### Lily Greig

**Based at:**University of Reading

Supervisors: David Ferreira (Reading)

Leads are fractures in sea ice. They provide a significant contribution to the polar heat balance despite making up only 5-10% of the sea ice cover, as gradients of sea ice concentration can result in lateral gradients in surface forcing and density gradients in the mixed layer. Through baroclinic instability, these fronts can energise submesoscale eddies. Submesoscale eddies have relatively fast time scales (hours to days), living in a parameter regime with finite Rossby and Richardson numbers. If energised they drive large horizontal exchange between ice-free and ice-covered ocean, and previous work showed that such dynamics could have an order 1 impact on the sea ice melt. Grid scales in the current generation of climate models are greater than the scale of submesoscale eddies and sea ice leads and ignore the effects of the sub-grid scale processes on the net polar heat balance. This project aims to explore these effects. It will start by building a mathematical model to develop understanding of the time and space scales of the density fronts formed under leads. Next it will explore under which conditions the density fronts may become unstable and spawn a submesoscale eddy field. Finally, this project will assess how subsmesoscale dynamics modulate air sea exchanges and if these processes should be included in climate models.

Leads are fractures in sea ice. They provide a significant contribution to the polar heat balance despite making up only 5-10% of the sea ice cover, as gradients of sea ice concentration can result in lateral gradients in surface forcing and density gradients in the mixed layer. Through baroclinic instability, these fronts can energise submesoscale eddies. Submesoscale eddies have relatively fast time scales (hours to days), living in a parameter regime with finite Rossby and Richardson numbers. If energised they drive large horizontal exchange between ice-free and ice-covered ocean, and previous work showed that such dynamics could have an order 1 impact on the sea ice melt. Grid scales in the current generation of climate models are greater than the scale of submesoscale eddies and sea ice leads and ignore the effects of the sub-grid scale processes on the net polar heat balance. This project aims to explore these effects. It will start by building a mathematical model to develop understanding of the time and space scales of the density fronts formed under leads. Next it will explore under which conditions the density fronts may become unstable and spawn a submesoscale eddy field. Finally, this project will assess how subsmesoscale dynamics modulate air sea exchanges and if these processes should be included in climate models.