avijit gangopadhyay with bisagni, gifford and batcheldar (ayan chaudhuri and carolina nobre)

Impacts of Climate and basin-scale variability on the seeding

and production of Calanus finmarchicus in the Gulf of Maine

and Georges Bank

Avijit GangopadhyayWith Bisagni, Gifford and Batcheldar

(Ayan Chaudhuri and Carolina Nobre)

WHOI meeting on June 23, 2008

GLOBEC P4B Results (Gangopadhyay, Bisagni, Batchelder and Gifford)

• The basin-scale North Atlantic model is spun-up using Levitus climatology and forced with adjusted NCEP High and Low NAO fields – 2 validations

• The Gulf Stream position is northward (southward) during High (Low) NAO years

• LSW advection in the GOMGB region during 1997-98 after 1996 Low-NAO

Progress Report and Status

Physical Model simulations are being written up – 1 PhD student; 1 MS student to complete next year.

Biological simulations started

Basin-scale model -- ROMS

1/6 degree resolution; 50 vertical levels

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

Gulf Stream Mean Positions for High and Low NAO Climatology simulations at 5m, 50m, 100m, 200m and 400m

5m

100m

400m

50m

200m

GS mean positions are computed at different depths for both High and Low NAO simulations for comparison and then integrated over the upper 450 m depth.

This four-panel figure shows the density signatures for the month of July during the four years of GLOBEC period in the present model simulation. The yellow region corresponds to the LSW density range of 27.2 through 27.4 σθ. Bluish waters are lighter, and redder waters are heavier than LSW. The advection of LSW in the WNA from 1995 (top-left) through 1998 (bottom-right) is believed to be due to the large drop of the NAO index during 1996. (From Chaudhuri et al., 2008)

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

Basin-Scale Physical Fields

• Are available from• www.smast.umassd.edu/modeling/ROMS.htm• Questions and Concerns: avijit@umassd.edu

3-D fields for GOM 1995-98• 5-day SST• FORMS non-dimensional fields from

Gangopadhyay et al., 2003 study• Supplemental Levitus non-dimensional

profiles for additional slope and shelf water

• Background ROMS runs for 1995-1998• Multiscale Objective Analysis• Coupled Slope Water State analysis