Observation and simulation of a floe drift near the North Pole

Abstract

The drift trajectory of a floe near the North Pole (87° N, 175° W) was observed during 8–19 August, 2010 based on the fourth Chinese National Arctic Research Expedition. The trajectory of the floe showed circular motions superimposed on straight drift. Each cycle had a period of about 12 h. The circular motion is inertial oscillation. The largest amplitude of inertial oscillation speed can reach 20 cm/s. After removing the inertial oscillation, the floe drift direction is about 40° on average to the right of the observed 10-m wind which is much larger than previous reports on the angle between sea-ice velocity and the geostrophic wind, and floe drift moves with a speed of about 1.4 % of the observed 10-m wind speed throughout the whole observation period. A simple dynamic sea ice-ocean coupled model and a three-dimensional sea ice-ocean coupled model are employed to simulate the floe drift. Both numerical models are with the widely used quadratic water-drag formulation, i.e., the stress is proportional to the square of the ice velocity relative to the ocean surface current. The inertial oscillation of the floe is successfully simulated by the simple passive drag model, while the floe drift amplitudes simulated from the three-dimensional model are relatively small.