Driving Mechanism of Regional Sea Level Changes in the Marginal Seas of Southeast Asia on Interannual to Decadal Time Scales

The tropical Pacific features some of the strongest sea level signals on decadal timescales with trends of more than 1 cm/yr and drastic consequences for the low lying islands in the area.

While these changes are well understood and a superposition of interannual and decadal changes of the zonal wind stress over the tropical Pacific can be identified as the most important driver, much less is known about the sea level variability in the adjacent marginal seas of Southeast Asia.

We use a series of global ocean models based on the new JRA55-do forcing to investigate the importance of remote and local forcing mechanism in the area.

A 1/4° reference configuration and associated sensitivity studies show that wind driven sea level anomalies from the tropical Pacific dominate the Celebes Sea, travel through the equatorial wave channel across the Archipelago and along the east coast of Australia. Indian Ocean wind forcing contributes to the variability along the east coasts from Peninsular Malaysia down to Timor. In contrast, the South China Sea is topographically shielded from the open ocean. Although sea level variability appears correlated to the Pacific modes of variability, it is found to be driven by local momentum and buoyancy fluxes.

In order to account for the complex topographic features of the region, our analysis is further supported by a high resolution configuration using a two way nesting- scheme, which resolves the area between 70°E – 180°W and 50°S – 25°N with an increased resolution of 1/20°.