Browsing by Author "Kokkonen, Iiro"

The Kara Sea is part of the seasonal sea ice zone in the Arctic, where the warming climate is rapidly changing the sea ice regime. The warm Atlantic water transported through the Barents Sea has a strong influence on the ice conditions in the northern Kara Sea. In this thesis, trends and interannual variability in sea ice conditions in the Kara Sea area studied. For this purpose, coupled sea ice-ocean model NEMO-LIM3 and sea ice concentration datasets derived from passive microwave satellite observations (SMMR, SSM/I and SSMIS) are used. Additionally, the model performance is assessed by comparing its output with the observations. The ice coverage examined in regional and local scales shows negative trends in all months in 1978-2015. The interannual variability of the total ice covered fraction increased in winter and spring when the ice regime shifted from full to partial ice cover over the sea. Meanwhile the variability in summer and autumn decreased. The annual ice free time rapidly extended in the area north of Novaya Zemlya where the warm Atlantic water enters the Kara Sea. The mean sea ice thickness, based on the sea ice-ocean model data in 1997-2015, has become thinner in all months. The model is generally in good agreement with the observations, with the exception of the northern Kara Sea where the model underestimated heat advection. The findings confirm that the sea ice conditions in the Kara Sea have changed towards a new regime with shorter and more variable ice seasons.