Existence of eddies at crossroad of the Indonesian seas
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An eddy-resolving Indo-Pacific ocean circulation model was applied to highlight the behavior of eddies throughout the Indonesian seas. The complexity of the topography and coastline at the entrance of the Makassar Strait induce an eddy-type throughflow, instead of a straightforward flow. A sill and a narrow passage in the Makassar strait creates a barrier and impedes the continuation of eddies from the Pacific ocean, but the existence of a steep deep basin (>500 m depth) between the Java and Flores seas indicates a possible area for eddies. Based on our numerical results, we described the presence of a unique eddy structure north of Lombok Island, which we designated the “Lombok Eddy” and verified it by performing a drifter release field experiment and reviewing monthly mean climatology data from the World Ocean Atlas 2001 and XBT PX2 track data. NCEP/NCAR reanalysis, satellite observation data, and mixed layer depth analysis were also used to confirm these processes. By analyzing numerical simulation results and available temperature datasets, two additional eddies were found. All eddies form primarily due to eastward local winds correlated with seasonal monsoon winds during the austral summer. These eddies vary synchronously at an interannual time scale. Together, they are referred to as the Lombok Eddy Train (LET), which affects the surface layer down to a depth of 60 m, and the intensity of the eddy system is strongly affected by mixed layer depth variability from December to February.
KeywordsLombok eddy train Wind stress February Upwelling-downwelling Cyclonic-anticyclinic
This work was funded by the Global Environment Research Fund (F-082) of the Ministry of the Environment, Japan, and a Grant-in-Aid for Scientific Research (A) (no. 18254003 and no. 21254002) from the JSPS (Japan Society for the Promotion of Science). The authors gratefully acknowledge the joint research cooperation, help, and support from the Research Center for Oceanography-Indonesian Institute of Sciences, directed by Prof. Suharsono, and the Research Center for Marine and Coastal Resources-Ministry of Marine Affairs and Fisheries of Indonesia, directed by Dr. Budi Sulistiyo. The authors gratefully acknowledge the support from Novi S. Adi and Adi Purwandhana during drifters release experiment. We benefited considerably from facilities offered by the JAMSTEC Yokohama office, which supported all of the running processes on their two supercomputers (SX-8R and SGI Altix4700) and provided timeseries validation data. The Indo-Pacific code uses the code of JCOPE2 developed by the JCOPE group. The first author has been supported by the scholarship for foreign students offered by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors gratefully acknowledge the useful comments and suggestions from the weekly JCOPE group meeting and the anonymous reviewers.
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