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Coastal radars provide new information about sea ice drift

Coastal radars provide new information about sea ice drift

There are tens of coastal radars along the Finnish coast line, which have been established for navigational purposes.

Finnish Meteorological Institute has instrumented three coastal radars for sea ice research. From a sequence of coastal radar images the sea ice drift can be detected in more detailed manner than has been possible with previously used methods. The results of a recently published study show that sea ice drift and deformation responds to changes in air temperature faster than assumed before.

Photo: Tuomas Niskanen

The evolution of sea ice cover is not determined only by the ice growth and melt. Also, the ice dynamics have an important impact on the ice mass. The ice cover is pushed by winds and ocean currents. However, the entire ice pack does not drift uniformly, which leads to fracturing of the ice cover. As a result, leads may open. Also, in the areas where ice floes are compressed, pressure ridges may be formed. These processes, called sea ice deformation, increase the ice mass significantly in winter. New ice is growing quickly in the opened leads, since the ice growth rate is the higher the lower is the ice thickness. On the other hand, the thickest ice is found in the pressure ridges, which can exceed the thickness of 20 meters. Therefore, the sensitivity of the ice cover to drift and deform is an important factor for the evolution of ice mass. Previously, the ice pack's sensitivity to deform has been assumed to vary from cold winter to warm springs and summer as the ice gets thinner, its strength decreases and the areas of open water expand. Now, a clearly faster response was found. This fast response indicates that the intensity of deformations depends also on how quickly cracks and leads are refrozen. This new finding will help to improve current sea ice models to produce realistic sea ice deformations and thereby more accurate estimations of the ice mass.

More information:

Researcher Annu Oikkonen, tel. +358 50 408 6748, annu.oikkonen@fmi.fi

Oikkonen, A., Haapala, J., Lensu, M., Karvonen, J. (2016). Sea ice drift and deformation in the coastal boundary zone, Geophysical Research Letters, 43,  doi:10.1002/2016GL06962.



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