Resting balloonfish near the Florida Keys. Credit: OAR/National Undersea Research Program (NURP); University of Maine

在佛罗里达群岛附近休息的气球鱼。图片来源：OAR/国家海底研究计划（NURP）； 缅因大学

“Many millions of years ago, not so long after animal life in the ocean got started, the entire global ocean circulation seemed to periodically shut down,” said Ridgwell. “We were not expecting to find that the movement of continents could cause surface waters and oxygen to stop sinking, and possibly dramatically affecting the way life evolved on Earth.”

“数百万年前，在海洋中的动物生命开始后不久，整个全球海洋环流似乎周期性地关闭，”里奇韦尔说。 “我们没想到会发现大陆的运动会导致地表水和氧气停止下沉，并可能极大地影响地球上生命的进化方式。”

Up until now, models used to investigate the evolution of marine oxygen over the last 540 million years were relatively simple and didn’t account for ocean circulation. In these models, ocean anoxia — times when oceanic oxygen disappeared — implied a drop in atmospheric oxygen concentrations.

到目前为止，用于研究过去 5.4 亿年海洋氧气演化的模型相对简单，没有考虑海洋环流。 在这些模型中，海洋缺氧，海洋氧气消失的时间，意味着大气中的氧气浓度会下降。

“Scientists previously assumed that changing oxygen levels in the ocean mostly reflected similar fluctuations in the atmosphere,” said Alexandre Pohl, first author of the study and former UCR paleoclimate modeler, now at Université Bourgogne Franche-Comté in France.

“科学家们之前认为，海洋中氧气含量的变化主要反映了大气中类似的波动，”该研究的第一作者、前 UCR 古气候建模师、现就职于法国勃艮第弗朗什孔泰大学的亚历山大·波尔说。

Diorama of ancient Ediacaran period sealife displayed at the Smithsonian Institution. Credit: Smithsonian

史密森学会展出的古代埃迪卡拉纪海洋生物立体模型。图片来源：史密森尼

For the first time,  this study used a model in which the ocean was represented in three dimensions, and in which ocean currents were accounted for. According to the results, collapse in global water circulation leads to a stark separation between oxygen levels in the upper and lower depths.

这项研究首次使用了一个模型，其中海洋以三个维度表示，并考虑了洋流。 根据结果，全球水循环的崩溃导致上部和下部深度的氧气水平明显分离。

That separation meant the entire seafloor, except for shallow places close to the coast, entirely lost oxygen for many tens of millions of years, until about 440 million years ago at the start of the Silurian period.

这种分离意味着整个海底，除了靠近海岸的浅水区域外，在数千万年的时间里完全失去了氧气，直到大约 4.4 亿年前的志留纪开始。

“Circulation collapse would have been a death sentence for anything that could not swim closer to the surface and the life-giving oxygen still present in the atmosphere,” Ridgwell said. Creatures of the deep include bizarre-looking fish, giant worms and crustaceans, squid, sponges, and more.

Ridgwell 说：“对于无法游近地表且大气中仍然存在提供生命的氧气的任何事物，循环崩溃将是死刑判决。” 深海生物包括长相奇特的鱼、巨型蠕虫和甲壳类动物、鱿鱼、海绵等等。

The paper does not address if or when Earth might expect a similar event in the future. In fact, it is difficult to identify when a collapse might occur, or what triggers it. However, existing climate models confirm that increasing global warming will weaken ocean circulation, and some models even predict an eventual collapse of the branch of circulation that starts in the North Atlantic.

该论文没有说明地球是否或何时可能会在未来发生类似事件。事实上，很难确定何时可能发生崩溃，或者是什么触发了它。 然而，现有的气候模型证实，全球变暖的加剧将削弱海洋环流，一些模型甚至预测始于北大西洋的环流分支最终会崩溃。

“We’d need a higher resolution climate model to predict a mass extinction event,” Ridgwell said. “That said, we do already have concerns about water circulation in the North Atlantic today, and there is evidence that the flow of water to depth is declining.”

“我们需要更高分辨率的气候模型来预测大规模灭绝事件，”里奇韦尔说。 “也就是说，我们确实已经对今天北大西洋的水循环感到担忧，并且有证据表明水流向深处的流量正在下降。”

In theory, an unusually warm summer or the erosion of a cliff could trigger a cascade of processes that upends life as it appears today, Ridgwell said.

Ridgwell 说，理论上，一个异常温暖的夏天或海边悬崖的侵蚀可能会引发一连串的过程，从而颠覆出现在今天的生命。

“You’d think the surface of the ocean, the bit you might surf or sail on, is where all the action is. But underneath, the ocean is tirelessly working away, providing vital oxygen to animals in the dark depths,” Ridgwell said.

“你会认为海洋的表面，你可能冲浪或航行的地方，是所有行动的地方。 但在下面，海洋正在不知疲倦地工作，为黑暗深处的动物提供重要的氧气，”里奇韦尔说。

“The ocean allows life to flourish, but it can take that life away again. Nothing rules that out as continental plates continue to move.”

“海洋让生命蓬勃发展，但它可以再次夺走生命。 随着大陆板块继续移动，没有什么可以排除这种情况。”