My research investigates the physical limnology of lakes and the biogeochemical and ecological consequences of changes in mixing dynamics. Studies are ongoing in Arctic and Subarctic lakes, Mono Lake, CA, and tropical lakes in East Africa and the Amazon Basin. My group also investigates the pathways of stream inflows into the coastal zone.
Our recent research has illustrated the importance of instabilities of non-linear internal waves for turbulence production in the thermocline near the boundaries of lakes and resulting nutrient and gas fluxes. We have also quantified turbulence at the air-water interface due to changes in rates of heating and cooling and differences in wind speed. With this information we are developing new models of the gas transfer coefficient as needed for accurate estimates of regional and global carbon fluxes.
We are currently establishing links between mixing events in individual lakes and large scale climate forcing. For example, more frequent mixing events occur in stratified arctic lakes when low pressure is to the north over the Arctic Ocean, and fewer events occur when the Arctic Dipole is present with high pressure to the north. The mixing dynamics of large tropical lakes vary during years with El Nino conditions versus La Nina conditions. Shallower thermoclines and a larger volume of anoxic water develop in Lake Victoria, East Africa, during El Nino years. In contrast, mixing is intensified in La Nina years. We are presently investigating the consequences of interannual variations in mixing regimes for the biogeochemistry of arctic and tropical lakes.