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Abstract Title: Permafrost Thaw and the Fate of Arctic River and Coastal Erosion Mercury Inputs to the Arctic Ocean
Presenter Name: Stefan Osterwalder
Company/Institution: ETH Zurich, Department of Environmental Systems Science (D-USYS), Institute of Agricultural Sciences
Session: Special Session - Climate-Driven Perturbations of Arctic Mercury Cycling
Day and Session: Friday 29th July - Session Three
Start Time: 13:00 UTC
Co-Authors: Stefan Osterwalder

Abstract Information :

Arctic warming leads to permafrost thaw and mobilization of mercury (Hg) from the large circumpolar soil pool. A part of that permafrost Hg is released to the Arctic Ocean (AO) via rivers and coastal erosion. Subsequent re-emission of terrestrial Hg inputs from the AO to the atmosphere is hypothesized to amplify the Arctic summertime maximum of gaseous elemental Hg (Hg0). However, it remains a matter of debate whether the observed summertime Hg0 peak originates from re-emission of terrestrial Hg or from re-emission of Hg deposited during atmospheric Hg depletion events (AMDEs). Here we show that the summertime Hg0 peak results mostly from re-emission of Hg deposited to the AO during AMDEs based on the similarities in their isotopic signatures. In order to identify the origin of the peak we investigate the Hg isotope variability of Arctic atmospheric Hg0 and HgII, snow HgII, surface AO particulate HgII, and Yenisei River dissolved HgII. We observe different ?202Hg, ?199Hg and ?200Hg signatures in atmospheric Hg0, and in Siberian terrestrial, river and AO marine Hg. Air mass back trajectory analysis supports that the summertime Hg0 peak originates from snow covered sea ice, snow covered coastal land, and snowmelt runoff into marine waters. This implies that terrestrial Hg inputs to the AO remain in the marine ecosystem, without substantial loss to the global atmosphere, but with possible effects on Arctic food webs.

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