IPCC AR6解读:全球和区域海平面变化的监测和预估

Interpretation of IPCC AR6 report:monitoring and projections of global and regional sea level change

IPCC第六次评估报告第一工作组报告第九章综合评估了与海平面相关的最新监测和数值模拟结果,指出目前(2006—2018年)的海平面上升速率处于加速状态(3.7 mm/a),并会在未来持续上升,且呈现不可逆的趋势。其中低排放情景(SSP1-1.9)和高排放情景(SSP5-8.5)下,到2050年,预估全球平均海平面(GMSL)分别上升0.15~0.23 m和0.20~0.30 m;到2100年,预估GMSL分别上升0.28~0.55 m和0.63~1.02 m。南极冰盖不稳定性是影响未来海平面上升预估的最大不确定性来源之一。区域海平面变化是影响沿海极端静水位的重要因素。

In the IPCC Sixth Assessment Report,the latest monitoring and simulation results indicate that the current rate of sea level rise is accelerating(3.7 mm/a)and will continue to rise in the future,showing an irreversible trend.Under low emission scenarios(SSP1-1.9)and high emission scenarios(SSP5-8.5),global mean sea level(GMSL)is projected to rise by 0.15-0.23 m and 0.20-0.30 m by 2050,respectively.By 2100,GMSL is projected to rise 0.28-0.55 m and 0.63-1.02 m,respectively.Antarctica ice sheet instabilities are significant sources of uncertainty affecting future sea level rise projections.Regional relative sea level rise is an important driving factor affecting extreme still water levels.Marine Ice Sheet Instability(MISI)and Marine Ice Cliff Instability(MICI)and the acceleration of ice streams will increase the estimated GMSL in the future.After 2100,with the continuous heat uptake of deep ocean and the continuous loss of ice sheet mass,sea level rise will last for thousands of years(high reliability).A major deficiency of present-day sea-level studies is the prediction of high sea-level scenarios at the end of the 21st century.Under the impacts of climate warming and polar amplification effect,the collapse of Antarctic ice shelf may accelerate.The intensification of hydrofracturing process and ocean stratification can increase the melting on and beneath the ice shelf,respectively.However,these physical processes have not been well implemented in the models.By the end of the 21st century,the tidal amplitude in most coastal regions of the world will change significantly.Human factors such as land reclamation and different land management policies in coastal areas will affect the impact of global sea level rise on tidal amplitude.Therefore,the impact of ice sheets on global and regional sea level changes has important practical and long-term significance for China’s future coastal infrastructure and ecological environment protection.