Watson Gregg (PI)
NASA Goddard Space Flight Center
watson.gregg@nasa.gov

Effects of Light Absorption by Ocean Phytoplankton on Ocean Circulation and Climate Predictions

IIt has recently been recognized that absorption of irradiance by ocean phytoplankton can affect the transfer of heat in the water column, and affect ocean circulation.  Specifically, this process may affect model representation of sea surface temperature, mixed layer depths, and vertical structure of the water column.  By affecting ocean circulation and ocean thermodynamical properties, this process may also contribute to the representation of climate change as predicted in coupled models.  Most models do not include these effects yet, especially climate prediction models.   This process can potentially be a source of error in ocean circulation and climate prediction models.  We propose to investigate the effects of ocean phytoplankton in the context of the GISS ocean circulation and climate models.  We plan a parallel stepwise approach, with a successive increase in complexity and realism.  We intend to first focus on the responses of ocean circulation due to spatially and temporally varying light attenuation obtained from ocean color satellites.  We intend to then investigate how this may affect climate change representation in a coupled model.  We will increase the complexity and realism of the analysis by including explicit biological and radiative effects using an established model.  Here we can investigate feedback mechanisms between biological, radiative, and physical processes, and partition the effects of optically active living and non-living components.  Again the next step will be to incorporate these feedback mechanisms into coupled model simulations.  We expect finally to proceed to assessments of the sensitivity of coupled model forecasts to these biological/radiative processes.  The incorporation of the ocean biological/radiative dynamics into the GISS models will set the stage for future investigations of carbon cycling and biologically-mediated aerosol production in the context of climate change scenarios.

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