HR: 12:08h
AN: B22A-10 INVITED    [Abstracts]
TI: Atmospheric Cold Fronts Affecting Cold-Water Corals in the Deep Straits of Florida
AU: * Eberli, G P
EM: geberli@rsmas.miami.edu
AF: Comparative Sedimentology Laboratory, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Grasmueck, M
EM: mgrasmueck@rsmas.miami.edu
AF: Comparative Sedimentology Laboratory, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Bang, I
EM: ibang@rsmas.miami.edu
AF: Division of Applied Marine Physics, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Mooers, C N
EM: cmooers@rsmas.miami.edu
AF: Division of Applied Marine Physics, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Viggiano, D
EM: dviggiano@rsmas.miami.edu
AB: The Straits of Florida (SoF) are considered an ideal habitat for cold-water corals with the north flowing Florida Current (FC) providing a continuous supply of food. The FC does, however, not fill the entire Straits and deep, opposing undercurrents and coastal countercurrents occur off Florida and the Bahamas. New observational and model data document that, in addition to the well-known perturbation of upper ocean currents by atmospheric cold front passages, the near-bottom current field in the SoF is also repeatedly perturbed by atmospheric cold fronts none of which is reflected in the cold-water mound morphology. Measurements of the near-bottom flow field by an Autonomous Underwater Vehicle (AUV), cruising 40 m above sea floor at five coral mound fields ranging from 14–48 km2 in 590–875 m water in December 2005, record a complicated current pattern in space and time. Near-bottom currents are bi-directional, dominated by semi- diurnal tides, on the lower slopes of the Bahamas where mounds form kilometer long ridges as high as 120 m. Near-bottom currents flow north in the middle of Straits but generally south along the Miami Terrace. The mound morphology varies widely between sites and no obvious (i.e., direct, linear) correlation exists between current strength and mound height. The 12 to 48 h AUV observational data at each site compare well with results of the quasi-operational 3D ocean circulation model EFSIS (East Florida Shelf Information System). The Model enables the analysis of the bottom currents over extended periods and confirms that the near-bottom flow field in the SoF is highly variable on time scales ranging from 6 hours to several days, with magnitudes of +/- 0.2 to 0.6 m/s, depending upon location. During the observation period of December 2005, a recurring current variability is due to a sequence of deep cyclonic eddies that originate approximately every ten days near Cay Sal Bank and move northward on the eastern side of the FC. Offshore Bimini, where the SoF narrows and shoals, and the FC accelerates, the near-bottom eddies intensify and start to move westward. When reaching the Miami Terrace the eddies occupy the entire water column. The timing of the eddies correlate remarkably well with the passage of atmospheric cold fronts. During cold front passages the FC axis is displaced offshore the Florida Keys. A probable mechanism for the generation of the near bottom cyclones is the interaction of FC meanders with Cay Sal Bank. The impact of these "cold-front" perturbations on the deep-water coral communities remains to be quantitatively assessed.
DE: 0416 Biogeophysics
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0466 Modeling
DE: 0499 New fields (not classifiable under other headings)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting