Abstract

The connection between the current systems and water masses in the Newfoundland Basin and the North Atlantic Subtropical Gyre has been controversial for some time. SOFAR floats have now been launched in the Newfoundland Basin, and others observed to move there. Floats were typically deployed in pairs at nominal depths of 700 m (thermocline level) and 2000 m (deep). A thermocline level float set in the North Atlantic Current near 45N drifted to about 50N before recirculating, whereas a deep float deployed concurrently eventually moved south and west around the Grand Banks. A float pair deployed in the interior of the Newfoundland Basin moved in the mean consistent with a recirculation that transports roughly 15 to 20 × 106 m3 s−1 above 2000 m depth. Three thermocline level floats have drifted from west of the Grand Banks into the Newfoundland Basin, whereas deep floats have not yet been observed to do so. A crude estimate of the implied transport above 2000 m depth branching from the Gulf Stream System into the North Atlantic Current is 15 to 20 × 106 m3 s−1 The evidence points to branching above but not below 2000 m. whereas the recirculation in the Newfoundland Basin penetrates below 2000 m in the float data.The float pair deployed in the interior of the Newfoundland Basin exhibited significantly less energetic eddy motion than the float pair deployed in the vicinity of the North Atlantic Current. The estimated eddy kinetic energy in the thermocline in the North Atlantic Current is comparable to that observed for the Gulf Stream, whereas the deep eddy kinetic energy is notably less. The general structure of the eddy field (and mean flow) points to the type of horizontal or geographical inhomogeneity from strong current to interior regimes similar to that observed for the subtropical gyre.

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