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1

76 FR 69720 - NaturEner Rim Rock Wind Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing...  

Federal Register 2010, 2011, 2012, 2013

...Commission [ Docket No. ER12-295-000] NaturEner Rim Rock Wind Energy, LLC; Supplemental Notice That Initial Market-Based...the above-referenced proceeding of NaturEner Rim Rock Wind Energy, LLC's application for market-based rate...

2011-11-09

2

Glacier winds and parameterisation of the related surface heat fluxes  

NASA Astrophysics Data System (ADS)

The katabatic flow over glaciers is studied with data from automatic weather stations (AWS). We analyse data from the Morteratschgletscher (Switzerland), Vatnajökull (Iceland) and West Greenland, and conclude that katabatic flow is very common over melting glacier surfaces and rarely disrupted by the large-scale flow. Over small and medium-size glaciers the height of the wind maximum is generally low (typically 10 m), and vertical temperature differences near the surface are very large (up to 15 K over 4 m). In glacier mass-balance models there is a great need for parameterisations of the surface heat flux. We develop a simple method to estimate the sensible heat flux Fh associated with the glacier wind. It is based on the classical Prandtl model for slope flows. We set the turbulent exchange coefficient proportional to the maximum wind speed (velocity scale) and the height of the wind maximum (length scale). The resulting theory shows that Fh increases quadratically with the temperature difference between the surface and the ambient atmosphere; Fh decreases with the square root of the potential temperature gradient of the ambient atmosphere; and Fh is independent of the surface slope.

Oerlemans, J.; Grisogono, B.

2002-10-01

3

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

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

4

Glaciers  

NASA Astrophysics Data System (ADS)

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.

Hambrey, Michael; Alean, Jürg

2004-12-01

5

Glaciers  

NSDL National Science Digital Library

Glaciers are found on every continent except Australia. This interactive feature provides an introduction to these moving streams of ice, which cover about 10 percent of Earth's land surface and hold between two and three percent of its water. Topics include what glaciers are, where and why they form, what influences their growth and decline, and how an apparently solid mass appears to flow like a river. There is also a brief description of some types of glaciers. A background essay and discussion questions are included.

2010-09-28

6

GLACIER VARIABILITY IN WYOMING’S WIND RIVER RANGE AND TETON RANGE  

NASA Astrophysics Data System (ADS)

The Wind River Range (WRR) in west central Wyoming is host to 63 glaciers, while the Teton Range (TR) is host to 10 named glaciers. These glaciers serve as natural water reservoirs, and the continued recession of glaciers will impact agricultural water supply in the region. Glacier area changes in the WRR were estimated for 44 glaciers using un-rectified high resolution (1 m) aerial photography from 1966 to 2006. Additionally, glacier area was also developed for ten of the 44 glaciers using resampled aerial photography at 10 m (SPOT), 15 m (ASTER), 22.5 m (IRS-LISS) and 30 m (Landsat) resolutions for 1966 and 2006. The total surface area of the 44 glaciers was calculated to be 45.9 ± 0.13 km2 in 1966 and 28.5 ± 0.11 km2 in 2006, an average decrease of 38% over the 40 year period. Small glaciers experienced noticeably more area reduction than large glaciers. Of the 44 glaciers analyzed, 22 had an area of greater than 0.5 km2 in 1966, while 22 were less than 0.5 km2 in 1966. The glaciers with a surface area less than 0.5 km2 experienced an average surface area loss (fraction of 1966 surface area) of 47%, while the larger glaciers (greater than 0.5 km2) experienced an average surface area loss of 36% in 2006. Of the ten glaciers analyzed by resampling, the total surface area (fraction of 1966 surface area) decreased by 36.8% using aerial photographs, 36.5% using SPOT images, 36.6% using ASTER images, 36.0% using IRS-LISS images and 37.1% using Landsat images. Glacier area changes in the TR were estimated for three glaciers using un-rectified aerial photography from 1967 to 2006. The total surface area of the three glaciers was calculated to be 0.53 ± 0.13 km2 in 1967 and 0.40 ± 0.10 km2 in 2006, an average decrease of 34% over the 39 year period. The smallest glacier Teepe experienced the most noticeable lost, losing 60% while the Teton glacier lost 17%. Applying area-volume scaling relationships for Teton, Middle Teton, and Teepe glaciers, volume loss was estimated to be 3.2 million cubic meters (MCM) over the 35 year period, which results in an estimated 4 to 10% contribution to warm season (July - September) streamflow. Accompanied with the calculation of glacier area loss, the amount of glacial volume lost was also determined for selected glaciers in the WRR from 1966 to 1989. A subset of 29 glaciers throughout two basins were analyzed as part of a paired watershed (glaciated vs. non-glaciated) analysis. Through the use of photogrammetric techniques, volume loss in the 17 glaciers of the Upper Green River sub-basin was estimated to be 319 x 106 m3 (14% area loss), while 12 glaciers in the Bull Lake sub-basin lost 369 x 106 m3 (16% area loss) over the 23 year period. The pure glacial ice melt contribution to late summer (Jul., Aug. and Sep.) downstream flow was 8% and 14%, respectively, for the basins above. Also, the paired watershed analysis indicated glaciers delayed spring snowmelt runoff to an extent where, in combination with glacial ice melt, the flow resulting from the glacial terminus was approximated as 40% of the late summer downstream flows.

Thompson, D.; Bell, J. E.; Edmunds, J.; Tootle, G. A.; Kerr, G.

2009-12-01

7

Estimates of Glacier Mass Loss and Contributions to Streamflow: Wind River Range (Wyoming, USA)  

NASA Astrophysics Data System (ADS)

The Wind River Range (WRR) of Wyoming is host to approximately 63 glaciers. Extensive research has been conducted using remote imagery to estimate the area changes of these glaciers, with the goal of estimating the potential impacts of these changes on watershed streamflow. Results show that the glaciers were mostly in recession from 1966 to 2006 with glacier area losses estimated at 38%. Recent research efforts (paired watershed analysis), which supplement the results from the remote imagery analyses, evaluated late summer [July-August-September (JAS)] streamflows from glaciated and non-glaciated watersheds. The difference in observed JAS flows between glaciated and non-glaciated watersheds ranged between 8% and 23% and glaciers accounted for 23% to 54% of the observed late summer (JAS) flow in glaciated watersheds. This was primarily attributed to the glaciers decelerating the snowmelt runoff through internal storage/delayed release of liquid water and, to a lesser extent, the loss of glacier mass. However, no estimates were made as to what percentage of late summer streamflow is attributed to glacier mass (volume) loss. Applying established empirical relationships between glacier area and volume, estimates of glacier volume loss and the contribution to late summer streamflow were estimated for two glaciated watersheds of the WRR, the Upper Green River basin (west slope) and Bull Lake Creek basin (east slope). The results show that glacier mass contributes 2% to 8% of late summer streamflow resulting in estimated glacier losses of 0.4 to 0.7 meters per year from 1966 to 2006.

Tootle, G. A.; Marks, J.; Kerr, G.

2011-12-01

8

Glacier winds in the Rongbuk Valley, north of Mount Everest: 2. Their role in vertical exchange processes  

Microsoft Academic Search

High ozone concentrations, combined with low humidity and strong, persistent glacier winds, were found at the surface of Rongbuk Valley, north of Mount Everest, with sharply increased ozone concentrations in their vertical profiles. Glacier winds and their roles in vertical exchange of the atmosphere were investigated numerically to understand the phenomena. A Lagrangian particle dispersion model was used to carry

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

2007-01-01

9

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

Microsoft Academic Search

Persistent glacier winds blowing from noon to midnight in summer are present in the Rongbuk Valley, north of Mount Everest, with a maximum speed of 10 m s-1 and a vertical thickness as high as 1 km. These glacier winds may bring upper level atmosphere ozone to the surface, having a significant impact on the atmospheric environment. Such phenomena may

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

2007-01-01

10

Glacier winds on Vatnajökull ice cap, Iceland, and their relation to temperatures of its lowland environs  

Microsoft Academic Search

During the ablation season, the ice cap Vatnajökull (8100 km2) develops its own microclimate that we describe by meteorological data collected during the summers of 1994-2003. Persistent glacier winds are generated down the melting ice cap, whose variations in speed can be related empirically to the temperature fluctuations of the lowland environs of the ice cap. This suggests that climate

Helgi Björnsson; Sverrir Gudmundsson; Finnur Pálsson

2005-01-01

11

Glacier winds in the Rongbuk Valley, north of Mount Everest: 2. Their role in vertical exchange processes  

NASA Astrophysics Data System (ADS)

High ozone concentrations, combined with low humidity and strong, persistent glacier winds, were found at the surface of Rongbuk Valley, north of Mount Everest, with sharply increased ozone concentrations in their vertical profiles. Glacier winds and their roles in vertical exchange of the atmosphere were investigated numerically to understand the phenomena. A Lagrangian particle dispersion model was used to carry out numerical experiments (forward-in-time simulations) and footprint analysis (backward-in-time simulations). The meteorological data inputs for these experiments were derived from the Advanced Regional Prediction System. Results showed that glacier winds may lead to significant downward transport of 1.5-2 km during the daytime from the northern slopes of Mount Everest. Glacier winds could advance down through the valley, with strong upward motions shown as a rolling up in front of their leading edge. Combining with upslope winds at two sidewalls of the valley or up-valley winds of tributaries, the lifting flows produced strong mixing of the atmosphere to a depth of approximately 3 km. Three-dimensional footprints derived from the particle dispersion model for the observational site, Rongbuk Monastery, clearly show influence from the mountainside of Mount Everest and from the southern part of the valley. The vertical extension of influence was as much as 2-3 km. Good correlation was found between the influence height and the ozone concentration. All the simulation results strongly indicate that the glacier winds and their related vertical exchange processes "pump down" ozone-rich air from upper levels to the surface of the valley.

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

2007-06-01

12

World Glacier Monitoring Service  

NSDL National Science Digital Library

The World Glacier Monitoring Service site contains online issues of Fluctuations of Glaciers and the Glacier Mass Balance Bulletin; glacier inventory data describing the spatial variability and glacier fluctuation data documenting changes in time; explanations of glacier monitoring strategy using glacier mass balance, length change, inventories, and data analysis; and a bibliography of related work.

13

Glacier Caves  

NSDL National Science Digital Library

Created by Charlie Anderson Jr. of the International Glaciospeleological Survey, Glacier Caves provides numerous fantastic photographs of glaciers, caves, and volcanoes located mainly in Northwestern United States. Visitors can sort through the images by topic or by location. Users can find various materials on eruptions, special features, and explorations of many famous Northwestern mountains including Mount St. Helens, Mount Hood, and Mount Rainer. The site features links to volcano web cameras.

14

Melting Glaciers  

NSDL National Science Digital Library

Due to the potential disastrous consequences to the environment and to numerous societies, scientists, governments, and civilians are concerned with the growing trend of glacial melt. This topic-in-depth explores various geographic regions where this phenomenon has recently been observed. Providing background into the study of glaciology, this report begins with a Web site (1) discussing the unique features of glaciers. The US Army Corps of Engineers offers visitors an insight to glacial properties including their locations, movements, and influences; along with a series educational images. The second site (2) explains the exceptionality of the two hundred sixty six glaciers at Glacier National Park. Through a collection of images, animations, and pictures provided by the National Park Service, users can learn about ice dams, climatic impacts, and the erosive powers of ice and water. The rest of the topic-in-depth discusses findings of glacial melting from around the world. NASA (3) addresses the Artic warming's affects on glacier formations. This Web site provides a few animations displaying ice sheet extent and the cracking of icebergs. On a positive note, visitors can learn how the decrease in glaciers has opened up new habitat for some Artic species. The next Web site (4), also by NASA, discusses the findings of a twenty-five year study of Patagonia's glaciers. Educators and students can discover how NASA utilized the Space Shuttle Endeavor to study the entire 17,200 square kilometer region. The site also discusses potential causes of the melting in this region, which has contributed to almost ten percent of the global sea-level change from mountain glaciers. As reported by the BBC (5), Dr. Harrison at the University of Oxford has determined that the glaciers in parts of Kazakhstan have been decreasing annually by almost two cubic kilometers between 1955 and 2000. Visitors can learn how the melting of these four hundred sixteen glaciers will adversely affect the region's rivers and its water supply. The Taipei Times (6) reports that the Swiss Alpine glacial melting has probably intensified due to this summer's record-breaking heat wave. This Web site provides short, intriguing descriptions of consequences of the "rush of melt water streaming from the ice wall." Users can learn about predictions in the 1990s that the glaciers would shrink to ten percent of their 1850 size by the end of the twenty first century. In the next Web site (7), the BBC provides a captivating illustration of the effects the Peruvian glacial melts may have on tourism, the country's water supply, and more. Students and educators can learn about NASA studies showing cracks in the ice, which could lead to the flooding of large cities. Visitors can also find out how the recent glacier recessions have affected some ancient spiritual traditions. The last site, by the USGS, (8) features excerpts from Myrna Hall and Daniel Fagre's 2003 research paper in BioScience. Visitors can discover the melt rate and spatial distributions of glaciers for two possible future climate situations. Providing an amazing animation, users will be amazed by the changes predicted by the model.

Enright, Rachel

15

Glacier Photograph Collection  

NSDL National Science Digital Library

These repeat photographs (also known as glacier pairs) are of special interest to scientists studying glaciers and climate. Glacier photographs taken from the same vantage point, but years apart in time, can reveal dramatic changes in the glacier terminus position, as a glacier either advances or retreats. Most glaciers around the world have retreated at unprecedented rates over the last century. These pairs of photographs can provide striking visual evidence of climate change.

Center, National S.

16

Northeast Glaciers  

NSDL National Science Digital Library

This reference guide provides a brief review of glaciers in the Northeastern U.S. It then focuses on the glacial affects in four areas, an inland basin near the Finger Lakes area of New York, the Appalachian/Piedmont through New York and Pennsylvania, the coastal plain and the exotic terrane of New England. Topics covered include glacial scouring, glacial deposits and periglacial features.

2003-01-01

17

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 ...

2010-07-14

18

South Cascade Glacier bibliography  

SciTech Connect

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

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

1984-01-01

19

Afghanistan Glacier Diminution  

Microsoft Academic Search

Glaciers in Afghanistan represent a late summer - early fall source of melt water for late season crop irrigation in a chronically drought-torn region. Precise river discharge figures associated with glacierized drainage basins are generally unavailable because of the destruction of hydrological gauging stations built in pre-war times although historic discharge data and prior (1960s) mapped glacier regions offer some

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

2008-01-01

20

The World Glacier Inventory  

NSDL National Science Digital Library

This web site is part of the National Snow and Ice Data Center's World Glacier Monitoring Service. The World Glacier Inventory contains information for over 67,000 glaciers throughout the world. Parameters within the inventory include: geographic location, area, length, orientation, elevation, and classification of morphological type and moraines. The inventory entries are based upon a single observation in time and can be viewed as a "snapshot" of the glacier at this time. These data are collected and digitized by the World Glacier Monitoring Service, Zurich. A point and click map of the world will also take users to the region of interest with a list of glaciated areas.

Haggerty, C.

21

Worthington Glacier Project  

NSDL National Science Digital Library

Funded by the National Science Foundation (NSF), the Worthington Glacier Project is a collaboration between researchers at the University of Wyoming and the University of Colorado. The objective of this project is to understand glacier flow dynamics "by comparing detailed measurements of glacier motion with numerical models for glacier flow." Summaries and diagrams are provided of the discussed topics: Borehole Video Observations, Radio-Echo Sounding, Crevassing, Surface Flow Field, Englacial Flow Field, 3-D Flow Field, and In-Situ Stress. Images of the Worthington Glacier fieldwork, future research, and publications are also available at the site.

22

Afghanistan Glacier Diminution  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

23

Recent changes of very small glaciers in the Swiss Alps  

NASA Astrophysics Data System (ADS)

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

Fischer, Mauro; Huss, Matthias; Hoelzle, Martin

2013-04-01

24

The thermophysics of glaciers  

SciTech Connect

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.

Zotikov, I.A.

1986-01-01

25

Glaciers and Rocks  

NSDL National Science Digital Library

This formative assessment item uncovers students' ideas about glacial erosion and how glaciers transport rocks and other sediment. The assessment is aligned with the National Science Education Standards. It contains instructional suggestions as well as links to other helpful resources dealing with glaciers and glacial movement.

Fries-Gaither, Jessica

26

Melting Mountain Glaciers  

NSDL National Science Digital Library

The world's glaciers are shrinking at alarming rates, and many scientists believe it is due to changes in climate. Dr. Lonnie Thompson of Ohio State University and Dr. Douglas Hardy of UMass-Amherst discuss glaciers and how they melt, and pay special attention to Africa's tallest mountain, Mt. Kilimanjaro. "Changing Planet" is produced in partnership with the National Science Foundation.

Learn, Nbc

2010-10-07

27

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 ...

2010-07-14

28

The Morteratsch Glacier  

Microsoft Academic Search

During my stay in the Engadine this summer I took the opportunity of making a few observations relative to the movement of the Morteratsch Glacier, which may be of interest to some of your readers. These observations were taken inside the artificial cave of the above glacier in preference to the surface, as I thereby obtained a more direct measurement

Hugo Leupold

1881-01-01

29

Mini Glacier Meltdown  

NSDL National Science Digital Library

This activity (located on page 3 of the PDF) is a full inquiry investigation about the different causes of glacial melt. Groups of learners will design their own experiment using frozen "glaciers", bricks and different energy sources (fans, and lights) to test how different conditions affect the rate of melting. The results might be surprising. Relates to linked video, DragonflyTV GPS: Glaciers.

Twin Cities Public Television, Inc.

2007-01-01

30

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...

2008-12-15

31

Modeling Glacier Erosion Through Time  

NSDL National Science Digital Library

Prior to this lab, students will have read and learned about valley glacier processes, glacier mass balance, warm-based and cold-based glaciers, and can identify various glacier landforms formed by erosion. They will also have had an introductory lecture on ice physics, but that is not necessary to complete this activity.

Connor, Cathy L.

32

Modelling Greenland Outlet Glaciers.  

National Technical Information Service (NTIS)

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 betwe...

C. vanderVeen

2001-01-01

33

A strategy for monitoring glaciers  

USGS Publications Warehouse

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.

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

1997-01-01

34

Moving Model Glacier  

NSDL National Science Digital Library

In this goopy activity, learners will model glacial movement with âgak,â a white glue and liquid starch mixture. Each fist-sized gob of gak represents a yearâs worth of snow, accumulating to form a âglacierâ on a model landscape. Learners will record the gakâs rate of travel as well as make observations of other glacier behaviors. Relates to the linked video, DragonflyTV GPS: Glaciers.

Twin Cities Public Television, Inc.

2007-01-01

35

Geological Field Trips: Glaciers  

NSDL National Science Digital Library

Students will utilize the Internet to take a virtual field trip to visit a glacier and discover what physical effects glaciers have on the land. They will also have the opportunity to virtually visit Vermont and trace the pictorial history of how a whale's fossils were found there. The site also contains a student worksheet for their visual field trip. The site also provides an explanation of the formation of fossils.

Zvanut, Patti

2000-03-23

36

Recent Acceleration of Thwaites Glacier.  

National Technical Information Service (NTIS)

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...

J. G. Ferrigno

1993-01-01

37

The GLIMS Glacier Database  

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

38

Exploring the links between transient water inputs and glacier velocity in a small temperate glacier in southeastern Alaska  

NASA Astrophysics Data System (ADS)

Glaciers along the Gulf of Alaska are thinning and retreating rapidly and over the last century this loss of ice has contributed measurably to global sea level rise. An important control on the rate at which ice is being lost is basal motion because higher glacier velocities increase the rate at which ice is delivered to ablation zones. Recent research has focused on understanding the effects of sub-glacial water storage on glacier basal motion. In this study, we examined how water inputs from large rainfall events as well as a glacier lake outburst flood affected the velocity of the Lemon Creek Glacier in southeastern Alaska. Lemon Creek Glacier is a moderately sized (~16~km2) temperate glacier at the margin of the Juneau Icefield. An ice- marginal lake forms at the head of the glacier and catastrophically drains once or twice every melt season. We have instrumented the glacier with two meteorological stations: one at the head of the glacier near the ice-marginal lake and another several kilometers below the terminus. These stations measure temperature, relative humidity, precipitation, incoming solar radiation and wind speed and direction. Lake stage in the ice- marginal lake was monitored with a pressure transducer. In addition, Lemon Creek was instrumented with a water quality sonde at the location of a US Geological Survey gaging station approximately 3 km downstream from the glacier terminus. The sonde provides continuous measurements of water temperature, dissolved oxygen, turbidity and conductivity. Finally, two Trimble NetRS dual frequency, differential GPS units were deployed on the glacier at approximately 1/3 and 2/3 down the centerline of the glacier. All of the instruments were run continuously from May-September 2008 and captured the outburst flood associated with the ice-marginal lake drainage as well as several large (>3~cm) rainfall events associated with frontal storms off of the Gulf of Alaska in late summer. Taken together, these data allow us to test the hypothesis that water inputs which overwhelm subglacial drainage networks result in increased rates of basal motion.

Habermann, M.; Hood, E.; Heavner, M.; Motyka, R.

2008-12-01

39

Fundamentals of Glacier Dynamics  

NASA Astrophysics Data System (ADS)

Glaciers form when snow melts and refreezes, or is compressed, to form ice. Spreading under their own weight, they flow seaward, channeled along preferred routes by the shape or composition of the underlying bedrock. Though we don't know why, some ice streams flow rapidly within slower-moving ice in Greenland and Antarctica. Glaciers exist on all continents except Australia, and at high enough elevations, they can be found even at the equator. Many are melting as global temperatures rise, but about 99% of glacier ice is in Greenland and Antarctica, where it is partly protected from global warming by low temperatures. Nevertheless, the coastal ice sheet in Greenland has thinned recently for unknown reasons, and we still don't know whether the far larger Antarctic ice sheet is growing or shrinking.

Thomas, Robert H.

40

Glaciers of Greenland  

USGS Publications Warehouse

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.

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

1995-01-01

41

Five 'Supercool' Icelandic Glaciers  

NASA Astrophysics Data System (ADS)

Sediment entrainment by glaciohydraulic supercooling has recently been demonstrated as an effective process at Matanuska glacier, Alaska. Although subfreezing meltwater temperatures have been recorded at several Alaskan glaciers, the link between supercooling and sediment accretion remains confined to Matanuska. This study presents evidence of glaciohydraulic supercooling and associated basal ice formation from five Icelandic glaciers: Skeidarárjökull, Skaftafellsjökull, Kvíárjökull, Flaájökull, and Hoffellsjökull. These observations provide the best example to-date of glaciohydraulic supercooling and related sediment accretion outside Alaska. Fieldwork undertaken in March, July and August 2001 confirmed that giant terraces of frazil ice, diagnostic of the presence of supercooled water, are forming around subglacial artesian vents. Frazil flocs retrieved from these vents contained localised sandy nodules at ice crystal boundaries. During periods of high discharge, sediment-laden frazil flocs adhere to the inner walls of vents, and continue to trap suspended sediment. Bands of debris-rich frazil ice, representing former vents, are texturally similar to basal ice exposures at the glacier margins, implying a process-form relationship between glaciohydraulic freeze-on and basal ice formation. It is hypothesised that glaciohydraulic supercooling is generating thick sequences of basal ice. Observations also confirm that in situ melting of basal ice creates thick sedimentary sequences, as sediment structures present in the basal ice can be clearly traced into ice-marginal ridges. Glaciohydraulic supercooling is an effective sediment entrainment mechanism at Icelandic glaciers. Supercooling has the capacity to generate thick sequences of basal ice and the sediments present in basal ice can be preserved. These findings are incompatible with established theories of intraglacial sediment entrainment and basal ice formation; instead, they concur with, and extend, the current model of Matanuska-type glaciohydraulic supercooling. This work adds a new dimension to the understanding of debris entrainment in temperate glaciers.

Knudsen, O.; Roberts, M. J.; Roberts, M. J.; Tweed, F. S.; Russell, A. J.; Lawson, D. E.; Larson, G. J.; Evenson, E. B.; Bjornsson, H.

2001-12-01

42

The health of glaciers: Recent changes in glacier regime  

USGS Publications Warehouse

Glacier wastage has been pervasive during the last century; small glaciers and those in marginal environments are disappearing, large mid-latitude glaciers are shrinking slightly, and arctic glaciers are warming. Net mass balances during the last 40 years are predominately negative and both winter and summer balances (accumulation and ablation) and mass turnover are increasing, especially after 1988. Two principal components of winter balance time-series explain about 50% of the variability in the data. Glacier winter balances in north and central Europe correlate with the Arctic Oscillation, and glaciers in western North America correlate with the Southern Oscillation and Northern Hemisphere air temperature. The degree of synchronization for distant glaciers relates to changes in time of atmospheric circulation patterns as well as differing dynamic responses.

Meier, M. F.; Dyurgerov, M. B.; McCabe, G. J.

2003-01-01

43

A dynamic physical characterization of the receding Mendenhall Glacier lake front terminus Juneau, Alaska  

NASA Astrophysics Data System (ADS)

Extrapolation of 2000-2009 GPS results from terminus position surveys of the Mendenhall Glacier near Juneau, Alaska suggests that the lake front glacier terminus will no longer be in contact with proglacial Mendenhall Lake by July 2011. Meteorologic stations located near the glacier terminus at 44m asl, on the glacier surface at 430m (Northstar Camp), and at 1569m near the Mendenhall-Taku Glacier ice divide, provide data from rainfall events and temperature variation which contribute to glacier velocity and ultimately ice mass transfer to the lower glacier. Mendenhall weather data in combination with wind direction, wind velocity, and lake water temperature profiles (0-40m) and bathymetric surveys in 2009 provide detailed information about the physical conditions of the glacier and lake which are also captured visually by hourly and 30 second image records of the glacier terminus. Cameras are located at 500m from the terminus on bedrock and at ~2km from the terminus at the USFS Mendenhall Glacier Visitor Center roof. Ice berg motions and their changing positions in Mendenhall Lake can be used to create a gyre model for lake circulation. Summer 2009 lake water column temperature profiles collected at 15 minute intervals can also be linked with met station data, and USGS discharge data for the Mendenhall River to identify subglacial meltwater discharge events into the lake. We present here a synthetic view of these sensor data to evaluate what can be inferred and what remains mysterious concerning Mendenhall Glacier recession. Webcam photo Mendenhall Glacier Terminus 01-Sept-2009 10:02 am http://seamonster.jun.alaska.edu/webcam/Mendterm

Connor, C. L.; Fatland, D. R.; Heavner, M.; Korzen, N.; Galbraith, J.; Sauer, D.; Hood, E. W.

2009-12-01

44

Glaciers and Glaciation  

NSDL National Science Digital Library

This site contains lecture notes to accompany one chapter/lecture of a physical geology course using the text, The Dynamic Earth: An Introduction to Physical Geology, 4th Edition, by Brian J. Skinner and Stephen C. Porter. Subtopics include glaciers, glacial deposits, glacial features, glaciation, and glacial ages.

Nelson, Stephen

45

Changing Planet: Melting Glaciers  

NSDL National Science Digital Library

This NBC Learn video features climate scientists doing their research on Mt. Kilimanjaro to study the climate of the past. The scientists put the recently observed changes on the glacier into perspective by comparing past climate fluctuations, stressing that the current observed rate of change is unprecedented.

Planet, Nbc L.; Universe, Windows T.

46

Melting Glaciers Threaten Peru  

NSDL National Science Digital Library

Thousands of people in the Andes mountains of Peru are having their lives affected in both a practical and cultural way by climate change, which is causing the region's glaciers to melt. This document explores the causes of the glacial melt and its impacts on the local cultures.

2003-10-09

47

Gifts of the Glaciers  

NSDL National Science Digital Library

This website highlights the glacial formation of the Great Lakes: - Lake Superior, Lake Huron, Lake Michigan, Lake Erie and Lake Ontario. This site provides photos and descriptions of the lakes and how they formed by the glaciers thousands of years ago.

Wittman, Stephen

1998-04-01

48

Columbia Glacier in 1984: disintegration underway  

Microsoft Academic Search

Columbia Glacier is a large, iceberg-calving glacier near Valdez, Alaska. The terminus of this glacier was relatively stable from the time of the first scientific studies in 1899 until 1978. During this period the glacier terminated partly on Heather Island and partly on a submerged moraine shoal. In December, 1978, the glacier terminus retreated from Heather Island, and retreat has

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

1985-01-01

49

The Natural Variability of Glaciers  

NASA Astrophysics Data System (ADS)

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.

Roe, G.

2012-04-01

50

Characteristics of Glacier Ecosystem and Glaciological Importance of Glacier Microorganisms  

NASA Astrophysics Data System (ADS)

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.

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

2004-12-01

51

Comparing the spatial variability of snow depth on glacierized and non- glacierized surfaces using a geostatistical approach  

NASA Astrophysics Data System (ADS)

Snow water storage is crucial for discharge generation in alpine headwater catchments. Hence, information on the snow pack and its spatial distribution and variation is of vital importance for the application of hydrological models. However, the assessment and quantification of the water equivalent stored in the snow cover is complicated due to several factors: i) wind or gravity driven relocation of snow results in heterogeneous spatial snow cover and snow depth patterns; ii) measuring snow characteristics (e.g. snow depth or snow water equivalent) and their spatial distribution is difficult in high alpine catchments and often limited to few point measurements only. Remote sensing can provide area-wide information on snow, but often the spatial resolution is too coarse and the temporal coverage is too low. Furthermore, sensors like MODIS or Landsat provide information on snow cover distribution only, but not on snow depth which is highly relevant for hydrological applications. Airborne Laser Scan (ALS) data can bridge this lack of information as there precise information on both distribution and depth of the snow cover is provided. In this paper, we analyse the spatial distribution of snow depth using data from ALS flights in the glacierized parts of the Oetztal Alps, Austria. Snow depth is calculated from consecutive ALS flights at the beginning and the end of the snow accumulation period. The analysis of the spatial distribution of snow depth on both glacierized and non-glacierized surfaces is based on a geostatistical approach. From ALS snow depth data, six subsets (350 m x 350 m, 1 m raster width) were selected for the analysis: two subsets from Hintereisferner glacier, two subsets from Kesselwandferner glacier, and two subsets from adjacent, non- glacierized areas. In order to avoid biased results, the subsets from glacierized surfaces were chosen on areas without crevasses. The variability of snow depth is analysed with respect to surface properties (i.e. glacierized or non-glacierized) and the direction of highest variability (e.g. resulting from wind drift). The variogram analyses indicate that spatial variability of snow depth is much lower on the glacierized areas than on the non- glacierized areas, which is due to the smooth surface of the glacierized areas and the distance from obstacles (e.g. huge boulders) influencing the wind field. However, even on glacierized surfaces the spatial variability of snow depth can vary substantially The high variability of snow depth (and hence snow water equivalent) on non-glacierized surfaces has to be taken into account when interpreting remote sensing snow data which does not include snow depth information, like MODIS or Landsat products. Assuming a homogenous snow depth will bias the estimated snow water equivalent and in consequence result in huge uncertainties with respect to runoff predictions.

Schneider, K.; Schöber, J.; Stötter, J.

2012-04-01

52

2008 Wind Energy Projects, Wind Powering America (Poster)  

SciTech Connect

The Wind Powering America program produces a poster at the end of every calendar year that depicts new U.S. wind energy projects. The 2008 poster includes the following projects: Stetson Wind Farm in Maine; Dutch Hill Wind Farm in New York; Grand Ridge Wind Energy Center in Illinois; Hooper Bay, Alaska; Forestburg, South Dakota; Elbow Creek Wind Project in Texas; Glacier Wind Farm in Montana; Wray, Colorado; Smoky Hills Wind Farm in Kansas; Forbes Park Wind Project in Massachusetts; Spanish Fork, Utah; Goodland Wind Farm in Indiana; and the Tatanka Wind Energy Project on the border of North Dakota and South Dakota.

Not Available

2009-01-01

53

Wind  

NSDL National Science Digital Library

This document examine wind power as an energy resource. The reading will define wind and discuss topics such as (1) The history of wind machines, (2) Today's windmills, and (3) Types of wind machines. This resource is structured as an informational handout to supplement your energy activities or to generate discussion questions. Copyright 2005 International Technology Education Association

National Energy Education Development (NEED) Project

2003-01-01

54

Glaciers and Glaciation  

NASA Astrophysics Data System (ADS)

Scientific interest in glaciers and glaciation dates back at least 200 years, but the knowledge explosion of the past 20 years has been truly breathtaking. Milutin Milankovitch's once unpopular belief that periodic variations of Earth's orbit regulate the timing of the glacial cycle is now embraced as mainstream orthodoxy. The detailed record of Ice Age climate preserved within the Greenland and Antarctic ice sheets is slowly being decoded and completely upsets the comfortable assumption that extreme climate change necessarily proceeds at a slow pace. Hoary discussion of the processes of glacial erosion and sedimentation has been replaced by serious attempts to observe the mechanical and hydrological processes active beneath mountain glaciers and polar ice streams.

Clarke, Garry K. C.

55

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 ...

56

Mass balance model parameter transferability on a tropical glacier  

NASA Astrophysics Data System (ADS)

The mass balance and melt water production of glaciers is of particular interest in the Peruvian Andes where glacier melt water has markedly increased water supply during the pronounced dry seasons in recent decades. However, the melt water contribution from glaciers is projected to decrease with appreciable negative impacts on the local society within the coming decades. Understanding mass balance processes on tropical glaciers is a prerequisite for modeling present and future glacier runoff. As a first step towards this aim we applied a process-based surface mass balance model in order to calculate observed ablation at two stakes in the ablation zone of Shallap Glacier (4800 m a.s.l., 9°S) in the Cordillera Blanca, Peru. Under the tropical climate, the snow line migrates very frequently across most of the ablation zone all year round causing large temporal and spatial variations of glacier surface conditions and related ablation. Consequently, pronounced differences between the two chosen stakes and the two years were observed. Hourly records of temperature, humidity, wind speed, short wave incoming radiation, and precipitation are available from an automatic weather station (AWS) on the moraine near the glacier for the hydrological years 2006/07 and 2007/08 while stake readings are available at intervals of between 14 to 64 days. To optimize model parameters, we used 1000 model simulations in which the most sensitive model parameters were varied randomly within their physically meaningful ranges. The modeled surface height change was evaluated against the two stake locations in the lower ablation zone (SH11, 4760m) and in the upper ablation zone (SH22, 4816m), respectively. The optimal parameter set for each point achieved good model skill but if we transfer the best parameter combination from one stake site to the other stake site model errors increases significantly. The same happens if we optimize the model parameters for each year individually and transfer these combinations to the other year. We show that multi-site and multi-year analyses are crucial before extrapolating ablation modeling to larger glacier areas. So far tested surface albedo schemes and respective parameterizations can obviously not satisfyingly reproduce the dynamics of glacier surface conditions at our study site and new solutions to the problem have to be explored.

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

2013-04-01

57

Chernobyl fallout on Alpine glaciers  

SciTech Connect

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.

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

1989-01-01

58

Mass balance modelling of a debris cover glacier: the case study of Miage Glacier, Italy  

NASA Astrophysics Data System (ADS)

The growing interest in the response of glaciers to a changing climate has put large attention on the development of models of glaciers response, and mass balance models in particular, and efforts are been made to improve their accuracy and predictive skills. A key component that is receiving increasing attention is the role played by debris cover on the response of glaciers. Thin layers of debris enhance melt by increasing absorption of shortwave radiation, while thicker covers reduce melt by insulating it. This has an effect on the surface energy balance, melt rates under debris, runoff production, mass balance and ultimately glacier flow. An accurate representation of the effect of debris seems therefore important, also in view of the significant increase of the debris cover extent over glaciers associated to a warming climate. Distributed debris energy-balance (EB) models have been recently developed to account for the melt rate enhancing/reduction due to a thin/thick debris layer, respectively. Application of EB models at the glacier and regional scale however is associated with an increase of computational efforts and large uncertainties related to the spatial changes in the debris cover properties (thickness and conductivity) as well as extrapolation of the input meteorological data such as wind, temperature and radiative fluxes. In this paper we present a model for simulations of past and future mass balance of debris covered glaciers that relies on more limited input data than required by a full EB model. The model is tested against simulations from an EB model. The new debris enhanced temperature-index model (DETI) accounts for the debris thickness feedback (Ostrem curve) through a parameterisation that includes variable debris thickness. The model is developed and then used for continuous simulations on the extensively debris-covered Miage Glacier, Italy. First, we run the distributed debris energy balance model for the ablation season 2005, when all the meteorological variables required as input to the physically based approach are available. To evaluate the performance of the empirical approach, we then compare the energy balance model outputs against the simulations of the new DETI model. The model outputs are also validated against ablation stake readings at 22 locations. Second, the empirical approach is run for the period 2005-2011 and continuous time series of glacier mass balance are compared to those obtained with the same empirical approach with simple reduction coefficients. Accumulation is modelled by spatially distributing precipitation with a gradient and accounting for redistribution of snow by gravity. Our main result is that an empirical approach accounting for the warming/insulating effect as a function of the debris thickness, as the DETI model, is able to simulate the glacier melt rate similarly to the more complex energy-balance model. We also show a clear difference with respect to the model with simple reduction parameters that does not take into account the variable effect of debris thickness.

Carenzo, Marco; Pellicciotti, Francesca; Mabillard, Johan; Reid, Tim; Brock, Ben; Burlando, Paolo

2013-04-01

59

Pine Island Glacier Calving (WMS)  

NSDL National Science Digital Library

The Pine Island Glacier is the largest discharger of ice in Antarctica and the continents fastest moving glacier. Even so, when a large crack formed across the glacier in mid 2000, it was surprising how fast the crack expanded, 15 meters per day, and how soon the resulting iceberg broke off, mid-November, 2001. This iceberg, called B-21, is 42 kilometers by 17 kilometers and contains seven years of glacier outflow released to the sea in a single event. This series of images from the MISR instrument on the Terra satellite not only shows the crack expanding and the iceberg breakoff, but the seaward moving glacial flow in the parts of the Pine Island Glacier upstream of the crack.

Perkins, Lori; Mitchell, Horace; Bindschadler, Bob; Diner, Dave

2005-03-09

60

Water, Ice, and Meteorological Measurements at Xiao Dongkemadi Glacier, Central Tibetan Plateau, Balance Years from 2008 to 2011  

NASA Astrophysics Data System (ADS)

The glaciers on Tibetan Plateau play an important role in the catchment hydrology and climatology of this region. However, our knowledge with respect to water circulation in this remote area is scarce. Xiao Dongkemadi Glacier (XDG) is located near Tanggula Pass (the highest point on the Lanzhou-Lhasa road 5231ma.s.l.), central Tibetan Plateau (33°04'N, 92°04'E). Here, glacier mass balance and runoff directly reflects the glacier's response to local climate change, and glacier changes on the Tibetan Plateau strongly influence human welfare since water supplies in this arid/semi-arid region are predominantly from glacier melt. Due to its remote location, the mass balance of XDG has been monitored discontinuously since 1988 by the direct glaciological method. Recently, a more complete and fine-grained glacier monitoring system has been established on the cap of XDG, and is expected to make further contributions to research on the change of the cryospheric and climatic environment in the area. Winter snow accumulation and summer snow and ice ablation were measured at XDG, to estimate glacier mass-balance quantities for balance years from 2008 to 2011. Runoff from the basin containing the glacier and from an adjacent nonglacierized basin was gaged during all or parts of water years from 2008 and 2011. Air temperature, wind speed, precipitation, and incoming solar radiation were measured at selected locations on and near the glacier.

Xiaobo, He; Baisheng, Ye; Yongjian, Ding; Jian, Zhang

2013-04-01

61

Explaining Glaciers, Accurately  

NSDL National Science Digital Library

What happens when a geology graduate student and two fourth-grade teachers collaborate on lessons for the classroom? They discover interesting and practical ways to explore geology and other scientific concepts, that's what! Here they share the glacial erosion lessons that grew out of the geologist's frustration at finding glacial erosion labs erroneously showing glaciers eroding by pushing rocks. Their goal was to find a way to show and explain glacial erosion more accurately and in a way that elementary age students could understand.

Tate, Mari; Faw, Mary; Scott, Nancy

2009-04-01

62

Canadian Glacier Hydrology, 2003-2007  

Microsoft Academic Search

Glacier hydrological research in Canada from 2002-2007 continues to advance, driven by new observations of glacier retreat in all regions of the country. New observation networks have been formed to study various aspects of glacier change and linkages with the hydrological system. Small- scale studies of accumulation and melt processes on glacier surfaces continue, and are being used to parameterize

Sarah Boon; Gwenn E. Flowers; D. Scott Munro

2009-01-01

63

Polythermal Glacier Hydrology: A Review  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

64

Widespread evidences of hoarfrost formation at a rock glacier in the Seckauer Tauern, Austria  

NASA Astrophysics Data System (ADS)

The mechanism of deep reversible air circulation (the so called "chimney effect" or "wind tube") is known to be a process of ground overcooling in the lower and deeper parts of porous sediments and related landforms such as scree slopes or intact and relict rock glaciers. Warm air outflow emerging from relatively small voids within these mostly coarse-grained sediment bodies is sometimes noticeable. However, easier to identify are associated phenomena such as snowmelt windows, snow cover depressions and hoarfrost formations. Generally, these indications for warm air outflow are found at the upper part of scree slopes or the rooting zone of rock glaciers. Here we present widespread field evidences of hoarfrost from the pseudo-relict Schöneben Rock Glacier in the Seckauer Tauern Range, Austria located at E14°40'26'' and N47°22'31''. Herewith, a pseudo-relict rock glacier is defined as an intermediate rock glacier type between a relict and a climatic-inactive rock glacier, hence a relict rock glacier with locally isolated patches of permafrost. The rock glacier covers an area of about 0.11km2, ranges from ca. 1720 to 1905 m a.s.l., and consists predominantly of coarse-grained gneissic sediments with blocks up to a size of several cubic metres at the surface. In particular the lower part and some ridges in the central and upper part are covered by dwarf pines (pinus mugo) mirroring the flow structure of the previously active rock glacier. Isolated permafrost occurs presumably at the rooting zone of the rock glacier as indicated by evidences from a neighbouring rock glacier in a comparable setting. Field observations in November 2011 showed widespread occurrences of hoarfrost crystals growing around the funnel edge indicating the sublimation of vapour from warm funnels. Such hoarfrost sites were found at more than 50 single locations distributed over the entire rock glacier from the tongue to the rooting zone generally. The occurrence of hoarfrost can get classified into the following classes: (a) at foot slope positions, (b) along linear structures or depressions of the rock glacier, (c) below vegetation patches of dwarf pines, (d) at the interface between younger fine-grained sediments (derived from debris flows) and the coarse-grained former rock glacier surface, and finally (e) hoarfrost occurrence at the rock glacier body without any identifiable structure in the vicinity. Examples from these different hoarfrost classes are presented and discussed.

Kellerer-Pirklbauer, A.; Winkler, G.; Pauritsch, M.

2012-04-01

65

Remote sensing of glaciers and ice sheets  

NASA Astrophysics Data System (ADS)

This chapter summarizes research on satellite remote sensing of glaciers and ice sheets. It covers a number of topics, including studies of the equilibrium line; characteristic glacier surface zones or glacier facies; glacier velocity; glacier mapping; change detection; surface features; and snow pack characteristics. Finally, we briefly outline new opportunities for northern hydrology with the utilization of recent and planned spaceborne sensors such as MODIS, ENVISAT MERIS and ASAR, ICESat, and CryoSat.

Winther, Jan-Gunnar; Bindschadler, Robert; König, Max; Scherer, Dieter

66

Middle Sister and Hayden Glacier  

USGS Multimedia Gallery

The North face of Middle Sister and Hayden Glacier, in Three Sisters Wilderness, Deschutes National Forest, Oregon. This Picture was taken while climbing Middle Sister. Middle Sister is also known as "Hope" and is an extinct stratovolcano....

2009-12-08

67

Glacier Sensitivity Across the Andes  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

68

Ancient carbon from a melting glacier gives high (14)C age in living pioneer invertebrates.  

PubMed

Glaciers are retreating and predatory invertebrates rapidly colonize deglaciated, barren ground. The paradox of establishing predators before plants and herbivores has been explained by wind-driven input of invertebrate prey. Here we present an alternative explanation and a novel glacier foreland food web by showing that pioneer predators eat locally produced midges containing 21,000 years old ancient carbon released by the melting glacier. Ancient carbon was assimilated by aquatic midge larvae, and terrestrial adults achieved a radiocarbon age of 1040 years. Terrestrial spiders, harvestmen and beetles feeding on adult midges had radiocarbon ages of 340-1100 years. Water beetles assumed to eat midge larvae reached radiocarbon ages of 1100-1200 years. Because both aquatic and terrestrial pioneer communities use ancient carbon, the term "primary succession" is questionable in glacier forelands. If our "old" invertebrates had been collected as subfossils and radiocarbon dated, their age would have been overestimated by up to 1100 years. PMID:24084623

Hågvar, Sigmund; Ohlson, Mikael

2013-10-02

69

Ancient carbon from a melting glacier gives high 14C age in living pioneer invertebrates  

PubMed Central

Glaciers are retreating and predatory invertebrates rapidly colonize deglaciated, barren ground. The paradox of establishing predators before plants and herbivores has been explained by wind-driven input of invertebrate prey. Here we present an alternative explanation and a novel glacier foreland food web by showing that pioneer predators eat locally produced midges containing 21,000 years old ancient carbon released by the melting glacier. Ancient carbon was assimilated by aquatic midge larvae, and terrestrial adults achieved a radiocarbon age of 1040 years. Terrestrial spiders, harvestmen and beetles feeding on adult midges had radiocarbon ages of 340–1100 years. Water beetles assumed to eat midge larvae reached radiocarbon ages of 1100–1200 years. Because both aquatic and terrestrial pioneer communities use ancient carbon, the term “primary succession” is questionable in glacier forelands. If our “old” invertebrates had been collected as subfossils and radiocarbon dated, their age would have been overestimated by up to 1100 years.

Hagvar, Sigmund; Ohlson, Mikael

2013-01-01

70

Glacier discharge and climate variations  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

71

Borehole video analysis of a temperate glacier' englacial and subglacial structure: Implications for glacier flow models  

Microsoft Academic Search

Video observations made in 16 boreholes drilled through a deforming valley glacier affirm that temperate glacier ice may be reasonably well represented as homogeneous in glacier flow models, but raise warnings about the complexities of basal boundary conditions and glacier sliding. Discrete englacial structures, including clear-ice layers, voids, and water conduits, compose a total of <3% of the ice mass.

Joel T. Harper; Neil F. Humphrey

1995-01-01

72

Reconstructing deglaciation of Kolahoi glacier, western Himalaya and validation through field observations  

NASA Astrophysics Data System (ADS)

Kolahoi glacier, western Himalaya is located in Jammu and Kashmir, India between N 340 07'-340 12' and E 750 19'-750 23'. The glacier makes the head of Liddar valley and provides origin to west Liddar river, draining into river Jhelum. Kolahoi is characterized by the frontal activities of westerly winds from Dec to March-April and by dry subtropical climate during summer season. The glacier represents a twin glacier system with one branch from two sides of Kolahoi peak-east and west, merging together to form a common ablation zone and a north facing snout. The first recorded visit to Kolahoi Glacier was made by E. F. Neve in 1909. The earliest attempt to establish the quaternary glacial history of Liddar valley can be attributed to Grinlinton (1928) followed by Terra & Patterson (1939). As a result of their work, the quaternary glaciation of Liddar valley has been divided into a main series of four glacial and three interglacial epochs, of which the first two glaciations were more intensive than the later two. A significant result of this history has been that as compared with the interglacial periods the glacial periods were much shorter, in SW Kashmir. Presence of various glacial features of fourth stage, observed in the valley were correlated with the literature, coordinates taken through GPS and built on a GIS platform with overlyering of satellite image time series of recent decades. Decadal history of Kolahoi glacier deglaciation was reconstructed based on the satellite image time series, indirect volume-area scaling methods and field experiments, indicating variable retreat rate contributing to a total recession of 485m in the snout of glacier and an area loss of 15% in previous four decades, since 1965. Annual measurement of mass balance for Kolahoi glacier were conducted through glaciologic method since the first drilling of ablation stakes in 2008, which indicate a range from -2.0 m.w.e. to -3.5 m.w.e. per annum for the glacier. However, field observance of huge rock masses (height ~35m) getting exposed from the interior of glacier, and presence of a secondary snout at the west branch of Kolahoi glacier, indicate a greater degree of mass wasting and detachment of two glacier branches, than the inferences drawn through imageries and indirect assessment methods. Kolahoi being located close to famous religious spot, Amarnath, visited by >300,000 pilgrims during a single month of summer season, the probability of glacier experiencing the coupled vulnerability of climate change forcers along with local anthropogenic influences need to be examined in detail.

Tayal, S.

2011-12-01

73

Significant total mass contained in small glaciers  

NASA Astrophysics Data System (ADS)

A single large glacier can contain hundreds of millions of times the mass of a small glacier. Nevertheless, small glaciers are so numerous that their contribution to the world's total ice volume is significant and may be a notable source of error if excluded. With current glacier inventories, total volume errors on the order of 10 % are possible at both global and regional scales. However, errors of less than 1 % require glaciers that are smaller than those available in some inventories. Such accuracy requires a global list of all glaciers and ice caps (GIC) as small as 1 km2, and for regional estimates requires substantially smaller sizes. For some regions, volume errors of less than 5 % require a complete list of all glaciers down to the smallest conceivable sizes. For this reason, sea-level rise estimates and other total mass and total volume analyses cannot ignore the world's smallest glaciers without careful justification.

Bahr, D. B.; Radi?, V.

2012-02-01

74

Rock glaciers of the Karakoram Himalaya and surrounding mountains, Inner Asia  

NASA Astrophysics Data System (ADS)

The transHimalayan upper Indus Basin contains thousands of rock glaciers. An exceptional diversity of forms and sizes exist, hitherto largely unresearched. They are in a well-defined elevation band across the mountains, usually less than 1400 m vertically, although total relief exceeds 7000 m. The zone varies from north to south, west to east, and with slope orientation. Interfluve elevations are primary constraints. Rock glaciers are absent below the lowest and the highest interfluves. They are uncommon in the highest Mustagh Karakoram, Nanga Parbat, and Hindu Kush where glacier ice blankets the elevations where they could develop. The heaviest concentrations occur in sub-ranges of intermediate elevation. A full spectrum of generative conditions is found; related to periglacial, talus, glacial, avalanche, wind-blown snow, and rock avalanche processes. Forms vary between north and south slopes; arid, rainshadowed and more snowy, humid valleys. Rock glacier complexes, where two or more join to create extensive lobes, may have tributaries with different source conditions. The larger examples are several kilometres in length,usually glacier-derived, evidently affected by Holocene glacial history, trans-glacial processes, and paraglacial instabilities. In lesser ranges, many smaller rock glaciers are associated with glacier-free cirques, glacially sculpted valley walls, and floors with abundant glacial deposits. In general, they are transitional in genesis, process, and spatially relative to glacierization, to the vertical cascade of moisture and debris, and climate change in the vertical. Their landscape roles include extensive fragmentation of drainage systems. Countless inactive rock glaciers occur, typically continuing below active ones.

Hewitt, Kenneth

2013-04-01

75

Get Close to Glaciers with Satellite Imagery.  

ERIC Educational Resources Information Center

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)

Hall, Dorothy K.

1986-01-01

76

Survey of glaciers in the northern Rocky Mountains of Montana and Wyoming; Size response to climatic fluctuations 1950-1996  

SciTech Connect

An aerial survey of Northern Rocky Mountain glaciers in Montana and Wyoming was conducted in late summer of 1996. The Flathead, Swan, Mission, and Beartooth Mountains of Montana were covered, as well as the Teton and Wind River Ranges of Wyoming. Present extent of glaciers in this study were compared to limits on recent USGS 15 and 7.5 topographic maps, and also from selected personal photos. Large cirque and hanging glaciers of the Flathead and Wind River Ranges did not display significant decrease in size or change in terminus position. Cirque glaciers in the Swan, Mission, Beartooth and Teton Ranges were markedly smaller in size; with separation of the ice body, growth of the terminus lake, or cover of the ice terminus with rockfalls. A study of annual snowfall, snowdepths, precipitation, and mean temperatures for selected stations in the Northern Rocky Mountains indicates no extreme variations in temperature or precipitation between 1950-1996, but several years of low snowfall and warmer temperatures in the 1980`s appear to have been sufficient to diminish many of the smaller cirque glaciers, many to the point of extinction. The disappearance of small cirque glaciers may indicate a greater sensitivity to overall climatic warming than the more dramatic fluctuations of larger glaciers in the same region.

Chatelain, E.E. [Valdosta State Univ., GA (United States)

1997-09-01

77

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

Microsoft Academic Search

Popocatépetl volcano is located 60 km southeast of Mexico City and is one of the three ice-clad volcanoes in Mexico. The two glaciers of Popocatépetl became extinct after a strong retreat due to the combination of at least three causes: global change, change in regional meteorological conditions (induced by the vicinity to highly polluted areas) and local enforcement (namely volcanic

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

2003-01-01

78

Influence of the orographic roughness of glacier valleys across the Transantarctic Mountains in an atmospheric regional model  

Microsoft Academic Search

Glacier valleys across the Transantarctic Mountains are not properly taken into account in climate models, because of their\\u000a coarse resolution. Nonetheless, glacier valleys control katabatic winds in this region, and the latter are thought to affect\\u000a the climate of the Ross Sea sector, frsater formation to snow mass balance. The purpose of this paper is to investigate the\\u000a role of

Nicolas C. Jourdain; Hubert Gallée

2011-01-01

79

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

NASA Astrophysics Data System (ADS)

Antarctic Peninsula is one of the regions, which have been exposed to the most rapid warming of the Earth since 1950. Consequences of climate changes are clearly documented by recent disintegration of ice shelves on both sides of the Antarctic Peninsula as well as by the retreat of land-based glaciers. James Ross Island, located close to the northernmost tip of the Antarctic Peninsula, represents an excellent place to study changes in the glacier mass-balance and their sensitivity to a regional warming trend. Two different types of glaciers of the Ulu Peninsula, the Whisky Glacier and the Davies Dome have been studied. Multi-temporal remote sensing data (aerial photographs, Landsat MSS, TM and ETM+ and Aster satellite optical and thermal multispectral data) and field survey allowed detecting changes in extent (2-D) as well as calculating glacier mass-balance changes (3-D) for these two glaciers from 1977 to 2009. The Whisky Glacier is a well-delimited valley glacier located mostly below the local Equilibrium line altitude (ELA). The glacier with high-flow velocities is fed by an intensive snow accumulation caused by prevailing southwestern winds. The Whisky Glacier covers an area of 2.3 km2 and its altitude varies from 215 to 475 m a.s.l. The Davies Dome is a flat-bottom dome glacier. Significant parts of its surface are located above the ELA and limited flow velocities are characteristic for the most parts of its body. However, the Davies Dome has a single 500-700 m wide southwestern outlet flowing towards the Whisky Bay. The Davies Dome extends an area of 6.7 km2 and its altitude ranges from 0 to 514 m a.s.l. Both glaciers experienced massive extension of their ice tongues towards the Brandy Bay during the mid Holocene. Lateral moraines located in front of the both glaciers heading down to the left coast of the Brandy Bay document this event. According to the remote sensing data and field investigations both glaciers have retreated since 1977. Between 2006 and 2009 repeated mapping of the Davies Dome was carried out and the results showed that the largest retreat ranging from 10 to 20 m occurred in the NW flat part of the glacier. Digital elevation models calculated on bases of aerial stereo-photographs from 1979 and 2006 allowed us to define mass-balance changes of the studied glaciers. Ground Penetrating Radar measurements taken on both glaciers helped with mass-balance investigations, furthermore, made it possible to increase the accuracy of the 3-D models. Annual mass balance measurements on the Davies Dome indicated a mean ablation about 20 cm between 2006 and 2009. On the Whisky Glacier, a network of 20 ablation stakes was established just recently (February 2009). Therefore, another 3-year investigation is necessary to bring comparable results. Acknowledgments: This research has been undertaken within a framework of the project No. 205/09/1876 funded by the Czech Science Foundation and by the R & D project VaV SP II 1a9/23/07.

Nývlt, Daniel; Kopa?ková, Veronika; Láska, Kamil; Engel, Zbyn?k.

2010-05-01

80

GLIMS Glacier Database: Status and Challenges  

NASA Astrophysics Data System (ADS)

GLIMS (Global Land Ice Measurements from Space) is an international initiative to map the world's glaciers and to build a GIS database that is usable via the World Wide Web. The GLIMS programme includes 70 institutions, and 25 Regional Centers (RCs), who analyze satellite imagery to map glaciers in their regions of expertise. The analysis results are collected at the National Snow and Ice Data Center (NSIDC) and ingested into the GLIMS Glacier Database. The database contains approximately 80 000 glacier outlines, half the estimated total on Earth. In addition, the database contains metadata on approximately 200 000 ASTER images acquired over glacierized terrain. Glacier data and the ASTER metadata can be viewed and searched via interactive maps at http://glims.org/. As glacier mapping with GLIMS has progressed, various hurdles have arisen that have required solutions. For example, the GLIMS community has formulated definitions for how to delineate glaciers with different complicated morphologies and how to deal with debris cover. Experiments have been carried out to assess the consistency of the database, and protocols have been defined for the RCs to follow in their mapping. Hurdles still remain. In June 2008, a workshop was convened in Boulder, Colorado to address issues such as mapping debris-covered glaciers, mapping ice divides, and performing change analysis using two different glacier inventories. This contribution summarizes the status of the GLIMS Glacier Database and steps taken to ensure high data quality.

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

2008-12-01

81

Mountain glacier identification from SAR images  

NASA Astrophysics Data System (ADS)

Because the terrain of mountain glacier is usually very rugged, it is hard to measure glaciers and estimated their changes in larger area by conventional measuring method. With fast development of remote sensing technique, synthetic aperture radar (SAR) interferometry is used for glacier monitoring with the ability of all-time and all-weather. Although interferometric coherence is a very good index to glacier, it is difficult to distinguish glacier area from non-glacier area when their coherence is similar. In this case, interferometric phase can play an important role to identify glacier. In this paper, phase texture analysis method is proposed to extract glacier. 8 texture features were analyzed based on co-occurrence matrix (COM), including mean, variance, homogeneity, contrast, dissimilarity, entropy, second moment, and correlation. Among them, variance, contrast and dissimilarity can distinguish glacier from non-glacier clearly most, so they are chosen for RGB combination. Then the RGB combination image is classified into several land covers by maximum likelihood classification (MLC). With post-classification processing, glacier area can be extracted accurately. Landsat TM images validate the proposed method.

Wu, Hong'an; Zhang, Yonghong; Zhong, Weifan; Sun, Guangtong

2011-11-01

82

Regional and global volumes of glaciers derived from statistical upscaling of glacier inventory data  

NASA Astrophysics Data System (ADS)

Very few global-scale ice volume estimates are available for mountain glaciers and ice caps, although such estimates are crucial for any attempts to project their contribution to sea level rise in the future. We present a statistical method for deriving regional and global ice volumes from regional glacier area distributions and volume area scaling using glacier area data from ˜123,000 glaciers from a recently extended World Glacier Inventory. We compute glacier volumes and their sea level equivalent (SLE) for 19 glacierized regions containing all mountain glaciers and ice caps on Earth. On the basis of total glacierized area of 741 × 103 ± 68 × 103 km2, we estimate a total ice volume of 241 × 103 ± 29 × 103 km3, corresponding to 0.60 ± 0.07 m SLE, of which 32% is due to glaciers in Greenland and Antarctica apart from the ice sheets. However, our estimate is sensitive to assumptions on volume area scaling coefficients and glacier area distributions in the regions that are poorly inventoried, i.e., Antarctica, North America, Greenland, and Patagonia. This emphasizes the need for more volume observations, especially of large glaciers and a more complete World Glacier Inventory in order to reduce uncertainties and to arrive at firmer volume estimates for all mountain glaciers and ice caps.

Radi?, Valentina; Hock, Regine

2010-03-01

83

The contribution of glacier melt to streamflow  

SciTech Connect

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.

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

2012-09-13

84

MOVEMENT OF WATER IN GLACIERS  

Microsoft Academic Search

A network of passages situated along three-grain intersections enables water to percolate through temperate glacier ice. The deformability of the ice allows the passages to expand and contract in response to changes in pressure, and melting of the passage walls by heat generated by viscous dissipation and carried by above-freezing water causes the larger passages gradually to increase in size

R. L. SHREVE

1972-01-01

85

Glacier Lakes Ecosystem Experiments Site.  

National Technical Information Service (NTIS)

The Glacier Lakes Ecosystem Experiment Site (GLEES), a 600 ha research watershed at 3200-3400 m elevation in the Snowy Range of SE Wyoming, has been established to examine the effects of atmospheric deposition on alpine and subalpine ecosystems. This docu...

R. C. Musselman

1994-01-01

86

Jakobshavn Glacier Ice Flow (WMS)  

NSDL National Science Digital Library

Since measurements of Jakobshavn Isbrae were first taken in 1850, the glacier has gradually receded, finally coming to rest at a certain point for the past 5 decades. However, from 1997 to 2003, the glacier has begun to recede again, this time almost doubling in speed. The finding is important for many reasons. For starters, as more ice moves from glaciers on land into the ocean, it raises sea levels. Jakobshavn Isbrae is Greenlands largest outlet glacier, draining 6.5 percent of Greenlands ice sheet area. The ice streams speed-up and near-doubling of ice flow from land into the ocean has increased the rate of sea level rise by about .06 millimeters (about .002 inches) per year, or roughly 4 percent of the 20th century rate of sea level increase. This animation shows a time-lapse sequence of the ice flowing toward the ocean. In recent years, even ice that has traditionally remained in place is now being pulled down to the edge of land.

Sokolowsky, Eric; Kekesi, Alex; Abdalati, Waleed

2005-03-30

87

Microbial Habitat on Kilimanjaro's Glaciers  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

88

Application Of Pollen Analysis For Seasonal Dating Of Alpine Glacier Ice Cores With Seasonal Missing Layers  

Microsoft Academic Search

Ice core studies from middle and low latitude glaciers have a problem that a reliable dating method has proved difficult due to wind erosion and vanishingly small amount of seasonal precipitation. They obscure the annual signal from the seasonal variations in chemical concentrations and oxygen isotope ratios that are typically used to date for ice cores. On the other hand,

F. Nakazawa; K. Fujita; N. Takeuchi; T. Fujiki; J. Uetake; V. Aizen; M. Nakawo

2004-01-01

89

Lithologic, Structural, and Topographic Influences on Snow-Avalanche Path Location, Eastern Glacier National Park, Montana  

Microsoft Academic Search

We examine the roles of lithology, structure, and topography as determinants of the location and morphology of snow-avalanche paths in east-central Glacier National Park, Montana. Most models of avalanche path location emphsize topographic interactions with prevailing winds and ignore the role of geologic influences. Landsat Thematic Mapper digital data, covering the study area, were enhanced through a combination of directional

David R. Butler; Stephen J. Walsh

1990-01-01

90

Impacts of debris cover on glaciers: research priorities and relation to glacier-climate interactions on clean-ice glaciers.  

NASA Astrophysics Data System (ADS)

Debris covered glaciers are a common feature in many high mountain environments. The presence of surficial debris fundamentally alters a number of glacier processes, and consequently the manner in which glaciers respond to climate. Incomplete understanding of these altered processes hampers (a) the use of records of glacier change as a means of unraveling former climate conditions, (b) the production of glacier runoff projections and (c) development of high quality hazard assessments of the future development of debris covered glaciers and associated ice dammed lakes. This presentation summarizes four key ways in which debris cover alters the behaviour of glaciers in ways that are relevant to solving both scientific and more practical problems: (1) surface energy balance and sensitivity to climate (2) ablation gradient of debris covered glaciers and their long profile evolution under changing climate conditions (3) differential ablation and the development of supraglacial ponds (4) sedimentary record of moraine deposition and impacts of this on climatic reconstruction and long term moraine stability The presentation concludes by outlining priority list of research required specifically on debris covered glaciers and how this could be integrated within research programs assessing the response of clean ice glaciers to ongoing climate change.

Nicholson, L. I.

2012-04-01

91

A theory of glacier surges  

NASA Astrophysics Data System (ADS)

We propose a model of glacier flow that is capable of explaining temperate glacier surges. The laws of conservation of mass and momentum are supplemented by the prescription of a sliding law that gives the basal shear stress ? as a function of the basal velocity u and the effective pressure N. The effective drainage pressure N is determined by a simple study of the subglacial hydraulic system. Following Röthlisberger, we determine N = NR for the case of drainage through a single subglacial tunnel. Alternatively, following Kamb, we find that the corresponding theory for a linked-cavity drainage system yields N = NK < NR. Furthermore, the stability of each drainage system depends on the velocity u, such that for large enough u, there is a transition from tunnel to cavity drainage. Consequently, one can write N = N(u). We then find that the sliding law ? = ?(u) is multivalued, and hence so also is the flux/depth relation Q = Q(H). An analysis of the resulting system of equations is sketched. For large enough accumulation rates, a glacier will undergo regular relaxation oscillations, resembling a surge. The surge is triggered at the point of maximum stress; from this point two hydraulic transition fronts travel up and down glacier to calculable boundary points. The speed of propagation is the order of 50 metres an hour. At these fronts, the tunnel drainage system collapses, and a high water pressure cavity drainage system is installed. This activated zone has high velocities and quickly relaxes (surges) to a quasi-equilibrium state. This relaxation is much like opening a sluice gate, in that a large wave front propagates forward. Behind this wave front, the velocity can decay oscillatorily, and thus the flow can be compressive. We conclude with some discussion of the effects of seasonal variation and of prospects for the current theory's applicability to soft-bedded glaciers.

Fowler, A. C.

1987-08-01

92

Calendar-dated, early 'Little Ice Age' glacier advance at Robson Glacier, British Columbia, Canada  

Microsoft Academic Search

Dendrochronological studies at Robson and Bennington Glaciers have provided the first calendar dating of an early 'Little Ice Age' glacier advance in North America. Dates derived from in-situ stumps indicate that Robson Glacier began over-riding forest between c. AD 1142 and 1150 and continued until at least AD 1350. The highest rates of glacier advance (c. 3.8 m yr-1 )

B. H. Luckman

1995-01-01

93

Glacier Surge Mechanism: 1982-1983 Surge of Variegated Glacier, Alaska  

Microsoft Academic Search

The hundredfold speedup in glacier motion in a surge of the kind that took place in Variegated Glacier in 1982-1983 is caused by the buildup of high water pressure in the basal passageway system, which is made possible by a fundamental and pervasive change in the geometry and water-transport characteristics of this system. The behavior of the glacier in surge

Barclay Kamb; C. F. Raymond; W. D. Harrison; Hermann Engelhardt; K. A. Echelmeyer; N. Humphrey; M. M. Brugman; T. Pfeffer

1985-01-01

94

GLACIER VIEW ROADLESS AREA, WASHINGTON.  

USGS Publications Warehouse

Surveys indicate little promise for the occurrence of metallic mineral resources in the Glacier View Roadless Area, Washington. Small, thin lenses of coal may be present at depth near the western edge of the area, but larger coal deposits occur at or near the surface outside the roadless area. Oil and gas may be in the subsurface, but the evaluation of the potential requires additional information obtainable only by drilling.

Evarts, Russell, C.; Barnes, Donald, J.

1984-01-01

95

Changes with elevation in the energy balance of an Andean Glacier, Juncal Norte Glacier, dry andes of central Chile  

NASA Astrophysics Data System (ADS)

The energy balance of snow and ice surfaces in the dry Andes of Chile is dominated by solar radiation. Sublimation is important at high elevations and radiative cooling at night is favoured by the absence of clouds. Because of the scarcity of data in the region, the interaction between glaciers and atmosphere, and the related processes of energy exchange, has been studied only partially, despite the fact that they control melt and runoff generation. We intend to explore the variations in the interaction between climate and surface snow and ice associated with elevation, as a premise to distributed modelling of glacier ablation in the region. Two Automatic Weather Stations (AWSs) were setup on Juncal Norte Glacier, central Chile, for a 3-month period from December 2008 to February 2009. The two locations are at 300 m difference in elevation, and differ also in terms of fetch available for the development of the katabatic wind. The surface energy balance is studied with an energy balance model including the subsurface heat conduction flux. Computations are driven by measurements of incoming and reflected shortwave radiation, wind speed and atmospheric temperature and humidity. The glacier surface temperature is simulated and used for computation of the longwave radiation and turbulent fluxes. These are simulated using the bulk aerodynamic method. We analyse meteorological forcing and the components of the energy balance and resulting ablation at the two stations. These show a very pronounced diurnal cycle, reflecting in the strong diurnal variability of runoff, mainly controlled by shortwave radiation. Net shortwave radiation and sensible heat fluxes are positive over the season, while net longwave radiation and latent heat fluxes are on average negative. We show that differential melt at the two AWSs sites (almost 10 mm w.e. per day on average) is caused by differences in albedo, resulting in a lower shortwave radiation flux at the uppermost station, and by differences in the sensible heat flux, associated with both lower air temperature and wind regime. Katabatic wind is evident at both stations, and together with air temperature governs the turbulent heat exchange. The heat flux into the snowpack is important at both sites.

Pellicciotti, Francesca; Helbing, Jakob; Carenzo, Marco; Burlando, Paolo

2010-05-01

96

Recent changes on Greenland outlet glaciers  

NASA Astrophysics Data System (ADS)

Aircraft laser-altimeter surveys during the 1990s showed near-coastal parts of the Greenland ice sheet to be thinning; despite slow thickening at higher elevations, the ice sheet lost mass to the ocean. Many outlet glaciers thinned more rapidly than could be explained by increased melting during the recent warmer summers, indicating dynamic imbalance between glacier velocity and upstream snow accumulation. Results from more recent surveys, presented here, show that thinning rates have increased in most coastal regions. For almost half of the surveys, these increases might have resulted from increases in summer melting, but rapid thinning on others is indicative of dynamic changes that increased with time. In particular, thinning rates on the three fastest glaciers increased to tens of m a-1 after 2000, and other observations show an approximate doubling in their velocities. The deep beds of these glaciers appear to have a strong influence on rates of grounding-line retreat and thickness change, with periods of glacier acceleration and rapid thinning initiated by flotation and break-up of lightly grounded glacier snouts or break-up of floating ice tongues. Near-simultaneous thinning of these widely separated glaciers suggests that warming of deeper ocean waters might be a common cause. Nearby glaciers without deep beds are thinning far more slowly, suggesting that basal lubrication as a result of increased surface melting has only a marginal impact on Greenland outlet-glacier acceleration

Thomas, R.; Frederick, E.; Krabill, W.; Manizade, S.; Martin, C.

97

How well do observations on bench mark glaciers represent a glacier system?  

NASA Astrophysics Data System (ADS)

The main source of uncertainty in knowledge of the global glacier regime is the limited number of direct mass balance observations. Since the spatial variability of glacier properties is huge the few benchmark glaciers chosen for continuous observations are unlikely to adequately represent the glacier system to which they belong. It is not feasible to suggest that the number of field-based observations will substantially increase in the future. Therefore, observations from space-based sensors will become more widely used to study the characteristics and status of the world's glaciers. In this paper we examine how the restricted number of mass balance observations in one well-monitored glacier system may be used to characterize the entire system, and examine the potential and limitations of monitoring glacier systems from space. We have developed a "template method" whereby mass balance measurements on a benchmark glacier can be extrapolated to estimate the mass balance of its glacier system. We test this method by applying it to the Scandinavia Glacier System (SGS), where standard and continuous mass balance observations have been carried out since the mid-20th century on several tens of glaciers. We analyze spatial variability of glacier mass balance, accumulation area ratio, ELA and hypsography for twenty benchmark glaciers in SGS to better understand the behavior of this glacier system, and connect the standard field measurement results to estimations of ELA from Landsat imagery. From this we estimate the mass balance of SGS, and predict extreme values in relation to climate change. We have found that only a few glaciers in this system may adequately represent the regime of SGS, and that those commonly believed to be representative are actually not. We quantify the uncertainty in the extrapolation.

Khalsa, S. S.; Raup, B. H.; Dyurgerov, M.

2005-12-01

98

FLUCTUATIONS OF CRILLON GLACIER SYSTEM, SOUTHEAST ALASKA  

Microsoft Academic Search

Crillon Glacier system (Lat. 58° 37? N, Long. 137° 23?w) consisting of two long feeding arms and a common T-shaped ending along the Fairweather Fault, with two cliffed termini, has been advancing. La Perouse's sketch map in 1786 suggests that North and South Crillon Glaciers were back far enough to have separate termini in Lituya Bay, so they must have

RICHARD P. GOLDTHWAIT; IAN C. Mc KELLAR; CASPAR CRONK

1963-01-01

99

Glaciers in 21st Century Himalayan Geopolitics  

Microsoft Academic Search

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.

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

2002-01-01

100

Glaciers in 21st Century Himalayan Geopolitics  

NASA Astrophysics Data System (ADS)

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.

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

2002-05-01

101

GLACIER PEAK ROADLESS AREA, WASHINGTON.  

USGS Publications Warehouse

A mineral survey outlined areas of mineral-resource potential in the Glacier Peak Roadless Area, Washington. Substantiated resource potential for base and precious metals has been identified in four mining districts included in whole or in part within the boundary of the roadless area. Several million tons of demonstrated base- and precious-metal resources occur in numerous mines in these districts. Probable resource potential for precious metals exists along a belt of fractured and locally mineralized rock extending northeast from Monte Cristo to the northeast edge of the roadless area.

Church, S. E.; Johnson, F. L.

1984-01-01

102

Modelling The Energy And Mass Balance Of A Black Glacier  

Microsoft Academic Search

A distributed energy balance hydrologic model has been implemented to simulate the melting season of the Belvedere glacier, situated in the Anza river basin (North- Western Italy) for a few years. The Belvedere Glacier is an example of SblackS glacier, ´ since the ablation zone is covered by a significant debris layer. The glacierSs termi- nus has an altitude of

G. Grossi; S. Taschner; R. Ranzi

2002-01-01

103

Black soot and the survival of Tibetan glaciers  

PubMed Central

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.

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

104

Simulation and forecast of the Tien Shan glacier's changes  

Microsoft Academic Search

Two mathematical models: glacial-covered areas\\/glacier numbers and glacial volume changes developed based on assessment of the glacier recession that occurred in a Tien Shan glacial massif for the last 60 years. According to estimations performed in the Akshiirak glacierized massif for the period from 1943 to 1977, change in mean altitude (Hm) of each individual glacier in the massif is

V. B. Aizen; V. A. Kuzmichenok; E. M. Aizen; A. B. Surazakov

2006-01-01

105

Proccedings of the Third Glacier Bay Science Symposium 1993.  

National Technical Information Service (NTIS)

The Third Glacier Bay Science Symposium was held at Glacier Bay Lodge in Glacier Bay National Park and Preserve, Alaska, on September 15-18, 1993. Like its predecessors, this meeting was jointly sponsored by the National Park Service, Friends of Glacier B...

D. R. Engstrom

1993-01-01

106

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

107

Geomicrobiology of a Supraglacial Stream on the Cotton Glacier, Victoria Land, Antarctica.  

NASA Astrophysics Data System (ADS)

The Cotton Glacier lies in the Transantarctic Mountains north of Cape Roberts and has a limited catchment area in the Clare and St. Johns ranges, but receives a large amount of sedimentary deposits from surrounding areas. The bedrock geology of the area is dominated by basement granite and Ferrar dolerite sills, with minor amounts of amphibolite and schist sandwiched between granite bodies. A unique fluvial system forms on the Cotton Glacier as a result of its location in the Transantarctic Mountains. The prevailing winds converge and deposit debris on the Cotton Glacier, warming up the surface and increasing meltwater production. During the austral summer of 2004-2005 we sampled a braided stream that flowed from mid glacier into a series of crevasses downstream. While low in dissolved organic carbon (44-47 ?M C) and nutrients the supraglacial stream on the Cotton Glacier is capable of sustaining life, with bacterial cell abundances from 2.7 - 8.2 x 104 cells ml-1, and bacterial production ranging from 58.84 - 293.18 ng C d-1. Isolates recovered from the Cotton Glacier produced a rainbow of pigment colors and were similar to those recovered from other icy systems (Cytophaga- Flavobateria-Bacteroides and ?-Proteobacteria lineages), suggesting that the occurrence of these related phylotoyes from diverse environs is due to similar survival strategies allowing them to remain active at sub- zero temperatures and survive multiple freeze-thaw events. Two isolates from the Cotton Glacier have been shown to possess ice nucleating activity. These bacteria can catalyze ice formation at -3.5°C and colder temperatures and likely possess Type I ice nuclei proteins. The fluorescence and absorbance spectra of the filtered Cotton Glacier water were analyzed to characterize the dissolved organic matter (DOM). The absorbance spectra of the Cotton Glacier sample exhibited a peak around 270 nm, which disappeared over time in the dark at 4°C. Analysis of excitation-emission matrices (EEMs) from the Cotton Glacier differed from typical DOM EEMs. The Cotton Glacier EEMs showed almost no fluorescence in the region of EEMs where peaks are normally present and have been attributed to the presence of humic and fulvic organic matter (Ex/Em 240/450 and 330/450). In contrast to most DOM EEMs, the Cotton Glacier EEMs were dominated by peaks in the amino-acid region (Ex/Em 240-270/300-350 nm). Thus, both the initial peak in absorbance at 270 nm and the EEM peaks in the amino-acid region suggest that the DOM present in this system is predominately proteinaceous material likely of microbial origin. This study demonstrates the presence of an active microbial assemblage in a supraglacial stream from a pristine Antarctic glacier. Recent discoveries over the past decade have shown that glacial ice contains an important record of microorganisms on our planet that theoretically could be used to assess biogeochemical processes and habitat types that occurred during past glacial and interglacial periods. This record may also contain information on microbial evolution and physiology, and provide new biotechnological innovations. Supraglacial streams provide an important example of contemporary microbial processes on the glacier surface.

Foreman, C. M.; Morris, C. E.; Cory, R. M.

2006-12-01

108

Quantifying global warming from the retreat of glaciers  

SciTech Connect

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.

Oerlemans, J. (Utrecht Univ. (Netherlands))

1994-04-08

109

Shrinking Alpine glaciers spell trouble for Europe's rivers  

NASA Astrophysics Data System (ADS)

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.

Schultz, Colin

2011-10-01

110

Climate Change and Glacier Retreat: Scientific Fact and Artistic Opportunity  

Microsoft Academic Search

Mountain glaciers continue to retreat rapidly over most of the globe. In North America, at Glacier National Park, Montana, recent research results from Sperry Glacier (2005-2007) indicate negative mass balances are now 3-4 times greater than in the 1950s. A geospatial model of glacier retreat in the Blackfoot-Jackson basin suggested all glaciers would be gone by 2030 but has proved

D. B. Fagre

2008-01-01

111

Glaciers in Patagonia: Controversy and prospects  

NASA Astrophysics Data System (ADS)

Lately, glaciers have been subjects of unceasing controversy. Current debate about planned hydroelectric facilities—a US$7- to $10-billion megaproject—in a pristine glacierized area of Patagonia, Chile [Romero Toledo et al., 2009; Vince, 2010], has raised anew the matter of how glaciologists and global change experts can contribute their knowledge to civic debates on important issues. There has been greater respect for science in this controversy than in some previous debates over projects that pertain to glaciers, although valid economic motivations again could trump science and drive a solution to the energy supply problem before the associated safety and environmental problems are understood. The connection between glaciers and climate change—both anthropogenic and natural—is fundamental to glaciology and to glaciers' practical importance for water and hydropower resources, agriculture, tourism, mining, natural hazards, ecosystem conservation, and sea level [Buytaert et al., 2010; Glasser et al., 2011]. The conflict between conservation and development can be sharper in glacierized regions than almost anywhere else. Glaciers occur in spectacular natural landscapes, but they also supply prodigious exploitable meltwater.

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

2012-05-01

112

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

113

Glacier Monitoring: Opportunities, Accomplishments, and Limitations.  

NASA Astrophysics Data System (ADS)

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.

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

2001-12-01

114

Monitoring of Grandes Jorasses hanging glacier (Aosta Valley, Italy): improving monitoring techniques for glaciers instability  

NASA Astrophysics Data System (ADS)

Grandes Jorasses serac is an unbalanced hanging glacier located on the south side of Mont Blanc Massif (Aosta Valley - Italy). It stands above Ferret Valley, a famous and most frequented touristic site both in winter and summer. Historical data and morphological evidences show that the glacier is subject to recurrent icefalls which can be dangerous especially in winter, as they can trigger catastrophic combined snow and ice avalanches. Serac dynamic was monitored in 1997-98 by prof. M Funk (ETH Zurich) by means of temperature and topographic measurement. These allowed to forecast the breakdown within a 2 days time. Thanks to a monitoring program, a new instability could be recognized in autumn 2008: a crevasse opening in the lower part of the hanging glacier. A new monitoring system was installed recently, consisting of stakes with prisms on serac surface and an automatic total station (theodolite plus distantiometer) sited on the valley floor. Monitoring is based on an empirically based power law (developed by ETH) that describes the increasing displacement rate before collapse. This monitoring system requires to measure displacement rate of the serac continuously. Although the topographic system is so far the state-of-the.art method, it implies some troubles: (i) the difficulty in placing stakes on the steep and dangerous glacier surface; (ii) potential instability of stakes themselves due to snow pressure in winter and surface ice melting in summer; (iii) impossibility to carry out measurement in case of cloudy or stormy weather, which is rather a frequent situation on Grandes Jorasses peak. Moreover, hazard and risk management require some more informations, such as the instable ice mass volume. New technologies have been applied, and are still under test, to achieve a more reliable monitoring system and a better understanding of the serac dynamics. Close-range photogrammetry techniques have been used, allowing to process helicopter-taken images and obtain quantitative data about the serac volume and crevasses widening. A low-cost GPS station has been installed in the upper part of the serac, in order to obtain long-term, continuous displacement data even in bad weather conditions. A seismograph has been installed to measure the seismic activity of the serac. The latter, as observed by ETH, significantly evolves before the seracfall; thus, the record of the seismic activity can be used to forecast the break-off. Finally, a ground-based SAR system has been tested to infer seracs displacement. Possible avalanches scenarios consequent to an icefall have been calculated by numerical simulation by the SLF Institute of Davos. In-situ measurement techniques have to be designed to resist often in the difficult environmental conditions (low temperature, frost, wind), dealing, e.g. with power supply and data transmission, and purpose-made technical solutions are often necessary. The development of these techniques will contribute to an improved understanding of the seracs dynamics and provide a more reliable monitoring tool.

Vagliasindi, Marco; Funk, Martin; Faillettaz, Jerome; Dalban, Pierre; Lucianaz, Claudio; Diotri, Fabrizio; Motta, Elena; Margreth, Stephan

2010-05-01

115

Alaska PaleoGlacier Atlas: A Geospatial Compilation of Pleistocene Glacier Extents  

NSDL National Science Digital Library

The Alaska PaleoGlacier (APG) Atlas is a recently released, web-based summary of Pleistocene glaciation across Alaska. Students can access a gallery of maps depicting the extent of glaciers during the late Wisconsin glaciation in Alaska as well as the maximum extent reached during the last 3 million years by valley glaciers, ice caps, and the northwestern Cordilleran Ice Sheet. a set of links is also provided to sites on galcial geology and glacial geospatial data.

Manley, William

116

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

117

Combining a Distributed Melt Model and Meteorological Data of Shackleton Glacier, Canadian Rockies  

NASA Astrophysics Data System (ADS)

Runoff from the Canadian Rocky Mountains into the Upper Columbia and Kootenay basins is strongly dominated by winter snow accumulation and spring melt, and it has been suggested that future reductions in snowpack will create increased competition for water between spring and early fall (Hamlet & Lettenmaier, 1999). Although the glacierised area is substantial for affecting summer flows in these basins, there are no measurements or quantified estimates of glacier runoff contribution. In an effort to provide an estimate of glacier runoff for the region, we measured ablation over 5 years, set up weather stations and temperature sensors in Summers 2009 and 2010 and developed a melt model for Shackleton Glacier (42.5 km2), the largest outlet of the Clemenceau Icefield Group (271 km2), which is the major local ice mass feeding into the Upper Columbia basin. Two HOBO weather stations (WS) were installed on the glacier for two weeks in Summer 2010, one near the left lateral moraine on very dirty ice, and one mid-glacier on relatively clean ice. Instrumentation included pyranometers (solar radiation and albedo), and temperature, wind speed and direction, relative humidity and barometric pressure sensors. A weather station off ice provided additional temperature and precipitation data. Other data included daily ablation stake measurements, surface roughness measurements, temperature data from Tidbit loggers on and off ice, and daily manual weather observations. Yearly ablation stake measurements and summer weather observations have been made by our team since 2005. A BC River Forecast Centre automatic snow pillow station provides additional temperature and precipitation data. Using these meteorological and ablation data for parameterisation and optimisation, a distributed GIS melt model was constructed from a simple energy balance model. The model is driven by hourly direct and diffuse radiation and DEM hillshading, an albedo parameterisation based on four ice/snow zones identified from a satellite image and field measurements, constant daily values of longwave radiation as a function of percent cloud cover, and sensible heat input as a function of air temperature, katabatic wind, surface roughness and elevation. Latent heat was considered negligible. Novel aspects of the melt model include a valley temperature threshold for katabatic wind (using on and off ice temperatures and katabatic wind speed) and slope corrected area melt and radiation calculations. In an attempt to quantify energy balance effects of tributary-trunk detachment due to glacier recession related glacier fragmentation, special attention was paid to the potential influence from lateral moraines and valley walls and very dirty ice on the ablation in ice marginal regions. Observations suggest that, when katabatic wind diminishes, heat advection from an even moderately warmer lateral moraine can raise nearby glacier temperature substantially. This suggests that a combination of katabatic wind fields and proximity to lateral moraines/rock walls may be important in calculations of sensible heat contribution to surface melt in recently fragmented glacier systems.

Mueller, M.; Jiskoot, H.

2010-12-01

118

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

NASA Astrophysics Data System (ADS)

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.

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

2002-12-01

119

Modeled Climate-Induced Glacier Change in Glacier National Park, 1850--2100  

NSDL National Science Digital Library

This peer-reviewed article from BioScience journal is about the glacier change in Glacier National park. The glaciers in the Blackfoot--Jackson Glacier Basin of Glacier National Park, Montana, decreased in area from 21.6 square kilometers (km2) in 1850 to 7.4 km2 in 1979. Over this same period global temperatures increased by 0.45 degrees C (+/- 0.15 degrees C). We analyzed the climatic causes and ecological consequences of glacier retreat by creating spatially explicit models of the creation and ablation of glaciers and of the response of vegetation to climate change. We determined the melt rate and spatial distribution of glaciers under two possible future climate scenarios, one based on carbon dioxide--induced global warming and the other on a linear temperature extrapolation. Under the former scenario, all glaciers in the basin will disappear by the year 2030, despite predicted increases in precipitation; under the latter, melting is slower. Using a second model, we analyzed vegetation responses to variations in soil moisture and increasing temperature in a complex alpine landscape and predicted where plant communities are likely to be located as conditions change.

MYRNA H. P. HALL and DANIEL B. FAGRE (;)

2002-02-01

120

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

121

Glacier Change in the Western Himalayas: A Case Study of Suru Glacier, Northern India  

NASA Astrophysics Data System (ADS)

Mountain glaciers are considered as primary indicators to monitor the impact of climate change on regional temperature and precipitation patterns. They are linked to the atmosphere through mass and energy exchange which determine accumulation and ablation throughout the year. Since the advent of satellite remote sensing and its data availability to researchers from 1972 onwards, mapping and monitoring of glaciers become more popular because of its improved multi-spectral, multi-temporal and multi-spatial resolution. The investigated Suru Glacier is located in the upper Zanskar catchment, a major southern tributary of the Indus valley in the western Himalayan Range, Northwest India. The 8 km long glacier ranges from about 4700 m up to 5800 m a.s.l. To detect the changes of Suru Glacier remote sensing data such as Corona from 1972, diverse IRS and Landsat data, as well as an additional topographic map from 1962 were used. In order to calculate the volumetric changes of the glacier, dGPS measurements were carried out in 2007 and 2008. These measurements were then related and compared to a digital elevation model, which was generated from the topographic map, and to a SRTM-DEM (version 4, 2000). The co-registered data show a glacier retreat of about 120 m between 1962 and 2009. Apart from the recession of the glacier snout a certain downwasting of the glacier is detectable.

Schmidt, Susanne; Nüsser, Marcus; Nathawat, M. S.; Ghosh, S.; Pandey, A. C.

2010-05-01

122

Climate change: Shrinking glaciers under scrutiny  

NASA Astrophysics Data System (ADS)

Melting glaciers contribute to sea-level rise, but measuring their mass loss over time is difficult. An analysis of satellite data on Earth's changing gravity field does just that, and delivers some unexpected results.

Bamber, Jonathan

2012-02-01

123

International Symposium on Fast Glacier Flow.  

National Technical Information Service (NTIS)

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 j...

C. S. Lingle

1990-01-01

124

Icebergs and Glaciers - Issue 15, August 2009  

NSDL National Science Digital Library

This issue of the free online magazine, Beyond Penguins and Polar Bears, contains content knowledge and instructional resources about icebergs and glaciers and the scientific principles of density and buoyancy.

University, The O.

125

Towards a complete World Glacier Inventory  

NASA Astrophysics Data System (ADS)

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.

Zemp, Michael

2013-04-01

126

A data set of world-wide glacier length fluctuations  

NASA Astrophysics Data System (ADS)

Glacier fluctuations contribute to variations in sea level and historical glacier length fluctuations are natural indicators of climate change. To study these subjects, long-term information of glacier change is needed. In this paper we present a~data set of global long-term glacier length fluctuations. The data set is a compilation of available information on changes in glacier length world-wide, including both measured and reconstructed glacier length fluctuations. All 471 length series start before 1950 and cover at least four decades. The longest record starts in 1534, but the majority of time series start after 1850. The number of available records decreases again after 1962. The data set has global coverage including records from all continents. However, the Canadian Arctic is not represented in the data set. The glacier length series show relatively small fluctuations until the mid-19th century followed by a global retreat that was strongest in the first half of the 20th century, although large variability in the length change of the different glaciers is observed. During the 20th century, calving glaciers retreated more than land terminating glaciers, but their relative length change was approximately equal. Besides calving, the glacier slope is the most important glacier property determining length change: steep glaciers have retreated less than glaciers with a gentle slope.

Leclercq, P. W.; Oerlemans, J.; Basagic, H. J.; Bushueva, I.; Cook, A. J.; Le Bris, R.

2013-09-01

127

Impacts of Change in Glacier Ice  

NSDL National Science Digital Library

This is a five-activity module that explores the evidence for and impacts of melting glacial ice, with resources from major institutions and scientists who study glaciers -- primarily in Arctic areas. The suite of activities includes both glaciers and melting ice, as well as the impact of melt water downstream. Each activity follows the 5E model of Engagement, Exploration, Explanation, Elaboration, and Evaluation.

Grant, Alaska S.

128

Recent changes on Greenland outlet glaciers  

Microsoft Academic Search

Aircraft laser-altimeter surveys during the 1990s showed near-coastal parts of the Greenland ice sheet to be thinning; despite slow thickening at higher elevations, the ice sheet lost mass to the ocean. Many outlet glaciers thinned more rapidly than could be explained by increased melting during the recent warmer summers, indicating dynamic imbalance between glacier velocity and upstream snow accumulation. Results

R. Thomas; E. Frederick; W. Krabill; S. Manizade; C. Martin

2009-01-01

129

ASTER Imaging and Analysis of Glacier Hazards  

Microsoft Academic Search

\\u000a Most scientific attention to glaciers, including ASTER and other satellite-derived applications in glacier science, pertains\\u000a to their roles in the following seven functions: (1) as signposts of climate change (Kaser et al. 1990; Williams and Ferrigno\\u000a 1999, 2002; Williams et al. 2008; Kargel et al. 2005; Oerlemans 2005), (2) as natural reservoirs of fresh water (Yamada and\\u000a Motoyama 1988; Yang

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

130

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

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

131

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

132

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

133

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

NASA Astrophysics Data System (ADS)

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.

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

2012-07-01

134

A micro-hydrometeorological study on the Peyto Glacier.  

NASA Astrophysics Data System (ADS)

A micrometeorological experiment was conducted in the summer of 2008, at Peyto Glacier, during three periods of dry, warm weather and one of moist, cool weather. The data include a breakdown of net radiation into its short- and long-wave components, as well as wind speed, temperature and humidity profile data for use in bulk transfer estimates of sensible heat and moisture transfer. In addition, a micro-hyrological experiment was conducted, the data comprising sonic sounder measurements of ablation and stage level records of discharge from a supra-glacial catchment. As expected, there is short-term divergence between energy budget and ablation estimates of meltwater production because of weathering crust development. Also, the conversion of stage level data into discharge from a supra-glacial catchment presents challenges, not the least of which is to define the area of the catchment. Nevertheless, it is clear that peak discharge can lag peak meltwater energy input by periods of four to six hours. This suggests that a substantial part of the delay in runoff from a glacierized basin is tied up in ice surface hydrological processes.

Munro, D. S.

2009-05-01

135

Creating improved ASTER DEMs over glacierized terrain  

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

136

Glacier Dynamics Within a Small Alpine Cirque  

NASA Astrophysics Data System (ADS)

Cirques, with their steep walls and overdeepened basins, have captivated the imagination of scientists since the mid-1800s. Glaciers in cirques, by generating these spectacular amphitheater-shaped landforms, contribute significantly to erosion in the core of mountain ranges and are one of the principal agents responsible for the relief structure at high elevations. Yet comprehensive studies of the dynamics of cirque glaciers, and their link to erosional processes, have never been undertaken. To this end, we acquired an extensive new set of measurements at the West Washmawapta Glacier, which sits in a cirque on the east side of Helmet Mountain in the Vermillion Range of the Canadian Rockies. Ice thickness surveys with ground penetrating radar revealed that the glacier occupies a classic bowl-shaped depression complete with a nearly continuous riegel. Using GPS-derived surface velocities of a glacier-wide grid network and the tilt of one borehole, we calculated the complete force balance of the glacier. This analysis also produced a map of basal sliding velocity and a value for the viscosity of temperate ice. We will discuss the implications of these findings for the problem of how cirques are formed by glacial erosion.

Sanders, J. W.; Cuffey, K. M.; MacGregor, K. R.; Kavanaugh, J. L.; Dow, C. F.

2008-12-01

137

Diverse calving patterns linked to glacier geometry  

NASA Astrophysics Data System (ADS)

Iceberg calving has been implicated in the retreat and acceleration of glaciers and ice shelves along the margins of the Greenland and Antarctic ice sheets. Accurate projections of sea-level rise therefore require an understanding of how and why calving occurs. Unfortunately, calving is a complex process and previous models of the phenomenon have not reproduced the diverse patterns of iceberg calving observed in nature. Here we present a numerical model that simulates the disparate calving regimes observed, including the detachment of large tabular bergs from floating ice tongues, the disintegration of ice shelves and the capsizing of smaller bergs from grounded glaciers that terminate in deep water. Our model treats glacier ice as a granular material made of interacting boulders of ice that are bonded together. Simulations suggest that different calving regimes are controlled by glacier geometry, which controls the stress state within the glacier. We also find that calving is a two-stage process that requires both ice fracture and transport of detached icebergs away from the calving front. We suggest that, as a result, rapid iceberg discharge is possible in regions where highly crevassed glaciers are grounded deep beneath sea level, indicating portions of Greenland and Antarctica that may be vulnerable to rapid ice loss through catastrophic disintegration.

Bassis, J. N.; Jacobs, S.

2013-10-01

138

Glacier Fluctuation and Climate Change: the NOAA/NSIDC Glacier Photo Digitization Project  

NASA Astrophysics Data System (ADS)

The study of historic glacier photographs is an excellent source of information about climate change. Glaciers are sensitive to temperature and precipitation patterns associated with climate change. Ice cores from glaciers can provide a long-term climate record and aid current scientific research in understanding changes that have occurred over tens of thousands of years. Within recent history, a warming climate has resulted in the unfortunate retreat and disappearance of glaciers around the world. Comparisons of glacial area and mass balance over time can help scientists understand a glacier's response to climate change. The National Snow and Ice Data Center is the repository of several thousand glacier photographs taken and collected by the American Geographical Society. The dates of the photographs range from the 1880s to the 1970s and the collection consists of both aerial and terrestrial photos. The digitization of these photographs will help inform users of their existence and will provide easier access to the images. It will also be an important first step in a project to display matching images of the same glaciers over time, thus providing an instantaneous visual representation of climate change. A searchable online database is being created for several thousand photographs and their accompanying metadata. Images will be retrievable by glacier name, photographer name, state, geographic coordinates, and subject keywords. This work is being done with funding by the National Oceanic and Atmospheric Administration's (NOAA) Climate Database Modernization Program (CDMP), whose goal is to make major climate databases available on the web.

Mullins, T. L.; Armstrong, R.; Machado, A.; Wang, I.; Ballagh, L.; Paserba, A.; Edwards, M.; Yohe, L.; Fetterer, F.

2002-12-01

139

Uncovering glacier dynamics beneath a debris mantle  

NASA Astrophysics Data System (ADS)

Debris-covered glaciers (DCGs) have an extensive sediment mantle whose low albedo influences their surface energy balance to cause a buffering effect that could enhance or reduce ablation rates depending on the sediment thickness. The last effect suggests that some DCGs may be less sensitive to climate change and survive for longer than debris-free (or 'clean') glaciers under sustained climatic warming. However, the origin of DCGs is debated and the precise impact of the debris mantle on their flow dynamics and surface geometry has not been quantified. Here we investigate these issues with a numerical model that encapsulates ice-flow physics and surface debris evolution and transport along a glacier flow-line, as well as couples these with glacier mass balance. We model the impact of surface debris on ablation rates by a mathematical function based on published empirical data (including Ostrem's curve). A key interest is potential positive feedback of ablation on debris thickening and lowering of surface albedo. Model simulations show that when DCGs evolve to attain steady-state profiles, they reach lower elevations than clean glaciers do for the same initial and climatic conditions. Their mass-balance profile at steady state displays an inversion near the snout (where the debris cover is thickest) that is not observed in the clean-glacier simulations. In these cases, where the mantle causes complete buffering to inhibit ablation, the DCG does not reach a steady-state profile, and the sediment thickness evolves to a steady value that depends sensitively on the glacier surface velocities. Variation in the assumed englacial debris concentration in our simulations also determines glacier behaviour. With low englacial debris concentration, the DCG retreats initially while its mass-balance gradient steepens, but the glacier re-advances if it subsequently builds up a thick enough debris cover to cause complete buffering. We identify possible ways and challenges of testing this model with field observations of DCGs, given the inherent difficulty that such glaciers may not be in steady state.

Lefeuvre, P.-M.; Ng, F. S. L.

2012-04-01

140

Climate sensitivity of Tibetan Plateau glaciers - past and future implications  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

141

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

NASA Astrophysics Data System (ADS)

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.

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

2003-12-01

142

Accelerating ice loss from the fastest Greenland and Antarctic glaciers  

Microsoft Academic Search

Progressive increase in ice discharge from fastest Greenland\\/Antarctic glaciersKey imortance of floating ice shelves to future behavior of many similar glacierLikelihood of continued, very large increases in ice discharge

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

2011-01-01

143

Observations of Glacier Dynamics in the St. Elias Mountains (Invited)  

NASA Astrophysics Data System (ADS)

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). The primary cause of such rapid mass loss is complex glacier flow dynamics, not increased melting due to temperature increases (Larsen et al., 2007). Indirect observations indicate these complex flow dynamics occur on many glaciers throughout Alaska, but no comprehensive measurements of flow velocities have been made. We are working to measure surface velocities on glaciers throughout Alaska using offset tracking with synthetic aperture radar (SAR). We focus on the flow dynamics on the Seward/Malaspina Glacier system and on surrounding St. Elias glaciers. Flow variations of approximately 80% are evident on the Seward during “quiescent” phases. An active surge is visible on the Agassiz Glacier and regional synchronous velocity fluctuations have been found.

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

2010-12-01

144

Glacial Hydrology: Bibliography on the Hydrology of Glacierized Areas.  

National Technical Information Service (NTIS)

Information on the runoff from glaciers and glacierized basins, its prediction for agricultural, power-supply and transportation purposes, and its control for irrigation and flood protection, are vital concerns to the peoples living in most mountain areas...

G. J. Young

1982-01-01

145

Linking glacier annual mass balance and glacier albedo from MODIS data  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

146

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

SciTech Connect

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.

Mernild, Sebastian Haugard [Los Alamos National Laboratory; Liston, Glen [COLORADO STATE UNIV.

2009-01-01

147

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

NSDL National Science Digital Library

This video contains a mix of live action video, stills, and computer animations of the Glacier Bay National Park in Glacier Bay, Alaska. Satellite mapping and imagery are used to show changes in the Glacier Bay area over a period of several years. Specific image processing techniques are discussed in relation to determining the evolution of glacier terminus points and in obtaining elevation data and how it is used to create fly-by visualizations of the area.

Starr, Cindy; Strong, Jim; Oneil, Pamela; Acuna, Andy; Hall, Dorothy; Benson, Carl

1996-02-23

148

Contemporary sediment production and transfer in high-altitude glaciers  

Microsoft Academic Search

The nature of fine-grained sediment production and transfer in high-altitude debris-covered glaciers was studied by examining the Rakhiot and Chungphar glaciers in the Nanga Parbat Himalaya, Northern Pakistan. Transport pathways, from the source areas to the glacier snout, were mapped and samples collected for particle size analysis and scanning electron microscopy. Positive down-glacier trends in sediment fining and increased weathering

Lewis A. Owen; Edward Derbyshire; Christine H. Scott

2003-01-01

149

Dynamics and Evolution of Taylor Glacier, Antarctica  

NASA Astrophysics Data System (ADS)

Taylor Glacier is a high-stress outlet glacier of East Antarctica. It originates on the Taylor Dome, flows eastward through the Transantarctic Mountains, and terminates in the famous Dry Valleys of Victoria Land. Here we summarize results from extensive new studies on its 80 km long ablation zone. Radar surveys show the basal topography is dominated by a deeply eroded central trough. Force balance and flow analyses yield estimates for basal temperature and demonstrate that basal motion of this glacier is non-existent or minor. A full-stress three-dimensional model of ice flow with no approximations in the mathematical framework is used to examine in detail how the glacier negotiates the complex mountainous topography and how the nonlinearity of ice deformation is manifest. We have also measured the stable isotope profile of surface ice along the lower 27 km of the central flowline, and thereby inferred ages of the ice at some locations. Analysis of these data reveal time-dependent behavior of the glacier over millennial timescales. Time-dependent planview models of the system are used to explore past incursions of ice into Taylor Valley.

Cuffey, K. M.; Kavanaugh, J. L.; Morse, D. L.; Aciego, S.; Bliss, A.

2005-12-01

150

Geophysical imaging of alpine rock glaciers  

NASA Astrophysics Data System (ADS)

Slope instabilities caused by the disappearance of ice within alpine rock glaciers are an issue of increasing concern. Design of suitable counter-measures requires detailed knowledge of the internal structures of rock glaciers, which can be obtained using geophysical methods. We examine benefits and limitations of diffusive electromagnetics, geoelectrics, seismics and ground-penetrating radar (georadar) for determining the depth and lateral variability of the active layer, the distributions of ice and water, the occurrence of shear horizons and the bedrock topography. In particular, we highlight new developments in data acquisition and data analysis that allow 2-D or even 3-D structures within rock glaciers to be imaged. After describing peculiarities associated with acquiring appropriate geophysical datasets across rock glaciers and emphasizing the importance of state-of-the-art tomographic inversion algorithms, we demonstrate the applicability of 2-D imaging techniques using two case studies of rock glaciers in the eastern Swiss Alps. We present joint interpretations of geoelectric, seismic and georadar data, appropriately constrained by information extracted from boreholes. A key conclusion of our study is that the different geophysical images are largely complementary, with each image resolving a different suite of subsurface features. Based on our results, we propose a general template for the cost-effective and reliable geophysical characterization of mountain permafrost.

Maurer, Hansruedi; Hauck, Christian

151

Improving Mass Balance Modeling of Benchmark Glaciers  

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

152

Decay of a long-term monitored glacier: the Careser glacier (Ortles-Cevedale, European Alps)  

NASA Astrophysics Data System (ADS)

The continuation of valuable, long-term glacier observation series is threatened by the accelerated mass loss which currently affects a large portion of so-called "benchmark" glaciers. In this work we present the evolution of the Careser glacier, from the beginning of systematic observation at the end of the nineteenth century to its current condition in 2012. In addition to having one of the longest and richest observation record among the Italian glaciers, Careser is unique in the Italian Alps for its 45 yr mass balance series started in 1967. In the present study, variations in the length, area and volume of the glacier since 1897 are examined, updating the series of direct mass balance observations and extending it into the past using the geodetic method. The glacier is currently strongly out of balance and in rapid decay; its average mass loss rate over the last three decades was -1.5 m water equivalent per year, increasing to -2.0 m water equivalent per year in the last decade. If mass loss continues at this pace, the glacier will disappear within a few decades, putting an end to this unique observation series.

Carturan, L.; Baroni, C.; Becker, M.; Bellin, A.; Cainelli, O.; Carton, A.; Casarotto, C.; Dalla Fontana, G.; Godio, A.; Martinelli, T.; Salvatore, M. C.; Seppi, R.

2013-07-01

153

Surface mass balance of Greenland mountain glaciers and ice caps  

Microsoft Academic Search

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

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

2009-01-01

154

Subpolar glaciers network as natural sensors of global warming evolution  

Microsoft Academic Search

In the expeditions carried out both to temperate and subpolar glaciers in both hemispheres, we have observed the existence of endoglacier and subglacier flows and drainages also in subpolar glaciers. Our main work hypothesis is centred on investigating the role played by subpolar glacier discharge in global warming, as we consider this discharge may represent that unknown third of sea

Adolfo Eraso

155

Assessing Glacier Hazards At Ghiacciaio Del Belvedere, Macugnaga, Italian Alps  

Microsoft Academic Search

The uppermost section of the Valle Anzasca behind and above the community of Macugnaga in the Italian Alps is one of the most spectacular high-mountain land- scapes in Europe, with gigantic rock walls and numerous steep hanging glaciers. Its main glacier, Ghiacciaio del Belvedere at the foot of the huge Monte Rosa east face, is a heavily debris-covered glacier flowing

W. Haeberli; M. Chiarle; G. Mortara; A. Mazza

2002-01-01

156

Glacier variation in boduizangbu basin in Southeast Tibet  

Microsoft Academic Search

Glacier variation, especially the alpine glacier, is a sensitive indicator of climatic change. Glacier plays a vital role in studying the global climate system. The climate of the Tibet plateau has direct and indirect effects on the lives and economic activities of approximately two-thirds of the world's population who live downstream of this elevated terrain. Despite this critical importance of

Xiaoli Wang; Songbing Zou; Shangzhe Zhou; Gao Xiang

2005-01-01

157

Marine Geophysical Surveying Along the Hubbard Glacier Terminus, Southeast Alaska  

Microsoft Academic Search

Tidewater glaciers are a challenging environment for marine investigations, owing to the dangers associated with calving and restrictions on operations due to dense floating ice. We report here on recent efforts to conduct marine geophysical surveys proximal to the ice face of Hubbard Glacier, in Disenchantment Bay, Alaska. Hubbard is an advancing tidewater glacier that has twice recently (1986 and

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

2010-01-01

158

The Role of Glaciers in the Hydrology of Nepal (Invited)  

Microsoft Academic Search

Glaciers are a component of the hydrologic regime of many large mountain ranges of the world, including the Himalaya. However, the hydrologic regime of Himalayan catchment basins and the role of glaciers in the hydrologic regime of this region are not well understood. Current concern regarding the impact of the retreat of Himalayan glaciers on water supplies poses an urgent

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

2010-01-01

159

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

NASA Astrophysics Data System (ADS)

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 0°C (up to ~10°C 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.

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

2013-04-01

160

A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus  

NASA Astrophysics Data System (ADS)

The glacier coverage in the Caucasus Mountains underwent considerable changes during the last decades. Besides a reduction in glacier area which in some areas is comparable to area changes in the European Alps, also the concentration of supra-glacial debris increased on many glaciers. Only a few glaciers in the Caucasus are monitored on a regular basis, while for most areas no field measurements are available on a continuous basis. In this study the regional differences between the well studied Adyl-su basin on the northern slope of the Caucasus is compared with a similar basin in the South (Zopkhito basin). Special focus is laid on the effect of supra-glacial debris cover on the melt conditions during the ablation season. Systematic differences can be shown for the distribution and temporal increase of the debris cover on the glaciers. While in the Adyl-su basin an extensive debris cover on the glacier tongues is common, only some low lying glacier tongues in the Zopkhito basin show considerable supra-glacial debris. Also the temporal increase in debris cover is decidedly stronger in the North. Field experiments show that the thermal resistance of the debris cover is somewhat higher than in other glacerised regions in the world. A simple ablation model which includes the effect of the debris cover on ice melt indicates considerably stronger melt rates in the northern basin, despite the much more widespread debris distribution. This is due to the different meteorological conditions with more frequent cloud cover and precipitation in the South. Still ablation is strongly influenced in both basins by the occurrence of supra-glacial debris cover, reducing the total amount of melt on the glacier by about 20%. Especially in the lower tongue areas this effect mitigates the area loss of the glaciers considerably.

Lambrecht, A.; Mayer, C.; Hagg, W.; Popovnin, V.; Rezepkin, A.; Lomidze, N.; Svanadze, D.

2011-02-01

161

ASTER Imaging and Analysis of Glacier Hazards  

NASA Astrophysics Data System (ADS)

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

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

162

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

SciTech Connect

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.

Wiles, G.C. [Columbia Univ., Palisades, NY (United States); Calkin, P.E. [Univ. of New York, Buffalo, NY (United States); Post, A. [Geological Survey, Vashon, WA (United States)

1995-08-01

163

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

NASA Astrophysics Data System (ADS)

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

Le Bris, Raymond; Paul, Frank

2013-03-01

164

Melting Himalayan Glaciers May Doom Towns  

NSDL National Science Digital Library

This news article describes how mountain lakes in Nepal and Bhutan have become so overfilled by water from melting glaciers that they are in danger of overflowing. Scientists from the United Nations Environment Program (UNEP), along with remote-sensing experts from the International Center for Integrated Mountain Development (ICIMOD), predict that in the next half decade or so, the Himalayas could experience intense flooding as mountain lakes overflow with water from glaciers and snowfields which are melting as a result of gradually rising global temperatures.

165

Deriving supraglacial debris thickness using satellite data on the Lirung Glacier in the Nepalese Himalayas  

NASA Astrophysics Data System (ADS)

Glaciers with debris-covered ablation zones are widely present in mountain ranges such as the Alps, the Himalayas and the Andes. An expansion of rock debris-covered areas has been documented in recent decades. It is therefore increasingly important to take the effect of debris cover into account in glacio-hydrological modelling. Debris thickness is a key control on a glacier's energy balance and it governs the melt rate beneath debris, hence the estimation of debris extent and thickness is crucial to predict melt. Data on debris thickness are scarce on most glaciers and thus simplified assumptions are commonly used. In this study we test a new, recently developed physically based method to produce debris thickness maps from satellite imagery. The model is based on a solution of the energy balance equation at the debris surface to reconstruct debris thickness as a residual in each satellite pixel. This approach requires ASTER thermal images and reanalysis meteorological data and has the potential to map distribution of debris thickness without the need for detailed field data. In a previous study we tested the model for glaciers with different characteristics and in different climatic regions of the world. The validation of debris thickness, however, is problematic due to data scarcity, the inhomogeneous debris distribution and the resolution of the ASTER product (90 m). The standard application of the model seems to work for glaciers for which debris characteristics such as the effective conductivity are known and reanalysis data are representative. In this study we additionally test the approach with a recently collected data set over the Lirung glacier in the Nepalese Himalayas, where initial application of the remote sensing method using reanalysis data led to a significant underestimation of debris thickness. Extensive field data were collected from May to October 2012 consisting of data from an AWS, spatially distributed air and surface temperature, effective conductivity and a large data set of debris thickness. Analyzing the data improved our understanding of spatial distribution of air temperature, the relationship of air and surface temperature and the thermal properties of the debris. We show how including this knowledge in the model changes the resulting debris thickness maps and we attribute the earlier underestimation of debris thickness mostly to the quality of reanalysis data and the use of literature values for debris characteristics and the air/surface temperature relationship. In particular we show that given the importance of turbulent fluxes, accurate knowledge of wind speed and temperature on the glacier is necessary. A sensitivity analysis identifies the most important inputs for the model and the method's applicability is discussed in relation to the quality of available field data.

Petersen, Lene; Schauwecker, Simone; Brock, Ben; Immerzeel, Walter; Pellicciotti, Francesca

2013-04-01

166

Simulation of seasonal snow-cover distribution for glacierized sites on Sonnblick, Austria, with the Alpine3D model  

NASA Astrophysics Data System (ADS)

A detailed model of Alpine surface processes is used to simulate the amount of preferential deposition as well as redistribution of snow due to snowdrift for two alpine glaciers (Goldbergkees and Kleinfleißkees, Austrian Alps). The sequence of snow-cover modelling consists of the simulation of the wind field with a mesoscale atmospheric model, a three-dimensional finite-element drift module, an energy-balance module and a snowpack module. All modules with the exception of the wind-field model are integrated within the Alpine3D model frame. The drift module of Alpine3D distinguishes between saltation and suspension and is able to capture preferential deposition of snow precipitation and redistribution of previously deposited snow. Validation of the simulated snow depth is done using the spatially dense snow-probing dataset collected during a campaign in May 2003. Simulated snow depths agree with measurements during winter 2002/03 at locations with detailed snow-height monitoring, taking into account the high spatial variability of snow depth on the glacier. Moreover, comparison of snow accumulation from model results with detailed probing on 1 May 2003 for the total glacier area shows that Alpine3D is able to capture major patterns of spatial distribution of snow accumulation. For the first time, the Alpine3D approach of using high-resolution wind fields from a meteorological model and a physical description of snow transport could be validated for a very steep glacierized area and for a full accumulation season. The results show that drift is a dominant factor to be considered for detailed glacier mass balances. Another dominant factor not considered in this study may be snow redistribution due to avalanches.

Mott, Rebecca; Faure, Françoise; Lehning, Michael; Löwe, Henning; Hynek, Bernhard; Michlmayer, Gernot; Prokop, Alexander; Schöner, Wolfgang

167

Brief communication "Historical glacier length changes in West Greenland"  

NASA Astrophysics Data System (ADS)

Past glacier fluctuations provide insight into glacier dynamics, climate change, and the contribution of glaciers to sea-level rise. Here, the length fluctuations since the 19th century of 18 local glaciers in West and South Greenland are presented, extending and updating the study by Weidick (1968). The studied glaciers all showed an overall retreat with an average of 1.2 ± 0.2 km over the 20th century, indicating a general rise of the equilibrium line along the west coast of Greenland during the last century. Furthermore, the average rate of retreat was largest in the first half of the 20th century.

Leclercq, P. W.; Weidick, A.; Paul, F.; Bolch, T.; Citterio, M.; Oerlemans, J.

2012-11-01

168

Sensitivity of glaciers and small ice caps to greenhouse warming.  

PubMed

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. PMID:17835895

Oerlemans, J; Fortuin, J P

1992-10-01

169

Contrasting response of South Greenland glaciers to recent climatic change  

SciTech Connect

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.

Warren, C.R.; Glasser, N.F. (Univ. of Edinburgh, Scotland (United Kingdom))

1992-05-01

170

Monitoring surging glaciers of the Pamirs, central Asia, from space  

NASA Astrophysics Data System (ADS)

The evolution of surging glaciers of the Pamirs, central Asia, has been studied using repeat remote-sensing surveys in the Institute of Geography, Russian Academy of Sciences, since the early 1970s. We use images obtained from national Resurs-F satellites (1972-91), as well as Landsat 7 and Terra (1999-2006), to provide a basis for monitoring of surging glaciers, aimed at developing their inventory, studying the causes and mechanisms of surges and examining the timing and extent of glacial catastrophes. The inventory from the early 1990s allows identification of 215 glaciers with a dynamically unstable regime. We discovered 51 surging glaciers. Up until 2006, 10 more surges had occurred. We use stereoscopic deciphering and photogrammetric processing of consecutive satellite images to study the morphology and ice-velocity changes of several compound surging glaciers. We analyze the results of monitoring of Bivachny and Oktyabr'sky glaciers from 1972 to 1991 and Sugran glacier from 1972 to 2006. Two surges of Sugran glacier occurred during this time: an internal surge in 1976-80, and a surge with glacier tongue advance as far as 4.5 km in 2000-05. The role of damming in compound glacier systems is examined. Satellite-based monitoring is now the only method for obtaining initial information about the state and fluctuations of such glaciers.

Kotlyakov, V. M.; Osipova, G. B.; Tsvetkov, D. G.

171

Improving estimation of glacier volume change: a GLIMS case study of Bering Glacier System, Alaska  

NASA Astrophysics Data System (ADS)

The Global Land Ice Measurements from Space (GLIMS) project has developed tools and methods that can be employed by analysts to create accurate glacier outlines. To illustrate the importance of accurate glacier outlines and the effectiveness of GLIMS standards we conducted a case study on Bering Glacier System (BGS), Alaska. BGS is a complex glacier system aggregated from multiple drainage basins, numerous tributaries, and many accumulation areas. Published measurements of BGS surface area vary from 1740 to 6200 km2, depending on how the boundaries of this system have been defined. Utilizing GLIMS tools and standards we have completed a new outline (3630 km2) and analysis of the area-altitude distribution (hypsometry) of BGS using Landsat images from 2000 and 2001 and a US Geological Survey 15-min digital elevation model. We compared this new hypsometry with three different hypsometries to illustrate the errors that result from the widely varying estimates of BGS extent. The use of different BGS hypsometries results in highly variable measures of volume change and net balance (bn). Applying a simple hypsometry-dependent mass-balance model to different hypsometries results in a bn rate range of -1.0 to -3.1 m a-1 water equivalent (W.E.), a volume change range of -3.8 to -6.7 km3 a-1 W.E., and a near doubling in contributions to sea level equivalent, 0.011 mm a-1 to 0.019 mm a-1. Current inaccuracies in glacier outlines hinder our ability to correctly quantify glacier change. Understanding of glacier extents can become comprehensive and accurate. Such accuracy is possible with the increasing volume of satellite imagery of glacierized regions, recent advances in tools and standards, and dedication to this important task.

Beedle, M. J.; Dyurgerov, M.; Tangborn, W.; Khalsa, S. J. S.; Helm, C.; Raup, B.; Armstrong, R.; Barry, R. G.

2008-04-01

172

Glacier regime on the northern slope of the Himalaya (Xixibangma glaciers)  

Microsoft Academic Search

The mass–energy exchange components and ice thickness of the Xixibangma glacier massif were evaluated during the Chinese–Russian glaciological expedition to the northern Himalaya in 1991. Long-term data from two Chinese meteorological stations were used to analyze the glacier-climatic regime in the surrounding area. It was determined that solar radiation income during the summer–autumn monsoon is half that theoretically possible because

V. B Aizen; E. M Aizen; S. A Nikitin

2002-01-01

173

Mass Balance modelling on Haut Glacier d'Arolla, Switzerland: how different levels of complexity of process representation affect predictions  

NASA Astrophysics Data System (ADS)

Correct modelling of glacier-climate interaction processes is necessary to assess the response of glaciers to future changes in the climate. Varying levels of complexity in the representation of both ablation, accumulation and glacier geometry evolution processes, could lead to significant variability in model predictions. In order to assess the range of model outputs of a mass balance model, we investigate the effect of various representations of the single model components. Ablation is calculated by means of two different approaches, a physically based energy-balance model (EB) and a more empirical enhanced temperature-index model (ETI). Accumulation is modelled by simply considering the spatial variability of precipitation by means of a gradient or, in a more complex approach, accounting for redistribution of snow by wind and gravity. Changes in glacier geometry are simulated by parameterising the changes in glacier surface elevation and ice thickness as a function of ice mass loss or neglecting the ice flux component. We run the distributed mass balance model on Haut Glacier d'Arolla, Switzerland, for the period 2001-2007, comparing model predictions and identifying the limitations of the single approach investigated. Initially, each component is validated individually; we use discrete ablation stake readings and continuous surface lowering measured by Ultrasonic Depth Gauges for the ablation, differences between LIDAR surveys and snow height measurements for the accumulation. Then the modelled ice volume losses are compared against the measured ones obtained as differences between Digital Elevation Models (DEMs), in this way validating the integrated model outputs. Our main result is that a distributed EB is very sensible to errors in the input data. Due to the uncertainties related to the extrapolation of a larger amount of meteorological input variables (generally measured off-glacier) ablation, and therefore mass balance, can be wrongly simulated, more than in a model that relies on less input data. We show that including preferential deposition of precipitation due to wind and gravitational mass transport leads to significant improvement in the accumulation modelling, by obtaining more reliable maps of snow height, and therefore of snow water equivalent (SWE). Although the simulation period covers only 7 years, the specific mass flux term contributes to model a more realistic ice thickness maps, avoiding underestimation of ice thickness loss on the glacier tongue and overestimation in the accumulation area.

Carenzo, M.; Pellicciotti, F.; Burlando, P.

2011-12-01

174

Glacier melting in a stratified ocean: Observations from outlet glaciers in Greenland (Invited)  

NASA Astrophysics Data System (ADS)

Submarine melting is an important balance term for tidewater outlet glaciers in Greenland, and has emerged as a potential trigger for their recent acceleration, necessitating its inclusion in future prognostic ice-sheet models. Yet, our present understanding of the process is limited, largely because of a lack of measurements. Most existing studies pertain to tidewater glaciers terminating in fjords with shallows sills that allow the inflow of a single oceanic water mass. Greenland’s fjords, on the other hand, are characterized by deep sills and a vigorous fjord/shelf exchange which allows both cold, fresh Arctic waters and warm, salty Atlantic waters, present on the shelf, to come in contact with the ice. As a result, submarine melting of outlet glaciers in Greenland occurs in strongly stratified waters. Here, we present oceanographic measurements from three major East Greenland glaciers, including winter measurements, which show that this stratification and, in particular, the density contrast between the Arctic and Atlantic waters, give rise to multiple overturning melt cells (as opposed to a single estuarine cell) at the ice-edge. The resulting heat transport and melt rate vary strongly with depth suggesting that the ocean waters around Greenland exert a strong control on the vertical profile of the glacier’s terminus.

Straneo, F.; Sutherland, D. A.; Hamilton, G. S.; Cenedese, C.; Stearns, L. A.

2010-12-01

175

Calibration of hydrological models in glacierized catchments  

NASA Astrophysics Data System (ADS)

Glacierized catchments are important source regions for water, and detailed knowledge of water availability is a prerequisite for good resource management strategies. Reliable and physically consistent runoff simulations become even more important if climate change impacts on alpine water resources are to be assessed. However, hydrological modeling of glacierized catchments is challenging ice melt which represents an additional source of water. Thus, adequate calibration strategies are needed especially in data scarce regions. An important question is how powerful a limited amount of data might be for model calibration. Accordingly, we analyzed the calibration power of limited discharge measurements, mass balance observations and the combination of by means of both Monte Carlo analyzes and multi-criteria model performance evaluation. Ensembles of 100 parameter sets were selected by evaluating the simulations based on a limited and discrete number of discharge measurements, glacier mass balance, and the combination of discharge and mass balance observations. Using these ensembles then the runoff was simulated and evaluated for the entire runoff series. The results for the Vernagtferner catchment and the Venter Ache catchment in Austria indicated that a single annual glacier mass balance observation contained useful information to constrain hydrological models. Combining mass balance observations with a few discharge data improved the internal consistency and significantly reduced the uncertainties compared to parameter set selections based on discharge measurements alone. Information on discharge was required for at least 3 days during the melting season to obtain good ensemble predictions.

Konz, Markus; Seibert, Jan; Braun, Ludwig; Burlando, Paolo

2010-05-01

176

Geology Fieldnotes: Glacier National Park, Montana  

NSDL National Science Digital Library

Glaciers have played an important role in shaping this park, which is part of the Rocky Mountain chain and shares a border with Canada's Waterton Lakes National Park. Information on this site includes park geology, visitor information, photographs, and links to other resources.

177

Resource Use in Glacier Bay National Preserve.  

National Technical Information Service (NTIS)

The report is a baseline description of resource use in the Dry Bay area, which in 1981 became Glacier Bay National Preserve. The study involved the joint cooperation of the NPS and the Subsistence Division of the Alaska Dept. of Fish and Game. The main p...

G. Gmelch

1982-01-01

178

Response of Italian Glaciers to Climatic Variations  

NASA Astrophysics Data System (ADS)

The glaciers of the southern alpine slope have been investigated using a variety of different methods. The most common ones are: a) glacial inventories, which consist of an overall description, the geographical location, the classification, and the area and volumetric measurements. Four such inventories, all focussed on the Italian Alps, were carried out in 1925, 1958, 1976 and in 1989 [1, 2]. The first one is the result of the consultation of I.G.M. topographic maps, the second comes from measurements in the field, and the latter two come from aerophotogrammetric observations. The data base for the last one was provided by Italy Flight 1988; b) annual glacial campaigns, during which snout variations of the ablating tongue are measured. The operation, carried out by land surveys, refers to a sample of about 15% of the total population of glaciers, and it includes almost all the glacial bodies of major dimension and importance [3]; c) mass balances, with the calculation of the volumetric variation of the glacier in time and its role in the local climatic evolution. Only a few sample glaciers, located in different parts of the Alpine range, are taken into consideration.

Biancotti, A.; Motta, M.

179

Surface energy balance in the ablation zone of Midtdalsbreen, a glacier in southern Norway: Interannual variability and the effect of clouds  

Microsoft Academic Search

We present a record of almost six years of data (2000–2006) from an automatic weather station (AWS) in the ablation zone of Midtdalsbreen, a glacier in southern Norway. Measured incoming longwave radiation is used to estimate cloudiness, revealing that high cloud fractions occur almost 50% of the time in all seasons. Measured wind speeds and humidity are higher for cloudy

R. H. Giesen; M. R. van den Broeke; J. Oerlemans; L. M. Andreassen

2008-01-01

180

The first glacier inventory for entire Greenland  

NASA Astrophysics Data System (ADS)

Detailed glacier data is becoming more and more important in the last decades to solve several research issues. One of the most prominent questions in this regard is the potential contribution of glaciers and icecaps (GIC) to global sea-level rise. Primarily, estimates are uncertain due to the globally still incomplete information about glacier location and size, as well as large uncertainties in future climate scenarios. Recent studies that calculate global sea-level rise from GIC have developed simplified approaches using information from glacier inventories or gridded data sets and a range of different global climate models and emission scenarios. However, for several strongly glacierized regions very rough assumptions about the ice distribution have to be made and an urgent demand for a globally complete glacier inventory is expressed. The GIC on Greenland are one of the regions with lacking information. Within the EU FP7 project ice2sea we mapped the GIC on Greenland using Landsat TM/ETM+ imagery acquired around the year 2000, along with an additional dataset in the North (DCW - Digital Chart of the World). A digital elevation model (DEM) with 90 m resolution (GIMP DEM) was used to derive drainage divides and henceforth topographic parameters for each entity. A major challenge in this regard is the application of a consistent strategy to separate the local GIC from the ice sheet. For this purpose we have defined different levels of connectivity (CL) of the local GIC with the ice sheet: CL0: Not connected. CL1: Connected but separable (either with drainage divides in the accumulation region or in touch only - and thus separable - in the ablation region). CL2: Connected but non-separable (the local GIC contribute to the flow of an ice sheet outlet in the ablation area). Up to now close to 12'000 GIC (only CL0 and CL1) with a total area of about 129'000 km2 have been mapped considering only entities larger than 0.1 km2. The area of the ice sheet itself is approximately 1'684'000 km2. The entire ice-covered area on Greenland is thus 1'813'000 km2. We will present the results of the GIC mapping along with an analysis of glacier inventory statistics.

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

2012-04-01

181

Constraining Glacier Sensitivity across the Andes: A Modeling Experiment  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

182

Glacier melt-model parameter sensitivity and transferability in the dry subarctic environment of the southwest Yukon  

NASA Astrophysics Data System (ADS)

Regional hydrology and eustatic sea-level are expected to change as a consequence of climate warming. Accurate projection of these changes requires glacier melt-models with high parameter transferability in space and time. We have assessed the parameter transferability and sensitivity of a suite of glacier melt-models for two glaciers 10 km apart in the dry subarctic environment of the St. Elias Mountains, Yukon, Canada. The melt models range in complexity from a classical temperature-index model to a simplified energy balance model. Two experiments are conducted: (1) the models are tuned to the output of a full energy balance model forced under idealized conditions to assess the sensitivity of model parameters to variations in glacier geometric attributes, surface conditions, and meteorological conditions; (2) the models are tuned to real ablation stake data from our two study glaciers over two melt seasons, and the parameter transferability between the two sites and the two melt seasons is evaluated. The parameters of the temperature-index models demonstrate high sensitivity to glacier aspect, mean surface elevation, albedo, wind speed, mean annual temperature, and temperature lapse rate. The simplified energy balance model is sensitive to snow albedo. The simplified energy balance model more often than not (in seven of twelve tests) produces the highest model transferability. In the remaining five tests the classical temperature-index model produces the highest transferability twice, and a temperature-index model, where the degree-day factor is a function of potential shortwave radiation, produces the highest transferability three times. The full energy balance model when forced with real data inputs produces higher model parameter transferability than the empirical melt models in nine out of twelve tests. These results suggest that caution should be observed when extending the use of melt models beyond the locations where they were developed and tested.

MacDougall, A. H.; Flowers, G. E.

2011-12-01

183

Holocene glacier fluctuations recorded in eastern Jotunheimen, southern Norway  

NASA Astrophysics Data System (ADS)

Sediment records from proglacial lake Russvatnet in eastern Jotunheimen central southern Norway comprise a complex combination of direct glacier-derived material from glaciers in the catchment as well as material from a variety of different episodic mass movement processes. To disentangle the sedimentary units we utilize a multi proxy approach analyzing sediment cores from Russvatnet and extract the glacier-derived signal from the complex multi-process record. The prevailing wintertime westerlies in the North Atlantic region leads to a strong west-east precipitation gradient across southern Norway, and the study area is, at present, located in the precipitation shadow of the Jotunheimen mountains. Comparing our reconstructed record of Holocene glacier activity with independent pollen-based reconstructions of temperature, we deduce the varying influence of temperature and winter precipitation on glacier fluctuations, and thus gain information on the dominating climate regime and strength/influence of the westerlies during the Holocene. During the Holocene thermal maximum (around 7000 cal. yr BP), the glacier signal is weak and glaciers were probably small. At about 4500 cal. yr BP glacier activity increased and results indicate a significant correlation between the reconstructed glacier fluctuations and summer temperatures over the following 2000 years (c. 4500-2500 cal. yr BP), arguably indicating a continental climate regime. After c. 2500 cal. yr BP there is no significant correlation between glacier variability and summer temperature, indicating a relative higher influence of a maritime climate regime, and a relative increase in winter precipitation.

Støren, E.; Dahl, S. O.

2012-04-01

184

The GLIMS Glacier Database: Status and Future Directions  

NASA Astrophysics Data System (ADS)

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 continues to expand both spatially and temporally: the number of glaciers represented, as well as the number of outlines from different times per glacier, are both increasing. As of August 2011, the database, located at NSIDC, contains outlines for approximately 95 000 glaciers, covering 290 000 km2. More datasets are expected soon, such as from GlobGlacier (e.g. all European Alps, western Greenland, Sweden, Baffin Island), and the Regional Centers for Svalbard, Argentina, Nepal, China, and others. Though the database does not yet cover the world's glaciers completely, approximately 670 glaciers have outlines from more than one time. This database increasingly enables analysis of global and regional glacier area and its distribution, glacier change, distribution of glaciers by different properties (e.g. morphology, debris-cover),and other yet-to-be imagined possibilities. In spite of steady progress, there remain some geographic areas that are not yet covered, including southernmost South America, Arctic Russia, the the periphery of most of Greenland and Antarctica. For applications such as sea level change studies that require complete global coverage of glaciers with at least moderate resolution, it is imperative that these gaps be filled soon. This will be addressed through adapting existing datasets to the GLIMS data model, using new satellite data and methods as they develop, and building analysis capacity worldwide to get more researchers involved in high accuracy glacier mapping.

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

2011-12-01

185

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

186

Microbial Energetics Beneath the Taylor Glacier, Antarctica  

NASA Astrophysics Data System (ADS)

Subglacial microbiology is controlled by glacier hydrology, bedrock lithology, and the preglacial ecosystem. These factors can all affect metabolic function by influencing electron acceptor and donor availability in the subglacial setting leaving biogeochemical signatures that can be used to determine ecosystem processes. Blood Falls, an iron-rich, episodic subglacial outflow from the Taylor Glacier in the McMurdo Dry Valleys Antarctica provides an example of how microbial community structure and function can provide insight into subglacial hydrology. This subglacial outflow contains cryoconcentrated, Pliocene-age seawater salts that pooled in the upper Taylor Valley and was subsequently covered by the advance of the Taylor Glacier. Biogeochemical measurements, culture-based techniques, and genomic analysis were used to characterize microbes and chemistry associated with the subglacial outflow. The isotopic composition of important geochemical substrates (i.e., ?34Ssulfate, ?33Ssulfate, ?18Osulfate, ?18Owater, ?14SDIC) were also measured to provide more detail on subglacial microbial energetics. Typically, subglacial systems, when driven to anoxia by the hydrolysis of organic matter, will follow a continuum of redox chemistries utilizing electron acceptors with decreasing reduction potential (e.g., Fe (III), sulfate, CO2). Our data provide no evidence for sulfate reduction below the Taylor Glacier despite high dissolved organic carbon (450 ?M C) and measurable metabolic activity. We contend that, in the case of the Taylor Glacier, the in situ bioenergetic reduction potential has been 'short-circuited' at Fe(III)-reduction and excludes sulfate reduction and methanogenesis. Given the length of time that this marine system has been isolated from phototrophic production (~2 Mya) the ability to degrade and consume increasingly recalcitrant organic carbon is likely an important component to the observed redox chemistry. Our work indicates that glacier hydrology imparts strong feedbacks on the availability of oxygen as an electron acceptor and may be a robust regulator of the in situ metabolism. This biogeochemical regulation in turn affects the chemical nature of subglacial efflux. Blood Falls demonstrates that measurements of geochemistry and microbial diversity can support models of subglacial hydrology.

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

2007-12-01

187

Glacier and climate change in Pakistan and Afghanistan  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

188

Sedimentological and Geochemical Aspects of Sediment and Water from Ten Alaskan Valley Glaciers.  

National Technical Information Service (NTIS)

The characteristics of superglacial sediments, suspended stream sediments, and meltwater from ten Alaskan valley glaciers were determined. The glaciers are eroding five different types of bedrock. Superglacial sediments from six glaciers are relatively un...

R. M. Slatt

1970-01-01

189

Present and future contribution of glacier storage change to runoff from macroscale drainage basins in Europe  

Microsoft Academic Search

Glaciers make a significant runoff contribution in macroscale drainage basinsThe impact of glacial melt water is recognizable with very small glacierizationThe retreat of alpine glaciers plays an important role in future water shortage

Matthias Huss

2011-01-01

190

36 CFR 13.1132 - What types of commercial fishing are authorized in Glacier Bay?  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false What types of commercial fishing are authorized in Glacier Bay? 13...Regulations-Glacier Bay National Park and Preserve Commercial Fishing § 13.1132 What types of commercial fishing are authorized in Glacier Bay?...

2010-07-01

191

36 CFR 13.1132 - What types of commercial fishing are authorized in Glacier Bay?  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false What types of commercial fishing are authorized in Glacier Bay? 13...Regulations-Glacier Bay National Park and Preserve Commercial Fishing § 13.1132 What types of commercial fishing are authorized in Glacier Bay?...

2009-07-01

192

Jakobshavns Glacier drainage basin - A balance assessment  

NASA Astrophysics Data System (ADS)

Maximum and minimum estimates are made of the drainage basin feeding the Jakobshavns Glacier by using surface elevation maps derived from Seasat altimetry. Benson's (1962) net balance measurements are used to calculate the balance flow within the basin. Comparisons of the balance flux at the terminus with estimates of actual flux suggest the basin is in overall equilibrium or slightly thickening. This agrees with measurements along the nearby EGIG traverse. Balance velocities accelerate rapidly within 100 km of the coast. Farther upstream, balance velocities are consistent with both measured velocities along the EGIG traverse and calculated deformation velocities. It is estimated that Jakobshavns Glacier discharges between 4.8 and 7.6 percent of the annual net balance over Greenland and drains between 3.7 and 5.8 percent of the ice sheet area.

Bindschadler, R. A.

1984-03-01

193

Satellite Image Atlas of Glaciers of the World: North America  

NSDL National Science Digital Library

This atlas contains Landsat images, aerial photographs, selected maps, and other data, which provide a baseline look (from the mid-1970's) at glaciation in Canada, the conterminous United States, and Mexico. The Landsat false-color imagery includes ice fields, outlet glaciers, valley glaciers, and cirque glaciers, as well as ice caps. Ice features are grouped by location and a full description is available for each.

194

Arthropod colonisation of a debris-covered glacier  

Microsoft Academic Search

The largest debris-covered glacier in the Alps (Miage Glacier, western Italian Alps) has been studied to explore the effects of debris-cover extent and depth on the spatial distribution of ground-dwelling arthropods. A multitaxa approach has been used to compare taxa richness and distribution to the functional role (dietary habits) of each taxon along the glacier tongue. Spiders and ground beetles

Mauro Gobbi; Marco Isaia; Fiorenza De Bernardi

2011-01-01

195

Glaciochemical investigation of an ice core from Belukha Glacier,Siberian Altai  

NASA Astrophysics Data System (ADS)

Little is known about climatic change and paleo-atmospheric composition in Siberia. The Altai is the only alpine region in this area covered by glaciers that might serve as archives for such studies. Moreover, it is located close to air pollution sources in East Kazakhstan and South Siberia (heavy metal mining, metallurgy) as well as to the nuclear test site of Semipalatinsk (release of radionuclides into the atmosphere). In order to reconstruct air pollution levels in the Altai region, a 140-meter ice core down to bedrock was recovered from the Belukha glacier (N49^o48'26", E86^o34'43", 4062 m asl) in July 2001. This site was selected based on the results of an exploratory study conducted in 2000. So far, the concentrations of major ionic species and the stable isotope ratio ?18O were determined in the approx. 90 topmost meters of the ice core covering about 200 years. Dating of the upper part of the ice core was performed by a combination of methods that include e.g. nuclear techniques and annual-layer counting. The annual net accumulation amounts to about 0.53 m weq. and indicates that snow at the Belukha glacier might be partly eroded by wind, a situation that is often observed for a glacier saddle. The borehole temperature (-16 ^oC at 80 m depth), the discernible fluctuations of the stable isotope and chemistry records as well as the linearity of the decrease of the log. 210Pb activities with depth indicate that the glaciochemical record is well preserved and not significantly altered by melting processes. In pre-industrial ice concentrations of carboxylic acids and ammonium are high, suggesting the surrounding forest as source of biogenic emissions.

Olivier, S.; Schwikowski, S.; Gäggeler, H. W.; Lüthi, M.; Eyrik, S.; Blaser, C.; Saurer, M.; Schotterer, U.

2003-04-01

196

Microbial Life beneath a High Arctic Glacier  

Microsoft Academic Search

The debris-rich basal ice layers of a high Arctic glacier were shown to contain metabolically diverse microbes that could be cultured oligotrophically at low temperatures (0.3 to 4°C). These organisms included aerobic chemoheterotrophs and anaerobic nitrate reducers, sulfate reducers, and methanogens. Colonies purified from subglacial samples at 4°C appeared to be predominantly psychrophilic. Aerobic chemoheterotrophs were metabolically active in unfrozen

MARK L. SKIDMORE; JULIA M. FOGHT; MARTIN J. SHARP

2000-01-01

197

Significant contribution to total mass from very small glaciers  

NASA Astrophysics Data System (ADS)

A single large glacier can contain tens of millions of times the mass of a small glacier. Nevertheless, very small glaciers (with area ?1 km2) are so numerous that their contribution to the world's total ice volume is significant and may be a notable source of error if excluded. With current glacier inventories, total global volume errors on the order of 10% are possible. However, to reduce errors to below 1% requires the inclusion of glaciers that are smaller than those recorded in most inventories. At the global scale, 1% accuracy requires a list of all glaciers and ice caps (GIC, exclusive of the ice sheets) larger than 1 km2, and for regional estimates requires a complete list of all glaciers down to the smallest possible size. For this reason, sea-level rise estimates and other total mass and total volume analyses should not omit the world's smallest glaciers. In particular, upscaling GIC inventories has been common practice in sea level estimates, but downscaling may also be necessary to include the smallest glaciers.

Bahr, D. B.; Radi?, V.

2012-07-01

198

West Antarctic Glacier Ice Flows and Elevation Change  

NASA Video Gallery

This animation shows glacier changes detected by ATM, ICESat and ice bridge data in the highly dynamic Amundsen Embayment of West Antarctica. Integrating these altimetry sources allows us to estimate surface height changes throughout the drainage regions of the most important glaciers in the region. We see large elevation changes at the coast on Thwaites glacier, at the center of the images, and large and accelerating elevation changes extending inland from the coast on Pine Island and Smith glaciers, to the left and right of the images, respectively.

Holly Zell

2011-11-03

199

GLACIER PEAK WILDERNESS STUDY AREA, WASHINGTON.  

USGS Publications Warehouse

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

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

1984-01-01

200

New Species in New Guinea / Melting Glaciers  

NSDL National Science Digital Library

The first segment of this radio broadcast discusses a recent expedition to the isolated Foja mountain range in western New Guinea, which has discovered several new species of birds, 20 new frog species, and four new butterfly species, as well as a rare bird which had not been seen for sixty years, and unusual plants. One of the explorers discusses the efforts to map the diversity of the island and the challenges in preserving such ecological treasures. This segment is 12 minutes and 21 seconds in length. The second segment consists of a conversation with researchers who travel the world documenting the retreat of mountain glaciers. Topics include efforts to build a global database of ice cores to document changes; a discussion of increased water flow from glaciers; the logistics of drilling ice cores at high altitude and moving them to a university lab; how annual snowfall is recorded in ice cores; and how retreating glaciers are exposing plants that were covered for six thousand years. This segment is 35 minutes and 20 seconds in length.

201

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

USGS Publications Warehouse

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

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

2008-01-01

202

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

USGS Publications Warehouse

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

Trabant, Dennis C.; Hawkins, Daniel B.

1997-01-01

203

Cryospheric Dynamics in the Central Chilean Andes: Multi-decadal Reconstruction and Multi-annual Monitoring of Rock Glaciers and a Debris-covered Glacier  

Microsoft Academic Search

In the semiarid Central Chilean Andes at 33.5°S, permafrost is widely present above 3500-4000 m a.s.l., especially in the form of ice-rich debris accumulations such as rock glaciers. While Chilean rock glacier are among the largest known rock glaciers, glaciers are mostly restricted to the highest summits and are affected by a significant retreat during the last decades. Rock glaciers

X. Bodin; F. Rojas; A. Brenning

2009-01-01

204

A new glacier inventory on southern Baffin Island, Canada, from ASTER data: II. Data analysis, glacier change and applications  

NASA Astrophysics Data System (ADS)

In part II of the paper we discuss the results obtained with the methods presented in part I. The analysis is separated in three sections: (1) a statistical analysis of the glacier inventory data (year 2000) and their mutual dependencies derived from the ASTER scene, (2) change assessment between the mapped LIA glacier extent and glacier outlines from 1975 and 2000, and (3) application of both data sets to derive further quantities (like volume change). The statistical analysis includes 664 glaciers and icecaps ranging in size from 0.02 to 125 km². The frequency distribution of the count and area per size class reveals that glaciers from 1-10 (count: 239), 10-50 (36) and >50 km² (8) cover each one third of the total area (2416 km²), while the 381 glaciers < 1 km² account only for 5%. There is a slight aspect dependency of the area covered towards the northern sectors (W-N-E). The mean elevation is 992 m (+/- 199 m) with a slight dependence on aspect (200 m lower for north facing glaciers), minimum and maximum elevation do strongly depend on glacier size, and mean slope is 18 (increasing towards smaller glaciers). For a sample of 264 glaciers area changes between LIA-1975-2000 have been calculated. The relative area change since the LIA (around 1920) is -7.3% to 1975 and -12.5% to 2000, which gives a slight increase in the rate of area loss for the latter period. Length changes reach up to 3.3 km from LIA to 2000 and show a high correlation with original glacier length (r=0.8). Mean glacier elevation has increased by 50 m which is about one half of what is expected due to the temperature increase since the 1920s and indicate that glacier geometries are not yet in balance with the current climate. Neglecting that glaciers might not be in a steady-state yet, we calculated for a sample of 194 glaciers the mean mass loss by combining the calculated cumulative length changes with the topographic glacier parameters from the inventory, yielding a mean mass balance of about -0.11 m w.e. per year.

Paul, F.; Svoboda, F.

2009-04-01

205

How to implement data for improved modelling - Results from an extensive field campaign on the debris covered Lirung Glacier in the Nepalese Himalayas  

NASA Astrophysics Data System (ADS)

Debris covered glaciers have become a focus of current research because of growing evidence of an increase in debris cover associated with a warming climate and the effect that debris has on melt rates. Mass balance models increasingly aim at including the melt rate enhancing/reduction effect due to a thin/thick debris layer, respectively. However, knowledge about debris cover and thickness, its distribution and characteristics is limited and data are scarce, especially in the HKKH region where debris-covered glaciers are numerous. In this work we present a data set that is complementary to modelling efforts carried out to improve our understanding of processes occurring at the debris cover surface and how debris effects can be implemented into melt and mass balance models of different complexity. A key requirement for distributed melt modelling is the availability of debris cover and thickness maps and knowledge about characteristics of the debris layer and their spatial variability. An extensive field campaign was conducted from May to October 2012 on the debris covered Lirung Glacier in the Nepalese Himalayas. The collected data set consists of observations from an automatic weather station (AWS) measuring wind direction, wind speed, air and surface temperature, incoming and outgoing shortwave radiation, relative humidity and snow height, 14 sensors measuring 2 m air temperature and 7 surface temperature sensors, 3 temperature systems (tinytags) measuring temperature at the debris surface and the ice below the debris layer and one thermistors chain (with 8 temperature sensors) measuring the temperature profile in the debris layer. In the study region there is a key difference between meteorological conditions during monsoon and the dry period. We analyze separately all meteorological records for these different climatic conditions and show how temperature, albedo, relative humidity and wind speed and direction are affected. Wind speed and direction show similar diurnal behaviour but wind speed maxima are lower during monsoon. The relationship of air and surface temperature is constant across the glacier but different for monsoon and the dry period. Further, even though incoming and outgoing shortwave radiation obviously change during monsoon, albedo is only slightly affected. We compare the main spatio-temporal variability to that of variables recorded off-glacier. We show for example that the presence of the glacier dampens the monsoon impact on temperature lapse rates. We also investigate the conductivity of debris across the glacier to test its spatial consistency and use the temperature profile in the debris layer to test the commonly made assumption of linearity. We compare the calculated values with those provided in the literature both for the Himalaya and other mountainous regions. We finally discuss how these data can be used for possible applications and improvements of models.

Petersen, Lene; Immerzeel, Walter; Shahi, Sonika; Baral, Prashant; Pellicciotti, Francesca

2013-04-01

206

Extending Glacier Monitoring into the Little Ice Age and Beyond  

NASA Astrophysics Data System (ADS)

Glaciers are among the best natural proxies of climatic changes and, as such, a key variable within the international climate observing system. The worldwide monitoring of glacier distribution and fluctuations has been internationally coordinated for more than a century. Direct measurements of seasonal and annual glacier mass balance are available for the past six decades. Regular observations of glacier front variations have been carried out since the late 19th century. Information on glacier fluctuations before the onset of regular in situ measurements have to be reconstructed from moraines, historical evidence, and a wide range of dating methods. The majority of corresponding data is not available to the scientific community which challenges the reproducibility and direct comparison of the results. Here, we present a first approach towards the standardization of reconstructed Holocene glacier front variations as well as the integration of the corresponding data series into the database of the World Glacier Monitoring Service (www.wgms.ch), within the framework of the Global Terrestrial Network for Glaciers (www.gtn-g.org). The concept for the integration of these reconstructed front variations into the relational glacier database of the WGMS was jointly elaborated and tested by experts of both fields (natural and historical sciences), based on reconstruction series of 15 glaciers in Europe (western/central Alps and southern Norway) and 9 in southern South America. The reconstructed front variation series extend the direct measurements of the 20th century by two centuries in Norway and by four in the Alps and in South America. The storage of the records within the international glacier databases guarantees the long-term availability of the data series and increases the visibility of the scientific research which - in historical glaciology - is often the work of a lifetime. The standardized collection of reconstructed glacier front variations from southern Norway, the western Alps and the southern Andes allows a direct comparison between different glaciers. It is a first step towards a worldwide compilation and free dissemination of Holocene glacier fluctuation series within the internationally coordinated glacier monitoring.

Nussbaumer, S. U.; Gärtner-Roer, I.; Zemp, M.; Zumbühl, H. J.; Masiokas, M. H.; Espizua, L. E.; Pitte, P.

2011-12-01

207

A note on the water budget of temperate glaciers  

NASA Astrophysics Data System (ADS)

In this note, the total dissipative melting in temperate glaciers is studied. The analysis is based on the notion that the dissipation is determined by the loss of potential energy due to the downward motion of mass (ice, snow, meltwater and rain). A mathematical formulation of the dissipation is developed and applied to a simple glacier geometry. In the next step, meltwater production resulting from enhanced ice motion during a glacier surge is calculated. The amount of melt energy available follows directly from the lowering of the centre of gravity of the glacier. To illustrate the concept, schematic calculations are presented for a number of glaciers with different geometric characteristics. Typical dissipative melt rates, expressed as water-layer depth averaged over the glacier, range from a few centimetres per year for smaller glaciers to half a metre per year for Franz Josef Glacier, one of the most active glaciers in the world (in terms of mass turnover). The total generation of meltwater during a surge is typically half a metre. For Variegated Glacier a value of 70 cm is found, for Kongsvegen 20 cm. These values refer to water layer depth averaged over the entire glacier. The melt textit{rate} depends on the duration of the surge. It is generally an order of magnitude greater than water production by `normal' dissipation. On the other hand, the additional basal melt rate during a surge is comparable in magnitude with the water input from meltwater and precipitation. This suggests that enhanced melting during a surge does not grossly change the total water budget of a glacier. Basal water generated by enhanced sliding is an important ingredient in many theories of glacier surges. It provides a positive feedback mechanism that actually makes the surge happen. The results found here suggest that this can only work if water generated by enhanced sliding accumulates in a part of the glacier base where surface meltwater and rain have no or very limited access. This finding seems compatible with the fact that, on many glaciers, surges are initiated in the lower accumulation zone.

Oerlemans, J.

2013-09-01

208

Patterns of Glacier Change in the American West  

NASA Astrophysics Data System (ADS)

We examine a century of glacier area change in the American West, exclusive of Alaska, using historic photography, historic maps, and recent aerial photos. Of the approximately 3200 glaciers and permanent snow masses, we track about 400 glaciers across a region that spans from Washington to California and Colorado to Montana. All glaciers have retreated since 1900 with the greatest change in Montana (Lewis Range) and the Sierra Nevada of California, and the least change in Washington including the North Cascades and the Olympic Peninsula. The pattern since 1970s is more complex, with the majority of glaciers having retreated since the 1970s, some vastly more than others. The glaciers that exhibit relatively little retreat are largely restricted to the high stratovolcanoes >3500m in elevation. In these cases we infer elevated snow accumulation at higher elevations compensates for increased ablation (melt) at lower elevations. In addition, many of the most stable glaciers are debris covered in their lower elevations, due to rock fall from the relatively weak volcanic edifice. Small glaciers, <1 km2, show great variability in their behavior, with a few glaciers at equilibrium or slightly advancing, to the majority retreating, with some losing 67% of their area. These differences are more difficult to explain. We infer that local climatic/topographic influences play a dominant role in the magnitude of change while regional climate patterns control the sign of the change. Temporal patterns of glacier change are very similar across broad regions while the magnitude of that change is particular to individual glaciers.

Fountain, A. G.; Basagic, H. J.; Hoffman, M. J.

2008-12-01

209

Glacier fluctuations, global temperature and sea-level change  

NASA Astrophysics Data System (ADS)

The current world-wide glacier retreat is a clear sign of global warming. In addition, glaciers contribute to sea-level rise as a consequence of the current retreat. In this thesis we use records of past glacier fluctuations to reconstruct past climate variations and the glacier contribution to sea-level change. Firstly, a coherent data set of world-wide glacier fluctuations over the past centuries is compiled. Most available information of glacier fluctuations concerns glacier length fluctuations. There is currently a large number of sources available, varying from field observations, satellite images and aerial photography to reconstructions from historical documents and geological evidence. The data set, resulting from the compilation of available data, contains 374 length records of glaciers from all continents and is described in Chapter 2. In Chapter 3, a climatic interpretation of the length fluctuations of Glaciar Frías is presented. This glacier in North Patagonia has the longest detailed length record in southern South America. The glacier behaviour is modelled with a simplified mass balance model that is coupled with a flow line model. A warming of North Patagonian climate with 1.16 °Csince the mid 17th century, or a decrease in precipitation of 34%, would best explain the observed retreat since 1639. Driving the glacier model with existing climate reconstructions shows that the uncertainties in these reconstructions are rather large. In addition, it appears that the length fluctuations are mainly driven by variations in temperature rather than variations in precipitation. The development of such detailed models is not feasible for all glaciers in the length fluctuations data set. In the next chapter a simplified approach is used to reconstruct global and hemispheric temperature for the period 1600-2000 from world-wide glacier length fluctuations. The reconstructions show that global temperature was more or less constant from 1600 until the middle of the 19th century. Since then, temperature rises until 2000, with a period of slight cooling from 1940 to 1970. Glacier-based reconstructions are completely independent from both other proxy-based reconstructions and from the instrumental record. Still, the reconstructed temperature agrees well with the instrumental record of the 20th century and it is in broad agreement with existing temperature reconstructions. However, according to the glacier length reconstruction the global warming starts in the middle of the 19th century instead of in the beginning of the 20th century, as indicated by several other reconstructions. The data set of glacier length changes can also be used to estimate the glacier contribution to sea-level change. In Chapter 5, a global glacier length signal is calculated from the available glacier length records. The global length signal is scaled to global volume change, which is calibrated on mass balance and geodetic observations of the period 1950-2005. The reconstructed glacier contribution is 8.4 ± 2.1 cm for the period 1800-2005 and 9.1 ± 2.3 cm for the period 1850-2005. These estimates are significantly higher than earlier estimates. Glacier retreat accounts for half the observed sea-level rise since the middle of the 19th century.

Leclercq, P. W.

2012-02-01

210

Localized basal motion of a polythermal Arctic glacier: McCall Glacier, Alaska, USA  

NASA Astrophysics Data System (ADS)

We analyzed the ice flow of McCall Glacier, Alaska, USA, by numerical glacier modeling and radio-echo sounding (RES). Model experiments were carried out with a higher-order numerical ice-flow model, and results were validated with measurements of annual ice velocities and compared with previous estimates of ice-flow dynamics. During the 2003 summer campaign, detailed RES measurements were carried out along the central flowline of the ablation area with a 5 MHz (central frequency) ice-penetrating radar, where 10 m ice temperatures are approximately -7.5°C. The bed reflection power (BRP) beneath this central flowline abruptly increases at one location area, followed by a slow decrease down-glacier. The model experiments show that basal sliding (<50%) is necessary to match the observed annual mean surface velocities in the area that is characterized by high BRP values. However, when thermomechanical effects are taken into account, a temperate basal ice layer is apparent in the ablation area, which locally softens the ice and can explain to a certain extent the anomalous flow field. The model results confirm that the present temperature field is a remnant of a larger glacier geometry that was near steady state before the onset of enhanced surface thinning in the 1970s.

Pattyn, Frank; Nolan, Matt; Rabus, Bernhard; Takahashi, Shuhei

211

Anisotropy of the Reflected Radiation Field Over Melting Glacier Ice  

Microsoft Academic Search

In this article we analyze the anisotropy of the reflected radiation field over melting glacier ice using 118 ground-based radiance measurements in Landsat TM Bands 2 and 4. The measurements were carried out on the tongue of the Morteratschgletscher, Switzerland. On the basis of directional measurements several bidirectional reflectance distribution functions (BRDFs) were derived for dirty and clean glacier ice

Wouter H. Knap; Carleen H. Reijmer

1998-01-01

212

Jökulhlaups: A reassessment of floodwater flow through glaciers  

Microsoft Academic Search

In glaciated catchments, glacier-generated floods (Jökulhlaups) put human activity at risk with large, sporadic Jökulhlaups accounting for most flood-related fatalities and damage to infrastructure. In studies of Jökulhlaup hydrodynamics the view predominates that floodwater travels within a distinct conduit eroded into the underside of a glacier. However, some Jökulhlaups produce subglacial responses wholly inconsistent with the conventional theory of drainage.

Matthew J. Roberts

2005-01-01

213

JÖkulhlaups: A reassessment of floodwater flow through glaciers  

Microsoft Academic Search

In glaciated catchments, glacier-generated floods (jökulhlaups) put human activity at risk with large, sporadic jökulhlaups accounting for most flood-related fatalities and damage to infrastructure. In studies of jökulhlaup hydrodynamics the view predominates that floodwater travels within a distinct conduit eroded into the underside of a glacier. However, some jökulhlaups produce subglacial responses wholly inconsistent with the conventional theory of drainage.

Matthew J. Roberts

2005-01-01

214

Dynamics of tidewater glaciers: comparison of three models  

Microsoft Academic Search

A minimal model of a tidewater glacier based solely on mass conservation is compared with two one-dimensional numerical flowline models, one with the calving rate proportional to water depth, and the other with the flotation criterion as a boundary condition at the glacier terminus. The models were run with two simplified bed geometries and two mass-balance formulations. The models simulate

F. M. Nick; J. Oerlemans

2006-01-01

215

Melting on glaciers: environmental controls examined with orbiting radar  

Microsoft Academic Search

Direct, in situ measurements of glacier mass balance are expensive. Remote sensing would be an attractive alternative if remotely observable quantities could be interpreted in terms of mass gain or loss. A system developed recently for the analysis of Radarsat browse images is used here to explore temporal and environmental controls of melting on glaciers on Axel Heiberg Island, Nunavut,

J. Graham Cogley; M. A. Ecclestone; D. T. Andersen

2001-01-01

216

What influences climate and glacier change in southwestern China?  

Microsoft Academic Search

The subject of climate change in the Tibetan Plateau (TP) and Himalayas has taken on increasing importance because of the availability of water resources from their mountain glaciers (Immerzeel et al 2010). Many of the glaciers over these regions have been retreating, while some are advancing and stable (Yao et al 2004, Scherler et al 2011). Other studies report that

Teppei J. Yasunari

2011-01-01

217

Hydrologic monitoring of supercooled meltwater from Icelandic glaciers  

NASA Astrophysics Data System (ADS)

Knowledge of how glaciers entrain sediment is central to understanding processes of glacier movement and products of glacial sediment deposition. Previous work has shown that if the total hydraulic potential of subglacial meltwater increases more rapidly than the resulting mechanical energy can be transformed into sensible heat, then supercooling and ice growth will result. This process causes frazil ice to grow onto adjacent glacier ice, which acts to trap sediment in flowing meltwater eventually producing sedimentary inclusions within glacier ice. Supercooling has been recognised as a sediment entrainment mechanism at glaciers in Alaska, and more recently at several temperate Icelandic glaciers. Here we present short-period temperature measurements and field evidence of glaciohydraulic supercooling from three Icelandic glaciers. Temperature measurements demonstrate that supercooling occurs over a range of hydrological conditions and that the process does not operate continuously at all instrumented sites. Measurements of supercooling during a small jökulhlaup are also presented. Progressive accretion of supercooled meltwater creates sediment-laden ice exposures adjacent to active artesian vents. Understanding controls on the efficacy and pervasiveness of hydraulic supercooling is important for decoding the sedimentary record of modern and ancient glaciers and ice sheets.

Tweed, Fiona S.; Roberts, Matthew J.; Russell, Andrew J.

2005-11-01

218

36 CFR 7.3 - Glacier National Park.  

Code of Federal Regulations, 2010 CFR

...Medicine entrance to Two Medicine Lake; from West Glacier entrance to the Camas Entrance; U.S. Highway 2 from Walton to Java; and the Going-to-the-Sun Road from West Glacier entrance to Lake McDonald Lodge and from St. Mary entrance to...

2010-07-01

219

Mass fluxes and dynamics of Moreno Glacier, Southern Patagonia Icefield  

Microsoft Academic Search

Accumulation, ablation, calving, and flow dynamics of Moreno Glacier, one of the main outlet glaciers of the Southern Patagonia Icefield, were studied based on field campaigns and on spaceborne radar imagery acquired by SIR-C\\/X-SAR. Ice velocities and ablation were measured through two summers and one winter. The ice depth was sounded seismically at a transect 8 km above the calving

Helmut Rott; Martin Stuefer; Andreas Siegel; Pedro Skvarca; Alfons Eckstaller

1998-01-01

220

Widespread acceleration of tidewater glaciers on the Antarctic Peninsula  

Microsoft Academic Search

Over the last half century, the Antarctic Peninsula (AP) has been among the most rapidly warming regions on Earth. This has led to increased summer snowmelt, loss of ice shelves, and retreat of 87% of marine and tidewater glacier fronts. Tidewater-glacier flow is sensitive to changes in basal water supply and to thinning of the terminus, and faster flow leads

H. D. Pritchard; D. G. Vaughan

2007-01-01

221

Low-latitude mountain glacier evidence for abrupt climate changes  

Microsoft Academic Search

Clear evidence that a widespread warming of Earth's climate system is now underway comes from low latitude mountain glaciers. Proxy temperature histories reconstructed from ice cores, and the rapidly accelerating loss of both the total ice area and ice volume on a near global scale suggest that these glaciers responding to increasing rates of melting. In situ observations reveal the

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

2004-01-01

222

Calving on tidewater glaciers amplified by submarine frontal melting  

NASA Astrophysics Data System (ADS)

While it has been shown repeatedly that ocean conditions exhibit an important control on the behaviour of grounded tidewater glaciers, modelling studies have focused largely on the effects of basal and surface melting. Here, a finite-element model of stresses near the front of a tidewater glacier is used to investigate the effects of frontal melting on calving, independently of the calving criterion used. Applications of the stress model to idealized scenarios reveal that undercutting of the ice front due to frontal melting can drive calving at up to ten times the mean melt rate. Factors which cause increased frontal melt-driven calving include a strong thermal gradient in the ice, and a concentration of frontal melt at the base of the glacier. These properties are typical of both Arctic and Antarctic tidewater glaciers. The finding that frontal melt near the base is a strong driver of calving leads to the conclusion that water temperatures near the bed of the glacier are critically important to the glacier front, and thus the flow of the glacier. These conclusions are robust against changes in the basal boundary condition and the choice of calving criterion, as well as variations in the glacier size or level of crevassing.

O'Leary, M.; Christoffersen, P.

2012-08-01

223

Calving on tidewater glaciers amplified by submarine frontal melting  

NASA Astrophysics Data System (ADS)

While it has been shown repeatedly that ocean conditions exhibit an important control on the behaviour of grounded tidewater glaciers, modelling studies have focused largely on the effects of basal and surface melting. Here, a finite-element model of stresses near the front of a tidewater glacier is used to investigate the effects of frontal melting on calving, independently of the calving criterion used. Applications of the stress model to idealized scenarios reveal that undercutting of the ice front due to frontal melting can drive calving at up to ten times the mean melt rate. Factors which cause increased frontal melt-driven calving include a strong thermal gradient in the ice, and a concentration of frontal melt at the base of the glacier. These properties are typical of both Arctic and Antarctic tidewater glaciers. The finding that frontal melt near the base is a strong driver of calving leads to the conclusion that water temperatures near the bed of the glacier are critically important to the glacier front, and thus the flow of the glacier. These conclusions are robust against changes in the basal boundary condition and the choice of calving criterion, as well as variations in the glacier size or level of crevassing.

O'Leary, M.; Christoffersen, P.

2013-01-01

224

Sensitivity and response of Bhutanese glaciers to atmospheric warming  

NASA Astrophysics Data System (ADS)

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

Rupper, Summer; Schaefer, Joerg M.; Burgener, Landon K.; Koenig, Lora S.; Tsering, Karma; Cook, Edward R.

2012-10-01

225

Dominant Bacteria and Biomass in the Kuytun 51 Glacier ? †  

PubMed Central

Dominant bacteria in the different habitats in the Kuytun 51 Glacier were investigated using a 16S rRNA gene clone library sequencing technique. Results showed diverse bacteria on the glacial surface, with the dominant phyla being Proteobacteria, Cyanobacteria, and Bacteroidetes. UniFrac data showed distinct community patterns between the Kuytun and Himalayan Rongbuk glaciers.

Xiang, Shu-Rong; Shang, Tian-Cui; Chen, Yong; Jing, Ze-Fan; Yao, Tandong

2009-01-01

226

Sierra Nevada Rock Glaciers: Biodiversity Refugia in a Warming World?  

Microsoft Academic Search

Rock glaciers and related periglacial rock-ice features (RIFs) are common landforms in high, dry mountain ranges, and widely distributed throughout canyons of the Sierra Nevada, California, USA (Millar & Westfall, in press). Due to insulating rock carapaces, active rock glaciers (ice-cored) have been documented to maintain ice longer, and thus contribute to more enduring hydrologic output, under past warming climates

C. I. Millar; R. D. Westfall

2007-01-01

227

AK-03 ALASKA: AK-03 Columbia Glacier "Cliff" (Narrated)  

NSDL National Science Digital Library

A video from the Extreme Ice Survey in which Dr. Tad Pfeffer and photographer Jim Balog discuss the dynamics of the Columbia glacier's retreat in recent years through this time-lapse movie. Key point: glacier size is being reduced not just by glacial melting but due to a shift in glacial dynamics brought on by climate change.

Balog, James; Pfeffer, Tad; Survey, Extreme I.

228

Large fluctuations in speed on Greenland's Jakobshavn Isbræ glacier  

Microsoft Academic Search

It is important to understand recent changes in the velocity of Greenland glaciers because the mass balance of the Greenland Ice Sheet is partly determined by the flow rates of these outlets. Jakobshavn Isbræ is Greenland's largest outlet glacier, draining about 6.5 per cent of the ice-sheet area, and it has been surveyed repeatedly since 1991 (ref. 2). Here we

Ian Joughin; Waleed Abdalati; Mark Fahnestock

2004-01-01

229

Reanalysis of the USGS Alaskan benchmark glacier dataset  

NASA Astrophysics Data System (ADS)

Resolving the relationship between glacier surface-forcing (climate) and glacier geometry changes is accomplished through mass-balance estimates which can be made with remote sensing methods or field-based observations. The small scale of Alaskan glaciers has prevented remote sensing methods until recently, and field data are essential for validating new techniques. Field data provide the only long duration record that can be studied with respect to climate. The United States Geological Survey has maintained a 44-year mass-balance program at Alaska’s Gulkana Glacier and Wolverine Glacier. We have reanalyzed the Alaskan benchmark glaciers mass balance time series so that all data are treated similarly and systematically. Both glaciers are undergoing sustained mass loss with an increasing rate in recent years. However, the magnitude of the calculated loss depends on the number and location of the data collection sites. We explore the sensitivity of the glacier-wide balance estimates to the method of integration used on the necessarily point data. The robustness of the balance is strengthened with use of independent photogrammetric measurements.

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

2010-12-01

230

Global distributions of glacier properties: A stochastic scaling paradigm  

Microsoft Academic Search

Many problems in global climate and Earth systems science require knowledge of regional- or global-scale distributions of glacier properties, which includes mass balance, ice velocity, flux, thickness, volume, and surface area, among others. With roughly 160,000 glaciers worldwide, obtaining information on the global probability distributions of most ice properties is expensive and often infeasible. Only surface area distributions are relatively

David B. Bahr

1997-01-01

231

Global distributions of glacier properties: A stochastic scaling paradigm  

Microsoft Academic Search

Many problems in global climate and Earth systems science require knowledge of regional- or global-scale distributions of glacier properties, which includes mass balance, ice velocity, flux, thickness, volume, and surface area, among others. With roughly 160,000 glaciers worlwide, obtaining information on the global probability distributions of most ice properties is expensive and often infeasible. Only surface area distributions are relatively

David B. Bahr

1997-01-01

232

Source-to-sink study of erosion at Grinnell Glacier, Glacier National Park, Montana  

NASA Astrophysics Data System (ADS)

Cirques have been used as proxies for past climatic conditions, yet the detailed physical processes that act to form cirques remain poorly understood. In July 2005, we continued a field study at Grinnell Glacier in Montana to examine the relevant glacial and geomorphic processes driving cirque development. As in July 2004, we installed a grid of nine velocity poles to measure ice motion using differential GPS, and several temperature sensors and snow stakes to monitor snow and ice melt across Grinnell Glacier. We supplemented these data with time-series of 15-minute measurements of snow and ice melt recorded by an ultrasonic ranging sensor. Air temperature and snowmelt correlate well, with diurnal fluctuations in melt corresponding to diurnal temperature fluctuations. The ultrasonic sensor recorded an average melt rate of snow over the 24-day period of observation of 3.5 cm d-1 (water equivalent), with average daily rates as high as 6 cm d-1. Melt rates declined as snowmelt revealed debris-covered ice below. These observations suggest that debris-cover may play an important role in insolating Grinnell Glacier from summer melt, particularly in coming decades as debris concentrations are expected to rise. Average velocity near the center of the glacier, where ice thickness was ~44 meters, was ~5 cm d-1 during this time. Our measurements span the period of earthquake activity that occurred in Montana July 25-27. Iceberg calving was associated with the ground shaking. Downstream from Grinnell Glacier, we collected 5 lake cores to document sedimentation rates in Swiftcurrent and Josephine Lakes, source areas for erosion in the drainage basin, and environmental change due to forest fires and changes in vegetation. Two cores from Swiftcurrent Lake and one core from Lake Josephine are >5 m in length, providing us one of the first high-resolution lake records in Glacier National Park. While the core analysis remains a work-in-progress, preliminary work indicates that the cores document changes in charcoal abundance, organic matter, and sedimentation rates during the Quaternary. Future work will focus on determining erosion rates of Grinnell Glacier based on sedimentation rates in downstream sediment cores.

Riihimaki, C. A.; MacGregor, K. R.

2005-12-01

233

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

NASA Astrophysics Data System (ADS)

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

Paul, Frank

2010-05-01

234

Glacier Erosion and Response to Climate in Chilean Patagonia  

NASA Astrophysics Data System (ADS)

A vibrant dimension in current research on landscape evolution is the potential impact of climate change on erosion rates due to differences in efficiency of glacial and non-glacial erosion processes. The climate-sensitive rate and spatial distribution of erosion can be as important as the tectonic environment in determining the development of mountain ranges. To evaluate properly how glacial erosion influences orogenic processes and reflects climate variability, it is necessary to understand how ice dynamics control erosion rates. The Patagonian Andes are a unique laboratory for documenting glacial erosion in a range of precipitation and thermal regimes, as zonal atmospheric circulation in the region creates strong latitudinal gradients. We will present relevant findings from two tidewater glaciers in Chilean Patagonia: San Rafael glacier, which drains the northern portion of the North Patagonian Icefield (46.6S, 74W), and Marinelli glacier, the largest glacier in the Cordillera Darwin of Tierra del Fuego (54.6S, 69W). Both glaciers have been in steady retreat during the latter half of the 20th century, and both calve into a fjord or lagoon, which provides an efficient trap for the sediment eroded by the glacier and deposited at the calving front. The reconstructed flux of ice into the glaciers is compared to the retreat of the ice fronts and to the sediment flux to examine the influence of ice dynamics on the rate of glacier erosion. NCEP-NCAR Reanalysis climate data, adjusted to local conditions by correlation with automatic weather stations installed at the glacier termini and coupled to a model of orographic enhancement of precipitation over the glacier basin, were used to reconstruct the daily precipitation input into and ablation output from the glaciers during the last 50 years. The sediment flux out of the glaciers during this period was calculated from acoustic reflection profiles of the sediments accumulated in the proglacial fjords, and used to infer erosion rates. Preliminary results indicate 1) that high rates of retreat of the ice front occur during years in which the total input of snow into the glacier is balanced by the total ablation, and hence the residual flux of ice at the terminus is insufficient to compensate for the calving, and 2) that the highest basin- wide erosion rates reflect years in which total ice accumulation is lower and retreat rates are high. Interestingly, basin-wide erosion rates from these glaciers are up to an order of magnitude higher than long- term exhumation rates derived from detrital apatite thermochronometry in the basins, indicating that current rates of erosion far exceed long-term rates, and are reflective of periods of warming climate and enhanced glacial retreat.

Koppes, M.; Hallet, B.; Stewart, R.

2006-12-01

235

Was there a 1930's Meltdown of Greenland Glaciers?  

NASA Astrophysics Data System (ADS)

While climate warming is suggested to have caused acceleration of Greenland Ice Sheet outlet glaciers, recent warming, however, is not without precedent. Examination of Greenland's meteorological stations confirms that 1920s through 1940s surface-air temperature anomalies were at least as equal in magnitude to the recent "global warming" decade, yet observations have not yet been compiled to confirm a similar glacier response. Mining The Ohio State University Libraries, this work compiles historical observations of glacier front positions and surface velocities from maps, photographs and other documentary evidence from mid 19th century Arctic expeditions. Of the glaciers reviewed, an acceleration and retreat indeed occurred between 1920 and 1940. The research put forth is thus consistent with a dynamical response in Greenland's outlet glaciers to the "roaring twenties" warming.

Box, J. E.; Herrington, A.

2007-12-01

236

The physical basis of glacier volume-area scaling  

USGS Publications Warehouse

Ice volumes are known for only a few of the roughly 160,000 glaciers worldwide but are important components of many climate and sea level studies which require water flux estimates. A scaling analysis of the mass and momentum conservation equations shows that glacier volumes can be related by a power law to more easily observed glacier surface areas. The relationship requires four closure choices for the scaling behavior of glacier widths, slopes, side drag and mass balance. Reasonable closures predict a volume-area scaling exponent which is consistent with observations, giving a physical and practical basis for estimating ice volumes. Glacier volume is insensitive to perturbations in the mass balance scaling, but changes in average accumulation area ratios reflect significant changes in the scaling of both mass balance and ice volume. Copyright 1997 by the American Geophysical Union.

Bahr, D. B.; Meier, M. F.; Peckham, S. D.

1997-01-01

237

Exploring tidewater glacier retreat using past and current observations at Columbia Glacier, Alaska. (Invited)  

NASA Astrophysics Data System (ADS)

Since fulfilling Austin Post’s prediction of impending retreat in the late 1970s, Columbia Glacier has repeatedly surprised both casual and careful observers with its ability for rapid change. Over the last three decades, Columbia Glacier has lost approximately 18 km of its original 66 km length, while thinning by approximately 50% at the present terminus. The total ice volume lost to the Gulf of Alaska Estimates upwards of 120 km3 constrain the total ice volume lost to the Gulf of Alaska. Recently, the terminus supported a ~1.5 km long floating tongue for over than a year, contradicting the common assumption that the mechanical properties of temperate ice prohibit flotation over sustained time intervals. The rich history of study offers an opportunity to better understand tidewater glacier retreat, and a valuable analog to the dynamic instability underway at several ice sheet outlet glaciers. Current research aims to improve processing resolution of existing aerial photographic data, while complimenting the 30-year photogrammetric record with a suite of field observations. Recent instrumentation includes: oblique time lapse and still imagery, semi-permanent GPS, airborne radar, mass balance, passive seismology and LiDAR. This presentation will focus on innovative methods developed in recent field seasons, sharing insight each has provided into the retreat process . 1The Columbia Glacier Consortium consists of: Fabian Walter (SIO), Kenichi Matsuoka (NPI), Ben Smith (UW), Ethan Welty (CU-Boulder), Chris Larsen (UAF), Dave Finnegan (CRREL), Dan McNamara (USGS), Yushin Ahn (OSU), Julie Markus (OSU), Adam LeWinter (EIS).

O'Neel, S.; Pfeffer, W. T.; Howat, I. M.; Conway, H.; Columbia Glacier Consortium

2010-12-01

238

Worldwide dataset of glacier thickness observations compiled by literature review  

NASA Astrophysics Data System (ADS)

The volume of glaciers and ice caps is still poorly known, although it is expected to contribute significantly to changes in the hydrological cycle and global sea level rise over the next decades. Studies presenting worldwide estimations are mostly based on modelling and scaling approaches and are usually calibrated with only few measurements. Direct investigations of glacier thickness, a crucial parameter for ice volume calculations, are rather sparse but nevertheless available from all around the globe. This study presents a worldwide compilation of glacier thickness observation data. Literature review revealed mean and/or maximum thickness values from 442 glaciers and ice caps, elevation band information and point measurements for 10 and 14 glaciers, respectively. Resulting in a dataset containing glaciers and ice caps with areas ranging from smaller than 0.1 km2 (e.g. Pizolgletscher, Switzerland) to larger than 10'000 km2 (e.g. Agassiz Ice Cap, Canada), mean ice thicknesses between 4 m (Blaueis, Germany) and 550 m (Aletschgletscher, Switzerland) and 64 values for ice masses with entries from different years. Thickness values are derived from various observation methods and cover a survey period between 1923 and 2011. A major advantage of the database is the included metadata, giving information about specific fields, such as the mean thickness value of Aletschgletscher, which is only valid for the investigation area Konkordiaplatz and not over the entire glacier. The relatively small collection of records in the two more detailed database levels reflects the poor availability of such data. For modelling purposes, where ice thicknesses are implemented to derive ice volumes, this database provides essential information about glacier and ice cap characteristics and enables the comparison between various approaches. However, the dataset offers a great variety of locations, thicknesses and surface areas of glaciers and ice caps and can therefore help to compare, calibrate and validate existing models and analyses to improve the broader understanding of sea-level rise contribution from glaciers and ice caps worldwide.

Naegeli, Kathrin; Gärtner-Roer, Isabelle; Hagg, Wilfried; Huss, Matthias; Machguth, Horst; Zemp, Michael

2013-04-01

239

Inter-annual and intra-seasonal flow variability of Hubbard Glacier - an advancing tidewater glacier in SE Alaska  

Microsoft Academic Search

Hubbard Glacier is an advancing tidewater glacier in southeast Alaska. Its continued advance raises the possibility that Russell Fjord will become a dammed freshwater lake and a potential flood hazard to the town of Yakutat and its fishery. In order to predict the closure of Russell Fjord, a program of glaciological, oceanographic and meteorological measurements is underway. We will describe

L. A. Stearns; G. S. Hamilton; D. E. Lawson; D. C. Finnegan

2010-01-01

240

Integrated research on mountain glaciers: Current status, priorities and future prospects  

Microsoft Academic Search

Mountain glaciers are sensitive probes of the local climate, and, thus, they present an opportunity and a challenge to interpret climates of the past and to predict future changes. Furthermore, glaciers can constitute hazards, including: glacier outburst floods; changes in the magnitude and timing of runoff in the mountains and adjacent regions; and, through worldwide loss of glacier ice, a

Lewis A. Owen; Glenn Thackray; Robert S. Anderson; Jason Briner; Darrell Kaufman; Gerard Roe; William Pfeffer; Chaolu Yi

2009-01-01

241

Glaciers and hydrological changes in the Tien Shan: simulation and prediction  

Microsoft Academic Search

In this study, we estimated the current glacier state and forecast the potential impact of global and regional climate change on the glaciers and glacier runoff in the Tien Shan. General (G) and detailed (D) simulations were developed based on assessment of the Tien Shan glacier recession between 1943 and 2003 using an iterative stepwise increase in the equilibrium line

V B Aizen; E M Aizen; V A Kuzmichonok

2007-01-01

242

In Situ ATP Bioluminescent Measurements in Subglacial Environments - The Engabreen Glacier in the Norwegian Arctic  

Microsoft Academic Search

Engabreen is a northern outlet glacier from the western Svartisen ice cap on the Nordland coast of Norway just inside the Arctic Circle. A unique feature of the glacier is a man-made tunnel system within the bedrock beneath the glacier that offers scientists direct access to the glacier-bedrock interface. This unique facility - called the Engabreen Subglacial Laboratory - is

D. C. Cullen; J. L. Wadham; R. Pancost; S. Kelly; M. J. Barnett; M. Jackson

2007-01-01

243

Solar-radiation-maintained glacier recession on Kilimanjaro drawn from combined ice-radiation geometry modeling  

Microsoft Academic Search

In the context of investigating modern glacier recession on Kilimanjaro, which began around 1880, this study addresses the glacier regime of the vertical ice walls that typically form the margins of Kilimanjaro's summit glaciers. These walls have suffered a continuous lateral retreat during the twentieth century. To evaluate the role of solar radiation in maintaining glacier recession on Kilimanjaro, a

Thomas Mölg; Douglas R. Hardy; Georg Kaser

2003-01-01

244

ADAPTING TO THE REALITY OF CLIMATE CHANGE AT GLACIER NATIONAL PARK, MONTANA, USA  

Microsoft Academic Search

The glaciers of Glacier National Park (GNP) are disappearing rapidly and likely will be gone by 2030. These alpine glaciers have been continuously present for approximately 7,000 years so their loss from GNP in another 25 years underscores the significance of current climate change. There are presently only 27 glaciers remaining of the 150 estimated to have existed when GNP

Daniel B. Fagre

245

Cold Debris Entrainment at Taylor Glacier, Antarctica: Implications for Its Basal Thermal Regime  

Microsoft Academic Search

Taylor Glacier is an outlet glacier from the East Antarctic Ice Sheet, draining continental flow through Taylor Valley and toward McMurdo Sound. As is the case for most glaciers from the Dry Valleys, Taylor Glacier was less extensive than at present during the last glacial maximum and has since expanded, reaching now its maximum Holocene extension. Bonney drift, which can

D. Samyn; S. J. Fitzsimons; R. D. Lorrain

2005-01-01

246

Hubbard Glacier Update: Another Closure of Russell Fjord in the Making?  

Microsoft Academic Search

Hubbard Glacier is located near the community of Yakutat in southeastern Alaska. It is the largest non-polar temperate tidewater glacier in the world and has been advancing since 1890 AD, currently at a rate of 35 m a-1. Hubbard Glacier has twice closed off Russell Fjord creating enormous glacier dam lakes, once in 1986 and again 2002. Both dams failed

R. J. Motyka; D. Lawson; D. Finnegan; G. Kalli; C. Lingle

2007-01-01

247

Assessing the Impact of Retreating Glaciers on Dry-Season Discharge in a Tropical Andean Watershed  

Microsoft Academic Search

Receding glaciers in the tropical Andes are causing concerns for future water supply in a region with thermal homogeneity and a strongly seasonal precipitation cycle. Dry season runoff from glacierized catchments is buffered by glacier melt that is not completely replaced by seasonal precipitation. Our objective is to trace the changing contribution of glacier meltwater to stream flow and to

B. G. Mark; J. M. McKenzie

2006-01-01

248

Latest Pleistocene and Holocene alpine glacier fluctuations in Scandinavia  

NASA Astrophysics Data System (ADS)

During the early Holocene abrupt, decadal to centennial-scale climate variations caused significant glacier variations in Norway. Increased freshwater inflow to the North Atlantic and Arctic Oceans has been suggested as one of the most likely mechanisms to explain the abrupt and significant Lateglacial and early Holocene climatic events in NW Europe. The largest early Holocene glacier readvances occurred ~11,200, 10,500, 10,100, 9700, 9200 and 8400-8000 cal. yr BP. The studied Norwegian glaciers apparently melted away at least once during the early/mid-Holocene. The period with the most contracted glaciers in Scandinavia was between 6600 and 6000 cal. yr BP. Subsequent to ~6000 cal. yr BP the glaciers started to advance and the most extensive glaciers existed at about ~5600, 4400, 3300, 2300, 1600 cal. yr BP, and during the ‘Little Ice Age'. Times with overall less glacier activity were apparently around 5000, 4000, 3000, 2000, and 1200 cal. yr BP. It has been proposed that several glacier advances occurred in Scandinavia (including northern Sweden) at ~8500-7900, 7400-7200, 6300-6100, 5900-5800, 5600-5300, 5100-4800, 4600-4200, 3400-3200, 3000-2800, 2700-2000, 1900-1600, 1200-1000, and 700-200 cal. yr BP. Glaciers in northern Sweden probably reached their greatest ‘Little Ice Age' extent between the 17th and the beginning of the 18th centuries. Evidence for early Holocene glacier advances in northern Scandinavia, however, has been questioned by more recent, multi-disciplinary studies. The early to mid-Holocene glacier episodes in northern Sweden may therefore be questioned. Most Norwegian glaciers attained their maximum ‘Little Ice Age' extent during the mid-18th century. Cumulative glacier length variations in southern Norway, based on marginal moraines dated by lichenometry and historic evidence, show an overall retreat from the mid-18th century until the 1930s-40s. Subsequently, most Norwegian glaciers retreated significantly. Maritime outlet glaciers with short frontal time lags (<10-15 years) started to advance in the mid-1950s, whereas long outlet glaciers with longer frontal time lags (>15-20 years) continued their retreat to the 1970s and 1980s. However, maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s. After 2000 several of the observed glaciers have retreated remarkably fast (annual frontal retreat >100 m) mainly due to high summer temperatures. The general glacier retreat during the early Holocene and the Neoglacial advances after 6000 cal. yr BP are in line with orbital forcing, due to the decrease of Northern Hemisphere summer solar insolation and the increase in winter insolation. In addition, regional weather modes, such as the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO), play a significant role with respect to decadal and multi-decadal climate variability.

Nesje, A.

2009-04-01

249

Glacier annual balance measurement, prediction, forecasting and climate correlations, North Cascades, Washington 1984-2006  

NASA Astrophysics Data System (ADS)

North Cascade glacier annual balance measured on 10 glaciers from 1984-2006 yielded mean annual balance (ba) of -0.54 m/a, and -12.38 m cumulatively. This is a significant loss for glaciers that average 30-60 m in thickness, representing 20-40% of their entire volume. Two observed glaciers, Lewis Glacier and Spider Glacier, no longer exist. The ba of North Cascade glaciers is reliably calculated based on 1 April snowpack water equivalent and ablation season temperature. 1 May forecasting of ba using the Pacific Decadal Oscillation and the Multivariate El Nino Southern Oscillation circulation indices correctly determined the sign of mass balance in 42 of 47 years. Glacier annual balance forecasting is an important step for summer water resource management in glacier runoff dominated stream systems. The forecast for North Cascade glaciers in 2007 is for a negative annual balance.

Pelto, M. S.

2007-06-01

250

Glacier Sliding With Cavitation Over Irregular Beds  

NASA Astrophysics Data System (ADS)

Pressurised subglacial water affects the sliding of glaciers over hard beds through the process of cavitation. In particular, it is widely recognised that sliding velocities depend not only on shear stress but also on the difference pe between overburden and drainage pressures. However, the precise form which such a sliding law should take is unclear, and many modellers opt for a heuristic power-law ub = C? bn pe-m. Here we show how Iken's (J. Glaciol., 27, 407-422) notion of a `critical pressure' at which sliding becomes unstable can be re-interpreted as an upper bound on the amount basal shear stress which a hard bed can support. Such an upper bound clearly contradicts the sliding law above. Motivated by the need to construct a more realistic sliding law which is not in conflict with Iken's bound, we present an analysis of hard bed sliding in the presence of cavitation which extends Fowler's (Proc. R. Soc. L. Ser. A., 407, 147--170) treatment to the case of irregular beds with many different bump sizes. Our results imply that generalised power-law sliding laws should not be used indiscriminately, particularly when discussing surge-type glacier flow. Furthermore, our results highlight the need to incorporate improved drainage models into the theory of hard bed sliding.

Schoof, C.

2002-12-01

251

Multi-decadal glacier surface lowering in the Antarctic Peninsula  

NASA Astrophysics Data System (ADS)

From approximately 400 glaciers of the western Antarctic Peninsula, no in situ records of mass balance exist and their recent contribution to sea level is consequently poorly constrained. We seek to address this shortcoming by using surface elevations from USGS and BAS airborne (1948-2005) and ASTER spaceborne (2001-2010) stereo imagery, combined by using a rigorous semi-automated registration approach, to determine multi-decadal glacier surface elevation changes in the western Antarctic Peninsula for 12 glaciers. All observed glaciers show near-frontal surface lowering and an annual mean lowering rate of 0.28 ± 0.03 m/yr at the lower portion of the glaciers during the ˜4 decades following the mid-1960s, with higher rates for the glaciers in the north-west parts of the Antarctic Peninsula. Increased lowering of up to 0.6 m/yr can be observed since the 1990s, in close correspondence to increased atmospheric positive degree days. In all cases, surface lowering reduces to zero within 5 km of the glacier front at around 400 m altitude. This lowering may have been at least partially compensated for by increased high-altitude accumulation.

Kunz, Matthias; King, Matt A.; Mills, Jon P.; Miller, Pauline E.; Fox, Adrian J.; Vaughan, David G.; Marsh, Stuart H.

2012-10-01

252

Monitoring of Gangotri glacier using remote sensing and ground observations  

NASA Astrophysics Data System (ADS)

In this study, Gangotri glacier was monitored using Indian Remote Sensing (IRS) LISS-III sensor data in combination with field collected snow-meteorological data for a period of seven years (2001-2008). An overall decreasing trend in the areal extent of seasonal snow cover area (SCA) was observed. An upward shifting trend of wet snow line was observed in the beginning of melt period, i.e., in May and dominant wet snow conditions were observed between May and October. Snow meteorological parameters collected in the Gangotri sub-basin suggest reduction in fresh snowfall amount during winter, increase in rainfall amount during summer, decrease in snowfall days, increase in rainfall days and rising trend of average temperature. The prevailing wet snow condition on glacier has caused scouring of slopes which led the excessive soil/debris deposition on the glacier surface. This was observed as one of the major factor for activating fast melting and affecting the glacier health significantly. Apart from climatic conditions, terrain factors were observed for changing the glacio-morphology. The significant changes on the glacier surface were observed in the regions of abrupt slope change. The above factors affecting the Gangotri glacier health were also validated using high resolution satellite imageries and field visit. A deglaciation of 6% in overall area of Gangotri glacier was observed between the years 1962 and 2006.

Negi, H. S.; Thakur, N. K.; Ganju, A.; Snehmani

2012-08-01

253

Glacier calving, dynamics, and sea-level rise. Final report  

SciTech Connect

The present-day calving flux from Greenland and Antarctica is poorly known, and this accounts for a significant portion of the uncertainty in the current mass balance of these ice sheets. Similarly, the lack of knowledge about the role of calving in glacier dynamics constitutes a major uncertainty in predicting the response of glaciers and ice sheets to changes in climate and thus sea level. Another fundamental problem has to do with incomplete knowledge of glacier areas and volumes, needed for analyses of sea-level change due to changing climate. The authors proposed to develop an improved ability to predict the future contributions of glaciers to sea level by combining work from four research areas: remote sensing observations of calving activity and iceberg flux, numerical modeling of glacier dynamics, theoretical analysis of the calving process, and numerical techniques for modeling flow with large deformations and fracture. These four areas have never been combined into a single research effort on this subject; in particular, calving dynamics have never before been included explicitly in a model of glacier dynamics. A crucial issue that they proposed to address was the general question of how calving dynamics and glacier flow dynamics interact.

Meier, M.F.; Pfeffer, W.T.; Amadei, B.

1998-08-01

254

Mass balance, runoff and surges of Bering Glacier, Alaska  

NASA Astrophysics Data System (ADS)

The historical net, ablation and accumulation daily balances, as well as runoff of Bering Glacier, Alaska are determined for the 1951-2011 period with the PTAA (precipitation-temperature-area-altitude) model, using daily precipitation and temperature observations collected at the Cordova and Yakutat weather stations, together with the area-altitude distribution of the glacier. The model mean annual balance for this 61 yr period is -0.6 m w.e., the accumulation balance is +1.4 and the ablation balance is -2.0 m w.e. Average annual runoff is 2.5 m w.e. Periodic surges of this glacier transport large volumes of ice to lower elevations where the ablation rate is higher, producing more negative balances and increasing runoff. Runoff from Bering Glacier (derived from simulated ablation and precipitation as rain) is highly correlated with four of the glacier surges that have occurred since 1951. Ice volume loss for the 1972-2003 period measured with the PTAA model is 2.7 km3 w.e. a-1 and closely agrees with losses for the same period measured with the geodetic method. It is proposed that the timing and magnitude of daily snow accumulation and runoff, both of which are controlled by the glacier's area-altitude distribution and are calculated with the PTAA model, can be used to determine the probability that a glacier will surge.

Tangborn, W.

2013-05-01

255

New glacier inventory of Salzburg 2007/09  

NASA Astrophysics Data System (ADS)

Glacier inventories are an important data basis for several investigations such as length-, area- and volume changes in the course of climate change. The new glacier inventory of Salzburg is part of the third Austrian glacier inventory (GI3) and is valid for the years 2007 and 2009 depending on each mountain range. The first inventory (GI1) was compiled in 1969 and the second one (GI2) represents the glacier state from 1998 to 2002. In Salzburg, 150 glaciers are located in the six mountain ranges: Ankogel, Glockner, Granatspitz, Sonnblick (Goldberg), Hochkönig and Venediger. The basis for the new mapping were orthophotos of 2007 and 2009 and the DEM of the southern part of Salzburg. On the basis of former inventories area-, height- and volume changes have been calculated. The biggest loss of glacier area per mountain range was found in the Ankogel range and on Hochkönig because of the disrupted structure of the thin glaciers. Referring to the absolute values, the largest changes took place in the Glockner- and Venediger mountain range with -10.11 km2 and -9.72 km2 during the period between GI1 (1969) and GI3 (2007/2009) respectively. Due to the lack of DEMs (only the southern part was available) volume changes have been calculated for about half of all glaciers in Salzburg. These are located at the Glockner, Granatspitz and Sonnblick mountain range and showed -0.335 km3 on average changes in height of 9.3 m. An extrapolation of these changes to all of the 150 glaciers in Salzburg results in a loss of about 0.7 km3 between GI1 and GI3.

Stocker-Waldhuber, M.; Wiesenegger, H.; Fischer, A.

2012-04-01

256

Detection of glacier lake using ALOS PALSAR data at Bhutan  

NASA Astrophysics Data System (ADS)

The retreat of mountain glaciers and expansion of glacial lakes are the common issue related to global warming and it sometimes causes a sudden flood, which is called as Glacier Lake Outburst Flood (GLOF). GLOF event occurs frequently in 1960s at Himalayan glaciers. Satellite data is a sophisticated tool for this research because it is difficult to operate frequent field survey due to severe weather condition and hard accessibility. However, the optical sensor equipped on satellite has one serious problem, which is weather condition of target area. It is very difficult to acquire cloud-free data at Himalayan region on a regular schedule. Therefore, it is necessary to find another way to avoid this problem. Synthetic Aperture Radar (SAR) is one possible way because SAR can observe under all weather condition and SAR image is able to distinguish water surface and other landcovers because water surface is smoother than the other landcovers, especially in the case of L-band wavelength scale. On the other hand, SAR image has geometric and radiometric distortion due to its observation mechanism and topographic feature. Geometric distortion is able to correct by applying systematic orthorectification using DEM data. However, radiometric distortion is still remained. Recently, several radiometric terrain correction (RTC) methods are proposed. This method corrects the radiometric distortion due to local topographic slope. After RTC, radiometric distortion due to topographic relief is suppressed and backscatter brightness of the image after RTC almost depend on landcovers. In this study, we used L-band ALOS/PALSAR (SAR) data after applying RTC, ALOS/AVNIR-2 (Optical Sensor) data and SRTM-3 (DEM) data. PALSAR data is used for detection of glacier lake to set threshold of radar brightness. AVNIR-2 data is used for making glacier mask area because radar brightness of smooth glacier or icecap area is as dark as water surface on the PALSAR image. To avoid this misdetection, we applied glacier mask by AVNIR-2 data. SRTM-3 data has two ways to use. One is source data for orthorectification of PALSAR data and the other is selection of candidate for glacier lake. The selection criteria for glacier lake candidate are surface slope and topographic height. Surface slope is criterion for surface flatness and topographic height is criterion for existence condition of liquid water. We used these criteria in combination for detection of glacier lakes. Preliminary consistency comparison result with ICIMODs' glacier lake inventory detected several mistakes of ICIMOD's inventory. We also have a plan to validate these glacier lake detection results with manual interpretation results of glacial lakes using optical sensor which compiled under SATREPS (Science and Technology Research Partnership for Sustainable Development) project by JICA and JST.

Yamanokuchi, T.; Tadono, T.; Tomiyama, N.

2010-12-01

257

Comparing In Situ Spectra and Multispectral Classifications of Glacier Surfaces  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

258

Analysis of the glacier retreat in the French Alps since the 1960s based on the new glacier inventory  

NASA Astrophysics Data System (ADS)

One of the most obvious impacts of climate change in high mountain areas is the glacial retreat. Since the French glacier inventory carried out by R. Vivian in the late 1960s within the context of the WGI, there was no updated data from the overall French alpine glaciers. We present here the first results of a new diachronic inventory of the French alpine glaciers based on different sources. Glacier outlines were manually delineated using 1/25,000 topographic maps of the french National Geographical Institute (IGN) from the end of the 1960s, and IGN 50-cm-pixel orthophotographs from 2006 to 2009. For Landsat 5 TM images (30 m resolution) dating from 1985-1986, and Landsat 5 TM and Landsat 7 ETM+ images (30 and 15 m resolutions) dating from 2003, an automatic delineation with the common NDSI method was used to determine glacier limits. Each glacier has been individually checked, with a special care for debris covered and shadowed areas to adjust the delineation, using a 542 spectral bands combination. For compounded glaciers, the same limits were manually adjusted for each period. Data were integrated into a GIS and a database including all the common items (surface area, minimal and maximal elevations, aspect, debris covered area, slope…) was generated. Topographic parameters were extracted from the IGN DEM (resolution of 25 m) for the topographic maps and Landsat images from the mid-80s, and the ASTER GDEM (resolution of 30 m) for the Landsat images of the early 2000s and the orthophotographs. . Current extension of the 593 French alpine glaciers is about 275 km2. It is ~20 % less than in 1985-1986 (end of the last glacial advance period), when glacier extension was 340 km2, and ~26 % less than at the end of the 1960s, when glacier coverage was about 375 km2. Different trends are observed across the French Alps, with a stronger glacial retreat in the southern massifs: for instance, glacier shrinkage in the Ecrins massif is more than three times stronger than in the French area of the Mont Blanc massif. The size distribution of the glaciers has changed within the last 40 years: the proportion of glaciers < 0.1 km2 increased from 31% to 51%, while glaciers 0.1-0,5 km2 and >1 km2 decreased from 41% to 31%, and 28 % to 18 %, respectively. The average minimal elevation of glacier fronts has risen from about 2670 m a.s.l. at the end of the 1960s to 2760 m (+ 90 m). Results from the analysis of the relationship between glaciers retreat and their aspect and elevation will be also presented. Finally, the reconstruction of glacier extensions at the end of the Little Ice Age, based on ancient maps and geomorphological study of the proglacial margins will be presented. As an example, glacier extension in the Vanoise massif has decreased by more than 50% since the end of the LIA.

Gardent, M.; Rabatel, A.; Dedieu, J. P.; Deline, P.; Schoeneich, P.

2012-04-01

259

Climate downscaling for estimating glacier mass balances in northwestern North America: Validation with a USGS benchmark glacier  

NASA Astrophysics Data System (ADS)

An atmosphere/glacier modeling system is described for estimating the mass balances of glaciers in both current and future climate in order to estimate their probable future contributions to rising sea level. Dynamically downscaled output from a regional atmospheric model, driven by global atmospheric reanalysis, is used to force a precipitation-temperature-area-altitude (PTAA) glacier mass balance model with daily maximum and minimum temperatures and precipitation. The modeling system is verified by hindcasting the mass balances of Gulkana Glacier, a U.S. Geological Survey (USGS) benchmark glacier in the Alaska Range, U.S.A., during a ten-year period from October 1994 to September 2004. The mass balances simulated with the atmosphere/glacier modeling system are comparable to the USGS measurements, and are also in good agreement with the meteorological station observation-forced PTAA simulations. The results suggest this is a promising approach for realistic estimation of the future mass balances of the glaciers of northwestern North America.

Zhang, Jing; Bhatt, Uma S.; Tangborn, Wendell V.; Lingle, Craig S.

2007-11-01

260

Chemical denudation and silicate weathering in Himalayan glacier basins: Batura Glacier, Pakistan  

Microsoft Academic Search

The major ion, SiO2 and minor element contents of Batura Glacier meltwaters in the headwaters of the Indus Basin, Pakistan are examined. The data are used to examine the controls upon solute acquisition by runoff and to estimate solute yields. Solute yield calculations include estimation of the total and silicate-derived cationic denudation rates following the application of simple solute provenance

Andy Hodson; Phil Porter; Andy Lowe; Paul Mumford

2002-01-01

261

Rapid erosion of soft sediments by tidewater glacier advance: Taku Glacier, Alaska, USA  

Microsoft Academic Search

Taku Glacier in southeast Alaska has advanced 7.5 km over the last 115 years, overriding its own glaciomarine and outwash sediments. We have documented rapid erosion of these sediments by comparing radio echo soundings (RES) along five transects (2003–2005) to earlier RES surveys (1989 and 1994) and to early bathymetric surveys of the proglacial fjord. Erosion rates, $\\\\dot{E}$, reached 3.9

Roman J. Motyka; Martin Truffer; Elsbeth M. Kuriger; Adam K. Bucki

2006-01-01

262

Glacier-specific elevation changes in western Alaska  

NASA Astrophysics Data System (ADS)

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.

Paul, Frank; Le Bris, Raymond

2013-04-01

263

Outlet Glacier-Ice Shelf-Ocean Interactions: Pine Island Glacier in the Amundsen Sea Embayment  

NASA Astrophysics Data System (ADS)

While the massive interior regions of the Antarctic and Greenland Ice Sheets are presently "resting quietly", the lower elevations of many outlet glaciers are experiencing dramatic adjustments due to changes in ice dynamics and/or surface mass balance. Oceanic and/or atmospheric forcing in these marginal regions often leads to mass deficits for entire outlet basins. Recent observations and theoretical studies indicate that the large and ongoing mass deficit in the Amundsen Sea sector of Antarctica is due to ice-ocean interactions and the subsequent propagation of these changes into the upstream reservoirs of the Pine Island and Thwaites Glaciers. Accurate assessments of future sea-level rise require careful consideration of potential forcings at the ice front as well as an understanding of the timing and extent of inland responses to those forcings. To this end, the higher-order flowline model used in this study incorporates both published data and 3-D model output as boundary and initial conditions to simulate the evolution of Pine Island Glacier over the centennial timescale. These SeaRISE experiments are focused on ice-flow sensitivity to changes in climate, subglacial sliding, and ocean-induced melting at the ice sheet perimeter.

Bertini, G. T.; Parizek, B. R.; Edwards, R. A.; Wolfe, D.; Walker, R. T.

2011-12-01

264

Geodetic observations of short-time-scale changes in glacier flow at Helheim and Kangerdlugssuaq Glaciers, East Greenland  

NASA Astrophysics Data System (ADS)

Evidence obtained by several workers during the past few years has shown that the major outlet glaciers in Greenland can both accelerate and decelerate more rapidly than previously appreciated. Some abrupt accelerations at the largest outlet glaciers, including Jakobshavn Isbrae and Helheim and Kangerdlugssuaq Glaciers, have been linked to large-scale calving events and glacial earthquakes (Nettles et al., 2008; Amundson et al., 2008). Many questions regarding the dynamics of these glaciers remain unresolved, including the nature and cause of rapid deceleration events and the influence of surface melting and hydrology on variations in glacier speed. We have operated a GPS network on the surface of Helheim Glacier during the four summers of 2006--2009, as well as during the fall of 2008, late spring of 2009, and fall of 2009. Several auxiliary geophysical sensors have also been operated nearby. This short four-year period has revealed both glacier acceleration and deceleration, occurring on interannual to sub-hour timescales. The number of glacial earthquakes observed during this time period has also varied significantly. During the summer of 2009, we also operated a GPS network on Kangerdlugssuaq Glacier, obtaining a full season of high-time-resolution observations of glacier motion and deformation. The GPS data acquired during 2009 come primarily from a low-cost GPS receiver system designed by the authors to provide data security and near-real-time data delivery via a combination of radio and satellite telemetry. Here, we present results from the extended 2008/2009 seasons at Helheim and Kangerdlugssuaq in the context of our previous observations and longer-term observations of other workers.

Nettles, M.; Elosegui, P.; Larsen, T.; Davis, J. L.; Hamilton, G. S.; Stearns, L. A.; Andersen, M. L.; de Juan, J.; Malikowski, E.; Gonzalez, I.; Okal, M.; Johns, B.; Ekstrom, G.; Ahlstrøm, A.; Stenseng, L.; Khan, S. A.; Schild, K. M.; Forsberg, R.; Veitch, S. A.

2009-12-01

265

Glaciers in a changing global climate: first results of worldwide glacier mass balance measurements 2000/2001  

NASA Astrophysics Data System (ADS)

Glacier signals from mountain areas are key elements of early detection strategies for dealing with possible man-induced climate change. The IPCC Third Assessment Report indeed defines mountain glaciers as one of the best natural indicators of atmospheric warming with the highest reliability ranking. In the chain of processes linking climate and glacier fluctuations, glacier length variation is the indirect/delayed response, whereas glacier mass change is the direct/undelayed reaction. Internationally coordinated long-term monitoring of glaciers started in 1894. The responsibility to collect and publish standardized data has been assumed since 1986 by the World Glacier Monitoring Service (WGMS). This work is primarily being carried out under the auspices of the International Commission on Snow and Ice (ICSI/IAHS) and the Federation of Astronomical and Geophysical Services (FAGS/ICSU). The WGMS maintains data exchange with the ICSU World Data Center A (WDC-A) for Glaciology in Boulder, Colorado. Corresponding data bases and measurement networks form an essential part of the Global Terrestrial Network for Glaciers (GTN-G: operated by the WGMS) as a pilot project within the Global Terrestrial Observing System (GTOS/GCOS). A network of 60 glacier mass balance observations provides information on presently observed rates of change in glacier mass, corresponding acceleration trends and regional distribution patterns. A preliminary calculation of the mass balance observations in 2000/2001 relating to 23 selected data sets provide a mean specific (annual) net balance of -367 mm w.e., 26 % of the observed balances were positive. The corresponding mean in six mountain ranges was -571 mm w.e. Such values indicate that mass losses in 2000/2001 have been less extreme than in the extraordinary years before but are still strongly negative. Over the past two decades glacier melt appears to continue at a considerable and possibly even an accelerating rate. The observed average changes in ice thickness interpreted as corresponding amounts of latent heat required for melting reflect an additional energy flux of a few W/m2 with an acceleration trend of some hundreds of a W/m2 per year. Such values are broadly consistent with model calculations. It should, however, be noted that the processes involved (energy balance, glacier dynamics) are complex and not fully understood.

Frauenfelder, R.; Hoelzle, M.; Haeberli, W.

2003-04-01

266

The mass balance and the flow of a polythermal glacier, McCall Glacier, Brooks Range, Alaska  

NASA Astrophysics Data System (ADS)

Studies of surface motion and geometry, ice thickness, and mass balance were carried out on the arctic McCall Glacier. They revealed characteristic processes of glacier flow and mass balance that independently reflect the polythermal temperature regime of the glacier, which consists of cold ice except for a discontinuous layer of temperate ice at the base. Analysis of the present flow of McCall Glacier showed the longitudinal stress coupling length to be significantly larger than on temperate glaciers. This is a consequence of the smaller mass balance gradients and associated lower strain rates of arctic glaciers. Furthermore, flow analysis suggests year-round basal sliding beneath a section of the lower glacier, which accounts for more than 70% of the total motion. This sliding anomaly is reflected in corresponding anomalies of the observed ice thickness and surface profiles. Changes in surface velocity, both on a decadal and on a seasonal scale, were also studied. Velocities during the short summer season increase by up to 75% above winter values as a result of enhanced basal sliding at the temperate glacier bed. The zone affected by this speed-up extends upglacier of any obvious sources of meltwater input to the bed. The mass balance of McCall Glacier exhibits a trend towards increasingly negative values. This is shown by both annual measurements during 1969-72 and 1993-96 and by comparing long-term values for two periods, 1957-71 and 1972-93. The contribution of refreezing surface water in the cold surface layers of firn and ice (internal accumulation) to the net accumulation was found to increase from about 40% in the 1970s to more than 90% in the 1990s. Comparative studies of long-term volume changes of neighboring glaciers showed that the McCall Glacier mass balance is regionally representative. Existing good correlations of the mass balance with meteorological parameters recorded by a weather station more than 400 km to the east furthermore suggest that McCall Glacier is representative on a synoptic scale and thus is a valuable indicator of climate change in the Arctic.

Rabus, Bernhard Theodor

267

Analysis of glacier facies using satellite techniques  

USGS Publications Warehouse

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

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

1991-01-01

268

Melting glaciers can change Earth's gravity field  

NASA Astrophysics Data System (ADS)

The Earth's rotation causes mass from the ductile mantle to bulge at the equator, making the radius of the Earth about 21 kilometers greater at the equator than at the poles. Over the past 20,000 or so years, the Earth has been becoming more round as it adjusts to the withdrawal of vast continental glaciers after the last ice age: Without the weight of ice pressing down, land has rebounded to give the Earth a more spherical shape. This in turn means that the Earth|'s geoid—the average gravity field across the globe—also became more round. However, in the early 1990s, scientists began to notice that postglacial rebound was starting to become offset by something else, causing the Earth's gravity field to cease changing shape.

Kumar, Mohi

2011-09-01

269

Glaciers and ice sheets as a biome.  

PubMed

The tundra is the coldest biome described in typical geography and biology textbooks. Within the cryosphere, there are large expanses of ice in the Antarctic, Arctic and alpine regions that are not regarded as being part of any biome. During the summer, there is significant melt on the surface of glaciers, ice caps and ice shelves, at which point microbial communities become active and play an important role in the cycling of carbon and other elements within the cryosphere. In this review, we suggest that it is time to recognise the cryosphere as one of the biomes of Earth. The cryospheric biome encompasses extreme environments and is typified by truncated food webs dominated by viruses, bacteria, protozoa and algae with distinct biogeographical structures. PMID:22000675

Anesio, Alexandre M; Laybourn-Parry, Johanna

2011-10-12

270

Glacier loss on Kilimanjaro continues unabated.  

PubMed

The dramatic loss of Kilimanjaro's ice cover has attracted global attention. The three remaining ice fields on the plateau and the slopes are both shrinking laterally and rapidly thinning. Summit ice cover (areal extent) decreased approximately 1% per year from 1912 to 1953 and approximately 2.5% per year from 1989 to 2007. Of the ice cover present in 1912, 85% has disappeared and 26% of that present in 2000 is now gone. From 2000 to 2007 thinning (surface lowering) at the summits of the Northern and Southern Ice Fields was approximately 1.9 and approximately 5.1 m, respectively, which based on ice thicknesses at the summit drill sites in 2000 represents a thinning of approximately 3.6% and approximately 24%, respectively. Furtwängler Glacier thinned approximately 50% at the drill site between 2000 and 2009. Ice volume changes (2000-2007) calculated for two ice fields reveal that nearly equivalent ice volumes are now being lost to thinning and lateral shrinking. The relative importance of different climatological drivers remains an area of active inquiry, yet several points bear consideration. Kilimanjaro's ice loss is contemporaneous with widespread glacier retreat in mid to low latitudes. The Northern Ice Field has persisted at least 11,700 years and survived a widespread drought approximately 4,200 years ago that lasted approximately 300 years. We present additional evidence that the combination of processes driving the current shrinking and thinning of Kilimanjaro's ice fields is unique within an 11,700-year perspective. If current climatological conditions are sustained, the ice fields atop Kilimanjaro and on its flanks will likely disappear within several decades. PMID:19884500

Thompson, L G; Brecher, H H; Mosley-Thompson, E; Hardy, D R; Mark, B G

2009-11-02

271

Glacier loss on Kilimanjaro continues unabated  

PubMed Central

The dramatic loss of Kilimanjaro's ice cover has attracted global attention. The three remaining ice fields on the plateau and the slopes are both shrinking laterally and rapidly thinning. Summit ice cover (areal extent) decreased ?1% per year from 1912 to 1953 and ?2.5% per year from 1989 to 2007. Of the ice cover present in 1912, 85% has disappeared and 26% of that present in 2000 is now gone. From 2000 to 2007 thinning (surface lowering) at the summits of the Northern and Southern Ice Fields was ?1.9 and ?5.1 m, respectively, which based on ice thicknesses at the summit drill sites in 2000 represents a thinning of ?3.6% and ?24%, respectively. Furtwängler Glacier thinned ?50% at the drill site between 2000 and 2009. Ice volume changes (2000–2007) calculated for two ice fields reveal that nearly equivalent ice volumes are now being lost to thinning and lateral shrinking. The relative importance of different climatological drivers remains an area of active inquiry, yet several points bear consideration. Kilimanjaro's ice loss is contemporaneous with widespread glacier retreat in mid to low latitudes. The Northern Ice Field has persisted at least 11,700 years and survived a widespread drought ?4,200 years ago that lasted ?300 years. We present additional evidence that the combination of processes driving the current shrinking and thinning of Kilimanjaro's ice fields is unique within an 11,700-year perspective. If current climatological conditions are sustained, the ice fields atop Kilimanjaro and on its flanks will likely disappear within several decades.

Thompson, L. G.; Brecher, H. H.; Mosley-Thompson, E.; Hardy, D. R.; Mark, B. G.

2009-01-01

272

Fast-flowing outlet glaciers on Svalbard ice caps  

SciTech Connect

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

Dowdeswell, J.A. (Univ. of Cambridge (England)); Collin, R.L. (University College of Wales, Aberystwyth (England))

1990-08-01

273

The contribution potential of glaciers to Himalaya river runoff  

NASA Astrophysics Data System (ADS)

Glaciers are reported to crucially contribute to the water availability for large population numbers around the Himalaya. They are expected to change their water storage capacity under the changing climate conditions with major detrimental consequences for fresh water supply. The potential to modify river runoff of both the storage capacity in glaciers and its variability differs in different climate regimes and decreases downriver. The lack of appropriate data records and model performance leaves us with only vague ideas for most river systems. We present a simple method to assess the contribution potential of glaciers to river runoff from data sets available. Glacier contribution to runoff is shown together with population numbers downriver. Respective results are presented and discussed in simple plots and in a summary map.

Kaser, Georg; Grosshauser, Martin

2010-05-01

274

Geology Fieldnotes: Glacier Bay National Park and Preserve, Alaska  

NSDL National Science Digital Library

This park is home to the Fairweather Mountains, which formed during the Laramide Orogeny, as well as many glaciers. The site includes introductory information about glacial formation and icebergs, links to park maps, and visitor information.

275

The Role of Glaciers in the Hydrology of Nepal (Invited)  

NASA Astrophysics Data System (ADS)

Glaciers are a component of the hydrologic regime of many large mountain ranges of the world, including the Himalaya. However, the hydrologic regime of Himalayan catchment basins and the role of glaciers in the hydrologic regime of this region are not well understood. Current concern regarding the impact of the retreat of Himalayan glaciers on water supplies poses an urgent need to resolve basic questions related to the components of the total water budget and, specifically, to determine the impact of glacier change on regional-scale water supplies. The ultimate goal of this project is to estimate the potential impact of continued glacier retreat across the entire Himalayan region, although the results presented here are limited to assessing and quantifying the role of glacier ice melt in the hydrologic regime of Nepal. There are approximately 3250 glaciers in the Nepal Himalaya, covering an area of slightly more than 5,300 km2, and containing some 460 km3 of ice. These glaciers are located on, or near, the crest of the Himalaya, with the bulk of the ice contained in basins that are at altitudes generally between 4,000 - 6000 meters above sea level. The methodology developed for this study involves establishing a relationship between the area-altitude distributions of catchment basins and glaciers, and associated water and energy exchange gradients. Two area-altitude distributed process models were developed: an orographic runoff model and a glacier melt model. The orographic runoff model is based on the relationship between basin mean specific runoff and the mean altitude of each basin with an area-altitude distribution of streamflow for each 1000 meter belt calculated as the product of the specific runoff depth and the area of the belt. The glacier melt model is based on melt from 100 meter area-altitude belts for the glacierized portion of each catchment and involves defining an “ablation gradient”, the rate of increasing specific ice melt with decreasing altitude in the ablation zone. Results indicate that the annual contribution of glacier melt water to streamflow in the Nepal Himalayas varies among catchment basins from 2 to 30%, averaging approximately 10% of the total annual flow volume measured at lower altitude hydrometric stations. This represents approximately 4% of the total annual streamflow volume of the rivers of Nepal. Results also suggest that neither the timing nor the volume of the streamflow of the rivers of Nepal will be significantly affected in the near future by a continued retreat of the glaciers. We are currently applying a similar methodology to assess the contribution of glacier and snow melt to the hydrology of the upper Indus Basin located at the extreme western end of the Greater Himalaya with a climate and glacier regime that differs significantly from that of Nepal. Preliminary results from the Indus study will also be presented.

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

2010-12-01

276

Snow and Glacier Investigations by ERS-1 SAR: First Results.  

National Technical Information Service (NTIS)

The backscattering behavior of snow and glacier ice was investigated using 12 ERS-1 Synthetic Aperture Radar (SAR) scenes acquired over the test site Otztal in the Austrian Alps between Apr. and Oct. 1992. Significant temporal changes of the backscatterin...

H. Rott T. Nagler

1993-01-01

277

Glacier elevation changes on the Tibetan Plateau derived by ICESat  

NASA Astrophysics Data System (ADS)

Glaciers are a sensitive indicator for climate change in high mountain regions where climate stations are rare or non-existent. In addition, glacier changes have a significant impact on the hydrological cycle of the vulnerable region of the Tibetan Plateau. Therefore a continuous monitoring of glaciers is necessary. In-situ measurements are essential but can only be conducted at a very limited number of glaciers in this large and remote region due to enormous logistical efforts and high costs. Remote sensing techniques are suitable to complement these in-situ measurements and address a large area simultaneously. Traditionally, mountain glaciers are monitored in terms of area changes from aerial or satellite image data. However, these changes show, in contrast to volume changes, a delayed signal to climate only. In order to estimate volume changes of glaciers on the Tibetan Plateau data from the Geoscience Laser Altimeter System (GLAS) carried on-board the Ice Cloud and Elevation Satellite (ICESat) was used for extraction of elevation changes for the period 2003 to 2009. GLAS shots over glaciers were selected using the Global Land Ice Measurements from Space (GLIMS) dataset with support of recent cloud free Landsat scenes obtained from USGS. ICESat repeat-tracks are spatially close but do not match exactly. They can be horizontally separated by up to 3000 m. Therefore, an independent reference surface is used for a multi-temporal comparison of GLAS shots. For this purpose we use a Digital Elevation Model (DEM) acquired in February 2000 by the Shuttle Radar Topography Mission (SRTM). Glaciers with an adequate ICESat data coverage (approximately 12% of the glaciers captured in the GLIMS database) were grouped according to the mountain chains in certain compact geographic regions. Mean trends in glacier elevation changes were estimated for these regions for the seven years of ICESat's lifetime. Preliminary results suggest a heterogeneous wastage of glaciers across the Tibetan Plateau with higher melting rates in the East, (e.g. Nyainqentanglha Mountains) and lower ones in the West (e.g. Kunlun Shan).

Neckel, N.; Kropacek, J.; Bolch, T.

2012-04-01

278

Glacier annual balance measurement, forecasting and climate correlations, North Cascades, Washington 1984-2006  

NASA Astrophysics Data System (ADS)

North Cascade glacier annual balance measured on 10 glaciers from 1984-2006 yielded mean annual balance (ba) of -0.54 m/a, and -12.38 m cumulatively. This is a significant loss for glaciers that average 30-60 m in thickness, 20-40% of their entire volume. Two observed glaciers, Lewis Glacier and Spider Glacier, no longer exist. The ba of North Cascade glaciers is reliably calculated, correlation coefficient 0.91, using 1 April snowpack water equivalent and ablation season temperature. Utilizing ba from 10 glaciers 1984-2006 and net balance (bn) from South Cascade 1960-2005, a set of forecast rules for glacier mass balance were derived utilizing October-April Pacific Decadal Oscillation and Multivariate El Nino Southern Oscillation index values. The forecast rules provide a correct assessment in 41 of the 46 years for South Cascade Glacier and 20 of 23 years for NCGCP glaciers. Glacier annual balance forecasting is an important step for summer water resource management in glacier runoff dominated stream systems. The forecast for North Cascade glaciers in 2007 is for a negative ba.

Pelto, M. S.

2008-01-01

279

Dynamics of calving glaciers: comparison of three models  

Microsoft Academic Search

A minimal model of a tidewater glacier based solely on mass conservation is compared with\\u000atwo one-dimensional numerical flowline models, one with the calving rate proportional to water depth,\\u000aand the other with the flotation criterion as a boundary condition at the glacier terminus. The models\\u000awere run with two simplified bed geometries and two mass-balance formulations. The models simulate

F. M. Nick; J. Oerlemans

2006-01-01

280

Eukaryotic microorganisms in cold environments: examples from Pyrenean glaciers  

PubMed Central

Little is known about the viability of eukaryotic microorganisms preserved in icy regions. Here we report on the diversity of microbial eukaryotes in ice samples derived from four Pyrenean glaciers. The species composition of eukaryotic communities in these glaciers is unknown mostly because of the presence of a multi-year ice cap, and it is not clear whether they harbor the same populations. The recent deglaciation of these areas is allowing an easy access to glacial layers that correspond to the “Little Ice Age” although some isolated deposits are attributed to previous glacial cycles. In this study, we use molecular 18S rRNA-based approaches to characterize some of the microbial eukaryotic populations associated with Pyrenean glaciers. Firstly, we performed a chemical and microscopical characterization of ice samples. Secondly, molecular analyses revealed interesting protist genetic diversity in glaciers. In order to understand the microbial composition of the ice samples the eukaryotic communities resident in the glacial samples were examined by amplifying community DNA and constructing clone libraries with 18S rRNA primers. After removal of potential chimeric sequences and dereplication of identical sequences, phylogenetic analysis demonstrated that several different protists could be identified. Protist diversity was more phylum rich in Aneto and Monte Perdido glaciers. The dominant taxonomic groups across all samples (>1% of all sequences) were Viridiplantae and Rhizaria. Significant variations in relative abundances of protist phyla between higher and lower glaciers were observed. At the genus level, significant differences were also recorded for the dominant genera Chloromonas, Raphidonema, Heteromita, Koliella, and Bodomorpha. In addition, protist community structure showed significant differences between glaciers. The relative abundances of protist groups at different taxonomic levels correlated with the altitude and area of glaciers and with pH of ice, but little or no relationships to other chemical characteristics were found.

Garcia-Descalzo, Laura; Garcia-Lopez, Eva; Postigo, Marina; Baquero, Fernando; Alcazar, Alberto; Cid, Cristina

2013-01-01

281

Observing Outlet Glacier Motion Using High Rate GPS  

Microsoft Academic Search

Observations of short-term variations in the flow speed of marine-terminating outlet glaciers are essential for understanding the dynamics of these systems in relation to changes in surface melting and calving. Due to their inaccessiblity and highly crevassed and unstable surfaces, there is little existing ice motion data for polar outlet glaciers at high-temporal and spatial resolution over multi-week timescales. Here

A. Brown; I. Howat; A. Behar; J. E. Box; S. Tulaczyk

2008-01-01

282

Late Pleistocene and Holocene palaeoclimate and glacier fluctuations in Patagonia  

Microsoft Academic Search

This paper presents the evidence for Late Pleistocene and Holocene palaeoclimate and glacier fluctuations of the two major icefields in Patagonia, the Hielo Patagónico Norte (47°00?S, 73°39?W) and the Hielo Patagónico Sur (between 48°50?S and 51°30?S). The palaeoenvironmental evidence suggests that glaciers still covered large areas of Patagonia at approximately 14,600 14C years BP. Uniform and rapid warming took place

Neil F. Glasser; Stephan Harrison; Vanessa Winchester; Masamu Aniya

2004-01-01

283

Glaciers, Climate and Society: Online Resources and Bibliography  

NSDL National Science Digital Library

Glaciers, Climate, and Society is designed to be a central location where students, teachers, parents, and researchers can begin their search for information and resources regarding glacier hazards, climate, water, and the human dimensions of these issues. Featuring many photos and embedded videos, the site provides K-12 education resources, issue summaries, information on Professor Mark Carey's research in the Andes, a resources and links page, and much more.

Carey, Mark

284

Pine Island Glacier - basal properties and sliding laws  

NASA Astrophysics Data System (ADS)

The dynamics of the Antarctic Ice Sheet can be well seen and studied on the behavior of Pine Island Glacier. Despite the long time believe in a slow response of the ice sheet to changing atmospheric and oceanic forcing, Pine Island has shown acceleration, thinning and a significant grounding line retreat in the past decades. These ongoing processes are coinciding with a concentrated mass loss in the area around Pine Island Glacier, the Amundsen Sea Embayment. The area is of additional interest due to its retrograde bed slope below the glacier. The postulated instability of the setting turns the glacier into an even more suitable object for modeling studies. Plenty of working groups have conducted modeling studies of Pine Island Glacier with varying model complexity and diverse focuses. We want to add to this by conducting model experiments with a diagnostic 3D full-stokes model of Pine Island Glacier. The model is thermo-mechanically coupled and implemented with the commercial finite-element package COMSOL Multiphysics©. We use remotely sensed surface velocity data to validate our results. The focus of our work lies on the basal properties below the glacier and the connection to sliding behavior. We believe that this is a crucial part, as different basal conditions might cause different responses to ongoing changes in the area. Recent studies presented evidence for the existence of a water saturated sediment basin below the main trunk of the glacier. We conduct a variety a numerical experiments with which we test different approaches of combining information about the basal properties with sliding laws.

Wilkens, Nina; Humbert, Angelika

2013-04-01

285

Temperate Ice Under Jakobshavn Isbrae and Other Greenland Glaciers  

Microsoft Academic Search

Jakobshavn Isbrae, western Greenland's largest outlet glacier, drains 6.5% of the ice sheet's area and therefore may be poised to make rapid contributions to global sea level rise. Indeed, in the late 1990s the glacier doubled in speed as its floating ice tongue disintegrated. Driving stresses up to 300 kPa suggest that a considerable amount of ice deformation combines with

K. E. Poinar; I. R. Joughin

2010-01-01

286

Fast-flowing outlet glaciers on Svalbard ice caps  

Microsoft Academic Search

Four well-defined outlet glaciers are present on the 2510 km² cap of Vestfonna in Nordaustlandet, Svalbard. Airborne radio echo sounding and aerial-photograph and satellite-image analysis methods are used to analyze the morphology and dynamics of the ice cap and its component outlet glaciers. The heavily crevassed outlets form linear depressions in the ice-cap surface and flow an order of magnitude

Julian A. Dowdeswell; R. Lindsay Collin

1990-01-01

287

Velocity change and ice discharge from Antarctic Peninsula Glaciers  

NASA Astrophysics Data System (ADS)

Satellite radar interferometry data from ERS-1/2 acquired in 1996 were employed to map the ice velocity of the outlet glaciers discharging ice along the eastern flank of the Peninsula from 64 south to 71 south, and along the former Wordie Ice Shelf in the west. Differential radar interferometry was employed to map the position of the glacier grounding lines. Estimates of ice thickness at the grounding line were obtained from hydrostatic equilibrium using existing topographic maps, or from direct measurement from radio echo sounding by BAS in 1994-2000 and CECS/NASA in 2002. The resulting glacier fluxes were compared to snow accumulation compiled by Turner et al. (2002) to deduce first-order estimates of the glacier mass balance. In places where ice shelves are known to have been retreating, we compared the 1996 velocities with older measurements as well as more recent estimates from ERS-1/2 (2000), Radarsat (2000-2003) and Aster (2002). On Fleming Glacier, we find a large increase in flow speed from 1972 to 1996, with no further increase after 1996, which suggests that the glacier did respond to the collapse of Wordie Ice Shelf several decades ago. On Drygakski glacier in the east, we confirm a large acceleration of the glacier following the collapse of Larsen B, as revealed by Rott et al. (2002), which is continuing to this date. We conclude on the effect of retreating ice shelves on the evolution of inland ice in this sector of Antarctica and on its impact on sea level rise.

Rignot, E.; Pritchard, H.; Vaughan, D.; Rivera, A.; Kanagaratnam, P.; Casassa, G.; Thomas, R.

2003-12-01

288

Tropical glaciers and climate dynamics: Resolving the linkages  

NASA Astrophysics Data System (ADS)

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

Mölg, Thomas

2013-04-01

289

High sensitivity of tidewater outlet glacier dynamics to shape  

NASA Astrophysics Data System (ADS)

Variability in tidewater outlet glacier behavior under similar external forcing has been attributed to differences in outlet shape (i.e., bed elevation and width), but this dependence has not been investigated in detail. Here we use a numerical ice flow model to show that the dynamics of tidewater outlet glaciers under external forcing are highly sensitive to width and bed topography. Our sensitivity tests indicate that for glaciers with similar discharge, the trunks of wider glaciers and those grounded over deeper basal depressions tend to be closer to flotation, so that less dynamically induced thinning results in rapid, unstable retreat following a perturbation. The lag time between the onset of the perturbation and unstable retreat varies with outlet shape, which may help explain intra-regional variability in tidewater outlet glacier behavior. Further, because the perturbation response is dependent on the thickness relative to flotation, varying the bed topography within the range of observational uncertainty can result in either stable or unstable retreat due to the same perturbation. Thus, extreme care must be taken when interpreting the future behavior of actual glacier systems using numerical ice flow models that are not accompanied by comprehensive sensitivity analyses.

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

2013-06-01

290

High sensitivity of tidewater outlet glacier dynamics to shape  

NASA Astrophysics Data System (ADS)

Variability in tidewater outlet glacier behavior under similar external forcing has been attributed to differences in outlet shape (i.e. bed elevation and width), but this dependence has not been investigated in detail. Here we use a numerical ice flow model to show that the dynamics of tidewater outlet glaciers under external forcing are highly sensitive to width and bed topography. Our sensitivity tests indicate that for glaciers with similar discharge, the trunks of wider glaciers and those grounded over deeper basal depressions tend to be closer to flotation, so that less dynamically induced thinning results in rapid, unstable retreat following a perturbation. The lag time between the onset of the perturbation and unstable retreat varies with outlet shape, which may help explain intra-regional variability in tidewater outlet glacier behavior. Further, because the perturbation response is dependent on the thickness relative to flotation, varying the bed topography within the range of observational uncertainty can result in either stable or unstable retreat due to the same perturbation. Thus, extreme care must be taken when interpreting the future behavior of actual glacier systems using numerical ice flow models that are not accompanied by comprehensive sensitivity analyses.

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

2013-02-01

291

Irreversible mass loss of Canadian Arctic Archipelago glaciers  

NASA Astrophysics Data System (ADS)

The Canadian Arctic Archipelago (CAA) contains the largest volume of glacier ice on Earth outside of Antarctica and Greenland. In the absence of significant calving, CAA glacier mass balance is governed by the difference between surface snow accumulation and meltwater runoff—surface mass balance. Here we use a coupled atmosphere/snow model to simulate present-day and 21st century CAA glacier surface mass balance. Through comparison with Gravity Recovery and Climate Experiment mass anomalies and in situ observations, we show that the model is capable of representing present-day CAA glacier mass loss, as well as the dynamics of the seasonal snow cover on the CAA tundra. Next, we force this model until 2100 with a moderate climate warming scenario (AR5 RCP4.5). We show that enhanced meltwater runoff from CAA glaciers is not sufficiently compensated by increased snowfall. Extrapolation of these results toward an AR5 multimodel ensemble results in sustained 21st century CAA glacier mass loss in the vast majority (>99%) of the ~7000 temperature realizations.

Lenaerts, Jan T. M.; Angelen, Jan H.; Broeke, Michiel R.; Gardner, Alex S.; Wouters, Bert; Meijgaard, Erik

2013-03-01

292

Cold-based mountain glaciers on Mars: Western Arsia Mons  

NASA Astrophysics Data System (ADS)

Surface environmental conditions on Mars are currently extremely cold and hyperarid, most equivalent to polar deserts on Earth. Coupling newly acquired Mars data with field-based observations regarding the flow, surface morphology, and depositional history of polar glaciers in Antarctica, we show that the multiple facies of an extensive fan-shaped deposit on the western flanks of Arsia Mons volcano are consistent with deposition from cold-based mountain glaciers. An outer ridged facies that consists of multiple laterally extensive, arcuate and parallel ridges, resting without disturbance on both well-preserved lava flows and an impact crater, is interpreted as drop moraines formed at the margin of an ablating and predominantly receding cold-based glacier. A knobby facies that consists of equidimensional knobs, each to several kilometers in diameter, is inward of the ridges; this facies is interpreted as a sublimation till derived from in situ downwasting of ash-rich glacier ice. A third facies comprising distinctive convex-outward lobes with concentric parallel ridges and aspect ratios elongated downslope likely represents rock-glacier deposits, some of which may still be underlain by a core of glacier ice. Taken together, these surficial deposits show that the western flank of Arsia Mons was occupied by an extensive mountain glacial system accumulating on, and emerging from, the upper slopes of the volcano and spreading downslope to form a piedmont-like fan.

Head, James W.; Marchant, David R.

2003-07-01

293

Feedbacks and mechanisms affecting the global sensitivity of glaciers to climate change  

NASA Astrophysics Data System (ADS)

Mass loss by glaciers has been an important contributor to sea level rise in the past and is projected to contribute a substantial fraction of total sea level rise during the 21st century. Here, we use a model of the world's glaciers in order to quantify equilibrium sensitivities of global glacier mass to climate change, and to investigate the role of changes in glacier hypsometry for long term mass changes. We find that 21st century glacier mass loss to a~large degree is governed by the glaciers responding to 20th century climate change. This limits the influence of 21st century climate change on glacier mass loss, and explains why there are relatively small differences in glacier mass loss under greatly different scenarios of climate change. Because of the geographic distribution of glaciers, both temperature and precipitation anomalies experienced by glaciers are vastly stronger than on global average. The projected increase in precipitation partly compensates for the mass loss caused by warming, but this compensation is negligible at higher temperature anomalies since an increasing fraction of precipitation at the glacier sites it liquid. Loss of low-lying glacier area, and more importantly, eventual complete disappearance of glaciers, strongly limit the projected sea level contribution from glaciers in coming centuries. The adjustment of glacier hypsometry to changes in the forcing reduces the sensitivity of global glacier mass to changes in global mean temperature by a factor of two to three. This result is a second reason for the relatively weak dependence of glacier mass loss on future climate scenario, and helps explain why glacier mass loss in the first half of the 20th century was of the same order of magnitude as in the second half of the 20th century, even though the rate of warming was considerably smaller.

Marzeion, B.; Jarosch, A. H.; Gregory, J. M.

2013-06-01

294

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

NASA Astrophysics Data System (ADS)

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-à-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.

Ganjoo, R. K.

2011-12-01

295

Glaciers and Late Quaternary glacial deposits of Turkey  

NASA Astrophysics Data System (ADS)

Turkish glaciers and Late Quaternary glacial deposits are observed in 3 regions: 1. The Taurus Mountain Range (Mediterranean coast and SE Turkey): Two thirds of the present day glaciers are concentrated in the SE part. Among these mountains, Mount Cilo (4168 m) alone supports more than ten glaciers, couple of them 4 km long. In the central part, Aladag (3756 m) and Bolkardag (3524 m) Mountains contain few small glaciers. Small ice caps developed on top of both mountains in Pleistocene. Several U-shaped valleys were carved by glaciers that formed different types of moraines. Even though there are signs of past glacial activity in Beydag (3086 m), Akdag (3016 m) and Sandiras Mountains (2295 m) no glaciers are present in the W Taurus Mountains today. 2. The Pontic Mountain Range (E Black Sea coast): The highest peak is Mount Kaçkar (3932 m) where five glaciers are developed. Several other mountains such as Verçenik (3710 m), Bulut (3562 m), Altiparmak (3353 m), Karagöl (3107 m) and Karadag (3331 m) also support various glaciers. Large U-shaped valleys containing terminal, lateral and ground moraines are observed although the present humid climatic conditions altered most of them. 3. Volcanoes and independent mountain chains scattered in the Anatolian Plateau: The volcanoes in the interior of the country support active glaciers and show signs of past glacial activity. Among them, Mount Agri (Ararat) (5165 m) is the only mountain on which a 10 km2 recent ice cap is developed. Eleven glaciers emerged from the summit, descending down to 3900 m on the N-facing slope and 4200 m on the S facing slope. The near absence of moraines can be explained by the lack of confining ridges to control valley glaciers, by insufficient debris load in the ice to form moraines and by volcanic eruptions that later covered the pre-existing moraines. Other important volcanoes, Mount Süphan (4058 m) and Mount Erciyes (3916 m) also contain active glaciers and well preserved moraines. Apart from the volcanoes, few other mountains in Central Anatolia, such as Uludag (2543 m), Mercan (3368 m) and Mescid (3239 m) bear signs of past glacial activity. The absence of dating of the morainic landforms makes it difficult to assign a precise age to the past glacial periods. However a project that aims to establish glacial chronlogies for the above mentioned mountains by using in situ cosmogenic 36Cl in the moraines, is recently developed. The data available on glaciers indicate that the most recent glacier retreat probably started at the beginning of the 20th century, becoming faster since the 1930's. This shrinkage trend is yet to be quantified by additional field observations in order to understand the glacier evolution of Turkey.

Çiner, A.

2003-04-01

296

Glacier change and glacier runoff variation in the Tuotuo River basin, the source region of Yangtze River in western China  

Microsoft Academic Search

Glaciers in the Tuotuo River basin, western China, have been monitored in recent decades by applying topographical maps and\\u000a high-resolution satellite images. Results indicate that most of glaciers in the Tuotuo River basin have retreated in the period\\u000a from 1968\\/1971 to 2001\\/2002, and their shrinkage area is 3.2% of the total area in the late 1960s. To assess the influence

Yong Zhang; Shiyin Liu; Junli Xu; Donghui Shangguan

2008-01-01

297

Glaciers and rock glaciers’ distribution at 28° SL, Dry Andes of Argentina, and some considerations about their hydrological significance  

Microsoft Academic Search

The area studied includes a little-known portion on the Dry Andes of the San Juan Frontal Cordillera, Argentina, where the\\u000a hydrological significance of glaciers and rock glaciers was earlier never studied. The surveyed sector includes Cerro El Potro\\u000a (5,870 m ASL) and nearby mountain chains (28°S). The predominant landforms in these areas were shaped in a periglacial environment\\u000a superimposed on an

Laura Perucca; María Yanina Esper Angillieri

298

Glacier dynamics over the last quarter of a century at Helheim, Kangerdlugssuaq and 14 other major Greenland outlet glaciers  

NASA Astrophysics Data System (ADS)

The Greenland ice sheet is experiencing increasing rates of mass loss, the majority of which results from changes in discharge from tidewater glaciers. Both atmospheric and ocean drivers have been implicated in these dynamic changes, but understanding the nature of the response has been hampered by the lack of measurements of glacier flow rates predating the recent period of warming. Here, using Landsat-5 data from 1985 onwards, we extend back in time the record of surface velocities and ice-front position for 16 of Greenland's fastest-flowing tidewater glaciers, and compare these to more recent data from Landsat-7 and satellite-borne synthetic-aperture radar. Climate re-analysis data and sea surface temperatures from 1982 show that since 1995 most of Greenland and its surrounding oceans have experienced significant overall warming, and a switch to a warming trend. During the period from 1985 to 1995 when Greenland and the surrounding oceans were not warming, major tidewater outlet glaciers around Greenland, including Kangerdlugssuaq and Helheim, were dynamically stable. Since the mid-1990s, glacier discharge has consistently been both greater and more variable. Together, these observations support the hypothesis that recent dynamic change is a rapid response to climate forcing. Both air and ocean temperatures in this region are predicted to continue to warm, and will therefore likely drive further change in outlet glacier discharge.

Bevan, S. L.; Luckman, A. J.; Murray, T.

2012-09-01

299

Meteorological drivers of ablation processes on a cold glacier in the semi-arid Andes of Chile  

NASA Astrophysics Data System (ADS)

Meteorological and surface change measurements collected during a 2.5 yr period are used to calculate surface mass and energy balances at 5324 m a.s.l. on Guanaco Glacier, a cold-based glacier in the semi-arid Andes of Chile. Meteorological conditions are marked by extremely low vapour pressures (annual mean of 1.1 hPa), strong winds (annual mean of 10 m s-1), shortwave radiation receipt persistently close to the theoretical site maximum during cloud-free days (mean annual 295 W m-2; summer hourly maximum 1354 W m-2) and low precipitation rates (mean annual 45 mm w.e.). Snowfall occurs sporadically throughout the year and is related to frontal events in the winter and convective storms during the summer months. Net shortwave radiation provides the greatest source of energy to the glacier surface, and net longwave radiation dominates energy losses. The turbulent latent heat flux is always negative, which means that the surface is always losing mass via sublimation, which is the main form of ablation at the site. Sublimation rates are most strongly correlated with net shortwave radiation, incoming shortwave radiation, albedo and vapour pressure. Low glacier surface temperatures restrict melting for much of the period, however episodic melting occurs during the austral summer, when warm, humid, calm and high pressure conditions restrict sublimation and make more energy available for melting. Low accumulation (131 mm w.e. over the period) and relatively high ablation (1435 mm w.e.) means that mass change over the period was negative (-1304 mm w.e.), which continued the negative trend recorded in the region over the last few decades.

MacDonell, S.; Kinnard, C.; Mölg, T.; Nicholson, L.; Abermann, J.

2013-09-01

300

Monitoring of Rock Glacier Äußeres Hochebenkar (Austria): an Overview  

NASA Astrophysics Data System (ADS)

Past and current interdisciplinary research at the rock glacier at Äußeres Hochebenkar in the Ötztal Alps are presented. Hochebenkar rock glacier (HK) is one of the most intensely studied rock glaciers in Austria with flow velocity measurements starting in the late 1930s. The current monitoring comprises measurements of surface flow, surface and subsurface temperature, local meteorology, runoff as well as water temperature and chemical composition of the rock glacier stream. During recent projects, extensive geological mapping has been carried out. Geological mapping shows that the bedrock of the drainage area is part of the Ötztal-Stubai Complex and consists mainly of paragneiss and mica schist. Ground penetrating radar measurements show a smooth bedrock surface without pronounced ridges or bumps. A maximum thickness of 49 m was recorded. On the surface a layer of coarse debris covers more fine grained material, which is exposed at the front and the margins of HK rock glacier. The average grain size of the debris mantle varies between 0.35 and 0.58 m. Velocities (horizontal displacements) of HK rock glacier culminated in the early 1960s with a maximum value of 3.9 m/yr near the front, followed by a period of low movement with velocities less than 0.5 m/yr until the early 1990s. A second peak is observed in 2004. While a positive correlation of surface movement and air temperature has been found until the early 2000s, recent data suggest a more complex or even reverse relation of surface displacement and air temperature. To determine the thermal regime of HK rock glacier, temperature loggers were installed across the rock glacier at an altitude of 2650 m. The temperature at the bottom of the winter snow cover (BTS) was found to decrease from the lateral parts towards the centre of HK rock glacier. Field campaigns carried out 2010 and 2011 to investigate the spatial distribution of BTS at HK rock glacier and surrounding areas suggest that the extent of permafrost ground decreased since a previous survey in 1976. The hydrological regime of HK shows high diurnal and seasonal variability. The melting of the winter snow pack typically causes discharge peaks during June, single peaks during summer are caused by heavy precipitation events. A high amount of solutes is released from HK during summer rising by a factor of 2 to 5 from the beginning of the melting season until autumn.

Abermann, J.; Fischer, A.; Hartl, L.; Krainer, K.; Nickus, U.; Schneider, H.; Span, N.; Thies, H.

2012-04-01

301

Rapid Changes of Large Tidewater Glaciers in SE Greenland  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

302

Interactions of the Greenland Petermann Glacier with the ocean: An initial perspective (Invited)  

NASA Astrophysics Data System (ADS)

Petermann Glacier is major outlet glacier that drains 6% of the area of the Greenland Ice Sheet in western North Greenland. It is one of four major outlet glaciers on Greenland with a grounding line substantially below sea level (about 500m) and one of two such glaciers to retain a substantial floating tongue. The floating ice tongue of Petermann glacier is thought to lose at least 80% of its mass through ocean interaction. Based on three opportunistic ocean surveys in Petermann Fjord, we present an overview of circulation at the fjord mouth, hydrographic structure beneath the ice tongue, oceanic heat delivered to the under-ice cavity and the fate of the resulting melt water. We also present an historical perspective on the August 2010 major calving event. The 1100m-deep fjord is separated from neighboring Hall Basin by a sill that is inferred to lie between 350m and 450m deep. Hall Basin is a section of Nares Strait that connects the Arctic Ocean (at the Lincoln Sea proceeding southward through Robeson Channel, Hall Basin, Kennedy Channel, Kane Basin and Smith Sound) to Baffin Bay. Sills in the Lincoln Sea (290m) and in Kane Basin (220m) restrict communication with the Arctic Ocean and Baffin Bay. The net flux of seawater through Nares Strait is southward and relatively fresh, conditioned by sources and processes within the Arctic Ocean and locally. Within Petermann Fjord, glacial melt water appears on the northeast side at 200-600m. A cyclonic gyre occurs within the fjord mouth, with outflow on the northeast side. Oceanic heat fluxes into the fjord are sufficient to account for the observed rate of basal melting. Cold, low salinity water intrudes far under the ice and likely limits basal melting to the inland half of the tongue. The recent major calving event resulted in a loss of 300 km2 or about 20% of the total area of the floating tongue, most of which remained intact as an ice island that garnered much media attention. Available observations show calving to be sporadic on a decadal timescale. Multiple factors likely contribute to calving events. These include the geometry of the fjord, absence of sea ice, preconditioning of the glacier by crevassing and melt related cracking and occurrence of strong katabatic or orographically channeled winds. The recent event falls within the realm of previously documented calving rates but the remaining tongue length is the shortest ever directly observed. Gaps in the 134 year record preclude final judgment about whether the recent calving is entirely unprecedented. Rising surface temperature trends and changed sea ice and ocean circulation patterns in the Arctic could render the tongue susceptible to collapse. As this could contribute to accelerated ice mass flux from Greenland, it is important to continue to observe and clarify processes operative in this system.

Falkner, K. K.; Johnson, H. L.; Melling, H.; Muenchow, A.; Samelson, R. M.; Friends Of Petermann

2010-12-01

303

Fifty-Year Record of Glacier Change Reveals Shifting Climate in the Pacific Northwest and Alaska, USA  

USGS Publications Warehouse

Fifty years of U.S. Geological Survey (USGS) research on glacier change shows recent dramatic shrinkage of glaciers in three climatic regions of the United States. These long periods of record provide clues to the climate shifts that may be driving glacier change. The USGS Benchmark Glacier Program began in 1957 as a result of research efforts during the International Geophysical Year (Meier and others, 1971). Annual data collection occurs at three glaciers that represent three climatic regions in the United States: South Cascade Glacier in the Cascade Mountains of Washington State; Wolverine Glacier on the Kenai Peninsula near Anchorage, Alaska; and Gulkana Glacier in the interior of Alaska (fig. 1).

U.S. Geological Survey

2009-01-01

304

Bent glacier tongues: A new look at Lliboutry's model of the evolution of the crooked Jatunraju Glacier (Parón Valley, Cordillera Blanca, Perú)  

NASA Astrophysics Data System (ADS)

The article tackles the issue of which factors may influence the flow direction and morphological shape of glacier tongues terminating at tributary junctions to the main valley in high mountain landscapes. A very particular morphological form of a glacier tongue shows the Jatunraju Glacier in the Cordillera Blanca (Perú). It terminates in the superior Parón Valley with a prominent crooked form, embedded in a 250 m-high moraine pedestal. Lliboutry (1977) has explained the deviation of the Jatunraju Glacier tongue as a result of a proglacial lake outburst. Alternative hypothetical models on a general scale have been developed for the causes determining the morphological characteristics of glacier tongues. These are based on empirical field evidence from the Parón Valley and from glaciers located in other high mountain areas, in particular in the Himalaya Region, where glacier tongues in confluence settings are abundant. The comparative investigations demonstrate that the pronounced crooked form of the Jatunraju Glacier may not be the result of a single extreme event, but may have been produced as well by gradual processes. In a general context, the study shows that crooked glacier tongues are common landforms in other mountain regions and mainly intrinsic to debris-covered glaciers. The morphological evolution of glacier tongues may involve a polygenetic process pattern over a longer geological time period. Apart from the steepness of the valley gradient of the main valley, the former confluence from the source glacier with the main glacier during times of a more extensive glaciation is regarded as one of the dominating factors controlling the later evolution of glacier tongues in general ("inherited confluence model").

Iturrizaga, Lasafam

2013-09-01

305

Temperate Ice Under Jakobshavn Isbrae and Other Greenland Glaciers  

NASA Astrophysics Data System (ADS)

Jakobshavn Isbrae, western Greenland's largest outlet glacier, drains 6.5% of the ice sheet's area and therefore may be poised to make rapid contributions to global sea level rise. Indeed, in the late 1990s the glacier doubled in speed as its floating ice tongue disintegrated. Driving stresses up to 300 kPa suggest that a considerable amount of ice deformation combines with basal sliding to produce Jakobshavn's fast speed. Boreholes and overturned icebergs have indicated the existence of a soft, temperate layer at the bottom of the ice, where shear deformation would be concentrated. The thickness and water content of the temperate ice layer determine how much of the motion it can provide. While we focus on Jakobshavn, we also apply our analysis to other Greenland outlet glaciers. This project uses an implicit finite-difference model to compute the temperate ice thickness and water content along multiple flowlines feeding Jakobshavn Isbrae and other Greenland glaciers, in an effort to identify the mechanisms for their rapid movement. In contrast to previous modeling studies, which chose ice velocities in order to match partial temperature profiles measured in boreholes, our model is constrained by satellite-observed surface velocities. The model calculates the temperature field and determines the sliding and internal deformation velocities, constrained by the velocity measurements, to make a self-consistent balance. Feedbacks between temperature, water content, and viscosity allow the temperate shear layer to evolve. Our model results for temperate ice thickness under Jakobshavn (150-300 meters) agree with previous estimates (100-700 meters) and recent observations (30 and 200-250 meters). This model is well suited for glaciers with deeply eroded bedrock troughs. Forthcoming observational campaigns such as NASA's IceBridge program will produce detailed basal topography data for other Greenland outlet glaciers. As these data come online, we will model the temperate ice thickness under Greenland glaciers where field studies of deep ice temperature have not been done.

Poinar, K. E.; Joughin, I. R.

2010-12-01

306

Modelling the outlet glaciers terminating in Godthåb fjord  

NASA Astrophysics Data System (ADS)

The mass loss of the Greenland ice sheet is mainly caused by direct melting on the surface and ice flow through the numerous outlet glaciers. The largest outlet glaciers, like Jabobshavn Isbræ, are studied in great detail, however, processes leading to their behaviour such as calving and basal melting are not well understood. In this study we focus on the glaciers terminating in Godthåb fjord, where the main contributor is the outlet glacier Kangiata Nunaata Sermia (KNS). The fjord is unique considering several outlet glaciers terminate in the complex fjord system contributing to the total fresh water flux into the fjord. Here, we aim to describe the present behaviour of KNS. The key parameters are a detailed fjord bathymetry and bedrock topography underneath the terminus of the glacier, recently acquired by the Greenland Climate Research Centre and CReSIS respectively. The parallel ice sheet model (PISM, developed at UAF) is used for the regional modelling applied to the identified KNS drainage basin. Recently, PISM demonstrated its regional modelling capability on the largest outlet glacier Jakobshavn Isbræ. Initially, PISM is used with untuned parameters on a 5 km grid with standard SEARISE forcing. The results show that PISM is able to model the surface velocity pattern of KNS that are sufficiently in agreement with InSAR observations. Hereafter, PISM is forced with HIRHAM high resolution regional climate model data provided by DMI. Combining the known geometry and the HIRHAM output, PISM will provide a accurate model of the region. It can support the melt water estimate that enters the fjord as fresh water, which can be compared to the fjord model and comprehensive observations. This study is conducted in affiliation with the Greenland Climate Research Centre in Nuuk.

Fitzner, A.; Dahl-Jensen, D.

2012-04-01

307

Glacier surface velocity fields in South Shetland Islands  

NASA Astrophysics Data System (ADS)

In this study surface velocity of glaciers in South Shetland Islands (Antarctic Peninsula) are calculated based on synthetic aperture radar data from ALOS PALSAR and TerraSAR-X as well as differential GPS measurements. The obtained glacier velocities will be used to calculate the total glacier mass budget and to better understand the contribution of the study areas to the sea level rise. Only recent studies have examined the region for mass balance and sea level rise estimates. However, larger scale mass budget computations are not yet available. Ice dynamics obtained from satellite data have only been derived in a few occasions, often due to lacking spatial resolution or temporal decorrelation. Hence, any spacebased information on ice dynamics can significantly improve estimates of calving fluxes and mass loss. In this study we analysed over 30 PALSAR and 30 TSX scenes acquired over the King George Island and Livingston Island, the two largest islands in the South Shetland Island group. In the study areas the glacier velocities are calculated using two independent data sets; namely satellite radar imagery and GPS. Feature-tracking methods are applied to the radar imagery to obtain glacier velocities using Gamma Interferometric SAR Processor and TU-Delft DORIS. Results from Gamma and Doris software packages are compared to each other as well as GPS measurements where available. For a subset of the study area tracking results from different acquisitions modes (stripmap and spotlight) and orbits are compared. Comparison of glacier velocities obtained by radar and GPS provide an estimate for the uncertainties in the measured rates. The results obtained from all data sets are then compiled to construct a map of glacier velocities for the entire island group.

Osmanoglu, B.; Giseke, H.; Navarro, F. J.; Rueckamp, M.; Falk, U.; Corcuera, M. I.; Braun, M.

2011-12-01

308

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)

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.

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

2011-12-01

309

Distributed ice thickness and volume of all glaciers around the globe  

NASA Astrophysics Data System (ADS)

A new physically based approach for calculating glacier ice thickness distribution and volume is presented and applied to all glaciers and ice caps worldwide. Combining glacier outlines of the globally complete Randolph Glacier Inventory with terrain elevation models (Shuttle Radar Topography Mission/Advanced Spaceborne Thermal Emission and Reflection Radiometer), we use a simple dynamic model to obtain spatially distributed thickness of individual glaciers by inverting their surface topography. Results are validated against a comprehensive set of thickness observations for 300 glaciers from most glacierized regions of the world. For all mountain glaciers and ice caps outside of the Antarctic and Greenland ice sheets we find a total ice volume of 170 × 103 ± 21 × 103 km3, or 0.43 ± 0.06 m of potential sea level rise.

Huss, Matthias; Farinotti, Daniel

2012-12-01

310

36 CFR 13.1132 - What types of commercial fishing are authorized in Glacier Bay?  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false What types of commercial fishing are authorized in Glacier Bay? 13.1132...Bay National Park and Preserve Commercial Fishing § 13.1132 What types of commercial fishing are authorized in Glacier Bay? Three...

2013-07-01

311

Changes in the dynamics of marine terminating outlet glaciers in west Greenland (2000–2009)  

Microsoft Academic Search

Asynchronous changes in west Greenland glacier dynamics occurred from 2000–2009Glaciers with grounded termini had pronounced changes in dynamicsThe time between large retreat and surface stabilization is related to slope

Ellyn M. McFadden; Ian M. Howat; Ian Joughin; Ben E. Smith; Yushin Ahn

2011-01-01

312

Cold-based Mountain Glaciers on Mars: Western Arsia Mons Fan-shaped Deposits  

NASA Astrophysics Data System (ADS)

A lobate deposit on Western Arsia Mons is analogous to cold-based glacier deposits in the Dry Valleys of Antarctica (ridged facies and drop moraines; knobby facies and sublimation tills; smooth facies and rock glaciers).

Head, J. W.; Marchant, D. R.

2003-03-01

313

Cold-based Glaciers in the Western Dry Valleys of Antarctica: Terrestrial Landforms and Martian Analogs  

NASA Astrophysics Data System (ADS)

A lobate deposit on Western Arsia Mons is analogous to cold-based glacier deposits in the Dry Valleys of Antarctica (ridged facies and drop moraines; knobby facies and sublimation tills; smooth facies and rock glaciers).

Head, J. W.; Marchant, D. R.

2003-07-01

314

Tongue-shaped Lobes on Mars: Morphology, Nomenclature, and Relation to Rock Glacier Deposits  

NASA Astrophysics Data System (ADS)

We outline the accepted two-fold genetic classification system for terrestrial rock glaciers and propose a non-genetic set of terms to be applied to tongue-shaped lobes on Mars, interpreted to be rock glacier deposits.

Marchant, D. R.; Head, J. W.

2003-07-01

315

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

316

A regional view of fluctuations in glacier length in southern South America  

NASA Astrophysics Data System (ADS)

Fluctuations in the length of 72 glaciers in the Northern and Southern Patagonia Icefield (NPI and SPI, respectively) and the Cordillera Darwin Icefield (CDI) were estimated between 1945 and 2005. The information obtained from historical maps based on 1945 aerial photographs was compared to ASTER and Landsat satellite images and to information found in the literature. The majority of glaciers have retreated considerably, with maximum values of 12.2 km for Marinelli Glacier in the CDI, 11.6 km for O'Higgins Glacier in the SPI and 5.7 km for San Rafael Glacier in the NPI. Among the 20 glaciers that have retreated the most relative to their size, small (less than 50 km²) and medium (between 50 and 200 km²) glaciers are the most affected. However, no direct relation between glacier retreat and size was found for the 72 glaciers studied. The highest percentage retreat in the CDI was by the CDI-03 Glacier (37.9%) and Marinelli Glacier (37.6%). In the SPI, relative retreats were heterogeneous and fluctuated between 27.2% (Amelia Glacier) and 0.4% (Viedma Glacier). In the NPI, relative retreat was very high for Strindberg and Cachet glaciers (35.9% and 27.6%, respectively) but for the remaining glaciers in this icefield it ranged between 11.8% (Piscis Glacier) and 3.6% (San Quintín Glacier). In addition to surface area, the surface slope (calculated on the basis of the DEM SRTM) was also related to the relative retreat and no straightforward relation was found. From a global point of view, we suggest that glacier retreat in the region is controlled firstly by atmospheric warming, as it has been reported in this area. Besides the general increase in temperature observed, no signal of a geographical pattern for the fluctuations in glacier length was found. Consequently, glaciers appear to initially react to local conditions most probably induced by their exposition, geometry and hypsometry. The heterogeneity of rates of retreat suggests that differences in basin geometry, glacier dynamics and response time are key features to explain fluctuations of each glacier.

Lopez, Paulina; Chevallier, Pierre; Favier, Vincent; Pouyaud, Bernard; Ordenes, Fernando; Oerlemans, Johannes

2010-03-01

317

Glacier Velocities and Elevation Change of the Juneau Icefield, Alaska  

NASA Astrophysics Data System (ADS)

Mass-loss from small icefields is the greatest contributor from the cryosphere to sea level rise at present. The Juneau Icefield is a small low-latitude glacier system in southeast Alaska. Remote-sensing data from SAR and optical instruments is examined for inter-annual and seasonal changes in glacier elevation and velocity. We use subpixel offset tracking of satellite SAR and optical images to construct a time-series of average horizontal velocities for the outlet glaciers of the icefield. Optical imagery is available from the ASTER instrument between 2000 and 2009. Eighty ASTER scene-pairs are used to generate pixel-offsets for the region. SAR imagery is available for pixel tracking between 1992-2000, although rapid decorrelation means that only repeat track images separated by 1-2 months are useful. The combined radar and optically derived time-series are compared with sparse GPS measurements made by the Juneau Icefield Research Program (JIRP). JIRP measurements and ASTER-derived velocities at the same points show a velocity of up to 1.1 m/day with differences between the two ranging from 0 to 20 cm/day over coherent areas of the ASTER pixel-offsets. Initial findings over Taku Glacier (the largest outlet glacier in the icefield) indicate that velocities from several ERS tandem-pairs, with short duration repeat passes, taken during the mid-1990s reveal velocities in the middle of Taku glacier of 1 m/day to 1.5 m/day over the faster-moving sections of the glacier. These results are within +/- 25 cm/day of velocities derived from the more recent ASTER scenes, which show a maximum average velocity of around 1.25 m/day. However, Taku Glacier is the only glacier in the icefield still advancing and is therefore not representative of the entire icefield. Data covering other outlet glaciers will be processed to determine overall trends in velocity. Several components of the ASTER processing-chain are tested. Output from two independent pixel-tracking software packages that use different algorithms is compared for consistency. Initial results indicate Ampcor, an open source package that forms part of the ROI-PAC software suite, generates similar results to CosiCorr, an open source module for the ENVI image processing software suite. Each package produces an average velocity of up to 1.25 m/day in the middle of Taku Glacier, with differences of up to +/- 10 cm/day over coherent areas. Relative DEMs from cloud-free ASTER pairs are used to determine average rates of surface elevation change over the outlet glaciers of the icefield. An automated DEM differencing tool removes bias in differences between DEMs due to satellite position and filters out clouds and outliers. Changing surface elevation change may be linked to changes in ice dynamics and mass. Deriving glacier velocities and elevation changes from remote-sensing data will provide a comprehensive overview of the "health" of the Juneau Icefield. Understanding the causes of variability in the observations will provide better constraints on how the icefield will react to future climate change.

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

2009-12-01

318

Glacier Lake Outburst Floods in Norway 2001 - 2009  

NASA Astrophysics Data System (ADS)

Several GLOFs or jøkulhlaups occurred in Norway during the first decade of the millennium, the most significant being several from Rundvassbreen, an outlet glacier of Blåmannsisen and one from Flatbreen, an outlet glacier of Jostedalsbreen. A number of minor flood events occurred also. Many of the glaciers in Norway, especially the maritime glaciers with high winter balance, demonstrated frontal advance and positive mass balance in the 1990s. However, since 2000 most glaciers have had a negative mass balance, and undergone frontal retreat and a corresponding decrease in area. The outburst flood from Flatbreen in 2004 was from a moraine-dammed lake that usually drains under the glacier itself. The immediate cause of the flood was a sudden period of warm, wet weather and the sudden increase of additional water into the lake caused the moraine to rupture. Over 50 000 m3 of water drained from the lake, and the resulting debris flow from the lake to the valley 1000 m lower had a volume of 240 000 m3. Fortunately there were no injuries from this flood, but extensive material damage to farmland on the valley floor. Previous, but smaller events occurred from this lake in 1924 and 1947. The moraine is still partially ruptured, thus the potential for a new jøkulhlaup of the same magnitude as that in 2004 is greatly reduced. Several floods occurred from a glacier-dammed lake at the glacier Blåmannsisen in Nothern Norway, the first occurring in 2001, and subsequently in 2005, 2007 and 2009. The jøkulhlaups all occurred in late summer, but at different water levels of the lake. The first two events occurred when the lake was full and 35 - 40 million m3 of water drained. However, the second event occurred a year after the lake had filled again, with the excess water in the meantime draining over a spillway and away from the glacier, as it had done prior to 2001. The two subsequent events occurred before the lake was completely full, and were half the size of the first two events at about 20 million m3 of water. The thickness of ice at the barrier has decreased over the past few decades, which instigated the first event. Comparing measurements in 1961 and 1998, the part of the glacier adjacent to the lake was up to 55 m thinner. Laser scanning performed in autumn 2002 showed a further 4-10 of thinning between 1998 and 2002. GPS measurements on the glacier surface showed that there was thinning of an average of 4.5 m from 2001 to 2004, and a further 5-10 m between 2004 and 2009. This further thinning led to the lake emptying under the glacier at a lower lake level than previously. There were no human or material damages from any of these events. In contrast, the floodwaters flowed into Sisovatn, a hydropower reservoir and were financially beneficial. No similar events have been recorded before the 2001 event. The lake is now expected to continue to empty under the glacier at fairly regular intervals.

Jackson, Miriam; Engeset, Rune

2010-05-01

319

3-D modelling of glacier calving processes (Invited)  

NASA Astrophysics Data System (ADS)

Calving from tidewater glacier tongues and ice shelves is an important mass loss mechanism for many mid- and high-latitude tidewater glaciers, ice caps and ice sheets, yet an adequate representation of calving is still missing from prognostic models of ice dynamics. Benn and others (2007) proposed a calving criterion appropriate for both grounded and floating glacier tongues or ice shelves. This criterion assumes that the calving is triggered by the downward propagation of transverse surface crevasses, near the calving front, as a result of the extensional stress regime. The crevasse depth is calculated following Nye (1957), assuming that the base of a field of closely spaced crevasses lies at a depth where the longitudinal tensile strain rate tending to open the crevasse equals the creep closure resulting from the ice overburden pressure. Crevasses partially or totally filled with water will penetrate deeper, because of the contribution of water pressure to the opening of the crevasse. This criterion is readily incorporated into glacier and ice sheet models, but has not been fully validated with observations. We apply a three-dimensional extension of Benn and others’ (2007) criterion, incorporated into a full-Stokes model of glacier dynamics, to estimate the current position of the calving front of Johnsons Glacier, Antarctica. The record of the front positions of Johnsons Glacier spans only a few years during the last decade, and during this observation period the front has remained at a nearly constant position, so a full modelling exercise of time evolution to follow the front-position changes of the glacier has not been possible. Instead, our modelling experiment is a diagnostic one, aimed at establishing whether the model adequately reproduces the current front position of Johnsons Glacier (Otero et al., 2010). We develop four experiments: (i) an straightforward three-dimensional extension of Benn and other’s (2007) model; (ii) an improvement to the latter that computes the tensile deviatoric stress opening the crevasse using the full-stress solution; (iii) a further improvement based on finding the depth at which the model-computed tensile deviatoric stress, considered as a function of depth, equals the ice overburden closure pressure; (iv) an experiment that adds, to the above, the effect of a threshold strain rate required for crevasses initiation. We found that the improvements considered in experiments (ii) and (iii) were necessary to reproduce accurately the observed calving front. In ongoing work, we intend to apply our model in a prognostic mode, to predict the observed front position changes of Hansbreen, a tidewater glacier in Svalbard. REFERENCES: Benn, D.I., R.J. Hulton and R.H. Mottram. 2007. Calving laws, sliding laws and the stability of tidewater glaciers. Ann. Glaciol., 46, 126-130. Nye, J.F. 1957. The distribution of stress and velocity in glaciers and ice-sheets. Proc. Roy. Soc., Ser. A, 239(1216), 113-133. Otero, J., F.J. Navarro, C. Martín, M.L. Cuadrado and M.I. Corcuera. 2010. A three-dimensional calving model: numerical experiments on Johnsons Glacier, Livingston Island, Antarctica. J. Glaciol., 56(196), 200-214.

Navarro, F. J.

2010-12-01

320

Glacier changes on Sierra Velluda massif, Chile (37° S): mountain glaciers of an intensively-used mid-latitude landscape  

NASA Astrophysics Data System (ADS)

The central-southern section of Chile is defined as one of the Latin American hot spots in the last IPCC Report due to the impact of glacier retreat on water resources, the transitional character of the climate, and its importance in terms of agricultural and forestry activities. In order to provide a better understanding of glacier behavior in this zone, this paper analyzes the volumetric changes of glaciers in the Sierra Velluda, located in the upper Bío Bío River Basin. Bibliographic sources, satellite images, and DEMs were used to estimate frontal, areal, and volumetric changes. An analysis of significance was performed in order to provide accurate estimations of the fluctuations. The results indicate that Sierra Velluda glaciers have suffered a significant reduction since the 1960s, despite some short periods of positive fluctuations. A maximum position of a glacier for the year 1828 was identified, which is in concordance with other proxies registered elsewhere in Chile. These changes agree with measurements of glacier fluctuation elsewhere in Chile. While short-term fluctuations are consistent with the inter-annual precipitation variability, lake levels records, and a warm phase of the El Niño Southern Oscillation (ENSO), the general shrinkage agrees with the shift of the ENSO (PDO) in 1976. Therefore, it is proposed that Sierra Velluda's glaciers are highly sensitive to high frequency climatic fluctuations and even to inter-annual variability. Considering that models project a reduction in Andean precipitation and an altitudinal increase in the 0 °C isotherm, these ice bodies are expected to continue to shrink.

Fernández, A.; Santana, A.; Jaque, E.; Martínez, C.; Sáez, R.

2011-02-01

321

Latest Pleistocene and Holocene Glacier Fluctuations in southernmost Patagonia  

NASA Astrophysics Data System (ADS)

Summer insolation has been proposed to explain long-term glacier fluctuations during the Holocene. If correct, the record of glacier fluctuations at high latitudes in the Southern Hemisphere should differ from that in the Northern Hemisphere. Testing this insolation hypothesis has been hampered by dating uncertainties of many Holocene glacier chronologies from Patagonia. We report on our ongoing research aimed at developing a regional glacier chronology at the southern end of the Andes north and west of Ushuaia, Argentina. We have found evidence for an advance of cirque glaciers at the end of the Pleistocene; one or locally two closely spaced moraines extend up to 2 km beyond Little Ice Age moraines. Radiocarbon dating of terrestrial macrofossils recovered from basal sediments behind two of these moraines yielded ages of 10,320 ± 25 and 10,330 ± 30 14C yr BP. These moraines may record glacier advances coeval with the Antarctic Cold Reversal; surface exposure dating of these moraines is currently in progress to test this hypothesis. We find no evidence of Holocene moraines older than 6800 14C yr BP, based on the distribution of Hudson tephra of that age. At some sites, there is evidence for an early Neoglacial advance of glaciers slightly beyond (< 0.5 km) Little Ice Age limits. Terrestrial macrofossils at the upper contact of basal till from one site yielded an age of 4505 ± 30 14C yr BP; this age overlaps the most probable age range of early Neoglacial ice expansion in southern Patagonia reported by Porter (2000) and the age of plants killed by expansion of the Quelccaya Ice Cap in Peru. We have documented multiple wood mats with stumps in growth position separated by till units in a 100 m section of the northeast lateral moraine at Stoppani Glacier (54.78 S, 68.98 W), 50 km west of Ushuaia. Ten radiocarbon ages on these wood mats range in age from 3510 ± 15 to 135 ± 15 14C yr BP. The mats decrease in age up-section; many overlap with published age ranges for Neoglacial advances in western Canada. Taken together, these data: a) do not support the summer insolation hypothesis for Holocene glacier fluctuations in southernmost Patagonia; b) confirm paleobotanical evidence for a warm, dry early Holocene; and c) suggest that many Neoglacial advances in southernmost Patagonia and western North America were synchronous.

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

2011-12-01

322

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

Microsoft Academic Search

Mountain glaciers are key indicators of global climate change. Changes in glacier volume, area, and length are determined by the climate and related mass flux\\/glacier flow. For several aspects of sustainable development in high-mountain regions (hydro-electric energy, water supply, tourism, etc.) it is crucial to estimate future glacier variations. Therefore, the interactions and relationships between individual meteorological and glaciological parameters

Stefan Winkler

2010-01-01

323

Holocene glacier variability: three case studies using an intermediate-complexity climate model  

Microsoft Academic Search

Synthetic glacier length records are generated for the Holocene epoch using a process-based glacier model coupled to the intermediate-complexity climate model ECBilt. The glacier model consists of a mass-balance component and an ice-flow component. The climate model is forced by the insolation change due to variations in the Earth's orbital parameters. We consider three glaciers, ranging from maritime to continental.

S. L. Weber; J. Oerlemans

2003-01-01

324

Glacier changes in the Tien Shan as determined from topographic and remotely sensed data  

Microsoft Academic Search

This research presents a precise evaluation of the Tien Shan glacier's recession based on data of geodetic surveys 1861–1869, aerial photographs from 1943, 1963, 1977, 1981, 1:25,000 scale topographic maps, SRTM, and ASTER data from 2000\\/2003 for the Akshiirak glacierized massif in the central Tien Shan with 178 glaciers covering 317.6 km2, and for the Ala Archa glacier basin in the

Vladimir B. Aizen; Valeriy A. Kuzmichenok; Arzhan B. Surazakov; Elena M. Aizen

2007-01-01

325

New Tools for Analyzing Glacier Changes From Space  

NASA Astrophysics Data System (ADS)

Efforts to compile a comprehensive global glacier inventory, such as that being undertaken by the Global Land Ice Measurements from Space (GLIMS) project, require ready access to high-resolution satellite imagery as well as tools for performing analyses on these data. In this paper we describe a study of ice extent and volume changes for the Petrov glacier system of the Akshiyrak Range in the interior Tien Shan of Central Asia. Glacier outlines were digitized from an orthorectified ASTER imagery using a freeware tool, GLIMSView. A digital elevation model (DEM) was extracted from an ASTER scene acquired in October 2002. From these results we determine ice area as a function of elevation using GIS tools. The resulting hypsography is then used in conjunction with field measurements of mass balance for another glacier in the same range to estimate the mass balance for the Petrov glacier as a function of observed equilibrium line altitude, and thus to predict how climate change will impact the hydrology of the region.

Khalsa, S. S.; Dyurgerov, M. B.; Raup, B.; Scharfen, G.; Barry, R. G.

2003-12-01

326

Projecting West Greenland's future tidewater glacier discharge with Monte Carlo  

NASA Astrophysics Data System (ADS)

Due to non-linear feed backs arising from the acceleration of outlet glaciers, it is difficult to forecast the future ice dynamic contribution of Greenland's tidewater glaciers to sea level rise. We perform Monte Carlo simulations of the form and flow of West Greenland over a wide parameter space using a 2-D (depth-integrated) thermo-mechanical ice flow model. Climate forcing is prescribed as a perturbation from the past and future surface mass balance rate predicted by MAR (Modèle Atmosphérique Régional). While more sophisticated ice sheet models exist (e.g. 3-D Navier-Stokes), employing a more computationally efficient model allows us to perform a large number of fully-transient simulations in order to quantify the cumulative uncertainty in projected tidewater glacier discharge stemming from poorly constrained or understood processes, such as the rheology of Wisconsin ice, ice temperature and basal sliding. Following a forward model selection approach, an ensemble filter is imposed following transient spin-up to ensure that only simulations that accurately reproduce contemporary observed glacier geometry and velocity are forced into the future; all other simulations are discarded. This approach therefore provides the opportunity to assimilate spatially and temporally diverse field observations into a predictive modeling framework. We present bounded estimates of the dynamic discharge of several well-observed West Greenland tidewater glaciers to the year 2100.

Colgan, William; Rajaram, Harihar; Fettweis, Xavier

2013-04-01

327

Reconnaissance hydrology of Portage Glacier basin, Alaska--1972  

USGS Publications Warehouse

Early reports of conditions in Portage Pass, Alaska, provide evidence that Portage Glacier was formerly larger and thicker. Past conditions, recent history, current retreat, and possible future changes are summarized from an analysis of reports, photographs of the glacier (1939, 1950, and annually since about 1960), and data on snow and ice balance and bathymetry (1972). Between 1900 and 1972, the glacier terminus retreated 3.4 kilometers, and the lower part of the glacier thinned 200 meters. Climatic change controlled the retreat until about 1930; since then deep water at the terminus has influenced the calving retreat. The calving rate and present terminus position cannot be sustained by current climatic conditions and rate of snow accumulation. Thus the glacier will continue to recede until the terminus stabilizes in shallower water, probably about 1.5 kilometers upvalley from the present terminus and in about year 2020, assuming no change in present climatic conditions and calving rate. Possible small climatic changes could cause a shift in the point at which annual snow accumulation equals annual ablation (500 meters) and a corresponding change in terminus behavior. Potential natural hazards include avalanches, outburst floods from ice-dammed lakes, and unstable icebergs. (Woodard-USGS)

Mayo, L. R.; Zenone, Chester; Trabant, Dennis

1977-01-01

328

The basal speed of valley glaciers: an inverse approach  

NASA Astrophysics Data System (ADS)

Geophysical inverse methods are used to calculate the basal motion of a glacier. They are applied to a one-dimensional forward model that can be linearized to make the analysis simpler. The inverse method finds a solution that fits the data within a given error. It selects for smooth solutions to discriminate against unrealistic oscillations. The method is applied to a simple model glacier of uniform shape and thickness to test how well a given basal motion field can be reconstructed. It shows, as expected, that optimizing for smoothness lowers maxima and increases minima of the solution. A step change in basal velocity is drawn out in the inversion over a distance that is given by the half-width of a resolving function. This is typically about three times the ice thickness, but is also affected by the sampling rate of the data. The method is then applied to two glaciers where suitable data are available: Brown Glacier on Heard Island, southern Indian Ocean, and McCall Glacier in the Brooks Range, Alaska, U.S.A.The McCall results agree well with earlier estimates of basal motion.

Truffer, Martin

329

Capturing fracture propagation in a glacier using passive seismology  

NASA Astrophysics Data System (ADS)

Alpine glaciers are known to be sensitive to climate change and form a major component of the global fresh water budget. Using a small 3-component passive seismic data set, we monitor the propagation of a surface fracture events through time at the Bench Glacier, AK. We search for small-amplitude surface events using a waveform cross-correlation algorithm characterized by a relatively strong Rayleigh-wave arrival. For events with a high correlation to our search wavelet, we rotate the waveforms to the principal axis components using the incident azimuth of the direct P-wave. After rotating, we manually pick the three (P-, SH- and Rayleigh-wave) arrival times. We input these travel time picks into a multi-mode travel-time inversion scheme and locate the events within Bench Glacier, with improved precision over methods based on a single wave mode (Rayleigh or body wave). As a result, we identify events on two closely-spaced but orthogonal fracture planes. Events on these fracture planes migrate ~55 meters over ~45 minutes. Besides travel times, we also study the amplitudes of these icequakes. This allows us to estimate the effective seismic attenuation in the glacier at the time. Finally, we discuss possible source magnitude and mechanisms, and the implications our observations have on glacier stress release and monitoring.

Smith, K. L.; Mikesell, T. D.; van Wijk, K.; Walter, F. T.; Bradford, J. H.

2010-12-01

330

Sea-level rise from glaciers and ice caps: A lower bound  

Microsoft Academic Search

One of the most easily measured dimensions of a glacier, the accumulation area, is linked to future changes in glacier volume and consequent changes in sea level. Currently observed accumulation areas are too small, forcing glaciers to lose 27% of their volume to attain equilibrium with current climate. As a result, at least 184 ± 33 mm of sea-level rise

David B. Bahr; Mark Dyurgerov; Mark F. Meier

2009-01-01

331

Sea-level rise from glaciers and ice caps: A lower bound  

Microsoft Academic Search

One of the most easily measured dimensions of a glacier, the accumulation area, is linked to future changes in glacier volume and consequent changes in sea level. Currently observed accumulation areas are too small, forcing glaciers to lose 27% of their volume to attain equilibrium with current climate. As a result, at least 184 +\\/- 33 mm of sea-level rise

David B. Bahr; Mark Dyurgerov; Mark F. Meier

2009-01-01

332

36 CFR 13.1116 - Do I need a camping permit in Glacier Bay?  

Code of Federal Regulations, 2013 CFR

... false Do I need a camping permit in Glacier Bay? 13.1116 Section 13.1116...UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve General...1116 Do I need a camping permit in Glacier Bay? From May 1 through September...

2013-07-01

333

36 CFR 13.1109 - Off-road vehicle use in Glacier Bay National Preserve.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Off-road vehicle use in Glacier Bay National Preserve. 13.1109 ...UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Administrative...13.1109 Off-road vehicle use in Glacier Bay National Preserve. The use...

2009-07-01

334

36 CFR 13.1116 - Do I need a camping permit in Glacier Bay?  

Code of Federal Regulations, 2010 CFR

... false Do I need a camping permit in Glacier Bay? 13.1116 Section 13.1116...UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve General...1116 Do I need a camping permit in Glacier Bay? From May 1 through September...

2009-07-01

335

36 CFR 13.1109 - Off-road vehicle use in Glacier Bay National Preserve.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Off-road vehicle use in Glacier Bay National Preserve. 13.1109 ...UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Administrative...13.1109 Off-road vehicle use in Glacier Bay National Preserve. The use...

2010-07-01

336

36 CFR 13.1150 - Is a permit required for a vessel in Glacier Bay?  

Code of Federal Regulations, 2013 CFR

... Is a permit required for a vessel in Glacier Bay? 13.1150 Section 13.1150...UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Vessel... Is a permit required for a vessel in Glacier Bay? A permit from the...

2013-07-01

337

36 CFR 13.1116 - Do I need a camping permit in Glacier Bay?  

Code of Federal Regulations, 2010 CFR

... false Do I need a camping permit in Glacier Bay? 13.1116 Section 13.1116...UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve General...1116 Do I need a camping permit in Glacier Bay? From May 1 through September...

2010-07-01

338

Portage Glacier and Portage Pass, Alaska: Little Ice Age dynamics and the chronology of glacial retreat  

Microsoft Academic Search

Portage Glacier currently acts as a lacustrine calving glacier discharging icebergs into Portage Lake, Alaska. This glacier advanced during the Little Ice Age, and from 1799 to 1911 completely filled the lake basin and deposited three large moraines downvalley of the modern lakeshore. During this time the glacial ablation regime was dominated by melting and a large outwash stream flowed

Kristine J. Crossen

2007-01-01

339

Competing Positive and Negative Feedbacks on Glacier Response to Climatic Changes  

Microsoft Academic Search

The adiabatic temperature lapse rate imparts a well-studied positive feedback on glacier changes in response to a given change in climate. For example, if temperature increases, the surface of the glacier thins into the warmer temperatures of the lower surface elevation, dependent upon the local lapse rate, which amplifies the glacier response to the original temperature. However, a less well-quantified

S. Rupper; C. E. Todd

2009-01-01

340

An energy-balance model for the debris layer on debris-covered glaciers  

Microsoft Academic Search

Many glacier ablation zones are mantled in near-continuous blankets of rock debris. These debris-covered glaciers are important drivers of the water cycle in many mountain regions, for example, in the headwaters of the Ganges and Indus Rivers. The debris layers have a very significant impact on glacier thermodynamics, and have been seen to expand in recent years, so it is

Tim Reid; Ben Brock

2010-01-01

341

A World of Changing Glaciers: Hazards, Opportunities, and Measures of Global Climate Change  

Microsoft Academic Search

Glaciers around the world are, with rare exceptions, stagnating or in hasty retreat. Whether growing or shrinking, significant changes in the extent of glaciers have major impacts on nature and humanity in their immediate vicinity, because land uses are utterly different depending on whether the land is covered by ice. Upon glacier retreat, new land uses may become possible: (1)

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

2002-01-01

342

Accelerating frontal retreat and seasonal variability in North West Svalbard glaciers  

Microsoft Academic Search

Calving flux is a significant mass balance component for Svalbard glaciers. Calving processes in relation to fjord conditions, glacier velocity and frontal positions are currently poorly understood despite their importance. We present an unprecedented series of data showing ice-front behaviour and surface velocities for NW Svalbard glaciers and discuss the fundamental controls on the calving processes between 1991 and 2008.

D. Mansell; A. Luckman; T. Murray

2009-01-01

343

Geometry changes on the Kronebreen-Holtedahlfonna glacier system, NW Svalbard  

Microsoft Academic Search

Kronebreen is one of Svalbard's fastest glaciers, moving at ~2 m d-1 at its tidewater calving front. The glacier drains an area of ~400 km2, including the Holtedahlfonna ice field and several smaller glaciers. We compile a variety of surface elevation data to calculate geometrical changes that have occurred since the first photogrammetric quality photographs were obtained in the 1960s.

B. Altena; J. Kohler; C. Nuth

2008-01-01

344

36 CFR 13.1312 - Climbing and walking on Exit Glacier.  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Climbing and walking on Exit Glacier. 13.1312 Section...Provisions § 13.1312 Climbing and walking on Exit Glacier. Except for areas designated by the Superintendent, climbing or walking on, in, or under Exit Glacier is...

2013-07-01

345

36 CFR 13.1312 - Climbing and walking on Exit Glacier.  

Code of Federal Regulations, 2010 CFR

... 2009-07-01 false Climbing and walking on Exit Glacier. 13.1312 Section...Provisions § 13.1312 Climbing and walking on Exit Glacier. Except for areas designated by the Superintendent, climbing or walking on, in, or under Exit Glacier is...

2009-07-01

346

36 CFR 13.1312 - Climbing and walking on Exit Glacier.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Climbing and walking on Exit Glacier. 13.1312 Section...Provisions § 13.1312 Climbing and walking on Exit Glacier. Except for areas designated by the Superintendent, climbing or walking on, in, or under Exit Glacier is...

2010-07-01

347

Cold-based Glaciers in the Western Dry Valleys of Antarctica: Terrestrial Landforms and Martian Analogs  

NASA Astrophysics Data System (ADS)

Cold-based glaciers in Antarctica Dry Valleys are characterized by landforms (drop moraines, sublimation tills, rock glaciers) that are often different than temperate or wet-based glaciers; these features are similar to deposits on Mars and may offer clues to their origin.

Marchant, D. R.; Head, J. W.

2003-03-01

348

Changes in the Harding Icefield and the Grewingk-Yalik Glacier Complex  

Microsoft Academic Search

Glacier changes in the mountains of the Kenai Peninsula, Alaska, have been analyzed in the Harding Icefield and the Grewingk-Yalik Glacier Complex, many of which originate in Kenai Fjords National Park (KEFJ). The Harding Icefield spawns more than 38 glaciers of which some are tidewater and others are land-based, or wholly or partially terminate in lakes. We used Landsat Multispectral

DOROTHY K. HALL; BRUCE A. GIFFEN; JANET Y. L. CHIEN

349

Cs137 Gamma Peak Detection in Snow Layers on Calderone Glacier  

Microsoft Academic Search

The Calderone glacier, located in the Gran Sasso d’Italia mountain group (Abruzzo, Italy), is the most southern glacier in Europe. The reduced dimension and the general conditions of the glacier make it a powerful environmental indicator in evaluating global change processes including the radio chemical pollution induced by human activity. Two high altitude samples of snow, collected during spring 1999,

Antonella Balerna; Enrico Bernieri; Adolfo Esposito; Massimo Pecci; Claudio Smiraglia

350

Surging glaciers and glacial floods in the Upper Indus Basin, Pakistan  

Microsoft Academic Search

A review of glacial hazards in the Upper Indus Basin, Pakistan, has identified 52 catastrophic floods that have occurred between 1826 and 2000 arising from ice dam failures and glacier lake outburst floods (GLOFs). Surging glaciers have formed large ice dams, where the rapid glacier advances have blocked the adjacent river, and have failed subsequently releasing up to 3 km^3

J. M. Reynolds

2003-01-01

351

Quantification of glacier elevation changes using ICESat and SRTM elevation data in the Upper Indus Basin  

Microsoft Academic Search

Recent studies carried out in the Karakoram Himalayas suggest an expansion of glaciers. Many studies conducted in the Himalayan region have focused on monitoring changes in the aerial extent of individual glaciers from remotely sensed data or through field surveys. Limited work, however, has been done in this region to estimate glacier volume changes using measurements of elevation change over

B. S. Naz; L. C. Bowling; M. M. Crawford

2010-01-01

352

Seismicity related to the glacier of Cotopaxi Volcano, Ecuador  

NASA Astrophysics Data System (ADS)

Significant seismic activity is generally recorded on volcanoes covered by an icecap. This work was carried out in order to quantify the role of the glaciers in the generation of seismicity for Cotopaxi volcano. We compared the seismic activity registered on the glacier and on the rock near the snout of the north flank glacier. We focused on the analysis of low frequency events (<5 Hz) similar to volcanic LP events when recorded on rock base. The particle motion analysis helps to estimate source locations, which are distributed in crevasses areas. High incident angles suggest a superficial origin. These events are interpreted as icequakes for which we propose as source mechanism a fluid-driven crack model triggered by ice cracking or hydraulic transients. The low quality factor values estimated are consistent with the resonance of an ice crack filled with water. This work shows that low frequency icequakes can be confusingly taken as volcanic LP events.

Métaxian, Jean-Philippe; Araujo, Sebastián; Mora, Mauricio; Lesage, Philippe

2003-05-01

353

Context for the Recent Massive Petermann Glacier Calving Event  

NASA Astrophysics Data System (ADS)

On 4 August 2010, about one fifth of the floating ice tongue of Petermann Glacier (also known as “Petermann Gletscher”) in northwestern Greenland calved (Figure 1). The resulting “ice island” had an area approximately 4 times that of Manhattan Island (about 253±17 square kilometers). The ice island garnered much attention from the media, politicians, and the public, who raised concerns about downstream implications for shipping, offshore oil and gas operations, and possible connections to Arctic and global warming. Does this event signal a change in the glacier's dynamics? Or can it be characterized as part of the glacier's natural variability? Understanding the known historical context of this event allows scientists and the public to judge its significance.

Falkner, Kelly K.; Melling, Humfrey; Münchow, Andreas M.; Box, Jason E.; Wohlleben, Trudy; Johnson, Helen L.; Gudmandsen, Preben; Samelson, Roger; Copland, Luke; Steffen, Konrad; Rignot, Eric; Higgins, Anthony K.

2011-04-01

354

Dynamic interactions between glacier and glacial lake in the Bhutan Himalaya  

NASA Astrophysics Data System (ADS)

A number of supraglacial lakes formed on the termini of debris-covered glaciers in the Bhutan Himalaya as a result of glacier retreat due to climate change. The terminal part of the lake-terminating glaciers flow faster than that of the land-terminating glaciers because the basal ice motion is enhanced by high subglacial water pressure generated by lake water. Increased ice flux caused by the accelerated glacier flow could be dissipated through the calving process which reduced the glacier thickness. It is important to understand the interaction between lake formation and glacier dynamics. Although glacier flow velocity has been measured by remote-sensing analysis in several regions of the Himalayas, glacier thinning rates have not been observed by neither in-situ nor remote-sensing approaches. The lack of field data raises limitation to interpretations for glacier dynamics. We investigate the influence of the presence/absence of glacial lakes on glacier dynamics and changes in surface elevation. We study two debris-covered glaciers in the Lunana region, the Bhutan Himalaya. Thorthormi Glacier is a land-terminating glacier with some supraglacial lakes while Lugge Glacier is a lake-terminating glaciers. We surveyed the surface elevation of debris-covered areas of the two glaciers in 2004 and 2011 by a differential GPS. Change in surface elevation of the lake-terminating Lugge Glacier (-5.4--2.4 m yr-1) was much more negative than that of the land-terminating Thorthormi Glacier (-3.3-0.6 m yr-1). Surface flow speed of the Thorthormi Glacier measured during 2002-2004 was faster in the upper reaches (~90 m yr-1) and reduced toward the downstream (40 m yr-1). In contrast, the surface flow speed at the Lugge Glacier measured in the same periods was 40-55 m yr-1 and the greatest at the lower most part. Observed spatial distribution of surface flow velocity at both glaciers were evaluated by a two-dimensional numerical flow model. Calculated emergence velocities are 1.9-18.8 m yr-1 at the Thorthormi Glacier while -12.0-2.7 m yr-1 at the Lugge Glacier. This result suggests that decreasing in flow velocity towards the terminus in the Thorthormi Glacier causes compressive flow. It suggests that the compressive flow of the Thorthormi Glacier counterbalanced surface melting, resulting in inhibition of the surface lowering. In contrast, the extensional flow of the Lugge Glacier accelerated the surface lowering. Speed up of glacier terminus induced extensional flow regime causes the thinning of ice and increase in basal motion, which will lead to further flow acceleration. Such positive feedbacks have been found over the ice streams in the polar ice sheets. In this study we showed the observational evidences, in which the similar feedbacks make contrast the terminus behaviors of glaciers in the Bhutan Himalaya. If the supraglacial lake on Thorthormi Glacier expanded, the surface lowering may be accelerated in the future.

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

2012-04-01

355

Prediction of alpine glacier sliding instabilities: a new hope  

NASA Astrophysics Data System (ADS)

Mechanical and sliding instabilities are the two processes which may lead to breaking-off events of large ice masses. Mechanical instabilities mainly affect unbalanced cold hanging glaciers. In the latter case, a prediction could be achieved based on data for surface velocities and seismic activity. The case of sliding instabilities is more problematic. This phenomenon occurs on temperate glacier tongues. Such instabilities are strongly affected by the subglacial hydrology: meltwater may cause (i) a lubrication of the bed, and (ii) a decrease in the effective pressure and consequently a decrease in basal friction. Available data from Allalingletscher (Valais) indicate that the glacier tongue experienced an active phase for 2-3 weeks with enhanced basal motion in late summer in most years. In order to scrutinize in more detail the processes governing the sliding instabilities, a numerical model developed to investigate gravitational instabilities in heterogeneous media was applied to Allalingletscher. This model made it possible to account for various geometric configurations, interaction between sliding and tension cracking and water flow at the bedrock. We could show that both a critical geometrical configuration of the glacier tongue and the existence of a distributed drainage network were the main causes of this catastrophic break-off. Moreover, the analysis of the modeling results diagnosed the phenomenon of recoupling of the glacier to its bed as a potential new precursory sign of the final break-off. This model casts a gleam of hope for a better understanding of the ultimate rupture process which results from such glacier sliding instabilities.

Faillettaz, J.; Funk, M.; Sornette, D.

2012-04-01

356

A Comparison of Seismic Records of Calving Glaciers  

NASA Astrophysics Data System (ADS)

Glacier calving is a key process in the cryosphere's contribution to sea level rise. It is responsible for virtually all of Antarctica's ice mass loss to the ocean and about half of Greenland's negative mass balance. As glacier calving is a highly complicated and variable phenomenon, its physical laws are poorly understood. For this reason "dynamical mass loss" is one of the critical mechanisms that have yet to be incorporated into large-scale ice sheet models that aim to predict future sea level variations. As calving environments are almost always difficult to access, data pertaining to calving processes are usually gathered remotely. Seismometers have recently proven to be a valuable tool for studying calving, even though they may be located far away from the calving front. Pre-existing global and regional seismic networks thus constitute a valuable resource for the study of glacier calving as they allow for automatic detection and monitoring of calving activity. Various sources occurring nearly simultaneously give rise to calving seismicity. Potential source mechanisms include fracturing, hydraulic transients, glacier acceleration, ocean wave action, and icebergs scraping the fjord walls, bottom, or terminus. Fracturing and hydraulic transients emit seismic energy above 1 Hz and are only recorded locally, whereas glacier acceleration, iceberg scraping, and ocean waves may produce waveforms with periods of 100's or 1000's of seconds and can be recorded by far-field seismometers. We present examples of such low-frequency seismicity from Jakobshavn Isbrae, Greenland, and Columbia and Yahtse Glaciers, Alaska. Finally, we discuss the possibility of remotely investigating calving behavior by comparing the seismic signature of individual calving events from different glaciological settings.

Walter, Fabian; Amundson, Jason M.; O'Neel, Shad; Clinton, John F.; Luethi, Martin P.; Bassis, Jeremy; Fricker, Helen Amanda

2010-05-01

357

Cold-based mountain glaciers on Mars: western Arsia Mons  

NASA Astrophysics Data System (ADS)

Surface environmental conditions on Mars are presently extremely cold and hyper-arid, most equivalent to polar deserts on Earth. Coupling newly acquired Mars MOLA and MOC data with field-based observations regarding the flow, surface morphology, and depositional history of polar glaciers in Antarctica, we show that the multiple facies of an extensive fan-shaped deposit on the western flanks of Arsia Mons, Tharsis Rise are consistent with deposition from cold-based mountain glaciers. An outer ridged facies that consists of multiple laterally extensive, arcuate and parallel ridges, resting without disturbance on both well-preserved lava flows and an impact crater, is interpreted as drop moraines formed at the margin of an ablating and predominantly receding cold-based glacier. Inward of the ridges lies a knobby facies that consists of irregular and closely spaced equidimensional knobs, each up to several kilometers in diameter; this facies is interpreted as a sublimation till derived from in situ downwasting of ash-rich glacier ice. A third facies comprising distinctive convex outward lobes with concentric parallel ridges and aspect ratios elongated downslope likely represents rock-glacier deposits, some of which may still be underlain by a core of glacier ice. Taken together, these surficial deposits show that the western flank of Arsia Mons was occupied by an extensive mountain glacial system accumulating on, and emerging from, the upper slopes of the volcano (above ~7000 m) and spreading downslope to form a piedmont-like fan. Similar deposits exist on the other Tharsis Montes, suggesting at least one phase of late Hesperian aged glaciation in the equatorial Tharsis region.

Head, J. W.; Marchant, D. R.

2003-04-01

358

An inventory of glacier changes between 1973 and 2011 for the Geladandong Mountain area, China  

NASA Astrophysics Data System (ADS)

The snow and ice of the Geladangong Mountain area supply the headwaters of the Yangtze River, and long-term changes to glaciers and ice masses in this region due to a warming climate are of great concern. An inventory of glacier boundaries and changes over decades for the Geladandong Mountain area in China has been conducted using remote sensing imagery from Landsat (MSS, TM, ETM+), CERBES CCD, and GIS techniques. Variations in glacier extent has been measured using a~series of digital images since 1973, including Landsat MSS in 1973, Landsat TM in 1992, Landsat ETM+ in 2004, and CBERS CCD in 2011. All Landsat data are snow-free outside the glacier boundaries, allowing an unsupervised classification method to be used to extract glacier area. For the CBERS CCD data, some areas were covered by clouds and snow, requiring an initial unsupervised classification method to divide glacier, clouds and snow from other land types, followed by a supervised visual interpretation to extract glacier area. The results show a decrease in glacier ice cover in the study area during the past 38 yr. From 1973 to 2011, glacier area decreased from 107 105 hectares to 94 220 hectares, or a change of -12%. The speed at which ice cover is being lost has been decreasing during the past 38 yr. The rate of glacier area loss was 0.47% yr-1 from 1973-1992, 0.19% yr-1 from 1992-2004, and 0.14% yr-1 from 2004-2011. While most of the glaciers are shrinking, some are expanding. For the 1973 to 2004 period, retreating glaciers exposed 14 447 hectares of land, and advancing glaciers spread over 2682 hectares that were not covered by ice in 1973. The net glacier area decrease is 11 765 hectares from 1973-2004. For the 1973 to 2011 period, glaciers expanded over 3791 hectares, and retreated from 16 504 hectares.

Zhang, J.; Braaten, D.; Li, X.; She, J.; Tao, F.

2013-02-01

359

Marine Geophysical Surveying Along the Hubbard Glacier Terminus, Southeast Alaska  

NASA Astrophysics Data System (ADS)

Tidewater glaciers are a challenging environment for marine investigations, owing to the dangers associated with calving and restrictions on operations due to dense floating ice. We report here on recent efforts to conduct marine geophysical surveys proximal to the ice face of Hubbard Glacier, in Disenchantment Bay, Alaska. Hubbard is an advancing tidewater glacier that has twice recently (1986 and 2002) impinged on Gilbert Point, which separates Russell Fiord from Disenchantment Bay, thereby temporarily creating a glacially-dammed Russell Lake. Continued advance will likely form a more permanent dam, rerouting brackish outflow waters into the Situk River, near Yakutat, Alaska. Our primary interest is in studying the development and motion of the morainal bank which, for an advancing tidewater glacier, stabilizes it against rapid retreat. For survey work, we operated with a small, fast, aluminum-hulled vessel and a captain experienced in operating in ice-bound conditions, providing a high margin of safety and maneuverability. Differencing of multibeam bathymetric data acquired in different years can identify and quantify areas of deposition and erosion on the morainal bank front and in Disenchantment Bay proper, where accumulation rates are typically > 1 m/yr within 1 km of the glacier terminus. The advance or retreat rate of the morainal bank can be determined by changes in the bed elevation through time; we document advance rates that average > 30 m/yr in Disenchantment Bay, but which vary substantially over different time periods and at different positions along the ice face. Georeferencing of available satellite imagery allows us to directly compare the position of the glacial terminus with the position of the morainal bank. From 1978 to 1999, and then to 2006, the advances in terminus and morainal bank positions were closely synchronized along the length of the glacier face. In the shallower Russell Fiord side of the terminus, a sediment ridge was mapped both in 1999 and 2008, but shifted substantially southward in the later survey. This ridge appears to be a push moraine associated with the maximum seasonal advance position of the ice margin. CHIRP seismic reflection data, although not penetrating well into morainal sediments, nevertheless display striking variations in seafloor echo character that may be used to distinguish gravels, diamict and bedrock. We observe evidence of outwash deposits from the retreating Variegated and Orange Glaciers mantling the eastern extent of the Hubbard Glacier morainal bank; these deposits are distinct in acoustic character from the potential bedrock outcrops and overconsolidated diamict within the ‘tidal channel’ at Gilbert Point and from the surface of the morainal bank within uppermost Disenchantment Bay.

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

2010-12-01

360

Investigating role of ice-ocean interaction on glacier dynamic: Results from numerical modeling applied to Petermann Glacier  

NASA Astrophysics Data System (ADS)

Calving of icebergs and bottom melting from ice shelves accounts for roughly half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. Petermann Glacier (north Greenland) with its ~17 km wide and ~ 60 km long floating ice-shelf is experiencing high rates of bottom melting. The recent partial disintegration of its shelf (in August 2010) presents a natural experiment to investigate the dynamic response of the ice sheet to its shelf retreat. We apply a numerical ice flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as shelf disintegration, bottom melting, sea ice or sikkusak disintegration and surface run off to the mass balance of Petermann Glacier and assess its stability. Our modeling study provides insights into the role of ice-ocean interaction, and on response of Petermann Glacier to its recent massive ice loss.

Nick, F. M.; van der Veen, C. J.; Vieli, A.; Pattyn, F.; Hubbard, A.; Box, J. E.

2010-12-01

361

Contribution potential of glaciers to water availability in different climate regimes  

PubMed Central

Although reliable figures are often missing, considerable detrimental changes due to shrinking glaciers are universally expected for water availability in river systems under the influence of ongoing global climate change. We estimate the contribution potential of seasonally delayed glacier melt water to total water availability in large river systems. We find that the seasonally delayed glacier contribution is largest where rivers enter seasonally arid regions and negligible in the lowlands of river basins governed by monsoon climates. By comparing monthly glacier melt contributions with population densities in different altitude bands within each river basin, we demonstrate that strong human dependence on glacier melt is not collocated with highest population densities in most basins.

Kaser, Georg; Grosshauser, Martin; Marzeion, Ben

2010-01-01

362

Debris cover and surface melt at a temperate maritime alpine glacier: Franz Josef Glacier, Southern Alps, New Zealand  

NASA Astrophysics Data System (ADS)

During the last few years, after three decades of generally positive mass balance, Franz Josef Glacier (Southern Alps, New Zealand) has entered into a phase of strong frontal retreat. This development is combined with significant downwasting of the lower glacier tongue and a concurrent increasing emergence of debris on the surface in the ablation zone. Previously, melt rates at Franz Josef Glacier have only been measured on bare ice, so a short-term study in February 2012 saw a network of 11 ablation stakes drilled into locations of varying supraglacial debris thickness on the lower glacier. Direct ablation measurements were accompanied by observations of air temperatures and mapping of debris thickness and its distribution on the lower glacier tongue in order to calculate the potential effect of reduced overall ablation. Mean ablation rates over 9 days varied over the range 1.2-10.1 cm d-1 and were closely related to debris thickness. Air temperatures provided a strong indicator of daily melt rates and by applying a degree-day approach, a range of degree-day factors between 1.1 and 8.1 mm d-1 °C-1 with a mean of 4.4 mm d-1 °C-1 was obtained. These values are comparable with rates reported in other studies. Mapping of the entire ablation zone revealed an area of 0.7 km2 (or 14.3 %) covered by debris of 1-50 cm thickness. Based on measured debris thicknesses and calculated degree-day factors, ablation on those debris-covered areas of the glacier is reduced by a total of 41%. For the entire ablation zone this equates to a 6% overall reduction in melt. This study highlights the usefulness of short-term surveys to gather representative ablation data.

Brook, Martin; Hagg, Wilfried; Winkler, Stefan

2013-04-01

363

Modelling distributed glacier ablation on Haut Glacier d'Arolla, Switzerland: a comparison of an energy-balance and an enhanced temperature-index model  

Microsoft Academic Search

Modelling melt rates across alpine glaciers is an essential step for studying the interannual evolution of snow-cover and glacier ice and for estimation of the total runoff from glacierised basins. Two approaches are commonly used to compute melt: physically-based energy-balance models in which each of the relevant energy fluxes at the glacier-surface interface is computed using energy-balance equations and more

Marco Carenzo; Francesca Pellicciotti; Jakob Helbing; Ruzica Dadic; Paolo Burlando

2010-01-01

364

Calving processes and the dynamics of calving glaciers  

NASA Astrophysics Data System (ADS)

Calving of icebergs is an important component of mass loss from the polar ice sheets and glaciers in many parts of the world. Calving rates can increase dramatically in response to increases in velocity and/or retreat of the glacier margin, with important implications for sea level change. Despite their importance, calving and related dynamic processes are poorly represented in the current generation of ice sheet models. This is largely because understanding the 'calving problem' involves several other long-standing problems in glaciology, combined with the difficulties and dangers of field data collection. In this paper, we systematically review different aspects of the calving problem, and outline a new framework for representing calving processes in ice sheet models. We define a hierarchy of calving processes, to distinguish those that exert a fundamental control on the position of the ice margin from more localised processes responsible for individual calving events. The first-order control on calving is the strain rate arising from spatial variations in velocity (particularly sliding speed), which determines the location and depth of surface crevasses. Superimposed on this first-order process are second-order processes that can further erode the ice margin. These include: fracture propagation in response to local stress imbalances in the immediate vicinity of the glacier front; undercutting of the glacier terminus by melting at or below the waterline; and bending at the junction between grounded and buoyant parts of an ice tongue. Calving of projecting, submerged 'ice feet' can be regarded as a third-order process, because it is paced by first- or second-order calving above the waterline. First-order calving can be represented in glacier models using a calving criterion based on crevasse depth, which is a function of longitudinal strain rate. Modelling changes in terminus position and calving rates thus reduces to the problem of determining the ice geometry and velocity distribution. Realistic solutions to the problem of modelling ice flow therefore depend critically on an appropriate choice of sliding law. Models that assume that basal velocities are controlled by basal drag can replicate much of the observed behaviour of calving glaciers with grounded termini, but an important limitation is that they cannot be used to model floating glacier termini or ice shelves. Alternative sliding laws that parameterise drag from the glacier margins provide more flexible and robust ways of representing calving in ice sheet models. Such models can explain a remarkable range of observed phenomena within a simple, unifying framework, including: downglacier increases in velocity and strain rates where basal and/or lateral drag diminishes; flow acceleration in response to thinning through time; the tendency for glaciers to stabilise at 'pinning points' in relatively shallow water or fjord narrowings; the constraints on ice shelf stability; and the contrasts in calving rates between tidewater and freshwater calving glaciers. Many unresolved issues remain, however, including the role played by the removal of backstress in the acceleration of retreating calving glaciers, and the controls on melting at and below the waterline.

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

2007-06-01

365

The design of the GLIMS (Global Land Ice Measurements from Space) glacier database.  

NASA Astrophysics Data System (ADS)

GLIMS (Global Land Ice Measurements from Space) is a collaborative project among approximately 40 international institutions, whose goal is to develop a database of information on the world's glaciers that enables the assessment of current world glacier extent and glacier change. The National Snow and Ice Data Center (NSIDC) is developing the information management system for GLIMS, the database for which has already been designed and is being implemented at NSIDC. This presentation addresses the scientific considerations that went into the design of the GLIMS database, which consists of more than twenty tables containing both time-dependent and time-independent data. The fundamental data unit in the database is the "glacier", in roughly the conventional sense, rather than contiguous ice masses. The design had several goals: 1) to store spatio-temporal data for many different types of glaciers around the world; 2) to be able to retrieve such data through many types of queries, including temporal or geographic constraints, specification of glacier names, etc.; 3) to model glacier data in a way consistent with historical treatment of glaciers; 4) to address explicitly issues of measurement errors and uncertainty; 5) to enable the concurrent generation and submission of glacier analysis results (including unique glacier identification numbers) by international collaborators. (There are additional goals for the data-retrieval part of the system.) These goals were met by designing a relational database which stores spatial and temporal glacier data in an efficient and flexible way.

Raup, B. H.; Scharfen, G. R.; Khalsa, S. S.; Kaeaeb, A.

2001-12-01

366

Dynamics and GPR stratigraphy of a polar rock glacier on James Ross Island, Antarctic Peninsula  

NASA Astrophysics Data System (ADS)

We describe field measurements (ground-penetrating radar (GPR), geodetic survey and ice-core drilling) to provide new information on the movement mechanism and internal structure of a polar rock glacier on James Ross Island, Antarctic Peninsula. We collected GPR data along longitudinal and transverse profiles. The longitudinal GPR profiles identify inter-bedded debris-rich layers that dip up-glacier, similar to the thrust structures in the compression zone of a valley glacier. The transverse GPR profiles indicate a syncline structure inclined towards the central part of the rock glacier, resembling the transverse foliation of a valley glacier. The stratigraphy of two boreholes shows that the rock glacier consists primarily of bubbly ice with thin debris-rich layers, an internal structure similar to the `nested spoons' structure common in the interior of valley glaciers. These results indicate that the glacier motion is controlled by shear movement, common in valley glaciers. The geodetic survey confirms that flow velocities decrease towards the lower part of the rock glacier. Such heterogeneous movement causes longitudinal compression and forms thrusts which then create the debris-rich layer by uplifting basal ice and debris. Pushing of the upstream ice against the downstream ice bends the surface layers, forming transverse ridges on the rock glacier surface.

Fukui, Kotaro; Sone, Toshio; Strelin, Jorge A.; Torielli, Cesar A.; Mori, Junko; Fujii, Yoshiyuki

367

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

SciTech Connect

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

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

1992-03-01

368

Wind effects on snow cover in Pascua-Lama, Dry Andes of Chile  

NASA Astrophysics Data System (ADS)

We present the application of a distributed snow model (SnowModel) on the instrumented site of Pascua-Lama in the Dry Andes (2600-5630 m above sea level, 29° S). A model experiment was performed to assess the effect of wind on snow cover patterns. A particular objective was to evaluate the role of blowing snow on the glacier formation. The model was run using the data from 11 weather stations over a complete snow season. First, a cross-validation of the meteorological variables interpolation model (MicroMet submodel) was performed to evaluate the performance of the simulated meteorological forcing. Secondly, two SnowModel simulations were set up: one without and the other with the wind transport submodel (SnowTran-3D). Results from both simulations were compared with in situ snow depth measurements and remotely sensed snow cover data. The inclusion of SnowTran-3D does not change the fact that the model is unable to capture the small-scale snow depth spatial variability (as captured by in situ snow depth sensors). However, remote sensing data (MODIS daily snow product) indicate that at broader scales the wind module produced an improved representation of the snow distribution near the glaciers (2-D correlation coefficient increased from R = 0.04 to R = 0.27). The model outputs show that a key process is the sublimation of blowing snow, which amounts to 18% of the total ablation over the whole study area, with a high spatial variability. The effect of snow drift is more visible on the glaciers, where wind-transported snow accumulates preferentially. Net deposition occurred for 43% of the glacier grid points, whereas it is only 23% of non-glacier grid points located above the minimum glacier altitude (4475 m).

Lhermitte, Stef; Gascoin, Simon; Kinnard, Christophe; Bortels, Kirsten; Liston, Glen E.

2013-04-01

369

Wind effects on snow cover in Pascua-Lama, Dry Andes of Chile  

NASA Astrophysics Data System (ADS)

We present the first application of a distributed snow model (SnowModel) in the instrumented site of Pascua-Lama in the Dry Andes (2600-5630 m above sea level, 29° S). A model experiment was performed to assess the effect of wind on the snow cover patterns. A particular objective was to evaluate the role of blowing snow on the glacier formation. The model was run using the data from 11 weather stations over a complete snow season. First, a cross-validation of the meteorological variables interpolation model (MicroMet submodel) was performed to evaluate the performance of the simulated meteorological forcing. Secondly, two SnowModel simulations were set up: one without and the other with the wind transport submodel (SnowTran-3D). Results from both simulations were compared with in situ snow depth measurements and remotely sensed snow cover data. The inclusion of SnowTran-3D does not change the fact that the model is unable to capture the small-scale snow depth spatial variability (as captured by in situ snow depth sensors). However, remote sensing data (MODIS daily snow product) indicate that at broader scales the wind module produced an improved representation of the snow distribution near the glaciers (2-D correlation coefficient increased from R = 0.04 to R = 0.27). The model outputs show that a key process is the sublimation of blowing snow, which amounts to 18% of the total ablation over the whole study area, with a high spatial variability. The effect of snow drift is more visible on the glaciers, where wind-transported snow accumulates preferentially. Net deposition occurred for 43% of the glacier grid points, whereas it is only 23% of non-glacier grid points located above the minimum glacier altitude (4475 m).

Gascoin, Simon; Lhermitte, Stefaan; Kinnard, Christophe; Bortels, Kirsten; Liston, Glen E.

2013-05-01

370

The recent evolution of Liligo glacier, Karakoram, Pakistan, and its present quiescent phase  

NASA Astrophysics Data System (ADS)

Liligo glacier, in the central eastern Karakoram, Pakistan, is a small, south-to-north-flowing glacier situated in a transverse valley on the left (south) side of Baltoro glacier. New processing of satellite imagery enables a better quantification of terminus oscillations over the past 30 years. From the beginning of the 1970s to the beginning of the 21st century, Liligo glacier advanced about 2 km (60 m a-1). The progress was characterized by a significant evolution of terminus morphology, similar to that observed on the same glacier during the advance event near the beginning of the 20th century, and to those of many other Karakoram glaciers. This suggests indications of a surge-type mechanism. Field observations performed in 2004 indicated there was probably no confluence at that time between Liligo and Baltoro glaciers and that a quiescent phase had started in the early years of the 21st century.

Belò, Marco; Mayer, Christoph; Smiraglia, Claudio; Tamburini, Andrea

371

Weather and mass balance in the ablation zone of the Taylor Glacier, Antarctica  

NASA Astrophysics Data System (ADS)

A simple model that predicts ablation from weather station measurements on the Taylor Glacier, Antarctica is presented along with ablation measurements at about 250 ablation stakes. The model output matches the ablation measurements at the weather station locations. Via extrapolation of the weather station measurements to the rest of the glacier, the model also makes predictions for the rest of the ablation zone. These predictions are compared with measurements of ablation, and errors and uncertainties are discussed. Sublimation is the dominant mass-loss mechanism for the majority of the glacier. In the current climate, melt is important only near the terminus and at the margins of the glacier during the summer. Unlike most Antarctic glaciers, the Taylor Glacier terminates on land so calving does not factor into the mass balance. Further development of this model will allow investigation of the mass balance of the Taylor Glacier in past and future climates.

Bliss, A. K.; Cuffey, K. M.; Kavanaugh, J.; Morse, D.

2005-12-01

372

Modeling the mass balance of the Wolverine Glacier Alaska USA using the PTAA model  

NASA Astrophysics Data System (ADS)

Glaciers in Alaska have been increasingly losing mass over the last several decades. This trend is especially apparent in South-Central Alaska where many glaciers are undergoing rapid changes and contributing substantially to rising sea levels (Arendt et al., 2002). It is important to understand the rates at which these glaciers are losing mass as well as the important climatic drivers to better prepare for what the future holds in this region and the rest of the world. This work compares glacier mass balance data modeled through the Precipitation-Temperature Area Altitude (PTAA) mass balance model for the Wolverine Glacier in the Kenai Peninsula in South-Central Alaska to observed data from the USGS “benchmark” glacier program in order to help validate the model. The mass balance data are also correlated with climate data in order to understand the main climatic drivers of the glacier mass balance in this region.

Korn, D.

2010-12-01

373

Influence of high-order mechanics on simulation of glacier response to climate change: insights from Haig Glacier, Canadian Rocky Mountains  

NASA Astrophysics Data System (ADS)

Evolution of glaciers in response to climate change has mostly been simulated using simplified dynamical models. Because these models do not account for the influence of high-order physics, corresponding results may exhibit some biases. For Haig Glacier in the Canadian Rocky Mountains, we test this hypothesis by comparing simulation results obtained from 3-D numerical models that deal with different assumptions concerning physics, ranging from simple shear deformation to comprehensive Stokes flow. In glacier retreat scenarios, we find a minimal role of high-order mechanics in glacier evolution, as geometric effects at our site (the presence of an overdeepened bed) result in limited horizontal movement of ice (flow speed on the order of a few meters per year). Consequently, high-order and reduced models all predict that Haig Glacier ceases to exist by ca. 2080 under ongoing climate warming. The influence of high-order mechanics is evident, however, in glacier advance scenarios, where ice speeds are greater and ice dynamical effects become more important. Although similar studies on other glaciers are essential to generalize such findings, we advise that high-order mechanics are important and therefore should be considered while modeling the evolution of active glaciers. Reduced model predictions may be adequate for other glaciologic and topographic settings, particularly where flow speeds are low and where mass balance changes dominate over ice dynamics in determining glacier geometry.

Adhikari, S.; Marshall, S. J.

2013-09-01

374

Seasonal Characteristics of Surface Meteorological and Radiative Fluxes on the East Rongbuk Glacier in Mt. Qomolangma (the Mt. Everest) Region  

NASA Astrophysics Data System (ADS)

Ground-based measurements are essential for understanding alpine glacier dynamics, especially in remote regions where in-situ measurements are extremely limited. The meteorological and radiative fluxes were measured over the accumulation area on the East Rongbuk Glacier, Mt. Qomolangma (the Mt. Everest) at elevation of 6,560 m a.s.l. Measurements were conducted using an automatic weather station (AWS) from May 1 through July 22, 2005 (spring-summer period) and from October 2 of 2007 through January 20 of 2008 (autumn-winter period). Surface meteorological and radiative characteristics were strongly controlled by two major synoptic circulation regimes: the southwesterly Indian monsoon regime in summer and the westerlies in winter. At the AWS site on the East Rongbuk Glacier, north or northwest winds prevail with higher wind speed (up to 35 ms-1 in January) in winter and south or southeast winds predominate after the onset of the southwesterly Indian monsoon with relatively low wind speed in summer. Intensity of incoming shortwave radiation is extremely high due to its high elevation and high reflective surrounding surface. The striking feature is that the observed 10-minute mean incoming shortwave radiative fluxes around local noon were frequently higher than the solar constant at the top of the atmosphere from May through July, 2005. The observed higher-than-solar-constant values are mainly due to the impact of local convective broken clouds and high surface reflectivity over the surrounding terrains. We estimated that horizontal component of received diffusive solar radiation from surrounding terrains ranged from 140 to 310 Wm-2, accounting for about 10 to 25% of the observed incoming shortwave radiation under clear sky conditions. This value could be even higher under overcast cloudy days. The mean surface albedo ranged from 0.72 during summer- spring period and 0.69 during the autumn-winter period. The atmospheric incoming longwave radiation was strongly controlled by cloud conditions and atmospheric moisture content. Overall impact of clouds on net radiation balance is negative in Mt. Qomolangma region. The daily mean net all-wave radiation was positive during the entire spring-summer period and mostly positive during the autumn-winter period except a few overcast cloudy days. On monthly basis, net all-wave radiation was always positive.

Yang, X.; Zhang, T.; Qin, D.; Kang, S.; Qin, X.; Liu, H.

2008-12-01

375

Post Little Ice Age Collapse of the Glacier Bay Icefield, Alaska  

NASA Astrophysics Data System (ADS)

Glacier Bay provides an excellent example of the tidewater glacier cycle proposed by Austin Post. It has a complete record of an advancing phase, stability, rapid calving and drawdown, lengthy retreat, and then readvance behind protective sediments. Glacier Bay currently consists of numerous discrete glaciers and small isolated icefields, but it recently contained a huge continuous icefield up to 2 km thick that covered more than 6000 km2 at the peak of the Little Ice Age (LIA) (1750 AD). Rapid calving and associated upstream drawdown lead to its collapse. In less than 160 yrs, the main trunk of the icefield retreated 120 km in fjords as deep as 500 m. We evaluated the LIA volume and topography of the Glacier Bay Icefield based on mapping of trimlines, lateral moraines and terminal moraines. We used light aircraft to identify these geomorphic markers as well as analysis of vertical airphotos, hydrographs, seismic profiles, and the SRTM digital elevation model. Our reconstruction indicates an ice volume loss of over 3000 km3 during the post-LIA collapse. This localized ice wastage represents the largest post-LIA deglaciation known to us, and is greater than the volume lost from all Alaskan and neighboring Canadian Glaciers from 1955-2002, greater in volume than the Larsen B 2002 ice shelf collapse, comparable in volume to Lake Huron, and equivalent to a global rise in sea level (SLE) of 8 mm. The collapse of the Glacier Bay icefield stranded many tributary glaciers. Some were entirely isolated from any source of accumulation and are now simply wasting away (e.g., Burroughs Glacier). Other glaciers in the region have had their accumulations areas severely reduced as the icefields feeding the LIA tidewater glaciers disappeared (e.g., Casement and Brady Glaciers). The vast loss of ice has lead to some of the highest rates of glacier rebound presently occurring in the world (32 mm/yr) with total uplift since the 18th century of as much as 5.8 m. Facilitated by infill of fjords from erosion and remobilization of subglacial sediments, several glaciers are now in the advancing phase of the tidewater glacier cycle despite the regional trend of glacier wastage. Post-LIA Glacier Bay could provide an analogue to collapse of other tidewater glacier systems and outlet glaciers from polar ice sheets.

Motyka, R. J.; Larsen, C. F.

2005-12-01

376

Sea-level rise: Melting glaciers and ice caps  

Microsoft Academic Search

The contribution of glaciers and ice caps to global sea-level rise is uncertain: they are incompletely counted and the calculation is challenging. A new estimate from the best available data suggests a contribution of about 12 cm by 2100.

Frank Paul

2011-01-01

377

Metagenome Sequencing of Prokaryotic Microbiota Collected from Byron Glacier, Alaska  

PubMed Central

Cold environments, such as glaciers, are large reservoirs of microbial life. The present study employed 16S rRNA gene amplicon metagenomic sequencing to survey the prokaryotic microbiota on Alaskan glacial ice, revealing a rich and diverse microbial community of some 2,500 species of bacteria and archaea.

Choudhari, Sulbha; Smith, Sean; Owens, Sarah; Gilbert, Jack A.; Shain, Daniel H.; Dial, Roman J.

2013-01-01

378

Glaciers and Climate Change: Perspectives from Oral Tradition  

Microsoft Academic Search

In northwestern North America, glaciers figure prominently in both indigenous oral traditions and narratives of geophysical sciences. These perspectives intersect in discussions about global warming, predicted to be extreme at Arctic and Subarctic latitudes and an area of concern for both local people and scientists. Indigenous people in northwestern North America have experienced climate variability associated with the latter phases

JULIE CRUIKSHANK

2001-01-01

379

Surface mass balance of Greenland mountain glaciers and ice caps  

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

380

REVIEW ARTICLES: Glaciers and other large ice masses  

Microsoft Academic Search

Substantial progress has been made in recent years with the help of new techniques for the investigation of glaciers and other large ice masses in four major study areas:Flow properties of ice. These can be considered as arising from processes on three distinct scales: (a) lattice-scale processes responsible for the flow characteristics of monocrystals as functions of temperature and stress;

W. F. Budd; U. Radok

1971-01-01

381

Glacier Peak- History and Hazards of a Cascade Volcano  

NSDL National Science Digital Library

This fact sheet discusses the eruptive history and hazards associated with Glacier Peak, the most remote of the five active volcanoes in Washington State. Topics include past eruptions, the potential for large, explosive eruptions with pyroclastic flows produced by collapse of lava domes, and prospects and preparations for future eruptions.

382

Fracture mechanics approach to penetration of bottom crevasses on glaciers  

Microsoft Academic Search

A simple model, based on linear elastic fracture mechanics, is used to investigate conditions allowing the existence of bottom crevasses. On grounded glaciers, these crevasses can only occur if the basal water pressure is close to the ice overburden pressure. If the piezometric head drops more than ?10 m below the flotation level, very large stretching rates are required for

C. J van der Veen

1998-01-01

383

Accelerating ice loss from the fastest Greenland and Antarctic glaciers  

NASA Astrophysics Data System (ADS)

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-1 by 2015, with velocities on PIG increasing to >10 km a-1 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-1.

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

2011-05-01

384

Biogeomorphic interactions in the Turtmann glacier forefield, Switzerland  

NASA Astrophysics Data System (ADS)

Glacier forefields are dynamic environments dominated by active paraglacial processes and simultaneous vegetation succession, triggered by glacier retreat since the Little Ice Age. While these dynamics are accelerating in the last decades owing to climate change, interactions between vegetation and geomorphic processes and components and the resulting patterns are only partly understood. Using a biomorphic approach based on preexisting geomorphic and glaciological data, geomorphic activity was classified and mapped in the Turtmann glacier forefield, Switzerland. Vegetation and environmental parameters were sampled. Vegetation analysis was subsequently carried out with vegetation classification and ordination for identifying relationships to environmental parameters. A paraglacial impact on vegetation succession could be shown and differentiated according to geomorphic activity on constant terrain age. Biogeomorphic concepts were then applied to explain these patterns. Three biogeomorphic succession phases were identified and related to degrees of activity, species composition, and strength of interactions. Integrating our results into the paraglacial concept, we show how the paraglacial adjustment of a glacier forefield is significantly affected by biogeomorphic interactions.

Eichel, Jana; Krautblatter, Michael; Schmidtlein, Sebastian; Dikau, Richard

2013-11-01

385

Post Little Ice Age Rebound in the Glacier Bay Region  

Microsoft Academic Search

Extreme uplift and sea level changes in southeast Alaska have been documented by (1) a regional GPS deformation array consisting of 74 sites; (2) 18 tide gage measurements of sea-level changes; and (3) 27 raised shoreline measurements of total uplift. The GPS data show peak uplift rates of 30 mm\\/ yr in Glacier Bay, and also delineated a second center

Roman J. Motyka; Christopher F. Larsen; Jeffrey T. Freymueller; Keith A. Echelmeyer

386

SYNOPTIC TEMPERATURE MEASUREMENTS OF A GLACIER LAKE AND ITS ENVIRONMENT  

Microsoft Academic Search

Temperature measurements of a small (area = 20.0 hectares), high (altitude = 1,620 m) lake located at the terminus of South Cascade Glacier, Washington, and its ice and rock environment were made with infrared radiometers (8-14\\/i range) during various météorologie regimes. By making simultaneous measurements of lake surface temperatures with four sensors it was found that the \\

William J. CAMPBELL

387

‘Little Ice Age’ glacier fluctuations, Gran Campo Nevado, southernmost Chile  

Microsoft Academic Search

Moraine systems of Glaciar Lengua (unofficial name) and neighbouring glaciers of Gran Campo Nevado (53°S) in the southernmost Andes were mapped and dated by dendrochronological means. They were formed around AD 1628, 1872\\/1875, 1886, 1902, 1912 and 1941 with the advance in the 1870s being calendar dated. Recessional moraines within each moraine system correspond to brief standstills or minor readvances.

Johannes Koch; Rolf Kilian

2005-01-01

388

Rapid increase deposition of Anthropogenic Aerosols in Southeast Tibetan Glacier  

Microsoft Academic Search

Since the so-called Asian Brown Cloud (ABC) occurred during dry season was coined by the international program of Indian Ocean Experiment (INDOEX) in 1999, it has received special attention due to its high loading of anthropogenic aerosols which may have important climatic and environmental effects, especially on accelerating glacier retreat in Himalayas. Yet little is known about its concentrations in

M. Wang; B. Xu; J. Cao

2008-01-01

389

Sea-level rise: Melting glaciers and ice caps  

NASA Astrophysics Data System (ADS)

The contribution of glaciers and ice caps to global sea-level rise is uncertain: they are incompletely counted and the calculation is challenging. A new estimate from the best available data suggests a contribution of about 12 cm by 2100.

Paul, Frank

2011-02-01

390

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

PubMed

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

Bray, J R

1964-04-17

391

Solute dynamics of meltwater of Gangotri glacier, Garhwal Himalaya, India  

NASA Astrophysics Data System (ADS)

The present study investigates solute dynamics of meltwater of Gangotri glacier system in terms of association of different chemical compounds with the geology of the area. In the meltwater, the presence of cations varied as c(Mg2+) > c(Ca2+) > c(Na+) > c(K+), while order of concentration of anions has been c(HCO3 -) > c(SO4 2-) > c(Cl-) > c(NO3 -) in years 2003 and 2004. The magnesium and calcium are found as the dominant cations along with bicarbonate and sulphate as dominant anions. The high ratios of c(Ca2+ + Mg2+)/total cations and c(Ca2+ + Mg2+)/c(Na+ + K+) indicate that the meltwater chemistry of the Gangotri glacier system catchment is mostly controlled by carbonate weathering. Attempts are made to develop rating curves for discharge and different cations. Sporadic rise in discharge without corresponding rise in concentration of most of cations is responsible for their loose correlation in a compound valley glacier like Gangotri glacier.

Kumar, Kireet; Miral, M. S.; Joshi, Sneh; Pant, Namrata; Joshi, Varun; Joshi, L. M.

2009-09-01

392

Examples of Fire Restoration in Glacier National Park  

Microsoft Academic Search

Covering just over 1 million acres, Glacier National Park straddles the Continental Divide in northwestern Montana. Diverse vegetation communities include moist western ce- dar-western hemlock ( Thuja plicata -Tsuga heterophylla ) old growth forests similar to those of the Pacific Coast, dry western grasslands and prairies, dense lodgepole pine for- ests (Pinus contorta var. latifolia), ponderosa pine (P. ponde- msa

Laurie L. Kurth

1996-01-01

393

Influence of tides and tidal current on Mertz Glacier, Antarctica  

Microsoft Academic Search

Mertz Glacier, East Antarctica, is characterized by a 140 km long, 25 km wide floating ice tongue. In this paper, we combine a large number of remotely sensed datasets, including in situ global positioning system measurements, satellite radar altimetry, airborne radio-echo sounding and satellite synthetic aperture radar imagery and interferometry. These various datasets allow us to study the interaction of

Benoît Legrésy; Anja Wendt; Ignazio Tabacco; Frédérique Rémy; Rei