近日，德国亥姆霍兹极地和海洋研究中心Hanna S. Knahl团队研究了在最后一次温室向冰室气候转型期间，环南极环流的格局。这一研究成果于2026年4月6日发表在《美国科学院院刊》杂志上。

在始新世-渐新世过渡期（约34.4至33.7百万年），重大的气候与构造变化启动了地球现今的冰室气候。板块运动加剧了造山作用，降低了大气中的二氧化碳浓度，并引发了全球变冷。至关重要的是，塔斯曼海道与德雷克海峡的开启，促使了南极绕极流（ACC）的形成——该洋流是当今地球上最强的洋流。然而，人们对ACC形成初期的初始结构仍知之甚少，这限制了学界对其当时如何控制全球环流模式和热量分布的理解。

研究组展示了经过数据验证的高分辨率气候-冰盖耦合模拟结果，模拟对象为早渐新世冰川最大值期（约33.7至33.2百万年）。结果表明，南极周边的早期海洋-大气环流与南大洋海道的几何形态以及早期南极冰盖的存在密切相关。然而，与今天不同的是，这些海道当时并未与西风带对齐，因此限制了ACC的发展，并促使了强烈的南极放大效应。

研究组得出结论：仅凭造山作用、二氧化碳浓度下降和南半球海道的开启，并不足以在约34百万年时形成强大的ACC。只有在后来西风带与开启的海洋海道相对齐之后，才得以增强跨半球的翻转环流，促进碳吸收，并实现地球冰室气候的长期稳定。

附：英文原文

Title: Configuration of circum-Antarctic circulation at the last green- to icehouse climate transition

Author: Knahl, Hanna S., Klages, Johann P., Ackermann, Lars, Hochmuth, Katharina, Niu, Lu, Golledge, Nicholas R., Lohmann, Gerrit

Issue&Volume: 2026-4-6

Abstract: During the Eocene–Oligocene Transition (～34.4 to 33.7 Ma), major climatic and tectonic changes initiated Earth’s current icehouse climate. Plate motion intensified mountain building, reduced atmospheric CO2, and triggered global cooling. Crucially, the opening of the Tasman Gateway and Drake Passage initiated the formation of the Antarctic Circumpolar Current (ACC), today Earth’s strongest ocean current. However, the ACC’s initial structure during its onset remains poorly understood, limiting our understanding in controlling global circulation patterns and heat distribution at the time. Here, we present data-validated, high-resolution coupled climate–ice sheet simulations of the Early Oligocene Glacial Maximum (～33.7 to 33.2 Ma), showing that early ocean–atmosphere circulation around Antarctica was closely tied to Southern Ocean gateway geometry and the presence of the early Antarctic Ice Sheet. Unlike today, however, these gateways were not aligned with the westerly wind belt, hence limiting ACC development and promoting strong Antarctic amplification. We conclude that orogenesis, CO2 drawdown, and Southern Hemisphere gateway opening alone were insufficient to establish a strong ACC ～34 Ma. Only the later alignment of westerly winds with open oceanic gateways enabled the enhancement of interhemispheric overturning circulation, promoted carbon uptake, and the long-term stabilization of Earth’s icehouse climate.

DOI: 10.1073/pnas.2520064123

Source: https://www.pnas.org/doi/abs/10.1073/pnas.2520064123