Submesoscale mixed layer eddy and sea ice interaction

Greig, L. (2024) Submesoscale mixed layer eddy and sea ice interaction. PhD thesis, University of Reading. doi: 10.48683/1926.00117693

Abstract/Summary

Oceanic submesoscale mixed layer eddies (SMLEs) are 0.1-10 km in horizontal scale and are ubiquitous in the global ocean. They are of emerging interest within oceanography due to the key role they play in surface layer tracer transport. In this thesis, the impacts of SMLEs on sea ice cover and air-sea interaction in polar regions are investigated. We set up SMLE-resolving simulations of the partially ice-covered ocean mixed layer (ML) using the MITgcm. The domain (75 km by 75 km at 250 m resolution) is a zonally re-entrant channel with ice-free conditions in the south and ice-covered conditions in the north, representing a lead or the marginal ice zone. 3D simulations with eddies are compared to 2D simulations without eddies. In summer Arctic conditions, eddies are found to decrease sea ice height by 17% (within the meridional extent of the eddies), increase shortwave radiation into the ice-covered region by 20%, and to triple heat transport into the ice-covered region. In Arctic winter conditions, eddies are found to reduce ML deepening by up to 80%. A simple analytical model of eddy-ice interaction is developed and is able to capture many of the eddy-ice interactions found in the MITgcm. I show that the eddy impacts are highly sensitive to ambient conditions. The Fox-Kemper et al. (2008) SMLE parameterisation (FK08) is tested in polar regions. FK08 depends strongly on the choice of ML depth estimate. Specifically, the parameterisation performs well if alterations to the current version are made to account for shallow (meter scale) surface stratification induced by melting in summer. In addition, it is found that FK08 is effective at 250 m (SMLE-resolving) and 9 km resolution (not SMLE-resolving), but it does not perform well at intermediate resolutions where SMLE are only partially resolved, despite being designed to smoothly adapt to resolution changes.

Item Type	Thesis (PhD)
URI	https://centaur.reading.ac.uk/id/eprint/117693
Identification Number/DOI	10.48683/1926.00117693
Divisions	Science > School of Mathematical, Physical and Computational Sciences
Date on Title Page	July 2023
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