DMS, originated from phytoplankton, is a significant source of marine sulfate aerosol and plays an important role in climate via modifying cloud properties. The sign and strength of phytoplankton-DMS-climate feedbacks are examined for the first time using fully coupled climate simulations with dynamic marine ecosystem and DMS calculations.
This study shows that oceanic DMS emissions have an important cooling effect in the climate system. There is a weak positive phytoplankton-DMS-climate feedback at the global scale, with large spatial variations. The oceanic uptake of carbon dioxide declines without DMS emissions to the atmosphere. This work highlights the need of considering phytoplankton, and both the sulfur and carbon cycles in climate projections.
Dimethyl sulfide (DMS) is a significant source of marine sulfate aerosol and plays an important role in modifying cloud properties. Fully coupled climate simulations using dynamic marine ecosystem and DMS calculations are conducted to estimate DMS fluxes under various climate scenarios and to examine the sign and strength of phytoplankton-DMS-climate feedbacks for the first time. Simulation results show that surface ocean DMS concentrations change significantly in the future climate scenario due to changes in phytoplankton production and competition. Comparisons between parallel simulations with and without DMS fluxes show that the climate will be much warmer without DMS fluxes due to the missing aerosol indirect effects on clouds. Our results show a tight coupling between the sulfur and carbon cycles. The ocean carbon uptake declines without DMS emissions to the atmosphere. The analysis shows the sign and strength of the feedback vary with climate states and phytoplankton groups. This highlights the importance of a dynamic marine ecosystem module and the sulfur cycle mechanism in climate projections.