Transport variability in the Lanzarote passage (eastern boundary current of the North Atlantic subtropical Gyre)

Abstract

Observations from a four-year current meter mooring at 281440N;131280W in the Lanzarote passage are used todescribe the transport variability of the Eastern Boundary Current of the North Atlantic Subtropical Gyre. Threedifferent water masses are found in the passage: North Atlantic Central Water in the upper levels (roughly 02600 m),Antarctic Intermediate Water (roughly 60021100 m) and Mediterranean Water in the layer above the bottom at1300 m:The mean southward transport of NACW is 0.8+-1.1 Sv (1 Sv=10 9 kg s-1 which is the transport of theeasternmost branch of the Canary Current. Fluctuations of NACW transport are large, ranging from -3:4Svs outhward to 1.7 Sv northward. Every autumn a consistent northward transport is observed, which may be related withthe eastern boundary upwelling dynamics. The mean transports of AAIW and MW are 0.1+-0.4 Sv northward and -0.05 +-0:09 Sv southward, respectively. Fluctuations of transport of AAIW and MW are large, from 1.0 to -1. 0Svand from -0.32 to 0.23 Sv;respectively. Thus, the mass transports for each water mass show a high standard deviationof comparable magnitude to the mean. This highlights the importance of the temporal variability of the currents in this passage. A remarkable feature of our observations is that the mean transports of NACW and AAIW during an El Niño event are significantly different.