Contemporary variability in dimethylsulfide flux in the Barents Sea and simulated change under 4xCO2 climate conditions

The impacts of climate change will likely be most pronounced in the Arctic, due to various climate feedbacks such as the sea-ice albedo effect and changes in the biogenic emission of marine aerosols. The Barents Sea is one of the most productive ecosystems in the Arctic Ocean, seems to be a hot spot of warming, and as such merits special attention. A biogeochemical model is used to simulate phytoplankton variability and dimethylsulfide (DMS) flux in year 2005. A Genetic Algorithm (GA) technique is used to calibrate the biogeochemical model parameters. The CMIP5 (Coupled Model Inter-comparison Project Phase 5) model output is used to provide changes in relevant model forcings under 1xCO(2) (contemporary) and 4xCO(2) (which could be reached by 2100 under worst case greenhouse gas emissions scenarios). Satellite data and meteorological forcings are used to characterize contemporary biophysical conditions in a region of the Barents Sea (70 degrees N-80 degrees N, 30 degrees E-40 degrees E). Under contemporary climate, meteorological forcings are studied for year 2003-2013. Mean concentrations of chlorophyll-a (CHL) reach a peak in late May and increase from north to south. Sea ice cover (ICE) decreases from March to September and is almost zero after year 2005 in the southern region (70 degrees N-75 degrees N). In the northern region (75 degrees N-80 degrees N), seasonal ice melt is closely related to the timing of the spring phytoplankton bloom. In general, the vernal increase of CHL coincides with an increase of sea surface temperature (SST) and decrease in surface wind speed (WIND). Under 4xCO(2) climate conditions, spring ICE decreases around 60% and the mixed layer depth (MLD) increases around 112%. The simulated deepening of the mixed layer leads to less favorable light conditions for phytoplankton growth. DMS sea-to-air flux hence decreases annual around 12%-46% due to a delay in the vernal bloom of phytoplankton. However, sea ice melt with concomitant increase in open waters promotes a DMS flux increase of around 9%-20% from May to mid of July. The change in DMS flux is influenced more by deepening of the MLD, rather than the increase in open water due to reduced sea ice cover. Importantly, these results contrast with previous studies that simulated increases in DMS sea-air flux in the Arctic Ocean under warming.

Automated summary

Research shows that the Barents Sea is one of the regions most affected by climate change in the Arctic, with phytoplankton growth in the northern region closely related to the timing of sea ice melt. Under 4xCO(2) climate conditions, decreased spring sea ice and deepening of the mixed layer inhibit phytoplankton growth, leading to a decrease in DMS sea-to-air flux.