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Modelling the evolution of Arctic melt ponds

Scott, F.; (2009) Modelling the evolution of Arctic melt ponds. Doctoral thesis, UCL (University College London). Green open access

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Abstract

During winter the ocean surface at the poles freezes over to form sea ice. Sea ice floats on the ocean surface and has a matrix structure caused by the rejection of salts during freezing. In the summer sea ice melts at its surface creating melt ponds. An accurate estimate of the fraction of the upper sea ice surface covered in melt ponds during the summer melt season is essential for a realistic estimate of the albedo for global climate models. I will present a melt-pond{sea-ice model that simulates the twodimensional (areal) evolution of melt ponds on an Arctic sea-ice surface. This advancements of this model compared to previous models are the inclusion of snow topography, a realistic hydraulic balance and calculation of drainage rates and the incorporation of a detailed one-dimensional thermodynamic model. Water transport across and through the sea-ice surface is described by the major hydraulic processes believed to be present. Thermodynamic processes are modelled using the mushy-layer equations in sea ice, heat diffusion equations in snow and using assumptions of turbulent heat flux in melt ponds, along with a three-layer two-stream radiation model. The model simulates a section of a sea ice floe considered to be in hydrostatic equilibrium, where edge effects such as the presence of leads are neglected and consists of a grid of cells, each of which can be in one of four possible configurations: snow covered ice; bare ice; melt pond covered ice or open water. Eventually, a cluster of adjacent cells each containing melt water may be considered to have formed a melt pond. Lateral and vertical melt water transport is described by Darcy's Law. The model is initialised with ice topographies that represent either first-year or multiyear sea ice, which are reconstructed from SHEBA ice thickness data using standard statistical methods. The roughness and thickness of the ice and snow surfaces were altered and the sensitivity of the model to the initial data was tested. First-year ice and multiyear ice simulations confirmed observed differences in individual pond size and depth. Sensitivity studies showed that pond fraction is most sensitive to mean initial snow depth in first-year ice simulations and reduction of ice permeability in all cases.

Type:Thesis (Doctoral)
Title:Modelling the evolution of Arctic melt ponds
Open access status:An open access version is available from UCL Discovery
Language:English
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Space and Climate Physics
UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Earth Sciences

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