Low-Frequency Variability and Projected Changes of Steric Sea Level in the Maritime Continent

Coastal zones in the Maritime Continent are one of the most vulnerable regions in the world to sea level rise and other climate-associated hazards. Ocean circulations transport mass, salt, and heat through the South China Sea (SCS) and the Southeast Asian Seas (SEAS), linking the western tropical Pacific and Indian Oceans. This process significantly influences regional sea-level changes, causing higher rates of sea-level rise than global. Current global general circulation models (GCMs) are mostly limited in resolving regional ocean circulation and boundary currents due to their coarse resolution. Therefore, dynamic downscaling of the global GCMs to regional scales using high-resolution ocean models is widely considered as an efficient solution to derive regional sea-level projections. In this study, we employ an eddy-resolving regional ocean model (NEMO) to dynamically downscale sea-level projections from the global climate model (EC-Earth3) for the SSP2-4.5 and SSP5-8.5 scenarios in the Maritime Continent, encompassing the South China Sea and other Southeast Asian Seas. A novel aspect of our approach is the use of WRF-based downscaled atmospheric fields from the same parent global climate model (EC-Earth3), to provide high resolution surface boundary conditions for the ocean model projections. This study further explores the low-frequency steric sea-level trend and variability, as well as associated heat flux and transport by prevailing climate modes in the region.