Direct observations of velocity and transport in the passages between the Intra‐Americas Sea and the Atlantic Ocean, 1984–1996

Abstract

Shipboard acoustic Doppler current profiler observations of the velocity in the upper 200 m of the water column collected during 1984–1996 using the National Oceanic and Atmospheric Administration R/V Malcolm Baldrige are used to examine the velocity structure and transport in the passages between the Atlantic Ocean and the Intra‐Americas Sea (IAS). Data were collected during 23 cruises along the following sections: across the Straits of Florida, in the Northwest Providence Channel (NWPC), across the northern passages into the Caribbean Sea (Windward, Mona, and Anegada), across the eastern Caribbean along 63°30′ W, thereby forming a closed quadrangle, and in the Grenada Passage. The Florida Current, the eastern Caribbean, and the Grenada Passage share a similar mean velocity structure characterized by high‐velocity, surface‐intensified flows with strong vertical and horizontal shears. The northern Caribbean passages (NWPC, Windward, Mona, and Anegada) share a different common mean velocity structure, with subsurface velocity maxima directed into the IAS, and surface‐intensified counterflows along one side of each passage. On average, there is a transport balance in the upper 200 m between waters entering and exiting the IAS, with the 16.5±2.4 Sv (1 Sv = 106 m3/s) transport of the Florida Current at 27°N comprised of 0.4±0.8 Sv from the NWPC, 2.2±1.5 Sv from the Windward Passage, 2.8±2.1 and 2.4±2.8 Sv from the Mona and Anegada passages, respectively, and 9.5±4.7 Sv across the eastern Caribbean, for a total of 17.3 Sv. The four passages north of 17°N (from NWPC to Anegada Passage) have a combined transport of 7.8 Sv, nearly half of the transport of the Florida Current in the upper 200 m. Of the 9.5 Sv flowing through the eastern Caribbean between 11°N and 17°N, 4.9±2.6 Sv, or more than half, come from the Grenada Passage. This is significant to the subject of cross‐equatorial exchange of mass, heat, and salt, as the Grenada Passage is where the highest transport of waters originating in the southern hemisphere is thought to enter the Caribbean.