Multi-Decadal Decline of Mercury in the North Atlantic Atmosphere Explained by Changing Subsurface Seawater Concentrations

[1] We analyze 1977–2010 trends in atmospheric mercury (Hg) from 21 ship cruises over the North Atlantic (NA) and 15 over the South Atlantic (SA). We find a steep 1990–2009 decline of −0.046 ± 0.010 ng m−3 a−1 (−2.5% a−1) over the NA (steeper than at Northern Hemispheric land sites) but no significa...

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Bibliographic Details
Published in:Geophysical Research Letters
Main Authors: Soerensen, Anne Laerke, Jacob, Daniel J., Streets, David G., Witt, Melanie L. I., Ebinghaus, Ralf, Mason, Robert P., Andersson, Maria, Sunderland, Elsie M.
Format: Article in Journal/Newspaper
Language:English
Published: American Geophysical Union 2012
Subjects:
Atlantic
Hg
atmosphere
mercury
ocean
trend
North Atlantic
Online Access:http://nrs.harvard.edu/urn-3:HUL.InstRepos:11917122
https://doi.org/10.1029/2012gl053736
Description
Summary:[1] We analyze 1977–2010 trends in atmospheric mercury (Hg) from 21 ship cruises over the North Atlantic (NA) and 15 over the South Atlantic (SA). We find a steep 1990–2009 decline of −0.046 ± 0.010 ng m−3 a−1 (−2.5% a−1) over the NA (steeper than at Northern Hemispheric land sites) but no significant decline over the SA. Surface water Hg0 measurements in the NA show a decline of −5.7% a−1since 1999, and limited subsurface ocean data show an ∼80% decline from 1980 to present. We use a coupled global atmosphere-ocean model to show that the decline in NA atmospheric concentrations can be explained by decreasing oceanic evasion from the NA driven by declining subsurface water Hg concentrations. We speculate that this large historical decline of Hg in the NA Ocean could have been caused by decreasing Hg inputs from rivers and wastewater and by changes in the oxidant chemistry of the atmospheric marine boundary layer. Engineering and Applied Sciences Version of Record

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