UCLA

The Antarctic cryosphere is undergoing rapid change. The melt of Antarctic ice shelves is accelerating at an unprecedented rate. This acceleration is in large part due to the transport of heat to their base by relatively warm ocean waters. Offshore of these ice shelves, there has been a steep decline in the extent of sea ice that floats in the Southern Ocean. How Antarctic ice shelves and sea ice will evolve in a warming climate is still an area of active research. This thesis leverages theory, numerical simulations, and observations to attempt to better understand the fundamental dynamics of how the ocean and cryosphere interact. The key results are as follows: (i) The net heat transport into ice shelf cavities can be predicted by the large-scale pressure gradient within ice shelf cavities, suggesting the inflow of heat is geostrophically constrained. (ii) Cavities can be broadly separated into "connected" and "disconnected" regimes, depending on whether they are filled with offshore waters, or dense waters formed by polynyas at their entrance. Their regime can be predicted by comparing the competing influences of ice shelf basal melt and sea ice formation on the buoyancy budget at the ice shelf front. (iii) Coherent vortices are ubiquitous features of the sea ice-covered Southern Ocean. In addition, anticyclones are "hotspots" of ocean-to-sea ice heat flux, and make up a significant fraction of the ocean-to-sea ice heat flux around Antarctica. The work in this thesis represents a substantial advance in our understanding of the ocean circulation within ice shelf cavities and improves our knowledge of the pathways of heat from the ocean to sea ice. These findings could aid in the prediction of future changes to the ocean and cryosphere.