South China coastline will face more furious storm surges at the end of the 21st century

Abstract

South China, with a long and meandering shoreline and well-developed economy, is highly vulnerable to tropical cyclone (TC)-caused storm surges and extreme sea states. The current global warming is expected to continue or even worsen in the rest of the 21st century. Therefore, the warmer sea surface temperature (SST) and lifted mean sea level tend to fuel much more ferocious storm surges. In this study, three severe landfalling TCs have been reproduced by a sophisticated air-wave-ocean coupled model of ultra-high spatial resolution (1-km atmosphere and 500-m wave and ocean). The present-day and pseudo-global warming context mimicking the 2090s have been simulated to investigate the climate change effect. Results indicate that the coupled model can accurately reproduce the air-wave-ocean status during the TC episodes. The 2090s thermodynamic status will effectively increase the intensity of the severe TCs. Typhoon Vicente (2012) even attained a 30% increase in 10-meter wind speed due to its 24-hour stagnant track over the northern South China Sea. On average, the maximum storm surges are lifted by 0.3-0.8 meters over the open sea while aggravating much higher along the coastline, especially for narrowing estuaries where the maximum surge level can be elevated up to 2 meters. Changes in maximum significant wave height show more complicated patterns due to their sensitivity to TC tracks. For Typhoon Vicente (2012), a more than 2-meter wave height increase is observed both in open sea and along the coastline. In the 2090s context, a combination of mean sea level rise, storm surge, and wave height can reach more than 4 meters increase in total water level at certain coastal hot spots.  This will cause much more severe damage and losses at the end of the 21st century.