PHY-03 Sea level rise: understanding, observing, and modelling
Modulation of atmospheric winds to extreme sea level under climate change framework
Linlin Fan* , College of Oceanic and Atmospheric Sciences, Ocean University of China
Ling Du, College of Oceanic and Atmospheric Sciences, Ocean University of China

Climate change has become the greatest threat to human survival and the future of the planet.  Under climate change framework, global coasts are suffering frequent high-intensity extreme sea levels (ESLs), and Northwest Pacific (NWP) where stood out in terms of intensity, duration and occurrence. In the context of sea level rise, setup has important implications for coastal flooding. Wind along the NWP coast is the most direct and dominant factor triggering strong setup, which is regulated by the joint modulation of wind speed, direction and acting time. As wind field becomes more complex with climate change, studying how climate change affects coastal ESLs by modulating the local wind fields is critical to coastal preparedness for climate change. The higher the wind speed, the more likely it is to bring about stronger setup, which can lead to destructive ESLs. With increasing wind speed, setup grows linearly even quadratically. It is an unexpected outcome that smaller winds are also capable of producing higher ESLs, mainly due to the regulation of wind direction. During 1960-2013, more than half of the ESLs events in the NWP were caused by onshore wind-driven piling-up and benefited more water rushing into coastal zones. In addition, notably, there were also 30% of the ESLs caused by the offshore winds which were even comparable to those onshore winds along the coast of Japan. Seasonal variations of wind direction are obvious in NWP, while the northeasterly winds are the dominant of ESLs along the coast of China. ESLs in Indonesian are significantly influenced by southerly winds in summer and northerly winds in winter, in addition to this, easterly winds are the main force of the strong ESLs trigger in both winter and summer. The ESLs off the coast of Japan coincide with the changes in the local wind field, with southwesterly winds influencing ESLs in summer and westerly winds in winter. Under the joint regulation of wind speed and direction, wind acting time also affects the intensity of setup. Winds are more likely to lead to stronger setup within 1-3 hours around high tide. In the northwest Pacific, typhoon is an important factor influencing local wind variability. More than 70% of ESLs events are involved in typhoons during the TC-summer along the coasts of China and Japan. Risk investigations of wind-driven ESLs are of critical importance for mitigating the effects of current and future coastal flooding hazards.