ALBERT

Description: Sea ice represents an additional oceanic source of the climatically active gas dimethylsulfide (DMS) for the Arctic atmosphere. To what extent this source contributes to the dynamics of summertime Arctic clouds is however not known due to scarcity of field measurements. In this study, we developed a coupled sea ice-ocean ecosystem-sulfur cycle model to investigate the potential impact of bottom-ice DMS and its precursor dimethylsulfoniopropionate (DMSP) on the oceanic production and emission of DMS in the Arctic. The result of the 1-D model simulation was compared with field data collected during May and June of 2010 in Resolute Passage. Our result reproduced the accumulation of DMS and DMSP in the bottom ice during the development of an ice algal bloom. The flushing of these sulfur species took place predominantly during the earlier phase of the melt period, resulting in an increase of DMS and DMSP in the underlying water column prior to the onset of an under-ice phytoplankton bloom. Processes that dominated the budgets of bottom- and under-ice DMS and DMSP were identified through an analysis of production and removal rates of processes considered in the model. When openings in the ice were taken into account, the simulated sea-air DMS flux during the melt period was dominated by episodic spikes of up to 5.6 μmol m−2 d−1. Further model simulations were conducted to assess the effects of the incorporation of sea-ice biogeochemistry on DMS production and emissions, as well as the sensitivity of our results to changes of uncertain model parameters of the sea-ice sulfur cycle. The results highlight the importance of taking into account both the sea-ice sulfur cycle and ecosystem in the flux estimates of oceanic DMS near the ice margins and identify key uncertainties in processes and rates that would be better constrained by new observations.