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Key Indicators of Regional Climate Change: Dissolved Organic Matter Composition and Flux in the Yukon River Basin: Jon O’Donnell
Project Title: Key Indicators of Regional Climate Change: Dissolved Organic Matter Composition and Flux in the Yukon River Basin
Mendenhall Fellow: Jon O’Donnell, (303) 541-3005, jodonnell@usgs.gov
Duty Station: Boulder, CO
Start Date: January 3, 2011
Education: Ph.D. Biological Sciences, University of Alaska Fairbanks, 2010
Research Advisors: George Aiken, (303) 541-3036, graiken@usgs.gov; Kim Wickland, (303) 541-3072, kpwick@usgs.gov; Brian Bergamaschi, (916) 278-3053, bbergama@usgs.gov
  Jon O'Donnell

Project Description: Soils in the northern circumpolar permafrost region account for 16 percent of the global land area and harbor approximately 50 percent of global organic carbon (C) stocks. Recent climate warming at high-latitudes will likely alter the processes governing soil C dynamics and, consequently, modify the global climate system. Of particular concern is the widespread degradation of permafrost and its impact on regional C balance and hydrology. Permafrost thaw may liberate large quantities of soil organic matter that have been frozen in soil since the last glacial maximum. Permafrost thaw may also alter watershed hydrology, as evidenced by recent increases in groundwater contributions to stream flow.  Some evidence suggests that permafrost degradation has modified the flux of dissolved organic carbon (DOC) fluxes in northern. DOC fluxes from terrestrial to aquatic ecosystems are an important component of the C cycle at high latitudes. The chemical composition of dissolved organic matter (DOM) in northern rivers reflects key physical and biological processes within soils and thus may serve as an indicator of landscape changes, such as permafrost thaw.

 

This project seeks to understand the fate of DOC following permafrost thaw in watersheds of the Yukon River Basin (YRB) in Alaska. To address this research question, I am using three complimentary approaches. First, I am analyzing spatial patterns in DOM optical properties during winter flow to assess the role of groundwater and permafrost thaw across the YRB. Second, I am conducting a suite of laboratory experiments to evaluate physical and biological controls on DOM reactivity in permafrost soils. Third, I am using the groundwater model SUTRA-ICE to simulate hydrology and DOC transport along hill slopes underlain by thawing permafrost. Together, these approaches will improve our understanding of DOC dynamics in permafrost soils and better constrain future projections of DOC fluxes from high-latitude watersheds. 

 

 

 

 


(LEFT) Soil exposure showing carbon-rich organic-soil horizons underlain by ice-rich permafrost. This site is located in a black spruce forest along the Taylor Highway, near Tok, Alaska.

 




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