HR: 1330h
AN: OS43A-16    [Abstracts]
TI: Three-layer Deep Exchange Between the Atlantic, Caribbean, and Gulf of Mexico
AU: * Sturges, W
EM: sturges@ocean.fsu.edu
AF: Florida State University, Department of Oceanography, Tallahassee, FL 32306-4320 United States
AB: The deep Caribbean Sea is renewed by sporadic flow over the two sills connecting it with the open Atlantic. The deep Gulf of Mexico is then renewed by flow from the Caribbean over the sill between Mexico and Cuba. The obvious question: if all this renewal water is coming in, what is going out? The mean vertical shear associated with the primary upper-layer flow is obvious and robust in historical observations. Surprisingly, this shear continues well below the limiting depth of the Straits of Florida, down to well below 1500 m. Thus there appears to be a three-layer mean deep flow in the Caribbean and the Gulf. The upper-most deep layer flowing into the Gulf is between 800 and 1100 m and is essentially continuous with the primary upper-layer flow. The deepest inflow is from the sporadic renewal just above sill depth. An intermediate (third) deep layer, at depths of approx. 1200 to 1900 m, containing the required mean outflow to achieve mass balance, is found between these first two flows. The transport in these deep flows into the Gulf and in the return flow is slightly less than 1 Sv. These conclusions are inferred from the computed mean vertical shear, conservation of potential vorticity in the deep layers, the observed salinity gradients, and the assumption that there can be no net flow between a density surface that does not pass through the Florida Straits, approx. 800 m, and 2000 m. Maps on surfaces of constant potential density as well as of potential vorticity suggest that deep waters of the Gulf of Mexico, having salinity 34.96 per mil, flow from Yucatan Channel all the way back to Jungfern Passage and leave the Caribbean above the entering deep renewal water. This work was supported by the U.S. Minerals Management Service and the National Science Foundation.
DE: 4512 Currents
DE: 4532 General circulation
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly