Impacts of Shifts in Phytoplankton Community on Clouds and Climate via the Sulfur Cycle

• Published in: Global Biogeochemical Cycles
• Main Authors: Wang, Shanlin, Maltrud, Mathew E., Burrows, Susannah M., Elliott, Scott M., Cameron‐Smith, Philip
• Language: unknown
• Published: 2022
• Subjects: 54 ENVIRONMENTAL SCIENCES; North Atlantic
• Online Access: http://www.osti.gov/servlets/purl/1558386; https://www.osti.gov/biblio/1558386; https://doi.org/10.1029/2017GB005862

Dimethyl sulfide (DMS) is an organosulfur compound primarily produced by marine organisms, and it contributes significantly to sulfate aerosol loading over the ocean after being oxidized in the atmosphere. In addition to exerting a direct radiative effect on climate, the resulting aerosol particles act as cloud condensation nuclei (CCN), modulating cloud properties and extent, with impacts on atmospheric radiative transfer and climate. Thus changes in pelagic ecosystems, such as phytoplankton physiology and community structure as they may influence organosulfur production, affect climate via the sulfur cycle. A fully coupled Earth system model, including prognostic calculations of marine ecosystems with the sulfur cycle, is used here to investigate the impacts of changes associated with individual phytoplankton groups on DMS emissions and climate. Simulations show that changes in phytoplankton community structure, DMS production efficiency and interactions of multi-element biogeochemical cycles can all lead to significant differences in DMS transfer to the atmosphere. Subsequent changes in sulfate aerosol burden plus CCN number and distribution are examined, since these are properties closely related to aerosol direct and indirect effects on radiative forcing. We find individual phytoplankton group-induced total cloud forcing change is up to 5 W/m2 of warming in the North Atlantic and surface temperature warming is enhanced by up to 2°C on regional scales in a simulation with radiative forcings at the 2100 level under an 8.5 scenario. Moreover, we note large shifts in (atmospheric) hydrological cycle indicators such as cloud fraction and liquid water path. However, the global mean temperature response is relatively small, with average increases only up to 0.1°C. Hence we speculate that major uncertainties associated with future marine sulfur cycling will involve strong region-to-region climate shifts and teleconnections between them. Further improvements in understanding of marine ecosystems and the relevant ...