Model-based Analyses of Nitrogen Cycling on the Middle Atlantic Bight Continental Shelf

Tian Tian, Old Dominion University, tian@ccpo.odu.edu
Marjorie Friedrichs, Virginia Institute of Marine Science, marjy@vims.edu (Presenter)
Eileen Hofmann, Old Dominion University, hofmann@ccpo.odu.edu

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 biogeochemical model developed for the U.S. eastern continental shelf were analyzed to assess nitrogen cycling processes. The one-dimensional model includes lower trophic level interactions and is forced by advective fields obtained from a corresponding three-dimensional biogeochemical model. Seven sub-regions of the Middle Atlantic Bight (MAB) were selected for detailed analysis of carbon and nitrogen cycling processes based on Taylor and target diagram analyses, which compared observed sea surface temperature (SST), salinity, and Sea-Wide-Field-of-Viewing (SeaWiFS) derived chlorophyll and particulate organic carbon (POC) with equivalent distributions obtained from the model simulations. Higher correlation coefficients and relatively lower unbiased root-mean-square values were obtained for the SST (R > 0.97) and salinity (R > 0.97) time series, while correspondence between SeaWiFS-derived chlorophyll and POC and the corresponding simulated distributions were less robust. The one-dimensional model suggested regional variability in the skill of simulated depth-integrated primary production (~300 g C m-2 yr-1) and mean euphotic chlorophyll. Low primary production and chlorophyll concentrations during summer in some of the 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 model simulations to 25% variations in 21 parameters was also tested. These analyses provided insights into adjustments that are needed for the rates and parameterizations used to simulate phytoplankton processes, and helped to identify and understand the important biogeochemical processes controlling nitrogen cycling over MAB.

Presentation Type:  Poster

Session:  Coupled Processes at Land-Atmosphere-Ocean Interfaces   (Mon 4:00 PM)

Associated Project(s): 

• Friedrichs, Marjy: Impacts of Changing Climate and Land Use on Carbon Cycling and Budgets of the Coastal Ocean Margin: Observations, Analysis, and Modeling ...details

Poster Location ID: 22