Inertial oscillations of Fletcher's Ice Island (T-3)

Abstract

Observations with improved Roberts current meters, tethered drogues, and fathogram highlights are used to show that Fletcher's Ice Island (T-3), in the Arctic Ocean, often moves in clockwise circles with a diameter of about 1 km and a period of about 12 hours. The motions are inertial oscillations which represent the transient response of a floating ice mass to changing wind stress. Since the winds are often fluctuating, T-3 responds often with inertial motion. The following arguments indicate that these motions are inertial oscillations: (1) the period of the motions is closer to the inertial period, at this latitude, of 12.05 hr than it is to the lunar semidiurnal tidal period of 12.42 hr; (2) the amplitude of the periodic motion and the local wind speed are closely correlated; (3) the phase of the motion changes irregularly with time; and (4) the motion is restricted to the ice and to the uppermost layers of water.