Satellite views of cross-strait sediment transport in the Taiwan Strait driven by Typhoon Morakot (2009)

Abstract

After landing on Taiwan Island, Typhoon Morakot crossed the Taiwan Strait and made a second landfall on the western coast of the strait. In this study, we investigated the impact of Typhoon Morakot on the marine environment and explored the dynamic mechanism for enhanced cross-strait sediment transport based on remote sensing data of sea surface temperature (SST) and total suspended matter (TSM) as well as wind vector data. The results showed that the SST significantly decreased along the typhoon path, while the TSM dramatically increased, with a tongue-shaped high-TSM water extending from coasts to the middle strait during the typhoon processes. The distributions of wind and the Ekman volume transport, calculated based on the wind stress, also revealed that the typhoon process was favorable for cross-strait sediment transport.The strong cyclonic wind stress associated with the typhoon could change the existing currents pattern and destroy the water stratification, which restricts sediment resuspension, and result in significant resuspension of seabed sediments, thereby increasing suspended particle concentration and mass transport flux in waters. Moreover, the cyclonic wind stress could produce typhoon-induced currents, leading to the redistribution of particles in the strait. Comparative analysis revealed that typhoon processes crossing either the Taiwan Strait or passing over the northern strait could significantly impact the pattern of sediment transport in the strait and increase the cross-strait transport of sediments, which are important to the formation of the mud belt in the middle of the Taiwan Strait.