DMS(P) distribution in Arctic sea ice related to algal community structure and ice dynamics – results from the MOSAiC expedition

This presentation is a contribution to the Multidisciplinary drifting Observatory for the Study of Arctic Climate(MOSAiC) expedition. The MOSAiC field campaign took place on board of RV Polarstern, drifting with the Arctic sea ice, from October 2019 to October 2020. As partner of the MOSAiC team, our project contributed to the production of a time series of sulphur compounds in Arctic sea ice and underlying seawater. The aim of our project was to address how seasonality, sea ice dynamics and water characteristics in the Arctic Ocean affect the cycling of organic sulfur compounds. The sampling of sea ice and surface water was part of the concerted actions of the BGC, ICE and ECO teams during MOSAiC.

A crucial compound for organisms to survive the cold and saline environment of sea ice is the organic sulfur compound dimethylsulfoniopropionate (DMSP) that is mainly synthesized by algae. Between 1 and 10% of total primary production is invested in DMSP, thereby making it a key compound in the lower - and potentially also higher - trophic levels. DMSP is also the precursor of the climate active semi-volatile compound dimethylsulfide (DMS).

Our work combines measurements of concentrations of DMSP, DMS and the (photo-)oxidation product of DMS, dimethyl sulfoxide (DMSO), transformation rates of these compounds using stable isotope additions and identification of the microorganisms driving these processes.

In this presentation, we will show persistent features of DMS(P) distribution in vertical profiles of the MOSAiC floe; link these profiles to algal community structure and discuss the connection between ice and surface water DMS(P) concentrations. We will present a conceptual model of how the growth of sea ice in the Central Arctic Ocean results in specific DMS(P) distribution patterns.