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Sample records for alaska lake ice

  1. Backscatter from ice growing on shallow tundra lakes near Barrow, Alaska, winter 1991-1992

    NASA Technical Reports Server (NTRS)

    Jeffries, M. O.; Wakabayashi, H.; Weeks, W. F.; Morris, K.

    1993-01-01

    The timing of freeze-up and break-up of Arctic lake ice is a potentially useful environmental indicator that could be monitored using SAR. In order to do this, it is important to understand how the properties and structure of the ice during its growth and decay affect radar backscatter and thus lake ice SAR signatures. The availability of radiometrically and geometrically calibrated digital SAR data time series from the Alaska SAR Facility has made it possible for the first time to quantify lake ice backscatter intensity (sigma(sup o)) variations. This has been done for ice growing on shallow tundra lakes near Barrow, NW Alaska, from initial growth in September 1991 until thawing and decay in June 1992. Field and laboratory observations and measurements of the lake ice were made in late April 1992. The field investigations of the coastal lakes near Barrow confirmed previous findings that, (1) ice frozen to the lake bottom had a dark signature in SAR images, indicating weak backscatter, while, (2) ice that was floating had a bright signature, indicating strong backscatter. At all sites, regardless of whether the ice was grounded or floating, there was a layer of clear, inclusion-free ice overlaying a layer of ice with dense concentrations of vertically oriented tubular bubbles. At some sites, there was a third layer of porous, snow-ice overlaying the clear ice.

  2. ERS-1 SAR backscatter changes associated with ice growing on shallow lakes in Arctic Alaska

    NASA Technical Reports Server (NTRS)

    Jeffries, M. O.; Wakabayashi, H.; Weeks, W. F.

    1993-01-01

    Spatial and temporal backscatter intensity (sigma(sup o)) variations from ice growing on shallow lakes during winter 1991-92 near Barrow, NW Alaska, have been quantified for the first time using ERS-I C-band SAR data acquired at the Alaska SAR Facility. A field and laboratory validation program, including measurements of the thickness and structure-stratigraphy of the ice, indicates that sigma(sup o) values are strongly dependent on whether the ice freezes to the lake bottom, or remains afloat. Backscatter intensity decreases significantly when the ice grounds on the bottom. Strong backscatter from floating ice is attributed to a specular ice-water interface and vertically oriented tubular bubbles. During the spring thaw, backscatter undergoes a reversal; sigma(sup o) values from ice that was grounded increase, while sigma(sup o) values from ice that was afloat decrease. This phenomenon has not previously been reported.

  3. A C-band backscatter model for lake ice in Alaska

    NASA Technical Reports Server (NTRS)

    Wakabayashi, H.; Weeks, W. F.; Jeffries, M. O.

    1993-01-01

    ERS-1 SAR imagery of lake ice growing on shallow tundra lakes in northern Alaska shows interesting radar backscatter variations. Based on the analysis of ice cores from these lakes, a multi-layer backscatter model comprised of the following elements has been developed: (1) specular air-ice; ice-water and ice-frozen soil boundaries; (2) an ice layer of variable thickness; (3) ice sub-layers with air inclusions of variable density, size and shape including spheres, prolate spheroids, and cylinders of finite length. Preliminary model results confirm that backscatter is a sensitive function of greater reflectivity than from an ice-frozen soil interface. The model has also been tested using bubble data derived from ice cores in April 1992. The modelled backscatter is compared with backscatter derived from ERS-1 SAR images obtained at the same time as the fieldwork.

  4. Recent lake ice-out phenology within and among lake districts of Alaska, U.S.A.

    USGS Publications Warehouse

    Arp, Christopher D.; Jones, Benjamin M.; Grosse, Guido

    2013-01-01

    The timing of ice-out in high latitudes is a fundamental threshold for lake ecosystems and an indicator of climate change. In lake-rich regions, the loss of ice cover also plays a key role in landscape and climatic processes. Thus, there is a need to understand lake ice phenology at multiple scales. In this study, we observed ice-out timing on 55 large lakes in 11 lake districts across Alaska from 2007 to 2012 using satellite imagery. Sensor networks in two lake districts validated satellite observations and provided comparison with smaller lakes. Over this 6 yr period, the mean lake ice-out for all lakes was 27 May and ranged from 07 May in Kenai to 06 July in Arctic Coastal Plain lake districts with relatively low inter-annual variability. Approximately 80% of the variation in ice-out timing was explained by the date of 0°C air temperature isotherm and lake area. Shoreline irregularity, watershed area, and river connectivity explained additional variation in some districts. Coherence in ice-out timing within the lakes of each district was consistently strong over this 6 yr period, ranging from r-values of 0.5 to 0.9. Inter-district analysis of coherence also showed synchronous ice-out patterns with the exception of the two arctic coastal districts where ice-out occurs later (June–July) and climatology is sea-ice influenced. These patterns of lake ice phenology provide a spatially extensive baseline describing short-term temporal variability, which will help decipher longer term trends in ice phenology and aid in representing the role of lake ice in land and climate models in northern landscapes.

  5. Shifting balance of thermokarst lake ice regimes across the Arctic Coastal Plain of northern Alaska

    USGS Publications Warehouse

    Arp, Christopher D.; Jones, Benjamin M.; Lu, Zong; Whitman, Matthew S.

    2012-01-01

    The balance of thermokarst lakes with bedfast- and floating-ice regimes across Arctic lowlands regulates heat storage, permafrost thaw, winter-water supply, and over-wintering aquatic habitat. Using a time-series of late-winter synthetic aperture radar (SAR) imagery to distinguish lake ice regimes in two regions of the Arctic Coastal Plain of northern Alaska from 2003–2011, we found that 18% of the lakes had intermittent ice regimes, varying between bedfast-ice and floating-ice conditions. Comparing this dataset with a radar-based lake classification from 1980 showed that 16% of the bedfast-ice lakes had shifted to floating-ice regimes. A simulated lake ice thinning trend of 1.5 cm/yr since 1978 is believed to be the primary factor driving this form of lake change. The most profound impacts of this regime shift in Arctic lakes may be an increase in the landscape-scale thermal offset created by additional lake heat storage and its role in talik development in otherwise continuous permafrost as well as increases in over-winter aquatic habitat and winter-water supply.

  6. Arctic sea ice decline contributes to thinning lake ice trend in northern Alaska

    NASA Astrophysics Data System (ADS)

    Alexeev, Vladimir A.; Arp, Christopher D.; Jones, Benjamin M.; Cai, Lei

    2016-07-01

    Field measurements, satellite observations, and models document a thinning trend in seasonal Arctic lake ice growth, causing a shift from bedfast to floating ice conditions. September sea ice concentrations in the Arctic Ocean since 1991 correlate well (r = +0.69, p < 0.001) to this lake regime shift. To understand how and to what extent sea ice affects lakes, we conducted model experiments to simulate winters with years of high (1991/92) and low (2007/08) sea ice extent for which we also had field measurements and satellite imagery characterizing lake ice conditions. A lake ice growth model forced with Weather Research and Forecasting model output produced a 7% decrease in lake ice growth when 2007/08 sea ice was imposed on 1991/92 climatology and a 9% increase in lake ice growth for the opposing experiment. Here, we clearly link early winter ‘ocean-effect’ snowfall and warming to reduced lake ice growth. Future reductions in sea ice extent will alter hydrological, biogeochemical, and habitat functioning of Arctic lakes and cause sub-lake permafrost thaw.

  7. Arctic sea ice decline contributes to thinning lake ice trend in northern Alaska

    USGS Publications Warehouse

    Alexeev, Vladimir; Arp, Christopher D.; Jones, Benjamin M.; Cai, Lei

    2016-01-01

    Field measurements, satellite observations, and models document a thinning trend in seasonal Arctic lake ice growth, causing a shift from bedfast to floating ice conditions. September sea ice concentrations in the Arctic Ocean since 1991 correlate well (r = +0.69,p < 0.001) to this lake regime shift. To understand how and to what extent sea ice affects lakes, we conducted model experiments to simulate winters with years of high (1991/92) and low (2007/08) sea ice extent for which we also had field measurements and satellite imagery characterizing lake ice conditions. A lake ice growth model forced with Weather Research and Forecasting model output produced a 7% decrease in lake ice growth when 2007/08 sea ice was imposed on 1991/92 climatology and a 9% increase in lake ice growth for the opposing experiment. Here, we clearly link early winter 'ocean-effect' snowfall and warming to reduced lake ice growth. Future reductions in sea ice extent will alter hydrological, biogeochemical, and habitat functioning of Arctic lakes and cause sub-lake permafrost thaw.

  8. 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

  9. ERS-1 SAR monitoring of ice growth on shallow lakes to determine water depth and availability in north west Alaska

    NASA Technical Reports Server (NTRS)

    Jeffries, Martin; Morris, Kim; Liston, Glen

    1996-01-01

    Images taken by the ERS-1 synthetic aperture radar (SAR) were used to identify and to differentiate between the lakes that freeze completely to the bottom and those that do not, on the North Slope, in northwestern Alaska. The ice thickness at the time each lake froze completely is determined with numerical ice growth model that gives a maximum simulated thickness of 2.2 m. A method combining the ERS-1 SAR images and numerical ice growth model was used to determine the ice growth and the water availability in these regions.

  10. Bedfast and floating ice lake talik properties measured using surface nuclear magnetic resonance on the North Slope, Alaska

    NASA Astrophysics Data System (ADS)

    Parsekian, A.; Jones, B. M.; Arp, C. D.; Creighton, A.; Daanen, R. P.; Gaedeke, A.; Bondurant, A.

    2015-12-01

    Lakes within permafrost regions have been identified as a source of carbon gas emissions, however the geometry of the thawed sediments and water content below these lakes that hold the carbon-rich source sediment remains difficult to measure. Surface nuclear magnetic resonance (NMR) is a geophysical measurement that is unambiguously sensitive to liquid water and therefore is well suited to discriminating between the sub-lake talik (thaw bulb) and surrounding permafrost. Here we report on talik thickness, water content, and pore scale properties observed using surface NMR in lakes located on the Arctic Coastal Plain of northern Alaska. The study lakes range in size from 0.5 km - 2 km in diameter. They have formed within a Pleistocene sand sheet deposit where permafrost extends 200 to 300 m below the surface. Lake depth ranges from less than 1 m (bedfast ice) to 5 m (floating ice); drained lake basins with no water or water ice were also measured for comparison. Floating ice lakes are interpreted to have a talik between 20 - 25 m below the surface. Bedfast ice lakes had either no measureable talik, a talik to < 20 m, or an isolated talik. Drained lake basins had either no measureable talik or an isolated talik. The presence of isolated taliks below some bedfast ice lakes and drained lake basins was a surprising result, suggesting that zones of unfrozen sediment may be present in the region even when the surface conditions suggest otherwise. These results of talik presence/absence and geometry bring new insight into permafrost-influenced lake subsurface hydrology and provide value data for validating hydrological modeling outputs. Our application of using surface NMR on Arctic Lakes will be extended to the region with numerous thermokarst lakes and drained lake basins north of Teshekpuk Lake next April.

  11. Integration of MODIS-derived metrics to assess interannual variability in snowpack, lake ice, and NDVI in southwest Alaska

    USGS Publications Warehouse

    Reed, B.; Budde, M.; Spencer, P.; Miller, A.E.

    2009-01-01

    Impacts of global climate change are expected to result in greater variation in the seasonality of snowpack, lake ice, and vegetation dynamics in southwest Alaska. All have wide-reaching physical and biological ecosystem effects in the region. We used Moderate Resolution Imaging Spectroradiometer (MODIS) calibrated radiance, snow cover extent, and vegetation index products for interpreting interannual variation in the duration and extent of snowpack, lake ice, and vegetation dynamics for southwest Alaska. The approach integrates multiple seasonal metrics across large ecological regions. Throughout the observation period (2001-2007), snow cover duration was stable within ecoregions, with variable start and end dates. The start of the lake ice season lagged the snow season by 2 to 3??months. Within a given lake, freeze-up dates varied in timing and duration, while break-up dates were more consistent. Vegetation phenology varied less than snow and ice metrics, with start-of-season dates comparatively consistent across years. The start of growing season and snow melt were related to one another as they are both temperature dependent. Higher than average temperatures during the El Ni??o winter of 2002-2003 were expressed in anomalous ice and snow season patterns. We are developing a consistent, MODIS-based dataset that will be used to monitor temporal trends of each of these seasonal metrics and to map areas of change for the study area.

  12. Hydrogeomorphic processes of thermokarst lakes with grounded-ice and floating-ice regimes on the Arctic coastal plain, Alaska

    USGS Publications Warehouse

    Arp, C.D.; Jones, Benjamin M.; Urban, F.E.; Grosse, G.

    2011-01-01

    Thermokarst lakes cover > 20% of the landscape throughout much of the Alaskan Arctic Coastal Plain (ACP) with shallow lakes freezing solid (grounded ice) and deeper lakes maintaining perennial liquid water (floating ice). Thus, lake depth relative to maximum ice thickness (1·5–2·0 m) represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behaviour. We studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum ice thickness by analysing remotely sensed, water quality, and climatic data over a 35-year period. Shoreline erosion rates due to permafrost degradation ranged from L) with periods of full and nearly dry basins. Shorter-term (2004–2008) specific conductance data indicated a drying pattern across lakes of all depths consistent with the long-term record for only shallow lakes. Our analysis suggests that grounded-ice lakes are ice-free on average 37 days longer than floating-ice lakes resulting in a longer period of evaporative loss and more frequent negative P − EL. These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum ice thickness in ACP lakes.

  13. 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)

  14. Ground penetrating radar detection of subsnow slush on ice-covered lakes in interior Alaska

    NASA Astrophysics Data System (ADS)

    Gusmeroli, A.; Grosse, G.

    2012-12-01

    Lakes are abundant throughout the pan-Arctic region. For many of these lakes ice cover lasts for up to two thirds of the year. The frozen cover allows human access to these lakes, which are therefore used for many subsistence and recreational activities, including water harvesting, fishing, and skiing. Safe traveling condition onto lakes may be compromised, however, when, after significant snowfall, the weight of the snow acts on the ice and causes liquid water to spill through weak spots and overflow at the snow-ice interface. Since visual detection of subsnow slush is almost impossible our understanding on overflow processes is still very limited and geophysical methods that allow water and slush detection are desirable. In this study we demonstrate that a commercially available, lightweight 1 GHz, ground penetrating radar system can detect and map extent and intensity of overflow. The strength of radar reflections from wet snow-ice interfaces are at least twice as much in strength than returns from dry snow-ice interface. The presence of overflow also affects the quality of radar returns from the base of the lake ice. During dry conditions we were able to profile ice thickness of up to 1 m, conversely, we did not retrieve any ice-water returns in areas affected by overflow.

  15. The Alaska Lake Ice and Snow Observatory Network (ALISON): Hands-on Experiential K- 12 Learning in the North

    NASA Astrophysics Data System (ADS)

    Morris, K.; Jeffries, M.

    2008-12-01

    The Alaska Lake Ice and Snow Observatory Network (ALISON) was initiated by Martin Jeffries (UAF polar scientist), Delena Norris-Tull (UAF education professor) and Ron Reihl (middle school science teacher, Fairbanks North Star Borough School District). The snow and ice measurement protocols were developed in 1999-2000 at the Poker Flat Research Range (PFRR) by Geophysical Institute, University of Alaska scientists and tested by home school teacher/students in winter 2001-2002 in Fairbanks, AK. The project was launched in 2002 with seven sites around the state (PFRR, Fairbanks, Barrow, Mystic Lake, Nome, Shageluk and Wasilla). The project reached its broadest distribution in 2005-2006 with 22 sites. The schools range from urban (Wasilla) to primarily Alaska native villages (Shageluk). They include public schools, charter schools, home schooled students and parents, informal educators and citizen scientists. The grade levels range from upper elementary to high school. Well over a thousand students have participated in ALISON since its inception. Equipment is provided to the observers at each site. Measurements include ice thickness (with a hot wire ice thickness gauge), snow depth and snow temperature (surface and base). Snow samples are taken and snow density derived. Snow variables are used to calculate the conductive heat flux through the ice and snow cover to the atmosphere. All data are available on the Web site. The students and teachers are scientific partners in the study of lake ice processes, contributing to new scientific knowledge and understanding while also learning science by doing science with familiar and abundant materials. Each autumn, scientists visit each location to work with the teachers and students, helping them to set up the study site, showing them how to make the measurements and enter the data into the computer, and discussing snow, ice and polar environmental change. A number of 'veteran' teachers are now setting up the study sites on

  16. Structural and stratigraphic features and ERS 1 synthetic aperture radar backscatter characteristics of ice growing on shallow lakes in NW Alaska, winter 1991-1992

    NASA Astrophysics Data System (ADS)

    Jeffries, M. O.; Morris, K.; Weeks, W. F.; Wakabayashi, H.

    1994-11-01

    Changes in ERS 1 C band synthetic aperture radar (SAR) backscatter intensity (σ°) from ice growing on shallow tundra lakes at three locations in NW Alaska are described. Ice core analysis shows that at all lakes on the coast at Barrow the ice, whether floating or frozen to the bottom, includes an inclusion-free layer overlying a layer of ice with tubular bubbles oriented parallel to the direction of growth. The clear ice may also be overlain by a discontinuous layer of bubbly snow ice. Backscatter is low (-16 to -22 dB) at the time of initial ice formation, probably due to the specular nature of the upper and lower ice surfaces causing the radar pulse to be reflected away from the radar. As the ice thickens during the autumn, backscatter rises steadily. Once the ice freezes to the lake bottom, regardless of the presence of forward scattering tubular bubbles, low backscatter values of-17 to -18 dB are caused by absorption of the radar signal in the lake bed. For ice that remains afloat all winter the ice-water interface and the tubular bubbles combine, presumably via an incoherent double-bounce mechanism, to cause maximum backscatter values of the order of -6 to -7 dB. The σ° saturates at -6 to -7 dB before maximum ice thickness and tubular bubble content are attained. A simple ice growth model suggests that the layer of ice with tubular bubbles need be only a few centimeters thick midway through the growth season to cause maximum backscatter from floating ice. During the spring thaw a previously unreported backscatter reversal is observed on the floating and grounded portions of the coastal lakes but not on the lakes farther inland. This reversal may be related to the ice surface topography and wetness plus the effects of a longer, cooler melt period by the coast. Time series of backscatter variations from shallow tundra lakes are a record of (1) the development of tubular bubbles in the ice and, by association, changes in the gas content of the underlying

  17. Structural and stratigraphic features and ERS 1 synthetic aperture radar backscatter characteristics of ice growing on shallow lakes in NW Alaska, winter 1991-1992

    NASA Technical Reports Server (NTRS)

    Jeffries, M. O.; Morris, K.; Weeks, W. F.; Wakabayashi, H.

    1994-01-01

    Changes in Earth Remote-Sensing Satellite (ERS) 1 C band synthetic aperture radar (SAR) backscatter intensity (sigma(exp 0)) from ice growing on shallow tundra lakes at three locations in NW Alaska are described. Ice core analysis shows that all lakes on the coast at Barrow the ice, whether floating or frozen to the bottom, includes an inclusion-free layer overlying a layer of ice with tubular bubbles oriented parallel to the direction of growth. The clear ice may also be overlain by a discontinuous layer of bubbly snow ice. Backscatter is low (-16 to -22 dB) at the time of initial ice formation, probably due to the specular nature of the upper and lower ice surfaces causing the radar pulse to be reflected away from the radar. As the ice thickens during the autumn, backscatter rises steadily. Once the ice freezes to the lake bottom, regardless of the presence of foward scattering tubular bubbles, low backscatter values of -17 to -18 dB are caused by absorption of the radar signal in the lake bed. For ice that remains afloat all winter the ice-water interface and the tubular bubbles combine, presumably via an incoherent double-bounce mechanism, to cause maximum backscatter values of the order of -6 to -7 dB. The sigma(exp 0) saturates at -6 to -7 dB before maximum ice thickness and tubular bubble content are attained. A simple ice growth model suggests that the layer of ice with tubular bubbles need be only a few centimeters thick midway through the growth season to cause maximum backscatter from floating ice. During the spring thaw a previously unreported backscatter reversal is observed on the floating and grounded portions of the coastal lakes but not on the lakes farther inland. This reversal may be related to the ice surface topography and wetness plus the effects of a longer, cooler melt period by the coast. Time series of backscatter variations from shallow tundra lakes are a record of (1) the development of tubular bubbles in the ice and, by association

  18. Stratigraphic evidence for rate of sedimentation in an ice-contact, proglacial lake, Bering Glacier, Alaska

    SciTech Connect

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

    1993-03-01

    A semi-continuous aerial photo record documents retreat positions of the eastern Bering Glacier and the development of a shallow embayment of ice-contact Tsiu Lake during the summer of 1986. An observed break out in August, 1989, abruptly dropped lake level 17 m and exposed lake sediments containing three annual couplets 54 cm thick. This continuous record of accumulation during a documented 3-year period yields an average annual accumulation rate of 18 cm/year. The lower portion of each annual couplet averages 11.5 cm in thickness and consists of fine, gray silt laminae, each approximately 0.7 mm thick. These grade upward into interlaminated light and dark gray silt and tan, very fine sand beds, each about 0.5 cm thick, with an average cumulative thickness of 6.5 cm. The sand is commonly cross bedded and contains subtle graded bedding. Because the uppermost interlaminated unit was the last to be deposited prior to the break out, it must represent summer-season sediments. This interpretation is consistent with intermittent higher summer discharge and associated currents that periodically introduce sand and hold silt in suspension. Lower energy conditions beneath frozen lakes during winter months favor quieter water and yield a thicker accumulation of uniform silt. Measurements of contemporary summer accumulation were made using cylinder sediment traps. Resulting data indicate that rates of sediment accumulation are directly related to length of collection column, trap depth, duration of sample period and turbidity, and may be an order of magnitude greater than that represented by the measured stratigraphic record. These field studies shed light on specific conditions of deposition and the glaciolacustrine environment during Laurentide retreat from central New York State.

  19. Response of ice cover on shallow lakes of the North Slope of Alaska to contemporary climate conditions (1950-2011): radar remote sensing and numerical modeling data analysis

    NASA Astrophysics Data System (ADS)

    Surdu, C. M.; Duguay, C. R.; Brown, L. C.; Fernández Prieto, D.

    2013-07-01

    Air temperature and winter precipitation changes over the last five decades have impacted the timing, duration, and thickness of the ice cover on Arctic lakes as shown by recent studies. In the case of shallow tundra lakes, many of which are less than 3 m deep, warmer climate conditions could result in thinner ice covers and consequently, to a smaller fraction of lakes freezing to their bed in winter. However, these changes have not yet been comprehensively documented. The analysis of a 20 yr time series of ERS-1/2 synthetic aperture radar (SAR) data and a numerical lake ice model were employed to determine the response of ice cover (thickness, freezing to the bed, and phenology) on shallow lakes of the North Slope of Alaska (NSA) to climate conditions over the last six decades. Analysis of available SAR data from 1991-2011, from a sub-region of the NSA near Barrow, shows a reduction in the fraction of lakes that freeze to the bed in late winter. This finding is in good agreement with the decrease in ice thickness simulated with the Canadian Lake Ice Model (CLIMo), a lower fraction of lakes frozen to the bed corresponding to a thinner ice cover. Observed changes of the ice cover show a trend toward increasing floating ice fractions from 1991 to 2011, with the greatest change occurring in April, when the grounded ice fraction declined by 22% (α = 0.01). Model results indicate a trend toward thinner ice covers by 18-22 cm (no-snow and 53% snow depth scenarios, α = 0.01) during the 1991-2011 period and by 21-38 cm (α = 0.001) from 1950-2011. The longer trend analysis (1950-2011) also shows a decrease in the ice cover duration by ∼24 days consequent to later freeze-up dates by 5.9 days (α = 0.1) and earlier break-up dates by 17.7-18.6 days (α = 0.001).

  20. Peat accumulation in drained thermokarst lake basins in continuous, ice-rich permafrost, northern Seward Peninsula, Alaska

    USGS Publications Warehouse

    Jones, Miriam C.; Grosse, Guido; Jones, Benjamin M.; Anthony, Katey Walter

    2012-01-01

    Thermokarst lakes and peat-accumulating drained lake basins cover a substantial portion of Arctic lowland landscapes, yet the role of thermokarst lake drainage and ensuing peat formation in landscape-scale carbon (C) budgets remains understudied. Here we use measurements of terrestrial peat thickness, bulk density, organic matter content, and basal radiocarbon age from permafrost cores, soil pits, and exposures in vegetated, drained lake basins to characterize regional lake drainage chronology, C accumulation rates, and the role of thermokarst-lake cycling in carbon dynamics throughout the Holocene on the northern Seward Peninsula, Alaska. Most detectable lake drainage events occurred within the last 4,000 years with the highest drainage frequency during the medieval climate anomaly. Peat accumulation rates were highest in young (50–500 years) drained lake basins (35.2 g C m−2 yr−1) and decreased exponentially with time since drainage to 9 g C m−2 yr−1 in the oldest basins. Spatial analyses of terrestrial peat depth, basal peat radiocarbon ages, basin geomorphology, and satellite-derived land surface properties (Normalized Difference Vegetation Index (NDVI); Minimum Noise Fraction (MNF)) from Landsat satellite data revealed significant relationships between peat thickness and mean basin NDVI or MNF. By upscaling observed relationships, we infer that drained thermokarst lake basins, covering 391 km2 (76%) of the 515 km2 study region, store 6.4–6.6 Tg organic C in drained lake basin terrestrial peat. Peat accumulation in drained lake basins likely serves to offset greenhouse gas release from thermokarst-impacted landscapes and should be incorporated in landscape-scale C budgets.

  1. 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.

  2. Effect of permafrost thaw on the dynamics of lakes recharged by ice-jam floods: case study in Yukon Flats, Alaska

    USGS Publications Warehouse

    Steve M. Jepsen,; Walvoord, Michelle Ann; Voss, Clifford I.; Rover, Jennifer R.

    2015-01-01

    Large river floods are a key water source for many lakes in fluvial periglacial settings. Where permeable sediments occur, the distribution of permafrost may play an important role in the routing of floodwaters across a floodplain. This relationship is explored for lakes in the discontinuous permafrost of Yukon Flats, interior Alaska, using an analysis that integrates satellite-derived gradients in water surface elevation, knowledge of hydrogeology, and hydrologic modeling. We observed gradients in water surface elevation between neighboring lakes ranging from 0.001 to 0.004. These high gradients, despite a ubiquitous layer of continuous shallow gravel across the flats, are consistent with limited groundwater flow across lake basins resulting from the presence of permafrost. Permafrost impedes the propagation of floodwaters in the shallow subsurface and constrains transmission to “fill-and-spill” over topographic depressions (surface sills), as we observed for the Twelvemile-Buddy Lake pair following a May 2013 ice-jam flood on the Yukon River. Model results indicate that permafrost table deepening of 1–11 m in gravel, depending on watershed geometry and subsurface properties, could shift important routing of floodwater to lakes from overland flow (fill-and-spill) to shallow groundwater flow (“fill-and-seep”). Such a shift is possible in the next several hundred years of ground surface warming, and may bring about more synchronous water level changes between neighboring lakes following large flood events. This relationship offers a potentially useful tool, well-suited to remote sensing, for identifying long-term changes in shallow groundwater flow resulting from thawing of permafrost.

  3. Depth, ice thickness, and ice-out timing cause divergent hydrologic responses among Arctic lakes

    USGS Publications Warehouse

    Arp, Christopher D.; Jones, Benjamin M.; Liljedahl, Anna K.; Hinkel, Kenneth M.; Welker, Jeffery A.

    2015-01-01

    Lakes are prevalent in the Arctic and thus play a key role in regional hydrology. Since many Arctic lakes are shallow and ice grows thick (historically 2-m or greater), seasonal ice commonly freezes to the lake bed (bedfast ice) by winter's end. Bedfast ice fundamentally alters lake energy balance and melt-out processes compared to deeper lakes that exceed the maximum ice thickness (floating ice) and maintain perennial liquid water below floating ice. Our analysis of lakes in northern Alaska indicated that ice-out of bedfast ice lakes occurred on average 17 days earlier (22-June) than ice-out on adjacent floating ice lakes (9-July). Earlier ice-free conditions in bedfast ice lakes caused higher open-water evaporation, 28% on average, relative to floating ice lakes and this divergence increased in lakes closer to the coast and in cooler summers. Water isotopes (18O and 2H) indicated similar differences in evaporation between these lake types. Our analysis suggests that ice regimes created by the combination of lake depth relative to ice thickness and associated ice-out timing currently cause a strong hydrologic divergence among Arctic lakes. Thus understanding the distribution and dynamics of lakes by ice regime is essential for predicting regional hydrology. An observed regime shift in lakes to floating ice conditions due to thinner ice growth may initially offset lake drying because of lower evaporative loss from this lake type. This potential negative feedback caused by winter processes occurs in spite of an overall projected increase in evapotranspiration as the Arctic climate warms.

  4. Depth, ice thickness, and ice-out timing cause divergent hydrologic responses among Arctic lakes

    NASA Astrophysics Data System (ADS)

    Arp, Christopher D.; Jones, Benjamin M.; Liljedahl, Anna K.; Hinkel, Kenneth M.; Welker, Jeffery A.

    2015-12-01

    Lakes are prevalent in the Arctic and thus play a key role in regional hydrology. Since many Arctic lakes are shallow and ice grows thick (historically 2 m or greater), seasonal ice commonly freezes to the lake bed (bedfast ice) by winter's end. Bedfast ice fundamentally alters lake energy balance and melt-out processes compared to deeper lakes that exceed the maximum ice thickness (floating ice) and maintain perennial liquid water below floating ice. Our analysis of lakes in northern Alaska indicated that ice-out of bedfast ice lakes occurred on average 17 days earlier (22 June) than ice-out on adjacent floating ice lakes (9 July). Earlier ice-free conditions in bedfast ice lakes caused higher open-water evaporation, 28% on average, relative to floating ice lakes and this divergence increased in lakes closer to the coast and in cooler summers. Water isotopes (18O and 2H) indicated similar differences in evaporation between these lake types. Our analysis suggests that ice regimes created by the combination of lake depth relative to ice thickness and associated ice-out timing currently cause a strong hydrologic divergence among Arctic lakes. Thus, understanding the distribution and dynamics of lakes by ice regime is essential for predicting regional hydrology. An observed regime shift in lakes to floating ice conditions due to thinner ice growth may initially offset lake drying because of lower evaporative loss from this lake type. This potential negative feedback caused by winter processes occurs in spite of an overall projected increase in evapotranspiration as the Arctic climate warms.

  5. Gravity anomaly at a Pleistocene lake bed in NW Alaska interpreted by analogy with Greenland's Lake Taserssauq and its floating ice tongue

    USGS Publications Warehouse

    Barnes, D.F.

    1987-01-01

    A possible example of a very deep glacial excavation is provided by a distinctive gravity low located at the front of a valley glacier that once flowed into glacial Lake Aniuk (formerly Lake Noatak) in the western Brooks Range. Geologic and geophysical data suggest that sediments or ice filling a glacially excavated valley are the most probable cause of the 30-50 mGal anomaly. Reasonable choices of geometric models and density contrasts indicate that the former excavation is now filled with a buried-ice thickness of 700 m or sediment thicknesses greater than 1 km. No direct evidence of efficient excavation was observed in Greenland, but efficient glacial erosion behind a floating polar ice tongue could explain the excavation that caused the Alaskan gravity anomaly. -from Author

  6. Teshekpuk Lake, Alaska

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This ASTER image of Teshekpuk Lake on Alaska's North Slope, within the National Petroleum Reserve, was acquired on August 15, 2000. It covers an area of 58.7 x 89.9 km, and is centered near 70.4 degrees north latitude, 153 degrees west longitude.

    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 images Earth to map and monitor the changing surface of our planet.

    ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

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

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

    Size: 58.7 by 89.9 kilometers (36.4 by 55.7 miles) Location: 70.4 degrees North latitude, 153 degrees West longitude Orientation: North at top Image Data: ASTER Bands 3, 2, and 1 Original Data Resolution: ASTER 30 meters (98.4 feet) Dates Acquired: August 15, 2000

  7. Response of ice cover on shallow lakes of the North Slope of Alaska to contemporary climate conditions (1950-2011): radar remote-sensing and numerical modeling data analysis

    NASA Astrophysics Data System (ADS)

    Surdu, C. M.; Duguay, C. R.; Brown, L. C.; Fernández Prieto, D.

    2014-01-01

    Air temperature and winter precipitation changes over the last five decades have impacted the timing, duration, and thickness of the ice cover on Arctic lakes as shown by recent studies. In the case of shallow tundra lakes, many of which are less than 3 m deep, warmer climate conditions could result in thinner ice covers and consequently, in a smaller fraction of lakes freezing to their bed in winter. However, these changes have not yet been comprehensively documented. The analysis of a 20 yr time series of European remote sensing satellite ERS-1/2 synthetic aperture radar (SAR) data and a numerical lake ice model were employed to determine the response of ice cover (thickness, freezing to the bed, and phenology) on shallow lakes of the North Slope of Alaska (NSA) to climate conditions over the last six decades. Given the large area covered by these lakes, changes in the regional climate and weather are related to regime shifts in the ice cover of the lakes. Analysis of available SAR data from 1991 to 2011, from a sub-region of the NSA near Barrow, shows a reduction in the fraction of lakes that freeze to the bed in late winter. This finding is in good agreement with the decrease in ice thickness simulated with the Canadian Lake Ice Model (CLIMo), a lower fraction of lakes frozen to the bed corresponding to a thinner ice cover. Observed changes of the ice cover show a trend toward increasing floating ice fractions from 1991 to 2011, with the greatest change occurring in April, when the grounded ice fraction declined by 22% (α = 0.01). Model results indicate a trend toward thinner ice covers by 18-22 cm (no-snow and 53% snow depth scenarios, α = 0.01) during the 1991-2011 period and by 21-38 cm (α = 0.001) from 1950 to 2011. The longer trend analysis (1950-2011) also shows a decrease in the ice cover duration by ~24 days consequent to later freeze-up dates by 5.9 days (α = 0.1) and earlier break-up dates by 17.7-18.6 days (α = 0.001).

  8. Digital data base of lakes on the North Slope, Alaska

    USGS Publications Warehouse

    Walker, Kim-Marie; York, James; Murphy, Dennis; Sloan, C.E.

    1986-01-01

    The National Mapping Division and Water Resources Division of the U.S. Geological Survey have produced a digital data base of approximately 23,330 lakes on the North Slope of Alaska. The inventoried region consists of the area north of the 69th parallel and is composed of sixteen 1 degree by 3 degree quadrangles. The data base includes (1) locations of lake centers in latitude and longitude, (2) a unique number for each lake within a quadrangle, and (3) acreage for water classes (deep, shallow or turbid, and ice) within each lake and lake total. The digital data base is an easily accessible storage and retrieval system that will allow for rapid identification of a particular lake or region of lakes and its characteristics. The data base is designed to accommodate field study data such as lake depth, water quality, volume of water, ice thickness, and other pertinent information. (Author 's abstract)

  9. Observing a catastrophic thermokarst lake drainage in northern Alaska

    USGS Publications Warehouse

    Jones, Benjamin M.; Arp, Christopher D.

    2015-01-01

    The formation and drainage of thermokarst lakes have reshaped ice-rich permafrost lowlands in the Arctic throughout the Holocene. North of Teshekpuk Lake, on the Arctic Coastal Plain of northern Alaska, thermokarst lakes presently occupy 22.5% of the landscape, and drained thermokarst lake basins occupy 61.8%. Analysis of remotely sensed imagery indicates that nine lakes (>10 ha) have drained in the 1,750 km2 study area between 1955 and 2014. The most recent lake drainage was observed using in situ data loggers providing information on the duration and magnitude of the event, and a nearby weather station provided information on the environmental conditions preceding the lake drainage. Lake 195 (L195), an 80 ha thermokarst lake with an estimated water volume of ~872,000 m3, catastrophically drained on 05 July 2014. Abundant winter snowfall and heavy early summer precipitation resulted in elevated lake water levels that likely promoted bank overtopping, thermo-erosion along an ice-wedge network, and formation of a 9 m wide, 2 m deep, and 70 m long drainage gully. The lake emptied in 36 hours, with 75% of the water volume loss occurring in the first ten hours. The observed peak discharge of the resultant flood was 25 m3/s, which is similar to that in northern Alaska river basins whose areas are more than two orders of magnitude larger. Our findings support the catastrophic nature of sudden lake drainage events and the mechanistic hypotheses developed by J. Ross Mackay.

  10. Shrinking sea ice, increasing snowfall and thinning lake ice: a complex Arctic linkage explained

    NASA Astrophysics Data System (ADS)

    Brock, Ben W.

    2016-09-01

    The dramatic shrinkage of Arctic sea ice is one of the starkest symptoms of global warming, with potentially severe and far-reaching impacts on arctic marine and terrestrial ecology (Post et al 2013 Science 341 519-24) and northern hemisphere climate (Screen et al 2015 Environ. Res. Lett. 10 084006). In their recent article, Alexeev et al (2016 Environ. Res. Lett. 11 074022) highlight another, and unexpected, consequence of Arctic sea ice retreat: the thinning of lake ice in northern Alaska. This is attributed to early winter ‘ocean effect’ snowfall which insulates lake surfaces and inhibits the formation of deep lake ice. Lake ice thinning has important consequences for Arctic lake hydrology, biology and permafrost degradation.

  11. Spatial manifestation of the Little Ice Age in Alaska

    NASA Astrophysics Data System (ADS)

    Clegg, B. F.; Tinner, W.; Henderson, A.; Bigler, C.; Hu, F.

    2005-12-01

    We present here climate reconstructions of the past 1000 years on the basis of multiproxy sediment analyses at six lakes in three regions of Alaska: the northwestern Alaskan Range (Farewell Lake), the southern Brooks Range (Takahula, Malamute, and Omega Lakes), and the Copper River Basin in southeastern Alaska (Grizzly and Moose Lakes). All three regions show a consistent decline in summer temperature of roughly 1.5 to 2 degrees C during Little Ice Age (LIA, 1480 - 1850 AD), in good agreement with previous estimates. However, effective-moisture reconstructions vary greatly among these regions. Oxygen isotopes, carbonate trace elements, and chironomid assemblages suggest that the SW and N portions of the Alaskan interior experienced a considerable effective-moisture increase and elevated lake levels during the LIA. At Takahula Lake, oxygen isotope analysis reveals that the rise in effective moisture occurred predominantly as a result of increased winter precipitation. In contrast, diatom-inferred water depths at Grizzly Lake dropped dramatically during the LIA, suggesting that the Copper River Basin became drier. The heterogeneity of the LIA moisture changes across our sites is consistent with the expected spatial pattern based on recent reconstructions of the position of the Aleutian Low (AL) during the LIA. Thus, variation of the strength/position of the AL appears to have been a major driver of the Alaskan climate over the last millennium.

  12. Sea Ice, Bristol Bay, Alaska, USA

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This north looking view shows the coast of Alaska, north of the Aleutians, and the eastern margin of the Bering Sea (58.0N, 159.5W). Bristol Bay is apparent in the foreground and Nunivak Island can be seen just below the Earth's horizon, at a distance of about 300 nautical miles. Similar views, photographed during previous missions, when analyzed with these recent views may yield information about regional ice drift and breakup of ice packs.

  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. Ice clouds over Fairbanks, Alaska

    NASA Astrophysics Data System (ADS)

    Kayetha, Vinay Kumar

    Arctic clouds have been recognized long ago as one of the key elements modulating the global climate system. They have gained much interest in recent years because the availability of new continuous datasets is opening doors to explore cloud and aerosol properties as never before. This is particularly important in the light of current climate change studies that predict changing weather scenarios around the world. This research investigates the occurrence and properties of a few types of ice clouds over the Arctic region with datasets available through the Arctic Facility for Atmospheric Remote Sensing (AFARS; 64.86° N, 147.84° W). This study exclusively focuses on ice clouds that form in the upper (cirrus clouds) and midlevels of the troposphere, and that are transparent to laser pulses (visible optical depth, tau < 3.0 -- 4.0). Cirrus clouds are ice-dominated clouds that are formed in the upper levels of the troposphere and are relatively thin such that their visual appearances range from bluish to gray in color. Mid-level ice clouds are those clouds primarily composed of ice crystals forming in the midlevels of the troposphere. It is hypothesized that unlike the basic midlevel cloud type (altostratus), other varieties of midlevel ice clouds exist at times over the Arctic region. The midlevel ice clouds studied here are also transparent to laser pulses and sometimes appear as a family of cirrus clouds to a surface observer. Because of their intermediate heights of occurrence in the troposphere, these could have microphysical properties and radiative effects that are distinct from those associated with upper level ice clouds in the troposphere. A ground-based lidar dataset with visual observations for identifying cloud types collected at AFARS over eight years is used to investigate this hypothesis. Cloud types over AFARS have been identified by a surface observer (Professor Kenneth Sassen) using established characteristics traits. Essential macrophysical

  15. Meteorology: dusty ice clouds over Alaska.

    PubMed

    Sassen, Kenneth

    2005-03-24

    Particles lofted into the atmosphere by desert dust storms can disperse widely and affect climate directly through aerosol scattering and absorption. They can also affect it indirectly by changing the scattering properties of clouds and, because desert dusts are particularly active ice-forming agents, by affecting the formation and thermodynamic phase of clouds. Here I show that dust storms that occurred in Asia early in 2004 created unusual ice clouds over Alaska at temperatures far warmer than those expected for normal cirrus-cloud formation.

  16. Ice Types in the Beaufort Sea, Alaska

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Determining the amount and type of sea ice in the polar oceans is crucial to improving our knowledge and understanding of polar weather and long term climate fluctuations. These views from two satellite remote sensing instruments; the synthetic aperture radar (SAR) on board the RADARSAT satellite and the Multi-angle Imaging SpectroRadiometer (MISR), illustrate different methods that may be used to assess sea ice type. Sea ice in the Beaufort Sea off the north coast of Alaska was classified and mapped in these concurrent images acquired March 19, 2001 and mapped to the same geographic area.

    To identify sea ice types, the National Oceanic and Atmospheric Administration (NOAA) National Ice Center constructs ice charts using several data sources including RADARSAT SAR images such as the one shown at left. SAR classifies sea ice types primarily by how the surface and subsurface roughness influence radar backscatter. In the SAR image, white lines delineate different sea ice zones as identified by the National Ice Center. Regions of mostly multi-year ice (A) are separated from regions with large amounts of first year and younger ice (B-D), and the dashed white line at bottom marks the coastline. In general, sea ice types that exhibit increased radar backscatter appear bright in SAR and are identified as rougher, older ice types. Younger, smoother ice types appear dark to SAR. Near the top of the SAR image, however, red arrows point to bright areas in which large, crystalline 'frost flowers' have formed on young, thin ice, causing this young ice type to exhibit an increased radar backscatter. Frost flowers are strongly backscattering at radar wavelengths (cm) due to both surface roughness and the high salinity of frost flowers, which causes them to be highly reflective to radar energy.

    Surface roughness is also registered by MISR, although the roughness observed is at a different spatial scale. Older, rougher ice areas are predominantly backward scattering to

  17. Astrobiology of Antarctic ice Covered Lakes

    NASA Astrophysics Data System (ADS)

    Doran, P. T.; Fritsen, C. H.

    2005-12-01

    Antarctica contains a number of permanently ice-covered lakes which have often been used as analogs of purported lakes on Mars in the past. Antarctic subglacial lakes, such as Lake Vostok, have also been viewed as excellent analogs for an ice covered ocean on the Jovian moon Europa, and to a lesser extend on Mars. Lakes in the McMurdo Dry Valleys of East Antarctica have ice covers that range from 3 to 20 meters thick. Water salinities range from fresh to hypersaline. The thinner ice-covered lakes have a well-documented ecology that relies on the limited available nutrients and the small amount of light energy that penetrates the ice covers. The thickest ice-covered lake (Lake Vida in Victoria Valley) has a brine beneath 20 m of ice that is 7 times sea water and maintains a temperature below -10 degrees Celsius. This lake is vastly different from the thinner ice-covered lakes in that there is no communication with the atmosphere. The permanent ice cover is so thick, that summer melt waters can not access the sub-ice brine and so the ice grows from the top up, as well as from the bottom down. Brine trapped beneath the ice is believed to be ancient, stranded thousands of years ago when the ice grew thick enough to isolate it from the surface. We view Lake Vida as an excellent analog for the last aquatic ecosystem to have existed on Mars under a planetary cooling. If, as evidence is now increasingly supporting, standing bodies of water existed on Mars in the past, their fate under a cooling would be to go through a stage of permanent ice cover establishment, followed by a thickening of that ice cover until the final stage just prior to a cold extinction would be a Lake Vida-like lake. If dust storms or mass movements covered these ancient lakes, remnants may well be in existence in the subsurface today. A NASA Astrobiology Science and Technology for Exploring Planets (ASTEP) project will drill the Lake Vida ice cover and access the brine and sediments beneath in

  18. RADARSAT-2 Polarimetry for Lake Ice Mapping

    NASA Astrophysics Data System (ADS)

    Pan, Feng; Kang, Kyung-Kuk; Duguay, Claude

    2016-04-01

    Changes in the ice regime of lakes can be employed to assess long-term climate trends and variability in high latitude regions. Lake ice cover observations are not only useful for climate monitoring, but also for improving ice and weather forecasts using numerical prediction models. In recent years, satellite remote sensing has assumed a greater role in observing lake ice cover for both purposes. Radar remote sensing has become an essential tool for mapping lake ice at high latitudes where cloud cover and polar darkness severely limits ice observations from optical systems. In Canada, there is an emerging interest by government agencies to evaluate the potential of fully polarimetric synthetic aperture radar (SAR) data from RADARSAT-2 (C-band) for lake ice monitoring. In this study, we processed and analyzed the polarization states and scattering mechanisms of fully polarimetric RADARSAT-2 data obtained over Great Bear Lake, Canada, to identify open water and different ice types during the freeze-up and break-up periods. Polarimetric decompositions were employed to separate polarimetric measurements into basic scattering mechanisms. Entropy, anisotropy, and alpha angle were derived to characterize the scattering heterogeneity and mechanisms. Ice classes were then determined based on entropy and alpha angle using the unsupervised Wishart classifier and results evaluated against Landsat 8 imagery. Preliminary results suggest that the RADARSAT-2 polarimetric data offer a strong capability for identifying open water and different lake ice types.

  19. Thickness of ice on perennially frozen lakes

    USGS Publications Warehouse

    McKay, C.P.; Clow, G.D.; Wharton, R.A.; Squyres, S. W.

    1985-01-01

    The dry valleys of southern Victoria Land, constituting the largest ice-free expanse in the Antarctic, contain numerous lakes whose perennial ice cover is the cause of some unique physical and biological properties 1-3. Although the depth, temperature and salinity of the liquid water varies considerably from lake to lake, the thickness of the ice cover is remarkably consistent1, ranging from 3.5 to 6m, which is determined primarily by the balance between conduction of energy out of the ice and the release of latent heat at the ice-water interface and is also affected by the transmission and absorption of sunlight. In the steady state, the release of latent heat at the ice bottom is controlled by ablation from the ice surface. Here we present a simple energy-balance model, using the measured ablation rate of 30 cm yr-1, which can explain the observed ice thickness. ?? 1985 Nature Publishing Group.

  20. Local response of a glacier to annual filling and drainage of an ice-marginal lake

    USGS Publications Warehouse

    Walder, J.S.; Trabant, D.C.; Cunico, M.; Fountain, A.G.; Anderson, S.P.; Anderson, R. Scott; Malm, A.

    2006-01-01

    Ice-marginal Hidden Creek Lake, Alaska, USA, outbursts annually over the course of 2-3 days. As the lake fills, survey targets on the surface of the 'ice dam' (the glacier adjacent to the lake) move obliquely to the ice margin and rise substantially. As the lake drains, ice motion speeds up, becomes nearly perpendicular to the face of the ice dam, and the ice surface drops. Vertical movement of the ice dam probably reflects growth and decay of a wedge of water beneath the ice dam, in line with established ideas about jo??kulhlaup mechanics. However, the distribution of vertical ice movement, with a narrow (50-100 m wide) zone where the uplift rate decreases by 90%, cannot be explained by invoking flexure of the ice dam in a fashion analogous to tidal flexure of a floating glacier tongue or ice shelf. Rather, the zone of large uplift-rate gradient is a fault zone: ice-dam deformation is dominated by movement along high-angle faults that cut the ice dam through its entire thickness, with the sense of fault slip reversing as the lake drains. Survey targets spanning the zone of steep uplift gradient move relative to one another in a nearly reversible fashion as the lake fills and drains. The horizontal strain rate also undergoes a reversal across this zone, being compressional as the lake fills, but extensional as the lake drains. Frictional resistance to fault-block motion probably accounts for the fact that lake level falls measurably before the onset of accelerated horizontal motion and vertical downdrop. As the overall fault pattern is the same from year to year, even though ice is lost by calving, the faults must be regularly regenerated, probably by linkage of surface and bottom crevasses as ice is advected toward the lake basin.

  1. NWS Alaska Sea Ice Program: Operations and Decision Support Services

    NASA Astrophysics Data System (ADS)

    Schreck, M. B.; Nelson, J. A., Jr.; Heim, R.

    2015-12-01

    The National Weather Service's Alaska Sea Ice Program is designed to service customers and partners operating and planning operations within Alaska waters. The Alaska Sea Ice Program offers daily sea ice and sea surface temperature analysis products. The program also delivers a five day sea ice forecast 3 times each week, provides a 3 month sea ice outlook at the end of each month, and has staff available to respond to sea ice related information inquiries. These analysis and forecast products are utilized by many entities around the state of Alaska and nationally for safety of navigation and community strategic planning. The list of current customers stem from academia and research institutions, to local state and federal agencies, to resupply barges, to coastal subsistence hunters, to gold dredgers, to fisheries, to the general public. Due to a longer sea ice free season over recent years, activity in the waters around Alaska has increased. This has led to a rise in decision support services from the Alaska Sea Ice Program. The ASIP is in constant contact with the National Ice Center as well as the United States Coast Guard (USCG) for safety of navigation. In the past, the ASIP provided briefings to the USCG when in support of search and rescue efforts. Currently, not only does that support remain, but our team is also briefing on sea ice outlooks into the next few months. As traffic in the Arctic increases, the ASIP will be called upon to provide more and more services on varying time scales to meet customer needs. This talk will address the many facets of the current Alaska Sea Ice Program as well as delve into what we see as the future of the ASIP.

  2. ROV dives under Great Lakes ice

    USGS Publications Warehouse

    Bolsenga, S.J.; Gannon, John E.; Kennedy, Gregory; Norton, D.C.; Herdendorf, Charles E.

    1989-01-01

    Observations of the underside of ice have a wide variety of applications. Severe under-ice roughness can affect ice movements, rough under-ice surfaces can scour the bottom disturbing biota and man-made structures such as pipelines, and the flow rate of rivers is often affected by under-ice roughness. A few reported observations of the underside of an ice cover have been made, usually by cutting a large block of ice and overturning it, by extensive boring, or by remote sensing. Such operations are extremely labor-intensive and, in some cases, prone to inaccuracies. Remotely operated vehicles (ROV) can partially solve these problems. In this note, we describe the use, performance in a hostile environment, and results of a study in which a ROV was deployed under the ice in Lake Erie (North American Great Lakes).

  3. Pathways of Snowmelt Water into an Ice-Covered Lake

    NASA Astrophysics Data System (ADS)

    Cortes, A.; MacIntyre, S.; Sadro, S.

    2015-12-01

    Discharge of water into ice-covered arctic lakes during snowmelt can be high, but no general framework exists to quantify the pathway of the flow into the lakes and the associated distribution of incoming resources including dissolved organic carbon (DOC) or greenhouse gases. In this study, we characterize the fate of the snowmelt water flowing into 1.5 km2 Toolik Lake, Alaska, in 2014 and 2015. We deployed arrays with temperature, conductivity, and oxygen sensors in the water column over the winter, performed high temporal and spatial resolution CTD surveys on four 500 m to 1 km long transect lines during spring, and obtained correlative meteorological and discharge data. During both study spring periods, we observed different snowmelt inflow regimes based on the discharge rate (low and high) which led to differences in the extent of vertical and horizontal dilution of the lake water. Our first estimates of horizontal dispersion of snowmelt water in Toolik Lake under a high discharge regime are in the upper range of values found for ice-covered lakes (O ~ (102) cm2 s-1). In both years, the incoming water spread over ~75% of the basin near the surface with associated loading of DOC and methane. Spring 2014 was typical of other years with a gradual snowmelt and restricted depth of penetration of the incoming water. In fact, the increased density gradient in the upper few meters created conditions which retarded subsequent mixing at ice off. In contrast, persistent high pressures over the Alaskan region caused an exceptionally warm spring and rapid snowmelt in 2015. The subsequent warming of stream waters meant that the within lake vertical density gradient was weakened and facilitated later mixing. The differences in magnitude of discharge and temperature of incoming water during the more average and the warm springs enable interpretations and predictions of the fate of solutes flowing into lakes during snowmelt under variable weather regimes.

  4. 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.

  5. Shifting ice regimes of Arctic thermokarst lakes and implications for permafrost and surface-water dynamics

    NASA Astrophysics Data System (ADS)

    Arp, C. D.; Jones, B.; Urban, F. E.; Grosse, G.; Whitman, M.

    2011-12-01

    Thermokarst lakes cover >20% of the landscape throughout much of the Arctic Coastal Plain (ACP) of northern Alaska with shallow lakes freezing solid (grounded ice) and deeper lakes maintaining perennial liquid water (floating ice). Thus, lake depth relative to maximum ice thickness represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behavior. We studied coupled hydrogeomorphic processes of 13 lakes in the Teshekpuk Lake Special Area (TLSA) representing a depth gradient across this threshold of maximum ice thickness by analyzing remotely sensed imagery, water quality surveys, and climatic data over a 35-year period. Shoreline erosion rates due to permafrost degradation ranged from <0.2 m/yr in very shallow lakes (0.4 m) up to 1.8 m/yr in the deepest lakes (2.6 m) and appear to be partly linked to variation in mean annual lake temperature (MALT). This pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines. Changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation (P-E) with periods of full and nearly dry basins. Our analysis suggests that grounded-ice lakes are ice-free on average 37 days longer than floating-ice lakes resulting in a longer period of evaporative loss and more frequent negative P-E. These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum ice thickness in ACP lakes. With respect to these findings there is particular interest in ACP lakes of depths encompassing the range of interannual variation in maximum ice thickness because these lakes will most readily show a shift of ice regimes with either a change in water balance or ice growth. For instance, a positive summer P-E and slow winter ice growth can result in a higher

  6. Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

    DOE PAGES

    Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.; Greene, S.; Thalasso, F.

    2014-09-12

    Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH4) and carbon dioxide (CO2) emissions from northern lakes. Here we assessed the relationship between CH4 and CO2 emission modes in 40 lakes along a latitudinal transect in Alaska to physicochemical limnology and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included Direct Ebullition, Diffusion, Storage flux, and a newly identified Ice-Bubble Storage (IBS) flux. We found that all lakes were net sources of atmospheric CH4 and CO2, but the climate warming impact of lake CH4more » emissions was two times higher than that of CO2. Ebullition and Diffusion were the dominant modes of CH4 and CO2 emissions respectively. IBS, ~ 10% of total annual CH4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH4 emissions from stratified, dystrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. Total CH4 emission was correlated with concentrations of phosphate and total nitrogen in lake water, Secchi depth and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. Our findings suggest that permafrost type plays important roles in determining CH4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less

  7. Modeling the impediment of methane ebullition bubbles by seasonal lake ice

    DOE PAGES

    Greene, S.; Walter Anthony, K. M.; Archer, D.; Sepulveda-Jauregui, A.; Martinez-Cruz, K.

    2014-07-15

    Microbial methane (CH4) ebullition (bubbling) from anoxic lake sediments comprises a globally significant flux to the atmosphere, but ebullition bubbles in temperate and polar lakes can be trapped by winter ice cover and later released during spring thaw. This "ice-bubble storage" (IBS) constitutes a novel mode of CH4 emission. Before bubbles are encapsulated by downward-growing ice, some of their CH4 dissolves into the lake water, where it may be subject to oxidation. We present field characterization and a model of the annual CH4 cycle in Goldstream Lake, a thermokarst (thaw) lake in interior Alaska. We find that summertime ebullition dominatesmore » annual CH4 emissions to the atmosphere. Eighty percent of CH4 in bubbles trapped by ice dissolves into the lake water column in winter, and about half of that is oxidized. The ice growth rate and the magnitude of the CH4 ebullition flux are important controlling factors of bubble dissolution. Seven percent of annual ebullition CH4 is trapped as IBS and later emitted as ice melts. In a future warmer climate, there will likely be less seasonal ice cover, less IBS, less CH4 dissolution from trapped bubbles, and greater CH4 emissions from northern lakes.« less

  8. Modeling the impediment of methane ebullition bubbles by seasonal lake ice

    DOE PAGES

    Greene, S.; Walter Anthony, K. M.; Archer, D.; Sepulveda-Jauregui, A.; Martinez-Cruz, K.

    2014-12-08

    Microbial methane (CH4) ebullition (bubbling) from anoxic lake sediments comprises a globally significant flux to the atmosphere, but ebullition bubbles in temperate and polar lakes can be trapped by winter ice cover and later released during spring thaw. This "ice-bubble storage" (IBS) constitutes a novel mode of CH4 emission. Before bubbles are encapsulated by downward-growing ice, some of their CH4 dissolves into the lake water, where it may be subject to oxidation. We present field characterization and a model of the annual CH4 cycle in Goldstream Lake, a thermokarst (thaw) lake in interior Alaska. We find that summertime ebullition dominatesmore » annual CH4 emissions to the atmosphere. Eighty percent of CH4 in bubbles trapped by ice dissolves into the lake water column in winter, and about half of that is oxidized. The ice growth rate and the magnitude of the CH4 ebullition flux are important controlling factors of bubble dissolution. Seven percent of annual ebullition CH4 is trapped as IBS and later emitted as ice melts. In a future warmer climate, there will likely be less seasonal ice cover, less IBS, less CH4 dissolution from trapped bubbles, and greater CH4 emissions from northern lakes.« less

  9. Holocene Age Methane and Carbon Dioxide Dominate Northern Alaska Thaw Lake Emissions

    NASA Astrophysics Data System (ADS)

    Elder, C.; Townsend-Small, A.; Hinkel, K. M.; Xu, X.; Czimczik, C. I.

    2015-12-01

    Lakes expanding into ice-rich permafrost can rapidly re-introduce large quantities of ancient organic carbon (C) to the atmosphere as carbon dioxide (CO2) or the more powerful greenhouse gas methane (CH4). Quantifying the sources of greenhouse gas emissions from arctic lakes will reduce large uncertainties in the magnitude and timing of the C-climate feedback from the Arctic, and thus trajectories of climate change. This work provides the first regional assessment of integrated whole-lake radiocarbon (14C) ages of dissolved CH4 and CO2 as a proxy for C emission sources in northern Alaska. We collected water samples from below ice along two 170 km north-south transects on the Arctic Coastal Plain (ACP) of Alaska in April 2012 and 2013. These lakes represent a network monitored by the US-NSF funded project, Circum-Arctic Lakes Observation Network (CALON), http://www.arcticlakes.org/. Dissolved CH4 and CO2 were extracted and analyzed for their 14C content. The presence of winter ice on the surface of lakes obstructs the emission of CH4 and CO2 originating from the perennially thawed sub-lake sediments. The trapped gases are forced to mix, thus measured 14C ages are integrated signatures representing the whole-lake emissions. Dissolved CH4 and CO2 ages do not correlate with latitude, yet seem to be driven by surficial geology. Of nearly 150 14C measurements, below-ice dissolved CH4 is the oldest (around 2145 ± 15 14C YBP) in a lake residing on "peaty, sandy lowland" on the northern ACP near the town of Barrow. Modern CH4 and CO2 dominate emissions from "eolian sandy lowlands" in the interior of the ACP. Across all lakes, dissolved CH4 (avg. 836 14C YBP) is older than dissolved CO2 (avg. 480 14C YBP) by a regional average of ca. 360 14C YBP. Results from this study indicate that decomposing Holocene-age organic material is the primary source of CH4 and CO2 emissions from the Alaskan ACP. This baseline dataset provides the foundation for future regional lake monitoring

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  11. Facies analysis of yedoma thermokarst lakes on the northern Seward Peninsula, Alaska

    NASA Astrophysics Data System (ADS)

    Farquharson, Louise; Anthony, Katey Walter; Bigelow, Nancy; Edwards, Mary; Grosse, Guido

    2016-07-01

    Thermokarst lakes develop as a result of the thaw and collapse of ice-rich, permanently frozen ground (permafrost). Of particular sedimentological importance are thermokarst lakes forming in late Pleistocene icy silt (yedoma), which dramatically alter the land surface by lowering surface elevation and redistributing upland sediment into lower basins. Our study provides the first description of yedoma thermokarst lake sedimentology based on the cross-basin sampling of an existing lake. We present lake sediment facies descriptions based on data from sediment cores from two thermokarst lakes of medium depth, Claudi and Jaeger (informal names), which formed in previously non thermokarst-affected upland yedoma on the northern Seward Peninsula, Alaska. We identify four prominent facies using sedimentological, biogeochemical, and macrofossil indicators: a massive silt lacking aquatic macrofossils and other aquatic indicators situated below a sub-lacustrine unconformity (Facies 1); two basal deposits: interbedded organic silt and chaotic silt (Facies 2-3); and a silt-rich mud (Facies 4). Facies 1 is interpreted as yedoma that has thawed during lake formation. Facies 3 formed adjacent to the margin due to thaw and collapse events from the lake shore. Material from Facies 3 was reworked by wave action to form Facies 2 in a medium energy margin environment. Facies 4 formed in a lower energy environment toward the lake basin center. This facies classification and description should enhance our ability (i) to interpret the spatial and temporal development of lakes and (ii) to reconstruct long-term patterns of landscape change.

  12. Fault-dominated deformation in an ice dam during annual filling and drainage of a marginal lake

    USGS Publications Warehouse

    Walder, J.S.; Trabant, D.C.; Cunico, M.; Anderson, S.P.; Anderson, R. Scott; Fountain, A.G.; Malm, A.

    2005-01-01

    Ice-dammed Hidden Creek Lake, Alaska, USA, outbursts annually in about 2-3 days. As the lake fills, a wedge of water penetrates beneath the glacier, and the surface of this 'ice dam' rises; the surface then falls as the lake drains. Detailed optical surveying of the glacier near the lake allows characterization of ice-dam deformation. Surface uplift rate is close to the rate of lake-level rise within about 400 m of the lake, then decreases by 90% over about 100 m. Such a steep gradient in uplift rate cannot be explained in terms of ice-dam flexure. Moreover, survey targets spanning the zone of steep uplift gradient move relative to one another in a nearly reversible fashion as the lake fills and drains. Evidently, the zone of steep uplift gradient is a fault zone, with the faults penetrating the entire thickness of the ice dam. Fault motion is in a reverse sense as the lake fills, but in a normal sense as the lake drains. As the overall fault pattern is the same from year to year, even though ice is lost by calving, the faults must be regularly regenerated, probably by linkage of surface and bottom crevasses as ice is advected toward the lake basin.

  13. Index to limnological data for southcentral Alaska Lakes

    USGS Publications Warehouse

    Maurer, M.A.; Woods, P.F.

    1987-01-01

    South-central Alaska lakes are a valuable natural resource and provide a variety of recreational opportunities to the public. Lakeside development has increased significantly in the past 10 years and several south-central Alaskan lakes have documented pollution problems. Cultural eutrophication, the process by which man-induced nutrient loading to a lake results in large increases in biological productivity, can also produce noxious algae blooms, dissolved oxygen depletion at depth, reduced water transparency, and fish kills. The potential for cultural eutrophication of south-central Alaska lakes prompted the U.S. Geological Survey (USGS) Water Resources Division and the Alaska Department of Natural Resources-Division of Geological and Geophysical Surveys (ADGGS) to provide lake researchers, managers, and the public with this index of published historical and current limnological references. The purpose of the index is to provide reference to the data which can be used to identify and monitor cultural eutrophication of south-central Alaska lakes. (Lantz-PTT)

  14. Physical and Chemical Implications of Mid-Winter Pumping of Trunda Lakes - North Slope, Alaska

    SciTech Connect

    Hinzman, Larry D.; Lilly, Michael R.; Kane, Douglas L.; Miller, D. Dan; Galloway, Braden K.; Hilton, Kristie M.; White, Daniel M.

    2005-09-30

    Tundra lakes on the North Slope, Alaska, are an important resource for energy development and petroleum field operations. A majority of exploration activities, pipeline maintenance, and restoration activities take place on winter ice roads that depend on water availability at key times of the winter operating season. These same lakes provide important fisheries and ecosystem functions. In particular, overwintering habitat for fish is one important management concern. This study focused on the evaluation of winter water use in the current field operating areas to provide a better understanding of the current water use practices. It found that under the current water use practices, there were no measurable negative effects of winter pumping on the lakes studied and current water use management practices were appropriately conservative. The study did find many areas where improvements in the understanding of tundra lake hydrology and water usage would benefit industry, management agencies, and the protection of fisheries and ecosystems.

  15. Disappearing Twelvemile Lake in Alaska's Discontinuous Permafrost: Scoping Analysis of Water Budget

    NASA Astrophysics Data System (ADS)

    Jepsen, S. M.; Voss, C. I.; Walvoord, M. A.; Minsley, B. J.; Rose, J.; Smith, B. D.

    2011-12-01

    The number and size of lakes in northern high-latitude regions have undergone significant changes over the last 3 decades or longer, possibly in association with climate warming. In the Yukon Flats Basin (YFB) of interior Alaska, a region underlain by discontinuous permafrost, these changes have not been uniform among lake drainage basins, suggesting the importance of local processes that are not well understood. As an example in the YFB, Twelvemile Lake has decreased in area by 60% since 1984, while neighboring Buddy Lake, 2 km to the southeast, has shown no significant change (see Figure). The objective of this study is to evaluate physical mechanisms that could account for the lowering of Twelvemile Lake, using a combination of water flux approximations, historical climate data and the permafrost distribution as interpreted from airborne electromagnetics (AEM). All possible in- and out-flux pathways to the lake are considered and compared with the observed rate of change in the lake's volume, to rank the importance of each pathway as a contributor to the change in lake level. Results from the AEM survey suggest the presence of a ~200 m diameter open-talik beneath the lake, and subsurface, channel-shaped depressions in the permafrost table ("channels") that may direct shallow groundwater (GW) flow into or out of the lake basin. An increase in potential evapotranspiration of only ~2 cm yr-1 from the period of 1950-1980 to 1981-2010 is found to be insignificant relative to the observed 13 cm yr-1 rate of lake level lowering since the early 1980's. Thus, alternative water pathways are needed to explain the lake level change. The following four processes are shown to potentially have a significant contribution to the observed rate of lake level change: (i) Reduced water inputs from decreased snowpacks; (ii) Increased infiltration of snowmelt due to changes in wintertime ice content of subnivean soil; (iii) Changes in GW flow through inlet and outlet channels to the

  16. Physiological and ecological effects of increasing temperature on fish production in lakes of Arctic Alaska

    USGS Publications Warehouse

    Carey, Michael P.; Zimmerman, Christian E.

    2014-01-01

    Lake ecosystems in the Arctic are changing rapidly due to climate warming. Lakes are sensitive integrators of climate-induced changes and prominent features across the Arctic landscape, especially in lowland permafrost regions such as the Arctic Coastal Plain of Alaska. Despite many studies on the implications of climate warming, how fish populations will respond to lake changes is uncertain for Arctic ecosystems. Least Cisco (Coregonus sardinella) is a bellwether for Arctic lakes as an important consumer and prey resource. To explore the consequences of climate warming, we used a bioenergetics model to simulate changes in Least Cisco production under future climate scenarios for lakes on the Arctic Coastal Plain. First, we used current temperatures to fit Least Cisco consumption to observed annual growth. We then estimated growth, holding food availability, and then feeding rate constant, for future projections of temperature. Projected warmer water temperatures resulted in reduced Least Cisco production, especially for larger size classes, when food availability was held constant. While holding feeding rate constant, production of Least Cisco increased under all future scenarios with progressively more growth in warmer temperatures. Higher variability occurred with longer projections of time mirroring the expanding uncertainty in climate predictions further into the future. In addition to direct temperature effects on Least Cisco growth, we also considered changes in lake ice phenology and prey resources for Least Cisco. A shorter period of ice cover resulted in increased production, similar to warming temperatures. Altering prey quality had a larger effect on fish production in summer than winter and increased relative growth of younger rather than older age classes of Least Cisco. Overall, we predicted increased production of Least Cisco due to climate warming in lakes of Arctic Alaska. Understanding the implications of increased production of Least Cisco to

  17. Physiological and ecological effects of increasing temperature on fish production in lakes of Arctic Alaska.

    PubMed

    Carey, Michael P; Zimmerman, Christian E

    2014-05-01

    Lake ecosystems in the Arctic are changing rapidly due to climate warming. Lakes are sensitive integrators of climate-induced changes and prominent features across the Arctic landscape, especially in lowland permafrost regions such as the Arctic Coastal Plain of Alaska. Despite many studies on the implications of climate warming, how fish populations will respond to lake changes is uncertain for Arctic ecosystems. Least Cisco (Coregonus sardinella) is a bellwether for Arctic lakes as an important consumer and prey resource. To explore the consequences of climate warming, we used a bioenergetics model to simulate changes in Least Cisco production under future climate scenarios for lakes on the Arctic Coastal Plain. First, we used current temperatures to fit Least Cisco consumption to observed annual growth. We then estimated growth, holding food availability, and then feeding rate constant, for future projections of temperature. Projected warmer water temperatures resulted in reduced Least Cisco production, especially for larger size classes, when food availability was held constant. While holding feeding rate constant, production of Least Cisco increased under all future scenarios with progressively more growth in warmer temperatures. Higher variability occurred with longer projections of time mirroring the expanding uncertainty in climate predictions further into the future. In addition to direct temperature effects on Least Cisco growth, we also considered changes in lake ice phenology and prey resources for Least Cisco. A shorter period of ice cover resulted in increased production, similar to warming temperatures. Altering prey quality had a larger effect on fish production in summer than winter and increased relative growth of younger rather than older age classes of Least Cisco. Overall, we predicted increased production of Least Cisco due to climate warming in lakes of Arctic Alaska. Understanding the implications of increased production of Least Cisco to

  18. Physiological and ecological effects of increasing temperature on fish production in lakes of Arctic Alaska

    PubMed Central

    Carey, Michael P; Zimmerman, Christian E

    2014-01-01

    Lake ecosystems in the Arctic are changing rapidly due to climate warming. Lakes are sensitive integrators of climate-induced changes and prominent features across the Arctic landscape, especially in lowland permafrost regions such as the Arctic Coastal Plain of Alaska. Despite many studies on the implications of climate warming, how fish populations will respond to lake changes is uncertain for Arctic ecosystems. Least Cisco (Coregonus sardinella) is a bellwether for Arctic lakes as an important consumer and prey resource. To explore the consequences of climate warming, we used a bioenergetics model to simulate changes in Least Cisco production under future climate scenarios for lakes on the Arctic Coastal Plain. First, we used current temperatures to fit Least Cisco consumption to observed annual growth. We then estimated growth, holding food availability, and then feeding rate constant, for future projections of temperature. Projected warmer water temperatures resulted in reduced Least Cisco production, especially for larger size classes, when food availability was held constant. While holding feeding rate constant, production of Least Cisco increased under all future scenarios with progressively more growth in warmer temperatures. Higher variability occurred with longer projections of time mirroring the expanding uncertainty in climate predictions further into the future. In addition to direct temperature effects on Least Cisco growth, we also considered changes in lake ice phenology and prey resources for Least Cisco. A shorter period of ice cover resulted in increased production, similar to warming temperatures. Altering prey quality had a larger effect on fish production in summer than winter and increased relative growth of younger rather than older age classes of Least Cisco. Overall, we predicted increased production of Least Cisco due to climate warming in lakes of Arctic Alaska. Understanding the implications of increased production of Least Cisco to

  19. Seasonal thaw settlement at drained thermokarst lake basins, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Liu, L.; Schaefer, K.; Gusmeroli, A.; Grosse, G.; Jones, B. M.; Zhang, T.; Parsekian, A. D.; Zebker, H. A.

    2013-12-01

    Drained thermokarst lake basins (DTLBs) are ubiquitous landforms on arctic tundra lowlands, but their present-day dynamic states are seldom investigated. Here we report results based on high-resolution Interferometric Synthetic Aperture Radar (InSAR) measurements using space-borne data for a study area located near Prudhoe Bay, Alaska where we focus on the seasonal thaw settlement within DTLBs, averaged between 2006 and 2010. The majority (14) of the 18 DTLBs in the study area analyzed exhibited seasonal thaw settlement of 3-4 cm. However, four of the DTLBs analyzed exceeded 4 cm of thaw settlement, with one basin experiencing up to 12 cm. Combining the InSAR observations with the in situ active layer thickness measured using ground penetrating radar and mechanical probing, we calculated thaw strain, an index of thaw settlement strength along a transect across the basin that underwent large thaw settlement. We found thaw strains of 10-35% at the basin center, suggesting the seasonal melting of ground ice as a possible mechanism for the large settlement. These findings emphasize the dynamic nature of permafrost landforms, demonstrate the capability of the InSAR technique to remotely monitor surface deformation of individual DTLBs, and illustrate the combination of ground-based and remote sensing observations to estimate thaw strain. Our study highlights the need for better description of the spatial heterogeneity of landscape-scale processes for regional assessment of surface dynamics on arctic coastal lowlands.

  20. Ice Processes and Growth History on Arctic and Sub-Arctic Lakes Using ERS-1 SAR Data

    NASA Technical Reports Server (NTRS)

    Morris, K.; Jeffries, M. O.; Weeks, W. F.

    1995-01-01

    A survey of ice growth and decay processes on a selection of shallow and deep sub-Arctic and Arctic lakes was conducted using radiometrically calibrated ERS-1 SAR images. Time series of radar backscatter data were compiled for selected sites on the lakes during the period ot ice cover (September to June) for the years 1991-1992 and 1992-1993. A variety of lake-ice processes could be observed, and significant changes in backscatter occurred from the time of initial ice formation in autumn until the onset of the spring thaw. Backscatter also varied according to the location and depth of the lakes. The spatial and temporal changes in backscatter were most constant and predictable at the shallow lakes on the North Slope of Alaska. As a consequence, they represent the most promising sites for long-term monitoring and the detection of changes related to global warming and its effects on the polar regions.

  1. The evolution of a thermokarst-lake landscape: Late Quaternary permafrost degradation and stabilization in interior Alaska

    NASA Astrophysics Data System (ADS)

    Edwards, Mary; Grosse, Guido; Jones, Benjamin M.; McDowell, Patricia

    2016-07-01

    Thermokarst processes characterize a variety of ice-rich permafrost terrains and often lead to lake formation. The long-term evolution of thermokarst landscapes and the stability and longevity of lakes depend upon climate, vegetation and ground conditions, including the volume of excess ground ice and its distribution. The current lake status of thermokarst-lake landscapes and their future trajectories under climate warming are better understood in the light of their long-term development. We studied the lake-rich southern marginal upland of the Yukon Flats (northern interior Alaska) using dated lake-sediment cores, observations of river-cut exposures, and remotely-sensed data. The region features thick (up to 40 m) Quaternary deposits (mainly loess) that contain massive ground ice. Two of three studied lakes formed ~ 11,000-12,000 cal yr BP through inferred thermokarst processes, and fire may have played a role in initiating thermokarst development. From ~ 9000 cal yr BP, all lakes exhibited steady sedimentation, and pollen stratigraphies are consistent with regional patterns. The current lake expansion rates are low (0 to < 7 cm yr- 1 shoreline retreat) compared with other regions (~ 30 cm yr- 1 or more). This thermokarst lake-rich region does not show evidence of extensive landscape lowering by lake drainage, nor of multiple lake generations within a basin. However, LiDAR images reveal linear "corrugations" (> 5 m amplitude), deep thermo-erosional gullies, and features resembling lake drainage channels, suggesting that highly dynamic surface processes have previously shaped the landscape. Evidently, widespread early Holocene permafrost degradation and thermokarst lake initiation were followed by lake longevity and landscape stabilization, the latter possibly related to establishment of dense forest cover. Partial or complete drainage of three lakes in 2013 reveals that there is some contemporary landscape dynamism. Holocene landscape evolution in the study area

  2. Lake ice cover and its influence on lake ecology in a Finnish lake district

    NASA Astrophysics Data System (ADS)

    Leppäranta, Matti; Arvola, Lauri

    2014-05-01

    A wintertime research program on the physics and biology of lakes in Häme lake district in Finland has been performed in the last five years. The set of study lakes contains a wide spectrum in size, depth and trophic status. In this region the lakes freeze over annually for 4-6 months and the mean ice thickness is around 0.5 m. The ice sheet consists of congelation ice and snow-ice. The snow-ice fraction ranges from 0 to 90 per cent depending on the snow fall history and its magnitude makes a major contribution to the ice properties and conditions in the water body beneath the ice, in particular the mechanical strength and optical thickness are much less than for congelation ice. The e-folding depth of light intensity was 50-100 cm for congelation ice and 5-10 cm for snow. A numerical model has been developed to simulate the annual cycle of ice stratigraphy, temperature and thickness. The water bodies had a 1-4 m thick upper mixed layer thick thermocline, and in deeper lakes a lower homogeneous layer. Fall cooling process was crucial to determine the temperature of the lower layer at freeze-up, anything within 0-4°C. Oxygen concentration decreased in winter, especially close to the bottom sediments, and carbon dioxide concentration increased due to respiration activity. Phytoplankton production and biomass level were low or very low and, therefore, heterotrophic and mixotrophic species were abundant. Oxygen depletion in the hypolimnium had several chemical and ecological consequences, such as release of phosphorus from the bottom sediments. In spring, just before the ice-out, photosynthesis was at a high level beneath the ice due to improved light conditions and started to elevate the oxygen concentration in the topmost water layer. Primary production under the ice is limited or prohibited by low level of available light.

  3. Dynamic ice-wallow relief of northern Alaska's nearshore.

    USGS Publications Warehouse

    Reimnitz, E.; Kempema, E.

    1982-01-01

    Contour maps with 0.5m depth interval were prepared for a small area seaward of Reindeer Island, a barrier island in the Beaufort Sea, Alaska, by repeated surveys with very accurate navigation and very close trackline spacing. The maps reveal numerous closed depressions and mounds, presumably related to grounded ice floes common in the area year round. These bedforms represent erosion and deposition caused by: a) intensified flow around stationary ice floes serving as obstacles and b) pulsating currents generated by vertical oscillations or rocking motions of grounded floes in a seaway. Because sediment transport occurs around the ice, not where it directly touches the sea floor, the depressions are much larger than the base of the acting floes. Ice-wallow bedforms, are characteristic of arctic nearshore regions with non-cohesive sediments. The bedforms studied here are highly active and must be considered in planning nearshore construction activities. -from Authors

  4. Vegetation and lake-level history at Birch Lake, interior Alaska

    SciTech Connect

    Edwards, M.E.; Finney, B.P.; Bigelow, N.H.; Gardner, D.G. ); Eisner, W.R. )

    1994-06-01

    In interior Alaska (mean ann. precip. ca 350 mm) lakes should be sensitive to changes in the P/E ratio. At Birch Lake, near Fairbanks, lake levels rose dramatically 11,000-9200 years ago, fell 9200-8500 years ago and then rose rapidly, probably in a few hundred years. Some major changes in vegetation appear coincident with the lake-level changes, but others do not, or are hard to interprete. Populus woodland expanded during the first transgression, but subsequently declined while lake levels were still high. 9000-8000 years ago Picea glauca expanded then decreased, its abundance apparently negatively correlated with moisture availability. The lake rise at ca 8000 yr B.P. is slightly preceded by regional expansion of Alnus. Data suggest that a complex interaction of climatic and non-climatic factors determined vegetation dynamics during the late-Quaternary in interior Alaska.

  5. Methane and carbon dioxide emissions from 40 lakes along a north-south latitudinal transect in Alaska

    NASA Astrophysics Data System (ADS)

    Sepulveda-Jauregui, A.; Anthony, K. M. Walter; Martinez-Cruz, K.; Greene, S.; Thalasso, F.

    2015-06-01

    Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH4) and carbon dioxide (CO2) emissions from northern lakes. Here we assessed the relationship between CH4 and CO2 emission modes in 40 lakes along a latitudinal transect in Alaska to lakes' physicochemical properties and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included direct ebullition, diffusion, storage flux, and a newly identified ice-bubble storage (IBS) flux. We found that all lakes were net sources of atmospheric CH4 and CO2, but the climate warming impact of lake CH4 emissions was 2 times higher than that of CO2. Ebullition and diffusion were the dominant modes of CH4 and CO2 emissions, respectively. IBS, ~10% of total annual CH4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH4 emissions from stratified, mixotrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. The relationship between CO2 emissions and geographic parameters was weak, suggesting high variability among sources and sinks that regulate CO2 emissions (e.g., catchment waters, pH equilibrium). Total CH4 emission was correlated with concentrations of soluble reactive phosphorus and total nitrogen in lake water, Secchi depth, and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. Our findings suggest that permafrost type plays important roles in determining CH4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing

  6. Seasonal variation in methane emissions from an interior Alaska thermokarst lake

    NASA Astrophysics Data System (ADS)

    Strohm, A. J.; Walter Anthony, K.; Thalasso, F.; Sepulveda-Jauregui, A.; Martinez Cruz, K. C.; Dove, K. L.

    2011-12-01

    Refining our knowledge of methane cycling in aquatic ecosystems and their emissions to the atmosphere is important for understanding their role in climate change. The contribution of northern high latitude lakes to terrestrial methane emissions has recently been recognized as significant, and is likely to contribute a positive feedback to increasing atmospheric temperatures. The data available for accurately defining seasonal and net annual methane emissions from northern high latitude lakes are presently limited by a seasonal imbalance in both gross and net production measurements, as well as a poor understanding of emissions pathways and geographic differences. To help fill in some of these data gaps, we conducted intensive year-round measurement of ebullition and diffusive methane flux from Goldstream Lake (informal name), a thermokarst lake in central Alaska. Additionally, we made less frequent measurements on 47 lakes in winter and summer along a latitudinal transect in Alaska from the Kenai Peninsula to Prudhoe Bay. We used several methods to measure methane flux over multiple seasons in order to better understand complexity in the fate and transport of methane. These include (i) static chamber measurements of seep ebullition, (ii) documentation of the fate of gas trapped in winter ice, (iii) dissolved gas measurements by both gas chromatography and Tunable Diode Laser Absorption Spectroscopy, and(iv) measurement of methane concentration in air above the lake surface by a LiCor 7700 Open Path Methane Analyzer. Of specific interest was seasonal variation in methane emissions and the fate of winter methane production, whose release to the atmosphere is restricted for seven months by increasingly thick ice cover.

  7. Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

    DOE PAGES

    Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.; Greene, S.; Thalasso, F.

    2015-06-02

    Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH4) and carbon dioxide (CO2) emissions from northern lakes. Here we assessed the relationship between CH4 and CO2 emission modes in 40 lakes along a latitudinal transect in Alaska to lakes' physicochemical properties and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included direct ebullition, diffusion, storage flux, and a newly identified ice-bubble storage (IBS) flux. We found that all lakes were net sources of atmospheric CH4 and CO2, but the climate warming impact of lakemore » CH4 emissions was 2 times higher than that of CO2. Ebullition and diffusion were the dominant modes of CH4 and CO2 emissions, respectively. IBS, ~10% of total annual CH4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH4 emissions from stratified, mixotrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. The relationship between CO2 emissions and geographic parameters was weak, suggesting high variability among sources and sinks that regulate CO2 emissions (e.g., catchment waters, pH equilibrium). Total CH4 emission was correlated with concentrations of soluble reactive phosphorus and total nitrogen in lake water, Secchi depth, and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. Our findings suggest that permafrost type plays important roles in determining CH4 emissions from lakes by both supplying organic matter to methanogenesis directly from

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  9. 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

  10. Landfast sea ice breakouts: Stabilizing ice features, oceanic and atmospheric forcing at Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Jones, Joshua; Eicken, Hajo; Mahoney, Andrew; MV, Rohith; Kambhamettu, Chandra; Fukamachi, Yasushi; Ohshima, Kay I.; George, J. Craig

    2016-09-01

    Landfast sea ice is an important seasonal feature along most Arctic coastlines, such as that of the Chukchi Sea near Barrow, Alaska. Its stability throughout the ice season is determined by many factors but grounded pressure ridges are the primary stabilizing component. Landfast ice breakouts occur when these grounded ridges fail or unground, and previously stationary ice detaches from the coast and drifts away. Using ground-based radar imagery from a coastal ice and ocean observatory at Barrow, we have developed a method to estimate the extent of grounded ridges by tracking ice motion and deformation over the course of winter and have derived ice keel depth and potential for grounding from cumulative convergent ice motion. Estimates of landfast ice grounding strength have been compared to the atmospheric and oceanic stresses acting on the landfast ice before and during breakout events to determine prevailing causes for the failure of stabilizing features. Applying this approach to two case studies in 2008 and 2010, we conclude that a combination of atmospheric and oceanic stresses may have caused the breakouts analyzed in this study, with the latter as the dominant force. Preconditioning (as weakening) of grounded ridges by sea level variations may facilitate failure of the ice sheet leading to breakout events.

  11. Seasonal thaw settlement at drained thermokarst lake basins, Arctic Alaska

    USGS Publications Warehouse

    Liu, Lin; Schaefer, Kevin; Gusmeroli, Alessio; Grosse, Guido; Jones, Benjamin M.; Zhang, Tinjun; Parsekian, Andrew; Zebker, Howard

    2014-01-01

    Drained thermokarst lake basins (DTLBs) are ubiquitous landforms on Arctic tundra lowland. Their dynamic states are seldom investigated, despite their importance for landscape stability, hydrology, nutrient fluxes, and carbon cycling. Here we report results based on high-resolution Interferometric Synthetic Aperture Radar (InSAR) measurements using space-borne data for a study area located on the North Slope of Alaska near Prudhoe Bay, where we focus on the seasonal thaw settlement within DTLBs, averaged between 2006 and 2010. The majority (14) of the 18 DTLBs in the study area exhibited seasonal thaw settlement of 3–4 cm. However, four of the DTLBs examined exceeded 4 cm of thaw settlement, with one basin experiencing up to 12 cm. Combining the InSAR observations with the in situ active layer thickness measured using ground penetrating radar and mechanical probing, we calculated thaw strain, an index of thaw settlement strength along a transect across the basin that underwent large thaw settlement. We found thaw strains of 10–35% at the basin center, suggesting the seasonal melting of ground ice as a possible mechanism for the large settlement. These findings emphasize the dynamic nature of permafrost landforms, demonstrate the capability of the InSAR technique to remotely monitor surface deformation of individual DTLBs, and illustrate the combination of ground-based and remote sensing observations to estimate thaw strain. Our study highlights the need for better description of the spatial heterogeneity of landscape-scale processes for regional assessment of surface dynamics on Arctic coastal lowlands.

  12. Seasonal thaw settlement at drained thermokarst lake basins, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Liu, L.; Schaefer, K.; Gusmeroli, A.; Grosse, G.; Jones, B. M.; Zhang, T.; Parsekian, A. D.; Zebker, H. A.

    2014-05-01

    Drained thermokarst lake basins (DTLBs) are ubiquitous landforms on Arctic tundra lowland. Their dynamic states are seldom investigated, despite their importance for landscape stability, hydrology, nutrient fluxes, and carbon cycling. Here we report results based on high-resolution Interferometric Synthetic Aperture Radar (InSAR) measurements using space-borne data for a study area located on the North Slope of Alaska near Prudhoe Bay, where we focus on the seasonal thaw settlement within DTLBs, averaged between 2006 and 2010. The majority (14) of the 18 DTLBs in the study area exhibited seasonal thaw settlement of 3-4 cm. However, four of the DTLBs examined exceeded 4 cm of thaw settlement, with one basin experiencing up to 12 cm. Combining the InSAR observations with the in situ active layer thickness measured using ground penetrating radar and mechanical probing, we calculated thaw strain, an index of thaw settlement strength along a transect across the basin that underwent large thaw settlement. We found thaw strains of 10-35% at the basin center, suggesting the seasonal melting of ground ice as a possible mechanism for the large settlement. These findings emphasize the dynamic nature of permafrost landforms, demonstrate the capability of the InSAR technique to remotely monitor surface deformation of individual DTLBs, and illustrate the combination of ground-based and remote sensing observations to estimate thaw strain. Our study highlights the need for better description of the spatial heterogeneity of landscape-scale processes for regional assessment of surface dynamics on Arctic coastal lowlands.

  13. Alaska shorefast ice: Interfacing geophysics with local sea ice knowledge and use

    NASA Astrophysics Data System (ADS)

    Druckenmiller, Matthew L.

    This thesis interfaces geophysical techniques with local and traditional knowledge (LTK) of indigenous ice experts to track and evaluate coastal sea ice conditions over annual and inter-annual timescales. A novel approach is presented for consulting LTK alongside a systematic study of where, when, and how the community of Barrow, Alaska uses the ice cover. The goal of this research is to improve our understanding of and abilities to monitor the processes that govern the state and dynamics of shorefast sea ice in the Chukchi Sea and use of ice by the community. Shorefast ice stability and community strategies for safe hunting provide a framework for data collection and knowledge sharing that reveals how nuanced observations by Inupiat ice experts relate to identifying hazards. In particular, shorefast ice break-out events represent a significant threat to the lives of hunters. Fault tree analysis (FTA) is used to combine local and time-specific observations of ice conditions by both geophysical instruments and local experts, and to evaluate how ice features, atmospheric and oceanic forces, and local to regional processes interact to cause break-out events. Each year, the Barrow community builds trails across shorefast ice for use during the spring whaling season. In collaboration with hunters, a systematic multi-year survey (2007--2011) was performed to map these trails and measure ice thickness along them. Relationships between ice conditions and hunter strategies that guide trail placement and risk assessment are explored. In addition, trail surveys provide a meaningful and consistent approach to monitoring the thickness distribution of shorefast ice, while establishing a baseline for assessing future environmental change and potential impacts to the community. Coastal communities in the region have proven highly adaptive in their ability to safely and successfully hunt from sea ice over the last 30 years as significant changes have been observed in the ice zone

  14. Microbiota within the perennial ice cover of Lake Vida, Antarctica.

    PubMed

    Mosier, Annika C; Murray, Alison E; Fritsen, Christian H

    2007-02-01

    Lake Vida, located in the McMurdo Dry Valleys, Antarctica, is an 'ice-sealed' lake with approximately 19 m of ice covering a highly saline water column (approximately 245 ppt). The lower portions of the ice cover and the lake beneath have been isolated from the atmosphere and land for circa 2800 years. Analysis of microbial assemblages within the perennial ice cover of the lake revealed a diverse array of bacteria and eukarya. Bacterial and eukaryal denaturing gradient gel electrophoresis phylotype profile similarities were low (<59%) between all of the depths compared (five depths spanning 11 m of the ice cover), with the greatest differences occurring between surface and deep ice. The majority of bacterial 16S rRNA gene sequences in the surface ice were related to Actinobacteria (42%) while Gammaproteobacteria (52%) dominated the deep ice community. Comparisons of assemblage composition suggest differences in ice habitability and organismal origin in the upper and lower portions of ice cover. Specifically, the upper ice cover microbiota likely reflect the modern day transport and colonization of biota from the terrestrial landscape, whereas assemblages in the deeper ice are more likely to be persistent remnant biota that originated from the ancient liquid water column of the lake that froze.

  15. Fathometer data from Bart Lake and Lake Dorothy near Juneau, Alaska, 1988-89

    USGS Publications Warehouse

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

    1990-01-01

    Lake Dorothy is located about 20 miles southeast of Juneau, Alaska in an undeveloped area south of Taku Inlet. It occupies a linear, glacially eroded depression at an altitude of 2,400 ft. Several studies have assessed the feasibility of hydropower generation by a tap of Lake Dorothy. One of the proposed alignments, a tunnel to transmit water from lake Dorothy to a powerhouse at tide water on Taku Inlet, crosses Bart Lake, a cirque lake at 986 ft altitude. Fathometer surveys show that Bart Lake is a relatively symmetrical bowl-shaped depression with a maximum depth of 543 ft, and Lake Dorothy is a north-south elongated depression with steep sides and a maximum depth of 569 ft. (USGS)

  16. Geography of Alaska Lake Districts: Identification, Description, and Analysis of Lake-Rich Regions of a Diverse and Dynamic State

    USGS Publications Warehouse

    Arp, Christopher D.; Jones, Benjamin M.

    2009-01-01

    Lakes are abundant landforms and important ecosystems in Alaska, but are unevenly distributed on the landscape with expansive lake-poor regions and several lake-rich regions. Such lake-rich areas are termed lake districts and have landscape characteristics that can be considered distinctive in similar respects to mountain ranges. In this report, we explore the nature of lake-rich areas by quantitatively identifying Alaska's lake districts, describing and comparing their physical characteristics, and analyzing how Alaska lake districts are naturally organized and correspond to climatic and geophysical characteristics, as well as studied and managed by people. We use a digital dataset (National Hydrography Dataset) of lakes greater than 1 hectare, which includes 409,040 individual lakes and represents 3.3 percent of the land-surface area of Alaska. The selection criteria we used to identify lake districts were (1) a lake area (termed limnetic ratio, in percent) greater than the mean for the State, and (2) a lake density (number of lakes per unit area) greater than the mean for the State using a pixel size scaled to the area of interest and number of lakes in the census. Pixels meeting these criteria were grouped and delineated and all groups greater than 1,000 square kilometers were identified as Alaska's lake districts. These lake districts were described according to lake size-frequency metrics, elevation distributions, geology, climate, and ecoregions to better understand their similarities and differences. We also looked at where lake research and relevant ecological monitoring has occurred in Alaska relative to lake districts and how lake district lands and waters are currently managed. We identified and delineated 20 lake districts in Alaska representing 16 percent of the State, but including 65 percent of lakes and 75 percent of lake area. The largest lake districts identified are the Yukon-Kuskokwim Delta, Arctic Coastal Plain, and Iliamna lake districts with

  17. Crystal alignments in the fast ice of Arctic Alaska

    SciTech Connect

    Weeks, W.F.; Gow, A.J.

    1980-02-20

    Field observations at 60 sites located in the fast or near-fast ice along a 1200-km stretch of the north coast of Alaska between the Bering Strait and Barter Island have shown that the great majority of the ice samples (95%) exhibit striking c axis alignments within the horizontal plane. In all cases the degree of preferred orientation increased with depth in the ice. Representative standard deviations around a mean direction in the horizontal plane are commonly less than +- 10/sup 0/ for samples collected near the bottom of the ice. At a given site the mean c axis direction X-bar/sub 0/ may vary as much as 20/sup 0/ with vertical location in the ice sheet. The c axis allignments in the nearshore region generally parallel the coast, with strong alignments occurring in the lagoon systems between the barrier islands and the coast and seaward of the barrier islands. In passes between islands and in entrances such as the opening to Kotzebue Sound the alignment is parallel to the channel. Only limited observations are available farther seaward over the inner (10- to 50-m isobaths) and outer (50-m isobath to shelf break) shelf regions. These indicate Ne-SW and E-W alignments, respectively, in the Beaufort Sea north of Prudhoe Bay.

  18. 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

  19. Does ice float in Titan’s lakes and seas?

    NASA Astrophysics Data System (ADS)

    Hofgartner, Jason D.; Lunine, Jonathan I.

    2013-03-01

    We model Titan’s lakes and seas as methane-ethane-nitrogen systems and model the buoyancy of solids in these systems assuming thermodynamic equilibrium. We find that ice will float in methane-rich lakes for all temperatures below the freezing point of pure methane and that ice will also float in ethane-rich seas provided the ice has an air porosity of greater than 5% by volume.

  20. Composition, Diversity, and Stability of Microbial Assemblages in Seasonal Lake Ice, Miquelon Lake, Central Alberta

    PubMed Central

    Bramucci, Anna; Han, Sukkyun; Beckers, Justin; Haas, Christian; Lanoil, Brian

    2013-01-01

    The most familiar icy environments, seasonal lake and stream ice, have received little microbiological study. Bacteria and Eukarya dominated the microbial assemblage within the seasonal ice of Miquelon Lake, a shallow saline lake in Alberta, Canada. The bacterial assemblages were moderately diverse and did not vary with either ice depth or time. The closest relatives of the bacterial sequences from the ice included Actinobacteria, Bacteroidetes, Proteobacteria, Verrucomicrobia, and Cyanobacteria. The eukaryotic assemblages were less conserved and had very low diversity. Green algae relatives dominated the eukaryotic gene sequences; however, a copepod and cercozoan were also identified, possibly indicating the presence of complete microbial loop. The persistence of a chlorophyll a peak at 25–30 cm below the ice surface, despite ice migration and brine flushing, indicated possible biological activity within the ice. This is the first study of the composition, diversity, and stability of seasonal lake ice. PMID:24832796

  1. Ice-age megafauna in Arctic Alaska: extinction, invasion, survival

    NASA Astrophysics Data System (ADS)

    Mann, Daniel H.; Groves, Pamela; Kunz, Michael L.; Reanier, Richard E.; Gaglioti, Benjamin V.

    2013-06-01

    Radical restructuring of the terrestrial, large mammal fauna living in arctic Alaska occurred between 14,000 and 10,000 years ago at the end of the last ice age. Steppe bison, horse, and woolly mammoth became extinct, moose and humans invaded, while muskox and caribou persisted. The ice age megafauna was more diverse in species and possibly contained 6× more individual animals than live in the region today. Megafaunal biomass during the last ice age may have been 30× greater than present. Horse was the dominant species in terms of number of individuals. Lions, short-faced bears, wolves, and possibly grizzly bears comprised the predator/scavenger guild. The youngest mammoth so far discovered lived ca 13,800 years ago, while horses and bison persisted on the North Slope until at least 12,500 years ago during the Younger Dryas cold interval. The first people arrived on the North Slope ca 13,500 years ago. Bone-isotope measurements and foot-loading characteristics suggest megafaunal niches were segregated along a moisture gradient, with the surviving species (muskox and caribou) utilizing the warmer and moister portions of the vegetation mosaic. As the ice age ended, the moisture gradient shifted and eliminated habitats utilized by the dryland, grazing species (bison, horse, mammoth). The proximate cause for this change was regional paludification, the spread of organic soil horizons and peat. End-Pleistocene extinctions in arctic Alaska represent local, not global extinctions since the megafaunal species lost there persisted to later times elsewhere. Hunting seems unlikely as the cause of these extinctions, but it cannot be ruled out as the final blow to megafaunal populations that were already functionally extinct by the time humans arrived in the region.

  2. Ice-age megafauna in Arctic Alaska: extinction, invasion, survival

    USGS Publications Warehouse

    Mann, Daniel H.; Groves, Pamela; Kunz, Michael L.; Reanier, Richard E.; Gaglioti, Benjamin V.

    2013-01-01

    Radical restructuring of the terrestrial, large mammal fauna living in arctic Alaska occurred between 14,000 and 10,000 years ago at the end of the last ice age. Steppe bison, horse, and woolly mammoth became extinct, moose and humans invaded, while muskox and caribou persisted. The ice age megafauna was more diverse in species and possibly contained 6× more individual animals than live in the region today. Megafaunal biomass during the last ice age may have been 30× greater than present. Horse was the dominant species in terms of number of individuals. Lions, short-faced bears, wolves, and possibly grizzly bears comprised the predator/scavenger guild. The youngest mammoth so far discovered lived ca 13,800 years ago, while horses and bison persisted on the North Slope until at least 12,500 years ago during the Younger Dryas cold interval. The first people arrived on the North Slope ca 13,500 years ago. Bone-isotope measurements and foot-loading characteristics suggest megafaunal niches were segregated along a moisture gradient, with the surviving species (muskox and caribou) utilizing the warmer and moister portions of the vegetation mosaic. As the ice age ended, the moisture gradient shifted and eliminated habitats utilized by the dryland, grazing species (bison, horse, mammoth). The proximate cause for this change was regional paludification, the spread of organic soil horizons and peat. End-Pleistocene extinctions in arctic Alaska represent local, not global extinctions since the megafaunal species lost there persisted to later times elsewhere. Hunting seems unlikely as the cause of these extinctions, but it cannot be ruled out as the final blow to megafaunal populations that were already functionally extinct by the time humans arrived in the region.

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

    USGS Publications Warehouse

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

    1997-01-01

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

  4. Ancient ice islands in salt lakes of the Central Andes

    USGS Publications Warehouse

    Hurlbert, S.H.; Chang, Cecily C.Y.

    1984-01-01

    Massive blocks of freshwater ice and frozen sediments protrude from shallow, saline lakes in the Andes of southwestern Bolivia and northeastern Chile. These ice islands range up to 1.5 kilometers long, stand up to 7 meters above the water surface, and may extend out tens of meters and more beneath the unfrozen lake sediments. The upper surfaces of the islands are covered with dry white sediments, mostly aragonite or calcite. The ice blocks may have formed by freezing of the fresh pore water of lake sediments during the "little ice age." The largest blocks are melting rapidly because of possibly recent increases in geothermal heat flux through the lake bottom and undercutting by warm saline lake water during the summer.

  5. Ancient ice islands in salt lakes of the central andes.

    PubMed

    Hurlbert, S H; Chang, C C

    1984-04-20

    Massive blocks of freshwater ice and frozen sediments protrude from shallow, saline lakes in the Andes of southwestern Bolivia and northeastern Chile. These ice islands range up to 1.5 kilometers long, stand up to 7 meters above the water surface, and may extend out tens of meters and more beneath the unfrozen lake sediments. The upper surfaces of the islands are covered with dry white sediments, mostly aragonite or calcite. The ice blocks may have formed by freezing of the fresh pore water of lake sediments during the "little ice age." The largest blocks are melting rapidly because of possibly recent increases in geothermal heat flux through the lake bottom and undercutting by warm saline lake water during the summer.

  6. Subglacial lake drainage detected beneath the Greenland ice sheet

    PubMed Central

    Palmer, Steven; McMillan, Malcolm; Morlighem, Mathieu

    2015-01-01

    The contribution of the Greenland ice sheet to sea-level rise has accelerated in recent decades. Subglacial lake drainage events can induce an ice sheet dynamic response—a process that has been observed in Antarctica, but not yet in Greenland, where the presence of subglacial lakes has only recently been discovered. Here we investigate the water flow paths from a subglacial lake, which drained beneath the Greenland ice sheet in 2011. Our observations suggest that the lake was fed by surface meltwater flowing down a nearby moulin, and that the draining water reached the ice margin via a subglacial tunnel. Interferometric synthetic aperture radar-derived measurements of ice surface motion acquired in 1995 suggest that a similar event may have occurred 16 years earlier, and we propose that, as the climate warms, increasing volumes of surface meltwater routed to the bed will cause such events to become more common in the future. PMID:26450175

  7. Response of ice cover on shallow Arctic lakes to contemporary climate conditions: Numerical modeling and remote sensing data analysis

    NASA Astrophysics Data System (ADS)

    Duguay, C.; Surdu, C.; Brown, L.; Samuelsson, P.

    2012-04-01

    Lake ice cover has been shown to be a robust indicator of climate variability and change. Recent studies have demonstrated that break-up dates, in particular, have been occurring earlier in many parts of the Northern Hemisphere over the last 50 years in response to warmer climatic conditions in the winter and spring seasons. The impacts of trends in air temperature and winter precipitation over the last five decades and those projected by global climate models will affect the timing and duration of ice cover (and ice thickness) on Arctic lakes. This will likely, in turn, have an important feedback effect on energy, water, and biogeochemical cycling in various regions of the Arctic. In the case of shallow tundra lakes, many of which are less than 3-m deep, warmer climate conditions could result in a smaller fraction of lakes that freeze to their bed in winter since thinner ice covers are expected to develop. Shallow lakes of the coastal plain of northern Alaska, and other similar regions of the Arctic, have likely been experiencing changes in seasonal ice thickness (and phenology) over the last few decades but these have not yet been documented. This paper presents results from a numerical lake ice modeling experiment and the analysis of ERS-1/2 synthetic aperture radar (SAR) data to elucidate the response of ice cover (thickness, freezing to bed, and phenology) on shallow lakes of the North Slope of Alaska (NSA)to climate conditions over the last three decades. New downscaled data specific for the Arctic domain (at a resolution of 0.44 degrees using ERA Interim Reanalysis as boundary condition) produced by the Rossby Centre regional atmospheric model (RCA4) was used to force the Canadian Lake Ice Model (CLIMo) for the period 1979-2010. Output from CLIMo included freeze-up and break-up dates as well as ice thickness on a daily basis. ERS-1/2 data was used to map areas of shallow lakes that freeze to bed and when this happens (timing) in winter for the period 1991

  8. Geomicrobiology of subglacial ice above Lake Vostok, Antarctica

    USGS Publications Warehouse

    Priscu, J.C.; Adams, E.E.; Lyons, W.B.; Voytek, M.A.; Mogk, D.W.; Brown, R.L.; McKay, C.P.; Takacs, C.D.; Welch, K.A.; Wolf, C.F.; Kirshtein, J.D.; Avci, R.

    1999-01-01

    Data from ice 3590 meters below Vostok Station indicate that the ice was accredit from liquid water associated with Lake Vostok. Microbes were observed at concentrations ranging from 2.8 x 103 to 3.6 x 104 cells per milliliter; no biological incorporation of selected organic substrates or bicarbonate was detected. Bacterial 165 ribosomal DNA genes revealed low diversity in the gene population. The phylotypes were closely related to extant members of the alpha- and beta-Proteobacteria and the Actinomycetes. Extrapolation of the data from accretion ice to Lake Vostok implies that Lake Vostok may support a microbial population, despite more than 106 years of isolation from the atmosphere.

  9. Diatom assemblages promote ice formation in large lakes.

    PubMed

    D'souza, N A; Kawarasaki, Y; Gantz, J D; Lee, R E; Beall, B F N; Shtarkman, Y M; Koçer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

    2013-08-01

    We present evidence for the directed formation of ice by planktonic communities dominated by filamentous diatoms sampled from the ice-covered Laurentian Great Lakes. We hypothesize that ice formation promotes attachment of these non-motile phytoplankton to overlying ice, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for ice nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (T(c)) as high as -3 °C. Ice nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of ice nucleation activity, the resulting production of frazil ice may provide a means for the diatoms to be recruited to the overlying lake ice, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal ice cover around the world.

  10. Diatom assemblages promote ice formation in large lakes

    PubMed Central

    D'souza, N A; Kawarasaki, Y; Gantz, J D; Lee, R E; Beall, B F N; Shtarkman, Y M; Koçer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

    2013-01-01

    We present evidence for the directed formation of ice by planktonic communities dominated by filamentous diatoms sampled from the ice-covered Laurentian Great Lakes. We hypothesize that ice formation promotes attachment of these non-motile phytoplankton to overlying ice, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for ice nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (Tc) as high as −3 °C. Ice nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of ice nucleation activity, the resulting production of frazil ice may provide a means for the diatoms to be recruited to the overlying lake ice, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal ice cover around the world. PMID:23552624

  11. Diatom assemblages promote ice formation in large lakes.

    PubMed

    D'souza, N A; Kawarasaki, Y; Gantz, J D; Lee, R E; Beall, B F N; Shtarkman, Y M; Koçer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

    2013-08-01

    We present evidence for the directed formation of ice by planktonic communities dominated by filamentous diatoms sampled from the ice-covered Laurentian Great Lakes. We hypothesize that ice formation promotes attachment of these non-motile phytoplankton to overlying ice, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for ice nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (T(c)) as high as -3 °C. Ice nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of ice nucleation activity, the resulting production of frazil ice may provide a means for the diatoms to be recruited to the overlying lake ice, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal ice cover around the world. PMID:23552624

  12. Multiyear ice transport and small scale sea ice deformation near the Alaska coast measured by air-deployable Ice Trackers

    NASA Astrophysics Data System (ADS)

    Mahoney, A. R.; Kasper, J.; Winsor, P.

    2015-12-01

    Highly complex patterns of ice motion and deformation were captured by fifteen satellite-telemetered GPS buoys (known as Ice Trackers) deployed near Barrow, Alaska, in spring 2015. Two pentagonal clusters of buoys were deployed on pack ice by helicopter in the Beaufort Sea between 20 and 80 km offshore. During deployment, ice motion in the study region was effectively zero, but two days later the buoys captured a rapid transport event in which multiyear ice from the Beaufort Sea was flushed into the Chukchi Sea. During this event, westward ice motion began in the Chukchi Sea and propagated eastward. This created new openings in the ice and led to rapid elongation of the clusters as the westernmost buoys accelerated away from their neighbors to the east. The buoys tracked ice velocities of over 1.5 ms-1, with fastest motion occurring closest to the coast indicating strong current shear. Three days later, ice motion reversed and the two clusters became intermingled, rendering divergence calculations based on the area enclosed by clusters invalid. The data show no detectable difference in velocity between first year and multiyear ice floes, but Lagrangian timeseries of SAR imagery centered on each buoy show that first year ice underwent significant small-scale deformation during the event. The five remaining buoys were deployed by local residents on prominent ridges embedded in the landfast ice within 16 km of Barrow in order to track the fate of such features after they detached from the coast. Break-up of the landfast ice took place over a period of several days and, although the buoys each initially followed a similar eastward trajectory around Point Barrow into the Beaufort Sea, they rapidly dispersed over an area more than 50 km across. With rapid environmental and socio-economic change in the Arctic, understanding the complexity of nearshore ice motion is increasingly important for predict future changes in the ice and the tracking ice-related hazards

  13. Limnology of Big Lake, south-central Alaska, 1983-84

    USGS Publications Warehouse

    Woods, Paul F.

    1992-01-01

    The limnological characteristics and trophic state of Big Lake in south-central Alaska were determined from the results of an intensive study during 1983-84. The study was begun in response to concern over the potential for eutrophication of Big Lake, which has experienced substantial residential development and recreational use because of its proximity to Anchorage. The east and west basins of the 1,213 square-hectometer lake were each visited 36 times during the 2-year study to obtain a wide variety of physical, chemical, and biological data. During 1984, an estimate was made of the lake's annual primary production. Big Lake was classified as oligotrophic on the basis of its annual mean values for total phosphorus (9.5 micrograms per liter), total nitrogen (209 micrograms per liter), chlorophyll-a (2.5 micrograms per liter), secchi-disc transparency (6.3 meters), and its mean daily integral primary production of 81.1 milligrams of carbon fixed per square meter. The lake was, however, uncharacteristic of oligotrophic lakes in that a severe dissolved-oxygen deficit developed within the hypolimnion during summer stratification and under winter ice cover. The summer dissolved-oxygen deficit resulted from the combination of strong and persistent thermal stratification, which developed within 1 week of the melting of the lake's ice cover in May, and the failure of the spring circulation to fully reaerate the hypolimnion. The autumn circulation did reaerate the entire water column, but the ensuing 6 months of ice and snow cover prevented atmospheric reaeration of the water column and led to development of the winter dissolved-oxygen deficit. The anoxic conditions that eventually developed near the lake bottom allowed the release of nutrients from the bottom sediments and facilitated ammonification reactions. These processes yielded hypolimnetic concentrations of nitrogen and phosphorus compounds, which were much larger than the oligotrophic concentrations measured

  14. Mathematical Modelling of Melt Lake Formation On An Ice Shelf

    NASA Astrophysics Data System (ADS)

    Buzzard, Sammie; Feltham, Daniel; Flocco, Daniela

    2016-04-01

    The accumulation of surface meltwater on ice shelves can lead to the formation of melt lakes. These structures have been implicated in crevasse propagation and ice-shelf collapse; the Larsen B ice shelf was observed to have a large amount of melt lakes present on its surface just before its collapse in 2002. Through modelling the transport of heat through the surface of the Larsen C ice shelf, where melt lakes have also been observed, this work aims to provide new insights into the ways in which melt lakes are forming and the effect that meltwater filling crevasses on the ice shelf will have. This will enable an assessment of the role of meltwater in triggering ice-shelf collapse. The Antarctic Peninsula, where Larsen C is situated, has warmed several times the global average over the last century and this ice shelf has been suggested as a candidate for becoming fully saturated with meltwater by the end of the current century. Here we present results of a 1-D mathematical model of heat transfer through an idealized ice shelf. When forced with automatic weather station data from Larsen C, surface melting and the subsequent meltwater accumulation, melt lake development and refreezing are demonstrated through the modelled results. Furthermore, the effect of lateral meltwater transport upon melt lakes and the effect of the lakes upon the surface energy balance are examined. Investigating the role of meltwater in ice-shelf stability is key as collapse can affect ocean circulation and temperature, and cause a loss of habitat. Additionally, it can cause a loss of the buttressing effect that ice shelves can have on their tributary glaciers, thus allowing the glaciers to accelerate, contributing to sea-level rise.

  15. Mathematical Modelling of Melt Lake Formation On An Ice Shelf

    NASA Astrophysics Data System (ADS)

    Buzzard, S. C.; Feltham, D. L.; Flocco, D.; Sammonds, P. R.

    2015-12-01

    The accumulation of surface meltwater on ice shelves can lead to the formation of melt lakes. These structures have been implicated in crevasse propagation and ice-shelf collapse; the Larsen B ice shelf was observed to have a large amount of melt lakes present on its surface just before its collapse in 2002. Through modelling the transport of heat through the surface of the Larsen C ice shelf, where melt lakes have also been observed, this work aims to provide new insights into the ways in which melt lakes are forming and the effect that meltwater filling crevasses on the ice shelf will have. This will enable an assessment of the role of meltwater in triggering ice-shelf collapse. The Antarctic Peninsula, where Larsen C is situated, has warmed several times the global average over the last century and this ice shelf has been suggested as a candidate for becoming fully saturated with meltwater by the end of the current century. Here we present results of a 1-D mathematical model of heat transfer through an idealized ice shelf. When forced with automatic weather station data from Larsen C, surface melting and the subsequent meltwater accumulation, melt lake development and refreezing are demonstrated through the modelled results. Furthermore, the effect of lateral meltwater transport upon melt lakes and the effect of the lakes upon the surface energy balance are examined. Investigating the role of meltwater in ice-shelf stability is key as collapse can affect ocean circulation and temperature, and cause a loss of habitat. Additionally, it can cause a loss of the buttressing effect that ice shelves can have on their tributary glaciers, thus allowing the glaciers to accelerate, contributing to sea-level rise.

  16. The influence of ice on southern Lake Michigan coastal erosion

    USGS Publications Warehouse

    Barnes, P.W.; Kempema, E.W.; Reimnitz, E.; McCormick, M.

    1994-01-01

    Coastal ice does not protect the coast but enhances erosion by displacing severe winter wave energy from the beach to the shoreface and by entraining and transporting sediment alongshore and offshore. Three aspects of winter ice in Lake Michigan were studied over a 3-year period and found to have an important influence on coastal sediment dynamics and the coastal sediment budget: (1) the influence of coastal ice on shoreface morphology, (2) the transport of littoral sediments by ice, and (3) the formation of anchor and underwater ice as a frequent and important event entraining and transporting sediment. The nearshore ice complex contains a sediment load (0.2 - 1.2 t/m of coast) that is roughly equivalent to the average amount of sand eroded from the coastal bluffs and to the amount of sand ice- rafted offshore to the deep lake basin each year. -from Authors

  17. Constraints on methane oxidation in ice-covered boreal lakes

    NASA Astrophysics Data System (ADS)

    Denfeld, Blaize A.; Ricão Canelhas, Monica; Weyhenmeyer, Gesa A.; Bertilsson, Stefan; Eiler, Alexander; Bastviken, David

    2016-07-01

    Boreal lakes can be ice covered for a substantial portion of the year at which time methane (CH4) can accumulate below ice. The amount of CH4 emitted at ice melt is partially determined by the interplay between CH4 production and CH4 oxidation, performed by methane-oxidizing bacteria (MOB). Yet the balance between oxidation and emission and the potential for CH4 oxidation in various lakes during winter is largely unknown. To address this, we performed incubations at 2°C to screen for wintertime CH4 oxidation potential in seven lakes. Results showed that CH4 oxidation was restricted to three lakes, where the phosphate concentrations were highest. Molecular analyses revealed that MOB were initially detected in all lakes, although an increase in type I MOB only occurred in the three lake water incubations where oxidation could be observed. Accordingly, the increase in CO2 was on average 5 times higher in these three lake water incubations. For one lake where no oxidation was measured, we tested if temperature and CH4 availability could trigger CH4 oxidation. However, regardless of incubation temperatures and CH4 concentrations, ranging from 2 to 20°C and 1-500 μM, respectively, no oxidation was observed. Our study indicates that some lakes with active wintertime CH4 oxidation may have low emissions during ice melt, while other and particularly nutrient poor lakes may accumulate large amounts of CH4 below ice that, in the absence of CH4 oxidation, will be emitted following ice melt. This variability in CH4 oxidation rates between lakes needs to be accounted for in large-scale CH4 emission estimates.

  18. Biogeochemical cycling of methylmercury in lakes and tundra watersheds of Arctic Alaska.

    PubMed

    Hammerschmidt, Chad R; Fitzgerald, William F; Lamborg, Carl H; Balcom, Prentiss H; Tseng, C Mao

    2006-02-15

    The fate of atmospherically deposited and environmentally active Hg is uncertain in the Arctic, and of greatest toxicological concern is the transformation to monometh-ylmercury (MMHg). Lake/watershed mass balances were developed to examine MMHg cycling in four northern Alaska lakes near the ecological research station at Toolik Lake (68 degrees 38' N, 149 degrees 36' W). Primary features of the cycle are watershed runoff, sedimentary production and mobilization, burial, and photodecomposition in the water column. The principal source of MMHg is in situ benthic production with 80-91% of total inputs provided by diffusion from sediments. The production and contribution of MMHg from tundra watersheds is modest. Photodecomposition, though confined to a short ice-free season, provides the primary control for MMHg (66-88% of total inputs) and greatly attenuates bioaccumulation. Solid-phase MMHg and gross potential rates of Hg methylation, assayed with an isotopic tracer, vary positively with the level of inorganic Hg in filtered pore water, indicating that MMHg production is Hg-limited in these lakes. Moreover, sediment-waterfluxes of MMHg (i.e., net production at steady state) are related to sediment Hg loadings from the atmosphere. These results suggest that loadings of Hg derived from atmospheric deposition are a major factor affecting MMHg cycling in arctic ecosystems. However, environmental changes associated with warming of the Arctic (e.g., increased weathering, temperature, productivity, and organic loadings) may enhance MMHg bioaccumulation by stimulating Hg methylation and inhibiting photodecomposition.

  19. Holocene Tephrochronology from Lake Sediments, Redoubt Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Schiff, C. J.; Kaufman, D. S.; Wallace, K. L.

    2006-12-01

    Lake sediments in volcanically active areas provide a geological archive of tephra-fall events because sedimentation often occurs continuously and organic material for 14C dating is commonly available; lake sediments, therefore, contain valuable information about tephra fall and associated hazards. Recovering tephra-fall records from lakes requires careful site selection, core recovery, and tephra age assignments. A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last ca. 8750 cal yr BP. A previous core taken from a shallow site at Bear Lake contains 38 tephra layers suggesting that a deeper site in lakes provides a more complete sediment record as shallow sites are susceptible to remobilization and have lower sedimentation rates. We use 12 AMS 14C ages, along with the 137Cs and 210Pb activities of the top 8.5 cm of sediment, to evaluate different models to determine the age-depth relation of sediment, and to determine the age of each tephra deposit. The selected age model is based on a cubic smooth spline function that was passed through the adjusted tephra-free depth of each dated layer; the age model provides an example of how best to date lake sediment in a volcanically active area where presumably instantaneous tephra deposition compounds a simple age-depth relationship. Using the age model we find that tephra-fall frequency at Bear Lake was among the highest during the past ~500 yr, with eight tephras deposited compared to an average of 3.7 per 500 yr over the last 8500 yr. Other periods of increased tephra fall occurred ca. 2500-3500, 4500-5000, and 7000-7500 cal yr BP. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall between shorter periods (500-1000 yr) of quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average

  20. An operational all-weather Great Lakes ice information system

    NASA Technical Reports Server (NTRS)

    Gedney, R. T.

    1975-01-01

    A description is given of the NASA developed all-weather ice information system for the Great Lakes winter navigation program. The system utilizes an X-band side looking airborne radar (SLAR) for determining type, location, and areal distribution of the ice cover in the Great Lakes and an airborne, S band, down looking short pulse radar for obtaining ice thickness. Digitized SLAR data are relayed in real time via the NOAA-GOES satellite in geosynchronous orbit. The SLAR images along with hand drawn interpretative ice charts for various Great Lakes winter shipping areas are broadcast to facsimile recorders aboard vessles is the area via the MARAD marine VHF-FM radio network. These data assist such vessels in navigating both through and around the ice.

  1. The evolution of a thermokarst-lake landscape: Late Quaternary permafrost degradation and stabilization in interior Alaska

    USGS Publications Warehouse

    Edwards, Mary E.; Grosse, Guido; Jones, Benjamin M.; McDowell, Patricia F.

    2016-01-01

    Thermokarst processes characterize a variety of ice-rich permafrost terrains and often lead to lake formation. The long-term evolution of thermokarst landscapes and the stability and longevity of lakes depend upon climate, vegetation and ground conditions, including the volume of excess ground ice and its distribution. The current lake status of thermokarst-lake landscapes and their future trajectories under climate warming are better understood in the light of their long-term development. We studied the lake-rich southern marginal upland of the Yukon Flats (northern interior Alaska) using dated lake-sediment cores, observations of river-cut exposures, and remotely-sensed data. The region features thick (up to 40 m) Quaternary deposits (mainly loess) that contain massive ground ice. Two of three studied lakes formed ~ 11,000–12,000 cal yr BP through inferred thermokarst processes, and fire may have played a role in initiating thermokarst development. From ~ 9000 cal yr BP, all lakes exhibited steady sedimentation, and pollen stratigraphies are consistent with regional patterns. The current lake expansion rates are low (0 to < 7 cm yr− 1 shoreline retreat) compared with other regions (~ 30 cm yr− 1 or more). This thermokarst lake-rich region does not show evidence of extensive landscape lowering by lake drainage, nor of multiple lake generations within a basin. However, LiDAR images reveal linear “corrugations” (> 5 m amplitude), deep thermo-erosional gullies, and features resembling lake drainage channels, suggesting that highly dynamic surface processes have previously shaped the landscape. Evidently, widespread early Holocene permafrost degradation and thermokarst lake initiation were followed by lake longevity and landscape stabilization, the latter possibly related to establishment of dense forest cover. Partial or complete drainage of three lakes in 2013 reveals that there is some contemporary landscape dynamism. Holocene landscape

  2. 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.

  3. Seasonal and Latitudinal Variations in Dissolved Methane from 42 Lakes along a North-South Transect in Alaska

    NASA Astrophysics Data System (ADS)

    Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K. C.; Anthony, P.; Thalasso, F.

    2013-12-01

    Armando Sepulveda-Jauregui,* Katey M. Walter Anthony,* Karla Martinez-Cruz,* ** Peter Anthony,* and Frederic Thalasso**. * Water and Environmental Research Center, Institute of Northern Engineering, University of Alaska Fairbanks, Fairbanks, Alaska. ** Biotechnology and Bioengineering Department, Cinvestav, Mexico city, D. F., Mexico. Northern lakes are important reservoirs and sources to the atmosphere of methane (CH4), a potent greenhouse gas. It is estimated that northern lakes (> 55 °N) contribute about 20% of the total global lake methane emissions, and that emissions from these lakes will increase with climate warming. Temperature rise enhances methane production directly by providing the kinetic energy to methanogenesis, and indirectly by supplying organic matter from thawing permafrost. Warmer lakes also store less methane since methane's solubility is inversely related to temperature. Alaskan lakes are located in three well-differentiated permafrost classes: yedoma permafrost with high labile carbon stocks, non-yedoma permafrost with lower carbon stocks, and areas without permafrost, also with generally lower carbon stocks. We sampled dissolved methane from 42 Alaskan lakes located in these permafrost cover classes along a north-south Alaska transect from Prudhoe Bay to the Kenai Peninsula during open-water conditions in summer 2011. We sampled 26 of these lakes in April, toward the end of the winter ice-covered period. Our results indicated that the largest dissolved methane concentrations occurred in interior Alaska thermokarst lakes formed in yedoma-type permafrost during winter and summer, with maximal concentrations of 17.19 and 12.76 mg L-1 respectively. In these lakes, emission of dissolved gases as diffusion during summer and storage release in spring were 18.4% and 17.4% of the annual emission budget, while ebullition (64.2 %) comprised the rest. Dissolved oxygen was inversely correlated with dissolved methane concentrations in both seasons; the

  4. 20th-century glacial-marine sedimentation in Vitus Lake, Bering Glacier, Alaska, U.S.A.

    USGS Publications Warehouse

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

    1996-01-01

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

  5. Temporal variation in fish mercury concentrations within lakes from the western Aleutian Archipelago, Alaska.

    PubMed

    Kenney, Leah A; Eagles-Smith, Collin A; Ackerman, Joshua T; von Hippel, Frank A

    2014-01-01

    We assessed temporal variation in mercury (Hg) concentrations of threespine stickleback (Gasterosteus aculeatus) from Agattu Island, Aleutian Archipelago, Alaska. Total Hg concentrations in whole-bodied stickleback were measured at two-week intervals from two sites in each of two lakes from June 1 to August 10, 2011 during the time period when lakes were ice-free. Across all sites and sampling events, stickleback Hg concentrations ranged from 0.37-1.07 µg/g dry weight (dw), with a mean (± SE) of 0.55 ± 0.01 µg/g dw. Mean fish Hg concentrations declined by 9% during the study period, from 0.57 ± 0.01 µg/g dw in early June to 0.52 ± 0.01 µg/g dw in mid-August. Mean fish Hg concentrations were 6% higher in Loon Lake (0.56 ± 0.01 µg/g dw) than in Lake 696 (0.53 ± 0.01 µg/g dw), and 4% higher in males (0.56 ± 0.01 µg/g dw) than in females (0.54 ± 0.01 µg/g dw). Loon Lake was distinguished from Lake 696 by the presence of piscivorous waterbirds during the breeding season. Mercury concentrations in stickleback from Agattu Island were higher than would be expected for an area without known point sources of Hg pollution, and high enough to be of concern to the health of piscivorous wildlife. PMID:25029042

  6. Temporal Variation in Fish Mercury Concentrations within Lakes from the Western Aleutian Archipelago, Alaska

    PubMed Central

    Kenney, Leah A.; Eagles-Smith, Collin A.; Ackerman, Joshua T.; von Hippel, Frank A.

    2014-01-01

    We assessed temporal variation in mercury (Hg) concentrations of threespine stickleback (Gasterosteus aculeatus) from Agattu Island, Aleutian Archipelago, Alaska. Total Hg concentrations in whole-bodied stickleback were measured at two-week intervals from two sites in each of two lakes from June 1 to August 10, 2011 during the time period when lakes were ice-free. Across all sites and sampling events, stickleback Hg concentrations ranged from 0.37–1.07 µg/g dry weight (dw), with a mean (± SE) of 0.55±0.01 µg/g dw. Mean fish Hg concentrations declined by 9% during the study period, from 0.57±0.01 µg/g dw in early June to 0.52±0.01 µg/g dw in mid-August. Mean fish Hg concentrations were 6% higher in Loon Lake (0.56±0.01 µg/g dw) than in Lake 696 (0.53±0.01 µg/g dw), and 4% higher in males (0.56±0.01 µg/g dw) than in females (0.54±0.01 µg/g dw). Loon Lake was distinguished from Lake 696 by the presence of piscivorous waterbirds during the breeding season. Mercury concentrations in stickleback from Agattu Island were higher than would be expected for an area without known point sources of Hg pollution, and high enough to be of concern to the health of piscivorous wildlife. PMID:25029042

  7. Temporal variation in fish mercury concentrations within lakes from the western Aleutian Archipelago, Alaska

    USGS Publications Warehouse

    Kenney, Leah A.; Eagles-Smith, Collin A.; Ackerman, Joshua T.; von Hippel, Frank A.

    2014-01-01

    We assessed temporal variation in mercury (Hg) concentrations of threespine stickleback (Gasterosteus aculeatus) from Agattu Island, Aleutian Archipelago, Alaska. Total Hg concentrations in whole-bodied stickleback were measured at two-week intervals from two sites in each of two lakes from June 1 to August 10, 2011 during the time period when lakes were ice-free. Across all sites and sampling events, stickleback Hg concentrations ranged from 0.37–1.07 µg/g dry weight (dw), with a mean (± SE) of 0.55±0.01 µg/g dw. Mean fish Hg concentrations declined by 9% during the study period, from 0.57±0.01 µg/g dw in early June to 0.52±0.01 µg/g dw in mid-August. Mean fish Hg concentrations were 6% higher in Loon Lake (0.56±0.01 µg/g dw) than in Lake 696 (0.53±0.01 µg/g dw), and 4% higher in males (0.56±0.01 µg/g dw) than in females (0.54±0.01 µg/g dw). Loon Lake was distinguished from Lake 696 by the presence of piscivorous waterbirds during the breeding season. Mercury concentrations in stickleback from Agattu Island were higher than would be expected for an area without known point sources of Hg pollution, and high enough to be of concern to the health of piscivorous wildlife.

  8. 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

  9. Preliminary volcano hazard assessment for the Emmons Lake volcanic center, Alaska

    USGS Publications Warehouse

    Waythomas, Christopher; Miller, Thomas P.; Mangan, Margaret T.

    2006-01-01

    The Emmons Lake volcanic center is a large stratovolcano complex on the Alaska Peninsula near Cold Bay, Alaska. The volcanic center includes several ice- and snow-clad volcanoes within a nested caldera structure that hosts Emmons Lake and truncates a shield-like ancestral Mount Emmons edifice. From northeast to southwest, the main stratovolcanoes of the center are: Pavlof Sister, Pavlof, Little Pavlof, Double Crater, Mount Hague, and Mount Emmons. Several small cinder cones and vents are located on the floor of the caldera and on the south flank of Pavlof Volcano. Pavlof Volcano, in the northeastern part of the center, is the most historically active volcano in Alaska (Miller and others, 1998) and eruptions of Pavlof pose the greatest hazards to the region. Historical eruptions of Pavlof Volcano have been small to moderate Strombolian eruptions that produced moderate amounts of near vent lapilli tephra fallout, and diffuse ash plumes that drifted several hundreds of kilometers from the vent. Cold Bay, King Cove, Nelson Lagoon, and Sand Point have reported ash fallout from Pavlof eruptions. Drifting clouds of volcanic ash produced by eruptions of Pavlof would be a major hazard to local aircraft and could interfere with trans-Pacific air travel if the ash plume achieved flight levels. During most historical eruptions of Pavlof, pyroclastic material erupted from the volcano has interacted with the snow and ice on the volcano producing volcanic mudflows or lahars. Lahars have inundated most of the drainages heading on the volcano and filled stream valleys with variable amounts of coarse sand, gravel, and boulders. The lahars are often hot and would alter or destroy stream habitat for many years following the eruption. Other stratocones and vents within the Emmons Lake volcanic center are not known to have erupted in the past 300 years. However, young appearing deposits and lava flows suggest there may have been small explosions and minor effusive eruptive activity

  10. Thermal and hydrological observations near Twelvemile Lake in discontinuous permafrost, Yukon Flats, interior Alaska, September 2010-August 2011

    USGS Publications Warehouse

    Jepsen, Steven M.; Koch, Joshua C.; Rose, Joshua R.; Voss, Clifford I.; Walvoord, Michelle A.

    2012-01-01

    A series of ground-based observations were made between September 2010 and August 2011 near Twelvemile Lake, 19 kilometers southwest of Fort Yukon, Alaska, for use in ongoing hydrological analyses of watersheds in this region of discontinuous permafrost. Measurements include depth to ground ice, depth to water table, soil texture, soil moisture, soil temperature, and water pressure above the permafrost table. In the drained basin of subsiding Twelvemile Lake, we generally find an absence of newly formed permafrost and an undetectable slope of the water table; however, a sloping water table was observed in the low-lying channels extending into and away from the lake watershed. Datasets for these observations are summarized in this report and can be accessed by clicking on the links in each section or from the Downloads folder of the report Web page.

  11. Lake Ice Cover of Shallow Lakes and Climate Interactions in Arctic Regions (1950-2011): SAR Data Analysis and Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Surdu, C.; Duguay, C.; Brown, L.; Fernàndez-Prieto, D.; Samuelsson, P.

    2012-12-01

    Lake ice cover is highly correlated with climatic conditions and has, therefore, been demonstrated to be an essential indicator of climate variability and change. Recent studies have shown that the duration of the lake ice cover has decreased, mainly as a consequence of earlier thaw dates in many parts of the Northern Hemisphere over the last 50 years, mainly as a feedback to increased winter and spring air temperature. In response to projected air temperature and winter precipitation changes by climate models until the end of the 21st century, the timing, duration, and thickness of ice cover on Arctic lakes are expected to be impacted. This, in turn, will likely alter the energy, water, and bio-geochemical cycling in various regions of the Arctic. In the case of shallow tundra lakes, many of which are less than 3-m deep, warmer climate conditions could result in a smaller fraction of lakes that fully freeze to the bottom at the time of maximum winter ice thickness since thinner ice covers are predicted to develop. Shallow thermokarst lakes of the coastal plain of northern Alaska, and of other similar Arctic regions, have likely been experiencing changes in seasonal ice phenology and thickness over the last few decades but these have not yet been comprehensively documented. Analysis of a 20-year time series of ERS-1/2 synthetic aperture radar (SAR) data and numerical lake ice modeling were employed to determine the response of ice cover (thickness, freezing to bed, and phenology) on shallow lakes of the North Slope of Alaska (NSA) to climate conditions over the last three decades. New downscaled data specific to the Arctic domain (at a resolution of 0.44 degrees using ERA Interim Reanalysis as boundary condition) produced by the Rossby Centre Regional Atmospheric Climate Model (RCA4) was used to drive the Canadian Lake Ice Model (CLIMo) for the period 1950-2011. In order to assess and integrate the SAR-derived observed changes into a longer historical context, and

  12. Lake Hoare, Antarctica: sedimentation through a thick perennial ice cover

    NASA Technical Reports Server (NTRS)

    Squyres, S. W.; Andersen, D. W.; Nedell, S. S.; Wharton, R. A. Jr; Wharton RA, J. r. (Principal Investigator)

    1991-01-01

    Lake Hoare in the Dry Valleys of Antarctica is covered with a perennial ice cover more than 3 m thick, yet there is a complex record of sedimentation and of growth of microbial mats on the lake bottom. Rough topography on the ice covering the lake surface traps sand that is transported by the wind. In late summer, vertical conduits form by melting and fracturing, making the ice permeable to both liquid water and gases. Cross-sections of the ice cover show that sand is able to penetrate into and apparently through it by descending through these conduits. This is the primary sedimentation mechanism in the lake. Sediment traps retrieved from the lake bottom indicate that rates of deposition can vary by large amounts over lateral scales as small as 1 m. This conclusion is supported by cores taken in a 3 x 3 grid with a spacing of 1.5 m. Despite the close spacing of the cores, the poor stratigraphic correlation that is observed indicates substantial lateral variability in sedimentation rate. Apparently, sand descends into the lake from discrete, highly localized sources in the ice that may in some cases deposit a large amount of sand into the lake in a very short time. In some locations on the lake bottom, distinctive sand mounds have been formed by this process. They are primary sedimentary structures and appear unique to the perennially ice-covered lacustrine environment. In some locations they are tens of centimetres high and gently rounded with stable slopes; in others they reach approximately 1 m in height and have a conical shape with slopes at angle of repose. A simple formation model suggests that these differences can be explained by local variations in water depth and sedimentation rate. Rapid colonization of fresh sand surfaces by microbial mats composed of cyanobacteria, eukaryotic algae, and heterotrophic bacteria produces a complex intercalation of organic and sandy layers that are a distinctive form of modern stromatolites.

  13. Lake Hoare, Antarctica: sedimentation through a thick perennial ice cover.

    PubMed

    Squyres, S W; Andersen, D W; Nedell, S S; Wharton, R A

    1991-01-01

    Lake Hoare in the Dry Valleys of Antarctica is covered with a perennial ice cover more than 3 m thick, yet there is a complex record of sedimentation and of growth of microbial mats on the lake bottom. Rough topography on the ice covering the lake surface traps sand that is transported by the wind. In late summer, vertical conduits form by melting and fracturing, making the ice permeable to both liquid water and gases. Cross-sections of the ice cover show that sand is able to penetrate into and apparently through it by descending through these conduits. This is the primary sedimentation mechanism in the lake. Sediment traps retrieved from the lake bottom indicate that rates of deposition can vary by large amounts over lateral scales as small as 1 m. This conclusion is supported by cores taken in a 3 x 3 grid with a spacing of 1.5 m. Despite the close spacing of the cores, the poor stratigraphic correlation that is observed indicates substantial lateral variability in sedimentation rate. Apparently, sand descends into the lake from discrete, highly localized sources in the ice that may in some cases deposit a large amount of sand into the lake in a very short time. In some locations on the lake bottom, distinctive sand mounds have been formed by this process. They are primary sedimentary structures and appear unique to the perennially ice-covered lacustrine environment. In some locations they are tens of centimetres high and gently rounded with stable slopes; in others they reach approximately 1 m in height and have a conical shape with slopes at angle of repose. A simple formation model suggests that these differences can be explained by local variations in water depth and sedimentation rate. Rapid colonization of fresh sand surfaces by microbial mats composed of cyanobacteria, eukaryotic algae, and heterotrophic bacteria produces a complex intercalation of organic and sandy layers that are a distinctive form of modern stromatolites. PMID:11538650

  14. 27 m of lake ice on an Antarctic lake reveals past hydrologic variability

    NASA Astrophysics Data System (ADS)

    Dugan, H. A.; Doran, P. T.; Wagner, B.; Kenig, F.; Fritsen, C. H.; Arcone, S.; Kuhn, E.; Ostrom, N. E.; Warnock, J.; Murray, A. E.

    2014-07-01

    Lake Vida, located in Victoria Valley, is one of the largest lakes in the McMurdo Dry Valleys. Unlike other lakes in the region, the surface ice extends at least 27 m, which has created an extreme and unique habitat by isolating a liquid-brine with salinity of 195 g L-1. Below 21 m, the ice is marked by well-sorted sand layers up to 20 cm thick, within a matrix of salty ice. From ice chemistry, isotopic abundances of 18O and 2H, ground penetrating radar profiles, and mineralogy, we conclude that the entire 27 m of ice formed from surface runoff, and the sediment layers represent the accumulation of fluvial and aeolian deposits. Radiocarbon and optically stimulated luminescence dating limit the maximum age of the lower ice to 6300 14C yr BP. As the ice cover ablated downwards during periods of low surface inflow, progressive accumulation of sediment layers insulated and preserved the ice and brine beneath; analogous to the processes that preserve shallow ground ice. The repetition of these sediment layers reveals climatic variability in Victoria Valley during the mid- to late Holocene. Lake Vida is an excellent Mars analog for understanding the preservation of subsurface brine, ice and sediment in a cold desert environment.

  15. Geothermal disruption of ice at Mount Spurr Volcano, 2004 - 2006: An unusual manifestation of volcanic unrest in Alaska

    USGS Publications Warehouse

    Coombs, Michelle L.; Neal, Christina A.; Wessels, Rick L.; McGimsey, Robert G.

    2006-01-01

    Mount Spurr, a 3,374-m-high stratovolcano in the Cook Inlet region of Alaska, showed signs of volcanic unrest beginning in 2004 and lasting through 2006. These signs included increases in heat flow, seismicity, and gas flux, which we interpret as the results of a magmatic intrusion in mid-2004. In response, debris-laden meltwater beneath the glacier in Mount Spurr's geothermally active summit basin accumulated as the overlying snow and ice melted. As heat output increased, the icecap subsided into a growing cavity over a meltwater lake, similar to that observed during subglacial volcanic activity in Iceland. An ice plug collapsed into the lake sometime between June 20 and July 8, 2004, forming an ice cauldron that continued to grow in diameter during 2004 and 2005. A freefall of ice and snow into the lake likely caused a mixture of water and debris to be displaced rapidly upward and outward along preexisting englacial and, possibly, subglacial pathways leading away and downslope from the summit basin. Where these pathways intersected crevasses or other weak points in the sloping icefield, the mixture debouched onto the surface, producing dark, fluid debris flows. In summer 2004, the occurrence of two sets of debris flows separated in time by as long as a week suggests two pulses of summit ice collapse, each producing a surge of water and debris from the lake. A single debris flow was also emplaced on May 2, 2005. This event, which was captured by a Web camera, occurred simultaneously with a lake-level drop of ~15 m. To the east of the ice cauldron, a spillway that fed the debris flows has apparently maintained a relatively constant lake level for months at a time. Aerial photographs show that the spillway is in the direction of a breach in the summit crater. Melting of snow and ice at the summit has continued through 2006, with a total meltwater volume of ~5.4 million m3 as of March 2006.

  16. Patterns and trends in Southern Ontario lake ice phenology.

    PubMed

    Futter, Martyn N

    2003-01-01

    An analysis is presented of 46 ice break up and 15 ice free season phenology data series obtained largely through volunteer monitoring efforts in Southern Ontario. Observations spanned the years 1853-2001. Available data included dates of ice formation and ice break up as well as the number of ice free days in a year. A high degree of temporal coherence in ice phenology between lakes was observed (137/365 pairwise correlations significant at P < 0.05). Significant monotonic trends towards earlier break up dates and longer ice free seasons were observed across the region both in the entire series and in the last thirty years of data. Trends in longer series may be associated with the end of the Little Ice Age. The significantly longer ice free seasons and earlier ice break up dates observed in the study area have important implications for lakes in other parts of Canada where climate change effects are predicted to be more extreme than in South-Central Ontario.

  17. McCall Glacier record of Arctic climate change: Interpreting a northern Alaska ice core with regional water isotopes

    NASA Astrophysics Data System (ADS)

    Klein, E. S.; Nolan, M.; McConnell, J.; Sigl, M.; Cherry, J.; Young, J.; Welker, J. M.

    2016-01-01

    We explored modern precipitation and ice core isotope ratios to better understand both modern and paleo climate in the Arctic. Paleoclimate reconstructions require an understanding of how modern synoptic climate influences proxies used in those reconstructions, such as water isotopes. Therefore we measured periodic precipitation samples at Toolik Lake Field Station (Toolik) in the northern foothills of the Brooks Range in the Alaskan Arctic to determine δ18O and δ2H. We applied this multi-decadal local precipitation δ18O/temperature regression to ∼65 years of McCall Glacier (also in the Brooks Range) ice core isotope measurements and found an increase in reconstructed temperatures over the late-20th and early-21st centuries. We also show that the McCall Glacier δ18O isotope record is negatively correlated with the winter bidecadal North Pacific Index (NPI) climate oscillation. McCall Glacier deuterium excess (d-excess, δ2H - 8*δ18O) values display a bidecadal periodicity coherent with the NPI and suggest shifts from more southwestern Bering Sea moisture sources with less sea ice (lower d-excess values) to more northern Arctic Ocean moisture sources with more sea ice (higher d-excess values). Northern ice covered Arctic Ocean McCall Glacier moisture sources are associated with weak Aleutian Low (AL) circulation patterns and the southern moisture sources with strong AL patterns. Ice core d-excess values significantly decrease over the record, coincident with warmer temperatures and a significant reduction in Alaska sea ice concentration, which suggests that ice free northern ocean waters are increasingly serving as terrestrial precipitation moisture sources; a concept recently proposed by modeling studies and also present in Greenland ice core d-excess values during previous transitions to warm periods. This study also shows the efficacy and importance of using ice cores from Arctic valley glaciers in paleoclimate reconstructions.

  18. Arctic lake physical processes and regimes with implications for winter water availability and management in the National Petroleum Reserve Alaska.

    PubMed

    Jones, Benjamin M; Arp, Christopher D; Hinkel, Kenneth M; Beck, Richard A; Schmutz, Joel A; Winston, Barry

    2009-06-01

    Lakes are dominant landforms in the National Petroleum Reserve Alaska (NPRA) as well as important social and ecological resources. Of recent importance is the management of these freshwater ecosystems because lakes deeper than maximum ice thickness provide an important and often sole source of liquid water for aquatic biota, villages, and industry during winter. To better understand seasonal and annual hydrodynamics in the context of lake morphometry, we analyzed lakes in two adjacent areas where winter water use is expected to increase in the near future because of industrial expansion. Landsat Thematic Mapper and Enhanced Thematic Mapper Plus imagery acquired between 1985 and 2007 were analyzed and compared with climate data to understand interannual variability. Measured changes in lake area extent varied by 0.6% and were significantly correlated to total precipitation in the preceding 12 months (p < 0.05). Using this relation, the modeled lake area extent from 1985 to 2007 showed no long-term trends. In addition, high-resolution aerial photography, bathymetric surveys, water-level monitoring, and lake-ice thickness measurements and growth models were used to better understand seasonal hydrodynamics, surface area-to-volume relations, winter water availability, and more permanent changes related to geomorphic change. Together, these results describe how lakes vary seasonally and annually in two critical areas of the NPRA and provide simple models to help better predict variation in lake-water supply. Our findings suggest that both overestimation and underestimation of actual available winter water volume may occur regularly, and this understanding may help better inform management strategies as future resource use expands in the NPRA.

  19. Arctic lake physical processes and regimes with implications for winter water availability and management in the National Petroleum Reserve Alaska.

    PubMed

    Jones, Benjamin M; Arp, Christopher D; Hinkel, Kenneth M; Beck, Richard A; Schmutz, Joel A; Winston, Barry

    2009-06-01

    Lakes are dominant landforms in the National Petroleum Reserve Alaska (NPRA) as well as important social and ecological resources. Of recent importance is the management of these freshwater ecosystems because lakes deeper than maximum ice thickness provide an important and often sole source of liquid water for aquatic biota, villages, and industry during winter. To better understand seasonal and annual hydrodynamics in the context of lake morphometry, we analyzed lakes in two adjacent areas where winter water use is expected to increase in the near future because of industrial expansion. Landsat Thematic Mapper and Enhanced Thematic Mapper Plus imagery acquired between 1985 and 2007 were analyzed and compared with climate data to understand interannual variability. Measured changes in lake area extent varied by 0.6% and were significantly correlated to total precipitation in the preceding 12 months (p < 0.05). Using this relation, the modeled lake area extent from 1985 to 2007 showed no long-term trends. In addition, high-resolution aerial photography, bathymetric surveys, water-level monitoring, and lake-ice thickness measurements and growth models were used to better understand seasonal hydrodynamics, surface area-to-volume relations, winter water availability, and more permanent changes related to geomorphic change. Together, these results describe how lakes vary seasonally and annually in two critical areas of the NPRA and provide simple models to help better predict variation in lake-water supply. Our findings suggest that both overestimation and underestimation of actual available winter water volume may occur regularly, and this understanding may help better inform management strategies as future resource use expands in the NPRA. PMID:19101761

  20. Arctic lake physical processes and regimes with implications for winter water availability and management in the national petroleum reserve alaska

    USGS Publications Warehouse

    Jones, Benjamin M.; Arp, C.D.; Hinkel, Kenneth M.; Beck, R.A.; Schmutz, J.A.; Winston, B.

    2009-01-01

    Lakes are dominant landforms in the National Petroleum Reserve Alaska (NPRA) as well as important social and ecological resources. Of recent importance is the management of these freshwater ecosystems because lakes deeper than maximum ice thickness provide an important and often sole source of liquid water for aquatic biota, villages, and industry during winter. To better understand seasonal and annual hydrodynamics in the context of lake morphometry, we analyzed lakes in two adjacent areas where winter water use is expected to increase in the near future because of industrial expansion. Landsat Thematic Mapper and Enhanced Thematic Mapper Plus imagery acquired between 1985 and 2007 were analyzed and compared with climate data to understand interannual variability. Measured changes in lake area extent varied by 0.6% and were significantly correlated to total precipitation in the preceding 12 months (p < 0.05). Using this relation, the modeled lake area extent from 1985 to 2007 showed no long-term trends. In addition, high-resolution aerial photography, bathymetric surveys, water-level monitoring, and lake-ice thickness measurements and growth models were used to better understand seasonal hydrodynamics, surface area-to-volume relations, winter water availability, and more permanent changes related to geomorphic change. Together, these results describe how lakes vary seasonally and annually in two critical areas of the NPRA and provide simple models to help better predict variation in lake-water supply. Our findings suggest that both overestimation and underestimation of actual available winter water volume may occur regularly, and this understanding may help better inform management strategies as future resource use expands in the NPRA. ?? 2008 Springer Science+Business Media, LLC.

  1. Microwave properties of ice from The Great Lakes

    NASA Technical Reports Server (NTRS)

    Vickers, R. S.

    1975-01-01

    The increasing use of radar systems as remote sensors of ice thickness has revealed a lack of basic data on the microwave properties of fresh-water ice. A program, in which the complex dielectric constant was measured for a series of ice samples taken from the Great Lakes, is described. The measurements were taken at temperatures of -5, -10, and -15 C. It is noted that the ice has considerable internal layered structure, and the effects of the layering are examined. Values of 3.0 to 3.2 are reported for the real part of the dielectric constant, with an error bar of + or - 0.01.

  2. Source Characterization and Temporal Variation of Methane Seepage from Thermokarst Lakes on the Alaska North Slope in Response to Arctic Climate Change

    SciTech Connect

    None, None

    2012-09-30

    The goals of this research were to characterize the source, magnitude and temporal variability of methane seepage from thermokarst lakes (TKL) within the Alaska North Slope gas hydrate province, assess the vulnerability of these areas to ongoing and future arctic climate change and determine if gas hydrate dissociation resulting from permafrost melting is contributing to the current lake emissions. Analyses were focused on four main lake locations referred to in this report: Lake Qalluuraq (referred to as Lake Q) and Lake Teshekpuk (both on Alaska's North Slope) and Lake Killarney and Goldstream Bill Lake (both in Alaska's interior). From analyses of gases coming from lakes in Alaska, we showed that ecological seeps are common in Alaska and they account for a larger source of atmospheric methane today than geologic subcap seeps. Emissions from the geologic source could increase with potential implications for climate warming feedbacks. Our analyses of TKL sites showing gas ebullition were complemented with geophysical surveys, providing important insight about the distribution of shallow gas in the sediments and the lake bottom manifestation of seepage (e.g., pockmarks). In Lake Q, Chirp data were limited in their capacity to image deeper sediments and did not capture the thaw bulb. The failure to capture the thaw bulb at Lake Q may in part be related to the fact that the present day lake is a remnant of an older, larger, and now-partially drained lake. These suggestions are consistent with our analyses of a dated core of sediment from the lake that shows that a wetland has been present at the site of Lake Q since approximately 12,000 thousand years ago. Chemical analyses of the core indicate that the availability of methane at the site has changed during the past and is correlated with past environmental changes (i.e. temperature and hydrology) in the Arctic. Discovery of methane seeps in Lake Teshekpuk in the northernmost part of the lake during 2009

  3. Widespread Degradation of Ice Wedges on the Arctic Coastal Plain in Northern Alaska in Response to the Recent Warmer Climate

    NASA Astrophysics Data System (ADS)

    Shur, Y.; Jorgenson, M. T.; Pullman, E. R.

    2003-12-01

    The continuous permafrost on the Arctic Coastal Plain in northern Alaska has been considered stable because permafrost temperatures remain low, even with an increase of several degrees during the last decades. Ice wedges, however, are particularly susceptible to degradation because only a very thin layer of permafrost (the transient layer) exists between the ice and the bottom of the active layer. An increase in the active layer during unusually warm periods causes the thawing front to encounter the underlying ice wedges and initiate degradation. Field observations and photogrammetric analysis of 1945, 1979, and 2001 aerial photography indicate that there has been widespread degradation of the ice wedges on the Arctic Coastal Plain west of the Colville Delta over the recent 57-year period, and indications are that most of the degradation occurred during the last two decades. Field sampling at 46 polygonal troughs and their intersections showed that ice wedge degradation has been relatively recent as indicated by newly drowned vegetation. We found thermokarst was widespread on a variety of terrain conditions, but most prevalent on, ice-rich centers of old drained lake basins and alluvial-marine terraces, which have the greatest ice wedge development in the studied landscape. Ice wedges on these terrains typically occupy from 10 to 20 % of the upper permafrost. We attributed the natural degradation to warm weather during the last decades, because disturbance of the ground surface, which could have similar impact on ice wedges, was not evident. While, ice-wedge degradation probably has been periodically occurring at low rates over the preceding centuries, it has greatly accelerated during the last several decades. We identified six stages of ice-wedge degradation and stabilization. They include: (1) the loss of transient layer of upper permafrost above ice wedges, leading to enhanced nutrient availability and vegetative growth; (2) thawing of ice wedges and surface

  4. Spatio-temporal analysis of gyres in oriented lakes on the Arctic Coastal Plain of northern Alaska based on remotely sensed images

    USGS Publications Warehouse

    Zhan, Shengan; Beck, Richard A.; Hinkel, Kenneth M.; Liu, Hongxing; Jones, Benjamin M.

    2014-01-01

    The formation of oriented thermokarst lakes on the Arctic Coastal Plain of northern Alaska has been the subject of debate for more than half a century. The striking elongation of the lakes perpendicular to the prevailing wind direction has led to the development of a preferred wind-generated gyre hypothesis, while other hypotheses include a combination of sun angle, topographic aspect, and/or antecedent conditions. A spatio-temporal analysis of oriented thermokarst lake gyres with recent (Landsat 8) and historical (Landsat 4, 5, 7 and ASTER) satellite imagery of the Arctic Coastal Plain of northern Alaska indicates that wind-generated gyres are both frequent and regionally extensive. Gyres are most common in lakes located near the Arctic coast after several days of sustained winds from a single direction, typically the northeast, and decrease in number landward with decreasing wind energy. This analysis indicates that the conditions necessary for the Carson and Hussey (1962) wind-generated gyre for oriented thermokarst lake formation are common temporally and regionally and correspond spatially with the geographic distribution of oriented lakes on the Arctic Coastal Plain. Given an increase in the ice-free season for lakes as well as strengthening of the wind regime, the frequency and distribution of lake gyres may increase. This increase has implications for changes in northern high latitude aquatic ecosystems, particularly if wind-generated gyres promote permafrost degradation and thermokarst lake expansion.

  5. Late Holocene climate change at Goat Lake, Kenai Mountains, south-central Alaska

    NASA Astrophysics Data System (ADS)

    Daigle, T. A.; Kaufman, D. S.

    2006-12-01

    Lake sediments, glacier extents, and tree rings were used to reconstruct late Holocene climate changes from Goat Lake in the Kenai Mountains, south-central Alaska (60° 14' N/149° 54' W). Two sediment cores (3.7 and 5.6 m long) were dated with 16 AMS 14C ages and record changes in watershed (organic- matter content) and within-lake (biogenic silica) productivity since ~9500 cal yr BP. Sediment analyses focused on the last 1000 yr; this interval includes a sharp transition from gyttja to inorganic mud at ~1660 AD, which marks the fist time since Pleistocene deglaciation that the north goat outlet glacier (NGO) of the Harding Icefield overtopped the drainage divide at 590 m asl to spill meltwater into Goat Lake. One 14C age of ~1535 AD from a subfossil log in the NGO valley requires ~125 yr for the NGO to thicken 150 m to the elevation of the drainage divide where it remained until ~1930. Since ~1930, the NGO has thinned 150 m and retreated 1.4 km. Equilibrium-line altitudes (ELA) were reconstructed for 12 cirque glaciers nearby Goat Lake based on the accumulation-area ratio (AAR) method following field mapping of ice-marginal features formed during the maximum Little Ice Age (LIA) in the 19th century. Maximum LIA ELA data (AAR = 0.58) were compared with 1950 ELA and yield an average lowering of 50 ± 20 m. Application of the local lapse rate of 0.47°C/100 m indicates an average ablation-season temperature reduction of 0.3°C during the maximum LIA compared to 1950, assuming no change in winter precipitation. A new tree-ring chronology from 27 hemlock trees in the Goat Lake watershed correlates with mean March through August temperature from Kenai airport (r = 0.35) and a 207 yr reconstruction indicates an average temperature reduction of 1.0°C from 1800-1900 compared with 1930-1950. Assuming no change in winter precipitation, then a 1°C cooling should have been associated with an ELA lowering by 200 m. This did not occur, and we suggest that some degree of

  6. Large subglacial lakes in East Antarctica at the onset of fast-flowing ice streams.

    PubMed

    Bell, Robin E; Studinger, Michael; Shuman, Christopher A; Fahnestock, Mark A; Joughin, Ian

    2007-02-22

    Water plays a crucial role in ice-sheet stability and the onset of ice streams. Subglacial lake water moves between lakes and rapidly drains, causing catastrophic floods. The exact mechanisms by which subglacial lakes influence ice-sheet dynamics are unknown, however, and large subglacial lakes have not been closely associated with rapidly flowing ice streams. Here we use satellite imagery and ice-surface elevations to identify a region of subglacial lakes, similar in total area to Lake Vostok, at the onset region of the Recovery Glacier ice stream in East Antarctica and predicted by ice-sheet models. We define four lakes through extensive, flat, featureless regions of ice surface bounded by upstream troughs and downstream ridges. Using ice velocities determined using interferometric synthetic aperture radar (InSAR), we find the onset of rapid flow (moving at 20 to 30 m yr(-1)) of the tributaries to the Recovery Glacier ice stream in a 280-km-wide segment at the downslope margins of these four subglacial lakes. We conclude that the subglacial lakes initiate and maintain rapid ice flow through either active modification of the basal thermal regime of the ice sheet by lake accretion or through scouring bedrock channels in periodic drainage events. We suggest that the role of subglacial lakes needs to be considered in ice-sheet mass balance assessments. PMID:17314977

  7. Great Lakes all-weather ice information system

    NASA Technical Reports Server (NTRS)

    Schertler, R. J.; Mueller, R. A.; Jirberg, R. J.; Cooper, D. W.; Heighway, J. E.; Holmes, A. D.; Gedney, R. T.; Mark, H.

    1975-01-01

    A system is described which utilizes an X-band Side-Looking-Airborne-Radar (SLAR) for determining type, location, and aerial distribution of the ice cover in the Great Lakes and an airborne, S-band, short pulse radar for obtaining ice thickness. The SLAR system is currently mounted aboard a U.S. Coast Guard C-130B aircraft. Digitized SLAR data are relayed in real-time via the NOAA-GOES-1 satellite in geosynchronous orbit to the U.S. Coast Guard Ice Center in Cleveland, Ohio. SLAR images along with hand-drawn interpretative ice charts for various winter shipping areas in the Great Lakes are broadcast to facsimile recorders aboard Great Lakes vessels. The operational aspects of this ice information system are being demonstrated by NASA, U.S. Coast Guard, and NOAA/National Weather Service. Results from the 1974-75 winter season demonstrated the ability of this system to provide all-weather ice information to shippers in a timely manner.

  8. 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.

  9. Paleolimnology of Lake Tubutulik, an iron-meromictic Eocene Lake, eastern Seward Peninsula, Alaska

    NASA Astrophysics Data System (ADS)

    Dickinson, Kendell A.

    1988-01-01

    Sideritic lacustrine mudstone was found in drill core from a uranium deposit in the Death Valley area in the eastern part of the Seward Peninsula, Alaska. The precursor sediments for this rock were deposited in an unusual "iron-meromictic" Eocene lake, herein named Lake Tubutulik, which occupied part of the Boulder Creek basin, a structural graben that is probably a southern extension of the larger Death Valley basin. The Boulder Creek basin is bounded on the west by granite of the Late Cretaceous Darby Pluton, on the east by Precambrian to Paleozoic metasedimentary rocks. The lake basin was formed by basaltic flows that dammed the river valley of the ancestral Tubutulik River in early Eocene time. Lake Tubutulik contained a nearshore facies of fine-grained organic mud and an offshore facies of laminated sideritic mud. The offshore (profundal) laminated mudstone consists of alternating layers of authigenic siderite and detrital layers containing mostly quartz and clay minerals. Both lacustrine facies contain turbidities. The lacustrine sediments graded laterally into an onshore facies of colluvial and fluvial sandstone, paludal mudstone, and coal. The ancient lake apparently occupied a small deep basin in a tectonically active area of high relief. Meromixus was probably stabilized by reduced iron and bicarbonate dissolved in the monimolimnion. The intensity of meromixus decreased as the lake became shallower from sediment filling. The source of the iron, abundant in the monimolimnion of Lake Tubutulik, was probably the Eocene basalt. Based on carbon isotope analysis of the siderite, the dissolved bicarbonate in the profundal facies was largely inorganic. Sideritic carbon in one sample from the onshore paludal facies has an isotopic signature ( δ13C = +16.9) consistent with residual carbon formed during methanogenic fermentation.

  10. Paleolimnology of Lake Tubutulik, an iron-meromictic Eocene Lake, eastern Seward Peninsula, Alaska

    USGS Publications Warehouse

    Dickinson, K.A.

    1988-01-01

    Sideritic lacustrine mudstone was found in drill core from a uranium deposit in the Death Valley area in the eastern part of the Seward Peninsula, Alaska. The precursor sediments for this rock were deposited in an unusual "iron-meromictic" Eocene lake, herein named Lake Tubutulik, which occupied part of the Boulder Creek basin, a structural graben that is probably a southern extension of the larger Death Valley basin. The Boulder Creek basin is bounded on the west by granite of the Late Cretaceous Darby Pluton, on the east by Precambrian to Paleozoic metasedimentary rocks. The lake basin was formed by basaltic flows that dammed the river valley of the ancestral Tubutulik River in early Eocene time. Lake Tubutulik contained a nearshore facies of fine-grained organic mud and an offshore facies of laminated sideritic mud. The offshore (profundal) laminated mudstone consists of alternating layers of authigenic siderite and detrital layers containing mostly quartz and clay minerals. Both lacustrine facies contain turbidities. The lacustrine sediments graded laterally into an onshore facies of colluvial and fluvial sandstone, paludal mudstone, and coal. The ancient lake apparently occupied a small deep basin in a tectonically active area of high relief. Meromixus was probably stabilized by reduced iron and bicarbonate dissolved in the monimolimnion. The intensity of meromixus decreased as the lake became shallower from sediment filling. The source of the iron, abundant in the monimolimnion of Lake Tubutulik, was probably the Eocene basalt. Based on carbon isotope analysis of the siderite, the dissolved bicarbonate in the profundal facies was largely inorganic. Sideritic carbon in one sample from the onshore paludal facies has an isotopic signature (??13C = +16.9) consistent with residual carbon formed during methanogenic fermentation. ?? 1988.

  11. Interlaminated ice-proximal glacimarine sediments in Muir Inlet, Alaska

    USGS Publications Warehouse

    Mackiewicz, N.E.; Powell, R.D.; Carlson, P.R.; Molnia, B.F.

    1984-01-01

    Muir Inlet in Glacier Bay, Alaska, is a glacial fjord receiving a tremendous volume of sediment annually. The rate of sediment accumulation is greatest proximal to Muir Glacier (about 9 m yr-1) and decreases away from the glacier. The primary sediment sources are meltwater streams discharging at subglacial and ice-marginal positions to form overflows, interflows, and underflows (continuous turbidity currents). Overflows and interflows interact with diurnal tidal currents and their volume and sediment concentration varies diurnally and annually with meltwater discharge. These effects produce cyclic deposits of a thin fine-grained sand or silt lamina that grades normally to a thicker poorly to very poorly sorted mud lamina. This lamina couplet is termed a cyclopel. Underflows are suggested to occur in this glacimarine environment because of conditions unique to subglacial fluvial systems. Underflow deposits occur only in proximal positions (177 ??m) is ubiquitous, though low (<5% by weight), and occurs as isolated particles, frozen pellets, or as lenses that in cores may have a lamina appearance. Proximally, ice-rafted debris is difficult to identify because proximal sediment is often as coarse-grained. Deposited sediment may be reworked by tidal currents, and sediment gravity flows. Depositional processes operating in Muir Inlet produce interlaminated sand/silt/clay that characterizes sediment proximal to a glacier and fines seaward to mud. Sediment is classified into one of three sediment types: 1. (1) Type I sediment is very fine grained (mean 8.65-7.17 ??), low in sand (0.1-11.2%), and very poorly to poorly sorted. It is the dominant sediment type in Muir Inlet, and is transported by plumes and deposited by suspension settling. 2. (2) Type II sediment is fine- to coarse-grained (mean 6.70-3.12 ??), low to high in sand (5.1-86.6%), and very poorly to moderately sorted. It represents reworked sediment, proximal plume deposits, or coarse-grained laminae of cyclopels

  12. Oxygen budget of a perennially ice-covered Antarctic lake

    NASA Technical Reports Server (NTRS)

    Wharton, R. A., Jr.; Mckay, C. P.; Simmons, G. M., Jr.; Parker, B. C.

    1986-01-01

    A bulk O2 budget for Lake Hoare, Antarctica, is presented. Five years of seasonal data show the lake to be persistently supersaturated with O2. Oxygen is carried into the lake in glacial meltstreams and is left behind when this water is removed as ice by ablation and sublimation. A diffusive loss of O2 from the lake through the summer moat is suggested. Measured values of the total O2 in the water column indicate that the time scale of O2 turnover is much longer than a year. Based on these results, it is suggested that the amount of O2 in the water does not change significantly throughout the year and that the lake is also supersaturated with N2.

  13. Lake Clark fault, assessment of tectonic activity based on reconnaissance mapping of glacial deposits, northwestern Cook Inlet Alaska

    NASA Astrophysics Data System (ADS)

    Reger, R. D.; Koehler, R. D.

    2009-12-01

    The Lake Clark fault extends ~247 km from the vicinity of Lake Clark in the Alaska-Aleutian Range batholith northeastward to the Castle Mountain fault along the northern margin of Cook Inlet. Documented Tertiary deformation along the fault includes dextral offsets (5-26 km) and north-side-up reverse displacements (500-1,000 m). The fault is along strike with the Holocene-active Castle Mountain fault and adjacent to the active northern Cook Inlet fold belt. As part of the STATEMAP program, the State of Alaska has begun a 2-year geologic mapping project in the vicinity of the Lake Clark fault, including assessment of Quaternary fault activity and its role in accommodating deformation in the Aleutian forearc. Here we present preliminary Quaternary mapping and tectonic geomorphic observations aimed at assessing the fault activity. Between the Beluga and Chakachatna rivers, large lateral moraines of the late Wisconsinan Naptowne glaciation cross the fault and are not displaced. In the vicinity of Lone Ridge, the fault is expressed as a ~25-m southeast-facing scarp in bedrock associated with springs and vertically offset Stage 4 or 6 moraines. In the Chuitna River drainage basin beyond the Naptowne ice limit, the fault extends across a fairly flat plateau with drumlins and ice-stagnation deposits related to Stage 4 or 6 glaciation. There the fault is expressed by subtle vegetation and tonal lineaments on air photos; however, scarps and lateral offsets were not observed. Stream profiles perpendicular to the fault along the Chuitna River and Chuitna Creek have convex profiles that could be related to tectonic folding. Our observations indicate that this part of the Lake Clark fault may be Quaternary active, but has been relatively quiescent in the late Pleistocene. Thus, blind thrust faults associated with the northern Cook Inlet fold belt may accommodate the majority of the tectonic deformation in this part of the Aleutian forearc. This information is applicable to

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

    NASA Technical Reports Server (NTRS)

    Ormsby, James P.; Hall, Dorothy D.

    1991-01-01

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

  15. Monitoring Sea Ice Conditions and Use in Arctic Alaska to Enhance Community Adaptation to Change

    NASA Astrophysics Data System (ADS)

    Druckenmiller, M. L.; Eicken, H.

    2010-12-01

    Sea ice changes in the coastal zone, while less conspicuous in relation to the dramatic thinning and retreat of perennial Arctic sea ice, can be more readily linked to local impacts. Shorefast ice is a unique area for interdisciplinary research aimed at improving community adaptation to climate through local-scale environmental observations. Here, geophysical monitoring, local Iñupiat knowledge, and the documented use of ice by the Native hunting community of Barrow, Alaska are combined to relate coastal ice processes and morphologies in the Chukchi Sea to ice stability and community adaption strategies for travel, hunting, and risk assessment. A multi-year effort to map and survey the community’s seasonal ice trails, alongside a detailed record of shorefast ice conditions, provides insight into how hunters evaluate the evolution of ice throughout winter and spring. Various data sets are integrated to relate the annual accretion history of the local ice cover to both measurements of ice thickness and topography and hunter observations of ice types and hazards. By relating changes in the timing of shorefast ice stabilization, offshore ice conditions, and winter wind patterns to ice characteristics in locations where spring bowhead whaling occurs, we are working toward an integrated scientific product compatible with the perspective of local ice experts. A baseline for assessing future change and community climate-related vulnerabilities may not be characterized by single variables, such as ice thickness, but rather by how changes in observable variables manifest in impacts to human activities. This research matches geophysical data to ice-use to establish such a baseline. Documenting human-environment interactions will allow future monitoring to illustrate how strategies for continued community ice-use are indicative of or responsive to change, and potentially capable of incorporating science products as additional sources of useable information.

  16. Heat flux at the base of lake ice cover estimated from fine structure of the ice-water boundary layer

    NASA Astrophysics Data System (ADS)

    Kirillin, Georgiy; Aslamov, Ilya; Kozlov, Vladimir; Granin, Nikolay; Engelhardt, Christof; Förster, Josephine

    2016-04-01

    Seasonal lake ice is a highly changeable part of the cryosphere undergoing remarkable impact by global warming. Vertical heat transport across the boundary layer under ice affects strongly the growth and melting of lake ice cover. The existing models of ice cover dynamics focus basically on the dependence of the ice thickness on the air temperature with implicit account of the snow cover effects. The heat flux at the water-ice boundary, in turn, is usually neglected or parameterized in a very simplistic form. However, neglecting of the basal ice melting due to heat flux at the ice-water interface produces appreciable errors in the modeled ice cover duration. We utilize fine-structure observations taken during 2009-2015 in ice-water boundary layers of Lake Baikal and arctic Lake Kilpisjärvi to reveal the major physical drivers of the heat exchange at the ice bottom and to explain the high geographical, spatial, and temporal variability in the heat flux magnitudes. The methods provide first detailed estimations of the heat exchange beneath the ice cover, available previously only from bulk estimations. The fluxes in Lake Baikal have magnitudes of 101 W m-2 and vary strongly between different parts of the lake being influenced by large-scale horizontal circulation with current velocities amounting at up to 7 cm s-1. The shallow lake fluxes, while an order of magnitude weaker, are highly non-stationary, being affected by the turbulence due to oscillating currents under ice. Our results demonstrate the role played by the boundary layer mixing in the ice growth and melting, as well as characterize the physical processes responsible for the vertical heat exchange and provide a basis for an improved parameterization of ice cover in coupled lake-atmosphere models.

  17. GIS-modeling of an ice-dammed lake in the Lake Onega depression ca 14500-12500 Yrs BP

    NASA Astrophysics Data System (ADS)

    Subetto, Dmitry; Zobkov, Mikhail; Potakhin, Maksim; Tarasov, Aleksey

    2016-04-01

    Palaeogeographical reconstructions of the Onego ice-dammed lake development ca 14500-125000 yrs BP were based on the GIS approach. The palaeo-water-level surfaces were interpolated using a point-kriging approach. 14500-14000 Yrs BP: An ice-dammed lake occupied the southern part of the Lake Onega depression. The level of this lake was at 130-120 m a.s.l. and was controlled by a threshold of the water divide between the River Oshta and River Oyat', with discharge southwestward into the Oyat' basin. The surface area of the ice-dammed lake was 3500 sq.km. 14000-13300 Yrs BP: When the ice melted away from the mouth of the River Svir, the lake level dropped to 85-80 m a.s.l. and runoff was directed into the Lake Ladoga - easternmost part of The Baltic Ice Lake at that time. 13300-12500 Yrs BP: As the glacier retreated from the Lake Onega depression, the ice-dammed lake was occupied it and reached the maximum sizes (the surface area was 33000 sq.km). The new threshold in the northern part was opened and runoff was directed into the White Sea basin. During the conference new digital paleogeographical maps of the Onego ice-dammed lake will be presented. The study has been financially supported by the Russian Science Foundation (#14-17-00766).

  18. Antarctic lakes (above and beneath the ice sheet): Analogues for Mars

    NASA Technical Reports Server (NTRS)

    Rice, J. W., Jr.

    1992-01-01

    The perennial ice covered lakes of the Antarctic are considered to be excellent analogues to lakes that once existed on Mars. Field studies of ice covered lakes, paleolakes, and polar beaches were conducted in the Bunger Hills Oasis, Eastern Antarctica. These studies are extended to the Dry Valleys, Western Antarctica, and the Arctic. Important distinctions were made between ice covered and non-ice covered bodies of water in terms of the geomorphic signatures produced. The most notable landforms produced by ice covered lakes are ice shoved ridges. These features form discrete segmented ramparts of boulders and sediments pushed up along the shores of lakes and/or seas. Sub-ice lakes have been discovered under the Antarctic ice sheet using radio echo sounding. These lakes occur in regions of low surface slope, low surface accumulations, and low ice velocity, and occupy bedrock hollows. The presence of sub-ice lakes below the Martian polar caps is possible. The discovery of the Antarctic sub-ice lakes raises possibilities concerning Martian lakes and exobiology.

  19. Declining Sea Ice Extent Links Early Winter Climate to Changing Arctic Lakes

    NASA Astrophysics Data System (ADS)

    Alexeev, V. A.; Arp, C. D.; Jones, B. M.; Cai, L.

    2015-12-01

    Lakes on the Alaskan North Slope regulate surface energy balance and interactions with permafrost as well as providing important habitat. Winter lake ice regimes (floating-ice or bedfast-ice conditions) determine whether lakes develop and maintain taliks and can support overwintering fish habitat. Lake ice thickness is a key variable determining whether a lake has a bedfast or floating-ice regime. Recent observations suggest a trend towards more lakes with floating-ice conditions due to thinner ice growth, but the broader scale associated climate conditions driving these regime shift are less certain. This study finds that the changing arctic summer/fall sea ice conditions might be affecting lake ice thickness on the North Slope. Late ocean freeze-up near the Alaskan coast leads to warmer weather and more snowfall in the early winter. Warmer early winters and thicker snowpack result in thinner lake ice the following winter thus potentially developing more ice-floating lakes before the start of the summer. Experiments with a regional atmospheric model WRF for two years with very different sea ice conditions indicate that the extent of open water next to the North Slope is a crucial factor for developing thicker snowpack, also warmer air temperature in early winter.

  20. Ice on rivers and lakes : a bibliographic essay

    USGS Publications Warehouse

    Ficke, Eleanore R.; Ficke, John F.

    1977-01-01

    Ice on rivers and lakes influences design and construction of structures, operation of shipping, flow and circulation, water quality, and other factors related to the use of water. Interest in understanding these influences has led to many programs of data collection, research, and investigations for a century or more. The body of literature reporting on these studies includes several thousand items in textbooks, proceedings, journals, and technical reports. By far, the largest portion of the studies were in the United States, Canada, or the Soviet Union. The literature can be classified as dealing with basic characteristics of ice; freezing and melting processes and their prediction and control on rivers, and on lakes; effects of river and lake ice on navigation, flow, and structures; and influences of ice on chemical, biological, and thermal aspects of water quality. This bibliography cites 750 publications, but the body of literature is large and this bibliography is not exhaustive. It does provide, however, a cross section of the scope of work in the field. (Woodard-USGS)

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

    SciTech Connect

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

    1992-03-01

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

  2. CARBON TRACE GASES IN LAKE AND BEAVER POND ICE NEAR THOMPSON, MANITOBA, CANADA

    EPA Science Inventory

    Concentrations of CO2, CO, and CH4 were measured in beaver pond and lake ice in April 1996 near Thompson, Manitoba to derive information on possible impacts of ice melting on corresponding atmospheric trace gas concentrations. CH4 concentrations in beaver pond and lake ice ranged...

  3. Mining cosmic dust from the blue ice lakes of Greenland

    NASA Technical Reports Server (NTRS)

    Maurette, M.; Brownlee, D. E.; Fehrenback, L.; Hammer, C.; Jehano, C.; Thomsen, H. H.

    1985-01-01

    Extraterrestrial material, most of which invisible settles to Earth's surface as dust particles smaller than a millimeter in size were investigated. Particles of 1/10 millimeter size fall at a rate of one/sq m/yr collection of extraterrestrial dust is important because the recovered cosmic dust particles can provide important information about comets. Comets are the most important source of dust in the solar system and they are probably the major source of extraterrestrial dust that is collectable at the Earth's surface. A new collection site for cosmic dust, in an environment where degradation by weathering is minimal is reported. It is found that the blue ice lakes on the Greenland ice cap provide an ideal location for collection of extraterrestrial dust particles larger than 0.1 mm in size. It is found that the lakes contain large amounts of cosmic dust which is much better preserved than similar particles recovered from the ocean floor.

  4. Decadally resolved quantitative temperature reconstruction spanning 5.6 ka at Kurupa Lake, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Boldt, B. R.; Kaufman, D. S.; Briner, J. P.

    2012-12-01

    Pre-instrumental quantitative temperature records, fundamental for placing recent warming in the context of long-term, natural climate variability, are scarce in Arctic Alaska. New non-destructive high-resolution core scanning methods provide a means of constructing downcore inference models for various paleoclimate signals. Here we use visible reflectance spectroscopy (VIS-RS) to measure organic pigment (chlorophyll derivative) concentration in sediments from Kurupa Lake to quantitatively reconstruct air temperature in the north-central Brooks Range, Alaska during the past 5.6 ka. Kurupa Lake (N 68.35°, W -154.61°) is 29.7 km2, 40 m at maximum depth, and is fed by several tributaries, including meltwater from eight rapidly disappearing cirque glaciers. A 6.2-m-long core composed of finely laminated (sub-mm to 5 cm) coarse-grained clays to medium-grained silts was collected in 2010 from the primary depocenter of Kurupa Lake (depth = 34 m). The age model for the core is based on six radiocarbon ages and a Pu profile to capture the 1963 spike and 1953 onset of Pu deposition from atmospheric weapons testing. The split-core face was scanned with a Konica Minolta CM-2600d spectrometer at 2 mm intervals, corresponding to 1-2 years. The relative absorption band depth at 660-670 nm (RABD660-670) was used to quantify total sedimentary organic pigments (primarily diagenetic products of chlorophyll-a) as a proxy for primary productivity. Gridded temperature data from the NCEP reanalysis dataset were used for this study because regional weather stations in the Brooks Range are scarce and records discontinuous. The gridded data perform well in this area and are highly correlated (r = 0.88) with the instrumental record from Barrow. Mean May-through-October (warm half-year) temperature (5-year smoothed) from NCEP reanalysis data (130 years) correlates with inferred organic pigment content from Kurupa Lake (r = 0.76, p < 0.001). We chose k-fold cross-validation (k = 10) to

  5. Remote sensing of frozen lakes on the North Slope of Alaska

    USGS Publications Warehouse

    French, N.; Savage, S.; Shuchman, R.; Edson, R.; Payne, J.; Josberger, E.

    2004-01-01

    We used synthetic aperture radar (SAR) images from the ERS-2 remote sensing satellite to map the freeze condition of lakes on Alaska's North Slope, the geographic region to the north of the Brooks Range. An mage from March 1997, to coincide with the period of maximum freeze depth, was used for the frozen lake mapping. Emphasis was placed on distinguishing between lakes frozen to the lakebed and lakes with some portion unfrozen to the bed (a binary classification). The result of the analysis is a map identifying lakes as frozen to the lakebed and lakes not frozen to the lakebed. This analysis of one SAR image has shown the feasibility of a simple technique for mapping frozen lake condition for supporting decision making and understanding impacts of climate change on the North Slope.

  6. Ice cover, landscape setting, and geological framework of Lake Vostok, East Antarctica

    USGS Publications Warehouse

    Studinger, M.; Bell, R.E.; Karner, G.D.; Tikku, A.A.; Holt, J.W.; Morse, D.L.; David, L.; Richter, T.G.; Kempf, S.D.; Peters, M.E.; Blankenship, D.D.; Sweeney, R.E.; Rystrom, V.L.

    2003-01-01

    Lake Vostok, located beneath more than 4 km of ice in the middle of East Antarctica, is a unique subglacial habitat and may contain microorganisms with distinct adaptations to such an extreme environment. Melting and freezing at the base of the ice sheet, which slowly flows across the lake, controls the flux of water, biota and sediment particles through the lake. The influx of thermal energy, however, is limited to contributions from below. Thus the geological origin of Lake Vostok is a critical boundary condition for the subglacial ecosystem. We present the first comprehensive maps of ice surface, ice thickness and subglacial topography around Lake Vostok. The ice flow across the lake and the landscape setting are closely linked to the geological origin of Lake Vostok. Our data show that Lake Vostok is located along a major geological boundary. Magnetic and gravity data are distinct east and west of the lake, as is the roughness of the subglacial topography. The physiographic setting of the lake has important consequences for the ice flow and thus the melting and freezing pattern and the lake's circulation. Lake Vostok is a tectonically controlled subglacial lake. The tectonic processes provided the space for a unique habitat and recent minor tectonic activity could have the potential to introduce small, but significant amounts of thermal energy into the lake. ?? 2002 Elsevier Science B.V. All rights reserved.

  7. 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.

  8. Ice-cover variability on shallow lakes at high latitudes: model simulations and observations

    NASA Astrophysics Data System (ADS)

    Duguay, Claude R.; Flato, Greg M.; Jeffries, Martin O.; Ménard, Patrick; Morris, Kim; Rouse, Wayne R.

    2003-12-01

    A one-dimensional thermodynamic model for simulating lake-ice phenology is presented and evaluated. The model can be driven with observed daily or hourly atmospheric forcing of air temperature, relative humidity, wind speed, cloud amount and snowfall. In addition to computing the energy balance components, key model output includes the temperature profile at an arbitrary number of levels within the ice/snow (or the water temperature if there is no ice) and ice thickness (clear ice and snow-ice) on a daily basis, as well as freeze-up and break-up dates. The lake-ice model is used to simulate ice-growth processes on shallow lakes in arctic, sub-arctic, and high-boreal forest environments. Model output is compared with field and remote sensing observations gathered over several ice seasons. Simulated ice thickness, including snow-ice formation, compares favourably with field measurements. Ice-on and ice-off dates are also well simulated when compared with field and satellite observations, with a mean absolute difference of 2 days. Model simulations and observations illustrate the key role that snow cover plays on the seasonal evolution of ice thickness and the timing of spring break-up. It is also shown that lake morphometry, depth in particular, is a determinant of ice-off dates for shallow lakes at high latitudes. Copyright

  9. Ice patterns and hydrothermal plumes, Lake Baikal, Russia - Insights from Space Shuttle hand-held photography

    NASA Technical Reports Server (NTRS)

    Evans, Cynthia A.; Helfert, Michael R.; Helms, David R.

    1992-01-01

    Earth photography from the Space Shuttle is used to examine the ice cover on Lake Baikal and correlate the patterns of weakened and melting ice with known hydrothermal areas in the Siberian lake. Particular zones of melted and broken ice may be surface expressions of elevated heat flow in Lake Baikal. The possibility is explored that hydrothermal vents can introduce local convective upwelling and disrupt a stable water column to the extent that the melt zones which are observed in the lake's ice cover are produced. A heat flow map and photographs of the lake are overlaid to compare specific areas of thinned or broken ice with the hot spots. The regions of known hydrothermal activity and high heat flow correlate extremely well with circular regions of thinned ice, and zones of broken and recrystallized ice. Local and regional climate data and other sources of warm water, such as river inlets, are considered.

  10. LANDSAT survey of near-shore ice conditions along the Arctic coast of Alaska

    NASA Technical Reports Server (NTRS)

    Stringer, W. J. (Principal Investigator)

    1975-01-01

    The author has identified the following significant results. On the basis of analysis of late winter 1973, 1974, and 1975 LANDSAT imagery of the Beaufort Sea coast of Alaska, the following conclusions regarding near-shore ice conditions were made: (1) by March, the seaward limit of contiguous ice is often beyond the 10 fathom contour. (2) During March, shearing can and does take place along a line roughly coincident with the 10 fathom contour. (3) Ice motions during these shearing events are not extremely great, generally on the order of 10 km. (4) Many large ice features have already been formed by late February. (5) Based on look-ahead at later LANDSAT imagery, it seems apparent that Beaufort Seas shore-fast ice was already formed by late February and may well be safe for exploratory activities from this data forward until the melt season.

  11. Collaborative Research: Climate Sensitivity of Thaw Lake Systems on the Alaska North Slope

    NASA Technical Reports Server (NTRS)

    Zhang, Tingjun; Jeffries, Martin O.

    2001-01-01

    There are thousands of thaw (thermokarst) lakes on the North Slope of Alaska, where they cover as much as 40% of the land area. Their very name recognizes the fact that they owe their origin to the impact they have on the ground thermal regime, but there have been few quantitative studies of the impact of the lakes on atmosphere-land interactions in this tundra region.

  12. 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.

  13. Perennially ice-covered Lake Hoare, Antarctica: physical environment, biology and sedimentation

    NASA Technical Reports Server (NTRS)

    Wharton, R. A. Jr; Simmons, G. M. Jr; McKay, C. P.; Wharton RA, J. r. (Principal Investigator)

    1989-01-01

    Lake Hoare (77 degrees 38' S, 162 degrees 53' E) is a perennially ice-covered lake at the eastern end of Taylor Valley in southern Victoria Land, Antarctica. The environment of this lake is controlled by the relatively thick ice cover (3-5 m) which eliminates wind generated currents, restricts gas exchange and sediment deposition, and reduces light penetration. The ice cover is in turn largely controlled by the extreme seasonality of Antarctica and local climate. Lake Hoare and other dry valley lakes may be sensitive indicators of short term (< 100 yr) climatic and/or anthropogenic changes in the dry valleys since the onset of intensive exploration over 30 years ago. The time constants for turnover of the water column and lake ice are 50 and 10 years, respectively. The turnover time for atmospheric gases in the lake is 30-60 years. Therefore, the lake environment responds to changes on a 10-100 year timescale. Because the ice cover has a controlling influence on the lake (e.g. light penetration, gas content of water, and sediment deposition), it is probable that small changes in ice ablation, sediment loading on the ice cover, or glacial meltwater (or groundwater) inflow will affect ice cover dynamics and will have a major impact on the lake environment and biota.

  14. Arctic continental shelf morphology related to sea-ice zonation, Beaufort Sea, Alaska

    USGS Publications Warehouse

    Reimnitz, E.; Toimil, L.; Barnes, P.

    1978-01-01

    Landsat-1 and NOAA satellite imagery for the winter 1972-1973, and a variety of ice and sea-floor data were used to study sea-ice zonation and dynamics and their relation to bottom morphology and geology on the Beaufort Sea continental shelf of arctic Alaska. In early winter the location of the boundary between undeformed fast ice and westward-drifting pack ice of the Pacific Gyre is controlled by major coastal promontories. Pronounced linear pressure- and shear-ridges, as well as hummock fields, form along this boundary and are stabilized by grounding, generally between the 10- and 20-m isobaths. Slippage along this boundary occurs intermittently at or seaward of the grounded ridges, forming new grounded ridges in a widening zone, the stamukhi zone, which by late winter extends out to the 40-m isobath. Between intermittent events along the stamukhi zone, pack-ice drift and slippage is continuous along the shelf edge, at average rates of 3-10 km/day. Whether slippage occurs along the stamukhi zone or along the shelf edge, it is restricted to a zone several hundred meters wide, and ice seaward of the slip face moves at uniform rates without discernible drag effects. A causal relationship is seen between the spatial distribution of major ice-ridge systems and offshore shoals downdrift of major coastal promontories. The shoals appear to have migrated shoreward under the influence of ice up to 400 m in the last 25 years. The sea floor seaward of these shoals within the stamukhi zone shows high ice-gouge density, large incision depths, and a high degree of disruption of internal sedimentary structures. The concentration of large ice ridges and our sea floor data in the stamukhi zone indicate that much of the available marine energy is expended here, while the inner shelf and coast, where the relatively undeformed fast ice grows, are sheltered. There is evidence that anomalies in the overall arctic shelf profile are related to sea-ice zonation, ice dynamics, and bottom

  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. Alaska index; streamflow, lake levels, and water-quality records to September 30, 1988

    USGS Publications Warehouse

    Still, Patsy J.; Cosby, Jennie M.

    1989-01-01

    Streamflow, lake levels, and water quality data are compiled for stations in the southeast, south-central, southwest, Yukon basin , northwest, and Arctic Slope subregions of Alaska. The report includes a map of each hydrologic subregion and tables listing types of data collected and periods of records. (USGS)

  17. The influence of a model subglacial lake on ice dynamics and internal layering

    NASA Astrophysics Data System (ADS)

    Gudlaugsson, Eythor; Humbert, Angelika; Kleiner, Thomas; Kohler, Jack; Andreassen, Karin

    2016-04-01

    As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocities and a draw down of isochrones and cold ice. The ice surface flattens as it adjusts to the lack of resisting forces at the base. The rapid transition in velocity induces changes in ice viscosity and releases deformation energy that can raise the temperature locally. Recent studies of Antarctic subglacial lakes indicate that many lakes experience very fast and possibly episodic drainage, during which the lake size is rapidly reduced as water flows out. Questions that arise are what effect this would have on internal layers within the ice and whether such past drainage events could be inferred from isochrone structures downstream. Here, we study the effect of a subglacial lake on ice dynamics as well as the influence that such short timescale drainage would have on the internal layers of the ice. To this end, we use a full Stokes, polythermal ice flow model. An enthalpy-gradient method is used to account for the evolution of temperature and water content within the ice. We find that a rapid transition between slow-moving ice outside the lake, and full sliding over the lake, can release considerable amounts of deformational energy, with the potential to form a temperate layer at depth in the transition zone. In addition, we provide an explanation for a characteristic surface feature commonly seen at the edges of subglacial lakes, a hummocky surface depression in the transition zone between little to full sliding. We also conclude that rapid changes in the horizontal extent of subglacial lakes and slippery patches, compared to the average ice column velocity, can create a traveling wave at depth within the isochrone structure that transfers downstream with the advection of ice, thus indicating the possibility of detecting past drainage events with ice penetrating radar.

  18. Methane sources in arctic thermokarst lake sediments on the North Slope of Alaska.

    PubMed

    Matheus Carnevali, P B; Rohrssen, M; Williams, M R; Michaud, A B; Adams, H; Berisford, D; Love, G D; Priscu, J C; Rassuchine, O; Hand, K P; Murray, A E

    2015-03-01

    The permafrost on the North Slope of Alaska is densely populated by shallow lakes that result from thermokarst erosion. These lakes release methane (CH4 ) derived from a combination of ancient thermogenic pools and contemporary biogenic production. Despite the potential importance of CH4 as a greenhouse gas, the contribution of biogenic CH4 production in arctic thermokarst lakes in Alaska is not currently well understood. To further advance our knowledge of CH4 dynamics in these lakes, we focused our study on (i) the potential for microbial CH4 production in lake sediments, (ii) the role of sediment geochemistry in controlling biogenic CH4 production, and (iii) the temperature dependence of this process. Sediment cores were collected from one site in Siqlukaq Lake and two sites in Sukok Lake in late October to early November. Analyses of pore water geochemistry, sedimentary organic matter and lipid biomarkers, stable carbon isotopes, results from CH4 production experiments, and copy number of a methanogenic pathway-specific gene (mcrA) indicated the existence of different sources of CH4 in each of the lakes chosen for the study. Analysis of this integrated data set revealed that there is biological CH4 production in Siqlukaq at moderate levels, while the very low levels of CH4 detected in Sukok had a mixed origin, with little to no biological CH4 production. Furthermore, methanogenic archaea exhibited temperature-dependent use of in situ substrates for methanogenesis, and the amount of CH4 produced was directly related to the amount of labile organic matter in the sediments. This study constitutes an important first step in better understanding the actual contribution of biogenic CH4 from thermokarst lakes on the coastal plain of Alaska to the current CH4 budgets. PMID:25612141

  19. Climatic changes near the Great Lakes inferred from 141 year ice records

    USGS Publications Warehouse

    Assel, Raymond A.; Robertson, Dale M.

    1992-01-01

    Freeze-up and break-up dates and duration of ice cover for lakes and rivers represent an integration of weather conditions prior to the specified event(s). Changes in mean ice conditions may be used as quantitative indicators of climatic changes if long homogenous ice records are accompanied by sufficiently homogenous air temperature records to calibrate the changes in mean ice cover in terms of climatic variables. Historical ice records dating back to 1855 are available for Lake Mendota, WI (located on the southwestern side of Lake Michigan) and back to 1851 for Grand Traverse Bay, MI (located on the northeastern side of Lake Michigan). Changes in the mean ice cover of these two systems were used to describe changes in fall, winter, and spring air temperatures in the area near the Great Lakes during the past 141 years. 

  20. Ice mass loss in Greenland, the Gulf of Alaska, and the Canadian Archipelago: Seasonal cycles and decadal trends

    NASA Astrophysics Data System (ADS)

    Harig, Christopher; Simons, Frederik J.

    2016-04-01

    Over the past several decades mountain glaciers and ice caps have been significant contributors to sea level rise. Here we estimate the ice mass changes in the Canadian Archipelago, the Gulf of Alaska, and Greenland since 2003 by analyzing time-varying gravimetry data from the Gravity Recovery and Climate Experiment. Prior to 2013, interannual ice mass variability in the Gulf of Alaska and in regions around Greenland remains within the average estimated over the whole data span. Beginning in summer 2013, ice mass in regions around Greenland departs positively from its long-term trend. Over Greenland this anomaly reached almost 500 Gt through the end of 2014. Overall, long-term ice mass loss from Greenland and the Canadian Archipelago continues to accelerate, while losses around the Gulf of Alaska region continue but remain steady with no significant acceleration.

  1. Potential subglacial lake locations and meltwater drainage pathways beneath the Antarctic and Greenland ice sheets

    NASA Astrophysics Data System (ADS)

    Livingstone, S. J.; Clark, C. D.; Woodward, J.; Kingslake, J.

    2013-11-01

    We use the Shreve hydraulic potential equation as a simplified approach to investigate potential subglacial lake locations and meltwater drainage pathways beneath the Antarctic and Greenland ice sheets. We validate the method by demonstrating its ability to recall the locations of >60% of the known subglacial lakes beneath the Antarctic Ice Sheet. This is despite uncertainty in the ice-sheet bed elevation and our simplified modelling approach. However, we predict many more lakes than are observed. Hence we suggest that thousands of subglacial lakes remain to be found. Applying our technique to the Greenland Ice Sheet, where very few subglacial lakes have so far been observed, recalls 1607 potential lake locations, covering 1.2% of the bed. Our results will therefore provide suitable targets for geophysical surveys aimed at identifying lakes beneath Greenland. We also apply the technique to modelled past ice-sheet configurations and find that during deglaciation both ice sheets likely had more subglacial lakes at their beds. These lakes, inherited from past ice-sheet configurations, would not form under current surface conditions, but are able to persist, suggesting a retreating ice-sheet will have many more subglacial lakes than advancing ones. We also investigate subglacial drainage pathways of the present-day and former Greenland and Antarctic ice sheets. Key sectors of the ice sheets, such as the Siple Coast (Antarctica) and NE Greenland Ice Stream system, are suggested to have been susceptible to subglacial drainage switching. We discuss how our results impact our understanding of meltwater drainage, basal lubrication and ice-stream formation.

  2. Seasonal Dynamics of a Drained Thermokarst Lake Basin on the North Slope of Alaska From InSAR

    NASA Astrophysics Data System (ADS)

    Zhang, T.; Liu, L.; Schaefer, K. M.; Parsekian, A.; Grosse, G.; Jones, B. M.; Zebker, H. A.

    2012-12-01

    Thermokarst lakes (or thaw lakes) are ubiquitous and dynamic landscape features on the Arctic coastal plain of Alaska. They form as ice-rich permafrost thaws and grow laterally and vertically, coalesce with other lakes, and often rapidly drain, forming a dry and depressed basin denoted as drained thermokarst lake basins (DTLBs). Vertical deformation of the ground from settlement and heave occurs during thermokarst evolution. These morphological variations are a result of changes in the thermal regime of the landscape and mechanical and hydrological changes in the sediment and surface vegetation. These changes also affect carbon exchange and stability of the permafrost carbon pool. We apply radar interferometry (InSAR) techniques using data acquired over a 100 km by 70 km area by the Advanced Land Observing Satellite (ALOS-PALSAR) to monitor surface deformation of DTLBs near Prudhoe Bay from space. Over the period 2007-2010, the entire tundra area experienced thaw settlement and frost heave on the order of 3 cm due to melting and refreezing of pore ice in the active layer. A vast majority of the DTLBs appear to be moving along with the surrounding tundra area, however our study in fine spatial and temporal detail reveals a unique and significant seasonal settlement and heave at one basin located at (70.138621N, 148.649614W). The area of deformation is bounded by a historical lake shore on its west edge and a residual low pond on its east side. The seasonal deformation increases from about 2 cm near the center of the basin to about 9 cm near the west edge, well exceeding the measurement precision that is of the order of 1 cm. The spatial pattern and magnitude of subsidence repeated in all four years. We attribute the seasonal deformation at this DTLB to one or more of three possible mechanisms: a thick active layer (> 1 m) over the DTLB, a thick talik (unfrozen) layer beneath the DTLB, and seasonal surface drainage and flooding as the DLTB is connected to a thaw lake

  3. The influence of a model subglacial lake on ice dynamics and internal layering

    NASA Astrophysics Data System (ADS)

    Gudlaugsson, E.; Humbert, A.; Kleiner, T.; Kohler, J.; Andreassen, K.

    2015-07-01

    As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocities and a subsequent draw-down of isochrones and cold ice from the surface. The ice surface flattens as it adjusts to the lack of resisting forces at the base. The rapid transition in velocity induces changes in temperature and ice viscosity, releasing deformation energy which raises the temperature locally. Recent studies of Antarctic subglacial lakes indicate that many lakes experience very fast and possibly episodic drainage, during which the lake size is rapidly reduced as water flows out. A question is what effect this would have on internal layers within the ice, and whether such past events could be inferred from isochrone structures downstream. Here, we study the effect of a subglacial lake on the dynamics of a model ice stream as well as the influence that such short timescale drainage would have on the internal layers of the ice. To this end, we use a Full-Stokes, polythermal ice flow model. An enthalpy gradient method is used to account for the evolution of temperature and water content within the ice. We find that the rapid transition between slow-moving ice outside the lake, and full sliding over the lake, releases large amounts of deformational energy, which has the potential to form a temperate layer at depth in the transition zone. In addition, we provide an explanation for a characteristic surface feature, commonly seen at the edges of subglacial lakes, a hummocky surface depression in the transition zone between little to full sliding. We also conclude that rapid changes in lake geometry or basal friction create a travelling wave at depth within the isochrone structure that transfers downstream with the advection of ice, thus indicating the possibility of detecting past events with ice penetrating radar.

  4. Founding events influence genetic population structure of sockeye salmon (Oncorhynchus nerka) in Lake Clark, Alaska

    USGS Publications Warehouse

    Ramstad, K.M.; Woody, C.A.; Sage, G.K.; Allendorf, F.W.

    2004-01-01

    Bottlenecks can have lasting effects on genetic population structure that obscure patterns of contemporary gene flow and drift. Sockeye salmon are vulnerable to bottleneck effects because they are a highly structured species with excellent colonizing abilities and often occupy geologically young habitats. We describe genetic divergence among and genetic variation within spawning populations of sockeye salmon throughout the Lake Clark area of Alaska. Fin tissue was collected from sockeye salmon representing 15 spawning populations of Lake Clark, Six-mile Lake, and Lake Iliamna. Allele frequencies differed significantly at 11 microsatellite loci in 96 of 105 pairwise population comparisons. Pairwise estimates of FST ranged from zero to 0.089. Six-mile Lake and Lake Clark populations have historically been grouped together for management purposes and are geographically proximate. However, Six-mile Lake populations are genetically similar to Lake Iliamna populations and are divergent from Lake Clark populations. The reduced allelic diversity and strong divergence of Lake Clark populations relative to Six-mile Lake and Lake Iliamna populations suggest a bottleneck associated with the colonization of Lake Clark by sockeye salmon. Geographic distance and spawning habitat differences apparently do not contribute to isolation and divergence among populations. However, temporal isolation based on spawning time and founder effects associated with ongoing glacial retreat and colonization of new spawning habitats contribute to the genetic population structure of Lake Clark sock-eye salmon. Nonequilibrium conditions and the strong influence of genetic drift caution against using estimates of divergence to estimate gene flow among populations of Lake Clark sockeye salmon.

  5. Rapid Ice Mass Loss: Does It Have an Influence on Earthquake Occurrence in Southern Alaska?

    NASA Technical Reports Server (NTRS)

    Sauber, Jeanne M.

    2008-01-01

    The glaciers of southern Alaska are extensive, and many of them have undergone gigatons of ice wastage on time scales on the order of the seismic cycle. Since the ice loss occurs directly above a shallow main thrust zone associated with subduction of the Pacific-Yakutat plate beneath continental Alaska, the region between the Malaspina and Bering Glaciers is an excellent test site for evaluating the importance of recent ice wastage on earthquake faulting potential. We demonstrate the influence of cumulative glacial mass loss following the 1899 Yakataga earthquake (M=8.1) by using a two dimensional finite element model with a simple representation of ice fluctuations to calculate the incremental stresses and change in the fault stability margin (FSM) along the main thrust zone (MTZ) and on the surface. Along the MTZ, our results indicate a decrease in FSM between 1899 and the 1979 St. Elias earthquake (M=7.4) of 0.2 - 1.2 MPa over an 80 km region between the coast and the 1979 aftershock zone; at the surface, the estimated FSM was larger but more localized to the lower reaches of glacial ablation zones. The ice-induced stresses were large enough, in theory, to promote the occurrence of shallow thrust earthquakes. To empirically test the influence of short-term ice fluctuations on fault stability, we compared the seismic rate from a reference background time period (1988-1992) against other time periods (1993-2006) with variable ice or tectonic change characteristics. We found that the frequency of small tectonic events in the Icy Bay region increased in 2002-2006 relative to the background seismic rate. We hypothesize that this was due to a significant increase in the rate of ice wastage in 2002-2006 instead of the M=7.9, 2002 Denali earthquake, located more than 100km away.

  6. Snow and Ice Climatology of the Western United States and Alaska from MODIS

    NASA Astrophysics Data System (ADS)

    Rittger, K. E.; Painter, T. H.; Mattmann, C. A.; Seidel, F. C.; Burgess, A.; Brodzik, M.

    2013-12-01

    The climate and hydroclimate of the Western US and Alaska are tightly coupled to their snow and ice cover. The Western US depends on mountain snowmelt for the majority of its water supply to agriculture, industrial and urban use, hydroelectric generation, and recreation, all driven by increasing population and demand. Alaskan snow and glacier cover modulate regional climate and, as with the Western US, dominate water supply and hydroelectric generation in much of the state. Projections of climate change in the Western US and Alaska suggest that the most pronounced impacts will include reductions of mountain snow and ice cover, earlier runoff, and a greater fraction of rain instead of snow. We establish a snow and ice climatology of the Western US and Alaska using physically based MODIS Snow Covered Area and Grain size model (MODSCAG) for fractional snow cover, the MODIS Dust Radiative Forcing in Snow model (MODDRFS) for radiative forcing by light absorbing impurities in snow, and the MODIS Permanent Ice model (MODICE) for annual minimum exposed snow. MODSCAG and MODDRFS use EOS MOD09GA historical reflectance data (2000-2012) to provide daily and 8-day composites and near real time products since the beginning of 2013, themselves ultimately composited to 8-day products. The compositing method considers sensor-viewing geometry, solar illumination, clouds, cloud shadows, aerosols and noisy detectors in order to select the best pixel for an 8-day period. The MODICE annual minimum exposed snow and ice product uses the daily time series of fractional snow and ice from MODSCAG to generate annual maps. With this project we have established an ongoing, national-scale, consistent and replicable approach to assessing current and projected climate impacts and climate-related risk in the context of other stressors. We analyze the products in the Northwest, Southwest, and Alaska/Arctic regions of the National Climate Assessment for the last decade, the nation's hottest on record

  7. Triple Isotope Water Measurements of Lake Untersee Ice using Off-Axis ICOS

    NASA Astrophysics Data System (ADS)

    Berman, E. S.; Huang, Y. W.; Andersen, D. T.; Gupta, M.; McKay, C. P.

    2015-12-01

    Lake Untersee (71.348°S, 13.458°E) is the largest surface freshwater lake in the interior of the Gruber Mountains of central Queen Maud Land in East Antarctica. The lake is permanently covered with ice, is partly bounded by glacier ice and has a mean annual air temperature of -10°C. In contrast to other Antarctic lakes the dominating physical process controlling ice-cover dynamics is low summer temperatures and high wind speeds resulting in sublimation rather than melting as the main mass-loss process. The ice-cover of the lake is composed of lake-water ice formed during freeze-up and rafted glacial ice derived from the Anuchin Glacier. The mix of these two fractions impacts the energy balance of the lake, which directly affects ice-cover thickness. Ice-cover is important if one is to understand the physical, chemical, and biological linkages within these unique, physically driven ecosystems. We have analyzed δ2H, δ18O, and δ17O from samples of lake and glacier ice collected at Lake Untersee in Dec 2014. Using these data we seek to answer two specific questions: Are we able to determine the origin and history of the lake ice, discriminating between rafted glacial ice and lake water? Can isotopic gradients in the surface ice indicate the ablation (sublimation) rate of the surface ice? The triple isotope water analyzer developed by Los Gatos Research (LGR 912-0032) uses LGR's patented Off-Axis ICOS (Integrated Cavity Output Spectroscopy) technology and incorporates proprietary internal thermal control for high sensitivity and optimal instrument stability. This analyzer measures δ2H, δ18O, and δ17O from water, as well as the calculated d-excess and 17O-excess. The laboratory precision in high performance mode for both δ17O and δ18O is 0.03 ‰, and for δ2H is 0.2 ‰. Methodology and isotope data from Lake Untersee samples are presented. Figure: Ice samples were collected across Lake Untersee from both glacial and lake ice regions for this study.

  8. Index for hazard of Glacier Lake Outburst flood of Lake Merzbacher by satellite-based monitoring of lake area and ice cover

    NASA Astrophysics Data System (ADS)

    Xie, Zunyi; ShangGuan, Donghui; Zhang, Shiqiang; Ding, Yongjian; Liu, Shiyin

    2013-08-01

    Previous studies show that the area of a moraine-dammed lake can provide a good indicator of the significance of its outburst. For a glacier-dammed lake however, because its area and depth fluctuates with the melting of its ice dam, it is difficult to predict the outburst of the glacier-dammed lake by using its area alone.A characteristic of the surface of Lake Merzbacher is a large amount of floating ice therefore, a method is proposed in this article to extract the area of floating ice on the lake and the area of ice free water in the lake by using Environment and Disaster Monitoring Small Satellite images respectively. Furthermore, based on the area of floating ice extracted through the image information of Lake Merzbacher in 2009 and 2010, we determined the relationship between the ice area and the outburst of the lake, then formulated the Index for hazard of Glacier Lake Outburst Flood (IGLOF) of Lake Merzbacher, which cannot only predict the flood outburst, but also determine the specific outburst period after the lake drainage had occurred. This can be shown in a recalculation of the lake drainages in the years 2009 and 2010. Research results indicate that when IGLOF is less than 0.5 and the lake area is larger than 3 km2, the outburst process is in early-warning period and GLOF will occur in the next 5-8 days. Also, the successful outburst prediction of Lake Merzbacher in 2011 showed that the index described in this paper provides a quick methodology for forecasting and warning against Lake Merzbacher outburst floods. However,as our research was based on a short observation period (2009-2011) and also cannot be supplemented by other images, it will still be needed to be checked and validated by continuous observation and improvement in future.

  9. Studies of contemporary glacier basal ice cryostructures to identify buried basal ice in the permafrost: an example from the Matanuska Glacier, Alaska.

    NASA Astrophysics Data System (ADS)

    Stephani, E.; Fortier, D.; Kanevskiy, M.; Dillon, M.; Shur, Y.

    2007-12-01

    In the permafrost, massive ice bodies occur as buried glacier ice, aufeis ice, recrystalized snow, massive segregated ice, injection ice, ice wedges or ice formed in underground cavities ("pool ice", "thermokarst-cave ice"). The origin of massive ice bodies in the permafrost bears considerable implications for the reconstructions of paleoenvironments and paleoclimates. Our work aims to help the permafrost scientists working on massive icy sediments to distinguish buried basal glacier ice from other types of buried ice. To do so, the properties and structure of contemporary basal ice must be well known. Field investigations at the Matanuska Glacier (Chugach range, South-central Alaska), consisted in descriptions and sampling of natural basal ice exposures. We have used the basal ice facies classification of Lawson (1979) which is simple, easy to use in the field and provides a good framework for the description of basal ice exposures. Cores were extracted and brought back to the laboratory for water and grain-size analyses. The sediments forming the cryostructure were mostly polymodal, poorly sorted gravelly silt to gravelly fine sand, with mud contents generally over 50%. These data will be used to calibrate three-dimensional (3D) models produced from micro-tomographic scans of basal ice which will produce quantitative estimates of volumetric ice and sediments contents of basal ice cryostructures. Ultimately, visual qualitative and quantitative characterization of the basal ice components of 3D models together with field observations and laboratory analysis will allow for a new micro-facies and cryostructures classification of the basal ice. Our work will also have applications in glaciology, glacial geology, geomorphology, Quaternary and paleo-climatological studies based on inferences made from the structure of basal glacier ice. This paper presents the internal composition of the basal ice facies in terms of cryostructures assemblages (Fortier et al.: 2007) and

  10. Effect of ice formation and streamflow on salmon incubation habitat in the lower Bradley River, Alaska

    USGS Publications Warehouse

    Rickman, R.L.

    1996-01-01

    A minimum flow of 40 cubic feet per second is required in the lower Bradley River, near Homer, Alaska, from November 2 to April 30 to ensure adequate salmon egg incubation habitat. The study that determined this minimum flow did not account for the effects of ice formation on habitat. An investigation was made during periods of ice formation. Hydraulic properties and field water-quality data were measured in winter only from March 1993 to April 1995 at six transects in the lower Bradley River. Discharge in the lower Bradley River ranged from 42.6 to 73.0 cubic feet per second (average 57 cubic feet per second) with ice conditions ranging from near ice free to 100 percent ice cover. Stream water velocity and depth were adequate for habitat protection for all ice conditions and discharges. No relation was found between percent ice cover and mean velocity and depth for any given discharge and no trends were found with changes in discharge for a given ice condition. Velocity distribution within each transect varied significantly from one sampling period to the next. Mean depth and velocity at flows of 40 cubic feet per second or less could not be predicted. No consistent relation was found between the amount of wetted perimeter and percent ice cover. Intragravel-water temperature was slightly warmer than surface-water temperature. Surface and intragravel-water dissolved-oxygen levels were adequate for all flows and ice conditions. No apparent relation was found between dissolved-oxygen levels and streamflow or ice conditions. Excellent oxygen exchange was indicated throughout the study reach. Stranding potential of salmon fry was found to be low throughout the study reach. The limiting factors for determining the minimal acceptable flow limit appear to be stream-water velocity and depth, although specific limits could not be estimated because of the high flows that occurred during this study.

  11. Changes in ice cover thickness and lake level of Lake Hoare, Antarctica - Implications for local climatic change

    NASA Technical Reports Server (NTRS)

    Wharton, Robert A., Jr.; Mckay, Christopher P.; Clow, Gary D.; Andersen, Dale T.; Simmons, George M., Jr.; Love, F. G.

    1992-01-01

    Results are reported from 10 years of ice-thickness measurements at perennially ice-covered Lake Hoare in southern Victoria Land, Antarctica. The ice cover of this lake had been thinning steadily at a rate exceeding 20 cm/yr during the last decade but seems to have recently stabilized at a thickness of 3.3 m. Data concerning lake level and degree-days above freezing are presented to show the relationship between peak summer temperatures and the volume of glacier-derived meltwater entering Lake Hoare each summer. From these latter data it is inferred that peak summer temperatures have been above 0 C for a progressively longer period of time each year since 1972. Possible explanations for the thinning of the lake ice are considered. The thickness of the ice cover is determined by the balance between freezing during the winter and ablation that occurs all year but maximizes in summer. It is suggested that the term most likely responsible for the change in the ice cover thickness at Lake Hoare is the extent of summer melting, consistent with the rising lake levels.

  12. 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

  13. New insights into the influence of ice on the coastal marine environment of the Beaufort Sea, Alaska

    NASA Technical Reports Server (NTRS)

    Barnes, P. W.; Reimnitz, E.

    1973-01-01

    Areal patterns from field data and ERTS-1 imagery have shown a close relationship between geologic processes and the influence of sea ice along Alaska's northern coast, perhaps the nation's least known continental margin. Ice acts as; (1) a bottom-gouging agent; (2) an influence on water circulation; (3) a carrier of sediments; and (4) an influence on water types.

  14. Winter 1994 Weather and Ice Conditions for the Laurentian Great Lakes.

    NASA Astrophysics Data System (ADS)

    Assel, Raymond A.; Janowiak, John E.; Young, Sharolyn; Boyce, Daron

    1996-01-01

    The Laurentian Great Lakes developed their most extensive ice cover in over a decade during winter 1994 [December-February 1993/94 (DJF 94)]. Extensive midlake ice formation started the second half of January, about 2 weeks earlier than normal. Seasonal maximal ice extent occurred in early February, again about 2 weeks earlier than normal. Winter 1994 maximum (normal) ice coverages on the Great Lakes are Lake Superior 96% (75%), Lake Michigan 78% (45%), Lake Huron 95% (68%), Lake Erie 97% (90%), and Lake Ontario 67% (24%). Relative to the prior 31 winters (1963-93), the extent of seasonal maximal ice cover for winter 1994 for the Great Lakes taken as a unit is exceeded by only one other winter (1979); however, other winters for individual Great Lakes had similar maximal ice covers.Anomalously strong anticyclonic circulation over the central North Pacific (extending to the North Pole) and an abnormally strong polar vortex centered over northern Hudson Bay combined to produce a circulation pattern that brought frequent air masses of Arctic and polar origin to the eastern third of North America. New records were set for minimum temperatures on 19 January 1994 at many locations in the Great Lakes region. A winter severity index consisting of the average November-February air temperatures averaged over four sites on the perimeter of the Great Lakes (Duluth, Minnesota; Sault Ste. Marie, Michigan; Detroit, Michigan; and Buffalo, New York) indicates that winter 1994 was the 21st coldest since 1779. The unseasonably cold air temperatures produced much-above-normal ice cover over the Great Lakes and created problems for lake shipping. Numerous fatalities and injuries were attributed to the winter weather, which included several ice and snow storms. The much-below-normal air temperatures resulted in enhanced lake-effect snowfall along downwind lake shores, particularly during early to midwinter, prior to extensive ice formation in deeper lake areas. The low air temperatures

  15. Oxygen supersaturation in ice-covered Antarctic lakes - Biological versus physical contributions

    NASA Technical Reports Server (NTRS)

    Craig, H.; Wharton, R. A., Jr.; Mckay, C. P.

    1992-01-01

    Lake Hoare is one of a number of ice-covered polar lakes in the Dry Valley Region of southern Victoria Land, Antarctica. Analysis of N2, O2, and Ar in bubbles from this lake's ice indicates that while O2 is about 2.4 times supersaturated in the water below the ice, only 11 percent of the O2 input to this lake is due to biological activity and the balance is derived from meltwater inflow. In Lake Hoare, as much as 70 percent of total gas loss may occur by advection through the ice cover; the remaining gas fractions are removed by respiration at the lower boundary in the case of O2, and by molecular exchange with the atmosphere in the peripheral summer moat around the ice.

  16. Sensitivity analysis of lake mass balance in discontinuous permafrost: the example of disappearing Twelvemile Lake, Yukon Flats, Alaska (USA)

    USGS Publications Warehouse

    Jepsen, S.M.; Voss, C.I.; Walvoord, M.A.; Rose, J.R.; Minsley, B.J.; Smith, B.D.

    2013-01-01

    Many lakes in northern high latitudes have undergone substantial changes in surface area over the last four decades, possibly as a result of climate warming. In the discontinuous permafrost of Yukon Flats, interior Alaska (USA), these changes have been non-uniform across adjacent watersheds, suggesting local controls on lake water budgets. Mechanisms that could explain the decreasing mass of one lake in Yukon Flats since the early 1980s, Twelvemile Lake, are identified via a scoping analysis that considers plausible changes in snowmelt mass and infiltration, permafrost distribution, and climate warming. Because predicted changes in evaporation (2 cmyr-1) are inadequate to explain the observed 17.5 cmyr-1 reduction in mass balance, other mechanisms are required. The most important potential mechanisms are found to involve: (1) changes in shallow, lateral groundwater flow to the lake possibly facilitated by vertical freeze-thaw migration of the permafrost table in gravel; (2) increased loss of lake water as downward groundwater flow through an open talik to a permeable subpermafrost flowpath; and (3) reduced snow meltwater inputs due to decreased snowpack mass and increased infiltration of snowmelt into, and subsequent evaporation from, fine-grained sediment mantling the permafrost-free lake basin.

  17. Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study.

    PubMed

    Paytan, Adina; Lecher, Alanna L; Dimova, Natasha; Sparrow, Katy J; Kodovska, Fenix Garcia-Tigreros; Murray, Joseph; Tulaczyk, Slawomir; Kessler, John D

    2015-03-24

    Methane emissions in the Arctic are important, and may be contributing to global warming. While methane emission rates from Arctic lakes are well documented, methods are needed to quantify the relative contribution of active layer groundwater to the overall lake methane budget. Here we report measurements of natural tracers of soil/groundwater, radon, and radium, along with methane concentration in Toolik Lake, Alaska, to evaluate the role active layer water plays as an exogenous source for lake methane. Average concentrations of methane, radium, and radon were all elevated in the active layer compared with lake water (1.6 × 10(4) nM, 61.6 dpm⋅m(-3), and 4.5 × 10(5) dpm⋅m(-3) compared with 1.3 × 10(2) nM, 5.7 dpm⋅m(-3), and 4.4 × 10(3) dpm⋅m(-3), respectively). Methane transport from the active layer to Toolik Lake based on the geochemical tracer radon (up to 2.9 g⋅m(-2)⋅y(-1)) can account for a large fraction of methane emissions from this lake. Strong but spatially and temporally variable correlations between radon activity and methane concentrations (r(2) > 0.69) in lake water suggest that the parameters that control methane discharge from the active layer also vary. Warming in the Arctic may expand the active layer and increase the discharge, thereby increasing the methane flux to lakes and from lakes to the atmosphere, exacerbating global warming. More work is needed to quantify and elucidate the processes that control methane fluxes from the active layer to predict how this flux might change in the future and to evaluate the regional and global contribution of active layer water associated methane inputs.

  18. Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study

    PubMed Central

    Paytan, Adina; Lecher, Alanna L.; Dimova, Natasha; Sparrow, Katy J.; Kodovska, Fenix Garcia-Tigreros; Murray, Joseph; Tulaczyk, Slawomir; Kessler, John D.

    2015-01-01

    Methane emissions in the Arctic are important, and may be contributing to global warming. While methane emission rates from Arctic lakes are well documented, methods are needed to quantify the relative contribution of active layer groundwater to the overall lake methane budget. Here we report measurements of natural tracers of soil/groundwater, radon, and radium, along with methane concentration in Toolik Lake, Alaska, to evaluate the role active layer water plays as an exogenous source for lake methane. Average concentrations of methane, radium, and radon were all elevated in the active layer compared with lake water (1.6 × 104 nM, 61.6 dpm⋅m−3, and 4.5 × 105 dpm⋅m−3 compared with 1.3 × 102 nM, 5.7 dpm⋅m−3, and 4.4 × 103 dpm⋅m−3, respectively). Methane transport from the active layer to Toolik Lake based on the geochemical tracer radon (up to 2.9 g⋅m−2⋅y−1) can account for a large fraction of methane emissions from this lake. Strong but spatially and temporally variable correlations between radon activity and methane concentrations (r2 > 0.69) in lake water suggest that the parameters that control methane discharge from the active layer also vary. Warming in the Arctic may expand the active layer and increase the discharge, thereby increasing the methane flux to lakes and from lakes to the atmosphere, exacerbating global warming. More work is needed to quantify and elucidate the processes that control methane fluxes from the active layer to predict how this flux might change in the future and to evaluate the regional and global contribution of active layer water associated methane inputs. PMID:25775530

  19. Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study.

    PubMed

    Paytan, Adina; Lecher, Alanna L; Dimova, Natasha; Sparrow, Katy J; Kodovska, Fenix Garcia-Tigreros; Murray, Joseph; Tulaczyk, Slawomir; Kessler, John D

    2015-03-24

    Methane emissions in the Arctic are important, and may be contributing to global warming. While methane emission rates from Arctic lakes are well documented, methods are needed to quantify the relative contribution of active layer groundwater to the overall lake methane budget. Here we report measurements of natural tracers of soil/groundwater, radon, and radium, along with methane concentration in Toolik Lake, Alaska, to evaluate the role active layer water plays as an exogenous source for lake methane. Average concentrations of methane, radium, and radon were all elevated in the active layer compared with lake water (1.6 × 10(4) nM, 61.6 dpm⋅m(-3), and 4.5 × 10(5) dpm⋅m(-3) compared with 1.3 × 10(2) nM, 5.7 dpm⋅m(-3), and 4.4 × 10(3) dpm⋅m(-3), respectively). Methane transport from the active layer to Toolik Lake based on the geochemical tracer radon (up to 2.9 g⋅m(-2)⋅y(-1)) can account for a large fraction of methane emissions from this lake. Strong but spatially and temporally variable correlations between radon activity and methane concentrations (r(2) > 0.69) in lake water suggest that the parameters that control methane discharge from the active layer also vary. Warming in the Arctic may expand the active layer and increase the discharge, thereby increasing the methane flux to lakes and from lakes to the atmosphere, exacerbating global warming. More work is needed to quantify and elucidate the processes that control methane fluxes from the active layer to predict how this flux might change in the future and to evaluate the regional and global contribution of active layer water associated methane inputs. PMID:25775530

  20. Characterizing C-band backscattering from thermokarst lake ice on the Qinghai-Tibet Plateau

    NASA Astrophysics Data System (ADS)

    Tian, Bangsen; Li, Zhen; Engram, Melanie J.; Niu, Fujun; Tang, Panpan; Zou, Pengfei; Xu, Juan

    2015-06-01

    On the basis of weather observations and field measurements of lake ice, this study investigates multi-temporal C-band VV-polarized radar backscattering values from the thermokarst lakes and alpine meadow on the QTP during the period 2003-2010. In order to understand the scattering mechanism of lake ice, a scattering model is developed for lake ice that updates some assumptions adopted in previously developed models, including the roughness of the ice-water interface and the shape of vertically stacked centimeter-sized bubbles in the lake ice. We conclude the following: First, with a incidence angle range near 24°, the backscattering intensities of C-band VV-polarized ENVISAT-ASAR data exhibit a strong dependence on time, which is related to the processes of ice growth and decay on the QTP. Some unique backscattering characteristics of lake ice in this high-altitude region, as compared to those for high-latitude regions, are also discussed and documented in the paper. Secondly, the timing of lake ice-on in fall and ice-off in spring for this region can be identified in radar images by using a threshold of -12 dB for the backscatter intensity of the surrounding alpine meadow. Finally, the results of applying the scattering model indicate that surface scattering from the ice-water interface and volume scattering from gas bubbles embedded in the lake ice are the dominant scattering mechanisms for C-band VV polarized SAR and that the roughness of the ice-water interface and also bubble size are the most sensitive factors.

  1. Lake ice records used to detect historical and future climatic changes

    USGS Publications Warehouse

    Robertson, Dale M.; Ragotzkie, R.A.; Magnuson, John J.

    1992-01-01

    With the relationships between air temperature and freeze and break up dates, we can project how the ice cover of Lake Mendota should respond to future climatic changes. If warming occurs, the ice cover for Lake Mendota should decrease approximately 11 days per 1 °C increase. With a warming of 4 to 5 °C, years with no ice cover should occur in approximately 1 out of 15 to 30 years.

  2. Biological Diversity Comprising Microbial Structures of Antarctic Ice Covered Lakes

    NASA Astrophysics Data System (ADS)

    Matys, E. D.

    2015-12-01

    Analysis of microbial membrane lipids is a rapid and non-selective method for evaluating the composition of microbial communities. To fully realise the diagnostic potential of these lipids, we must first understand their structural diversity, biological sources, physiological functions, and pathways of preservation. Particular environmental conditions likely prompt the production of different membrane lipid structures. Antarctica's McMurdo Dry Valleys host numerous ice-covered lakes with sharp chemical gradients that vary in illumination, geochemical structure, and benthic mat morphologies that are structured by nutrient availability and water chemistry. The lipid contents of these benthic mats have not received extensive study nor have the communities yet been thoroughly characterized. Accordingly, a combination of lipid biomarker and nucleic acid sequence data provides the means of assessing species diversity and environmental controls on the composition and diversity of membrane lipid assemblages. We investigated the richness and diversity of benthic microbial communities and accumulated organic matter in Lake Vanda of the McMurdo Dry Valleys. We have identified diverse glycolipids, aminolipids, and phospholipids in addition to many unknown compounds that may be specific to these particular environments. Light levels fluctuate seasonally, favoring low-light-tolerant cyanobacteria and specific lipid assemblages. Adaptations to nutrient limitations are reflected in contrasting intact polar lipid assemblages. For example, under P-limiting conditions, phospholipids are subsidiary to membrane-forming lipids that do not contain P (i.e. ornithine, betaine, and sulfolipids). The bacteriohopanepolyol (BHP) composition is dominated by bacteriohopanetetrol (BHT), a ubiquitous BHP, and 2-methylhopanoids. The relative abundance of 2-methylhopanoids is unprecedented and may reflect the unusual seasonal light regime of this polar environment. By establishing correlations

  3. Coast Guard/NOAA/NASA Great Lakes Project Icewarn. [ice mapping for winter navigation

    NASA Technical Reports Server (NTRS)

    Brennan, T. D.; Gedney, R. T.

    1975-01-01

    The operational feasibility of using remote sensing to provide all weather ice formation for Great Lakes winter navigation is explored. A combination airborne pulsed radar system to measure actual ice thickness, a satellite data link system, and a hand drawn interpretive ice chart proved valuable for extending winter navigation through the icepack.

  4. Simulating the decadal- to millennial-scale dynamics of morphology and sequestered carbon mobilization of two thermokarst lakes in NW Alaska

    NASA Astrophysics Data System (ADS)

    Kessler, M. A.; Plug, L. J.; Walter Anthony, K. M.

    2012-06-01

    Thermokarst lakes alter landscape topography and hydrology in widespread permafrost regions and mobilize significant permafrost carbon pools, including releasing methane (CH4) to the atmosphere. Despite this, the dynamics of lake evolution, permafrost thawing, and carbon mobilization are not well known. We present a 3-D numerical model of thermokarst lakes on organic-rich yedoma permafrost terrains with surface water flow and pooling naturally defining lakes that deepen, expand laterally, and drain due to talik formation, bank retreat, and both gradual and catastrophic drainage. We predict the 3-D pattern of microbial methane production within the talik over time. As a first model test and calibration, beginning with small protolakes, we simulated 10,000 years of evolution of Pear and Claudi lakes, two neighboring thermokarst features on the northern Seward Peninsula, Alaska. Simulated lakes approximated observed bathymetry, but results are sensitive to initial topography and soil ice content. Local topography caused markedly different dynamics for the two lakes. Pear expanded rapidly across low-relief topography, fully drained multiple times, and released little methane in later stages due to Pleistocene carbon depletion by the first and largest lake generation. Claudi grew slowly and continuously across high-relief topography, forming high subaerial banks; partial drainages left remnant horseshoe lakes that continued to expand into virgin yedoma, mobilizing carbon at roughly the same rate irrespective of lake drainage. The ˜2× discrepancy between simulated CH4 production and observed emission rates in Claudi likely results from misestimation of hot spot ebullition, labile carbon content, CH4:CO2 production ratio, or microbial CH4 oxidation.

  5. Mapping the Distribution of Traditional Iñupiat Ice Cellars in Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Klene, A. E.; Nyland, K.; Brown, J.; Shiklomanov, N. I.; Nelson, F. E.

    2012-12-01

    Historically, ice cellars excavated in permafrost have been essential to the Iñupiat residents of Barrow, Alaska, and remain so today. These traditional facilities, ranging in age from more than a century to newly excavated, allow secure, year-round frozen storage of subsistence harvests over long periods. Temperatures within the cellars are critical because bacteria can damage meat even at temperatures below the freezing point, and have traditionally been close to those of surrounding permafrost. Climatic change has been suspected of compromising and causing some ice cellars in Barrow to fill with water. Temperatures were monitored in five ice cellars, with little change observed over five years of observation, although sloughing was observed in one cellar. The lack of knowledge about the ice cellars as part of the local infrastructure led to a collaboration begun in 2012 with the North Slope Borough's Department of Planning and Community Services. Several meetings were held in August 2012 with local residents and stakeholders to assemble a GIS data layer of ice-cellar locations and conditions for use by researchers and by Borough representatives. Applications range from developing plans for snow plowing and construction to the protection of foodstuff quality and important cultural resources. Results from this collaboration will lead to improved understanding of the practical aspects of ice cellars use and maintenance in this urban Arctic environment.

  6. Snettisham Hydroelectric Project, Alaska second stage development, Crater lake. Final foundation report. Final report

    SciTech Connect

    Not Available

    1992-09-04

    The important geologic features and methods used to construct the Crater Lake stage of the Snettisham Hydroelectric project, built between 1985 and 1989, are discussed. The project added 31 megawatts of non-polluting, renewable electric power for Juneau, Alaska and the surrounding area. Features of the report include the power tunnel and access adits, penstock excavation, surge shaft, gate shaft and lake top. Construction aspects include the general geology, design features, construction methods, geologic conditions encountered, ground support requirements, grouting, instrumentation and tunnel filling. Foundation conditions for the Crater Lake status were excellent, permitting the power and penstock tunnel and shafts to be constructed essentially unlined. The basic rock type throughout the project is a high-quality, quartz diorite gneiss with randomly spaced, subparallel basalt dikes.... Unlined rock tunnels, Power tunnel, Penstocks, Lake tap, Surge shaft.

  7. Microbiological and Biogeochemical Investigations of the Accreted Ice Above Subglacial Lake Vostok, Antarctica

    NASA Astrophysics Data System (ADS)

    Christner, B. C.; Foreman, C. F.; Arnold, B. R.; Welch, K. A.; Lyons, W. B.; Priscu, J. C.

    2004-12-01

    Subglacial Lake Vostok is located ~4 km beneath the surface of the East Antarctic ice sheet and has been isolated from the atmosphere for at least 15 million years. The lake has a surface area near 14,000 km2 and a depth exceeding 1000 m. While the nature of the environment within Subglacial Lake Vostok remains uncertain, if a sustained microbial ecosystem is present, life in this subsurface environment operates under arguably the most extreme conditions in the biosphere (i.e., high pressure, constant cold, high oxygen concentrations, and no light). The lake represents an analogue for ecosystems that may exist in Europa's ice-covered ocean and also provides an Earthly-based model for the evaluation of technology to search for life in icy extraterrestrial subsurface environments. Concerns for environmental protection have prevented direct sampling of the lake water thus far, as a prudent sampling plan that will not contaminate this pristine environment has yet to be developed and tested. However, an ice core has been retrieved at Vostok Station in which the bottom ~85 meters consists of lake water that has accreted to the bottom of the ice sheet, providing frozen samples of water from the lakes' surface. The ice from 3539 to 3609 mbs (accretion ice I) contains visible inclusions due to accretion in the shallow embayment or western grounding line, whereas ice from 3610-3623 mbs (accretion ice II) is very clean, forming above the deep eastern basin of the main lake. Using a multifaceted protocol to monitor cellular and molecular decontamination of ice cores, we show that the microbiology and geochemistry (i.e., dissolve organic carbon, nutrients, and ions) of accretion ice is very different from the overlying glacial ice. The numbers of cells are 2- to 7-fold higher in accretion ice I than in the overlying glacial ice, and decrease with increasing depth in accretion ice II. Cell viability in accretion ice samples has been confirmed by the measurable respiration of 14C

  8. Water-quality data from lakes in the Yukon Flats, Alaska, 2010-2011

    USGS Publications Warehouse

    Halm, Douglas R.; Griffith, Brad

    2014-01-01

    Over a two-year period (2010–2011), in-place measurements were made and water-quality samples were collected from 122 lakes in the Yukon Flats, Alaska, during a U.S. Geological Survey lake biological diversity inventory. The U.S. Geological Survey National Research Program performed the chemical analyses on the retrieved water-quality samples. Results from the analyses of water samples for dissolved carbon gases and carbon isotopes, hydrogen and oxygen stable isotopes, dissolved organic carbon, and major cations and anions, along with supporting site data, are presented in this report.

  9. Emmons Lake Volcanic Center, Alaska Peninsula: Source of the Late Wisconsin Dawson tephra, Yukon Territory, Canada

    USGS Publications Warehouse

    Mangan, M.T.; Waythomas, C.F.; Miller, T.P.; Trusdell, F.A.

    2003-01-01

    The Emmons Lake Volcanic Center on the Alaska Peninsula of southwestern Alaska is the site of at least two rhyolitic caldera-forming eruptions (C1 and C2) of late Quaternary age that are possibly the largest of the numerous caldera-forming eruptions known in the Aleutian arc. The deposits produced by these eruptions are widespread (eruptive volumes of >50 km3 each), and their association with Quaternary glacial and eolian deposits on the Alaska Peninsula and elsewhere in Alaska and northwestern Canada enhances the likelihood of establishing geochronological control on Quaternary stratigraphic records in this region. The pyroclastic deposits associated with the second caldera-forming eruption (C2) consist of loose, granular, airfall and pumice-flow deposits that extend for tens of kilometres beyond Emmons Lake caldera, reaching both the Bering Sea and Pacific Ocean coastlines north and south of the caldera. Geochronological and compositional data on C2 deposits indicate a correlation with the Dawson tephra, a 24 000 14C BP (27 000 calibrated years BP), widespread bed of silicic ash found in loess deposits in west-central Yukon Territory, Canada. The correlation clearly establishes the Dawson tephra as the time-stratigraphic marker of the last glacial maximum.

  10. Late Glacial-Holocene Pollen-Based Vegetation History from Pass Lake, Prince of Wales Island, Southeastern Alaska

    USGS Publications Warehouse

    Ager, Thomas A.; Rosenbaum, Joseph G.

    2009-01-01

    A radiocarbon-dated history of vegetation development since late Wisconsin deglaciation has been reconstructed from pollen evidence preserved in a sediment core from Pass Lake on Prince of Wales Island, southeastern Alaska. The shallow lake is in the south-central part of the island and occupies a low pass that was filled by glacial ice of local origin during the late Wisconsin glaciation. The oldest pollen assemblages indicate that pine woodland (Pinus contorta) had developed in the area by ~13,715 cal yr B.P. An abrupt decline in the pine population, coinciding with expansion of alder (Alnus) and ferns (mostly Polypodiaceae) began ~12,875 yr B.P., and may have been a response to colder, drier climates during the Younger Dryas climatic interval. Mountain hemlock (Tsuga mertensiana) began to colonize central Prince of Wales Island by ~11,920 yr B.P. and was soon followed by Sitka spruce (Picea sitchensis). Pollen of western hemlock (Tsuga heterophylla) began to appear in Pass Lake sediments soon after 11,200 yr B.P. The abundance of western hemlock pollen in the Pass Lake core during most of the Holocene appears to be the result of wind transport from trees growing at lower altitudes on the island. The late Holocene pollen record from Pass Lake is incomplete because of one or more unconformities, but the available record suggests that a vegetation change occurred during the late Holocene. Increases in pollen percentages of pine, cedar (probably yellow cedar, Chamaecyparis nootkatensis), and heaths (Ericales) suggest an expansion of muskeg vegetation occurred in the area during the late Holocene. This vegetation change may be related to the onset of cooler, wetter climates that began as early as ~3,774 yr B.P. in the region. This vegetation history provides the first radiocarbon-dated Late Glacial-Holocene terrestrial paleoecological framework for Prince of Wales Island. An analysis of magnetic properties of core sediments from Pass Lake suggests that unconformities

  11. Chronological framework for the deglaciation of the Lake Michigan lobe of the Laurentide ice sheet from ice-walled lake deposits

    USGS Publications Warehouse

    Curry, B.; Petras, J.

    2011-01-01

    A revised chronological framework for the deglaciation of the Lake Michigan lobe of the south-central Laurentide Ice Sheet is presented based on radiocarbon ages of plant macrofossils archived in the sediments of low-relief ice-walled lakes. We analyze the precision and accuracy of 15 AMS 14C ages of plant macrofossils obtained from a single ice-walled lake deposit. The semi-circular basin is about 0.72km wide and formed of a 4- to 16-m-thick succession of loess and lacustrine sediment inset into till. The assayed material was leaves, buds and stems of Salix herbacea (snowbed willow). The pooled mean of three ages from the basal lag facies was 18 270??50 14C a BP (21 810cal. a BP), an age that approximates the switch from active ice to stagnating conditions. The pooled mean of four ages for the youngest fossil-bearing horizon was 17 770??40 14C a BP (21 180cal. a BP). Material yielding the oldest and youngest ages may be obtained from sediment cores located at any place within the landform. Based on the estimated settling times of overlying barren, rhythmically bedded sand and silt, the lacustrine environment persisted for about 50 more years. At a 67% confidence level, the dated part of the ice-walled lake succession persisted for between 210 and 860cal. a (modal value: 610cal. a). The deglacial age of five moraines or morainal complexes formed by the fluctuating margin of the Lake Michigan lobe have been assessed using this method. There is no overlap of time intervals documenting when ice-walled lakes persisted on these landforms. The rapid readvances of the lobe during deglaciation after the last glacial maximum probably occurred at some point between the periods of ice-walled lake sedimentation. ?? 2011 John Wiley & Sons, Ltd.

  12. Spring and aufeis (icing) hydrology in Brooks Range, Alaska

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Kenji; Hinzman, Larry D.; Kane, Douglas L.

    2007-12-01

    Remote sensing studies and field hydrometeorological and geophysical investigations were employed to characterize several aufeis fields in the Brooks Range, Alaska. Geochemical studies were undertaken together with field hydrological measurements to better understand the chemical and thermal properties of stream base flow (groundwater spring) that contributes to winter aufeis development. The spring water temperature was measured at several major aufeis fields using data loggers throughout the year. Aufeis is an important water storage component in the Arctic and influences local ecology and geomorphology. Synthetic aperture radar (SAR) is a useful and sensitive sensor for aufeis detection and for estimating the total volume of storage as well as freeze/thaw conditions. The SAR analysis indicated that the volume of aufeis formed in winter is 27-30% of the annual groundwater discharge in the Kuparuk River. Visible and near-IR satellite imagery indicated many of the high-discharge springs (more than 10-1000 1/s) and aufeis fields are centered around an elevation of 600 m a.s.l. in limestone areas with glacial morphology. Geomorphological investigations indicate that many of springs have continually existed from at least the last glaciation. Microwave data (SAR), thermal infrared, short wave infrared, and visible and near-IR bands were all used to observe the growth, decay, and distribution of aufeis deposits. The remotely sensed data indicate that the distribution of the aufeis deposits today is nearly the same as it was in past colder periods; this was mainly determined by mapping the distributed carbonate precipitates. Also, spring water temperatures and discharge volumes are predictable from the aufeis field size using remotely sensed techniques.

  13. Modern thermokarst lake dynamics in the continuous permafrost zone, northern Seward Peninsula, Alaska

    USGS Publications Warehouse

    Jones, Benjamin M.; Grosse, G.; Arp, C.D.; Jones, M.C.; Walter, Anthony K.M.; Romanovsky, V.E.

    2011-01-01

    Quantifying changes in thermokarst lake extent is of importance for understanding the permafrost-related carbon budget, including the potential release of carbon via lake expansion or sequestration as peat in drained lake basins. We used high spatial resolution remotely sensed imagery from 1950/51, 1978, and 2006/07 to quantify changes in thermokarst lakes for a 700 km2 area on the northern Seward Peninsula, Alaska. The number of water bodies larger than 0.1 ha increased over the entire observation period (666 to 737 or +10.7%); however, total surface area decreased (5,066 ha to 4,312 ha or -14.9%). This pattern can largely be explained by the formation of remnant ponds following partial drainage of larger water bodies. Thus, analysis of large lakes (>40 ha) shows a decrease of 24% and 26% in number and area, respectively, differing from lake changes reported from other continuous permafrost regions. Thermokarst lake expansion rates did not change substantially between 1950/51 and 1978 (0.35 m/yr) and 1978 and 2006/07 (0.39 m/yr). However, most lakes that drained did expand as a result of surface permafrost degradation before lateral drainage. Drainage rates over the observation period were stable (2.2 to 2.3 per year). Thus, analysis of decadal-scale, high spatial resolution imagery has shown that lake drainage in this region is triggered by lateral breaching and not subterranean infiltration. Future research should be directed toward better understanding thermokarst lake dynamics at high spatial and temporal resolution as these systems have implications for landscape-scale hydrology and carbon budgets in thermokarst lake-rich regions in the circum-Arctic.

  14. Modeling the Thickness of Perennial Ice Covers on Stratified Lakes of the Taylor Valley, Antarctica

    NASA Technical Reports Server (NTRS)

    Obryk, M. K.; Doran, P. T.; Hicks, J. A.; McKay, C. P.; Priscu, J. C.

    2016-01-01

    A one-dimensional ice cover model was developed to predict and constrain drivers of long term ice thickness trends in chemically stratified lakes of Taylor Valley, Antarctica. The model is driven by surface radiative heat fluxes and heat fluxes from the underlying water column. The model successfully reproduced 16 years (between 1996 and 2012) of ice thickness changes for west lobe of Lake Bonney (average ice thickness = 3.53 m; RMSE = 0.09 m, n = 118) and Lake Fryxell (average ice thickness = 4.22 m; RMSE = 0.21 m, n = 128). Long-term ice thickness trends require coupling with the thermal structure of the water column. The heat stored within the temperature maximum of lakes exceeding a liquid water column depth of 20 m can either impede or facilitate ice thickness change depending on the predominant climatic trend (temperature cooling or warming). As such, shallow (< 20 m deep water columns) perennially ice-covered lakes without deep temperature maxima are more sensitive indicators of climate change. The long-term ice thickness trends are a result of surface energy flux and heat flux from the deep temperature maximum in the water column, the latter of which results from absorbed solar radiation.

  15. Measurements of supraglacial lake drainage and surface streams over West Greenland and effects on ice dynamics

    NASA Astrophysics Data System (ADS)

    Tedesco, M.; Willis, I. C.; Alexander, P. M.; Banwell, A. F.

    2011-12-01

    During the summer of 2011 we measured the filling and draining of two surface lakes in the Paakitsoq region of the West Greenland Ice Sheet (49.79 W, 69.57 N), together with the level of streams flowing into the basins feeding the lakes. We also used GPS to record the horizontal and vertical movement of the ice sheet surface at five locations surrounding the lakes for a two week period (overlapping the draining of the two lakes). In this talk we report results concerning the processes of lake filling and draining between the two lakes. 'Lake Half Moon', with a smaller catchment area, filled slowly at a steady rate over several days, then drained gradually over a 24 hour period as an existing moulin located outside the bottom of the lake became active; the lake level continued to drop very slowly over the remaining week as the surface stream leading from the lake to the moulin incised. 'Lake Ponting', with the larger catchment area, filled more rapidly and at an accelerating rate as depressions upstream of the lake filled with water, overflowed and delivered increasing volumes of water to the lake. Lake Ponting drained by hydrofracture following a particularly rapid rise in water level, generating a new ~ 800m long extensional crevasse on the ice sheet surface. The entire ~ 3 x 106 m3 lake drained within a few hours. For the Lake Pointing, we show, for the first time, a movie of the lake draining, showing many features that we observed right after its drainage. The rate of lake level lowering during the drainage varied; initially moderately rapid while the fractures formed and accommodated the water, then exceptionally rapid as the fractures reached the bed allowing the lake to drain completely. The analysis of the GPS data suggest that the different styles of lake draining affect the vertical and horizontal movement of the ice sheet in different ways. We also anticipate that the effect of the draining of Lake Ponting was affecting the GPS sensors in a different

  16. An interesting natural phenomenon - giant rings on Lake Baikal ice

    NASA Astrophysics Data System (ADS)

    Kouraev, Alexei; Shimaraev, Michail; Remy, Frederique; Ivanov, Andrei; Golubov, Boris

    2010-05-01

    Starting from May 2009 scientific community and large public have been puzzled by the formation of giant rings on Baikal ice. These rings (diameter 5-7 km, thickness of dark layer - 1 - 1.8 km) have almost perfect circular shape what makes them so interesting and attractive not only to scientists, but also for large public. . The rings have been observed since 1999 by various satellites and sensors (AVHRR, MODIS, Landsat, SPOT) as early as 1999 but probably also in 1984 and 1994 (Shuttle missions). These rings are usually well observed in April, when snow cover is thin or absent. Rings have been observed in the southern tip of the lake (2009), and in three places in the central part: near Krestovskiy cape (1999, 2003, 2005 and 2008), near Turka (2008), and near Cape Nizhnee Izgolovye (2009). All these places are located in the region of steep bottom topography, over depths of more than 500 m. According to in situ measurements done by the Limnological Institute in Irkutsk in 2009, ice thickness is about 70 cm in the center and on the outside of the ring, and 40 cm in the ring itself. It is known that the Baikal lake has important hydrothermal activity, and there are numerous observations of gas (methane etc) seepage from its 7 km-thick layer of bottom sediments. Local-scale absence of ice cover (steamthroughs or "propariny") is typical for some places in Lake Baikal. They result from gas emissions (associated with rise of warm water), near capes and straits (due to better vertical mixing), thermal sources, outlets of large rivers. Often they are observed near Capes Big and Small Kadil'niy, and in the Olkhonskiye vorota strait. However they size ranges from just a half a meter to several hundreds of meters (but not several kilometers) and this could not be an explanation for the formation of giant rings. We present several existing hypotheses of the origin of these rings including gas emission, heat flux, cyclonic subsurface currents and mega-bubble formation due to

  17. Methane turnover and environmental change from Holocene biomarker records in a thermokarst lake in Arctic Alaska

    USGS Publications Warehouse

    Elvert, Marcus; Pohlman, John; Becker, Kevin W.; Gaglioti, Benjamin V.; Hinrichs, Kai-Uwe; Wooller, Matthew J.

    2016-01-01

    Arctic lakes and wetlands contribute a substantial amount of methane to the contemporary atmosphere, yet profound knowledge gaps remain regarding the intensity and climatic control of past methane emissions from this source. In this study, we reconstruct methane turnover and environmental conditions, including estimates of mean annual and summer temperature, from a thermokarst lake (Lake Qalluuraq) on the Arctic Coastal Plain of northern Alaska for the Holocene by using source-specific lipid biomarkers preserved in a radiocarbon-dated sediment core. Our results document a more prominent role for methane in the carbon cycle when the lake basin was an emergent fen habitat between ~12,300 and ~10,000 cal yr BP, a time period closely coinciding with the Holocene Thermal Maximum (HTM) in North Alaska. Enhanced methane turnover was stimulated by relatively warm temperatures, increased moisture, nutrient supply, and primary productivity. After ~10,000 cal yr BP, a thermokarst lake with abundant submerged mosses evolved, and through the mid-Holocene temperatures were approximately 3°C cooler. Under these conditions, organic matter decomposition was attenuated, which facilitated the accumulation of submerged mosses within a shallower Lake Qalluuraq. Reduced methane assimilation into biomass during the mid-Holocene suggests that thermokarst lakes are carbon sinks during cold periods. In the late-Holocene from ~2700 cal yr BP to the most recent time, however, temperatures and carbon deposition rose and methane oxidation intensified, indicating that more rapid organic matter decomposition and enhanced methane production could amplify climate feedback via potential methane emissions in the future.

  18. Precursory seismicity associated with frequent, large ice avalanches on Iliamna Volcano, Alaska, USA

    USGS Publications Warehouse

    Caplan-Auerbach, Jacqueline; Huggel, C.

    2007-01-01

    Since 1994, at least six major (volume>106 m3) ice and rock avalanches have occurred on Iliamna volcano, Alaska, USA. Each of the avalanches was preceded by up to 2 hours of seismicity believed to represent the initial stages of failure. Each seismic sequence begins with a series of repeating earthquakes thought to represent slip on an ice-rock interface, or between layers of ice. This stage is followed by a prolonged period of continuous ground-shaking that reflects constant slip accommodated by deformation at the glacier base. Finally the glacier fails in a large avalanche. Some of the events appear to have entrained large amounts of rock, while others comprise mostly snow and ice. Several avalanches initiated from the same source region, suggesting that this part of the volcano is particularly susceptible to failure, possibly due to the presence of nearby fumaroles. Although thermal conditions at the time of failure are not well constrained, it is likely that geothermal energy causes melting at the glacier base, promoting slip and culminating in failure. The frequent nature and predictable failure sequence of Iliamna avalanches makes the volcano an excellent laboratory for the study of ice avalanches. The prolonged nature of the seismic signal suggests that warning may one day be given for similar events occurring in populated regions.

  19. Interaction Between Lakes and Terrestrial Ecosystem Dynamics in the Yukon River Floodplain, in Interior Alaska, USA

    NASA Astrophysics Data System (ADS)

    Patil, V.; Griffith, B.; Euskirchen, E. S.

    2012-12-01

    Lakes have been decreasing in size and abundance in boreal ecosystems around the world. However, while as many as 35% of lakes in parts of interior Alaska are smaller than they were 50 years ago, up to 20% of lakes in the same regions experience large annual and intra-annual fluctuations in area (flooding), which have been linked to climate patterns via winter snowpack densities and the timing of spring thaw. Lake drying and flooding regime may influence plant community dynamics (e.g. succession), productivity, nutrient availability, and respiration, and thereby affect the carbon sink strength of boreal lake-margin wetlands. Climate change is likely to amplify drying trends and alter flooding patterns simultaneously. Predicting the future dynamics of boreal wetland complexes therefore requires quantifying the effects of flooding and drying on ecosystem processes, and the relative importance of these two mechanisms. In this study, we test the following hypotheses: 1) Both drying trends and flooding regime significantly affect lake-margin productivity, composition, and C storage by affecting soil moisture and soil nutrient concentrations, 2) frequently flooding lakes are associated with elevated soil moisture and productivity, but reduced soil carbon and nitrogen content, due to the differential influence of moisture on photosynthesis and decomposition, while drying lakes should show opposite trends. This study was conducted in the Yukon Flats National Wildlife Refuge, located 150 miles north of Fairbanks Alaska. We measured aboveground biomass, aboveground net primary productivity (ANPP), and a suite of soil characteristics within 100m of the lakeshore at 16 lakes in 2011 and 2012. Soil measurements included soil moisture, peat depth, seasonal thaw depth, total soil carbon and nitrogen, and available inorganic nitrogen. We classified lakes as drying, frequently flooding, or stable using remotely sensed measurements of long term trends as well as annual & intra

  20. Stratigraphy of Lake Vida, Antarctica: hydrologic implications of 27 m of ice

    NASA Astrophysics Data System (ADS)

    Dugan, H. A.; Doran, P. T.; Wagner, B.; Kenig, F.; Fritsen, C. H.; Arcone, S. A.; Kuhn, E.; Ostrom, N. E.; Warnock, J. P.; Murray, A. E.

    2015-03-01

    Lake Vida, located in Victoria Valley, is one of the largest lakes in the McMurdo dry valleys and is known to contain hypersaline liquid brine sealed below 16 m of freshwater ice. For the first time, Lake Vida was drilled to a depth of 27 m. Below 21 m the ice is marked by well-sorted sand layers up to 20 cm thick within a matrix of salty ice. From ice chemistry, isotopic composition of δ18O and δ2H, and ground penetrating radar profiles, we conclude that the entire 27 m of ice formed from surface runoff and the sediment layers represent the accumulation of surface deposits. Radiocarbon and optically stimulated luminescence dating limit the maximum age of the lower ice to 6300 14C yr BP. As the ice cover ablated downwards during periods of low surface inflow, progressive accumulation of sediment layers insulated and preserved the ice and brine beneath, analogous to the processes that preserve shallow ground ice. The repetition of these sediment layers reveals hydrologic variability in Victoria Valley during the mid- to late Holocene. Lake Vida is an exemplar site for understanding the preservation of subsurface brine, ice, and sediment in a cold desert environment.

  1. Semi-automated Digital Imaging and Processing System for Measuring Lake Ice Thickness

    NASA Astrophysics Data System (ADS)

    Singh, Preetpal

    Canada is home to thousands of freshwater lakes and rivers. Apart from being sources of infinite natural beauty, rivers and lakes are an important source of water, food and transportation. The northern hemisphere of Canada experiences extreme cold temperatures in the winter resulting in a freeze up of regional lakes and rivers. Frozen lakes and rivers tend to offer unique opportunities in terms of wildlife harvesting and winter transportation. Ice roads built on frozen rivers and lakes are vital supply lines for industrial operations in the remote north. Monitoring the ice freeze-up and break-up dates annually can help predict regional climatic changes. Lake ice impacts a variety of physical, ecological and economic processes. The construction and maintenance of a winter road can cost millions of dollars annually. A good understanding of ice mechanics is required to build and deem an ice road safe. A crucial factor in calculating load bearing capacity of ice sheets is the thickness of ice. Construction costs are mainly attributed to producing and maintaining a specific thickness and density of ice that can support different loads. Climate change is leading to warmer temperatures causing the ice to thin faster. At a certain point, a winter road may not be thick enough to support travel and transportation. There is considerable interest in monitoring winter road conditions given the high construction and maintenance costs involved. Remote sensing technologies such as Synthetic Aperture Radar have been successfully utilized to study the extent of ice covers and record freeze-up and break-up dates of ice on lakes and rivers across the north. Ice road builders often used Ultrasound equipment to measure ice thickness. However, an automated monitoring system, based on machine vision and image processing technology, which can measure ice thickness on lakes has not been thought of. Machine vision and image processing techniques have successfully been used in manufacturing

  2. 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.

  3. Soil Physicochemical Characteristics from Ice Wedge Polygons, Barrow, Alaska, Ver. 1

    DOE Data Explorer

    Chowdhury, Taniya; Graham, David

    2013-12-08

    This dataset provides details about soil cores (active layer and permafrost) collected from ice-wedge polygons during field expeditions to Barrow Environmental Observatory, Alaska in April, 2012 and 2013. Core information available are exact core locations; soil horizon descriptions and characteristics; and fundamental soil physico-chemical properties. In February 2016, two columns (carbon and carbon:nitrogen in soil layer) were added to the data but no existing data values changed. See documentation. The new filename is version 2. In July 2016, data for two soil cores were added. The new filename is version 3.

  4. Perennial snow and ice volumes on Iliamna Volcano, Alaska, estimated with ice radar and volume modeling

    USGS Publications Warehouse

    Trabant, Dennis C.

    1999-01-01

    The volume of four of the largest glaciers on Iliamna Volcano was estimated using the volume model developed for evaluating glacier volumes on Redoubt Volcano. The volume model is controlled by simulated valley cross sections that are constructed by fitting third-order polynomials to the shape of the valley walls exposed above the glacier surface. Critical cross sections were field checked by sounding with ice-penetrating radar during July 1998. The estimated volumes of perennial snow and glacier ice for Tuxedni, Lateral, Red, and Umbrella Glaciers are 8.6, 0.85, 4.7, and 0.60 cubic kilometers respectively. The estimated volume of snow and ice on the upper 1,000 meters of the volcano is about 1 cubic kilometer. The volume estimates are thought to have errors of no more than ?25 percent. The volumes estimated for the four largest glaciers are more than three times the total volume of snow and ice on Mount Rainier and about 82 times the total volume of snow and ice that was on Mount St. Helens before its May 18, 1980 eruption. Volcanoes mantled by substantial snow and ice covers have produced the largest and most catastrophic lahars and floods. Therefore, it is prudent to expect that, during an eruptive episode, flooding and lahars threaten all of the drainages heading on Iliamna Volcano. On the other hand, debris avalanches can happen any time. Fortunately, their influence is generally limited to the area within a few kilometers of the summit.

  5. Mapping Of Lake Ice In Northern Europe Using Dual-Polarization RadarSAT-2 Data

    NASA Astrophysics Data System (ADS)

    Hindberg, Heidi; Malnes, Erik

    2013-12-01

    In this paper, we investigate the potential of including cross-polarization data in an unsupervised classification method based on SAR data to determine ice extent over lakes in Northern Europe. By introducing cross-pol data we can increase the separability between open water and ice, and we can decrease misclassifications where open water with waves is classified as ice. Cross-pol data also helps with labelling of the classes. However, cross-pol data can decrease the separability between the classes if the ice on the lake is very thin.

  6. Measurement of lake ice thickness with a short-pulse radar system

    NASA Technical Reports Server (NTRS)

    Cooper, D. W.; Mueller, R. A.; Schertler, R. J.

    1976-01-01

    Measurements of lake ice thickness were made during March 1975 at the Straits of Mackinac by using a short-pulse radar system aboard an all-terrain vehicle. These measurements were compared with ice thicknesses determined with an auger. Over 25 sites were explored which had ice thicknesses in the range 29 to 60 cm. The maximum difference between radar and auger measurements was less than 9.8 percent. The magnitude of the error was less than + or - 3.5 cm. The NASA operating short-pulse radar system used in monitoring lake ice thickness from an aircraft is also described.

  7. The study of fresh-water lake ice using multiplexed imaging radar

    USGS Publications Warehouse

    Leonard, Bryan M.; Larson, R.W.

    1975-01-01

    The study of ice in the upper Great Lakes, both from the operational and the scientific points of view, is receiving continued attention. Quantitative and qualitative field work is being conducted to provide the needed background for accurate interpretation of remotely sensed data. The data under discussion in this paper were obtained by a side-looking multiplexed airborne radar (SLAR) supplemented with ground-truth data.Because of its ability to penetrate adverse weather, radar is an especially important instrument for monitoring ice in the upper Great Lakes. It has previously been shown that imaging radars can provide maps of ice cover in these areas. However, questions concerning both the nature of the surfaces reflecting radar energy and the interpretation of the radar imagery continually arise.Our analysis of ice in Whitefish Bay (Lake Superior) indicates that the combination of the ice/water interlace and the ice/air interface is the major contributor to the radar backscatter as seen on the imagery At these frequencies the ice has a very low relative dielectric permittivity (< 3.0) and a low loss tangent Thus, this ice is somewhat transparent to the energy used by the imaging SLAR system. The ice types studied include newly formed black ice, pancake ice, and frozen and consolidated pack and brash ice.Although ice thickness cannot be measured directly from the received signals, it is suspected that by combining the information pertaining to radar backscatter with data on the meteorological and sea-state history of the area, together with some basic ground truth, better estimates of the ice thickness may be provided. In addition, certain ice features (e.g. ridges, ice-foot formation, areas of brash ice) may be identified with reasonable confidence. There is a continued need for additional ground work to verify the validity of imaging radars for these types of interpretations.

  8. The Effects of Changing Sea Ice on Marine Mammals and Their Hunters in Northern Alaska

    NASA Astrophysics Data System (ADS)

    Huntington, H.; Quakenbush, L.; Nelson, M.

    2015-12-01

    Marine mammals are important sources of food for indigenous residents of northern Alaska. Changing sea ice patterns affect the animals themselves as well as access by hunters. Documenting the traditional knowledge of Iñupiaq and Yupik hunters concerning marine mammals and sea ice makes accessible a wide range of information and insight relevant to ecological understanding, conservation action, and the regulation of human activity. We interviewed hunters in villages from northern Bering Sea to the Beaufort Sea, focusing on bowhead whales, walrus, and ice seals. Hunters reported extensive changes in sea ice, with resulting effects on the timing of marine mammal migrations, the distribution and behavior of the animals, and the efficacy of certain hunting methods, for example the difficulty of finding ice thick enough to support a bowhead whale for butchering. At the same time, hunters acknowledged impacts and potential impacts from changing technology such as more powerful outboard engines and from industrial activity such as shipping and oil and gas development. Hunters have been able to adapt to some changes, for example by hunting bowhead whales in fall as well as spring on St. Lawrence Island, or by focusing their hunt in a shorter period in Nuiqsut to accommodate work schedules and worse weather. Other changes, such as reduced availability of ice seals due to rapid retreat of pack ice after spring break-up, continue to defy easy responses. Continued environmental changes, increased disturbance from human activity, and the introduction of new regulations for hunting may further challenge the ability of hunters to provide food as they have done to date, though innovation and flexibility may also provide new sources of adaptation.

  9. Patterns and rates of riverbank erosion involving ice-rich permafrost (yedoma) in northern Alaska

    NASA Astrophysics Data System (ADS)

    Kanevskiy, Mikhail; Shur, Yuri; Strauss, Jens; Jorgenson, Torre; Fortier, Daniel; Stephani, Eva; Vasiliev, Alexander

    2016-01-01

    Yedoma, a suite of syngenetically frozen silty ice- and organic-rich deposits with large ice wedges that accumulated during the late Pleistocene, is vulnerable to thermal degradation and erosion because of the extremely high ice contents. This degradation can result in significant surface subsidence and retreat of coastal bluffs and riverbanks with large consequences to landscape evolution, infrastructure damage, and water quality. We used remote sensing and field observations to assess patterns and rates of riverbank erosion at a 35-m-high active yedoma bluff along the Itkillik River in northern Alaska. The total volumetric ground-ice content-including wedge, segregated, and pore ice-was estimated to be ~ 86%. The process of riverbank erosion and stabilization include three main stages typical of the areas with ice-rich permafrost: (1) thermal erosion combined with thermal denudation, (2) thermal denudation, and (3) slope stabilization. Active riverbank erosion at the main study site started in July 1995, when the Itkillik River changed its channel. The total retreat of the riverbank during 1995-2010 within different segments of the bluff varied from 180 to 280 m; the average retreat rate for the most actively eroded part of the riverbank was almost 19 m/y. From August 2007 to August 2011, the total retreat varied from 10 to almost 100 m. The average retreat rate for the whole 680-m-long bluff was 11 m/y. For the most actively eroded central part of the bluff (150 m long) it was 20 m/y, ranging from 16 to 24 m/y. More than 180,000 m3 of ground ice and organic-rich frozen soil, or almost 70,000 metric tons (t) of soil solids including 880 t of organic carbon, were transported to the river from the retreating bank annually. This study reports the highest long-term rates of riverbank erosion ever observed in permafrost regions of Eurasia and North America.

  10. Lake

    ERIC Educational Resources Information Center

    Wien, Carol Anne

    2008-01-01

    The lake is blue black and deep. It is a glaciated finger lake, clawed out of rock when ice retracted across Nova Scotia in a northerly direction during the last ice age. The lake is narrow, a little over a mile long, and deep, 90 to 190 feet in places according to local lore, off the charts in others. The author loves to swim there, with a sense…

  11. Ice Cover as a Factor Driving Microbial Community Structure in the Laurentian Great Lakes

    NASA Astrophysics Data System (ADS)

    McKay, R. M.; Beall, B.; Oyserman, B.; Smith, D.; Bullerjahn, G.; Morris, P.; Twiss, M. R.

    2013-12-01

    Lakes serve as rapid responding sentinels of human influence on the natural environment rendering them powerful tools to advance our understanding of a changing climate on microbial community structure and function. Whereas we possess a baseline knowledge of microbial diversity in the Great Lakes, we know little about how these communities respond to the manifestations of climate change. Through collaboration with U.S.- and Canadian Coast Guards, winter surveys have been conducted on Lake Erie since 2007. The surveys have captured extremes in ice extent ranging from expansive ice cover through 2011 to nearly ice-free waters in winter 2012, a condition driven by a warm positive Arctic Oscillation. We showed that dramatic changes in annual ice cover were accompanied by equally dramatic shifts in phytoplankton community structure. Expansive ice cover documented for Lake Erie in winters 2010 and 2011 supported ice-associated phytoplankton blooms dominated by physiologically robust, filamentous centric diatoms. Transcriptomic analysis of the winter bloom offers insights into the success of this psychrophilic community. By comparison, ice free conditions promoted the growth of small-sized cells supported by analysis of size-fractionated chlorophyll a and flow cytometry. The phytoplankton community in winter 2013 was dominated by microplankton-sized filamentous diatoms, coincident with expansive ice cover and thus returning to the size structure of the 2010 and 2011 communities. Reduced size is recognized as a universal ecological response to global warming in aquatic systems although it usually marks a response to climate warming over multiple years, not a single season as reported here. Fig. 1. Winter surveys conducted on Lake Erie over two years demonstrated tight coupling between microplankton Chl a biomass and total Chl a during winter 2010-11 (purple, green), a year of expansive ice cover. A warm positive Arctic Oscillation resulted in negligible ice cover on Lake

  12. Potential methane emission from north-temperate lakes following ice melt

    USGS Publications Warehouse

    Michmerhuizen, C.M.; Striegl, R.G.; McDonald, M.E.

    1996-01-01

    Methane, a radiatively active 'greenhouse' gas, is emitted from lakes to the atmosphere throughout the open-water season. However, annual lake CH4 emissions calculated solely from open-water measurements that exclude the time of spring ice melt may substantially underestimate the lake CH4 source strength. We estimated potential spring CH4 emission at the time of ice melt for 19 lakes in northern Minnesota and Wisconsin. Lakes ranged in area from 2.7 to 57,300 ha and varied in littoral zone sediment type. Regression analyses indicated that lake area explained 38% of the variance in potential CH4 emission for relatively undisturbed lakes; as lake area increases potential CH4 emission per unit area decreases. Inclusion of a second term accounting for the presence or absence of soft organic-rich littoral-zone sediments explained 83% of the variance in potential spring CH4 emission. Total estimated spring CH4 emission for 1993 for all Minnesota lakes north of 45?? with areas ???4 ha was 1.5 x 108 mol CH4 assuming a 1 : 1 ratio of soft littoral sediment to hard littoral sediment lakes. Emission estimates ranged from 5.3 x 107 tool assuming no lakes have soft organic-rich littoral sediments to 4.5 x 108 mol assuming all lakes have soft organic-rich littoral sediments. This spring CH4 pulse may make up as much as 40% of the CH4 annually emitted to the atmosphere by small lakes.

  13. Evidence of deep circulation in two perennially ice-covered Antarctic lakes

    USGS Publications Warehouse

    Tyler, S.W.; Cook, P.G.; Butt, A.Z.; Thomas, J.M.; Doran, P.T.; Lyons, W.B.

    1998-01-01

    The perennial ice covers found on many of the lakes in the McMurdo Dry Valley region of the Antarctic have been postulated to severely limit mixing and convective turnover of these unique lakes. In this work, we utilize chlorofluorocarbon (CFC) concentration profiles from Lakes Hoare and Fryxell in the McMurdo Dry Valley to determine the extent of deep vertical mixing occurring over the last 50 years. Near the ice-water interface, CFC concentrations in both lakes were well above saturation, in accordance with atmospheric gas supersaturations resulting from freezing under the perennial ice covers. Evidence of mixing throughout the water column at Lake Hoare was confirmed by the presence of CFCs throughout the water column and suggests vertical mixing times of 20-30 years. In Lake Fryxell, CFC-11, CFC-12, and CFC-113 were found in the upper water column; however, degradation of CFC-11 and CFC-12 in the anoxic bottom waters appears to be occurring with CFC-113 only present in these bottom waters. The presence of CFC-113 in the bottom waters, in conjunction with previous work detecting tritium in these waters, strongly argues for the presence of convective mixing in Lake Fryxell. The evidence for deep mixing in these lakes may be an important, yet overlooked, phenomenon in the limnology of perennially ice-covered lakes.

  14. Glacial Lake Musselshell: Late Wisconsin slackwater on the Laurentide ice margin in central Montana, USA

    USGS Publications Warehouse

    Davis, N.K.; Locke, W. W.; Pierce, K.L.; Finkel, R.C.

    2006-01-01

    Cosmogenic surface exposure ages of glacial boulders deposited in ice-marginal Lake Musselshell suggest that the lake existed between 20 and 11.5 ka during the Late Wisconsin glacial stage (MIS 2), rather than during the Late Illinoian stage (MIS 6) as traditionally thought. The altitude of the highest ice-rafted boulders and the lowest passes on the modern divide indicate that glacial lake water in the Musselshell River basin reached at least 920-930 m above sea level and generally remained below 940 m. Exposures of rhythmically bedded silt and fine sand indicate that Lake Musselshell is best described as a slackwater system, in which the ice-dammed Missouri and Musselshell Rivers rose and fell progressively throughout the existence of the lake rather than establishing a lake surface with a stable elevation. The absence of varves, deltas and shorelines also implies an unstable lake. The changing volume of the lake implies that the Laurentide ice sheet was not stable at its southernmost position in central Montana. A continuous sequence of alternating slackwater lake sediment and lacustrine sheetflood deposits indicates that at least three advances of the Laurentide ice sheet occurred in central Montana between 20 and 11.5 ka. Between each advance, it appears that Lake Musselshell drained to the north and formed two outlet channels that are now occupied by extremely underfit streams. A third outlet formed when the water in Lake Musselshell fully breached the Larb Hills, resulting in the final drainage of the lake. The channel through the Larb Hills is now occupied by the Missouri River, implying that the present Missouri River channel east of the Musselshell River confluence was not created until the Late Wisconsin, possibly as late as 11.5 ka. ?? 2005 Elsevier B.V. All rights reserved.

  15. Tracing the Complex Ice Cover Evolution of Lake Vida, Antarctica Through Noble Gases

    NASA Astrophysics Data System (ADS)

    Malone, J. L.; Castro, M. C.; Hall, C. M.; Doran, P. T.; Kenig, F.; McKay, C. P.

    2008-12-01

    Unlike other lakes in the McMurdo Dry Valleys in Antarctica, Lake Vida has a very thick (~19 m) ice cover and a liquid brine body of unusually high salinity (~245 g/L). Because noble gases (He, Ne, Ar, Kr and Xe) are conservative in nature, they can be used to understand physical processes taking place during ice formation (e.g., partitioning of noble gases between the ice and residual liquid, bubble formation at the ice-liquid interface) thus, providing information with respect to the temporal evolution of the dry valley lakes. In an attempt to constrain the conditions under which the atypical Lake Vida ice cover formed and evolved, we collected 19 ice samples along a vertical profile from the surface down to a depth of ~14 m as well as three liquid brine samples from briny ice at a depth of ~16 m for analysis of all noble gases. Our results show that the broad pattern of noble gas concentrations for the Lake Vida ice cover and associated brines is fundamentally different from that expected for air saturated water (ASW). Overall, ice samples are relatively enriched in He, slightly depleted in Ne, and strongly depleted in the heavier noble gases (Ar, Kr, Xe) with respect to ASW. By contrast, brine samples are very enriched in heavy noble gases. To understand the mechanisms responsible for the observed noble gas distribution and fractionation in the Lake Vida cover, a conceptual three-phase (ice, brine, bubbles) partition model was tested. The model allows the lighter noble gases (He and Ne) to reside interstitially in ice while Ar, Kr, and Xe are totally excluded, causing supersaturation in the residual liquid as freezing progresses and formation of gas bubbles occurs at the ice-liquid interface. These bubbles are subsequently incorporated into the ice. While the general noble gas enrichment and depletion patterns of the model are consistent with our brine and ice data, quantitative agreement with output values is not as good under similar model conditions (e

  16. Overseas trip report, CV 990 underflight mission. [Norwegian Sea, Greenland ice sheet, and Alaska

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Crawford, J.; Hardis, L.

    1980-01-01

    The scanning microwave radiometer-7 simulator, the ocean temperature scanner, and an imaging scatterometer/altimeter operating at 14 GHz were carried onboard the NASA CV-990 over open oceans, sea ice, and continental ice sheets to gather surface truth information. Data flights were conducted over the Norwegian Sea to map the ocean polar front south and west of Bear Island and to transect several Nimbus-7 footprints in a rectangular pattern parallel to the northern shoreline of Norway. Additional flights were conducted to obtain correlative data on the cryosphere parameters and characteristics of the Greenland ice sheet, and study the frozen lakes near Barrow. The weather conditions and flight path way points for each of the nineteen flights are presented in tables and maps.

  17. 1,500-Year Cycle in Holocene Climate from Burial Lake, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Finkenbinder, M. S.; Abbott, M. B.; Dorfman, J. M.; Finney, B.; Stoner, J. S.

    2014-12-01

    Millennial-scale fluctuations in climate conditions are commonly observed in Holocene paleoclimate archives, however the meaning of these variations including whether they might arise from internal or external forcing are still actively debated. Proxy evidence of millennial-scale variability is most clearly present in a few specific parts of the world (e.g. North Atlantic region), whereas a lack of evidence from many other regions may result from a lack of observations or a lack of signal. Here we present the first evidence for such variations in Arctic Alaska using sedimentological and geochemical analyses from Burial Lake (68.43°N, 159.17°W; 460 m above sea level) in the western Brooks Range. We measured biogenic silica (BSi), total organic carbon, total nitrogen, C/N ratios, dry bulk density, magnetic susceptibility and magnetic remanence measurements, and elemental abundances from scanning XRF and use radiocarbon dating on terrestrial macrofossils to establish age control. Large fluctuations in biogenic silica and related proxies at millennial time scales over the last 10,000 cal yr BP are attributed to changes in aquatic productivity, which is indirectly mediated by climate through changes in the duration of the ice-free growing season and the availability of limiting nutrients. Spectral and wavelet analysis of the BSi record indicates a significant 1,500-yr cycle (above 95% confidence) emerges by ~6,000 cal yr BP. Comparison of BSi with reconstructed total solar irradiance reveals a low correlation (r2 = 0.01), suggesting no direct solar forcing of aquatic productivity. A comparison with Northern Hemisphere wide records shows no consistent phase relationship between the timing of maxima/minima in our BSi record. These results are consistent with previous work showing a strong middle Holocene transition into a ~1500-yr cycle. Similar timing for the emergence of an ~1500-yr cycle are found in proxies sensitive to thermohaline circulation and deep water

  18. Evidence of recent changes in the ice regime of lakes in the Canadian High Arctic from spaceborne satellite observations

    NASA Astrophysics Data System (ADS)

    Surdu, Cristina M.; Duguay, Claude R.; Fernández Prieto, Diego

    2016-05-01

    Arctic lakes, through their ice cover phenology, are a key indicator of climatic changes that the high-latitude environment is experiencing. In the case of lakes in the Canadian Arctic Archipelago (CAA), many of which are ice covered more than 10 months per year, warmer temperatures could result in ice regime shifts. Within the dominant polar-desert environment, small local warmer areas have been identified. These relatively small regions - polar oases - with longer growing seasons and greater biological productivity and diversity are secluded from the surrounding barren polar desert. The ice regimes of 11 lakes located in both polar-desert and polar-oasis environments, with surface areas between 4 and 542 km2, many of unknown bathymetry, were documented. In order to investigate the response of ice cover of lakes in the CAA to climate conditions during recent years, a 15-year time series (1997-2011) of RADARSAT-1/2 ScanSAR Wide Swath, ASAR Wide Swath, and Landsat acquisitions were analyzed. Results show that melt onset occurred earlier for all observed lakes. With the exception of Lower Murray Lake, all lakes experienced earlier summer ice minimum and water-clear-of-ice (WCI) dates, with greater changes being observed for polar-oasis lakes (9-24 days earlier WCI dates for lakes located in polar oases and 2-20 days earlier WCI dates for polar-desert lakes). Additionally, results suggest that some lakes may be transitioning from a perennial/multiyear to a seasonal ice regime, with only a few lakes maintaining a multiyear ice cover on occasional years. Aside Lake Hazen and Murray Lakes, which preserved their ice cover during the summer of 2009, no residual ice was observed on any of the other lakes from 2007 to 2011.

  19. Trends in ice formation at Lake Neusiedl since 1931 and large-scale oscillation patterns

    NASA Astrophysics Data System (ADS)

    Soja, Anna-Maria; Maracek, Karl; Soja, Gerhard

    2013-04-01

    Ice formation at Lake Neusiedl (Neusiedler See, Fertitó), a shallow steppe lake (area 320 km2, mean depth 1.2 m) at the border of Austria/Hungary, is of ecological and economic importance. Ice sailing and skating help to keep a touristic off-season alive. Reed harvest to maintain the ecological function of the reed belt (178 km2) is facilitated when lake surface is frozen. Changes in ice formation were analysed in the frame of the EULAKES-project (European Lakes under Environmental Stressors, www.eulakes.eu), financed by the Central Europe Programme of the EU. Data records of ice-on, ice duration and ice-off at Lake Neusiedl starting with the year 1931, and air temperature (nearby monitoring station Eisenstadt - Sopron (HISTALP database and ZAMG)) were used to investigate nearly 80 winters. Additionally, influences of 8 teleconnection patterns, i.e. the Atlantic Multidecadal Oscillation (AMO), the East Atlantic pattern (EAP), the East Atlantic/West Russia pattern (EA/WR), the Eastern Mediterranean Pattern (EMP), the Mediterranean Oscillation (MO) for Algiers and Cairo, and for Israel and Gibraltar, resp., the North Atlantic Oscillation (NAO) and the Scandinavia pattern (SCA) were assessed. Ice cover of Lake Neusiedl showed a high variability between the years (mean duration 71±27 days). Significant trends for later ice-on (p=0.02), shorter ice duration (p=0.07) and earlier ice-off (p=0.02) for the period 1931-2011 were found by regression analysis and trend analysis tests. On an average, freezing of Lake Neusiedl started 2 days later per decade and ice melting began 2 days earlier per decade. Close relationships between mean air temperature and ice formation could be found: ice-on showed a dependency on summer (R=+0.28) and autumn air temperatures (R=+0.51), ice duration and ice off was related to autumn (R=-0.36 and -0.24), winter (R=-0.73 and -0.61) and concurrent spring air temperatures (R=-0.44). Increases of air temperature by 1° C caused an 8.4 days later

  20. Analysis of the variability of ice phenology on Great Bear Lake and Great Slave Lake, 2002-2009, from AMSR-E measurements

    NASA Astrophysics Data System (ADS)

    Kang, K.; Duguay, C. R.; Howell, S.

    2009-12-01

    Lake ice cover is a significant component of the Canadian terrestrial cryosphere. It is both a sensitive indicator of climate conditions and it plays a significant role in the energy and water balance of northern regions. Knowledge about the temporal and spatial variability of ice phenology (ice-on/ice-off dates and ice duration) is critical for improving our understanding of surface-atmosphere interactions at high latitudes within the context of a changing climate. Remote sensing in the most viable tool for obtaining frequent observations of ice cover conditions over large lakes and across large areas of the North. Obtaining ice phenological parameters with optical satellite sensors such as MODIS and AVHRR is difficult, especially during the freeze-up period due to polar darkness and extensive cloud cover. However, passive microwave satellite remote sensing can provide regular and weather-independent information on ice phenology over large northern lakes such Great Bear Lake (GBL) and Great Slave Lake (GSL), Northwest Territories, Canada. In this paper, the temporal evolution of brightness temperature at 18.7, 23.5, and 36.5 GHz from AMSR-E passive microwave measurements is analyzed to determine freeze-onset/melt-onset, ice-on/ice-off, and ice cover duration on GBL and GSL. In order to examine the interannual variability in ice cover on the two lakes, the polarization difference and horizontal polarized brightness temperature at various frequencies are explored to derive ice phenological parameters for ice seasons 2002-2003 to 2008-2009. Preliminary results show a difference of approximately two to four weeks in ice-on/ice-off dates between cold and warm winters. Passive microwave is shown to be an effective means for monitoring lake ice phenology and could, in part, replace the lost ground-based observational ice network for GBL and GSL.

  1. Insights into supraglacial lake evolution on the Larsen-B ice shelf

    NASA Astrophysics Data System (ADS)

    Leeson, A.; Shepherd, A.; Gilbert, L.; Ligtenberg, S.; van den Broeke, M.

    2015-12-01

    The Larsen-B ice shelf was the second largest component of the Larsen ice shelf system in the Antarctic Peninsula. It collapsed in 2002, losing an area more than double the size of London (~3200 km2) to the sea. The collapse of Larsen-B has been attributed to a range of factors, although the dominant control over the fidelity of the ice shelf is thought to be climatological (melting on the ice shelf was three times higher in 2002 than the 1998-2001 average). Supraglacial lakes in particular have been implicated in the collapse; by repeatedly filling and draining, they likely weaken an ice shelf and precondition it for disintegration. However, abundant supraglacial lake coverage has been observed on Larsen-B for many years prior to its break-up and, in fact, surface conditions have been conducive to lake formation for several decades. Here, we use satellite observations and a hydrological model forced with estimates of melting and runoff from a regional climate model in order to investigate the response of supraglacial lakes to extreme melting in 2002 specifically, in contrast with typical supraglacial lake evolution in previous years. We also use state-of-the-art observations of ice shelf topography acquired by CryoSat-2 to examine the potential role of supraglacial lakes on the fate of the Larsen remnant, currently thought to be at risk of collapse by 2020.

  2. Characteristics and indications of hydrogen and oxygen isotopes distribution in lake ice body.

    PubMed

    Zhen, Zhi-Lei; Li, Chang-You; Zhang, Sheng; Li, Wen-Bao; Shi, Xiao-Hong; Sun, Biao

    2015-01-01

    Stable isotopes have been used to identify the characteristics of precipitation, evaporation, basin hydrology, and residence times. However, lakes in the cold regions are usually covered by ice for 5-6 months. To get a better understanding of stable isotopes characteristics and indications in lake ice bodies, ice and water were sampled during the icebound season in both the ice and water bodies in Dali Lake, and deuterium, oxygen-18 total nitrogen (TN), and the major ions were analyzed. The results showed that deuterium and oxygen-18 compositions (δD-δ¹⁸O) compositions in the ice body were greater than in the water body beneath, scattered on a straight line, and deviating downward from the global meteoric water line in the top right. The ice profile showed that the δD-δ¹⁸O compositions increased from the ice surface downward and decreased near to the bottom. In contrast, the TN and the major ions in the ice decreased from the ice surface downward and increased near to the bottom, meaning that the concentrations of δ¹⁸O had a negative correlation with the concentrations of TN and major ions. These indicated that stable isotopes can be used for tracing the nutriment and ion transport processes in the ice body.

  3. Connecting Indigenous Knowledge to Thaw Lake Cycle Research on the Arctic Coastal Plain of Alaska

    NASA Astrophysics Data System (ADS)

    Eisner, W. R.; Cuomo, C. J.; Hinkel, K. M.; Jones, B. M.; Hurd, J.

    2005-12-01

    Thaw lakes cover about 20% of the Arctic Coastal Plain of Alaska. Another 26% is scarred by basins that form when lakes drain, and these drained thaw-lake basins are sites for preferential carbon accumulation as plant biomass. Recent studies in the continuous permafrost zone of Western Siberia suggest that lakes have been expanding in the past several decades in response to regional warming. Anticipated regional warming would likely mobilize sequestered soil organic carbon, resulting in the emission of CO2 and CH4. Our understanding of the processes leading to thaw lake formation, expansion, and drainage in northern Alaska has been limited because models are specific to the flat, young Outer (seaward) Coastal Plain comprising 1/3 of the region. Furthermore, spatial and temporal analysis of lake dynamics is largely restricted to the period since 1948, when aerial photographs first became available across large regions of the Coastal Plain. In order to fill these gaps, we have been interviewing Iñupiaq elders, hunters, and berry pickers from the villages of Atqasuk and Barrow. The objective of these interviews is to obtain accounts of lake formation, expansion and drainage that have occurred within living or oral memory, and extend the record back several generations. To date, we have interviewed fifteen Iñupiat; most of these are people who travel the tundra frequently and have done so for decades. They have first-hand experience of lake drainage, sea cliff and river bank erosion, permafrost degradation, and other landscape changes. Many informants expressed concern that landscape changes are occurring at an increasingly rapid rate. They have identified lakes that have drained, areas where the permafrost is thawing, and places where the sea and river coastline is eroding. We have been able to corroborate reports of lake drainage from our informants with a series of aerial photographs, satellite images, and radiocarbon dates. In many instances, the elders have

  4. ALBEDO MODELS FOR SNOW AND ICE ON A FRESHWATER LAKE. (R824801)

    EPA Science Inventory

    Abstract

    Snow and ice albedo measurements were taken over a freshwater lake in Minnesota for three months during the winter of 1996¯1997 for use in a winter lake water quality model. The mean albedo of new snow was measured as 0.83±0.028, while the...

  5. SIMULATED CLIMATE CHANGE EFFECTS ON DISSOLVED OXYGEN CHARACTERISTICS IN ICE-COVERED LAKES. (R824801)

    EPA Science Inventory

    A deterministic, one-dimensional model is presented which simulates daily dissolved oxygen (DO) profiles and associated water temperatures, ice covers and snow covers for dimictic and polymictic lakes of the temperate zone. The lake parameters required as model input are surface ...

  6. Great Lakes Ice Cover Classification and Mapping Using Satellite Synthetic Aperture Radar (SAR) Data

    NASA Technical Reports Server (NTRS)

    Nghiem, S.; Leshkevich, G.; Kwok, R.

    1998-01-01

    Owing to the size and extent of the Great Lakes and the variety of ice types features found there, the timely and objective qualities inherent in computer processing of satellite data make it well suited for monitoring and mapping ice cover.

  7. The geomorphology of Patagonian ice dammed lake basins: Insights from remote sensing of a modern lake and reconstruction of a Late Quaternary lake drainage event

    NASA Astrophysics Data System (ADS)

    Thorndycraft, Varyl

    2016-04-01

    The geomorphology of ice dammed lake basins can be complex due to geomorphic responses to multiple base level changes from repeated filling and emptying, as well as the potential for catastrophic drainage events. Refining landscape models of Quaternary ice dammed palaeolake systems has the potential to improve our understanding of glacier and meltwater dynamics during deglaciation phases. In this poster two case studies are presented to shed light on the range of geomorphic processes exhibited within ice dammed lake basins. Using Google Earth Pro and repeat LANDSAT imagery the geomorphology resulting from multiple base level changes of an ice dammed lake of the Viedma Glacier (Southern Patagonia Icefield) is presented. The LANDSAT imagery shows transgressive lake phases inundating already formed delta and terrace surfaces, whilst the high resolution Google Earth Pro images reveal a complex suite of incised terrace levels developed on the valley floor following lake drainage events. Secondly, the impact of catastrophic drainage of the Late Pleistocene Palaeolake Cochrane (Northern Patagonia Icefield) is investigated through geomorphological mapping. Here an outburst flood and rapid lowering of the lake has led to large scale eddy scouring of glacio-lacustrine sediments, with scarp slopes of ca. 30-40 m in height, and the formation of boulder bars during the final stages of lake fall. The implications of the mapping for interpretations of Late Quaternary palaeolake sediment-landform assemblages and rates of landscape change are discussed.

  8. Simultaneous observations of ice motion, calving and seismicity on the Yahtse Glacier, Alaska. (Invited)

    NASA Astrophysics Data System (ADS)

    Larsen, C. F.; Bartholomaus, T. C.; O'Neel, S.; West, M. E.

    2010-12-01

    We observe ice motion, calving and seismicity simultaneously and with high-resolution on an advancing tidewater glacier in Icy Bay, Alaska. Icy Bay’s tidewater glaciers dominate regional glacier-generated seismicity in Alaska. Yahtse emanates from the St. Elias Range near the Bering-Bagley-Seward-Malaspina Icefield system, the most extensive glacier cover outside the polar regions. Rapid rates of change and fast flow (>16 m/d near the terminus) at Yahtse Glacier provide a direct analog to the disintegrating outlet systems in Greenland. Our field experiment co-locates GPS and seismometers on the surface of the glacier, with a greater network of bedrock seismometers surrounding the glacier. Time-lapse photogrammetry, fjord wave height sensors, and optical survey methods monitor iceberg calving and ice velocity near the terminus. This suite of geophysical instrumentation enables us to characterize glacier motion and geometry changes while concurrently listening for seismic energy release. We are performing a close examination of calving as a seismic source, and the associated mechanisms of energy transfer to seismic waves. Detailed observations of ice motion (GPS and optical surveying), glacier geometry and iceberg calving (direct observations and timelapse photogrammetry) have been made in concert with a passive seismic network. Combined, the observations form the basis of a rigorous analysis exploring the relationship between glacier-generated seismic events and motion, glacier-fiord interactions, calving and hydraulics. Our work is designed to demonstrate the applicability and utility of seismology to study the impact of climate forcing on calving glaciers.

  9. Patterns and Potential Drivers of a Seasonal Glacial Sediment Plume derived from Landsat CDR Data, Lake Clark, Alaska

    NASA Astrophysics Data System (ADS)

    Baughman, C. A.; Jones, B. M.; Bartz, K. K.; Young, D. B.; Zimmerman, C. E.

    2015-12-01

    Lake Clark is large freshwater lake in Southcentral Alaska. Central to Lake Clark National Park and Preserve, Lake Clark is an important nursery lake for sockeye salmon (Oncorhynchus nerka) in the headwaters of Bristol Bay, Alaska, the most productive wild salmon fishery in the world. Lake Clark water clarity is seasonally influenced by a dynamic glacier fed sediment plume. We reconstructed lake-wide water clarity for Lake Clark using the Landsat TM and ETM+ Climate Data Record archive. Our study period consisted of May - October for 1985-2015. We found 151 (98 partial- and 53 whole-lake) Landsat scenes that captured the lake and/or sediment plume. Water clarity fluctuated on an annual basis with specific conditions common to certain months. Plume development and peak turbidity dates could be estimated for a number of years and mid-season gyres appear to represent wind-induced mixing of lake water. Our results showed short term (sub-decadal) trends in water clarity but little to no long term trend between 1991 and 2014. We did, however, detect interannual variation that exhibited a non-significant (r2 = 0.20) but positive correlation (r = 0.20) with regional mean summer air temperature and found the month of May exhibited a significant positive trend (r2 = 0.68, p-value = 0.02) in turbidity between 2000 and 2014. These results are important because reductions in water clarity within Alaska lake systems as a result of increased glacial runoff have been shown to reduce salmon production via reduced abundance of preferred prey items of juvenile salmon, such as zooplankton and macroinvertebrates.

  10. Basal ice flow regime influenced by glacial lake formation in Rhonegletscher, Switzerland

    NASA Astrophysics Data System (ADS)

    Nishimura, D.; Tsutaki, S.; Sugiyama, S.

    2010-12-01

    After the retreat of glacier terminus over a bedrock bump, a glacial lake has formed in front of Rhonegletscher, Switzerland. It is suspected that ice flow regime is now significantly influenced by the lake water. To investigate the impact of lake formation on glacier dynamics, we carried out surface and borehole observations in the terminus region of Rhonegletscher. In 2008 and 2009 summer seasons, we drilled more than 20 boreholes to measure borehole deformation by repeated inclinometry. Ice surface speed was measured by surveying stakes installed nearby the boreholes. We used a borehole televiewer to measure basal sliding speed by tracking stones and markers at the bottom of the boreholes. We also measured basal sediment layer thickness by hammering a penetrometer at the bottom of the boreholes. Our measurements showed clear decrease in the ice deformation rate near the lake (Fig. 1). Ice deformation accounted for 60-80% in the upper part of our study site (e.g. boreholes 1 and 5), whereas it is less than 10% near the lake (e.g. boreholes 7, 10 and 11). This result suggests that the basal ice flow near the lake is enhanced by the lake water. According to the basal sliding speed measurement in borehole 2, sliding accounted for less than 10% of basal flow speed from 2 to 31 August 2009. Deformation of a subglacial sediment layer is thus important in this region. The penetrometer measurement confirmed that the study site is underlain by a subglacial sediment layer whose thickness was in a range of 0-70 m. Fig.1 Terminus of Rhonegletscher and proglacial lakes indicated by the shaded areas. The columns show ice surface and deformation speeds measured at each borehole site from 9 July to 5 September in 2009. Ice deformation speed was negligibly small at boreholes 7, 10, and 11. Surface contour spacing is 20 m.

  11. Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

    USGS Publications Warehouse

    Schiff, C.J.; Kaufman, D.S.; Wallace, K.L.; Werner, A.; Ku, T.-L.; Brown, T.A.

    2008-01-01

    A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS 14C ages, along with the 137Cs and 210Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of the core, and to determine the age of each tephra deposit. The selected age model is based on a mixed-effect regression that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages ??105 yr (95% confidence intervals). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7/500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of one every 130 yr. ?? 2007 Elsevier Ltd. All rights reserved.

  12. Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

    SciTech Connect

    Schiff, C J; Kaufman, D S; Wallace, K L; Werner, A; Ku, T L; Brown, T A

    2007-02-25

    A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS {sup 14}C ages, along with the {sup 137}Cs and {sup 210}Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of sediment, and to determine the age of each tephra deposit. The age model is based on a cubic smooth spline function that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages {+-} 105 yr (1{sigma}). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7 per 500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of once every 130 yr.

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

    USGS Publications Warehouse

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

    2013-01-01

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

  14. Towards automated mapping of lake ice using RADARSAT-2 and simulated RCM compact polarimetric data

    NASA Astrophysics Data System (ADS)

    Duguay, Claude

    2016-04-01

    The Canadian Ice Service (CIS) produces a weekly ice fraction product (a text file with a single lake-wide ice fraction value, in tenth, estimated for about 140 large lakes across Canada and northern United States) created from the visual interpretation of RADARSAT-2 ScanSAR dual-polarization (HH and HV) imagery, complemented by optical satellite imagery (AVHRR, MODIS and VIIRS). The weekly ice product is generated in support of the Canadian Meteorological Centre (CMC) needs for lake ice coverage in their operational numerical weather prediction model. CIS is interested in moving from its current (manual) way of generating the ice fraction product to a largely automated process. With support from the Canadian Space Agency, a project was recently initiated to assess the potential of polarimetric SAR data for lake ice cover mapping in light of the upcoming RADARSAT Constellation Mission (to be launched in 2018). The main objectives of the project are to evaluate: 1) state-of-the-art image segmentation algorithms and 2) RADARSAT-2 polarimetric and simulated RADARSAT Constellation Mission (RCM) compact polarimetric SAR data for ice/open water discrimination. The goal is to identify the best segmentation algorithm and non-polarimetric/polarimetric parameters for automated lake ice monitoring at CIS. In this talk, we will present the background and context of the study as well as initial results from the analysis of RADARSAT-2 Standard Quad-Pol data acquired during the break-up and freeze-up periods of 2015 on Great Bear Lake, Northwest Territories.

  15. Measured Hydrologic Storage Characteristics of Three Major Ice Wedge Polygon Types, Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Chamberlain, A. J.; Liljedahl, A.; Wilson, C. J.; Cable, W.; Romanovsky, V. E.

    2014-12-01

    Model simulations have suggested that the hydrologic fluxes and stores of Arctic wetlands are constrained by the micro-topographical features of ice wedge polygons, which are abundant in lowland tundra landscapes. Recently observed changes in ice wedge polygon landscapes - in particular, ice wedge degradation and trough formation - emphasize the need to better understand how differing ice wedge polygon morphologies affect the larger hydrologic system. Here we present three seasons of measured end-of-winter snow accumulation, continuous soil moisture and water table elevations, and repeated frost table mapping. Together, these describe the hydrologic characteristics of three main ice wedge polygon types: low centered polygons with limited trough development (representative of a ~500 year old vegetated drained thaw lake basin), and low- and high-centered polygons with well-defined troughs. Dramatic spatiotemporal variability exists both between polygon types and between the features of an individual polygon (e.g. troughs, centers, rims). Landscape-scale end-of-winter snow water equivalent is similar between polygon types, while the sub-polygon scale distribution of the surface water differs, both as snow and as ponded water. Some sub-polygon features appear buffered against large variations in water levels, while others display periods of prolonged recessions and large responses to rain events. Frost table elevations in general mimic the ground surface topography, but with spatiotemporal variability in thaw rate. The studied thaw seasons represented above long-term average rainfall, and in 2014, record high June precipitation. Differing ice wedge polygon types express dramatically different local hydrology, despite nearly identical climate forcing and landscape-scale snow accumulation, making ice wedge polygons an important component when describing the Arctic water, nutrient and energy system.

  16. Water-quality data of lakes and wetlands in the Yukon Flats, Alaska, 2007–2009

    USGS Publications Warehouse

    Halm, Douglas R.; Guldager, Nikki

    2013-01-01

    Over a three-year period (2007–2009), in-situ measurements were taken and water-quality samples were collected from 111 lakes and wetlands located in the Yukon Flats, Alaska, during a U.S. Fish and Wildlife Service wetlands inventory. The U.S. Geological Survey performed the chemical analyses on the retrieved water-quality samples. Results from the analyses of water samples for dissolved carbon gases and carbon isotopes, hydrogen and oxygen stable isotopes, dissolved organic carbon, and major cations and anions, along with supporting site data, are presented in this report.

  17. Northern Cordilleran Ice Sheet Dynamics in Coastal Alaska from MIS 3 to the Present: Initial Results

    NASA Astrophysics Data System (ADS)

    Penkrot, M. L.; Jaeger, J. M.; LeVay, L.; St-Onge, G.; Mix, A. C.; Bahlburg, H.; Davies-Walczak, M.; Gulick, S. P. S.

    2014-12-01

    Establishing the timing of northwestern Cordilleran ice sheet (NCIS) advance-retreat cycles in southern Alaska allows for investigation of global synchronicity in glacial-age climate forcing. Integrated Ocean Drilling Program Expedition 341 targeted the glacial dynamics of the NCIS in the coastal St. Elias range. Sediment cores from Site U1419 encompass times of global ice advance and retreat from MIS 3 to the present, based on a preliminary age model with 5-kya resolution developed using oxygen isotopes from benthic and planktonic foraminifera and stratigraphic correlation with a previously C-14 dated site survey core (Davies et al., 2011; doi:10.1029/2010PA002051). CT images of cores were used to identify sedimentary facies and relative ice sheet proximity. Six sedimentary facies were identified in the images; massive mud with and without lonestones, laminations with and without lonestones, massive and stratified diamict (>1 clast/cm). Elemental scanning XRF data were used to delineate possible downcore changes in sediment provenance using provenance-sensitive transition metals. Diamict and gravelly mud are the most common facies, indicative of persistent glacial input interpreted as marine-terminating glacial systems. Stratified diamicts are interpreted as periods of maximum ice extent (~18-20 ka), whereas massive mud (~14 ka-present) suggests terminus retreat. Intervals of laminated mud with and without lonestones are interpreted as periods of reduced ice cover, with the most recent (~14.5 kya) coinciding with the Bølling Interstade of northern Europe/Greenland (Davies et al., 2011). Downcore changes in Al-normalized metal XRF counts vary along with sedimentary lithoficies, suggesting changes in sediment provenance that may be related to the quantity of glacigenic sediment delivery to this location.

  18. Light transmission and reflection in perennially ice-covered Lake Hoare, Antarctica

    NASA Technical Reports Server (NTRS)

    Mckay, C. P.; Clow, G. D.; Andersen, D. T.; Wharton, R. A., Jr.

    1994-01-01

    We have investigated the transmission and albedo of the perennial ice cover on Lake Hoare, Antarctica. Our database consists of year-round measurements of the photosynthetically active radiation (400-700 nm) under the ice, measurements of the spatial variation of the under-ice light in midsummer, and spectrally resolved measurements from 400 to 700 nm of the albedo and transmission of the ice cover in early (November) and in midsummer (January). Our results show that the transmission decreases in the first part of summer, dropping by a factor of approximately 4 from November to January. We suggest that this is due to heating in the upper layers of the ice cover and the formation of Tyndall figures. Later in the summer when a significant liquid water fraction occurs within the ice cover, the transmission increases. In the fall when the ice cover freezes solid the transmission drops markedly. The spectrally resolved measurements from 400 to 700 nm show that approximately 2-5% of the incident light in this spectral region penetrates the 3.5-m thick ice cover. We have analyzed the spectral data using a two-stream scattering solution to the radiative transfer equation with three vertical layers in the ice cover. A surficial glaze of scattering ice 1 cm thick overlies a layer of sandy, bubbly ice about a meter thick, and below this is a thick layer of sand-free ice with bubbles. We find that the ice cover is virtually opaque at wavelengths longer than 800 nm. The net transmission of solar energy is approximately 2%. Significant changes in the thickness of the ice cover have been reported at Lake Hoare. These are due primarily to changes in the thickness of the bottom layer only. Because this layer is relatively clear, the effect on the transmission through the ice cover from these changes is less than would be predicted assuming a homogeneous ice cover.

  19. Beach profile modification and sediment transport by ice: an overlooked process on Lake Michigan

    USGS Publications Warehouse

    Barnes, P.W.; Kempema, E.W.; Reimnitz, E.; McCormick, M.; Weber, W.S.; Hayden, E.C.

    1993-01-01

    Coastal lake ice includes a belt of mobile crash and slush ice and a stable nearshore-ice complex (NIC). Sediment concentrations indicate that the NIC and the belt of brash and slush contains 180 to 280 t (113 to 175m3) of sand per kilometer of coast. This static sediment load is roughly equivalent to the average amount of sand eroded from the bluffs and to the amount accumulating in the deep lake basin each year. Sediment is being rafted alongshore in the mobile brash and slush at rates of 10 to 30 cm/sec. -from Authors

  20. Perennial Antarctic lake ice: an oasis for life in a polar desert

    NASA Technical Reports Server (NTRS)

    Priscu, J. C.; Fritsen, C. H.; Adams, E. E.; Giovannoni, S. J.; Paerl, H. W.; McKay, C. P.; Doran, P. T.; Gordon, D. A.; Lanoil, B. D.; Pinckney, J. L.

    1998-01-01

    The permanent ice covers of Antarctic lakes in the McMurdo Dry Valleys develop liquid water inclusions in response to solar heating of internal aeolian-derived sediments. The ice sediment particles serve as nutrient (inorganic and organic)-enriched microzones for the establishment of a physiologically and ecologically complex microbial consortium capable of contemporaneous photosynthesis, nitrogen fixation, and decomposition. The consortium is capable of physically and chemically establishing and modifying a relatively nutrient- and organic matter-enriched microbial "oasis" embedded in the lake ice cover.

  1. The drainage and freezing behaviour of lakes from all parts of the Greenland Ice Sheet (Invited)

    NASA Astrophysics Data System (ADS)

    Selmes, N.; Murray, T.; James, T.

    2013-12-01

    The rapid drainage of supraglacial lakes is capable of causing accelerations in ice-sheet flow even when efficient subglacial drainage prevents slower meltwater inputs from affecting ice velocity. In addition, the fractures generated during drainage are a major source of connections between the supraglacial and subglacial hydrological systems. However, a previous study has shown that only 13 % of lakes drain in this manner. It has been suggested that lakes can have one of three fates: sudden drainage to the ice bed, slower supraglacial drainage through incision of a drainage channel, or freezing at the end of the melt season. These processes have never been quantified at the ice-sheet scale, and little is known about their distribution. We took a combination of MODIS visible imagery, MODIS land surface temperature data, and a pre-existing database of lake-area time-series, and used these data to classify 2600 lakes from all parts of the ice sheet over the period 2005-2009 into the three proposed lake-types: fast-draining, slow-draining, and freezing. Of the lakes studied, 34 % slow-drained, presumably supraglacially, and 47 % froze over at the end of the melt season. Previous studies have found a lack of moulins and reduced melt/velocity feedback in the higher part of the lake-forming zone. We find that lakes in this area are very unlikely to drain to the bed of the ice sheet, and instead lakes are far more likely to freeze, despite apparently having sufficient size and lifespan to drain. We suggest that this is evidence that lake drainage may be inhibited at higher elevations. At lower elevations fast and slow-draining lakes dominate, and frequently switch drainage-types interannually. Fast-draining, slow-draining, and freezing lakes are easily confused if infrequent observations are used, a fact worth considering for future remote-sensing studies to avoid overestimating the amount and rate of meltwater delivery to the ice-bed.

  2. Hydrology and Glacier-Lake-Outburst Floods (1987-2004) and Water Quality (1998-2003) of the Taku River near Juneau, Alaska

    USGS Publications Warehouse

    Neal, Edward G.

    2007-01-01

    The Taku River Basin originates in British Columbia, Canada, and drains an area of 6,600 square miles at the U.S. Geological Survey's Taku River gaging station. Several mines operated within the basin prior to 1957, and mineral exploration has resumed signaling potential for future mining developments. The U.S. Geological Survey in cooperation with the Douglas Indian Association, Alaska Department of Environmental Conservation, and the U.S. Environmental Protection Agency conducted a water-quality and flood-hydrology study of the Taku River. Water-quality sampling of the Taku River from 1998 through 2003 established a baseline for assessing potential effects of future mining operations on water quality. The annual mean discharge of the Taku River is 13,700 cubic feet per second. The monthly mean discharge ranges from a minimum of 1,940 cubic feet per second in February to a maximum of 34,400 cubic feet per second in June. Nearly 90 percent of the annual discharge is from May through November. The highest spring discharges are sourced primarily from snowmelt and moderate discharges are sustained throughout the summer by glacial meltwaters. An ice cover usually forms over the Taku River in December persisting through the winter into March and occasionally into April. Glacier-lake-outburst floods originating from two glacier-dammed lakes along the margin of the Tulsequah Glacier in British Columbia, Canada, are the source of the greatest peak discharges on the Taku River. The largest flood during the period of record was 128,000 cubic feet per second on June 25, 2004, resulting from an outburst of Lake No Lake. Lake No Lake is the larger of the two lakes. The outburst-flood contribution to peak discharge was 80,000 cubic feet per second. The volume discharged from Lake No Lake is relatively consistent indicating drainage may be triggered when the lake reaches a critical stage. This suggests prediction of the timing of these outburst floods might be possible if lake

  3. Characterization of subglacial Lake Vostok as seen from physical and isotope properties of accreted ice.

    PubMed

    Lipenkov, Vladimir Ya; Ekaykin, Alexey A; Polyakova, Ekaterina V; Raynaud, Dominique

    2016-01-28

    Deep drilling at the Vostok Station has reached the surface of subglacial Lake Vostok (LV) twice-in February 2012 and January 2015. As a result, three replicate cores from boreholes 5G-1, 5G-2 and 5G-3 became available for detailed and revalidation analyses of the 230 m thickness of the accreted ice, down to its contact with water at 3769 m below the surface. The study reveals that the concentration of gases in the lake water beneath Vostok is unexpectedly low. A clear signature of the melt water in the surface layer of the lake, which is subject to refreezing on the icy ceiling of LV, has been discerned in the three different properties of the accreted ice: the ice texture, the isotopic and the gas content of the ice. These sets of data indicate in concert that poor mixing of the melt (and hydrothermal) water with the resident lake water and pronounced spatial and/or temporal variability of local hydrological conditions are likely to be the characteristics of the southern end of the lake. The latter implies that the surface water may be not representative enough to study LV's behaviour, and that direct sampling of the lake at different depths is needed in order to move ahead with our understanding of the lake's hydrological regime. PMID:26667912

  4. Characterization of subglacial Lake Vostok as seen from physical and isotope properties of accreted ice.

    PubMed

    Lipenkov, Vladimir Ya; Ekaykin, Alexey A; Polyakova, Ekaterina V; Raynaud, Dominique

    2016-01-28

    Deep drilling at the Vostok Station has reached the surface of subglacial Lake Vostok (LV) twice-in February 2012 and January 2015. As a result, three replicate cores from boreholes 5G-1, 5G-2 and 5G-3 became available for detailed and revalidation analyses of the 230 m thickness of the accreted ice, down to its contact with water at 3769 m below the surface. The study reveals that the concentration of gases in the lake water beneath Vostok is unexpectedly low. A clear signature of the melt water in the surface layer of the lake, which is subject to refreezing on the icy ceiling of LV, has been discerned in the three different properties of the accreted ice: the ice texture, the isotopic and the gas content of the ice. These sets of data indicate in concert that poor mixing of the melt (and hydrothermal) water with the resident lake water and pronounced spatial and/or temporal variability of local hydrological conditions are likely to be the characteristics of the southern end of the lake. The latter implies that the surface water may be not representative enough to study LV's behaviour, and that direct sampling of the lake at different depths is needed in order to move ahead with our understanding of the lake's hydrological regime.

  5. Ice-Covered Lakes in Gale Crater Mars: The Cold and Wet Hypothesis

    NASA Astrophysics Data System (ADS)

    Kling, Alexandre; Haberle, Robert; McKay, Christopher P.; Bristow, Thomas

    2016-10-01

    Recent geological discoveries from the Mars Science Laboratory provide evidence that Gale crater may have intermittently hosted a fluvio-lacustine environment during the Hesperian, with individual lakes lasting for a period of tens to hundreds of thousands of years. (Grotzinger et al., Science, 350 (6257), 2015). Estimates of the CO2 content of the atmosphere at the time the Gale sediments formed are far less than needed by any climate model to warm early Mars (Bristow et al., Geology, submitted), given the low solar energy input available at Mars 3.5 Gya. We have therefore explored the possibility that the lakes in Gale during the Hesperian were perennially covered with ice using the Antarctic Lakes as an analog. Using our best estimate for the annual mean surface temperature at Gale at this time (~230K) we computed the thickness of an ice-covered lake. These thickness range from 10-30 meters depending on the ablation rate and ice transparency and would likely inhibit sediments from entering the lake. Thus, a first conclusion is that the ice must not be too cold. Raising the mean temperature to 245K is challenging, but not quite as hard as reaching 273K. We found that a mean annual temperature of 245K ice thicknesses range from 3-10 meters. These values are comparable to the range of those for the Antarctic lakes (3-6 m), and are not implausible. And they are not so thick that sediments cannot penetrate the ice. For the ice-covered lake hypothesis to work, however, a melt water source is needed. This could come from subaqueous melting of a glacial dam in contact with the lakes (as is the case for Lake Untersee) or from seasonal melt water from nearby glaciers (as is the case for the Dry Valley lakes). More work is needed to better assess these possibilities. However, the main advantage of the ice-covered lake model (and the main reason we pursued it) is that it relaxes the requirement for a long-lived active hydrological cycle involving rainfall and runoff, which

  6. Stable isotopic biogeochemistry of carbon and nitrogen in a perennially ice-covered Antarctic lake

    NASA Technical Reports Server (NTRS)

    Wharton, R. A. Jr; Lyons, W. B.; Des Marais, D. J.; Wharton RA, J. r. (Principal Investigator)

    1993-01-01

    Lake Hoare (77 degrees 38' S, 162 degrees 53' E) is an amictic, oligotrophic, 34-m-deep, closed-basin lake in Taylor Valley, Antarctica. Its perennial ice cover minimizes wind-generated currents and reduces light penetration, as well as restricts sediment deposition into the lake and the exchange of atmospheric gases between the water column and the atmosphere. The biological community of Lake Hoare consists solely of microorganisms -- both planktonic populations and benthic microbial mats. Lake Hoare is one of several perennially ice-covered lakes in the McMurdo Dry Valleys that represent the end-member conditions of cold desert and saline lakes. The dry valley lakes provide a unique opportunity to examine lacustrine processes that operate at all latitudes, but under an extreme set of environmental conditions. The dry valley lakes may also offer a valuable record of catchment and global changes in the past and present. Furthermore, these lakes are modern-day equivalents of periglacial lakes that are likely to have been common during periods of glacial maxima at temperate latitudes. We have analyzed the dissolved inorganic carbon (DIC) of Lake Hoare for delta 13C and the organic matter of the sediments and sediment-trap material for delta 13C and delta 15N. The delta 13C of the DIC indicates that 12C is differentially removed in the shallow, oxic portions of the lake via photosynthesis. In the anoxic portions of the lake (27-34 m) a net addition of 12C to the DIC pool occurs via organic matter decomposition. The dissolution of CaCO3 at depth also contributes to the DIC pool. Except near the Canada Glacier where a substantial amount of allochthonous organic matter enters the lake, the organic carbon being deposited on the lake bottom at different sites is isotopically similar, suggesting an autochthonous source for the organic carbon. Preliminary inorganic carbon flux calculations suggest that a high percentage of the organic carbon fixed in the water column is

  7. River Ice and Flood Detection Products Derived from Suomi NPP VIIRS Satellite Data to Support Hydrologic Forecast Operations in Alaska

    NASA Astrophysics Data System (ADS)

    van Breukelen, C. M.; Plumb, E. W.; Li, S.; Holloway, E.; Stevens, E.

    2015-12-01

    A lack of river ice data during spring break-up in Alaska creates many forecast challenges for National Weather Service (NWS) forecasters. Limited and infrequent ice conditions and flood observations are provided by river observers, community officials, and pilots. Although these observations are invaluable, there are extensive spatial and temporal data gaps across Alaska during spring break-up. The Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) satellite imagery has proved to be an extremely beneficial situational awareness and decision support tool for NWS forecast operations. In particular, the VIIRS satellite imagery became highly effective in identifying extensive flooding of many Alaskan rivers due to ice jams during the 2013 spring breakup season. A devastating ice jam flood in the Yukon River community of Galena prompted the development of river ice and flood detection products derived from the VIIRS satellite imagery with the support of the Joint Polar Satellite System/Proving Ground and Risk Reduction (JPSS/PGRR) Program. The two new products from S-NPP/VIIRS imagery provided critical decision making information to NWS forecasters responsible for issuing flood warnings for the region. Since 2013, the NWS continues to evaluate the use of these products in an operational forecast setting, and has expanded the evaluation period to include summertime flooding. There are limitations of these products due to cloud cover, sun zenith angles, product validation, and other issues unique to Alaska. The NWS will continue to provide feedback to the JPSS/PGRR Program in order to further refine and improve the algorithms used to create the river ice and flood detection products. This presentation will demonstrate how these products have been integrated into the NWS forecast process for several types of flood events in Alaska.

  8. Passive microwave studies of frozen lakes

    NASA Technical Reports Server (NTRS)

    Hall, D. K.; Foster, J. L.; Rango, A.; Chang, A. T. C.

    1978-01-01

    Lakes of various sizes, depths and ice thicknesses in Alaska, Utah and Colorado were overflown with passive microwave sensors providing observations at several wavelengths. A layer model is used to calculate the microwave brightness temperature, T sub B (a function of the emissivity and physical temperatures of the object), of snowcovered ice underlain with water. Calculated T sub B's are comparable to measured T sub B's. At short wavelengths, e.g., 0.8 cm, T sub B data provide information on the near surface properties of ice covered lakes where the long wavelength, 21.0 cm, observations sense the entire thickness of ice including underlying water. Additionally, T sub B is found to increase with ice thickness. 1.55 cm observations on Chandalar Lake in Alaska show a T sub B increase of 38 K with an approximate 124 cm increase in ice thickness.

  9. The geochemistry of methane in Lake Fryxell, an amictic, permanently ice-covered, antarctic lake

    USGS Publications Warehouse

    Smith, R.L.; Miller, L.G.; Howes, B.L.

    1993-01-01

    The abundance and distribution of dissolved CH4 were determined from 1987-1990 in Lake Fryxell, Antarctica, an amictic, permanently ice-covered lake in which solute movement is controlled by diffusion. CH4 concentrations were < 1 ??M in the upper oxic waters, but increased below the oxycline to 936 ??M at 18 m. Sediment CH4 was 1100 ??mol (1 sed)-1 in the 0-5 cm zone. Upward flux from the sediment was the source of the CH4, NH4 +, and DOC in the water column; CH4 was 27% of the DOC+CH4 carbon at 18 m. Incubations with surficial sediments indicated that H14CO3 - reduction was 0.4 ??mol (1 sed)-1 day-1 or 4?? the rate of acetate fermentation to CH4. There was no measurable CH4 production in the water column. However, depth profiles of CH4, NH4, and DIC normalized to bottom water concentrations demonstrated that a significant CH4 sink was evident in the anoxic, sulfate-containing zone of the water column (10-18 m). The ??13CH4 in this zone decreased from -72 % at 18 m to -76% at 12 m, indicating that the consumption mechanism did not result in an isotopic enrichment of 13CH4. In contrast, ??13CH4 increased to -55 % at 9 m due to aerobic oxidation, though this was a minor aspect of the CH4 cycle. The water column CH4 profile was modeled by coupling diffusive flux with a first order consumption term; the best-fit rate constant for anaerobic CH4 consumption was 0.012 yr-1. On a total carbon basis, CH4 consumption in the anoxic water column exerted a major effect on the flux of carbonaceous material from the underlying sediments and serves to exemplify the importance of CH4 to carbon cycling in Lake Fryxell. ?? 1993 Kluwer Academic Publishers.

  10. Examining Dual Frequency X- and Ku-band Backscatter of Snow on Lake Ice and First-Year Sea Ice in the Sub-Arctic Hudson Bay Lowlands

    NASA Astrophysics Data System (ADS)

    Gunn, G. E.; Duguay, C. R.; Howell, S.; Kelly, R. E.; Silis, A.

    2011-12-01

    Fully polarimetric dual frequency ground-based scatterometer observations were collected at X- and Ku-band (9.6 and 17.2 GHz, respectively) near Churchill, Manitoba, Canada in the winter of 2010-11 as part of the Canadian Snow and Ice Experiment (CASIX). Backscatter measurements were collected for five landcover types: lake ice, sea ice, dry tundra, open forest and wetland tundra (sedge fen); the combination of which comprises a unique dataset of dual-frequency backscatter signatures. Correlative data collected, including snow and ice properties, are utilized to characterize active microwave interactions and contribute to the development of snow/ice retrieval algorithms. This study presents backscatter signatures for lake and sea ice obtained during winter 2010-11. The seasonal backscatter evolution is compared to changes in snow and ice properties, including depth, density, snow water equivalent (SWE), ice thickness, ice type, and bubble concentration within the ice. Results over lake ice suggest that increases in backscatter at both X- and Ku-band frequencies correspond to increases in SWE, but are confounded by changes in the sub-nivian ice composition. Surface ice types (snow ice, rafted ice), high bubble concentrations at the ice/water interface and pressure/deformation cracks in the ice serve to confound backscatter at several monitoring sites. Over sea ice, preliminary results indicate that increased salinity levels near the ice/snow interface is the predominate factor influencing backscatter signatures. Physical phenomena encountered at sea ice sites are further explored to assess potential influences on scattering signatures. Preliminary findings presented here document the first ground-based dual frequency X- and Ku-band backscatter signatures collected over first year sea ice, and contribute to the scientific objectives of the proposed Cold Regions Hydrology High-resolution Observatory (CoReH2O), a candidate Earth Explorer mission of the European Space

  11. Historical abundance and morphology of Didymosphenia species in Naknek Lake, Alaska

    USGS Publications Warehouse

    Pite, D.P.; Lane, K.A.; Hermann, A.K.; Spaulding, S.A.; Finney, B.P.

    2009-01-01

    Since the 1980s, nuisance blooms of Didymosphenia geminata (Lyngbye) M. Schmidt have been documented in sites that are warmer and more mesotrophic than historical records indicate. While the invasion of D. geminata in New Zealand is well documented, it is less clear whether nuisance blooms in North America are a new phenomenon. In order to test the hypothesis that D. geminata blooms have increased in recent years, we examined the historical record of this species in sediments of Naknek Lake, in Katmai National Park, Alaska. Chronological control was established by relating the presence of two ash layers to known volcanic eruptions. We identified two species of Didymosphenia within the sediment record: D. geminata and D. clavaherculis (Ehrenberg) Metzeltin et Lange-Bertalot. This is the first published record of D. clavaherculis in North America. We found no statistically significant change in the numerical presence of D. geminata or D. clavaherculis, as a group, in Naknek Lake between the years 1218 and 2003. While there has been no sudden, or recent, increase in abundance of Didymosphenia in Naknek Lake, morphological features of D. geminata populations in Naknek Lake are distinct compared to morphological features of D. geminata in streams containing nuisance blooms from sites in North America and New Zealand. Variance in the morphology of Didymosphenia cells may help determine relationships between distinct sub-populations and establish the history of habitat invasion.

  12. Diffusion model validation and interpretation of stable isotopes in river and lake ice

    USGS Publications Warehouse

    Ferrick, M.G.; Calkins, D.J.; Perron, N.M.; Cragin, J.H.; Kendall, C.

    2002-01-01

    The stable isotope stratigraphy of river- and lake-ice archives winter hydroclimatic conditions, and can potentially be used to identify changing water sources or to provide important insights into ice formation processes and growth rates. However, accurate interpretations rely on known isotopic fractionation during ice growth. A one-dimensional diffusion model of the liquid boundary layer adjacent to an advancing solid interface, originally developed to simulate solute rejection by growing crystals, has been used without verification to describe non-equilibrium fractionation during congelation ice growth. Results are not in agreement, suggesting the presence of important uncertainties. In this paper we seek validation of the diffusion model for this application using large-scale laboratory experiments with controlled freezing rates and frequent sampling. We obtained consistent, almost constant, isotopic boundary layer thicknesses over a representative range of ice growth rates on both quiescent and well-mixed water. With the 18O boundary layer thickness from the laboratory, the model successfully quantified reduced river-ice growth rates relative to those of a nearby lake. These results were more representative and easier to obtain than those of a conventional thermal ice-growth model. This diffusion model validation and boundary layer thickness determination provide a powerful tool for interpreting the stable isotope stratigraphy of floating ice. The laboratory experiment also replicated successive fractionation events in response to a freeze-thaw-refreeze cycle, providing a mechanism for apparent ice fractionation that exceeds equilibrium. Analysis of the composition of snow ice and frazil ice in river and lake cores indicated surprising similarities between these ice forms. Published in 2002 by John Wiley & Sons, Ltd.

  13. Ice-age endurance: DNA evidence of a white spruce refugium in Alaska.

    PubMed

    Anderson, Lynn L; Hu, Feng Sheng; Nelson, David M; Petit, Rémy J; Paige, Ken N

    2006-08-15

    Paleorecords offer key information for evaluating model simulations of species migration in response to forecast climatic change. However, their utility can be greatly compromised by the existence of glacial refugia that are undetectable in fossil records (cryptic refugia). Despite several decades of investigation, it remains controversial whether Beringia, the largely unglaciated area extending from northeastern Siberia to the Yukon Territory, harbored small populations of certain boreal tree species during the last glaciation. Here, we present genetic evidence for the existence of a glacial refuge in Alaska that helps to resolve this long-standing controversy. We sequenced chloroplast DNA (cpDNA) of white spruce (Picea glauca), a dominant boreal tree species, in 24 forest stands across northwestern North America. The majority of cpDNA haplotypes are unique, and haplotype diversity is relatively high in Alaska, arguing against the possibility that this species migrated into the region from areas south of the Laurentide Ice Sheet after the end of the last glaciation. Thus, white spruce apparently survived long glacial episodes under climatic extremes in a heterogeneous landscape matrix. These results suggest that estimated rates of tree migration from fossil records may be too high and that the ability of trees to track anthropogenic warming may be more limited than previously thought.

  14. Simulation of lake ice and its effect on the late-Pleistocene evaporation rate of Lake Lahontan

    USGS Publications Warehouse

    Hostetler, S.W.

    1991-01-01

    A model of lake ice was coupled with a model of lake temperature and evaporation to assess the possible effect of ice cover on the late-Pleistocene evaporation rate of Lake Lahontan. The simulations were done using a data set based on proxy temperature indicators and features of the simulated late-Pleistocene atmospheric circulation over western North America. When a data set based on a mean-annual air temperature of 3?? C (7?? C colder than present) and reduced solar radiation from jet-stream induced cloud cover was used as input to the model, ice cover lasting ??? 4 months was simulated. Simulated evaporation rates (490-527 mm a-1) were ??? 60% lower than the present-day evaporation rate (1300 mm a-1) of Pyramid Lake. With this reduced rate of evaporation, water inputs similar to the 1983 historical maxima that occurred in the Lahontan basin would have been sufficient to maintain the 13.5 ka BP high stand of Lake Lahontan. ?? 1991 Springer-Verlag.

  15. Integration of geophysical, ground surface, and remote sensing methods to identify ice features in discontinuous permafrost near Fairbanks, Alaska

    NASA Astrophysics Data System (ADS)

    Douglas, T. A.; Bjella, K.; Hiemstra, C. A.; Newman, S. D.; Anderson, J.; Edwards, J.; Arcone, S. A.; Wagner, A. M.; Barbato, R.; Berkowitz, J.; Deeb, E. J.

    2014-12-01

    Ground ice features such as ice wedges, segregation ice, and thermokarst cave ice are present in the subsurface in a variety of spatial scales and patterns. Accurately identifying the character and extent of these ice features in permafrost terrains allows engineers and planners to cost effectively create innovative infrastructure designs to withstand the changing environment. We are assembling a holistic view of how a variety of surficial and standoff geophysical measurements can be combined with classic ground based measurements to delineate subsurface permafrost features. We are combining horizontal geophysical measurements; borehole mapping; multispectral and radar remote sensing; airborne and ground-based LiDAR; snow, soil, and vegetation mapping; and subsurface thermal measurements and modeling at three field sites in discontinuous permafrost of Interior Alaska. Our sites cross transects representing upland and lowland permafrost and a variety of soil and vegetation compositions. With our measurements we identified and mapped a 300 meter wide swath of ice rich frozen peat at one of our lowland field sites. The high ice content was confirmed with borehole measurements. This ice rich permafrost region yields higher electrical resistivity values than the nearby permafrost and is associated with anomalously low seasonal thaw depths compared to other sites nearby. Surface soils in the ice rich region have high soil moisture contents, low redox potential (30-100 mV), and elevated soil microbial activity. The ice rice region yields low phase changes from paired interferometric synthetic aperture radar measurements collected in late spring and late summer. One interpretation of this result is that the ice rich area experiences minimal summer season subsidence. Taken in total, our results suggest the ice rich peat region has distinct surface signatures and subsurface geophysical characteristics that may be extrapolated to other areas to identify ice rich permafrost in

  16. Predictors of River Ice Breakup Severity on the Yukon River in Interior Alaska: an Examination of the Past 15 Years

    NASA Astrophysics Data System (ADS)

    van Breukelen, C. M.

    2015-12-01

    On the major interior rivers of Alaska, spring river ice breakup is the single largest annual flood threat and can result in fatalities in addition to millions of dollars of damages. Unlike freeze up, which is a gradual, months-long progression, breakup is a quick process during which an entire winters worth of ice lifts and moves downstream in a short time frame (hours to days). Breakup types range between thermal and dynamic. A thermal breakup is relatively slow; ice degrades in place before moving downstream. A dynamic breakup is quicker; the ice is relatively strong before the breakup front moves past. Severe breakup flooding is typically a result of a dynamic breakup. Because the ice has not yet deteriorated, large, strong sheets of ice become jammed on islands, river bends, or other ice sheets, creating an ice jam. The water levels behind an ice jam can rise rapidly and with little warning. The goal of this study is to better understand predictors of breakup flood severity on the Upper and Middle Yukon River; between Eagle and Nulato, Alaska. We examine end of winter snowpack, ESRL Temperature Reanalysis data, and breakup-related flood observations from 2000 to 2015. Experience has shown that those years which have a large end of winter snowpack and a rapid spring warm-up have an above average chance of flooding, but this study seeks to expand on that knowledge base. What about years where only one of those factors (quick warm up or large snowpack) is present? Also, are there cases of years where the April antecedent conditions were similar, but the outcome of breakup was different? Why? Is flooding at a certain location an indicator that there will be flooding at another location downstream? This study is an in-depth examination of the past 15 years of breakup on the Yukon. A better understanding of these past events will lead to greater skill at predicting future events, and a better service for our stakeholders.

  17. Heating the Ice-Covered Lakes of the McMurdo Dry Valleys, Antarctica - Decadal Trends in Heat Content, Ice Thickness, and Heat Exchange

    NASA Astrophysics Data System (ADS)

    Gooseff, M. N.; Priscu, J. C.; Doran, P. T.; Chiuchiolo, A.; Obryk, M.

    2014-12-01

    Lakes integrate landscape processes and climate conditions. Most of the permanently ice-covered lakes in the McMurdo Dry Valleys, Antarctica are closed basin, receiving glacial melt water from streams for 10-12 weeks per year. Lake levels rise during the austral summer are balanced by sublimation of ice covers (year-round) and evaporation of open water moats (summer only). Vertical profiles of water temperature have been measured in three lakes in Taylor Valley since 1988. Up to 2002, lake levels were dropping, ice covers were thickening, and total heat contents were decreasing. These lakes have been gaining heat since the mid-2000s, at rates as high as 19.5x1014 cal/decade). Since 2002, lake levels have risen substantially (as much as 2.5 m), and ice covers have thinned (1.5 m on average). Analyses of lake ice thickness, meteorological conditions, and stream water heat loads indicate that the main source of heat to these lakes is from latent heat released when ice-covers form during the winter. An aditional source of heat to the lakes is water inflows from streams and direct glacieal melt. Mean lake temperatures in the past few years have stabilized or cooled, despite increases in lake level and total heat content, suggesting increased direct inflow of meltwater from glaciers. These results indicate that McMurdo Dry Valley lakes are sensitive indicators of climate processes in this polar desert landscape and demonstrate the importance of long-term data sets when addressing the effects of climate on ecosystem processes.

  18. Peatland Carbon Dynamics on the North Slope of Alaska During the Holocene: The Role of Climate, Sea Ice, and Buried Peat

    NASA Astrophysics Data System (ADS)

    Yu, Zicheng; Massa, Charly; Cleary, Kathleen; Jones, Benjamin; Grosse, Guido

    2014-05-01

    Our recent and ongoing data syntheses indicate that peatlands accumulated more carbon (C) during past warm climate intervals in the circum-Arctic region, including Alaska. In particular, peak C accumulations have been observed during the Holocene Thermal Maximum (HTM) in the early Holocene when summer insolation was higher. However, we do not know the regional patterns and impacts of sea-ice change on Holocene peat C accumulation, especially around the Arctic Ocean where increased vegetation productivity has already been linked to sea ice declines in recent decades. Here we review Holocene peatland and tundra C accumulation records on the North Slope, along with our preliminary results, to investigate spatiotemporal pattern of C accumulation and the possible role of sea-ice change. As in many other northern high-latitude regions, most peatlands on the North Slope initiated in the early Holocene. Several discontinuous and low-resolution peat accumulation records from the region appear to show high accumulation rates or high C content in the early Holocene. In addition, we note that many peatlands that existed during the earlier Holocene on the North Slope have disappeared and are presently covered by mineral soils under tundra or eolian sandy deposits, indicating that current peatland extent is only a fraction of early Holocene extent. In contrast to highest C accumulation rates in the early Holocene, our preliminary results from a 70-cm-long peat core (lat. 70.71 N; long. 153.87 W) from northwest Teshekpuk Lake, near the Teshekpuk Lake Observatory on the Arctic Coastal Plain, about 10 km from the Arctic Ocean, shows a very different pattern. The highest C accumulation of 12.7 gC/m2/yr is observed after 2.9 ka, much higher than the rate of 3.8 gC/m2/yr at 8.1-2.9 ka. Furthermore, the period with high C rates after 2.9 ka at this site was dominated by well-preserved peat mosses (Sphagnum) and with abundant leaf fragments, likely from dwarf birch (Betula nana). This

  19. A late quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska

    USGS Publications Warehouse

    Muhs, D.R.; Ager, T.A.; Been, J.; Bradbury, J.P.; Dean, W.E.

    2003-01-01

    Recent stratigraphic studies in central Alaska have yielded the unexpected finding that there is little evidence for full-glacial (late Wisconsin) loess deposition. Because the loess record of western Alaska is poorly exposed and not well known, we analyzed a core from Zagoskin Lake, a maar lake on St. Michael Island, to determine if a full-glacial eolian record could be found in that region. Particle size and geochemical data indicate that the mineral fraction of the lake sediments is not derived from the local basalt and is probably eolian. Silt deposition took place from at least the latter part of the mid-Wisconsin interstadial period through the Holocene, based on radiocarbon dating. Based on the locations of likely loess sources, eolian silt in western Alaska was probably deflated by northeasterly winds from glaciofluvial sediments. If last-glacial winds that deposited loess were indeed from the northeast, this reconstruction is in conflict with a model-derived reconstruction of paleowinds in Alaska. Mass accumulation rates in Zagoskin Lake were higher during the Pleistocene than during the Holocene. In addition, more eolian sediment is recorded in the lake sediments than as loess on the adjacent landscape. The thinner loess record on land may be due to the sparse, herb tundra vegetation that dominated the landscape in full-glacial time. Herb tundra would have been an inefficient loess trap compared to forest or even shrub tundra due to its low roughness height. The lack of abundant, full-glacial, eolian silt deposition in the loess stratigraphic record of central Alaska may be due, therefore, to a mimimal ability of the landscape to trap loess, rather than a lack of available eolian sediment. ?? 2003 University of Washington. Published by Elsevier Inc. All rights reserved.

  20. Evidence for Pacific Climate Regime Shifts as Preserved in a Southeast Alaska Ice Core

    NASA Astrophysics Data System (ADS)

    Porter, S. E.; Mosley-Thompson, E. S.; Thompson, L. G.

    2012-12-01

    Climate modes emanating from the Pacific sector have far-reaching effects across the globe. The El Niño/Southern Oscillation (ENSO) reflects anomalies in the sea surface temperature and pressure fields over the tropical Pacific, but climate implications from these anomalies extend to monsoon regions of Asia to North America and even Europe. The Pacific Decadal Oscillation (PDO) explains sea surface temperature anomalies in the North Pacific sector and influences the long-term behavior of the ENSO cycle as well as the storm track over North America expressed as the Pacific/North American Pattern (PNA). The impacts of both climate change and drastically reduced Arctic sea ice cover on these teleconnection patterns are poorly understood, and with little knowledge about their past behavior, predicting the changes in these climate modes is extremely difficult. An ice core from the col between Mt. Bona and Mt. Churchill in southeast Alaska provides an opportunity to examine the PDO prior to both the start of instrumental records and the more recent effects of anthropogenic climate change. The Bona-Churchill records of isotopic, dust, and chemical composition are compared to nearby meteorological station and 20th century reanalysis data to evaluate their strength as climate recorders. Climate indices such as the PDO and PNA, along with indices created to describe the strength and position of the Aleutian Low and Siberian High, are incorporated into the analysis to determine if proxy relationships are altered under different climate regimes. Satellite records of sea ice extent within the Sea of Okhotsk and the Bering Sea, when compared to the Bona-Churchill data, show a distinct change in behavior in the mid-1990s possibly in response to the temporary negative shift in the PDO. This behavioral shift is explored and placed into a broader climate context to determine whether similar events have occurred in the past or if this shift is unique to a rapidly warming Arctic.

  1. Estimating Trapped Gas Concentrations as Bubbles Within Lake Ice Using Ground Penetrating Radar

    NASA Astrophysics Data System (ADS)

    Fantello, N.; Parsekian, A.; Walter Anthony, K. M.

    2015-12-01

    Climate warming is currently one of the most important issues that we are facing. The degradation of permafrost beneath thermokarst lakes has been associated with enhanced methane emissions and it presents a positive feedback to climate warming. Thermokarst lakes release methane to the atmosphere mainly by ebullition (bubbling) but there are a large number of uncertainties regarding the magnitude and variability of these emissions. Here we present a methodology to estimate the amount of gas released from thermokarst lakes through ebullition using ground-penetrating radar (GPR). This geophysical technique is well suited for this type of problem because it is non-invasive, continuous, and requires less effort and time than the direct visual inspection. We are studying GPR data collected using 1.2 GHz frequency antennas in Brooklyn Lake, Laramie, WY, in order to quantify the uncertainties in the method. Although this is not a thermokarst lake, gas bubbles are trapped in the ice and spatial variability in bubble concentration within the ice is evident. To assess the variability in bulk physical properties of the ice due to bubbles, we gathered GPR data from different types of ice. We compared the velocity of the groundwave and reflection obtained from radargrams, and found on each case a larger value for the groundwave velocity suggesting a non-homogeneous medium and that the concentration of bubbles is prone to be near the surface instead of at greater depths. We use a multi-phase dielectric-mixing model to estimate the amount of gas present in a sample of volume of ice and found an uncertainty in relative permittivity (estimated using reflection velocity) of 0.0294, which translates to an uncertainty of 1.1% in gas content; and employing groundwave velocity we found 0.0712 and 2.9%, respectively. If locations of gas seeps in lakes could be detected and quantified using GPR along with field measurements, this could help to constrain future lake-source carbon gas

  2. Principal Facts for 463 Gravity Stations in the Vicinity of Tangle Lakes, East-Central Alaska

    USGS Publications Warehouse

    Morin, Robert L.; Glen, Jonathan M.G.

    2002-01-01

    During the summer of 2001, a gravity survey was conducted in the vicinity of Tangle Lakes, east-central Alaska. Measurements of 87 gravity stations were made. The Tangle Lakes area is located about 25 km west of Paxson and north of the Denali Highway. The gravity survey is located on the southwest corner of the Mt. Hayes and the northwest corner of the Gulkana 1:250,000 scale USGS topographic maps. The boundaries of the study area are 62 deg 30' to 63 deg 30' N. latitude and 145 deg 30' to 147 deg 00' W. longitude. A map showing the location of the study area is shown in figure 1. One gravity base station was used for control for this survey. This base station, TLIN is located at the Tangle Lakes Inn. The observed gravity of this station was calculated based on multiple ties to base stations ANCU in Anchorage, PALH in Palmer, BD27 in Gulkana, and base stations D42, and D57 along the Denali Highway.

  3. Lipophilic pigments from the benthos of a perennially ice-covered Antarctic lake

    NASA Technical Reports Server (NTRS)

    Palmisano, A. C.; Wharton, R. A. Jr; Cronin, S. E.; Des Marais, D. J.; Wharton RA, J. r. (Principal Investigator)

    1989-01-01

    The benthos of a perennially ice-covered Antarctic lake, Lake Hoare, contained three distinct 'signatures' of lipophilic pigments. Cyanobacterial mats found in the moat at the periphery of the lake were dominated by the carotenoid myxoxanthophyll; carotenoids: chlorophyll a ratios in this high light environment ranged from 3 to 6.8. Chlorophyll c and fucoxanthin, pigments typical of golden-brown algae, were found at 10 to 20 m depths where the benthos is aerobic. Anaerobic benthic sediments at 20 to 30 m depths were characterized by a third pigment signature dominated by a carotenoid, tentatively identified as alloxanthin from planktonic cryptomonads, and by phaeophytin b from senescent green algae. Pigments were not found associated with alternating organic and sediment layers. As microzooplankton grazers are absent from this closed system and transformation rates are reduced at low temperatures, the benthos beneath the lake ice appears to contain a record of past phytoplankton blooms undergoing decay.

  4. On the relationship between Arctic ice clouds and polluted air masses over the North Slope of Alaska in April 2008

    NASA Astrophysics Data System (ADS)

    Jouan, C.; Pelon, J.; Girard, E.; Ancellet, G.; Blanchet, J. P.; Delanoë, J.

    2014-02-01

    Recently, two types of ice clouds (TICs) properties have been characterized using the Indirect and Semi-Direct Aerosol Campaign (ISDAC) airborne measurements (Alaska, April 2008). TIC-2B were characterized by fewer (< 10 L-1) and larger (> 110 μm) ice crystals, and a larger ice supersaturation (> 15%) compared to TIC-1/2A. It has been hypothesized that emissions of SO2 may reduce the ice nucleating properties of ice nuclei (IN) through acidification, resulting in a smaller concentration of larger ice crystals and leading to precipitation (e.g., cloud regime TIC-2B). Here, the origin of air masses forming the ISDAC TIC-1/2A (1 April 2008) and TIC-2B (15 April 2008) is investigated using trajectory tools and satellite data. Results show that the synoptic conditions favor air masses transport from three potential SO2 emission sources into Alaska: eastern China and Siberia where anthropogenic and biomass burning emissions, respectively, are produced, and the volcanic region of the Kamchatka/Aleutians. Weather conditions allow the accumulation of pollutants from eastern China and Siberia over Alaska, most probably with the contribution of acidic volcanic aerosol during the TIC-2B period. Observation Monitoring Instrument (OMI) satellite observations reveal that SO2 concentrations in air masses forming the TIC-2B were larger than in air masses forming the TIC-1/2A. Airborne measurements show high acidity near the TIC-2B flight where humidity was low. These results support the hypothesis that acidic coating on IN could be at the origin of the formation of TIC-2B.

  5. On the relationship between Arctic ice clouds and polluted air masses over the north slope of Alaska in April 2008

    NASA Astrophysics Data System (ADS)

    Jouan, C.; Pelon, J.; Girard, E.; Ancellet, G.; Blanchet, J. P.; Delanoë, J.

    2013-02-01

    Recently, two Types of Ice Clouds (TICs) properties have been characterized using ISDAC airborne measurements (Alaska, April 2008). TIC-2B were characterized by fewer (<10 L-1) and larger (>110 μm) ice crystals, a larger ice supersaturation (>15%) and a fewer ice nuclei (IN) concentration (<2 order of magnitude) when compared to TIC-1/2A. It has been hypothesized that emissions of SO2 may reduce the ice nucleating properties of IN through acidification, resulting to a smaller concentration of larger ice crystals and leading to precipitation (e.g. cloud regime TIC-2B) because of the reduced competition for the same available moisture. Here, the origin of air masses forming the ISDAC TIC-1/2A (1 April 2008) and TIC-2B (15 April 2008) is investigated using trajectory tools and satellite data. Results show that the synoptic conditions favor air masses transport from the three potentials SO2 emission areas to Alaska: eastern China and Siberia where anthropogenic and biomass burning emission respectively are produced and the volcanic region from the Kamchatka/Aleutians. Weather conditions allow the accumulation of pollutants from eastern China/Siberia over Alaska, most probably with the contribution of acid volcanic aerosol during the TIC-2B period. OMI observations reveal that SO2 concentrations in air masses forming the TIC-2B were larger than in air masses forming the TIC-1/2A. Airborne measurements show high acidity near the TIC-2B flight where humidity was low. These results strongly support the hypothesis that acidic coating on IN are at the origin of the formation of TIC-2B.

  6. Evidence of recent warming and El Nino-related variations in ice breakup of Wisconsin lakes

    USGS Publications Warehouse

    Anderson, W.L.; Robertson, D.M.; Magnuson, J.J.

    1996-01-01

    Ice breakup dates from 1968 to 1988 were examined for 20 Wisconsin lakes to determine whether consistent interannual and long-term changes exist. Each ice record had a trend toward earlier breakup dates, as demonstrated by a negative slope with time, indicating a recent warming trend. The average change in breakup dates was 0.82 d earlier per year for the lakes in southern Wisconsin, which was more extreme than that for the northern Wisconsin lakes (0.45 d yr-1). Interannual variation in breakup dates was related to the warm phase of El Nino/Southern Oscillation (ENSO) episodes. El Nino events occurred five times during this period (1965, 1972, 1976, 1982, and 1986). Average breakup dates were significantly earlier than average (5-14 d) during the mature phase of El Nino. This variability was affected by the location of the lake: El Nino-related variation was more evident for the southern lakes than the northern lakes. This difference was caused by the average date of breakup for the southern lakes being in late March directly following the period when air temperatures were strongly related to El Nino events, whereas the average dates of breakup of the northern lakes was in mid- to late April following a period when air temperatures were not significantly related to El Nino events. Overall, the interannual and long-term patterns across Wisconsin were relatively consistent, indicating that recent warming and El Nino- related variation are regional climatic responses.

  7. Climate regulates alpine lake ice cover phenology and aquatic ecosystem structure

    NASA Astrophysics Data System (ADS)

    Preston, Daniel L.; Caine, Nel; McKnight, Diane M.; Williams, Mark W.; Hell, Katherina; Miller, Matthew P.; Hart, Sarah J.; Johnson, Pieter T. J.

    2016-05-01

    High-elevation aquatic ecosystems are highly vulnerable to climate change, yet relatively few records are available to characterize shifts in ecosystem structure or their underlying mechanisms. Using a long-term data set on seven alpine lakes (3126 to 3620 m) in Colorado, USA, we show that ice-off dates have shifted 7 days earlier over the past 33 years and that spring weather conditions—especially snowfall—drive yearly variation in ice-off timing. In the most well studied lake, earlier ice-off associated with increases in water residence times, thermal stratification, ion concentrations, dissolved nitrogen, pH, and chlorophyll a. Mechanistically, low spring snowfall and warm temperatures reduce summer stream flow (increasing lake residence times) but enhance melting of glacial and permafrost ice (increasing lake solute inputs). The observed links among hydrological, chemical, and biological responses to climate factors highlight the potential for major shifts in the functioning of alpine lakes due to forecasted climate change.

  8. Climate regulates alpine lake ice cover phenology and aquatic ecosystem structure

    USGS Publications Warehouse

    Preston, Daniel L.; Caine, Nel; McKnight, Diane M.; Williams, Mark W.; Hell, Katherina; Miller, Matthew P.; Hart, Sarah J.; Johnson, Pieter T.J.

    2016-01-01

    High-elevation aquatic ecosystems are highly vulnerable to climate change, yet relatively few records are available to characterize shifts in ecosystem structure or their underlying mechanisms. Using a long-term dataset on seven alpine lakes (3126 to 3620 m) in Colorado, USA, we show that ice-off dates have shifted seven days earlier over the past 33 years and that spring weather conditions – especially snowfall – drive yearly variation in ice-off timing. In the most well-studied lake, earlier ice-off associated with increases in water residence times, thermal stratification, ion concentrations, dissolved nitrogen, pH, and chlorophyll-a. Mechanistically, low spring snowfall and warm temperatures reduce summer stream flow (increasing lake residence times) but enhance melting of glacial and permafrost ice (increasing lake solute inputs). The observed links among hydrological, chemical, and biological responses to climate factors highlight the potential for major shifts in the functioning of alpine lakes due to forecasted climate change.

  9. Implications of optical properties of ocean, lake, and ice for ultrahigh-energy neutrino detection

    SciTech Connect

    Price, P.B.

    1997-03-01

    The collecting power and imaging ability of planned ultrahigh-energy neutrino observatories depend on wavelength-dependent absorption and scattering coefficients for the detector medium. Published data are compiled for deep ice at the South Pole, for deep fresh water at Lake Baikal, and for deep seawater. The effective scattering coefficient is smallest for the clearest deep ocean sites, whereas the absorption coefficient is an order of magnitude smaller for deep ice than for the ocean and lake sites. The effective volume per detector element as a function of energy is calculated for electromagnetic cascades produced by electron neutrinos interacting at the various sites. It is largest for deep bubble-free ice, smallest for shallow bubbly ice, and intermediate for lake and seawater. The effective volume per element is calculated for detection of positrons resulting from the capture of a few megaelectron volt supernova neutrinos by protons in the medium. This volume is proportional to the absorption length and independent of the scattering length; it is larger for ice than for seawater or lake water. {copyright} 1997 Optical Society of America

  10. Temperature fluctuations underneath the ice in Diamond Lake, Hennepin County, Minnesota

    NASA Astrophysics Data System (ADS)

    Kletetschka, Gunther; Fischer, Tomas; Mls, Jiří; DěDeček, Petr

    2013-06-01

    Diamond Lake in Minnesota is covered every winter with ice and snow providing a modified thermal insulation between water and air. Autonomous temperature sensors, data loggers, were placed in this lake so that hourly measurements could be obtained from the snow-covered ice and water. The sensors that became frozen measured damped and delayed thermal response from the air-temperature fluctuation. Those sensors that were deeper within the snow-covered ice measured continuous, almost constant, temperature values near freezing. Several of them were within the liquid water and responded with a fluctuation of 24 h periods of amplitudes up to 0.2°C. Our analysis of the vertical temperature profiles suggested that the source of periodic water heating comes from the lake bottom. Because of the absence of daily temperature variations of the snow-covered ice, the influence of the air-temperature fluctuation can be ruled out. We attribute the heating process to the periodic inflow of groundwater to the lake and the cooling to the heat diffusion to the overlying ice cover. The periodic groundwater inflow is interpreted due to solid Earth tides, which cause periodic fluctuations of the groundwater pressure head.

  11. Asynchronous ice lobe retreat and glacial Lake Bascom: Deglaciation of the Hoosic and Vermont valleys, southwestern Vermont

    SciTech Connect

    Small, E.; Desimone, D. . Dept. of Geology)

    1993-03-01

    Deglaciation of the Hoosic River drainage basin in southwestern Vermont was more complex than previously described. Detailed surficial mapping, stratigraphic relationships, and terrace levels/delta elevations reveal new details in the chronology of glacial Lake Bascom: (1) a pre-Wisconsinan proglacial lake was present in a similar position to Lake Bascom as ice advanced: (2) the northern margin of 275m (900 ft) glacial Lake Bascom extended 10 km up the Vermont Valley; (3) the 215m (705 ft) Bascom level was stable and long lived; (4) intermediate water planes existed between 215m and 190m (625 ft) levels; and (5) a separate ice tongue existed in Shaftsbury Hollow damming a small glacial lake, here named glacial Lake Emmons. This information is used to correlate ice margins to different lake levels. Distance of ice margin retreat during a lake level can be measured. Lake levels are then used as control points on a Lake Bascom relative time line to compare rate of retreat of different ice tongues. Correlation of ice margins to Bascom levels indicates ice retreat was asynchronous between nearby tongues in southwestern Vermont. The Vermont Valley ice tongue retreated between two and four times faster than the Hoosic Valley tongue during the Bascom 275m level. Rate of retreat of the Vermont Valley tongue slowed to one-half of the Hoosic tongue during the 215m--190m lake levels. Factors responsible for varying rates of retreat are subglacial bedrock gradient, proximity to the Hudson-Champlain lobe, and the presence of absence of a calving margins. Asynchronous retreat produced splayed ice margins in southwestern Vermont. Findings from this study do not support the model of parallel, synchronous retreat proposed by many workers for this region.

  12. 2005 Crater Lake Formation, Lahar, Acidic Flood, and Gas Emission From Chiginagak Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Schaefer, J. R.; Scott, W. E.; McGimsey, R. G.; Jorgenson, J.

    2005-12-01

    A 400-m-wide crater lake developed in the formerly snow-and-ice-filled crater of Mount Chiginagak volcano sometime between August 2004 and June 2005, presumably due to increased heat flux from the hydrothermal system. We are also evaluating the possible role of magma intrusion and degassing. In early summer 2005, clay-rich debris and an estimated 5.6 million cubic meters of acidic water from the crater exited through tunnels in the base of a glacier that breaches the south crater rim. Over 27 kilometers downstream, the acidic waters of the flood reached approximately 1.5 meters above current water levels and inundated an important salmon spawning drainage, acidifying at least the surface water of Mother Goose Lake (approximately 1 cubic kilometer in volume) and preventing the annual salmon run. No measurements of pH were taken until late August 2005. At that time the pH of water sampled from the Mother Goose Lake inlet, lake surface, and outlet stream (King Salmon River) was 3.2. Defoliation and leaf damage of vegetation along affected streams, in areas to heights of over 70 meters in elevation above flood level, indicates that a cloud of detrimental gas or aerosol accompanied the flood waters. Analysis of stream water, lake water, and vegetation samples is underway to better determine the agent responsible for the plant damage. This intriguing pattern of gas-damaged vegetation concentrated along and above the flood channels is cause for further investigation into potential hazards associated with Chiginagak's active crater lake. Anecdotal evidence from local lodge owners and aerial photographs from 1953 suggest that similar releases occurred in the mid-1970s and early 1950s.

  13. Temporal coherence in water temperature and chemistry under the ice of boreal lakes (Finland).

    PubMed

    Järvinen, M; Rask, M; Ruuhijärvi, J; Arvola, L

    2002-09-01

    Temporal coherence was assessed for 11 limnological variables--water temperature, oxygen, conductivity, alkalinity, pH, colour, calcium (Ca), iron, aluminium, total phosphorus and total nitrogen--between 28 boreal lakes in southern Finland for the winter ice-covered period. The lakes were mainly small (<0.2 km2) and brown-coloured, and located within a circle of 10-km radius. A mean Pearson correlation coefficient for all lake pairs and variables averaged 0.37. Temporal coherence of variables across lake pairs was highest for conductivity, Ca, water temperature and alkalinity. The lake pairs with a direct surface water channel connection had a higher coherence than the lake pairs not connected by a stream. The size of the lake or catchment area had little effect on the coherence between the lakes. Temporal coherence was not strongly related to the difference in water colour (dystrophy) between the lakes. However, between polyhumic lakes (colour > 100 g Pt m(-3)) the coherence was generally higher than between less coloured lakes. Year-to-year variation in limnological characteristics could be partly explained by the variation in local weather. In March, water temperature and chemistry were infrequently related to winter weather, rather they correlated with the weather conditions of the previous autumn, while the ambient late winter weather seemed to have a stronger influence on lake conditions in April. Temporal variation in some variables was related to the atmospheric pressure changes over the North Atlantic (the North Atlantic Oscillation, NAO). Our results suggest that the potential effects of climatic change on lakes can be generalised regionally for brown-coloured dystrophic lakes. PMID:12405403

  14. Bubbles trapped in arctic lake ice: Potential implications for methane emissions

    NASA Astrophysics Data System (ADS)

    Wik, Martin; Crill, Patrick M.; Bastviken, David; Danielsson, Åsa; NorbäCk, Elin

    2011-09-01

    The amount of methane (CH4) emitted from northern lakes to the atmosphere is uncertain but is expected to increase as a result of arctic warming. A majority of CH4 is thought to be released through ebullition (bubbling), a pathway with extreme spatial variability that limits the accuracy of measurements. We assessed ebullition during early and late winter by quantifying bubbles trapped in the ice cover of two lakes in a landscape with degrading permafrost in arctic Sweden using random transect sampling and a digital image processing technique. Bubbles covered up to ˜8% of the lake area and were largely dominated by point source emissions with spatial variabilities of up to 1056%. Bubble occurrence differed significantly between early and late season ice, between the two lakes and among different zones within each lake (p < 0.001). Using a common method, we calculated winter fluxes of up to 129 ± 486 mg CH4 m-2 d-1. These calculations are, on average, two times higher than estimates from North Siberian and Alaskan lakes and four times higher than emissions measured from the same lakes during summer. Therefore, the calculations are likely overestimates and point to the likelihood that estimating CH4 fluxes from ice bubble distributions may be more difficult than believed. This study also shows that bubbles quantified using few transects will most likely be unsuitable in making large-scale flux estimates. At least 19 transects covering ˜1% of the lake area were required to examine ebullition with high precision in our studied lakes.

  15. Trends of ice cover duration in Finnish lakes in 1963-2015

    NASA Astrophysics Data System (ADS)

    Kuusisto, Esko

    2016-04-01

    Long data series of freezing and breakup observations are available from the lakes in Finland. Some of these series were started already in the former half of the 19th century. In this study, the duration of ice cover, together with the freezing and breakup dates in 1963-2015 have been analyzed for 50 lakes covering the whole country. A statistically significant linear trend (99.9%) towards a shorter duration was detected in 30 lakes. Fifteen lakes had a shortening trend with a significance of 99 per cent and the rest, three lakes with a significance of 95 per cent. For freezing, the corresponding numbers for a delaying date were seven, 14 and 20, for an earlier breakup they were 39, eight and three. None of the stations had opposite trends. In about half of the lakes, the shortening of the ice duration was 26-34 days. The shortening was almost twice as long in Southern Finland than in Northern Finland. For freezing date, half of the shifts were between 17-24 days, for breakup date between 11-14 days. Many lakes in Southern and Central Finland had their record early breakup in spring 2014. Most of the longest series had the previous record from the spring of 1921. By far the latest breakup during the observation history had occurred in 1867. In Southern and Central Finland, the difference from that breakup date to the second latest is typically 2-3 weeks.

  16. The distribution, structure, and composition of freshwater ice deposits in Bolivian salt lakes

    USGS Publications Warehouse

    Hurlbert, S.H.; Chang, Cecily C.Y.

    1988-01-01

    Freshwater ice deposits are described from seven, high elevation (4117-4730 m), shallow (mean depth <30 cm), saline (10-103 g l-1) lakes in the southwestern corner of Bolivia. The ice deposits range to several hundred meters in length and to 7 m in height above the lake or playa surface. They are located near the lake or salar margins; some are completely surrounded by water, others by playa deposits or salt crusts. Upper surfaces and sides of the ice deposits usually are covered by 20-40 cm of white to light brown, dry sedimentary materials. Calcite is the dominant crystalline mineral in these, and amorphous materials such as diatom frustules and volcanic glass are also often abundant. Beneath the dry overburden the ice occurs primarily as horizontal lenses 1-1000 mm thick, irregularly alternating with strata of frozen sedimentary materials. Ice represents from 10 to 87% of the volume of the deposits and yields freshwater (TFR <3 g l-1) when melted. Oxygen isotope ratios for ice are similar to those for regional precipitation and shoreline seeps but much lower than those for the lakewaters. Geothermal flux is high in the region as evidenced by numerous hot springs and deep (3.0-3.5 m) sediment temperatures of 5-10??C. This flux is one cause of the present gradual wasting away of these deposits. Mean annual air temperatures for the different lakes probably are all in the range of -2 to 4??C, and mean midwinter temperatures about 5??C lower. These deposits apparently formed during colder climatic conditions by the freezing of low salinity porewaters and the building up of segregation ice lenses. ?? 1988 Dr W. Junk Publishers.

  17. Stratified distribution of nutrients and extremophile biota within freshwater ice covering the surface of Lake Baikal.

    PubMed

    Bondarenko, Nina A; Belykh, Olga I; Golobokova, Ludmila P; Artemyeva, Olga V; Logacheva, Natalia F; Tikhonova, Irina V; Lipko, Irina A; Kostornova, Tatyana Ya; Parfenova, Valentina V; Khodzher, Tamara V; Ahn, Tae-Seok; Zo, Young-Gun

    2012-02-01

    Biological entities and gradients of selected chemicals within the seemingly barren ice layers covering Lake Baikal were investigated. Ice cores 40-68 cm long were obtained from in shore and offshore sites of Southern Lake Baikal during the cold period of a year (March-April) in 2007 and 2008. In microscopic observations of the melted ice, both algae and bacteria were found in considerable numbers (>10(3) cells/L and >10(4) cells/ml, respectively). Among all organisms found, diatom was generally the most predominant taxon in the ice. Interestingly, both planktonic and benthic algae were present in considerable numbers (2-4×10(4) cells/L). Dominant phototrophic picoplankton were comprised of small green algae of various taxa and cyanobacteria of Synechococcus and Cyanobium. The bacterial community consisted mostly of short rod and cocci cells, either free-living or aggregated. Large numbers of yeast-like cells and actinomycete mycelium were also observed. Concentrations of silica, phosphorus, and nitrate were low by an order of magnitude where biota was abundant. The profile of the ice could be interpreted as vertical stratification of nutrients and biomass due to biological activities. Therefore, the organisms in the ice were regarded to maintain high activity while thriving under freezing conditions. Based on the results, it was concluded that the freshwater ice covering the surface of Lake Baikal is considerably populated by extremophilic microorganisms that actively metabolize and form a detritus food chain in the unique large freshwater ecosystem of Lake Baikal. PMID:22367932

  18. Seismic and Geodetic Investigation of the 1996-1998 Earthquake Swarm at Strandline Lake, Alaska

    NASA Astrophysics Data System (ADS)

    Kilgore, W.; Roman, D. C.; Power, J. A.; Hansen, R. A.; Biggs, J.

    2009-12-01

    Microearthquake (< M3.0) swarms occur frequently in volcanic environments, but do not always culminate in an eruption. Such non-eruptive swarms may be caused by stresses induced by magma intrusion, hydrothermal fluid circulation, or regional tectonic processes, such as slow-slip earthquakes. Strandline Lake, located 30 km northeast of Mount Spurr volcano in south-central Alaska, experienced a strong earthquake swarm between August 1996 and August 1998. The Alaska Volcano Observatory (AVO) catalog indicates that a total of 2,999 earthquakes were detected during the swarm period, with a maximum magnitude of Mw 3.1 and a depth range of 0-30 km below sea level (with the majority of catalog hypocenters located between 5-10 km BSL). The cumulative seismic moment of the swarm was 2.03e15 N m, equivalent to a cumulative magnitude of Mw 4.2. Because of the swarm's distance from the nearest Holocene volcanic vent, seismic monitoring was poor and gas and deformation data for the swarm period do not exist. However, combined waveforms from a dense seismic network on Mount Spurr and from several regional seismic stations allowed us to re-analyze the swarm earthquakes. We first developed a new 1-D velocity model for the Strandline Lake region by re-picking and inverting precise arrival times for 27 large Strandline Lake earthquakes. The new velocity model reduced the average RMS for these earthquakes from 0.16 to 0.11s, and the average horizontal and vertical location errors from 3.3 to 2.5 km and 4.7 to 3.0 km, respectively. Depths of the 27 earthquakes ranged from 10.5 to 22.1 km with an average depth of 16.6 km. A moderately high b-value of 1.33 was determined for the swarm period, possibly indicative of magmatic activity. However, a similarly high b-value of 1.25 was calculated for the background period. 28 well-constrained fault plane solutions for both swarm and background earthquakes indicate a diverse mixture of strike-slip, dip-slip, and reverse faulting beneath

  19. Preservation of labile organic matter in soils of drained thaw lakes in Northern Alaska

    NASA Astrophysics Data System (ADS)

    Mueller, Carsten W.; Rethemeyer, Janet; Kao-Kniffin, Jenny; Löppmann, Sebastian; Hinkel, Kenneth; Bockheim, James

    2014-05-01

    A large number of studies predict changing organic matter (OM) dynamics in arctic soils due to global warming. In contrast to rather slowly altering bulk soil properties, single soil organic matter (SOM) fractions can provide a more detailed picture of the dynamics of differently preserved SOM pools in climate sensitive arctic regions. By the study of the chemical composition of such distinctive SOM fractions using nuclear magnetic resonance spectroscopy (NMR) together with radiocarbon analyses it is possible to evaluate the stability of the major OM pools. Approximately 50-75% of Alaska's Arctic Coastal Plain is covered with thaw lakes and drained thaw lakes that follow a 5,000 yr cycle of development (between creation and final drainage), thus forming a natural soil chronosequence. The drained thaw lakes offer the possibility to study SOM dynamics affected by permafrost processes over millennial timescales. In April 2010 we sampled 16 soil cores (including the active and permanent layer) reaching from young drained lakes (0-50 years since drainage) to ancient drained lakes (3000-5500 years since drainage). Air dried soil samples from soil horizons of the active and permanent layer were subjected to density fractionation in order to differentiate particulate OM and mineral associated OM. The chemical composition of the SOM fractions was analyzed by 13C CPMAS NMR spectroscopy. For a soil core of a young and an ancient drained thaw lake basin we also analyzed the 14C content. For the studied soils we can show that up to over 25 kg OC per square meter are stored mostly as labile, easily degradable organic matter rich in carbohydrates. In contrast only 10 kg OC per square meter were sequestered as presumably more stable mineral associated OC dominated by aliphatic compounds. Comparable to soils of temperate regions, we found small POM (< 20 µm) occluded in aggregated soil structures which differed in the chemical composition from larger organic particles. This was

  20. The influence of wind and ice on spring walrus hunting success on St. Lawrence Island, Alaska

    NASA Astrophysics Data System (ADS)

    Huntington, Henry P.; Noongwook, George; Bond, Nicholas A.; Benter, Bradley; Snyder, Jonathan A.; Zhang, Jinlun

    2013-10-01

    St. Lawrence Island Yupik hunters on St. Lawrence Island, Alaska, take hundreds of Pacific walrus (Odobenus rosmarus divergens) each year. The harvest and associated effort (hunting trips taken), however, are variable from year to year and also from day to day, influenced by physical environmental factors among other variables. We used data from 1996 to 2010 to construct generalized additive models (GAMs) to examine several relationships among the variables. Physical factors explained 18% of the variability in harvest in Savoonga and 25% of the variability in effort; the corresponding figures for Gambell were 24% and 32%. Effort alone explained 63% of the harvest in Savoonga and 59% in Gambell. Physical factors played a relatively smaller role in determining hunting efficiency (walrus taken per hunting trip), explaining 15% of the variability in efficiency in Savoonga and 22% in Gambell, suggesting that physical factors play a larger role in determining whether to hunt than in the outcome of the hunt once undertaken. Combining physical factors with effort explained 70% of the harvest variability in Savoonga and 66% in Gambell. Although these results indicate that other factors (e.g. fuel prices, socioeconomic conditions) collectively cause a greater share of variability in harvest and effort than ice and wind, at least as indicated by the measures used as predictors in the GAMs, they also suggest that environmental change is also likely to influence future harvest levels, and that climate models that yield appropriately scaled data on ice and wind around St. Lawrence Island may be of use in determining the magnitude and direction of those influences.

  1. Changes in winter air temperatures near Lake Michigan, 1851-1993, as determined from regional lake-ice records

    USGS Publications Warehouse

    Assel, R.A.; Robertson, Dale M.

    1995-01-01

    Records of freezeup and breakup dates for Grand Traverse Bay, Michigan, and Lake Mendota, Wisconsin, are among the longest ice records available near the Great Lakes, beginning in 185 1 and 1855, respectively. The timing of freezeup and breakup results from an integration of meteorological conditions (primarily air temperature) that occur before these events. Changes in the average timing of these ice-events are translated into changes in air temperature by the use of empirical and process-driven models. The timing of freezeup and breakup at the two locations represents an integration of air temperatures over slightly different seasons (months). Records from both locations indicate that the early winter period before about 1890 was - 15°C cooler than the early winter period after that time; the mean temperature has, however, remained relatively constant since about 1890. Changes in breakup dates demonstrate a similar 1.0-1 .5”C increase in late winter and early spring air temperatures about 1890. More recent average breakup dates at both locations have been earlier than during 1890-1940, indicating an additional warming of 1.2”C in March since about 1940 and a warming of 1 . 1°C in January-March since about 1980. Ice records at these sites will continue to provide an early indication of the anticipated climatic warming, not only because of the large response of ice cover to small changes in air temperature but also because these records integrate climatic conditions during the seasons (winter-spring) when most warming is forecast to occur. Future reductions in ice cover may strongly affect the winter ecology of the Great Lakes by reducing the stable environment required by various levels of the food chain. 

  2. EO-based lake-ice cover and surface temperature products: Advancing process understanding and modeling capabilities of lake-atmosphere interactions in cold regions

    NASA Astrophysics Data System (ADS)

    Duguay, C. R.; Kheyrollah Pour, H.; Ochilov, S.

    2011-12-01

    Our ability to determine the energy and water budgets of lakes is critical to modeling high latitude weather and climate. In recent years, the proper representation of lake processes in numerical weather prediction (NWP) and regional climate (RCM) models has become a topic of much interest by the scientific community. With the increased resolution of the NWP models and RCMs, it has now become possible and necessary to improve the representation of lake-atmosphere interactions to better describe the energy exchange between the atmosphere and the lake surface. Among other lake properties, knowledge about lake surface temperature and ice-coverage is critical. These two parameters can either be obtained from observations or through simulations. Although much progress is being made with lake models, as implemented in NWP/RCM models, the assimilation of data on lake temperature and fractional ice coverage has been identified as highly desirable. Spatially and temporally consistent lake ice and lake surface temperature (LST) products are invaluable in this respect. These can be derived from Earth Observation (EO) systems. However, satellite-based products must be compared with existing lake models, as well as validated and further improved as needed, to generate lake ice and LST products for operational use by the modeling community. The European Space Agency (ESA) is supporting the international efforts coordinated by the Climate and Cryosphere (CliC) project of the World Climate Research Programme (WCRP) to exploit the use of EO technology, models and in situ data to improve the characterization of river and lake ice processes and their contribution to the Northern Hydrology system. The ESA-sponsored North Hydrology project aims to develop a portfolio of novel multi-mission geo-information products, maximizing the use of ESA satellite data, to respond to the scientific requirements of the CliC community and the operational requirements of the weather and climate

  3. A decade of sedimentation in ice-contact, proglacial lakes, Bering Glacier, AK

    NASA Astrophysics Data System (ADS)

    Fleisher, P. Jay; Bailey, Palmer K.; Cadwell, Donald H.

    2003-08-01

    Bathymetric surveys during the 1991-2000 decade in two ice-contact, proglacial lakes on the eastern sector of Bering piedmont lobe captured the buildup effects of the 1993-1995 surge. Following ice-front advance of 1.0-1.5 km into Tsivat and Tsiu Lakes, the basins were significantly altered by surge-related sedimentation including the impact of a subglacial outburst into Tsivat Lake. The subsequent changes in basin shape, size, and morphology were monitored by six bathymetric surveys. Measured changes in water depth serve as a proxy for determining increments of sediment accumulation. Upwelling, ice-front vents fed by subglacial tunnels transported suspended fine sediment directly into the lake system. The rate of suspension settling within both lakes varied from 0.6 to 1.2 m year -1 prior to the surge. Suspended load during surge years increased sixfold from 1.7 to 13.9 g l -1, accompanied by increased sediment accumulation of 2.2-3.1 m year -1. Vent-related aggradation and subsequent filling of Tsivat Lake caused sediment bypassing to Tsiu Lake, where encroachment by delta growth contributed to a postsurge rate of bottomset accumulation of 3.0 m year -1. The total sediment influx from subglacial sources is represented by the sum of bathymetrically determined accumulation, plus an estimated volume of sediment that remained suspended, thus passing through the lake system. Total sediment flux along the eastern Bering piedmont lobe from 1991 to 2000 is approximately 227 million cubic meters.

  4. Statistical characterization of trapped bubbles in subarctic lake ice: Potential implications for methane emissions

    NASA Astrophysics Data System (ADS)

    Wik, M.; Crill, P. M.; Bastviken, D.; Danielsson; Norbäck, E.

    2010-12-01

    Methane (CH4) emissions from northern lakes to the atmosphere are highly uncertain but estimated to increase due to arctic climate change and subsequent permafrost thaw and sediment warming. A large amount of CH4, if not the most, is thought to be released through ebullition (bubbling), a pathway with extreme spatial patchiness that challenges the accuracy of measurements and budget extrapolations. The spatial variability of ebullition can be assessed on northern lakes because bubbles are trapped in the ice during winter. This study statistically characterized trapped bubbles over various depths across two ice covered subarctic lakes in a changing discontinuous permafrost landscape in northern Sweden. Observations were made through a 0.64 m2 quadrat that was placed every third meter along a large number of randomly distributed transects. This stratified random sampling design combined with a digital image processing technique determined that bubble patterns on average covered up to 7.7% of the lake area and were dominated by ebullition from frequently occurring but highly spatially dispersed point sources with variabilities of up to 1056%. Bubble frequency differed significantly between early and late season lake ice, between the two lakes and among different zones within each lake (p<0.001). Based on the high spatial variability it was calculated that almost 1% of a lake area was required to be measured along 15 randomly distributed transects to examine the patchiness of bubbles with high precision. Thus, the number and variability of bubbles observed along a small number of transects will most likely be unsuitable variables in large scale estimates and extrapolations aiming to reduce uncertainties in the budget of atmospheric CH4.

  5. Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica

    NASA Astrophysics Data System (ADS)

    Barbante, C.; Gabrielli, P.; Turetta, C.; Planchon, F.; Boutron, C.; Petit, J. R.; Bulat, S.; Hong, S.; Cozzi, G.; Cescon, P.

    2009-12-01

    We report the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8-56 pg g-1 for Ce and 0.0035- 0.24 pg g-1 for Lu in glacier ice, and between <0.1-24 pg g-1 for Ce and <0.0004-0.02 pg g-1 for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC1;characterized by visible aggregates containing a mixture of very fine terrigenous particles) and in the deeper accreted ice (AC2; characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC1 formation. Interestingly, if the LREE enrichment found in AC1 was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.

  6. Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica

    NASA Astrophysics Data System (ADS)

    Gabrielli, Paolo; Planchon, Frederic; Barbante, Carlo; Boutron, Claude F.; Petit, Jean Robert; Bulat, Sergey; Hong, Sungmin; Cozzi, Giulio; Cescon, Paolo

    2009-10-01

    This paper reports the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8-56 pg g -1 for Ce and 0.0035-0.24 pg g -1 for Lu in glacier ice, and between <0.1-24 pg g -1 for Ce and <0.0004-0.02 pg g -1 for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC 1; characterized by visible aggregates containing a mixture of very fine terrigenous particles) and in the deeper accreted ice (AC 2; characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC 1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC 1 formation. Interestingly, if the LREE enrichment found in AC 1 was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.

  7. Ecology of Subglacial Lake Vostok (Antarctica), Based on Metagenomic/Metatranscriptomic Analyses of Accretion Ice

    PubMed Central

    Rogers, Scott O.; Shtarkman, Yury M.; Koçer, Zeynep A.; Edgar, Robyn; Veerapaneni, Ram; D’Elia, Tom

    2013-01-01

    Lake Vostok is the largest of the nearly 400 subglacial Antarctic lakes and has been continuously buried by glacial ice for 15 million years. Extreme cold, heat (from possible hydrothermal activity), pressure (from the overriding glacier) and dissolved oxygen (delivered by melting meteoric ice), in addition to limited nutrients and complete darkness, combine to produce one of the most extreme environments on Earth. Metagenomic/metatranscriptomic analyses of ice that accreted over a shallow embayment and over the southern main lake basin indicate the presence of thousands of species of organisms (94% Bacteria, 6% Eukarya, and two Archaea). The predominant bacterial sequences were closest to those from species of Firmicutes, Proteobacteria and Actinobacteria, while the predominant eukaryotic sequences were most similar to those from species of ascomycetous and basidiomycetous Fungi. Based on the sequence data, the lake appears to contain a mixture of autotrophs and heterotrophs capable of performing nitrogen fixation, nitrogen cycling, carbon fixation and nutrient recycling. Sequences closest to those of psychrophiles and thermophiles indicate a cold lake with possible hydrothermal activity. Sequences most similar to those from marine and aquatic species suggest the presence of marine and freshwater regions. PMID:24832801

  8. Physical background of the development of oxygen depletion in ice-covered lakes.

    PubMed

    Golosov, S; Maher, O A; Schipunova, E; Terzhevik, A; Zdorovennova, G; Kirillin, G

    2007-03-01

    The effect of the heat interaction between a water column and sediments on the formation, development, and duration of existence of anaerobic zones in ice-covered lakes is estimated based on observational data from five frozen lakes located in northwestern Russia and North America. A simple one-dimensional model that describes the formation and development of the dissolved oxygen deficit in shallow ice-covered lakes is suggested. The model reproduces the main features of dissolved oxygen dynamics during the ice-covered period; that is, the vertical structure, the thickness, and the rate of increase of the anaerobic zone in bottom layers. The model was verified against observational data. The results from the verification show that the model adequately describes the dissolved oxygen dynamics in winter. The consumption rates of DO by bacterial plankton and by bottom sediments, which depend on the heat transfer through the water-sediment interface, are calculated. The results obtained allow the appearance of potentially dangerous anaerobic zones in shallow lakes and in separate lake areas, which result from thermal regime changes, to be predicted.

  9. Ice Flow Dynamics and Outlet Zone Morphology of Subglacial Lake Ellsworth

    NASA Astrophysics Data System (ADS)

    Ross, N.; Smith, A.; Woodward, J.; Siegert, M. J.; Hindmarsh, R. C.; Corr, H.; King, E. C.; Vaughan, D.; Gillet-Chaulet, F.; Jay-Allemand, M.

    2009-12-01

    Subglacial Lake Ellsworth (SLE) is located beneath 2.95-3.28 km of ice at the base of a deep subglacial trench ~30 km from the central ice divide of the West Antarctic Ice Sheet. Seismic reflection surveys indicate a maximum water column thickness of 155 m. Radio-echo sounding (RES) data have been used to map the lake, the morphology of the subglacial catchment and the structure and thickness of the overlying ice sheet. Direct access, measurement and sampling of the lake waters and underlying sediments will be undertaken during the 2012-13 Antarctic field season by the Lake Ellsworth Consortium. Internal ice sheet layers throughout the SLE catchment have been picked and transformed into 3D surfaces as input for radar layer modelling. SLE is bounded on either side by steep, ~2 km high, mountainous subglacial topography. Over the lake, anomalies between modelled and observed internal layers are recognised near the steeper bedrock wall. We have sought to understand these in terms of perturbations to the velocity field from higher order mechanical effects as well as being caused by melt anomalies. A closely-spaced grid of RES lines (area coverage 7.5 x 7.5 km, line spacing ~500 m or less) has been used to map the outlet area of the lake in detail, with the aim of identifying possible drainage routes. The downstream margin of the lake is characterised by a pronounced topographic ridge, trending obliquely to ice flow, which rises ~200 m above the elevation of the water surface. Beyond the ridge a 5 km by 0.75 km linear depression has been mapped. A narrow, low-lying breach in the ridge that connects to this depression may provide a subglacial hydrological outlet from SLE. Potential mechanisms for the formation of these features include: i) subaerial or subglacial processes pre-dating ice sheet development; ii) water discharge from SLE. Such models are not necessarily mutually exclusive. The origins of the subglacial geomorphology and its possible influence on the routing

  10. Thaw bulb dimensions determined using electrical imaging across thermokarst lakes, Seward Peninsula, Alaska

    NASA Astrophysics Data System (ADS)

    Nolan, J. T.; Slater, L. D.; Parsekian, A.; Plug, L. J.; Grosse, G.; Walter Anthony, K. M.

    2009-12-01

    Geophysical imaging of thaw bulb dimensions underlying thermokarst lakes may provide data required to validate models for thaw bulb evolution and to quantify availability of previously frozen soil carbon to atmospheric emission. Direct measurements by drilling are costly in remote arctic regions and are limited by poor spatial resolution. We report the results of an experiment to test the use of electrical resistivity imaging for determining thaw bulb dimensions of thermokarst lakes on the Seward Peninsula, Alaska. Continuous resistivity measurements were collected using a floating array of electrodes pulled by a motorized inflatable boat. The inversion of the resistivity data was conducted using a one dimensional laterally constrained inversion routine that solves for thickness and resistivity based on three layer model. Since the water layer is partly constrained in terms of thickness (from depth sounder measurements) and resistivity (from measurements made with a conductance probe), and the thaw bulb and permafrost resistivity are known from coring, the only totally unconstrained parameter is the thickness of the thaw bulb sediments. This overdetermined inverse problem yields a high degree of confidence in the resulting model, as evident from low model residuals and parameter covariance analysis. Results from this experiment show that electrical resistivity imaging is a relatively low cost method for determining the thaw bulb dimensions along a laterally continuous survey line.

  11. Metamorphism in the Tlikakila Complex, Lake Clark National Park, Alaska: Does it Record the Collision of the Peninsular Terrane With Alaska?

    NASA Astrophysics Data System (ADS)

    Amato, J. M.; Bogar, M. J.; Calvert, A. T.

    2001-12-01

    The Tlikakila complex is a ~80 km x ~5 km belt of variably metamorphosed and deformed rocks thought to be part of the Peninsular terrane of southern Alaska. This project uses detailed mapping, structural analysis, and thermochronology to address the tectonic evolution of rocks thought to be part of the Peninsular terrane in southern Alaska. Both meta-igneous and metasedimentary rocks of Triassic (?) age are exposed. Meta-igneous protoliths include mafic (gabbro, basalt) and ultramafic rocks. Metasedimentary protoliths include limestone, chert, and other siliceous sediments. Metapelites are rare. Metamorphic rocks in the study area include two distinct occurrences. Smaller outcrops, appear to be roof pendants in Tertiary plutons. At Kasna Creek, near Kontrashibuna Lake, limestone beds were contact metamorphosed with copper sulfide mineralization within a mafic pluton. Larger outcrops in the Tlikakila complex are more continuous, more pervasively deformed, and more recrystallized. A new 40Ar/39Ar analysis of white mica from a metasedimentary rock in the Tlikakila complex located just southwest of Saddle Lake yielded a monotonically increasing age spectrum, with the oldest high-temperature step giving a date of around 160 Ma, and the low-temperature step giving a date of 60.5 Ma. The oldest date could represent the timing of greenschist facies metamorphism of the Tlikakila complex. It is interesting that this 160 Ma date is similar to the youngest of the Middle to Late Jurassic plutons (174-158 Ma) in the Alaska-Aleutian Range batholith, considered to be part of the Peninsular terrane. Metamorphism in the Tlikakila complex could be related to the onset of the collision of the Peninsular terrane with Alaska, which also resulted in the cessation of arc magmatism. The youngest date from this sample overlaps with existing 59-63 Ma K-Ar dates from Tertiary volcanic and plutonic rocks in the area and records new mica growth associated with Tertiary magmatism.

  12. Preliminary tephra-fall records from three lakes in the Anchorage, Alaska area: advances towards a regional tephrochronostratigraphic framework

    NASA Astrophysics Data System (ADS)

    Wallace, K. L.; Kaufman, D. S.; Schiff, C. J.; Kathan, K.; Werner, A.; Hancock, J.; Hagel, L. A.

    2010-12-01

    Sediment cores recovered from three kettle lakes, all within 10 km of Anchorage, Alaska contain a record of tephra fall from major eruptive events of Cook Inlet volcanoes during the past 11250 yr. Prominent tephra layers from multiple cores within each lake were first correlated within each basin using physical properties, major-oxide glass geochemistry, and constrained by bracketing radiocarbon age. Distinct tephra from each lake were then correlated among all three lakes using the same criteria to develop a composite tephrostratigraphic framework for the Anchorage area. Lorraine Lake, the northern-most lake contains 17 distinct tephra layers; Goose Lake, the eastern most lake contains 10 distinct tephra layers; and Little Campbell Lake, to the west, contains 7 distinct tephra layers. Thinner, less-prominent tephra layers, reflecting smaller or more distant eruptions, also occur but are not included as part of this study. Of the 33 tephra layers, only two could be confidently correlated among all three lakes, and four other correlative deposits were recognized in two of the three lakes. The minimum number of unique major tephra-fall events in the Anchorage area is 22 in the past 11200 years, or about 1 event every 500 years. This number underestimates the actual number of eruptions because not attempt was made to locate crypto-tephra. All but perhaps one tephra deposit originated from Cook Inlet volcanoes with the most prolific source being Mount Spurr/Crater Peak, which is accountable for at least 8 deposits. Combining radiocarbon ages to produce an independent age model for each lake is in progress and will aid in confirming correlations and assigning detailed modeled-tephra age and uncertainty to each tephra layer.

  13. Drainage network structure and hydrologic behavior of three lake-rich watersheds on the Arctic Coastal Plain, Alaska

    USGS Publications Warehouse

    Arp, C.D.; Whitman, M.S.; Jones, Benjamin M.; Kemnitz, R.; Grosse, G.; Urban, F.E.

    2012-01-01

    Watersheds draining the Arctic Coastal Plain (ACP) of Alaska are dominated by permafrost and snowmelt runoff that create abundant surface storage in the form of lakes, wetlands, and beaded streams. These surface water elements compose complex drainage networks that affect aquatic ecosystem connectivity and hydrologic behavior. The 4676 km2 Fish Creek drainage basin is composed of three watersheds that represent a gradient of the ACP landscape with varying extents of eolian, lacustrine, and fluvial landforms. In each watershed, we analyzed 2.5-m-resolution aerial photography, a 5-m digital elevation model, and river gauging and climate records to better understand ACP watershed structure and processes. We show that connected lakes accounted for 19 to 26% of drainage density among watersheds and most all channels initiate from lake basins in the form of beaded streams. Of the > 2500 lakes in these watersheds, 33% have perennial streamflow connectivity, and these represent 66% of total lake area extent. Deeper lakes with over-wintering habitat were more abundant in the watershed with eolian sand deposits, while the watershed with marine silt deposits contained a greater extent of beaded streams and shallow thermokarst lakes that provide essential summer feeding habitat. Comparison of flow regimes among watersheds showed that higher lake extent and lower drained lake-basin extent corresponded with lower snowmelt and higher baseflow runoff. Variation in baseflow runoff among watersheds was most pronounced during drought conditions in 2007 with corresponding reduction in snowmelt peak flows the following year. Comparison with other Arctic watersheds indicates that lake area extent corresponds to slower recession of both snowmelt and baseflow runoff. These analyses help refine our understanding of how Arctic watersheds are structured and function hydrologically, emphasizing the important role of lake basins and suggesting how future lake change may impact hydrologic

  14. Microbial processes in the ice cover of a newly detected subglacial lake in Antarctica

    NASA Astrophysics Data System (ADS)

    Sattler, B.; Dieser, M.; Wille, A.; Sipiera, P.; Psenner, R.

    2003-04-01

    A subglacial water body, called Lake Paula, was detected in Patriot Hills in the West Antarctic in 2002 and sampled for the first time ever for microbial life within the ice cover and the pelagic zone. It is permanently covered with an ice sheet of approximately 2,5 m thickness and the water body has a depth of about 10 m. The lake is situated near a moraine which partly ablates from snow and provides meltwater from the slopes to the lake during austral summer. These running waters which are kept liquid by the heating up of the dark soil are penetrating the lower ice cover and inoculating it with nutrients, microbes and diatoms of terrestrial origin, thus dividing the ice cover laterally in two different sections. The upper part which is exposed to the atmosphere and never in contact with meltwater is harboring an extremely low abundance of bacteria (811 ml-1), whereas bacterial numbers increase in the lower meter up to 1,14*105 ml-1. A similar pattern can be observed concerning bacterial production: The upside part shows carbon production of 0,2ng l-1h-1, the lakeside end of the ice core which is softened up by the intrusion had a nearly 10fold increase with 2,8 ng carbon l-1 h-1. Temperature sensitivity of the embedded microbes reveal completely diverse pictures as well: Bacteria isolated from the upper part showed growth optima at 10^oC, the lower part at 25^oC, phylogenetic affiliations done by 16s rDNA still have to be done. These results proof once more as already known from the unique Dry Valley Lakes that even in this harsh environment like the Antarctic continent microbial ice aggregates can be sustained and kept in a dynamic system as long as the supply of liquid water which is essential for an active bacterial metabolism is provided at least for a small time frame.

  15. 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

  16. Imaging radar observations of frozen Arctic lakes

    NASA Technical Reports Server (NTRS)

    Elachi, C.; Bryan, M. L.; Weeks, W. F.

    1976-01-01

    A synthetic aperture imaging L-band radar flown aboard the NASA CV-990 remotely sensed a number of ice-covered lakes about 48 km northwest of Bethel, Alaska. The image obtained is a high resolution, two-dimensional representation of the surface backscatter cross section, and large differences in backscatter returns are observed: homogeneous low returns, homogeneous high returns and/or low returns near lake borders, and high returns from central areas. It is suggested that a low return indicates that the lake is frozen completely to the bottom, while a high return indicates the presence of fresh water between the ice cover and the lake bed.

  17. Links Between Acceleration, Melting, and Supraglacial Lake Drainage of the Western Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Hoffman, M. J.; Catania, G. A.; Newmann, T. A.; Andrews, L. C.; Rumrill, J. A.

    2012-01-01

    The impact of increasing summer melt on the dynamics and stability of the Greenland Ice Sheet is not fully understood. Mounting evidence suggests seasonal evolution of subglacial drainage mitigates or counteracts the ability of surface runoff to increase basal sliding. Here, we compare subdaily ice velocity and uplift derived from nine Global Positioning System stations in the upper ablation zone in west Greenland to surface melt and supraglacial lake drainage during summer 2007. Starting around day 173, we observe speedups of 6-41% above spring velocity lasting approximately 40 days accompanied by sustained surface uplift at most stations, followed by a late summer slowdown. After initial speedup, we see a spatially uniform velocity response across the ablation zone and strong diurnal velocity variations during periods of melting. Most lake drainages were undetectable in the velocity record, and those that were detected only perturbed velocities for approximately 1 day, suggesting preexisting drainage systems could efficiently drain large volumes of water. The dynamic response to melt forcing appears to 1) be driven by changes in subglacial storage of water that is delivered in diurnal and episodic pulses, and 2) decrease over the course of the summer, presumably as the subglacial drainage system evolves to greater efficiency. The relationship between hydrology and ice dynamics observed is similar to that observed on mountain glaciers, suggesting that seasonally large water pressures under the ice sheet largely compensate for the greater ice thickness considered here. Thus, increases in summer melting may not guarantee faster seasonal ice flow.

  18. Links Between Acceleration, Melting, and Supraglacial Lake Drainage of the Western Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Hoffman, M. J.; Catania, G. A.; Neumann, T. A.; Andrews, L. C.; Rumrill, J. A.

    2011-01-01

    The impact of increasing summer melt on the dynamics and stability of the Greenland Ice Sheet is not fully understood. Mounting evidence suggests seasonal evolution of subglacial drainage mitigates or counteracts the ability of surface runoff to increase basal sliding. Here, we compare subdaily ice velocity and uplift derived from nine Global Positioning System stations in the upper ablation zone in west Greenland to surface melt and supraglacial lake drainage during summer 2007. Starting around day 173, we observe speedups of 6-41% above spring velocity lasting 40 days accompanied by sustained surface uplift at most stations, followed by a late summer slowdown. After initial speedup, we see a spatially uniform velocity response across the ablation zone and strong diurnal velocity variations during periods of melting. Most lake drainages were undetectable in the velocity record, and those that were detected only perturbed velocities for approx 1 day, suggesting preexisting drainage systems could efficiently drain large volumes of water. The dynamic response to melt forcing appears to (1) be driven by changes in subglacial storage of water that is delivered in diurnal and episodic pulses, and (2) decrease over the course of the summer, presumably as the subglacial drainage system evolves to greater efficiency. The relationship between hydrology and ice dynamics observed is similar to that observed on mountain glaciers, suggesting that seasonally large water pressures under the ice sheet largely compensate for the greater ice thickness considered here. Thus, increases in summer melting may not guarantee faster seasonal ice flow.

  19. 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.

  20. Regional sea level change in response to ice mass loss in Greenland, the West Antarctic and Alaska

    NASA Astrophysics Data System (ADS)

    Brunnabend, S.-E.; Schröter, J.; Rietbroek, R.; Kusche, J.

    2015-11-01

    Besides the warming of the ocean, sea level is mainly rising due to land ice mass loss of the major ice sheets in Greenland, the West Antarctic, and the Alaskan Glaciers. However, it is not clear yet how these land ice mass losses influence regional sea level. Here, we use the global Finite Element Sea-ice Ocean Model (FESOM) to simulate sea surface height (SSH) changes caused by these ice mass losses and combine it with the passive ocean response to varying surface loading using the sea level equation. We prescribe rates of fresh water inflow, not only around Greenland, but also around the West Antarctic Ice Sheet and the mountain glaciers in Alaska with approximately present-day amplitudes of 200, 100, and 50 Gt/yr, respectively. Perturbations in sea level and in freshwater distribution with respect to a reference simulation are computed for each source separately and in their combination. The ocean mass change shows an almost globally uniform behavior. In the North Atlantic and Arctic Ocean, mass is redistributed toward coastal regions. Steric sea level change varies locally in the order of several centimeters on advective timescales of decades. Steric effects to local sea level differ significantly in different coastal locations, e.g., at North American coastal regions the steric effects may have the same order of magnitude as the mass driven effect, whereas at the European coast, steric effects remain small during the simulation period.

  1. Detection and spatiotemporal analysis of methane ebullition on thermokarst lake ice using high-resolution optical aerial imagery

    NASA Astrophysics Data System (ADS)

    Lindgren, P. R.; Grosse, G.; Anthony, K. M. Walter; Meyer, F. J.

    2016-01-01

    Thermokarst lakes are important emitters of methane, a potent greenhouse gas. However, accurate estimation of methane flux from thermokarst lakes is difficult due to their remoteness and observational challenges associated with the heterogeneous nature of ebullition. We used high-resolution (9-11 cm) snow-free aerial images of an interior Alaskan thermokarst lake acquired 2 and 4 days following freeze-up in 2011 and 2012, respectively, to detect and characterize methane ebullition seeps and to estimate whole-lake ebullition. Bubbles impeded by the lake ice sheet form distinct white patches as a function of bubbling when lake ice grows downward and around them, trapping the gas in the ice. Our aerial imagery thus captured a snapshot of bubbles trapped in lake ice during the ebullition events that occurred before the image acquisition. Image analysis showed that low-flux A- and B-type seeps are associated with low brightness patches and are statistically distinct from high-flux C-type and hotspot seeps associated with high brightness patches. Mean whole-lake ebullition based on optical image analysis in combination with bubble-trap flux measurements was estimated to be 174 ± 28 and 216 ± 33 mL gas m-2 d-1 for the years 2011 and 2012, respectively. A large number of seeps demonstrated spatiotemporal stability over our 2-year study period. A strong inverse exponential relationship (R2 > = 0.79) was found between the percent of the surface area of lake ice covered with bubble patches and distance from the active thermokarst lake margin. Even though the narrow timing of optical image acquisition is a critical factor, with respect to both atmospheric pressure changes and snow/no-snow conditions during early lake freeze-up, our study shows that optical remote sensing is a powerful tool to map ebullition seeps on lake ice, to identify their relative strength of ebullition, and to assess their spatiotemporal variability.

  2. Detection of Supra-Glacial Lakes on the Greenland Ice Sheet Using MODIS Images

    NASA Astrophysics Data System (ADS)

    Verin, Gauthier; Picard, Ghislain; Libois, Quentin; Gillet-Chaulet, Fabien; Roux, Antoine

    2015-04-01

    During melt season, supra-glacial lakes form on the margins of the Greenland ice sheet. Because of their size exceeding several kilometers, and their concentration, they affect surface albedo leading to an amplification of the regional melt. Furthermore, they foster hydro-fracturing that propagate liquid water to the bedrock and therefore enhance the basal lubrication which may affect the ice motion. It is known that Greenland ice sheet has strongly responded to recent global warming. As air temperature increases, melt duration and melt intensity increase and surface melt area extends further inland. These recent changes may play an important role in the mass balance of the Greenland ice sheet. In this context, it is essential to better monitor and understand supra-glacial spatio-temporal dynamics in order to better assess future sea level rise. In this study MODIS (Moderate Resolution Imaging Spectroradiometer) images have been used to detect supra-glacial lakes. The observation site is located on the West margin of the ice sheet, between 65°N and 70°N where the concentration of lake is maximum. The detection is performed by a fully automatic algorithm using images processing techniques introduced by Liang et al. (2012) which can be summarized in three steps: the selection of usable MODIS images, mainly we exclude images with too many clouds. The detection of lake and the automatic correction of false detections. This algorithm is capable to tag each individual lake allowing a survey of all lake geometrical properties over the entire melt season. We observed a large population of supra-glacial lakes over 14 melt seasons, from 2000 to 2013 on an extended area of 70.000 km2. In average, lakes are observed from June 9 ± 8.7 days to September 13 ± 13.9 days, and reach a maximum total area of 699 km2 ± 146 km2. As the melt season progresses, lakes form higher in altitude up to 1800 m above sea level. Results show a very strong inter-annual variability in term of

  3. The interdependence of lake ice and climate in central North America

    NASA Technical Reports Server (NTRS)

    Jelacic, A. J. (Principal Investigator)

    1972-01-01

    There are no author-identified significant results in this report. This investigation is to identify any correlations between the freeze/ thaw cycles of lakes and regional weather variations. ERTS-1 imagery of central Canada and north central United States is examined on a seasonal basis. The ice conditions of certain major study lakes are noted and recorded on magnetic tape, from which the movement of a freeze/thaw transition zone may be deduced. Weather maps and tables are used to establish any obvious correlations. The process of selecting major study lakes is discussed, and a complete lake directory is presented. Various routines of the software support library are described, accompanied by output samples. Procedures used for ERTS imagery processing are presented along with the data analysis plan. Application of these procedures to selected ERTS imagery has demonstrated their utility. Preliminary results show that the freeze/thaw transition zone can be monitored from ERTS.

  4. Ice-walled-lake plains: Implications for the origin of hummocky glacial topography in middle North America

    USGS Publications Warehouse

    Clayton, L.; Attig, J.W.; Ham, N.R.; Johnson, M.D.; Jennings, C.E.; Syverson, K.M.

    2008-01-01

    Ice-walled-lake plains are prominent in many areas of hummocky-till topography left behind as the Laurentide Ice Sheet melted from middle North America. The formation of the hummocky-till topography has been explained by: (1) erosion by subglacial floods; (2) squeezing of subglacial till up into holes in stagnant glacial ice; or (3) slumping of supraglacial till. The geomorphology and stratigraphy of ice-walled-lake plains provide evidence that neither the lake plains nor the adjacent hummocks are of subglacial origin. These flat lake plains, up to a few kilometers in diameter, are perched as much as a few tens of meters above surrounding depressions. They typically are underlain by laminated, fine-grained suspended-load lake sediment. Many ice-walled-lake plains are surrounded by a low rim ridge of coarser-grained shore sediment or by a steeper rim ridge of debris that slumped off the surrounding ice slopes. The ice-walled lakes persisted for hundreds to thousands of years following glacial stagnation. Shells of aquatic molluscs from several deposits of ice-walled-lake sediment in south-central North Dakota have been dated from about 13 500 to 10 500??B.P. (calibrated radiocarbon ages), indicating a climate only slightly cooler than present. This is confirmed by recent palaeoecological studies in nearby non-glacial sites. To survive so long, the stagnant glacial ice had to be well-insulated by a thick cover of supraglacial sediment, and the associated till hummocks must be composed primarily of collapsed supraglacial till. ?? 2007 Elsevier B.V. All rights reserved.

  5. Snow Pack and Lake Ice Pack Remote Sensing using Wideband Autocorrelation Radiometry

    NASA Astrophysics Data System (ADS)

    Mousavi, S.; De Roo, R. D.; Sarabandi, K.; England, A. W.

    2015-12-01

    A novel microwave radiometric technique, wideband autocorrelation radiometry (WiBAR), offers a deterministic method of remotely sensing the propagation time τdelay of microwaves through low loss layers at the bottom of the atmosphere. Terrestrial examples are the snow and lake ice packs. This technique is based on the Planck radiation from the surface beneath the pack which travels upwards through the pack towards the radiometer; such a signal we call a direct signal. On the other hand, part of this radiation reflects back from the pack's upper interface then from its lower interface, before traveling towards the radiometer's antenna. Thus, there are two signals received by the radiometer, the direct signal and a delayed copy of it. The microwave propagation time τdelay through the pack yields a measure of its vertical extent. We report a time series of measurements of the ice pack on Lake Superior from February to April 2014 to demonstrate this technique. The observations are done at frequencies from 7 to 10 GHz. At these frequencies, the volume and surface scattering are small in the ice pack. This technique is inherently low-power since there is no transmitter as opposed to active remote sensing techniques. The results of this paper is to present the WiBAR technique and show that the microwave travel time within a dry snow pack and lake ice pack can be deterministically measured for different thicknesses using this technique.

  6. 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.

  7. Dissolved gases in perennially ice-covered lakes of the McMurdo Dry Valleys, Antarctica

    NASA Technical Reports Server (NTRS)

    Andersen, D. T.; McKay, C. P.; Wharton, R. A. Jr; Wharton RA, J. r. (Principal Investigator)

    1998-01-01

    Measurements of dissolved N2, O2, Ar, CO2, and CH4 were made in perennially ice-covered Lake Hoare. Results confirm previous reports that O2 concentrations in the upper water column exceed atmospheric equilibrium and that N2 and Ar are supersaturated throughout the water column. The mean supersaturation of N2 was found to be 2.0 (+/- 0.37) and Ar was 3.8 (+/- 1.1). The ratios of N2/Ar (20.3 +/- 13.8), and O2/Ar (22.5 +/- 4.0) at the ice-water interface are consistent with those previously measured, suggesting that bubble formation is the main process for removing gas from the lake. However, the saturations of N2 and Ar greatly exceed those previously predicted for degassing by bubble formation only at the ice-water interface. The data support the hypothesis that removal of gas by bubbles occurs in the water column to a depth of 11 m in Lake Hoare. CO2 concentration increases from near zero at the ice-water interface to 80-100 times saturation at and below the chemocline at c. 28 m. There is considerable variability in the gas concentrations throughout the water column; samples separated in depth by one metre may vary by more than 50% in gas content. It is likely that this phenomenon results from the lack of turbulent mixing in the water column. Methane (c. 2 micrograms l-1) was detected below the chemocline and immediately above the sediment/water interface at a depth of 30 m. Samples from lakes Vanda, Joyce, and Miers, also show supersaturations of O2, N2, and Ar at levels similar to levels found in Lake Hoare.

  8. Dissolved gases in perennially ice-covered lakes of the McMurdo Dry Valleys, Antarctica.

    PubMed

    Andersen, D T; McKay, C P; Wharton, R A

    1998-06-01

    Measurements of dissolved N2, O2, Ar, CO2, and CH4 were made in perennially ice-covered Lake Hoare. Results confirm previous reports that O2 concentrations in the upper water column exceed atmospheric equilibrium and that N2 and Ar are supersaturated throughout the water column. The mean supersaturation of N2 was found to be 2.0 (+/- 0.37) and Ar was 3.8 (+/- 1.1). The ratios of N2/Ar (20.3 +/- 13.8), and O2/Ar (22.5 +/- 4.0) at the ice-water interface are consistent with those previously measured, suggesting that bubble formation is the main process for removing gas from the lake. However, the saturations of N2 and Ar greatly exceed those previously predicted for degassing by bubble formation only at the ice-water interface. The data support the hypothesis that removal of gas by bubbles occurs in the water column to a depth of 11 m in Lake Hoare. CO2 concentration increases from near zero at the ice-water interface to 80-100 times saturation at and below the chemocline at c. 28 m. There is considerable variability in the gas concentrations throughout the water column; samples separated in depth by one metre may vary by more than 50% in gas content. It is likely that this phenomenon results from the lack of turbulent mixing in the water column. Methane (c. 2 micrograms l-1) was detected below the chemocline and immediately above the sediment/water interface at a depth of 30 m. Samples from lakes Vanda, Joyce, and Miers, also show supersaturations of O2, N2, and Ar at levels similar to levels found in Lake Hoare. PMID:11541288

  9. Lost Jim Lava Flow, Seward Peninsula, Alaska as an analog for lava-ice interactions on Mars

    NASA Astrophysics Data System (ADS)

    Marcucci, E.; Hamilton, C.; Herrick, R. R.

    2015-12-01

    On Mars, volcanism within Elysium Planitia may have occurred as recently as ~10 million years ago, which associated lava flows being emplaced with ice-bearing permafrost. On Earth, there are few active volcanic regions that are cold enough to support permafrost, but the Seward Peninsula in Alaska is a prime location to study recent volcano-ice interactions. In the early 2000s, J.E. Beget and J.S. Kargel explored two areas in Alaska that exhibit features characteristic of explosive volcanism that may be the result of lava-ice interaction. These locations include the Lost Jim Lava Flow (65°29'N, 163°17'W) and several large maars (66°23'N, 164°29'W). The work presented here focuses on the Lost Jim Lava Flow, emanating from Lost Jim Cone and flowing West and North. The flow was erupted 1000-2000 years ago, covers ~225 km2, and ranges 3-30 m in thickness. Previous fieldwork identified pits along the margins of the flow that were interpreted to be collapse features (i.e., thermokarst) that formed as ground-ice beneath the lava melted due to heat transfer from the overlaying lava flow. This investigation utilizes stereo photogrammetry to generate high-resolution digital terrain models (DTMs) of these flow features to assess if these pits are indeed the products of thermokarstification, or if they are lava-rise pits formed by lava flow inflation. The DTMs were generated from ALOS PRISM data and DigitalGlobe Worldview 1 and 2 panchromatic satellite images taken as stereo-pairs or -triplets. With these new models the extent and morphology of the flow and pits will be categorized across the entire flow. These results are also compared to young lava flows on Mars, which may have experienced lava-ice interactions. Understanding the expression of such interactions on Earth may aid in the identification and interpretation of analogous eruptions on Mars.

  10. Formation and character of an ancient 19-m ice cover and underlying trapped brine in an “ice-sealed” east Antarctic lake

    PubMed Central

    Doran, Peter T.; Fritsen, Christian H.; McKay, Christopher P.; Priscu, John C.; Adams, Edward E.

    2003-01-01

    Lake Vida, one of the largest lakes in the McMurdo Dry Valleys of Antarctica, was previously believed to be shallow (<10 m) and frozen to its bed year-round. New ice-core analysis and temperature data show that beneath 19 m of ice is a water column composed of a NaCl brine with a salinity seven times that of seawater that remains liquid below −10°C. The ice cover thickens at both its base and surface, sealing concentrated brine beneath. The ice cover is stabilized by a negative feedback between ice growth and the freezing-point depression of the brine. The ice cover contains frozen microbial mats throughout that are viable after thawing and has a history that extends to at least 2,800 14C years B.P., suggesting that the brine has been isolated from the atmosphere for as long. To our knowledge, Lake Vida has the thickest subaerial lake ice cover recorded and may represent a previously undiscovered end-member lacustrine ecosystem on Earth. PMID:12518052

  11. Formation and character of an ancient 19-m ice cover and underlying trapped brine in an "ice-sealed" east Antarctic lake.

    PubMed

    Doran, Peter T; Fritsen, Christian H; McKay, Christopher P; Priscu, John C; Adams, Edward E

    2003-01-01

    Lake Vida, one of the largest lakes in the McMurdo Dry Valleys of Antarctica, was previously believed to be shallow (<10 m) and frozen to its bed year-round. New ice-core analysis and temperature data show that beneath 19 m of ice is a water column composed of a NaCl brine with a salinity seven times that of seawater that remains liquid below -10 degrees C. The ice cover thickens at both its base and surface, sealing concentrated brine beneath. The ice cover is stabilized by a negative feedback between ice growth and the freezing-point depression of the brine. The ice cover contains frozen microbial mats throughout that are viable after thawing and has a history that extends to at least 2,800 (14)C years B.P., suggesting that the brine has been isolated from the atmosphere for as long. To our knowledge, Lake Vida has the thickest subaerial lake ice cover recorded and may represent a previously undiscovered end-member lacustrine ecosystem on Earth.

  12. Dating the Little Ice Age Advance of Jakobshavn Isbrae, Greenland, Using Pro-glacial Lake Sediments.

    NASA Astrophysics Data System (ADS)

    Stewart, H. A.; Briner, J. P.; Csatho, B. M.

    2009-05-01

    The Greenland Ice Sheet's (GIS) largest and fastest outlet glacier, Jakobshavn Isbrae, is one of the most significant contributors to GIS mass loss, draining an estimated 6.5% of the GIS area (Rignot and Kanagaratnam, 2006). Jakobshavn Isbrae has retreated significantly since the Little Ice Age (LIA, ca. 1250- 1900; Csatho et al., 2008), and continues to exhibit rapid changes in velocity and ice calving front position (Joughin et al., 2004). However, it is unknown for how long Jakobshavn Isbrae was at or near its extensive LIA position because there is a lack of chronological control on the LIA advance phase. We collected sediment cores from lakes just beyond the LIA margin to constrain the time when the advancing glacier's silt-laden meltwater entered the lake basins. Sediment cores from South Oval and Ice Boom lakes (informal names), which no longer receive glacial meltwater from Jakobshavn Isbrae because it has retreated out of their catchments, contain gyttja/glacial-silt/gyttja sequences that represent their non-glacial/pro-glacial/non-glacial histories. One additional site, ice-dammed Lake Morten (informal name), completely drained sometime between 1985 and 2001 AD. Outcrops of laminated sediments in the lake basin overly an intact tundra landscape. Four AMS radiocarbon dates from macrofossils immediately below the LIA sediments from the three lake basins reveal that Jakobshavn Isbrae reached its LIA maximum extent between 530±10 and 370±60 cal yr BP (1400-1640 AD). Furthermore, the continuous nature of the LIA-sediment units in all sites indicates that Jakobshavn Isbrae remained at or near its LIA maximum position between 1400-1640 AD and into the 20th century. Finally, pre-LIA organic-rich sediments at all sites continue uninterrupted down to basal sediments deposited during regional deglaciation in the Early Holocene. AMS radiocarbon ages on macrofossils from basal sediments at all sites range from 7220±40 to 8130±60 cal yr BP. We therefore interpret

  13. Extreme events, trends, and variability in Northern Hemisphere lake-ice phenology (1855-2005)

    USGS Publications Warehouse

    Benson, Barbara J.; Magnuson, John J.; Jensen, Olaf P.; Card, Virginia M.; Hodgkins, Glenn; Korhonen, Johanna; Livingstone, David M.; Stewart, Kenton M.; Weyhenmeyer, Gesa A.; Granin, Nick G.

    2012-01-01

    Often extreme events, more than changes in mean conditions, have the greatest impact on the environment and human well-being. Here we examine changes in the occurrence of extremes in the timing of the annual formation and disappearance of lake ice in the Northern Hemisphere. Both changes in the mean condition and in variability around the mean condition can alter the probability of extreme events. Using long-term ice phenology data covering two periods 1855–6 to 2004–5 and 1905–6 to 2004–5 for a total of 75 lakes, we examined patterns in long-term trends and variability in the context of understanding the occurrence of extreme events. We also examined patterns in trends for a 30-year subset (1975–6 to 2004–5) of the 100-year data set. Trends for ice variables in the recent 30-year period were steeper than those in the 100- and 150-year periods, and trends in the 150-year period were steeper than in the 100-year period. Ranges of rates of change (days per decade) among time periods based on linear regression were 0.3−1.6 later for freeze, 0.5−1.9 earlier for breakup, and 0.7−4.3 shorter for duration. Mostly, standard deviation did not change, or it decreased in the 150-year and 100-year periods. During the recent 50-year period, standard deviation calculated in 10-year windows increased for all ice measures. For the 150-year and 100-year periods changes in the mean ice dates rather than changes in variability most strongly influenced the significant increases in the frequency of extreme lake ice events associated with warmer conditions and decreases in the frequency of extreme events associated with cooler conditions.

  14. Winter severity determines functional trait composition of phytoplankton in seasonally ice-covered lakes.

    PubMed

    Özkundakci, Deniz; Gsell, Alena S; Hintze, Thomas; Täuscher, Helgard; Adrian, Rita

    2016-01-01

    How climate change will affect the community dynamics and functionality of lake ecosystems during winter is still little understood. This is also true for phytoplankton in seasonally ice-covered temperate lakes which are particularly vulnerable to the presence or absence of ice. We examined changes in pelagic phytoplankton winter community structure in a north temperate lake (Müggelsee, Germany), covering 18 winters between 1995 and 2013. We tested how phytoplankton taxa composition varied along a winter-severity gradient and to what extent winter severity shaped the functional trait composition of overwintering phytoplankton communities using multivariate statistical analyses and a functional trait-based approach. We hypothesized that overwintering phytoplankton communities are dominated by taxa with trait combinations corresponding to the prevailing winter water column conditions, using ice thickness measurements as a winter-severity indicator. Winter severity had little effect on univariate diversity indicators (taxon richness and evenness), but a strong relationship was found between the phytoplankton community structure and winter severity when taxon trait identity was taken into account. Species responses to winter severity were mediated by the key functional traits: motility, nutritional mode, and the ability to form resting stages. Accordingly, one or the other of two functional groups dominated the phytoplankton biomass during mild winters (i.e., thin or no ice cover; phototrophic taxa) or severe winters (i.e., thick ice cover; exclusively motile taxa). Based on predicted milder winters for temperate regions and a reduction in ice-cover durations, phytoplankton communities during winter can be expected to comprise taxa that have a relative advantage when the water column is well mixed (i.e., need not be motile) and light is less limiting (i.e., need not be mixotrophic). A potential implication of this result is that winter severity promotes different

  15. Winter severity determines functional trait composition of phytoplankton in seasonally ice-covered lakes.

    PubMed

    Özkundakci, Deniz; Gsell, Alena S; Hintze, Thomas; Täuscher, Helgard; Adrian, Rita

    2016-01-01

    How climate change will affect the community dynamics and functionality of lake ecosystems during winter is still little understood. This is also true for phytoplankton in seasonally ice-covered temperate lakes which are particularly vulnerable to the presence or absence of ice. We examined changes in pelagic phytoplankton winter community structure in a north temperate lake (Müggelsee, Germany), covering 18 winters between 1995 and 2013. We tested how phytoplankton taxa composition varied along a winter-severity gradient and to what extent winter severity shaped the functional trait composition of overwintering phytoplankton communities using multivariate statistical analyses and a functional trait-based approach. We hypothesized that overwintering phytoplankton communities are dominated by taxa with trait combinations corresponding to the prevailing winter water column conditions, using ice thickness measurements as a winter-severity indicator. Winter severity had little effect on univariate diversity indicators (taxon richness and evenness), but a strong relationship was found between the phytoplankton community structure and winter severity when taxon trait identity was taken into account. Species responses to winter severity were mediated by the key functional traits: motility, nutritional mode, and the ability to form resting stages. Accordingly, one or the other of two functional groups dominated the phytoplankton biomass during mild winters (i.e., thin or no ice cover; phototrophic taxa) or severe winters (i.e., thick ice cover; exclusively motile taxa). Based on predicted milder winters for temperate regions and a reduction in ice-cover durations, phytoplankton communities during winter can be expected to comprise taxa that have a relative advantage when the water column is well mixed (i.e., need not be motile) and light is less limiting (i.e., need not be mixotrophic). A potential implication of this result is that winter severity promotes different

  16. Measurements of Mass, Momentum and Energy fluxes over an ice/snow covered lake

    NASA Astrophysics Data System (ADS)

    Salgado, Rui; Potes, Miguel; Mammarella, Ivan; Provenzale, Maria

    2016-04-01

    A better understanding of the interactions between ice and snow and the atmosphere requires improved measurements of energy, mass and momentum fluxes, which continue to have a high degree of uncertainty. In this communication, observed near surface fluxes of momentum, heat and mass (H2O and CO2) over a boreal lake during a freezing period (winter 2015/2016) will be analysed and compared with observations over ice free lakes. Continuously measurements of near surface fluxes of momentum, heat and mass (H2O and CO2) are obtained with a new eddy covariance (EC) system, the Campbell Scientific's IRGASON Integrated Open-Path CO2/H2O Gas Analyzer and 3D Sonic Anemometer, over lake Vanajavesi in Finland. The measurement site is located in a tip of narrow peninsula on the lake (61.133935° N ; 24.259119° E), offering very good conditions for eddy covariance flux measurements. The EC system was installed at 2.5m height above the lake surface and was oriented against the prevailing wind direction in the site.

  17. Methods to assess natural and anthropogenic thaw lake drainage on the western Arctic coastal plain of northern Alaska

    NASA Astrophysics Data System (ADS)

    Hinkel, Kenneth M.; Jones, Benjamin M.; Eisner, Wendy R.; Cuomo, Chris J.; Beck, Richard A.; Frohn, Robert

    2007-06-01

    Thousands of lakes are found on the Arctic Coastal Plain of northern Alaska and northwestern Canada. Developed atop continuous permafrost, these thaw lakes and associated drained thaw lake basins are the dominant landscape elements and together cover 46% of the 34,570 km2 western Arctic Coastal Plain (WACP). Lakes drain by a variety of episodic processes, including coastal erosion, stream meandering, and headward erosion, bank overtopping, and lake coalescence. Comparison of Landsat multispectral scanner (MSS) imagery from the mid-1970s to Landsat 7 enhanced thematic mapper (ETM+) imagery from around 2000 shows that 50 lakes completely or partially drained over the approximately 25 year period, indicating landscape stability. The lake-specific drainage mechanism can be inferred in some cases and is partially dependant on geographic settings conducive to active erosion such as riparian and coastal zones. In many cases, however, the cause of drainage is unknown. The availability of high-resolution aerial photographs for the Barrow Peninsula extends the record back to circa 1950; mapping spatial time series illustrates the dynamic nature of lake expansion, coalescence, and drainage. Analysis of these historical images suggests that humans have intentionally or inadvertently triggered lake drainage near the village of Barrow. Efforts to understand landscape processes and identify events have been enhanced by interviewing Iñupiaq elders and others practicing traditional subsistence lifestyles. They can often identify the year and process by which individual lakes drained, thereby providing greater dating precision and accuracy in assessing the causal mechanism. Indigenous knowledge has provided insights into events, landforms, and processes not previously identified or considered.

  18. Methods to assess natural and anthropogenic thaw lake drainage on the western Arctic coastal plain of northern Alaska

    USGS Publications Warehouse

    Hinkel, Kenneth M.; Jones, Benjamin M.; Eisner, Wendy R.; Cuomo, Chris J.; Beck, R.A.; Frohn, R.

    2007-01-01

    Thousands of lakes are found on the Arctic Coastal Plain of northern Alaska and northwestern Canada. Developed atop continuous permafrost, these thaw lakes and associated drained thaw lake basins are the dominant landscape elements and together cover 46% of the 34,570 km2western Arctic Coastal Plain (WACP). Lakes drain by a variety of episodic processes, including coastal erosion, stream meandering, and headward erosion, bank overtopping, and lake coalescence. Comparison of Landsat multispectral scanner (MSS) imagery from the mid-1970s to Landsat 7 enhanced thematic mapper (ETM+) imagery from around 2000 shows that 50 lakes completely or partially drained over the approximately 25 year period, indicating landscape stability. The lake-specific drainage mechanism can be inferred in some cases and is partially dependant on geographic settings conducive to active erosion such as riparian and coastal zones. In many cases, however, the cause of drainage is unknown. The availability of high-resolution aerial photographs for the Barrow Peninsula extends the record back to circa 1950; mapping spatial time series illustrates the dynamic nature of lake expansion, coalescence, and drainage. Analysis of these historical images suggests that humans have intentionally or inadvertently triggered lake drainage near the village of Barrow. Efforts to understand landscape processes and identify events have been enhanced by interviewing Iñupiaq elders and others practicing traditional subsistence lifestyles. They can often identify the year and process by which individual lakes drained, thereby providing greater dating precision and accuracy in assessing the causal mechanism. Indigenous knowledge has provided insights into events, landforms, and processes not previously identified or considered.

  19. Arctic Summer Surface Energy Balance at Two Coastal Drained Lake Basins, Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Liljedahl, A.; Hinzman, L.; Harazono, Y.; Zona, D.; Oechel, W.

    2008-12-01

    We examined the partitioning of the summer surface energy balance at two coastal drained lake basins using measurements from two eddy covariance towers in Barrow, Alaska. Drained lake basins are a common land feature covering approximately one fourth of the Arctic Coastal Plain but have been given limited attention. Overall, wetlands are extensive in the region in spite of an annual precipitation close to a desert and a negative summer P-ET. Included in the analysis was summer 2007, which experienced unusually high air temperatures and low precipitation compared to the long term mean. During the five analyzed summers, most of the energy available at the ground surface was partitioned into sensible heat flux despite saturated or nearly saturated near-surface soils. The maritime conditions resulted in a cool and close to saturated air mass with a few exceptions on individual days. With a ground surface often warmer than the air above and limited air vapor pressure deficits, the dissipation of the available heat at the ground surface was mainly partitioned into sensible heat flux resulting in midday Bowen Ratios (sensible divided by latent heat flux) above unity. Total daily latent heat flux presented in mm of water varied between 0.2 - 4.2 mm/day with a Jun-Aug mean of 1.5 mm. In 80% of the analyzed days, mean midday evapotranspiration occurred below the equilibrium rate resulting in a Priestley-Taylor alpha value below unity. The equilibrium evaporation rates of inland arctic wetlands have previously shown to occur at or above equilibrium rate. Further, the energy balance partitioning of a wetland located in a maritime or continental climate show differences such as in the Bowen Ratio. It is therefore necessary to analyze coastal and inland areas separately when examining the hydrological response of wetlands to climate changes.

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

    USGS Publications Warehouse

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

    1988-01-01

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

  1. A multi-proxy reconstruction of temperature and aridity from lake sediments north of the Brooks Range, Alaska for the past 30,000 years

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Russell, J. M.; Longo, W. M.; Daniels, W.; Giblin, A. E.

    2015-12-01

    Paleoclimate reconstructions from the northern Alaska tundra since the LGM have mainly relied on paleoecological proxies such as pollen and chironomids. However, lack of trees, non-analogue assemblages, and limited species diversity present significant challenges to quantitative reconstructions. The abnormally warm LGM conditions implied by pollen assemblages, supported by the CCSM3 but contradicted by CCSM4 simulations, have been a source of great confusion. Here we present a synthesis of results from a NSF-funded project, aiming at utilizing a full suite of organic geochemical and paleolimnological proxies, in conjunction with model comparison, to quantitatively reconstruct temperature and moisture changes since the LGM. Compound specific hydrogen isotopic ratios of plant leaf waxes from Lake E5 near Toolik Lake suggest summer temperature at the LGM is ~ 7 degrees colder than the early Holocene and there is a temperature decline of 2-3 degrees over the Holocene, coherent with greenhouse and insolation forcings respectively. A similar LGM to present temperature gradient is found in the alkenone-inferred early summer temperatures, although an expanded Arctic sea ice in the early Holocene significantly suppressed this temperature. The LGM to present temperature gradient is further supported by temperatures inferred by br-GDGTs from our sediment core, which also display an early Holocene to present temperature decline of 2 to 3 degrees. Our paleotemperature data are supported by model results using CCSM4, with its use of newer generation ice sheet configuration, indicating lower LGM temperatures than present. Our paleohydrological reconstructions based on hydrogen isotopic contrast between inferred precipitation and lake water isotopic ratios, and carbon isotopic fractionation of terrestrial plant leaf waxes, suggesting an arid last glacial relative to the Holocene. This presentation will also summarize all geochemical measurements including TOC, bulk C and N

  2. Sources of Sulfate Found in Mounds and Lakes at the Lewis Cliffs Ice Tongue, Transantarctic

    NASA Technical Reports Server (NTRS)

    Socki, Richard; Sun, Tao; Harvey, Ralph P.; Bish, David L.; Tonui, Eric; Bao, Huiming; Niles, Paul B.

    2012-01-01

    Massive but highly localized Na-sulfate mounds (mirabilite, Na2SO4.10H2O) have been found at the terminal moraine of the Lewis Cliffs Ice Tongue (LCIT), Antarctica. (Sigma)34S and (Sigma)18O values of LCIT mirabilite range from +48.8 to +49.3% (CDT), and -16.6 to -17.1% (V-SMOW), respectively, while (Delta)17O average -0.37% (V-SMOW). LCIT mirabilite mounds are isotopically different from other mirabilite mounds found in coastal regions of Antarctica, which have isotope values close to seawater compositions. (Sigma)18O and (Delta)17O values suggest the incorporation of isotopically light glacial water. Data point to initial sulfate formation in an anoxic water body, either as a stratified anoxic deep lake on the surface, a sub-glacial water reservoir, or a sub-glacial lake. Several surface lakes of varying size are also present within this region of the LCIT, and in some cases are adjacent to the mirabilite mounds. O and D isotope compositions of surface lakes confirm they are derived from a mixture of glacial ice and snow that underwent moderate evaporation. (Sigma)18O and (Sigma)D (V-SMOW) values of snow, ice, and lake water range from -64.2 to -29.7%, and -456.0 to -231.7%, respectively. However, the isotope chemistry of these surface lakes is extremely different from the mounds. Dissolved SO4-2 (Sigma)34S and (Sigma)18O values range from +12.0 to +20.0% and -12.8 to -22.2% (the most negative (Sigma)18O of terrestrial sulfate ever reported), respectively, with sulfate (Delta)17O ranging from +0.93 to 2.24%. Ion chromatography data show that lake water is fresh to brackish in origin, with TDS less than 1500 ppm, and sulfate concentration less than 431 ppm. Isotope and chemical data suggest that these lakes are unlikely the source of the mirabilite mounds. We suggest that lake water sulfate is potentially composed of a mixture of atmospheric sulfate and minor components of sulfate of weathering origin, much like the sulfate in the polar plateau soils of the Mc

  3. Quantifying supraglacial lake volumes on the Greenland ice sheet from spaceborne optical sensors

    NASA Astrophysics Data System (ADS)

    Moussavi, Mahsa S.

    The acceleration of mass loss from the Greenland ice sheet (GrIS) over the last two decades is of great significance when considering the associated increasing rates of its contribution to sea level rise. With meltwater runoff accounting for more than half of Greenland's contribution to sea level, it is imperative to improve our understanding of the ice sheet hydrologic processes. This dissertation describes research to quantify surface meltwater volumes, specifically stored in supraglacial lakes, over large areas of the ablation region from spaceborne observations made by current and future optical sensors. Methods for remote-derivation and validation of supraglacial water depths from WorldView-2, Landsat 7's Enhanced Thematic Mapper (ETM+), and Landsat 8's Operational Land Imager (OLI) are discussed. While enabling large-scale assessments of lake volumes with unprecedented levels of accuracy and precision, these methods address the major limitation of spaceborne bathymetry, which is its dependence on the availability of costly in-situ measurements. This dissertation also investigates the potential capability of the future ICESat-2 laser altimetry mission in providing depth information over supraglacial lakes, which could be used in conjunction with passive optical data to assess lake volumes. A nominal (first-order) prediction of ICESat-2's performance suggests that it might be able to retrieve lake depths down to 6 m. Given such a premise, this dissertation takes one step further to develop an automatic depth-retrieval algorithm from simulated ICESat-2 datasets, provided by the mission's Project team at Goddard Space Flight Center (GSFC). By developing a surface detection algorithm for the most complex surfaces that ICESat-2 will be looking at, namely forested ecosystems, this dissertation provides a method applicable to land ice, sea ice, and water surfaces. Furthermore, as part of ICESat-2's science definition team efforts and in direct support of the mission

  4. Carbon dioxide partial pressure and 13C content of north temperate and boreal lakes at spring ice melt

    USGS Publications Warehouse

    Striegl, R.G.; Kortelainen, Pirkko; Chanton, J.P.; Wickland, K.P.; Bugna, G.C.; Rantakari, M.

    2001-01-01

    Carbon dioxide (CO2) accumulates under lake ice in winter and degasses to the atmosphere after ice melt. This large springtime CO2 pulse is not typically considered in surface-atmosphere flux estimates, because most field studies have not sampled through ice during late winter. Measured CO2 partial pressure (pCO2) of lake surface water ranged from 8.6 to 4,290 Pa (85-4,230 ??atm) in 234 north temperate and boreal lakes prior to ice melt during 1998 and 1999. Only four lakes had surface pCO2 less than or equal to atmospheric pCO2, whereas 75% had pCO2 >5 times atmospheric. The ??13CDIC (DIC = ??CO2) of 142 of the lakes ranged from -26.28??? to +0.95.???. Lakes with the greatest pCO2 also had the lightest ??13CDIC, which indicates respiration as their primary CO2 source. Finnish lakes that received large amounts of dissolved organic carbon from surrounding peatlands had the greatest pCO2. Lakes set in noncarbonate till and bedrock in Minnesota and Wisconsin had the smallest pCO2 and the heaviest ??13CDIC, which indicates atmospheric and/or mineral sources of C for those lakes. Potential emissions for the period after ice melt were 2.36 ?? 1.44 mol CO2 m-2 for lakes with average pCO2 values and were as large as 13.7 ?? 8.4 mol CO2 m-2 for lakes with high pCO2 values.

  5. A multi-proxy reconstruction of environmental change spanning the last 37,000 years from Burial Lake, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Finkenbinder, M. S.; Abbott, M. B.; Finney, B. P.; Stoner, J. S.; Dorfman, J. M.

    2015-10-01

    Sediment cores from Burial Lake located in the western Brooks Range in Arctic Alaska record paleoenvironmental changes that span the last 37,000 calendar years before present (cal yr BP). We identified four distinct lithologic subunits based on physical properties (dry bulk density, magnetic susceptibility), sediment composition, and geochemical proxies (organic matter, biogenic silica, C/N, organic matter δ13C and δ15N, and elemental data from scanning X-ray fluorescence). The multi-proxy approach and relatively high temporal resolution (at multi-decadal to centennial time scales) of our proxy analysis, compared with previous studies of intermediate water depth cores from Burial Lake, provide new insights into the paleoenvironmental history of the region spanning the period prior to the Last Glacial Maximum. Relatively high lake-levels and gradually decreasing in-lake and terrestrial productivity occur during the mid-Wisconsin interstadial from 37,200 to 29,600 cal yr BP. The subsequent period is defined by falling and lower lake-levels with decreasing effective-moisture, windier conditions, and sustained low aquatic productivity throughout the LGM between 29,600 and 19,600 cal yr BP. The last deglaciation that commenced by 19,600 cal yr BP is characterized by gradual changes in several sediment physical and geochemical proxies, including increasing C/N ratios and terrestrial productivity, decreasing magnetic susceptibility and clastic sediment flux, along with rising and relatively higher lake-levels. A decrease in aeolian activity after 16,500 cal yr BP is inferred from the appearance of fine (very fine sandy silt) sediment, compared to coarse sediments through the LGM and last deglaciation. The highest levels of terrestrial inputs along with increasing and variable aquatic productivity occur during the Lateglacial to early Holocene interval between 16,500 and 8800 cal yr BP. The absence of multi-proxy evidence for a strong climatic reversal during the Younger

  6. Airborne Polarimetric, Two-Color Laser Altimeter Measurements of Lake Ice Cover: A Pathfinder for NASA's ICESat-2 Spaceflight Mission

    NASA Technical Reports Server (NTRS)

    Harding, David; Dabney, Philip; Valett, Susan; Yu, Anthony; Vasilyev, Aleksey; Kelly, April

    2011-01-01

    The ICESat-2 mission will continue NASA's spaceflight laser altimeter measurements of ice sheets, sea ice and vegetation using a new measurement approach: micropulse, single photon ranging at 532 nm. Differential penetration of green laser energy into snow, ice and water could introduce errors in sea ice freeboard determination used for estimation of ice thickness. Laser pulse scattering from these surface types, and resulting range biasing due to pulse broadening, is assessed using SIMPL airborne data acquired over icecovered Lake Erie. SIMPL acquires polarimetric lidar measurements at 1064 and 532 nm using the micropulse, single photon ranging measurement approach.

  7. Bottom Fixed Platform Dynamics Models Assessing Surface Ice Interactions for Transitional Depth Structures in the Great Lakes: FAST8 – IceDyn

    SciTech Connect

    Karr, Dale G.; Yu, Bingbin; Sirnivas, Senu

    2015-04-01

    To create long-term solutions for offshore wind turbines in a variety of environmental conditions, CAE tools are needed to model the design-driving loads that interact with an offshore wind turbine system during operation. This report describes our efforts in augmenting existing CAE tools used for offshore wind turbine analysis with a new module that can provide simulation capabilities for ice loading on the system. This augmentation was accomplished by creating an ice-loading module coupled to FAST8, the CAE tool maintained by the NREL for simulating land-based and offshore wind turbine dynamics. The new module includes both static and dynamic ice loading that can be applied during a dynamic simulation of the response of an offshore wind turbine. The ice forces can be prescribed, or influenced by the structure’s compliant response, or by the dynamics of both the structure and the ice floe. The new module covers ice failure modes of spalling, buckling, crushing, splitting, and bending. The supporting structure of wind turbines can be modeled as a vertical or sloping form at the waterline. The Inward Battered Guide Structure (IBGS) foundation designed by Keystone Engineering for the Great Lakes was used to study the ice models coupled to FAST8. The IBGS foundation ice loading simulations in FAST8 were compared to the baseline simulation case without ice loading. The ice conditions reflecting those from Lake Huron at Port Huron and Lake Michigan at North Manitou were studied under near rated wind speed of 12 m/s for the NREL 5-MW reference turbine. Simulations were performed on ice loading models 1 through 4 and ice model 6 with their respective sub-models. The purpose of ice model 5 is to investigate ice loading on sloping structures such as ice-cones on a monopile and is not suitable for multi-membered jacketed structures like the IBGS foundation. The key response parameters from the simulations, shear forces and moments from the tower base and IBGS foundation

  8. POTENTIAL CLIMATE WARMING EFFECTS ON ICE COVERS OF SMALL LAKES IN THE CONTIGUOUS U.S. (R824801)

    EPA Science Inventory

    Abstract

    To simulate effects of projected climate change on ice covers of small lakes in the northern contiguous U.S., a process-based simulation model is applied. This winter ice/snow cover model is associated with a deterministic, one-dimensional year-round water tem...

  9. Unanticipated Geochemical and Microbial Community Structure under Seasonal Ice Cover in a Dilute, Dimictic Arctic Lake.

    PubMed

    Schütte, Ursel M E; Cadieux, Sarah B; Hemmerich, Chris; Pratt, Lisa M; White, Jeffrey R

    2016-01-01

    Despite most lakes in the Arctic being perennially or seasonally frozen for at least 40% of the year, little is known about microbial communities and nutrient cycling under ice cover. We assessed the vertical microbial community distribution and geochemical composition in early spring under ice in a seasonally ice-covered lake in southwest Greenland using amplicon-based sequencing that targeted 16S rRNA genes and using a combination of field and laboratory aqueous geochemical methods. Microbial communities changed consistently with changes in geochemistry. Composition of the abundant members responded strongly to redox conditions, shifting downward from a predominantly heterotrophic aerobic community in the suboxic waters to a heterotrophic anaerobic community in the anoxic waters. Operational taxonomic units (OTUs) of Sporichthyaceae, Comamonadaceae, and the SAR11 Clade had higher relative abundances above the oxycline and OTUs within the genus Methylobacter, the phylum Lentisphaerae, and purple sulfur bacteria (PSB) below the oxycline. Notably, a 13-fold increase in sulfide at the oxycline was reflected in an increase and change in community composition of potential sulfur oxidizers. Purple non-sulfur bacteria were present above the oxycline and green sulfur bacteria and PSB coexisted below the oxycline, however, PSB were most abundant. For the first time we show the importance of PSB as potential sulfur oxidizers in an Arctic dimictic lake. PMID:27458438

  10. Unanticipated Geochemical and Microbial Community Structure under Seasonal Ice Cover in a Dilute, Dimictic Arctic Lake.

    PubMed

    Schütte, Ursel M E; Cadieux, Sarah B; Hemmerich, Chris; Pratt, Lisa M; White, Jeffrey R

    2016-01-01

    Despite most lakes in the Arctic being perennially or seasonally frozen for at least 40% of the year, little is known about microbial communities and nutrient cycling under ice cover. We assessed the vertical microbial community distribution and geochemical composition in early spring under ice in a seasonally ice-covered lake in southwest Greenland using amplicon-based sequencing that targeted 16S rRNA genes and using a combination of field and laboratory aqueous geochemical methods. Microbial communities changed consistently with changes in geochemistry. Composition of the abundant members responded strongly to redox conditions, shifting downward from a predominantly heterotrophic aerobic community in the suboxic waters to a heterotrophic anaerobic community in the anoxic waters. Operational taxonomic units (OTUs) of Sporichthyaceae, Comamonadaceae, and the SAR11 Clade had higher relative abundances above the oxycline and OTUs within the genus Methylobacter, the phylum Lentisphaerae, and purple sulfur bacteria (PSB) below the oxycline. Notably, a 13-fold increase in sulfide at the oxycline was reflected in an increase and change in community composition of potential sulfur oxidizers. Purple non-sulfur bacteria were present above the oxycline and green sulfur bacteria and PSB coexisted below the oxycline, however, PSB were most abundant. For the first time we show the importance of PSB as potential sulfur oxidizers in an Arctic dimictic lake.

  11. Unanticipated Geochemical and Microbial Community Structure under Seasonal Ice Cover in a Dilute, Dimictic Arctic Lake

    PubMed Central

    Schütte, Ursel M. E.; Cadieux, Sarah B.; Hemmerich, Chris; Pratt, Lisa M.; White, Jeffrey R.

    2016-01-01

    Despite most lakes in the Arctic being perennially or seasonally frozen for at least 40% of the year, little is known about microbial communities and nutrient cycling under ice cover. We assessed the vertical microbial community distribution and geochemical composition in early spring under ice in a seasonally ice-covered lake in southwest Greenland using amplicon-based sequencing that targeted 16S rRNA genes and using a combination of field and laboratory aqueous geochemical methods. Microbial communities changed consistently with changes in geochemistry. Composition of the abundant members responded strongly to redox conditions, shifting downward from a predominantly heterotrophic aerobic community in the suboxic waters to a heterotrophic anaerobic community in the anoxic waters. Operational taxonomic units (OTUs) of Sporichthyaceae, Comamonadaceae, and the SAR11 Clade had higher relative abundances above the oxycline and OTUs within the genus Methylobacter, the phylum Lentisphaerae, and purple sulfur bacteria (PSB) below the oxycline. Notably, a 13-fold increase in sulfide at the oxycline was reflected in an increase and change in community composition of potential sulfur oxidizers. Purple non-sulfur bacteria were present above the oxycline and green sulfur bacteria and PSB coexisted below the oxycline, however, PSB were most abundant. For the first time we show the importance of PSB as potential sulfur oxidizers in an Arctic dimictic lake. PMID:27458438

  12. Cumulative geoecological effects of 62 years of infrastructure and climate change in ice-rich permafrost landscapes, Prudhoe Bay Oilfield, Alaska.

    PubMed

    Raynolds, Martha K; Walker, Donald A; Ambrosius, Kenneth J; Brown, Jerry; Everett, Kaye R; Kanevskiy, Mikhail; Kofinas, Gary P; Romanovsky, Vladimir E; Shur, Yuri; Webber, Patrick J

    2014-04-01

    Many areas of the Arctic are simultaneously affected by rapid climate change and rapid industrial development. These areas are likely to increase in number and size as sea ice melts and abundant Arctic natural resources become more accessible. Documenting the changes that have already occurred is essential to inform management approaches to minimize the impacts of future activities. Here, we determine the cumulative geoecological effects of 62 years (1949-2011) of infrastructure- and climate-related changes in the Prudhoe Bay Oilfield, the oldest and most extensive industrial complex in the Arctic, and an area with extensive ice-rich permafrost that is extraordinarily sensitive to climate change. We demonstrate that thermokarst has recently affected broad areas of the entire region, and that a sudden increase in the area affected began shortly after 1990 corresponding to a rapid rise in regional summer air temperatures and related permafrost temperatures. We also present a conceptual model that describes how infrastructure-related factors, including road dust and roadside flooding are contributing to more extensive thermokarst in areas adjacent to roads and gravel pads. We mapped the historical infrastructure changes for the Alaska North Slope oilfields for 10 dates from the initial oil discovery in 1968-2011. By 2010, over 34% of the intensively mapped area was affected by oil development. In addition, between 1990 and 2001, coincident with strong atmospheric warming during the 1990s, 19% of the remaining natural landscapes (excluding areas covered by infrastructure, lakes and river floodplains) exhibited expansion of thermokarst features resulting in more abundant small ponds, greater microrelief, more active lakeshore erosion and increased landscape and habitat heterogeneity. This transition to a new geoecological regime will have impacts to wildlife habitat, local residents and industry. PMID:24339207

  13. Cumulative geoecological effects of 62 years of infrastructure and climate change in ice-rich permafrost landscapes, Prudhoe Bay Oilfield, Alaska.

    PubMed

    Raynolds, Martha K; Walker, Donald A; Ambrosius, Kenneth J; Brown, Jerry; Everett, Kaye R; Kanevskiy, Mikhail; Kofinas, Gary P; Romanovsky, Vladimir E; Shur, Yuri; Webber, Patrick J

    2014-04-01

    Many areas of the Arctic are simultaneously affected by rapid climate change and rapid industrial development. These areas are likely to increase in number and size as sea ice melts and abundant Arctic natural resources become more accessible. Documenting the changes that have already occurred is essential to inform management approaches to minimize the impacts of future activities. Here, we determine the cumulative geoecological effects of 62 years (1949-2011) of infrastructure- and climate-related changes in the Prudhoe Bay Oilfield, the oldest and most extensive industrial complex in the Arctic, and an area with extensive ice-rich permafrost that is extraordinarily sensitive to climate change. We demonstrate that thermokarst has recently affected broad areas of the entire region, and that a sudden increase in the area affected began shortly after 1990 corresponding to a rapid rise in regional summer air temperatures and related permafrost temperatures. We also present a conceptual model that describes how infrastructure-related factors, including road dust and roadside flooding are contributing to more extensive thermokarst in areas adjacent to roads and gravel pads. We mapped the historical infrastructure changes for the Alaska North Slope oilfields for 10 dates from the initial oil discovery in 1968-2011. By 2010, over 34% of the intensively mapped area was affected by oil development. In addition, between 1990 and 2001, coincident with strong atmospheric warming during the 1990s, 19% of the remaining natural landscapes (excluding areas covered by infrastructure, lakes and river floodplains) exhibited expansion of thermokarst features resulting in more abundant small ponds, greater microrelief, more active lakeshore erosion and increased landscape and habitat heterogeneity. This transition to a new geoecological regime will have impacts to wildlife habitat, local residents and industry.

  14. Temperature profile for glacial ice at the South Pole: implications for life in a nearby subglacial lake.

    PubMed

    Price, P Buford; Nagornov, Oleg V; Bay, Ryan; Chirkin, Dmitry; He, Yudong; Miocinovic, Predrag; Richards, Austin; Woschnagg, Kurt; Koci, Bruce; Zagorodnov, Victor

    2002-06-11

    Airborne radar has detected approximately 100 lakes under the Antarctic ice cap, the largest of which is Lake Vostok. International planning is underway to search in Lake Vostok for microbial life that may have evolved in isolation from surface life for millions of years. It is thought, however, that the lakes may be hydraulically interconnected. If so, unsterile drilling would contaminate not just one but many of them. Here we report measurements of temperature vs. depth down to 2,345 m in ice at the South Pole, within 10 km from a subglacial lake seen by airborne radar profiling. We infer a temperature at the 2,810-m deep base of the South Pole ice and at the lake of -9 degrees C, which is 7 degrees C below the pressure-induced melting temperature of freshwater ice. To produce the strong radar signal, the frozen lake must consist of a mix of sediment and ice in a flat bed, formed before permanent Antarctic glaciation. It may, like Siberian and Antarctic permafrost, be rich in microbial life. Because of its hydraulic isolation, proximity to South Pole Station infrastructure, and analog to a Martian polar cap, it is an ideal place to test a sterile drill before risking contamination of Lake Vostok. From the semiempirical expression for strain rate vs. shear stress, we estimate shear vs. depth and show that the IceCube neutrino observatory will be able to map the three-dimensional ice-flow field within a larger volume (0.5 km(3)) and at lower temperatures (-20 degrees C to -35 degrees C) than has heretofore been possible. PMID:12060731

  15. Islands in the ice stream: were spawning habitats for native salmonids in the Great Lakes created by paleo-ice streams?

    USGS Publications Warehouse

    Riley, Stephen; Binder, Thomas R.; Tucker, Taaja R.; Menzies, John; Eyles, Nick; Janssen, John; Muir, Andrew M.; Esselman, Peter C.; Wattrus, Nigel J.; Krueger, Charles C.

    2016-01-01

    Lake trout Salvelinus namaycush, lake whitefish Coregonus clupeaformis and cisco Coregonus artedi are salmonid fishes native to the Laurentian Great Lakes that spawn on rocky substrates in the fall and early winter. After comparing the locations of spawning habitat for these species in the main basin of Lake Huron with surficial substrates and the hypothesized locations of fast-flowing Late Wisconsinan paleo-ice streams, we hypothesize that much of the spawning habitat for these species in Lake Huron is the result of deposition and erosion by paleo-ice streams. This hypothesis may represent a new framework for the identification and protection of spawning habitat for these native species, some of which are currently rare or extirpated in some of the Great Lakes. We further suggest that paleo-ice streams may have been responsible for the creation of native salmonid spawning habitat elsewhere in the Great Lakes and in other glaciated landscapes.

  16. SARAL/AltiKa observations for the studies of ice cover on lakes and oceans

    NASA Astrophysics Data System (ADS)

    Kouraev, Alexei; Zakharova, Elena; Remy, Frederique; Fleury, Sara; Guerreiro, Kevin; Willmes, Sascha; Suknev, Andrei

    2015-04-01

    With the launch of SARAL/AltiKa satellite mission scientific community has now a new source of information to study ice cover on water bodies and oceans. AltiKa observations provide a continuity with the previous satellite radar altimetry observations from ERS-1, -2 and ENVISAT mission that have the same orbit. Moreover, with the new Ka-band altimeter it gives new insights into the ice cover structure and properties. We present studies of ice cover on lakes (Lake Baikal) and Arctic ocean (for leads and polynyas detection). For Lake Baikal we use the synergy of simultaneous active (radar altimeter) and passive (radiometer) observations from radar altimetric satellites - SARAL/Altika and also TOPEX/Poseidon, Jason-1, ENVISAT and Geosat Follow-On. We present ice discrimination methodology from different satellite missions and discuss specificity of AltiKa observations. We analyse temporal variability of altimetric waveform parameters over ice-covered and ice-free surface for AltiKa and complement this analysis by satellite imagery (MODIS, Landsat), as well as our dedicated field observations of ice cover properties along the AltiKa tracks in spring 2013 and 2014. For the Arctic ocean we investigate the performance of SARAL/AltiKa to detect the leads and the coastal polynyas as well as its ability to represent spatial and temporal dynamic of water openings. The method consists first in analysis of along-track radar waveforms with collocated high-resolution Landsat images in order to localise ice/water transitions. We discuss the potential of several techniques that could be used for leads and polynya studies and for freeboard estimation. This research has been done in the framework of the Russian-French cooperation GDRI "CAR-WET-SIB", CNES TOSCA AO, ANR "CLASSIQUE", IDEX Transversalité InHERA, CNRS-Russia "Franco-Siberian Center for Research and Education" and PICS BaLaLaICA, ESA Proposal C1P.13132, Russian FZP 1.5 and EU FP7 "MONARCH-A" projects.

  17. 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

  18. Lake level and watershed vegetation changes from C and N isotopic analysis of lacustrine organic matter: Implications for late Quaternary hydroclimate variability in Interior Alaska

    NASA Astrophysics Data System (ADS)

    Brady, S.; Finney, B. P.

    2012-12-01

    Understanding climate controls over lake level and watershed vegetation changes throughout the Holocene is important to determine how future hydroclimates will affect freshwater and terrestrial systems. This study seeks to provide a detailed record of late Quaternary climate variability for interior Alaska by quantifying lake level and vegetation changes via C and N isotopic compositions of lacustrine organic matter. C and N stable isotopes are important paleoclimate proxies from lake sediments that identify general plant types growing in and around lakes at the time of deposition. At Little Harding Lake (N 64.409207, W 146.902278), low lake levels are inferred around 12,285 cal yr BP, a time when sediment organic matter is characterized by enriched δ13C and low C/N ratios, carbonate deposition occurred, and herb vegetation dominated the landscape. Concentration dependent mixing models suggest that terrestrial organic matter contributed 51% to lake sediments during this time. An intensified Aleutian Low during the latter half of the Younger Dryas may have created cold, dry conditions in the Alaskan interior. Lake level fluctuated and began to rise after 11,400 cal yr BP as moisture delivery increased to the Alaskan interior and birch expanded in the region. Rising lake level and C3 plant expansion are documented by depleted δ13C, higher C/N ratios, and a 30% increase in terrestrial organic matter contribution to Little Harding Lake. Further increases in lake level until 8,400 cal yr BP correlate with expansion of poplar, spruce and alder and higher organic matter accumulation rates. C3 tree expansion and increasing lake levels into the middle Holocene may be attributed to greater summer precipitation in the interior as the result of an increased East Asian trough to the west accompanied by ridging over Alaska. Comparisons with other regional records will be assessed to determine likely patterns of past atmospheric circulation that may explain late Quaternary lake

  19. Summit crater lake observations, and the location, chemistry, and pH of water samples near Mount Chiginagak volcano, Alaska: 2004-2012

    USGS Publications Warehouse

    Schaefer, Janet R.; Scott, William E.; Evans, William C.; Wang, Bronwen; McGimsey, Robert G.

    2013-01-01

    Mount Chiginagak is a hydrothermally active volcano on the Alaska Peninsula, approximately 170 km south–southwest of King Salmon, Alaska (fig. 1). This small stratovolcano, approximately 8 km in diameter, has erupted through Tertiary to Permian sedimentary and igneous rocks (Detterman and others, 1987). The highest peak is at an elevation of 2,135 m, and the upper ~1,000 m of the volcano are covered with snow and ice. Holocene activity consists of debris avalanches, lahars, and lava flows. Pleistocene pyroclastic flows and block-and-ash flows, interlayered with andesitic lava flows, dominate the edifice rocks on the northern and western flanks. Historical reports of activity are limited and generally describe “steaming” and “smoking” (Coats, 1950; Powers, 1958). Proximal tephra collected during recent fieldwork suggests there may have been limited Holocene explosive activity that resulted in localized ash fall. A cluster of fumaroles on the north flank, at an elevation of ~1,750 m, commonly referred to as the “north flank fumarole” have been emitting gas throughout historical time (location shown in fig. 2). The only other thermal feature at the volcano is the Mother Goose hot springs located at the base of the edifice on the northwestern flank in upper Volcano Creek, at an elevation of ~160 m (fig. 2, near sites H1, H3, and H4). Sometime between November 2004 and May 2005, a ~400-m-wide, 100-m-deep lake developed in the snow- and ice-filled summit crater of the volcano (Schaefer and others, 2008). In early May 2005, an estimated 3 million cubic meters (3×106 m3) of sulfurous, clay-rich debris and acidic water exited the crater through tunnels at the base of a glacier that breaches the south crater rim. More than 27 km downstream, these acidic flood waters reached approximately 1.3 m above normal water levels and inundated a fertile, salmon-spawning drainage, acidifying the entire water column of Mother Goose Lake from its surface waters to its

  20. Field Investigation of Surface-Lake Processes on Ice Shelves: Results of the 2015/16 Field Campaign on McMurdo Ice Shelf, Antarctica

    NASA Astrophysics Data System (ADS)

    MacAyeal, Doug; Banwell, Alison; Willis, Ian; Macdonald, Grant

    2016-04-01

    Ice-shelf instability and breakup of the style exhibited by Larsen B Ice Shelf in 2002 remains the most difficult glaciological process of consequence to observe in detail. It is, however, vital to do so because ice-shelf breakup has the potential to influence the buttressing controls on inland ice discharge, and thus to affect sea level. Several mechanisms enabling Larsen B style breakup have been proposed, including the ability of surface lakes to introduce ice-shelf fractures when they fill and drain, thereby changing the surface loads the ice-shelf must adjust to. Our model suggest that these fractures resulted in a chain-reaction style drainage of >2750 surface lakes on the Larsen B in the days prior to its demise. To validate this and other models, we began a field project on the McMurdo Ice Shelf (MIS) during the 2015/16 austral summer. Advantages of the MIS study site are: there is considerable surface melting during 3-6 weeks of the summer season, the ice is sufficiently thin (< 30 m in places) to allow observable viscoelastic responses to relatively small loads, and it is close to a center of logistical support (McMurdo Station). Here we show initial results from the field campaign, including GPS and water-depth observations of a lake that has filled and drained over multiple week timescales in previous austral summers. We also report on the analysis of high-resolution WorldView satellite imagery from several summers that reveals the complexity of surface meltwater movement in channels and subsurface void spaces. Initial reconnaissance of the largest surface-lake features reveal that they have a central circular depression surrounded by an uplifted ring, which supports one of the central tenets of our ice-shelf flexure theory. A second field season is anticipated for the 2016/17 austral summer.

  1. 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

  2. Climate-Ice Sheet Interactions through the Pliocene-Pleistocene: Preliminary Results from IODP Expedition 341 (Gulf of Alaska)

    NASA Astrophysics Data System (ADS)

    Müller, J.; McClymont, E.; Sanchez Montes, M. L.; Moy, C. M.; Romero, O. E.; Lloyd, J. M.

    2014-12-01

    Since the Pliocene, global climate history is distinguished by the transition into a colder world, dominated by the onset and intensification of major Northern Hemisphere glaciations which have also changed in their duration and intensity. Potential drivers for these events include falling atmospheric CO2, progressive sub-glacial erosion, tectonic uplift, and associated feedbacks. At present, isolating climate as the driver of evolving continental ice volume since the Pliocene is hindered by the limited long term data sets which directly link climate changes to evidence for ice-sheet advance/retreat, erosion, and tectonic evolution over million year timescales. IODP Expedition 341 drilled a cross-margin transect in the Gulf of Alaska from ice-proximal sites on the continental shelf to distal sites in the deep Pacific. This study focuses on the distal site (Site U1417, c.4190 m water depth) which contains variable biogenic and terrigenous contributions, and evidence for deposition through pelagic, mass movement and glacial processes. Our aim is to investigate links between north-east Pacific paleoceanography and the history of the north-west Cordilleran ice sheet, neither of which are fully understood given limited data pre-dating the Last Glacial Maximum. We reconstruct SSTs during the mid-Pliocene, Plio-Pleistocene Transition (PPT) and mid-Pleistocene transition (MPT) using the UK37' index. We consider the interaction between SSTs and primary production by examining the absolute and relative abundances of plankton biomarkers (e.g. for haptophytes, diatoms and dinoflagellates), carbon/nitrogen ratios, stable isotopes (δ13C, δ15N) and diatom assemblages. Links between these climatic events and the north-west Cordilleran ice-sheet advance/retreat history are initially made using shipboard stratigraphy; emerging data sets on ice-rafting from members of the Expedition 341 Scientific Party will refine these relationships.

  3. Mercury deposition to snow and ice provides a link between the lower atmosphere and the cryosphere in northern Alaska

    NASA Astrophysics Data System (ADS)

    Douglas, T. A.; Sturm, M.; Simpson, W. R.; Alvarez-Aviles, L.; Blum, J. D.; Perovich, D. K.; Keeler, G. J.; Lammers, A.; Biswas, A.

    2005-12-01

    We investigated a wide range of snow and ice forms as potential scavengers of atmospheric mercury during mercury depletion events (MDEs). Our work was part of a large campaign near Barrow, Alaska in the spring of 2005 (LEADEX-2005). Gaseous and reactive phase mercury, ozone and halogen oxide measurements were made at numerous locations along the Arctic Ocean Coast as part of the campaign and allowed us to identify when MDEs were occurring. Results from previous work implicated sea ice leads and the near shore coastal snow pack as locations where elevated mercury concentrations in frost flowers (75-185 ng/L) and surface hoar (~900 ng/L) were likely. In LEADEX-2005 the previous work was expanded by sampling snow along transects away from the lead edge and from daily sampling of diamond dust and surface snow at a site located 6 kilometers inland from the lead. Vapor condensate was also collected on chilled sample bottles hoisted above the lead on a 2 m2 kite and from a 2-m high pole. We also sampled surface hoar, rime ice, wind slab, fresh snow and blowing snow near the leads. Diamond dust was collected in glass trays and rime was scraped from the leading edge of an unmanned aerial vehicle wing. Nilas and frost flowers of varying ages were collected from a boat in open water at the lead. Elevated mercury concentrations were measured in virtually every type of vapor deposited snow or ice form, including some samples that yielded concentrations well over 1000 ng/L. Our results suggest that deposition of mercury to snow and ice during MDEs is controlled by four processes: 1) scavenging during crystallization or snow fall, 2) impaction of mercury laden aerosols onto crystalline surfaces, 3) sublimation of snow and ice, and 4) condensation driven by temperature gradients. We believe these four factors combine to control elevated mercury concentrations where the lower atmosphere and cryosphere meet.

  4. Morphometric analysis of ice-walled lake plains in Northern Illinois: Implications of lake elongation by wind-induced dual-cycle currents

    NASA Astrophysics Data System (ADS)

    Allred, Kory; Luo, Wei; Konen, Mike; Curry, B. Brandon

    2014-09-01

    Ice-walled lake plains (IWLPs) are rounded, flat-topped mounds that formed in stagnant ice environments along the margins of the Laurentide Ice Sheet. We conducted detailed morphometric and statistical analyses of the shape, size, and orientation of more than 400 IWLPs identified from aerial photos aided with LiDAR data in DeKalb County, Illinois, USA. Lake elongation theories include extraterrestrial impact (e.g. the Carolina Bays), ice flow dynamics and crevasses, and wind induced currents that preferentially erode the shorelines perpendicular to the dominant wind direction. The results indicate that elliptical IWLPs with a perimeter greater than 3050 m have preferred orientations roughly normal to the paleo-wind direction as indicated by contemporaneous parabolic dunes located 50 km to the west. The orientations of the IWLPs with a perimeter less than 1220 m are scattered and show no apparent trend. The IWLP orientation is not related to ice flow dynamics or glacial crevasses because no statistically significant relationship exists with regard to the ice flow as proxied by the moraine direction. The orientation of large IWLPs in DeKalb County are consistent with wind-induced lake elongation observed in modern permafrost thaw lakes, suggesting that the prevailing wind also played an important role in controlling the orientation of IWLPs during the last glacial period and led to the preferred orientation we see today.

  5. Sedimentology and geochemistry of a perennially ice-covered epishelf lake in Bunger Hills Oasis, East Antarctica.

    PubMed

    Doran, P T; Wharton, R A; Lyons, W B; Des Marais, D J; Andersen, D T

    2000-01-01

    A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years.

  6. Sedimentology and geochemistry of a perennially ice-covered epishelf lake in Bunger Hills Oasis, East Antarctica

    NASA Technical Reports Server (NTRS)

    Doran, P. T.; Wharton, R. A. Jr; Lyons, W. B.; Des Marais, D. J.; Andersen, D. T.; Wharton RA, J. r. (Principal Investigator)

    2000-01-01

    A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years.

  7. Sedimentology and geochemistry of a perennially ice-covered epishelf lake in Bunger Hills Oasis, East Antarctica.

    PubMed

    Doran, P T; Wharton, R A; Lyons, W B; Des Marais, D J; Andersen, D T

    2000-01-01

    A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years. PMID:11543521

  8. Expansion rate and geometry of floating vegetation mats on the margins of thermokarst lakes, northern Seward Peninsula, Alaska, USA

    USGS Publications Warehouse

    Parsekian, A.D.; Jones, Benjamin M.; Jones, M.; Grosse, G.; Walter, Anthony K.M.; Slater, L.

    2011-01-01

    Investigations on the northern Seward Peninsula in Alaska identified zones of recent (<50years) permafrost collapse that led to the formation of floating vegetation mats along thermokarst lake margins. The occurrence of floating vegetation mat features indicates rapid degradation of near-surface permafrost and lake expansion. This paper reports on the recent expansion of these collapse features and their geometry is determined using geophysical and remote sensing measurements. The vegetation mats were observed to have an average thickness of 0.57m and petrophysical modeling indicated that gas content of 1.5-5% enabled floatation above the lake surface. Furthermore, geophysical investigation provides evidence that the mats form by thaw and subsidence of the underlying permafrost rather than terrestrialization. The temperature of the water below a vegetation mat was observed to remain above freezing late in the winter. Analysis of satellite and aerial imagery indicates that these features have expanded at maximum rates of 1-2myr-1 over a 56year period. Including the spatial coverage of floating 'thermokarst mats' increases estimates of lake area by as much as 4% in some lakes. ?? 2011 John Wiley & Sons, Ltd.

  9. Measuring the Ice Floe Sizes of the Lake Akkeshi Broken by 2011 Tohoku Pacific-Coast Earthquake

    NASA Astrophysics Data System (ADS)

    Abe, T.; Yoshikawa, Y.

    2012-12-01

    Water level fluctuations in an open sea can sometimes cause large oscillations of water level in partially enclosed bodies of water such as lakes and bays. In cold and snowy regions, flooding caused by water level fluctuation and scattering of ice floes can occur due to these secondary undulation of tide, which little studies have assessed. The tsunami caused by 2011 Tohoku Pacific-Coast Earthquake reached the coast of Hokkaido, Japan. This tsunami broke up the ice on an unprecedented scale in the Lake Akkeshi, which is connected with Akkeshi Bay. Also, the intermittent tsunami intrusion caused a serious damage to local oyster fishery. On the other hand, lake ice was not broken in other lakes near the coast lines unconnected to the open sea. Therefore, in the Lake Akkeshi, the main cause of the ice breakup is thought to have been the tsunami intrusion. In this study, the sizes of floating lake ice were measured to clarify the effect of the tsunami and the water level fluctuation on lake ice. We used satellite images by WorldView-2 sensor obtained on March 9 and March 12, 2011. We measured the sizes and areas of lake ice by GIS analysis to compare these with the results from other sea ice size measurement and then attempted to clarify the difference in sizes from ice formed in sea ice zones. Firstly, we measured the area of lake ice formed before the tsunami intrusions. From the photograph obtained on March 12, we extracted the contours of ice floes formed by the tsunami. Based on the contours, we measured the areas and diameter d of floes. In the photograph obtained on March 9, the area of lake ice was estimated as about 15 km2. The figure shows a cumulative number distribution of floe diameter d on March 12. It is noticed from the figure that the graph is almost linear for the d between 8m and 20m. In other words, this means for this range N(d) behaves like d-α; that is, the floe size distribution is basically self-similar. Note that the value α=3.0 is

  10. Polarimetric analysis of snow-covered and bare lake ice from Ku and X-band scatterometer data

    NASA Astrophysics Data System (ADS)

    Ben Khadhra, K.; Gunn, G. E.; Duguay, C. R.; Kelly, R. E.

    2011-12-01

    Lake ice plays a key role in regional climate, and has significant physical, biological and socio-economic impacts (e.g. fish overwintering habitat, winter-road transportation, public safety). In the last two decades, there has been growing interest by the international remote sensing community to explore radar polarimetry for glaciological investigations, mainly for glaciers and ice sheet. Polarimetric synthetic aperture radar (SAR) could be a potential tool for lake ice cover mapping and ice thickness estimation. In this paper, we represent results from the first investigation of fully polarimetric Ku and X-band (9.6 and 17.2 GHz, respectively) scatterometer data collected over lake near Churchill, Manitoba. Several controlled and calibrated experimental measurements were carried out during winter 2010-2011, as a contribution to the Cold Regions Hydrology High-resolution Observatory (CoReH2O) candidate mission of the European Space Agency (ESA). Scatterometer scans were made on several occasions at five undisturbed static sites on Ramsey Lake. Measurements characterizing snow and ice properties were also gathered immediately after scatterometer scans. Snow depth and density, snow water equivalent, gain size, ice thickness, ice composition and air inclusion in ice volume were determined at each site. This field data set was very important for the interpretation of the polarimetric parameters, e.g. the copolarization ratio, the copolarization phase and the depolarization ratio. First, the polarimetric parameters have been analysed for the two layers (snow and ice) covariance matrix and where snow subsequently removed. Thus, the influence of the snow layer on the polarimetric data could be quantified. Also, the Pauli and Cloude/Pottier polarimetric decompositions were applied for the two-layer and one-layer scattering mechanisms (removed snow) to quantify the effectiveness of these decompositions. Results show that the polarimetric SAR could explain the different

  11. Sea ice type maps from Alaska synthetic aperture radar facility imagery: An assessment

    NASA Technical Reports Server (NTRS)

    Fetterer, Florence M.; Gineris, Denise; Kwok, Ronald

    1994-01-01

    Synthetic aperture radar (SAR) imagery received at the Alaskan SAR Facility is routinely and automatically classified on the Geophysical Processor System (GPS) to create ice type maps. We evaluated the wintertime performance of the GPS classification algorithm by comparing ice type percentages from supervised classification with percentages from the algorithm. The root mean square (RMS) difference for multiyear ice is about 6%, while the inconsistency in supervised classification is about 3%. The algorithm separates first-year from multiyear ice well, although it sometimes fails to correctly classify new ice and open water owing to the wide distribution of backscatter for these classes. Our results imply a high degree of accuracy and consistency in the growing archive of multiyear and first-year ice distribution maps. These results have implications for heat and mass balance studies which are furthered by the ability to accurately characterize ice type distributions over a large part of the Arctic.

  12. Hellas as a possible site of ancient ice-covered lakes on Mars

    USGS Publications Warehouse

    Moore, Johnnie N.; Wilhelms, D.E.

    2001-01-01

    Based on topographic, morphologic, and stratigraphic evidence, we propose that ancient water-laid sediment is the dominant component of deposits within Hellas Planitia, Mars. Multiple-layered sediment is manifested by alternating benches and scarps visible in Mars orbiting camera narrow-angle (MOC NA) images. Viking Orbiter camera and MOC NA images were used to map contacts and stratigraphically order the different materials units within Hellas. Mars orbiting laser altimeter (MOLA) data reveal that the contacts of these sedimentary units, as well as a number of scarps or other abrupt changes in landscape texture, trace contours of constant elevation for thousands of km, and in one case all around the basin. Channels, consensually interpreted to be cut by water, lead into the basin. MOLA results indicate that the area encompassed by greater Hellas' highest closed contour is nearly one-fifth that of the entire northern plains, making the Hellas "drainage" area much larger than previously reported. If lakes formed under climatic conditions similar to the modern Martian climate, they would develop thick ice carapaces, then the lakes would eventually sublimate away. Two units within Hellas exhibit a reticulate or honeycomb pattern, which we speculate are impressions made by lake-lowered ice blocks grounding into initially soft mud.

  13. Hellas as a Possible Site of Ancient Ice-Covered Lakes on Mars

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.; Wilhelms, Don E.; DeVincenzi, Donald (Technical Monitor)

    2002-01-01

    Based on topographic, morphologic, and stratigraphic evidence, we propose that ancient water-laid sediment is the dominant component of deposits within Hellas Planitia, Mars. Multiply layered sediment is manifested by alternating benches and scarps visible in Mars Orbiting Camera narrow-angle (MOC NA) images. Viking Orbiter camera and MOC NA images were used to map contacts and stratigraphically order the different materials units within Hellas. Mar's Orbiting Laser Altimeter (MOLA) data reveal that the contacts of these sedimentary units, as well as a number of scarps or other abrupt changes in landscape texture, trace contours of constant elevation for thousands of km, and in one case all around the basin. Channels, consensually interpreted to be cut by water, lead into the basin. MOLA results indicate that the area encompassed by greater Hellas' highest closed contour is nearly one-fifth that of the entire northern plains, making the Hellas 'drainage' area much larger than previously reported. If lakes formed under climatic conditions similar to the modern Martian climate, they would develop thick ice carapaces, then the lakes would eventually sublimate away. Two units within Hellas exhibit a reticulate or honeycomb pattern we speculate are impressions made by lake-lowered ice blocks grounding into initially soft mud.

  14. Sub-Ice Microalgal and Bacterial Communities in Freshwater Lake Baikal, Russia.

    PubMed

    Bashenkhaeva, Maria V; Zakharova, Yulia R; Petrova, Darya P; Khanaev, Igor V; Galachyants, Yuri P; Likhoshway, Yelena V

    2015-10-01

    The sub-ice environment of Lake Baikal represents a special ecotope where strongly increasing microbial biomass causes an "ice-bloom" contributing therefore to the ecosystem functioning and global element turnover under low temperature in the world's largest freshwater lake. In this work, we analyzed bacterial and microalgal communities and their succession in the sub-ice environment in March-April 2010-2012. It was found out that two dinoflagellate species (Gymnodinium baicalense var. minor and Peridinium baicalense Kisselew et Zwetkow) and four diatom species (Aulacoseira islandica, A. baicalensis, Synedra acus subsp. radians, and Synedra ulna) predominated in the microalgal communities. Interestingly, among all microalgae, the diatom A. islandica showed the highest number of physically attached bacterial cells (up to 67 ± 16 bacteria per alga). Bacterial communities analyzed with pyrosequencing of 16S rRNA gene fragments were diverse and represented by 161 genera. Phyla Proteobacteria, Verrucomicrobia, Actinobacteria, Acidobacteria, Bacteroidetes, and Cyanobacteria represented a core community independently on microalgal composition, although the relative abundance of these bacterial phyla strongly varied across sampling sites and time points; unique OTUs from other groups were rare.

  15. The deglacial history of the Lake Michigan lobe in Illinois, USA, fleshed out by chronologies associated with ice-walled lakes

    NASA Astrophysics Data System (ADS)

    Curry, B.

    2009-12-01

    The onset of deglaciation of the Lake Michigan lobe (LML) in the western Great Lakes region of North America is well-defined by radiocarbon ages from terrestrial plant material that was buried by proglacial lake sediment and till. A small portion of the lobe began its final retreat during the Marengo Phase at about 24,780 C-14 yr BP (29,630 cal yr BP) [CalPal]; most of the lobe began its final retreat during the Shelby Phase starting at about 19,350 C-14 yr BP (23,010 cal yr BP)[Calib 5.02]. New radiocarbon ages from tundra plant fossils encased in the deposits of ice-walled lakes allow estimation periods of ice stagnation vs. margin advance as well as constraining the age of important events during the late Wisconsin Episode. For example, radiocarbon ages from fossils in ice-walled deposits indicate the LML margin began its final retreat from Illinois at the onset of the Mackinaw lake phase by about 13,650 C-14 yr BP (16,250 cal yr BP). Located on the Marseilles Morainic System, the oldest dated ice-walled lake deposit known in Illinois began to form at 18,210 C-14 yr BP (21,680 cal yr BP). From its end moraine located near Peoria to Chicago on the shores of southern Lake Michigan, the LML extended about 230 km. Collectively, the ages indicate that the outer 100 km of the LML margin retreated about three times faster than the inner 130 km (7.5 x 10-2 km/yr vs. 2.4 x 10-2 km/yr). Changes in ice thickness and dynamics, debris concentration, climate, and regional drainage are some of the likely factors that affected the difference in rate. The existing data provide conservative estimates for the formation of two moraines, the lake-border Deerfield Moraine (720 cal yrs) and the Tinley Moraine (850 cal yrs). Periods of stagnations, marked by radiocarbon ages from fossils in the ice-walled lake sediments, include about 320 years (Deerfield Moraine), 520 cal yrs (Tinley Moraine), 500 cal yrs (Woodstock Moraine), and 710 years (Ransom Moraine). These and other ages

  16. Effects of changing sea ice on marine mammals and subsistence hunters in northern Alaska from traditional knowledge interviews.

    PubMed

    Huntington, Henry P; Quakenbush, Lori T; Nelson, Mark

    2016-08-01

    Marine mammals are important sources of food for indigenous residents of northern Alaska. Changing sea ice patterns affect the animals themselves as well as access to them by hunters. Documenting the traditional knowledge of Iñupiaq and Yupik hunters concerning marine mammals and sea ice makes accessible a wide range of information relevant to understanding the ecosystem to which humans belong. We interviewed hunters in 11 coastal villages from the northern Bering Sea to the Beaufort Sea. Hunters reported extensive changes in sea ice and weather that have affected the timing of marine mammal migrations, their distribution and behaviour and the efficacy of certain hunting methods. Amidst these changes, however, hunters cited offsetting technological benefits, such as more powerful and fuel-efficient outboard engines. Other concerns included potential impacts to subsistence hunting from industrial activity such as shipping and oil and gas development. While hunters have been able to adjust to some changes, continued environmental changes and increased disturbance from human activity may further challenge their ability to acquire food in the future. There are indications, however, that innovation and flexibility provide sources of resilience. PMID:27555644

  17. Antarctica, Greenland and Gulf of Alaska Land-ice Evolution from an Iterated GRACE Global Mascon Solution

    NASA Technical Reports Server (NTRS)

    Luthcke, Scott B.; Sabaka, T. J.; Loomis, B. D.; Arendt, A. A.; McCarthy, J. J.; Camp, J.

    2013-01-01

    We have determined the ice mass evolution of the Antarctica and Greenland ice sheets (AIS and GIS) and Gulf of Alaska (GOA) glaciers from a new GRACE global solution of equal-area surface mass concentration parcels (mascons) in equivalent height of water. The mascons were estimated directly from the reduction of the inter-satellite K-band range-rate (KBRR) observations, taking into account the full noise covariance, and formally iterating the solution. The new solution increases signal recovery while reducing the GRACE KBRR observation residuals. The mascons were estimated with 10 day and 1 arc degree equal-area sampling, applying anisotropic constraints. An ensemble empirical mode decomposition adaptive filter was applied to the mascon time series to compute annual mass balances. The details and causes of the spatial and temporal variability of the land-ice regions studied are discussed. The estimated mass trend over the total GIS, AIS and GOA glaciers for the time period 1 December 2003 to 1 December 2010 is -380 plus or minus 31 Gt a(exp -1), equivalent to -1.05 plus or minus 0.09 mma(exp -1) sea-level rise. Over the same time period we estimate the mass acceleration to be -41 plus or minus 27 Gt a(exp -2), equivalent to a 0.11 plus or minus 0.08 mm a(exp -2) rate of change in sea level. The trends and accelerations are dependent on significant seasonal and annual balance anomalies.

  18. Antarctica, Greenland and Gulf of Alaska Land-Ice Evolution from an Iterated GRACE Global Mascon Solution

    NASA Technical Reports Server (NTRS)

    Luthcke, Scott B.; Sabaka, T. J.; Loomis, B. D.; Arendt, A. A.; McCarthy, J. J.; Camp, J.

    2013-01-01

    We have determined the ice mass evolution of the Antarctica and Greenland ice sheets (AIS and GIS) and Gulf of Alaska (GOA) glaciers from a new GRACE global solution of equal-area surface mass concentration parcels (mascons) in equivalent height of water. The mascons were estimated directly from the reduction of the inter-satellite K-band range-rate (KBRR) observations, taking into account the full noise covariance, and formally iterating the solution. The new solution increases signal recovery while reducing the GRACE KBRR observation residuals. The mascons were estimated with 10 day and 1 arc degree equal-area sampling, applying anisotropic constraints. An ensemble empirical mode decomposition adaptive filter was applied to the mascon time series to compute annual mass balances. The details and causes of the spatial and temporal variability of the land-ice regions studied are discussed. The estimated mass trend over the total GIS, AIS and GOA glaciers for the time period 1 December 2003 to 1 December 2010 is -380 plus or minus 31 Gt a(exp -1), equivalent to -1.05 plus or minus 0.09 mma(exp -1) sea-level rise. Over the same time period we estimate the mass acceleration to be -41 plus or minus 27 Gt a(exp -2), equivalent to a 0.11 plus or minus 0.08 mm a(exp -2) rate of change in sea level. The trends and accelerations are dependent on significant seasonal and annual balance anomalies.

  19. Effects of changing sea ice on marine mammals and subsistence hunters in northern Alaska from traditional knowledge interviews.

    PubMed

    Huntington, Henry P; Quakenbush, Lori T; Nelson, Mark

    2016-08-01

    Marine mammals are important sources of food for indigenous residents of northern Alaska. Changing sea ice patterns affect the animals themselves as well as access to them by hunters. Documenting the traditional knowledge of Iñupiaq and Yupik hunters concerning marine mammals and sea ice makes accessible a wide range of information relevant to understanding the ecosystem to which humans belong. We interviewed hunters in 11 coastal villages from the northern Bering Sea to the Beaufort Sea. Hunters reported extensive changes in sea ice and weather that have affected the timing of marine mammal migrations, their distribution and behaviour and the efficacy of certain hunting methods. Amidst these changes, however, hunters cited offsetting technological benefits, such as more powerful and fuel-efficient outboard engines. Other concerns included potential impacts to subsistence hunting from industrial activity such as shipping and oil and gas development. While hunters have been able to adjust to some changes, continued environmental changes and increased disturbance from human activity may further challenge their ability to acquire food in the future. There are indications, however, that innovation and flexibility provide sources of resilience.

  20. Effects of changing sea ice on marine mammals and subsistence hunters in northern Alaska from traditional knowledge interviews

    PubMed Central

    Quakenbush, Lori T.; Nelson, Mark

    2016-01-01

    Marine mammals are important sources of food for indigenous residents of northern Alaska. Changing sea ice patterns affect the animals themselves as well as access to them by hunters. Documenting the traditional knowledge of Iñupiaq and Yupik hunters concerning marine mammals and sea ice makes accessible a wide range of information relevant to understanding the ecosystem to which humans belong. We interviewed hunters in 11 coastal villages from the northern Bering Sea to the Beaufort Sea. Hunters reported extensive changes in sea ice and weather that have affected the timing of marine mammal migrations, their distribution and behaviour and the efficacy of certain hunting methods. Amidst these changes, however, hunters cited offsetting technological benefits, such as more powerful and fuel-efficient outboard engines. Other concerns included potential impacts to subsistence hunting from industrial activity such as shipping and oil and gas development. While hunters have been able to adjust to some changes, continued environmental changes and increased disturbance from human activity may further challenge their ability to acquire food in the future. There are indications, however, that innovation and flexibility provide sources of resilience. PMID:27555644

  1. LANDSAT survey of near-shore ice conditions along the Arctic coast of Alaska

    NASA Technical Reports Server (NTRS)

    Stringer, W. J. (Principal Investigator); Barrett, S. A.

    1978-01-01

    The author has identified the following significant results. Winter and spring near-shore ice conditions were analyzed for the Beaufort Sea 1973-77, and the Chukchi Sea 1973-76. LANDSAT imagery was utilized to map major ice features related to regional ice morphology. Significant features from individual LANDSAT image maps were combined to yield regional maps of major ice ridge systems for each year of study and maps of flaw lead systems for representative seasons during each year. These regional maps were, in turn, used to prepare seasonal ice morphology maps. These maps showed, in terms of a zonal analysis, regions of statistically uniform ice behavior. The behavioral characteristics of each zone were described in terms of coastal processes and bathymetric configuration.

  2. Quantifying the influence of sea ice on ocean microseism using observations from the Bering Sea, Alaska

    USGS Publications Warehouse

    Tsai, V.C.; McNamara, D.E.

    2011-01-01

    Microseism is potentially affected by all processes that alter ocean wave heights. Because strong sea ice prevents large ocean waves from forming, sea ice can therefore significantly affect microseism amplitudes. Here we show that this link between sea ice and microseism is not only a robust one but can be quantified. In particular, we show that 75-90% of the variability in microseism power in the Bering Sea can be predicted using a fairly crude model of microseism damping by sea ice. The success of this simple parameterization suggests that an even stronger link can be established between the mechanical strength of sea ice and microseism power, and that microseism can eventually be used to monitor the strength of sea ice, a quantity that is not as easily observed through other means. Copyright 2011 by the American Geophysical Union.

  3. Quantifying the influence of sea ice on ocean microseism using observations from the Bering Sea, Alaska

    USGS Publications Warehouse

    Tsai, Victor C.; McNamara, Daniel E.

    2011-01-01

    Microseism is potentially affected by all processes that alter ocean wave heights. Because strong sea ice prevents large ocean waves from forming, sea ice can therefore significantly affect microseism amplitudes. Here we show that this link between sea ice and microseism is not only a robust one but can be quantified. In particular, we show that 75–90% of the variability in microseism power in the Bering Sea can be predicted using a fairly crude model of microseism damping by sea ice. The success of this simple parameterization suggests that an even stronger link can be established between the mechanical strength of sea ice and microseism power, and that microseism can eventually be used to monitor the strength of sea ice, a quantity that is not as easily observed through other means.

  4. Unusual ice diamicts emplaced during the December 15, 1989 eruption of redoubt volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Waitt, R. B.; Gardner, C. A.; Pierson, T. C.; Major, J. J.; Neal, C. A.

    1994-08-01

    Ice diamict comprising clasts of glacier ice and subordinate rock debris in a matrix of ice (snow) grains, coarse ash, and frozen pore water was deposited during the eruption of Redoubt Volcano on December 15, 1989. Rounded clasts of glacier ice and snowpack are as large as 2.5 m, clasts of Redoubt andesite and basement crystalline rocks reach 1 m, and tabular clasts of entrained snowpack are as long as 10 m. Ice diamict was deposited on both the north and south volcano flanks. On Redoubt's north flank along the east side of Drift piedmont glacier and outwash valley, ice diamict accumulated as at least 3 units, each 1-5 m thick. Two ice-diamict layers underlie a pumice-lithic fall tephra that accumulated on December 15 from 10:15 to 11:45 AST. A third ice diamict overlies the pumiceous tephra. Some of the ice diamicts have a basal 'ice-sandstone' layer. The north side icy flows reached as far as 14 km laterally over an altitude drop of 2.3 km and covered an area of about 5.7 km 2. On Crescent Glacier on the south volcano flank, a composite ice diamict is locally as thick as 20 m. It travelled 4.3 km over an altitude drop of 1.7 km, covering about 1 km 2. The much higher mobility of the northside flows was influenced by their much higher water contents than the southside flow(s). Erupting hot juvenile andesite triggered and turbulently mixed with snow avalanches at snow-covered glacier heads. These flows rapidly entrained more snow, firn, and ice blocks from the crevassed glacier. On the north flank, a trailing watery phase of each ice-diamict flow swept over and terraced the new icy deposits. The last (and perhaps each) flood reworked valley-floor snowpack and swept 35 km downvalley to the sea. Ice diamict did not form during eruptions after December 15 despite intervening snowfalls. These later pyroclastic flows swept mainly over glacier ice rather than snowpack and generated laharic floods rather than snowflows. Similar flows of mixed ice grains and pyroclastic

  5. Revised 14C dating of ice wedge growth in interior Alaska (USA) to MIS 2 reveals cold paleoclimate and carbon recycling in ancient permafrost terrain

    NASA Astrophysics Data System (ADS)

    Lachniet, Matthew S.; Lawson, Daniel E.; Sloat, Alison R.

    2012-09-01

    Establishing firm radiocarbon chronologies for Quaternary permafrost sequences remains a challenge because of the persistence of old carbon in younger deposits. To investigate carbon dynamics and establish ice wedge formation ages in Interior Alaska, we dated a late Pleistocene ice wedge, formerly assigned to Marine Isotope Stage (MIS) 3, and host sediments near Fairbanks, Alaska, with 24 radiocarbon analyses on wood, particulate organic carbon (POC), air-bubble CO2, and dissolved organic carbon (DOC). Our new CO2 and DOC ages are up to 11,170 yr younger than ice wedge POC ages, indicating that POC is detrital in origin. We conclude an ice wedge formation age between 28 and 22 cal ka BP during cold stadial conditions of MIS 2 and solar insolation minimum, possibly associated with Heinrich event 2 or the last glacial maximum. A DOC age for an ice lens in a thaw unconformity above the ice wedge returned a maximum age of 21,470 ± 200 cal yr BP. Our variable 14C data indicate recycling of older carbon in ancient permafrost terrain, resulting in radiocarbon ages significantly older than the period of ice-wedge activity. Release of ancient carbon with climatic warming will therefore affect the global 14C budget.

  6. A catastrophic flood caused by drainage of a caldera lake at Aniakchak Volcano, Alaska, and implications for volcanic hazards assessment

    USGS Publications Warehouse

    Waythomas, C.F.; Walder, J.S.; McGimsey, R.G.; Neal, C.A.

    1996-01-01

    Aniakchak caldera, located on the Alaska Peninsula of southwest Alaska, formerly contained a large lake (estimated volume 3.7 ?? 109 m3) that rapidly drained as a result of failure of the caldera rim sometime after ca. 3400 yr B.P. The peak discharge of the resulting flood was estimated using three methods: (1) flow-competence equations, (2) step-backwater modeling, and (3) a dam-break model. The results of the dam-break model indicate that the peak discharge at the breach in the caldera rim was at least 7.7 ?? 104 m3 s-1, and the maximum possible discharge was ???1.1 ?? 106 m3 s-1. Flow-competence estimates of discharge, based on the largest boulders transported by the flood, indicate that the peak discharge values, which were a few kilometers downstream of the breach, ranged from 6.4 ?? 105 to 4.8 ?? 106 m3 s-1. Similar but less variable results were obtained by step-backwater modeling. Finally, discharge estimates based on regression equations relating peak discharge to the volume and depth of the impounded water, although limited by constraining assumptions, provide results within the range of values determined by the other methods. The discovery and documentation of a flood, caused by the failure of the caldera rim at Aniakchak caldera, underscore the significance and associated hydrologic hazards of potential large floods at other lake-filled calderas.

  7. Preliminary Cosmogenic Surface Exposure Ages on Laurentide Ice-sheet Retreat and Opening of the Eastern Lake Agassiz Outlets

    NASA Astrophysics Data System (ADS)

    Leydet, D.; Carlson, A. E.; Sinclair, G.; Teller, J. T.; Breckenridge, A. J.; Caffee, M. W.; Barth, A. M.

    2015-12-01

    The chronology for the eastern outlets of glacial Lake Agassiz holds important consequences for the cause of Younger Dryas cold event during the last deglaciation. Eastward routing of Lake Agassiz runoff was originally hypothesized to have triggered the Younger Dryas. However, currently the chronology of the eastern outlets is only constrained by minimum-limiting radiocarbon ages that could suggest the eastern outlets were still ice covered at the start of the Younger Dryas at ~12.9 ka BP, requiring a different forcing of this abrupt climate event. Nevertheless, the oldest radiocarbon ages are still consistent with an ice-free eastern outlet at the start of the Younger Dryas. Here we will present preliminary 10-Be cosmogenic surface exposure ages from the North Lake, Flat Rock Lake, glacial Lake Kaministiquia, and Lake Nipigon outlets located near Thunder Bay, Ontario. These ages will date the timing of the deglaciation of the Laurentide ice sheet in the eastern outlet region of glacial Lake Agassiz. This will provide an important constraint for the hypothesized freshwater forcing of the cause of Younger Dryas cold event.

  8. Late-Holocene Fluctuations of the Greenland Ice Sheet: Insights from a south Greenland threshold lake

    NASA Astrophysics Data System (ADS)

    Sinclair, G.; Carlson, A. E.; Reilly, B.

    2015-12-01

    Several centennial-scale climate fluctuations during the late-Holocene make it an ideal test case for examining the effects of climate change on sea level at societally-relevant timescales. Across much of the Arctic, glaciers and ice sheets reached their maximum late-Holocene extent during the Little Ice Age (LIA, 1400-1900 C.E.), approximately coincident with the global temperature minima observed during this time. However, ongoing work suggests the south Greenland Ice Sheet (sGrIS) may have behaved differently during the late-Holocene, with several outlet glaciers retreating, rather than advancing, during the LIA, possibly due to regional warming in the region different from the Arctic trend. The Qassimiut lobe, a low-lying piedmont-like extension of the sGrIS, may be especially sensitive to late-Holocene climate changes. Geomorphic evidence outboard of Naujaat Sermia, an outlet glacier draining the Qassimiut lobe, suggests three distinct periods of land exposure. We hypothesize these occurred during the last deglacial period, after an advance from near or behind the present margin during the Neoglacial, and during warming following the Little Ice Age in the last 1-2 centuries. Here, we present data from threshold lake cores immediately outboard of the presumed Neoglacial moraine. A sharp contact divides glacial sands and silts from organic gyttja, indicating glacial retreat from the moraine and subsequent meltwater diversion. The contact is accompanied by several geochemical changes, including increased Fe/Ti ratios, increased Br, and decreased Si and K, indicating a switch from more clastic to organic sedimentation. Radiocarbon ages from eight macrofossils immediately above this contact are calibrated to 1350-1950 C.E., suggesting the ice sheet may have retreated from its late-Holocene maximum during the Little Ice Age, but the wide range in ages suggests reworking of organic material may be significant in this region.

  9. Modelling the influence of Lake Agassiz on Glacial Isostatic Adjustment and deglaciation of the Laurentide ice sheet

    NASA Astrophysics Data System (ADS)

    Berends, Tijn; van de Wal, Roderik; de Boer, Bas; Bradley, Sarah

    2016-04-01

    ANICE is a 3-D ice-sheet-shelf model, which simulates ice dynamics on the continental scale. It uses a combination of the SIA and SSA approximations and here it is forced with benthic δ18O records using an inverse routine. It is coupled to SELEN, a model, which solves the gravitationally self-consistent sea-level equation and the solid earth deformation of a spherically symmetrical rotating Maxwell visco-elastic earth, accounting for all major GIA effects. The coupled ANICE-SELEN model thus captures ice-sea-level feedbacks and can be used to accurately simulate variations in local relative sea-level over geological time scales. In this study it is used to investigate the mass loss of the Laurentide ice-sheet during the last deglaciation, accounting in particular for the presence of the proglacial Lake Agassiz by way of its GIA effects and its effect on the ice sheet itself. We show that the mass of the water can have a significant effect on local relative sea-level through the same mechanisms as the ice-sheet - by perturbing the geoid and by deforming the solid earth. In addition we show that calving of the ice-shelf onto the lake could have had a strong influence on the behaviour of the deglaciation. In particular, when allowing lake calving, the ice-sheet retreats rapidly over the deepening bed of Hudson Bay during the deglaciation, resulting in a narrow ice dam over Hudson Strait. This dam collapses around 8.2 Kyr causing a global sea level rise of approximately 1 meter - an observation that agrees well with field data (for example, LaJeunesse and St. Onge, 2008). Without lake calving the model predicts a drainage towards the Arctic ocean in the North.

  10. Protist diversity in a permanently ice-covered Antarctic lake during the polar night transition.

    PubMed

    Bielewicz, Scott; Bell, Elanor; Kong, Weidong; Friedberg, Iddo; Priscu, John C; Morgan-Kiss, Rachael M

    2011-09-01

    The McMurdo Dry Valleys of Antarctica harbor numerous permanently ice-covered lakes, which provide a year-round oasis for microbial life. Microbial eukaryotes in these lakes occupy a variety of trophic levels within the simple aquatic food web ranging from primary producers to tertiary predators. Here, we report the first molecular study to describe the vertical distribution of the eukaryotic community residing in the photic zone of the east lobe (ELB) and west lobe (WLB) of the chemically stratified Lake Bonney. The 18S ribosomal RNA (rRNA) libraries revealed vertically stratified populations dominated by photosynthetic protists, with a cryptophyte dominating shallow populations (ELB-6 m; WLB-10 m), a haptophyte occupying mid-depths (both lobes 13 m) and chlorophytes residing in the deepest layers (ELB-18 and 20 m; WLB-15 and 20 m) of the photic zone. A previously undetected stramenopile occurred throughout the water column of both lobes. Temporal variation in the eukaryotic populations was examined during the transition from Antarctic summer (24-h sunlight) to polar night (complete dark). Protist diversity was similar between the two lobes of Lake Bonney due to exchange between the photic zones of the two basins via a narrow bedrock sill. However, vertical and temporal variation in protist distribution occurred, indicating the influence of the unique water chemistry on the biology of the two dry valley watersheds.

  11. Protist diversity in a permanently ice-covered Antarctic lake during the polar night transition.

    PubMed

    Bielewicz, Scott; Bell, Elanor; Kong, Weidong; Friedberg, Iddo; Priscu, John C; Morgan-Kiss, Rachael M

    2011-09-01

    The McMurdo Dry Valleys of Antarctica harbor numerous permanently ice-covered lakes, which provide a year-round oasis for microbial life. Microbial eukaryotes in these lakes occupy a variety of trophic levels within the simple aquatic food web ranging from primary producers to tertiary predators. Here, we report the first molecular study to describe the vertical distribution of the eukaryotic community residing in the photic zone of the east lobe (ELB) and west lobe (WLB) of the chemically stratified Lake Bonney. The 18S ribosomal RNA (rRNA) libraries revealed vertically stratified populations dominated by photosynthetic protists, with a cryptophyte dominating shallow populations (ELB-6 m; WLB-10 m), a haptophyte occupying mid-depths (both lobes 13 m) and chlorophytes residing in the deepest layers (ELB-18 and 20 m; WLB-15 and 20 m) of the photic zone. A previously undetected stramenopile occurred throughout the water column of both lobes. Temporal variation in the eukaryotic populations was examined during the transition from Antarctic summer (24-h sunlight) to polar night (complete dark). Protist diversity was similar between the two lobes of Lake Bonney due to exchange between the photic zones of the two basins via a narrow bedrock sill. However, vertical and temporal variation in protist distribution occurred, indicating the influence of the unique water chemistry on the biology of the two dry valley watersheds. PMID:21390078

  12. Phytoplankton successions under ice cover in four lakes located in north-eastern Sweden: effects of liming.

    PubMed

    Wahlström, G; Danilov, R A

    2003-01-01

    Phytoplankton successions under ice cover (January-March) were determined in four oligotrophic lakes (Burtjärn, Aspen, Vialamptjärn and Storkorstjärn) located in North-Eastern Sweden. The total phosphorus concentration in the lakes was less than 10 micrograms/L. Lake Burtjärn (reference lake) had a similar hydrology as Lake Aspen. Storkorstjärn and Vialamptjärn were of similar hydrology and had heavily colored water (> 100 mgpt/L). Aspen as well as vialamptjärn became continuously limed with calcium carbonate annually during the last decades. Biodiversity was considerably higher in the limed lakes (Aspen and Vialamptjärn) than in the untreated lakes (Burtjärn and Storkorstjärn). In Lake Burtjärn the most frequent species were Rhodomonas lacustris, Tabellaria flocculosa and Botryococcus braunii. Cryptophyceae (R. lacustris and Cryptomonas marssonii) and Dinophyceae (especially Gymnodinium lantzschii) were common phytoplankton groups in Lake Aspen. Tabellaria flocculosa was also the most common organism in both humic lakes Storkorstjärn and Vialamptjärn, other phytoplankton groups were in the humic lakes scarce. Liming was found to have profound effects on phytoplankton communities studied.

  13. Ice-gouged microrelief on the floor of the eastern Chukchi Sea, Alaska: a reconnaissance survey

    USGS Publications Warehouse

    Toimil, Lawrence J.

    1978-01-01

    Side-scan sonar and bathymetric records obtained from 1,800 km of trackline from the eastern Chukchi Sea continental shelf, between water depths of 20 and 70 m show the ubiquitous presence of furrow-like linear depressions produced by gouging of the sea bed by ice keels. These sea bed micro-features are regionally widespread but are not uniformly distributed. Furthermore, the microrelief, texture, and lithologic structure of sea bed sediments have been significantly modified by the disruptive processes associated with ice gouge formation. An analysis of some 10,.200 individual gouges shows that the density of ice gouges increases with increasing latitude, increasing slope gradients, and decreasing water depth. Across the northern half of the shelf few trackline segments are free of ice gouges; in the southern portion numerous segments contain no ice gouges. However, ice gouges extend at least as far south as Cape Prince of Wales Shoal. Densities of over 200 gouges per km of trackline are not uncommon in water depths less than 30 m ,but no values higher than 50 km are encountered in water deeper than 50 m. No ice gouges have been observed in water depths exceeding 58 m. Saturation ice gouge densities (greater than 300/Pan) occur along the eastern side 6f Barrow Sea Valley and the northeast flank of Hanna Shoal. Maximum gouge incision depths per km of trackline are greatest in water 36 to 50 m deep . A maximum incision depth of 4.5 m occurs in the 35-40 m water depth interval. Individual ice gouge events wider than 100 m, most produced by multi-keeled ice fragments, are found between 31 and 45 m depths. The dominant azimuth of gouge furrows shows no preferred orientation on the Chukchi Sea shelf; only locally does bathmetric control of the trend of gouges appear. The occurrence of current-produced bedforms within individual ice gouges suggests an interaction between slow-moving grounded or gouging ice keels and swift currents. In other cases, current

  14. Late Quaternary environmental changes inferred from stable carbon, nitrogen and oxygen isotope values at Teshekpuk Lake, North Slope, Alaska

    NASA Astrophysics Data System (ADS)

    Randall, J. J.; Booth, A. L.; Wooller, M. J.; Jones, B. M.; Gaglioti, B.

    2012-12-01

    Global surface air temperatures increased by ~0.74°C between 1906-2005, with average temperatures in the Arctic increasing at almost twice the rate as the rest of the planet. The Arctic Coastal Plain of Alaska is particularly susceptible and responsive to these fluctuations in climate. Better understanding both short- and long-term climate variability is important as this ecosystem provides food and habitat for hundreds of thousands of migratory birds and caribou. Despite the ecological importance of the Arctic Coastal Plain, relatively few studies exist that provide multi-proxy paleoclimatic data for the region and thus the rate at which climate and ecosystems have changed during the past century lack a longer term context. Here we present stable carbon and nitrogen isotope values from the analysis of bulk organic matter in samples from a ~6 m sediment core from Teshekpuk Lake, 80 miles southeast of Barrow, Alaska. AMS 14C dates on a nearby core indicate a basal age of ~15 kyr. The relatively low C/N values (mean <11) throughout the core infer that the organic matter is largely composed of autochthonous organic matter. Stable carbon isotope values from analyses of this organic material increase from ~-27‰ at the base of the core to peaks of ~-23‰ between ~10 and 8 kyr, inferring highs in lake production during this time. We also present stable oxygen isotope values from analyses of chironomid and aquatic invertebrate chitin preserved in the core. Non-biting midges in the family Chironomidae begin their lifecycles in freshwater. During their larval stages chironomids synthesize and molt chitinous head capsules. These head capsules record the oxygen isotopic composition of the lake water present at the time of synthesis, and are well preserved in lake sediments. These isotopic results are interpreted in terms of other recent isotope data from the north slope of Alaska in addition to a pollen reconstruction from the same core and their implications in terms of

  15. 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

  16. Geochemistry of the Johnson River, Lake Clark National Park and Preserve, Alaska

    USGS Publications Warehouse

    Brabets, Timothy P.; Riehle, James R.

    2003-01-01

    The Johnson River Basin, located in Lake Clark National Park and Preserve, drains an area of 96 square miles. A private inholding in the upper part of the basin contains a gold deposit that may be developed in the future. To establish a natural baseline to compare potential effects on water quality if development were to occur, the upper part of the Johnson River Basin was studied from 1999 to 2001 as part of a cooperative study with the National Park Service. Two basic rock types occur within the drainage basin of the study: the Jurassic Talkeetna Formation of interbedded volcanic and volcaniclastic rocks, and the slightly younger plutonic rocks of the Aleutian-Alaska Ranges batholith. The Johnson River gold prospect reflects widespread, secondary mineralization and alteration of the Talkeetna Formation. Metals found at the prospect proper are: arsenic, cadmium, copper, gold, iron, lead, mercury, molybdenum, selenium, silver, and zinc. The Johnson River prospect is located in the East Fork Ore Creek Basin, a 0.5 square mile watershed that is a tributary to the Johnson River. Water quality data from this stream reflect the mineralization of the basin and the highest concentrations of several trace elements and major ions of the water column were found in this stream. Presently, pH in this stream is normal, indicating that there is sufficient buffering capacity. At the Johnson River streamgage, which drains approximately 25 mi2 including the East Fork Ore Creek, concentrations of these constituents are significantly lower, reflecting the runoff from Johnson Glacier and Double Glacier, which account for approximately 75 percent of the total discharge. Streambed concentrations of cadmium, lead, and zinc from East Fork Ore Creek and its receiving stream, Ore Creek, typically exceed concentrations where sediment dwelling organisms would be affected. Similar to the water column chemistry, concentrations of these elements are lower at the Johnson River streamgage

  17. Interannual and seasonal variability in landfast sea ice growth and properties at Barrow, Alaska: A comparison between observations and CICE model simulations

    NASA Astrophysics Data System (ADS)

    Oggier, M.; Jin, M.; Eicken, H.

    2014-12-01

    Studies of long-term, regional variations of growth and properties of sea ice are best served by a combination of field measurements and model simulations. We explore the utility of the Community Ice Code (CICE) model, designed for fully coupled global climate models. CICE was run in standalone mode, with an integrated module that includes ice salinity as a prognostic variable (Turner et al., doi:10.1002/jgrc.20171). We examine performance of the CICE salinity module by hindcasting interannual variability in the seasonal cycle of first-year ice salinity and temperature. Landfast ice, monitored at Barrow, Alaska since 1999 (SIZONet.org), provides a suitable test case and reference. The model is forced with 6-hr weather data from the National Climate Data Center, except for precipitation and humidity provided by the NCEP reanalysis model. Simulations were run for the period 1948-2013, with a focus on 1999 to 2013 when observation data are available. Based on validation with measured ice and snow thicknesses, a non-zero ocean-to-ice heat flux has to be specified to reproduce the full seasonal cycle. The model captures the broad seasonal trends of key ice properties and thickness, especially during the growth season. During melt, significant deviations between observations and model output for ice temperature and salinity are observed, in particular near the ice surface where meltwater flushing is only partially captured by the CICE mushy-layer salinity module. With the exception of two years, the model captures interannual variability of ice thickness and bulk ice salinity well. Further work is required to improve the accuracy of the full seasonal range of modeled salinity variations, especially during the melt season when processes at the ice interface are not well reproduced by the model. However, in conjunction with local validation data, CICE may serve as a tool to assess regional variations in key ice properties on interannual to decadal time scales.

  18. 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

  19. A 37,000-year environmental magnetic record of aeolian dust deposition from Burial Lake, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Dorfman, J. M.; Stoner, J. S.; Finkenbinder, M. S.; Abbott, M. B.; Xuan, C.; St-Onge, G.

    2015-11-01

    Environmental magnetism and radiocarbon dating of Burial Lake sediments constrain the timing and magnitude of regional aeolian deposition for the Noatak region of western Arctic Alaska for the last ˜37,000 years. Burial Lake (68.43°N, 159.17°W, 21.5 m water depth) is optimally located to monitor regional dust deposition because it is perched above local drainage and isolated from glacial processes. Cores collected in the summer of 2010 were studied through the application of magnetizations and progressive alternating field (AF) demagnetization of u-channel samples, with additional data provided by computed tomography (CT) derived density, hysteresis measurements, isothermal remanent magnetization (IRM) acquisition experiments, organic carbon content, biogenic silica, physical grain size, radiocarbon dating of wood, seeds, and plant macrofossils, point source magnetic susceptibility, and X-ray fluorescence (XRF). With similar magnetic properties to regional Alaskan loess deposits, low coercivity, highly magnetic material deposited during the late-Pleistocene contrasts with a high coercivity, weakly magnetic component found throughout the record, consistent with locally-derived detritus. The relative proportion of low coercivity to high coercivity magnetic material, defined by the S-Ratios, is used to reconstruct the regional input of dust to the basin over time. A four-fold decrease in the low coercivity component through the deglacial transition is interpreted to reflect diminished dust input to the region. Comparisons with potential sources of dust show that the timing of deposition in Burial Lake is largely consistent with general aridity, lack of vegetative cover, and increased windiness, rather than glacial advances or retreats. The influence from subaerial exposure of continental shelves cannot be ruled out as a significant far-field source of dust to interior Alaska during the Last Glacial Maximum (LGM), but is unlikely to have been the sole source, or to

  20. Monitoring phenological changes in lake ice as a robust indicator of regional climate change using the AVHRR

    SciTech Connect

    Wynne Randolph, H.; Lillesand, T.M. )

    1993-06-01

    The length of the growing season, effectively defined by the onset or breakup of ice, may be one of the more important ways in which climate change is likely to influence lake environments. In addition, interannual variation in the dates of lake ice formation and breakup has been shown to be an effective climate change indicator. We explored the use of data from the Advanced Very High Resolution Radiometer (AVHRR) to discriminate the presence of lake ice during the winter of 1990-1991 on the 45 lakes and reservoirs in Wisconsin with a surface area of greater than 1,000 hectares. Our results suggest both the feasibility of using the AVHRR to determine the date of lake ice breakup as well as the strong correlation (R=[minus]0.87) of the dates so derived with January-March mean local temperatures. These results indicate the inherent promise of utilizing archive satellite to detect the climate expected as a result of greenhouse warming.

  1. When a habitat freezes solid: Microorganisms over-winter within the ice column of a coastal Antarctic lake

    USGS Publications Warehouse

    Foreman, C.M.; Dieser, M.; Greenwood, M.; Cory, R.M.; Laybourn-Parry, J.; Lisle, J.T.; Jaros, C.; Miller, P.L.; Chin, Y.-P.; McKnight, Diane M.

    2011-01-01

    A major impediment to understanding the biology of microorganisms inhabiting Antarctic environments is the logistical constraint of conducting field work primarily during the summer season. However, organisms that persist throughout the year encounter severe environmental changes between seasons. In an attempt to bridge this gap, we collected ice core samples from Pony Lake in early November 2004 when the lake was frozen solid to its base, providing an archive for the biological and chemical processes that occurred during winter freezeup. The ice contained bacteria and virus-like particles, while flagellated algae and ciliates over-wintered in the form of inactive cysts and spores. Both bacteria and algae were metabolically active in the ice core melt water. Bacterial production ranged from 1.8 to 37.9??gCL-1day-1. Upon encountering favorable growth conditions in the melt water, primary production ranged from 51 to 931??gCL-1day-1. Because of the strong H2S odor and the presence of closely related anaerobic organisms assigned to Pony Lake bacterial 16S rRNA gene clones, we hypothesize that the microbial assemblage was strongly affected by oxygen gradients, which ultimately restricted the majority of phylotypes to distinct strata within the ice column. This study provides evidence that the microbial community over-winters in the ice column of Pony Lake and returns to a highly active metabolic state when spring melt is initiated. ?? 2011 Federation of European Microbiological Societies.

  2. Testing the sub-ice lake model for chaotic terrains on Mars: a numerical simulation

    NASA Astrophysics Data System (ADS)

    Roda, Manuel; Govers, Rob; Zegers, Tanja

    2013-04-01

    The identification of Hesperian chaotic terrains as the source of the outflow channels has led to a general scenario where water is rapidly discharged from the subsurface resulting in catastrophic outflows. However, the process leading to chaotic terrain formation and collection and discharge of catastrophic volumes of water has remained controversial. Geological and hydrological analysis of Aram Chaos suggests that a single, rapid and catastrophic event is sufficient to carve the outflow channel of Aram Chaos and the resulting Aram Chaos morphology imply large amount of subsidence (up to 1.5 km). These observations are in agreement with the sub-Ice lake hypothesis of catastrophic collapse of sediments induced as a consequence of melting of a buried ice sheet [1]. We use time-dependent numerical models to test different aspects of the hypothesis. The simulation starts from the complete freezing of an intra-crater lake. Subsequent ice melting and eventual destabilization is driven by planetary heat loss in combination with sediment blanketing and loading. The simulation ends when the complete sediments filling of the crater occurs. The results show that initial freezing occurs very rapidly, 360-1300 kyr, depending on the planetary heat flux (10-25 mW/m^2). Subsequent melting of the buried ice is slow and depends on the heat flux and sedimentation rate. For the lowest heat flux (10 mW/m^2) no melting occurs. The ice melting rate decreases linearly with increasing sedimentation rate, from 150 m/Myr for the fastest (0.1 mm/yr) sedimentation to 1.5 m/Myr for the slowest (0.001 mm/yr) The mechanical system remains stable until the complete filling of the crater, except in the case of slowest sedimentation (0.001 mm/yr) and 25 mW/m2 heat flow. Here, a complete top-bottom fracturing of the overburden starts at the transition between the wall and the floor of the crater, when the molten ice layer reaches a thickness of 1.5-1.6 km. The thickness of water generated beneath

  3. 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.

  4. Suppression of ice fog from the Fort Wainwright, Alaska, cooling pond. Special report

    SciTech Connect

    Walker, K.E.; Brunner, W.

    1982-10-01

    Ice fog near the Ft. Wainwright cooling pond creates a visibility hazard. Observations show a substantial reduction in visibility along both private and public roadways in the path of the cooling pond's ice fog plume. This reduction in visibility increases as the ambient air temperature decreases. Visibility was less than 215 m (700 ft) on the Richardson Highway on the average of 8 days for each of the 3 data years. Data collected during the winters of 1979-80, 1980-81 and 1981-82 statistically show that use of a monomolecular film evaporation suppressant, hexadecanol (C16H33OH), on the pond to reduce ice fog is ineffective. There is an immediate need for a driver warning system when visibility is affected by the ice fog.

  5. The 2013 eruption of Pavlof Volcano, Alaska: a spatter eruption at an ice- and snow-clad volcano

    USGS Publications Warehouse

    Waythomas, Christopher F.; Haney, Matthew M.; Fee, David; Schneider, David J.; Wech, Aaron G.

    2014-01-01

    The 2013 eruption of Pavlof Volcano, Alaska began on 13 May and ended 49 days later on 1 July. The eruption was characterized by persistent lava fountaining from a vent just north of the summit, intermittent strombolian explosions, and ash, gas, and aerosol plumes that reached as high as 8 km above sea level and on several occasions extended as much as 500 km downwind of the volcano. During the first several days of the eruption, accumulations of spatter near the vent periodically collapsed to form small pyroclastic avalanches that eroded and melted snow and ice to form lahars on the lower north flank of the volcano. Continued lava fountaining led to the production of agglutinate lava flows that extended to the base of the volcano, about 3–4 km beyond the vent. The generation of fountain-fed lava flows was a dominant process during the 2013 eruption; however, episodic collapse of spatter accumulations and formation of hot spatter-rich granular avalanches was a more efficient process for melting snow and ice and initiating lahars. The lahars and ash plumes generated during the eruption did not pose any serious hazards for the area. However, numerous local airline flights were cancelled or rerouted, and trace amounts of ash fall occurred at all of the local communities surrounding the volcano, including Cold Bay, Nelson Lagoon, Sand Point, and King Cove.

  6. Surface exposure dating of glacial lake shorelines: implications for constraining ice margin positions and meltwater outbursts during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Dube-Loubert, Hugo; Roy, Martin; Schaefer, Joerg

    2016-04-01

    The Laurentide ice sheet (LIS) played an important role in the climate variability of the last deglaciation, notably through large discharges of meltwater to the North Atlantic that disturbed the ocean's circulation and heat transport. Deglaciation of the northeastern sector of the LIS was complex and included the development of large ice-dammed lakes that were confined within the main river valleys draining northward into Ungava Bay. The history of these lakes is closely related to the temporal evolution of the Labrador ice dome, but large uncertainties regarding the position and dynamic of the ice margin through time currently limit our understanding of these glacial lakes. In the Ungava lowlands, glacial lake Naskaupi invaded the George River valley, leaving a series of well-developed shorelines and deltas. These spectacular raised shorelines are 10 to 20 meters wide and can be followed for several kilometers. Our field investigations and remote sensing analysis indicate that Lake Naskaupi experienced a complex history, as shown by the succession of shorelines that likely reflect the opening of new topographic outlets during ice retreat. Constraining the timing of the different phases of the lake and its drainage has traditionally been challenging, as organic material suitable for radiocarbon dating is scarce or lacking. Recent progress in Surface Exposure Dating (SED) by cosmogenic nuclides now inspires novel approaches to glacial and deglacial geomorphology. Here we apply 10Be SED to boulders that form part of these shorelines and mark the main (high-level) stage of Lake Naskaupi. We sampled 4-6 multi-meter size boulders at 4 different sites. Preliminary results show high internal consistency and, indicate that the main lake phase developed very late in the regional deglaciation, which extends from about 8500 to 6800 cal. yr BP (Dyke and Prest, 1987). We also present SED results from boulders deposited by a substantial outburst flood presumably associated with

  7. Time-varying imagery of ice features dynamic scattering in presence climate change: polytypical lakes Ladoga and Peipus as example

    NASA Astrophysics Data System (ADS)

    Melentyev, V.; Melentyev, K.; Pettersson, L.; Mushkudiany, M.

    2009-04-01

    The Problem of dynamical instability of ice conditions and modification of ice regime of polytypical lakes owing to global warming was investigated using time-varying satellite imagery. Deep-water Lake Ladoga and shallow-water Lake Peipus both situated at the north-western part of Russian Federation in moderate climatic zone but possessed different heat capacity were used for comparative studies. The comprehensive analysis of ERS/RADARSAT/Envisat SAR images was provided using the results of long-term studies of thermal structures of these inland water bodies and peculiarities of their variability during open water season as well calculations of heat supply in different weather conditions. 1993-2008 NERSC/NIERSC SAR archive as well materials sub-satellite experiments on board research vessel and research aircraft since 1960-s is used. Shipborne observations were used for validation satellite information. Thematic interpretation of satellite data shows that SAR signature of ice could be applied as tracer of various natural processes and phenomena, including climatically and ecologically important ones. As result dependence of hydrological features and the time of freeze-up and ice destruction in both selected lakes in consequence of climate change and softening of winter severity in nowadays was assessed. Wind regime patterns (speed and direction) were analyzed using algorithm CMOD 4 and in the upshot the increase of seasonal and regional variability of windy weather in studied regions was fixed. In frame of these studies wind cadastre appurtenant to the NW part of RF was composed on the basis of satellite SAR survey. In particular the modification of "wind climate" was disclosed. And what is more: it was revealed that intensification of windy weather resulted in intensification of dynamic range of water and ice exchange between the central part of both studied polytypical lakes and their gulfs. These natural processes took place due to widening duration of the open

  8. Time-varying imagery of ice features dynamic scattering in presence climate change: polytypical lakes Ladoga and Peipus as example

    NASA Astrophysics Data System (ADS)

    Melentyev, V. V.; Melentyev, K. V.; Pettersson, L. H.; Mushkudany, M. I.

    2009-04-01

    Problem of dynamical instability of ice conditions and modification of ice regime of polytypical lakes owing to global warming were investigated using time-varying satellite imagery. Deep-water Lake Ladoga and shallow-water Lake Peipus both situated at the north-western part of Russian Federation in moderate climatic zone but possessed different heat capacity were used for comparative studies. The comprehensive analysis of ERS/RADARSAT/Envisat SAR images was provided using the results of long-term studies of thermal structures of these inland waterbodies and peculiarities of their variability during open water season as well calculations of heat supply in different weather conditions. 1993-2008 NERSC/NIERSC SAR archive as well materials sub-satellite experiments onboard research vessel and research aircraft since 1960-s is used. Shipborne observations were used for validation satellite information. Thematic interpretation of satellite data shows that SAR signature of ice could be applied as tracer of various natural processes and phenomena, including climatically and ecologically important ones. As result dependence of hydrological features and the time of freeze-up and ice destruction in both selected lakes in consequence of climate change and softening of winter severity in nowadays was assessed. Wind regime patterns (speed and direction) were analyzed using algorithm CMOD 4 and in the upshot the increase of seasonal and regional variability of windy weather in studied regions was fixed. In frame of these studies wind cadastre appurtenant to the NW part of RF was composed on the basis of satellite SAR survey. In particular the modification of "wind climate" was disclosed. And what is more: it was revealed that intensification of windy weather resulted in intensification of dynamic range of water and ice exchange between the central part of both studied polytypical lakes and their gulfs. These natural processes took place due to widening duration of the open water

  9. Volcano-ice interactions precursory to the 2009 eruption of Redoubt Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Bleick, Heather A.; Coombs, Michelle L.; Cervelli, Peter F.; Bull, Katharine F.; Wessels, Rick L.

    2013-06-01

    In late summer of 2008, after nearly 20 years of quiescence, Redoubt Volcano began to show signs of abnormal heat flow in its summit crater. In the months that followed, the excess heat triggered melting and ablation of Redoubt's glaciers, beginning at the summit and propagating to lower elevations as the unrest accelerated. A variety of morphological changes were observed, including the creation of ice cauldrons, areas of wide-spread subsidence, punctures in the ice carved out by steam, and deposition from debris flows. In this paper, we use visual observations, satellite data, and a high resolution digital elevation model of the volcanic edifice to calculate ice loss at Redoubt as a function of time. Our aim is to establish from this time series a proxy for heat flow that can be compared to other data sets collected along the same time interval. Our study area consists of the Drift glacier, which flows from the summit crater down the volcano's north slope, and makes up about one quarter of Redoubt's total ice volume of ~ 4 km3. The upper part of the Drift glacier covers the area of recent volcanism, making this part of ice mass most susceptible to the effect of volcanic heating. Moreover, melt water and other flows are channeled down the Drift glacier drainage by topography, leaving the remainder of Redoubt's ice mantle relatively unaffected. The rate of ice loss averaged around 0.1 m3/s over the last four months of 2008, accelerated to over twenty times this value by February 2009, and peaked at greater than 22 m3/s, just prior to the first major explosion on March 22, 2009. We estimate a cumulative ice loss over this period of about 35 million cubic meters (M m3).

  10. A hydrothermal contribution to the Vostok subglacial lake (Antarctica) suggested from bacterial gene analysis and the stable isotope composition of deep ice core samples

    NASA Astrophysics Data System (ADS)

    Petit, J. R.; Alekhina, I. A.; Bulat, S. A.

    The largest subglacial lake (14,000 km2) underlies the Russian station of Vostok in Antarctica by 3.750 m of ice. Due to a particular setting of the glacier flow and the subglacial relief, the glacier-lake interface is inclined making a slope of 600 m over the 250 km of the lake length. This leads the deep glacier ice to melt and the high level of lake water (under Vostok area) to freeze. A 3623 m deep ice coring was performed at Vostok station for paleoclimate study, and was stopped 130 m above the lake interface. The last 85 m of the ice core was formed by refreezing from the water, and the ice samples represent good template of the lake for biological and chemical content. We performed bacterial 16S ribosomal gene analysis on several lake ice samples. Only one phylotype from 16 initially detected, was kept with confident relevance to the lake environment. On the other hand, the 15 other were presumed to be contamination on the basis of indexing contaminant criteria developed for the thorough ice samples processing. The retained phylotype represents the extant thermophilic bacterium Hydrogenophilus thermoluteolus (beta-Proteobacteria) that is encountered until now in only hot springs, and is potentially capable to grow as a chemolithoautotroph. Hot springs in the subglacial bedrock around Vostok are counterintuitive. On the other hand, assuming the lake is in steady state, a hydrothermal contribution is suggested by the stable isotope composition of the lake ice. Using the Deuterium and 18O content, an 18O enrichment of the lake ice (output) is observed with respect to composition of the melting ice (input). This effect (so-called 18O shift) characterize geothermal areas and may result from the 18O exchanges at hot temperature between water and silicates. The Vostok subglacial lake is an extreme environment and appear mostly germ free. On the other hand, we suggest some niches inside some bedrock faults of a hydrothermal system. We invoke scarce flushing events

  11. Preliminary observations of voluminous ice-rich and water-rich lahars generated during the 2009 eruption of Redoubt, Alaska

    USGS Publications Warehouse

    Waythomas, Christopher F.; Pierson, Thomas C.; Major, Jon J.; Scott, William E.

    2012-01-01

    Redoubt Volcano in south-central Alaska began erupting on March 15, 2009, and by April 4, 2009, had produced at least 20 explosive events that generated plumes of ash and lahars. The 3,108-m high, snow- and -ice-clad stratovolcano has an ice-filled summit crater that is breached to the north. The volcano supports about 4 km3 of ice and snow and about 1 km3 of this makes up the Drift glacier on the northern side of the volcano. Explosive eruptions between March 22 and April 4, which included the destruction of at least two lava domes, triggered significant lahars in the Drift River valley on March 23 and April 4 and several smaller lahars between March 24 and March 31. High-flow marks, character of deposits, areas of inundation, and estimates of flow velocity revealed that the lahars on March 23 and April 4 were the largest of the eruption. In the 2-km-wide upper Drift River valley, average flow depths were about 3–5 m. Average peak-flow velocities were likely between 10 and 15 ms-1, and peak discharges were on the order of 104–105 m3s-1. The area inundated by lahars on March 23 was at least 100 km2 and on April 4 about 125 km2. The lahars emplaced on March 23 and April 4 had volumes on the order of 107–108 m3 and were similar in size to the largest lahar of the 1989–90 eruption. The March 23 lahars were primarily flowing slurries of snow and ice entrained from the Drift glacier and seasonal snow and tabular blocks of river ice from the Drift River valley. Only a single, undifferentiated deposit up to 5 m thick was found and contained about 80–95 percent of poorly sorted, massive to imbricate assemblages of snow and ice. The deposit was frozen soon after it was emplaced and later eroded and buried by the April 4 lahar. The lahar of April 4, in contrast, was primarily a hyperconcentrated flow, as interpreted from 1- to 6-m thick deposits of massive to horizontally stratified sand-to-fine-gravel. Rock material in the April 4 lahar deposit is predominantly

  12. Comparison of the Microbial Diversity and Abundance Between the Freshwater Land-Locked Lakes of Schirmacher Oasis and the Perennially Ice-Covered Lake Untersee in East Antarctica

    NASA Technical Reports Server (NTRS)

    Huang, Jonathan; Hoover, Richard B.; Swain, Ashit; Murdock, Chris; Bej, Asim K.

    2010-01-01

    Extreme conditions such as low temperature, dryness, and constant UV-radiation in terrestrial Antarctica are limiting factors of the survival of microbial populations. The objective of this study was to investigate the microbial diversity and enumeration between the open water lakes of Schirmacher Oasis and the permanently ice-covered Lake Untersee. The lakes in Schirmacher Oasis possessed abundant and diverse group of microorganisms compared to the Lake Untersee. Furthermore, the microbial diversity between two lakes in Schirmacher Oasis (Lake L27C and L47) was compared by culture-based molecular approach. It was determined that L27Chad a richer microbial diversity representing 5 different phyla and 7 different genera. In contrast L47 consisted of 4 different phyla and 6 different genera. The difference in microbial community could be due to the wide range of pH between L27C (pH 9.1) and L47 (pH 5.7). Most of the microbes isolated from these lakes consisted of adaptive biological pigmentation. Characterization of the microbial community found in the freshwater lakes of East Antarctica is important because it gives a further glimpse into the adaptation and survival strategies found in extreme conditions.

  13. Spatial Analysis of Great Lakes Regional Icing Cloud Liquid Water Content

    NASA Technical Reports Server (NTRS)

    Ryerson, Charles C.; Koenig, George G.; Melloh, Rae A.; Meese, Debra A.; Reehorst, Andrew L.; Miller, Dean R.

    2003-01-01

    Abstract Clustering of cloud microphysical conditions, such as liquid water content (LWC) and drop size, can affect the rate and shape of ice accretion and the airworthiness of aircraft. Clustering may also degrade the accuracy of cloud LWC measurements from radars and microwave radiometers being developed by the government for remotely mapping icing conditions ahead of aircraft in flight. This paper evaluates spatial clustering of LWC in icing clouds using measurements collected during NASA research flights in the Great Lakes region. We used graphical and analytical approaches to describe clustering. The analytical approach involves determining the average size of clusters and computing a clustering intensity parameter. We analyzed flight data composed of 1-s-frequency LWC measurements for 12 periods ranging from 17.4 minutes (73 km) to 45.3 minutes (190 km) in duration. Graphically some flight segments showed evidence of consistency with regard to clustering patterns. Cluster intensity varied from 0.06, indicating little clustering, to a high of 2.42. Cluster lengths ranged from 0.1 minutes (0.6 km) to 4.1 minutes (17.3 km). Additional analyses will allow us to determine if clustering climatologies can be developed to characterize cluster conditions by region, time period, or weather condition. Introduction

  14. Deformation of the Batestown till of the Lake Michigan lobe, Laurentide ice sheet

    USGS Publications Warehouse

    Thomason, J.F.; Iverson, N.R.

    2009-01-01

    Deep, pervasive shear deformation of the bed to high strains (>100) may have been primarily responsible for flow and sediment transport of the Lake Michigan lobe of the Laurentide ice sheet. To test this hypothesis, we sampled at 0.2 m increments a basal till from one advance of the lobe (Batestown till) along vertical profiles and measured fabrics due to both anisotropy of magnetic susceptibility and sand-grain preferred orientation. Unlike past fabric studies, interpretations were guided by results of laboratory experiments in which this till was deformed in simple shear to high strains. Fabric strengths indicate that more than half of the till sampled has a <5% probability of having been sheared to moderate strains (7-30). Secular changes in fabric azimuth over the thickness of the till, probably due to changing ice-flow direction as the lobe receded, indicate that the bed accreted with time and that the depth of deformation of the bed did not exceed a few decimeters. Orientations of principal magnetic susceptibilities show that the state of strain was commonly complex, deviating from bed-parallel simple shear. Deformation is inferred to have been focused in shallow, temporally variable patches during till deposition from ice.

  15. 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.

  16. In situ and satellite-derived ablation season temperature and surface characteristics of clean and debris-covered ice at Matanuska glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Casey, K.

    2012-12-01

    Outside of the ice sheets and the Himalayas, Alaska contains one of the largest masses of ice on Earth. The rapid loss of ice in Alaska in recent decades is the subject of intense investigation (Berthier et al., 2010). An under quantified factor in the understanding of ice mass loss is the role in which different surface glacier dust and debris types and thicknesses play on the ablation process. Ground-based measurements of surface temperature of several glacier debris types were collected in July 2012 at Matanuska glacier in Alaska. Wet, dry, moderately covered and cleaner ice sites were observed over a two week period. Temperatures were recorded every 20 minutes. Significant diurnal and debris type temperature variability were observed. Satellite-based shortwave and thermal infrared analysis of debris covered ice is used to estimate surface debris mineralogy. Thermal satellite data is further used to derive entire glacier surface temperatures. Terminal glacier in situ temperature observations are compared with satellite derived surface temperatures. In situ measurements are also evaluated with respect to Foster et al. (2012) physically based method for estimating surface glacier debris thickness. E. Berthier, E. Schiefer, G.K.C. Clarke, B. Menounos, F. Rémy, 2010, Contribution of Alaskan glaciers to sea-level rise derived from satellite imagery, Nature Geoscience, 3, 92-95. L.A. Foster, B.W. Brock, M.E.J. Cutler, F. Diotri, 2012, Instruments and Methods: A physically based method for estimating supraglacial debris thickness from thermal band remote-sensing data, Journal of Glaciology, 58, 210, 677-691.

  17. Selective occurrence of Rhizobiales in frost flowers on the surface of young sea ice near Barrow, Alaska and distribution in the polar marine rare biosphere.

    PubMed

    Bowman, J S; Larose, C; Vogel, T M; Deming, J W

    2013-08-01

    Frost flowers are highly saline ice structures that grow on the surface of young sea ice, a spatially extensive environment of increasing importance in the Arctic Ocean. In a previous study, we reported organic components of frost flowers in the form of elevated levels of bacteria and exopolymers relative to underlying ice. Here, DNA was extracted from frost flowers and young sea ice, collected in springtime from a frozen lead offshore of Barrow, Alaska, to identify bacteria in these understudied environments. Evaluation of the distribution of 16S rRNA genes via four methods (microarray analysis, T-RFLP, clone library and shotgun metagenomic sequencing) indicated distinctive bacterial assemblages between the two environments, with frost flowers appearing to select for Rhizobiales. A phylogenetic placement approach, used to evaluate the distribution of similar Rhizobiales sequences in other polar marine studies, indicated that some of the observed strains represent widely distributed members of the marine rare biosphere in both the Arctic and Antarctic.

  18. Remote profiling of lake ice using an S-band short pulse radar aboard an all-terrain vehicle

    NASA Technical Reports Server (NTRS)

    Cooper, D. W.; Mueller, R. A.; Schertler, R. J.

    1975-01-01

    An airborne short-pulse radar system to measure ice thickness was designed. The system supported an effort to develop an all-weather Great Lakes Ice Information System to aid in extending the winter navigation season. Experimental studies into the accuracy and limitations of the system are described. A low power version was operated from an all-terrain vehicle on the Straits of Mackinac during March 1975. The vehicle allowed rapid surveying of large areas and eliminated the ambiguity in location between the radar system and the ground truth ice auger team. It was also possible to the effects of snow cover, surface melt water, pressure ridging, and ice type upon the accuracy of the system. Over 25 sites were explored which had ice thicknesses from 29 to 60 cm. The maximum radar overestimate was 9.8 percent, while the maximum underestimate was 6.6 percent. The average error of the 25 measurements was 0.1 percent.

  19. Limnological and water-quality data from Wonder Lake, Chilchukabena Lake, and Lake Minchumina, Denali National Park and Preserve and surrounding area, Alaska, June 2006-August 2008

    USGS Publications Warehouse

    Long, D.A.; Arp, C.D.

    2011-01-01

    Growing visitor traffic and resource use, as well as natural and anthropogenic land and climatic changes, can place increasing stress on lake ecosystems in Denali National Park and Preserve. Baseline data required to substantiate impact assessment in this sub-arctic region is sparse to non-existent. The U.S. Geological Survey, in cooperation with the National Park Service, conducted a water-quality assessment of several large lakes in and around the Park from June 2006 to August 2008. Discrete water-quality samples, lake profiles of pH, specific conductivity, dissolved-oxygen concentration, water temperature, turbidity, and continuous-record temperature profile data were collected from Wonder Lake, Chilchukabena Lake, and Lake Minchumina. In addition, zooplankton, snow chemistry data, fecal coliform, and inflow/outflow water-quality samples also were collected from Wonder Lake.

  20. Ecological relationship between freshwater sculpins (Genus cottus) and beach-spawning sockeye salmon (Oncorhynchus nerka) in Iliamna Lake, Alaska

    USGS Publications Warehouse

    Foote, C.J.; Brown, G.S.

    1998-01-01

    The interaction between two sculpin species, Cottus cognatus and Cottus aleuticus, and island beach spawning sockeye salmon (Oncorhynchus nerka) was examined in Iliamna Lake, Alaska. We conclude that sculpins actively move to specific spawning beaches and that the initiation of their movements precedes the start of spawning. Sculpin predation on sockeye eggs is positively dependent on sculpin size and on the state of the eggs (fresh versus water hardened), with the largest sculpins able to consume nearly 50 fresh eggs at a single feeding and 130 over a 7-day period. The number of sculpins in sockeye nests is greatest at the beginning of the spawning run, lowest in the middle, and high again at the end, with peak numbers of over 100 sculpins per nest (1 m2). We discuss the results in terms of energy flow of marine-derived nutrients into an oligotrophic system and in terms of the coevolution of sockeye spawning behavior and the predatory behavior of sculpins.

  1. Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake.

    PubMed

    Jungblut, Anne D; Hawes, Ian; Mackey, Tyler J; Krusor, Megan; Doran, Peter T; Sumner, Dawn Y; Eisen, Jonathan A; Hillman, Colin; Goroncy, Alexander K

    2016-01-01

    Lake Fryxell is a perennially ice-covered lake in the McMurdo Dry Valleys, Antarctica, with a sharp oxycline in a water column that is density stabilized by a gradient in salt concentration. Dissolved oxygen falls from 20 mg liter(-1) to undetectable over one vertical meter from 8.9- to 9.9-m depth. We provide the first description of the benthic mat community that falls within this oxygen gradient on the sloping floor of the lake, using a combination of micro- and macroscopic morphological descriptions, pigment analysis, and 16S rRNA gene bacterial community analysis. Our work focused on three macroscopic mat morphologies that were associated with different parts of the oxygen gradient: (i) "cuspate pinnacles" in the upper hyperoxic zone, which displayed complex topography and were dominated by phycoerythrin-rich cyanobacteria attributable to the genus Leptolyngbya and a diverse but sparse assemblage of pennate diatoms; (ii) a less topographically complex "ridge-pit" mat located immediately above the oxic-anoxic transition containing Leptolyngbya and an increasing abundance of diatoms; and (iii) flat prostrate mats in the upper anoxic zone, dominated by a green cyanobacterium phylogenetically identified as Phormidium pseudopriestleyi and a single diatom, Diadesmis contenta. Zonation of bacteria was by lake depth and by depth into individual mats. Deeper mats had higher abundances of bacteriochlorophylls and anoxygenic phototrophs, including Chlorobi and Chloroflexi. This suggests that microbial communities form assemblages specific to niche-like locations. Mat morphologies, underpinned by cyanobacterial and diatom composition, are the result of local habitat conditions likely defined by irradiance and oxygen and sulfide concentrations. PMID:26567300

  2. Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake.

    PubMed

    Jungblut, Anne D; Hawes, Ian; Mackey, Tyler J; Krusor, Megan; Doran, Peter T; Sumner, Dawn Y; Eisen, Jonathan A; Hillman, Colin; Goroncy, Alexander K

    2015-11-13

    Lake Fryxell is a perennially ice-covered lake in the McMurdo Dry Valleys, Antarctica, with a sharp oxycline in a water column that is density stabilized by a gradient in salt concentration. Dissolved oxygen falls from 20 mg liter(-1) to undetectable over one vertical meter from 8.9- to 9.9-m depth. We provide the first description of the benthic mat community that falls within this oxygen gradient on the sloping floor of the lake, using a combination of micro- and macroscopic morphological descriptions, pigment analysis, and 16S rRNA gene bacterial community analysis. Our work focused on three macroscopic mat morphologies that were associated with different parts of the oxygen gradient: (i) "cuspate pinnacles" in the upper hyperoxic zone, which displayed complex topography and were dominated by phycoerythrin-rich cyanobacteria attributable to the genus Leptolyngbya and a diverse but sparse assemblage of pennate diatoms; (ii) a less topographically complex "ridge-pit" mat located immediately above the oxic-anoxic transition containing Leptolyngbya and an increasing abundance of diatoms; and (iii) flat prostrate mats in the upper anoxic zone, dominated by a green cyanobacterium phylogenetically identified as Phormidium pseudopriestleyi and a single diatom, Diadesmis contenta. Zonation of bacteria was by lake depth and by depth into individual mats. Deeper mats had higher abundances of bacteriochlorophylls and anoxygenic phototrophs, including Chlorobi and Chloroflexi. This suggests that microbial communities form assemblages specific to niche-like locations. Mat morphologies, underpinned by cyanobacterial and diatom composition, are the result of local habitat conditions likely defined by irradiance and oxygen and sulfide concentrations.

  3. Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake

    PubMed Central

    Hawes, Ian; Mackey, Tyler J.; Krusor, Megan; Doran, Peter T.; Sumner, Dawn Y.; Eisen, Jonathan A.; Hillman, Colin; Goroncy, Alexander K.

    2015-01-01

    Lake Fryxell is a perennially ice-covered lake in the McMurdo Dry Valleys, Antarctica, with a sharp oxycline in a water column that is density stabilized by a gradient in salt concentration. Dissolved oxygen falls from 20 mg liter−1 to undetectable over one vertical meter from 8.9- to 9.9-m depth. We provide the first description of the benthic mat community that falls within this oxygen gradient on the sloping floor of the lake, using a combination of micro- and macroscopic morphological descriptions, pigment analysis, and 16S rRNA gene bacterial community analysis. Our work focused on three macroscopic mat morphologies that were associated with different parts of the oxygen gradient: (i) “cuspate pinnacles” in the upper hyperoxic zone, which displayed complex topography and were dominated by phycoerythrin-rich cyanobacteria attributable to the genus Leptolyngbya and a diverse but sparse assemblage of pennate diatoms; (ii) a less topographically complex “ridge-pit” mat located immediately above the oxic-anoxic transition containing Leptolyngbya and an increasing abundance of diatoms; and (iii) flat prostrate mats in the upper anoxic zone, dominated by a green cyanobacterium phylogenetically identified as Phormidium pseudopriestleyi and a single diatom, Diadesmis contenta. Zonation of bacteria was by lake depth and by depth into individual mats. Deeper mats had higher abundances of bacteriochlorophylls and anoxygenic phototrophs, including Chlorobi and Chloroflexi. This suggests that microbial communities form assemblages specific to niche-like locations. Mat morphologies, underpinned by cyanobacterial and diatom composition, are the result of local habitat conditions likely defined by irradiance and oxygen and sulfide concentrations. PMID:26567300

  4. Massive regime shifts and high activity of heterotrophic bacteria in an ice-covered lake.

    PubMed

    Bižić-Ionescu, Mina; Amann, Rudolf; Grossart, Hans-Peter

    2014-01-01

    In winter 2009/10, a sudden under-ice bloom of heterotrophic bacteria occurred in the seasonally ice-covered, temperate, deep, oligotrophic Lake Stechlin (Germany). Extraordinarily high bacterial abundance and biomass were fueled by the breakdown of a massive bloom of Aphanizomenon flos-aquae after ice formation. A reduction in light resulting from snow coverage exerted a pronounced physiological stress on the cyanobacteria. Consequently, these were rapidly colonized, leading to a sudden proliferation of attached and subsequently of free-living heterotrophic bacteria. Total bacterial protein production reached 201 µg C L(-1) d(-1), ca. five times higher than spring-peak values that year. Fluorescence in situ hybridization and denaturing gradient gel electrophoresis at high temporal resolution showed pronounced changes in bacterial community structure coinciding with changes in the physiology of the cyanobacteria. Pyrosequencing of 16S rRNA genes revealed that during breakdown of the cyanobacterial population, the diversity of attached and free-living bacterial communities were reduced to a few dominant families. Some of these were not detectable during the early stages of the cyanobacterial bloom indicating that only specific, well adapted bacterial communities can colonize senescent cyanobacteria. Our study suggests that in winter, unlike commonly postulated, carbon rather than temperature is the limiting factor for bacterial growth. Frequent phytoplankton blooms in ice-covered systems highlight the need for year-round studies of aquatic ecosystems including the winter season to correctly understand element and energy cycling through aquatic food webs, particularly the microbial loop. On a global scale, such knowledge is required to determine climate change induced alterations in carbon budgets in polar and temperate aquatic systems.

  5. Erosion and accretion along the arctic coast of Alaska. The influence of ice and climate

    USGS Publications Warehouse

    Barnes, Peter W.; Rollyson, Bonnie P.

    1991-01-01

    Coastline comparison on 1951 and 1981 charts to determine erosion and accretion showed that ocean-facing coastal bluffs were retreating while deltas were rapidly expanding. Where the coast is fronted by a lagoon, and coast-parallel sand and gravel islands, bluff retreat was reduced. The extensive bluff erosion was volumetrically balanced by accretion at the mouths of deltas. Coastal erosion is driven by ice-related processes, aided by the presence of an ice-eroded shelf. Rapid delta expansion is interpreted to have begun in the last 200 years, perhaps related to observed permafrost warming.

  6. Twentieth century thinning of Mendenhall Glacier, Alaska, and its relationship to climate, lake calving, and glacier run-off

    NASA Astrophysics Data System (ADS)

    Motyka, Roman J.; O'Neel, Shad; Connor, Cathy L.; Echelmeyer, Keith A.

    2003-01-01

    Mendenhall Glacier is a dynamic maritime glacier in southeast Alaska that is undergoing substantial recession and thinning. The terminus has retreated 3 km during the 20th century and the lower part of the glacier has thinned 200 m or more since 1909. Glacier-wide volume loss between 1948 and 2000 is estimated at 5.5 km 3. Wastage has been the strongest in the glacier's lower reaches, but the glacier has also thinned at higher elevations. The shrinkage of Mendenhall Glacier appears to be due primarily to surface melting and secondarily to lake calving. The change in the average rate of thinning on the lower glacier, <1 m a -1 between 1948 and 1982 and >2 m a -1 since 1982, agrees qualitatively with observed warming trends in the region. Mean annual temperatures in Juneau decreased slightly from 1947 to 1976; they then began to increase, leading to an overall warming of ˜1.6 °C since 1943. Lake calving losses have periodically been a small but significant fraction of glacier ablation. The portion of the terminus that ends in the lake is becoming increasingly vulnerable to calving because of a deep pro-glacial lake basin. If current climatic trends persist, the glacier will continue to shrink and the terminus will recede onto land at a position about 500 m inland within one to two decades. The glacier and the meltwaters that flow from it are integral components of the Mendenhall Valley hydrologic system. Approximately 13% of the recent average annual discharge of the Mendenhall River is attributable to glacier shrinkage. Glacier melt contributes 50% of the total river discharge in summer.

  7. Effects of glacial meltwater inflows and moat freezing on mixing in an ice-covered antarctic lake as interpreted from stable isotope and tritium distributions

    USGS Publications Warehouse

    Miller, L.G.; Aiken, G.R.

    1996-01-01

    Perennially ice-covered lakes in the McMurdo Dry Valleys have risen several meters over the past two decades due to climatic warming and increased glacial meltwater inflow. To elucidate the hydrologic responses to changing climate and the effects on lake mixing processes we measured the stable isotope (??18O and ??D) and tritium concentrations of water and ice samples collected in the Lake Fryxell watershed from 1987 through 1990. Stable isotope enrichment resulted from evaporation in stream and moat samples and from sublimation in surface lake-ice samples. Tritium enrichment resulted from exchange with the postnuclear atmosphere in stream and moat samples. Rapid injection of tritiated water into the upper water column of the make and incorporation of this water into the ice cover resulted in uniformly elevated tritium contents (> 3.0 TU) in these reservoirs. Tritium was also present in deep water, suggesting that a component of bottom water was recently at the surface. During summer, melted lake ice and stream water forms the moat. Water excluded from ice formation during fall moat freezing (enriched in solutes and tritium, and depleted in 18O and 2H relative to water below 15-m depth) may sink as density currents to the bottom of the lake. Seasonal lake circulation, in response to climate-driven surface inflow, is therefore responsible for the distribution of both water isotopes and dissolved solutes in Lake Fryxell.

  8. Diatoms in sediments of perennially ice-covered Lake Hoare, and implications for interpreting lake history in the McMurdo Dry Valleys of Antarctica

    USGS Publications Warehouse

    Spaulding, S.A.; McKnight, Diane M.; Stoermer, E.F.; Doran, P.T.

    1997-01-01

    Diatom assemblages in surficial sediments, sediment cores, sediment traps, and inflowing streams of perennially ice-covered Lake Hore, South Victorialand, Antarctica were examined to determine the distribution of diatom taxa, and to ascertain if diatom species composition has changed over time. Lake Hoare is a closed-basin lake with an area of 1.8 km2, maximum depth of 34 m, and mean depth of 14 m, although lake level has been rising at a rate of 0.09 m yr-1 in recent decades. The lake has an unusual regime of sediment deposition: coarse grained sediments accumulate on the ice surface and are deposited episodically on the lake bottom. Benthic microbial mats are covered in situ by the coarse episodic deposits, and the new surfaces are recolonized. Ice cover prevents wind-induced mixing, creating the unique depositional environment in which sediment cores record the history of a particular site, rather than a lake=wide integration. Shallow-water (<1 m) diatom assemblages (Stauroneis anceps, Navicula molesta, Diadesmis contenta var. parallela, Navicula peraustralis) were distinct from mid-depth (4-16 m) assemblages (Diadesmis contenta, Luticola muticopsis fo. reducta, Stauroneis anceps, Diadesmis contenta var. parallela, Luticola murrayi) and deep-water (2-31 m) assemblages (Luticola murrayi, Luticola muticopsis fo. reducta, Navicula molesta. Analysis of a sediment core (30 cm long, from 11 m water depth) from Lake Hoare revealed two abrupt changes in diatom assemblages. The upper section of the sediment core contained the greatest biomass of benthic microbial mat, as well as the greatest total abundance and diversity of diatoms. Relative abundances of diatoms in this section are similar to the surficial samples from mid-depths. An intermediate zone contained less organic material and lower densities of diatoms. The bottom section of core contained the least amount of microbial mat and organic material, and the lowest density of diatoms. The dominant process

  9. Direct Observations of Melt-Water Lake Drainage and the Establishment of an Efficient Surface to Basal Water Connection on the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Das, S. B.; Joughin, I.; Behn, M. D.; Howat, I.; King, M. A.; Lizarralde, D.; Bhatia, M. P.

    2007-12-01

    Melt water lakes are recurrent features on the surface of the Greenland Ice Sheet margin that collect a large fraction of the annual surface melt across the ablation region. Many of these lakes fill and drain seasonally and are hypothesized to be a significant source of surface melt water to the ice sheet bed. We present results from field campaigns during the summers of 2006 and 2007 to investigate the filling and draining of two lakes, and the dynamic response of the ice sheet to drainage events. Measurements include air temperature, lake-water level, seismicity and local ice motion. One of the instrumented lakes was observed to be actively discharging water through a meltwater-cut channel in the side of the lake basin, which followed a deeply incised (5-10 m) supraglacial stream for nearly a kilometer before cascading into a moulin. The second instrumented lake drained catastrophically through a series of fractures and moulins that opened beneath the lake and that were subsequently mapped in the field following drainage. At this site, the 2.7-km-diameter lake, holding on the order of 0.03 km3 of water, drained entirely through 1 km of ice thickness in less than 2 hours. The peak rate of water flow during this event exceeds the average flow over Niagara Falls. This drainage event coincided with increased seismicity as well as rapid glacier uplift (1.2 m) and horizontal acceleration to nearly 8 km/yr as measured on the ice surface near the lake shoreline. Subsequent subsidence and deceleration of the ice sheet occurred over the following 24 hours. These observations provide evidence for the injection of surface melt water directly to the ice sheet bed, and also indicate the presence of an efficient basal drainage system that can quickly disperse large inputs of surface melt water.

  10. 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

  11. Over-wintering of Supraglacial Lakes on the Greenland Ice Sheet from Sentinel-1 and Landsat-8 Data

    NASA Astrophysics Data System (ADS)

    Benedek, C. L.; Tedesco, M.

    2015-12-01

    Supra-glacial lakes on the GrIS have become a focus of research relating to the contribution of the GrIS to sea level rise. Lakes have been observed to appear during the summer melt season. Though it appears that the quantity of water collected on the surface is small, it is thought that the fracture and drainage of these lakes delivers significant pulses of water to the ice sheet bed, influencing the dynamic movement of glaciers towards the sea. The pattern of this transport mechanism may be a central driver of its influence over dynamic losses, as the flow of the viscoelastic ice sheet will differ if the water is delivered in a short pulse or a slower constant supply. A number of studies have catalogued the traits of lakes with an aim to quantify lake areas, depths, and timing of formation and cessation using visible and near infrared remote sensing instruments mostly focused on the summer melt season. Little is known about the behaviour of the surface lakes over the winter. A recent examination of the over-wintering of surface lakes has been conducted by Koenig et al. [2015] using airborne radar. While the study is extensive in area covered, it is limited in its temporal resolution by the availability of Operation IceBridge data, typically at one pass per year. This study seeks to observe the development of lakes over the winter period. Sentinel-1A radar images are used to track the presence of surface lakes and their variation in three study sites on the Greenland ice sheet. The sites are as follows: upstream of Ryder glacier, upstream of Petermann glacier, and upstream of Jakobshavn glacier. Water masks are created based on summer Landsat-8 images following NDWIice and then compared to Sentinel images at monthly temporal resolution through the winter of 2014-2015. These radar images show persistence of liquid water through the winter in agreement with previous research as well as variation in the buried lake area over the span of the year studied.

  12. Lake carbonate-δ18 records from the Yukon Territory, Canada: Little Ice Age moisture variability and patterns

    USGS Publications Warehouse

    Anderson, Lesleigh; Finney, Bruce P.; Shapley, Mark D.

    2011-01-01

    A 1000-yr history of climate change in the central Yukon Territory, Canada, is inferred from sediment composition and isotope geochemistry from small, groundwater fed, Seven Mile Lake. Recent observations of lake-water δ18O, lake level, river discharge, and climate variations, suggest that changes in regional effective moisture (precipitation minus evaporation) are reflected by the lake’s hydrologic balance. The observations indicate that the lake is currently 18O-enriched by summer evaporation and that during years of increased precipitation, when groundwater inflow rates to the lake increase, lake-water δ18O values decrease. Past lake-water δ18O values are inferred from oxygen isotope ratios of fine-grained sedimentary endogenic carbonate. Variations in carbonate δ18O, supplemented by those in carbonate and organic δ13C, C/N ratios, and organic carbon, carbonate and biogenic silica accumulation rates, document changes in effective moisture at decada