Influence of short-term synoptic events and snow depth on DMS, DMSP, and DMSO dynamics in Antarctic spring sea ice

Gauthier Carnat,Chris Fritsen,Jean-Louis Tison,Isabelle Dumont,Martin Vancoppenolle,Frédéric Brabant,Stephen F Ackley,Bruno Delille

doi:10.12952/journal.elementa.000135

Abstract

Abstract Temporal changes in the concentration profiles of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO) were measured in pack ice from the Bellingshausen Sea (Antarctica) during the winter-spring transition of 2007. Two sites with contrasting snow and ice thicknesses were sampled, with high concentrations of DMS, DMSP, and DMSO observed at both sites, especially in surface ice. These high concentrations were shown to correspond to the development of a surface ice microalgal community dominated by strong DMSP producers (flagellates and dinoflagellates) following flooding of the ice cover. Several short-term synoptic events were observed and shown to influence strongly the dynamics of sea ice DMS, DMSP, and DMSO. In particular, a cold spell event was associated with drastic changes in the environmental conditions for the sea ice microbial communities and to a remarkable increase in the production of dimethylated sulfur compounds at both sites. A good correlation between all dimethylated sulfur compounds, sea ice temperature, and brine salinity suggested that the observed increase was triggered mainly by increased thermal and osmotic stresses on microalgal cells. Atmospheric forcing, by controlling sea ice temperature and hence the connectivity and instability of the brine network, was also shown to constrain the transfer of dimethylated sulfur compounds in the ice towards the ocean via brine drainage. Analysis of the two contrasting sampling sites shed light on the key role played by the snow cover in the sea ice DMS cycle. Thicker snow cover, by insulating the underlying sea ice, reduced the amplitude of environmental changes associated with the cold spell, leading to a weaker physiological response and DMS, DMSP, and DMSO production. Thicker snow also hampered the development of steep gradients in sea ice temperature and brine salinity, thereby decreasing the potential for the release of dimethylated sulfur compounds to the ocean via brine drainage.

Highlights

The volatile organic compound dimethylsulfide (DMS) is the dominant biogenic sulfur compound in the ocean and the main contributor to the global biogenic sulfur flux to the atmosphere (Bates et al, 1992)
Concentrations measured at Ice Station Belgica (ISB) were compared with the synthesis of Antarctic sea ice DMS and DMSP data sets provided in Carnat et al (2014) and the recent works of Nomura et al (2011) and Damm et al (2016)
These results indicate that the conditions prevailing at the time of sampling at ISB were favorable for DMSP pro duction

Summary

Introduction

The volatile organic compound dimethylsulfide (DMS) is the dominant biogenic sulfur compound in the ocean and the main contributor to the global biogenic sulfur flux to the atmosphere (Bates et al, 1992). Oceanic DMS is mainly produced by the enzymatic cleavage of the algal metabolite dimethylsulfoniopropionate (DMSP); its synthesis depends strongly on algal abundance, taxonomy, and various environmental stressors (Stefels et al, 2007). DMS is found supersaturated in all oceanic waters, leading to significant fluxes to the atmosphere where it is quickly oxidized in climateactive sulfate aerosol particles. These particles can potentially cool the climate by scattering and absorbing

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