Iceberg and sea ice drift tracking and analysis off north-east Greenland

Abstract

Drifting icebergs and sea ice floes can be serious threats to offshore structures in the Arctic; however, information about their drift is limited. We performed GPS tracking of 9 icebergs and 10 ice floes in the Kanumas area of the Greenland Sea during 2012–2014. The obtained coordinates were used to analyse the drift trajectories, derived velocities, spectra and relative drift of the icebergs and sea ice. This paper presents statistical data on the drift velocities and demonstrates the differences between drifts in the shear ice zone and the central pack or marginal ice zone. The maximum drift speed reached by an iceberg was 1.66m/s, which happened during strong southerly wind at 66°N. The relative drift of icebergs and adjacent sea ice is strongly dependent on ice conditions and wind, but also it is determined by the different types of applied drag forces. Then, spectral analysis revealed that GPS errors may prevent capturing processes faster than one cycle per hour. In addition, for the first time, we measured the rotation of four icebergs around their vertical axes. Icebergs make an average of between one and two revolutions per day under the periodic tidal current. However, the instantaneous angular velocity reached 0.001rad/s at some moments. Finally, this paper proposes an iceberg drift model including the rotation. The modelling results are in good agreement with the measured evolution of the icebergs’ yaw angles. The drift data and the rotation model can be used when planning offshore activities in the area or as an input for numerical models involving sea ice.