Synthesis & Modeling Project
Modeling mesoscale biogeochemical processes in a TOPEX/POSEIDON
diamond surrounding the U.S.JGOFS Bermuda Atlantic Time Series
NASA, 36 months
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
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.
Dennis McGillicuddy has provided software and model results via his website at:
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.
McGillicuddy "The role of
eddies in basin-scale biogeochemical budgets of the North Atlantic"
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