OS025-0003
Impact of the ENSO on oceanic heat transport in the South China Sea and the Indonesian Seas
Impact of the ENSO on oceanic heat transport in the South China Sea and the Indonesian Seas
Thursday, 10 December 2020
Poster
Abstract:
The South China Sea (SCS) and the Indonesian Seas play an important role in development of the Walker circulation by increased sea surface temperature (SST) that promotes transport of water mass and heat from the Pacific to the Indian Ocean through the Indonesian Throughflow. These areas are connected to the Pacific at the Luzon strait and the Celebes Sea by intrusions of the Kuroshio and the Mindanao Current. However, little has been known about how significantly the SCS and the Indonesian Seas are affected by the tropical western Pacific through these two Western Boundary Currents (WBCs). Here we examine interannual variability of regional circulations formed in these areas with a particular attention to the influences of the Pacific ENSO due to heat transport.
We developed a 3-D downscaling ocean circulation model based on the Regional Oceanic Modeling System (ROMS) at a lateral resolution of 5 km with tides, initialized and forced by the Hybrid Coordinate Ocean Model (HYCOM) non-tidal global reanalysis product. A twin numerical experiment was conducted with the HYCOM-ROMS model in synoptic and climatological modes, which enables us to explicitly extract interannual variability including the ENSO.
A comparison of the synoptic and the climatological models exhibits that during an El Niño, the incoming heat flux through the Luzon Strait is enhanced to increase SST in the southern SCS by 1℃ and the heat flux to the Celebes Sea is reduced to decrease SST in the Indonesian Seas also by 1℃. We found it through a heat budget analysis that the interannual SST variability in the SCS and the Indonesian Seas are strongly influenced not only by the monsoon, but also pronouncedly by the WBCs due to the meridional shift of the bifurcation latitude of the WBCs associated with the ENSO. Therefore, the alteration of the oceanic structure of the subtropical and tropical western Pacific is important for the interannual variability of advective heat transport into the SCS and the Indonesian Seas, which is influential to the Walker circulation that could feed back again to the ENSO.
We developed a 3-D downscaling ocean circulation model based on the Regional Oceanic Modeling System (ROMS) at a lateral resolution of 5 km with tides, initialized and forced by the Hybrid Coordinate Ocean Model (HYCOM) non-tidal global reanalysis product. A twin numerical experiment was conducted with the HYCOM-ROMS model in synoptic and climatological modes, which enables us to explicitly extract interannual variability including the ENSO.
A comparison of the synoptic and the climatological models exhibits that during an El Niño, the incoming heat flux through the Luzon Strait is enhanced to increase SST in the southern SCS by 1℃ and the heat flux to the Celebes Sea is reduced to decrease SST in the Indonesian Seas also by 1℃. We found it through a heat budget analysis that the interannual SST variability in the SCS and the Indonesian Seas are strongly influenced not only by the monsoon, but also pronouncedly by the WBCs due to the meridional shift of the bifurcation latitude of the WBCs associated with the ENSO. Therefore, the alteration of the oceanic structure of the subtropical and tropical western Pacific is important for the interannual variability of advective heat transport into the SCS and the Indonesian Seas, which is influential to the Walker circulation that could feed back again to the ENSO.