Investigation of ice formation and water mass modification in eastern Laptev Sea polynyas by means of satellites and models.

Krumpen, Thomas (2010) Investigation of ice formation and water mass modification in eastern Laptev Sea polynyas by means of satellites and models. (Doctoral thesis/PhD), Jacobs University Bremen, Bremen, X, 131 pp. DOI hdl:10013/epic.37102.d001.

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Abstract

Salt expelled during the formation of ice in polynyas leads to a downward precipitation of brine that causes thermohaline convection and erodes the density stratification of the water column. In this thesis we investigate by means of flux models and satellite data the ability of the Western New Siberian (WNS) flaw polynya to modify the stratification of the water column and to form saline bottom water. The accuracy of existent microwave satellite-based polynya monitoring methods is assessed by a comparison of derived estimates with airborne electromagnetic ice thickness measurements and aerial photographs taken across the polynya. The cross-validation indicates that in the narrow flaw polynyas of the Laptev Sea the coarse resolution of commonly used microwave channel combinations provokes errors through mixed signals at the fast and pack ice edges. Likewise, the accuracy of flux models is tested by comparing model results to ice thickness and ice production estimates derived from high-resolution thermal infrared satellite observations. We find that if a realistic fast ice boundary and parameterization of the collection depth H is used and if the movement of the pack ice edge is prescribed correctly, the model is an appropriate tool for studying polynya dynamics and estimating associated fluxes. Hence, a flux model is used to examine the effect of ice production on the
stratification of the water column. The ability of the polynya to form dense shelf bottom water is investigated by adding the brine released during an except ionally strong WNS polynya event in 2004 to the average winter density stratification of the water body. Owing to the strong density stratification and the apparent lack of extreme polynya events in the eastern Laptev Sea, we find the likelihood of convective mixing down to the bottom to be extremely low. We conclude that the recently observed breakdown of the stratification during polynya events is therefore predominantly related to wind- and tidally-driven turbulent mixing.

Document Type: Thesis (Doctoral thesis/PhD)
Thesis Advisors: Gerdes, Rüdiger and Thomsen, Laurenz
Keywords: Climate Sciences; Marine physics; Sea ice physics; Sea ice - atmosphere - ocean - ecosystem interactions; Arctic Ocean; Laptev Sea; Polynya
Research affiliation: AWI
Open Access Journal?: Yes
DOI etc.: hdl:10013/epic.37102.d001
Projects: Polynya, Laptev Sea System
Date Deposited: 17 Dec 2014 11:39
Last Modified: 17 Dec 2014 11:39
URI: http://oceanrep.geomar.de/id/eprint/26568

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