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1

Glaciers, Water and Wind, Oh My!  

NSDL National Science Digital Library

This hands-on activity explores five different forms of erosion (chemical, water, wind, glacier and temperature). Students rotate through stations and model each type of erosion on rocks, soils and minerals.

Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder

2012-04-23

2

Glaciers  

NSDL National Science Digital Library

This interactive Flash exercise and animation explores glaciers, including their formation, growth, and retreat. This resource provides animations, diagrams, models in which students can see the influence of temperature and precipitation on glacier growth, and supplementary information that may serve as an overview or review of glaciers for introductory level physical geology or Earth science students at the high school or undergraduate level.

Smoothstone; Mifflin, Houghton

3

Glacier Area and Mass Variability in the Wind River Range (Wyoming, USA): 2006 to 2012  

NASA Astrophysics Data System (ADS)

The Wind River Range (WRR) is a continuous mountain range approximately 160 km in length in west-central Wyoming, USA. The Wind River Range is host to roughly 680 snow and ice bodies with 63 of these considered glaciers including seven of the ten largest glaciers in the American Rocky Mountains. The presence of glaciers results in meltwater contributions to streamflow during the late summer (July, August, and September - JAS) when snowmelt is decreasing, temperatures are high, precipitation is low, and irrigation demand peaks. Most studies indicate that the glaciers in the Wind River Range have been retreating since the 1850's, the approximate end of the Little Ice Age. Thus, the quantification of glacier meltwater (e.g., volume, mass) contributions to late-summer/early-fall streamflow is important given this resource is dwindling due to glacier recession. In this study, we selected glaciers in the WRR and obtained satellite products of study region. The ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) Level 1B imageries which are at 15 m spatial resolution between 2006~2012 were classified using supervised method and the glacier boundaries were extracted for tracking their changes. By combining ASTER L1B imageries of different years with two remote sensing derived DEM (Digital Elevation Model) datasets: ASTER GDEM (ASTER Global Digital Elevation), which is at 30 m spatial resolution and acquired prior to 2006 and Global Multi-resolution Terrain Elevation Data (GMTED 2010) which is at 250 m, 500 m and 1 km, and acquired in 2010, the 3D-view glacier volumetric loss extent could also be mapped and quantified. Assessing glacier area and volume variability is very important for evaluating and predicting glacier change in response to a changing environment.

Maloof, A.; Fang, B.; Tootle, G. A.; Lakshmi, V.; Kerr, G.

2013-12-01

4

Wind-driven modulation of warm water supply to a proglacial fjord, Jorge Montt Glacier, Patagonia  

NASA Astrophysics Data System (ADS)

Projections of sea level rise due to ice loss from the land to the ocean have been hampered by a lack of understanding of the role the ocean is playing in glacier retreat, including the processes that contribute to the supply of warm water to the ice-ocean interface. Here shipboard, moored, and weather station data collected off Jorge Montt, a rapidly retreating glacier in Patagonia, are analyzed to understand the influence of wind forcing. During summer, synoptic-scale down-fjord wind events enhance an estuarine-like two-layer flow, increasing the inflow of oceanic deep water. During up-fjord wind events, the inflow of deep water is significantly reduced, and a three-layer exchange flow develops. Overall, along-fjord wind forcing is shown to modulate the inflow of warm water to the fjord by a factor of 2.5 The results suggest that local, channelized winds can be an important process modulating warm water supply and melting of tidewater glaciers.

Moffat, Carlos

2014-06-01

5

Wind influence on snow depth distribution and accumulation over glaciers  

Microsoft Academic Search

In mountain regions wind is known to cause snow redistribution. While physically based models of snow redistribution have been developed for flat to gently rolling terrain, extension of these findings to steep terrain has been limited by the complexity of wind fields in such areas. In this study, we applied a nonhydrostatic and compressible atmospheric prediction model to steep alpine

R. Dadic; R. Mott; M. Lehning; P. Burlando

2010-01-01

6

Benchmark Glaciers  

NSDL National Science Digital Library

The United States Geological Survey (USGS) operates a long-term "benchmark" glacier program to intensively monitor climate, glacier motion, glacier mass balance, glacier geometry, and stream runoff at a few select sites. The data collected are used to understand glacier-related hydrologic processes and improve the quantitative prediction of water resources, glacier-related hazards, and the consequences of climate change. This page presents some of the balance, runoff, and temperature data for three glaciers: Gulkana, South Cascade and Wolverine. Reports for each of these glaciers uses the collected data to draw many conclusions. There is also a section with common questions and myths about glaciers.

7

Glacier Melt  

NSDL National Science Digital Library

This short video shows an example of melting alpine glaciers in the Austrian Alps (Goldberg Glacier). Disappearing alpine glaciers have social and environmental impacts, including the decline of fresh water supplies and contributing to sea level rise.

Geographic, National

8

Glacier Webquest  

NSDL National Science Digital Library

A project to learn about ice cores and Antarctica. Use handout lab (Webquest: Glaciers) and follow instructions given for each procedure. Go to Ice Core Changes Go to Glacial Loss Go to Glacial Cover Animation Go to Snow Cover Go to Gulkana Glacier Home Page Go to Glacial Topography Go to Glacial Picture Archive Go to Additional Glacier Pictures ...

Kio, Mr.

2008-11-06

9

Fastest Glacier  

NSDL National Science Digital Library

This video from a 2005 NOVA program features scientists who study how the Jakobshavn Isbrae glacier in western Greenland is shrinking and moving faster due to increased melting over the past ten years. The video includes footage of scientists in the field explaining methods and animation of ice sheet dynamics leading to faster glacier movement.

Sciencenow, Nova

10

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

11

Glacier microseismicity  

USGS Publications Warehouse

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

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

2010-01-01

12

Alpine Glaciers  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Released 27 August 2003

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

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

2003-01-01

13

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

14

Glacier (?) National Park  

NSDL National Science Digital Library

This activity engages learners in examining data pertaining to the disappearing glaciers in Glacier National Park. After calculating percentage change of the number of glaciers from 1850 (150) to 1968 (50) and 2009 (26), students move on to the main glacier-monitoring content of the module--area vs. time data for the Grinnell Glacier, one of 26 glaciers that remain in the park. Using a second-order polynomial (quadratic function) fitted to the data, they extrapolate to estimate when there will be no Grinnell Glacier remaining (illustrating the relevance of the question mark in the title of the module).

Mcllrath, University O.; Curriculum/serc, Spreadsheets A.

15

Muir Glacier in Glacier Bay National Monument 1941  

USGS Multimedia Gallery

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

16

Online Glacier Photograph Database  

NSDL National Science Digital Library

This image collection from the National Snow and Ice Data Center features 14 pairs of Alaskan glacier photographs. Each photographic pair consists of a late-19th or early-20th century photograph and a 21st century photograph taken from the same location. The comparative photographs clearly show substantial changes in glacier position and size and document significant landscape evolution and vegetative succession. The site also provides links to pairs of photographs of glaciers in Switzerland, a repeat photography project at Glacier National Park by the USGS, a glacier database which features satellite images and maps, and further information on glaciers.

The National Snow and Ice Data Center (NSIDC)

17

Pine Island Glacier  

article title:  Pine Island Glacier, Antarctica     View Larger Image ... (MISR) images of the Pine Island Glacier in western Antarctica was acquired on December 12, 2000 during Terra orbit 5246. At left ...

2013-04-16

18

Glaciers: A water resource  

USGS Publications Warehouse

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

Meier, Mark; Post, Austin

1995-01-01

19

Reconstructing glaciers: Sedimentary sources, sinks and fingerprints  

NASA Astrophysics Data System (ADS)

Glaciers are natural systems that shape and influence their geological surroundings through erosion and redistribution of sediments and rocks from one place to another. Their presence are determined by the landscape, regional climatic parameters such as wind, precipitation and temperature, and for these reasons they are valuable proxies of present and past climatic change. During the last four decades researchers have attempted to develop and assess methods that reliably and accurately reproduce continuous glacier variability over timescales extending thousands of years back in time. At the core of this multi-disciplinary endeavour is a strong desire to enhance our knowledge about how glaciers respond to a wider spectre of climatic change beyond what has been observed and documented for the last ~100 years. By far the majority of existing continuous glacier reconstructions are based on empirical evidence derived from soft sediment archives - mainly from lakes and fjords - making it quintessential to understand the sedimentary sources and sinks operating in glacierized catchment systems. If paleoclimatic inferences are to be made from such glacier reconstructions it is imperative that relevant sources of noise is considered, identified and, preferentially, eliminated. Here we review some of the problems and prospects of reconstructing temperate mountain or cirque glaciers as well as basic assumptions underlying most continuous glacier reconstructions. We will illustrate this challenge by presenting new data from a glacierized catchment surrounding a small lake called Blåvatnet located in Northern Norway at 68°N. A suit of piston and short gravity cores from the lake have been analysed and the results have been tested and corroborated by catchment samples from different sedimentary sources - an approach that is deemed to be of critical value when it comes to fingerprinting the glacier signal. Methodological emphasis is put on rock magnetism, which we demonstrate to be exceptionally well suited for identifying different sedimentary sources and characteristics typical for glacierized catchments. High sedimentation rates allow for a decadal glacier reconstruction covering the last 4000 years. Specifically, we observe major fluctuations in glacier activity that corresponds to an Equilibrium-Line-Altitude (ELA) variability of +/- 100 m. Peak activity is associated with the 'Little Ice Age' (1400-1800 AD) and a Neoglacial Maximum which occurred around 2500 years ago.

Paasche, O.; Lovlie, R.; Bakke, J.; Hirt, A. M.

2012-12-01

20

World Glacier Inventory  

NSDL National Science Digital Library

The National Snow and Ice Data Center (NSIDC) provides the World Glacier Inventory data, which was collected by the World Glacier Monitoring Service. This inventory contains geographic location, area, length, orientation, elevation, and classification of morphological type and moraines of more than 67,000 glaciers throughout the world. The data may be downloaded via FTP or through form-based queries.

21

Glacier Ecosystems of Himalaya  

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. In this presentation, we will briefly introduce glacier ecosystems in Himalaya; ecology and behavior of glacier animals, altitudinal zonation of snow algal communities, and the structure of their habitats in the glacier. Since the microorganisms growing on the glacier surface are stored in the glacial strata every year, ice-core samples contain many layers with these microorganisms. We showed that the snow algae in the ice-core are useful for ice core dating and could be new environmental signals for the studies on past environment using ice cores. These microorganisms in the ice core will be important especially in the studies of ice core from the glaciers of warmer regions, in which chemical and isotopic contents are often heavily disturbed by melt water percolation. Blooms of algae and bacteria on the glacier can reduce the surface albedo and significantly affect the glacier melting. For example, the surface albedo of some Himalayan glaciers was significantly reduced by a large amount of dark-colored biogenic material (cryoconite) derived from snow algae and bacteria. It increased the melting rates of the surfaces by as much as three-fold. Thus, it was suggested that the microbial activity on the glacier could affect the mass balance and fluctuation of the glaciers.

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

2012-12-01

22

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.

23

In Brief: Melting glaciers  

NASA Astrophysics Data System (ADS)

Glaciers in Patagonia and Alaska have been losing their mass, and for longer than glaciers elsewhere in the world, according to a 7 December report compiled by the United Nations Environment Programme (UNEP). “Climate change is causing significant mass loss of glaciers in high mountains worldwide,” notes the report, which calls for accelerated research, monitoring, and modeling of glaciers and snow and their role in water supplies. The report “also highlights the vulnerability and exposure of people dependent upon [glacier-fed] rivers to floods, droughts and eventually shortages as a result of changes in the melting and freezing cycles linked with climate change and other pollution impacts,” according to UNEP executive director Achim Steiner. For more information, visit http://www.grida.no/publications/high­mountain-glaciers/.

Showstack, Randy; Tretkoff, Ernie

2010-12-01

24

Fast Glacier Flow  

NASA Astrophysics Data System (ADS)

An AGU Chapman Conference on Fast Glacier Flow was held at Whistler Village, Canada, from May 4 to 8, 1986. The timing of the conference seemed particularly propitious because of results of recent observational programs, such as the breakup of the tidewater Columbia Glacier in Alaska, the imbalance of Ice Stream B in Antarctica and the existence of deforming sediment under it, and the surge of Variegated Glacier in Alaska.

Whillans, Ian M.; Harrison, William D.

25

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

26

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

27

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

28

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

29

Columbia Glacier Calving  

USGS Multimedia Gallery

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

2010-07-14

30

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

31

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

32

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

USGS Publications Warehouse

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

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

2005-01-01

33

Proposed Glacier Bay Wilderness, Glacier Bay National Monument.  

National Technical Information Service (NTIS)

The National Park Service proposes to establish 2,052,700 acres as wilderness in Glacier Bay National Monument. The area contains rugged mountains; enormous complex glaciers; ice-sculptured fjords; and large areas of vegetation, displaying the entire spec...

1973-01-01

34

Knik Glacier; Alaska, May 1979 monument and glacier survey  

USGS Publications Warehouse

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

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

1979-01-01

35

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

36

Iceland Glacier Recession 1973 to 2000, Glacier Terminus contrast emphasized  

NSDL National Science Digital Library

This animation shows glacier recesion at the Breidamerkurjokull glacier in Iceland. The data from 1973 is taken from Landsat 1 and the 2000 data is from Landsat 7. The Breidamerkurjokull glacier in Iceland has been measured by Landsat to be receding since 1973. The glacierologists in Iceland and here at Nasas Goddard Space Flight Center have measured the recession throughout the entire glacier and found different rates of recession in different areas. In genral, the glacier seems to be receding at about 2% annually. It is extremely controversial whether this recession is caused by global warming.

Perkins, Lori; Hall, Dorothy

2001-04-09

37

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. 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 two seasons of the effect of hydrologic controls (from large rainfall events as well as a glacier lake outburst floods) on 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, multiple Trimble NetRS dual frequency, differential GPS units were deployed on the glacier along the centerline of the glacier. All of the instruments were run continuously from May-September 2008 and May-September 2009 and captured threee outburst floods 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. 2008 was an extremely rainy summer, and the (single) lake drainage occurred during the largest precipitation even of the summer. 2009 on the other hand, was comparatively dry and sunny for the majority of the summer--the first lake drainage occurred during a several day stretch of sunny weather. The lake refilled during an extreme rainfall (20 cm of rain was recorded in a 24 hour period at a met station 16 km away and about 500 m lower in elevation) and then subsequently drained during a rainy period. We focus on the comparison of the data from two years, including the glacial response to the lake drainage with and without accompanying precipitation inputs.

Heavner, M.; Habermann, M.; Hood, E. W.; Fatland, D. R.

2009-12-01

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

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

40

Glaciers and Icebergs  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on glaciers and icebergs, specifically, glacial scraping and landforms left behind by glaciers, and information about icebergs in the oceans. Students do a lab simulating glacial scouring. It includes objectives, materials, procedures, discussion questions, evaluation ideas, extensions, suggested readings, and vocabulary. There are videos available to order which complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

Weisel, Frank

41

Svalbard surging glacier landsystems  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

42

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.

43

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

44

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

45

Taking a Glacier's Pulse  

NSDL National Science Digital Library

This article profiles Dr. Leigh Stearns, a research scientist with the National Science Foundation's Science and Technology Center for Remote Sensing of Ice Sheets (CReSIS) and Assistant Professor in Geology at the University of Kansas who studies glaciers in Greenland.

Landis, Carol

46

Glacier Goo Erosion Experiments  

NSDL National Science Digital Library

Using a glacier proxy, students design an experiment to connect glacial erosion with glacial flow. Students choose from a variety of materials, determined what question they want their experiment or experiments to answer, design the procedure, test the experiment, and write up a lab report on the experiment.

Headley, Rachel

47

Observed changes in glaciers in China  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

48

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

49

Glacier National Park  

NSDL National Science Digital Library

This is the homepage of Glacier National Park. Users can access materials on the park's ecology and environment (plants and animals, biodiversity and air quality, geology, and fires), the culture and history of the park, park activities, and publications on naturalist activities. There are also video clips of park wildlife and scenery, a photo gallery, and live webcams. Links are provided to additional information, such as research activities on bear DNA and global climate change.

50

Muir Glacier in Glacier Bay National Monument 1950  

USGS Multimedia Gallery

This August 1950 photo documents the significant changes that occurred during the 9 years between photographs A and B. Muir Glacier has retreated more than 2 miles, exposing Muir Inlet, and thinned 340 feet or more. However, it still is connected with tributary Riggs Glacier....

51

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

USGS Publications Warehouse

Winter snow accumulation and summer snow and ice ablation were measured at South Cascade Glacier, Washington, to estimate glacier mass balance quantities for balance years 2006 and 2007. Mass balances were computed with assistance from a new model that was based on the works of other glacier researchers. The model, which was developed for mass balance practitioners, coupled selected meteorological and glaciological data to systematically estimate daily mass balance at selected glacier sites. The North Cascade Range in the vicinity of South Cascade Glacier accumulated approximately average to above average winter snow packs during 2006 and 2007. Correspondingly, the balance years 2006 and 2007 maximum winter snow mass balances of South Cascade Glacier, 2.61 and 3.41 meters water equivalent, respectively, were approximately equal to or more positive (larger) than the average of such balances since 1959. The 2006 glacier summer balance, -4.20 meters water equivalent, was among the four most negative since 1959. The 2007 glacier summer balance, -3.63 meters water equivalent, was among the 14 most negative since 1959. The glacier continued to lose mass during 2006 and 2007, as it commonly has since 1953, but the loss was much smaller during 2007 than during 2006. The 2006 glacier net balance, -1.59 meters water equivalent, was 1.02 meters water equivalent more negative (smaller) than the average during 1953-2005. The 2007 glacier net balance, -0.22 meters water equivalent, was 0.37 meters water equivalent less negative (larger) than the average during 1953-2006. The 2006 accumulation area ratio was less than 0.10, owing to isolated patches of accumulated snow that endured the 2006 summer season. The 2006 equilibrium line altitude was higher than the glacier. The 2007 accumulation area ratio and equilibrium line altitude were 0.60 and 1,880 meters, respectively. Accompanying the glacier mass losses were retreat of the terminus and reduction of total glacier area. The terminus retreated at a rate of about 13 meters per year during balance year 2006 and at a rate of about 8 meters per year during balance year 2007. Glacier area near the end of balance years 2006 and 2007 was 1.74 and 1.73 square kilometers, respectively. Runoff from the basin containing the glacier and from an adjacent nonglacierized basin was gaged during all or parts of water years 2006 and 2007. Air temperature, wind speed, precipitation, and incoming solar radiation were measured at selected locations on and near the glacier. Air-temperature over the glacier at a height of 2 meters generally was less than at the same altitude in the air mass away from the glacier. Cooling of the air by the glacier increased systematically with increasing ambient air temperature. Empirically based equations were developed to estimate 2-meter-height air temperature over the glacier at five sites from site altitude and temperature at a non-glacier reference site.

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

2010-01-01

52

Water, ice, and meteorological measurements at South Cascade Glacier, Washington, 1995 balance year  

USGS Publications Warehouse

Winter snow accumulation and summer snow, firn, and ice melt were measured at South Cascade Glacier, Washington to determine the winter and net balances for the 1995 balance year. The 1995 winter balance, averaged over the glacier, was 2.86 meters, and the net balance was -0.69 meter. The winter balance was approximately 0.5 meter greater than the 1977-94 average winter balance. The net balance was approximately 0.3 meter less negative than the 1977-94 average net balance. Runoff was measured from the glacier and an adjacent non-glacierized basin. Air temperature, precipitation, barometric pressure, solar radiation, and wind speed were measured adjacent to the glacier. This report makes these data available to the glaciological and climatological community.

Krimmel, R. M.

1996-01-01

53

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

54

Denali Fault: Black Rapids Glacier  

USGS Multimedia Gallery

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

2008-12-15

55

Glaciers and the Changing Earth  

NSDL National Science Digital Library

In this lesson, students will investigate how glaciers affect the landscape in the context of wondering how the rocks used in the stone walls first got into the ground. Following a directed reading and discussion, they will perform an activity in which they use ice cubes and a bucket of sand to simulate the effects of a glacier.

56

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

USGS Publications Warehouse

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

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

2007-01-01

57

Malaspina Glacier, Alaska  

NASA Technical Reports Server (NTRS)

This image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra satellite covers an area of 55 by 40 kilometers (34 by 25 miles) over the southwest part of the Malaspina Glacier and Icy Bay in Alaska. The composite of infrared and visible bands results in the snow and ice appearing light blue, dense vegetation is yellow-orange and green, and less vegetated, gravelly areas are in orange. According to Dr. Dennis Trabant (U.S. Geological Survey, Fairbanks, Alaska), the Malaspina Glacier is thinning. Its terminal moraine protects it from contact with the open ocean; without the moraine, or if sea level rises sufficiently to reconnect the glacier with the ocean, the glacier would start calving and retreat significantly. ASTER data are being used to help monitor the size and movement of some 15,000 tidal and piedmont glaciers in Alaska. Evidence derived from ASTER and many other satellite and ground-based measurements suggests that only a few dozen Alaskan glaciers are advancing. The overwhelming majority of them are retreating.

This ASTER image was acquired on June 8, 2001. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next six years to map and monitor the changing surface of our planet.

ASTER is one of five Earth-observing instruments launched December 18,1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. science team leader; Bjorn Eng of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The Terra mission is part of NASA's Earth Science Enterprise, along-term research and technology program designed to examine Earth's land, oceans, atmosphere, ice and life as a total integrated system.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

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

2001-01-01

58

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

59

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

60

Empirical downscaling of atmospheric key variables above a tropical glacier surface (Cordillera Blanca, Peru)  

NASA Astrophysics Data System (ADS)

Glaciers in the outer tropical Cordillera Blanca (Peru, South America) are of major socio-economic importance, since glacier runoff represents the primary water source during the dry season, when little or no rainfall occurs. Due to their location at high elevations, the glaciers moreover provide important information about climate change in the tropical troposphere, where measurements are sparse. This study targets the local reconstruction of air temperature, specific humidity and wind speed above the surface of an outer tropical glacier from NCEP/NCAR reanalysis data as large scale predictors. Since a farther scope is to provide input data for process based glacier mass balance modelling, the reconstruction pursues a high temporal resolution. Hence an empirical downscaling scheme is developed, based on a few years' time series of hourly observations from automatic weather stations, located at the glacier Artesonraju and nearby moraines (Northern Cordillera Blanca). Principal component and multiple regression analyses are applied to define the appropriate spatial downscaling domain, suitable predictor variables, and the statistical transfer functions. The model performance is verified using an independent data set. The best predictors are lower tropospheric air temperature and specific humidity, at reanalysis model grid points that represent the Bolivian Altiplano, located in the South of the Cordillera Blanca. The developed downscaling model explaines a considerable portion (more than 60%) of the diurnal variance of air temperature and specific humidity at the moraine stations, and air temperature above the glacier surface. Specific humidity above the glacier surface, however, can be reconstructed well in the seasonal, but not in the required diurnal time resolution. Wind speed can only be poorly determined by the large scale predictors (r² lower than 0.3) at both sites. We assume a complex local interaction between valley and glacier wind system to be the main cause for the differences between model and observations.

Hofer, M.; Kaser, G.; Mölg, T.; Juen, I.; Wagnon, P.

2009-04-01

61

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

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

Recent behaviour of Slovenian glaciers  

NASA Astrophysics Data System (ADS)

Just two glaciers, below the peaks of Triglav (2864 m) and Skuta (2532 m), are persisting in Slovenian Alps, both on a relatively very low elevation. Their present surfaces do not exceed one hectare, thus we can speak only about two glacierets or very small glaciers. The Anton Melik Geographical Institute of the Scientific Research Centre at the Slovenian Academy of Sciences and Arts has regularly performed measurements since 1946. The size of the Triglav glacier, measured in 1946, was 14.4 hectares, and by the year 2012 the glacier had shrunk to a half of a hectare. The direct vicinity of the meteorological station on Mt. Kredarica makes possible an analysis of the dependency of the glacier's fluctuation on weather changes. Several methods of measuring have been applied. Since 1999 we have regularly performed photogrammetric measurements of the glacier, which render possible exact calculations of changes in the glacier's area and volume by individual years. In addition, we also performed georadar measurements in 2000 and 2013. Besides regular annual measurements performed at the end of melting seasons, the Triglav glacier has also been photographed monthly since 1976, from two fixed positions on Mt. Kredarica. In 2012, we performed aerial laser scanning (LIDAR) of the Triglav glacier. While for the last decade of the 20th century we reported that the Triglav glacier has not only retreated but literally disintegrated, in the first decade of the 21st century we can observe its stagnation. Due to the present concave form of the glacier's surface, snow remains on it late into summer, and since the year 2007, the ice of the lower part of the glacier has not been revealed even at the end of the melting season but has remained covered with the firn and snow of previous winters. Should such weather conditions continue and the amount of winter precipitation further increase, the remainder of the Triglav glacier will, though very small in size, continue to exist for next ten years or even more.

Gabrovec, Matej; Ferk, Mateja; Ortar, Jaka

2014-05-01

64

Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier. 1: Observations  

NASA Technical Reports Server (NTRS)

Measurements of glacier flow velocity and basal water pressure at two sites on Columbia Glacier, Alaska, are combined with meteorological and hydrologic data to provide an observational basis for assessing the role of water storage and basal water pressure in the rapid movement of this large glacier. During the period from July 5 to August 31, 1987, coordinated observations were made of glacier surface motion and of water level in five boreholes drilled to (or in one case near to) the glacier bed at two sites, 5 and 12 km from the terminus. Glacier velocities increased downglacier in this reach from about 4 m/d to about 7 m/d. Three types of time variation in velocity and other variables were revealed: (1) Diurnal fluctuation in water input/output, borehole water level, and ice velocity (fluctuation amplitude 5 to 8%); (2) Speed-up events in glacier motion (15-30% speed-up), lasting about three days, and ocurring at times of enhanced input of water, in some cases from rain and in others from ice ablation enhanced by strong, warm winds; (3) 'Extra-slowdown' events, in which, after a speed-up event, the ice velocity decreased in about 3 days to a level consistently lower than that prior to the speed-up event. All of the time variations were due, directly or indirectly, to variations in water input to the glacier.

Meier, Mark; Lundstrom, Scott; Stone, Dan; Kamb, Barclay; Engelhardt, Hermann; Humphrey, Neil; Dunlap, William W.; Fahnestock, Mark; Krimmel, Robert M.; Walters, Roy

1994-01-01

65

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

USGS Publications Warehouse

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

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

2004-01-01

66

Glaciers and why they surge  

NASA Astrophysics Data System (ADS)

Researchers studying southern Alaska's Variegated Glacier believe they have found an explanation for why the 24-km-long ice mass, like other "surging" glaciers, periodically speeds up in its movement down valley. The surges, they propose, have to do with increases in water pressure beneath the glacier— the result of inhibited drainage at the base of the ice—that cause it to become more slippery and to flow faster.The Variegated Glacier, located northwest of Juneau near the village of Yakutat, is small among surging glaciers, but it has been one of the most extensively studied in this century. Every 18-20 years, it begins to accelerate its flow rate. The last time such a surge began was in January 1982. The glacier reached a peak velocity of 9 m per day by summertime, then returned to near normal flow rates of 1-2 m per day by early fall. It started up again in November 1982, however, and by the next spring was speeding along at 54 m per day. Then, in early July 1983, the surge stopped abruptly when large amounts of water drained out of the glacier.

1984-04-01

67

Aletsch Glacier, Switzerland  

NASA Technical Reports Server (NTRS)

Aletsch Glacier, the largest glacier of Europe, covers more than 120 square kilometers (more than 45 square miles)in southern Switzerland. At its eastern extremity lies a glacierlake, Mdrjelensee (2,350 meters/7,711 feet above sea level). To the west rises Aletschhorn (4,195 meters/13,763 feet), which was first climbed in 1859. The Rhone River flows along the southern flank of the mountains.

This image was acquired on July 23, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. The Terra mission is part of NASA's Earth Science Enterprise, a long-term research and technology program designed to examine Earth's land, oceans, atmosphere, ice and life as a total integrated system.

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

2002-01-01

68

Water, ice, and meteorological measurements at South Cascade Glacier, Washington, 2000-01 balance years  

USGS Publications Warehouse

Winter snow accumulation and summer snow, firn, and ice melt were measured at South Cascade Glacier, Washington, to determine the winter and net balances for the 2000 and 2001 balance years. In 2000, the winter balance, averaged over the glacier, was 3.32 meters, and the net balance was 0.38 meters. The winter balance was the ninth highest since the record began in 1959. The net balance was greater than 33 of the 41 years since 1959. In 2001, the winter balance was 1.90 meters, and net balance was -1.57 meters. The winter balance was lower than all but 4 years since 1959, and the net balance was more negative than all but 5 other years. Runoff was measured from the glacier basin and an adjacent non-glacierized basin. Air temperature, precipitation, humidity, wind speed and solar radiation were measured nearby. Ice displacements were measured for the 1998-2001 period.

Krimmel, Robert M.

2002-01-01

69

Water, ice, and meteorological measurements at South Cascade Glacier, Washington, 1994 balance year  

USGS Publications Warehouse

Winter snow accumulation and summer snow, firn, and ice melt were measured at South Cascade Glacier, Washington to determine the winter and net balances for the 1994 balance year. The 1994 winter balance, averaged over the glacier, was 2.39 meters, and the net balance was -1.60 meters. The winter balance was approximately that of the 1977-94 average winter balance. The net balance was more negative than the 1977-94 average net balance of -1.02 meters. Runoff was measured from the glacier and an adjacent non- glacierized basin. Air temperature, precipitation, barometric pressure, solar radiation, and wind speed were measured nearby. This report makes these data available to the glaciological and climatological community.

Krimmel, R. M.

1995-01-01

70

Columbia Glacier, Alaska, 1986-2011  

NASA Video Gallery

The Columbia Glacier in Alaska is one of many vanishing around the world. Glacier retreat is one of the most direct and understandable effects of climate change. The consequences of the decline in ...

71

Arctic polynya and glacier interactions  

NASA Astrophysics Data System (ADS)

Major uncertainties surround future estimates of sea level rise attributable to mass loss from the polar ice sheets and ice caps. Understanding changes across the Arctic is vital as major potential contributors to sea level, the Greenland Ice Sheet and the ice caps and glaciers of the Canadian Arctic archipelago, have experienced dramatic changes in recent times. Most ice mass loss is currently focused at a relatively small number of glacier catchments where ice acceleration, thinning and calving occurs at ocean margins. Research suggests that these tidewater glaciers accelerate and iceberg calving rates increase when warming ocean currents increase melt on the underside of floating glacier ice and when adjacent sea ice is removed causing a reduction in 'buttressing' back stress. Thus localised changes in ocean temperatures and in sea ice (extent and thickness) adjacent to major glacial catchments can impact hugely on the dynamics of, and hence mass lost from, terrestrial ice sheets and ice caps. Polynyas are areas of open water within sea ice which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~50,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas play a vital role in the heat balance of the polar oceans and strongly impact regional oceanography. Where polynyas develop adjacent to tidewater glaciers their influence on ocean circulation and water temperatures may play a major part in controlling subsurface ice melt rates by impacting on the water masses reaching the calving front. Areas of open water also play a significant role in controlling the potential of the atmosphere to carry moisture, as well as allowing heat exchange between the atmosphere and ocean, and so can influence accumulation on (and hence thickness of) glaciers and ice caps. Polynya presence and size also has implications for sea ice extent and therefore potentially the buttressing effect on neighbouring tidewater glaciers. The work presented discusses preliminary satellite observations of concurrent changes in the North Water and Nares Strait polynyas and neighbouring tidewater glaciers in Greenland and the Canadian Arctic where notable thinning and acceleration of glaciers have been observed. Also included is an outline of how these observations will fit into a much wider project on the topic involving ocean, atmosphere and sea ice modelling and short-term and longer-term in-situ measurements.

Edwards, Laura

2013-04-01

72

Seasonal and annual mass balances of Mera and Pokalde glaciers (Nepal Himalaya) since 2007  

NASA Astrophysics Data System (ADS)

In the Everest region, Nepal, ground-based monitoring programmes were started on the debris-free Mera Glacier (27.7° N, 86.9° E; 5.1 km2, 6420 to 4940 m a.s.l.) in 2007 and on the small Pokalde Glacier (27.9° N, 86.8° E; 0.1 km2, 5690 to 5430 m a.s.l., ~ 25 km north of Mera Glacier) in 2009. These glaciers lie on the southern flank of the central Himalaya under the direct influence of the Indian monsoon and receive more than 80% of their annual precipitation in summer (June to September). Despite a large inter-annual variability with glacier-wide mass balances ranging from -0.67 ± 0.28 m w.e. in 2011-2012 (Equilibrium-line altitude (ELA) at ~ 5800 m a.s.l.) to +0.46 ± 0.28 m w.e. in 2010-2011 (ELA at ~ 5340 m a.s.l.), Mera Glacier has been shrinking at a moderate mass balance rate of -0.08 ± 0.28 m w.e. yr-1 since 2007. Ice fluxes measured at two distinct transverse cross sections at ~ 5350 m a.s.l. and ~ 5520 m a.s.l. confirm that the mean state of this glacier over the last one or two decades corresponds to a limited mass loss, in agreement with remotely-sensed region-wide mass balances of the Everest area. Seasonal mass balance measurements show that ablation and accumulation are concomitant in summer which in turn is the key season controlling the annual glacier-wide mass balance. Unexpectedly, ablation occurs at all elevations in winter due to wind erosion and sublimation, with remobilised snow potentially being sublimated in the atmosphere. Between 2009 and 2012, the small Pokalde Glacier lost mass more rapidly than Mera Glacier with respective mean glacier-wide mass balances of -0.72 and -0.23 ± 0.28 m w.e. yr-1. Low-elevation glaciers, such as Pokalde Glacier, have been usually preferred for in-situ observations in Nepal and more generally in the Himalayas, which may explain why compilations of ground-based mass balances are biased toward negative values compared with the regional mean under the present-day climate.

Wagnon, P.; Vincent, C.; Arnaud, Y.; Berthier, E.; Vuillermoz, E.; Gruber, S.; Ménégoz, M.; Gilbert, A.; Dumont, M.; Shea, J. M.; Stumm, D.; Pokhrel, B. K.

2013-11-01

73

Seasonal and annual mass balances of Mera and Pokalde glaciers (Nepal Himalaya) since 2007  

NASA Astrophysics Data System (ADS)

In the Everest region, Nepal, ground-based monitoring programs were started on the debris-free Mera Glacier (27.7° N, 86.9° E; 5.1 km2, 6420 to 4940 m a.s.l.) in 2007 and on the small Pokalde Glacier (27.9° N, 86.8° E; 0.1 km2, 5690 to 5430 m a.s.l., ˜ 25 km North of Mera Glacier) in 2009. These glaciers lie on the southern flank of the central Himalaya under the direct influence of the Indian monsoon and receive more than 80% of their annual precipitation in summer (June to September). Despite a large inter-annual variability with glacier-wide mass balances ranging from -0.77± 0.40 m w.e. in 2011-2012 (Equilibrium-line altitude (ELA) at ˜ 6055 m a.s.l.) to + 0.46 ± 0.40 m w.e. in 2010-2011 (ELA at ˜ 5340 m a.s.l.), Mera Glacier has been shrinking at a moderate mass balance rate of -0.10± 0.40 m w.e. yr-1 since 2007. Ice fluxes measured at two distinct transverse cross sections at ˜ 5350 m a.s.l. and ˜ 5520 m a.s.l. confirm that the mean state of this glacier over the last one or two decades corresponds to a limited mass loss, in agreement with remotely-sensed region-wide mass balances of the Everest area. Seasonal mass balance measurements show that ablation and accumulation are concomitant in summer which in turn is the key season controlling the annual glacier-wide mass balance. Unexpectedly, ablation occurs at all elevations in winter due to wind erosion and sublimation, with remobilized snow likely being sublimated in the atmosphere. Between 2009 and 2012, the small Pokalde Glacier lost mass more rapidly than Mera Glacier with respective mean glacier-wide mass balances of -0.72 and -0.26 ± 0.40 m w.e. yr-1. Low-elevation glaciers, such as Pokalde Glacier, have been usually preferred for in-situ observations in Nepal and more generally in the Himalayas, which may explain why compilations of ground-based mass balances are biased toward negative values compared with the regional mean under the present-day climate.

Wagnon, P.; Vincent, C.; Arnaud, Y.; Berthier, E.; Vuillermoz, E.; Gruber, S.; Ménégoz, M.; Gilbert, A.; Dumont, M.; Shea, J. M.; Stumm, D.; Pokhrel, B. K.

2013-07-01

74

Glacier Mass Balance measurements in Bhutan  

NASA Astrophysics Data System (ADS)

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

Jackson, Miriam; Tenzin, Sangay; Tashi, Tshering

2014-05-01

75

Analysis of time series of glacier speed: Columbia Glacier, Alaska  

USGS Publications Warehouse

During the summer of 1984 and 1985, laser measurements were made of the distance from a reference location to markers on the surface of the lower reach of Columbia Glacier, Alaska. The speed varies from 7 to 15 m/d and has three noteworthy components: 1) a low-frequency perturbation in speed with a time scale of days related to increased precipitation, 2) semidiurnal and diurnal variations related to sea tides, and 3) diurnal variations related to glacier surface melt. -from Authors

Walters, R. A.; Dunlap, W. W.

1987-01-01

76

Increased glacier runoff enhances the penetration of warm Atlantic Water into a large Greenland fjord  

NASA Astrophysics Data System (ADS)

The retreat and acceleration of Greenland's marine-terminating outlet glaciers have been linked to ocean warming. However the mechanisms which control the transmission of this warming along fjords towards the glacier termini remain poorly understood. Here we aim to elucidate observed changes in water properties in Kangerdlugssuaq Fjord (KF), east Greenland, between 1993 and 2004 using the Bergen Ocean Model (BOM). Model outputs are compared with observed potential temperature, salinity and velocity data to determine the principal controls on heat transport within KF. The BOM includes wind, tidal and glacier runoff forcing and is able to replicate observed temperature and salinity profiles. Model results describe a robust four-layer estuarine flow, consisting of two distinct circulations. The shallow circulation (0 - ˜60 m) is forced by surface wind stress and to a lesser extent supraglacial runoff, while the intermediate circulation (˜60 - 500 m) is driven by runoff discharged into the fjord subglacially. AtlanticWater (AW) and warm Polar Surface Water (PSWw) are drawn into the fjord by the intermediate and shallow circulation cells respectively, in a pattern consistent with observations, and AW reaches Kangerdlugssuaq Glacier (at the fjord head) over a single summer. Along-fjord heat transport towards KG increases significantly with both glacier runoff and coastal water temperature. A doubling of glacier runoff produces a 29 % (48 %) amplification of mean annual (summer) heat transport towards the KG terminus. Our model shows, in agreement with observations, that maximum submarine melt rates occur when AW and PSWw are present at the fjord mouth and, crucially, glacier runoff is also high. Rising ice sheet runoff therefore increases the sensitivity of KG (and other Greenland marine-terminating glaciers) to ocean warming.

Sole, Andrew; Payne, Anthony; Nienow, Peter; Christoffersen, Poul; Cottier, Finlo; Inall, Mark

2013-04-01

77

Warm Oceans, Fast Glaciers: the connections  

Microsoft Academic Search

Over the last decade many outlet glaciers from the Greenland Ice Sheet have accelerated and thinned, and in a number of cases their termini have retreated. There is much in common from glacier to glacier that emerges as these changes are studied, yet the actual physical mechanisms remain unclear. One can show that the spatial patterns and timing of outlet

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

2009-01-01

78

Tidal flexure of Jakobshavns Glacier, West Greenland  

Microsoft Academic Search

Jakobshavns Glacier, a floating outlet glacier on the West Greenland coast, was surveyed during July 1976. The vertical displacements of targets along two profiles perpendicular to the fjord wall bounding the north margin of the glacier were analyzed to determine the effect of flexure caused by tidal oscillations within the fjord. An analysis based on the assumption that vertical displacements

Craig S. Lingle; Terence J. Hughes; Ronald C. Kollmeyer

1981-01-01

79

Tidal Flexure of Jakobshavns Glacier, West Greenland  

Microsoft Academic Search

Jakobshavns Glacier, a floating outlet glacier on the West Greenland coast, was surveyed during July 1976. The vertical displacements of targets along two profiles perpendicular to the fjord wall bounding the north margin of the glacier were analyzed to determine the effect of flexure caused by tidal oscillations within the fjord. An analysis based on the assumption that vertical displacements

Craig S. Lingle; Terence J. Hughes; Ronald C. Kollmeyer

1981-01-01

80

Muir Glacier and Muir Inlet 1980  

USGS Multimedia Gallery

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

81

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

82

Flow velocities of Alaskan glaciers  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

83

Glacier recession in Iceland and Austria  

NASA Technical Reports Server (NTRS)

It has been possible to measure glacier recession on the basis of Landsat data, in conjunction with comparisons of the magnitude of recession of a glacier margin with in situ measurements at fixed points along the same margin. Attention is presently given to the cases of Vatnajokull ice cap, in Iceland, and the Pasterze Glacier, in Austria, on the basis of satellite data from 1973-1987 and 1984-1990, respectively. Indications of a trend toward negative mass balance are noted. Nevertheless, while most of the world's small glaciers have been receding, some are advancing either due to local climate or the tidewater glacier cycle.

Hall, Dorothy K.; Williams, Richard S., Jr.; Bayr, Klaus J.

1992-01-01

84

Light Iceland Glacier Recession 1973 to 2000  

NSDL National Science Digital Library

This animation shows glacier recesion at the Breidamerkurjokull glacier in Iceland. The data from 1973 is taken from Landsat 1 and the 2000 data is from Landsat 7. The Breidamerkurjokull glacier in Iceland has been measured by Landsat to be receding since 1973. The glacierologists in Iceland and here at NASAs Goddard Space Flight Center have measured the recession throughout the entire glacier and found different rates of recession in different areas. In genral, the glacier seems to be receding at about 2% annually. It is extremely controversial whether or not this recession is caused by global warming.

Perkins, Lori; Hall, Dorothy

2001-04-09

85

Glacier recession in Iceland and Austria  

NASA Astrophysics Data System (ADS)

It has been possible to measure glacier recession on the basis of Landsat data, in conjunction with comparisons of the magnitude of recession of a glacier margin with in situ measurements at fixed points along the same margin. Attention is presently given to the cases of Vatnajokull ice cap, in Iceland, and the Pasterze Glacier, in Austria, on the basis of satellite data from 1973-1987 and 1984-1990, respectively. Indications of a trend toward negative mass balance are noted. Nevertheless, while most of the world's small glaciers have been receding, some are advancing either due to local climate or the tidewater glacier cycle.

Hall, Dorothy K.; Williams, Richard S., Jr.; Bayr, Klaus J.

1992-03-01

86

The effect of glaciers on streamflow variations.  

USGS Publications Warehouse

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

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

1985-01-01

87

Spatially heterogeneous wastage of Himalayan glaciers  

PubMed Central

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

Fujita, Koji; Nuimura, Takayuki

2011-01-01

88

Winds  

NSDL National Science Digital Library

In this problem-based learning (PBL) scenario, students prepare a presentation for investors showing how their fishing company has a significant advantage because it locates upwelling zones and fishing areas using TRMM (Tropical Rainfall Measuring Mission) and other satellite data. Prior to launching the PBL, students learn about wind: the topics of air pressure, coriolis effect, upwelling and the role of differential heating on the atmosphere are explored in classroom demonstrations. Materials required include a beaker, coffee grounds, drinking straw, balloon, flashlight, and turntable. The resource includes teacher background information, glossary, assessment rubric, and an appendix introducing problem-based learning.

89

UV - GLACIER NATIONAL PARK MT  

EPA Science Inventory

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

90

Icebergs and Glaciers: Unit Outlines  

NSDL National Science Digital Library

This article assembles free resources from the Icebergs and Glaciers issue of the Beyond Penguins and Polar Bears cyberzine into a unit outline based on the 5E learning cycle framework. Outlines are provided for Grades K-2 and 3-5.

Fries-Gaither, Jessica

91

Numerical modelling of glacier systems  

Microsoft Academic Search

The aim of the project is to develop a scheme to model the dynamics of any given glacier system from the input data of bedrock distribution and accumulation or ablation (or balance) distribution as functions of time. The emphasis is on matching reality to provide a practical means of interpreting the history of change of an ice mass. The full

W. F. Budd; D. Jenssen

92

Mountain Glaciers and Ice Caps  

USGS Publications Warehouse

Projections of future rates of mass loss from mountain glaciers and ice caps in the Arctic focus primarily on projections of changes in the surface mass balance. Current models are not yet capable of making realistic forecasts of changes in losses by calving. Surface mass balance models are forced with downscaled output from climate models driven by forcing scenarios that make assumptions about the future rate of growth of atmospheric greenhouse gas concentrations. Thus, mass loss projections vary considerably, depending on the forcing scenario used and the climate model from which climate projections are derived. A new study in which a surface mass balance model is driven by output from ten general circulation models (GCMs) forced by the IPCC (Intergovernmental Panel on Climate Change) A1B emissions scenario yields estimates of total mass loss of between 51 and 136 mm sea-level equivalent (SLE) (or 13% to 36% of current glacier volume) by 2100. This implies that there will still be substantial glacier mass in the Arctic in 2100 and that Arctic mountain glaciers and ice caps will continue to influence global sea-level change well into the 22nd century.

Ananichheva, Maria; Arendt, Anthony; Hagen, Jon-Ove; Hock, Regine; Josberger, Edward G.; Moore, R. Dan; Pfeffer, William Tad; Wolken, Gabriel J.

2011-01-01

93

The status of glaciers in Sikkim Himalaya  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

94

A direct measured glacier thinning in the southern Tibetan Plateau (Xixiabangma, Yangbajing, Naimon'nyi Glacier)  

NASA Astrophysics Data System (ADS)

Various work confirmed the fast retreating of Tibetan Plateau glacier in recent decades due to global warming, especially the area shrinkage by remote sensing method. In recent years, more concern is focused on the effect of glacier melting on available water resource surrounding the glacier region. Consequently, the glacier ice volume change is of more importance in this sense. In this work, we present a result from directly measured glacier surface altitude change by differential GPS. By comparing the preciously measured altitude change from 2007 to 2011 at three glaciers in the southern Tibetan Plateau, we can give a reliable glacier thinning ratio in the past few years. The measured results from Gurenhekou Glacier, Yangbajing, show the ice depth loss is 3.96m in past 4 years from 2007 to 2011. In Kangwure glacier, Xixiabangma, the average depth loss is 2.70m in 3 years, and thus the annual glacier depth loss is 0.90m based on the observation from September 2007 to August 2010. The glacier depth loss is 1.4m on Naimon'nyi Glacier, one of the largest glaciers in west Himalayas, with an average annual loss of 0.7meter. Although the monitoring period is still limited, the quite similar ice losing ratio (0.7-1.0 m per year) in the southern Himalayas indicating the quite homogenous ice losing in different regions and with different glacier size and orientation. This work also finds that both ablation zone and accumulation zone are losing their ice, indicating the glacier flowing is also involves in the glacier thinning rather than the surface melting. This result also emphasizes the importance of GPS measurement compared to the stake-based mass balance observation. We are stilling working on even longer period monitoring and more glaciers to get more representative data to evaluate the glacier melting trends in the Tibetan Plateau.

Tian, L.; Zong, J.; Yao, T.; Ma, L.; Pu, J.

2012-12-01

95

Energy balance of a glacier surface: Analysis of automatic weather station data from the Morteratschgletscher, Switzerland  

Microsoft Academic Search

We describe and analyze a complete 1-yr data set from an automatic weather station (AWS) located on the snout of the Morteratschgletscher, Switzerland. The AWS stands freely on the glacier surface and measures pressure, windspeed, wind direction, air temperature and humidity, incoming and reflected solar radiation, incoming and outgoing longwave radiation, snow temperature, and change in surface height (giving melt

J. Oerlemans; E. J. Klok

2002-01-01

96

Hasty retreat of glaciers in northern Patagonia  

NASA Astrophysics Data System (ADS)

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

Paul, Frank; Mölg, Nico

2014-05-01

97

Glaciers in the Rupal Valley (Nanga Parbat)  

NASA Astrophysics Data System (ADS)

The widely discussed controversy about Himalayan glacier changes instigated a current boom in studies on a regional scale. In contrast to often simplified assumptions of general and mostly rapid glacier retreat, recent studies show a more complex pattern with stable, advancing and retreating glaciers. Furthermore, changes of debris covered glaciers are discussed controversial. Due to the great vertical span and steep relief, large ice streams in the Himalaya and Karakoram are often primarily fed by avalanches. Their impact on glacier mass balances is often unconsidered in present studies. However, Hewitt (2014) highlighted the crucial role of snow and ice re-distribution by avalanches for Karakoram glaciers. He used a concept of glacier typology based on different nourishment processes introduced at the beginning of the 20th century. By using this concept, Hewitt classified large glaciers in order to identify the effect of avalanches on the mass balance, because many Karakoram glaciers show low down-wasting or even thickening processes described as the "Karakoram anomaly" (Hewitt 2005). Also in the Nanga Parbat region, the western corner of the High Himalaya, the topography is characterized by steep rock walls with vertical distances up to 4700 m. The debris covered glaciers reach down to 2920 m a.s.l. and are regularly fed by small and large avalanches. Our field based investigations show that the glaciers are characterized by small retreating rates since 1857, when Adolph Schlagintweit has mapped them for the first time; others such as the Raikot Glacier are fluctuating since 1934. Furthermore, the extent of down-wasting varies between different glaciers. By using multi-temporal satellite data, topographical maps, sketches and terrestrial photographs changes of glacier lengths were measured. In order to calculate the down-wasting rates, a digital elevation model (DEM) with a spatial resolution of 30x30 m² was derived from the digitized contour lines of the topographic map of 1934 and compared to the SRTM-DEM. Furthermore, based on topographical parameters derived from the SRTM-DEM, the glaciers were classified, using Hewitt's concept. The area of steep rock walls and the ratio between accumulation and ablation zones were calculated for each glacier basin. References: Hewitt, K. 2005: The Karakoram anomaly? Glacier expansion and the 'elevation effect', Karakoram Himalaya. Mountain Research and Development 25 (4), S. 332-340 Hewitt, K. 2014: Glaciers of the Karakoram Himalaya: Glacial Environments, Processes, Hazards and Resources. Springer. Dordrecht.

Schmidt, Susanne; Nüsser, Marcus

2014-05-01

98

Rock glacier dynamics and paleoclimatic implications  

NASA Astrophysics Data System (ADS)

Many rock glaciers contain massive ice that may be useful in paleoclimate studies. Interpreting geochemical ice-core records from rock glaciers requires a thorough understanding of rock glacier structure and dynamics. High-precision surface-velocity data were obtained for the Galena Creek rock glacier, Absaroka Mountains, Wyoming. Surface velocities range from 0 to 1.00 m/yr and vary across the rock glacier in a manner similar to true glaciers. We used Glen's flow law to calculate the thickness of the deforming ice layer. The modeled ice thickness ranges from 0 to 50 m, and is confirmed by direct observations. This agreement shows that rock glacier movement can be entirely explained by deformation of massive ice within the rock glacier; neither basal sliding nor deformation of basal debris is necessary. Recovered ice cores (to depths of 25 m) contain thin debris layers associated with summer ablation in the accumulation zone. The ages of four samples of organic material removed from several debris layers inthe southern half of the rock glacier range from 200 ± 40 to 2250 ± 35 14C yr B.P., demonstrating that the rock glacier formed well before the Little Ice Age and may contain ice dating to the middle Holocene or earlier.

Konrad, S. K.; Humphrey, N. F.; Steig, E. J.; Clark, D. H.; Potter, N., Jr.; Pfeffer, W. T.

1999-12-01

99

Mass balance, meteorology, area altitude distribution, glacier-surface altitude, ice motion, terminus position, and runoff at Gulkana Glacier, Alaska, 1996 balance year  

USGS Publications Warehouse

The 1996 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier Basin were evaluated on the basis of meteorological, hydrological, and glaciological data. Averaged over the glacier, the measured winter snow balance was 0.87 meter on April 18, 1996, 1.1 standard deviation below the long-term average; the maximum winter snow balance, 1.06 meters, was reached on May 28, 1996; and the net balance (from August 30, 1995, to August 24, 1996) was -0.53 meter, 0.53 standard deviation below the long-term average. The annual balance (October 1, 1995, to September 30, 1996) was -0.37 meter. Area-averaged balances were reported using both the 1967 and 1993 area altitude distributions (the numbers previously given in this abstract use the 1993 area altitude distribution). Net balance was about 25 percent less negative using the 1993 area altitude distribution than the 1967 distribution. Annual average air temperature was 0.9 degree Celsius warmer than that recorded with the analog sensor used since 1966. Total precipitation catch for the year was 0.78 meter, 0.8 standard deviations below normal. The annual average wind speed was 3.5 meters per second in the first year of measuring wind speed. Annual runoff averaged 1.50 meters over the basin, 1.0 standard deviation below the long-term average. Glacier-surface altitude and ice-motion changes measured at three index sites document seasonal ice-speed and glacier-thickness changes. Both showed a continuation of a slowing and thinning trend present in the 1990s. The glacier terminus and lower ablation area were defined for 1996 with a handheld Global Positioning System survey of 126 locations spread out over about 4 kilometers on the lower glacier margin. From 1949 to 1996, the terminus retreated about 1,650 meters for an average retreat rate of 35 meters per year.

March, Rod S.

2003-01-01

100

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

NASA Astrophysics Data System (ADS)

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

Mayer, H.; Herzfeld, U. C.

2003-12-01

101

Google Earth Tours of Glacier Change  

NSDL National Science Digital Library

To prepare for this assignment students have already used Google Earth to examine beach erosion, but they have not yet created any new content with Google Earth. Students are already competent navigators and are accustomed to the perspective views used in Google Earth. In this assignment students first go through a prepared Google Earth tour on Juneau Icefield glaciers, and answer questions about glacier features. Then students create their own Google Earth tour, using placemarks to identify key features of their glacier.

Pelto, Mauri

102

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

103

Antarctica: measuring glacier velocity from satellite images  

SciTech Connect

Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

Lucchitta, B.K.; Ferguson, H.M.

1986-11-28

104

Antarctica: Measuring glacier velocity from satellite images  

USGS Publications Warehouse

Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

Lucchitta, B. K.; Ferguson, H. M.

1986-01-01

105

Internationally coordinated glacier monitoring: strategy and datasets  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

106

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

107

Advances in Modelling of Valley Glaciers  

NASA Astrophysics Data System (ADS)

For glaciological conditions typical of valley glaciers, the central idea of this research lies in understanding the effects of high-order mechanics and parameterizing these for simpler dynamical and statistical methods in glaciology. As an effective tool for this, I formulate a new brand of dynamical models that describes distinct physical processes of deformational flow. Through numerical simulations of idealized glacier domains, I calculate empirical correction factors to capture the effects of longitudinal stress gradients and lateral drag for simplified dynamical models in the plane-strain regime. To get some insights into real glacier dynamics, I simulate Haig Glacier in the Canadian Rocky Mountains. As geometric effects overshadow dynamical effects in glacier retreat scenarios, it appears that high-order physics are not very important for Haig Glacier, particularly for evaluating its fate. Indeed, high-order and reduced models all predict that Haig Glacier ceases to exist by about AD2080 under ongoing climate warming. This finding regarding the minimal role of high-order physics may not be broadly valid, as it is not true in advance scenarios at Haig Glacier and it may not be representative of other glaciological settings. Through a 'bulk' parameterization of high-order physics, geometric and climatic settings, sliding conditions, and transient effects, I also provide new insights into the volume-area relation, a widely used statistical method for estimating glacier volume. I find a steady-state power-law exponent of 1:46, which declines systematically to 1:38 after 100 years of sustained retreat, in good accord with the observations. I recommend more accurate scaling relations through characterization of individual glacier morphology and degree of climatic disequilibrium. This motivates a revision of global glacier volume estimates, of some urgency in sea level rise assessments.

Adhikari, Surendra

108

Energy Balance and Hydrological Modelling of Zongo Glacier, Bolivia, Using ERA-40 Reanalysis Data  

NASA Astrophysics Data System (ADS)

In the Andes several regions profit significantly from glacial melt water for drink water supply and electricity production. During the dry season, glacier melt is significant source of water in the semi-arid region of La Paz, Bolivia. The Andean glaciers are retreating and water resources after reaching a culmination, will decrease. This implicates serious environmental and socio-economical consequences. For an effective attenuation, it is crucial to furnish quantitative predictions of the glacier mass loss and its effects on the water resources in these regions. A distributed energy balance model has been developed to model mass balance and melt induced discharge of tropical glaciers. We want to predict the changes in glacier melt discharge in response to future climate change for the region of La Paz, Bolivia and later regionalize the model to a larger area. The model operates on daily steps, has a 20 m grid resolution, and is forced by daily data of air temperature, humidity, wind speed, global radiation and precipitation. As a test basin, we calibrate the model at Glaciar Zongo, Bolivia, 16°15'S , 68°°10'W which is monitored by the French Institute for Research for the Development (IRD) . Zongo Glacier is a 1,8 km2 large and the catchment is 63% glacierized. Mass balance, weather station and discharge data are available on daily basis from 1991 onward. The measurements have gaps and only two years (1994-95 and 1999-00) with continuous data are available. In order to allow for multi-year simulations we force the model by daily ERA-40 reanalysis data from the European Center for Weather Forecast (ECMWF). To downscale the data we compare the daily data 1991-2002 to the observations at the glacier. Results indicate a fair agreement for air temperature, but a rather poor correlation between the ERA-40 data and the observations for wind speed, global radiation and precipitation. The correlation is improved using monthly values. So far, test runs of the model using downscaled ERA-40 data for the Zongo Glacier show good agreement for the mass balances (r2=0.88) and relatively good estimate of the monthly melt discharge (r2=0.74). The transition between the wet and dry season is well captured by the model

Duguay, M.; Hock, R.; Sicart, J.; Coudrain, A.

2008-12-01

109

Increased glacier runoff enhances the penetration of warm Atlantic water into a large Greenland fjord  

NASA Astrophysics Data System (ADS)

The retreat and acceleration of Greenland's marine-terminating outlet glaciers have been linked to ocean warming. However the mechanisms which control the transmission of this warming along fjords towards the glaciers remain poorly understood. The aim of this paper is to elucidate observed changes in water properties in Kangerdlugssuaq Fjord (KF), East Greenland using the Bergen Ocean Model (BOM). Model outputs are compared with observed potential temperature, salinity and velocity data to determine the principal controls on heat transport within KF and to estimate resulting submarine ice front melt rates of Kangerdlugssuaq Glacier (KG). The BOM includes wind, tidal and glacier runoff forcing and is able to replicate observed temperature and salinity profiles. Model results describe a robust four-layer estuarine flow, consisting of two distinct circulations. The shallow circulation (0-~ 60 m) is forced by surface wind stress and to a lesser extent supraglacial runoff, while the intermediate circulation (~ 60-500 m) is driven by runoff discharged into the fjord subglacially. Atlantic Water (AW) and warm Polar Surface Water (PSWw) are drawn into the fjord by the intermediate and shallow circulation cells respectively, in a pattern consistent with observations, and AW reaches KG over a single summer. Along-fjord heat transport towards KG increases significantly with both glacier runoff and coastal water temperature. A doubling of glacier runoff produces a 29% (48%) amplification of mean annual (summer) heat transport towards the KG terminus, increasing estimated mean annual (summer) submarine melt rates from 211 to 273 (842 to 1244) m yr-1. In contrast, heat transport towards KG in the surface ~ 60 m of the fjord decreases with rising glacier runoff because the enhanced down-fjord component of the intermediate circulation interferes with the up-fjord part of the shallow circulation. Thus, as ice sheet runoff increases, KG's dynamic response to oceanic forcing will likely be driven primarily by enhanced submarine ice front melting and consequent undercutting rather than through diminished buttressing from seasonal sea ice and ice mélange. Our model shows, in agreement with observations, that maximum submarine melt rates occur when AW and PSWw are present at the fjord mouth and, crucially, glacier runoff is also high. Rising ice sheet runoff therefore increases the sensitivity of KG (and other Greenland marine-terminating glaciers) to ocean warming.

Sole, A. J.; Payne, A. J.; Nienow, P. W.; Christoffersen, P.; Cottier, F. R.; Inall, M. E.

2012-11-01

110

Ice thickness, ablation, and other glaciological measurements on upper Fremont Glacier, Wyoming  

USGS Publications Warehouse

Glaciological investigations of the Upper Fremont Glacier in the Wind River Range of Wyoming were conducted during 1990-1991. The glaciological data will provide baseline information for monitoring future changes to the glacier and support ongoing research utilizing glacial-ice-core composition to reconstruct paleoenvironmental records. Ice thickness, determined by radio-echo sounding, ranged from 60 to 172 m in the upper half of the glacier. Radio-echo sounding of ice thickness at one point was confirmed by drilling 159.7 m to bedrock. Annual ablation (including snow, firn, and ice) measured for the 1990-1991 period averaged about 0.93 m/a. Surface ice velocity and direction were monitored from July 1990 to August 1991. Ice velocity decreased in a downslope direction. The largest measured velocity was about 3.1 m/a and the smallest was 0.8 m/a. -from Authors

Naftz, D. L.; Smith, M. E.

1993-01-01

111

Geographical variations in Sr and Nd isotopic ratios of cryoconite on Asian glaciers  

NASA Astrophysics Data System (ADS)

Cryoconite is a dark-coloured surface dust deposited on glaciers that consists of wind-blown mineral particles, as well as organic matter derived from microbes living on glaciers. In this paper, we analyse the Sr and Nd isotopic ratios of four mineral fractions (i.e., the saline, carbonate, phosphate, and silicate mineral fractions), as well as the organic fraction, of cryoconite samples obtained from six Asian glaciers (the Altai, Pamir, Tien Shan, Qillian Shan, and Himalayan regions), and discuss their geographical variations in terms of the geological origins of the mineral particles and the biogeochemical processes on the glaciers. The silicate mineral fraction showed lower Sr and higher Nd ratios for the glaciers located to the north (Altai, 87Sr/86Sr: 0.713?490–0.715?284, ?Nd(0): ?6.4 to ?5.6), while higher Sr and lower Nd ratios for the glaciers located to the south (Himalayas, 87Sr/86Sr: 0.740?121–0.742?088, ?Nd(0): ?16.4 to ?15.7) the ratios were similar to those of desert sand, loess, and river sediments in the respective regions of the glaciers. This result suggests that the silicate minerals within the cryoconites were derived from different sources depending on the geographical locations of the glaciers. The isotopic ratios of the saline, carbonate, and phosphate mineral fractions were distinct from those of the silicate fraction, and were similar to those of evaporites and apatite deposits from the Asian deserts, but also varied geographically, indicating that they are likely to reflect their geological origin. The Sr isotopic ratios of the organic fraction were similar to those of the saline and carbonate fractions from glaciers in the central area (Tien Shan and Qillian Shan), but were higher than those of the saline and carbonate fractions, and lower than the phosphate mineral fraction, in the northern and southern areas. The ratios of organic fraction may be determined from the mixing ratio of calcium sources incorporated by microbes on the glaciers.

Nagatsuka, Naoko; Takeuchi, Nozomu; Nakano, Takanori; Shin, Kicheol; Kokado, Emi

2014-04-01

112

Earth tide forcing of glacier drainage  

Microsoft Academic Search

Fourier analysis reveals that winter electrical self potential (SP), water pressure (PW), and electrical conductivity (EC) time series collected beneath Haut Glacier d'Arolla, Switzerland, are forced by earth and atmospheric tides. Forcing is dominant during periods of expanding bedrock, consistent with glacier substrate deformation periodically driving water from the ice body into the bed. This may modify the strength of

Bernd Kulessa; Bryn Hubbard; Giles H. Brown; Julia Becker

2003-01-01

113

Muir Glacier and Muir Inlet 2003  

USGS Multimedia Gallery

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

114

Glacier surges past and present  

NASA Astrophysics Data System (ADS)

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

Benn, D.; Kristensen, L.

2009-04-01

115

Iceland Glacier Recession 1997 to 2000  

NSDL National Science Digital Library

This animation is a close up zoom into largest area of glacier recesion at the Breidamerkurjokull glacier in Iceland. The data from 1997 is taken from Landsat 5 and the 2000 data is from Landsat 7. The Breidamerkurjokull glacier in Iceland has been measured by Landsat to be receding since 1973. In 1997, Landsat 5 took several other images of the glacier. It was thought by some glacierologists that this particular glacier was receding quicker in the late 1990s than it did in the late 1980s or 1970s. After careful analysis Goddards Glacierologist, Dorothy Hall, concluded that the recession from 1997 to 2000 occurs at a similar rate to the recession between 1973 and 2000. It is extremely controversial whether or not this recession is caused by global warming.

Perkins, Lori; Hall, Dorothy

2001-04-09

116

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

117

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

NASA Astrophysics Data System (ADS)

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

Machguth, H.; Huss, M.

2014-05-01

118

Early Holocene and Younger Dryas age glacier advances in Patagonia  

NASA Astrophysics Data System (ADS)

Reliable dating of Southern Hemisphere glacier fluctuations since the Last Glacial Maximum (LGM) is crucial to resolving debates about millennial-scale climate change. Here we present 10Be dates for lateral, valley-mouth and cross-valley moraines formed between the contemporary South American North Patagonian Icefield (NPI) and its LGM position in four separate valleys around 47oS. This is an area of climate sensitivity, near the core of the precipitation-bearing southern westerly winds (SWW). The dates indicate that outlet glaciers from an expanded NPI advanced to form large moraines at 10.8 ± 0.5 / 11.0 ± 0.6, 11.2 ± 0.6, 11.5 ± 0.6 and 12.5 ± 0.7 ka (Putnam southern hemisphere production rates and Dunai scaling scheme, zero-erosion). The first four ages are statistically indistinguishable and probably represent a single, regional ice advance. With a likely assumed boulder erosion rate of 2mm/ka, these ages become 11.0 ± 0.5 / 11.2 ± 0.6, 11.5 ± 0.6, 11.7 ± 0.6 and 12.8 ± 0.7 ka. With a higher (less likely) assumed boulder erosion rate of 10mm/ka these ages become 12.0 ± 0.5 / 12.1 ± 0.6, 12.4 ± 0.6, 12.8 ± 0.6 and 14.0 ± 0.7 ka. The dates indicate that glaciers in Patagonia were larger during these times than at any point since the LGM and provide evidence in Patagonia for glacier advances during the very early Holocene, around the time of the European Younger Dryas (12.9 to 11.7 ka) and the Antarctic Cold Reversal (ACR; 14.5 to 12.9 ka). Although palaeoclimatic records from this area are often contradictory, these glacier advances were probably associated with a period of regionally increased precipitation related to the changes in the position of the SWW or meltwater pulses associated with the ACR.

Glasser, N. F.; Harrison, S.; Schnabel, C.; Fabel, D.; Jansson, K.

2012-12-01

119

Title: Climate-glacier Relationship of Retreating Alaskan Glaciers Author: Elliott Mazur and Umesh K. Haritashya  

NASA Astrophysics Data System (ADS)

Portage, Whittier, Eklutna, as well as many other well-known "tourism glaciers" in the vicinity of Anchorage, Alaska are known to have retreated in the past 20 years. This begs the question, "what of the other lesser-known glaciers? Do they follow the same patterns and minimal glacier models?" Glaciers such as Byron, Leonard, Matanuska, Raven and Spencer may fit a minimal model. Information on Byron and Leonard is sparse, as both have become hanging glaciers. Other glaciers, such as Raven, are small enough to be deemed insignificant, yet may have information to give. Consequently our objective is to study five Alaskan glaciers and determine wide-ranging variability to changing regional climate. To do this we obtained field geo-location data and characterized glaciers based on the satellite imagery and climate reevaluation. Our result shows that glaciers are retreating and thinning irrespective of their aspects, location and altitudinal variability. Moreover, our presentation establishes the strong climate-glacier relationship and defines retreating snowline patterns over the last few decades.

Mazur, E. M.

2012-12-01

120

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

121

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

122

Glacier Change and an Updated Glacier Inventory of Mongolia using Landsat 8  

NASA Astrophysics Data System (ADS)

Mountain glaciers and ice caps around the world are recognized as significant contributors to both global sea level and local and regional water resources, especially for arid regions. However, the remote and rugged nature of glaciers in many parts of Asia hinders their study. To complicate the picture, not only are glaciers in High Mountain / Central / North Asia exhibiting considerable regional variability in mass balance, but different measurement methods are painting significantly different pictures of glacier health. Mongolia provides a subset of the global glacier inventory which exemplifies low data availability and seemingly contradictory results. Based on previous studies, Mongolia is home to ~500 glaciers totaling ~650 km2, but these figures are quite rough. Regional glacier mass balance estimates vary from -2 × 1 Gt / yr to 3 × 6 Gt / yr. However, the glaciers are important to the local environment and agriculture, as Mongolian glaciers are estimated to store 10% of Mongolia's fresh water. The glaciers have lost ~6% of their area from the 1960s to the 1990s. Most recent studies of high mountain Asia (the large group of glaciated ranges between the Tien Shan, Qilian Mountains, and the Himalayas) show accelerated losses in recent years. Therefore, from within this uncertainty, we harness newly available data from Landsat 8's Operational Land Imager (OLI) to build an updated glacier inventory for Mongolia. Prior regional studies have focused of a variety of sub-ranges across many different epochs within the Altai (i.e. Munkh Khairkhan, Tavan Bogd, Turgen, Kharkhiraa, Munkhkhairkhan, Sair, and Tsambagarav Mountains); here, we unify the picture of recent change for all of Mongolia's glaciers (i.e., the additional glaciated areas eastward of the Altai). In addition to highlighting the ease and utility of Landsat 8's OLI, we will take advantage of a further suite of data (i.e. Landsat archival imagery, ICESat, ASTER, SPOT-5, or submeter imagery) to further document glacier change in the Mongolian Altai.

Pope, A.; Scambos, T. A.

2013-12-01

123

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

NASA Astrophysics Data System (ADS)

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

Paul, Frank

2014-05-01

124

A field and glacier modelling based approach to determine the timing and extent of glaciation in southern Africa  

NASA Astrophysics Data System (ADS)

Moraines identified at high-altitude sites in southern Africa and dated to the last glacial maximum (LGM) indicate that the climate in this region was cold enough to support glaciers. Small glaciers are very sensitive to changes in temperature and precipitation and the identification of LGM moraines in southern Africa has important palaeoclimatic implications concerning the magnitude of temperature change and the seasonality of precipitation during the last glacial cycle. This paper presents a refined time-frame for likely glaciations based on surface exposure dating using Cl-36 at sites in Lesotho and reports results of a 2D glacier energy balance and ice flow modelling approach (Plummer and Phillips, 2003) to evaluate the most likely climatic scenarios associated with mapped moraine limits. Samples for surface exposure dating were collected from glacially eroded bedrock at several locations and yield ages within the timescale of the LGM. Scatter in the ages may be due to insufficient erosion of the bedrock surface due to the small and relatively thin nature of the glaciers. To determine the most likely climatic conditions that may have caused the glaciers to reach their mapped extent, we use a glacier-climate model, driven by data from local weather stations and a 30m (ASTER) DEM (sub-sampled to 10m) representation of the topographic surface. The model is forced using modern climate data for primary climatic controls (temperature and precipitation) and for secondary climatic parameters (relative humidity, cloudiness, wind speed). Various sensitivity tests were run by dropping temperature by small increments and by varying the amount of precipitation and its seasonality relative to present-day values. Results suggest that glaciers could have existed in the Lesotho highlands with a temperature depression of ~5-6 ºC and that the glaciers were highly sensitive to small changes in temperature. The additional accumulation of mass through wind redistribution appears to have been important at all but a few sites, suggesting that this must be taken into account when trying to determine a regional climate signal from small glaciers. Our dating and glacier-climate model simulations reinforce the idea that small glaciers existed in the Lesotho Highlands during the LGM, under climatic scenarios that are consistent with other proxy records. Plummer, M.A. and Phillips, F.M. (2003) 2-D numerical model of snow/ice energy balance and ice flow for paleoclimatic interpretation of glacial geomorphic features. Quaternary Science Reviews, 22, 1389-1406.

Mills, Stephanie C.; Rowan, Ann V.; Barrow, Timothy T.; Plummer, Mitchell A.; Smith, Michael; Grab, Stefan W.; Carr, Simon J.; Fifield, L. Keith

2014-05-01

125

Utilizing physical sediment variability in glacier-fed lakes for continuous glacier reconstructions during the Holocene, northern Folgefonna, western Norway  

Microsoft Academic Search

The maritime plateau glacier of northern Folgefonna in western Norway has a short (subdecadal) response time to climatic shifts, and is therefore well suited for reconstructing high-resolution glacier fluctuations. The reconstruction presented here is based on physical parameters of glaciolacustrine sediments retrieved from two glacier-fed lakes and a peat bog north of the ice cap. Bulk density and modelled glacier

Jostein Bakke; øyvind Lie; Atle Nesje; Svein Olaf Dahl; øyvind Paasche

2005-01-01

126

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

127

Interaction between glacier and glacial lake in the Bhutan, Himalaya  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

128

Response of Himalayan debris-covered glaciers to climate warming: from observations to predictive modeling  

NASA Astrophysics Data System (ADS)

Field observations and remote-sensing studies have shown that Himalayan debris-covered glaciers tend to follow distinctive evolutionary pathways during periods of negative mass balance. Initially, debris-covered glacier tongues downwaste rather than retreat, resulting in thinning and a reduction of ice surface gradient. Reduced driving stresses lead to lower velocities and eventual stagnation of the tongue. These geometrical and dynamic changes reduce the efficiency of the hydrological system, leading to increased retention of meltwater and the formation of ephemeral supraglacial lakes. High ablation rates around lakes and internal ablation in association with englacial conduits serve to accelerate mass loss and downwasting. In some cases, this evolutionary cascade results in the formation of moraine-dammed lakes, which can present significant outburst flood risks if large lake volumes coincide with weak moraine dams . While this evolutionary sequence has been observed on numerous glaciers, numerical prediction of future glacier behavior requires quantification or parameterization of several complex processes. In addition, system behavior is highly non-linear with multiple process thresholds, creating considerable modeling challenges. An essential first step is to develop robust mass-balance models, including patterns of snow accumulation in extreme terrain and the effects of both debris and climate on melting. Accumulation models need to incorporate vertical variations in precipitation as well as redistribution by wind and avalanching. Newly available precipitation estimates from satellite data can provide important model input. Ablation modeling can be done using a range of approaches, including degree-day and full energy balance models. Mass balance gradients calculated using the latter approach indicate ablation maxima some distance above the glacier termini, where debris cover is relatively thin. Mass balance modeling also indicates that in monsoonal regions, temperature increases have a strong impact on glacier mass balance, increasing melt and the altitude of the rain-snow transition in the summer accumulation season. At a more detailed level, melt models can simulate evolving surface topography and backwasting in response to variations in debris thickness. Recent simulations using coupled mass-balance - flow models can mimic key aspects of the observed behavior of debris-covered glaciers, including debris thickness - melt rate feedbacks, asymmetric advance - retreat cycles, as well as detachment and stagnation of glacier tongues in response to ELA rise. Future modeling challenges include parameterization of lake expansion and deepening processes, developing criteria for switching between ablation regimes, and upscaling the effects of spatially and temporally variable local processes. In the foreseeable future, advanced modeling efforts informed closely by observational studies should enable quantitative predictions to be made about the fate of debris-covered glaciers in the Himalaya.

Benn, D.; Lefeuvre, P.; Ng, F.; Nicholson, L. I.

2012-12-01

129

The state and fate of Himalayan glaciers.  

PubMed

Himalayan glaciers are a focus of public and scientific debate. Prevailing uncertainties are of major concern because some projections of their future have serious implications for water resources. Most Himalayan glaciers are losing mass at rates similar to glaciers elsewhere, except for emerging indications of stability or mass gain in the Karakoram. A poor understanding of the processes affecting them, combined with the diversity of climatic conditions and the extremes of topographical relief within the region, makes projections speculative. Nevertheless, it is unlikely that dramatic changes in total runoff will occur soon, although continuing shrinkage outside the Karakoram will increase the seasonality of runoff, affect irrigation and hydropower, and alter hazards. PMID:22517852

Bolch, T; Kulkarni, A; Kääb, A; Huggel, C; Paul, F; Cogley, J G; Frey, H; Kargel, J S; Fujita, K; Scheel, M; Bajracharya, S; Stoffel, M

2012-04-20

130

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

131

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

132

Predicting the response of seven Asian glaciers to future climate scenarios using a simple linear glacier model  

Microsoft Academic Search

Observations from seven Central Asian glaciers (35–55°N; 70–95°E) are used, together with regional temperature data, to infer uncertain parameters for a simple linear model of the glacier length variations. The glacier model is based on first order glacier dynamics and requires the knowledge of reference states of forcing and glacier perturbation magnitude. An adjoint-based variational method is used to optimally

Diandong Ren; David J. Karoly

2008-01-01

133

Predicting the response of seven Asian glaciers to future climate scenarios using a simple linear glacier model  

Microsoft Academic Search

Observations from seven Central Asian glaciers (35-55°N 70-95°E) are used, together with regional temperature data, to infer uncertain parameters for a simple linear model of the glacier length variations. The glacier model is based on first order glacier dynamics and requires the knowledge of reference states of forcing and glacier perturbation magnitude. An adjoint-based variational method is used to optimally

Diandong Ren; David J. Karoly

2008-01-01

134

Glacier acceleration, glacial earthquakes, and ice loss at Helheim Glacier, Greenland  

NASA Astrophysics Data System (ADS)

Satellite observations during the last decade have shown dramatic changes in flow speed at Greenland's outlet glaciers, often accompanied by retreats of several km in calving-front location and increasing numbers of glacial earthquakes. Geodetic, seismological, and oceanographic data collected as part of a multidisciplinary field experiment at Helheim Glacier, East Greenland, over three summer seasons (2006--2008), together with satellite imagery, place new constraints on the processes responsible for these changes. Analysis of high-rate GPS data from 2007 reveals several large, sudden increases in flow speed at Helheim Glacier. These abrupt accelerations are detected along the length of the glacier (~20~km) spanned by the GPS network, and coincide in time with major calving events and teleseismically detected glacial earthquakes. The calving events are implicated in the earthquake source process. Further, our results link changes in glacier velocity directly to calving-front behavior at Greenland's large outlet glaciers, on timescales as short as minutes to hours. No large earthquakes occurred at Helheim Glacier during the 2006 field campaign, providing the opportunity for comparison between seismically active and quiescent modes of glacier behavior. Data recorded in 2008 include near-field broadband seismic recordings and time-lapse photography, allowing us to refine our understanding of both the glacial earthquake source process and the glacier response to major ice loss events.

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.; Schild, K. M.

2008-12-01

135

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.

136

Common Misconceptions about Icebergs and Glaciers  

NSDL National Science Digital Library

This article describes some common misconceptions that elementary students may have about icebergs and glaciers (including density and buoyancy). It also includes suggestions for formative assessment and teaching for conceptual change.

Fries-Gaither, Jessica

137

In Brief: Glacier photo database update  

NASA Astrophysics Data System (ADS)

More than 1200 photographs of Greenland glaciers have been digitized and are now available at the Online Glacier Photograph Database, housed at the National Snow and Ice Data Center (NSIDC) in Boulder, Colo. The database includes 50 photographs taken between 1890 and 1996 of glaciers in Colorado and New Zealand as well as a series of photos of New Zealand's Franz Josef Glacier taken between 1951 and 1964. NSIDC has partnered with the NOAA Climate Database Modernization Program and the National Geophysical Data Center to scan selected photographs that compose the online database. For information about these updates or to access the data, visit the Web site: http://nsidc.org/data/g00472.html.

Showstack, Randy

2007-11-01

138

Glacier Retreat in the Southern Peruvian Andes: Climate Change, Environmental Impacts, Human Perception and Social Response  

NASA Astrophysics Data System (ADS)

This paper presents results from recent environmental and anthropological research near glacierized areas in the department of Cusco, Peru, home to the well-known Quelccaya Ice Cap and to the peak of Ausangate (6384 m). Glaciers in the region are in negative mass balance, losing volume and area, with upslope movement of the glacier fronts. Somewhat paradoxically, flows in many streams close to the glaciers are reduced, particularly in the dry season, due to a shift in the seasonal distribution of melting, to increased evaporation and to increased percolation into newly-exposed sands and gravels. Associated with this reduction in flow is a desiccation of some anthropogenic and natural wetlands, reducing the availability of dry season forage to wild (vicuna) and domesticated (alpaca, llama) ruminants. Interviews and ethnographic observations with local populations of Quechua-speaking herders at elevations of 4500-5200 meters provide detailed comments on these changes. They have an extensive vocabulary of terms for glacial features associated with retreat. They link this treat with environmental factors (higher temperatures, greater winds that deposit dust on lower portions of glaciers) and with religious factors (divine punishment for human wrong-doing, failure of humans to respect mountain spirits). They describe a variety of economic and extra-economic impacts of this retreat on different spatial, social and temporal scales. Though they face other issues as well (threats of pollution from new mining projects, inadequacy of government services), glacier retreat is their principal concern. Many herders express extreme distress over this unprecedented threat to their livelihoods and communities, though a few propose responses - out-migration, the formation of an association of neighboring communities, development of irrigation works - that could serve as adaptations.

Orlove, B.

2007-12-01

139

Mechanisms and causes of glacier variations  

Microsoft Academic Search

Glaciers are aperiodical physical systems subject to variations forced by variable external influences on gravitational energy and bonds; moreover, self-exciting of variations is possible since they are nonlinear systems with internal energy sources. As glaciers are completely dissipative systems, the auto-variations are of relaxational character and are connected with non-uniformity of the system in time. The field of stable equilibrium

P. A. Shumsky

140

Radar Sounding of Fast-Flowing Glaciers  

Microsoft Academic Search

A major challenge in radio glaciology is sounding of fast-flowing glaciers such as Jakobshavn, Helheim, and Kangardlussuq in Greenland. Weak ice-bed echoes from fast-flowing glaciers are masked by off-vertical surface clutter. We need fine resolution both in the along-track and cross-track directions to reduce surface clutter. Synthetic Aperture Radar (SAR) techniques can be used to improve resolution in the along-track

S. Gogineni; C. Leuschen; J. Li; L. Smith; J. Plummer; A. Hoch

2008-01-01

141

USGS Repeat Photography Project: Glacier National Park  

NSDL National Science Digital Library

This project, conducted by the United States Geological Survey (USGS), documents changes over time in the landscape of Glacier National Park, particularly the retreat of the park's glaciers. The project involves pairing historic photos from the park's archives with recent photos to illustrate how the landscape has changed. Users can view and download the photos in pairs with dates and a caption describing the scene and the changes that have taken place.

142

Glacier Inventory: A Case in Semiarid Chile  

Microsoft Academic Search

\\u000a Glaciers are the most important water reservoirs found in the Andes. While the scientific community has conducted more extensive\\u000a glaciological studies in southern Chile, it is only recently that attention has been focused on northern Chile. In the Chilean\\u000a “Norte Chico” region, where glaciation is restricted to the highest summits, the sparse glacier network provides the majority\\u000a of water to

Jorge Marín; José Araos

143

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

144

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

NASA Astrophysics Data System (ADS)

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 250m 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 four glaciers in the French Alps including Saint Sorlin Glacier during the ablation season. The annual mass balance of each 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. J.; Guillot, A.; Décaux, L.; Rabatel, A.; Six, D.; Arnaud, Y.

2012-12-01

145

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

146

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

147

A data set of worldwide 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 past 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 worldwide, 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 1535, 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 available glacier length series show relatively small fluctuations until the mid-19th century, followed by a global retreat. The retreat 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.

2014-04-01

148

Glaciers in the Earth's Hydrological Cycle: Assessments of Glacier Mass and Runoff Changes on Global and Regional Scales  

NASA Astrophysics Data System (ADS)

Changes in mass contained by mountain glaciers and ice caps can modify the Earth's hydrological cycle on multiple scales. On a global scale, the mass loss from glaciers contributes to sea-level rise. On regional and local scales, glacier meltwater is an important contributor to and modulator of river flow. In light of strongly accelerated worldwide glacier retreat, the associated glacier mass losses raise concerns over the sustainability of water supplies in many parts of the world. Here, we review recent attempts to quantify glacier mass changes and their effect on river runoff on regional and global scales. We find that glacier runoff is defined ambiguously in the literature, hampering direct comparison of findings on the importance of glacier contribution to runoff. Despite consensus on the hydrological implications to be expected from projected future warming, there is a pressing need for quantifying the associated regional-scale changes in glacier runoff and responses in different climate regimes.

Radi?, Valentina; Hock, Regine

2014-05-01

149

Changing features of the climate and glaciers in China's monsoonal temperate glacier region  

Microsoft Academic Search

Climatic data, ice core records, the tree ring index, and recorded glacier variations have been used to reconstruct a history of climatic and glacial changes in the monsoonal temperate glacier region of southwestern China during the last 400 years. The region's temperature has increased in a fluctuating manner during the twentieth century after two cold stages of the Little Ice

Yuanqing He; Zhonglin Zhang; Wilfred H. Theakstone; Tuo Chen; Tandong Yao; Hongxi Pang

2003-01-01

150

Decay of a long-term monitored glacier: 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 19th century to its current condition in 2012. In addition to having one of the longest and richest observation records among the Italian glaciers, Careser is unique in the Italian Alps for its 46 yr mass balance series that started in 1967. In the present study, variations in the length, area and volume of the glacier since 1897 are examined, updating and validating the series of direct mass balance observations and adding to the mass balance record 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 3 decades was 1.5 m water equivalent per year, increasing to 2.0 m water equivalent per year in the last decade. Although these rates are not representative at a regional scale, year-to-year variations in mass balance show an unexpected increase in correlation with other glaciers in the Alps, during the last 3 decades. 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.

2013-12-01

151

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

Microsoft Academic Search

The Global Land Ice Measurement from Space (GLIMS) project is a cooperative effort of over sixty institutions world-wide with the goal of inventorying a majority of the world's estimated 160000 glaciers. Each institution (called a Regional Center, or RC) oversees the analysis of satellite imagery for a particular region containing glacier ice. Data received by the GLIMS team at the

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

2007-01-01

152

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

153

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

NASA Astrophysics Data System (ADS)

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

Le Bris, R.; Paul, F.

2012-04-01

154

A new method for deriving glacier centerlines applied to glaciers in Alaska and northwest Canada  

NASA Astrophysics Data System (ADS)

This study presents a new method to derive centerlines for the main branches and major tributaries of a set of glaciers, requiring glacier outlines and a digital elevation model (DEM) as input. The method relies on a "cost grid-least-cost route approach" that comprises three main steps. First, termini and heads are identified for every glacier. Second, centerlines are derived by calculating the least-cost route on a previously established cost grid. Third, the centerlines are split into branches and a branch order is allocated. Application to 21 720 glaciers in Alaska and northwest Canada (Yukon, British Columbia) yields 41 860 centerlines. The algorithm performs robustly, requiring no manual adjustments for 87.8% of the glaciers. Manual adjustments are required primarily to correct the locations of glacier heads (7.0% corrected) and termini (3.5% corrected). With corrected heads and termini, only 1.4% of the derived centerlines need edits. A comparison of the lengths from a hydrological approach to the lengths from our longest centerlines reveals considerable variation. Although the average length ratio is close to unity, only ~ 50% of the 21 720 glaciers have the two lengths within 10% of each other. A second comparison shows that our centerline lengths between lowest and highest glacier elevations compare well to our longest centerline lengths. For > 70% of the 4350 glaciers with two or more branches, the two lengths are within 5% of each other. Our final product can be used for calculating glacier length, conducting length change analyses, topological analyses, or flowline modeling.

Kienholz, C.; Rich, J. L.; Arendt, A. A.; Hock, R.

2014-03-01

155

Four+ Years of Measurements from the Mendenhall Glacier Terminus  

NASA Astrophysics Data System (ADS)

We describe the instrumentation, power, communications, and lessons learned from ongoing four+ years of measurements at the terminus of Mendenhall Glacier. In this presentation we focus on the most successful microserver deployment. The microserver is a simple rugged computer with a radio modem that can survive and operate outdoors in harsh environments like Antarctica. The system is called a microserver because of the networking capabilities, particularly as it may act as anchor points for localized lightweight sensor networks. SEAMONSTER, the SouthEast Alaska MOnitoring Network for Science, Technology, Education and Research, is a demonstration sensor web effort. The microserver design for SEAMONSTER is intended to provide general capabilities that could be used in harsh environments specifically for cryospheric observations. At the Mendenhall terminus the observations included meteorologic data and repeat digital photography. Other SEAMONSTER stations included snow accumulation and density, precision GPS, seismic, water pressure, and other measurements. Power generation at the Mendenhall deployment is both solar and wind.

Heavner, M.; Fatland, D. R.

2012-12-01

156

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

157

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

NASA Astrophysics Data System (ADS)

Northwestern China currently experiences a climate change with fundamental consequences for the hydrological cycle. In the strongly arid region where water resources are essential for agriculture and food production, glaciers represent important water resources, contributing significantly to streamflow. The debris is an important glaciological feature of the region and has major impact on melt rates. It is essential to understand and quantify the interaction of climate and sub-debris melt in order to assess the current situation and to predict future water yield. Note that the surface energy balance determines glacier melt. However, little is known about the variability characteristics of the surface energy fluxes in this region. For this reason, we set up two automatic weather stuation (AWSs) in the ablation area of Keqicar Glacier. Keqicar Glacier is located in the Tarim River basin (largest inland river basin in China), southwestern Tien Shan, China. It is a representative debris-covered glacier with a length of 26.0 km and a total surface area of 83.6 km2. The thickness of the debris layer varies from 0.0 to 2.50 m in general. In some places large rocks are piled up to several meters. In this study, we report on analysis of meteorological data for the period 1 July-13 September 2003, from two automatic weather stations, aimed at studying the relationship between climate and ablation. One station is located on the lower part of the ablation area where the glacier is covered by debris layer, and the other near the equilibrium line altitude (ELA). All sensors were sampled every 10 seconds, and data were stored as hourly averages. The stations were visited regularly for maintenance at two weeks intervals depending on the weather conditions and location of the AWS. A total of 17 ablation stakes were drilled into the glacier at different elevations to monitor glacier melt during the study period. Readings were taken regularly in connection with AWS maintenance. The weather station on the glacier measured an average temperature of 2.6 °C (at 2m height above surface). The lapse rate of air temperature is close to the standard free atmospheric lapse rate (0.6 °C per 100m), which shows the cold effect of glacier is not significant. The local mountain-valley winds is significant, the speed of which is 2.3 m s-1 (at 2m height). Glacier is dominated by the convectional precipitation, 75% of which occurs in day time. The ablation stakes indicate a specific mass balance of -2.5 m w.e. between 1 July and 13 September. The specific mass balance calculated from the surface energy balance, -2.6 m w.e., is in close correspondence to this. The thermal processes on the debris layer are quite different from those on bare ice or snow. The main physical characteristics of the debris layer are the thermal conductivity and albedo that control heat conduction to the ice-debris interface. Net radiation is the main melt energy whether the debris layer is taken into consideration or not, which is lager between July and the middle of August, and then decreases. This is coincides with the glacier ablation. On the debris-covered area, the sensible- and latent-heat fluxes contribute 19.6% of the melt energy, higher than that on the debris-free ice (4.1%). Hence, due to the existing debris layer, the ablation shows a significant spatial distribution.

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

2009-04-01

158

The History of the Glacier Facies Concept  

NASA Astrophysics Data System (ADS)

The concept of glacier facies developed as a result of physical measurements made in Greenland on repeated traverses that went inland from the west coast at two latitudes (77 N and 70 N) and north to south along the crest of the ice sheet. Snow pits and shallow cores showed discontinuities in physical characteristics that defined the facies boundaries. Some refinement have resulted from research in Antarctica and on Alaskan mountain glaciers. Thirty years after the facies were defined, based on field measurements, it was found that radar data (SAR) from satellites show the boundary between the percolation and dry snow facies in Greenland. They also show the percolation facies of the Greenland ice sheet to be the brightest radar reflector on earth. The dry snow facies is rare except on the major ice sheets (Greenland and Antarctica), but it is present on mountains that exceed 4000 m in Alaska and the Yukon. In particular, Mt. Wrangell, Alaska was selected for continued study of glacier facies because it has a large and accessible area above 4000 m. Mt. Wrangell has proven to have the full spectrum of glacier facies, and these can be seen on the SAR map of Alaska. Refinements in the definition of the lower end of the wet snow facies, to deal with a slush zone and a superimposed ice zone, resulted from Fritz Mueller's research on Axel Heiberg Island and from studies on the McCall Glacier of Alaska. Minor refinements in defining the dry snow facies resulted from comparing Antarctica and Greenland in places where mean annual temperature and accumulation rates were essentially equal. The glacier facies concept also provides a way of comparing the two polar regions and of speculating on the glacier facies that existed on the Pleistocene continental ice sheets.

Benson, C. S.

2001-12-01

159

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

NASA Astrophysics Data System (ADS)

Calving glaciers around the world have recently undergone a rapid retreat and are important contributors to global sea level rise. Due to their greatly increased mass loss, tidewater glaciers in particular have long received much attention, whereas lake calving glaciers have just been identified as significant contributors. In southeast Alaska, numerous glaciers have experienced rapid retreat and significant thinning during the last several decades. To better understand the causes for these rapid changes we have focused on Yakutat Glacier, a lake calving glacier in southeast Alaska. Yakutat Glacier is part of the Yakutat Ice field and drains into Harlequin Lake, which has depths of over 300 m at the calving face. The ice field covers an area of 668 sq km and lies in a maritime area off the coast of the Gulf of Alaska. The average precipitation in the nearby town of Yakutat is over 3800 mm per year. However, the ice field divide is essentially at or below the current equilibrium line altitude (ELA) of 800 - 900 m for this region, thereby ensuring the glacier will continue to thin, provided the current trend of regional warming does not reverse. The ongoing thinning continues to lower the glaciers average elevation, increasing its average ablation, even under constant climate. This forms a positive feedback loop that is known as the Bovardsson effect. In addition, radio echo sounding shows much of the glacier base near or below sea level, indicating that lake calving will remain playing a role in the retreat. We obtained a 40 m-grid digital elevation model (DEM) derived from September 3, 2007 SPOT imagery and obtained under the IPY SPIRIT program. We used August 26, 2007 laser altimetry profiles to check the accuracy of the DEM and found a mean difference of 2 m (DEM greater) with a standard deviation of 2.3 m. We differenced this DEM from a DEM from the February 2000 Shuttle Radar Topography Mission to determine the extent of the volume change and thinning. During this period, the Yakutat Ice field lost about 22.4 ± 7.5 cubic km of ice, with thinning rates increasing down glacier, especially towards the glacier's grounding line. Just up glacier from this grounding line, we found elevation changes of over 10 m per year. The same trend is visible in a comparison between the 2007 Spot DEM and a July 2009 DEM generated from photogrammetry imagery. Little change in surface elevation occurred over the 2-km-long floating tongue during this time period, but recently the entire floating tongue has started to disintegrate.

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

2010-12-01

160

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

161

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

162

Pine Island Glacier, Antarctica, MISR Multi-angle Composite  

article title:  Pine Island Glacier, Antarctica, MISR Multi-angle Composite     ... iceberg has finally separated from the calving front of Antarctica's Pine Island Glacier. Scientists first detected a rift in the ...

2013-12-17

163

Glaciological investigations beneath an active polar glacier  

NASA Astrophysics Data System (ADS)

Meserve Glacier, Antarctica, was used as a natural laboratory for research on the effective viscosity of subfreezing polycrystalline ice, and on the interaction of cold-based glaciers with their beds. A tunnel was excavated through basal layers of this glacier, which allowed sampling of ice for subsequent measurements of physical and chemical properties and allowed in-situ measurements of ice deformation and glacier sliding. Analyses of deformation reveal a direct dependence of strain rate on crystal size, which reflects an important role for grain-size-sensitive deformation mechanisms such as grain boundary sliding. The sensitivity of strain rate to chemical impurity content and rock particle content is found to be very low. Variations of crystal size probably are an important control on shear enhancement in the ice sheets. The enhanced shear strain rate inferred from tilt of the Dye 3 borehole can be explained as a result of combined fabric and crystal size variations. I infer that interactions between Meserve glacier and its bed are influenced by the presence of liquid water films at ice-rock interfaces despite the low temperature of -17°C. Such films allow slip at ice-rock interfaces and cause in-situ segregation of ice into clean lenses amidst dirty layers. Using slip rate and bed surface roughness measurements I infer la liquid film thickness of at least tens of nanometers. Such films should generally be present in polar glaciers, and will have a thickness controlled by soluble impurities and temperature. Analyses of gas and isotopic composition of basal ices reveal that entrainment of bed material into this glacier actively occurs without bulk freeze-on and conventional regelation. Cold-based glaciers have the capacity to striate and erode their beds, and to create glacial landforms. I reinterpret the clear and persistent relationship between d18O and dD of polar precipitation, which allows isotopic composition to be an important tool for studying glacier-bed interactions and deuterium excess measurements on ice cores to reveal subtropical paleoclimate. I argue that the isotopic composition of precipitation is determined by water-vapor equilibrium to temperatures as low as -35°C. This implies deuterium excess is not sensitive to cloud supersaturation.

Cuffey, Kurt Marshall

164

Optical Flow for Glacier Motion Estimation  

NASA Astrophysics Data System (ADS)

Quantitative measurements of glacier flow over time are an important ingredient for glaciological research, for example to determine the mass balances and the evolution of glaciers. Measuring glacier flow in multi-temporal images involves the estimation of a dense set of corresponding points, which in turn define the flow vectors. Furthermore glaciers exhibit rather difficult radiometry, since their surface usually contains homogeneous areas as well as weak texture and contrast. To date glacier flow is usually observed by manually measuring a sparse set of correspondences, which is labor-intensive and often yields rather irregular point distributions, with the associated problems of interpolating over large areas. In the present work we propose to densely compute motion vectors at every pixel, by using recent robust methods for optic flow computation. Determining the optic flow, i.e. the dense deformation field between two images of a dynamic scene, has been a classic, long-standing research problem in computer vision and image processing. Sophisticated methods exist to optimally balance data fidelity with smoothness of the motion field. Depending on the strength of the local image gradients these methods yield a smooth trade-off between matching and interpolation, thereby avoiding the somewhat arbitrary decision which discrete anchor points to measure, while at the same time mitigating the problem of gross matching errors. We evaluate our method by comparing with manually measured point wise ground truth.

Vogel, C.; Bauder, A.; Schindler, K.

2012-07-01

165

Exploration of Uncertainty in Glacier Modelling  

NASA Technical Reports Server (NTRS)

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

Thompson, David E.

1999-01-01

166

Progresses in the ice formation of glaciers in China  

Microsoft Academic Search

Glaciers, formed by snowfall and characterized by movement and size, are the most sensitive indicators to climate change.\\u000a The ice formation of glaciers (the processes, mechanisms and results of transformation from snow to ice) can indicate the\\u000a growth condition, the formation process and the physical characteristics of glaciers. Its spatial variation can also reflect\\u000a glacier change, and further reveal climate

Xiangying Li; Shiyin Liu; Donghui Shangguan; Aigang Lu

2008-01-01

167

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

168

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

169

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

170

Asynchroneity of maximum glacier advances in the central Spanish Pyrenees  

Microsoft Academic Search

The deglaciation history of the Escarra and Lana Mayor glaciers (Upper Gállego valley, central Spanish Pyrenees) had been reconstructed on the basis of detailed geomorphological studies of glacier deposits, sedimentological and palynological analyses of glacial lake sediments and an accelerator mass spectrometry (AMS) 14C chronology based on minimum ages from glacial lake deposits. The maximum extent of the Pyrenean glaciers

José M. García-Ruiz; Blas L. Valero-Garcés; Carlos Martí-Bono; Penélope González-Sampériz

2003-01-01

171

Extracting a Climate Signal from 169 Glacier Records  

Microsoft Academic Search

I constructed a temperature history for different parts of the world from 169 glacier length records. Using a first-order theory of glacier dynamics, I related changes in glacier length to changes in temperature. The derived temperature histories are fully independent of proxy and instrumental data used in earlier reconstructions. Moderate global warming started in the middle of the 19th century.

J. Oerlemans

2005-01-01

172

Chemical weathering in the foreland of a retreating glacier  

Microsoft Academic Search

Chemical denudation rates and strontium isotope ratios in streams vary substantially and systematically in the foreland of the retreating Bench Glacier in south-central Alaska. To study weathering of young glacier sediments, we sampled 12 streams draining a chronosequence of till and moraine soils derived from Cretaceous metagraywacke–metapelite bedrock. Both sediment age and vegetation cover increase with distance from the glacier.

Suzanne Prestrud Anderson; James I Drever; Carol D Frost; Pete Holden

2000-01-01

173

Snow and glacier mapping with polarimetric SAR  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

174

Response of glaciers in northwestern North America to future climate change: an atmosphere\\/glacier hierarchical modeling approach  

Microsoft Academic Search

The response of glaciers to changing climate is explored with an atmosphere\\/glacier hierarchical modeling approach, in which global simulations are downscaled with an Arctic MM5 regional model which provides temperature and precipitation inputs to a glacier mass-balance model. Themass balances of Hubbardand BeringGlaciers, south-central Alaska, USA, aresimulated for October 1994-September 2004. The comparisons of the mass-balance simulations using dynamically-downscaled vs

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

2007-01-01

175

Comparative metagenome analysis of an Alaskan glacier.  

PubMed

The temperature in the Arctic region has been increasing in the recent past accompanied by melting of its glaciers. We took a snapshot of the current microbial inhabitation of an Alaskan glacier (which can be considered as one of the simplest possible ecosystems) by using metagenomic sequencing of 16S rRNA recovered from ice/snow samples. Somewhat contrary to our expectations and earlier estimates, a rich and diverse microbial population of more than 2,500 species was revealed including several species of Archaea that has been identified for the first time in the glaciers of the Northern hemisphere. The most prominent bacterial groups found were Proteobacteria, Bacteroidetes, and Firmicutes. Firmicutes were not reported in large numbers in a previously studied Alpine glacier but were dominant in an Antarctic subglacial lake. Representatives of Cyanobacteria, Actinobacteria and Planctomycetes were among the most numerous, likely reflecting the dependence of the ecosystem on the energy obtained through photosynthesis and close links with the microbial community of the soil. Principal component analysis (PCA) of nucleotide word frequency revealed distinct sequence clusters for different taxonomic groups in the Alaskan glacier community and separate clusters for the glacial communities from other regions of the world. Comparative analysis of the community composition and bacterial diversity present in the Byron glacier in Alaska with other environments showed larger overlap with an Arctic soil than with a high Arctic lake, indicating patterns of community exchange and suggesting that these bacteria may play an important role in soil development during glacial retreat. PMID:24712530

Choudhari, Sulbha; Lohia, Ruchi; Grigoriev, Andrey

2014-04-01

176

Recent climate trends, Glacier Bay, Alaska  

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

177

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

Microsoft Academic Search

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

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

2009-01-01

178

Glacier volume response time and its links to climate and topography based on a conceptual model of glacier hypsometry  

NASA Astrophysics Data System (ADS)

Glacier volume response time is a measure of the time taken for a glacier to adjust its geometry to a climate change. It has been previously proposed that the volume response time is given approximately by the ratio of glacier thickness to ablation at the glacier terminus. We propose a new conceptual model of glacier hypsometry (area-altitude relation) and derive the volume response time where climatic and topographic parameters are separated. The former is expressed by mass balance gradients which we derive from glacier-climate modelling and the latter are quantified with data from the World Glacier Inventory. Aside from the well-known scaling relation between glacier volume and area, we establish a new scaling relation between glacier altitude range and area, and evaluate it for seven regions. The presence of this scaling parameter in our response time formula accounts for the mass balance elevation feedback and leads to longer response times than given by the simple ratio of glacier thickness to ablation at the terminus. Volume response times range from decades to thousands of years for glaciers in maritime (wet-warm) and continental (dry-cold) climates respectively. The combined effect of volume-area and altitude-area scaling relations is such that volume response time can increase with glacier area (Axel Heiberg Island and Svalbard), hardly change (Northern Scandinavia, Southern Norway and the Alps) or even get smaller (The Caucasus and New Zealand).

Raper, S. C. B.; Braithwaite, R. J.

2009-08-01

179

Glacier volume response time and its links to climate and topography based on a conceptual model of glacier hypsometry  

NASA Astrophysics Data System (ADS)

Glacier volume response time is a measure of the time taken for a glacier to adjust its geometry to a climate change. It is currently believed that the volume response time is given approximately by the ratio of glacier thickness to ablation at the glacier terminus. We propose a new conceptual model of glacier hypsometry (area-altitude relation) and derive the volume response time where climatic and topographic parameters are separated. The former is expressed by mass balance gradients which we derive from glacier-climate modelling and the latter are quantified with data from the World Glacier Inventory. Aside from the well-known scaling relation between glacier volume and area, we establish a new scaling relation between glacier altitude range and area, and evaluate it for seven regions. The presence of this scaling parameter in our response time formula accounts for the mass balance elevation feedback and leads to longer response times than given by the simple ratio of glacier thickness to ablation. Volume response times range from decades to thousands of years for glaciers in maritime (wet-warm) and continental (dry-cold) climates, respectively. The combined effect of volume-area and altitude-area scaling relations is such that volume response time can increase with glacier area (Axel Heiberg Island and Svalbard), hardly change (Northern Scandinavia, Southern Norway and the Alps) or even get smaller (The Caucasus and New Zealand).

Raper, S. C. B.; Braithwaite, R. J.

2009-03-01

180

Glacier area and length changes in Norway from repeat inventories  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

181

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

NASA Astrophysics Data System (ADS)

During summer 2001, a 140 m long ice core was recovered from the Belukha glacier (49°48'26''N, 86°34'43''E, 4062 m a.s.l.) in the Siberian Altai. The englacial temperature of -17°C indicates that this unique glaciochemical record is well preserved and suitable for the reconstruction of air pollution levels in this previously unexplored region. The upper 86 m were dated by 210Pb and cover the period 1862-2001. A lack of strong winter minima was observed in the ?18O record and attributed to the small amount of precipitation during that season and to wind erosion. The ion concentrations are comparable to those observed in Swiss glaciers, except for ammonium and formate, where enhanced concentrations indicate biogenic emissions from Siberian forests. Sulfate, ammonium and nitrate records all show anthropogenic impacts despite the remoteness of this site.

Olivier, Susanne; Schwikowski, Margit; Brütsch, Sabina; Eyrikh, Stella; Gäggeler, Heinz W.; Lüthi, Martin; Papina, Tatyana; Saurer, Matthias; Schotterer, Ulrich; Tobler, Leonhard; Vogel, Edith

2003-10-01

182

A complex relationship between calving glaciers and climate  

USGS Publications Warehouse

Many terrestrial glaciers are sensitive indicators of past and present climate change as atmospheric temperature and snowfall modulate glacier volume. However, climate interpretations based on glacier behavior require careful selection of representative glaciers, as was recently pointed out for surging and debris-covered glaciers, whose behavior often defies regional glacier response to climate [Yde and Paasche, 2010]. Tidewater calving glaciers (TWGs)mountain glaciers whose termini reach the sea and are generally grounded on the seaflooralso fall into the category of non-representative glaciers because the regional-scale asynchronous behavior of these glaciers clouds their complex relationship with climate. TWGs span the globe; they can be found both fringing ice sheets and in high-latitude regions of each hemisphere. TWGs are known to exhibit cyclic behavior, characterized by slow advance and rapid, unstable retreat, largely independent of short-term climate forcing. This so-called TWG cycle, first described by Post [1975], provides a solid foundation upon which modern investigations of TWG stability are built. Scientific understanding has developed rapidly as a result of the initial recognition of their asynchronous cyclicity, rendering greater insight into the hierarchy of processes controlling regional behavior. This has improved the descriptions of the strong dynamic feedbacks present during retreat, the role of the ocean in TWG dynamics, and the similarities and differences between TWG and ice sheet outlet glaciers that can often support floating tongues.

Post, A.; O'Neel, S.; Motyka, R. J.; Streveler, G.

2011-01-01

183

Rheology of rock glaciers: a preliminary assessment  

Microsoft Academic Search

Movement of rock debris under the influence of gravity, i.e., mass movement, generates a range of phenomena from soil creep, through solifluction,debris flows and rock glaciers to rock falls. Whereas the resultant forms of these phenomena are different, common elements in the mechanics of movement are utilized in the basic interpretation of the processes of formation. Measurements of morphologic variables

J. R. Giardino; J. D. Vitek; E. R. Hoskins

1985-01-01

184

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

185

Stream temperature response to glacier retreat (Invited)  

NASA Astrophysics Data System (ADS)

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

Moore, R. D.

2013-12-01

186

Slow Erosion by a Fast Glacier  

Microsoft Academic Search

The dramatic imprints left on landscapes by Quaternary glaciations provide abundant evidence that glaciers can be efficient erosive agents. Understanding their erosive capability is key to unravelling the complex coupling of climate and the dynamics of the solid earth. Recent studies have focused on quantifying rates of glacial erosion to provide key data for understanding the physics that drives glacial

A. D. Huerta; J. P. Winberry

2007-01-01

187

Triaxial experinlents on iceberg and glacier ice  

Microsoft Academic Search

Triaxial experiments, at confining pressures in the range 0- 13.79 MPa, have been performed on glacial ice collected from four icebergs and one glacier. Tests were conducted at strain rates in the range of 5 x 10 .'J to 5 x 10 2 S I and at four temperatures in the range of 10 to -16 °C. Depending on test

R. E. GAG

188

Remote Sensing Characterization of Glaciers in the N. Himachal Pradesh  

NASA Astrophysics Data System (ADS)

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

Le, D.; Catania, G. A.

2012-12-01

189

Changes in the Surface Area of Glaciers in Northern Eurasia  

NASA Astrophysics Data System (ADS)

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

Khromova, T.; Nosenko, G.

2012-12-01

190

Jökulhlaup triggering: Observations at Kennicott Glacier, Alaska  

NASA Astrophysics Data System (ADS)

Jökulhlaups, sudden releases of water impounded by a glacier, produce large floods unrelated to weather events. We draw on observations from 90 years of annual jökulhlaups from Hidden Creek Lake, Kennicott Glacier, Alaska and from detailed monitoring in 1999 and 2000, to examine conditions that trigger outburst floods. For the class of jökulhlaups caused by subglacial drainage, the trigger must be related to formation of subglacial conduits, a pivotal problem in glaciology. Hidden Creek Lake water level at drainage has declined over the last century, during which time the glacier has thinned. The water level trend is mirrored by a tendency toward earlier release dates in the summer. These observations suggest that a minimum threshold lake level must be exceeded for drainage to occur, and that this threshold is related to ice thickness. The release date varies by over a month, however, and lake level varies by as much as 10 m over spans of a few years, which indicates that more is involved than simple exceedance of a threshold. Kennicott Glacier impounds several other small lakes. In two summers with fairly complete observations of their behavior, these lakes drained in sequence from nearest to furthest from the terminus. More frequent observations have been made of drainage of one of these lakes: Erie Lake, located roughly the same distance from the terminus as Hidden Creek Lake, along a major tributary to the Kennicott Glacier, usually drains within days of Hidden Creek Lake. These patterns are consistent with a trigger that is related to glacier-wide evolution of the hydrologic system, rather than each drainage reflecting purely local conditions. Perhaps there is a linkage between timing of outbursts and seasonal upglacier extension of the subglacial conduit system. While we have no direct information on annual evolution of the conduit system at Kennicott Glacier, some have suggested that conduits and the snowline move upglacier in tandem. In 1999 and 2000, the snowline had retreated far upglacier, beyond Hidden Creek Lake, before it drained. Estimated melt rates in the days preceding Hidden Creek Lake outbursts, calculated with a degree day model, show no pattern: lake drainage has occurred during times of both low and high melt production. Jökulhlaup triggering appears to be controlled by a number of conditions, among them the height of the ice barrier, organization of the subglacial hydrologic system, and specific, probably transient, conditions within that system at the time of drainage.

Anderson, S. P.; Walder, J. S.; Fountain, A. G.; Anderson, R. S.; Trabant, D. C.

2003-12-01

191

Ice flow dynamics of Alaska glaciers  

NASA Astrophysics Data System (ADS)

Understanding long-term ice dynamic response to climate change remains of the utmost importance with respect to constraining sea level rise (SLR) projections for 2100. SLR contributions from Alaska approximate those from Greenland and may be dominated by mass losses from changes in flow dynamics. But due to a lack of data on flow dynamics, projections for future mass change in Alaska only consider surface mass balance. Here we present the first regionally extensive dataset of mountain glacier flow velocities in Alaska---covering 28,022 km2 of ice. This dataset reveals that more than 50% of the mass flux in Alaska comes from only eleven key glacier systems that have high mass fluxes due to high balance velocities and are not necessarily linked to tidewater glacier retreat. In south central Alaska, we find that the rate of mass loss from tidewater calving is equivalent to 75% of the total net mass loss annually; thus surface mass balance alone is inadequate to project future statewide mass losses. Our dataset also enables a close examination of a surge (periodic acceleration) event on Bering Glacier, the largest surging glacier in the world. There, velocities exceed quiescent speeds by 18 times over two periods lasting a total of 3 years. Results suggest that downstream propagation of the surge is closely linked to the evolution of the driving stress during the surge because driving stress appears to be tied to the spatial variability of resistive stress provided by the bed. Finally, we are able to examine regional changes in wintertime flow velocities and find that wintertime flow speed is inversely correlated with summertime positive degree days. We propose that this relationship is the result of a negative feedback mechanism whereby increased meltwater production enlarges subglacial conduit systems that are more effective at discharging water from subglacial cavities. As cavities close during the fall, less remaining water reduces bed separation during winter and thus engenders slower sliding velocities. We find this mechanism exerts a secondary control on glacier surge triggering, encouraging/discouraging initiation after cold/warm summers. This mechanism could have important ice dynamic implications when forced by a changing climate. Increases in summertime temperatures could result in a gradual slowing of land terminating ice, thus providing a negative feedback (self correcting) mechanism that could slightly slow projected mass losses from land terminating glaciers.

Burgess, Evan Windam

192

Meltwater Induced Glacier Landslides - Waxell Ridge, AK  

NASA Astrophysics Data System (ADS)

Within the past year, two large landslides have originated from south-facing peaks on Waxell Ridge, the bedrock massif that separates the Bagley Icefield from Bering Glacier, Alaska. Each involves a near-summit hanging glacier. In each instance, the presence of meltwater appears to be a triggering factor. The largest of the two, which occurred on September 14, 2005, originated from just below the summit of 3,236-m-high Mt Steller and landed on the surface of Bering Glacier, nearly 2,500 m below. The Alaska Volcano Observatory estimated the volume of this landslide, which consisted of rock, glacier ice, and snow, to be approximately 50 million cubic meters. Unlike most large Alaskan glacier-related landslides, this one was not triggered by an earthquake. However, the energy that the slide released was intense enough to generate a seismic signal that was recorded around the world with magnitudes of 3.8 to greater than 5. The slide extended ~10 km down the Bering Glacier from the point of impact. Much of the surface on which the slide occurred had a slope >50 degrees. The second landslide, located ~6 km to the west of Mt Steller, originated from a secondary summit of a 2,500- m-high unnamed peak. The date of its occurrence is unknown, but its toe sits on winter 2005-2006 snow. Both slides have been examined from helicopter and fixed-wing overflights, and with a variety of vertical and oblique aerial photographs. Oblique aerial photographs obtained of the Mt Steller slide on September 15, 2005 depict a 10-15-m-diameter moulin or englacial stream channel in the truncated 30-m-thick glacier ice that comprises the east wall of the landslide scarp. The presence of this unusual glacial-hydrologic feature at an elevation above 3,000 m, suggests that a large volume of water had recently been flowing on Mt Steller's east ridge and that the water might have had a role in triggering the landslide. Similarly, there is evidence of an englacial channel on the west flank of the summit scarp of the second slide. The presence of large volumes of meltwater close to the crest of Waxell Ridge raises questions about regional climate change and its role in the future generation of landslides at higher elevations. This presentation summarizes the findings produced from the analysis of aerial photography and field observations made between September 2005 and September 2006.

Molnia, B. F.; Angeli, K. M.; Bratton, D. A.; Keeler, R. H.; Noyles, C.

2006-12-01

193

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

194

Surge of a Complex Glacier System - The Current Surge of the Bering-Bagley Glacier System, Alaska  

NASA Astrophysics Data System (ADS)

Understanding fast glacier flow and glacial accelerations is important for understanding changes in the cryosphere and ultimately in sea level. Surge-type glaciers are one of four types of fast-flowing glaciers --- the other three being continuously fast-flowing glaciers, fjord glaciers and ice streams --- and the one that has seen the least amount of research. The Bering-Bagley Glacier System, Alaska, the largest glacier system in North America, surged in 2011 and 2012. Velocities decreased towards the end of 2011, while the surge kinematics continued to expand. A new surge phase started in summer and fall 2012. In this paper, we report results from airborne observations collected in September 2011, June/July and September/October 2012 and in 2013. Airborne observations include simultaneously collected laser altimeter data, videographic data, GPS data and photographic data and are complemented by satellite data analysis. Methods range from classic interpretation of imagery to analysis and classification of laser altimeter data and connectionist (neural-net) geostatistical classification of concurrent airborne imagery. Results focus on the characteristics of surge progression in a large and complex glacier system (as opposed to a small glacier with relatively simple geometry). We evaluate changes in surface elevations including mass transfer and sudden drawdowns, crevasse types, accelerations and changes in the supra-glacial and englacial hydrologic system. Supraglacial water in Bering Glacier during Surge, July 2012 Airborne laser altimeter profile across major rift in central Bering Glacier, Sept 2011

Herzfeld, U. C.; McDonald, B.; Trantow, T.; Hale, G.; Stachura, M.; Weltman, A.; Sears, T.

2013-12-01

195

Numerical Modelling of Katabatic Flow Over a Melting Outflow Glacier  

NASA Astrophysics Data System (ADS)

A realistic simulation of katabatic flows is not a straightforward task for numerical models. One complicating factor is that katabatic flows develop within a stably stratified boundary layer, which is poorly resolved and described in many numerical models. To capture the jet-shaped shallow flow a model set-up with high vertical resolution is also required. In this study, ‘a state of the art’ mesoscale numerical model is applied in a simulation of katabatic flow over a melting glacier. A basic agreement between observations and model results is found. From scale analysis, it is concluded that the simulated flow can be classified as katabatic. Although the background flow varies in strength and direction, the simulated katabatic flow over Breidamerkurjökull is persistent. Two factors vital for this persistence are identified. First, the melting snow maintains the surface temperature close to 0 °C while the air temperature warms adiabatically as it descends the slope. This provides a ‘self enhanced’ negative buoyancy that drives the flow to a balance with local friction. Second, the jet-like shape of the resulting flow gives rise to a large ‘curvature term’ in the Scorer parameter, which becomes negative in the upper jet. This prevents vertical wave propagation and isolates the katabatic layer of the influence from the free troposphere aloft. Our results suggest that the formation of local microclimates dominated by katabatic flow is a general feature over melting glaciers. The modelled turbulence structure illustrates the importance of non-local processes. Neglecting the vertical transport of turbulence in katabatic flows is not a valid assumption. It is also found that the local friction velocity remains larger than zero through the katabatic jet, due to directional shear where the scalar wind speed approaches its maximum.

Söderberg, Stefan; Parmhed, Oskar

2006-09-01

196

Origin, Evolution, and Preservation of Cold Based Debris Covered Glaciers: Quantifying Sublimation Rates of Ancient Buried Ice in Antarctica  

NASA Astrophysics Data System (ADS)

Growing interest in our planet's climate history has placed a premium on acquiring detailed records of past climate change. Of considerable interest are archives of ancient atmosphere trapped within the debris-covered alpine glaciers of the western Dry Valleys region of Antarctica. The Mullins Valley debris-covered glacier (~8 km in length) is sourced from local snowfall at the steep headwall of the valley. The first 1.2 km of this glacier is generally free of overlying debris except for isolated cobbles and boulders. Thereafter, the ice surface is covered with a thin, continuous sheet of dolerite-rich rubble. Factors that influence the origin and modification of this ice include atmospheric temperature and relative humidity, precipitation, incoming solar radiance, surface albedo, till texture, winds, surface roughness, salts, and secondary ice lenses. We applied a diffusion model to track vapor flux within a sublimation till overlying the Mullins Valley debris-covered glacier, purportedly the world's oldest debris-covered alpine glacier. As input, we used meteorological data from HOBO data loggers that captured climate change and till temperatures. Results show that vapor flows into and out of the sublimation till at rates dependent on the non-linear variation of soil temperature with depth. Sublimation rates along the Mullins Glacier varied as a function of till thickness, local climate (using a calculated regional lapse rate of 0.88°C per 100 m), and till texture. Ice loss during the study interval (November 27, 2006 to December 24, 2006) ranged from as high as 2.12 mm for exposed glacier ice in the upper ablation zone, to as low as 0.01 mm for buried ice beneath till >50 cm in thickness. Averaged over the entire ablation zone (6.7 km2), this yields a net ice-surface lowering of 0.32 mm during the study interval. Numerical modeling suggests that a modest ice accumulation rate at the headwall of ~1 cm a-1 appears sufficient to maintain current ice volumes. Overall, our model results are consistent with an inferred Miocene age for distal portions of the Mullins Valley debris-covered glacier and suggests that ancient atmosphere may be preserved in buried glaciers in the western Dry Valleys region.

Kowalewski, D. E.; Marchant, D. R.

2007-12-01

197

Radar Sounding of Fast-Flowing Glaciers  

NASA Astrophysics Data System (ADS)

A major challenge in radio glaciology is sounding of fast-flowing glaciers such as Jakobshavn, Helheim, and Kangardlussuq in Greenland. Weak ice-bed echoes from fast-flowing glaciers are masked by off-vertical surface clutter. We need fine resolution both in the along-track and cross-track directions to reduce surface clutter. Synthetic Aperture Radar (SAR) techniques can be used to improve resolution in the along-track direction. However, SAR technique is not useful to synthesize a long-aperture in the cross-track direction unless data can be collected over a grid with a line spacing of about 1 m at 150 MHz. This is impossible to do with an airborne radar. We developed a high-sensitivity radar with array-processing capability in the cross-track direction to reduce clutter. The radar is designed to measure signals as low as 2 nV with a loop sensitivity of about 215 dB with peak power of about 800 W. We have successfully used this radar to obtain ice thickness and bed topography of three outlet glaciers. The radar soundings over Jakobshavn reveal a complex topography with a thickness of about 800 m at calving front and increasing to 2.7 km at about 40 km from the front. In this paper we will provide a brief review of the system that allowed first successful radar soundings of several fast-flowing glaciers, show sample results, and bed topography of a few glaciers.

Gogineni, S.; Leuschen, C.; Li, J.; Smith, L.; Plummer, J.; Hoch, A.

2008-12-01

198

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

NASA Astrophysics Data System (ADS)

Sediment records from distal glacier-fed lakes have been used in numerous reconstructions of past glacier activity, where the basic assumption is that the amount of minerogenic material deposited in the lake is directly proportional to the amount of upstream glacier erosion. However, the minerogenic component of the sediments in a distal glacier-fed lake is commonly derived from several different sources, not only subglacial erosion. Furthermore, glacier reconstructions tend to focus on individual mountain glaciers, which due to local effects might not always reflect regional scale glacier variability. Presently, certain high-resolution analysis techniques allow for fast multi-proxy analyses of sediment cores, which improve the basis for inferring the provenance of lake sediments; however, the only way of actually testing such inferences is to identify the different sediment sources in the adjacent catchment and characterize them using the same proxy measurements as in the lake core. Multi-proxy sedimentary fingerprinting techniques are labor-intensive, however, and proxies such as bulk geochemistry may prove of little use in differentiating between source areas if the bedrock lithology is uniform across the catchment. Here we present a simple method based on environmental magnetism that allow for tracking lake sediments to their sources in catchments where the bedrock lithology is uniform. Unlike ferro- and ferrimagnetic minerals, the magnetic susceptibility of paramagnetic minerals is inversely proportional to temperature. Thus, by measuring the bulk magnetic susceptibility (chi-Bulk) of a sediment sample both at room temperature (293K) and after freezing in liquid nitrogen (77K), the relative contribution from paramagnetic minerals to the total chi-Bulk can be inferred from the ratio of chi-Bulk77K over chi-Bulk293K. Theoretically, a ratio of 3.8 will indicate a purely paramagnetic sample, whereas progressively lower values reflect an increasing contribution from ferro- or ferrimagnetic minerals. We found that in the catchment of Nerfloen, a distal lake draining a large (440 km2) catchment in western Norway that contains 52 separate glaciers, there was a systematic decrease in the chi-Bulk77K/chi-Bulk293K-ratio with increasing altitude and proximity to the glaciers. We have not studied the magnetic mineralogy of our samples in detail, but infer from our data that the relative amount of paramagnetic minerals increase as soil formation progresses, thereby creating the contrasting ratios between samples collected at different altitudes. In the lake core we observe rapid shifts between sedimentary regimes dominated by high- and low-altitude source areas, which can best be explained by regional-scale growth and decay of mountain glaciers in the lake catchment.

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

2014-05-01

199

Glacier Changes in the Bhutanese Himalaya - Present and Future  

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. The most conservative results indicate that, even if climate were to remain at the present-day mean values (1980-2000), almost 10% of Bhutan's glacierized area would vanish and the meltwater flux would drop by as much as 30%. New mapping of glacierized area from 2000-2010 shows a significant change in glacierized area of 4-6%. Thus the conservative steady-state area changes predicted by the model are already being realized. Under the conservative scenario of an additional 1°C regional warming, glacier retreat is predicted to continue until about 25% of Bhutan's glacierized area will have disappeared and the annual meltwater flux, after an initial spike, would drop by as much as 65%.

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

2012-12-01

200

Land Cover Change Impacts on Tropical Mountain Climate and Glaciers  

NASA Astrophysics Data System (ADS)

Glacier loss has traditionally been investigated as a dependent of larger-scale climate change. Here we attempt to quantify the "home-made" effect of local land cover change (LCC) on glacier mass loss, using glacier shrinkage on Kilimanjaro (East Africa) as a test case, which has been extensively studied in terms of multi-scale climatic controls. A new approach that enables to downscale large-scale climate dynamics to the glacier's mass balance (MB) in a fully physical way (Moelg and Kaser 2011, J. Geophys. Res. 116) allows us to isolate this local effect from the large-scale forcings. The novel element concerns the linking of a process-based glacier MB model and a limited-area (mesoscale) atmospheric model (LAM) without statistical downscaling at their interface. We perform sensitivity studies by varying the land cover distribution (1976 or present) at the lower boundary of the LAM, in order to determine (1) the resultant changes in atmospheric state and dynamics over the mountain and (2) their effect on glacier MB. Results are expected to demonstrate how forcings of glacier shrinkage are partitioned between large-scale flow and local (partly human-controlled) LCC and, in a wider context, which glacier types are vulnerable to local LCC. The study can also serve as a template for attribution of glacier changes anywhere in the world, and thus help to correctly interpret the climate signal that receding glaciers exhibit.

Moelg, T.; Grosshauser, M.; Hemp, A.; Hofer, M.; Marzeion, B.

2011-12-01

201

Assessing streamflow sensitivity to variations in glacier mass balance  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

202

A study of discrete glacier motion  

NASA Astrophysics Data System (ADS)

Knowledge of process which control glacial dynamics are imperative in quantifying the response of a glacier or ice sheet to external forcing. This dissertation focuses mainly upon the characterization of sliding ice over a bed in an unstable fashion. I investigate unstable sliding through instances where it is observed in passive seismology as well as a focused laboratory study. The laboratory study attempts to isolate specific aspects of the sliding interface, which could lead to unstable sliding. Implications of unstable sliding with regards to erosion are also dealt with. Initially the TAMSEIS array is used to observe a unique set of seismicity originating at the base of David Glacier Antarctica in which ˜ 20,000 events were located over a ˜300 day period as the ice slid over an asperity. Tidal effects at the terminus modulated the interevent spacing and magnitude of events allowing for a basic analysis of healing process between a glacier and its bed. The 300 day period of repeat seismicity is hypothesized to arise from advection of debris rich ice over the asperity. Next the erosion implications of stick slip sliding are investigated. Sudden advancement associated with seismic energy generation is hypothesized to rapidly expand water filled cavities, which form in lee of bedrock highs. The rapid expansion creates a drop in water pressure within the cavity resulting in a pressure gradient leading to rapid fracture of bedrock. During the interseismic period of a stick slipping glacier the static coefficient of friction transfers a larger shear stress to the bed than the dynamic coefficient of friction from stably sliding glacier would. Next laboratory experimentation is conducted using a biaxial shearing apparatus in order to test the hypothesis that debris rich ice can affect the stability regime of a sliding glacier. This is preformed on a suite of ice-debris samples with range entrained debris percentages and temperatures. Both synthetic ice constructed in the laboratory and natural ice taken from the base of Engabreen Glacier were tested. Transition from a velocity strengthening to velocity weakening interface was observed for a constant velocity if the debris amount was increased thus validating the initial hypothesis. These exterminations were followed by a set of experiments in which the biax was de-stiffened in order to replicate the elastic strain, which would be accumulated at the base of a glacier. When driven under conditions previously identified in the unstable slip regime unstable sliding did occur. This allowed for exploration unstable slip parameters. Specifically comparisons of stress drop with recurrence interval, and peak-sliding velocity was investigated. Next POLENET seismic data was used to investigate a set of repeating ruptures occurring near the Executive Committee Range of Marie Byrd Land Antarctica, a known source of volcanic activity. Surface velocities as low as V ? 30 m yr--1 in this region exist indicating the source of glacially generated seismicity was atypical. A proposed source of a sudden addition of basal melt water from an increase in geothermal heat flux is hypothesized to result in the seismic signature observed. Lastly the POLENET dataset was used to investigate calving events located at the terminus of Thwaites Glacier. The seismicity displayed a monochromatic signal. A new calving mechanism, which could produce such a source of seismicity, is theorized as resonating within the block, which is being calved off.

Zoet, Lucas K.

203

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

204

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

205

Controlling mechanisms of Thwaites Glacier, West Antarctica  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

206

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

207

Till deformation beneath Black Rapids Glacier, Alaska, and its implication on glacier motion  

NASA Astrophysics Data System (ADS)

The motion of a glacier is largely determined by the nature of its bed. The basal morphology and its reaction to the overlying ice mass have been subject to much speculation, because the glacier bed is usually difficult to access, and good field data are sparse. In spring 1997 a commercial wireline drill rig was set up on Black Rapids Glacier, Alaska, to extract cores of basal ice, subglacial till, and underlying bedrock. One of the boreholes was equipped with three tiltmeters to monitor till deformation, and a piezometer to record pore water pressure. The surface velocity and ice deformation in a borehole were also measured. The drill successfully reached bedrock twice after penetrating a till layer, some 5 to 7 m in thickness, confirming an earlier seismic interpretation. The till consisted of a sandy matrix containing clasts up to boulder size. Bedrock and till lithology indicated that all the drill holes were located to the north of the Denali Fault, a major tectonic boundary along which the glacier flows. The mean annual surface velocity of the glacier was 60 ma-1 , of which 20 to 30 ma-1 were ice deformation, leaving 30 to 40 ma-1 of basal motion. The majority of this basal motion occurred at a depth of more than 2 m in the till, contradicting previously held ideas about till deformation. Basal motion could occur as sliding of till over the underlying bedrock, or on a series of shear layers within the till. This finding has implications for the interpretation of the geologic record of former ice sheets, for geomorphology, and for glacier dynamics. The effect of a thick till layer on ice flow and on quantities observable at the glacier surface was calculated. These include velocity changes on secular, seasonal, and shorter time scales. A mechanism for uplift events and dye tracing responses was suggested. An easy surface observation that could serve to clearly distinguish a glacier underlain by till from the more traditional view of a glacier underlain by bedrock could not be identified.

Truffer, Martin

208

Remote Sensing Applications for the Bering Glacier, Alaska  

NASA Astrophysics Data System (ADS)

Satellite remote sensing is an invaluable tool to monitor and characterize the Bering Glacier System. The Bering Glacier is located in coastal, south-central Alaska and is the largest and longest glacier in continental North America, with an area of approximately 5,175 km2, and a length of 190 km. It is also the largest surging glacier in America, having surged at least five times during the twentieth century. The last great surge occurred in 1993- 1995. Bering Glacier alone covers more than 6 percent of the glacier covered area of Alaska and may contain 15- 20 percent of Alaska's total glacier ice. Applications of glacier remote sensing include but are not limited to: mapping extent and features, ice velocities through sequential observations, glacier terminus locations, snow line location, glacier albedo, changes in glacier volume, iceberg surveys and calving rates, hydrographic and water quality parameters in ice marginal lakes, and land cover classification maps. Historical remote sensing images provide a much needed geospatial time record of the dynamic changes Bering Glacier has undergone, including changes due to its surge behavior and response to climate change. Remote sensing images dating back to the early 1990s have been used to map the glacier terminus retreat of approximately five to seven kilometers which has resulted in Vitus Lake increasing in volume approximately 260 percent since 1995 to the current (2006) volume of 9.4 km3 of water. Using elevation data obtained from remote sensing and GPS surface points, we have determined that the glacier elevation has decreased approximately 150 m in elevation at the terminus and 30 m at a position 300 m below the present (2006) equilibrium line (~1,300 m) since 1972. Satellite observations have recorded the upward migration in altitude of the equilibrium line to its present position (slightly > 1,200 m). The decrease in glacier volume, obtained using remote sensing derived elevation data, from 1957 to 2004 is estimated at approximately 104 km3. Remote sensing data has also mapped the sediment rich (rock flower) water flowing into Vitus Lake providing insight into the hydrologic circulation of the Bering Glacier system, showing major glacier discharge from the Abandoned River, Arrowhead Point, and Lamire Bay in the area of Vitus Lake west of Taggland.

Liversedge, L.; Shuchman, R.; Josberger, E.; Payne, J.; Hatt, C.; Spaete, L.

2007-12-01

209

Modelling Feedbacks between Ocean Stratification, Atmospheric Forcing, Sea-Ice Growth, and Glacier Terminus Melting in Fjords  

NASA Astrophysics Data System (ADS)

In many locations, ice sheets discharge into the ocean via marine-terminating glaciers. This provides a coupling where the ice-sheet mass balance can respond to changing ocean forcing, which is of interest for predictions of sea level rise. Models and observations suggest that the melting of a marine glacier terminus depends critically on the ocean temperature and salinity stratification. However, there is uncertainty about which processes provide the dominant control on the ocean conditions in fjords. I develop a simplified conceptual model of a fjord circulation coupled to a melting glacier terminus. This provides a tool to assess the impact of a range of processes on glacial melting, including the inflow of ocean waters at the fjord mouth, the estuarine circulation of glacial meltwater, vertical mixing driven by atmospheric forcing, and sea ice formation. The model describes the seasonal evolution of vertical profiles of temperature, salinity, and velocity in the fjord, using a horizontally-averaged finite volume method. The temperature and salinity stratification control the glacial melting rate via a meltwater plume rising along the glacier terminus, which in turn drives an estuarine-style circulation in the fjord interior. Further advective transport and vertical mixing are driven by atmospheric forcing, via winds and surface buoyancy fluxes. Finally, modelled sea ice growth enhances the buoyancy-driven mixing as a result of brine rejection from growing sea ice, but reduces the transmission of wind stresses through fast ice into the ocean. A scaling analysis reveals the relative significance of each of these processes for transport and mixing in the fjord over a range of forcing conditions. The model is applied to simulate the seasonal evolution of glacial melting for several case studies that are representative of Greenland fjords, and the inherent coupled feedback mechanisms are explored. If the ocean is weakly stratified at the fjord mouth, then vertical mixing plays a significant role in modulating both the fjord stratification, and the vertical distribution and magnitude of glacier terminus melting.

Wells, A.

2013-12-01

210

Basaltic micrometeorites from the Novaya Zemlya glacier  

NASA Astrophysics Data System (ADS)

A large number of micrometeorites (MMs) was recovered from glacier deposits located at the north-eastern passive margin of the Novaya Zemlya glacier sheet. Melted, scoriaceous, and unmelted micrometeorites (UMMs) are present. Unmelted micrometeorites are dominated mostly by chondritic matter, but also a few achondritic MMs are present. Here we report the discovery of four UMMs that, according to their texture, mineralogy, and chemistry, are identified as basaltic breccias. Mineral chemistry and Fe/Mn ratios of two basaltic micrometeorites indicate a possible relationship with eucrites and/or mesosiderites, whereas two others seem to have parents, which appear not to be present in our meteorite collections. The basaltic breccia UMMs constitute 0.5% of the total population of the Novaya Zemlya MM suite. This content should be lowered to 0.25% because the Novaya Zemlya MM collection appears to be biased with carbonaceous UMMs being underrepresented.

Badjukov, Dmitry D.; Brandstätter, Franz; Raitala, Jouko; Kurat, Gero

2010-09-01

211

Jakobshavns Glacier drainage basin - A balance assessment  

NASA Technical Reports Server (NTRS)

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.

1984-01-01

212

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

213

Polythermal glacier hydrology and ice flow dynamics  

NASA Astrophysics Data System (ADS)

Measurements at polythermal John Evans Glacier, Ellesmere Island, indicate strong links between spatial and temporal variations in subglacial hydrology and changes in surface velocity. Radio-echo sounding was used to determine ice thicknesses and bed topography, which allowed reconstruction of likely subglacial flow routing. Spatial patterns in residual bed reflection power (BRPr) enabled identification of warm and cold areas of the glacier bed. Within warm areas, the detailed pattern of BRPr was similar to the pattern of predicted subglacial water flow. Long-term ice motion measurements along a centre-line of 20 stakes indicate summer velocities slightly higher than overwinter levels in the accumulation area, but up to double overwinter levels in the ablation area. To assess the importance of basal motion in accounting for these patterns, expected ice deformation rates were calculated based on the likely range of ice temperatures and longitudinal coupling lengths at the glacier. In the accumulation and upper ablation areas, predicted motion due to ice deformation closely matched observations in both summer and winter. In the lower ablation area, basal motion was required in addition to ice deformation, with the largest basal velocities centred over the areas of predicted subglacial drainage. In addition, there was a rapid onset to summer basal motion directly below a set of moulins which provide the main route for surface meltwater to reach the glacier bed. Short-term ice motion measurements record three short-term (two- to four-day) high velocity events in summer 1998 and 1999, with velocities >100% above overwinter levels. These events were associated with periods of rapidly increasing meltwater input to the subglacial drainage system. The first events in 1998 and 1999 occurred at the start of the melt season at the transition from a snow covered to an ice covered surface. A second event in 1999 occurred midway through the summer as surface melting resumed following a cold period, and was strongly localised along a predicted subglacial drainage axis.

Copland, Luke

2001-07-01

214

Bacteria in Snow and Glacier Ice  

Microsoft Academic Search

By definition, the cryosphere is the portion of the Earth where water is in solid form as snow or ice. It includes vast areas\\u000a of sea ice, freshwater ice, glaciers, ice sheets, snow cover and permafrost. Because of the extremely harsh climatic conditions,\\u000a these frozen environments had been considered for a long time to be devoid of life or serving

Vanya Miteva

215

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

NASA Technical Reports Server (NTRS)

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

Hall, Dorothy K.

1997-01-01

216

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

217

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.

218

A study of the atmospheric surface layer and roughness lengths on the high-altitude tropical Zongo glacier, Bolivia  

NASA Astrophysics Data System (ADS)

atmospheric surface layer of high-altitude tropical glaciers is inadequately understood, particularly concerning turbulent fluxes. Measurements have shown that sublimation reduces melt energy in the dry season, but the errors are large when a katabatic wind maximum occurs at a low height. This study analyzed wind and temperature vertical profiles measured by a 6 m mast in the ablation area of the tropical Zongo glacier (16°S, 5060 m above sea level) in the dry seasons of 2005 and 2007. Surface roughness lengths for momentum and temperature were derived from least squares fits of hourly wind and temperature profile data. Measurement errors were explored, focusing on the poorly defined reference level for sensor heights. A katabatic wind maximum at heights between 2 and 3 m was regularly observed during low wind speed and strong inversion conditions, or about ~50%of the time, greatly reducing the surface layer depth. The glacier surface, experiencing melting conditions in the early afternoon and strong cooling at night, remained relatively smooth with z0 ~ 1 mm and zT ~ 0.1 mm. Sensible heat flux measured at ~1 m was not very sensitive to the zero reference level due to two opposite effects: when measurement heights increase, profile-derived roughness lengths increase but temperature and wind gradients decrease. The relation between zT/z0 and the roughness Reynolds number Re* roughly agrees with the surface renewal model. However, this is mostly due to self-correlation because of the shared variable z0 in zT/z0 and Re*, which prevents a sound experimental validation of the model.

Sicart, Jean Emmanuel; Litt, Maxime; Helgason, Warren; Tahar, Vanessa Ben; Chaperon, Thomas

2014-04-01

219

Global Terrestrial Network for Glaciers: Databases and Web interfaces  

NASA Astrophysics Data System (ADS)

The Global Terrestrial Network for Glaciers (GTN-G) is an umbrella organization with links to the Global Climate Observing System (GCOS), Global Terrestrial Observing System (GTOS), and UNESCO (all organizations under the United Nations), for the curation of several glacier-related databases. It is composed of the World Glacier Monitoring Service (WGMS), the U.S. National Snow and Ice Data Center (NSIDC), and the Global Land Ice Measurements from Space (GLIMS) initiative. The glacier databases include the World Glacier Inventory (WGI), the GLIMS Glacier Database, the Glacier Photograph Collection at NSIDC, and the Fluctuations of Glaciers (FoG) and Mass Balance databases at WGMS. We are working toward increased interoperability between these related databases. For example, the Web interface to the GLIMS Glacier Database has also included queryable layers for the WGI and FoG databases since 2008. To improve this further, we have produced a new GTN-G web portal (http://www.gtn-g.org/), which includes a glacier metadata browsing application. This web application allows the browsing of the metadata behind the main GTN-G databases, as well as querying the metadata in order to get to the source, no matter which database holds the data in question. A new glacier inventory, called the Randolph Glacier Inventory 1.0, has recently been compiled. This compilation, which includes glacier outlines that do not have the attributes or IDs or links to other data like the GLIMS data do, was motivated by the tight deadline schedule of the sea level chapter of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Now served from the GLIMS website (http://glims.org/), it is designed to serve that narrowly focused research goal in the near term, and in the longer term will be incorporated into the multi-temporal glacier database of GLIMS. For the required merging of large sets of glacier outlines and association of proper IDs that tie together outlines that pertain to the same glacier (perhaps at different points in time), we at NSIDC have written software to examine geospatial relationships between the sets of outlines and assign attributes and linkages accordingly.

Raup, B.; Armstrong, R.; Fetterer, F.; Gartner-Roer, I.; Haeberli, W.; Hoelzle, M.; Khalsa, S. J. S.; Nussbaumer, S.; Weaver, R.; Zemp, M.

2012-04-01

220

Volume Estimation for Glaciers in China Based on Topographical Parameters  

NASA Astrophysics Data System (ADS)

Glaciers outside of Greenland and Antarctic ice sheets have attracted continuous attention due to the large contribution to global sea level rise during the last century and in future. However, this depends on the volume estimation of mountain glaciers except for knowledge of their dynamic response to climate change. Thicknesses of some glaciers in China were measured by pulse RADAR sounding equipment in the 1980s and the measured samples increased in the 2010s. The early data are important base for the volume and water resource storage estimation of glaciers in China and this estimation has not updated by now although new measurements and method are available, for example ice thickness along the flow line of a glacier based on digital elevation model and shallow ice approximation simplification. The method is applied here with the available thickness data acquired in the 1980s and 2010s as well as glacier boundaries and digital elevation models. It is found that there exists good relationship between average basal shear stress and topographic parameters. The method is validated for the estimation of the ice volume of well-studied glaciers inventoried from the photogrammetrical mapping and glaciated trimlines based on field investigation. This provides an update to the estimation of glacier ice volume and a base for modeling of glacier response to climate change.

Wei, J.; Liu, S.; Guo, W.

2012-12-01

221

Inventory of Glaciers in the North Cascades, Washington  

USGS Publications Warehouse

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

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

1971-01-01

222

Characteristics of the turbulent flow in the surface layer of a Tropical Glacier  

NASA Astrophysics Data System (ADS)

Energy balance studies on glaciers mostly use aerodynamic profile methods, assuming hypotheses of Monin-Obukhov similarity theory are valid, in order to compute sensible and latent turbulent heat fluxes. Nevertheless, various turbulence measurements have shown that the turbulent flow in the surface layer is not in equilibrium and stationnary within mountainous rough topography. Few of these studies focus on tropical glaciers, and little is known about the dynamics of the surface layer in these environnments. We thus have deployed an extensive micro-meteorological experiment within the atmospheric surface layer over the ablation zone of the tropical Zongo glacier, Bolivia, during the dry season from July to August, 2007. Stations were installed around 5050 m a.s.l. They included two complete eddy covariance systems at a 2-m mean level and a 6-m mast measuring the mean profiles of air temperature and of wind speed. Data is used to characterize the conditions in the surface layer. Weakly stable conditions prevailed in the first meters above the ice or snow surface. With weak large scale forcing, a katabatic downslope flow with a wind maximum at about 2-m height usually appeared in the middle of the afternoon and maintained itself during most of the night. Profile data is fitted to derive roughness lenghts and characterize their evolution. The study of statistical moments of high frequency wind speed and temperature data shows that the wind regime was highly gusty and irregular. Stationary conditions were rarely encountered. Characteristics and structure of the turbulent flow were studied using spectral analysis. It shows that the observed turbulence cannot be generated only by local shear and that low frequency perturbations interact with the surface layer turbulence and lead to divergence from the classical Kansas surface layer curves. We compare the spectra for different typical meteorological conditions and katabatic wind maximum heights. It gives us insights on the extent of these perturbations regarding to the conditions. We test the influence of the nearness of the wind maximum on eddy covariance measurements and flux divergence in the few meters above the surface.

Litt, Maxime; Sicart, Jean-Emmanuel

2013-04-01

223

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

224

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

225

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 a 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 cm per year for smaller glaciers to half a meter 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 meter. 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 rate depends on the duration of the surge. It is generally an order of magnitude larger than the water production by "normal" dissipation. On the other hand, the additional basal melt rate during a surge is comparable in magnitude to 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 of 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 is accumulating in a part of the glacier base where surface meltwater and rain has 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.

2013-06-01

226

Climatic Controls on the Distribution of Surging Glaciers  

NASA Astrophysics Data System (ADS)

Surge-type glaciers are scattered in a non-random fashion, gathered in clusters in some glaciated regions. One group of clusters forms an Arctic and Sub-Arctic 'crescent', spanning from Alaska-Yukon, through Arctic Canada, West and East Greenland, Iceland, Svalbard and Novaya Zemlya. Another cluster occurs in western High Asia, including the Karakoram Mountains. Although several studies have assessed the influence of environmental controls on surging, so far none has provided a satisfactory explanation for the geographical location of these clusters. The distribution of such glaciers undoubtedly holds the keys of a better understanding on the controls on surging behaviour. For this study, two glacier populations are considered. First, a global inventory of glacier surges has been compiled, based on published observations, field reports and remote sensing studies. This digital database is structured in three tables, respectively providing information on the location and geometry of each surge-type glacier, surge dates and magnitude, and methodology employed at the time of observation. This global dataset is compared to the population of "non-surge-type glaciers" based on the Randolph Glacier Inventory version 2.0 excluding the inventoried surging glaciers. In both populations, glaciers are classified depending on their geometry and thermal regime. Downscaled climatic datasets are used to identify climatic envelopes associated with clusters of surging glaciers. We identified which environments are most prone to be associated to glacier surging, and examined the influence of these parameters on the surge cycle duration and character. These results emphasize the importance of external controls on surging (as against individual surges), and promote the need to study this behaviour in the frame of an energy-balance budget.

Sevestre, H.; Benn, D.

2012-12-01

227

Climate Change and Glacier Retreat: Scientific Fact and Artistic Opportunity  

NASA Astrophysics Data System (ADS)

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 too conservative. Accelerated glacier shrinkage since the model was developed has mirrored an increase in actual annual temperature that is almost twice the rate used in the model. The glaciers in Glacier National Park are likely to be gone well before 2030. A variety of media, curricula, and educational strategies have been employed to communicate the disappearance of the glaciers as a consequence of global warming. These have included everything from print media and television coverage to podcasts and wayside exhibits along roads in the park. However, a new thrust is to partner with artists to communicate climate change issues to new audiences and through different channels. A scientist-artist retreat was convened to explore the tension between keeping artistic products grounded in factually-based reality while providing for freedom to express artistic creativity. Individual artists and scientists have worked to create aesthetic and emotional images, using painting, poetry, music and photography, to convey core messages from research on mountain ecosystems. Finally, a traveling art exhibit was developed to highlight the photography that systematically documents glacier change through time. The aim was to select photographs that provide the most compelling visual experience for an art-oriented viewer and also accurately reflect the research on glacier retreat. The exhibit opens on January 11, 2009

Fagre, D. B.

2008-12-01

228

Holocene glacier history from alpine speleothems, Milchbach cave, Switzerland  

NASA Astrophysics Data System (ADS)

Mountain glaciers and their sediments are prominent witnesses of climate change, responding sensitively to even small modifications in meteorological parameters. Even in such a classical and thoroughly studied area as the European Alps the record of Holocene glacier mass-balance is only incompletely known. Here we explore a novel and continuous archive of glacier fluctuations in a cave system adjacent to the Upper Grindelwald Glacier in the Swiss Alps. Milchbach cave became partly ice-free only recently and hosts Holocene speleothems. Four coeval stalagmites show consistent petrographic and stable isotopic changes between 9.2 and 2.0 ka which can be tied to abrupt modifications in the cave environment as a result of the closing and opening of multiple cave entrances by the waxing and waning of the nearby glacier. During periods of Holocene glacier advances, columnar calcite fabric is characterized by ? 18O values of about -8.0‰ indicative of speleothem growth under quasi-equilibrium conditions, i.e. little affected by kinetic effect related to forced degassing or biological processes. In contrast, fabrics formed during periods of glacier minima are typical of bacterially mediated calcite precipitation within caves overlain by an alpine soil cover. Moreover, ? 18O values of the bacterially mediated calcite fabrics are consistent with a ventilated cave system fostering kinetic fractionation. These data suggest that glacier retreats occurred repeatedly before 5.8 ka, and that the amplitudes of glacier retreats became substantially smaller afterwards. Our reconstruction of the Upper Grindelwald Glacier fluctuations agrees well with paleoglaciological studies from other sites in the Alps and provides a higher temporal resolution compared to traditional analyses of peat and wood remains found in glacier forefields.

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

2011-02-01

229

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

230

Monitoring Tidewater Glacier Processes Using A Long-Range Terrestrial LiDAR Scanner; Comparative Results From Helheim Glacier Southeast Greenland and Hubbard Glacier Southeast Alaska  

NASA Astrophysics Data System (ADS)

Tidewater glaciers exhibit dynamic behaviors across a range of spatial and temporal scales, posing a challenge to both in situ and remote sensing observations. In situ measurements capture variability over very short time intervals, but with limited spatial coverage and significant cost and risk to employ. Conversely, airborne and satellite remote sensing is capable of measuring changes over large spatial extents but at limited temporal sampling. Terrestrial LiDAR Scanning (TLS) combines rapid acquisition capabilities of in situ measurements with the broad spatial coverage of traditional remote sensing. This paper describes efforts to develop and field a new long-range (6-10 km) terrestrial full-waveform LiDAR scanner that is optimized for glaciated environments. Our work seeks to gain insights into the processes of glacier flow and terminus dynamics on two of the world's most active tidewater glaciers. Helheim Glacier, a large East Greenland outlet glacier is known to move at speeds >25 m/d near its terminus; rapid readjustments in speed are also know to occur following terminus retreat. Hubbard Glacier, located in southeast Alaska an outlet glacier flowing 90Km out of the St Elias mountains is ~13km across at its terminus, exhibits flow rates up to 5m/d and is advancing and thickening. These two glacial systems have similar characteristics yet represent inverse phases of tidewater glacier activity. Our understanding of these processes is limited by incomplete observational datasets. Most TLS instruments operate in the near-infrared spectrum (1550 nm), which greatly limits range (<150 m) and its application as a tool for long-range standoff glaciology. High spatial and temporal resolution surveys were conducted at Helheim Glacier during the summer of 2012 and 2013 and surveys were conducted at Hubbard Glacier in the spring of 2013. Both were conducted over multi-day periods ranging from 3-7 days. Preliminary results from these surveys have allowed us to quantify short-term horizontal displacement rates and terminus activities at temporal and spatial resolutions previously not possible. Furthermore, these results allow for a comparative analysis of two similar yet different tidewater glacier systems representing altering phases of dynamic activity. Identifying the operational limitations of these sensors in our work is a key guide to the optimal design characteristics for new, improved LiDAR instruments for campaign deployments in glacierized environments.

Finnegan, D. C.; Hamilton, G. S.; Stearns, L. A.; LeWinter, A.; Fowler, A.

2013-12-01

231

Micrometeorological conditions and surface mass and energy fluxes on Lewis glacier, Mt Kenya, in relation to other tropical glaciers  

NASA Astrophysics Data System (ADS)

The Lewis Glacier on Mt Kenya is one of the best-studied tropical glaciers, but full understanding of the interaction of the glacier mass balance and climate forcing has been hampered by a lack of long term meteorological data. Here we present 2.5 yr of meteorological data collected from the glacier surface from October 2009-February 2012, which indicate that mean meteorological conditions in the upper zone of Lewis Glacier are comparable to those experienced in the ablation zones of South American tropical glaciers. In the context of other glaciated mountains of equatorial east Africa, the summit zone of Mt Kenya shows strong diurnal cycles of convective cloud development as opposed to the Rwenzoris where cloud cover persists throughout the diurnal cycle and Kilimanjaro where clear skies prevail. Surface energy fluxes were calculated for the meteorological station site using a physical mass- and energy-balance model driven by hourly measured meteorological data and additional input parameters that were determined by Monte Carlo optimization. Sublimation rate was lower than those reported on other tropical glaciers and melt rate was high throughout the year, with the glacier surface reaching the melting point on an almost daily basis. Surface mass balance is influenced by both solid precipitation and air temperature, with radiation providing the greatest net source of energy to the surface. Cloud cover typically reduces the net radiation balance compared to clear sky conditions, and thus the more frequent formation of convective clouds over the summit of Mt Kenya, and the associated higher rate of snow accumulation are important in limiting the rate of mass loss from the glacier surface. The analyses shown here are the basis for glacier-wide mass and energy balance modeling to determine the climate proxy offered by the glaciers of Mt Kenya.

Nicholson, L.; Prinz, R.; Mölg, T.; Kaser, G.

2012-12-01

232

Rapid retreat and acceleration of Helheim Glacier, east Greenland  

Microsoft Academic Search

A significant amount of the measured coastal thinning of the Greenland ice sheet may be due to recent acceleration of outlet glaciers. Using remote sensing, we measured two major periods of speedup on Helheim Glacier between 2000 and 2005 that increased peak speeds from approximately 8 to 11 km\\/yr. These speedups coincided with rapid retreats of the calving front, totaling

I. M. Howat; I. Joughin; S. Tulaczyk; S. Gogineni

2005-01-01

233

Instruments and Methods Geophysical imaging of alpine rock glaciers  

Microsoft Academic Search

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

Hansruedi MAURER; Christian HAUCK

2007-01-01

234

Crustal and Lithospheric Structural Controls on Thwaites Glacier, West Antarctica  

Microsoft Academic Search

Thwaites Glacier in the Amundsen Sea Embayment of West Antarctica is changing rapidly. Satellite observations show that the glacier is accelerating, its grounding line is retreating, and its floating portion is thinning. These changes are dynamic and could be related to the nature of the sub-ice geology, though the geology is not well- understood. We know from the Ross Sea

T. M. Diehl; D. D. Blankenship; T. A. Jordan; D. A. Young

2007-01-01

235

GLACIER HAZARD ASSESSMENT IN MOUNTAINS USING SATELLITE OPTICAL DATA  

Microsoft Academic Search

Process interactions and chain reactions, the shift of cryospheric hazard zones due to climate change, and the far reach of glacier disasters make it necessary to apply modern remote sensing techniques for the assessment of glacier hazards. In the present contribution we provide an over- view of spaceborne optical methods suitable for glacial hazard assessment and disaster manage- ment. Digital

Andreas Kääb; Christian Huggel; Samuel Guex; Frank Paul; Nadine Salzmann; Kostia Schmutz; Demian Schneider; Yvo Weidmann

2005-01-01

236

Exploring the mobility of cryoconite on High-Arctic glaciers  

Microsoft Academic Search

There has been a growing awareness of the significance of biologically active dust (cryoconite) on the energy balance of, and nutrient cycling at glacier surfaces. Moreover, researchers have estimated the mass of biological material released from glacier ice to downstream environments and ecosystems, including the melt-out of cells from emergent ice in the ablation area. However, the processes, rates and

T. D. Irvine-Fynn; A. J. Hodson; J. W. Bridge; H. Langford; A. Anesio; N. Ohlanders; S. Newton

2010-01-01

237

Rock glaciers in the South Shetland Islands, Western Antarctica  

Microsoft Academic Search

Rock glaciers are found in the peripheral regions of Antarctica particularly in the Antarctic Peninsula region. Study of these features is relevant for the palaeoenvironmental reconstruction of maritime Antarctica because they are indicators of permafrost and periglacial conditions. This paper reports and analyzes the results of an inventory of rock glaciers and protalus lobes in the South Shetland Islands. Nine

Enrique Serrano; Jerónimo López-Mart??nez

2000-01-01

238

Comparison of thermal structure and evolution between neighboring subarctic glaciers  

NASA Astrophysics Data System (ADS)

The distribution of cold and temperate ice within glaciers and ice sheets affects processes relevant to englacial and basal hydrology, sliding, and material rheology. Thermal regimes, in turn, are shaped by glacier and ice sheet dynamics, as well as environmental setting. We investigate the thermal structures of two small (<7 km2) neighboring glaciers in the St. Elias Mountains of southwestern Yukon, Canada, using ice-penetrating radar and borehole temperature measurements. Our data reveal polythermal regimes in both glaciers that are strongly influenced by accumulation zone meltwater entrapment, suggesting a climatic control on thermal structure. Differences in hypsometry and glacier dynamics nevertheless result in observed variations in the distribution of temperate ice between the two sites. Experiments with a thermomechanically coupled flow band model corroborate the strong control of meltwater entrapment on thermal structure and suggest a generally minimal role for strain heating. An exception to this occurs where localized basal sliding produces lateral shearing and thus enhanced heat generation. Time-dependent model simulations suggest that the future thermal evolution of the two glaciers may differ, and therefore simple parameterizations of thermal response based on regional climate may not capture realistic variability between individual glaciers. Despite these differences, both glaciers are ultimately expected to become fully cold prior to disappearing under negative mass balance conditions.

Wilson, Nat J.; Flowers, Gwenn E.; Mingo, Laurent

2013-09-01

239

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

240

Variability in glacier hazards across the Himalayan range  

NASA Astrophysics Data System (ADS)

The dynamic response of Himalayan glaciers to recent (decadal) climatic changes varies across the range, reflecting local precipitation and temperature patterns. Glaciers in the eastern (Nepal) Himalaya are widely in recession, with mass loss dominated by surface lowering rather than terminus retreat. The formation of large glacial lakes, either behind morainic sediments or remnant glacier ice, is an ongoing concern. Topographic and surface velocity data suggest that the largest glacial lakes are situated on stagnant glacier ice, at relatively low-elevation and on glaciers with a large elevation range, reflecting the greater climatic sensitivity of low-elevation termini. In the western (Karakoram) Himalaya, an increasing number of glaciers have been reported to be advancing and thickening. Here, breaching from ice-dammed lakes, formed as glacier tongues advance across trunk valleys, is potentially the most destructive hazard. Surface velocity data reveal ice movement of 'block flow' type that is likely to influence dam formation and breaching, and also reveal local changes in ablation that regulate ice dynamics once a lake has formed. Multi-temporal satellite data show that many of the glaciers historically responsible for ice-dammed lake formation are advancing, and two that are of particular concern, are highlighted.

Quincey, D. J.

2011-12-01

241

Visualizing Glaciers and Sea Ice via Google Earth  

Microsoft Academic Search

The NOAA team at NSIDC manages over 60 distinct cryospheric and related data products. With an emphasis on data rescue and in situ data, these products hold value for both the scientific and non-scientific user communities. The overarching goal of this presentation is to promote products from two components of the cryosphere (glaciers and sea ice). Our Online Glacier Photograph

L. M. Ballagh; F. Fetterer; T. M. Haran; K. Pharris

2006-01-01

242

Sensitivity and Response of Bhutanese Glaciers to Atmospheric Warming  

NASA Technical Reports Server (NTRS)

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%. Citation

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

2013-01-01

243

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

244

Derivation of glacier velocity from SAR data with feature tracking  

NASA Astrophysics Data System (ADS)

Mountain glaciers are especially sensitive to climate variations. Monitoring temperate glacier activity has become more and more necessary for economical and security reasons and as an indicator of the local effects of global climate. Glacier flow velocity plays an important role in climate monitoring and casualty forecasting, however, available velocity data is hitherto not abundant. The most studied variable in ice dynamics in the literature is ice velocity. From remotely sensed images, mainly two types of methods have been used for the estimation of glacier flow velocities: feature tracking and differential interferometric synthetic aperture radar (DInSAR). In this paper velocities of the Keqikaer glacier are acquired from ALOS (Advanced Land Observing Satellite) SAR data with feature tracking. The results show that different window size in correlation calculation of feature tracking leads to different flow field. We developed a new method to determine the best window size, and the method is testified by using SAR data.

Huang, Lei; Li, Zhen

2009-09-01

245

Bathymetric control of tidewater glacier mass loss in northwest Greenland  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

246

Planetary science: are there active glaciers on Mars?  

PubMed

Head et al. interpret spectacular images from the Mars Express high-resolution stereo camera as evidence of geologically recent rock glaciers in Tharsis and of a piedmont ('hourglass') glacier at the base of a 3-km-high massif east of Hellas. They attribute growth of the low-latitude glaciers to snowfall during periods of increased spin-axis obliquity. The age of the hourglass glacier, considered to be inactive and slowly shrinking beneath a debris cover in the absence of modern snowfall, is estimated to be more than 40 Myr. Although we agree that the maximum glacier extent was climatically controlled, we find evidence in the images to support local augmentation of accumulation from snowfall through a mechanism that does not require climate change on Mars. PMID:16340962

Gillespie, Alan R; Montgomery, David R; Mushkin, Amit

2005-12-01

247

Changes of climate, glaciers and runoff in China's monsoonal temperate glacier region during the last several decades  

Microsoft Academic Search

Changes of climate, glaciers and runoff during the last several decades in China's monsoonal temperate glacier region have been studied. Temperature has increased in a fluctuating manner during the last several decades, and temperature rise has accelerated since the 1980s. Net accumulation of Dasuopu ice core has consistently declined, and the precipitation decrease was also obvious from the end of

Li Zongxing; He Yuanqing; Pu Tao; Jia Wenxiong; He Xianzhong; Pang Hongxi; Zhang Ningning; Liu Qiao; Wang Shijing; Zhu Guofeng; Wang Shuxin; Chang Li; Du Jiankuo; Xin Huijuan

2010-01-01

248

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

Microsoft Academic Search

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

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

2011-01-01

249

Geographic Names of Iceland's Glaciers: Historic and Modern  

USGS Publications Warehouse

Climatic changes and resulting glacier fluctuations alter landscapes. In the past, such changes were noted by local residents who often documented them in historic annals; eventually, glacier variations were recorded on maps and scientific reports. In Iceland, 10 glacier place-names are to be found in Icelandic sagas, and one of Iceland's ice caps, Snaefellsjokull, appeared on maps of Iceland published in the 16th century. In the late 17th century, the first description of eight of Iceland's glaciers was written. Therefore, Iceland distinguishes itself in having a more than 300-year history of observations by Icelanders on its glaciers. A long-term collaboration between Oddur Sigurdsson and Richard S. Williams, Jr., led to the authorship of three books on the glaciers of Iceland. Much effort has been devoted to documenting historical glacier research and related nomenclature and to physical descriptions of Icelandic glaciers by Icelanders and other scientists from as far back as the Saga Age to recent (2008) times. The first book, Icelandic Ice Mountains, was published by the Icelandic Literary Society in 2004 in cooperation with the Icelandic Glaciological Society and the International Glaciological Society. Icelandic Ice Mountains was a glacier treatise written by Sveinn Palsson in 1795 and is the first English translation of this important scientific document. Icelandic Ice Mountains includes a Preface, including a summary of the history and facsimiles of page(s) from the original manuscript, a handwritten copy, and an 1815 manuscript (without maps and drawings) by Sveinn Palsson on the same subject which he wrote for Rev. Ebenezer Henderson; an Editor's Introduction; 82 figures, including facsimiles of Sveinn Palsson's original maps and perspective drawings, maps, and photographs to illustrate the text; a comprehensive Index of Geographic Place-Names and Other Names in the treatise; References, and 415 Endnotes. Professional Paper 1746 (this book) is the second of the three books; it is being published in both English and Icelandic editions. This book provides information about all named glaciers in Iceland, historic and modern. Descriptions, with geographic coordinates, and bibliographic citations to all glacier place-names on published maps, books, and scientific articles are included. Maps, oblique aerial photographs, ground photographs, and satellite images document each of the 269 modern named glaciers of Iceland. The third book, Glaciers of Iceland, is Chapter D of the 11-chapter [volume] U.S. Geological Survey Professional Paper 1386-A-K. Chapter D includes a 1:500,000-scale Map of the Glaciers of Iceland; it is a comprehensive historical and modern review and assessment of what is currently known about glaciers in Iceland's eight Regional Glacier Groups from a review of the scientific literature and from analysis of maps and remotely sensed data (ground, airborne, and satellite); topics include geology and geography, climate and climate variability, types of glaciers, history of glacier variation (including the 21 surge-type glaciers), and frequency and magnitude of volcanic and lacustrine jokulhlaups.

Sigurdsson, Oddur; Williams, Richard S., Jr.

2008-01-01

250

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

Microsoft Academic Search

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

R. J. Motyka; C. F. Larsen

2005-01-01

251

Bacterial diversity in the foreland of the Tianshan No. 1 glacier, China  

Microsoft Academic Search

There is compelling evidence that glaciers are retreating in many mountainous areas of the world due to global warming. With this glacier retreat, new habitats are being exposed that are colonized by microorganisms whose diversity and function are less well studied. Here, we characterized bacterial diversity along the chronosequences of the glacier No. 1 foreland that follows glacier retreat. An

Xiukun Wu; Wei Zhang; Guangxiu Liu; Xuan Yang; Ping Hu; Tuo Chen; Gaosen Zhang; Zhongqin Li

2012-01-01

252

Recession and morphogeometrical changes of Dokriani glacier (1962-1995) Garhwal Himalaya, India  

Microsoft Academic Search

Dokriani glacier is one of the well -developed, m edium- sized (7.0 km2) valley glaciers of Gangotri group of glaciers in the Garhwal Himalaya. The glacier was originally mapped in 1962 -63 and was remapped in 1995 by the Survey of India. The snout, surface area and elevation changes were determined by a compari- son of these two topographic maps

D. P. Dobhal; J. T. Gergan; Renoj J. Thayyen

253

The potential of satellite radar interferometry and feature tracking for monitoring flow rates of Himalayan glaciers  

Microsoft Academic Search

The stagnation of Himalayan glaciers will only be exacerbated by a warming climate, increasing hazards associated with glacier lake development. Frontal recession is a poor indicator of negative balance in this region where most glaciers are debris covered, but reduced glacier flow rates provide a valuable warning of stagnation. In-situ measurements of velocity are understandably rare and remote sensing measurements

Adrian Luckman; Duncan Quincey; Suzanne Bevan

2007-01-01

254

Movement of Glaciers, Sea Ice, and Ice Shelves in Canisteo Peninsula, West Antarctica Observed by 4-Pass SAR Interferometry  

NASA Astrophysics Data System (ADS)

We have extracted a surface deformation map of a part of Canisteo Peninsula on Amundsen Sea in West Antarctica by applying 4-pass differential interferometric SAR (DInSAR) technique to two ERS-1/2 tandem pairs, and analyzed changes of glaciers, sea ice, ice shelves, and their interactions. As there is no digital elevation model of Antarctica with details enough for 2-pass DInSAR, we used 4-pass DInSAR method in which one tandem interferogram, obtained on October 20-21, 1995, was used to estimate the topographic phase (topo-pair) to be subtracted from the other tandem interferogram, obtained on March 9-10, 1996 that contains phases by surface deformation (diff-pair). October is spring in Antarctica where ice begins to melt. The motion of glaciers, sea ice, ice shelves, and their kinematic interactions were imprinted in the diff-pair. Sea ice disappeared completely by the acquisition time of topo-pair in March. We observed fast motion of glaciers pushing the adjoining sea ice. Some interferometric phases indicate the up rise of sea ice of which type is thought to be land-fast ice to exert repulsive force against the pushing glacier. There were other glaciers and sea ice that moved to the same direction, suggesting that the sea ice in these regions was land-fast ice weakly harnessed to sea bottom or pack ice not harnessed at all. Sea ice patches showing no interferometric phases were drift ice that was moving fast by wind or tide. Several small circular fringes on ice shelves suggested that islands or seamounts on the bottom of ice shelves deterred the movement of ice shelves, resulting in the rise of ice surface. So far, we could analyze the mechanism of moving glaciers and the reaction of sea ice, classify sea ice type and the interaction of bottom topography underneath ice shelves. More detailed numerical analysis on the dynamic relationships between glaciers, sea ice, and ice shelves remains as an ongoing research.

Han, H.; Lee, H.

2008-12-01

255

Glacier-like forms on Mars  

NASA Astrophysics Data System (ADS)

Over 1300 glacier-like forms (GLFs) are located in Mars' mid-latitudes. These GLFs are visually similar to terrestrial valley glaciers, being predominantly composed of ice-dust mixtures and showing signs of downhill viscous deformation and of an expanded former extent. However, several fundamental aspects of their behaviour are virtually unknown, including temporal and spatial variations in mass balance, ice motion, landscape erosion and deposition, and hydrology. Here, we investigate the physical glaciology of martian GLFs. We use satellite-based images of specific examples and case studies to build on existing knowledge relating to: (i) GLF current and former extent, exemplified via a GLF located in Phlegra Montes; (ii) indicators of GLF motion, focusing on the presence of surface crevasses on several GLFs; (iii) processes of GLF debris transfer, focusing on mapping and interpreting boulder trains on one GLF located in Protonilus Mensae, the analysis of which suggests a minimum GLF flow speed of 7.5 mm a-1, and (iv) GLF hydrology, focusing on possible supraglacial gulley networks on several GLFs. On the basis of this information we summarise the current state of knowledge of the glaciology of martian GLFs and identify future research avenues.

Hubbard, B.; Souness, C.; Brough, S.

2014-06-01

256

Numerical Modeling of Glaciers in Martian Paleoclimates  

NASA Technical Reports Server (NTRS)

Numerous geologic features suggest the presence of ice flow on the surface of mars. These features include lobate debris aprons, concentric crater fill, and lineated valley fill. The lateral extent of these features can range from 100 meters to over 20 km. Previous work has demonstrated that these features could not have formed in current Martian conditions. It has long been speculated that changes in Mars orbital properties, namely its obliquity, eccentricity, and argument of perihelion, can result in dramatic changes to climate. Recent climate model studies have shown that at periods of increased obliquity north polar water ice is mobilized southward and deposited at low ad mid latitudes. Mid latitude accumulation of ice would provide the necessary conditions for rock glaciers to form. A time-marching, finite element glacier model is used to demonstrate the ability of ice and ice-rock mixtures to flow under Martian paleoclimate conditions. Input to this model is constrained by the NASA Ames Mars General Circulation Model (MGCM).

Colaprete, A.; Haberle, R. M.; Montmessin, F.; Scheaffer, J.

2004-01-01

257

Hydrometeorological relationships on Haig Glacier, Alberta, Canada  

NASA Astrophysics Data System (ADS)

We investigate the relationships between meteorological, hydrological and glaciological data collected at Haig Glacier, Alberta, Canada, for the 2002 and 2003 ablation seasons. Correlation, lag cross-correlation and multivariate regression analyses are employed to assess the seasonal evolution of relationships between temperature, temperature residuals, total daily radiation, albedo, accumulation-area ratio (AAR) and total daily discharge (Qi). Early-season melt is temperature-dependent, when AAR remains high and the hydraulic properties of the snowpack limit both diurnal discharge variability and a rapid hydrologic response. As the melt season progresses, a decreasing AAR and ripening of the snowpack induce a glacier-wide decrease in albedo, and a structured radiation discharge response is observed. Radiation-detrended temperature values offer modest improvements over physical temperature values in multivariate regression models estimating daily discharge values. Using a detrended-temperature indexed melt model, we assess the transport efficiency of the glacial hydrologic system through a comparison of total modelled daily melt and observed discharge. Transport efficiency values support the notion of a purge effect during freezing events and at the end of the ablation season, and suggest that it is the evolution of the supraglacial drainage system that controls diurnal discharge variability.

Shea, J. M.; Anslow, F. S.; Marshall, S. J.

258

Glaciers and Ice Sheets Mapping Orbiter concept  

NASA Astrophysics Data System (ADS)

We describe a concept for a spaceborne radar system designed to measure the surface and basal topography of terrestrial ice sheets and to determine the physical properties of the glacier bed. Our primary objective is to develop this new technology for obtaining spaceborne estimates of the thickness of the polar ice sheets with an ultimate goal of providing essential information to modelers estimating the mass balance of the polar ice sheets and estimating the response of ice sheets to changing climate. Our new technology concept employs VHF and P-band interferometric radars using a novel clutter rejection technique for measuring surface and bottom topographies of polar ice sheets from aircraft and spacecraft. Our approach will enable us to reduce signal contamination from surface clutter, measure the topography of the glacier bed at better than 1 km intervals with an accuracy of 20 m, and paint a picture of variations in bed characteristics. The technology will also have applications for planetary exploration including studies of the Martian ice caps and the icy moons of the outer solar system. Through the concept developed here we believe that we can image the base and map the three-dimensional basal topography beneath an ice sheet at up to 5 km depth.

Jezek, Kenneth; Rodríguez, Ernesto; Gogineni, Prasad; Freeman, Anthony; Curlander, John; Wu, Xiaoqing; Paden, John; Allen, Chris

2006-05-01

259

Instrument for Analysis of Greenland's Glacier Mills  

NASA Technical Reports Server (NTRS)

A new instrument is used to study the inner workings of Greenland s glacier mills by riding the currents inside a glacier s moulin. The West Greenland Moulin Explorer instrument was deployed into a tubular shaft to autonomously record temperature, pressure, 3D acceleration, and location. It is built with a slightly positive buoyancy in order to assist in recovery. The unit is made up of several components. A 3-axis MEMS (microelectromechanical systems) accelerometer with 0.001-g resolution forms the base of the unit. A pressure transducer is added that is capable of withstanding 500 psi (=3.4 MPa), and surviving down to -40 C. An Iridium modem sends out data every 10 minutes. The location is traced by a GPS (Global Positioning System) unit. This GPS unit is also used for recovery after the mission. Power is provided by a high-capacity lithium thionyl chloride D-sized battery. The accelerometer is housed inside a cylindrical, foot-long (=30 cm) polyvinyl chloride (PVC) shell sealed at each end with acrylic. The pressure transducer is attached to one of these lids and a MEMS accelerometer to the other, recording 100 samples per second per axis.

Behar, Alberto E.; Matthews, Jaret B.; Tran, Hung B.; Steffen, Konrad; McGrath, Dan; Phillips, Thomas; Elliot, Andrew; OHern, Sean; Lutz, Colin; Martin, Sujita; Wang, Henry

2010-01-01

260

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

261

Biodiversity under threat in glacier-fed river systems  

NASA Astrophysics Data System (ADS)

Freshwater biodiversity is under threat across the globe, with climate change being a significant contributor. One impact of climate change is the rapid shrinking of glaciers, resulting in a reduction in glacial meltwater contribution to river flow in many glacierized catchments. These changes potentially affect the biodiversity of specialized glacier-fed river communities. Perhaps surprisingly then, although freshwater biodiversity is a major conservation priority, the effects of shrinkage and disappearance of glaciers on river biodiversity have hitherto been poorly quantified. Here we focus on macroinvertebrates (mainly insect larvae) and demonstrate that local (?) and regional (?) diversity, as well as turnover among reaches (?-diversity), will be consistently reduced by the shrinkage of glaciers. We show that 11-38% of the regional species pools, including endemics, can be expected to be lost following complete disappearance of glaciers in a catchment, and steady shrinkage is likely to reduce taxon turnover in proglacial river systems and local richness at downstream reaches where glacial cover in the catchment is less than 5-30%. Our analysis demonstrates not only the vulnerability of local biodiversity hotspots but also that extinction will probably greatly exceed the few known endemic species in glacier-fed rivers.

Jacobsen, Dean; Milner, Alexander M.; Brown, Lee E.; Dangles, Olivier

2012-05-01

262

MODIS albedo products used to detect ELA on Svalbard glaciers  

NASA Astrophysics Data System (ADS)

MODIS L3 albedo products (MCD43A3) for the period 2000-2011 are used to derive a proxy for the equilibrium line altitude (ELA) using a simple threshold method to determine the location of the annual snow line on the glacier. This albedo-derived ELA proxy is then compared to ELA determined from glacier mass balance measurements made on selected glaciers in Svalbard, which range in size from 5-500 km2. There is a good 1:1 correlation between the proxy and observed ELA on the larger study glaciers, which are covered by many MODIS pixels, with no need for calibration of the relation. Detecting the snow line on the smaller glaciers, which are covered by only a small number of MODIS pixels, does not work as well. There is the expected negative relation between minimum albedo and ELA, but the relation must be calibrated for individual glaciers. Nevertheless, the distribution of icefields and large glaciers in Svalbard allows the threshold method to be used to determine the spatial distribution of ELA around the archipelago.

Kohler, J.; Nuth, C.; König, M.; Hagen, J. O.

2012-12-01

263

Changes in ice front position on Greenland's outlet glaciers from 1992 to 2007  

Microsoft Academic Search

Previous studies in Greenland show that retreat of tidewater glaciers may be linked to recent increases in ice loss, raising Greenland's contribution to sea level rise. We examined ice front changes of 203 tidewater glaciers, land-terminating glaciers, and glaciers terminating with ice shelves to understand Greenland glacier behavior over three periods: 1992–2000, 2000–2006, and 2006–2007. We observed synchronous, ice sheet–wide

Twila Moon; Ian Joughin

2008-01-01

264

A GIS and Remote Sensing Based Approach to Monitoring the Bering Glacier System  

Microsoft Academic Search

The Bering Glacier is the largest and longest glacier in continental North America, with an area of approximately 5,175 km2, and a length of 190 km. It is also the largest surging glacier in America, having surged at least five times during the twentieth century. The last surge of the Bering Glacier occurred in 1993-1995, since then, the glacier has

Sean Savage; Robert Shuchman; Edward G. Josberger; John Payne; Chris Noyles; Scott Guyer; Guy Meadows

265

Numerical modeling of a remote Himalayan glacier constrained by satellite data  

Microsoft Academic Search

Himalayan glaciers are amongst the least studied and understood glaciers on Earth, yet their future behavior and water budget is crucial for densely-populated areas in south, central, and eastern Asia. Here, we use remotely-sensed glacier-surface velocities from a glacier in the upper Tons valley of western Uttaranchal in the Indian Himalaya, to evaluate the results from a numerical glacier model.

Dirk Scherler; Daniel Farinotti; Robert S. Anderson; Manfred R. Strecker

2010-01-01

266

Spatial Variability Within Subglacial Sediment Behaviour at an Icelandic Glacier.  

NASA Astrophysics Data System (ADS)

During August 2000 fieldwork was carried out at Vestari-Hagafellsjokull in Iceland to study the subglacial processes occurring and their spatial variability. Vestari-Hagafellsjokull is one of two surge type outlet glaciers on the southern side of the Langjokull ice cap. The two outlet glaciers surged in the 1980's, with the neighbouring glacier surging again in 1999, which suggests that Vestari-Hagafellsjokull may surge in the near future. The glacier rests on a combination of eroded sediments and lava bedrock. The proglacial area has a variable till cover ranging from exposed striated bedrock, through till drapes a few centimetres thick to large scale druminloid features composed of till with a bedrock core. The glacier is drained subglacially by a series of discrete drainage channels feeding a few portals along the glacier margin. Hot water drilling was undertaken at a site approximately 700m from the glacier margin through ice about 60m thick. Four ploughmeters and three tiltmeters, alongside two types of dragspool were successfully inserted and monitored over a six-month period over an area of the glacier approximately 100m by 100m. Results from the tiltmeter instrumentation indicate the presence of a thin (less than 10cm) deforming layer within the subglacial sediment, as only the upper tiltcells in each pair recorded significant tilt variations over the period of the study. High spatial variations in terms of sediment strength, deformation rates and diurnal variability were also observed providing a detailed snapshot of the sediment characteristics beneath the glacier during non-surge conditions.

Eyre, N. S.; Payne, T.; Baldwin, D.

2001-12-01

267

Ocean-Glacier Interactions in Alaska and Comparison to Greenland  

NASA Astrophysics Data System (ADS)

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

Motyka, R. J.; Truffer, M.

2011-12-01

268

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

269

Small Glacier Area Studies: A New Approach for Turkey  

NASA Technical Reports Server (NTRS)

Many regions of Earth have glaciers that have been neglected for study because they are small. We report on a new approach to overcome the problem of studying small glaciers, using Turkey as an example. Prior to our study, no reliable estimates of Turkish glaciers existed because of a lack of systematic mapping, difficulty in using Landsat data collected before 1982, snowpack vs. glacier ice differentiation using existing satellite data and aerial photography, the previous high cost of Landsat images, and a lack of high-resolution imagery of small Turkish glaciers. Since 2008, a large number of < 1 m satellite images have become available at no cost to the research community. In addition, Landsat data are now free of charge from the U.S. Geological Survey, enabling the use of multiple images. We used 174 Landsat and eight high-resolution satellite images to document the areal extent of Turkish glaciers from the 1970s to 2007-2011. Multiple Landsat images, primarily Thematic Mapper (TM) data from 1984 to 2011, enabled us to minimize differentiation problems between snow and glacier ice, a potential source of error. In addition, we used Ikonos, Quickbird, and World View-1 & -2 very high-resolution imagery to evaluate our TM accuracies and determine the area of nine smaller glaciers in Turkey. We also used five Landsat-3 Return Beam Videcon (RBV) 30 m pixel resolution images, all from 1980, for six glaciers. The total area of Turkish glaciers decreased from 23 km2 in the 1970s to 10.1 km2 in 2007-2011. By 2007-2011, six Turkish glaciers disappeared, four were < 0.3 km2, and only three were 1.0 km2 or larger. No trends in precipitation from 1970 to 2006 and cloud cover from 1980 to 2010 were found, while surface temperatures increased, with summer minimum temperatures showing the greatest increase. We conclude that increased surface temperatures during the summer were responsible for the 56% recession of Turkish glaciers from the 1970s to 2006-2011.

Yavasli, Dogukan D.; Tucker, Compton J.

2012-01-01

270

Summer energy balance and ablation of high elevation glaciers in the central Chilean Andes  

NASA Astrophysics Data System (ADS)

Glaciers of the semi-arid central Chilean Andes are an important freshwater source for the populous Central Valley region of Chile, but have been shrinking in recent decades. The surface energy balance of these glaciers is of high scientific interest as summer ablation occurs through both sublimation and melt. During the 2012-13 Austral Summer a glacio-meteorological monitoring programme was established on Olivares Alfa (3.9 km2, 4130-4800 m elevation) and Beta (8.3 km2, 3620-4850 m elevation) Glaciers and their forelands in the Upper Olivares Valley, 33°00'-33°11' S, 70°05'-70°15' W, approximately 50 km north-east of Santiago. This included complete automatic weather stations (AWSs) with sonic rangers to record surface ablation on the ablation zones of the two glaciers, and one AWS in the proglacial area of Olivares Alfa Glacier including precipitation gauge. To complement these point data, daily images of the glaciers were captured with fixed cameras in order to calculate snow cover and albedo distributions. To calculate the surface energy balance and rates of melt and sublimation, a model was developed which uses direct AWS measurements of the radiative fluxes and calculates the turbulent fluxes of sensible and latent heat using the bulk aerodynamic approach. The model also calculates the subsurface heat flux and includes a simple scheme to estimate refreezing of melt water within surface snow or ice. Meteorological data and model results for the December to May period will be presented in this paper. Model calculations match closely the cumulative ablation curve of the sonic ranger at Olivares Alfa, with a slight overestimation, and overestimate cumulative ablation recorded by the sonic ranger at Olivares Beta, possibly due, at least in part, to uncertain snow density values. Modelled cumulative ablation in the December-April period is 2.2 m water equivalent (w.e.) at Olivares Alfa (0.10 m sublimation, 2.10 m melt) and 2.34 m w.e. at Olivares Beta (0.18 m sublimation, 2.16 m melt). The surface energy balance is dominated by shortwave radiation, which is the only net energy input, apart from a minor contribution from sensible heat, while the main outputs of energy are net longwave radiation, melt and sublimation. Ablation is dominated by melt during the warmer midsummer months at the two AWS sites, with mean rates exceeding 30 mm w.e. per day. However, due to the high latent heat of sublimation, it is only in January and February that the melt energy flux clearly exceeds the sublimation energy flux. Sublimation rates are typically ~1 mm w.e. per day and are 50 to 100 % higher at Olivares Beta as a result of higher wind speed and surface temperature, despite similar air temperatures at the two sites. Melt rates are around twice as high in summer months with mean air temperature > -2° C, compared with cooler months. This implies that future atmospheric warming will accelerate shrinkage of these glaciers as the ablation regime switches increasingly from sublimation to a more efficient melt regime.

Brock, Benjamin; Rivera, Andres; Burger, Flavia; Bravo, Claudio

2014-05-01

271

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

272

Response of major Greenland outlet glaciers to oceanic and atmospheric forcing: Results from numerical modeling on Petermann, Jakobshavn and Helheim Glacier.  

NASA Astrophysics Data System (ADS)

Oceanic forcing has been suggested as a major trigger for dynamic changes of Greenland outlet glaciers. Significant melting near their calving front or beneath the floating tongue and reduced support from sea ice or ice melange in front of their calving front can result in retreat of the terminus or the grounding line, and an increase in calving activities. Depending on the geometry and basal topography of the glacier, these oceanic forcing can affect the glacier dynamic differently. Here, we carry out a comparison study between three major outlet glaciers in Greenland and investigate the impact of a warmer ocean on glacier dynamics and ice discharge. We present results from a numerical ice-flow model applied to Petermann Glacier in the north, Jakobshavn Glacier in the west, and Helheim Glacier in the southeast of Greenland.

Nick, F. M.; Vieli, A.; Pattyn, F.; Van de Wal, R.

2011-12-01

273

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

274

Effects of light absorbing impurities on the glacier albedo in the Tibetan Plateau: a case study of Zhadang glacier  

NASA Astrophysics Data System (ADS)

Light absorbing aerosols, such as black carbon (BC, or element carbon) and mineral dust, can deposit and accumulate on glacier surface through dry and wet deposition, hence reducing the surface albedo and resulting in more solar radiation absorption, thus accelerates the melting of glaciers. Glaciers in the Tibetan Plateau (TP) can be affected by BC and dust from the surrounding areas. To investigate effects of BC and dust on the glacier albedo, we collected surface firn/ice samples in July and fresh snow samples in August, 2012, and measured albedo in Zhadang glacier (southern Tibetan Plateau). Concentrations of BC (DRI method) (80.9 - 472.6 ppbm) and dust (33.6 - 1891.9 ppmm) are much higher in firn/ice than these of BC (40.8 - 59.4 ppbm) and dust (3.4 - 8.2 ppmm) in fresh snow, indicating that BC and dust can accumulate when snow starts melt. Both BC and dust concentrations in snow reduced while albedo increased when elevation increased. Snow ice aerosol radiative (SNICAR) model were used to quantify the contribution rate of BC and dust to the snow albedo reduction. BC and dust in fresh snow contributed 47.7% and 13.6% for the reduction of glacier albedo, respectively, meanwhile other factors (snow particle size, moisture content changes) contributed 38.7%, suggesting BC was a major factor for snow melting in Zhadang glacier. However, the contribution of dust to albedo reduction could be as high as 71% when the glacier experienced strong melting when the surface coverage was almost entirely dirty bare ice. The radiative forcing (RF) caused by dust could reach 33.9 Wm-2, while that caused by BC was only 4.5 Wm-2, indicating that dust, rather than BC, was the most dominant factor on the melting of glacier during the intensive melting season.

Kang, Shichang; Qu, Bin; Ming, Jing

2014-05-01

275

Bathymetry of Patagonia glacier fjords and glacier ice thickness from high-resolution airborne gravity combined with other data  

NASA Astrophysics Data System (ADS)

The North and South Patagonia Ice fields are the largest ice masses outside Antarctica in the Southern Hemisphere. During the period 1995-2000, these glaciers lost ice at a rate equivalent to a sea level rise of 0.105 ± 0.001 mm/yr. In more recent years, the glaciers have been thinning more quickly than can be explained by warmer air temperatures and decreased precipitation. A possible cause is an increase in flow speed due to enhanced ablation of the submerged glacier fronts. To understand the dynamics of these glaciers and how they change with time, it is critical to have a detailed view of their ice thickness, the depth of the glacier bed below sea or lake level, how far inland these glaciers remain below sea or lake level, and whether bumps or hollows in the bed may slow down or accelerate their retreat. A grid of free-air gravity data over the Patagonia Glaciers was collected in May 2012 and October 2012, funded by the Gordon and Betty Moore Foundation (GBMF) to measure ice thickness and sea floor bathymetry. This survey combines the Sander Geophysics Limited (SGL) AIRGrav system, SGL laser altimetry and Chilean CECS/UCI ANDREA-2 radar. To obtain high-resolution and high-precision gravity data, the helicopter operates at 50 knots (25.7 m/s) with a grid spacing of 400m and collects gravity data at sub mGal level (1 Gal =1 Galileo = 1 cm/s2) near glacier fronts. We use data from the May 2012 survey to derive preliminarily high-resolution, high-precision thickness estimates and bathymetry maps of Jorge Montt Glacier and San Rafael Glacier. Boat bathymetry data is used to optimize the inversion of gravity over water and radar-derived thickness over glacier ice. The bathymetry maps will provide a breakthrough in our knowledge of the ice fields and enable a new era of glacier modeling and understanding that is not possible at present because ice thickness is not known.

An, L.; Rignot, E.; Rivera, A.; Bunetta, M.

2012-12-01

276

Irreversible mass loss from Canadian Arctic glaciers  

NASA Astrophysics Data System (ADS)

The Canadian Arctic Archipelago (CAA) contains the largest volume of glacier ice outside Greenland and Antarctica, equivalent to 0.22±0.03 m eustatic sea level. In the absence of significant solid ice discharge (D~5 Gt yr-1), CAA mass balance is largely dominated by surface mass balance (SMB), the difference between snow accumulation and meltwater runoff. Results from the Gravity Recovery and Climate Experiment (GRACE) satellites show that, following a recent atmospheric warming (1-2 K), CAA mass loss increased from 31±8 Gt yr-1 in 2004-2006 to 92±12 Gt yr-1 in the period 2007-2009. As yet, it has been unclear if this sharp increase in mass loss can be attributed to natural variability on decadal time scales, or that it marks the onset of a long-term warming and consequent CAA mass loss. In this study we use a high-resolution regional atmospheric climate model (RACMO2), coupled with a sophisticated snow/firn/ice column physics model, driven by ERA-reanalyses (1960-2011) to assess past and present-day CAA mass balance. Since we neglect D in the mass balance, mass anomalies can be attributed to SMB only, which enables direct comparison between RACMO2 and GRACE (RL04). In the period 2004-2011, CAA lost ice at a rate of 64±10 Gt yr-1 according to RACMO2, which agrees with GRACE (72±6 Gt yr-1). The longer temporal coverage of the RACMO2 results enables us to put the recent mass loss in a longer-term perspective. RACMO2 suggests that NCAA was in approximate mass balance before the year 2000, whereas the Southern CAA (SCAA) also lost mass in 1960-2000 at a rate of 15±11 Gt yr-1, a finding that agrees with recent estimates from altimetry and stereographic imaginery (-11±4 Gt yr-1 in 1963-2006). To assess CAA mass loss for the remainder of the 21st century, RACMO2 was forced at the lateral boundaries by HadGEM2-ES, a fully coupled CMIP5 general circulation model (GCM). This GCM in turn was forced with the modest warming scenario RCP45, resulting in a 21st century warming that is similar to the average of all AR5 scenarios. Mean CAA glacier SMB decreases to -144±33 Gt yr-1, and mass loss is then larger in NCAA (82±31 Gt yr-1) than in SCAA (62±10 Gt yr-1). Mass loss is dominated by meltwater runoff, only partially (~30%) compensated by increasing precipitation. We apply the significant correlation between CAA SMB and CAA T2m to all AR5 multi-model realizations (~6500 single years) and found out this estimate is relatively conservative. More importantly, CAA glacier growth (SMB>0) is predicted in only 0.15% of the ensemble members, rendering it highly unlikely that current CAA glacier mass loss will be reversed. Based on the full AR5 ensemble, we estimate the total CAA mass loss at 12400±8500 Gt yr-1 until 2100, equivalent to 0.35±0.24 mm yr-1. This makes CAA the largest cryospheric contributor to 21st century sea level rise outside Greenland and Antarctica.

Lenaerts, J.; van Angelen, J.; van den Broeke, M. R.; Gardner, A. S.; Wouters, B.; van Meijgaard, E.

2012-12-01

277

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

278

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

279

Holocene glacier fluctuations in the American Cordillera  

NASA Astrophysics Data System (ADS)

In many areas of the American Rocky Mountains (Colorado, Wyoming, Utah, Idaho, Montana), Cascade Range (Washington, Oregon), and the Sierra Nevada (California), radiocarbon ages suggest that ice receded to near present limits before 10 ka BP. A pre-Altithermal readvance or stillstand left moraines ca. 1-3 km beyond and ca. 50-300 m below present glacier margins. At one locality on Glacier Peak in Washington, these deposits are perhaps dated to the early Holocene, but in general these deposits are probably at least 10 ka old. Glacial advances during the Altithermal (ca. 8 to 5 ka BP) elsewhere are rare; radiocarbon evidence for Altithermal glacial advances in the Colorado Front Range is questionable. The earliest radiocarbon-dated Neoglacial advances occurred about 5 ka BP in the Washington Cascades; moraines and related deposits believed to be of early Neoglacial age (i.e. 5 to 3 ka BP) elsewhere are poorly dated. For example, moraines believed to date to the early Neoglacial in Colorado (Triple Lakes) and Wyoming (Temple Lake) are actually late Pleistocene age, based on radiocarbon ages derived from lake sediments at the type localities. Although relative-age data (i.e. lichens, rock weathering, soils) from many areas suggest a three-fold Neoglacial sequence, little supporting radiocarbon evidence is available. However, tephrochronology distinguishes three Neoglacial advances near Mount Rainier in Washington. In most mountain ranges of the western United States, fresh, unweathered, sharp-crested moraines usually adjacent to present ice margins, or near headwalls in empty cirques, date to the Little Ice Age of the last several centuries. However, detailed photographic or other historical records of glacial fluctuations during the last century are rare, and detailed mass balance studies rarer still. Whether or not pre-Little Ice Age glacial fluctuations in the American Cordillera are synchronous must await better radiometric dating of local moraine sequences.

Davis, P. Thompson

280

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

281

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.

282

Suspended-Sediment Transport Relationships for Four Alaskan Glacier Streams.  

National Technical Information Service (NTIS)

Estimates of suspended-sediment transport for four Alaskan glacier streams were made for the 1973 summer melt season. Two types of field data are requisite for establishing linear models relating discharge and suspended sediment concentration: (1) Suspend...

B. L. Gaddis

1974-01-01

283

The Use of Surface Energy Balance Models As a Means to Quantify Changes in Glacier Mass Balance: Application to the Collier Glacier, OR  

NASA Astrophysics Data System (ADS)

Changes in glacier size and volume reflect an integrated response to fluctuations in precipitation and surface energy balance resulting from climate change and variability. Alpine glaciers are particularly sensitive to such changes in climate, with response times measured from centennial to decadal time scales. Our understanding of the response of alpine glaciers to climate change and their contribution to 21st century sea level rise is incomplete because mass balance measurements are limited to a handful of glaciers worldwide. Energy- and mass-balance glacier models provide an opportunity to model past and future response of glaciers to climate change and to simulate mass balance on remote glaciers. Here we present ongoing mass balance measurements being conducted for the past two years on the Collier Glacier, OR, a small (0.70 km2), alpine glacier located in the Oregon Cascades (44° 10’ N, 121° 47’ W). The Collier glacier has a unique photo record of retreat throughout the 20th Century thus making it one of the best-recorded glaciers in the Oregon Cascades. As part of the study, we have installed and maintained automated weather stations and snow-depth monitors to collect data needed to apply and validate the OSU surface energy balance model. Preliminary results indicate that the model is capable of capturing the seasonal pattern of mass balance on the glacier.

Beedlow, A. C.; Clark, P. U.; Hostetler, S. W.

2010-12-01

284

Satellite Observations of Surface Flow Variations at Southeast Alaskan Glaciers  

NASA Astrophysics Data System (ADS)

Glaciers in southeast Alaska are undergoing rapid changes that affect global sea level rise, lake formation and water levels, and flood risks. A key to understanding the ice dynamics is knowledge of the surface ice velocities and how they vary through time. Here we present updated maps of surface velocities for several glaciers in southeast Alaska produced through a pixel tracking technique using synthetic aperature radar data (ALOS, TerraSAR-X) and high-resolution optical imagery (WorldView, QuickBird, IKONOS, GeoEye). We focus on several glaciers that have enough data to form multi-year timeseries, including Hubbard, Yakutat, and LeConte. Hubbard Glacier is the largest non-polar tidewater glacier in the world and is currently in the advance phase of the tidewater glacier cycle. The glacier shows strong seasonal variations of more than 5 m/day along the terminal lobe, with the highest speeds occurring between late December and early February and the lowest speeds occurring in late summer/early fall. The region directly above the terminal lobe displays a smaller seasonal variation in speed. Near the terminus of the glacier, an increase in speed from ~8 m/day to more than 11 m/day is observed between Winter 2008 and Winter 2010. The Valerie Glacier, which is separated from the terminal lobe of the Hubbard by a medial moraine, displays a decrease in speed from ~8 m/day to ~4 m/day between March 2009 and March 2011. LeConte Glacier, which is located in the southern Stikine Icefield, appears to have retreated to a stable position. In contrast to Hubbard, the observed speeds along the lower part of LeConte do not vary significantly between years. Peak speeds at the terminus reach ~22 m/day in both 2008 and 2012. The lake-terminating Yakutat Glacier is in a state of collapse, with rapid retreat creating two separate termini in late summer 2011. Our dataset allows us to document the surface velocity variations that occurred during this time and the subsequent years as the retreat has continued.

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

2013-12-01

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

Field observations of subglacial processes beneath an Antarctic polythermal glacier  

Microsoft Academic Search

This paper reports observations and measurements of ice structure and deformation made in two tunnels excavated into the margin of Taylor Glacier. The excavations reveal a complex, rapidly deforming 4.5 m-thick basal ice sequence. Measurements conducted over a year demonstrate that about 55% of glacier surface velocity can be attributed to deformation within the debris-rich basal ice. Strain measurements show

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

2009-01-01

287

Reconstructing 50 years of glacier mass changes in Central Asia  

NASA Astrophysics Data System (ADS)

Recent studies assessing the glacier mass balance at the regional to global scale, have tried to consider different data sources in order to increase the robustness of the results. The combined use of data from satellite gravimetry, satellite altimetry, as well as from in-situ and geodetic mass balance measurements is increasingly found in the literature. Constrained by the need of simultaneous data availability from the various sources, however, such studies have typically focused on rather short time frames. For Central Asia, and the Tien Shan mountain range in particular, analyses have mostly been addressing the time period 2003-2009, concluding that the total mass change rate of the glaciers in the region has to be approximately -7 Gt water equivalent (w.e.) per year. In this contribution, we use an ensemble approach based on data from (a) the Gravity Recovery and Climate Experiment (GRACE), (b) the Ice, Cloud and land Elevation Satellite (ICESat) mission, and (c) in-situ glacier mass balance measurements, for validating a glacier mass balance model that we use for reconstructing a continuous time series for the glacier mass-change of the Tien Shan mountain range during the period 1961-2012. Our model ensemble takes into account a series of different possibilities for process description, inter- and extrapolation methods, as well as meteorological drivers. Our results confirm previous estimates derived for the period 2003-2009, and highlight an accelerating trend in glacier mass loss. For 1961-2012, we estimate an average glacier mass-change rate of -6.1±5.4 Gt w.e. a-1, whilst the average mass-change rate for the decade 2003-2012 is estimated with -7.5±5.5 Gt w.e. a-1. This further increases the concern about the future of a region that significantly depends on glacier melt for water supply.

Farinotti, Daniel; Güntner, Andreas; Longuevergne, Laurent; Moholdt, Geir; Steffen, Holger; Düthmann, Doris; Gafurov, Abror

2014-05-01

288

Radiometric age of the snout ice of Nehnar glacier  

Microsoft Academic Search

The surface ice taken from the snout of the Nehnar glacier (Kashmir) in western Himalaya has been dated using radioisotopes32Si and210Pb to be 500 years. Based on the age distribution of ice and the expected activity of32Si in the fallout, the average rate of glacier movement over a period of the last few centuries is estimated to be about 6

N. Bhandari; D. I. Bhatt; V N Nijampurkar; R K Singh; D. Srivatsava; C P Vohra

1981-01-01

289

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

290

Mass balance investigation of alpine glaciers through LANDSAT TM data  

NASA Technical Reports Server (NTRS)

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

Bayr, Klaus J.

1989-01-01

291

Rapdily recurring Jøkulhlaups from Koppangsbreen glacier, Northern Norway  

NASA Astrophysics Data System (ADS)

A jøkulhlaup (Glacier Lake Outburst Flood) from a glacier-dammed lake at the glacier Koppangsbreen in northern Norway occurred on 4th June 2013. Approximately two million cubic metres of water were released from the lake over eleven hours, and reached the village of Koppangen down-valley only minutes later. This was followed by another six events over the next thirty days, at intervals of three to ten days. Previous events had occurred from this glacier in the three preceding years, but only one event in each of 2010 and 2011, and two small events in 2012. Thus, the short intervals between each flood in 2013 were unprecedented. Some of the events were connected to rainfall but not all of them, thus this wasn't the only trigger. The almost periodic nature of the events also argues against tunnel collapse and re-opening initiating a new event. However, by considering the input to the lake from a combination of precipitation, snow melt and, as the season progressed, glacier melt, it is shown that in just a few days the lake level increases enough for the water to escape under the glacier.

Jackson, Miriam

2014-05-01

292

A one-dimensional snow-firn layer model for glaciers subjected to seasonal melting  

NASA Astrophysics Data System (ADS)

Geochemical analysis of the ice cores provides valuable information about past climate change. The correct interpretation of such data demands knowledge of an annual layer structure formation process. A one-dimensional model for the glacier snow-firn layer subjected to melting is presented here. The melting occurs due to the warm summer temperatures and intensive sun radiation. As a result the melt water penetrates into the deeper layers and re-freezes there. Moreover, snow is subjected to the creep resulting in its compaction. The model allows for investigating the snow layer composition and density changes at various scenarios of climate change. Our model takes into account the snow-atmosphere interaction (the snow surface temperature is defined from the surface heat budget and depends on the atmosphere parameters such as a wind speed, specific humidity, atmosphere pressure and temperature); albedo feedback (the melted water decreases the snow albedo and intensifies melting). The model was applied to the Grigoriev Ice Cap (41.979^o N; 77.916^o E; 4625 m), where two long snow-ice cores were extracted during summer of 1990 and 2001 years. The comparison of the calculated and measured annual layers structures allowed for formulating the effective heat source parameters connected with latent heat releasing due to water freezing. These parameters are needed for reconstruction of the past climate and prediction of the glacier evolution.

Nagornov, O.; Sergienko, O.

2003-04-01

293

Glacier changes in the Karakoram region mapped by multimission satellite imagery  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

294

Reconstructing glacier retreat since the Little Ice Age in SE Tibet by glacier mapping and equilibrium line altitude calculation  

NASA Astrophysics Data System (ADS)

Temperate glaciers in the eastern Nyainqêntanglha Range, southeastern Tibet, are highly sensitive to climate change and therefore of particular high interest for research on late Holocene changes of the monsoonal climate in High Asia. However, because of the remoteness of the area, the scarcity of empirical data, and the challenges to remote sensing work posed by cloud and snow cover, knowledge about the glacier dynamics and changes in this region is still very limited. In this study, we applied a remote sensing approach in which 1964 glaciers were mapped from a Landsat ETM+ scene and subsequently parameterized by DEM-supported measurements. Geomorphological evidence, i.e., trimlines and latero-frontal moraines, were used to obtain quantitative data on the glaciers' morphological characteristics and the changes since the Little Ice Age (LIA) maximum glacier advance. Statistical analysis of glacier length change revealed an average retreat of ~ 27% and a trend toward stronger retreat for smaller glaciers. An evaluation of different methods to calculate equilibrium line altitudes (ELAs) indicates that an optimized toe-to-ridge altitude method (TRAM) is more suitable than other methods in settings with complex topography and a lack of mass balance measurements. A large number of glacier measurements are crucial for high quality of TRAM results, and special attention has to be paid to different glacier characteristics. In order to determine the best-fitting TRAM ratio value and to test the quality of the calculated ELAs, a remote sensing approach was applied: for each investigated glacier, the altitudes of transient snowlines visible in the late summer Landsat scene were measured from the DEM and compared to TRAM results. The interpolated ELA results show a SE–NW gradient ranging from 4400 to 5600 m asl and an average ELA rise of ~ 136 m since the LIA. Because of the high spatial resolution of measurements, the ELA distribution reveals topographic effects down to the catchment scale, specifically orographic rainfall and leeward shielding. The interpretation of these patterns reveals that the eastern Nyainqêntanglha Range is influenced by both, the Indian (ISM) and East Asian summer monsoon (EASM). However, the EASM does not reach the western part of the study area. The results indicate that the monsoonal temperate glaciers' high sensitivity to climate change is driven by two double forcings owing to the coincidence of accumulation and ablation phases.

Loibl, David; Lehmkuhl, Frank; Grießinger, Jussi

2014-06-01

295

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

NASA Astrophysics Data System (ADS)

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

Takeuchi, Nozomu

2013-09-01

296

Sediment connectivity evolution on an alpine catchment undergoing glacier retreat  

NASA Astrophysics Data System (ADS)

Climate changes can result in a wide range of variations of natural environment including retreating glaciers. Melting from glaciers will have a significant impact on the sediment transport characteristics of glacierized alpine catchments that can affect downstream channel network. Sediment connectivity assessment, i.e. the degree of connections that controls sediment fluxes between different segments of a landscape, can be useful in order to address management activity on sediment fluxes changes of alpine streams. Through the spatial characterization of the connectivity patterns of a catchment and its potential evolution it is possible to both define sediment transport pathways and estimate different contributions of the sub-catchment as sediment sources. In this study, a topography based index (Cavalli et al., 2013) has been applied to assess spatial sediment connectivity in the Navisence catchment (35 km2), an alpine basin located in the southern Walliser Alps (Switzerland) characterized by a complex glacier system with well-developed lateral moraines on glacier margins already crossed by several lateral channels. Glacier retreat of the main glacial edifice will provide a new connectivity pattern. At present the glacier disconnects lateral slopes from the main talweg: it is expected that its retreat will experience an increased connectivity. In order to study this evolution, two high resolution (2 m) digital terrain models (DTMs) describing respectively the terrain before and after glacier retreat have been analyzed. The current DTM was obtained from high resolution photogrammetry (2 m resolution). The future DTM was derived from application of the sloping local base level (SLBL) routine (Jaboyedoff et al., 2004) on the current glacier system, allowing to remove the ice body by reconstituting a U-shaped polynomial bedrock surface. From this new surface a coherent river network was drawn and slight random noise was added. Finally the river network was burned into the rough surface of the SLBL results. The impact of sediment dynamic changes on the study catchment due to glacier retreat has been assessed by comparing predictions deriving from model application on different scenarios. Simulations allowed the analysis of sediment connectivity evolution over decade scales suggesting an increase of potential sediment transfer and connections in areas close to the main channel network. References: Cavalli, M., Trevisani, S., Comiti, F., Marchi, L., 2013. Geomorphometric assessment of spatial sediment connectivity in small Alpine catchments. Geomorphology 188, 31-41. Jaboyedoff M., Bardou E., Derron M.-H. 2004. Sloping local base level: a tool to estimate potential erodible volume and infilling alluvial sediment of glacial valleys. Swiss Geo-Scientists meeting, November 2004, Lausanne.

Goldin, Beatrice; Rudaz, Benjamin; Bardou, Eric

2014-05-01

297

Characteristics of the turbulent flow in the boundary layer of a Tropical Glacier  

NASA Astrophysics Data System (ADS)

An extensive micro-meteorological experiment has been deployed within the atmospheric boundary layer over the ablation zone of the tropical Zongo glacier, Bolivia, during the dry season from July to August, 2007. It included two complete eddy correlation systems (Campbell CSAT and LICOR7500) at a 2-m mean level and a 6-m mast measuring the mean profiles of air temperature (type-T artificially ventilated thermocouples) and of wind speed (Vector A100R). Weakly stable conditions prevailed in the first meters above the ice or snow surface. With weak large scale forcing, a katabatic downslope flow with a wind maximum at about 2-m height usually appeared in the middle of the afternoon and maintained itself during most of the night. Characteristics and structure of the turbulent flow were studied using spectral and quadrant analysis, along with the study of statistical moments of high frequency wind speed and temperature data. The wind regime was found to be highly gusty and irregular: more than 50% of the flux was exchanged during less than 10% of the time. Stationary conditions were rarely encountered. The spectral analysis shows that the observed turbulence cannot be generated only by local shear, and that some outside layer perturbations must transport kinetic energy in the vicinity of the surface. Flux exchanges are thus found to be greater than predicted by aerodynamic approaches which use mean temperature and wind speed measurements and stability-correction functions based on the Monin-Obukhov similarity theory. The net surface energy balance is quantified during selected periods using fusion measurements derived from height variations of the ice surface (measured with an ultrasonic depth gauge). It is compared to the energy balance computed from radiative balance along with mean wind speed and temperature or eddy covariance fluxes.This data helps us to quantify errors made with classical similarity methods, and their variation regarding to meteorological forcings.

Litt, M.; Sicart, J.

2012-12-01

298

Experimental Testing of Glacier Sliding Laws  

NASA Astrophysics Data System (ADS)

Glacier sliding laws exist in various forms and are applied in modeling of glacier dynamics. Sliding laws have been, in most cases, theoretically derived but not experimentally tested. Under certain conditions ice sliding over a rigid bed will generate cavities in the lees of bedrock bumps. These cavities will redistribute shear stress to regions of the bed that are in contact with ice. Sliding laws that incorporate cavity formation relate drag to the maximum adverse slope of the region of ice-bed contact. Sinusoidal and stepped-bed geometries are, therefore, predicted to affect basal drag differently. A sinusoidal bed is predicted to have a double-valued drag response as a function of sliding velocity, whereas the steady-state drag on a stepped bed with linear adverse slopes is expected to be independent of sliding velocity. We have conducted an experimental study of sliding laws using a ring shear apparatus that slides ice over a rigid bed. The device rotates a ring of ice that is 20 cm wide, 20 cm tall, with outer diameter of 90 cm. The sliding speed at the ice ring's centerline was incrementally stepped between 7.25--324 m/yr, and a vertical stress of 500 kPa was applied to the ice ring. The ice consisted initially of randomly oriented crystals that with sliding quickly developed a fabric like those observed in ice near glacier beds. The temperature of the ice is held at the pressure melting point and is regulated to ~0.01oC by a bath of circulating fluid that surrounds the sample chamber. Experiments have been conducted on a stepped bed with a constant slope of 8.3 and a sinusoidal bed with a wavelength of 183.3 mm and an amplitude of 15.3 mm. Water was allowed to drain from cavities, so effective stress at the bed was equal to the total vertical stress. Our experimental results differ from theoretical predictions. For the stepped bed, a decrease in shear stress of ~50% over a 12-fold increase in velocity is observed, in contrast to theoretical predictions of a constant shear stress. This rate weakening could be attributed to spatial variability in the rheological properties of the ice, or an unresolved three-dimensional effect. Rheological variability could result from steep gradients in deviatoric stress in ice as it moves from above the cavity to the bed. The results from the sinusoidal bed demonstrate a decrease in shear stress with increasing sliding velocity that is larger than with the stepped bed. Thus, the well-described theoretical effect of a sinusoidal bed on rate weakening is augmented by whatever effect is responsible for rate weakening with the stepped bed. These results provide the first experimental targets for models of sliding that attempt to assess effects of ice-bed separation.

Zoet, L.; Iverson, N. R.

2013-12-01

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

On the influence of debris in glacier melt modelling: a new temperature-index model accounting for the debris thickness feedback  

NASA Astrophysics Data System (ADS)

The increase of rockfalls from the surrounding slopes and of englacial melt-out material has led to an increase of the debris cover extent on Alpine glaciers. In recent years, distributed debris energy-balance models have been developed to account for the melt rate enhancing/reduction due to a thin/thick debris layer, respectively. However, such models require a large amount of input data that are not often available, especially in remote mountain areas such as the Himalaya. Some of the input data such as wind or temperature are also of difficult extrapolation from station measurements. Due to their lower data requirement, empirical models have been used in glacier melt modelling. However, they generally simplify the debris effect by using a single melt-reduction factor which does not account for the influence of debris thickness on melt. In this paper, we present a new temperature-index model accounting for the debris thickness feedback in the computation of melt rates at the debris-ice interface. The empirical parameters (temperature factor, shortwave radiation factor, and lag factor accounting for the energy transfer through the debris layer) are optimized at the point scale for several debris thicknesses against melt rates simulated by a physically-based debris energy balance model. The latter has been validated against ablation stake readings and surface temperature measurements. Each parameter is then related to a plausible set of debris thickness values to provide a general and transferable parameterization. The new model is developed on Miage Glacier, Italy, a debris cover glacier in which the ablation area is mantled in near-continuous layer of rock. Subsequently, its transferability is tested on Haut Glacier d'Arolla, Switzerland, where debris is thinner and its extension has been seen to expand in the last decades. The results show that the performance of the new debris temperature-index model (DETI) in simulating the glacier melt rate at the point scale is comparable to the one of the physically based approach. The definition of model parameters as a function of debris thickness allows the simulation of the warming/insulating effect suggested by the Ostrem curve. We show that it is important indeed to take into account the effect of debris thickness also in empirical approaches, especially for thin debris mantles. The new DETI model is an innovative approach that can be included in continuous mass balance models of debris-covered glaciers, because of its limited data requirements. As such, we expect its application to lead to an improvement in simulations of the debris covered glacier response to climate.

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

2013-04-01

301

Glacier contribution to streamflow in two headwaters of the Huasco River, Dry Andes of Chile  

NASA Astrophysics Data System (ADS)

Quantitative assessment of glacier contribution to present-day streamflow is a prerequisite to the anticipation of climate change impact on water resources in the Dry Andes. In this paper we focus on two glaciated headwater catchments of the Huasco Basin (Chile, 29° S). The combination of glacier monitoring data for five glaciers (Toro 1, Toro 2, Esperanza, Guanaco, Estrecho and Ortigas) with five automatic streamflow records at sites with glacier coverage of 0.4 to 11% allows the estimation of the mean annual glacier contribution to discharge between 2003 and 2008. In addition, direct manual measurements of glacier runoff were conducted in summer at the snouts of four glaciers, which provide the instantaneous contribution of glacier meltwater to stream runoff during summer. The results show that the mean annual glacier contribution to streamflow ranges between 3.3 and 23%, which is greater than the glaciated fraction of the catchments. We argue that glacier contribution is partly enhanced by the effect of snowdrift from the non-glacier area to the glacier surface. Glacier mass loss is evident over the study period, with a mean of -0.84 m w.e. y-1 for the period 2003-2008, and also contributes to increase glacier runoff. An El Niño episode in 2002 resulted in high snow accumulation, modifying the hydrological regime and probably reducing the glacier contribution in favor of seasonal snowmelt during the subsequent 2002-2003 hydrological year. At the hourly timescale, summertime glacier contributions are highly variable in space and time, revealing large differences in effective melting rates between glacierets and glaciers.

Gascoin, S.; Kinnard, C.; Ponce, R.; Lhermitte, S.; MacDonell, S.; Rabatel, A.

2010-11-01

302

Glacier contribution to streamflow in two headwaters of the Huasco River, Dry Andes of Chile  

NASA Astrophysics Data System (ADS)

Quantitative assessment of glacier contribution to present-day streamflow is a prerequisite to the anticipation of climate change impact on water resources in the Dry Andes. In this paper we focus on two glaciated headwater catchments of the Huasco Basin (Chile, 29° S). The combination of glacier monitoring data for five glaciers (Toro 1, Toro 2, Esperanza, Guanaco, Estrecho and Ortigas) with five automatic streamflow records at sites with glacier coverage of 0.4 to 11 % allows the estimation of the mean annual glacier contribution to discharge between 2003/2004 and 2007/2008 hydrological years. In addition, direct manual measurements of glacier runoff were conducted in summer at the snouts of four glaciers, which provide the instantaneous contribution of glacier meltwater to stream runoff during summer. The results show that the mean annual glacier contribution to streamflow ranges between 3.3 and 23 %, which is greater than the glaciated fraction of the catchments. We argue that glacier contribution is partly enhanced by the effect of snowdrift from the non-glacier area to the glacier surface. Glacier mass loss is evident over the study period, with a mean of -0.84 m w.e. yr-1 for the period 2003/2004-2007/2008, and also contributes to increase glacier runoff. An El Niño episode in 2002 resulted in high snow accumulation, modifying the hydrological regime and probably reducing the glacier contribution in favor of seasonal snowmelt during the subsequent 2002/2003 hydrological year. At the hourly timescale, summertime glacier contributions are highly variable in space and time, revealing large differences in effective melting rates between glaciers and glacierets (from 1 mm w.e. h-1 to 6 mm w.e. h-1).

Gascoin, S.; Kinnard, C.; Ponce, R.; Lhermitte, S.; MacDonell, S.; Rabatel, A.

2011-12-01

303

Modeling the effect of glacier recession on streamflow response using a coupled glacio-hydrological model  

NASA Astrophysics Data System (ADS)

We describe an integrated spatially distributed hydrologic and glacier dynamic model, and use it to investigate the effect of glacier recession on streamflow variations for the upper Bow River basin, a tributary of the South Saskatchewan River, Alberta, Canada. Several recent studies have suggested that observed decreases in summer flows in the South Saskatchewan River are partly due to the retreat of glaciers in the river's headwaters. Modeling the effect of glacier changes on streamflow response in river basins such as the South Saskatchewan is complicated due to the inability of most existing physically based distributed hydrologic models to represent glacier dynamics. We compare predicted variations in glacier extent, snow water equivalent (SWE), and streamflow discharge with satellite estimates of glacier area and terminus position, observed glacier mass balance, observed streamflow and snow water-equivalent measurements, respectively over the period of 1980-2007. Observations of multiple hydroclimatic variables compare well with those simulated with the coupled hydrology-glacier model. Our results suggest that, on average, the glacier melt contribution to the Bow River flow upstream of Lake Louise is approximately 22% in summer. For warm and dry years, however, the glacier melt contribution can be as large as 47% in August, whereas for cold years, it can be as small as 15% and the timing of the glacier melt signature can be delayed by a month. The development of this modeling approach sets the stage for future predictions of the influence of warming climate on streamflow in partially glacierized watersheds.

Naz, B. S.; Frans, C. D.; Clarke, G. K. C.; Burns, P.; Lettenmaier, D. P.

2014-02-01

304

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

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

Glacier Seismicity on Svalbard: Icequakes and Tidally-modulated Tremors  

NASA Astrophysics Data System (ADS)

Using seismic signals to monitor glacier activity has become a popular approach in recent years. In this study we use several years of seismic data recorded on permanent broadband stations on Svalbard to locate and analyze icequakes in the northwestern and southern part of Spitsbergen, the main island of the archipelago. In the northwestern part in the area around Kongsfjorden close to the seismic station KBS (Ny-Ålesund) we observe a high number of seismic events. There is clear evidence that they are of glacial origin with at least three spatial icequake clusters related to different glaciers in the area. We apply automatic detection methods to the continuous KBS record in order to obtain a more complete catalog. The icequake clusters show a clear seasonal variability, i.e. much more events are observed from late summer on to end of autumn, in accordance with expected variability of glacier activity. Furthermore, seismic signals show a clear peak in the amplitude spectrum between 1 and 5 Hz, a characteristic feature which has been observed at calving glaciers in Alaska and on Greenland. A second type of glacier-related seismic emission is observed on KBS which are tidally modulated tremor-like signals. Their occurrence is correlated with the time of tidal maxima as well as the tidal range in Ny-Ålesund. In order to better understand glacier seismicity in this area and to link local and regional icequake observations, we installed a temporary local seismic network in spring 2013. We also observe clusters of icequakes in southern Spitsbergen. Events in the Hornsund area show the same seasonality and signal character as in in the Northwest. Another class of icequakes with different spectral properties and temporal patterns is observed within the area of the Nathorstbreen glacier system, which had a major surging phase recently.

Köhler, A.; Nuth, C.; Schweitzer, J.; Weidle, C.

2013-12-01

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

Surge-type Glaciers in the West Kunlun Shan, NW Tibet  

NASA Astrophysics Data System (ADS)

Surge-type glaciers oscillate between long-quiescent phase and short-active phase (i.e. decades of slow flow and shorter periods of rapid flow). Surge-type glaciers are distributed around the world and cluster around specific region and it's believed that at least 1 % of world glacier caused surge. Direct observations are difficult due to decades surge cycle and remote situation. To identify surge-type glacier, surface structures, such as looped-moraine and maze-crevasse, are used alternatively. The mechanisms of glacier surges are still not understood completely but recent studies suggest that glacier surge is likely a result of changing hydrological and/or thermal conditions. Many mountain glaciers are developed in West Kunlun Shan (WKS) located in NW Tibetan plateau. Scherler et al. (2011) mentioned that unusual low velocities at frontal part were associated with past surges in WKS but there are no reports of spatio-temporal data of glacier surge, to our knowledge. We detected glacier surge and its velocity change in WKS. We used offset tracking method based on Synthetic Aperture Radar (SAR) data, assumed that glaciers flow parallel to surface topography derived from SRTM4 digital elevation model and converted offset-results to surface velocity field. Also, we detected glacier front change using SAR intensity images and Landsat optical images. We paid attention to 36 glaciers in WKS. Among 5 glaciers were obviously classified as surge-type glacier. Surface velocity of these glaciers gradually accelerated and decelerated, accompanied by advance of glacier terminus. For example, Chongce glacier on the south slope of WKS was active phase in 1990's. Surface velocity increased up to ~700m/year in 1996. No surge signal detected from 2003. Velocity profile of Chongce glacier dramatically changed. The upper part was ~20-30m/year but the lower part was ~0-5m/year. We detected same behavior at Zhongfeng glacier (branch 1) on the south slope. Except for Chongce glacier and Zhongfeng glacier (branch 1), many glaciers in WKS had stagnant flow and probably classified as surge-type glaciers. However, dead ice caused stagnant flow. Continuous monitoring is necessarily to elucidate entire surge cycle in WKS.

Yasuda, T.; Furuya, M.

2012-12-01

309

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

310

Velocities of Thwaites and Land glaciers  

NASA Technical Reports Server (NTRS)

Changes in the area of volume of polar ice sheets are intricately linked to changes in global climate and may severely impact the densely populated coastal regions on Earth. An ice sheet's velocity is a critical parameter, which, together with ice thickness, allows the determination of discharge rates. Using moderate-resolution satellite images such as Landsat, the velocity of floating ice can be measured quickly and relatively inexpensively by tracing crevasse patterns on shelves and ice tongues. Errors in measured velocities are as little as 0.02 km per year, if the following criteria are met: (1) the time interval is longer than 10 years; (2) the velocity is higher than 0.5 km per year; (3) the coregistration points are well dispersed and enclose the area to be measured; and (4) the image pair includes a Landsat 4 or 5 image. The fewer of these conditions that are met, the less accurate the results become; but even for poor conditions, the velocities are generally reliable to near 0.1 km per year. We are in the process of obtaining velocities of all ice shelves and ice tongues along the Bakutis and Ruppert coasts, wherever suitable crevasse patterns exist. So far, we have obtained velocities for the Thwaites and Land glacier tongues.

Lucchitta, B. K.; Mullins, Kevin F.; Ferrigno, J. G.

1993-01-01

311

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

312

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

313

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

314

Physicochemical impacts of dust particles on alpine glacier meltwater at the Laohugou Glacier basin in western Qilian Mountains, China.  

PubMed

This work discusses the temporal variation of various physicochemical species in the meltwater runoff of Laohugou Glacier No. 12 (4260ma.s.l.) in central Asia, and their correlation with dust particles, based on a two-year field observation in summer 2012 and 2013, mainly focusing on dust concentration and size distribution, meltwater chemistry, particles SEM-EDX analysis in the meltwater, and MODIS atmospheric optical depth fields around the Qilian Mountains in central Asia. We find that, the volume-size distribution of dust particles in the meltwater is mainly composed of three parts, which includes fine aerosol particles (with diameter of 0~3.0?m, mainly PM 2.5), atmospheric dust (with diameter of 3.0~20?m), and local dust particles (20~100?m), respectively. Comparison of dust particles in the snowpack and meltwater runoff indicates that, large part of dust particles in the meltwater may have originated from atmospheric dust deposition to the snow and ice on the glacier, and transported into the meltwater runoff. Moreover, temporal variation of dust and major ions (especially crustal species) is very similar with each other, showing great influence of dust particles to the chemical constituents of the glacier meltwater. SPM and TDS implied significant influences of dust to the physical characteristics of the glacier meltwater. Results showed that, accelerated glacier melting may affect physicochemical characteristics of the meltwater at an alpine basin under global warming. MODIS atmospheric optical depth (AOD) fields derived using the Deep Blue algorithm, showed great influence of regional dust transportation over western Qilian Mountains in springtime. SEM-EDX analysis shows that dust particles in the glacier meltwater contain Si-, Al-, Ca-, K-, and Fe-rich materials, such as quartz, albite, aluminate, and fly ash, similar to that deposited in snowpack. These results showed great and even currently underestimated influences of atmospheric dust deposition to glacier meltwater physicochemistry at an alpine basin in central Asia. PMID:25010943

Dong, Zhiwen; Qin, Dahe; Chen, Jizu; Qin, Xiang; Ren, Jiawen; Cui, Xiaoqing; Du, Zhiheng; Kang, Shichang

2014-09-15

315

Terminus Geometry as Main Control on Outlet Glacier Velocity  

NASA Astrophysics Data System (ADS)

Ice flow velocities close to the terminus of major outlet glaciers of the Greenland Ice Sheet can vary on the time scale of years to hours. Observations at Jakobshavn Isbræ show that slowing in winter and speedup in spring are related to the formation and disintegration of a floating terminus, and that removal of 400 m long parts from the terminus in big calving events leads to immediate increase of glacier flow velocity. Such flow speed variations can be explained as the reaction to changes in terminus geometry with help of a 3D full-Stokes ice flow model on a fjord topography that is typical for Greenland outlet glaciers. Starting from an initial steady state geometry, parts of an initially 7 km long floating terminus are removed. Flow velocity increases everywhere up to 4 km upstream of the grounding line, and complete removal of the floating terminus leads to a doubling of flow speed. The model results conclusively show that the observed velocity variations of outlet glaciers is dominated by the terminus geometry, even in absence of friction or pinning of the floating terminus. Since terminus geometry is mainly controlled by calving processes and melting under the floating portion, changing ocean conditions most probably have triggered the recent geometry and velocity variations of Greenland outlet glaciers.

Lüthi, M. P.

2009-04-01

316

Bacterial succession in a glacier foreland of the High Arctic  

PubMed Central

Succession is defined as changes in biological communities over time. It has been extensively studied in plant communities, but little is known about bacterial succession, in particular in environments such as High Arctic glacier forelands. Bacteria carry out key processes in the development of soil, biogeochemical cycling, and facilitating plant colonization. In this study we sampled two roughly parallel chronosequences in the foreland of Midre Lovén glacier on Svalbard, Norway and tested whether any of several factors were associated with changes in the structure of bacterial communities, including time after glacier retreat, horizontal variation caused by the distance between chronosequences, and vertical variation at two soil depths. The structures of soil bacterial communities at different locations were compared using terminal restriction fragment length polymorphisms (T-RFLP) of 16S rRNA genes, and the data were analyzed by sequential analysis of log-linear statistical models. While no significant differences in community structure were detected between the two chronosequences, statistically significant differences between sampling locations in the surface and mineral soils could be demonstrated even though glacier forelands are patchy and dynamic environments. These findings suggest bacterial succession occurs in High Arctic glacier forelands but may differ in different soil depths.

Schutte, Ursel M.E.; Abdo, Zaid; Bent, Stephen J.; Williams, Christopher J.; Schneider, G. Maria; Solheim, Bj?rn; Forney, Larry J.

2009-01-01

317

Modeling on the Steady State of Thwaites Glacier  

NASA Astrophysics Data System (ADS)

Thwaites Glacier (TWG) is the second largest ice stream in West Antarctica in terms of ice discharge, and the broadest ice stream in Antarctica (120 km wide). Observations and theory suggest that its configuration is inherently unstable in a warming climate. Satellite observations have revealed grounding line retreat, ice thinning, ice stream broadening and in more recent years ice flow acceleration. The most important part of the glacier evolution involves its grounding line dynamics and the impact of ice-ocean interactions. In a region between the grounding line and the limit of the flexure zone, some 10 km downstream, however, the glacier is not in hydrostatic equilibrium. Proper treatment of the grounding line dynamics requires full Stokes solution. Here, we model the grounding line of TWG in 2D, full Stokes, with the goal to examine whether the glacier is in a steady state configuration or not. The model treats ice sheet and ice shelf as two fluids coupled through the ice mass flux (Nowicki, 2008). Water stress is used as a constraint on the ice shelf instead of hydrostatic equilibrium. We use radar interferometry (InSAR) measurements of ice velocity and grounding line position through time, Bedmap2 and IceBridge thickness, and surface mass balance from RACMO to constrain the model. The results are used to conclude on the state of dynamic balance of the glacier. This work is funded by NASA Cryospheric Science Program.

Yu, H.; Rignot, E. J.; Morlighem, M.; Seroussi, H.

2013-12-01

318

Changing Hydrology in Glacier-fed High Altitude Andean Peatbogs  

NASA Astrophysics Data System (ADS)

Montane peatbogs in the glacierized Andean highlands of Peru and Bolivia provide critical forage for camelids (llama and alpaca) in regionally extensive pastoral agriculture systems. During the long dry season, these wetlands often provide the only available green forage. A key question for the future of these peatbog systems, and the livelihoods they support, is the impact of climate change and glacier recession on their hydrology, and thus forage production. We have already documented substantial regional glacier recession, of, on average, approximately 30% of surface area over the past two decades. As glaciers begin to retreat under climate change, there is initially a period of increased meltwater outflow, culminating in a period of "peak water", and followed by a continual decline in outflows. Based on previous work, we know that some glaciers in the region have already passed peak water conditions, and are now declining. To better understand the impacts of these processes on peatbog hydrology and productivity, we have begun collecting a variety of surface data at several study sites in both Bolivia and Peru. These include precipitation, stream flow, water levels, water chemistry and isotope analyses, and peatbog biodiversity and biomass. These measurements will be used in conjunction with a regional model driven by satellite data to predict likely future impacts. We will present the results from these initial surface measurements, and an overview of satellite datasets to be used in the regional model.

Slayback, D. A.; Yager, K.; Baraer, M.; Mohr, K. I.; Argollo, J.; Wigmore, O.; Meneses, R. I.; Mark, B. G.

2012-12-01

319

Growth of a post-Little Ice Age submarine fan, Glacier Bay, Alaska  

Microsoft Academic Search

A small Holocene fan is forming where Queen Inlet, a hanging valley, enters West Arm fjord, Glacier Bay, Alaska. Queen fan\\u000a formed in the last 80 years following retreat of the Little Ice Age glacier that filled Glacier Bay about 200 yr BP. It was\\u000a built mainly by a turbidite system originating from Carroll Glacier delta, as the delta formed

P. R. Carlson; E. A. Cowan; R. D. Powell; J. Cai

1999-01-01

320

Theoretical calving rates from glaciers along ice walls grounded in water of variable depths  

Microsoft Academic Search

Calving has been studied for glaciers ranging from slow polar glaciers that calve on dry land, such as on Deception Island (63.0-degrees-S, 60.6-degrees-W) in Antarctica, through temperate Alaskan tide-water glaciers, to fast outlet glaciers that float in fiords and calve in deep water, such as Jakobshavns Isbrae (69.2-degrees-N, 49.9-degrees-W) in Greenland. Calving from grounded ice walls and floating ice shelves

Terence J. Hughes

1992-01-01

321

The Urumqi River source Glacier No. 1, Tianshan, China: Changes over the past 45 years  

Microsoft Academic Search

This study analyzes long-term climate and glacier records to examine climate change and glacier response over the past 45 years in Urumqi River source region, the Tianshan Mountains of China. The results show that summer temperature and annual precipitation near the glacier increased by 0.8°C and 87 mm (19%), respectively, during the study period. The glacier continuously retreated from 1962

Baisheng Ye; Daqing Yang; Keqin Jiao; Tianding Han; Zhefan Jin; Huian Yang; Zhongqin Li

2005-01-01

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

Harnessing Wind  

NSDL National Science Digital Library

Students are introduced to the ways that engineers study and harness the wind. They learn about the different kinds of winds and how to measure wind direction. In addition, they learn how air pressure creates winds and how engineers design and test wind turbines to harness renewable wind energy.

Integrated Teaching And Learning Program

324

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

325

Continuous Monitoring of Permafrost Deformation in a Warm Rock Glacier in the Swiss Alps  

Microsoft Academic Search

This study focuses on rock-glacier creep, which is downslope deformation of perennially frozen talus. Field observations were performed on a small rock glacier lying close to the boundary between permafrost and non- permafrost terrains in the Swiss Alps from 1998 to 2005. The studied rock glacier, Büz North (BN), consists of an upper lobe 70 m long and lower lobe

A. Ikeda; N. Matsuoka; A. Kääb

2006-01-01

326

Dynamics and mass balance of Taylor Glacier, Antarctica: 2. Force balance and longitudinal coupling  

Microsoft Academic Search

Taylor Glacier, Antarctica, exemplifies an ice sheet outlet that flows through a region of rugged topography and dry climate. In contrast to other well-studied outlets, Taylor Glacier moves very slowly, despite a thickness of order 1 km and driving stresses averaging 1.5 bars. Here we analyze new measurements of glacier geometry and surface velocity to elucidate flow dynamics of Taylor

J. L. Kavanaugh; K. M. Cuffey

2009-01-01

327

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

328

Modelling Glacier Surface Temperature Using Weather Station Data and Synoptic Weather Conditions  

Microsoft Academic Search

Glacier temperature can be directly measured at selected locations, but extrapolation is often required as data at high elevations are sparse and glacier-wide temperatures are needed for distributed melt models. A new model to extrapolate summer temperatures (May - August) is developed from data collected at Haig Glacier to address this need. Air temperatures are computed using the new model

Nicole Schaffer

2010-01-01

329

Modelling Glacier Surface Temperature Using Weather Station Data and Historical Climate Reconstructions  

Microsoft Academic Search

Models of glacier response to climate change and snow\\/ice melt require knowledge of air temperatures at the glacier surface. This can be directly measured at selected locations, but distributed models of glacier melt require temperature information over an entire surface. Furthermore, in many practical applications, temperature must be estimated for locations where no data is available. A new and more

N. Schaffer; S. J. Marshall

2009-01-01

330

Changes in glacier extent on north Novaya Zemlya in the twentieth century  

Microsoft Academic Search

Glacier retreat on north Novaya Zemlya for the past century was documented by registering glacier terminus positions from expedition and topographic maps and remotely sensed images. Recession of tidewater calving glaciers on north Novaya Zemlya in the first half of the twentieth century was relatively rapid (>300 m yr-1), consistent with post-‘Little Ice Age’ warming documented by a 122-year instrumental

Jaapjan Zeeberg; Steven L. Forman

2001-01-01

331

Simulation of runoff processes of a continental mountain glacier in the Tian Shan, China  

Microsoft Academic Search

Based on calculations of energy, water and mass balance and on measurements of water routine, a model is developed to simulate glacial runoff processes for Glacier No. 1, a continental mountain glacier at the source of the Urumqi River in the Chinese Tian Shan. The melt at the equilibrium line is related to the mean melt of the glacier. The

KANG ERSI; ATSUMU OHMURA; HERBERT LANG

332

Ice speed of a calving glacier modulated by small fluctuations in basal water pressure  

Microsoft Academic Search

Ice flow acceleration has played a crucial role in the rapid retreat of calving glaciers in Alaska, Greenland and Antarctica. Glaciers that calve in water flow much faster than those that terminate on land, as a result of enhanced basal ice motion where basal water pressure is high. However, a scarcity of subglacial observations in calving glaciers limits a mechanistic

Shin Sugiyama; Pedro Skvarca; Nozomu Naito; Hiroyuki Enomoto; Shun Tsutaki; Kenta Tone; Sebastián Marinsek; Masamu Aniya

2011-01-01

333

Culturable Bacteria in Subglacial Sediments and Ice from Two Southern Hemisphere Glaciers  

Microsoft Academic Search

Viable prokaryotes have been detected in basal sediments beneath the few Northern Hemisphere glaciers that have been sampled for microbial communities. However, parallel studies have not previously been conducted in the Southern Hemisphere, and subglacial environments in general are a new and underexplored niche for microbes. Unfrozen subglacial sediments and overlying glacier ice samples collected aseptically from the Fox Glacier

J. Foght; J. Aislabie; S. Turner; C. E. Brown; J. Ryburn; D. J. Saul; W. Lawson

2004-01-01

334

The influence of drifting snow on the location of glaciers on western Spitsbergen, Svalbard  

Microsoft Academic Search

On western Spitsbergen, Svalbard, the amount of winter precipitation is insufficient to maintain the present-day mass balance of the local glaciers. Additional snow mass must be added to the precipitation to reach the observed accumulation rates of the glaciers. It was assumed in previous work that this additional mass is transported onto the glaciers by drifting snow and snow avalanches.

Christian Jaedicke; Peter Gauer

2005-01-01

335

Geophysical imaging of a temperate glacier's hydrologic system in 1, 2, and 3 dimensions  

Microsoft Academic Search

Between 1999 and 2007, we conducted a series of geophysical experiments on Bench Glacier in the Chugach Range of southeast Alaska. Objectives of the experiments include measuring 1) the distribution of water in the snow pack, 2) water storage and routing within the glacier, and 3) the geometry of flow paths at the bed of the glacier. To accomplish these

J. H. Bradford; W. Clement; J. Nichols; J. Brown; D. Mikesell; J. Harper; N. Humphrey; T. Tschetter

2007-01-01

336

Rock glaciers and protalus landforms: Analogous forms and ice sources on Earth and Mars  

Microsoft Academic Search

The basic features and terminology of terrestrial ``rock glaciers'' are reviewed together with associated forms termed ``protalus lobes'' and ``protalus ramparts.'' Two basic models of rock glacier formation and flow invoke either the creep of ice derived from permafrost or glacial\\/former glacial activity; a third possible mechanism invokes landslide emplacement. Observations on terrestrial rock glaciers and similar forms suggest that

W. Brian Whalley; Fethi Azizi

2003-01-01

337

The role of glaciers in stream flow from the Nepal Himalaya  

Microsoft Academic Search

Recent concerns related to the potential impacts of the retreat of Himalayan glaciers on the hydrology of rivers originating in the catchment basins of the Himalaya have been accompanied by few analyses describing the role of glaciers in the hydrologic regime of these mountains. This is, at least in part, a result of the relative inaccessibility of the glaciers of

D. Alford; R. Armstrong

2010-01-01

338

Glacier contribution to streamflow in two headwaters of the Huasco River, Dry Andes of Chile  

Microsoft Academic Search

Quantitative assessment of glacier contribution to present-day streamflow is a prerequisite to the anticipation of climate change impact on water resources in the Dry Andes. In this paper we focus on two glaciated headwater catchments of the Huasco Basin (Chile, 29° S). The combination of glacier monitoring data for five glaciers (Toro 1, Toro 2, Esperanza, Guanaco, Estrecho and Ortigas)

S. Gascoin; C. Kinnard; R. Ponce; S. Lhermitte; S. MacDonell; A. Rabatel

2010-01-01

339

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

340

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

341

The Holocene Sedimentary Record of Climate Change from Gualas Glacier, Golfo Elefantes, Northern Patagonia (46.5°S)  

NASA Astrophysics Data System (ADS)

Gualas Glacier is an outlet glacier of the Northern Patagonian Icefield (NPI), one of the largest temperate ice bodies on Earth. NPI is nourished by moisture from the Pacific Ocean, which is transported by the southern hemisphere Westerlies and results in year-round precipitation. This system also creates a strong West to East gradient due to the rain shadow effect of the Andes (Warren, 1993). Most glaciers of the NPI, including Gualas Glacier, are currently receding from their historical maximum position, which was reached during the northern hemisphere Little Ice Age (LIA) (Harrison and Winchester, 2000). However, virtually nothing is known about the Holocene behavior of NPI outlet glaciers prior to the LIA, although it is generally assumed that they followed the pattern of Neoglacial advances described for the Southern Patagonian Icefield (SPI) by Mercer (1965, 1968, 1976). The lack of data in this sensitive area of the Patagonian Andes, the only continental cordillera in the Southern Hemisphere that intersects the entire Westerly Wind Belt, limits our understanding of climate processes that relate mid-latitude circulation patterns with low and high latitudes as well as the inter-hemispheric coupling of climate changes. We present the results of a marine geological survey at Golfo Elefantes, the depositional basin of Gualas Glacier. The dataset includes swath bathymetry, single channel seismic data and sediment cores analyses. The studied sedimentary record spans, with some hiatuses, at least the last 10.5 Ka. No evidences of ice proximal or till deposits were found in the area, and seismic records show no evidence of basin-wide erosional hiatuses. This implies that the arcuate terminal moraines that occur along the edges of Golfo Elefantes, which have been suggested to represent Neoglacial advances of Gualas Glacier, were instead formed during the waning stages of the local LGM (Late Pleistocene) after ~12.6 ka according to paleogeographical reconstructions (Turner, 2005). Between 10.5 and 4.3 ka, the basin filled with fine-grained sediments deposited from low concentration density currents to form subhorizontal layers that filled topographic lows. A depositional hiatus of unknown duration, but likely spanning ~2400-3300 years, separates early Holocene sediments from late Holocene strata (<1-1.9 ka) that were deposited from high density turbidity flows. Estimates of sediment flux, based on Syvitski et al.’s (2007) model for sediment discharge imply that low sediment discharge occurred during the early Holocene, whereas the middle-late Holocene was characterized by periods when sediment discharge was several times higher than predicted by this model. This excess sediment discharge is interpreted as the result of purging of sediments stored either in proglacial lakes or in the subglacial environment of Gualas Glacier, in addition to increased sediment flux caused by increased precipitation.

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

2010-12-01

342

Surface Energy Balance Model of the Helheim Glacier, Southeast Greenland  

NASA Astrophysics Data System (ADS)

We present a distributed surface energy balance model of Helheim Glacier based on data collected by Automatic Weather Stations (AWSs) in the summer of 2008. Measurements were made at two sites in the ablation zone, at different elevations, overlapping in operation period. Using a digital elevation model we quantify the melt over the entire glacier taking topographic shading and reflection effects into account. A spatial model of the melt rates can be used to search for a correlation between these and occurrences of rapid glacier movement as a test of the hypothesis of melt water-lubricated enhanced flow. This correlation can also provide a basis for estimating the time-lag between melt water generation at the surface and its arrival at the bed through moulins, channels and the like. In addition to quantifying direct mass-loss processes, the model output has multiple uses in future efforts, e.g. crevasse-spreading models or salinity studies of the fjord.

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

2008-12-01

343

Characterization and Interpretation of Polythermal Structure in Two Subarctic Glaciers  

NASA Astrophysics Data System (ADS)

I use ice-penetrating radar to probe the thermal structure in two small glaciers in the Saint Elias Range, southwestern Yukon. I develop processing workflows to separate bed and englacial reflections in radar and use these to build maps of both bed topography and englacial scattering. Comparison with borehole data shows that englacial scattering occurs in ice at the freezing point. The pattern in thermal structure suggests that the observed regime is dominated by accumulation zone processes. I develop a numerical model to simulate steady and time-dependent thermal regimes in glaciers. Diagnostic simulations support the hypothesis that meltwater entrapment is a critical control on the observed structure. Sensitivity tests suggest a climate sensitivity such that thinning and retreat of the near-surface aquifer may dramatically alter the thermal structure. Prognostic simulations illustrate scenarios in which these polythermal glaciers may cool as climate warms in the future.

Wilson, Nat

344

Acceleration in thinning rate on western Svalbard glaciers  

NASA Astrophysics Data System (ADS)

Geodetic measurements indicate that a number of glaciers in western Svalbard ranging in size from 5-1000 km2 are losing mass at an accelerating rate. The average thinning rate for Midtre Lovénbreen, the glacier with the best data coverage, has increased steadily since 1936. Thinning rates for 2003-2005 are more than 4 times the average for the first measurement period 1936-1962 and are significantly greater than presented previously. On Slakbreen, thinning rates for the latest measurement period 1990-2003 are more than 4 times that of the period 1961-1977. Thinning of several glaciers along a previously measured airborne lidar profile in Wedel Jarls Land has also increased, doubling between the period 1990-1996 and 1996-2002. Our results imply an increased sea level contribution from Svalbard. In addition, the mass loss is an important influence on measured rates of rebound on western Svalbard and should be factored into analysis of GRACE results.

Kohler, J.; James, T. D.; Murray, T.; Nuth, C.; Brandt, O.; Barrand, N. E.; Aas, H. F.; Luckman, A.

2007-09-01

345

Turbulence Characteristics Of The Stable Boundary Layer Over A Mid-Latitude Glacier. Part Ii: Pure Katabatic Forcing Conditions  

NASA Astrophysics Data System (ADS)

Observations obtained over a glacier surface in a predominantlykatabatic flow and with a distinctwind maximum below 13-m height are presented. The data werecollected using a 13-m high profilemast and two sonic anemometers (at about 2.5-m and 10-m heights).The spectra at frequencies belowthat of the turbulence range appear to deviate considerably fromthe curves obtained by Kaimal andco-workers during the 1968 Kansas experiment. The characteristicsof these deviations are compared tothe observations of others in surface-layers disturbed by anykind of large-scale outer-layer (orinactive) turbulence. In our case the disturbances arelikely to be induced by the highmountain ridges that surround the glacier. Moreover, the deviationsobserved in the cospectra seemto result from an, as yet, unspecified interaction between theinactive outer-layer turbulenceand the local surface-layer turbulence. Near the distinctwind maximum turbulence production ceasedwhile turbulence itself did not, probably the result ofturbulence transport from other levels. Consequently, we studied thelocal similarity relations using w instead of u* as an alternative velocity scale. Wellbelow the wind maximum, and for relatively low stability(0g g > 0.2), and near or above the wind maximum, the boundary-layer structure conforms tothat of z-less stratification suggesting that the eddy sizeis restricted by the local stability ofthe flow. In line with this we observed that the sensibleheat fluxes relate remarkably well to thelocal flow parameters.

Smeets, C. J. P. P.; Duynkerke, P. G.; Vugts, H. F.

346

Glacier and Ice Shelves Studies Using Satellite SAR Interferometry  

NASA Technical Reports Server (NTRS)

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

Rignot, Eric

1999-01-01

347

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

348

Slow surge of Trapridge Glacier, Yukon Territory, Canada  

NASA Astrophysics Data System (ADS)

Trapridge Glacier, a polythermal surge-type glacier located in the St. Elias Mountains, Yukon Territory, Canada, passed through a complete surge cycle between 1951 and 2005. Air photos (1951-1981) and ground-based optical surveys (1969-2005) are used to quantify the modifications in flow and geometry that occurred over this period. Yearly averaged flow records suggest that the active phase began ˜1980, and lasted until ˜2000. The average velocity in the central area of the glacier went from 16 m yr-1 in 1974 to 39 m yr-1 in 1980; it peaked at 42 m yr-1 in 1984, and remained above 25 m yr-1 until 2001. Over that interval, the flow decelerated by steps, in 4-year pulses. After a particularly vigorous acceleration in 1997-1999, the glacier gradually slowed to presurge velocities. In 2005, the flow was less than 9 m yr-1. Digital elevation models are generated by stereographic analysis of air photos for 1951, 1970, 1972, 1977, and 1981. These models are updated annually using ground-based survey data and a novel implementation of Bayesian kriging. Over the course of the surge, the front of active ice advanced 450 m and the glacier area increased by 10%, with an associated thinning of the ice. The previous surge of Trapridge Glacier, starting before 1939 and ending before 1951, led to a terminus advance of ˜1 km. Comparison of the two surges suggests that the 1930s surge started with a slow progression similar to what we observed in the 1980s and 1990s, and switched to a faster flow mode after 1941. This second phase was never attained in the recent surge, probably owing to a lack of mass.

Frappé, Tom-Pierre; Clarke, Garry K. C.

2007-09-01

349

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

350

Revisited Inventory of Glaciers on Axel Heiberg Island, Nunavut  

NASA Astrophysics Data System (ADS)

As documented in the IPCC's Climate Change 2007 report, the high latitude regions of the Northern Hemisphere are experiencing the highest rates of warming. Given that 35% of the global glacial ice exists within the Arctic Archipelago, this region provides an excellent laboratory for monitoring the anticipated degree of glacial recession [1]. Evidence of arctic warming through negative mass balance trends has been detected in several studies already [e.g., 2]. Here, we show the importance and value of historical records in the task of monitoring glacial retreat. A highly detailed inventory developed by S. Ommanney in 1969 [3], has been revisited and transformed into digital format for the purposes of integration with modern inventories. The Ommanney inventory covers the entirety of Axel Heiberg Island , NU, and includes details often lacking in present day inventories, including orientations (accumulation and ablation zones), elevations (highest, lowest, elevation of the snowline, and the mean elevations of both the accumulation and ablation areas), length (of the ablation area, exposed ice, and of the total glacier including debris cover), area (of the ablation area, exposed ice, and of the total glacier), accumulation area ratio (AAR), depth, volume, and a six digit code which gives qualitative details on glacier attributes. This report is one of the most thorough and comprehensive glacier inventory report ever published in Canada. More recent inventories used for comparison include the glacier extents created by the National Topographic System based on photography from 1980-1987, as well as extents developed by Dr. Luke Copland for the Global Land Ice Measurements from Space (GLIMS) database using 1999-2000 satellite imagery. Our preliminary results show that approximately 90% of ice bodies under 0.2km on Axel Heiberg Island have disappeared entirely in the 40 year period of interest. The issue of glacier definition will be discussed as a possible cause of these drastic changes in the status of small, remnant glaciers. Recession trends will also be discussed with respect to glacier characteristics and regional distribution. [1] Barry, R. G., Progress in Physical Geography, 2006. 30(3): p. 285-306; [2] Dowdeswell, J. A., et al., Quaternary Research, 1997. 40: p. 1-14; [3] Ommanney, C. S. L., McGill Subarctic Research Paper, 1969. 40: p. 5-67.

Thomson, L.; Osinski, G.

2009-05-01

351

Mercury in Glaciers over Western China: Distribution, Deposition and History  

NASA Astrophysics Data System (ADS)

Mercury (Hg) has been recognized as a global contaminant due to its long-range transport via the atmosphere, biomagnification in ecosystems, and its intrinsic toxicity. Western China is home to the largest aggregate of glaciers outside the polar regions, yet little is known about how the glaciers in this area affect the transport and cycling of Hg regionally and globally. From 2005 to 2010, 14 snowpits were dug from 9 glaciers over western China, total Hg (THg) concentrations ranged from <1 to 43.6 ng L-1, and exhibited clear seasonal variations with lower values in summer than in winter. Spatially, higher THg concentrations were typically observed in glacier snows from the northern region (Figure 1). Glacier snowpit Hg was largely dependent on particulate matters and was associated with particulate Hg (PHg). Consecutive snowpit sampling at Zhadang glacier during summer melt season further revealed that Hg tends to accumulate in the dust layers during its percolation down to lower snow stratum. Since Hg in glaciers is mainly preserved in the form of PHg which is less prone to post-depositional changes, glacier Hg record most likely represents a valuable record of atmospheric Hg deposition. Estimated atmospheric Hg depositional fluxes ranged from 0.74 to 7.89 ?g m-2 yr-1, agreeing very well with the global natural values. A high-resolution Hg record reconstructed by the Mt.Geladiandong ice core provided insight into historical variation of atmospheric Hg during the past 500 years. Elevated THg concentrations were observed since 1940s, which coincides the increase of global Hg production, especially the Asian Hg production history. Reconstructed Hg depositional flux for post-1940s era is 6.4 times higher than that of pre-20th century, which clearly indicated the anthropogenic influence on the regional, perhaps even the global background (Figure 2).; Figure 1. THg concentrations and estimated annual atmospheric depositional fluxes of Hg at sampling sites ; Figure 2. Historical Hg flux reconstructed from the Mt.Geladiandong ice core

Zhang, Q.

2012-12-01

352

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

353

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

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

354

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

355

Glacier changes in Chinese Altay Mountains during the last ~50 years  

NASA Astrophysics Data System (ADS)

Mountain glaciers are not only indicator of climate change, but also important water resources for oases and for the sustainable development of the ecological environment, industry and agriculture. However, due to climate warming, most of glaciers are in a state of rapid retreating. Altay Mountains, located in the border of China, Russia and Mongolia, foster the highest latitude glaciated region in China, providing important water resources for local economic development and people living. However, research on glacier change is limited in the Altay Mountains. Taking this into account, based on topographic maps in 1959, ASTER remote sensing data in 2008 and digital elevation models (DEMs), glacier changes in the Altay Mountains including glacier area, length, thickness and volume changes were analyzed in the support of 3S technology. Results showed that the total area and number of 226 glaciers investigated have reduced by 32.5% and 27.9% from 1959 to 2008. The average area reduction rate of glaciers with size <1 km2 and in 1-5 km2 is -66.7% and 27.9%, respectively. The reduction rate is more than 70% for the glaciers with size less than 0.5 km2. Glaciers have retreated by 253 m with the reduction rate of 18.3%. Furthermore, for 58 selected glaciers in the Youyi Area, the mean ice elevation decrease by 24.12 m with the volume loss of 2.649 km3, corresponding to the annual glacier runoff of 4.88×106 m3 during 1959-2008. Analysis indicated that the relative area reductions of small glaciers were usually higher than those of large ones, which exhibited larger absolute loss, indicating that the small glaciers were more sensitive to climate change than large ones. Glacier changes exhibited obvious spatial differences, indicating that the reduction rate of glaciers in the south slope of the Youyi Area was larger than in the north.

Li, Zhongqin; Li, Huilin; Wang, Feiteng

2014-05-01

356

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

NASA Astrophysics Data System (ADS)

The release of water as snowmelt and ice melt in high elevation catchments has significant social and economic impacts for population living in mountain areas. This is even more critical under the current conditions of glacier retreat as a consequence of global warming. Therefore, it is important to understand the role of ice and snow meltwater on runoff dynamics and groundwater recharge in glacierized environments. This task can be effectively accomplished by integrating isotopic and other tracers that are widely recognized as useful tools for the identification of the main water sources contributing to streamflow. In this work, we collected water samples from different sources in the Saldur catchment (Eastern Italian Alps). The catchment (area: 62 km², elevation range: 1600-3700 m a.s.l.) hosts a small glacier (2.8 km²) in its upper portion. Samples of rainfall, snow, snowmelt, glacier melt, stream water (main stream and tributaries) and spring water have been manually collected between April-October 2011 and April-November 2012 approximately on a monthly basis. Furthermore, 24-hour samplings with hourly collection frequency were performed at two cross sections during five melt-runoff events. The composition in stable water isotopes was determined by laser spectroscopy and mass spectrometry. Electrical conductivity (EC) and water temperature were measured in the field. Additionally, deuterium excess (DE) was computed for all samples based on the relationship between deuterium and 18-oxygen. The isotopic composition of rainfall and snow shows marked altitudinal and seasonal variations. A strong positive correlation is also evident in the relationship between DE of spring waters and elevation. Rainfall and snow samples fall perfectly on the Global Meteoric Water Line, revealing a predominant Atlantic origin of air masses producing precipitation in the study area. EC and water temperature linearly increase with the distance from the glacier snout, suggesting a decreasing influence of snow and glacier melt water (cold and little conductive) and an increasing contribution of non-glacierized areas moving downstream. Stream water shows a strong daily variability in isotopic composition and EC correlated well with discharge and air temperature, suggesting the relevant contribution of meltwater on runoff. Moreover, a seasonal trend is also observable in stream water and groundwater, with the most isotopically enriched and highest EC values found at low flow conditions (no melting periods), in early spring and late autumn. In agreement with these observations, end-member mixing analysis shows that summer precipitation plays a minor role on runoff temporal variability compared to glacier melt and snowmelt. Two- and three-component hydrograph separation for the summer melt-runoff events confirms the significant contribution of melting-event water (up to 73% for the upper station) and the importance of snowmelt and glacier melt (up to 37% and 28%, respectively) as water sources for streamflow at the daily scale in the study catchment. These results underline the critical role played by meltwater stored in glaciers and snow on water availability in mountain regions. Moreover, this works reveals the usefulness of a multi-tracer approach for the analysis of the main contributors to streamflow in glacierized catchments. Keywords: water stable isotopes, deuterium excess, electrical conductivity, snowmelt, glacier melt.

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

2013-04-01

357

Processes of annual moraine formation at a temperate alpine valley glacier: glacier dynamics and climatic controls  

NASA Astrophysics Data System (ADS)

This paper presents the first detailed sedimentological study of annual moraines formed by an alpine valley glacier. The moraines have been formed since at least AD 1980 by a subsidiary lobe of Gornergletscher, Switzerland, that advances up a reverse bedrock slope. They reach heights of 0.5-1.5 m, widths of up to 6 m and lengths of up to several hundreds of metres. Sediments in these moraines comprise proglacial outwash and debris flow units; subglacial traction till is absent entirely. Based on four representative sections, three genetic process combinations have been identified. (1) Inefficient bulldozing of a gently-sloping ice margin transfers proglacial sediments onto the ice, causing differential ablation and dead-ice incorporation upon retreat. (2) Terrestrial ice-contact fans are formed by the dumping of englacial and supraglacial material from point sources such as englacial conduit fills. Debris flows and associated fluvial sediments are stacked against a temporarily stationary margin at the start, and deformed during glacier advance in the remainder, of the accumulation season. (3) A steep ice margin without supraglacial input leads to efficient bulldozing and deformation of pre-existing foreland sediments by wholesale folding. Ice surface slope appears to be a key control on the type of process responsible for moraine formation in any given place and year. The second and third modes result in stable and higher moraines that have a higher preservation potential than those containing dead ice. Analysis of the spacing and climatic records at Gornergletscher reveal that winter temperature controls marginal retreat and hence moraine formation. However, any climatic signal is complicated by other factors, most notably the presence of a reverse bedrock slope, so that the extraction of a clear climatic signal is not straightforward. This study highlights the complexity of annual moraine formation in high-mountain environments and suggests avenues for further research.

Lukas, S.

2012-04-01

358

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

359

Loch Lomond Stadial glaciers in North Harris, Outer Hebrides, North-West Scotland: glacier reconstruction and palaeoclimatic implications  

NASA Astrophysics Data System (ADS)

Geomorphological mapping of North Harris provides evidence for the former existence of 10 glaciers with a total area of ca 35 km 2. A Loch Lomond (Younger Dryas) Stadial age (ca 12.9-11.5 kyr BP) for this glacial episode is inferred from glacier configuration, landsystems dominated by hummocky recessional moraines, and relationships with Lateglacial periglacial phenomena. Equilibrium line altitudes (ELAs) of 150-289 m were calculated for individual glaciers. ELA variability mainly reflects differences in snow-contributing area. The area-weighted mean ELA (204 m) is consistent with a northwards decline in ELAs along the western seaboard of the British Isles of 69.5 m (100 km) -1, equivalent to a northwards ablation-season temperature decrease of 0.42 °C (100 km) -1. This latitudinal temperature gradient implies a mean July sea-level temperature of ca 7.2 °C for the coldest part of the stade, roughly 6 °C lower than at present. Sea-level precipitation at the time of the LLS glacial maximum is inferred to have been between ca 1970±200 and 2350±200 mm yr -1, implying that LLS precipitation was up to 25% greater than now. Patterns of recessional moraines indicate that the glaciers remained close to climatic equilibrium as they retreated to their sources, though moraine belts implying near-stationary or readvancing ice margins on flat valley floors are separated by moraine-free zones indicating uninterrupted retreat. Calculation of ELAs for 'residual' glaciers in former source areas suggests that summer warming of ?1.0 °C would have resulted in shrinkage of the glaciers to their sources.

Ballantyne, Colin K.

2007-12-01

360

Responses of two branches of Glacier No. 1 to climate change from 1993 to 2005, Tianshan, China  

Microsoft Academic Search

Clear understanding of how alpine glaciers respond to climate change is critical to accurately evaluate water resources and to retrieve climate information from the alpine glaciers. However, different glaciers may have different responses to climate change. This study focuses on two branches of Glacier No. 1 at the head of Urumqi River, Tianshan, China. These two branches, West Branch (WB)

Xiangke Xu; Baolin Pan; En Hu; Yanjun Li; Yuehua Liang

2011-01-01

361

Sublimation on the glaciers of the upper Huasco valley, Chile, using eddy covariance data and energy balance modelling  

Microsoft Academic Search

On the cold, arid glaciers of the Norte Chico region, Chile, sublimation plays an important role in mass loss from the glacier surface. The ratio of sublimation : melt on these glaciers dictates not only the amount of meltwater delivered to the watershed, but it also drives the development of morphological features on the glacier surface, such as penitentes. As

Shelley MacDonell; Nicolas Cullen; Lindsey Nicholson; Thomas Mölg; Christophe Kinnard

2010-01-01

362

Influence of watershed glacier coverage on summer streamflow in British Columbia, Canada  

NASA Astrophysics Data System (ADS)

This study examined the effects of glacier cover on summer streamflow across British Columbia, Canada, by applying nonparametric tests to assess trends in August discharge. Field-significant negative streamflow trends were found for glacierized catchments but not for those lacking glaciers. Effects of interannual climatic variations were accounted for by regressing August streamflow against August temperature and precipitation and July streamflow (to account for carryover storage). Trend analyses of the regression residuals suggested first-order stationarity for unglacierized basins, but revealed widespread negative trends for glacier-fed rivers, particularly from 1976 to 1996, consistent with the effects of glacier retreat.

Stahl, K.; Moore, R. D.

2006-06-01

363

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

364

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

365

Mechanisms and simulation of accelerated shrinkage of continental glaciers: A case study of Urumqi Glacier No. 1 in eastern Tianshan, Central Asia  

Microsoft Academic Search

Similar to most mountain glaciers in the world, Urumqi Glacier No. 1 (UG1), the best observed glacier in China with continued\\u000a glaciological and climatological monitoring records of longer than 50 years has experienced an accelerated recession during\\u000a the past several decades. The purpose of this study is to investigate the acceleration of recession. By taking UG1 as an example,\\u000a we

Zhongqin Li; Huilin Li; Yaning Chen

2011-01-01

366

Rewriting Ice Sheet "Glacier-ology"  

NASA Astrophysics Data System (ADS)

The revolution in glaciology driven by the suite of increasingly sophisticated satellite instruments has been no more extreme than in the area of ice dynamics. Years ago, glaciologists were (probably unwittingly) selective in what properties of mountain glaciers were also applied to ice sheets. This reinforced the view that they responded slowly to their environment. Notions of rapid response driven by the ideas of John Mercer, Bill Budd and Terry Hughes were politely rejected by the centrists of mainstream glaciological thought. How the tables have turned--and by the ice sheets themselves, captured in the act of rapidly changing by modern remote sensors! The saw-toothed record of sea-level change over past glacial-interglacial cycles required the existence of rapid ice loss processes. Satellite based observations, supported by hard-earned field observations have extended the time scale over which ice sheets can suddenly change to ever shorter intervals: from centuries, to decades, to years to even minutes. As changes continue to be observed, the scientific community is forced to consider new or previously ignored processes to explain these observations. The penultimate goal of ice-sheet dynamics is to credibly predict the future of both the Greenland and Antarctic ice sheets. In this important endeavor, there is no substitute for our ability to observe. Without the extensive data sets provided by remote sensing, numerical models can be neither tested nor improved. The impact of remote sensing on our existing ability to predict the future must be compared to our probable state of knowledge and ability were these data never collected. Among many satellite observed phenomena we would be largely or wholly ignorant of are the recent acceleration of ice throughout much of coastal Greenland; the sudden disintegration of multiple ice shelves along the Antarctic Peninsula; and the dramatic thinning and acceleration of the Amundsen Sea sector of West Antarctica. These observations are driving increased concern about rapidly increasing sea level, a process dominated by ice-sheet dynamics and largely identified, quantified, studied and monitored by satellite sensors.

Bindschadler, R.

2006-12-01

367

Modeling the effect of glacier recession on streamflow response using a coupled glacio-hydrological model  

SciTech Connect

We describe an integrated spatially distributed hydrologic and glacier dynamic model, and use it to investigate the effect of glacier recession on streamflow variations for the Upper Bow River basin, a tributary of the South Saskatchewan River. Several recent studies have suggested that observed decreases in summer flows in the South Saskatchewan River are partly due to the retreat of glaciers in the river's headwaters. Modeling the effect of glacier changes on streamflow response in river basins such as the South Saskatchewan is complicated due to the inability of most existing physically-based distributed hydrologic models to represent glacier dynamics. We compare predicted variations in glacier extent, snow water equivalent and streamflow discharge made with the integrated model with satellite estimates of glacier area and terminus position, observed streamflow and snow water equivalent measurements over the period of 1980 2007. Simulations with the coupled hydrology-glacier model reduce the uncertainty in streamflow predictions. Our results suggested that on average, the glacier melt contribution to the Bow River flow upstream of Lake Louise is about 30% in summer. For warm and dry years, however, the glacier melt contribution can be as large as 50% in August, whereas for cold years, it can be as small as 20% and the timing of glacier melt signature can be delayed by a month.

Naz, Bibi S [ORNL] [ORNL; Frans, Chris [University of Washington, Seattle] [University of Washington, Seattle; Clarke, Garry [University of British Columbia, Vancouver] [University of British Columbia, Vancouver; Burns, [Watershed Sciences Inc. (WSI), Portland] [Watershed Sciences Inc. (WSI), Portland; Lettenmaier, Dennis [University of Washington, Seattle] [University of Washington, Seattle

2014-01-01

368