Date of Award
2026
Degree Type
Thesis
Degree Name
Master of Science in Oceanography
Specialization
Physical Oceanography
Department
Oceanography
First Advisor
Kathleen Donohue
Abstract
The Antarctic Circumpolar Current (ACC) is the strongest ocean current. As the only current that flows completely around the globe without continental interruption, the ACC forms a barrier separating the subantarctic and Southern Ocean waters. Along its path, the ACC must negotiate several ocean ridge complexes where it becomes unstable and eddy activity increases dramatically. These resulting ocean ‘hotspots’ are sites of elevated cross-frontal fluxes of heat, carbon, nutrients, and freshwater. One hotspot is the Southeast Indian Ridge (SEIR), where the ACC fronts are steered together to navigate narrow fracture zones in the ridge crest.
Using 30 years (1993-2023) of satellite altimetry, we document a statistically significant increase in SEIR sea surface height (SSH) variance of 26% and eddy kinetic energy (EKE) of 39%. These changes are spatially heterogeneous: the standing meander crest has migrated southward, SSH variance has increased most strongly over the second standing meander crest relative to the first crest, and cyclonic eddies have increased in the eastern portion of the region.
We hypothesize that the growing SSH variance in the SEIR region is related to increasing zonal wind stress and a positive Southern Annular Mode during the 30- year time period. Using SSH variance as a proxy for eddy heat flux, we determine that poleward eddy heat flux has nearly doubled in the past 30 years which con- tributes to a 5% increase in circumpolar poleward eddy heat transport. Elevated regions of strong poleward eddy heat flux (EHF) could lead to local along-stream warming and/or increases in air-sea heat fluxes. The SEIR exhibits some of the strongest increases in SSH variance and EHF of any ACC hotspot. Identifying the drivers of this accelerated change and downstream and water-column consequences will be important to understanding the Southern Ocean’s response to a changing climate.
Recommended Citation
Yates, Sophia V., "INCREASING EDDY ACTIVITY IN AN ANTARCTIC CIRCUMPOLAR CURRENT HOTSPOT: THREE DECADES OF CHANGE AT THE SOUTHEAST INDIAN RIDGE" (2026). Open Access Master's Theses. Paper 2742.
https://digitalcommons.uri.edu/theses/2742