Collaborative Research: Impacts of Recent Climate and Emissions Changes on Mercury Bioaccumulation in Arctic Marine Food-Webs

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This project aims to improve our understanding of the factors controlling mercury (Hg) concentrations in the Arctic and their trends over the past three decades (1980-2010). It will develop an atmospheric model for mercury in the Arctic, based on the global GEOS-Chem chemical transport model (CTM) simulation for Hg developed at Harvard, and will be calibrated extensively and evaluated with observations. GEOS-Chem includes dynamical coupling of the atmosphere with surface ocean and land reservoirs. Atmospheric oxidation of Hg(0) to Hg(II), driving Hg(II) deposition, is primarily by bromine (Br) atoms. Model representation of Br chemistry in the Arctic will be tested and improved using recent observations from aircraft and satellites. At all stages of this research, the different model components as well as the coupled model will be evaluated in detail with a large body of atmospheric observations.The project will produce the first coupled simulation of atmospheric Hg dynamics in the Arctic with the ocean and land components in the existing GEOS-Chem model. This can be a powerful tool for relating changes in anthropogenic emissions and climate to biological Hg concentrations in the Arctic and its strong physical basis will make it a fundamental vehicle to test different hypotheses for Hg cycling and bioaccumulation in the Arctic. Sensitivity analyses using the model will identify areas of greatest uncertainty and help guide future research. This work will enable scientists and policymakers to better assess the impacts of policy decisions aimed at protecting the arctic environment.