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.