Detecting the Signature of Permafrost Thaw in Arctic Rivers

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AbstractGlobal warming mobilization of the large (up to 50% of global) reservoirs of reduced organic carbon associated with northern permafrost regions of the Arctic, and conversion to radiatively important atmospheric (greenhouse) gases such as CO2 and CH4 presents a positive warming feed back of potentially considerable strength. Currently there is a lack of understanding of how fast and to what extent this stored organic matter is microbially transformed within Arctic watersheds and Arctic coastal systems. Despite the marked ?old? (14C depleted) label of permafrost carbon compared to contemporary organic matter, the comparitive lack of an ?aged? C signature in the downstream Arctic river systems presents something of a conundrum. Further, the rapid remineralization of permafrost reduced carbon is not consistent with the notion that reduced (permafrost) carbon is recalcitrant.This research aims to examine the partition, chemical and isotopic compositions, and ages of carbon species, including organic and inorganic/dissolved and particulate carbon, as well as lignin/lipid biomarkers in three subarctic/arctic rivers (Chena, Porcupine, and Sagavanirktok) and their basins. This will enable a comparison along a latitudinal gradient covering sporadic, discontinuous and continuous permafrost exposures, as well as along temporal scales from initial spring freshet to full summer and fall season and freeze-up.