21世纪格陵兰冰川不同的融化季节对海平面变化的影响

摘要

利用三维海洋环流模式(parallel ocean program, POP),探讨典型浓度路径(representative concentration pathway, RCP)情景下21世纪格陵兰冰川不同的融化季节对海平面变化的影响。结果表明：在RCP4.5情景下,当格陵兰冰川以7%×a-1的加速度快速融化时,相比于只在夏半年融化,全年融化会导致动力海平面在北冰洋、北大西洋副极地海域加速上升,而在欧洲西北部和北大西洋副热带海域加速下降；比容海平面在北美沿岸加速上升,热带大西洋和南大西洋副热带海域也有所上升,北冰洋、欧洲西北部和北大西洋副热带则显著下降。格陵兰冰川不同的融化季节对海平面变化影响的不同,主要是由于相比于只在夏半年融化,格陵兰冰川全年融化会造成大量较冷较淡的融冰水被滞留在格陵兰岛南部海域,在冬半年,会导致上层海洋层化加强和大西洋经向翻转流进一步减弱,一方面造成大量海水在北大西洋副极地海域堆积；另一方面导致向北的热盐输运减弱,从而造成了北冰洋、北大西洋副极地和副热带海域东部的热比容海平面显著下降和盐比容海平面加速上升。%The influence of different melting time of Greenland ice sheet on sea level of the global and regional oceans were studied using the ocean model parallel ocean program (POP) under the representative concentration pathway 4.5 (RCP 4.5) scenario for the 21st century. Results showed that the Greenland ice sheet melting with 7%×a-1 acceleration in the year round has more notably influence on the global and regional sea level variation than melting only in the summer months from May to October. The dynamic sea level rise shows acceleration in the Arctic and subpolar North Atlantic, but it decreases in the west coast of Europe and subtropical North Atlantic. The steric sea level rises fast along the coast of North America, subpolar North Atlantic, tropical Atlantic, and the subtropical South Atlantic, but falls in the Arctic, the west coast of Europe and subtropical North Atlantic. The different influences of the Greenland ice sheet melting on sea level change between the year round and the summer months cases mainly due to the notably weakened meridional overturning caused by strengthened stratification of the upper ocean and weakened deep convection because of a lot of freshwater input regions near Greenland in the high rate of melting Greenland ice sheet. The accumulation of water in the subpolar North Atlantic caused by weakened meridional overturning, which leads to dynamic sea level rise in the subpolar North Atlantic. The weakened transport of heat and salt from the tropical Atlantic to high-latitude ocean was caused by weakened meridional overturning, so that more high temperature and saline water was stranded in the tropical Atlantic; part of high temperature and high salinity water was brought by the Gulf Stream to the Gulf Stream region, leading to accelerated thermosteric sea level rise and significant halosteric sea level decrease in the Gulf Stream and tropical North Atlantic. The waters of the subpolar North Atlantic and Arctic cool and become less saline, some cold and less saline water was brought by the wind-driven circulation to the subtropical North Atlantic, which led to opposite change of thermosteric and halosteric sea level to tropical North Atlantic.