The variations of the upper ocean heat content and thermostatic sea level around 21st century Marine Silk Road

Under the background of climatic warming, the global ocean temperature increased and the sea level rose significantly, imposing enormous challenges to the sustainable development of human society. The upper ocean heat condition is one of the dominant factors of sea level change. Focusing on the 21st century Silk Road Maritime Region (SRMR), the local spatial and temporal characteristics of the upper ocean heat content were analyzed, furthermore, the change and evolution characteristics of thermosteric sea level and associated impaction were discussed, in order to give the services supporting for marine environment security of "21st century Maritime Silk Road". The analysis results show that, since the 1970s, the upper layer (0-700 m) ocean of SRMR began to warm obviously, and especially presented significant larger warming from the middle of 1990s. Recently 60 years, in tropical oceans of the SRMR, the North Equatorial Current and its north sea area in the western Pacific, the China seas including the north and the south of the South China Sea (SCS) and the Kuroshio valley in East China Sea, the northwest coastal waters in Arabian sea, the sea area of northwest of Malaysia and south part of the Indian Ocean had a long-term heating trend. The warming of the whole region of tropical western Pacific warm pool was not obvious, and presented mainly anti-phase change with the central Indian Ocean, which were modulated by seasonal and interannual variability. The coastal zones of the eastern China seas near the Changjiang River Estuary, the north of the SCS, the southern of Indo-China Peninsula, the northwestern of Arabian Sea had an obviously long-term warming. Since the middle of the 1990s, the thermosteric sea level in costal zones of the east and west of Indo-China Peninsula, the west of Australia and the China seas have rose obviously. The seasonal evolution of thermosteric sea level rising can cause a certain degree of impact on social and economic development in coastal zones. In addition, the East Asian summer monsoon was significantly associated with the thermosteric sea level rising in eastern China seas, at the same time, the ENSO, the PDO and the IOD also related distinctly to the thermosteric sea level rising in coastal zones in China seas and the western Indian Ocean. Particularly, in climate warming scenario, due to the synergy impaction of regional disaster-causing factors and climate variability, the social and economic development and the disaster prevention and mitigation in coastal zones in SRMR would be subject to huge challenges. The study of comprehensive risk of coastal zones by global change has become the top priority.