是什么導(dǎo)致地球周期性地進出冰河時代

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.

溫暖的海水倒轉(zhuǎn)的“河流”可能是導(dǎo)致南極洲冰架斷裂、海平面上升的原因之一。但一項新的研究表明，在更冷的氣候下，海冰的增加可能會導(dǎo)致地球氣候發(fā)生更具破壞性的變化——另一個冰河時代。

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.

利用計算機模擬，研究表明，海冰的增加可能會顯著改變海洋的環(huán)流，最終導(dǎo)致海洋中二氧化碳含量的增加和空氣中二氧化碳含量的減少，從而逆轉(zhuǎn)溫室效應(yīng)。

“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.”

“該領(lǐng)域的一個關(guān)鍵問題仍然是，是什么導(dǎo)致地球周期性地進出冰河時代，”芝加哥大學(xué)教授、該研究的合著者馬特·詹森(Malte Jansen)在一份聲明中說。“我們非常確信大氣和海洋之間的碳平衡肯定已經(jīng)改變了，但我們不太清楚是如何改變的，也不知道為什么會改變。”

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.

上一個主要的冰河時代在更新世末期結(jié)束，大約250萬年前，冰川周期性地增長，然后變小。研究人員認為，地球軌道的變化可能是造成地球部分變冷的部分原因，但詹森補充說，可能還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.”

“最合理的解釋是，碳在大氣和海洋之間的分配方式發(fā)生了一些變化，”詹森繼續(xù)說。“關(guān)于這是如何發(fā)生的，有很多想法，但不太清楚它們是如何結(jié)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.

研究人員還認為，小冰河期可能發(fā)生在大約12800年前。它可能源于一次“震撼北半球”的小行星撞擊，并導(dǎo)致了更年輕的Dryas氣候事件。

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，南極洲周圍的南大洋由于該地區(qū)的深水而“在海洋環(huán)流中起著關(guān)鍵作用”，這將導(dǎo)致“嚴重后果”。

“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.”

“這表明這是一個反饋循環(huán)，”該研究的主要作者愛麗絲·馬佐基(Alice Marzocchi)說。“隨著氣溫下降，釋放到大氣中的碳減少，從而引發(fā)更多的降溫。”

“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補充說:“讓我驚訝的是，這些增加的儲存有多少是單獨歸因于物理變化，南極海冰是關(guān)鍵因素。”他指出，未來對海洋及其在碳循環(huán)中所扮演的角色的研究可以幫助模擬“未來的環(huán)境變化”。

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

這項研究發(fā)表在科學(xué)雜志《自然地球科學(xué)》上。