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Patrick F. Cummins, Lawrence A. Mysak, and Kevin Hamilton

Abstract

The Rossby wave field generated by the annual cycle of the observed wind stress curl over the North Pacific Ocean (15°N–53°, 100°W–175°E) has been obtained through numerical integration of the linearized, reduced-gravity vorticity equation in spherical coordinates. The dominant source region of Rossby waves is adjacent to the eastern boundary between 20°–44°N. More specifically this source is shown to be made up essentially of two distinct parts: a southern region off California-Baja California, which was first identified by White and Saur, and a northern region corresponding to a generation area first proposed by Mysak. In addition, a second, midocean generation region has been identified over the central North Pacific from 35° to 45°N, 150° to 160°W.

The behavior of the model is strongly affected by wave refraction due to the variation of phase velocity with latitude as described in Schopf et al. As waves emanate from the eastern boundary they are refracted such that the wavenumber vector, initially aligned zonally, becomes reoriented to the northwest. Associated with this is a turning of the group velocity vector and of wave rays towards the southwest.

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Peter Hamilton, Jimmy C. Larsen, Kevin D. Leaman, Thomas N. Lee, and Evans Waddell

Abstract

Transports were calculated for four sections of the Florida Current from Key West to Jupiter, Florida, using a moored current-meter array and voltages from cross-channel telephone cables at the western and northern ends of the Straits of Florida. In addition, moored arrays were used to estimate transport through the Northwest Providence, Santaren, and Old Bahama Channels that connect the Florida Current to the southwestern part of the North Atlantic Ocean. Transport measurements were obtained for an 11-month period from December 1990 to November 1991. Mean transports of ∼25 Sv (1 Sv ≡ 106 m3 s−1) for the flow across the western ends of the straits, which agree quite well with recent estimates of 23.8 ± 1 Sv entering the Gulf of Mexico through the Yucatan Channel, were obtained from both the Key West to Havana cable and the moored array. This estimate is about 5 Sv less than the generally accepted transport through the northern end of the straits at 27°N. This difference was partially accounted for by inflows through the side channels with more transport from the Old Bahama than the Northwest Providence Channel. The variability in the southern part of the straits was larger than at 27°N and included large diversions of the Florida Current south of the Cay Sal Bank and into the Santaren Channel that were caused by large meanders of the flow. The variability of transport in the side channels contributed to the variability of the Florida Current and reduces the correlations of the transports at the ends of the straits. Therefore, the well-measured transport at 27°N is not an accurate indicator of the transport of the Loop Current out of the Gulf of Mexico.

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