Filters: Tags: thermokarst (X)
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Intensification of permafrost thaw has increased the frequency and magnitude of large permafrost slope disturbances (mega slumps) in glaciogenic terrain of northwestern Canada. Individual thermokarst disturbances up to 40 ha in area have made large volumes of previously frozen, highly weatherable fine-grained sediments available for leaching and transport to adjacent streams, significantly increasing sediment and solute loads in these systems. To test the effects of this climate-sensitive disturbance regime on the ecology of Arctic streams, we explored the relationship between physical and chemical variables and benthic macroinvertebrate communities in disturbed and undisturbed stream reaches in the Peel Plateau...
Categories: Publication;
Types: Citation;
Tags: Arctic streams,
benthic macroinvertebrate,
permafrost degradation,
sedimentation,
thaw slump,
We examined the effects of fire disturbance on permafrost degradation and thaw settlement across a series of wildfires (from ~1930 to 2010) in the forested areas of collapse-scar bog complexes in the Tanana Flats lowland of interior Alaska. Field measurements were combined with numerical modeling of soil thermal dynamics to assess the roles of fire severity and climate history in postfire permafrost dynamics. Field-based calculations of potential thaw settlement following the loss of remaining ice-rich permafrost averaged 0.6 m. This subsidence would cause the surface elevations of forests to drop on average 0.1 m below the surface water level of adjacent collapse-scar features. Up to 0.5 m of thaw settlement was...
Categories: Publication;
Types: Citation;
Tags: 0439 Ecosystems: structure and dynamics,
0475 Permafrost,
0702 Permafrost,
0708 Thermokarst,
and high-latitude processes,
This dataset supports a published study on the effects of permafrost thaw on greenhouse gas fluxes and microbial activities at the Alaska Peatland Experiment (APEX), part of the Bonanza Creek LTER, in interior Alaska. The dataset includes autochamber CO2 and CH4 fluxes, net ecosystem exchange, ecosystem respiration, soil temperatures, climate data, microbial qPCR data, soil physical chemistry, soil extract chemistry, and rates of microbial activities, both from lab incubations, and rates derived from an isotope based process model.
Categories: Data;
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: Alaska,
Bonanza Creek Experimental Forest,
USGS Science Data Catalog (SDC),
alaska,
biota,
The current state of permafrost in Alaska and meaningful expectations for its future evolution are informed by long-term perspectives on previous permafrost degradation. Thermokarst processes in permafrost landscapes often lead to widespread lake formation and the spatial and temporal evolution of thermokarst lake landscapes reflects the combined effects of climate, ground conditions, vegetation, and fire. This study provides detailed analyses of thermokarst lake sediments of Holocene age from the southern loess uplands of the Yukon Flats; including bathymetry and sediment core analyses across a water depth transect. The sediment core results, dated by radiocarbon and 210Pb, indicate the onset of finely laminated...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1111/gcb.12757/abstract): The landscape of the Barrow Peninsula in northern Alaska is thought to have formed over centuries to millennia, and is now dominated by ice-wedge polygonal tundra that spans drained thaw-lake basins and interstitial tundra. In nearby tundra regions, studies have identified a rapid increase in thermokarst formation (i.e., pits) over recent decades in response to climate warming, facilitating changes in polygonal tundra geomorphology. We assessed the future impact of 100 years of tundra geomorphic change on peak growing season carbon exchange in response to: (i) landscape succession associated with the thaw-lake cycle; and (ii) low, moderate,...
Categories: Publication;
Types: Citation;
Tags: Alaska CASC,
Data Visualization & Tools,
Science Tools for Managers,
arctic,
carbon balance,
We examined the effects of fire disturbance on permafrost degradation and thaw settlement across a series of wildfires (from ~1930 to 2010) in the forested areas of collapse-scar bog complexes in the Tanana Flats lowland of interior Alaska. Field measurements were combined with numerical modeling of soil thermal dynamics to assess the roles of fire severity and climate history in postfire permafrost dynamics. Field-based calculations of potential thaw settlement following the loss of remaining ice-rich permafrost averaged 0.6 m. This subsidence would cause the surface elevations of forests to drop on average 0.1 m below the surface water level of adjacent collapse-scar features. Up to 0.5 m of thaw settlement was...
Categories: Publication;
Types: Citation;
Tags: 0439 Ecosystems: structure and dynamics,
0475 Permafrost,
0702 Permafrost,
0708 Thermokarst,
and high-latitude processes,
This 1:50,000 scale geologic map describes the distribution of unconsolidated deposits, identifies local geologic hazards, and provides information about the depositional environment and basic engineering properties of common surficial-geologic materials in and around Shaktoolik, Alaska. Map units are the result of combined field observations and aerial imagery interpretation. A suite of local ground observations were collected over a two-week period in July 2011 by a helicopter-supported team of DGGS geologists and collaborators. Field investigations included soil test pits, sample collection, soil and rock description, oblique aerial photography, and documentation of landscape morphology.
This map shows the distribution of unconsolidated deposits and undifferentiated bedrock exposed at the surface in the Sagavanirktok A-3, A-4, B-3, B-4, and portions of the Sagavanirktok A-5 and B-5 quadrangles. Units were mapped by interpretation of stereo pairs of approximately 1:65,000-scale false-color infrared aerial photographs taken in June and August 1978, as well as 2.5 m and 10 m resolution SPOT imagery collected in 2009 and 2010. Fieldwork was completed in 2008.
This report describes the progress made by the Integrated Ecosystem Model (IEM) for Alaska and Northwest Canada Project for the full duration of the project (September 1, 2011 through August 31, 2016).This primary goal in this project was to develop the IEM modeling framework to integrate the driving components for and the interactions among disturbance regimes, permafrost dynamics, hydrology, and vegetation succession/migration for Alaska and Northwest Canada. The major activities of the project include (1) development and delivery of input data sets, (2) model coupling, (3) evaluation and applications of fire and vegetation dynamics, (4) evaluation and application of ecosystem carbon and energy balance, (5) evaluation...
Categories: Publication;
Types: Citation;
Tags: Alaska,
Alaska CASC,
Biogeochemistry,
Carbon Dioxide,
Climate Change,
This map shows the distribution of surficial deposits and undifferentiated bedrock in parts of the Livengood C-3 and C-4 quadrangles, Tolovana mining district.
Abstract (from http://onlinelibrary.wiley.com/doi/10.1002/2014JG002683/abstract): Changes in vegetation and soil properties following permafrost degradation and thermokarst development in peatlands may cause changes in net carbon storage. To better understand these dynamics, we established three sites in Alaska that vary in permafrost regime, including a black spruce peat plateau forest with stable permafrost, an internal collapse scar bog formed as a result of thermokarst, and a rich fen without permafrost. Measurements include year-round eddy covariance estimates of carbon dioxide (CO2 ), water, and energy fluxes, associated environmental variables, and methane (CH4 ) fluxes at the collapse scar bog. The ecosystems...
Categories: Publication;
Types: Citation;
Tags: Alaska CASC,
Alaska CASC,
Glaciers and Permafrost,
Water, Coasts and Ice,
black spruce,
During recent decades, lake levels in the Yukon Flats region of interior Alaska have fluctuated dramatically. However, prior to recorded observations, no data are available to indicate if similar or more extreme variations occurred during past centuries and millennia. This study explores the history of Yukon Flats lake origins and lake levels for the past approximately 5,500 years from sediment analyses guided by previous work on permafrost extent, thermokarst, and modern isotope hydrology. Sediments dated by 210Pb and AMS radiocarbon indicate stable chronologies following initial lake initiation. Subsequent lithology is autochthonous, and oxygen isotope ratios of endogenic carbonate reflect lake level change at...
Categories: Data;
Tags: Alaska,
Holocene,
Land Use Change,
USGS Science Data Catalog (SDC),
Yukon Flats,
Intensification of permafrost thaw has increased the frequency and magnitude of large permafrost slope disturbances (mega slumps) in glaciogenic terrain of northwestern Canada. Individual thermokarst disturbances up to 40 ha in area have made large volumes of previously frozen, highly weatherable fine-grained sediments available for leaching and transport to adjacent streams, significantly increasing sediment and solute loads in these systems. To test the effects of this climate-sensitive disturbance regime on the ecology of Arctic streams, we explored the relationship between physical and chemical variables and benthic macroinvertebrate communities in disturbed and undisturbed stream reaches in the Peel Plateau...
Categories: Publication;
Types: Citation;
Tags: Arctic streams,
benthic macroinvertebrate,
permafrost degradation,
sedimentation,
thaw slump,
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