Variability of Near-Surface Currents Observed during the Pole Experiment

Abstract

Variability of near-surface Currents over a 20-Day period in a 15O km diameter region of the central North Pacific is described using vertical profiles from a current meter and the tracks of 25 drifting buoys. Energetic fluctuations of order 0.10 m s?1 having time scales of a few days and vertical scales in excess of 100 m were found, apparently coherent with the wind forcing. Buoy tracks disclose a small-scale (<15 km) short-period (less than a few days) variability with speeds of the order 0.05 m s?1 and an energetic mesoscale motion with speeds of the order 0.07 m s?1, space scales of the order 40 km and time scales exceeding 20 days. Additionally, the difference between the mean current observed over the experiment. having a speed of aboutO.03 m s?1, and the climatological norm inferred from ship-drift. with a speed of about 0.10 m s?1, suggests a larger scale variability not adequately resolved.