[A-OS12] Physical, biogeochemical, and ecological processes and variability in the Indian Ocean

[AOS12-03] On long-lived cyclonic eddies off western Australia

*Peien Xu¹、Zhendong Hu^2,3、Tomoki Tozuka¹、Zhiyu Liu² (1.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo、2.State Key Laboratory of Marine Environmental Science & College of Ocean and Earth Sciences, Xiamen University、3.GEOMAR Helmholtz Centre for Ocean Research Kiel)

キーワード：Mesoscale eddies, Eddy longevity, Southern Indian Ocean, Satellite altimetry

Mesoscale eddies are key features of ocean circulation and play critical roles in the mixing, mass transport as well as energy cascade. Over the last decade, there has been a growing research interest in long-lived eddies due to their significant impact on mass and energy redistribution. This research begins with a global analysis of eddy lifespan, pinpointing the western coast of Australia as a hotspot for generating long-lived (with lifespans ≧ 365 days) cyclonic eddies (LLCEs). Since previous studies have not paid much attention to this phenomenon and have not provided adequate explanations, this study aims to show the distinctiveness of LLCEs off western Australia by comparing them statistically with LLCEs present in other eastern boundary regions. Additionally, this research tries to comprehend the mechanisms that contribute to the longevity of LLCEs by examining their structural characteristics and comparing them with the features of other eddies that have shorter lifespans within the same region. It is indicated that LLCEs off western Australia have distinct structural features that tend to be rounder in shape and have faster speed, larger amplitude, and lower speed contour height. These characteristics suggest that the longevity of LLCEs is associated with strong coherent features and high potential and kinetic energy during their generation phase. This research highlights the uniqueness and necessity of understanding global LLCEs, as well as their longevity mechanisms, especially for the region off western Australia.