北极海冰减退引起的北极放大机理与全球气候效应

自20世纪70年代以来,全球气温持续增高,对北极产生了深刻的影响。21世纪以来,北极的气温变化是全球平均水平的2倍,被称为"北极放大"现象。北极海冰覆盖范围呈不断减小的趋势,2012年北极海冰已经不足原来的40%,如此大幅度的减退是过去1 450年以来独有的现象。科学家预测,不久的将来,将会出现夏季无冰的北冰洋。全球变暖背景下北极内部发生的正反馈过程是北极放大现象的关键,不仅使极区的气候发生显著变化,而且对全球气候产生非常显著的影响,导致很多极端天气气候现象的发生。北极科学的重要使命之一是揭示这些正反馈过程背后的机理。北极放大有关的重大科学问题主要与气—冰—海相互作用有关,海冰是北极放大中最活跃的因素,要明确海冰结构的变化,充分考虑融池、侧向融化、积雪和海冰漂移等因素,将海冰热力学特性的改变定量表达出来。海洋是北极变化获取能量的关键因素,是太阳能的转换器和储存器,要认识海洋热通量背后的能量分配问题,即能量储存与释放的联系机理,认识淡水和跃层结构变化对海气耦合的影响。全面认识北极气候系统的变化是研究北极放大的最终目的,要揭示气—冰—海相互作用过程、北极海洋与大气之间反馈的机理、北极变化过程中的气旋和阻塞过程、北极云雾对北极变化的影响。在对北极海冰、海洋和气候深入研究的基础上,重点研究极地涡旋罗斯贝波的核心作用,以及罗斯贝波变异的物理过程,深入研究北极变化对我国气候影响的主要渠道、关键过程和机理。

Arctic Amplification Produced by Sea Ice Retreat and Its Global Climate Effects

Since the 1970s, the continuous global warming has impacted the Arctic environment. The temperature increasing rate of Arctic during this century is nearly twice that of the global average, which is named as Arctic Amplification phenomena. Sea ice coverage of Arctic Ocean varied in a declined trend. Summer sea ice extent in 2012 was less than 40% of that in last century. The serious retreat of Arctic sea ice coverage is a unique phenomenon during the past 1 450 years. It is projected that an ice-free summer Arctic will happen in the near future. The positive feedback processes inside the Arctic are considered to be the key factors to drive the Arctic amplification under the background of global warming, which result in the Arctic and global climate changes, and drive many extreme meteorological and climatological events. An important mission of Arctic science is to reveal the physical mechanisms that drive these positive feedbacks. The main scientific issues of Arctic amplification are all related to the air-ice-sea interaction. Sea ice is the most active factor of Arctic amplification. The variations of sea ice microstructure and the thermal dynamical features need to be clarified quantitatively by considering the melt pond, lateral melting, snow cover, and ice drifting. Ocean is the key factor to acquire and store the solar energy for Arctic change. Oceanic heat flux is very important for the energy reallocation (energy storage and release), which is influenced by fresh water content and pycnocline structure to form the air-sea coupling. The main goal of researches for the Arctic Amplification is to understand the variation of Arctic climate system, the air-ice-sea interaction, feedback between ocean and atmosphere, variation in cyclones and blocks, influence of cloud and fog on Arctic change. On the basis of better understanding of variation of sea ice, ocean, and climate Arctic, the dominant function and physical processes of the vortex Rossby-waves will be the main issue to reveal the gateways and processes for the influence of Arctic change on China’s climate.