Author(s): Runa A. Skarbo; Renat Yulmetov; Sveinung Loset
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Abstract: Collisions with icebergs are a hazard for ships and offshore structures in the Arctic. Precise iceberg drift forecasting is thus required to assess the probabilities of possible collisions and damage. The conventional methods of forecasting in open water account for the wind and ocean current velocities, sea surface gradients and waves. Forecasting of icebergs in sea ice is challenging, mainly because there is little knowledge about the additional resistance associated with the surrounding ice. In this paper, we study the relative drift of icebergs and sea ice. We investigate two cases in which icebergs and adjacent ice floes were tracked by using GPS in the Greenland Sea in 2013. The icebergs differ greatly in size: the larger iceberg has a mass exceeding 16 times that of the smaller iceberg. Characteristic relative drift velocities are obtained and appear to vary between the cases. The variation is caused by differences in both the iceberg mass and local ice concentrations. A drift forecasting model is proposed and tested by hindcasting and comparing against the measured drift. The model demonstrates an acceptable level of accuracy for short-term forecasting in this region, where knowledge about winds and ocean current profiles is insufficient. In addition, we compare simulations of the model, both with and without the sea ice forcing. Results indicate that sea ice forcing significantly affects the drift of the small iceberg but that it hardly influences the large iceberg. Finally, the presented model provides accurate estimates of the relative drift. The model can be further developed to create an operational model, which would require further testing with more accurate input data and for more case studies.
Year: 2016