Becky Alexander

 

Deposition of MSA in Antarctica has frequently been used as an indicator of sea ice extent based on observational evidence of high surface dimethylsulfide (DMS) concentrations associated with seasonally melting sea ice. A series of model experiments with a global chemical transport model (GEOS-Chem) over the period 1985 - 2004 show lifetimes of DMS and MSA are longer by 300% and 40%, respectively in the southern high-latitudes than the global mean, and that net transport of sulfur derived from DMS emissions in sea ice is northward. Our model runs suggest that DMS emissions from the sea ice zone may account for 26 - 62% of MSA deposition at the Antarctic coast, and 36 - 95% in inland Antarctica, depending strongly on the magnitude of DMS emissions fluxes from the sea ice and ocean surrounding Antarctica. We find that interannual variability in sea ice extent contributes only 11 - 30% of the interannual variability of DMS emissions around Antarctica. Wind also plays a role in variability in DMS emissions, but its contribution relative to that of sea ice variability is strongly dependent on the assumed DMS concentrations. Improved understanding of both DMS concentrations in the sea ice and of the DMS emissions flux from the sea ice zone are required to better assess the impact of interannual sea ice variability on MSA deposition to Antarctica.

(a) and (b) MSA snow concentration (ppb) from DMS emissions in the sea ice zone, and  (c) and (d) Fraction of total MSA deposition originating from the sea ice using the Simo and Dachs (2002) (top) and Kettle et al. (1999) (bottom) sea water DMS concentrations.
(a) and (b) MSA snow concentration (ppb) from DMS emissions in the sea ice zone, and (c) and (d) Fraction of total MSA deposition originating from the sea ice using the Simo and Dachs (2002) (top) and Kettle et al. (1999) (bottom) sea water DMS concentrations.

People

Paul Hezel, Cecilia Bitz, Becky Alexander, and Eric Steig, University of Washington

References

  • Hezel, P.J, B. Alexander, C.M. Bitz and E.J. Steig, Modeled methanesulfonic acid (MSA) deposition in Antarctica and its relationship to sea ice, submitted to J. Geophys. Res. (2011).
  • Simo, R., and Dachs, a. J.: Global ocean emissions of dimethylsulfide predicted from biogeophysical date, Glob. Biogeochem. Cycle, 16, 1078, 2002.
  • Kettle, A.J., Andreae, M.O., Amouroux, D., Andreae, T.W., Bates, T.S., Berresheim, ., H., Bingemer, H., Boniforti, R., Curran, M.A.J., DiTullio, G.R., Helas, G., Jones, G.B., Keller, M.D., Kiene, R.P., Leck, C., Levasseur, M., Malin, G., Maspero, M., Matrai, P., McTaggart, A.R., Mihalopoulos, N., Nguyen, B.C., Novo, A., Putaud, J.P., Rapsomanikis, S., Roberts, G., Schebeske, G., Sharma, S., Simo, R., Staubes, R., Turner, S., Uher, and G.: A global database of sea surface dimethylsulfide (DMS) measurements and a procedure to predict sea surface DMS as a function of latitude, longitude, and month, Glob. Giogeochem. Cycle, 13, 399-444, 1999.

Funding

NSF-ANT 0739127

Source: http://www.atmos.washington.edu/~beckya/nobackup/MSA_SeaIce.htm