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Local and deep-ocean forcing contributions to anomalous water
properties on the WFS
Robert Weisberg and Ruoying He
College of Marine ScienceUniversity of South Florida
St. Petersburg, FL
HYCOM P.I. Mtg.8/19/03
Approach
A Coordinated Program of:
1) In-situ Measurements:(Sea level, Currents, Winds, Surface heat fluxes, Rivers,
Temperature, Salinity, Nutrients, Primary productivity andother biological indicators)
and
2) Models:(Ocean Circulation and Ecology)
Desoto Canyon
Loop Current
Mississippi River
Mobile River
Apalachicola RiverSuwannee River
Hillsborough River
Shark River
Peace River
Wind
Heat FluxLocal forcing:Local forcing:•• WindsWinds•• Surface heat fluxSurface heat flux•• River runoffsRiver runoffs
Deep Ocean forcing:Deep Ocean forcing:•• Loop Current and Loop Current and adjacent wateradjacent water
Loop CurrentLoop Current
To simulate the Loop Current interacting with the To simulate the Loop Current interacting with the shelfshelf--break, we control S.L. along the boundary.break, we control S.L. along the boundary.
Up and Downwelling
sequence at theDeSoto Canyon
Transect
Type 1June 2000
Loop CurrentLoop Current
(1) (2) (3) (4)(1) (2) (3) (4)
10 years Time series of Topex/Poseidon Data10 years Time series of Topex/Poseidon Data
25o N
Loop CurrentLoop Current
Track 26
Track 26
Type 2
(1) October 1996 October 1996 –– February, 1997February, 1997(2) June 1997 (2) June 1997 –– November 1997November 1997(3) March 1998 (3) March 1998 –– July 1998 July 1998 (4) September 1998 (4) September 1998 –– November 1998November 1998
Hetland R.D. et al , A Loop Current induced jet along Hetland R.D. et al , A Loop Current induced jet along the edge of west Florida shelf, the edge of west Florida shelf, Geophys. Res. LettGeophys. Res. Lett. 1999. 1999
Local forcing onlyLocal forcing only Local forcing + LCLocal forcing + LC
Bottom Ekman layer currents transport these waters to the coast.
18º
(A)(A)
(B)(B)
Cold, nutrient-rich water upwells onto the shelf by thecombined effects of local and LC forcing.
Lagrangian trajectories for near bottom,
neutrally buoyant particles released
on the 50m and 100misobaths in
summer 1998
Vertical Velocity at mid-depth on 05/15/98
Vertical Velocity alongSarasota Transect on05/15/98
OI analysis of EDAS and Buoy windsOI analysis of EDAS Winds
Model and observed across-shelf momentum analysis
Modeled and observed along-shelf momentum analysis
Summary1. WFS currents result from both local and deep-ocean
forcing.
2. Deep-ocean forcing sets the height of materialisopleths at the shelf-break and under specialconditions can also set shelf currents in motion.
3. Local forcing drives offshore properties onto the shelf.
4. The bottom Ekman layer is the conduit for the across-shelf transport of nutrient rich waters upwelled at the shelf-break.
5. Inter-annual variations in local and deep-ocean forcing cause inter-annual variations in WFS ecology.
References and WebsitesWeisberg, R.H. and R He (2003). Local and deep-ocean
forcing contributions to anomalous water properties on the West Florida Shelf. J. Geophys. Res., 108, C6, 15, (doi10.1029/2002JC001407).
Walsh, J.J. et al. (2003). Phytoplankton response to intrusions of slope water on the West Florida Shelf. J. Geophys. Res., 108, C6, 21, (doi10.1029/2002JC001406).
Data and other products from R.H. Weisberg’s group at USF
http://ocg6.marine.usf.edu
Real time data from the COMPS Programhttp://comps.marine.usf.edu
Some Other Activities
1. A SEA-COOS domain modeling effort.
2. Application of a finite volume model to the WFS for the purpose of linking the estuaries with the shelf.
3. Comparative hindcast studies using POM, FVM, and ROMS.
Tampa Bay
Charlotte Harbor
Zoom view of Tampa Bay, Charlotte Harbor, and the inner-shelf