Velocity and transport variability of the Labrador Current using TOPEX/Poseidon and hydrographic data

TOPEX/POSEIDON altimeter data from 1992 to 1996 are analyzed in conjunction with density and wind data to examine currents and transports in the Labra dor Sea, with a focus on the seasonal variability of the Labrador Current. A method based on the linearized momentum equations is developed, in which vertically averaged velocities normal to selected sections are computed wit h the sea surface being the level of known motion measured by the altimeter . The Labrador Current transport from the 300-m isobath seaward has seasona l ranges from 17 Sv at the Nain Section, to 10 Sv at the Hamilton Section a nd 5 Sv at the Newfoundland Section, with a maximum in winter/fall and a mi nimum in spring. The barotropic effect associated with sea surface slope is most important over the shelf break and upper continental slope at the Nai n and Hamilton Sections, and has a magnitude comparable to that of the baro clinic effect associated with density gradients at the Newfoundland Section . The contribution from the Ekman transport forced by local wind stress is negligible. A mean transport of 23 (+/-10) Sv in the Labrador Current (shor eward of the 2500-m isobath) and 50 (+/-23) Sv in the basin-scale circulati on of the Labrador Sea are obtained, which are comparable to the results of some numerical models. (C) 1999 Elsevier Science Ltd. All rights reserved.