On kelvin wave propagation effects on Indonesian throughflow in the Makassar strait

A numerical modeling study with the Spectral Element Ocean Model (SEOM) has been used to understand Kelvin wave propagation in the Indian Ocean and the internal Indonesian Seas, and to study its effect on Indonesian throughflow. A prescribed 50-day period Kelvin wave signal at the northwestern coast of Sumatra shows that a Kelvin wave propagates along the coast of Sumatra, Jawa, and Bali and goes through Lombok Strait to enter the internal Indonesian Seas. The energy flux entering Lombok Strait is approximately 77% of the incoming energy flux in the Indian Ocean; only 4% goes further to the Lesser Sunda Islands. This indicates that Lombok Strait may be a primary channel of energy redistribution from the Indian Ocean to the internal Indonesian Seas.

Using a more detailed grid in the Makassar Strait, we simulate Kelvin wave propagation by forcing in the northern mouth of Lombok Strait. The model indicates that within Makassar Strait Kelvin waves propagate northward along the western coast of Makassar Strait and then separate into two branches at the Labani channel. One branch, which carries approximately 48% of the total energy flux, goes through the Labani channel, and only 32% enters the Sulawesi Sea; the other 52% of the energy moves back southward following the eastern coast of the Makassar Strait. The remaining16% of the energy passing through the Labani Channel may be lost due to bottom friction, or trapped within the Makassar Strait. Kelvin wave propagation affects the Indonesian throughflow by producing several days of relaxation of the throughflow transport. Kelvin wave propagation also reduces the total energy/volume ratio in the whole region.

The experiments in this research are performed with one-and-a-half layer, reduced gravity physics. Though dynamically simple, the finite element model gives a better geometric representation of Kelvin wave propagation and current systems in the complex coastline morphology of the Makassar Strait and the Sulawesi Sea as well as has a better spatial resolution than previous studies.