Scotian Slope circulation and eddy variability from TOPEX/Poseidon and frontal analysis data

Abstract

Sea level observations from TOPEX/Poseidon (T/P) altimetry, in conjunction with concurrent frontal analysis data from infrared imagery, are used to study temporal and spatial variability of sea‐surface currents over the Scotian Slope. Geostrophic surface current anomalies normal to ground tracks are derived from the sea level anomalies relative to local means for the study period. The altimetric results reveal prominent spatial variability of cross‐track currents with an overall intensification toward the west and south, typically 20–30 cm/s over the upper and lower slope, 20–50 cm over the continental rise, and up to 70–75 cm/s near the Gulf Stream northern wall. A rapid westward intensification on the western slope contrasts with nearly uniform distribution on the eastern slope. The intensification seems to be associated with the high occurrence of Gulf Stream warm core rings (WCR) and with the close proximity to the Gulf Stream. Crossover analyses of altimetric current anomalies indicate that the total current variability can be estimated by a factor of 1.5 from the cross‐track current variability and the variance is isotropic to within 14%. The rotational speed of the Gulf Stream rings can reach 1–2 m/s over the Scotian Slope, with the root‐mean‐square variability of ∼60 cm/s. The relative vorticity of the interior core is estimated to be ∼1.5 ×10−5 1/s. When combined with CTD data, T/P observations can produce the vertical profile of the total geostrophic current that is in approximate agreement with ADCP measurements.