students discover/uncover topics, equilibrium demonstrations, instructional strategies, and flaws to kinetic…

  6. Evidence for a water system transition beneath Thwaites Glacier, West Antarctica

    PubMed Central

    Schroeder, Dustin M.; Blankenship, Donald D.; Young, Duncan A.

    2013-01-01

    Thwaites Glacier is one of the largest, most rapidly changing glaciers on Earth, and its landward-sloping bed reaches the interior of the marine West Antarctic Ice Sheet, which impounds enough ice to yield meters of sea-level rise. Marine ice sheets with landward-sloping beds have a potentially unstable configuration in which acceleration can initiate or modulate grounding-line retreat and ice loss. Subglacial water has been observed and theorized to accelerate the flow of overlying ice dependent on whether it is hydrologically distributed or concentrated. However, the subglacial water systems of Thwaites Glacier and their control on ice flow have not been characterized by geophysical analysis. The only practical means of observing these water systems is airborne ice-penetrating radar, but existing radar analysis approaches cannot discriminate between their dynamically critical states. We use the angular distribution of energy in radar bed echoes to characterize both the extent and hydrologic state of subglacial water systems across Thwaites Glacier. We validate this approach with radar imaging, showing that substantial water volumes are ponding in a system of distributed canals upstream of a bedrock ridge that is breached and bordered by a system of concentrated channels. The transition between these systems occurs with increasing surface slope, melt-water flux, and basal shear stress. This indicates a feedback between the subglacial water system and overlying ice dynamics, which raises the possibility that subglacial water could trigger or facilitate a grounding-line retreat in Thwaites Glacier capable of spreading into the interior of the West Antarctic Ice Sheet. PMID:23836631

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

    NASA Technical Reports Server (NTRS)

    1994-01-01

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

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

    SciTech Connect

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

    1992-10-02

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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

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

    SciTech Connect

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

    1985-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    NASA Technical Reports Server (NTRS)

    Hall, D. K.

    1998-01-01

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

  15. Chronology for fluctuations in late Pleistocene Sierra Nevada glaciers and lakes

    USGS Publications Warehouse

    Phillips, F.M.; Zreda, M.G.; Benson, L.V.; Plummer, M.A.; Elmore, D.; Sharma, Prakash

    1996-01-01

    Mountain glaciers, because of their small size, are usually close to equilibrium with the local climate and thus should provide a test of whether temperature oscillations in Greenland late in the last glacial period are part of global-scale climate variability or are restricted to the North Atlantic region. Correlation of cosmogenic chlorine-36 dates on Sierra Nevada moraines with a continuous radiocarbon-dated sediment record from nearby Owens Lake shows that Sierra Nevada glacial advances were associated with Heinrich events 5, 3, 2, and 1.

  16. Chronology for fluctuations in late pleistocene Sierra Nevada glaciers and lakes

    SciTech Connect

    Phillips, F.M.; Zreda, M.G.; Plummer, M.A.

    1996-11-01

    Mountain glaciers, because of their small size, are usually close to equilibrium with the local climate and thus should provide a test of whether temperature oscillations in Greenland late in the last glacial period are part of global-scale climate variability or are restricted to the North Atlantic region. Correlation of cosmogenic chlorine-36 dates on Sierra Nevada moraines with a continuous radiocarbon-dated sediment record from nearby Owens Lake shows that Sierra Nevada glacial advances were associated with Heinrich events 5, 3, and 1. 27 refs., 2 figs., 1 tab.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Munir, Siraj

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

  19. 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.

  20. Static debris-covered glaciers and rock glaciers in Tröllaskagi Peninsula (northern Iceland): The cases of Hóladalur and Fremri-Grjótárdalur.

    NASA Astrophysics Data System (ADS)

    Tanarro, Luis Miguel; Palacios, David; Andres, Nuria; María Fernández, Jose

    2015-04-01

    delineated with GPS. The analysis and interpretation of the morphological characteristics clearly show the almost complete absence of changes in the superficial structure of both the Fremri-Grjótárdalur rock glacier and the Hóladalur debris-covered glacier during the time interval studied, detecting the same flow structures (transversal crests and grooves and flow lines) located in the same position. Similarly, the external limit or shape shows hardly any variations. The rock glacier may be considered to have remained practically stable from 1946 to the present. This assertion contrasts with the observations made by Wangensteen et al., 2006, who also used photogrammetric techniques and detected displacements in the interior of the rock glacier during the 9 year period from 1985 to 1994. In conclusion, the geomorphological survey of the 1946 aerial photograph and of the 2000- 2013 orthophotos, and their comparison using photogrammetric techniques has allowed us to detect the total stability of both the rock glacier and the debris-covered glacier over the last 50 years. Reference.- Wangensteen, B., Gudmundsson, A., Eiken, T., Kääb, A., Farbrot, H., Etzelmüller, B., 2006, Surface displacements and surface age estimates for creeping slope landforms in northen and easthern Iceland using digital photogrametry. Geomorphology 80:59-79. Research funded by Cryocrisis project (CGL2012-35858), Government of Spain, and Nils Mobility projects (EEA GRANTS)

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

    USGS Publications Warehouse

    Josberger, Edward G.; Bidlake, William R.

    2010-01-01

    The long-term USGS measurement and reporting of mass balance at South Cascade Glacier was assisted in balance years 2006 and 2007 by a new mass balance model. The model incorporates a temperature-index melt computation and accumulation is modeled from glacier air temperature and gaged precipitation at a remote site. Mass balance modeling was used with glaciological measurements to estimate dates and magnitudes of critical mass balance phenomena. In support of the modeling, a detailed analysis was made of the "glacier cooling effect" that reduces summer air temperature near the ice surface as compared to that predicted on the basis of a spatially uniform temperature lapse rate. The analysis was based on several years of data from measurements of near-surface air temperature on the glacier. The 2006 and 2007 winter balances of South Cascade Glacier, computed with this new, model-augmented methodology, were 2.61 and 3.41 mWE, respectively. The 2006 and 2007 summer balances were -4.20 and -3.63 mWE, respectively, and the 2006 and 2007 net balances were -1.59 and -0.22 mWE. PDF version of a presentation on the mass balance of South Cascade Glacier in Washington state. Presented at the American Geophysical Union Fall Meeting 2010.

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

    USGS Publications Warehouse

    Brugman, Melinda M.; Post, Austin

    1981-01-01

    The cataclysmic eruption of Mount St. Helens May 18, 1980, removed 2.9 km2 (about 0.13 km3) of glacier snow and ice including a large part of Shoestring, Forsyth, Wishbone, Ape, Nelson, and all of Loowit and Leschi Glaciers. Minor eruptions and bulging of the volcano from March 27 to May 17 shattered glaciers which were on the deforming rock and deposited ash on other glaciers. Thick ash layers persisted after the May 18 eruption through the summer on most of the remaining snow and ice, and protected winter snow from melting on Swift and Dryer Glaciers. Melting and recrystalization of snow and ice surviving on Mount St. Helens could cause and lubricate mudflows and generate outburst floods. Study of glaciers that remain on this active volcano may assist in recognizing potential hazards on other volcanoes and lead to new contributions to knowledge of the transient response of glaciers to changes in mass balance or geometry.

  3. Subglacial till: the deforming glacier bed

    NASA Astrophysics Data System (ADS)

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

    2003-07-01

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

  4. Stream temperature response to glacier retreat (Invited)

    NASA Astrophysics Data System (ADS)

    Moore, R. D.

    2013-12-01

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

  5. Asia High Mountain Glacier Mass Balance

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The Asian High Mountain encompassing the Qinghai-Tibetan Plateau has the largest glaciated regions in the world outside of Greenland and Antarctica. The Tibetan Plateau is the source or headwater of many major river systems, which provide water resources to more than a billion people downstream. The impact of climate change on the Tibetan Plateau physical processes, including mountain glacier wastage, permafrost active layer thickening, the timing and the quantity of the perennial snowpack melt affecting upstream catchments, river runoffs, land-use, have significant effects on downstream water resources. Exact quantification of the Asian High Mountain glacier wastage or its mass balance on how much of the melt water contributes to early 21st century global sea-level rise, remain illusive or the published results are arguably controversial. The recent observed significant increase of freshwater storage within the Tibetan Plateaus remains a limitation to exactly quantify mountain glacier wastage. Here, we provide an updated estimate of Asia high mountain glacier mass balance using satellite geodetic observations during the last decade, accounting for the hydrologic and other processes, and validated against available in situ mass balance data.

  6. A Facies Model for Temperate Continental Glaciers.

    ERIC Educational Resources Information Center

    Ashley, Gail Mowry

    1987-01-01

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

  7. The Bay in Place of a Glacier.

    ERIC Educational Resources Information Center

    Howell, Wayne

    1997-01-01

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

  8. The first glacier inventory for entire Greenland

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Winger, Katja; Sushama, Laxmi; Marshall, Shawn

    2016-04-01

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

  11. Ocean mixing beneath Pine Island Glacier Ice Shelf

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  12. Model based historical runoff contribution from an Alpine glacier

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  13. Modelling bed overdeepenings for the glaciers in the Himalaya-Karakoram region using GlabTop2

    NASA Astrophysics Data System (ADS)

    Linsbauer, Andreas; Frey, Holger; Haeberli, Wilfried; Machguth, Horst

    2014-05-01

    modified and named GlabTop2. While the original approach relied on so called glacier branch lines that had to be digitized manually, GlabTop2 is fully automated and requires only a DEM and glacier outlines as an input. The result is the same: ice thickness distribution and bed topographies, which can be used for volume calculations and for model simulations concerning glacier retreat scenarios and future landscapes. According to the model output there are about 15'000 overdeepenings covering an area of about 2000 km2 and having a total volume of about 120 km3 (3-4% of the now existing glacier volume) in the Himalaya-Karakoram region. In a statistical analysis concerning the morphological characteristics of these overdeepenings, mean and maximum values of the parameters surface area, length, width, depth, volume, frontal/adverse slope and their statistical interrelations are determined with their corresponding uncertainty ranges and compared with a corresponding analysis for the Swiss Alps. While the modelled overdeepenings based on model runs with different data input differ in shape, the locations of the overdeepenings are robust and the values for the extracted parameters are comparable.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    PubMed

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

    2015-11-01

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

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

    PubMed

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

    2015-11-01

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

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

    PubMed Central

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

    2015-01-01

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

  18. 52 glaciers and one lake: how to reconstruct past regional glacier variability

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  19. Chemical Principles Revisited: Chemical Equilibrium.

    ERIC Educational Resources Information Center

    Mickey, Charles D.

    1980-01-01

    Describes: (1) Law of Mass Action; (2) equilibrium constant and ideal behavior; (3) general form of the equilibrium constant; (4) forward and reverse reactions; (5) factors influencing equilibrium; (6) Le Chatelier's principle; (7) effects of temperature, changing concentration, and pressure on equilibrium; and (8) catalysts and equilibrium. (JN)

  20. Response reactions: equilibrium coupling.

    PubMed

    Hoffmann, Eufrozina A; Nagypal, Istvan

    2006-06-01

    It is pointed out and illustrated in the present paper that if a homogeneous multiple equilibrium system containing k components and q species is composed of the reactants actually taken and their reactions contain only k + 1 species, then we have a unique representation with (q - k) stoichiometrically independent reactions (SIRs). We define these as coupling reactions. All the other possible combinations with k + 1 species are the coupled reactions that are in equilibrium when the (q - k) SIRs are in equilibrium. The response of the equilibrium state for perturbation is determined by the coupling and coupled equilibria. Depending on the circumstances and the actual thermodynamic data, the effect of coupled equilibria may overtake the effect of the coupling ones, leading to phenomena that are in apparent contradiction with Le Chatelier's principle. PMID:16722770

  1. Monitoring glaciers and indications of subglacial volcanic activity using small-scale Top-Hat reflectors - An IsViews experiment on Myrdalsjökull, Iceland

    NASA Astrophysics Data System (ADS)

    Minet, Christian; Duque Biarge, Sergi; Jaenicke, Julia; Münzer, Ulrich; Mayer, Christoph; Franke, Jonas; Guðmundsson, Águst; Parizzi, Alessandro; Fritz, Thomas; Eineder, Michael

    2014-05-01

    Subglacial volcanic eruptions often provide indications of activity some time before the actual catastrophic event. Surface undulations appear on top of the ice cap and meltwater torrents can occur at the glacier margin. Even large scale uplifts of ice caps have been observed. Within the project IsViews a processing chain, based on high spatially and temporally resolved remote sensing imagery, will be developed in order to automatically identify such early indications. The main data used for this analysis are acquired by the TerraSAR-X, TanDEM-X and RapidEye satellites. First investigations concerning the feasibility of the near real-time warning system and the general baseline conditions are carried out on two large plateau glaciers in southern Iceland, namely Mördalsjökull and Vatnajökull. Within the 2013 IsViews field work an experiment was started in order to test a new way of glacier monitoring. Two test sites were established on the Mördalsjökull ice cap (one at the equilibrium line and one below), each consisting of a permanent GPS station and two nearby RADAR reflectors. These RADAR reflectors are specially designed Top-Hat reflectors, which are cheap to manufacture, small (50 cm diameter) and lightweight and therefore easy to handle, transport and deploy. Their special design makes them visible in SAR images independent of orientation, so different acquisition geometries and even different sensors can be used. The drawback of the small, low reflecting Top-Hat can be overcome by using the newly implemented Staring Spotlight Mode of the German SAR Satellite TerraSAR-X, providing an unprecedented resolution of down to 20 cm in the azimuth direction. The reflectors, as point targets, allow absolute positioning within the cm-level in the TerraSAR-X data. Time series of SAR data can be used to derive position and altitude changes of the reflector itself and possibly even melting rates by exploiting the different signal paths. The visibility of the Top

  2. Computing Equilibrium Chemical Compositions

    NASA Technical Reports Server (NTRS)

    Mcbride, Bonnie J.; Gordon, Sanford

    1995-01-01

    Chemical Equilibrium With Transport Properties, 1993 (CET93) computer program provides data on chemical-equilibrium compositions. Aids calculation of thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93/PC is version of CET93 specifically designed to run within 640K memory limit of MS-DOS operating system. CET93/PC written in FORTRAN.

  3. Internationally coordinated glacier monitoring - a timeline since 1894

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  4. A study of discrete glacier motion

    NASA Astrophysics Data System (ADS)

    Zoet, Lucas K.

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

  5. Glacier changes since Local Last Glacial Maximum in the South-West slope of Nevado Hualcán, Cordillera Blanca, Peru, deduced from moraine mapping and GIS-based analysis

    NASA Astrophysics Data System (ADS)

    Giráldez, Claudia; Palacios, David; Haeberli, Wilfried; Úbeda, Jose; Schauwecker, Simone; Torres, Judith

    2014-05-01

    Anticipating and assessing hazards and risks associated with the shrinking of surface and subsurface ice in cold mountain chains is facilitated by empirical-quantitative data on present and past rates of change, as well as by a general understanding of related landforms and landscape evolution through time. Rock/ice avalanches and devastating outburst floods from glacial lakes indeed constitute a major cause of severe damage in populated mountain areas such as the Cordillera Blanca whose combination of tectonic, topographic and glaciological characteristics make it a threatened region. This study focuses on the Río Chucchún catchment above the city of Carhuaz, which was recently affected by a flood/debris flow from a rock/ice avalanche impacting a recently grown lake (Laguna 513). Traces left by past glaciations strongly affect the current geomorphodinamic behaviour of the catchment. For instance, a prominent sediment-filled glacial overdeepening behind Younger Dryas (YD) moraines (Pampa de Shonquil) with its retention function strongly influenced the chain of processes initiated by the outburst of Laguna 513. The aim of this study is to reconstruct earlier glacial phases in the SW slope of Nevado Hualcán (Río Chucchún catchment), in order to compile quantitative information on surface areas and Equilibrium Line Altitudes (ELAs). To do so, glacier stages were assigned to five different glacial phases, through photointerpretation and moraine cartography: 2003; 1962; Hualcán-I-LIA (15th to 18th centuries); Hualcán-II-YD (~12,5 ka BP); and Hualcán-III-LLGM (~34 to 21 ka BP). Glacial stages Hualcán-I-LIA, Hualcán-II-YD and Hualcán-III-LLGM present relative dating based on previous studies from different authors in the Peruvian Andes. Once glaciers were delimited, their surface areas and Equilibrium Line Altitudes (ELAs) were calculated. For ELA estimation three different methods were used: the mid-range elevation, the Accumulation Area Ratio (AAR), and the

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

    NASA Astrophysics Data System (ADS)

    Serrano, Enrique; López-Martínez, Jerónimo

    2000-10-01

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

  7. Assessing streamflow sensitivity to variations in glacier mass balance

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Glacierized change in the Himalayas affects river-discharge, hydro-energy and agricultural production, and Glacial Lake Outburst Flood potential, but its quantification and extent of impacts remains highly uncertain. Here we present conservative, comprehensive and quantitative predictions for glacier area and meltwater flux changes in Bhutan, monsoonal Himalayas. In particular, we quantify the uncertainties associated with the glacier area and meltwater flux changes due to uncertainty in climate data, a critical problem for much of High Asia. Based on a suite of gridded climate data and a robust glacier melt model, our results show that glacier area and meltwater change projections can vary by an order of magnitude for different climate datasets. The most conservative results indicate that, even if climate were to remain at the present-day mean values (1980-2000), almost 10% of Bhutan's glacierized area would vanish and the meltwater flux would drop by as much as 30%. New mapping of glacierized area from 2000-2010 shows a significant change in glacierized area of 4-6%. Thus the conservative steady-state area changes predicted by the model are already being realized. Under the conservative scenario of an additional 1°C regional warming, glacier retreat is predicted to continue until about 25% of Bhutan's glacierized area will have disappeared and the annual meltwater flux, after an initial spike, would drop by as much as 65%.

  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. Climatic Teleconnections Recorded By Tropical Mountain Glaciers

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  11. 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

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

    NASA Astrophysics Data System (ADS)

    Kargel, Jeffrey; Leonard, Gregory; Regmi, Dhananjay; Haritashya, Umesh; Chand, Mohan; Pradhan, Suresh; Sapkota, Nawaraj; Byers, Alton; Joshi, Sharad; McKinney, Daene; Mool, Pradeep; Somos-Valenzuela, Marcelo; Huggel, Christian

    2015-04-01

    Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, i.e., most likely to cause death and destruction in case of a glacier lake outburst flood (GLOF). Imja Lake and the associated Imja and Lhoste-Shar glaciers have been intensively studied; Thulagi Glacier and its lake are much less studied. Collectively, we have undertaken a series of increasingly thorough bathymetric and land surveys and satellite remote sensing analyses of Imja Lake and its glacier setting. We are analyzing several expeditions' data to build a detailed assessment of the glacier and lake to better establish the dynamical evolution of the system and its future GLOF potential. Our most recent, most complete bathymetric survey of Imja Lake has revealed a much greater volume (75,200,000 cubic meters) and maximum depth (149.8 m) than found before. Our analysis suggests that not all possible Imja GLOF scenarios would result in devastation. Some moraine melt-through or down-cutting mechanisms -- perhaps induced by extreme monsoon precipitation or an earthquake -- could generate outbursts lasting from 10,000-100,000 seconds ("slow GLOFs"), thus limiting peak flows and downstream damage. The potential damage from a slow GLOF from Imja Lake -- even if there is a large total volume -- is lessened by the relatively low peak discharge and because the major villages downstream from Imja Lake are situated just outside of and above a deep, broad outwash and debris-flow channel system. Imja and other glaciers in the area have built a large fan, now deeply trenched, which is able to accommodate the peak discharges of potential slow GLOFs, such that Dingboche and other villages would be spared. However, local geomorphology also bears evidence of "fast GLOFs," such as may be issued by a tsunami, which could be initiated by a large mass movement into Imja Lake and which might override and damage the end moraine in <100 seconds. Dingboche and other villages are vulnerable to

  13. 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

  14. Recent Activity of Glaciers of Mount Rainier, Washington

    USGS Publications Warehouse

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

    1972-01-01

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

  15. Glacier and climate change in Pakistan and Afghanistan

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    While alpine glaciers in montane regions represent the largest flux of dissolved organic matter (DOM) from global ice melt no research has examined the bioavailability of DOM melted out of glacial ice in the western continental United States. Furthermore, rock glaciers are an order of magnitude more abundant than ice glaciers in U.S., yet are not included in budgets for perennial ice carbon stores. Our research aims to understand differences in the bioavailability of carbon from ice glaciers and rock glaciers along the Central Rocky Mountains of Colorado. Identical microbial communities were fed standardized amounts of DOM from four different ice glacier-rock glaciers pairs. Using laboratory incubations, paired with mass spectrometry based metabolomics and 16S gene sequencing; we were able to examine functional definitions of DOM lability in glacial ice. We hypothesized that even though DOM quantities are similar in the outputs of both glacial types in our study area, ice glacial DOM would be more bioavailable than DOM from rock glaciers due to higher proportions of byproducts from microbial metabolism than rock glacier DOM, which has higher amounts of "recalcitrant" plant material. Our results show that DOM from ice glaciers is more labile than DOM from geologically and geographically similar paired rock glaciers. Ice glacier DOM represents an important pool of labile carbon to headwater ecosystems of the Rocky Mountains. Metabolomic analysis shows numerous compounds from varying metabolite pathways, including byproducts of nitrification before and after incubation, meaning that, similar to large maritime glaciers in Alaska and Europe, subglacial environments in the mountain ranges of the United States are hotspots for biological activity and processing of organic carbon.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  19. Glaciers and ice caps outside Greenland

    USGS Publications Warehouse

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

    2015-01-01

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

  20. Mass loss on Himalayan glacier endangers water resources

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

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

  1. Equilibrium games in networks

    NASA Astrophysics Data System (ADS)

    Li, Angsheng; Zhang, Xiaohui; Pan, Yicheng; Peng, Pan

    2014-12-01

    It seems a universal phenomenon of networks that the attacks on a small number of nodes by an adversary player Alice may generate a global cascading failure of the networks. It has been shown (Li et al., 2013) that classic scale-free networks (Barabási and Albert, 1999, Barabási, 2009) are insecure against attacks of as small as O(logn) many nodes. This poses a natural and fundamental question: Can we introduce a second player Bob to prevent Alice from global cascading failure of the networks? We proposed a game in networks. We say that a network has an equilibrium game if the second player Bob has a strategy to balance the cascading influence of attacks by the adversary player Alice. It was shown that networks of the preferential attachment model (Barabási and Albert, 1999) fail to have equilibrium games, that random graphs of the Erdös-Rényi model (Erdös and Rényi, 1959, Erdös and Rényi, 1960) have, for which randomness is the mechanism, and that homophyly networks (Li et al., 2013) have equilibrium games, for which homophyly and preferential attachment are the underlying mechanisms. We found that some real networks have equilibrium games, but most real networks fail to have. We anticipate that our results lead to an interesting new direction of network theory, that is, equilibrium games in networks.

  2. More Than the Sum of Its Parts: Increased Information Content through a Combination of Ground-Penetrating-Radar and Seismic Methods on Temperate Glaciers.

    NASA Astrophysics Data System (ADS)

    Rabenstein, L.; Maurer, H.; Merz, K.; Lüthi, M. P.

    2014-12-01

    Over temperate glaciers images obtained from ground-penetrating-radar (GPR) are often blurred because electromagnetic waves are scattered on water pockets or by complex glacial bed topography, or damped due to a higher overall water content within the glacier. A combination of seismic and GPR surveying can increase the data information content and aid interpretation of subsurface structure. In September 2012 we acquired surface and borehole GPR and seismic data in the ablation zone of the Rhone Glacier located in central Switzerland. GPR data were acquired using antenna frequencies of 25, 50 and 100 MHz. Active reflection seismic data were recorded along a coincident profile across the glacier. Seismic waves were generated with small explosive sources spaced at 4m, and recorded on 30 Hz geophones at 2 m spacing. Both methods resulted in images showing a maximum depth of the glacier of approximately 130 m. However, the seismic image of the glacier bed was of much higher resolution and showed a clear primary reflection from the base, whereas the GPR image often showed several reflections of similar amplitude, above and from the bedrock interface, or no reflection at all. We interpreted a series of crenulations along the glacier bed reflector in the seismic image as melt water channels. This interpretation was supported by the intermittent nature of GPR glacier bed reflections, which are expected to be more sensitive to changes in water content than to the ice-rock interface. First break travel time inversions of the surface seismic data yielded velocities of 3320 m/s near the top of the glacier, and remarkably constant values of 3720 m/s at depths below 4.5m. However, travel time inversion of seismic data between boreholes which penetrated as far as the glacier bed, indicate a 3D anisotropy of seismic velocity, ranging from 3650 m/s horizontally across the glacier to 3850 m/s horizontally along the line of the glacier. Vertical seismic velocity was found to lie

  3. A macroscopic approach to glacier dynamics

    USGS Publications Warehouse

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

    2003-01-01

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

  4. Pathways of Petermann Glacier meltwater, Greenland

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Radar and satellite observations suggest that the floating ice shelf of Petermann Glacier loses up to 80% of its mass through basal melting, caused by the intrusion of warm Atlantic Water into the fjord and under the ice shelf. The fate of Petermann's glacial meltwater is still largely unknown. It is investigated here, using hydrographic observations collected during a research cruise on board I/B Oden in August 2015. Two methods are used to detect the meltwater from Petermann: a mathematical one that provides the concentration of ice shelf meltwater, and a geometrical one to distinguish the meltwater from Petermann and the meltwater from other ice shelves. The meltwater from Petermann mostly circulates on the north side of the fjord. At the sill, 0.5 mSv of meltwater leave the fjord, mostly on the northeastern side between 100 and 350 m depth, but also in the central channel, albeit with a lesser concentration. Meltwater from Petermann is found in all the casts in Hall Basin, notably north of the sill by Greenland coast. The geometrical method reveals that the casts closest to the Canadian side mostly contain meltwater from other, unidentified glaciers. As Atlantic Water warms up, it is key to monitor Greenland melting glaciers and track their meltwater to properly assess their impact on the ocean circulation and sea level rise.

  5. Dielectric Signatures of Annealing in Glacier Ice

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  6. GLACIER PEAK WILDERNESS STUDY AREA, WASHINGTON.

    USGS Publications Warehouse

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

    1984-01-01

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

  7. Batura-Glacier - mass balance and 'Karakoram Anomaly' (Upper Hunza, Karakoram)

    NASA Astrophysics Data System (ADS)

    Boerst, U.; Winiger, M.; Bookhagen, B.

    2013-12-01

    In line with an almost worldwide trend the (non-surging) glaciers in the Hindukush-Karakoram-Himalaya Range manifest a remarkable down melting of their tongues and retreating of their terminuses in the last few decades. A series of recent studies prove an overall negative mass balance for most of the Himalayan glaciers. Contrary to these statements various publications register stable or positive mass balances for a number of glaciers located in the NW-Karakoram Mountains - postulating the so-called 'Karakoram-Anomaly'. Unlike the many investigations in the Himalaya, the Karakoram records very few detailed local investigations emphasizing the spatial and temporal development of glaciers. This presentation focuses on the Batura Glacier in NW-Karakorum in Gilgit-Baltistan (Pakistan). With a west-to-east extension of ~ 57 km and an elevation range of 5.3 km (2.500 - 7.800 masl), the Batura Glacier belongs to the worldwide largest glaciers in the mid and low latitudes. Detailed mapping and further ground-based investigations have been carried out in the 1920ies, 1953/59, 1974/5 and in the past few years by different research teams. In order to determine the glacier's mass balance for the last 50 years we relied on Digital Elevation Models (DEMs): digitized maps from 1959 and 1974 are compared to DEMs derived through stereogrammetry from ASTER-scenes for 2001, 2006, 2008, 2010 and 2011. The ASTER-DEMs were post-processed with various correction methods and techniques to insure the relative DEM comparability and include corrections for aspect, altitude, and tilt. Next, we calculated surface differences from the ice and snow-free areas with respect to the SRTM C-Band DEM. Our remote sensing techniques are supplemented by differential GPS measurements and ice-surface profiles from 2013 as well as by multi-temporal photography matching. Preliminary results indicate a significant down melting of the glacier tongue from 1959 to the present day and acceleration during the past

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

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.

    1997-01-01

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

  9. Inventory of glaciers in the Sierra Nevada, California

    USGS Publications Warehouse

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

    2006-01-01

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

  10. Response of debris-covered glaciers to climate change

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

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

    NASA Technical Reports Server (NTRS)

    1995-01-01

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

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

    USGS Publications Warehouse

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

    1979-01-01

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

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

    USGS Publications Warehouse

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

    2008-01-01

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

  14. Application of Depth of Investigation index method to process resistivity imaging models from glacier forfield

    NASA Astrophysics Data System (ADS)

    Glazer, Michał; Dobinski, Wojciech; Grabiec, Mariusz

    2015-04-01

    At the end of August 2014 ERT measurements were carried out at the Storglaciären glacier forefield (Tarfala Valley, Northern Sweden) to study permafrost occurrence. This glacier has been retreating since 1910. It is one of the most well studied mountain glaciers in the world due to initiation of the first continuous glacier mass balance research program. Near the vicinity of its frontal margin three perpendicular and two parallel resistivity profile lines were located. They varied in terms of number of roll-along extensions and used electrode spacing. At least Schlumberger and dipole-dipole protocols were utilized on every measurement site. Surface of glacier forefield is characterized by occurrence of large moraine deposits which consists of rock blocks with air voids on one hand and voids filled with clay material on the other. It caused large variations of electrodes contact resistance on profile line. Furthermore, possibility of using only weak currents in the research, and presence of high resistivity contrast structures in geological medium made inversion process and interpretation of received resistivity models demanding. To stabilize inversion process efforts were made to erase most noisy and systematic error data. In order to assess the reliability of resistivity models at depth and in terms of the presence of artifacts left by the inversion process Depth of Investigation (DOI) index was applied. It describes accuracy of prepared model with respect to variable parameters of inversion. For preparing DOI maps two inversions on the same data set using different reference models are necessary. Then the results are compared to each other. In regions where the model depend strongly on data DOI will take values near zero, while in regions where resistivity values depend more on inversion parameters DOI will rise. Additionally several synthetic models were made which led to better understanding of resistivity images of some geological structures observed on the

  15. Immunity by equilibrium.

    PubMed

    Eberl, Gérard

    2016-08-01

    The classical model of immunity posits that the immune system reacts to pathogens and injury and restores homeostasis. Indeed, a century of research has uncovered the means and mechanisms by which the immune system recognizes danger and regulates its own activity. However, this classical model does not fully explain complex phenomena, such as tolerance, allergy, the increased prevalence of inflammatory pathologies in industrialized nations and immunity to multiple infections. In this Essay, I propose a model of immunity that is based on equilibrium, in which the healthy immune system is always active and in a state of dynamic equilibrium between antagonistic types of response. This equilibrium is regulated both by the internal milieu and by the microbial environment. As a result, alteration of the internal milieu or microbial environment leads to immune disequilibrium, which determines tolerance, protective immunity and inflammatory pathology.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  17. 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.

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

    USGS Publications Warehouse

    Trabant, Dennis C.; Hawkins, Daniel B.

    1997-01-01

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

  19. Analysis of a 24-Year photographic record of Nisqually glacier, Mount Rainier National Park, Washington

    USGS Publications Warehouse

    Veatch, Fred M.

    1969-01-01

    A systematic coverage of Nisqually Glacier by photographs taken from a network of stations on the ground was begun in 1942 to explore the value and limitations of such photographs as an aid in glacier study. Principles developed may be of value elsewhere, especially for the program 'Measurement of Glacier Variations on a World-Wide Basis' of the International Hydrological Decade. Nisqually Glacier in Mount Rainier National Park, Wash., covers 2.5 square miles (6.5 square kilometers) (1961) and extends from an altitude of about 14,300 feet (4,400 meters) near the top of Mount Rainier down to 4,700 feet (1,400 meters), in a horizontal distance of 4.1 miles (6.6 kilometers). Analyses were made of the annual photographs taken by the writer for 24 years from about 20 stations. A number of pictures taken sporadically from 1884 to 1941 by others were also available for use in the study. Where possible, the results obtained from photographs were compared with those from the available engineering surveys. Such detailed analysis of an extensive photographic coverage of a single glacier may be unique. Photographs illustrating the retreat and advance of the glacier's west ice margin in a reach extending for about a mile (1.6 kilometers) downstream from Wilson Glacier show that, by 1965, most of the ice thickness lost in that area between 1890 and 1944 had been recovered. Withering of the stagnant valley tongue down glacier from the nunatak is portrayed, as is its spectacular reactivation in the 1960's by a vigorous advance of fresh ice. Some of the visible characteristics of advancing and receding termini are noted. Annual values of the glacier's surface slope (5 to 10 degrees) at a cross profile were measured on photographs with respect to a projected vertical line identifiable in each picture. The results were found to average about 2 degrees less than those obtained from the 5-year topographic maps, but they are thought to be a little more accurate owing to lack of a

  20. 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)

  1. Inventory of Glaciers in the North Cascades, Washington

    USGS Publications Warehouse

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

    1971-01-01

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

  2. Little Ice Age glaciers in the Mediterranean mountains

    NASA Astrophysics Data System (ADS)

    Hughes, Philip

    2014-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    The Global Terrestrial Network for Glaciers (GTN-G) is an umbrella organization with links to the Global Climate Observing System (GCOS), Global Terrestrial Observing System (GTOS), and UNESCO (all organizations under the United Nations), for the curation of several glacier-related databases. It is composed of the World Glacier Monitoring Service (WGMS), the U.S. National Snow and Ice Data Center (NSIDC), and the Global Land Ice Measurements from Space (GLIMS) initiative. The glacier databases include the World Glacier Inventory (WGI), the GLIMS Glacier Database, the Glacier Photograph Collection at NSIDC, and the Fluctuations of Glaciers (FoG) and Mass Balance databases at WGMS. We are working toward increased interoperability between these related databases. For example, the Web interface to the GLIMS Glacier Databas