Collaborative Research: Biological and physical controls on DMS production and emission during VOCALS

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Ocean-atmosphere exchange of the radiatively active biogenic trace gas, dimethylsulfide (DMS), is a major source of atmospheric sulfate aerosols: a key element of the global climate system. Climate affects this exchange by determining the physical-chemical characteristics of the upper ocean, thus shaping the marine planktonic ecosystem and the source strength of DMS. Attaining a more complete understanding of the interactions between the marine ecosystem and climate is an exciting challenge, which has barely begun to be explored. In this study, researchers at the Bigelow Laboratory for Ocean Sciences and the University of Hawaii at Manoa will examine the impact of light levels, sea surface temperature, upwelled nutrients, and winds on the production of DMS and its emission to the atmosphere. These critical linkages in the CLAW Hypothesis potentially determine whether this physical-biological feedback will be positive or negative. Does a modest change in PAR and UV increase or decrease DMS production and emission to the atmosphere? This will be studied in the context of complementary VOCALS projects studying atmospheric portions of CLAW: the oxidation of DMS to sulfate aerosols and their impact on clouds and the Earth?s radiation budget. Evaluating the magnitude and sign of such biotic feedbacks is of major societal and scientific importance. Specifically, the research will address the following themes in the South East Pacific (SEP) waters: (a) how far does the biogeochemical impact of upwelling on DMS production and air-sea flux extend offshore, (b) how do fewer clouds affect biological DMS production and SW concentrations, and (c) How do spatial gradients of SW DMS concentration and flux-controlling factors (e.g., winds) affect DMS fluxes to the atmosphere. The ultimate goal, in the synthesis phase of VOCALS REx and in collaboration with other participating investigators, would be to determine the significance of biotic feedbacks in controlling the radiation budget of the Southeast Pacific. The project will have several broader impacts. Training of one postdoctoral associate (Bigelow) and one graduate student (Hawaii) will be supported. In addition, the Bigelow PI will continue her participation in rural (local) K-8 programs as well as in the Grant Management Advisory Panel for the NSF ITEST grant Communities for Rural Education, Stewardship, and Technology led by the Island Institute (Rockland, ME). The Hawaii PI will use this data as examples (for problem sets and test questions) in his undergraduate and graduate level oceanography and atmospheric chemistry classes. Both PIs will participate in the VOCALS REx-coordinated broader outreach activities.