Influence of topography and winds on the distribution of water masses on the Antarctic Continental Shelf
Chris Bull (Northumbria University, Newcastle)
| When |
Nov 10, 2023
from 11:00 to 12:00 |
|---|---|
| Where | Amphi PC |
| Contact Name | Louis Couston |
| Attendees |
Chris Bull |
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The Antarctic Slope Front determines how much warm water flows onto the continental shelf and the subsequent heat that is available to melt Antarctica's ice shelves. This talk explores the impact of basin geometry and wind shifts on the large-scale ocean circulation around Antarctica's continental shelf with a focus on understanding changes in shelf temperature near an imagined Ice Front. As the shelf temperature changes are largely driven by ocean circulation changes, understanding these becomes our focus.
This talk uses a primitive equation ocean model to explore how the circulation regime and changes in surface stress influence the temperature structure on Antarctica's shelf seas. A simple barotropic model is used to describe the linear theory of the difference between throughflow and gyres regimes, and their expected response to changes in forcing. This theory informs our understanding of the barotropic circulation response of the primitive equation model where a momentum budget confirms that over the simulated equilibrated timescales with surface forcing changes, the response is first-order linear. Consistent with previous findings, we find that climate change projection-like wind shifts (stronger westerlies that shift south) have a direct influence on Ekman processes across the shelf break and upwell warmer waters onto the shelf. We also find that the circulation regime (throughflow or gyre -- determined by basin geometry), influences the mean shelf temperature and how susceptible the existing shelf temperatures are to changes in surface stress. While the throughflow regime can experience a complete transition in on-shelf temperatures when the transition between westerly and easterly winds shifts southward, we find relatively modest bottom intensified warming at the Ice Front in a gyre regime. Wind perturbation simulations suggest why some regions are more sensitive to shifts in winds than others. These findings highlight an underappreciated yet fundamentally important topographical constraint under future changes in winds.