Dynamics of Interannual Eddy Kinetic Energy Variability in the Sulawesi Sea Revealed by OFAM3

• Published in: Journal of geophysical research. Oceans Vol. 127; no. 8
• Main Authors: Hao, Zhanjiu, Xu, Zhenhua, Feng, Ming, Zhang, Peiwen, Yin, Baoshu
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-08-2022
• Subjects: Annual variations; Barotropic instability; Barotropic mode; Boundary currents; Bridges; Coastal currents; Dynamics; Eddies; Eddy currents; Eddy kinetic energy; Energy; Energy conversion; Flow stability; Forecasting; Geophysics; Indonesian Throughflow; interannual variation; Interannual variations; Intrusion; Kinetic energy; Loop Current; Marginal basins; Marginal seas; Mathematical models; Mesoscale eddies; mesoscale eddy; Mesoscale phenomena; Mindanao Current; Nonlinear dynamics; Nonlinear systems; Ocean circulation; Oceans; Pacific western boundary current; Retroreflection; Sulawesi Sea; Undercurrents; Variability; Variation; Western boundary currents; New Guinea; Australia; Sulawesi; Indonesia
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2022JC018815

Interannual variations in eddy kinetic energy (EKE) in the Sulawesi Sea and their driving mechanisms are investigated based on the outputs of Ocean Forecasting Australia Model version 3 from 1979 to 2014. The interannual EKE variability is found to be primarily modulated by the Mindanao Current intrusion transport (MCIT). By regulating the intensity of barotropic instability of the cyclonic loop current in the Sulawesi Sea, the MCIT fluctuation leads to the downstream interannual EKE variations. Further analysis suggests that the paths of Mindanao Current (MC) and New Guinea Coastal Current and Undercurrent (NGCC/NGCUC) influence the interannual MCIT variability. During high‐EKE periods, the NGCC/NGCUC is weakened, and the MC retroflection extends to south of 5°N, which causes MCIT to increase by 0.60 Sv and strengthens the barotropic energy conversion from mean kinetic energy to EKE in the Sulawesi Sea. During low‐EKE periods, the NGCC/NGCUC is intensified whereas the MC retroflection retreats to a northernmost path, resulting in a decrease of 0.58 Sv in MCIT and thus a low EKE level. In addition, mesoscale eddies to the east of the Sulawesi Sea in the western Pacific also have an impact on the MC intrusion. This study highlights the significance of the nonlinear dynamics of western boundary currents in modulating eddy activities in the formation region of the Indonesian Throughflow.
Plain Language Summary
Mesoscale eddies are essential for the distribution of thermohaline and biochemical properties and act as a bridge for the energy cascade between large‐scale circulation and submesoscale dynamical processes. The Sulawesi Sea is the primary entrance for the western path of the Indonesian Throughflow (ITF) and the most active region of mesoscale eddies in the Indonesian Seas. However, the interannual evolution of eddy kinetic energy (EKE), an indicator of eddy activity intensity, in this vital formation region of ITF remains unclear. The interannual EKE variations and their causes in the Sulawesi Sea are clarified based on the outputs of Ocean Forecasting Australia Model version 3. The interannual EKE variability in this marginal basin results from the barotropic instability of mean flow, which is regulated by the Mindanao Current (MC) intrusion. The paths of two western boundary currents (WBC), that is, MC and New Guinea Coastal Current and Undercurrent (NGCC/NGCUC), are the primary drivers modulating the strength of MC intrusion. The mesoscale eddies to the east of the Sulawesi Sea in the western Pacific are another factor. This study is a step forward in understanding the role of WBC in the marginal seas' eddy activities and the interbasin connections.
Key Points
The interannual eddy kinetic energy (EKE) variability in the Sulawesi Sea is derived from Ocean Forecasting Australia Model version 3
The barotropic instability of the mean flow dominates the interannual variations of EKE
The Mindanao Current intrusion impacted by Pacific western boundary current paths and mesoscale eddies modulates the barotropic instability