近日，比利时布鲁塞尔自由大学François Fripiat团队研究了极地南大洋的去冰分层。2026年2月2日出版的《美国科学院院刊》杂志发表了这项成果。

学界普遍认为，北半球冰盖融水曾驱动大西洋经向翻转环流变化，进而影响全球气候。相比之下，尽管南大洋在深海通气过程中起核心作用，关于南极冰盖对南大洋翻转环流影响的数据仍较为缺乏。

研究组通过硅藻结合态氮同位素证据表明，在冰消期，随着南极开阔海域风生上升流增强，南极冰盖融化加剧了南极极区海域的密度分层。这一变化与冰融水排放的重建数据吻合，且与包含南极冰盖融水强迫的全球变暖模型模拟结果一致。淡水的瞬态输入及其带来的浮力增强削弱了南大洋的"下层环流"（该环流出露于南极极区海域），而此时南极开阔海域的"上层环流"却在增强。

鉴于有证据显示深海通气与二氧化碳释放在冰消早期即已持续进行，研究组的数据表明南极开阔海域（而不仅是极区海域）能够直接对深海水体进行通气。末次冰消期期间，南极极区海域最强的密度分层出现在南极冷逆转事件前夕，此时南半球增温暂停而北半球急剧变暖（即波令-阿勒罗德暖期）。研究组认为，当更强的风生上升流与淡水输入共同作用时，上升水体偏离深水形成区而转向强化上层环流，这会加深全球温跃层，从而促进波令-阿勒罗德时期北大西洋深水的重新形成。若此推论成立，则两个半球极区海域的淡水注入共同驱动了冰消期的"两极跷跷板"气候事件。

附：英文原文

Title: Deglacial stratification of the polar Southern Ocean

Author: Fripiat, Franois, Sigman, Daniel M., Ai, Xuyuan E., Dumoulin, Cédric, Moretti, Simone, Studer, Anja S., Diekmann, Bernhard, Esper, Oliver, Frederichs, Thomas, Lamy, Frank, Liu, Ling, Pattyn, Frank, Schmitt, Mareike, Tiedemann, Ralf, Haug, Gerald H., Martínez-García, Alfredo

Issue&Volume: 2026-2-2

Abstract: It is widely accepted that meltwater from northern ice sheets drove changes in the Atlantic Meridional Overturning Circulation, impacting global climate. In contrast, data are lacking on the Antarctic Ice Sheet’s (AIS) effect on Southern Ocean overturning, despite the Southern Ocean’s central role in ventilating the ocean interior. Here, we present diatom-bound nitrogen isotope evidence indicating that during deglaciations, as wind-driven upwelling in the open Antarctic Ocean increased, AIS melting strengthened density stratification in the polar Antarctic Ocean. This change coincides with reconstructions of meltwater discharge and resembles model simulations of global warming including AIS meltwater forcing. The transient input of freshwater and, thus, buoyancy weakened Southern Ocean’s “lower cell” that outcrops in the polar Antarctic Ocean even as open Antarctic Ocean’s “upper cell” strengthened. Given evidence that deep-ocean ventilation and CO2 release were ongoing early in deglaciation, our data suggest that the open Antarctic Ocean, and not solely the most polar Antarctic Ocean, can directly ventilate the deep ocean. During the last deglaciation, the strongest density stratification in the polar Antarctic Ocean occurred just before the Antarctic Cold Reversal, when southern hemisphere warming paused and the northern hemisphere warmed sharply (i.e., during the Blling–Allerd period). We propose that when combined with stronger wind-driven upwelling, the freshwater-driven redirection of upwelled water away from deep water formation and toward the upper cell deepened the global pycnocline, working to restart North Atlantic deep water formation in the Blling–Allerd period. If so, polar ocean freshening in both hemispheres drove the “bipolar seesaw” events of deglaciation.

DOI: 10.1073/pnas.2502076123

Source: https://www.pnas.org/doi/abs/10.1073/pnas.2502076123