Extreme natural acidification in the East Siberian Arctic Shelf: Effects of permafrost thawing and seawater freshening

Thursday, 17 December 2015
Poster Hall (Moscone South)
Igor Peter Semiletov1,2, Irina Pipko3, Orjan Gustafsson4, Leif G Anderson5, Valentin Sergienko6, Svetlana Pugach3, Oleg Dudarev3, Alexander N Charkin3, Alexander Gukov2, Lisa Bröder7, August Andersson4 and Natalia E Shakhova8, (1)Pacific Oceanological Institute, Far Eastern Branch of the Russian Academy of Sciences, Laboratory of Arctic Research, Vladivostok, Russia, (2)National Tomsk Research Polytech University, Russia, Tomsk, Russia, (3)Pacific Oceanological Institute FEB RAS, Vladivostok, Russia, (4)Stockholm University, Stockholm, Sweden, (5)University of Gothenburg, Gothenburg, Sweden, (6)Russian Academy of Sciences, Institute of Chemistry, Vladivostok, Russia, (7)Stockholm University, Analytical Scemistry and Environmental Sciences, Stockholm, Sweden, (8)University of Alaska Fairbanks, Fairbanks, AK, United States
Ocean acidification (OA) is a direct, fast, and strong effect of anthropogenic carbon dioxide (CO2), which is challenging marine ecosystems and carbon cycling. The Arctic Ocean is particularly sensitive and exhibits the highest levels of OA (lowest pH) because more CO2 can dissolve in cold water. We here use decadal data to show that extreme and extensive OA in the East Siberian Arctic Shelf (ESAS) is caused not by direct uptake of atmospheric CO2 but rather by naturally-driven processes: carbon mobilization from thawing coastal permafrost/coastal ice complexes, and freshening due to growing Arctic river runoff and ice melt, which transport carbon along with freshwater to the ESAS. These processes compose a unique acidifying phenomenon that causes persistent, and potentially increasing, aragonite under-saturation of the entire water column. Extreme aragonite under-saturation in the western near-shore ESAS is associated with >80% depression of the total calcifying benthic biomass. Massive OA on the ESAS, the largest sea shelf system of the World Ocean, illustrates the complexity of the Earth system interacting with increasing anthropogenic pressure.