Typhoon induced summer cold shock advected by Kuroshio off eastern Taiwan

- The typhoon induced cool wake off eastern Taiwan is related to summer cold shocks.
- The cold shocks could impact aquaculture activities.
- This paper reports a synthesis of the results of real and idealised experiments.
- The offshore wind and Kuroshio are responsible for generation of the upwelling.
- The impact is transported downstream of the Kuroshio.

In this study, we used satellite observations, in-situ measurements, and numerical modelling to investigate an extreme temperature change triggered by a typhoon in the ocean near the Kuroshio region off eastern Taiwan. With the westward passage of Typhoon Morakot in 2009 through Taiwan, a distinct cool wake was generated at the southeastern corner of Taiwan (CWSET) and moved towards the downstream Kuroshio region; it involved a precipitous cooling of at least 4 °C within 10-20 km of the coast. Rapid and drastic temperature drops triggered by the CWSET and advected by the strong conveyor belt effect of the Kuroshio Current are highly probable sources of cold shocks in summer. We clarified the mechanism that generated the CWSET through a series of sensitivity experiments using the Regional Oceanic Modeling System. The cold shock was mainly triggered by local wind stress associated with the typhoon. In addition, the Kuroshio Current was demonstrated to have played a crucial role in both the generation of upwelling off the southeastern coast of Taiwan during the passage of the typhoon and the transporting of this impact downstream. This process was verified through a systematic analysis of all typhoons moving westward through Taiwan from 2005 to 2013. Cold-shock stress is thought to be linked with naturally occurring 'fish kills', and obtaining a more thorough understanding of the CWSET will be helpful for protecting aquaculture off the eastern coast of Taiwan from the impacts of cold shocks triggered by typhoons moving westward through Taiwan in summer.