Date of Award

Summer 2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Ocean, Earth and Atmospheric Sciences

Committee Director

Eileen E. Hofmann

Committee Member

Marjorie A. M. Friedrichs

Committee Member

Chester E. Grosch

Call Number for Print

Special Collections LD4331.O35 T49 2011

Abstract

The biogeochemistry of continental shelf systems is an important, but poorly quantified, component of the global cycling of nitrogen and carbon. In this study, simulations obtained from a one-dimensional (ID) biogeochemical model developed for the Middle Atlantic Bight (MAB) portion of the U.S. eastern continental shelf were analyzed to investigate nitrogen cycling processes. The 1D model included lower trophic level interactions and was forced by advective fields obtained from a corresponding three-dimensional biogeochemical model. Taylor and target diagram analyses, which compared in situ measurements of sea surface temperature (SST) and salinity, and chlorophyll and particulate organic carbon (POC) derived from Sea-Wide-Field-of-Viewing (Sea WiFS) observations with equivalent distributions obtained from the model simulations, were used to select sub-regions of the MAB for detailed analysis of lower trophic level interactions and nitrogen cycling with the 1D model. Higher correlation coefficients and relatively lower unbiased root-mean-square values were obtained for the SST (R > 0.97) and salinity (R > 0.97), while correspondence between Sea WiFS-derived chlorophyll and POC and the corresponding simulated distributions were less robust. The 1D model simulations showed regional variability in the skill of modeled depth-integrated primary production (~300 g C m-2 yr-1) and mean euphotic zone chlorophyll. Low primary production and chlorophyll concentrations during summer in some of the MAB sub regions resulted from reduced light availability and stronger stratification. Regional nitrogen budgets constructed from the simulated distributions showed that regenerated production, small detritus remineralization, nitrification, and zooplankton assimilation were lower in these regions by a factor of 1.5 compared with other sub-regions. The sensitivity of the simulations to 25% variations in the value of selected parameters was also tested. These analyses provided insights into adjustments for the rates and parameterizations used to simulate phytoplankton processes, and helped to identify and understand the important biogeochemical processes controlling nitrogen cycling in the MAB continental shelf waters.

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DOI

10.25777/0swb-0x67

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