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Climate Driven Destabilization of Arctic Watersheds and a New Reactivity Paradigm for Carbon Cycling in Arctic Rivers

Arctic Research Initiative
2007 Funded Project

Abstract

The Arctic Ocean is a semi-enclosed basin surrounded by immense watersheds that drain the polar and sub-polar regions of Eurasia and North America. Each year, Arctic rivers deliver proportionately more freshwater to the Arctic Ocean than to any other ocean basin. Dissolved and suspended material loads within Arctic rivers also entrain enormous quantities of nutrients, salts, minerals and organic carbon. The Arctic atmosphere, land and ocean are all linked through the hydrological cycle, which is under severe pressure from climate driven change. Arctic precipitation and river discharge have both increased, the duration and extent of lake and river ice cover has decreased, the timing of the annual ice/snow melt has advanced to earlier in the year and the permafrost is beginning to melt. Recent studies suggest these changes are accelerating. Climate change is both impacting the functioning of the Arctic hydrological cycle and altering feedbacks from the Arctic to the global climate system.

One of the most significant potent impacts of climate driven change in the Arctic to marine ecosystems and the ocean carbon cycle is the introduction of organic carbon and nutrients from the continents. Nearly half the global inventory of organic carbon stored in soils is sequestered in Arctic watersheds. Presently, through erosion and weathering, Arctic rivers annually deliver some 30-50 x 1012g of this carbon to the coastal zone. Current paradigm holds that soil organic carbon is the residue of carbon cycling in terrestrial ecosystems, and is therefore old and nonreactive. If Arctic soil carbon is not reactive, it will cycle passively through the Arctic Ocean and its impact will be muted. However, new observations suggest that a large fraction of Arctic river carbon is both fresh and reactive. If these observations prove to be correct, introduction of organic carbon and nutrients will act to fertilize and restructure the Arctic Ocean ecosystem. We propose to establish a collaboration between organic geochemists and microbiologists at WHOI and Arctic system scientists at the Woods Hole Research Center to investigate the transfer of carbon and organic nutrients from Arctic watersheds to the Arctic Ocean.

We propose to synchronously sample two large Russian rivers (Lena, Ob’) and one North American River (Colville) during their high flow/high carbon flux periods when most carbon is delivered to the ocean. We will make key measurements on riverine organic matter to measure its age (radiocarbon), composition (stable isotopes, biomarkers, mass and nuclear magnetic resonance spectral analyses), reactivity (microbial incubations) and impacts on the microbial community (genetics of microbial community structure). Through these measurements we plan to establish a long term multi-investigator collaboration supported by external funding to study carbon cycling in Arctic Rivers. This proposal also compliments and shares some sampling aspects to the proposal “Mineral Weathering in the Arctic” submitted to the WHOI Arctic Initiative by Drs. Bernhard Puecker-Ehrenbrink and Olivier Rouxel in the Department of Marine Chemistry & Geochemistry, WHOI

Last updated: September 17, 2014