Strong Eddy Kinetic Energy Anomalies Induced by Baroclinic Instability in the Southwest Region of the Kerguelen Plateau,East Antarctic

Abstract

Eddy activities are particularly prominent in the Southern Ocean due to the instabilities of the Antarctic Circumpolar Current (ACC), which plays a critical role in energy transport of the global ocean. The Indian sector of the Southern Ocean is not only a typical eddy-rich region with strong Eddy Kinetic Energy (EKE) and associated energy conversions among different energy reservoirs (kinetic energy and potential energy of the eddy and mean flow), but also events of extreme EKE. In this study, a systematic energetics analysis framework is employed to examine the notable anomalies of an intensified EKE event observed in the southwest region of the Kerguelen Plateau in 2017 based on a reanalysis product. The EKE anomaly existing at all depths emerges in April, reaches its peak during the austral winter, and persists into the following summer. Energetics analysis indicates that the strong anomalous EKE is primarily determined by baroclinic instability, with distinct governing mechanisms at the surface and in the internal ocean. The anomalous intrusion of warm Circumpolar Deep Water intensifies the baroclinic energy conversion in the subsurface, which contributes to the observed EKE anomalies. Moreover, the anomalous strong wind-induced Ekman pumping serves to amplify the lifting of isopycnals, which enhances the baroclinic instability and subsequently intensifies the EKE anomalies. This study sheds new light on underlying mechanisms governing local polar dynamics and provides insights into the intricate interaction between ocean dynamics and energy distribution in the Antarctic.