Climate warming increases global oceanic dimethyl sulfide emissions

Area of Science:

• * Atmospheric Chemistry and Climate Science
• * Biogeochemical Cycles
• * Ocean-Atmosphere Interactions

Background:

• * Oceanic dimethyl sulfide (DMS) is the primary natural source of atmospheric sulfur.
• * DMS oxidation products influence aerosol formation, cloud properties, and Earth's radiative budget.
• * Current climate model projections for DMS emissions under global warming are uncertain and contradictory.

Purpose of the Study:

• * To reduce uncertainty in climate model projections of DMS emissions.
• * To simulate future seawater DMS concentrations using machine learning and CMIP6 data.
• * To assess the changing relative importance of DMS in climate regulation.

Main Methods:

• * Utilized machine-learning models trained on biome-resolved global DMS observations.
• * Incorporated physico-chemical and biological predictors from eight Coupled Model Intercomparison Project Phase 6 (CMIP6) models.
• * Simulated seawater DMS concentrations from 1850 to 2100.

Main Results:

• * Machine learning models significantly reduced scatter in current DMS projection uncertainties.
• * Globally averaged seawater DMS concentrations are predicted to decrease in the near future.
• * Global DMS emissions are projected to increase due to rising sea surface temperatures and wind speeds, contradicting previous assessments.

Conclusions:

• * Future increases in DMS emissions are expected due to climate change impacts on oceans.
• * The relative contribution of DMS to sulfate aerosol formation and its cooling effect may increase.
• * This highlights the critical need to accurately model DMS in climate change scenarios.