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1

Utility of late summer transient snowline migration rate on Taku Glacier, Alaska  

NASA Astrophysics Data System (ADS)

On Taku Glacier, Alaska a combination of field observations of snow water equivalent (SWE) from snowpits and probing in the vicinity of the transient snowline (TSL) are used to quantify the mass balance gradient. The balance gradient derived from the TSL and SWE measured in snowpits at 1000 m from 1998-2010 ranges from 2.6-3.8 mm m-1. Probing transects from 950 m-1100 m directly measure SWE and yield a slightly higher balance gradient of 3.3-3.8 mm m-1. The TSL on Taku Glacier is identified in MODIS and Landsat 4 and 7 Thematic Mapper images for 31 dates during the 2004-2010 period to assess the consistency of its rate of rise and reliability in assessing ablation for mass balance assessment. For example, in 2010, the TSL was 750 m on 28 July, 800 m on 5 August, 875 m on 14 August, 925 m on 30 August, and 975 m on 20 September. The mean observed probing balance gradient was 3.3 mm m-1, combined with the TSL rise of 3.7 m day-1 yields an ablation rate of 12.2 mm day-1 from mid-July to mid-Sept, 2010. The TSL rise in the region from 750-1100 m on Taku Glacier during eleven periods each covering more than 14 days during the ablation season indicates a mean TSL rise of 3.7 m day-1, the rate of rise is relatively consistent ranging from 3.1 to 4.4 m day-1. This rate is useful for ascertaining the final ELA if images or observations are not available near the end of the ablation season. The mean ablation from 750-1100 m during the July-September period determined from the TSL rise and the observed balance gradient is 11-13 mm day-1 on Taku Glacier during the 2004-2010 period. The potential for providing an estimate of bn from TSL observations late in the melt season from satellite images combined with the frequent availability of such images provides a means for efficient mass balance assessment in many years and on many glaciers.

Pelto, M.

2011-12-01

2

Alaska Glaciers and Rivers  

NASA Technical Reports Server (NTRS)

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image on October 7, 2007, showing the Alaska Mountains of south-central Alaska already coated with snow. Purple shadows hang in the lee of the peaks, giving the snow-clad land a crumpled appearance. White gives way to brown on the right side of the image where the mountains yield to the lower-elevation Susitna River Valley. The river itself cuts a silver, winding path through deep green forests and brown wetlands and tundra. Extending from the river valley, are smaller rivers that originated in the Alaska Mountains. The source of these rivers is evident in the image. Smooth white tongues of ice extend into the river valleys, the remnants of the glaciers that carved the valleys into the land. Most of the water flowing into the Gulf of Alaska from the Susitna River comes from these mountain glaciers. Glacier melt also feeds glacier lakes, only one of which is large enough to be visible in this image. Immediately left of the Kahiltna River, the aquamarine waters of Chelatna Lake stand out starkly against the brown and white landscape.

2007-01-01

3

Malaspina Glacier, Alaska  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

2001-01-01

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

Surface Velocity Changes on the Taku Glacier System 1993 to 2007 Compiled By  

E-print Network

, Washington JIRP OPEN FILE SURVEY REPORT--2007 #12;Foundation for Glacier and Environmental Research Juneau summer since 1993 with survey-grade, real-time differential GPS by the Juneau Icefield Research Program remained steady. During the summer of 2007, eight of these profiles were re- surveyed. For the first time

6

Regional Observations of Alaska Glacier Dynamics  

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). Complex glacier flow dynamics, frequently related to tidewater environments, is the primary cause of such rapid mass loss (Larsen et al., 2007). Indirect observations indicate these complex flow dynamics occur on many glaciers throughout Alaska, but no comprehensive velocity measurements exist. We are working to measure glacier surface velocities throughout Alaska using synthetic aperture radar (SAR) offset tracking. This work focuses on the Seward/Malaspina, Bering, Columbia, Kaskawulsh, and Hubbard Glaciers and uses a MODIS land surface temperature "melt-day" product (Hall et al., 2006, 2008) to identify potential links between velocity variability and summertime temperature fluctuations. Hall, D., R. Williams Jr., K. Casey, N. DiGirolamo, and Z. Wan (2006), Satellite-derived, melt-season surface temperature of the Greenland Ice Sheet (2000-2005) and its relationship to mass balance, Geophysical Research Letters, 33(11). Hall, D., J. Box, K. Casey, S. Hook, C. Shuman, and K. Steffen (2008), Comparison of satellite-derived and in-situ observations of ice and snow surface temperatures over Greenland, Remote Sensing of Environment, 112(10), 3739-3749. Larsen, C. F., R. J. Motyka, A. A. Arendt, K. A. Echelmeyer, and P. E. Geissler (2007), Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise, J. Geophys. Res. Luthcke, S., A. Arendt, D. Rowlands, J. McCarthy, and C. Larsen (2008), Recent glacier mass changes in the Gulf of Alaska region from GRACE mascon solutions, Journal of Glaciology, 54(188), 767-777.

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

2010-12-01

7

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

USGS Publications Warehouse

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

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

1987-01-01

8

Columbia Glacier, Alaska, 1986-2011 - Duration: 0:29.  

NASA Video Gallery

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

9

ICESat Observations of Southern Alaska Glaciers  

NASA Technical Reports Server (NTRS)

In late February and March, 2003, the Ice, Cloud, and land Elevation Satellite (ICESat) measured ice and land elevations along profiles across southern Alaska. During this initial data acquisition stage ICESat observations were made on 8-day repeat tracks to enable calibration and validation of the ICESat data products. Each profile consists of a series of single point values derived from centroid elevations of an $\\approx$70 m diameter laser footprint. The points are s4pakated by $\\approx$172 m along track. Data siets of 8-day observations (an ascending and descending ground track) crossed the Bering and Malaspina Glacier. Following its 1993--1995 surge; the Bering Glacier has undergone major terminus retreat as well as ike thinning in the abtation zone. During the later part of the 20th century, parts of the Malaspina thinned by about 1 m/yr. The multiple observation profiles across the Bering and Malaspina piedmont lobes obtained in February/March are being geolocated on Landsat images and the elevation profiles will be used for a number o scientific objectives. Based on our simulations of ICESat performance over the varied ice surface of the Jakobshavn Glacier of GReenland, 2003, we expect to measure annual, and possibly seasonal, ice elevation changes on the large Alaskan glaciers. Using elevation data obtained from a second laser, we plan to estimate ice elevation changes on the Bering Glacier between March and October 2003.

Sauber, Jeanne; Molnia, Bruce F.; Mitchell, Darius

2003-01-01

10

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.

William Manley

11

Malaspina Glacier, Alaska, Perspective with Landsat Overlay  

NASA Technical Reports Server (NTRS)

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

This perspective view was created from a Landsat satellite image and an elevation model generated by the Shuttle Radar Topography Mission (SRTM). Landsat views both visible and infrared light, which have been combined here into a color composite that generally shows glacial ice in light blue, snow in white, vegetation in green, bare rock in grays and tans, and the ocean (foreground) in dark blue. The back (northern) edge of the data set forms a false horizon that meets a false sky.

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

Glaciers are sensitive indicators of climatic change. They can grow and thicken with increasing snowfall and/or decreased melting. Conversely, they can retreat and thin if snowfall decreases and/or atmospheric temperatures rise and cause increased melting. Landsat imaging has been an excellent tool for mapping the changing geographic extent of glaciers since 1972. The elevation measurements taken by SRTM in February 2000 now provide a near-global baseline against which future non-polar region glacial thinning or thickening can be assessed.

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

2003-01-01

12

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.

Cindy Starr

1996-02-23

13

Columbia Glacier, Alaska: changes in velocity 1977-1986  

USGS Publications Warehouse

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

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

1987-01-01

14

Dendrochronology and Late Holocene History of Bering Piedmont Glacier, Alaska  

Microsoft Academic Search

Fluctuations of the piedmont lobe of Bering Glacier and its sublobe Steller Glacier over the past two millennia are reconstructed using 34 radiocarbon dates and tree-ring data from 16 sites across the glaciers' forelands. The general sequence of glacial activity is consistent with well-dated fluctuations of tidewater and land-terminating glaciers elsewhere along the Gulf of Alaska. Extensive forested areas along

Gregory C. Wiles; Austin Post; Ernest H. Muller; Bruce F. Molnia

1999-01-01

15

Malaspina Glacier, Alaska, Anaglyph with Landsat Overlay  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

2003-01-01

16

Malaspina Glacier, Alaska as seen from STS-66 Atlantis  

NASA Technical Reports Server (NTRS)

Malaspina Glacier can be seen in this north-northeastern photograph taken in November, 1994. The glacier, located in the south shore of Alaska is a classic example of a piedmont glacier lying along the foot of a mountain range. The principal source of ice for the glacier is provided by the Seward Ice Field to the north (top portion of the view) which flows through three narrow outlets onto the coastal plain. The glacier moves in surges that rush earlier-formed moraines outward into the expanding concentric patterns along the flanks of the ice mass.

1994-01-01

17

Ocean-Glacier Interactions in Alaska and Comparison to Greenland  

NASA Astrophysics Data System (ADS)

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

Motyka, R. J.; Truffer, M.

2011-12-01

18

Glacier Change and Biologic Succession: a new Alaska Summer Research Academy (ASRA) Science Camp Module for Grades 8-12 in Glacier Bay National Park, Alaska  

Microsoft Academic Search

During the summer of 2008, university faculty and instructors from southeast Alaska joined the University Alaska Fairbanks(UAF)Alaska Summer Research Academy(ASRA)to initiate a 12-day module on glacier change and biologic succession in Glacier Bay National Park. Nine students from Alaska, Colorado, Massachusetts, and Texas, made field observations and collected data while learning about tidewater glacier dynamics, plant succession, post-glacial uplift, and

C. L. Connor; J. Drake; C. Good; R. Fatland; M. Hakala; R. Woodford; R. Donohoe; R. Brenner; T. Moriarty

2008-01-01

19

BASINWIDE SEDIMENTATION PROCESSES AT GLACIER-DAMMED ICEBERG LAKE, SOUTHCENTRAL ALASKA  

E-print Network

BASINWIDE SEDIMENTATION PROCESSES AT GLACIER-DAMMED ICEBERG LAKE, SOUTHCENTRAL 2012 BASINWIDE SEDIMENTATION PROCESSES AT GLACIER-DAMMED ICEBERG LAKE, SOUTHCENTRAL ALASKA by Katie E examining sedimentation rates and varve thickness at Iceberg Lake, a glacier-dammed proglacial lake

Loso, Michael G.

20

Pleistocene Maximum and Late Wisconsinan glacier extents across Alaska, Darrell S. Kaufman 1  

E-print Network

Pleistocene Maximum and Late Wisconsinan glacier extents across Alaska, U.S.A. Darrell S. Kaufman 1 geologists working in Alaska to produce an updated compilation of statewide glacier extents. It summarises for this digital map segment the state and adjacent territories into several tiles); (2) the Alaska PaleoGlacier

Ingólfsson, �lafur

21

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

22

Satellite Observations of Glacier Surface Velocities in Southeast Alaska  

NASA Astrophysics Data System (ADS)

Glaciers in southeast Alaska are undergoing rapid changes and are significant contributors to sea level rise. A key to understanding the ice dynamics is knowledge of the surface velocities, which can be used with ice thickness measurements to derive mass flux rates. For many glaciers in Alaska, surface velocity estimates either do not exist or are based on data that are at least a decade old. Here we present updated maps of glacier surface velocities in southeast Alaska produced through a pixel tracking technique using synthetic aperture radar data and high-resolution optical imagery. For glaciers with previous velocity estimates, we will compare the results and discuss possible implications for ice dynamics. We focus on Glacier Bay and the Stikine Icefield, which contain a number of fast-flowing tidewater glaciers including LeConte, Johns Hopkins, and La Perouse. For the Johns Hopkins, we will also examine the influence a massive landslide in June 2012 had on flow dynamics. Our velocity maps show that within Glacier Bay, the highest surface velocities occur on the tidewater glaciers. La Perouse, the only Glacier Bay glacier to calve directly into the Pacific Ocean, has maximum velocities of 3.5 - 4 m/day. Johns Hopkins Glacier shows 4 m/day velocities at both its terminus and in its upper reaches, with lower velocities of ~1-3 m/day in between those two regions. Further north, the Margerie Glacier has a maximum velocity of ~ 4.5 m/day in its upper reaches and a velocity of ~ 2 m/day at its terminus. Along the Grand Pacific terminus, the western terminus fed by the Ferris Glacier displays velocities of about 1 m/day while the eastern terminus has lower velocities of < 0.5 m/day. The lake terminating glaciers along the Pacific coast have overall lower surface velocities, but they display complex flow patterns. The Alsek Glacier displays maximum velocities of 2.5 m/day above where it divides into two branches. Velocities at the terminus of the northern branch reach 1 m/day while the terminus of the southern branch moves about 2 m/day. Grand Plateau Glacier also divides into two main branches, with a northern branch displaying peak velocities of 1.5 m/day and a southern branch flowing at a rate of 1 m/day. The Stikine Icefield contains a number of large tidewater glaciers showing maximum velocities near their termini. At the terminus of the South Sawyer Glacier, velocities reach a peak of about 2 m/day. Along the terminus of the Dawes Glacier, velocities reach 3.5 m/day. The Baird Glacier displays lower velocities of 1-1.5 m/day. LeConte Glacier has 2-3 m/day velocities in its upper regions with higher velocities near its terminus. In contrast to the pattern shown by the surrounding glaciers, the Great Glacier has a peak velocity of 2 m/day in the upper portion of the glacier and a velocity of only 0.5 m/day near its terminus.

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

2012-12-01

23

Alaska tidewater glacier velocities and frontal ablation, 1985-2012  

NASA Astrophysics Data System (ADS)

Despite their potential importance to sea level rise, little is known about the proportion of mass loss due to frontal ablation (the sum of ice loss through calving and submarine melt) from tidewater glaciers outside of the Greenland and Antarctic ice sheets. Frontal ablation contributes about half of the mass loss from the ice sheets, and lack of both understanding of and data on these important processes has been cited as a major hindrance to accurate predictions of global sea level rise. First, we present a 64 year record of length change for 50 Alaska tidewater glaciers, derived from manually digitizing aerial mapping photographs and Landsat scenery. Then, we present a 27 year record of surface velocity and frontal ablation for 20 Alaska tidewater glaciers (representing 80% of the total tidewater glacier area in the region), derived using a feature tracking algorithm, all available cloud-free Landsat 5 and 7 scenes, and estimates of glacier ice thickness derived from an inversion of surface topography. In general, the 50 glaciers studied retreated over the period 1948-2012, though these changes are not constant - several glaciers both retreated and advanced over the time period. We find the total mean rate of frontal ablation for these 20 glaciers over the period 1985-2012 is 16.2×6.5$ Gt a-1; scaling this result by area to the remaining 30 tidewater glaciers in Alaska, we estimate a mean rate of frontal ablation of 18.3×7.3 Gt a-1 over the period 1985-2012. Two glaciers in particular, Hubbard and Columbia, account for over 50% of the frontal ablation signal of the set of 20 glaciers. Seasonal changes in surface velocity match well with seasonal changes in length, indicating that rates of frontal ablation do not remain constant throughout the year. Despite coming from 15% of the glacierized area in the region, frontal ablation is a significant contributor to the regional mass budget. We estimate a specific mass loss through frontal ablation for all Alaska glaciers of 0.21 m w.e. a-1, equivalent to estimates from Svalbard, and over three times the rate for Greenland.

McNabb, R. W.; Hock, R.

2013-12-01

24

GLACIER DAMMED LAKES AND OUTBURST FLOODS IN ALASKA  

Microsoft Academic Search

h 4 INTRODUcrION Glaciers in Alaska cover an area of about 73,800 square kilometers (28,500 square miles). They are most highly concentrated along the Pacific Coast and in the south-central part of the State. Many of these g1aciers;as elsewhere in the world, flow across the mouths of adjoining valleys and cause lakes to form behind the ice streams. These glacier

Austin Post; Lawrence R. Mayo; ATLAS HA

1971-01-01

25

GLACIER DAMMED ICE MARGINAL LAKES OF ALASKA: CHANGES SINCE 1971  

E-print Network

GLACIER DAMMED ICE MARGINAL LAKES OF ALASKA: CHANGES SINCE 1971 by David F. G. Wolfe PresentedRuwe for pulling through with me during long hours in the GIS lab. Dr. Leslie Cornick guided statistical procedures. Jason Geck helped guide the initial GIS framework and satellite imagery processing procedures

Loso, Michael G.

26

POPULATION DYNAMICS AND DEMOGRAPHY OF HUMPBACK WHALES IN GLACIER BAY AND ICY STRAIT, ALASKA  

E-print Network

POPULATION DYNAMICS AND DEMOGRAPHY OF HUMPBACK WHALES IN GLACIER BAY AND ICY STRAIT, ALASKA JAMES F--Standardized sight-resight data of Humpback Whales (Megaptera novaeangliae) in Glacier Bay and Icy Strait, Alaska-recapture, Glacier Bay National Park and Preserve, Humpback Whale, Icy Strait, Megaptera novaeangliae, population

DeSante, David F.

27

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

Microsoft Academic Search

Glaciers along the Gulf of Alaska are thinning and retreating rapidly. An important control on the rate at which ice is being lost is basal motion because higher glacier velocities increase the rate at which ice is delivered to ablation zones. Recent research has focused on understanding the effects of sub-glacial water storage on glacier basal motion. In this study,

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

2009-01-01

28

Elevation change (2000-2004) on the Malaspina Glacier, Alaska  

NASA Technical Reports Server (NTRS)

The glaciers of the southeastern Alaska coastal region are the largest temperate glacier meltwater source on Earth and may contribute one third of the total glacier meltwater entering the global ocean. Since melt onset and refreeeze timing in this region show a tendency toward earlier onset and longer ablation seasons, accelerated glacier wastage may be occurring. In this study we focus on one of the largest temperate glacier systems on Earth, the Malaspina Glacier. This glacier, with a length of approximately 110 km and an area of approximately square 5,000 km, has the largest piedmont lobe of any temperate glacier. The entire lobe, which lies at elevations below 600 m, is within the ablation zone. We report and interpret ice elevation change between a digital elevation model (DEM) derived from the Shuttle Radar Topography Mission (SRTM C band) observations in Feb. 2000 and ICESat Laser 1-3 observations between Feb. 2003 and Nov. 2004. We use these elevation change results, along with earlier studies, to address the spatial and temporal variability in wastage of the piedmont lobe. Between 2000 and 2004 ice elevation changes of 10-30 meters occurred across the central Malaspina piedmont lobe. From 1972/73 (USGS DEM) to 1999 (SRTM corrected for estimated winter snow accumulation) Malaspina's (Agassiz, Seward Lobe, and Marvine) mean ice thinning was estimated at -47 m with maximum thinning on parts of the lobes to -160 m. The Malaspina's accumulation area is only slightly larger than its ablation area (2,575 km2 vs. 2,433 km2); unfortunately few glaciological observations are available from this source region. Snow accumulation rates have been largely inferred from low-altitude precipitation and temperature data. Comparing sequential ICESat observations in the Malaspina source region, we estimated short-term elevation increases of up to 5 meters during the winter of 2003/04.

Sauber, J.; Molnia, B.; Carabajal, C.; Luthcke, S.; Muskett, R.

2005-01-01

29

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

30

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

31

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

Microsoft Academic Search

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

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

2009-01-01

32

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

Microsoft Academic Search

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

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

2008-01-01

33

Dendrochronology and late Holocene history of Bering piedmont glacier, Alaska  

USGS Publications Warehouse

Fluctuations of the piedmont lobe of Bering Glacier and its sublobe Steller Glacier over the past two millennia are reconstructed using 34 radiocarbon dates and tree-ring data from 16 sites across the glaciers' forelands. The general sequence of glacial activity is consistent with well-dated fluctuations of tidewater and land-terminating glaciers elsewhere along the Gulf of Alaska. Extensive forested areas along 25 km of the Bering ice margin were inundated by glacio-lacustrine and glacio-fluvial sediments during a probable ice advance shortly before 500 cal yr A.D. Regrowth of forests followed the retreating ice as early as the 7th century A.D., with frequent interruptions of tree growth due to outwash aggradation. Forests overrun by ice and buried in outwash indicate readvance about 1080 cal yr A.D. Retreat followed, with ice-free conditions maintained along the distal portions of the forefield until the early 17th century after which the ice advanced to within a few kilometers of its outer Neoglacial moraine. Ice reached this position after the mid-17th century and prior to 200 yr ago. Since the early 20th century, glacial retreat has been punctuated by periodic surges. The record from forests overrun by the nonsurging Steller Lobe shows that this western ice margin was advancing by 1250 A.D., reaching near its outer moraine after 1420 cal yr A.D. Since the late 19th century, the lobe has dominantly retreated.

Wiles, G.C.; Post, A.; Muller, E.H.; Molnia, B.F.

1999-01-01

34

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

USGS Publications Warehouse

A small Holocene fan is forming where Queen Inlet, a hanging valley, enters West Arm fjord, Glacier Bay, Alaska. Queen fan formed in the last 80 years following retreat of the Little Ice Age glacier that filled Glacier Bay about 200 yr BP. It was built mainly by a turbidite system originating from Carroll Glacier delta, as the delta formed in the early 1900s at the head of Queen Inlet. The Late Holocene Queen fan is comparable to large Pleistocene fans that formed in the Gulf of Alaska and differs from trough-mouth fans formed by cooler climate glacier systems.

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

1999-01-01

35

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

36

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

37

Glaciers along the Copper River, Alaska, Controlled by Landslides, Vegetation, Lakes, Rivers (and Climate)  

NASA Astrophysics Data System (ADS)

98% of glaciers in Alaska are retreating or thinning at low elevations due to warming; some are thickening at high elevations due to rising precipitation. Anomalous surge and tidewater glaciers are much studied. Debris-covered, freshwater-calving glaciers and juxtaposed land-terminating glaciers have their own peculiar dynamics, as exemplified by glaciers in the Copper River corridor, Alaska. Those glaciers are losing area and mass, consistent with Alaska's general trend and recent climate change. Other factors can exceed or negate climatic influences on individual glaciers or parts of glaciers. For example, the terminus of Childs Glacier has been almost stable for a century due to thermal/mechanical buffering by undercutting and calving in the Copper River. Thick debris insulates glacier ice and retards glacier thinning and retreat. This protective effect is enhanced when vegetation becomes established on glacier debris cover and cools the glacier's surface. However, debris and vegetation also impedes drainage and can cause runaway lake growth. Further complexity is caused by unsteady inputs of landslide debris, size-dependent glacier response times, and influences of ice-contact lakes on glacier energy balance. Landslides can load and accelerate glaciers in the first years afterward, and on century time scales thick debris insulates and promotes vegetation growth, which first tends to stabilize glaciers, but the debris and vegetation eventually induce supraglacial ponding, lake growth and glacier disintegration. Allen Glacier exhibits composite effects of (1) calving into the Copper River at the peak of the Little Ice Age, (2) slow response to the termination of the Little Ice Age; (3) landslides, debris insulation, and vegetational cooling; (4) nonlinear lake growth; and (5) decades of warming climate, renewed melting, and disarticulation.

Kargel, J. S.; Furfaro, R.; Banks, M.; Fischer, L.; Hoelzle, M.; Huggel, C.; Leonard, G.; Molnia, B.; Roer, I.; Wessels, R.; Wolfe, D.; Bianchi, L.

2008-12-01

38

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.

39

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

40

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

41

Glacier Erosion and Convergent Tectonics in Southern Alaska  

NASA Astrophysics Data System (ADS)

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

Merrand, Y.; Hallet, B.

2001-12-01

42

Patterns of Alaska glacier mass balance over 20-years from UAF/Operation Ice Bridge altimetry  

NASA Astrophysics Data System (ADS)

Glaciers along the Gulf Alaska represent the largest single contribution to sea level rise outside of the ice sheets (Gardner et al., 2013). Since 1993, the University of Alaska (UAF) has performed aircraft laser altimetry surveys throughout the Gulf of Alaska to monitor patterns of mass loss (Arendt et al., 2002; Johnson et al., 2013; Echelmeyer et al., 1996). Efforts have increased in recent years as Operation IceBridge has enabled more extensive surveys then ever achieved previously. Here we present the first comprehensive overview of this unprecedented dataset and examine regional patterns of geodetic glacier mass balance on 200+ mountain glaciers over 20 years. The data reveal coherent patterns in glacier mass balance related to geometry, glacier size and climate but also contain a remarkable amount of spatial and temporal variability. Regional surface mass balance modeling and velocity mapping help to reveal the mechanisms responsible for observed patterns.

Burgess, E. W.; Larsen, C. F.; Arendt, A. A.; Murphy, N.; Johnson, A.; Oneel, S.; Zirnheld, S. L.; Rich, J.; Claus, P.

2013-12-01

43

Muir and Riggs Glaciers, Muir Inlet, Alaska - 1941  

USGS Multimedia Gallery

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

44

Multitemporal Landsat multispectral scanner and thematic mapper data of the Hubbard Glacier region, southeast Alaska  

USGS Publications Warehouse

In late May 1986, the advancing Hubbard Glacier blocked the entrance to Russell Fiord near Yakutat, Alaska, creating a large ice-dammed lake. Runoff from the surrounding glaciated mountains raised the level of the lake to about 25 m above sea level by 8 October, when the ice dam failed. Remote sensing offers one method to monitor this large tidal glacier system, particularly the glacier activity that would portend the re-closure of Russell Fiord. -Authors

Walker, K.-M.; Zenone, C.

1988-01-01

45

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

NASA Astrophysics Data System (ADS)

Glaciers along the Gulf of Alaska are thinning and retreating rapidly. An important control on the rate at which ice is being lost is basal motion because higher glacier velocities increase the rate at which ice is delivered to ablation zones. Recent research has focused on understanding the effects of sub-glacial water storage on glacier basal motion. In this study, we examined two seasons of the effect of hydrologic controls (from large rainfall events as well as a glacier lake outburst floods) on the velocity of the Lemon Creek Glacier in southeastern Alaska. Lemon Creek Glacier is a moderately sized (~16~km2) temperate glacier at the margin of the Juneau Icefield. An ice-marginal lake forms at the head of the glacier and catastrophically drains once or twice every melt season. We have instrumented the glacier with two meteorological stations: one at the head of the glacier near the ice-marginal lake and another several kilometers below the terminus. These stations measure temperature, relative humidity, precipitation, incoming solar radiation and wind speed and direction. Lake stage in the ice-marginal lake was monitored with a pressure transducer. In addition, Lemon Creek was instrumented with a water quality sonde at the location of a US Geological Survey gaging station approximately 3 km downstream from the glacier terminus. The sonde provides continuous measurements of water temperature, dissolved oxygen, turbidity and conductivity. Finally, multiple Trimble NetRS dual frequency, differential GPS units were deployed on the glacier along the centerline of the glacier. All of the instruments were run continuously from May-September 2008 and May-September 2009 and captured threee outburst floods associated with the ice-marginal lake drainage as well as several large (>3~cm) rainfall events associated with frontal storms off of the Gulf of Alaska in late summer. Taken together, these data allow us to test the hypothesis that water inputs which overwhelm subglacial drainage networks result in increased rates of basal motion. 2008 was an extremely rainy summer, and the (single) lake drainage occurred during the largest precipitation even of the summer. 2009 on the other hand, was comparatively dry and sunny for the majority of the summer--the first lake drainage occurred during a several day stretch of sunny weather. The lake refilled during an extreme rainfall (20 cm of rain was recorded in a 24 hour period at a met station 16 km away and about 500 m lower in elevation) and then subsequently drained during a rainy period. We focus on the comparison of the data from two years, including the glacial response to the lake drainage with and without accompanying precipitation inputs.

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

2009-12-01

46

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

47

Quiescent-phase evolution of a surge-type glacier: Black Rapids Glacier, Alaska, U.S.A.  

USGS Publications Warehouse

Black Rapids Glacier, a surge-type glacier in the Alaska Range, most recently surged in 1936-37 and is currently in its quiescent phase. Mass balance, ice velocity and thickness change have been measured at three to ten sites from 1972 to 1994. The annual speed has undergone cyclical fluctuations of as much as 45% about the mean speed. Ice thickness and surface slope did not change enough to cause the speed fluctuations through changes in ice deformation, which indicates that they are being driven by changes in basal motion. The behavior of Black Rapids Glacier during this quiescent phase is significantly different from that of Variegated Glacier, another well-studied surge-type glacier in Alaska. The present medial-moraine configuration of Black Rapids Glacier indicates that a surge could occur at any time. However, ice velocity data indicate that the next surge may not be imminent. We believe that there is little chance that the next surge will cross and dam the Delta River.

Heinrichs, T.A.; Mayo, L.R.; Echelmeyer, K.A.; Harrison, W.D.

1996-01-01

48

Stream temperature response to variable glacier coverage in coastal watersheds of northern southeast Alaska  

NASA Astrophysics Data System (ADS)

Glaciers in southeast Alaska are experiencing high rates of ice thinning and retreat. These ongoing changes in glacier volume are altering the proportion of streamflow derived from glacial runoff, which can be an important control on the thermal regime of streams in the region. We measured stream temperature continuously during the 2011 summer runoff season (May through October) in nine watersheds of southeast Alaska that provide spawning habitat for Pacific salmon. Six of the nine watersheds have glacier coverage ranging from 2 to 63%. Our goal was to determine how air temperature and watershed land cover, particularly glacier coverage, influence stream temperature across the seasonal hydrograph. Multiple linear regression identified mean watershed elevation, which is tied to glacier extent, and watershed lake coverage (%) as the strongest landscape controls on mean monthly stream temperature, with the weakest (May) and strongest (July) models explaining 86% and 97% of the temperature variability, respectively. Mean weekly stream temperature was significantly related to mean weekly air temperature in seven of the nine streams; however, the relationships were weak to non-significant in the streams dominated by glacial runoff. Peak summer stream temperatures occurred much earlier in the glacial streams (typically around late May) and glaciers also had a cooling effect on monthly mean stream temperature during the summer (July through September) equivalent to a decrease of 1.1°C for each 10% increase in glacier coverage. Streams with >30% glacier coverage demonstrated decreasing stream temperatures with rising summer air temperatures, while those with <30% glacier coverage exhibited summertime warming. The maximum weekly average temperature (MWAT, an index of thermal suitability for salmon species) in the six glacial streams was substantially below the lower threshold for optimum salmonid growth. This finding suggests that, while glaciers are important for moderating summer stream temperatures, future reductions in glacier runoff may actually improve the thermal suitability of some streams in northern southeast Alaska for salmon.

Hood, E. W.; Fellman, J. B.; Nagorski, S. A.; Vermilyea, A.; Pyare, S.; Scott, D.

2012-12-01

49

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

50

Combined Ice and Water Balances of Maclure Glacier, California, South Cascade Glacier, Washington, and Wolverine and Gulkana Glaciers, Alaska, 1967 Hydrologic Year  

USGS Publications Warehouse

Combined ice and water balances were measured in the 1967 hydrologic year (October 1-September 30) on four glaciers in western North America ranging in latitude from 37 deg to 63 deg N. This hydrologic year was characterized by heavier than normal winter precipitation in California and Washington and abnormally dry winter conditions in coastal Alaska. In summer the western conterminous states were abnormally dry and central and southern Alaska experienced very wet conditions. Maclure Glacier (lat 37 deg 45' N., 3,650-m (metres) mean equilibrium line altitude) had an above normal winter balance of 3.46 m and a positive annual balance of 1.05 m (metres of water equivalent). South Cascade Glacier (lat 48 deg 22' N., 1900-m mean equilibrium line altitude) had a winter balance of 3.28 m, slightly above average. Above normal summer ablation resulted in a final annual balance of -0.58 m, slightly more negative than has been the case for the past decade. Wolverine Glacier's (lat 60 deg 24' N., 1,200-m mean equilibrium line altitude) winter balance was 1.17 m, considerably below normal; the annual balance was -2.04 m. Gulkana Glacier (lat 63 deg 15' N., 1,700-m mean equilibrium line altitude) had a winter balance of 1.05 m, approximately normal for this glacier; the final annual balance was -0.30 m.

Tangborn, Wendell V.; Mayo, Lawrence R.; Scully, David R.; Krimmel, Robert M.

1977-01-01

51

Multiple controls on glacier dynamics in the Copper River Basin, Alaska  

NASA Astrophysics Data System (ADS)

In the Copper River Basin, south-central Alaska, glaciers are shaped by a complex set of various processes acting on different temporal and spatial scales. Beside climatic controls, they are strongly influenced by unsteady inputs of large landslides related to the vicinity to the active tectonic system (with earthquakes such as the one of 1964 with a magnitude of 8.4 on the Richter scale). Thick debris insulates the ice and retards glacier thinning and retreat. This protective effect is enhanced when vegetation becomes established on glacier debris cover and cools the glaciers surface. However, debris and vegetation may also impede drainage and lead to lake formation and growth. In addition, some glacier fronts are influenced by calving processes. These multiple controls make this glacial environment highly dynamic and susceptible to changes. Accordingly, glaciers in the Copper River Basin are loosing mass and area, consistent with Alaska's general trend and recent climatic developments. Other factors can exceed or negate climatic influences on individual glaciers or parts of glaciers. We present here first analyses within a multi-disciplinary project, with a focus on ground-based field campaigns and complementary remote sensing studies.

Gaertner-Roer, I.; Kargel, J. S.; Banks, M.; Fischer, L.; Furfaro, R.; Hoelzle, M.; Huggel, C.; Wessels, R.; Wolfe, D.

2009-04-01

52

Columbia Glacier, Alaska, photogrammetry data set, 1981-82 and 1984-85  

USGS Publications Warehouse

Photogrammetric processing of 12 sets of vertical aerial photography of the Columbia Glacier, Alaska, has measured the altitude and velocity fields of the lowest 14,000 m of the glacier during the periods of September 1981 to October 1982 and October 1984 to September 1985. The data set consists of the location of 3,604 points on the glacier, 1,161 points along the glacier terminus, and 1,116 points along the top of the terminus ice cliff. During the 1981 to 1985 period the terminus of the glacier receded 1,350 m, the ice near the terminus thinned at a rate of 18 m/year, and ice velocity near the terminus tripled, reaching as much as 6,000 m/year. (Author 's abstract)

Krimmel, R.M.

1987-01-01

53

Distribution and spawning dynamics of capelin (Mallotus villosus) in Glacier Bay, Alaska: A cold water refugium  

USGS Publications Warehouse

Pacific capelin (Mallotus villosus) populations declined dramatically in the Northeastern Pacific following ocean warming after the regime shift of 1977, but little is known about the cause of the decline or the functional relationships between capelin and their environment. We assessed the distribution and abundance of spawning, non-spawning adult and larval capelin in Glacier Bay, an estuarine fjord system in southeastern Alaska. We used principal components analysis to analyze midwater trawl and beach seine data collected between 1999 and 2004 with respect to oceanographic data and other measures of physical habitat including proximity to tidewater glaciers and potential spawning habitat. Both spawning and non-spawning adult Pacific capelin were more likely to occur in areas closest to tidewater glaciers, and those areas were distinguished by lower temperature, higher turbidity, higher dissolved oxygen and lower chlorophyll a levels when compared with other areas of the bay. The distribution of larval Pacific capelin was not sensitive to glacial influence. Pre-spawning females collected farther from tidewater glaciers were at a lower maturity state than those sampled closer to tidewater glaciers, and the geographic variation in the onset of spawning is likely the result of differences in the marine habitat among sub-areas of Glacier Bay. Proximity to cold water in Glacier Bay may have provided a refuge for capelin during the recent warm years in the Gulf of Alaska.

Arimitsu, M.L.; Piatt, J.F.; Litzow, M.A.; Abookire, A.A.; Romano, Marc D.; Robards, M.D.

2008-01-01

54

A Century of Retreat at Portage Glacier, South-Central Alaska  

USGS Publications Warehouse

Introduction: The Portage Glacier, in south-central Alaska, is viewed by thousands of visitors annually who come to the U.S. Forest Service Begich, Boggs Visitor Center located on the road system between Anchorage and Whittier, Alaska. During the past century, the terminus of the glacier has retreated nearly 5 kilometers to its present location (fig. 1). Like other glaciers that terminate in water, such as Columbia Glacier near Valdez or Mendenhall Glacier near Juneau, Portage Glacier has experienced accelerated retreats in recent decades that likely were initially triggered by climate change begun at the end of the Little Ice Age in the mid-1800s and subsequently controlled in recent history primarily by calving of the glacier terminus. Photographic records of the terminus covering 1914 until present day track the patterns of retreat. These data, coupled with USGS climate information collected from the southern end of the ice field, provide insight to the patterns of retreat that might be observed in the future.

Kennedy, Ben W.; Trabant, Dennis C.; Mayo, Lawrence R.

2006-01-01

55

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

56

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

NSDL National Science Digital Library

This video shows how a NASA glaciologist has learned about glaciers and how their formation could be related to climate change. It features nine fly-bys over 3-dimensional glaciers, live video footage of ice fronts calving into the sea, and picture sequences of historical and satellite data.. Length:13:15.

1996-01-01

57

Muir and Riggs Glaciers, Muir Inlet, Alaska - 2004  

USGS Multimedia Gallery

The second repeat photograph documents 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 more than 7 kilometers northwest. Riggs Glacier has retre...

58

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.

59

Multiple controls on glacier dynamics in the Copper River Basin, Alaska  

Microsoft Academic Search

In the Copper River Basin, south-central Alaska, glaciers are shaped by a complex set of various processes acting on different temporal and spatial scales. Beside climatic controls, they are strongly influenced by unsteady inputs of large landslides related to the vicinity to the active tectonic system (with earthquakes such as the one of 1964 with a magnitude of 8.4 on

I. Gaertner-Roer; J. S. Kargel; M. Banks; L. Fischer; R. Furfaro; M. Hoelzle; C. Huggel; R. Wessels; D. Wolfe

2009-01-01

60

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

USGS Publications Warehouse

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 detennine glacier volume changes in southeast Alaska and adjoining Canada. SRTM accuracy was assessed at ??5 in through comparison with airborne laser altimetry and control locations measured with GPS. Glacier surface elevations lowered over 95% of the 14,580 km2 glacier-covered area analyzed, with some glaciers thinning as much as 640 in. A combination of factors have contributed to this wastage, including calving retreats of tidewater and lacustrine glaciers and climate change. Many glaciers in this region are particularly sensitive to climate change, as they have large areas at low elevations. However, several tidewater glaciers that had historically undergone calving retreats are now expanding and appear to be in the advancing stage of the tidewater glacier cycle. The net average rate of ice loss is estimated at 16.7 ?? 4.4 km3/yr, equivalent to a global sea level rise contribution of 0.04 ?? 0.01 mm/yr. Copyright 2007 by the American Geophysical Union.

Larsen, C.F.; Motyka, R.J.; Arendt, A.A.; Echelmeyer, K.A.; Geissler, P.E.

2007-01-01

61

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

62

Assessing glacier response to changing climate using new and historical field observations on the Kahiltna Glacier in the Central Alaska Range  

NASA Astrophysics Data System (ADS)

Like many remote mountain ranges in Alaska, British Columbia and the Yukon, the Central Alaska Range is a highly glaciated but relatively sparsely monitored region in terms of glacier mass balance and meteorological ground measurements. To date, long-term trends and balance gradients are poorly known, though these are of particular importance for calibrating melt models and evaluating remote sensing techniques aimed at assessing glacier response to climate change. Among the best field-based data available for the region are approximately 20 years of National Park Service mass balance measurements on the Kahiltna Glacier. A land-terminating valley glacier with a wide range of altitudes and non-surge-type behavior, the Kahiltna Glacier is often taken as a benchmark for the current mass balance state of Central Alaska Range glaciers. However, mass balance has historically only been sampled at a single location on the glacier, allowing for the possibility of substantial scaling error when these findings are extrapolated spatially. Here we present an extended campaign of field-based observations on the Kahiltna Glacier in 2010 and 2011, used to expand data from the single National Park Service index site to the entire glacier in order to reconstruct the historical mass balance record. Measurements include summer melt at 13 ablation stake positions, winter accumulation surveys along a centerline and several lateral profiles, summer temperatures at five elevations, and meteorological variables such as incoming/reflected solar radiation and wind speed/direction at a representative ablation area site. Calibrated against the observed temperature gradients, a set of modeling tools has been developed for the glacier using a fully distributed positive degree day approach. Derived mass change estimates provide key information for assessing the little known state of health of Central Alaska Range glaciers. By serving as a template, balance and temperature gradients observed on the Kahiltna Glacier can enable mass balance estimates for other glaciers in the region with as little as a single stake measurement. Moreover, mass changes derived from this study will provide seasonal corrections to remote sensing estimates from repeat laser altimetry, and will assist in calibrating regionally downscaled GRACE gravimetry measurements. Ultimately, this research hopes to provide crucial information for determining past and current glacier melt evolution for the Kahiltna Glacier and Central Alaska Range glaciers as a whole.

Young, J. C.; Arendt, A. A.

2011-12-01

63

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.

64

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

65

Monitoring change in the Bering Glacier region, Alaska: Using Landsat TM and ERS-1 imagery  

SciTech Connect

The Bering Glacier is the largest (5,180 km{sup 2}) and longest (191 km) glacier in continental North America. This glacier is one of about 200 temperate glaciers in the Alaska/Canada region that are known to surge. Surges at the Bering Glacier typically occur on a 20-30 year cycle. The objective of this project was to extract information regarding the position of the terminus of the glacier from historic aerial photography, early 20{sup th} century ground photography, Landsat Thematic Mapper (TM) satellite data, and European Space Agency, Synthetic Aperture RADAR (ERS-1 SAR) data and integrate it into a single digital database that would lend itself to change detection analysis. ERS-1 SAR data was acquired from six dates between 1992-95 and was terrain corrected and co-registered A single Landsat TM image from June 1991 was used as the base image for classifying land cover types. Historic locations of the glacier terminus were generated using traditional photo interpretation techniques from aerial and ground photography. The result of this platform combination, along with the historical data, is providing land managers with the unique opportunity to generate complete assessments of glacial movement this century and determine land cover changes which may impact wildlife and recreational opportunities.

Payne, J.F. [Bureau of Land Management, Anchorage, AK (United States); Coffeen, M. [Bureau of Land Management, Glennallen, AK (United States); Macleod, R.D. [Ducks Unlimited, Inc., Sacramento, CA (United States)] [and others

1997-06-01

66

Spectral properties of fog over the Malaspina Glacier, Alaska, in comparison to snow, ice, and clouds  

NASA Technical Reports Server (NTRS)

Analysis of Landsat 5 Thematic Mapper (TM) data of the Malaspina Glacier in southeastern Alaska has shown that fog overlying the glacier ice has reflectance characteristics similar to the ice below and that the spectral reflectance of fog can be different from other types of clouds. Fog is more reflective in the visible and near-infrared wavelengths compared to snow, ice, and cumulus clouds. The differentiation between clouds, fog, and the ice below can be enhanced by combining TM bands in the visible part of the spectrum.

Ormsby, James P.; Hall, Dorothy D.

1991-01-01

67

Muir and Riggs Glaciers, Muir Inlet, Alaska - 1950  

USGS Multimedia Gallery

This, the first of two repeat photographs, documents significant changes that have occurred during the nine years between photographs A and B. Although Muir Glacier has retreated more than 3 kilometers and thinned more than 100 meters, exposing Muir Inlet, it remains connected with tributary Riggs G...

68

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

USGS Publications Warehouse

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 rivers penetrating coastal ranges. Discharge from glaciers and icefields accounts for 47% of total freshwater discharge, with 10% coming from glacier volume loss associated with rapid thinning and retreat of glaciers along the GOA. Our results indicate the region of the GOA from Prince William Sound to the east, where glacier runoff contributes 371 km3 yr -1, is vulnerable to future changes in freshwater discharge as a result of glacier thinning and recession. Changes in timing and magnitude of freshwater delivery to the GOA could impact coastal circulation as well as biogeochemical fluxes to near-shore marine ecosystems and the eastern North Pacific Ocean. Copyright ?? 2010 by the American Geophysical Union.

Neal, E.G.; Hood, E.; Smikrud, K.

2010-01-01

69

Neoglacial fluctuations of terrestrial, tidewater, and calving lacustrine glaciers, Blackstone-Spencer Ice Complex, Kenai Mountains, Alaska  

NASA Astrophysics Data System (ADS)

The glaciers surrounding the Blackstone-Spencer Ice Complex display a variety of termini types: Tebenkov, Spencer, Bartlett, Skookum, Trail, Burns, Shakespeare, Marquette, Lawrence, and Ripon glaciers end in terrestrial margins; Blackstone and Beloit glaciers have tidewater termini; and Portage Glacier has a calving lacustrine margin. In addition, steep temperature and precipitation gradients exist across the ice complex from the maritime environment of Prince William Sound to the colder, drier interior. The Neoglacial history of Tebenkov Glacier, as based on overrun trees near the terminus, shows advances ca. 250- 430 AD (calibrated date), ca. 1215-1275 AD (calibrated date), and ca. 1320-1430 AD (tree ring evidence), all intervals of glacier advance around the Gulf of Alaska. However, two tidewater glaciers in Blackstone Bay retreated from their outermost moraines by 1350 AD, apparently asynchronously with respect to the regional climate signal. The most extensive Kenai Mountain glacier expansions during Neoglaciation occurred in the late Little Ice Age. The outermost moraines are adjacent to mature forest stands and bog peats that yield dates as old as 5,600 BP. Prince William Sound glaciers advanced during two Little Ice Age cold periods, 1380-1680 and 1830-1900 AD. The terrestrial glaciers around the Blackstone-Spencer Ice Complex all built moraines during the 19th century and began retreating between 1875 and 1900 AD. Portage and Burns glaciers began retreating between 1790 and 1810 AD, but their margins remained close to the outermost moraines during the 19th century. Regional glacier fluctuations are broadly synchronous in the Gulf of Alaska region. With the exception of the two tidewater glaciers in Blackstone Bay, all glaciers in the Kenai Mountains, no matter their sizes, altitudes, orientations, or types of margins, retreated at the end of the Little Ice Age. The climate signal, especially temperature, appears to be the strongest control on glacier behavior during the last millennium.

Crossen, Kristine June

1997-12-01

70

Glacier Ice Mass Fluctuations and Fault Instability in Tectonically Active Southern Alaska  

NASA Technical Reports Server (NTRS)

Across southern Alaska the northwest directed subduction of the Pacific plate is accompanied by accretion of the Yakutat terrane to continental Alaska. This has led to high tectonic strain rates and dramatic topographic relief of more than 5000 meters within 15 km of the Gulf of Alaska coast. The glaciers of this area are extensive and include large glaciers undergoing wastage (glacier retreat and thinning) and surges. The large glacier ice mass changes perturb the tectonic rate of deformation at a variety of temporal and spatial scales. We estimated surface displacements and stresses associated with ice mass fluctuations and tectonic loading by examining GPS geodetic observations and numerical model predictions. Although the glacial fluctuations perturb the tectonic stress field, especially at shallow depths, the largest contribution to ongoing crustal deformation is horizontal tectonic strain due to plate convergence. Tectonic forces are thus the primary force responsible for major earthquakes. However, for geodetic sites located < 10-20 km from major ice mass fluctuations, the changes of the solid Earth due to ice loading and unloading are an important aspect of interpreting geodetic results. The ice changes associated with Bering Glacier s most recent surge cycle are large enough to cause discernible surface displacements. Additionally, ice mass fluctuations associated with the surge cycle can modify the short-term seismicity rates in a local region. For the thrust faulting environment of the study region a large decrease in ice load may cause an increase in seismic rate in a region close to failure whereas ice loading may inhibit thrust faulting.

SauberRosenberg, Jeanne M.; Molnia, Bruce F.

2003-01-01

71

Hazard assessment of the Tidal Inlet landslide and potential subsequent tsunami, Glacier Bay National Park, Alaska  

Microsoft Academic Search

An unstable rock slump, estimated at 5 to 10???106 m3, lies perched above the northern shore of Tidal Inlet in Glacier Bay National Park, Alaska. This landslide mass has the potential\\u000a to rapidly move into Tidal Inlet and generate large, long-period-impulse tsunami waves. Field and photographic examination\\u000a revealed that the landslide moved between 1892 and 1919 after the retreat of the

Gerald F. Wieczorek; Eric L. Geist; Roman J. Motyka; Matthias Jakob

2007-01-01

72

Factors Associated With Recent Ice-Marginal Glacier Dammed Lake Loss, Persistence, and Emergence Across Alaska  

Microsoft Academic Search

Ice-marginal glacier-dammed lakes (GDLs), prone to repeated catastrophic sudden drainages, and amenable to remote monitoring, pose unique hazards to human habitation downstream. Both GDLs and flood potential can be evaluated with satellite imagery and GIS tools. Using a baseline map and ASTER imagery, I determined impoundment longevity (absent, persisting, new) of nearly 700 Alaska\\/adjacent Canada GDL basins. I present here

D. F. Wolfe

2008-01-01

73

Continuous Measurements of Ice Motion and Associated Seismicity at Bering Glacier, Alaska.  

NASA Astrophysics Data System (ADS)

In April 2007, we established an array of GPS and seismic stations on the Bering Glacier, Alaska, to investigate the relationship between glacier motion and glacier-generated seismicity. Bering Glacier is North America's largest mountain glacier and has an area of more than 5000 km2. Dual-frequency GPS data were recorded continuously at 15 second intervals at five stations on the glacier from April to September. Four of the GPS glacier stations were established in a strain diamond located roughly halfway between the equilibrium line and the terminus, at a distance of 40 km from a GPS base station located near the terminus. These four GPS glacier stations were co-located with seismometers, which, together with a fifth seismometer located at center of the strain diamond, form a cross pattern seismic array with a 4-km aperture. The fifth GPS station is located 20 km up glacier from the strain diamond and seismic array, at a point where the upper icefield feeds into a narrow gate to the lower glacier. GPS antennas were fixed to tripods constructed of steel poles drilled 5-7 m deep into the surface of the glacier. This provides a stable reference relative to the glacier surface, which is subject to several meters of annual ablation at the elevation of the strain diamond. The GPS data have been processed using the GAMIT kinematic utility Track. The motion recorded at all sites is rapid (3+ m/day) but smooth and steady down to the temporal resolution of the data. Specifically, we find no evidence for sudden motion events in the timeseries, but rather find only small perturbations superimposed on slowly varying velocities. The seismic records from short period (L-22) and broadband (6TD) instruments reveal frequent icequakes including both emergent low frequency events and impulsive high frequency events. Many of the events recorded show strong time domain correlations across the array. We will construct a timeseries of seismicty using an automatic icequake detector, allowing comparison of the GPS and seismic timeseries. The effect of alternative processing methods for the GPS data, such as GYPSY precise point positioning analysis, will also be explored.

Larsen, C. F.; Truffer, M.; Leblanc, L.; O'Neel, S.; West, M.; None, N.

2007-12-01

74

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

75

Logs and Geologic Data from a Paleoseismic Investigation of the Susitna Glacier fault, Central Alaska Range, Alaska  

USGS Publications Warehouse

This report contains field and laboratory data from a paleoseismic study of the Susitna Glacier fault, Alaska. The initial M 7.2 subevent of the November 3, 2002, M 7.9 Denali fault earthquake sequence produced a 48-km-long set of complex fault scarps, folds, and aligned landslides on the previously unknown, north-dipping Susitna Glacier thrust fault along the southern margin of the Alaska Range in central Alaska. Most of the 2002 folds and fault scarps are 1-3 m high, implying dip-slip thrust offsets (assuming a near-surface fault dip of approximately 20 degrees)of 3-5 m. Locally, some of the 2002 ruptures were superimposed on preexisting scarps that have as much as 5-10 m of vertical separation and are evidence of previous surface-rupturing earthquakes on the Susitna Glacier fault. In 2003-2005, we focused follow-up studies on several of the large scarps at the 'Wet fan' site in the central part of the 2002 rupture to determine the pre-2002 history of large surface-rupturing earthquakes on the fault. We chose this site for several reasons: (1) the presence of pre-2002 thrust- and normal-fault scarps on a gently sloping, post-glacial alluvial fan; (2) nearby natural exposures of underlying fan sediments revealed fine-grained fluvial silts with peat layers and volcanic ash beds useful for chronological control; and (3) a lack of permafrost to a depth of more than 1 m. Our studies included detailed mapping, fault-scarp profiling, and logging of three hand-excavated trenches. We were forced to restrict our excavations to 1- to 2-m-high splay faults and folds because the primary 2002 ruptures mostly were superimposed on such large scarps that it was impossible to hand dig through the hanging wall to expose the fault plane. Additional complications are the pervasive effects of cryogenic processes (mainly solifluction) that can mask or mimic tectonic deformation. The purpose of this report is to present photomosaics, trench logs, scarp profiles, and fault slip, radiocarbon, tephrochronologic, and unit description data obtained during this investigation. We do not attempt to use the data presented herein to construct a paleoseismic history of the Susitna Glacier fault; that history will be the subject of a future report. When completed, our results will be used to compare the Susitna Glacier fault paleoseismic record with results of similar studies on the nearby Denali fault to determine if the simultaneous rupture of these two faults during the 2002 Denali fault earthquake sequence is typical or atypical of their long-term interaction.

Personius, Stephen F.; Crone, Anthony J.; Burns, Patricia A.; Beget, James E.; Seitz, Gordon G.; Bemis, Sean P.

2010-01-01

76

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

77

Morainal bank progradation and sediment accumulation in Disenchantment Bay, Alaska: Response to advancing Hubbard Glacier  

NASA Astrophysics Data System (ADS)

Morainal banks are primary features at the margins of advancing and stable to quasi-stable temperate tidewater glaciers, yet their roles in glacier dynamics and terminus stability are poorly defined by submarine observations. Analysis of new and archival multibeam data and Landsat images of the advancing Hubbard Glacier, southeast Alaska, reveal that between 1978 and 2010 the ice face and morainal bank advanced together at an average rate of ˜34 m/yr, varying spatially and temporally between 14 and 80 m/yr. Morphological features including gullies and a boulder lag suggest cyclical deposition and gravitational erosion on the proximal slope of the morainal bank (15-18°), and possible ice pushing in an area without recent sedimentation. In contrast, the morainal bank of the nearby, quasi-stable (surging) Turner Glacier advanced steadily since 1978 by proximal sedimentation on the steep fjord wall below its hanging valley. Sedimentation in the deep (>220 m) basin of Disenchantment Bay increased from 0.88 m/yr spanning 1978 to 1999, to 1.22 m/yr thereafter. This change appears to be a combined response to glacier advance and sediment dispersal farther down-fjord, and to an increase in sediment yield from other glacial and non-glacial sources. Analysis of Hubbard Glacier illustrates the direct correlation between movement of the terminus and morainal bank in advancing the grounding line of a marine-terminating glacier, and that morainal banks provide a fundamental stabilizing role for advance into a deep-water fjord, compensating for changes in water depth at the grounding line.

Goff, John A.; Lawson, Daniel E.; Willems, Bryce A.; Davis, Marcy; Gulick, Sean P. S.

2012-06-01

78

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

79

Methane seeps along boundaries of receding glaciers in Alaska and Greenland  

NASA Astrophysics Data System (ADS)

Glaciers, ice sheets, and permafrost form a 'cryosphere cap' that traps methane formed in the subsurface, restricting its flow to the Earth's surface and atmosphere. Despite model predictions that glacier melt and degradation of permafrost open conduits for methane's escape, there has been a paucity of field evidence for 'subcap' methane seepage to the atmosphere as a direct result of cryosphere disintegration in the terrestrial Arctic. Here, we document for the first time the release of sub-cryosphere methane to lakes, rivers, shallow marine fjords and the atmosphere from abundant gas seeps concentrated along boundaries of receding glaciers and permafrost thaw in Alaska and Greenland. Through aerial and ground surveys of 6,700 lakes and fjords in Alaska we mapped >150,000 gas seeps identified as bubbling-induced open holes in seasonal ice. Using gas flow rates, stable isotopes, and radiocarbon dating, we distinguished recent ecological methane from subcap, geologic methane. Subcap seeps had anomalously high bubbling rates, 14C-depletion, and stable isotope values matching microbial sources associated with sedimentary deposits and coal beds as well as thermogenic methane accumulations in Alaska. Since differential ice loading can overpressurize fluid reservoirs and cause sediment fracturing beneath ice sheets, and since the loss of glacial ice reduces normal stress on ground, opens joints, and activates faults and fissures, thereby increasing permeability of the crust to fluid flow, we hypothesized that in the previously glaciated region of Southcentral Alaska, where glacial wastage continues presently, subcap seeps should be disproportionately associated with neotectonic faults. Geospatial analysis confirmed that subcap seep sites were associated with faults within a 7 km belt from the modern glacial extent. The majority of seeps were located in areas affected by seismicity from isostatic rebound associated with deglaciation following the Little Ice Age (LIA; ca. 1650-1850 C.E.). Across Alaska, we found a relationship between methane stable isotopes, radiocarbon age, and distance to faults. Faults appear to allow the escape of deeper, more 14C-depleted methane to the atmosphere, whereas seeps away from faults entrained 14C-enriched methane formed in shallower sediments from microbial decomposition of younger organic matter. Additionally, we observed younger subcap methane seeps in lakes of Greenland's Sondrestrom Fjord that were associated with ice-sheet retreat since the LIA. These correlations suggest that in a warming climate, continued disintegration of glaciers, permafrost, and parts of the polar ice sheets will weaken subsurface seals and further open conduits, allowing a transient expulsion of methane currently trapped by the cryosphere cap.

Walter Anthony, K. M.; Anthony, P. M.; Grosse, G.; Chanton, J.

2012-12-01

80

Modeling past and future mass balance and discharge of Gulkana Glacier, Alaska  

NASA Astrophysics Data System (ADS)

The trends of climate change indicate that glacier melt will continue to increase. It is imperative that we understand and quantify how this will affect freshwater river runoff and downstream hydrology in order to better inform local response, policy, and resource management. The purpose of this study was to calibrate a model of discharge and mass balance of Gulkana Glacier and predict the glacier’s response to climate change. Gulkana Glacier is a U.S. Geological Survey (USGS) benchmark glacier located on the south flank of the eastern Alaska Range with an area of 15 km2. Using a temperature-index model including potential clear-sky direct radiation, discharge and mass balance of Gulkana Glacier were simulated over the period of 1967-2009 with a daily time step and a 40 m resolution DEM. Input data for the model were daily temperatures and precipitation data obtained from the USGS climate station near the glacier. Model parameters including precipitation lapse rate, precipitation correction, snowfall correction, melt factor, radiation melt factor for ice, and radiation melt factor for snow, were calibrated until the best agreement between measured and simulated discharged and winter, summer, and annual mass balance data was obtained. Future climate data defined by three time slices (2010-2019, 2050-2059, and 2090-2099) were obtained by a hierarchical climate modeling system, in which the CCSM3 simulations were downscaled with the high resolution regional model Arctic MM5. The 21st century climate is based on the middle-of-the-road A1B scenario, which represents balanced fossil and non-fossil fuel use. The mean temperature difference between each time slice and the mean measured temperature for 2000-2009 was found. These values were added to the daily temperatures for 2000-2009 and the model was used to calculate future discharge and mass balance for each time slice. Precipitation input was the measured 2000-2009 data for each time slice. Compared to the 2000-2009 time slice, mean daily discharge for each time slice increased 57%, 126%, and 178% respectively and maximum discharge for each time slice increased 45%, 71%, and 80% respectively. The increase in discharge has implications for flooding of downstream areas in the future. The mean measured annual balance for 2000-2009 was -0.7 m yr-1 water equivalent (w.e.). The mean annual balance of each time slice was 3.7 times (271%), 7.3 times (629%), and 10.1 times (914%) the 2000-2009 value. This study highlights important changes predicted for Gulkana Glacier and the associated downstream hydrology.

Roth, A. C.; Hock, R. M.; Arendt, A. A.; Zhang, J.

2010-12-01

81

The Propagation of a Surge Front on Bering Glacier, Alaska, 2001-2011  

NASA Technical Reports Server (NTRS)

Bering Glacier, Alaska, USA, has a 20 year surge cycle, with its most recent surge reaching the terminus in 2011. To study this most recent activity a time series of ice velocity maps was produced by applying optical feature-tracking methods to Landsat-7 ETM+ imagery spanning 2001-11. The velocity maps show a yearly increase in ice surface velocity associated with the down-glacier movement of a surge front. In 2008/09 the maximum ice surface velocity was 1.5 plus or minus 0.017 kilometers per a in the mid-ablation zone, which decreased to 1.2 plus or minus 0.015 kilometers per a in 2009/10 in the lower ablation zone, and then increased to nearly 4.4 plus or minus 0.03 kilometers per a in summer 2011 when the surge front reached the glacier terminus. The surge front propagated down-glacier as a kinematic wave at an average rate of 4.4 plus or minus 2.0 kilometers per a between September 2002 and April 2009, then accelerated to 13.9 plus or minus 2.0 kilometers per a as it entered the piedmont lobe between April 2009 and September 2010. Thewave seems to have initiated near the confluence of Bering Glacier and Bagley Ice Valley as early as 2001, and the surge was triggered in 2008 further down-glacier in the mid-ablation zone after the wave passed an ice reservoir area.

Turrin, James; Forster, Richard R.; Larsen, Chris; Sauber, Jeanne

2013-01-01

82

Rock avalanches and glacier dynamics: a case study in the Chugach Mountains, Alaska  

NASA Astrophysics Data System (ADS)

Massive rock slope failures resulting in rock avalanches in glacierized environments can have serious consequences for downstream areas. Furthermore they are important drivers of erosion. The Chugach Mountains in south-central Alaska are a vast remote and strongly glacierized area with evidence of numerous rock avalanches, although a systematic documentation and assessment of their role as geomorphic agents is missing so far. Here we use glaciers as a unique archive of rock avalanches that have deposited extensive debris sheets on glaciers. A number of well preserved rock avalanche deposits from past years and decades furthermore facilitate the quantification of hitherto poorly known historic glacier surface velocities in the region. The principal objective of this work was first to create an inventory of rock avalanches on the basis of Landsat satellite images in the Chugach Mountains, and to analyze their characteristics regarding lithology, climate, runout-distance, area and volume, as well as their spatial distribution. The runout distances of mass movements are generally larger in glacial environments than in non-glacial environments. This characteristic was also shown in the studied cases as they always travelled over glaciers, firn or snow. The distribution of the rock avalanches was compared with the occurrence of earthquakes in the region. It has been shown in this study, that especially big earthquakes trigger rock avalanches. Smaller earthquakes do not appear to have enough energy to trigger rock avalanches. Furthermore, the climate conditions were analyzed of being responsible for the spatial pattern of the rock avalanches. The south-eastern part of the Chugach Mountains is affected by high precipitation and mild temperatures. Concentration of rock avalanches occurs in the same area. To analyze glacier dynamics over more than 20 years, rock avalanche deposits on the glaciers were used to derive simple but robust measures of flow velocities over periods of several years to decades. Such long-term averaged flow velocities are difficult to be achieved by measurement techniques such as satellite based SAR or GPS as they operate over much shorter periods of time. Most of the inferred flow velocities are in the range of 50 to 100 m/a. A few calving or surging glaciers displayed flow velocities of > 300 m/a. In the case of several rock avalanche deposits on the same glacier, differential flow velocities were evaluated, which confirmed the expected patterns of faster velocities in the middle of the glacier and slower velocities at the margins. This study adds important evidence on the spatio-temporal distribution of rock avalanches in glacial environments, their relation to seismic triggers and climate. The successful identification of glacier flow velocities over a larger mountain region and a larger period of time is unique and can provide important insights into glacier dynamics and change in a region that is highly sensitive to climate change, and the contribution to sea level rise from melting glaciers under ongoing debate.

Uhlmann, Manuela; Fischer, Luzia; Huggel, Christian; Kargell, Jeffrey; Korup, Oliver

2010-05-01

83

Comparison of geodetic and glaciological mass-balance techniques, Gulkana Glacier, Alaska, U.S.A  

USGS Publications Warehouse

The net mass balance on Gulkana Glacier, Alaska, U.S.A., has been measured since 1966 by the glaciological method, in which seasonal balances are measured at three index sites and extrapolated over large areas of the glacier. Systematic errors can accumulate linearly with time in this method. Therefore, the geodetic balance, in which errors are less time-dependent, was calculated for comparison with the glaciological method. Digital elevation models of the glacier in 1974, 1993 and 1999 were prepared using aerial photographs, and geodetic balances were computed, giving - 6.0??0.7 m w.e. from 1974 to 1993 and - 11.8??0.7 m w.e. from 1974 to 1999. These balances are compared with the glaciological balances over the same intervals, which were - 5.8??0.9 and -11.2??1.0 m w.e. respectively; both balances show that the thinning rate tripled in the 1990s. These cumulative balances differ by <6%. For this close agreement, the glaciologically measured mass balance of Gulkana Glacier must be largely free of systematic errors and be based on a time-variable area-altitude distribution, and the photography used in the geodetic method must have enough contrast to enable accurate photogrammetry.

Cox, L.H.; March, R.S.

2004-01-01

84

Evaluation of conditions along the grounding line of temperate marine glaciers: An example from Muir Inlet, Glacier Bay, Alaska  

USGS Publications Warehouse

In the marine environment, stability of the glacier terminus and the location of subglacial streams are the dominant controls on the distribution of grounding-line deposits within morainal banks. A morainal bank complex in Muir Inlet, Glacier Bay, SE Alaska, is used to develop a model of terminus stability and location of subglacial streams along the grounding line of temperate marine glaciers. This model can be used to interpret former grounding-line conditions in other glacimarine settings from the facies architecture within morainal bank deposits. The Muir Inlet morainal bank complex was deposited between 1860 A.D. and 1899 A.D., and historical observations provide a record of terminus positions, glacial retreat rates and sedimentary sources. These data are used to reconstruct the depositional environment and to develop a correlation between sedimentary facies and conditions along the grounding line. Four seismic facies identified on the high-resolution seismic-reflection profiles are used to interpret sedimentary facies within the morainal bank complex. Terminus stability is interpreted from the distribution of sedimentary facies within three distinct submarine geomorphic features, a grounding-line fan; stratified ridges, and a field of push ridges. The grounding-line fan was deposited along a stable terminus and is represented on seismic-reflection profiles by two distinct seismic facies, a proximal and a distal fan facies. The proximal fan facies was deposited at the efflux of subglacial streams and indicates the location of former glacifluvial discharges into the sea. Stratified ridges formed as a result of the influence of a quasi-stable terminus on the distribution of sedimentary facies along the grounding line. A field of push ridges formed along the grounding line of an unstable terminus that completely reworked the grounding-line deposits through glacitectonic deformation. Between 1860 A.D. and 1899 A.D. (39 years), 8.96 x 108 m3 of sediment were deposited within the Muir Inlet morainal bank complex at an average annual sediment accumulation rate of 2.3 x 107 m3/a. This rate represents the annual sediment production capacity of the glacier when the Muir Inlet drainage basin is filled with glacial ice.

Seramur, K.C.; Powell, R.D.; Carlson, P.R.

1997-01-01

85

Late Holocene environmental change at three glacier-fed lakes, southern Alaska  

NASA Astrophysics Data System (ADS)

Lake-sediment cores and glacial geomorphology were used to infer late Holocene paleoenvironmental changes at three glacier-fed lakes across southern Alaska. The lakes form a 730-km-long transect around 60N lat, and they span the transition zone between two centers of opposite surface air-temperature responses attributed to fluctuations in the strength of the Aleutian Low, the primary indicator of winter climate in the North Pacific. Sediment cores from Hallet Lake in the NE Chugach Range display varying concentrations of biogenic silica (BSi), a measure of overall lake production. A transfer function was developed to infer summer temperature from downcore BSi content. The reconstruction shows clear evidence of first millennium AD cooling, warmth from 1300-1500 AD, Little Ice Age (LIA) cooling between 1750 and 1900 AD, and recent warming beginning ca. 1900 AD. During the last 30 yr, summer temperatures were nearly 2C warmer than the reconstructed mean of the past 2 millennia. Goat Lake is near treeline in the Kenai Mountains, and about 1 km from an outlet glacier of the Harding Icefield. Pollen assemblages show increasing abundances of mountain hemlock from 700-1200 AD, which we interpret as an expansion of treeline. The expansion was terminated around 1230 AD when 10 cm of tephra was deposited in the lake. Treeline above the modern and prior to the LIA is further indicated by a 14C age of 1470 ± 85 AD on logs exposed below till at the present glacier terminus. By 1660 AD the outlet glacier thickened by 150 m where it overtopped its drainage divide and spilled meltwater into Goat Lake, which continued until around 1890 AD. Since then, hemlock pollen has increased to levels comparable to the 1200 AD peak, and the outlet glacier has retreated 1.4 km to the location of the 1470 AD logs. At Cascade Lake, sediment traps installed for 2 yr collected 77% less BSi when spring and summer temperatures were lower, suggesting that BSi flux in the lake is related to growing-season conditions. BSi was at its minimum early during the first millennium AD. It peaked around 700 AD, then decreased during the next 400 yr. BSi flux was relatively constant until the 19th century when it decreased to near-minima values, then attained its highest values of the last 2000 yr late during the 20th century. BSi and hemlock pollen are probably related more strongly to summer conditions than to winter, whereas glaciers respond to a combination of winter and summer climate variability. Late Holocene moraines in the forefields of cirque glaciers around all study lakes were mapped and dated roughly with lichenometry. The moraines delimit maximum glacier positions attained late in the 19th century, when glacier snouts generally descended less than 100 m in elevation relative to their 1950-1970 positions. This limited LIA expansion, together with tree-ring and other independent evidence for decades-long LIA summer cooling of at least 0.8çC in south-central Alaska, indicates a reduction in accumulation-season precipitation during the LIA. A simultaneous reduction in winter precipitation across southern Alaska is difficult to ascribe to a shift in the Aleutian Low pressure system because instrumental data show dipolar responses across this region. This implies a longer- term, more general climate forcing that supersedes inter-decadal variability in the Aleutian Low.

Kaufman, D. S.; Anderson, R. S.; Daigle, T. A.; Kathan, K. M.; McKay, N. P.; Michelutti, N. N.; Werner, A.

2007-12-01

86

Iceberg calving during transition from grounded to floating ice: Columbia Glacier, Alaska  

USGS Publications Warehouse

The terminus of Columbia Glacier, Alaska, unexpectedly became ungrounded in 2007 during its prolonged retreat. Visual observations showed that calving changed from a steady release of low-volume bergs, to episodic flow-perpendicular rifting, propagation, and release of very large icebergs - a style reminiscent of calving from ice shelves. Here, we compare passive seismic and photographic observations through this transition to examine changes in calving. Mechanical changes accompany the visible changes in calving style post flotation: generation of seismic energy during calving is substantially reduced. We propose this is partly due to changes in source processes.

Walter, Fabian; O'Neel, Shad; McNamara, Daniel; Pfeffer, W.T.; Bassis, Jeremy N.; Fricker, Helen Amanda

2010-01-01

87

Modern pollen rain and vegetational history of the Malaspina Glacier district, Alaska  

NASA Astrophysics Data System (ADS)

Seventy surface pollen samples from coastal forest, coastal meadow, muskeg, tree line, and alpine tundra communities form a basis for interpreting fossil pollen assemblages in the Malaspina Glacier district, Alaska. Poflen and macrofossil analyses of three radiocarbon-dated fossil sections from Icy Cape indicate that vegetational changes resulting from plant succession can be distinguished from those of migrational and climatic origin. Vegetation of the early Holocene xerothermic interval (10,000-7600 yr B.P.) was dominated by Alnus communities. Wetter conditions ensued, enabling generative muskeg surfaces to develop and first Picea sitchensis, then Tsuga heterophylla to expand from areas southeastward. Climatic cooling in more recent millennia (3500 yr B.P. to the present) is indicated by the appearance and persistent growth of Tsuga mertensiana and Selaginella selaginoides along this portion of the Gulf of Alaska coastline.

Peteet, Dorothy M.

1986-01-01

88

Late Holocene glacial history of the Copper River Delta, coastal south-central Alaska, and controls on valley glacier fluctuations  

NASA Astrophysics Data System (ADS)

Fluctuations of four valley glaciers in coastal south-central Alaska are reconstructed for the past two millennia. Tree-ring crossdates on 216 glacially killed stumps and logs provide the primary age control, and are integrated with glacial stratigraphy, ages of living trees on extant landforms, and historic forefield photographs to constrain former ice margin positions. Sheridan Glacier shows four distinct phases of advance: in the 530s to c.640s in the First Millennium A.D., and the 1240s to 1280s, 1510s to 1700s, and c.1810s to 1860s during the Little Ice Age (LIA). The latter two LIA advances are also recorded on the forefields of nearby Scott, Sherman and Saddlebag glaciers. Comparison of the Sheridan record with other two-millennia long tree-ring constrained valley glacier histories from south-central Alaska and Switzerland shows the same four intervals of advance. These expansions were coeval with decreases in insolation, supporting solar irradiance as the primary pacemaker for centennial-scale fluctuations of mid-latitude valley glaciers prior to the 20th century. Volcanic aerosols, coupled atmospheric-oceanic systems, and local glacier-specific effects may be important to glacier fluctuations as supplemental forcing factors, for causing decadal-scale differences between regions, and as a climatic filter affecting the magnitude of advances.

Barclay, David J.; Yager, Elowyn M.; Graves, Jason; Kloczko, Michael; Calkin, Parker E.

2013-12-01

89

Mass balances and dynamic changes of the Bering, Malaspina, and Icy Bay glacier systems of Alaska, United States, and Yukon, Canada  

Microsoft Academic Search

The Bering and the Malaspina Glacier systems of south-central Alaska, U.S.A., and southwest Yukon Territory, Canada, in the Saint Elias Mountains constitute the two largest temperate surge-type piedmont glaciers on Earth. This is largest region of glaciers and icefields in continental North America. Determining and understanding the causes of wastage of these two glaciers is important to understanding the linkages

Reginald R. Muskett

2007-01-01

90

Hazard assessment of the Tidal Inlet landslide and potential subsequent tsunami, Glacier Bay National Park, Alaska  

USGS Publications Warehouse

An unstable rock slump, estimated at 5 to 10????????10 6 m3, lies perched above the northern shore of Tidal Inlet in Glacier Bay National Park, Alaska. This landslide mass has the potential to rapidly move into Tidal Inlet and generate large, long-period-impulse tsunami waves. Field and photographic examination revealed that the landslide moved between 1892 and 1919 after the retreat of the Little Ice Age glaciers from Tidal Inlet in 1890. Global positioning system measurements over a 2-year period show that the perched mass is presently moving at 3-4 cm annually indicating the landslide remains unstable. Numerical simulations of landslide-generated waves suggest that in the western arm of Glacier Bay, wave amplitudes would be greatest near the mouth of Tidal Inlet and slightly decrease with water depth according to Green's law. As a function of time, wave amplitude would be greatest within approximately 40 min of the landslide entering water, with significant wave activity continuing for potentially several hours. ?? 2007 Springer-Verlag.

Wieczorek, G.F.; Geist, E.L.; Motyka, R.J.; Jakob, M.

2007-01-01

91

Masked Correlation for Improvement of 2D Glacier Motion Estimation Based on Terrasar-x Imagery  

NASA Astrophysics Data System (ADS)

In this paper, the impacts of the non-glacier information in the template window used in cross-correlation calculation for 2D motion estimation of glaciers are discussed and illustrated by the example of the Taku glacier, which is the biggest glacier in the Juneau Icefield, Alaska. For this, the glacier motion maps are extracted by the traditional normalized cross-correlation technique and the masked cross-correlation method, which uses a manually generated binary mask to threshold the non-glacier pixels, based on geocoded high resolution TerraSAR-X images. Based on the comparison of the different results, it was found that without the disturbing information (e.g., mountain, water) the accuracy of the cross-correlation of sequential patches in masked cross-correlation method is improved and the estimation results are much more reasonable, which respect the law that glacier flows like a river with higher velocity in the middle and than that in the sides.

Fang, L.; Stilla, U.

2014-09-01

92

Glaciers  

NSDL National Science Digital Library

This is a great site to help you learn about glaciers! On this webpage, you will learn what glaciers are, how they are formed, the different types of glaciers, their anatomy, how they move, and about glacial erosion. This site also has a model that helps you to understand glacial growth and retreat.

2010-01-01

93

Rapid Submarine Melting Driven by Subglacial Discharge, LeConte Glacier, Alaska  

NASA Astrophysics Data System (ADS)

Submarine melting impacts the stability of tidewater glaciers worldwide, but the connections between the ocean, a warming climate, and retreat of outlet glaciers are poorly known. Clearly warm seawater plays an important role, but the tremendous heat potential resident in oceans and fjords must first be brought into contact with outlet glacier termini in order to affect them. We show here that for many glaciers, the principal process driving high rates of submarine melting is subglacial discharge of freshwater. This buoyant discharge draws in warm seawater, entraining it in a turbulent upwelling convective flow along the submarine face that melts glacier ice. To capture the effect of changing subglacial discharge on submarine melting, we conducted four days of hydrographic transects during late summer 2012 at LeConte Glacier, Alaska. A major rainstorm allowed us to directly measure the influence of large changes in subglacial discharge. We found strong submarine melt rates that increased from 9.0×1.0 to 16.8×1.3 m/d (ice face equivalent frontal ablation) as subglacial discharge increased from 130 to 440 m^3/s over a four day period. This subglacial discharge drove influx of warm seawater (thermal forcing ~ 8° C) to the terminus with fluxes increasing from 1800 to 4000 m3/s. Our ice equivalent frontal ablation rates due to submarine melting are two to three times values found for Greenland glaciers, where thermal forcing is substantially lower (~ 1 - 4 °C) and termini are wider. Together, these studies confirm the importance of submarine melting at grounded glaciers. At LeConte, the total frontal ablation rate (calving flux plus submarine melting) is ~ 3.0 x10^6 m^3/d w.e., which far surpasses surface ablation. One-half to two-thirds of the frontal ablation during September 2012 can be attributed to submarine melting. A two-layer model driven by a buoyant plume of subglacial discharge has been previously invoked to describe the proglacial fjord circulation pattern. Although this circulation pattern is generally supported by our results, we also see evidence of eddying both at the terminus and down fjord, which adds complexity to the simple two layer model. Our results demonstrate that turbulent subglacial discharge is a key driver of ice-proximal fjord circulation that entrains warm seawater and melts submarine glacial ice. With projected continued global warming and increased glacial runoff, our results highlight the direct impact that increases in subglacial discharge will have on the stability of polar and subpolar tidewater outlet systems. These effects and feedbacks must be considered when modeling glacier response to future warming and increased runoff. Our results have direct implications for predicting future behavior at the ice sheet ocean interface, which constitutes the major uncertainty for future predictions of ice loss and sea-level rise.

Motyka, R. J.; Dryer, W. P.; Amundson, J. M.; Truffer, M.; Fahnestock, M. A.

2013-12-01

94

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

95

Columbia Glacier, Alaska recent ice loss and its relationship to seasonal terminal embayments, thinning and glacial flow  

USGS Publications Warehouse

In 1974 the U.S. Geological Survey began an intensive investigation of the stability of Columbia Glacier, a calving tidewater galcier terminating in Columbia Bay, near Valdez, Alaska. Aerial photographs taken in 1957 and a sequence of photographs taken at about 2-month intervals since 1976, when analyzed photogrammetrically, provided detailed data on changes in Columbia Glacier 's thickness, flow rate, and terminal position. Annual embayments in the glacier 's terminus form during the summer-autumn season in most years; the size of embayments appears to be related to (1) the thickness of the glacier, and (2) the position and nature of subglacial freshwater discharge. Embayments have apparently increased in size in recent years; the largest embayments yet observed formed in 1975, 1976, 1977, and 1978. From April 1, 1977, to April 1, 1978, the total volume of ice calved was about 1.0 cubic kilometer. By January 1979 the glacier front had retreated from Heather Island. Glacier flow varies seasonally and synchronously in the lower 17 kilometers of the glacier; large accelerations occur near the terminus in response to embayment formation. Daily speed within 5 kilometers of the terminus increased from about 1.9 meters per day between 1963 and 1968 to about 2.7 meters per day between 1977 and 1978. In the lowest 15 kilometers, the glacier surface was lowered about 9 meters between 1957 and 1974, and about 13 meters between 1974 and 1978. Columbia Glacier is being reduced in mass due, in part, to recent losses caused by large embayments forming annually. If such reduction continues it will result in a drastic retreat. (USGS)

Sikonia, W.G.; Post, Austin

1980-01-01

96

Constraining GRACE Solutions for Gulf of Alaska Glaciers using Field and Airborne Observations (Invited)  

NASA Astrophysics Data System (ADS)

We investigate methods for improving the spatial resolution of GRACE mass balance estimates for Gulf of Alaska glaciers through the incorporation of field and aircraft altimetry data. Our field data are derived from a new inventory of point mass balances spanning the entire Alaska region, and our aircraft data are from NASA's Operation IceBridge campaigns. We use the aircraft data to constrain spatial patterns in mass change, and the higher temporal resolution field data to constrain the seasonal signal. Further spatial and temporal gaps are filled using a simple degree-day mass balance model. The spatially-distributed mass balances are then included in our Level-1 GRACE processing, producing maps of what GRACE would observe under the simulated mass change signal. Comparing this to the actual GRACE observations yields residuals that we use to further improve our simulations in an iterative fashion. We discuss progress towards these new iterated solutions and how they can be used to identify further sources of uncertainty associated with terrestrial water storage and glacial isostatic adjustments.

Arendt, A. A.; Luthcke, S. B.; Larsen, C. F.; Oneel, S.; Burgess, E. W.; Rich, J.

2013-12-01

97

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

98

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

99

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.

100

Ice surface morphology and flow on Malaspina Glacier, Alaska: Implications for regional tectonics in the Saint Elias orogen  

NASA Astrophysics Data System (ADS)

Saint Elias Mountains in southern Alaska are located at a structural syntaxis where the coastal thrust and fold belt of the Fairweather plate boundary intersects thrust faults and folds generated by collision of the Yakutat Terrane. The axial trace of this syntaxis extends southeastward out of the Saint Elias Mountains and beneath Malaspina Glacier where it is hidden from view and cannot be mapped using conventional methods. Here we examine the surface morphology and flow patterns of Malaspina Glacier to infer characteristics of the bedrock topography and organization of the syntaxis. Faults and folds beneath the eastern part of the glacier trend northwest and reflect dextral transpression near the terminus of the Fairweather fault system. Those beneath the western part of the glacier trend northeast and accommodate folding and thrust faulting during collision and accretion of the Yakutat Terrane. Mapping the location and geometry of the structural syntaxis provides important constraints on spatial variations in seismicity, fault kinematics, and crustal shortening beneath Malaspina Glacier, as well as the position of the collisional deformation front within the Yakutat Terrane. We also speculate that the geometrical complexity of intersecting faults within the syntaxis formed a barrier to rupture propagation during two regional Mw 8.1 earthquakes in September 1899.

Cotton, Michelle M.; Bruhn, Ronald L.; Sauber, Jeanne; Burgess, Evan; Forster, Richard R.

2014-04-01

101

Muir Glacier in Glacier Bay National Monument 1941  

USGS Multimedia Gallery

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

102

Glaciers  

NSDL National Science Digital Library

In this online activity, learners adjust mountain snowfall and temperature to see how glaciers grow and shrink. They will use scientific tools to measure thickness, velocity and glacial budget. This activity includes an online simulation, sample learning goals, teaching ideas, and translations in over 20 languages.

2012-11-14

103

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

USGS Publications Warehouse

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 R.; Larsen, Christopher F.; Rupert, Natalia; Hansen, Roger

2010-01-01

104

Variations in Sr and Nd isotopic ratios of cryoconite on glaciers in Asia, Alaska, and Greenland  

NASA Astrophysics Data System (ADS)

Recent shrinkages of glacial mass are not only due to global warming, but also possibly to accumulation of cryoconite on the glacial surface. Cryoconite is a biogenic surface dust consisting of organic matter mainly derived from living microbes on the glaciers, and mineral particles originated from basal till and/or wind-blown dust. Since cryoconite is dark color, it can reduce surface albedo of glaciers and accelerate their melting. Thus, it is important to understand their sources and formation process on the glaciers. The characteristics of cryoconite vary among geographical locations. For example, there are small amounts of cryoconite on Arctic glaciers and their glacial surface is clean. In contrast, large amounts of cryoconite accumulate on Asian glaciers and their glacial surface appears very dirty. These differences in cryoconite are likely to affect on surface albedo and melting of each glacier. However, the formation process of cryoconite, especially origins of minerals and production process of organic matters are still not well understood. Stable isotopic ratios of strontium (Sr) and neodymium (Nd) provide a means of identifying sources of substances and have been commonly used in loess or sediment studies. Furthermore, Sr isotope has been used as a tracer of Ca ion in studies of geochemical process, because its chemical characteristics are similar to Ca. Thus, Sr in organic matter including such organisms on the glacier may reveal their nutrient sources and ecology of them. In this study, we analyzed Sr and Nd isotopic ratios of four mineral and organic fractions in cryoconite on Asian and Polar glaciers. Based on the isotopic ratios, we identified origins of minerals in cryoconite and mineral sources used as nutrients by microbes on the glaciers. Sr and Nd isotopic ratios in the mineral fractions, especially silicate minerals, which are major components of mineral particles, vary significantly among the glaciers. Cryoconite on Asian glaciers showed higher Sr and lower Nd ratios in the north and also showed little variation within a glacier. On the other hand, those on Alaskan glacier showed lower Sr and large spatial variation in Nd on a glacier. Cryoconite on Greenlandic glaciers showed further high Sr and low Nd than the other glaciers. This suggests that origins of silicate minerals in cryoconite are substantially different among the glaciers. Compared with the isotopic ratios of silicate minerals in moraine, desert, and loess reported over the regions, those in cryoconite on Asian, Alaskan, and Greenlandic glaciers were close to those in respective regions. This result indicates that silicate minerals in cryoconite were derived from surrounding the glaciers. The Sr isotopic ratios of organic matter in cryoconite also varied among the glaciers. They may reflect the minerals used by glacial microbes as nutrients.

Nagatsuka, N.; Takeuchi, N.; Nakano, T.

2012-12-01

105

A continental shelf sedimentary record of Little Ice Age to modern glacial dynamics: Bering Glacier, Alaska  

NASA Astrophysics Data System (ADS)

The Bering Glacier System is the world's largest surging temperate glacier with seven events occurring over the past century under a range of north Pacific climatic conditions. Onshore records reveal changes in glacial termini positions and evidence of late Holocene glacial advances, but the Little Ice Age (LIA) record of potential glacial surging and associated flooding has not been examined. A 13.6 m-long jumbo core collected on the adjacent continental shelf reveals a 600-yr-long record of sedimentation associated with changing glacifluvial discharge. The chronology is based on 210Pb geochronology and five radiocarbon dates, and the core can be separated into three distinct lithologic units based on the examination of X-radiographs and physical properties: (1) an uppermost unit dating from ?125 cal yr BP to the present characterized by bioturbated mud interbedded with laminated, thick (5-20 cm) low-bulk density clay-rich beds; (2) a middle unit dating from ?120-400 cal yr BP that includes numerous interlaminated-to-interbedded low- and high-bulk density beds with infrequent evidence of bioturbation; thick laminated clay-rich beds are rare; (3) a lowermost unit that predates ?400 cal yr BP and is composed of rare laminated beds grading down into mottled to massive mud. In each of these units, the laminated lithofacies from this mid-shelf location indicates both flood deposition and likely sediment transport in the wave-current bottom-boundary layer. The thick low-density, clay-rich beds in the uppermost unit correlate with historic outburst floods associated with known surge events. Based on previous terrestrial studies, the terminus was at its Holocene Neoglacial maximum extent close to the modern coastline at some point in the middle to late stages of the LIA in southern Alaska (100-350 cal yr BP). During the LIA, preservation of bioturbated intervals is rare while laminated intervals are common. This style of interbedding indicates frequent (<10 yr recurrence interval) event-scale mud deposition, suggesting that frequent summer flooding and redistribution by winter storms were more prevalent during the LIA rather than the outburst flooding typical of the past century. Rare event-scale bedding indicative of outburst flooding and possible surge events is found within the middle unit, and may correspond to periods with similar climatic trends as in the 20th century. The infrequent deposition of event layers in the lowermost unit could be attributed to the less frequent flooding and/or enhanced diversion of glacial drainage to the eastern terminus instead of present day Seal River. The thickness and depositional frequency of event-scale bedding can be related to Gulf of Alaska tree-ring proxy temperature reconstructions, where more numerous event bed formation occurs when there are more frequent, higher-amplitude temperature excursions. These frequent fluctuations may have prevented the decadal-long periods of positive mass balance required to enable numerous surge events during this period.

Jaeger, John M.; Kramer, Branden

2014-09-01

106

Hydrometeorology and basal sliding on the Kennicott Glacier, Alaska, USA: Evidence for seasonal, diurnal, and event-scale glacier velocity fluctuations due to varying meltwater inputs and precipitation events  

NASA Astrophysics Data System (ADS)

We examine GPS-derived glacier ice surface velocities along with on- and near-glacier hydrometeorologic data to investigate the linkage between subglacial hydrology and basal sliding on the Kennicott Glacier in southeastern Alaska. Connections between ice dynamics and glacier hydrology remain poorly understood, yet are critical for understanding and forecasting modern sea level rise. In addition, basal sliding is an important process in glacial erosion and, therefore, alpine landscape evolution. We differentially process 30-second GPS data at four monuments along the glacier centerline over the 2012 and 2013 melt seasons. In addition, we overwinter one GPS monument on the glacier, allowing us to observe glacier behavior through a full annual cycle. We monitor stage on ice-marginal lakes, supraglacial streams, and the outlet river with pressure transducers and timelapse cameras. In both years we observe complex early season hydrologic behavior, with a ice-marginal lake draining and filling many times before emptying for the season. This likely records the interplay between varying melt inputs and the evolution of the glacier's ability to transmit flow subglacially. Concurrent with these stage variations, we observe large diurnal velocity fluctuations superimposed on a sustained increase in glacier velocity, likely reflecting the glacier's sensitivity to melt inputs in the early season. In 2012, we observe glacier velocity during the annual outburst flood of Hidden Creek Lake, which drains ~25×106 m3 of water beneath the Kennicott Glacier. The flood hydrograph from an ice-marginal lake shows remarkable consistency from year to year despite differences in the timing of the flood and meteorology leading up to the jökulhlaup. As the flood wave passes through the glacier, ice surface velocity increases from ~0.3 m d-1 to ~1.5 m d-1 for a short time. We see speedups of a similar magnitude in autumn 2012 that appear to correlate precipitation events. In addition, we analyze ten years of high-resolution (~0.5 m pixel) satellite imagery to identify and characterize the evolution of moulins, which serve as point inputs to the glacier hydrologic system. We validate a number of satellite-identified moulins with field observations and characterize the diurnal cycle of meltwater inputs into one moulin via salt dilution discharge estimates. We extract glacier surface velocity fields from these satellite images, which provide a context for our GPS-derived point velocities. We investigate this suite of data in light of radar estimates of ice thickness and bed topography to better understand the importance and effect of glacier hydrology on basal sliding of the Kennicott Glacier.

Armstrong, W. H.; Anderson, R. S.; Pettit, E. C.; Rajaram, H.

2013-12-01

107

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 ...

108

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

109

Gulkana Glacier, Alaska-Mass balance, meteorology, and water measurements, 1997-2001  

USGS Publications Warehouse

The measured winter snow, maximum winter snow, net, and annual balances for 1997-2001 in the Gulkana Glacier basin are determined at specific points and over the entire glacier area using the meteorological, hydrological, and glaciological data. We provide descriptions of glacier geometry to aid in estimation of conventional and reference surface mass balances and descriptions of ice motion to aid in the understanding of the glacier's response to its changing geometry. These data provide annual estimates for area altitude distribution, equilibrium line altitude, and accumulation area ratio during the study interval. New determinations of historical area altitude distributions are given for 1900 and annually from 1966 to 2001. As original weather instrumentation is nearing the end of its deployment lifespan, we provide new estimates of overlap comparisons and precipitation catch efficiency. During 1997-2001, Gulkana Glacier showed a continued and accelerated negative mass balance trend, especially below the equilibrium line altitude where thinning was pronounced. Ice motion also slowed, which combined with the negative mass balance, resulted in glacier retreat under a warming climate. Average annual runoff augmentation by glacier shrinkage for 1997-2001 was 25 percent compared to the previous average of 13 percent, in accordance with the measured glacier volume reductions.

March, Rod S.; O'Neel, Shad

2011-01-01

110

Quantifying Ice Marginal and Submarine Environments During Seasonal Advance and Retreat, Hubbard Glacier, Southeast Alaska USA  

Microsoft Academic Search

Hubbard Glacier has been advancing into Disenchantment Bay for ~300 years and with its high accumulation area ratio (0.95) will likely continue to advance for the foreseeable future, barring an extreme change in climate increasing its ELA significantly. The continuing advance of Hubbard Glacier may create a permanent dam at Gilbert Point, a high bedrock ridge between Disenchantment Bay and

D. E. Lawson; D. C. Finnegan; T. Waller; W. Butler; P. Gadomski

2009-01-01

111

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

112

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

113

An integrated geospatial approach to monitoring the Bering Glacier system, Alaska  

USGS Publications Warehouse

The Bering Glacier is the largest and longest glacier in continental North America, with an area of approximately 5,175 km2, and a length of 190 km. It is also the largest surging glacier in America, having surged at least five times during the twentieth century. The last surge of the Bering Glacier occurred in 1993-1995, since then, the glacier has undergone constant and significant retreat thereby expanding the boundaries of Vitus Lake and creating a highly dynamic system, both ecologically and hydrologically. This study utilized GIS to integrate remote sensing observations, with detailed bathymetric, hydrographic and in situ water quality measurements of the rapidly expanding Vitus Lake. Vitus Lake has nearly doubled in surface area from 58.4 km2 to 108.8 km2, with a corresponding increase in water volume from 6.1 km3 to 10.5 km3 over the same period. The remote sensing observations were used to direct a systematic bathymetric, hydrographic and water quality measurement survey in Vitus Lake which revealed a complex three dimensional structure that is the result of sea water inflow, convection generated by ice melting and the injection of fresh water from beneath the glacier.

Josberger, E.G.; Payne, J.; Savage, S.; Shuchman, R.; Meadows, G.

2004-01-01

114

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

115

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

116

Streamflow changes in Alaska between the cool phase (1947-1976) and the warm phase (1977-2006) of the Pacific Decadal Oscillation: The influence of glaciers  

USGS Publications Warehouse

Streamflow data from 35 stations in and near Alaska were analyzed for changes between the cool phase (1947-1976) and the warm phase (1977-2006) of the Pacific Decadal Oscillation. Winter, spring, and summer flow changes and maximum annual flow changes were different for glaciated basins (more than 10% glacier-covered area) than for nonglaciated basins, showing the influence of glaciers on historical streamflowchanges. Mean February flows, for example, increased for the median of available stations by 45% for glaciated basins and by 17% for nonglaciated ones.

Hodgkins, Glenn A.

2009-01-01

117

Neoglacial fluctuations of terrestrial, tidewater, and calving lacustrine glaciers, Blackstone-Spencer Ice Complex, Kenai Mountains, Alaska.  

E-print Network

??The glaciers surrounding the Blackstone-Spencer Ice Complex display a variety of termini types: Tebenkov, Spencer, Bartlett, Skookum, Trail, Burns, Shakespeare, Marquette, Lawrence, and Ripon glaciers… (more)

Crossen, Kristine June

1997-01-01

118

Use of the Coastal and Marine Ecological Classification Standard (CMECS) for Geological Studies in Glacier Bay, Alaska  

NASA Astrophysics Data System (ADS)

The U S Geological Survey (USGS) is one of four primary organizations (along with the National Oceanographic and Atmospheric Administration, the Evironmental Protection Agency, and NatureServe) responsible for the development of the Coastal and Marine Ecological Classification Standard (CMECS) over the past decade. In June 2012 the Federal Geographic Data Committee approved CMECS as the first-ever comprehensive federal standard for classifying and describing coastal and marine ecosystems. The USGS has pioneered the application of CMECS in Glacier Bay, Alaska as part of its Seafloor Mapping and Benthic Habitat Studies Project. This presentation briefly describes the standard and its application as part of geological survey studies in the Western Arm of Glacier Bay. CMECS offers a simple, standard framework and common terminology for describing natural and human influenced ecosystems from the upper tidal reaches of estuaries to the deepest portions of the ocean. The framework is organized into two settings, biogeographic and aquatic, and four components, water column, geoform, substrate, and biotic. Each describes a separate aspect of the environment and biota. Settings and components can be used in combination or independently to describe ecosystem features. The hierarchical arrangement of units of the settings and components allows users to apply CMECS to the scale and specificity that best suits their needs. Modifiers allow users to customize the classification to meet specific needs. Biotopes can be described when there is a need for more detailed information on the biota and their environment. USGS efforts focused primarily on the substrate and geoform components. Previous research has demonstrated three classes of bottom type that can be derived from multibeam data that in part determine the distribution of benthic organisms: soft, flat bottom, mixed bottom including coarse sediment and low-relief rock with low to moderate rugosity, and rugose, hard bottom. The West Arm of Glacier Bay has all of these habitats, with the greatest abundance being soft, flat bottom. In Glacier Bay, species associated with soft, flat bottom habitats include gastropods, algae, flatfish, Tanner crabs, shrimp, sea pen, and other crustaceans; soft corals and sponge dominate areas of boulder and rock substrate. Video observations in the West Arm suggest that geological-biological associations found in central Glacier Bay to be at least partially analogous to associations in the West Arm. Given that soft, mud substrate is the most prevalent habitat in the West Arm, it is expected that the species associated with a soft bottom in the bay proper are the most abundant types of species within the West Arm. While mud is the dominant substrate throughout the fjord, the upper and lower West Arm are potentially very different environments due to the spatially and temporally heterogeneous influence of glaciation and associated effects on fjord hydrologic and oceanographic conditions. Therefore, we expect variations in the distribution of species and the development of biotopes for Glacier Bay will require data applicable to the full spectrum of CMECS components.

Cochrane, G. R.; Hodson, T. O.; Allee, R.; Cicchetti, G.; Finkbeiner, M.; Goodin, K.; Handley, L.; Madden, C.; Mayer, G.; Shumchenia, E.

2012-12-01

119

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

120

Spatial pattern analysis of cruise ship-humpback whale interactions in and near Glacier Bay National Park, Alaska.  

PubMed

Understanding interactions between large ships and large whales is important to estimate risks posed to whales by ships. The coastal waters of Alaska are a summer feeding area for humpback whales (Megaptera novaeangliae) as well as a prominent destination for large cruise ships. Lethal collisions between cruise ships and humpback whales have occurred throughout Alaska, including in Glacier Bay National Park (GBNP). Although the National Park Service (NPS) establishes quotas and operating requirements for cruise ships within GBNP in part to minimize ship-whale collisions, no study has quantified ship-whale interactions in the park or in state waters where ship traffic is unregulated. In 2008 and 2009, an observer was placed on ships during 49 different cruises that included entry into GBNP to record distance and bearing of whales that surfaced within 1 km of the ship's bow. A relative coordinate system was developed in ArcGIS to model the frequency of whale surface events using kernel density. A total of 514 whale surface events were recorded. Although ship-whale interactions were common within GBNP, whales frequently surfaced in front of the bow in waters immediately adjacent to the park (west Icy Strait) where cruise ship traffic is not regulated by the NPS. When ships transited at speeds >13 knots, whales frequently surfaced closer to the ship's midline and ship's bow in contrast to speeds slower than 13 knots. Our findings confirm that ship speed is an effective mitigation measure for protecting whales and should be applied to other areas where ship-whale interactions are common. PMID:21983996

Harris, Karin; Gende, Scott M; Logsdon, Miles G; Klinger, Terrie

2012-01-01

121

Spatial Pattern Analysis of Cruise Ship-Humpback Whale Interactions in and Near Glacier Bay National Park, Alaska  

NASA Astrophysics Data System (ADS)

Understanding interactions between large ships and large whales is important to estimate risks posed to whales by ships. The coastal waters of Alaska are a summer feeding area for humpback whales ( Megaptera novaeangliae) as well as a prominent destination for large cruise ships. Lethal collisions between cruise ships and humpback whales have occurred throughout Alaska, including in Glacier Bay National Park (GBNP). Although the National Park Service (NPS) establishes quotas and operating requirements for cruise ships within GBNP in part to minimize ship-whale collisions, no study has quantified ship-whale interactions in the park or in state waters where ship traffic is unregulated. In 2008 and 2009, an observer was placed on ships during 49 different cruises that included entry into GBNP to record distance and bearing of whales that surfaced within 1 km of the ship's bow. A relative coordinate system was developed in ArcGIS to model the frequency of whale surface events using kernel density. A total of 514 whale surface events were recorded. Although ship-whale interactions were common within GBNP, whales frequently surfaced in front of the bow in waters immediately adjacent to the park (west Icy Strait) where cruise ship traffic is not regulated by the NPS. When ships transited at speeds >13 knots, whales frequently surfaced closer to the ship's midline and ship's bow in contrast to speeds slower than 13 knots. Our findings confirm that ship speed is an effective mitigation measure for protecting whales and should be applied to other areas where ship-whale interactions are common.

Harris, Karin; Gende, Scott M.; Logsdon, Miles G.; Klinger, Terrie

2012-01-01

122

Quantifying Ice Marginal and Submarine Environments During Seasonal Advance and Retreat, Hubbard Glacier, Southeast Alaska USA  

NASA Astrophysics Data System (ADS)

Hubbard Glacier has been advancing into Disenchantment Bay for ~300 years and with its high accumulation area ratio (0.95) will likely continue to advance for the foreseeable future, barring an extreme change in climate increasing its ELA significantly. The continuing advance of Hubbard Glacier may create a permanent dam at Gilbert Point, a high bedrock ridge between Disenchantment Bay and Russell Fiord. To analyze the mechanics of ice dam formation and stability, we began investigating the channel environment in 2008 with multibeam swath bathymetry, side scan sonar, terrestrial scanning LiDAR and ADCP. These studies were done in combination with our ongoing (since 2005) motion surveys of the ice face, monitoring of climate and repeat time-lapse and satellite imaging of the terminus. Our dam site study took place in October when the Hubbard margin was near its seasonal minimum position and the channel was about 360 m wide in its narrowest section. The three-dimensional topography of the channel bed between the calving ice face and shoreline shows that it is mostly of low relief and shallow (< 40 m bsl) and that the active moraine at the base of the ice face lies at a relatively shallow depth (~ 5 to 25 m bsl) with 15 to 20 m local relief. Various subglacial and submarine features associated with both ice advance and retreat were also revealed. Streamlined and flow-related bedforms (flutes, scours, boulder-trains) suggest that the glacier largely slides across the channel bed, with limited deformation of underlying materials. In 2008, the ice face advanced at an average of ~ 3 m/d from March to May, slowing to about 1.5 m/d through the end of June when recession began; a submarine moraine marks this seasonal maximum position of 2008. Seasonal retreat of the ice margin at rates similar to those during the advance produced small morainal ridges at temporarily stable positions evident in our data. Previous year’s moraines were not preserved beyond the maximum ice position, probably being removed by strong tidal currents leaving only the coarsest boulders as a lag on the channel floor. Current velocity measured during our survey exceeded 5 m/s, with limited bed load evident and suggesting a hard and armored sea bed. The shallow sea bed and streamlined bedforms indicate relatively thin ice is advancing by sliding across the channel, in contrast with the much thicker central part of the terminal lobe which is advancing into a deep (> 250m) basin by morainal bank migration. These observations have important implications for the mechanics of ice dam closure and potential for long term stability.

Lawson, D. E.; Finnegan, D. C.; Waller, T.; Butler, W.; Gadomski, P.

2009-12-01

123

Ice-proximal sediment dynamics and their effect on the stability of Muir Glacier, Alaska: A case study of non-climatic glacier response  

SciTech Connect

Recent studies have shown that water depth at tidewater termini affect calving rates and, therefore, glacier mass balance and terminus stability. Grounding-line water depths are themselves governed by glacial and marine processes that interact during the formation of morainal bank depocenters. These morainal banks can fluctuate 10s of meters in height within an interval of a few weeks. Recent investigations in Glacier Bay have focused on quantitatively assessing sediment budgets in the ice-proximal environment. The monitoring of morainal banks in upper Muir Inlet has included repeated bathymetric mapping, sediment trap studies, bottom grab sampling, glacier and iceberg sampling, and submersible ROV investigations within 1 km of the terminus. Such relationships are important in interpreting recent changes in the dynamics of Muir Glacier where a century of retreat has been succeeded by quasi stability. The new glacier regime has accompanied basin infilling from approximately 100 m depth to a maximum of 52 m at the grounding line. Two large grounding-line fans have aggraded to deltas and reduced the length of the calving margin from 900 m to 290 m wide. These effects have reduced the ice flow velocities by 45%. Annual morainal bank growth ranged from 10[sup 6] to 10[sup 7] m[sup 3] and is the result of glacifluvial dumping, suspension settling from turbid overflow plumes, debris dumping from ice-cliff and iceberg melting, glacier squeezing and pushing of morainal bank sediment, and sediment gravity flow processes. Each of these processes are an integral facet of the morainal bank dynamics and glacier response. These studies of Muir Glacier indicate that glacier response to sediment dynamics need to be addresses before climatic implications are made.

Hunter, L.E.; Powell, R.D. (Northern Illinois Univ., Dekalb, IL (United States). Dept. of Geology)

1992-01-01

124

Diurnal discharge fluctuations and streambed ablation in a supraglacial stream on the Vaughan-Lewis and Gilkey glaciers, Juneau Icefield, Alaska  

SciTech Connect

The study reported here focuses on the dynamics of two supraglacial streams on the Juneau Icefield in southeast Alaska. Data on streambed ablation (melting) rates, stream discharge, radiation, and air temperature and humidity were collected in August 1990 and 1991. Radiation had the greatest effect on stream discharge. Daily peak discharges occurred only 30 minutes after peak radiation, but two hours after peak temperature. Factors influencing variation in discharge of the streams were velocity, stream depth, and stream width, in decreasing order of importance. Streambed ablation due to radiation was greater than glacier surface ablation due to radiation. Streambed ablation due to frictional heating was very small.

Stock, J.W. [Univ. of Canterbury, Christchurch (New Zealand). Dept. of Geology; [Pacific Science Center, Seattle, WA (United States). Foundation for Glacier and Environmental Research; Pinchak, A.C. [Case Western Reserve Univ., Cleveland, OH (United States). Mechanical and Aerospace Engineering; [Pacific Science Center, Seattle, WA (United States). Foundation for Glacier and Environmental Research

1995-12-31

125

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.

126

Disruption of Drift glacier and origin of floods during the 1989-1990 eruptions of Redoubt Volcano, Alaska  

USGS Publications Warehouse

Melting of snow and glacier ice during the 1989-1990 eruption of Redoubt Volcano caused winter flooding of the Drift River. Drift glacier was beheaded when 113 to 121 ?? 106 m3 of perennial snow and ice were mechanically entrained in hot-rock avalanches and pyroclastic flows initiated by the four largest eruptions between 14 December 1989 and 14 March 1990. The disruption of Drift glacier was dominated by mechanical disaggregation and entrainment of snow and glacier ice. Hot-rock avalanches, debris flows, and pyroclastic flows incised deep canyons in the glacier ice thereby maintaining a large ice-surface area available for scour by subsequent flows. Downvalley flow rheologies were transformed by the melting of snow and ice entrained along the upper and middle reaches of the glacier and by seasonal snowpack incorporated from the surface of the lower glacier and from the river valley. The seasonal snowpack in the Drift River valley contributed to lahars and floods a cumulative volume equivalent to about 35 ?? 106 m3 of water, which amounts to nearly 30% of the cumulative flow volume 22 km downstream from the volcano. The absence of high-water marks in depressions and of ice-collapse features in the glacier indicated that no large quantities of meltwater that could potentially generate lahars were stored on or under the glacier; the water that generated the lahars that swept Drift River valley was produced from the proximal, eruption-induced volcaniclastic flows by melting of snow and ice. ?? 1994.

Trabant, D.C.; Waitt, R.B.; Major, J.J.

1994-01-01

127

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 ...

128

Distribution of Ground-Nesting Marine Birds Along Shorelines in Glacier Bay, Southeastern Alaska: An Assessment Related to Potential Disturbance by Back-Country Users  

USGS Publications Warehouse

With the exception of a few large colonies, the distribution of ground-nesting marine birds in Glacier Bay National Park in southeastern Alaska is largely unknown. As visitor use increases in back-country areas of the park, there is growing concern over the potential impact of human activities on breeding birds. During the 2003i??05 breeding seasons, the shoreline of Glacier Bay was surveyed to locate ground-nesting marine birds and their nesting areas, including wildlife closures and historical sites for egg collection by Alaska Native peoples. The nesting distribution of four common ground-nesting marine bird species was determined: Arctic Tern (Sterna paradisaea), Black Oystercatcher (Haematopus bachmani), Mew Gull (Larus canus), and Glaucous-winged Gull (Larus glaucescens). Observations of less abundant species also were recorded, including Herring Gull (Larus argentatus), Red-throated Loon (Gavia stellata), Canada Goose (Branta canadensis), Willow Ptarmigan (Lagopus lagopus), Semipalmated Plover (Charadrius semipalmatus), Spotted Sandpiper (Actitis macularia), Least Sandpiper (Calidris minutilla), Parasitic Jaeger (Stercorarius parasiticus), and Aleutian Tern (Sterna aleutica). Nesting distribution for Arctic Terns was largely restricted to the upper arms of the bay and a few treeless islets in the lower bay, whereas Black Oystercatchers were more widely distributed along shorelines in the park. Mew Gulls nested throughout the upper bay in Geikie Inlet and in Fingers and Berg Bays, and most Glaucous-winged Gull nests were found at wildlife closures in the central and lower bays. Several areas were identified where human disturbance could affect breeding birds. This study comprises the first bay-wide survey for the breeding distribution of ground-nesting marine birds in Glacier Bay National Park, providing a minimum estimate of their numbers and distribution within the park. This information can be used to assess future human disturbance and track natural changes in nesting bird distribution over time.

Arimitsu, M.L.; Piatt, J.F.; Romano, Marc D.

2007-01-01

129

Alaska  

NASA Technical Reports Server (NTRS)

Lower elevations are thawing out, while higher mountain ranges are still covered in snow in this MODIS image of Alaska from May 14, 2002. At right, the Aleutian Range falls along Alaska's eastern coastline. At upper right, a thin white line traversing generally south-southwest across the state is the Yukon River, still mostly frozen, although the high-resolution image shows a few dark places along the river's length that could be thawed. Sediment fills the waters along the southwestern coastline, with some blue-green color that could be phytoplankton, as well.

2002-01-01

130

The Border Ranges fault system in Glacier Bay National Park, Alaska: Evidence for major early Cenozoic dextral strike-slip motion  

USGS Publications Warehouse

The Border Ranges fault system of southern Alaska, the fundamental break between the arc basement and the forearc accretionary complex, is the boundary between the Peninsular-Alexander-Wrangellia terrane and the Chugach terrane. The fault system separates crystalline rocks of the Alexander terrane from metamorphic rocks of the Chugach terrane in Glacier Bay National Park. Mylonitic rocks in the zone record abundant evidence for dextral strike-slip motion along north-northwest-striking subvertical surfaces. Geochronologic data together with regional correlations of Chugach terrane rocks involved in the deformation constrain this movement between latest Cretaceous and Early Eocene (???50 Ma). These findings are in agreement with studies to the northwest and southeast along the Border Ranges fault system which show dextral strike-slip motion occurring between 58 and 50 Ma. Correlations between Glacier Bay plutons and rocks of similar ages elsewhere along the Border Ranges fault system suggest that as much as 700 km of dextral motion may have been accommodated by this structure. These observations are consistent with oblique convergence of the Kula plate during early Cenozoic and forearc slivering above an ancient subduction zone following late Mesozoic accretion of the Peninsular-Alexander-Wrangellia terrane to North America.

Smart, K.J.; Pavlis, T.L.; Sisson, V.B.; Roeske, S.M.; Snee, L.W.

1996-01-01

131

Dramatic increase in the relative abundance of large male dungeness crabs Cancer magister following closure of commercial fishing in Glacier Bay, Alaska  

USGS Publications Warehouse

The size structure of the population of the Dungeness crab Cancer magister was studied at six sites in or near Glacier Bay, Alaska, before and after the closure of commercial fishing. Seven years of preclosure and 4 years of postclosure data are presented. After the closure of Glacier Bay to commercial fishing, the number and size of legal-sized male Dungeness crabs increased dramatically at the experimental sites. Female and sublegal-sized male crabs, the portions of the population not directly targeted by commercial fishing, did not increase in size or abundance following the closure. There was not a large shift in the size-abundance distribution of male crabs at the control site that is still open to commercial fishing. Marine protected areas are being widely promoted as effective tools for managing fisheries while simultaneously meeting marine conservation goals and maintaining marine biodiversity. Our data demonstrate that the size of male Dungeness crabs can markedly increase in a marine reserve, which supports the concept that marine reserves could help maintain genetic diversity in Dungeness crabs and other crab species subjected to size-limit fisheries and possibly increase the fertility of females. ?? 2004 by the American Fisheries Society.

Taggart, S.J.; Shirley, T.C.; O'Clair, C. E.; Mondragon, J.

2004-01-01

132

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

133

In Brief: Melting glaciers  

NASA Astrophysics Data System (ADS)

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

Showstack, Randy; Tretkoff, Ernie

2010-12-01

134

Glacier microseismicity  

USGS Publications Warehouse

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

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

2010-01-01

135

Imaging Evidence for Hubbard Glacier Advances and Retreats since the Last Glacial Maximum in Disenchantment and Yakutat Bays, Alaska  

NASA Astrophysics Data System (ADS)

As glaciers advance and retreat, they leave erosional surfaces, retreat sequences, morainal banks, and terminal moraines. These features can be imaged and interpreted in seismic reflection data to gain insight into ice routing, ice-sediment processes, and preserved glacial history. High-resolution 2-D multichannel seismic data gathered on the August 2012 UTIG-USGS National Earthquake Hazards Reduction Program survey of Disenchantment and Yakutat Bays have provided understanding of the advance pathways of the Hubbard Glacier and the glacial history of the bays. These data show evidence of three unconformities appearing in the form of channels and interpreted to be glacial advance and retreat paths. The youngest observable channel in Disenchantment Bay is ~2 km wide, forming morainal banks along the edges of the bay. The depth below modern sea level in two-way travel time (twtt) shallows from 510 ms in the middle of the bay to 400 ms ~4 km north of the entrance to Yakutat Bay. The sediment contained within the youngest channel measured from the seafloor thins southward from a twtt thickness of 260 ms to 115 ms. Beneath the youngest channel lies an older, 2.2 km-wide channel which is observed at ~580 ms below sea level, and is filled with sediments ranging in thickness from 480 ms to 180 ms at the terminus. This older channel extends from Disenchantment Bay into Yakutat Bay, staying to the northeast of Yakutat Bay, then turns southward at Knight Island and shallows to 450 ms twtt before forming a terminal moraine ~10 km north of the mouth of Yakutat Bay. Evidence for the third and oldest unconformity can only be seen within a very small number of short seismic lines in Disenchantment Bay. It is the largest of the channels, at ~3 km wide and 720 ms below modern sea level. The evidence of three nested unconformities suggests that the Hubbard Glacier has had at least three major advances in recent history. Radiocarbon dating of wooden branches in moraine deposits confirms at least two of these advances to be during the Holocene while the oldest may represent the Last Glacial Maximum. The most recent advance likely reached its terminal position at the mouth of Disenchantment Bay, never entering Yakutat Bay. Our interpretation suggests that the Hubbard Glacier has repeatedly advanced around the east side of Yakutat Bay in Knight Island Channel, possibly due to the presence of Malaspina Glacier cutting off access to the central Yakutat Bay during a time of mutual advance. Within the range of the seismic data available for the area, it seems unlikely that the Hubbard Glacier fills all of Yakutat Bay when it advances.

Zurbuchen, J.; Gulick, S. P.; Levoir, M. A.; Goff, J. A.; Haeussler, P. J.

2013-12-01

136

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

137

Delineation of landform and lithologic units for Ecological Landtype-Association analysis in Glacier Bay National Park, Southeast Alaska  

USGS Publications Warehouse

In this study, landforms were classified-by using topographic maps and personal experience-into eight categories similar to those used by the U.S. Forest Service. The 90 bedrock-lithologic units on the current Glacier Bay geologic map were classified into 13 generalized lithologic units corresponding exactly to those used by the U.S. Forest Service. Incomplete storm-track, storm-intensity, and limited climatic information have also been compiled.

Brew, David A.

2008-01-01

138

Muir Glacier and Muir Inlet 1980  

USGS Multimedia Gallery

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

139

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

140

Geochronology of plutonic rocks and their tectonic terranes in Glacier Bay National Park and Preserve, southeast Alaska: Chapter E in Studies by the U.S. Geological Survey in Alaska, 2008-2009  

USGS Publications Warehouse

We have identified six major belts and two nonbelt occurrences of plutonic rocks in Glacier Bay National Park and Preserve and characterized them on the basis of geologic mapping, igneous petrology, geochemistry, and isotopic dating. The six plutonic belts and two other occurrences are, from oldest to youngest: (1) Jurassic (201.6–145.5 Ma) diorite and gabbro of the Lituya belt; (2) Late Jurassic (161.0–145.5 Ma) leucotonalite in Johns Hopkins Inlet; (3) Early Cretaceous (145.5–99.6 Ma) granodiorite and tonalite of the Muir-Chichagof belt; (4) Paleocene tonalite in Johns Hopkins Inlet (65.5–55.8 Ma); (5) Eocene granodiorite of the Sanak-Baranof belt; (6) Eocene and Oligocene (55.8–23.0 Ma) granodiorite, quartz diorite, and granite of the Muir-Fairweather felsic-intermediate belt; (7) Eocene and Oligocene (55.8–23.0 Ma) layered gabbros of the Crillon-La Perouse mafic belt; and (8) Oligocene (33.9–23.0 Ma) quartz monzonite and quartz syenite of the Tkope belt. The rocks are further classified into 17 different combination age-compositional units; some younger belts are superimposed on older ones. Almost all these plutonic rocks are related to Cretaceous and Tertiary subduction events. The six major plutonic belts intrude the three southeast Alaska geographic subregions in Glacier Bay National Park and Preserve, from west to east: (1) the Coastal Islands, (2) the Tarr Inlet Suture Zone (which contains the Border Ranges Fault Zone), and (3) the Central Alexander Archipelago. Each subregion includes rocks assigned to one or more tectonic terranes. The various plutonic belts intrude different terranes in different subregions. In general, the Early Cretaceous plutons intrude rocks of the Alexander and Wrangellia terranes in the Central Alexander Archipelago subregion, and the Paleogene plutons intrude rocks of the Chugach, Alexander, and Wrangellia terranes in the Coastal Islands, Tarr Inlet Suture Zone, and Central Alexander Archipelago subregions.

Brew, David A.; Tellier, Kathleen E.; Lanphere, Marvin A.; Nielsen, Diane C.; Smith, James G.; Sonnevil, Ronald A.

2014-01-01

141

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

142

The use of multi-channel ground penetrating radar and stream monitoring to investigate the seasonal evolution of englacial and subglacial drainage systems at the terminus of Exit Glacier, Alaska  

NASA Astrophysics Data System (ADS)

Concerns regarding the issue of climate change and, in particular, the rapid retreat of glaciers around the world, have placed great importance on glacial monitoring. Some of the methods most commonly used to observe glacial change---direct mass balance measurements and remote sensing---provide valuable information about glacier change. However, these methods do not address the englacial and subglacial environments. Surface meltwater that enters englacial and subglacial hydrological networks can contribute to acceleration of ice flow, increased calving on marine-terminating glaciers, surges or outburst floods, and greater overall ablation rates. Because subsurface drainage systems often freeze during the winter and re-form each summer, examining the seasonal evolution of these networks is crucial for assessing the impact that internal drainage may have on the behavior of a glacier each year. The goal of this study is to determine the role englacial and subglacial drainage system evolution plays in influencing summer ablation and discharge at the terminus of Exit Glacier, a small valley glacier located in South-central Alaska. During the summers of 2010 and 2011, we used ground-penetrating radar (GPR) to locate internal drainage features on the lower 100 meters of the glacier. GPR surveys were conducted in June and August of each year in an effort to observe the evolution of the drainage systems over the course of an ablation season. Three antenna frequencies---250, 500, and 800 MHz---were used on a dual frequency GPR so that various resolutions and depths in the ice could be viewed simultaneously. Stream monitoring was conducted to document discharge in the proglacial stream throughout the 2011 season. These data were compared with weather records to differentiate noticeable meltwater releases from precipitation events. Additionally, morphological changes in the glacier were observed through photographic documentation. Throughout the observation period, significant subglacial tunnels appeared, followed by the collapse of terminal ice above the tunnels. This phenomenon was most noticeable in 2011. These observations indicate that the internal drainage systems near the terminus of Exit Glacier became very well-developed each summer, and contributed approximately 75 meters of ice loss between June, 2010 and August, 2011.

Kilgore, Susan Marlena

143

Bivachnyy Glacier  

USGS Multimedia Gallery

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

144

Glacier Melt  

NSDL National Science Digital Library

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

Geographic, National

145

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

146

Neogene marine sedimentary record of the Gulf of Alaska: from the glaciers to the distal submarine fan systems  

NASA Astrophysics Data System (ADS)

The marine sedimentary record of Miocene to Pleistocene tectonics and glaciation is well preserved along the southern Alaska convergent margin. This margin is well suited for linking proximal to distal sediment transport processes because sediment is being generated by glacial erosion in the highest coastal mountain range on earth and subsequently being transported to the Aleutian subduction zone. We will discuss the sedimentary record from two end members of this system: (1) the proximal marine record now exposed onshore in the high peaks of the coastal ranges, and (2) the offshore distal record preserved in the Surveyor submarine fan system that was cored during the 2013 IODP Expedition 341. Onshore the Miocene non-glacial strata are represented by the Poul Creek Fm. This unit is 2000 m thick and in its upper part consists of mudstone, thin sandstone beds (10-30 cm thick), and thick bedded (1-2 m) highly bioturbated green sandstone beds that contain hummocky stratification. We interpret this unit as being deposited mainly in marine shelf environments. A gradational contact between the Poul Creek and the overlying upper Miocene-Pleistocene Yakataga Formation is marked by a transition to mudstone, thick bedded sandstone and glacial diamictite. This transition to glacial dominated deposition is interpreted to have occurred around 5 Ma based on previous studies. The onshore glacimarine strata are 5 km thick and grade up section from submarine fan to marine shelf strata. In the distal submarine fan record at IODP Site U1417, the upper Miocene strata in the lower part of the Site consist of 340 m of highly bioturbated gray to green mud interbedded with coarse sand and sandy diamict. These coarse-grained units are lithic rich with mainly sedimentary, volcanic, and coal clasts. We interpret these units as being derived from coal-bearing sedimentary strata exposed in the onshore thrust belt. These facies are interbedded with diatom ooze; we interpret this combination of facies as representing deposition of coarse-grained detritus originating from sedimentary gravity flows followed by longer periods of hemipelagic deposition. The first clear record of glacial sediment input in the distal submarine fan environment is late Pliocene - early Pleistocene muddy diamict beds that probably are the products of ice-rafting. This unit is about 30 m in thickness. The overlying 260 m of the core are mainly dark gray mud with thin beds of volcanic ash and sand/silt beds. Lonestones are common and are mainly argillite and metasiltstone clasts suggesting at least a component of sediment derivation from onshore metamorphosed parts of the Mesozoic accretionary prism. In general, the overall Neogene sedimentary record in both the proximal and distal marine settings appears to be similar but requires a sediment link between the proximal strata deposited on the Yakutat microplate and the Surveyor fan system deposited on the Pacific Plate.

Ridgway, K. D.; Bahlburg, H.; Childress, L. B.; Cowan, E. A.; Forwick, M.; Moy, C. M.; Müller, J.; Ribeiro, F.; Gupta, S.; Gulick, S. P.; Jaeger, J. M.

2013-12-01

147

Mass-balance characteristics of arctic glaciers  

Microsoft Academic Search

A survey of available mass-balance data shows that glaciers on arctic islands, i.e. mountain glaciers and ice caps in northern Canada, Greenland, Svalbard and the Eurasian islands, share mass-balance characteristics of low annual amplitude and small interannual variability. By contrast, glaciers around the Arctic (e.g. in Alaska, Iceland, mainland Scandinavia and northern Eurasia) can have exceptionally large annual amplitude and

Roger J. Braithwaite

2005-01-01

148

Glacier Maker  

NSDL National Science Digital Library

This site contains hands-on activities that explore the structure of glaciers. Students identify the contents of a glacier like those found in Patagonia; construct a mini glacier model in class; and compare and contrast the classroom model with Patagonian glaciers. Topics included in this page are: Instructional objectives, background materials, activity, procedure, evaluation and web resources.

149

Alexander Archipelago, Southeastern Alaska  

NASA Technical Reports Server (NTRS)

West of British Columbia, Canada, and south of the Yukon Territory, the southeastern coastline of Alaska trails off into the islands of the Alexander Archipelago. The area is rugged and contains many long, U-shaped, glaciated valleys, many of which terminate at tidewater. The Alexander Archipelago is home to Glacier Bay National Park. The large bay that has two forks on its northern end is Glacier Bay itself. The eastern fork is Muir inlet, into which runs the Muir glacier, named for the famous Scottish-born naturalist John Muir. Glacier Bay opens up into the Icy Strait. The large, solid white area to the west is Brady Icefield, which terminates at the southern end in Brady's Glacier. To locate more interesting features from Glacier Bay National Park, take a look at the park service map. As recently as two hundred years ago, a massive ice field extended into Icy Strait and filled the Glacier Bay. Since that time, the area has experienced rapid deglaciation, with many large glaciers retreating 40, 60, even 80 km. While temperatures have increased in the region, it is still unclear whether the rapid recession is part of the natural cycle of tidewater glaciers or is an indicator of longer-term climate change. For more on Glacier Bay and climate change, read an online paper by Dr. Dorothy Hall, a MODIS Associate Science Team Member. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

2002-01-01

150

Alaska: A frontier divided  

SciTech Connect

The superlatives surrounding Alaska are legion. Within the borders of the 49th US state are some of the world's greatest concentrations of waterfowl, bald eagles, fur seals, walrus, sea lions, otters, and the famous Kodiak brown bear. Alaska features the highest peak of North America, the 20,320-foot Mount McKinley, and the longest archipelago of small islands, the Aleutians. The state holds the greatest percentage of protected wilderness per capita in the world. The expanse of some Alaskan glaciers dwarfs entire countries. Like the periodic advance and retreat of its glaciers, Alaska appears with some regularity on the national US agenda. It last achieved prominence when President Jimmy Carter signed the Alaska National Interest Lands Conservation Act in 1980. Since then the conflict between environmental protection and economic development has been played out throughout the state, and Congress is expected to turn to Alaskan issues again in its next sessions.

O'Dell, R. (Conservation Foundation Latter, Washington, DC (USA))

1986-09-01

151

Alaska marine ice atlas  

SciTech Connect

A comprehensive Atlas of Alaska marine ice is presented. It includes information on pack and landfast sea ice and calving tidewater glacier ice. It also gives information on ice and related environmental conditions collected over several years time and indicates the normal and extreme conditions that might be expected in Alaska coastal waters. Much of the information on ice conditions in Alaska coastal waters has emanated from research activities in outer continental shelf regions under assessment for oil and gas exploration and development potential. (DMC)

LaBelle, J.C.; Wise, J.L.; Voelker, R.P.; Schulze, R.H.; Wohl, G.M.

1982-01-01

152

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

E-print Network

An 850 year record of climate and fluctuations of the iceberg- calving NellieJuan Glacier, south that subse- quent slow retreat changed to rapid iceberg-calving retreat after 1935, and that the tide- water temperature and radiation. However, rapid iceberg-calving retreat did not begin until 40years of slow retreat

Barclay, David J.

153

Intrusive rocks and plutonic belts of southeastern Alaska, U.S.A.  

USGS Publications Warehouse

About 30 percent of the 175,000-km2 area of southeastern Alaska is underlain by intrusive igneous rocks. Compilation of available information on the distribution, composition, and ages of these rocks indicates the presence of six major and six minor plutonic belts. From west to east, the major belts are: the Fairweather-Baranof belt of early to mid-Tertiary granodiorite; the Muir-Chichagof belt of mid-Cretaceous tonalite and granodiorite; the Admiralty-Revillagigedo belt of porphyritic granodiorite, quartz diorite, and diorite of probable Cretaceous age; the Klukwan-Duke belt of concentrically zoned or Alaskan-type ultramafic-mafic plutons of mid-Cretaceous age within the Admiralty-Revillagigedo belt; the Coast Plutonic Complex sill belt of tonalite of unknown, but perhaps mid-Cretaceous, age; and the Coast Plutonic Complex belt I of early to mid-Tertiary granodiorite and quartz monzonite. The minor belts are distributed as follows: the Glacier Bay belt of Cretaceous and(or) Tertiary granodiorite, tonalite, and quartz diorite lies within the Fair-weather-Baranof belt; layered gabbro complexes of inferred mid-Tertiary age lie within and are probably related to the Fairweather-Baranof belt; the Chilkat-Chichagof belt of Jurassic granodiorite and tonalite lies within the Muir-Chichagof belt; the Sitkoh Bay alkaline, the Kendrick Bay pyroxenite to quartz monzonite, and the Annette and Cape Fox trondhjemite plutons, all interpreted to be of Ordovician(?) age, together form the crude southern southeastern Alaska belt within the Muir-Chichagof belt; the Kuiu-Etolin mid-Tertiary belt of volcanic and plutonic rocks extends from the Muir-Chichagof belt eastward into the Admiralty-Revillagigedo belt; and the Behm Canal belt of mid- to late Tertiary granite lies within and next to Coast Plutonic Complex belt II. In addition, scattered mafic-ultramafic bodies occur within the Fairweather-Baranof, Muir-Chichagof, and Coast Plutonic Complex belts I and II. Palinspastic reconstruction of 200 km of right-lateral movement on the Chatham Strait fault does not significantly change the pattern of the major belts but does bring parts of the minor mid-Tertiary and Ordovician(?) belts closer together. The major belts are related to the stratigraphic-tectonic terranes of Berg, Jones, and Coney (1978) as follows: the Fairweather-Baranof belt is largely in the Chugach, Wrangell (Wrangellia), and Alexander terranes; the Muir-Chichagof belt is in the Alexander and Wrangell terranes; the Admiralty-Revillagigedo belt is in the Gravina and Taku terranes; the Klukwan-Duke belt is in the Gravina, Taku, and Alexander terranes; the Coast Plutonic Complex sill belt is probably between the Taku and Tracy Arm terranes; and the Coast Plutonic Complex belts I and II are in the Tracy Arm and Stikine terranes. Significant metallic-mineral deposits are spatially related to certain of these belts, and some deposits may be genetically related. Gold, copper, and molybdenum occurrences may be related to granodiorites of the Fairweather-Baranof belt. Magmatic copper-nickel deposits occur in the layered gabbro within that belt. The Juneau gold belt, which contains gold, silver, copper, lead, and zinc occurrences, parallels and lies close to the Coast Plutonic Complex sill belt; iron deposits occur in the Klukwan-Duke belt; and porphyry molybdenum deposits occur in the Behm Canal belt. The Muir-Chichagof belt of mid-Cretaceous age and the Admiralty-Revillagigedo belt of probable Cretaceous age are currently interpreted as possible magmatic arcs associated with subduction events. In general, the other belts of intrusive rocks are spatially related to structural discontinuities, but genetic relations, if any, are not yet known. The Coast Plutonic Complex sill belt is probably related to a post-Triassic, pre-early Tertiary suture zone that nearly corresponds to the boundary between the Tracy Arm and Taku terranes. The boundary between the Admiralty-Revillagigedo and Muir-Chichagof belts coincides nearly with the Seymour Canal-Clarence Strait lineament and also is probably a

Brew, David A.; Morrell, Robert P.

1983-01-01

154

Columbia Glacier in 1984: disintegration underway  

SciTech Connect

Columbia Glacier is a large, iceberg-calving glacier near Valdez, Alaska. The terminus of this glacier was relatively stable from the time of the first scientific studies in 1899 until 1978. During this period the glacier terminated partly on Heather Island and partly on a submerged moraine shoal. In December, 1978, the glacier terminus retreated from Heather Island, and retreat has accelerated each year since then, except during a period of anomalously low calving in 1980. Although the glacier has not terminated on Heather Island since 1978, a portion of the terminus remained on the crest of the moraine shoal until the fall of 1983. By December 8, 1983, that feature had receded more than 300 m from the crest of the shoal, and by December 14, 1984, had disappeared completely, leaving most of the terminus more than 2000 meters behind the crest of the shoal. Recession of the glacier from the shoal has placed the terminus in deeper water, although the glacier does not float. The active calving face of the glacier now terminates in seawater that is about 300 meters deep at the glacier centerline. Rapid calving appears to be associated with buoyancy effects due to deep water at the terminus and subglacial runoff. 12 refs., 10 figs.

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

1985-01-01

155

The role of thrust faulting in the formation of the eastern Alaska Range: Thermochronological constraints from the Susitna Glacier Thrust Fault region of the intracontinental strike-slip Denali Fault system  

NASA Astrophysics Data System (ADS)

along restraining bends of strike-slip faults is often partitioned into a vertical component via splay faults. The active Susitna Glacier Thrust Fault (SGTF), as shown by its initiation of the 2002 M7.9 Denali Fault earthquake, lies south of, and intersects the dextral strike-slip Denali Fault. Geochronology and thermochronology data from samples across the SGTF constrain the region's tectonic history and the role of thrusting in the formation of the eastern Alaska Range south of the Denali fault. U-Pb zircon ages indicate intrusion of plutons in the footwall (~57 Ma) and hanging wall (~98 Ma). These U-Pb zircon ages correlate to those from the Ruby Batholith/Kluane Terrane ~400 km east along the Denali Fault, supporting geologic correlations and hence constraints on long-term slip rates. 40Ar/39Ar mica and K-feldspar data from footwall and hanging wall samples (~54 to ~46 Ma) reflect cooling following magmatism and/or regional Eocene metamorphism related to ridge subduction. Combined with apatite fission track data (ages 43-28 Ma) and thermal models, both sides of the SGTF acted as a coherent block during the Eocene and early Oligocene. Contrasting apatite (U-Th)/He ages across the Susitna Glacier (~25 Ma footwall, ~15 Ma hanging wall) suggest initiation of faulting during the middle Miocene. Episodic cooling and exhumation is related to thrusting on known or hypothesized faults that progressively activate due to varying partition of strain along the Denali Fault associated with changing kinematics and plate interaction (Yakutat microplate collision, flat-slab subduction and relative plate motion change) at the southern Alaskan plate margin.

Riccio, Steven J.; Fitzgerald, Paul G.; Benowitz, Jeff A.; Roeske, Sarah M.

2014-11-01

156

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

... 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...

2014-07-01

157

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

158

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

159

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

Code of Federal Regulations, 2011 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...

2011-07-01

160

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

... 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...

2014-07-01

161

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

Code of Federal Regulations, 2010 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...

2010-07-01

162

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

163

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

Code of Federal Regulations, 2012 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...

2012-07-01

164

Characterizing Eklutna Glacier's Response to Climate Through Measurements of Mass Balance, Geometry, and Motion  

E-print Network

Characterizing Eklutna Glacier's Response to Climate Through Measurements of Mass Balance, Geometry of Environmental Science 2011 #12;December 2011 CHARACTERIZING EKLUTNA GLACIER'S RESPONSE TO CLIMATE THROUGH the students of Alaska Pacific University's annual Glaciology and Glacier Travel field courses, Ann Marie

Loso, Michael G.

165

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

166

Tropical Glaciers  

NASA Astrophysics Data System (ADS)

The term "tropical glacier" calls to mind balmy nights and palm trees on one hand and cold, blue ice on the other. Certainly author Gabriel Garcia Marqez exploited this contrast in One Hundred Years of Solitude. We know that tropical fish live in warm, Sun-kissed waters and tropical plants provide lush, dense foliage populated by colorful tropical birds. So how do tropical glaciers fit into this scene? Like glaciers everywhere, tropical glaciers form where mass accumulation—usually winter snow—exceeds mass loss, which is generally summer melt. Thus, tropical glaciers exist at high elevations where precipitation can occur as snowfall exceeds melt and sublimation losses, such as the Rwenzori Mountains in east Africa and the Maoke Range of Irian Jaya.

Fountain, Andrew

167

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

Microsoft Academic Search

The knowledge about the recent glacier change in the Chugach Mountains of southcentral Alaska is still scarce. In an effort to fill this gap we took an interdisciplinary approach and reconstructed the history of ten selected glaciers in the vicinity of Valdez (e.g., Valdez Glacier) and Cordova (e.g., Sheridan, Childs and Allen Glacier): Historical data such as early maps and

Christian Kienholz; Anupma Prakash; Samuel Nussbaumer; Heinz Zumbühl

2010-01-01

168

The History of the Glacier Facies Concept  

NASA Astrophysics Data System (ADS)

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

Benson, C. S.

2001-12-01

169

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.

170

Western Glacier Stonefly  

USGS Multimedia Gallery

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

171

Western Glacier Stonefly  

USGS Multimedia Gallery

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

172

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.

173

The Bay in Place of a Glacier.  

ERIC Educational Resources Information Center

The cultural resource specialist at Glacier Bay National Park (Alaska) explains the collaborative efforts of park staff and the Hoonah Tlingit to overcome language and cultural barriers in documenting park place names and clan oral history and traditions. The new park-community relationship, which follows decades of conflict, includes training…

Howell, Wayne

1997-01-01

174

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

175

Inventory of Glaciers in the North Cascades, Washington  

USGS Publications Warehouse

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

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

1971-01-01

176

Phase transition in MgSiO3 perovskite in the earth's lower mantle Taku Tsuchiya*, Jun Tsuchiya, Koichiro Umemoto, Renata M. Wentzcovitch  

E-print Network

Phase transition in MgSiO3 perovskite in the earth's lower mantle Taku Tsuchiya*, Jun Tsuchiya April 2004; accepted 11 May 2004 Abstract A new polymorph of MgSiO3 more stable than the Pbnm-perovskite to those in which a phase transition in MgSiO3-perovskite has been observed by in situ angle dispersive X

Vocadlo, Lidunka

177

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

178

Jakobshavn Glacier  

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

2013-04-17

179

Southeastern Alaska tectonostratigraphic terranes revisited  

SciTech Connect

The presence of only three major tectonostratigraphic terranes (TSTs) in southeastern Alaska and northwestern British Columbia (Chugach, Wrangell, and Alexander) is indicated by critical analysis of available age, stratigraphic, and structural data. A possible fourth TST (Stikine) is probably an equivalent of part or all of the Alexander. The Yakutat block belongs to the Chugach TST, and both are closely linked to the Wrangell and Alexander(-Stikine) TSTs; the Gravina TST is an overlap assemblage. THe Alexander(-Stikine) TSTs is subdivided on the basis of age and facies. The subterranes within it share common substrates and represent large-scale facies changes in a long-lived island-arc environment. The Taku TSTs is the metamorphic equivalent of the upper part (Permian and Upper Triassic) of the Alexander(-Stikine) TSTs with some fossil evidence preserved that indicates the age of protoliths. Similarly, the Tracy Arm TST is the metamorphic equivalent of (1) the lower (Ordovician to Carboniferous) Alexander TST without any such fossil evidence and (2) the upper (Permian to Triassic) Alexander(-Stikine) with some newly discovered fossil evidence. Evidence for the ages of juxtaposition of the TSTs is limited. The Chugach TST deformed against the Wrangell and Alexander TSTs in late Cretaceous. Gravina rocks were deformed at the time and also earlier. The Wrangell TST was stitched to the Alexander(-Stikine) by middle Cretaceous plutons but may have arrived before its Late Jurassic plutons were emplaced. The Alexander(-Stikine) and Cache Creek TSTs were juxtaposed before Late Triassic.

Brew, D.A.; Ford, A.B.

1985-04-01

180

Fast tidewater glaciers  

Microsoft Academic Search

Some iceburg-calving outlet glaciers flow continuously at speeds normally associated with surging glaciers and exhibit dramatic instability scenarios related to those suggested for marine ice sheets. No temperature tidewater glaciers are known to have floating termini, but many polar and subpolar tidewater glaciers do. The fast flow of temperature calving glaciers is almost entirely due to basal sliding and appears

M. F. Meier; Austin Post

1987-01-01

181

Columbia Glacier in 1986; 800 meters retreat  

USGS Publications Warehouse

Columbia Glacier, in Prince William Sound, Alaska, continued its rapid retreat in 1986, with a retreat of 800 m. Average velocity of the lower portion of the glacier, 10 September 1986 to 26 January 1987, was three km/yr, or about one-half of the velocity during similar periods for the previous three years. This reduced velocity is a new development in the progression of the retreat, and if the calving rate follows the pattern of previous years, will result in continued retreat. (Author 's abstract)

Krimmel, R.M.

1987-01-01

182

Shepard Glacier, Glacier National Park, Montana - 2005  

USGS Multimedia Gallery

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

183

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

184

Glacier (?) National Park  

NSDL National Science Digital Library

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

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

185

Online Glacier Photograph Database  

NSDL National Science Digital Library

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

The National Snow and Ice Data Center (NSIDC)

186

Ice Worms and Their Habitats on North Cascade Glaciers  

NSDL National Science Digital Library

This article describes ice worms (Mesenchytraeus solifugus) that live on glaciers in southern Alaska, the Coastal range and British Columbia, and in the Olympics and North Cascades as far south as Mt. St. Helens. Pictures of the ice worms and information on their habitat, physiolology, diet, and behavior are provided.

Hartzell, Paula

187

Remote sensing of global snowpack energy and mass balance: In-situ measurements on the snow of interior and Arctic Alaska  

NASA Technical Reports Server (NTRS)

This project is continuing along the lines of the semiannual report dated January 1993. Four major tasks have been addressed: analysis of variability in the seasonal snow of interior and arctic Alaska, the interpretation of microwave brightness temperature across Alaska on transects from south to north, study of nonclimatic controls which affect glaciers, and the location of glacier facies boundaries.

Benson, Carl S.

1994-01-01

188

Repeated Rapid Retreats of Bering Glacier by Disarticulation - The Cyclic Dynamic Response of an Alaskan Glacier System  

NASA Astrophysics Data System (ADS)

Bering Glacier is the largest glacier in continental North America, with an area greater than 5,000 square kilometers. Alone, it accounts for more than 6% of the glacier-covered area of Alaska and perhaps 15% of Alaska's glacier ice. In places, its bed is more than 250 m below sea level. It is also the largest surging temperate glacier on Earth. Surges, some with maximum ice displacements exceeding 13 km, occurred at least five times during the 20th century. Analysis of aerial photography, dating from 1936, and satellite imagery, dating from 1972, documents that following each of the last four surges, Bering Glacier experienced post-surge, decadal-scale, cyclic episodes of rapid retreat. In each instance, the primary mechanism responsible for the rapid retreat was a buoyancy-driven process, here named `disarticulation.' Abundant imagery exists to carefully document the post-surge retreat pattern during the two most recent cycles, 1967-1992 and 1996-present. In each cycle retreat began by calving. However, within a few years, as the piedmont lobe rapidly thinned, often by more than 20 m/yr, the dominant process transitioned to disarticulation, and the rate of retreat greatly increased. Disarticulation events occur when the thinning, low-gradient, distal end of the glacier's piedmont lobe reaches a state of buoyancy and separates from its bed. As it begins to float, large tabular pieces of ice up to a kilometer in maximum dimension passively separate from the terminus. Separation usually occurs along old crevasse and fracture planes and may begin at distances of more than 2 km behind the terminus. Often, hundreds of large icebergs simultaneously separate. Disarticulation events were also identified as being underway on photographs from 1936 and 1948. These followed surge that ended in the 1920s and 1940. In both 1936 and 1948, disarticulation was occurring at the same location. This location was also a focal point for disarticulation during the last two post-surge cycles. The post-1967 surge cycle spanned 25 years and resulted in a maximum of 10.7 km of terminus recession. Maximum annual recession exceeded 2.5 km. In the post-1996 cycle, maximum retreat is more than 6 km. Disarticulation is not unique to Bering Glacier, and probably not unique to Alaska. A 2005 aerial survey of Alaskan coastal glaciers identified more than a dozen glaciers, many former tidewater and calving glaciers, including Grand Plateau, Alsek, Bear, and Excelsior Glaciers that were rapidly retreating through disarticulation.

Molnia, B. F.

2005-12-01

189

Observations and analysis of self-similar branching topology in glacier networks  

USGS Publications Warehouse

Glaciers, like rivers, have a branching structure which can be characterized by topological trees or networks. Probability distributions of various topological quantities in the networks are shown to satisfy the criterion for self-similarity, a symmetry structure which might be used to simplify future models of glacier dynamics. Two analytical methods of describing river networks, Shreve's random topology model and deterministic self-similar trees, are applied to the six glaciers of south central Alaska studied in this analysis. Self-similar trees capture the topological behavior observed for all of the glaciers, and most of the networks are also reasonably approximated by Shreve's theory. Copyright 1996 by the American Geophysical Union.

Bahr, D.B.; Peckham, S.D.

1996-01-01

190

Climatic Controls on the Distribution of Surging Glaciers  

NASA Astrophysics Data System (ADS)

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

Sevestre, H.; Benn, D.

2012-12-01

191

Pine Island Glacier  

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

2013-04-16

192

Columbia Glacier stake location, mass balance, glacier surface altitude, and ice radar data, 1978 measurement year  

USGS Publications Warehouse

A 1 year data-collection program on Columbia Glacier, Alaska has produced a data set consisting of near-surface ice kinematics, mass balance, and altitude change at 57 points and 34 ice radar soundings. These data presented in two tables, are part of the basic data required for glacier dynamic analysis, computer models, and predictions of the number and size of icebergs which Columbia Glacier will calve into shipping lanes of eastern Prince William Sound. A metric, sea-level coordinate system was developed for use in surveying throughout the basin. Its use is explained and monument coordinates listed. A series of seven integrated programs for calculators were used in both the field and office to reduce the surveying data. These programs are thoroughly documented and explained in the report. (Kosco-USGS)

Mayo, L.R.; Trabant, D.C.; March, Rod; Haeberli, Wilfried

1979-01-01

193

All About Glaciers  

NSDL National Science Digital Library

This National Snow and Ice Data Center's site contains information for wide range of audiences from glaciologists to grade school students. Data and Science offers links to glacier research, projects, and glaciological organizations online. Another section offers glacier facts, questions and answers, a glossary, a photo gallery, bibliography and links to glacier information on the web. Recent global newsworthy events are chronicled, and a tutorial offering a quick tour through the life of a glacier is available.

Armstrong, Richard

194

The Atmospheric Radiation Measurement Program North Slope, Alaska Bringing Climate Change Into The Classroom  

E-print Network

cover, glaciers, tundra, permafrost, boreal forests, and peatlands all respond to small changes Into The Classroom http://www.arm.gov/ Teaching Time: 45 ­ 60 minutes Materials · Map of Alaska · Use of computers

Mojzsis, Stephen J.

195

World Glacier Inventory  

NSDL National Science Digital Library

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

196

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.

C. Haggerty

197

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

198

Alaska volcanoes guidebook for teachers  

USGS Publications Warehouse

Alaska’s volcanoes, like its abundant glaciers, charismatic wildlife, and wild expanses inspire and ignite scientific curiosity and generate an ever-growing source of questions for students in Alaska and throughout the world. Alaska is home to more than 140 volcanoes, which have been active over the last 2 million years. About 90 of these volcanoes have been active within the last 10,000 years and more than 50 of these have been active since about 1700. The volcanoes in Alaska make up well over three-quarters of volcanoes in the United States that have erupted in the last 200 years. In fact, Alaska’s volcanoes erupt so frequently that it is almost guaranteed that an Alaskan will experience a volcanic eruption in his or her lifetime, and it is likely they will experience more than one. It is hard to imagine a better place for students to explore active volcanism and to understand volcanic hazards, phenomena, and global impacts. Previously developed teachers’ guidebooks with an emphasis on the volcanoes in Hawaii Volcanoes National Park (Mattox, 1994) and Mount Rainier National Park in the Cascade Range (Driedger and others, 2005) provide place-based resources and activities for use in other volcanic regions in the United States. Along the lines of this tradition, this guidebook serves to provide locally relevant and useful resources and activities for the exploration of numerous and truly unique volcanic landscapes in Alaska. This guidebook provides supplemental teaching materials to be used by Alaskan students who will be inspired to become educated and prepared for inevitable future volcanic activity in Alaska. The lessons and activities in this guidebook are meant to supplement and enhance existing science content already being taught in grade levels 6–12. Correlations with Alaska State Science Standards and Grade Level Expectations adopted by the Alaska State Department of Education and Early Development (2006) for grades six through eleven are listed at the beginning of each activity. A complete explanation, including the format of the Alaska State Science Standards and Grade Level Expectations, is available at the beginning of each grade link at http://www.eed.state.ak.us/tls/assessment/GLEHome.html.

Adleman, Jennifer N.

2011-01-01

199

Integrated Ground-Based LiDAR and Global Fiducials Program Satellite Imagery Time Series Analysis of the Terminus of Bering Glacier, Alaska During the 2008-2011 Surge  

NASA Astrophysics Data System (ADS)

Satellite imagery from the Global Fiducials Program (GFP: classified satellite imagery released to the general public for science use: http://gfl.usgs.gov) tracked the 2008-2011 surge of the Bering Glacier, the largest and longest glacier in North America. The terminus displacement began in late 2010, with maximum velocities of greater than 20 meters per day by late January 2011, as measured using feature tracking with GFP imagery. By July, the velocities had decreased to less than 10 m/d. We used the GFP imagery to locate three helicopter accessible targets on the terminus of the Bering Glacier to collect high-resolution (0.5-4 cm spot spacing) 4D time-series tripod/terrestrial LiDAR (T-LiDAR) data. During the week of July 24, 2011 we collected hourly and daily T-LiDAR data to resolve spatially and temporally varied advancement rates at each of the sites. The first site was located on the west side of Tashalich arm on the western side of the Bering Lobe terminus proximal to the region where the maximum GFP velocities had previously been measured. Using the T-LiDAR data, we found that the terminus advanced 5.4 m over 76 hours of observation. The hourly advancement rates for the same location are a very consistent 4.2 cm/h during our daylight hours of observation (0900-1800 local) and when daily rate are extrapolated to the full 76 hours, we should have measured 3.2 m of horizontal displacement: this is a discrepancy between the total and hourly measured displacements of an additional 2.2 m of motion during the night and early morning hours (1800-0900 local). The additional motion may be explained by accelerated terminus velocity associated with daily thermal heating and resulting melt. Motion may also be explained by rain on the second day of the survey that "lubricated" the glacier bed thereby allowing it to advance at a faster velocity. The second site was on Arrowhead Island, located on the eastern side of the terminus where the vertical relieve of the glacier terminus was significantly lower than at the fist site that had the elevated velocities. Here the T-LiDAR data measured a much slower advancement rate of 0-2.0 cm/h. The third T-LiDAR site also on Arrowhead Island, approximately 300 meters to the west, measured 7.3 cm/h of motion where the Bering Glacier entered Vitus Lake. We will compare the T-LiDAR and GFP velocities with GPS hourly data collected within the nearby Glacier Ablation Sensor Systems that are deployed on the glacier's surface to assess if the daily variations at the terminus are observed elsewhere during this surge event.

Bawden, G. W.; Molnia, B. F.; Howle, J.; Bond, S.; Angeli, K.; Shuchman, R. A.

2012-12-01

200

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

201

All about glaciers  

NSDL National Science Digital Library

The National Snow and Ice Data Center created this website to educate everyone, from grade school students to glaciologists, about glaciers. At the Data and Science link, researchers can learn about glaciological organizations, publications, and research projects as well as how to obtain glacial data. Students and educators can find a glaciology glossary, answers to many of their questions, and amazing images of glaciers at the General Information link. The website also provides a detailed portrayal of the life of glaciers.

202

Glaciers and Climate Change  

Microsoft Academic Search

Although my book focuses on valley glaciers, it is not intended\\u000ato provide a basic course in glaciology, nor does it claim to\\u000agive a state-of-the-art picture of glacier research. It consists\\u000amainly of the personal reflections of a meteorologist who\\u000agradually became interested in glaciers and is written primarily\\u000afor persons with a general interest in the physics of

J. Oerlemans

2001-01-01

203

Regional projections of glacier volume and runoff in response to twenty-first century climate scenarios (Invited)  

NASA Astrophysics Data System (ADS)

Changes in mass contained by mountain glaciers and ice caps can modify the Earth's hydrological cycle on multiple scales. On a global scale, the mass loss from glaciers contributes to sea level rise. On regional and local scales, glacier melt-water is an important contributor to and modulator of river flow. In this study we use an elevation-dependent glacier mass balance model to project annual volume changes and monthly runoff from all mountain glaciers and ice caps in the world (excluding those in the Antarctic periphery) for the 21st century forced by temperature and precipitation scenarios from 14 global climate models. The largest contributors to projected total volume loss are the glaciers in the Canadian and Russian Arctic, Alaska and glaciers peripheral to Greenland ice sheet. 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 75% of their volume by 2100. The magnitude and sign of trends in annual runoff totals differ considerably among regions depending on the balance between enhanced melt and the reduction of the glacier reservoir by glacier retreat and shrinkage. Most regions show strong declines in glacier runoff indicating that the effect of glacier shrinkage is more dominant than increased melting rates. Some high-latitude regions (Arctic Canada North, Russian Arctic and Greenland) exhibit increases in runoff totals. Iceland and Svalbard show an increase in runoff followed by a multi-decadal decrease in annual runoff.

Radic, V.; Bliss, A. K.; Hock, R.

2013-12-01

204

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

205

Glaciers and Icebergs  

NSDL National Science Digital Library

This lesson plan provides instruction to teachers for creating a glacier in the classroom to demonstrate how glaciation affects landforms. Learning objectives include student understanding that as glaciers move, they create a variety of patterns on landforms by a process called glacial scraping, that the scraping patterns left by a glacier depend on how the glacier moved over the landform, and that the evidence of glaciation left by glacial scraping provides clues to the climate in a particular place over a long period of time. The site also includes relevant vocabulary words with sound recordings for pronunciation. There are ideas presented for more advanced activities, discussion questions, and additional sources to consult.

Frank Weisel

206

Glaciers: Teacher's Guide  

NSDL National Science Digital Library

The Glaciers Teacher's Guide Web site was created by Arizona educator Patti Greenleaf. The site provides everything needed to complete the online activity, which is geared to students in grades 4 to 5. Objectives of the lesson include having students define what a glacier is, correctly use some terminology related to glaciers, describe how they form and move, and finally be able to tell where glaciers are located today. These objectives are accomplished by having the students read the provided text as well as looking at various photographs and movies. The structure and material of the site are its highlight, both of which are simple but effective.

Nichols, Marilyn.

1969-12-31

207

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

208

HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF DOME AT CENTER REAR. SAME VIEW AT CA-157-2. LOOKING NNE. GIS: N-37' 43 44.3 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

209

2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF DOME AT CENTER REAR. LOOKING NNE. GIS N-37 43 44.3 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

210

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

211

The GLIMS Glacier Database  

Microsoft Academic Search

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 \\

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

2007-01-01

212

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.

Jessica Fries-Gaither

213

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

214

Glacier Peak, Washington  

NSDL National Science Digital Library

This site features links to all aspects of Glacier Peak, a volcano in the Cascade Range, including its geographic setting, and geologic and eruptive history. Glacier Peak is not prominently visible from any major metropolitan centers, and thus its attractions, as well as its hazards, tend to be overlooked. Yet, Glacier Peak has produced larger and more explosive eruptions than any other Washington volcano except Mount St. Helens. Glacier Peak was not known by settlers to be a volcano until the 1850s, when Native Americans mentioned it to naturalist George Gibbs. Not until 1898 did Glacier Peak appear on a published map under its current name. Links labeled 'Special Items of Interest' include information about volcanic highlights and features, and points of interest. Other links lead to maps, graphics, images, publications, reports, and other items of interest involving this volcano and others.

215

ALASKA MARINE Alaska Marine Mammal Observer Program  

E-print Network

ALASKA MARINE MAMMAL PROGRAM 2012 #12;2012 Alaska Marine Mammal Observer Program Observer Manual Contents Section 1: The Alaska Marine Mammal Observer Program 1.0 Introduction 1.1 Marine Mammal Stock Program 1.5 Alaska Marine Mammal Observer Program Section 2: The Southeast Alaska Environment 2

216

National Park Glaciers Knowledge Center  

NSDL National Science Digital Library

This interactive resource explains what glaciers are, where they are found, how they form, and how they move. The types and parts of glaciers are discussed, as well as ice ages, the different types of landforms that may result from glaciation, and how scientists monitor glaciers. Examples from our national parks are also highlighted as case studies to illustrate how glaciers have created landscapes.

2005-08-01

217

Ground-based portable radar interferometer for imaging glacier flow, ocean-glacier ice interactions, and river ice breakup  

NASA Astrophysics Data System (ADS)

Over the last 18 months we have deployed new 17 GHz imaging radars from Gamma Remote Sensing to document flow on land terminating and tidewater glaciers in Greenland and Alaska; to image glacier response to tides and calving; to track floating ice in fjords; and to document river ice movement, ice jams, and associated flooding during breakup on the Tanana River in Alaska. During these deployments we have learned much about atmospheric influences on interferometric measurements; combination of flow direction determinations from feature tracking in amplitude imagery with short-term flow variability from interferometry. We show examples documenting measurement capabilities and limitations from each of these deployments. These radars represent unique tools for study of rapid changes in dynamic parts of the cryosphere.

Fahnestock, M. A.; Cassotto, R.; Truffer, M.

2013-12-01

218

Associations between accelerated glacier mass wastage and increased summer temperature in coastal regions  

USGS Publications Warehouse

Low-elevation glaciers in coastal regions of Alaska, the Canadian Arctic, individual ice caps around the Greenland ice sheet, and the Patagonia Ice Fields have an aggregate glacier area of about 332 ?? 103 km 2 and account for approximately 42% of all the glacier area outside the Greenland and Antarctic ice sheets. They have shown volume loss, especially since the end of the 1980s, increasing from about 45% in the 1960s to nearly 67% in 2003 of the total wastage from all glaciers on Earth outside those two largest ice sheets. Thus, a disproportionally large contribution of coastal glacier ablation to sea level rise is evident. We examine cumulative standardized departures (1961-2000 reference period) of glacier mass balances and air temperature data in these four coastal regions. Analyses indicate a strong association between increases in glacier volume losses and summer air temperature at regional and global scales. Increases in glacier volume losses in the coastal regions also coincide with an accelerated rate of ice discharge from outlet glaciers draining the Greenland and West Antarctic ice sheets. These processes imply further increases in sea level rise. ?? 2006 Regents of the University of Colorado.

Dyurgerov, M.; McCabe, G.J.

2006-01-01

219

Using Global Fiducials Program Imagery to Document 50 Years of North American Glacier Change  

NASA Astrophysics Data System (ADS)

As part of the International Geophysical Year (IGY), nine glaciers in Alaska and Washington were imaged and mapped at a 1:10,000 scale by the American Geographical Society (AGS) to: "provide the basis for more satisfactory and more accurate interpretation of the response of these glaciers to meteorological and other factors." Prophetic words indeed. In commemoration of the 50th anniversary of the publication of these maps, the Global Fiducials Program (GFP) systematically re-photographed these glaciers, along with several additional glacier sites, to determine the extent of change at each of these sites. In a new US Geological Survey (USGS) series, maps produced from recently collected GFP imagery, closely following AGS's original map format, are being made for the original nine glaciers. New maps will also be produced for the USGS' three benchmark glaciers and for four new sites--two in California, one in Montana, and one in Nevada. All are either current or proposed GFP sites. Newly acquired and historical imagery will be used to determine changes in terminus position, produce digital elevation models (DEMs), and generate velocity fields from crevasse migration. Where possible, area and volume changes are being determined. Each pair of glacier maps will be accompanied with a summary document describing the changes that have occurred at that glacier. Changes mapped for the Benchmark Glaciers are in agreement with the annual mass balance records compiled by detailed USGS field investigations.

Josberger, E. G.; Fahey, M. J.; Friesen, B. A.; Molnia, B. F.

2012-12-01

220

Mapping the Glaciers  

NSDL National Science Digital Library

This earth systems field lab begins with an in-class guided inquiry experience which uses Minnesota Geological Survey 3-D maps of the upper Midwest to determine where they believe glaciers may have had an influence. They will determine this by looking at landscapes and compiling their own evidence from the maps. They will also offer evidence for a hypothesis they generate which involves the direction that the glacier was traveling. The two-day lesson ends (after student presentations on their findings about glaciers) with a field investigation of one of our parking lot snow banks. Students will compare and contrast what they know about glaciers, with one of our parking lot snow banks, determining any similarities with how the landscape may have appeared during the Pleistocene.

221

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

222

A Transect of Glacier Bay Ocean Currents Measured by Acoustic Doppler Current Profiler (ADCP)  

E-print Network

but then depletion (0-2 M) in Glacier Bay, presumably due to phytoplankton consumption. We postulate that turbulence at a depth of 5 m. During the cruise in the Gulf of Alaska, 98 CTD casts were taken. The accurate CTD

223

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

224

Getting the Shot, Grinnell Glacier, Glacier National Park.  

USGS Multimedia Gallery

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

225

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

226

Mass balance modeling of a large glacier with sparse ground observations, and comparison to three remote sensing techniques  

NASA Astrophysics Data System (ADS)

Like many mountain ranges in Alaska, the Central Alaska Range is a highly glacierized but sparsely monitored region in terms of glacier mass balance and meteorological ground observations. The Kahiltna Glacier, a large (522 km2), remote mountain glacier with a wide range of altitudes and few in-situ measurements, is a challenge for traditional melt models that rely heavily on input of accurate melt gradients, air temperatures and lapse rates, and spatial distribution of snowfall. In order to supplement historical measurements from a single National Park Service mass balance stake, extensive campaigns of field observations were carried out on the glacier in 2010 and 2011, and remaining spatial and temporal gaps have been filled using available climate data products. Here we present a method for modeling twenty years of glacier-wide mass balance evolution for the Kahiltna Glacier, by expanding on sparse ground observations from a single site. We use NCEP-NCAR reanalysis time series' of air temperature and precipitation adjusted to on-glacier conditions, and characterize the spatial distribution of precipitation by sampling a gridded climate product (PRISM) along the glacier centerline. These data serve as input into a fully distributed degree-day melt model. To assess the model results, mass balance estimates obtained from this method are also compared to those derived from several other techniques: DEM differencing, repeat laser altimetry, and regionally downscaled GRACE gravimetry. As well as providing a method for modeling mass balance for a large glacier with a broad elevation range and sparse observational data, this multidisciplinary study will help bridge the gap between modeling and remote sensing techniques for estimating glacier mass balance.

Young, J. C.; Arendt, A. A.; Hock, R. M.; Motyka, R. J.

2012-12-01

227

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

228

Glacier mass-balance standards  

Microsoft Academic Search

Deep-sea cores and ice cores from the late Cenozoic show that the Earth's climate changes significantly. Glacier fluctuations are but one indication of this change. Glaciers are both an active component of the environmental system, regulating mountain streamflow, and a passive one, responding to climatic change. Thus, an understanding of the link between climate and glaciers is needed in order

A. G. Fountain; D. Trabant; M. M. Brugman; C. S. L. Ommanney; S. Monroe

1991-01-01

229

Engineering geomorphology of rock glaciers  

NASA Astrophysics Data System (ADS)

A partnership between geomorphology and engineering is facilitating human development in this harsh environment. Rock glaciers provide locations for urban water sources, construction borrow sources, drill sites, shaft and tunnel portals, ski tower supports, and dam abutments. Rock glaciers, as dynamic landforms, necessitate proper identification in the field. Placing structures on, in, or adjacent to rock glaciers requires an appreciation and understanding of their temporal stability. Internal and surface characteristics provide important clues to the development and deformation of rock glaciers. Rock glaciers play a significant role in the alpine debris transport system. Active movement and mass wasting are perhaps the most obvious geologic hazards affecting engineered works. The structure of the rock glacier is conducive to the production of a steady, continuous supply of meltwater during summer months. Thus, rock glaciers serve as alpine aquifers. Consideration of rock glaciers as potential aquifer sources requires caution because of the long-term impact of climate change on the temporal nature of the landform. From the rock glaciers that we have monitored for water quality characteristics, it appears that they provide quality potable water. This paper provides a foundation for appreciation and understanding of rock glaciers from an engineering geomorphologic point of view. The approach taken in this paper provides practical, important information to aid the engineer and engineering geologist in prudent evaluations of rock glaciers as potential sites for human development and uses. The bottom line of our paper is: rock glaciers must be avoided for essentially all structures.

Burger, K. C.; Degenhardt, J. J.; Giardino, J. R.

1999-12-01

230

Methods of Measuring Glacier Change  

Microsoft Academic Search

In the 19th century measuring glacier change was limited to measuring the position of the glacier front, or terminus. By the mid 20th century, change measurements expanded to include aerial photogrammetry and field-based mass balance methods. The latter were typically based on stakes drilled into a glacier, against which snow accumulation and ice loss were measured. Knowing the density of

A. G. Fountain

2001-01-01

231

Denali Fault: Black Rapids Glacier  

USGS Multimedia Gallery

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

2008-12-15

232

Iceland Glacier Recession 1973 to 2000, Glacier Terminus contrast emphasized  

NSDL National Science Digital Library

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

Perkins, Lori; Hall, Dorothy

2001-04-09

233

Greenland Glacier Albedo Variability  

NASA Technical Reports Server (NTRS)

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

2004-01-01

234

Winter speed-up of quiescent surge-type glaciers in Yukon, Canada  

NASA Astrophysics Data System (ADS)

Glacier surge is known to often initiate in winter, but the mechanisms remain unclear in light of the summer speed-up at normal glaciers. We examined spatial-temporal changes in the ice velocity of surge-type glaciers near the border of Alaska and Yukon, and found significant upstream accelerations from fall to winter, regardless of surging episodes. Moreover, whereas the summer speed-up was observed downstream, the winter speed-up propagated from upstream to downglacier. Given the absence of upstream surface meltwater input in winter, we speculate the presence of water storages near the base that do not directly connect to the surface but can promote basal sliding through increased water pressure as winter approaches. Our findings have implications for modeling of glacial hydrology in winter time, and its link to glacier dynamics and subglacial erosion.

Abe, T.; Furuya, M.

2014-05-01

235

Northern Illinois University: Glaciers  

NSDL National Science Digital Library

Northern Illinois University offers illustrative summary of glaciers and glacial processes. The website provides a timeline of the glacial advances into Illinois. Students and educators can learn a few of the landscape features that scientists use to interpret geologic history. Users can learn how glaciers affected Illinois's topography and waterbodies. The site furnishes educational maps of Illinois's bedrock geology and shaded relief. The text is linked to a glossary to assist users with glacial terminology. While this website does concentrate on the state of Illinois, everyone can learn basic characteristics of glacial movements.

236

A Disintegrating Glacier  

NSDL National Science Digital Library

Recent satellite images have revealed two new icebergs floating off the Antarctic coast. The icy behemoths are fragments of the Ninnis Glacier. This NASA fact sheet uses text and remotely sensed imagery to describe the events of January 2000, in which a large tongue of the Ninnis Galcier broke off and split into two gigantic icebergs. The breakup of the Ninnis Glacier Tongue has important implications regarding the Antarctic Ice Sheet's potential response to global climate change and its effect on global sea level. Links to other related sites are also included.

2000-12-06

237

Svalbard surging glacier landsystems  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

238

Glacier Goo Erosion Experiments  

NSDL National Science Digital Library

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

Rachel Headley

239

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

240

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

241

Taking a Glacier's Pulse  

NSDL National Science Digital Library

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

Landis, Carol

242

Sediment Control of Convection in Glacier Dammed Lakes  

NASA Astrophysics Data System (ADS)

During August, 2001, measurements of bathymetry, temperature, and conductivity from Berg Lake, a freshwater lake dammed by Steller Glacier, and Vitus Lake, a tidally influenced lake at the terminus of Bering Glacier, Alaska, show intense vertical convection that is controlled by suspended sediment in the former lake and salt in the latter lake. The temperature profiles from Berg Lake show a vertical structure that consists of a 10 m thick surface layer where the temperature drops from near 9 C to approximately 4 C, the temperature of maximum density for fresh water. Below this depth the temperature decreases to 0 C in the deepest portions of the lake, approximately 75 m. Superimposed on this general unstable temperature profile are spatially variable fine structure details that include vertical steps and temperature inversions. While the temperature profiles indicate a highly unstable situation, the sub-glacial discharge has a suspended sediment load sufficient to marginally stabilize the density structure in the lake. This sediment laden water flows out from below the glacier and spreads horizontally throughout Berg Lake. As the suspended sediment settles, vertical thermal convection occurs that yields the observed fine structure in the temperature profiles. In contrast, Vitus Lake is connected to the Gulf of Alaska via the 8 m deep, 7.3 km long Seal River. Measurements in this lake show strong saline stratification in the deeper portions of the lake. Thermal diffusion across the pycnocline may produce frazil ice growth, while melting of the glacier terminus produces convection at the margin of the lake, not the interior, as was observed in Berg Lake.

Josberger, E. G.; Meadows, G. A.; Shuchman, R. A.; Payne, J.

2001-12-01

243

Deep-seated gravitational slope deformations near the Trans-Alaska Pipeline, east-central Alaska Range, Alaska, USA  

NASA Astrophysics Data System (ADS)

Multiple, active, deep-seated gravitational slope deformations (DSGSD) are present near the Trans-Alaska Pipeline and Richardson Highway in the east-central Alaska Range, Alaska, USA. We documented spatial and temporal variations in rates of surface movement of the DSGSDs between 2003 and 2011 using RADARSAT-1 and RADARSAT-2 D-InSAR images. Deformation rates exceed 10 cm/month over very large areas (>1 km2) of many rock slopes. Recent climatic change and strong seismic shaking, especially during the 2002 M 7.9 Denali Fault earthquake, appear to have exacerbated slope deformation. We also mapped DSGSD geological and morphological characteristics using field- and GIS-based methods, and constructed a conceptual 2D distinct-element numerical model of one of the DSGSDs. Preliminary results indicate that large-scale buckling or kink-band slumping may be occurring. The DSGSDs are capable of generating long-runout landslides that might impact the Trans-Alaska Pipeline and Richardson Highway. They could also block tributary valleys, thereby impounding lakes that might drain suddenly. Wrapped 24-day RADARSAT-2 descending spotlight interferogram showing deformation north of Fels Glacier. The interferogram is partially transparent and is overlaid on a 2009 WorldView-1 panchromatic image. Acquisition interval: August 2 - August 26, 2011. UTM Zone 6N.

Newman, S. D.; Clague, J. J.; Rabus, B.; Stead, D.

2013-12-01

244

Mt. Kilimanjaro's Receding Glaciers  

NASA Technical Reports Server (NTRS)

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

2002-01-01

245

Postglacial vegetation history of Mitkof Island, Alexander Archipelago, southeastern Alaska  

Microsoft Academic Search

An AMS radiocarbon-dated pollen record from a peat deposit on Mitkof Island, southeastern Alaska provides a vegetation history spanning ?12,900 cal yr BP to the present. Late Wisconsin glaciers covered the entire island; deglaciation occurred >15,400 cal yr BP. The earliest known vegetation to develop on the island (?12,900 cal yr BP) was pine woodland (Pinus contorta) with alder (Alnus), sedges (Cyperaceae) and

Thomas A. Ager; Paul E. Carrara; Jane L. Smith; Victoria Anne; Joni Johnson

2010-01-01

246

A possible Younger Dryas record in southeastern Alaska  

Microsoft Academic Search

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

D. R. Engstrom; B. C. S. Hansen; H. E. Jr. Wright

1990-01-01

247

Biogeochemistry of glacial runoff along the Gulf of Alaska  

NASA Astrophysics Data System (ADS)

Glaciers and ice sheets represent the second largest reservoir of water in the global hydrologic system and glacier ecosystems cover 10% of the Earth, however the biogeochemistry of glacier discharge has not been well characterized. Preliminary investigations have shown that runoff from glaciers can be an important contributor of dissolved organic carbon (DOC) and macro- and micro- nutrients such as P and Fe to downstream aquatic ecosystems. There is also mounting evidence that glacier ecosystems may be a source of anthropogenically derived constituents such as fossil fuel combustion by-products and persistent organic pollutants that are deposited in precipitation and released in melting glacier ice. As a result, it is critical to develop our understanding of glacial biogeochemistry, particularly in near-shore marine ecosystems along glacially-dominated coastal margins that receive large volumes of glacial runoff. To examine the spatial and temporal variability in the biogeochemical properties of glacial runoff, we sampled snow, ice melt, and glacial runoff at the Mendenhall Glacier near Juneau, Alaska during the summer of 2012. Mendenhall Glacier extends from near-sea level to >1700 m.a.s.l. and encompasses ~120 km2 of the 3900 km2 Juneau Icefield. The main sub-glacial drainage channel was sampled weekly throughout the glacier melt season (May-October) for a suite of physical (temperature, conductivity, suspended sediment) and biogeochemical (C, N, P, Fe and trace metals) parameters. In addition, we did opportunistic sampling of snow in the glacier accumulation zone and supra-glacial meltwater streams on the glacier surface. We also analyzed particulate and dissolved Hg in glacial runoff to quantify the export of Hg to downstream aquatic ecosystems. Preliminary results show that concentrations of dissolved organic carbon in snow, ice melt, and sub-glacial runoff were typically low (<0.5 mg C/L) and not well correlated with discharge. Recent research has shown that glacier-derived DOC represents a quantitatively significant energy subsidy of ancient, yet highly bioavailable carbon to downstream ecosystems. This runs counter to the standard perception of the age-reactivity relationship for DOC, in which the least reactive material withstands degradation the longest and is therefore the oldest. To investigate this phenomenon and determine the origin of glacially-derived DOC, we focused on characterizing the dissolved organic matter being exported from Mendenhall across the melt season. This talk will present results from a variety of organic matter characterization techniques including: carbon isotopes (13C and 14C), fluorescence spectrophotometry, and electrospray ionization coupled to FTICR-MS.

Hood, E.; Scott, D.; Vermilyea, A.; Stubbins, A.; Raymond, P.; Spencer, R.

2012-04-01

248

Icefall on the Lambert Glacier  

NASA Technical Reports Server (NTRS)

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

2002-01-01

249

University of Alaska Fairbanks CONSTRUCTION PROJECTS 2014  

E-print Network

replacement Construction: May - Oct 1, 2014 Closure: May - Aug, 2014 Gruening Building Roof Replacement - Sept, 2014 New Roundabout. Expect flaggers and some delays Roof Drain Modifications Construction: May Restroom Remodel Construction: June - August Replace Sidewalk from Taku Lot with Metal Stairs Construction

Ickert-Bond, Steffi

250

Secular glacier mass balances derived from cumulative glacier length changes  

Microsoft Academic Search

Glacier mass changes are considered to represent natural key variables with respect to strategies for early detection of enhanced greenhouse effects on climate. The main problem, however, with interpreting worldwide glacier mass balance evolution concerns the question of representativity. One important key to deal with such uncertainties and to assess the spatio-temporal representativity of the few available measurements is the

M. Hoelzle; W. Haeberli; M. Dischl; W. Peschke

2003-01-01

251

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

252

University of Alaska Graduate Survey  

E-print Network

University of Alaska Graduate Survey 2012 Prepared for: University of Alaska March 2013 #12;University of Alaska Graduate Survey 2012 Prepared for: University of Alaska Prepared by: Juneau · Anchorage ............................................................................................................................... 60 Survey Instrument

Ickert-Bond, Steffi

253

Insights into physical and biological controls on the export of organic matter and nutrients from glacier ecosystems  

NASA Astrophysics Data System (ADS)

Glaciers and ice sheets represent the second largest reservoir of water in the global hydrologic system and contribute labile dissolved organic carbon (DOC) and macro- and micro- nutrients such as P and Fe to downstream aquatic ecosystems. There is increasing evidence that the biogeochemistry of runoff from glaciers can be substantially modified by microbial activity within glacier ecosystems. To date, there have been relatively few comprehensive studies of the biogeochemistry of glacier runoff from large (>100 square kilometers) glaciers over the full runoff season. We sampled snow, ice melt, and glacial runoff at the Mendenhall Glacier near Juneau, Alaska during the summer of 2011. Mendenhall Glacier extends from near-sea level to >1700 m.a.s.l. and encompasses ~120 km2 of the 3900 km2 Juneau Icefield. The main sub-glacial drainage channel was sampled weekly throughout the glacier melt season (May-October) for a suite of physical (temperature, conductivity, suspended sediment) and biogeochemical (C, N, P, Fe and trace metals) parameters. In addition, we did opportunistic sampling of snow in the glacier accumulation zone and supra-glacial meltwater streams on the glacier surface. A primary goal of our research is to characterize the spatial and temporal variability of the chemical character of glacier-derived organic matter. Concentrations of DOC in snow, ice melt, and sub-glacial runoff were typically low (<0.5 mg C/L) and not well correlated with discharge. To determine the quality and origin of glacially-derived DOC, we employed a suite of organic matter characterization techniques including: carbon isotopes (13C and 14C) and fluorescence spectrophotometry. In addition, we combined estimates of glacier discharge with solute concentrations to calculate fluxes of organic matter and nutrients from the Mendenhall Glacier. These fluxes provide new insights into the role that glacier ecosystems play in exporting organic matter and nutrients to downstream freshwater and marine ecosystems. Finally, the combination of physical and biogeochemical measurements across the melt season provides the opportunity to examine how physical (e.g. seasonal evolution of the glacier drainage system) and biological (e.g. microbial abundance and activity) processes influence the biogeochemistry of glacier runoff.

Hood, E. W.; Scott, D.; Vermilyea, A.; Spencer, R. G.; Stubbins, A.; Raymond, P.

2012-12-01

254

Listening to Glaciers: Passive hydroacoustics near marine-terminating glaciers  

USGS Publications Warehouse

The catastrophic breakup of the Larsen B Ice Shelf in the Weddell Sea in 2002 paints a vivid portrait of the effects of glacier-climate interactions. This event, along with other unexpected episodes of rapid mass loss from marine-terminating glaciers (i.e., tidewater glaciers, outlet glaciers, ice streams, ice shelves) sparked intensified study of the boundaries where marine-terminating glaciers interact with the ocean. These dynamic and dangerous boundaries require creative methods of observation and measurement. Toward this effort, we take advantage of the exceptional sound-propagating properties of seawater to record and interpret sounds generated at these glacial ice-ocean boundaries from distances safe for instrument deployment and operation.

Pettit, E.C.; Nystuen, J.A.; O'Neel, Shad

2012-01-01

255

Status and distribution of the Kittlitz's Murrelet Brachyramphus brevirostris along the Alaska Peninsula and Kodiak and Aleutian Islands, Alaska  

USGS Publications Warehouse

The Kittlitz's Murrelet Brachyramphus brevirostris is adapted for life in glacial-marine ecosystems, being concentrated in the belt of glaciated fjords in the northern Gulf of Alaska from Glacier Bay to Cook Inlet. Most of the remaining birds are scattered along coasts of the Alaska Peninsula and Aleutian Islands, where they reside in protected bays and inlets, often in proximity to remnant glaciers or recently deglaciated landscapes. We summarize existing information on Kittlitz's Murrelet in this mainly unglaciated region, extending from Kodiak Island in the east to the Near Islands in the west. From recent surveys, we estimated that ~2400 Kittlitz's Murrelets were found in several large embayments along the Alaska Peninsula, where adjacent ice fields feed silt-laden water into the bays. On Kodiak Island, where only remnants of ice remain today, observations of Kittlitz's Murrelets at sea were uncommon. The species has been observed historically around the entire Kodiak Archipelago, however, and dozens of nest sites were found in recent years. We found Kittlitz's Murrelets at only a few islands in the Aleutian chain, notably those with long complex shorelines, high mountains and remnant glaciers. The largest population (~1600 birds) of Kittlitz's Murrelet outside the Gulf of Alaska was found at Unalaska Island, which also supports the greatest concentration of glacial ice in the Aleutian Islands. Significant populations were found at Atka (~1100 birds), Attu (~800) and Adak (~200) islands. Smaller numbers have been reported from Unimak, Umnak, Amlia, Kanaga, Tanaga, Kiska islands, and Agattu Island, where dozens of nest sites have been located in recent years. Most of those islands have not been thoroughly surveyed, and significant pockets of Kittlitz's Murrelets may yet be discovered. Our estimate of ~6000 Kittlitz's Murrelets along the Alaska Peninsula and Aleutian Islands is also likely to be conservative because of the survey protocols we employed (i.e. early seasonal timing of surveys, strip transects).

Madison, Erica N.; Piatt, John F.; Arimitsu, Mayumi L.; Romano, Marc D.; van Pelt, Thomas I.; Nelson, S. Kim; Williams, Jeffrey C.; DeGange, Anthony R.

2011-01-01

256

ASTER Image of Gangotri Glacier  

USGS Multimedia Gallery

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

257

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

258

1, 1739, 2007 Glacier balance  

E-print Network

TCD 1, 17­39, 2007 Glacier balance measurement, forecasting M. S. Pelto Title Page Abstract The Cryosphere Discussions is the access reviewed discussion forum of The Cryosphere Glacier annual balance balance measurement, forecasting M. S. Pelto Title Page Abstract Introduction Conclusions References

Paris-Sud XI, Université de

259

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

260

Digital outlines and topography of the glaciers of the American West  

USGS Publications Warehouse

Alpine glaciers have generally receded during the past century (post-“Little Ice Age”) because of climate warming (Oerlemans and others, 1998; Mann and others, 1999; Dyurgerov and Meier, 2000; Grove, 2001). This general retreat has accelerated since the mid 1970s, when a shift in atmospheric circulation occurred (McCabe and Fountain, 1995; Dyurgerov and Meier, 2000). The loss in glacier cover has had several profound effects. First, the shrinkage of glaciers results in a net increase in stream flow, typically in late summer when water supplies are at the lowest levels (Fountain and Tangborn, 1985). This additional water is important to ecosystems (Hall and Fagre, 2003) and to human water needs (Tangborn, 1980). However, if shrinkage continues, the net contribution to stream flow will diminish, and the effect upon these benefactors will be adverse. Glacier shrinkage is also a significant factor in current sea level rise (Meier, 1984; Dyurgerov and Meier, 2000). Second, many of the glaciers in the West Coast States are located on stratovolcanoes, and continued recession will leave oversteepened river valleys. These valleys, once buttressed by ice are now subject to failure, creating conditions for lahars (Walder and Driedger, 1994; O’Connor and others, 2001). Finally, reduction or loss of glaciers reduce or eliminate glacial activity as an important geomorphic process on landscape evolution and alters erosion rates in high alpine areas (Hallet and others, 1996). Because of the importance of glaciers to studies of climate change, hazards, and landscape modification, glacier inventories have been published for Alaska (Manley, in press), China (http://wdcdgg.westgis.ac.cn/DATABASE/Glacier/Glacier.asp), Nepal (Mool and others, 2001), Switzerland (Paul and others, 2002), and the Tyrolian Alps of Austria (Paul, 2002), among other locales. To provide the necessary data for assessing the magnitude and rate of glacier change in the American West, exclusive of Alaska (fig. 1), we are constructing a geographic information system (GIS) database. The data on glacier location and change will be derived from maps, ground-based photographs, and aerial and satellite images. Our first step, reported here, is the compilation of a glacier inventory of the American West. The inventory is compiled from the 1:100,000 (100K) and 1:24,000 (24K)-scale topographic maps published by the U.S. Geological Survey (USGS) and U.S. Forest Service (USFS). The 24K-scale maps provide the most detailed mapping of perennial snow and ice features. This report informs users of the data about the challenges we faced in compiling the data and discusses its errors and uncertainties. We rely on the expertise of the original cartographers in distinguishing “permanent snow and ice” from seasonal snow, although we know, through personal experience, of cartographic misjudgments. Whether “permanent” means indefinite or resident for several years is impossible to determine within the scope of this study. We do not discriminate between “glacier,” defined as permanent snow or ice that moves (Paterson, 1994), and stagnant snow and ice features. Therefore, we leave to future users the final determination of seasonal versus permanent snow features and the discrimination between true glaciers and stagnant snow and ice bodies. We believe that future studies of more regional focus and knowledge can most accurately refine our initial inventory. For simplicity we refer to all snow and ice bodies in this report as glaciers, although we recognize that most probably do not strictly meet the requirements; many may be snow patches.

Fountain, Andrew G.; Hoffman, Matthew; Jackson, Keith; Basagic, Hassan; Nylen, Thomas; Percy, David

2007-01-01

261

Indicators of recent environmental change in Alaska  

SciTech Connect

Climate models predict that global warming due to the effects of increasing trace gases will be amplified in northern high latitude regions, including Alaska. Several environmental indicators, including tree-ring based temperature reconstructions, borcal forest growth measurements and observations of glacial retreat all indicate that the general warming of the past century has been significant relative to prior centuries to millenia. The tree-ring records for central and northern Alaska indicate that annual temperature increased over the past century, peaked in the 1940s, and are still near the highest level for the past three centuries (Jacoby and D`Arrigo 1995). The tree-ring analyses also suggest that drought stress may now be a factor limiting growth at many northern sites. The recent warming combined with drier years may be altering the response of tree growth to climate and raising the likelihood of forest changes in Alaska and other boreal forests. Other tree-ring and forest data from southern and interior Alaska provide indices of the response of vegetation to extreme events (e.g., insect outbreaks, snow events) in Alaska (Juday and marler 1996). Historical maps, field measurements and satellite imagery indicate that Alaskan glaciers have receded over the past century (e.g., Hall and Benson 1996). Severe outbreaks of bark beetles may be on the increase due to warming, which can shorten their reproductive cycle. Such data and understanding of causes are useful for policy makers and others interested in evaluation of possible impacts of trace-gas induced warming and environmental change in the United States.

Jacoby, G.C.; D`Arrigo, R.D.; Juday, G.

1997-12-31

262

Termini of calving glaciers as self-organized critical systems  

NASA Astrophysics Data System (ADS)

Over the next century, one of the largest contributions to sea level rise will come from ice sheets and glaciers calving ice into the ocean. Factors controlling the rapid and nonlinear variations in calving fluxes are poorly understood, and therefore difficult to include in prognostic climate-forced land-ice models. Here we analyse globally distributed calving data sets from Svalbard, Alaska (USA), Greenland and Antarctica in combination with simulations from a first-principles, particle-based numerical calving model to investigate the size and inter-event time of calving events. We find that calving events triggered by the brittle fracture of glacier ice are governed by the same power-law distributions as avalanches in the canonical Abelian sandpile model. This similarity suggests that calving termini behave as self-organized critical systems that readily flip between states of sub-critical advance and super-critical retreat in response to changes in climate and geometric conditions. Observations of sudden ice-shelf collapse and tidewater glacier retreat in response to gradual warming of their environment are consistent with a system fluctuating around its critical point in response to changing external forcing. We propose that self-organized criticality provides a yet unexplored framework for investigations into calving and projections of sea level rise.

Åström, J. A.; Vallot, D.; Schäfer, M.; Welty, E. Z.; O'Neel, S.; Bartholomaus, T. C.; Liu, Yan; Riikilä, T. I.; Zwinger, T.; Timonen, J.; Moore, J. C.

2014-12-01

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

Alaska's Economy: What's Ahead?  

ERIC Educational Resources Information Center

This review describes Alaska's economic boom of the early 1980s, the current recession, and economic projections for the 1990s. Alaska's economy is largely influenced by oil prices, since petroleum revenues make up 80% of the state government's unrestricted general fund revenues. Expansive state spending was responsible for most of Alaska's…

Alaska Review of Social and Economic Conditions, 1987

1987-01-01

265

Climate variations and changes in mass of three glaciers in western North America  

USGS Publications Warehouse

Time series of net and seasonal mass balances for three glaciers in western North America, one in the Pacific Northwest and two in Alaska, show various relationships to Pacific hemisphere climate indexes. During the winter season the two coastal, maritime-regime glaciers, over 2000 km apart, are affected almost identically, albeit inversely, by atmospheric and oceanic conditions in both the tropical and North Pacific. The two Alaska glaciers, only 350 km apart, have almost no coherence. Lag correlations show that in winter the maritime glaciers are influenced by concurrent conditions in the North Pacific, but by conditions in the tropical Pacific in August-September of the prior northern summer. The winter balance variations contain interannual El Nino-Southern Oscillation variability superimposed on North Pacific interdecadal variability; the interdecadal 1976-77 climate regime shift is clearly evident. The summer balances and the continental-regime glacier have a general lack of correlations, with no clear, strong, consistent patterns, probably a result of being influenced more by local processes or by circulation patterns outside the Pacific Ocean basin. The results show the Pacific Northwest is strongly influenced by conditions in the tropical Pacific, but that this teleconnection has broken down in recent years, starting in 1989. During the seven years since then (1989-95), all three glaciers have shown, for the first time, coherent signals, which were net mass loss at the highest rate in the entire record. The authors' results agree with those of other recent studies that suggest these recent years are unusual and may be a signature of climate warming.

Hodge, S.M.; Trabant, D.C.; Krimmel, R.M.; Heinrichs, T.A.; March, R.S.; Josberger, E.G.

1998-01-01

266

UNIVERSITY of ALASKA ANCHORAGE ALASKA JUSTICE FORUM  

E-print Network

. Total Number of Charges, Age 6­17 Column percentages. Source of data: Alaska Division of Juvenile Vol. 27, No. 1 Please see Sex offenders, page 7 Sex Offenders in the Alaska Juvenile Justice System André B. Rosay and Ronald S. Everett This article looks at the characteristics of 29 juvenile sex

Pantaleone, Jim

267

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

268

Instructions for Glacier Recession Lesson Objective: Students will learn  

E-print Network

Instructions for Glacier Recession Lesson Objective: Students will learn: - about the connection between glaciers and climate, - why glacial studies are important, - how glacier recession affects humanity, and - how humans are affecting glaciers. Materials: Movie ­ Inconvenient Truth For Exercise

269

The Gravina Sequence: Remnants of a Mid-Mesozoic oceanic arc in southern southeast Alaska  

NASA Astrophysics Data System (ADS)

Fragments of Upper Jurassic to Lower Cretaceous volcanic and basinal strata constitute the Gravina belt in southeast Alaska. In the Ketchikan area the Gravina belt is made up of two lithotectonic units. The lower unit consists of coarse marine pyroclastic and volcaniclastic strata, mafic flows, breccia, and fine-grained tuff which are locally intruded by hypabyssal bodies of diorite and quartz diorite. The volcanic rocks are characterized by tholeiitic arc basalts, lack felsic volcanic strata, and overlie Upper Triassic and older strata of the Alexander terrane. Augite and/or hornblende-bearing porphyritic rocks are common and locally intrude the Alexander terrane basement, where they are thought to represent the intrusive equivalents of lavas within the section. Age constraints for the volcanic unit, based on structural and stratigraphic relations with adjacent units, are late Middle to Late Jurassic. The Gravina belt upper unit consists of fine- to coarse-grained turbidites and related conglomeratic channel-fill deposits. The basinal rocks unconformably overlie Permian and Triassic rocks of the Taku terrane and remnants of the lower volcanic part of the Gravina sequence which overlie the Alexander terrane. The conglomerate units contain mostly volcanic and plutonic lithic clasts, some of which yield Pb-U zircon ages of 154-158 Ma. The predominance of pyroclastic deposits interbedded with massive flows, tuff, breccia, and argillaceous turbidites, and the lithologic and chemical composition of the volcanic rocks indicate a submarine volcanic arc setting for the Gravina sequence. The basinal pyroclastic rocks are inferred to have been shed from submarine stratovolcanos during the Late Jurassic. Epiclastic rocks were deposited as submarine fans, derived in part from erosion of a magmatic arc. The presence of fine-grained tuffaceous turbidites implies ongoing, but distant, volcanism. The pyroclastic and volcaniclastic rocks represent remnants of a Late Jurassic oceanic arc constructed on a composite basement consisting of the Alexander and Taku terranes. The strata accumulated in an intra-arc basin on the eastern edge of the Alexander terrane. The volcanic and basinal rocks were deformed during a major mid-Cretaceous intra-arc contractional event, in conjunction with the emplacement of a distinctly younger, arc-related plutonic suite.

Rubin, Charles M.; Saleeby, Jason B.

1991-08-01

270

Characteristics of sediment discharge in the subarctic Yukon River, Alaska  

USGS Publications Warehouse

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 and temperature near the estuary and in the middle of Yukon River by using self-recording turbidimeters and temperature data loggers. The water turbidity (ppm) was converted to suspended sediment concentration (SSC; mg/l) of river water, using a relation between simultaneous turbidity and SSC at each of the two sites, and then, the suspended sediment discharge, approximately equal to water discharge times SSC, was numerically obtained every 1 or 2 h. It should be noted that the sediment discharge in the Yukon River is controlled by SSC rather than water discharge. As a result, a peak sediment discharge occurred in mid or late August by local sediment runoffs due to glacier-melt (or glacier-melt plus rainfall), while a peak water discharge was produced by snowmelt in late June or early July. Application of the "extended Shields diagram" indicates that almost all the river-transported sediments are under complete suspension. ?? 2002 Elsevier Science B.V. All rights reserved.

Chikita, K.A.; Kemnitz, R.; Kumai, R.

2002-01-01

271

Glacier Shrinkage and Effects on Alpine Hydrology  

NASA Astrophysics Data System (ADS)

Alpine glaciers cover an area of about 553 km2 in seven western states of the American West. With few exceptions, all glaciers have been shrinking over the past century and the rate of shrinkage has accelerated over the past few decades. Overall, smaller glaciers exhibit greatest shrinkage, relative to their size, compared to larger glaciers. Preliminary results from studies of glacier change in several national parks reveal the spatial pattern of glacier change. Glacier shrinkage, while contributing to global sea level change, has two important local effects. First, the net release of water from its storage in the frozen state enhances overall stream discharge. Second, the shrinking area of glaciers reduces their moderating effect on stream flow, particularly during late-summer and drought periods, and shifts peak runoff towards early summer. Consequently these alpine basins become more susceptible to future drought. In addition to these "clean" glaciers, debris-covered glaciers are probably important as well. Debris-covered glaciers melt at much slower rates than adjacent "clean" glaciers, with reduced daily variations in melt because of the insulation provided by the surface debris layer. The number and extent of debris-covered glaciers in the American west is not well known therefore their hydrological contribution is uncertain. However, if the number of debris-covered glaciers can be scaled from an inventory of those in the Rocky Mountain National Park (Achuff, 2003), the volume of debris-covered ice may be considerable. From an ecological perspective, the greatest effects are in the high alpine regions where glacier recession opens new areas for biological expansion, and where the hydrological dependence on glaciers is greatest. Lesser effects, related to suspended sediment loads, are felt well downstream (10's km) from glaciers.

Basagic, H.; Fountain, A. G.; Clark, D. H.

2004-12-01

272

Taku Elementary School 20072008 Taku Elementary provides a welcoming, safe  

E-print Network

teachers; music, art, library and PE teachers; and two bilingual tutors. We also added a Health, and is fortunate to have an active PTA. We work together for the benefit of all students, providing many enriching Education Program. AEIN is funded under a $9.3 million grant from the U.S. Department of Education

Pantaleone, Jim

273

Seaonalities of glacier changes on the polythermal glaciers, Nyainqêntanglha Range  

NASA Astrophysics Data System (ADS)

The climatic variables are supposed to be the influential factors for the summer accumulation type glaciers in the Nyainqêntanglha Range, Tibetan Plateau. There are certainly unique regional climate regimes within this area during different seasons. In the summer season, the prevailing regional climate is controlled by a plenty of moisture transported by the warm summer monsoons, while it is getting colder and drier by the westerlies from the inland of Eurasia in the winter season. The impact of the resultant local hydro-thermal condition fluctuation on the the glacier dynamics is still not well understood. In this study, the seasonal patterns of glacier behaviors are estimated in terms of glacier surface displacements under a certain climatological state (2006-2009). The glacier surface displacements are derived from Landsat imageries by using the feature tracking method. The land surface temperatures and precipitations are selected as the representative parameters of the regional climate in the Nyainqêntanglha Range. According to the tendency analysis, the apparent annual cycle of precipitation and land surface temperature are recognized. At the same time, the diurnal change of land surface temperature (>0°C mostly in the daytime,

Shi, Junchao; Menenti, Massimo

2014-05-01

274

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

Microsoft Academic Search

Equilibrium-line altitudes (ELAs) of modem glaciers in the northern Rocky Mountains are known to correspond with regional climate, but strong subregional gradients such as across the Continental Divide in Glacier National Park, Montana, also exert topoclimatic influences on the ELA. This study analyzed the relationships between glacier and snowfield morphology, ELA, and surrounding topography. Glaciers and perennial snowfields were mapped

Thomas R. Allen

1998-01-01

275

Alaska Volcano Observatory  

USGS Publications Warehouse

Steam plume from the 2006 eruption of Augustine volcano in Cook Inlet, Alaska. Explosive ash-producing eruptions from Alaska's 40+ historically active volcanoes pose hazards to aviation, including commercial aircraft flying the busy North Pacific routes between North America and Asia. The Alaska Volcano Observatory (AVO) monitors these volcanoes to provide forecasts of eruptive activity. AVO is a joint program of the U.S. 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). AVO is one of five USGS Volcano Hazards Program observatories that monitor U.S. volcanoes for science and public safety. Learn more about Augustine volcano and AVO at http://www.avo.alaska.edu.

Venezky, Dina Y.; Murray, Tom; Read, Cyrus

2008-01-01

276

Aletsch Glacier, Switzerland  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

2002-01-01

277

Modelling Greenland Outlet Glaciers  

NASA Technical Reports Server (NTRS)

The objective of this project was to develop simple yet realistic models of Greenland outlet glaciers to better understand ongoing changes and to identify possible causes for these changes. Several approaches can be taken to evaluate the interaction between climate forcing and ice dynamics, and the consequent ice-sheet response, which may involve changes in flow style. To evaluate the icesheet response to mass-balance forcing, Van der Veen (Journal of Geophysical Research, in press) makes the assumption that this response can be considered a perturbation on the reference state and may be evaluated separately from how this reference state evolves over time. Mass-balance forcing has an immediate effect on the ice sheet. Initially, the rate of thickness change as compared to the reference state equals the perturbation in snowfall or ablation. If the forcing persists, the ice sheet responds dynamically, adjusting the rate at which ice is evacuated from the interior to the margins, to achieve a new equilibrium. For large ice sheets, this dynamic adjustment may last for thousands of years, with the magnitude of change decreasing steadily over time as a new equilibrium is approached. This response can be described using kinematic wave theory. This theory, modified to pertain to Greenland drainage basins, was used to evaluate possible ice-sheet responses to perturbations in surface mass balance. The reference state is defined based on measurements along the central flowline of Petermann Glacier in north-west Greenland, and perturbations on this state considered. The advantage of this approach is that the particulars of the dynamical flow regime need not be explicitly known but are incorporated through the parameterization of the reference ice flux or longitudinal velocity profile. The results of the kinematic wave model indicate that significant rates of thickness change can occur immediately after the prescribed change in surface mass balance but adjustments in flow rapidly diminish these rates to a few cm/yr at most. The time scale for adjustment is of the order of a thousand years or so.

vanderVeen, Cornelis; Abdalati, Waleed (Technical Monitor)

2001-01-01

278

The Alaska Climate Research Center  

NSDL National Science Digital Library

The University of Fairbanks's Alaska Climate Research Center offers a host of materials about its climate research and about Alaska's climate in general. The website supplies abstracts of the Center's research projects such as _The Urban Heat Island Effect at Fairbanks, Alaska_ and _Radiation Climatology of Alaska_. Researchers can find data and statistics on Alaska's temperature, humidity, precipitation, cloudiness, pressure, and wind. The website provides Climographs for various areas throughout the state. Students can discover how latitude, continentiality, and elevation affect Alaska's climate.

279

High Altitude Glaciers in the Tropics  

NSDL National Science Digital Library

While it may seem like a contradiction, glaciers do exist in the tropical latitudes. In this video produced by ThinkTV, learn about tropical glaciers and why scientists are studying them to better understand global climate change.

Thinktv

2010-11-30

280

NASA's DESDynI in Alaska  

NASA Astrophysics Data System (ADS)

In 2007 the National Research Council Earth Science Decadal Survey, Earth Science Applications from Space, recommended an integrated L-band InSAR and multibeam Lidar mission called DESDynI (Deformation, Ecosystem Structure, and Dynamics of Ice) and it is scheduled for launch in 2017. The NASA InSAR and Lidar mission is optimized for studying geohazards and global environmental change. The complex plate boundary in southern coastal Alaska provides an excellent setting for testing DESDynI capabilities to recover fundamental parameters of glacio-seismotectonic processes. Also, aircraft and satellites acquisitions of Lidar and L-band SAR have been made in this region in the last decade that can be used for DESDynI performance simulations. Since the Lidar observations would penetrate most vegetation, the accurate bald Earth elevation profiles will give new elevation information beyond the standard 30-m digital elevation models (DEM) and the Lidar-derived elevations will provide an accurate georeferenced surface for local and regional scale studies. In an earlier study we demonstrated how the Lidar observations could be used in combination with SAR to generate an improved InSAR derived DEM in the Barrow, Alaska region [Atwood et al., 2007]; here we discuss how Lidar could be fused with L-band SAR in more rugged, vegetated terrane. Based on simulations of multi-beam Lidar instrument performance over uplifted marine terraces, active faults and folds, uplift associated with the 1899 Yakataga seismic event (M=8), and elevation change on the glaciers in southern, coastal Alaska, we report on the significance of the DESDynI Lidar contiguous 25 m footprint elevation profiles for EarthScope related studies in Alaska. We are using the morphology and dynamics of glaciers derived from L-band SAR ice velocities to infer the large scale sub-ice structures that form the structural framework of the Seward-Bagley Basins. Using primarily winter acquisitions of L-band SAR data from ALOS/PALSAR (Mode: Fine beam, HH) we have been able to estimate ice velocities from offset-tracking in the Upper and Lower Seward Basin even though the acquisitions are 46 days apart. We anticipate with the shorter repeat time for DESDynI-SAR acquisitions that we will be able to estimate seasonal ice velocities over a larger range of regions within both the ablation and accumulation zones.

Sauber, J. M.; Hofton, M. A.; Bruhn, R. L.; Forster, R. R.; Burgess, E. W.; Cotton, M. M.

2010-12-01

281

Glacier Mass Balance measurements in Bhutan  

NASA Astrophysics Data System (ADS)

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

Jackson, Miriam; Tenzin, Sangay; Tashi, Tshering

2014-05-01

282

Dissolved organic matter export in glacial and non-glacial streams along the Gulf of Alaska  

NASA Astrophysics Data System (ADS)

The Gulf of Alaska drainage basin contains more than 75,000 km2 of glaciers, many of which are rapidly thinning and receding. We are using a paired watershed approach to evaluate how changes in glacier ecosystems will impact the export dissolved organic matter (DOM) into the Gulf of Alaska. Our primary study watersheds, Lemon Creek and Montana Creek, are similar in size, bedrock lithology and elevation range and extend from near sea level to the margin or interior of the Juneau Icefield. Lemon Creek has a glacial coverage of ~60%, while Montana Creek is free of glacier ice. Our goal is to evaluate seasonal differences in the quantity, chemical character and reactivity of DOM being exported from these watersheds to downstream near-shore marine ecosystems. In addition, we are monitoring a variety of physical parameters that influence instream DOM metabolism in both watersheds. Our initial results from the 2009 runoff season indicate that concentrations of dissolved organic carbon (DOC) are substantially higher in the non-glacial watershed. However, fluorescence analyses indicate that DOM from the glacier watershed has a higher protein and lower humic material content compared to DOM from the non-glacial watershed. After the spring snowmelt season, physical parameters between the two watersheds diverged, with higher streamflow and turbidity as well as colder water temperatures in the glacial watershed. Although our previous yield calculations show significantly higher DOC fluxes from the forested watershed, our results here suggest that glacier watersheds may be an important source of labile carbon to the near shore marine ecosystem. The contrast in the physical habitat between the two rivers (e.g glacier stream = cold, low light penetration, unstable substrate) supports the hypothesis that that in-stream DOM processing is limited within glacier dominated rivers, therefore delivering a higher percentage of labile DOM downstream.

Hood, E. W.; Scott, D.; Jeffery, A.; Schreiber, S.; Heavner, M.; Edwards, R.; D'Amore, D. V.; Fellman, J.

2009-12-01

283

Glaciers and icecaps: Storehouses of freshwater  

NSDL National Science Digital Library

Glacier: Complete description of what glaciers and icecaps are and why they are important to us. Maps show the location of glaciers and icecaps. This resource is part of the "Water Science for Schools" collection at the United States Geological Survey.

2008-05-28

284

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

285

Four+ Years of Measurements from the Mendenhall Glacier Terminus  

NASA Astrophysics Data System (ADS)

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

Heavner, M.; Fatland, D. R.

2012-12-01

286

ALASKA CRUISE SHIP INITIATIVE  

EPA Science Inventory

During the course of the annual vacation season, luxury cruise ships carrying up to 3000 passengers visit the coastal cities and small towns of Alaska. Alaska is the first state to impose regulations requiring such vessels to submit to inspection and monitoring of gray water and...

287

Alaska Library Directory, 1996.  

ERIC Educational Resources Information Center

This directory of Alaska's Libraries lists: members of the Alaska Library Association (AkLA) Executive Council and Committee Chairs; State Board of Education members; members of the Governor's Advisory Council on Libraries; school, academic and public libraries and their addresses, phone and fax numbers, and contact persons; personal,…

Jennings, Mary, Ed.

288

Alaska geothermal bibliography  

SciTech Connect

The Alaska geothermal bibliography lists all publications, through 1986, that discuss any facet of geothermal energy in Alaska. In addition, selected publications about geology, geophysics, hydrology, volcanology, etc., which discuss areas where geothermal resources are located are included, though the geothermal resource itself may not be mentioned. The bibliography contains 748 entries.

Liss, S.A.; Motyka, R.J.; Nye, C.J. (comps.)

1987-05-01

289

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

290

The effect of glaciers on streamflow variations.  

USGS Publications Warehouse

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

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

1985-01-01

291

Glacier recession in Iceland and Austria  

SciTech Connect

It has been possible to measure glacier recession on the basis of Landsat data, in conjunction with comparisons of the magnitude of recession of a glacier margin with in situ measurements at fixed points along the same margin. Attention is presently given to the cases of Vatnajokull ice cap, in Iceland, and the Pasterze Glacier, in Austria, on the basis of satellite data from 1973-1987 and 1984-1990, respectively. Indications of a trend toward negative mass balance are noted. Nevertheless, while most of the world's small glaciers have been receding, some are advancing either due to local climate or the tidewater glacier cycle. 21 refs.

Hall, D.K.; Williams, R.S. Jr.; Bayr, K.J. (NASA, Goddard Space Flight Center, Greenbelt, MD (United States) USGS, Reston, VA (United States) Keene State College, NH (United States))

1992-03-01

292

Glacier recession in Iceland and Austria  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

293

Light Iceland Glacier Recession 1973 to 2000  

NSDL National Science Digital Library

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

Perkins, Lori; Hall, Dorothy

2001-04-09

294

Glaciomarine deposits of Miocene through Holocene age in the Yakataga Formation along the Gulf of Alaska margin, Alaska  

USGS Publications Warehouse

Perhaps the world's longest and most complete onshore sedimentary record of late Cenozoic glaciation is preserved in the Gulf of Alaska Tertiary province that extends 800 km along the coast of southern Alaska. The Yakataga Formation, with an aggregate outcrop thickness of about 5,000 m, is characterized by variable amounts of distinctive neritic marine tillite-like diamictite and laminated siltstone containing dropstones interpreted as ice-rafted glacial debris. The lithology, sedimentary structures and molluscan fauna of the formation suggest that active tidal glaciers or an ice shelf were present along the landward margin of the basin possibly beginning in early or early middle Miocene time. Dropstone distribution in outcrop sections indicates that glaciers reached tidewater intermittently during the Miocene and were almost continually present throughout the Pliocene and much of the Pleistocene. Paleomagnetic and nannoplankton dating of the upper 1,181 m of the Yakataga Formation at Middleton Island indicate that this part of the sequence probably was entirely deposited during the Matuyama reversed polarity epoch of the Pleistocene during which the sedimentation rate was of the order of 1 m/1,000 years. Lithologically similar deposits of poorly consolidated sandy mud and pebbly mud continue to accumulate locally near tidal glaciers in the same area, and older late Quaternary deposits are undoubtedly present offshore. The anomalous late Cenozoic glaciation recorded in the sediments along the Gulf of Alaska margin reflects a fortuitous combination of a subsiding shelf basin adjacent to an area of extremely high elevations and exceptionally heavy precipitation, an environment that persists to the present.

Plafker, George; Addicott, W.O.

1976-01-01

295

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.

296

Alaska Historical Society  

NSDL National Science Digital Library

This visually arresting site from the Alaska Historical Society is a superb resource for teachers of history and social studies, or for anyone fascinated by the 49th state. Discover AlaskaâÂÂs History is a great place to start. After perusing the FAQs, readers may wish to look at the subheading, For Teachers and Students, where Alaskan history has been divided into easily digestible categories such as 1989 Exxon Valdez Oil Spill, Great Alaska Earthquake of 1964, and Alaska Statehood and Constitutional Convention 1955/1956, with corresponding articles and links. The For Researchers section offers links to helpful resources around the web. The weekly AHS Blog is a well-composed and informative romp through AlaskaâÂÂs past, with posts covering canneries and gold camps, baseball and boats.

297

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

298

A database of worldwide glacier thickness observations  

NASA Astrophysics Data System (ADS)

One of the grand challenges in glacier research is to assess the total ice volume and its global distribution. Over the past few decades the compilation of a world glacier inventory has been well-advanced both in institutional set-up and in spatial coverage. The inventory is restricted to glacier surface observations. However, although thickness has been observed on many glaciers and ice caps around the globe, it has not yet been published in the shape of a readily available database. Here, we present a standardized database of glacier thickness observations compiled by an extensive literature review and from airborne data extracted from NASA's Operation IceBridge. This database contains ice thickness observations from roughly 1100 glaciers and ice caps including 550 glacier-wide estimates and 750,000 point observations. A comparison of these observational ice thicknesses with results from area- and slope-dependent approaches reveals large deviations both from the observations and between different estimation approaches. For glaciers and ice caps all estimation approaches show a tendency to overestimation. For glaciers the median relative absolute deviation lies around 30% when analyzing the different estimation approaches. This initial database of glacier and ice caps thickness will hopefully be further enlarged and intensively used for a better understanding of the global glacier ice volume and its distribution.

Gärtner-Roer, I.; Naegeli, K.; Huss, M.; Knecht, T.; Machguth, H.; Zemp, M.

2014-11-01

299

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.

300

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

301

Spatially heterogeneous wastage of Himalayan glaciers  

PubMed Central

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

Fujita, Koji; Nuimura, Takayuki

2011-01-01

302

The status of glaciers in Sikkim Himalaya  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

303

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

304

Mountain Glaciers and Ice Caps  

USGS Publications Warehouse

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

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

2011-01-01

305

Icebergs and Glaciers: Unit Outlines  

NSDL National Science Digital Library

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

Jessica Fries-Gaither

306

Response of debris-covered glaciers to climate change  

Microsoft Academic Search

The presence of supraglacial debris strongly influences glacier ablation, and the mass balance of debris-covered glaciers differs significantly from that of clean glaciers in similar climatic settings. Predicting the response of debris-covered glaciers to climate change is important for hazard mitigation strategies in many high mountain environments, especially where temporary lakes are likely to form on stagnating glacier tongues. Accurate

D. I. Benn; N. Lindsey; H. Kathryn

2004-01-01

307

Quantifying Global Warming from the Retreat of Glaciers  

Microsoft Academic Search

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

Johannes Oerlemans

1994-01-01

308

Spatial variability in the flow of a valley glacier: Deformation of a large array of boreholes  

NASA Astrophysics Data System (ADS)

Measurements of the deformation of a dense array of boreholes in Worthington Glacier, Alaska, show that the glacier moves with generally bed-parallel motion. Strain in the 200 m deep valley glacier is constant near the surface but follows a nonlinear vertical profile below a depth of about 120 m. By a depth of 180 m, the octahedral strain rate reaches 0.35 yr-1. The three-dimensional velocity field shows spatial complexity with significant deviations from plane strain, despite relatively simple valley geometry in the vicinity of the 6×106 m3 study volume. No evidence was found for time-varying deformation or movement along localized shear planes. Observations were made by repeatedly measuring the long-axis geometry of 31 closely spaced boreholes over a 70 day period, and three additional holes after 1 full year of deformation. The holes were spaced 15 to 30 m apart. Installation and measurement of such a large number of boreholes required the development of a semiautomated hot water drilling system that creates straight and vertical boreholes with uniform walls. The equipment and procedures enables borehole profiles to be measured without the use of hole casing. Inclinometry measurements collected in the holes were processed, analyzed for error, and visualized as a fully three-dimensional data set. The new methods offer unique insight into small-scale spatial and temporal variations in the pattern of flow in a valley glacier.

Harper, Joel T.; Humphrey, Neil F.; Pfeffer, W. Tad; Huzurbazar, Snehalata V.; Bahr, David B.; Welch, Brian C.

2001-05-01

309

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

310

Alaska Resource Data File, Nabesna quadrangle, Alaska  

USGS Publications Warehouse

Descriptions of the mineral occurrences shown on the accompanying figure follow. See U.S. Geological Survey (1996) for a description of the information content of each field in the records. The data presented here are maintained as part of a statewide database on mines, prospects and mineral occurrences throughout Alaska.

Hudson, Travis L.

2003-01-01

311

ALASKA JUSTICE FORUM UNIVERSITY of ALASKA ANCHORAGE  

E-print Network

Vol. 23, No. 4 Please see Expenditures, page 10 HIGHLIGHTS INSIDE THIS ISSUE · A detailed review of a book on terrorism and the U.S. Constitution in the era of the war on terror (page 2). · Results;2 Alaska Justice Forum 23(4), Winter 2007 Review Essay Terrorism and the Constitution: Security, Civil

Pantaleone, Jim

312

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

313

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

Microsoft Academic Search

Glacier volume response time is a measure of the time taken for a glacier to adjust its geometry to a climate change. It has been previously proposed that the volume response time is given approximately by the ratio of glacier thickness to ablation at the glacier terminus. We propose a new conceptual model of glacier hypsometry (area-altitude relation) and derive

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

2009-01-01

314

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

315

GLACIER HAZARDS AT BELVEDERE GLACIER AND THE MONTE ROSA EAST FACE, ITALIAN ALPS: PROCESSES AND MITIGATION  

E-print Network

are extending towards danger zones in the cryospheric systems. A number of recent glacier hazards and disasters particularly affects terrestrial systems where surface and sub-surface ice is involved. Changes in glacier

Kääb, Andreas

316

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.

2008-11-04

317

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.

318

NOAA Fisheries Alaska Region  

E-print Network

Mondragon Catch Accounting/Data Quality Alan Kinsolving Fishery Regulation Specialist Jason Gasper ResourceNOAA Fisheries Alaska Region Glenn Merrill Assistant Regional Administrator for Sustainable Fisheries Rachel Baker CSP, Allocation Forrest Bowers Fishery Management Specialist Gretchen Harrington

319

Alaska telemedicine: growth through collaboration.  

PubMed

The last thirty years have brought the introduction and expansion of telecommunications to rural and remote Alaska. The intellectual and financial investment of earlier projects, the more recent AFHCAN Project and the Universal Service Administrative Company Rural Health Care Division (RHCD) has sparked a new era in telemedicine and telecommunication across Alaska. This spark has been flamed by the dedication and collaboration of leaders at he highest levels of organizations such as: AFHCAN member organizations, AFHCAN Office, Alaska Clinical Engineering Services, Alaska Federal Health Care Partnership, Alaska Federal Health Care Partnership Office, Alaska Native health Board, Alaska Native Tribal health Consortium, Alaska Telehealth Advisory Council, AT&T Alascom, GCI Inc., Health care providers throughout the state of Alaska, Indian Health Service, U.S. Department of Health and Human Services, Office of U.S. Senator Ted Steens, State of Alaska, U.S. Department of Homeland Security--United States Coast Guard, United States Department of Agriculture, United States Department of Defense--Air Force and Army, United States Department of Veterans Affairs, University of Alaska, and University of Alaska Anchorage. Alaska now has one of the largest telemedicine programs in the world. As Alaska moves system now in place become self-sustaining, and 2) collaborating with all stakeholders in promoting the growth of an integrated, state-wide telemedicine network. PMID:15709313

Patricoski, Chris

2004-12-01

320

HIGH ICE, Continuation Some glacier image analysis capabilities  

E-print Network

, 20002000 lake outlines from Benn and others, 2000 #12;ASTER Level 2 relative DEM over western Axel Heiberg Island glaciers ASTER 3NASTER 3N #12;View from top ofView from top of Llewellyn GlacierLlewellyn Glacier

321

1. PARKING LOT AT GLACIER POINT. HALF DOME AT CENTER ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. PARKING LOT AT GLACIER POINT. HALF DOME AT CENTER REAR. LOOKING NE. GIS: N-36 43 45.8 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

322

5. GLACIER POINT ROAD VIEW AT SENTINEL DOME PARKING AREA. ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. GLACIER POINT ROAD VIEW AT SENTINEL DOME PARKING AREA. LOOKING E. GIS: N-37 42 43.8 / W-119 35 12.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

323

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

324

Winter speed-up of ice flow at quiescent surge-type glaciers in Yukon, Canada  

NASA Astrophysics Data System (ADS)

Glacier surge exhibits order-of-magnitude faster velocity and km-scale terminus advance during its short active phase after a long quiescent period. The observations of glacier surge are still limited, and the mechanisms of glacier surge cycle remain elusive. Moreover, with the exception of several well-examined glaciers, the glacier dynamics during their quiescent periods remains even more uncertain due to the paucity of surface velocity measurement data. Here we examined spatial-temporal changes in the ice surface velocity of surge-type glaciers in the St. Elias Mountains near the border of Alaska and Yukon during the period from December 2006 to March 2011. We applied the offset-tracking (feature-tracking) technique to the L-band synthetic aperture radar (SAR) images derived from the Japanese Advanced Land Observation Satellite (ALOS). The Chitina, Anderson, Walsh, and Logan Glaciers, the major subpolar surge-type glaciers of the Chitina River valley system, could be examined with the highest temporal resolution because of the overlap of multiple satellite tracks. We have found significant upstream accelerations from fall to winter at a number of glaciers during their quiescence. Moreover, whereas the upstream propagating summer speed-up was observed, the winter speed-up propagated from upstream to downglacier. Although the winter speed-up seems to be at odds with the well-known summer speed-up, these observations are consistent with the fragmentary but well-known fact of glacier surge that often initiates in winter, suggesting that some of the mechanisms would be valid even during quiescent phases. Ice surface velocity at mountain glaciers and ice sheets typically exhibits the greatest acceleration from spring to early summer, followed by deceleration in mid-summer to fall, and is slowest in winter. These short-term velocity changes are attributed to subglacial slip associated with water pressure changes that occur because of the seasonal variability of meltwater input, and the evolution of the englacial and subglacial hydrologic systems. Meltwater penetration to the bed in the early melt season enhances the basal water pressure in the subglacial drainage systems, lubricating the interface between the ice and the bed. As the meltwater flux increases further, the cavities grow as a result of frictional wall melting, and the water pressure is reduced, leading to slow down of surface velocities. Meanwhile, the initiation of glacier surge has been often observed in winter, which has been interpreted as an inefficient subglacial drainage system and subsequent high water pressure to trigger a surge. However, it has been uncertain how and where water can accumulate in winter. Because the examined surge-type glaciers are largely in sub-polar settings, the present findings of winter speed-up would further reinforce the paradoxical water storage problem in the surge triggering mechanism. The seasonal evolution of subglacial drainage systems and water pressure seems to have been modeled on the assumption of hard bed, which seems more difficult to store water in winter. One possible interpretation of the winter speed-up is, instead of accelerated sliding in winter, an enhanced deformation of subglacial till whose strength is weakened due to the higher pore-water pressure inside the till. We will discuss other speculations on the causes of the winter speed-up.

Furuya, M.; Abe, T.

2013-12-01

325

Mapping Svalbard Glaciers with the Cryowing Uas  

NASA Astrophysics Data System (ADS)

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

Solbø, S.; Storvold, R.

2013-08-01

326

Attribution of glacier fluctuations to climate change  

NASA Astrophysics Data System (ADS)

Glacier retreat is a worlwide phenomenon, which started around the middle of the 19th century. During the period 1800-1850 the number of retreating and advancing glaciers was roughly equal (based on 42 records from different continents). During the period 1850-1900 about 92% of all mountain glaciers became shorter (based on 65 records). After this, the percentage of shrinking glaciers has been around 90% until the present time. The glacier signal is rather coherent over the globe, especially when surging and calving glaciers are not considered (for such glaciers the response to climate change is often masked by length changes related to internal dynamics). From theoretical studies as well as extensive meteorological work on glaciers, the processes that control the response of glaciers to climate change are now basically understood. It is useful to make a difference between geometric factors (e.g. slope, altitudinal range, hypsometry) and climatic setting (e.g. seasonal cycle, precipitation). The most sensitive glaciers appear to be flat glaciers in a maritime climate. Characterizing the dynamic properties of a glacier requires at least two quantities: the climate sensitivity, expressing how the equilibrium glacier state depends on the climatic conditions, and the response time, indicating how fast a glacier approaches a new equilibrium state after a stepwise change in the climatic forcing. These quantities can be estimated from relatively simple theory, showing that differences among glaciers are substantial. For larger glaciers, climate sensitivities (in terms of glacier length) vary from 1 to 8 km per 100 m change in the equilibrium-line altitude. Response times are mainly in the range of 20 to 200 years, with most values between 30 and 80 years. Changes in the equilibrium-line altitude or net mass balance of a glacier are mainly driven by fluctuations in air temperature, precipitation, and global radiation. Energy-balance modelling for many glaciers shows that, globally speaking, a 1 K temperature increase has the same effect as a ~25% decrease in precipitation, or a ~15% increase in global radiation. However, the relative importance of these drivers depends significantly on the climatic setting (notably continentality). In this contribution I will give a brief survey of glacier fluctuations over the past few centuries, and provide arguments that on the worldwide scale air temperature must have been the main driver of these fluctuations. A history of global mean temperature that explains the observed glacier fluctuations best will be discussed. On smaller spatial (regional) and temporal (decades) scales, changes in precipitation become important. Both with respect to the attribution problem (what caused the glacier fluctuations in the past?) and the projection issue (what will happen in the next 100 years?), it is important that many more glaciers are explicitly studied with numerical models. I will argue that for non-calving glaciers these models can be relatively simple.

Oerlemans, J.

2012-04-01

327

Modeling of glacier bed topography from glacier outlines, central branch lines, and a DEM  

Microsoft Academic Search

Due to the expected future climate change, glacier ice as a resource will be further diminished and its sea-level rise contribution further increased. A key for a more accurate determination of future glacier evolution is to improve our currently sparse knowledge on glacier bedrock topography. Here, we present a simplified method implemented in a geographic information system to approximate subglacial

Frank Paul; Andreas Linsbauer

2012-01-01

328

Glac Modeled Glacier Change Animation  

NSDL National Science Digital Library

Animation of Modeled Climate-Induced Glacier Change in Glacier National Park, 1850- 2100. The simulation reflects the predicted exponential rise in atmospheric CO2 concentrations, a 2xCO2 "global warming" scenario, with a concurrent warming of 2-3 degrees centigrade (4-5 degrees Fahrenheit) by the year 2050. In addition it assumes that precipitation, primarily in the form of rain, will increase over the same time period about 10 percent (based on the research of Dr. Steven Running, University of Montana). The animation view of the Blackfoot-Jackson basin along the Continental Divide, includes Gunsight Lake in the foreground and a portion of Lake Ellen Wilson visible over Gunsight Pass.

Myrna H. P. Hall

329

Fluffy Snow to Glacier Ice  

NSDL National Science Digital Library

In this activity, students build on their growing knowledge of ice and glacier growth. The students examine images of core samples and make observations about the decreasing size of gas bubbles with increasing depth in the core. The students model permeability. From this experiment, they will develop an understanding of the movement of air through snow and ice and why this information is critical to researchers studying the past climate of our Earth.

Sharon Shutey

330

Antarctica: measuring glacier velocity from satellite images  

SciTech Connect

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

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

1986-11-28

331

Internationally coordinated glacier monitoring: strategy and datasets  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

332

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

333

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

2014-01-01

334

Alaska Resource Data File: Chignik quadrangle, Alaska  

USGS Publications Warehouse

Descriptions of the mineral occurrences can be found in the report. See U.S. Geological Survey (1996) for a description of the information content of each field in the records. The data presented here are maintained as part of a statewide database on mines, prospects and mineral occurrences throughout Alaska. There is a website from which you can obtain the data for this report in text and Filemaker Pro formats

Pilcher, Steven H.

2000-01-01

335

Building the Alaska Oil Pipeline  

NSDL National Science Digital Library

This video segment adapted from AMERICAN EXPERIENCE tells the story of how environmentalists, Alaska Native peoples, and engineers concerned about the effects of permafrost challenged plans for the Alaska oil pipeline.

2008-11-04

336

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

PubMed

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

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

2014-08-22

337

Flood frequency in Alaska  

USGS Publications Warehouse

Records of peak discharge at 183 sites were used to study flood frequency in Alaska. The vast size of Alaska, its great ranges of physiography, and the lack of data for much of the State precluded a comprehensive analysis of all flood determinants. Peak stream discharges, where gaging-station records were available, were analyzed for 2-year, 5-year, 10-year, 25-year, and 50-year average-recurrence intervals. A regional analysis of the flood characteristics by multiple-regression methods gave a set of equations that can be used to estimate floods of selected recurrence intervals up to 50 years for any site on any stream in Alaska. The equations relate floods to drainage-basin characteristics. The study indicates that in Alaska the 50-year flood can be estimated from 10-year gaging- station records with a standard error of 22 percent whereas the 50-year flood can be estimated from the regression equation with a standard error of 53 percent. Also, maximum known floods at more than 500 gaging stations and miscellaneous sites in Alaska were related to drainage-area size. An envelope curve of 500 cubic feet per second per square mile covered all but 2 floods in the State.

Childers, J.M.

1970-01-01

338

Supplementary Material: Glacier melt contribution to streamflow  

E-print Network

variations in the surface mass balance of 18 Svalbard glaciers from the Moderate Resolution Imaging of direct mass balance of Hintereisferner. Global and Planetary Change, 71, 13-26. Greuell, W., Kohler, J, J.-E. and Carenzo, M. 2008. A study of the energy balance and melt regime on Juncal Norte Glacier

Washington at Seattle, University of

339

Recent acceleration of glacier thinning in Svalbard  

Microsoft Academic Search

Geodetic data comprising archive maps, contemporary lidar, and photogrammetric digital elevation models show that the rate of volume loss of two Svalbard glaciers, Midtre Lovénbreen (ML) and Slakbreen (SL), has accelerated in recent years. At ML, the thinning rate as averaged over the whole glacier has increased steadily over the latter part of the 20th century. The mean thinning rate

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

2006-01-01

340

GLIMS: Progress in Mapping the World's glaciers  

Microsoft Academic Search

The Global Land Ice Measurements from Space (GLIMS) initiative has built a database of glacier outlines and related attributes, derived primarily from satellite imagery, such as from ASTER and Landsat. Each snapshot of a glacier is from a specific time, and the database is designed to store multiple snapshots representative of different times. The database currently contains outlines for approximately

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

2009-01-01

341

Using Metaphorical Models for Describing Glaciers  

ERIC Educational Resources Information Center

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

Felzmann, Dirk

2014-01-01

342

Muir Glacier and Muir Inlet 2003  

USGS Multimedia Gallery

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

343

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

344

GLIMS Glacier Database: Status and Challenges  

Microsoft Academic Search

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

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

2008-01-01

345

Components: The GLIMS Geospatial Glacier Database  

E-print Network

Components: The GLIMS Geospatial Glacier Database http://glims.colorado.edu/glacierdata/ Bruce Raup Table of attributes in query results Map of query results Selected glacier is highlighted Political of GIS data formats. Planned enhancements to the database itself include increasing the volume of data

346

GIS-based glacier inventory of China  

Microsoft Academic Search

The project of the Glacier Inventory of China initialized in 1979 was just accomplished in 2000. This inventory was complied based on numerous LandSat TM images, aerial photographs, and topographic maps. More than 40 Chinese glaciologists made their great efforts in this work. With the newest statistics from the inventory, there are total 46,928 glaciers in China; the total area

X. Li; L.-Z. Wu

2003-01-01

347

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.

348

Accretion of southern Alaska  

USGS Publications Warehouse

Paleomagnetic data from southern Alaska indicate that the Wrangellia and Peninsular terranes collided with central Alaska probably by 65 Ma ago and certainly no later than 55 Ma ago. The accretion of these terranes to the mainland was followed by the arrival of the Ghost Rocks volcanic assemblage at the southern margin of Kodiak Island. Poleward movement of these terranes can be explained by rapid motion of the Kula oceanic plate, mainly from 85 to 43 Ma ago, according to recent reconstructions derived from the hot-spot reference frame. After accretion, much of southwestern Alaska underwent a counterclockwise rotation of about 50 ?? as indicated by paleomagnetic poles from volcanic rocks of Late Cretaceous and Early Tertiary age. Compression between North America and Asia during opening of the North Atlantic (68-44 Ma ago) may account for the rotation. ?? 1987.

Hillhouse, J.W.

1987-01-01

349

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

350

Iceland Glacier Recession 1997 to 2000  

NSDL National Science Digital Library

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

Perkins, Lori; Hall, Dorothy

2001-04-09

351

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

352

Mapping Glacier Data and Photographs via GeoServer and Virtual Globes  

Microsoft Academic Search

Two extensively used glacier data sets include the World Glacier Inventory and the Glacier Photograph Collection. Both data sets are hosted at the National Snow and Ice Data Center in Boulder, Colorado. The World Glacier Inventory encompasses over 100,000 records of glacier data and the Glacier Photograph Collection houses approximately 9,000 digitized photographs. The online Glacier Photograph Collection has doubled

L. M. Ballagh; I. Wang; A. Wallace

2008-01-01

353

Radio-echo sounding of Caucasus glaciers  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

354

Monitoring Glacial Advance and Retreat of the Skaftafellsjökull Glacier, Iceland  

Microsoft Academic Search

Visual documentation of glaciers can provide daily, seasonal, and yearly statistics concerning their advance and retreat, as well as contribute to historical record. Recognizing how glaciers change will improve glacier models, which leads to a better understanding of climate and ice-sheet interactions. Obtaining frequent images of glaciers can be difficult since they are often located in remote locations with rugged

Bryce L. Carmichael; Amber E. Smith

355

Results from the new Swiss Glacier Inventory 2000  

Microsoft Academic Search

For the new Swiss Glacier Inventory 2000 Landsat TM images from 1985, 1992 and 1998\\/9 were processed in a GIS environment. Thresholded TM4 \\/ TM5 ratio images were used to classify clean glacier ice and the combination with a DEM provided 3D glacier parameters. The 1973 Swiss glacier inventory was digitized and used as the base data set as well

F. Paul; A. Kaeaeb; M. Maisch; T. Kellenberger; W. Haeberli

2003-01-01

356

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. PMID:19996173

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

357

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

NASA Astrophysics Data System (ADS)

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

Pope, A.; Scambos, T. A.

2013-12-01

358

Field-based Digital Mapping of the November 3, 2002 Susitna Glacier Fault Rupture - Integrating remotely sensed data, GIS, and photo-linking technologies  

Microsoft Academic Search

In July 2003, the U.S. Geological Survey and the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted field studies on the Susitna Glacier Fault (SGF), which ruptured on November 2002 during the M 7.9 Denali fault earthquake. The DGGS assumed responsibility for Geographic Information System (GIS) and data management, integrating remotely sensed imagery, GPS data, GIS, and photo-linking software

L. A. Staft; P. A. Craw

2003-01-01

359

Repeat Photography of Alaskan Glaciers and Landscapes as Both Art and as a Means of Communicating Climat Change  

NASA Astrophysics Data System (ADS)

For nearly 15 years, I have used repeat photography of Alaskan glaciers and landscapes to communicate to fellow scientists, policymakers, the media, and society that Alaskan glaciers and landscapes have been experiencing significant change in response to post-Little Ice Age climate change. I began this pursuit after being contacted by a U.S. Department of the Interior senior official who requested unequivocal and unambiguous documentation that climate change was real and underway. After considering several options as to how best respond to this challenge, I decided that if a picture is worth a thousand words, then a pair of photographs, both with the same field of view, spanning a century or more, and showing dramatic differences, would speak volumes to documenting that dynamic climate change is occurring over a very broad region of Alaska. To me, understating the obvious with photographic pairs was the best mechanism to present irrefutable, unambiguous, nonjudgmental, as well as unequivocal visual documentation that climate change was both underway and real. To date, more than 150 pairs that meet these criteria have been produced. What has surprised me most is that the many of the photographs contained in the pairs present beautiful images of stark, remote landscapes that convey the majestic nature of this dynamic region with its unique topography and landscapes. Typically, over periods of just several decades, the photographed landscapes change from black and white to blue and green. White ice becomes blue water and dark rock becomes lush vegetation. Repeat photography is a technique in which a historical photograph and a modern photograph, both having the same field of view, are compared and contrasted to quantitatively and qualitatively determine their similarities and differences. I have used this technique from both ground-based photo stations and airborne platforms at Alaskan locations in Kenai Fjords National Park, Glacier Bay National Park and Preserve, Wrangell-St. Elias National Park and Preserve, Denali National Park and Preserve, the northern and northwestern Prince William Sound area of the Chugach National Forest, and the Mendenhall Glacier area of the Tongass National Forest to document and determine the extent of changing glaciers and landscapes. The use of repeat photography to document temporal change is not new. It originated as a glacier-monitoring technique in the European Alps more than 150 years ago. What is unique in this Alaskan application of repeat photography is the systematic approach being used to obtain photographic documentation of glacier and landscape change for every glacier-hosting fiord in western southcentral Alaska, as well as at many Alaskan valley glacier sites. What is also unique is the development of an annotated website which presents many pairs of these photographs as well as ancillary materials to help convey the basics of Alaskan glaciers and climate change. The website, titled 'Glacier and Landscape Change in Response to Changing Climate', (http://www.usgs.gov/climate_landuse/glaciers/) was awarded the 2010 USGS Shoemaker External Communications Award.

Molnia, B. F.

2013-12-01

360

Reconstructing glaciers: Sedimentary sources, sinks and fingerprints  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

361

Englacial hydrology of Annette Plateau, a temperate alpine glacier, Southern Alps, New Zealand.  

E-print Network

??The movement of water through temperate glaciers is important for understanding fundamental issues within glaciology. These include glacier induced floods, glacier dynamics and run-off prediction.… (more)

Schaller, Kolja

2013-01-01

362

Safeguarding Alaska's Waters  

NSDL National Science Digital Library

In this interactive activity, learn about strategies used in Prince William Sound, Alaska, to help avoid oil spills and to identify and contain environmental contaminants. The activity features videos adapted from the Prince William Sound Regional Citizens' Advisory Council, KTOO, and NOVA: The Big Spill.

Foundation, Wgbh E.

2009-03-13

363

Alaska's Cold Desert.  

ERIC Educational Resources Information Center

Explores the unique features of Alaska's Arctic ecosystem, with a focus on the special adaptations of plants and animals that enable them to survive in a stressful climate. Reviews the challenges facing public and private land managers who seek to conserve this ecosystem while accommodating growing demands for development. Includes classroom…

Brune, Jeff; And Others

1996-01-01

364

Source Book on Alaska.  

ERIC Educational Resources Information Center

The bases for the development of this resource book were notes and a course outline used in teaching Alaska History at the junior high school level. It can be used as a checklist, a guide to organizing lesson plans, selecting classroom and testing materials, and as a source of concepts and information for any grade level. Most of the material is…

Peratrovich, Robert J., Jr., Comp.

365

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.

366

Current Ethnomusicology in Alaska.  

ERIC Educational Resources Information Center

The systematic study of Eskimo, Indian, and Aleut musical sound and behavior in Alaska, though conceded to be an important part of white efforts to foster understanding between different cultural groups and to maintain the native cultural heritage, has received little attention from Alaskan educators. Most existing ethnomusical studies lack one or…

Johnston, Thomas F.

367

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

368

2012 Alaska Performance Scholarship Outcomes Report  

ERIC Educational Resources Information Center

As set forth in Alaska Statute 14.43.840, Alaska's Departments of Education & Early Development (EED) and Labor and Workforce Development (DOLWD), the University of Alaska (UA), and the Alaska Commission on Postsecondary Education (ACPE) present this first annual report on the Alaska Performance Scholarship to the public, the Governor,…

Rae, Brian

2012-01-01

369

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

NASA Astrophysics Data System (ADS)

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

Pillai, J.; Patel, L. K.

2011-12-01

370

Striated boulder pavements within glaciomarine diamicts of the Yakataga Formation, Middleton Island, Alaska  

SciTech Connect

The presence of striated boulder pavements in glacial sequences is often cited as evidence of transport and deposition by grounded glacier ice. However, recent reports show that striated pavements also form in non-glacial environments by the abrasion of boulder lag surfaces by floating glacier and seasonal ice. Several striated boulder pavements are identified within Early Pleistocene upper Yakataga Formation sediments exposed on Middleton Island close to the southern edge of the Gulf of Alaska continental shelf. The sequence is dominated by thick stratiform units of massive and stratified diamict formed by the settling of fine-grained sands and muds from suspension together with ice-rafted debris. Boulder pavements outcrop as extensive planar horizons within the diamicts, can be traced for several kilometers along strike and consist of single lines of clasts with faceted upper surfaces showing consistently oriented striation directions. Clasts are not preferentially aligned, however, and do not have the characteristic bullet shape of boulders transported at a glacier base and deposited by lodgement processes. Striated boulder pavements on Middleton Island appear to have formed as boulder lag surfaces generated by wave and tidal current reworking of diamict on relatively shallow banks. Lags were then overridden and abraded by a grounding ice shelf. The glacially-abraded boulder pavements on Middleton Island record the repeated expansion of a continuous ice shelf to the edge of the Gulf of Alaska continental shelf during the Early Pleistocene.

Eyles, C.H.

1985-01-01

371

Glacial erosion and convergent tectonics in Southern Alaska  

NASA Astrophysics Data System (ADS)

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

Merrand, Y.; Hallet, B.

2003-04-01

372

Economic impacts of the S. S. Glacier Bay oil spill: Social and economic studies. Technical report (Final)  

SciTech Connect

On July 2, 1987, an oil spill occurred in Cook Inlet when the S.S. Glacier Bay hit a submerged obstacle while enroute to Kenai Pipeline Company facilities to offload oil. The 1987 commercial fishery in Cook Inlet was barely underway when the S.S. Glacier Bay oil spill occurred, and the largest salmon return in history was moving up the inlet. The sockeye salmon run alone totaled over 12 million, providing a seasonal catch of 9.25 million salmon. The 1987 sport fishery in Cook Inlet was in mid-season at the time of the spill. The S.S. Glacier Bay oil spill represents an opportunity to study the economic impacts of an oil spill event in Alaska, particularly with regard to commercial fishing impacts and the public costs of cleanup. The report evaluates the existing information on the spill, response measures, and economic impacts, and adds discussions with individuals and groups involved in or affected by the spill to this data base. The report reviewed accounts of the oil spill and its costs; identified types and sources of data, developed protocol, and contacted groups and people for data collection and verification; and described, analyzed, and prepared reports of the economic effects of the S.S. Glacier Bay oil spill.

Burden, P.; Isaacs, J.; Richardson, J.; Braund, S.; Witten, E.

1990-11-01

373

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

374

Hidden Lake in Glacier National Park, Montana  

USGS Multimedia Gallery

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

375

What Are the Physical Effects of Glaciers?  

NSDL National Science Digital Library

This text explains how glaciers scour and grind the Earth's surface, and about the sorts of deposits they leave behind. Emphasis is on glaciation in the mountains and valleys of Vermont. Links to related topics are included.

376

Distinct patterns of seasonal Greenland glacier velocity  

NASA Astrophysics Data System (ADS)

Greenland Ice Sheet mass loss due to ice dynamics requires a complete understanding of spatiotemporal velocity fluctuations and related control mechanisms. We present a 5 year record of seasonal velocity measurements for 55 marine-terminating glaciers distributed around the ice sheet margin, along with ice-front position and runoff data sets for each glacier. Among glaciers with substantial speed variations, we find three distinct seasonal velocity patterns. One pattern indicates relatively high glacier sensitivity to ice-front position. The other two patterns are more prevalent and appear to be meltwater controlled. These patterns reveal differences in which some subglacial systems likely transition seasonally from inefficient, distributed hydrologic networks to efficient, channelized drainage, while others do not. The difference may be determined by meltwater availability, which in some regions may be influenced by perennial firn aquifers. Our results highlight the need to understand subglacial meltwater availability on an ice sheet-wide scale to predict future dynamic changes.

Moon, Twila; Joughin, Ian; Smith, Ben; Broeke, Michiel R.; Berg, Willem Jan; Noël, Brice; Usher, Mika

2014-10-01

377

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

378

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

379

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

380

Greenland's pronounced glacier retreat not irreversible  

NASA Astrophysics Data System (ADS)

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

Schultz, Colin

2012-02-01

381

Assessment of particulate accumulation climatology under inversions in Glacier Bay for the 2008 tourist season using WRF/Chem data  

NASA Astrophysics Data System (ADS)

Each summer, roughly one million tourists come to Southeast Alaska aboard cruise ships to see the pristine landscape and wildlife. Tourism is an integral component in the economy for most of the towns and villages on the Alaska Panhandle. With ship emissions only modestly regulated, there have been some concerns regarding the potential environmental impacts that cruise ships have on air quality, wildlife, and visitor experience. Cruise ships travel to remote regions, and are frequently the only anthropogenic emissions source in federally protected parks, such as Glacier Bay National Park and Preserve. In the absence of winds and synoptic scale storm systems common in the Gulf of Alaska, temperature inversions frequently develop inside Glacier Bay due to radiative cooling influenced by the complex topography inside the park. Inversions act as a lid, and may trap pollutants from cruise-ship emissions depending on the meteorological conditions present. Since meteorological observations are sparse and frequently skewed to easily accessible locations, data from the Weather Research and Forecasting Model, coupled with a chemistry package (WRF/Chem), were used to examine the physical and chemical processes that are impossible to determine through direct observations. Model simulation data for 124 days during the 2008 tourist season (May 15 to September 15), including a cruise-ship emission inventory for all 225 cruise ship entries in Glacier Bay, was analyzed. Evaluation of WRF/Chem through meteorological observations reveals that the model accurately captures the synoptic conditions for most of the summer, despite problems with complex topography. WRF/Chem simulated quasi-multi-day inversion events, with strengths as high as 6.7 K (100 m)-1. Inversions were present in all grid-cell locations in Glacier Bay, with inversions occurring on average of 42% of the days during the tourist season. WRF/Chem was able to model PM 10 (particulate matter with diameter less than 10 micrometers) concentrations from cruise ships, but the absence of aerosol monitoring sites does not allow us to confirm the results. However, no simulated particulates ever exceed the daily average National Ambient Air Quality Standard (NAAQS) of 150 micrograms per cubic meter. The high variability of particle concentrations in Glacier Bay suggests the need for an air quality observational network to further assess local air quality issues.

Pirhalla, Michael A.

382

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

NASA Astrophysics Data System (ADS)

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

Radi?, Valentina; Hock, Regine

2014-05-01

383

Impacts of climate warming on alpine glacier tourism and adaptive measures: A case study of Baishui Glacier No. 1 in Yulong Snow Mountain, Southwestern China  

Microsoft Academic Search

Alpine glaciers usually feature with best hydrothermal condition in mountain climate, and present beautiful glacier scenery,\\u000a various glacier landforms, rich biodiversity, and easier accessibility, compared with continental glaciers or ice sheets.\\u000a Nevertheless, Alpine glaciers are more sensitive to climate warming, and climate warming has seriously affected Alpine glaciers\\u000a and surrounding environment. The quality and attractiveness of Alpine glaciers to tourism

Shijin Wang; Yuanqing He; Xiaodong Song

2010-01-01

384

Early and late Holocene glacial fluctuations and tephrostratigraphy, Cabin Lake, Alaska  

USGS Publications Warehouse

Marked changes in sediment types deposited in Cabin Lake, near Cordova, Alaska, represent environmental shifts during the early and late Holocene, including fluctuations in the terminal position of Sheridan Glacier. Cabin Lake is situated to receive meltwater during periods when the outwash plain of the advancing Sheridan Glacier had aggraded. A brief early Holocene advance from 11.2 to 11.0 cal ka is represented by glacial rock flour near the base of the sediment core. Non-glacial lake conditions were restored for about 1000 years before the water level in Cabin Lake lowered and the core site became a fen. The fen indicates drier-than-present conditions leading up to the Holocene thermal maximum. An unconformity spanning 5400 years during the mid-Holocene is overlain by peat until 1110 CE when meltwater from Sheridan Glacier returned to the basin. Three intervals of an advanced Sheridan Glacier are recorded in the Cabin Lake sediments during the late Holocene: 1110–1180, 1260–1540 and 1610–1780 CE. The sedimentary sequence also contains the first five reported tephra deposits from the Copper River delta region, and their geochemical signatures suggest that the sources are the Cook Inlet volcanoes Redoubt, Augustine and Crater Peak, and possibly Mt Churchill in the Wrangell Volcanic field.

Zander, Paul D.; Kaufman, Darrell S.; Kuehn, Stephen C.; Wallace, Kristi L.; Anderson, R. Scott

2013-01-01

385

What Influences Climate and Glacier Change in the Southwestern China?  

NASA Technical Reports Server (NTRS)

The subject of climate change in the areas of the Tibetan Plateau (TP) and the Himalayas has taken on increasing importance because of available water resources from their mountain glaciers. Many of these glaciers over the region have been retreating, while some are advancing and stable. Other studies report that some glaciers in the Himalayas show acceleration on their shrinkage. However, the causes of the glacier meltings are still difficult to grasp because of the complexity of climatic change and its influence on glacier issues. However, it is vital that we pursue further study to enable the future prediction on glacier changes.

Yasunari, Teppei J.

2012-01-01

386

RESPONSE OF GLACIERS AND GLACIER RUNOFF IN ICELAND TO CLIMATE CHANGE  

Microsoft Academic Search

Climate changes are likely to have a substantial effect on glaciers and runoff from glaciated areas in the Nordic countries in the future. Many glaciers and ice caps are project ed to essentially disappear over the next 100-200 years. As a part of the Nordic CWE and CE research projects, a dynamical ice flow model coupled with a degree-day mass

Tómas Jóhannesson; Guðfinna Aðalgeirsdóttir; Helgi Björnsson; Finnur Pálsson; Oddur Sigurðsson

387

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

Microsoft Academic Search

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

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

2010-01-01

388

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

Microsoft Academic Search

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

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

2007-01-01

389

TRACY ARM-FORDS TERROR WILDERNESS STUDY AREA AND VICINITY, ALASKA.  

USGS Publications Warehouse

The Tracy Arm-Fords Terror Wilderness study area lies on the southwest flank of the Coast Range about 45 mi southeast of Juneau, Alaska. A mineral-resource survey of the area identified two areas with substantiated mineral-resource potential: the Sumdum Glacier mineral belt with gold, copper, and zinc potential; and the Endicott Peninsula area with zinc, silver, and gold potential. The Sumdum Glacier belt is estimated to contain between 3 and 15 mineral deposits and there are 5 known mining areas in the Endicott Peninsula. Further work, particularly in the southern part of the belt, would be of significant help in refining the evaluation of that area. Relatively little activity has occurred in the Endicott Peninsula area; intense geochemical and geophysical work would remove many of the present uncertainties and probably would refine the present limit of the favorable areas. 2 refs.

Brew, David A.; Kimball, A.L.

1984-01-01

390

Sediment delivery to the Gulf of Alaska: source mechanisms along a glaciated transform margin  

USGS Publications Warehouse

Sediment delivery to the Gulf of Alaska occurs via four areally extensive deep-water fans, sourced from grounded tidewater glaciers. During periods of climatic cooling, glaciers cross a narrow shelf and discharge sediment down the continental slope. Because the coastal terrain is dominated by fjords and a narrow, high-relief Pacific watershed, deposition is dominated by channellized point-source fan accumulations, the volumes of which are primarily a function of climate. The sediment distribution is modified by a long-term tectonic translation of the Pacific plate to the north along the transform margin. As a result, the deep-water fans are gradually moved away from the climatically controlled point sources. Sets of abandoned channels record the effect of translation during the Plio-Pleistocene.

Dobson, M.R.; O'Leary, D.; Veart, M.

1998-01-01

391

Submarine landforms in the fjords of southern Chile: implications for glacimarine processes and sedimentation in a mild glacier-influenced environment  

NASA Astrophysics Data System (ADS)

Chilean fjords are the lowest latitude at which glaciers reach the sea today. High accumulation and mass throughput sustain tidewater glacier margins in this relatively mild climatic and oceanographic setting. 27,000 km2 of swath bathymetry allow mapping of sea-floor landforms and inferences on glacimarine sediments and sedimentation. Tidewater glaciers are present in several fjords. Beyond retreating Tempano glacier, a terminal moraine marks the limit of probable Little Ice Age advance with smaller transverse ridges closer to the glacier. Beyond advancing Pio XI Glacier there are few signs of organised submarine landforms. Older moraine ridges along several fjords formed at still-stands during deglaciation. Elsewhere, meltwater-fed braided rivers connect the glacial and marine sedimentary systems. Swath imagery shows glacifluvial and fluvial deltas with small channels and chutes that develop into long and sinuous turbidity-current channels. Few iceberg ploughmarks and submarine slope failures were observed, but several fields of pockmarks were present. The fjords of Chile are dominated by sediment delivery from turbid meltwater which distributes fine-grained debris widely, producing sorted and laminated fine-grained ice-proximal wedges and draping ice-distal seismic architecture to give a predominantly smooth sea floor. Turbidity currents also transfer sediments to some ice-distal environments. The Chilean fjordlands represent the mildest climatic and oceanographic end-member of a continuum of glacier-influenced marine settings; similar to south-east Alaska in the northern hemisphere. Components of a landform-assemblage model for climatically mild meltwater-dominated fjords include ice-contact moraine ridges, glacifluvial and fluvial deltas, and turbidity-current channels. Full-glacial and deglacial streamlined subglacial landforms are likely to have been buried in many areas by subsequent glacimarine sedimentation.

Dowdeswell, J. A.; Vásquez, M.

2013-03-01

392

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

393

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

394

Alaska Airlines Operating costs and  

E-print Network

SYS-461 Alaska Airlines Operating costs and Productivity Daric Megersa #12;Airline Business Model · Is an airline based in the Seattle suburb of SeaTac, Washington · Major, low-fare U.S. carrier · Seventh expense, interest capitalized and some other costs · The trend shows that Alaska airlines has shown

395

Coal resources of northwest Alaska  

Microsoft Academic Search

Rural areas in Alaska depend almost entirely on expensive imported fuel oil for heat and power generation. Following the drastic price increase in petroleum a few years ago, local governments and state agencies have shown considerable interest in determining the potential for northwest Alaska as an alternative energy source. A compilation of earlier work by the US Geological Survey, Bureau

G. R. Eakins; J. G. Clough; J. E. Callahan; M. M. Menge; A. C. Jr. Banet

1985-01-01

396

Global-scale modeling of glacier mass balances for water resources assessments: Glacier mass changes between 1948 and 2006  

NASA Astrophysics Data System (ADS)

Glaciers play an important role for freshwater resources, but in global-scale freshwater assessments, their impact on river flows has not yet been taken into account. As a first step, we developed a global glacier model that can be coupled to global land surface and hydrological models. With a spatial resolution of 0.5° by 0.5°, the glacier model HYOGA computes glacier mass balance by a simple degree-day approach for 50 m sub-grid elevation bands, modeling all glaciers within a grid cell as one glacier. The model is tuned individually for each grid cell against observed glacier mass balance data. HYOGA is able to compute glacier mass balances reasonably well, even those of summer accumulation type glaciers. Still, model uncertainty is high, which is, among other reasons, due to the uncertainty of global data sets of temperature and precipitation which do not represent well the climatic situation at glacier sites. We developed a 59-yr (1948-2006) time series of global glacier mass balance and glacier area by driving HYOGA with daily near-surface atmospheric data. According to our computations, most glaciers have lost mass during the study period. Compared to estimates derived from a rather small number of observed glacier mass balances, HYOGA computes larger glacier mass losses in Asia, Europe, Canadian Arctic islands and Svalbard. In accordance with the estimates, average annual mass losses have increased strongly after 1990 as compared to the 30 yrs before. The sea level equivalent of the melt water from glaciers is 0.76 mm/yr water equivalent after 1990 as compared to only 0.34 mm/yr water equivalent before. We computed an acceleration of glacier mass losses after 1990 for all world regions except South America, where the number of gauge observations of precipitation is very small after 1980.

Hirabayashi, Yukiko; Döll, Petra; Kanae, Shinjiro

2010-09-01

397

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

398

Can shrubs help to reconstruct historical glacier retreats?  

NASA Astrophysics Data System (ADS)

In the 21st century, most of the world’s glaciers are expected to retreat due to further global warming. The range of this predicted retreat varies widely as a result of uncertainties in climate and glacier models. To calibrate and validate glacier models, past records of glacier mass balance are necessary, which often only span several decades. Long-term reconstructions of glacier mass balance could increase the precision of glacier models by providing the required calibration data. Here we show the possibility of applying shrub growth increments as an on-site proxy for glacier summer mass balance, exemplified by Salix shrubs in Finse, Norway. We further discuss the challenges which this method needs to meet and address the high potential of shrub growth increments for reconstructing glacier summer mass balance in remote areas.

Buras, Allan; Hallinger, Martin; Wilmking, Martin

2012-12-01

399

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

400

Test of a simple glacier retreat parameterization for two Norwegian ice cap glaciers  

NASA Astrophysics Data System (ADS)

In Norway, the ice cap glacier retreat will be an important phenomena under climate change projections and will largely influence water resources.Three new versions of a glacier retreat algorithm based on the parameterization proposed by Huss et al. (2010) are implemented and tested on the Distributed Element Water Model of the Norwegian Water Resources and Energy Directorate. After selection of the best performing algorithm version, the glacier retreat parameters of the model are calibrated on observed discharge and mass balance data for two ice cap glaciers in Norway: Nigardsbreen (maritime glacier) and Midtdalsbreen (semi continental glacier). The calibration performance is acceptable: ice thickness is reproduced with a Root Mean Square Error of 20 respectively 15 m for the two case studies; glacier annual mass balance is overestimated for negative years; daily discharge is reproduced with a Nash Sutcliffe performance criterion between 0.80-0.86 for the period of 1961-1990: Climate change projections are performed for these 2 glaciers using downscaled Regional Climate Models (RCMs) from IPCC A1B emission scenario for greenhouse gases. According to our results, these glaciers are going to decrease dramatically: the ice volume could be reduced by 70 to 80 % in 2100, the annual discharge could increase by 30% till 2070-2080. The annual daily regime can also be assumed to change: the simulation results show that the maximum discharge during summer will decrease whereas winter discharge will increase after a longer recession period in autumn. The beginning of the melting period will not change substantially. The model sensitivity of the applied glacier retreat parameterization (Huss et al. 2010) is analyzed with two approaches: 1/ comparing the ice volume evolution for all Huss parameters sets obtained through calibration in this study to the ones proposed in literature; 2/ varying one parameter after the other keeping the three others fixed. The evolution of the ice volume largely varies in function of the glacier retreat parameters and the parameter sets proposed in Huss et al. 2010 seem not to be able to capture the behavior of ice cap glaciers . From this study, the Huss parameterization implemented produced satisfying results and can be apply to ice cap in nordic countries for glacier retreat parameters calibrated. A classification of the ice cap could be necessary in order to widely apply this model without calibration process.

Alesina, Samuel; Beldring, Stein; Melvold, Kjetil; Schaefli, Bettina

2014-05-01

401

An 'Older Little Ice Age' ~3 kyr ago? Evidence from mountain glaciers in northern mid-latitudes  

NASA Astrophysics Data System (ADS)

The 'Little Ice Age' (LIA, CE 1300-1860) has been identified in many climate records in the Northern Hemisphere and is widely seen as the culmination of a multi-millennia cooling trend throughout the middle and late Holocene. This cooling trend is commonly related to the astronomical forcing represented by decreasing northern summer insolation. Less is known about the extent and duration of LIA-type cold-excursions earlier in the Holocene, mostly due to missing historical evidence and low-resolution climate records. Based on precise cosmogenic Be-10 surface exposure dating, we here present surveys of Holocene fluctuations of glaciers in the Swiss Alps (46°N), which are highly sensitive to regional climate changes and in particular, to summer temperature variations. Our results show that the most extensive Holocene glacier culminations in the Alps occurred during the earliest Holocene. No moraines are preserved from the mid-Holocene, consistent with the scenario of small glaciers during this time. However, we dated moraine fragments close to the LIA moraines to the period between ~3.2 to 2.8 kyr ago, indicating LIA-type climate conditions as early as 3 kyr ago. This finding from the Alps is in agreement with our glacier records from the Western US as well as with existing glacier studies in Alaska, British Columbia and Greenland. Beyond, north Atlantic bottom water temperature records indicate an abrupt, 'LIA' level cold excursion around this time. Taken together, we will discuss this 'older LIA' phenomenon in a hemispheric climate context, challenging the view that Holocene climate was quasi-continuously cooling over several millennia prior to the LIA cold peak.

Schimmelpfennig, I.; Schaefer, J. M.; Putnam, A. E.; Akçar, N.; Ivy-Ochs, S.; Finkel, R. C.; Schlüchter, C.

2012-12-01

402

2013 Alaska Performance Scholarship Outcomes Report  

ERIC Educational Resources Information Center

In accordance with Alaska statute the departments of Education & Early Development (EED) and Labor and Workforce Development (DOLWD), the University of Alaska (UA), and the Alaska Commission on Postsecondary Education (ACPE) present this second annual report on the Alaska Performance Scholarship (APS). Among the highlights: (1) In the public…

Rae, Brian

2013-01-01

403

Antarctic glaciers shrinking due to ice shelf collapse  

NSDL National Science Digital Library

Mass and velocity measurements taken from satellites and airplanes between 1995 and 2004 were studied to determine if glaciers on the West Antarctic Peninsula were growing or shrinking. It was found that loss of glacier mass from melting and movement into the ocean exceeded snowfall accumulation for several glaciers on the peninsula. The authors propose that as the region continues to warm, the Wordie Bay glaciers will melt more quickly, causing sea level to rise.

Al., Rignot E.; Agu

404

Measuring Greenland Glacier Dynamics with Remotely Sensed Data  

E-print Network

in 2000 [A] and 2004-5 [B]. [Howat et. al., 2005]. Helheim Glacier System GIS Workflow 1. Download 2. Mosaic 3. Project 4. Subset (or clip) ____________________________________________________________________________ 5. Repeat 1-4 for NIR 8...Measuring Greenland Glacier Dynamics with Remotely Sensed Data Steve Foga University of Kansas, Geography M.A. Student Photo by: Phil Pasquini The importance of studying glacier ice Study area Difference in ice velocity of Helheim Glacier...

Foga, Steve

2013-01-15

405

Exploration of Uncertainty in Glacier Modelling  

NASA Technical Reports Server (NTRS)

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

Thompson, David E.

1999-01-01

406

Snow Cover Effects on Glacier Ice Surface Temperature Margherita Maggioni*{  

E-print Network

Snow Cover Effects on Glacier Ice Surface Temperature Margherita Maggioni*{ Michele Freppaz* Paolo.maggioni@unito.it Abstract Snowpack evolution and glacier ice surface temperatures were studied on the Indren glacier of an artificial increase in the snow density was evaluated. During the season rich in snow there was a prevalence

Williams, Mark W.

407

Contrasting responses of Central Asian rock glaciers to global warming  

PubMed Central

While the responses of Tien Shan glaciers – and glaciers elsewhere – to climatic changes are becoming increasingly well understood, this is less the case for permafrost in general and for rock glaciers in particular. We use a novel approach to describe the climate sensitivity of rock glaciers and to reconstruct periods of high and low rock glacier activity in the Tien Shan since 1895. Using more than 1500 growth anomalies from 280 trees growing on rock glacier bodies, repeat aerial photography from Soviet archives and high-resolution satellite imagery, we present here the world's longest record of rock glacier movements. We also demonstrate that the rock glaciers exhibit synchronous periods of activity at decadal timescales. Despite the complex energy-balance processes on rock glaciers, periods of enhanced activity coincide with warm summers, and the annual mass balance of Tuyuksu glacier fluctuates asynchronously with rock glacier activity. At multi-decadal timescales, however, the investigated rock glaciers exhibit site-specific trends reflecting different stages of inactivation, seemingly in response to the strong increase in air temperature since the 1970s. PMID:25657095

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

2015-01-01

408

Mass balance of three Svalbard glaciers reconstructed back to 1948  

Microsoft Academic Search

A simple model using upper-air meteorological variables in the NCEP-NCAR Reanalysis database is used to model seasonal components of mass balance of three glaciers in Svalbard. The model was originally developed for glaciers in North America, and has been applied to glaciers in Norway, Sweden and Iceland. Over the period for which mass balance data are available for the three

L. A. Rasmussen; J. Kohler

2007-01-01

409

Glaciers and their contribution to sea level change  

Microsoft Academic Search

Increased melting of glaciers and ice caps, excluding Greenland and Antarctica, will probably represent the second largest contribution to global sea level rise by 2100. The temperature sensitivity of sea level rise depends upon the global distribution of glacier areas, the temperature sensitivity of glacier mass balance in each region, the expected change of climate in each region, and changes

Roger J. Braithwaite; Sarah C. B. Raper

2002-01-01

410

Contrasting responses of Central Asian rock glaciers to global warming.  

PubMed

While the responses of Tien Shan glaciers - and glaciers elsewhere - to climatic changes are becoming increasingly well understood, this is less the case for permafrost in general and for rock glaciers in particular. We use a novel approach to describe the climate sensitivity of rock glaciers and to reconstruct periods of high and low rock glacier activity in the Tien Shan since 1895. Using more than 1500 growth anomalies from 280 trees growing on rock glacier bodies, repeat aerial photography from Soviet archives and high-resolution satellite imagery, we present here the world's longest record of rock glacier movements. We also demonstrate that the rock glaciers exhibit synchronous periods of activity at decadal timescales. Despite the complex energy-balance processes on rock glaciers, periods of enhanced activity coincide with warm summers, and the annual mass balance of Tuyuksu glacier fluctuates asynchronously with rock glacier activity. At multi-decadal timescales, however, the investigated rock glaciers exhibit site-specific trends reflecting different stages of inactivation, seemingly in response to the strong increase in air temperature since the 1970s. PMID:25657095

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

2015-01-01

411

Extracting a Climate Signal from 169 Glacier Records  

Microsoft Academic Search

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

J. Oerlemans

2005-01-01

412

Rapid disintegration of Alpine glaciers observed with satellite data  

Microsoft Academic Search

Analyses of multispectral satellite data indicate accelerated glacier decline around the globe since the 1980s. By using digitized glacier outlines inferred from the 1973 inventory and Landsat Thematic Mapper (TM) satellite data from 1985 to 1999, we obtained area changes of about 930 Alpine glaciers. The 18% area reduction as observed for the period 1985 to 1999 (-1.3% a-1) corresponds

Frank Paul; Andreas Kääb; Max Maisch; Tobias Kellenberger; Wilfried Haeberli

2004-01-01

413

The physical basis of glacier volume-area scaling  

Microsoft Academic Search

Ice volumes are known for only a few of the roughly 160,000 glaciers worldwide but are important components of many climate and sea level studies which require water flux estimates. A scaling analysis of the mass and momentum conservation equations shows that glacier volumes can be related by a power law to more easily observed glacier surface areas. The relationship

David B. Bahr; Mark F. Meier; Scott D. Peckham

1997-01-01

414

Glacier melt contribution to streamflow1 Neil Schaner1  

E-print Network

1 Glacier melt contribution to streamflow1 Neil Schaner1 , Nathalie Voisin2 , Bart Nijssen1), the global contribution of glaciers to water supply is33 not well known (Armstrong, 2010). While some vulnerability. Armstrong (2010) summarizes the current state41 of understanding of glacier contributions

Washington at Seattle, University of

415

WATER FLOW THROUGH TEMPERATE GLACIERS Andrew G. Fountain1  

E-print Network

WATER FLOW THROUGH TEMPERATE GLACIERS Andrew G. Fountain1 Department of Geology Portland State, Washington Abstract. Understanding water movement through a glacier is fundamental to several critical issues glacierized drainage basins. To this end we have synthesized a conceptual model of water movement through

Fountain, Andrew G.

416

Historic Glacier Change using a GIS: Progress and problems  

Microsoft Academic Search

We are exploring the potential wealth of information on glacier extent and topography contained in historic maps. If successful, we can examine the spatial and temporal patterns of historic glacier change where glaciological studies are typically absent. Our project is focused on the American West and data on glacier extent and topography is derived from aerial and ground-based photographs, paper

F. Granshaw; A. G. Fountain; D. Percy; A. Ebnet

2004-01-01

417

GLACIER MONITORING FROM ASTER IMAGERY: ACCURACY AND APPLICATIONS  

E-print Network

GLACIER MONITORING FROM ASTER IMAGERY: ACCURACY AND APPLICATIONS A. Kääb1 , C. Huggel1 , F. Paul1 and Reflection Radiometer) on board the Terra satellite offers new possibilities for worldwide glacier monitoring be expected. (b) Automatic glacier mapping using the ASTER bands 3 (15 m resolution) and 4 (30 m resolution

Oldenburg, Carl von Ossietzky Universität

418

Combined technologies allow rapid analysis of glacier changes  

Microsoft Academic Search

Monitoring of glacier changes plays an important role within the Global Climate Observing System (GCOS) [Haeberli et al., 2000] and Landsat imagery has proven to be a useful tool for monitoring glacier changes over large and remote areas [Aniya et al., 1996; Li et al., 1998]. An accurate glacier map can be obtained by simple segmentation of a ratio image

Frank Paul

2002-01-01

419

Rapid disintegration of Alpine glaciers observed with satellite data  

Microsoft Academic Search

Analyses of multispectral satellite data indicate accelerated glacier decline around the globe since the 1980s. By using digitized glacier outlines inferred from the 1973 inventory and Landsat Thematic Mapper (TM) satellite data from 1985 to 1999, we obtained area changes of about 930 Alpine glaciers. The 18% area reduction as observed for the period 1985 to 1999 (?1.3% a?1) corresponds

Frank Paul; Andreas Kääb; Max Maisch; Tobias Kellenberger; Wilfried Haeberli

2004-01-01

420

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

421

Deformation during terrane accretion in the Saint Elias orogen, Alaska  

USGS Publications Warehouse

The Saint Elias orogen of southern Alaska and adjacent Canada is a complex belt of mountains formed by collision and accretion of the Yakutat terrane into the transition zone from transform faulting to subduction in the northeast Pacific. The orogen is an active analog for tectonic processes that formed much of the North American Cordillera, and is also an important site to study (1) the relationships between climate and tectonics, and (2) structures that generate large- to great-magnitude earthquakes. The Yakutat terrane is a fragment of the North American plate margin that is partly subducted beneath and partly accreted to the continental margin of southern Alaska. Interaction between the Yakutat terrane and the North American and Pacific plates causes significant differences in the style of deformation within the terrane. Deformation in the eastern part of the terrane is caused by strike-slip faulting along the Fairweather transform fault and by reverse faulting beneath the coastal mountains, but there is little deformation immediately offshore. The central part of the orogen is marked by thrusting of the Yakutat terrane beneath the North American plate along the Chugach-Saint Elias fault and development of a wide, thin-skinned fold-and-thrust belt. Strike-slip faulting in this segment may he localized in the hanging wall of the Chugach-Saint Elias fault, or dissipated by thrust faulting beneath a north-northeast-trending belt of active deformation that cuts obliquely across the eastern end of the fold-and-thrust belt. Superimposed folds with complex shapes and plunging hinge lines accommodate horizontal shortening and extension in the western part of the orogen, where the sedimentary cover of the Yakutat terrane is accreted into the upper plate of the Aleutian subduction zone. These three structural segments are separated by transverse tectonic boundaries that cut across the Yakutat terrane and also coincide with the courses of piedmont glaciers that flow from the topographic backbone of the Saint Elias Mountains onto the coastal plain. The Malaspina fault-Pamplona structural zone separates the eastern and central parts of the orogen and is marked by reverse faulting and folding. Onshore, most of this boundary is buried beneath the western or "Agassiz" lobe of the Malaspina piedmont glacier. The boundary between the central fold-and-thrust belt and western zone of superimposed folding lies beneath the middle and lower course of the Bering piedmont glacier. ?? 2004 Geological Society of America.

Bruhn, R.L.; Pavlis, T.L.; Plafker, G.; Serpa, L.