A5035122464- Climate change and permafrost
- Soil and Water Nutrient Dynamics
- Hydrology and Watershed Management Studies
- Cryospheric studies and observations
- Fish Ecology and Management Studies
- Peatlands and Wetlands Ecology
- Marine and coastal ecosystems
- Arctic and Antarctic ice dynamics
- Atmospheric and Environmental Gas Dynamics
- Freshwater macroinvertebrate diversity and ecology
- Groundwater and Isotope Geochemistry
- Hydrology and Sediment Transport Processes
- Geological Studies and Exploration
- Smart Materials for Construction
- Methane Hydrates and Related Phenomena
- Groundwater flow and contamination studies
- Geology and Paleoclimatology Research
- Archaeology and Natural History
- Soil erosion and sediment transport
- Aquatic Invertebrate Ecology and Behavior
- Insect and Arachnid Ecology and Behavior
- Arsenic contamination and mitigation
- Water Quality and Pollution Assessment
- Hydrological Forecasting Using AI
- Water Quality and Resources Studies
University of Alaska Fairbanks
2015-2024
University of Oklahoma
2022
Michigan Department of Environment, Great Lakes, and Energy
2018
United States Geological Survey
2010
Pacific Northwest Research Station
2010
University of Florida
2010
University of Saskatchewan
2010
University of Vermont
2009
Bonanza Creek Long Term Ecological Research
2008
University of Nevada, Las Vegas
1997-2000
Approximately 1700 Pg of soil carbon (C) are stored in the northern circumpolar permafrost zone, more than twice as much C atmosphere. The overall amount, rate, and form released to atmosphere a warmer world will influence strength feedback climate change. We used survey quantify variability perception vulnerability Experts were asked provide quantitative estimates change response four scenarios warming. For highest warming scenario (RCP 8.5), experts hypothesized that release from zone...
As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release offset by increased production Arctic boreal biomass; however, lack robust estimates net balance increases risk further overshooting international emissions targets. Precise empirical or model-based assessments critical factors driving are unlikely in near future, so address gap, we present from 98...
Abstract As high latitudes warm, a portion of the large organic carbon pool stored in permafrost will become available for transport to aquatic ecosystems as dissolved (DOC). If DOC is biodegradable, much be mineralized atmosphere freshwater systems before reaching ocean, accelerating transfer from atmosphere, whereas if recalcitrant, it reach marine where may persist over long time periods. We measured biodegradable (BDOC) water flowing collapsing (thermokarst) on North Slope Alaska and...
Abstract Release of greenhouse gases from thawing permafrost is potentially the largest terrestrial feedback to climate change and one most likely occur; however, estimates its strength vary by a factor thirty. Some this uncertainty stems abrupt thaw processes known as thermokarst (permafrost collapse due ground ice melt), which alter controls on carbon nitrogen cycling expose organic matter meters below surface. Thermokarst may affect 20–50% tundra uplands end century; little about effect...
Hyporheic metabolism in a Sonoran Desert stream was examined, focusing on the sources of detritus supporting hyporheic respiration. Two alternative hypotheses were specifically addressed: (1) organic matter derived from surface supports respiration, and (2) buried during flash flood As predicted for surface—derived hypothesis, respiration lowest immediately following floods increased significantly with time after (P < 0.001). ranged 0.05 mgO 2 °L sediments — 1 °h to as high 4.41 0 late...
Frequent measurements of stream chemistry during snowmelt and summer storms were used in three watersheds that differ permafrost coverage (high, 53%; medium, 18%; low, 4%) to determine the role water flow paths on fluxes carbon, nitrogen, major solutes from Alaskan catchments. Permafrost was important seasonal pattern as there a distinct shift winter through into permafrost‐dominated catchment. Furthermore, active layer above for late release NO 3 − DOC, suggesting deeper may increase N C...
Nitrification in the hyporheic zone of Sycamore Creek, a Sonoran Desert stream, was examined, focusing on association between respiration and nitrate production. Subsurface Creek is highest regions hydrologic downwelling where organic matter derived from stream surface transported into zone. Similarly, nitrification closely related to exchange averaged 13.1 μ gNO<sub>3</sub>-N· L sediments<sup>-1</sup>· h<sup>-1</sup> compared with 1.7 upwelling regions. Hyporheic also varies temporally as...
Abstract. As high latitudes warm, vast stocks of carbon and nitrogen stored in permafrost will become available for transport to aquatic ecosystems. While there is a growing understanding the potential effects collapse (thermokarst) on biogeochemical cycles, neither spatial extent nor temporal duration these known. To test hypotheses concerning patterns persistence elemental export from upland thermokarst, we sampled hydrologic outflow 83 thermokarst features various stages development...
This paper assesses the resilience of Alaska’s boreal forest system to rapid climatic change. Recent warming is associated with reduced growth dominant tree species, plant disease and insect outbreaks, thawing permafrost, drying lakes, increased wildfire extent, postfire recruitment deciduous trees, safety hunters traveling on river ice. These changes have modified key structural features, feedbacks, interactions in forest, including effects upland permafrost regional hydrology, expansion...
Abstract Nitrate ( NO 3 – ) export coupled with high inorganic nitrogen (N) concentrations in Alaskan streams suggests that N cycles of permafrost‐influenced ecosystems are more open than expected for N‐limited ecosystems. We tested the hypothesis soil thaw depth governs retention and removal soils due to vertical patterns dominant transformation pathways. Using an situ , push–pull method, we estimated rates uptake denitrification during snow melt, summer, autumn, as soil–stream flowpaths...
During the past ∼50 years, number and area of lakes have declined in several regions boreal forests. However, there has been substantial finer-scale heterogeneity; some decreased area, showed no trend, others increased. The objective this study was to identify primary mechanisms underlying heterogeneous trends closed-basin lake area. Eight characteristics (δ18O, electrical conductivity, surface : volume index, bank slope, floating mat width, peat depth, thaw depth at shoreline, forest...
In the North American low arctic, increased retrogressive thaw slump frequency and headwall retreat rates have been linked with climate warming trends since midtwentieth century, but specific weather drivers of initiation timing are less clear. We examined relationships among annual air temperature, precipitation, snow cover using time series satellite imagery station data in northwest Alaska. Synthetic aperture RADAR optical were used to examine between 1997 2010. Over 80% features this...
Transport and retention of particulate organic matter (POM) were examined in the channels on floodplains two low-gradient headwater streams Coastal Plain southeastern Virginia. During base discharge, POM was primarily retained as it settled onto sediment surface, but during high debris dams became primary retainers. overbank flooding much coarse (CPOM) moved from floodplains. The mean distance that wood over a year at Colliers Creek, which had low current velocity broad, frequently inundated...
Climate warming and permafrost degradation at high latitudes will likely impact watershed hydrology, consequently, alter the concentration character of dissolved organic carbon (DOC) in northern rivers. We examined seasonal variation DOC chemistry 16 streams Yukon River basin, Alaska. Our primary objective was to evaluate relationship between source water (shallow versus deep groundwater flow paths) chemical composition. Using base cation principal component analysis, we observed...
Permafrost thawing is increasing in the Arctic and sub‐Arctic [ Osterkamp Romanovsky , 1996; 2007] response to climate warming Hassol 2004]. One consequence of permafrost development thermokarst (physical depression ground surface) because reduced support overlying soil Jorgenson et al. 2006]. Thermokarst lakes, for example, result from changes surface energy balance, which drive thaw locally, such that a topographic develops captures water, forming lake or pond. Climate past several decades...