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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.

    2015-11-01

    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.

  2. 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.

  3. Spatial climatic variation and its control on glacier equilibrium line altitude in Taylor Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Fountain, Andrew G.; Lewis, Karen J.; Doran, Peter T.

    1999-10-01

    The altitude of the equilibrium line (ELA) is an important variable describing a glacier because it helps to define the relation between the local climate and distribution of glacier mass. For the glaciers in the McMurdo Dry Valleys of Antarctica, the ELA rises rapidly with distance from the coast at a rate of about 30 m km -1, which is almost an order of magnitude greater than rates found in temperate glacier regimes. In one of the dry valleys, Taylor Valley, the ELA trend is not smooth but exhibits an abrupt shift of about 700 m yielding a local gradient of about 70 m km -1. The geographic location of the shift coincides with the Nussbaum Riegel, a ridge in the middle of the valley, which apparently exerts a strong control on the climatic pattern in Taylor Valley. To reveal the specific climatic factors responsible for the abrupt shift in ELA, we applied a theoretical analysis of ELA response to step changes in climate. Model results predicted an ELA rise of 729 m, which compares favorably to the observed 700 m change. The two most important climatic factors are differences in precipitation and wind speed. Whereas precipitation is expected to be a major factor determining ELA position for glaciers worldwide, because it determines the rate of mass accumulation, wind speed has not been previously recognized. In polar regions, where melting is typically absent, sublimation is the only significant process by which glaciers lose mass and its rate largely depends on wind speed rather than temperature. These findings highlight the sensitivity of polar glaciers to climatic differences over short distances, which have profound effects on the ELA and, in turn, glacier geometry. This study also points to the importance of understanding spatial differences in climates before piecing together a temporal climatic history based on data derived from different glaciers.

  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.

    2015-03-01

    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 and New Zealand.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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 years BP in South America and New Zealand.

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

    NASA Astrophysics Data System (ADS)

    Loibl, David; Lehmkuhl, Frank

    2014-05-01

    Temperate glaciers in the eastern Nyainqêntanglha range, southeastern Tibet, are highly sensitive to climate change and are therefore of particular high interest for research on late Holocene changes of the monsoonal climate in High Asia. However, due to the remoteness of the area, the scarcity of empirical data, and the challenges to remote sensing work posed by cloud and snow cover, knowledge about the glacier dynamics and changes is still very limited. We applied a remote sensing approach that allowed a comprehensive regional glacier survey despite the few available data. Geomorphologic characteristics, distribution and late Holocene changes of 1964 glaciers were mapped from one of the few appropriate late summer satellite images: a Landsat ETM+ scene from September 23, 1999. The glacier dataset was subsequently parameterized by DEM supported measurements. Complex climate-relief-glacier interactions were studied in detail for three large glaciers in neighboring valleys. Despite their spatial proximity, these display strong heterogeneity in terms of catchment morphology, debris cover, and glacier characteristics. The results of this case study then provided the conceptual basis to use geomorphological evidence, i.e. trimlines and latero-frontal moraines, to obtain quantitative data on the changes since the Little Ice Age (LIA) maximum glacier advance. Statistical analysis of glacier length change revealed an average retreat of ~ 40 % and a trend towards stronger retreat for smaller glaciers. An evaluation of different methods to calculate equilibrium line altitudes (ELAs) indicates that an optimized toe-to-ridge altitude method (TRAM) outperforms other methods in settings with complex topography and a lack of mass-balance measurements. However, a large number of glacier measurements is crucial for high quality TRAM results and special attention has to be paid to different morphological glacier characteristics: debris-cover, reconstitution, valley floor limitation, and detachment of glacier tributaries, are criteria that prevent reliable ELA calculations. In order to determine the best-fitting TRAM ratio value and to test the quality of the calculated ELAs, a remote sensing approach was applied: the altitudes of transient snowlines visible in the late summer Landsat scene were measured from the DEM and compared to TRAM results for each glacier. The interpolated ELA results show a southeast-northwest gradient ranging from 4,400 to 5,600 m a.s.l. and an average ELA rise of ~ 98 m since the LIA. Due to the large amount of measurements, the ELA distribution reveals topographic effects down to the catchment scale, i.e. orographic rainfalls and leeward shielding. Contrasting to the expectations for subtropical settings, glaciers on south facing slopes have not retreated strongest and ELAs on south facing slopes did not rise furthest. Instead, highly heterogeneous spatial patterns emerge that show a strong imprint of both, topography and monsoonal dynamics. The interpretation of these patterns provides insights into the monsoonal system and the characteristics of late Holocene glacier change in southeastern Tibet. For example, the ELA distribution reveals that the study area is influenced by both, Indian summer monsoon and East Asian summer monsoon, but that the latter does not reach the Tibetan Plateau.

  7. 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.

  8. Glacier equilibrium line altitudes as palaeoclimatic information sources - examples from the Alpine Younger Dryas.

    NASA Astrophysics Data System (ADS)

    Kerschner, H.; Sailer, R.; Hertl, A.; Schuh, M.

    2003-04-01

    Equilibrium line altitudes (ELA) and flucutations of the ELA (dELA) of well dated glacial advances are valuable terrestrial sources for palaeoclimatic information, which are physically well understood (Kuhn 1981, Kaser and Osmaston 2001). Values of dELA can be used to infer quantitatively standard climatic parameters like precipitation and precipitation change. ELAs of former glaciers are usually calculated from maps of the glacier topography based on the moraines and related geomorphological features. Then either the analytical glacial-meterological model for ELA fluctuations by Kuhn (1981) or the statistical parameterization of the climate at the ELA in terms of "summer temperature" and "precipitation" by Ohmura et al. (1992) can be used for palaeoclimatic interpretation. As dELA is influenced both by factors governing accumulation and ablation, some external climatic information on one parameter is necessary to obtain the other. Moraines of the Younger Dryas "Egesen-Stadial" can be found throughout the Alps. Early Younger Dryas (Egesen-I, Ivy-Ochs et al. 1996) dELAs show a distinct spatial pattern. They were highest (ca. 450-600 m against "present-day") in areas exposed towards the West and Northwest. In the central valleys, it was in the order of -300 m and less. Presently, almost 200 data points are available. Summer temperature depression (dTs) can be derived from the Younger Dryas timberline depression and other proxy data (Ammann and Oldfield 2000). It seems to be in the order of -3.5 K in the central Alps. Along the northern and western fringe of the Alps, it may be somewhat larger (-4 to -4.5 K). dELA and dTs values are then used to calculate precipitation change (dP). Early Younger Dryas climate in the central valleys of the Alps seems to have been considerably drier than today (dP -30%). In areas open to the West and Northwest, precipitation seems to have been the same as today or even slightly higher (dP 0 - +10%). These results agree well with the results from permafrost-climate studies (Sailer et al. 2000) and the qualitative information from biological proxy data. They also support the results from Atmospheric General Circulation models for the Younger Dryas in Europe, which point towards a more zonal type of circulation. Parts of the study were financially supported by the Austrian Science Foundation (FWF) under grant P12600-GEO. References: Ammann, B., F.Oldfield (ed.).2000. Palaeo3 159(2-4). Ivy-Ochs, S., Ch. Schluechter, P.W.Kubik, H.A.Synal, J.Beer, H. Kerschner. 1996. Eclogae Geol. Helv. 89(3), 1049-1063. Kuhn, M. 1981. IAHS publ. 131, 3-20. Kaser, G., H.Osmaston. 2001. Tropical Glaciers. Cambridge University Press. Kerschner, H., G.Kaser, R.Sailer. 2000. Ann. Glaciol. 31, 80-84. Ohmura, A., P.Kasser and M.Funk. 1992. J.Glaciol., 38(130), 397 - 411.

  9. 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 automatic functions within the GIS operating environment. To reconstruct the ELAs of the glaciers, the Area x Altitude Balance Ratio (AABR) method was used. This method is extensively described in Osmaston (2005). To determine the rates of deglaciation, variations observed for 2007 in surface areas and ELAs against their values in 1986, 1955 and the Little Ice Age (LIA) were used as geoindicators. Establishing deglaciation rates has allowed forecasts to be made as to when the complete disappearance of ice mass could occur for three future scenarios, considering the hypothetical reproduction in each scenario of the rates of deglaciation observed since 1986 (Scenario 1), 1955 (Scenario 2) and the LIA (Scenario 3). To determine the chronology of the last maximum advance of the glaciers and the last volcanic manifestations, samples were taken from moraine blocks and glaciated rocky thresholds, and also from lava ejected during the last eruption, in the eastern sector of the complex. Due to their recent external appearance, since they have been channeled by glacial valleys and have been affected by ice masses only at the head, these lavas had been dated as Holocene. Absolute dating was performed using cosmogenic methods (Cl36). As a result of applying the proposed method, glacial system surface areas have been estimated for 2007 (47 km2), 1986 (54 km2) and 1955 (56 km2), implying a reduction of ~18% in 52 years. The process appears to have speeded up in the last decades (~13% in only 21 years). Surfaces were also estimated and ELAs reconstructed for the NE and SE groups in 2007, 1986, 1955, the Little Ice Age and during the last maximum advance. Glaciers from the NE group show an area during all periods (2.3, 2.7, 2.9, 3.3 and 30 km2) smaller than SE group glaciers (8.1, 9.9, 10.3, 11.9 and 66.5 km2). An individual analysis of glaciers in the NE and SE groups in 2007 shows a reduction in surface area two to four times greater than that observed between 1955 and 1986. ELAs are also higher for all periods in the Northern section (5968, 5930, 5923, 5886 and 5186 m) than in the Southern section (5862, 5806, 5787 and 4951 m). The depression in ELAs during the LIA was similar in the NE (~82 m) and in the SE (~86 m). However, the 2007 ELA shows a depression of 106 m in the Southern direction. The magnitude of this depression has shown a marked tendency towards reduction in recent decades (136 m in 1955 and 124 m in 1986). Furthermore, the decrease in ELA depression seems to occur faster, with ↓Z ~12 m between 1955 and 1986 and ↓Z ~18 m between 1986 and 2007. However, during the Little Ice Age (~110 m) that value was closer to the current value (106 m). Depression in ELAs during the last maximum glacier advance has been estimated at ~782 m (NE) and ~847 m (SE). During that period, the N-S depression reached a maximum value of 235 m. These results agree with those obtained for the eastern range of the Central Andes (Smith et al. 2005 a and b) and are also within the depression intervals and trends proposed in regional-scale studies (Kelin et al. 1999). Analyses performed on a sample from a block situated on a lateral moraine in the Queñua Ranra Quebrada (NE group of the complex) suggest a chronology of ~17 Cl36 ky. for the last maximum ice mass advance. This date is in agreement with the depression in SST temperature during the same period, deduced from analyzing Mg/Ca ratios in marine foraminifera shells from the Galapagos Islands (Lea, 2006). Using surfaces and ELAs as geoindicators, deglaciation rates and the Horizon without glaciers (H0) have been calculated globally, for the complete glacier system in scenarios 1 and 2, and for glaciers in the pilot group in scenarios 1, 2 and 3. Results show that the deglaciation process is occurring differentially. Whereas several masses could disappear in a few decades, others could be preserved for centuries. Regarding the last phase of volcanic activity, a lava sample has been dated at only ~2 Cl36 ky. Testing the proposed method has allowed the modeling of glacier evolution using variations observed in surfaces and ELAs as geoindicators. Results from the global-scale analysis are only a preliminary approximation to the problem. Detailed analysis of the glaciers in the NE and SE groups has yielded more precise results. Forecasts about future glacier retreat, interest in finding out about their past evolution and the absolute chronology of the last phase of volcanic activity, which confirms their recent character, suggest the need to extend our understanding of the evolution of the Nevado Coropuna's volcanic complex and glacier system. References Klein, A.G., Seltzer, G.O. & Isacks, B.L., 1999. Modern and Local Last Glacial Maximum snowlines in the Central Andes of Peru, Bolivia and Northern Chile. Quaternary Research Reviews, 18: 3-84. Lea, D.W., D.K. Pak, C.L. Belanger, H.J. Spero, M.A. Hall, and N.J. Shackleton, 2006. Galapagos paleoclimate history of surface waters over the last 135,000 yr. Quaternary Science Reviews, 25 (11-12): 1152-1167. 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. Smith, J., Seltzer, G.O., Rodbellb, D.T. & Klein, A.G., 2005 a. Regional synthesis of last glacial maximum snowlines in the tropical Andes, South America. Quaternary International, 138-139:145-167. Smith, JA, Seltzer, GO, Farber, DL, Rodbell, DT & Finkel, R.C., 2005 b. Early Local Last Glacial Maximum in the Tropical Andes. Science, 308. Ubeda, J., 2007. Geomorphological characterization of the northern sector of the Central Volcanic Zone of the Central Andes. Approach to a case study: the glacier of the volcano Nevado Coropuna complex. Research work to obtain the Diploma of Advanced Studies, Universidad Complutense de Madrid, Madrid, 312 pp.

  10. 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.

  11. 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 these Swiss glacier systems. We will apply the model to other regions in order to further elucidate the variability and sensitivity in the climate system during the YD, and provide insight into the primary drivers of those changes.

  12. 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.

  13. Lateglacial and early Holocene palaeoclimatic reconstruction based on glacier fluctuations and equilibrium-line altitudes at northern Folgefonna, Hardanger, western Norway

    NASA Astrophysics Data System (ADS)

    Bakke, Jostein; Olaf Dahl, Svein; Nesje, Atle

    2005-02-01

    Northern Folgefonna (c. 23 km2), is a nearly circular maritime ice cap located on the Folgefonna Peninsula in Hardanger, western Norway. By combining the position of marginal moraines with AMS radiocarbon dated glacier-meltwater induced sediments in proglacial lakes draining northern Folgefonna, a continuous high-resolution record of variations in glacier size and equilibrium-line altitudes (ELAs) during the Lateglacial and early Holocene has been obtained. After the termination of the Younger Dryas (c. 11 500 cal. yr BP), a short-lived (100-150 years) climatically induced glacier readvance termed the Jondal Event 1 occurred within the Preboreal Oscillation (PBO) c. 11 100 cal. yr BP. Bracketed to 10 550-10 450 cal. yr BP, a second glacier readvance is named the Jondal Event 2. A third readvance occurred about 10 000 cal. yr BP and corresponds with the Erdalen Event 1 recorded at Jostedalsbreen. An exponential relationship between mean solid winter precipitation and ablation-season temperature at the ELA of Norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ELA and an independent proxy for summer temperature. Compared to the present, the Younger Dryas was much colder and drier, the Jondal Event 1/PBO was colder and somewhat drier, and the Jondal Event 2 was much wetter. The Erdalen Event 1 started as rather dry and terminated as somewhat wetter. Variations in glacier magnitude/ELAs and corresponding palaeoclimatic reconstructions at northern Folgefonna suggest that low-altitude cirque glaciers (lowest altitude of marginal moraines 290 m) in the area existed for the last time during the Younger Dryas. These low-altitude cirque glaciers of suggested Younger Dryas age do not fit into the previous reconstructions of the Younger Dryas ice sheet in Hardanger.

  14. Reconstruction of glacier equilibrium-line altitudes for the Last Glacial Maximum on the High Plain of Bogotá, Eastern Cordillera, Colombia: climatic and topographic implications

    NASA Astrophysics Data System (ADS)

    Mark, Bryan G.; Helmens, Karin F.

    2005-10-01

    The High Plain of Bogotá in the Andes of Colombia provides an exceptionally detailed record of glaciation. A two-stage Last Glacial Maximum (LGM) is noted in Bogotá; the older stage (max) presents an opportunity to reconstruct individual valley glaciers and explore spatial patterns. Well-mapped geomorphic features on topographic base maps permit the reconstruction of 23 palaeoglacier surfaces. Glacier extent varies across the region, with lower altitudes reached farther to the east. Equilibrium line altitudes (ELAs) are reconstructed using the area-altitude balance ratio (AABR) method, with BRs in three groups reflecting the W-E gradient in glacier extent and selected by minimising variation from group means. Average LGM ELA for all palaeoglaciers is 3488 m with a standard deviation of 182 m. The average lowering in ELA from LGM to modern of ca. 1300 m is best explained by a considerable drop in temperature. Significant intra-regional variance in LGM ELA can be ascribed to topography and its influence on precipitation and/or glacier form, with lower headwall elevations being correlated to larger accumulation areas.

  15. 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)

    Mara Fernndez, 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 Pea Trevinca (4214'33'' N, 647'46'' W; 2127 m) and Pea Negra (4214'58'' N, 647'39'' 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 the ELAs, which are different from the values obtained by the methods mentioned above. AABR and AAR are shown to be the most reliable methods as they do not depend on the conservation level of geomorphological features. The estimated paleoELA in our case study is in an intermediate position between those estimated in nearby glaciers of the same type during the MIE in the Serra da Estrela and la Sierra de Bjar, at 1650 and 2010 m. The contrast is more difficult, however, with the Cordillera Cantbrica, with ELAs ranging from 1100 to 2000 m, depending on orientation. Research funded by Cryocrisis project (CGL2012-35858), Government of Spain

  16. The equilibrium flow and mass balance of the Taku Glacier, Alaska 1950 2006

    NASA Astrophysics Data System (ADS)

    Pelto, M. S.; Miller, M. M.; Adema, G. W.; Beedle, M. J.; McGee, S. R.; Sprenke, K. F.; Lang, M.

    2008-11-01

    The Taku Glacier, Alaska has advanced 7.5 km since the late nineteenth century, while all other primary outlet glaciers of the Juneau Icefield are in retreat. The Juneau Icefield Research Program has completed field work on the Taku Glacier annually since 1946. The collected observations of surface mass balance, glacier velocity and glacier thickness at Profile IV 29 km above the terminus and 4 km above the equilibrium line provide a means to assess the equilibrium nature of the Taku Glacier. Annual velocity measured and summer velocity measurements completed at a Profile IV from 1950 2006 indicate insignificant variations in velocity seasonally or from year to year. The consistency of velocity over the 56-year period indicates that in the vicinity of the equilibrium line, the flow of the Taku Glacier has been in an equilibrium state. Surface mass balance was positive from 1946 1988 averaging +0.42 m a-1. This led to glacier thickening. From 1988 2006 an important change has occurred and annual balance has been -0.14 m a-1, and the glacier thickness has ceased increasing along Profile IV. Field measurements of ice depth and surface velocity allow calculation of the volume flux at Profile IV. Volume flux is then compared with the surface balance flux from the region of the glacier above Profile IV, determined annually in the field. Above Profile IV the observed mean surface flux from 1950 2006 is 5.50×108 m3 a-1 (±5%), while the calculated volume flux range for the same period flowing through profile IV is 5.00 5.47×108 m3 a-1. The mean surface flux has been greater than the volume flux, which has led to slow thickening of the Taku Glacier up to 1988. The thickening has not led to a change in the flow of Taku Glacier at Profile IV.

  17. The equilibrium flow and mass balance of the Taku Glacier, Alaska 1950-2006

    NASA Astrophysics Data System (ADS)

    Pelto, M. S.; McGee, S. R.; Adema, G. W.; Beedle, M. J.; Miller, M. M.; Sprenke, K. F.; Lang, M.

    2008-05-01

    The Taku Glacier, Alaska has advanced 7.5 km since the late nineteenth century, while all other primary outlet glaciers of the Juneau Icefield are in retreat. The Juneau Icefield Research Program has completed field work on the Taku Glacier annually since 1946. The collected observations of surface mass balance, glacier velocity and glacier thickness at Profile IV 29 km above the terminus and 4 km above the equilibrium line provide a means to assess the equilibrium nature of the Taku Glacier. Velocity measured over a twelve month span and annual summer velocity measurements completed at a Profile IV from 1950-2006 indicate insignificant variations in velocity seasonally or from year to year. The consistency of velocity over the 56-year period indicates that in the vicinity of the equilibrium line, the flow of the Taku Glacier has been in an equilibrium state. Surface mass balance was positive from 1946-1988 averaging +0.42 m a-1. This led to glacier thickening. From 1988-2006 an important change has occurred and annual balance has been -0.14 m a-1, and the glacier thickness has ceased increasing along Profile IV. Field measurements of ice depth and surface velocity allow calculation of the volume flux at Profile IV. Volume flux is then compared with the surface balance flux from the region of the glacier above Profile IV, determined annually in the field. Above Profile IV the observed mean surface flux is 5.50×108 m3/a (±5%), while the calculated volume flux range flowing through profile IV is 5.00-5.47×108 m3/a. The mean surface flux has been greater than the volume flux, which has led to slow thickening of the Taku Glacier up to 1988. The thickening has not led to a change in the flow of Taku Glacier at Profile IV.

  18. Automating the implementation of an equilibrium profile model for glacier reconstruction in a GIS environment

    NASA Astrophysics Data System (ADS)

    Frew, Craig R.; Pellitero, Ramón; Rea, Brice R.; Spagnolo, Matteo; Bakke, Jostein; Hughes, Philip D.; Ivy-Ochs, Susan; Lukas, Sven; Renssen, Hans; Ribolini, Adriano

    2014-05-01

    Reconstruction of glacier equilibrium line altitudes (ELAs) associated with advance stages of former ice masses is widely used as a tool for palaeoclimatic reconstruction. This requires an accurate reconstruction of palaeo-glacier surface hypsometry, based on mapping of available ice-marginal landform evidence. Classically, the approach used to define ice-surface elevations, using such evidence, follows the 'cartographic method', whereby contours are estimated based on an 'understanding' of the typical surface form of contemporary ice masses. This method introduces inherent uncertainties in the palaeoclimatic interpretation of reconstructed ELAs, especially where the upper limits of glaciation are less well constrained and/or the age of such features in relation to terminal moraine sequences is unknown. An alternative approach is to use equilibrium profile models to define ice surface elevations. Such models are tuned, generally using basal shear stress, in order to generate an ice surface that reaches 'target elevations' defined by geomorphology. In areas where there are no geomorphological constraints for the former ice surface, the reconstruction is undertaken using glaciologiaclly representative values for basal shear stress. Numerical reconstructions have been shown to produce glaciologically "realistic" ice surface geometries, allowing for more objective and robust comparative studies at local to regional scales. User-friendly tools for the calculation of equilibrium profiles are presently available in the literature. Despite this, their use is not yet widespread, perhaps owing to the difficult and time consuming nature of acquiring the necessary inputs from contour maps or digital elevation models. Here we describe a tool for automatically reconstructing palaeo-glacier surface geometry using an equilibrium profile equation implemented in ArcGIS. The only necessary inputs for this tool are 1) a suitable digital elevation model and 2) mapped outlines of the former glacier terminus position (usually a frontal moraine system) and any relevant geomorphological constraints on ice surface elevation (e.g. lateral moraines, trimlines etc.). This provides a standardised method for glacier reconstruction that can be applied rapidly and systematically to large geomorphological datasets.

  19. A semi-automatic method to create central glacier flow lines: A pilot study with Alaskan glaciers

    NASA Astrophysics Data System (ADS)

    Le Bris, R.; Paul, F.

    2012-04-01

    Glacier length is an important, but largely missing parameter in digital glacier inventories as it has to be digitized by hand (with the related variability). Length changes of glaciers are key indicators of climate change, but can only be measured in the field for a few hundred selected glaciers globally. Its vector representation (a central flow line) is a most important input for modelling future glacier evolution, but only seldom available from digital databases. Hence, there is an urgent need to generate such flow lines for a large number of glaciers from automated methods. The study describes a new method to automatically create central flowlines of glaciers along with an application to a study site where its suitability to automatically derive changes in glacier length is demonstrated. Our new method will likely strongly facilitate the number of available data on both issues (length values and changes) and thus help to improve the assessment and modelling of climate change impacts on glaciers. This new algorithm is based on Python scripting and additional libraries (GDAL / OGR) and requires only a DEM and glacier outlines as an input. The core of the method is based on a glacier axis concept that is combined with geometry rules such as the k-d Tree, Nearest Neighbour and crossing test theory. We have applied the method to 400 glaciers located in Western Alaska, where a new glacier inventory was recently created. The accuracy of the method was assessed by a quantitative and qualitative (outline overlay) comparison with a manually digitized data set for 20 glaciers. This comparison revealed for 17 out of the 20 glaciers a length value that is within the range of the manual digitizations. Other potential methods to determined glacier length performed less good. Combined with previous glacier outlines from the same region we determined and analysed length changes for 390 glaciers over a c. 50 year period.

  20. An automatic method to create flow lines for determination of glacier length: A pilot study with Alaskan glaciers

    NASA Astrophysics Data System (ADS)

    Le Bris, Raymond; Paul, Frank

    2013-03-01

    Glacier length is a key parameter in global glacier inventories, but difficult to determine in a consistent way and subject to frequent change. Its vector representation (a flow line) is a most important input for modeling future glacier evolution, but only seldom available from digital databases. Hence, there is an urgent need to generate such flow lines for a large number of glaciers from automated methods. We here present a new algorithm that is based on Python scripting and additional libraries (GDAL and OGR) and requires only a DEM and glacier outlines as an input. The core of the method is based on a glacier axis concept that is combined with geometry rules such as the k-d Tree, Nearest Neighbor and crossing test theory. We have applied the method to 400 glaciers located in Western Alaska, where a new glacier inventory was recently created. The accuracy of the method was assessed by a quantitative and qualitative (outline overlay) comparison with a manually digitized dataset for 20 glaciers. This comparison revealed for 17 out of the 20 glaciers a length value within the range of the manual digitizations. Other potential methods performed less well. Combined with previous glacier outlines from the same region (Digital Line Graph) we automatically determined length changes for 390 glaciers over a c. 50 year period.

  1. Equilibrium-Line Altitudes In Cold Hyperarid Settings

    NASA Astrophysics Data System (ADS)

    Jigjidsuren, B.; Gillespie, A. R.

    2012-12-01

    Equilibrium-line altitude (ELA) is a climatically sensitive elevation on the glacier surface where annual accumulation equals annual ablation. Although local effects including debris cover, slope and aspect can influence the mass balance, ELA responds most strongly to snowfall and summer temperature (positive degree days). ELA can be estimated from the distribution and elevations of glacial deposits and is thus a useful parameter in the study of paleoclimate, although it is highly sensitive to extraneous factors, especially for small glaciers confined to cirques. This problem can be overcome by examining numerous nearby glaciated drainages, instead of point studies, for example with remote sensing using images and DEMs provided there is chronologic control from field work. However, the concept of ELA was developed and most studies of ELA have been undertaken in temperate regions with relatively high mean annual snowfall where ablation increases at lower elevations and there actually is a well-defined altitude of equilibrium. In cold arid regions such as Central Asia or parts of the Andes, snowfall can be so low (<150 mm/yr) that solar irradiation alone is sufficient to evaporate the accumulation directly (sublimation), in contrast to regions in which high amounts of snowfall require warm temperatures for melting. In these hyperarid regions, the ELA may be a poorly defined concept since the entire glacier experiences ablation, not just the lower elevations. However, because glaciers in these settings can only exist where there is no melting, the precipitation-limited arid paleoglaciers are easy to distinguish and map from the temperature-controlled glaciers, which occur hundreds of meters lower. Remote mapping can therefore be used to map the ~150 mm/yr isohyet in continental settings.

  2. 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.

  3. Modeling the grounding line dynamics of Thwaites Glacier, West Antarctica using full Stokes and lower order models

    NASA Astrophysics Data System (ADS)

    Yu, H.; Rignot, E. J.; Morlighem, M.; Seroussi, H. L.; Larour, E. Y.

    2014-12-01

    Thwaites Glacier (TG) is one of the largest ice streams in West Antarctica and the broadest (about 110 km wide). Satellite observations have revealed that the grounding line is retreating rapidly, ice is thinning meters per year, the fast portion of the ice stream is widening, and since 2006 the main portion of the glacier has been accelerating following a period of relatively steady speed. Here, we use the JPL/UCI Ice Sheet System Model (ISSM) to study the grounding line dynamics of Thwaites Glacier to determine its stability and sensitivity to changes in ice-ocean interactions. We use a full Stokes model, a higher order (HO) approximation and a shelfy-stream approximation (SSA) in 2D and try to best fit observations of ice flow, ice surface elevation and ice thickness across the grounding line by tuning basal friction on land and bottom melt rates on the floating ice tongue. The motion of the grounding line is treated as a contact problem with Full Stokes and using hydrostatic equilibrium with HO and SSA. We show that only the Full Stokes model can correctly represent the balance of stresses and a near steady state profile of the glacier across the grounding line. The work is then extended in 3D to estimate the sensitivity of the glacier's grounding line to changes in ice melt rates.

  4. 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.

  5. 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

  6. Late Quaternary glaciation and equilibrium-line altitudes of the Mayan Ice Cap, Guatemala, Central America

    NASA Astrophysics Data System (ADS)

    Roy, Alex J.; Lachniet, Matthew S.

    2010-07-01

    The Sierra los Cuchumatanes (3837 m), Guatemala, supported a plateau ice cap and valley glaciers around Montaña San Juan (3784 m) that totaled ˜ 43 km 2 in area during the last local glacial maximum. Former ice limits are defined by sharp-crested lateral and terminal moraines that extend to elevations of ˜ 3450 m along the ice cap margin, and to ca. 3000-3300 m for the valley glaciers. Equilibrium-line altitudes (ELAs) estimated using the area-altitude balance ratio method for the maximum late Quaternary glaciation reached as low as 3470 m for the valley glaciers and 3670 m for the Mayan Ice Cap. Relative to the modern altitude of the 0°C isotherm of ˜ 4840 m, we determined ELA depressions of 1110-1436 m. If interpreted in terms of a depression of the freezing level during maximal glaciation along the modern lapse rate of - 5.3°C km - 1 , this ΔELA indicates tropical highland cooling of ˜ 5.9 to 7.6 ± 1.2°C. Our data support greater glacial highland cooling than at sea level, implying a high tropical sensitivity to global climate changes. The large magnitude of ELA depression in Guatemala may have been partially forced by enhanced wetness associated with southward excursions of the boreal winter polar air mass.

  7. Glaciers in Equilibrium - Results from the McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Fountain, A. G.; Nylen, T. H.; Doran, P. T.

    2004-12-01

    Since 1993 the mass balance of two glaciers in the McMurdo Dry Valleys, Antarctica (163° E 77.5° S) has been measured. The magnitude of annual mass gain or loss does not exceed 10 cm water equivalent averaged over each glacier, consistent with the local climate of a polar desert. The overall trend in mass balance shows that the glaciers are in approximate balance with the current climate and no obvious trends exist in either the winter or summer balances. These are similar to a set of mass balance measurements made in another part of the dry valleys during the 1970s (Chinn, 1985). Recent analysis of the climate of the dry valleys shows this region is cooling at a rate of 0.7° C per decade during this period since 1986, which is reflected in the overall lowering of lake levels, decreased primary productivity of the lakes, and declining number of invertebrates (Doran et al., 2002). Although an unusually warm period occurred in the summer of 2001-2002, annual temperatures continue to cool. This region seems to be isolated from the warming elsewhere in Antarctica and the cooling in this part of the Ross Sea region may be due to El Nino forcing (Bertler et al, 2004). The sluggish behavior of the glaciers results from a low mass exchange and an apparent climatic buffering, which supports evidence from the geologic record that these glaciers have not advanced more than a few hundred meters over the past 3 million years (Hall et al., 1993). Many of the glaciers, however, are advancing which probably results from a slow time-scale response from warming conditions in the past millennium.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  9. Active water exchange and life near the grounding line of an Antarctic outlet glacier

    NASA Astrophysics Data System (ADS)

    Sugiyama, Shin; Sawagaki, Takanobu; Fukuda, Takehiro; Aoki, Shigeru

    2014-08-01

    The grounding line (GL) of the Antarctic ice sheet forms the boundary between grounded and floating ice along the coast. Near this line, warm oceanic water contacts the ice shelf, producing the ice sheet's highest basal-melt rate. Despite the importance of this region, water properties and circulations near the GL are largely unexplored because in-situ observations are difficult. Here we present direct evidence of warm ocean-water transport to the innermost part of the subshelf cavity (several hundred meters seaward from the GL) of Langhovde Glacier, an outlet glacier in East Antarctica. Our measurements come from boreholes drilled through the glacier's ∼400-m-thick grounding zone. Beneath the grounding zone, we find a 10-24-m-deep water layer of uniform temperature and salinity (-1.45 °C; 34.25 PSU), values that roughly equal those measured in the ocean in front of the glacier. Moreover, living organisms are found in the thin subglacial water layer. These findings indicate active transport of water and nutrients from the adjacent ocean, meaning that the subshelf environment interacts directly and rapidly with the ocean.

  10. 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.

  11. 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.

  12. Topographic context of glaciers and perennial snowfields, Glacier National Park, Montana

    NASA Astrophysics Data System (ADS)

    Allen, Thomas R.

    1998-01-01

    Equilibrium-line altitudes (ELAs) of modem glaciers in the northern Rocky Mountains are known to correspond with regional climate, but strong subregional gradients such as across the Continental Divide in Glacier National Park, Montana, also exert topoclimatic influences on the ELA. This study analyzed the relationships between glacier and snowfield morphology, ELA, and surrounding topography. Glaciers and perennial snowfields were mapped using multitemporal satellite data from the Landsat Thematic Mapper and aerial photography within an integrated Geographic Information System (GIS). Relationships between glacier morphology and ELA were investigated using discriminant analysis. Four morphological categories of perennial snow and ice patches were identified: cirque glacier, niche glacier, ice cap, and snowfield. ELA was derived from overlaid glacier boundaries and Digital Elevation Models (DEMs) within the GIs. DEMs provided topographic variables and models of solar radiation and wind exposure/shelteredness. Regression analysis showed the effects of exposure; on snow accumulation, the strong influence of local topography through upslope zone morphology such as cirque backwalls, and the tendency for glaciers with high ELAs to exhibit compactness in morphology. Results highlight the relatively compact shape and larger area of glaciers adjacent to the Continental Divide. Discriminant analysis correctly predicted the type of glacier morphology in more than half the observations using factored variables of glacier shape, elevation range, and upslope area.

  13. 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 mountain ecosystems are highly sensitive to climate changes. The Russian Altai Mountains are located in the Inner Asia on the border of Russia, Mongolia, China and Kazakhstan. The Department of Geography and Geoecology of SPbSU has been organizing annual field expeditions to this region during the last 20 yrs. The uniqueness of the Altai landscapes lies in its great variety as these mountains are higher than 4 km and located on the zonal border between steppes and semi-deserts and between continental and sharply continental climates. This research deals with space-time features of regional climate changes and the dynamics of high-altitude landscapes. The 1940-2004 time series of seasonal air temperature and precipitation from 14 weather stations from 300 to 2600 m a.s.l. were statistically analyzed applying regression, correlation, spectral and cluster analyses. To extend time series over the past 350-400 yrs, mean summer temperature and precipitation were reconstructed applying dendroclimatological methods and using the WSL Dendro data base. Comparing to the Northern Hemisphere tendency of temperature increase in the second half of the 20th century over the Altai has been observed generally earlier, since 1950s. Maximum warming rate in the last quarter of the 20th century is typical to winter in the Altai (0,85°/10 yrs) as well as the entire Northern Hemisphere. Synchronous changes in the Altai and the Northern Hemisphere are observed in all seasons only in 1975-2004. At the turn of the XX-XXI centuries warming rates slow down in the region while temperature level is still high. These changes are partly associated with circulation epochs. Spectral analysis revealed important role of natural cyclical recurrence in climate changes, for example quasi-biennial, solar and Brückner cycles. According to dendrochronological reconstruction mean summer temperature increased from the end of the Little Ice Age (LIA) to its maximum in the 1990s by approximately 2°C, to 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.

  14. Snow-Line Changes on Irian Jaya Glaciers Between 1971 and 2000 Record Temperature Changes in the Lower Troposphere (600 mb) of the Far Western Tropical Pacific

    NASA Astrophysics Data System (ADS)

    Prentice, M. L.; Brackett, T.

    2002-05-01

    Long-term fluctuations in the size and surface mass balance of glaciers in the wet tropics dominantly reflect temperature change in the lower troposphere. Hence, altitudinal changes in the snow- or equilibrium-line (ELA) on these glaciers approximate the height history of the mean annual 0oC isotherm. We report here changes in the size and mass balance of glaciers in the far western tropical Pacific region of Irian Jaya (4o S, 137o E) between 1971 and 2000. In 1971, the glaciers occupied about 12km2 of the Puncak Jaya region between 4400 and 4900 m above sea level (masl) (600 mb). By 2001, ice area was reduced to about 2 km2. Relying primarily on photogrammetric observations provided by PT Freeport Indonesia, we estimate that, between 1972 and 1995, the average ELA for the principle glaciers rose about 70 m from 4650 masl to 4724 masl based on clearly visible snow-lines. Between 1995 and 1997, the ELA appears to have risen an additional 50 m, reaching 4780 masl. Though net snow accumulation for 1995-1997 varied laterally across the glacier surfaces, almost all ice surfaces lowered for 1995-1997. Between 1997 and 2000, net balances were substantially more positive than for 1995-1997, indicating ELA lowering by 10s of meters. Patches of net surface-elevation increase and decrease were only partially related to altitude. Significant areas of net positive balance were apparent down to 4740 masl. Assuming that there was no long-term trend in precipitation in this region, we infer that regional temperature increase drove the ELA rise on these glaciers. If the lapse rate on Puncak Jaya held at 0.7oC/100 m, then the ELA changes signify a net warming of the lower troposphere of nearly 0.9 oC between 1971 and 1997. The apparent net ELA lowering from 1997 to 2000 is consistent with nearly offsetting warming and cooling in this interval measured by PT Freeport Indonesia. For 1971-2000, the ELA-based temperature trends mimick those derived from tropical radiosonde data. Hence, the geological record of past ELA changes in New Guinea presents the opportunity to reconstruct regional lower tropospheric conditions back in time.

  15. 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.

  16. Grounding line retreat of Totten Glacier, East Antarctica, 1996 to 2013

    NASA Astrophysics Data System (ADS)

    Li, Xin; Rignot, Eric; Morlighem, Mathieu; Mouginot, Jeremie; Scheuchl, Bernd

    2015-10-01

    Totten Glacier, East Antarctica, a glacier that holds a 3.9 m sea level change equivalent, has thinned and lost mass for decades. We map its grounding line positions in 1996 and 2013 using differential radar interferometry (InSAR) data and develop precise, high-resolution topographies of its ice surface and ice draft using NASA Operation IceBridge data, InSAR data, and a mass conservation method. We detect a 1 to 3 km retreat of the grounding line in 17 years. The retreat is asymmetrical along a two-lobe pattern, where ice is only grounded a few 10 m above sea level, or ice plain, which may unground further with only modest amounts of ice thinning. The pattern of retreat indicates ice thinning of 12 m in 17 years or 0.70.1 m/yr at the grounding line on average. Sustained thinning will cause further grounding line retreat but may not be conducive to a marine instability.

  17. A code for line blanketing without local thermodynamic equilibrium

    NASA Astrophysics Data System (ADS)

    Anderson, L. S.

    A numerical code has been written which is designed to calculate radiation transport and atmospheric structure under the constraints of statistical equilibrium in atomic transitions and radiative and hydrostatic equilibrium in the medium. In addition to the complete linearization and variable Eddington factor techniques of Auer and Mihalas, it uses a multi-frequency/multi-gray algorithm which admits the inclusion of many spectral lines in full statistical equilibrium. The program can comfortably accept up to about 300 specific lines arising from about 30 lower states and any number of continua. Cleverly constructed artificial model atoms can extend the number of lines to 3000 or more, where opacity sampling techniques can begin to approximate the blanketing accomplished by Kurucz in LTE. By way of example, a model of a stellar atmosphere is presented with effective temperature 35,000 K and surface gravity 10 to the 4 cm per second squared. The calculation includes 98 bound-free transitions and 93 bound-bound transitions (57 with radiative rates) between 91 states in 36 ions of nine cosmically abundant species.

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

    SciTech Connect

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

    1995-08-01

    The histories of four iceberg-calving outlet-glacier systems in the Kenai Fjords National Park underscore the importance of fiord depth, sediment supply, and fiord geometry on glacier stability. These parameters, in turn, limit the reliability of calving glacier chronologies as records of climatic change. Tree-ring analysis together with radiocarbon dating show that the Northwestern and McCarty glaciers, with large drainage basins, were advancing in concert with nearby land-terminating glaciers about A.D. 600. After an interval of retreat and possible nonclimatically induced extension during the Medieval Warm Period, these ice margins advanced again through the Little Ice Age and then retreated synchronously with the surrounding land-terminating glaciers about A.D. 1900. In contrast, Holgate and Aialik glaciers, with deeper fiords and smaller basins, retreated about 300 yr earlier. Reconstructions of Little Ice Age glaciers suggest that equilibrium-line altitudes of Northwestern and McCarty glaciers were, respectively, 270 and 500 m lower than now. Furthermore, the reconstructions show that these two glaciers were climatically sensitive when at their terminal moranies. However, with ice margins at their present recessional positions and accumulation area ratios between 0.8 and 0.9, only McCarty Glacier shows evidence of advance. Aialik and Holgate glaciers were climatically insensitive during the Little Ice Age maxima and remain insensitive to climate. 40 refs., 7 figs., 2 tabs.

  19. 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 THAR with ratios 0.2; 0.4 and 0.5 tend to underestimate it's position. Research funded by Cryocrisis project (CGL2012-35858), Government of Spain.

  20. 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.

  1. Using glacier inventory data to determine the sea-level contribution of glaciers

    NASA Astrophysics Data System (ADS)

    Paul, Frank

    2014-05-01

    Glaciers are widely considered as the best natural climate indicators. While this is certainly the case for glacier changes (length, volume), it also applies to glaciers itself as they can only exist within a certain range of climate conditions. A key parameter for the climatic classification of glaciers is their equilibrium line altitude (ELA) when referring to a balanced mass budget (ELA0). The ELA0 can be approximated by the mean or median elevation that is readily available for individual glaciers from inventories. Using well-established relations between temperature and precipitation at the ELA0, precipitation can be derived from mean elevations. Annual precipitation sums are indicative of the climatic regime and can be used to infer mass balance gradients. Once these are known, mass loss by melt can be approximated for each glacier under balanced conditions. By shifting the ELA0 upwards, the ablation region is increased and in combination with the mass balance gradient the additional glacier melt can be calculated for each glacier. In this contribution we applied the above methods to all glaciers in the Swiss Alps using glacier outlines from the mid 1970s and a digital elevation model (DEM) from the mid 1980s as an input. The mass balance gradients derived from annual precipitation are within the range of known values (measured and modeled). The modelled ablation under balanced conditions is rather similar to the observed precipitation amounts over glaciers (considering measurement uncertainties). For a one degree temperature increase, specific mass loss increases by about 0.65 m / yr (the mass balance sensitivity) which gives a total mass loss of about 1 Gt / year over a glacier area of 1000 sqkm and for a temperature increase of 1.5 degrees. These values are in good agreement with the observed annual mass changes of glaciers in the Alps over the past two decades, thus confirming the observed temperature increase in the mid 1980s.

  2. Variations in Melt-Flow Acceleration Above and Below the Greenland Equilibrium Line

    NASA Astrophysics Data System (ADS)

    Zwally, H.; Saba, J. L.; Steffen, K.

    2013-12-01

    Initial observations of accelerated ice flow at the equilibrium line in West-central Greenland during summer melt periods (1996 to 1999) indicated that surface melt-water rapidly propagated to the base and enhanced the basal sliding. Since then numerous observational and theoretical results have provided additional information on the melt-acceleration effect, while leading to some differing conclusions about the climatological and hydrological processes involved. Additional velocity measurements since 1999 show further characteristics of the melt-acceleration in the ice flowline though Swiss Camp, which terminates on land, and in a nearby flowline, which terminates in an outlet glacier. Accelerations as large as three times the average winter velocity are observed during stronger melt events. At downstream locations, accelerations begin earlier in the melt season, but accelerations at multiple sites along a flow line occur simultaneously later in the season. At the equilibrium line, a short period of surface uplift of about 50 cm occurs when the flow abruptly changes from acceleration to deceleration, apparently caused by ice compression during the transition. At downstream locations, the surface rises at the beginning of the melt season and drops at the end of melting suggesting an uplift forced by sub-ice water and sediment. Equivalence of the net additional displacement at upstream and downstream sites indicates no net longitudinal ice strain after the acceleration-deceleration periods. Approximate equivalence of the ratio of peak summer velocities to average winter velocities along the flowline indicate that local melt-acceleration is occurring at and above the equilibrium as well as from longitudinal coupling of downstream effects. High-frequency velocity observations show that the ice flow continues to accelerate with increasing water production during melt events, follow by an abrupt deceleration after the event, indicating that saturation of the acceleration effect from production of efficient sub-glacial channelization is not generally occurring. As the EL migrates inland with climatic warming, the melt-acceleration effect has also been migrating. The net additional displacement of several meters during the summer is about 3 to 5% of the total annual displacement, and is increasing as summer temperatures and surface melting increases.

  3. Modeling the response of glacier systems to climate warming in China

    NASA Astrophysics Data System (ADS)

    Xie, Zi-Chu; Wang, Xin; Feng, Qing-Hua; Kang, Er'si; Liu, Chao-Hai; Li, Qiao-Yuan

    A glacier system is regarded as the ensemble of many glaciers sharing the same region, influenced by a similar climate and organized by certain intrinsic laws. It can be either 'sensitive' or 'steady'. On the basis of the structure of the glacier system and the nature of the equilibrium-line altitudes at the steady state, functional models of a glacier system responding to climate warming were established, using the Kotlyakov-Krenke equation relating annual glacier ablation and mean summer temperature and the glacier system's median size. The modeling results under the climatic scenarios with a rate of temperature increase of 0.01, 0.03 and 0.05 K a-1 indicate that by the end of this century the glacial area of China will be reduced by -14%, -40%and -60% respectively. However, model results show distinct differences between the sensitive glacier system and the steady glacier system.

  4. Analysis of Snow Line and Albedo Conditions By Means of Time-Lapse Photography on Tapado Glacier, Chile

    NASA Astrophysics Data System (ADS)

    Vivero, S.; MacDonell, S.; McPhee, J. P.

    2014-12-01

    In the semiarid Coquimbo Region of Chile, high-altitude glaciers and seasonal snow are important sources of freshwater for irrigated agriculture and urban consumption. Due to the aridity of the environment, losses due to sublimation are large which means that accurate melt modelling is essential in order to reliably estimate streamflow. Since 2008, the CEAZA glaciology group has been studying the energy and mass balance of the largest glacier in the catchment, the Tapado Glacier using field and remote sensing measurements, and numerical modelling. The Tapado glacier system (30°08' S, 69°55' W) is a complex assemblage of uncovered and debris-covered ice located at the head of the Elqui basin between 4500 and 5536 m a.s.l. Energy balance modelling studies at the site have been limited in scope due to the development of ice pinnacles or penitentes on snow and ice surfaces. These features complicate energy distribution across the surface, due to modifications of parameters such as albedo. In this paper, we use time-lapse photography and automatic weather station (AWS) measurements to investigate how the development of penitentes impacts the spatial and temporal variability of albedo across the glacier surface and whether terrestrial photography is appropriate for use at such locations. Oblique photographs obtained from a high vantage point were georeferenced using a high resolution digital elevation model available for the entire glacier and its environs. By comparing the photographic data with point albedo measurements made at an AWS, distributed albedo maps were produced. Preliminary results suggest that distributed albedo values may be underestimated by the formation and development of penitentes during the ablation season. Moreover, it was observed that the evolution of the snow line during summer was not only topographically controlled but also modified by occasional convective snowfalls. Time-lapse photography provided to be a cost-effective tool for monitoring remote and high-altitude glaciers at high temporal resolution.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  6. 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.

  7. 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.

  8. 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 show that the presence of the shear bands modifies the buttressing state in the ice shelf, i.e. the amount of back stress transmitted to the grounding line. The discharge of grounded ice in response to a calving event is thus influenced by the estimation of the ice shelf rheology. This suggests that future projections of PIG behaviour will have to carefully evaluate the ice-shelf stress pattern and its evolution.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  10. 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%.

  11. Constraining Glacier Sensitivity across the Andes: A Modeling Experiment

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Valley glaciers are sensitive indicators of climate change. Records of former glacial fluctuations have been extensively used to reconstruct paleoclimatic conditions at different temporal and spatial scales. These reconstructions typically do not account for variations in regional climate conditions. Based on modeling results, it has been suggested these regional climate conditions could play an important role modulating the magnitude of glacier response for large scale climate perturbations. The climatically diverse Andes mountain range represents an ideal setting to test hypothesis of glacier sensitivity variability. Here, we quantify glacier sensitivity to climate change in different climatic regimes across the Andean. By applying a regional Surface Energy Mass Balance model (SEMB), we analyze the change in the Equilibrium Line Altitude (ELA) for a sample of 234 glaciers, under different climatic perturbations. Our results suggest that ELAs of Andean glaciers respond linearly to changes in temperature, with rates that oscillate between 153 and 186 m/°C. For example, with a perturbation of -6°C (~Global LGM), our model predicts a drop in the ELA of 916 m for the least sensitive glaciers and 1117 m for the more sensitive ones. This glacier sensitivity variability exhibits a very distinctive spatial distribution. The most sensitive glaciers are located in Central Chile (south of 31°C), and the Western Cordillera of Peru (north of 13°S). In contrast, lower sensitivity glaciers are situated in the inner Tropics, Eastern Cordillera of Peru and Bolivia (south of 13°S), and part of southern Patagonia and Tierra del Fuego. When analyzing the response of glaciers to changes in accumulation, our results suggest that under a scenario of increasing precipitation, glacier behavior is nonlinear. A statistical cluster analysis of glacier sensitivity divides our 234 glaciers into three distinct groups. The most sensitive glaciers correspond to those situated in western Cordillera of Peru and Bolivia (south of 15°S), the north of Chile-Argentina (north of 19°S), and Central Chile, between 27° and 38°S. Similar to our results with temperature, the inner tropical glaciers are the least responsive to precipitation changes. With our regional approach, we expect to explore the mechanisms responsible for the spatial variability of glacier sensitivity across the Andes, thus improving our understanding of climate-glacial dynamic interaction. These mechanisms will provide a framework to study the causes of past episodes of glacial fluctuations and ultimately to predict the response of glaciers to future climate change scenarios.

  12. 36Cl Exposures Ages and Equilibrium Line Altitude (ELA) of the Ampato Volcanic Complex (Southern Peru).

    NASA Astrophysics Data System (ADS)

    Alcalá, J.; Palacios, D.; Vázquez-Selém, L.

    2012-04-01

    In this work we present the results obtained from the reconstruction of the ancient glacial Equilibrium Line Altitude (paleoELA) and the dating of various glacial phases on the Ampato volcanic complex (15°24´S-15°51´S, 73° W; 6.288 m asl), in the Central Andes. In order to calculate the paleoELAs we used two methods: the Accumulation Area Ratio (AAR) and the Area X Altitude Balance Ratio (AABR). The dating was obtained by cosmogenic methods (36Cl). We sampled: 1) boulders, in a stable position, larger than 1m and located on the crest of the moraines; and 2) polished and striated bedrock outcrops, which indicate the retreat of ice. In every studied valley we found voluminous moraines related to the Local Last Glacial Maximum of the Pleistocene (LLGMP). The dating obtained from the sampled boulders ranges from 17.9 ± 0.1 to 13.6 ± 0.1 kyr. We estimate that the most significant deglaciation process started at 12 ka on the Ampato volcanic complex and adjacent areas also covered by ice, such as the Patapampa altiplano. In certain valleys we found re-advance moraines such as in Huayuray valley, located on the Northern slope of the volcanic complex, dated at 11.4 ± 0.21 kyr. The last generalised advance is related to the Little Ice Age (LIA). During this event the glaciers formed small moraines which are close to the current glacial fronts. In Huayuray valley we estimated a paleoELA (AAR) of ~5,200 m during the LLGMP asl and ~5.810 m asl during the LIA. Similar data was obtained using the AABR method: ~5.150 m asl during the LLGMP, and ~5.750 m asl during the LIA. In Mollebaya valley (East face of the volcanic complex) the paleoELA (AAR) during the LLGMP was at ~5.350 m asl and during the LIA it reached ~5.740 m asl. Using the AABR method the LLGMP and LIA paleoELAs are ~5.070 and ~5.700 m asl, respectively. In Pujro-Huayjo valley, to the Soutwest, the paleoELA (AAR) during the LLGMP was ~5.390 m asl. LIA moraines are absent in this valley. We calculated the ELA from the glacier in 1955 at ~5.725 m asl. Using the AABBR method, the ELA was lower: ~4.940 m asl during LLGMP and ~5.635 m asl in 1955. Finally, in the Mucurca valley, West face of the volcanic complex, the LLGMP paleoELA was at ~4.930 m asl and at 5.100 m asl during the most recent advance (Lateglacial phase). Using the AABR method we obtained a value of ~4.865 m asl for the LLGMP paleoELA and ~5.015 m asl for the Late glacial phase. On average the the LLGMP ELA was 5220 m asl (AAR) and 5010 m asl (AABR). Based on the modern (1955) ELA from Pujro-Hayjo valley, the LLGMP ELA lowering was ~550 m (AAR) and ~625 m (AABR). Research funded by CGL2009-7343 project, Government of Spain.

  13. 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.

  14. Thermal Equilibrium of Vortex Lines in Counterflowing He II

    NASA Astrophysics Data System (ADS)

    Nemirovskii, Sergey K.

    2016-01-01

    The problem of the statistics of a set of chaotic vortex lines in counterflowing superfluid helium is studied. We introduced a Langevin-type force into the equation of motion of the vortex line in the presence of relative velocity {v_{ns}} . This random force is supposed to be Gaussian satisfying the fluctuation-dissipation theorem. The corresponding Fokker-Planck equation for probability functional in the vortex loop configuration space is shown to have a solution in the form of Gibbs distribution with the substitution E{s}→}E({s}-P(vn-vs)} , where E{s} is the energy of the vortex configuration {s} and P is the Lamb impulse. Some physical consequences of this fact are discussed.

  15. Bivachnyy Glacier

    Photograph of Bivachnyy Glacier, a surging valley glacier in the central Pamir Mountains. The glacier has a thick debris cover derived from adjacent mountains. Photograph courtesy of V.M. Kotlyakov, Russian Academy of Sciences, Moscow....

  16. 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 -0.590.40 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 2002-2013 observation period. The negative gradients can be explained by the thickness of debris cover that increases with decrease in altitude, thus protecting the glacier more efficiently at lower altitudes. Mass balance is strongly dependent on debris cover, exposure (solar radiation) and the shading effect of surrounding steep slopes.

  17. 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.

  18. 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.

  19. 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.

  20. Plasma Equilibrium in a Magnetic Field with Stochastic Field-Line Trajectories

    NASA Astrophysics Data System (ADS)

    Krommes, J. A.; Reiman, A. H.

    2008-11-01

    The nature of plasma equilibrium in a magnetic field with stochastic field lines is examined, expanding upon the ideas first described by Reiman et al. The magnetic partial differential equation (PDE) that determines the equilibrium Pfirsch-Schlüter currents is treated as a passive stochastic PDE for μj/B. Renormalization leads to a stochastic Langevin equation for μ in which the resonances at the rational surfaces are broadened by the stochastic diffusion of the field lines; even weak radial diffusion can significantly affect the equilibrium, which need not be flattened in the stochastic region. Particular attention is paid to satisfying the periodicity constraints in toroidal configurations with sheared magnetic fields. A numerical scheme that couples the renormalized Langevin equation to Ampere's law is described. A. Reiman et al, Nucl. Fusion 47, 572--8 (2007). J. A. Krommes, Phys. Reports 360, 1--351.

  1. Seasonal and interannual variations in snow cover thickness, glacier mass balance, and gravity-induced dynamics in a high Arctic valley glacier watershed.

    NASA Astrophysics Data System (ADS)

    Prokop, Alexander; Tolle, Florian; Bernard, Eric; Friedt, Jean-Michel; Griselin, Madeleine

    2015-04-01

    For 3 consecutive years, terrestrial laser scanning surveys have been conducted in the glacier basin of Austre Lovénbreen (Svalbard, 79°N). Each year, high density point clouds were acquired on the glacier surface and on the surrounding slopes. Two yearly scanning sessions were required in order to spatialize and quantify snow cover. The first session was done late April at the expected annual snow maximum. The second session was done in August near the end of the melting season. On the glacier itself, laser scans were produced on the glacier snout, in the area close to the equilibrium line, and in the upper reaches of the glacier. Manual snow drilling measurements and glacier mass balance data were subsequently used to validate snow cover results. In the steep slopes surrounding the glacier, scans were acquired on slopes at various altitudes and orientations in order to get a representative view of different snow cover settings. Particular attention was granted to snowdrift and avalanche processes, and their consequences on remaining packed snow stored in perennial snow accumulation at the bottom of slopes. A good knowledge of the dynamics of the snow cover is of particular interest in a glacier undergoing a clear retreat. Snow is protecting the ice from melting for part of the season, and snow is also providing what will constitute future glacier ice in the upper reaches of the basin. Snow on slopes is also of importance as avalanches reaching on the glacier can contribute to the overall mass balance. Snow cover, by keeping the slopes permafrost from thawing early in the season, or by providing liquid water affecting it later in the season, is also playing a key role in the glacier basin morphology and its interactions with the glacier body.

  2. 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.

  3. 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.

  4. Detailed Vibrational-Chemical Kinetics and Transport Properties in a Non-Equilibrium Stagnation Line Flow

    NASA Astrophysics Data System (ADS)

    Orsini, A.; Rini, P.; Taviani, V.; Fletcher, D.; Kustova, E. V.; Nagnibeda, E. A.

    2008-12-01

    A self-consistent model of fluid dynamics and non-equilibrium vibrational-chemical kinetics in a high temperature viscous N2/N mixture flow along the stagnation line is proposed. The model takes into account detailed state-to-state kinetics and state dependent transport phenomena; the state-to-state kinetic and transport terms are properly coupled to fluid dynamics equations. The sensitivity of the macroscopic flow parameters and heat transfer to the accuracy of fluid dynamics equations, to the scheme of chemical reactions and vibrational transitions, and to the rates of non-equilibrium processes is evaluated.

  5. 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 terminus retreated at a rate of about 13 meters per year during balance year 2006 and at a rate of about 8 meters per year during balance year 2007. Glacier area near the end of balance years 2006 and 2007 was 1.74 and 1.73 square kilometers, respectively. Runoff from the basin containing the glacier and from an adjacent nonglacierized basin was gaged during all or parts of water years 2006 and 2007. Air temperature, wind speed, precipitation, and incoming solar radiation were measured at selected locations on and near the glacier. Air-temperature over the glacier at a height of 2 meters generally was less than at the same altitude in the air mass away from the glacier. Cooling of the air by the glacier increased systematically with increasing ambient air temperature. Empirically based equations were developed to estimate 2-meter-height air temperature over the glacier at five sites from site altitude and temperature at a non-glacier reference site.

  6. 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 for Mera Glacier than for Chhota Shigri Glacier. However our method shows promising results and may be used to reconstruct the annual mass balance of glaciers with contrasted seasonal cycles in the western part of the HKH mountain range since the early 2000s when MODIS images became available.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    It has been suggested that glaciers on two stratovolcanoes in the Cascade Range of Washington state, Mt. Baker and Glacier Peak, achieved their maximum extent of the past 10,000 years during the early Holocene. These findings differ from most evidence in western North America, which indicates that Little Ice Age moraines represent the most extensive glacier advances of the Holocene. Significant early Holocene advances are difficult to reconcile with the documented warm, dry conditions at this time in western North America. Our data indicate that glaciers on these volcanoes responded similarly to Holocene climatic events as glaciers in other areas in Washington and British Columbia. Heavy winter accumulation and favorable hypsometry have been proposed as the explanations for the unusual behavior of glaciers on volcanoes compared to similar-sized glaciers elsewhere in the Cascade Range. However, glacier mass balance on the volcanoes is controlled by not only these factors, but also by glacier geometry, snow erosion and ablation. Accumulation zones of glaciers on isolated Cascade stratovolcanoes are high, but are narrow at the top. For example, the accumulation zone of Deming Glacier on the southwest side of Mt. Baker extends above 3000 m asl, but due to its wedge shape lies largely below 2500 m asl. Furthermore, glaciers on Mt. Baker and other symmetrical volcanoes have high ablation rates because they are not shaded, and south-southwest aspects are subject to erosion of snow by prevailing southwesterly winds. Modern glacier observations in the North Cascades quantify the important influence of aspect and snow erosion on glacier mass balance. For example, average equilibrium line altitude (ELA) of Easton Glacier on the south flank of Mt. Baker is 2160 m, whereas the ELA of a north-facing cirque glacier 25km to the east is 2040m. Our research at Mt. Baker contradicts the claim of extensive early Holocene advances on the south flank of the volcano. Tephra set SC, which has been radiocarbon dated to about 8850 14C yr old, is found on ridges that were previously mapped as moraines younger than the tephra. This relation indicates that "early Holocene" ridges are more than 8850 14C yr old, with their maximum age unconstrained. Most of the radial ridges previously mapped as moraines cannot be conclusively shown to be moraines; they could be lahar levees or diamict-covered bedrock ridges, which are common on Cascade stratovolcanoes. Our data indicate that the record of middle and late Holocene glaciation on Mt. Baker is similar, if not identical, to that reported from the British Columbia Coast Mountains. Consequently, there is no reason to believe that the history of Holocene glaciation on Cascade volcanoes is radically different than elsewhere in western North America.

  9. NON-EQUILIBRIUM IONIZATION EFFECTS ON THE DENSITY LINE RATIO DIAGNOSTICS OF O IV

    SciTech Connect

    Olluri, K.; Gudiksen, B. V.; Hansteen, V. H.

    2013-04-10

    The dynamic timescales in the solar atmosphere are shorter than the ionization and recombination times of many ions used for line ratio diagnostics of the transition region and corona. The long ionization and recombination times for these ions imply that they can be found far from their equilibrium temperatures, and spectroscopic investigations require more care before being trusted in giving correct information on local quantities, such as density and temperature. By solving the full time-dependent rate equations for an oxygen model atom in the three-dimensional numerical model of the solar atmosphere generated by the Bifrost code, we are able to construct synthetic intensity maps and study the emergent emission. We investigate the method of electron density diagnostics through line ratio analysis of the O IV 140.1 nm to the 140.4 nm ratio, the assumptions made in carrying out the diagnostics, and the different interpretations of the electron density. The results show big discrepancies between emission in statistical equilibrium and emission where non-equilibrium (NEQ) ionization is treated. Deduced electron densities are up to an order of magnitude higher when NEQ effects are accounted for. The inferred electron density is found to be a weighted mean average electron density along the line of sight and has no relation to the temperature of emission. This study shows that numerical modeling is essential for electron density diagnostics and is a valuable tool when the ions used for such studies are expected to be out of ionization equilibrium. Though this study has been performed on the O IV ion, similar results are also expected for other transition region ions.

  10. 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 glaciers having 40 % debris cover, 8% of deglaciation was observed. However, orientation of glaciers did not show any considerable pattern on glacial change. The study inferences that the glaciers which are debris free, located below mean altitude of snowline, smaller in size, gentle slope,and located at lower altitude has experienced higher rate of shrinkage.

  11. 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.

  12. 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.

  13. 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.

  14. 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 gaged during all or parts of water years 2004 and 2005. Air temperature, wind speed, precipitation, and incoming solar radiation were measured at selected locations on and near the glacier.

  15. Modeling the Climatic Controls and Topographic Form of Modern and Late Pleistocene Tropical Peruvian Glaciers

    NASA Astrophysics Data System (ADS)

    Mark, B. G.; Stansell, N.; Fairman, J. G.; Plummer, M. A.; Rodbell, D. T.

    2010-12-01

    Glaciers in the tropical highlands are important and highly sensitive indicators of global climate change over different time scales. Simulating glacier extent from basic climatic and topographic input elucidates understanding of present glacier-climate processes, climate control over past glacial extent, and future impacts of changing climate. We apply a physically based, 2-D, glacier model to reconstruct steady-state glacier forms and mass distributions for a range of tropical climatic conditions in the Cordillera Blanca, Peru (8-10°S). The model is based on gridded digital elevation data, computes the effects of topography on the largest component of surface energy balance, shortwave solar insolation, calculates 2-D, in the horizontal-plane, distribution of snow accumulation using a surface mass and energy balance approach, and reconstructs resultant glacier shape with a 2-D flow model. We are able to reconstruct modern glacier extent to match satellite imagery using climate data assimilated from over 30 Andean stations located between 9-11°S, including current observations at glacier elevations, and compute a modern equilibrium line at ˜5000 m asl. We then apply the model in an inverse approach to infer paleoclimate conditions for late Pleistocene moraine positions mapped in specific valleys with global positioning system positions and dated by radiocarbon dates on lake and peat sediments. Simulations confirm that with no precipitation changes, a cooling of 4.5°C is required to achieve equilibrium glacier shapes terminating at moraine positions bounding Laguna Queshque (4300 m asl 9°50'S; 77°25'W). Alternatively, increasing precipitation by 1.5 times the modern values requires a temperature reduction of 3.75°C for the model to reach the same ELA position. A model sensitivity analysis highlights the importance of both moisture availability and temperature changes in driving tropical Andean glacier fluctuations. Results also indicate that temperature reductions of 1°C are required to reconstruct equilibrium glacier shapes to match the modern glacier tongue in the Queshque valley. Under modern climate conditions, the remaining valley glacier volume will disappear within three decades.

  16. Surface elevation changes on glaciers in 1974-2010 in the Mt. Naimona'Nyi region in the Himalayas

    NASA Astrophysics Data System (ADS)

    Zong, J.; YE, Q.; Tian, L.; Gou, P.

    2013-12-01

    Glaciers, especially those in mountain regions, are considered as one of the sensitive indicators of climate change nowadays. Glacier mass changes on the Tibetan Plateau significantly affect water resources and eco-systems in Asia. In this paper, surface elevation changes on glaciers were studied by DEMs and in-situ measurements. A DEM in Naimona'Nyi region was generated by Takeo Tanado at JAXA using stereo pairs from ALOS/PRISM in 2006, which was evaluated and calibrated by in-situ differential GPS points measured in 2012 and ICESat/GLAS points in non-glacier area. The 1:50,000 topographic maps and the base 1:50,000 DEM in 1974 was projected into WGS84 UTM 44N and then co-registered to PRISM DEM. The elevation change on glacier surface was calculated by PRISM DEM and 1974 DEM. The results suggested that the surface elevation was decreased rapidly on most glaciers, with an average downwasting rate of 0.7×0.2m per year. The in-situ measurement of glacier surface elevation indicated a decrease of ~1.4m (~0.7m per year) from 2008 to 2010 by Ground Penetrating Radar (GPR)differential GPS. It also showed that glacier ice on south slope downwasting faster than those on north slope. According to glacier surface elevation changes at different altitudes, the Equilibrium Line Altitude (ELA) might reach about 6300m a.s.l.

  17. The Bossons glacier protects Europe's summit from erosion

    NASA Astrophysics Data System (ADS)

    Godon, C.; Mugnier, J. L.; Fallourd, R.; Paquette, J. L.; Pohl, A.; Buoncristiani, J. F.

    2013-08-01

    The contrasting efficiency of erosion beneath cold glacier ice, beneath temperate glacier ice, and on ice-free mountain slopes is one of the key parameters in the development of relief during glacial periods. Detrital geochronology has been applied to the subglacial streams of the north face of the Mont-Blanc massif in order to estimate the efficiency of erosional processes there. Lithologically this area is composed of granite intruded at ~303 Ma within an older polymetamorphic complex. We use macroscopic features (on ~10,000 clasts) and U-Pb dating of zircon (~500 grains) to establish the provenance of the sediment transported by the glacier and its subglacial streams. The lithology of sediment collected from the surface and the base of the glacier is compared with the distribution of bedrock sources. The analysis of this distribution takes into account the glacier's surface flow lines, the surface areas beneath temperate and cold ice above and below the Equilibrium Line Altitude (ELA), and the extent of the watersheds of the three subglacial meltwater stream outlets located at altitudes of 2300 m, 1760 m and 1450 m. Comparison of the proportions of granite and metamorphics in these samples indicates that (1) glacial transport does not mix the clasts derived from subglacial erosion with the clasts derived from supraglacial deposition, except in the lower part of the ice tongue where supraglacial streams and moulins transfer the supraglacial load to the base of the glacier; (2) the glacial erosion rate beneath the tongue is lower than the erosion rate in adjacent non-glaciated areas; and (3) glacial erosion beneath cold ice is at least 16 times less efficient than erosion beneath temperate ice. The low rates of subglacial erosion on the north face of the Mont-Blanc massif mean that its glaciers are protecting "the roof of Europe" from erosion. A long-term effect of this might be a rise in the maximum altitude of the Alps.

  18. 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.

    2014-06-01

    Few glaciological field data are available on glaciers in the Hindu Kush - Karakoram - Himalaya (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 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 snowline 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, mostly not accessible from space during the monsoon, was still preserved later thanks to strong winter winds blowing away snow and in turn exposing again the late monsoon surface. AMAAG was subsequently revealed in the post-monsoon period. 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 for Mera Glacier than for Chhota Shigri Glacier. However our method shows promising results and may be used to reconstruct the annual mass balance of glaciers with contrasted seasonal cycles in the western part of the HKH mountain range since the early 2000s when MODIS images became available.

  19. Line-Tied Magnetic Flux Ropes in the Laboratory: Equilibrium Force Balance and Eruptive Instabilities

    NASA Astrophysics Data System (ADS)

    Myers, Clayton E.; Yamada, M.; Belova, E. V.

    2013-07-01

    Flux-rope-based models of solar eruptions rely on the formation of a line-tied flux rope equilibrium that persists until an ideal instability or a breakdown in force balance triggers an eruption. In this paper, we present a quantitative study of equilibrium force balance in solar-relevant flux ropes, focusing primarily on the role of the potential magnetic field in controlling the flux rope behavior. This study was conducted using a newly constructed laboratory experiment in conjunction with supporting three-dimensional MHD simulations that directly model the experimental geometry. The flux ropes studied here, which are produced in the Magnetic Reconnection Experiment (MRX), evolve quasi-statically over many Alfvén times and have footpoints that are line-tied to two fixed electrodes [E. Oz, C. E. Myers, M. Yamada, et al., Phys. Plasmas 18, 102107 (2011)]. They are formed within a solar-relevant potential magnetic field configuration that can be systematically modified between discharges. Detailed in situ magnetic measurements from the experiments are compared directly to results from the simulations in order to quantitatively evaluate the various contributions to the equilibrium force balance. We find that forces derived from the applied toroidal guide field contribute significantly to the equilibrium—so much so that the flux ropes are often well confined even in the absence of a "strapping" arcade. These observed guide field forces arise from changes in the toroidal magnetic pressure and tension that result from a combination of effects within the expanding flux rope. With regard to eruptions, the aforementioned guide field forces supplement the well-known strapping field forces to largely prevent the flux ropes from erupting. In particular, many regimes were explored where the strapping field configuration is predicted to be "torus unstable" and yet the flux ropes do not erupt. Eruptions are observed in some regimes, however, and we will discuss the physical mechanisms that may explain this behavior.

  20. Monsoonal forcing of Holocene glacier fluctuations in Ganesh Himal (Central Nepal) constrained by cosmogenic 3He exposure ages of garnets

    NASA Astrophysics Data System (ADS)

    Gayer, E.; Lavé, J.; Pik, R.; France-Lanord, C.

    2006-12-01

    In the Himalayas, the late Pleistocene glacier oscillations have produced spectacular glacial landforms. Detailed reconstructions of the chronology and extent of these oscillations are essential to document the sensitivity of the Himalayan glaciers to past and future climatic changes. In this paper, we present a new cosmogenic helium 3 ( 3He c) dating on garnets, that were sampled on moraine blocks and ice-scoured surfaces in a small glaciated valley of the Central Nepal (the Mailun valley), and that provided a detailed chronology of Himalayan glacier fluctuations during the Holocene. Soon after the Younger Dryas, the glacier of the Mailun valley underwent a significant retreat around 10 ka. This retreat was followed by relative stability of the extent of the glacier between ˜ 8.5 and ˜ 7.5 ka. A second phase of rapid retreat occurred at ˜ 7 ka, but rapidly slowed down at ˜ 5-6 ka. Finally, a last phase of re-advance occurred between 0 and 1 ka. The interpretation of the Equilibrium Line Altitude (ELA) variation, deduced from this chronology (for the Holocene period) and carbon 14 ( 14C) dating (for the Pleistocene period), shows that the early history of the Mailun valley deglaciation (late Pleistocene) is in good agreement with the global paleoclimatic records. The main extent of the glacier and the major ice volume drop are in phase with the global Last Glacial Maximum (25-17 ka) and with the major worldwide temperature increase following the Younger Dryas, respectively, indicating that the Mailun glacier was primarily driven by temperature oscillations during the late Pleistocene. In contrast, the glacier chronology during the Holocene suggests that the Mailun glacier was modulated by the variation in annual precipitation, and is asynchronous relative to most glaciers of the Northern Hemisphere. The significant sensitivity of the Himalayan glaciers to precipitation might explain the striking lack of synchronism of the Himalayan glaciers both along and across the Himalayan arc.

  1. 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.

  2. 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' N., North Cascades, Wash.) - equilibrium-line altitude 1,900 m, activity index 17 mm/m, winter balance 3.1 m, and annual exchange 6.6 m; and Maclure Glacier (lat 37 deg 45' N., Sierra Nevada, Calif.) - equilibrium-line altitude 3,600 m, activity index 23 mm/m, winter balance 2.3 m, and annual exchange 4.6 m. Mass balances of these four glaciers and their drainage basins are measured annually by standard glaciological techniques. In addition, the hydrologic balance is calculated using streamflow and precipitation measurements. Combining these independent measurements results in fairly well defined values of water and ice balance for the glaciers and drainage basins. A revision of the standard International Hydrological Decade mass-balance system permits combination of annual and stratigraphic terms. The annual balance of South Cascade Glacier at the end of the 1965 hydrologic year was slightly positive (+0.07 m averaged over the glacier), but continued ablation and deficient accumulation in October 1965 resulted in slightly negative net balances for both the glacier and the drainage basin. Factors tending to produce this near-zero balance were the above-average late-winter balance (3.48 m) and the numerous summer snowfalls. Ice ablation averaged about 39 mm of water per day during the main melt season. Runoff during the summer ablation season was lower than the 1958-64 average. The South Cascade Glacier annual balance in 1966 (-0.94 m) was considerably more negative mainly owing to the deficient winter snowpack (the late-winter balance was only 2.52 m) and the warm dry summer. Ice ablation averaged about 44 mm of water per day during the melt season. The loss in storage of this and other glaciers in the North Cascades increased the runoff of many valley streams by approximately 50 percent during August and September. The 1966 Gulkana Glacier annual balance was slightly positive (+0.06 m); on the basis of past observations and the rapid terminus ret

  3. Growing and Advancing Calving Glaciers in Alaska

    NASA Astrophysics Data System (ADS)

    Trabant, D. C.; March, R. S.; Molnia, B. F.

    2002-12-01

    In stark contrast with the majority of glaciers in Alaska that are losing volume and retreating in response to climate forcing, about 10 large glaciers are increasing in volume and advancing. All of these are calving glaciers that are advancing into seawater. Hubbard Glacier, at the head of Disenchantment Bay near Yakutat, Alaska, is one of the advancing glaciers and is the largest calving glacier on the North American Continent. Hubbard Glacier?s current advance began shortly before 1895 and has recently been newsworthy because its advance blocked the entrance to Russell Fiord between June and August 2002. Other prominent examples are Meares Glacier, at the head of Unakwik Inlet in Prince William Sound, which is advancing into old-growth forest, and Harvard Glacier, at the head of College Fiord, which has a well-documented history of advance beginning between 1905 and 1911. Calving glaciers that are currently growing and advancing have at least four things in common. All of them (1) are at the heads of long fiords, (2) have undergone massive retreats during the last thousand or more years, (3) presently calve over relatively shallow moraine shoals, and (4) have strongly positive mass balances that are a consequence of a surface-area distributions that have unusually small ablation areas compared to the accumulation areas. For example, Hubbard Glacier retreated about 61 kilometers between 1000 A.D. and late in the 19th century. The depth of seawater at the calving terminus averages between 60 and 80 meters in a fiord that reaches 230 meters below sea level in front of the glacier and 400 meters below sea level under the ice. The accumulation area of Hubbard Glacier is 95 percent of the entire glacier area and, like the other advancing glaciers, is far from being in equilibrium with climate on the positive mass balance side. Glaciologists often point out that glaciers are sensitive indicators of climate. This paradigm should not be applied to calving glaciers. During most of the calving glacier cycle, the slow advances and relatively rapid retreats are not very sensitive to climate. For example, the calving glaciers that are currently growing and advancing in the face of global warming, were retreating throughout the little ice age. Calving glaciers become sensitive to climate only late in the advancing phase, when the mass flux out of the accumulation area approaches the mass lost by melting in the ablation area and losses due to calving can no longer be replaced. No reasonable change in climate will change this imbalance and stop the advances of these few glaciers.

  4. Shear viscosities away from the melting line: A comparison of equilibrium and nonequilibrium molecular dynamics

    SciTech Connect

    Holian, B.L.; Evans, D.J.

    1983-04-15

    Doubts about the validity of the nonequilibrium molecular dynamics (NEMD) methods of computing shear viscosity have persisted, partly because of the apparent disagreement (approx.25%) between NEMD and equilibrium Green--Kubo (GK) results for the Lennard-Jones system near its triple point. This region of the phase diagram near the melting line is the so-called ''molasses'' regime where the tail of the shear-stress autocorrelation function is quite large, deviating from ''exponential'' decay at a level of about 10%. In order to see whether the effects of the ''molasses tail'' might be obscuring a more profound difference between NEMD and GK results, we have carried out independent NEMD and GK calculations for a state in the LJ fluid far away from this troublesome molasses region, namely at a temperature twice critical and a density between the triple and critical points. We find the NEMD and GK results for the linear shear viscosity to be in good agreement.

  5. A preliminary assessment of the role of glaciers in the hydrologic regime of the Nepal Himalaya

    NASA Astrophysics Data System (ADS)

    Armstrong, R.; Alford, D.; Racoviteanu, A.

    2009-04-01

    The hydrologic regime of the Himalaya is not well-defined and there is a lack of a basic data to support the understanding of the runoff sources and timing in many mountain rivers of the region. Because of this absence of data, applying of hydrologic concepts and models developed for mountain catchments in Europe or North America is often impossible and likely to be inappropriate. Thus, determining the impact of the retreat of Himalayan glaciers on regional-scale water supplies is problematic. Current concerns about the retreat of Himalayan glaciers have been accompanied by little, if any, comprehensive analysis of the actual role of glaciers in the total hydrologic regime and such assessments have typically disregarded mass balance relationships across the approximately 3,000 meters of topographic relief between the glacier termini and the highest accumulation zones. The ultimate purpose of the study described here is to assess, and begin to quantify, the role of complete glacier systems in the hydrologic regime of the Nepal Himalaya, and to develop estimates of the potential impact of a continued retreat of these glaciers. There are approximately 3250 glaciers in the Nepal Himalaya, covering an area of slightly more than 5,300 km2, and containing some 460 km3 of ice. These glaciers cover approximately 4% of the total 147,000 km2 surface area of Nepal, and are located on, or near, the crest of the Himalaya, with the bulk of the ice contained in basins that are at altitudes generally between 4,000 - 6000 meters above sea level. In this study we apply methods which disaggregate available data sets to reflect the altitudinal gradients that define the mountain hydrologic regime. For glacier mass balance estimates, the input variables are: 1) surface areas of both basins and glaciers, 2) basin and glacier area-altitude distributions, 3) glacier equilibrium line altitudes, 4) slope of the ablation gradient for the glaciers of Nepal, 5) maximum altitude of the 00 C. isotherm each year, and the altitudinal range through which it moves annually. For orographic runoff estimates, the variables are: 1) area-altitude distribution of each catchment basin studied, and 2) disaggregated hydrometric data, to reflect the importance of scale and location in the analysis of mountain hydrologic systems. The ablation gradient, the rate of increasing specific ice melt with decreasing altitude in the ablation zone, is determined to be 1.4m/100m, a probable value for the latitude of the Nepal Himalaya based on measurements found in the literature which are representative of a range of latitudes. The mean maximum altitude of the 00 C. isotherm during the ablation period is approximately 5400 m, determined by extrapolating low altitude air temperature values. This altitude defines the location of an equilibrium line altitude (ELA), the dividing line between zones of net accumulation and ablation on the glacier surface. The volume of ablation between the ELA and the glacier terminus is estimated as the product of specific ice melt values taken from the ablation gradient and the area-altitude values of corresponding belts in the glacier ablation zone. The resulting mass balance calculations are considered to be "best-estimate" meso-scale approximations which could be refined with field measurements. It is currently estimated that the contribution of glacier melt water to annual streamflow volume in the study area varies among catchment basins from 2-13% of total annual flow measured at low altitude hydrometric stations, and represents 2-3% of the total annual streamflow volume of the rivers flowing out of Nepal. The preliminary results from this continuing study indicate that this relationship will not be affected significantly in the near future by a continued retreat of the glaciers.

  6. Western Glacier Stonefly

     The rare western glacier stonefly (Zapada glacier) is native to Glacier National Park and is seeking habitat at higher elevations due to warming stream temperature and glacier loss due to climate warming. ...

  7. Western Glacier Stonefly

    The rare western glacier stonefly (Zapada glacier) is native to Glacier National Park and is seeking habitat at higher elevations due to warming stream temperature and glacier loss due to climate warming. ...

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    The climate sensitivity of Abrahamsenbreen, a 20 km long surge-type glacier in northern Spitsbergen, is studied with a simple glacier model. A scheme to describe the surges is included, which makes it possible to account for the effect of surges on the total mass budget of the glacier. A climate reconstruction back to AD 1300, based on ice-core data from Lomonosovfonna and climate records from Longyearbyen, is used to drive the model. The model is calibrated by requesting that it produces the correct Little Ice Age maximum glacier length and simulates the observed magnitude of the 1978-surge. Abrahamsenbreen is strongly out of balance with the current climate. If climatic conditions will remain as they were for the period 1989-2010, the glacier will ultimately shrink to a length of about 4 km (but this will take hundreds of years). For a climate change scenario involving a 2 m yr-1 rise of the equilibrium line from now onwards, we predict that in the year 2100 Abrahamsenbreen will be about 12 km long. The main effect of a surge is to lower the mean surface elevation and to increase the ablation area, thereby causing a negative perturbation of the mass budget. We found that the occurrence of surges leads to a somewhat stronger retreat of the glacier in a warming climate. Because of the very small bed slope, Abrahamsenbreen is sensitive to small perturbations in the equilibrium-line altitude E. For a decrease of E of only 160 m, the glacier would steadily grow into the Woodfjorddalen until after 2000 years it would reach the Woodfjord and calving could slow down the advance.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  12. Seasonal and interannual variations in snow cover thickness, water equivalent, and gravity-induced dynamics in a high Arctic valley glacier watershed.

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    For 3 consecutive years, terrestrial laser scanning surveys have been conducted in the glacier basin of Austre Lovénbreen (Svalbard, 79°N). Each year, high density point clouds were acquired on the glacier surface and on the surrounding slopes. Two yearly scanning sessions were required in order to spatialize and quantify snow cover. The first session was done late April at the expected annual snow maximum. The second session was done in August near the end of the melting season and before the first potential significant snow falls. On the glacier itself, laser scans were produced on the glacier snout, in the area close to the equilibrium line, and in the upper reaches of the glacier. Manual snow drilling measurements and glacier mass balance data were subsequently used to validate snow cover results. In the steep slopes surrounding the glacier, scans were acquired on slopes at various altitudes and orientations in order to get a representative view of different snow cover settings. Particular attention was granted to snowdrift and avalanche processes, and their consequences on remaining packed snow stored in perennial snow accumulation at the bottom of slopes. A good knowledge of the dynamics of the snow cover is of particular interest in a glacier undergoing a clear retreat. Snow is slowing the melting of the ice for part of the season, and snow is also providing what will constitute future glacier ice in the upper reaches of the basin. Snow on slopes is also of importance as avalanches reaching on the glacier can contribute to the overall mass balance. Snow cover, by keeping the slopes permafrost from thawing early in the season, or by providing liquid water affecting it later in the season, is also playing a key role in the glacier basin morphology and its interactions with the glacier body.

  13. Climate change impacts on glaciers and runoff in Tien Shan (Central Asia)

    NASA Astrophysics Data System (ADS)

    Sorg, A. F.; Bolch, T.; Stoffel, M.; Solomina, O.; Beniston, M.

    2012-12-01

    Climate-driven changes in glacier-fed streamflow regimes have direct implications on freshwater supply, irrigation and hydropower potential. Reliable information about current and future glaciation and runoff is crucial for water allocation and, hence, for social and ecological stability. Although the impacts of climate change on glaciation and runoff have been addressed in previous work undertaken in the Tien Shan (known as the 'water tower of Central Asia'), a coherent, regional perspective of these findings has not been presented until now. In our study, we explore the range of changes in glaciation in different climatic regions of the Tien Shan based on existing data. We show that the majority of Tien Shan glaciers experienced accelerated glacier wasting since the mid-1970s and that glacier shrinkage is most pronounced in peripheral, lower-elevation ranges near the densely populated forelands, where summers are dry and where snow and glacial meltwater is essential for water availability. The annual glacier area shrinkage rates since the middle of the twentieth century are 0.38-0.76% per year in the outer ranges, 0.15-0.40% per year in the inner ranges and 0.05-0.31% per year in the eastern ranges. This regionally non-uniform response to climate change implies that glacier shrinkage is less severe in the continental inner ranges than in the more humid outer ranges. Glaciers in the inner ranges react with larger time lags to climate change, because accumulation and thus mass turnover of the mainly cold glaciers are relatively small. Moreover, shrinkage is especially pronounced on small or fragmented glaciers, which are widely represented in the outer regions. The relative insensitivity of glaciers in the inner ranges is further accentuated by the higher average altitude, as the equilibrium line altitude ranges from 3'500 to 3'600 masl in the outer ranges to 4'400 masl in the inner ranges. For our study, we used glacier change assessments based both on direct data (mass balance measurements) and on indirect data (aerial and satellite imagery, topographic maps). Latter can be plagued with high uncertainties and considerable errors. For instance, glaciated area has been partly overestimated in the Soviet Glacier catalogue (published in 1973, with data from the 1940s and 1950s), probably as a result of misinterpreted seasonal snowcover on aerial photographs. Studies using the Soviet Glacier catalogue as a reference are thus prone to over-emphasize glacier shrinkage. A valuable alternative is the use of continued in situ mass balance and ice thickness measurements, but they are currently conducted for only a few glaciers in the Tien Shan mountains. Efforts should therefore be encouraged to ensure the continuation and re-establishment of mass balance measurements on reference glaciers, as is currently the case at Karabatkak, Abramov and Golubin glaciers. Only on the basis of sound data, past glacier changes can be assessed with high precision and future glacier shrinkage can be estimated according to different climate scenarios. Moreover, the impact of snowcover changes, black carbon and debris cover on glacier degradation needs to be studied in more detail. Only with such model approaches, reflecting transient changes in climate, snowcover, glaciation and runoff, can appropriate adaptation and mitigation strategies be developed within a realistic time horizon.

  14. The status of glaciers in Sikkim Himalaya

    NASA Astrophysics Data System (ADS)

    basnett, S.; Kulkarni, A. V.; Bolch, T.

    2013-12-01

    This study focuses on the influence of lakes and debris cover on the glacier area changes, in the data scarce Sikkim Himalayas, between 1990 and 2010, using Landsat TM and IRS images. A new technique of estimating 'interpretation uncertainty' while mapping glacier terminus on satellite images, is introduced. The overall study showed (i) a glacier area loss of 3 × 0.8 % in 20 years. We also observed the presence of lakes on many debris-covered glaciers, and its expansion accelerated the glacier retreat by 9 ×1.4 %. Though some 'debris-covered glaciers' showed stable fronts, the gradual development and coalescence of supraglacial lakes led to the formation of moraine dam lakes at the terminus. This investigation suggests that 'debris cover' on glaciers can enhance the development of glacial lakes. As a consequence, the retreat of debris-covered glaciers associated with lakes is clearly higher than that of debris-free glaciers. Location of glacier in Sikkim. The map shows the location of glaciers studied in this investigation. : Evolution and coalescence of a supra glacial lake and the formation of a moraine dam. Figs. a and b show no frontal change between 1990 and 1997. Fig. b shows the evolution of a supraglacial lake and fig. c shows the coalescence of supraglacial lake, which occupies glacier area between two lateral moraines. Fig. d shows the formation of a moraine dam lake leading to glacierarea loss.(The yellow line represents the glacier boundary for the year 1990; and red line is the glacier terminus for the year 2009). The four imagesused is a false colour composite with a band combination of red, NIR and SWIR.

  15. 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.

  16. Jakobshavn Glacier

    Atmospheric Science Data Center

    2013-04-17

    ... are visible in the bright white ice. A scattering of small icebergs in Disco Bay adds a touch of glittery sparkle to the scene. The ... for a large portion of the western side of the ice sheet. Icebergs released from the glacier drift slowly with the ocean currents and ...

  17. 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.

  18. Shore-line displacement in the Murchisonfjorden area, Nordaustlandet, Svalbard - Indications for ice-free Younger Dryas and Mid-Holocene regrowth of glaciers

    NASA Astrophysics Data System (ADS)

    Kultti, S.; Salonen, V.

    2012-12-01

    In Late Pleistocene, the Svalbard area was part of Barents-Kara Ice Sheet during three glacial events, correlated to marine isotope stages (MIS) 5d, 4, and 2. The shape of emergence rate isolines indicates a thicker and more extensive glaciation to the eastern parts of the archipelago than to the western parts. Also in the Murchisonfjorden area, evidence of three glacial events was found. Earlier studies concluded that glaciers in western Svalbard were at same size or smaller than today during the Younger Dryas, whereas in eastern Svalbard evidence of growing glaciers is found. This study focuses on the ice-free strip of land along Murchisonfjorden, the westernmost part of Nordaustlandet, Svalbard. The shore-line displacement was studied by the data set, that includes a total of 16 radiocarbon dated driftwood samples and isolation horizons of lake sediments. The age range for raised beaches is ca. 12 660-4800 Cal BP, and the altitude of the dated beaches varies between the present sea level and 54 m a.s.l. The average rate of emergence for the Early Holocene (11 500-8100 Cal BP) is ca. 15 mm yr-1 and for the Mid-Holocene (7400-5500 Cal BP) ca. 4.5 mm yr-1, and total emergence rates are 24 mm yr-1 and 7.5 mm yr-1, respectively. No evidence from shorelines above the present sea level and younger than ca. 4600 Cal BP was found. Higher shorelines between 54 m a.s.l. and ca. 60 m a.s.l. were observed, but suitable material for age determinations was not recovered. The marine sediment below the isolation contact of the lake Einstaken (54 m a.s.l.) was AMS-dated from foraminifera samples, and it shows an age of 12 700 Cal BP. The bulk lake sediment above the isolation contact was dated back to 13 300 Cal BP, but since the bulk 14C-dates are problematic in Arctic regions, it was not used for interpretation. The age of the contact indicates that at least locally the Mucrhinsonfjorden area was ice-free during the Younger Dryas stadial. The Early Holocene record obtained in this study indicates rapid land uplift until ca. 8100 Cal BP. Between ca. 8000-7000 Cal BP rate of the relative land uplift gradually slowed down leading finally to a transgressional phase, which coinsides approximately the age of the diamicton in nearby Isvika marine section. This may indicate a local glacier advance and/or calving glacier front at the vicinity of the site. The results show relatively steady land uplift from ca. 7000 Cal BP until 5500 Cal BP. The last 5000 years the shore line has remained stable, possibly below present sea level except for the recent centuries.

  19. 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 2009 repeated mapping of the Davies Dome was carried out and the results showed that the largest retreat ranging from 10 to 20 m occurred in the NW flat part of the glacier. Digital elevation models calculated on bases of aerial stereo-photographs from 1979 and 2006 allowed us to define mass-balance changes of the studied glaciers. Ground Penetrating Radar measurements taken on both glaciers helped with mass-balance investigations, furthermore, made it possible to increase the accuracy of the 3-D models. Annual mass balance measurements on the Davies Dome indicated a mean ablation about 20 cm between 2006 and 2009. On the Whisky Glacier, a network of 20 ablation stakes was established just recently (February 2009). Therefore, another 3-year investigation is necessary to bring comparable results. Acknowledgments: This research has been undertaken within a framework of the project No. 205/09/1876 funded by the Czech Science Foundation and by the R & D project VaV SP II 1a9/23/07.

  20. 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.

  1. 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

  2. Recent glacier variations on active ice capped volcanoes in the Southern Volcanic Zone (37-46S), Chilean Andes

    NASA Astrophysics Data System (ADS)

    Rivera, Andrs; Bown, Francisca

    2013-08-01

    Glaciers in the southern province of the Southern Volcanic Zone (SVZ) of Chile (37-46S) have experienced significant frontal retreats and area losses in recent decades which have been primarily triggered by tropospheric warming and precipitation decrease. The resulting altitudinal increase of the Equilibrium Line Altitude or ELA of glaciers has lead to varied responses to climate, although the predominant volcanic stratocone morphologies prevent drastic changes in their Accumulation Area Ratios or AAR. Superimposed on climate changes however, glacier variations have been influenced by frequent eruptive activity. Explosive eruptions of ice capped volcanoes have the strongest potential to destroy glaciers, with the most intense activity in historical times being recorded at Nevados de Chilln, Villarrica and Hudson. The total glacier area located on top of the 26 active volcanoes in the study area is ca. 500 km2. Glacier areal reductions ranged from a minimum of -0.07 km2 a -1 at Mentolat, a volcano with one of the smallest ice caps, up to a maximum of -1.16 km2 a -1 at Volcn Hudson. Extreme and contrasting glacier-volcano interactions are summarised with the cases ranging from the abnormal ice frontal advances at Michinmahuida, following the Chaitn eruption in 2008, to the rapid melting of the Hudson intracaldera ice following its plinian eruption of 1991. The net effect of climate changes and volcanic activity are negative mass balances, ice thinning and glacier area shrinkage. This paper summarizes the glacier changes on selected volcanoes within the region, and discusses climatic versus volcanic induced changes. This is crucial in a volcanic country like Chile due to the hazards imposed by lahars and other volcanic processes.

  3. Pine Island Glacier, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

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

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

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

  4. Shepard Glacier, Glacier National Park, Montana - 2005

    The thick, crevassed, ice flows of historic Shepard Glacier have been diminished to less than 0.1 square kilometer in area by 2005. According to the criteria set by the USGS Repeat Photography Project, Shepard Glacier is now considered to be too small to be defined as a glacier. (Blase Reardon)...

  5. 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

    We have reconstructed the Equilibrium Line Altitude (ELA) in seven valleys on the SW slope of Nevado Hualcán (9°S, 77°W; 6122 m asl) and on the SE slope of Nevado Coropuna (15°S, 72°W; 6377masl) using the Area x Altitude Balance Ratio method (Osmaston 2005). We have also deduced the paleotemperatures using the following equation: ΔT=ATLR•ΔELA; being ΔT (°C) the paleotemperature depression; ATLR (°C/m) the Atmospheric Temperature Lapse Rate; and ΔELA (m) the ELA depression. The ATLR for Coropuna was deduced through the use of data loggers. For Hualcán we used the value ATLR =0.0065°C/m, valid for the tropics (Kaser and Osmaston, 2002). We obtained the following results: 1) Hualcán: a) ELAs: 5124m (2003); 5018m (1962); 4994m during the Little Ice Age (LIA); and 4652m during the last studied maximum advance considered to be the Younger Dryas (YD, ~13-11ka) by correlation with nearby mountains (Glasser et al., 2009). b) ΔELAs: 106m (1962); 130m (LIA); and 199m (YD). c) ΔT: -0.69°C (1962); -0.85°C (LIA); -3.07°C (YD). 2) Coropuna: a) ELAs: 5862m (2007); 5853m (1986); 5787m (1955); 5776 (LIA); and 4951m in the 13-1136Cl ka phase (Ubeda, 2011). b) ΔELA: 9m (1986); 66m (1955); 86m (LIA); and 911m in 13-1136Cl ka. C) ΔT: -0.20°C (1986); -0.71°C (1955); and -7.65°C (13-1136Cl ka). The values ΔT during LIA in Hualcán and Coropuna (0.85 and 0.72°C) are consistent with the global warming considered to be 0,74°C between 1906 and 2005 (IPCC, 2007). During the mid XXth century and the LIA, ΔT is higher in Hualcán (0.69°C and 0.85°C) than in Coropuna (0.55°C and 0.72°C), with a regional gradient of -0.02°C per degree of latitude (°C/°). However, during the YD (13-1136Cl ka), ΔT was higher in Coropuna (7.65°C) than in Hualcán (3.07°C), with a gradient of 0.76°C/°. Although other evidences exist of a pantropical cooling of >5°C during the last glaciation, in Coropuna this cooling was strengthened by the retro-alimentation of its glacial 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.

  6. Columbia Glacier Terminus

    View of Columbia Glacier's terminus as it enters the waters of Prince William Sound. Columbia Glacier is one of Alaska's many tidewater glaciers, and it has been the focus of numerous studies due to its unusually high rate of retreat. The glacier has retreated nearly 20 km (12.43 mi) since 1980. In ...

  7. Investigation of thermodynamic equilibrium in laser-induced aluminum plasma using the Hα line profiles and Thomson scattering spectra

    NASA Astrophysics Data System (ADS)

    Cvejić, M.; DzierŻega, K.; Pieta, T.

    2015-07-01

    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 Hα, 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 Hα 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.

  8. 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.

  9. Responses to climatic changes since the Little Ice Age on Maladeta Glacier (Central Pyrenees)

    NASA Astrophysics Data System (ADS)

    Cía, J. Chueca; Andrés, A. Julián; Sánchez, M. A. Saz; Novau, J. Creus; Moreno, J. I. López

    2005-06-01

    The evolution of Maladeta Glacier (Maladeta massif, central Spanish Pyrenees) since the Little Ice Age maximum is analyzed in this work. The extent of the glacier was mapped into 10 stages using morainic deposits and graphic documents. Climatic data (temperature and precipitation) were reconstructed by using dendroclimatic techniques complemented by recent instrumental records. The results thus obtained confirm the control of the above mentioned climatic factors, particularly annual temperature and winter precipitation, in the evolution of Maladeta Glacier, which has receded from an extent of 152.3 ha in 1820-1830 to 54.5 ha in 2000, a 35.7% reduction in size. The rate of ice wastage has varied during that period, defining several phases of glacial stabilization (1820-1830 to 1857; 1914-1920 to 1934-1935; 1957 to 1981), moderated glacial depletion (1901-1904 to 1914-1920; 1934-1935 to 1957) and marked glacial depletion (1857 to 1901-1904; 1981 to 2000). The evolution of Maladeta Glacier is also in keeping with trends observed from other alpine Mediterranean glaciers, which have experienced a consistent rise in their equilibrium line altitudes during the 19th and 20th centuries as well as associated and prolonged periods of negative mass balance.

  10. Non-local thermodynamical equilibrium line formation for Ca I/II: an importance for a determination of stellar parameters

    NASA Astrophysics Data System (ADS)

    Mashonkina, L.; Korn, A.; Przybilla, N.

    2007-10-01

    Non-local thermodynamical equilibrium (NLTE) line formation for neutral and singly-ionized calcium is considered through a range of spectral types when the Ca abundance varies from the solar value down to [Ca/H] = -5. Departures from LTE significantly affect the profiles of the Ca I lines. At [Ca/H] ≥ -2, NLTE abundance correction of individual lines may be small in absolute value due to the different influence of NLTE effects on the line wings and the line core. At lower Ca abundances, NLTE leads to systematically depleted total absorption in the line and positive abundance corrections, exceeding +0.5 dex for Ca I λ4226 at [Ca/H] = -4.9. In contrast, NLTE effects strengthen the Ca II lines and lead to negative abundance corrections. For the astrophysically important Ca II triplet at 8498 A, 8542 A, and 8662 A, they grow in absolute value with decreasing Ca abundance exceeding 0.4 dex in metal-poor stars with [Fe/H] ≤-3. Theoretical results are applied to determine Ca abundances in the Sun and seven metal-poor stars on the basis of plane-parallel LTE model atmospheres using high S/N and high-resolution spectra at visual and near-IR wavelengths. For each object, NLTE leads to consistent abundances from the lines of two ionization stages, Ca I and Ca II. The derived absolute solar Ca abundance (from Ca I and Ca II lines) is log\\varepsilon_{Ca,⊙} = 6.38±0.01. We inspect the possibility of using CaI / CaII line-strength ratios as indicators of surface gravity for extremely metal-poor stars.

  11. Two-dimensional nonlocal thermodynamic equilibrium transfer computations of resonance lines in quiescent prominences

    SciTech Connect

    Vial, J.C.

    1982-03-15

    We use the two-dimensional transfer code of Mihalas, Auer, and Mihalas to compute emergent profiles of resonance lines of H I, Mg II, and Ca II. The model (a uniform slab limited in two directions) and the thermodynamic and radiative quantities are described. Metallic line profiles are sensitive to the ionization degree (n/sub p//n/sub 1/ varying from 1 to 10). Some modifications are implemented in the code (especially, the true incident profiles of chromospheric lines). Two-dimensional and one-dimensional profiles are compared. A good agreement between computed and observed profiles is found for LY..cap alpha.. and Ca II, but not for Mg II lines. Radial velocities improve the agreement. We discuss necessary improvements in the computations and the observations of resonance lines in prominences.

  12. 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.

  13. Two-dimensional nonlocal thermodynamic equilibrium transfer computations of resonance lines in quiescent prominences

    NASA Astrophysics Data System (ADS)

    Vial, J. C.

    1982-03-01

    The two-dimensional transfer code of Mihalas, Auer and Mihalas (1978) is used to compute emergent profiles of resonance lines of H I, Mg II, and Ca II. The model (a uniform slab limited in two directions) and the radiative and thermodynamic quantities are described. The metallic line profiles are sensitive to the ionization degree, which is fixed at a certain value. Some modifications are implemented in the code, in particular, the true incident profiles of chromospheric lines. A comparison is made between two-dimensional and one-dimensional profiles. Good agreement between computed and observed profiles is found for Ly-alpha and Ca II but not for Mg II lines.

  14. 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.

  15. 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, flux rope eruptions are observed in these experiments, but only in regimes with sufficiently low external toroidal field where the tension force is reduced. These results constitute a new condition for the prediction of line-tied magnetic flux rope eruptions: that of low external toroidal field.

  16. Muir Glacier in Glacier Bay National Monument 1941

    This August 1941 photograph is of Muir Glacier in Glacier Bay National Monument, Alaska. It shows the lower reaches of Muir Glacier, then a large, tidewater calving valley glacier and its tributary, Riggs Glacier. For nearly two centuries before 1941, Muir Glacier had been retreating. In places, a t...

  17. 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.

  18. Glaciers: A water resource

    USGS Publications Warehouse

    Meier, Mark; Post, Austin

    1995-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Glaciers are melting at unprecedented rates worldwide, releasing bioavailable minerals and nutrients and altering downstream biogeochemistry. Though much research has focused on the recession of ice-glaciers in alpine environments, far less is known about the melt dynamics and biogeochemistry of rock glaciers. Rock glaciers, which are mixtures of ice and rocks that flow like a glacier, are far more abundant in mountainous regions of the western United States than ice glaciers. Little is known about their influence on downstream hydrology and water quality. We report here preliminary results of a west-wide survey of the influence of glaciers and rock glaciers on headwater properties. Measurements of specific conductance, nitrate (NO3-), ammonium (NH4+), dissolved silica, and dissolved organic matter were compared between glaciers, rock glaciers, and snow-fed reference streams from three basins in the Colorado Front Range. Samples were collected from ice, where possible, and downstream at 500m intervals from the first flowing water to tree line. UV and fluorescence data were analyzed using excitation emission matrices (EEMs) and PARAFAC modeling. High concentrations of NH4+ were only found in ice and the most upstream locations; NH4+ was below detection at all lower elevation sites, whereas NO3- concentrations were low in the headwaters and higher downstream. The fluorescence spectrum of DOC from both ice and the highest elevations had a strong autochthonous (microbial or algal) signal that was replaced by a more allochtonous, terrestrially-derived DOC as it approached tree line. Rock glacier stream chemistry was intermediate between glacier-fed streams and strictly snow fed drainages. DOC levels for ice glaciers ranged 2-3mg/L with increasing values downstream, while rock glaciers ranged from 1-2.5 mg/L with attenuation downstream. Snowfed only streams had DOC values at detection <0.5mg/L, with the exception at Lake Husted outflow, with an upland wetland, unlike the other snow-fed streams sampled. SUVA 254, an index of aromaticity of the dissolved organic matter, was lower in streams fed by rock glaciers than ice glaciers and snow fed streams. This is potentially indicative of microbial processing in streams fed by rock glaciers. Fluorescence index was highest for ice glaciers (1.44), lowest for snow-fed streams (1.33), and a medial value for rock glaciers (1.42). Freshness index, which indicates the proportion of recently produced dissolved organic matter, was highest for ice glacier streams, and lowest for rock glacier streams, and showed the most variability between sites with snow-fed streams. More research is planned, but rock glaciers appear more similar to ice glaciers than snow-fed streams in their influence on alpine stream chemistry on biology, suggesting a trajectory of change of the mountains as ice features waste away.

  20. 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, 25 10Be [13.10-12.00 ka] and four minimum-limiting 14C ages from lakes impounded by moraines show that glaciers existed up to 10 km beyond LIA glacier limits during the YD. These glaciers thus had ELAs that were 300-500 m lower than contemporary glaciers. We are currently performing high-resolution (

  1. Detailed Reconstructions of Fluctuations of Seven Glaciers during the "little Ice Age" in the Northern Caucasus, Russian Federation

    NASA Astrophysics Data System (ADS)

    Bushueva, I.

    2012-12-01

    The main task of this work is the development of detailed reconstructions of mountain glaciers' fluctuations with precise spatial references in the Northern Caucasus, their analyses in terms of glacier length, area and volume changes and identification of climate role in these fluctuations. The studied glaciers (Alibek, Ullukam, Terskol, Kashkatash, Bezingi, Mijirgi, Tsey) are situated along the Bolshoy Caucasus Range from the very west (Teberda river basin) to the east (Tseydon river basin). These valley glaciers have different size, aspect and percent of debris-cover. Basing on instrumental data (since the middle of 20th century), remote sensing images (CORONA, Geoeye, Cartosat, IRS, ASTER, etc.), aerial photos of 1950s-1980s, maps (since 1887), old photographs, as well as proxy data (historical descriptions, lichenometry, dendrochronology, 14C, 10Be), we reconstructed 15-20 positions of the glaciers tongues for each glacier and produced maps showing variations of the glaciers with precise spatial reference since their maximum in the mid 17th or first half of 19th century. For example, for Alibek glacier seven former front positions and eleven moraines were photo-identified and dated. We obtained the carbon dating of intermorainal peat-bog (103%), moraine dating based on isotopes of 10Be (1900±12) and determined minimum age of most distant moraine according to dendrochronological analysis of trees (Abies nordmanniana), growing on its surface (more than 200 years). At that time (1895) the glacier was 290 m longer than today, its surface was 0.31 km2 larger (5.94 km2 in 1895, 5.63 km2 in 2008). We calculated glaciers' length and area changes, using different methods (GLIMS; Bhambri et al., 2012) and analyzed advantages and disadvantages of each method in case of their application for Caucasian glaciers. Based on our measurements we evaluated changes of equilibrium line altitude and volume. Volume changes have been reconstructed using the model offered by Lüthi et al. (2010). The obtained data can be used as the base for reconstructions of different climatic parameters, it is important contribution to the global paleoclimatic reconstructions (e.g. Leclercq and Oerlemans, 2011), where Caucasus is strongly underrepresented. The results of this study are also important for verification of other reconstructions with the lower spatial and temporal resolutions (Shahgedanova, 2009).

  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 Glacier and thus projections of future retreat should be more closely tied to climate.

  3. 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.

  4. 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 Maoist insurgency. (5) Glacier lakes are in many cases very fragile and their natural dams routinely rupture, causing devastating floods. A rising regional terrorist threat in several countries could target these dams and precipitate calamitous and terrifying results. (6) Over the next century, retreating glaciers may open new corridors for trade and human migration across the Himalaya and pave the way for possible new economic, military and political alliances in the region. (7) Glacier retreat might open new sanctuaries for terrorists and open new corridors for possible ground-based military offensive action across the HKH ranges. The documentation of glacier characteristics that may influence their trafficability, and projections of future glacier extent and behavior are relevant to wide ranging concerns of the region's inhabitants. Satellite remote sensing and mapping of glaciers is one approach to defining and monitoring the problems and opportunities presented by HKH glaciers. Global Land Ice Measurements from Space (GLIMS) is a joint USGS/NASA Pathfinder project that has formed a global consortium of glaciologists in several regional centers that are mapping and monitoring the HKH glaciers using repeat-pass ASTER and Landsat ETM+ data. We are currently building a comprehensive satellite multispectral image and GIS database that is providing detailed information on the state and rates of change of each glacier in the HKH region and other areas of the world. Merging these results with DEMs allows a predictive capability that could be useful in policy development and security planning.

  5. 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.

  6. Fast tidewater glaciers

    NASA Astrophysics Data System (ADS)

    Meier, M. F.; Post, Austin

    1987-08-01

    Some iceberg-calving outlet glaciers flow continuously at speeds normally associated with surging glaciers arid exhibit dramatic instability scenarios related to those suggested for marine ice sheets. No temperate tidewater glaciers are known to have floating termini, but many polar and subpolar tidewater glaciers do. The fast flow of temperate calving glaciers is almost entirely due to basal sliding and appears to be a function of the effective pressure on the bed, which may approach zero, and the longitudinal back stress on the terminus. The terminus boundary condition (the calving relation) is imperfectly known yet is vital to the dynamics of these glaciers. Calving relations for grounded tidewater glaciers have been suggested on empirical grounds but have not been rigorously tested; the calving relations for floating termini are virtually unknown. This, together with the imperfect understanding of basal sliding, inhibits confidence in our understanding of the stability of these glaciers. Columbia Glacier (Alaska) is an instructive example because observations have been made on the major changes in its geometry, calving rate, and dynamics that have occurred in less than 10 years. The calving flux has increased more rapidly than the glacier flux, causing thinning and retreat; as a result, the ice velocity has increased markedly. The short-term velocity changes relate to changes in back pressure (ice recession, tidal changes) and the flux of water injected to the bed. These results have relevance to the mechanisms of basal sliding, glacier surges, and the stability of marine ice streams.

  7. Glacier dynamics after the disintegration of Wordie Ice Shelf, Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Wendt, Anja; Bown, Francisca; Rivera, Andrés.; Wendt, Jens; Zamora, Rodrigo; Bravo, Claudio; Zenteno, Pablo; Casassa, Gino; Carrasco, Jorge; Quintana, Juan

    2010-05-01

    The retreat of Wordie Ice Shelf in the 1980s was the first recent episode in a series of ice-shelf collapse events which culminated in a substantial break-up of Wilkins Ice Shelf in April 2009. This widespread behaviour of ice shelves in the Antarctic Peninsula has been attributed to atmospheric and oceanic warming. While atmospheric warming leads to a prolonged melt season and increased melt ponding, oceanic warming increases bottom melting eroding ice shelves from below. Glaciers feeding into these ice shelves are known to accelerate because of the loss of the buttressing force the ice shelf exerted. Although the loss of the ice shelf itself does not contribute to sea level rise, the increased glacier outflow results in a surface lowering of the grounded glaciers associated with a mass loss and a positive contribution to sea level. Based on remote sensing, airborne and in-situ data collected during 3 recent field campaigns, we study the behaviour of glaciers flowing into Wordie Bay and its relationship to ice-shelf history and local meteorological conditions. Satellite images from different optical and radar sensors (ASTER, Landsat, ERS, and Envisat) were used to map the ice-shelf extent throughout recent years and show an almost complete disappearance of Wordie Ice Shelf. The comparison of surface elevations acquired by airborne laser scanning on Fleming Glacier in 2004 and 2008 reveals a surface elevation decrease of up to 4 m/yr at the grounding line. GPS measurements at sites first surveyed in the 1970s show that the glacier maintains higher ice flow velocities than before the retreat of Wordie Ice Shelf. A continuous GPS station deployed at the upper reaches of Fleming Glacier for one year allows studying changes in ice flow velocity throughout the year. In summary, high ice flow velocities together with the marked surface elevation at the grounding line indicate that the glaciers in Wordie Bay are still losing mass and have not attained a new equilibrium stage after ice shelf removal.

  8. Melt trends above the equilibrium line of the Greenland Ice Sheet during the period of 2003-2012 (Invited)

    NASA Astrophysics Data System (ADS)

    de la Peña, S.; Howat, I. M.; van den Broeke, M. R.; Price, S. F.; Nienow, P. W.; Mosley-Thompson, E. S.

    2013-12-01

    Warming in the Arctic has raised concern about the effects that increased fresh water input from Greenland and other ice caps into the oceans could have on sea level rise and on the thermohaline ocean circulation. Melt over the Greenland Ice Sheet (GIS) has been increasing steadily over the last 20 years, and although mass loss has been limited to the margins, the departure from the 1979-1999 mean melt rate in the last decade has become particularly large in the interior. This has resulted in variable conditions that make ice volume changes derived from remote sensing measurements difficult to interpret, and an equilibrium line that is continuously migrating. We present a combined analysis of field measurements obtained in western Greenland and results from the Regional Atmospheric Climate Model to estimate trends in melt and refreezing rates over the interior of the Greenland ice sheet. The combined dataset show the evolution of melt intensity in regions with little or no meltwater runoff during the last 20 years. We estimated a threefold increase in the total area experiencing significant melt in the last decade, and an amount of refrozen meltwater larger than the total mass balance of the ice sheet. Conditions observed after the extreme melt event of July 2012 at and above the 2000 m elevation line contrast sharply with previous studies, and illustrate the current and future state of the Greenland interior if warming trends continue. We will discuss changes during the last decade in surface mass balance conditions, and the melting and refreezing processes occurring above the equilibrium line of the GIS. Additionally, we will summarize some implications these processes may have in estimating mass balance from altimetry techniques, and how in-situ data and models can help improving altimetry-derived results. The intensity of melt and the huge ice reservoirs found in the field are an indication that percolation facies are no longer just an interesting feature with no real relevance other than their effects in radar altimetry signals, but rather the result of an intense melting process of at least the same scale as the total mass imbalance of the GIS.

  9. 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 rapidly diminish these rates to a few cm/yr at most. The time scale for adjustment is of the order of a thousand years or so.

  10. Dynamics of Glacier Calving at the Ungrounded Margin of Helheim Glacier, South-East Greenland

    NASA Astrophysics Data System (ADS)

    Murray, T.; Selmes, N.; James, T.; Edwards, S.; Martin, I.; O'Farrell, T.; Aspey, R. A.; Nettles, M.; Rutt, I. C.

    2014-12-01

    Iceberg calving is a key mass loss mechanism for tidewater glaciers, and has been the major contributor to increased contribution to sea-level rise from several regions of Greenland, including the south-east. In summer 2013 we installed a network of 19 GNSS sensors at the margin of Helheim Glacier in south-east Greenland together with 5 oblique cameras to study iceberg calving mechanisms. The network collected data at rates up to every 7 seconds and was designed to be robust to the loss of sensor nodes as the glacier calved. Data collection covered 55 days during July through to early September 2013, and many sensors survived in locations right at the glacier front to the time of iceberg calving. The observation period included a number of significant calving events, and in consequence the glacier retreated ~1.5 km. Throughout the summer the glacier was seen to calve by a process of buoyancy-force-induced bottom-crevassing in which the ice downglacier of flexion zones rotates upwards 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 collected. Tracking of the oblique camera images allows identification and characterisation of the flexion zones and their propagation downglacier. Interpretation of the GNSS data and camera data in combination allows us to place constraints on the geometry of the basal cavity that forms beneath the rotating ice downglacier of the flexion zone before calving. Theoretical considerations suggest that the process of bottom crevasse propagation is strongly enhanced when the glacier base is deeper than buoyant equilibrium. We therefore suggest that this calving mechanism will be prevalent whenever this occurs. Interactions between the fjord water and the glacier are likely to enhance calving rates and the process also has implications for mixing in the proglacial fjord.

  11. Line-by-line radiative excitation model for the non-equilibrium atmosphere: Application to CO[sub 2] 15-[mu]m emission

    SciTech Connect

    Wintersteiner, P.P. ); Picard, R.H.; Sharma, R.D.; Winick, J.R. )

    1992-11-20

    We describe a new line-by-line (LBL) algorithm for radiative excitation in infrared bands in a non-local thermodynamic equilibrium (non-LTE) planetary atmosphere. Specifically, we present a predictive model for the terrestrial CO[sub 2] 15[mu]m emission that incorporates this generic algorithm, and validate the model by comparing its results with emission spectra obtained in a limb-scanning rocket experiment. The unique features of the reactive-excitation algorithm are discussed in this paper. These features contribute to accurate radiative transfer results and reliable atmospheric cooling rates. For altitudes above 40 km, we present results of model calculations of CO[sub 2]([nu][sub 2]) vibrational temperatures, 15-[mu]m limb spectral radiances, and cooling rates, for the main band and for weaker hot and isotopic bands. We calculate the excitation and deexcitation rates due to different processes. We compare the predicted limb radiance with earthlimb spectral scans obtained in the SPIRE rocket experiment over Poker Flat, Alaska, and get excellent agreement as a function of both wavelength and tangent height. This constitutes the first validation of a long-wavelength CO[sub 2] non-LTE emission model using an actual atmospheric data set and verifies the existence of certain aeronomic features that have only been predicted by models and constrains the previously unknown value of the very important rate constant for deactivation of the CO[sub 2] bending mode by atomic oxygen to the range of 5-6 [times] 10[sup [minus]12] cm[sup 3]/(mol s) at mesospheric and lower thermospheric temperatures. We discuss the significance of this large value for terrestrial and Venusian thermospheres and the convergence rate of the iterative scheme, the model's sensitivity to the background atmosphere, the importance of the lower boundary surface contribution, and the effects of the choice of the layer thickness and the neglect of line overlap. 86 refs., 20 figs., 5 tabs.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  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

    In many applications, a realistic description of air temperature inversions is essential for accurate snow and glacier ice melt, and glacier mass-balance simulations. A physically based snow-evolution modeling system (SnowModel) was used to simulate eight years (1998/99 to 2005/06) of snow accumulation and snow and glacier ice ablation from numerous small coastal marginal glaciers on the SW-part of Ammassalik Island in SE Greenland. These glaciers are regularly influenced by inversions and sea breezes associated with the adjacent relatively low temperature and frequently ice-choked fjords and ocean. To account for the influence of these inversions on the spatiotemporal variation of air temperature and snow and glacier melt rates, temperature inversion routines were added to MircoMet, the meteorological distribution sub-model used in SnowModel. The inversions were observed and modeled to occur during 84% of the simulation period. Modeled inversions were defined not to occur during days with strong winds and high precipitation rates due to the potential of inversion break-up. Field observations showed inversions to extend from sea level to approximately 300 m a.s.l., and this inversion level was prescribed in the model simulations. Simulations with and without the inversion routines were compared. The inversion model produced air temperature distributions with warmer lower elevation areas and cooler higher elevation areas than without inversion routines due to the use of cold sea-breeze base temperature data from underneath the inversion. This yielded an up to 2 weeks earlier snowmelt in the lower areas and up to 1 to 3 weeks later snowmelt in the higher elevation areas of the simulation domain. Averaged mean annual modeled surface mass-balance for all glaciers (mainly located above the inversion layer) was -720 {+-} 620 mm w.eq. y{sup -1} for inversion simulations, and -880 {+-} 620 mm w.eq. y{sup -1} without the inversion routines, a difference of 160 mm w.eq. y{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 neighbouring high peaks. Glacier size is apparently key in controlling a glacier's ability to keep pace with rock uplift.

  15. Black carbon concentrations from a Tibetan Plateau ice core spanning 1843-1982: recent increases due to emissions and glacier melt

    NASA Astrophysics Data System (ADS)

    Jenkins, M.; Kaspari, S.; Kang, S.; Grigholm, B.; Mayewski, P. A.

    2013-10-01

    Black carbon (BC) deposited on snow and glacier surfaces can reduce albedo and lead to accelerated melt. An ice core recovered from Guoqu glacier on Mt. Geladaindong and analyzed using a Single Particle Soot Photometer provides the first long-term (1843-1982) record of BC concentrations from the Central Tibetan Plateau. The highest concentrations are observed from 1975-1982, which corresponds to a 2.0-fold and 2.4-fold increase in average and median values, respectively, relative to 1843-1940. BC concentrations post-1940 are also elevated relative to the earlier portion of the record. Causes for the higher BC concentrations include increased regional BC emissions and subsequent deposition, and melt induced enrichment of BC, with the melt potentially accelerated due to the presence of BC at the glacier surface. A qualitative comparison of the BC and Fe (used as a dust proxy) records suggests that if changes in the concentrations of absorbing impurities at the glacier surface have influenced recent glacial melt, the melt may be due to the presence of BC rather than dust. Guoqu glacier has received no net ice accumulation since the 1980s, and is a potential example of a glacier where an increase in the equilibrium line altitude is exposing buried high impurity layers. That BC concentrations in the uppermost layers of the Geladaindong ice core are not substantially higher relative to deeper in the ice core suggests that some of the BC that must have been deposited on Guoqu glacier via wet or dry deposition between 1983 and 2005 has been removed from the surface of the glacier, potentially via supraglacial or englacial meltwater.

  16. 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.

  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. Glacier Erosion and Convergent Tectonics in Southern Alaska

    NASA Astrophysics Data System (ADS)

    Merrand, Y.; Hallet, B.

    2001-12-01

    The Chugach-St. Elias Mountains of South Alaska reach over 5500m elevation above the Gulf of Alaska. This region of extreme relief occurs at the corner of Northwest America, a region of focused tectonic activity. Moderately low temperatures and heavy precipitation on the coastal side of the range produce the largest modern temperate glacial systems on earth. Frequent and large injections of water to the glacier bed result into very dynamic ice masses that slide rapidly over the landscape. Rapid advection of ice over highly fractured lithologies translates into high basin wide erosion rates (order of 1 cm per year; Hallet et al, 1996). These rates are computed on the basis of sedimentation that has occurred in fjords and lakes since the onset of the post Little Ice Age retreat; they are thus temporal averages for the latest Holocene which has been characterized by widespread tidewater glacier retreat in the region. Our continuing work in South Alaska seeks to document rates of sediment delivery in carefully chosen natural sediment traps in order to infer erosion rates accounting for a wide range of glacier dynamics because, for surging and tidewater glaciers, ice flux varies widely in time (with speeds ranging by up to 3 orders of magnitude). In particular, studies of sediment fluxed in fjords have allowed us to downscale erosion rates characteristic of tidewater retreat to that representative of mean ice flux conditions. The maintenance of high mountain belts in regions of rapid tectonic convergence and erosion over long period of times (millions of years) suggest a dynamic equilibrium between the processes that build and those that diminish landscapes. Our numerical model of glacial landscape evolution suggests that the pattern of tectonic uplift has to match the spatial distribution of erosion for the hypsometry of the landscape, which gives rise to large glaciers, is to be sustained over the long term. Inverting the erosional patterns imposed by modern glacial systems to map rock uplift patterns in steady state orogens is thus a straight forward means of assessing the spatial permanence of exhumation as reflected in the distribution of metamorphic rock grades at the earth surface. Under conditions of spatial-temporal equilibrium between forcings, the highest modern topography tends to be associated with the deepest troughs dissecting the range. In addition, the presence of a major divide near the equilibrium line altitude of massive through-going glacial ice bodies reinforces the suggestion of positive feedback between exhumation and tectonics in the St. Elias Mountains. A model that is tuned with modern rates of erosion and that is constrained by glacier observations indicates that relief reached a limit in the St. Elias Mountains, and did so over the course of a few glacial cycles provided that modern exhumation rates are representative of long-term average erosion.

  19. Topography, relief, climate and glaciers: a global prespective

    NASA Astrophysics Data System (ADS)

    Champagnac, Jean-Daniel; Valla, Pierre; Herman, fred

    2014-05-01

    The examination of the relationship between Earth's topography and present and past climate (i.e. long-term elevation of glaciers Equilibrium Line Altitude) reveals that the elevation of mountain ranges may be limited or controlled by glaciations. This is of prime importance, because glacial condition would lead to a limit the mountain development, hence the accumulation of gravitational energy and prevent the development of further glacial conditions as well as setting the erosion in (peri)glacial environments. This study examines the relationships between topography and the global Equilibrium Line Altitude of alpine glaciers around the world (long term snowline, i.e. the altitude where the ice mass balance is null). Two main observations can be drawn: 1) The distance between the (averaged and maximum) topography, and the ELA decreases pole ward the poles, and even become reversed (mean elevation above to ELA) at high latitude. Correlatively, the elevation of very large portion of land at mid-latitude cannot be related to glaciations, simply because it was never glaciated (large distance between topography and long-term mean ELA). The maximum distance between the ELA and the topography is greater close to the equator and decreases poleward. In absence of glacial and periglacial erosion, this trend cannot have its origin in glacial and periglacial processes. Moreover, the ELA elevation shows a significant (1000 - 1500m) depression in the intertropical zone. This depression of the ELA is not reflected at all in the topography. 2) The distribution of relief on Earth, if normalized by the mean elevation of mountain ranges (as a proxy for available space to create relief) shows a latitudinal band of greater relief between 40° and 60° (or between ELA of 500m to 2500m a.s.l.). This mid-latitude relatively greater relief challenges the straightforward relationship between glaciations, erosion and topography. Oppositely, it suggests that glacier may be more efficient agent in temperate area, with important amplitude between glacial and interglacial climate. This is consistent with the view of a very variable glacier erodibility that can erode and protect the landscape, as well as with studies documenting a bimodal location of the preferred glacial erosion, at relatively high elevation (around the long-term ELA), and at much lower elevation (close to the glacial maximum lower reaches), thanks to efficient water lubrication of the glacier bases that greatly enhance the sliding velocity. These findings show that the relation between the mountain topography and the long term snowline is not as straightforward as previously proposed. Beside the role of tectonic forcing highlighted by several authors, the importance of the glacial erosion appears to be crucial at mid latitude, but more complex at both high and low latitude. Moreover, the relief at mid latitude appears to be higher, hence suggesting a positive correlation between relief and topographic control of glacier on the landscape.

  20. Columbia Glacier Calving

    A dramatic iceberg calving from Columbia Glacier in Prince William Sound, Alaska. The iceberg has just broken free from under the water and shot to the surface, spinning towards the ice face. The ice cliff here is about 70 m (229.7 ft) tall. Icebergs are calved as stress fractures in the glacier mer...

  1. Photographer Overlooking Columbia Glacier

    Photographer Tad Pfeffer capturing images of Columbia Glacier in Prince William Sound, Alaska. He is looking down-glacier towards the ice front, which faces open water in the fjord. This open water is extremely rare, and has not happened again since 2005. The fjord is typically covered with iceberg ...

  2. Denali Fault: Susitna Glacier

    Helicopters and satellite phones were integral to the geologic field response. Here, Peter Haeussler is calling a seismologist to pass along the discovery of the Susitna Glacier thrust fault. View is to the north up the Susitna Glacier. The Denali fault trace lies in the background where the two lan...

  3. Muir Glacier Retreats

    Muir Glacier has retreated out of the field of view and is now nearly 5 miles to the northwest. Riggs Glacier has retreated as much as 2000 ft and thinned by more than 800 feet. Note the dense vegetation that has developed. Also note the correlation between Muir Glacier’s 1941 thickness and th...

  4. 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

  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. 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.

  7. 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.

  8. Melting beneath Greenland outlet glaciers and ice streams

    NASA Astrophysics Data System (ADS)

    Alexander, David; Perrette, Mahé; Beckmann, Johanna

    2015-04-01

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

  9. Probabilistic estimation of glacier volume and glacier bed topography: the Andean glacier Huayna West

    NASA Astrophysics Data System (ADS)

    Moya Quiroga, V.; Mano, A.; Asaoka, Y.; Udo, K.; Kure, S.; Mendoza, J.

    2013-08-01

    Glacier retreat will increase sea level and decrease fresh water availability. Glacier retreat will also induce morphologic and hydrologic changes due to the formation of glacial lakes. Hence, it is important not only to estimate glacier volume, but also to understand the spatial distribution of ice thickness. There are several approaches for estimating glacier volume and glacier thickness. However, it is not possible to select an optimal approach that works for all locations. It is important to analyse the relation between the different glacier volume estimations and to provide confidence intervals of a given solution. The present study presents a probabilistic approach for estimating glacier volume and its confidence interval. Glacier volume of the Andean glacier Huayna West was estimated according to different scaling relations. Besides, glacier volume and glacier thickness were estimated assuming plastic behaviour. The present study also analysed the influence of considering a variable glacier density due to ice firn densification. It was found that the different estimations are described by a lognormal probability distribution. Considering a confidence level of 90%, the estimated glacier volume is 0.0275 km3 ± 0.0052 km3. Considering a confidence level of 90%, the estimated glacier thickness is 24.98 m with a confidence of ±4.67 m. The mean basal shear stress considering plastic behaviour is 82.5 kPa. The reconstruction of glacier bed topography showed the future formation of a glacier lake with a maximum depth of 32 m.

  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 subsequently absent or very small until a short-lived glacier event is seen in the lake sediments ˜8200 cal yr BP. The ice cap was most likely completely melted until a new glacier event occurred around ˜5300 cal yr BP, coeval with the onset of the Neoglacial at several other glaciers in southwestern Norway. Ålfotbreen was thereafter absent (or very small) until the onset of the Neoglacial period ˜1400 cal yr BP. The 'Little Ice Age' (LIA) ˜650-50 cal yr BP was the largest glacier advance of Ålfotbreen since deglaciation, with a maximum extent at ˜400-200 cal yr BP, when the ELA was lowered approximately 200 m relative to today. The late onset of the Neoglacial at Ålfotbreen is suggested to be a result of its low altitude relative to the regional ELA. A synthesis of Neoglacial ELA fluctuations along the coast of Norway indicates a time-transgressive trend in the maximum extent of the LIA, which apparently seems to have occurred progressively later as we move northwards. We suggest that this trend is likely due to regional winter precipitation differences along the coast of Norway.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  13. Bruggen Glacier, Chile

    NASA Technical Reports Server (NTRS)

    2002-01-01

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

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  16. A new glacier monitoring site in West Greenland

    NASA Astrophysics Data System (ADS)

    Abermann, J.; van As, D.; Petersen, D.; Nauta, M.

    2014-12-01

    Greenland's mountain glaciers and ice caps have recently been shown to significantly contribute to current and future sea-level rise. Despite their importance in this respect they are heavily undersampled with only about 5 currently monitored glaciers out of more than 20000 distributed over complexly varying climatic regions. In 2012, Asiaq, Greenland Survey initiated therefore a glacier mass balance program at Qassinnguit glacier (64°9'N, 51°17'W), approx. 18 km East of Nuuk, Greenland's capital. The glacier is a representative example for mountain glaciers in South-West Greenland both in terms of size (ca 1 km2) and orientation (N). A dense stake network gives the basis for the determination of the surface mass balance with the glaciological method as well as flow velocity measurements and the first two complete years are presented. An automated camera is used to monitor ablation patterns and the evolution of the snow line. In early 2014, a ground-penetrating radar campaign was performed to determine the glacier volume. Ice thicknesses up to 50 m were measured with a 100 MHz antenna and the glacier was found to be largely cold-based with some minor temperate parts. In addition to direct glaciological measurements at the site, the monitoring program complements a 7 year long time series of runoff, which allows for quantifying Qassinnguit glacier's cryospheric contribution to the total catchment. In summer 2014 an on-glacier automated weather station was installed that measures parameters to determine the surface energy balance. Preliminary results will be presented and put into a larger spatial context by relating them to measurements with the same setup at an outlet glacier of the Greenland ice sheet approximately 100 km further East. Climate between these sites differs considerably with a marked negative West - East precipitation gradient.

  17. Dynamics of rock glaciers and debris-covered glaciers in the Central Chilean Andes over the last 50 years

    NASA Astrophysics Data System (ADS)

    Bodin, Xavier; Brenning, Alexander; Rojas Marchini, Fernanda

    2010-05-01

    In the semiarid Central Andes of Chile at 33.5°S., mountain permafrost is widely present above 3500-4000 m asl, especially in the form of rock glaciers, which often coexist with glaciers and debris-covered glaciers. This peculiar configuration of the cryosphere involves complex and poorly known responses of its components to climate change. Our study area in the Laguna Negra catchment is part of a watershed that provides up to two-thirds of the drinking water supplies to Chile's capital Santiago (5.5 million inhabitants) during the dry summer months. The 35 km² watershed contains 2.3 km² of uncovered glaciers, 0.9 km² of debris-covered glacier area and 4.3 km² of rock glaciers, and hosts the longest series of glacier mass balance measurement in Chile (Echaurren Norte glacier). Using orthorectified aerial photographs of 1956 and 1996 and a high resolution satellite image of 2008, we mapped the geometric changes that affected the glacier and the debris-covered glacier of the Punta Negra sub-catchment during the last 50 years. Surface displacements and volume changes were estimated based on 1956 and 1996 digital elevation models (DEMs), and the total loss of water equivalent in the catchment was quantified. At a shorter time scale, rock glaciers and a debris-covered glacier are being monitored since 2004, providing insights into their kinematics and near-surface thermal regime. The orthophotos reveal a 44.7% reduction of the uncovered glacier area between 1955 and 1996, and only small surface changes between 1996 and 2008. The volume reduction of both uncovered and debris-covered glaciers is estimated at at least 3.9 million m3 water equivalent between 1955 and 1996. The second noticeable change is the growth of the thermokarst areas on the debris-covered glacier, with the formation of new and the widening and deepening of existing melt-out depressions between 1955 and 2008. The thermal monitoring revealed that, in 2003/04, the mean annual ground surface temperature ranged from 7.9°C at 2987 m asl to 0.8°C at 4020 m asl, displaying a linear relationship with altitude similar to the air temperature lapse rate and that the snow cover lasted between 3 and 8 months. A negative winter thermal equilibrium was observed only at the highest (4020 m asl) site, suggesting the presence of perennial frozen ground underneath. GPS monitoring of the surface displacement between 2004 and 2009 revealed horizontal velocities ranging from 0.25 to 0.5 m/yr on the rock glaciers and the debris-covered glacier. The latter is affected by stronger vertical lowering (12-22 cm/yr), which is attributed to the intense downwasting and thermokarst development. As depicted by our study, the evolution of the cryosphere in the Central Chilean Andes during the last 50 years highlights the very different responses of glacier and permafrost to climate change. It also suggests an increasing relative importance of debris-covered glaciers and especially rock glaciers as stores of water compared to uncovered glaciers and thus ongoing changes in geomorphic and hydrological processes that still need to be investigated.

  18. 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.

  19. Marine ice sheet dynamics: Hysteresis and neutral equilibrium

    NASA Astrophysics Data System (ADS)

    Durand, G.; Gagliardini, O.; de Fleurian, B.; Zwinger, T.; Le Meur, E.

    2009-09-01

    The stability of marine ice sheets and outlet glaciers is mostly controlled by the dynamics of their grounding line, i.e., where the bottom contact of the ice changes from bedrock or till to ocean water. The last report of the Intergovernmental Panel on Climate Change has clearly underlined the poor ability of models to capture the dynamics of outlet glaciers. Here we present computations of grounding line dynamics on the basis of numerical solutions of the full Stokes equations for ice velocity, coupled with the evolution of the air ice- and sea ice-free interfaces. The grounding line position is determined by solving the contact problem between the ice and a rigid bedrock using the finite element code Elmer. Results of the simulations show that marine ice sheets are unstable on upsloping beds and undergo hysteresis under perturbation of ice viscosity, confirming conclusions from boundary layer theory. The present approach also indicates that a 2-D unconfined marine ice sheet sliding over a downsloping bedrock does not exhibit neutral equilibrium. It is shown that mesh resolution around the grounding line is a crucial issue. A very fine grid size (<100 m spacing) is needed in order to achieve consistent results.

  20. Marine ice sheet dynamics: Hysteresis and neutral equilibrium

    NASA Astrophysics Data System (ADS)

    Durand, G.; Gagliardini, O.; de Fleurian, B.; Zwinger, T.; Le Meur, E.

    The stability of marine ice sheets and outlet glaciers is mostly controlled by the dynamics of their grounding line, i.e., where the bottom contact of the ice changes from bedrock or till to ocean water. The last report of the Intergovernmental Panel on Climate Change has clearly underlined the poor ability of models to capture the dynamics of outlet glaciers. Here we present computations of grounding line dynamics on the basis of numerical solutions of the full Stokes equations for ice velocity, coupled with the evolution of the air ice- and sea ice-free interfaces. The grounding line position is determined by solving the contact problem between the ice and a rigid bedrock using the finite element code Elmer. Results of the simulations show that marine ice sheets are unstable on upsloping beds and undergo hysteresis under perturbation of ice viscosity, confirming conclusions from boundary layer theory. The present approach also indicates that a 2-D unconfined marine ice sheet sliding over a downsloping bedrock does not exhibit neutral equilibrium. It is shown that mesh resolution around the grounding line is a crucial issue. A very fine grid size (<100 m spacing) is needed in order to achieve consistent results.

  1. 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.

  2. Debris-Free Plateau Glacier

    Small debris-free plateau glacier with glacier lakes at Gangrinchemzoe Pass at 5,200 m, south of the main Himalayan divide, Bhutan. Image courtesy of Shuji Iwata, Tokyo Metropolitan University, Japan....

  3. Comparing In Situ Spectra and Multispectral Classifications of Glacier Surfaces

    NASA Astrophysics Data System (ADS)

    Pope, A.; Rees, G.; Willis, I. C.; Arnold, N. S.

    2011-12-01

    Glaciers can be divided into distinct surface zones (or facies) such as new snow, firn, slush, and glacier ice, which can then be quantitatively linked to the mass balance state of a glacier. Due to similarities in reflective properties, persistent difficulty is had identifying the snow line and accumulation area rather than the more distinct glacier ice-firn line. Yet, it is the snow line rather than the firn line which provides a sensitive indicator of how a given year's climate influences a glacier. As small icecaps and glaciers contribute significantly to current sea level rise and will continue to do so in the coming decades, it would be highly beneficial to develop a technique which measures a glacier mass balance proxy - the glacier accumulation area ratio - using widespread, high resolution multispectral imagery. In situ glacier surface spectra (350-2300 nm) were measured on Midtre Lovénbreen (Svalbard) in August 2010 and Langjökull (Iceland) in August 2011 using an ASD field spectroradiometer. The full-spectrum reflectance measurements allow simulation of various airborne and spaceborne multispectral sensors including the Airborne Thematic Mapper, Landsat ETM+, MODIS or MERIS, and ESA's forthcoming Sentinel 2. Published studies have applied methods such as spectral band ratios, normalized indices, thresholding, principal component analysis, unsupervised classification, supervised classification, and spectral mixing analysis to classify glacier surfaces. The work presented here uses the collected in situ surface reflectance data to inform interpretation of ISODATA classification schemes of airborne and satellite multispectral imagery, can provide end member points for spectral mixing studies, and gives a starting point from which to further develop useful analysis strategies for remote imagery. Future research directions could integrate elevation and intensity data from airborne LiDAR campaigns. While spectra and classifications of airborne/satellite multispectral imagery match reasonably for Svalbard data, this is not the case between in situ measurements from Svalbard and imagery from Iceland. This paper will investigate not only the potential causes of differing spectral properties of glacier surfaces in Svalbard and Iceland, but also use the in situ spectra to evaluate classification techniques and inform more effective and reliable strategies for remotely measuring a glacier's accumulation area.

  4. Glaciers of Greenland

    USGS Publications Warehouse

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

    1995-01-01

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

  5. Denali Fault: Black Rapids Glacier

    View eastward along Black Rapids Glacier. The Denali fault follows the trace of the glacier. These very large rockslides went a mile across the glacier on the right side. Investigations of the headwall of the middle landslide indicate a volume at least as large as that which fell, has dropped a mete...

  6. Greenland Glacier Albedo Variability

    NASA Technical Reports Server (NTRS)

    2004-01-01

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

  7. Snow and glacier monitoring service using Earth Observation data

    NASA Astrophysics Data System (ADS)

    Nagler, T.; Heidinger, M.; Rott, H.; Bippus, G.; Hetzenecker, M.; Scharrer, K.

    2012-04-01

    Snow cover and glaciers, storing large amounts of fresh water, respond sensitively to climate change. Accurate inventories and monitoring of these resources is therefore important for climate impact assessment, water resources management, and hydrology. The Project "ASaG - Preparation for a GMES Downstream service for snow and glacier Monitoring in Alpine Regions", supported by the Austrian Research Promotion Agency (FFG), aims at the implementation of a satellite-based services for spatially detailed monitoring of snow cover and glaciers over extended area. Algorithms and processing lines for retrieval of snow extent from medium resolution optical and SAR satellite imagery are further improved in the project in order to optimally match the needs of users. The snow cover products are generated using data of the MODIS sensor operating on the Terra platform of NASA. The products are made available in near real time and are used in pre-operational tests for initialization and validation of hydrological models and distributed snow process models. Statistical snow information like snow area - elevation curves are generated for user specified basins using this information for runoff simulation and forecasting and for water management tasks. For mountain glaciers a processing line has been implemented for satellite-based products on glacier area, outlines, glacier zones (snow, ice) and ice velocity maps to be used for updating glacier inventories. The glacier products are generated for major Austrian glacier regions using new high resolution optical satellite data (SPOT-5) and SAR (TerraSAR-X, Cosmo-Skymed). The products comply with the European rules for geospatial information according to the INSPIRE directive in order to ensure interoperability of the data sets and are made accessible to users via internet. Project results are also exploited in wider within the EC-FP7 project "CryoLand - GMES Service Snow and Land Ice", a GMES Downstream Service developed under the lead of ENVEO (started in February 2011).

  8. Svalbard surging glacier landsystems

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    The percentage of Svalbard glaciers thought to be of surge-type is somewhere between 13-90% according to different sources variously based on statistical analysis and observations of diagnostic glaciological and geomorphological features, e.g. looped moraines. Developing a better understanding of which of these figures, if either, is most realistic is important in the context of glacier dynamics and related contributions of small glaciers and ice caps to sea level change in the immediate future. We present detailed geomorphological assessments of the margins of several known surge-type glaciers in Svalbard in order to update and improve the existing framework by which they are identified, and to provide a foundation for future reassessments of the surge-type glacier population based on distinct landform-sediment assemblages. Three landsystems are proposed: (1) Surges of small valley glaciers produce a prominent ice-cored latero-frontal moraine at their surge maximum and are characterised by an inner zone of ice stagnation terrain (hummocky topography, kettle lakes, debris flows) with no or only very few poorly-defined bedforms (crevasse squeeze ridges, eskers and flutes) and no recessional moraines. Many of these glaciers may have surged in the past but show no signs that they have the capability to do so again in the future. (2) Larger land-terminating glaciers, often with several tributaries, typically produce a push moraine complex which contains evidence for multiple advances, as identified from ridge-meltwater channel relationships. The inner zone often contains a large lagoon, partly dammed by the push moraine complex, and widespread ice stagnation terrain. Crevasse squeeze ridges, eskers and flutes are well-defined but small and limited in number and distribution. (3) Surges of large tidewater glaciers produce distinctive, often multi-generational, landform assemblages both in submarine and lateral terrestrial positions. The well-preserved submarine record is characterised by large cross-fjord push moraines of fjord floor sediments with lobe-shaped debris flows on their distal slope, glacial lineations, dense rhombohedral networks of crevasse squeeze ridges, and eskers. Annual push moraines associated with the quiescent phase are also observed and are unique to the submarine record. The terrestrial record consists of large lateral moraine systems alongside the fjord which contain outer push ridges composed of shallow marine sediments and an inner zone of ice stagnation terrain. Eskers, flutes and large, sharp-crested crevasse fill ridges in dense networks are superimposed on this inner zone; the latter are similar in character to their submarine counterparts but typically higher. We suggest that these three landsystems broadly characterise the geomorphology of the vast majority of known Svalbard surge-type glaciers and may allow previously unknown surge-type glaciers to be identified, both in the field and from aerial photographs and sea floor imagery.

  9. Change in longitudinal profile on three North Cascades glaciers during the last 100 years

    NASA Astrophysics Data System (ADS)

    Pelto, Mauri S.; Hartzell, Paula

    2004-04-01

    Centreline surface elevation longitudinal profiles have been completed for three different points in time from historic photographs (1900), US Geological Survey maps (1964 and 1985), and field measurements (annually between 1984 and the present) for three North Cascade glaciers. Comparison of thinning and terminus behaviour over this time period indicates substantial overall volume loss during this century for each glacier.Mean thickness changes along the longitudinal profile of Easton Glacier are losses of 46 m (0.68 m year-1) of ice thickness between 1916 and 1984 and 13 m (0.72 m year-1) between 1984 and 2002. Its terminus has retreated a net distance of 2123 m. Lower Curtis Glacier lost an average of 45 m (0.60 m year-1) thickness from 1908 to 1984 and 6 m (0.33 m year-1) from 1984 to 2002, with a net terminus retreat of 522 m. On Columbia Glacier, ice thickness loss was 57 m (0.78 m year-1) from 1911 to 1984 and 8 m (0.44 m year-1) from 1984 to 2002. The net terminus retreat for Columbia was 640 m. Thickness changes are approximately equal in the accumulation zone of the Columbia and Lower Curtis Glacier during the 20th century and from 1984 to 2002. This suggests that there is no position to which the glacier can retreat and achieve equilibrium. The changes on each glacier, which today average less than 75 m in thickness, represent the loss of 35-50% in their volume since the turn of the century, and 10-15% of this volume since 1984. Their ongoing thinning indicates that these three glaciers will continue to retreat in the foreseeable future, the Columbia Glacier likely disappearing. Long-term monitoring of these glaciers should continue in order to assess the impact on downstream flow, which is utilized for hydropower on Easton and Lower Curtis Glaciers and a salmon hatchery on Columbia Glacier.

  10. Pine Island Glacier

    Atmospheric Science Data Center

    2013-04-16

    ... this representation, clouds show up as light purple. Blue to orange gradations on the surface indicate a transition in ice texture from smooth to rough. For example, the bright orange "carrot-like" features are rough crevasses on the glacier's tongue. In ...

  11. 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.

  12. 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.

  13. On the role of buoyant flexure in glacier calving

    NASA Astrophysics Data System (ADS)

    Wagner, Till J. W.; James, Timothy D.; Murray, Tavi; Vella, Dominic

    2016-01-01

    Interactions between glaciers and the ocean are key for understanding the dynamics of the cryosphere in the climate system. Here we investigate the role of hydrostatic forces in glacier calving. We develop a mathematical model to account for the elastic deformation of glaciers in response to three effects: (i) marine and lake-terminating glaciers tend to enter water with a nonzero slope, resulting in upward flexure around the grounding line; (ii) horizontal pressure imbalances at the terminus are known to cause hydrostatic in-plane stresses and downward acting torque; (iii) submerged ice protrusions at the glacier front may induce additional buoyancy forces that can cause calving. Our model provides theoretical estimates of the importance of each effect and suggests geometric and material conditions under which a given glacier will calve from hydrostatic flexure. We find good agreement with observations. This work sheds light on the intricate processes involved in glacier calving and can be hoped to improve our ability to model and predict future changes in the ice-climate system.

  14. 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 Glacier Paradise is the glacier palace. Since summer 2011 this tourist attraction can be accessed via two elevators leading to an ice tunnel about 12 meters below the glaciers surface. Interesting thermal interactions exist between the permafrost bedrock that is in direct contact to the glacier ice. Great care has to be taken that there is no heat transfer from buildings to the glacier ice. Degradation of permafrost due to climatic change and human interference may become a serious threat to many installations of high mountain tourist centers. These facilities need appropriate management. Permafrost scientists may provide the necessary expertise for a proper hazard management.

  15. Observed changes in glaciers in China

    NASA Astrophysics Data System (ADS)

    Li, L.; Li, H.; Wang, F.

    2012-04-01

    Small glaciers are highly sensitive to changes in temperature and precipitation making them important indicators of regional climate change. At present, worldwide evaluation and prediction of glacier change are based on or aided by detailed observations from a small number of glaciers due to the inaccessibility of many glacier areas. Thus, the ground-based detailed glacier monitoring is of strong need and extremely important for glacier variability evaluation in both regional and global scale. China has 46,377 glaciers with a total area of 59,425 km2 and 5600 km3 in volume. Most of the glaciers have experienced rapid and accelerated shrinkage during last few decades. Although some of the glaciers have been investigated or observed through field expeditions and ground-based monitoring, the information of the glacier changes are poorly documented and relatively new to international community. This paper summarizes the observed changes of 9 reference glaciers in China: 1) Urumqi Glacier No. 1, located at the headwaters of Urumqi River in eastern Tianshan which is the best observed glacier in China; 2) Haxilegen Glacier No. 51, at Kuitun River in eastern Tianshan; 3) Qingbingtan Glacier No.72, located at the upper reach of Aksu River in the middle of Tianshan; 4) Miaoergou ice cap, located in the most east part of Tianshan; 5) Laohugou Glacier No. 12, located in Shule River in Qinlian Mountains; 6) Qi Yi glacier (also named as July First Glacier), located in Qinlian Mountains; 7) Dongkemadi Glacier located in Tianggula Mountains in Qinghai-Xizang (Tibetan) Plateau; 8) Rongbu Glacier at the north slop of Mt. Everest in Himalaya Mountains; and 9) Baishui Glacier No. 1, the only temperate glacier in this glacier group, located at Yulong Snow Mountain. Geographically those reference glaciers well represent the glaciers in the major high mountain system in western China. In addition, they have been monitored for 5-53 years and promise the best datasets for glacier changes in their regions.

  16. 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.

  17. Mt. Kilimanjaro's Receding Glaciers

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Mt. Kilimanjaro (Tanzania), the highest point in all Africa, was photographed by the crew of Space Shuttle mission STS-97 on December 2, 2000 (STS097-701-17). Kilimanjaro (Kilima Njaro or 'shining mountain' in Swahili) is capped by glaciers on its southern and southwestern flanks. The glaciers and snow cap covered a far greater area ten years prior to the view above. Compare the photograph above with a photograph of Kilimanjaro taken in November 1990 by the Space Shuttle mission STS-38 crew. Shuttle photograph provided by the Earth Sciences and Image Analysis Laboratory, Johnson Space Center. Additional photographs taken by astronauts and cosmonauts can be viewed via the NASA - JSC Gateway to Astronaut Photography of Earth.

  18. 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.

  19. 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 Holocene glaciers occurred during the European Little Ice Age period.

  20. 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 -0.65 m / year) are very similar to the mean of the lake-calving and tidewater glaciers (about -0.6 m / year), but much more negative than for the land-terminating glaciers (about -0.24 m / year). The two mass balance glaciers are thus well representative for the entire region, but not for their own class. The different ways of considering positive elevation changes (e.g. setting them to zero or no data) influence the total values, but has otherwise little impact on the results (e.g. the correction factors are similar). The massive elevation loss of Columbia Glacier (-2.8 m / year) is exceptional and strongly influences the statistics when area-weighting is used to determine the regional mean. For the entire region this method yields more negative values for land-terminating and tidewater glaciers than the arithmetically averaged values, but for the lake-calving glaciers both are about the same.

  1. Getting the Shot, Grinnell Glacier, Glacier National Park.

    USGS scientist shoots a repeat photograph of Grinnell Glacier in Glacier National Park to illustrate glacial recession due to impacts of climate change.  *note – logo on scientists hat is logo from USGS Northern Rocky Mountain Science Center, not private....

  2. Getting the Shot, Grinnell Glacier, Glacier National Park.

    USGS scientist shoots a repeat photograph of Grinnell Glacier in Glacier National Park to illustrate glacial recession due to impacts of climate change. *note – logo on scientists hat is logo from USGS Northern Rocky Mountain Science Center, not private. ...

  3. 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 the morphostratigraphic characteristics of Younger Dryas (Egesen) stadial with multiple, sharp crested moraine ridges (e.g. Ivy-Ochs et al. 2008), the unusual large glacier extent is due to the rock avalanche debris cover and its insulating effect. In both cases the maximum elevation of lateral moraines (MELM - method) gave the most reliable estimates of ELAs with reconstructed low AARs of around 0.5 compared to the standard assumption for Lateglacial glaciers with a ratio around 0.65. Thus, stratigraphic correlations of moraines should be done not until morphological features and lithofacies have been analyzed considering the whole geological setting. Ivy-Ochs, S., Kerschner, H., Reuther, A., Preusser, F., Heine, K., Maisch, M., Kubik, P.W. and Ch. Schlüchter (2008):Chronology of the last glacial cycle in the Northern European Alps. Journal of Quaternary Science 23(6-7), 559-573.

  4. Tidal rifting of the Mertz glacier tongue

    NASA Astrophysics Data System (ADS)

    Legresy, Benoit; Lescarmontier, Lydie; Coleman, Richard; Young, Neal; Testut, Laurent

    2010-05-01

    The IPY CRAC-ICE project is aimed at monitoring the calving of the Mertz Glacier tongue in East Antarctica, which extends 140km from its grounding line. Legresy et al. (2004) observed dramatic ice flow changes at daily time scales linked to tide currents, using limited GPS observations and SAR interferometry. In November 2007, we deployed a network of GPS beacons on the glacier. Two months of GPS data were collected at the end of the field season from two stations straddling the main rift. We have analyzed ERS INSAR, SAR, Landsat and SPOT images, Radio echo sounding and the GPS data together to draw an overall description of the rifting and calving process for the Mertz glacier tongue. We describe the history of this rifting during the available 14 years observation period. The ice tongue is freely floating and has a longitudinal velocity of about 3m/day. It is clear that the ice flow is affected at daily time scales by the tides. A kind of stick-slip effect appears to also occur at daily scales. We see a modulation of the flow at fortnightly time scales; however, we also observe that the maximum speed occurs a few days after the spring tides. The ice tongue moves in an E-W direction in response to the force exerted by tide currents at all time scales. We find that the rifting is likely initiated by the tide current induced lateral hinging of the ice tongue, creating regularly spaced (~1km) weak lines on the glacier tongue across flow. The rifts further propagate into these weakness lines. Now that the rifts on both east and west sides of the glacier have significantly progressed, the daily to seasonal scale hinging is now happening between the down stream and upstream parts of the ice tongue. The rift is opening quickly at some 0.12 m/day at an angle of 35° from the main flow direction. We observe a residual rotation of the rift opening with a radius of 15 km. The rotation center is situated in the eastern part of the rift, which appears active at the daily scale. We present the results with an emphasis on the future possible calving scenarios.

  5. 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 technology program designed to examine Earth's land, oceans, atmosphere, ice and life as a total integrated system.

    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.

    Size: 55 by 40 kilometers (34 by 25 miles) Location: 60.0 degrees North latitude, 140.7 degrees West longitude Orientation: North at top Image Data: ASTER bands 2, 3 and 4 Original Data Resolution: 15 meters (49 feet) Date Acquired: June 8, 2001

  6. ASTER Image of Gangotri Glacier

    Sept 9, 2001 ASTER image showing the position of the terminus of Gangotri Glacier, India, between 1780 and 2001. Image from Jesse Allen, NASA's Earth Observatory. Glacier retreat boundaries courtesy of the U.S. Land Processes Distributed Active Archive Center...

  7. 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.

  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

    2015-07-01

    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. 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 morphology and physical properties, wetlands Evaluation, thermal pollution monitoring, coral reef degradation, surface temperature mapping of soils and geology, and measuring surface heat balance.

  10. Glacier and Ice Shelves Studies Using Satellite SAR Interferometry

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1999-01-01

    Satellite radar interferometry is a powerful technique to measure the surface velocity and topography of glacier ice. On ice shelves, a quadruple difference technique separates tidal motion from the steady creep flow deformation of ice. The results provide a wealth of information about glacier grounding lines , mass fluxes, stability, elastic properties of ice, and tidal regime. The grounding line, which is where the glacier detaches from its bed and becomes afloat, is detected with a precision of a few tens of meters. Combining this information with satellite radar altimetry makes it possible to measure glacier discharge into the ocean and state of mass balance with greater precision than ever before, and in turn provide a significant revision of past estimates of mass balance of the Greenland and Antarctic Ice Sheets. Analysis of creep rates on floating ice permits an estimation of basal melting at the ice shelf underside. The results reveal that the action of ocean water in sub-ice-shelf cavities has been largely underestimated by oceanographic models and is the dominant mode of mass release to the ocean from an ice shelf. Precise mapping of grounding line positions also permits the detection of grounding line migration, which is a fine indicator of glacier change, independent of our knowledge of snow accumulation and ice melting. This technique has been successfully used to detect the rapid retreat of Pine Island Glacier, the largest ice stream in West Antarctica. Finally, tidal motion of ice shelves measured interferometrically provides a modern, synoptic view of the physical processes which govern the formation of tabular icebergs in the Antarctic.

  11. 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 hydrologically. An up-glacier branching, arborescent network of channels incised into the basal ice conveys water rapidly. Much of the water flux to the bed probably enters directly into the arborescent channel network, which covers only a small fraction of the glacier bed. More extensive spatially is a nonarborescent network, which commonly includes cabities (gaps between the glacier sole and bed), channels incised into the bed, and a layer of permeable sediment. The nonarborescent network conveys water slowly and is usually poorly connected to the arborescent system. The arborescent channel network largely collapses during winter but reforms in the spring as the first flush of meltwater to the bed destabilizes the cavities within the nonarborescent net6work. The volume of water stored by a glacier varies diurnally and seasonally. Small, temperate alpine glaciers seem to attain a maximum seasonal water storage of ~200 mm of water averaged over the area of the glacier bed, with daily fluctuations of as much as 20-30 mm. The likely storage capacity of subglacial cavities is insufficient to account for estimated stored water volumes, so most water storage may actually occur englacially. Sotred water may also be released abruptly and catastrophically in the form of outburst floods.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    We present the results of the study of tidewater glacier depositional basins, across a broad latitudinal transect from central Patagonia (46°S) to the Antarctic Peninsula (65°S). Based on sediment cores and seismic records, we estimate accumulation rates at several timescales as well as sediment-volume derived erosion rates (Er) for millennial time scales. In the Antarctic Peninsula, accumulation rates are ~100 mm/yr for centennial and millennial timescales. In Patagonia, proximal basins are in general well isolated and have short timescale (decadal-centennial) sedimentary records and high accumulation rates, whereas medial (more distal) basins have millennial scale sedimentary records and low accumulation rates. We hypothesize that the "Saddler effect" in the accumulation rates of the Patagonian study areas exists because Neoglacial advance and recent post-Little Ice Age retreat has left well isolated proximal basins that effectively trap sediments. This, along with high sediment yields, produces high decadal accumulation rates. There is no such organization of basins in the Antarctic Peninsula fjords and bays and no such clear manifestation of Neoglacial advances or morphologies. Erosion rates span two orders of magnitude from 0.03 mm/yr for Lapeyrère Bay at Anvers Island, Antarctica (~64.5°S), to 1.09 mm/yr for San Rafael Glacier in northern Patagonia (~46.5°S). Rates for Antarctic Peninsula glaciers are in general lower than those of temperate Patagonian glaciers. A good correlation of erosion rates and modern sea level annual temperature was found. A latitudinal decrease in millennial erosion rates is interpreted as a result of decreasing annual temperature although decreasing annual precipitation may also be a factor. However, local variability within each region might be influenced by differences in bedrock geology (e.g. Herbert Sound versus Lapeyrère and Andvord bays ) and drainage basin morphology (hypsometry, number of glaciers and length of overall calving front, topography). Particularly, the interplay between equilibrium line altitude and glacier hypsometry, which influences mass balance and glacier dynamics, seems to have a strong effect on the erosion capability of glaciers (e.g. Europa versus San Rafael and Marinelli glaciers). Erosion rates on the Antarctic Peninsula, based on the volumes of sediments delivered to the continental shelf and rise, are, for the last 9.5 Myr, between 0.07 and 0.12 mm/yr and did not vary significantly between 2.9-9.5 Ma. These values are similar to those obtained for millennial scale (Holocene) erosion rates at Andvord and Lapeyrère bays, suggesting that long-term erosion rates have not varied significantly in this region through geologic time. In addition, old (Miocene and older) thermochronology ages have been obtained for the Antarctic Peninsula. Thus, we suggest that long-term glacial cover in cold regions hinders erosion, preserving morphological features and allowing mountain growth through tectonic processes.

  13. Partition Equilibrium

    NASA Astrophysics Data System (ADS)

    Feldman, Michal; Tennenholtz, Moshe

    We introduce partition equilibrium and study its existence in resource selection games (RSG). In partition equilibrium the agents are partitioned into coalitions, and only deviations by the prescribed coalitions are considered. This is in difference to the classical concept of strong equilibrium according to which any subset of the agents may deviate. In resource selection games, each agent selects a resource from a set of resources, and its payoff is an increasing (or non-decreasing) function of the number of agents selecting its resource. While it has been shown that strong equilibrium exists in resource selection games, these games do not possess super-strong equilibrium, in which a fruitful deviation benefits at least one deviator without hurting any other deviator, even in the case of two identical resources with increasing cost functions. Similarly, strong equilibrium does not exist for that restricted two identical resources setting when the game is played repeatedly. We prove that for any given partition there exists a super-strong equilibrium for resource selection games of identical resources with increasing cost functions; we also show similar existence results for a variety of other classes of resource selection games. For the case of repeated games we identify partitions that guarantee the existence of strong equilibrium. Together, our work introduces a natural concept, which turns out to lead to positive and applicable results in one of the basic domains studied in the literature.

  14. 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.

  15. 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.

  16. 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 along an adverse slope, ice thickening, and ablation of the ice surface such that the ratio of the angle of the adverse slope to ice surface slope oscillates around the supercooling threshold.

  17. 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. Atlas of Paleoclimate and Paleoenvironments of the Northern Hemisphere: Late Pleistocene - Holocene. Geogr. Res. Institute, G. Fischer Verlag, Budapest-Stuttgart.

  18. 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

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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.

  1. 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.

  2. Transition of flow regime along a marine-terminating outlet glacier in East Antarctica

    NASA Astrophysics Data System (ADS)

    Callens, D.; Matsuoka, K.; Steinhage, D.; Smith, B.; Witrant, E.; Pattyn, F.

    2014-05-01

    We present results of a multi-methodological approach to characterize the flow regime of West Ragnhild Glacier, the widest glacier in Dronning Maud Land, Antarctica. A new airborne radar survey points to substantially thicker ice (>2000 m) than previously thought. With a discharge estimate of 13-14 Gt yr-1, West Ragnhild Glacier thus becomes of the three major outlet glaciers in Dronning Maud Land. Its bed topography is distinct between the upstream and downstream section: in the downstream section (<65 km upstream of the grounding line), the glacier overlies a wide and flat basin well below the sea level, while the upstream region is more mountainous. Spectral analysis of the bed topography also reveals this clear contrast and suggests that the downstream area is sediment covered. Furthermore, bed-returned power varies by 30 dB within 20 km near the bed flatness transition, suggesting that the water content at bed/ice interface increases over a short distance downstream, hence pointing to water-rich sediment. Ice flow speed observed in the downstream part of the glacier (~250 m yr-1) can only be explained through very low basal friction, leading to a substantial amount of basal sliding in the downstream 65 km of the glacier. All the above lines of evidence (sediment bed, wetness and basal motion) and the relatively flat grounding zone give the potential for West Ragnhild Glacier to be more sensitive to external forcing compared to other major outlet glaciers in this region, which are more stable due to their bed geometry (e.g. Shirase Glacier).

  3. 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 a total integrated system.

    Size: 60 x 56 km (37.2 x 34.7 miles) Location: 46.5 deg. North lat., 8.0 deg. East long. Orientation: North at top Image Data: ASTER bands 1,2, and 3. Original Data Resolution: 15 m Date Acquired: July 23, 2001

  4. 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.

  5. The Lateglacial to Holocene transition as recorded by glacier fluctuations

    NASA Astrophysics Data System (ADS)

    Schindelwig, I.; Akçar, N.; Kubik, P. W.; Schlüchter, C.

    2009-04-01

    Examination of glacier associated records may contribute to a better understanding of the ice-continent-ocean-atmosphere interactions, since glacial deposits related to short-term temperature fluctuations, driven by climate change, might be preserved. Surface exposure dating (SED) of such glacial deposits can improve the chronology of climate records. The western Swiss Alps repeatedly hosted mountain glaciers during the Pleistocene, and even during the Last Glacial-Interglacial transition, with abundant stadial and interstadial transitions during the Lateglacial (e.g. Björck et al. 1998). In this study, the adjacent valleys of Belalp and Great Aletsch (catchment area is generally south facing) in the western Swiss Alps are investigated. The slow responding Great Aletsch valley glacier shows only one confirmed moraine ridge related to the Lateglacial (Egesen stadial) (Kelly et al. 2004). However, the rather fast responding Unnerbäch cirque (recent) glacier at the Belalp (a similarly exposed - and tributary - valley to the Great Aletsch valley), features 6 individual lateral-terminal moraine ridges related to Lateglacial and early Holocene times. In the Belalp valley, 22 erratic boulders from four out of six well-preserved moraines were sampled in order to establish a detailed chronological framework. From the Great Aletsch valley four samples (boulder and ice moulded bedrock) of the lateral moraine were collected for SED. Our 10Be exposure dates suggest a stabilization of the Great Aletsch moraine related to the Egesen advance in the beginning of the Younger Dryas, assuming that the ages of the oldest erratic boulders on a single moraine ridge are representative for the time of moraine stabilization (Putkonen & Swanson, 2003). According to our investigations on the right-lateral moraine and the dataset (recalculated from Kelly et al. 2004) for the left-lateral moraine, the Egesen stadial is the first preserved re-advance after the last deglaciation. In contrast, the glacier at the Belalp shows multiple advances during the Lateglacial to early Holocene. 10Be exposure age data suggest that the outer moraine ridge can be an advance older than the Egesen stadial and younger than the LGM. This is in concert with other Younger Dryas related glacial landsystems in Switzerland (reviewing the outer moraine ages e.g. Julier Pass, Ivy-Ochs et al. 1996, 2008). A large number of Lateglacial moraines have been identified and relative correlations on the basis of elevation, equilibrium line altitude (Gross et al. 1977; Maisch, 1987) and morphological characteristics have been established. Nevertheless, it remains important to refine the absolute chronology in order to put further temporal constraints on these relative frameworks. This allows the allocation of such absolutely dated deposits to distinguished cold phases (Preboreal oscillation, Younger Dryas, Aegelsee oscillation) thus underlining their potential significance in the context of regional, as well as global Lateglacial climate conditions. The 10Be exposure ages from an inner moraine ridge are in a good agreement with the recalculated previously published 10Be exposure ages from the Egesen moraines in the Alps. This suggests a synchronicity of the Egesen stadial in the European Alps at the end of the Younger Dryas cold phase. REFERENCES Björck, S., Walker, M. J.C., Cwynar, L.C., Johnson, S., Knudsen, K-L., Lowe, J. J. & Wohlfarth, B. (1998): An event stratigraphy for the Last Termination in the North Atlantic region based on the Greenland ice-core record: a proposal by the INTIMATE group. Journal of Quarternary Science, 13, 283-292. Gross, G., Kerschner, H. & Patzelt, G. (1977): Methodische Untersuchungen über die Schneegrenze in alpinen Gletschergebieten. Zeitschrift für Gletscherkunde und Glazialgeologie, 12, 223-251. Ivy-Ochs, S., Kerschner, H., Reuther, A., Preusser, F., Heine, K., Maisch, M., Kubik, P.W. & Schlüchter, C. (2008): Chronology of the last glacial cycle in the European Alps. Journal of Quaternary Science, 23, 559-573. Ivy-Ochs, S., Schlüchter, C., Kubik, P. W., Synal, H.-A., Beer, J., Kerschner, H. (1996): The exposure age of an Egesen moraine at Julier Pass, Switzerland, measured with the cosmogenic radionuclides 10Be, 26Al and 36Cl. Eclogae geol. Helv., 89, 1049-1063. Kelly, M.A., Kubik, P.W., von Blanckenburg, F. & Schlüchter, C. (2004): Surface exposure dating of the Great Aletsch Glacier Egesen moraine system, western Swiss Alps, using the cosmogenic nuclide 10Be. Journal of Quarternary Science, 19, 431-441. Maisch, M. (1987): Zur Gletschergeschichte des alpinen Spätglazials: Analyse und Interpretation von Schneegrenzdaten. Geographica Helvetica, 42, 63-71. Putkonen, J. & Swanson, T. (2003): Accuracy of cosmogenic ages for moraines. Quarternary Research, 59, 255-261.

  6. 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.

  7. 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 thickness of 36 ± 11 m was calculated for 1998. Comparisons with geophysical surveys (13 GPR profiles) revealed that ice thickness is mostly within the ± 30 % model uncertainty range and locations of potential future lakes are robust. Future work will focus on further model validation and optimization. References: Geilhausen, M., Morche, D., Otto, J.-C. & L. Schrott (2013): Sediment discharge from the proglacial zone of a retreating Alpine glacier (Obersulzbachkees, Hohe Tauern, Austria). Zeitschrift für Geomorphologie Vol. 57, Suppl. 2:29-53. Linsbauer, A., Paul, F. & Haeberli, W. (2012): Modeling glacier thickness distribution and bed topography over entire mountain ranges with GlabTop: Application of a fast and robust approach. J. Geophys. Res. 117. F03007, doi:10.1029/2011JF002313.

  8. 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

  9. 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 tidewater glaciers. The work presented discusses preliminary satellite observations of concurrent changes in the North Water and Nares Strait polynyas and neighbouring tidewater glaciers in Greenland and the Canadian Arctic where notable thinning and acceleration of glaciers have been observed. Also included is an outline of how these observations will fit into a much wider project on the topic involving ocean, atmosphere and sea ice modelling and short-term and longer-term in-situ measurements.

  10. Snow line altitude evolution in the Franco-Italian Alps over the 1984-2010 period reconstructed using optical remote sensing images

    NASA Astrophysics Data System (ADS)

    Rabatel, A.; Dedieu, J.; Letréguilly, A.; Thibert, E.; Six, D.; Vincent, C.

    2011-12-01

    For mid-latitude mountain glaciers, the snow line altitude (SLA) at the end of the hydrological year is a good indicator of the equilibrium line altitude and thus of the annual mass balance. This enables SLA evolution to be reconstructed for long time periods from remote sensing data, as the snow line is generally easy to identify using aerial photographs and satellite images. Consequently, this enables researchers to study the climate-glacier relationship at the massif scale, particularly in remote areas where no direct measurements are available. In this study, we present series of reconstructed SLA for approximately 50 glaciers in the Franco-Italian Alps over the period 1984-2010. More than 130 images have been used, registred by the following satellites: Landsat 4TM, 5TM, 7 ETM+, SPOT 1 to 5 and ASTER, with spatial resolutions ranging between 2.5 and 30 m. To facilitate the identification of the snow line on the Landsat and SPOT-ASTER images, we used a combination of the spectral bands 542 and 431, respectively, with radiometric thresholds for bands 2, 4 and 1, 3. On each image, the snow line has been manually delineated. Its average altitude has been calculated for only the central part of the glaciers to avoid border effects on the glacier banks, which could generate snow line position dependence on local conditions (shadows from surrounding slopes, additional snow input by avalanches or due to wind drift). A comparison between SLA time-series and in-situ measurements of glacier mass balance was set for three French glaciers where direct mass balance measurements are available over the whole time-period (Argentière, Saint Sorlin and Gébroulaz glaciers). Results show high correlation (0.74 < r2 < 0.98, p < 0.01, n = 27), underlying the quality of the SLA dataset and strenghtening the interest of the SLA as a key indicator of the climate-glacier relationship. Considering the complete time period, the average SLA of the studied glaciers has increased by about 160 m (ranging between 0 and 380 m depending of the glacier). However, this increase is in the range of the interannual variability (±112 m). Considering each glacier individually, a meridional effect appears; the SLA is about 100 m higher for the glaciers located in the southern sector of the study area (i.e. the Ecrins Massif at 44°50' N), than for the those located in the nothern sector (i.e. the Mont Blanc Massif at 45°55' N). Considering summer temperatures and winter accumulation, this observation can be attributed to warmer and drier conditions in the southern Alps. However, this meridional effect does not affect the evolution of SLA over the study period. Exposure appears to be the most important factor controlling the SLA evolution, with glaciers exposed to the East experiencing the most important SLA increase. Finally, we present a preliminary study regarding the sensitivity of the SLA to both winter accumulation and summer temperatures.

  11. Lake Trout Sampling in Glacier National Park

    Montana Cooperative Fishery Research Unit – Sean Townsend paddles across Kintla Lake in Glacier National Park, sampling for invasive lake trout. Native bull trout are negatively affected by invasives such as lake trout and runoff from upstream glaciers....

  12. 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

  13. 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 research in mountain biosphere reserves.

  14. Glacier Mass Balance measurements in Bhutan

    NASA Astrophysics Data System (ADS)

    Jackson, Miriam; Tenzin, Sangay; Tashi, Tshering

    2014-05-01

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

  15. Mountain glaciers caught on camera

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2011-12-01

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

  16. Flow velocities of Alaskan glaciers.

    PubMed

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

    2013-01-01

    Our poor understanding of tidewater glacier dynamics remains the primary source of uncertainty in sea level rise projections. On the ice sheets, mass lost from tidewater calving exceeds the amount lost from surface melting. In Alaska, the magnitude of calving mass loss remains unconstrained, yet immense calving losses have been observed. With 20% of the global new-water sea level rise coming from Alaska, partitioning of mass loss sources in Alaska is needed to improve sea level rise projections. Here we present the first regionally comprehensive map of glacier flow velocities in Central Alaska. These data reveal that the majority of the regional downstream flux is constrained to only a few coastal glaciers. We find regional calving losses are 17.1 Gt a(-1), which is equivalent to 36% of the total annual mass change throughout Central Alaska. PMID:23857302

  17. 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.

  18. Erosion by an Alpine glacier.

    PubMed

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

    2015-10-01

    Assessing the impact of glaciation on Earth's surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years. PMID:26450208

  19. Muir Glacier and Muir Inlet 1980

    This ship-deck-based August 1980 photograph of Muir Glacier and Muir Inlet, Glacier Bay National Park and Preserve, St. Elias Mountains, Alaska, shows the nearly 200-ft-high retreating tidewater end of Muir Glacier with part of its face capped by a few angular pinnacles of ice, called séracs....

  20. Longitudinal surface structures (flowstripes) on Antarctic glaciers

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  1. 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)

  2. 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.

  3. 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%.

  4. Reconstruction of mass balance of Nevado Coropuna glaciers (Southern Peru) for Late Pleistocene, Little Ice Age and the present.

    NASA Astrophysics Data System (ADS)

    Ubeda, J.; Palacios, D.

    2009-04-01

    The Nevado Coropuna volcanic complex (15th 31'S-72 ° 39 ° W) is the quaternary stratovolcano northernmost of the central volcanic zone (CVZ) in the western flank of the Central Andes (Southern Peru). This consists in four adjacent volcanic buildings that are occupied over 5.100-5.700 masl by a system of glaciers covering an area of 47 Km2 in 2007 (Ubeda et al, 2008). The maximum expansion of glaciers during the Pleistocene affected an area of ~449 Km2, dropping to altitudes around 3.600-4800 m (Ubeda et al, 2007). In this work were mapped several hundreds of moraines which constitute a record of climate change since the last glacial maximum (LGM). Current glacier system is formed by dozen of glaciers descending slope down in all directions. Coropuna complex is an excellent laboratory for to investigate the control that climate change, tectonics and volcanism exert on the dynamics of glaciers, a scale of tens of years (by studying current glaciers) and also of tens of thousands of years (by analyzing the geomorphological evidence of its evolution in the past). Ubeda et al. (2008) analyzed the evolution of eighteen glaciers of Nevado Coropuna using indicators as surfaces and Equilibrium Line Altitudes (ELAs) of ice masses in 2007, 1986, 1955, Little the Ice Age (LIA) and Last Glacial Maximum (LGM). The glaciers were grouped into two sets: NE group (seven glaciers) and SE group (eleven glaciers). The work included statistical series of ELAs in each phase, estimates by Area x Altitud Balance Ratio (AABR) method, which was proposed by Osmaston (2005), in addition with estimates of timing (~17Cl36 Ka) and magnitude (~ 782-911 m) of ELA depression during LGM. The work included statistical series of ELAs in each phase, estimates by the method Area x Altitud Balance Ratio (AABR) proposed by Osmaston (2005), and in addition estimates of the timing (~17Cl36 Ka) and magnitude (~ 782-911 m) of ELA depression during LGM. The objective of this work is to estimate the current and past mass balance of glaciers in these phases (2007, 1986, 1955, LIA and LGM) in order to assess the current state of glaciers and deduct the regimes of temperature and precipitation for present and for LGM. To achieve this target were installed in 2007 in the gorge of Queñua Ranra (NE quadrant of Coropuna complex) four stations, that are respectively at 4886 m (E1), 5564 m (E2), 5694 (E3) m and 5822 m (E4). The stations consist of a sensor in air and one (E3) or two sensors in ground (E1). The sensors record temperature at intervals of 30 minutes (sensors 12, 13, 22 and 32) or 45 minutes (11, 21, 31 and 41), with precision of tenths of a degree Celsius (° C). The first digit of the name of the sensors referred to the station (arranged in increasing altitude) and the second at his position (eg 11-air, 12-ground and 13-deep ground, in the station E1). The records of Ta and Ts have allowed to define homogeneous data sets of 365 days (12-11-2007/11-11-2008). With these data have been calculated for each day and each sensor the average temperatures, and the minimum and maximum temperature variations and was used to estimate the vertical thermal gradient (^T/^Z) between the stations. In E1, Ta = 3.9 ° C and Ts =6.8°C. At E3, Ta=-2.9°C and Ts=1.3°C. The rain has been extrapolated from the average of the 1965-2003 series (39 years) from the station of Andahua (15 ˚ 29'36 "S-72 ˚ 20'56" W, 3587 m), 20 km to NE of the eastern summit of Coropuna, resulting in the level E1 (4886 m) a value of P = 494 mm. The availability of the temperature series has allowed develop the model of mass balance using an adaptation of the method Klein et al. (1999) developed from an earlier proposal (Kaser 1995). The method is to solve two equations. Equation 1: a=?m/Lm[(Qr+α(Ta-Ts)], where a is the value of the ablation (mm), ?m duration of ablation (days), Lm the latent heat of fusion (3.34x105J/kg), Qr heat available for melting in the form of net radiation (MJ/day/m), α a coefficient of mass transferred by heat sensitive (0864 MJ/day), and Ta and Ts air and soil temperature, respectively. Equation 2: b=c-a, where b is the mass balance (mm) and a the ablation (mm). Using the equation 1, maintaining constant Lm, and α, the values of Ta, Ts, ?m, a, c and Qr in each altitude has been estimated as follows: The values of Ta, Ts have been deducted respectively of the data from the sensors 11-31 and 12-32, using the linear temperature gradients (^T/^Z) previously deducted. c values have been deducted from the data of Andahua using the linear gradient of accumulation used by Klein et al (1999): ^c/^Z=0,1 mm/m. The values of ?m and Qr have been deducted from the value of Ta, whereas at the level Za where Ta=0, ?m=0 and Qr =0, and applying from that altitude gradients linear ^?m/^Z=0,4day/m y ^Qr/^Z=0,1°C/m (Klein et al, 1999), positive if Z>0 and negative if Z0) ELA AABBR and climate are in disequilibrium and the loss of volume, the effect of ablation, is evident across the surface of the glaciers below the level Zb=0. In gorge Santiago (Z

  5. Glacier Change of China during the Last 50 Years As Revealed By Glacier Inventories

    NASA Astrophysics Data System (ADS)

    Liu, S.; Guo, W.; Yao, X.; Xu, J.; Shangguan, D.; Wei, J.; Liu, Q.; Wang, X.; Jiang, Z.

    2014-12-01

    The study is based on a new glacier inventory derived from the recent Landsat TM/ETM+ and ASTER images and the modified first glacier inventory from topographical maps of China. Results indicate that glaciers have been generally in retreat during the late 1950s when there were available maps and ~2010, with very few glaciers in advance. The sample glaciers with two inventories covering 83% of the total area of glaciers first mapped during late 1950s and early 1980s have lost 18.1% of their total area in the past 50 years with an annual rate of -0.54%/a or -243.7 km2/a. Some small glaciers have vanished and some large glaciers have disintegrated into several small glaciers. Of all the mountains in China, glaciers in Altai, Gandise and Sawir Mountains are those with the largest area reduction, over 1/3 of the area of their glaciers in the time of first glacier inventory has disappeared, while the area reduction by 20~30% has been found for glaciers in Himalaya, Tangula, Nyainqêntanglha, Tianshan, eastern Pamir, Qilian and Hengduan Mountains. Glaciers in Karakoram, Kunlun (including Altun) and the central Tibetan Plateau are among the least decrease in area of all glaciers in China, their shrinkages are 11.3~ to 8.4%. The spatial pattern is also confirmed while expressing the area reduction of glaciers in annual percentage, i.e., glaciers of the Qangtang Plateau of the Tibetan Plateau show the smallest shrinkage with gradual increase in annual reduction rate in the surrounding mountains over the Tibetan Plateau. We have measured length changes of >1500 glaciers with a total area of 19628km2, 12.7 km2 in average. Only 53 glaciers with average area of 32.8 km2 displayed the obvious advance during the last 50 years. All glaciers with length measurements have lost 8.7% of their total area in the considered period. All advancing glaciers are mostly located in the Tianshan, eastern Pamir, Karakoram and Kunlun Mountains, with 18 glaciers in Karakoram with almost double annual rate of 17.7m/a compared to 9.6m/a of advancing glaciers in other mountains. The big glaciers might experience less area shrinkage, for example, 65 glaciers larger than 50 km2 in China have lost a total area of 577 km2, -3.8% or -0.1%/a. The general retreat of glaciers may be a result of the regional warming especially during the recent 20 years in western China.

  6. 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…

  7. Glacier sensitivity to climate change in the Nepalese Himalaya quantified using higher-order modelling

    NASA Astrophysics Data System (ADS)

    Rowan, A. V.; Egholm, D. L.; Glasser, N. F.; Quincey, D. J.

    2013-12-01

    Recent studies of glaciers in the eastern Himalaya have identified rapid changes in ice volume with small changes in climate indicating that these glaciers are highly sensitive to primary climate variables (e.g. daily variations in air temperature and monsoon precipitation). However, quantifying Himalayan glacier sensitivity to climate change is challenging due to: (1) a lack of information about how glaciological and geomorphological factors influence the balance of large debris-covered glaciers; (2) the local modification of meteorological variables by the interaction of high topography with regional atmospheric circulation systems; and (3) the simple representation of ice dynamics in many numerical glacier models which limits their usefulness in regions with steep terrain. To quantify the sensitivity of Himalayan glaciers to climate change we apply the integrated second-order shallow ice approximation (iSOSIA) [Egholm et al. 2011, Journal of Geophysical Research-Earth Surface] to large debris-covered glaciers on the southern slopes of Mt. Everest in the Khumbu Himal, Nepal. iSOSIA considers both the longitudinal and transverse stresses that drive mountain glacier flow in regions with steep terrain--a more suitable approach for Himalayan glaciers than those models based on approximations developed for shallow ice sheets. We apply iSOSIA at a 100-m resolution on a regular grid using a daily timestep to Nepalese glaciers including Khumbu, Ngozumpa and Lhotse. Our mass balance model development has focused on the dynamic representation of snow avalanching onto the glacier surfaces as this accounts for up to 75% of accumulation. We investigate Himalayan glacier sensitivities to primary climatological, glaciological and geological variables including air temperature, supraglacial debris cover, and catchment hypsometry. Furthermore, we aim to improve the representation of climate in glacier models for the Himalaya by testing a range of methods to describe these variables: (1) simple elevation-dependent rates for accumulation and ablation with empirical values for melt along a flow line beneath supraglacial debris; (2) climate-elevation relationships derived from local automatic weather stations in the Khumbu valley; and (3) 3-D surface energy balance calculations using regional meteorological data. Once we have described glacier-climate sensitivities in the Khumbu Himal, we will use these results to predict the likely magnitude and timescales of glacier mass loss under IPCC future climate change scenarios, and quantify the uncertainties associated with these predictions. Future work will consider: how glacier hydrology modifies variations in ice dynamics; how the spatial distribution of supraglacial debris modifies glacier balance sensitivity; how rock debris is transported within and on these glaciers; and how rates of rock debris delivery from hillslopes affects glacier balance and dynamics. Fieldwork in Nepal is planned for 2014 to collect data from debris-covered Khumbu Glacier with which to validate our numerical model.

  8. 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.

  9. 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. 103 colony forming units/ml) levels from John Evans Glacier and Victoria Upper Glacier. Identification of these organisms has revealed similarities to bacteria isolated previously from glacier ice and arctic and antarctic terrestrial environments. Organic acid concentrations are higher in the basal ice than in the glacier ice at John Evans Glacier and Victoria Upper Glacier. These results suggest that environmental conditions, such as overridden soil and vegetation type, influence the characteristics of DOC and that microbial cycling of OC is active in glacier systems.

  10. 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.

  11. The effect of glaciers on streamflow variations.

    USGS Publications Warehouse

    Fountain, A.G.; Tangborn, W.V.

    1985-01-01

    The effect of temperate glaciers on runoff variations is examined for the North Cascade Mountains of Washington State. An algorithm is presented that calculates the coefficient of variation of runoff for any arbitrary glacier cover. The results suggest that a minimum in year-to-year variation occurs for basins about 36% glacierized. On a month-to-month basis, maximum variation occurs in July and August for basins with less than 10% glacier cover but is a minimum for basins with glacier covers greater than 30%. -from Authors

  12. Changing Climate Drives Lagging and Accelerating Glacier Responses and Accelerating Adjustments of the Hazard Regime

    NASA Astrophysics Data System (ADS)

    Kargel, Jeffrey

    2013-04-01

    It is virtually universally recognized among climate and cryospheric scientists that climate and greenhouse gas abundances are closely correlated. Disagreements mainly pertain to the fundamental triggers for large fluctuations in climate and greenhouse gases during the pre-industrial era, and exactly how coupling is achieved amongst the dynamic solid Earth, the Sun, orbital and rotational dynamics, greenhouse gas abundances, and climate. Also unsettled is the climate sensitivity defined as the absolute linkage between the magnitude of climate warming/cooling and greenhouse gas increase/decrease. Important questions concern lagging responses (either greenhouse gases lagging climate fluctuations, or vice versa) and the causes of the lags. In terms of glacier and ice sheet responses to climate change, there also exist several processes causing lagging responses to climate change inputs. The simplest parameterization giving a glacier's lagging response time, τ, is that given by Jóhanneson et al. (1989), modified slightly here as τ = b/h, where b is a measure of ablation rate and h is a measure of glacier thickness. The exact definitions of τ, b, and h are subject to some interpretive license, but for a back-of-the-envelope approximation, we may take b as the magnitude of the mean ablation rate over the whole ablation area, and h as the mean glacier thickness in the glacier ablation zone. τ remains a bit ambiguous but may be considered as an exponential time scale for a decreasing response of b to a climatic step change. For some climate changes, b and h can be taken as the values prior to the climate change, but for large climatic shifts, this parameterization must be iterated. The actual response of a glacier at any time is the sum of exponentially decreasing responses from past changes. (Several aspects of glacier dynamics cause various glacier responses to differ from this idealized glacier-response theory.) Some important details relating to the retreat (or advances) of glaciers due to historic and future anthropogenic and longer term climate change relate to a changing glacier hazard regime. Climate change is connected to changes in the geographic distribution and magnitudes of potentially hazardous glacier lakes, large rock and ice avalanches, ice-dammed rivers, and surges. I shall consider these changes in hazard environment in relation to response-time theory and dynamical divergences from idealized response-time theory. Case histories of certain hazard-prone regions, including developments in fast-response-type glaciers and slow-response glaciers and ice sheets will also be discussed. In short, there will be a strong tendency of the hazard regimes of glacierized regions to shift far more rapidly in the 21st century than they did in the 20th century. The magnitude of the shifts will be more dramatic than any simple linear scaling to climate warming would suggest; this is largely because, due to lagging responses, glaciers are still trying to catch up to a new equilibrium for 20th century climate, while climate change remains a moving target that will drive accelerating glacier responses (including responses in hazard environments) in most glacierized regions.

  13. 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 decreasing influence of snow and glacier melt water (cold and little conductive) and an increasing contribution of non-glacierized areas moving downstream. Stream water shows a strong daily variability in isotopic composition and EC correlated well with discharge and air temperature, suggesting the relevant contribution of meltwater on runoff. Moreover, a seasonal trend is also observable in stream water and groundwater, with the most isotopically enriched and highest EC values found at low flow conditions (no melting periods), in early spring and late autumn. In agreement with these observations, end-member mixing analysis shows that summer precipitation plays a minor role on runoff temporal variability compared to glacier melt and snowmelt. Two- and three-component hydrograph separation for the summer melt-runoff events confirms the significant contribution of melting-event water (up to 73% for the upper station) and the importance of snowmelt and glacier melt (up to 37% and 28%, respectively) as water sources for streamflow at the daily scale in the study catchment. These results underline the critical role played by meltwater stored in glaciers and snow on water availability in mountain regions. Moreover, this works reveals the usefulness of a multi-tracer approach for the analysis of the main contributors to streamflow in glacierized catchments. Keywords: water stable isotopes, deuterium excess, electrical conductivity, snowmelt, glacier melt.

  14. Spatially heterogeneous wastage of Himalayan glaciers

    PubMed Central

    Fujita, Koji; Nuimura, Takayuki

    2011-01-01

    We describe volumetric changes in three benchmark glaciers in the Nepal Himalayas on which observations have been made since the 1970s. Compared with the global mean of glacier mass balance, the Himalayan glaciers showed rapid wastage in the 1970s–1990s, but similar wastage in the last decade. In the last decade, a glacier in an arid climate showed negative but suppressed mass balance compared with the period 1970s–1990s, whereas two glaciers in a humid climate showed accelerated wastage. A mass balance model with downscaled gridded datasets depicts the fate of the observed glaciers. We also show a spatially heterogeneous distribution of glacier wastage in the Asian highlands, even under the present-day climate warming. PMID:21808042

  15. 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.

  16. 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.

  17. 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.

  18. UV - GLACIER NATIONAL PARK MT

    EPA Science Inventory

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

  19. 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.

  20. Linking modern glaciological data to early Holocene glaciers: The scaling problem

    NASA Astrophysics Data System (ADS)

    Fischer, Andrea

    2015-04-01

    Modern directly measured glaciological comprise more than 50 years now and are complemented by additional 125 years of length change records and 200 years of instrumental climate data. The direct mass balance data comprises a number of ablation and accumulation measurements at a few percentage of today's Alpine glaciers, revealing today's linkage of meteorological parameters to mass balance. The length records cover a higher percentage of glaciers and are much longer than mass balance data, but still show a general glacier retreat. Early instrumental data is not available in the vicinity of glaciers, and is biased towards lower elevations. Despite of those limitations, a number of empirical and theoretical models of the glacier-climate interaction have been developed which can be applied to relate glacier stages from the last glacial maximum (LGM) onwards to specific climatic conditions. Independent from the specific model, a number of basic principles as well as unknown boundary conditions leave room for a large bandwidth of possible climatic interpretations. To be able to quantify at least the magnitude of this bandwidth, from the basic principles of glacier-climate interaction the path dependence and the spatial and temporal scale problem have to be taken into account, as well as the idea of non-equilibrium states causing moraines. From today's models, the boundary conditions of cloud cover and surface texture (and thus radiative balance) as well as unknown thermal and basal properties of the ice might play an important role. These factors are illustrated and quantified by long time series of the Austrian Alps. Changes of these parameters are often neglected also in numerical modelling of today's glaciers. Nevertheless, today's field data in combination with simple models allow a first rough estimate of possible uncertainties in interpretation of previous climatic conditions. Much longer, but nevertheless important to keep in mind, remains although the list of open questions.

  1. Mass loss and imbalance of glaciers along the Andes Cordillera to the sub-Antarctic islands

    NASA Astrophysics Data System (ADS)

    Mernild, Sebastian H.; Beckerman, Andrew P.; Yde, Jacob C.; Hanna, Edward; Malmros, Jeppe K.; Wilson, Ryan; Zemp, Micheal

    2015-10-01

    Here, we examine available glacier mass-balance records between 1993 and 2012 for Andes Cordillera, South America (6.5°N-45.8°S), and the sub-Antarctic islands around the northern tip of the Antarctic Peninsula (62.7°S-63.8°S) to determine their recent mass loss and imbalance with the present climate. The mean annual observed mass-balance Ba changed from - 620 ± 390 (1993-2002) to - 740 ± 240 kg m- 2 yr- 1 (2003-2012) and for this past decade showed a decrease in Ba from south to north. These glaciers had a mean accumulation area ratio of 0.42, which is below the AAR value for glaciers in equilibrium, reflecting mean area and volume imbalances of 23% and 27%, respectively. Glaciers in the northern part of Andes Cordillera are most out of balance with the present climate (33%), while glaciers on the sub-Antarctic islands are only slightly out of balance (4%). We identified a spatiotemporal cycle of Ba that distinguishes glaciers on the sub-Antarctic islands from glaciers in the Andes using an Empirical Orthogonal Function analysis. This analysis also revealed that South America should be divided into three individual glacier regions, and not two regions as earlier stated. Overall, the spatiotemporal cycles identified correlate to the multivariate El Niño Southern Oscillation Index instantaneously (zero-year lag-time) and to the Pacific Decadal Oscillation with an approximately eight-year lag-time.

  2. Hasty retreat of glaciers in northern Patagonia

    NASA Astrophysics Data System (ADS)

    Paul, Frank; Mölg, Nico

    2014-05-01

    Mapping glacier extent from optical satellite data has become a most efficient tool to create or update glacier inventories and determine glacier changes over time. A most valuable archive in this regard is the nearly 30-year time series of Landsat Thematic Mapper (TM) data that is freely available (already orthorectified) for most regions in the world from the USGS. One region with a most dramatic glacier shrinkage and a missing systematic assessment of changes, is the Palena province in Chile, located south of Puerto Montt in northern Patagonia. A major bottleneck for accurate determination of glacier changes in this region is related to the huge amounts of snow falling in this very maritime region, hiding the perimeter of glaciers throughout the year. Consequently, we found only three years with Landsat scenes that can be used to map glacier extent through time. We here present the results of a glacier change analysis from six Landsat scenes (path-rows 232-89/90) acquired in 1985, 2000 and 2011 covering the Palena district in Chile and neighbouring regions. Clean glacier ice was mapped automatically with a standard technique (TM3/TM band ratio) and manual editing was applied to remove wrongly classified lakes and to add debris-covered glacier parts. The digital elevation model (DEM) from ASTER (GDEM2) was used to derive drainage divides, determine glacier specific topographic parameters, and analyse the area changes in regard to topography. The scene from the year 2000 has the best snow conditions and was used to eliminate seasonal snow in the other two scenes by digital combination of the binary glacier masks and neighbourhood analysis. The derived mean relative area loss over the entire study area is 25%, showing a large spatial variability and a strong dependence on elevation. While small mountain glaciers at high elevations and steep slopes show only little change over the 26-year period, ice at low elevations from large valley glaciers shows a dramatic decline (area and thickness loss). Some glaciers retreated more than 3 km over this time period or even disappeared completely. Typically, these glaciers lost contact to the accumulation areas of tributaries and melted away as dead ice. Furthermore, numerous proglacial lakes formed or expanded rapidly, increasing the local hazard potential. On the other hand, some glaciers located on or near to (still active) volcanoes have also slightly advanced over the same time period. Observed trends in temperature (decreasing) are in contrast to the observed strong glacier shrinkage, indicating that also other factors must play a role.

  3. 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.

  4. The calving glaciers of southern South America

    NASA Astrophysics Data System (ADS)

    Warren, Charles; Aniya, Masamu

    1999-10-01

    Calving glaciers constitute a great majority of all glaciers in Patagonia and Tierra del Fuego, and are dynamically important elements of the southern South American icefields. Large numbers of tidewater glaciers calve into the Chilean fjords, and many outlet glaciers terminate in proglacial lakes. Most probably, all are temperate and grounded, with steep mass balance gradients. A majority of these glaciers remained largely unknown to science until very recently. This paper reviews recent research in the region in the context of glaciological and Quaternary debates, and discusses current understanding and uncertainties. During the 20th century most glaciers have retreated, but the particular dynamics of calving glaciers have produced some striking exceptions to this regional trend, producing sustained advances (e.g., Glaciar Pio XI, Glaciar Perito Moreno), accelerated retreats (e.g., Glaciar O'Higgins, Glaciar Marinelli), and long-maintained stillstands of glaciers with very high accumulation area ratios (e.g., Glaciar Calvo). The relative importance of climatic, topographic, and glaciodynamic controls on regional patterns of glacier fluctuation remain an enigma, especially in the Cordillera Darwin, but space-borne radar imagery is now yielding much information. Key research themes in recent years include: (1) glacier inventory work using remotely-sensed data; (2) calving rates and calving dynamics, particularly the contrast between calving rates in tidewater and freshwater; (3) glacier/climate relationships, both in historic and longer timeframes; and (4) geographic contrasts in glacier behaviour, especially the relative significance of precipitation and temperature for glacier mass balance in this region of steep climatic gradients. Many intriguing and important questions cannot presently be resolved due to the paucity of mass balance and climatic data, but current research is yielding data that have regional, interhemispheric and theoretical significance.

  5. Assessing Geometric Controls on Tidewater Glacier Sensitivity to Frontal Perturbations Using a Numerical Ice Flow Model

    NASA Astrophysics Data System (ADS)

    McFadden, E. M.; Howat, I. M.

    2010-12-01

    Marine-terminating glaciers worldwide have undergone rapid changes in their dynamics in response to external forcing. Observations from the Greenland coast, however, reveal that outlet glaciers in close proximity to each other, likely sharing a similar external forcing, can exhibit dramatically different behavior. These behavioral differences may result from differences in glacier shape, such as the presence of basal overdeepenings and lateral constrictions near the terminus. Understanding how shape influences glacier response to forcing at the terminus is critical for predicting future change. The dependence of ice flow on shape is non-linear and complex and, therefore, best examined using numerical methods. We employ a numerical ice flow model to investigate how the shape of marine-terminating glaciers (i.e. basal topography, thickness and width) influences the dynamic response to perturbations in the stress boundary condition at the front caused by front retreat and thinning. Governing model equations are compiled from various numerical models derived for a lightly grounded outlet glaciers, grounded retreat through basal over-deepenings, and calving of marine-terminating outlet glaciers. The model is designed for tidewater glaciers confined to narrow channels so that the stress balance components consist of substantial longitudinal and lateral stresses in addition to basal drag. Emphasis is placed on conditions at the grounding zone, as it is particularly sensitive to changes in basal drag and longitudinal stress. The effect of ice softening at the shear margins as a result of glacial acceleration is also considered. Boundary conditions at the front are categorized by two different calving criteria: (1) the buoyancy stress criterion prescribed by Durand et al. (2009), and (2) the modified flotation criterion derived by Vieli et al. (2001). The model is applied to a range of glacier bed and width geometries and perturbed from steady state by prescribing increased longitudinal stress at the ice/water boundary. Results from our model are compared to recent glaciological observations to determine if an ice-flow numerical model with simplified geometry can reasonably describe observed glacier dynamics. Durand, G., O. Gagliardini, B. de Fleurian, T. Zwinger, and E. Le Meur (2009), Marine ice sheet dynamics: Hysteresis and neutral equilibrium, Journal of Geophysical Research, 114(F03009), doi: 10.1029/2008JF001170. Vieli, A., M. Funk, and H. Blatter (2001), Flow dynamics of tidewater glaciers: a numerical modelling approach, Journal of Glaciology, 47(159), 595-606.

  6. Effect of near-terminus subglacial hydrology on tidewater glacier submarine melt rates

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Submarine melting of Greenlandic tidewater glacier termini is proposed as a possible mechanism driving their recent thinning and retreat. We use a general circulation model, MITgcm, to simulate water circulation driven by subglacial discharge at the terminus of an idealized tidewater glacier. We vary the spatial distribution of subglacial discharge emerging at the grounding line of the glacier and examine the effect on submarine melt volume and distribution. We find that subglacial hydrology exerts an important control on submarine melting; under certain conditions a distributed system can induce a factor 5 more melt than a channelized system, with plumes from a single channel inducing melt over only a localized area. Subglacial hydrology also controls the spatial distribution of melt, which has the potential to control terminus morphology and calving style. Our results highlight the need to constrain near-terminus subglacial hydrology at tidewater glaciers if we are to represent ocean forcing accurately.

  7. 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

  8. 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, suggesting that small glaciers efficiently limit topography. The situation in the Lost River Range is less clear as a glacial signature is not apparent in either slope-elevation profiles or the hypsometry. In the rapidly uplifting Teton Range, the distribution of ELAs appears superficially to correspond to maximum topography, hypsometry, and slope-elevations profiles, with regression lines on maximum elevations offset by ~ 700 and ~ 350 m from the LGM and mean Quaternary ELA respectively. However, Grand Teton and Mt. Moran represent high-elevation "Teflon Peaks" that appear impervious to glacial erosion, formed in the hard crystalline bedrock at the core of the range. Glacier size and drainage density, rock uplift rate, and bedrock lithology are all important considerations when assessing the ability of glaciers to limit mountain range topography. In the northern Basin and Range, it is only under exceptional circumstances in the Teton Range that small glaciers appear to be incapable of imposing a fully efficient glacial buzzsaw, emphasising that high peaks represent an important caveat to the glacial buzzsaw hypothesis.

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

    NASA Astrophysics Data System (ADS)

    Monnier, S.; Kinnard, C.

    2012-04-01

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

  10. Impact of monsoonal rainfall on specific mass balance in ablation zone of Chhota Shigri Glacier in 2008, Himachal Pradesh, India

    NASA Astrophysics Data System (ADS)

    Sharma, P.; Ramanathan, A.; Linda, A.; Wagnon, P.; Arnod, Y.; Jose, P. G.; Chevallier, P.

    2009-04-01

    The Mass Balance of the Chhota Shigri glacier (32.2°N, 77.5°E; 15.7 km2, 4050 to 6263m a.m.s.l., 9 km long) located in Lahaul and Spiti valley, Himachal Pradesh, India has been monitored from 2002 to 2008 using glaciological method. In 2008, an additional field survey during 3- 10th August was undertaken to understand the impact of monsoonal rainfall on specific mass balance at various points on the ablation zone of this glacier that is alternatively influenced by the Indian monsoon and the mid-latitude westerlies. Specific Annual Mass Balance is negative (0.93 mweq), Equilibrium Line Altitude (ELA) is 5120m and Accumulation Area Ratio (AAR) is 38% in the 2007-08 hydrological year. In 2008 data obtained from nearest Weather station at Keylong show that the monsoon hit the Spiti valley in the middle of June (15 days earlier than normal date ) .The results reveal that 70% of total specific mass balance occurred by the first week of August indicating that most of the melting occurred in the first half of ablation season, dominated by monsoonal rainfall. The rainfall may accelerate ablation rate by supplying ( heat ) energy even it is very low and exposing bare dirty ice thereby decreasing albedo. In part A of the glacier, the mean vertical gradient of ablation up to August 08 is 0.67 m w.e. 100 m-1 between 4350 and 4850 m a.s.l., (area free of debris) and for part B, it is 0.41 m w.e. 100 m-1 between 4600m a.s.l. and 5000m a.s.l. From August 08 up to 1st week of October, mean vertical gradient of the ablation for part A is 0.54m w.e. 100 m-1 and it is 0.61 m w.e. 100 m-1 in part B for the same altitude ranges. Below 4350m a.s.l. the whole glacier is covered by debris and the melting rate is significantly reduced. Overall, ablation rate is influenced by rainfall, incoming solar radiation and debris cover.

  11. 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 setting of active deformation and by the feedback between shortening and uplift, glacial erosion, and orographic effects on climate accompanying mountain building.

  12. Mapping Svalbard Glaciers with the Cryowing Uas

    NASA Astrophysics Data System (ADS)

    Solbø, S.; Storvold, R.

    2013-08-01

    The remoteness of most Svalbard glaciers makes it difficult to perform regular in situ monitoring, especially in the melting season. Terminus areas (into the sea) and crevassed areas are in practice only accessible from the air. In this paper, first investigations on the feasibility of UAS based 3D measurements of glacier elevation is performed. The results show that UAS can be a valuable tool for glacier measurements in remote areas like Svalbard, where the only real alternative to measure glacier elevation in the ablation zone during the melt season is by manned aircraft. Imagery from repeated observations within a few days can be used to estimate dynamic mass loss rates when coupled to 3D modeling and feature tracking. Retrieval of these data is valuable, especially for glaciers terminating in the sea and surging glaciers.

  13. Nitrogen fixation on Arctic glaciers, Svalbard

    NASA Astrophysics Data System (ADS)

    Telling, Jon; Anesio, Alexandre M.; Tranter, Martyn; Irvine-Fynn, Tristram; Hodson, Andy; Butler, Catriona; Wadham, Jemma

    2011-09-01

    Glacier surfaces contain a wide diversity of microorganisms and can host a range of microbial activities. However, microbial nutrient cycling on glaciers is poorly understood. This study is the first to document nitrogen fixation (nitrogenase activity) on glaciers and demonstrate its importance in supporting microbial growth. Rates of nitrogen fixation (nitrogenase activity) in cryoconite holes on three valley glaciers in Svalbard ranged from <2.0 to 99.9 ?mol ethylene m-2 d-1 with rates inversely correlated to concentrations of available inorganic nitrogen. Annual inputs of nitrogen by nitrogen fixation on a glacier catchment scale are more than 2 orders of magnitude lower than the combined nitrogen inputs from snowmelt and rain. However, nitrogen fixation can be important for supporting microbial growth on the glaciers during the middle to late melt season after the snowline has retreated upslope.

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

    NASA Astrophysics Data System (ADS)

    Trussel, Barbara Lea

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

  15. Monitoring of High Mountain Glaciers in the Vicinity of Everest (Himalaya) using Remote Sensing Capability

    NASA Astrophysics Data System (ADS)

    Thakuri, S.; Salerno, F.; Bolch, T.; Smiraglia, C.; Tartari, G.

    2014-12-01

    Himalayan glaciers are of crucial interest due to their role in the cryospheric system and hydrology. This contribution examines glacier changes between 1960s and 2013 using satellite data. The study is focused in 3 basins in Nepal: Upper Sun Koshi (USKB; 2850 km2), Dudh Koshi (DKB; 3720 km2), and Tamor (TB; 5875 km2). We observed an overall glacier surface loss of 0.19 ± 0.26 % a-1 (146.1 to 136.9 km2) in SKB for 1975-2013 period; 0.27 ± 0.06 % a-1 (404.6 to 351.8 km2) in the DKB for 1962-2011, and 8.4% (0.25 ± 0.29 % a-1; 610.9 to 559.3 km2) in the TB for 1975-2009 period. In the DKB, we observed an upward shift of snow-line altitude (ΔSLA) by more than 180 m, a terminus retreat of on average ~ 400 m, and an increase of 17.6 ± 3.1% in debris coverage between 1962 and 2011. Moreover, we observed that (i) glaciers with increased debris cover have experienced a reduced termini retreat; (ii) negative mass balances (i.e., ΔSLA) induce increases of debris coverage; (iii) slight, but statistically insignificant acceleration of the surface area loss since early 1990s; but a significant loss for the largest glaciers (>10 km2) that have accumulation zones at higher elevations and along the preferable south-north direction of the monsoon; (iv) a significant ΔSLA; moreover, the largest glaciers present median ΔSLA that are nearly double than that of the smallest; this finding leads to a hypothesis that these glaciers are shrinking, not only due to warming temperatures, but also as a result of decreasing precipitation due to a weakening Asian monsoons registered over the last few decades. Furthermore, we present first results on the geodetic glacier mass and velocity changes of selected glaciers, and climatic trends. In fact, less accumulation due to the observed decrease of precipitation should cause lower glacier flow velocity until to the ice stagnation of tongues as observed by other previous studies in the region. Finally, we compared our findings with other studies in the high mountain Asia and conclude that the shrinkage of these glaciers are less than that of western and eastern Himalaya, and southern and eastern Tibetan Plateau. The location in higher elevations have likely reduced the impact of warming on these glaciers, but have not been excluded from a relentlessly continuous and slow recession process over the past 50 yrs.

  16. 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

  17. 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

  18. 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.

  19. Helical axis stellarator equilibrium model

    SciTech Connect

    Koniges, A.E.; Johnson, J.L.

    1985-10-01

    An asymptotic model is developed to study magnetohydrodynamic equilibria in toroidal systems with a helical magnetic axis. Using a characteristic coordinate system based on the vacuum field lines, the equilibrium problem is reduced to a two-dimensional generalized partial differential equation of the Grad--Shafranov type. A stellarator-expansion free-boundary equilibrium code is modified to solve the helical-axis equations. The expansion model is used to predict the equilibrium properties of toroidal asperator devices. Numerically determined flux surfaces, magnetic well, transform, and shear are presented. The equilibria show a toroidal Shafranov shift.

  20. Helical axis stellarator equilibrium model

    SciTech Connect

    Koniges, A.E.; Johnson, J.L.

    1985-02-01

    An asymptotic model is developed to study MHD equilibria in toroidal systems with a helical magnetic axis. Using a characteristic coordinate system based on the vacuum field lines, the equilibrium problem is reduced to a two-dimensional generalized partial differential equation of the Grad-Shafranov type. A stellarator-expansion free-boundary equilibrium code is modified to solve the helical-axis equations. The expansion model is used to predict the equilibrium properties of Asperators NP-3 and NP-4. Numerically determined flux surfaces, magnetic well, transform, and shear are presented. The equilibria show a toroidal Shafranov shift.

  1. 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.

  2. 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.

  3. Numerical Simulation and Sensitivity Analysis of Subglacial Meltwater Plumes: Implications for Ocean-Glacier Coupling in Rink Isbrae, West Greenland

    NASA Astrophysics Data System (ADS)

    Carroll, D.; Sutherland, D.; Shroyer, E.; Nash, J. D.

    2014-12-01

    The rate of mass loss from the Greenland Ice Sheet quadrupled over the last two decades and may be due in part to changes in ocean heat transport to marine-terminating outlet glaciers. Meltwater commonly discharges at the grounding line in these outlet glacier fjords, generating a turbulent upwelling plume that separates from the glacier face when it reaches neutral density. This mechanism is the current paradigm for setting the magnitude of net heat transport in Greenland's glacial fjords. However, sufficient observations of meltwater plumes are not available to test the buoyancy-driven circulation hypothesis. Here, we use an ocean general circulation model (MITgcm) of the near-glacier field to investigate how plume water properties, terminal height, centerline velocity and volume transport depend on the initial conditions and numerical parameter choices in the model. These results are compared to a hydrodynamic mixing model (CORMIX), typically used in civil engineering applications. Experiments using stratification profiles from the continental shelf quantify the errors associated with using far-field observatons to initialize near-glacier plume models. The plume-scale model results are then integrated with a 3-D fjord-scale model of the Rink Isbrae glacier/fjord system in west Greenland. We find that variability in the near-glacier plume structure can strongly control the resulting fjord-scale circulation. The fjord model is forced with wind and tides to examine how oceanic and atmospheric forcing influence net heat transport to the glacier.

  4. Internationally coordinated glacier monitoring: strategy and datasets

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Internationally coordinated monitoring of long-term glacier changes provide key indicator data about global climate change and began in the year 1894 as an internationally coordinated effort to establish standardized observations. Today, world-wide monitoring of glaciers and ice caps is embedded within the Global Climate Observing System (GCOS) in support of the United Nations Framework Convention on Climate Change (UNFCCC) as an important Essential Climate Variable (ECV). The Global Terrestrial Network for Glaciers (GTN-G) was established in 1999 with the task of coordinating measurements and to ensure the continuous development and adaptation of the international strategies to the long-term needs of users in science and policy. The basic monitoring principles must be relevant, feasible, comprehensive and understandable to a wider scientific community as well as to policy makers and the general public. Data access has to be free and unrestricted, the quality of the standardized and calibrated data must be high and a combination of detailed process studies at selected field sites with global coverage by satellite remote sensing is envisaged. Recently a GTN-G Steering Committee was established to guide and advise the operational bodies responsible for the international glacier monitoring, which are the World Glacier Monitoring Service (WGMS), the US National Snow and Ice Data Center (NSIDC), and the Global Land Ice Measurements from Space (GLIMS) initiative. Several online databases containing a wealth of diverse data types having different levels of detail and global coverage provide fast access to continuously updated information on glacier fluctuation and inventory data. For world-wide inventories, data are now available through (a) the World Glacier Inventory containing tabular information of about 130,000 glaciers covering an area of around 240,000 km2, (b) the GLIMS-database containing digital outlines of around 118,000 glaciers with different time stamps and (c) the Randolph Glacier Inventory (RGI), a new and globally complete digital dataset of outlines from about 180,000 glaciers with some meta-information, which has been used for many applications relating to the IPCC AR5 report. Concerning glacier changes, a database (Fluctuations of Glaciers) exists containing information about mass balance, front variations including past reconstructed time series, geodetic changes and special events. Annual mass balance reporting contains information for about 125 glaciers with a subset of 37 glaciers with continuous observational series since 1980 or earlier. Front variation observations of around 1800 glaciers are available from most of the mountain ranges world-wide. This database was recently updated with 26 glaciers having an unprecedented dataset of length changes from from reconstructions of well-dated historical evidence going back as far as the 16th century. Geodetic observations of about 430 glaciers are available. The database is completed by a dataset containing information on special events including glacier surges, glacier lake outbursts, ice avalanches, eruptions of ice-clad volcanoes, etc. related to about 200 glaciers. A special database of glacier photographs contains 13,000 pictures from around 500 glaciers, some of them dating back to the 19th century. A key challenge is to combine and extend the traditional observations with fast evolving datasets from new technologies.

  5. 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, support the notion that temperatures during the ACR in New Zealand were ˜2-3 °C cooler than today.

  6. The effect of black carbon on reflectance of snow in the accumulation area of glaciers in the Baspa basin, Himachal Pradesh, India

    NASA Astrophysics Data System (ADS)

    Kulkarni, A. V.; Vinay Kumar, G.; Negi, H. S.; Srinivasan, J.; Satheesh, S. K.

    2013-04-01

    Himalayan glaciers are being extensively debated in scientific and public forums, as changes in their distribution can significantly affect the availability of water in many rivers originating in the region. The distribution of glaciers can be influenced by mass balance, and most of the glaciers located in the Pir Panjal and Greater Himalayan mountain ranges are losing mass at the rate of almost a meter per year. The Equilibrium Line Altitude (ELA) has also shifted upward by 400 m in the last two decades. This upward migration of ELA and the loss in mass could have been influenced by changes in temperature, precipitation and by the deposition of black carbon in the accumulation area of glaciers. The deposition of black carbon can reduce the albedo of snow in the accumulation area leading to faster melting of snow and causing more negative mass balance. In this investigation, a change in reflectance in the accumulation area of the Baspa basin is analysed for the year 2009, as the region has experienced extensive forest fires along with northern Indian biomass burning. The investigation has shown that: (1) The number of forest fires in the summer of 2009 was substantially higher than in any other year between 2001 and 2010; (2) the drop in reflectance in the visible region from April to May in the accumulation area was significantly higher in the year 2009 than in any other year from 2000 to 2012; (3) the temperature of the region was substantially lower than the freezing point during the active fire period of 2009, indicating the small influence of liquid water and grain size; (4) the drop in reflectance was observed only in the visible region, indicating role of contamination; (5) in the visible region, a mean drop in reflectance of 21± 5% was observed during the active fire period in the accumulation area. At some places, the drop was as high as 50 ± 5%. This can only be explained by the deposition of black carbon. The study suggests that a change in snow albedo in the accumulation area due to the deposition of black carbon from anthropogenic and natural causes can influence the mass balance of the glaciers in the Baspa basin, Himachal Pradesh, India.

  7. Glacier mass balances (1993-2001), Taylor Valley, McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Fountain, Andrew G.; Nylen, Thomas H.; Macclune, Karen L.; Dana, Gayle L.

    Mass balances were measured on four glaciers in Taylor Valley, Antarctica, from 1993 to 2001. We used a piecewise linear regression, which provided an objective assessment of error, to estimate the mass balance with elevation. Missing measurements were estimated from linear regressions between points and showed a significant improvement over other methods. Unlike temperate glaciers the accumulation zone of these polar glaciers accumulates mass in summer and winter and the ablation zone loses mass in both seasons. A strong spatial trend of smaller mass-balance values with distance inland (r2 = 0.80) reflects a climatic gradient to warmer air temperatures, faster wind speeds and less precipitation. Annual and seasonal mass-balance values range only several tens of millimeters in magnitude and no temporal trend is evident. The glaciers of Taylor Valley, and probably the entire McMurdo Dry Valleys, are in equilibrium with the current climate, and contrast with glacier trends elsewhere on the Antarctic Peninsula and in temperate latitudes.

  8. 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).

  9. Rapid submarine melting of the calving faces of West Greenland glaciers

    NASA Astrophysics Data System (ADS)

    Rignot, Eric; Koppes, Michele; Velicogna, Isabella

    2010-03-01

    Widespread glacier acceleration has been observed in Greenland in the past few years associated with the thinning of the lower reaches of the glaciers as they terminate in the ocean. These glaciers thin both at the surface, from warm air temperatures, and along their submerged faces in contact with warm ocean waters. Little is known about the rates of submarine melting and how they may affect glacier dynamics. Here we present measurements of ocean currents, temperature and salinity near the calving fronts of the Eqip Sermia, Kangilerngata Sermia, Sermeq Kujatdleq and Sermeq Avangnardleq glaciers in central West Greenland, as well as ice-front bathymetry and geographical positions. We calculate water-mass and heat budgets that reveal summer submarine melt rates ranging from 0.7+/-0.2 to 3.9+/-0.8md-1. These rates of submarine melting are two orders of magnitude larger than surface melt rates, but comparable to rates of iceberg discharge. We conclude that ocean waters melt a considerable, but highly variable, fraction of the calving fronts of glaciers before they disintegrate into icebergs, and suggest that submarine melting must have a profound influence on grounding-line stability and ice-flow dynamics.

  10. New Insights in the Existence of Lakes Beneath the Recovery Glacier Drainage Basin, Antarctica

    NASA Astrophysics Data System (ADS)

    Steinhage, D.; Helm, V.; Kasper, D.; Kleiner, T.; Humbert, A.

    2014-12-01

    The Recovery Glacier is draining about 8% of the East Antarctic ice sheet and feeds into the Filchner Ice Shelf. There were suggestions that the dynamics of the glacier is driven by large subglacial lakes that initiate the ice stream flow (Bell et al., 2008). As the Recovery Glacier is one of the least surveyed ice streams due to its remote location, this hypothesis could not be tested rigorously so far. In austral summer 2013/14 AWI carried out a survey of the Recovery Glacier including radio echo sounding, gravimetry, magnetics, and laser scanner. In total more than 22000 km survey lines were flown. Here we present an ice thickness map of the main trunk of the Recovery Glacier, as well as its tributaries Blackwall and Ramp glaciers. The ice thickness varies between 70 m in the vicinity of the Shackleton Range and nearly 3800 m close to the Bell lakes. Using different DEMs including one CryoSat-2 DEM (Helm et al., 2014), we determine the basal topography and the hydraulic head. We estimate the basal reflection coefficient and assess by this locations with potentially wet ice base. The distribution shows that few of the formerly proposed lakes show indeed a wet base, while others are missing clear lake like basal reflections.

  11. Daily and seasonal glacier velocity change on Kronebreen, Svalbard, as measured using FORMOSAT-2 imagery and in situ continuous GPS

    NASA Astrophysics Data System (ADS)

    Kohler, J.; Berthier, E.; Reijmer, C. H.; Nuth, C.

    2011-12-01

    Glacier response to climate change is often heralded by changes in the velocity field. Remote sensing can be used to map changes in glacier speed. Visible satellite imagery provides high resolution products in convenient to use format, but is hampered by the presence of clouds. The high-resolution (2-m pixel nominal resolution in panchromatic mode) FORMOSAT-2 satellite has a daily revisit capability, allowing programmed acquisitions to capture occasional periods with few or no clouds. Here we use FORMOSAT-2 to derive glacier-wide velocities on the lower 10 km of Kronebreen, Svalbard's fastest-moving glacier, which has peak summer season speeds of up to 2 m d^{-1}. We present FORMOSAT-derived velocity fields for the summer melt seasons of 2007 to 2011, obtained using 4-8 images, the exact number depending on the year. We also compare the data from 2009 onward to 3-hourly measurements of speed made using a number of in situ code-phase GPS units deployed at various points on the glacier tongue. The FORMOSAT-derived data have good spatial resolution and show how velocity increases start at the front of the glacier and move upstream. The GPS data have high temporal resolution and show how the glacier reacts to meltwater inputs. The GPS data are also used to verify the spatial variability of the remote-sensing data since the receivers are located along the flow line as well as on a transect across the flow line.

  12. Ground-penetrating radar observations of winter snow accumulation on Alaska Glaciers.

    NASA Astrophysics Data System (ADS)

    Gusmeroli, A.; Wolken, G. J.; Arendt, A. A.; Campbell, S. W.; O'Neel, S.; Marshall, H.

    2012-12-01

    Understanding the spatial variability of winter snow in glacierized watersheds is vital for estimating glacier changes, forecasting freshwater delivery to riverine and marine ecosystems and informing Earth loading models for studies of seasonal variations in crustal uplift. Accurately reproducing snow distribution within glacier-models still remains a challenge due to the difficulty obtaining in-situ measurements and large local or regional variability in snow thicknesses. Between March and July 2012, high frequency (200-500 MHz) Ground-Penetrating Radar (GPR) surveys designed to obtain spatially distributed measurements of snow accumulation, were collected on a number of different glaciers in south-central Alaska, USA. The surveys span a range of climatic zones including continental and maritime glaciers. Several modes of travel were employed, including helicopter-borne, snowmobile and ski-towed. Preliminary results from the Valdez Glacier suggest that the agreement between 200 MHz-GPR-derived snow-depth and 17 manually measured snow-depths is ± 10% using an estimated radar velocity of 0.22 m/ns, as one example. Additionally, GPR profiles in the accumulation areas showed firn-stratigraphy of previous summer surfaces, thus, making it possible to distinguish the elevation of the firn line and indicating that in the accumulation zone it may be possible to estimate annual net mass balance if density can be estimated. In this presentation we will illustrate the characteristics of snow accumulation on this suite of Alaska Glaciers as derived by GPR and discuss our results in terms of the usefulness and challenges associated with using GPR to determine the winter and annual mass balance of these glaciers.

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

    PubMed

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

    2014-08-22

    The ongoing global glacier retreat is affecting human societies by causing sea-level rise, changing seasonal water availability, and increasing geohazards. Melting glaciers are an icon of anthropogenic climate change. However, glacier response times are typically decades or longer, which implies that the present-day glacier retreat is a mixed response to past and current natural climate variability and current anthropogenic forcing. Here we show that only 25 ± 35% of the global glacier mass loss during the period from 1851 to 2010 is attributable to anthropogenic causes. Nevertheless, the anthropogenic signal is detectable with high confidence in glacier mass balance observations during 1991 to 2010, and the anthropogenic fraction of global glacier mass loss during that period has increased to 69 ± 24%. PMID:25123485

  14. 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

  15. Microbial biodiversity in glacier-fed streams.

    PubMed

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

    2013-08-01

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

  16. 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…

  17. Muir Glacier and Muir Inlet 2003

    This photo was taken in September 2003; in the 23 years between photographs, Muir Glacier has retreated more than a mile and ceased to have a tidewater terminus. Since 1980, Muir Glacier has thinned by more than 600 ft, permitting a view of a mountain with a summit elevation of greater than 4000 ft,...

  18. Calving at Pine Island Glacier

    NASA Astrophysics Data System (ADS)

    Humbert, A.; Wilkens, N.; Braun, M.; Floricioiu, D.; Plate, C.; Müller, R.

    2012-04-01

    The calving mechanism of tabular icebergs is one of the major unknowns in glaciology and hence calving events at locations where the glaciological variables of ice shelves or ice tongues are well known are ideal natural setups for studying these mechanisms. Pine Island Glacier, a marine based outlet glacier of the West Antarctic Ice Sheet, reaches velocities of up to 4 km/a in the vicinity of the calving front. Its floating tongue has an average thickness of about 500m. This floating tongue loses mass by strong basal melting and calving events of large tabular icebergs. In October 2011 a new 24 km long rift has formed and propagated to a length of 28km in the subsequent weeks. Since then an area of about 750km2 is suspected to calve off in the near future. We will present the temporal evolution of this well surveyed calving event using high resolution radar imagery obtained by the TerraSAR-X satellite. This includes rift length and width, as well as the changes in the flow velocities estimated using speckle tracking. Furthermore, we will discuss the changes of the shear margin and the melange area that constrains the tongue at its eastern side over the past decade. In particular, the changes at an ice rise located in the shear margin and in the vicinity of the rift will be investigated using SAR interferometry. The decline of the formerly dome-like grounded spot has contributed to a widening of the shear margin and the formation of a heterogeneous ice melange. This changes the lateral (stress) boundary condition that the floating part of the glacier experiences. Therefore, we compare the rift creation and evolution of the upcoming calving event with the one in 2007.

  19. Glacier surges past and present

    NASA Astrophysics Data System (ADS)

    Benn, D.; Kristensen, L.

    2009-04-01

    Investigations of the glacial geologic record commonly use modern analogues to underpin reconstructions of former environments. While this approach is very powerful, it is not without problems and is vulnerable to changing paradigms (or fashions) in glaciology. A well-known example is the ascendancy of the 'deforming bed' model in the 1980s and 1990s, which was subsequently challenged by the 'ploughing bed' model. These models have contrasting implications for till genesis and subglacial sediment transport, but rigorous testing is hampered by the difficulty of directly observing modern glacier beds and the lack of unambiguous diagnostic criteria for interpreting ancient tills. We address this issue by examining sediment-landform assemblages formed by surging glaciers in Svalbard. Surges leave a distinctive imprint on fjord floors, including fluted subglacial till, crevasse-fill ridges, thrust block moraines, and extensive proglacial mud flows. The latter have been interpreted as either masses of extruded subglacial till or the collapsed fronts of oversteepened thrust moraines. The 'extrusion hypothesis' implies significant subglacial sediment flux towards the margin, consistent with a metres-thick deforming layer, whereas the 'moraine failure' hypothesis implies dominantly proglacial transport. We show that both fjord-floor and terrestrial 'mud aprons' consist of masses of marine sediment which were pushed in front of the advancing glacier, while undergoing more or less continuous gravitational failure. The subaqueous moraines and mud flows are therefore interpreted as end-member glacitectonic landforms, formed by similar processes to thrust-block moraines. These results indicate highly episodic glacial sediment transport in Svalbard fjords, accomplished largely by ice-push during surges. The survival of transverse (moraine) ridges below megaflutings in some fjords suggests that subglacial sediment transport is relatively unimportant, and that the 'ploughing model' best describes the behaviour of the ice-bed interface during surges. We suggest that similar glacitectonic processes may have been important for delivering sediment to the margins of Pleistocene marine ice sheets.

  20. Scientific visualization of glacier changes for public communication: the example of Findelengletscher, Switzerland

    NASA Astrophysics Data System (ADS)

    Rastner, Philipp; Jörg, Philipp Claudio; Huss, Matthias; Zemp, Michael

    2013-04-01

    The melting of glaciers and ice caps has been recognized as one of the best natural indicators for global climate change. In Switzerland, the early onset of both glacier research and detailed mapping of the country resulted in a wealth of historical material documenting glacier changes over the past 160 years. Fife years ago, the Universities of Zurich and Fribourg, along with the Swiss energy utility Axpo, launched the Glacier Laserscanning Experiment Obervallis (GLAXPO). In this project three laserscanning flights were performed on Findelengletscher in order to create high resolution Digital Elevation Models (DEM). These DEM provide a precise mapping of the glacier surface topography and serve as reference surface for the co-registration of past DEMs computed from digitized historical maps. In addition to that distributed numerical glacier models were run with ensembles of climate change scenarios in order to calculate glacier changes over the 21st century. The present work makes use of this great data pool for a scientifically correct visualization of 3-dimensional changes of Findelengletscher from AD 1850 to 2100 for public communication. We therefore collected ten different historical maps with the earliest dating from 1862 (plane survey sheet of the Dufour map). The pre-processing included georeferencing and digitalization of contour lines for the creation of different historical DEMs. Afterwards all historical DEMs were co-registered to one of the latest high resolution laserscanning DEM (from 2005). In between years with available DEMs, surface changes were interpolated linearly to create a sequence for the computer animation. For future developments, modeled glacier elevation changes where added/subtracted from the latest DEM (from 2010). Finally, two animations, showing glacier changes from 1850-2010 and 2010-2100, were composed and rendered in the animation program Visual Nature Studio 3. In cooperation with professional booth and model builders, these animations were set up as a glacier exhibit including an interactive touchscreen, a large panoramic view of the Findelen Valley, and an additional interactive monitor providing related background information in French and German. Beginning of 2013, the glacier exhibit was launched as permanent part of the Axporama visitor center and ready for more than 10,000 public visitors a year.

  1. Englacial Drainage Systems in Himalayan Debris-covered Glaciers, and Implications for Supraglacial Lake Evolution

    NASA Astrophysics Data System (ADS)

    Benn, D.; Gulley, J.; Thompson, S. S.

    2011-12-01

    Rates of mass loss on Himalayan debris-covered glaciers are controlled by a complex web of processes, including melting below debris, melting of exposed ice, and calving around supraglacial lakes. Ablation rates around lakes are typically one to two orders of magnitude higher than beneath supraglacial debris, so the extent and lifespan of supraglacial lakes exert strong controls on rates of glacier downwasting. Using a combination of speleological observations of englacial conduits and ASTER image analysis, we show that there is a close coupling between lake evolution and englacial hydrology. Surface meltwater on Himalayan glaciers commonly drains via shallow englacial conduits, formed by the incision of surface streams that become isolated from the surface by roof closure ('cut and closure'). Cut-and-closure conduits are typically beneath less than 30 m of ice, where low rates of creep closure allow them to persist for several years even after active enlargement has ceased. How conduits affect lake life cycle depends on whether lakes are 'perched' or at 'base level'. Moraine dams at debris-covered glacier snouts determine hydrological base level for the drainage system. Lakes at elevations above the moraine dam (perched lakes) can drain when connections are made to active or relict englacial conduits, which offer lines of high hydraulic conductivity through otherwise impermeable ice. Englacial drainage of warm lake water can then cause significant conduit enlargement, roof collapse and glacier surface subsidence. Regions of subsidence, particularly where bare ice is exposed, can then act as nuclei for the formation of new supraglacial lakes. In contrast, base-level lakes cannot drain englacially. Conduits connecting with base-level lakes, however, can encourage rapid lake growth and integration, by providing lines of enhanced internal ablation. Links between englacial and supraglacial hydrology and conduit formation and collapse result in strongly non-linear mass loss of debris-covered glaciers in the Himalayas, and may be important on debris-covered glaciers in other regions.

  2. Preliminary results of a radio echo sounding survey of the Recovery Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Humbert, Angelika; Kleiner, Thomas; Steinhage, Daniel

    2014-05-01

    The Recovery Glacier is draining about 8% of the East Antarctic ice sheet and feeds into the Filchner Ice Shelf. This ice shelf might be subjected in future to increasing basal melting (Hellmer et al., 2012) forcing potentially grounding line retreat. Compared to other areas in Antarctica this glacier is been surveyed very sparse and hence does not allow modeling studies yet. As many large and small subglacial lakes are present underneath this ice stream at different locations along the flow, the question of the influence of the lakes on ice stream genesis and ice stream dynamics arose. For investigating this influence by observation and subsequent modelling, an airborne campaign of the Alfred Wegener Institute was carried out in January 2014, covering the Recovery Ice Stream and two smaller glaciers merging with it, the Ramp Glacier and the Blackwall Glacier. The radar system uses a carrier frequency of 150MHz and a 600ns pulse. The survey includes several flights along flow lines in order to assess the basal roughness of the ice stream. Here we present the first preliminary data analysis.

  3. The influence of supraglacial debris cover on glacier hydrology: Miage Glacier, Italy.

    NASA Astrophysics Data System (ADS)

    Fyffe, C. L.; Brock, B. W.; Kirkbride, M. P.; Mair, D. W. F.

    2012-04-01

    The Miage Glacier is a debris-covered glacier in the western Italian Alps. An integrated study of its hydrology, including dye tracing, glacier velocity measurements and water chemistry analysis of the proglacial stream was performed throughout the 2010 and 2011 ablation seasons. These data were used to elucidate the structure and seasonal evolution of the hydrological system. Slower and smaller streams were found to occur on the more thickly debris covered lower glacier, which gave traces indicative of an inefficient subglacial system. This may be due to the uneven topography of the lower glacier, which is characterised by small supraglacial catchments with low ablation rates. The largest streams were found draining the debris free upper glacier, and these gave faster and more peaked returns. This means that unlike on clean glaciers, the tracer velocity was faster with increasing distance up-glacier. The glacier responds dynamically to variations in meltwater input over periods of a few days at the beginning of the melt season, as well as after cooler weather in July. The delaying influence of the debris cover is highlighted in the reduced amplitude of diurnal variations in meltwater discharge, especially early in the season when the upper glacier is snow covered.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  5. 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

  6. Black soot and the survival of Tibetan glaciers.

    PubMed

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

    2009-12-29

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

  7. Accelerated wastage of the Monte Perdido Glacier in the Spanish Pyrenees during recent stationary climatic conditions

    NASA Astrophysics Data System (ADS)

    López-Moreno, J. I.; Revuelto, J.; Rico, I.; Chueca-Cía, J.; Julián, A.; Serreta, A.; Serrano, E.; Vicente-Serrano, S. M.; Azorín-Molina, C.; Alonso-González, E.; García-Ruiz, J. M.

    2015-09-01

    This paper analyzes the evolution of the Monte Perdido Glacier, the third largest glacier of the Pyrenees, from 1981 to the present. We assessed the evolution of the glacier's surface area by use of aerial photographs from 1981, 1999, and 2006, and changes in ice volume by geodetic methods with digital elevation models (DEMs) generated from topographic maps (1981 and 1999), airborne LIDAR (2010) and terrestrial laser scanning (TLS, 2011, 2012, 2013, and 2014). We interpreted the changes in the glacier based on climate data from a nearby meteorological station. The results indicate an accelerated degradation of this glacier after 2000, with a rate of ice surface loss that was almost three-times greater from 2000 to 2006 than for earlier periods, and a doubling of the rate of ice volume loss from 1999 to 2010 (the ice depth decreased 8.98 ± 1.8 m, -0.72 ± 0.14 m w.e. yr-1) compared to 1981 to 1999 (the ice depth decreased 8.35 ± 2.12 m, -0.39 ± 0.1 m w.e. yr-1). This loss of glacial ice has continued from 2011 to 2014 (the ice depth decreased 2.1 ± 0.4 m, -0.64 ± 0.36 m w.e. yr-1). Local climatic changes during the study period cannot explain the acceleration in wastage rate of this glacier, because local precipitation and snow accumulation increased slightly, and local air temperature during the ablation period did not significantly increase. The accelerated degradation of this glacier in recent years can be explained by the lack of equilibrium between the glacier and the current climatic conditions. In particular, the average air temperature increased by at least 0.9 °C in this region since the end of the Little Ice Age (LIA) in the mid-1800s. Thus, this glacier shrinks dramatically during years with low accumulation or high air temperatures during the ablation season, but cannot recover during years with high accumulation or low air temperatures during the ablation season. The most recent TLS data support this interpretation. These data indicated that two consecutive markedly anomalous wet winters and cool summers (2012-13 and 2013-14) led to near zero mass balance conditions, with significant losses of ice in some areas. These anomalous periods could not counteract the dramatic shrinkage that occurred during the dry and warm period of 2011-2012.

  8. 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.

  9. 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

  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. PMID:25941518

  11. 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.

  12. Using upper-air conditions to estimate South Cascade Glacier (Washington, U.S.A.) summer balance

    NASA Astrophysics Data System (ADS)

    Rasmussen, Lowell A.; Conway, Howard B.

    A simple model uses once-daily meteorological values in the U.S. National Centers for Environmental Prediction and U.S. National Center for Atmospheric Research (NCEP-NCAR) re-analysis database to estimate summer balance of South Cascade Glacier, Washington, U.S.A., each year over 1959-99.The rms error, 0.30 m w.e. (r2 = 0.71), is comparable to measurement error.The model relates summer balance linearly to temperature T > 0°C at 2000 m and to snow flux at 1650 m, the altitudes in recent years of the equilibrium line and terminus. The snow flux is the product of the humidity and westerly wind component at 850 hPa when temperature T < +2°C at 1650 m. Temperatures are interpolated linearly between the 850 and 700 hPa levels. Both the positive 2000 m temperature and the snow flux are summed from 26 April to 4 October.When the summer estimates are combined with those from a winter balance model using the same database, the rms error in estimating net balance is 0.40 m (r2 = 0.81).The indicated sensitivities of balance to warming of 1°C are-0.51m for summer and-0.24 m for winter. On the assumption that the total -0.75m °C-1 sensitivity exists at all altitudes, a warming of only 0.7°C would be sufficient to overcome the 1986-98 average net balance +0.5 m at the top of the glacier.

  13. Energy Balance Modeling of Interannual Snow and Ice Storage in High Altitude Region by Dynamic Equilibrium Concept

    NASA Astrophysics Data System (ADS)

    Johnson, R. J.; Ohara, N.

    2014-12-01

    Snow models in the field of hydrologic engineering have barely incorporated the long-term effect of the inter-annual snow storage such as glaciers because the time scale of glacier dynamics is much longer than those of river flow and seasonal snowmelt. This study proposes an appropriate treatment for inland glaciers as systems in dynamic equilibrium that stay constant under a static climate condition. It is supposed that the snow/ice vertical movement from high elevation areas to valleys (lower elevation areas) by means of wind re-distribution, avalanches, and glaciation, may be considered as an equilibrator of the glacier system because it stimulates snow/ice ablation. The implicit physically-based modeling of such a dynamic equilibrium snow system is introduced and discussed for the long-term snow simulation at a regional scale. The developed model has been coupled with the Weather Research and Forecasting (WRF) model to compute the snow surface energy balance.

  14. 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.

  15. 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 transverse ridges and furrows that arch across the surface, which indicates flow produced via ice. Class 5 rock glaciers have ridges and furrows that appear linear in the direction of flow, indicating reduced flow from limited internal ice; and class 6 rock glaciers have subdued surface topography because the movement of the rock glacier has ceased. Ice content decreases from 25-45%, to 10-25%, to < 10% from class 4 to 6, respectively. Examples from digital imagery, aerial photographs, and field photographs are provided for each class. The classification scheme can be used to identify and map debris-covered glaciers and rock glaciers to create an inventory. This will help improve recognition of these landforms as an important water resource in the dry Andes of Chile, which will aid in sustainable planning and development in basins that hold the majority of the population and support a large share of the economic activity in Chile.

  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. Measurement of the Dissociation-Equilibrium Constants for Low Affinity Antibiotic Binding Interaction with Bacterial Ribosomes by the T2 (CPMG) and Line-Broadening Methods

    NASA Astrophysics Data System (ADS)

    Verdier, L.; Gharbi-Benarous, J.; Bertho, G.; Mauvais, P.; Girault, J.-P.

    1999-10-01

    In this study the dissociation constants of the low antibiotic-ribosomes interaction were determined by the T2 (CPMG), the Carr-Purcell-Meiboom-Gill spin-echo decay rate and the line-broadening methods. Three MLSB antibiotics were studied, a macrolide roxithromycin, a ketolide HMR 3647 and a lincosamide clindamycin for their weak interaction with three bacterial ribosomes, E. coli, Staphylococcus aureus sensitive and resistant to erythromycin. Nous avons mesuré la constante de dissociation, Kd correspondant à l'interaction faible antibiotique-ribosome bactérien pour des antibiotiques de différentes classes, un macrolide (roxithromycine), un kétolide (HMR 3647) et une lincosamide (clindamycine) avec des ribosomes de différentes souches bactériennes (E. coli, Staphylococcus aureus sensible ou résistant à l'erythromycin) par deux méthodes : l'une basée sur la variation des largeurs de raies et l'autre sur les temps de relaxation transversaux T2 en utilisant une séquence CPMG.

  18. Runoff Routing Beneath Marine-terminating Glaciers in Central West Greenland

    NASA Astrophysics Data System (ADS)

    Fried, M.; Catania, G. A.; Bartholomaus, T.; Black, C.; Duncan, D.; Davis, M. B.; Stearns, L. A.; Nash, J. D.; Shroyer, E.; Sutherland, D.; Walker, R. T.

    2014-12-01

    Subglacial discharge at the grounding line of marine-terminating glaciers plays an important role in subaqueous melting, calving and, in turn, ice dynamic change from back-stress perturbations. Subglacial discharge (or runoff) can directly melt glacier termini as freshwater plumes rise buoyantly and entrain warm seawater at depth. Runoff can also impact fjord circulation and thus heat transport to the terminus face. As a result, it is important to understand the spatio-temporal distribution in submarine runoff at the grounding line of marine-terminating glaciers. This information may prove critical for predicting changes in the terminus position and shape through time, as the rate of submarine melt is predicted to vary nonlinearly on the maximum subglacial discharge, and not just its annual volume. Here, we link a predictive model of subglacial water routing to observations of subglacial discharge (both from satellite remote sensing and multibeam bathymetry) for three tidewater glaciers in central West Greenland. Our predictive model identifies the location of several large subglacial channels as point sources for discharge at the grounding line. Channel locations are confirmed through observations of turbid sediment plume formation, polynya formation within the ice mélange, localized thermal undercutting of the calving face and bathymetric morphology of the terminus face and sea floor. We examine the identified subglacial channels in terms of their impact on ice front position over six melt seasons and find that for some glaciers the largest seasonal ice front retreat occurs in sectors that have the most active subglacial discharge. Overall, we find that while subglacial water is routed through complex paths inland, its outlet at the terminus is ultimately controlled by the geometry of the near-terminus region. The outlets remain fixed in space over long time periods for those glaciers not experiencing rapid retreat.

  19. Glacier surge triggered by massive rock avalanche: Teleseismic and satellite image study of long-runout landslide onto RGO Glacier, Pamirs

    NASA Astrophysics Data System (ADS)

    Stark, C. P.; Wolovick, M.; Ekstrom, G.

    2012-12-01

    Glacier surges are thought to result from changes in resistance to sliding at the base of the ice mass. The reasons for such changes in basal conditions are not entirely understood, and this is in part because empirical constraints are severely limited. Recent work in the Karakoram and Pamir mountains, home to the majority of Earth's surging mountain glaciers, has boosted observational data, but has led to diametrically opposed interpretations of their glacier surging mechanics, ranging from thermal to hydrological switching. In this context we describe a surge of the RGO (Russian Geographical Society) Glacier in the Pamirs triggered by a massive rock avalanche off Mt Garmo in 2001. Initial reports pegged the RGO Glacier landslide as having been triggered in 2002 by strong ground motion originating from a nearby tectonic earthquake. We used multitemporal satellite imagery to establish failure must have struck in August-September 2001. This revised date was confirmed by reexamining teleseismic data recorded at stations in central Asia: it became clear that a landslide seismic source of magnitude Msw≈5.4 on 2001/09/02 had been misinterpreted as two tectonic sources located within kilometers of Mt Garmo. Exploiting a new technique we have developed for inverting long-period seismic waveforms, we show that a mass of rock and ice around 2.8×{}1011 kg collapsed to the SSE from an elevation of around 5800m, accelerated to a peak speed of about 60m/s, collided with the valley wall ˜ 2 km to the south and turned east to run out a further 6km over significant fractions of the accumulation and ablation zones of the RGO Glacier. Based on this estimate of landslide mass, we deduce that the supraglacial debris blanket generated by this rock avalanches averaged about 20m in thickness. By this reckoning, the Mt Garmo landslide is one of the largest in the last 33 years. Next we mapped the velocity field of the RGO Glacier over time using multitemporal satellite imagery. We performed image correlation velocimetry (sometimes known as feature tracking or optical flow velocimetry) using around 120 Landsat 7 ETM+ scenes spanning 1999 through 2012. Reliable velocity fields were generated even after the loss of scan-line correction (SLC-off scenes) in 2003. Our preliminary results reveal two phases of glacier surge. The first began within a few months of the rock avalanche during the winter of 2001, with ice flow speeds rising by more than an order of magnitude to nearly 1000m/y mid-glacier at the landslide toe, and propagating as a wave down-glacier in less than a year. This phase ended in 2002-3. The second, milder surge phase began in 2005 and ended in 2007. Each phase led to an advance of the terminus over several 100m. We interpret surge initiation as being the direct consequence of rock avalanche deposition on the glacier. To explore the apparent link between rock avalanching and glacier surging, we have developed a 2D thermomechanical, higher-order, flowline model coupled to a basal hydrology scheme. We conclude with a discussion of the behavior of this model when heavily perturbed by abrupt debris deposition, and we explore whether the occurrence of landslide-triggered surging can in any way advance our understanding of glacier surge mechanics in general.

  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 Valley, Central Eastern Alps, indicated by dendrochronological analysis of living trees and subfossil logs. Vegetation History and Archaeobotany 14, 221-234. Patzelt, G., Bortenschlager, S., 1973. Die postglazialen Gletscher- und Klimaschwankungen in der Venedigergruppe (Hohe Tauern, Ostalpen). Zeitschrift für Geomorphologie N.F. Supplementband 16, 25-72.

  1. 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.

  2. Reconsidering the glacier to rock glacier transformation problem: New insights from the central Andes of Chile

    NASA Astrophysics Data System (ADS)

    Monnier, Sébastien; Kinnard, Christophe

    2015-06-01

    The glacier to rock glacier transformation problem is revisited from a previously unseen angle. A striking case in the Juncal Massif (located in the upper Aconcagua Valley, Chilean central Andes) is documented. There, the Presenteseracae debris-covered glacier has advanced several tens of metres and has developed a rock glacier morphology in its lower part over the last 60 years. The conditions for a theoretically valid glacier to rock glacier transformation are discussed and tested. Permafrost probability in the area of the studied feature is highlighted by regional-scale spatial modelling together with on-site shallow ground temperature records. Two different methods are used to estimate the mean surface temperature during the summer of 2014, and the sub-debris ice ablation rates are calculated as ranging between 0.05 and 0.19 cm d- 1, i.e., 0.04 and 0.17 m over the summer. These low ablation rates are consistent with the development of a coherent surface morphology over the last 60 years. Furthermore, the rates of rock wall retreat required for covering the former glacier at Presenteseracae lie within the common 0.1-2 mm y- 1 range, assuming an average debris thickness and a range of debris-covering time intervals. The integration of the geomorphological observations with the numerical results confirms that the studied debris-covered glacier is evolving into a rock glacier.

  3. 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 sheet with 37 parameters as per the UNESCO/TTS format, 11 additional parameters associated with the de-glaciated valley as per the suggestions of Space Application Center Ahmadabad and 9 newly introduced parameters of present study. The data sheet provides glacier wise details for each glacier on the significant glacier parameters like morphology, dimensions, orientation, elevation, etc. for both the active glacier component as well as the associated de-glaciated valley features. Assessment of recent variation in the glacierized area between 2001 and 2011. Results indicate that 231 glaciers covering an area of 391.56 ±3.76 km2. in 2001 has been reduced to 385.17 ±3.71 km2. in 2011; a loss of 1.63 ±1.0% in glacierized area within a period of 10 years. The present paper brings out the methodology adopted and salient results of the glacier inventory carried out which will help to enrich the existing database required for water resources assessment of the country and also meet the requirements of various researches working on climate change related studies.

  4. 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 valuable information about glacial processes and ice covered bedrock.

  5. Complex Greenland outlet glacier flow captured

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  6. 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

  7. 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.

    Elevation data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on February 11, 2000. The mission used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar that flew twice on the Space Shuttle Endeavour in 1994. The Shuttle Radar Topography Mission was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency of the U.S. Department of Defense, and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC. Size: 55 kilometers wide x 55 kilometers distance (34 x 34 miles) Location: 60 deg N latitude, 140 deg W longitude Orientation: View North, 2X vertical exaggeration Image Data: Landsat Thematic Mapper false-color image Original Data Resolution: SRTM 1 arcsecond (30 meters or 98 feet), Landsat 30 meters (98 feet) Date Acquired: February 2000 (SRTM), 31 August 2000 (Landsat)

  8. Hidden Lake in Glacier National Park, Montana

    Hidden Lake in Glacier National Park, Montana, USA, a high mountain lake in an alpine setting. This lake is kept full of water mainly from precipitation runoff from the surrounding hills and, in the spring, from snowmelt....

  9. 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

  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. PMID:12917679

  11. Underwater acoustic signatures of glacier calving

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    Climate-driven ice-water interactions in the contact zone between marine-terminating glaciers and the ocean surface show a dynamic and complex nature. Tidewater glaciers lose volume through the poorly understood process of calving. A detailed description of the mechanisms controlling the course of calving is essential for the reliable estimation and prediction of mass loss from glaciers. Here we present the potential of hydroacoustic methods to investigate different modes of ice detachments. High-frequency underwater ambient noise recordings are combined with synchronized, high-resolution, time-lapse photography of the Hans Glacier cliff in Hornsund Fjord, Spitsbergen, to identify three types of calving events: typical subaerial, sliding subaerial, and submarine. A quantitative analysis of the data reveals a robust correlation between ice impact energy and acoustic emission at frequencies below 200 Hz for subaerial calving. We suggest that relatively inexpensive acoustic methods can be successfully used to provide quantitative descriptions of the various calving types.

  12. Towards a complete World Glacier Inventory

    NASA Astrophysics Data System (ADS)

    Zemp, Michael

    2013-04-01

    The need for an inventory of the world's glaciers evolved during the International Hydrological Decade (1965-74). As a result, guidelines were established in the mid 1970s to compile a worldwide detailed inventory of existing perennial snow and ice masses. Following these international guidelines, several countries started compiling national glacier inventories based primarily on aerial photographs and maps. In the 1980s, the World Glacier Inventory (WGI) database was launched together with a status report about global and regional glacierised surface areas for the second half of the 20th century. These estimates were based on the detailed inventory data together with preliminary estimates of the remaining glacierised regions derived from early satellite imagery. In the late 1990s, the Global Land Ice Measurements from Space (GLIMS) database was initiated to continue the inventory task with space-borne sensors. In the WGI, glaciers are represented by geographical point coordinates. The GLIMS database includes digital outlines. Both include exact time stamps and tabular information on glacier classifications, length, area, orientation, and altitude range. Both are regularly updated with newly available data: the WGI stores point information for the second half of the 20th century whereas the GLIMS includes digital outlines for the 21st century. Since these detailed glacier inventories are not (yet) globally complete, there have been several efforts towards preliminary estimates of the overall global glacier coverage. A first, well elaborated one was included in the original status report of the WGI, published in 1989, and was refined in 2005 with information from other sources by Dyurgerov and Meier. Other studies used the detailed WGI, or an extended format by Cogley, for regional or global up-scaling of glacier extents. In 2003, Cogley published a global map of percentage glacier coverage per 1°x1° grid box (GGHydro) that is widely used for modeling at global scale. A first globally and almost complete map with (generalized) digital outlines of all ice covered regions (incl. Greenland but excluding Antarctica) was derived from ESRI's Digital Chart of the World (DCW) and other sources by Raup and colleagues in 2000. Most recently, Arendt and colleagues produced the Randolph dataset which combines available outlines from the GLIMS, DCW, and WGI datasets as well as from many other (often unpublished) sources by using the highest quality version in each region. However, while having the advantage of being almost complete, these global estimates lack time stamps and attributes for individual glaciers. The present work provides a brief review of the various efforts, its methodological differences, and findings towards the completion of a World Glacier Inventory.

  13. 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)

  14. International Symposium on Fast Glacier Flow

    NASA Technical Reports Server (NTRS)

    Lingle, Craig S.

    1990-01-01

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

  15. 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.

  16. 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.

  17. 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 modeled bathymetry. A good understanding of the bathymetry at and around the grounding line of the major outlet glaciers of West Antarctica is essential to the understanding of their grounding history, the access of sea water to the grounding zone and the distribution of the flow of the ice. These data also provide vital constraints for models of the future of the West Antarctic ice sheet. Jenkins, A, Dutrieux, P, Jacobs, SS, McPhail, SD, Perrett, JR, Webb, AT and White, D (2010). Observations beneath Pine Island Glacier in West Antarctica and implications for its retreat. Nature Geoscience, 3, 468-472.

  18. New Gravity-Derived Grounding Line Depths Highlight Role Bathymetry Plays in Ongoing Greenland Ice Sheet Change

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Bathymetry has been a missing piece in understanding ice-ocean interactions of marine-terminating glaciers in Greenland. As bathymetry in fjords often controls the flow of warm water to the terminus of the glacier, and the grounding line depth of the glacier can modulate the effect of this warm water on the glacier. Study of Tracy and Heilprin Glaciers, a pair of neighboring glaciers in northwest Greenland, has indicated that when exposed to similar external forcings, the glacier with the deeper grounding line will retreat more rapidly. The new comprehensive mapping of grounding line depths with Operation IceBridge gravity inversions provides the basis for examining this question for all of Greenland's glaciers. We consider 54 distinct glaciers in our analysis. Grounding line depths for these 54 come from data collected by Operation IceBridge from 2010-2012. New grounding line depths for 36 glaciers are derived from gravity measurements in locations where radar is unable to retrieve grounding line depths. 18 grounding line depths come from CReSIS Multichannel Coherent Depth Sounder radar data. Offshore bathymetry in all 54 fjords is gravity-derived. The gravity-derived bathymetry is always constrained onshore by radar, and when possible pinned offshore to acoustic bathymetric measurements.Here we present the gravity-derived grounding line depths along with recent glacier behavior, including surface lowering and terminus retreat, of these 54 glaciers. In general, the glaciers with deeper grounding lines are experiencing greater mass loss. This relationship between grounding line depth and mass balance extends to much of Greenland. We systematically discuss this relationship in the different major regions of Greenland, and note that the relationship is strongest in the southeast, and weakest in the north.

  19. 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.

  20. 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.

  1. Glacier, glacier lake and permafrost distribution in the Brahmaputra river basin

    NASA Astrophysics Data System (ADS)

    Kb, A.; Frauenfelder, R.; Hoelzle, M.; Sossna, I.; Avian, M.

    2009-04-01

    Glacier distribution, glacier changes, glacier lakes and their changes, and mountain permafrost occurrence are investigated and compared to climate scenarios in order to assess the influence of melting glaciers and degrading permafrost on the long-term runoff of the Upper Brahmaputra River. In this contribution we derive glacier inventories for three test areas in the Upper Brahmaputra River Basin based on semi-automatic classification of Landsat data of 2000 and supplementary ASTER data. The resulting glacier outlines are intersected with the glacier outlines of the Chinese Glacier Inventory from about the 1970s-1980s and compared to selected Corona satellite data from the 1960s. In total, an area loss of about 18% was observed over the period investigated. We estimate the according ice volume loss to be on the order of 20%. Using the Chinese Glacier Inventory and our inventory results we upscale the above glacier change to the entire Upper Brahmaputra River Basin. Glacier lakes are mapped for the boundary region between Bhutan and Tibet using 1990 and 2000 Landsat imagery. Changes in lake area are compared to the observed glacier changes. The permafrost distribution in the study region is estimated using regionally adapted versions of two empirical models, both originally developed to estimate the permafrost distribution on a regional scale in the Swiss Alps. One model (PERMAKART) applies a topo-climatic key, based on the relation between altitude above sea level, aspect, and permafrost probability. The second model (PERMAMAP) is based on a linear spatial relation between the bottom temperature of the winter snow cover (BTS), the mean annual air temperature (MAAT) and the potential direct solar radiation. Adaptation of the models is done through the inclusion of ground based meteorological data and validated using distribution patterns of rock glaciers. The latter are mapped from high resolution satellite data such as CORONA and Quickbird imagery. Both, the observed glacier changes and the modelled permafrost distribution are compared to climate simulations in order to estimate the recent and near-future climate change impact on the glaciers and mountain permafrost in the Upper Brahmaputra River basin.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Glaciers and ice sheets are among the largest unstable parts of the solid Earth. Generally, glaciers are devoid of resources (other than water), are dangerous, are unstable and no infrastructure is normally built directly on their surfaces. Areas down valley from large alpine glaciers are also commonly unstable due to landslide potential of moraines, debris flows, snow avalanches, outburst floods from glacier lakes, and other dynamical alpine processes; yet there exists much development and human occupation of some disaster-prone areas. Satellite remote sensing can be extremely effective in providing cost-effective and time- critical information. Space-based imagery can be used to monitor glacier outlines and their lakes, including processes such as iceberg calving and debris accumulation, as well as changing thicknesses and flow speeds. Such images can also be used to make preliminary identifications of specific hazardous spots and allows preliminary assessment of possible modes of future disaster occurrence. Autonomous assessment of glacier conditions and their potential for hazards would present a major advance and permit systematized analysis of more data than humans can assess. This technical leap will require the design and implementation of Artificial Intelligence (AI) algorithms specifically designed to mimic glacier experts’ reasoning. Here, we introduce the theory of Fuzzy Cognitive Maps (FCM) as an AI tool for predicting and assessing natural hazards in alpine glacier environments. FCM techniques are employed to represent expert knowledge of glaciers physical processes. A cognitive model embedded in a fuzzy logic framework is constructed via the synergistic interaction between glaciologists and AI experts. To verify the effectiveness of the proposed AI methodology as applied to predicting hazards in glacier environments, we designed and implemented a FCM that addresses the challenging problem of autonomously assessing the Glacier Lake Outburst Flow Potential and Impound Water Upstream Flow Potential. The FCM is constructed using what is currently our understanding of how glacier lake outbursts occur, whereas the causal connection between concepts is defined to capture the expertise of glacier scientists. The proposed graph contains 27 nodes and a network of connections that represent the causal link between concepts. To test the developed FCM, we defined three scenarios representing glacier lake environmental conditions that either occurred or that are likely to occur in such highly dynamic environments. For each case, the FCM has been initialized using observables extracted from hypothesized remote sensing imagery. The map, which converges to a fixed point for all of the test scenarios within 15 iterations, shows reasoning consistent with that of glacier experts. The FCM-based cognitive approach has the potential to be the AI core of real-time operational hazards assessment and detection systems.

  3. Recent glacier retreat over Kerguelen archipelago (49°S, 69°E) derived from field data, satellite imagery and modelling

    NASA Astrophysics Data System (ADS)

    Verfaillie, Deborah; Favier, Vincent; Dumont, Marie; Jomelli, Vincent; Gilbert, Adrien; Brunstein, Daniel; Frenot, Yves

    2013-04-01

    Situated in the Indian Ocean at 49° S, 69° E, Kerguelen archipelago represents a unique sub-polar observational site. Located at low altitude and on islands, the glaciers are particularly sensitive to oceanic and atmospheric variations (e.g. Poggi, 1977a,b; Vallon, 1987). The cryosphere on Kerguelen showed important fluctuations during the last 2 centuries (Frenot et al., 1993). After a small stable period until 1961, the ice cap showed a huge and extremely quick retreat, losing 20% of its surface during the last 40 years (Berthier et al., 2009). Relating directly this acceleration with the fluctuations of temperature and precipitation inferred from direct meteorological measurements is attractive and was generally performed (e.g. Frenot et al., 1993, 1997; Berthier et al., 2009). However, it was recently discovered that the drastic temperature change may be mainly due to changes in meteorological station characteristics in 1973 (Météo France, personal communication), challenging previous interpretation. The analysis of field data collected on Ampere glacier since 2010 presented here provides a first approach in our aim to understand the recent rapid retreat of its cryosphere. In this area, short term mass balance data from previous studies (Vallon 1977a,b, 1987) were compared to recent mass balance measurements. The analysis revealed that the spatial distribution of SMB significantly changed in 40 years. Collecting spatially distributed data of the surface characteristics and ablation was crucial to better interpret our field data. Recent variations (from 2000 to 2012) of the equilibrium line altitude (ELA) of Cook ice cap derived from MODIS imagery confirmed that the ELA rose about 100m since 2000. Additionally, we analysed meteorological and reanalysis data over Kerguelen from 1950 to 2012, in order to assess the causes and processes involved in the retreat of the ice cap, and present additional SMB and ELA estimates from a simple positive degree-day model. We concluded that the parameter with the largest variation was precipitation, which was associated to a decrease in cloud cover. The direct impact of these changes was a rise of the 0°C level that led to a reduction of the occurrence of solid precipitation at low elevation. These retroactions demonstrate that Kerguelen's glaciers are extremely sensitive to small climatic changes. These results on glaciological processes of Ampere glacier are an important base to constrain modelling approaches to assess past, present and future ice cap variations. In this framework, regional scale simulations of mass balance processes over Kerguelen archipelago have been initiated with a downscaling scheme (SMHiL) and with the regional climate model MAR (Modèle Atmosphérique Régional).

  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. Greenland's pronounced glacier retreat not irreversible

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-02-01

    In recent decades, the combined forces of climate warming and short-term variability have forced the massive glaciers that blanket Greenland into retreat, with some scientists worrying that deglaciation could become irreversible. The short history of detailed glacier observations, however, makes pinning the ice loss to either short-term dynamics or long-term change difficult. Research by Young et al. detailing the effects of two bouts of sudden and temporary cooling during an otherwise warm phase in Greenland's climate history could help answer that question by showing just how heavy a hand short-term variability can have in dictating glacier dynamics. Along the western edge of Greenland the massive Jakobshavn Isbræ glacier reaches out to the coast, its outflow dropping icebergs into Baffin Bay during the summer months. Flanking the glacier's tongue are the Tasiussaq and Marrait moraines—piles of rock marking the glacier's former extent. Researchers suspected the moraines were tied to two periods of abrupt cooling that hit Greenland 9300 and 8200 years ago, and that association was reinforced by the authors' radiocarbon and beryllium isotope analyses of the area surrounding the moraines. Beryllium-10 forms when cosmic radiation travels through the atmosphere and strikes the Earth's surface, with surface rock concentrations indicating how long it has been ice-free.

  6. The impact of sampling density on glacier mass balance determination

    NASA Astrophysics Data System (ADS)

    Pelto, Mauri S.

    2000-12-01

    To assess the impact of sampling density on the determination of a glacier's annual mass balance, we used varying densities of measurements to determine annual mass balance on Columbia Glacier, Washington and Lemon Creek Glacier, Alaska. Mass balance was determined solely from field measurements. The density of the mass balance networks ranged from 1 to 375 points km-2. The smaller networks were subsamples of the highest measurement density network. The results on both glaciers indicate significant improvement in accuracy resulting from increasing the total number of measurements from 1 to 4 points km-2 on Lemon Creek Glacier and 12 to 46 points km-2 on Columbia Glacier. There was no significant improvement in accuracy on the smaller Columbia Glacier for utilizing more than 46 points km-2. On Lemon Creek Glacier there was little improvement in mass balance assessment for a network greater than 4 points km-2. On both glaciers this represented a network of 40 measurement sites.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

    Cenedese, C.

    2014-12-01

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

  9. 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 ∼50-150 m, taking the BEW with it. Strong GRW (≳ 2000 m3 s-1) yields vigorous, buoyant DMRW, which has sufficient vertical momentum to break the sea surface before sinking and flowing seaward, thereby leaving much of the BEW largely intact. Whilst these modes of glacier-ocean interaction significantly affect the ice-ocean interaction in the upper water column (0-200 m), below 200 m both RG and SG are dominated by the weak forced convection/diffusional (herein termed ubiquitous) melting due to the presence of SPMW.

  10. 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 glacier compared to rates found using ERS data in the mid-90s. Speeds have at least doubled at some of the smaller glaciers that feed the Matusevich from the south. We investigate the causes of acceleration at both archipelagoes by comparing sea surface temperatures and passive microwave observations of the timing and duration of ice surface melting.

  11. 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.

  12. Cirque glacier sensitivity to 21st century warming: Sperry Glacier, Rocky Mountains, USA

    NASA Astrophysics Data System (ADS)

    Brown, Joel; Harper, Joel; Humphrey, Neil

    2010-11-01

    The interpretation of climate change based on the behavior of small cirque glaciers is not always straightforward or unique. In this study of Sperry Glacier, Glacier National Park, Montana, we model future change of the glacier under 11 different warming scenarios. The scenarios vary from no warming from present conditions to warming at a linear rate of 10 °C/century. We assume constant precipitation and only consider change invoked by warming. Our cellular automata model is based on simple rules that account for mass balance gradient, aspect, avalanching, and the flow of ice to redistribute mass. We constrain the model with glaciological data including georadar-measured ice depth, field-measured surface mass balance, and field-mapped ice surface topography. Under the most probable temperature increase based on downscaled OA-GCM output for the IPCC A1B scenario, we conservatively estimate the glacier persisting through at least 2080. By comparing glacier volume responses to different warming scenarios we elucidate a relationship between the magnitude of temperature change and the sensitivity of the glacier to small variations in the temperature increase. We find that the greater the magnitude of the temperature increase, the less sensitive the glacier area and volume become to slight differences in the warming rate. If we generalize this relationship to the region, we expect that a small change in climate will produce varying responses for glaciers throughout the region, whereas the glacier response to a large change in climate will likely be very similar over the entire region.

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

  14. The relative impacts of greenhouse gas and aerosol climate forcing on mountain glacier melt at the third pole

    NASA Astrophysics Data System (ADS)

    Wilcox, E. M.

    2010-12-01

    The third pole region resides within a hot spot for atmospheric brown clouds owing to the widespread emissions of dust, soot, and organic carbon aerosols in South and East Asia. As much as one-half of the regional climate warming over South Asia in the later 20th and early 21st centuries has been attributed to the direct radiative heating of the troposphere by aerosol solar absorption. The other half is attributed to the global greenhouse gas forcing. While the increase in temperature and infrared back radiation attributable to greenhouse gas warming is expected to accelerate melting of Himalayan glaciers, aerosol radiative forcing, and the climate response to it, contribute a host of additional impacts on mountain glaciers, many of which exacerbate the melting. These impacts include atmospheric warming, increased infrared back radiation, reduced surface insolation, surface albedo modification by soot deposition, and reductions in monsoon precipitation. The contributions of each of these effects upon melting of Himalayan mountain glaciers is explored in a glacier mass model based on energy balance calculations. The surface energy balance from the base to the top of several glaciers is calculated based on remote sensing and in-situ time series of radiative fluxes and precipitation. The model is calibrated against recent in-situ measurements of glacier mass balance and equilibrium altitude where available. Perturbations to the radiative fluxes and precipitation are then imposed on the mass balance calculations based on published estimates of the aerosol radiative forcing magnitudes and observed changes in regional temperature and precipitation over the modern era. In light of the substantial uncertainty surrounding regional forcing values and mountain glacier characteristics, the study emphasizes sensitivity studies comparing the relative responses of glaciers to the components of aerosol and greenhouse gas forcing mentioned above. Of particular interest are: (a) the balance between aerosol radiative warming of the atmosphere and aerosol radiative cooling of the surface; (b) estimates of the magnitude of soot deposition required to cause melting rates comparable to those caused by regional warming; and (c) the relative contributions of aerosol warming of the atmosphere and the associated decrease in monsoon precipitation to total glacier mass change. The modeling framework presented here is offered as a means of providing additional quantitative constraints on recent speculation about the role of black carbon aerosols and the fate of the Himalayan glaciers.

  15. 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:20829791

  16. 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.

  17. 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; Nol, 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

  18. 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.

  19. Columbia Glacier, Alaska, 1986-2011 - Duration: 29 seconds.

    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 ...

  20. 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)

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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 blocks of ice are caught up in the deposits and then melt, locally collapsing the deposit. The combination of Landsat imagery and SRTM elevation data used in this stereoscopic display is very effective in visualizing these and other features of this terrain.

    The stereoscopic effect of this anaglyph was created by registering a Landsat image to the SRTM elevation model and then generating two differing perspectives, one for each eye. When viewed through special glasses, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions. Anaglyph glasses cover the left eye with a red filter and cover the right eye with a blue filter.

    Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and substantially helps in analyzing the large and growing Landsat image archive.

    Elevation data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on February 11, 2000. The mission used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar that flew twice on the Space Shuttle Endeavour in 1994. The Shuttle Radar Topography Mission was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency of the U.S. Department of Defense, and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC. Size: 55 x 55 kilometers (34 x 34 miles) Location: 60 deg N latitude, 140 deg W longitude Orientation: North at top Image Data: Landsat Thematic Mapper visible and infrared band mix Original Data Resolution: SRTM 1 arcsecond (30 meters or 98 feet), Landsat 30 meters (98 feet) Date Acquired: February 2000 (SRTM), 31 August 2000 (Landsat)

  6. 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

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

    PubMed

    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

  8. Muir and Riggs Glaciers, Muir Inlet, Alaska - 1941

    This northeast-looking photograph, on the southeastern side of White Thunder Ridge ,shows the lower reaches of Muir Glacier, then a large tidewater calving valley glacier, and its tributary Riggs Glacier. The séracs in the lower right-hand corner of the photograph mark Muir Glacier’s te...

  9. Recent climate trends, Glacier Bay, Alaska

    NASA Astrophysics Data System (ADS)

    Kopczynski, S. E.; Bigl, S. R.; Lawson, D. E.; Finnegan, D. C.

    2003-12-01

    Glaciers and ice caps respond to changes in regional climate at decadal scales and can thus serve as indicators of regional climate change. Many of the tidewater and terrestrial glaciers in Glacier Bay, Alaska have been in a state of rapid retreat since the late 1700s, with highly disparate rates of recession occurring in the western versus eastern arms, yet the combination of environmental and glaciological factors that must exist to catalyze these rapid changes is not clearly understood. The Cold Regions Research and Engineering Laboratory (CRREL) initiated the first systematic analyses of weather and precipitation patterns across Glacier Bay National Park in 2000 by establishing 26 meteorological stations with the long-term objective of better understanding regional and global factors, that control terrestrial and marine physical systems. Initial temperature and precipitation trends show rapid seasonal and annual shifts. This is consistent with apparent paleo-trends in climate and glacier advance and recession over the last 9K years, as well as the historical record that indicate the area is climatically sensitive. Comparisons of summer and winter precipitation totals show a precipitation gradient increasing northward from the lower bay to the head of Muir Inlet (east arm), and decreasing northwestward in the West Arm. Monthly averages of air temperatures span about 3.5 C between the warmest and coldest sites near sea level. Winter temperatures averaged more than 1 C colder in the West Arm than the East. We also found large gradients of increasing rainfall from north to south in the east arm, from north to south in the Western arm. Average temperatures in October decreased westward in the northern half of the Park and were milder at sites within the larger southern Bay. Continuing a long-term climate-monitoring program in Glacier Bay will assist with quantifying climate trends in the context of glacial movement, helping to determine the overall sensitivity of the regional glacial system to regional climate signals.

  10. 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. PMID:24712530

  11. Streamflow response of partially glacierized river basins to glacier recession using a coupled glacio-hydrological model

    NASA Astrophysics Data System (ADS)

    Naz, B. S.; Frans, C. D.; Burns, P. J.; Cuo, L.; Duan, K.; Clarke, G. K.; Nolin, A. W.; Istanbulluoglu, E.; Lettenmaier, D. P.

    2012-12-01

    Despite the well publicized risk posed by declining glaciers to water supply in partially glacierized high mountain river systems, our ability to accurately predict the sensitivity of the runoff contribution from glaciers in these basins is limited. Modeling the effect of glacier changes on streamflow in such river basins is complicated by limited meteorological and glaciological data, and by the fact that areas subject to glacier retreat often transition to seasonally ephemeral snow cover. To represent these effects accurately, glacier dynamics must be represented explicitly in hydrological models. Here, we describe the integration of the physically based spatially distributed University of British Columbia glacier dynamics model into the widely used Distributed Hydrology-Soil-Vegetation Model (DHSVM) in order to investigate the effect of glacier recession on streamflow dynamics. The integrated model was used to simulate glacier and streamflow dynamics in five test river basins globally where the effects of declining glacier extent on water supply is of concern: the Upper Bow River basin in the Western Canada, the Llanganuco Basin in the Cordillera Blanca, Peru, the Zongo glacier basin in the Cordillera Real, Bolivia, the Dongkemadi River Basin in the Tibetan Plateau region and the Astore River basin in the Western Himalayas. We tested the coupled glacio-hydrologic model performance through comparison of predicted variations in glacier extent, snow water equivalent and streamflow discharge, using satellite-derived glacier/snow cover and measured discharge and snow data. Evaluation of our model predictions confirms that representation of glacier cover changes as result of glacier dynamics reduces errors in streamflow simulations in these basins. Subsequently, we evaluate the effects of changing glacier extent on seasonal low flows (to which water supply is most sensitive) in each of the river basins.

  12. 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)

  13. Long-term mass and energy balance monitoring of Himalayan glaciers (GLACIOCLIM project) : some results for Chhota Shigri Glacier (India), Mera and Changri Nup glaciers (Nepal)

    NASA Astrophysics Data System (ADS)

    Wagnon, P.; Ramanathan, A. L.; Arnaud, Y.; Azam, F.; Vincent, C.

    2012-04-01

    Two white Himalayan glaciers, Chhota Shigri Glacier (16 km2, 32°N, India, arid-monsoon transition climate) and Mera Glacier (10 km2, 27°N, Nepal, Indian monsoon climate) have been monitored for mass, energy and hydrological balances since 2002 and 2007 respectively. Both glaciers belong now to the GLACIOCLIM observatory aiming at monitoring over a long term selected glaciers representative of different climates of the world. Additionally, a debris-covered glacier, Changri Nup Glacier (4 km2, 28°N, Nepal) has been monitored for mass and energy balances since 2009. During the period 2002-2011, Chhota Shigri Glacier experienced a negative glacier-wide mass balance (MB) of -0.59 ± 0.40 m water equivalent per year (w.e. yr-1), measured with the glaciological method. A recent study of the dynamic behaviour of the glacier showed that the glacier has probably experienced a period of near zero or slightly positive mass balance in the 1990s, before shifting to an imbalance in the 21st century. There is no sign of large recession of glaciers in Lahaul and Spiti region (Northern India) over the last 2 decades, the ice wastage being only limited to the last decade. On Mera Glacier, between 2007 and 2011, the cumulative mass balance is very close to zero. Melting is mainly driven by the radiative fluxes, the albedo being a key variable of the surface energy balance. The turbulent fluxes are only important in winter, when melting is insignificant and sublimation high.

  14. 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

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

    PubMed

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

    2013-07-23

    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

  16. Testing geographical and climatic controls on glacier retreat

    NASA Astrophysics Data System (ADS)

    Freudiger, Daphné; Stahl, Kerstin; Weiler, Markus

    2015-04-01

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

  17. 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.

  18. 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.

  19. Reconstruction of surface area and volume variations of a small alpine valley glacier since the Little Ice Age the case-study of Dosdè Est Glacier (central Alps, Italy)

    NASA Astrophysics Data System (ADS)

    Diolaiuti, G.; D Agata, C.; Pavan, M.; Belo, M.; Smiraglia, C.

    2003-04-01

    Reconstructing past glacier fluctuations and understanding them to forecast future trend of water availability in the Alps is an aim of general interest. For this reason continuous monitoring on sample glaciers is required to collect mass balance data, area and volume changes, ice thickness variations. The case-study of Dosdè Est Glacier, Piazzi-Campo Group, Italian Alps, representative of Italian small valley glaciers, is a good example of long term documentation of the evolution of this kind of glacier in the Central Alps. Dosdè Est Glacier is a North facing valley glacier, located in Italian Lombardy Alps (46 23 30 N, 10 13 05 E). In 2002 its area was approximately 2 kmq, extending from 2580 to 3294 m a.s.l., with a maximum widht of about 1000 m and a maximum lenght of about 2000 m. Observations to monitor the evolution of the glacier and to reconstruct past areas and volumes involve (in descending order of accuracy) direct mass balance measurements since 1995, topographic surveys (GPS) since 1996, GPR survey in order to evaluate ice thickness in 1999, seismic prospection and geoelectrical survey (VES) in 1997, glacier terminus variations field measurements from 1934 up to now (thanks to CGI operators), reconstruction of the 20th century maximum and of the LIA maximum using the well preserved moraines. Since hydrological year 1995-1996, mass balance of the glacier has been surveyed every year by glaciological field method. The stakes position is calculated by GPS technique and is used also to evaluate glacier surface velocity. The net mass balance during the 7 years of measurements was almost always negative with only one positive value recorded in the year 2001. During the 7 years of measures Dosdè Est Glacier lost about 7 m of ice thickness, it means 14.000.000 mc w.e. The mean yearly value of mass balance on 7 years of measures is -0,85 m w.e. and the mass balance gradient is 0,60 m w.e./100 m of altitude. Since 1925 Dosdè Est Glacier terminus variations were measured yearly by operators of Italian Glaciological Committee. The glacier had a continuous and uninterrupted retreating phase from 1934 to 1972 (-525m, mean value -25 m/y). Then an advancing phase occured from 1973 to 1986 (+100m, mean value +7.7 m/y). After that year the glacier resumed a continuous and uninterrupted frontal retreat. From 1934 to 2000 the glacier retreated of 602 m (mean yearly value, -12.5 m/y) and -165 m from 1987 up to now (mean yearly value of -15.8 m/y). In the last years, the glacier has been topographically surveyed by GPS techniques: from 1999 to 2001 the terminus was mapped yearly, in 2002 a large number of point positions in GPS Kinematic (about 6000 points) were collected to calculate surface glacier DEM. The stakes position measurements allowed to calculate the displacements of the stakes which resulted of about 30 m/y, with an accuracy of + - 1,5 m. The surface topography of the glacier was mapped by GPS data; a kriging technique was applied to GPS data, using a grid with a 10 m spacing to interpolate the 6000 measured values of position. On Dosdè Est Glacier different geophysical surveys were applied in order to evaluate ice thickness and bedrock morphology. In 1997 geoeletrical survey (VES) was used; the maximum value of ice thickness was evaluated more than 50 m; in 1997 seismic reflection method was applied to evaluate the glacier thickness along 1 longitudinal line (L1) and 2 trasversal lines (T1 and T2) situated in the centre of the glacier (Merlanti et alii, 2001).The maximum ice thickness was of about 90 m with a mean value of about 50 m. Moreover in 1999 GPR technique was used to obtain high-resolution topography of the glacier bed. A Pulse Ekko (Sensor and Software Company) GPR operating at a frequency of 50 MHz was used. The maximum ice thickness calculated is of about 90 m in the central area of the glacier, according to seismic prospection data. A kriging technique was applied to the radar data, using a grid with a 10 m spacing to interpolate the values of ice thickness between the GPR profiles. A topographic map of the glacier bed was then obtained by subtracting the ice thickness from the surface elevation determined by GPS survey. The determination of ice volume was obtained by the comparison of the two DEMs (surface topography DEM and glacier bed DEM). The moraines attributed to LIA and to second half of 20th century glacier advances, and relationships with glacier dynamic and climatic changes, have also been studied (Rossi et alii, 2003; Diolaiuti, 2001). The youngest evidences, named neoformation moraines, located near the present glacier snout from 0 to 200 m far away, have been surveyed. This moraine complex is characterized by 3 concentric ridges, each formed by a large number of segments. Moraine morphology, morphometry and sediment grain size analyses permit to formulate interpretation of the origin of these moraines. Comparison between morphological and vegetational features of the moraines and frontal variation data suggests that these morphologies may be attributed to the recent glacier advance. Two older moraine complexes are present, located downvalley respect to neoformation moraines position. These geomorphological evidences are characterized by 2 concentric ridges. The first and lower moraines complex is ascribed to LIA; these moraines are the largest ones and present an almost total vegetational cover and pedogenetical processes well started. The second and intermediate complex is ascribed to the advancing phase of 1920; its moraines are less covered by vegetation than LIA ones and show less advanced pedogenetic processes. With GPS technique it was possible, during the summers 1999 and 2000, to map the moraines positions and to calculate by GIS software the past glacier surficial extension and volume. This work was conducted as part of 2001 MIUR Project: Glacial retreat in the Italian Alps and the climatic change since deglaciation to the present phase. National Coordinator: Prof. R. Federici, Local Coordinator: Prof. C. Smiraglia

  20. Glacier dynamics at Helheim and Kangerdlugssuaq glaciers, southeast Greenland, since the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Khan, S. A.; Kjeldsen, K. K.; Kjær, K. H.; Bevan, S.; Luckman, A.; Aschwanden, A.; Bjørk, A. A.; Korsgaard, N. J.; Box, J. E.; van den Broeke, M.; van Dam, T. M.; Fitzner, A.

    2014-08-01

    Observations over the past decade show significant ice loss associated with the speed-up of glaciers in southeast Greenland from 2003, followed by a deceleration from 2006. These short-term, episodic, dynamic perturbations have a major impact on the mass balance on the decadal scale. To improve the projection of future sea level rise, a long-term data record that reveals the mass balance beyond such episodic events is required. Here, we extend the observational record of marginal thinning of Helheim and Kangerdlugssuaq glaciers from 10 to more than 80 years. We show that, although the frontal portion of Helheim Glacier thinned by more than 100 m between 2003 and 2006, it thickened by more than 50 m during the previous two decades. In contrast, Kangerdlugssuaq Glacier underwent minor thinning of 40-50 m from 1981 to 1998 and major thinning of more than 100 m after 2003. Extending the record back to the end of the Little Ice Age (prior to 1930) shows no thinning of Helheim Glacier from its maximum extent during the Little Ice Age to 1981, while Kangerdlugssuaq Glacier underwent substantial thinning of 230 to 265 m. Comparison of sub-surface water temperature anomalies and variations in air temperature to records of thickness and velocity change suggest that both glaciers are highly sensitive to short-term atmospheric and ocean forcing, and respond very quickly to small fluctuations. On century timescales, however, multiple external parameters (e.g. outlet glacier shape) may dominate the mass change. These findings suggest that special care must be taken in the projection of future dynamic ice loss.

  1. 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.

  2. 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.

  3. Surface change detection in glacier regions using ALOS PALSAR data

    NASA Astrophysics Data System (ADS)

    Tomiyama, N.; Ono, M.

    2010-12-01

    Mountainous glaciers are important water resources in the high mountainous region. The glaciers not only supply water for drinking and agriculture, but also produce energy in hydroelectric power plants to local communities. The recent rapid glacier retreat is at high risk for severe water shortage in the near future. And the melting water of glacier sometimes leads to landslide disaster or glacier lake outburst flood (GLOF). Actually, the debris flow happened and damaged the buildings at the valley of Pacuni glacier in Bolivia in December 2007. Consequently, the monitoring of the glacier regions is very important both to manage water resources and to mitigate the damage from landslide disaster. The Advanced Land Observing Satellite “DAICHI” (ALOS) has three sensors, two visible imagers and one L-band polarimetric SAR, and has been observing the land surface since 2006. This study discusses the availability of the Phased-Array type L-band Synthetic Aperture Radar (PALSAR) of ALOS for surface change detection in glacier regions in Bolivia. The observation by PALSAR is unaffected by weather. And this characteristic is the most important for the glacier monitoring. Some glaciers and their surrounding mountainous regions are selected as a test sites for this study and many landslides near Pacuni glacier were detected by Differential Interferometric SAR (DInSAR) technique using PALSAR data of ALOS.

  4. 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.

  5. 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

    The glacial and periglacial environment - linked to the extensive presence of permafrost- which predominates in the Tröllaskagi Peninsula (NE Iceland), has been conducive to the development of numerous glaciers, covered glaciers and rock glaciers located at most of its valley headwalls. This is the case in the Vidinesdalur valley, north of Hólar, where there is a debris-covered glacier (65°42'N-65°44'N and 18°56'W-19°00'W) at the bottom of the Hóladalur valley, one of its tributary valleys, and an extensive rock glacier at the bottom of the Fremri-Grjótárdalur, another tributary valley to the west. These two valleys have been monitored using digital photogrammetry to evaluate their activity in relation to displacement and velocity rates. As a detailed aerial photo from 1946 and also two orthophotos dated 2000 and 2013 were available, our aim was to study the advance rate of the two glaciers from the changes observed in their morphology at these three dates. The methodological approach adopted consisted of a combination of a geomorphological field survey 2012-2014 and photogrammetric analysis of the available material from these three years. The 1946 photograms were scanned in high resolution and georeferenced in the GIS ArcMap 10.1 (ESRI ArcGIS), using the Georeferencing module, with the 2000-2013 orthophotos as support. Between 49 and 63 control points were used for each photo, located along the outer edges of the glaciers. The transformation, applying a third degree polynomial function, obtained an RMS error of 16.10480 m and 9.42038 m respectively. The geomorphological traits were then digitized and observation of the images was carried out in a CAD environment (Bentley MicroStation V8i), which also allowed us to overlay a grid and work simultaneously with various views, facilitating the detection of possible changes in the surface of the rock glacier. During the 2014 fieldwork the limits and main geomorphological units of the two glaciers were 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)

  6. Earthly and Otherworldly Glaciers on Mars: Expressed Subsurface Subpolar Ice and "Plate Tectonic" South Polar Ices

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.

    2003-12-01

    DIRTY SUBPOLAR GLACIERS: Deeply etched internal structures of debris-covered glaciers or rock glaciers occur widely on Mars at middle latitudes. Differentially sublimated folds, crevasses, medial moraines and flow lines are expressed now as a variety of pits, troughs, hummocks, and ridges; they reveal much about the extent of sublimation and the history of flow and accumulation that originally gave rise to these structures. In many regards, they appear like usual terrestrial debris-covered glaciers (including rock glaciers). These sublimated remnant structures are not uniformly distributed on the planet; they exhibit a definite relationship to latitude. The more deeply etched icy flows occur generally in the latitude belt from 30 to 40 degrees (north and south), where possibly very little ice remains near the surface. Between 40 and 55 degrees, most of these partly sublimated flows appear to be still icy. Poleward of that, many of them show very little evidence of any sublimational loss of ice, and instead appear as thick mantling blankets sometimes having subtle flow lines. Inferences for the distribution of ground ice and the role of sublimation are similar to those inferred from the distribution and morphology of small polygons; these results are also consistent with theoretical models of the distribution of ground ice and with Mars Odyssey neutron spectroscopy of the distribution of hydrogen in the upper meter of Mars. A peculiar aspect of dirty glaciers on Mars is their current lack of an evident zone of atmospherically driven accumulation; instead, accumulation of some dirty glaciers appears to be due to load-driven expression of ice originating probably in massive crustal layers; for others, atmospheric accumulation may occur at other times during the obliquity cycle of Mars. SOUTH POLAR ICE SHEET: Previously I have reported on evidence for flowing, faulting, folding south polar ice, with the evidence for the more ductile types of deformation concentrated within the area of perennial CO2 ice. This part of the polar cap exhibits strong evidence for convergent flow tending to close the quasi-spiral structured troughs, as predicted by finite-element modelers. A rich phenomenology accompanies this closure. In some cases, good evidence exists for one icy sheet overriding another. Elastic plate flexural responses, with attendant small-scale tectonism, is quite common, as is evidence for ductile deformation. Analogs drawn from Earth's lithosphere provide compelling explanations for some of these features. Smooth, topographically enclosed flat areas in the south polar deposits may be the surface expressions of subglacial lakes or refrozen lakes.

  7. Canadian Arctic glacier melt is accelerating and irreversible

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-04-01

    Ongoing glacier loss in the Canadian high Arctic is accelerating and probably irreversible, new model projections by Lenaerts et al. suggest. The Canadian high Arctic is home to the largest clustering of glacier ice outside of Greenland and Antarctica—146,000 square kilometers of glacier ice spread across 36,000 islands. In the past few years, the mass of the glaciers in the Canadian Arctic archipelago has begun to plummet. Observations from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites suggest that from 2004 to 2011 the region's glaciers shed approximately 580 gigatons of ice. Aside from glacier calving, which plays only a small role in Canadian glacier mass loss, the drop is due largely to a shift in the surface mass balance, with warming-induced meltwater runoff outpacing the accumulation of new snowfall.

  8. Past fluctuations and current status of the Gangotri Glacier

    NASA Astrophysics Data System (ADS)

    Haritashya, U. K.; Bishop, M. P.; Bolch, T.; Copland, L.; Owen, L. A.; Mani, S.

    2013-12-01

    Himalayan glaciers have been in a state of general retreat since the last century (Mayewski and Jeschke, 1979; Mayewski et al., 1980) with accelerated losses in the last decade (Ageta and Iwata, 1999; Rai, 2005), but their fluctuations across the entire Himalaya or any one of the region (east, west or central) has yet to be adequately characterized or understood in terms of climate-glacier dynamics. When it comes to glacier fluctuations in the Indian Himalaya, our research generally takes us to the Gangotri Glacier which has been considered to be a rapidly retreating glacier. However, our study indicates the complex climate-glacier dynamics and numerous feedback mechanisms operating throughout the glacier, which requires more analysis than just a frontal fluctuation. Overall, this is a multifaceted issue and these findings indicate the urgency of a systematic and comprehensive assessment across the region.

  9. 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.

  10. 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.

  11. Glacier National Park Bighorn Sheep Studies

    The USGS studies bighorn sheep movements, population structures, and habitat use in and near Glacier National Park. Here, USGS scientist Tabitha Graves sets up remote camera at a salt lick in the park as a sheep stands in background....

  12. 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.

  13. 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…

  14. 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)

  15. Panoramic of Glaciers in the Caucasus Moutains

    Panoramic photographic mosaic of several glaciers on the northern slope of Gora Elbrus, a volcanic massif in the Central Caucasus Mountains. The photographic survey was done by N. Nikulin in 1957 during the International Geophysical Year. Photograph courtesy of V.M. Kotlyakov, Russian Academy of Sci...

  16. 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

  17. Mass budget of the grounded ice in the Lambert Glacier-Amery Ice Shelf system

    NASA Astrophysics Data System (ADS)

    Jiahong, Wen; Yafeng, Wang; Jiying, Liu; Jezek, Kenneth C.; Huybrechts, Philippe; Csathó, Beata M.; Farness, Katy L.; Bo, Sun

    We used remote-sensing and in situ measurements of surface accumulation rate, ice surface velocity, thickness and elevation to evaluate the mass budgets of grounded ice-flow regimes that form the Lambert Glacier-Amery Ice Shelf system. Three distinct drainage regimes are considered: the western and eastern margins of the ice shelf, and the southern grounding line at the major outlet glacier confluence, which can be identified with drainage zones 9, 11 and 10 respectively of Giovinetto and Zwally (2000). Our findings show the entire grounded portion of the basin is approximately in balance, with a mass budget of -4.2±9.8 Gta-1. Drainages 9, 10 and 11 are within balance to the level of our measurement uncertainty, with mass budgets of -2.5±2.8 Gta-1, -2.6±7.8 Gta-1 and 0.9±2.3 Gta-1, respectively. The region upstream of the Australian Lambert Glacier basin (LGB) traverse has a net mass budget of 4.4±6.3 Gta-1, while the downstream region has -8.9±9.9 Gta-1. These results indicate that glacier drainages 9, 10 and 11, upstream and downstream of the Australian LGB traverse, are in balance to within our measurement error.

  18. 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.

  19. 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.

  20. 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.

  1. Changes in the Surface Area of Glaciers in Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Khromova, T.; Nosenko, G.

    2012-12-01

    Glaciers are widely recognized as key indicators of climate change. Recent evidence suggests an acceleration of glacier mass loss in several key mountain regions. Glacier recession implies the landscape changes in the glacial zone, origin of new lakes and activation of natural disaster processes, catastrophic mudflows, ice avalanches, outburst floods, and etc. The presence of glaciers in itself threats to human life, economic activity and growing infrastructure. Economical and recreational human activity in mountain regions requires relevant information on snow and ice objects. Absence or inadequacy of such information results in financial and human losses. A more comprehensive evaluation of glacier changes is imperative to assess ice contributions to global sea level rise and the future of water resources from glacial basins. One of the urgent steps is a full inventory of all ice bodies, their volume and changes The first estimation of glaciers state and glaciers distribution in the big part of Northern Eurasia has been done in the USSR Glacier Inventory published in 1966 -1980 as a part of IHD activity. The Inventory is based on topographic maps and air photos and reflects the status of the glaciers in 1957-1970y. There is information about 23796 glaciers with area of 78222.3 km2 in the Inventory. It covers 23 glacier systems on Northern Eurasia. In the 80th the USSR Glacier Inventory has been transformed in the digital form as a part of the World Glacier Inventory. Recent satellite data provide a unique opportunity to look again at these glaciers and to evaluate changes in glacier extent for the second part of XX century. In the paper we report about 15 000 glaciers outlines for Caucasus, Pamir, Tien-Shan, Altai, Syntar-Khayata, Cherskogo Range, Kamchatka and Russian Arctic which have been derived from ASTER and Landsat imagery and could be used for glacier changes evaluation. The results show that glaciers are retreating in all these regions. There is, however, a rather large variability in degree of reduction very much depending on special local conditions and this was particularly notable with regard to smaller glaciers.

  2. Hasty retreat of glaciers in the Palena province of Chile

    NASA Astrophysics Data System (ADS)

    Paul, F.; Mölg, N.; Bolch, T.

    2013-12-01

    Mapping glacier extent from optical satellite data has become a most efficient tool to create or update glacier inventories and determine glacier changes over time. A most valuable archive in this regard is the nearly 30-year time series of Landsat Thematic Mapper (TM) data that is freely available (already orthorectified) for most regions in the world from the USGS. One region with a most dramatic glacier shrinkage and a missing systematic assessment of changes, is the Palena province in Chile, south of Puerto Montt. A major bottleneck for accurate determination of glacier changes in this region is related to the huge amounts of snow falling in this very maritime region, hiding the perimeter of glaciers throughout the year. Consequently, we found only three years with Landsat scenes that can be used to map glacier extent through time. We here present the results of a glacier change analysis from six Landsat scenes (path-rows 232-89/90) acquired in 1985, 2000 and 2011 covering the Palena district in Chile. Clean glacier ice was mapped automatically with a standard technique (TM3/TM band ratio) and manual editing was applied to remove wrongly classified lakes and to add debris-covered glacier parts. The digital elevation model (DEM) from SRTM was used to derive drainage divides, determine glacier specific topographic parameters, and analyse the area changes in regard to topography. The scene from 2000 has the best snow conditions and was used to eliminate seasonal snow in the other two scenes by digital combination of the binary glacier masks. The observed changes show a huge spatial variability with a strong dependence on elevation and glacier hypsometry. While small mountain glaciers at high elevations and steep slopes show virtually no change over the 26-year period, ice at low elevations from large valley glaciers shows a dramatic decline (area and thickness loss). Some glaciers retreated more than 3 km over this time period or even disappeared completely. Typically, these glaciers lost contact to the accumulation areas of tributaries and now consist of an ablation area only. Furthermore, numerous pro-glacial lakes formed or expanded rapidly, increasing the local hazard potential. On the other hand, some glaciers located on or near to (still active) volcanoes have also advanced in the same time period. Observed trends in temperature (decreasing) are in contrast to the observed strong glacier shrinkage.

  3. 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 Chtelier'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, ?eq, 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 ?eq, 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.

  4. 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

    Calculating ice thickness distribution and bed topographies for large glacier samples is an essential task to estimate stored ice volumes with their potential for sea level rise and to model possible future retreat scenarios of glacier evolution under conditions of continued warming. Modelling such bed topographies to become exposed in the near future by continued glacier retreat also enables modelling of future landscapes with their landforms, processes and interactions. As the erosive power of glaciers can form numerous and sometimes large closed topographic bed depressions, many overdeepenings are commonly found in formerly glaciated mountain ranges. Where such overdeepend parts are becoming exposed and filled with water rather than sediments new lakes can come into existence. GlabTop (Glacier bed Topography) has been used to model ice thickness distribution and bed topographies of large glacier samples. It is an ice dynamical approach, based on the assumption of perfect plasticity of ice, which relates glacier thickness to its local surface slope via the basal shear stress estimated for each glacier based on an empirical relation between shear stress and elevation range as a governing factor of mass turnover. From comparison with radio-echo soundings in the Swiss Alps, the uncertainty range of local ice thicknesses calculated with GlabTop is estimated at about ±30%. The spatial variability of ice depths, i.e. the glacier-bed topography, primarily depends on surface slope as provided by DEMs and is quite robust. For the entire Swiss Alps, GlabTop revealed a considerable number (more than 500) of (partly large) overdeepenings in the modelled glacier beds with a total area of about 50-60 km2 and a total volume of about 1.5-2.5 km3. A number of lakes have formed in such modelled overdeepenings during the past years and decades. To calculate bed topographies with their overdeepenings for the 28'100 glaciers of the Himalaya-Karakoram region the GlabTop-approach was 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.

  5. 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 from ferro- or ferrimagnetic minerals. We found that in the catchment of Nerfloen, a distal lake draining a large (440 km2) catchment in western Norway that contains 52 separate glaciers, there was a systematic decrease in the chi-Bulk77K/chi-Bulk293K-ratio with increasing altitude and proximity to the glaciers. We have not studied the magnetic mineralogy of our samples in detail, but infer from our data that the relative amount of paramagnetic minerals increase as soil formation progresses, thereby creating the contrasting ratios between samples collected at different altitudes. In the lake core we observe rapid shifts between sedimentary regimes dominated by high- and low-altitude source areas, which can best be explained by regional-scale growth and decay of mountain glaciers in the lake catchment.

  6. 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

  7. 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

  8. In-situ glacier monitoring in Zackenberg (NE Greenland): Freya Glacier and A.P. Olsen Ice Cap

    NASA Astrophysics Data System (ADS)

    Hynek, Bernhard; Hillerup Larsen, Signe; Binder, Daniel; Weyss, Gernot; Citterio, Michele; Schöner, Wolfgang; Ahlstrøm, Andreas Peter

    2015-04-01

    Due to the scarceness of glacier mass balance measurements from glaciers and local ice caps in East Greenland and the strong impact that local glaciers and ice caps outside the Ice Sheet are expected to exert on sea level rise in the present century, in 2007 and 2008 two glaciological monitoring programmes of peripheral Greenlandic glaciers started to operate near the Zackenberg Research Station in NE Greenland (74° N, 21° W). Freya (Fröya) Glacier is a 6 km long valley glacier situated on Clavering Island 10 km southeast of the Zackenberg research station with a surface area of 5.3 km2 (2013), reaching from 1305 m to 273 m a.s.l. The glacier is mainly oriented to NW and surrounded by high mountain ridges on both sides. A.P. Olsen Ice Cap is a 295 km2 peripheral ice cap located 35 km northeast of Zackenberg. The mass balance monitoring network is situated on the SE outlet glacier reaching from 1425 m to 525 m which drains into the hydrological basin of Zackenberg. This outlet glacier dams a lake which caused several glacial outburst floods within the period of investigation. The two studied glaciers are very close to each other (35 km), but they are complementary in many ways. Apart from the difference in size, which requires different monitoring strategies, Freya Glacier is nearer to the coast and therefore exposed to a more maritime climate with higher winter accumulation. The different area-altitude distribution of both glaciers is one of the main reason for the significantly more positive mean specific mass balance of A.P. Olsen Ice Cap compared to Freya Glacier. In this talk we present the glaciological monitoring on both glaciers and the main results of the first seven years of data.

  9. Spatially distributed reconstruction of the surface mass balance of Pasterze glacier, Austria, employing a full Stokes model

    NASA Astrophysics Data System (ADS)

    Binder, Daniel; Zwinger, Thomas; Hauser, Beate; Hynek, Bernhard; Schöner, Wolfgang; Weyss, Gernot

    2014-05-01

    The Pasterze glacier is the largest Austrian glacier (17.7 km², 2003) based in the 'Hohe Tauern' region of the Eastern Alps. In the period from 1980 to 1997, surface mass balance (SMB) measurements were carried out by the Verbund-Austrian Hydro Power (AHP) Company. Since 2004 SMB measurements of the Pasterze glacier were reinstalled by the ZAMG using the glaciological method (stakes, snow pits,…). Current specific SMB rates correspond to a mean surface ice loss of ~1.5 m per balance year. Since 2005 kinematics of the ablation stakes have been determined through regular differential GPS surveys. Based on the high spatial sampling by the installed ablation stake network (~50-60 stakes), a high quality ablation and flow velocity data set has been gathered for the ablation area of the Pasterze glacier. As a next step we deployed a full stress computational model (http://elmerice.elmerfem.org) to investigate the dynamics of Pasterze glacier. We employed a high resolution digital elevation model (DEM) of the bedrock and high quality DEM's of the surface taken at different times (1969, 1998, 2012) as input for diagnostic simulations. After tuning the model parameters (e.g. sliding) to the in-situ determined dynamics, we reconstructed the spatial SMB distribution of the glacier and compared it to the measurements. The reconstruction of the SMB from diagnostic simulations can be an effective technique in order to - on top of measurements that usually are confined to centre-lines of glaciers - get additional information on the spatial SMB distribution by utilizing easier accessible surface DEM's as well as for SMB homogenization approaches.

  10. 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 the laboratory and natural ice taken from the base of Engabreen Glacier were tested. Transition from a velocity strengthening to velocity weakening interface was observed for a constant velocity if the debris amount was increased thus validating the initial hypothesis. These exterminations were followed by a set of experiments in which the biax was de-stiffened in order to replicate the elastic strain, which would be accumulated at the base of a glacier. When driven under conditions previously identified in the unstable slip regime unstable sliding did occur. This allowed for exploration unstable slip parameters. Specifically comparisons of stress drop with recurrence interval, and peak-sliding velocity was investigated. Next POLENET seismic data was used to investigate a set of repeating ruptures occurring near the Executive Committee Range of Marie Byrd Land Antarctica, a known source of volcanic activity. Surface velocities as low as V ≤ 30 m yr--1 in this region exist indicating the source of glacially generated seismicity was atypical. A proposed source of a sudden addition of basal melt water from an increase in geothermal heat flux is hypothesized to result in the seismic signature observed. Lastly the POLENET dataset was used to investigate calving events located at the terminus of Thwaites Glacier. The seismicity displayed a monochromatic signal. A new calving mechanism, which could produce such a source of seismicity, is theorized as resonating within the block, which is being calved off.

  11. 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…

  12. 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%.

  13. Glacier response to climate perturbations: an accurate linear geometric model

    NASA Astrophysics Data System (ADS)

    Roe, G.; Baker, M. B.

    2014-12-01

    The basic physics of a glacier's response to small perturbations in climate forcing is of longstanding and intrinsic interest in glaciology, and it is also of some applied importance for predicting future glacier change and for inferring the climate history that drove past glacier fluctuations. In order to understand the fundamental parameters governing glacier advance and retreat, and also the spectral properties of fluctuations in glacier length in response to noisy weather, we examine outputs of a numerical flowline model solving the shallow-ice equations with sliding. The numerical results reveal a surprising simplicity: the time evolution and spectral shape of glacierexcursions depend on a single parameter, a time constant determined by the geometrical properties of the glacier. Furthermore, the numerical results reveal that perturbations in mass balance over the glacier surface set in motion a sequence of events that can be roughly described as occurring in three overlapping stages: (1) changes in interior thickness drive (2) changes in terminus flux, which in turn drive (3) changes in glacier length. A simple, third-order linear differential equation, which extends previous models in the literature, successfully captures these important features of the glacier flow. This three-stage linear model is readily invertible to recover climate history. It provides clear physical insight and analytical expressions for some important metrics of glacier behavior, such as variance, sensitivity and excursion probabilities. Finally, it facilitates uncertainty analysis. The linear model can also beadapted for arbitrary catchment geometry, and is applied to Nigardsbreen, Norway.

  14. 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-Hat reflectors has been confirmed in various test acquisitions shortly after their deployment, and initial position measurements have been carried out. Further acquisitions will be recorded once the reflectors emerge from the winter snow cover, and correlation of the measurements will be performed once the data of the GPS stations are received in March 2014. The ease of deploying these new reflectors combined with the high-resolution capabilities of the TerraSAR-X satellite provides new monitoring possibilities, not only for glacial flow dynamics but also for rock movements and deformation of infrastructure.

  15. Glacier volume changes at Mt. Everest/Qomolangma 1962 - 2007

    NASA Astrophysics Data System (ADS)

    Bolch, Tobias; Piezconka, Tino; Chen, Feng; Kang, Shichang; Buchroithner, Manfred

    2010-05-01

    The larger glaciers at Mt. Everest are heavily covered with supra-glacial debris like many other glaciers in the Himalaya. Most glacier change studies concentrate on area change only. However, the melting of debris-covered glaciers is most recognisable through downwasting. Hence, multi-temporal DEM analysis is needed to study the reaction of these glaciers to climate change in detail. We generated a time series of DEMs based on stereo corona (years 1962 and 1972) aerial images (1984), ASTER (2001) and Cartosat-1 data (2007) for the southern side of Mt. Everest (investigated glaciers: Khumbu, Nuptse, Lhotse, Lhotse Nup, Lhotse Shar and Imja) and two DEMs for the northern side (Rongbuk Glacier) based on a topographic map (1974) and ASTER data (2003). IceSat GLAS data, topographic maps and field GPS measurements are used for validation. The Cartosat-1 DEM was chosen to be the master DEM due to the highest accuracy and the other DEMs were co-registered to it. The characteristics of the downwasting are similar for all investigated glaciers: The downwasting is pronounced in the upper part with thin debris-cover and less pronounced but still recognisable in the lower parts with thick debris-cover. The highest surface lowering at the southern side is found at the possible transition zone between the active and stagnant glacier parts. The average downwasting for the investigated Eastern Rongbuk Glacier seems to be little higher (0.81 ± 0.53 m/a) than the value for Khumbu Glacier (0.42 ± 0.21 m/a). Both the accumulation and ablation area of Khumbu Glacier showed a surface lowering. Volume loss is detected for all glaciers and investigated time periods.

  16. Microbial Energetics Beneath the Taylor Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

  17. 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 Jaya reinforce the hypothesis that large-scale tropical processes dominate recent tropical glacier retreat. The observed widespread melting of glaciers is consistent with model predictions of a vertical amplification of temperature, which is documented by increasing isotopic enrichment in ice cores from high elevation glaciers throughout the Tropics.

  18. 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 glacier in regions that could not be surveyed with surface vessels. We observed a number of intricate geomorphic features in the raw images that are to our knowledge without precedent. Of particular interest are a series of barchan-shaped bedforms that may provide evidence of significant turbidity flows down the face of the morainal bank.

  19. Velocity Estimates of Fast-Moving Outlet Glaciers on the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Abdalati, Waleed; Krabill, W. B.

    1998-01-01

    In recent years, airborne laser altimetry has been used with great success to investigate the mass balance characteristics of the Greenland ice sheet. One spinoff of this activity has been the application of these measurements to the study of surface velocities in some of Greenland's fast-moving drainage glaciers. This is accomplished by tracking the motion of elevation features, primarily crevasses, in pairs of aircraft laser altimetry surveys. Detailed elevation measurements are made along or across glaciers of interest with a scanning swath of 150 to 200 meters, and the surveys are repeated several days later, typically to within better than 50 meters of the previous flight line. Surface elevation features are identified in each image, and their offsets are compared yielding detailed velocities over narrow regions. During the 1998 field season, repeat flights were made over three glaciers for the purpose of estimating their surface velocities. These were the Kangerdlugssuaq and Helheim glaciers on the east coast and the Jakobshavn Isbrae on the west coast. Each flows at such high speeds (on the order of a few kilometers per year) that their flow rates are difficult to assess by means of radar interferometry. The flexibility of the aircraft platform, however, allows for detailed measurements of the elevation and flow of these drainage areas, which are responsible for a significant portion of the ice discharge from the Greenland ice sheet. Velocity estimates for transects that span these glaciers will be presented, and where the ice thickness values are available (provided by researchers from the University of Kansas) the fluxes will be calculated.

  20. 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 Area x Altitude Balance Ratio (AABR). The results show a decrease in surface area with respect to Hualcán-III-LLGM of 16% for Hualcán-II-YD; 50% for Hualcán-I-LIA; and 74% for 2003. With respect to 2003, ELAs shifted ~520 m since the Local Last Glacial Maximum (LLGM), ~470 m since a marked late-glacial stage (YD?), ~130 m since the Little Ice Age (LIA) and about ~100 m since 1962. If the changes are exclusively attributed to temperature effects, warming since LLGM can be estimated at some 3°C and since the maximum glacier extent of LIA at about 0.8°C. Such values are rather close to mean global temperature change during the corresponding intervals. Most of the ELA shift since LIA appears to have taken place during recent decades characterized by very rapid glacier shrinkage, although air temperature does not seem to have risen considerably during the last 30 years. These results along with other environmental and social approaches will contribute to a better understanding of impacts from climate change and glacier shrinkage in order to develop adaptation, mitigation and disaster risk reduction strategies in the Peruvian Andes.

  1. Modeling the response of Pine Island Glacier, West Antarctica, to external forcings for the next 50 years

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Pine Island Glacier experienced spectacular changes over the past decades. This glacier has been thinning and accelerating since the 1970's at least and its grounding line has been retreating inland at a rate of about 1 km/yr. Initiation of these changes is usually attributed to warmer ocean waters in the Amundsen Sea affecting the floating part of Pine Island. By buttressing grounded ice flow and controlling the discharge of inland ice to the ocean, the ice shelf of Pine Island plays a major role in the stability of the glacier. Interactions between the ice shelf and ice stream remain poorly understood, which limits the ability to predict the future evolution of major outlet glaciers and ice streams and their contribution to sea level rise. We use the Ice Sheet System Model (ISSM) and a three-dimensional higher-order model to simulate the evolution of the glacier for the next fifty years and assess the effect of changes in several climate forcings and model parameters, namely basal melting under the floating part, ice front position, atmospheric conditions and grounding line retreat. Simulation results show the dominant effect of basal melting and of grounding line retreat. Results also show that changes are not limited to the ice shelf and the grounding line area but propagate far inland, almost to the ice divide. We find that enhanced basal melting or grounding line retreat are each associated with a distinct pattern of ice thinning and acceleration. We compare the simulation results with remote sensing observations of velocity changes and grounding line evolution to elucidate which forcing is more likely to have caused the recent acceleration of Pine Island Glacier. In general, our simulations indicate that Pine Island Glacier has much potential to continue changing over the coming years. This work was performed at the University of California Irvine and the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration, Cryospheric Sciences and Modeling, Analysis and Prediction Programs. HS is supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, administered by Oak Ridge Associated Universities through a contract with NASA.

  2. Recent changes of very small glaciers in the Swiss Alps

    NASA Astrophysics Data System (ADS)

    Fischer, Mauro; Huss, Matthias; Hoelzle, Martin

    2013-04-01

    Present knowledge about Alpine glaciers is not representative in terms of glacier size distribution. More than 80% of all Swiss glaciers are smaller than 0.5 km2 and hence belong to the class of very small glaciers. In the context of fast glacier wastage in the European Alps, the near-future development of the size class distribution will most probably be in favour of very small glaciers which will comparably increase in number. However, there has been little research carried out about very small glaciers so far. It is not clear whether findings and theoretical concepts elaborated for medium and large valley glaciers (> 3 km2) can be directly transferred to very small glaciers, whose accumulation patterns are, for instance, characteristically exceptional because winter precipitation is multiplied by wind drift and avalanching. The extent of glaciers in the European Alps has recently been mapped and inventoried spatio-temporally consistently. Nevertheless, such glacier outlines derived by satellite remote-sensing techniques are not accurate enough for the special case of investigating changes in very small glaciers. Therefore, glacier outlines are digitized manually using high-resolution (25 cm) orthophotographs covering the entire Swiss Alps acquired twice for every scene (both in the early and late noughties). In contrast to the known shortcomings of satellite remote-sensing based approaches, the margins of very small glaciers are (with few exceptions) clearly distinguishable on these orthophotos, even in shaded, snow- or debris-covered areas. For the eastern Swiss Alps (east of the rivers Reuss and Ticino), about one third of all glaciers has vanished since 1973. The total area presently still glacierized amounts to 140 km2, whereof very small glaciers cover only 25% but account for almost 90% of the total number of glaciers. Retreat rates are highest for very small glaciers but seem to be stabilizing or even decreasing since the early noughties, implying that many of them have retreated far back into shaded cirques and below headwalls. Downwasting and disintegration into different ice patches has become the dominant process of mass loss. Furthermore, we evaluate changes in ice volume over the last three decades for a large set of Swiss glaciers by combining the glacier outlines for the late noughties with a new precision DEM (swissALTI3D) for the same date with outlines and elevation information from around 1980. Ice volume changes are compared to measured and estimated total glacier ice volume in order to quantify relative volume losses over the last decades. Moreover, annual surface mass balance was determined for three very small glaciers complementing the analysis of recent changes in this glacier size class. Very small glaciers in the Swiss Alps show fast mass loss but the picture is not uniform both in space and time.

  3. 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 such a "fast GLOF." Thulagi lake, on the other hand, exhibits a much larger hazard potential even from slow GLOFs simply because downstream developments -- particularly Tal village -- are established on the lowest part of the floodplain of an outwash channel system, and there is a lack of deep channel entrenchment. We will present some details of both glacier-lake systems from our recent bathymetric and satellite remote sensing of glacier behavior and the characteristics of downstream developments to explain why the two lakes pose different likelihoods of causing downstream devastation. Neither system is safe, but the hazards differ.

  4. 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 abandonment was dated. Outwash in three areas was deposited by melt-water of Tahoma Glacier before A.D. 1862, 1873, and 1910, respectively. Flood channels or melt-water channels on either side of Carbon River near Carbon Glacier dated from about 1901 to 1907. Melt-water channels of three different ages cut through Emmons Glacier moraines were dated as being abandoned before 1865, 1871, and 1917, respectively. Although the evidence at Mount Rainier indicates a sequence of glacial advance and retreat and of melt-water flow through different channels at different times, their climatic and hydrologic significance is not yet known.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  6. 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.

  7. Flow and mixing around a