Reflection And Penetration Of The Equatorial Kelvin Waves In The Eastern Indian Ocean

Based on current observations in the eastern Indian Ocean and Indonesian seas,the reflection and penetration of the equatorial Kelvin waves in the eastern Indian Ocean are investigated using ocean models,continuously stratified model and analytical wave model.The propagation of these waves in the Indonesian seas and their impact on the currents variations in the northern Indonesian seas are also studied.A strong eastward spring Wyrtki Jet with the velocity of 1.2 m/s is observed from the satellite-tracked drifters.The bifurcation of the jet and westward flow at the eastern boundary are also observed,suggesting the propagation and reflection of the Kelvin waves in the eastern Indian Ocean.These phenomena are successfully simulated by the LICOM model.The equatorial waves extracted from the model simulation show downwelling Kelvin waves forced by the zonal wind and Rossby waves reflected at the eastern boundary.The wave dynamics of the observed eastward currents show the first meridional mode of the second baroclinic mode Rossby waves produce most of the strong spring Wyrtki Jet,indicating the significance of the eastern boundary reflection in affecting the circulation in the eastern Indian Ocean.The lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter through fall seasons are significant in observations and global ocean general circulation model simulations,which suggest the IOD-forced interannual thermocline anomalies will propagate to the east and lead to ENSO.The analysis using a linear continuously stratified model suggests the penetration of the Indian Ocean Kelvin wave through the Indonesian seas is the dominant mechanism of oceanic connection between the tropical Indian and Pacific Oceans.The control experiments show that,the interannual Kelvin waves from the Indian Ocean propagate into the Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10% ~ 15% in the LCSM,and particularly of 15% for the first baroclinic mode.The penetration rate is found to be dependent only on the southern tip latitude of the barrier between the two basins,and independent of the shapes,lengths and gaps of the barrier.The high-resolution regional INDESO model configured in the Indonesian seas from 2008 to 2016 and an analytical wave model is used to study the variability of the currents in the northern Indonesian seas forced by the Indian Ocean oceanic anomalies.The INDESO model simulation compares reasonably with the seasonal to interannual variability of the moored current meter observations in the upper 350 m or so of the Maluku Channel.Based on which,the interannual variability of the currents in the northern Indonesian seas in the model is found to be associated with both the Pacific and Indian Ocean remote forcing.Both the equatorial Kelvin waves from the Indian Ocean and the coastally trapped Kelvin waves from the western Pacific along the Philippine coast can propagate through the Indonesian seas and arrive at the Maluku Channel.In particular during the strong 2015/2016 El Ni?o event,the Indian Ocean Kelvin waves are found to significantly impact the SLA variability in the Maluku Channel.The results indicate the importance of the equatorial Kelvin waves to the interannual variability of the currents at the entrance of the Sulawesi Sea in the western Pacific Ocean affected by the remote Indian Ocean.