Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
Clim. Past, 13, 39-59, 2017
https://doi.org/10.5194/cp-13-39-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
16 Jan 2017
Sea ice and pollution-modulated changes in Greenland ice core methanesulfonate and bromine
Olivia J. Maselli1,a, Nathan J. Chellman1, Mackenzie Grieman2, Lawrence Layman1, Joseph R. McConnell1, Daniel Pasteris1, Rachael H. Rhodes3, Eric Saltzman2, and Michael Sigl1 1Department of Hydrologic Sciences, Desert Research Institute, Reno, NV, USA
2Department of Earth System Science, University of California Irvine, Irvine, CA, USA
3Department of Earth Sciences, University of Cambridge, Cambridge, UK
anow at: Department of Chemistry, University of Adelaide, Adelaide, Australia
Abstract. Reconstruction of past changes in Arctic sea ice extent may be critical for understanding its future evolution. Methanesulfonate (MSA) and bromine concentrations preserved in ice cores have both been proposed as indicators of past sea ice conditions. In this study, two ice cores from central and north-eastern Greenland were analysed at sub-annual resolution for MSA (CH3SO3H) and bromine, covering the time period 1750–2010. We examine correlations between ice core MSA and the HadISST1 ICE sea ice dataset and consult back trajectories to infer the likely source regions. A strong correlation between the low-frequency MSA and bromine records during pre-industrial times indicates that both chemical species are likely linked to processes occurring on or near sea ice in the same source regions. The positive correlation between ice core MSA and bromine persists until the mid-20th century, when the acidity of Greenland ice begins to increase markedly due to increased fossil fuel emissions. After that time, MSA levels decrease as a result of declining sea ice extent but bromine levels increase. We consider several possible explanations and ultimately suggest that increased acidity, specifically nitric acid, of snow on sea ice stimulates the release of reactive Br from sea ice, resulting in increased transport and deposition on the Greenland ice sheet.

Citation: Maselli, O. J., Chellman, N. J., Grieman, M., Layman, L., McConnell, J. R., Pasteris, D., Rhodes, R. H., Saltzman, E., and Sigl, M.: Sea ice and pollution-modulated changes in Greenland ice core methanesulfonate and bromine, Clim. Past, 13, 39-59, https://doi.org/10.5194/cp-13-39-2017, 2017.
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Short summary
We analysed two Greenland ice cores for methanesulfonate (MSA) and bromine (Br) and concluded that both species are suitable proxies for local sea ice conditions. Interpretation of the records reveals that there have been sharp declines in sea ice in these areas in the past 250 years. However, at both sites the Br record deviates from MSA during the industrial period, raising questions about the value of Br as a sea ice proxy during recent periods of high, industrial, atmospheric acid pollution.
We analysed two Greenland ice cores for methanesulfonate (MSA) and bromine (Br) and concluded...
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