Characterization and quantification of biosphere-climate interactions is critical to understanding and predicting climate change. The feedback between biosphere and climate is mediated to a significant degree by the dynamics of radiatively active, biogenic trace gases. Quantifying the dynamics and air-sea exchange of these gases is a major objective of the new I.G.B.P. (International Biosphere-Geosphere Program) program SOLAS, the Surface Ocean Lower Atmosphere Study. The biogenic production and subsequent ventilation of dimethyl sulfide (DMS) is climatically important as it has been postulated that DMS and its atmospheric oxidation products are part of a cloud albedo feedback mechanism which links global biosphere and climate.
Progress in understanding biosphere-climate interactions is hampered largely because it is difficult to accurately constrain, parameterize, or validate models. There are simply not enough field observations collected in conjunction with the appropriate ancillary data to assess forcing factors in a mechanistic and predictive way.
In this project, scientists at the Woods Hole Oceanographic Institution and the Bermuda Biological Station for Research will collect and study new time-series data set of DMS dynamics, including critical pool and rate measurements vital to assess not only the long-term variability of the DMS pool (and major associated compounds) but also the short-term dynamics of DMS and dimethylsulfoniopropionate (DMSP - the main precursor of DMS in ocean water) that underlie this long-term variability. By revisiting the same oceanic gyre, this new study will represent the first long term comparison of DMS and DMSP concentrations anywhere in deep ocean. The measurements made in the first study will be repeated now, more than a decade later, in addition to a broader suite of measurements to address new hypotheses about the factors controlling DMS dynamics. Monthly measurements will include key turnover dynamics of DMS and dissolved DMSP in surface waters using new 35S tracer methods, aqueous DMSO concentrations, and diel variations in atmospheric DMS during the BATS cruises. This comprehensive time-series and process sampling scheme will allow us to describe mechanistically the controls on key DMS, DMSP, and DMSO turnover rates and will serve as a unique validation data set for past and future modeling efforts.
Broader Impacts: Results from this study should improve our understanding of the underlying mechanisms controlling DMSP and DMS concentrations in oligotrophic waters and also provide key variables for model calibration and validation, thereby improving our ability to simulate and predict future biosphere-climate feedbacks. This research will also support the research of a student and a postdoctoral investigator, and encourage multifaceted interactions with scientists in several institutions in the US and Europe.
