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Sample records for alaska range glaciers

  1. The altitudinal distribution of snow algae on an Alaska glacier (Gulkana Glacier in the Alaska Range)

    NASA Astrophysics Data System (ADS)

    Takeuchi, Nozomu

    2001-12-01

    The altitudinal distribution of a snow algal community was investigated on an Alaska glacier (Gulkana Glacier in the Alaska Range) from 1270 to 1770 m a.s.l.. Seven species of snow and ice algae (Chlorophyta and cyanobacteria) were observed on the glacier surface. These species were Chlamydomonas nivalis, Mesotaenium berggrenii, Ancylonema nordenskioldii, Cylindrocystis brébissonii, Raphidonema sp., and two Oscillatoriaceae cyanobacteria. The altitudinal distribution of snow algae was different among the species: Cd. nivalis was distributed on the middle to upper area, M. berggrenii; A. nordenskioldii, and one Oscillatoriaceae cyanobacterium on the middle to lower area; Raphidonema sp. on the middle area; and Cyl. brébissonii and one Oscillatoriaceae cyanobacterium on the lower area. The total cell concentration and the cell volume biomass of the snow algae ranged from 4·4 × 103 to 9·9 × 105 cells ml-1 and from 33 to 2211 µl m-2 respectively. The cell volume biomass changed with altitude; the biomass increased with altitude below 1600 m a.s.l., and decreased above 1600 m a.s.l. The community structure showed that glacier, and that glacier. The altitudinal distribution of snow algae is discussed in terms of the physical and chemical condition of the glacier surface, and is compared with that on a Himalayan glacier. A larger biomass in the snow area on the Alaska glacier than that of the Himalayan glacier is likely due to less frequent snow cover in summer in Alaska. Small amounts of filamentous cyanobacteria on the Alaska glacier may allow washouts of unicellular green algae by running melt water and may cause a different pattern of altitudinal distribution of algal biomass on the ice area from the Himalayan glacier

  2. Photogrammetrically Derived Estimates of Glacier Mass Loss in the Upper Susitna Drainage Basin, Alaska Range, Alaska

    NASA Astrophysics Data System (ADS)

    Wolken, G. J.; Whorton, E.; Murphy, N.

    2014-12-01

    Glaciers in Alaska are currently experiencing some of the highest rates of mass loss on Earth, with mass wastage rates accelerating during the last several decades. Glaciers, and other components of the hydrologic cycle, are expected to continue to change in response to anticipated future atmospheric warming, thus, affecting the quantity and timing of river runoff. This study uses sequential digital elevation model (DEM) analysis to estimate the mass loss of glaciers in the upper Susitna drainage basin, Alaska Range, for the purpose of validating model simulations of past runoff changes. We use mainly stereo optical airborne and satellite data for several epochs between 1949 and 2014, and employ traditional stereo-photogrammetric and structure from motion processing techniques to derive DEMs of the upper Susitna basin glaciers. This work aims to improve the record of glacier change in the central Alaska Range, and serves as a critical validation dataset for a hydrological model that simulates the potential effects of future glacier mass loss on changes in river runoff over the lifespan of the proposed Susitna-Watana Hydroelectric Project.

  3. Glaciers of North America - Glaciers of Alaska

    USGS Publications Warehouse

    Molnia, Bruce F.

    2008-01-01

    Glaciers cover about 75,000 km2 of Alaska, about 5 percent of the State. The glaciers are situated on 11 mountain ranges, 1 large island, an island chain, and 1 archipelago and range in elevation from more than 6,000 m to below sea level. Alaska's glaciers extend geographically from the far southeast at lat 55 deg 19'N., long 130 deg 05'W., about 100 kilometers east of Ketchikan, to the far southwest at Kiska Island at lat 52 deg 05'N., long 177 deg 35'E., in the Aleutian Islands, and as far north as lat 69 deg 20'N., long 143 deg 45'W., in the Brooks Range. During the 'Little Ice Age', Alaska's glaciers expanded significantly. The total area and volume of glaciers in Alaska continue to decrease, as they have been doing since the 18th century. Of the 153 1:250,000-scale topographic maps that cover the State of Alaska, 63 sheets show glaciers. Although the number of extant glaciers has never been systematically counted and is thus unknown, the total probably is greater than 100,000. Only about 600 glaciers (about 1 percent) have been officially named by the U.S. Board on Geographic Names (BGN). There are about 60 active and former tidewater glaciers in Alaska. Within the glacierized mountain ranges of southeastern Alaska and western Canada, 205 glaciers (75 percent in Alaska) have a history of surging. In the same region, at least 53 present and 7 former large ice-dammed lakes have produced jokulhlaups (glacier-outburst floods). Ice-capped volcanoes on mainland Alaska and in the Aleutian Islands have a potential for jokulhlaups caused by subglacier volcanic and geothermal activity. Because of the size of the area covered by glaciers and the lack of large-scale maps of the glacierized areas, satellite imagery and other satellite remote-sensing data are the only practical means of monitoring regional changes in the area and volume of Alaska's glaciers in response to short- and long-term changes in the maritime and continental climates of the State. A review of the

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

    USGS Publications Warehouse

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

    2010-01-01

    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

  5. Alaska Glaciers and Rivers

    NASA Technical Reports Server (NTRS)

    2007-01-01

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

  6. Malaspina Glacier, Alaska

    NASA Technical Reports Server (NTRS)

    2001-01-01

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

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

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

  7. Columbia Glacier, Alaska, 1986-2011

    NASA Video Gallery

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

  8. Surface melt dominates Alaska glacier mass balance

    USGS Publications Warehouse

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

    2015-01-01

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

  9. Surface melt dominates Alaska glacier mass balance

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  10. Malaspina Glacier, Alaska as seen from STS-66 Atlantis

    NASA Technical Reports Server (NTRS)

    1994-01-01

    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.

  11. A new satellite-derived glacier inventory for Western Alaska

    NASA Astrophysics Data System (ADS)

    Le Bris, Raymond; Frey, Holger; Paul, Frank; Bolch, Tobias

    2010-05-01

    Glaciers and ice caps are essential components of studies related to climate change impact assessment. Glacier inventories provide the required baseline data to perform the related analysis in a consistent and spatially representative manner. In particular, the calculation of the current and future contribution to global sea-level rise from heavily glacierized regions is a major demand. One of the regions, where strong mass losses and geometric changes of glaciers have been observed recently is Alaska. Unfortunately, the digitally available data base of glacier extent is quite rough and based on rather old maps from the 1960s. Accordingly, the related calculations and extrapolations are imprecise and an updated glacier inventory is urgently required. Here we present first results of a new glacier inventory for Western Alaska that is prepared in the framework of the ESA project GlobGlacier and is based on freely available orthorectified Landsat TM and ETM+ scenes from USGS. The analysed region covers the Tordrillo, Chigmit and Chugach Mts. as well as the Kenai Peninsula. In total, 8 scenes acquired between 2002 and 2009 were used covering c. 20.420 km2 of glaciers. All glacier types are present in this region, incl. outlet glaciers from icefields, glacier clad volcanoes, and calving glaciers. While well established automated glacier mapping techniques (band rationing) are applied to map clean and slightly dirty glacier ice, many glaciers are covered by debris or volcanic ash and outlines need manual corrections during post-processing. Prior to the calculation of drainage divides from DEM-based watershed analysis, we performed a cross-comparative analysis of DEMs from USGS, ASTER (GDEM) and SRTM 1 for Kenai Peninsula. This resulted in the decision to use the USGS DEM for calculating the drainage divides and most of the topographic inventory parameters, and the more recent GDEM to derive minimum elevation for each glacier. A first statistical analysis of the results

  12. Regional Observations of Alaska Glacier Dynamics

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Alaska glaciers contribute more to sea level rise than any other glacierized mountain region in the world. Alaska is loosing ~84 Gt of ice annually, which accounts for ~0.23 mm/yr of SLR (Luthcke et al., 2008). Complex glacier flow dynamics, frequently related to tidewater environments, is the primary cause of such rapid mass loss (Larsen et al., 2007). Indirect observations indicate these complex flow dynamics occur on many glaciers throughout Alaska, but no comprehensive velocity measurements exist. We are working to measure glacier surface velocities throughout Alaska using synthetic aperture radar (SAR) offset tracking. This work focuses on the Seward/Malaspina, Bering, Columbia, Kaskawulsh, and Hubbard Glaciers and uses a MODIS land surface temperature "melt-day" product (Hall et al., 2006, 2008) to identify potential links between velocity variability and summertime temperature fluctuations. Hall, D., R. Williams Jr., K. Casey, N. DiGirolamo, and Z. Wan (2006), Satellite-derived, melt-season surface temperature of the Greenland Ice Sheet (2000-2005) and its relationship to mass balance, Geophysical Research Letters, 33(11). Hall, D., J. Box, K. Casey, S. Hook, C. Shuman, and K. Steffen (2008), Comparison of satellite-derived and in-situ observations of ice and snow surface temperatures over Greenland, Remote Sensing of Environment, 112(10), 3739-3749. Larsen, C. F., R. J. Motyka, A. A. Arendt, K. A. Echelmeyer, and P. E. Geissler (2007), Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise, J. Geophys. Res. Luthcke, S., A. Arendt, D. Rowlands, J. McCarthy, and C. Larsen (2008), Recent glacier mass changes in the Gulf of Alaska region from GRACE mascon solutions, Journal of Glaciology, 54(188), 767-777.

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

    USGS Publications Warehouse

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

    1996-01-01

    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.

  14. Southern Alaska Glaciers: Spatial and Temporal Variations in Ice Volume

    NASA Astrophysics Data System (ADS)

    Sauber, J.; Molnia, B. F.; Luthcke, S.; Rowlands, D.; Harding, D.; Carabajal, C.; Hurtado, J. M.; Spada, G.

    2004-12-01

    footprint returns to estimate glacier ice elevations and surface characteristics. To obtain the optimal ICESat results, we are reprocessing the ICESat data from Alaska to provide a well-calibrated regional ICESat solution. We anticipate that our ICESat results combined with earlier data will provide new constraints on the temporal and spatial variations in ice volume of individual Alaskan mountain ranges. These results allow us to address how recent melting of the southern Alaska glaciers contribute to short-term sea-level rise. Our results will also enable us to quantify crustal stress changes due to ice mass fluctuations and to assess the influence of ice mass changes on the seismically active southern Alaskan plate boundary zone.

  15. Recent climate trends, Glacier Bay, Alaska

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

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

    USGS Publications Warehouse

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

    1987-01-01

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

  17. Long-term linkages between glaciers, permafrost and hydrology at two glacierized watersheds in Alaska

    NASA Astrophysics Data System (ADS)

    Gaedeke, A.; Liljedahl, A. K.; Gatesman, T.; Campbell, S. W.; Hock, R.; Oneel, S.

    2015-12-01

    Climate warming is expected to have considerable impact on the regional water balance of high latitude Arctic and sub-Arctic glacerized watersheds. In this study we combine field observations and the physically based Water Balance Simulation Model WaSiM to refine our understanding of the linkages between glaciers, permafrost and hydrology at two nearby basins with contrasting precipitation regimes: Jarvis Cr. watershed (630 km2) on the north (rain-shadow) side of Eastern Alaska Range and the south facing Phelan Cr. (32 km2), which include the US Geological Survey benchmark site Gulkana Glacier. Both are characterized by a semi-arid climate and are sub-watersheds of the Tanana River basin (12,000 km2). Our research questions include: How has glacier water storage and release varied in the past and how are they expected to change in the future? And what are the subsequent effects on lowland runoff and regional groundwater recharge? Our analyses show i) an increase in air temperature and summer warmth index (the sum of all mean monthly air temperature above 0 °C) in recent decades and ii) a continued negative glacier mass balance. Our findings suggest that, on the larger spatial scale (Tanana River basin), the reduced glacier coverage and increased glacier wastage has, in combination with limited changes in precipitation, lead to (i) increased mean annual and (ii) late winter (March) runoff. We postulate that this is due to increased groundwater recharge, which has been fueled by the 20% reduction in glacier coverage of the Tanana River basin. Here we aim to assess the combined effect of climate change, glacier shrinkage and thawing permafrost on the regional sub-arctic mountain- to lowland hydrologic system, which may transition into a regime with less surface and more subsurface water availability.

  18. Hypsometric control on glacier mass balance sensitivity in Alaska

    NASA Astrophysics Data System (ADS)

    McGrath, D.; Sass, L.; Arendt, A. A.; O'Neel, S.; Kienholz, C.; Larsen, C.; Burgess, E. W.

    2015-12-01

    Mass loss from glaciers in Alaska is dominated by strongly negative surface balances, particularly on small, continental glaciers but can be highly variable from glacier to glacier. Glacier hypsometry can exert significant control on mass balance sensitivity, particularly if the equilibrium line altitude (ELA) is in a broad area of low surface slope. In this study, we explore the spatial variability in glacier response to future climate forcings on the basis of hypsometry. We first derive mass balance sensitivities (30-70 m ELA / 1° C and 40-90 m ELA / 50% decrease in snow accumulation) from the ~50-year USGS Benchmark glaciers mass balance record. We subsequently assess mean climate fields in 2090-2100 derived from the IPCC AR5/CMIP5 RCP 6.0 5-model mean. Over glaciers in Alaska, we find 2-4° C warming and 10-20% increase in precipitation relative to 2006-2015, but a corresponding 0-50% decrease in snow accumulation due to rising temperatures. We assess changes in accumulation area ratios (AAR) to a rising ELA using binned individual glacier hypsometries. For an ELA increase of 150 m, the mean statewide AAR drops by 0.45, representing a 70% reduction in accumulation area on an individual glacier basis. Small, interior glaciers are the primary drivers of this reduction and for nearly 25% of all glaciers, the new ELA exceeds the glacier's maximum elevation, portending eventual loss. The loss of small glaciers, particularly in the drier interior of Alaska will significantly modify streamflow properties (flashy hydrographs, earlier and reduced peak flows, increased interannual variability, warmer temperatures) with poorly understood downstream ecosystem and oceanographic impacts.

  19. Glaciers along proposed routes extending the Copper River Highway, Alaska

    USGS Publications Warehouse

    Glass, R.L.

    1996-01-01

    Three inland highway routes are being considered by the Alaska Department of Transportation and Public Facilities to connect the community of Cordova in southcentral Alaska to a statewide road system. The routes use part of a Copper River and Northwest Railway alignment along the Copper River through mountainous terrain having numerous glaciers. An advance of any of several glaciers could block and destroy the roadway, whereas retreating glaciers expose large quantities of unconsolidated, unvegetated, and commonly ice-rich sediments. The purpose of this study was to map historical locations of glacier termini near these routes and to describe hazards associated with glaciers and seasonal snow. Historical and recent locations of glacier termini along the proposed Copper River Highway routes were determined by reviewing reports and maps and by interpreting aerial photographs. The termini of Childs, Grinnell, Tasnuna, and Woodworth Glaciers were 1 mile or less from a proposed route in the most recently available aerial photography (1978-91); the termini of Allen, Heney, and Schwan Glaciers were 1.5 miles or less from a proposed route. In general, since 1911, most glaciers have slowly retreated, but many glaciers have had occasional advances. Deserted Glacier and one of its tributary glaciers have surge-type medial moraines, indicating potential rapid advances. The terminus of Deserted Glacier was about 2.1 miles from a proposed route in 1978, but showed no evidence of surging. Snow and rock avalanches and snowdrifts are common along the proposed routes and will periodically obstruct the roadway. Floods from ice-dammed lakes also pose a threat. For example, Van Cleve Lake, adjacent to Miles Glacier, is as large as 4.4 square miles and empties about every 6 years. Floods from drainages of Van Cleve Lake have caused the Copper River to rise on the order of 20 feet at Million Dollar Bridge.

  20. Ocean-Glacier Interactions in Alaska and Comparison to Greenland

    NASA Astrophysics Data System (ADS)

    Motyka, R. J.; Truffer, M.

    2011-12-01

    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

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

    USGS Publications Warehouse

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

    1977-01-01

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

  2. GLACIER BAY NATIONAL MONUMENT WILDERNESS STUDY AREA, ALASKA.

    USGS Publications Warehouse

    Brew, David A.; Kimball, Arthur L.

    1984-01-01

    Glacier Bay National Monument is a highly scenic and highly mineralized area about 100 mi west of Juneau, Alaska. Four deposits with demonstrated resources of nickel, copper, zinc, and molybdenum have been identified within the monument and eleven areas of probable or substantiated mineral-resource potential have been identified. The monument is highly mineralized in comparison with most areas of similar size elsewhere in southeastern Alaska, and present estimates of mineral resources are considered conservative.

  3. Surge-like behavior at the non-surge type Matanuska Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Furuya, M.; Abe, T.

    2014-12-01

    Seasonal glacier velocity changes are attributed to subglacial slip associated with water pressure changes that occur because of the seasonal variability of meltwater input. Abe and Furuya (2014) reported winter speed-up signals and their downglacier propagation at a number of glaciers near the border of Alaska and Yukon, based on ALOS/PALSAR radar image analyses. Here we perform the similar analyses at the Chugach mountain range of South Central Alaska, and report the spatial-temporal evolution of the Matanuska Glacier. Matanuska Glacier is the largest accessible glacier in Alaska with its nearly 40 km length and 5 km width near the terminus. Comparing the winter velocity images in 2007, 2008 and 2010, those in 2010 were about 1.5-2 times faster than those during the previous two years. In addition, comparing the fall and winter velocities, winter velocities were apparently faster at every 2007-2008, 2009-2010, and 2010-2011 season. These data indicate winter speed-up or mini-surge signals even at a temperate and non-surgetype Matanuska Glacier. We also examine the spatial-temporal elevation changes, using data from the LiDAR altimeter in the Icebridge mission, and found significant elevation increase near the terminus. Winter speed-up may not be uncommon at Alaskan/Yukon glaciers. Lingle and Fatland (2003) detected faster speed in winter than in fall at non-surging Seward Glacier in the St. Elias Mountains; this is the only published and unambiguous report of winter speed-up, to our knowledge. Combined with earlier glacier hydrological studies, Lingle and Fatland proposed englacial water storage and gravity-driven water flow toward the bed in winter regardless of whether a given glacier is surge-type or not, and considered that the capacity of englacial water storage would control if a given glacier was surge-type or not. We consider that our measurements are complementary to Lingle and Fatland's observations and lend further support for their hypothesis. Basal

  4. Response of glacier mass balance and discharge to future climate change, upper Susitna basin, Alaska

    NASA Astrophysics Data System (ADS)

    Aubry-Wake, C.; Hock, R.; Braun, J. L.; Zhang, J.; Wolken, G. J.; Liljedahl, A.

    2013-12-01

    As glaciers retreat, they highly alter the characteristics of the overall water budget of the larger drainage basin. Understanding and quantifying glacier melt is key to effectively project future changes in watershed-scale stream flow from glacierized landscapes. In glacierized Southcentral Alaska, the State of Alaska is reviving analyses of the Susitna River's hydroelectric potential and impact by supporting a multitude of field and modeling studies. Here, we focus on the response of discharge to projected climate change through the end-of-the century. The analyzed sub-catchment is largely untouched by humans, and covers an area of 2,230 km2 (740 - 4000 m a.s.l.) of which 25% is glacierized. We use a distributed temperature index model (DETIM), which uses daily air temperature and precipitation to compute runoff, ice and snow melt/accumulation. Model calibration included daily discharge and annual mass balance point measurements between 1955 and 2012. Output from the CCSM global climate model forced by three emission scenarios (A1B, A2 and B1) was downscaled to project future runoff and glacier mass balance until 2100. Depending on the climate scenario, runoff is projected to increase by 22 to 39% (yrs 2005-2100) due to increased mean annual air temperature ranging from 3.0 to 4.9°C and precipitation increase between 23 and 34%. During the same period, the glaciers are projected to lose between 11 to 14% of their area. The future projections show no trend in winter glacier mass balance, but suggest an increasingly negative specific summer mass balance. The DETIM model, despite its hydrologic simplicity and focus on snow and ice melt and accumulation, is able to reproduce well the observations in basin discharge and glacier mass balance.

  5. The slow advance of a calving glacier: Hubbard Glacier, Alaska, U.S.A

    USGS Publications Warehouse

    Trabant, D.C.; Krimmel, R.M.; Echelmeyer, K.A.; Zirnheld, S.L.; Elsberg, D.H.

    2003-01-01

    Hubbard Glacier is the largest tidewater glacier in North America. In contrast to most glaciers in Alaska and northwestern Canada, Hubbard Glacier thickened and advanced during the 20th century. This atypical behavior is an important example of how insensitive to climate a glacier can become during parts of the calving glacier cycle. As this glacier continues to advance, it will close the seaward entrance to 50 km long Russell Fjord and create a glacier-dammed, brackish-water lake. This paper describes measured changes in ice thickness, ice speed, terminus advance and fjord bathymetry of Hubbard Glacier, as determined from airborne laser altimetry, aerial photogrammetry, satellite imagery and bathymetric measurements. The data show that the lower regions of the glacier have thickened by as much as 83 m in the last 41 years, while the entire glacier increased in volume by 14.1 km3. Ice speeds are generally decreasing near the calving face from a high of 16.5 m d-1 in 1948 to 11.5 m d-1 in 2001. The calving terminus advanced at an average rate of about 16 m a-1 between 1895 and 1948 and accelerated to 32 m a-1 since 1948. However, since 1986, the advance of the part of the terminus in Disenchantment Bay has slowed to 28 m a-1. Bathymetric data from the lee slope of the submarine terminal moraine show that between 1978 and 1999 the moraine advanced at an average rate of 32 m a-1, which is the same as that of the calving face.

  6. Point measurements of surface mass balance, Eklutna Glacier, Alaska, 2008-2015

    USGS Publications Warehouse

    Sass, Louis; Loso, Michael G; Geck, Jason

    2017-01-01

    This data set consists of a time-series of direct measurements of glacier surface mass balance, at Eklutna Glacier, Alaska. It includes seasonal measurements of winter snow accumulation and summer snow and ice ablation.

  7. 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)

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

    2014-11-01

    Horizontal-slip 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.

  8. Ice elevations and surface change on the Malaspina Glacier, Alaska

    USGS Publications Warehouse

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

    2005-01-01

    Here we use Ice, Cloud and land Elevation Satellite (ICESat)-derived elevations and surface characteristics to investigate the Malaspina Glacier of southern Alaska. Although there is significant elevation variability between ICESat tracks on this glacier, we were able to discern general patterns in surface elevation change by using a regional digital elevation model (DEM) as a reference surface. Specifically, we report elevation differences between ICESat Laser 1-3 observations (February 2003 - November 2004) and a Shuttle Radar Topography Mission (SRTM)-derived DEM from February 2000. Elevation decreases of up to 20-25 m over a 3-4 year time period were observed across the folded loop moraine on the southern portion of the Malaspina Glacier. Copyright 2005 by the American Geophysical Union.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  10. Glacier-specific elevation changes in western Alaska

    NASA Astrophysics Data System (ADS)

    Paul, Frank; Le Bris, Raymond

    2013-04-01

    Deriving glacier-specific elevation changes from DEM differencing and digital glacier outlines is rather straight-forward if the required datasets are available. Calculating such changes over large regions and including glaciers selected for mass balance measurements in the field, provides a possibility to determine the representativeness of the changes observed at these glaciers for the entire region. The related comparison of DEM-derived values for these glaciers with the overall mean avoids the rather error-prone conversion of volume to mass changes (e.g. due to unknown densities) and gives unit-less correction factors for upscaling the field measurements to a larger region. However, several issues have to be carefully considered, such as proper co-registration of the two DEMs, date and accuracy of the datasets compared, as well as source data used for DEM creation and potential artefacts (e.g. voids). In this contribution we present an assessment of the representativeness of the two mass balance glaciers Gulkana and Wolverine for the overall changes of nearly 3200 glaciers in western Alaska over a ca. 50-year time period. We use an elevation change dataset from a study by Berthier et al. (2010) that was derived from the USGS DEM of the 1960s (NED) and a more recent DEM derived from SPOT5 data for the SPIRIT project. Additionally, the ASTER GDEM was used as a more recent DEM. Historic glacier outlines were taken from the USGS digital line graph (DLG) dataset, corrected with the digital raster graph (DRG) maps from USGS. Mean glacier specific elevation changes were derived based on drainage divides from a recently created inventory. Land-terminating, lake-calving and tidewater glaciers were marked in the attribute table to determine their changes separately. We also investigated the impact of handling potential DEM artifacts in three different ways and compared elevation changes with altitude. The mean elevation changes of Gulkana and Wolverine glaciers (about -0

  11. Reconnaissance hydrology of Portage Glacier basin, Alaska--1972

    USGS Publications Warehouse

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

    1977-01-01

    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)

  12. Marine Geophysical Surveying Along the Hubbard Glacier Terminus, Southeast Alaska

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Tidewater glaciers are a challenging environment for marine investigations, owing to the dangers associated with calving and restrictions on operations due to dense floating ice. We report here on recent efforts to conduct marine geophysical surveys proximal to the ice face of Hubbard Glacier, in Disenchantment Bay, Alaska. Hubbard is an advancing tidewater glacier that has twice recently (1986 and 2002) impinged on Gilbert Point, which separates Russell Fiord from Disenchantment Bay, thereby temporarily creating a glacially-dammed Russell Lake. Continued advance will likely form a more permanent dam, rerouting brackish outflow waters into the Situk River, near Yakutat, Alaska. Our primary interest is in studying the development and motion of the morainal bank which, for an advancing tidewater glacier, stabilizes it against rapid retreat. For survey work, we operated with a small, fast, aluminum-hulled vessel and a captain experienced in operating in ice-bound conditions, providing a high margin of safety and maneuverability. Differencing of multibeam bathymetric data acquired in different years can identify and quantify areas of deposition and erosion on the morainal bank front and in Disenchantment Bay proper, where accumulation rates are typically > 1 m/yr within 1 km of the glacier terminus. The advance or retreat rate of the morainal bank can be determined by changes in the bed elevation through time; we document advance rates that average > 30 m/yr in Disenchantment Bay, but which vary substantially over different time periods and at different positions along the ice face. Georeferencing of available satellite imagery allows us to directly compare the position of the glacial terminus with the position of the morainal bank. From 1978 to 1999, and then to 2006, the advances in terminus and morainal bank positions were closely synchronized along the length of the glacier face. In the shallower Russell Fiord side of the terminus, a sediment ridge was mapped both

  13. Southern Alaska Glaciers: Spatial and Temporal Variations in Ice Volume

    NASA Technical Reports Server (NTRS)

    Sauber, J.; Molnia, B. F.; Lutchke, S.; Rowlands, D.; Harding, D.; Carabajal, C.; Hurtado, J. M.; Spade, G.

    2004-01-01

    Although temperate mountain glaciers comprise less than 1% of the glacier-covered area on Earth, they are important because they appear to be melting rapidly under present climatic conditions and, therefore, make significant contributions to rising sea level. In this study, we use ICESat observations made in the last 1.5 years of southern Alaska glaciers to estimate ice elevation profiles, ice surface slopes and roughness, and bi-annual and/or annual ice elevation changes. We report initial results from the near coastal region between Yakutat Bay and Cape Suckling that includes the Malaspina and Bering Glaciers. We show and interpret ice elevations changes across the lower reaches of the Bagley Ice Valley for the period between October 2003 and May 2004. In addition, we use off-nadir pointing observations to reference tracks over the Bering and Malaspina Glaciers in order to estimate annual ice elevation change. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Shuttle Radar Topography Mission (SRTM) derived DEMs are used to estimate across track regional slopes between ICESat data acquisitions. Although the distribution and quantity of ICESat elevation profiles with multiple, exact repeat data is currently limited in Alaska, individual ICESat data tracks, provide an accurate reference surface for comparison to other elevation data (e.g. ASTER and SRTM X- and C-band derived DEMs). Specifically we report the elevation change over the Malaspina Glacier's piedmont lobe between a DEM derived from SRTM C-band data acquired in Feb. 2000 and ICESat Laser #2b data from Feb.-March 2004. We also report use of ICESat elevation data to enhance ASTER derived absolute DEMs. Mountain glaciers generally have rougher surfaces and steeper regional slopes than the ice sheets for which the ICESat design was optimized. Therefore, rather than averaging ICESat observations over large regions or relying on crossovers, we are working with well-located ICESat

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

    USGS Publications Warehouse

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

    2010-01-01

    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.

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

    USGS Publications Warehouse

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

    1999-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Korn, D.

    2010-12-01

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

  17. Dendrochronology and late Holocene history of Bering piedmont glacier, Alaska

    USGS Publications Warehouse

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

    1999-01-01

    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.

  18. Seismic detection and analysis of icequakes at Columbia Glacier, Alaska

    USGS Publications Warehouse

    O'Neel, Shad; Marshall, Hans P.; McNamara, Daniel E.; Pfeffer, William Tad

    2007-01-01

    Contributions to sea level rise from rapidly retreating marine-terminating glaciers are large and increasing. Strong increases in iceberg calving occur during retreat, which allows mass transfer to the ocean at a much higher rate than possible through surface melt alone. To study this process, we deployed an 11-sensor passive seismic network at Columbia Glacier, Alaska, during 2004–2005. We show that calving events generate narrow-band seismic signals, allowing frequency domain detections. Detection parameters were determined using direct observations of calving and validated using three statistical methods and hypocenter locations. The 1–3 Hz detections provide a good measure of the temporal distribution and size of calving events. Possible source mechanisms for the unique waveforms are discussed, and we analyze potential forcings for the observed seismicity.

  19. Processes on a glacier-dominated coast, Alaska

    USGS Publications Warehouse

    Molnia, Bruce F.

    1985-01-01

    The 500 km long Gulf of Alaska coastline between Cape Suckling and Cape Spencer can be characterized by constant rapid change in an environment of glaciers, stormy climate, high relief, and extreme oceanographic parameters. During a more than 200-year history of observation, bays have completely filled with sediment, new bays have appeared, glaciers have advanced and retreated as much as 40 km, streams have been captured, and spits have grown as much as 10 km in length, earthquakes have uplifted the coast as much as 15 m, and in general, few features have been static. More than 250 km of coastline have undergone erosion and retreat, with maximum retreat exceeding 4 km at Icy Bay.

  20. High porosity of basal till at Burroughs glacier, southeastern Alaska

    SciTech Connect

    Ronnert, L.; Mickelson, D.M. )

    1992-09-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    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).

  2. Observations of Dynamic Changes at an Advancing Tidewater Glacier: Hubbard Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Elliott, J.; Stearns, L. A.; Pritchard, M. E.; Bartholomaus, T.

    2015-12-01

    Hubbard Glacier, located in southeast Alaska, is the largest non-polar tidewater glacier in the world and one of a small number of glaciers that is steadily advancing. These attributes make it an intriguing target for observations of variations in ice dynamics over time. We use synthetic aperture radar data (ALOS and TerraSAR-X) and high-resolution optical imagery (WorldView and Quickbird) with a pixel tracking technique to map surface velocities from 2008 to the present, lengthening and broadening the time series of ice velocities presented in previous studies. A key result from our analysis is that Hubbard displays peak speeds of up to 12 m/day during the winter months (December - February) and minimum speeds during late summer (August - September). The times of peak and minimum speeds is quite different from those found in previous studies of Hubbard surface velocities derived from Landsat imagery, GPS, and photogrammetric methods. Those studies found peak speeds during late spring (May - June) and minimum speeds in fall (October-November), a pattern observed generally at tidewater glaciers. A second major feature we observe in our time series is the dramatic seasonal variation in surface speeds. The minimum speeds we find along the terminal lobe of the glacier are much lower than those found in previous studies, with values decreasing to near zero. Such a dramatic slow down of a tidewater glacier has not been widely observed. This result, along with the recent pattern of seasonal velocity peaks and minimas, suggests that Hubbard has undergone a change in ice dynamics.

  3. End-of-winter snow depth variability on glaciers in Alaska

    NASA Astrophysics Data System (ADS)

    McGrath, Daniel; Sass, Louis; O'Neel, Shad; Arendt, Anthony; Wolken, Gabriel; Gusmeroli, Alessio; Kienholz, Christian; McNeil, Christopher

    2015-08-01

    A quantitative understanding of snow thickness and snow water equivalent (SWE) on glaciers is essential to a wide range of scientific and resource management topics. However, robust SWE estimates are observationally challenging, in part because SWE can vary abruptly over short distances in complex terrain due to interactions between topography and meteorological processes. In spring 2013, we measured snow accumulation on several glaciers around the Gulf of Alaska using both ground- and helicopter-based ground-penetrating radar surveys, complemented by extensive ground truth observations. We found that SWE can be highly variable (40% difference) over short spatial scales (tens to hundreds of meters), especially in the ablation zone where the underlying ice surfaces are typically rough. Elevation provides the dominant basin-scale influence on SWE, with gradients ranging from 115 to 400 mm/100 m. Regionally, total accumulation and the accumulation gradient are strongly controlled by a glacier's distance from the coastal moisture source. Multiple linear regressions, used to calculate distributed SWE fields, show that robust results require adequate sampling of the true distribution of multiple terrain parameters. Final SWE estimates (comparable to winter balances) show reasonable agreement with both the Parameter-elevation Relationships on Independent Slopes Model climate data set (9-36% difference) and the U.S. Geological Survey Alaska Benchmark Glaciers (6-36% difference). All the glaciers in our study exhibit substantial sensitivity to changing snow-rain fractions, regardless of their location in a coastal or continental climate. While process-based SWE projections remain elusive, the collection of ground-penetrating radar (GPR)-derived data sets provides a greatly enhanced perspective on the spatial distribution of SWE and will pave the way for future work that may eventually allow such projections.

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

    USGS Publications Warehouse

    ,

    2009-01-01

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

  5. Glacier-volcano interactions in the north crater of Mt. Wrangell, Alaska

    USGS Publications Warehouse

    Abston, Carl; Motyka, Roman J.; McNutt, Stephen; Luthi, Martin; Truffer, Martin

    2007-01-01

    Glaciological and related observations from 1961 to 2005 at the summit of Mt Wrangell (62.008 N, 144.028W; 4317 m a.s.l.), a massive glacier-covered shield volcano in south-central Alaska, show marked changes that appear to have been initiated by the Great Alaska Earthquake (MW = 9.2) of 27 March 1964. The 4 x 6 km diameter, ice-filled Summit Caldera with several post-caldera craters on its rim, comprises the summit region where annual snow accumulation is 1–2 m of water equivalent and the mean annual temperature, measured 10 m below the snow surface, is –20°C. Precision surveying, aerial photogrammetry and measurements of temperature and snow accumulation were used to measure the loss of glacier ice equivalent to about 0.03 km3 of water from the North Crater in a decade. Glacier calorimetry was used to calculate the associated heat flux, which varied within the range 20–140W m–2; total heat flow was in the range 20–100 MW. Seismicity data from the crater’s rim show two distinct responses to large earthquakes at time scales from minutes to months. Chemistry of water and gas from fumaroles indicates a shallow magma heat source and seismicity data are consistent with this interpretation.

  6. Seismicity, seawater and seasonality: New insights into iceberg calving from Yahtse Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Bartholomaus, Timothy Chester

    At many of the largest glaciers and ice sheets on Earth, more than half of the annual ice loss occurs through iceberg calving into the ocean. Calving is also responsible for the most rapid ice mass changes, both directly (through the mechanical loss of ice at the terminus) and indirectly (through dynamic thinning of upstream ice initiated by terminus retreat). Yet, the mechanisms and factors that control calving are poorly understood. Recordings of glaciogenic seismic waves, known as "icequakes," produced during iceberg calving offer opportunities for insight that cannot be gleaned through other methods. In order to better understand iceberg calving and its links to calving icequakes, we conducted a 2-yr study of rapidly advancing Yahtse Glacier, site of one of the densest clusters of calving icequakes in southern Alaska. By synchronizing video of iceberg calving events with locally-recorded seismograms, we found that most icequake energy is produced after subaerial iceberg detachment from the glacier terminus, while the iceberg impacts and descends below the sea surface. Cavitation beneath the water surface generates the largest amplitude portions of icequakes---those that are detectable over several hundred km distances. Numerical simulations of these iceberg-sea surface interactions predict sources with durations that are consistent with the 1-5 Hz frequency content of calving icequakes. Oceanographic measurements in Icy Bay, where Yahtse Glacier terminates, reveal that warm water may melt most of the ice reaching the submarine terminus. During the summer, water with temperature > 10 °C flows from the Gulf of Alaska coast to within 2 km of Yahtse Glacier's terminus. We find that heat transport between 5 and 40x109 W can readily melt the submarine glacier terminus at a rate that matches the speed with which ice flows towards the glacier terminus (17 m/d). Subaerial iceberg calving rates may be paced by submarine melt rates. To place our calving and submarine

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

    USGS Publications Warehouse

    Meier, Mark Frederick; Tangborn, Wendell V.; Mayo, Lawrence R.; Post, Austin

    1971-01-01

    Glaciers occur in northwestern North America between lat 37 deg and 69 deg N. in two major mountain systems. The Pacific Mountain System, near the west coast, receives large amounts of precipitation, has very mild temperatures, and contains perhaps 90 percent of the glacier ice. The Rocky Mountain or Eastern System, on the other hand, receives nearly an order of magnitude less precipitation, has temperatures that range from subpolar to subtropic, and contains glaciers that are much smaller in both size and total area. As a contribution to the International Hydrological Decade program on combined balances at selected glaciers, the U.S. Geological Survey is conducting studies of ice and water balance on four glaciers in the Pacific Mountain System: Wolverine and Gulkana Glaciers in Alaska, South Cascade Glacier in Washington, and Maclure Glacier in California. Similar data are being collected by other organizations at five glaciers in western Canada, including two in the Rocky Mountain System, and at one glacier in the Rocky Mountain System in northern Alaska. Gulkana, Wolverine, South Cascade, and Maclure Glaciers have dissimilar mass balances, and each is fairly representative of the glaciers for its particular region. Gulkana Glacier (lat 63 deg 15' N., Alaska Range, Alaska) normally has an equilibrium line at an altitude of 1,800 m (meters), an activity index of about 6 mm/m (millimeters per meter), a winter balance of about 1.0 m, and an annual exchange of about 2.2 m. (Balance values are given in terms of water-equivalent measure; the winter balance of 1 m, for example, indicates a volume of ice equal in mass to a volume of water 1 m in depth covering the area of the glacier.) The normal approximate parameters for the other glaciers studied are as follows: Wolverine Glacier (lat 60 deg 24' N., Kenai Mountains, Alaska) - equilibrium-line altitude 1,200 m, activity index 9 mm/m, winter balance 2.5 m, and annual exchange 5.5 m; South Cascade Glacier (lat 48 deg 22

  8. Twenty-first century changes in the hydrology, glaciers, and permafrost of the Susitna Basin, Alaska

    NASA Astrophysics Data System (ADS)

    Bliss, A. K.; Hock, R.; Wolken, G. J.; Zhang, J.; Whorton, E.; Braun, J. L.; Gusmeroli, A.; Liljedahl, A.; Schulla, J.

    2014-12-01

    In the face of climate change, the hydrology of the upper Susitna Basin in South-Central Alaska is expected to change. This would impact the quantity and seasonality of river flow into a proposed hydroelectric dam, if it were to be built. The upper Susitna Basin catchment area is 13,289 km², ranging from 450-4000 m a.s.l. It is 4% glacierized and is characterized by sparse vegetation, discontinuous permafrost, and little human development. We present field measurements and results from hydrological modeling. We present new field data from spring and fall 2014 along with field measurements from the 1980's, 2012, and 2013. These data are used to calibrate and validate the hydrological model. Traditional glacier mass balance measurements show that the glaciers lost more mass in 2012 and 2013 than in 1981, 1982, or 1983. Springtime snow radar surveys of the glaciers allow us to extrapolate from point measurements of snow depth to the whole glacier area. Snow depth measurements at tundra sites as well as tundra vegetation and soil characterizations help us choose appropriate model parameters for the tundra portions of the basin. Meteorological data (temperature, humidity, and precipitation) from over 20 stations in the basin show the summertime temperature lapse rate to be smaller over glacier surfaces compared to ice-free surfaces. Precipitation is highly variable across the basin. Energy balance measurements from two meteorological stations, one located on West Fork Glacier and one on a nunatak near Susitna Glacier, are used for more detailed modeling of summertime glacier melt and runoff. We run a physically-based hydrological model to project 21st century river discharge: Water Flow and Balance Simulation Model (WaSiM). Climate inputs come from a CCSM CMIP5 RCP6.0 scenario downscaled to a 20km-5km nested grid using the Weather Research and Forecasting (WRF) Model. From 2010-2029 to 2080-2099 the basin-wide mean-annual temperature will rise 2.5 degrees and total

  9. Short-term velocity measurements at Columbia Glacier, Alaska; August-September 1984

    USGS Publications Warehouse

    Vaughn, B.H.; Raymond, C.F.; Rasmussen, Lowell A.; Miller, D.S.; Michaelson, C.A.; Meier, M.F.; Krimmel, R.M.; Fountain, A.G.; Dunlap, W.W.; Brown, C.S.

    1985-01-01

    Ice velocity data are presented for the lower reach of Columbia Glacier, Alaska. The data span a 29 day period and contain 1,072 angle sightings from two survey stations to 22 markers placed on the ice surface, and 1,621 laser measurements of the distance to one of those markers (number 11) from another station. These short-interval observations were made to investigate the dynamics of the glacier and to provide input to models for estimation of future retreat and iceberg discharge. The mean ice velocity (at marker number 11) was approximately 9 m/day and ranged from 8 to < 15 m/day. The data set includes a well defined 2-day, 50% velocity increase and a clear pattern of velocity fluctuations of about 5% with approximately diurnal and semiurnal periods. (Author 's abstract)

  10. Mass and Energy Balance Modeling of Glaciers in the Upper Susitna Basin, Alaska

    NASA Astrophysics Data System (ADS)

    Hoffman, A.; Hock, R.; Aubry-Wake, C.; Bliss, A.; Gusmeroli, A.; Liljedahl, A.; Gillispie, L.; Wolken, G. J.

    2014-12-01

    The State of Alaska is reviving analyses of the Susitna River's hydroelectric potential by supporting a multitude of field and modeling studies for the proposed Susitna-Watana Hydroelectric project. Critical to any effective hydroelectric development is a firm understanding of the basin-wide controls on river runoff and how seasonal reservoir recharge may change over the course of the structure's life-span. Effectively projecting future changes in watershed-scale stream flow for the Susitna river demands understanding and quantifying glacier melt in the Alaskan range. Our research is restricted to a sub-catchment of the upper Susitna basin that feeds the Susitna River covering 2,230 km2, of which 25% is glacierized. The goals of our study are to investigate the spatial and seasonal variations of the energy balance and its components across the glaciers and to model resulting streamflow from the catchment for the summer of 2013 using two models of different complexity. We apply DEBAM, a distributive energy balance model and DETIM, an enhanced temperature-index model, both coupled to a linear-reservoir runoff model, to simulate hourly surface energy fluxes, melt rates and glacier runoff using meteorological observations from an automated weather station located in the ablation zone of the West Fork glacier. Model results are compared to measurements of streamflow and mass balance at 20 ablation stakes across the glacierized area. The largest source of energy contributing to 85% of melt is net radiation followed by the sensible and latent heat fluxes. Both models capture well the seasonal and diurnal variations in streamflow and show good agreement with the mass balance point observations. The discrepancies between modeled and measured discharge can be attributed to the high uncertainty in precipitation and initial snow cover across the unglaciated part of the basin which accounts for over 75% of the modeled area.

  11. Isolation of oligotrophic yeasts from supraglacial environments of different altitude on the Gulkana Glacier (Alaska).

    PubMed

    Uetake, Jun; Yoshimura, Yoshitaka; Nagatsuka, Naoko; Kanda, Hiroshi

    2012-11-01

    Psychrophilic yeasts have been isolated from supra- and subglacial ice at many sites worldwide. To understand the ecology of psychrophilic yeasts on glaciers, we focused on their adaptation to wide range of nutrient concentrations and their distribution with altitude on the Gulkana Glacier in Alaska. We found various culturable psychrophilic yeasts on the ice surfaces of the glacier, and 11 species were isolated with incubation at 4 °C in four different dilutions of agar medium. Some of our isolated species (Rhodotorula psychrophenolica, Rhodotorula aff. psychrophenolica, Rhodotorula glacialis, and Basidiomycota sp. 1) can grow on the low dissolved organic matter (DOC) concentrations medium (7.6 mg L(-1)) which is close to the typical level of supraglacial melt water, suggesting that these species can inhabit in any supraglacial meltwater. Otherwise, most of other species were isolated only from higher DOC concentration medium (183 mg L(-1) -18.3 g L(-1)), suggesting that these are inhabitant around the cryoconite, because DOC concentrations in melted surface-ice contained cryoconite is much higher than in melted water. Similarity of altitudinal distribution between culturable yeast and algal biomass suggests that the ecological role played by the cold-adapted yeasts is as organic matter decomposers and nutrient cyclers in glacier ecosystem.

  12. Earthshots: Satellite images of environmental change – Hubbard Glacier, Alaska, USA

    USGS Publications Warehouse

    Adamson, Thomas

    2015-01-01

    These Landsat images illustrate an unusual event that was observed twice at the terminus of Hubbard Glacier. Hubbard temporarily blocked Russell Fjord (a long, narrow inlet of the sea) from the rest of Disenchantment Bay and the Gulf of Alaska. It’s even possible that the glacier could one day permanently block the fjord.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    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

  14. Glacier ice mass fluctuations and fault instability in tectonically active Southern Alaska

    USGS Publications Warehouse

    Sauber, J.M.; Molnia, B.F.

    2004-01-01

    Across the plate boundary zone in south central Alaska, tectonic strain rates are high in a region that includes large glaciers undergoing wastage (glacier retreat and thinning) and surges. For the coastal region between the Bering and Malaspina Glaciers, the average ice mass thickness changes between 1995 and 2000 range from 1 to 5 m/year. These ice changes caused solid Earth displacements in our study region with predicted values of -10 to 50 mm in the vertical and predicted horizontal displacements of 0-10 mm at variable orientations. Relative to stable North America, observed horizontal rates of tectonic deformation range from 10 to 40 mm/year to the north-northwest and the predicted tectonic uplift rates range from approximately 0 mm/year near the Gulf of Alaska coast to 12 mm/year further inland. The ice mass changes between 1995 and 2000 resulted in discernible changes in the Global Positioning System (GPS) measured station positions of one site (ISLE) located adjacent to the Bagley Ice Valley and at one site, DON, located south of the Bering Glacier terminus. In addition to modifying the surface displacements rates, we evaluated the influence ice changes during the Bering glacier surge cycle had on the background seismic rate. We found an increase in the number of earthquakes (ML???2.5) and seismic rate associated with ice thinning and a decrease in the number of earthquakes and seismic rate associated with ice thickening. These results support the hypothesis that ice mass changes can modulate the background seismic rate. During the last century, wastage of the coastal glaciers in the Icy Bay and Malaspina region indicates thinning of hundreds of meters and in areas of major retreat, maximum losses of ice thickness approaching 1 km. Between the 1899 Yakataga and Yakutat earthquakes (Mw=8.1, 8.1) and prior to the 1979 St. Elias earthquake (M s=7.2), the plate interface below Icy Bay was locked and tectonic strain accumulated. We used estimated ice mass

  15. Monitoring population status of sea otters (Enhydra lutris) in Glacier Bay National Park and Preserve, Alaska: options and considerations

    USGS Publications Warehouse

    Esslinger, George; Esler, Daniel N.; Howlin, S.; Starcevich, L.A.

    2015-06-25

    After many decades of absence from southeast Alaska, sea otters (Enhydra lutris) are recolonizing parts of their former range, including Glacier Bay, Alaska. Sea otters are well known for structuring nearshore ecosystems and causing community-level changes such as increases in kelp abundance and changes in the size and number of other consumers. Monitoring population status of sea otters in Glacier Bay will help park researchers and managers understand and interpret sea otter-induced ecosystem changes relative to other sources of variation, including potential human-induced impacts such as ocean acidification, vessel disturbance, and oil spills. This report was prepared for the National Park Service (NPS), Southeast Alaska Inventory and Monitoring Network following a request for evaluation of options for monitoring sea otter population status in Glacier Bay National Park and Preserve. To meet this request, we provide a detailed consideration of the primary method of assessment of abundance and distribution, aerial surveys, including analyses of power to detect interannual trends and designs to reduce variation around annual abundance estimates. We also describe two alternate techniques for evaluating sea otter population status—(1) quantifying sea otter diets and energy intake rates, and (2) detecting change in ages at death. In addition, we provide a brief section on directed research to identify studies that would further our understanding of sea otter population dynamics and effects on the Glacier Bay ecosystem, and provide context for interpreting results of monitoring activities.

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    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

  17. Devonian volcanogenic massive sulfide deposits and occurrences, southern Yukon-Tanana Terrace, eastern Alaska Range, Alaska

    USGS Publications Warehouse

    Lange, I.M.; Nokleberg, W.J.; Newkirk, S.R.; Aleinikoff, J.N.; Church, S.E.; Krouse, H.R.

    1993-01-01

    A belt of volcanogenic massive sulfide deposits extends for over 150km along the southern margin of the Yukon-Tanana terrane of the eastern Alaska Range. Located north of the Denali fault, the Yukon-Tanana terrane forms a major basement unit in east-central Alaska. The volcanogenic massive sulfide deposits are primarily in the Jarvis Creek Glacier subterrane, which consists of a volcanogenic massive sulfide-bearing metavolcanic rock member and a metasedimentary rock member. Two periods of regional metamorphism and penetrative deformation are indicated: an older, Early Cretaceous, amphibolite facies event and a younger, mid-Cretaceous lower greenschist facies event. The occurrence, mineralogy and sulphur isotope values are discussed. -from Authors

  18. Variability in glacier hazards across the Himalayan range

    NASA Astrophysics Data System (ADS)

    Quincey, D. J.

    2011-12-01

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

  19. Rapid wastage of Alaska glaciers and their contribution to rising sea level.

    PubMed

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

    2002-07-19

    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 (SLE) of 0.14 +/- 0.04 mm/year. Repeat measurements of 28 glaciers from the mid-1990s to 2000-2001 suggest an increased average rate of thinning, -1.8 m/year. This leads to an extrapolated annual volume loss from Alaska glaciers equal to -96 +/- 35 km3/year, or 0.27 +/- 0.10 mm/year SLE, during the past decade. These recent losses are nearly double the estimated annual loss from the entire Greenland Ice Sheet during the same time period and are much higher than previously published loss estimates for Alaska glaciers. They form the largest glaciological contribution to rising sea level yet measured.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  1. Assessing the sensitivity of Alaska's Coastal Ecosystem to Changes in Glacier Runoff

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The timing and magnitude of freshwater discharge to the Gulf of Alaska impacts rates of sea level change and the health of near shore ecosystems and fisheries. Glaciers strongly modulate the freshwater flux into this region and contribute to approximately 50% of its annual freshwater budget. It is generally assumed that persistently negative annual mass balances, forced by recent climate changes, are driving increases in glacier stream discharge. However, increases in runoff also depend on increased mass turnover rates, wherein the amplitude of seasonal mass balance increases due to enhanced snowfall and summer melt intensity. To quantify and partition runoff into the Gulf of Alaska we examine 1966-2010 US Geological Survey glacier mass balance and streamflow records from the Gulkana/Wolverine glaciers located in continental/maritime Alaska climate regimes. We compare annual, summer and winter balances with associated discharge magnitudes at each glacier to determine the primary controls on runoff magnitude and timing. We find that both glaciers have experienced increases in runoff and mass turnover, but only the Gulkana Glacier shows increases in stream discharge due to long term changes in annual mass balance. Conversely, Wolverine Glacier runoff is more sensitive to the amplitude of winter accumulation. The data suggest that changes in summer climate forcing are occurring over broader spatial scales than are changes in winter forcing. The analyses demonstrate that care is warranted when formulating assumptions relating glacier volume change to surface water hydrologic processes. Predicting future changes in runoff and implications for sea level rise, water resources and biological resources in this highly productive region requires that we better understand the processes that produce and modulate glacier runoff.

  2. Analysis of a GRACE global mascon solution for Gulf of Alaska glaciers

    USGS Publications Warehouse

    Arendt, Anthony; Luthcke, Scott; Gardner, Alex; O'Neel, Shad; Hill, David; Moholdt, Geir; Abdalati, Waleed

    2013-01-01

    We present a high-resolution Gravity Recovery and Climate Experiment (GRACE) mascon solution for Gulf of Alaska (GOA) glaciers and compare this with in situ glaciological, climate and other remote-sensing observations. Our GRACE solution yields a GOA glacier mass balance of –65 ± 11 Gt a–1 for the period December 2003 to December 2010, with summer balances driving the interannual variability. Between October/November 2003 and October 2009 we obtain a mass balance of –61 ± 11 Gt a–1 from GRACE, which compares well with –65 ± 12 Gt a–1 from ICESat based on hypsometric extrapolation of glacier elevation changes. We find that mean summer (June–August) air temperatures derived from both ground and lower-troposphere temperature records were good predictors of GRACE-derived summer mass balances, capturing 59% and 72% of the summer balance variability respectively. Large mass losses during 2009 were likely due to low early melt season surface albedos, measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) and likely associated with the 31 March 2009 eruption of Mount Redoubt, southwestern Alaska. GRACE data compared well with in situ measurements at Wolverine Glacier (maritime Alaska), but poorly with those at Gulkana Glacier (interior Alaska). We conclude that, although GOA mass estimates from GRACE are robust over the entire domain, further constraints on subregional and seasonal estimates are necessary to improve fidelity to ground observations.

  3. Analysis of a GRACE Global Mascon Solution for Gulf of Alaska Glaciers

    NASA Technical Reports Server (NTRS)

    Arendt, Anthony; Luthcke, Scott B.; Gardner, Alex; O'Neel, Shad; Hill, David; Moholdt, Geir; Abdalati, Waleed

    2013-01-01

    We present a high-resolution Gravity Recovery and Climate Experiment (GRACE) mascon solution for Gulf of Alaska (GOA) glaciers and compare this with in situ glaciological, climate and other remote-sensing observations. Our GRACE solution yields a GOA glacier mass balance of -6511 Gt a(exp.-1) for the period December 2003 to December 2010, with summer balances driving the interannual variability. Between October/November 2003 and October 2009 we obtain a mass balance of -6111 Gt a(exp. -1) from GRACE, which compares well with -6512 Gt a(exp. -1) from ICESat based on hypsometric extrapolation of glacier elevation changes. We find that mean summer (June-August) air temperatures derived from both ground and lower-troposphere temperature records were good predictors of GRACE-derived summer mass balances, capturing 59% and 72% of the summer balance variability respectively. Large mass losses during 2009 were likely due to low early melt season surface albedos, measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) and likely associated with the 31 March 2009 eruption of Mount Redoubt, southwestern Alaska. GRACE data compared well with in situ measurements atWolverine Glacier (maritime Alaska), but poorly with those at Gulkana Glacier (interior Alaska). We conclude that, although GOA mass estimates from GRACE are robust over the entire domain, further constraints on subregional and seasonal estimates are necessary to improve fidelity to ground observations.

  4. Differential erosion by different-sized glaciers as reflected in 10Be-derived erosion rates of glacier valley walls, Kichatna Mts., Alaska

    NASA Astrophysics Data System (ADS)

    Ward, D.; Anderson, R. S.

    2009-12-01

    The Kichatna Mountains, Alaska Range, Alaska comprise a dramatic landscape carved into a small ~65 Ma granitic pluton about 100 km west of Denali, in which kilometer-tall rock walls and “cathedral” spires tower over a radial array of over a dozen individual valley glaciers. The sheer scale of the relief speaks to the relative rates of valley incision by glaciers and rockwall retreat, but absolute rates are difficult to determine. We use cosmogenic 10Be to measure rockwall backwearing rates (and discuss several very important caveats to this use) on timescales of 103-104 yr, with a straightforward sampling strategy that exploits ablation-dominated medial moraines. In simple cases, a medial moraine and its associated englacial debris serve as a conveyor belt that brings supraglacial rockfall debris from the accumulation zone valley wall to a moraine crest in the ablation zone. Our samples come from the largest medial moraine on each of three glaciers. The northeast-flowing Trident glacier is the largest (15 km long, 1.4 km wide) and most deeply incised, and it has the lowest modern snowline in the range (~1200 m). Its primary medial moraine is sourced from west-facing sidewalls. The north-flowing Shadows glacier is slightly smaller (13 km long, 0.8 km wide) and has a large moraine sourced in dominantly east-facing sidewalls. The south-flowing Caldwell glacier is the smallest of the three (7 km long, 0.7 km wide), has a high modern snowline (~1500 m), and is nearly completely covered in debris. Its primary moraine is sourced from all south-facing aspects. These three glaciers share divides in their headwaters, and so are sourced in identical rock. Sidewall relief is similar (~1 km) in all three catchments. Each sample was amalgamated from 25-35 clasts collected over a 1 km longitudinal transect of each moraine. Replicate samples are internally consistent. The lowest 10Be concentrations (8000 at/g), and thus the highest inferred sidewall erosion rates (1.4 mm

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

    USGS Publications Warehouse

    Krimmel, R.M.

    1987-01-01

    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)

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

    USGS Publications Warehouse

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

    2008-01-01

    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.

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

    USGS Publications Warehouse

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

    2006-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

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

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

    USGS Publications Warehouse

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

    2007-01-01

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

  10. Reindeer ranges inventory in western Alaska

    NASA Technical Reports Server (NTRS)

    George, T. H.

    1981-01-01

    The use of LANDSAT data as a tool for reindeer range inventory on the tundra of northwestern Alaska is addressed. The specific goal is to map the range resource and estimate plant productivity of the Seward Peninsula. Information derived from these surveys is needed to develop range management plans for reindeer herding and to evaluate potential conflicting use between reindeer and caribou. The development of computer image classification techniques is discussed.

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

    NASA Astrophysics Data System (ADS)

    Pelto, M.

    2011-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    The Wind River Range (WRR) in west central Wyoming is host to 63 glaciers, while the Teton Range (TR) is host to 10 named glaciers. These glaciers serve as natural water reservoirs, and the continued recession of glaciers will impact agricultural water supply in the region. Glacier area changes in the WRR were estimated for 44 glaciers using un-rectified high resolution (1 m) aerial photography from 1966 to 2006. Additionally, glacier area was also developed for ten of the 44 glaciers using resampled aerial photography at 10 m (SPOT), 15 m (ASTER), 22.5 m (IRS-LISS) and 30 m (Landsat) resolutions for 1966 and 2006. The total surface area of the 44 glaciers was calculated to be 45.9 ± 0.13 km2 in 1966 and 28.5 ± 0.11 km2 in 2006, an average decrease of 38% over the 40 year period. Small glaciers experienced noticeably more area reduction than large glaciers. Of the 44 glaciers analyzed, 22 had an area of greater than 0.5 km2 in 1966, while 22 were less than 0.5 km2 in 1966. The glaciers with a surface area less than 0.5 km2 experienced an average surface area loss (fraction of 1966 surface area) of 47%, while the larger glaciers (greater than 0.5 km2) experienced an average surface area loss of 36% in 2006. Of the ten glaciers analyzed by resampling, the total surface area (fraction of 1966 surface area) decreased by 36.8% using aerial photographs, 36.5% using SPOT images, 36.6% using ASTER images, 36.0% using IRS-LISS images and 37.1% using Landsat images. Glacier area changes in the TR were estimated for three glaciers using un-rectified aerial photography from 1967 to 2006. The total surface area of the three glaciers was calculated to be 0.53 ± 0.13 km2 in 1967 and 0.40 ± 0.10 km2 in 2006, an average decrease of 34% over the 39 year period. The smallest glacier Teepe experienced the most noticeable lost, losing 60% while the Teton glacier lost 17%. Applying area-volume scaling relationships for Teton, Middle Teton, and Teepe glaciers, volume loss was

  13. Influence of glacier runoff on ecosystem structure in Gulf of Alaska fjords

    USGS Publications Warehouse

    Arimitsu, Mayumi; Piatt, John F.; Mueter, Franz J.

    2016-01-01

    To better understand the influence of glacier runoff on fjord ecosystems, we sampled oceanographic conditions, nutrients, zooplankton, forage fish and seabirds within 4 fjords in coastal areas of the Gulf Alaska. We used generalized additive models and geostatistics to identify the range of glacier runoff influence into coastal waters within fjords of varying estuarine influence and topographic complexity. We also modeled the response of depth-integrated chlorophyll a concentration, copepod biomass, fish and seabird abundance to physical, nutrient and biotic predictor variables. The effects of glacial runoff were traced at least 10 km into coastal fjords by cold, turbid, stratified and generally nutrient-rich near-surface conditions. Glacially modified physical gradients, nutrient availability and among-fjord differences explained 67% of the variation in phytoplankton abundance, which is a driver of ecosystem structure at higher trophic levels. Copepod, euphausiid, fish and seabird distribution and abundance were related to environmental gradients that could be traced to glacial freshwater input, particularly turbidity and temperature. Seabird density was predicted by prey availability and silicate concentrations, which may be a proxy for upwelling areas where this nutrient is in excess. Similarities in ecosystem structure among fjords were attributable to an influx of cold, fresh and sediment-laden water, whereas differences were likely related to fjord topography and local differences in estuarine vs. ocean influence. We anticipate that continued changes in the timing and volume of glacial runoff will ultimately alter coastal ecosystems in the future.

  14. Bedload component of glacially discharged sediment: Insights from the Matanuska Glacier, Alaska

    USGS Publications Warehouse

    Pearce, J.T.; Pazzaglia, F.J.; Evenson, E.B.; Lawson, D.E.; Alley, R.B.; Germanoski, D.; Denner, J.D.

    2003-01-01

    The flux of glacially derived bedload and the proportions of the suspended and bedload components carried by proglacial streams are highly debated. Published data indicate a large range-from 75%-in the bedload percentage of the total load. Two "vents," where supercooled subglacial meltwater and sediment are discharged, were sampled over the course of an entire melt season in order to quantify the flux of glacially delivered bedload at the Matanuska Glacier, Alaska. The bedload component contributed by these vents, for the one melt season monitored, is negligible. Furthermore, the bedload fluxes appear to be strongly supply limited, as shown by the poorly correlated discharge, bedload-flux magnitude, and grain-size caliber. Thus, in this case, any attempt to employ a predictive quantitative expression for coarse-sediment production based on discharge alone would be inaccurate. A nonglaciated basin proximal to the Matanuska Glacier terminus yielded higher bedload sediment fluxes and larger clast sizes than delivered by the two monitored vents. Such nonglaciated basins should not be overlooked as potentially major sources of coarse bedload that is reworked and incorporated into valley outwash.

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  16. Preliminary bathymetry of McCarty Fiord and Neoglacial changes of McCarty Glacier, Alaska

    USGS Publications Warehouse

    Post, Austin

    1980-01-01

    Preliminary bathymetry (at 1:20,000 scale) and other scientific studies of McCarty Fiord, Alaska, Conducted by the Research Vessel Growler in 1978, showed this 15 mile-long waterway to be a narrow, deeply scoured basin enclosed by a terminal-moraine shoal. This valley was formerly filled by McCarty Glacier, which began a drastic retreat shortly after 1909; the glacier reached shallow water at the head of the fiord around 1960. The relative rate of retreat in deep water and on land is disclosed by the slower melting of stagnent ice left in a side valley. Soundings and profiles show the main channel to extend to a depth as great as 957 feet and to have the typical ' U ' shape of a glacier-eroded valley; since the glacier 's retreat, sediments have formed a nearly level deposit in the deepest part of the fiord. Old forest debris dated by carbon-14 indicates that a neoglacial advance of the glacier began before 3,395 years B.P. (before present); by 1,500 B.P. the glacier filled most of the fiord, and before the glacier culminated its advance around 1860 , two glacier-dammed lakes were formed in side valleys. (USGS)

  17. Holocene glacier fluctuations inferred from lacustrine sediment, Emerald Lake, Kenai Peninsula, Alaska

    NASA Astrophysics Data System (ADS)

    LaBrecque, Taylor S.; Kaufman, Darrell S.

    2016-01-01

    Physical and biological characteristics of lacustrine sediment from Emerald Lake were used to reconstruct the Holocene glacier history of Grewingk Glacier, southern Alaska. Emerald Lake is an ice-marginal threshold lake, receiving glaciofluvial sediment when Grewingk Glacier overtops the topographic divide that separates it from the lake. Sub-bottom acoustical profiles were used to locate core sites to maximize both the length and resolution of the sedimentary sequence recovered in the 4-m-long cores. The age model for the composite sequence is based on 13 14C ages and a 210Pb profile. A sharp transition from the basal inorganic mud to organic-rich mud at 11.4 ± 0.2 ka marks the initial retreat of Grewingk Glacier below the divide of Emerald Lake. The overlaying organic-rich mud is interrupted by stony mud that records a re-advance between 10.7 ± 0.2 and 9.8 ± 0.2 ka. The glacier did not spill meltwater into the lake again until the Little Ice Age, consistent with previously documented Little Ice Ages advances on the Kenai Peninsula. The retreat of Grewingk Glacier at 11.4 ka took place as temperature increased following the Younger Dryas, and the subsequent re-advance corresponds with a climate reversal beginning around 11 ka across southern Alaska.

  18. Evaluate ERTS imagery for mapping and detection of changes of snowcover on land and on glaciers. [Washington, Alaska, British Columbia, and U.S.S.R.

    NASA Technical Reports Server (NTRS)

    Meier, M. F. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. The standard error of measurement of snow covered areas in major drainage basins in the Cascade Range, Washington, using single measurements of ERTS-1 images, was found to range from 11% to 7% during a typical melt season, but was as high as 32% in midwinter. Many dangerous glacier situations in Alaska, Yukon, and British Columbia were observed on ERTS-1 imagery. Glacier dammed lakes in Alaska are being monitored by ERTS-1. Embayments in tidal glaciers show changes detectable by ERTS-1. Surges of Russell and Tweedsmuir Glaciers, now in progress, are clearly visible. The Tweedsmuir surge is likely to dam the large Alsek River by mid-November, producing major floods down-river next summer. An ERTS-1 image of the Pamir Mountains, Tadjik S.S.R., shows the surging Medvezhii (Bear) Glacier just after its surge of early summer which dammed the Abdukagor Valley creating a huge lake and later a flood in the populous Vanch River Valley. A map was compiled from an ERTS-1 image of the Lowell Glacier after its recent surge, compared with an earlier map compiled from pain-stakingly compiled from a mosaic of many aerial photographs, in a total elapsed time of 1.5 hours. This demonstrates the value of ERTS-1 for rapid mapping of large features.

  19. Monitoring of oceanographic properties of Glacier Bay, Alaska 2004

    USGS Publications Warehouse

    2005-01-01

    Glacier Bay is a recently (300 years ago) deglaciated fjord estuarine system that has multiple sills, very deep basins, tidewater glaciers, and many streams. Glacier Bay experiences a large amount of runoff, high sedimentation, and large tidal variations. High freshwater discharge due to snow and ice melt and the presence of the tidewater glaciers makes the bay extremely cold. There are many small- and large-scale mixing and upwelling zones at sills, glacial faces, and streams. The complex topography and strong currents lead to highly variable salinity, temperature, sediment, primary productivity, light penetration, stratification levels, and current patterns within a small area. The oceanographic patterns within Glacier Bay drive a large portion of the spatial and temporal variability of the ecosystem. It has been widely recognized by scientists and resource managers in Glacier Bay that a program to monitor oceanographic patterns is essential for understanding the marine ecosystem and to differentiate between anthropogenic disturbance and natural variation. This year’s sampling marks the 12th continuous year of monitoring the oceanographic conditions at 23 stations along the primary axes within Glacier Bay, AK, making this a very unique and valuable data set in terms of its spatial and temporal coverage.

  20. 77 FR 13683 - Alaska Federal Lands Long Range Transportation Plan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-07

    ... Federal Highway Administration Alaska Federal Lands Long Range Transportation Plan AGENCY: Federal Highway..., announced the availability of the draft Alaska Federal Lands Long Range Transportation Plans (LRTP) for... Alaska Federal Lands draft Long Range Transportation Plans. The draft Plans are available on our...

  1. Evaluating glacier movement fluctuations using remote sensing: A case study of the Baird, Patterson, LeConte, and Shakes glaciers in central Southeastern Alaska

    NASA Astrophysics Data System (ADS)

    Davidson, Robert Howard

    Global Land Survey (GLS) data encompassing Landsat Multispectral Scanner (MSS), Landsat 5's Thematic Mapper (TM), and Landsat 7's Enhanced Thematic Mapper Plus (ETM+) were used to determine the terminus locations of Baird, Patterson, LeConte, and Shakes Glaciers in Alaska in the time period 1975-2010. The sequences of the terminuses locations were investigated to determine the movement rates of these glaciers with respect to specific physical and environmental conditions. GLS data from 1975, 1990, 2000, 2005, and 2010 in false-color composite images enhancing ice-snow differentiation and Iterative Self-Organizing (ISO) Data Cluster Unsupervised Classifications were used to 1) quantify the movement rates of Baird, Patterson, LeConte, and Shakes Glaciers; 2) analyze the movement rates for glaciers with similar terminal terrain conditions and; 3) analyze the movement rates for glaciers with dissimilar terminal terrain conditions. From the established sequence of terminus locations, movement distances were quantified between the glacier locations. Movement distances were then compared to see if any correlation existed between glaciers with similar or dissimilar terminal terrain conditions. The Global Land Ice Measurement from Space (GLIMS) data was used as a starting point from which glacier movement was measured for Baird, Patterson, and LeConte Glaciers only as the Shakes Glacier is currently not included in the GLIMS database. The National Oceanographic and Atmospheric Administration (NOAA) temperature data collected at the Petersburg, Alaska, meteorological station (from January 1, 1973 to December 31, 2009) were used to help in the understanding of the climatic condition in this area and potential impact on glaciers terminus. Results show that glaciers with similar terminal terrain conditions (Patterson and Shakes Glaciers) and glaciers with dissimilar terminal terrain conditions (Baird, Patterson, and LeConte Glaciers) did not exhibit similar movement rates

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

    NASA Astrophysics Data System (ADS)

    Wolfe, D. F.

    2008-12-01

    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 characterizations of these groups of basins and their 214 damming glaciers. Over 50% of historic GDLs, mapped by USGS in 1971, persisted. Of particular importance to proposed/existing infrastructure downstream, 34% of GDLs showing on recent satellite imagery were new since 1971; 44% of the glaciers damming these new GDLs did not previously dam GDLs. For absent GDLs, 70% of ice dam loss was related to glacier thinning; 27% was related to terminus retreat. Numbers of lakes and form of dam loss differed by damming glacier complexity and terminus type. Persisting lakes differed significantly (p=.005) from absent lakes in their: distance up the damming glacier in percent of its total length and in horizontal distance from terminus; and vertical distance below the mean glacier altitude. The predominant aspect of now-absent historic ice dams appeared to have strong oro-topographic origins. Emerging lake ice dam aspects, and the persistence of ice dams, by contrast, appear driven more by climate in that they predominantly face aspects of minimal solar input. Newly forming GDLs were significantly higher and 20% further up the length of damming glaciers than the now-absent historic lakes were, and 95% of all GDLs had glacier surface gradients of 6° or less below the GDL. This is of interest as GDL releases can flush waters stored within the glacier system, creating a larger than expected flood peak and/or duration, and gradients of 6° or less have been found to promote water storage within a glacier system. This work corroborates findings of dramatic

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

    SciTech Connect

    Payne, J.F.; Coffeen, M.; Macleod, R.D.

    1997-06-01

    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.

  4. Hydrography and circulation of ice-marginal lakes at Bering Glacier, Alaska, U.S.A.

    USGS Publications Warehouse

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

    2006-01-01

    An extensive suite of physical oceanographic, remotely sensed, and water quality measurements, collected from 2001 through 2004 in two ice-marginal lakes at Bering Glacier, Alaska-Berg Lake and Vitus Lake-show that each has a unique circulation controlled by their specific physical forcing within the glacial system. Conductivity profiles from Berg Lake, perched 135 m a.s.l., show no salt in the lake, but the temperature profiles indicate an apparently unstable situation, the 4??C density maximum is located at 10 m depth, not at the bottom of the lake (90 m depth). Subglacial discharge from the Steller Glacier into the bottom of the lake must inject a suspended sediment load sufficient to marginally stabilize the water column throughout the lake. In Vitus Lake, terminus positions derived from satellite imagery show that the glacier terminus rapidly retreated from 1995 to the present resulting in a substantial expansion of the volume of Vitus Lake. Conductivity and temperature profiles from the tidally influenced Vitus Lake show a complex four-layer system with diluted (???50%) seawater in the bottom of the lake. This lake has a complex vertical structure that is the result of convection generated by ice melting in salt water, stratification within the lake, and freshwater entering the lake from beneath the glacier and surface runoff. Four consecutive years, from 2001 to 2004, of these observations in Vitus Lake show little change in the deep temperature and salinity conditions, indicating limited deep water renewal. The combination of the lake level measurements with discharge measurements, through a tidal cycle, by an acoustic Doppler Current Profiler (ADCP) deployed in the Seal River, which drains the entire Bering system, showed a strong tidal influence but no seawater entry into Vitus Lake. The ADCP measurements combined with lake level measurements established a relationship between lake level and discharge, which when integrated over a tidal cycle, gives a

  5. Observations of the surge-type Black Rapids Glacier, Alaska, during a quiescent period, 1970-92

    USGS Publications Warehouse

    Heinrichs, Thomas A.; Mayo, L.R.; Trabant, D.C.; March, R.S.

    1995-01-01

    This report presents 23 years (1970 to 1992) of observations of Black Rapids Glacier, Alaska. Black Rapids Glacier is a surge-type glacier which most recently surged in 1936-37, and is currently in its quiescent phase. This glacier is of special interest because it is a potential hazard to the trans-Alaska oil pipeline. Ten sites on the glacier were monitored from 1972 to 1987, and three sites were monitored from 1988 to 1992. The measurement program presented here includes observations of surface mass balance, ice velocity, and surface altitude made twice each year. Additional one-time data include observations of ice thickness, previously unreported observations of the 1936-37 surge, establishment of the geodetic control monuments, and a new map of Black Rapids Glacier.

  6. Dust transport from glacierized rivers of southern Alaska to the Gulf of Alaska: Interannual variability in magnitude and sources

    NASA Astrophysics Data System (ADS)

    Crusius, J.; Schroth, A. W.; Campbell, R. W.; Resing, J.; Gasso, S.

    2014-12-01

    Dust from high latitudes is underappreciated and little studied. We recently identified new sites of dust formation, and a new dust generation mechanism, from the southern AK coastline, in Crusius et al, 2011. Dust is generated each autumn from glacierized river valleys as river levels and discharge decrease following summer peak glacier melt. The most prominent such river is the Copper River, the single largest freshwater source to the Gulf of Alaska. Each autumn the exposed river floodplains contain abundant, fine glacial flour and represent a large dust source region, prior to significant snowfall. Strong katabatic winds channeled down mountain river valleys generate dust from the fine glacial flour, which is transported as much as several hundred kilometers into the ocean. This dust is an important source of Fe to the Gulf of Alaska, where phytoplankton growth is limited by available Fe (a micronutrient). Glaciers are rapidly losing mass in this region, so there is an increasing supply of fine glacial flour during the summer melt season, and possibly increased deposition of fine glacial flour in the dust source regions. We initiated continuous, year-round time-series measurements of dust concentration, and its geochemical composition, in August of 2011 on Middleton Island, AK, which lies in the path of the dust plume extending from the Copper River valley. Dust is clearly generated from other glacierized river valleys along the southern coast of AK, as well. We will discuss results from our continuous record spanning three dust seasons, which prominently shows these events each autumn, and displays substantial interannual variability. Dust appears to remain in the boundary layer, but is transported hundreds of kilometers into the ocean, into Fe-limited waters. It is also possible that some of this dust is redeposited on snow or glacier surfaces, enhancing melting. This dust source is not accounted for in typical global dust models.

  7. Surface expression of subglacial meltwater movement, Bering Glacier, Alaska

    SciTech Connect

    Cadwell, D.H. ); Fleisher, P.J. . Dept. of Earth Sciences); Bailey, P.K. )

    1993-03-01

    Longitudinal topographic profiles (1988--1992) across the thermokarst terminus of the Grindle Hills Ice-tongue and interlobate moraine of the Bering Piedmont Glacier document annual changes in crevasse patterns and fluctuations in surface elevation related to subglacial water movement. A semi-continuous record of aerial photos (1978--1990), plus field observations (1988--1992), reveal the progressive enlargement of two lateral collapse basin on both sides of the thermokarst, connected by a transverse collapse trough. Seasonally generated meltwater at depth rises within the glacier, fills the basins and other depressions and lifts the thermokarst terminus of the ice-tongue a few meters by buoyancy and hydrostatic pressure. The resulting surface tension creates a chaotic crevasse pattern unrelated to normal glacier movement. The crevasses open (2 m wide, 8--10 m deep) in response to increased water accumulation at depth and close during subsidence as the ice-tongue settles following evacuation of subglacier water. A network of open conduits (>10 m diameter), exposed by surface ablation, provides evidence for the scale of englacial passageways beneath the thermokarst and represents a form of subglacial ablation that leads to removal of support and collapse in stagnant glacier masses.

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

    NASA Astrophysics Data System (ADS)

    Crossen, Kristine June

    1997-12-01

    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

  9. Radar remote sensing of glacial features, Malaspina Glacier, Alaska

    SciTech Connect

    Molnia, B.F.; Jones, J.E. )

    1990-05-01

    Two types of radar investigations were conducted at Malaspina glacier, the largest piedmont glacier lobe in North America. Digital x-band side-looking airborne radar (SLAR) data were collected to image surface features; ice-surface, ice-penetrating radar was employed to measure ice thickness and to identify the configuration of subglacial bed rock SLAR revealed a complex pattern of surface backscatter responses related to three types of channellike features on the glacier surface, which mimic the configuration of its underlying bed rock. The features resemble (1) glacially eroded valleys with cirque-like indentations, (2) dendritic stream valleys, and (3) a greater than 40-km-long, arcuate, east-west lineament that corresponds to the Fairweather fault. Field examinations of the three types of features were made to determine relief, slope, and other conditions. The channel-like features had elevations as much as 40 m lower than adjacent high areas and were characterized by fewer crevasses, minimal surface relief, a sediment veneer, and standing and running water. Hundred-m-spaced ice-penetrating radar soundings showed that the ice thickness over these low areas is much greater than over adjacent highs. About 50 ice-thickness measurements were made elsewhere on the glacier. The maximum ice thickness measured exceeded 850 m, whereas the minimum thickness was less than 150 m. Comparison of ice-thickness measurements and ice-surface elevations at each site suggests that the Malaspina Glacier occupies a deep basin or series of basins extending well below sea level.

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

    NASA Technical Reports Server (NTRS)

    SauberRosenberg, Jeanne M.; Molnia, Bruce F.

    2003-01-01

    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.

  11. Rapid thinning and collapse of lake calving Yakutat Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Trussel, Barbara Lea

    Glaciers around the globe are experiencing a notable retreat and thinning, triggered by atmospheric warming. Tidewater glaciers in particular have received much attention, because they have been recognized to contribute substantially to global sea level rise. However, lake calving glaciers in Alaska show increasingly high thinning and retreat rates and are therefore contributors to sea level rise. The number of such lake calving systems is increasing worldwide as land-terminating glaciers retreat into overdeepened basins and form proglacial lakes. Yakutat Glacier in Southeast Alaska is a low elevation lake calving glacier with an accumulation to total area ratio of 0.03. It experienced rapid thinning of 4.43 +/- 0.06 m w.e. yr-1 between 2000-2010 and terminus retreat of over 15 km since the beginning of the 20th century. Simultaneously, adjacent Yakutat Icefield land-terminating glaciers thinned at lower but still substantial rates (3.54 +/- 0.06 m w.e. yr -1 for the same time period), indicating lake calving dynamics help drive increased mass loss. Yakutat Glacier sustained a ˜3 km long floating tongue for over a decade, which started to disintegrate into large tabular icebergs in 2010. Such floating tongues are rarely seen on temperate tidewater glaciers. The floating ice was weakened by surface ablation, which then allowed rifts to form and intersect. Ice velocity from GPS measurements showed that the ice on the floating tongue was moving substantially faster than grounded ice, which was attributed to rift opening between the floating and grounded ice. Temporal variations of rift opening were determined from time-lapse imagery, and correlated well with variations in ice speeds. Larger rift opening rates occurred during and after precipitation or increased melt episodes. Both of these events increased subglacial discharge and could potentially increase the subaqueous currents towards the open lake and thus increase drag on the ice underside. Simultaneously

  12. Photogrammetric Data Set, 1957-2000, and Bathymetric Measurements for Columbia Glacier, Alaska

    USGS Publications Warehouse

    Krimmel, Robert M.

    2001-01-01

    Major changes in the length, speed, surface altitude, and calving rate of Columbia Glacier, Alaska have been recorded with stereo vertical photography acquired on 119 dates from 1957 to 2000. Photogrammetric analysis of this photographic record has resulted in precise measurement of these changes. From 1982 to 2000 Columbia Glacier retreated 12 kilometers, reduced its thickness by as much as 400 meters, increased its speed from about 5 to 30 meters per day, and increased its calving rate from 3 to 18 million cubic meters per day. All photogrammetric data for Columbia Glacier from 1957 to 2000 are included in this report, as well as supplemental data of ice-dammed lake surface levels, stagnant ice ablation rate, forebay bathymetry, ground control, and camera calibrations. These data are contained in 481 files, all preserved on a CD-ROM included with this report.

  13. Effect of glacier ablation on the Snettisham Hydroelectric Project, Long Lake and Crater Lake Basins, Alaska

    USGS Publications Warehouse

    Sloan, C.E.; Emery, P.A.; Fair, Diana

    1986-01-01

    Long Lake Basin in the Snettisham Project Area southeast of Juneau, Alaska, yields water used for the production of hydroelectric power. Development of adjacent Crater Lake is planned to increase the Project 's generating capacity. Estimates of the hydroelectric potential of the lakes are based on streamflow records which are influenced by glaciers that cover 25% of the combined basins. Analysis of streamflow records shows that the quality and extent of records in the area are sufficient to predict flow from the Crater Creek basin with a fairly high degree of confidence. Comparison of aerial photographs indicates that glacier ablation and recession have been continuous since at least 1929. Estimates of ice-volume change from photogrammetric measurements indicate that less than 2.5% of the average runoff from the basins of Long and Crater Lakes has been from reduction in glacier-ice storage. (Author 's abstract)

  14. Alaska: Glaciers of Kenai Fjords National Park and Katmai National Park and Preserve (Chapter 12)

    NASA Technical Reports Server (NTRS)

    Giffen, Bruce A.; Hall, Dorothy K.; Chien, Janet Y.L.

    2007-01-01

    Much recent research points to the shrinkage of the Earth's small glaciers, however, few studies have been performed to quantify the amount of change over time. We measured glacier-extent changes in two national parks in southeastern Alaska. There are hundreds of glaciers in Kenai Fjords National Park (KEFJ) and Katmai National Park and Preserve (KATM) covering over 2373 sq km of parkland. There are two primary areas of glaciation in KEFJ - the Harding Icefield and the Grewingk-Yalik Glacier Complex, and three primary areas of glaciation in KATM - the Mt. Douglas area, the Kukak Volcano to Mt. Katmai area and the Mt. Martin area. We performed glacier mapping using satellite imagery, from the 1970s, 1980s, and from 2000. Results of the analysis show that there has been a reduction in the amount of glacier ice cover in the two parks over the study period, of approximately 22 sq km of ice, approximately - 1.6% from 1986 to 2000 (for KEFJ), and of approximately 76 sq km of glacier ice, or about -7.7% from 1986187 to 2000 (for KATM). In the future, measurements of surface elevation changes of these ice masses should be acquired; together with our extent-change measurements, the volume change of the ice masses can then be determined to estimate their contribution to sea-level rise. The work is a continuation of work done in KEFJ, but in KATM, our measurements represent the first comprehensive study of the glaciers in this remote, little-studied area.

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

    USGS Publications Warehouse

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

    2008-01-01

    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.

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

    USGS Publications Warehouse

    Trabant, Dennis C.; Hawkins, Daniel B.

    1997-01-01

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

  17. Geologic characteristics of benthic habitats in Glacier Bay, southeast Alaska

    USGS Publications Warehouse

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

    2006-01-01

    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.

  18. Subglacial environment inferred from bedrock-coating siltskins, Mendenhall Glacier, Alaska, U. S. A.

    NASA Astrophysics Data System (ADS)

    Carter, Carissa L.; Dethier, David P.; Newton, Robert L.

    2003-12-01

    Retreat of Mendenhall Glacier near Juneau, Alaska, U. S. A., has exposed a bedrock ridge spotted with ''siltskins'', patchy coatings of calcite-cemented clay-to sand-sized lithic grains. Coatings 0.5-20 mm thick occur in two distinct morphologies. Thin, striated siltskins coat mainly stoss faces. Thicker, corrugated siltskins on lee faces consist of parallel micro-ridges elongated downslope. Thin-section analysis shows that siltskins consist of a basal, calcite-rich layer overlain by microlaminated layers of calcite-cemented lithic grains. Scanning electron microscope (SEM) energy-dispersive spectrometer (EDS) analysis of laminae and surfaces shows laterally persistent Ca/Si differences. Isotopic values for δO18and δO13ranged from -19.52‰ to ^12.74‰ and -6.18‰ to -3.44‰, respectively, consistent with deposition from subglacial waters of varying isotopic composition and with derivation of carbon from inorganic sources. Corrugated siltskins are complex depositional features modified by erosional processes. Parallel micro-ridges spaced 1-10 mm apparently formed as sediment-rich water dripped down lee-slope rock faces. Ice-rock separation, flow energy and the transported sediment controlled the layering and depositional forms. Siltskins probably formed when a subglacial cavity system was active on the rock ridge and provide clues about how microscale hydrologic processes interact with larger-scale subglacial systems.

  19. Preliminary bathymetry of Blackstone Bay and Neoglacial changes of Blackstone Glaciers, Alaska

    USGS Publications Warehouse

    Post, Austin

    1980-01-01

    Preliminary bathymetry (at 1:20,000 scale) and scientific studies of Blackstone Bay Alaska, by the Research Vessel Growler in 1978 disclose that the head of the bay consists of two basins separated by Willard Island and a submarine ridge. Both basins are closed on the north by terminal-moraine bars where Blackstone Glacier and its tributaries terminated as recently as about A.D. 1350; a carbon-14 date of 580 years before present on Badger Point, and old trees farther up the bay, disclose that the glaciers retreated to two narrow inlets at the head of the bay before 1400. The inlets were still glacier-covered until at least 1909. Glaciers in both inlets have continued to retreat; at present they terminate at the head of tidewater, where they discharge small icebergs. Only relatively thin sediments have accumulated in the eastern basin south of the terminal-moraine bar, and most of the bottom is hard and irregular as disclosed by soundings and profiles. The northern part of Blackstone Bay is very deep; at more than 1,100 feet below sea level a large, level accumulation of sediment is present which is presumably as much as 1,000 feet deep and has been accumulating since late Pleistocene glaciers retreated. (USGS)

  20. Multibeam bathymetry and selected perspective views of main part of Glacier Bay, Alaska

    USGS Publications Warehouse

    Carlson, Paul R.; Hooge, Philip; Cochrane, Guy; Stevenson, Andrew; Dartnell, Pete; Lee, Kristen

    2002-01-01

    Glacier Bay is a diverse fjord ecosystem with multiple tidewater glaciers and complex biological, geological, and oceanographic patterns that vary greatly along its length. The bay was completely glaciated prior to the 1700's, and subsequently experienced the fastest glacial retreat recorded in historical times. As a result, some of the highest rates of glacial sedimentation and uplift are observed here. Glacier Bay is the deepest silled fjord in Alaska, with depths of over 450 meters. The variety of physical processes and depths creates many diverse habitats within a relatively small area. Mapping benthic (seafloor) habitats is thus crucial to understanding and managing Glacier Bay's complex marine ecosystem and the marine species therein. High-resolution multibeam mapping of the bay, funded jointly by USGS and the National Park System, provides an unprecedented new baseline for resource and habitat assessment. Full integration of the new data set will require additional ground-truthing data (sampling) and analysis. The USGS goal is to develop integrated geological and oceanographic habitat models for the marine benthos in Glacier Bay, as a step toward determining the habitat relationships of critical species and resources within the Park.

  1. Surface Mass Balance of the Columbia Glacier, Alaska, 1978 and 2010 Balance Years

    USGS Publications Warehouse

    O'Neel, Shad

    2012-01-01

    Although Columbia Glacier is one of the largest sources of glacier mass loss in Alaska, surface mass balance measurements are sparse, with only a single data set available from 1978. The dearth of surface mass-balance data prohibits partitioning of the total mass losses between dynamics and surface forcing; however, the accurate inclusion of calving glaciers into predictive models requires both dynamic and climatic forcing of total mass balance. During 2010, the U.S. Geological Survey collected surface balance data at several locations distributed over the surface of Columbia Glacier to estimate the glacier-wide annual balance for balance year 2010 using the 2007 area-altitude distribution. This report also summarizes data collected in 1978, calculates the 1978 annual surface balance, and uses these observations to constrain the 2010 values, particularly the shape of the balance profile. Both years exhibit balances indicative of near-equilibrium surface mass-balance conditions, and demonstrate the importance of dynamic processes during the rapid retreat.

  2. Status and trend of the Kittlitz's Murrelet Brachyramphus brevirostris in Glacier Bay, Alaska

    USGS Publications Warehouse

    Piatt, J.F.; Arimitsu, M.; Drew, G.; Madison, E.N.; Bodkin, J.; Romano, Marc D.

    2011-01-01

    We conducted standardized surveys for marine birds in Glacier Bay in seven years between 1991 and 2008. From our most recent survey, a combination of line- and strip-transect methods completed in 2008, we estimated that 4981 (95% CI 1293-8670) Kittlitz's Murrelets Brachyramphus brevirostris resided in Glacier Bay during the month of June, together with 12 195 (5607-18 783) Marbled Murrelets B. marmoratus. When counts were prorated to assign unidentified Brachyramphus murrelets to species, population estimates increased to 5641 Kittlitz's Murrelets and 13 810 Marbled Murrelets. Our surveys of bird numbers in Glacier Bay between 1991 and 2008 revealed that Kittlitz's Murrelet declined by ???85% during this period. Trend analysis suggested a rate of decline between -10.7% and -14.4% per year. No direct human impacts (e.g., bycatch, oil pollution, vessel disturbance) in our study area could fully account for a decline of this magnitude. Widespread declines of Brachyramphus murrelets and Harbor Seals Phoca vitulina in the Gulf of Alaska during the 1980s-1990s suggest large-scale influences on these marine predators, perhaps related to climate-mediated cycles in food supply. Other natural factors that may impact Glacier Bay populations include predation by avian and terrestrial predators, widespread glacial retreat and its effect on nesting and foraging habitats, and competition for food with marine predators whose abundance in Glacier Bay has increased markedly in recent years (Humpback Whales Megaptera novaeangliae and Steller Sea Lions Eumetopias jubatus).

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

    NASA Technical Reports Server (NTRS)

    Meigs, Andrew; Sauber, Jeanne

    2000-01-01

    Southern Alaska is a continent-scale region of ongoing crustal deformation within the Pacific-North American plate boundary zone. Glaciers and glacial erosion have dictated patterns of denudation in the orogen over the last approx. 5 My. The orogen comprises three discrete topographic domains from south to north, respectively: (1) the Chugach/St. Elias Range; (2) the Wrangell Mountains; and (3) the eastern Alaska Range. Although present deformation is distributed across the orogen, much of the shortening and uplift are concentrated in the Chugach/St. Elias Range. A systematic increase in topographic wavelength of the range from east to west reflects east-to-west increases in the width of a shallowly-dipping segment of the plate interface, separation of major upper plate structures, and a decrease in the obliquity of plate motion relative to the plate boundary. Mean elevation decays exponentially from approx. 2500 m to approx. 1100 m from east to west, respectively. Topographic control on the present and past distribution of glaciers is indicated by close correspondence along the range between mean elevation and the modern equilibrium line altitude of glaciers (ELA) and differences in the modern ELA, mean annual precipitation and temperature across the range between the windward, southern and leeward, northern flanks. Net, range- scale erosion is the sum of: (1) primary bedrock erosion by glaciers and (2) erosion in areas of the landscape that are ice-marginal and are deglaciated at glacial minima. Oscillations between glacial and interglacial climates controls ice height and distribution, which, in turn, modulates the locus and mode of erosion in the landscape. Mean topography and the mean position of the ELA are coupled because of the competition between rock uplift, which tends to raise the ELA, and enhanced orographic precipitation accompanying mountain building, which tends to lower the ELA. Mean topography is controlled both by the 60 deg latitude and maritime

  4. Turbidity-current channels in Queen Inlet, Glacier Bay, Alaska

    USGS Publications Warehouse

    Carlson, P.R.; Powell, R.D.; Rearic, D.M.

    1989-01-01

    Queen Inlet is unique among Glacier Bay fjords because it alone has a branching channel system incised in the Holocene sediment fill of the fjord floor. Queen Inlet and other known channel-containing fjords are marine-outwash fjords; the tidewater glacial fjords do not have steep delta fronts on which slides are generated and may not have a sufficient reservoir of potentially unstable coarse sediment to generate channel-cutting turbidity currents. Presence or absence of channels, as revealed in the ancient rock record, may be one criterion for interpreting types of fjords. -Authors

  5. Latest Pleistocene advance and collapse of the Matanuska - Knik glacier system, Anchorage Lowland, southern Alaska

    NASA Astrophysics Data System (ADS)

    Kopczynski, Sarah E.; Kelley, Samuel E.; Lowell, Thomas V.; Evenson, Edward B.; Applegate, Patrick J.

    2017-01-01

    At the end of the last ice age, glacier systems worldwide underwent dramatic retreat. Here, we document the advance and retreat of a glacier system with adjacent marine- and land-based components during the latter part of the Termination. We utilize three lines of evidence: lithologic provenance, geomorphic mapping, and radiocarbon ages derived from lake cores to reconstruct glacier extent and timing of advance and retreat within our study area centered at N 61.50°, W 149.50°, just north of Anchorage, Alaska. Two glaciers, sourced in the Talkeetna and Chugach Mountains, flowed down the Matanuska and Knik Valleys forming a coalesced lobe that advanced onto the Anchorage Lowlands and terminated at Elmendorf Moraine. We use the presence of lithologies unique to the Matanuska catchment in glacial drift to delineate the paleoflow lines and to estimate the suture line of the two glacier systems. The eastern side of the lobe, attributed to ice flow from the Knik Valley, was in contact with elevated marine waters within the Knik Arm fjord, and thus retreat was likely dominated by calving. Geomorphic evidence suggests the western side of the lobe, attributed to ice flow from Matanuska Valley, retreated due to stagnation. We constrain retreat of the combined Matanuska and Knik lobe with thirteen new radiocarbon ages, in addition to previously published radiocarbon ages, and with geomorphic evidence suggesting the retreat occurred in two phases. Retreat from the Elmendorf Moraine began between 16.8 and 16.4 ka BP. A second, faster retreat phase occurred later and was completed by 13.7 ka BP. With the 140 km of total retreat occurring over ∼3000 years or less. This pattern of glacial advance and retreats agrees well with the deglacial histories from the southern sectors of the Cordilleran Ice Sheet, as well as many other alpine glacier systems in the western U.S. and northern Alaska. This consistent behavior of glacier systems may indicate that climate oscillated over

  6. Variations in melt inputs and basal sliding velocity on the Kennicott Glacier, Alaska, USA

    NASA Astrophysics Data System (ADS)

    Armstrong, W. H.; Barnhart, K. R.; Anderson, R. S.; Rajaram, H.

    2012-12-01

    We present glacier surface motion, meteorologic, and hydrologic observations from the 2012 melt season on the Kennicott Glacier near McCarthy, Alaska. We record 15-second global positioning system (GPS) data from five monuments along the glacier centerline, 10-minute water level data from pressure sensors in four ice-marginal basins and one on the glacier outlet river, 10-minute air temperature and ablation rates, and one-hour time-lapse photography on two ice-marginal basins and the outlet stream. We use these data to investigate linkages between subglacial hydrology and glacier basal sliding velocity. Time-lapse imagery and pressure sensor time series capture a complicated early season fill-and-drain sequence on an ice-marginal lake, likely reflecting the interplay between melt supply and development of a hydrologic link between the basin and a presumed nearby low-pressure subglacial conduit. We also capture a midsummer jökulhlaup in which 20-30 x 10^6 cubic meters of water drain from the ice-dammed Hidden Creek Lake over the course of 60 hours. The flood wave propagates down-glacier, reaching the glacier terminus 15 kilometers away about 30 hours after the initiation of lake drainage. The flood wave raises stage by many tens of meters in ice-marginal basins and doubles discharge on the outlet stream. We compare water level records to differential GPS time series to monitor the glacier sliding response to seasonal, daily, and event-based variations in water inputs. This study builds on our 2006 research in the area by increasing GPS monument density, extending the monitoring season, and including time-lapse photography. These improvements allow us to resolve in greater temporal and spatial detail the glacier's response to hydrologic conditions throughout the melt season. Although the 2012 summer was generally cooler than summer 2006, we find remarkable similarity between the outburst flood hydrographs for the two years, indicating similarities in the evolution

  7. Subglacial Environment Inferred from Bedrock-Coating Siltskins, Mendenhall Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Carter, C. L.; Dethier, D. P.; Newton, R.

    2002-12-01

    In the past two decades, retreat of the Mendenhall Glacier near Juneau, Alaska has exposed a bedrock ridge spotted with 'siltskins', patchy coatings of calcite-cemented clay to sand-sized lithic grains. Coatings range from 0.5 to 20 mm thick and occur in two distinct morphologies. Striated siltskins are thin, located mainly on stoss faces, and preserve local striation direction. Thicker, corrugated skins preserved on lee faces consist of parallel microridges elongated downslope. Thin section analysis shows that siltskins consist of a basal, calcite-rich layer overlain by microlaminated layers of calcite-cemented lithic grains. Microstrata in layers of corrugated siltskins display complex internal structures including wavy microlaminae, truncated cross-bedding, convolute forms, and pockets of larger grains. SEM/EDS analysis of siltskin laminae and surfaces show laterally persistent Ca/Si differences. Isotopic values of ΔO18 and ΔC13 ranged from -19.52 to -12.74 and -6.18 to -3.44, respectively in five samples of cement, consistent with deposition from subglacial waters of varying isotopic concentrations and with derivation of carbon from inorganic sources. Regelation processes probably caused precipitation of the basal calcite layer from ice enriched in Ca. After the basal layer reached a limiting thickness, deposition of microlaminae of the upper layer dominated. The relatively thick corrugated siltskins we studied are depositional features enhanced by erosional processes. Wavelengths of parallel microridges generally range from 1 to 10 mm and apparently formed as sediment-rich water dripped or oozed down lee slope rock faces. Ice-rock separation, flow energy, and the amount and grain size of transported sediment controlled the layering and depositional forms. Deposition of siltskins depended on macro-scale processes in the glacier system, outcrop-scale features of the rock ridge, and micro-scale interactions of the ice, bedrock, and thin films of water in the

  8. Methane seeps along boundaries of receding glaciers in Alaska and Greenland

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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

  9. Glacier Basal Sliding in Two-Dimensions Quantified from Correlation of High-Resolution Satellite Imagery: A Case Study on Kennicott Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Armstrong, W. H., Jr.; Anderson, R. S.; Allen, J.; Rajaram, H.; Anderson, L. S.

    2014-12-01

    The coupling of glacial hydrology and sliding is a source of uncertainty for both ice flow modeling and prediction of future sea level rise. As basal sliding is required for a glacier to erode its bed, the spatial pattern of glacier sliding is also important for understanding alpine landscape evolution. We use multi-temporal WorldView satellite imagery (0.5 m pixel) to monitor the seasonal progression of glacier velocity across the terminal ~50 km2of Kennicott Glacier, Alaska. We employ the free image correlation software COSI-Corr to construct multiple velocity maps, using 2013 imagery with repeat times from 15 to 38 days. These short intervals between images allow us to analyze variations in glacier velocity over weekly to monthly timescales associated with hydrologically-induced basal sliding. By assuming that spring (March-April) glacier velocity results solely from viscous deformation, we produce spatially distributed maps of glacier sliding speed by differencing summer and spring ice surface speeds. For a given time, a large portion of our study reach slides with roughly uniform speed, despite significant variation in deformation speed. This suggests that glacier flow models in which basal sliding is taken simply to scale as ice surface velocity are unfounded. The upglacier end of our study reach slides at speeds that vary through the summer, whereas the terminal reach slides at a steady speed. The proportion of glacier motion due to sliding increases dramatically moving downglacier, making basal sliding especially important in the terminal region. Many formulations express glacier sliding as a function of effective pressure (ice pressure minus water pressure). If such formulations are correct, effective pressure varies little over large areas or is averaged over lengthscales equivalent to ~10 glacier thicknesses. Also, effective pressure is steady in the terminal region through the summer. We explore existing sliding laws to find which best describes the

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

    NASA Astrophysics Data System (ADS)

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

    1999-11-01

    The authors examine the net winter, summer, and annual mass balance of six glaciers along the northwest coast of North America, extending from Washington State to Alaska. The net winter (NWB) and net annual (NAB) mass balance anomalies for the maritime glaciers in the southern group, located in Washington and British Columbia, are shown to be positively correlated with local precipitation anomalies and storminess (defined as the rms of high-passed 500-mb geopotential anomalies) and weakly and negatively correlated with local temperature anomalies. The NWB and NAB of the maritime Wolverine glacier in Alaska are also positively correlated with local precipitation, but they are positively correlated with local winter temperature and negatively correlated with local storminess. Hence, anomalies in mass balance at Wolverine result mainly from the change in moisture that is being advected into the region by anomalies in the averaged wintertime circulation rather than from a change in storminess. The patterns of the wintertime 500-mb circulation and storminess anomalies associated with years of high NWB in the southern glacier group are similar to those associated with low NWB years at the Wolverine glacier, and vice versa.The decadal ENSO-like climate phenomenon discussed by Zhang et al. has a large impact on the NWB and NAB of these maritime glaciers, accounting for up to 35% of the variance in NWB. The 500-mb circulation and storminess anomalies associated with this decadal ENSO-like mode resemble the Pacific-North American pattern, as do 500-mb composites of years of extreme NWB of South Cascade glacier in Washington and of Wolverine glacier in Alaska. Hence, the decadal ENSO-like mode affects precipitation in a crucial way for the NWB of these glaciers. Specifically, the decadal ENSO-like phenomenon strongly affects the storminess over British Columbia and Washington and the moisture transported by the seasonally averaged circulation into maritime Alaska. In contrast

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

    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.

  12. Future glacier and runoff changes in the Upper Susitna basin, Alaska

    NASA Astrophysics Data System (ADS)

    Braun, J. L.; Liljedahl, A. K.; Hock, R. M.; Wolken, G. J.

    2012-12-01

    Traditionally, construction of hydropower dams have been guided by statistical flow analyses of historical discharge datasets. This assumes that the future hydrologic conditions (70+ years) will remain similar to what has been observed in the past. In glaciated Southcentral Alaska, the State is reviving studies of the Susitna River's hydroelectric potential. We combine field measurements and computational modeling to improve estimates of runoff into the proposed 81 km2 and 63 km long reservoir of the Susitna-Watana Hydroelectric Project. Approximately 4% the watershed area (14,774 km2) is glacierized. Changes in glacier extent in response to climate warming and/or altered precipitation regimes have the potential to substantially alter the magnitude and timing of runoff. Therefore, we apply the physically-based, fully distributed hydrologic model "Water Balance Simulation Model" (WaSiM). WaSiM is a well established tool for simulating the spatial and temporal variability of hydrologic processes in complex basins. The glacier module, which includes the shrinkage and expansion of glaciers, allows us to specifically evaluate the role of glacier melt on river runoff during the lifespan of the proposed dam. Here, the model is calibrated against multiple discharge and glacier mass balance measurements and is forced by daily temperature and precipitation grids. Downscaled climate projections serve to inform the hydrologic model in order to produce refined estimates of future seasonality and magnitude of flow. An application of a physically-based hydrologic model, which is first validated in order to quantify its uncertainty, has the potential to extend statistical analyses into the future and ultimately inform management decisions.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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

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

    USGS Publications Warehouse

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

    2004-01-01

    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.

  15. Preliminary bathymetry of Aialik Bay and Neoglacial changes of Aialik and Pederson glaciers, Alaska

    USGS Publications Warehouse

    Post, Austin

    1980-01-01

    Preliminary bathymetry (at 1:20,000 scale) and scientific studies of Aialik Bay, Alaska, by the Research Vessel Growler in 1978 disclose that the head of the bay consists of a deep basin enclosed by a terminal-moraine shoal. A much smaller basin, into which Aialik Glacier discharges icebergs, is located west of two islands and a submarine ridge. Comparison of 1978 soundings with U.S. Coast and Geodetic Survey (now National Oceanic and Atmospheric Administration) data obtained in 1912 shows shoaling of about 64 feet in the deepest part of the small basin nearest the glacier and of about 40 feet in the large basin. The time of retreat of Aialik Glacier from the moraine bar is unknown; a faint ' trimline ' is still visible in the forest on the east side of the fiord, and a carbon-14 date suggests the retreat could have taken place as recently as 1800. The time of Aialik Glcier 's neoglacial advance to the moraine is unknown. Pederson Glacier, which terminates in part in a tidal lagoon or lake, has retreated about 0.90 mile from a moraine judged by Grant and Higgins to have been in contact with the ice about 1896. (USGS)

  16. Glaciological and marine geological controls on terminus dynamics of Hubbard Glacier, southeast Alaska

    USGS Publications Warehouse

    Stearns, Leigh A.; Hamilton, Gordon S.; van der Veen, C. J.; Finnegan, D. C.; O'Neel, Shad; Scheick, J. B.; Lawson, D. E.

    2015-01-01

    Hubbard Glacier, located in southeast Alaska, is the world's largest non-polar tidewater glacier. It has been steadily advancing since it was first mapped in 1895; occasionally, the advance creates an ice or sediment dam that blocks a tributary fjord (Russell Fiord). The sustained advance raises the probability of long-term closure in the near-future, which will strongly impact the ecosystem of Russell Fiord and the nearby community of Yakutat. Here, we examine a 43-year record of flow speeds and terminus position to understand the large-scale dynamics of Hubbard Glacier. Our long-term record shows that the rate of terminus advance has increased slightly since 1895, with the exception of a slowed advance between approximately 1972 and 1984. The short-lived closure events in 1986 and 2002 were not initiated by perturbations in ice velocity or environmental forcings, but were likely due to fluctuations in sedimentation patterns at the terminus. This study points to the significance of a coupled system where short-term velocity fluctuations and morainal shoal development control tidewater glacier terminus position.

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

    USGS Publications Warehouse

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

    1997-01-01

    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

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

    USGS Publications Warehouse

    Post, Austin

    1967-01-01

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

  19. Energy Efficiency, Water Efficiency, and Renewable Energy Site Assessment: Mendenhall Glacier Visitor Center, Juneau, Alaska

    SciTech Connect

    Salasovich, James; LoVullo, David; Kandt, Alicen

    2016-01-21

    This report summarizes results from the energy efficiency, water efficiency, and renewable energy site assessment of the Mendenhall Glacier Visitor Center and site in Juneau, Alaska. The assessment is an American Society of Heating, Refrigerating, and Air-Conditioning Engineers Level 2 audit and meets Energy Independence and Security Act requirements. A team led by the U.S. Department of Energy's National Renewable Energy Laboratory conducted the assessment with U.S. Forest Service personnel August 19-20, 2015, as part of ongoing efforts by USFS to reduce energy and water use.

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

    USGS Publications Warehouse

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

    2010-01-01

    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.

  1. Quantifying periglacial erosion: Insights on a glacial sediment budget, Matanuska Glacier, Alaska

    USGS Publications Warehouse

    O'Farrell, C. R.; Heimsath, A.M.; Lawson, D.E.; Jorgensen, L.M.; Evenson, E.B.; Larson, G.; Denner, J.

    2009-01-01

    Glacial erosion rates are estimated to be among the highest in the world. Few studies have attempted, however, to quantify the flux of sediment from the periglacial landscape to a glacier. Here, erosion rates from the nonglacial landscape above the Matanuska Glacier, Alaska are presented and compare with an 8-yr record of proglacial suspended sediment yield. Non-glacial lowering rates range from 1??8 ?? 0??5 mm yr-1 to 8??5 ?? 3??4 mm yr-1 from estimates of rock fall and debris-flow fan volumes. An average erosion rate of 0??08 ?? 0??04 mm yr-1 from eight convex-up ridge crests was determined using in situ produced cosmogenic 10Be. Extrapolating these rates, based on landscape morphometry, to the Matanuska basin (58% ice-cover), it was found that nonglacial processes account for an annual sediment flux of 2??3 ?? 1??0 ?? 106 t. Suspended sediment data for 8 years and an assumed bedload to estimate the annual sediment yield at the Matanuska terminus to be 2??9 ?? 1??0 ?? 106 t, corresponding to an erosion rate of 1??8 ?? 0??6 mm yr-1: nonglacial sources therefore account for 80 ?? 45% of the proglacial yield. A similar set of analyses were used for a small tributary sub-basin (32% ice-cover) to determine an erosion rate of 12??1 ?? 6??9 mm yr-1, based on proglacial sediment yield, with the nonglacial sediment flux equal to 10 ?? 7% of the proglacial yield. It is suggested that erosion rates by nonglacial processes are similar to inferred subglacial rates, such that the ice-free regions of a glaciated landscape contribute significantly to the glacial sediment budget. The similar magnitude of nonglacial and glacial rates implies that partially glaciated landscapes will respond rapidly to changes in climate and base level through a rapid nonglacial response to glacially driven incision. ?? 2009 John Wiley & Sons, Ltd.

  2. The break-up of a lacustrine floating ice tongue, Yakutat Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Yakutat Glacier has been exposed to calving retreat for more than a century with a total terminus retreat of over 15 km since 1903. This temperate glacier in Southeast Alaska calves into over 300 m deep Harlequin Lake. Cold, non-stratified lake water with uniform temperatures of around 1 °C combined with the large lake depth allowed this glacier to form a 17.2 km2 floating tongue. This floating tongue existed for over a decade between 2000 and 2010. Thinning in this terminus area exceeds 6 m during the summer. Digital elevation model differencing shows annual thinning rates of around 9 m yr-1 in the terminus area with a glacier wide mean of 4.07±0.03 m yr-1 (2007-2010). Calving rates are highly variable with periods of rapid retreat followed by periods of relative stability. The most recent period of rapid retreat began in 2010, when the floating tongue disintegrated into large tabular ice bergs. Those ice bergs calve as crevasses transform into rifts, a process supported by rapid thinning. Once the rifts intersect, large tabular icebergs are able to disconnect from the tongue and float away, generally without rolling over. This episodic style of calving also produces a large number of small ice bergs. Tidewater glaciers in the vicinity of Yakutat Glacier are exposed to a similar climate, but they neither form nor maintain a stable floating tongue, nor do they calve large tabular icebergs, even when retreating into over-deepened basins. We hypothesize that the different calving behavior is caused by the presence or absence of submarine melt as the glacier retreats into an over-deepening. In the case of a tidewater glacier, submarine melt can be large leading to instability and retreat. In a lacustrine system, subaquatic melt is negligible, allowing floating tongues to form. The recent break-up of this floating tongue shows certain similarities to the disintegration of ice shelves in Antarctica, but on a much smaller scale and in temperate ice. To better

  3. Preliminary hydrodynamic analysis of landslide-generated waves in Tidal Inlet, Glacier Bay National Park, Alaska

    USGS Publications Warehouse

    Geist, Eric L.; Jakob, Matthias; Wieczoreck, Gerald F.; Dartnell, Peter

    2003-01-01

    A landslide block perched on the northern wall of Tidal Inlet, Glacier Bay National Park (Figure 1), has the potential to generate large waves in Tidal Inlet and the western arm of Glacier Bay if it were to fail catastrophically. Landslide-generated waves are a particular concern for cruise ships transiting through Glacier Bay on a daily basis during the summer months. The objective of this study is to estimate the range of wave amplitudes and periods in the western arm of Glacier Bay from a catastrophic landslide in Tidal Inlet. This study draws upon preliminary findings of a field survey by Wieczorek et al. (2003), and evaluates the effects of variations in landslide source parameters on the wave characteristics.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  5. Twenty-first century changes in the hydrology, glaciers, and permafrost of the Susitna Basin, Alaska

    NASA Astrophysics Data System (ADS)

    Bliss, A. K.; Braun, J. L.; Daanen, R. P.; Hock, R.; Liljedahl, A.; Wolken, G. J.; Zhang, J.

    2013-12-01

    In South-Central Alaska, the Susitna River is the site of a proposed hydroelectric dam. The catchment of the reservoir in the upper Susitna watershed (13,289 km^2, 450-4000 m a.s.l.) is 4% glacierized and is characterized by sparse vegetation, discontinuous permafrost, and little human development. Glaciers, permafrost, and the water cycle are expected to change in response to anticipated future atmospheric warming by the end of this century, thus impacting water yields to the hydroelectric reservoir. We aim to quantify future changes in glacier wastage, surface- and groundwater, permafrost, and evapotranspiration. We apply the physically-based hydrological model WaSiM using daily air temperature and precipitation data from station observations and gridded climate products. The model is calibrated with runoff and glacier mass balance measurements from the 1980s and validated with measurements from ongoing field campaigns which started in spring 2012. With the past and present data, the model is able to match both the magnitude and timing of observed river discharge. However, the scarcity of meteorological observations from the upper Susitna basin presents a major challenge to simulating the catchment hydrology. We present methods for extrapolation of the spatially-sparse long-term data across the catchment, with particular emphasis on high-elevation precipitation. To project future changes in river runoff, we run WaSiM with air temperature and precipitation downscaled from global climate models and compare results from several emission scenarios (selected from CMIP5). We discuss the anticipated changes in basin hydrology as the climate warms, permafrost thaws, and glaciers shrink.

  6. Seasonal evolution of glacier velocity and portraits of basal motion across southeast Alaska via cross-correlation of optical satellite imagery

    NASA Astrophysics Data System (ADS)

    Armstrong, W. H., Jr.; Anderson, R. S.; Moon, T. A.; Fahnestock, M. A.

    2015-12-01

    We investigate how glacier geometry and geographic setting govern a glacier's response to meltwater and precipitation inputs. Does the up-glacier limit of enhanced summer basal motion vary across glaciers? Do non-surge glaciers show consistent spatial patterns of basal motion from year to year? We investigate such questions by documenting the seasonal-to-annual evolution of surface velocity for over 25 surge- and non-surge type glaciers in the Wrangell-St Elias ranges of southeast Alaska, USA, during 2013-2015. We use the Python-implemented PYCORR image cross-correlation software to estimate ice surface velocity fields over ~35,000 km2 covered by four Landsat-8 (L8) scenes. PYCORR is an optimized version of IMCORR, and takes less than 5 minutes to process a full L8 scene. This computational efficiency allows us to calculate dozens of velocity fields for each scene to provide high temporal resolution. We automate the extraction of velocity profiles along longitudinal glacier profiles to document their temporal evolution over timespans ranging from 16 days to greater than one year at spatial resolution of several tens to several hundred meters. This method provides much greater spatial coverage than GPS-derived velocities, and succeeds in terrain of rough surface texture and significant temporal elevation change, both of which present substantial challenges for deriving InSAR velocities. Preliminary data on Kennicott Glacier (Figure 1) resolve the annual velocity cycle in which speeds are lowest over winter and highest in summer reflecting meltwater-induced basal motion. We find notable seasonal velocity fluctuations at distances of more than 30 km from the glacier terminus. While longitudinal stress gradient coupling may explain a portion of these velocity variations, local basal motion must contribute, as the relatively thin (~500 m) ice cannot transmit longitudinal stresses over such distances. Regions downstream of tributary junctions show consistently

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

    SciTech Connect

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

    2009-01-01

    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.

  8. Preliminary assessment of landslide-induced wave hazards, Tidal Inlet, Glacier Bay National Park, Alaska

    USGS Publications Warehouse

    Wieczorek, Gerald F.; Jakob, Matthias; Motyka, Roman J.; Zirnheld, Sandra L.; Craw, Patricia

    2003-01-01

    A large potential rock avalanche above the northern shore of Tidal Inlet, Glacier Bay National Park, Alaska, was investigated to determine hazards and risks of landslide-induced waves to cruise ships and other park visitors. Field and photographic examination revealed that the 5 to 10 million cubic meter landslide moved between AD 1892 and 1919 after the retreat of Little Ice Age glaciers from Tidal Inlet by AD 1890. The timing of landslide movement and the glacial history suggest that glacial debuttressing caused weakening of the slope and that the landslide could have been triggered by large earthquakes of 1899-1900 in Yakutat Bay. Evidence of recent movement includes fresh scarps, back-rotated blocks, and smaller secondary landslide movements. However, until there is evidence of current movement, the mass is classified as a dormant rock slump. An earthquake on the nearby active Fairweather fault system could reactivate the landslide and trigger a massive rock slump and debris avalanche into Tidal Inlet. Preliminary analyses show that waves induced by such a landslide could travel at speeds of 45 to 50 m/s and reach heights up to 76 m with wave runups of 200 m on the opposite shore of Tidal Inlet. Such waves would not only threaten vessels in Tidal Inlet, but would also travel into the western arm of Glacier Bay endangering large cruise ships and their passengers.

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

    USGS Publications Warehouse

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

    2007-01-01

    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.

  10. Controls on interannual and seasonal terminus velocity and position of Yahtse Glacier in SE Alaska

    NASA Astrophysics Data System (ADS)

    Durkin, W. J., IV; Melkonian, A. K.; Pritchard, M. E.; Willis, M. J.; Bartholomaus, T.

    2015-12-01

    We construct a 30 year velocity time-series for comparison with recent studies on the submarine melt rate (Bartholomaus et al., 2013), calving rate (Bartholomaus et al., 2013b), velocities (McNabb et al., 2014), and subglacial discharge (Bartholomaus et al., 2015) of Yahtse Glacier in southeast Alaska. Velocities are constructed from feature tracking on Landsat, ALOS, and ASTER satellite imagery spanning 1985-2015. Yahtse is undergoing an interannual advance of ~82 m yr-1 that is concurrent with deceleration between 1996 and 2015 of -0.55 m day-1yr-1 measured 2.5km down-glacier from the icefall. We estimate that up to 35% of the slowdown is due to divergence associated with thickening near the terminus of ~7 m yr-1measured by differencing WorldView and SRTM DEMs. Much of the remaining deceleration may be due to greater basal and lateral drag as ongoing advance increases the contact area between the terminus and bedrock. We observe a seasonal cycle in centerline terminus speeds superimposed on the interannual deceleration. Terminus speeds climb from a minimum in October to a maximum in May, then decline until October. The timing of this cycle is in phase with the seasonality of subglacial discharge at the front of Yahtse and salinity levels measured in the Gulf of Alaska, which agrees with models of subglacial channel development proposed for many glaciers. Seasonal speed changes measured 1 km up-glacier from the front are associated with terminus advance and retreat. The terminus is in a retracted position following the deceleration to a minimum speed in October and elevated submarine melt rates in summer and early autumn. The front holds this position from November through February as speeds there accelerate to their seasonal maximum and submarine melt is reduced. Yahtse Glacier then advances between 200 and 500 m during the spring as frontal speeds decrease by ~10% from their highest level. This slowdown may be caused by a decrease in buoyancy due to the terminus

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

    USGS Publications Warehouse

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

    2007-01-01

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

  12. Developing an Ice Volume Estimate of Jarvis Glacier, Alaska, using Ground-Penetrating Radar and High Resolution Satellite Imagery

    NASA Astrophysics Data System (ADS)

    Wu, N. L.; Campbell, S. W.; Douglas, T. A.; Osterberg, E. C.

    2013-12-01

    Jarvis Glacier is an important water source for Fort Greely and Delta Junction, Alaska. Yet with warming summer temperatures caused by climate change, the glacier is melting rapidly. Growing concern of a dwindling water supply has caused significant research efforts towards determining future water resources from spring melt and glacier runoff which feeds the community on a yearly basis. The main objective of this project was to determine the total volume of the Jarvis Glacier. In April 2012, a centerline profile of the Jarvis Glacier and 15 km of 100 MHz ground-penetrating radar (GPR) profiles were collected in cross sections to provide ice depth measurements. These depth measurements were combined with an interpreted glacier boundary (depth = 0 m) from recently collected high resolution WorldView satellite imagery to estimate total ice volume. Ice volume was calculated at 0.62 km3 over a surface area of 8.82 km2. However, it is likely that more glacier-ice exists within Jarvis Glacier watershed considering the value calculated with GPR profiles accounts for only the glacier ice within the valley and not for the valley side wall ice. The GLIMS glacier area database suggests that the valley accounts for approximately 50% of the total ice covered watershed. Hence, we are currently working to improve total ice volume estimates which incorporate the surrounding valley walls. Results from this project will be used in conjunction with climate change estimates and hydrological properties downstream of the glacier to estimate future water resources available to Fort Greely and Delta Junction.

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

    SciTech Connect

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

    1995-08-01

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

  14. Decadal Glacier Mass Balance over West Nyainqentanglha Range and its Contribution to Nam Co Lake Increasing

    NASA Astrophysics Data System (ADS)

    Li, Gang; Lin, Hui

    2016-08-01

    Nyainqentanglha Range locates in the south-eastern center of Inner Tibetan Plateau. Glaciers in the whole range covered an area of 795 km2 in 2001 and locate at the transection zone between continental and maritime glaciers. Their melting at the northwestern slope feeds Nam Co Lake. Elevation of Nam Co Lake increased at a rate of 0.26m/a during 2003-2009 by ICESat laser altimetry monitoring which implied that retreating of glaciers within its drainage might accelerated. Previous study applied in situ observations on Zhadang Glacier's height change (-0.59m/a) and yielded during 1999 and 2010 glacier melting contributed 28.7% of the lake increasing (Lei et al., 2013). However, Zhadang Glacier only occupies less than 1% of the whole glacier area and almost bellows zero equilibrium line (ZEL), therefore the result should be biased and with large error. In this study, aiming on analyzing glacier melting's contribution to the endorheic lake increasing we applied DEM differencing method to quantify glacier mass balance at Nyainqentanglha Range by using SRTM and newly obtained bistatic TanDEM-X and TerraSAR-X images.

  15. Using surface velocities to calculate ice thickness and bed topography: A case study at Columbia Glacier, Alaska, USA

    USGS Publications Warehouse

    McNabb, R.W.; Hock, R.; O'Neel, Shad; Rasmussen, Lowell A.; Ahn, Y.; Braun, M.; Conway, H.; Herreid, S.; Joughin, I.; Pfeffer, W.T.; Smith, B.E.; Truffer, M.

    2012-01-01

    Information about glacier volume and ice thickness distribution is essential for many glaciological applications, but direct measurements of ice thickness can be difficult and costly. We present a new method that calculates ice thickness via an estimate of ice flux. We solve the familiar continuity equation between adjacent flowlines, which decreases the computational time required compared to a solution on the whole grid. We test the method on Columbia Glacier, a large tidewater glacier in Alaska, USA, and compare calculated and measured ice thicknesses, with favorable results. This shows the potential of this method for estimating ice thickness distribution of glaciers for which only surface data are available. We find that both the mean thickness and volume of Columbia Glacier were approximately halved over the period 1957–2007, from 281m to 143 m, and from 294 km3 to 134 km3, respectively. Using bedrock slope and considering how waves of thickness change propagate through the glacier, we conduct a brief analysis of the instability of Columbia Glacier, which leads us to conclude that the rapid portion of the retreat may be nearing an end.

  16. Submarine sedimentary features on a fjord delta front, Queen Inlet, Glacier Bay, Alaska

    USGS Publications Warehouse

    Carlson, Paul R.; Powell, Ross D.; Phillips, Andrew C.

    1992-01-01

    Side-scan sonar images provide a view of an actively changing delta front in a marine outwash fjord in Glacier Bay, Alaska. Numerous interconnected gullies and chute-like small channels form paths for the transport of sand and coarse silt from the braided glacial outwash streams on the delta plain to the sinuous turbidity-current channels incised into the fjord floor. These turbidity-current channels carry coarse sediment through the fjord and into the adjoining glacial trunk valley. Several sedimentary processes affect the development of this delta front: overflow plumes deposit fine sediment; sediment gravity flows result from episodic delivery of large loads of coarse sediment; and mass movement may be triggered by earthquakes and, more regularly, by spring-tidal drawdown or hydraulic loading.

  17. Glaciers

    NASA Astrophysics Data System (ADS)

    Hambrey, Michael; Alean, Jürg

    2004-12-01

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

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

    USGS Publications Warehouse

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

    2004-01-01

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

  19. Investigation of Subglacial and Englacial Hydrology Using Borehole Slug Tests; Bench Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Shaha, J. M.; Harper, J. T.; Humphrey, N. F.; Pfeffer, W. T.

    2003-12-01

    Slug tests have long been used to determine the hydraulic conductivity of aquifer formations in the immediate vicinity of monitoring wells. However, slug tests have rarely been used to help determine englacial and subglacial hydrological characteristics. A series of slug tests were performed on Bench Glacier, Alaska in order to characterize the subglacial and englacial hydrology. A total of 16 slug tests were performed over a period of one week in early June 2002, with an additional 20 slug tests performed over a period of 10 days in June 2003. The slug tests were performed at various times of the day in boreholes drilled to the bed of the glacier. During the 2002 field season, water levels were recorded in the slug hole and an adjacent hole approximately 10 meters away. In 2003, water levels were recorded in the slug hole and 5 adjacent holes (within a grid of 16 boreholes) located between 20 and 60 meters away. Responses to the slug of water varied from an overdamped, slow drain to an underdamped, oscillation of the borehole water level. Modeling of the amplitude and frequency for the underdamped response reveals information on the structure of the subglacial and englacial drainage systems, as well as provides constraints on the amount of water in the system. Analysis of the slug tests within the grid shows both temporal and spatial changes in the response and thus the system, providing insight into the development of the subglacial and englacial hydrologic systems.

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

    USGS Publications Warehouse

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

    2013-01-01

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

  1. The potential for retreating alpine glaciers to alter alpine ecosystems in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Hall, E.; Baron, J.

    2013-12-01

    Glaciers are retreating at an unprecedented rate. In mid-latitude alpine ecosystems the presence of glaciers and rock glaciers govern rates and ecology of alpine and sub-alpine ecosystems. Changes in the thermal environment due to the loss of isothermal habitat and inputs from glacier melt chemistry are altering alpine ecosystems in unpredictable ways. In particular, glacier may be a source of nitrogen that is altering alpine ecosystem dynamics. Loch Vale Watershed (LVWS) located within Rocky Mountain National Park. LVWS contains a surface glacier (Andrew's glacier) and a rock glacier (Taylor's glacier) at the headwater of each of the two drainages within the watershed. We collected precipitation from a National Atmospheric Deposition Site and surface water from multiple alpine lakes and streams during a particularly high and low snow year in the Colorado Front Range. We also sampled stream and lake sediments at each site to analyze the associated microbial community. Concentrations of nitrate and ammonium, relative abundance of amoA (the gene responsible for a key step in the microbial nitrification pathway), and the dual isotope signal to nitrate all point to snow melt as a key deliverer of nitrogen to ecosystems along the Colorado Front Range. However, late summer surface water chemistry is isotopically similar to the chemistry of glacial ice. This suggests that retreating glacier may be an additional source of N to alpine ecosystems and have the potential to alter microbial community composition, biogeochemical rate processes, and ecosystem function. These dynamics are most likely not unique to the Colorado Front Range and should be globally distributed as glaciers continue to retreat in high altitude ecosystems around the world.

  2. 76 FR 77300 - Alaska Federal Lands Long Range Transportation Plan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-12

    ... Federal Highway Administration Alaska Federal Lands Long Range Transportation Plan AGENCY: Federal Highway.... SUMMARY: The Federal Highway Administration, along with the Bureau of Land Management, Fish and Wildlife... Lands Long Range Transportation Plans (LRTP) for public review and comment. The draft plans outline...

  3. Imaging evidence for Hubbard Glacier advances and retreats since the last glacial maximum in Yakutat and Disenchantment Bays, Alaska

    NASA Astrophysics Data System (ADS)

    Zurbuchen, Julie M.; Gulick, Sean P. S.; Walton, Maureen A. L.; Goff, John A.

    2015-06-01

    High-resolution 2-D multichannel seismic data, collected during the 2012 UTIG-USGS National Earthquake Hazards Reduction Program survey of Disenchantment and Yakutat Bays in southeast Alaska, provide insight into their glacial history. These data show evidence of two unconformities, appearing in the form of channels, and are interpreted to be advance pathways for Hubbard Glacier. The youngest observable channel, thought to have culminated near the main phase of the Little Ice Age (LIA), is imaged in Disenchantment Bay and ends at a terminal moraine near Blizhni Point. An older channel, thought to be from an advance that culminated in the early phase of the LIA, extends from Disenchantment Bay into the northeastern edge of Yakutat Bay, turning southward at Knight Island and terminating on the southeastern edge of Yakutat Bay. Our interpretation is that 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 central Yakutat Bay during times of mutual advance. We observe two distinct erosional surfaces and retreat sequences of Hubbard Glacier in Yakutat Bay, supporting the hypothesis that minor glacial advances in fjords do not erode all prior sediment accumulations. Interpretation of chaotic seismic facies between these two unconformities suggests that Hubbard Glacier exhibits rapid retreats and that Disenchantment Bay is subject to numerous episodes of outburst flooding and morainal bank collapse. These findings also suggest that tidewater glaciers preferentially reoccupy the same channels in bay and marine settings during advances.

  4. Mountain and Glacier Terrain Study and Related Investigations in the Juneau Icefield Region, Alaska-Canada

    DTIC Science & Technology

    1975-09-01

    nunataks where the coldest air is able readily to drain away with night cooling. The range Is greatest at the most Interior Icefleld camps (e.g., C...British Columbia, it consists primarily of high n~vhs, interspersed with barren Ice- carved nunataks and nunatak groups separating deep glacier-filled...the preceding sections is still under the influence of the maritime zone. It is located on a low bedrock shoulder of a nunatak , some 300 feet (100 m

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

    USGS Publications Warehouse

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

    2005-01-01

    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.

  6. High-resolution modeling of coastal freshwater discharge and glacier mass balance in the Gulf of Alaska watershed

    NASA Astrophysics Data System (ADS)

    Beamer, J. P.; Hill, D. F.; Arendt, A.; Liston, G. E.

    2016-05-01

    A comprehensive study of the Gulf of Alaska (GOA) drainage basin was carried out to improve understanding of the coastal freshwater discharge (FWD) and glacier volume loss (GVL). Hydrologic processes during the period 1980-2014 were modeled using a suite of physically based, spatially distributed weather, energy-balance snow/ice melt, soil water balance, and runoff routing models at a high-resolution (1 km horizontal grid; daily time step). Meteorological forcing was provided by the North American Regional Reanalysis (NARR), Modern Era Retrospective Analysis for Research and Applications (MERRA), and Climate Forecast System Reanalysis (CFSR) data sets. Streamflow and glacier mass balance modeled using MERRA and CFSR compared well with observations in four watersheds used for calibration in the study domain. However, only CFSR produced regional seasonal and long-term trends in water balance that compared favorably with independent Gravity Recovery and Climate Experiment (GRACE) and airborne altimetry data. Mean annual runoff using CFSR was 760 km3 yr-1, 8% of which was derived from the long-term removal of stored water from glaciers (glacier volume loss). The annual runoff from CFSR was partitioned into 63% snowmelt, 17% glacier ice melt, and 20% rainfall. Glacier runoff, taken as the sum of rainfall, snow, and ice melt occurring each season on glacier surfaces, was 38% of the total seasonal runoff, with the remaining runoff sourced from nonglacier surfaces. Our simulations suggests that existing GRACE solutions, previously reported to represent glacier mass balance alone, are actually measuring the full water budget of land and ice surfaces.

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

    SciTech Connect

    Hunter, L.E.; Powell, R.D. . Dept. of Geology)

    1992-01-01

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

  8. 1. Characterizing contributions of glacier melt and groundwater in alpine glacierized watersheds of the Saint-Elias Mountain range (Canada)

    NASA Astrophysics Data System (ADS)

    Bouchard, Emilie; Baraer, Michel; Chesnokova, Anna

    2016-04-01

    Changes in the hydrological processes of alpine glacierized watersheds have been observed in most regions of the world; these have an important impact on water resources and can affect downstream ecosystems and populations. Subarctic catchments such as those found in southern Yukon (Canada) are particularly sensitive to climate related hydrological changes. To further understand the ongoing evolution of subarctic hydrological systems, we applied natural tracers based investigations in the Saint-Elias mountain range of the Yukon. The main goal was to identify water sources and their relative contributions to outflows in an alpine glacierized catchment. During the summer of 2015, we collected more than 100 water samples in two sub-watersheds of the glacier-fed Duke River watershed. Samples were analyzed for organic carbon, major ions and stable water isotopes (δ18O and δ2H). The resulting dataset was then processed using statistical methods and the hydrochemical basin characterization method (HBCM). Results show that on the sampling period, watershed outflows consisted mainly of glacier meltwater with a non-negligible contribution of other water sources such as icings and ice-cored moraines. In this study, supraglacial processes are shown playing a particularly important role in the watersheds' hydrology.

  9. High-Resolution Modeling of Freshwater Discharge and Glacier Mass Balance in the Gulf of Alaska Drainage

    NASA Astrophysics Data System (ADS)

    Beamer, J. P.; Hill, D. F.; Arendt, A. A.; Liston, G. E.; Hood, E. W.

    2014-12-01

    A comprehensive study of the Gulf of Alaska (GOA) hydrology has been carried out in order to improve understanding of the coastal freshwater discharge (FWD) magnitude and spatial distribution, and mass changes from GOA glaciers. FWD along the coastline and surface mass balance (SMB) for all glacier surfaces in the GOA drainage were modeled using a suite of physically-based, spatially distributed weather, energy-balance snow/ice melt, and runoff-routing models at a high resolution (1-km horizontal grid; 3-h time step). SnowModel simulations of air temperature, precipitation, surface runoff, and glacier SMB were completed for the entire GOA drainage from 1979-2009. HydroFlow was used to route the SnowModel-derived runoff to the GOA coastline. Meteorological forcing was provided by the North American Regional Reanalysis (NARR) dataset. The NARR data was bias-corrected using monthly gridded climate data to more accurately reflect the strong spatial gradients in air temperature and precipitation, while retaining the temporal attributes of NARR. The most recent version of the Alaska Glacier Inventory was used to define the glacier cover for the model simulations. The modeling system was validated and calibrated in several glaciated catchments containing long-term streamflow and glacier mass balance datasets, as well as several non-glaciated catchments with only streamflow data. The overall GOA mean annual FWD volumes from HydroFlow agree well with previous estimates. Glacier SMB simulated by SnowModel from 2004-2009 produced seasonal storage changes and long term trends consistent with GRACE satellite-based estimates. Both SnowModel and GRACE data suggest a negative SMB trend which indicates that recent glacier volume loss contributes significantly to GOA FWD. The final product of this study is a 30-year record of daily streamflow at every coastal grid cell (1-km resolution) in the GOA drainage, which includes the runoff signal from glacier melt and volume loss. This

  10. Climate Change Impacts on the Cryosphere of Mountain Regions: Validation of a Novel Model Using the Alaska Range

    NASA Astrophysics Data System (ADS)

    Mosier, T. M.; Hill, D. F.; Sharp, K. V.

    2015-12-01

    Mountain regions are natural water towers, storing water seasonally as snowpack and for much longer as glaciers. Understanding the response of these systems to climate change is necessary in order to make informed decisions about prevention or mitigation measures. Yet, mountain regions are often data sparse, leading many researchers to implement simple or enhanced temperature index (ETI) models to simulate cryosphere processes. These model structures do not account for the thermal inertia of snowpack and glaciers and do not robustly capture differences in system response to climate regimes that differ from those the model was calibrated for. For instance, a temperature index calibration parameter will differ substantially in cold-dry conditions versus warm-wet ones. To overcome these issues, we have developed a cryosphere hydrology model, called the Significantly Enhanced Temperature Index (SETI), which uses an energy balance structure but parameterizes energy balance components in terms of minimum, maximum and mean temperature, precipitation, and geometric inputs using established relationships. Additionally, the SETI model includes a glacier sliding model and can therefore be used to estimate long-term glacier response to climate change. Sensitivity of the SETI model to changing climate is compared with an ETI and a simple temperature index model for several partially-glaciated watersheds within Alaska, including Wolverine glacier where multi-decadal glacier stake measurements are available, to highlight the additional fidelity attributed to the increased complexity of the SETI structure. The SETI model is then applied to the entire Alaska Range region for an ensemble of global climate models (GCMs), using representative concentration pathways 4.5 and 8.5. Comparing model runs based on ensembles of GCM projections to historic conditions, total annual snowfall within the Alaska region is not expected to change appreciably, but the spatial distribution of snow

  11. Recent Elevation Changes on Bagley Ice Valley, Guyot and Yahtse Glaciers, Alaska, from ICESat Altimetry, Star-3i Airborne, and SRTM Spaceborne DEMs

    NASA Astrophysics Data System (ADS)

    Muskett, R. R.; Sauber, J. M.; Lingle, C. S.; Rabus, B. T.; Tangborn, W. V.; Echelmeyer, K. A.

    2005-12-01

    .5 m at 1562 m altitude, -2.6 ± 2.8 m at 1378 m altitude, 6.1 ± 3.5 m at 1142 m altitude, 1.4 ± 12.1 m at 1232 m altitude, -4.0 ± 4.2 m at 250 m to 1217 m altitude, -1.8 ± 3.3 m at 1200 m altitude, and 8.0 ± 6.4 m at 940 m altitude. One ICESat-derived track-to-DEM comparison on Guyot Glacier indicates a preliminary mean elevation change in the 478 m to 1150 m altitude range of -2.8 ± 14.1 m. Results, including additional comparisons to small-aircraft laser altimeter data, with more fully-corrected for estimated snow and ice accumulation / ablation between acquisitions times, will be presented. [Muskett, R.R., C.S. Lingle, W.V. Tangborn, and B.T. Rabus, Multi-decadal elevation changes on Bagley Ice Valley and Malaspina Glacier, Alaska, GRL, 30 (16), 1857, doi:10.1029/2003GL017707, 2003.

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

    USGS Publications Warehouse

    Hupp, C.R.

    2000-01-01

    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. Copyright ?? 2000 John Wiley & Sons, Ltd.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

  13. Glacier retreat since the Little Ice Age in the eastern Nyainqêntanglha Range, southeastern Tibet

    NASA Astrophysics Data System (ADS)

    Loibl, David; Grießinger, Jussi; Lehmkuhl, Frank

    2014-05-01

    The remote eastern Nyainqêntanglha Range in southeastern Tibet is situated in a transition zone between warm-wet subtropical and cold-dry plateau climate conditions. In this high mountain environment, intense summer monsoon rainfalls support numerous temperate glaciers despite the latitude of ~29° to ~31°N. Due to the outstanding importance of the monsoonal airmasses for the water cycle of the whole region, it is a key area to study climate and subsequent glacier change in High Asia. Here, we present the results of a study in which 1964 glaciers were mapped by remote sensing from a Landsat ETM+ scene and subsequently parameterized by DEM supported measurements. Geomorphological evidence, such as glacier trimlines and latero-frontal moraines, was used to delineate the Little Ice Age (LIA) maximum glacier advance terminus positions. Statistical analysis of glacier length change revealed an average retreat of ~40 % and a trend towards stronger retreat for smaller glaciers. Calculated ELAs show a southeast-northwest gradient ranging from 4,400 to 5,600 m a.s.l. and an average ELA rise of ~98 m since the LIA. Due to the large amount of measurements the ELA distribution reveals topographic effects down to the catchment scale, i.e. orographic rainfall and leeward shielding. This gives numerous hints on the relief-climate-glacier interactions and allows a simplified reconstruction of the flow patterns of the monsoonal air masses. Contrasting to the expectations for subtropical settings, glaciers on south facing slopes have not retreated strongest and ELAs on south facing slopes did not rise furthest. Instead, highly heterogeneous spatial patterns emerge that show a strong imprint of both, topography and monsoonal dynamics. Our results indicate that the monsoonal temperate glaciers' high sensitivity to climate change is driven by two double forcings due to the coincidence of accumulation and ablation phases. First, monsoon intensity directly controls the amount of

  14. Cretaceous Olistostrome Model, Brooks Range, Alaska

    SciTech Connect

    Crane, R.C.

    1985-04-01

    The foothills area of the Brooks Range thrust belt in the area between the Itkillik River and the Etivluk River is composed dominantly of shallow, thrusted olistostrome sheets. Three olistostrome units can be recognized based on the dominant lithology of contained olistoliths and age of the matrix shales. The lower unit is Thithonian to mid-Valanginian in age and is characterized by abundant graywacke and turbidite, mafic rocks, black cherts, olistoliths of Norian-Rhaetic shales, Nuka sands, and glide sheets of Upper Devonian to Lower Mississippian rocks. Olistolights were derived from the Misheguk, Ipnavik, and Nuka Ridge allochthonous sequences. The middle unit is of late Valanginian age and has olistoliths of Norian shales; more abundant Upper Triassic chert; Otuk Formation; variegated, radiolarian, black and white cherts; Siksikpuk facies red, green and black shales; Upper Jurassic graywacke; and minor occurrences of mafic rocks. The unit is characterized by glide sheets of Triassic white and multicolor cherts. Olistoliths are derived from Nuka Ridge and Brooks Range sequences. The upper unit is Hauterivian in age and olistoliths included reworked material from all older units. Olistoliths are few and widely scattered. Isolated outcrops of white chert and conglomerate boulders are characteristic.

  15. Geology of the Byrd Glacier Discontinuity (Ross Orogen): New survey data from the Britannia Range, Antarctica

    USGS Publications Warehouse

    Carosi, R.; Giacomini, F.; Talarico, F.; Stump, E.

    2007-01-01

    Field activities in the Britannia Range (Transantarctic Mountains, Antarctica) highlighted new geological features around the so-called Byrd Glacier discontinuity. Recent field surveys revealed the occurrence of significant amounts of medium- to high-grade metamorphic rocks, intruded by abundant coarse-grained porphyritic granitoids. Most of the granitoids are deformed, with foliation parallel to the regional foliation in the metamorphics. Two main episodes of deformation are observed. Tight to isoclinal folds and penetrative axial plane foliation are related to the D1 phase, open folds to the D2. The main foliation (D1) trends nearly E-W in agreement with the trend in the southern portion of the Byrd Glacier. In most outcrops, granitic dykes are folded and stretched by the D2 deformation, which shows similar characteristics with the D2 deformation south of the Byrd Glacier. This suggests the occurrence in the Ross orogen of an orogen-normal structure south and north of the Byrd Glacier.

  16. Geologic strip map along the Hines Creek Fault showing evidence for Cenozoic displacement in the western Mount Hayes and northeastern Healy quadrangles, eastern Alaska Range, Alaska

    USGS Publications Warehouse

    Nokleberg, Warren J.; Aleinikoff, John N.; Bundtzen, Thomas K.; Hanshaw, Maiana N.

    2013-01-01

    Geologic mapping of the Hines Creek Fault and the adjacent Trident Glacier and McGinnis Glacier Faults to the north in the eastern Alaska Range, Alaska, reveals that these faults were active during the Cenozoic. Previously, the Hines Creek Fault, which is considered to be part of the strike-slip Denali Fault system (Ridgway and others, 2002; Nokleberg and Richter, 2007), was interpreted to have been welded shut during the intrusion of the Upper Cretaceous Buchanan Creek pluton (Wahrhaftig and others, 1975; Gilbert, 1977; Sherwood and Craddock, 1979; Csejtey and others, 1992). Our geologic mapping along the west- to west-northwest-striking Hines Creek Fault in the northeastern Healy quadrangle and central to northwestern Mount Hayes quadrangle reveals that (1) the Buchanan Creek pluton is truncated by the Hines Creek Fault and (2) a tectonic collage of fault-bounded slices of various granitic plutons, metagabbro, metabasalt, and sedimentary rock of the Pingston terrane occurs south of the Hines Creek Fault.

  17. Snow algal communities on glaciers in the Suntar-Khayata Mountain Range in eastern Siberia, Russia

    NASA Astrophysics Data System (ADS)

    Tanaka, Sota; Takeuchi, Nozomu; Miyairi, Masaya; Fujisawa, Yuta; Kadota, Tsutomu; Shirakawa, Tatsuo; Kusaka, Ryo; Takahashi, Shuhei; Enomoto, Hiroyuki; Ohata, Tetsuo; Yabuki, Hironori; Konya, Keiko; Fedorov, Alexander; Konstantinov, Pavel

    2016-09-01

    Snow and ice algal communities were investigated on four glaciers in the Suntar-Khayata Mountain Range in eastern Siberia in Russia over three melting seasons from 2012 to 2014. Two taxa of green algae and five taxa of cyanobacteria were observed on the glaciers. The algal community was dominated by green algae: Ancylonema nordenskioldii in the lower bare ice area and Chloromonas sp. in the upper snow area. The total algal bio-volume showed altitudinal variation, ranging from 0.03 to 4.0 mL m-2, and was greatest in the middle of the glaciers. The altitudinal variations in the algal community were similar on all studied glaciers, suggesting that they are typical in this region. Observations over the three years revealed that there was no significant change in the community structure, but a significant change in the total biomass. Since the mean summer air temperature was significantly higher in 2012 when algal biomass was greater, the difference in algal biomass among the years is probably due to the duration of surface melting. The community structure on the studied glaciers is similar to those on glaciers in Arctic and sub-Arctic regions.

  18. A geochemical sampling technique for use in areas of active alpine glaciation: an application from the central Alaska Range

    USGS Publications Warehouse

    Stephens, G.C.; Evenson, E.B.; Detra, D.E.

    1990-01-01

    In mountainous regions containing extensive glacier systems there is a lack of suitable material for conventional geochemical sampling. As a result, in most geochemical sampling programs a few stream-sediment samples collected at, or near, the terminus of valley glaciers are used to evaluate the mineral potential of the glaciated area. We have developed and tested a technique which utilizes the medial moraines of valley glaciers for systematic geochemical exploration of the glacial catchment area. Moraine sampling provides geochemical information that is site-specific in that geochemical anomalies can be traced directly up-ice to bedrock sources. Traverses were made across the Trident and Susitna glaciers in the central Alaska Range where fine-grained (clay to sand size) samples were collected from each medial moraine. These samples were prepared and chemically analyzed to determine the concentration of specific elements. Fifty pebbles were collected at each moraine for archival purposes and for subsequent lithologic identification. Additionally, fifty cobbles and fifty boulders were examined and described at each sample site to determine the nature and abundance of lithologies present in the catchment area, the extent and nature of visible mineralization, the presence and intensity of hydrothermal alteration and the existence of veins, dikes and other minor structural features. Results from the central Alaska Range have delineated four distinct multi-element anomalies which are a response to potential mineralization up-ice from the medial moraine traverse. By integrating the lithologic, mineralogical and geochemical data the probable geological setting of the geochemical anomalies is determined. ?? 1990.

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

    USGS Publications Warehouse

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

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Muskett, Reginald R.

    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 of glacier mass balance to climate change, glacier dynamics, and the contributions of the glaciers of northwestern North America to rising sea level. Presented are the first detailed estimate of the net mass balances of the Bering and Malaspina Glacier systems, the effects of glacier dynamics on their accumulation areas, and the wastage of the tidewater glaciers of Icy Bay. The combined wastage of the Bering and Malaspina Glacier systems from 1972 to 2003, 254 +/- 16 km 3 water equivalent over a glacier area of 7734 km2, is equivalent to an area-average mass balance of -1.06 +/- 0.07 m/y over that time period. This represents a contribution to global sea-level rise of 0.70 +/- 0.05 mm, 0.023 +/- 0.002 mm/yr from 1972 to 2003. This is roughly 0.8% of the modern sea-level rise as estimated from tide-gauges and satellites, and roughly 9% of the contribution from non-polar glaciers and ice caps. Glacier wastage has been caused by climate warming (negative mass balance) superimposed on the effects of glacier dynamics. Near-concurrent surge of the three largest glaciers of the Malaspina Glacier piedmont were observed during 1999 to 2002. In addition, the tidewater Tyndall Glacier, whose retreat since 1910 was interrupted in 1964 by a major surge, also surged during 1999 to 2002. These four surges have occurred roughly 23 years after the 1976/77 shift of the Pacific Decadal Oscillation to its current warm-wet phase. Despite the increase of high-elevation snow accumulation observed on Mt. Logan, the accumulation areas of the Bering and Malaspina Glacier systems

  1. Populations and productivity of seabirds at South Marble Island, Glacier Bay, Alaska, during May-July, 1999

    USGS Publications Warehouse

    Zador, Stephani G.; Piatt, John F.

    1999-01-01

    In the course of directed research on glaucous-winged gulls, we investigated the numbers and activities of all breeding and non-breeding seabirds associated with South Marble Island in Glacier Bay, Alaska, during mid-May to late July, 1999. Most observations were made from the island; additional observations were made during transportation to and from the island. Data were collected on the presence and numbers of all seabirds observed. Detailed information on breeding chronology and productivity were also collected for glaucous-winged gulls (Larus glaucescens), pigeon guillemots (Cepphus columba), black-legged kittiwakes (Rissa tridactyla), and black oystercatchers (Haemantopus bachmani).

  2. Changing exhumation patterns during Cenozoic growth and glaciation of the Alaska Range: Insights from detrital thermochronology and geochronology

    NASA Astrophysics Data System (ADS)

    Lease, Richard O.; Haeussler, Peter J.; O'Sullivan, Paul

    2016-04-01

    Cenozoic growth of the Alaska Range created the highest topography in North America, but the space-time pattern and drivers of exhumation are poorly constrained. We analyzed U/Pb and fission-track double dates of detrital zircon and apatite grains from 12 catchments that span a 450 km length of the Alaska Range to illuminate the timing and extent of exhumation during different periods. U/Pb ages indicate a dominant Late Cretaceous to Oligocene plutonic provenance for the detrital grains, with only a small percentage of grains recycled from the Mesozoic and Paleozoic sedimentary cover. Fission-track ages record exhumation during Alaska Range growth and incision and reveal three distinctive patterns. First, initial Oligocene exhumation was focused in the central Alaska Range at ~30 Ma and expanded outward along the entire length of the range until 18 Ma. Oligocene exhumation, coeval with initial Yakutat microplate collision >600 km to the southeast, suggests a far-field response to collision that was localized by the Denali Fault within a weak Mesozoic suture zone. Second, the variable timing of middle to late Miocene exhumation suggests independently evolving histories influenced by local structures. Time-transgressive cooling ages suggest successive rock uplift and erosion of Mounts Foraker (12 Ma) through Denali (6 Ma) as crust was advected through a restraining bend in the Denali Fault and indicate a long-term slip rate ~4 mm/yr. Third, Pliocene exhumation is synchronous (3.7-2.7 Ma) along the length of the Alaska Range but only occurs in high-relief, glacier-covered catchments. Pliocene exhumation may record an acceleration in glacial incision that was coincident with the onset of Northern Hemisphere glaciation.

  3. Changing exhumation patterns during Cenozoic growth and glaciation of the Alaska Range: Insights from detrital thermochronology and geochronology

    USGS Publications Warehouse

    Lease, Richard O.; Haeussler, Peter J.; O'Sullivan, Paul

    2016-01-01

    Cenozoic growth of the Alaska Range created the highest topography in North America, but the space-time pattern and drivers of exhumation are poorly constrained. We analyzed U/Pb and fission-track double dates of detrital zircon and apatite grains from 12 catchments that span a 450 km length of the Alaska Range to illuminate the timing and extent of exhumation during different periods. U/Pb ages indicate a dominant Late Cretaceous to Oligocene plutonic provenance for the detrital grains, with only a small percentage of grains recycled from the Mesozoic and Paleozoic sedimentary cover. Fission-track ages record exhumation during Alaska Range growth and incision and reveal three distinctive patterns. First, initial Oligocene exhumation was focused in the central Alaska Range at ~30 Ma and expanded outward along the entire length of the range until 18 Ma. Oligocene exhumation, coeval with initial Yakutat microplate collision >600 km to the southeast, suggests a far-field response to collision that was localized by the Denali Fault within a weak Mesozoic suture zone. Second, the variable timing of middle to late Miocene exhumation suggests independently evolving histories influenced by local structures. Time-transgressive cooling ages suggest successive rock uplift and erosion of Mounts Foraker (12 Ma) through Denali (6 Ma) as crust was advected through a restraining bend in the Denali Fault and indicate a long-term slip rate ~4 mm/yr. Third, Pliocene exhumation is synchronous (3.7–2.7 Ma) along the length of the Alaska Range but only occurs in high-relief, glacier-covered catchments. Pliocene exhumation may record an acceleration in glacial incision that was coincident with the onset of Northern Hemisphere glaciation.

  4. Geochemical evidence for a brooks range mineral belt, Alaska

    USGS Publications Warehouse

    Marsh, S.P.; Cathrall, J.B.

    1981-01-01

    Geochemical studies in the central Brooks Range, Alaska, delineate a regional, structurally controlled mineral belt in east-west-trending metamorphic rocks and adjacent metasedimentary rocks. The mineral belt extends eastward from the Ambler River quadrangle to the Chandalar and Philip Smith quadrangles, Alaska, from 147?? to 156??W. longitude, a distance of more than 375 km, and spans a width from 67?? to 69??N. latitude, a distance of more than 222 km. Within this belt are several occurrences of copper and molybdenum mineralization associated with meta-igneous, metasedimentary, and metavolcanic rocks; the geochemical study delineates target areas for additional occurrences. A total of 4677 stream-sediment and 2286 panned-concentrate samples were collected in the central Brooks Range, Alaska, from 1975 to 1979. The -80 mesh ( 2.86) nonmagnetic fraction of the panned concentrates from stream sediment were analyzed by semiquantitative spectrographic methods. Two geochemical suites were recognized in this investigation; a base-metal suite of copper-lead-zinc and a molybdenum suite of molybdenum-tin-tungsten. These suites suggest several types of mineralization within the metamorphic belt. Anomalies in molybdenum with associated Cu and W suggest a potential porphyry molybdenum system associated with meta-igneous rocks. This regional study indicates that areas of metaigneous rocks in the central metamorphic belt are target areas for potential mineralized porphyry systems and that areas of metavolcanic rocks are target areas for potential massive sulfide mineralization. ?? 1981.

  5. The contribution of glacier melt to stream flow in the Wind River Range, WY

    NASA Astrophysics Data System (ADS)

    Cable, J. M.; Williams, D. G.; Bachman, S. A.

    2008-12-01

    The Wind River Range (Wyoming) boasts the largest concentration of glaciers in the American Rockies, and together with adjacent mountain ranges is the source of several major river systems in the western US. Declines in the volume of these glaciers associated with recent climate warming are well documented. Such declines of alpine glaciers will reduce the amount of water available for agricultural and domestic use, especially in late summer and fall. The contribution of glacial melt to stream flow remains largely unquantified in many parts of the U.S., particularly in Wyoming. In this study, we estimated the fractional contribution of glacier melt water from Dinwoody Glacier to flow in Dinwoody Creek in the Wind River Range on diurnal, seasonal, and interannual time scales. The stable isotope composition of water from the Dinwoody Creek watershed was determined on spatially and temporally intensive scales in 2007 and 2008. Spatially intensive sampling took place in the summers of both years; water samples were collected from (1) above and below major confluences along Dinwoody Creek, from (2) Dinwoody Glacier, (3) rain water, and (4) snow. Stream samples were collected over the entire melt season using an automated stream sampler placed beside an unimpaired USGS gauging station low in the watershed. Glacial melt contributed significantly to stream flow during periods of peak daily discharge (afternoon) and during late summer peak flow (late-August). In 2008, snow persisted late into the summer, so snowmelt was the main source of streamflow in mid-summer (July). Disappearance of glaciers in this watershed will affect both ecosystem and human water supplies during the late summer period, particularly in years when snowfields do not persist late into the summer.

  6. Timing of ore-related magmatism in the western Alaska Range, southwestern Alaska

    USGS Publications Warehouse

    Taylor, Ryan D.; Graham, Garth E.; Anderson, Eric D.; Selby, David

    2014-01-01

    This report presents isotopic age data from mineralized granitic plutons in an area of the Alaska Range located approximately 200 kilometers to the west-northwest of Anchorage in southwestern Alaska. Uranium-lead isotopic data and trace element concentrations of zircons were determined for 12 samples encompassing eight plutonic bodies ranging in age from approximately 76 to 57.4 millions of years ago (Ma). Additionally, a rhenium-osmium age of molybdenite from the Miss Molly molybdenum occurrence is reported (approx. 59 Ma). All of the granitic plutons in this study host gold-, copper-, and (or) molybdenum-rich prospects. These new ages modify previous interpretations regarding the age of magmatic activity and mineralization within the study area. The new ages show that the majority of the gold-quartz vein-hosting plutons examined in this study formed in the Late Cretaceous. Further work is necessary to establish the ages of ore-mineral deposition in these deposits.

  7. Tsivat Basin conduit system persists through two surges, Bering Piedmont Glacier, Alaska

    USGS Publications Warehouse

    Fleisher, P.J.; Cadwell, D.H.; Muller, E.H.

    1998-01-01

    The 1993-1995 surge of Bering Glacier, Alaska, occurred in two distinct phases. Phase 1 of the surge began on the eastern sector in July, 1993 and ended in July, 1994 after a powerful outburst of subglacial meltwater into Tsivat Lake basin on the north side of Weeping Peat Island. Within days, jokulhlaup discharge built a 1.5 km2 delta of ice blocks (25-30 m) buried in outwash. By late October 1994, discharge temporarily shifted to a vent on Weeping Peat Island, where a second smaller outburst dissected the island and built two new sandar. During phase 2, which began in spring 1995 and ended within five months, continuous discharge issued from several vents along the ice front on Weeping Peat Island before returining to the Tsivat Basin. Surge related changes include a five- to six-fold increase in meltwater turbidity; the redirection of supercooled water in two ice-contact lakes; and an increase in the rate of glaciolacustrine sedimentation. US Geological Survey aerial photos by Austin Post show large ice blocks in braided channels indicating excessive subglacial discharge in a similar position adjacent to Weeping Peat Island during the 1966-1967 surge. During the subsequent three decades of retreat, the location of ice-marginal, subglacial discharge vents remained aligned on a linear trend that describes the position of a persistent subglacial conduit system. The presence of a major conduit system, possibly stabilized by subglacial bedrock topography, is suggested by: 1) high-level subglacial meltwater venting along the northern side of Weeping Peat Island during the 1966-1967 surge, 2) persistent low-level discharge between surges, and 3) the recurrence of localizing meltwater outbursts associated with both phases of the 1993-1005 surge.

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

    SciTech Connect

    Kurtak, J.M.

    1985-01-01

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

  9. Geomorphology and Ice Content of Glacier - Rock Glacier &ndash; Moraine Complexes in Ak-Shiirak Range (Inner Tien Shan, Kyrgyzstan)

    NASA Astrophysics Data System (ADS)

    Bolch, Tobias; Kutuzov, Stanislav; Rohrbach, Nico; Fischer, Andrea; Osmonov, Azamat

    2015-04-01

    Meltwater originating from the Tien Shan is of high importance for the runoff to the arid and semi-arid region of Central Asia. Previous studies estimate a glaciers' contribution of about 40% for the Aksu-Tarim Catchment, a transboundary watershed between Kyrgyzstan and China. Large parts of the Ak-Shiirak Range drain into this watershed. Glaciers in Central and Inner Tien Shan are typically polythermal or even cold and surrounded by permafrost. Several glaciers terminate into large moraine complexes which show geomorphological indicators of ice content such as thermo-karst like depressions, and further downvalley signs of creep such as ridges and furrows and a fresh, steep rock front which are typical indicators for permafrost creep ("rock glacier"). Hence, glaciers and permafrost co-exist in this region and their interactions are important to consider, e.g. for the understanding of glacial and periglacial processes. It can also be assumed that the ice stored in these relatively large dead-ice/moraine-complexes is a significant amount of the total ice storage. However, no detailed investigations exist so far. In an initial study, we investigated the structure and ice content of two typical glacier-moraine complexes in the Ak-Shiirak-Range using different ground penetrating radar (GPR) devices. In addition, the geomorphology was mapped using high resolution satellite imagery. The structure of the moraine-rock glacier complex is in general heterogeneous. Several dead ice bodies with different thicknesses and moraine-derived rock glaciers with different stages of activities could be identified. Few parts of these "rock glaciers" contain also massive ice but the largest parts are likely characterised by rock-ice layers of different thickness and ice contents. In one glacier forefield, the thickness of the rock-ice mixture is partly more than 300 m. This is only slightly lower than the maximum thickness of the glacier ice. Our measurements revealed that up to 20% of

  10. Mendenhall Glacier (Juneau, Alaska) icequake seismicity and its relationship to the 2012 outburst flood and other environmental forcing

    NASA Astrophysics Data System (ADS)

    Morgan, P. M.; Walter, J. I.; Peng, Z.; Amundson, J. M.; Meng, X.

    2013-12-01

    Glacial outburst floods occur when ice-dammed lakes or other reservoirs on the glacier release large volumes of water usually due to the failure of an ice dam. In 2011 and 2012 these types of floods have occurred at Mendenhall Glacier in Southeast Alaska, 15 km northwest of Juneau. The floods emanated from a lake within a remnant branch of Mendenhall Glacier, called Suicide Basin, and rapidly changed the levels of Mendenhall Lake. Homes on the shore of Mendenhall Lake were threatened by rapidly rising lake levels during such floods. We analyze data from a set of 4 short and broadband period seismometers placed in ice-boreholes in an array on Mendenhall Glacier for a period of 4 months in 2012. We also examine the outburst flood that occurred between July 4th and 8th 2012. We first manually pick icequakes as high-frequency bursts recorded by at least two stations. Next, we use a matched-filter technique to help complete the icequake record by detecting missed events with similar waveforms to those hand-picked events. While high-frequency noise was present during the flooding, the impulsive icequake activity did not appear to be modulated significantly during periods of flooding, suggesting that the flooding does not significantly deform the overlying ice. Impulsive icequake activity appears to show strongly diurnal periodicity, indicating that the icequakes were mainly caused by expansion/contraction of ice during daytime. We also analyze the activity in concert with GPS velocity and meteorological data from the area. By analyzing the temporal and spatial patterns of the events we hope to reveal more about the fundamental processes occurring beneath Mendenhall Glacier.

  11. Alaska: Glaciers of Kenai Fjords National Park and Katmai National Park and Preserve

    NASA Technical Reports Server (NTRS)

    Giffens, Bruce A.; Hall, Dorothy K.; Chien, Janet Y. L.

    2014-01-01

    There are hundreds of glaciers in Kenai Fjords National Park (KEFJ) and Katmai National Park and Preserve (KATM) covering over 2,276 sq km of park land (ca. 2000). There are two primary glacierized areas in KEFJ (the Harding Icefield and the Grewingk-Yalik Glacier Complex) and three primary glacierized areas in KATM (the Mt. Douglas area, the Kukak Volcano to Mt. Katmai area, and the Mt. Martin area). Most glaciers in these parks terminate on land, though a few terminate in lakes. Only KEFJ has tidewater glaciers, which terminate in the ocean. Glacier mapping and analysis of the change in glacier extent has been accomplished on a decadal scale using satellite imagery, primarily Landsat data from the 1970s, 1980s, and from2000. Landsat Multispectral Scanner (MSS),Thematic Mapper (TM), and Enhanced Thematic Mapper Plus (ETM) imagery was used to map glacier extent on a park-wide basis. Classification of glacier ice using image-processing software, along with extensive manual editing, was employed to create Geographic Information System (GIS)outlines of the glacier extent for each park. Many glaciers that originate in KEFJ but terminate outside the park boundaries were also mapped. Results of the analysis show that there has been a reduction in the amount of glacier ice cover in the two parks over the study period. Our measurements show a reduction of approximately 21 sq km, or 1.5(from 1986 to 2000), and 76 sq km, or 7.7 (from19861987 to 2000), in KEFJ and KATM, respectively. This work represents the first comprehensive study of glaciers of KATM. Issues that complicate the mapping of glacier extent include debris cover(moraine and volcanic ash), shadows, clouds, fresh snow, lingering snow from the previous season, and differences in spatial resolution between the MSS,TM, or ETM sensors. Similar glacier mapping efforts in western Canada estimate mapping errors of 34. Measurements were also collected from a suite of glaciers in KEFJ and KATM detailing terminus positions

  12. Alaska: Glaciers of Kenai Fjords National Park and Katmai and Lake Clark National Parks and Preserve

    NASA Technical Reports Server (NTRS)

    Giffen, bruce A.; Hall, Dorothy K.; Chien, Janet Y. L.

    2011-01-01

    There are hundreds of glaciers in Kenai Fjords National Park (KEFJ) and Katmai National Park and Preserve (KATM) covering over 2276 sq km of park land (circa 2000). There are two primary glacierized areas in KEFJ -- the Harding Icefield and the Grewingk-Yalik Glacier Complex, and three primary glacierized areas in KATM - the Mt. Douglas area, the Kukak Volcano to Mt. Katmai area and the Mt. Martin area. Most glaciers in these parks terminate on land, though a few terminate in lakes. Only KEFJ has tidewater glaciers, which terminate in the ocean. Glacier mapping and analysis of the change in glacier extent has been accomplished on a decadal scale using satellite imagery, primarily Landsat data from the 1970s, 1980s, and from 2000. Landsat Multispectral Scanner (MSS), Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) imagery was used to map glacier extent on a park-wide basis. Classification of glacier ice using image processing software, along with extensive manual editing, was employed to create Geographic Information System (GIS) outlines of the glacier extent for each park. Many glaciers that originate in KEFJ but terminate outside the park boundaries were also mapped. Results of the analysis show that there has been a reduction in the amount of glacier ice cover in the two parks over the study period. Our measurements show a reduction of approximately 21 sq km, or -1.5% (from 1986 to 2000), and 76 sq km, or -7.7% (from 1986/87 to 2000), in KEFJ and KATM, respectively. This work represents the first comprehensive study of glaciers of KATM. Issues that complicate the mapping of glacier extent include: debris-cover (moraine and volcanic ash), shadows, clouds, fresh snow, lingering snow from the previous season, and differences in spatial resolution between the MSS and TM or ETM+ sensors. Similar glacier mapping efforts in western Canada estimate mapping errors of 3-4%. Measurements were also collected from a suite of glaciers in KEFJ and KATM detailing

  13. Surface mass balance reanalysis of Taku and Lemon Creek glaciers, Alaska: 1946-2015

    NASA Astrophysics Data System (ADS)

    McNeil, Christopher

    We reanalyzed geodetic and glaciological surface mass balance records of Taku and Lemon Creek glaciers for the period 1946--2015 to determine what has driven the contradictory behavior of these glaciers. During the past century, Taku Glacier has been increasing in area and mass, while Lemon Creek Glacier has simultaneously shrunk in area and mass. Between 1948 and 1999 geodetic mass balance rates are +0.33+/-0.34 m w.e. a--1 for Taku Glacier and 0.61+/-0.34 m w.e. a--1 for Lemon Creek Glacier. Geodetic mass balance rates decreased to +0.01+/-0.23 m w.e. a--1 and --0.65 +/-0.23 m w.e. a--1 for Taku and Lemon Creek glaciers respectively, between 1999 and 2013. We updated the glaciological analysis of annual field data, and found no significant difference between updated and previous annual mass balance solutions (p--value < 0.001). We used the geodetic mass balance to calibrate annual glaciological estimates between 1946 and 2015, removing systematic biases of +0.06 m w.e. a--1 from the Taku Glacier record and --0.06 m w.e. a --1 from the Lemon Creek Glacier record. Comparing mass balance anomalies we determined inter--annual variability of surface mass balance is the same for Taku and Lemon Creek glaciers. However, differences in glacier specific hypsometry and mass balance profile drive systematic differences in both annual and long--term glacier mass balance rates.

  14. Surface depressions (Lacunas) on Bering Glacier, Alaska: a product of downwasting through differential ablation

    NASA Astrophysics Data System (ADS)

    Fleisher, P. J.

    2014-05-01

    Bering Glacier lacunas are steep-sided, flat-floored hollows ranging in size from 40 to 60 m wide, 80 to 120 m long, and 35 to 50 m in deep. They are confined within a band of clean ice (1.5 km wide, 5 km long) paralleling the eastern margin of the Bering piedmont lobe. The 1993-1995 surge displaced the lacuna band several kilometers onto the foreland. Specifically significant is the formation of a new band of lacunas 5-6 years later in the same location occupied by the displaced band prior to the surge. Conditions essential to lacuna formation were initiated during the surge as overriding ice was thrust into position across the trend of a subglacial trough, leading to stagnation of ice within the trough. Stagnation combined with saturation at depth altered ice texture and density. Exposure of this ice through normal ablation led to areas of differential ablation and the formation of lacunas.

  15. Using NASA Warm Ice Sounding Explorer (WISE) Data to Reexamine the Bed Morphology of Malaspina Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Molnia, B. F.; Snyder-Deaton, L. E.; Angeli, K.

    2015-12-01

    In 1988, a USGS ice-penetrating radar (IPR) survey of eastern Malaspina Glacier was conducted (Molnia and others, 1990) to determine the configuration of the glacier's bed and to measure ice thickness at more than 50 locations. The IPR survey results suggested that much of the glacier area investigated was underlain by fiord channels that extended as much as 50 km inland from the present Gulf of Alaska coastline. Maximum measured fiord channel bed depths exceeded 200 m below sea level, while the maximum ice thickness measured was more than 850 m. The IPR survey was conducted to test a hypothesis (Molnia and Jones, 1989) that unusual airborne radar backscatter features observed on a November 1986 X-band, high-resolution, synthetic aperture radar (SAR) image of the glacier's surface were expressions of the glacier's bed morphology, surface topography, surface wetness, ice structure, and ice flow characteristics. The most significant type of feature seen on the SAR image were several 10-25 km-long by 1.5-2.5-km-wide, north-south trending fiord-like glacial valleys, each with adjacent cirque-like amphitheaters. Field surveys in 1989 showed the valleys were topographic lows, while the cirque-like features were heavily crevassed topographic highs. Closely spaced IPR soundings showed that the ice associated with the valleys is substantially thicker than the ice over the adjacent cirques. In 2008 and again in 2012, NASA's airborne Warm Ice Sounding Explorer (WISE) was flown over Malaspina Glacier, producing more than 500 km of new soundings. Not only did this provide an opportunity to better map the glacier's bed, calculate ice thickness, and determine ice surface elevations, it also provided an opportunity to reexamine the Molnia and Jones hypothesis. Bed morphology profiles generated from the WISE data were co-registered to and compared with the 1986 X-band radar image. The results show a strong correlation between radar surface low backscatter surface channel features

  16. Lithofacies and seismic-reflection interpretation of temperate glacimarine sedimentation in Tarr Inlet, Glacier Bay, Alaska

    USGS Publications Warehouse

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

    1997-01-01

    High-resolution seismic-reflection profiles of sediment fill within Tart Inlet of Glacier Bay, Alaska, show seismic facies changes with increasing distance from the glacial termini. Five types of seismic facies are recognized from analysis of Huntec and minisparker records, and seven lithofacies are determined from detailed sedimentologic study of gravity-, vibro- and box-cores, and bottom grab samples. Lithofacies and seismic facies associations, and fjord-floor morphology allow us to divide the fjord into three sedimentary environments: ice-proximal, iceberg-zone and ice-distal. The ice-proximal environment, characterized by a morainal-bank depositional system, can be subdivided into bank-back, bank-core and bank-front subenvironments, each of which is characterized by a different depositional subsystem. A bank-back subsystem shows chaotic seismic facies with a mounded surface, which we infer consists mainly of unsorted diamicton and poorly sorted coarse-grained sediments. A bank-core depositional subsystem is a mixture of diamicton, rubble, gravel, sand and mud. Seismic-reflection records of this subsystem are characterized by chaotic seismic facies with abundant hyperbolic diffractions and a hummocky surface. A bank-front depositional subsystem consists of mainly stratified and massive sand, and is characterized by internal hummocky facies on seismic-reflection records with significant surface relief and sediment gravity flow channels. The depositional system formed in the iceberg-zone environment consists of rhythmically laminated mud interbedded with thin beds of weakly stratified diamicton and stratified or massive sand and silt. On seismic-reflection profiles, this depositional system is characterized by discontinuously stratified facies with multiple channels on the surface in the proximal zone and a single channel on the largely flat sediment surface in the distal zone. The depositional system formed in the ice-distal environment consists of interbedded

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

    USGS Publications Warehouse

    March, Rod S.; O'Neel, Shad

    2011-01-01

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

  18. Ice loss and sea level rise contribution from Alaskan glaciers

    NASA Astrophysics Data System (ADS)

    Berthier, E.; Schiefer, E.; Clarke, G. K.; Menounos, B.; Rémy, F.; Cazenave, A. A.

    2009-12-01

    Over the last 50 years, retreating glaciers and ice caps (GIC) contributed 0.5 mm/yr to SLR, and one third is believed to originate from ice masses bordering the Gulf of Alaska. However, these estimates of ice wastage in Alaska are based on methods that directly measure mass changes from a limited number of glaciers and extrapolate the results to estimate ice loss for the many thousands of others. Here, using a new glacier inventory with elevation changes derived from sequential digital elevation models (DEMs), we found that, between 1962 and 2006, Alaskan glaciers lost 41.9 ± 8.6 km**3/yr water equivalent (w.e.) and contributed 0.12 ± 0.02 mm/yr to SLR. Our ice loss is 34% lower than previous estimates. Reasons for our lower values include the higher spatial resolution of the glacier inventory used in our study and the complex pattern of ice elevation changes at the scale of individual glaciers and mountain ranges which was not resolved in earlier work. Our ice elevation changes reveal that glacier dynamics (surges, phase of the tidewater cycle, etc...) have a profound effect on the wastage of Alaska glaciers. 3D satellite view of Columbia glacier, Chugach Mountains, Alaska. (Copyright CNES 2007, Distribution Spot Image, processing E. Berthier CNRS)

  19. Geochemistry and source waters of rock glacier outflow, Colorado Front Range

    USGS Publications Warehouse

    Williams, M.W.; Knauf, M.; Caine, N.; Liu, F.; Verplanck, P.L.

    2006-01-01

    We characterize the seasonal variation in the geochemical and isotopic content of the outflow of the Green Lake 5 rock glacier (RG5), located in the Green Lakes Valley of the Colorado Front Range, USA. Between June and August, the geochemical content of rock glacier outflow does not appear to differ substantially from that of other surface waters in the Green Lakes Valley. Thus, for this alpine ecosystem at this time of year there does not appear to be large differences in water quality among rock glacier outflow, glacier and blockslope discharge, and discharge from small alpine catchments. However, in September concentrations of Mg2+ in the outflow of the rock glacier increased to more than 900 ??eq L-1 compared to values of less than 40 ??eq L-1 at all the other sites, concentrations of Ca2+ were greater than 4,000 ??eq L-1 compared to maximum values of less than 200 ??eq L-1 at all other sites, and concentrations of SO42- reached 7,000 ??eq L-1, compared to maximum concentrations below 120 ??eq L-1 at the other sites. Inverse geochemical modelling suggests that dissolution of pyrite, epidote, chlorite and minor calcite as well as the precipitation of silica and goethite best explain these elevated concentrations of solutes in the outflow of the rock glacier. Three component hydrograph separation using end-member mixing analysis shows that melted snow comprised an average of 30% of RG5 outflow, soil water 32%, and base flow 38%. Snow was the dominant source water in June, soil water was the dominant water source in July, and base flow was the dominant source in September. Enrichment of ?? 18O from - 10??? in the outflow of the rock glacier compared to -20??? in snow and enrichment of deuterium excess from +17.5??? in rock glacier outflow compared to +11??? in snow, suggests that melt of internal ice that had undergone multiple melt/freeze episodes was the dominant source of base flow. Copyright ?? 2005 John Wiley & Sons, Ltd.

  20. Llama-supported geologic fieldwork in Brooks Range, Alaska

    SciTech Connect

    Dillion, J.T.; Faiks, J.L.

    1985-04-01

    For the first time since their camelid ancestors migrated from Asia, across the Bering Sea land bridge, into the Brooks Range, and eventually south to the Andes during the Late Pleistocene, domestic llamas trekked through Arctic Alaska mountains. During August 1981, six llamas carrying 520 lb of gear supported a field party of eight people that traveled 80 mi over 11 days. The route followed left the Dietrich Trans-Alaska Pipe line camp on the Dalton Highway and went eastward over the 5000 ft mountains separating the Dietrich and Matthews Rivers, then north to the headwaters of the Matthews River, and finally west to the Dietrich River drainage north of Snowsden Mountain. Although none had packing experience, all of the llamas were friendly and easy to handle. They carried 60-2100 lbs each, depending on their age. Only blocky talus and very steep slopes were obstacles. The llamas easily traversed fine loose rock, making ascents and descents as steep as 1000 ft/mi (190 m/km), bashed through alder scrub, slogged over muskeg, and forded rivers. Since they are avid foragers, minimal food was packed for the llamas. Bears were sighted during the trip, but none approached the group. Dall sheep and llamas puzzled at each other from a distance.

  1. Nearshore distribution and abundance of Dungeness crabs in Glacier Bay National Park, Alaska

    USGS Publications Warehouse

    O'Clair, Charles E.; Freese, J. Lincoln; Stone, Robert P.; Shirley, Thomas C.; Leder, Erica H.; Taggart, S. James; Kruse, Gordon H.; Engstrom, Daniel R.

    1995-01-01

    As part of an ongoing, multi-agency study to determine the effects of closure of the commercial fishery for Dungeness crabs, Cancer magister, on crab population structure we examined patterns of distribution and abundance of crabs in nearshore habitats at five locations in and near Glacier Bay National Park. Sampling was conducted in April and September 1992 and April 1993 prior to the anticipated closure of the fishery in the park. Divers censused crabs by sex and reproductive state (ovigerous/nonovigerous females) along belt transects (2m x 100m) laid perpendicular to shore in the depth range 0 m (mean lower low water) to 18 m.Preliminary results from the first three sampling periods revealed that the average densities of Dungeness crabs at the five locations ranged from 78 to 2012 crabs/ha. Crab densities differed between populations depending on sex, reproductive state of females and sampling period. Male crabs showed reduced densities at Gustavus Flats in April 1992 (P<0.01) and 1993 (P<0.001). Ovigerous females had greater density at Bartlett Cove in April 1993 (P<0.001). Sex ratios were frequently skewed toward females. At Bartlett Cove and Gustavus Flats females outnumbered males in April 1992 and 1993 (P<0.001). Most of the females at Bartlett Cove and Gustavus Flats in April 1992 and 1993 were ovigerous (P-0.001). Males tended to occupy greater depths than females in April 1992 (P<0.05) but not April 1993 (P-005). The mean depth of males shifted from deeper to shallower water between April and September 1992 (P<0.001). The depth distribution of ovigerous crabs did not differ from that of nonovigerous female crabs. Future research prior to the anticipated closure of the commercial Dungeness crab fishery in Glacier Bay will include a tagging study to determine the extent of crab movement and further study of the temporal as well as the spatial variability observed in the structure of these populations.

  2. Tracking seasonal subglacial drainage evolution of alpine glaciers using radiogenic Nd and Sr isotope systematics: Lemon Creek Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Clinger, A. E.; Aciego, S.; Stevenson, E. I.; Arendt, C. A.

    2014-12-01

    The transport pathways of water beneath a glacier are subject to change as melt seasons progress due to variability in the balance between basal water pressure and water flux. Subglacial hydrology has been well studied, but the understanding of spatial distribution is less well constrained. Whereas radiogenic isotopic tracers have been traditionally used as proxies to track spatial variability and weathering rates in fluvial and riverine systems, these techniques have yet to be applied extensively to the subglacial environment and may help resolve ambiguity in subglacial hydrology. Research has shown the 143Nd/144Nd values can reflect variation in source provenance processes due to variations in the age of the continental crust. Correlating the 143Nd/144Nd with other radiogenic isotope systematics such as strontium (87Sr/86Sr) provides important constraints on the role of congruent and incongruent weathering processes. Our study presents the application of Nd and Sr systematics using isotopic ratios to the suspended load of subglacial meltwater collected over a single melt season at Lemon Creek Glacier, USA (LCG). The time-series data show an average ɛNd ~ -6.83, indicating a young bedrock (~60 MYA). Isotopic variation helps track the seasonal expansion of the subglacial meltwater channels and subsequent return to early season conditions due to the parabolic trend towards less radiogenic Nd in June and towards more radiogenic Nd beginning in mid-August. However, the high variability in July and early August may reflect a mixture of source as the channels diverge and derive sediment from differently aged lithologies. We find a poor correlation between 143Nd/144Nd and 87Sr/86Sr (R2= 0.38) along with a slight trend towards more radiogenic 87Sr/86Sr values with time ((R2= 0.49). This may indicate that, even as the residence time decreases over the melt season, the LCG subglacial system is relatively stable and that the bedrock is congruently weathered. Our study

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

    USGS Publications Warehouse

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

    2004-01-01

    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.

  4. Evaluate ERTS imagery for mapping and detection of changes of snowcover on land and on glaciers. [North Cascades, Washington and Tweedsmuir Glacier, Alaska

    NASA Technical Reports Server (NTRS)

    Meier, M. F. (Principal Investigator)

    1974-01-01

    The author has identified the following significant results. Snowlines on a small (6 sq km) drainage basin were accurately measured without use of digital processing, and snow patches as small as 150 m (maximum dimension) were correctly identified, proving that the resolution of ERTS is ample for snow mapping needs. The area of snow cover on 10 individual drainage basins in the North Cascades, Washington, has been determined at 12 different times; these data can be used for more accurate forecasts of streamflow. Progress has been made in distinguishing snow in trees using multispectral analysis. Motion of the surging Tweedsmuir Glacier was measured. Velocities ranged from 2 to 88 m per day; a zone of intense crevassing also appeared to spread up and down the glacier (at about 200 m per day upglacier). This tentative result may be of great importance to an understanding of surging glacier dynamics. ERTS images also show that the most recent debris flow (20-21 August 1973) from Mount Baker can be clearly discerned and mapped, in order to monitor this potential hazard.

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

    NASA Astrophysics Data System (ADS)

    Waythomas, C. F.

    2010-12-01

    Two large lahars with volumes of 0.4-0.6 km3 and several smaller lahars with volumes of 0.05-0.1 km3 inundated the Drift River valley on the north flank of Redoubt Volcano during its 2009 eruption. Significant lahars were produced on March 22-23 during the initial explosive phase of the eruption following about 8 months of precursory unrest that included increased fumarolic melting of glacier ice and snow in the summit crater and upper Drift glacier. From the beginning of unrest in late July 2008 through March 20, 2009 about 3-7 x 106 m3 of glacier ice and snow were lost from upper Drift glacier as a result of fumarolic emissions and associated melting. Water and debris outflow during this period was minor and posed no downstream flow hazard beyond the base of the volcano. On March 22-23, explosive eruptions from a summit crater vent destroyed a significant amount of ice in upper Drift glacier and produced a funnel-shaped explosion crater within the larger summit crater. Glacier ice, 50-100 m thick, in the gorge below the vent was stripped to bedrock by pyroclastic flows and melt water. By the next available clear views of the volcano on March 26, about 0.5-1.0 x 108 m3 of ice had been removed from upper Drift glacier including part of the ice field in the summit crater. Melt water liberated by eruptive activity on March 22-23 also eroded or removed most of the river ice and snowpack present in the Drift River valley which may have added an additional 0.1-0.2 km3 of water to the lahars produced during that time. Additional explosions from March 26-April 4 caused further melting of Drift glacier and produced small lahars, but the extent of ice loss and lahar inundation during this period could not be determined because clouds obscured the volcano and much of the Drift River valley. The final explosive event and lahar of the eruption occurred on April 4 when pyroclastic flows produced by lava dome collapse swept over upper Drift glacier and a portion of its piedmont

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

  7. 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)

    Dorava, Joseph M.; Milner, Alexander M.

    2000-10-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Newman, Stephen Delmont, Jr.

    I investigated active deep-seated gravitational slope deformation (DSGSD) near the Trans-Alaska Pipeline and Richardson Highway in the east-central Alaska Range, Alaska, USA. I documented the presence, spatial extent, and rates of DSGSD using field-geology methods and optical, SAR, and D-InSAR remote-sensing images. I also documented and mapped many of the morphological, geological, and structural characteristics of slopes undergoing DSGSD, and constructed conceptual numerical models to better understand potential deformation mechanisms. Results confirm that many large DSGSD slopes in the study area are actively deforming. Deformation rates range from less than a millimetre per month to more than ten centimetres per month, and are spatially and temporally varient within each slope. Deforming slopes are characterized by differential movement of kilometre-scale rock blocks. Recent climatic changes and strong seismic shaking, especially during the recent 2002 Denali Fault earthquake, have exacerbated ongoing deformation. Study-area DSGSDs should be considered capable of generating long-runout rock avalanches that could directly sever the Trans-Alaska Pipeline and Richardson Highway, or that could dam up valleys and lead to the buildup and catastrophic failure of landslide-dammed lakes capable of impacting said infrastructure. Keywords: Deep-seated gravitational slope deformation; sackung; Trans-Alaska Pipeline; geomorphology; InSAR; Alaska Range.

  9. 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

    Hodgkins, Glenn A.

    2009-01-01

    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.

  10. Mountain permafrost, glacier thinning, and slope stability - a perspective from British Columbia (and Alaska)

    NASA Astrophysics Data System (ADS)

    Geertsema, Marten

    2016-04-01

    The association of landslides with thinning glaciers and mapped, or measured, mountain permafrost is increasing. Glacier thinning debuttresses slopes and promotes joint expansion. It is relatively easy to map. Permafrost, a thermal condition, is generally not visually detectible, and is difficult to map. Much mountain permafrost may have been overlooked in hazard analysis. Identifying, and characterizing mountain permafrost, and its influence on slope instability is crucial for hazard and risk analysis in mountainous terrain. Rock falls in mountains can be the initial event in process chains. They can transform into rock avalanches, debris flows or dam burst floods, travelling many kilometres, placing infrastructure and settlements at risk.

  11. 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

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

    2011-01-01

    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.

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

    PubMed Central

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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

  15. Application of photogrammetry to the study of volcano-glacier interactions on Mount Wrangell, Alaska

    NASA Technical Reports Server (NTRS)

    Benson, C. S.; Follett, A. B.

    1986-01-01

    Most Alaskan volcanoes are glacier covered and provide excellent opportunities to study interactions between glaciers and volcanoes. The present paper is concerned with such a study, taking into account the Mt. Wrangell (4317 m) which is the northernmost active volcano (solfatara activity) on the Pacific Rim (62 deg N; 144 deg W). While the first photographs on the summit of Mt. Wrangell were published more than 75 years ago, research there began in 1953 and 1954. Satellite images reveal activity at the summit of Mt. Wrangell. However, the resolution is not sufficient for conducting important measurements regarding ice volume losses. For this reason, vertical aerial photographs of the summit were obtained, and a field trip to the summit was conducted. Aspects of photogrammetry are discussed, taking into account questions of ground control, aerial photography, topographic mapping, digital cross sections, and orthophotos.

  16. Cement stratigraphy of the Lisburne Group, northeastern Brooks Range, Alaska

    SciTech Connect

    Carlson, R.C.; Goldstein, R.H. . Geology Dept.)

    1992-01-01

    Cement stratigraphy serves as a descriptive framework for the interpretation of the diagenetic history of the Carboniferous Lisburne Group, northeastern Brooks Range, Alaska. The Lisburne is a sequence of shallow-water, marine carbonate rocks that have experienced a wide spectrum of diagenetic events: early marine diagenesis, early subaerial exposure, significant erosion and karstification following final Lisburne deposition, deep burial of at least 3,000 meters, compressional tectonism, and final uplift into modern mountain ranges. Compositional zones in the calcite cements were identified by using stains for ferroan calcite and cathodoluminescence microscopy. The cements are, from oldest to youngest: A1-nonferroan, nonluminescent or multibanded calcite; B1-nonferroan to low-ferroan, dull luminescent calcite; C1-ferroan, very-dull luminescent calcite; B2-nonferroan, dull luminescent calcite; A2-nonferroan calcite with 1 or 2 sets of nonluminescent and bright zones; C2-ferroan, very-dull luminescent calcite; Be-nonferroan, dull luminescent calcite. Petrographic studies of cross-cutting relationships show that A1 cements predate or are synchronous with surfaces of subaerial exposure within the Lisburne Group. The cross-cutting relationships include truncation of cements by early fractures, non-marine fissure fills, and at clast margins of autoclastic breccias. Similarly, B1 and C1 cements predate the major unconformity at the top of the Lisburne Group, hence, these cements are pre-Permian in age and may well have precipitated from fresh groundwaters introduced during development of the sub-Permian unconformity. B2 and C2 cements are present in the Permian Echooka formation overlying the Lisburne Group and, thus, can be dated as post-Pennsylvanian. B3 cements are Cretaceous or younger in age.

  17. Fracture density as a controlling factor of postglacial fluvial incision rate, Granite Range, Alaska.

    NASA Astrophysics Data System (ADS)

    Champagnac, J.-D.; Sternai, P.; Herman, F.; Guralnik, B.; Beaud, F.

    2012-04-01

    The relations between lithosphere and atmosphere to shape the landscape are disputed since the last two decades. The classical "chicken or egg" problem raised the idea that erosion can promote creation of topography thanks to isostatic compensation of eroded material and subsequent positive feedback. Quaternary glaciations and high erosion rates are supposed to be the main agent of such process. More recently, "tectonic activity" has been considered not only as a rock uplift agent, but also as a rock crusher, that in turn promote erosion, thanks to the reduction of size of individual rock elements, more easily transported. The Granite Range in Alaska presents a contrasted morphology: its western part shows preserved glacial landscape, whereas its eastern part presents a strong fluvial / hillslope imprint, and only a few relicts of glacial surfaces. We quantify these differences by 1) qualitative appreciation of the landscape, 2) quantification of post-glacial erosion, and 3) hypsometric quantification of the landscape. On the field, the eastern part appears to be highly fractured, with many, large, penetrative faults, associated with km-thick fault gouges and cataclasites. The westernmost part shows massive bedrock, with minor, localised faults. Remote-sensed fracture mapping confirms this: fracture density is much higher to the east, where hypsometric parameters (HI and HIP) display anomalies, and where high post-glacial incision (up to 600m) is observed. We provide here an impressive case study for tectonic-erosion interactions through rock crushing effect, and document that half of the sediments coming out of the range come from the ~10% of the most fractured area, all other being equal. This challenges the usual view of tectonic "driving" rock uplift, while erosion removes material: In our case, tectonics is the main erosional agent, rivers and glaciers being (efficient) transport agents.

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

    SciTech Connect

    Bird, BW; Abbott, MB; Finney, BP; Kutchko, B

    2009-01-01

    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 (r (2) = 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 varvetemperature 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. Varve-inferred summer temperatures and precipitation decreased after 730 AD, averaging 0.4A degrees C above the last millennial average (LMA = 4.2A degrees C) from 730 to 850 AD, and 0.1A degrees C above the LMA from 850 to 980 AD. Cooling culminated between 980 and 1030 AD with temperatures 0.7A degrees C below the LMA. Varve-inferred summer temperatures increased between 1030 and 1620 AD to the LMA, though the period between 1260 and 1350 AD was 0.2A degrees C below the LMA. Although there is no equivalent to the European Medieval Warm Period in the Blue Lake record, two warm intervals occurred from 1350 to 1450 AD and 1500 to 1620 AD (0.4 and 0.3A degrees C above the LMA, respectively). During the Little Ice Age (LIA; 1620 to 1880 AD), inferred summer temperature averaged 0.2A degrees C below the LMA. After 1880 AD, inferred summer temperature increased to 0.8A degrees C above the LMA, glaciers retreated, but aridity persisted based on a number of regional paleoclimate records. Despite warming and glacial retreat, varve thicknesses have not achieved pre-730 AD levels. This reflects limited sediment availability and transport due to a less extensive retreat compared to the first millennium, and continued relative aridity. Overall, the Blue Lake record is similar to varve records from the

  19. The Glacial Buzzsaw in the Northern Basin and Range: the Importance of Glacier Size and Uplift Rates

    NASA Astrophysics Data System (ADS)

    Foster, D.; Brocklehurst, S. H.; Gawthorpe, R. L.

    2007-12-01

    The role of glaciers in limiting mountain range elevations is an important component of studies linking tectonic uplift and climate-driven erosion. Recent investigations suggesting that a glacial buzzsaw effect can efficiently offset rock uplift in tectonically active settings have concentrated on regions that have held large glaciers (10s km long at Last Glacial Maximum, LGM). However, little work has addressed the role small glaciers may play in controlling range topography. This study looks at the effectiveness of smaller (<10 km) glaciers at limiting peak and ridge elevations in both slow and relatively rapid rock uplift settings. The Lost River and Lemhi Ranges, Idaho, and the Beaverhead-Bitterroot Mountains, Idaho-Montana all experience slow rock uplift, with slip rates <0.3 mm/yr on the range-bounding normal faults. Here, swath-elevation profiles show that maximum elevations correlate well to estimates of both LGM and mean Quaternary equilibrium line altitudes (ELAs). Furthermore, peaks in hypsometry and minima in slope-elevation profiles correspond to ELAs, suggesting that small glaciers can efficiently limit range elevations where rock uplift is slow. The Teton Range, Wyoming, experiences 5-10 times faster rock uplift. In general, elevations, slope profiles, and hypsometry all correlate to both LGM and mean Quaternary ELA estimates, although supra-elevated peaks do penetrate through this zone. Comparisons of valley long-profiles show that glacier size is important in controlling valley form under more rapid rock uplift. Small (<5km) glacial valleys perched high on the range front have profiles that have steepened in response to the rapid rock uplift. In contrast, larger (>8km) valleys extend back beyond the high peaks of the range front, and have housed glaciers that have eroded deep into the range, maintaining shallow gradients. Feedback mechanisms are important in snow accumulation on the larger glaciers, which receive extra inputs of snow from the

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    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.

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

    PubMed

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

    2012-01-01

    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.

  2. Structural problems of the Brooks Range ophiolite, Alaska

    SciTech Connect

    Harris, R.A.; Bickerstaff, D. . Dept. of Geology); Stone, D.B. . Geophysical Inst.)

    1993-04-01

    Structural and paleogeographic restorations of the Brooks Range ophiolite (hereafter BRO) and other associated mafic and ultramafic bodies of N. Alaska are difficult because of ambiguous relations between sheeted dikes, cover sediments, and steep NW and SE dipping magmatic flow fabrics. Paleomagnetically enhanced structural studies at Misheguk, Avan, and Siniktanneyak Mountains provide new constraints for the initial dip and sequence of deformation for various structural features of the BRO. The angle between magmatic layers near the petrologic moho and the paleomagnetic inclination of these layers is 50--63[degree] at Misheguk. High level gabbro layers that are disrupted by syn- and post-cooling intrusions display a greater variation. Assuming that the characteristic magnetization is primary, and that the primary inclination was > 80[degree], magmatic layers and the moho had initial dips from 17--40[degree]. These layers now dip 40--70[degree]SE suggesting some post-magmatic tilt. The variation of inclinations with depth in the ophiolite suggest that high level gabbro has tilted most. Sheeted dikes are documented at the Maiyumerak and Siniktanneyak ophiolite bodies. At both locations the dikes dip steeply and strike NE-SW. Sedimentary and volcanic flow layers associated with the dikes have the same strike and dip 0--30[degree]. Parallelism between various planar features throughout the BRO indicates that rotations about a vertical axis are either uniform throughout the ophiolite belt or negligible. Assuming the later, the BRO may represent a linear zone of SSZ magmatism that was oriented NE-SW prior to collision. Post-emplacement long wavelength folding of the ophiolite lid can account for its variation in facing direction and some steepening of magmatic layers.

  3. Colonization and development of stream communities across a 200-year gradient in Glacier Bay National Park, Alaska

    USGS Publications Warehouse

    Milner, Alexander M.; Knudsen, E. Eric; Soiseth, Chad; Robertson, Anne L.; Schell, Don; Phillips, Ian T.; Magnusson, Katrina

    2000-01-01

    In May 1997, physical and biological variables were studied in 16 streams of different ages and contrasting stages of development following glacial recession in Glacier Bay National Park, southeast Alaska. The number of microcrustacean and macroinvertebrate taxa and juvenile fish abundance and diversity were significantly greater in older streams. Microcrustacean diversity was related to the amount of instream wood and percent pool habitat, while the number of macroinvertebrate taxa was related to bed stability, amount of instream wood, and percent pool habitat. The percent contribution of Ephemeroptera to stream benthic communities increased significantly with stream age and the amount of coarse benthic organic matter. Juvenile Dolly Varden (Salvelinus malma) were dominant in the younger streams, but juvenile coho salmon (Oncorhynchus kisutch) abundance was greater in older streams associated with increased pool habitat. Upstream lakes significantly influenced channel stability, percent Chironomidae, total macroinvertebrate and meiofaunal abundance, and percent fish cover. Stable isotope analyses indicated nitrogen enrichment from marine sources in macroinvertebrates and juvenile fish in older streams with established salmon runs. The findings are encapsulated in a conceptual summary of stream development that proposes stream assemblages to be determined by direct interactions with the terrestrial, marine, and lake ecosystems.

  4. Structure of the Red Dog District, western Brooks Range, Alaska

    USGS Publications Warehouse

    de Vera, Jean-Pierre P.; McClay, K. R.

    2004-01-01

    The Red Dog district of the western Brooks Range of northern Alaska, which includes the sediment-hosted Zn-Pb-Ag ± Ba deposits at Red Dog, Su-Lik, and Anarraaq, contains one of the world's largest reserves of zinc. This paper presents a new model for the structural development of the area and shows that understanding the structure is crucial for future exploration efforts and new mineral discoveries in the district. In the Red Dog district, a telescoped Late Devonian through Jurassic continental passive margin is exposed in a series of subhorizontally stacked, internally imbricated, and regionally folded thrust sheets. These sheets were emplaced during the Middle Jurassic to Late Cretaceous Brookian orogeny and subsequently were uplifted by late tectonic activity in the Tertiary. The thrust sheet stack comprises seven tectonostratigraphically distinct allochthonous sheets, three of which have been subject to regional and detailed structural analysis. The lowermost of these is the Endicott Mountains allochthon, which is overlain by the structurally higher Picnic Creek and Kelly River allochthons. Each individual allochthon is itself internally imbricated into a series of tectonostratigraphically coherent and distinct thrust plates and subplates. This structural style gives rise to duplex development and imbrication at a range of scales, from a few meters to tens of kilometers. The variable mechanical properties of the lithologic units of the ancient passive margin resulted in changes in structural styles and scales of structures across allochthon boundaries. Structural mapping and analysis of the district indicate a dominant northwest to west-northwest direction of regional tectonic transport. Local north to north-northeast transport of thrust sheets is interpreted to reflect the influence of underlying lateral and/or oblique ramps, which may have been controlled by inherited basin margin structures. Some thrust-sheet stacking patterns suggest out

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

    NASA Astrophysics Data System (ADS)

    Mazur, E. M.

    2012-12-01

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

  6. Evolving force balance at Columbia Glacier, Alaska, during its rapid retreat

    USGS Publications Warehouse

    O'Neel, S.; Pfeffer, W.T.; Krimmel, R.; Meier, M.

    2005-01-01

    Changes in driving and resistive stresses play an essential role in governing the buoyancy forces that are important controls on the speed and irreversibility of tidewater glacier retreats. We describe changes in geometry, velocity, and strain rate and present a top-down force balance analysis performed over the lower reach of Columbia Glacier. Our analysis uses new measurements and estimates of basal topography and photogrammetric surface velocity measurements made between 1977 and 2001, while assuming depth-independent strain. Sensitivity tests show that the method is robust and insensitive to small changes in the calculation parameters. Spatial distributions of ice speed show little correspondence with driving stress. Instead, spatial patterns of ice speed exhibit a nonlinear correspondence with basal drag. Primary resistance to flow comes from basal drag, but lateral drag becomes increasingly more important throughout the retreat, which may account for observed increases in speed. Maximum basal drag is always located in a prominent constriction located ~12 km upstream from the preretreat terminus. Once the terminus retreated into deep water off the terminal moraine marking the modern maximum extent, the upstream location of this maximum basal drag helped to promote thinning and decrease effective pressure in the lower region by limiting replenishing ice flow from upstream. An increase in both ice velocity and calving resulted, initiating what appears to be an irreversible retreat. Copyright 2005 by the American Geophysical Union.

  7. Alaska

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Though it's not quite spring, waters in the Gulf of Alaska (right) appear to be blooming with plant life in this true-color MODIS image from March 4, 2002. East of the Alaska Peninsula (bottom center), blue-green swirls surround Kodiak Island. These colors are the result of light reflecting off chlorophyll and other pigments in tiny marine plants called phytoplankton. The bloom extends southward and clear dividing line can be seen west to east, where the bloom disappears over the deeper waters of the Aleutian Trench. North in Cook Inlet, large amounts of red clay sediment are turning the water brown. To the east, more colorful swirls stretch out from Prince William Sound, and may be a mixture of clay sediment from the Copper River and phytoplankton. Arcing across the top left of the image, the snow-covered Brooks Range towers over Alaska's North Slope. Frozen rivers trace white ribbons across the winter landscape. The mighty Yukon River traverses the entire state, beginning at the right edge of the image (a little way down from the top) running all the way over to the Bering Sea, still locked in ice. In the high-resolution image, the circular, snow-filled calderas of two volcanoes are apparent along the Alaska Peninsula. In Bristol Bay (to the west of the Peninsula) and in a couple of the semi-clear areas in the Bering Sea, it appears that there may be an ice algae bloom along the sharp ice edge (see high resolution image for better details). Ground-based observations from the area have revealed that an under-ice bloom often starts as early as February in this region and then seeds the more typical spring bloom later in the season.

  8. Dispersion of adult Cancer magister at Glacier Bay, Alaska: Variation with spatial scale, sex, and reproductive status

    USGS Publications Warehouse

    O'Clair, Charles E.; Shirley, Thomas C.; Taggart, S. James

    1996-01-01

    Patterns of micro- to mesoscale distribution of Dungeness crabs (Cancer magister) in nearshore habitats at five locations in and near Glacier Bay National Park were revealed using subtidal transects. Sampling was conducted in April and September 1992 and 1993 and April 1994. Divers censused crabs by sex and reproductive status (ovigerous/nonovigerous females) along belt transects (2 m x 100 m) perpendicular to shore in the depth range 0 m (mean lower low water) to 18 m. A sample estimator of Morisita's index (Î*Δ) was used to quantify crab dispersion at 10 scales of measurement ranging from 20 m2 to 200 m2 at each location during each sampling period.Values of Î*Δ in ovigerous female C. magister deviated significantly (P < 0.05) from 1.0 (random distribution) toward contagion more frequently than did Î*Δ for nonovigerous female and male crabs. Ovigerous crabs also usually had higher Î*Δ than did nonovigerous female and male crabs, especially at smaller measurement scales (20-80 m2). Morisita's index for all three groups of crabs decreased more frequently than it increased with an increase in measurement scale. We observed no relationship between t and crab density in nonovigerous female and male crabs, whereas Î*Δ was positively correlated with the density of ovigerous crabs. A total of 13 dense aggregations of ovigerous C. magister were observed nearshore (depth range 0-10 m) at the five study locations. About half of these were repeatedly observed at the same microsite over the course of this study. Ovigerous Dungeness crabs at Glacier Bay were usually aggregated, often forming dense aggregations with high site fidelity. These dense aggregations may concentrate a significant proportion of the brood stock of this species in a limited number of patches of optimal brooding habitat at Glacier Bay.

  9. Geodetic mass balance of surge-type Black Rapids Glacier, Alaska, 1980-2001-2010, including role of rockslide deposition and earthquake displacement

    NASA Astrophysics Data System (ADS)

    Kienholz, C.; Hock, R.; Truffer, M.; Arendt, A. A.; Arko, S.

    2016-12-01

    We determine the geodetic mass balance of surge-type Black Rapids Glacier, Alaska, for the time periods 1980-2001 and 2001-2010 by combining modern interferometric synthetic aperture radar (InSAR)-derived digital elevation models (DEMs), DEMs derived from archival aerial imagery, laser altimetry data, and in situ surface elevation measurements. Our analysis accounts for both the large rockslides and terrain displacements caused by the 2002 M7.9 earthquake on the Denali fault, which runs through Black Rapids Glacier. To estimate uncertainties, we apply Monte Carlo simulations. For the earthquake-triggered rockslides we find a volume of 56.62 ± 2.86 × 106 m3, equivalent to an average debris thickness of 4.44 ± 0.24 m across the 11.7 km2 deposit area on the glacier. Terrain displacement due to the earthquake corresponds to an apparent glacier volume change of -53.1 × 106 m3, which would cause an apparent specific mass balance of -0.19 meter water equivalent (mwe) if not taken into account. The geodetic mass balance of Black Rapids Glacier is -0.48 ± 0.07 mwe a-1 for the entire 30 year period, but more negative for the period 2001-2010 (-0.64 ± 0.11 mwe a-1) than the period 1980-2001 (-0.42 ± 0.11 mwe a-1), in agreement with trends indicated by in situ mass balance measurements. Elevation data indicate no net thickening of the surge reservoir between 1980 and 2010, in contrast to what is expected during the quiescent phase. A surge of Black Rapids Glacier in the near future is thus considered unlikely.

  10. A geochemical perspective of Red Mountain: an unmined volcanogenic massive sulfide deposit in the Alaska Range

    USGS Publications Warehouse

    Giles, Stuart A.; Eppinger, Robert G.

    2014-01-01

    The U.S. Geological Survey (USGS) has investigated the environmental geochemistry of a group of unmined volcanogenic massive sulfide (VMS) deposits in the Bonnifield mining district, Alaska Range, east-central Alaska. The spectacularly colored Red Mountain deposit is the best exposed of these and provides excellent baseline geochemical data for natural environmental impacts of acidic rock drainage, metal dissolution and transport, and acidic salt and metal precipitation from an exposed and undisturbed VMS deposit.

  11. Effects of Bedrock Lithology and Subglacial Till on the Motion of Ruth Glacier, Alaska, Deduced from Five Pulses from 1973-2012

    NASA Technical Reports Server (NTRS)

    Turrin, J.; Forster, R.; Sauber, Jeanne; Hall, Dorothy K.; Bruhn, R.

    2013-01-01

    A pulse is a type of unstable glacier flow intermediate between normal flow and surging. Using Landsat MSS, TM, and ETM+ imagery and feature tracking software, a time-series of mostly annual velocity maps from 1973 to 2012 was produced that reveals five pulses of Ruth Glacier, Alaska. Peaks in ice velocity were found in the 1981, 1989, 1997, 2003, and 2010; approximately every 7 years. During these peak years the ice velocity increased 300%, from approximately 40 m/yr to 160 m/yr, and occurred in an area of the glacier underlain by sedimentary bedrock. Based on the spatio-temporal behavior of Ruth Glacier during the pulse cycles, we suggest the pulses are due to enhanced basal motion via deformation of a subglacial till. The cyclical nature of the pulses is theorized to be due to a thin till, with low permeability, that causes incomplete drainage of the till between the pulses, followed by eventual recharge and dilation of the till. These findings suggest care is needed when attempting to correlate changes in regional climate with decadal-scale changes in velocity, because in some instances basal conditions may have a greater influence on ice dynamics than climate.

  12. Initial AUV Investigation of the Dynamic Morainal Bank Environment of the Advancing Hubbard Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Lawson, D. E.; Gulick, S. P. S.; Goff, J. A.

    2015-12-01

    Hubbard Glacier has been steadily advancing into tidewater > 200 years; advance over last 40 years has averaged ~34 m/yr, although at spatially variable rates across the terminus (14-80 m/yr) and with a seasonal advance and retreat cycle of ~100 m to 300 m, but as much as 600 m. The advance of the terminus is synchronous with the movement of the morainal bank that underlies it. The mechanics of this motion and the related sedimentological processes responsible for this coordinated advance of the grounding line are based largely on inferences from geophysical surveys of remnant morainal banks. In situ and repeated observations of the submarine margin are required to improve our understanding of how the terminus advances into deep fjords. We conducted initial submarine observations using a Bluefin 9M AUV (Autonomous Underwater Vehicle) and acquired high-resolution swath bathymetry and sidescan backscatter along a ~2 km long section of the ice face of the glacier. Onboard oceanographic measurements and surface CTD casts were obtained during AUV deployment. Decimeter-scale imagery of the seabed reveals numerous erosional and depositional bedforms and gravitational features next to the ice face and down the morainal bank's proximal slope. The moraine surface adjacent to the ice face is coarse, apparently swept clear of finer materials, exhibits gravel stripes and boulder lags. The slope into the fjord displays a sequence of bedforms from barchan-shaped dunes up to 15 m on a side to barchanoid transverse ridges >50 m long to transverse ridges >100 m long. This transition implies increased sand supply to the bed downslope. Channels, erosional gullies and scours cross the upper slope, while localized slump and flow failures occur sporadically across the face. We speculate that high concentration bottom flows originating from turbulent subglacial discharge are likely processes creating the barchan forms and that the flow velocity reduces with distance from the grounding

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

    SciTech Connect

    Stock, J.W. |; Pinchak, A.C. |

    1995-12-31

    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.

  14. Object-Based Image Classification of Floating Ice Used as Habitat for Harbor Seals in a Tidewater Glacier Fjord in Alaska

    NASA Astrophysics Data System (ADS)

    McNabb, R. W.; Womble, J. N.; Prakash, A.; Gens, R.; Ver Hoef, J.

    2014-12-01

    Tidewater glaciers play an important role in many landscape and ecosystem processes in fjords, terminating in the sea and calving icebergs and discharging meltwater directly into the ocean. Tidewater glaciers provide floating ice for use as habitat for harbor seals (Phoca vitulina richardii) for resting, pupping, nursing, molting, and avoiding predators. Tidewater glaciers are found in high concentrations in Southeast and Southcentral Alaska; currently, many of these glaciers are retreating or have stabilized in a retracted state, raising questions about the future availability of ice in these fjords as habitat for seals. Our primary objective is to investigate the relationship between harbor seal distribution and ice availability at an advancing tidewater glacier in Johns Hopkins Inlet, Glacier Bay National Park, Alaska. To this end, we use a combination of visible and infrared aerial photographs, object-based image analysis (OBIA), and statistical modeling techniques. We have developed a workflow to automate the processing of the imagery and the classification of the fjordscape (e.g., individual icebergs, brash ice, and open water), providing quantitative information on ice coverage as well as properties not typically found in traditional pixel-based classification techniques, such as block angularity and seal density across the fjord. Reflectance variation in the red channel of the optical images has proven to be the most important first-level criterion to separate open water from floating ice. This first-level criterion works well in areas without dense brash ice, but tends to misclassify dense brash ice as single icebergs. Isolating these large misclassified regions and applying a higher reflectance threshold as a second-level criterion helps to isolate individual ice blocks surrounded by dense brash ice. We present classification results from surveys taken during June and August, 2007-2013, as well as preliminary results from statistical modeling of the

  15. Subglacial source of meltwater discharge in an emerging ice-marginal channel, Bering Glacier, Alaska

    SciTech Connect

    Priscott, G.; Fleisher, P.J. . Dept. of Earth Sciences)

    1993-03-01

    The retreating eastern margin of Bering Piedmont Glacier terminates in two ice-contact lakes separated by an island that has been uncovered in the last decade. A semi-continuous aerial photo record (1978--1991) and field observations (1992) confirms a newly-developed ice-marginal channel linking these two lakes that is fed by a persistent subglacial conduit system. This investigation documents channel characteristic, discharge, turbidity, water temperature and the location of the present ice margin. Bathymetry along the channel reveals a highly irregular profile consisting of low-gradient reaches 3--5 m deep interrupted by shallow sills (< 1 m) of grounded, subaqueous ice and a 40 m basin among ice islands. Channel dimensions measured in 5 cross section reveal abrupt, small-scale changes typical of sub-bottom ice. Discharge varies from 72.24 cms near a node of upwelling to 40.38 cms 2 km down stream, then back up to 42.25 cms within 0.4 km, where the channel enters a lake. Turbidity values between 1.67 g/l and 4.20 g/l, of 10 water samples vary irregularly along the channel and with depth at-a-station. Early July water temperatures from 7 widely-spaced locations indicate the thermocline occurs at depths from 1 to 3 m and separates surface water at +1.1 C from supercooled water at [minus]1.0 C. Clusters of in situ platy frazil ice crystals several centimeters in diameter were observed on floating ice in the area of upwelling supercooled water. The presence of upwelling, highly-turbid, supercooled water indicates that the primary meltwater source is a subglacial conduit network at the ice margin, from which flow separates and discharges through a leaky channel into both lakes.

  16. Map, tables, and summary of fossil and isotopic age data, Mount Hayes Quadrangle, eastern Alaska range, Alaska

    USGS Publications Warehouse

    Nokleberg, Warren J.; Aleinikoff, John N.; Dutro, J. Thomas; Lanphere, Marvin A.; Silberling, Norman J.; Silva, Steven R.; Smith, Thomas E.; Turner, Donald L.

    1992-01-01

    This report describes, summarizes, and interprets all known bedrock fossil and isotopic age studies for the Mount Hayes quadrangle, eastern Alaska Range, Alaska. The accompanying map shows the location of all known bedrock fossil and isotopic sample localities in the quadrangle on a generalized geologic base map. These fossil and isotopic age data are obtained from new studies, unpublished data of the U.S. Geological Survey, contributed unpublished data, and published data. This report is one result of a five-year mineral resource assessment of the quadrangle that was done during the summers of 1978 through 1982, with additional topical studiesin 1985 and 1986. This report is one part of a folio on the geological, geochemical, geophysical, and mineral-resource assessment studies of the quadrangle prepared as part of the Alaskan Mineral Resource Assessment Program (AMRAP) of the U.S. Geological Survey.

  17. 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

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

    2014-01-01

    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.

  18. Range expansion of nonindigenous caribou in the Aleutianarchipelago of Alaska

    USGS Publications Warehouse

    Ricca, Mark A.; Weckerly, Floyd W.; Duarte, Adam; Williams, Jeffrey C.

    2012-01-01

    Caribou (Rangifer tarandus) are nonindigenous to all but the eastern-most island of the Aleutian archipelago of Alaska. In 1958–1959, caribou were intentionally introduced to Adak Island in the central archipelago, and the population has at least tripled in recent years subsequent to the closure of a naval air facility. Although dispersal of caribou to adjacent islands has been suspected, no historical documentation has occurred to date. Herein, we report consistent detections of caribou sign on the adjacent island of Kagalaska over 2 summer field seasons (2010–2011), and visual detection of caribou on that island during the summer of 2011. Ecological impacts of caribou on Kagalaska are not strongly apparent at the present time and we do not know how many animals permanently occupy the island. However, establishment of a reproductively viable resident population on Kagalaska is worrisome and could set the stage for a step-wise invasion of additional nearby islands.

  19. UNIT, ALASKA.

    ERIC Educational Resources Information Center

    Louisiana Arts and Science Center, Baton Rouge.

    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…

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

    USGS Publications Warehouse

    March, Rod S.

    2003-01-01

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

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

    USGS Publications Warehouse

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

    1994-01-01

    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.

  2. Widespread decadal-scale decrease of glacier speed revealed using repeat optical satellite images

    NASA Astrophysics Data System (ADS)

    Heid, T.; Kääb, A.

    2012-04-01

    Matching of repeat optical satellite images to derive glacier velocities is an approach that is much used within glaciology. Lately, focus has been put into developing, improving, automating and comparing different image matching methods. This makes it now possible to investigate glacier dynamics within large regions of the world and also between regions to improve knowledge about glacier dynamics in space and time. In this study we investigate whether the negative glacier mass balance seen over large parts of the world has caused the glaciers to change their speeds. The studied regions are Pamir, Caucasus, Penny Ice Cap, Alaska Range and Patagonia. In addition we derive speed changes for Karakoram, a region assumed to have positive mass balance and that contains many surge-type glaciers. We find that the mapped glaciers in the five regions with negative mass balance have decreased their speeds over the last decades, Pamir by 43 % in average per decade, Caucasus by 8 % in average per decade, Penny Ice Cap by 25 % in average per decade, Alaska Range by 11 % in average per decade and Patagonia by 20 % in average per decade. Glaciers in Karakoram have generally increased their speeds, but surging glaciers and glaciers with flow instabilities are most prominent in this area.

  3. Worldwide widespread decadal-scale decrease of glacier speed revealed using repeat optical satellite images

    NASA Astrophysics Data System (ADS)

    Heid, T.; Kääb, A.

    2011-10-01

    Matching of repeat optical satellite images to derive glacier velocities is an approach that is much used within glaciology. Lately, focus has been put into developing, improving, automating and comparing different image matching methods. This makes it now possible to investigate glacier dynamics within large regions of the world and also between regions to improve knowledge about glacier dynamics in space and time. In this study we investigate whether the negative glacier mass balance seen over large parts of the world has caused the glaciers to change their speeds. The studied regions are Pamir, Caucasus, Penny Ice Cap, Alaska Range and Patagonia. In addition we derive speed changes for Karakoram, a region assumed to have positive mass balance and that contains many surge-type glaciers. We find that the mapped glaciers in the five regions with negative mass balance have decreased their speeds over the last decades, Pamir by 43 % in average per decade, Caucasus by 8 % in average per decade, Penny Ice Cap by 25 % in average per decade, Alaska Range by 11 % in average per decade and Patagonia by 20 % in average per decade. Glaciers in Karakoram have generally increased their speeds, but surging glaciers and glaciers with flow instabilities are most prominent in this area.

  4. Seasonal changes of surface velocity and elevation of Columbia Glacier, Alaska using time-series TerraSAR-X/TanDEM-X data

    NASA Astrophysics Data System (ADS)

    Vijay, Saurabh; Braun, Matthias

    2015-04-01

    Alaskan glaciers are a major contributor to global sea-level rise from glaciers and ice caps outside the polar ice sheets. Columbia Glacier is a large tidewater glacier located on the coast of south-central Alaska. The glacier has retreated ˜ 21 km and lost half of its volume during 1957-2007, more rapidly after 1980. It is now split into two branches, known as Main/East and West branch. In this study, we used time series of high-resolution TerraSAR-X/TanDEM-X stripmap satellite imagery during 2011-2014 to investigate the temporal development of glacier surface velocities, elevation and mass changes. The active SLC images of the bistatic TanDEM-X acquisitions, acquired over 11 or 22 days repeat intervals, are utilized to derive surface velocity fields using SAR intensity offset tracking. We observed a very strong seasonal variability in the surface velocities. Maximum values at the ice front reach up to 14.43 m/day in May and reduced to 2 m/day in October in the year 2012. However, at a distance of 17.5 km from the ice front, almost no seasonal variability can be observed. A significant influence in the distance to the terminus and elevation was detected. We attributed this temporal and spatial variability of surface velocity to changes in the basal hydrology and lubrification of the glacier bed. Similar fluctuations are observed in consecutive years. In a second step, we exploited TanDEM-X data by interferometrically generating time series of digital elevation models (DEMs) . For quantitative volume change estimates, we used DEMs of almost similar months of the observational years in order to minimize errors resulting from variable X-band radar penetration. The main branch gained a volume of 12.77± 2.89km^3in 2011-12, but lost -18.94± 3.21km^3in 2012-13 . A slight gain was observed with 1.05± .88km^3in 2013-14. However, the west branch gained volume only in 2011-12 and lost in the consecutive years. Moreover, the west branch retreated by ˜ 3km and lost its

  5. Assessing streamflow sensitivity to variations in glacier mass balance

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  6. 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

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

    2007-01-01

    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

  7. Relict rock glaciers as groundwater storage in alpine catchments - the example of the Seckauer Tauern Range

    NASA Astrophysics Data System (ADS)

    Wagner, Thomas; Pauritsch, Marcus; Winkler, Gerfried

    2015-04-01

    Debris accumulations like relict rock glaciers (RRG) might act as groundwater storages in alpine catchments influencing the discharge dynamics of mountain streams. The degree of influence is related to the hydrometeorological conditions and changes seasonally. Especially during drought and flood events, the storage/buffer abilities of RRGs have an impact on the downstream river network. Stream flow could be assured during low flow periods and peak flows might be dampened during storm events. The assessment of the impact is investigated in the Seckauer Tauern Range, the easternmost subunit of the Niedere Tauern Range. In more detail, the discharge of a spring (Schöneben spring) emerging at the front of a RRG draining a catchment of 0.67 km² and discharges at gauging stations Finsterliesing and Unterwald further downstream with areal extents of 7.26 and 44.10 km² respectively are used as input for a lumped-parameter rainfall-runoff model, a modified version of the GR4J (Perrin et al., 2003). The Schöneben spring is 100% influenced by the RRG groundwater storage, as the whole catchment drains through the RRG. The flow dynamics of the other catchments are influenced only partially by RRGs with 15 and 12% as only headwater sections of it are drained by RRGs. The areal extend of the RRG (sub-) catchments, vegetation, debris in general and bare rock are compared to the storage parameters (routing and production store) of the rainfall-runoff model. As such, the influence of RRGs can be identified even in the overall catchment. It can be concluded that RRGs, due to their storage and buffer capabilities and abundance in the Seckauer Tauern Range are important for stream basin management and as a water resource for the sensitive ecosystem in alpine catchments. References: Perrin, C., Michel, C., Andréassian, V. (2003): Improvement of a parsimonious model for streamflow simulation. Journal of Hydrology 279, 275-289.

  8. Antarctic Peninsula Tidewater Glacier Dynamics

    NASA Astrophysics Data System (ADS)

    Pettit, E. C.; Scambos, T. A.; Haran, T. M.; Wellner, J. S.; Domack, E. W.; Vernet, M.

    2015-12-01

    The northern Antarctic Peninsula (nAP, north of 66°S) is a north-south trending mountain range extending transverse across the prevailing westerly winds of the Southern Ocean resulting in an extreme west-to-east precipitation gradient. Snowfall on the west side of the AP is one to two orders of magnitude higher than the east side. This gradient drives short, steep, fast-flowing glaciers into narrow fjords on the west side, while longer lower-sloping glaciers flow down the east side into broader fjord valleys. This pattern in ice dynamics affects ice-ocean interaction on timescales of decades to centuries, and shapes the subglacial topography and submarine bathymetry on timescales of glacial cycles. In our study, we calculate ice flux for the western and eastern nAP using a drainage model that incorporates the modern ice surface topography, the RACMO-2 precipitation estimate, and recent estimates of ice thinning. Our results, coupled with observed rates of ice velocity from InSAR (I. Joughin, personal communication) and Landsat 8 -derived flow rates (this study), provide an estimate of ice thickness and fjord depth in grounded-ice areas for the largest outlet glaciers. East-side glaciers either still terminate in or have recently terminated in ice shelves. Sedimentary evidence from the inner fjords of the western glaciers indicates they had ice shelves during LIA time, and may still have transient floating ice tongues (tabular berg calvings are observed). Although direct oceanographic evidence is limited, the high accumulation rate and rapid ice flux implies cold basal ice for the western nAP glaciers and therefore weak subglacial discharge relative to eastern nAP glaciers and or other tidewater fjord systems such as in Alaska. Finally, despite lower accumulation rates on the east side, the large elongate drainage basins result in a greater ice flux funneled through fewer deeper glaciers. Due to the relation between ice flux and erosion, these east-side glaciers

  9. Thrust involvement of metamorphic rocks, southwestern Brooks Range, Alaska

    SciTech Connect

    Till, A.B.; Schmidt, J.M.; Nelson, S.W. )

    1988-10-01

    Most models for the tectonic history of the western Brooks Range treat Proterozoic and lower Paleozoic metamorphic rocks exposed in the southern part of the range as passive structural basement vertically uplifted late in the Mesozoic orogenic episode. Mapping in the metamorphic rocks shows that they can de divided into two structurally and metamorphically distinct belts, both of which were folded and thrust during the orogeny. Recognition of these belts and the nature of the contact separating them is critical to construction of accurate tectonic models of the Brooks Range fold and thrust belt.

  10. Repeat optical satellite images reveal widespread and long term decrease in land-terminating glacier speeds

    NASA Astrophysics Data System (ADS)

    Heid, T.; Kääb, A.

    2012-04-01

    By matching of repeat optical satellite images it is now possible to investigate glacier dynamics within large regions of the world and also between regions to improve knowledge about glacier dynamics in space and time. In this study we investigate whether the negative glacier mass balance seen over large parts of the world has caused the glaciers to change their speeds. The studied regions are Pamir, Caucasus, Penny Ice Cap, Alaska Range and Patagonia. In addition we derive speed changes for Karakoram, a region assumed to have positive mass balance and that contains many surge-type glaciers. We find that the mapped glaciers in the five regions with negative mass balance have over the last decades decreased their velocity at an average rate per decade of: 43 % in the Pamir, 8 % in the Caucasus, 25 % on Penny Ice Cap, 11 % in the Alaska Range and 20 % in Patagonia. Glaciers in Karakoram have generally increased their speeds, but surging glaciers and glaciers with flow instabilities are most prominent in this area. Therefore the calculated average speed change is not representative for this area.

  11. Geospatial compilation of results from field sample collection in support of mineral resource investigations, Western Alaska Range, Alaska, July 2013

    USGS Publications Warehouse

    Johnson, Michaela R.; Graham, Garth E.; Hubbard, Bernard E.; Benzel, William M.

    2015-07-16

    This Data Series summarizes results from July 2013 sampling in the western Alaska Range near Mount Estelle, Alaska. The fieldwork combined in situ and camp-based spectral measurements of talus/soil and rock samples. Five rock and 48 soil samples were submitted for quantitative geochemi­cal analysis (for 55 major and trace elements), and the 48 soils samples were also analyzed by x-ray diffraction to establish mineralogy and geochemistry. The results and sample photo­graphs are presented in a geodatabase that accompanies this report. The spectral, mineralogical, and geochemical charac­terization of these samples and the sites that they represent can be used to validate existing remote-sensing datasets (for example, ASTER) and future hyperspectral studies. Empiri­cal evidence of jarosite (as identified by x-ray diffraction and spectral analysis) corresponding with gold concentrations in excess of 50 parts per billion in soil samples suggests that surficial mapping of jarosite in regional surveys may be use­ful for targeting areas of prospective gold occurrences in this sampling area.

  12. Crustal implications of bedrock geology along the Trans-Alaska Crustal Transect (TACT) in the Brooks Range, northern Alaska

    USGS Publications Warehouse

    Moore, T.E.; Wallace, W.K.; Mull, C.G.; Adams, K.E.; Plafker, G.; Nokleberg, W.J.

    1997-01-01

    Geologic mapping of the Trans-Alaska Crustal Transect (TACT) project along the Dalton Highway in northern Alaska indicates that the Endicott Mountains allochthon and the Hammond terrane compose a combined allochthon that was thrust northward at least 90 km in the Early Cretaceous. The basal thrust of the combined allochthon climbs up section in the hanging wall from a ductile shear zone, in the south through lower Paleozoic rocks of the Hammond terrane and into Upper Devonian rocks of the Endicott Mountains allochthon at the Mount Doonerak antiform, culminating in Early Cretaceous shale in the northern foothills of the Brooks Range. Footwall rocks north of the Mount Doonerak antiform are everywhere parautochthonous Permian and Triassic shale of the North Slope terrane rather than Jurassic and Lower Cretaceous strata of the Colville Basin as shown in most other tectonic models of the central Brooks Range. Stratigraphic and structural relations suggest that this thrust was the basal detachment for Early Cretaceous deformation. Younger structures, such as the Tertiary Mount Doonerak antiform, deform the Early Cretaceous structures and are cored by thrusts that root at a depth of about 10 to 30 km along a deeper detachment than the Early Cretaceous detachment. The Brooks Range, therefore, exposes (1) an Early Cretaceous thin-skinned deformational belt developed during arc-continent collision and (2) a mainly Tertiary thick-skinned orogen that is probably the northward continuation of the Rocky Mountains erogenic belt. A down-to-the-south zone of both ductile and brittle normal faulting along the southern margin of the Brooks Range probably formed in the mid-Cretaceous by extensional exhumation of the Early Cretaceous contractional deformation. copyright. Published in 1997 by the American Geophysical Union.

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

    USGS Publications Warehouse

    Molnia, B.F.

    2007-01-01

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

  14. A numerical groundwater model to assess the hydrogeological behavior of a relict rock glacier aquifer (Niedere Tauern Range, Austria)

    NASA Astrophysics Data System (ADS)

    Pauritsch, Marcus; Wagner, Thomas; Winkler, Gerfried; Birk, Steffen

    2016-04-01

    A three dimensional numerical groundwater model representing a relict rock glacier with an extent of 0.17 km², located in the Eastern Alps (Schöneben rock glacier, Niedere Tauern Range, Austria) is used to highlight the impact of the major internal aquifer structures and the morphology of the aquifer base on the discharge behavior. The model is implemented in MODFLOW and calibrated using the discharge data of the spring. The recharge is determined based on precipitation and evapotranspiration which is calculated using a simple soil water balance model in combination with the monthly potential evapotranspiration. Data are provided by an automatic weather station on the Schöneben rock glacier where precipitation and air temperature are continuously measured. It is renounced to use a snow model in order to keep the model as simple as possible. Therefore the investigation is limited to the time periods from late summer to the beginning of the snowmelt in spring. The aquifer geometry and in particular the morphology of the aquifer base are based on geophysical investigations (ground penetrating radar and seismic refraction). However, due to gaps of the geophysical investigations the interpolation of the aquifer base at the margin of the rock glacier is related to uncertainties. Therefore, two different morphologies of the aquifer base were used which mainly differ in the slope of the south-eastern margin. Several model setups with increasing complexity of the internal structure (from homogeneous to heterogeneous) were applied to demonstrate the effects of the vertical (layering) and horizontal (preferential flow) aquifer heterogeneity on the discharge behavior. The results show that a model with a homogeneous setup cannot satisfyingly reproduce the discharge dynamics observed at the Schöneben rock glacier. With a heterogeneous setup, the model fit greatly improves but shows differences between the horizontally and vertically heterogeneous setups. The morphology of

  15. Differences in dissolved organic matter lability between alpine glaciers and alpine rock glaciers of the American West

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    While alpine glaciers in montane regions represent the largest flux of dissolved organic matter (DOM) from global ice melt no research has examined the bioavailability of DOM melted out of glacial ice in the western continental United States. Furthermore, rock glaciers are an order of magnitude more abundant than ice glaciers in U.S., yet are not included in budgets for perennial ice carbon stores. Our research aims to understand differences in the bioavailability of carbon from ice glaciers and rock glaciers along the Central Rocky Mountains of Colorado. Identical microbial communities were fed standardized amounts of DOM from four different ice glacier-rock glaciers pairs. Using laboratory incubations, paired with mass spectrometry based metabolomics and 16S gene sequencing; we were able to examine functional definitions of DOM lability in glacial ice. We hypothesized that even though DOM quantities are similar in the outputs of both glacial types in our study area, ice glacial DOM would be more bioavailable than DOM from rock glaciers due to higher proportions of byproducts from microbial metabolism than rock glacier DOM, which has higher amounts of "recalcitrant" plant material. Our results show that DOM from ice glaciers is more labile than DOM from geologically and geographically similar paired rock glaciers. Ice glacier DOM represents an important pool of labile carbon to headwater ecosystems of the Rocky Mountains. Metabolomic analysis shows numerous compounds from varying metabolite pathways, including byproducts of nitrification before and after incubation, meaning that, similar to large maritime glaciers in Alaska and Europe, subglacial environments in the mountain ranges of the United States are hotspots for biological activity and processing of organic carbon.

  16. Glacier microseismicity

    USGS Publications Warehouse

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

    2010-01-01

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

  17. Small valley glaciers and the effectiveness of the glacial buzzsaw in the northern Basin and Range, USA

    NASA Astrophysics Data System (ADS)

    Foster, David; Brocklehurst, Simon H.; Gawthorpe, Rob L.

    2008-12-01

    The glacial buzzsaw hypothesis suggests that efficient erosion limits topographic elevations in extensively glaciated orogens. Studies to date have largely focussed on regions where large glaciers (tens of kilometres long) have been active. In light of recent studies emphasising the importance of lateral glacial erosion in lowering peaks and ridgelines, we examine the effectiveness of small glaciers in limiting topography under both relatively slow and rapid rock uplift conditions. Four ranges in the northern Basin and Range, Idaho, Montana, and Wyoming, USA, were chosen for this analysis. Estimates of maximum Pleistocene slip rates along normal faults bounding the Beaverhead-Bitterroot Mountains (~ 0.14 mm y - 1 ), Lemhi Range (~ 0.3 mm y - 1 ) and Lost River Range (~ 0.3 mm y - 1 ) are an order of magnitude lower than those on the Teton Fault (~ 2 mm y - 1 ). We compare the distribution of glacial erosion (estimated from cirque floor elevations and last glacial maximum (LGM) equilibrium line altitude (ELA) reconstructions) and fault slip rate with three metrics of topography in each range: the along-strike maximum elevation swath profile, hypsometry, and slope-elevation profiles. In the slowly uplifting Beaverhead-Bitterroot Mountains, and Lemhi and Lost River Ranges, trends in maximum elevation parallel ELAs, independent of variations in fault slip rate. Maximum elevations are offset ~ 500 m from LGM ELAs in the Lost River Range, Lemhi Range, and northern Beaverhead-Bitterroot Mountains, and by ~ 350 m in the southern Beaverhead-Bitterroot Mountains, where glacial extents were less. The offset between maximum topography and mean Quaternary ELAs, inferred from cirque floor elevations, is ~ 350 m in the Lost River and Lemhi Ranges, and 200-250 m in the Beaverhead-Bitterroot Mountains. Additionally, slope-elevation profiles are flattened and hypsometry profiles show a peak in surface areas close to the ELA in the Lemhi Range and Beaverhead-Bitterroot Mountains

  18. In Brief: Melting glaciers

    NASA Astrophysics Data System (ADS)

    Showstack, Randy; Tretkoff, Ernie

    2010-12-01

    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/.

  19. Glacier Ecosystems of Himalaya

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  20. Mass balance, meteorological, ice motion, surface altitude, runoff, and ice thickness data at Gulkana Glacier, Alaska, 1995 balance year

    USGS Publications Warehouse

    March, Rod S.

    2000-01-01

    The 1995 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier basin were evaluated on the basis of meteorological, hydrological, and glaciological data obtained in the basin. Averaged over the glacier, the measured winter snow balance was 0.94 meter on April 19, 1995, 0.6 standard deviation below the long-term average; the maximum winter snow balance, 0.94 meter, was reached on April 25, 1995; the net balance (from September 18, 1994 to August 29, 1995) was -0.70 meter, 0.76 standard deviation below the long-term average. The annual balance (October 1, 1994, to September 30, 1995) was -0.86 meter. Ice-surface motion and altitude changes measured at three index sites document seasonal ice speed and glacier-thickness changes. Annual stream runoff was 2.05 meters averaged over the basin, approximately equal to the long-term average. The 1976 ice-thickness data are reported from a single site near the highest measurement site (180 meters thick) and from two glacier cross profiles near the mid-glacier (270 meters thick on centerline) and low glacier (150 meters thick on centerline) measurement sites. A new area-altitude distribution determined from 1993 photogrammetry is reported. Area-averaged balances are reported from both the 1967 and 1993 area-altitude distribution so the reader may directly see the effect of the update. Briefly, loss of ablation area between 1967 and 1993 results in a larger weighting being applied to data from the upper glacier site and hence, increases calculated area-averaged balances. The balance increase is of the order of 15 percent for net balance.

  1. Assessing streamflow sensitivity to variations in glacier mass balance

    USGS Publications Warehouse

    O'Neel, Shad; Hood, Eran; Arendt, Anthony; Sass, Louis

    2014-01-01

    The purpose of this paper is to evaluate relationships among seasonal and annual glacier mass balances, glacier runoff and streamflow in two glacierized basins in different climate settings. We use long-term glacier mass balance and streamflow datasets from the United States Geological Survey (USGS) Alaska Benchmark Glacier Program to compare and contrast glacier-streamflow interactions in a maritime climate (Wolverine Glacier) with those in a continental climate (Gulkana Glacier). Our overall goal is to improve our understanding of how glacier mass balance processes impact streamflow, ultimately improving our conceptual understanding of the future evolution of glacier runoff in continental and maritime climates.

  2. 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

    Taggart, S.J.; Shirley, Thomas C.; O'Clair, Charles E.; Mondragon, Jennifer

    2004-01-01

    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.

  3. Geological mapping in Doonerak Fenster, Central Brooks Range, Alaska

    SciTech Connect

    Mull, C.C.; Adams, K.E.; Dillon, J.T.

    1985-04-01

    Mapping of the north flank of the Doonerak fenster has traced the Amawk thrust, the sole fault of the Endicott Mountains allochthon, from the North Fork of the Koyukuk River - Mount Doonerak area eastward for more than 40 km (25 mi) to the east plunge of the Doonerak anticline at Koyuktuvuk Creek near the Dietrich River. Mapping has concentrated on the structural style of the area and on the autochthonous or parautochthonous Carboniferous Lisburne Group, Kayak shale, Kekiktuk Conglomerate - which are present along most of the anticline - and Triassic Karen Creek Sandstone, Triassic Shublik Formation, and Permian-Triassic Sadlerochit Group - which are present only in the west. This Triassic to Mississippian section closely resembles the coeval autochthonous to Parautochthonous Ellesmerian section of the subsurface to the north and in the Brooks Range to the northeast.

  4. Structural architecture of the central Brooks Range foothills, Alaska

    USGS Publications Warehouse

    Moore, Thomas E.; Potter, Christopher J.; O'Sullivan, Paul B.

    2002-01-01

    Five structural levels underlie the Brooks Range foothills, from lowest to highest: (1) autochthon, at a depth of ~9 km; (2) Endicott Mountains allochthon (EMA), thickest under the northern Brooks Range (>15 km) and wedging out northward above the autochthon; (3) higher allochthons (HA), with a composite thickness of 1.5+ km, wedging out northward at or beyond the termination of EMA; (4) Aptian-Albian Fortress Mountain Formation (FM), deposited unconformably on deformed EMA and HA and thickening northward into a >7-km-thick succession of deformed turbidites (Torok Formation); (5) gently folded Albian-Cenomanian deltaic deposits (Nanushuk Group). The dominant faulting pattern in levels 2-3 is thin-skinned thrusting and thrust-related folds formed before deposition of Cretaceous strata. These structures are cut by younger steeply south-dipping reverse faults that truncate and juxtapose structural levels 1-4 and expose progressively deeper structural levels to the south. Structural levels 4-5 are juxtaposed along a north-dipping zone of south-vergent folds and thrusts. Stratigraphic and fission-track age data suggest a kinematic model wherein the foothills belt was formed first, by thrusting of HA and EMA as deformational wedges onto the regionally south-dipping authochon at 140-120Ma. After deposition of FM and Torok during mid-Cretaceous hinterland extension and uplift, a second episode of contractional deformation at 60 Ma shortened the older allochthonous deformational wedges (EMA, HA) and overlying strata on north-vergent reverse faults. To the north, where the allochthons wedge out, shortening caused duplexing in the Torok and development of a triangle zone south of the Tuktu escarpment.

  5. 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

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

    2013-01-01

    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.

  6. Tectonic evolution of the Brooks Range ophiolite, Alaska

    SciTech Connect

    Harris, R.A. . Dept. of Geology)

    1993-04-01

    Detailed studies of the composition, internal structure, and age of the Brooks Range ophiolite (BRO) and its metamorphic sole reveal new constraints for its tectonic evolution. The BRO consists of six separate thrust masses of consanguineous composition, internal organization, structure and age. Subophiolite metamorphic rocks are locally preserved along its structural base, which is well exposed in several places. The metamorphic sole is locally transitional with mafic volcanic sequences, chert, tuffs, and minor clastic sedimentary material of the Copter Peak Complex, which is correlative with the Angayucham terrane. This terrane is much older than, and chemically distinct from the BRO. The internal structure of the BRO is characterized by NE-SW trending igneous layers that expose the transition zone from crust to mantle. Residual mantle material consists of tectonized peridotite in abrupt contact with dunite pods up to 4 km thick. Ductile and brittle structures of the BRO preserve various phases of its dynamic evolution from a magma body to a fragmented thrust sheet. The earliest deformational effects are recorded by ductile lattice and shape fabrics in dunites and the layered series of the BRO. Magmatic flow planes generally parallel the petrologic moho, and dip 40[degree]--70[degree] to the NW and SE. Flow lineations consistently plunge ESE-ENE from 39[degree]--54[degree]. Igneous laminations and compositional layers represent patterns of magmatic flow in, and plastic deformation of, a cumulate sequence -- not the deposition pattern of cumulate layers. In the upper layered series, amphiboles with a shape-preferred orientation yield Ar/Ar plateau ages of 163--169 Ma. These ages overlap with plateau ages of the same kind from amphibolite of the metamorphic sole. This concordance in age indicates that cooling of the BRO coincided with its tectonic emplacement.

  7. Diagenesis of the Lisburne Group, northeastern Brooks Range, Alaska

    SciTech Connect

    Carlson, R.C.; Goldstein, R.H.; Enos, P.

    1995-05-01

    Petrographic cathodoluminescence studies of the cement stratigraphy of the Lisburne Group yield insights on its diagenetic history. Crosscutting relationships between features of subaerial exposure and calcite cements show that early generations of nonferroan, nonluminescent and multibanded-luminescent calcites are synchronous with or postdated by subaerial exposure surfaces within the Lisburne. Surfaces of subaerial exposure occur at 18 horizons within the Lisburne and are distinguished by features as laminated crusts, rhizoliths, autoclastic breccia, fissure fills, mud cracks, and erosional surfaces. Crosscutting relationships also occur between calcite cements and clasts in karst breccias and conglomerates that formed along the sub-Permian unconformity at the top of the Lisburne. The sub-Permian unconformity postdates later generations of calcite cement. These cements formed in the following sequence: nonferroan to low-ferroan, dully luminescent calcite; ferroan, very-dully luminescent calcite; and second generation of nonferroan, multibanded calcite. The crosscutting relationships not only constrain the timing of cement precipitation, but also suggest that the cements probably were precipitated from meteoric groundwaters introduced during subaerial exposure of the Lisburne platform. Late cements in the Lisburne postdate the Permian Echooka Formation. These cements are low-ferroan, moderately-bright to dully luminescent calcite, followed by a second generation of ferroan, very-dully luminescent calcite. Features of compaction and pressure solution are coincident with the precipitation of the late ferroan calcite and further constrain its timing to deep burial of the Lisburne. The youngest phase of calcite cement precipitated in the Lisburne Group is nonferroan, very-dully luminescent calcite. It commonly fills tectonically-induced shear fractures, indicating precipitation after the onset of Cretaceous (and/or Cenozoic) tectonism in the northeastern Brooks Range.

  8. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1992 balance year

    USGS Publications Warehouse

    March, R.S.; Trabant, D.C.

    1996-01-01

    The 1992 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier basin were evaluated on the basis of meteorological, hydrological, and glaciological data measured in the basin and are reported herein. Averaged over the glacier, the measured winter snow balance was 0.97 meters on March 26, 1992; the maximum winter snow balance was 1.05 meters on May 19, 1992; the net balance (from September 8, 1991 to August 17, 1992) was -0.29 meters; and the annual balance (October 1, 1991 to September 30, 1992) was -0.38 meters. Ice surface, motion, and altitude changes measured at three index sites document seasonal changes in ice speed and glacier thickness. Annual stream runoff was 1.24 meters averaged over the basin.

  9. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1994 balance year

    USGS Publications Warehouse

    March, Rod S.

    1998-01-01

    The 1994 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier basin were evaluated on the basis of meteorological, hydrological, and glaciological data obtained in the basin. Averaged over the glacier, the measured winter snow balance was 1.34 meters on April 29, 1994, 0.9 standard deviation above the long-term average; the maximum winter snow balance, 1.43 meters, was reached on April 18, 1994; the net balance (from September 8, 1993 to September 17, 1994) was -0.72 meter, 0.7 standard deviation below the long-term average. The annual balance (October 1, 1992, to September 30, 1993) was -0.88 meter. Ice-surface motion and altitude changes measured at three index sites document seasonal ice speed and glacier-thickness changes. Annual stream runoff was 1.93 meters averaged over the basin, approximately equal to the long-term average.

  10. Alaska

    SciTech Connect

    Jones, B.C.; Sears, D.W.

    1981-10-01

    Twenty-five exploratory wells were drilled in Alaska in 1980. Five oil or gas discovery wells were drilled on the North Slope. One hundred and seventeen development and service wells were drilled and completed, primarily in the Prudhoe Bay and Kuparuk River fields on the North Slope. Geologic-geophysical field activity consisted of 115.74 crew months, an increase of almost 50% compared to 1979. These increases affected most of the major basins of the state as industry stepped up preparations for future lease sales. Federal acreage under lease increased slightly, while state lease acreage showed a slight decline. The year's oil production showed a increase of 16%, while gas production was down slightly. The federal land freeze in Alaska showed signs of thawing, as the US Department of Interior asked industry to identify areas of interest onshore for possible future leasing. National Petroleum Reserve in Alaska was opened to private exploration, and petroleum potential of the Arctic Wildlife Refuge will be studied. One outer continental shelf lease sale was held in the eastern Gulf of Alaska, and a series of state and federal lease sales were announced for the next 5 years. 5 figures, 5 tables.

  11. Flow velocities of Alaskan glaciers.

    PubMed

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

    2013-01-01

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

  12. Use of a new ultra-long-range terrestrial LiDAR system to monitor the mass balance of very small glaciers in the Swiss Alps

    NASA Astrophysics Data System (ADS)

    Fischer, M.; Huss, M.; Hoelzle, M.

    2015-12-01

    Measuring glacier mass balance is important as it directly reflects the climatic forcing on the glacier surface. Today, repeated comparison of digital elevation models (DEMs) is a popular and widely used approach to derive surface elevation, volume and mass changes for a large number of glaciers. In high-mountain environments, airborne laser scanning (ALS) techniques currently provide the most accurate and highest resolution DEMs on the catchment scale, allowing the computation of glacier changes on an annual or even semi-annual basis. For monitoring individual glaciers though, terrestrial laser scanning (TLS) is easier and more cost-efficiently applied on the seasonal timescale compared to ALS. Since most recently, the application of the latest generation of ultra-long-range near infrared TLS systems allows the acquisition of surface elevation information over snow and ice of unprecedented quality and over larger zones than with previous near infrared TLS devices. Although very small glaciers represent the majority in number in most mountain ranges on Earth, their response to climatic changes is still not fully understood and field measurements are sparse. Therefore, a programme was set up in 2012 to monitor both the seasonal and annual surface mass balance of six very small glaciers across the Swiss Alps using the direct glaciological method. As often nearly the entire surface is visible from one single location, TLS is a highly promising technique to generate repeated high-resolution DEMs as well as to derive seasonal geodetic mass balances of very small ice masses. In this study, we present seasonal surface elevation, volume and geodetic mass changes for five very small glaciers in Switzerland (Glacier de Prapio, Glacier du Sex Rouge, St. Annafirn, Schwarzbachfirn and Pizolgletscher) derived from the comparison of seasonally repeated high-resolution DEMs acquired since autumn 2013 with the new ultra-long-range TLS device Riegl VZ-6000. We show the different

  13. Stratigraphy, structure, and palinspastic synthesis of the western Brooks Range, northwestern Alaska

    USGS Publications Warehouse

    Mayfield, Charles F.; Tailleur, Irvin L.; Ellersieck, Inyo

    1983-01-01

    This report is an effort to describe and decipher the mid-Paleozoic to Lower Cretaceous stratigraphy and the orogenic evolution of the western Brooks Range. The western Brooks Range primarily is composed of stacks of complexly deformed thrust sheets that contain mostly coeval sequences of rocks with slightly different lithologic facies. In order to simplify the thrust-faulted stratigraphy and palinspastic restoration, the rocks are grouped into eight principal structural levels. The lowest structural level is believed to be autochthonous or parautochthonous and above that, each succeeding level is designated allochthon one through seven. Allochthon seven is composed of the remnants of an extensive ophiolite sheet. Allochthon six is composed of pillow basalt with subordinate intermediate volcanic rocks, chert, and Devonian limestone. It is not certain whether this allochthon was formed in a continental or oceanic setting. Allochthons five through one consist of distinctive and coeval sequences of Devonian to Lower Cretaceous sedimentary rocks that were deposited in a continental setting. The present geographic distribution of each structural level is shown on the allochthon map of the western Brooks Range. The stratigraphy of the southern part of northern Alaska has been reconstructed by systematically unstacking lower allochthons to the north of higher allochthons. The palinspastic map that results from this procedure shows that the minimum thrust displacement between allochthon seven and the autochthon is approximately 700 to 800 km. Schematic cross sections drawn across the palinspastic map show how the stratigraphy of the southern part of northern. Alaska most likely appeared prior to the orogeny. During Devonian and Mississippian time, the sedimentary sequences that are now part of allochthons one to five are inferred to have been deposited in an ensialic basin with both northern and southern margins. During Pennsylvanian time, the sequences seem to have become

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

    USGS Publications Warehouse

    Brew, David A.

    2008-01-01

    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.

  15. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1993 balance year

    USGS Publications Warehouse

    March, Rod; Trabant, Dennis

    1997-01-01

    The 1993 measured winter snow, maximum winter snow, net, and annual balances in the Gulkana Glacier basin were evaluated on the basis of meteorological, hydrological, and glaciological data measured in the basin and are reported herein. Averaged over the glacier, the measured winter snow balance was 0.81 meter on March 31, 1993, 1.2 standard deviations below the long-term average; the maximum winter snow balance, 0.84 meter, was reached on May 10, 1993 and remained until May 11, 1993; the net balance (from August 18, 1992 to September 8, 1993) was 1.80 meters, the most negative balance year on record at 2.8 standard deviations below the long-term average. The annual balance (October 1, 1992 to September 30, 1993) was 1.64 meters. Ice-surface motion and altitude changes measured at three index sites document seasonal ice speed and glacier thickness changes. Annual stream runoff was 1.996 meters averaged over the basin, 0.2 standard deviations above the long-term average.

  16. Contribution of Alaskan glaciers to sea-level rise derived from satellite imagery

    NASA Astrophysics Data System (ADS)

    Berthier, E.; Schiefer, E.; Clarke, G. K. C.; Menounos, B.; Rémy, F.

    2010-02-01

    Over the past 50 years, retreating glaciers and ice caps contributed 0.5mmyr-1 to sea-level rise, and one third of this contribution is believed to come from ice masses bordering the Gulf of Alaska. However, these estimates of ice loss in Alaska are based on measurements of a limited number of glaciers that are extrapolated to constrain ice wastage in the many thousands of others. Uncertainties in these estimates arise, for example, from the complex pattern of decadal elevation changes at the scale of individual glaciers and mountain ranges. Here we combine a comprehensive glacier inventory with elevation changes derived from sequential digital elevation models. We find that between 1962 and 2006, Alaskan glaciers lost 41.9+/-8.6km3yr-1 of water, and contributed 0.12+/-0.02mm yr-1 to sea-level rise, 34% less than estimated earlier. Reasons for our lower values include the higher spatial resolution of our glacier inventory as well as the reduction of ice thinning underneath debris and at the glacier margins, which were not resolved in earlier work. We suggest that estimates of mass loss from glaciers and ice caps in other mountain regions could be subject to similar revisions.

  17. Devonian-Mississippian carbonate sequence in the Maiyumerak Mountains, western Brooks Range, Alaska

    SciTech Connect

    Dumoulin, J.A. ); Harris, A.G. )

    1990-05-01

    Essentially continuous, dominantly carbonate sedimentation occurred from at least the Early Devonian through the Mississippian in the area that is now the Maiyumerak Mountains, western Brooks Range. This succession is in striking contrast to Paleozoic sequences in the eastern Brooks Range and in the subsurface across northern Alaska, where uppermost Devonian-Mississippian clastic and Carboniferous carbonates unconformably overlie Proterozoic or lower Paleozoic metasedimentary or sedimentary rocks. Conodonts obtained throughout the Maiyumerak Mountains sequence indicate that any hiatus is less than a stage in duration, and there is no apparent physical evidence of unconformity within the succession. The sequence is best exposed northwest of the Eli River, where Emsian-Eifelian dolostones (Baird Group) are conformably overlain by Kinderhookian-Osagian sandy limestones (Utukok Formation) and Osagian-Chesterian fossiliferous limestones (Kogruk Formation) of the Lisburne Group. Conodont species assemblages and sedimentary structures indicate deposition in a range of shallow-water shelf environments. The sequence extends at least 30 km, from the Noatak Quadrangle northeast into the Baird Mountains Quadrangle; its easternmost extent has not been definitively determined. The Ellesmerian orogeny, thought to have produced the extensive middle Paleozoic unconformity seen through much of northern Alaska apparently had little effect on this western Brooks Range sedimentary succession.

  18. Middle Cambrian fossils from the Doonerak anticlinorium, central Brooks Range, Alaska.

    USGS Publications Warehouse

    Dutro, J.T.; Palmer, A.R.; Repetski, J.E.; Brosge, W.P.

    1984-01-01

    Middle Cambrian fossils collected near Wolf Creek in the Wiseman quadrangle, northern Alaska, include trilobites and paraconodonts. Trilobites date the strata as early Middle Cambrian, correlative with the Amgan Stage of Siberia. The assemblage includes: Kootenia cf. K. anabarensis Lermontova, cf. 'Parehmania' lata Chernysheva and Pagetia sp. Specimens of the paracondont genus Westergaardodina, from the same sample as the megafossils, record the earliest known occurrence of this taxon. These fossils, the first to establish an age for part of the sedimentary sequence in the Doonerak Anticlinorium, are the oldest fossils yet taken from the central and western Brooks Range.-Authors

  19. Factors Affecting Haul-Out Behavior of Harbor Seals (Phoca vitulina) in Tidewater Glacier Inlets in Alaska: Can Tourism Vessels and Seals Coexist?

    PubMed

    Blundell, Gail M; Pendleton, Grey W

    2015-01-01

    Large numbers of harbor seals (Phoca vitulina) use habitat in tidewater glaciers in Alaska for pupping, breeding, and molting. Glacial fjords are also popular tourist destinations; however, visitation by numerous vessels can result in disturbance of seals during critical life-history phases. We explored factors affecting haul-out behavior of harbor seals at a glacial site frequented by tourism vessels. In 2008-10, we deployed VHF transmitters on 107 seals in Endicott Arm, Alaska. We remotely monitored presence and haul-out behavior of tagged seals and documented vessel presence with time-lapse cameras. We evaluated the influence of environmental and physical factors on the probability of being hauled out, duration of haul-out bouts, and as factors associated with the start and end of a haulout. Location, season, hour, and interactions of location by year, season, hour, and sex significantly influenced haul-out probability, as did ice, weather, and vessels. Seals were more likely to be hauled out with greater ice availability during the middle of the day, and less likely to be hauled out if vessels were present. Cruise ships had the strongest negative effect; however, most vessel types negatively affected haul-out probability. Haul-out duration was longest in association with starting on incoming tides, clear skies, no precipitation, occurring in the middle of the day, and ending in the late afternoon or evening. End of haulouts was associated with increasing cloud cover, low ice availability, and vessel presence; large-sized tourism vessels or all-vessel-types combined were significant predictors of ending a haul-out bout. Probability of being hauled out was highest in June, during pupping season. Potential disturbances of harbor seals could be reduced, enabling longer resting times for seals and fewer interruptions for nursing pups, if vessels focused the majority of visits to glacial habitat to before or after the hours of 08:00-17:00 or, less optimally, 09:00-16:00.

  20. Comparison of annual accumulation rates derived from in situ and ground penetrating radar methods across Alaskan glaciers

    NASA Astrophysics Data System (ADS)

    McGrath, D.; Gusmeroli, A.; Oneel, S.; Sass, L. C.; Arendt, A. A.; Wolken, G. J.; Kienholz, C.; McNeil, C.

    2013-12-01

    Constraining annual snowfall accumulation in mountain glacier environments is essential for determining the annual mass balance of individual glaciers and predicting seasonal meltwater runoff to river and marine ecosystems. However, large spatial and elevation gradients, coupled with sparse point measurements preclude accurate quantification of this variable using traditional methods. Here, we report on an extensive field campaign conducted in March-May 2013 on key benchmark glaciers in Alaska, including Taku Glacier near Juneau, Scott Glacier near Cordova, both Eklutna and Wolverine Glacier near Anchorage and Gulkana Glacier in the interior Alaska Range. Over 50 km of 500 MHz common-offset ground penetrating radar (GPR) surveys were collected on each glacier, with an emphasis on capturing spatial variability in the accumulation zone. Frequent in situ observations were collected for comparison with the GPR, including probe depths, snow pits and shallow firn cores (~8 m). We report on spatial and elevation gradients across this suite of glaciers and across numerous climatic zones and discuss differences between GPR and in situ derived annual accumulation estimates. This comparison is an essential first step in order to effectively evaluate regional atmospheric re-analysis products.

  1. Nesting by Golden Eagles on the North Slope of the Brooks Range in Northeastern Alaska

    USGS Publications Warehouse

    Young, Donald D.; McIntyre, Carol L.; Bente, Peter J.; McCabe, Thomas R.; Ambrose, Robert E.

    1995-01-01

    Twenty-two Golden Eagle (Aquila chrysaetos) nesting territories and 31 occupied eagle nests were documented on the north slope of the Brooks Range in northeastern Alaska, 1988-1990, in an area previously thought to be marginal breeding habitat for eagles. The mean number of young/successful nest was 1.25 in 1988, 1.27 in 1989, and 1.13 in 1990; means did not differ significantly among years. Eighty percent (20/25) of the nestlings for which age was estimated were assumed to have successfully fledged. Nesting success was 79% (11/14) in 1989, the only year nesting success could be determined. Laying dates ranged from 23 March (1990) to 11 May (1989) with mean estimated laying dates differing significantly among years. Annual variation in nesting phenology coincided with annual differences in snow accumulations during spring. These results indicate that Golden Eagles consistently and successfully breed at the northern extent of their range in Alaska, although, productivity may be lower than that for eagles at more southern latitudes.

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

    NASA Astrophysics Data System (ADS)

    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

    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

  3. 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

    Partridge, Steve; Smith, Tom; Lewis, Tania

    2009-01-01

    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.

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

    USGS Publications Warehouse

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

    2010-01-01

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

  5. Range Expansion of Moose in Arctic Alaska Linked to Warming and Increased Shrub Habitat.

    PubMed

    Tape, Ken D; Gustine, David D; Ruess, Roger W; Adams, Layne G; Clark, Jason A

    2016-01-01

    Twentieth century warming has increased vegetation productivity and shrub cover across northern tundra and treeline regions, but effects on terrestrial wildlife have not been demonstrated on a comparable scale. During this period, Alaskan moose (Alces alces gigas) extended their range from the boreal forest into tundra riparian shrub habitat; similar extensions have been observed in Canada (A. a. andersoni) and Eurasia (A. a. alces). Northern moose distribution is thought to be limited by forage availability above the snow in late winter, so the observed increase in shrub habitat could be causing the northward moose establishment, but a previous hypothesis suggested that hunting cessation triggered moose establishment. Here, we use recent changes in shrub cover and empirical relationships between shrub height and growing season temperature to estimate available moose habitat in Arctic Alaska c. 1860. We estimate that riparian shrubs were approximately 1.1 m tall c. 1860, greatly reducing the available forage above the snowpack, compared to 2 m tall in 2009. We believe that increases in riparian shrub habitat after 1860 allowed moose to colonize tundra regions of Alaska hundreds of kilometers north and west of previous distribution limits. The northern shift in the distribution of moose, like that of snowshoe hares, has been in response to the spread of their shrub habitat in the Arctic, but at the same time, herbivores have likely had pronounced impacts on the structure and function of these shrub communities. These northward range shifts are a bellwether for other boreal species and their associated predators.

  6. Range Expansion of Moose in Arctic Alaska Linked to Warming and Increased Shrub Habitat

    PubMed Central

    Tape, Ken D.

    2016-01-01

    Twentieth century warming has increased vegetation productivity and shrub cover across northern tundra and treeline regions, but effects on terrestrial wildlife have not been demonstrated on a comparable scale. During this period, Alaskan moose (Alces alces gigas) extended their range from the boreal forest into tundra riparian shrub habitat; similar extensions have been observed in Canada (A. a. andersoni) and Eurasia (A. a. alces). Northern moose distribution is thought to be limited by forage availability above the snow in late winter, so the observed increase in shrub habitat could be causing the northward moose establishment, but a previous hypothesis suggested that hunting cessation triggered moose establishment. Here, we use recent changes in shrub cover and empirical relationships between shrub height and growing season temperature to estimate available moose habitat in Arctic Alaska c. 1860. We estimate that riparian shrubs were approximately 1.1 m tall c. 1860, greatly reducing the available forage above the snowpack, compared to 2 m tall in 2009. We believe that increases in riparian shrub habitat after 1860 allowed moose to colonize tundra regions of Alaska hundreds of kilometers north and west of previous distribution limits. The northern shift in the distribution of moose, like that of snowshoe hares, has been in response to the spread of their shrub habitat in the Arctic, but at the same time, herbivores have likely had pronounced impacts on the structure and function of these shrub communities. These northward range shifts are a bellwether for other boreal species and their associated predators. PMID:27074023

  7. Seasonal variability in hydrologic-system response to intense rain events, Matanuska Glacier, Alaska, U.S.A.

    USGS Publications Warehouse

    Denner, J.C.; Lawson, D.E.; Larson, G.J.; Evenson, E.B.; Alley, R.B.; Strasser, J.C.; Kopczynski, S.

    1999-01-01

    Two rain events at Matanuska Glacier illustrate how subglacial drainage system development and snowpack conditions affect hydrologic response at the terminus. On 21 and 22 September 1995, over 56 mm of rain fell in the basin during a period usually characterized by much drier conditions. This event caused an 8-fold increase in discharge and a 47-fold increase in suspended-sediment concentration. Peak suspended-sediment concentration exceeded 20 kg m-3, suggesting rapid evacuation of stored sediment. While water discharge returned to its pre-storm level nine days after the rain ceased, suspended-sediment concentrations took about 20 days to return to pre-storm levels. These observations suggest that the storm influx late in the melt season probably forced subglacial water into a more distributed system. In addition, subglacially transported sediments were supplemented to an unknown degree by the influx of storm-eroded sediments off hillslopes and from tributary drainage basins. A storm on 6 and 7 June 1997, dropped 28 mm of rain on the basin demonstrating the effects of meltwater retention in the snowpack and englacial and subglacial storage early in the melt season. Streamflow before the storm event was increasing gradually owing to warming temperatures; however, discharge during the storm and the following week increased only slightly. Suspended-sediment concentrations increased only a small amount, suggesting the drainage system was not yet well developed, and much of the runoff occurred across the relatively clean surface of the glacier or through englacial channels.

  8. Frozen debris lobes, permafrost slope instability, and a potential infrastructure hazard in the south-central Brooks Range of Alaska

    NASA Astrophysics Data System (ADS)

    Daanen, R. P.; Darrow, M.; Grosse, G.; Jones, B. M.

    2012-12-01

    Here we report on investigations carried out at unusual debris mass-movement features (frozen debris lobes) on permafrost slopes in the south central portion of the Brooks Range of northern Alaska. The features under investigation are located in mountainous terrain near the southern border of continuous permafrost. The frozen debris lobes consist mainly of boulders, cobles, platy gravel sand and silt frozen debris derived from weathering mountain tops. The general dimensions of these lobes are either lobate or tongue shaped with widths up to 500 m and lengths up to 1200 m. In accumulation zones where slopes converge, the debris slowly moves as solifluction lobes, mud flows and potentially sliding toward the valley. These features were previously referred to as stable rock glaciers in the past, as evidenced by a dense cover of vegetation, and exhibiting no known downslope movement. Our investigations however, have shown that these features are indeed moving downslope as a result of creep, slumping, viscous flow, blockfall and leaching of fines in the summer; and in cold seasons by creep and sliding of frozen sediment slabs. Movement indicators observed in the field include toppling trees, slumps and scarps, detachment slides, striation marks on frozen sediment slabs, recently buried trees and other vegetation, mudflows, and large cracks in the lobe surface. Ground-based measurements on one frozen debris-lobe over three years (2008-2010) revealed average movement rates of approximately 1 cm day-1, which is substantially larger than rates measured in historic aerial photography from the 1950s to 1980s. Current observations , through lidar, ifsar, insar and ground based measurements using boreholes, geophysics and repeat photography of these features show an increase in movement activity that could be the result of rising summer temperatures in the region. Warming of ice rich permafrost slopes and frozen debris lobes in the Brooks Range pose a direct threat to the

  9. Pliocene Cosmogenic Nuclide Burial Ages of the Nenana Gravel: Progress in Dating and Implications for Alaska Range Evolution

    NASA Astrophysics Data System (ADS)

    Goehring, B. M.; Bemis, S. P.; Ward, D.; Caffee, M. W.; Sortor, R. N.

    2015-12-01

    The Nenana Gravel is an up to 1.2 km thick foreland basin deposit that spans the north flank of the Alaska Range. It is uplifted relative to the active foreland basin to the north. It is also deformed to various degree dependent on its location within the northern Alaska Range thrust system. Because this foreland basin sequence records the unroofing and northward propagation of the Alaska Range, direct dating of the Nenana Gravel, especially over wide spatial distribution along the Alaska Range, will substantially advance our understanding of the style and timing of deformation of the Alaska Range. At present though, age estimates for the Nenana Gravel are limited to a single maximum limiting age and uncertain minimum limiting age with no little or no insight as to the spatial variation in Nenana Gravel deposition timing. We present the first direct dates of deposition ages of the Nenana Gravel using cosmogenic nuclide burial dating. Results indicate that deposition of the Nenana Gravel began ca. 6.5 Ma, in stratigraphic agreement with a maximum limiting tephra age from the underlying Usibelli Group. Additional samples from the Nenana Gravel basal contact and higher in the section are presently underway. The resultant burial ages are amongst the oldest 26Al-10Be burial ages ever produced and highlight the potential of the method to directly date sediments in the Pliocene, particularly given recent advancements in the accelerator mass spectrometry measurement of 26Al/27Al isotope ratios.

  10. Caledonian Deformation in Polydeformed Pre-Mississippian Rocks of the Northeast Brooks Range, Alaska

    NASA Astrophysics Data System (ADS)

    Johnson, B. G.; Toro, J.; Benowitz, J.

    2013-12-01

    In the northeastern Brooks Range of Alaska there are polydeformed metasedimentary and metavolcanic rocks exposed below a major pre-Mississippian unconformity. Elsewhere in northern Alaska it has been challenging to correlate the tectonic fabrics of these early Paleozoic to Neoproterozoic rocks to the different orogenic events of the Arctic because of the strong overprint of Mesozoic and Tertiary Brookian deformation. However, our recent field investigations along the Kongakut and Aichiklik rivers of ANWR have identified an older (pre-Brookian) structural event based on the orientation of penetrative cleavage planes and a contrast in folding style to Brookian structures. Many of the cleavage planes are north dipping and orientated parallel to the axial planes of south-vergent folds. Although metamorphic grade is generally low, in localized areas the cleavage planes contain white micas, whose petrologic and isotopic characteristics indicate that they crystallized during fabric formation. 40Ar/39Ar dating of the white micas yield a metamorphic age of ~400 Ma (Early Devonian). This is evidence for a south-directed structural event which is contemporaneous with Caledonian deformation in East Greenland and Svalbard. Stratigraphicaly, the basement consists of a diverse package of highly deformed marine clastic sediments, and a thick section of basaltic to andesitic flows and volcaniclastic rocks, the Whale Mountain volcanics, which have a sharp southern contact but grade northward and upwards into the clastic rocks. All units are metamorphosed to lower greenschist facies. We are currently investigating the age and geochemical characteristics of the Whale Mountain volcanics to determine their tectonic affinity and role in the assemblage of the North Slope block of Northern Alaska.

  11. Multi-resolution Changes in the Spatial Extent of Perennial Arctic Alpine Snow and Ice Fields with Potential Archaeological Significance in the Central Brooks Range, Alaska

    NASA Astrophysics Data System (ADS)

    Tedesche, M. E.; Freeburg, A. K.; Rasic, J. T.; Ciancibelli, C.; Fassnacht, S. R.

    2015-12-01

    Perennial snow and ice fields could be an important archaeological and paleoecological resource for Gates of the Arctic National Park and Preserve in the central Brooks Range mountains of Arctic Alaska. These features may have cultural significance, as prehistoric artifacts may be frozen within the snow and ice. Globally significant discoveries have been made recently as ancient artifacts and animal dung have been found in melting alpine snow and ice patches in the Southern Yukon and Northwest Territories in Canada, the Wrangell mountains in Alaska, as well as in other areas. These sites are melting rapidly, which results in quick decay of biological materials. The summer of 2015 saw historic lows in year round snow cover extent for most of Alaska. Twenty mid to high elevation sites, including eighteen perennial snow and ice fields, and two glaciers, were surveyed in July 2015 to quantify their areal extent. This survey was accomplished by using both low flying aircraft (helicopter), as well as with on the ground in-situ (by foot) measurements. By helicopter, visual surveys were conducted within tens of meters of the surface. Sites visited by foot were surveyed for extent of snow and ice coverage, melt water hydrologic parameters and chemistry, and initial estimates of depths and delineations between snow, firn, and ice. Imagery from both historic aerial photography and from 5m resolution IKONOS satellite information were correlated with the field data. Initial results indicate good agreement in permanent snow and ice cover between field surveyed data and the 1985 to 2011 Landsat imagery-based Northwest Alaska snow persistence map created by Macander et al. (2015). The most deviation between the Macander et al. model and the field surveyed results typically occurred as an overestimate of perennial extent on the steepest aspects. These differences are either a function of image classification or due to accelerated ablation rates in perennial snow and ice coverage

  12. Long-range transported dissolved organic matter, ions and black carbon deposited on Central Asian snow covered glaciers

    NASA Astrophysics Data System (ADS)

    Schmale, Julia; Kang, Shichang; Peltier, Richard

    2014-05-01

    Ninety percent of the Central Asian population depend on water precipitated in the mountains stored in glaciers and snow cover. Accelerated melting of the snow and ice can be induced by the deposition of airborne impurities such as mineral dust, black carbon and co-emitted species leading to significant reductions of the surface albedo. However, Central Asia is a relatively understudied region and data on the source regions, chemical and microphysical characteristics as well as modelling studies of long-range transported air pollution and dust to the Tien Shan mountains is very scarce. We studied the atmospheric aerosol deposited most likely between summer 2012 and summer 2013on three different glaciers in the Kyrgyz Republic. Samples were taken from four snow pits on the glaciers Abramov (2 pits, 39.59 °N, 71.56 °E, 4390 m elevation, 240 cm deep, and 39.62°N, 71.52 °E, 4275 m elevation, 125 cm deep), Ak-Shiirak (41.80 °N, 78.18 °E, 4325 m elevation, 75 cm deep) and Suek (41.78 °N, 77.75 °E, 4341 m elevation, 200 cm deep). The latter two glaciers are located roughly within 6 and 38 km of an operating gold mine. The snow was analyzed for black carbon, ions, metals and organic carbon. We here focus on the results of inorganic ion measurements and organic carbon speciation based on analysis with an Aerodyne high-resolution time-of-flight aerosol spectrometer (HR-ToF-AMS) and potential pollution sources that can be deduced from the chemical information as well as back trajectories. Average contributions of snow impurities measured by the HR-ToF-AMS were dominated by organic carbon. Relative concentrations of organic carbon, sulfate, nitrate and ammonium in snow were 86 %, 3 %, 9 % and 2 % respectively for Abramov, 92 %, 1 %, 5 % and 1 % for Suek, and 95 %, 1 %, 3 % and 1 % for Ak-Shiirak. Generally, impurities on Suek and Ak-Shiirak were three and five times higher than on Abramov. Mass concentrations of organic carbon were on average 6 times higher in samples

  13. Upper triassic continental margin strata of the central alaska range: Implications for paleogeographic reconstruction

    USGS Publications Warehouse

    Till, A.B.; Harris, A.G.; Wardlaw, B.R.; Mullen, M.

    2007-01-01

    Reexamination of existing conodont collections from the central Alaska Range indicates that Upper Triassic marine slope and basin rocks range in age from at least as old as the late Carnian to the early middle Norian. The conodont assemblages typical of these rocks are generally cosmopolitan and do not define a distinct paleogeographic faunal realm. One collection, however, containsEpigondolella multidentata sensu Orchard 1991c, which appears to be restricted to western North American autochthonous rocks. Although paleogeographic relations cannot be determined with specificity, the present distribution of biofaces within the Upper Triassic sequence could not have been the result of simple accordion-style collapse of the Late Triassic margin.

  14. Reindeer range inventory in western Alaska from computer-aided digital classification of LANDSAT data

    NASA Technical Reports Server (NTRS)

    George, T. H.; Stringer, W. J.; Baldridge, J. N.

    1977-01-01

    An inventory of reindeer-range resources was conducted for the USDA Soil Conservation Service of 1.6 million hectares of wildlands in western Alaska using clustering techniques with digital Landsat data. Computer-aided digital analysis produced a provisional map of rangeland types which was used to design the field collection of vegetation and soil types data. This field data facilitated refinement of the inventory map and was used to describe the map units. The informational classes important to range resources were wet, moist and alpine tundra, tidal marsh, brush and open spruce forest. A significant feature of the study was the extraction of acreage figures by administrative boundaries within the study area. In addition to soil and vegetation association map products (at scales of 1:250,000 and 1:63,360) acreage values were tallied from the digital data for each of the four grazing permit areas established by the Bureau of Land Management.

  15. Zoned Cr, Fe-spinel from the La Perouse layered gabbro, Fairweather Range, Alaska

    USGS Publications Warehouse

    Czamanske, G.K.; Himmelberg, G.R.; Goff, F.E.

    1976-01-01

    Zoned spinel of unusual composition and morphology has been found in massive pyrrhotite-chalcopyrite-pent-landite ore from the La Perouse layered gabbro intrusion in the Fairweather Range, southeastern Alaska. The spinel grains show continuous zoning from cores with up to 53 wt.% Cr2O3 to rims with less than 11 wt.% Cr2O3. Their composition is exceptional because they contain less than 0.32 wt.% MgO and less than 0.10 wt.% Al2O3 and TiO2. Also notable are the concentrations of MnO and V2O3, which reach 4.73 and 4.50 wt.%, respectively, in the cores. The spinel is thought to have crystallized at low oxygen fugacity and at temperatures above 900??C, directly from a sulfide melt that separated by immiscibility from the gabbroic parental magma. ?? 1976.

  16. Factors Affecting Haul-Out Behavior of Harbor Seals (Phoca vitulina) in Tidewater Glacier Inlets in Alaska: Can Tourism Vessels and Seals Coexist?

    PubMed Central

    2015-01-01

    Large numbers of harbor seals (Phoca vitulina) use habitat in tidewater glaciers in Alaska for pupping, breeding, and molting. Glacial fjords are also popular tourist destinations; however, visitation by numerous vessels can result in disturbance of seals during critical life-history phases. We explored factors affecting haul-out behavior of harbor seals at a glacial site frequented by tourism vessels. In 2008-10, we deployed VHF transmitters on 107 seals in Endicott Arm, Alaska. We remotely monitored presence and haul-out behavior of tagged seals and documented vessel presence with time-lapse cameras. We evaluated the influence of environmental and physical factors on the probability of being hauled out, duration of haul-out bouts, and as factors associated with the start and end of a haulout. Location, season, hour, and interactions of location by year, season, hour, and sex significantly influenced haul-out probability, as did ice, weather, and vessels. Seals were more likely to be hauled out with greater ice availability during the middle of the day, and less likely to be hauled out if vessels were present. Cruise ships had the strongest negative effect; however, most vessel types negatively affected haul-out probability. Haul-out duration was longest in association with starting on incoming tides, clear skies, no precipitation, occurring in the middle of the day, and ending in the late afternoon or evening. End of haulouts was associated with increasing cloud cover, low ice availability, and vessel presence; large-sized tourism vessels or all-vessel-types combined were significant predictors of ending a haul-out bout. Probability of being hauled out was highest in June, during pupping season. Potential disturbances of harbor seals could be reduced, enabling longer resting times for seals and fewer interruptions for nursing pups, if vessels focused the majority of visits to glacial habitat to before or after the hours of 08:00-17:00 or, less optimally, 09

  17. Range expansion of moose in arctic Alaska linked to warming and increased shrub habitat

    USGS Publications Warehouse

    Tape, Ken D.; Gustine, David D.; Reuss, Roger W.; Adams, Layne G.; Clark, Jason A.

    2016-01-01

    Twentieth century warming has increased vegetation productivity and shrub cover across northern tundra and treeline regions, but effects on terrestrial wildlife have not been demonstrated on a comparable scale. During this period, Alaskan moose (Alces alces gigas) extended their range from the boreal forest into tundra riparian shrub habitat; similar extensions have been observed in Canada (A. a. andersoni) and Eurasia (A. a. alces). Northern moose distribution is thought to be limited by forage availability above the snow in late winter, so the observed increase in shrub habitat could be causing the northward moose establishment, but a previous hypothesis suggested that hunting cessation triggered moose establishment. Here, we use recent changes in shrub cover and empirical relationships between shrub height and growing season temperature to estimate available moose habitat in Arctic Alaska c. 1860. We estimate that riparian shrubs were approximately 1.1 m tall c. 1860, greatly reducing the available forage above the snowpack, compared to 2 m tall in 2009. We believe that increases in riparian shrub habitat after 1860 allowed moose to colonize tundra regions of Alaska hundreds of kilometers north and west of previous distribution limits. The northern shift in the distribution of moose, like that of snowshoe hares, has been in response to the spread of their shrub habitat in the Arctic, but at the same time, herbivores have likely had pronounced impacts on the structure and function of these shrub communities. These northward range shifts are a bellwether for other boreal species and their associated predators.

  18. Continuous Monitoring of Greenland Outlet Glaciers Using an Autonomous Terrestrial LiDAR Scanning System: Design, Development and Testing at Helheim Glacier

    NASA Astrophysics Data System (ADS)

    LeWinter, A. L.; Finnegan, D. C.; Hamilton, G. S.; Stearns, L. A.; Gadomski, P. J.

    2014-12-01

    Greenland's fast-flowing tidewater outlet glaciers play a critical role in modulating the ice sheet's contribution to sea level rise. Increasing evidence points to the importance of ocean forcing at the marine margins as a control on outlet glacier behavior, but a process-based understanding of glacier-ocean interactions remains elusive in part because our current capabilities for observing and quantifying system behavior at the appropriate spatial and temporal scales are limited. A recent international workshop on Greenland's marine terminating glaciers (US CLIVAR, Beverly, MA, June 2013) recommended the establishment of a comprehensive monitoring network covering Greenland's largest outlet glacier-fjord systems to collect long-term time series of critical in situ glaciological, oceanographic and atmospheric parameters needed to understand evolving relationships between different climate forcings and glacier flow. Given the remote locations and harsh environments of Greenland's glacial fjords, the development of robust autonomous instrumentation is a key step in making the observing networks a reality. This presentation discusses the design and development of a fully-autonomous ground-based Light Detection and Ranging (LiDAR) system for monitoring outlet glacier behavior. Initial deployment of the system is planned for spring 2015 at Helheim Glacier in southeast Greenland. The instrument will acquire multi-dimensional point-cloud measurements of the mélange, terminus, and lower-reaches of the glacier. The heart of the system is a long-range, 1064 nm wavelength Terrestrial Laser Scanner (TLS) that we have previously used in campaign-style surveys at Helheim Glacier and at Hubbard Glacier in Alaska. We draw on this experience to design and fabricate the power and enclosure components of the new system, and use previously acquired data from the instrument, collected August 2013 and July 2014 at Helheim, to optimize our data collection strategy and design the data

  19. 33 CFR 334.1280 - Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force. 334.1280 Section 334.1280 Navigation and Navigable... REGULATIONS § 334.1280 Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force....

  20. 33 CFR 334.1280 - Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force. 334.1280 Section 334.1280 Navigation and Navigable... REGULATIONS § 334.1280 Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force....

  1. 33 CFR 334.1280 - Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force. 334.1280 Section 334.1280 Navigation and Navigable... REGULATIONS § 334.1280 Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force....

  2. 33 CFR 334.1280 - Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force. 334.1280 Section 334.1280 Navigation and Navigable... REGULATIONS § 334.1280 Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force....

  3. 33 CFR 334.1280 - Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force. 334.1280 Section 334.1280 Navigation and Navigable... REGULATIONS § 334.1280 Bristol Bay, Alaska; air-to-air weapon range, Alaskan Air Command, U.S. Air Force....

  4. Comparison of bacterial diversity in proglacial soil from Kafni Glacier, Himalayan Mountain ranges, India, with the bacterial diversity of other glaciers in the world.

    PubMed

    Srinivas, T N R; Singh, S M; Pradhan, Suman; Pratibha, M S; Kishore, K Hara; Singh, Ashish K; Begum, Z; Prabagaran, S R; Reddy, G S N; Shivaji, S

    2011-11-01

    Two 16S rRNA gene clone libraries (KF and KS) were constructed using two soil samples (K7s and K8s) collected near Kafni Glacier, Himalayas. The two libraries yielded a total of 648 clones. Phyla Actinobacteria, Bacteroidetes, Chloroflexi Firmicutes, Proteobacteria, Spirochaetae, Tenericutes and Verrucomicrobia were common to the two libraries. Phyla Acidobacteria, Chlamydiae and Nitrospirae were present only in KF library, whereas Lentisphaerae and TM7 were detected only in KS. In the two libraries, clones belonging to phyla Bacteroidetes and Proteobacteria were the most predominant. Principal component analysis (PCA) revealed that KF and KS were different and arsenic content influenced the differences in the percentage of OTUs. PCA indicated that high water content in the K8s sample results in high total bacterial count. PCA also indicated that bacterial diversity of KF and KS was similar to soils from the Pindari Glacier, Himalayas; Samoylov Island, Siberia; Schrimacher Oasis, Antarctica and Siberian tundra. The eleven bacterial strains isolated from the above two soil samples were phylogenetically related to six different genera. All the isolates were psychro-, halo- and alkalitolerant. Amylase, lipase and urease activities were detected in the majority of the strains. Long chain, saturated, unsaturated and branched fatty acids were predominant in the psychrotolerant bacteria.

  5. Middle Jurassic U-Pb crystallization age for Siniktanneyak Mountain ophiolite, Brooks Range, Alaska

    SciTech Connect

    Moore, T.E. ); Aleinikoff, J.N.; Walter, M. )

    1993-04-01

    The authors report here a U-Pb age for the Siniktanneyak Mountain Ophiolite klippe in the west-central Brooks Range, the first U-Pb ophiolite age in northern Alaska. Like klippen of mafic and ultramafic rocks in the Brooks Range, the Siniktanneyak Mountain klippe is composed of a lower allochthon of Devonian and younger( ) diabase and metabasalt with trace-element characteristics of seamount basalts and an upper allochthon of ophiolite. The ophiolite is partial, consisting of (1) abundant dunite and subordinate harzburgite and wehrlite; (2) cumulate clinopyroxene gabbro, and (3) minor noncumulate clinopyroxene gabbro and subordinate plagiogranite; no sheeted dikes or volcanic rocks are known in the ophilitic allochthon. The plagiogranite forms small dikes and stocks that intrude the noncumulate gabbro and consists of zoned Na-rich plagioclase + clinopyroxene with interstial quartz and biotite. Five fractions of subhedral, tan zircon from the plagiogranite yield slightly discordant U-Pb data with an upper intercept age of 170 [+-] 3 Ma. The U-Pb data indicate that the Siniktanneyak Mountain ophiolite crystallized in the Middle Jurassic and was emplaced by thrusting onto mafic accretionary prism rocks within about 10 m.y. of crystallization. The U-Pb data provide an upper limit to the age of initiation of the Brookian orogeny.

  6. 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

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

    1992-03-01

    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.

  7. Magmatic responses to Late Cretaceous through Oligocene tectonic evolution of the western Alaska Range

    NASA Astrophysics Data System (ADS)

    Todd, E.; Jones, J. V., III; Karl, S.; Ayuso, R. A.; Bradley, D. C.; Box, S. E.; Haeussler, P. J.

    2014-12-01

    New geochemistry, U/Pb geochronology, and radiogenic isotopes, together with existing datasets, contribute to a refined model of the petrogenetic history of magmatism in the western Alaska Range. Plutons within the study area were emplaced into Kahiltna basin Mesozoic turbiditic strata. The Kahiltna sequence overlies Mesozoic Peninsular oceanic terrane rocks in the SE half of the basin and Proterozoic to Paleozoic Farewell continental terrane rocks to the NW. This study focuses on successive intrusion suites, most of which are thought to intrude Kahiltna or underlying Farewell terrane rocks, but include older, perhaps more deeply exhumed rocks emplaced in Peninsular terrane basement to the SE. The chemically diverse sequence records magmatism associated with major tectonic reorganization events on the southern Alaska circum-Pacific subduction margin. The oldest pluton suite (~100-80 Ma) is mostly intermediate to evolved calcalkaline granite and coincides with final closure of the Kahiltna basin and a regional transition to transpression-dominated tectonics. The post-closure magmatic pulse (~75-67 Ma) is compositionally varied, including primitive subalkaline melts, peraluminous high-K granites, and a subset of sodic, adakite-like granites. A Paleocene (~63-57 Ma) magmatic flare-up follows, dominated by extremely fractionated subalkaline melts. Rare, more primitive melts of this suite are metaluminous, from gabbro to syenite. This stage may represent relaxed melt productivity or shallowing of the slab dip, yielding more laterally diffuse melting. An early Eocene magmatic hiatus precedes middle Eocene circum-Pacific tectonic reorganization, regionally resulting in initiation of proto-Aleutian/Meshik arc magmatism, and locally in the 44-37 Ma emplacement of subalkaline intermediate to felsic plutons associated with andesite to rhyolite volcanic deposits. An Oligocene (~31-25 Ma) magmatic pulse involved emplacement of a compositionally variable suite ranging from

  8. Ice loss and sea level rise contribution from Alaskan glaciers derived from satellite imagery

    NASA Astrophysics Data System (ADS)

    Berthier, Etienne; Schiefer, Erik; Clarke, Garry; Menounos, Brian; Rémy, Frédérique

    2010-05-01

    Over the last 50 years, retreating glaciers and ice caps (GIC) contributed 0.5 mm/yr to SLR, and one third is believed to originate from ice masses bordering the Gulf of Alaska. However, these estimates of ice wastage in Alaska are based on methods that directly measure mass changes from a limited number of glaciers and extrapolate the results to estimate ice loss for the many thousands of others. Here, using a new glacier inventory with elevation changes derived from sequential digital elevation models, we found that, between 1962 and 2006, Alaskan glaciers lost 41.9 ± 8.6 km**3/yr water equivalent (w.e.) and contributed 0.12 ± 0.02 mm/yr to SLR. Our ice loss is 34% lower than previous estimates. Reasons for our lower values include the higher spatial resolution of the glacier inventory used in our study and the complex pattern of ice elevation changes at the scale of individual glaciers and mountain ranges which was not resolved in earlier work. Estimates of mass loss from GIC in other mountain regions could be subject to similar revisions.

  9. Glaciers of Asia

    USGS Publications Warehouse

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

    2010-01-01

    This chapter is the ninth to be released in U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of Glaciers of the World, a series of 11 chapters. In each of the geographic area chapters, remotely sensed images, primarily from the Landsat 1, 2, and 3 series of spacecraft, are used to analyze the specific glacierized region of our planet under consideration and to monitor glacier changes. Landsat images, acquired primarily during the middle to late 1970s and early 1980s, were used by an international team of glaciologists and other scientists to study various geographic regions and (or) to discuss related glaciological topics. In each glacierized geographic region, the present areal distribution of glaciers is compared, wherever possible, with historical information about their past extent. The atlas provides an accurate regional inventory of the areal extent of glacier ice on our planet during the 1970s as part of a growing international scientific effort to measure global environmental change on the Earth?s surface. The chapter is divided into seven geographic parts and one topical part: Glaciers of the Former Soviet Union (F-1), Glaciers of China (F-2), Glaciers of Afghanistan (F?3), Glaciers of Pakistan (F-4), Glaciers of India (F-5), Glaciers of Nepal (F?6), Glaciers of Bhutan (F-7), and the Paleoenvironmental Record Preserved in Middle-Latitude, High-Mountain Glaciers (F-8). Each geographic section describes the glacier extent during the 1970s and 1980s, the benchmark time period (1972-1981) of this volume, but has been updated to include more recent information. Glaciers of the Former Soviet Union are located in the Russian Arctic and various mountain ranges of Russia and the Republics of Georgia, Kyrgyzstan, Tajikistan, and Kazakstun. The Glacier Inventory of the USSR and the World Atlas of Ice and Snow Resources recorded a total of 28,881 glaciers covering an area of 78,938 square kilometers (km2). China includes many of the mountain-glacier

  10. Home ranges and movements of arctic fox (Alopex lagopus) in western Alaska

    USGS Publications Warehouse

    Anthony, R. Michael

    1997-01-01

    During the period from 1985 to 1990, radio collars were attached to 61 arctic foxes (Alopex lagopus) in the coastal region of the Yukon-Kuskokwim Delta in western Alaska. Radio tracking using hand-held receivers from aircraft, and from fixed towers was conducted to determine daily and seasonal movements of foxes. Intensive radio tracking of 18 foxes from May through July indicated that males used larger areas (x=10.22i??6.18 km2) than females (x=4.57i??1.94 km2) regardless of breeding status. Generally foxes were relocated near (x=3.4i??2.4 km) their summer home ranges during other seasons of the year. There were no complex social groups of foxes among the marked population. Foxes did not have a definitive preference for any plant community, probably because of the even distribution and abundance of prey throughout all communities. Thirty foxes were relocated repeatedly during a period of at least 10 months, which included the denning season of one year and the breeding season of the next. Of 24 confirmed deaths of collared foxes, 16 were caused by shooting or trapping by local residents and 8 had unidentified causes. Maximum distance moved between relocations was 48.4 km. Males moved farther from initial capture sites in the winter following capture than did females, largely because of greater than 20 km movements by two foxes. There were no seasonal differences in movements between males and females.

  11. Crustal structure of the alaska range orogen and denali fault along the richardson highway

    USGS Publications Warehouse

    Fisher, M.A.; Pellerin, L.; Nokleberg, W.J.; Ratchkovski, N.A.; Glen, J.M.G.

    2007-01-01

    A suite of geophysical data obtained along the Richardson Highway crosses the eastern Alaska Range and Denali fault and reveals the crustal structure of the orogen. Strong seismic reflections from within the orogen north of the Denali fault dip as steeply as 25?? north and extend downward to depths between 20 and 25 km. These reflections reveal what is probably a shear zone that transects most of the crust and is part of a crustal-scale duplex structure that probably formed during the Late Cretaceous. These structures, however, appear to be relict because over the past 20 years, they have produced little or no seismicity despite the nearby Mw = 7.9 Denali fault earthquake that struck in 2002. The Denali fault is nonreflective, but we interpret modeled magnetotelluric (MT), gravity, and magnetic data to propose that the fault dips steeply to vertically. Modeling of MT data shows that aftershocks of the 2002 Denali fault earthquake occurred above a rock body that has low electrical resistivity (>10 ohm-m), which might signify the presence of fluids in the middle and lower crust. Copyright ?? 2007 The Geological Society of America.

  12. Neocomian source and reservoir rocks in the western Brooks Range and Arctic Slope, Alaska

    SciTech Connect

    Mull, C.G.; Reifenstuhl, R.R.; Harris, E.E.; Crowder, R.K.

    1995-04-01

    Detailed (1:63,360) mapping of the Tingmerkpuk sandstone and associated rocks in the Misheguk Mountain and DeLong Mountains guadrangles of the western Brooks Range thrust belt documents potential hydrocarbon source and reservoir rocks in the northern foothills of the western Delong Mountains and adjacent Colville basin of northwest Alaska. Neocomian (?) to Albian micaceous shale, litharenite, and graywacke that overlies the Tingmerkpuk represents the onset of deposition of orogenic sediments derived from the Brooks Range to the south, and the merging of northern and southern sediment sources in the Colville basin. Both the proximal and distal Tingmerkpuk facies contain clay shale interbeds and overlie the Upper Jurassic to Neocomian Kingak Shale. Preliminary geochemical data show that in the thrust belt, these shales are thermally overmature (Ro 1.4-1.6), but are good source rocks with total organic content (TOC) that ranges from 1.2 to 1.8 percent. Shale in the overlying Brookian rocks is also thermally overmature (Ro 1.2-1.5 percent), but contains up to 1.8 percent TOC from a dominantly terrigenous source, and has generated gas. In outcrops at Surprise Creek, in the foothills north of the thrust belt, the Kingak (1.9 percent TOC) and underlying Triassic Shublik Formation (4.6 percent TOC) are excellent oil source rocks with thermal maturity close to peak oil generation stage (Ro0.75-0.9 percent). These rocks have lower thermal maturity values than expected for their stratigraphic position within the deeper parts of the Colville basin and indicate anomalous burial and uplift history in parts of the basin. Preliminary apatite fission-track (AFTA) data from the thrust belt indicate a stage of rapid uplift and cooling at about 53.61 Ma.

  13. Identification and assessment of groundwater flow and storage components of the relict Schöneben Rock Glacier, Niedere Tauern Range, Eastern Alps (Austria)

    NASA Astrophysics Data System (ADS)

    Winkler, Gerfried; Wagner, Thomas; Pauritsch, Marcus; Birk, Steffen; Kellerer-Pirklbauer, Andreas; Benischke, Ralf; Leis, Albrecht; Morawetz, Rainer; Schreilechner, Marcellus G.; Hergarten, Stefan

    2016-06-01

    More than 2,600 relict rock glaciers are known in the Austrian Alps but the knowledge of their hydraulic properties is severely limited. The relict Schöneben Rock Glacier (Niedere Tauern Range, Austria), with an extension of 0.17 km2, was investigated based on spring data (2006-2014) and seismic refraction survey. Spring-discharge hydrographs and natural and artificial tracer data suggest a heterogeneous aquifer with a layered internal structure for the relict rock glacier. The discharge behavior exhibits a fast and a delayed flow component. The spring discharge responds to recharge events within a few hours but a mean residence time of several months can also be observed. The internal structure of the rock glacier (up to several tens of meters thick) consists of: an upper blocky layer with a few meters of thickness, which lacks fine-grained sediments; a main middle layer with coarse and finer-grained sediments, allowing for fast flow; and an approximately 10-m-thick basal till layer as the main aquifer body responsible for the base flow. The base-flow component is controlled by (fine) sandy to silty sediments with low hydraulic conductivity and high storage capacity, exhibiting a difference in hydraulic conductivity to the upper layer of about three orders of magnitude. The high storage capacity of relict rock glaciers has an impact on water resources management in alpine catchments and potentially regulates the risk of natural hazards such as floods and related debris flows. Thus, the results highlight the importance of such aquifer systems in alpine catchments.

  14. Ocean forcing drives glacier retreat sometimes

    NASA Astrophysics Data System (ADS)

    Bassis, J. N.; Ultee, E.; Ma, Y.

    2015-12-01

    Observations show that marine-terminating glaciers respond to climate forcing nonlinearly, with periods of slow or negligible glacier advance punctuated by abrupt, rapid retreat. Once glacier retreat has initiated, glaciers can quickly stabilize with a new terminus position. Alternatively, retreat can be sustained for decades (or longer), as is the case for Columbia Glacier, Alaska where retreat initiated ~1984 and continues to this day. Surprisingly, patterns of glacier retreat show ambiguous or even contradictory correlations with atmospheric temperature and glacier surface mass balance. Despite these puzzles, observations increasingly show that intrusion of warm subsurface ocean water into fjords can lead to glacier erosion rates that can account for a substantial portion of the total mass lost from glaciers. Here we use a simplified flowline model to show that even relatively modest submarine melt rates (~100 m/a) near the terminus of grounded glaciers can trigger large increases in iceberg calving leading to rapid glacier retreat. However, the strength of the coupling between submarine melt and calving is a strong function of the geometry of the glacier (bed topography, ice thickness and glacier width). This can lead to irreversible retreat when the terminus is thick and grounded deeply beneath sea level or result in little change when the glacier is relatively thin, grounded in shallow water or pinned in a narrow fjord. Because of the strong dependence on glacier geometry, small perturbations in submarine melting can trigger glaciers in their most advanced—and geometrically precarious—state to undergo sudden retreat followed by much slower re-advance. Although many details remain speculative, our model hints that some glaciers are more sensitive than others to ocean forcing and that some of the nonlinearities of glacier response to climate change may be attributable to variations in difficult-to-detect subsurface water temperatures that need to be better

  15. Depositional settings, correlation, and age carboniferous rocks in the western Brooks Range, Alaska

    USGS Publications Warehouse

    Dumoulin, Julie A.; Harris, Anita G.; Blome, Charles D.; Young, Lorne E.

    2004-01-01

    The Kuna Formation (Lisburne Group) in northwest Alaska hosts the Red Dog and other Zn-Pb-Ag massive sulfide deposits in the Red Dog district. New studies of the sedimentology and paleontology of the Lisburne Group constrain the setting, age, and thermal history of these deposits. In the western and west-central Brooks Range, the Lisburne Group includes both deep- and shallow-water sedimentary facies and local volcanic rocks that are exposed in a series of thrust sheets or allochthons. Deep-water facies in the Red Dog area (i.e., the Kuna Formation and related rocks) are found chiefly in the Endicott Mountains and structurally higher Picnic Creek allochthons. In the Red Dog plate of the Endicott Mountains allochthon, the Kuna consists of at least 122 m of thinly interbedded calcareous shale, calcareous spiculite, and bioclastic supportstone (Kivalina unit) overlain by 30 to 240 m of siliceous shale, mudstone, calcareous radiolarite, and calcareous lithic turbidite (Ikalukrok unit). The Ikalukrok unit in the Red Dog plate hosts all massive sulfide deposits in the area. It is notably carbonaceous, is generally finely laminated, and contains siliceous sponge spicules and radiolarians. The Kuna Formation in the Key Creek plate of the Endicott Mountains allochthon (60–110 m) resembles the Ikalukrok unit but is unmineralized and has thinner carbonate layers that are mainly organic-rich dolostone. Correlative strata in the Picnic Creek allochthon include less shale and mudstone and more carbonate (mostly calcareous spiculite). Conodonts and radiolarians indicate an age range of Osagean to early Chesterian (late Early to Late Mississippian) for the Kuna in the Red Dog area. Sedimentologic, faunal, and geochemical data imply that most of the Kuna formed in slope and basin settings characterized by anoxic or dysoxic bottom water and by local high productivity.

  16. Spatio-temporal Variation in Glacier Ice as Habitat for Harbor Seals in an Alaskan Tidewater Glacier Fjord

    NASA Astrophysics Data System (ADS)

    Womble, J. N.; McNabb, R. W.; Gens, R.; Prakash, A.

    2015-12-01

    Some of the largest aggregations of harbor seals (Phoca vitulina richardii) in Alaska occur in tidewater glacier fjords where seals rest upon icebergs that are calved from tidewater glaciers into the marine environment. The distribution, amount, and size of floating ice in fjords are likely important factors influencing the spatial distribution and abundance of harbor seals; however, fine-scale characteristics of ice habitat that are used by seals have not been quantified using automated methods. We quantified the seasonal changes in ice habitat for harbor seals in Johns Hopkins Inlet, a tidewater glacier fjord in Glacier Bay National Park, Alaska, using aerial photography, object-based image analysis, and spatial models. Aerial photographic surveys (n = 53) were conducted of seals and ice during the whelping (June) and molting (August) seasons from 2007-2014. Surveys were flown along a grid of 12 transects and high-resolution digital photos were taken directly under the plane using a vertically aimed camera. Seal abundance and spatial distribution was consistently higher during June (range: 1,672-4,340) than August (range: 1,075-2,582) and corresponded to the spatial distribution and amount of ice. Preliminary analyses from 2007 suggest that the average percent of icebergs (ice ≥ than 1.6m2) and brash ice (ice < 1.6m2) per scene were greater in June (icebergs: 1.8% ± 1.6%; brash ice: 43.8% ± 38.9%) than August (icebergs: 0.2% ± 0.7%; brash ice; 15.8% ± 26.4%). Iceberg angularity (an index of iceberg shape) was also greater in June (1.7 ± 0.9) than August (0.9 ± 0.9). Potential factors that may influence the spatio-temporal variation in ice habitat for harbor seals in tidewater glacier fjords include frontal ablation rates of glaciers, fjord circulation, and local winds. Harbor seals exhibit high seasonal fidelity to tidewater glacier fjords, thus understanding the relationships between glacier dynamics and harbor seal distribution will be critical for

  17. “Our vanishing glaciers”: One hundred years of glacier retreat in Three Sisters Area, Oregon Cascade Range

    USGS Publications Warehouse

    O'Connor, James E.

    2014-01-01

    In August 1910, thirty-nine members of the Mazamas Mountaineering Club ascended the peaks of the Three Sisters in central Oregon. While climbing, geologist Ira A. Williams photographed the surrounding scenery, including images of Collier Glacier. One hundred years later, U.S. Geological Survey research hydrologist Jim E. O’Connor matched those documented photographs with present day images — the result of which is a stunning lapse of glacial change in the Three Sister region. O’Connor asserts that “glaciers exist by the grace of climate,” and through a close examination of the history of the region’s glaciers, he provides an intriguing glimpse into the history of geological surveys and glacial studies in the Pacific Northwest, including their connection to significant scientific advances of the nineteenth century. The work of scientists and mountaineers who have monitored and recorded glacier changes for over a century allows us to see dramatic changes in a landscape that is especially sensitive to ongoing climate change.

  18. Conodont biostratigraphy and biofacies of the Wahoo Limestone (Carboniferous), Sadlerochit Mountains, northeast Brooks Range, Alaska

    SciTech Connect

    Krumhardt, A.P. ); Harris, A.G. )

    1990-05-01

    The Wahoo Limestone forms the upper part of the Lisburne Group (Carboniferous) in the Sadlerochit Mountains. The Lisburne Group is a thick (> 600 m) sequence of platform carbonate rocks that extends across the Brooks Range of northern Alaska and beneath the North Slope. At Prudhoe Bay, the Lisburne Group forms a major hydrocarbon reservoir. In the easternmost Sadlerochit Mountains, the Wahool Limestone is divisible into informal lower (64 m) and upper (192 m) members. The basal 46 m is chiefly bryozoan and pelmatozoan packstone that formed on a relatively shallow platform during the latest Mississippian lower muricatus subzone (as shown by the occurrence of the zonal index with representatives of Cavusgnathus). Cavusgnathus is dominant in this part of the section and occurs with representatives of Kladognathus, Ghathodus, Adetognathus, Hindeodus, and Rhachistognathus (in order of decreasing abundance). Declinognathodus noduliferus, the index for the base of the Pennsylvanian, first occurs at 49 m above the base of the Wahoo and 1 m above a discontinuity surface that marks the Mississippian-Pennsylvanian boundary. The unconformity represents the highest conodont subzone of the Mississippian and probably part of the earliest Pennsylvanian. Previously, the Mississippian-Pennsylvanian boundary was placed t the lower-upper Wahoo contact based on endothyroids; conodont data now indicate that this boundary is 15 m lower. The remaining lower Wahoo is possibly of noduliferus-primus zone age and chiefly yields, in order of decreasing abundance, species of Adetognathus, Declinognathodus, and Rhachistognathus, as well as redeposited Mississipian conodonts. The lower 15 m of the upper member of the Wahoo contains silty (5-40%) carbonate rock types that yield very few conodonts. Conodonts no older than the minutus-sinuatus zone are relatively abundant from 15 to 106 m above the base of the upper Wahoo.

  19. Frozen debris lobe morphology and movement: an overview of eight dynamic features, southern Brooks Range, Alaska

    NASA Astrophysics Data System (ADS)

    Darrow, Margaret M.; Gyswyt, Nora L.; Simpson, Jocelyn M.; Daanen, Ronald P.; Hubbard, Trent D.

    2016-05-01

    Frozen debris lobes (FDLs) are elongated, lobate permafrost features that mostly move through shear in zones near their bases. We present a comprehensive overview of eight FDLs within the Dalton Highway corridor (southern Brooks Range, Alaska), including their catchment geology and rock strengths, lobe soil characteristics, surface movement measurements collected between 2012 and 2015, and analysis of historic and modern imagery from 1955 to 2014. Field mapping and rock strength data indicate that the metasedimentary and metavolcanic bedrock forming the majority of the lobe catchments has very low to medium strength and is heavily fractured, thus easily contributing to FDL formation. The eight investigated FDLs consist of platy rocks typical of their catchments, organic debris, and an ice-poor soil matrix; massive ice, however, is present within FDLs as infiltration ice, concentrated within cracks open to the surface. Exposure of infiltration ice in retrogressive thaw slumps (RTSs) and associated debris flows leads to increased movement and various stages of destabilization, resulting in morphological differences among the lobes. Analysis of historic imagery indicates that movement of the eight investigated FDLs has been asynchronous over the study period, and since 1955, there has been an overall increase in movement rates of the investigated FDLs. The formation of surface features, such as cracks, scarps, and RTSs, suggests that the increased movement rates correlate to general instability, and even at their current distances, FDLs are impacting infrastructure through increased sediment mobilization. FDL-A is the largest of the investigated FDLs. As of August 2015, FDL-A was 39.2 m from the toe of the Dalton Highway embankment. Based on its current distance and rate of movement, we predict that FDL-A will reach the Dalton Highway alignment by 2023.

  20. Developing a Validated Long-Term Satellite-Based Albedo Record in the Central Alaska Range to Improve Regional Hydroclimate Reconstructions

    NASA Astrophysics Data System (ADS)

    Kreutz, K. J.; Godaire, T. P.; Burakowski, E. A.; Winski, D.; Campbell, S. W.; Wang, Z.; Sun, Q.; Hamilton, G. S.; Birkel, S. D.; Wake, C. P.; Osterberg, E. C.; Schaaf, C.

    2015-12-01

    Mountain glaciers around the world, particularly in Alaska, are experiencing significant surface mass loss from rapid climatic shifts and constitute a large proportion of the cryosphere's contribution to sea level rise. Surface albedo acts as a primary control on a glacier's mass balance, yet it is difficult to measure and quantify spatially and temporally in steep, mountainous settings. During our 2013 field campaign in Denali National Park to recover two surface to bedrock ice cores, we used an Analytical Spectral Devices (ASD) FieldSpec4 Standard Resolution spectroradiometer to measure incoming solar radiation, outgoing surface reflectance and optical grain size on the Kahiltna Glacier and at the Kahiltna Base Camp. A Campbell Scientific automatic weather station was installed on Mount Hunter (3900m) in June 2013, complementing a longer-term (2008-present) station installed at Kahiltna Base Camp (2100m). Use of our in situ data aids in the validation of surface albedo values derived from Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat satellite imagery. Comparisons are made between ASD FieldSpec4 ground measurements and 500m MODIS imagery to assess the ability of MODIS to capture the variability of surface albedo across the glacier surface. The MODIS MCD43A3 BRDF/Albedo Product performs well at Kahiltna Base Camp (<5% difference from ASD shortwave broadband data), but low biases in MODIS albedo (10-28% relative to ASD data) appear to occur along the Kahiltna Glacier due to the snow-free valley walls being captured in the 500m MODIS footprint. Incorporating Landsat imagery will strengthen our interpretations and has the potential to produce a long-term (1982-present) validated satellite albedo record for steep and mountainous terrain. Once validation is complete, we will compare the satellite-derived albedo record to the Denali ice core accumulation rate, aerosol records (i.e. volcanics and biomass burning), and glacier mass balance data. This

  1. A centennial-scale record of Holocene effective moisture from the southern Brooks Range, Alaska

    NASA Astrophysics Data System (ADS)

    Clegg, B. F.; Hu, F.

    2006-12-01

    Several decades of paleoecological research resulted in a dense network of pollen records for vegetational reconstruction in Alaska and adjacent regions. Much of this work was motivated by the importance of understanding the responses of boreal ecosystems to climatic change. However, pollen-independent evidence of climatic change remains sparse. We analyzed sediments from Takahula Lake (67°21.12'N, 153°39.89'W) in the south-central Brooks Range to infer variations in effective moisture (precipitation minus evaporation) over the last 8000 years. To help constrain the paleoclimate reconstruction, we conducted δ 18O and δ 2H analyses of monthly surface-water samples as well as inlet and groundwater samples collected from Takahula Lake during the summers of 2002 and 2004. Several lines of evidence indicate that Takahula Lake is isotopically highly sensitive to effective-moisture fluctuations. First, the δ 18O and δ 2H values of lake-water samples fall on an evaporation line with a slope of 5.14, indicating that Takahula Lake experiences evaporative enrichment with respect to input water by up to 3.3?. Second, the difference in the degree of evaporative enrichment of lake water between 2002 and 2004, as inferred from lake-water δ 18O and δ 2H values, corresponds to differences in cumulative precipitation and heating degree-days of these two years. Third, the lake water became progressively more enriched in 18O and 2H from June to September. We analyzed sediment cores from Tukahula Lake at about centennial resolution for a suite of climatic proxies. These proxies include lithology, organic and inorganic carbon content, and δ 18O and δ 13C of Chara carbonate encrustations. The chronology is based on a 210Pb profile and eight 14C dates. We inferred lake-level changes from lithologic features and variation in the δ 18O-δ 13C correlation of authigenic carbonate. This information was used to help interpret large fluctuations (up to 6‰) in the carbonate δ 18O

  2. Changing Lake Bathymetry with Deglaciation: The Mendenhall Glacier System

    NASA Astrophysics Data System (ADS)

    Connor, C.; Korzen, N.; Knuth, E.; Sauer, D.; Heavner, M.

    2008-12-01

    Ongoing rapid ice ablation and glacier thinning has continued the buoyancy-driven, large-scale calving events and ice terminus collapse of the Mendenhall Glacier. New bathymetric data collected from Mendenhall Lake between 2004 and 2008 reveal lake shallowing adjacent to the 2008 glacier terminus. Since 2000, the lake has expanded beyond its former 3.4 km2 footprint to 4.02 km2 and enlarged its volume from 0.05 km3 to 0.23 km3 as it elongates to the north, following the receding lakefront terminus and filling its Pleistocene ice-scoured cirque basin. In 2004, the northeastern-most deep in the lake basin reached a maximum depth of ~97 meters below mean lake level. Since that time this deep has shallowed to the north decreasing along the 2008 glacier terminus to depths ranging from 79.85 to 0 m below mean lake level. This new bathymetric data will be used for ongoing mass balance studies as well as for determination of changes in lake sedimentation rates and lake basin morphology since the 1970s when original lake surveys were conducted by the Alaska Dept of Fish and Game personnel. Comparison of lake basin volume with river discharge data will help to better define the seasonal contribution of glacier melt water to Mendenhall River summer discharge, which reached 50 percent during the summer of 1998.

  3. Inventory of rock avalanches in western Glacier Bay National Park and Preserve, Alaska, 1984-2016: a baseline data set for evaluating the impact of climate change on avalanche magnitude, mobility, and frequency

    USGS Publications Warehouse

    Bessette-Kirton, Erin; Coe, Jeffrey A.

    2016-01-01

    The effects of climate change have the potential to impact slope stability. Negative impacts are expected to be greatest at high northerly latitudes where degradation of permafrost in rock and soil, debuttressing of slopes as a result of glacial retreat, and changes in ocean ice-cover are likely to increase the susceptibility of slopes to landslides. In the United States, the greatest increases in air temperature and precipitation are expected to occur in Alaska. In order to assess the impact that these environmental changes will have on landslide size (magnitude), mobility, and frequency, inventories of historical landslides are needed. These inventories provide baseline data that can be used to identify changes in historical and future landslide magnitude, mobility, and frequency.  This data release presents GIS and attribute data for an inventory of rock avalanches in a 5000 km2 area of western Glacier Bay National Park and Preserve, Alaska. We created the inventory from 30 m resolution Landsat imagery acquired from June 1984 to September 2016.  For each calendar year, we visually examined a minimum of one Landsat image obtained between the months of May and October. We examined a total of 104 Landsat images. The contrast between the spectral signatures of freshly exposed rock avalanche source areas and deposits and surrounding undisturbed snow and ice was typically significant enough to detect surficial changes. We identified and mapped rock avalanches by locating areas with 1) high contrast compared to surrounding snow and ice, 2) different spectral signatures between successive Landsat images, and 3) lobate forms typical of rock-avalanche deposits. Using these criteria, we mapped a total of 24 rock avalanches ranging in size from 0.1 to 22 km2.Attribute data for each rock avalanche includes: a date, or range in possible dates, of occurrence; the name of the Landsat image(s) used to identify and map the avalanche; the total area covered by the rock avalanche

  4. Alexander Archipelago, Southeastern Alaska

    NASA Technical Reports Server (NTRS)

    2002-01-01

    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

  5. Glacier fluctuations during the past 2000 years

    NASA Astrophysics Data System (ADS)

    Solomina, Olga N.; Bradley, Raymond S.; Jomelli, Vincent; Geirsdottir, Aslaug; Kaufman, Darrell S.; Koch, Johannes; McKay, Nicholas P.; Masiokas, Mariano; Miller, Gifford; Nesje, Atle; Nicolussi, Kurt; Owen, Lewis A.; Putnam, Aaron E.; Wanner, Heinz; Wiles, Gregory; Yang, Bao

    2016-10-01

    A global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions (excluding Antarctica) highlights the nature of glacier fluctuations during the late Holocene. The dataset includes 275 time series of glacier fluctuations based on historical, tree ring, lake sediment, radiocarbon and terrestrial cosmogenic nuclide data. The most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and, when available, winter precipitation reconstructions, the most important parameters for glacier mass balance. In many cases major glacier advances correlate with multi-decadal periods of decreased summer temperature. In a few cases, such as in Arctic Alaska and western Canada, some glacier advances occurred during relatively warm wet times. The timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region. However, the number of glacier advances shows a clear pattern for the high, mid and low latitudes and, hence, points to common forcing factors acting at the global scale. Globally, during the first millennium CE glaciers were smaller than between the advances in 13th to early 20th centuries CE. The precise extent of glacier retreat in the first millennium is not well defined; however, the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th/early 21st centuries. Other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the European Alps, in the 3rd-6th and 9th centuries in Norway, during the 10th-13th centuries in southern Alaska, and in the 18th century in Spitsbergen. However, no single period of common global glacier retreat of centennial duration, except for the past century, has yet been identified. In contrast, the view that the Little Ice Age was a period of global glacier expansion beginning in the 13th century

  6. Sedimentology and stratigraphy of the Kanayut Conglomerate, central Brooks Range, Alaska; report of 1980 field season

    USGS Publications Warehouse

    Nilsen, T.H.; Moore, T.E.; Balin, D.F.; Johnson, S.Y.

    1982-01-01

    The Upper Devonian Kanayut Conglomerate crops out along the crest of the Brooks Range of northern Alaska for a distance of almost 1000 km. It ranges in thickness from 2600 m in the Atigun River area to 700 m south of Anaktuvuk Pass and has been subdivided into four regionally persistent members: (a) the basal sandstone member, consisting of marine sandstone and shale with some conglomerate; (b) the lower shale member, consisting of nonmarine quartzite, conglomerate and shale; (c) the middle conglomerate member, consisting of nonmarine pebble and cobble conglomerate and quartzite; and (d) the Stuver Member, consisting of nonmarine sandstone and shale. The Kanayut conformably overlies the Upper Devonian marine Hunt Fork Shale and is conformably overlain by the Mississippian marine Kayak Shale. The Kanayut is wholly allochthonous and has probably been transported northward on a series of thrust plates. The basal sandstone member of the Kanayut Conglomerate, which overlies prodelta turbidites of the Hunt Fork Shale, contains marginal-marine coarsening-upward channel-mouth bar sequences. It is conformably overlain by the lower shale member. Measured sections of the nonmarine members of the Kanayut show that the lower shale member ranges in thickness from 120 m to 1115 m and consists of fining-upward cycles interpreted to have been deposited by meandering streams on a broad floodplain. These cycles contain, in ascending order, channelized basal conglomerate, trough cross-stratified sandstone, and ripple-marked siltstone. The cycles are interpreted to be channel and point-bar deposits. Individual cycles average about 10 m in thickness and are separated by intervals of black, brown or maroon floodplain shale deposits. These typically contain thin coarsening-upward units that probably represent prograding levee sequences and irregular and ungraded sandstone bodies interpreted to be crevasse-splay deposits. In the Okokmilaga River area, the lower shale member contains a

  7. Mafic and ultramafic rocks of the northwestern Brooks Range of Alaska produce nearly symmetric gravity anomalies

    SciTech Connect

    Morin, R.L. )

    1993-04-01

    An arc of mafic and ultramafic rocks is mapped from Asik Mountain to Siniktanneyak Mountain in the northwestern Brooks Range of Alaska. Gravity data, although not very detailed, have been collected over the region and show some very conspicuous circular or oval gravity highs over portions of the mapped mafic-ultramafic bodies. Bodies which have large associated gravity anomalies are Asik Mountain (80 mGal), Avon Hills (20 mGal), Misheguk Mountain (30 mGal), and Siniktanneyak Mountain (20 mGal). Gabbros of the Siniktanneyak Mountain complex, where the gravity coverage is best, have densities of about 3.0 g/cm[sup 3] while the densities of the surrounding sedimentary rocks are about 2.6 g/cm[sup 3]. Volcanic rocks in the area have average densities of about 2.7 g/cm[sup 3]. Three-dimensional modeling indicates that the largest anomaly, on the southwestern part of the complex, could be caused by a polygonal prism of gabbro with vertical sides, about 6 km across and about 4.5 km deep. A smaller lobe of the anomaly on the northeast of the complex could be caused by another oblong polygonal prism about 4 km long and 2 km wide trending northeast and about 1.5 km deep. Modeling this anomaly with densities lower than gabbro would require greater thicknesses to produce the same anomaly. Modeling each anomaly along this arc in 2 1/2-dimensions shows many possible solutions using different body shapes and different density contrasts. There are several other gravity anomalies in this vicinity which could represent unexposed high density rocks. One such anomaly is in the Maiyumerak Mountains northeast of Asik Mountain (30 mGal). Another anomaly is to the northwest of Asik Mountain (20 mGal). There is also an anomaly at Uchugrak (20 mGal) east of Avan Hills. Although many of the anomalies in this region are poorly controlled, an attempt has been made to interpret the data to show possible solutions.

  8. Digital Data for the Geology of the Southern Brooks Range, Alaska

    USGS Publications Warehouse

    Geologic map compiled by Till, Alison B.; Dumoulin, Julie A.; Harris, Anita G.; Moore, Thomas E.; Bleick, Heather; Siwiec, Benjamin; Digital files prepared by Labay, Keith A.; Wilson, Frederic H.; Shew, Nora

    2008-01-01

    The growth in the use of Geographic Information Systems (GIS) has highlighted the need for digital geologic maps that have been attributed with information about age and lithology. Such maps can be conveniently used to generate derivative maps for manifold special purposes such as mineral-resource assessment, metallogenic studies, tectonic studies, and environmental research. This report is part of a series of integrated geologic map databases that cover the entire United States. Three national-scale geologic maps that portray most or all of the United States already exist; for the conterminous U.S., King and Beikman (1974a,b) compiled a map at a scale of 1:2,500,000, Beikman (1980) compiled a map for Alaska at 1:2,500,000 scale, and for the entire U.S., Reed and others (2005a,b) compiled a map at a scale of 1:5,000,000. A digital version of the King and Beikman map was published by Schruben and others (1994). Reed and Bush (2004) produced a digital version of the Reed and others (2005a) map for the conterminous U.S. The present series of maps is intended to provide the next step in increased detail. State geologic maps that range in scale from 1:100,000 to 1:1,000,000 are available for most of the country, and digital versions of these state maps are the basis of this product. The digital geologic maps presented here are in a standardized format as ARC/INFO export files and as ArcView shape files. The files named __geol contain geologic polygons and line (contact) attributes; files named __fold contain fold axes; files named __lin contain lineaments; and files named __dike contain dikes as lines. Data tables that relate the map units to detailed lithologic and age information accompany these GIS files. The map is delivered as a set 1:250,000-scale quadrangle files. To the best of our ability, these quadrangle files are edge-matched with respect to geology. When the maps are merged, the combined attribute tables can be used directly with the merged maps to make

  9. Alaska: A frontier divided

    SciTech Connect

    O'Dell, R. )

    1986-09-01

    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.

  10. Groundwater discharge and base flow variability in the Brooks Range, North Slope, Alaska

    NASA Astrophysics Data System (ADS)

    Yoshikawa, K.; Hinzman, L.; Kane, D.

    2004-12-01

    More than 30,000 liters/sec. of spring water discharges along the eastern part of foothills of the Brooks Range, North Slope, Alaska. These springs flow all year around and cover wide areas with aufeis every winter. In Arctic regions, aufeis is among the biggest temporary storage of freshwater during winter period (more than 8 months). This study examines the historical volume of the aufeis using aerial photographs and satellite imagery as well as MODIS Airborne Simulator (MAS). The energy balance of the aufeis is also an important parameter for estimating perennial aufeis formations. We estimate the Holocene ice volume of aufeis using CaCO3 deposits in the soil. Carbonate material distributions and 13C isotope enrichment signals are indicative of the area occupied by aufeis. Thermal enrichment of the 13C spring water was around 0 to -2 permil at the Hulahula River aufeis area. The 13C isotope of the area immediately outside the aufeis field is around -25 permil and is also very low in carbonate content. The analysis of in-situ soil sample for d13C complemented with remote sensing analyses reveals historic aufeis distributions. The CaCO3 deposits appears to possess a characteristic spectral signature that is evident in the 2300 and 2550 nm wavelength range (two absorption bands 2500-2550 nm and 2300-2350 nm and a band between those two at ~ 2400 nm (2375-2425nm ). The aufeis area was not much greater during historical times such as Little Ice Age (LIA) or Last Glacial Maximum(LGM). However, some of the aufeis and springs (at least Shubik and Sadlerochit springs) survived during LGM. In case of the Sadlerochit spring, the total winter discharge (16,510,000 m3) was almost all turned to aufeis,(15,988,866 m3) preserved as ice on the tundra terrain. Questions of the spring water's ground residence time and infiltration processes are also examined in this study. We collected water from springs, wells, surface water, and precipitation samples for isotope (C, O, H, Sr

  11. Origin of narrow terranes and adjacent major terranes occurring along the denali fault in the eastern and central alaska range, alaska

    USGS Publications Warehouse

    Nokleberg, W.J.; Richter, D.H.

    2007-01-01

    Several narrow terranes occur along the Denali fault in the Eastern and Central Alaska Range in Southern Alaska. These terranes are the Aurora Peak, Cottonwood Creek, Maclaren, Pingston, and Windy terranes, and a terrane of ultramafic and associated rocks. Exterior to the narrow terranes to the south is the majorWrangellia island arc composite terrane, and to the north is the major Yukon Tanana metamorphosed continental margin terrane. Overlying mainly the northern margin of the Wrangellia composite terrane are the Kahiltna overlap assemblage to the west, and the Gravina- Nutzotin-Gambier volcanic-plutonic- sedimentary belt to the east and southeast. The various narrow terranes are interpreted as the result of translation of fragments of larger terranes during two major tectonic events: (1) Late Jurassic to mid-Cretaceous accretion of the Wrangellia island arc composite terrane (or superterrane composed of the Wrangellia, Peninsular, and Alexander terranes) and associated subduction zone complexes; and (2) starting in about the Late Cretaceous, dextral transport of the Wrangellia composite terrane along the Denali fault. These two major tectonic events caused: (1) entrapment of a lens of oceanic lithosphere along the suture belt between the Wrangellia composite terrane and the North American Craton Margin and outboard accreted terranes to form the ultramafic and mafic part of the terrane of ultramafic and associated rocks, (2) subsequent dextral translation along the Denali fault of the terrane of ultramafic and associated rocks, (3) dextral translation along the Denali fault of the Aurora Peak, Cottonwood Creek, and Maclaren and continental margin arc terranes from part of the Coast plutonic-metamorphic complex (Coast-North Cascade plutonic belt) in the southwest Yukon Territory or Southeastern Alaska, (4) dextral translation along the Denali fault of the Pingston passive continental margin from a locus along the North American Continental Margin, and (5

  12. Taku Glacier: Proglacial Deformation and Subglacial Erosion

    NASA Astrophysics Data System (ADS)

    Kuriger, E. M.; Motyka, R. J.; Truffer, M.; Bucki, A. K.

    2003-12-01

    Taku Glacier has advanced about 7~km since 1890 and is continuing its advance today. Located in southeastern Alaska, this glacier flows from the Juneau Ice Field down to sea level. In the last several decades the glacier has bulldozed a berm of marine and fluvial sediments from the fjord bottom; this berm now separates the terminus from tidewater. The force of the advancing glacier is causing large-scale deformation within these sediments. In 2001, a series of thrust scarps began to form in front of a 200~m section of the terminus. These scarps were active for several months and produced a series of bulges that grew to be several meters in height above the surrounding sediments. Ground penetrating radar (GPR) was used to image the internal structure of these bulges. A trench dug into one of the proglacial ridges revealed that a >2~m clay/sand layer might have played an important role as a thrust zone during deformation. This layer could also be identified in the GPR returns. Beside these scarp-formed bulges there are numerous indicators of the continued advance. Push moraines along the terminus range in height from 1~m to a towering 10~m. In some areas the advancing ice has dug into the sediments and has lifted the vegetation from below. We also observed up to 1~m thick debris freeze-on layers that, when exposed at the terminus, melt and contribute to the development of some moraines. In addition to these observations we performed a series of radio echo-soundings over a grid that extends about 5~km upglacier. These data are compared with depth measurements made in 1989. Since then the glacier has advanced about 180~m. Within 1~km of the present terminus the glacier has deepened its bed by about 15~m, which indicates an erosion rate of about 1~my-1 in this area. This rate agrees with the one observed over the past 100~years. Entrenchment plays an important role in the glacier's dynamics and needs to be taken into account when measuring volume changes.

  13. Hydrograph separation of a sub-arctic glacial watershed, Interior Alaska

    NASA Astrophysics Data System (ADS)

    Gatesman, T.; Douglas, T. A.; Liljedahl, A. K.; Trainor, T.

    2015-12-01

    Glacier melt affect several Alaska rivers and thus far, the contribution to larger-scale watershed runoff has attracted limited attention, and in particular, a quantitative assessment. Geochemically-based hydrograph separation techniques in combination with glacier mass balance and runoff measurements can help refine our understanding of the contributing sources and therefore, support the refinement of both short-term flood forecasts and long-term runoff projections. Our study was designed to quantify the contribution of glacier melt, snow melt and rainfall to lowland streamflow of a sub-arctic basin and to assess hydrologic pathways of glacier wastage. Jarvis Creek watershed (634 km2), Interior Alaska, drains the north-facing Eastern Alaska Range, starting at the Jarvis Glacier (6.7 km2) and flows 69 km to its outlet in the Delta River, Delta Junction. Glacial contribution accounts for at least 15% of total runoff as estimated from measured glacier melt and lowland runoff. Daily stable water isotope samples near the Jarvis Creek outlet show distinct chemical signatures in contributing sources and large seasonal and interannual δ18O variability. For example, geochemical measurements from 2011 show low rainfall contribution into Jarvis Creek, whereas 2014 show high input of rainfall; and, unlike 2014, spring 2013 show a strong snowmelt contribution in late spring. Stable water isotopes will be the primary signature to inform our end-member volumetric mixing modeling efforts, while dissolved ion concentrations will support a differentiation between glacier- and groundwater sources. Ultimately, the combination of glacier mass balance, hydrological and geochemical measurements will allow us to gain a fundamental knowledge about the current regional hydrologic system.

  14. A glacier runoff extension to the Precipitation Runoff Modeling System

    NASA Astrophysics Data System (ADS)

    Van Beusekom, A. E.; Viger, R. J.

    2016-11-01

    A module to simulate glacier runoff, PRMSglacier, was added to PRMS (Precipitation Runoff Modeling System), a distributed-parameter, physical-process hydrological simulation code. The extension does not require extensive on-glacier measurements or computational expense but still relies on physical principles over empirical relations as much as is feasible while maintaining model usability. PRMSglacier is validated on two basins in Alaska, Wolverine, and Gulkana Glacier basin, which have been studied since 1966 and have a substantial amount of data with which to test model performance over a long period of time covering a wide range of climatic and hydrologic conditions. When error in field measurements is considered, the Nash-Sutcliffe efficiencies of streamflow are 0.87 and 0.86, the absolute bias fractions of the winter mass balance simulations are 0.10 and 0.08, and the absolute bias fractions of the summer mass balances are 0.01 and 0.03, all computed over 42 years for the Wolverine and Gulkana Glacier basins, respectively. Without taking into account measurement error, the values are still within the range achieved by the more computationally expensive codes tested over shorter time periods.

  15. Permian and Triassic sedimentation in the northeastern Brooks Range, Alaska: Deposition of the Sadlerochit Group: Reply

    SciTech Connect

    Crowder, R.K. )

    1991-12-01

    This paper was written in defense of this authors previous paper on the Ledge Sandstone member of the Ivishak Formation, Arctic National Wildlife Refuge, Alaska. This author has previously written a paper (Crowder, 1990) which discussed the depositional environments and sedimentation of these reservoir-quality sandstones and conglomerates, and developed a geologic model for source materials and deposition. As a response to this paper, another author (McMillen, 1991) questioned numerous conclusions reached by this author. The former author cited the lack of use of paleocurrent information to determine source areas and the misinterpretation of sandstone body geometry. Both papers and rebuttals have been individually entered into the data base.

  16. Mass-balance characteristics of arctic glaciers

    NASA Astrophysics Data System (ADS)

    Braithwaite, Roger J.

    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 interannual variability but otherwise share characteristics with glaciers in lower latitudes. The arctic island glaciers occur in areas with low annual precipitation and high annual temperature variability, i.e. in dry-cold or continental regions. Most glaciers surrounding the Arctic (Alaska, Iceland and Scandinavia) occur in areas with high annual precipitation and low annual temperature variability, i.e. in wet-warm or maritime regions. Earlier mass-balance modelling showed that arctic island glaciers have low sensitivity to temperature changes consistent with their low mass-balance amplitude. However, very large changes in mass balance could occur on arctic island glaciers if the sea ice surrounding the arctic islands were reduced so that the climate of the arctic islands becomes more maritime.

  17. Alaska marine ice atlas

    SciTech Connect

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

    1982-01-01

    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)

  18. Lithostratigraphy, microlithofacies, and conodont biostratigraphy and biofacies of the Wahoo Limestone (Carboniferous), eastern Sadlerochit Mountains, Northeast Brooks Range, Alaska

    SciTech Connect

    Krumhardt, A.P.; Harris, A.G.; Watts, K.F.

    1996-12-31

    The Lisburne Group (chiefly Carboniferous) is a wide-spread succession of platform carbonate rocks that apparently developed along a south-facing passive continental margin in northern Alaska. Marine transgressions onlapped northward across northeast Alaska allowing the Lisburne platform to extend over terrigenous deposits of the Endicott Group and local pre-Mississippian paleotopographic highs. The Wahoo Limestone is the youngest formation of the Lisburne Group in northeasternmost Alaska, ranging from latest Mississippian (latest Chesterian) to Middle Pennsylvanian (at least early Atokan) in age. The Wahoo Limestone was systematically sampled for lithostratigraphy and conodont biostratigraphy and biofacies at a relatively continuous section (about 262 m in thickness) in the eastern Sadlerochit Mountains. Existing Carboniferous conodont zonations could not be readily applied to the study section because most zonal indicators are absent. Species diversity is low for a section that spans at least 10 million years. Twenty-four species, distributed among 14 genera, were identified in 72 productive samples; no new species were distinguished. The following biostratigraphic zones and faunal intervals were recognized: Upper muricatus Subzone (latest Chesterian); noduliferus-primus Zone (earliest Morrowan); minutus Fauna (Morrowan) containing a lower subdivision (lower minutus Fauna of early to middle? Morrowan age); and an Idiognathodus Fauna (Morrowan? to early Atokan). The presence of Idiognathodus incurvus? and Rhachistognathus minutus subspp. above the first occurrence of the foraminifer Pseudostaffella sp. in the uppermost part of the Wahoo Limestone indicates that the youngest beds are early Atokan in age. The Mississippian-Pennsylvanian boundary is placed at 56 m above the base of the lower member of the Wahoo Limestone on the basis of the lowest occurrence of Declinognathodus noduliferus japonicus above forms transitional from Gnathodus girtyl simplex.

  19. Columbia Glacier in 1984: disintegration underway

    SciTech Connect

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

    1985-01-01

    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.

  20. International Symposium on Fast Glacier Flow

    NASA Technical Reports Server (NTRS)

    Lingle, Craig S.

    1990-01-01

    Cryospheric Sciences Program "International Symposium on Fast Glacier Flow" (PI, C. Lingle) provided partial support for publication of Annals of Glaciology 36 by the International Glaciological Society. Annals of Glaciology is a peer-reviewed journal. Annals 36, which was published in 2003, contains 39 peer-reviewed and edited papers from the International Symposium on Fast Glacier Flow, which was held in Yakutat, Alaska, 10-14 June 2002.

  1. New U/Pb ages from granite and granite gneiss in the Ruby geanticline and southern Brooks Range, Alaska ( USA).

    USGS Publications Warehouse

    Patton, W.W.; Stern, T.W.; Arth, Joseph G.; Carlson, C.

    1987-01-01

    New U/Pb zircon ages from the Ray Mountains of central Alaska clarify the plutonic history of the Ruby geanticline and support earlier suggestions that the Ruby geanticline and S Brooks Range were once parts of the same tectonostratigraphic terrane. U/Pb zircon ages of 109 to 112 Ma from the Ray Mountains pluton confirm previously reported mid-Cretaceous K/Ar ages and rule out the possibility that the earliest intrusive phase of the pluton is older than mid-Cretaceous K/Ar ages and rule out the possibility that the earliest intrusive phase of the pluton is older than mid- Cretaceous. New U/Pb zircon ages from 4 granite gneiss samples in the Ray Mountains indicate a Devonian protolith age of 390+ or -12 Ma and suggest that the Ruby geanticline, like the S Brooks Range, underwent a major plutonic event in mid-Paleozoic time.-Authors

  2. Environmental Restoration of Diesel-Range Organics from Project Chariot, Cape Thompson, Alaska

    SciTech Connect

    Kautsky, Mark; Hutton, Rick; Miller, Judy

    2016-03-06

    The Chariot site is located in the Ogotoruk Valley in the Cape Thompson region of northwest Alaska. Project Chariot was part of the Plowshare Program, created in 1957 by the US Atomic Energy Commission (AEC), a predecessor agency of the US Department of Energy (DOE), to study peaceful uses for atomic energy. Project Chariot began in 1958 when a scientific field team chose Cape Thompson as a potential site to excavate a harbor using a series of nuclear explosions. AEC, with assistance from other agencies, conducted more than 40 pretest bioenvironmental studies of the Cape Thompson area between 1959 and 1962; however, the Plowshare Program work at the Project Chariot site (Figure 1) was cancelled because of strong public opposition [1]. No nuclear explosions were ever conducted at the site.

  3. Geologic studies in Alaska by the U.S. Geological Survey, 1996

    USGS Publications Warehouse

    Gray, John E.; Riehle, James R.

    1998-01-01

    This collection of 12 papers continues the annual series of U.S. Geological Survey (USGS) reports on geologic investigations in Alaska. The annual volume presents results from new or ongoing studies in Alaska that are of interest to scientists in academia, industry, land and resource managers, and the general public. The Geological Studies in Alaska volume reports the results of studies that cover a broad spectrum of earth science topics from many parts of the state (fig. 1).The papers in this volume are organized under the topics Environment and Climate, Resources, and Geologic Framework, in order to reflect the objectives and scope of USGS programs that are currently active in Alaska. Environmental studies are the focus of two articles in this volume: One study addresses the relation between glaciers and aquatic habitat on the Kenai River and another study evaluates the geochemistry of water draining chromite deposits in Alaska. Two papers address mineral resources in southwestern Alaska including a geochemical study of the Fortyseven Creek prospect and a geological and geochemical study of the Stuyahok area. Eight geologic framework studies apply a variety of techniques to a wide range of subjects throughout Alaska, including biostratigraphy, geochemistry, geochronology, paleomagnetism, sedimentology, and tectonics.Two bibliographies at the end of the volume list reports about Alaska in USGS publications released in 1996 and reports about Alaska by USGS authors in non-USGS publications in 1996.

  4. The 24 July 2008 outburst flood at the western Zyndan glacier lake and recent regional changes in glacier lakes of the Teskey Ala-Too range, Tien Shan, Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Narama, C.; Duishonakunov, M.; Kääb, A.; Daiyrov, M.; Abdrakhmatov, K.

    2010-04-01

    On 24 July 2008, a glacier lake outburst flood (GLOF) occurred at the western (w-) Zyndan glacier lake in the Tong District of Ysyk-Köl Oblast, Kyrgyzstan. The flood killed three people and numerous livestock, destroyed infrastructure, and devastated potato and barley crops as well as pastures. Tuurasuu village and a downstream reservoir on the Zyndan river escaped heavy damage because the main flood was diverted toward the Tong river. RTK-GPS and satellite data (Landsat 7 ETM+, ALOS/PRISM, and ALOS/AVNIR-2) reveal that the flood reduced the lake area from 0.0422 km2 to 0.0083 km2, discharging 437 000 m3 of water. This glacier lake was not present in a Landsat 7 ETM+ image taken on 26 April 2008. It formed rapidly over just two and half months from early May to the late July, when large amounts of snow and glacier melt water became trapped in a basin in the glacier terminus area, blocked by temporary closure of the drainage channel through the terminal moraine that included much dead-ice. In the same mountain region, most other glacier-lake expansions were not particularly large during the period from 1999-2008. Although events like the w-Zyndan glacier lake outburst occur infrequently in the high Central Asian mountains, such fast developing, short-lived lakes are particularly dangerous and not easy to monitor using satellite data. Appropriate measures to protect against such lake outburst hazards in this region include educating residents on glacier hazards and monitoring techniques, providing frequently updated maps of glacier lakes, and planning and monitoring land-use, including house locations.

  5. 36 CFR 13.1116 - Do I need a camping permit in Glacier Bay?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Glacier Bay? 13.1116 Section 13.1116 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve General Provisions § 13.1116 Do I need a camping permit in Glacier Bay? From May...

  6. 36 CFR 13.1150 - Is a permit required for a vessel in Glacier Bay?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... vessel in Glacier Bay? 13.1150 Section 13.1150 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Vessel Permits § 13.1150 Is a permit required for a vessel in Glacier Bay? A permit...

  7. 36 CFR 13.1109 - Off-road vehicle use in Glacier Bay National Preserve.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Glacier Bay National Preserve. 13.1109 Section 13.1109 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Administrative Provisions § 13.1109 Off-road vehicle use in Glacier Bay...

  8. 36 CFR 13.1109 - Off-road vehicle use in Glacier Bay National Preserve.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Glacier Bay National Preserve. 13.1109 Section 13.1109 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Administrative Provisions § 13.1109 Off-road vehicle use in Glacier Bay...

  9. 36 CFR 13.1150 - Is a permit required for a vessel in Glacier Bay?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... vessel in Glacier Bay? 13.1150 Section 13.1150 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Vessel Permits § 13.1150 Is a permit required for a vessel in Glacier Bay? A permit...

  10. 36 CFR 13.1116 - Do I need a camping permit in Glacier Bay?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Glacier Bay? 13.1116 Section 13.1116 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve General Provisions § 13.1116 Do I need a camping permit in Glacier Bay? From May...

  11. 36 CFR 13.1116 - Do I need a camping permit in Glacier Bay?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Glacier Bay? 13.1116 Section 13.1116 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve General Provisions § 13.1116 Do I need a camping permit in Glacier Bay? From May...

  12. 36 CFR 13.1116 - Do I need a camping permit in Glacier Bay?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Glacier Bay? 13.1116 Section 13.1116 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve General Provisions § 13.1116 Do I need a camping permit in Glacier Bay? From May...

  13. 36 CFR 13.1150 - Is a permit required for a vessel in Glacier Bay?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... vessel in Glacier Bay? 13.1150 Section 13.1150 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Vessel Permits § 13.1150 Is a permit required for a vessel in Glacier Bay? A permit...

  14. 36 CFR 13.1109 - Off-road vehicle use in Glacier Bay National Preserve.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Glacier Bay National Preserve. 13.1109 Section 13.1109 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Administrative Provisions § 13.1109 Off-road vehicle use in Glacier Bay...

  15. 36 CFR 13.1150 - Is a permit required for a vessel in Glacier Bay?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... vessel in Glacier Bay? 13.1150 Section 13.1150 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Vessel Permits § 13.1150 Is a permit required for a vessel in Glacier Bay? A permit...

  16. 36 CFR 13.1109 - Off-road vehicle use in Glacier Bay National Preserve.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Glacier Bay National Preserve. 13.1109 Section 13.1109 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Administrative Provisions § 13.1109 Off-road vehicle use in Glacier Bay...

  17. 36 CFR 13.1150 - Is a permit required for a vessel in Glacier Bay?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... vessel in Glacier Bay? 13.1150 Section 13.1150 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Vessel Permits § 13.1150 Is a permit required for a vessel in Glacier Bay? A permit...

  18. 36 CFR 13.1109 - Off-road vehicle use in Glacier Bay National Preserve.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Glacier Bay National Preserve. 13.1109 Section 13.1109 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Administrative Provisions § 13.1109 Off-road vehicle use in Glacier Bay...

  19. Alaska volcanoes guidebook for teachers

    USGS Publications Warehouse

    Adleman, Jennifer N.

    2011-01-01

    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

  20. Implications of Glacier Volume Change for Ice-Ocean Interactions

    NASA Astrophysics Data System (ADS)

    Hood, E. W.; O'Neel, S.; Fellman, J.; Bidlack, A.; Arendt, A. A.; Arimitsu, M.; Spencer, R. G.

    2015-12-01

    Changes in climate are forcing complex glaciological responses that can be transmitted to downstream ecosystems via glacier runoff. Along the Gulf of Alaska, rates of glacier mass loss are among the highest measured on Earth. Changes in glacier volume in this region are altering the amount of glacier runoff delivered to the coastal ocean. Moreover, shifts in glacier extent are changing the location of the ice-ocean interface and, in cases where tidewater glaciers become grounded, fundamentally altering circulation in glacierized fjords. The runoff from glacier ecosystems is unique in terms of its physical and chemical properties when compared to runoff from non-glacial ecosystems. For example, the silt and chemical constituents in glacier discharge alter light penetration and the nutrient regime in near-shore marine ecosystems, which, in turn, influence levels of marine primary productivity. Future changes in the magnitude, timing, and location of glacier runoff have important implications for biogeochemical and ecological processes in glacially-dominated fjords and estuaries. This talk will highlight research from glacierized watersheds and fjords to synthesize what is known about the physical, chemical, and biological linkages that characterize icefield-ocean ecosystems along the Gulf of Alaska.

  1. Blood concentrations of some persistent organohalogens in free-ranging spotted seals (Phoca largha) from Bristol Bay, Alaska.

    PubMed

    Neale, Jennifer C C; Small, Robert J; Schmelzer, Kara R; Tjeerdema, Ronald S

    2007-10-01

    In recent years, the relatively high levels of organochlorine contaminants and increasing levels of brominated flame retardants found in tissues of marine mammals have raised concerns that exposure to these marine pollutants may compromise individual health. In this pilot study, levels of 11 polychlorinated biphenyls, 3 polybrominated diphenyl ethers, and the DDT metabolite p,p'-diphenyldichloroethylene were analyzed in whole blood of 7 free-ranging spotted seals (Phoca largha) from Bristol Bay, Alaska, sampled during 2000 and 2001. Blood concentrations of analytes were generally low (<1 ppb wet weight). Open-ocean foraging and feeding on a lower trophic level may contribute to the relatively lower levels of organohalogens found in this species as compared to the closely related harbor seal, Phoca vitulina, occurring in Bristol Bay.

  2. Spatial variations in focused exhumation along a continental-scale strike-slip fault: The Denali fault of the eastern Alaska Range

    USGS Publications Warehouse

    Benowitz, J.A.; Layer, P.W.; Armstrong, P.; Perry, S.E.; Haeussler, P.J.; Fitzgerald, P.G.; VanLaningham, S.

    2011-01-01

    40Ar/39Ar, apatite fission-track, and apatite (U-Th)/He thermochronological techniques were used to determine the Neogene exhumation history of the topographically asymmetric eastern Alaska Range. Exhumation cooling ages range from ~33 Ma to ~18 Ma for 40Ar/39Ar biotite, ~18 Ma to ~6 Ma for K-feldspar minimum closure ages, and ~15 Ma to ~1 Ma for apatite fission-track ages, and apatite (U-Th)/He cooling ages range from ~4 Ma to ~1 Ma. There has been at least ~11 km of exhumation adjacent to the north side of Denali fault during the Neogene inferred from biotite 40Ar/39Ar thermochronology. Variations in exhumation history along and across the strike of the fault are influenced by both far-field effects and local structural irregularities. We infer deformation and rapid exhumation have been occurring in the eastern Alaska Range since at least ~22 Ma most likely related to the continued collision of the Yakutat microplate with the North American plate. The Nenana Mountain region is the late Pleistocene to Holocene (~past 1 Ma) primary locus of tectonically driven exhumation in the eastern Alaska Range, possibly related to variations in fault geometry. During the Pliocene, a marked increase in climatic instability and related global cooling is temporally correlated with an increase in exhumation rates in the eastern Alaska Range north of the Denali fault system.

  3. Terrain, vegetation, and landscape evolution of the R4D research site, Brooks Range Foothills, Alaska

    USGS Publications Warehouse

    Walker, D.A.; Binnian, Emily F.; Evans, B. M.; Lederer, N.D.; Nordstrand, E.A.; Webber, P.J.

    1989-01-01

    Maps of the vegetation and terrain of a 22 km2 area centered on the Department of Energy (DOE) R4D (Response, Resistance, Resilience to and Recovery from Disturbance in Arctic Ecosystems) study site in the Southern Foothills Physiographic Province of Alaska were made using integrated geobotanical mapping procedures and a geographic-information system. Typical land forms and surface f orms include hillslope water tracks, Sagavanirktok-age till deposits, nonsorted stone stripes, and colluvial-basin deposits. Thirty-two plant communities are described; the dominant vegetation (51% of the mapped area) is moist tussock-sedge, dwarf-shrub tundra dominated by Eriophorum vaginatum or Carex bigelowii. Much of the spatial variation in the mapped geobotanical characters reflects different-aged glaciated surfaces. Shannon-Wienerin dices indicate that the more mature landscapes, represented by retransported hillslope deposits and basin colluvium, are less heterogeneous than newer landscapes such as surficial till deposits and floodplains. A typical toposequence on a mid-Pleistocene-age surface is discussed with respect to evolution of the landscape. Thick Sphagnum moss layers occur on lower hillslopes, and the patterns of moss-layer development, heat flux, active layer thickness, and ground-ice are seen as keys to developing thermokarst-susceptibility maps.

  4. U/Pb dating of subduction-collision in the Brooks Range: implications for Mesozoic geodynamics of Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Lemonnier, Nicolas; Labrousse, Loic; Agard, Philippe; McClelland, Bill; Cobble, Mattew; Till, Alison; Roeske, Sarah

    2016-04-01

    The paleogeographic and geodynamic evolution of Northern Alaska is crucial to understand the connection between the Arctic and Pacific realms. The opening of the Canada Basin (CB) is debated both in terms of inception time (between 190 and 140 Ma) and driving mechanisms. The prevalent model assumes that CB opened in a back-arc position within the Arctic-Alaska-Chukotka (AAC) terrane following a change in subduction polarity from S- to N-dipping subduction The adjacent Brooks Range orogen (BRO) is thought to have formed when the Koyukuk volcanic arc collided with the southern extension of AAC. This collision therefore potentially provides key information for Arctic geodynamics, and for the mechanisms of CB opening, but neither the detailed timing of this collisional history nor its duration are well known. In order to constrain the timing of the collision, we performed in-situ zircon U-Pb SIMS analyses on eclogites from the BRO s.l. (BR and Seward Peninsula), which indicate that peak burial (at 510 ± 60°C, 1.6 ± 0.2 GPa) during continental subduction and subsequent collision occurred at 141 ± 6 Ma (n=10, MSWD = 1.6). Eclogite metamorphism therefore postdates the initial rifting stage of the CB but predates effective sea-floor spreading. Younger zircon domains (114 ± 13 Ma) associated with retrograde assemblages could indicate a late thermal pulse or recrystallisation during exhumation in the collisional wedge. Combined with all available information on timing, these new age constraints are used to build a tectonic model for coeval evolution of the Brooks Range and the Canada Basin. The intra-Kingak "Jurassic Unconformity" at the Jurassic Cretaceous Boundary (Houseknecht, pers. communication) could actually be considered as the signature of the AAC-Koyukuk arc collision stage in the CB.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  6. Spatial variability of biotic and abiotic tree establishment constraints across a treeline ecotone in the Alaska Range

    USGS Publications Warehouse

    Stueve, K.M.; Isaacs, R.E.; Tyrrell, L.E.; Densmore, R.V.

    2011-01-01

    Throughout interior Alaska (USA), a gradual warming trend in mean monthly temperatures occurred over the last few decades (;2-48C). The accompanying increases in woody vegetation at many alpine treeline (hereafter treeline) locations provided an opportunity to examine how biotic and abiotic local site conditions interact to control tree establishment patterns during warming. We devised a landscape ecological approach to investigate these relationships at an undisturbed treeline in the Alaska Range. We identified treeline changes between 1953 (aerial photography) and 2005 (satellite imagery) in a geographic information system (GIS) and linked them with corresponding local site conditions derived from digital terrain data, ancillary climate data, and distance to 1953 trees. Logistic regressions enabled us to rank the importance of local site conditions in controlling tree establishment. We discovered a spatial transition in the importance of tree establishment controls. The biotic variable (proximity to 1953 trees) was the most important tree establishment predictor below the upper tree limit, providing evidence of response lags with the abiotic setting and suggesting that tree establishment is rarely in equilibrium with the physical environment or responding directly to warming. Elevation and winter sun exposure were important predictors of tree establishment at the upper tree limit, but proximity to trees persisted as an important tertiary predictor, indicating that tree establishment may achieve equilibrium with the physical environment. However, even here, influences from the biotic variable may obscure unequivocal correlations with the abiotic setting (including temperature). Future treeline expansion will likely be patchy and challenging to predict without considering the spatial variability of influences from biotic and abiotic local site conditions. ?? 2011 by the Ecological Society of America.

  7. Flow instabilities of Alaskan glaciers

    NASA Astrophysics Data System (ADS)

    Turrin, James Bradley

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

  8. The Glaciers of HARMONIE

    NASA Astrophysics Data System (ADS)

    Mottram, Ruth; Gleeson, Emily; Pagh Nielsen, Kristian

    2016-04-01

    Developed by the large ALADIN-HIRLAM consortium, the numerical weather prediction (NWP) model system HARMONIE is run by a large number of national weather services and research institutions in Europe, the Middle East and North Africa for weather forecasting. It is now being adopted for climate research purposes as a limited area model in a form known as HCLIM. It is currently run for a number of domains, mostly in Europe but also including Greenland, at a very high resolution (~2.5 km). HARMONIE is a convection permitting non-hydrostatic model that includes the multi-purpose SURFEX surface model. By improving the characterization of glacier surfaces within SURFEX we show that weather forecast errors over both the Greenland ice sheet and over Icelandic glaciers can be significantly reduced. The improvements also facilitate increasingly accurate ice melt and runoff computations, which are important both for ice surface mass balance estimations and hydropower forecasting. These improvements will also benefit the operational HARMONIE domains that cover the Svalbard archipelago, the Alps and the Scandinavian mountain glaciers. Future uses of HCLIM for these regions, where accurately characterizing glacial terrain will be crucial for climate and glaciological applications, are also expected to benefit from this improvement. Here, we report the first results with a new glacier surface scheme in the HARMONIE model, validated with observations from the PROMICE network of automatic weather stations in Greenland. The scheme upgrades the existing surface energy balance over glaciers by including a new albedo parameterization for bare glacier ice and appropriate coefficients for calculating the turbulent fluxes. In addition the snow scheme from the SURFEX land surface module has been upgraded to allow the retention and refreezing of meltwater in the snowpack. These changes allow us to estimate surface mass balance over glaciers at a range of model resolutions that can take full

  9. The Bay in Place of a Glacier.

    ERIC Educational Resources Information Center

    Howell, Wayne

    1997-01-01

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

  10. THIAFENTANIL-AZAPERONE-XYLAZINE AND CARFENTANIL-XYLAZINE IMMOBILIZATIONS OF FREE-RANGING CARIBOU (RANGIFER TARANDUS GRANTI) IN ALASKA, USA.

    PubMed

    Lian, Marianne; Beckmen, Kimberlee B; Bentzen, Torsten W; Demma, Dominic J; Arnemo, Jon M

    2016-04-28

    Carfentanil-xylazine (CX) has been the primary drug combination used for immobilizing free-ranging ungulates in Alaska, US since 1986. We investigated the efficacy of a potential new drug of choice, thiafentanil (Investigational New Animal Drug A-3080). Captive trials indicated that thiafentanil-azaperone-medetomidine could provide good levels of immobilization. However, field trials conducted in October 2013 on free-ranging caribou ( Rangifer tarandus granti) calves showed the combination too potent, causing three respiratory arrests and one mortality. The protocol was revised to thiafentanil-azaperone-xylazine (TAX), with good results. The induction time was not significantly different between the two combinations. However, the recovery time was significantly shorter for the TAX group than for the CX group. A physiologic evaluation was performed on 12 animals immobilized on CX and 15 animals on TAX. Arterial blood was collected after induction and again after 10 min of intranasal oxygen supplements (1 L/min). Both groups had significant increases in partial pressure of arterial oxygen after oxygen treatment. There was a concurrent significant increase in partial pressure of arterial carbon dioxide in both groups. Rectal temperature increased significantly in both groups during the downtime, which is consistent with other studies of potent opioids in ungulates. On the basis of our results, we found TAX to be a potential alternative for the current CX protocol for immobilizing free-ranging caribou calves via helicopter darting.

  11. Seasonal variability and detection range modeling of baleen whale calls in the Gulf of Alaska, 1999-2002.

    PubMed

    Stafford, Kathleen M; Mellinger, David K; Moore, Sue E; Fox, Christopher G

    2007-12-01

    Five species of large whales, including the blue (Balaenoptera musculus), fin (B. physalus), sei (B. borealis), humpback (Megaptera novaeangliae), and North Pacific right (Eubalaena japonica), were the target of commercial harvests in the Gulf of Alaska (GoA) during the 19th through mid-20th Centuries. Since this time, there have been a few summer time visual surveys for these species, but no overview of year-round use of these waters by endangered whales primarily because standard visual survey data are difficult and costly. From October 1999-May 2002, moored hydrophones were deployed in six locations in the GoA to record whale calls. Reception of calls from fin, humpback, and blue whales and an unknown source, called Watkins' whale, showed seasonal and geographic variation. Calls were detected more often during the winter than during the summer, suggesting that animals inhabit the GoA year-round. To estimate the distance at which species-diagnostic calls could be heard, parabolic equation propagation loss models for frequencies characteristic of each of each call type were run. Maximum detection ranges in the subarctic North Pacific ranged from 45 to 250 km among three species (fin, humpback, blue), although modeled detection ranges varied greatly with input parameters and choice of ambient noise level.

  12. Range overlap and individual movements during breeding season influence genetic relationships of caribou herds in south-central Alaska

    USGS Publications Warehouse

    Roffler, Gretchen H.; Adams, Layne G.; Talbot, Sandra L.; Sage, George K.; Dale, Bruce W.

    2012-01-01

    North American caribou (Rangifer tarandus) herds commonly exhibit little nuclear genetic differentiation among adjacent herds, although available evidence supports strong demographic separation, even for herds with seasonal range overlap. During 1997–2003, we studied the Mentasta and Nelchina caribou herds in south-central Alaska using radiotelemetry to determine individual movements and range overlap during the breeding season, and nuclear and mitochondrial DNA (mtDNA) markers to assess levels of genetic differentiation. Although the herds were considered discrete because females calved in separate regions, individual movements and breeding-range overlap in some years provided opportunity for male-mediated gene flow, even without demographic interchange. Telemetry results revealed strong female philopatry, and little evidence of female emigration despite overlapping seasonal distributions. Analyses of 13 microsatellites indicated the Mentasta and Nelchina herds were not significantly differentiated using both traditional population-based analyses and individual-based Bayesian clustering analyses. However, we observed mtDNA differentiation between the 2 herds (FSTM = 0.041, P

  13. Glacial runoff strongly influences food webs in Gulf of Alaska fjords

    NASA Astrophysics Data System (ADS)

    Arimitsu, M.; Piatt, J. F.; Mueter, F. J.

    2015-12-01

    Melting glaciers contribute large volumes of freshwater to the Gulf of Alaska coast. Rates of glacier volume loss have increased markedly in recent decades, raising concern about the eventual loss of glaciers as a source of freshwater in coastal waters. To better understand the influence of glacier melt water on fjord ecosystems, we sampled oceanography, nutrients, zooplankton, forage fish, and seabirds within four fjords in the coastal Gulf of Alaska. We used generalized additive models and geostatistics to identify the range of influence of glacier runoff in fjords of varying estuarine and topographic complexity. We also modeled the responses of chlorophyll a concentration, copepod biomass, fish and seabird abundance to physical, nutrient and biotic predictor variables. Physical and nutrient signatures of glacial runoff extended 10-20 km into coastal fjords. Glacially modified physical gradients and among-fjord differences explained 66% of the variation in phytoplankton abundance, which drives ecosystem structure at higher trophic levels. Copepod, euphausiid, fish and seabird distribution and abundance were also related to environmental gradients that could be traced to glacial freshwater input. Seabird density was predicted by prey availability and silica concentrations, which may indicate upwelling areas where this nutrient is in excess. Similarities in ecosystem structure among fjords were due to influx of cold, fresh, sediment and nutrient laden water, while differences were due to fjord topography and the relative importance of estuarine vs. ocean influences. We anticipate continued changes in the volume and magnitude of glacial runoff will affect coastal marine food webs in the future.

  14. An Initial AUV Investigation of the Morainal Bank and Ice-Proximal Submarine Processes of the Advancing Hubbard Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Lawson, D. E.; Gulick, S. P. S.; Goff, J. A.; O'Halloran, W.

    2014-12-01

    The movement of an advancing tidewater glacier occurs in concert with the morainal bank that underlies its terminus. The mechanics of motion and sedimentological processes responsible for this advance of the morainal bank with the calving terminus are not well-defined and based largely on inferences from geophysical analyses of remnant morainal banks on fjord floors. There is a general absence of in situ or direct observation of the submarine margin because it is nearly impossible to access the immediate area of the ice face by boat safely. In order to obtain such data, in June 2014 we tested the ability of a Bluefin 9M AUV (autonomous underwater vehicle) to acquire high resolution swath bathymetry and sidescan backscatter across a ~2 km long section of the ice face of Hubbard Glacier (see also Goff et al., this meeting). Additionally onboard oceanographic measurements were taken that can be compared with surface cast CTD profiles obtained during AUV deployment, including locations with subglacial discharges. The AUV test provides details on the geometry of the morainal bank and nature of the fjord wall surfaces. The decimeter-scale imagery of the seabed reveals numerous erosional and depositional bedforms and gravitational features on the morainal bank's proximal slope. Closer to the ice face, the morainal bank surface appears much coarser, with textural patterns of unknown origin, and gravel lags including boulder fields. Comparing the water depth from the AUV survey with that of NOAA bathymetric data from 2004/2006 shows the morainal bank continued to advance in pace with ice advance into fjord waters over 200m deep, water depths shoaling up to 100m near the present ice margin. The glimpse of the morainal bank afforded by the AUV test clearly demonstrated the value of this technology to ice marginal submarine investigations.

  15. Composition and sources of atmospheric dusts in snow at 3200 meters in the St. Elias Range, southeastern Alaska, USA

    USGS Publications Warehouse

    Hinkley, T.K.

    1994-01-01

    Dusts in snow from the accumulation zone in the St. Elias Range appear from their chemical compositions to have come from terranes of rocks of ferromagnesian composition. These dusts, with respect to their composition and to the moderate degree of variation that occurs through a depositional year, are similar those deposited in Greenland. The high portion of the St. Elias Range is isolated from dominance by any local dust source terranes, because of altitude and the extent of the surrounding glacierized and snow-covered region. In Greenland the altitude is typically lower, but local sources are even less likely to dominate the character of the dusts deposited into the ice record there. The similar compositions and moderate compositional variations of dusts from these two places bear on the question of whether the dusts that are transported over long distances by the atmosphere under modern and glacial-period conditions are uniform and representative of a broad regional or even hemispheric background dust. The dusts in the snow were measured by means of a suite of major, minor, and trace rock-forming metals chosen to give information about rock types, their constituent minerals, degree of degradation (weathering), and energies of atmospheric uptake from source. The variations in amounts of rock dust through the year in the St. Elias Range snowpack have no time-stratigraphic correspondence to the also large variations in concentrations of other species that are not constituents of rock-derived dusts, such the anions chloride, sulfate, and nitrate; the highs and lows of the two types of materials are apparently completely independent. The structure revealed by the moderately fine-scale sampling of the present study (??? 10 increments/y) serves as a background for the interpretation of analysis of ice core samples, in which annual layers may be too compressed to permit analysis of sub-annual samples. ?? 1994.

  16. Composition and sources of atmospheric dusts in snow at 3200 meters in the St. Elias Range, southeastern Alaska, USA

    SciTech Connect

    Hinkley, T.K. )

    1994-08-01

    Dusts in snow from the accumulation zone in the St. Elias Range appear from their chemical compositions to have come from terranes of rocks of ferromagnesian composition. These dusts, with respect to their composition and to the moderate degree of variation that occurs through a depositional year, are similar to those deposited in Greenland. The high portion of the St. Elias Range is isolated from dominance by any local dust source terranes, because of altitude and the extent of the surrounding glacierized and snow-covered region. In Greenland the altitude is typically lower, but local sources are even less likely to dominate the character of the dusts deposited into the ice record there. The similar compositions and moderate compositional variations of dusts from these two places bear on the question of whether the dusts that are transported over long distances by the atmosphere under modern and glacial-period conditions are uniform and representative of a broad regional or even hemispheric background dust. The dusts in the snow were measured by means of a suite of major, minor, and track rock-forming metals chosen to give information about rock types, their constituent minerals, degree of degradation (weathering), and energies of atmospheric uptake from source. The variations in amounts of rock dust through the year in the St. Elias Range snowpack have no time-stratigraphic correspondence to the also-large variations in concentrations of other species that are not constituents of rock-derived dusts, such the anions chloride, sulfate, and nitrate; the highs and lows of the two types of materials are apparently completely independent. The structure revealed by the moderately fine-scale sampling of the present study ([approximately]10 increments/y) serves as a background for the interpretation of analysis of ice core samples, in which annual layers may be too compressed to permit analysis of sub-annual samples.

  17. Deformation and the timing of gas generation and migration in the eastern Brooks Range foothills, Arctic National Wildlife Refuge, Alaska

    USGS Publications Warehouse

    Parris, T.M.; Burruss, R.C.; O'Sullivan, P. B.

    2003-01-01

    Along the southeast border of the 1002 Assessment Area in the Arctic National Wildlife Refuge, Alaska, an explicit link between gas generation and deformation in the Brooks Range fold and thrust belt is provided through petrographic, fluid inclusion, and stable isotope analyses of fracture cements integrated with zircon fission-track data. Predominantly quartz-cemented fractures, collected from thrusted Triassic and Jurassic rocks, contain crack-seal textures, healed microcracks, and curved crystals and fluid inclusion populations, which suggest that cement growth occurred before, during, and after deformation. Fluid inclusion homogenization temperatures (175-250??C) and temperature trends in fracture samples suggest that cements grew at 7-10 km depth during the transition from burial to uplift and during early uplift. CH4-rich (dry gas) inclusions in the Shublik Formation and Kingak Shale are consistent with inclusion entrapment at high thermal maturity for these source rocks. Pressure modeling of these CH4-rich inclusions suggests that pore fluids were overpressured during fracture cementation. Zircon fission-track data in the area record postdeposition denudation associated with early Brooks Range deformation at 64 ?? 3 Ma. With a closure temperature of 225-240??C, the zircon fission-track data overlap homogenization temperatures of coeval aqueous inclusions and inclusions containing dry gas in Kingak and Shublik fracture cements. This critical time-temperature relationship suggests that fracture cementation occurred during early Brooks Range deformation. Dry gas inclusions suggest that Shublik and Kingak source rocks had exceeded peak oil and gas generation temperatures at the time structural traps formed during early Brooks Range deformation. The timing of hydrocarbon generation with respect to deformation therefore represents an important exploration risk for gas exploration in this part of the Brooks Range fold and thrust belt. The persistence of gas high at

  18. Pingos in the Brooks Range, northern Alaska, U.S.A.

    USGS Publications Warehouse

    Hamilton, T.D.; Obi, Curtis M.

    1982-01-01

    Some 70 pingos occur at 27 separate localities within and near the Brooks Range. The pingos are distributed through mountain valleys at altitudes up to 725m and in terrain glaciated as recently as late Wisconsinan time. Pingos are particularly abundant in the Koyukuk and Chandalar drainage systems of the south-central Brooks Range, where they may be associated with structural features of regional extent.-from Authors

  19. Ocean Observing System Demonstrated in Alaska

    NASA Astrophysics Data System (ADS)

    Schoch, G. Carl; Chao, Yi

    2010-05-01

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

  20. Seismic images of the Brooks Range fold and thrust belt, Arctic Alaska, from an integrated seismic reflection/refraction experiment

    USGS Publications Warehouse

    Levander, A.; Fuis, G.S.; Wissinger, E.S.; Lutter, W.J.; Oldow, J.S.; Moore, T.E.

    1994-01-01

    We describe results of an integrated seismic reflection/refraction experiment across the Brooks Range and flanking geologic provinces in Arctic Alaska. The seismic acquisition was unusual in that reflection and refraction data were collected simultaneously with a 700 channel seismograph system deployed numerous times along a 315 km profile. Shot records show continuous Moho reflections from 0-180 km offset, as well as numerous upper- and mid-crustal wide-angle events. Single and low-fold near-vertical incidence common midpoint (CMP) reflection images show complex upper- and middle-crustal structure across the range from the unmetamorphosed Endicott Mountains allochthon (EMA) in the north, to the metamorphic belts in the south. Lower-crustal and Moho reflections are visible across the entire reflection profile. Travel-time inversion of PmP arrivals shows that the Moho, at 33 km depth beneath the North Slope foothills, deepens abruptly beneath the EMA to a maximum of 46 km, and then shallows southward to 35 km at the southern edge of the range. Two zones of upper- and middle-crustal reflections underlie the northern Brooks Range above ~ 12-15 km depth. The upper zone, interpreted as the base of the EMA, lies at a maximum depth of 6 km and extends over 50 km from the range front to the north central Brooks Range where the base of the EMA outcrops above the metasedimentary rocks exposed in the Doonerak window. We interpret the base of the lower zone, at ~ 12 km depth, to be from carbonate rocks above the master detachment upon which the Brooks Range formed. The seismic data suggest that the master detachment is connected to the faults in the EMA by several ramps. In the highly metamorphosed terranes south of the Doonerak window, the CMP section shows numerous south-dipping events which we interpret as a crustal scale duplex involving the Doonerak window rocks. The basal detachment reflections can be traced approximately 100 km, and dip southward from about 10-12 km

  1. Inventory of Glaciers in the North Cascades, Washington

    USGS Publications Warehouse

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

    1971-01-01

    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.

  2. Glacier-derived August runoff in northwest Montana

    USGS Publications Warehouse

    Clark, Adam; Harper, Joel T.; Fagre, Daniel B.

    2015-01-01

    The second largest concentration of glaciers in the U.S. Rocky Mountains is located in Glacier National Park (GNP), Montana. The total glacier-covered area in this region decreased by ∼35% over the past 50 years, which has raised substantial concern about the loss of the water derived from glaciers during the summer. We used an innovative weather station design to collect in situ measurements on five remote glaciers, which are used to parameterize a regional glacier melt model. This model offered a first-order estimate of the summer meltwater production by glaciers. We find, during the normally dry month of August, glaciers in the region produce approximately 25 × 106 m3 of potential runoff. We then estimated the glacier runoff component in five gaged streams sourced from GNP basins containing glaciers. Glacier-melt contributions range from 5% in a basin only 0.12% glacierized to >90% in a basin 28.5% glacierized. Glacier loss would likely lead to lower discharges and warmer temperatures in streams draining basins >20% glacier-covered. Lower flows could even be expected in streams draining basins as little as 1.4% glacierized if glaciers were to disappear.

  3. Operation IceBridge Alaska

    NASA Astrophysics Data System (ADS)

    Larsen, C.

    2015-12-01

    The University of Alaska Fairbanks (UAF) has flown LiDAR missions for Operation IceBridge in Alaska each year since 2009, expanding upon UAF's airborne laser altimetry program which started in 1994. These observations show that Alaska's regional mass balance is -75+11/-16 Gt yr-1 (1994-2013) (Larsen et al., 2015). A surprising result is that the rate of surface mass loss observed on non-tidewater glaciers in Alaska is extremely high. At these rates, Alaska contributes ~1 mm to global sea level rise every 5 years. Given the present lack of adequate satellite resources, Operation IceBridge airborne surveys by UAF are the most effective and efficient method to monitor this region's impact on global sea level rise. Ice depth measurements using radar sounding have been part of these airborne surveys since 2012. Many of Alaska's tidewater glaciers are bedded significantly below sea level. The depth and extent of glacier beds below sea level are critical factors in the dynamics of tidewater retreat. Improved radar processing tools are being used to predict clutter using forward simulation. This is essential to properly sort out true bed returns, which are often masked or obscured by valley wall returns. This presentation will provide an overview of the program, highlighting recent findings and observations from the most recent campaigns, and focusing on techniques used for the extrapolation of surface elevation changes to regional mass balances.

  4. Sedimentology and stratigraphy of the Kanayut Conglomerate, central and western Brooks Range, Alaska; report of 1981 field season

    USGS Publications Warehouse

    Nilsen, T.H.; Moore, T.E.

    1982-01-01

    The Upper Devonian and Lower Mississippian(?) Kanayut Conglomerate forms a major stratigraphic unit along the crest of the Brooks Range of northern Alaska. It crops out for an east-west distance of about 900 km and a north-south distance of about 65 km. The Kanayut is wholly allochthonous and has probably been transported northward on a series of thrust plates. The Kanayut is as thick as 2,600 m in the east-central Brooks Range. It thins and fines to the south and west. The Kanayut forms the middle part of the allochthonous sequence of the Endicott Group, an Upper Devonian and Mississippian clastic sequence underlain by platform limestones of the Baird Group and overlain by platform limestone, carbonaceous shale, and black chert of the Lisburne Group. The Kanayut overlies the marine Upper Devonian Noatak Sandstone or, where it is missing, the marine Upper Devonian Hunt Fork Shale. It is overlain by the marine Mississippian Kayak Shale. The Kanayut Conglomerate forms the fluvial part of a large, coarse-grained delta that prograded to the southwest in Late Devonian time and retreated in Early Mississippian time. Four sections of the Kanayut Conglomerate in the central Brooks Range and five in the western Brooks Range were measured in 1981. The sections from the western Brooks Range document the presence of fluvial cycles in the Kanayut as far west as the shores of the Chukchi Sea. The Kanayut in this area is generally finer grained than it is in the central and eastern Brooks Range, having a maximum clast size of 3 cm. It is probably about 300 m thick. The upper and lower contacts of the Kanayut are gradational. The lower Kanayut contains calcareous, marine-influenced sandstone within channel deposits, and the upper Kanayut contains probable marine interdistributary-bay shale sequences. The members of the Kanayut Conglomerate cannot be differentiated in this region. In the central Brooks Range, sections of the Kanayut Conglomerate at Siavlat Mountain and Kakivilak

  5. Lisburne Group (Mississippian-Lower Permian) petrography, paragenesis, and hydrocarbon potential, central Brooks Range, Alaska

    SciTech Connect

    Krutak, P.R.

    1989-03-01

    Subsurface Lisburne Group (Wahoo) rocks at Prudhoe Bay-Kuparuk fields produce 2 million bbl of oil/day and contain 2-3 billion bbl of oil in place. Lisburne reservoirs are early diagenetic dolomites encased in thick platform carbonates. Petrographic and geochemical study of 264 samples from eight newly discovered surface Lisburne sections comprising 4568 ft of strata in the Central Brooks Range provide new data concerning paragenesis and hydrocarbon potential of Lisburne facies farther west. A generalized paragenetic sequence for Lisburne equivalents of this region is (1) initial carbonate skeletal growth (both aragonite and calcite) during the Carboniferous, (2) subsequent recrystallization and inversion of aragonite to calcite, the change to calcite proceeding throughout late Paleozoic and Permian-Triassic time, (3) dolomitization in the Middle and Late Carboniferous, (4) chertification and silicification, postdating slightly or overlapping dolomitization, (5) development of porosity (moldic, intracrystal, etc.) in the middle to late Mesozoic, (6) formation of fracture porosity concurrent with the Brooks Range orogeny during Middle Jurassic-Cretaceous time, (7) oil generation, migration, and emplacement in Late Cretaceous-Tertiary time. Lisburne dolomites from the Central Brooks Range bear heavy hydrocarbons. Rock-Eval pyrolysis indicates part of the section is in the oil window and near the peak wet-gas generation zone. Shale samples from this region display thermal alteration indices and vitrinite reflectance values near the oil floor and also indicate potential for sourcing dry gas. Conodont color alteration indices show part of the Lisburn could produce dry gas.

  6. Facies comparison of autochthonous and allochthonous Permian and Triassic units, north-central Brooks Range, Alaska

    SciTech Connect

    Adams, K.E.

    1985-04-01

    Eight stratigraphic sections of Permian and Triassic rocks have been studied over a 30 km by 150 km area in the Endicott and Philip Smith Mountains of the central Brooks Range. Six of the sections are located on the Endicott Mountains allochthon, and the remaining two are parautochthonous columns in the Mount Doonerak area. The sections record a facies transition between the autochthonous Sadlerochit Group and Shublik Formation of the northeastern Brooks Range and the characteristically siliceous rocks of the allochthonous Siksikpuk and Otuk formations of the western Brooks Range. Laterally continuous and bioturbated beds of fine-grained sandstone, siltstone, and shale dominantly compose the Permian sequence, whereas the Triassic rocks consist of black shales, thin rhythmically bedded siliceous mudstones, and fossiliferous limestones. When the allochthonous sections are restored to a position south of the Mount Doonerak area, a general shallowing trend from southwest to northwest becomes evident within the reconstructed marine basin. To the south and west, the Permian sediments show a marked increase in silica content, with the occurrence of barite and a corresponding decrease in the thickness of the basal, coarser grained clastics. The Triassic formations also document an increase in silica and the presence of barite to the south and west, while becoming significantly sooty and phosphatic to the north and east. Ongoing petrographic and micropaleontologic studies of the field data will clarify these general paleogeographic relationships.

  7. Structure, metamorphism, and geochronology of the Cosmos Hills and Ruby Ridge, Brooks Range schist belt, Alaska

    USGS Publications Warehouse

    Christiansen, Peter B.; Snee, Lawrence W.

    1994-01-01

    The boundary of the internal zones of the Brooks Range orogenic belt (the schist belt) is a fault contact that dips toward the hinterland (the Yukon-Koyukuk province). This fault, here referred to as the Cosmos Hills fault zone, juxtaposes oceanic rocks and unmetamorphosed sedimentary rocks structurally above blueschist-to-greenschist facies metamorphic rocks of the schist belt. Near the fault contact, schist belt rocks are increasingly affected by a prominent, subhorizontal transposition foliation that is locally mylonitic in the fault zone. Structural and petrologic observations combined with 40Ar/39Ar incremental-release geochronology give evidence for a polyphase metamorphic and deformational history beginning in the Middle Jurassic and continuing until the Late Cretaceous. Our 40Ar/39Ar cooling age for Jurassic metamorphism is consistent with stratigraphic and other evidence for the onset of Brooks Range orogenesis. Jurassic metamorphism is nearly everywhere overprinted by a regional greenschist-facies event dated at 130–125 Ma. Near the contact with the Cosmos Hills fault zone, the schist belt is increasingly affected by a younger greenschist metamorphism that is texturally related to a prominent foliation that folds and transposes an older fabric. The 40Ar/39Ar results on phengite and fuchsite that define this younger fabric give recrystallization ages ranging from 103 to less than 90 Ma. We conclude that metamorphism that formed the transposition fabric peaked around 100 Ma and may have continued until well after 90 Ma. This age for greenschist metamorphism is broadly synchronous with the depositional age of locally derived, shallow-marine clastic sedimentary strata in the hanging wall of the fault zone and thus substantiates the interpretation that the fault zone accommodated extension in the Late Cretaceous. This extension unroofed and exhumed the schist belt during relative subsidence of the Yukon-Koyukuk province.

  8. Sandia National Laboratories land use permit for operations at Oliktok Alaska Long Range Radar Station.

    SciTech Connect

    Catechis, Christopher Spyros

    2013-02-01

    The property subject to this Environmental Baseline Survey (EBS) is located at the Oliktok Long Range Radar Station (LRRS). The Oliktok LRRS is located at 70À 30 W latitude, 149À 53 W longitude. It is situated at Oliktok Point on the shore of the Beaufort Sea, east of the Colville River. The purpose of this EBS is to document the nature, magnitude, and extent of any environmental contamination of the property; identify potential environmental contamination liabilities associated with the property; develop sufficient information to assess the health and safety risks; and ensure adequate protection for human health and the environment related to a specific property.

  9. Structural provinces of the northeastern Brooks Range, Arctic National Wildlife Refuge, Alaska

    SciTech Connect

    Wallace, W.K.; Hanks, C.L. )

    1990-07-01

    The dominant Cenozoic structures of the northeastern Brooks Range are anticlinoria with cores of sub-Mississippian rocks, reflecting a regional north-vergent duplex with a floor thrust in the sub-Mississippian sequence and a roof thrust in the Mississippian Kayak Shale. The number of horses forming each anticlinorium and the structural style of the overlying Mississippian and younger cover sequence varies regionally, providing a basis for dividing the northeastern Brooks Range into structural provinces. In the western province, each anticlinorium contains a single horse, and shortening above the Kayak Shale was accommodated mainly by detachment folds. To the north in the Sadlerochit Mountains, the Kayak Shale is depositionally discontinuous and rocks elsewhere separated by this detachment deformed together. In the eastern province, each anticlinorium contains multiple horses, and shortening above the Kayak Shale was accommodated largely by thrust duplication of Mississippian through Triassic rocks. In the narrow central province, the Devonian Okpilak batholith was detached from its roots, internally shortened along shear zones and by penetrative strain, and transported northward. Because the Kayak Shale is locally absent, the Mississippian and younger cover sequence deformed in part penetratively along with the batholith. 13 figs.

  10. A gravity study of the northern part of the Arctic National Wildlife Range, Alaska

    USGS Publications Warehouse

    Kososki, B.A.; Reiser, H.N.; Cavit, C.D.; Detterman, R.L.

    1978-01-01

    Interpretation of all publicly available onshore gravity data provides a basis for outlining regional elements of the basement and overlying structure in the northern part of the Arctic National Wildlife Range. Major post-Carboniferous sedimentary basins whose centers lie offshore on the Beaufort Shelf extend onshore in the northern part of the study area. There is strong evidence that dense basement rocks beneath these onshore extensions rise to relatively shallow depths along the northeast Alaskan coast. Geologic studies and interpretation of the gravity data indicate that the gross structural and stratigraphic framework of this area is similar to that of the Prudhoe Bay region to the west. A high potential for petroleum accumulation in the Wildlife Range is indicated by the surface presence of oil seeps, oil sands, and outcrops of reservoir and source rocks along the southern margins of the onshore basinal areas. Present data suggest that the greatest potential for onshore accumulations of hydrocarbons lies in the area south and east of Barter Island and that possibilities exist there for commercially substantial reserves. The potential of this area cannot be fully assessed, however, until the subsurface extent of several major unconformities is known. Unfortunately, gravity data alone are of little use in such determinations. South of the mountain front, large granitic intrusions are marked by a sharply defined gravity minimum. The subsurface distribution of these bodies could probably be mapped by detailed gravity surveys. Detailed aeromagnetic surveys should serve equally well for such a purpose.

  11. The Cenozoic structural evolution of a fold-and-thrust belt, northeastern Brooks Range, Alaska

    SciTech Connect

    Hanks, C.L. )

    1993-03-01

    A Cenozoic fold-and-thrust belt in the eastern structural province of the northeastern Brooks Range exposes polydeformed low-grade metasedimentary and metavolcanic rocks of the pre-Mississippian basement and its sedimentary cover immediately adjacent to much younger foredeep deposits. Analysis of mesoscopic and map-scale structures in the range-front region suggests that at least one pre-Mississippian deformational event was recorded into the basement sequence by north-vergent fold-and-thrust structures and associated penetrative structures. Most of later Cenozoic shortening of the pre-Mississippian rocks was accommodated by thrust duplication, with little development of penetrative mesoscopic structures. Although separated from the underlying basement rocks by a major regional decollement horizon, Cenozoic deformation in the overlying Mississippian through Lower Cretaceous cover sequence also was primarily by thrust duplication. Although local and regional structural trends within the cover sequence suggest that Cenozoic deformation was north-northwest directed, east-west Cenozoic structural trends within the pre-Mississippian rocks may reflect an inherited pre-Mississippian structural grain and/or pre-Mississippian-age structures reactivated during Cenozoic deformation. A regional balanced cross section of the eastern structural province was constructed. 29 refs., 14 figs.

  12. POP and PAH contamination in the southern slopes of Mt. Everest (Himalaya, Nepal): Long-range atmospheric transport, glacier shrinkage, or local impact of tourism?

    PubMed

    Guzzella, Licia; Salerno, Franco; Freppaz, Michele; Roscioli, Claudio; Pisanello, Francesca; Poma, Giulia

    2016-02-15

    Due to their physico-chemical properties, POPs and PAHs are subjected to long-range atmospheric transport (LRAT) and may be deposited in remote areas. In this study, the contamination with DDx, PCBs, PBDEs, and PAHs was investigated in sediments and soils collected on the southern slopes of Mt. Everest (Himalaya, Nepal) in two different sampling campaigns (2008 and 2012). The results showed a limited contamination with POPs and PAHs in both soil and sediment samples. Therefore, the southern slopes of Mt. Everest can be considered a remote area in almost pristine condition. The LRAT mechanism confirmed its primary role in the transfer of contaminants to remote regions, while the gradual melting of glaciers, due to global warming, and the subsequent release of contaminants was suggested to be a secondary source of pollution of the lake sediments. In addition, the increase of tourism in this area during the last decades might have influenced the present concentrations of PAHs in the sediments and soils.

  13. Jakobshavn Glacier

    Atmospheric Science Data Center

    2013-04-17

    ... 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 ...

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    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.

  15. Estimated range of black carbon dry deposition and the related snow albedo reduction over Himalayan glaciers during dry pre-monsoon periods

    NASA Astrophysics Data System (ADS)

    Yasunari, Teppei J.; Tan, Qian; Lau, K.-M.; Bonasoni, Paolo; Marinoni, Angela; Laj, Paolo; Ménégoz, Martin; Takemura, Toshihiko; Chin, Mian

    2013-10-01

    One of the major factors attributed to the accelerated melting of Himalayan glaciers is the snow darkening effect of atmospheric black carbon (BC). The BC is the result of incomplete fossil fuel combustion from sources such as open biomass burning and wood burning cooking stoves. One of the key challenges in determining the darkening effect is the estimation uncertainty of BC deposition (BCD) rate on surface snow cover. Here we analyze the variation of BC dry deposition in seven different estimates based on different dry deposition methods which include different atmospheric forcings (observations and global model outputs) and different spatial resolutions. The seven simulations are used to estimate the uncertainty range of BC dry deposition over the southern Himalayas during pre-monsoon period (March-May) in 2006. Our results show BC dry deposition rates in a wide range of 270-4700 μg m-2 during the period. Two global models generate higher BC dry deposition rates due to modeled stronger surface wind and simplification of complicated sub-grid surface conditions in this region. Using ice surface roughness and observation-based meteorological data, we estimate a better range of BC dry deposition rate of 900-1300 μg m-2. Under dry and highly polluted conditions, aged snow and sulfate-coated BC are expected to possibly reduce visible albedo by 4.2-5.1%. Our results suggest that for estimating aerosol-induced snow darkening effects of Himalaya snowpacks using global and regional models, realistic physical representation of ice or snow surface roughness and surface wind speed are critical in reducing uncertainties on the estimate of BC deposition over snow surface.

  16. High fidelity does not preclude colonization: range expansion of molting Black Brant on the Arctic coast of Alaska

    USGS Publications Warehouse

    Flint, Paul L.; Meixell, Brandt W.; Mallek, Edward J.

    2014-01-01

    High rates of site fidelity have been assumed to infer static distributions of molting geese in some cases. To test this assumption, we examined movements of individually marked birds to understand the underlying mechanisms of range expansion of molting Black Brant (Branta bernicla nigricans) on the Arctic Coastal Plain (ACP) of Alaska. The Teshekpuk Lake Special Area (TLSA) on the ACP was created to protect the primary molting area of Brant. When established in 1977, the TLSA was thought to include most, if not all, wetlands used by molting Brant on the ACP. From 2010 to 2013, we surveyed areas outside the TLSA and counted an average of 9800 Brant per year, representing 29–37% of all molting Brant counted on the ACP. We captured and banded molting Brant in 2011 and 2012 both within the TLSA and outside the TLSA at the Piasuk River Delta and Cape Simpson to assess movements of birds among areas across years. Estimates of movement rates out of the TLSA exceeded those into the TLSA, demonstrating overall directional dispersal. We found differences in sex and age ratios and proportions of adult females with brood patches, but no differences in mass dynamics for birds captured within and outside the TLSA. Overall fidelity rates to specific lakes (0.81, range = 0.49–0.92) were unchanged from comparable estimates obtained in the early 1990s. We conclude that Brant are dispersing from the TLSA into new molting areas while simultaneously redistributing within the TLSA, likely as a consequence of changes in relative habitat quality. Shifts in distribution resulted from colonization of new areas by young birds as well as low levels of directional dispersal of birds that previously molted in the TLSA. Based on combined counts, the overall number of molting Brant across the ACP has increased substantially.

  17. Late Mesozoic and Cenozoic thermotectonic evolution of the central Brooks Range and adjacent North Slope foreland basin, Alaska: Including fission track results from the Trans-Alaska Crustal Transect (TACT)

    USGS Publications Warehouse

    O'Sullivan, P. B.; Murphy, J.M.; Blythe, A.E.

    1997-01-01

    Apatite fission track data are used to evaluate the thermal and tectonic history of the central Brooks Range and the North Slope foreland basin in northern Alaska along the northern leg of the Trans-Alaska Crustal Transect (TACT). Fission track analyses of the detrital apatite grains in most sedimentary units resolve the timing of structures and denudation within the Brooks Range, ranging in scale from the entire mountain range to relatively small-scale folds and faults. Interpretation of the results indicates that rocks exposed within the central Brooks Range cooled rapidly from paleotemperatures 110?? to 50??C during discrete episodes at ???100??5 Ma, ???60??4 Ma, and ???24??3 Ma, probably in response to kilometer-scale denudation. North of the mountain front, rocks in the southern half of the foreland basin were exposed to maximum paleotemperatures 110??C in the Late Cretaceous to early Paleocene as a result of burial by Upper Jurassic and Cretaceous sedimentary rocks. Rapid cooling from these elevated paleotemperatures also occurred due to distinct episodes of kilometer-scale denudation at ???60??4 Ma, 46??3 Ma, 35??2 Ma, and ???24??3 Ma. Combined, the apatite analyses indicate that rocks exposed along the TACT line through the central Brooks Range and foreland basin experienced episodic rapid cooling throughout the Late Cretaceous and Cenozoic in response to at least three distinct kilometer-scale denudation events. Future models explaining orogenic events in northern Alaska must consider these new constraints from fission track thermochronology. Copyright 1997 by the American Geophysical Union.

  18. Lateral continuity of the Blarney Creek Thrust, Doonerak Windown, Central Brooks Range, Alaska

    SciTech Connect

    Seidensticker, C.M.; Julian, F.E.; Phelps, J.C.; Oldow, J.S.; Avellemant, H.G.

    1985-04-01

    The contact between Carboniferous and lower Paleozoic rocks, exposed along the northern margin of the Doonerak window in the central Brooks Range, is a major thrust fault called the Blarney Creek thrust (BCT). The BCT has been traced over a distance of 25 km, from Falsoola Mountain to Wien Mountain. The tectonic nature of this contact is demonstrated by: (1) omission of stratigraphic units above and below the BCT; (2) large angular discordance in orientation of first-generation cleavage at the BCT; (3) numerous thrust imbricates developed in the upper-plate Carboniferous section that sole into the BCT; and (4) truncation of an upper-plate graben structure at the BCT. Lack of evidence for pre-Carboniferous deformation in the lower plate casts doubt on the interpretation of the contact as an angular unconformity. However, the localized presence below the BCT of Mississippian Kekiktuk Conglomerate and Kayak Shale, in apparent depositional contact with lower Paleozoic rocks, suggests that the BCT follows an originally disconformable contact between the Carboniferous and lower Paleozoic rocks. The juxtaposition of younger over older rocks at the BCT is explained by calling upon the BCT to act as the upper detachment surface of a duplex structure. Duplex development involves initial imbrication of the Carboniferous section using the BCT as a basal decollement, followed by formation of deeper thrusts in the lower Paleozoic section, which ramp up and merge into the BCT.

  19. The crustal section of the Siniktanneyak Mountain ophiolite, Brooks Range, Alaska

    SciTech Connect

    Bickerstaff, D.; Harris, R.A.; Miller, M.A. . Dept. of Geology and Geography)

    1993-04-01

    Fragments of the upper crustal section of the Brooks Range Ophiolite on the west flank of Siniktanneyak Mountain expose important contact relations and paleohorizontal indicators. The nearly complete crustal sequence faces northwest. Based on field observations, the crustal units encountered at Siniktanneyak Mountain from bottom to top are: (1) layered gabbro, (2) isotropic gabbro, (3) high level and late-stage intrusions of diorite and diabase, (4) rare sheeted dikes, (5) basalt, and (6) a bedded volcanic tuff. Potassium feldspar-bearing pegmatites are also found. Of particular interest is the orientation of the layered gabbro, sheeted dikes, and the bedded volcanic tuff. The steeply dipping gabbro layers strike N-S, the adjacent vertical sheeted dikes strike NE-SW. Bedded volcanic tuff and lavas are flat lying. Contacts within the upper crust units are often covered by talus. Contacts between various plutonic rocks are both sharp and gradational, suggesting syn- and post-cooling intrusions. Contacts between plutonic rock and higher volcanic rock appear to be fault contacts.

  20. Plutonic rocks of Jurassic age in the Alaska-Aleutian Range batholith: chemical variation and polarity.

    USGS Publications Warehouse

    Reed, B.I.; Miesch, A.T.; Lanphere, M.A.

    1983-01-01

    Plutonic rocks of Jurassic age exposed on the Pacific side of this batholith form a compositionally continuous calc-alkaline suite that ranges from hornblende gabbro to quartz monzonite. Tonalite and quartz diorite are the dominant rock types. Trend-surface analysis of 102 samples indicates that the direction of slope of the trend is approximately normal to the Jurassic magmatic arc. K2O and SiO2 increase towards the E-SE and the other oxides towards the W-NW. If the chemical trends reflect the approximate geometry of a palaeo-subduction zone, the polarity of the Jurassic magmatic arc is to the NW, i.e. subduction was directed towards the SE. Thus the palaeo-subduction zone is on the opposite side of the arc from the position that has generally been assumed, indicating that the Jurassic plutonic rocks were not generated in response to classical Andean-type convergent plate margins. The magmatic arc may have been formed in an intra-ocean environment and subsequently has been rafted northwards and accreted to this part of the N Pacific rim during the late Mesozoic. Middle and Upper Jurassic clastics underlying Cook Inlet to the SE and derived from the magmatic arc are classified as back-arc deposits, rather than as an arc-trench gap sequence.-L.C.H.

  1. Multistory duplexes with forward dipping roofs, north central Brooks Range, Alaska

    USGS Publications Warehouse

    Wallace, W.K.; Moore, T.E.; Plafker, G.

    1997-01-01

    The Endicott Mountains allochthon has been thrust far northward over the North Slope parautochthon in the northern Brooks Range. Progressively younger units are exposed northward within the allochthon. To the south, the incompetent Hunt Fork Shale has thickened internally by asymmetric folds and thrust faults. Northward, the competent Kanayut Conglomerate forms a duplex between a floor thrust in Hunt Fork and a roof thrust in the Kayak Shale. To the north, the competent Lisburne Group forms a duplex between a floor thrust in Kayak and a roof thrust in the Siksikpuk Formation. Both duplexes formed from north vergent detachment folds whose steep limbs were later truncated by south dipping thrust faults that only locally breach immediately overlying roof thrusts. Within the parautochthon, the Kayak, Lisburne, and Siksikpuk-equivalent Echooka Formation form a duplex identical to that in the allochthon. This duplex is succeeded abruptly northward by detachment folds in Lisburne. These folds are parasitic to an anticlinorium interpreted to reflect a fault-bend folded horse in North Slope "basement," with a roof thrust in Kayak and a floor thrust at depth. These structures constitute two northward tapered, internally deformed wedges that are juxtaposed at the base of the allochthon. Within each wedge, competent units have been shortened independently between detachments, located mainly in incompetent units. The basal detachment of each wedge cuts upsection forward (northward) to define a wedge geometry within which units dip regionally forward. These dips reflect forward decrease in internal structural thickening by forward vergent folds and hindward dipping thrust faults. Copyright 1997 by the American Geophysical Union.

  2. Structure and petrology of the La Perouse gabbro intrusion, Fairweather Range, southeastern Alaska.

    USGS Publications Warehouse

    Loney, R.A.; Himmelberg, G.R.

    1983-01-01

    The gabbro was intruded during the Middle Tertiary into a Mesozoic granulite-facies metamorphic environment dominated by strike-slip fault movement, compression and possible minor subduction. The asymmetric funnel form of the intrusion is due to subsidence from magmatic loading at high T, coupled with control from pre-existing structures, and not from tectonic compression. The intrusion is 12 X 27 km and has exposed cumulate layering of approx 6000 m. Probe analyses of olivines (24), Ca-poor pyroxenes (28), augites (22) and plagioclases (35) are tabulated. Cumulus mineral compositions in the basal cumulates are: olivine Fo86-71, plagioclase An81-63, bronzite Ca3Mg82Fe15 - Ca4Mg75Fe21, augite Ca45Mg47Fe8 - Ca42Mg48Fe10. The layered gabbro above the basal cumulates consists dominantly of lenticularly interlayered plagioclase-augite-orthopyroxene-olivine, plagioclase-augite- olivine and plagioclase-orthopyroxene-augite cumulates, the composition ranges being olivine Fo75-50, plagioclase An78-42, orthopyroxene and inverted pigeonite Ca2.8Mg76.4Fe20.8 - Ca1.4Mg31.0Fe67.6, augite Ca43.1Mg46.9Fe10.0 - Ca40.5Mg27.1Fe32.4. The most iron-rich pyroxene and albite-rich plagioclase occur in a zone near the margin of the intrusion and are probably related to exchange reactions with the country rock. It is considered that the gabbro did not accumulate by simple fractional crystallization of a single or even several large batches of magma, but by numerous influxes of previously fractionated magma from a deeper reservoir. Conditions of crystallization are interpreted as approx 1055oC, 5.4 kbar and fO2 near the wustite-magnetite buffer.-R.A.H.

  3. Multistory duplexes with forward dipping roofs, north central Brooks Range, Alaska

    NASA Astrophysics Data System (ADS)

    Wallace, Wesley K.; Moore, Thomas E.; Plafker, George

    1997-01-01

    The Endicott Mountains allochthon has been thrust far northward over the North Slope parautochthon in the northern Brooks Range. Progressively younger units are exposed northward within the allochthon. To the south, the incompetent Hunt Fork Shale has thickened internally by asymmetric folds and thrust faults. Northward, the competent Kanayut Conglomerate forms a duplex between a floor thrust in Hunt Fork and a roof thrust in the Kayak Shale. To the north, the competent Lisburne Group forms a duplex between a floor thrust in Kayak and a roof thrust in the Siksikpuk Formation. Both duplexes formed from north vergent detachment folds whose steep limbs were later truncated by south dipping thrust faults that only locally breach immediately overlying roof thrusts. Within the parautochthon, the Kayak, Lisburne, and Siksikpuk-equivalent Echooka Formation form a duplex identical to that in the allochthon. This duplex is succeeded abruptly northward by detachment folds in Lisburne. These folds are parasitic to an anticlinorium interpreted to reflect a fault-bend folded horse in North Slope "basement," with a roof thrust in Kayak and a floor thrust at depth/These structures constitute two northward tapered, internally deformed wedges that are juxtaposed at the base of the allochthon. Within each wedge, competent units have been shortened independently between detachments, located mainly in incompetent units. The basal detachment of each wedge cuts upsection forward (northward) to define a wedge geometry within which units dip regionally forward. These dips reflect forward decrease in internal structural thickening by forward vergent folds and hindward dipping thrust faults.

  4. A Storm-by-Storm Analysis of Alpine and Regional Precipitation Dynamics at the Mount Hunter Ice Core Site, Denali National Park, Central Alaska Range

    NASA Astrophysics Data System (ADS)

    Saylor, P. L.; Osterberg, E. C.; Kreutz, K. J.; Wake, C. P.; Winski, D.

    2014-12-01

    In May-June 2013, an NSF-funded team from Dartmouth College and the Universities of Maine and New Hampshire collected two 1000-year ice cores to bedrock from the summit plateau of Mount Hunter in Denali National Park, Alaska (62.940291, -151.087616, 3912 m). The snow accumulation record from these ice cores will provide key insight into late Holocene precipitation variability in central Alaska, and compliment existing precipitation paleorecords from the Mt. Logan and Eclipse ice cores in coastal SE Alaska. However, correct interpretation of the Mt. Hunter accumulation record requires an understanding of the relationships between regional meteorological events and micrometeorological conditions at the Mt. Hunter ice core collection site. Here we analyze a three-month window of snow accumulation and meteorological conditions recorded by an Automatic Weather Station (AWS) at the Mt. Hunter site during the summer of 2013. Snow accumulation events are identified in the Mt. Hunter AWS dataset, and compared on a storm-by-storm basis to AWS data collected from the adjacent Kahiltna glacier 2000 m lower in elevation, and to regional National Weather Service (NWS) station data. We also evaluate the synoptic conditions associated with each Mt. Hunter accumulation event using NWS surface maps, NCEP-NCAR Reanalysis data, and the NOAA HYSPLIT back trajectory model. We categorize each Mt. Hunter accumulation event as pure snow accumulation, drifting, or blowing snow events based on snow accumulation, wind speed and temperature data using the method of Knuth et al (2009). We analyze the frequency and duration of events within each accumulation regime, in addition to the overall contribution of each event to the snowpack. Preliminary findings indicate that a majority of Mt. Hunter accumulation events are of pure accumulation nature (55.5%) whereas drifting (28.6%) and blowing (15.4%) snow events play a secondary role. Our results will characterize the local accumulation dynamics on

  5. Regional variations in the fluvial Upper Devonian and Lower Mississippian(?) Kanayut Conglomerate, Brooks Range, Alaska

    USGS Publications Warehouse

    Moore, T.E.; Nilsen, T.H.

    1984-01-01

    The wholly allochthonous Upper Devonian and Lower Mississippian(?) Kanayut Conglomerate is one of the most extensive fluvial deposits in North America. It crops out for 950 km along the crest of the Brooks Range in a series of thrust plates and is as thick as 2615 m. The Kanayut forms the fluvial part of a large, coarse-grained delta. The lower part of the Kanayut (the Ear Peak Member) overlies marginal-marine and prodelta turbidite deposits and consists of fining-upward meandering-stream-channel cycles of conglomerate and sandstone within black to maroon floodplain shale deposits. The middle part of the Kanayut (the Shainin Lake Member) lacks shale and consists of fining-upward couplets of channelized conglomerate and parallel- to cross-stratified sandstone interpreted as braidplain deposits. These deposits contain the largest clasts (23 cm) and were deposited during maximum progradation of the fluvial sequence. The upper part of the Kanayut (the Stuver Member), which consists of fining-upward meandering stream cycles similar to those of the lower part, grades upward into overlying Lower Mississippian tidal and marginal-marine deposits. Paleocurrent data and distribution of largest clasts indicate that the Kanayut was deposited by southwest-flowing streams fed by at least two major trunk streams that drained a mountainous region to the north and east. Comparison of stratigraphic and sedimentologic data collected at three selected locations representative of proximal, intermediate and distal parts of the Kanayut basin reveal regional variations in its fluvial character. These include a decrease in total thickness of fluvial strata, an increase in total thickness of associated marine sandstone, the pinch-out of the coarse-grained middle part of the Kanayut and decreases in the conglomerate/sandstone and sandstone/shale ratios from proximal to distal areas of the basin. The coarse-grained parts of the fluvial cycles decrease in thickness and lateral extent from

  6. Mesozoic and Cenozoic tectonics of the eastern and central Alaska Range: Progressive basin development and deformation in a suture zone

    USGS Publications Warehouse

    Ridgway, K.D.; Trop, J.M.; Nokleberg, W.J.; Davidson, C.M.; Eastham, K.R.

    2002-01-01

    Analysis of late Mesozoic and Cenozoic sedimentary basins, metamorphic rocks, and major faults in the eastern and central Alaska Range documents the progressive development of a suture zone that formed as a result of collision of an island-arc assemblage (the Wrangellia composite terrane) with the former North American continental margin. New basin-analysis, structural, and geochronologic data indicate the following stages in the development of the suture zone: (1) Deposition of 3-5 km of Upper Jurassic-Upper Cretaceous marine strata (the Kahiltna assemblage) recorded the initial collision of the island-arc assemblage with the continental margin. The Kahiltna assemblage exposed in the northern Talkeetna Mountains represents a Kimmeridgian-Valanginian backarc basin that was filled by northwestward-flowing submarine-fan systems that were transporting sediment derived from Mesozoic strata of the island-arc assemblage. The Kahiltna assemblage exposed in the southern Alaska Range represents a Valanginian-Cenomanian remnant ocean basin filled by west-southwestward-flowing submarine-fan systems that were transporting sediment derived from Paleozoic continental-margin strata uplifted in the along-strike suture zone. A belt of retrograde metamorphism and a regional anticlinorium developed along the continental margin from 115 to 106 Ma, roughly coeval with the end of widespread deposition in the Kahiltna sedimentary basins. (2) Metamorphism of submarine-fan deposits of the Kahiltna basin, located near the leading edge of the island-arc assemblage, occurred at ca. 74 Ma, as determined from a new U-Pb zircon age for a synkinematic sill. Coeval with metamorphism of deposits of the Kahiltna basin in the southern part of the suture zone was development of a thrust-top basin, the Cantwell basin, in the northern part of the suture zone. Geologic mapping and compositional data suggest that the 4 km of Upper Cretaceous nonmarine and marginal marine sedimentary strata in this basin

  7. Three-dimensional model of an ultramafic feeder system to the Nikolai Greenstone mafic large igneous province, central Alaska Range

    USGS Publications Warehouse

    Glen, J.M.G.; Schmidt, J.M.; Connard, G.G.

    2011-01-01

    The Amphitheater Mountains and southern central Alaska Range expose a thick sequence of Triassic Nikolai basalts that is underlain by several mafic-ultramafic complexes, the largest and best exposed being the Fish Lake and Tangle (FL-T) mafic-ultramafic sills that flank the Amphitheater Mountains synform. Three-dimensional (3-D) modeling of gravity and magnetic data reveals details of the structure of the Amphitheater Mountains, such as the orientation and thickness of Nikolai basalts, and the geometry of the FL-T intrusions. The 3-D model (50 ?? 70 km) includes the full geographic extent of the FL-T complexes and consists of 11 layers. Layer surfaces and properties (density and magnetic susceptibility) were modified by forward and inverse methods to reduce differences between the observed and calculated gravity and magnetic grids. The model suggests that the outcropping FL-T sills are apparently connected and traceable at depth and reveals variations in thickness, shape, and orientation of the ultramafic bodies that may identify paths of magma flow. The model shows that a significant volume (2000 km3) of ultramafic material occurs in the subsurface, gradually thickening and plunging westward to depths exceeding 4 km. This deep ultramafic material is interpreted as the top of a keel or root system that supplied magma to the Nikolai lavas and controlled emplacement of related magmatic intrusions. The presence of this deep, keel-like structure, and asymmetry of the synform, supports a sag basin model for development of the Amphitheater Mountains structure and reveals that the feeders to the Nikolai are much more extensive than previously known. Copyright 2011 by the American Geophysical Union.

  8. Alpine Glaciers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 27 August 2003

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

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

  9. Supporting data for “A glacier runoff extension to the precipitation runoff modeling system”

    USGS Publications Warehouse

    Van Beusekom, Ashley; Viger, Roland

    2017-01-01

    This product is an archive of the modeling artifacts used to produce a journal paper (Van Beusekom and Viger, 2016). The abstract for that paper follows. A module to simulate glacier runoff, PRMSglacier, was added to PRMS (Precipitation Runoff Modeling System), a distributed-parameter, physical-process hydrological simulation code. The extension does not require extensive on-glacier measurements or computational expense but still relies on physical principles over empirical relations as much as is feasible while maintaining model usability. PRMSglacier is validated on two basins in Alaska, Wolverine, and Gulkana Glacier basin, which have been studied since 1966 and have a substantial amount of data with which to test model performance over a long period of time covering a wide range of climatic and hydrologic conditions. When error in field measurements is considered, the Nash-Sutcliffe efficiencies of streamflow are 0.87 and 0.86, the absolute bias fractions of the winter mass balance simulations are 0.10 and 0.08, and the absolute bias fractions of the summer mass balances are 0.01 and 0.03, all computed over 42 years for the Wolverine and Gulkana Glacier basins, respectively. Without taking into account measurement error, the values are still within the range achieved by the more computationally expensive codes tested over shorter time periods.

  10. GLACIER SLIDING,

    DTIC Science & Technology

    The theory of the sliding of glaciers presented in earlier papers has been generalized (1) by taking into account the resistance to sliding offered...bed at the downstream side of an obstacle. The sliding velocities and controlling obstacle sizes which are found from the generalized theory are...magnitude smaller in thickness than the height of the controlling obstacles can cause an appreciable increase in the sliding velocity. The generalized

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

    Small but hydrologically significant shifts in climate have affected the rates of glacier volume change at the three U.S. Geological Survey Benchmark glaciers. Rate changes are detected as inflections in the cumulative conventional and reference-surface mass-balances of Wolverine and Gulkana Glaciers in Alaska and South Cascade Glacier in Washington. The cumulative mass balances are robust and have recently been corroborated by geodetic determinations of glacier volume change. Furthermore, the four-decade length of record is unique for the western hemisphere. Balance trends at South Cascade Glacier in Washington are generally in the opposite sense compared with Wolverine Glacier in Alaska; NCEP correlation of winter balance with local winter temperatures is positive at 0.59 for Wolverine and -0.64 for South Cascade Glacier. At Wolverine Glacier, the negative trend of cumulative mass balances, since measurements began in 1965, was replaced by a growth trend \\(positive mass balances\\) during the late 1970s and 1980s. The positive mass-balance trend was driven by increased precipitation during the 1976/77 to 1989 period. At Gulkana Glacier, the cumulative mass-balance trend has been negative throughout its measurement history, but with rate-change inflection points that coincide with the interdecadal climate-regime shifts in the North Pacific indices. At South Cascade Glacier, the mass-loss trend, observed since measurements began in 1953, was replaced by a positive trend between 1970 and 1976 then became strongly and continuously negative until 1997 when the rate of loss generally decreased. Since 1989, the trends of the glaciers in Alaska have also been strongly negative. These loss rates are the highest rates in the entire record. The strongly negative trends during the 1990s agree with climate studies that suggest that the period since the 1989 regime shift has been unusual. Volume response time and reference surface balance are the current suggested methods for

  12. 3D potential-field model of a Triassic Nikolai large igneous province vent, central Alaska Range

    NASA Astrophysics Data System (ADS)

    Glen, J. M.; Schmidt, J. M.; Connard, G. G.

    2009-12-01

    The southern flank of the Alaska Range in south central Alaska exposes a thick, fresh sequence of Middle to Late Triassic Nikolai Greenstone. At least 5 ultramafic intrusive complexes and numerous gabbroic sills of similar age intrude Pennsylvanian to Triassic volcanogenic and sedimentary rocks below the Nikolai. The 2 largest and best exposed ultramafic complexes are the Fish Lake and Tangle ultramafic sills on the north, and south flanks, respectively of the Amphitheater Mountains synform. Three-dimensional (3D) modeling of gravity and magnetic data, using the GMSYS-3D modeling software, shows details of the Amphitheater Mountains structure, Nikolai basalt thickness, and geometry of the apparently connected Fish Lake and Tangle ultramafic sills. Modeling is based on a compilation of existing regional and newly-acquired detailed profile gravity data, a compilation of regional and high-resolution aeromagnetic surveys, and numerous rock-property data (including density, susceptibility, and magnetic remanence measurements of outcrops, hand samples, and drill cores). Eight intersecting 2D models, constructed prior to the 3D model, suggested the presence of an elongate ultramafic keel below the Amphitheater synform axis and extensive gabbroic satellite sills below the Fish Lake and Tangle ultramafic complexes. The 3D model (50x70km) includes the full geographic extent of the Fish Lake and Tangle bodies, as well as parts of the Rainy and Canwell complexes to the north and east of the Amphitheater Mountains. Eleven layers were initially constructed from horizons we exported from the 2D models and gridded to form layer surfaces. Individual 3D model layers were subsequently modified by both forward and inverse methods applied to the layer surfaces and properties (density and magnetic susceptibility) to reduce differences between the observed and calculated gravity and magnetic grids. Up to 2 km of Nikolai basalts form the center of the asymmetric, west-plunging, 50 km long

  13. Tertiary tectonics of the Border Ranges Fault system, north-central Chugach Mountains, Alaska: Sedimentation, deformation and uplift along the inboard edge of a subduction complex

    SciTech Connect

    Little, T.A.

    1988-01-01

    In south-central Alaska the Border Ranges Fault system (BRFS) separates lower Paleogene rocks of a forearc basin sequence from a Cretaceous subduction complex. In a north-central part of the Chugach Mountains the upper Paleocene-lower Eocene Chickaloon Formation was deposited along the seaward margin of the forearc basin as an alluvial fan complex. A field study combining geologic mapping of a {approximately}200 km{sup 2} region, stratigraphic studies, K-Ar and fission-track geochronology, metamorphic petrology, and detailed structural analysis of deformed rocks on both sides of the BRFS has been used to reconstruct the Tertiary history of displacements and uplift events along the inboard edge of Alaska's subduction-accretion complex.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  15. VEGETATION MEDIATED THE IMPACTS OF POSTGLACIAL CLIMATIC CHANGE ON FIRE REGIMES IN THE SOUTHCENTRAL BROOKS RANGE, ALASKA

    SciTech Connect

    Higuera, P E; Brubaker, L B; Anderson, P M; Hu, F S; Brown, T A

    2008-10-28

    We examine direct and indirect impacts of millennial-scale climatic change on fire regimes in the southcentral Brooks Range, Alaska, using four lake-sediment records and existing paleoclimate interpretations. New techniques are introduced to identify charcoal peaks semi-objectively and detect statistical differences in fire regimes. Peaks in charcoal accumulation rates (CHARs) provide estimates of fire return intervals (FRIs) which are compared between vegetation zones described by fossil pollen and stomata. Climatic warming from ca 15-9 ka BP (calendar years before CE 1950) coincides with shifts in vegetation from herb tundra to shrub tundra to deciduous woodlands, all novel species assemblages relative to modern vegetation. Two sites cover this period and show increased CHARs and decreased FRIs with the transition from herb to shrub tundra ca 13.3-14.3 ka BP. Short FRIs in the Betula-dominated shrub tundra (mean [m] FRI 144 yr; 95% CI 119-170) primarily reflect the effects of flammable, continuous fuels on the fire regime. FRIs increased significantly with the transition to Populus-dominated deciduous woodlands ca 10.5 ka BP (mFRI 251 yr [158-352]), despite evidence of warmer- and drier-than-present summers. We attribute reduced fire activity under these conditions to low flammability of deciduous fuels. Three sites record the mid to late Holocene, when cooler and moister conditions allowed Picea glauca forest-tundra and P. mariana boreal forests to establish ca 8 and 5.5 ka BP. Forest-tundra FRIs did not differ significantly from the previous period (mFRIs range from 131-238 yr), but FRIs decreased with the transition to boreal forest (mFRI 145 yr [129-163]). Overall, fire-regime shifts in the study area showed greater correspondence with vegetation characteristics than with inferred climate, and we conclude that vegetation mediated the impacts of millennial-scale climatic change on fire regimes by modifying landscape flammability. Our findings emphasize the

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    We use a combination of field observations, remote sensing, and digital elevation data to demonstrate how the topographic character of the Alaska Range (Alaska, USA) has been influenced by the exhumation of Tertiary granitic plutons among more erodible sedimentary and metamorphic rocks. Observations that the mean elevations of many tectonically active mountain ranges follow closely the elevation of the mean Cenozoic snowline or glacial equilibrium line (ELA), rather than rates of tectonic rock uplift, have led to the “glacial buzzsaw hypothesis” - that terrain raised above the ELA is rapidly denuded by glaciers. The Alaska Range stands in prominent exception to this observation. Much of the range is developed on pervasively fractured sedimentary and metamorphic rocks and has local relief of 1000-1500 m. In contrast, early and mid-Tertiary plutons of relatively intact granite support most of the range's impressive mountains (including Mt. McKinley, or Denali, the highest mountain in North America at 6194 m), with 2500-5000 m of local relief. Moreover, these plutons are where the range's modern glaciers originate, as the high peaks protrude in some cases kilometers above modern snowlines. These glaciers flow off of the plutons onto the surrounding, softer rocks, where mean summit elevations are similar to modern snowline elevations. We exploit the Denali massif and the Kichatna Mountains to its west to illustrate the direct ways in which exhumation of granite plutons affects glacial erosion, glacier long profiles, the glacial drainage network, and the effectiveness of periglacial processes. We use simple scaling calculations to explore the potential feedbacks of relief enhancement - specifically, that of avalanching from steep valley walls - on the health of the glaciers occupying the valleys, and describe ways in which peaks can be preserved and allowed to grow to great heights. Our work indicates that most of the Alaska Range has developed in accordance with

  17. Mineralogical maps showing distribution of selected ore-related minerals in the nonmagnetic, heavy-mineral-concentrate fraction of stream sediment from the Mount Hayes 1 degree by 3 degrees Quadrangle, eastern Alaska Range, Alaska

    USGS Publications Warehouse

    Tripp, Richard B.; Curtin, Gary C.; Nokleberg, Warren J.; Huston, David L.; Hampton, James R.

    1993-01-01

    Exploratory geochemical sampling was done in 1979, 1980, and 1981. The collection of composite samples of stream sediment or glacial debris was emphasized the first 2 years; the last year was spent collecting mineralized stream pebbles, float, and outcrop samples. The stream-sediment and heavy- mineral-concentrate samples were collected at 795 sites on tributary streams having drainage basins ranging from 1 to 5 mi 2 in area. The glacial debris samples were collected at 116 sites on tributary glaciers also having drainage basins ranging from 1 to 5 mi2 in area. All of these samples were analyzed for 31 elements by six-step semiquantitative emission spectrography (Grimes and Marranzino, 1968). In addition, all samples were analyzed for zinc by an atomic absorption method (Ward and others, 1969). The spectrographic and chemical results are available in O'Leary and others (1982).

  18. Comparative metagenome analysis of an Alaskan glacier.

    PubMed

    Choudhari, Sulbha; Lohia, Ruchi; Grigoriev, Andrey

    2014-04-01

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

  19. OMEGA - an operational glacier monitoring system

    NASA Astrophysics Data System (ADS)

    Pellikka, P. K. E.

    2003-04-01

    Glacier changes reflect local climate changes and are one of the most important direct indicators of global climate change. In general, the glaciers are retreating in Europe, but some glaciers are advancing. However, even in small areas glacier responses can be different. The application of glaciers as indicators requires sufficient amount of glaciers, which is possible only with remote sensing methods. Remote sensing data have been used for glacier monitoring from the late 19th century, first as terrestrial photographs, but later as aerial photographs. A new era began in the 1970’s as optical satellite data became available. Since late 1990’s the glacier monitoring could be performed with numerous satellite and airborne sensors ranging from satellite radar data to airborne laser scanner data. All together, the development of new remote sensing technologies and methods provides many possibilities for studies of glacier features and parameters. The glacier parameters of interest in operational monitoring are the changes of glacier area and volume, and the variation of glacier zones, such as snow, firn and ice. These parameters enable the estimation of relative volume change, AAR and equilibrium line, for example. Operational monitoring involves that the remote sensing data to be used is available continuously, the image processing methods are accurate and the processing chain is developed so that the derivation of the aimed parameters works fluently. The OMEGA project aims at the development of an operational glacier monitoring system applying all the potential remote sensing data. The objectives are to develop workflows and semi-automatic image processing methodologies for different data types in order to retrieve glacier parameters, to construct databases of the study glaciers and to develop the prototype of an operational monitoring system. The test glaciers are Hintereisferner in Austria and Engabreen in Norway. The deliverable of the project is the OMEGA

  20. 36 CFR 13.1116 - Do I need a camping permit in Glacier Bay?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Do I need a camping permit in Glacier Bay? 13.1116 Section 13.1116 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National...

  1. First results of repeated Terrestrial Laserscanning monitoring processes at the rock fall area Burgstall/Pasterze Glacier, Hohe Tauern Range, Central Austria

    NASA Astrophysics Data System (ADS)

    Avian, M.

    2012-04-01

    In July 2007 a large rock fall event at the NW-SE tending ridge of the mountain Mittlerer Burgstall (N47°05´, E12°44´) released appr. 57.000 m3 of rock accumulated at both sides of the ridge partly covering the tongue of Pasterze Glacier, the largest glacier in the Eastern European Alps. First analyses on the event were carried out based on pre- and post event airborne laserscanning as well as photogrammetric data. Ongoing large rock falls in 2008 led to the decision to establish a Terrestrial Laser Scanning (TLS) network to acquire high resolution 3D-surface data. The TLS position is complementary to the existing monitoring network installed in 2006, consisting of ground surface and near surface temperature sensors (projects: ALPCHANGE 2006 - 2011; permaNET 2008-2011; permAfrost 2010 - 2012). In August 2009 first investigations to install a permanent position for TLS to monitor affected rock fall areas were carried out. Unfavourable geometric as well as terrain conditions inhibited the installation of a position to monitor the SW-facing flank of Mittlerer Burgstall mountain. An ideal position to monitor the NE- facing area as well as the S- and E-flank of the nearby Hoher Burgstall was installed in September 2010 at the proglacial area of the Wasserfallwinkelkees glacier. This glacier was once contributing ice masses to the tongue of Pasterze Glacier and is now located about 400 m above the present surface of Pasterze Glacier. Similar to Mittlerer Burgstall, also both flanks of Hoher Burgstall show evidences of imminent larger rock falls which can be hazardous due to the fact that a frequented hiking trail leads to the Oberwalder Hütte alpine hut crosses the lower left part of the E-flank. This hut is a high alpine training centre of the Austrian Alpine club (OEAV) and well visited in during summer. First measurements of both study areas were carried out in September 2010 in mean distances of 600m to the scanning area of Mittlerer Burgstall (MBUG) and 100m to

  2. Geophysical data reveal the crustal structure of the Alaska Range orogen within the aftershock zone of the Mw 7.9 Denali fault earthquake

    USGS Publications Warehouse

    Fisher, M.A.; Ratchkovski, N.A.; Nokleberg, W.J.; Pellerin, L.; Glen, J.M.G.

    2004-01-01

    Geophysical information, including deep-crustal seismic reflection, magnetotelluric (MT), gravity, and magnetic data, cross the aftershock zone of the 3 November 2002 Mw 7.9 Denali fault earthquake. These data and aftershock seismicity, jointly interpreted, reveal the crustal structure of the right-lateral-slip Denali fault and the eastern Alaska Range orogen, as well as the relationship between this structure and seismicity. North of the Denali fault, strong seismic reflections from within the Alaska Range orogen show features that dip as steeply as 25?? north and extend downward to depths between 20 and 25 km. These reflections reveal crustal structures, probably ductile shear zones, that most likely formed during the Late Cretaceous, but these structures appear to be inactive, having produced little seismicity during the past 20 years. Furthermore, seismic reflections mainly dip north, whereas alignments in aftershock hypocenters dip south. The Denali fault is nonreflective, but modeling of MT, gravity, and magnetic data suggests that the Denali fault dips steeply to vertically. However, in an alternative structural model, the Denali fault is defined by one of the reflection bands that dips to the north and flattens into the middle crust of the Alaska Range orogen. Modeling of MT data indicates a rock body, having low electrical resistivity (>10 ??-m), that lies mainly at depths greater than 10 km, directly beneath aftershocks of the Denali fault earthquake. The maximum depth of aftershocks along the Denali fault is 10 km. This shallow depth may arise from a higher-than-normal geothermal gradient. Alternatively, the low electrical resistivity of deep rocks along the Denali fault may be associated with fluids that have weakened the lower crust and helped determine the depth extent of the after-shock zone.

  3. Principles of Glacier Mechanics

    NASA Astrophysics Data System (ADS)

    Waddington, Edwin D.

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

  4. Neogene transpressional foreland basin development on the north side of the central alaska range, usibelli group and nenana gravel, tanana basin

    USGS Publications Warehouse

    Ridgway, K.D.; Thoms, E.E.; Layer, P.W.; Lesh, M.E.; White, J.M.; Smith, S.V.

    2007-01-01

    Neogene strata of the Tanana basin provide a long-term record of a northwardpropagating, transpressional foreland-basin system related to regional shortening of the central Alaska Range and strike-slip displacement on the Denali fault system. These strata are ???2 km thick and have been deformed and exhumed in thrust faults that form the foothills on the north side of the Alaska Range. The lower part of the sedimentary package, the Usibelli Group, consists of 800 m of mainly Miocene strata that were deposited in fluvial, lacustrine, and peat bog environments of the foredeep depozone of the foreland-basin system. Compositional data from conglomerate and sandstone, as well as recycled Upper Cretaceous palynomorphs, indicate that the Miocene foreland-basin system was supplied increasing amounts of sediment from lithologies currently exposed in thrust sheets located south of the basin. The upper part of the sedimentary package, the Nenana Gravel, consists of 1200 m of mainly Pliocene strata that were deposited in alluvial-fan and braidplain environments in the wedge-top depozone of the foreland-basin system. Compositional data from conglomerate and sandstone, as well as 40Ar/39Ar dating of detrital feldspars in sandstone and from granitic clasts in conglomerate, indicate that lithologies exposed in the central Alaska Range provided most of the detritus to the Pliocene foreland-basin system. 40Ar/39Ar dates from detrital feldspar grains also show that two main suites of plutons contributed sediment to the Nenana Gravel. Detrital feldspars with an average age of 56 Ma are interpreted to have been derived from the McKinley sequence of plutons located south of the Denali fault. Detrital feldspars with an average age of 34 Ma are interpreted to have been derived from plutons located north of the Denali fault. Plutons located south of the Denali fault provided detritus for the lower part of the Nenana Gravel, whereas plutons located north of the Denali fault began to

  5. South Cascade Glacier bibliography

    SciTech Connect

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

    1984-01-01

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

  6. GeoFORCE Alaska, A Successful Summer Exploring Alaska's Geology

    NASA Astrophysics Data System (ADS)

    Wartes, D.

    2012-12-01

    and minority students into the geosciences. View them as they explore the permafrost tunnel in Fairbanks, sand dunes in Anchorage, Portage Glacier, Matanuska-Susitna Glacier, and the Trans-Alaska pipeline damage from the earthquake of 2002.

  7. Sea otter studies in Glacier Bay National Park and Preserve

    USGS Publications Warehouse

    Bodkin, J.L.; Kloecker, K.A.; Esslinger, G.G.; Monson, D.H.; DeGroot, J.D.; Doherty, J.

    2002-01-01

    Following translocations to the outer coast of Southeast Alaska in 1965, sea otters have been expanding their range and increasing in abundance. We began conducting surveys for sea otters in Cross Sound, Icy Strait, and Glacier Bay, Alaska in 1994, following initial reports (in 1993) of their presence in Glacier Bay. Since 1995, the number of sea otters in Glacier Bay proper has increased from around 5 to more than 1500. Between 1993 and 1997 sea otters were apparently only occasional visitors to Glacier Bay, but in 1998 long-term residence was established as indicated by the presence of adult females and their dependent pups. Sea otter distribution is limited to the Lower Bay, south of Sandy Cove, and is not continuous within that area. Concentrations occur in the vicinity of Sita Reef and Boulder Island and between Pt. Carolus and Rush Pt. on the west side of the Bay (Figure 1). We describe the diet of sea otters during 2001 in Glacier Bay based on visual observations of prey during 456 successful forage dives. In Glacier Bay, diet consisted of 62% clam, 15% mussel, 9% crab, 7% unidentified, 4& urchins, and 4% other. Most prey recovered by sea otters are commercially, socially, or ecologically important species. Species of clam include Saxidomus gigantea, Protothaca staminea, and Mya truncata. Urchins are primarily Strongylocentrotus droebachiensis and the mussel is Modiolus modiolus. Crabs include species of three genera: Cancer, Chinoecetes, and Telmessus. Although we characterize diet at broad geographic scales, we found diet to vary between sites separated by as little as several hundred meters. Dietary variation among and within sites can reflect differences in prey availability and individual specialization. We estimated species composition, density, biomass, and sizes of subtidal clams, urchins, and mussels at 9 sites in lower Glacier Bay. All sites were selected based on the presence of abundant clam siphons. Sites were not selected to allow inference to

  8. Attribution of glacier fluctuations to climate change

    NASA Astrophysics Data System (ADS)

    Oerlemans, J.

    2012-04-01

    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

  9. 40Ar/39Ar Dating of Zn-Pb-Ag Mineralization in the Northern Brooks Range, Alaska

    USGS Publications Warehouse

    Werdon, Melanie B.; Layer, Paul W.; Newberry, Rainer J.

    2004-01-01

    The 40Ar/39Ar laser step-heating method potentially can be used to provide absolute ages for a number of formerly undatable, low-temperature ore deposits. This study demonstrates the use of this method by determining absolute ages for Zn-Pb-Ag sediment-hosted massive sulfide deposits and vein-breccia occurrences found throughout a 300-km-long, east-west-trending belt in the northern Brooks Range, Alaska. Massive sulfide deposits are hosted by Mississippian to Pennsylvanian(?) black carbonaceous shale, siliceous mudstone, and lesser chert and carbonate turbidites of the Kuna Formation (e.g., Red Dog, Anarraaq, Lik (Su), and Drenchwater). The vein-breccia occurrences (e.g., Husky, Story Creek, West Kivliktort Mountain, Vidlee, and Kady) are hosted by a deformed but only weakly metamorphosed package of Upper Devonian to Lower Mississippian mixed continental and marine clastic rocks (the Endicott Group) that stratigraphically underlie the Kuna Formation. The vein-breccias are mineralogically similar to, but not spatially associated with, known massive sulfide deposits. The region's largest shale-hosted massive sulfide deposit is Red Dog; it has reserves of 148 Mt grading 16.6 percent zinc, 4.5 percent lead, and 77 g of silver per tonne. Hydrothermally produced white mica in a whole-rock sample from a sulfide-bearing igneous sill within the Red Dog deposit yielded a plateau age of 314.5 Ma. The plateau age of this whole-rock sample records the time at which temperatures cooled below the argon closure temperature of the white mica and is interpreted to represent the minimum age limit for massive sulfide-related hydrothermal activity in the Red Dog deposit. Sulfide-bearing quartz veins at Drenchwater crosscut a hypabyssal intrusion with a maximum biotite age of 337.0 Ma. Despite relatively low sulfide deposition temperatures in the vein-breccia occurrences (162°-251°C), detrital white mica in sandstone immediately adjacent to large vein-breccia zones was partially to

  10. Dynamics and internal structure of an Alaskan debris-covered glacier from repeat airborne photogrammetry and surface geophysics

    NASA Astrophysics Data System (ADS)

    Holt, John; Levy, Joseph; Petersen, Eric; Larsen, Chris; Fahnestock, Mark

    2016-04-01

    Debris-covered glaciers and rock glaciers encompass a range of compositions and activity, and can be useful paleoclimate indicators. They also respond differently to ongoing climate change than glaciers without a protective cover. Their flow dynamics are not well understood, and their unique surface morphologies, including lobate fronts and arcuate ridges, likely result from viscous flow influenced by a combination of composition, structure, and climatic factors. However, basic connections between flow kinematics and surface morphology have not yet been established, limiting our ability to understand these features. In order to begin to address this problem we have undertaken airborne and surface studies of multiple debris-covered glaciers in Alaska and the western U.S. Sourdough Rock Glacier in the St. Elias Mountains, Alaska, is completely debris-covered and exhibits numerous transverse compressional ridges. Its trunk also exhibits highly regular bumps and swales with a wavelength of ~175 m and amplitudes up to 12 m. In the middle trunk, lineations (boulder trains and furrows) bend around a point roughly 200m from the eastern edge. We acquired five high-resolution airborne surveys of Sourdough Rock Glacier between late 2013 and late 2015 using lidar and photogrammetry to assess annual and seasonal change at the sub-meter level. Differencing the DTMs provides vertical change while feature tracking in orthophotos provide horizontal velocities that indicate meters of annual motion. The flow field is highly correlated with surface features; in particular, compressional ridges in the lower lobe. Stranded, formerly active lobes are also apparent. Surface geophysical studies were undertaken to constrain internal structure and composition using a combination of ground-penetrating radar (GPR) at 50 and 100 MHz in six transects, and time-domain electromagnetic (TDEM) measurements at 47 locations, primarily in an along-flow transect and two cross-flow transects. We infer

  11. Persistent organic pollutants in the blood of free-ranging sea otters (Enhydra lutris ssp.) in Alaska and California.

    PubMed

    Jessup, David A; Johnson, Christine K; Estes, James; Carlson-Bremer, Daphne; Jarman, Walter M; Reese, Stacey; Dodd, Erin; Tinker, M Tim; Ziccardi, Michael H

    2010-10-01

    As part of tagging and ecologic research efforts in 1997 and 1998, apparently healthy sea otters of four age-sex classes in six locations in Alaska and three in California were sampled for persistent organic pollutants (POPs) and other chemicals of ecologic or environmental concern (COECs). Published techniques for the detection of POPs (specifically ∑polychlorinated biphenyls [PCBs], ∑DDTs, ∑hexachlorocyclohexanes [HCHs], ∑polycyclic aromatic hydrocarbons [PAHs], ∑chlordanes [CHLs], hexachlorobenzene [HCB], dieldrin, and mirex) in the tissue of dead otters were modified for use with serum from live sea otters. Toxic equivalencies (TEQs) were calculated for POPs with proven bioactivity. Strong location effects were seen for most POPs and COECs; sea otters in California generally showed higher mean concentrations than those in Alaska. Differences in contaminant concentrations were detected among age and sex classes, with high levels frequently observed in subadults. Very high levels of ∑DDT were detected in male sea otters in Elkhorn Slough, California, where strong freshwater outflow from agricultural areas occurs seasonally. All contaminants except mirex differed among Alaskan locations; only ∑DDT, HCB, and chlorpyrifos differed within California. High levels of ∑PCB (particularly larger, more persistent congeners) were detected at two locations in Alaska where associations between elevated PCBs and military activity have been established, while higher PCB levels were found at all three locations in California where no point source of PCBs has been identified. Although POP and COEC concentrations in blood may be less likely to reflect total body burden, concentrations in blood of healthy animals may be more biologically relevant and less influenced by state of nutrition or perimortem factors than other tissues routinely sampled.

  12. Persistent organic pollutants in the blood of free-ranging sea otters (Enhydra lutris ssp.) in Alaska and California

    USGS Publications Warehouse

    Jessup, David A.; Johnson, Christine K.; Estes, James; Carlson-Bremer, Daphne; Jarman, Walter M.; Reese, Stacey; Dodd, Erin; Tinker, M. Tim; Ziccardi, Michael H.

    2010-01-01

    As part of tagging and ecologic research efforts in 1997 and 1998, apparently healthy sea otters of four age-sex classes in six locations in Alaska and three in California were sampled for persistent organic pollutants (POPs) and other chemicals of ecologic or environmental concern (COECs). Published techniques for the detection of POPs (specifically Σpolychlorinated biphenyls [PCBs], ΣDDTs, Σhexachlorocyclohexanes [HCHs], Σpolycyclic aromatic hydrocarbons [PAHs], Σchlordanes [CHLs], hexachlorobenzene [HCB], dieldrin, and mirex) in the tissue of dead otters were modified for use with serum from live sea otters. Toxic equivalencies (TEQs) were calculated for POPs with proven bioactivity. Strong location effects were seen for most POPs and COECs; sea otters in California generally showed higher mean concentrations than those in Alaska. Differences in contaminant concentrations were detected among age and sex classes, with high levels frequently observed in subadults. Very high levels of ΣDDT were detected in male sea otters in Elkhorn Slough, California, where strong freshwater outflow from agricultural areas occurs seasonally. All contaminants except mirex differed among Alaskan locations; only ΣDDT, HCB, and chlorpyrifos differed within California. High levels of ΣPCB (particularly larger, more persistent congeners) were detected at two locations in Alaska where associations between elevated PCBs and military activity have been established, while higher PCB levels were found at all three locations in California where no point source of PCBs has been identified. Although POP and COEC concentrations in blood may be less likely to reflect total body burden, concentrations in blood of healthy animals may be more biologically relevant and less influenced by state of nutrition or perimortem factors than other tissues routinely sampled.

  13. ISEA (International geodetic project in SouthEastern Alaska) for Rapid Uplifting Caused by Glacial Retreat: (2) Establishment of Continuous GPS Sites (CGPS)

    NASA Astrophysics Data System (ADS)

    Kaufman, A. M.; Freymueller, J. T.; Miura, S.; Cross, R. S.; Sato, T.; Sun, W.; Fujimoto, H.

    2006-12-01

    Rapid disintegration and thinning of Glacier Bay's tidewater glaciers and ice fields followed the end of the Little Ice Age. Geodetic studies by Larsen et al. have quantified average rates of post-glacial isostatic rebound (PGR) in the vicinity of Glacier Bay in Southeast Alaska. PGR continues today with maximum uplift rates of 30 mm/yr in Glacier Bay's upper West Arm and 32 mm/yr in the Yakutat Icefield. ISEA is a collaborative Japanese-American project which will combine CGPS measurements of uplift with absolute gravity and gravity tide observations in Southeast Alaska. ISEA will build on previous work in Glacier Bay with a multi-pronged geophysical approach similar to that used by Sato et al. in Svalbard, Norway. CGPS data sets from Gustavus and elsewhere in Alaska show seasonal variability in vertical velocity. We hypothesize this is due to winter snow loading and summer ice loss in adjacent mountain ranges. If uplift rates are found to accelerate over the five year span of this project, this would suggest increasing rates of present day ice loss in Glacier Bay. CGPS measurements of seasonal crustal deformation might be used as a powerful integrating tool for mass balance monitoring over an extensive, glacierized area. ISEA supplements existing CGPS stations [U.S. Coast Guard and Plate Boundary Observatory (PBO)] and improves the spatial array with new stations in and around Glacier Bay. During June and September of 2006, an ISEA field team established five new CGPS stations. Two new sites within Glacier Bay National Park, at Blue Mouse Cove and Queen Inlet, are near the zone of maximum uplift. The third CGPS was placed to the east, on Eldred Rock, in northern Lynn Canal. The fourth site, to the west near Dry Bay, completes a 200 km east-west "transect" through this uplift peak. The fifth site lies to the northeast along the Haines Highway in Yukon, Canada. A sixth site in the Tatshenshini River region, north of Glacier Bay, is proposed for 2007. Site

  14. Glaciers of South America

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1998-01-01

    Landsat images, together with maps and aerial photographs, have been used to produce glacier inventories, define glacier locations, and study glacier dynamics in the countries of South America, along with the Andes Mountains. In Venezuela, Colombia, Ecuador, and Bolivia, the small glaciers have been undergoing extensive glacier recession since the late 1800's. Glacier-related hazards (outburst floods, mud flows, and debris avalanches) occur in Colombia, in Ecuador, and associated with the more extensive (2,600 km2) glaciers of Peru. The largest area of glacier ice is found in Argentina and Chile, including the northern Patagonian ice field (about 4,200 km2) and the southern Patagonian ice field (about 13,000 km2), the largest glacier in the Southern Hemisphere outside Antarctica.

  15. Glaciers of Europe

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1993-01-01

    ALPS: AUSTRIAN: An overview is provided on the occurrence of the glaciers in the Eastern Alps of Austria and on the climatic conditions in this area, Historical documents on the glaciers have been available since the Middle Ages. Special glaciological observations and topographic surveys of individual glaciers were initiated as early as 1846. Recent data in an inventory based on aerial photographs taken in 1969 show 925 glaciers in the Austrian Alps with a total area of 542 square kilometers. Present research topics include studies of mass and energy balance, relations of glaciers and climate, physical glaciology, a complete inventory of the glaciers, and testing of remote sensing methods. The location of the glacier areas is shown on Landsat multispectral scanner images; the improved capabilities of the Landsat thematic mapper are illustrated with an example from the Oztaler Alpen group. ALPS: SWISS: According to a glacier inventory published in 1976, which is based on aerial photography of 1973, there are 1,828 glacier units in the Swiss Alps that cover a total area of 1fl42 square kilometers. The Rhonegletscher, currently the ninth largest in the country, was one of the first to be studied in detail. Its surface has been surveyed repeatedly; velocity profiles were measured, and the fluctuations of its terminus were mapped and recorded from 1874 to 1914. Recent research on the glacier has included climatological, hydrological, and massbalance studies. Glaciological research has been conducted on various other glaciers in Switzerland concerning glacier hydrology, glacier hazards, fluctuations of glacier termini, ice mechanics, ice cores, and mass balance. Good maps are available showing the extent of glaciers from the latter decades of the 19th century. More recently, the entire country has been mapped at scales of 1:25,000, 1:50,000, 1:100,000, 1:200,000, and 1:500,000. The 1:25,000-scale series very accurately represents the glaciers as well as locates

  16. The susitna glacier thrust fault: Characteristics of surface ruptures on the fault that initiated the 2002 denali fault earthquake

    USGS Publications Warehouse

    Crone, A.J.; Personius, S.F.; Craw, P.A.; Haeussler, P.J.; Staft, L.A.

    2004-01-01

    The 3 November 2002 Mw 7.9 Denali fault earthquake sequence initiated on the newly discovered Susitna Glacier thrust fault and caused 48 km of surface rupture. Rupture of the Susitna Glacier fault generated scarps on ice of the Susitna and West Fork glaciers and on tundra and surficial deposits along the southern front of the central Alaska Range. Based on detailed mapping, 27 topographic profiles, and field observations, we document the characteristics and slip distribution of the 2002 ruptures and describe evidence of pre-2002 ruptures on the fault. The 2002 surface faulting produced structures that range from simple folds on a single trace to complex thrust-fault ruptures and pressure ridges on multiple, sinuous strands. The deformation zone is locally more than 1 km wide. We measured a maximum vertical displacement of 5.4 m on the south-directed main thrust. North-directed backthrusts have more than 4 m of surface offset. We measured a well-constrained near-surface fault dip of about 19?? at one site, which is considerably less than seismologically determined values of 35??-48??. Surface-rupture data yield an estimated magnitude of Mw 7.3 for the fault, which is similar to the seismological value of Mw 7.2. Comparison of field and seismological data suggest that the Susitna Glacier fault is part of a large positive flower structure associated with northwest-directed transpressive deformation on the Denali fault. Prehistoric scarps are evidence of previous rupture of the Sustina Glacier fault, but additional work is needed to determine if past failures of the Susitna Glacier fault have consistently induced rupture of the Denali fault.

  17. Rapid movement of frozen debris-lobes: implications for permafrost degradation and slope instability in the south-central Brooks Range, Alaska

    USGS Publications Warehouse

    Daanen, R.P.; Grosse, G.; Darrow, M.M.; Hamilton, T.D.; Jones, Benjamin M.

    2012-01-01

    We present the results of a reconnaissance investigation of unusual debris mass-movement features on permafrost slopes that pose a potential infrastructure hazard in the south-central Brooks Range, Alaska. For the purpose of this paper, we describe these features as frozen debris-lobes. We focus on the characterisation of frozen debris-lobes as indicators of various movement processes using ground-based surveys, remote sensing, field and laboratory measurements, and time-lapse observations of frozen debris-lobe systems along the Dalton Highway. Currently, some frozen debris-lobes exceed 100 m in width, 20 m in height and 1000 m in length. Our results indicate that frozen debris-lobes have responded to climate change by becoming increasingly active during the last decades, resulting in rapid downslope movement. Movement indicators observed in the field include toppling trees, slumps and scarps, detachment slides, striation marks on frozen sediment slabs, recently buried trees and other vegetation, mudflows, and large cracks in the lobe surface. The type and diversity of observed indicators suggest that the lobes likely consist of a frozen debris core, are subject to creep, and seasonally unfrozen surface sediment is transported in warm seasons by creep, slumping, viscous flow, blockfall and leaching of fines, and in cold seasons by creep and sliding of frozen sediment slabs. Ground-based measurements on one frozen debris-lobe over three years (2008–2010) revealed average movement rates of approximately 1 cm day−1, which is substantially larger than rates measured in historic aerial photography from the 1950s to 1980s. We discuss how climate change may further influence frozen debris-lobe dynamics, potentially accelerating their movement. We highlight the potential direct hazard that one of the studied frozen debris-lobes may pose in the coming years and decades to the nearby Trans Alaska Pipeline System and the Dalton Highway, the main artery for transportation

  18. Rapid movement of frozen debris-lobes: implications for permafrost degradation and slope instability in the south-central Brooks Range, Alaska

    NASA Astrophysics Data System (ADS)

    Daanen, R. P.; Grosse, G.; Darrow, M. M.; Hamilton, T. D.; Jones, B. M.

    2012-05-01

    We present the results of a reconnaissance investigation of unusual debris mass-movement features on permafrost slopes that pose a potential infrastructure hazard in the south-central Brooks Range, Alaska. For the purpose of this paper, we describe these features as frozen debris-lobes. We focus on the characterisation of frozen debris-lobes as indicators of various movement processes using ground-based surveys, remote sensing, field and laboratory measurements, and time-lapse observations of frozen debris-lobe systems along the Dalton Highway. Currently, some frozen debris-lobes exceed 100 m in width, 20 m in height and 1000 m in length. Our results indicate that frozen debris-lobes have responded to climate change by becoming increasingly active during the last decades, resulting in rapid downslope movement. Movement indicators observed in the field include toppling trees, slumps and scarps, detachment slides, striation marks on frozen sediment slabs, recently buried trees and other vegetation, mudflows, and large cracks in the lobe surface. The type and diversity of observed indicators suggest that the lobes likely consist of a frozen debris core, are subject to creep, and seasonally unfrozen surface sediment is transported in warm seasons by creep, slumping, viscous flow, blockfall and leaching of fines, and in cold seasons by creep and sliding of frozen sediment slabs. Ground-based measurements on one frozen debris-lobe over three years (2008-2010) revealed average movement rates of approximately 1 cm day-1, which is substantially larger than rates measured in historic aerial photography from the 1950s to 1980s. We discuss how climate change may further influence frozen debris-lobe dynamics, potentially accelerating their movement. We highlight the potential direct hazard that one of the studied frozen debris-lobes may pose in the coming years and decades to the nearby Trans Alaska Pipeline System and the Dalton Highway, the main artery for transportation

  19. Columbia Bay, Alaska: an 'upside down' estuary

    USGS Publications Warehouse

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

    1988-01-01

    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.

  20. Improving Mass Balance Modeling of Benchmark Glaciers

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  1. The GAMDAM glacier inventory: a quality-controlled inventory of Asian glaciers

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    We present a new glacier inventory for high-mountain Asia named "Glacier Area Mapping for Discharge from the Asian Mountains" (GAMDAM). Glacier outlines were delineated manually using 356 Landsat ETM+ scenes in 226 path-row sets from the period 1999-2003, in conjunction with a digital elevation model (DEM) and high-resolution Google EarthTM imagery. Geolocations are largely consistent between the Landsat imagery and DEM due to systematic radiometric and geometric corrections made by the United States Geological Survey. We performed repeated delineation tests and peer review of glacier outlines in order to maintain the consistency and quality of the inventory. Our GAMDAM glacier inventory (GGI) includes 87 084 glaciers covering a total area of 91 263 ± 13 689 km2 throughout high-mountain Asia. In the Hindu Kush-Himalaya range, the total glacier area in our inventory is 93% that of the ICIMOD (International Centre for Integrated Mountain Development) inventory. Discrepancies between the two regional data sets are due mainly to the effects of glacier shading. In contrast, our inventory represents significantly less surface area (-24%) than the recent global Randolph Glacier Inventory, version 4.0 (RGI), which includes 119 863 ± 9201 km2 for the entirety of high Asian mountains. Likely causes of this disparity include headwall definition, effects of exclusion of shaded glacier areas, glacier recession since the 1970s, and inclusion of seasonal snow cover in the source data of the RGI, although it is difficult to evaluate such effects quantitatively. Further rigorous peer review of GGI will both improve the quality of glacier inventory in high-mountain Asia and provide new opportunities to study Asian glaciers.

  2. Erosion by an Alpine glacier

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  3. Regional structural framework and petroleum assessment of the Brooks Range foothills and southern coastal plain, National Petroleum Reserve, Alaska

    USGS Publications Warehouse

    Potter, Christopher J.; Moore, Thomas E.; O'Sullivan, Paul B.; Miller, John J.

    2002-01-01

    The transects, along with other seismic-reflection examples, illustrate four play concepts being used in the deformed area for the 2002 U.S. Geological Survey oil and gas assessment of the National Petroleum Reserve-Alaska (NPRA). The Brookian topset structural play includes broad west-northwest-trending anticlines in the Cretaceous Nanushuk Group, developed above structurally thickened Torok mudstones in the incipiently-deformed, most northerly part of the thrust system. The Torok structural play includes prominent anticlines affecting deep-basin sandstones, many of which are detached from folds exposed at the surface. The Ellesmerian structural play includes closures developed in the clastic part of the Ellesmerian sequence, mainly above a detachment in the Shublik Formation. The thrust belt play includes antiformal stacks of allochthonous Endicott Group clastic rocks and Lisburne Group carbonates; these stacks were assembled at about 120 Ma, and were transported to their present positions in the foothills at about 60 Ma.

  4. Geophysical investigation of the Denali fault and Alaska Range orogen within the aftershock zone of the October-November 2002, M = 7.9 Denali fault earthquake

    USGS Publications Warehouse

    Fisher, M.A.; Nokleberg, W.J.; Ratchkovski, N.A.; Pellerin, L.; Glen, J.M.; Brocher, T.M.; Booker, J.

    2004-01-01

    The aftershock zone of the 3 November 2002, M = 7.9 earthquake that ruptured along the right-slip Denali fault in south-central Alaska has been investigated by using gravity and magnetic, magnetotelluric, and deep-crustal, seismic reflection data as well as outcrop geology and earthquake seismology. Strong seismic reflections from within the Alaska Range orogen north of the Denali fault dip as steeply as 25°N and extend to depths as great as 20 km. These reflections outline a relict crustal architecture that in the past 20 yr has produced little seismicity. The Denali fault is nonreflective, probably because this fault dips steeply to vertical. The most intriguing finding from geophysical data is that earthquake aftershocks occurred above a rock body, with low electrical resistivity (>10 Ω·m), that is at depths below ∼10 km. Aftershocks of the Denali fault earthquake have mainly occurred shallower than 10 km. A high geothermal gradient may cause the shallow seismicity. Another possibility is that the low resistivity results from fluids, which could have played a role in locating the aftershock zone by reducing rock friction within the middle and lower crust.

  5. Unusually loud ambient noise in tidewater glacier fjords: a signal of ice melt

    USGS Publications Warehouse

    Pettit, Erin C.; Lee, Kevin M.; Brann, Joel P.; Nystuen, Jeffrey A.; Wilson, Preston S.; O'Neel, Shad

    2015-01-01

    In glacierized fjords, the ice-ocean boundary is a physically and biologically dynamic environment that is sensitive to both glacier flow and ocean circulation. Ocean ambient noise offers insight into processes and change at the ice-ocean boundary. Here we characterize fjord ambient noise and show that the average noise levels are louder than nearly all measured natural oceanic environments (significantly louder than sea ice and non-glacierized fjords). Icy Bay, Alaska has an annual average sound pressure level of 120 dB (re 1 μPa) with a broad peak between 1000 and 3000 Hz. Bubble formation in the water column as glacier ice melts is the noise source, with variability driven by fjord circulation patterns. Measurements from two additional fjords, in Alaska and Antarctica, support that this unusually loud ambient noise in Icy Bay is representative of glacierized fjords. These high noise levels likely alter the behavior of marine mammals.

  6. Erosion by an Alpine glacier.

    PubMed

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

    2015-10-09

    Assessing the impact of glaciation on Earth's surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years.

  7. Erosion by an Alpine glacier

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    Assessing the impact of glaciation on Earth’s surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years.

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

    USGS Publications Warehouse

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

    1979-01-01

    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)

  9. NASA's DESDynI in Alaska

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    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

  10. High Resolution Modeling of the Water Cycle to Refine GRACE Signal Analysis in the Gulf of Alaska Drainage

    NASA Astrophysics Data System (ADS)

    Beamer, J.; Hill, D. F.; Arendt, A. A.; Luthcke, S. B.; Liston, G. E.

    2015-12-01

    A comprehensive study of the Gulf of Alaska (GOA) drainage basin was carried out to improve understanding of the coastal freshwater discharge (FWD) and surface mass balance (SMB) of glaciers. Coastal FWD and SMB for all glacier surfaces were modeled using a suite of physically based, spatially distributed weather, energy-balance snow/ice melt, soil water balance, and runoff routing models at a high resolution (1 km horizontal grid; daily time step). A 35 year hind cast was performed, providing complete records of precipitation, runoff, snow water equivalent (SWE) depth, evapotranspiration, coastal FWD and glacier SMB. Meteorological forcing was provided by the North American Regional Reanalysis (NARR), Modern Era Retrospective Analysis for Research and Applications (MERRA), and NCEP Climate Forecast System Reanalysis (CFSR) datasets. A fourth dataset was created by bias-correcting the NARR data to recently-developed monthly weather grids based on PRISM climatologies (NARR-BC). Each weather dataset and model combination was individually calibrated using PRISM climatologies, streamflow, and glacier mass balance measurements from four locations in the study domain. Simulated mean annual FWD into the GOA ranged from 600 km3 yr-1 using NARR to 850 km3 yr-1 from NARR-BC. The CFSR-forced simulations with optimized model parameters produced a simulated regional water storage that compared favorably to data from the NASA/DLR Gravity Recovery and Climate Experiment (GRACE) high resolution mascon solutions (Figure). Glacier runoff, taken as the sum of rainfall, snow and ice melt occurring on glacier surfaces, ranged from 260 km3 yr-1 from MERRA to 400 km3 yr-1 from NARR-BC, approximately one half of the signal from both glaciers and surrounding terrain. The large contribution from non-glacier surfaces to the seasonal water balance is likely not being fully removed from GRACE solutions aimed at isolating the glacier signal alone. We will discuss methods to use our simulations

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

    USGS Publications Warehouse

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

    1996-01-01

    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.

  12. Results of geological and geochemical investigations in an area northwest of the Chulitna River, central Alaska Range

    USGS Publications Warehouse

    Hawley, C.C.; Clark, A.L.; Herdrick, M.A.; Clark, S.H.B.

    1969-01-01

    Sedimentary and volcanic rock units of Paleozoic and Mesozoic age, faults, and elongate bodies of intrusive rock, particularly serpentinites, have a dominant northeasterly trend in an area northwest of the Chulitna River between Eldridge Glacier and Bull River. The serpentinites locally contain abnormal (as much as 0.5 percent) concentrations of nickel, have one newly identified occurrence of chromite, and are hosts to small epigenetic lodes containing copper, gold, and silver. Other epigenetic concentrations of copper or other metals occur in interlayered basalt and limestone at Partin and Canyon Creeks in the southwestern part of the area and in porphyry near Costello Creek in the northern part of the area. Tin occurs in greisen on upper Ohio Creek, and abnormal concentrations of tin also characterize mineralized rocks along Canyon Creek and at a prospect near Long Creek. Mineralized rocks characterized by silver, lead, and zinc crop out near Lookout Mountain. Anomalous concentrations of gold and other metals occur in stream sediments at isolated sites in upper Long Creek and at Coal Creek, as well as in several areas near known lode mineral occurrences. Shotgun and McCallie Creeks both contain stream sediments with anomalous concentrations of metals and both head into the basalt-limestone unit which is the host rock at Partin and Canyon Creeks; these facts suggest that other concentrations may be found.

  13. Recruiting first generation college students into the Geosciences: Alaska's EDGE project

    NASA Astrophysics Data System (ADS)

    Prakash, A.; Connor, C.

    2008-12-01

    Funded in 2005-2008, by the National Science Foundation's Geoscience Education Division, the Experiential Discoveries in Geoscience Education (EDGE) project was designed to use glacier and watershed field experiences as venues for geospatial data collected by Alaska's grade 6-12 middle and high school teachers and their students. EDGE participants were trained in GIS and learned to analyze geospatial data to answer questions about the warming Alaska environment and to determine rates of ongoing glacier recession. Important emphasis of the program was the recruitment of Alaska Native students of Inupiat, Yup'ik, Athabascan, and Tlingit populations, living in both rural and urban areas around the state. Twelve of Alaska's 55 school districts have participated in the EDGE program. To engage EDGE students in the practice of scientific inquiry, each was required to carry out a semester scale research project using georeferenced data, guided by their EDGE teacher and mentor. Across Alaska students investigated several Earth systems processes including freezing conditions of lake ice; the changes in water quality in storm drains after rainfall events; movements of moose, bears, and bison across Alaskan landscapes; changes in permafrost depth in western Alaska; and the response of migrating waterfowl to these permafrost changes. Students correlated the substrate beneath their schools with known earthquake intensities; measured cutbank and coastal erosion on northern rivers and southeastern shorelines; tracked salmon infiltration of flooded logging roads; noted the changing behavior of eagles during late winter salmon runs; located good areas for the use of tidal power for energy production; tracked the extent and range of invasive plant species with warming; and the change of forests following deglaciation. Each cohort of EDGE students and teachers finished the program by attended a 3-day EDGE symposium at which students presented their research projects first in a

  14. 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)

    Benson, Carl S.

    1994-01-01

    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.

  15. Environmental geochemistry at Red Mountain, an unmined volcanogenic massive sulphide deposit in the Bonnifield district, Alaska Range, east-central Alaska

    USGS Publications Warehouse

    Eppinger, R.G.; Briggs, P.H.; Dusel-Bacon, C.; Giles, S.A.; Gough, L.P.; Hammarstrom, J.M.; Hubbard, B.E.

    2007-01-01

    The unmined, pyrite-rich Red Mountain (Dry Creek) deposit displays a remarkable environmental footprint of natural acid generation, high metal and exceedingly high rate earth element (REE) concentrations in surface waters. The volcanogenic massive sulphide deposit exhibits well-constrained examples of acid-generating, metal-leaching, metal-precipitation and self-mitigation (via co-precipitation, dilution and neutralization) processes that occur in an undisturbed natural setting, a rare occurrence in North America. Oxidative dissolution of pyrite and associated secondary reactions under near-surface oxidizing conditions are the primary causes for the acid generation and metal leaching. The deposit is hosted in Devonian to Mississippian felsic metavolcanic rocks of the Mystic Creek Member of the Totatlanika Schist. Water samples with the lowest pH (many below 3.5), highest specific conductance (commonly >2500 ??S/cm) and highest major- and trace-element concentrations are from springs and streams within the quartz-sericite-pyrite alteration zone. Aluminum, Cd, Co, Cu, Fe, Mn, Ni, Pb, Y, Zn and, particularly, the REEs are found in high concentrations, ranging across four orders of magnitude. Waters collected upstream from the alteration zone have near-neutral pH, lower specific conductance (370 to 830 ??S/cm), lower metal concentrations and measurable alkalinities. Water samples collected downstream of the alteration zone have pH and metal concentrations intermediate between these two extremes. Stream sediments are anomalous in Zn, Pb, S, Fe, Cu, As, Co, Sb and Cd relative to local and regional background abundances. Red Mountain Creek and its tributaries do not, and probably never have, supported significant aquatic life. ?? 2007 AAG/ Geological Society of London.

  16. 36 CFR 13.1130 - Is commercial fishing authorized in the marine waters of Glacier Bay National Park?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... authorized in the marine waters of Glacier Bay National Park? 13.1130 Section 13.1130 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Commercial Fishing § 13.1130 Is...

  17. 36 CFR 13.1130 - Is commercial fishing authorized in the marine waters of Glacier Bay National Park?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... authorized in the marine waters of Glacier Bay National Park? 13.1130 Section 13.1130 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL PARK SYSTEM UNITS IN ALASKA Special Regulations-Glacier Bay National Park and Preserve Commercial Fishing § 13.1130 Is...

  18. Ellesmerian (. ) and Brookian deformation in the Franklin Mountains, northeastern Brooks Range, Alaska, and its bearing on the origin of the Canada Basin

    SciTech Connect

    Oldow, J.S.; Ave Lallemant, H.G.; Julian, F.E.; Seidensticker, C.M.

    1987-01-01

    Structural analysis of deformed rocks in the Franklin Mountains, northeastern Alaska, indicates that (1) pre-Carboniferous rocks were transported southeastward during mid-Devonian (Ellesmerian.) thrusting, (2) Cretaceous and older rocks were transported northward during Mesozoic-Cenozoic Brookian thrusting, and (3) the pre-Carboniferous rocks were strongly involved in the Brookian deformation. The strong involvement of these rocks in Brookian structures suggests that the magnitude of northward thrusting during Brookian tectonism is virtually uniform from west to east along the axis of the Brooks Range fold and thrust belt. In addition, the newly recognized southern vergence of pre-Carboniferous structures is comparable with that of coeval structures exposed in Arctic Canada to the east. These data are not easily reconciled with the orocline model for the origin of the Canada Basin but are consistent with left-lateral transport on a north-south-striking transform fault along the Canadian Arctic islands. 19 references.

  19. Glaciers in 21st Century Himalayan Geopolitics

    NASA Astrophysics Data System (ADS)

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

    2002-05-01

    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.

  20. The Middle Fork Plutonic Complex: A plutonic association of coeval peralkaline and metaluminous magmas in the north-central Alaska Range

    SciTech Connect

    Solie, D.N.

    1988-01-01

    The 57 m.y. Middle Fork Plutonic Complex (MFPC) intrudes Paleozoic metasedimentary rocks south of the Farewell Fault zone in the north-central Alaska Range. Though spatially related to the late Cretaceous - Early Tertiary subduction-related Alaska Range batholith, MFPC is more characteristic of an extensional or anorogenic setting. A swarm of basalt, hawaiite and rhyolite dikes east of the complex intruded, and was intruded by, the plutonic rocks. Approximately 30% of the exposed rock in the 125 km[sup 2] complex is hedenbergite - fayalite syenite, [approx equal]20% is peralkalin arfvedsonite-biotite alkali-feldspar granite (AF granite), and [le]20% is pyroxene-olivine-biotite gabbro. The rest is a mixed unit including clinopyroxene-biotite-amphibole diorite, and hornblende-biotite granite (HB granite). K-Ar and Rb-Sr radiometric dating of rock types shows that they are coeval. Their close spatial and temporal relationships led to complex magmatic interactions. Calculated initial [sup 87]Sr/[sup 86]Sr for gabbro and diorite group is around 0.705 to 0.706. HB granites are heterogeneous, but fall mostly around 0.707 to 0.708. Hypersolvus syenites and AF granites form an isochron with initial [sup 87]Sr/[sup 86]Sr of 0.70965. These groupings suggest that at least three different magmas formed the MFPC; scatter of isotopic data reflects mutual contamination and assimilation. Consanguinous hypersolvus syenite and AF granite mineralogy appears to be controlled by fluorine in the magma chamber. Eruptive stratigraphy, as predicted by intrusive history of MFPC, compares favorably with volcanic stratigraphies of peralkaline volcanic systems worldwide, and MFPC may be modelled as the root zone of a peralkaline volcanic system.