Master Thesis by Matilde Brandt Jensen – Niels Bohr Institute - University of Copenhagen

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Master Thesis by Matilde Brandt Jensen

Arctic sea ice variability and trends 1979-2007

Abstract:
The variability of the Arctic sea ice cover over the period 1979-2007 is here analyzed, bythe use of different satellite sensor data sets and meteorological reanalysis data. 
An analysis of the sea ice concentration from the newly reprocessed passive microwave data set from OSISAF, reveals highly significant negative trends for the Arctic sea ice extent and area for the period 1979-2007 of -75.2(±9.1)•106km2/year (-7.1(±0.9)%/decade)and -65.6(±7.2)•106km2/year (-8.4(±0.9)%/decade).

The monthly mean sea ice drift speed and deformation rate in a defined region confining the central Arctic Ocean was studied, using the NSIDC Polar Pathfinder ice motion vectors, to evaluate a possible role of dynamic processes in the reduction of ice extent and area. It was found that the sea ice mean speed has substantially decreased over the period 1979-2006, with a trend of 2.2(±0.1)•10-2cm•sec-1•year-1. The strong annual dependence of the sea ice speed is found to have its maximum in November, with to local minimums in March and July, and with a local maximum in May. The monthly mean total deformation rate and shearing rate was also found to have increased over the same period.
Correlations of the sea ice mean speed with the AO index and reanalysis mean wind speeds over the Arctic Ocean, shows no evidence of higher atmospheric forcing. Furthermore, from sea ice backscatter satellite data from the last decade, it was roughly estimatedthat the mount of multiyear ice has diminished over the period 2002-2007, indicating aoverall thinning of the Arctic sea ice cover over that period.

Finally, looking for an explanation to this decrease in multiyear ice area, the southward component of the ice drift out of Fram strait was found to be significantly positive for the monthly means and the seasonal winter means over the period 1979-2000, the latter having a trend of 30.3(±8.7)•10-2cm•sec-1•year-1.
Supervisor: Eigil Kaas, Niels Bohr Institutet