Impact of surface waves on sea ice and ocean in the polar regions
Wave height in the Arctic is increasing and this is expected to continue as summer sea ice cover declines. The summer Marginal Ice Zone (MIZ), an area consisting of severely fragmented sea ice undergoing frequent collisions, is also expanding in the Arctic. Current climate and forecasting models are...
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| Format: | Thesis |
| Language: | English |
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University of Southampton
2017
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| Online Access: | https://eprints.soton.ac.uk/428655/ https://eprints.soton.ac.uk/428655/1/thesis.pdf |
| Summary: | Wave height in the Arctic is increasing and this is expected to continue as summer sea ice cover declines. The summer Marginal Ice Zone (MIZ), an area consisting of severely fragmented sea ice undergoing frequent collisions, is also expanding in the Arctic. Current climate and forecasting models are not adapted to simulate these conditions, yet accurate models are required because of climate change and the increasing human activity in the region. This project aims to improve such models by including wave-related processes that are currently lacking. A main focus is on sea ice rheology. A combined Collisional and Elastic-Viscous-Plastic (EVP) rheology is implemented in an idealised model configuration and in a global sea ice-ocean general circulation model. The combined rheology reflects both the granular behaviour of sea ice in the MIZ and the EVP rheology appropriate for pack ice conditions. This replaces the standard EVP rheology currently used in models. The effect of sea ice floe size, determined by wave break-up and thermodynamics, is also examined using a new floe size distribution (FSD) formulation. Finally, an existing wave mixing formulation is modied to use consistent wave information from the model rather than parameterisations. The combined rheology is found to be capable of maintaining a MIZ at high resolution in idealised simulations due to internal sea ice mechanisms only, while EVP is not. It also aaffects sea ice distribution and motion in the global model. Using a FSD results in a decreased ice thickness and concentration through increased lateral melting. The new wave mixing formulation gives a large decrease in surface roughness resulting in a decreased mixed layer depth. The associated reductions in heat diffusion result in increased ice thickness in large parts of the Arctic. Inclusion of the wave-dependent floe size distribution permits a positive feedback mechanism as wave height increases that can accelerate ice decline. Stronger wave activity will give larger surface roughness and hence ... |
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