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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 Mller 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 Mller 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. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

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

    1993-05-01

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

  11. 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.

  12. Reconstruction of glacier equilibrium-line altitudes for the Last Glacial Maximum on the High Plain of Bogot, 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 Bogot in the Andes of Colombia provides an exceptionally detailed record of glaciation. A two-stage Last Glacial Maximum (LGM) is noted in Bogot; 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Equilibrium line altitudes and climate during the Late Holocene glacial maximum in the Andes

    NASA Astrophysics Data System (ADS)

    Sagredo, E. A.; Lowell, T. V.; Kelly, M. A.; Aravena, J.

    2012-12-01

    Documenting the spatial and temporal pattern of climate change associated with widespread glacial fluctuations during Late Holocene time is critical for understanding the mechanisms underlying these climatic/glacial events. Here, we estimate the change in equilibrium line altitudes (ELAs) associated with the most prominent glacial advance during the last millennium for four alpine glaciers in different climatic regimes in the Andes. We reconstruct scenarios of the climatic conditions (temperature and precipitation anomalies) that accommodate the ELA depressions. The glaciers studied are an unnamed glacier in the Cordillera Vilcanota (13S), Tapado glacier (30S), Cipreses glacier (34S) and Tranquilo glacier (47S). Results from the combined geomorphic analysis and application of a surface energy and mass balance model suggest that there is not a unique combination of temperature and precipitation conditions that accommodates the ELA change recorded since the Late Holocene maximum at the four sites. Assuming no change in precipitation, the ELA depressions could be explained by a cooling (with respect to present-day values) of at least -0.7C at Cordillera Vilcanota, -1.0C at Tapado glacier, -0.5C at Cipreses glacier and -1.3C at Tranquilo glacier. In contrast, assuming no change in temperature, the ELA depressions could be explained by an increase in the precipitation of at least 0.51 m (63% of the annual precipitation) at Cordillera Vilcanota, 0.33 m (95%) at Tapado glacier, 0.17 m (21%) at Cipreses glacier and 0.68 m (62%) at Tranquilo glacier. Our results serve as targets to test predictions from models of global climate dynamics for the last millennium and contribute to the understanding of the mechanisms underlying the Late Holocene glacial fluctuations.

  18. 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.

  19. 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.

  20. Line radiative transfer and statistical equilibrium

    NASA Astrophysics Data System (ADS)

    Kamp, Inga

    2015-09-01

    Atomic and molecular line emission from protoplanetary disks contains key information of their detailed physical and chemical structures. To unravel those structures, we need to understand line radiative transfer in dusty media and the statistical equilibrium, especially of molecules. I describe here the basic principles of statistical equilibrium and illustrate them through the two-level atom. In a second part, the fundamentals of line radiative transfer are introduced along with the various broadening mechanisms. I explain general solution methods with their drawbacks and also specific difficulties encountered in solving the line radiative transfer equation in disks (e.g. velocity gradients). I am closing with a few special cases of line emission from disks: Radiative pumping, masers and resonance scattering. 9th Lecture of the Summer School "Protoplanetary Disks: Theory and Modelling Meet Observations"

  1. 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.

  2. 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

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

    NASA Astrophysics Data System (ADS)

    Machguth, H.; Huss, M.

    2014-05-01

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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Sensitivities of the equilibrium line altitude to temperature and precipitation changes along the Andes

    NASA Astrophysics Data System (ADS)

    Sagredo, Esteban A.; Rupper, Summer; Lowell, Thomas V.

    2014-03-01

    Equilibrium line altitudes (ELAs) of alpine glaciers are sensitive indicators of climate change and have been commonly used to reconstruct paleoclimates at different temporal and spatial scales. However, accurate interpretations of ELA fluctuations rely on a quantitative understanding of the sensitivity of ELAs to changes in climate. We applied a full surface energy- and mass-balance model to quantify ELA sensitivity to temperature and precipitation changes across the range of climate conditions found in the Andes. Model results show that ELA response has a strong spatial variability across the glaciated regions of South America. This spatial variability correlates with the distribution of the present-day mean climate conditions observed along the Andes. We find that ELAs respond linearly to changes in temperature, with the magnitude of the response being prescribed by the local lapse rates. ELA sensitivities to precipitation changes are nearly linear and are inversely correlated with the emissivity of the atmosphere. Temperature sensitivities are greatest in the inner tropics; precipitation becomes more important in the subtropics and northernmost mid-latitudes. These results can be considered an important step towards developing a framework for understanding past episodes of glacial fluctuations and ultimately for predicting glacier response to future climate changes.

  9. Quasi-equilibrium electron density along a magnetic field line

    SciTech Connect

    Mao, Hann-Shin; Wirz, Richard

    2012-11-26

    A methodology is developed to determine the density of high-energy electrons along a magnetic field line for a low-{beta} plasma. This method avoids the expense and statistical noise of traditional particle tracking techniques commonly used for high-energy electrons in bombardment plasma generators. By preserving the magnetic mirror and assuming a mixing timescale, typically the elastic collision frequency with neutrals, a quasi-equilibrium electron distribution can be calculated. Following the transient decay, the analysis shows that both the normalized density and the reduction fraction due to collision converge to a single quasi-equilibrium solution.

  10. 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.

  11. The length of the world's glaciers - a new approach for the global calculation of center lines

    NASA Astrophysics Data System (ADS)

    Machguth, H.; Huss, M.

    2014-09-01

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

  12. 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.

  13. Deep Bed in the Vicinity of the Grounding Line of Pine Island Glacier, West Antarctica

    NASA Astrophysics Data System (ADS)

    Morlighem, M.; Goldberg, D. N.; Cornford, S. L.; Rignot, E. J.

    2014-12-01

    Pine Island glacier is one of the major ice streams of the Antarctic Ice Sheet and has been experiencing dramatic changes for the past four decades. Its grounding line has been retreating at a rate of 1 km/a since 1992. It has been suggested that this retreat would not stop and that the entire basin would unground because of the geometry of its bed. The bed topography indeed controls to a large extent the behavior of the grounding line because of its reverse shape, which makes Pine Island susceptible to the Marine Ice Sheet Instability. Using three model-based approaches, we analyze the bed topography of Pine Island, and any potential errors inherent in its representation. While all three approaches are based on the conservation of mass and momentum, they differ both in terms of the glaciological flow model used, and their estimation methodology. Nevertheless, all three produce similar bed corrections that suggest that the bed is several hundreds of meters below the most recent bed compilation of Bedmap-2, and has a flatter shape. We attribute the inconsistency with Bedmap-2 to noise and ambiguity in radar echograms due to the presence of crevasses, as well as large cross-over errors and sparse flight-line data in this region. This new description of the bed topography of Pine Island Glacier has vast implications for the modeling of its evolution in the coming decades. Models of the glacier are likely to exhibit more subtle amplification of retreat rate, since the bed is less steep, but may also begin to retreat more readily, since the present day discharge is greater and the ice surface elevation closer to floatation. Our results also provide guidelines for future mission deployments.

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

    NASA Astrophysics Data System (ADS)

    Alcal, 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.

  15. 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.

  16. 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Pillai, J.; Patel, L. K.

    2011-12-01

    Glaciers in the Indian Himalayan Region (IHR) are the prime lifeline of Indian Subcontinent. There are about nine thousand glaciers of different size in this region. It is located within the latitudes 270N to 360N and longitude 720E to 960E. The second largest glacier, outside the polar and sub polar regions, Siachen glacier of length 74 km, is located in IHR. Many rivers in this continent originated from these glaciers. Study on the fluctuations especially of the snow cover and related parameters are important for the proper management of these rivers. Annual balance, fluctuations of glaciers, hydrological behaviour and the assessment of the winter snow pack are also critical for the proper flow and control of Himalayan Rivers. There are many hydroelectric and irrigation facilities in these snow fed rivers. Glacial melt is important as far as the river flow is concerned. Researchers had observed that the glacial mass balance has been found to show an inverse relationship with the monsoon. Glacial hydrometry and glacial melt are important aspects as far the studies of glaciers in this region. Himalayan glaciers are also important for ecosystem stability. In this perspective attempts had been made to examine the various environmental parameters of Pindari glacier and the upper reaches of the Pindari river. Pindari glacier is located in the Central Himalayan region. It is of length 8 Km. A few records available with Geological Survey of India for a period of hundred years reveals that Pindari glacial have an annual retreat of 8-10 M. Pindrai glacier had retreated about 425 M with in a period of fifty seven years. Pindari river originates from the buffer zone of Nanda Devi Biosphere Reserve (NDBR) and is located in the lower regime of Pindari glacier. It is one of the prominent tributaries of Alaknanda. Tributaries of Pindari river are from Maktoli glacier, Kafani glacier and Sunderdhunga glacier. The changes in the Pindiari catchment area had been examined from the year 1990. Remote Sensing data of different years were used to analyze the changes in aerial extent of the pindari glacier. Pindari landscap is formed by the combined geomorphological process of fluvial and glacial. These processes are also maintaining the ecosystem balance of the catchment area. Snow covers area of this higher landscapet had been reduced considerably. The timberline of this region is shifting upper side of the glaciers, whereas the equilibrium line is also retreating. The spatial invasion in timber line and the retreat of the equilibrium line will further establish the negative mass balance of this glacier. However, the climatic variation may exacerbate the ecosystem balance of the region. All the reports on the glaciers in IHR regions review a negative mass balance and annual retreat up the glaciers. The observation records of these glaciers in IHR are about a period of hundred years this is quite in sufficient it establishes the relation between climate change and the glaciers retreat. However it is a known fact that the impact of rise in temperature due to anthropogenic effect may overstretch the rate the natural process of glacier retreat. The present study also discusses the unique phenomena of glacier melt due to climatic variations and its catastrophe.

  19. 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.

  20. Complex Behaviour of Glaciers in Ladakh Mountains (J & K State, India) : Case Study

    NASA Astrophysics Data System (ADS)

    Ganjoo, R. K.

    2011-12-01

    The Ladakh Mountains house approximately 4500 glaciers in its two major basins, namely Indus (1800 glaciers) and Shyok (2700 glaciers).Glaciers in Indian Himalaya have been under monitor for past about five decades. Monitoring of scores of glaciers have been both in terms of documentary record and field studies of the glaciers in northwest Himalaya. The studies suggest that glaciers of Ladakh mountains show an extremely different behavior as compared to the glaciers of rest of northwest Himalaya. Four glaciers, namely Durung Drung, Kangriz, Machoi and Siachen, representing the Indus and Shyok basin are dealt herein. Sufficient documentary and field evidences of these four glaciers support the view that glaciers housed in Ladakh mountains contradict the commonly accepted concept of fast melting glaciers in Himalaya (Ganjoo and Koul 2009; Ganjoo et al. 2010). The studies further suggest that the secular movement of glaciers in Ladakh mountains is a complex phenomena of several micro and macro-climatic factors, terrain morphology, and tectonics (Ganjoo 2009, Koul and Ganjoo 2010). The change in the morphology of glaciers is not necessarily related with the change in climate as commonly believed and hyped. Ganjoo, R.K. (2009) Holocene Tectonics and Climate of Durung Drung Glacier Basin, Zanskar Himalaya, India (Abstract). The 5th International Symposium on Tibetan Plateau and 24th Himalaya- Karakorum-Tibet Workshop, Aug. 11-14, Beijing, China. Ganjoo, R.K. and Koul, M.N. (2009) Is the Siachen glacier melting? Current Science, 97(3), 309-310. Ganjoo, RK; Koul, MN; Ajai; Bahuguna, IM (2010) Glaciers of Nubra valley, Karakorum mountains, Ladakh (India) vis--vis climate change (abstract). 7th Annual Meeting of Asia Oceania Geosciences Society, Hyderabad. Koul, M.N. and Ganjoo, R.K. (2010) Impact of inter- and intra-annual variation in weather parameters on mass balance and equilibrium line altitude of Naradu glacier (Himachal Pradesh), NW Himalaya, India. Climatic Change, 99, 119-139.

  1. 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.

  2. Linking glacier annual mass balance and glacier albedo retrieved from MODIS data

    NASA Astrophysics Data System (ADS)

    Dumont, M.; Gardelle, J.; Sirguey, P.; Guillot, A.; Six, D.; Rabatel, A.; Arnaud, Y.

    2012-12-01

    Albedo is one of the variables controlling the mass balance of temperate glaciers. Multispectral imagers, such as MODerate Imaging Spectroradiometer (MODIS) on board the TERRA and AQUA satellites, provide a means to monitor glacier surface albedo. In this study, different methods to retrieve broadband glacier surface albedo from MODIS data are compared. The effect of multiple reflections due to the rugged topography and of the anisotropic reflection of snow and ice are particularly investigated. The methods are tested on the Saint Sorlin Glacier (Grandes Rousses area, French Alps). The accuracy of the retrieved albedo is estimated using both field measurements, at two automatic weather stations located on the glacier, and albedo values derived from terrestrial photographs. For summers 2008 and 2009, the root mean square deviation (RMSD) between field measurements and the broadband albedo retrieved from MODIS data at 250 m spatial resolution was found to be 0.052 or about 10% relative error. The RMSD estimated for the MOD10 daily albedo product is about three times higher. One decade (2000-2009) of MODIS data were then processed to create a time series of albedo maps of Saint Sorlin Glacier during the ablation season. The annual mass balance of Saint Sorlin Glacier was compared with the minimum albedo value (average over the whole glacier surface) observed with MODIS during the ablation season. A strong linear correlation exists between the two variables. Furthermore, the date when the average albedo of the whole glacier reaches a minimum closely corresponds to the period when the snow line is located at its highest elevation, thus when the snow line is a good indicator of the glacier equilibrium line. This indicates that this strong correlation results from the fact that the minimal average albedo values of the glacier contains considerable information regarding the relative share of areal surfaces between the ablation zone (i.e. ice with generally low albedo values) and the accumulation zone (i.e. snow with a relatively high albedo). As a consequence, the monitoring of the glacier surface albedo using MODIS data can provide a useful means to evaluate the interannual variability of the glacier mass balance. Finally, the albedo in the ablation area of Saint Sorlin Glacier does not exhibit any decreasing trend over the study period, contrasting with the results obtained on Morteratsch Glacier in the Swiss Alps.

  3. 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.

  4. The effect of bed topography on modeled grounding line migration in a conditional simulation of Thwaites Glacier, West Antarctica

    NASA Astrophysics Data System (ADS)

    Waibel, M. S.; Jackson, C. S.; Hulbe, C. L.; Martin, D. F.; Goff, J. A.

    2014-12-01

    Chief among the challenges involved with accurately modeling grounding line migration of marine terminating ice sheets is integrating grounding line dynamics together with accurate sub-kilometer scale bed topography. We address this challenge using a Berkeley Ice Sheet Initiative for Climate at Extreme Scales (BISICLES) ice sheet model with a new 250 m resolution conditional simulation of the bed beneath Thwaites Glacier and its catchment area. The new bed topography was created by interpolating aerogeophysical observations to a fine grid using inhomogeneous statistics with channelized morphology and a realistic small-scale roughness. The primary interest here is understanding how (and why) the more realistic bed geometry affects model behavior and projections of future change, relative to projections made using simpler bed geometries. We use the same forcing as prior work on the Thwaites and Pine Island Glacier systems--parameterized warm water incursion beneath the floating glacier terminus--and compare the resulting grounding line retreat to retreat simulated using the same model with a standard 1 km resolution basal elevation data set.

  5. 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.

  6. Accurate delineation of the grounding line from kinematic GPS measurements. Application to an outlet glacier in East Antarctica

    NASA Astrophysics Data System (ADS)

    Le Meur, E.; Sacchettini, M.; Durand, G.; Drouet, A.; Rignot, E. J.; Mouginot, J.; Young, D. A.; Blankenship, D.; Greenbaum, J.

    2011-12-01

    Polar ice sheets have a huge potential in terms of sea level rise. Recent measurements show clear evidence of a generalized speeding up of outlet glaciers in Greenland and West Antarctica and the question whether similar behaviors are to be expected in East Antarctica is all the more crucial as this latter represents the largest ice reservoir. Moreover, many glaciers in the Wilkes-Terre Adlie sector are in a supposedly unstable configuration due to a landward downsloping bedrock. As a consequence, the Astrolabe Glacier (Terre Adlie land) was selected as a test zone for extensive field surveys like surface and bedrock heights, surface velocities, mass balance measurements. Among those, the exact position of the grounding line is fundamental as it represents a strong transition in the flow regime when the basal drag of the grounded ice reduces to virtually zero when this latter starts to float over the ocean. We here propose a method based on GPS measurements along various profiles in order to identify the presence or not of tidal movements of the ice surface indicating floating ice. The amplitude of the tides of the order of a meter requires accurate data only possible with the differential GPS method. Processing of these GPS data along selected profiles allows us to propose a position for the grounding line (hydrostatic one) which we then compare to that obtained from remote techniques (Landsat-7, ICESat, differential satellite synthetic-aperture radar interferometry). The exact position of the grounding line as well as the exact surface height along a radar transect across the glacier (giving the underlying bedrock topography) is also used to infer a mean density for the whole ice column by applying the hydrostatic criterion and a firn depth correction.

  7. 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.

  8. 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%.

  9. Linking glacier annual mass balance and glacier albedo retrieved from MODIS data

    NASA Astrophysics Data System (ADS)

    Dumont, M.; Gardelle, J.; Sirguey, P.; Guillot, A.; Six, D.; Rabatel, A.; Arnaud, Y.

    2012-07-01

    Albedo is one of the variables controlling the mass balance of temperate glaciers. Multispectral imagers, such as MODerate Imaging Spectroradiometer (MODIS) on board the TERRA and AQUA satellites, provide a means to monitor glacier surface albedo. In this study, different methods to retrieve broadband glacier surface albedo from MODIS data are compared. The effect of multiple reflections due to the rugged topography and of the anisotropic reflection of snow and ice are particularly investigated. The methods are tested on the Saint Sorlin Glacier (Grandes Rousses area, French Alps). The accuracy of the retrieved albedo is estimated using both field measurements, at two automatic weather stations located on the glacier, and albedo values derived from terrestrial photographs. For summers 2008 and 2009, the Root Mean Square Deviation (RMSD) between field measurements and the broadband albedo retrieved from MODIS data at 250 m spatial resolution was found to be 0.052 or about 10% relative error. The RMSD estimated for the MOD10 daily albedo product is about three times higher. One decade (2000-2009) of MODIS data were then processed to create a time series of albedo maps of Saint Sorlin Glacier during the ablation season. The annual mass balance of Saint Sorlin Glacier was compared with the minimum albedo value (average over the whole glacier surface) observed with MODIS during the ablation season. A strong linear correlation exists between the two variables. Furthermore, the date when the average albedo of the whole glacier reaches a minimum closely corresponds to the period when the snowline is located at its highest elevation, thus when the snowline is a good indicator of the glacier equilibrium line. This indicates that this strong correlation results from the fact that the minimal average albedo values of the glacier contains a considerable information regarding the relative share of areal surfaces between the ablation zone (i.e. ice with generally low albedo values) and the accumulation zone (i.e. snow with a relatively high albedo). As a consequence, the monitoring of the glacier surface albedo using MODIS data can provide a useful means to evaluate the inter-annual variability of the glacier mass balance. Finally, the albedo in the ablation area of Saint Sorlin Glacier does not exhibit any decreasing trend over the study period, contrasting with the results obtained on Morteratsch Glacier in the Swiss Alps.

  10. 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.

  11. Variations in ELA of glaciers in the Tibetan Plateau over the past two decades and their implications for future glacier change

    NASA Astrophysics Data System (ADS)

    Wang, N.; Pu, J.; Duan, K.; Yao, T.

    2013-05-01

    The equilibrium line altitude (ELA) is a theoretical line on a glacier at which annual mass accumulation equals annual mass loss. Glacier behaviors such as advancing or retreating are controlled by the variations in ELA. Relative to its steady state, a glacier advances when its ELA falls, retreats when its ELA rises, or melts entirely when its ELA rises above its summit. In contrast to variations in glacier length or area, variations in ELA respond almost simultaneously to climate change. With global warming, studying ELA variations is of prime importance for understanding the behaviors of glaciers. Based on observations of the ELAs of the Qiyi Glacier in the Qilian Mountains, the Meikuang Glacier in the Kunlun Mountains and the Xiaodongkemadi Glacier in the Tanggula Mountains in the Tibetan Plateau, we found that the ELAs have risen about 160-180m since 1989. After analyzing the correlations between the ELAs and air temperature and precipitation, it was found that the warm season air temperature was the leading climatic factor influencing ELA. The present ELAs of those observed glaciers are much higher than their ELAs under the status of that their mass balances are zero. This suggests that those glaciers will continue to retreat in the near future.

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

    NASA Astrophysics Data System (ADS)

    Alcal, J.; Palacios, D.; Vzquez-Selm, 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 (1524S-1551S, 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. Quality controlled glacier inventory in high Asian mountains

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Glacier inventories provide a basic information for the water resources, glacier mass balance and ice volume at continental areas. Although glaciers in the Asian mountain are thought to play an important role for the regional water resources (Immerzeel et al., 2010), glacier distribution in the Asia have been poorly understood. Our GAMDAM (Glacier Area Mapping for Discharge in Asian Mountains) project have conducted to establish a glacier inventory with the aim of estimating glacier runoff contribution to river runoff. Our target region covers the High Mountain Asia, extending from 27 to 52 degrees N and from 68 to 104 degrees E. Glacier outlines were manually delineated using more than 260 of LANDSAT images taken from 1999 to 2003. Thermal infrared band was also used to delineate termini of debris-covered glaciers with help of high resolution images on Google Earth. The manual delineation has been conducted for more than two years by 5-7 operators. We conducted several tests, along which the operators delineated the same regions, and assessed the quality and criteria, and fed them back to the operators. At the end of June 2013, the inventory was completed 80% with about 63000 glaciers covering 7.8 10^4 km^2. Median elevation of glaciers has been interpreted as a proxy for the equilibrium line altitude (ELA), at which the accumulation and ablation were equal and thus the mass balance was zero (Braithwaite and Raper, 2009). Distribution of the median altitude derived from the GAMDAM glacier inventory was well consistent with that previously reported (Shi et al., 1980).

  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. Equilibrium number of quantized vortex lines in rotating3He-B

    NASA Astrophysics Data System (ADS)

    Xu, Wen; Plaais, B.; Ruutu, V. M.; Krusius, M.

    1996-01-01

    A slow cool-down at constant rotation velocity ? from the normal to the superfluid state is expected to give the equilibrium state of vortex lines. We have checked this by counting the number of vortex lines in3He-B using cw NMR. Our measurements with 0???0.28 rad/s confirm the expectation.

  16. Bivachnyy Glacier

    USGS Multimedia Gallery

    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....

  17. 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.

  18. Linking glacier annual mass balance and glacier albedo from MODIS data

    NASA Astrophysics Data System (ADS)

    Dumont, M.; Gardelle, J.; Arnaud, Y.; Guillot, A.; Sirguey, P.; Six, D.

    2012-04-01

    The albedo is one of the variables controlling the mass balance of temperate glaciers. Multispectral imagers, such as MODIS on board TERRA and AQUA, provide a means to monitor glacier albedo. In this study, different methods to retrieve broadband glacier albedo from MODIS data are compared. In particular, the effect of the multiple reflections due to the rugged topography and that of the anisotropic reflection of snow and ice are investigated. The methods are tested on the Saint Sorlin glacier (Grandes Rousses area, French Alps). The accuracy of the retrieved albedo is estimated using both field measurements and albedo derived from terrestrial photographs. The root mean square deviation between field measurements and the broadband albedo retrieved from MODIS pixels at 250m spatial resolution was found to be less than 0.06. One decade (2000-2010) of MODIS data were then processed to create a time series of albedo maps of Saint Sorlin glacier during the ablation season. It appears that the albedo in the ablation area of the glacier does not exhibit any marked decreasing trend during the decade under study. This contrasts with the situation observed on other glaciers in the Alps. In addition, the annual mass balance of Saint Sorlin Glacier was compared with the minimum albedo value (spatial averaged over the whole glacier) observed with MODIS during the ablation season. A high linear correlation exists between the two variables. Furthermore, the day on which the albedo reaches a minimum over the glacier closely corresponds to the day on which the snowline is found to be at its highest elevation, thus close to the glacier's equilibrium line. This indicates that the high correlation can be explained by the fact that this minimal albedo contains a high degree of information regarding the relative share of areal surfaces between the ablation zone (i.e., ice with a generally lower albedo) and the accumulation zone (i.e., snow with a relatively high albedo). This implies that monitoring the albedo of glacier with MODIS data can provide a useful means to approach the inter-annual variability of the glacier's mass balance.

  19. 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.

  20. 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.

  1. 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.

  2. 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 Lovnbreen (Svalbard, 79N). 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.

  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. 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.

  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. Field line twist and field-aligned currents in an axially symmetric equilibrium magnetosphere. [of Uranus

    NASA Technical Reports Server (NTRS)

    Voigt, Gerd-Hannes

    1986-01-01

    Field-aligned Birkeland currents and the angle of the magnetic line twist were calculated for an axially symmetric pole-on magnetosphere (assumed to be in MHD equilibrium). The angle of the field line twist was shown to have a strong radial dependence on the axisymmetric magnetotail as well as on the ionospheric conductivity and the amount of thermal plasma contained in closed magnetotail flux tubes. The field line twist results from the planetary rotation, which leads to the development of a toroidal magnetic B-sub-phi component and to differentially rotating magnetic field lines. It was shown that the time development of the toroidal magnetic B-sub-phi component and the rotation frequency are related through an induction equation.

  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)

    Ma?ecki, 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. 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.

  13. 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 (8-10S). 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 9-11S, 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 4.5C is required to achieve equilibrium glacier shapes terminating at moraine positions bounding Laguna Queshque (4300 m asl 950'S; 7725'W). Alternatively, increasing precipitation by 1.5 times the modern values requires a temperature reduction of 3.75C 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 1C 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.

  14. 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.

  15. 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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Golledge, Nicholas R.; Phillips, Emrys

    2008-07-01

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

  18. 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.

  19. 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

  20. Modelling the impact of submarine frontal melting and ice mlange on glacier dynamics

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  1. 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.

  2. Spatial distribution of glacial erosion rates in the St. Elias range, Alaska, inferred from a realistic model of glacier dynamics

    NASA Astrophysics Data System (ADS)

    Headley, Rachel; Hallet, Bernard; Roe, Gerard; Waddington, Edwin D.; Rignot, Eric

    2012-09-01

    Glaciers have been principal erosional agents in many orogens throughout much of the recent geological past. A modern example is the St. Elias Mountains in southeastern Alaska; it is a highly convergent, complex orogen, which has been glaciated for much of its history. We examine the Seward-Malaspina Glacier system, which comprises two of the largest temperate glaciers in the world. We focus on the pattern of erosion within its narrow passage through the St. Elias Mountains, the Seward Throat. Measured glacier surface velocities and elevations provide constraints for a full-stress numerical flowband model that enables us to quantitatively determine the glacier thickness profile, which is not easily measured on temperate glaciers, and the basal characteristics relevant for erosion. These characteristics at the bed, namely the water pressure, normal and shear stresses, and sliding velocity, are then used to infer the spatial variation in erosion rates using several commonly invoked erosion laws. The calculations show that the geometry of the glacier basin exerts a far stronger control on the spatial variation of erosion rates than does the equilibrium line altitude, which is often assumed to be important in studies of glaciated orogens. The model provides a quantitative basis for understanding why erosion rates are highest around the Seward Throat, which is generally consistent with local and large-scale geological observations and thermochronologic evidence. Moreover, model results suggest how glacier characteristics could be used to infer zones of active or recent uplift in ice-mantled orogens.

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

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1986-01-01

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

  4. Western Glacier Stonefly

    USGS Multimedia Gallery

     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. ...

  5. Western Glacier Stonefly

    USGS Multimedia Gallery

    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. ...

  6. Shrinkage of selected southcentral Alaskan glaciers AD 1900-2010 - a spatio-temporal analysis using photogrammetric, GIS-based and historical techniques

    NASA Astrophysics Data System (ADS)

    Kienholz, Christian; Prakash, Anupma; Nussbaumer, Samuel; Zumbhl, Heinz

    2010-05-01

    The knowledge about the recent glacier change in the Chugach Mountains of southcentral Alaska is still scarce. In an effort to fill this gap we took an interdisciplinary approach and reconstructed the history of ten selected glaciers in the vicinity of Valdez (e.g., Valdez Glacier) and Cordova (e.g., Sheridan, Childs and Allen Glacier): Historical data such as early maps and photographs allowed for refining the glacier outlines of the early 20th century. Based upon photogrammetric methods, we further derived elevation models and orthomosaics from various airborne images. The Alaska High Altitude Program (AHAP) imagery, taken during the late 1970s, were the primary data of interest and provided a valuable source of information, primarily because they had not been quantitatively evaluated before. Together with the first USGS maps from the1950s and most recent data (airborne LiDAR; as well as air- and space-borne optical data), they allowed for determining the volume and area changes that have occurred within the last 60 years. A GIS analysis revealed that the recent decades have been characterized by rising equilibrium lines and thus retreating and thinning glaciers. The glaciers did not show a consistent recession pattern, which might partly be attributed to the varying area-altitude distributions. Simple hypsographic modeling indicated that the glaciers generally are far away from a state of equilibrium. Given the current climate scenarios and the unfavorable hypsography of most glaciers, the hitherto prevailing trend of glacier melt and recession is likely to continue or accelerate in the upcoming years. Reliably predicting the extents and characteristics of these glaciers at the end of the century remains an important yet poorly answered research question.

  7. The response of glaciers to climate change

    NASA Astrophysics Data System (ADS)

    Klok, Elisabeth Jantina

    2003-12-01

    The research described in this thesis addresses two aspects of the response of glaciers to climate change. The first aspect deals with the physical processes that govern the interaction between glaciers and climate change and was treated by (1) studying the spatial and temporal variation of the glacier albedo from satellite images, (2) investigating the spatial distribution of the surface energy and mass balance of a glacier, and (3) investigating the sensitivity of the mass balance to climate change. All of these studies are focused on Morteratschgletscher in Switzerland. The second aspect is the climatic interpretation of glacier length fluctuations. This was studied by developing a model that calculates historical mass balance records from global glacier length fluctuations. To increase our understanding of the variations in glacier albedo, we derived surface albedos from 12 Landsat images. This constituted a stringent test for the retrieval methodology applied because Morteratschgletscher is very steep and rugged, which strongly influences the satellite signal. We aimed to retrieve surface albedos while taking into account all important processes that influence the relationship between the satellite signal and the surface albedo, e.g. the topographic effects on incoming solar radiation, and the anisotropic nature of the reflection pattern of ice and snow surfaces. We then analysed the spatial and temporal pattern of the surface albedo. We developed a two-dimensional mass balance model based on the surface energy balance to study the spatial distribution of the energy and mass balance fluxes of Morteratschgletscher. Meteorological data from weather stations in the vicinity of Morteratschgletscher serve as input for the model. We corrected incoming solar radiation for shading, aspect, slope, reflection from surrounding slopes, and obstruction of the sky. Ignoring these effects results in an increase in solar radiation of 37%, causing a decrease in the mass balance of 0.34 m w.e. We modelled the mass balance for 1999 and 2000 and analysed the spatial distribution. We then ran the model for a period of 23 years and calculated the mass balance sensitivity to climate change by perturbing air temperature and precipitation. The mass balance sensitivity to temperature and precipitation are 0.59 m w.e. a-1 K-1 and 0.17 m w.e. a-1 per 10 percent respectively. We also used three other albedo parameterisations to calculate the mass balance sensitivity since albedo parameterisations are often regarded as a main source of error in mass balance models. We concluded that an accurate estimate of the mass balance sensitivity requires a parameterisation that captures the process of a decreasing snow albedo when a snow pack gets older or thinner. To extract a climate signal from worldwide glacier length fluctuations, we developed a simple model. The climate signal is represented as a reconstruction of the mass balance and the equilibrium line altitude (ELA). The model was tested on seventeen European glacier length records and then applied to nineteen glacier length records from different parts of the world. Between 1910 and 1959, the average increase in the reconstructed ELAs is 33 m. This implies that during the first half of the twentieth century, the climate was warmer or drier than before. The reconstructed ELAs decrease to lower elevations after 1960 and up till 1980, when most of the reconstructions end. The results can be translated into a global temperature increase of about 0.8 K for the period 1910-1959

  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. 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.

  13. Glaciers and Global Climate

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.

    1999-01-01

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

  14. Spatial variation of glacial erosion rates in the St. Elias range, Alaska, inferred from a realistic model of glacier dynamics

    NASA Astrophysics Data System (ADS)

    Headley, R. M.; Hallet, B.; Roe, G.; Waddington, E. D.

    2011-12-01

    Glaciers have been principal erosional agents in many tectonically active orogens throughout much of the recent geological past. The St. Elias Mountains in southeastern Alaska are a surface expression of a highly convergent, complex orogen that was likely glaciated for much of its history. We examine the Seward-Malaspina Glacier system, part of one of the largest temperate glacier systems in the world, and focus on the Seward Throat, which is a narrow passage of the glacier through the St. Elias Mountains. It is within this region that we examine the pattern of erosion where ice velocities are exceptionally high. The glacier surface velocities and elevations, which are known, provide constraints for a numerical, full-stress flowband model that enables us to infer the glacier thickness, which is not easily measured on temperate glaciers, and the corresponding sliding velocity and other basal properties. This in turn allows us to produce one of the first studies of the current spatial distribution of erosion under an active glacier; erosion rates are inferred using the flow model guided by glaciological observations and several commonly invoked erosion laws that depend upon the sliding velocity and basal shear stress. The spatial variation of current erosion rates is strongly controlled by the geometry of the glacier and less influenced by other factors, such as the equilibrium line altitude or the choice of erosion law. Inferred erosion rates are highest within the narrow, central portion of the Seward Throat, consistent with both local and regional geological observations. The numerical model used in conjunction with surface glaciological measurements is a powerful tool for investigating ice thickness, basal properties, and the spatial variation of glacial erosion rates for many temperate glaciers, where little is known aside from surface properties. The glaciological data and model results have potential use for inferring local regions of active uplift in the vicinity of the Seward Throat and for investigating the role of glacial erosion within the broader tectonic setting of the St. Elias Mountains.

  15. Jakobshavn Glacier

    Atmospheric Science Data Center

    2013-04-17

    ... gives rise to the green color of the water; and blue-colored melt ponds are visible in the bright white ice. A scattering of small icebergs in Disco Bay adds a touch of glittery ... Glacier location: Greenland Arctic Ocean thumbnail: ...

  16. 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.

  17. Fatal accidents on glaciers: forensic, criminological, and glaciological conclusions.

    PubMed

    Ambach, E; Tributsch, W; Henn, R

    1991-09-01

    The rare event of a corpse immersed in glacier ice becoming exposed on a glacier surface is closely connected with the glaciological conditions at the scene and the site of the accident. Provided that the time since death is known, certain questions relative to the circumstances of a mountain accident can only be answered by considering glaciological aspects. How the scene of an accident can be reconstructed by inference from the site of discovery is discussed by means of three exemplary cases that occurred on Tyrolean glaciers (Austria) during the past 40 years: (1) Two corpses were discovered close above the equilibrium line in the accumulation area after 25 years. The two victims had fallen down a rock face after the breaking off of a cornice and had come to rest in the uppermost part of the accumulation area. (2) A victim was discovered in the lower ablation area 8 years after falling down a crevasse in the middle part of the ablation area. (3) A female alpinist was discovered at the very end of the glacier after 29 years; it was concluded that the accident must have happened in the accumulation area. PMID:1955834

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    Here we present the results of a comprehensive glaciological investigation of Union Glacier (7946' S/8324' W) in the West Antarctic Ice Sheet (WAIS), a major outlet glacier within the Ellsworth Mountains. Union Glacier flows into the Ronne Ice Shelf, where recent models have indicated the potential for significant grounding line zone (GLZ) migrations in response to changing climate and ocean conditions. To elaborate a glaciological base line that can help to evaluate the potential impact of this GLZ change scenario, we installed an array of stakes on Union Glacier in 2007. The stake network has been surveyed repeatedly for elevation, velocity, and net surface mass balance. The region of the stake measurements is in near-equilibrium, and ice speeds are 10 to 33 m a-1. Ground-penetrating radars (GPR) have been used to map the subglacial topography, internal structure, and crevasse frequency and depth along surveyed tracks in the stake site area. The bedrock in this area has a minimum elevation of -858 m a.s.l., significantly deeper than shown by BEDMAP2 data. However, between this deeper area and the local GLZ, there is a threshold where the subglacial topography shows a maximum altitude of 190 m. This subglacial condition implies that an upstream migration of the GLZ will not have strong effects on Union Glacier until it passes beyond this shallow ice pinning point.

  20. Alpine Glaciers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 27 August 2003

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

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

  1. 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.

  2. Late Glacial Mountain Glacier culmination in Arctic Norway 14,000 years ago consistent to southern mid-latitudes

    NASA Astrophysics Data System (ADS)

    Wittmeier, H. E.; Schaefer, J. M.; Bakke, J.; Rupper, S.; Paasche, O.; Schwartz, R.; Finkel, R. C.

    2014-12-01

    The culmination of Scandinavian glaciers during the Late Glacial period (16-11 ka) has been connected to the Younger Dryas stadial (12.9-11.7 ka). Here we present a detailed geomorphic, chronologic and model reconstruction of LG and Holocene fluctuations of Rdhetta Glacier on the Island of Arnya in Arctic Norway. Our comprehensive Late Glacial through Holocene 10Be mountain glacier moraine chronology indicates that the Late Glacial culmination occurred 14.1 ka ago, more than 1000 years prior to the onset of the Younger Dryas stadial. The Younger Dryas glacier advances, with an onset around 12.3 ka ago, were significantly smaller in amplitude than the earlier LG culmination, and Rdhetta Glacier slightly retreated through the Younger Dryas stadial with the final culmination 11.5 ka ago. No subsequent culminations took place during the Holocene until the Little Ice Age. Glacier modeling indicates an Equilibrium Line Altitude lowering compared to present-day (695 m a.s.l.) for the Late Glacial moraine sequence of ~220 m, for the Younger Dryas of ~130 m, and for the Little Ice Age of ~80 m. The most likely climate conditions during the moraine formation periods are represented by summer temperature coolings compared to present-day by Late Glacial ~3.2 C, Younger Dryas ~1.9 C, and Little Ice Age ~0.8 C. We show that this Late Glacial mountain glacier pattern of Arctic glacier culminations and retreat during the Late Glacial period and the Younger Dryas stadial is consistent with updated glacier records in the North Atlantic region. Recent 10Be moraine chronologies from the southern mid-latitudes are strikingly similar.

  3. 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.

  4. 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.

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

    USGS Multimedia Gallery

    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)...

  6. 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.

  7. 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.

  8. Muir Glacier Retreats

    USGS Multimedia Gallery

    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 Glaciers 1941 thickness and th...

  9. Columbia Glacier Terminus

    USGS Multimedia Gallery

    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 ...

  10. Principles of Glacier Mechanics

    NASA Astrophysics Data System (ADS)

    Waddington, Edwin D.

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

  11. Dynamics of a Younger-Dryas glacier system framed by Blling-Allerd and Preboreal landslides

    NASA Astrophysics Data System (ADS)

    Reindl, Martin; Bichler, Mathias G.; Husler, Hermann; Reitner, Jrgen M.

    2013-04-01

    The head of the Httwinkl valley in the Austrian province of Salzburg, north of the Hoher Sonnblick (3106m asl) in the Hohe Tauern alpine range provides an excellent opportunity to reconstruct a Younger-Dryas (Egesen stadial) glacier system and its relation to prominent landslides from the onset of the ice advance to the retreat phase. The landslide events (13ka BP and 10ka BP) as well as the glacial advance (12.5ka BP) and retreat (11ka BP) were dated using terrestrial in-situ cosmogenic nuclides (TCN), 10Be in this case, and, partly, organic 14C from peat. To produce a extensive chronology, seven TCN samples from the landslides, and eleven TCN boulder samples and two TCN polished bedrock samples related to glacier history were processed. Detailed sedimentary evidence allows us to constrain the starting position of glaciers before the Younger Dryas advance, as well reconstructing a confluence situation of the two local glaciers (Goldbergkees and Pilatuskees), producing a glacier system with a maximum surface area of 10 km2, as well as shedding some light on the glacial dynamics during the retreat phases of the Egesen. In addition, surface models revealed in one case a reconstituted glacier geometry. We employed various methods for calculating Equilibrium-Line-Altitudes (Maximum Elevation of Lateral Moraines, Toe-to-Headwall-Altitude Ratio, Area x Altitude, Area x Altitude Balance Ratio, and Accumulation Area Ratio) and compared them to already available data from western Austria and Switzerland. With this data, we are able to reconstruct temperature and precipitation change of the local climate and glacier dynamics during the maximum of the Younger-Dryas in the central part of the European Eastern Alps.

  12. Green's functions in equilibrium and nonequilibrium from real-time bold-line Monte Carlo

    NASA Astrophysics Data System (ADS)

    Cohen, Guy; Gull, Emanuel; Reichman, David R.; Millis, Andrew J.

    2014-03-01

    Green's functions for the Anderson impurity model are obtained within a numerically exact formalism. We investigate the limits of analytical continuation for equilibrium systems, and show that with real time methods even sharp high-energy features can be reliably resolved. Continuing to an Anderson impurity in a junction, we evaluate two-time correlation functions, spectral properties, and transport properties, showing how the correspondence between the spectral function and the differential conductance breaks down when nonequilibrium effects are taken into account. Finally, a long-standing dispute regarding this model has involved the voltage splitting of the Kondo peak, an effect which was predicted over a decade ago by approximate analytical methods but never successfully confirmed by numerics. We settle the issue by demonstrating in an unbiased manner that this splitting indeed occurs. Yad Hanadiv-Rothschild Foundation, TG-DMR120085, TG-DMR130036, NSF CHE-1213247, NSF DMR 1006282, DOE ER 46932.

  13. SAR investigations of glaciers in northwestern North America

    NASA Technical Reports Server (NTRS)

    Lingle, Craig S.; Harrison, William D.

    1995-01-01

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

  14. 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.

  15. Muir Glacier in Glacier Bay National Monument 1941

    USGS Multimedia Gallery

    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...

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The temperature and moisture history of the equatorial lower free troposphere over the last few hundred years is important for evaluating and predicting global warming. New evidence constrains the freezing level height (FLH) in the western equatorial Pacific over the last 200 years using the snow-line altitude (ELA) on glaciers at elevations of 4000 to 5000 m (600 hPa) on Mt. Jayawijaya, Papua Province, Indonesia (4oS, 136oE). The ELA of these wet tropical glaciers is closely coupled to the mean annual 0oC isotherm. The areal recession of the Jayawijaya glaciers continued to May 2011 by which time 95 percent of the ice cover that existed between 1936 and 1942 disappeared; 1 km2 remained. For the periods 2000-2006 and 2006-2011, the ELA was above 4950 m above sea level (asl). Revised reconstructions of the glaciers from 1936 to 1942 based on aerial photographs indicate that the concurrent ELA was at 4610 10 m asl. The glaciers were interpreted to be in mass balance equilibrium between 1936 and 1942 because no appreciable areal change was detected and the glacier fronts had steep profiles. We assumed an accumulation area ratio of 0.8, typical of tropical glaciers. Extensive, fresh moraines downvalley from the 1936 ice margin indicate that the glaciers were more extensive and had lower ELAs in recent centuries. We define the most extensive, fresh moraine system of the Jayawijaya glaciers as representing the local Little Ice Age (LLIA) maximum and, following previous work, assign its age as ~1850. Our reconstruction of the Jayawijaya glaciers at the LLIA maximum based on moraines and current topographic divides indicates that they covered an area of 30 km2, considerably more than previous estimates. A concurrent ELA at ~4450 m asl was calculated assuming an accumulation area ratio of 0.8. The moraines indicate that the glaciers were in equilibrium. Taken together, glacier ELAs on Mt. Jayawijaya, approximating the FLH, have risen 500 m since the LLIA maximum. The average ELA and FLH rose at ~100 m/decade from 1972 to 2005, after which they exceeded 4950 m. For 125 years before 1972, the ELA rose on average at less than 20 m/decade. We seek a link between the rise in FLH, atmospheric warming, and western Pacific sea-surface temperature change.

  17. 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?

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  19. 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 (190012) 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 Lthi 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).

  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. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    Past fluctuations in climatically sensitive tropical glaciers provide important insight into regional paleoclimatic trends and forcings, but well-dated chronologies are scarce, particularly during the Holocene. We have established precise cosmogenic 10Be surface exposure ages of moraine sequences in the Cordillera Vilcabamba (1320S latitude), located in the outer tropics of southern Peru. Results indicate the dominance of two major glacial culminations and associated climatic shifts in the Vilcabamba, including an early Holocene glacial interval and a somewhat less extensive glaciation late in the Little Ice Age (LIA) period. Lichenometric measurements on the youngest moraines support the 10Be ages, but uncertainties in the lichen ages arise from the lack of a local lichen growth curve. The Peruvian glacier chronologies differ from a recently-developed New Zealand record but are broadly correlative with well-dated glacial records in Europe, suggesting climate linkages between the tropics and the North Atlantic region. For the latest Holocene, our leading hypothesis is that climate forcings involving southward migration of the Atlantic Intertropical Convergence Zone can explain concurrent glaciations in tropical South America and northern high latitudes, but the influence of other climate drivers such as the El Nio/Southern Oscillation may have also played a role. Estimated differences between equilibrium-line altitudes (ELAs) on modern glaciers and those inferred for expanded latest Holocene glaciers reveal an ELA rise of 165-200 m since the LIA, suggesting that temperatures 1.1-1.3C cooler than present could have sustained glaciers at their LIA maximum positions if temperature was the only control, and thus providing an upper bound on temperature depression during the LIA. However, further work is required to constrain the likely role of precipitation changes. These new Peruvian glacier chronologies and ELA reconstructions complement ice core and lacustrine paleoclimate records in the vicinity, thereby increasing spatial and temporal coverage for identifying patterns of climate change in the tropical Andes during the Holocene.

  3. 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 Pea, 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.

  4. Glacier Ecosystems of Himalaya

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  5. Satellite Observations of Mass Changes and Glacier Motions at the Patagonian Icefields, South America

    NASA Astrophysics Data System (ADS)

    Willis, M. J.; Melkonian, A. K.; Pritchard, M. E.; Ramage, J. M.

    2011-12-01

    The 4000 km2 Northern Patagonian Icefield (NPI), 13,000 km2 Southern Patagonian Icefield (SPI) and the 2500 km2 Cordillera Darwin Icefields (CDI) form the main ice bodies of the Patagonian Icefields of South America. Analysis of satellite imagery, derived digital elevation models (DEMs) and spaceborne laser altimetry confirm that each of the icefields is currently losing mass. The NPI lost mass at a rate of 3.400.07 Gt/yr between 2001 and 2011, equivalent to 0.0090.0002 mm/yr of sea level rise. This contribution is a lower bound as we do not include sub-aqueous mass loss or area changes in our calculations. About 80% of the mass loss occurred from thinning over the ablation areas of the outlet glaciers of the icefield while the remaining 20% occurred at higher elevation above the equilibrium line altitude. Mass loss is especially concentrated at the low elevation southwestern and mid-western parts of the icefield. There, ice in the ablation zone approximately doubled in speed between 2007 and 2011. Passive microwave observations indicate that the glacier surface in these regions was "wet" for almost the entire study period. We suggest that the acceleration is linked to the reduction of friction at the bed of the glaciers via water making its way to the glacier sole. The glaciers that accelerated make up only a small proportion of the NPI and we find no evidence of accelerating mass loss from the NPI over the period considered. The SPI lost an average of 13.10.2 km3/yr of ice between 2001 and 2011. This rate is almost identical to previous studies, but the masks observations of rapidly accelerating thinning occuring at several of the outlet glaciers. Previous studies find that the peak rate of thinning at the HPS12 Glacier was 28 m/yr between 1995 and 2000. We find this slowed to 213 m/yr between 2000 and 2006, before accelerating to a rate of 5713 m/yr between 2005 and 2011. Between 2000 and 2011 the HPS12 Glacier continued its rapid retreat, with the front receding 4.2 km. Maximum thinning rates have also increased dramatically at the tidewater Jorge Montt Glacier, from 207 m/yr between 2000 and 2005 to 6011 m/yr between 2005 and 2011 and at the Upsala Glacier, which thinned at a peak rate of 10.02.0 m/yr from 2000 to 2005, accelerating to 24.82.4 m/yr from 2005 to 2011. Ice near the front of the retreating Jorge Montt and HPS12 glaciers is moving rapidly, at more than 20 m/day. Large thinning rates and rapid motions imply that ice dynamics are an important component of the volume changes observed at these outlet glaciers. The CDI lost volume at a rate of 1.950.13 km3/yr between 2001 and 2011. The loss is concentrated at the ablation zones of the Marinelli, CDI-08 and Darwin glaciers. The volume loss at the CDI is large compared to the small size of the icefield. We do not have enough acquisitions to detect speed changes, but provide baseline measurement of glacier speeds for most of the icefield. We find a total volume loss of about 19.1 km3/yr from the Patagonian Icefields between 2000 and 2011. This estimate should be considered a lower bound as we do not take into account area changes.

  6. Glaciers in 21st Century Himalayan Geopolitics

    NASA Astrophysics Data System (ADS)

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

    2002-05-01

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

  7. Reconstructing glacier-based climates of LGM Europe and Russia Part 1: Numerical modelling and validation methods

    NASA Astrophysics Data System (ADS)

    Allen, R.; Siegert, M. J.; Payne, A. J.

    2008-11-01

    The mountain environments of mid-latitude Europe and Arctic Russia contain widespread evidence of Late-Quaternary glaciers that have been attributed to the Last Glacial Maximum (LGM). This glacial-geological record has yet to be used to quantitatively reconstruct the LGM climate of these regions. Here we describe a simple glacier-climate model that can be used to derive regional temperature and precipitation information from a known glacier distribution. The model was tested against the present day distribution of glaciers in Europe. The model is capable of adequately predicting the spatial distribution, snowline and equilibrium line altitude climate of glaciers in the Alps, Scandinavia, Caucasus and Pyrenees Mountains. This verification demonstrated that the model can be used to investigate former climates such as the LGM. Reconstructions of LGM climates from proxy evidence are an important method of assessing retrospective general circulation model (GCM) simulations. LGM palaeoclimate reconstructions from glacial-geological evidence would be of particular benefit to investigations in Europe and Russia, where to date only fossil pollen data have been used to assess continental-scale GCM simulations.

  8. Reconstructing glacier-based climates of LGM Europe and Russia - Part 1: Numerical modelling and validation methods

    NASA Astrophysics Data System (ADS)

    Allen, R.; Siegert, M. J.; Payne, A. J.

    2007-10-01

    The mountain environments of mid-latitude Europe and Arctic Russia contain widespread evidence of Late-Quaternary glaciers that have been prescribed to the Last Glacial Maximum (LGM). This glacial-geological record has yet to be used to quantitatively reconstruct the LGM climate of these regions. Here we describe a simple glacier-climate model that can be used to derive regional temperature and precipitation information from a known glacier distribution. The model was tested against the present day distribution of glaciers in Europe. The model is capable of adequately predicting the spatial distribution, snowline and equilibrium line altitude climate of glaciers in the Alps, Scandinavia, Caucasus and Pyrenees Mountains. This verification demonstrated that the model can be used to investigate former climates such as the LGM. Reconstructions of LGM climates from proxy evidence are an important method of assessing retrospective general circulation model (GCM) simulations. LGM palaeoclimate reconstructions from glacial-geological evidence would be of particular benefit to investigations in Europe and Russia, where to date only fossil pollen data have been used to assess continental-scale GCM simulations.

  9. 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.

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

    SciTech Connect

    De Avillez, Miguel A.; Breitschwerdt, Dieter

    2012-12-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  12. 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.

  13. 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.

  14. Bathymetric control of tidewater glacier mass loss in northwest Greenland

    NASA Astrophysics Data System (ADS)

    Porter, David F.; Tinto, Kirsty J.; Boghosian, Alexandra; Cochran, James R.; Bell, Robin E.; Manizade, Serdar S.; Sonntag, John G.

    2014-09-01

    It has been suggested that fjord geometry could be an important contributor to the observed mass loss variability in Greenland by modulating the flow of warm water to marine-terminating glaciers. New gravity-derived bathymetry of Greenlandic fjords confirms the link between the grounding line depth and rates of glacier mass loss, a relationship previously predicted only in ice models. We focus on two neighboring glaciers to minimize differences in external forcing and therefore isolate the role of the fjord bathymetry. Tracy Glacier has a deeper grounding line and has been retreating since 1892 with a contemporary mass budget of -1.63 Gt a-1. Heilprin Glacier has a shallower grounding line depth, a stable ice terminus, and a mass budget of only -0.53 Gt a-1. Because of its deeper grounding line, Tracy has more ice in contact with warm subsurface water, leaving it more vulnerable to changes in ocean forcing and therefore mass loss.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Glacier activity at the Lateglacial / Holocene transition inferred from the Swiss Alps

    NASA Astrophysics Data System (ADS)

    Schindelwig, Inga; Akar, Naki; Lukas, Sven; Kubik, Peter W.; Schlchter, Christian

    2010-05-01

    High-alpine environments react sensitively to changes in climate. Depending on size, catchment area and valley topography, mountain glaciers response relatively fast with advances and recessions to shifts in temperature and precipitation (e.g. Oerlemans, 2005). About half of the present glaciers in the Swiss Alps are located in the highest mean altitudes areas. Past glacier activity beyond actual glacier extent is sometimes easily identified, such as the moraines related to the Little Ice Age. Records of older glacier activity, however, are usually less abundant. Lateglacial glacier advances are often documented by moraine complexes. By comparing geomorphological characteristics within and between several investigated sites across the Swiss Alps, a relative chronology of glacier oscillations and re-advances was established. A cross-correlation of moraines in the same high-alpine climatic region allows to conclude that moraine ridges in comparable relative positions with similar morphologies and characterized by similar equilibrium line altitude depressions (Gross et al. 1977; Maisch, 1987), may be allocated to the same supra-regional trends in climate change. Surface exposure dating on well defined moraines gives the absolute chronology for the relative framework. More than 50 samples from erratic boulders on the crestline of moraines and glacially abraded bedrock were dated using the radionuclide 10Be. According to the results on boulders of the outer moraines, the oldest ridge coincides in time with the initial phase of the Younger Dryas (e.g. Gerzensee Oscillation). In addition, a number of Lateglacial and early Holocene advances have been identified (Preboreal Oscillation, Younger Dryas and Gerzensee Oscillation). 10Be exposure ages on moraines of the innermost Lateglacial complexes, but distinctly downvalley from Little Ice Age moraines point to cold conditions in the Alps during the early Holocene. REFERENCES Gross, G., Kerschner, H. & Patzelt, G. (1977): Methodische Untersuchungen ber die Schneegrenze in alpinen Gletschergebieten. Zeitschrift fr Gletscherkunde und Glazialgeologie, 12, 223-251. Maisch, M. (1987): Zur Gletschergeschichte des alpinen Sptglazials: Analyse und Interpretation von Schneegrenzdaten. Geographica Helvetica, 42, 63-71. Oerlemans, J. (2005): Extracting a Climate Signal from 169 Glacier Records. Science, 308, 675-677.

  2. 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.

  3. 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.

  4. 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.

  5. 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 0C 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 ~2.10.4C (relative to modern) and increased about 0.6 to 1C 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.

  6. Columbia Glacier Calving

    USGS Multimedia Gallery

    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...

  7. Photographer Overlooking Columbia Glacier

    USGS Multimedia Gallery

    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 ...

  8. Denali Fault: Susitna Glacier

    USGS Multimedia Gallery

    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...

  9. 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

  10. 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

  11. 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.

  12. Melting beneath Greenland outlet glaciers and ice streams

    NASA Astrophysics Data System (ADS)

    Alexander, David; Perrette, Mah; 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.

  13. 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.

  14. Analysis of the relationship between glacier ELA with climatic and morpho-topographic parameters, for tropical glaciers in the Peruvian Andes

    NASA Astrophysics Data System (ADS)

    Loarte, Edwin; Rabatel, Antoine

    2013-04-01

    In recent decades, climate change has produced an important glacier shrinkage in the Peruvian mountain chains, with accelerated melting of ice and snow masses and an increase in the equilibrium-line altitude (ELA). These changes have led to conflicts on water availability for local and regional populations and increasing glacier risks (proglacial lakes formation). In this study we have determined the spatio-temporal variations of ELA obtained through the snowline altitude (SLA) for a total of 17 glaciers of the Cordillera Blanca (Peru, 9S) during the period 2001-2010. These time series have been analysed in function to climate and morpho-topographic parameters in order to quantify their influences on the spatio-temporal variations of the ELA. The investigation is based on optical remote-sensing images and geographic information systems (GIS). The relationship between the snowline measured on the satellite images recorded during the dry season and the ELA has been validated on four glaciers where mass balance field measurements are conducted since the early 2000s. For the study period, the average ELA at the scale of the Cordillera Blanca is about ~ 4920 m a.s.l. and an increasing trend (~ 11 m / year) is observed. The comparison with climatic and morpho-topographic parameters, shows that the average ELA over the study period is mainly controlled by morpho-topographic parameters, but the interannual variations are mainly driven by climate conditions (the best correlation being found when comparing ELA anomalies with temperature at 500 hPa anomalies).

  15. 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; Baug, 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.

  16. 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.

  17. Ablation of Martian glaciers

    NASA Technical Reports Server (NTRS)

    Moore, Henry J.; Davis, Philip A.

    1987-01-01

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

  18. 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.

  19. A strategy for monitoring glaciers

    USGS Publications Warehouse

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

    1997-01-01

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

  20. 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.

  1. 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 33.5S., 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 km watershed contains 2.3 km of uncovered glaciers, 0.9 km of debris-covered glacier area and 4.3 km 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 7.9C at 2987 m asl to 0.8C 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.

  2. 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.

  3. Knik Glacier; Alaska, May 1979 monument and glacier survey

    USGS Publications Warehouse

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

    1979-01-01

    From 1915, or earlier, to 1966, with the exception of 1963, Knik Glacier annually formed and released Lake George, the largest glacier-dammed lake in Alaska. Eleven geodetically controlled survey stations were defined in the basin, and 22 glacier surface altitudes were measured. This is the first effort in a continuing program whose goal is predicting the future behavior of Knik Glacier and Lake George. (Kosco-USGS)

  4. Modeling 2 m air temperatures over mountain glaciers: Exploring the influence of katabatic cooling and external warming

    NASA Astrophysics Data System (ADS)

    Ayala, A.; Pellicciotti, F.; Shea, J. M.

    2015-04-01

    Air temperature is one of the most relevant input variables for snow and ice melt calculations. However, local meteorological conditions, complex topography, and logistical concerns in glacierized regions make the measuring and modeling of air temperature a difficult task. In this study, we investigate the spatial distribution of 2 m air temperature over mountain glaciers and propose a modification to an existing model to improve its representation. Spatially distributed meteorological data from Haut Glacier d'Arolla (Switzerland), Place (Canada), and Juncal Norte (Chile) Glaciers are used to examine approximate flow line temperatures during their respective ablation seasons. During warm conditions (off-glacier temperatures well above 0C), observed air temperatures in the upper reaches of Place Glacier and Haut Glacier d'Arolla decrease down glacier along the approximate flow line. At Juncal Norte and Haut Glacier d'Arolla, an increase in air temperature is observed over the glacier tongue. While the temperature behavior over the upper part can be explained by the cooling effect of the glacier surface, the temperature increase over the glacier tongue may be caused by several processes induced by the surrounding warm atmosphere. In order to capture the latter effect, we add an additional term to the Greuell and Bhm (GB) thermodynamic glacier wind model. For high off-glacier temperatures, the modified GB model reduces root-mean-square error up to 32% and provides a new approach for distributing air temperature over mountain glaciers as a function of off-glacier temperatures and approximate glacier flow lines.

  5. The GLIMS Glacier Database

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

  6. Debris-Free Plateau Glacier

    USGS Multimedia Gallery

    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....

  7. 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.

  8. Karakoram glacier surge dynamics

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  9. 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.

  10. Denali Fault: Black Rapids Glacier

    USGS Multimedia Gallery

    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...

  11. Greenland Glacier Albedo Variability

    NASA Technical Reports Server (NTRS)

    2004-01-01

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

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

    Starting in summer 2000, Belvedere Glacier, near Macugnaga, Italian Alps, developed an extraordinary change in flow, geometry and surface appearance. A surge-type flow acceleration started in the lower parts of the Monte-Rosa east face, leading to strong crevassing and deformation of Belvedere Glacier, accompanied by bulging of its orographic right margin. In September 2001, a small supraglacial lake developed on the glacier. High water pressure and accelerated movement lasted into winter 2001/2002. The ice, in places, started to override moraines from the Little Ice Age. In late spring and early summer 2002, the supraglacial lake grew at extraordinary rates reaching a maximum area of more than 150'000 m2 by end of June. The evolution of such a large supraglacial lake, a rather unique feature in the Alps, was probably enabled by changes in the subglacial drainage system in the course of the surge-like developments with high water pressure in the glacier. At the end of June, an enhanced growth of the lake level with a rise of about 1 m per day was observed such that the supraglacial lake became a urgent hazard problem for the community of Macugnaga. Emergency measures had to be taken by the Italian Civil Protection. The authors thereby acted as the official expert advisers. Temporal evacuations were ordered and a permanent monitoring and alarm system was installed. Pumps with a maximum output of 1 m3/s were brought to the lake. Bathymetric studies yielded a maximum lake depth of 55 m and a volume of 3.3 millions of cubic meters of water. Aerial photography of 1995, 1999, September 2001 and October 2001 was used to calculate ice flow velocities and changes in surface altitude. Compared to the period of 1995 to 1999, the flow accelerated by about five times in 2001 (max. speeds up to 200 m/yr). Surface uplift measured was about 10-15 m/yr. The results of the photogrammetric studies were used to evaluate different possible lake-outburst scenarios, in particular overtopping and failure of ice dam with catastrophic subglacial drainage. In consideration of the current bathymetric studies and ice thickness measurements from the 1980ies, it was assumed that the floatation equilibrium was possibly reached by end of June. In case of an ice dam, the maximum discharge of a related subglacial drainage was estimated at 200 m3/s, probably involving a large debris flow. Extension and nature of thermokarst processes of the lake/ice interface are currently studied by repeated bathymetric measurements and adaption of corresponding models. In July/August 2002, geodetic ice flow velocity measurements showed that the enhanced flow velocities have decreased probably indicat ing the end of the surge-like movement. In conclusion, the developments at Macugnaga are an excellent example illustrating the need for inte grated hazard assessments in consideration of complex process chains. The current situation requires studies on different aspects, such as rock instabilities, glacier dynamics and hydrology, geomorphody namics, and mitigation-construction planning.

  14. Experimental Determination of the Liquid Line of Descent of Anhydrous Mantle Derived Tholeiitic Liquids by Fractional and Equilibrium Crystallisation at 1.0 GPa

    NASA Astrophysics Data System (ADS)

    Villiger, S.; Ulmer, P.; Thompson, A. B.; Muentener, O.

    2003-12-01

    To constrain phase equilibria as well as solid and liquid compositions along the liquid line of descent of primary basaltic magmas in reservoirs that are located at the base of the continental crust, two series of anhydrous experiments have been performed in end-loaded piston cylinder apparatus at 1.0 GPa pressure and temperatures in the range 1060 to 1330 C. As starting material an experimentally produced mantle-derived tholeiitic basalt that is in equilibrium with a lherzolitic residue at 1.5 GPa and 1300 C (Hirose & Kushiro, 1993; EPSL 114, 477-489) was used. The first series are equilibrium crystallisation experiments on a single bulk composition. For the second series a step-wise approach was used to achieve near-perfect fractional crystallisation: Melting experiments where performed with temperature steps of 30 C and starting compositions corresponding to the liquid composition of the previous, higher temperature glass composition. Liquids of fractional crystallisation experiments evolve through constant silica increase from basalts to dacites, whereas liquids from equilibrium crystallisation experiments remain basaltic and display only a moderate SiO_ {2} increase accompanied by more pronounced alumina enrichment. Responsible for these contrasting trends are suppression of the peritectic olivine + liquid = opx reaction and earlier plagioclase saturation in the fractionation experiments compared to the equilibrium experiments. At high pressure both processes form large volumes of ultramafic cumulates related to the suppression of plagioclase crystallisation relative to pyroxenes. This is in contrast to fractionation of tholeiitic liquids at low pressures, where silica is enriched in the latest stage of differentiation and early fractionation of plagioclase lead to the production of troctolites followed by (olivine-)gabbros. Compositional variation of pyroxenes and plagioclase are influenced by the fractionation process. In fractional crystallisation experiments, the Al content systematically decreases at lower temperature while in equilibrium crystallisation it does not. Thermodynamic calculations using the MELTS program indicates that the Al activity in the liquid exerts a fundamental control on Al partitioning between liquid and pyroxenes. Likewise different An contents in plagioclase at similar CaO/Na_ {2}O ratios in the liquid are controlled by Na and K activity in the residual liquid. This suggests that liquid composition potentially is an important factor in controlling crystal-liquid partitioning.

  15. 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.

  16. 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 ...

  17. 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.

  18. 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.

  19. 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.

  20. Variable glacier response to atmospheric warming, 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.

    2012-09-01

    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 data for glacier classification, morphology, area, length or altitude. This paper firstly classifies the area, length, altitude, slope, aspect, geomorphology, type and hypsometry of 194 glaciers on Trinity Peninsula, Vega Island and James Ross Island in 2009 AD. Secondly, this paper documents glacier change 1988-2009. In 2009, the glacierised area was 8140262 km2. From 1988-2001, 90% of glaciers receded, and from 2001-2009, 79% receded. This equates to an area change of -4.4% for Trinity Peninsula eastern coast glaciers, -0.6% for western coast glaciers, and -35.0% for ice-shelf tributary glaciers from 1988-2001. Tidewater glaciers on the drier, cooler eastern Trinity Peninsula experienced fastest shrinkage from 1988-2001, with limited frontal change after 2001. Glaciers on the western Trinity Peninsula shrank less than those on the east. Land-terminating glaciers on James Ross Island shrank fastest in the period 1988-2001. This east-west difference is largely a result of orographic temperature and precipitation gradients across the Antarctic Peninsula, with warming temperatures affecting the precipitation-starved glaciers on the eastern coast more than on the western coast. Reduced shrinkage on the western Peninsula may be a result of higher snowfall, perhaps in conjunction with the fact that these glaciers are mostly grounded. Rates of area loss on the eastern side of Trinity Peninsula are slowing, which we attribute to the floating ice tongues receding into the fjords and reaching a new dynamic equilibrium. The rapid shrinkage 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, reaching equilibrium more quickly.

  1. High Sensitivity of Tidewater Glacier Dynamics to Shape

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  2. The Natural Variability of Glaciers

    NASA Astrophysics Data System (ADS)

    Roe, G.

    2012-04-01

    Glaciers respond to both the natural variability that is intrinsic to a constant climate and also to the trends and shifts that constitute actual climate change. Over the last ten years a series of studies has shown, for a variety of climatic and glacier settings, that the standard deviation (1 sigma) of natural glacier-length fluctuations may range from 300 to 600 m. By definition of the standard deviation, a glacier will spend approximately 5% of its time outside 2? (and 1% of its time outside of 3?). Thus, fluctuations of several kilometers can be expected to occur every few centuries, even without any climate change. Because these magnitudes rival those commonly interpreted as reflecting Holocene climate changes, it is vital to improve our understanding of these natural glacier fluctuations. The physical basis for this behavior is presented. The magnitude and duration of natural glacier fluctuations depends straightforwardly on the geometry and average climate of the glacier setting, and the probability distribution of interannual climate variability. Such dependence can be demonstrated in a simple linear glacier model. The analyses are supplemented by detailed dynamical flowline modeling of glaciers around Mt. Baker in Washington State, and Franz Josef glacier in New Zealand.

  3. 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.

  4. 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.

  5. 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.

  6. Laboratory Evidence That Line-Tied Toroidal Magnetic Fields Can Suppress Loss-of-Equilibrium Flux Rope Eruptions in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Myers, C. E.; Yamada, M.; Belova, E.; Ji, H.; Yoo, J.; Fox, W. R., II; Jara-Almonte, J.

    2014-12-01

    Loss-of-equilibrium mechanisms such as the ideal torus instability [Kliem & Trk, Phys. Rev. Lett. 96, 255002 (2006)] are predicted to drive arched flux ropes in the solar corona to erupt. In recent line-tied flux rope experiments conducted in the Magnetic Reconnection Experiment (MRX), however, we find that quasi-statically driven flux ropes remain confined well beyond the predicted torus instability threshold. In order to understand this behavior, in situ measurements from a 300 channel 2D magnetic probe array are used to comprehensively analyze the force balance between the external (potential) and internal (plasma-generated) magnetic fields. We find that forces due to the line-tied toroidal magnetic field, which are not included in the basic torus instability theory, can play a major role in preventing eruptions. The dependence of these toroidal magnetic forces on various potential field and flux rope parameters will be discussed. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the NSF/DoE Center for Magnetic Self-Organization (CMSO).

  7. Laboratory evidence that line-tied tension forces can suppress loss-of-equilibrium flux rope eruptions in the solar corona

    NASA Astrophysics Data System (ADS)

    Myers, C. E.; Yamada, M.; Belova, E.; Ji, H.; Yoo, J.; Fox, W.; Jara-Almonte, J.; Gao, L.

    2014-10-01

    Loss-of-equilibrium mechanisms such as the ideal torus instability [Kliem & Trk, Phys. Rev. Lett. 96, 255002 (2006)] are predicted to drive arched flux ropes in the solar corona to erupt. In recent line-tied flux rope experiments conducted in the Magnetic Reconnection Experiment (MRX), however, we find that quasi-statically driven flux ropes remain confined well beyond the predicted torus instability threshold. In order to understand this behavior, in situ measurements from a 300 channel 2D magnetic probe array are used to comprehensively analyze the force balance between the external (vacuum) and internal (plasma-generated) magnetic fields. We find that the line-tied tension force--a force that is not included in the basic torus instability theory--plays a major role in preventing eruptions. The dependence of this tension force on various vacuum field and flux rope parameters will be discussed. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the NSF/DoE Center for Magnetic Self-Organization (CMSO).

  8. Icefall on the Lambert Glacier

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Lambert Glacier in Antarctica is the world's largest glacier. The focal point of this image is an icefall that feeds into the Lambert glacier from the vast ice sheet covering the polar plateau. Ice flows like water, albeit much more slowly. Cracks can be seen in this icefall as it bends and twists on its slow-motion descent 1300 feet (400 meters) to the glacier below. This image was acquired by Landsat 7's Enhanced Thematic Mapper plus (ETM+) sensor on December 2, 2000. This is a false-color composite image made using infrared, red, and green wavelengths. The image has also been sharpened using the sensor's panchromatic band.

  9. 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.

  10. 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.

  11. Muir Glacier in Glacier Bay National Monument 2004

    USGS Multimedia Gallery

    This August 2004 photo further documents the significant changes that have occurred during the 63 years between photographs A and C, and during the 54 years between photographs B and C. Muir Glacier has retreated out of the field of view and is now nearly 5 miles to the northwest. Riggs Glacier has ...

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

    USGS Multimedia Gallery

    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....

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

    USGS Multimedia Gallery

    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. ...

  14. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  16. 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 Florncio; Maier, der Leandro Bayer; Simes, 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 Nio-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.

  17. 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.

  18. ASTER Image of Gangotri Glacier

    USGS Multimedia Gallery

    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...

  19. 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.

  20. 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 (6.5N-45.8S), and the sub-Antarctic islands around the northern tip of the Antarctic Peninsula (62.7S-63.8S) 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 Nio Southern Oscillation Index instantaneously (zero-year lag-time) and to the Pacific Decadal Oscillation with an approximately eight-year lag-time.

  1. Ice Flow and Strain Rate over Campbell Glacier in East Antarctica Observed from COSMO-SkyMed InSAR Images

    NASA Astrophysics Data System (ADS)

    Han, H.; Lee, H.

    2013-12-01

    Campbell Glacier (7425?S 16422?E), originated from the end of Mesa Range in Victoria Land, East Antarctica, is a fast-flowing outlet glacier with length of about 110 km approximately. Campbell Glacier flows into northern Terra Nova Bay in Ross Sea and forms a seaward extension of the glacier named as Campbell Glacier Tongue. Campbell Glacier Tongue experiences gravitational ice flow as well as the vertical tidal deflection responding to tide variations. The ice beyond the hinge zone of Campbell Glacier Tongue is not free-floating but in a partially hydrostatic equilibrium state by 96%. In this study, we extracted surface displacement of Campbell Glacier from the 14 COSMO-SkyMed one-day tandem InSAR pairs obtained from January to November 2011. The topographic phases were removed by using ASTER Global Digital Elevation Model. As the DInSAR signals of Campbell Glacier Tongue contain both gravitational ice flow and the vertical tidal deflection, we removed the signals of tidal deflection by using the map of tide deflection rate of the glacier that was generated by Double-differential InSAR images. We then extracted one-day ice flow velocity and strain rate of Campbell Glacier. Campbell Glacier showed steady ice flow during the DInSAR observations. The maximum ice flow velocity was 0.7 m/day at the seaward edge of Campbell Glacier Tongue, while minimum ice flow velocity of 0.2 m/day was observed over the upper grounded part of the glacier. The crevasses on the grounded part of Campbell Glacier appeared near the tensile zone, while that disappeared at the compression zone. The moraines of the glacier migrated downstream along the shear zone. Campbell Glacier Tongue showed shear strain in general, from which we could investigate the nonlinear rotation of the glacier tongue. As a conclusion, we could accurately analyze the ice flow velocity and strain rate of Campbell Glacier from COSMO-SkyMed one-day tandem InSAR images by removing the signals of tidal deflection of the glacier. The glacier showed different flow velocity and strain rate along the streamline. By this research, we could conclude that the ice flow of outlet glacier from InSAR images should be estimated after removing the signals of tidal deflection of the glacier.

  2. 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.

  3. Temporal behavior of line-to-continuum ratios and ion fractions as a means of assessing thermodynamic equilibrium in laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Moon, Heh-Young; Smith, Benjamin W.; Omenetto, Nicol

    2012-04-01

    Two diagnostic approaches, aimed at evaluating the departure from local thermodynamic equilibrium (LTE) in laser-induced plasmas, are discussed in this paper. The first approach is based upon the observed temporal behavior of the ratio between selected atomic transitions and the nearby spectral continuum, while the second approach makes use of the plot of the ion fraction of different elements as a function of their respective ionization potentials. Both approaches are known in atomic emission spectroscopy: the former has been described and used in the case of a high pressure surfatron argon plasma, and the latter follows directly from the classic work dealing with d.c. arc emission in general, and a d.c. copper arc in particular. Such approaches, however, have not yet been applied to laser-induced plasmas. It is shown that the experimental results obtained with both methods agree with those reported in the literature using more conventional approaches. For example, in this work, the well-known outcome that the excitation temperature and the ion (electron) temperature differ substantially at early delays after the formation of the plasma is clearly supported by the line-to-continuum approach applied to atomic and ionic transitions of Cu and Fe. In addition, the agreement between the experimental and theoretical behavior of the ion fraction versus the ionization potential for the elements Cu, Fe, Ni, Mg and Ti improves as the delay time increases.

  4. 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.

  5. Application of Near-Surface Geophysics to Problems in Glacier Dynamics, Pitted Outwash Plain Formation, and Glaciotectonics, Matanuska Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Baker, G. S.; Pyke, K.; Evenson, E.; Lawson, D.; Larson, G.; Alley, R. B.

    2005-05-01

    From 2000 to 2004, near-surface geophysics data in various forms was collected near the active terminus of Matanuska Glacier, Alaska, to address several specific hypotheses and also provide general subsurface information in several relatively unsampled zones of the subsurface. (1) Seismic reflection data was collected on the glacier to test the predicted thickening of debris-rich basal ice in response to the motion of the glacier out of a localized overdeepening. The seismic data imaged the 5-to-10 meter thick basal ice at depths of 50-150 m, and clearly showed a 50 percent thicking--supporting the glaciohydraulic supercooling mechanism for basal ice formation. An interesting result of this basal-freeze-on mechanism of forced equilibrium is the concept of the "graded glacier" that has implications of sediment-pumping effects in response to changes in the surface slope of the glacier in response to climate change. (2) Seismic reflection, GPR, and electrical resistivity data were collected in a proximal pitted outwash plain abutting the active margin of Matanuska Glacier. These data indicate the presence of laterally continuous "slabs" of buried ice, in places possibly in duplex-like structures formed during readvances. The formation of thermokarst resulting in pits (sinkholes) in the surface of the outwash plain are therefore interpreted to result from preferential pathways of melting (relict moulins?) in the buried ice slabs, rather than from discreet blocks of ice. (3) 4-D GPR data (3-D through time) were collected at the terminus of Matanuska Glacier in an attempt to examine the formation of debris-flow-generated stratigraphy during the collapse of a portion of an ice-cored moraine complex. During a 30-m readvance of the glacier (2002-2003, between "snapshots" of data collection) glaciotectonic deformation of the moraine stratigraphy was observed. The GPR data indicate that the readvancing glacier impacted the rigid buried ice within the moraine, passively translating and deforming the overlying sediment in response to occasional brittle faulting and thrusting of the buried ice.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    We use a combination of field observations, remote sensing, and digital elevation data to demonstrate how the topographic character of the Alaska Range (Alaska, USA) has been influenced by the exhumation of Tertiary granitic plutons among more erodible sedimentary and metamorphic rocks. Observations that the mean elevations of many tectonically active mountain ranges follow closely the elevation of the mean Cenozoic snowline or glacial equilibrium line (ELA), rather than rates of tectonic rock uplift, have led to the glacial buzzsaw hypothesis - that terrain raised above the ELA is rapidly denuded by glaciers. The Alaska Range stands in prominent exception to this observation. Much of the range is developed on pervasively fractured sedimentary and metamorphic rocks and has local relief of 1000-1500 m. In contrast, early and mid-Tertiary plutons of relatively intact granite support most of the range's impressive mountains (including Mt. McKinley, or Denali, the highest mountain in North America at 6194 m), with 2500-5000 m of local relief. Moreover, these plutons are where the range's modern glaciers originate, as the high peaks protrude in some cases kilometers above modern snowlines. These glaciers flow off of the plutons onto the surrounding, softer rocks, where mean summit elevations are similar to modern snowline elevations. We exploit the Denali massif and the Kichatna Mountains to its west to illustrate the direct ways in which exhumation of granite plutons affects glacial erosion, glacier long profiles, the glacial drainage network, and the effectiveness of periglacial processes. We use simple scaling calculations to explore the potential feedbacks of relief enhancement - specifically, that of avalanching from steep valley walls - on the health of the glaciers occupying the valleys, and describe ways in which peaks can be preserved and allowed to grow to great heights. Our work indicates that most of the Alaska Range has developed in accordance with the glacial buzzsaw hypothesis, except where resistant granite has been exhumed among the weaker rocks. Differential erosion has progressively localized divides on the plutons as they were exhumed, leading to focused glaciation there. However, glacier long profiles provide evidence that glacial incision is less efficient on the granite. Cirques cannot form on the steep valley walls that are maintained by detachment of rock slabs along sheeting joints. The strong granites can therefore sustain steep walls that act as Teflon, efficiently shedding snow to the valley below. These avalanches can greatly enhance the health and the erosive power of the modern glaciers in parts of the range. During glaciations, mass is removed efficiently from the surrounding sedimentary landscape, promoting isostatic uplift of the granitic massifs. We conclude that, in places such as Denali, unusual combinations of tectonic uplift rate and rock strength have enacted a set of feedbacks that allowed the development of the highest relief in North America by enhancing glacial erosion in the valleys while preserving the peaks.

  7. Non-temperate glaciers: should the `Shrevian ideal' be reassessed?

    NASA Astrophysics Data System (ADS)

    Irvine-Fynn, T. D.; Hodson, A. J.; Ng, F.; Moorman, B. J.

    2006-12-01

    Shreve (1972) and Rothlisberger (1972) provided theoretical frameworks which have been crucial to understanding glacier hydrology. However, their concepts were formulated for temperate (alpine) glaciers, and therefore have `limitations' in applicability for ice sheets and non-temperate glaciers. The `Shrevian ideal' has been applied implicitly for several non-temperate glaciers because modelled hydraulic potential can be used as a proxy for probability of hydrological connections. For such glaciers, alternative hypotheses of hydrological structures have been published and supported by field observations, but are rarely considered in any depth. In particular, the manner in which intraglacial meltwater escapes through or beneath a cold-ice margin still remains poorly understood or characterised. Here, we present two lines of evidence from non-temperate, Arctic glaciers which challenge the Shrevian ideal for glacier drainage architecture. Firstly, repeated ground penetrating radar surveys indicate a spatially dynamic englacial system within the ablation area of Stagnation Glacier (Bylot Island). Such dynamic hydrology suggests unstable flow pathways due to reactivation and desertion of relict features. Secondly, dye tracing experiments at Midtre Lovnbreen (Svalbard) indicate rapid flow behaviour such as found in supraglacial channels, significant annual switches in drainage configuration, and flow divergence within the en- and/or subglacial system close to the injection sites. Combined, these observations imply an abundance of relict and/or advected conduits, crevasses and fractures which are inconsistent with hydrological routes dominated by an arborescent conduit network. While these interpretations provide nothing more than a conceptual model, they do contradict a Shrevian dendritic en- and/or subglacial drainage. Glacial researchers in Arctic regions must address these uncertainties. Given the typically reduced surface to interior coupling, extensive englacial drainage in non- temperate glaciers may have significant impact on the hydrochemical fluxes and ecological characteristics within the en- and subglacial environments. And further exploration of drainage within non-temperate glaciers is necessary to provide insights regarding how water penetrates polar ice masses, which is critical to understanding surface melt control on basal dynamics.

  8. 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.

  9. Recent evolution and mass balance of Cordn Martial glaciers, Cordillera Fueguina Oriental

    NASA Astrophysics Data System (ADS)

    Strelin, Jorge; Iturraspe, Rodolfo

    2007-10-01

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

  10. Formation condition of debris-covered glaciers in the Bhutan Himalaya

    NASA Astrophysics Data System (ADS)

    Nagai, H.; Fujita, K.; Nuimura, T.

    2011-12-01

    Debris-covered glaciers are widely distributed along the Himalayas. It is well known that insulation effect of debris mantle and heterogeneous topography make the response of the debris-covered glaciers to climate change complex. Furthermore, glacial lakes, which have often caused outburst floods and thus threatened Himalayan countries, are formed at the termini of debris-covered glaciers. It is little understood, however, what kinds of geomorphological and climatic environments determine the glacier termini as debris-covered or debris-free. In this study, we analyze remotely sensed satellite data to describe formation condition of debris-covered glaciers. We first delineated glaciers, debris-covered areas, and surrounding slopes using ALOS AVNIR-2, visible ortho-rectified images. We analyzed inclinations and aspects of the surrounding slopes using ASTER-GDEM by assuming that the debris mantle was supplies from the slope steeper than 40 degrees.We also estimated surface temperature distribution using thermal infrared data of ASTER because freeze-thaw activity on the bedrock should produce debris mantle. More than 1,200 glaciers in the Bhutan Himalaya including north-facing glaciers on the Tibetan side were delineated. Spatial analysis shows that the debris-covered glaciers have ten times larger area of steep slopes than the debris-free glaciers. Spatial distribution of surface temperature obtained from the nighttime ASTER TIR data shows a significant negative correlation with the altitude whereas daytime data shows no dependency on altitude. The surface exceeding 0 degrees Celsius is found on the south-facing steep slopes even in a winter season. It suggests that the more south-facing steep slope should have more active freeze-melt cycles and provide more debris onto glaciers. We also find a significant positive correlation among the areas of south-facing steep slopes and of debris-covered surface. In addition, the ablation areas of the south-facing debris-covered glaciers are fully covered by debris mantle, which seems to be supplied from the widely distributed south-facing steep slopes. On the other hand, the north-facing glaciers have elongated debris-covered areas along the flow lines of the glaciers, on which debris mantle seems to be supplied from very limited south-facing steep slopes within the glacier catchment. Our analysis suggest that the spatial distribution of south-facing steep slopes determines the extent and the shape of a debris-covered area of glaciers in the Bhutan Himalaya.

  11. Flow instabilities of Alaskan glaciers

    NASA Astrophysics Data System (ADS)

    Turrin, James Bradley

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

  12. 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.

  13. Rapid Glacier Thinning Along the Amundsen Coast, West Antarctica

    NASA Astrophysics Data System (ADS)

    Shepherd, A.; Wingham, D. J.; Mansley, J. A.

    2001-12-01

    Together with the Pine Island glacier (PIG), the Thwaites (TG) and Smith (SG) glaciers are the principal drainage systems of the Amundsen Sea (AS) sector of the West Antarctic ice-sheet. We use satellite radar altimetry to show that a rapid thinning of ice has occurred along the AS coastline, and satellite radar interferometry (SRI) to show that the pattern of thinning was restricted to the fastest flowing sections of the outlet glaciers. Between 1991 and 2001, the TG and SG thinned by more than 25 and 45 m at their grounding lines, and a total of 157 cubic kilometres of ice was lost from the AS sector into the ocean. Using BEDMAP elevation data, we show that the thickness changes may have caused the PIG, TG and SG to retreat inland by over 8, 4 and 7 km respectively. This is in line with ours and other independent estimates of grounding line retreat rates derived from SRI. If the glaciers continue to thin at the present rates they will become afloat within 150-1500 years.

  14. Surface melt dominates Alaska glacier mass balance

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  15. Surface melt dominates Alaska glacier mass balance

    USGS Publications Warehouse

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

    2015-01-01

    Mountain glaciers comprise a small and widely distributed fraction of the world's terrestrial ice, yet their rapid losses presently drive a large percentage of the cryosphere's contribution to sea level rise. Regional mass balance assessments are challenging over large glacier populations due to remote and rugged geography, variable response of individual glaciers to climate change, and episodic calving losses from tidewater glaciers. In Alaska, we use airborne altimetry from 116 glaciers to estimate a regional mass balance of ?75??11?Gt?yr?1 (19942013). Our glacier sample is spatially well distributed, yet pervasive variability in mass balances obscures geospatial and climatic relationships. However, for the first time, these data allow the partitioning of regional mass balance by glacier type. We find that tidewater glaciers are losing mass at substantially slower rates than other glaciers in Alaska and collectively contribute to only 6% of the regional mass loss.

  16. 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.

  17. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  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. 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.

  1. 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).

  2. Glacier Sensitivity Across the Andes

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  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. Glacier discharge and climate variations

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  6. 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.; Letrguilly, 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 (Argentire, Saint Sorlin and Gbroulaz 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 4450' N), than for the those located in the nothern sector (i.e. the Mont Blanc Massif at 4555' 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.

  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 km) or insufficient DEM coverage. We found 165 overdeepenings (> 0.01 km) with the potential of forming proglacial lakes when glacier retreat reveals the bed. The total area and volume of all overdeepenings is approx. 10 km and 236 Mio m respectively and 33 lakes will be larger than 1 km. A total glacier volume of 16 5 km 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 fr 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. Surface mass balance of Greenland mountain glaciers and ice caps

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  10. 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.

  11. Erosion by an Alpine glacier

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  12. Lake Trout Sampling in Glacier National Park

    USGS Multimedia Gallery

    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....

  13. 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

  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 jkulhlaups 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. Fast shrinkage of tropical glaciers in Colombia

    NASA Astrophysics Data System (ADS)

    Ceballos, Jorge Luis; Eusctegui, Christian; Ramrez, Jair; Caon, 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.

  16. 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

  17. 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.

  18. Erosion by an Alpine glacier

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    Assessing the impact of glaciation on Earths 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.

  19. 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

  20. Muir Glacier and Muir Inlet 1980

    USGS Multimedia Gallery

    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....

  1. 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.

  2. 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)

  3. 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.

  4. 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%.

  5. 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.

  6. 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, ?, is that given by Jhanneson et al. (1989), modified slightly here as ? = b/h, where b is a measure of ablation rate and h is a measure of glacier thickness. The exact definitions of ?, 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. ? 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.

  7. 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.

  8. Recent fluctuations of the Argentinian glaciers

    NASA Astrophysics Data System (ADS)

    Leiva, Juan Carlos

    1999-10-01

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

  9. Dynamic (in)stability of Thwaites Glacier, West Antarctica

    NASA Astrophysics Data System (ADS)

    Parizek, B. R.; Christianson, K.; Anandakrishnan, S.; Alley, R. B.; Walker, R. T.; Edwards, R. A.; Wolfe, D. S.; Bertini, G. T.; Rinehart, S. K.; Bindschadler, R. A.; Nowicki, S. M. J.

    2013-06-01

    Thwaites Glacier, West Antarctica, has the potential to directly contribute 1 m to sea level and currently is losing mass and thinning rapidly. Here, we report on regional results for the Sea-level Response to Ice Sheet Evolution (SeaRISE) experiments and investigate the impact of i) spatial resolution within existing data sets, ii) grounding-zone processes, and iii) till rheology on the dynamics of this outlet glacier. In addition to the SeaRISE data sets, we use detailed aerogeophysical and satellite data from Thwaites Glacier as input to a coupled ice stream/ice-shelf/ocean-plume model that includes oceanic influences across a several kilometers wide grounding zone suggested by new, high-resolution data. Our results indicate that the ice tongue provides limited stability, and that while future atmospheric warming will likely add mass to the surface of the glacier, strong ice stream stabilization on bedrock highs narrower than the length of the grounding zone may be ephemeral if circulating waters substantially reduce basal resistance and enhance melting beneath grounded ice within this zone. However, we find that stability is significantly enhanced by effectively plastic till beds. Accurate projections of future sea level change relies on correct understanding of the till rheology as well as local basal processes near the grounding line.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  11. 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.

  12. 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 ...

  13. 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.

  14. 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.

  15. Hasty retreat of glaciers in northern Patagonia

    NASA Astrophysics Data System (ADS)

    Paul, Frank; Mlg, 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.

  16. Glacier area changes in Northern Eurasia

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  17. Regional scale climatic trends derived from Younger Dryas glaciers in the U.K.

    NASA Astrophysics Data System (ADS)

    Pearce, D.; Rea, B. R.; Barr, I.; Small, D.; McDougall, D.

    2014-12-01

    In the U.K., the glacial geomorphological record has been utilised to infer paleo-glacier geometries and ice dynamics, with much of this work focussing on the Scottish Highlands during the Younger Dryas (YD; c. 12.9 - 11.7 ka BP). During the YD the West Highlands Ice-cap covered the majority of the Scottish Highlands (c. 13,000 sq mi), which is thought to have affected accumulation rates beyond the ice-cap margins, resulting in a steep (c. 80%) easterly decline in precipitation and smaller ice-masses. We present multi-proxy data investigating YD glaciation in the Tweedsmuir Hills, Southern Uplands, Scotland (5546' N, 0334' W), suggesting conditions were less arid. The area forms the most easterly upland region in the Southern Uplands and south of the West Highlands Ice-cap, reaching an altitude of 840 m and covering c. 200 sq mi. Results of air-photo interpretation and field mapping, which utilised a morphostratigraphic approach, have demonstrated a more extensive glaciation than previously mapped. The reconstruction consists of two separate icefields covering an area c. 40 sq mi. and new 14C dates of basal contact organics place the ice-mass within the context of the YD but new Cosmogenic Nuclide Analysis (CNA) of bedrock and in situ boulders are inconclusive, implying limited erosion and limited resetting during the YD. Equilibrium Line Altitudes are calculated to have ranged from c. 419 - 634 m. Paleo-precipitation values were derived using two precipitation-temperature relationships and suggest slightly lower totals than YD ice-masses located on the west coast of the U.K. but do not support a significant easterly reduction in precipitation. Analysis of present-day (c. 30 year) meteorological data across the U.K. demonstrates a pronounced reduction in precipitation of c. 50% on the east coast. This disparity between present-day and glacier-based YD precipitation patterns is partly attributable to the methodology employed in glacier reconstruction and represents an avenue for future research. These results differ significantly from the traditional paradigm which due to low accumulation rates, only restricted ice-masses developed in the Tweedsmuir Hills. Within a wider context this data questions the steep precipitation gradients thought to have been present during the YD.

  18. Glacier-derived permafrost ground ice, Bylot Island, Nunavut

    NASA Astrophysics Data System (ADS)

    Coulombe, S.; Fortier, D.; Lacelle, D.; Godin, E.; Veillette, A.

    2014-12-01

    Massive icy bodies are important components of permafrost geosystems. In situ freezing of water in the ground by ice-segregation processes forms most of these icy bodies. Other hypotheses for the origin of massive ice include the burial of ice (e.g. glacier, snow, lake, river, sea). The analysis of ground-ice characteristics can give numerous clues about the geomorphologic processes and the thermal conditions at the time when permafrost developed. Massive underground ice therefore shows a great potential as a natural archive of the earth's past climate. Identifying the origin of massive ice is a challenge for permafrost science since the different types of massive ice remain difficult to distinguish on the sole basis of field observations. There is actually no clear method to accurately assess the origin of massive ice and identification criteria need to be defined. The present study uses physico-chemical techniques to characterize buried glacier ice observed on Bylot Island, Nunavut. Combined to the analysis of cryostratigraphy, massive-ice cores crystallography and high-resolution imagery of the internal structure of the ice cores were obtained using micro-computed tomography techniques. These techniques are well suited for detailed descriptions (shape, size, orientation) of crystals, gas inclusions and sediment inclusions. Oxygen and hydrogen isotopes ratios of massive-ice cores were also obtained using common equilibrium technique. Preliminary results suggest the occurrence of two types of buried massive-ice of glacial origin similar to those found on contemporary glaciers: 1) Englacial ice: clear to whitish ice, with large crystals (cm) and abundant gas bubbles at crystal intersections; 2) Basal glacier ice: ice-rich, banded, micro-suspended to suspended cryostructures and ice-rich lenticular to layered cryostructures, with small ice crystals (mm) and a few disseminated gas bubbles. Glacier-derived permafrost contains antegenetic ice, which is ice that predates the aggradation of the permafrost. Remnants of glacier ice represent unique environmental archives and offer the possibility to reconstruct climate anterior to the formation of permafrost.

  19. 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.

  20. 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.

  1. Fjord floor landforms and processes at the termini of Kongsvegen and Kronebreen Glaciers, Svalbard

    NASA Astrophysics Data System (ADS)

    Kehrl, L. M.; Hawley, R. L.; Powell, R. D.; Brigham-Grette, J.

    2009-12-01

    Glacimarine sediment deposition reduces relative water depth, thereby increasing the potential for tidewater glacier stability. Here we relate glacier stability and sedimentation processes to the fjord floor morphology in front of the Kronebreen-Kongsvegen glacial system, Kongsfjorden, Svalbard. We used 28 kHz and 200 kHz echosounding to map the bathymetry of the fjord floor over a total survey area of 5 km2. The Kronebreen-Kongsvegen glacier complex has retreated significantly since Kongsvegens last surge ended in 1956. In the last 20 years, Kongsvegen has retreated back onto land and a new ice-marginal delta has emerged in front of the glacier. We link different sediment sources to the observed features on the fjord floor, including the ice-marginal delta, grounding-line fans, and morainal banks. We compare our results to a similar echosounding study from 2005.

  2. 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.

  3. 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

  4. Food web structure in a harsh glacier-fed river.

    PubMed

    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 denwinkelkees 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

  5. Recent acceleration of Thwaites Glacier

    NASA Technical Reports Server (NTRS)

    Ferrigno, J. G.

    1993-01-01

    The first velocity measurements for Thwaites Glacier were made by R. J. Allen in 1977. He compared features of Thwaites Glacier and Iceberg Tongue on aerial photography from 1947 and 1967 with 1972 Landsat images, and measured average annual displacements of 3.7 and 2.3 km/a. Using his photogrammetric experience and taking into consideration the lack of definable features and the poor control in the area, he estimated an average velocity of 2.0 to 2.9 km/a to be more accurate. In 1985, Lindstrom and Tyler also made velocity estimates for Thwaites Glacier. Using Landsat imagery from 1972 and 1983, their estimates of the velocities of 33 points ranged from 2.99 to 4.02 km/a, with an average of 3.6 km/a. The accuracy of their estimates is uncertain, however, because in the absence of fixed control points, they assumed that the velocities of icebergs in the fast ice were uniform. Using additional Landsat imagery in 1984 and 1990, accurate coregistration with the 1972 image was achieved based on fixed rock points. For the period 1972 to 1984, 25 points on the glacier surface ranged in average velocity from 2.47 to 2.76 km/a, with an overall average velocity of 2.62 +/- 0.02 km/a. For the period 1984 to 1990, 101 points ranged in velocity from 2.54 to 3.15 km/a, with an overall average of 2.84 km/a. During both time periods, the velocity pattern showed the same spatial relationship for three longitudinal paths. The 8-percent acceleration in a decade is significant. This recent acceleration may be associated with changes observed in this region since 1986. Fast ice melted and several icebergs calved from the base of the Iceberg Tongue and the terminus of Thwaites Glacier. However, as early as 1972, the Iceberg Tongue had very little contact with the glacier.

  6. 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.

  7. 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.

  8. 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.

  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. 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.

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

    NASA Astrophysics Data System (ADS)

    Mayer, H.; Herzfeld, U. C.

    2003-12-01

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

  12. 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.

  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. 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

  17. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  19. Drainage events from a glacier-dammed lake, Bear Glacier, Alaska: Remote sensing and field observations

    NASA Astrophysics Data System (ADS)

    Wilcox, A. C.; Wade, A. A.; Evans, E. G.

    2014-09-01

    We investigated drainage events from a glacier-dammed lake on Bear Glacier, Alaska, and associated outburst floods and hazards. The glacier-dammed lake, which we call Ice Lake, is 17.5 km up-glacier from Bear Glacier's terminus at Bear Glacier Lake. We combine field observations and remote sensing to examine temporal changes in the size of Ice Lake, the frequency and timing of its drainage, and down-glacier propagation of its outburst floods. We found that in recent years, Ice Lake has likely drained every year or two, in late summer or fall (August-October), with outbursts generally following the damming of sufficient water to create a lake area of between 0.35 and 0.5 km2. Ice Lake has migrated downvalley to the south since the 1990s, likely as a result of thinning of the glacier that dams it. In situ measurements of a drainage event in October 2010 showed that Ice Lake drained over a period of days, which manifested at Bear Glacier Lake as a gradual, multiday increase and then decrease in water levels. Glacial lake outburst flooding at Bear Glacier creates risks for sea kayakers in Bear Glacier Lake and may be relevant to understanding the effects of climate warming on glacier-dammed and proglacial lakes.

  20. 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.

  1. 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.

  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. 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.

  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. Climate during the Last Glacial Maximum in the Wasatch Mountains Inferred from Glacier Mass-Balance and Ice-Flow Modeling

    NASA Astrophysics Data System (ADS)

    Bash, E. A.; Laabs, B. J.

    2006-12-01

    The Wasatch Mountains of northern Utah contained numerous valley glaciers east and immediately downwind of Lake Bonneville during the Last Glacial Maximum (LGM). While the extent and chronology of glaciation in the Wasatch Mountains and the rise and fall of Lake Bonneville are becoming increasingly well understood, inferences of climatic conditions during the LGM for this area and elsewhere in the Rocky Mountains and northern Great Basin have yielded a wide range of temperature depression estimates. For example, previous estimates of temperature depression based on glacier and lake reconstructions in this region generally range from 7 to 9 C colder than modern. Glacier modeling studies for Little Cottonwood Canyon (northern Wasatch Mountains) suggest that such temperature depressions would have been accompanied by precipitation increases of about 3 to 1x modern, respectively (McCoy and Williams, 1985; Laabs et al., 2006). However, interpretations of other proxies suggest that temperature depression in this area may have been significantly greater, up to 13 C (e.g., Kaufman 2003), which would likely have been accompanied by less precipitation than modern. To address this issue, we reconstructed ice extent in the American Fork Canyon of the Wasatch Mountains and applied glacier modeling methods of Plummer and Phillips (2003) to infer climatic conditions during the LGM. Field mapping indicates that glaciers occupied an area of more than 20 km2 in the canyon and reached maximum lengths of about 9 km. To link ice extent to climatic changes, a physically based, two- dimensional numerical model of glacier mass balance and ice flow was applied to these valleys. The modeling approach allows the combined effects of temperature, precipitation and solar radiation on net mass balance of a drainage basin to be explored. Results of model experiments indicate that a temperature depression of less than 9 C in the American Fork Canyon would have been accompanied by greater precipitation than modern, whereas greater temperature depressions would have required less-than-modern precipitation to sustain glaciers in the Wasatch Mountains. Without independent estimates of either temperature or precipitation for the LGM, model results do not provide a unique combination of these two variables based on simulated ice extent. However, the reconstructed pattern of glaciation in the Wasatch and Uinta Mountains indicates a sharp westward decline in glacier equilibrium- line altitudes in valleys immediately downwind of Lake Bonneville (Munroe et al, 2006), which suggests that precipitation in the Wasatch Mountains was enhanced during the LGM. Therefore, model results can be used to set limits on the temperature and precipitation. We estimate that, if temperatures during the LGM were 6 to 8 C less than modern, precipitation was 3 to 1.5x modern. Such precipitation increases would reflect the importance of Lake Bonneville as a moisture source for valleys in the Wasatch Mountains, as suggested by previous studies.

  6. Static debris-covered glaciers and rock glaciers in Trllaskagi Peninsula (northern Iceland): The cases of Hladalur and Fremri-Grjtrdalur.

    NASA Astrophysics Data System (ADS)

    Tanarro, Luis Miguel; Palacios, David; Andres, Nuria; Mara Fernndez, Jose

    2015-04-01

    The glacial and periglacial environment - linked to the extensive presence of permafrost- which predominates in the Trllaskagi 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 Hlar, where there is a debris-covered glacier (6542'N-6544'N and 1856'W-1900'W) at the bottom of the Hladalur valley, one of its tributary valleys, and an extensive rock glacier at the bottom of the Fremri-Grjtrdalur, 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-Grjtrdalur rock glacier and the Hladalur 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., Kb, A., Farbrot, H., Etzelmller, 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)

  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. GLIMS: Progress in Mapping the World's glaciers

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    The Global Land Ice Measurements from Space (GLIMS) initiative has built a database of glacier outlines and related attributes, derived primarily from satellite imagery, such as from ASTER and Landsat. Each snapshot of a glacier is from a specific time, and the database is designed to store multiple snapshots representative of different times. The database currently contains outlines for approximately 83,000 glaciers. Of these, 549 glaciers have outlines from more than one time, which can be studied for change. The glacier-by-glacier area-change signal over large areas tends to be noisy, but the mode of the distribution of area change for these 549 glaciers is -5%. We have implemented two web-based interfaces to the database. One enables exploration of the data via interactive maps (Web map server), while the other allows searches based on text-field constraints. The Web map server creates interactive maps on our Web site, www.glims.org, and can also supply glacier layers to other servers over the Internet. As a service to the GLIMS community, the database contains metadata on all ASTER imagery (approximately 200,000 images) acquired over glacierized terrain. Reduced-resolution images can be viewed either as a layer in the MapServer application, or overlaid on the virtual globe within Google Earth. The system allows users to download their selected glacier data in a choice of formats. The results of a query based on spatial selection (using a mouse) or text-field constraints can be downloaded in any of these formats: ESRI shapefiles, KML (Google Earth), MapInfo, GML (Geography Markup Language) and GMT (Generic Mapping Tools). This "clip-and-ship" function allows users to download only the data they are interested in. In this presentation we describe our flexible Web interfaces to the database, which includes various ancillary layers, facilitates enhanced analysis of glacier systems, their distribution, and their impacts on other Earth systems.

  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. Geomorphological and sedimentological record of accelerated deglaciation of small mountain glacier, Ragnarbreen, Svalbard

    NASA Astrophysics Data System (ADS)

    Ewertowski, Marek

    2010-05-01

    Most of the Svalbrad glaciers have been in retreat since the end of the Little Ice Age (LIA). Hence, they give a good opportunity to study the geomorphological and sedimentological record of deglaciation. The aim of the study is to describe main landsystem elements of Ragnar glacier and relate them to different stages of the glacier recession. The Ragnar glacier is located in the Svalbard archipelago, in the central part of the West Spitsbergen Isle, in the north branch of Billefjorden. Ragnar is a small (~ 6 km2), outlet glacier, which current clean ice edge has retreated ca. 1500 m from the position related to the maximum LIA extent. Fieldworks of the study comprised detailed geomorphological mapping and sedimentary works. Four main elements of the landsystem of the Ragnar glacier can be distinguished: 1) Clean glacier surface. Currently, the ice surface of Ragnar glacier is almost completely debris-free and with only several supraglacial streams. 2) Ice-marginal lake. The lake started to form after 1980 year. Since that time, its length has reached 1000 m. Distant (from the ice-edge) part of the lake is shallow (< 2 m) with several small islands. Part proximal to the current ice edge is deeper (up to 16 m) and devoid of islands. At the bottom of the lake some ice (probable of glacier origin) was detected. 3) Lateral moraines - were developed along the both valley sides, from frontal moraine complex - to ca. 2 km upward the glacier valley. 4) Frontal moraine complex. This complex comprises of several chains of ridges and depressions and is relatively distinct - elevated about 35 m above the valley bottom. The elements of the landsystem of the Ragnar glacier have undergone several transformations since the LIA maximum: 1) Formation of the frontal moraine complex can be related to the state of dynamic equilibrium of the glacier during the LIA maximum. During formation of the complex and shortly after it the main depositional agents were intense debris flows, which are recorded by thick covers of the old debris flow deposits. Nowadays, despite of ice-cores, frontal moraine complex is much more stable than the lateral moraines or ice-marginal lake. 2) As a consequence of lowering of the clean glacier surface and formation of the distinct lateral moraines, the debris delivering from the valley sides is limited only to very narrow zone of the glacier (i.e. only to the lateral moraine). 3) Accelerated recession of the ice mouth and limitation in delivery of debris from sides of the valley caused that amount of deposits released in the ice front is small. 4) Increasing amount of water flowing from the glacier was blocked by frontal moraine complex and the ice marginal lake was created. 5) The debris cover on the lateral moraines is relatively thin. In addition, as a consequence of the clean ice surface lowering, slopes of the lateral moraines are very steep. It causes that mass movement processes (especially debris flows) are ubiquitous. Contemporary, lateral moraines are the elements undergoing the most intense transformations. Observations made in the Ragnar marginal zone revealed spatial-temporal changes in distribution of the sediments and landforms. They also add some premises that in the first stage of deglaciation debris flow and other mass wasting processes are most common. In the later phase glaciolacustrine and glaciofluvial deposition also plays important role in transformation of landforms and sediments.

  12. Uses of Several Photographic Methods to Detect Changes of Glaciers in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Nolan, M.; Takahashi, S.

    2004-12-01

    We have employed several photographic methods to detect changes on glaciers in Arctic Alaska. On Okpilak and McCall Glaciers in the eastern Brooks Range, we have re-occupied photo-locations from 1906 and 1958 respectively. These photos unambiguously document that a large loss of ice mass has been on-going here over the past 100 years. The Okpilak Glacier photos also unambiguously reveal that retreat from the most recently exposed moraines did not begin until near the turn of the century, supporting lichenometric evidence that the change in weather patterns that marked the end of the Little Ice Age here occurred sometime around 1890. A time-series of photos from this photo-site since 1906 reveals the influence of glacier geometry on volume loss rates. Comparing these photos with modern survey data has also allowed us to better quantify the ice loss observed. On McCall Glacier, we have employed time-lapse photography in several ways. By installing a camera on a ridge high above the glacier, we can watch the snow-line move up-glacier in summer. By placing a camera in the accumulation area in front of a large ruler, we can record the rate of snow accumulation throughout the year. By placing a camera in front of our weather stations located on the glacier surface, we can both improve our interpretations of the weather data as well as help troubleshoot the causes for equipment malfunctions. Because shading plays such an important role in patterns of surface mass balance in these steep mountain valleys, we have used both optical and infrared time-series of photos to document both shading and the resulting impact on surface temperature within the valley. We are also using these time-series to help validate models of surface energy balance that incorporate shading.

  13. 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.

  14. 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

  15. 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

  16. Microbial biodiversity in glacier-fed streams

    PubMed Central

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

    2013-01-01

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

  17. Muir Glacier and Muir Inlet 2003

    USGS Multimedia Gallery

    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. Using Metaphorical Models for Describing Glaciers

    ERIC Educational Resources Information Center

    Felzmann, Dirk

    2014-01-01

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

  19. 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 ? 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 ? diversity. Biofilms in the glacier-fed streams had intermediate ? diversity and species sorting by local environmental conditions likely shaped their community composition. ? diversity of streamwater and biofilm communities decreased with elevation, possibly reflecting less diverse sources of microorganisms upstream in the catchment. In contrast, ? 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

  20. Calving at Pine Island Glacier

    NASA Astrophysics Data System (ADS)

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

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

    NASA Astrophysics Data System (ADS)

    Rastner, Philipp; Jrg, 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.

  2. Effects of basal debris on glacier flow.

    PubMed

    Iverson, Neal R; Cohen, Denis; Hooyer, Thomas S; Fischer, Urs H; Jackson, Miriam; Moore, Peter L; Lappegard, Gaute; Kohler, Jack

    2003-07-01

    Glacier movement is resisted partially by debris, either within glaciers or under glaciers in water-saturated layers. In experiments beneath a thick, sliding glacier, ice containing 2 to 11% debris exerted shear traction of 60 to 200 kilopascals on a smooth rock bed, comparable to the total shear traction beneath glaciers and contrary to the usual assumption that debris-bed friction is negligible. Imposed pore-water pressure that was 60 to 100% of the normal stress in a subglacial debris layer reduced shear traction on the debris sufficiently to halt its deformation and cause slip of ice over the debris. Slip resistance was thus less than debris shearing resistance. PMID:12843389

  3. Radio-echo sounding of Caucasus glaciers

    NASA Astrophysics Data System (ADS)

    Lavrentiev, Ivan; Kutuzov, Stanislav; Vasilenko, Evgeny; Macheret, Yuri

    2013-04-01

    Accurate glacier volume and ice-thickness estimations are highly important for many glaciological applications. Recent glacier reduction is affecting local river discharge and contributes to the global sea level rise. However, direct measurements of ice thickness are very sparse due to its high cost and laboriousness. One of the glacierized mountain regions with a lack of direct ice-thickness measurements is Caucasus. So far data for several seismic and GPR profiles have been reported for only 3 glaciers from more than 1.7 thousands located in Caucasus. In 2010-2012 a number of ground base and airborne radio-echo sounding surveys have been accomplished in Caucasus Mountains using 20 MHz monopulse radar VIRL-6. Special aerial version of this ground penetrating radar was designed for helicopter-born measurements. The radar has a relatively long (10 m) receiving and transmitting antennas, which together with receiving, recording and transmitting devices can be mounted on a special girder, being suspended from a helicopter. VIRL-6 radar is light weight and can be quickly transformed into ground version. Equipment has been used on 16 glaciers including biggest glacier in Caucasus - Bezengi (36 km2) most of which have a highly crevassed surfaces and heterogeneous internal structure. Independent data were obtained also for two glaciers using ground version of the same VIRL-6 radar. In total more than 120 km of radar profiles were obtained. Results showed good agreement between ground and aerial measurements. Ice-thickness values exceeded 420 m for some of the Central Caucasus glaciers. Successful use of VIRL-6 radar in Caucasus opens up the possibility of using such equipment on different types of glaciers in polar and mountain regions, including temperate, polythermal and surging glaciers.

  4. 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 mesur la constante de dissociation, Kd correspondant l'interaction faible antibiotique-ribosome bactrien pour des antibiotiques de diffrentes classes, un macrolide (roxithromycine), un ktolide (HMR 3647) et une lincosamide (clindamycine) avec des ribosomes de diffrentes souches bactriennes (E. coli, Staphylococcus aureus sensible ou rsistant l'erythromycin) par deux mthodes : l'une base sur la variation des largeurs de raies et l'autre sur les temps de relaxation transversaux T2 en utilisant une squence CPMG.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. Shrinking Alpine glaciers spell trouble for Europe's rivers

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2011-10-01

    Within the frosted peaks of the Swiss Alps, the cycle of winter precipitation accumulation and springtime melt provides a seasonal flow of water to much of western Europe. Research into the freshwater contributions of Alpine glaciers has predominantly looked to measure water released directly from glacier melt. A glacier's overall water storage, however, which takes into account the snow that resides on the glacier's surface, more accurately describes the role Swiss glaciers play in feeding European streams. A new analysis by Huss that investigated the effects of changing Swiss glacier storage on the flows of four of Europe's largest rivers suggests that glaciers may be more important than previously realized.

  12. 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

  13. 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

  14. 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.

  15. Glaciers in Patagonia: Controversy and prospects

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    Lately, glaciers have been subjects of unceasing controversy. Current debate about planned hydroelectric facilitiesa US7- to 10-billion megaprojectin 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 changeboth anthropogenic and naturalis 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.

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

    NASA Astrophysics Data System (ADS)

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

    2001-12-01

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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

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

    SciTech Connect

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

    2011-01-01

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

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Sevestre, Hedi; Benn, Douglas I.; Hulton, Nicholas R. J.; Blum, Karoline

    2015-10-01

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

  4. Adiabatic evolution of plasma equilibrium

    PubMed Central

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

    1975-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Racoviteanu, A.

    2014-12-01

    High rates of glacier retreat for the last decades are often reported, and believed to be induced by 20th century climate changes. However, regional glacier fluctuations are complex, and depend on a combination of climate and local topography. Furthermore, in ares such as the Hindu-Kush Himalaya, there are concerns about warming, decreasing monsoon precipitation and their impact on local glacier regimes. Currently, the challenge is in understanding the magnitude of feedbacks between large-scale climate forcing and small-scale glacier behavior. Spatio-temporal patterns of glacier distribution are still llimited in some areas of the high Hindu-Kush Himalaya, but multi-temporal satellite imagery has helped fill spatial and temporal gaps in regional glacier parameters in the last decade. Here I present a synopsis of the behavior of glaciers across the Himalaya, following a west to east gradient. In particular, I focus on spatial patterns of glacier parameters in the eastern Himalaya, which I investigate at multi-spatial scales using remote sensing data from declassified Corona, ASTER, Landsat ETM+, Quickbird and Worldview2 sensors. I also present the use of high-resolution imagery, including texture and thermal analysis for mapping glacier features at small scale, which are particularly useful in understanding surface trends of debris-covered glaciers, which are prevalent in the Himalaya. I compare and contrast spatial patterns of glacier area and lvation changes in the monsoon-influenced eastern Himalaya (the Everest region in the Nepal Himalaya and Sikkim in the Indian Himalaya) with other observations from the dry western Indian Himalaya (Ladakh and Lahul-Spiti), both field measurements and remote sensing-based. In the eastern Himalaya, results point to glacier area change of -0.24 % 0.08% per year from the 1960's to the 2006's, with a higher rate of retreat in the last decade (-0.43% /yr). Debris-covered glacier tongues show thinning trends of -30.8 m 39 m on average over the last four decades, similar to other studies in the same climatic area. However, at small scales, the behavior of glaciers is highly heterogenous, with contrasting patterns of thickening glacier termini versus retreating nad thinning glacier tongues.

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

    NASA Astrophysics Data System (ADS)

    Monnier, Sbastien; 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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)

  15. Warm Oceans, Fast Glaciers: the connections

    NASA Astrophysics Data System (ADS)

    Truffer, M.; Fahnestock, M. A.; Amundson, J. M.

    2009-12-01

    Over the last decade many outlet glaciers from the Greenland Ice Sheet have accelerated and thinned, and in a number of cases their termini have retreated. There is much in common from glacier to glacier that emerges as these changes are studied, yet the actual physical mechanisms remain unclear. One can show that the spatial patterns and timing of outlet glacier changes around Greenland coincide with changes in sea surface temperature and length of the sea-ice-free season in the surrounding ocean, and that large glacier changes appear to initiate within one to a few years of shifts in these conditions. While ocean warming has a direct impact on rates of melting at the glacier ice/ocean interface, its impact on ice flow is less direct. The spatial and temporal coincidence between changing ocean conditions and speedup is compelling, but the causal link between warmer ocean water and rapid responses from outlet glaciers around Greenland is more complex. Observations of rapid calving retreats, the appearance of calving-related long-period seismicity at some large glaciers undergoing change, and the loss of floating ice tongues all suggest that the direct impact of ocean-driven change is on the stability of the lowest reach of these tidewater outlets. In glaciers with a floating tongue, enhanced basal melt may be destabilizing by thinning the tongue to below its structural integrity; at grounded termini this effect is lacking. However, rapid melt at the near-vertical face can play a significant role for slowly flowing systems. For large grounded glaciers with terminus flow rates of meters per day, the impact of increased melt in summer would seem less important. At such glaciers the link between ocean temperatures, sea ice cover and terminus stability manifests itself by the cessation of calving in fall and winter, which leads to terminus advance and the formation of a floating tongue. The loss of sea ice cover in early spring leads to a disintegration of the seasonal floating tongue and the calving of grounded ice. We use data from Jakobshavns Isbrae in West Greenland to illustrate this effect. The ocean thus appears to have a direct influence on the seasonal behavior. Shorter winter advances can increase the glaciers exposure to grounded calving. This provides a mechanism by which year-to-year variations in coastal ocean conditions are linked rapidly to changes in the stability of glacier termini. The tight connection in time between warming ocean surface waters and changes in glacier termini observed in Greenland have far-reaching implications for the rapidity of response we may see from the Antarctic; not only from the marine based West Antarctic Ice Sheet, but from any outlet glacier that is exposed to ocean water.

  16. 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.

  17. Hidden Lake in Glacier National Park, Montana

    USGS Multimedia Gallery

    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....

  18. The geochemical record in rock glaciers

    USGS Publications Warehouse

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

    1998-01-01

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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. The GLIMS geospatial glacier database: A new tool for studying glacier change

    NASA Astrophysics Data System (ADS)

    Raup, Bruce; Racoviteanu, Adina; Khalsa, Siri Jodha Singh; Helm, Christopher; Armstrong, Richard; Arnaud, Yves

    2007-03-01

    The Global Land Ice Measurement from Space (GLIMS) project is a cooperative effort of over sixty institutions world-wide with the goal of inventorying a majority of the world's estimated 160 000 glaciers. Each institution (called a Regional Center, or RC) oversees the analysis of satellite imagery for a particular region containing glacier ice. Data received by the GLIMS team at the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado are ingested into a spatially-enabled database (PostGIS) and made available via a website featuring an interactive map, and a Web-Mapping Service (WMS). The WMS, an Open Geospatial Consortium (OGC)-compliant web interface, makes GLIMS glacier data available to other data servers. The GLIMS Glacier Database is accessible on the World Wide Web at " http://nsidc.org/glims/". There, users can browse custom maps, display various data layers, query information within the GLIMS database, and download query results in different GIS-compatible formats. Map layers include glacier outlines, footprints of ASTER satellite optical images acquired over glaciers, and Regional Center information. The glacier and ASTER footprint layers may be queried for scalar attribute data, such as analyst name and date of contribution for glacier data, and acquisition time and browse imagery for the ASTER footprint layer. We present an example analysis of change in Cordillera Blanca glaciers, as determined by comparing data in the GLIMS Glacier Database to historical data. Results show marked changes in that system over the last 30 years, but also point out the need for establishing clear protocols for glacier monitoring from remote-sensing data.

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Cenedese, C.

    2014-12-01

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

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Chauch, 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.

  13. 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.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Glaciers are effective agents of erosion for many mountainous regions, but primary rates of erosion are difficult to quantify due to unknown conditions at the glacier bed. We develop a numerical model of subglacial erosion and passively couple it to a vertically integrated ice flow model (UBC regional glaciation model). The model accounts for seasonal changes in water pressure at the glacier bed which affect rates of abrasion and quarrying. We apply our erosion model to Peyto Glacier, and compare estimates of glacier erosion to the mass of fine sediment contained in a lake immediately down valley from the glacier. A series of experiments with our model and ones based on subglacial sliding rates are run to explore model sensitivity to bedrock hardness, seasonal hydrology, changes in mass balance, and longer-term dimensional changes of the glacier. Our experiments show that, as expected, erosion rates are most sensitive to bedrock hardness and changes in glacier mass balance. Silt and clay contained in Peyto Lake primarily originate from the glacier, and represent sediments derived from abrasion and comminution of material produced by quarrying. Average specific sediment yield during the period AD1917-1970 from the lake is 467190 Mg km-2yr-1 and reaches a maximum of 928 Mg km-2yr-1 in AD1941. Converting to a specific sediment yield, modelled average abrasion and quarrying rates during the comparative period are 14244 Mg km-2yr-1 and 1167213 Mg km-2yr-1 respectively. Modelled quarrying accounts for approximately 85-95% of the erosion occurring beneath the glacier. The basal sliding model estimates combined abrasion and quarrying. During the comparative period, estimated yields average 427136 Mg km-2yr-1, lower than the combined abrasion and quarrying models. Both models predict maximum sediment yield when Peyto Glacier reached its maximum extent. The simplistic erosion model shows higher sensitivity to climate, as seen by accentuated sediment yield peaks during the Little Ice Age. In all of our experiments to date, modelled sediment yield closely follow maximum ice cover. In contrast, sediment yields obtained from the lake indicate that maximum sediment delivery to the lake lagged maximum ice cover and occurred during a period of rapid glacier retreat. We interpret this lag to indicate removal of stored sediments beneath the glacier and subaerial erosion from recently exposed sediments in the glacier forefield rather than an increase in primary erosion of bedrock.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  17. Thermal Regime Change of a Retreating Polythermal Glacier from Repeat Ground Penetrating Radar

    NASA Astrophysics Data System (ADS)

    Rippin, D. M.; Willis, I. C.; Sevestre, H.

    2014-12-01

    Polythermal glaciers (i.e. glaciers that consist of some combination of both warm and cold ice) are common in the Arctic (e.g. Aschwanden and Blatter, 2005). Recent work (e.g. Rippin et al. 2011; Gusmeroli et al., 2012; Wilson and Flowers, 2013; Wilson et al., 2013) has focussed on how their polythermal structure might change in response to a warming climate. These studies suggest that the nature of future thermal regime change is complex, such that the relative volume of temperate ice in a shrinking glacier may increase or decrease, depending on local geographical, meteorological and hydrological parameters. Here, we present a unique data-set from the well-studied glacier Midtre Lovnbreen in Svalbard, which has shown continued and sustained retreat in recent years. We have a network of ground penetrating radar (GPR) lines from this glacier, first surveyed in 2006 and then repeat-surveyed along exactly the same lines in 2012. Despite significant retreat and thinning, our data suggests that minimal changes in thermal regime have taken place over this period, reinforcing previous observations of a significant lag in the rate at which the thermal regime responds to mass balance changes (cf. Rippin et al., 2011). Such a 'thermal lag' has implications for evolving hydrological and dynamical behaviour of these glaciers, and also for the future mass balance response. In this paper, we comment on the observed changes and consider the implications for our understanding of future thermal regime evolution. ReferencesAschwanden, A., and H. Blatter. 2005. Meltwater production due to strain heating in Storglaciren, Sweden. JGR, 110, doi:10.1029/2005JF000,328. Rippin, D.M., J.L. Carrivick and C. Williams. 2011. Evidence towards a thermal lag in the response of Krsaglaciren, northern Sweden, to climate change. J. Glac., 57(205), 895-903. Gusmeroli, A., P. Jansson, R. Pettersson and T. Murray. 2012. Twenty years of cold surface layer thinning at Storglaciaren, sub-Arctic Sweden, 1989-2009. J. Glac., 58(207), 3-10. Wilson, N.J., G.E. Flowers and L. Mingo. 2013. Comparison of thermal structure and evolution between neighboring subarctic glaciers. JGR, 118(3), 1443-1459. Wilson, N.J. and G.E. Flowers. 2013. Environmental controls on the thermal structure of alpine glaciers. The Cryosphere, 7(1), 167-182.

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

    Small but hydrologically significant shifts in climate have affected the rates of glacier volume change at the three U.S. Geological Survey Benchmark glaciers. Rate changes are detected as inflections in the cumulative conventional and reference-surface mass-balances of Wolverine and Gulkana Glaciers in Alaska and South Cascade Glacier in Washington. The cumulative mass balances are robust and have recently been corroborated by geodetic determinations of glacier volume change. Furthermore, the four-decade length of record is unique for the western hemisphere. Balance trends at South Cascade Glacier in Washington are generally in the opposite sense compared with Wolverine Glacier in Alaska; NCEP correlation of winter balance with local winter temperatures is positive at 0.59 for Wolverine and -0.64 for South Cascade Glacier. At Wolverine Glacier, the negative trend of cumulative mass balances, since measurements began in 1965, was replaced by a growth trend \\(positive mass balances\\) during the late 1970s and 1980s. The positive mass-balance trend was driven by increased precipitation during the 1976/77 to 1989 period. At Gulkana Glacier, the cumulative mass-balance trend has been negative throughout its measurement history, but with rate-change inflection points that coincide with the interdecadal climate-regime shifts in the North Pacific indices. At South Cascade Glacier, the mass-loss trend, observed since measurements began in 1953, was replaced by a positive trend between 1970 and 1976 then became strongly and continuously negative until 1997 when the rate of loss generally decreased. Since 1989, the trends of the glaciers in Alaska have also been strongly negative. These loss rates are the highest rates in the entire record. The strongly negative trends during the 1990s agree with climate studies that suggest that the period since the 1989 regime shift has been unusual. Volume response time and reference surface balance are the current suggested methods for analyzing the response of glaciers to climate. Volume response times are relatively simple to determine and can be used to evaluate the temporal, areal, and volumetric affects of a climate change. However, the quasi-decadal period between the recent climate-regime shifts is several times less than the theoretical volume readjustment response times for the benchmark glaciers. If hydrologically significant climate shifts recur at quasi-decadal intervals and if most glaciers' volume-response times are several times longer \\(true for all but a few small, steep glaciers\\), most medium and large glaciers are responding to the current climate and a fading series of regime shifts which, themselves, vary in magnitude. This confused history of driver trends prevent conventional balances from being simply correlated with climate. Reference-surface balances remove the dynamic response of glaciers from the balance trend by holding the surface area distribution constant. This effectively makes the reference surface balances directly correlated with the current climatic forcing. The challenging problem of predicting how a glacier will respond to real changes in climate may require a combination of the volume response time and reference surface mass balances applied to a long time-series of measured values that contain hydrologically significant variations.

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

    PubMed

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

    2010-09-01

    Millennial-scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions. The presence of the Younger Dryas stadial (approximately 12.9 to approximately 11.7 kyr ago) is established throughout much of the Northern Hemisphere, but the global timing, nature and extent of the event are not well established. Evidence in mid to low latitudes of the Southern Hemisphere, in particular, has remained perplexing. The debate has in part focused on the behaviour of mountain glaciers in New Zealand, where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent. The interhemispheric behaviour of the climate system during the Younger Dryas thus remains an open question, fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period. Here we show that New Zealand's glaciers retreated after approximately 13 kyr bp, at the onset of the Younger Dryas, and in general over the subsequent approximately 1.5-kyr period. Our evidence is based on detailed landform mapping, a high-precision (10)Be chronology and reconstruction of former ice extents and snow lines from well-preserved cirque moraines. Our late-glacial glacier chronology matches climatic trends in Antarctica, Southern Ocean behaviour and variations in atmospheric CO(2). The evidence points to a distinct warming of the southern mid-latitude atmosphere during the Younger Dryas and a close coupling between New Zealand's cryosphere and southern high-latitude climate. These findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the North Atlantic led to a strong interhemispheric thermal gradient during late-glacial times, in turn leading to increased upwelling and CO(2) release from the Southern Ocean, thereby triggering Southern Hemisphere warming during the northern Younger Dryas. PMID:20829791

  20. 46 CFR 42.20-12 - Conditions of equilibrium.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Conditions of equilibrium. 42.20-12 Section 42.20-12 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) LOAD LINES DOMESTIC AND FOREIGN VOYAGES BY SEA Freeboards 42.20-12 Conditions of equilibrium. The following conditions of equilibrium are regarded as satisfactory: (a) Downflooding....

  1. 46 CFR 42.20-12 - Conditions of equilibrium.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Conditions of equilibrium. 42.20-12 Section 42.20-12 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) LOAD LINES DOMESTIC AND FOREIGN VOYAGES BY SEA Freeboards § 42.20-12 Conditions of equilibrium. The following conditions of equilibrium are regarded as satisfactory: (a) Downflooding....

  2. USGS collects ice core through Alpine glacier

    NASA Astrophysics Data System (ADS)

    Naftz, David L.; Miller, Kirk A.

    1992-01-01

    On August 24, 1991, a U.S. Geological Survey study team from Wyoming completed a core hole to bedrock underlying Upper Fremont Glacier in the Wind River Range of central Wyoming. During the month of core drilling, the team collected a 160-m ice core from the glacier at an elevation of 4000 m above sea level using a solar-powered thermal drill (See photo). The drill was constructed and operated by personnel from the Polar Ice Coring Office (PICO) in Fairbanks, Alaska.The 1991 drilling project is part of ongoing research conducted by the USGS since 1988 on temperate glaciers in the Wind River Range of Wyoming. The objective of the project is to use variations in concentrations of chemical and isotopic constituents in samples of ice cores to reconstruct records of the chemical quality of atmospheric deposition and to extend long-term climatic records. A maximum of 300-500 years of record is estimated to be available in upper accumulation zones of the Wind River Range glaciers. The proximity of the Wind River Range glaciers to atmospheric pollution sources in the western United States makes them unique environmental records. Cooperating in the project were the Shoshone and Arapaho Indian tribes, Wyoming Water Development Commission, PICO, Wyoming State Engineer, and the U.S. Bureau of Land Management.

  3. 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

  4. 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.

  5. Improving Mass Balance Modeling of Benchmark Glaciers

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  6. Mathematical challenges in glacier modeling (Invited)

    NASA Astrophysics Data System (ADS)

    jouvet, G.

    2013-12-01

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

  7. Predicting the Effect of Mountain Glacier Recession on Water Resources: A Modeling Study on the Bow Glacier, Alberta

    NASA Astrophysics Data System (ADS)

    Nolin, A. W.; Lettenmaier, D. P.; Clarke, G. K.; Naz, B. S.; Burns, P. J.

    2011-12-01

    Meltwater from alpine glaciers provides critical water supply for vulnerable populations in the western Andes, the Himalayas and the eastern Canadian Rockies. Glacier recession is of major concern in these climate-sensitive regions where we seek to predict changes in watershed hydrology in selected glacierized river basins. The overarching research question of this investigation asks: How have changes in headwater glaciers affected water supply reliability in those parts of the world where streamflow dynamics are most affected by glacier sources? Our approach uses a process-based model that incorporates snow, glaciers, soil, groundwater, vegetation, and topography. The model is a newly modified version of the spatially distributed hydrology model, DHSVM, in which we have added a dynamic glacier submodel. The glacier submodel is initialized with satellite remote sensing-derived maps of glacier extent and a digital elevation model. It assumes conservation of mass, solving the continuity equation for ice and assumes Glen's ice creep law, a sliding law, and the shallow ice approximation. The glacier model can also handle transport and melt-out of debris cover, ice rheology, and isostatic adjustment for long model runs. Using the Bow Glacier, Alberta as an example, this presentation will focus on recent advances in the integrated modeling of glacier and snowmelt runoff and state-of-the-art remote sensing of glacier extent from ASTER and Landsat.

  8. 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 ...

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  10. 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)

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

    NASA Astrophysics Data System (ADS)

    Rastogi, G.; Ajai

    2014-11-01

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

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

    USGS Publications Warehouse

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

    1987-01-01

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

  13. 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)

  14. Malaspina Glacier, Alaska, Anaglyph with Landsat Overlay

    NASA Technical Reports Server (NTRS)

    2003-01-01

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

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

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

  15. Subglacial melting of glaciers by catchment streams is a missing link in temperate glacier mass balance

    NASA Astrophysics Data System (ADS)

    Alexander, David; Shulmeister, James; Davies, Tim; Callow, Nik

    2013-04-01

    The influence of snowmelt and rain water on subglacial hydrology and glacier mass balance of temperate valley glaciers is poorly understood. We present a thermo-hydraulic melt model to improve understanding of the potential influence that streams sourced from snowmelt and rain have on the subglacial hydrology and melting of the high-precipitation Franz Josef Glacier, New Zealand. The model simulates conduit expansion due to melting caused by heat advection and contraction to due ice deformation at an hourly time-step to obtain an annual melt rate along the length of individual subglacial conduits fed from terrestrial streams that enter the glacier from the ice-free sub-catchments surrounding it. These streams are fed by snowmelt and rainfall that enter the glacier well above 0C (up to ~10C at low altitudes). Our model is calibrated using terrestrial stream temperature data and is validated with field measurements of surface and proglacial meltwater temperatures, as well as internal water flow velocities. Modelled outputs based on the best available data from measurements and observations indicate that streams entering the Franz Josef Glacier contribute an estimated 7% to the total glacier melt. This is the equivalent of more than twice the surface rainfall heat flux, which shows that rain and snowmelt may melt significant quantities of ice within a glacier. Not accounting for this melting mechanism in glaciological models where streams enter glaciers may lead to: 1) an incorrect characterisation of the subglacial hydrological drainage system; and 2) a potentially serious bias error in mass balance estimations. The second implication is fundamentally important for model robustness given that glaciological models are increasingly being used to predict the effects of future climate change.

  16. Impact of debris cover on glacier ablation and atmosphere-glacier feedbacks in the Karakoram

    NASA Astrophysics Data System (ADS)

    Collier, E.; Maussion, F.; Nicholson, L. I.; Mlg, T.; Immerzeel, W. W.; Bush, A. B. G.

    2015-04-01

    The Karakoram range of the Hindu-Kush-Himalaya is characterized by both extensive glaciation and a widespread prevalence of surficial debris cover on the glaciers. Surface debris exerts a strong control on glacier surface-energy and mass fluxes and, by modifying surface boundary conditions, has the potential to alter atmosphere-glacier feedbacks. To date, the influence of debris on Karakoram glaciers has only been directly assessed by a small number of glaciological measurements over short periods. Here, we include supraglacial debris in a high-resolution, interactively coupled atmosphere-glacier modelling system. To investigate glaciological and meteorological changes that arise due to the presence of debris, we perform two simulations using the coupled model from 1 May to 1 October 2004: one that treats all glacier surfaces as debris-free and one that introduces an simplified specification for mapping debris thickness. The basin-averaged impact of debris is a reduction in ablation of ~7%, although the difference exceeds 2.5 m w.e. on the lowest-altitude glacier tongues. The modest reduction in mean mass loss results in part from non-negligible sub-debris melt rates under thicker covers and from compensating increases in melt under thinner debris, and may help to explain the lack of distinct differences in recent elevations changes between clean and debris-covered ice. The presence of debris also strongly alters the surface boundary condition and thus heat exchanges with the atmosphere; near-surface meteorological fields at lower elevations and their vertical gradients; and the atmospheric boundary layer development. These findings are relevant for glacio-hydrological studies on debris-covered glaciers and contribute towards an improved understanding of glacier behaviour in the Karakoram.

  17. Impact of debris cover on glacier ablation and atmosphere-glacier feedbacks in the Karakoram

    NASA Astrophysics Data System (ADS)

    Collier, E.; Maussion, F.; Nicholson, L. I.; Mlg, T.; Immerzeel, W. W.; Bush, A. B. G.

    2015-08-01

    The Karakoram range of the Hindu-Kush Himalaya is characterized by both extensive glaciation and a widespread prevalence of surficial debris cover on the glaciers. Surface debris exerts a strong control on glacier surface-energy and mass fluxes and, by modifying surface boundary conditions, has the potential to alter atmosphere-glacier feedbacks. To date, the influence of debris on Karakoram glaciers has only been directly assessed by a small number of glaciological measurements over short periods. Here, we include supraglacial debris in a high-resolution, interactively coupled atmosphere-glacier modeling system. To investigate glaciological and meteorological changes that arise due to the presence of debris, we perform two simulations using the coupled model from 1 May to 1 October 2004: one that treats all glacier surfaces as debris-free and one that introduces a simplified specification for the debris thickness. The basin-averaged impact of debris is a reduction in ablation of ~ 14 %, although the difference exceeds 5 m w.e. on the lowest-altitude glacier tongues. The relatively modest reduction in basin-mean mass loss results in part from non-negligible sub-debris melt rates under thicker covers and from compensating increases in melt under thinner debris, and may help to explain the lack of distinct differences in recent elevation changes between clean and debris-covered ice. The presence of debris also strongly alters the surface boundary condition and thus heat exchanges with the atmosphere; near-surface meteorological fields at lower elevations and their vertical gradients; and the atmospheric boundary layer development. These findings are relevant for glacio-hydrological studies on debris-covered glaciers and contribute towards an improved understanding of glacier behavior in the Karakoram.

  18. Determining Crevasse Sequences in Surging Glaciers using Neural Network Classification from Remotely Sensed Images of Bering Glacier, AK

    NASA Astrophysics Data System (ADS)

    Bobeck, J.; Herzfeld, U. C.; Goetz-Weiss, L.; Hale, G.

    2014-12-01

    Bering Glacier in Alaska is a surging glacier; one of the most understudied glacier classes in the cryospheric sciences. By using a neural network created with a new method for extracting crevasse patterns, and remotely sensed images acquired from World View 1, it is possible to not only to classify crevasses formed during Bering's surges, but also to determine whether glacier crevasses form in pattern sequences. In order to understand the relationship between the geographic location of the crevasse types and the geophysical formation of those crevasses, an analysis of glacier flow, velocity, and the dependency on the type of force acting upon the glacier, will be used over a time sequence of Wold View 1 images. The importance of this study will allow for better understanding of the geophysical processes that occurs on surging glaciers, along with allowing for future prediction of crevasse formation which will be useful in determining hazardous regions of Bering glacier, ultimately allowing for higher safety for researchers.

  19. 36 CFR 7.3 - Glacier National Park.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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

  20. 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

  1. Widespread Alaska glacier retreat likely not due to climate change

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2014-06-01

    Alaska's Columbia Glacier, which has shed half its mass since 1957, is a dramatic example of how quickly glaciers can shrink. Yet while Columbia has shown a huge decline, a new analysis by McNabb and Hock has found that other glaciers in the region have retreated far less, or even advanced, over the past 6 decades.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    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.

  3. 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

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

    USGS Multimedia Gallery

    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...

  5. 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

  6. 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)

  7. 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

  8. 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

  9. 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

  10. Testing geographical and climatic controls on glacier retreat

    NASA Astrophysics Data System (ADS)

    Freudiger, Daphn; 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.

  11. 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.

  12. 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.

  13. The Increasing of Glacial Runoff in Response to Climate Warming in Glacier No.1 at the Headwaters of the Urumqi River, Tianshan Mountains

    NASA Astrophysics Data System (ADS)

    Li, Jing; Liu, Shiyin

    2010-05-01

    Based on hydrological observations and calculations of water balance?the annual meltwater runoff of Glacier No.1 which locates at the Headwaters of the Urumqi River, Tianshan Mountains has been computed. It shows an elevated trend during the last several decades.The mean meltwater runoff depth is 936.6mm during the period of 1986 to 2001, comparing to 508.4mm during the period of 1958 to 1985. Data analysis shows that the proportion of liquid precipitation which can form runoff over the glacier surface has also been raised ,with the annual mean air temperature at the glacier terminus in the period of 1986 to 2001 increased by 0.5? to the period of 1958 to 1985.We also found that the ablation occurred in the position corresponding approximately to the equilibrium altitude in the glacier kept pace well with the glacier meltwater runoff. We conclude that the ablation on that altitude can represent the glacial meltwater runoff to a certain extent. Considering the climate shift in northwest of China, it is necessary to realize the glacial meltwater runoff sensitivity to climate change. We applied the degree-day model which has performed well for reconstructing mass balance of this glacier to simulate glacial meltwater runoff.

  14. 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.

  15. Coseismic-initiated calving at a freshwater-terminating glacier: Tasman Glacier, New Zealand

    NASA Astrophysics Data System (ADS)

    Dykes, R. C.; Lube, G.; Brook, M. S.

    2012-04-01

    Glacier retreat resulting from iceberg calving represents one of the major controls on ice loss from water-terminating glaciers (ice sheets, tidewater and freshwater glaciers) globally. However, the impact that calving has on the transfer of mass between the cryosphere and hydrosphere is still heavily debated, and the physical mechanisms behind calving remain poorly understood. Hitherto, the initiation of calving events has largely been attributed to underlying glaciological mechanisms (including fracturing of ice due to high longitudinal stress gradients) and changes in the proglacial water-body characteristics. We present evidence for a large-magnitude calving event following high magnitude (>Mw 6) earthquakes as a potentially important triggering mechanism of calving in tectonically-active areas. We describe the response of Tasman Glacier, New Zealand, a freshwater-terminating glacier undergoing accelerated calving retreat, to the Mw 6.3, 5.7 and 4.5 Christchurch 22 February 2011 earthquakes and the subsequent calving event. Time-series analysis of timed video and photographic records of the glacier terminus immediately pre-, co- and post- the 22 February earthquakes demonstrates that the large calving event on the 22 February 2011 occurred in direct response to a resonance effect caused by shear (S-) waves oscillating the terminus at the ice-water interface. We suggest that, in this instance, the magnitude of calving was amplified because Tasman Glacier had reached a critical threshold for buoyancy-induced calving in relation to perturbations in lake level. Prior to this event, small- to intermediate magnitude calving, leading to terminus retreat, had been dominated by thermo-erosional notching at the waterline, destabilising the subaerial ice cliff. Indeed, recent (post-2006) large calving events have primarily been driven by torque-induced, buoyancy-driven calving. Hence, in tectonically-active areas, coseismic-initiated calving can have an episodic, but strong control on retreat, potentially destabilising a glacier system and leading to accelerated recession, accentuating climate-forced mass balance changes.

  16. 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.; Kjr, K. H.; Bevan, S.; Luckman, A.; Aschwanden, A.; Bjrk, 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.

  17. 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.

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

    NASA Technical Reports Server (NTRS)

    Hall, D. K.

    1998-01-01

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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. The landform and sediment assemblage produced by a tidewater glacier surge in Kongsfjorden, Svalbard

    NASA Astrophysics Data System (ADS)

    Bennett, Matthew R.; Hambrey, Michael J.; Huddart, David; Glasser, Neil F.; Crawford, Kevin

    1999-08-01

    This paper describes the landform and sediment assemblage produced by a surge (in 1948) of the Kongsvegen/Kronebreen tidewater glacier complex in northwest Spitsbergen. The main geomorphological products of this advance are two large thrustmoraine complexes on opposite sides of the fjord, and a system of geometrical ridges revealed on glacier decay. The thrust-moraines are composed largely of diamicton, sandy and muddy gravel, gravelly sand, sand and mud, with minor laminites. All of these appear to be derived from the fjord floor and represent both fine fjord basin sediments and coarse grounding-line fan deposits. Thrusting was the principal mode of emplacement of the sediment onto the adjacent land areas during the 1948 advance. However, the geomorphology of the thrust-moraine complexes on either side of the fjord is quite different, reflecting a transpressive regime on the southwest side (mainly long ridges) and a normal compressive regime on the northeast side (short ridges and pinnacles of a 'hummocky' nature). The advance which produced the moraine complex has previously been attributed to a surge of Kongsvegen, but the glaciological and geomorphological evidence suggests that the advance involved both Kongsvegen and Kronebreen. Comparison of the landform assemblage produced by this event with that produced by other tidewater glacier surges demonstrates the diverse range of landform assemblages associated with glacier surges, or other episodes of rapid flow, within glaciomarine environments.

  5. a Seismic Reflection Study on the Ablation Area of the Taku Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Zechmann, J. M.; Gusmeroli, A.; Booth, A.; Truffer, M.

    2014-12-01

    Active-source seismic reflection techniques have been frequently used to document temporal and spatial variability in subglacial conditions beneath the ice sheets. Seismic surveys may provide the topography of the subglacial landscape as well as information about the properties of subglacial sediments and water. The former is achieved by standard 2D seismic imaging, the latter by amplitude analysis of the base-ice reflection. Seismic techniques for subglacial characterization have not yet been fully explored on mountain glaciers, where the ice is warmer and more attenuative to seismic energy, and the area available for survey is often more restrictive. In March 2014 we collected a high-resolution seismic reflection survey on the lower ablation area of the Taku Glacier in South-East Alaska. The survey line was composed of 120 geophones buried 0.5 m in the snowpack and spaced by 5 meters. The surface of the glacier was covered by a spatially variable 2-6 m thick snow cover. Shots, 99 charges of the binary explosive kinepak (152 grams), were drilled to 6 meters below surface. We present preliminary seismic images, attenuation estimates and amplitude analysis as well as a discussion of the challenges of seismic studies in the ablation area of large mountain glaciers where spatially variable snowpack, rough topography and hidden crevasses hamper standard seismic interpretation and render successful data interpretation more difficult.

  6. 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.

  7. 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.

  8. 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.

  9. Panoramic of Glaciers in the Caucasus Moutains

    USGS Multimedia Gallery

    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...

  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. 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

  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. Glacier National Park Bighorn Sheep Studies

    USGS Multimedia Gallery

    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....

  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. 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…

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

    SciTech Connect

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

    1996-11-01

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

  17. 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.

  18. 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.

  19. 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, in