A main goal of my research projects both in the coastal and Southern Ocean is to understand linkages between physical processes and biological productivity. I use budget-based estimates for macronutrients and biologically-mediated gases along with measurements of stable isotope composition of different biologically-active species to estimate rates of net community and gross primary production. In the ocean, the rate of net community production in terms of carbon is of particular importance because over significant spatial and temporal scales it must equal the rate of carbon export to the deep ocean. In many coastal systems offshore Ekman transport drives near-shore upwelling that supplies nutrients to the surface ocean that in turn supports net biological production; in offshore regions, upwelling driven by the curl of the wind stress is important as a supply of new nutrients. Wind also influences the biological productivity of the surface ocean by influencing the depth of the mixed layer that can in turn control the availability of light to photoautotrophs. Understanding how variability in physical variables relates to biological productivity is vital to understanding potential impacts of climate change on aquatic ecosystems.
The rate of carbon export to the deep ocean largely determines the strength of the biological pump which controls the distribution of nutrients between the surface and deep ocean and is an important control on the partial pressure of carbon dioxide in the surface ocean and atmosphere. My interest in marine biological productivity stems mainly from the important role marine productivity plays in controlling the air-sea exchange of carbon dioxide. Because the ocean absorbs nearly 40% of all anthropogenic carbon released to the atmosphere, understanding the linkages between climate variability, biological production, and air-sea gas exchange is vital to understanding how future variability will impact the strength of the oceanic carbon sink and the level of carbon dioxide in the atmosphere. My research in both the coastal and Southern Ocean has focused on how variability in physical parameters such as wind and net biological production relates to air-sea exchange of carbon dioxide over a range of spatial and temporal scales.