Integrated 3D numerical modeling during La Niña and El Niño events using Regional Ocean Modeling System (ROMS) in Makassar Strait: preliminary study

Abstract

This research showed the difference of thermocline layer depth during La Niña and El Niño events in the Makassar Strait, the main passage connecting the Pacific and Indian Oceans. La Niña event represented by 2011 and El Niño event represented by 2015. Three-dimensional numerical modeling using Regional Ocean Modeling System (ROMS) is used to determine ocean dynamic characteristics. The tides and atmospheric factor used as generating forces for coupled Ocean-Atmosphere-Wave-Sediment simulation model. Tidal elevation verification results from January to February 2017 showed a high confidence with RMSE = 0.148 m and MAPE = 13.51 %. Ocean circulation showed that water flows from north to south of the Makassar Strait in both conditions, El Niño and La Niña, indicating a transport from the Pacific to the Indian Oceans during those time. Two-dimensional seasonal sea surface temperature (SST) was used to determine the variability of thermocline layer depth. In general, based on simulation results, the depth of thermocline during La Niña was deeper than that during El Niño. The upper threshold of thermocline layer during El Niño phenomenon was shallower (average 27.29 m) compare to the threshold during La Niña (average 39.25 m). So do the lower threshold, during El Niño was shallower (average 160.47 m) compare to the threshold during La Niña (average 165.70 m). The thermocline thickness during El Niño (133.19 m) was found to be thicker compared to La Niña (126.43 m).