Principal Investigator: David Bitterman
Collaborating scientist(s):
Mark Bushnell
Bob Roddy
Doug Anderson
Ryan Smith
Objective: To obtain direct measurements of the volume of water passing through the Straits of Florida between the Florida peninsula and the Bahamas.
Rationale: An undersea cable is being used to continuously measure the transport (volume of water flowing) through the Straits of Florida. As sea water flows north, the earth's magnetic field causes an electrical voltage to be generated across the flow. By measuring the voltage difference between one end of the cable near Palm Beach, Florida and the other end at Settlement Point in the Bahamas, the transport can be estimated. In order to calibrate and verify the cable measurements, periodic direct measurements of the transport are made by AOML personnel.
Method: The transport is computed by multiplying the average current by the cross sectional area through which it flows. To estimate the transport through the Straits of Florida, average current measurements are made at 9 fixed locations between Florida and the Bahamas. The cross sectional area is known from the station spacing and the water depth. To measure the average current at each station, a small float is allowed to sink to the bottom where it releases a weight and then floats back to the surface. By measuring the time from release until it resurfaces (DT) and the distance it moves (DX), the average current can be computed (DX/DT). To measure the time and distance accurately, a Global Positioning System (GPS) navigation receiver is mounted in the float which continuously stores position and very accurate time information whenever the float is on the surface.
Accomplishment: A series of 10 - 12 direct transport measurements spaced over a period of 20 to 30 days are made twice each year plus single trip measurements are made several other times to provide sufficient data to evaluate the performance of the cable measurements. The transport measurements have been performed continuously since 1982 and an extensive historical database of the Gulf Stream transport has been developed.
Key reference:

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