Physical Oceanography of Georges Bank and Its Impact on Biology Update – June 2004 Grant Period: 7/02-7/05 Bob Beardsley, Ken Brink, Dick Limeburner, Jim Churchill, Jim Ledwell, Jim Irish, Mike Caruso, Jim Lerczak (WHOI) Charles Flagg (BNL) Changsheng Chen, Jim Bisagni (UMD) Ron Schlitz (NMFS)

Primary Objectives 1)To understand the physical dynamics and interactions of several specific processes (e.g., the seasonal evolution of stratification on the Bank, the crucial flow field over the Northeast Peak, and cross- frontal exchange within the tidal mixing and northern flank fronts) that are thought to play critical roles in zooplankton and fish recruitment. 2)To combine these observationally based process synthesis studies into model-based studies to provide our best descriptions of the Bank's physical environment and its variability on time scales from minutes to monthly to seasonal for the GLOBEC field years. 3)To provide other Phase IV investigators with as complete a description and understanding of the basic physical processes affecting their observations as possible.

Activities 1.JGR-Oceans Special Section 2.Environmental Chronology Stratification and Flow Synthesis 4.Process Studies and Interannual Variability on Bank Edges Tidal Mixing Front over Southern Flank 6.FVCOM Development, Application, and Evaluation

U.S. GLOBEC: Physical processes on Georges Bank JGR-Oceans Special Section GLOBEC (Georges Bank), Nov Stratification Study: surface forcing; temperature & salt balances; bottom stress & tidal boundary layer; slope water intrusions Frontal Studies: northern flank tidal & subtidal variability, cross-frontal fluxes and mixing. 1997, 1999 Scotian Shelf Water “cross-overs”: spring 1997; winter-spring Bank/Seasonal Scale: surface drifter flow; ADCP flow. Seasonal/interannual Scale: Halifax section variability; Nitrate supply and new production on GB Model Process Studies: diurnal heating on GB stratification; wind- forced cross-front exchange on GB; temperature and flow influences on Calanus in Gulf of St. Lawrence and Scotian Shelf

,14 4,5,6,7,8,11 9,10, 1,2,15

Environmental Chronology 1.Processing of 1999 Eastern Flank Frontal Exchange moored array and drifter data completed (Limeburner) 2.Reprocessing of Long-Term moored array data completed (Irish, Caruso, Limeburner, Beardsley) 3.Preparation of WHOI Tech Report on LT data set including description of the measurements at all sites plus a physical chronology at the Southern Flank site (Irish, Caruso, Beardsley - July 2004 completion date!!!) 4.Analysis of LT moored data started (Brink)

GLOBEC moored arrays

1999 Stratification and Flow Synthesis 1.Characterization of subtidal oscillatory flow (Limeburner) 2.Description of eastern flank physical variability based on LT and FE moored data to be started (Beardsley, Limeburner,Flagg) Process Studies and Interannual Variability on Bank Edges 1.Seasonal and Interannual Variability of the Shelf-Slope Front Between 75° and 50° W (Bisagni) 2.Instability of Northern Flank Jet Study started (Brink, Pringle)

1999 Tidal Mixing Front over Southern Flank 1.Analysis of TMF ADCP array (Lerczak, Schlitz) 2.Analysis of 1999 Ledwell tracer release experiment started (Churchill,Ledwell) FVCOM Development, Application, Evaluation 1.GoM MM5 developed to produce surface forcing for 1995 and 1999 (Chen, Beardsley) 2.FVCOM simulation of 1995 and 1999 stratification seasons completed (Chen) 3.FVCOM comparison with other coastal models (POM, ROMS) on test problems (Chen, Cowles, Hedstrom, Beardsley) 4.FVCOM simulation for Houghton 1999 tracer release experiment completed (Chen, Houghton, Beardsley) 5.First FVCOM Users’ Workshop - June 2004 (Chen, Cowles, Beardsley)

Next Activities (Incomplete Draft 6/21) 1.Complete LT moored array Tech Report (Irish, Caruso, Beardsley) 2.Write up analysis of 1999 TMF ADCP array (Lerczak, Schlitz) 3.Write up Houghton 1999 tracer release FVCOM results (Chen,….) 4.Start analysis of Ledwell 1999 tracer release data (Churchill, Ledwell) 5.Complete LT moored array analysis, description of 1999 Eastern Flank variability (Brink, Limeburner, Flagg, Beardsley) 6.Evaluate FVCOM 1995 and 1999 stratification season simulations (Chen, Beardsley, …) 7.Complete northern flank jet instability study (Brink, Pringle, Chen) 8.Continue FVCOM development and scientific testing 9.Others ????

The FVCOM GOM/GB Physical Model Wind stress, heat flux GOM/GB MM5 Real-time tidal forcing River discharges Scotian shelf water input SST Hydrographic survey CTD ADCP Moored current meter data Assimilation Boundary forcings Meteorological forcing The 1995 and 1999 GOM/GB Model Experiments

Primary GLOBEC Data Sets Data TypeObservation AreaObservationsContact PersonData Status SatelliteRegionAVHRRBisagniOnline CTDRegionT/S/Fluor/X/PAR/ O18 MountainOnline ShipboardRegionT/S/Fluor/Met/AD CP FlaggOnline (Met?) MooringS FlankT/S/UV/Met/BP/ ADCP/BO Irish/Limeburner, Schlitz, Beardsley Some online G S ChannelT/S/UV/ADCPSchlitz CrestT/S/BOIrish/Limeburner NE PeakT/S/UV/ADCP/ME T/BO Irish/Limeburner SE FlankT/S/UVSmithOnline NE ChannelT/S/UVSmithOnline Scotian ShelfT/S/UVSmithOnline Browns BankT/S/UVSmithOnline DriftersRegionARGOSLimeburnerOnline S&N FlanksGPSChurchill Dye StudiesS&N FlanksDye spreadingLedwell, Houghton

1. FVCOM application and evaluation Realistic simulations (tidal forcing, surface forcing (stress, Q, E-P), runoff, upstream forcing (Fss) Process studies (diurnal heat flux on stratified tidal rectification; cross-front exchange across NF frontal jet) Evaluation (comparison of time series, event behavior (Jan-Feb,1995; Apr-Jun,1999), statistical comparisons)

3. Stratification and Flow Use FVCOM to hindcast currents and T,S stratification during GLOBEC field years Feb-Aug 1995 (can FVCOM predict accurately flow over 1-8 months; extend SF T/S budget analysis to other parts of Bank) Jan-Jun 1999

4. Process Studies and Interannual Variability on the Bank Edges Analysis of existing data for NF, NE Peak, NE Channel, Scotian Shelf to provide synoptic pictures of physical properties and biological content of NEP region FVCOM simulations 1999 (realistic surface forcing; effect of WCRs on SSCs; effect of alternative wind stress on surface cross-front Ekman transport)

5. Tidal Mixing Front over Southern Flank Detailed analysis of 1999 TMF physical data (moored, shipbroad, dye, ….) FVCOM simulation of Mar-Jun 1999 TMF results (test of MY mixing through dye studies, VPR, drifters,..) Extension to 1997 and 1995 periods of extensive SF TMF sampling

Proposed Work - Year 1: Complete FVCOM dev & diurnal heating/tidal mixing front process study (1) Physical component online environmental chronology (2) Synthesis of 1999 bank-wide stratification data (3) Assessment of interannual variability for SSCs on Northeast Peak from historical hydrographic database (4) Synthesis of 1999 southern TMF physical/biological data (5) Analysis of structure, variability, and loss potential of SSF (3, 4) Start Realistic FVCOM simulations of 1995, 1999 stratification seasons (1, 3) Realistic FVCOM simulation of 1999 dye dispersion/mixing data (5) Process FVCOM studies of frontal exchange mechanisms along northern flank (1)

Year 2: Complete Assessment of SSC interannual variability using satellite SST and TOPEX/Poseidon altimeter data Evaluation of FVCOM 1995 and 1999 seasonal simulations Evaluation of FVCOM 1999 tidal mixing front simulations Process FVCOM studies of interannual variability for SSCs using a linear superposition of wind and upstream perturbations to the mean circulation Combined analysis of towed, shipboard, and moored acoustic descriptions of zoo-plankton distributions

BIO Work Plan Topic A: What are the impacts of Scotian Shelf Cross-overs on the population dynamics of the target species? Model studies of interannual variability of SSC events, including analysis of historical hydrographic data and altimetry and modeling of interannual drift variability using Chen’s model (Brickman, Smith, Han, Hannah) Model study of physical mechanisms driving SSCs (Smith, Brickman). ELS modeling of cod and haddock in SSCs,including effects of temperature, food supply, etc on growth and survival, and possibly demographics of adults stocks. (Brickman, Frank). Topic C: How do large-scale interannual and interdecadal variabilities affect population dynamics of the target species? Analysis of upstream sources of water masses and biota, including historical hydrographic data, freshwater sources, etc. (Smith, Hannah, Loder) Study of interannual variability of sea level (‘92-’00) using TOPEX/POSEIDON altimetry (Han, Smith, Loder).

SSF GSNW