Velocity and Eddy Kinetic Energy of the Gulf Stream System from 700-m SOFAR Floats Subsampled to Simulate Pop-up Floats

Abstract

Velocity and eddy kinetic energy were calculated from SOFAR (sound fixing and ranging) float trajectories using original daily values and values subsampled at intervals of 15, 30, and 60 days to simulate pop-up floats that surface for position fixing at these time intervals. The mean velocity is well reproduced by the 15-day subsampled data. With the 30-day data, the peak velocity in the Gulf Stream is reduced, and its width is increased substantially. With the 60-day data, the Gulf Stream is highly modified, and its southern flanking countercurrent is no longer resolved. Calculated eddy kinetic energy is strongly diminished by subsampling; peak energy in the Gulf Stream of 710 cm2 s?1 using daily values is reduced to 64 cm2 S?2 using 60-day data. Calculated energy in the Sargasso Sea near 25°N, 60°W is reduced from 20 to 8 cm2 s?2. The larger percent decrease of calculated energy in the vicinity of the Gulf Stream, 30°?40°N, is due to energetic higher-frequency eddy motion in this area.