Emanuele Di Lorenzo (PI)
Georgia Institute of Technology
edl@eas.gatech.edu

Modeling, Assimilating and Predicting Physical-Biological Climate Variations of the California Current System

The California Current System (CCS) is among the most biologically productive and economically important regions in the ocean. In the Southern California Bight (SCB) sub-region, from Point Conception to San Diego, data have been collected since 1949 by the California Cooperative Oceanic Fisheries Investigations (CalCOFI) at roughly 70 km resolution. During the past 20 or so years, however, satellite and remotely sensed drifter observations of SST, sea level, currents, and ocean color have revealed intense oceanic mesoscale variations. This indicated that the low space and time resolution of the CalCOFI sampling is inadequate to properly resolve the variability of the mesoscale processes that control the changes of the dominant biogeochemical and physical features, such as localized upwelling cells, meandering fronts and filaments, and thermocline eddies.      The focus of this project is to use remotely sensed data (AVHRR / MODIS SST, TOPEX / ERS-1 altimetry, QuikSCAT / SeaWinds wind fields, and CZCS / SeaWiFS / MODIS ocean color) in conjunction with in situ CalCOFI data (temperature, salinity, currents, nitrate, chlorophyll-a, bulk zooplankton) to quantify, diagnose and predict the scales and processes of physical and biogeochemical variability which have been inadequately resolved in the SCB. Specifically, we will produce a time-dependent picture of the physical and biogeochemical dynamics during the period 1950-present using individual CalCOFI cruise observations and associated satellite data. This will expand the interpretation of CalCOFI from the classic time-aliased view to the modern time-evolving view of physical balances of and biogeochemical response to upwelling, eddy formation and variable external forcing.  We propose to use the Regional Ocean Modeling System (ROMS) tangent linear and adjoint models to assimilate the existing subsurface CalCOFI biological, chemical and physical data and remotely sensed surface data (ocean color, SST, winds, sea level height) to:  a) fit a regional, eddy-resolving, dynamical, ocean model to  satellite and in situ CalCOFI data and use the solutions to diagnose physical dynamics in the SCB over monthly, interannual and decadal timescales. b) fit a regional 3D biogeochemical model, driven by the physical model,  to satellite and in situ CalCOFI data and use the solutions to diagnose  biogeochemical dynamics in the SCB over monthly, interannual and decadal timescales. c) determine the predictive timescales of the atmospherically forced and  intrinsically varying physical and biogeochemical dynamics in the SCB.    The scientific goals are to resolve the time evolution of the ocean physics and biogeochemistry observed during the CalCOFI cruise periods and to ascertain the processes controlling the evolution and predictability of the physical-biogeochemical SCB system.  Among the Key ESE Research Questions to be addressed here are: How is the ocean circulation varying on interannual and decadal timescales? How can predictions of climate variability and change be improved? How well can transient climate variations be understood and predicted?  How well can long-term climatic trends be assessed or predicted?  The technical goals include improving the data assimilation techniques, biological models and dynamical interpretation of ROMS, which is being used by NASA scientists at JPL in ocean modeling applications.

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