Use of satellite-derived CDOM Absorption to estimate ocean mixed layer depths
John
Roland
Moisan, NASA/GSFC, john.r.moisan@nasa.gov
(Presenting)
The seasonal variability in ocean surface Chromophoric Dissolved Organic Matter (CDOM) is primarily due to net loss from photobleaching within the surface mixed layer and net input through entrainment of unphotobleached sub-mixed layer CDOM. This direct relationship between mixed layer variability and CDOM dynamics makes CDOM a novel optical tracer for studies on both CDOM and ocean mixed layer dynamics. A series of increasingly complex CDOM models is presented that aims to demonstrate the role that mixed layer depth variability plays in developing the satellite-observed upper ocean CDOM fields. The model coefficients are derived from observations from a global 2° latitude x 5° longitude resolution data set by individually fitting the coefficients within each if the grids using satellite observations of CDOM, surface wind velocities and shortwave solar radiation and in situ observations (NODC) mixed layer depths. Results from this modeling study are used to estimate deepwater (below mixed layer) CDOM concentrations and the rate at which CDOM is photobleached or degraded from the surface ocean. In addition, variations in the seasonal cycle of CDOM—a potential analog to variations in the seasonal cycle of mixed layer depths—may also be a predictor of the magnitude of annual chlorophyll variations for specific ocean regions whose new production is limited by entrainment of nutrients from depth during the prior wintertime mixing period. Results will be present the skills of several mixed-layer models to use CDOM and other satellite data in order to model the seasonal cycle and interannual variability of CDOM and mixed layer depths. Additional results allow us to determine the turnover times of CDOM in the surface waters of the global ocean and to improve our understanding of CDOM dynamics in the ocean.
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