Beyond the bipolar seesaw: Toward a process understanding of interhemispheric coupling
Beyond the bipolar seesaw: Toward a process understanding of interhemispheric coupling
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DOI：
10.1016/j.quascirev.2018.05.005
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发表时间：
2018-07
影响因子：
4
通讯作者：
J. Pedro;M. Jochum;C. Buizert;F. He;S. Barker;S. Rasmussen
中科院分区：
文献类型：
--
作者：
J. Pedro;M. Jochum;C. Buizert;F. He;S. Barker;S. Rasmussen
热双极海洋跷跷板假说由Stocker和Johnsen（2003）提出，作为解释Dansgaard-Oeschger （DO）和南极同位素极大期（AIM）事件之间时间关系的“可能最简单的热力学模型”。本文结合古气候观测、理论和大气环流模式实验，从概念模式向半球间耦合和AIM事件强迫的过程理解推进。结果表明：(1)热跷跷板引起的大西洋热输运变化被全球大气和太平洋热输运的相反变化部分补偿。这种补偿是半球间耦合的一个组成部分，对全球气候异常格局有重大影响。(2)我们支持热储在半球间耦合中的作用，但认为其位置是南极环极流（ACC）以北的全球内洋，而不是通常假设的南大洋。(3)能量收支分析表明，AIM事件期间驱动南极变暖的过程是海冰退缩和南大洋表面变暖导致大气向极地热湿输送的增加。(4)南极海冰退缩本身是由横跨ACC的涡旋热通量驱动的，海冰反照率反馈放大了这一过程。AMOC崩塌后南极变暖的滞后反映了热量在ACC以北的海洋内部（主要是1500 米以上）积累所需的时间，然后才能被涡流混合穿过这个动力屏障。
The thermal bipolar ocean seesaw hypothesis was advanced by Stocker and Johnsen (2003) as the ‘simplest possible thermodynamic model’ to explain the time relationship between Dansgaard–Oeschger (DO) and Antarctic Isotope Maxima (AIM) events. In this review we combine palaeoclimate observations, theory and general circulation model experiments to advance from the conceptual model toward a process understanding of interhemispheric coupling and the forcing of AIM events. We present four main results: (1) Changes in Atlantic heat transport invoked by the thermal seesaw are partially compensated by opposing changes in heat transport by the global atmosphere and Pacific Ocean. This compensation is an integral part of interhemispheric coupling, with a major influence on the global pattern of climate anomalies. (2) We support the role of a heat reservoir in interhemispheric coupling but argue that its location is the global interior ocean to the north of the Antarctic Circumpolar Current (ACC), not the commonly assumed Southern Ocean. (3) Energy budget analysis indicates that the process driving Antarctic warming during AIM events is an increase in poleward atmospheric heat and moisture transport following sea ice retreat and surface warming over the Southern Ocean. (4) The Antarctic sea ice retreat is itself driven by eddy-heat fluxes across the ACC, amplified by sea-ice–albedo feedbacks. The lag of Antarctic warming after AMOC collapse reflects the time required for heat to accumulate in the ocean interior north of the ACC (predominantly the upper 1500 m), before it can be mixed across this dynamic barrier by eddies.