1. An analysis of transport and water masses in the Straits of Florida and the Bahamas Moulin Aurélie Moulin Department of Marine and Environmental Systems Florida Institute of Technology Wednesday 17 th, July 2001

2. Background Florida Current originates the Gulf Stream Structure of the water column indicates what is subject to be in the layers Water masses are defined by the area where they are formed

3. Current Circulation in the Intra- Americas Sea (Mooers and Maul, 1993)

4. Previous Studies Numerous studies in the Straits of Florida. Transport evaluated at 25x10 6 m 3.s -1 Variability observed depending on the seasons and topography Water masses in the Straits were already identified, but in the Bahamas they were only assumed

5. Questions addressed How high was the transport in the Straits of Florida in February 2001? How were the velocities distributed across the Straits of Florida? What water masses form the water column in the Straits of Florida and the Bahamas?

6. Significance of the study Fisheries: fish populations, larvae and food are transported within the currents Tourism: marine activities Ship traffic: knowledge of currents path and velocities could save money to large cargo companies Ecosystem conservation and public health concerns: fate and transport of hazardous pollutant depend on the path of currents and water masses present

7. Significance of the study Army: water column structure used for submarine operations Impact on climate: Florida Current originates the Gulf Stream and its consequent heat flux. This warm flow travels through the North Atlantic Ocean and governs the global climate.

8. Study Area 16 sections within the Straits of Florida and the Bahamas, gathering 108 stations Sections across the stream or downstream Depth range from 150m to 4200m

9. Study area

10. Methods – Data collection Hydrographic data collected with a CTD SBE 911 Plus. CTD casts conducted onboard the R/V Walton Smith.

11. R/V Walton Smith Belongs to the Rosentiel School of Marine and Atmospheric Science, University of Miami Catamaran 96ft long, 40ft wide, 5.5ft draft put into commission in February 2000 Designed for shallow and deep water research Features dynamic positioning thanks to bow thrusters, controllable pitch propellers and independent rudders

12. Methods – Data Analysis Using temperature, salinity and density measurements, dynamic heights were calculated. From there velocities were computed and then used to evaluate transport. TS diagrams were drawn to analyze water column structure

13. TS diagram

14. Velocities and transport in the Straits of Florida Mean velocity: 91 cm.s -1 ± 0.34 cm.s -1. Mean transport: 16.2x10 6 m 3.s -1. Cross-sections Velocity (m/s) Transport (m 3 /s) Keys0.59 11.9 x 10 6 Biscayne Bay 0.91 21.2 x 10 6 Miami1.22 15.7 x 10 6

15. Uncertainties in transport

16. Velocities and transport in the Straits of Florida Velocity increasing northward Highest values in the northwestern part of the Straits Reversals noticed at the easternmost stations of Biscayne Bay and Miami sections

17. Velocities and transport in the Straits of Florida Flow coming from the Gulf of Mexico and going northward around the Florida Peninsula Increased velocity due to the narrowing of the Straits and additional flow from Santaren Channel Reversals due to Bahama Bank Topography

18. Water masses analysis Surface variations in cross sections in the Straits of Florida

19. Water masses analysis Same TS diagrams shape for downstream and cross-stream sections in the Bahamas

20. Water masses analysis Same water masses in the Straits of Florida and the Bahamas More variability at surface in the Straits of Florida due to water from the Gulf of Mexico

21. Water column structure Surface layer  maximum temperature Subtropical Underwater  Salinity maximum Large thermocline  North Atlantic Common Water Antarctic Intermediate Water  Salinity minimum North Atlantic Deep Water in the deepest stations  increase in salinity below AAIW Antarctic Bottom Water in the deeper stations  lower temperature

22. Conclusions Transport lower than expected Identical water masses in the Bahamas and the Straits of Florida than in the whole Caribbean Basin

23. Acknowledgments Dr. Olson, RSMAS Dr. Maul, FIT QUESTIONS?