Seasonal variability of eddy kinetic energy in the Banda Sea revealed by an ocean model: An energy budget perspective

Seasonal eddy kinetic energy (EKE) variability in the Banda Sea during 1993-2014 is studied from an energy budget perspective, based on the outputs of Ocean Forecasting Australian Model version 3. High EKE is confined within the upper 300 m of the western Banda Sea with the largest intensity exceeding 3 x 103 J/m2 in the northwest monsoon (NWM) season. In this strong EKE region during NWM, eddies derive almost two thirds of their kinetic energy from the direct wind power input (WP), with additional contributions from the barotropic (BT) and baroclinic instability (BC) of the background flow. Both WP and BT modulate the EKE seasonality and drive the peak energy during NWM, while BC strengthens in the southeast monsoon (SEM) season because of the intensified baroclinicity of the upper circulation. The westerly wind bursts associated with the Madden-Julian Oscillation (MJO), together with steep topography, facilitate more cyclonic eddy generation events in the western Banda Sea during NWM. During SEM, EKE becomes relatively moderate across the Banda Sea but with a regional peak to the southwest of the Buru Island, which can be attributed to island wake effect. Over the Banda Sea, WP, BT and BC contribute 74% (42%), 14% (19%) and 12% (39%) of total energy to EKE during NWM (SEM), respectively. The majority of EKE generated is diverged horizontally by pressure work and dissipated by turbulent viscosity, with dissipation depleting the most. This study highlights the importance of both monsoon and MJO wind forcing in generating EKE variability along the pathway of the Indonesian Throughflow.

Automated summary

Seasonal eddy kinetic energy (EKE) variability in the Banda Sea from 1993 to 2014 is studied using an energy budget approach. The study finds that high EKE is observed in the western Banda Sea during the northwest monsoon (NWM) season, with wind power input, barotropic and baroclinic instability contributing to its intensity. The Madden-Julian Oscillation and steep topography facilitate the generation of cyclonic eddies in this region during the NWM season. EKE during the southeast monsoon (SEM) season is relatively moderate, with a regional peak observed to the southwest of Buru Island. The majority of EKE generated is horizontally diverged and dissipated through pressure work and turbulent viscosity.