Velocity and transport of the Labrador Current determined from altimetric, hydrographic, and wind data

Seasonal change of velocity and transport in the Labrador Current is studied using 3.5 years of TOPEX/Poseidon altimeter data, in conjunction with concurrent wind data and climatological density data, A method based on the linearized momentum equation is developed, in which vertically averaged velocities and volume transports normal to selected sections across the Labrador Sea are computed with the sea surface being the level of known motion measured by the altimeter. The three data sources have significantly different temporal and spatial scales, and thus a smoothing technique has been applied to ensure their consistency. Error analyses are performed to estimate the uncertainty in altimetric measurements and geophysical corrections and in density data. The seasonal range of the Labrador Current transport from the 300-m isobath seaward to the deepest ocean varies from 17 Sv at the Nain Section to 10 Sv at the Hamilton Section and 5 Sv at the northern Newfoundland Section, with a maximum in winter or fall and a minimum in spring. The barotropic effect associated with sea surface slope is most important over the shelf break and upper continental slope at the Nain and Hamilton Sections. At the northern Newfoundland Section the baroclinic effect associated with density gradients has a magnitude comparable with that of the barotropic effect. The largest baroclinic variability occurs offshore of the main density front over the lower continental slope of the Hamilton Section, The Ekman transport variability forced by local wind stress is negligible.