Detecting the signature of permafrost thaw in Arctic rivers

• Published in: Geophysical Research Letters
• Main Authors: Spencer, Robert, Mann, Paul, Dittmar, Thorsten, Eglinton, Timothy, McIntyre, Cameron, Holmes, Robert, Zimov, Nikita, Stubbins, Aron
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2015
• Subjects: C500 Microbiology; F100 Chemistry; F700 Ocean Sciences; F800 Physical and Terrestrial Geographical and Environmental Sciences; Arctic; Kolyma; Climate change; Detecting the Signature of Permafrost Thaw in Arctic Rivers; kolyma river; permafrost
• Online Access: https://nrl.northumbria.ac.uk/id/eprint/21999/; https://doi.org/10.1002/2015GL063498; https://nrl.northumbria.ac.uk/id/eprint/21999/5/grl52870.pdf

Climate change induced permafrost thaw in the Arctic is mobilizing ancient dissolved organic carbon (DOC) in to headwater streams, however DOC exported from the mouth of major arctic rivers appears predominantly modern. Here we highlight that ancient (>20,000 ybp) permafrost-DOC is rapidly utilized by microbes (~50% DOC loss in <7 days), and that permafrost-DOC decay rates (0.12 to 0.19 d-1) exceed those for DOC in a major arctic river (Kolyma: 0.09 d-1). Permafrost-DOC exhibited unique molecular signatures, including high levels of aliphatics that were rapidly utilized by microbes. As microbes processed permafrost-DOC, its distinctive chemical signatures were degraded and converged towards those of DOC in the Kolyma River. The extreme biolability of permafrost-DOC and the rapid loss of its distinct molecular signature may explain the apparent contradiction between observed permafrost-DOC release to headwaters and the lack of a permafrost signal in DOC exported via major arctic rivers to the ocean.