1. Impacts of Climate and basin-scale variability on the seeding and production of Calanus finmarchicus in the Gulf of Maine and Georges Bank
Avijit Gangopadhyay
With Bisagni, Gifford and Batcheldar
(PhD student: Ayan Chaudhuri)
GLOBEC meeting, WHOI
29 October 2007

2. List of Investigators
Avijit Gangopadhyay (PI – Basin-scale physical modeling)
Jim Bisagni (UMass Dartmouth) – Satellite SST field, Hydrographic analysis
Dian Gifford (URI) – Zooplankton data analysis
Hal Batchelder (OSU) – IBM modeling

3. Goals and Objectives
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.

4. Methodology (1)
Set up and run an individual based model (IBM) for the Northwest Atlantic, using the high-NAO ( ) and low-NAO ( ) forced physical fields from an ongoing eddy-resolving North Atlantic simulation.
Perform a set of eddy-resolving basin-scale model simulations during starting from already existing high-NAO simulations (from the ongoing NASA project) and run the IBM to study the interannual variability of C. finmarchicus seeding and production in this region.

5. Methodology (2)
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 ( ), and validate the basin-scale physical and biological fields to develop a broader understanding of C. finmarchicus seeding and production.
Generate four-dimensional high-resolution (5-km) physical fields using basin-scale fields and available data during , 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.

6. Current/Future Work
The High NAO simulation will be used as initial condition to run the ROMS model for GLOBEC years ( )
SOC forcing available from will be used to force the model instead of the NCEP climatology
Model output is used to track the 1998 event of southwestward inflow of Labrador Current
Melding of ROMS with FORMS for using 5-day SST fields
Run IBM for sensitivity tests for different hypotheses
Maybe this slide should be titled model validation?

7. Basin-scale model -- ROMS
1/6 degree resolution; 50 vertical levels

8. Validation Criterion
The Gulf Stream position is northward (southward) during High (Low) NAO years.
The model is spun-up using Levitus climatology for the North Atlantic Basin and subsequently forced with adjusted NCEP High and Low NAO fields.
GS mean positions are computed at different depths for both High and Low NAO simulations for comparison
Maybe this slide should be titled model validation?

9. 50m 5m
200m
100m
We may want to re-organize this slide to look better also I did not include a title.
Gulf Stream Mean Positions for High and Low NAO Climatology simulations at 5m, 50m, 100m, 200m and 400m
400m

10. Upper Layer Integrated Path
Note the surface was not included in the mean
Model simulation validates our hypothesis that GS is northward (southward) during High (Low) NAO years

11. Advection of LSW
1995
1996
1997
1998
Sigma_theta = 27.2 – 27.4

12. Basin-Scale Physical Fields
Are available from
Questions and Concerns:

13. Proposed Biological simulations
Individual-based models (HPB)
Lagrangian pathways
Zooplankton data as initial and validation fields (DG)
Seeding vs. production hypothesis testing
Impact of Labrador water inflow on Slope sea and GOMGB regions

14. Creating high resolution fields
Use Feature oriented regional modeling system (FORMS) for GOMGB (Gangopadhyay et al., 2003; Brown et al. 2007a-b)
270 non-dimensional structure functions for temperature and salinity along and across seven features in the Gulf/Bank
Calibrate with SST 5-day composite (Bisagni’s lab)
Use basin-scale simulations as background
Multiscale Objective analysis will meld basin-to-regional scale fields
Use these high-resolution fields for biological simulations

15. High-Res fields for GOM
SST on 11/26/93
270 Circulation feature – related locations
Synthetic t-s profiles

16. On Pan-Regional Synthesis
Current Basin-scale North Atlantic model will be nested within a CLIMATE-scale model
Retrospective 50-year analysis
Pan-Atlantic synthesis
Atlantic-Pacific comparison when forced with large-scale atmospheric forcing

17. Summary Basin-scale simulations are complete
Advection of LSW during is realized in the model simulation
Will use this set-up to start GLOBEC period high-resolution simulations and nowcasting
Biological IBM towards understanding impact of climate and BSV on calfin seeding and production