Physical Oceanography Seminar, April 12

Speaker

Lilian Dove, Postdoctoral Fellow, Brown University

Secrets of the Southern Ocean: Investigating Ocean Ventilation Using Underwater Autonomous Vehicles

Abstract

The Southern Ocean exerts a strong control on global climate as the primary site of both deep water ventilation and subduction of newly formed intermediate water masses. Thirty years of satellite altimetry has shown that eddy kinetic energy (EKE) in the Southern Ocean varies spatially as a result of interactions of the eastward flow of the Antarctic Circumpolar Current with bathymetric features. In high-EKE regions, there is a rich mesoscale O(100 km) eddy field. These eddies stir and strain the surface density field, leading to frontogenesis and generating motions at O(1-10 km) scales, known as the ocean’s submesoscale. Processes at the submesoscale have been shown to play a leading-order role in connecting the ocean interior to the surface, particularly in high-EKE regions of the ocean. However, they have been traditionally difficult to observe and measure due to their small spatial and temporal scales.

Here, I take advantage of the autonomous revolution of oceanography to observe interactions between physics and biology in the Southern Ocean. Specifically, biogeochemical-Argo floats, ocean gliders, and instrumented marine mammals provide the data I use to understand how water exchanges between the surface and interior ocean. Across the Southern Ocean, high subsurface oxygen is correlated with regions of high-EKE, suggesting processes at the submesoscale, shaped by mesoscale stirring, have a defining role in the observed ventilation. This result has implications for the global overturning circulation as well as ecosystem maintenance across the Southern Ocean.