Impacts of Climate and Basin-Scale Variability on Seeding and Production of Calanus finmarchicus in the Gulf of Maine/Georges Bank Region

A. Gangopadhyay (UMassD), H. Batchelder (OSU), D. Gifford (URI), J. Bisagni (UMassD)

The proposed work is centered on Calanus finmarchicus populations in the Northwest Atlantic Ocean. It is rooted in the study of basin-scale circulation changes within the western North Atlantic on time scales more than one year, and the combined effects of these changes on C. finmarchicus populations over the entire region, including Georges Bank. Evidence presented below suggests a connection between climate variability, basin-scale circulation, and both physical and biological oceanographic conditions in the Northwest Atlantic.

The primary objective of the research is to probe the connections between Calanus finmarchicus distributions and the physical oceanographic properties, climate variability, and basin-scale circulation changes that are likely to affect the copepod's transport onto Georges Bank. We will do this using a combination of numerical model simulations and observational data.

Intellectual Merit:

The processes linking the Georges Bank, Scotian Shelf, Slope Sea and Gulf of Main ecosystems to climate variability-induced, basin-scale circulation changes caused by large-scale atmospheric effects such as the North Atlantic Oscillation (NAO) appear to occur over at least two different time scales: (1) multi-decadal variability, such as the large multi-decadal variation in Labrador Current transport noted between 1945 and 1990 (Petrie and Drinkwater, 1993; and others), and (2) interannual variability, such as that observed for boundary fluxes of waters entering the Gulf of Maine between 1993 and 1997 (Smith et al., 2001).

In order to address variability over these time scales, we propose to do the following during the two-year duration of the project:

(1) Set up and run an individual based model (IBM) for the Northwest Atlantic, using the high-NAO (1980-1993) and low-NAO (1962-1971) forced physical fields from an ongoing eddy-resolving North Atlantic simulation to understand multidecadal variability of Calanus finmarchicus seeding and production in this region.

(2) Perform a set of eddy-resolving basin-scale model simulations during 1988-1999 starting from already existing high-NAO simulations (from an ongoing NASA project) and run the IBM to study the interannual variability of C. finmarchicus seeding and production in this region.

(3) Analyze long-term in-situ physical and biological datasets and satellite-derived sea surface temperature (SST) along with in-situ physical, biological, and chemical data collected during the GLOBEC core-measurement period (1995- 1999), and validate the basin-scale physical and biological fields to develop a broader understanding of C. finmarchicus seeding and production.

(4) Generate four-dimensional high-resolution (5-km) physical fields using basinscale fields and available data during 1993-1999, and run a series of IBM simulations at higher resolution in order to address questions relating ecosystem variability on the Scotian Shelf, on Slope Sea and within the Gulf of Maine and on Georges Bank to the large-scale fluctuations of the NAO.

Broader Impacts: Our study on the impacts of large-scale climatic and basin-scale forcing on the regional ecosystem of the NWA/GB region will enhance the scientific understanding of such processes. We will train two graduate students during the two years of this project. Results will be disseminated in peer-reviewed scientific publications and presentations at national conferences. We will make the model output and several value-added fields available via a website linked to the GLOBEC Georges Bank website. ]