Synthesis & Modeling Project
Dennis McGillicuddy
Valery Kosnyrev
Modeling mesoscale biogeochemical processes in a TOPEX/POSEIDON diamond surrounding the U.S.JGOFS Bermuda Atlantic Time Series

NASA, 36 months

PROJECT DESCRIPTION: The overall goal of the proposed research is to investigate the role of mesoscale dynamics and upper ocean processes on biogeochemical fluxes in the Sargasso Sea. The general approach is to use a three-dimensional coupled physical and biological model together with in situ observations and a full complement of remotely sensed information (altimetry, ocean color, scatterometry and AVHRR) to study the biological and chemical ramifications of spatially and temporally intermittent physical processes. The coupled model system will be configured in a "Topex/Poseidon (T/P) Diamond" surrounding the U.S. JGOFS Bermuda Atlantic Time Series Study (BATS) site.  This implementation will make it possible to prescribe the necessary physical model boundary conditions directly from T/P altimetry. Assimilation of additional data available in the interior (from moorings, BATS hydrography, and ERS altimetry) will facilitate the construction of optimal estimates of the three dimensional structure of the water column as it evolves. These space-time continuous representations of oceanic fields will constitute a novel basis for interpretation of SeaWiFS and OCTS imagery by providing the ability to analyze ocean color variations in the context of the underlying circulation patterns.

A nitrogen based planktonic ecosystem model which has been incorporated into the circulation model will serve as a vehicle for the analysis of the biogeochemical response to physical forcing.  The specific process of interest here is the role of mesoscale eddies in nutrient supply to the upper ocean.  Recent modeling studies (McGillicuddy et al., 1995; McGillicuddy and Robinson, 1997) indicate substantial nutrient flux associated with the formation of cyclonic eddies and subsequent intensification caused by interaction with adjacent features.  Long term simulations in the Sargasso Sea based on statistically realistic mesoscale flow fields suggest that this eddy upwelling mechanism is the dominant mode of nutrient transport in the annual budget for the region.  Data driven coupled physical-biological simulations of the type proposed here will be used to test this hypothesis and thus should help to reconcile the longstanding controversy concerning nutrient supply in the oligotrophic waters of the open ocean. In addition, these hindcast simulations will be used to conduct a retrospective analysis of the BATS data to help differentiate between spatial and temporal variability in the time series record. The possibility of using this interdisciplinary model system in a nowcast/forecast mode to contribute to optimal resource deployment in future observational activities will be evaluated.

DATA: Dennis McGillicuddy has provided software and model results via his website at: http://science.whoi.edu/users/mcgillic/tpd/tpd.html
Or download a TAR of model results (498M).
Model results are also avilable via SMP LAS


McGillicuddy, D.J., Robinson, A.R., Siegel, D.A., Jannasch, H.W., Johnson, R., Dickey, T.D., McNeil, J., Michaels, A.F. and A.H. Knap. 1998. Influence of mesoscale eddies on new production in the Sargasso Sea. Nature, 394, p 263-266.

McGillicuddy, D.J., Johnson, R.J. Siegel, D.A., Michaels, A.F., Bates, N.R., and A.H. Knap. 1999. Mesoscale variations of biogeochemical properties in the Sargasso Sea, J. Geophys. Res., 104, p 13,381-13,394.

McNeil, J.D., Jannasch, H.W., Dickey, T.D., McGillicuddy, D.J., Brzezinski, M. and C.M. Sakamoto. 1999. New chemical, bio-optical and physical observations of upper ocean response to the passage of a mesoscale eddy off Bermuda, J. Geophys. Res., 104, p 15,537-15,548.

Siegel, D.A., McGillicuddy, D.J. and E.A. Fields. 1999. Mesoscale eddies, satellite altimetry and new production in the Sargasso Sea, J. Geophys. Res., 104, p 13,359-13,379.

Garcon, V.C., Oschlies, A., Doney, S.C., McGillicuddy, D.J. and J. Waniek. 2001. The role of mesoscale variability on plankton dynamics in the North Atlantic, Deep-Sea Res. II, 48, p 2199-2226.

McGillicuddy, D.J., Kosnyrev, V.K., Ryan, J.P. and J.A. Yoder. 2001. Covariation of mesoscale ocean color and sea surface temperature patterns in the Sargasso Sea, Deep-Sea Res. II, 48, p 1823-1836.

McGillicuddy, D.J. and V.K. Kosnyrev. 2001. Dynamical Interpolation of Mesoscale Flows in the Topex/Poseidon Diamond Surrounding the U.S. JGOFS Bermuda Atlantic Time-series Site, J. Geophys. Res., 106, p 16,641-16,656.

McGillicuddy, D.J. 2001. Models of small-scale patchiness, In: Encyclopedia of Ocean Sciences - Vol. 5 (S), Steele, J.H., Turekian, K.K. and S.A. Thorpe (eds.), Academic Press, London, pp. 2820-2833.

Sweeney, E.N. 2001. Monthly Variability in upper ocean biogeochemistry due to mesoscale eddy activity in the Sargasso Sea. Masters Thesis, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 72 pp.

Sweeney, E.N., McGillicuddy, D.J. and K.O. Buesseler. 2003. Biogeochemical impacts due to mesoscale eddy activity in the Sargasso Sea as measured at the Bermuda Atlantic Time Series (BATS) site. Deep-Sea Res. II, in press.

RELATED PROJECTS: McGillicuddy  "The role of eddies in basin-scale biogeochemical budgets of the North Atlantic"

McGillicuddy  "Impacts of mesoscale processes on biogeochemical fluxes in the North Atlantic: Basins-scale eddy-resolving simulations"

Dennis McGillicuddy
Department of Applied Ocean Physics and Engineering
Woods Hole Oceanographic Institution
98 Water Street, MS#12
Woods Hole, MA 02543
tel: (508) 289-2683
fax: (508) 457-2194
web site

Valery Kosnyrev
Department of Applied Ocean Physics and Engineering
Woods Hole Oceanographic Institution
Woods Hole, MA 02543
tel: (508) 289-3513
web site