Wind-Driven Upwelling in Lakes: Water Clarity and Fish Mortality
Todd
Steissberg, University of California, Davis, tsteissberg@ucdavis.edu
(Presenting)
Simon
Hook, Jet Propulsion Laboratory (NASA/JPL), simon.j.hook@jpl.nasa.gov
Geoffrey
Schladow, University of California, Davis, gschladow@ucdavis.edu
Belen
Marti, Universidad Politecnica de Catalunya, belen.marti@upc.edu
Thermal infrared images acquired by high- and moderate-resolution satellite instruments can be used to observe wind-driven upwelling in lakes and can provide a measure of their spatial variability and horizontal distribution, information that conventional field-based measurements cannot provide. The surface temperature maps derived from MODIS, ASTER, and Landsat ETM+ images enabled the characterization of wind-driven upwelling at Lake Tahoe, CA-NV and the Salton Sea, CA. At Lake Tahoe, the satellite images, paired with time series of in situ buoy-mounted surface thermistor and meteorological data, have shown that partial upwelling events occur at least twice monthly, on average, throughout the spring and summer stratified period, transporting water from intermediate depths to the surface. Partial upwelling events were found to generally decrease lake clarity, although deeper (full) upwelling events can increase clarity. At the Salton Sea, strong winds induced upwelling of hypolimnetic water, which due to their high concentrations of ammonium and hydrogen sulfide and low concentration of oxygen, are likely responsible for the massive fish kills reported there. Several fish-kill events at the Salton Sea were investigated using a combination of in situ wind data and MODIS thermal infrared images. Major fish kills occurred 1 - 5 days after strong sustained wind events in 12 of the 14 cases analyzed, suggesting that these fish kills are caused by wind-driven upwelling. Evaluation of satellite-derived surface temperature maps, available for five of these events verified that wind-driven upwellings did occur, confirming the relationship between wind-driven upwelling and fish-kill events in the Salton Sea.