The Structure and Transport of the Gulf Stream at 73°W

Abstract

Between September 1980 and May 1983, 16 sections of temperature and velocity were obtained with the Pegasus instrument along a transect crossing the Gulf Stream at 73°W. The mean temperature and velocity fields of the upper 2000 meters were calculated. The transport above 2000 meters calculated from the sections had a mean of 87.8 (± 17.3) × 10⁶ m³ s⁻¹. A comparison with mass flux measurements obtained by previous investigators at Cape Fear indicated that the addition to the transport of the Stream in the region was uniform with depth above 800 meters. The mean inflow measured at the Pegasus line was found to be uniform above 800 meters and to decrese substantially below this depth. The increase in transport at the line estimated from the mean cross-stream velocity field was 15.4 (± 5.8) × 10⁶ m³ s⁻¹ per 100 km downstream distance. The temporal fluctuation of the Pegasus transport measurements was consistent with an annual cycle with a maximum in April. The mean eddy kinetic energy at the surface was 1500 cm² s⁻², of which 1000 cm² s⁻² was due to the meandering of the current. The velocity structure of the front was remarkably constant: the eddy kinetic energy attributable to structural changes of the front was SW 500 cm² s⁻², only three times as great as midocean values.