Eddy energy sources and mesoscale eddies in the Sea of Okhotsk

TL;DR

This study uses an ocean model to analyze the sources of eddy kinetic energy in the Sea of Okhotsk, highlighting the dominant role of wind stress and baroclinic instability in mesoscale variability, especially along the western boundary.

Contribution

It identifies the primary mechanisms driving mesoscale eddy variability in the Sea of Okhotsk, emphasizing seasonal and regional differences, based on model analysis and observational data.

Findings

Wind stress is the main source of mesoscale variability.

Baroclinic instability dominates over barotropic instability.

Seasonal variation shows maximum EKE in winter and minimum in summer.

Abstract

Based on an eddy-permitting ocean circulation model, the eddy kinetic energy (EKE) sources are studied in the Sea of Okhotsk. An analysis of the spatial distribution of the EKE showed that intense mesoscale variability occurs along the western boundary of the Sea of Okhotsk, where the East-Sakhalin Current extends. It was found a pronounced seasonally varying EKE with its maximal magnitudes in winter, and its minimal magnitudes in summer. An analysis of the EKE sources and the energy conversions showed that time-varying (turbulent) wind stress is a main contribution to mesoscale variability along the western boundary of the Sea of Okhotsk. The contribution of baroclinic instability to the generation of mesoscale variability predominates over that of barotropic instability along the western boundary of the Sea of Okhotsk. To demonstrate the mechanism of baroclinic instability, the circulation was considered along the western boundary of the Sea of Okhotsk from January to April 2005. An analysis of hydrological conditions showed outcropping isopycnals and being strong vertical shear of the along-shore velocity from January to May 2005. In April, mesoscale eddies are observed along the western boundary of the Sea of Okhotsk. It was established that seasonal variability of turbulent wind stress and the baroclinic instability of the East-Sakhalin Current are major reasons of mesoscale variability along the western boundary of the Sea of Okhotsk.