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1

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

Microsoft Academic Search

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

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

2006-01-01

2

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

NASA Astrophysics Data System (ADS)

Taku Glacier in southeast Alaska has advanced 7.5 km over the last 115 years, overriding its own glaciomarine and outwash sediments. We have documented rapid erosion of these sediments by comparing radio echo soundings (RES) along five transects (2003-2005) to earlier RES surveys (1989 and 1994) and to early bathymetric surveys of the proglacial fjord. Erosion rates, $\\dot{E, reached 3.9 +/- 0.8 m a-1 (1989-2003) at a distance, L, of 5.4 km from the 2003 terminus, where ice thickness, H, is 610 m. $\\dot{E averaged 2.0 +/- 0.1 m a-1 (1940-2005) at L = 3 km (H = 350 m), and 1.5 +/- 0.2 m a-1 (1952-2005) at L = 1.5 km (H = 250 m). Detailed mapping over a 4 km2 area of the terminus revealed a deeply incised channel in line with a major outlet stream. Glaciofluvial processes must play the dominant role in the subglacial erosion and removal of these unlithified sediments.

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

2006-12-01

3

Glacier Velocities and Elevation Change of the Juneau Icefield, Alaska  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

4

Lack of trophic competition among wild and hatchery juvenile chum salmon during early marine residence in Taku Inlet, Southeast Alaska  

Microsoft Academic Search

Early marine trophic interactions of wild and hatchery chum salmon (Oncorhynchus keta) were examined as a potential cause for the decline in harvests of adult wild chum salmon in Taku Inlet, Southeast Alaska.\\u000a In 2004 and 2005, outmigrating juvenile chum salmon were sampled in nearshore habitats of the inlet (spring) and in epipelagic\\u000a habitat at Icy Strait (summer) as they

Molly V. Sturdevant; Emily Fergusson; Nicola Hillgruber; Carl Reese; Joe Orsi; Rick Focht; Alex Wertheimer; Bill Smoker

5

Health Consultation: Polychlorinated Biphenyl (PCB) Contamination: Taku Gardens, Fort Wainwright, Alaska, April 26, 2010.  

National Technical Information Service (NTIS)

The Agency for Toxic Substances and Disease Registry (ATSDR) recognizes your need for more information about potential past exposures to polychlorinated biphenyls (PCBs) in the Taku Garden area. Our primary objective in writing this health consultation is...

2010-01-01

6

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

7

Geology of the western flank of the Coast Mountains between Cape Fanshaw and Taku Inlet, southeastern Alaska  

Microsoft Academic Search

The western flank of the Coast Mountains batholith between Cape Fanshaw and Taku Inlet is underlain primarily by Jura-Cretaceous strata of the Gravina belt; pre-Permian(?), Permian, and Triassic strata of the Taku terrane; and mid-Proterozoic(?) to upper Paleozoic rocks of continental margin affinity. The continental margin rocks include mid-Proterozoic(?) to lower Paleozoic(?) quartzite and marble of the Tracy Arm assemblage;

George E. Gehrels; William C. McClelland; Scott D. Samson; P. Jonathan Patchett; Michael J. Orchard

1992-01-01

8

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

9

Marine Geophysical Surveying Along the Hubbard Glacier Terminus, Southeast Alaska  

Microsoft Academic Search

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

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

2010-01-01

10

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

11

FLUCTUATIONS OF CRILLON GLACIER SYSTEM, SOUTHEAST ALASKA  

Microsoft Academic Search

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

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

1963-01-01

12

Mass balance, runoff and surges of Bering Glacier, Alaska  

NASA Astrophysics Data System (ADS)

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

Tangborn, W.

2013-05-01

13

Surge dynamics on Bering Glacier, Alaska, in 2008-2011  

NASA Astrophysics Data System (ADS)

A 2008-2011 surge of Bering Glacier, Alaska is examined using observations of surface velocity and surface elevation change. Velocity measurements are obtained using synthetic aperture radar (SAR) offset tracking and elevation data are obtained from the University of Alaska Fairbanks LiDAR altimetry program. Bering Glacier began to surge in May 2008 and had two phases of accelerated flow. The first phase accelerated progressively for at least 10 months and reached peak observed velocities of ~7 m d-1. Results suggest that during the quiescent phase, prior to the surge, periods of accelerated flow increased driving stresses up to 70% in a ~10 km-long section of the Lower Bering. When the first phase of the surge initiated, synchronous acceleration occurred throughout much of the glacier length, indicating widespread pressurization of the bed, but the largest accelerations initiated at the location where driving stress built up during quiescence. From there, rapid flow velocities propagated upstream and downstream across much of the glacier length and transpired as small, transient and unorganized propagation fronts. The second phase occurred in 2011 and was of comparable scale to the surge in 1993-1995, with velocities exceeding 9 m d-1 or ~18 times quiescent velocities.

Burgess, E. W.; Forster, R. R.; Larsen, C. F.; Braun, M.

2012-03-01

14

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

15

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

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

16

Reconnaissance hydrology of Portage Glacier basin, Alaska--1972  

USGS Publications Warehouse

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

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

1977-01-01

17

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

18

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

Microsoft Academic Search

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

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

2010-01-01

19

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

20

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

21

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

NASA Astrophysics Data System (ADS)

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

Korn, D.

2010-12-01

22

Rapid Wastage of Alaska Glaciers and Their Contribution to Rising Sea Level  

Microsoft Academic Search

We have used airborne laser altimetry to estimate volume changes of 67 glaciers in Alaska from the mid-1950s to the mid-1990s. The average rate of thickness change of these glaciers was -0.52 m\\/year. Extrapolation to all glaciers in Alaska yields an estimated total annual volume change of -52 +\\/- 15 km3\\/year (water equivalent), equivalent to a rise in sea level

Anthony A. Arendt; Keith A. Echelmeyer; William D. Harrison; Craig S. Lingle; Virginia B. Valentine

2002-01-01

23

High porosity of basal till at Burroughs glacier, southeastern Alaska  

SciTech Connect

Debris-rich basal ice at Burroughs glacier, southeastern Alaska, has 60 vol% to 70 vol% debris. Recently deposited basal till exceeds 60 vol% sediment with 30% to almost 40% porosity. Where basal ice is very rich in debris, basal till is deposited through melt out with only slight compaction of the debris. Porosity this high in till is commonly associated with subglacially deforming and dilated sediment. However, the recently deposited basal melt-out till at Burroughs glacier has not been deformed after deposition, but has porosity values similar to tills elsewhere interpreted to be subglacially deforming and dilated in an unfrozen state. High porosity can occur in basal melt-out till deposited directly by basal melt out.

Ronnert, L.; Mickelson, D.M. (Univ. of Wisconsin, Madison (United States))

1992-09-01

24

Ice Penetrating Radar Sounding Over Glaciers in Alaska and Greenland  

NASA Astrophysics Data System (ADS)

Using low-frequency (1-5 MHz) ice penetrating radar, we have measured the thickness of "warm" ice over outlet glaciers in Alaska and Greenland. The radar mainly consists of control software for National Instrument (NI) boards, a custom-made transmitter, a receiver, and an antenna towed at the back of an airplane. The radar can operate with either a short or a chirp exciter pulse. The same antenna receives echoes bounced from the surface and sub-surface ice layers. The echoes are digitized after being passed through a band-pass filter. We have run the radar in burst mode so that there is no pulse in air while receiving the echoes. To make a radar sounder image, multiple bursts are vertically stacked together in a 2-dimensional format named as echogram. The horizontal axis corresponds to aircraft motion, while the vertical axis corresponds to the arrival time inside a burst. Because the transmitted signal is reflected from various interfaces at different distances, the received echo has multiple peaks. The earliest and strongest peak is caused by the interface between the atmosphere and ice surface. It is very sharp for a flat surface, while becoming diffusive and relatively weak for a rough or sloped surface. After the initial rise, more complex and weak echoes follow. These are caused by various sources such as subsurface deposits, discontinuities in dielectric layers, and, most often, off-nadir surface reflections called surface clutter. We have applied an omega-k method to reduce the along-track surface clutter and thereby enhance the sub-surface features. In this way, we have been able to see 1.5 km deep ice bed at Jakobshavn glacier in Greenland and about 1 km deep glacier bed at Bering Glacier in Alaska. This radar is still in the development and improvement stage, and is expected to continue providing complementary data to existing airborne radar sounders.

Gim, Y.; Safaeinili1, A.; Rignot, E.; Kirchner, D.; Robison, W.

2008-12-01

25

Probing the till beneath Black Rapids Glacier, Alaska, USA  

NASA Astrophysics Data System (ADS)

A heavy down-hole hammer actuated from the surface by a light composition rope was used to place instrumented probes into the active, 7 m thick, clast-rich till underlying a site on Black Rapids Glacier, Alaska, USA, where the ice is 500 m thick. A till penetration of about 2.5 m was obtained, and greater depths seem possible. The probes measured pore-water pressure and two axes of tilt, which they broadcasted, without wires, to a receiver just above the ice till interface.

Harrison, William D.; Truffer, Martin; Echelmeyer, Keith A.; Pomraning, Dale A.; Abnett, Kevin A.; Ruhkick, Richard H.

26

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

NASA Astrophysics Data System (ADS)

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

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

27

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

USGS Publications Warehouse

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

U.S. Geological Survey

2009-01-01

28

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

29

Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise  

Microsoft Academic Search

The digital elevation model (DEM) from the 2000 Shuttle Radar Topography Mission (SRTM) was differenced from a composite DEM based on air photos dating from 1948 to 1987 to determine glacier volume changes in southeast Alaska and adjoining Canada. SRTM accuracy was assessed at +\\/-5 m through comparison with airborne laser altimetry and control locations measured with GPS. Glacier surface

Christopher F. Larsen; Roman J. Motyka; Anthony A. Arendt; Keith A. Echelmeyer; Paul E. Geissler

2007-01-01

30

Medial moraines of glaciers of the Copper River Basin, Alaska: Discrete landslides dominate over other sources  

Microsoft Academic Search

Medial moraines are visually dominant structures of most large valley glaciers in the Copper River Basin (CRB), Alaska. Areally extensive but thin (usually <20 cm) accumulations of debris pose challenges for glacier mapping based on multispectral imagery, as done, for instance, in the GLIMS project. The sources of this material include large discrete landslides from wallrocks and from lateral moraines;

J. S. Kargel; L. Fischer; R. Furfaro; C. Huggel; O. Korup; G. J. Leonard; M. Uhlmann; R. L. Wessels; D. F. Wolfe

2009-01-01

31

Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise  

Microsoft Academic Search

The digital elevation model (DEM) from the 2000 Shuttle Radar Topography Mission (SRTM) was differenced from a composite DEM based on air photos dating from 1948 to 1987 to determine glacier volume changes in southeast Alaska and adjoining Canada. SRTM accuracy was assessed at ±5 m through comparison with airborne laser altimetry and control locations measured with GPS. Glacier surface

Christopher F. Larsen; Roman J. Motyka; Anthony A. Arendt; Keith A. Echelmeyer; Paul E. Geissler

2007-01-01

32

Airborne Laser Altimetry Measurements of Glacier Wastage in Alaska and NW Canada  

NASA Astrophysics Data System (ADS)

Laser altimetry elevation profiles of glaciers in NW North America (Alaska, Yukon, and NW British Columbia) have been collected by the University of Alaska Geophysical Institute (UAF-GI) beginning in 1993. Since then, more than 200 glaciers throughout NW North America have been measured, many of them multiple times with typical repeat intervals of 3 to 5 years. All of the largest glaciers here have been profiled, including at least some representative glaciers from every major icefield in NW North America. Over 40 glaciers were surveyed again in the summer of 2009, a significant and unusually large annual addition to our database of surface elevation changes. Beginning in August 2009 we flew the surveys using the new UAF-GI swath mapping LiDAR system which records a 0.5 km wide 3-d map of survey points on an approximately 1 m x 1 m grid along the glacier centerlines. Over 40 glaciers and icefields have now been surveyed 3 or more times over the past 15 years, and these regions have been analyzed for changes in their rates of wastage. These regions include the Stikine Icefield of southeast Alaska, the Columbia Glacier, the Bering-Bagley and Seward-Malaspina systems, the Yakutat Icefield, Glacier Bay, the Harding Icefield, and the Alaska Range. Increased melt rates are generally observed over the most recent 3 to 5 year interval when compared to the previous 5 to 10 years, with many glaciers experiencing a factor of two or greater in their recent area-averaged thinning rates. Hypsometry appears to be a significant factor, with those areas that have relatively low average elevation and low accumulation areas showing stronger effects of the accelerated thinning. In particular, those icefields near the Gulf of Alaska coast, such as the Yakutat, Harding and Brady Icefields, are now rapidly wasting. A few areas that have relatively high elevation accumulation areas appear to have steady rates of thinning, such as within the St. Elias Mountains.

Larsen, C. F.; Hock, R. M.; Arendt, A. A.; Zirnheld, S. L.

2009-12-01

33

Probing the till beneath Black Rapids Glacier, Alaska  

NASA Astrophysics Data System (ADS)

Black Rapids is a surge-type glacier in the Alaska Range which last surged in 1936. Seismic studies and wire-line drilling have shown that its central, most active part, is underlain by several meters of till, processes in which account for more than half of the present surface motion. We recently developed a 400 kg down-hole hammer system to place instrumented probes as deeply as possible into the till. The hammer is operated from the surface with a cathead and a composition rope. In 2002 we penetrated about 2.5 m into the till under 500 m of ice. To circumvent problems with probe placement and survival of communication with the surface, the probes are wireless and broadcast pressure and two axes of tilt data to a down-hole receiver placed slightly above the ice-till interface. Results from two probes in separate holes 4.1 m apart showed almost identical, complex patterns of tilt rate, relativey quiescent periods punctuated by rapid tilt events. One tilt event was accompanied by an almost 90 degree change in the direction of tilt. The tilt events show some correlation with motion events measured at the surface.

Harrison, W.; Trufffer, M.

2003-04-01

34

Bursts of calving activity and controls on the terminus position of Yahtse Glacier, Alaska  

NASA Astrophysics Data System (ADS)

The tidewater glacier terminus is the interface that links oceanic and glaciological processes. Tidewater glaciers contribute large amounts of cold, fresh water to their fjords. Ocean heat exerts a significant control on glacier mass balance. On the Gulf of Alaska, the terminus of tidewater Yahtse Glacier has advanced slowly since its 1990 post-Little Ice Age minimum. At Yahtse's terminus, ice flowing at 18 m/d encounters water with temperatures of up to 10.5°C (measured 1.5 km from the terminus). Profiles of temperature and salinity in Icy Bay, in which Yahtse Glacier terminates, have revealed a strongly stratified, single-cell circulation pattern. Fresh, glacier outflow exits the bay atop warm, saline Gulf of Alaska water. The Alaska Coastal Current, a major source of Icy Bay water, has warmed by 1°C over the last 40 years. These observations prompt the question of how a tidewater advance may be sustained in spite of warming ocean and atmosphere temperatures. Superimposed on Yahtse Glacier's longer-term advance have been smaller-scale summer retreats and winter-spring re-advances. These smaller fluctuations indicate that factors that change on short timescales, such as ocean conditions and weather, also have an important control on terminus position. Observed bursts in calving frequency are a further reflection of the unsteady conditions at the glacier terminus. In the present study, we use seismograms recorded on bedrock within 500 m of the glacier terminus as a calving counter. The epicenters of a significant majority of glacier-generated seismic events within the St. Elias Mountains have been located to within 15 km of the terminus of Yahtse Glacier. Previous study at Yahtse Glacier has revealed that at least 75% of these seismic events originate from calving processes, most notably through the interactions between iceberg and water. Calving frequency is characterized by a relatively steady rate of background events, punctuated by bursts of calving activity. These bursts are correlated with rain-associated speed-ups that are present along at least 75% of the glacier length. Our analysis of these results considers the relative importance of three potential calving-related processes: along-glacier coupling in glacier flow that forces ice off the end of a submarine terminal moraine, submarine melt and undercutting of the terminus, and enhanced subaerial melt of serac pillars by rainwater that weakens the foundations of these pillars.

Bartholomaus, T. C.; Larsen, C. F.; West, M. E.; Oneel, S.

2011-12-01

35

Interpretation of fine and coarse sediment yield from Bench Glacier, Alaska  

Microsoft Academic Search

Quantifying the rate of bedrock erosion by glaciers is crucial to our understanding of alpine landscape evolution. We document basin-averaged sediment evacuation for three summers at the 7-km-long Bench Glacier, Alaska, based on 15-minute gaging of stream stage and turbidity, together with manual sampling of sediment concentrations and bedload transport in the exit stream. Sediment evacuation was equivalent to 1-2

C. A. Riihimaki; K. R. MacGregor; R. S. Anderson; S. P. Anderson; M. G. Loso

2003-01-01

36

Holocene climate and glacier variability at Hallet and Greyling Lakes, Chugach Mountains, south-central Alaska  

Microsoft Academic Search

Evidence from lake sediments and glacier forefields from two hydrologically isolated lake basins is used to reconstruct Holocene\\u000a glacier and climate history at Hallet and Greyling Lakes in the central Chugach Mountains of south-central Alaska. Glacial\\u000a landform mapping, lichenometry, and equilibrium-line altitude reconstructions, along with changes in sedimentary biogenic-silica\\u000a content, bulk density, and grain-size distribution indicate a dynamic history of

Nicholas P. McKay; Darrell S. Kaufman

2009-01-01

37

Continuous profiles of electromagnetic wave velocity and water content in glaciers: an example from Bench Glacier, Alaska, USA  

Microsoft Academic Search

We conducted two-dimensional continuous multi-offset georadar surveys on Bench Glacier, south-central Alaska, USA, to measure the distribution of englacial water. We acquired data with a multichannel 25 MHz radar system using transmitter-receiver offsets ranging from 5 to 150 m. We towed the radar system at 5-10 km h-1 with a snow machine with transmitter\\/receiver positions established by geodetic-grade kinematic differentially

John H. Bradford; Joshua Nichols; T. Dylan Mikesell; Joel T. Harper

2009-01-01

38

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

Microsoft Academic Search

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

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

1985-01-01

39

Glacier mass-balance fluctuations in the Pacific Northwest and Alaska, USA  

NASA Astrophysics Data System (ADS)

The more than 40 year record of net and seasonal mass-balance records from measurements made by the United States Geological Survey on South Cascade Glacier, Washington, and Wolverine and Gulkana Glaciers, Alaska, shows annual and interannual fluctuations that reflect changes in the controlling climatic conditions at regional and global scales. As the mass-balance record grows in length, it is revealing significant changes in previously described glacier mass-balance behavior, and both inter-glacier and glacier-climate relationships. South Cascade and Wolverine Glaciers are strongly affected by the warm and wet maritime climate of the northeast Pacific Ocean. Their net balances have generally been controlled by winter accumulation, with fluctuations that are strongly related to the Pacific Decadal Oscillation (PDO). Recently, warm dry summers have begun to dominate the net balance of the two maritime glaciers, with a weakening of the correlation between the winter balance fluctuations and the PDO. Non-synchronous periods of positive and negative net balance for each glacier prior to 1989 were followed by a 1989-2004 period of synchronous and almost exclusively negative net balances that averaged -0.8 m for the three glaciers.

Josberger, Edward G.; Bidlake, William R.; March, Rod S.; Kennedy, Ben W.

2007-10-01

40

Assessing the Response of Alaska's Glaciers to Post-Little Ice Age Climate Change  

NASA Astrophysics Data System (ADS)

A comprehensive survey of the eleven mountain ranges and three island areas in Alaska that presently support glaciers was conducted to determine how glaciers in each area have responded to post-Little Ice Age (LIA) climate change. Today, glaciers cover 5 percent of Alaska, about 75,000 sq. km., range in elevation from 6,000 m to below sea level, and span latitudes from south of 55 degrees N to north of 69 degrees N. During the LIA, Alaskan glaciers expanded significantly, covering 10 percent more area than today. Many different types of data were used to construct baselines and determine glacier change. These include: published descriptions of glaciers (1794 - 2000), historic and modern maps (1794 - 2000), aerial photography (1926 - 2001), ground photography (1884 - 2001), airborne radar (1981 - 1991), satellite radar (1978 - 1998), space photography (1984 - 1994), multi-spectral satellite imagery (1972 - 2001), aerial reconnaissance and field observations by the author (1968 - 2001), and various types of proxy data. Data available varied for each region and glacier. Every mountain range and island group investigated is characterized by significant glacier retreat, thinning, and/or stagnation, especially at lower elevations. At some locations, glaciers have completely disappeared during the twentieth century. In other areas, retreat that started as early as the early eighteenth century, has continued into the twenty-first century. Ironically, in several areas, retreat is resulting in the number of glaciers is actually increasing, but the volume and area of ice is decreasing. The key survey findings are: ALEXANDER ARCHIPELAGO, KODIAK ISLAND, ALEUTIAN ISLANDS: every glacier examined showed evidence of thinning and retreat. Some have disappeared since last being mapped in the mid-twentieth century; COAST MOUNTAINS, ST. ELIAS MOUNTAINS, CHUGACH MOUNTAINS, KENAI MOUNTAINS, WRANGELL MOUNTAINS, ALASKA RANGE, AND THE ALEUTIAN RANGE: more than 95 percent of glaciers ending below an elevation of 1,500 m are retreating, thinning, and/or stagnating. Some advancing glaciers have tidewater termini. The two largest glaciers, Bering and Malaspina Glaciers, are thinning and retreating, losing several cubic kilometers of ice each year to melting and calving; TALKEETNA MOUNTAINS, AHKLUN-WOOD RIVER MOUNTAINS, KIGLUAIK MOUNTAINS, AND THE BROOKS RANGE: every glacier examined is retreating. Some disappeared during the twentieth century. Glaciers at higher elevations show little or no change. Perhaps, at these locations, regional climate change has not resulted in temperatures being elevated to a level where they impact existing glacier ice. Increases in precipitation may also be compensating for increases in melting. Throughout Alaska, in response to post-Little Ice Age climate change, all but a few glaciers that descent below an elevation of 1,500 m have thinned, stagnated, and/or retreated. Of the nearly 700 named Alaskan glaciers, less than a dozen are currently advancing.

Molnia, B. F.

2001-12-01

41

Mass-Balance Fluctuations of Glaciers in the Pacific Northwest and Alaska, USA  

NASA Astrophysics Data System (ADS)

The mass balance of mid-latitude glaciers of the Pacific Northwest and southern Alaska fluctuates in response to changes in the regional and global atmospheric climate. More than 40 years of net and seasonal mass balance records by the U.S. Geological Survey for South Cascade Glacier, Washington, and Wolverine and Gulkana Glaciers, Alaska, show annual and inter-annual fluctuations that reflect the controlling climatic conditions. South Cascade and Wolverine Glaciers are strongly affected by the warm and wet maritime climate of the Northeast Pacific Ocean, and the winter balances are strongly related to the Pacific Decadal Oscillations (PDO). Gulkana Glacier is more isolated from maritime influences and the net balance variation is more closely linked to the summer balance. By the late 1970's, mass-balance records for the three were long enough to reflect the 1976-77 shift in PDO from negative to positive. Both maritime glaciers responded, with net balance of South Cascade Glacier becoming consistently negative and that of Wolverine Glacier becoming predominantly positive. The overall trend of negative mass balance continued through 2004 for South Cascade Glacier, where the 1977 to 2004 cumulative net balance was about -22 meters water equivalent (mweq). After a gain of about 7 mweq, the trend of positive net balance for Wolverine Glacier ended in 1989. Beginning in 1989, the net balance trend for Wolverine Glacier became predominantly negative and the cumulative net balance for 1989 to 2004 was about -14 mweq. Net balance of Gulkana Glacier did not respond appreciably to the 1976-77 PDO shift. The cumulative net balance for Gulkana Glacier from the beginning of the record (1966) through 1988 was about -3 mweq. The major change in trend of mass balance occurred in 1989, when net balance became almost exclusively negative. The cumulative net balance during 1989 through 2004 was about 13 mweq. As a result trends in net balance had become strongly negative for more than a decade at all three bench mark glaciers.

Josberger, E. G.; Bidlake, W. R.; March, R. S.; Kennedy, B. W.

2006-12-01

42

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

NSDL National Science Digital Library

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

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

43

Contribution of glacier runoff to freshwater discharge into the Gulf of Alaska  

Microsoft Academic Search

Watersheds along the Gulf of Alaska (GOA) are undergoing climate warming, glacier volume loss, and shifts in the timing and volume of freshwater delivered to the eastern North Pacific Ocean. We estimate recent mean annual freshwater discharge to the GOA at 870 km3 yr?1. Small distributed coastal drainages contribute 78% of the freshwater discharge with the remainder delivered by larger

Edward G. Neal; Eran Hood; Kathy Smikrud

2010-01-01

44

Contribution of glacier runoff to freshwater discharge into the Gulf of Alaska  

Microsoft Academic Search

Watersheds along the Gulf of Alaska (GOA) are undergoing climate warming, glacier volume loss, and shifts in the timing and volume of freshwater delivered to the eastern North Pacific Ocean. We estimate recent mean annual freshwater discharge to the GOA at 870 km3 yr-1. Small distributed coastal drainages contribute 78% of the freshwater discharge with the remainder delivered by larger

Edward G. Neal; Eran Hood; Kathy Smikrud

2010-01-01

45

Macroinvertebrate community succession in Wolf Point Creek, Glacier Bay National Park, Alaska  

Microsoft Academic Search

SUMMARY 1. Macroinvertebrate community development in Wolf Point Creek in Glacier Bay National Park, Alaska formed by ice recession was investigated from 1991 to 1994 as part of a long-term study of colonization now exceeding 20 years. Chironomidae, the first taxon to colonize the stream, still dominated the community comprising 75-95% by number, but species succession was apparent. 2. Species

E. A. Flory; A. M. MILNERyz

2000-01-01

46

An update on surge-type glaciers and spatial constraint of surge behavior in the Alaska Range  

NASA Astrophysics Data System (ADS)

The Alaska Range is host to many surge-type glaciers as originally identified by Post in the 1960s. A reanalysis of Post's Alaska Range surge-type glacier inventory and updates by Wilbur and Clarke has been compiled from the literature, USGS maps, nadir and oblique aerial photographs and satellite imagery with a combined time span of 1949 to 2011. Glaciers in the Alaska Range show a spectrum of surge behavior, from episodic "pulsing" (or acceleration) of a tributary glacier into a major glacier trunk, to full glacier participation resulting in kilometers of displacement. To address this spectrum a classification scheme was developed and applied to show both magnitude of surge behavior and provide a confidence index of surge-type glacier identification. Of the 356 glaciers in the Alaska Range with a surface area greater than 1 km2, 28 glaciers comprising 38% of the total glacier surface area show some degree of surge behavior. 19 major surge events have been observed or temporally constrained with imagery. To better spatially constrain surge behavior, tributary branches of surge-type glaciers were assessed individually for surge participation. The extent of displacement from the most recent surge was identified from surface expressions where possible. Pre- and post-surge moraine structures for glaciers known to have major surges since the 1990s were mapped, illustrating ice displacement and the evolution of glacier geometry during the quiescent phase. Moraine geometries of Black Rapids and Susitna glaciers were also mapped. Both are well studied glaciers whose predicted surges have not occurred. Elevation data collected along a centerline of Yanert Glacier before and after a surge in 2000-01 show a mass transfer of (6.2 ± 0.3) x 10^8 m3. These data also show the location of the hinge line or boundary between reservoir and receiving areas. Using these data as well as additional direct hinge line measurements made in the Alaska Range and elsewhere in Alaska, a 70/30 surface area ratio between the reservoir and receiving areas was derived. This ratio was applied to surge-type glaciers in the Alaska Range lacking direct hinge line measurements. We propose that knowing the location of the hinge line can aid surge forecasting.

Herreid, S. J.; Truffer, M.; Harrison, W. D.; Hock, R. M.

2011-12-01

47

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.

48

Bering Glacier, Alaska: Uncertainty in estimation of mass balance in response to climate  

NASA Astrophysics Data System (ADS)

Bering Glacier, the largest in Alaska, is a complex glacier system comprising multiple drainage basins, numerous individual ice streams, and many accumulation areas. Estimates of the total surface area for Bering Glacier vary from 1740 km2 to 6200 km2, varying according to how the boundaries of this system have been defined. The determination of mass balance and volume change is subject to significant error if the outlines that define Bering Glacier are incorrect. We have completed a new outline and area-altitude distribution (hypsometry) of Bering Glacier. We compared this new outline with three previous outlines to illustrate the inconsistencies in total area. Integration of all four outlines with modeled mass balance (PTAA Model and Template Method) reveals the errors that arise when utilizing outlines that differ significantly. Our analysis shows that the use of different Bering Glacier outlines results in widely divergent estimates of annual mass balances (-1.0 m to -4.4 m water equivalent). We conclude that studies predicting the response of Bering and other glaciers to climate change may be inaccurate.

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

2006-12-01

49

Medial moraines of glaciers of the Copper River Basin, Alaska: Discrete landslides dominate over other sources  

NASA Astrophysics Data System (ADS)

Medial moraines are visually dominant structures of most large valley glaciers in the Copper River Basin (CRB), Alaska. Areally extensive but thin (usually <20 cm) accumulations of debris pose challenges for glacier mapping based on multispectral imagery, as done, for instance, in the GLIMS project. The sources of this material include large discrete landslides from wallrocks and from lateral moraines; diffuse contributions from rock falls and talus creep; rocks delivered via snow and ice avalanches; ingestion of lateral moraines along tributary convergences; and basal erosional debris. Evidence indicates that in CRB glaciers, discrete large avalanches predominate as the major contributors of moraine mass. Subglacial erosional debris is predominantly pulverized to small grain sizes and flushed. Many large, young avalanches exist on CRB glaciers. Evidence from colorimetry indicates that many medial moraines actually are landslides that have been sheared and swept downglacier, thus mimicking the form of other types of medial moraines formed where tributaries coalesce and flow down valley. Landcover classification of ASTER imagery, qualitative observations from air photos, and semiquantitative field-based estimations of rock color types indicate that on Allen Glacier, and other CRB glaciers, landslides are the sources of most medial moraines. On Allen and Root Glacier, for example, we see very few boulders with obvious signs of basal abrasion, whereas nearly all boulders exhibit signs of irregular fracture, for example in landslides. Such landslides have large effects on the thermal and mass balance of CRB glaciers, sometimes opposing or in other cases accentuating the effects of global/regional climate change. Considering the link between landslides and seismicity, and that Magnitude 8-9 earthquakes may occur nearby only about once a century, which is also the characteristic response time of large glaciers to climate shifts, seismicity must be considered along with climate change induced glacier responses in the CRB. Ultimately, climate has the final word, and already this is evident in the glacier record. Glacial flour is probably almost entirely from bed erosion. We will present estimates of the contributions of landslides and subglacially pulverized glacial rock flour to the overall rock mass budget of Allen Glacier. Each of the components of the rock mass budget differs in its probable distribution on the surface and within a typical glacier. We will present some preliminary empirical determinations of the influence of various thicknesses of supraglacial rock debris on the local mass balance of Allen Glacier; the net zero influence is exhibited for debris thicknesses on the order of 1 cm of fine debris or ~50% coverage by cobbles or boulders.

Kargel, J. S.; Fischer, L.; Furfaro, R.; Huggel, C.; Korup, O.; Leonard, G. J.; Uhlmann, M.; Wessels, R. L.; Wolfe, D. F.

2009-12-01

50

Metagenome Sequencing of Prokaryotic Microbiota Collected from Byron Glacier, Alaska  

PubMed Central

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

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

2013-01-01

51

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

USGS Publications Warehouse

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

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

2008-01-01

52

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

NASA Astrophysics Data System (ADS)

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

Nolan, M.; Takahashi, S.

2004-12-01

53

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

USGS Publications Warehouse

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

Trabant, Dennis C.; Hawkins, Daniel B.

1997-01-01

54

Coupling between Primary Terrestrial Succession and the Trophic Development of Lakes at Glacier Bay, Alaska  

Microsoft Academic Search

The natural eutrophication of lakes is still an accepted concept in limnology, arising as it does from the earliest efforts\\u000a to classify lakes and place them in an evolutionary sequence. Recent studies of newly formed lakes at Glacier Bay, Alaska,\\u000a only partially support this idea, and suggest more variable trends in lake trophic development which are under local (catchment-level)\\u000a control.

D. R. Engstrom; S. C. Fritz

2006-01-01

55

Geologic characteristics of benthic habitats in Glacier Bay, southeast Alaska  

USGS Publications Warehouse

In April 2004, more than 40 hours of georeferenced submarine digital video was collected in water depths of 15-370 m in Glacier Bay to (1) ground-truth existing geophysical data (bathymetry and acoustic reflectance), (2) examine and record geologic characteristics of the sea floor, and (3) investigate the relation between substrate types and benthic communities, and (4) construct predictive maps of seafloor geomorphology and habitat distribution. Common substrates observed include rock, boulders, cobbles, rippled sand, bioturbated mud, and extensive beds of living horse mussels and scallops. Four principal sea-floor geomorphic types are distinguished by using video observations. Their distribution in lower and central Glacier Bay is predicted using a supervised, hierarchical decision-tree statistical classification of geophysical data.

Harney, Jodi N.; Cochrane, Guy R.; Etherington, Lisa L.; Dartnell, Pete; Golden, Nadine E.; Chezar, Hank

2006-01-01

56

Expanding Peatlands in Alaska Caused by Accelerated Glacier Melting Under a Warming Climate  

NASA Astrophysics Data System (ADS)

Most mountain glaciers worldwide have been retreating over the last century due to global warming. This is particularly true around the Gulf of Alaska, where glacier recession has further accelerated since 1988. It is well known that glacier meltwater plays a critical role in the global sea level rise, but its effects on structure and functioning of peatland ecosystems remain poorly understood. We have observed in the field that many peatlands in the Susitna Basin, south-central Alaska, are expanding. As high moisture conditions are needed to promote peatland development and expansion, a regional change toward wetter conditions is likely responsible for the ongoing paludification of these peatlands. However, instrumental climatic data from this region show no increase in precipitation but an increase in temperature (and presumably evaporation) over the last decades. We hypothesize that climatically-induced glacier melting is modifying the local/regional climate, especially air humidity during the growing season, promoting the expansion of peatlands. To document recent peatland vertical growth and lateral expansion, we collected two long peat cores and twelve 30-cm-long monoliths in 2008 along a 110-m transect from an expanding peatland margin toward the peatland center. Ecohydrologic changes were reconstructed from testate amoebae and plant macrofossils assemblages. Preliminary results from both long cores revealed a change in the vegetation assemblages from a mesotrophic fen dominated by sedges and brown mosses to a Sphagnum-dominated peat bog at 11 cm, suggesting a very recent modification of the local hydrologic regime. A simultaneous increase in moisture was reconstructed from testate amoebae records. These unusual shifts in peatland development and hydrology (e.g., wet conditions triggering the fen-bog transition) imply a recent increase of atmospheric water to these peatlands. Our ongoing lead-210 dating and additional proxy analysis will help us resolve the timing and nature of recent peatland changes. These data, together with glacier history and climate records, will allow us to further test our hypothesis that the increase in glacier meltwater is causing peatland expansion By acting as water sinks, peatlands located in glacierized watersheds may mediate the contribution of meltwater to present and future sea-level rise. Increases in peat accumulation rates due to favorable hydroclimatic conditions are also expected to promote carbon sequestration by these ecosystems. In contrast to the expected desiccation of peatlands under a warmer climate, enhanced growth due to glaciers-climate feedbacks in high-latitude regions may thus promote peatland expansion, even just temporally.

Loisel, J.; Yu, Z.; Jones, M. C.

2009-05-01

57

Oceanography of Glacier Bay, Alaska: Implications for biological patterns in a glacial fjord estuary  

USGS Publications Warehouse

Alaska, U.S.A, is one of the few remaining locations in the world that has fjords that contain temperate tidewater glaciers. Studying such estuarine systems provides vital information on how deglaciation affects oceanographic conditions of fjords and surrounding coastal waters. The oceanographic system of Glacier Bay, Alaska, is of particular interest due to the rapid deglaciation of the Bay and the resulting changes in the estuarine environment, the relatively high concentrations of marine mammals, seabirds, fishes, and invertebrates, and the Bay's status as a national park, where commercial fisheries are being phased out. We describe the first comprehensive broad-scale analysis of physical and biological oceanographic conditions within Glacier Bay based on CTD measurements at 24 stations from 1993 to 2002. Seasonal patterns of near-surface salinity, temperature, stratification, turbidity, and euphoric depth suggest that freshwater input was highest in summer, emphasizing the critical role of glacier and snowmelt to this system. Strong and persistent stratification of surface waters driven by freshwater input occurred from spring through fall. After accounting for seasonal and spatial variation, several of the external physical factors (i.e., air temperature, precipitation, day length) explained a large amount of variation in the physical properties of the surface waters. Spatial patterns of phytoplankton biomass varied throughout the year and were related to stratification levels, euphotic depth, and day length. We observed hydrographic patterns indicative of strong competing forces influencing water column stability within Glacier Bay: high levels of freshwater discharge promoted stratification in the upper fjord, while strong tidal currents over the Bay's shallow entrance sill enhanced vertical mixing. Where these two processes met in the central deep basins there were optimal conditions of intermediate stratification, higher light levels, and potential nutrient renewal. These conditions were associated with high and sustained chlorophyll a levels observed from spring through fall in these zones of the Bay and provide a framework for understanding the abundance patterns of higher trophic levels within this estuarine system. ?? 2007 Estuarine Research Federation.

Etherington, L. L.; Hooge, P. N.; Hooge, E. R.; Hill, D. F.

2007-01-01

58

Interannual to Decadal Variability in Climate and the Glacier Mass Balance in Washington, Western Canada, and Alaska*.  

NASA Astrophysics Data System (ADS)

The authors examine the net winter, summer, and annual mass balance of six glaciers along the northwest coast of North America, extending from Washington State to Alaska. The net winter (NWB) and net annual (NAB) mass balance anomalies for the maritime glaciers in the southern group, located in Washington and British Columbia, are shown to be positively correlated with local precipitation anomalies and storminess (defined as the rms of high-passed 500-mb geopotential anomalies) and weakly and negatively correlated with local temperature anomalies. The NWB and NAB of the maritime Wolverine glacier in Alaska are also positively correlated with local precipitation, but they are positively correlated with local winter temperature and negatively correlated with local storminess. Hence, anomalies in mass balance at Wolverine result mainly from the change in moisture that is being advected into the region by anomalies in the averaged wintertime circulation rather than from a change in storminess. The patterns of the wintertime 500-mb circulation and storminess anomalies associated with years of high NWB in the southern glacier group are similar to those associated with low NWB years at the Wolverine glacier, and vice versa.The decadal ENSO-like climate phenomenon discussed by Zhang et al. has a large impact on the NWB and NAB of these maritime glaciers, accounting for up to 35% of the variance in NWB. The 500-mb circulation and storminess anomalies associated with this decadal ENSO-like mode resemble the Pacific-North American pattern, as do 500-mb composites of years of extreme NWB of South Cascade glacier in Washington and of Wolverine glacier in Alaska. Hence, the decadal ENSO-like mode affects precipitation in a crucial way for the NWB of these glaciers. Specifically, the decadal ENSO-like phenomenon strongly affects the storminess over British Columbia and Washington and the moisture transported by the seasonally averaged circulation into maritime Alaska. In contrast, ENSO is only weakly related to NWB of these glaciers because (i) the large-scale circulation anomalies associated with ENSO do not produce substantial anomalies in moisture advection into Alaska, and (ii) the storminess and precipitation anomalies associated with ENSO are far to the south of the southern glacier group.Finally, the authors discuss the potential for short-term climate forecasts of the mass balance for the maritime glaciers in the northwest of North America.

Bitz, C. M.; Battisti, D. S.

1999-11-01

59

The dynamic response of Kennicott Glacier, Alaska, USA, to the Hidden Creek Lake outburst flood  

NASA Astrophysics Data System (ADS)

Glacier sliding is commonly linked with elevated water pressure at the glacier bed. Ice surface motion during a 3 week period encompassing an outburst of ice-dammed Hidden Creek Lake (HCL) at Kennicott Glacier, Alaska, USA, showed enhanced sliding during the flood. Two stakes, 1.2 km from HCL, revealed increased speed in two episodes, both associated with uplift of the ice surface relative to the trajectory of bed-parallel motion. Uplift of the surface began 12 days before the flood, initially stabilizing at a value of 0.25 m. Two days after lake drainage began, further uplift (reaching 0.4 m) occurred while surface speed peaked at 1.2 m d 1. Maximum surface uplift coincided with peak discharge from HCL, high water level in a down-glacier ice-marginal basin, and low solute concentrations in the Kennicott River. Each of these records is consistent with high subglacial water pressure. We interpret the ice surface motion as arising from sliding up backs of bumps on the bed, which enlarges cavities and produces bed separation. The outburst increased water pressure over a broad region, promoting sliding, inhibiting cavity closure, and blocking drainage of solute-rich water from the distributed system. Pressure drop upon termination of the outburst drained water from and depressurized the distributed system, reducing sliding speeds. Expanded cavities then collapsed with a 1 day time-scale set by the local ice thickness.

Anderson, Robert S.; Walder, Joseph S.; Anderson, Suzanne P.; Trabant, Dennis C.; Fountain, Andrew G.

60

Effects of the March 1964 Alaska earthquake on glaciers: Chapter D in The Alaska earthquake, March 27, 1964: effects on hydrologic regimen  

USGS Publications Warehouse

The 1964 Alaska earthquake occurred in a region where there are many hundreds of glaciers, large and small. Aerial photographic investigations indicate that no snow and ice avalanches of large size occurred on glaciers despite the violent shaking. Rockslide avalanches extended onto the glaciers in many localities, seven very large ones occurring in the Copper River region 160 kilometers east of the epicenter. Some of these avalanches traveled several kilometers at low gradients; compressed air may have provided a lubricating layer. If long-term changes in glaciers due to tectonic changes in altitude and slope occur, they will probably be very small. No evidence of large-scale dynamic response of any glacier to earthquake shaking or avalanche loading was found in either the Chugach or Kenai Mountains 16 months after the 1964 earthquake, nor was there any evidence of surges (rapid advances) as postulated by the Earthquake-Advance Theory of Tarr and Martin.

Post, Austin

1967-01-01

61

Southern Alaska as an example of the long-term consequences of mountain building under the influence of glaciers  

Microsoft Academic Search

Southern Alaska is a continent-scale region of ongoing crustal deformation within the Pacific–North American plate boundary zone. Glaciers and glacial erosion have dictated patterns of denudation in the orogen over the last ?5Myr. The orogen comprises three discrete topographic domains from south to north, respectively: (1) the Chugach\\/St. Elias Range; (2) the Wrangell Mountains; and (3) the eastern Alaska Range.

Andrew Meigs; Jeanne Sauber

2000-01-01

62

Overcharging the Subglacial Hydrologic Network: Sliding at Kennicott Glacier, Alaska, When Water Inputs Exceed Outputs  

NASA Astrophysics Data System (ADS)

Basal sliding of Kennicott Glacier, Alaska, occurs when water storage within the glacier is increasing. During the 2006 melt season, we deployed five GPS receivers on the ice surface along the glacier centerline, lake level sensors in four ice-marginal lakes, a stage sensor above the glacier outlet river, and temperature sensors on the ice surface. Outlet water chemistry was monitored with a conductivity sensor and near-daily water samples. These instruments allowed us to assess the relationship between ice motion and glacier hydrology at 1 hr or finer resolution and indicate that when water is entering the glacier faster than it drains out, ice surface velocity increases on both diurnal and seasonal timescales. The largest increase in ice surface speed occurred on a third timescale, that of the outburst of ice-dammed Hidden Creek Lake 15 km from the terminus. During the peak in rate of water storage in the glacier during the jokulhlaup, ice surface motion below the lake increased to 3.0 m/d, up to 6 times faster than non-flood times. Low solute concentrations in the river discharge from the terminus during periods of increasing storage support the view that water from the linked cavity system is prevented from leaving the subglacial hydrologic network by an over-pressurized conduit system. When water inputs exceed what conduits can transmit, the system develops backpressure, and the cavity-to-conduit hydraulic gradients expected in steady state are reversed. The pressurized conduits drive water into and increase pressure in the linked cavity system, promoting basal sliding. A simple numerical model, driven by a calculated water balance time series, predicts water partitioning between the subglacial and englacial reservoirs and ice motion at speeds that closely resemble the observed speeds. These observations and models suggest that persistent high melt rates will not sustain high sliding rates, as over time, the efficiency of the subglacial conduit system will increase. However, large discrete inputs of water to the bed can incite hydraulic transients and associated sliding, potentially explaining recent accelerations of the Greenland Ice Sheet, where rapid drainage of large melt ponds delivers water through cold polar ice.

Anderson, R. S.; Bartholomaus, T. C.; Anderson, S. P.

2007-12-01

63

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

64

Glaciers  

NASA Astrophysics Data System (ADS)

Glaciers are among the most beautiful natural wonders on Earth, as well as the least known and understood, for most of us. Michael Hambrey describes how glaciers grow and decay, move and influence human civilization. Currently covering a tenth of the Earth's surface, glacier ice has shaped the landscape over millions of years by scouring away rocks and transporting and depositing debris far from its source. Glacier meltwater drives turbines and irrigates deserts, and yields mineral-rich soils as well as a wealth of valuable sand and gravel. However, glaciers also threaten human property and life. Our future is indirectly connected with the fate of glaciers and their influence on global climate and sea level. Including over 200 stunning photographs, the book takes the reader from the High-Arctic through North America, Europe, Asia, Africa, New Zealand and South America to the Antarctic. Michael Hambrey is Director of the Centre for Glaciology at the University of Wales, Aberystwyth. A past recipient of the Polar Medal, he was also given the Earth Science Editors' Outstanding Publication Award for the first edition of Glaciers (Cambridge, 1995). Hambrey is also the author of Glacial Environments (British Columbia, 1994). JÜrg Alean is Professor of Geography at the Kantonsschule ZÜrcher Unterland in BÜlach, Switzerland.

Hambrey, Michael; Alean, Jürg

2004-12-01

65

Glaciers  

NSDL National Science Digital Library

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

2010-09-28

66

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

National Technical Information Service (NTIS)

Southern Alaska is a continent-scale region of ongoing crustal deformation within the Pacific-North American plate boundary zone. Glaciers and glacial erosion have dictated patterns of denudation in the orogen over the last approx. 5 My. The orogen compri...

A. Meigs J. Sauber

2000-01-01

67

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

SciTech Connect

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

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

1995-08-01

68

Integrated hydrologic and hydrochemical observations of Hidden Creek Lake jökulhlaups, Kennicott Glacier, Alaska  

NASA Astrophysics Data System (ADS)

Hidden Creek Lake (HCL), an ice-marginal lake impounded by Kennicott Glacier, Wrangell Mountains, Alaska, fills annually to ˜20 to 30 × 106 m3 and then drains subglacially within 2 to 3 days. During the 1999 and 2000 jökulhlaups, we carried out a series of planned observations around the lake and in the Kennicott River, which drains the glacier. Approximately 20% of the lake volume was contained within a subglacial water "wedge" beneath the ice dam. The entire volume of the lake drains through the wedge; hydraulic head loss through this constriction may be responsible for the fairly symmetrical shape of the HCL outflow hydrographs, deduced from lake level records, basin hypsometry, and collapse of the ice dam. The flood hydrographs in the Kennicott River are similar in shape to the outflow hydrographs, and within error, lake volume matched the river flood volume in both years. Up to 12 × 106 m3 of water was temporarily stored within the glacier during the 2000 jökulhlaup. During the 2000 jökulhlaup the background flow in the Kennicott River shifted to a dilute chemical composition. As the HCL jökulhlaup progressed, Donoho Falls Lake filled with water whose chemistry was closer to that of the background flow in Kennicott River than to HCL water. Comparison of these chemical signals with typical summer variations in Kennicott River chemistry suggests that the jökulhlaup created high subglacial water pressure that impeded normal drainage of solute-rich water from a distributed drainage system into a conduit system at the glacier bed and even caused flow direction locally to reverse.

Anderson, Suzanne P.; Walder, Joseph S.; Anderson, Robert S.; Kraal, Erin R.; Cunico, Michelle; Fountain, Andrew G.; Trabant, Dennis C.

2003-12-01

69

The role of changing synoptic circulation patterns on the climate of McCall Glacier, Alaska  

NASA Astrophysics Data System (ADS)

A recently funded project is seeking to relate ice core proxies from McCall Glacier, Alaska to climate change in northeastern Alaska over the past 250 years. One goal of this project is to relate changes in synoptic weather patterns to signals recorded in the ice core. A synoptic climatology for this region has been constructed based on atmospheric reanalysis data using the method of self-organizing maps (SOMs). The synoptic climatology has identified 35 sea level pressure patterns that describe the range of synoptic conditions that influence this area. Temperature and precipitation anomalies are calculated for each pattern providing a link between the synoptic patterns and warm or cold and wet or dry days which influence the signal recorded in the ice core. The synoptic climatology is also used to assess the role of varying synoptic weather pattern frequency to observed changes in temperature and precipitation over the past 50 years. This analysis has been applied to a shift in climate centered on 1976 and also on recent (past 15 years) changes in climate in Alaska. The ultimate goal of this project is to identify a relationship between the ice core proxies and changes in the frequency of synoptic weather patterns that influenced the area during the last 50 years. With this relationship we hope to develop a paleo-synoptic climatology based on the full 250 year record contained in the ice core.

Cassano, E.; Cassano, J. J.; Nolan, M.

2010-12-01

70

Alaska Fishery Research Bulletin. Volume 3, Number 1, Summer 1996.  

National Technical Information Service (NTIS)

Contents: Spot Shrimp Growth in Unakwik Inlet. Prince William Sound, Alaska; Abundance of the Chinook Salmon Escapement in the Taku River, 1989 to 1990; Relative Effects of Mixed Stock Fisheries on Specific Stocks of Concern: A Simplified Model and Brief ...

R. L. Wilbur

1996-01-01

71

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

72

Real-time Hydrologic Observations of Hidden Creek Lake Jökulhlaups, Kennicott Glacier, Alaska  

NASA Astrophysics Data System (ADS)

Few glacier outburst floods (jökulhlaups) have been monitored in detail as they occur. Hidden Creek Lake (HCL), an ice-marginal lake impounded by Kennicott Glacier, Wrangell Mountains, Alaska, fills annually to a volume of about 20 to 30 million m3 and then drains subglacially within about 2 to 3 days. In 1999, we measured lake-surface elevation, ice-dam deformation, and discharge in the Kennicott River (which drains the glacier) during the HCL outburst floods. In 2000 we collected comparable data beginning 3 weeks before lake drainage, and also measured flow in Hidden Creek, the main source of HCL water. Sources and sinks were in balance; any leakage from HCL prior to the 2000 jökulhlaup was too small to resolve. An important complication revealed by the deformation data was water storage in a "wedge" beneath the ice dam. During the 3 weeks before drainage in 2000, at least 1/3 of the total input to HCL went into the subglacial "wedge". The HCL outflow hydrograph was determined from lake-level records, basin hypsometry, and measured downdrop of the ice dam. In both 1999 and 2000, about 20% of the total water volume was stored in the subglacial "wedge". Both hydrographs were considerably more symmetrical about the peak than the canonical jökulhlaup hydrograph commonly mentioned in the literature. The relatively long tail on the outflow hydrograph may have been due to the fact that the entire lake had to evacuate through the subglacial "wedge", which became progressively more constricted with time. The flood hydrograph measured near the glacier terminus (16 km from the lake) is also fairly symmetrical. The flood peak in both years occurred about 12 h after the peak in the outflow hydrograph, implying a mean transit time of about 0.4 m/s. Integrated flood volume and lake volume agree fairly well in both years. Water-quality measurements are difficult to interpret: suspended sediment concentration in flood water peaked about 12 h before discharge, and the chemistry of flood waters is not readily explained by any sort of simple mixing models. As the HCL outburst flood progresses, Donoho Falls Lake--a normally dry ice-marginal basin that fills and drains during the HCL jökulhlaup--filled with water whose chemistry was closer to that of the background flow in Kennicott River than to HCL water, suggesting that the outburst flood created high subglacial water pressure that impeded normal drainage and even caused flow direction locally to reverse. Water levels recorded in boreholes also indicate the HCL jökulhlaup caused widespread disturbance in the glacier's pre-existing drainage system.

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

2002-12-01

73

Glaciological observations on McCall glacier, Alaska, in 2003-2004  

NASA Astrophysics Data System (ADS)

Glaciological observations were done on McCall glacier in Alaska in May, 2004. Snow and ice core sampling were done by a hand auger at 7 points along a line from a basin in accumulation area to a ridge. From this sampling a thickness change of firn layer was obtained, by which the formation of internally accumulated ice layer was outlined. Internal ice layers were detected by GPR (Ground Penetrating Radar), by which distribution of snow accumulation in the accumulation area was observed. By an image recorder, snow accumulation was observed everyday in a year. The maximum accumulation was about 1 m cm in snow depth, but it was all melt and the surface mass balance was negative in the accumulation area in 2003-2004.

Takahashi, S.; Satow, K.; Uetake, J.; Sato, K.; Nolan, M.; Igarashi, M.; Fuji, Y.

2005-12-01

74

Marine benthic habitat mapping of the West Arm, Glacier Bay National Park and Preserve, Alaska  

USGS Publications Warehouse

Seafloor geology and potential benthic habitats were mapped in West Arm, Glacier Bay National Park and Preserve, Alaska, using multibeam sonar, groundtruthed observations, and geological interpretations. The West Arm of Glacier Bay is a recently deglaciated fjord system under the influence of glacial and paraglacial marine processes. High glacially derived sediment and meltwater fluxes, slope instabilities, and variable bathymetry result in a highly dynamic estuarine environment and benthic ecosystem. We characterize the fjord seafloor and potential benthic habitats using the recently developed Coastal and Marine Ecological Classification Standard (CMECS) by the National Oceanic and Atmospheric Administration (NOAA) and NatureServe. Due to the high flux of glacially sourced fines, mud is the dominant substrate within the West Arm. Water-column characteristics are addressed using a combination of CTD and circulation model results. We also present sediment accumulation data derived from differential bathymetry. These data show the West Arm is divided into two contrasting environments: a dynamic upper fjord and a relatively static lower fjord. The results of these analyses serve as a test of the CMECS classification scheme and as a baseline for ongoing and future mapping efforts and correlations between seafloor substrate, benthic habitats, and glacimarine processes.

Hodson, Timothy O., Cochrane, Guy R.; Powell, Ross D.

2013-01-01

75

Hydrological discharges and ntotion of Fels and Black Rapids Glaciers, Alaska, U.S.A.: intplications for the structure of their drainage  

Microsoft Academic Search

Char acter istics of the hyd rology and mot ion of Black Rapids and Fels Glacier s, Alaska, were obse rved from 19 86 to 19 89. Hydro logical meas uremen ts incl uded stage, electrical conduct ivity and suspen ded-sedi ment concentr ation in the di scharge str eam of each glacier, and were made at 0. 5-1 h

W. D. HARRISON; K. A. ECHELMEYER; M. STURM

1995-01-01

76

Discovery of 100-160-year-old iceberg gouges and their relation to halibut habitat in Glacier Bay, Alaska  

USGS Publications Warehouse

Side-scan sonar and multibeam imagery of Glacier Bay, Alaska, revealed complex iceberg gouge patterns at water depths to 135 m on the floor of Whidbey Passage and south to the bay entrance. These previously undiscovered gouges likely formed more than 100 years ago as the glacier retreated rapidly up Glacier Bay. Gouged areas free of fine sediment supported greater biodiversity of Pacific halibut Hippoglossus stenolepsis than nearby sediment-filled gouges, probably due to increased habitat complexity. Small Pacific halibut were forund more frequently in sediment-free gouged areas, presumably due to higher prey abundance. In contrast, large Pacific halibut were found more frequently on soft substrates such as sediment-filled gouges, where they could bury themselves and ambush prey.

Carlson, P. R.; Hooge, P. N.; Cochrane, G. R.

2005-01-01

77

BED TOPOGRAPHY AND MASS-BALANCE DISTRIBUTION OF COLUMBIA GLACIER, ALASKA, U.S.A., DETERMINED FROM SEQUENTIAL AERIAL PHOTOGRAPHY  

Microsoft Academic Search

An internally consistent data set of geometry and flow variables for the lower part of Columbia Glacier, south-ce ntral Alaska, is derived entirely from vertical aerial photograph y. The principle of mass conservation is imposed on the data in the form of a centered finite-d ifference approxim ation of the continuity equation. It is applied on a 120-node section of

L. A. RASMUSSEN

1988-01-01

78

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

NASA Astrophysics Data System (ADS)

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

Rabus, Bernhard Theodor

79

Analysis of meteorological data and the surface energy balance of McCall Glacier, Alaska, USA  

NASA Astrophysics Data System (ADS)

We report on analysis of meteorological data for the period 27 May 20 August 2004, from two automatic weather stations on McCall Glacier, Alaska, USA, aimed at studying the relationship between climate and ablation. One station is located on a mountain ridge and the other in the ablation area where we also analyzed the energy balance. The weather station on the glacier measured an average temperature of 5.3°C (at 2 m height above surface) and wind speed of 3.1 m s-1 (at 3 m height). A sonic height ranger and ablation stakes indicate a specific mass balance of -1.94 ± 0.09 m w.e between 15 June and 20 August. The specific mass balance calculated from the surface energy balance, -2.06 ± 0.18 m w.e., is in close correspondence to this. The latter is the sum of 0.12 m w.e. of snowfall, 0.003 m w.e. of deposition and -2.18 m w.e. of melt. Net radiation contributes 74% of the melt energy. Compared to ablation measurements in the early 1970s, summer ablation was large. This increase is explained by a combination of a relatively higher net radiation, a lower albedo and larger turbulent heat fluxes that led to more energy being available for melting. No single meteorological variable can be isolated as being the principal reason for the high ablation, however. The lower ice albedo (0.19) is possibly due to ash deposits from forest fires.

Klok, E. J.; Nolan, M.; van den Broeke, M. R.

80

Volume change of McCall Glacier, Arctic Alaska, USA, 1956-2003  

NASA Astrophysics Data System (ADS)

A long history of research documents that McCall Glacier, Arctic Alaska, USA, continues to lose mass at a rate that is likely increasing with time. We present a photo comparison (1958-2003) that visually documents these volume changes, along with survey measurements that quantify these losses. Measurements of longitudinal profiles initially acquired from airborne laser altimetry, and repeated by ground-based surveys, indicate that the areally averaged rate of thinning increased between 1956-93 and 1993-2002, from 0.35 ± 0.07 m a-1 to 0.47 ± 0.03 m a-1, respectively; total volume loss was (8.3 × 107) ± (1.7 × 107) m3 and (2.7 × 107) ± (0.2 × 107) m3 (all in water equivalent) for these two time periods. These profiles also indicate that a 1 km stretch of the mid-ablation area is behaving differently from this trend, with a rate of thinning that is not changing with time. Lastly we present a comparison of several methods for calculating volume change and assess their relative errors.

Nolan, Matt; Arendt, Anthony; Rabus, Bernhard; Hinzman, Larry

81

Numerical modeling of the temperature and flow field of McCall Glacier, Alaska, constrained by borehole temperature data  

NASA Astrophysics Data System (ADS)

During IPY, an extensive field programme was set up on McCall Glacier, Alaska including borehole drilling to the bed at three locations. These holes were instrumented with a continuously-logging thermistor strings. Despite the low mean annual air temperatures (-10°C), temperate ice throughout the borehole in the accumulation area was observed, explained by the latent heat release due to refreezing of surface melt water in the firn. A 200m deep hole drilled in a cirque further down-glacier (2123m) shows that it is actually cooling substantially: the site has switched from accumulation to ablation area, ablating the firn away completely. This allows cold air temperatures to penetrate deeper in the ice, gradually cooling the upper part of the glacier. A third hole in the ablation area (1717m) is the coldest of all, though temperate at the bed because of large frictional heating rates due to basal sliding. Using a 3D higher-order thermodynamical model we simulated the time-dependent increase in equilibrium line altitude and associated reduction of the accumulation area. The temperature profiles were used as constraints to control the change from warm to cold conditions in the upper part of the glacier. Further constraints stem from accumulation/ablation measurements as well as repeat surface velocity measurements along the central flowline of the glacier. Results of these experiments show that the cooling trend in the lower cirque is going on for at least 40 years, which is corroborated by previous mass balance reconstructions of the glacier.

Delcourt, Charlotte; Pattyn, Frank; Nolan, Matt

2010-05-01

82

The Neoglacial landscape and human history of Glacier Bay, Glacier Bay National Park and Preserve, southeast Alaska, USA  

USGS Publications Warehouse

The Neoglacial landscape of the Huna Tlingit homeland in Glacier Bay is recreated through new interpretations of the lower Bay's fjordal geomorphology, late Quaternary geology and its ethnographic landscape. Geological interpretation is enhanced by 38 radiocarbon dates compiled from published and unpublished sources, as well as 15 newly dated samples. Neoglacial changes in ice positions, outwash and lake extents are reconstructed for c. 5500?????"200 cal. yr ago, and portrayed as a set of three landscapes at 1600?????"1000, 500?????"300 and 300?????"200 cal. yr ago. This history reveals episodic ice advance towards the Bay mouth, transforming it from a fjordal seascape into a terrestrial environment dominated by glacier outwash sediments and ice-marginal lake features. This extensive outwash plain was building in lower Glacier Bay by at least 1600 cal. yr ago, and had filled the lower bay by 500 cal. yr ago. The geologic landscape evokes the human-described landscape found in the ethnographic literature. Neoglacial climate and landscape dynamism created difficult but endurable environmental conditions for the Huna Tlingit people living there. Choosing to cope with environmental hardship was perhaps preferable to the more severely deteriorating conditions outside of the Bay as well as conflicts with competing groups. The central portion of the outwash plain persisted until it was overridden by ice moving into Icy Strait between AD 1724?????"1794. This final ice advance was very abrupt after a prolonged still-stand, evicting the Huna Tlingit from their Glacier Bay homeland. ?? 2009 SAGE Publications.

Connor, C.; Streveler, G.; Post, A.; Monteith, D.; Howell, W.

2009-01-01

83

Columbia Glacier Terminus  

USGS Multimedia Gallery

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

2010-07-14

84

Iceberg calving as a primary source of regional-scale glacier-generated seismicity in the St. Elias Mountains, Alaska  

NASA Astrophysics Data System (ADS)

Since the installation of the Alaska Regional Seismic Network in the 1970s, data analysts have noted nontectonic seismic events thought to be related to glacier dynamics. While loose associations with the glaciers of the St. Elias Mountains have been made, no detailed study of the source locations has been undertaken. We performed a two-step investigation surrounding these events, beginning with manual locations that guided an automated detection and event sifting routine. Results from the manual investigation highlight characteristics of the seismic waveforms including single-peaked (narrowband) spectra, emergent onsets, lack of distinct phase arrivals, and a predominant cluster of locations near the calving termini of several neighboring tidewater glaciers. Through these locations, comparison with previous work, analyses of waveform characteristics, frequency-magnitude statistics and temporal patterns in seismicity, we suggest calving as a source for the seismicity. Statistical properties and time series analysis of the event catalog suggest a scale-invariant process that has no single or simple forcing. These results support the idea that calving is often a response to short-lived or localized stress perturbations. Our results demonstrate the utility of passive seismic instrumentation to monitor relative changes in the rate and magnitude of iceberg calving at tidewater glaciers that may be volatile or susceptible to ensuing rapid retreat, especially when existing seismic infrastructure can be used.

O'Neel, Shad; Larsen, Christopher F.; Rupert, Natalia; Hansen, Roger

2010-12-01

85

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

86

Results of 1985 Bureau of Mines investigations in the Johns Hopkins Inlet-Margerie Glacier area, Glacier Bay, Alaska  

SciTech Connect

This report describes the mineral investigations of specific sites in the Johns Hopkins-Margerie Glacier area. Approximately 17 square miles were mapped, and over 99 rock and placer samples were collected in an effort to determine possible extensions of known mineralization. Several rock samples contained anomalous copper and gold values, and anomalous gold was detected in several placer samples. The area has been found to contain copper, zinc, molybdenum, and gold.

Kurtak, J.M.

1985-01-01

87

Subglacial deformation associated with fast ice flow, from the Columbia Glacier, Alaska  

Microsoft Academic Search

The Columbia Glacier is a large well studied tidewater glacier which has one of the highest non-surging modern glacier flow rates. Previous studies from ice drilling have tentatively suggested the presence of a deforming bed. This study examined the recently deglaciated (since 1974) foreland and concluded there were features indicative of deforming bed conditions, i.e., streamlined subglacial bedforms, squeeze-type push

Jane K. Hart; Barnaby Smith

1997-01-01

88

Estimates of Glacier Mass Change in the St.~Elias Mountains of Alaska, USA and Yukon Territory, Canada: a Strategy for Combining GRACE and Aircraft Laser Altimetry Data  

NASA Astrophysics Data System (ADS)

We describe a strategy for estimating the contribution of mountain glaciers to rising sea level by combining two independent geodetic techniques: (1) repeat-pass aircraft laser altimetry measurements of glacier surface elevations; and (2) Gravity Recovery and Climate Experiment (GRACE) estimates of variations in Earth mass. Repeated laser altimetry measurements provide elevation changes along the central flowline of individual glaciers, but extrapolating these to entire glacier regions is a challenge, especially for glaciers with complex dynamics. Conversion of elevation to mass changes can also be problematic, especially over short measurement intervals. GRACE yields a direct measure of mass change over broad regions, but corrections must be made for non-glacier sources of mass change in order to isolate the glacier mass balance signal. In some cases, uncertainties in models or observations of non-glacier sources of mass change, such as glacial isostatic adjustments, can be large. By combining GRACE with aircraft altimetry, we are developing more robust regional estimates of mass change and can make a better assessment of errors in each approach. We apply these methods to glaciers of the St.~Elias Mountains, home to approximately one-half of glaciers (by surface area) in Alaska and northwestern Canada. Most glaciers in this region receive abundant precipitation and terminate in lakes or at tidewater, and many have a large proportion of their surface area at low elevations, making them particularly sensitive to changes in climate. Our GRACE solutions show that this region had the highest rate of mass loss during 2003-2007, relative to all other regions in Alaska/northwestern Canada. During August 2007 we collected laser altimetry surface elevation data along flight paths last measured during August 2003 and, in some cases, September 2005. By calculating the difference between these elevations, and extrapolating to all glaciers in the region, we obtain the net contribution of this region to rising sea level. These new altimetry data are the first regional glacier mass change dataset to be collected concurrently with data from GRACE, and will provide an independent dataset for validation of GRACE estimates. Our updated assessment of glacier mass changes in the St.~Elias Mountains will provide new insights into the response of glaciers to regional climate changes.

Arendt, A.; Luthcke, S.; Abdalati, W.; Larsen, C.; Lingle, C.; Echelmeyer, K.; Rowlands, D.; Krabill, W.

2007-12-01

89

Organic matter and nutrient cycling in linked glacier-stream ecosystems along the Gulf of Alaska  

Microsoft Academic Search

Glacial ecosystems cover approximately 10% of the Earth's surface and contribute large volumes of runoff to rivers and coastal oceans. Moreover, anticipated future changes in glacial runoff are markedly larger than those projected for non-glacial river systems. Recent research on the biogeochemistry of glacier ecosystems has shown that glacier environments contain abundant microbial communities and are more biogeochemically active than

D. Scott; E. W. Hood; M. Q. Nassry; A. Vermilyea

2010-01-01

90

Hubbard Glacier, Alaska: 2002 closure and outburst of Russell Fjord and postflood conditions at Gilbert Point  

Microsoft Academic Search

Hubbard Glacier, the largest temperate tidewater glacier in the world, has been advancing since 1895 AD and has now twice dammed 60-km-long Russell Fjord, once in 1986 and more recently in 2002. This paper focuses on the 2002 event, when a strong spring advance pushed shallow submarine proglacial sediments against Gilbert Point, closing off Russell Fjord by late June. As

Roman J. Motyka; Martin Truffer

2007-01-01

91

Holocene history of Hubbard Glacier in Yakutat Bay and Russell Fiord, southern Alaska  

Microsoft Academic Search

Stratigraphic and geomorphic data de- fined by radiocarbon ages, tree-ring dates, and historical observations provide evi- dence of three major Holocene expansions of Hubbard Glacier. Early in each advance the Hubbard Glacier margin blocked Rus- sell Fiord to create Russell lake, raising base level and causing stream beds and fan deltas throughout the Russell drainage ba- sin to aggrade. Each

David J. Barclay; Parker E. Calkin; Gregory C. Wiles

2001-01-01

92

UltraRapid Landscape Response and Sediment Yield Following Glacier Retreat, Icy Bay, Southern Alaska  

Microsoft Academic Search

Glaciers control base level in glaciated landscapes. Rates and magnitude of base level changes vary as a function of down-valley expansion and thickening and up-valley retraction and thinning of glaciers that accompany glacial advance and retreat, respectively. Timescales and magnitudes of sediment routing in glaciated basins, modification of glacial valley forms by fluvial processes, and the rate of landscape evolution

A. J. Meigs; W. C. Krugh; K. Davis; G. Bank

2002-01-01

93

The storage and release of water from a large glacier-dammed lake; Russell Lake near Yakutat, Alaska, 1986  

USGS Publications Warehouse

In May 1986, the entrance to Russell Fiord, Alaska, was blocked by the advancing Hubbard Glacier, forming a 34-mile long ice-dammed lake. Runoff to the lake, mainly runoff from melting snow and glacier ice, filled the lake to an elevation of 83 feet above sea level by October 8, when the ice dam failed. The lake level rose at an average rate of 0.6 ft/day, and average daily inflow to the lake was calculated to be 16,500 cu ft/sec. After failure of the ice dam, the water level fell to the former high tide level of Russell Fiord within 24 hours. Average discharge through the breach in the ice dam during a 4-hr period of maximum water level decline is estimated to have been 3.8 million cu ft/sec. The formation and breakout of the lake is expected to be repeated as the Hubbard Glacier continues to advance, though the timing of the phenomenon cannot be predicted with certainty. (USGS)

Seitz, H. R.; Thomas, D. S.; Tomlinson, Bud

1986-01-01

94

ASTER and Ground Observations of Vegetation Primary Succession and Habitat Development near Retreating Glaciers in Alaska and Nepal  

NASA Astrophysics Data System (ADS)

Like active volcanoes, glaciers are among the most dynamic components of the Earth's solid surface. All of the main surface processes active in these areas have an ability to suddenly remake or "resurface" the landscape, effectively wiping the land clean of vegetation and habitats, and creating new land surface and aqueous niches for life to colonize and develop anew. This biological and geomorphological resurfacing may remove the soil or replace it with inorganic debris layers. The topographical, hydrological, and particle size-frequency characteristics of resurfaced deglaciated landscapes typically create a high density of distinctive, juxtaposed niches where differing plant communities may become established over time. The result is commonly a high floral and faunal diversity and fecundity of life habitats. The new diverse landscape continues to evolve rapidly as ice-cored moraines thaw, lakes drain or fill in with sediment, as fluvial dissection erodes moraine ridges, as deltaic sedimentation shifts, and other processes (coupled with primary succession) take place in rapid sequence. In addition, climate dynamics which may have caused the glaciers to retreat may continue. We will briefly explore two distinctive glacial environments-(1) the maritime Copper River corridor through the Chugach Mountains (Alaska), Allen Glacier, and the river's delta; and (2) Nepal's alpine Khumbu valley and Imja Glacier. We will provide an example showing how ASTER multispectral and stereo-derived elevation data, with some basic field-based constraints and observations, can be used to make automatic maps of certain habitats, including that of the Tibetan snowcock. We will examine geomorphic and climatic domains where plant communities are becoming established in the decades after glacier retreat and how these link to the snowcock habitat and range. Snowcock species have previously been considered to have evolved in close association with glacial and tectonic history of South and Central Asia (B. An et al., 2009, Molecular Phylogenetics and Evolution 50: 526-533; R. Luzhang et al., 2010, Animal Biology 60: 449-465). The new maps and some observations of the snowcock's habits, ecological relationships to other species and landscapes, and physiological limitations support that basic model. Our new data and mapping carries some profound implications for past, present, and future coevolution of these birds and glaciers. Using insights derived from ASTER remote sensing based habitat mapping, we will explore some specific processes that may drive snowcock habitat, population, and genetic dynamics. Although the ecological fabric differs from one region to another, some basic insights from the Himalayan Khumbu valley may be applied to the Chugach Range.

Kargel, J. S.; Leonard, G. J.; Furfaro, R.

2011-12-01

95

Carbon Fluxes Between the Atmosphere, Terrestrial, and River Systems Across a Glacier-Dominated Landscape in Southcentral Alaska  

NASA Astrophysics Data System (ADS)

The coastal Gulf of Alaska region is experiencing rapid and accelerating changes due to local and regional warming. Predicted high latitude warming may result in rapid recession of glaciers with subsequent changes in river discharge, nutrient fluxes into the rivers, shifts in landscape vegetation cover, and altered CO2 fluxes affecting the regional carbon balance. As glaciers recede an increase in glacier-dominated river discharge and a change in seasonality of the river discharge are expected. Recently deglaciated landscapes will, over time, be occupied by a succession of vegetation cover that are likely to alter the fluxes of carbon both between the atmosphere and terrestrial ecosystems, and between terrestrial ecosystems and stream and river systems. As the landscape evolves from deglaciated forelands it is expected that there is low to no CO2 fluxes between the atmosphere and the recently deglaciated landscape, as well as dissolved organic and inorganic carbon inputs into rivers and streams. These recently deglaciated landscapes will transition to early successional plant species and on towards mature spruce forests. Each transitional terrestrial ecosystem will have different carbon cycling between the atmosphere, terrestrial, and aquatic systems until the mature spruce forests which is expected to have high carbon uptake and sequestration as well as increased inputs of dissolved organic and inorganic carbon into the rivers and streams. A new research project was initiated in the summer of 2011 focusing on glacier-dominated landscapes within the Wrangell-St. Elias National Park and Preserve in southcentral Alaska with the objective to quantify how the transition from deglaciated forelands to mature spruce forests (a successional sequence) alters the patterns and magnitudes of CO2 exchange, the dissolved carbon inputs from terrestrial to aquatic systems and the extent to which these are manifested due to changes in glacier coverage. We seek to examine present-day carbon cycling along a vegetation successional sequence and plan to use a space-for-time substitution to make predictions about the future evolution of carbon cycling between the atmosphere, terrestrial landscape, and the river and stream systems This year we have established a 30m eddy covariance tower in a mature spruce forest to investigate the magnitude and patterns of carbon exchange between the atmosphere and terrestrial ecosystem as well as water sampling from adjacent rivers and streams to analyze for dissolved organic and inorganic carbon fluxes from the forested ecosystem into the river and stream systems. High rates of carbon sequestration into the mature spruce forests indicate that these forests along the glacier-dominated Copper River watershed are important sinks for carbon and may be contributing large amounts of inorganic carbon to the rivers which are transported downstream to and eventually into the marine ecosystem of the Gulf of Alaska.

Zulueta, R. C.; Welker, J. M.; Tomco, P. L.

2011-12-01

96

Melt Season Surface Velocities at the Kennicott Glacier, Alaska, Including Response to the 2006 Hidden Creek Lake Outburst Flood  

NASA Astrophysics Data System (ADS)

The annual growth and collapse of the subglacial hydrologic system of the 40 km long Kennicott Glacier, Alaska, is disrupted each summer by the drainage of ice-dammed Hidden Creek Lake (HCL), 15 km from the terminus. Ice surface velocities, water levels in ice-marginal lakes (including HCL), and discharge at the outlet stream show the relationship between basal water pressure and sliding velocity. The 5 July 2006 HCL jökulhlaup produced the largest peak discharge since 1996, despite the fact that the HCL level was not higher than in prior years. Over 2 to 3 months spanning the melt season, 5 GPS receivers spaced at about 3 km intervals on the glacier surface showed average speeds of 0.25 - 0.5 m/day. Each receiver recorded a short duration speed-up to 2 m/day. High velocities propagated down-glacier in a wave that coincided with the passage of HCL floodwaters. While the speed-up lasted approximately one day between HCL and the terminus, ice speeds remained high for several days 3 km up-glacier of HCL. The glacier speed-up was highly correlated in space and time with peaks in the water level of several down-valley ice marginal lakes during the passage of floodwater. Most GPS station trajectories reflect steady down-valley motion, presumably indicating the mean local bed slope. The slopes decrease down-valley, and at the lowest GPS station become reversed. This station slid steadily up, rising 1.5 meters over 2 months, a trend that can be attributed either to compression in the terminus region or to motion on an englacial thrust fault. During the rapid acceleration at each site associated with the jökulhlaup, the surface ice trajectories departed from this general pattern, instead moving upward approximately 10° relative to mean bed-parallel slope. We interpret this as bed separation caused by rapid sliding up the stoss side of bumps on the glacier bed. This separation, of up to 0.5 m, collapsed upon the slowdown associated with passage of the flood tail, and the surface ice trajectory returned to mean bed- parallel motion. The characteristic time scale for this collapse was 1 day, consistent with theoretical estimates of cavity closure under ice thicknesses of order 200-400 m. The sliding behavior at the ca. 400 km2 Kennicott Glacier is similar to that observed at the diminutive Bench Glacier (7 km2): sliding occurs when water storage is high and is accompanied by surface uplift. The timescale for relaxation of the surface downward is shorter for the thicker Kennicott Glacier, as predicted by theory. This suggests that thick ice may be susceptible to high water pressure and sliding events multiple times in a melt season.

Bartholomaus, T. C.; Anderson, R. S.; Anderson, S. P.

2006-12-01

97

Motion patterns of glaciers in the eastern Wrangell Mountains, Alaska, seen on ERS-1 SAR Interferograms  

NASA Astrophysics Data System (ADS)

Mt. Wrangell, an active volcano, rises 4,317 meters from the Copper River Valley lowlands. The summit and the surrounding mountainous areas, i.e., the Wrangell Mountains, are covered by numerous alpine glaciers. To get a clearer picture of the glacial dynamics and mass balance in the area, and their changes in relation to volcanic heating and climate changes, we study the motion patterns of glaciers in the eastern Wrangell Mountains using the European Remote Sensing satellite, ERS-1, SAR images acquired in early 1994 when the satellite repeated its orbits every three days. Pairs of coherent single-look complex SAR images acquired 3 days apart are co-registered precisely and interferograms are formed after the difference of the phase values of individual pixels on the two SAR images are calculated pixel by pixel. Differential Interferometric SAR (DInSAR) technique has been used to remove the impact of topography on interferograms using an existing digital elevation model (DEM). The resulting interferograms reveal glacier motion patterns at sub-wavelength (centimeter) sensitivity. Adjustment of displacement for surface slope and motion direction is necessary because the direct measurement is made along the radar line-of-sight. The dense fringes parallel to the sidewalls of glaciers suggest strong shear between the central lines and sidewalls of glaciers. Nabesna glacier moves at a velocity about 0.4-0.6 m/day. A similar velocity about 0.5 m/day is derived for the upper section of Chisana Glacier. Near its terminus, Jacksina Glacier has a velocity a few centimeters a day. Investigation is in progress.

Li, S.; Benson, C.; Gens, R.; Lingle, C.

2006-12-01

98

Glacier Destruction and Lahar Generation during the 2009 Eruption of Redoubt Volcano, Alaska  

NASA Astrophysics Data System (ADS)

Two large lahars with volumes of 0.4-0.6 km3 and several smaller lahars with volumes of 0.05-0.1 km3 inundated the Drift River valley on the north flank of Redoubt Volcano during its 2009 eruption. Significant lahars were produced on March 22-23 during the initial explosive phase of the eruption following about 8 months of precursory unrest that included increased fumarolic melting of glacier ice and snow in the summit crater and upper Drift glacier. From the beginning of unrest in late July 2008 through March 20, 2009 about 3-7 x 106 m3 of glacier ice and snow were lost from upper Drift glacier as a result of fumarolic emissions and associated melting. Water and debris outflow during this period was minor and posed no downstream flow hazard beyond the base of the volcano. On March 22-23, explosive eruptions from a summit crater vent destroyed a significant amount of ice in upper Drift glacier and produced a funnel-shaped explosion crater within the larger summit crater. Glacier ice, 50-100 m thick, in the gorge below the vent was stripped to bedrock by pyroclastic flows and melt water. By the next available clear views of the volcano on March 26, about 0.5-1.0 x 108 m3 of ice had been removed from upper Drift glacier including part of the ice field in the summit crater. Melt water liberated by eruptive activity on March 22-23 also eroded or removed most of the river ice and snowpack present in the Drift River valley which may have added an additional 0.1-0.2 km3 of water to the lahars produced during that time. Additional explosions from March 26-April 4 caused further melting of Drift glacier and produced small lahars, but the extent of ice loss and lahar inundation during this period could not be determined because clouds obscured the volcano and much of the Drift River valley. The final explosive event and lahar of the eruption occurred on April 4 when pyroclastic flows produced by lava dome collapse swept over upper Drift glacier and a portion of its piedmont lobe. This event removed about 0.5-1.0 x 108 m3 of glacier ice and initiated a lahar, just slightly larger than the March 22-23 lahar, that inundated an area of about 125 km2 in the Drift River valley from the piedmont lobe to the Cook Inlet coastline about 35 km distant. Pre-eruptive Drift glacier ice volume was about 1 km3 and the total ice removed by the 2009 eruption was 0.1-0.2 km3 or about 10-20% of the total. The total amount of Drift glacier ice removed during the 1989-90 eruption was about 0.1 km3, roughly half of that removed during the 2009 eruption. The largest and most energetic event of the 1989-90 Redoubt eruption on January 2, 1990 removed about 0.25 x 108 m3 of ice from Drift glacier and initiated a lahar of about 0.2 km3, the largest of that eruption. Both the March 22-23 and April 4, 2009 events resulted in greater ice loss and larger lahars than did the January 2, 1990 event. The upper part of Drift glacier is narrow and confined by steep valley walls that restrict the lateral spreading of pyroclastic debris generated by lava dome collapse. This enhances the efficiency of ice melt by funneling pyroclastic flows over the glacier and mechanical erosion and thermal interaction leads to the production of large volumes of melt water and correspondingly large lahars downstream.

Waythomas, C. F.

2010-12-01

99

Role of lake regulation on glacier-fed rivers in enhancing salmon productivity: the Cook Inlet watershed, south-central Alaska, USA  

NASA Astrophysics Data System (ADS)

Rivers fed by glaciers constitute a major part of the freshwater runoff into the Cook Inlet basin of south-central Alaska. This basin is very important to the economy of the State of Alaska because it is home to more than half of the population and it supports multi-million dollar commercial, subsistence and sport fisheries. Hence an understanding of how glacial runoff influences biological productivity is important for managing rivers that drain into Cook Inlet. This paper examines the ways in which the regulation of glacier-fed rivers by proglacial lakes affects salmon productivity, with particular reference to the Kenai River. Salmon escapement per unit channel length on the Kenai River is between two and ten times that found for rain-and-snowmelt dominated rivers and glacier-fed rivers lacking lake regulation.Lakes are shown to influence biological processes in glacier-fed rivers by attenuating peak flows, sustaining high flows throughout the summer, supplementing winter low flows, settling suspended sediment, and increasing river temperatures. Downstream from large lakes, glacier-fed rivers are less disturbed, channels are relatively stable and have well-developed salmonid habitats. The positive influences are indicated by the high diversity and abundances of benthic macroinvertebrates, which are important food resources for juvenile salmonids. High summer flows allow access for up-river salmon runs and lakes also provide both overwintering and rearing habitat.

Dorava, Joseph M.; Milner, Alexander M.

2000-10-01

100

Automated Lagrangian Water-Quality Assessment System (ALWAS) Measurements of North Slope Lakes and the Bering Glacier, Alaska  

NASA Astrophysics Data System (ADS)

ALWAS is an inexpensive, free-floating, sail-powered or jet-driven water quality measuring and watershed evaluation buoy. It is capable of measuring data points with multiple parameters (depth, temperature, conductivity, salinity, total dissolved solids, dissolved oxygen, pH, oxidation reduction potential, turbidity, chlorophyll-a, blue-green algae, nitrate, ammonium, chloride, latitude/longitude, date, time, speed, and barometric pressure) as rapidly as every 40 seconds. Data is transmitted for real-time viewing and is stored for future retrieval and analysis. The collected data are easily downloaded into geographic databases (ESRI shapefile) and spreadsheet formats. ALWAS uses state-of-the-art sensors to measure water quality parameters and GPS data. Field demonstrations of the ALWAS technology from the Bering Glacier and the North Slope of Alaska will be presented. The ALWAS buoy will also be described as well as ALWAS data sharing, web-based mapping, and decision support tools.

Shuchman, R.; Meadows, G.; Liversedge, L.; Hatt, C.; Vansumeren, H.; Payne, J.

2007-12-01

101

Interactions between instream wood and hydrogeomorphic development within recently deglaciated streams in Glacier Bay National Park, Alaska  

NASA Astrophysics Data System (ADS)

The physical and structural characteristics of instream wood were examined within five streams that represented 200 years of stream development following glacial recession within Glacier Bay National Park, Alaska. Wood characteristics altered with watershed age as terrestrial succession progressed and wood was recruited into the riverine environment. The influence of wood characteristics on the development of geomorphic diversity and hydraulic variability within the streams were assessed using detailed habitat mapping, sediment analysis, and hydraulic assessment using an Acoustic Doppler Current Profiler at a number of transects upstream, downstream, and adjacent to wood. Results show that the size, complexity, and orientation of wood accumulations are the main drivers in determining the degree of influence instream wood have on stream geomorphic and hydraulic complexity. Adjacent terrestrial vegetation must be of a sufficient stage of development (in terms of size and maturity) in order to elicit significant hydrogeomorphic changes to benefit aquatic biota such as fish, macroinvertebrates, and plants.

Klaar, Megan J.; Hill, David F.; Maddock, Ian; Milner, Alexander M.

2011-07-01

102

Modelling historical and recent mass loss of McCall Glacier, Alaska, USA  

NASA Astrophysics Data System (ADS)

Volume loss of valley glaciers is now considered to be a significant contribution to sea level rise. Understanding and identifying the processes involved in accelerated mass loss are necessary to determine their impact on the global system. Here we present results from a series of model experiments with a higher-order thermomechanically coupled flowline model (Pattyn, 2002). Boundary conditions to the model are parameterizations of surface mass balance, geothermal heating, observed surface and 10 m ice depth temperatures. The time-dependent experiments aim at simulating the glacier retreat from its LIA expansion to present according to different scenarios and model parameters. Model output was validated against measurements of ice velocity, ice surface elevation and terminus position at different stages. Results demonstrate that a key factor in determining the glacier retreat history is the importance of internal accumulation (>50%) in the total mass balance. The persistence of a basal temperate zone characteristic for this polythermal glacier depends largely on its contribution. Accelerated glacier retreat since the early nineties seems directly related to the increase in ELA and the sudden reduction in AAR due to the fact that a large lower elevation cirque - previously an important accumulation area - became part of the ablation zone.

Delcourt, C.; Pattyn, F.; Nolan, M.

2007-11-01

103

Modelling historical and recent mass loss of McCall Glacier, Alaska, USA  

NASA Astrophysics Data System (ADS)

Volume loss of valley glaciers is now considered to be a significant contribution to sea level rise. Understanding and identifying the processes involved in accelerated mass loss are necessary to determine their impact on the global system. Here we present results from a series of model experiments with a higher-order thermomechanically coupled flowline model (Pattyn, 2002). Boundary conditions to the model are parameterizations of surface mass balance, geothermal heating, observed surface and 10 m ice depth temperatures. The time-dependent experiments aim at simulating the glacier retreat from its LIA expansion to present according to different scenarios and model parameters. Model output was validated against measurements of ice velocity, ice surface elevation and terminus position at different stages. Results demonstrate that a key factor in determining the glacier retreat history is the importance of internal accumulation (>50%) in the total mass balance. The persistence of a basal temperate zone characteristic for this polythermal glacier depends largely on its contribution. Accelerated glacier retreat since the early nineties seems directly related to the increase in ELA and the sudden reduction in AAR due to the fact that a large lower elevation cirque - previously an important accumulation area - became part of the ablation zone.

Delcourt, C.; Pattyn, F.; Nolan, M.

2008-03-01

104

Columbia Glacier in 1984: disintegration underway  

Microsoft Academic Search

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

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

1985-01-01

105

Time-dependent basal stress conditions beneath Black Rapids Glacier, Alaska, USA, inferred from measurements of ice deformation and surface motion  

Microsoft Academic Search

Observations of surface motion and ice deformation from 2002-03 were used to infer mean stress fields in a cross-section of Black Rapids Glacier, Alaska, USA, over seasonal timescales. Basal shear stresses in a well-defined zone north of the center line (orographic left) were approximately 7% and 16% lower in spring and summer, respectively, than in winter. Correspondingly higher stresses were

Jason M. Amundson; Martin Truffer; Martin P. Lüthi

2006-01-01

106

An 850year record of climate and fluctuations of the iceberg calving NellieJuan Glacier, south central Alaska, U.S.A  

Microsoft Academic Search

Tree-ring cross-dates of 46 glacially killed trees show that the tidewater Nellie Juan Glacier, Alaska, advanced seawardduringthe16thand17thcenturies AD.Ice- scarredtrees at the late-Holocene end moraine indicate that theterminus wasat its recent maximum from 1842 to 1893. Historical observations and photographs show that subse- quent slow retreat changed to rapid iceberg-calving retreat after 1935, and that the tide- water terminus had withdrawn

David J. BARCLAY; Gregory C. WILES; Parker E. CALKIN

107

Comparison of the 2008-2011 and 1993-1995 Surges of Bering Glacier, Alaska  

NASA Astrophysics Data System (ADS)

The 1993-1995 surge of Bering Glacier, Earth's largest surging temperate glacier, was intensively studied. A new surge, which began prior to March 9, 2009, was still active in early August 2011. As was the 1993-1995 surge, the current surge is being studied using multiple remote sensing and ground-based methodologies. The wealth of observations available of both surges permit comparisons to be drawn about similarities and differences regarding processes, timing, intensities, and related topics. For more than a year prior to each surge, the intensity of calving and the rate of terminus retreat in Tashalich Arm increased dramatically, approaching 4 m/d in late 2010. This was abruptly followed by a significant terminus advance. In the current surge, maximum advance rates exceeded 19 m/d between March 18 and May 10, 2011. Through July 20, maximum terminus advance approached 3.2 km with velocities above 8 m/d. Similar rates applied in the earlier surge. Each surge has resulted in a rapid and significant advance of the central Bering Lobe's terminus into Vitus Lake. The terminus advance results from the transfer of a substantial volume of ice from the Bagley Ice Valley into the expanding piedmont lobe. In both surges, conspicuous evidence of tens of meters of glacier surface lowering is visible on the south wall of Juniper Island. In the 1993-1995 surge, terminus advance between October 17, 1993 and May 16, 1994 was nearly 7.8 km, an average advance rate of more than 36 m/d. With the current surge, between January 8 and 14, 2011, the terminus advanced a maximum of 125 m, averaging nearly 21 m/d. By July 11, 2011, maximum velocities still approached 15 m per day, with maximum ice displacements of nearly 2 km and a maximum terminus advance of 1.7 km. In the 1993-1995 surge, the first evidence of surge activity was observed in April 1993, the development of a fractured ice bulge on the northwest side of the Grindle Hills. The surge front reached Bering's terminus at the end of August 1993 and left it heavily fractured. With the current surge, until July 2009, surface displacements were restricted to the area from west of, to northeast of the Grindle Hills. By November 18, 2010, the surge front reached Bering's terminus and left it more heavily fractured than in 1993. The current surge shows the same style and types of surface disruptions and deformations at the same locations as did the earlier surge. For example, in both surges, sinusoidal crevasses were first noted north of the Grindle Hills, while rifts were noted in the upper central piedmont lobe. The current surge has produced much more fracturing of the Medial Moraine Band than did the 1993-95 surge. Similarly, the extent of surface fracturing up-glacier from the piedmont lobe is significantly greater in the current surge. During the 1993-95 surge, surface expression of the surge extended about 45 km east of the western end of Juniper Island. In late July 2011, surge-related surface fractures extended nearly 90 km to the east. The Steller lobe of the Bering Glacier System has not been involved in either surge. Continued observations of the current surge, in the context of the 1993-95 surge, are providing significant insights into repeatable patterns of surging glacier behavior. Bering Glacier is an amazing natural laboratory at which to conduct these observations.

Molnia, B. F.; Angeli, K.

2011-12-01

108

20th-century glacial-marine sedimentation in Vitus Lake, Bering Glacier, Alaska, U.S.A.  

USGS Publications Warehouse

Vitus Lake, the ice-marginal basin at the southeastern edge of Bering Glacier, Alaska, U.S.A., is a site of modern, rapid, glacial-marine sedimentation. Rather than being a fresh-water lake, Vitus Lake is a tidally influenced, marine to brackish embayment connected to the Pacific Ocean by an inlet, the Seal River. Vitus Lake consists of five deep bedrock basins, separated by interbasinal highs. Glacial erosion has cut these basins as much as 250 m below sea level. High-resolution seismic reflection surveys conducted in 1991 and 1993 of four of Vitus Lake's basins reveal a complex, variable three-component acoustic stratigraphy. Although not fully sampled, the stratigraphy is inferred to be primarily glacial-marine units of (1) basal contorted and deformed glacial-marine and glacial sediments deposited by basal ice-contact processes and submarine mass-wasting; (2) acoustically well-stratified glacial-marine sediment, which unconformably overlies the basal unit and which grades upward into (3) acoustically transparent or nearly transparent glacial-marine sediment. Maximum thicknesses of conformable glacial-marine sediment exceed 100 m. All of the acoustically transparent and stratified deposits in Vitus Lake are modern in age, having accumulated between 1967 and 1993. The basins where these three-part sequences of "present-day" glacial-marine sediment are accumulating are themselves cut into older sequences of stratified glacial and glacial-marine deposits. These older units outcrop on the islands in Vitus Lake. In 1967, as the result of a major surge, glacier ice completely filled all five basins. Subsequent terminus retreat, which continued through August 1993, exposed these basins, providing new locations for glacial-marine sediment accumulation. A correlation of sediment thicknesses measured from seismic profiles at specific locations within the basins, with the year that each location became ice-free, shows that the sediment accumulation at some locations exceeds 10 m year-1.

Molnia, B. F.; Post, A.; Carlson, P. R.

1996-01-01

109

Serologic surveillance of pathogens in a declining harbor seal (Phoca vitulina) population in Glacier Bay National Park, Alaska, USA and a reference site.  

PubMed

The harbor seal population in Glacier Bay National Park, Alaska, has declined by over 70% since 1992. The reasons for this decline are not known. We examined serum antibodies and feces for evidence of exposure to multiple pathogens in this population. We also studied harbor seals from a reference site on Kodiak Island. In 2007, we found antibodies against Leptospira spp. in 31% of specimens from harbor seals in Glacier Bay, but no detectable serum antibodies in samples from Kodiak. In 2008, no samples had detectable antibodies against Leptospira spp. No serum antibodies against Toxoplasma gondii, morbilliviruses, or presence of Cryptosporidium in fecal samples were detected. However, Giardia was found in 6% of the fecal samples from Glacier Bay. Our results indicate that the harbor seal population in Glacier Bay National Park could be immunologically naïve to distemper viruses and therefore vulnerable to these pathogens. Given the relatively low prevalence of antibodies and low titers, pathogens likely are not the reason for the harbor seal decline in Glacier Bay. PMID:22102671

Hueffer, Karsten; Holcomb, Darce; Ballweber, Lora R; Gende, Scott M; Blundell, Gail; O'Hara, Todd M

2011-10-01

110

A 30-year record of surface mass balance (1966-95) and motion and surface altitude (1975-95) at Wolverine Glacier, Alaska  

USGS Publications Warehouse

Scientific measurements at Wolverine Glacier, on the Kenai Peninsula in south-central Alaska, began in April 1966. At three long-term sites in the research basin, the measurements included snow depth, snow density, heights of the glacier surface and stratigraphic summer surfaces on stakes, and identification of the surface materials. Calculations of the mass balance of the surface strata-snow, new firn, superimposed ice, and old firn and ice mass at each site were based on these measurements. Calculations of fixed-date annual mass balances for each hydrologic year (October 1 to September 30), as well as net balances and the dates of minimum net balance measured between time-transgressive summer surfaces on the glacier, were made on the basis of the strata balances augmented by air temperature and precipitation recorded in the basin. From 1966 through 1995, the average annual balance at site A (590 meters altitude) was -4.06 meters water equivalent; at site B (1,070 meters altitude), was -0.90 meters water equivalent; and at site C (1,290 meters altitude), was +1.45 meters water equivalent. Geodetic determination of displacements of the mass balance stake, and glacier surface altitudes was added to the data set in 1975 to detect the glacier motion responses to variable climate and mass balance conditions. The average surface speed from 1975 to 1996 was 50.0 meters per year at site A, 83.7 meters per year at site B, and 37.2 meters per year at site C. The average surface altitudes were 594 meters at site A, 1,069 meters at site B, and 1,293 meters at site C; the glacier surface altitudes rose and fell over a range of 19.4 meters at site A, 14.1 meters at site B, and 13.2 meters at site C.

Mayo, Lawrence R.; Trabant, Dennis C.; March, Rod S.

2004-01-01

111

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

National Technical Information Service (NTIS)

Glaciers occur in northwestern North America between lat 37 degrees and 69 degrees N. in two major mountain systems. The Pacific Mountain System, near the west coast, receives large amounts of precipitation, has very mild temperatures, and contains perhap...

A. Post L. R. Mayo M. F. Meier W. V. Tangborn

1971-01-01

112

Photographer Overlooking Columbia Glacier  

USGS Multimedia Gallery

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

2010-07-14

113

Geochemical evidence for late Paleozoic and mid Mesozoic arc volcanism, Gravina Belt and Taku Terrane, Coast Ranges, SE AK  

SciTech Connect

Metavolcanic rocks along the western flank of the Coast Plutonic Complex (CPC), northern SE Alaska comprise three sequences based on age and the nature of interlayered metasedimentary rocks (from W--E): subgreenschist to greenschist facies rocks of the Jurassic-Cretaceous Gravina (Gr) belt, greenschist facies rocks of the Permian-Triassic western Taku (Tk) terrane, and dominantly amphibolite facies rocks of the eastern Taku/Yukon (T/Y) terrane. Metasedimentary strata are distinctive; however, all suggest a marine origin: immature marine sandstones, siltstones, mudstones, and conglomerates (Gr); siltstones, fossiliferous carbonates, conglomerates, and shales (western Tk); laminated slates and schists with ripple marks, and micaceous quartzites (eastern Tk). Concentrations of high field strength elements, rare earth elements (REE), and some transition elements from highly-strained and less-strained specimens are indistinguishable, suggesting immobility of these elements. Variable concentrations of alkali elements, and other transition elements suggest mobility during sea-floor alteration and/or metamorphism. Discrimination diagrams, and chondrite-normalized REE and MORB-normalized Spider diagrams suggest that all three groups of metavolcanic rocks are of island arc basalt or arc-rift basalt affinity. Gr and western Tk metabasalts are inferred to have a non oceanic rift-related origin, likely, within a magmatic arc; however, Gr rocks are distinct in age and in chemistry. Eastern Tk metabasalts are interpreted as island arc tholeiites. Tk arc volcanic rocks suggest a late Paleozoic arc developed on rocks of probable North American affinity. Gr arc volcanic rocks represent initial development of a magmatic arc developed on the eastern boundary of the Alexander terrane and western edge of the T/Y terranes during the Mid-Mesozoic. This arc may signify the onset of E-dipping subduction beneath N America which culminated in development of the CPC during the early Tertiary.

Stowell, H.H.; Green, N.L. (Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Geology)

1993-03-01

114

Glacier runoff as a source of labile dissolved organic matter for near-shore marine ecosystems in the Gulf of Alaska  

NASA Astrophysics Data System (ADS)

Northern rivers transport large quantities of dissolved organic matter (DOM), however this organic material is typically thought to be refractory and therefore of little significance for the biogeochemistry of downstream marine ecosystems. Recent research in both the arctic and sub-arctic has shown that terrigenous DOM may be more bioavailable than was previously thought. These findings suggest that riverine DOM has the potential to support both heterotrophic metabolism and primary productivity in near-shore marine ecosystems. Along the Gulf of Alaska (GOA), the ongoing loss of glacier ice in coastal watersheds is altering the land-to-ocean transfer of freshwater and DOM. In particular, DOM derived from glacial runoff appears to be derived largely from microbial precursor material while DOM in watersheds with little or no glacier coverage is predominantly derived from terrestrial plants. The purpose of this study was to test the hypothesis that the character and bioavailability of riverine DOM being exported to the GOA will be altered as glaciers recede and contribute less to streamflow. We sampled rivers draining 12 coastal watersheds along a 500 mile stretch of the GOA during the peak glacier runoff season in the summer of 2008. The study watersheds were typical of the thousands of moderately sized (50-450 km2) watersheds draining the coast mountains along the GOA and ranged in watershed glacier coverage from 0 to >60%. Concentrations of DOC were relatively low in all 12 watersheds ranging from 0.6-2.2 mg C L-1. However, the chemical character of DOM varied widely across the watersheds. As watershed glacial coverage increased and glacier runoff comprised a large proportion of streamflow, riverine DOM became enriched in 13C-DOC and protein content as measured by fluorescence spectroscopy. These findings are consistent with the idea that DOM in pro-glacial streams is largely derived from sub-glacial microbial populations. Moreover, incubations of riverine DOM from all twelve sites that were inoculated with near-shore marine water from the GOA showed substantial losses of DOC (23-66%) over the course of a week. The percentage of bioavailable DOC was positively correlated (p=0.01) with the percentage of watershed covered by glacier ice suggesting that glacier runoff is an important source of labile DOM for heterotrophic bacteria in near-shore marine ecosystems around the GOA. Taken together, our results suggest that changes in watershed glacial coverage may alter the magnitude and bioavailability of riverine DOM entering productive near-shore ecosystems in the GOA.

Hood, E.; Fellman, J.; Spencer, R.; Edwards, R.; D'Amore, D.

2008-12-01

115

Damming of Russell Fiord by Tidewater Hubbard Glacier, Alaska: Role of Subglacial Meltwater in Preventing Closure in 2010  

Microsoft Academic Search

The Hubbard Glacier is advancing into tidewater at a net annual average rate of ~32 m\\/yr resulting from a seasonal cycle of advance and retreat ranging from less than 100 meters to over 600 meters per year. The eastern margin of the glacier fronts on Gilbert Point where a tidal channel connecting Disenchantment Bay and Russell Fiord could be dammed

D. E. Lawson; G. S. Hamilton; D. C. Finnegan; L. A. Stearns; B. A. Willems; S. O'Neel; J. A. Goff; S. P. Gulick; M. B. Davis

2010-01-01

116

Airborne and spaceborne DEM- and laser altimetry-derived surface elevation and volume changes of the Bering Glacier system, Alaska, USA, and Yukon, Canada, 1972-2006  

NASA Astrophysics Data System (ADS)

Using airborne and spaceborne high-resolution digital elevation models and laser altimetry, we present estimates of interannual and multi-decadal surface elevation changes on the Bering Glacier system, Alaska, USA, and Yukon, Canada, from 1972 to 2006. We find: (1) the rate of lowering during 1972-95 was 0.9±0.1 m a-1; (2) this rate accelerated to 3.0±0.7 m a-1 during 1995-2000; and (3) during 2000-03 the lowering rate was 1.5±0.4 m a-1. From 1972 to 2003, 70% of the area of the system experienced a volume loss of 191±17 km3, which was an area-average surface elevation lowering of 1.7±0.2 m a-1. From November 2004 to November 2006, surface elevations across Bering Glacier, from McIntosh Peak on the south to Waxell Ridge on the north, rose as much as 53 m. Up-glacier on Bagley Ice Valley about 10 km east of Juniper Island nunatak, surface elevations lowered as much as 28 m from October 2003 to October 2006. NASA Terra/MODIS observations from May to September 2006 indicated muddy outburst floods from the Bering terminus into Vitus Lake. This suggests basal-englacial hydrologic storage changes were a contributing factor in the surface elevation changes in the fall of 2006.

Muskett, Reginald R.; Lingle, Craig S.; Sauber, Jeanne M.; Post, Austin S.; Tangborn, Wendell V.; Rabus, Bernhard T.; Echelmeyer, Keith A.

117

UNIT, ALASKA.  

ERIC Educational Resources Information Center

THE UNIT DESCRIBED IN THIS BOOKLET DEALS WITH THE GEOGRAPHY OF ALASKA. THE UNIT IS PRESENTED IN OUTLINE FORM. THE FIRST SECTION DEALS PRINCIPALLY WITH THE PHYSICAL GEOGRAPHY OF ALASKA. DISCUSSED ARE (1) THE SIZE, (2) THE MAJOR LAND REGIONS, (3) THE MOUNTAINS, VOLCANOES, GLACIERS, AND RIVERS, (4) THE NATURAL RESOURCES, AND (5) THE CLIMATE. THE…

Louisiana Arts and Science Center, Baton Rouge.

118

Neoglacial fluctuations and sedimentation of an iceberg-calving glacier resolved with tree rings (kenai Fjords national park, Alaska)  

Microsoft Academic Search

The McCarty Fjord iceberg-calving glacier and its land-terminating tributaries have fluctuated with some asynchroneity during the past two millennia. During advance, McCarty Glacier shed outwash along the fjord, and into ice-dammed tributaries inundating forests. A radioacarbon framework has revealed at least two major late Holocene glacial advances that occurred following a poorly documented expansion about 3600 BP. These two later

Gregory C. Wiles; Parker E. Calkin

1993-01-01

119

Measurements of Fast ice Flow of the Malaspina Glacier to Explore Connections Between Glacial Erosion and Crustal Deformation in the St. Elias Mountains, Alaska  

NASA Astrophysics Data System (ADS)

In the St. Elias range of southern Alaska, dynamic tectonics and massive, fast-moving temperate glaciers provide an ideal opportunity to explore linkages between concentrated glacial erosion and localized deformation. With the potential for rapid erosion, the Seward Throat funnels a large volume of ice through the St. Elias Mountains, slicing through inactive and active structures alike and spreading out to form the Malaspina piedmont glacier. While glacial erosion processes are complex, erosion rates tend to scale with the sliding velocity, making it a useful indicator of erosive potential. In simple glacial valleys, conservation of mass dictates that reaches with high ice speeds tend to be relatively shallow; interestingly, these areas where the glacier bed is relatively high are precisely where the erosion is expected to be fastest. Hence, bedrock uplift must be concentrated for the elevated parts of the glacier bed to maintain their positions. Systematic studies of glacier speed and ice thickness hold considerable promise for elucidating patterns of active tectonics. We investigate the variation in velocity, and thus the probable variation in erosion rate, along a portion of the glacier's length. In late July 2007, 10 targets were placed on the lower Seward Throat and surveyed for 8 days. 7 targets were placed along 6 km of a flow line to define the velocity variation through steep and gentle sections of the glacier. Preliminary determination of surface velocities reveal large longitudinal strain rates with velocities varying from ~1400 m/year to ~1800 m/year within 1500 m with surface slopes ranging from ~1° to 3°. Previously calculated balance velocities, which suggest that most of the motion results from sliding, compare encouragingly. Assuming a 1 bar basal shear stress to estimate the ice thickness, basal sliding comprises between 83% and 95% of the surface velocity. To extend the spatial coverage of our measurements, our survey results will be examined in the context of detailed, unpublished velocity measurements collected by the USGS (Robert Krimmel and Austin Post) in the 1970s, as well as surface velocities derived from Radarsat-1 interferometric synthetic aperture radar data collected from 2000 to the present. The InSAR velocities were derived using a speckle tracking technique over 24- day periods, describing the interannual as well as seasonal variability in speed. The velocities from different time periods are influenced by climate and possible surge behavior; hence we expect temporal variations in the absolute values of the velocities but not in the spatial pattern. Analysis of the surface strain rates will enable us to improve calculations of basal velocities by relaxing assumptions such as uniform basal shear stress and negligible sidewall drag. An enhanced understanding of the glacier's dynamics, combined with information about ice depth from upcoming air-borne ice penetrating radar measurements, will enable us to better investigate areas with high erosive potential in the context of the active deformation and seismic activity in the region studied by the St. Elias Erosion/Tectonics Project.

Headley, R.; Hallet, B.; Rignot, E.

2007-12-01

120

Gagiwdul.at: Brought Forth To Reconfirm. The Legacy of a Taku River Tlingit Clan.  

ERIC Educational Resources Information Center

The six legends told here, in Tlingit on the left page and in English on the right page, are told by Elizabeth Nyman, a Tlingit elder of the Taku River clan. The narratives represent a portion of the clan's oral history. Introductory sections provide some historical background concerning the clan, the story teller, and the traditions with which…

Nyman, Elizabeth; Leer, Jeff

121

Gagiwdul.at: Brought Forth To Reconfirm. The Legacy of a Taku River Tlingit Clan.  

ERIC Educational Resources Information Center

|The six legends told here, in Tlingit on the left page and in English on the right page, are told by Elizabeth Nyman, a Tlingit elder of the Taku River clan. The narratives represent a portion of the clan's oral history. Introductory sections provide some historical background concerning the clan, the story teller, and the traditions with which…

Nyman, Elizabeth; Leer, Jeff

122

Mercury and water-quality data from Rink Creek, Salmon River, and Good River, Glacier Bay National Park and Preserve, Alaska, November 2009-October 2011  

USGS Publications Warehouse

Glacier Bay National Park and Preserve (GBNPP), Alaska, like many pristine high latitude areas, is exposed to atmospherically deposited contaminants such as mercury (Hg). Although the harmful effects of Hg are well established, information on this contaminant in southeast Alaska is scarce. Here, we assess the level of this contaminant in several aquatic components (water, sediments, and biological tissue) in three adjacent, small streams in GBNPP that drain contrasting landscapes but receive similar atmospheric inputs: Rink Creek, Salmon River, and Good River. Twenty water samples were collected from 2009 to 2011 and processed and analyzed for total mercury and methylmercury (filtered and particulate), and dissolved organic carbon quantity and quality. Ancillary stream water parameters (discharge, pH, dissolved oxygen, specific conductance, and temperature) were measured at the time of sampling. Major cations, anions, and nutrients were measured four times. In addition, total mercury was analyzed in streambed sediment in 2010 and in juvenile coho salmon and several taxa of benthic macroinvertebrates in the early summer of 2010 and 2011.

Nagorski, Sonia A.; Neal, Edward G.; Brabets, Timothy P.

2013-01-01

123

Proccedings of the Third Glacier Bay Science Symposium 1993.  

National Technical Information Service (NTIS)

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

D. R. Engstrom

1993-01-01

124

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

NASA Astrophysics Data System (ADS)

Alaska glaciers contribute more to sea level rise than any other glacierized mountain region in the world. Alaska is loosing ~84 Gt of ice annually, which accounts for ~0.23 mm/yr of SLR (Luthcke et al., 2008). The primary cause of such rapid mass loss is complex glacier flow dynamics, not increased melting due to temperature increases (Larsen et al., 2007). Indirect observations indicate these complex flow dynamics occur on many glaciers throughout Alaska, but no comprehensive measurements of flow velocities have been made. We are working to measure surface velocities on glaciers throughout Alaska using offset tracking with synthetic aperture radar (SAR). We focus on the flow dynamics on the Seward/Malaspina Glacier system and on surrounding St. Elias glaciers. Flow variations of approximately 80% are evident on the Seward during “quiescent” phases. An active surge is visible on the Agassiz Glacier and regional synchronous velocity fluctuations have been found.

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

2010-12-01

125

Abundant, seasonally variable supply of glacier flour-derived iron drives high nitrate consumption in Copper River plume and adjacent Gulf of Alaska continental shelf  

NASA Astrophysics Data System (ADS)

Recent work has suggested that high iron supply may contribute to a northward increase in phytoplankton biomass along the U.S. west coast, consistent with “bottom-up” control of these coastal ecosystems. We examine this hypothesis in waters of the Copper River plume and nearby continental shelf in the northern Gulf of Alaska (GoA). These are the first data we know of examining “bottom up” control of this coastal ecosystem by the supply of nitrate and iron. These are also the first data we know of that examine seasonal variability in the mechanisms that supply iron to this region, and in the iron concentrations. High concentrations (several hundred nM) of “total dissolveable” Fe (unfiltered, pH ~2) were present in surface waters spanning the continental shelf in early April 2010, from resuspension of fine glacial flour. Concentrations decreased dramatically beyond the shelf break. This fine particulate matter represents a large source of “dissolved” Fe to these waters. Surface-water nitrate concentrations were fairly uniform (~15 uM) across the entire shelf at this time, due to deep winter mixing. By late July this shelf particulate Fe source is greatly diminished, owing to strong stratification. Yet there is abundant “total dissolveable” Fe (several mM) at this time from the Copper River plume (largest single freshwater source to the GoA) and lower (several hundred nM) concentrations in the AK coastal current (that reflect the cumulative impact of melting glaciers from further south). By late July this abundant supply of iron in the Copper River vicinity, together with strong stratification, lead to complete consumption of surface-water nitrate across the entire shelf (and extending tens of km beyond the shelf). These data are consistent with the idea that high primary productivity in this region is fueled by abundant wintertime surface-water nitrate, together with iron supply from fine, labile, glacier-derived particulate matter from seasonally variable sources.

Crusius, J.; Schroth, A. W.; Campbell, R. W.; Nielsen, J. L.; Hoyer, I. R.; Brooks, W.

2010-12-01

126

The Significance of Shifts in Precipitation Patterns: Modelling the Impacts of Climate Change and Glacier Retreat on Extreme Flood Events in Denali National Park, Alaska  

PubMed Central

In glacier-fed systems climate change may have various effects over a range of time scales, including increasing river discharge, flood frequency and magnitude. This study uses a combination of empirical monitoring and modelling to project the impacts of climate change on the glacial-fed Middle Fork Toklat River, Denali National Park, Alaska. We use a regional calibration of the model HBV to account for a paucity of long term observed flow data, validating a local application using glacial mass balance data and summer flow records. Two Global Climate Models (HADCM3 and CGCM2) and two IPCC scenarios (A2 and B2) are used to ascertain potential changes in meteorological conditions, river discharge, flood frequency and flood magnitude. Using remote sensing methods this study refines existing estimates of glacial recession rates, finding that since 2000, rates have increased from 24m per year to 68.5m per year, with associated increases in ablation zone ice loss. GCM projections indicate that over the 21st century these rates will increase still further, most extensively under the CGCM2 model, and A2 scenarios. Due to greater winter precipitation and ice and snow accumulation, glaciers release increasing meltwater quantities throughout the 21st century. Despite increases in glacial melt, results indicate that it is predominantly precipitation that affects river discharge. Three of the four IPCC scenarios project increases in flood frequency and magnitude, events which were primarily associated with changing precipitation patterns, rather than extreme temperature increases or meltwater release. Results suggest that although increasing temperatures will significantly increase glacial melt and winter baseflow, meltwater alone does not pose a significant flood hazard to the Toklat River catchment. Projected changes in precipitation are the primary concern, both through changing snow volumes available for melt, and more directly through increasing catchment runoff.

Crossman, Jill; Futter, Martyn N.; Whitehead, Paul G.

2013-01-01

127

Apogean-perigean signals encoded in tidal flats at the fluvio-estuarine transition of Glacier Creek, Turnagain Arm, Alaska; implications for ancient tidal rhythmites  

USGS Publications Warehouse

Turnagain Arm is a macrotidal fjord-style estuary. Glacier Creek is a small, glacially fed stream which enters the estuary tangentially near Girdwood, Alaska. Trenches and daily sedimentation measurements were made in a mudflat along the fluvio-estuarine transition of Glacier Creek during several summers since 2003. Each year, the flats appear to erode during the winter and then accrete vertically in the spring and summer. In each of the years studied, tidal laminae in vertically thickening and thinning laminae bundles were deposited by twice daily tides in neap-spring tidal cycles. In 2004, bundles of thickening and thinning laminae couplets were noted in trenches cut into the flats. Five laminae bundles alternated between thicker and thinner bundles, corresponding to the perigean (high spring) and apogean (low spring) tides. Well-preserved apogean-perigean cycles have rarely been documented in modern tidal flat sediments. At this location, vertical accretion of tidal rhythmites with well-developed neap-spring cyclicity is possible because of the near-complete removal of the flat from the previous year, which creates accommodation space for vertical accretion without significant reworking. Macrotidal conditions, no reworking by infaunal invertebrates, protection from the main tidal channel by a gravel bar and protection from storm waves and fluvial erosion by a recess in the sedge marsh that surrounds the flats all aid in preservation of rhythmites during aggradation. The position of the flats relative to tidal range allows for accumulation of complete spring cycles and incomplete neap cycles. In the summer of 2004, apogee and perigee were closely aligned with the new and full moons, resulting in successive strong perigee and apogee tides which probably aided in the accumulation of successive thick-thin spring cycles encoding the apogean and perigean tidal cycle. The apogean-perigean signal was not observed in subsequent years. ?? 2011 The Authors.

Greb, S. F.; Archer, A. W.; Deboer, D. G.

2011-01-01

128

The significance of shifts in precipitation patterns: modelling the impacts of climate change and glacier retreat on extreme flood events in denali national park, alaska.  

PubMed

In glacier-fed systems climate change may have various effects over a range of time scales, including increasing river discharge, flood frequency and magnitude. This study uses a combination of empirical monitoring and modelling to project the impacts of climate change on the glacial-fed Middle Fork Toklat River, Denali National Park, Alaska. We use a regional calibration of the model HBV to account for a paucity of long term observed flow data, validating a local application using glacial mass balance data and summer flow records. Two Global Climate Models (HADCM3 and CGCM2) and two IPCC scenarios (A2 and B2) are used to ascertain potential changes in meteorological conditions, river discharge, flood frequency and flood magnitude. Using remote sensing methods this study refines existing estimates of glacial recession rates, finding that since 2000, rates have increased from 24m per year to 68.5m per year, with associated increases in ablation zone ice loss. GCM projections indicate that over the 21(st) century these rates will increase still further, most extensively under the CGCM2 model, and A2 scenarios. Due to greater winter precipitation and ice and snow accumulation, glaciers release increasing meltwater quantities throughout the 21(st) century. Despite increases in glacial melt, results indicate that it is predominantly precipitation that affects river discharge. Three of the four IPCC scenarios project increases in flood frequency and magnitude, events which were primarily associated with changing precipitation patterns, rather than extreme temperature increases or meltwater release. Results suggest that although increasing temperatures will significantly increase glacial melt and winter baseflow, meltwater alone does not pose a significant flood hazard to the Toklat River catchment. Projected changes in precipitation are the primary concern, both through changing snow volumes available for melt, and more directly through increasing catchment runoff. PMID:24023925

Crossman, Jill; Futter, Martyn N; Whitehead, Paul G

2013-09-02

129

Black and Brown Bear Activity at Selected Coastal Sites in Glacier Bay National Park and Preserve, Alaska: A Preliminary Assessment Using Noninvasive Procedures  

USGS Publications Warehouse

A number of efforts in recent years have sought to predict bear activity in various habitats to minimize human disturbance and bear/human conflicts. Alaskan coastal areas provide important foraging areas for bears (Ursus americanus and U. arctos), particularly following den emergence when there may be no snow-free foraging alternatives. Additionally, coastal areas provide important food items for bears throughout the year. Glacier Bay National Park and Preserve (GLBA) in southeastern Alaska has extensive coastal habitats, and the National Park Service (NPS) has been long interested in learning more about the use of these coastal habitats by bears because these same habitats receive extensive human use by park visitors, especially kayaking recreationists. This study provides insight regarding the nature and intensity of bear activity at selected coastal sites within GLBA. We achieved a clearer understanding of bear/habitat relationships within GLBA by analyzing bear activity data collected with remote cameras, bear sign mapping, scat collections, and genetic analysis of bear hair. Although we could not quantify actual levels of bear activity at study sites, agreement among measures of activity (for example, sign counts, DNA analysis, and video record) lends support to our qualitative site assessments. This work suggests that habitat evaluation, bear sign mapping, and periodic scat counts can provide a useful index of bear activity for sites of interest.

Partridge, Steve; Smith, Tom; Lewis, Tania

2009-01-01

130

Marine benthic habitat mapping of Muir Inlet, Glacier Bay National Park and Preserve, Alaska, with an evaluation of the Coastal and Marine Ecological Classification Standard III  

USGS Publications Warehouse

Seafloor geology and potential benthic habitats were mapped in Muir Inlet, Glacier Bay National Park and Preserve, Alaska, using multibeam sonar, ground-truth information, and geological interpretations. Muir Inlet is a recently deglaciated fjord that is under the influence of glacial and paraglacial marine processes. High glacially derived sediment and meltwater fluxes, slope instabilities, and variable bathymetry result in a highly dynamic estuarine environment and benthic ecosystem. We characterize the fjord seafloor and potential benthic habitats using the Coastal and Marine Ecological Classification Standard (CMECS) recently developed by the National Oceanic and Atmospheric Administration (NOAA) and NatureServe. Substrates within Muir Inlet are dominated by mud, derived from the high glacial debris flux. Water-column characteristics are derived from a combination of conductivity temperature depth (CTD) measurements and circulation-model results. We also present modern glaciomarine sediment accumulation data from quantitative differential bathymetry. These data show Muir Inlet is divided into two contrasting environments: a dynamic upper fjord and a relatively static lower fjord. The accompanying maps represent the first publicly available high-resolution bathymetric surveys of Muir Inlet. The results of these analyses serve as a test of the CMECS and as a baseline for continued mapping and correlations among seafloor substrate, benthic habitats, and glaciomarine processes.

Trusel, Luke D.; Cochrane, Guy R.; Etherington, Lisa L.; Powell, Ross D.; Mayer, Larry A.

2010-01-01

131

Operation IceBridge Alaska  

Microsoft Academic Search

Alaskan and adjoining Canadian glaciers represent the largest area of ice cover outside of the polar regions. Since 1993, the University of Alaska (UAF) has performed light aircraft laser altimetry surveys of over 200 glaciers across the region. Analysis of these survey data led to the discovery that glaciers here are losing mass so rapidly that they contribute significantly to

C. F. Larsen; A. Johnson; S. L. Zirnheld; P. Claus

2010-01-01

132

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

133

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

134

Deglaciation and latest Pleistocene and early Holocene glacier readvances on the Alaska Peninsula: Records of rapid climate change due to transient changes in solar intensity and atmospheric CO sub 2 content  

SciTech Connect

Geologic mapping near Windy Creek, Katmai National Park, identified two sets of glacial deposits postdating late-Wisconsin Iliuk moraines and separated from them by volcaniclastic deposits laid down under ice-free conditions. Radiocarbon dating of organic material incorporated in the younger Katolinat till and in adjacent peat and lake sediments suggests that alpine glaciers on the northern Alaska Peninsula briefly expanded between ca. 8500 and 10,000 years B.P. Stratigraphic relationships and radiocarbon dates suggest an age for the older Ukak drift near the Pleistocene-Holocene boundary between ca. 10,000 and 12,000 years B.P. The authors suggest that rapid deglaciation following deposition of the Iliuk drift occurred ca. 13,000-12,000 years B.P. in response to large increases in global atmospheric greenhouse gas content, including C02. Short-term decreases in these concentrations, as recorded in polar ice cores, may be linked with brief periods of glacier expansion during the latest Pleistocene and early Holocene. A transient episode of low solar intensity may also have occurred during parts of the early Holocene. Rapid environmental changes and glacial fluctuations on the Alaska Peninsula may have been in response to transient changes in the concentration of atmospheric greenhouse gases and solar intensity.

Pinney, D.S.; Beget, J.E.

1992-03-01

135

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

Microsoft Academic Search

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

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

2007-01-01

136

World Glacier Monitoring Service  

NSDL National Science Digital Library

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

137

Water Resources of Alaska  

NSDL National Science Digital Library

The Water Resources of Alaska homepage is provided by the US Geological Survey. The goal of this project is to study and understand Alaska's hydrology (surface water, ground water, and water quality) for use and management of the nation's water resources. The site features a list of published reports and information about current projects as well as a vast amount of hydrologic data such as surface water, ground water, water quality, glaciers, water use, and hydrologic data reports.

Geological Survey (U.S.). Water Resources Division. Alaska District.

1999-01-01

138

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

139

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

Code of Federal Regulations, 2010 CFR

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

2009-07-01

140

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

Code of Federal Regulations, 2010 CFR

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

2009-07-01

141

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

142

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

143

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

144

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

Microsoft Academic Search

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

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

145

Glacier Caves  

NSDL National Science Digital Library

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

146

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

147

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

NASA Astrophysics Data System (ADS)

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

Le Bris, Raymond; Paul, Frank

2013-03-01

148

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

149

Radiocarbon Dates Link Marine Incursion and Neoglacial Ice Terminus Advance With Tlingit Ethnohistory and Archeology in Lower Glacier Bay  

Microsoft Academic Search

Radiocarbon dates from wood, organic sediments, and marine shells were collected from eroded beach terraces and upper beach sediments in the Beardslee Islands and Berg Bay in Glacier Bay National Park, Alaska. These provide a timetable for the the outwash plain construction and final advance of the Late Neoglacial glacier front over this outwash plain into lower Glacier Bay. On

C. L. Connor; D. Monteith; W. Howell; G. Strevelar; M. Leirer

2004-01-01

150

Glacier Photograph Collection  

NSDL National Science Digital Library

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

Center, National S.

151

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

152

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

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

153

Reanalysis of the USGS Alaskan benchmark glacier dataset  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

154

Alaska Science Center: Biological Science Office  

NSDL National Science Digital Library

This United States Geological Survey (USGS) site provides summaries of biology projects in Alaska. Topics include ecosystems and habitats (Valdez oil spill, Glacier Bay National Park, coastal habitats, terrestrial habitats), birds, mammals (brown bears, caribou, polar bears, sea otters, wolves, and walrus), fisheries, as well as current and emerging issues in Alaska. This branch of the USGS is responsible for research of trust lands and waters in Alaska, and providing scientific information essential for resource management decisions.

155

South Cascade Glacier bibliography  

SciTech Connect

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

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

1984-01-01

156

Assessment Of Errors In Long-Term Mass Balance Records From Alaska, USA  

NASA Astrophysics Data System (ADS)

The USGS maintains a long-term glacier mass balance monitoring program at Gulkana and Wolverine glaciers in Alaska. The records produced by this program are a major component of the world’s mountain glacier balance inventory due to the scarcity of such long-term measurements. Recent data that show rapid glacier volume loss in Alaska further emphasize the importance of these records. An integral part of the long-term mass balance program is repeated assessment of the validity of the methods because bias errors in mass balance data are cumulative. Long-term glacier mass balance records in Alaska have previously been shown to be in good agreement with geodetically determined volume changes despite a minimal network of mass balance stakes. Because the rates of negative mass balance and change in glacier geometry have recently increased, this work reassess whether or not the existing stake networks and method of determining glacier-average balance are still working adequately.

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

2009-12-01

157

Subglacial `Supercavitation' as a Cause of the Rapid Advances of Glaciers  

Microsoft Academic Search

THE rapid advance of the Otto Fjord Glacier reported by Hattersley-Smith1 seems to be very similar to the catastrophic advances which happened in the Alaska Range2 and in the Andes of Santiago3. As observed on the Muldrow Glacier, the flood of the lower part of the glacier is associated with a collapse of the upper one. It is a slip

L. Lliboutry

1964-01-01

158

Late Pleistocene Glaciation of the Southwestern Ahklun Mountains, Alaska  

Microsoft Academic Search

Glacial deposits in the southwestern Ahklun Mountains, southwestern Alaska, record two major glacier advances during the late Pleistocene. The Arolik Lake and Klak Creek glaciations took place during the early and late Wisconsin, respectively. During the Arolik Lake glaciation, outlet glaciers emanated from an ice cap centered over the central portion of the Ahklun Mountains and expanded beyond the present

Jason P. Briner; Darrell S. Kaufman

2000-01-01

159

Improving Mass Balance Modeling of Benchmark Glaciers  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

160

Afghanistan Glacier Diminution  

Microsoft Academic Search

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

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

2008-01-01

161

Hydrologic monitoring of supercooled meltwater from Icelandic glaciers  

NASA Astrophysics Data System (ADS)

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

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

2005-11-01

162

Population Trends, Diet, Genetics, and Observations of Steller Sea Lions in Glacier Bay National Park  

Microsoft Academic Search

We are using demographics, scat analysis, and genetic measurements of Steller sea lions (SSLs)to understand the factors affecting population status throughout Alaska. Steller sea lions are listed as threatened throughout Southeast Alaska including Glacier Bay National Park where they frequent at least five terrestrial sites, including a recently established rookery on Graves Rock. Breeding season counts in GBNP increased at

Tom Gelatt; Andrew W. Trites; Kelly Hastings; Lauri Jemison; Ken Pitcher; Greg O'Corry-Crowe

163

Patterns of Glacier Change in the American West  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

164

Post Little Ice Age Rebound in the Glacier Bay Region  

Microsoft Academic Search

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

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

165

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.

166

Worthington Glacier Project  

NSDL National Science Digital Library

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

167

Columbia Bay, Alaska: an 'upside down' estuary  

USGS Publications Warehouse

Circulation and water properties within Columbia Bay, Alaska, are dominated by the effects of Columbia Glacier at the head of the Bay. The basin between the glacier terminus and the terminal moraine (sill depth of about 22 m) responds as an 'upside down' estuary with the subglacial discharge of freshwater entering at the bottom of the basin. The intense vertical mixing caused by the bouyant plume of freshwater creates a homogeneous water mass that exchanges with the far-field water through either a two- or a three-layer flow. In general, the glacier acts as a large heat sink and creates a water mass which is cooler than that in fjords without tidewater glaciers. The predicted retreat of Columbia Glacier would create a 40 km long fjord that has characteristics in common with other fjords in Prince William Sound. ?? 1988.

Walters, R. A.; Josberger, E. G.; Driedger, C. L.

1988-01-01

168

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

SciTech Connect

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

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

1992-03-01

169

Afghanistan Glacier Diminution  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

170

Late nineteenth to early twenty-first century behavior of Alaskan glaciers as indicators of changing regional climate  

USGS Publications Warehouse

Alaska's climate is changing and one of the most significant indications of this change has been the late 19th to early 21st century behavior of Alaskan glaciers. Weather station temperature data document that air temperatures throughout Alaska have been increasing for many decades. Since the mid-20th century, the average change is an increase of ?????2.0????C. In order to determine the magnitude and pattern of response of glaciers to this regional climate change, a comprehensive analysis was made of the recent behavior of hundreds of glaciers located in the eleven Alaskan mountain ranges and three island areas that currently support glaciers. Data analyzed included maps, historical observations, thousands of ground-and-aerial photographs and satellite images, and vegetation proxy data. Results were synthesized to determine changes in length and area of individual glaciers. Alaskan ground photography dates from 1883, aerial photography dates from 1926, and satellite photography and imagery dates from the early 1960s. Unfortunately, very few Alaskan glaciers have any mass balance observations. In most areas analyzed, every glacier that descends below an elevation of ?????1500??m is currently thinning and/or retreating. Many glaciers have an uninterrupted history of continuous post-Little-Ice-Age retreat that spans more than 250??years. Others are characterized by multiple late 19th to early 21st century fluctuations. Today, retreating and/or thinning glaciers represent more than 98% of the glaciers examined. However, in the Coast Mountains, St. Elias Mountains, Chugach Mountains, and the Aleutian Range more than a dozen glaciers are currently advancing and thickening. Many currently advancing glaciers are or were formerly tidewater glaciers. Some of these glaciers have been expanding for more than two centuries. This presentation documents the post-Little-Ice-Age behavior and variability of the response of many Alaskan glaciers to changing regional climate. ?? 2006.

Molnia, B. F.

2007-01-01

171

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

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

172

The thermophysics of glaciers  

SciTech Connect

This volume presents the results of experimental and theoretical work on the thermodynamics of ice sheets and glaciers. The author has carried out extensive field work in both the Soviet Union and Antarctica over the last 25 years and has contributed to the understanding of the thermophysics of glaciers. The topics covered in this volume embrace heat flow measurement and temperature distributions in glaciers, the thermal drilling of glaciers, the melting and freezing of ice sheets, and other thermophysical problems. Also included are topics of relevance to glacial engineering.

Zotikov, I.A.

1986-01-01

173

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

174

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

175

The Morteratsch Glacier  

Microsoft Academic Search

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

Hugo Leupold

1881-01-01

176

Mini Glacier Meltdown  

NSDL National Science Digital Library

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

Twin Cities Public Television, Inc.

2007-01-01

177

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

178

Dendrochronology to the Beat of a Different Drummer: Lakes Dammed by a Tidewater Glacier Out of Phase with Climate  

NASA Astrophysics Data System (ADS)

Glacier-dammed lakes typically form during glacier advance or retreat that is in phase with climate change. Most glacier-dammed lakes that have formed in the past century are located in closed basins created by glacier retreat and downwasting. However, tidewater glaciers can be relatively insensitive to climate and can advance when adjacent land-based glaciers are in retreat. The regimen of tidewater glaciers is strongly controlled by the nature of the terminus. When a morainal shoal or fjord constriction limits mass loss due to calving, the glacier may remain stable or advance even in a warming climate. However, a small perturbation in climate can cause the terminus to retreat off a shoal or beyond a constriction into deeper, open water. Once this happens, more mass is lost through calving than is replenished and the glacier may catastrophically retreat. Because many tidewater glaciers are large, this cycle can be several hundred years in length, thereby lagging climatic perturbations that affect other glaciers. Many tidewater glaciers have dammed lakes as they advanced over the past century. Brady Glacier, at the head of Taylor Bay in southeast Alaska, advanced through most of the 20th century. When George Vancouver's party mapped Taylor Bay in 1794, the glacier terminus was a steep calving front. In 1880 John Muir visited the glacier and commented that it was advancing onto an outwash plain that it had built. It continued to advance until the 1960s and has remained at almost the same position since then, despite thinning many tens of meters. As Brady Glacier advanced, it buried trees along the walls of the fjord and impounded large lakes in tributary valleys. At least two of these lakes formed on opposite sides of the glacier in areas occupied by mature forest. We collected incremental cores and discs of trees killed by overriding ice and rising lake waters in order to establish a dendrochronological history of the last glacier advance and the filling of the lakes. The samples are from rooted subfossil trees located at different elevations within the lake basins and below the previous limit of the glacier. The elevation and location of each tree base were determined with a differential GPS. The results show that the Brady was advancing through the area in the early 1800s and that it killed trees along the valley margins at progressively higher levels through time. The oldest and lowest trees that were sampled in the Spur Lake basin on the east side of the glacier were killed in the early 1800s. The lake rose tens of meters over a few decades. The oldest and lowest trees sampled in the North Trick Lake basin on the west side of the glacier were killed in the early 1830s. Like Spur Lake, North Trick Lake increased in depth over a few decades. Many of these trees in both Spur and North Trick lakes were over 300 years old, which indicates that the glacier had been less extensive than today for at least that long. Just to the east, the tidewater glacier in Glacier Bay had advanced about a century earlier than Brady Glacier, underscoring non-climatic controls on glacier activity in the area. As Glacier Bay ice retreated and presumably ice-dammed lakes drained in Glacier Bay, Brady Glacier advanced, damming lakes at its margins. The lakes impounded by Brady Glacier and frequent jökulhlaups derived from them affect glacier motion, mass balance, and glacier stability. The lakes extend beneath portions of the glacier, and significant ice mass is lost to the lakes by calving. Jökulhlaups carve channels into the base of Brady Glacier and could erode the outwash plain at the glacier terminus. Both processes could initiate catastrophic retreat of the glacier.

Capps, D.; Wiles, G.; Clague, J.

2009-04-01

179

Modeling Glacier Erosion Through Time  

NSDL National Science Digital Library

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

Connor, Cathy L.

180

Holocene Loess and Paleosols in Central Alaska: A Proxy Record of Holocene Climate Change.  

National Technical Information Service (NTIS)

Episodic Holocene loess deposition and soil formation in the sediments of the Nenana valley of Central Alaska may reflect Holocene climate change. Periods of loess deposition seem to correlate with times of alpine glacier activity, while paleosols corresp...

J. E. Beget N. H. Bigelow

1992-01-01

181

Late Pleistocene Cosmogenic 36Cl Glacial Chronology of the Southwestern Ahklun Mountains, Alaska  

Microsoft Academic Search

Thirty-two cosmogenic 36Cl surface exposure ages constrain the timing of two late Pleistocene glacial advances in the western Ahklun Mountains, southwestern Alaska. Boulders were sampled from one early Wisconsin (sensu lato) and six late Wisconsin moraines deposited by ice-cap outlet glaciers and local alpine glaciers. Four moraine boulders deposited during an extensive early Wisconsin ice-cap outlet glacier advance have a

Jason P. Briner; Terry W. Swanson; Marc Caffee

2001-01-01

182

Geologic studies in Alaska by the U. S. Geological survey during 1987  

SciTech Connect

The reports presented in this book begin with an article on the advance of Hubbard Glacier and its damming of Russell Fiord in southern Alaska followed by 40 short papers related to the five regional subdivision of Alaska and to areas offshore on the Alaska continental shelf. These papers provide a representative sample of current U.S. Geological Survey (USGS) research in Alaska. Two bibliographies cover reports about Alaska in USGS publications released in 1987 and reports about Alaska by USGS authors in outside publications in 1987.

Galloway, J.P.; Hamilton, T.D.

1988-01-01

183

Contribution to future sea level rise of glacier melt in response to modeled global climate scenarios from CMIP5  

NASA Astrophysics Data System (ADS)

A large component of present-day sea-level change is due to the melt of glaciers other than ice sheets. Our recent projections of their contribution to sea level rise by 2100 range between 7 and 18 cm, while the main sources of uncertainty are incomplete glacier inventories and the choice of global climate models (GCMs) to force the glacier mass balance model. Regions with the most incomplete inventories, such as Arctic Canada, Alaska, and glaciers at the periphery of Antarctic and Greenland ice sheet, are also the main contributors of glacier melt to future sea level rise. Here, we attempt to narrow the range of uncertainties by using updated glacier inventories in these regions. We combine recently updated glacier outlines with available DEMs and run a flow-shed algorithm in order to delineate individual glaciers in these regions. This information is necessary input to our mass balance model, which is forced by climate reanalysis (ERA-40 and ERA-Interim) to assess glacier volume changes in the period 1961-2005. The model is calibrated and validated against all available observations of glacier mass changes on local and regional scale. Finally, the future time series of regional glacier volume change is produced by forcing the model with downscaled temperature and precipitation from all available GCMs from CMIP5.

Radic, V.; Hock, R. M.; Clarke, G. K.; Cogley, J. G.

2011-12-01

184

Modelling Greenland Outlet Glaciers.  

National Technical Information Service (NTIS)

The objective of this project was to develop simple yet realistic models of Greenland outlet glaciers to better understand ongoing changes and to identify possible causes for these changes. Several approaches can be taken to evaluate the interaction betwe...

C. vanderVeen

2001-01-01

185

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

186

Moving Model Glacier  

NSDL National Science Digital Library

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

Twin Cities Public Television, Inc.

2007-01-01

187

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

188

A snow algal community on Akkem glacier in the Russian Altai mountains  

NASA Astrophysics Data System (ADS)

Snow algae are cold-tolerant algae growing on snow and ice and have been reported on glaciers in many parts of the world. Blooms of snow algae can reduce the surface albedo of snow and ice and significantly affect their melting. In addition, snow algae found in ice cores can be potential indicators of the paleo-environment, making them of great interest both to the biology and the geophysics of glaciers. A snow algal community was investigated in 2002 and 2003 on Akkem glacier in the Russian Altai mountains, where no information on its biological community has previously been available. Five species of snow algae including green algae and cyanobacteria were observed on the glacier. Red snow due to a bloom of algae (Chloromonas sp.) was visually apparent in the snow area during our study periods. The total algal cell-volume biomass on the glacier ranged from 97 to 1156 ?L m-2, which is equivalent to that reported previously on glaciers in the Himalaya and Alaska. The community structure showed that Mesotaenium berggrenii and/or Ancylonema nordenskioeldii, which are common species on glaciers in the Northern Hemisphere, were dominant in the ice area, while Chloromonas sp. was dominant in the snow area. Such community structures are similar to those on Alaskan and Arctic glaciers but differ from those on Himalayan and Tibetan glaciers, even though the Altai mountains are geographically closer to the Himalaya and Tibet than to Alaska. The difference in algal communities between the Altaic and other glaciers is discussed together with physical and chemical conditions affecting the algae.

Takeuchi, Nozomu; Uetake, Jun; Fujita, Koji; Aizen, Vladimir B.; Nikitin, Stanislav D.

189

The mysterious case of the vanishing permafrost - Gruben Rock Glacier, Switzerland  

NASA Astrophysics Data System (ADS)

As glaciers are losing ice volume in the Alps, as elsewhere, so is mountain permafrost. This has been recognised by increased rockfall activity from steep mountain faces. The presence of ice-rich permafrost and reduction of volume is more difficult to detect where the slope angle is lower than that of free rock faces. The lagged response makes it difficult to detect melting and any consequent surface lowering. Rock glaciers have been viewed as indicative of the result of flow of ice-rich permafrost and thus indicators of mat of < 1.5 °C. Although the 'permafrost' model has been contested, the alternative, 'glacier core' model does not deny that permafrost conditions can exist for some rock glaciers exhibiting ice cores and thus differentiation is difficult just by viewing or imaging the surface topographic feature. The rock glacier at Grubengletscher (Wallis, Switzerland) has been studied since the 1970s and has been used as an exemplar of rock glaciers that indicate mountain permafrost. The site has been examined over several years because of potential water flooding (jokulhlaups) affecting a village in the valley. Published mapping of the feature shows the portion mapped as 'rock glacier' (= permafrost) has been increasingly reduced over the last 20 years. The upstream area has been indicated to be glacier ice-cored as small thermokarst lakes have formed. Field examination of the whole feature shows that small glacier ice exposures exist even in the 'rock glacier'. This view of 'hidden glacier ice' is confirmed by examining topographic maps from about 1850 CE where the whole of the basin is shown as being glacier covered. The debris covering and protecting the glacier-derived ice must date from after this (Late Little Ice Age) period. Other recent examples of exposed glacier ice below debris can also be seen at mountain locations as diverse as Turkey and Alaska as well as from the length of the Rockies. The conclusion is that care must be taken in using rock glaciers anywhere as necessarily indicating permafrost, whether present day features or mapped as paleo-permafrost indicators used in climatic reconstructions. As global temperatures increase, continued observation at rock glacier sites should confirm or deny the general presence of glacier ice cores or actual permafrost-bound ice.

Whalley, B.

2011-12-01

190

Recent Acceleration of Thwaites Glacier.  

National Technical Information Service (NTIS)

The first velocity measurements for Thwaites Glacier were made by R. J. Allen in 1977. He compared features of Thwaites Glacier and Iceberg Tongue on aerial photography from 1947 and 1967 with 1972 Landsat images, and measured average annual displacements...

J. G. Ferrigno

1993-01-01

191

The basal speed of valley glaciers: an inverse approach  

NASA Astrophysics Data System (ADS)

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

Truffer, Martin

192

Understanding Landslide Tsunami Hazard in Alaska Fjords for Tsunami Inundation Mapping  

Microsoft Academic Search

Several communities of the southern coast of Alaska are located in glacial fjords, which are fed by major rivers and creeks draining nearby glaciers and depositing sediments into the bays at a high rate. Sediment accumulation on the steep underwater slopes contributes to the landslide tsunami hazard in these communities. During the Great Alaska Earthquake of 1964, the majority of

E. Suleimani; R. Hansen

2007-01-01

193

The GLIMS Glacier Database  

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

194

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

195

Anthropogenic aerosols as a source of ancient dissolved organic matter in glaciers  

NASA Astrophysics Data System (ADS)

Glacier-derived dissolved organic matter represents a quantitatively significant source of ancient, yet highly bioavailable carbon to downstream ecosystems. This finding runs counter to logical perceptions of age-reactivity relationships, in which the least reactive material withstands degradation the longest and is therefore the oldest. The remnants of ancient peatlands and forests overrun by glaciers have been invoked as the source of this organic matter. Here, we examine the radiocarbon age and chemical composition of dissolved organic matter in snow, glacier surface water, ice and glacier outflow samples from Alaska to determine the origin of the organic matter. Low levels of compounds derived from vascular plants indicate that the organic matter does not originate from forests or peatlands. Instead, we show that the organic matter on the surface of the glaciers is radiocarbon depleted, consistent with an anthropogenic aerosol source. Fluorescence spectrophotometry measurements reveal the presence of protein-like compounds of microbial or aerosol origin. In addition, ultrahigh-resolution mass spectrometry measurements document the presence of combustion products found in anthropogenic aerosols. Based on the presence of these compounds, we suggest that aerosols derived from fossil fuel burning are a source of pre-aged organic matter to glacier surfaces. Furthermore, we show that the molecular signature of the organic matter is conserved in snow, glacier water and outflow, suggesting that the anthropogenic carbon is exported relatively unchanged in glacier outflows.

Stubbins, Aron; Hood, Eran; Raymond, Peter A.; Aiken, George R.; Sleighter, Rachel L.; Hernes, Peter J.; Butman, David; Hatcher, Patrick G.; Striegl, Robert G.; Schuster, Paul; Abdulla, Hussain A. N.; Vermilyea, Andrew W.; Scott, Durelle T.; Spencer, Robert G. M.

2012-03-01

196

Fundamentals of Glacier Dynamics  

NASA Astrophysics Data System (ADS)

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

Thomas, Robert H.

197

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

198

Characteristics of sediment discharge in the subarctic Yukon River, Alaska  

Microsoft Academic Search

The characteristics of sediment discharge in the Yukon River, Alaska were investigated by monitoring water discharge, water turbidity and water temperature. The river-transported sediment, 90 wt.% or more, consists of silt and clay (grain size?62.5 ?m), which probably originated in the glacier-covered mountains mostly in the Alaska Range. For early June to late August 1999, we continuously measured water turbidity

Kazuhisa A. Chikita; Richard Kemnitz; Ryuji Kumai

2002-01-01

199

Late Pleistocene mountain glaciation in Alaska: key chronologies  

Microsoft Academic Search

ABSTRACT: Moraine,sequences,of mountain,glaciers can be used,to infer spatial and,temporal patterns of climate change,across the globe. Alaska is an accessible high-latitude location in the Northern Hemisphere and contains a rich record of alpine glaciation. Here, we highlight the key chronologies,from three mountain,ranges in Alaska that reveal the timing and spatial extent of Late Pleistocene glaciation, and pay particular attention to age

Jason P. Briner; Darrell S. Kaufman

2008-01-01

200

The health of glaciers: Recent changes in glacier regime  

USGS Publications Warehouse

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

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

2003-01-01

201

Glacier surge mechanism based on linked cavity configuration of the basal water conduit system  

Microsoft Academic Search

Based on observations of the 1982-1983 surge of Variegated Glacier, Alaska, a model of the surge mechanism is developed in terms of a transition from the normal tunnel configuration of the basal water conduit system to a linked cavity configuration that tends to restrict the flow of water, resulting in increased basal water pressures that cause rapid basal sliding. The

Barclay Kamb

1987-01-01

202

Rates of erosion and sediment evacuation by glaciers: A review of field data and their implications  

NASA Astrophysics Data System (ADS)

Diverse field data on glacial sediment yields are assembled in the context of the current interest in sedimentary basin development in glaciated regions, and in controversial linkages between global climate and topography. Attention herein is directed at sediment yields, including both overall bedrock erosion and evacuation of sediments stored in glaciated basins over several years or decades. These yields, expressed as effective rates of glacial erosion, vary by orders of magnitude from 0.01 mm yr -1 for polar glaciers and thin temperate plateau glaciers on crystalline bedrock, to 0.1 mm yr -1 for temperate valley glaciers also on resistant crystalline bedrock in Norway, to 1.0 mm yr -1 for small temperate glaciers on diverse bedrock in the Swiss Alps, and to 10-100 mm yr -1 for large and fast-moving temperate valley glaciers in the tectonically active ranges of southeast Alaska. In Alaska, current sediment yields generally increase with the extent of glacial ice cover, and are particularly high in the large heavily-glaciated basins of southern Alaska, where they exceed those of basins from other regions by about one order of magnitude. These results, supported by comparisons of sediment yields between glaciated and nonglaciated basins in Alaska, Norway and Iceland, suggest that climatic conditions favorable for the expansion of temperate valley glaciers tend to increase both mechanical and chemical denudation rates. The results are discussed in the broader context of linking erosion and climate during the ice ages of the Quaternary, and interpreting records of sedimentation from glaciated regions.

Hallet, B.; Hunter, L.; Bogen, J.

1996-03-01

203

Glaciers and Glaciation  

NSDL National Science Digital Library

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

Nelson, Stephen

204

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.

205

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

206

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

207

Progress toward Consensus Estimates of Regional Glacier Mass Balances for IPCC AR5  

NASA Astrophysics Data System (ADS)

Glaciers are potentially large contributors to rising sea level. Since the last IPCC report in 2007 (AR4), there has been a widespread increase in the use of geodetic observations from satellite and airborne platforms to complement field observations of glacier mass balance, as well as significant improvements in the global glacier inventory. Here we summarize our ongoing efforts to integrate data from multiple sources to arrive at a consensus estimate for each region, and to quantify uncertainties in those estimates. We will use examples from Alaska to illustrate methods for combining Gravity Recovery and Climate Experiment (GRACE), elevation differencing and field observations into a single time series with related uncertainty estimates. We will pay particular attention to reconciling discrepancies between GRACE estimates from multiple processing centers. We will also investigate the extent to which improvements in the glacier inventory affect the accuracy of our regional mass balances.

Arendt, A. A.; Gardner, A. S.; Cogley, J. G.

2011-12-01

208

Rapid uplift of southern Alaska caused by recent ice loss  

Microsoft Academic Search

Changing surface loads, such as melting glaciers, can induce deformation of the Earth's crust. The speed of the Earth's response to load changes and the pattern of deformation they cause can be used to infer material properties of the lithosphere and mantle. Rapid uplift of southern Alaska has been measured with tide gauges, Global Positioning System (GPS) measurements and studies

Christopher Fairlamb Larsen

2003-01-01

209

The Natural Variability of Glaciers  

NASA Astrophysics Data System (ADS)

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

Roe, G.

2012-04-01

210

A Comparison of Seismic Records of Calving Glaciers  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

211

Electrifying Alaska  

Microsoft Academic Search

Alaska's diverse systems for electric power include only 4% by private utilities. Large distances and small markets make transmission impractical for the most part. Rates are variable, although the state average is low. Energy sources, except nuclear, are abundant: half the US coal reserves are in Alaska. In addition, it has geothermal, tidal, biomass, solar, wind, and hydroelectric power. Energy

Reinemer

2009-01-01

212

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

NASA Astrophysics Data System (ADS)

Glaciers around the world are, with rare exceptions, stagnating or in hasty retreat. Whether growing or shrinking, significant changes in the extent of glaciers have major impacts on nature and humanity in their immediate vicinity, because land uses are utterly different depending on whether the land is covered by ice. Upon glacier retreat, new land uses may become possible: (1) Transportation corridors may become feasible where previously there were barriers. (2) Exposure of the lithosphere may yield mineral riches that previously were inaccessible. (3) New wildlife habitat and migration routes may develop, thus promoting genetic diffusion/interbreeding of previously isolated populations. Glacier impacts go well beyond the locality where they occur. Many glaciers regulate water flow, and contribute to annual water availability and hydropower production. In some regions, such in the Hindu Kush-Himlaya (HKH), especially the western provinces of China, the carrying capacity of the land and further economic development and well-being of the populace is partly dependent on melting glaciers. In India, \\8 billion worth of hydroelectric power (at U.S. electric rates) is generated each year; 50% of that is attributable to runoff from Himalayan glaciers and high-altitude snow fields. Nearly \\1 billion worth of hydroelectric power is due to the current negative mass balance of glaciers. In Nepal, glaciogenic hydropower is even more crucial. Although it may be many decades in coming, the ongoing sharp reduction in glacier area in the HKH will eventually be reflected in heightened water shortages in a region where water already is in short supply. Other glaciers store large amounts of meltwater and release it suddenly, causing havoc and taking lives downstream. This is a major problem in the HKH region and is significant locally in other heavily glaciated regions, such as Alaska. Sea level is a global issue impacted significantly by melting glaciers wherever they occur. Receding and wasting glaciers is a chief telltale sign that global climate change is real and accelerating. Although details of glacier responses to climate change are very complex and not always according to inuition, the basic idea that glaciers tend to melt when the climate warms is understood by the public. Thus, public knowledge of glacier change may help prompt millions of individuals to modify their climate-altering behaviors. The net loss or benefit of receding glaciers has not been calculated, but the effect is apt to be sharply negative. Long-term, negative economic impacts related to water resources and sea level are likely to be the largest concerns. However, an objective accounting must consider positives as well. In Alaska alone, an estimated 20,000 square km of "new land" will emerge from beneath ice over the next century. At present rates of generation of goods and services averaged over Alaska's whole area, this land will be worth at least \\$360M per year, plus other noneconomic benefits. For a variety of reasons, its actual value will likely be far greater, thus partly offsetting the considerable disruptive effects of glacier recession.

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

2002-05-01

213

Glaciers and Glaciation  

NASA Astrophysics Data System (ADS)

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

Clarke, Garry K. C.

214

Muir Glacier in Glacier Bay National Monument 2004  

USGS Multimedia Gallery

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

215

Alaska Commercial Fisheries Statistics.  

National Technical Information Service (NTIS)

The following statistical reports and booklets were compiled, published, and distributed: (1) 1973 Alaska commercial fishing vessel register; (2) Weekly Alaska Salmon casepack reports; (3) Monthly Alaska shellfish reports; (4) Alaska tables for the INPFC ...

J. F. Jewell

1974-01-01

216

Chernobyl fallout on Alpine glaciers  

SciTech Connect

Measurements of the gross beta activity of snow samples from four Alpine glaciers contaminated by radioactive fallout from the Chernobyl nuclear accident and a gamma-spectrum analysis of selected samples are reported. The results are discussed with respect to possible risks to the population from using meltwater from these glaciers as drinking water.

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

1989-01-01

217

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

218

Assessing How Marine-Terminating Glacier Geometry Controls Dynamic Sensitivity to Calving Using a Numerical Ice Flow Model  

NASA Astrophysics Data System (ADS)

Over the past decade, widespread and rapid changes in front position, surface elevation, and flow speed have been observed at marine-terminating outlet glaciers in southeast Alaska, the Antarctic Peninsula, and west and southeast Greenland. Analytical and numerical modeling studies have indicated that these changes in dynamics are initiated by external forcing at the glacier terminus (i.e., increased calving, thinning, and retreat) and propagate to the interior in the form of a kinematic wave. Over areas with a high concentration of outlet glaciers, such as the west Greenland coast, we observe a high degree of variability in the timing and magnitude of change. Since these glaciers are likely undergoing similar external forcing (i.e., increased surface and submarine melting) the variability suggests that geometry, such presence of basal over-deepenings or lateral constrictions near the terminus, may be an important control on glacier response to front perturbations. Understanding how differences in glacier geometry influence the dynamic response to changes in external forcing at the terminus is critical for predicting future change. We employ a depth-integrated ice flow model to compare the dynamic sensitivity of tidewater glaciers to changes in external forcing at the terminus for differing glacier geometries (i.e., basal topography, thickness, and width). The model is designed for tidewater glaciers confined to narrow channels, similar to real-world geometries observed in Greenland, so that the stress balance components consist of substantial basal and lateral drag as well as gradients in longitudinal stress. Glacier response to increased longitudinal stress at the ice/water boundary is assessed for multiple steady-state geometries. Results from the model are compared to recent glaciological observations to determine if a numerical ice flow model with simplified geometry can reasonably describe variability in observed glacier dynamics.

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

2011-12-01

219

Explaining Glaciers, Accurately  

NSDL National Science Digital Library

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

Tate, Mari; Faw, Mary; Scott, Nancy

2009-04-01

220

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

221

Polythermal Glacier Hydrology: A Review  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

222

Remote sensing of glaciers and ice sheets  

NASA Astrophysics Data System (ADS)

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

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

223

Muldrow Glacier and the effect of debris cover on geodetic volume change estimates from DEM and LiDAR elevation measurements  

NASA Astrophysics Data System (ADS)

Since 1993, the University of Alaska (UAF) Glaciers Group has monitored glacier volume changes across Alaska and northern Canada using light aircraft laser altimetry surveys. These surveys are currently part of NASA's Operation IceBridge. As part of the ongoing study, we examine the volume and topography changes in Muldrow Glacier, located in the Central Alaska Range, from 1952 through 2010 using a combination of DEMs, centerline laser altimetry (1994, 2001, and 2008) and LiDAR data (2010), and debris cover maps. Current data show that the volume loss rate for Muldrow Glacier has increased significantly during this period from a mean rate of ~-0.02 km3/yr from 1952 to 1976 to a mean rate of ~-0.19 km3/yr from 2008 to 2010. Flight path laser altimetry data are used to track elevations when no DEM data are available. Laser altimetry and LiDAR measure elevation changes along the centerline of the glacier with an accuracy of ±30cm and are then extrapolated over the entire glacier using the best available DEM. Debris cover on glaciers often has significant and spatially variable effects on the melt rate of glaciers. Due to the spatial variability of debris cover on a glacier, it can represent a source of uncertainty when extrapolating the centerline elevation data to the entire glacier. In order to improve the extrapolation of the centerline elevation data for all glaciers currently being surveyed by UAF, we concentrate on the elevation changes of and spatial distribution of rock debris on Muldrow Glacier. We compare elevation changes based on DEMs from 1952 (from the National Elevation Database), 1976 (a digitized version of Bradford Washburn's topographic map of Muldrow), and 2006 (from AeroMetric, Inc.). We use debris field maps acquired during the mid-1970s and ~2006 in combination with the DEMs to investigate the insulation effects of debris on differential melt rates across the glacier. By also comparing the DEM and debris cover data with data from the aircraft laser altimetry and LiDAR surveys, we can better estimate the effect of surface debris on the volume changes estimated from the centerline elevation changes for all debris-covered glaciers included in these surveys.

Murphy, N.; Larsen, C. F.; Herreid, S. J.

2011-12-01

224

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

NASA Astrophysics Data System (ADS)

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 objectives, we have deployed georadar at frequencies ranging from 5 MHz to 1 GHz in 1D, 2D, and 3D single and multi-offset configurations. We have conducted time lapse georadar monitoring of the glacier at the annual, seasonal, daily, and minute time scales. We have employed state of the art data processing and analysis tools such as reflection tomography to produce accurate radar velocity profiles, and 3D coherence cube imaging to identify the 3D distribution of voids and fractures within the glacier. We have conducted passive seismic monitoring, 3D seismic reflection imaging, and shear wave seismic reflection surveying designed to both to image hydrologic structures and to provide a direct measure of the glaciers elastic properties. Here we provide an overview of the project and to present notable findings to date. These findings include 1) that there is lateral heterogeneity in the liquid water content of the snow and significant lateral flow within the snow pack, 2) that Bench Glacier is stratified with an upper layer containing few voids and little water, and a lower layer containing significantly greater water content and many voids, and 3) the void spaces in the lower layer appear to be comprised of both fractures and randomly distributed irregular void space. Video borehole measurements coupled with azimuthal anisotropy in the geophysical measurements indicate that the voids are primarily subvertically oriented, have a preferred azimuthal orientation that is oblique to the glacier flow direction, and are present at scales ranging from mm to 10s of m.

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

2007-12-01

225

Satellite image atlas of glaciers of the world  

USGS Publications Warehouse

U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of Glaciers of the World, contains 11 chapters designated by the letters A through K. Chapter A provides a comprehensive, yet concise, review of the "State of the Earth's Cryosphere at the Beginning of the 21st Century: Glaciers, Global Snow Cover, Floating Ice, and Permafrost and Periglacial Environments," and a "Map/Poster of the Earth's Dynamic Cryosphere," and a set of eight "Supplemental Cryosphere Notes" about the Earth's Dynamic Cryosphere and the Earth System. The next 10 chapters, B through K, are arranged geographically and present glaciological information from Landsat and other sources of historic and modern data on each of the geographic areas. Chapter B covers Antarctica; Chapter C, Greenland; Chapter D, Iceland; Chapter E, Continental Europe (except for the European part of the former Soviet Union), including the Alps, the Pyrenees, Norway, Sweden, Svalbard (Norway), and Jan Mayen (Norway); Chapter F, Asia, including the European part of the former Soviet Union, China, Afghanistan, Pakistan, India, Nepal, and Bhutan; Chapter G, Turkey, Iran, and Africa; Chapter H, Irian Jaya (Indonesia) and New Zealand; Chapter I, South America; Chapter J, North America (excluding Alaska); and Chapter K, Alaska. Chapters A–D each include map plates.

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

1988-01-01

226

Middle Sister and Hayden Glacier  

USGS Multimedia Gallery

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

2009-12-08

227

Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier. 2: Interpretation  

Microsoft Academic Search

The data presented in part 1 of this paper (Meier et al., 1994) are here used to assess the role of water input\\/output, water storage, and basal water pressure in the rapid movement of Columbia Glacier, Alaska. Consistently high basal water pressures, mostly in the range from 300#kPa below to 100#kPa above the ice overburden pressure, are responsible in an

Barclay Kamb; Hermann Engelhardt; Mark A. Fahnestock; Neil Humphrey; Mark Meier; Dan Stone

1994-01-01

228

Mapping Sub-Glacier Geomorphology and Strucutre in a Collisional Orogen; AN Example from the Agassiz and Malaspina Glaciers, AK  

NASA Astrophysics Data System (ADS)

Structural boundaries in the Saint Elias Mountains of southern Alaska and Yukon, Canada are covered in ice, concealing the underlying geology and making a tectonic interpretation difficult. The Malaspina Glacier covers the active deformation front formed by the subduction of the Yakutat micro-plate beneath southern Alaska. The Malaspina fault is an active structure located beneath the Agassiz lobe of the Malaspina glacier and is the primary focus of this study which aims to constrain the orientation of the fault in the sub surface.We analyzed ice surface topography, ice velocity fields, and folds and crevasses to infer bedrock topographic features with the anticipation of deriving the geologic structures that will clarify the tectonic transition from transform to subduction in the micro-plate. Calculation of the ice velocity field is done by cross-correlating temporal sequences of Landsat images. The topography and structures of the glacier are mapped using Digital Elevation Models, ICESat profiles, and optical imagery. Perturbations in the ice-velocity field, topography, and glacial structures reflect the orientation of ridges and troughs that form from by glacial erosion of geologic structures. To reinforce the observations made on the Malaspina glacier analog models were constructed in the lab to physically model glacial ice flow as it moves over basins and ridges that may reflect faulting and folding at depth. Results indicate that the Agassiz lobe flows eastward across the gentle west dipping back limb of the Malaspina fault propagation fold, implying that the Malaspina fault dips westward but crops out beneath the ice to the east, where the steep forelimb of the fold lies buried. The east facing topographic escarpment through which the Agassiz lobe flows is therefore an erosional feature of the fold, and not a direct expression of the Malaspina fault. Steeply dipping beds of the fold's forelimb are buried where the Agassiz lobe merges with the main body of the Malaspina glacier. Further work is being done to refine the location of the fold limbs, and project the position of the Malaspina fault tip in that area

Cotton, M. M.; Bruhn, R. L.; Sauber, J. M.

2010-12-01

229

Glacier Sensitivity Across the Andes  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

230

Glacier discharge and climate variations  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

231

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

Microsoft Academic Search

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

Joel T. Harper; Neil F. Humphrey

1995-01-01

232

Co-occurrence of Pacific sleeper sharks Somniosus pacificus and harbor seals Phoca vitulina in Glacier Bay  

USGS Publications Warehouse

We present evidence that Pacific sleeper sharks Somniosus pacificus co-occur with harbor seals Phoca vitulina in Glacier Bay, Alaska, and that these sharks scavenge or prey on marine mammals. In 2002, 415 stations were fished throughout Glacier Bay on a systematic sampling grid. Pacific sleeper sharks were caught at 3 of the 415 stations, and at one station a Pacific halibut Hippoglossus stenolepis was caught with a fresh bite, identified as the bite of a sleeper shark. All 3 sharks and the shark-bitten halibut were caught at stations near the mouth of Johns Hopkins Inlet, a glacial fjord with the highest concentration of seals in Glacier Bay. Using a bootstrap technique, we estimated the probability of sampling the sharks (and the shark-bitten halibut) in the vicinity of Johns Hopkins Inlet. If sharks were randomly distributed in Glacier Bay, the probability of sampling all 4 pots at the mouth of Johns Hopkins Inlet was very low (P = 0.00002). The highly non-random distribution of the sleeper sharks located near the largest harbor seal pupping and breeding colony in Glacier Bay suggests that these 2 species co-occur and may interact ecologically in or near Johns Hopkins Inlet. Copyright ?? 2005 by the Alaska Department of Fish and Game.

Taggart, S. J.; Andrews, A. G.; Mondragon, J.; Mathews, E. A.

2005-01-01

233

Significant total mass contained in small glaciers  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

234

Unveiling the climate memory of an Arctic polythermal glacier: a combined radar and thermomechanical modeling approach  

NASA Astrophysics Data System (ADS)

Based on borehole temperature measurements and radio-echo sounding surveys on McCall Glacier, Alaska (USA) we were able to identify and map the Cold Transition Surface (CTS) marking the limit between cold and warm ice of a polythermal glacier. In the accumulation area, the ice column is observed to be warm throughout, while in the ablation area, the amount of cold ice at the top of the ice column increases downstream, hence lowering the CTS. High englacial temperatures in the accumulation are explained by the latent heat release due to percolating meltwater and precipitation, hence warming the ice column. With increasing atmospheric temperatures and increasing ablation rates, reduction of the perennial snowpack results in surface runoff and ice cooling. Using a transient thermomechanically-coupled higher-order glacier model, the timing of the cooling was determined from which past equilibrium-line altitudes (ELA) were constructed, which are in accord with ELAs measured since the 1950s (IGY). The paper therefore shows that (i) mapping of the CTS allows reconstructing the recent climate history of polythermal glaciers, and (ii) with a warming climate, McCall Glacier tends to cool down in a counterintuitive way.

Delcourt, C.; Van Liefferinge, B.; Pattyn, F.; Nolan, M.

2011-12-01

235

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

236

Contribution of deep-seated bedrock landslides to erosion of a glaciated basin in southern Alaska  

Microsoft Academic Search

Landslides represent a key component of catchment-scale denudation, though their relative contribution to the erosion of glaciated basins is not well known. Bedrock landslide contri- bution was investigated on the surface of one of eleven glaciers on a glaciated ridge in the Chugach-St Elias Range of southern Alaska, where the debris from four major landslides is easily distinguished from moraines

Ann M. Arsenault; Andrew J. Meigs

2005-01-01

237

The North Slope of Alaska and Tourism: Potential Impacts on the Arctic National Wildlife Refuge (ANWR)  

Microsoft Academic Search

The hydrocarbon industry of Alaska is currently the leading producer of revenue for the Alaskan state economy. Second only to hydrocarbons is the tourism industry. Tourism has been a viable industry since the 1890's when cruises touted the beauty of glaciers and icebergs along the Alaskan coastline. This industry has seen a steady growth for the past few decades throughout

L. R. Everett

2004-01-01

238

Ocean Observing System Demonstrated in Alaska  

NASA Astrophysics Data System (ADS)

To demonstrate the utility of an ocean observing and forecasting system with diverse practical applications—such as search and rescue, oil spill response (perhaps relevent to the current Gulf of Mexico oil spill), fisheries, and risk management—a unique field experiment was conducted in Prince William Sound, Alaska, in July and August 2009. The objective was to quantitatively evaluate the performance of numerical models developed for the sound with an array of fixed and mobile observation platforms (Figure 1). Prince William Sound was chosen for the demonstration because of historical efforts to monitor ocean circulation following the 1989 oil spill from the Exxon Valdez tanker. The sound, a highly crenulated embayment of about 10,000 square kilometers at approximately 60°N latitude along the northern coast of the Gulf of Alaska, includes about 6900 kilometers of shoreline, numerous islands and fjords, and an extensive system of tidewater glaciers descending from the highest coastal mountain range in North America. Hinchinbrook Entrance and Montague Strait are the two main deep water connections with the Gulf of Alaska. The economic base of communities in the region is almost entirely resource-dependent. For example, Cordova's economy is based on commercial fishing and Valdez's economy is supported primarily by the trans-Alaska oil pipeline terminal.

Schoch, G. Carl; Chao, Yi

2010-05-01

239

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

Microsoft Academic Search

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

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

2003-01-01

240

Estimating glacier mass changes by GRACE satellite gravimetry in the Pamir and Tien-Shan mountains  

NASA Astrophysics Data System (ADS)

In 2002, the Gravity Recovery and Climate Experiment (GRACE) satellite mission was launched, to obtain more information about the Earth's geoid and gravity field. The satellites measure the changes of the Earth's gravity field on a monthly basis until today. These data can be used to estimate glacier mass balance. Previous studies have mainly focused on the large ice sheets and glaciers of Greenland and Antarctica. In recent years, the GRACE data was also applied to mountain glaciers, e.g. in the St Elias Mountains in Alaska (Arendt et al. 2008) and in the Himalayas (Muskett 2010). In this study, the mass change data of GRACE are applied to the Pamir and Tien-Shan mountains. Mass balance measurements, mass balance and volume estimations, and other data are used to compare and verify the results of the GRACE estimates. Obstacles in this area are especially the inadequate glacier mass balance data, their representativeness, the availability of data, the time coverage, the insufficient spatial mapping, and the influence of other mass changing signals in the area (e.g. lake Issyk-Kul). Therefore, much attention is given to specify the corresponding uncertainties. The results of this study are rough estimations of the mass change development sine 2002, but give a good assessment of the usability of GRACE in this area. Arendt, A.A., Luthcke, S.B., Larsen, C.F., Abdalati, W., Krabill, W.B. & Beedle, M.J. (2008): Validation of high-resolution GRACE mascon estimates of glacier mass changes in the St Elias Mountains, Alaska, USA, using aircraft laser altimetry. Journal of Glaciology, 54: 778-787. Muskett, R.R. (2010): Water Mass Loss of the Himalayas from GRACE, ICESat and SRTM. EGU 2010, Number 20101037.

Baumann, S.; Menzel, A.; Seitz, F.

2012-04-01

241

Glaciers as a source of ancient and labile organic matter to the marine environment.  

PubMed

Riverine organic matter supports of the order of one-fifth of estuarine metabolism. Coastal ecosystems are therefore sensitive to alteration of both the quantity and lability of terrigenous dissolved organic matter (DOM) delivered by rivers. The lability of DOM is thought to vary with age, with younger, relatively unaltered organic matter being more easily metabolized by aquatic heterotrophs than older, heavily modified material. This view is developed exclusively from work in watersheds where terrestrial plant and soil sources dominate streamwater DOM. Here we characterize streamwater DOM from 11 coastal watersheds on the Gulf of Alaska that vary widely in glacier coverage (0-64 per cent). In contrast to non-glacial rivers, we find that the bioavailability of DOM to marine microorganisms is significantly correlated with increasing (14)C age. Moreover, the most heavily glaciated watersheds are the source of the oldest ( approximately 4 kyr (14)C age) and most labile (66 per cent bioavailable) DOM. These glacial watersheds have extreme runoff rates, in part because they are subject to some of the highest rates of glacier volume loss on Earth. We estimate the cumulative flux of dissolved organic carbon derived from glaciers contributing runoff to the Gulf of Alaska at 0.13 +/- 0.01 Tg yr(-1) (1 Tg = 10(12) g), of which approximately 0.10 Tg is highly labile. This indicates that glacial runoff is a quantitatively important source of labile reduced carbon to marine ecosystems. Moreover, because glaciers and ice sheets represent the second largest reservoir of water in the global hydrologic system, our findings indicate that climatically driven changes in glacier volume could alter the age, quantity and reactivity of DOM entering coastal oceans. PMID:20033045

Hood, Eran; Fellman, Jason; Spencer, Robert G M; Hernes, Peter J; Edwards, Rick; D'Amore, David; Scott, Durelle

2009-12-24

242

UAFSmoke Modeling in Alaska  

Microsoft Academic Search

Alaska wildfires have strong impact on air pollution on regional Arctic, Sub-Arctic and even hemispheric scales. In response to a high number of wildfires in Alaska, emphasis has been placed on developing a forecast system for wildfire smoke dispersion in Alaska. We have developed a University of Alaska Fairbanks WRF\\/Chem smoke (UAFSmoke) dispersion system, which has been adapted and initialized

M. Stuefer; G. Grell; S. Freitas; G. Newby

2008-01-01

243

GLIMS Glacier Database: Status and Challenges  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

244

Mountain glacier identification from SAR images  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

245

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

NASA Astrophysics Data System (ADS)

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

Radi?, Valentina; Hock, Regine

2010-03-01

246

The contribution of glacier melt to streamflow  

SciTech Connect

Ongoing and projected future changes in glacier extent and water storage globally have lead to concerns about the implications for water supplies. However, the current magnitude of glacier contributions to river runoff is not well known, nor is the population at risk to future glacier changes. We estimate an upper bound on glacier melt contribution to seasonal streamflow by computing the energy balance of glaciers globally. Melt water quantities are computed as a fraction of total streamflow simulated using a hydrology model and the melt fraction is tracked down the stream network. In general, our estimates of the glacier melt contribution to streamflow are lower than previously published values. Nonetheless, we find that globally an estimated 225 (36) million people live in river basins where maximum seasonal glacier melt contributes at least 10% (25%) of streamflow, mostly in the High Asia region.

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

2012-09-13

247

MOVEMENT OF WATER IN GLACIERS  

Microsoft Academic Search

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

R. L. SHREVE

1972-01-01

248

Glacier Lakes Ecosystem Experiments Site.  

National Technical Information Service (NTIS)

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

R. C. Musselman

1994-01-01

249

Jakobshavn Glacier Ice Flow (WMS)  

NSDL National Science Digital Library

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

Sokolowsky, Eric; Kekesi, Alex; Abdalati, Waleed

2005-03-30

250

Microbial Habitat on Kilimanjaro's Glaciers  

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

251

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

NASA Astrophysics Data System (ADS)

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

Nicholson, L. I.

2012-04-01

252

A theory of glacier surges  

NASA Astrophysics Data System (ADS)

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

Fowler, A. C.

1987-08-01

253

Geologic methane seeps along boundaries of Arctic permafrost thaw and melting glaciers  

NASA Astrophysics Data System (ADS)

Methane, a potent greenhouse gas, accumulates in subsurface hydrocarbon reservoirs, such as coal beds and natural gas deposits. In the Arctic, permafrost and glaciers form a `cryosphere cap' that traps gas leaking from these reservoirs, restricting flow to the atmosphere. With a carbon store of over 1,200Pg, the Arctic geologic methane reservoir is large when compared with the global atmospheric methane pool of around 5Pg. As such, the Earth's climate is sensitive to the escape of even a small fraction of this methane. Here, we document the release of 14C-depleted methane to the atmosphere from abundant gas seeps concentrated along boundaries of permafrost thaw and receding glaciers in Alaska and Greenland, using aerial and ground surface survey data and in situ measurements of methane isotopes and flux. We mapped over 150,000 seeps, which we identified as bubble-induced open holes in lake ice. These seeps were characterized by anomalously high methane fluxes, and in Alaska by ancient radiocarbon ages and stable isotope values that matched those of coal bed and thermogenic methane accumulations. Younger seeps in Greenland were associated with zones of ice-sheet retreat since the Little Ice Age. Our findings imply that in a warming climate, disintegration of permafrost, glaciers and parts of the polar ice sheets could facilitate the transient expulsion of 14C-depleted methane trapped by the cryosphere cap.

Walter Anthony, Katey M.; Anthony, Peter; Grosse, Guido; Chanton, Jeffrey

2012-06-01

254

Virtual Globes and Glacier Research: Integrating research, collaboration, logistics, data archival, and outreach into a single tool  

NASA Astrophysics Data System (ADS)

Virtual Globes are a paradigm shift in the way earth sciences are conducted. With these tools, nearly all aspects of earth science can be integrated from field science, to remote sensing, to remote collaborations, to logistical planning, to data archival/retrieval, to PDF paper retriebal, to education and outreach. Here we present an example of how VGs can be fully exploited for field sciences, using research at McCall Glacier, in Arctic Alaska.

Nolan, M.

2006-12-01

255

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

Microsoft Academic Search

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

B. H. Luckman

1995-01-01

256

GLACIER VIEW ROADLESS AREA, WASHINGTON.  

USGS Publications Warehouse

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

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

1984-01-01

257

Recent changes on Greenland outlet glaciers  

NASA Astrophysics Data System (ADS)

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

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

258

A reconciled estimate of glacier contributions to sea level rise: 2003 to 2009.  

PubMed

Glaciers distinct from the Greenland and Antarctic Ice Sheets are losing large amounts of water to the world's oceans. However, estimates of their contribution to sea level rise disagree. We provide a consensus estimate by standardizing existing, and creating new, mass-budget estimates from satellite gravimetry and altimetry and from local glaciological records. In many regions, local measurements are more negative than satellite-based estimates. All regions lost mass during 2003-2009, with the largest losses from Arctic Canada, Alaska, coastal Greenland, the southern Andes, and high-mountain Asia, but there was little loss from glaciers in Antarctica. Over this period, the global mass budget was -259 ± 28 gigatons per year, equivalent to the combined loss from both ice sheets and accounting for 29 ± 13% of the observed sea level rise. PMID:23687045

Gardner, Alex S; Moholdt, Geir; Cogley, J Graham; Wouters, Bert; Arendt, Anthony A; Wahr, John; Berthier, Etienne; Hock, Regine; Pfeffer, W Tad; Kaser, Georg; Ligtenberg, Stefan R M; Bolch, Tobias; Sharp, Martin J; Hagen, Jon Ove; van den Broeke, Michiel R; Paul, Frank

2013-05-17

259

Do Continental Shelf Strata Contain Evidence of Rapid Late 20th Century Glacial Melting and Increased Runoff in Alaska?  

Microsoft Academic Search

Over the past two decades coincident with Arctic climate warming, Alaskan glaciers have accelerated their melt rate. This potentially large release of Alaskan meltwater might be reflected in an increased fluvial discharge of both freshwater and sediment to the ocean. To test this hypothesis, historical (1950-2002) fluvial discharge records from rivers in south-central Alaska were compared to sedimentary proxy records

J. M. Jaeger; W. Vienne; J. E. Channell; J. Stoner; B. Finney

2006-01-01

260

The Impact that Elevation Has on the ENSO Signal in Precipitation Records from the Gulf of Alaska Region  

Microsoft Academic Search

In this paper we attempt to reconcile seemingly contradictory research concerning the existence of an El-Niño Southern Oscillation (ENSO) signal in precipitation records from the Gulf of Alaska region. A number of studies based on records from primarily coastal stations and the mass balance of low elevation glaciers suggest there is at best a weak relationship between ENSO and precipitation

G. W. K. Moore; Keith Alverson; Gerald Holdsworth

2003-01-01

261

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

262

Northern Alaska Hydrocarbon Resources.  

National Technical Information Service (NTIS)

This report on Northern Alaska hydrocarbon resources brings together the private, federal, and state oil and gas initiatives in Northern Alaska over the past 35 years. It treats Northern Alaska oil and gas provinces as a planning unit, rather than using t...

J. D. Kreitner

1978-01-01

263

Alaska Natives & the Land.  

ERIC Educational Resources Information Center

|Pursuant to the Native land claims within Alaska, this compilation of background data and interpretive materials relevant to a fair resolution of the Alaska Native problem seeks to record data and information on the Native peoples; the land and resources of Alaska and their uses by the people in the past and present; land ownership; and future…

Arnold, Robert D.; And Others

264

Regional and global projections of twenty-first century glacier mass changes in response to climate scenarios from global climate models  

NASA Astrophysics Data System (ADS)

A large component of present-day sea-level rise is due to the melt of glaciers other than the ice sheets. Recent projections of their contribution to global sea-level rise for the twenty-first century range between 70 and 180 mm, but bear significant uncertainty due to poor glacier inventory and lack of hypsometric data. Here, we aim to update the projections and improve quantification of their uncertainties by using a recently released global inventory containing outlines of almost every glacier in the world. We model volume change for each glacier in response to transient spatially-differentiated temperature and precipitation projections from 14 global climate models with two emission scenarios (RCP4.5 and RCP8.5) prepared for the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. The multi-model mean suggests sea-level rise of 155 ± 41 mm (RCP4.5) and 216 ± 44 mm (RCP8.5) over the period 2006-2100, reducing the current global glacier volume by 29 or 41 %. The largest contributors to projected global volume loss are the glaciers in the Canadian and Russian Arctic, Alaska, and glaciers peripheral to the Antarctic and Greenland ice sheets. Although small contributors to global volume loss, glaciers in Central Europe, low-latitude South America, Caucasus, North Asia, and Western Canada and US are projected to lose more than 80 % of their volume by 2100. However, large uncertainties in the projections remain due to the choice of global climate model and emission scenario. With a series of sensitivity tests we quantify additional uncertainties due to the calibration of our model with sparsely observed glacier mass changes. This gives an upper bound for the uncertainty range of ±84 mm sea-level rise by 2100 for each projection.

Radi?, Valentina; Bliss, Andrew; Beedlow, A. Cody; Hock, Regine; Miles, Evan; Cogley, J. Graham

2013-04-01

265

Glaciers in 21st Century Himalayan Geopolitics  

Microsoft Academic Search

Glaciers are ablating rapidly the world over. Nowhere are the rates of retreat and downwasting greater than in the Hindu Kush-Himalaya (HKH) region. It is estimated that over the next century, 40,000 square kilometers of present glacier area in the HKH region will become ice free. Most of this area is in major valleys and the lowest glaciated mountain passes.

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

2002-01-01

266

Glaciers in 21st Century Himalayan Geopolitics  

NASA Astrophysics Data System (ADS)

Glaciers are ablating rapidly the world over. Nowhere are the rates of retreat and downwasting greater than in the Hindu Kush-Himalaya (HKH) region. It is estimated that over the next century, 40,000 square kilometers of present glacier area in the HKH region will become ice free. Most of this area is in major valleys and the lowest glaciated mountain passes. The existence and characteristics of glaciers have security impacts, and rapidly changing HKH glaciers have broad strategic implications: (1) Glaciers supply much of the fresh water and hydroelectric power in South and Central Asia, and so glaciers are valuable resources. (2) Shared economic interests in water, hydroelectricity, flood hazards, and habitat preservation are a force for common cause and reasoned international relations. (3) Glaciers and their high mountains generally pose a natural barrier tending to isolate people. Historically, they have hindered trade and intercultural exchanges and have protected against aggression. This has further promoted an independent spirit of the region's many ethnic groups. (4) Although glaciers are generally incompatible with human development and habitation, many of the HKH region's glaciers and their mountains have become sanctuaries and transit routes for militants. Siachen Glacier in Kashmir has for 17 years been "the world's highest battlefield," with tens of thousands of troops deployed on both sides of the India/Pakistan line of control. In 1999, that conflict threatened to trigger all-out warfare, and perhaps nuclear warfare. Other recent terrorist and military action has taken place on glaciers in Kyrgyzstan and Tajikistan. As terrorists are forced from easily controlled territories, many may tend to migrate toward the highest ground, where definitive encounters may take place in severe alpine glacial environments. This should be a major concern in Nepali security planning, where an Army offensive is attempting to reign in an increasingly robust and brutal Maoist insurgency. (5) Glacier lakes are in many cases very fragile and their natural dams routinely rupture, causing devastating floods. A rising regional terrorist threat in several countries could target these dams and precipitate calamitous and terrifying results. (6) Over the next century, retreating glaciers may open new corridors for trade and human migration across the Himalaya and pave the way for possible new economic, military and political alliances in the region. (7) Glacier retreat might open new sanctuaries for terrorists and open new corridors for possible ground-based military offensive action across the HKH ranges. The documentation of glacier characteristics that may influence their trafficability, and projections of future glacier extent and behavior are relevant to wide ranging concerns of the region's inhabitants. Satellite remote sensing and mapping of glaciers is one approach to defining and monitoring the problems and opportunities presented by HKH glaciers. Global Land Ice Measurements from Space (GLIMS) is a joint USGS/NASA Pathfinder project that has formed a global consortium of glaciologists in several regional centers that are mapping and monitoring the HKH glaciers using repeat-pass ASTER and Landsat ETM+ data. We are currently building a comprehensive satellite multispectral image and GIS database that is providing detailed information on the state and rates of change of each glacier in the HKH region and other areas of the world. Merging these results with DEMs allows a predictive capability that could be useful in policy development and security planning.

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

2002-05-01

267

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

268

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

269

Modelling The Energy And Mass Balance Of A Black Glacier  

Microsoft Academic Search

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

G. Grossi; S. Taschner; R. Ranzi

2002-01-01

270

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

271

Simulation and forecast of the Tien Shan glacier's changes  

Microsoft Academic Search

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

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

2006-01-01

272

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

273

Quantifying global warming from the retreat of glaciers  

SciTech Connect

Records of glacier fluctuations compiled by the World Glacier Monitoring Service can be used to derive an independent estimate of global warming during the last 100 years. Records of different glaciers are made comparable by a two-step scaling procedure; one allowing for differences in glacier geometry, the other for differences in climate sensitivity. The retreat of glaciers during the last 100 years appears to be coherent over the globe. On the basis of modeling of the climate sensitivity of glaciers, the observed glacier retreat can be explained by a linear warming trend of 0.66 kelvin per century.

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

1994-04-08

274

Shrinking Alpine glaciers spell trouble for Europe's rivers  

NASA Astrophysics Data System (ADS)

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

Schultz, Colin

2011-10-01

275

Climate Change and Glacier Retreat: Scientific Fact and Artistic Opportunity  

Microsoft Academic Search

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

D. B. Fagre

2008-01-01

276

Glaciers in Patagonia: Controversy and prospects  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

277

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

278

A possible Younger Dryas record in southeastern Alaska  

SciTech Connect

A stratigraphic record of climatic cooling equal in timing and severity to the Younger Dryas event of the North Atlantic region has been obtained form lacustrine sediments in the Glacier Bay area of southeastern Alaska. Fossil pollen show that a late Wisconsin pine parkland was replaced about 10,800 years ago by shrub- and herb-dominated tundra, which lasted until about 9,800 years ago. This vegetational change is matched by geochemical evidence for loss of organic matter from catchment soils and increased mineral erosion. If this event represents the Younger Dryas, then an explanation for a hemisphere-wide propagation of a North Atlantic climatic perturbation must be sought.

Engstrom, D.R.; Hansen, B.C.S.; Wright, H.E. Jr. (Univ. of Minnesota, Minneapolis (United States))

1990-12-07

279

Glacier Monitoring: Opportunities, Accomplishments, and Limitations.  

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

280

Geologic map of the Gulkana B-1 quadrangle, south-central Alaska  

SciTech Connect

The quadrangle includes the Capital Mountain Volcano and the northern part of Mount Sanford Volcano in the Wrangell Mountains of south-central Alaska. The Capital Mountain volcano is a relatively small, andesitic shield volcano of Pleistocene age, which contains a 4-km-diameter summit caldera and a spectacular post-caldera radial dike swam. Lava flows from the younger Pleistocene Mount Sanford Volcano overlap the south side of the Capital Mountain Volcano. Copper-stained fractures in basaltic andesite related to a dike-filled rift of the North Sanford eruptive center are the only sign of mineralization in the quadrangle. Rock glaciers, deposits of Holocene and Pleistocene valley glaciers and Pleistocene Copper River basin glaciers mantle much of the volcanic bedrock below elevations of 5,500 ft.

Richter, D.H.; Ratte, J.C.; Schmoll, H.R.; Leeman, W.P.; Smith, J.G.; Yehle, L.A.

1989-01-01

281

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

282

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

283

Holocene loess and paleosols in central Alaska: A proxy record of Holocene climate change  

SciTech Connect

Episodic Holocene loess deposition and soil formation in the sediments of the Nenana valley of Central Alaska may reflect Holocene climate change. Periods of loess deposition seem to correlate with times of alpine glacier activity, while paleosols correspond to times of glacial retreat These variations may reflect changes in solar activity Stuiver and Braziunas, 1989. Other mechanisms, such as orbitally forced changes in seasonality, volcanism, and atmospheric C02 variability may also have affected Holocene climates and loess deposition.

Bigelow, N.H.; Beget, J.E.

1992-03-01

284

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

NSDL National Science Digital Library

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

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

2002-02-01

285

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

286

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

287

Ice Dynamics on a 2008 - 2011 surge of the Bering Glacier, AK  

NASA Astrophysics Data System (ADS)

We examine a 2008 - 2011 surge of the Bering Glacier using observations of surface velocity and surface elevation change. Velocity measurements are obtained using synthetic aperture radar (SAR) offset tracking. Elevation data are obtained via the University of Alaska Fairbanks airborne LiDAR altimetry program. L-Band PALSAR offset tracking proves exceptionally effective at tracking glacier velocities in the extreme maritime environments prevalent in southern Alaska. Results show rapid acceleration occurred May 2008 - February 2009, eventually reaching velocities of ~ 7 m d-1 or ~14 times quiescent flow. In January - April 2010, quiescent velocities returned to the Lower Bering where peak velocities were the prior year, but accelerated velocities remained in the BIV and near the terminus. In 2011, the Bering accelerated again throughout the active surge zone reaching velocities of ~9m d-1 and continues to surge as of July 20, 2011. We find that '08 - '10 surge dynamics don't conform to a classic surge evolution. The main acceleration period lasted 10 months, with most of the acceleration occurring in fall. During this period, the Bering accelerated along most of its length in unison, with no upstream and little downstream propagation.

Burgess, E. W.; Forster, R. R.; Larsen, C. F.; Braun, M.

2011-12-01

288

Regional Modeling of Outlet Glaciers Using the Parallel Ice Sheet Model (PISM)  

NASA Astrophysics Data System (ADS)

The Parallel Ice Sheet Model (PISM) is an open source code developed at the University of Alaska, Fairbanks. To date, PISM has primarily modeled the dynamic evolution of whole ice sheets including the Greenland and Antarctic ice sheets. Here we extend the capability of PISM by adding tools for regional-scale dynamical modeling of outlet glaciers of ice sheets. One tool automatically generates the drainage basin of an outlet glacier. Thereby a model basin can be found merely by identifying a terminus and supplying a DEM. Another tool is a force-to-thickness mechanism which is applied outside of the identified drainage basin; this isolates evolution of the modeled ice surface within the basin from dynamics in other basins. These tools allow us to perform high-resolution modeling of an outlet glacier (e.g. < 1 km grid resolution) without modeling the entire ice sheet. Potentially, these tools can be automatically applied basin-by-basin to each outlet system in an ice sheet. As a demonstration we focus on regional modeling of the Jakobshavn Isbrae in Greenland, for which CReSIS provides recently updated high-resolution bedrock maps. Adding a mass balance model developed from the results of Ettema et al. (2009), and applying the SIA+SSA hybrid stress balance and enthalpy-based polythermal models in PISM, we are able to run a high-resolution (500 m) numerical simulation of the Jakobshavn Isbrae as it evolves over the next century.

Dellagiustina, D. N.; Bueler, E.; Aschwanden, A.; Khroulev, C.; Hock, R. M.

2010-12-01

289

Little Ice Age Glaciation in Alaska: A record of recent global climatic change  

SciTech Connect

General global cooling and temperature fluctuation accompanied by expansion of mountain glaciers characterized the Little Ice Age of about A.D. 1200 through A.D. 1900. The effects of such temperature changes appear first and are strongest at high latitudes. Therefore the Little Ice Age record of glacial fluctuation in Alaska may provide a good proxy for these events and a test for models of future climatic change. Holocene expansions began here as early as 7000 B.P. and locally show a periodicity of 350 years after about 4500 years B.P. The Little Ice Age followed a late Holocene interval of minor ice advance and a subsequent period of ice margin recession lasting one to seven centuries. The timing of expansions since about A.D. 1200 have often varied between glaciers, but these are the most pervasive glacial events of the Holocene in Alaska and frequently represent ice marginal maxima for this interval. At least two major expansions are, apparent in forefields of both land-terminating and fjord-calving glaciers, but the former display the most reliable and detailed climatic record. Major maxima occurred by the 16th century and into the mid-18th century. Culmination of advances occurred throughout Alaska during the 19th century followed within a few decades by general glacial retreat. Concurrently, equilibrium line altitudes have been raised 100-400 m, representing a rise of 2-3 deg C in mean summer temperature.

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

1992-03-01

290

Climate change: Shrinking glaciers under scrutiny  

NASA Astrophysics Data System (ADS)

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

Bamber, Jonathan

2012-02-01

291

International Symposium on Fast Glacier Flow.  

National Technical Information Service (NTIS)

Cryospheric Sciences Program "International Symposium on Fast Glacier Flow" (PI, C. Lingle) provided partial support for publication of Annals of Glaciology 36 by the International Glaciological Society. Annals of Glaciology is a peer-reviewed j...

C. S. Lingle

1990-01-01

292

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.

293

Investigation of a slowly deforming, glacially debuttressed rock slope in the Alaska Range using InSAR, LiDAR and two-dimensional numerical modeling  

Microsoft Academic Search

Field investigation of a large, actively deforming rock slope at Fels Glacier in the east-central Alaska Range during summer 2010 confirmed the presence of more than 100 normal and antislope scarps and numerous other deformation features indicative of deep-seated gravitational slope deformation. Movement is occurring on foliation planes in micaceous schist in response to debuttressing of the slope by rapid

S. D. Newman; J. J. Clague; B. Rabus; D. H. Shugar

2010-01-01

294

Towards a complete World Glacier Inventory  

NASA Astrophysics Data System (ADS)

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

Zemp, Michael

2013-04-01

295

A data set of world-wide glacier length fluctuations  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

296

Impacts of Change in Glacier Ice  

NSDL National Science Digital Library

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

Grant, Alaska S.

297

Recent changes on Greenland outlet glaciers  

Microsoft Academic Search

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

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

2009-01-01

298

ASTER Imaging and Analysis of Glacier Hazards  

Microsoft Academic Search

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

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

299

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

300

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

301

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

302

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

303

Creating improved ASTER DEMs over glacierized terrain  

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

304

Glacier Dynamics Within a Small Alpine Cirque  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

305

Diverse calving patterns linked to glacier geometry  

NASA Astrophysics Data System (ADS)

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

Bassis, J. N.; Jacobs, S.

2013-10-01

306

Buried glacier ice in permafrost, a window to the past: examples from Bylot Island, Canadian Arctic  

NASA Astrophysics Data System (ADS)

Bylot Island is located north of Baffin Island (73°N, 80°W) and is extensively covered by an ice cap and its outlet glaciers flowing towards the arctic lowland of the Lancaster formation. During summers of 2009 and 2011 several active-layer detachment slides exposed large massive ice bodies and other types of debris-rich ice that were interpreted as buried glacier ice. The upper part of the massive ice and debris-rich ice were usually in contact with various types of ice-contact or glacio-fluvial sediments and in some cases they were covered by mass wasting/colluvial deposits. This suggests that their preservation was likely related to burial of the ice and refreezing of the overlying sediments following permafrost aggradation. A preliminary analysis of the ice facies and ice crystals revealed the presence of four distinct types of ice: 1) clear-ice bodies with very few sediment and no organic inclusions. The ice crystals were large (cm), randomly oriented and air bubbles were observed at the junction of crystals. These characteristics could potentially indicate an englacial (snow-neve metamorphism) origin for these clear ice bodies; 2) large, meter thick, clear ice layers with no sediment, nor organics. The ice crystals were large (cm), several cm long, oriented in the same direction, and vertically aligned. These characteristics could potentially point to water that refroze in a tunnel incised in englacial ice; 3) Successive, mm to cm thick, ice layers, separated by undulating sand and gravel bands also containing cobles to boulder size rock fragments. These characteristics could potentially represent regelation ice formed at the base of glaciers and incorporated to the glacier sole; 4) mm to cm suspended aggregate of fine-grained sediments in clear ice. These micro-suspended and suspended cryostructures were sometimes deformed and aligned in the form of thin (mm) undulating layers. These micro-structures were very similar to basal ice facies, presumably related to glacio-hydrologic supercooling, that we observed at the Matanuska Glacier in Alaska. Interestingly, the various types of ice contained in buried glacier ice permafrost date back to the englacial ice formation and its subsequent deformation by glacier flow and glacio-hydrological dynamics. It is thus older by several centuries to millennia than the permafrost aggradation itself (burial and active layer development) and we used the term antegenetic, in opposition to epigenetic or syngenetic, to characterize this type of permafrost. Buried glacier ice is a window to the past and a unique tool to reconstruct the paleogeography and paleoclimatology of Arctic regions. In a warming climate, as glaciers are receding, the burial of ice in the proglacial environment will offer opportunities to characterize antegenetic permafrost aggradation and its related cryofacies. In warming permafrost environments, as active layers on slope deepen and detachment slides are triggered, more buried Pleistocene glacier ice will likely be exposed.

Fortier, D.; Coulombe, S.; Kanevskiy, M. Z.; Paquette, M.; Shur, Y.; Stephani, E.

2011-12-01

307

The Alaska Quaternary Center  

NSDL National Science Digital Library

This website illustrates the Alaska Quaternary Center's (at the University of Alaska, Fairbanks) commitment "to the promotion of interdisciplinary research and the enhancement of interdisciplinary instruction in Quaternary sciences." Users can view images of the field work and learn how to obtain quaternary data from the AQC Quaternary Research Geodatabase.

1969-12-31

308

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

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

309

Alaska Volcano Observatory  

NSDL National Science Digital Library

This is the homepage of the Alaska Volcano Observatory, a joint program of the United States Geological Survey (USGS), the Geophysical Institute of the University of Alaska Fairbanks (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS). Users can access current information on volcanic activity in Alaska and the Kamchatka Penninsula, including weekly and daily reports and information releases about significant changes in any particluar volcano. An interactive map also directs users to summaries and activity notifications for selected volcanoes, or through links to webcams and webicorders (recordings of seismic activity). General information on Alaskan volcanoes includes descriptions, images, maps, bibliographies, and eruptive histories. This can be accessed through an interactive map or by clicking on an alphabetic listing of links to individual volcanoes. There is also an online library of references pertinent to Quaternary volcanism in Alaska and an image library.

310

Uncovering glacier dynamics beneath a debris mantle  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

311

Alaska SeaLife Center  

NSDL National Science Digital Library

Located in Seward, Alaska, the Alaska SeaLife Center is a non-profit marine science facility dedicated to understanding and maintaining the integrity of the marine ecosystem of Alaska through research, rehabilitation and public education. The Center's research and rehabilitation facilities and naturalistic exhibits immerse visitors in the dynamic marine ecosystems of Alaska. Includes links to additional resources for students and teachers.

312

Energy and the states: Alaska  

Microsoft Academic Search

In Alaska, energy policy simply means oil and gas. The state gets 85% of its revenue from oil and gas, and the nation gets about 25% of its domestic oil production from Alaska. Therefore, oil and gas production is important to Alaska, and the state's energy policies reflect this fact. Three separate policy initiatives comprise the strategy for realizing Alaska's

Eason

2009-01-01

313

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

314

Accelerating ice loss from the fastest Greenland and Antarctic glaciers  

Microsoft Academic Search

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

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

2011-01-01

315

Glacial Hydrology: Bibliography on the Hydrology of Glacierized Areas.  

National Technical Information Service (NTIS)

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

G. J. Young

1982-01-01

316

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

317

Glacial Isostatic Adjustment in Alaska and British Columbia  

NASA Astrophysics Data System (ADS)

The glaciers and icefields of coastal Alaska and British Columbia have lost an enormous amount of ice since the end of the Little Ice Age (LIA), with the collapse of the Glacier Bay Icefield alone equivalent to 8 mm of global sea level rise. Rapid mass wastage continues today, and both the total mass loss and present rates are generally well constrained. We have studied the mass changes and the Earth's response to it through a combination of glacial history observations, dating of raised shorelines, small aircraft laser altimetry, DEM differencing, permanent and temporary tide gauge data, GPS, and relative and absolute gravity change. Our observations show that extreme uplift in southeast Alaska began about 1770 AD, with relative sea level (RSL) change as large as 5.7 m, and rapid present-day uplift. We observe uplift rates >30 mm/yr in two regions, Glacier Bay and the area of the Yakutat Icefields, and regional uplift rates >10 mm/yr over a large area. Tide gauge records show that rapid uplift has persisted for decades. One site near Harlequin Lake, SE of Yakutat, has uplifted >80 mm/yr over the last two years due to extreme localized ice mass wastage. The known ice load history explains the present day uplift and gravity change rates well, given an Earth model consisting of an elastic lithosphere with a thickness of 54 (45-65) km over a low viscosity asthenosphere 110 km thick and a higher viscosity upper mantle. The upper mantle viscosity is assumed from larger-scale studies because the scale of the ice load is not small enough to make models sensitive to this value. The best estimate for asthenosphere viscosity is 6 (4.0-12.0) * 10^18 Pa-s, which is quite similar to the value estimated from postseismic deformation studies 800 km to the west in the region of the 1964 Prince William Sound earthquake.

Freymueller, J. T.; Larsen, C. F.; Motyka, R. J.; Sato, T.; Miura, S.; Sun, W.

2011-12-01

318

Contemporary sediment production and transfer in high-altitude glaciers  

Microsoft Academic Search

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

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

2003-01-01

319

Dynamics and Evolution of Taylor Glacier, Antarctica  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

320

Geophysical imaging of alpine rock glaciers  

NASA Astrophysics Data System (ADS)

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

Maurer, Hansruedi; Hauck, Christian

321

AVO: Alaska Volcano Observatory  

NSDL National Science Digital Library

This site illustrates the Alaska Volcano Observatory's (AVO) objective to monitor Alaska's volcanoes for the purpose of forecasting volcanic activity and alleviating hazards. AVO's seismometers and satellite imagery allow visitors to obtain current information on selected volcanoes. Because AVO is responsible for volcanic emergencies, people in Alaska can visit the Web site to determine their vulnerability. The site also features AVO's research in geological mapping, modeling of magnetic systems, and development of new instrumentation for predication and interpretation of volcanic unrest. Everyone can appreciate the images of past volcanic eruptions.

322

Alaska Science Forum  

NSDL National Science Digital Library

The Alaska Science Forum Web site is provided by the Geophysical Institute of the University of Alaska Fairbanks. The forum consists of articles written about various science subjects by scientists from the Geophysical Institute. Categories include the aurora, earthquakes, fun science facts, historic Alaska, mountains, rocks and geology, volcanoes, weather, and more. One of the latest articles, by Ned Rozell, is titled: Bogs, Permafrost and the Global Carbon Equation. Each of the articles is listed along with the author's name and a direct link to the online publication, most of which are fairly short and geared towards nonscientists making reading easy and interesting. [JAB

323

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

324

Surface mass balance of Greenland mountain glaciers and ice caps  

Microsoft Academic Search

Mountain glaciers and ice caps contribute roughly half of eustatic sea-level rise. Greenland has thousands of small mountain glaciers and several ice caps > 1000 sq. km that have not been included in previous mass balance calculations. To include small glaciers and ice caps in our study, we use Polar WRF, a next-generation regional climate data assimilation model is run

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

2009-01-01

325

Subpolar glaciers network as natural sensors of global warming evolution  

Microsoft Academic Search

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

Adolfo Eraso

326

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

Microsoft Academic Search

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

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

2002-01-01

327

Glacier variation in boduizangbu basin in Southeast Tibet  

Microsoft Academic Search

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

Xiaoli Wang; Songbing Zou; Shangzhe Zhou; Gao Xiang

2005-01-01

328

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

Microsoft Academic Search

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

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

2010-01-01

329

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

330

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

331

Geothermal Technologies Program: Alaska  

SciTech Connect

This fact sheets provides a summary of geothermal potential, issues, and current development in Alaska. This fact sheet was developed as part of DOE's GeoPowering the West initiative, part of the Geothermal Technologies Program.

Not Available

2005-02-01

332

Alaska Earthquake Information Center  

NSDL National Science Digital Library

Housed at the Geophysical Institute at the University of Alaska Fairbanks, the Alaska Earthquake Information Center reports and provides information on seismic activity in Alaska. While its southern Pacific coast colleague, California, gets a lot more attention when it comes to earthquakes, Alaska experienced a magnitude 6.7 earthquake already this summer and was rocked by a 7.9 in 2002. The site offers links to general information about the center, general earthquake information, research activities at the center, education and outreach materials (including information on seismology education projects), and much more. The site is well populated with materials and should provide a great resources for those interested in North American seismic events.

333

1964 Alaska Earthquake  

NSDL National Science Digital Library

This video adapted from the Valdez Museum & Historical Archive, explores what happened during the Great Alaska Earthquake of 1964 through original footage, first-person accounts, and animations illustrating plate tectonics.

Foundation, Wgbh E.

2009-02-25

334

Alaska's Mineral Industry, 1989.  

National Technical Information Service (NTIS)

Alaska's mineral industry experienced positive growth during 1989, especially in the hard-rock mining and exploration sectors, but suffered declines in mineral development expenditures, in sand-and-gravel, and in stone production. Overall value of mineral...

T. K. Bundtzen R. C. Swainbank J. R. Deagen J. L. Moore

1990-01-01

335

Alaska's Land-1974.  

National Technical Information Service (NTIS)

The 1974 annual report reviews the Commission's activities. A statewide Resources inventory of Alaska was completed and the Commission's structure was reorganized to better develop policies on anticipated land use planning issues.

1975-01-01

336

ASTER Imaging and Analysis of Glacier Hazards  

NASA Astrophysics Data System (ADS)

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

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

337

Alaska looks HOT!  

Microsoft Academic Search

Production in Alaska has been sluggish in recent years, with activity in the Prudhoe Bay region in the North Slope on a steady decline. Alaska North Slope (ANS) production topped out in 1988 at 2.037 MMbo\\/d, with 1.6 MMbo\\/d from Prudhoe Bay. This year operators expect to produce 788 Mbo\\/d from Prudhoe Bay, falling to 739 Mbo\\/d next year. ANS

Belcher

1997-01-01

338

Snow and ice volume on Mount Spurr Volcano, Alaska, 1981  

USGS Publications Warehouse

Mount Spurr (3,374 meters altitude) is an active volcano 130 kilometers west of Anchorage, Alaska, with an extensive covering of seasonal and perennial snow, and glaciers. Knowledge of the volume and distribution of snow and ice on a volcano aids in assessing hydrologic hazards such as floods, mudflows, and debris flows. In July 1981, ice thickness was measured at 68 locations on the five main glaciers of Mount Spurr: 64 of these measurements were made using a portable 1.7 megahertz monopulse ice-radar system, and 4 measurements were made using the helicopter altimeter where the glacier bed was exposed by ice avalanching. The distribution of snow and ice derived from these measurements is depicted on contour maps and in tables compiled by altitude and by drainage basins. Basal shear stresses at 20 percent of the measured locations ranged from 200 to 350 kilopascals, which is significantly higher than the 50 to 150 kilopascals commonly referred to in the literature as the 'normal' range for glaciers. Basal shear stresses higher than 'normal' have also been found on steep glaciers on volcanoes in the Cascade Range in the western United States. The area of perennial snow and ice coverage on Mount Spurr was 360 square kilometers in 1981, with an average thickness of 190?50 meters. Seasonal snow increases the volume about 1 percent and increases the area about 30 percent with a maximum in May or June. Runoff from Mount Spurr feeds the Chakachatna River and the Chichantna River (a tributary of the Beluga River). The Chakachatna River drainage contains 14 cubic kilometers of snow and ice and the Chichantna River drainage contains 53 cubic kilometers. The snow and ice volume on the mountain was 67?17 cubic kilometers, approximately 350 times more snow and ice than was on Mount St. Helens before its May 18, 1980, eruption, and 15 times more snow and ice than on Mount Rainier, the most glacierized of the measured volcanoes in the Cascade Range. On the basis of these relative quantities, hazard-producing glaciovolcanic phenomena at Mount Spurr could be significantly greater than similar phenomena at Cascade Volcanoes.

March, Rod S.; Mayo, Lawrence R.; Trabant, Dennis C.

1997-01-01

339

Melting Himalayan Glaciers May Doom Towns  

NSDL National Science Digital Library

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

340

Alaska looks HOT!  

SciTech Connect

Production in Alaska has been sluggish in recent years, with activity in the Prudhoe Bay region in the North Slope on a steady decline. Alaska North Slope (ANS) production topped out in 1988 at 2.037 MMbo/d, with 1.6 MMbo/d from Prudhoe Bay. This year operators expect to produce 788 Mbo/d from Prudhoe Bay, falling to 739 Mbo/d next year. ANS production as a whole should reach 1.3 MMbo/d this year, sliding to 1.29 MMbo/d in 1998. These declining numbers had industry officials and politicians talking about the early death of the Trans-Alaskan Pipeline System-the vital link between ANS crude and markets. But enhanced drilling technology coupled with a vastly improved relationship between the state government and industry have made development in Alaska more economical and attractive. Alaska`s Democratic Gov. Tommy Knowles is fond of telling industry {open_quotes}we`re open for business.{close_quotes} New discoveries on the North Slope and in the Cook Inlet are bringing a renewed sense of optimism to the Alaska exploration and production industry. Attempts by Congress to lift a moratorium on exploration and production activity in the Arctic National Wildlife Refuge (ANWR) have been thwarted thus far, but momentum appears to be with proponents of ANWR drilling.

Belcher, J.

1997-07-01

341

Brief communication "Historical glacier length changes in West Greenland"  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

342

Sensitivity of glaciers and small ice caps to greenhouse warming.  

PubMed

Recent field programs on glaciers have supplied information that makes simulation of glacier mass balance with meteorological models meaningful. An estimate of world-wide glacier sensitivity based on a modeling study of 12 selected glaciers situated in widely differing climatic regimes shows that for a uniform 1 K warming the area-weighted glacier mass balance will decrease by 0.40 meter per year. This corresponds to a sea-level rise of 0.58 millimeter per year, a value significantly less than earlier estimates. PMID:17835895

Oerlemans, J; Fortuin, J P

1992-10-01

343

Contrasting response of South Greenland glaciers to recent climatic change  

SciTech Connect

A unique geographical configuration of glaciers exists in the Narsarsuaq district of South Greenland. Two large outlet glaciers divide into seven distributaries, such that each glacier system has land-terminating, tidewater-calving, and fresh-water-calving termini. Despite a similar climatic regime, these seven glaciers have exhibited strongly contrasting terminal behavior in historical time, as shown by historical records, aerial photographs, and fieldwork in 1989. The behavior of the calving glaciers cannot be accounted for with reference solely to climatic parameters. The combination of iceberg calving dynamics and topographic control has partially decoupled them from climatic forcing such that their oscillations relate more closely to glaciodynamic than glacioclimatic factors.

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

1992-05-01

344

Kinematic and dynamic rupture models of the November 3, 2002 Mw7.9 Denali, Alaska, earthquake  

Microsoft Academic Search

Regional seismic waveforms, continuous and campaign-mode GPS data, and surface slip measurements were used to obtain a kinematic model of the rupture process of the November 3, 2002 Mw 7.9 Denali, Alaska, earthquake. The event initiated as a Mw 7.0 reverse slip event on the north-dipping Susitna Glacier fault with subsequent right-lateral slip distributed over approximately 300 km of the

Douglas S. Dreger; David D. Oglesby; Ruth Harris; Natalia Ratchkovski; Roger Hansen

2004-01-01

345

Alaska Resource Data File, Point Lay quadrangle, Alaska  

USGS Publications Warehouse

This report gives descriptions of the mineral occurrences in the Point Lay 1:250,000-scale quadrangle, Alaska. The data presented here are maintained as part of a statewide database on mines, prospects and mineral occurrences throughout Alaska.

Grybeck, Donald J.

2006-01-01

346

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

NASA Astrophysics Data System (ADS)

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

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

347

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

Microsoft Academic Search

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

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

2002-01-01

348

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

349

Geomorphology of the lower Copper River, Alaska  

USGS Publications Warehouse

The Copper River, located in southcentral Alaska, drains an area of more than 24,000 square miles. About 30 miles above its mouth, this large river enters Miles Lake, a proglacial lake formed by the retreat of Miles Glacier. Downstream from the outlet of Miles Lake, the Copper River flows past the face of Childs Glacier before it enters a large, broad, alluvial flood plain. The Copper River Highway traverses this flood plain and in 1995, 11 bridges were located along this section of the highway. These bridges cross parts of the Copper River and in recent years, some of these bridges have sustained serious damage due to the changing course of the Copper River. Although the annual mean discharge of the lower Copper River is 57,400 cubic feet per second, most of the flow occurs during the summer months from snowmelt, rainfall, and glacial melt. Approximately every six years, an outburst flood from Van Cleve Lake, a glacier-dammed lake formed by Miles Glacier, releases approximately 1 million acre-feet of water into the Copper River. When the outflow rate from Van Cleve Lake reaches it peak, the flow of the Copper River will increase between 150,000 to 190,000 cubic feet per second. Data collected by bedload sampling and continuous seismic reflection indicated that Miles Lake traps virtually all the bedload being transported by the Copper River as it enters the lake from the north. The reservoir-like effect of Miles Lake results in the armoring of the channel of the Copper River downstream from Miles Lake, past Childs Glacier, until it reaches the alluvial flood plain. At this point, bedload transport begins again. The lower Copper River transports 69 million tons per year of suspended sediment, approximately the same quantity as the Yukon River, which drains an area of more than 300,000 square miles. By correlating concurrent flows from a long-term streamflow-gaging station on the Copper River with a short-term streamflow-gaging station at the outlet of Miles Lake, long-term flow characteristics of the lower Copper River were synthesized. Historical discharge and cross-section data indicate that as late as 1970, most of the flow of the lower Copper River was through the first three bridges of the Copper River Highway as it begins to traverse the alluvial flood plain. In the mid 1980's, a percentage of the flow had shifted away from these three bridges and in 1995, only 51 percent of the flow of the Copper River passed through them. Eight different years of aerial photography of the lower Copper River were analyzed using Geographical Information System techniques. This analysis indicated that no major channel changes were caused by the 1964 earthquake. However, a flood in 1981 that had a recurrence interval of more than 100 years caused significant channel changes in the lower Copper River. A probability analysis of the lower Copper River indicated stable areas and the long-term locations of channels. By knowing the number of times a particular area has been occupied by water and the last year an area was occupied by water, areas of instability can be located. A Markov analysis of the lower Copper River indicated that the tendency of the flood plain is to remain in its current state. Large floods of the magnitude of the 1981 event are believed to be the cause of major changes in the lower Copper River.

Brabets, Timothy P.

1997-01-01

350

Geomorphology of the lower Copper River, Alaska  

USGS Publications Warehouse

The Copper River, located in southcentral Alaska, drains an area of more than 24,000 square miles. About 30 miles above its mouth, this large river enters Miles Lake, a proglacial lake formed by the retreat of Miles Glacier. Downstream from the outlet of Miles Lake, the Copper River flows past the face of Childs Glacier before it enters a large, broad, alluvial flood plain. The Copper River Highway traverses this flood plain and in 1996, 11 bridges were located along this section of the highway. These bridges cross parts or all of the Copper River and in recent years, some of these bridges have sustained serious damage due to the changing course of the Copper River. Although the annual mean discharge of the lower Copper River is 57,400 cubic feet per second, most of the flow occurs during the summer months from snowmelt, rainfall, and glacial melt. Approximately every six years, an outburst flood from Van Cleve Lake, a glacier-dammed lake formed by Miles Glacier, releases approximately 1 million acre-feet of water into the Copper River. At the peak outflow rate from Van Cleve Lake, the flow of the Copper River will increase an additional 140,000 and 190,000 cubic feet per second. Bedload sampling and continuous seismic reflection were used to show that Miles Lake traps virtually all the bedload being transported by the Copper River as it enters the lake from the north. The reservoir-like effect of Miles Lake results in the armoring of the channel of the Copper River downstream from Miles Lakes, past Childs Glacier, until it reaches the alluvial flood plain. At this point, bedload transport begins again. The lower Copper River transports 69 million tons per year of suspended sediment, approximately the same quantity as the Yukon River, which drains an area of more than 300,000 square miles. By correlating concurrent flows from a long-term streamflow- gaging station on the Copper River with a short-term streamflow-gaging station at the outlet of Miles Lake, long-term flow characteristics of the lower Copper River were synthesized. Historical discharge and cross-section data indicate that as late as 1970, most of the flow of the lower Copper River was through the first three bridges of the Copper River Highway as it begins to traverse the alluvial flood plain. In the mid 1980's, a percentage of the flow had shifted away from these three bridges and in 1995, only 51 percent of the flow of the Copper River passed through them. Eight different years of aerial photography of the lower Copper River were analyzed using Geographical Information System techniques. This analysis indicated that no major channel changes were caused by the 1964 earthquake. A flood in 1981 that had a recurrence interval of more than 100 years caused significant channel changes in the lower Copper River. A probability analysis of the lower Copper River indicated stable areas and the long-term locations of channels. By knowing the number of times a particular area has been occupied by water and the last year an area was occupied by water, areas of instability can be located. A Markov analysis of the lower Copper River indicated that the tendency of the flood plain is to remain in its current state. Large floods of the magnitude of the 1981 event are believed to be the cause of major changes in the lower Copper River.

Brabets, T. P.

1996-01-01

351

Alaska Native Teens Help Researchers  

NSDL National Science Digital Library

In this video adapted from KUAC-TV and the Geophysical Institute at the University of Alaska, Fairbanks, Alaska Native students contribute to research on how their environment is changing as a result of global warming.

Foundation, Wgbh E.

2009-01-13

352

Alaska Native Parkinson's Disease Registry.  

National Technical Information Service (NTIS)

This registry initiates a program of epidemiological assessments of PS among Alaska Natives to study the natural history and clinical management of PS, and establishes a database of Alaska native people with PS for public health, research and educational ...

B. A. Trimble

2008-01-01

353

Calibration of hydrological models in glacierized catchments  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

354

Geology Fieldnotes: Glacier National Park, Montana  

NSDL National Science Digital Library

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

355

Response of Italian Glaciers to Climatic Variations  

NASA Astrophysics Data System (ADS)

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

Biancotti, A.; Motta, M.

356

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

357

Four kingdoms on glacier ice: convergent energetic processes boost energy levels as temperatures fall.  

PubMed Central

A diverse group of glacially obligate organisms coexist on temperate glaciers between Washington State and Alaska. A fundamental challenge for these and other cold-adapted species is the necessity to maintain an energy flux capable of sustaining life at low physiological temperatures. We show here that ice-adapted psychrophiles from four kingdoms (Animalia, Eubacteria, Fungi, Protista) respond to temperature fluctuations in a similar manner; namely, ATP levels and the total adenylate pool increase as temperatures fall (within their viable temperature limits, respectively), yet growth rate increases with temperature. By contrast, mesophilic representatives of each kingdom respond in an opposite manner (i.e. adenylates increase with temperature). These observations suggest that elevated adenylate levels in psychrophiles may offset inherent reductions in molecular diffusion at low physiological temperatures.

Napolitano, Michael J; Shain, Daniel H

2004-01-01

358

Active Tectonics of Southern Alaska and the Role of the Yakutat Block Constrained by GPS  

NASA Astrophysics Data System (ADS)

GPS data from southern Alaska and the northern Canadian Cordillera have helped redefine the region's tectonic landscape. Instead of a comparatively simple interaction between the Pacific and North American plates, with relative motion accommodated on a single boundary fault, the margin is made up of a number of small blocks and deformation zones with relative motion distributed across a variety of structures. Much of this complexity can be attributed to the Yakutat block, an allochthonous terrane that has been colliding with southern Alaska since the Miocene. We present GPS data from across the region and use it to constrain a tectonic model for the Yakutat block collision and its effects on southern Alaska and eastern Canada. According to our model, the Yakutat block itself moves NNW at a rate of 50 mm/yr. Along its eastern edge, the Yakutat block is fragmenting into small crustal slivers. Part of the strain from the collision is transferred east of the Fairweather - Queen Charlotte fault system, causing the region inboard of the Fairweather fault to undergo a distinct clockwise rotation into the northern Canadian Cordillera. About 5% of the relative motion is transferred even further east, causing small northeasterly motions well into the northern Cordillera. Further north, the GPS data and model results indicate that the current deformation front between the Yakutat block and southern Alaska runs along the western side of the Malaspina Glacier. The majority of the ~37 mm/yr of relative convergence is accommodated along a narrow band of thrust faults concentrated in the southeastern part of the St. Elias orogen. Near the Bering Glacier, the tectonic regime abruptly changes as crustal thrust faults give way to subduction of the Yakutat block beneath the western St. Elias orogen and Prince William Sound. This change aligns with the Gulf of Alaska shear zone, implying that the Pacific plate may be fragmenting in response to the Yakutat collision. From the Bering Glacier, the subduction interface extends north and west beneath much of the Chugach mountain range. The Bering Glacier region is undergoing internal deformation that may correspond to the final stage of accretion of the Yakutat block sedimentary layers. At the western end of our study region, our model suggests that the crust is laterally escaping along the Aleutian forearc.

Elliott, J.; Freymueller, J. T.; Larsen, C. F.

2011-12-01

359

Constraining Glacier Sensitivity across the Andes: A Modeling Experiment  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

360

Holocene glacier fluctuations recorded in eastern Jotunheimen, southern Norway  

NASA Astrophysics Data System (ADS)

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

Støren, E.; Dahl, S. O.

2012-04-01

361

Modelling the present and future behaviour of the glaciers terminating into Godthåbsfjord, West Greenland  

NASA Astrophysics Data System (ADS)

The mass loss of the Greenland ice sheet is caused by changing surface mass balance, direct melting on the surface, ice flow through the numerous outlet glaciers, and basal melt. 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 fjord system, Godthåbsfjord, near Nuuk in West Greenland. Godthåbsfjord is a unique fjord with its length of about 300 km and a shallow sill at the fjord entrance that protects the fjord system. There are several tidewater glaciers terminating into the fjord contributing to the fresh water content in the fjord. The largest contributor is Kangiata Nunâta Sermia (KNS). Also, comprehensive oceanographic measurements in Godthåbsfjord are compared to link the ice sheet model to the fjord system. Here we aim to describe the present and future behaviour of KNS. The Parallel Ice Sheet Model (PISM), developed at the University of Alaska Fairbanks, is used for the regional modelling applied to the KNS drainage basin. Climatic forcing is provided by the Danish Meteorological Institute in form of HIRHAM5 ERA-Interim reanalysis model output covering the 1989 - 2011 period. PISM is able to show seasonal variability in the modelled fluxes when monthly means of the climatic forcing are applied. Observed surface velocities from InSAR and GPSs, ice thickness, and solid ice flux estimates at the terminus are used to determine the best parameter setting describing the present state of KNS. Those settings are then used for future projections (until 2050) to estimate solid ice flux and basal melt, that enters the fjord system as fresh water. This study is conducted in affiliation with the Greenland Climate Research Centre in Nuuk.

Fitzner, Antje; Dahl-Jensen, Dorthe

2013-04-01

362

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

363

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

364

Treasure Hunt in Alaska  

NSDL National Science Digital Library

This is a Web-based story of three children who venture out to find their great-grandfather's treasure box that was lost in the remote state of Alaska. Using simple terminology, the story integrates complex Earth and space science concepts, such as the formation of gold deposits and the operation of satellites. The children model creative thinking, acquire and interpret radar images, plan a treasure hunt, work systematically, and learn about Alaska. They also experience the successes and setbacks of actual research. The story provides opportunities for readers to engage in coloring activities, model building, unit conversions, and math calculations. Additionally, readers can interactively view an image from different heights and compare the size of Alaska to other U.S. states.

2006-02-01

365

Alaska Native Science Commission  

NSDL National Science Digital Library

This is the homepage of the Alaska Native Science Commission (ANSC), an organization dedicated to bringing together research and science in partnership with the Native community. Site materials include information on Alaska Native communities; a searchable database of contacts for community knowledge and a directory of local, statewide, and federally recognized Alaska Native agencies. There is also information on organizational ethics and protocols, regulatory agencies, a browsable database of research projects, and information on sources of funding. The Key Issues page provides information on issues of concern, such as avian flu, climate change, observations about contaminants and environmental change, traditional knowledge systems, traditional foods, and views on climate change and ecology. For students, there is information on einternship and scholarship opportunities. The publications page provides access to archived newsletters, presentations, and reports.

2010-10-05

366

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

367

78 FR 53137 - Flint Hills Resources Alaska, LLC, BP Pipelines (Alaska) Inc., ConocoPhillips Transportation...  

Federal Register 2010, 2011, 2012, 2013

...Docket Nos. OR13-31-000] Flint Hills Resources Alaska, LLC, BP Pipelines (Alaska) Inc., ConocoPhillips Transportation Alaska...LLC (FHR or Complainant) filed a formal complaint against BP Pipelines (Alaska) Inc., ConocoPhillips Transportation...

2013-08-28

368

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

369

Glacier and climate change in Pakistan and Afghanistan  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

370

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

National Technical Information Service (NTIS)

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

R. M. Slatt

1970-01-01

371

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

372

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

373

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

Code of Federal Regulations, 2010 CFR

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

2009-07-01

374

Jakobshavns Glacier drainage basin - A balance assessment  

NASA Astrophysics Data System (ADS)

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

Bindschadler, R. A.

1984-03-01

375

Satellite Image Atlas of Glaciers of the World: North America  

NSDL National Science Digital Library

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

376

Arthropod colonisation of a debris-covered glacier  

Microsoft Academic Search

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

Mauro Gobbi; Marco Isaia; Fiorenza De Bernardi

2011-01-01

377

ECOREGIONS OF ALASKA  

EPA Science Inventory

A map of ecoregions of Alaska has been produced as a framework for organizing and interpreting environmental data for state, national, and international inventory, monitoring, and research efforts. he map and descriptions for 20 ecological regions were derived by synthesizing inf...

378

Alaska Earthquake Information Center  

NSDL National Science Digital Library

The Alaska Earthquake Information Center contains information on seismology and tsunami research, education and outreach projects, and earthquake preparedness. There are also maps, reports, and a database on recent earthquakes and a map of historical Alaskan earthquakes, active faults, and rupture zones.

379

Alaska Peninsula Alutiiq Workbook.  

ERIC Educational Resources Information Center

|This workbook contains materials for teachers to use in the classroom. An alphabet book, the Pledge of Allegiance, songs, a play, and units on various subjects, such as hunting, picking berries, making a garden, and spring cleaning, are included. The materials are presented in both Alaska Peninsula Alutiiq (Sugpiaq) and English. (CFM)|

Christiansen, Matrona; And Others

380

Suicide in Northwest Alaska.  

ERIC Educational Resources Information Center

|Between 1975 and 1979 the Alaskan Native suicide rate (90.9 per 100,000) in Northwest Alaska was more than seven times the national average. Alienation, loss of family, low income, alcohol abuse, high unemployment, and more education were factors related to suicidal behavior. Average age for suicidal behavior was 22.5. (Author/MH)|

Travis, Robert

1983-01-01

381

Alaska's Discovery School.  

ERIC Educational Resources Information Center

After years of watching administrators bully children, teachers, and parents into reform, a Fairbanks (Alaska) elementary principal decided to be a facilitator, not a dictator. Assuming a "servant leadership" role, this principal garnered community support for transforming an old, unwanted school into a new math-science learning center emphasizing…

Hagstrom, David

1992-01-01

382

Microbial Life beneath a High Arctic Glacier  

Microsoft Academic Search

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

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

2000-01-01

383

Significant contribution to total mass from very small glaciers  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

384

West Antarctic Glacier Ice Flows and Elevation Change  

NASA Video Gallery

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

Holly Zell

2011-11-03

385

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

386

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.

387

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

Microsoft Academic Search

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

X. Bodin; F. Rojas; A. Brenning

2009-01-01

388

Effects of changing glacial coverage on the physical and biogeochemical properties of coastal streams in southeastern Alaska  

NASA Astrophysics Data System (ADS)

Runoff from mountain glaciers and icecaps is a critical control on physical and chemical conditions of aquatic ecosystems in glaciated watersheds. To date, there has been little research on the biogeochemistry of proglacial streams. Here we use a space for time substitution to evaluate how stream water physical conditions and concentrations of carbon, nitrogen, and phosphorus may be altered by diminishing glacial coverage. For a full annual hydrograph, we sampled six watersheds in southeastern Alaska that ranged in glacier coverage from 0 to 55%. We found that during the summer runoff season (May-October), stream water temperature and specific conductivity were negatively correlated with the percentage of the watershed covered by glacial ice, while stream water turbidity showed a significant positive correlation. Stream water concentrations of dissolved organic carbon (DOC) were typically low (0.5-3.0 mg C L-1) and showed a significant trend toward higher concentrations as watershed glacier coverage decreased. Concentrations of dissolved organic nitrogen (DON) and dissolved inorganic nitrogen also increased significantly with decreasing glacial coverage. In contrast, concentrations of soluble reactive phosphorus decreased with lower glacial coverage. Interestingly, we found that the DOC:DON ratio of stream water dissolved organic matter (DOM) decreased with increasing glacier coverage, suggesting that glaciers may be a source of N-rich DOM. During winter low flows (November-April) there were few differences in stream water physical and biogeochemical conditions across the six watersheds as glacial inputs diminished and streamflow was dominated by groundwater. Our findings suggest that in southeastern Alaska ongoing glacial recession and the associated land cover change will impact physical and biogeochemical conditions in coastal streams, with implications for salmon spawning habitat, aquatic ecosystem productivity, and fluxes of reactive nutrients to downstream nearshore marine ecosystems.

Hood, Eran; Berner, Logan

2009-09-01

389

Increases and fluctuations in thermal activity at Mount Wrangell, Alaska  

SciTech Connect

The objectives of this study were to document and interpret changes in thermal activity at two of three craters located on the rim of the ice-filled summit caldera of Mount Wrangell, an active glacier-clad shield volcano in south-central Alaska. The technique of glacier calorimetry was developed, through which changes in the volume of glacier ice in the craters and caldera were measured and related to changes in heat flow. Chemical analysis of gases and acid-thermal waters provided information on the underlying heat source. In 1965, thermal activity began increasing at both the North and West Craters. During the ensuing years, heat flow increased significantly at the North Crater, although in a highly fluctuating manner, while gradually declining at the West Crater. Pulses in heat flow at the North Crater occurred in 1966-68 and 1972-74, with both pulses followed by a four year decline in activity. Increases in heat flow began again in 1978-79 and have continued unabated through the summer of 1983. Over 80% of the 4.4 x 10/sup 7/m/sup 3/ ice volume within the crater in 1966 was melted by 1982, and the meltwaters have drained or evaporated from the crater. The subsequent rapid development of numerous fumaroles, the large dry-gas proportion of SO/sub 2/ (27%), and the inferred presence of gaseous HCl indicate that a shallow degassing magma body is the source of heat driving the thermal system. Seismically induced fracturing above the magma body is hypothesized to explain the initial increases in thermal activity.

Motyka, R.J.

1983-01-01

390

Holocene geologic and climatic history around the Gulf of Alaska  

USGS Publications Warehouse

Though not as dramatic as during the last Ice Age, pronounced climatic changes occurred in the northeastern Pacific over the last 10,000 years. Summers warmer and drier than today's accompanied a Hypsithermal interval between 9 and 6 ka. Subsequent Neoglaciation was marked by glacier expansion after 5-6 ka and the assembly of modern-type plant communities by 3-4 ka. The Neoglacial interval contained alternating cold and warm intervals, each lasting several hundred years to one millennium, and including both the Medieval Warm Period (ca. AD 900-1350) and the Little Ice Age (ca. AD 1350-1900). Salmon abundance fluctuated during the Little Ice Age in response to local glaciation and probably also to changes in the intensity of the Aleutian Low. Although poorly understood at present, climate fluctuations at all time scales were intimately connected with oceanographic changes in the North Pacific Ocean. The Gulf of Alaska region is tectonically highly active, resulting in a history of frequent geological catastrophes during the Holocene. Twelve to 14 major volcanic eruptions occurred since 12 ka. At intervals of 20-100 years, large earthquakes have raised and lowered sea level instantaneously by meters and generated destructive tsunamis. Sea level has often varied markedly between sites only 50-100 km apart due to tectonism and the isostatic effects of glacier fluctuations.

Mann, D. H.; Crowell, A. L.; Hamilton, T. D.; Finney, B. P.

1998-01-01

391

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

NASA Astrophysics Data System (ADS)

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

Paul, F.; Svoboda, F.

2009-04-01

392

A 2000 year varve-based climate record from the central Brooks Range, Alaska  

SciTech Connect

Varved minerogenic sediments from glacial-fed Blue Lake, northern Alaska, are used to investigate late Holocene climate variability. Varve thickness measurements track summer temperature recorded at Atigun Pass, located 41 km east at a similar elevation (r2 = 0.31, P = 0.08). Results indicate that climate in the Brooks Range from 10 to 730 AD (varve year) was warm with precipitation inferred to be higher than during the twentieth century. The varve-temperature relationship for this period was likely compromised and not used in our temperature reconstruction because the glacier was greatly reduced, or absent, exposing sub-glacial sediments to erosion from enhanced precipitation.

Bird, B.W.; Abbott, M.B.; Finney, B.P.; Kutchko, Barbara

2009-01-01

393

76 FR 67635 - Alaska Regulatory Program  

Federal Register 2010, 2011, 2012, 2013

...AK-007-FOR; Docket ID OSM-2011-0017] Alaska Regulatory Program AGENCY: Office of Surface...announcing receipt of a proposed amendment to the Alaska regulatory program (hereinafter, the ``Alaska program'') under the Surface Mining...

2011-11-02

394

75 FR 53331 - Alaska Native Claims Selection  

Federal Register 2010, 2011, 2012, 2013

...to Hadohdleekaga, Incorporated, for the Native village of Hughes, Alaska, pursuant to the Alaska Native Claims Settlement Act...K'oyitl'ots'ina, Limited. The lands are in the vicinity of Hughes, Alaska, and are located in: Kateel River Meridian,...

2010-08-31

395

Quantifying the spatial distribution of rapid exhumation from glacial detritus, St. Elias Range (Alaska)  

NASA Astrophysics Data System (ADS)

We present a provenance analysis, zircon (U-Th)/He thermochronometer cooling ages, and petrologic characterization of exhumation processes active under the Malaspina Glacier, St. Elias Range, Alaska. The collision of the Yakutat Terrane with North America formed the St. Elias Range in southeast Alaska. This region is subject to active faulting, high seismicity, and intense glacial erosion. Recent thermochronology studies document rapid rock exhumation at the Yakutat corner where strike-slip deformation transitions to convergence. Published detrital zircon fission track ages from sand samples of the Seward - Malaspina Glacier yielded a young age population of 2 Ma, suggesting a region of rapid exhumation somewhere in the glacier drainage basin. However, the glaciers cover the area and prevent direct observation and sampling, thereby inhibiting detailed bedrock exhumation studies of the Yakutat corner region. We investigate the lithologies of the bedrock at the Yakutat corner to quantify patterns of rock exhumation using clasts collected from the toe of the Malaspina Glacier. Seven different locations 50 km around the glacier were sampled and lithologies characterized by point counting in the field. In total, 1998 clasts were analyzed. We identified six main lithological groups that are assignable to specific geological units. Most of the detritus is gneiss and granulite (26%), micashist and phyllite (26%), and granite (11%) and are typical lithologies of the Chugach Terrane located at the southern margin of the North American plate. Mafic rocks of amphibolite, gabbro, and basalts (21%), and metapelite, sandstone, quartzite and breccia (14%) were also present and are typical for the colliding Yakutat Terrane. Two percent of the clasts are tightly foliated and mylonitic. These clasts are inferred to originate from the Contact Fault, an old suture zone that has been reactivated during Yakutat Terrane collision. Individual clasts from each sample locality and from all lithological groups were measured for zircon (U-Th)/He thermochronometer cooling ages. Furthermore, thin sections of 80 clasts were analyzed for petrographic characterization of the lithological groups. The zircon and titanite grains of 50 clasts have been separated and prepared for U-Th/He dating, degassed for He, and await final measurement of U-Th concentrations. We will report a comparison of these cooling ages with published bedrock and detrital low-temperature thermochronometer ages from neighboring areas. These cooling ages and their associated lithologies will allow identification of the spatial distribution of exhumation and the different magnitudes of exhumation between the two plates (Chugach vs. Yakutat).

Grabowski, D.; Enkelmann, E.; Ehlers, T. A.

2012-04-01

396

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

397

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

398

Glacier fluctuations, global temperature and sea-level change  

NASA Astrophysics Data System (ADS)

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

Leclercq, P. W.

2012-02-01

399

The Alaska Climate Research Center  

NSDL National Science Digital Library

The Alaska Climate Research Center provides a variety of weather data and data summaries for the State of Alaska. Materials include current conditions and forecasts, daily and monthly summaries and statistics, and climate data for locations across the state. There are also weather summaries, historical data, and current weather for the city of Fairbanks and the University of Alaska campus. Seasonal links provide information on fire weather, sea ice, and hydrologic analyses.

400

Alaska's Digital Archives  

NSDL National Science Digital Library

The basic premise of Alaska's Digital Archives is quite simple: to provide a single easy-to-use way for institutions across the state to share their historical resources. A vast swath of history is covered here, from the world of the Inuit to the rough and tumble gold rushes in the 19th and 20th centuries. Visitors can wander through the FAQ area for a bit of an orientation, check out the Help area, and learn about institutional Partners before moving on to the materials themselves. There are over a dozen collections here, and the items within them include moving images, oral histories, physical objects, and photograph albums. Users shouldn't miss the Sitka Tribe of Alaska & Sitka Historical Society collection. Here they can look over interviews with tribal citizens and listen to audio of paddling commands. [KMG

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