是什么导致地球周期性地进出冰河时代

Upside-down “rivers” of warm ocean water may be one of the causes of Antarctica’s ice shelves breaking up, leading to a rise in sea levels. But a new study suggests an increase in sea ice in a colder climate may lead to a much more devastating change in the Earth’s climate — another ice age.

温暖的海水倒转的“河流”可能是导致南极洲冰架断裂、海平面上升的原因之一。但一项新的研究表明，在更冷的气候下，海冰的增加可能会导致地球气候发生更具破坏性的变化——另一个冰河时代。

Using computer simulations, the research suggests that an increase in sea ice could significantly alter the circulation of the ocean, ultimately leading to a reverse greenhouse effect as carbon dioxide levels in the ocean increase and levels in the air decrease.

利用计算机模拟，研究表明，海冰的增加可能会显著改变海洋的环流，最终导致海洋中二氧化碳含量的增加和空气中二氧化碳含量的减少，从而逆转温室效应。

“One key question in the field is still what caused the Earth to periodically cycle in and out of ice ages,” University of Chicago professor and the study’s co-author, Malte Jansen, said in a statement.“We are pretty confident that the carbon balance between the atmosphere and ocean must have changed, but we don’t quite know how or why.”

“该领域的一个关键问题仍然是，是什么导致地球周期性地进出冰河时代，”芝加哥大学教授、该研究的合著者马特·詹森(Malte Jansen)在一份声明中说。“我们非常确信大气和海洋之间的碳平衡肯定已经改变了，但我们不太清楚是如何改变的，也不知道为什么会改变。”

The last major ice age ended at the end of the Pleistocene era, about 2.5 million years ago, as glaciers have periodically grown and then gotten smaller. Researchers believe that changes to the Earth’s orbit may be partly responsible for some of the Earth’s cooling, but additional factors have likely played a part, Jensen added.

上一个主要的冰河时代在更新世末期结束，大约250万年前，冰川周期性地增长，然后变小。研究人员认为，地球轨道的变化可能是造成地球部分变冷的部分原因，但詹森补充说，可能还有其他因素在起作用。

“The most plausible explanation is that there was some change in how carbon was divided between the atmosphere and the ocean,” Jansen continued. “There’s no shortage of ideas about how this happens, but it’s not quite clear how they all fit together.”

“最合理的解释是，碳在大气和海洋之间的分配方式发生了一些变化，”詹森继续说。“关于这是如何发生的，有很多想法，但不太清楚它们是如何结合在一起的。”

Researchers also believe a mini-ice age may have occurred roughly 12,800 years ago. It likely stems from an asteroid impact that “rocked the Northern Hemisphere” and led to the Younger Dryas climate event.

研究人员还认为，小冰河期可能发生在大约12800年前。它可能源于一次“震撼北半球”的小行星撞击，并导致了更年轻的Dryas气候事件。

Jansen pointed out that the Southern Ocean around Antarctica “plays a key role in ocean circulation” due to the deep waters in the region, leading it to have “outsize[d] consequences.”

Jansen指出，南极洲周围的南大洋由于该地区的深水而“在海洋环流中起着关键作用”，这将导致“严重后果”。

“What this suggests is that it’s a feedback loop,” said the study’s lead author, Alice Marzocchi. “As the temperature drops, less carbon is released into the atmosphere, which triggers more cooling.”

“这表明这是一个反馈循环，”该研究的主要作者爱丽丝·马佐基(Alice Marzocchi)说。“随着气温下降，释放到大气中的碳减少，从而引发更多的降温。”

“What surprised me is how much of this increased storage can be attributed to physical changes alone, with Antarctic sea-ice cover being the key player,” Marzocchi added, noting that future study of the ocean and the role it plays in the carbon cycle can help simulate “future environmental change.”

Marzocchi补充说:“让我惊讶的是，这些增加的储存有多少是单独归因于物理变化，南极海冰是关键因素。”他指出，未来对海洋及其在碳循环中所扮演的角色的研究可以帮助模拟“未来的环境变化”。

The research has been published in the scientific journal Nature Geoscience.

这项研究发表在科学杂志《自然地球科学》上。