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Climate change is rapidly warming the Earth and altering ecosystems on land and at sea that produce our food. In the oceans, most added heat from climate warming is still near the surface and will take centuries to work down into deeper waters. But as this happens, it will change ocean circulation patterns and make ocean food chains less productive. 气候变化使得地球温度急速上升，改变了为我们供应食物的陆地与海洋生态系统。 在海洋中，气候变暖带来的绝大部分热量还在海平面，需要几个世纪的时间才能进入更深的海域。但是，随着这种情况的出现，海洋环流模式就会改变，海洋食物链的生产力也会下降。 In a recent study, I worked with colleagues from five universities and laboratories to examine how climate warming out to the year 2300 could affect marine ecosystems and global fisheries. We wanted to know how sustained warming would change the supply of key nutrients that support tiny plankton, which in turn are food for fish. 在最近的一项研究中，我与来自五所大学和实验室的同事们一起研究了到2300年气候变化如何影响海洋生态系统和全球渔业。我们想知道持续变暖将如何改变支持微型浮游生物（鱼类的食物来源）生存的主要营养物质的供应。 We found that warming on this scale would alter key factors that drive marine ecosystems, including winds, water temperatures, sea ice cover and ocean circulation. The resulting disruptions would transfer nutrients from surface waters down into the deep ocean, leaving less at the surface to support plankton growth. 我们发现，这种规模的变暖将改变驱动海洋生态系统的关键因素，如：风、水温、海冰覆盖和海洋环流。由此产生的干扰会将地表水中的营养物质转移到深海中，减少海平面上支持浮游生物生存的营养物质。 As marine ecosystems become increasingly nutrient-starved over time, we estimate global fish catch could be reduced 20 percent by 2300, and by nearly 60 percent across the North Atlantic. This would be an enormous reduction in a key food source for millions of people. 随着海洋生态系统中营养物质的逐渐减少，我们估计全球鱼类捕捞量可能会减少23%，北大西洋鱼类捕捞量减少60%。将减少数百万人的主要食物来源。 Ocean food production and the biological pump 海洋食品生产与生物泵 Marine food production starts when the sun shines on the ocean’s surface. Single-celled, mostly microscopic organisms called phytoplankton – the plants of the oceans – use sunlight to photosynthesize and grow in a process called net primary production. They can only do this in the sunlit surface layer of the ocean, down to about 100 meters (330 feet). But they also need nutrients to grow, particularly nitrogen and phosphorus, which can be scarce in surface waters. 当太阳照射到海平面的时候，海洋食物的生产就开始了。单细胞生物（大部分的微生物都被称为浮游植物，是海洋中的植物）利用太阳光在净初级生产过程中进行光合作用和生长。这些浮游生物只能在阳光照射的海洋表层和海平面以下约100米（330英尺）之间的地方进行光合作用。但是，它们也需要养分，尤其是在海平面可能较为稀有的氮和磷。  Phytoplankton, the plants of the ocean. NOAA 浮游植物，海洋中的植物 Phytoplankton are consumed by zooplankton (tiny animals), which in turn provide food for small fish, and so on all the way up the food chain to top predators like dolphins and sharks. Unconsumed phytoplankton and other organic matter, such as dead zooplankton and fish, decompose in surface waters, releasing nutrients that support new phytoplankton growth. 浮游植物被浮游动物（微型动物）吃掉，反过来，这些浮游动物又被小鱼吃掉，如此顺着食物链一直到海豚和鲨鱼等顶级食肉动物。未被吃掉的浮游植物和其他有机物质，如死亡的浮游动物和鱼类，会在表层水域分解，释放出能够支持新的浮游植物生长的营养物质。 Some of this material sinks down into the deeper ocean, providing food for deep sea ecosystems. Carbon, nitrogen, phosphorus and other nutrients in this sinking organic matter ultimately are decomposed and released at depth. 其中一些物质沉入深海，为深海生态系统提供食物。这种沉没的有机物质中的碳、氮、磷和其他营养物质最终被分解，并在海洋深处释放出来。 This process, which is known as the biological pump, continually removes nutrients from surface waters and transfers them to the deeper ocean. Under normal conditions, winds and currents cause mixing that eventually brings nutrients back up to the sunlit surface waters. If this did not happen, the phytoplankton eventually would completely run out of nutrients, which would affect the entire ocean food chain. 这一过程就被称为生物泵，持续不断地去除表层水域中的营养物质，并将它们转移到更深的海洋中。在正常情况下，风和洋流一起发挥作用，最终将营养物质带回阳光照射的表层水域。如果这些营养物质未被带回，浮游植物终会完全耗尽营养，从而给整个海洋食物链造成影响。 Sea ice, winds and nutrient upwelling 海冰、风和营养物质上升流 Nutrients that sink to the deep ocean eventually return to the surface mainly in the Southern Ocean around Antarctica. North of Antarctica, strong westerly winds push surface waters away from Antarctica. As this happens, deep ocean waters that are rich in nutrients rise up to the surface all around Antarctica, replacing the waters that are being pushed away. The zone where this upwelling occurs is called the Antarctic Divergence. 沉入深海的营养物质最终会返回到南极洲附近的南大洋海面。在南极北部，强劲的西风将海平面的水吹离南极洲。这时，富含营养物质的深水海域上升到南极周围的水面，取代被吹走的水域。发生这种上升流的区域被称为南极辐散带。  When winds displace surface ocean waters, nutrient-rich colder waters well up from below. NOAA 当风吹走表面的海水时，营养丰富但温度较低的海水从下方上升。 Today there isn’t a lot of phytoplankton growth in the Southern Ocean. Heavy sea ice cover prevents much sunlight from reaching the oceans. Concentrations of iron (another key nutrient) in the water are low, and cold water temperatures limit plankton growth rates. As a result, most nitrogen and phosphorus that upwells in this area flows northwards in surface waters. Eventually, when these nutrients reach warmer waters throughout the lower latitudes, they support plankton growth over most of the Pacific, Indian and Atlantic oceans. 今天，南大洋海域并没有太多的浮游植物生长。厚重的海冰使得太阳光无法照进海洋。水中的铁（另一种主要的营养物质）浓度很低，冰冷的海水减缓了浮游生物的生长速度。因此，该地区上升的大部分氮和磷随着海平面向北流动。最终，当这些营养物质抵达较低纬度地区的温暖水域时，将支持太平洋、印度洋和大西洋大多数浮游生物的生长。 Trapping nutrients in the deep ocean 在深海捕获营养物质 Our study demonstrated that sustained, multicentury global warming could short-circuit this process, leaving all ocean areas to the north of this Antarctic zone increasingly starved for nitrogen and phosphorus. 我们的研究表明持续长期的全球变暖可能会使这一过程缩短，使南极北部地区的所有海域越来越缺乏氮和磷。 We used a climate model simulation that assumed nations continued to use fossil fuels until global reserves were exhausted. This climate path would raise mean surface air temperature by 9.6 degrees Celsius (17.2 degrees Fahrenheit) by 2300 – nearly 10 times the warming beyond pre-industrial levels recorded up to the present. Scientists already know that the poles are warming faster than the rest of the planet, and in this scenario that pattern continues. Eventually the oceans would no longer freeze over near the poles, even in winter. 我们使用气候模型模拟，假设各国继续使用化石燃料，直到将全球储量耗尽。这条气候路径将使平均地表气温在2300年上升9.6摄氏度（17.2华氏度）——是前工业化时代至今变暖程度的近十倍。科学家们已经知道，两极的变暖速度比地球的其他地方要快；在这种情况下，气候变暖还在继续。最后出现的情况就是，即使在冬季，两极附近的海洋可能都不会结冰。 Warmer ocean waters without sea ice, aided by shifts in winds that are also driven by strong climate warming, would greatly improve growth conditions around Antarctica for phytoplankton. This increased growth would trap nutrients that well up near Antarctica, preventing them from flowing northwards and supporting low-latitude ecosystems worldwide. 温暖的海洋没有海冰，以及气候变暖导致的风的变化，将大大改善南极洲周围浮游植物的生长条件。这种生长条件的改善会捕获南极附近的营养物质，阻止它们向北流动，使得它们无法支持全球的低纬度生态系统。 In our simulation, these trapped nutrients eventually mix back to the deep ocean and accumulate there. Nitrogen and phosphorus concentrations in the upper 1,000 meters (3,300 feet) of the ocean steadily decrease. In the deep ocean, below 2,000 meters, they steadily increase. 在我们的模拟中，这些被捕获的营养物质最终会汇合并堆积到深海。海洋上层1000米（3300英尺）的氮和磷浓度稳步下降；在2000米以下的深海中，浓度稳步上升。  Large, brilliant clouds of blue in the dark waters of the South Atlantic are phytoplankton blooms. Nutrients drifting north from Antarctica fuel these blooms, which provide food for larger plankton and fish. Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC 在大西洋南部的黑暗水域里，这些蓝色、灿烂的巨大云朵就是大量繁殖的浮游植物。从南极洲向北漂流的营养物质为这些浮游植物提供养料，从而为更大的浮游生物和鱼类提供食物。 Far fewer fish 鱼类比我们想象中少得多 As marine ecosystems become increasingly nutrient-starved, phytoplankton growth and net primary production throughout most of the world’s oceans would decline. We estimate that as these impacts ripple up the food chain, global fish catches could be reduced 20 percent by 2300, with decreases of more than 50 percent across the North Atlantic and several other regions. Moreover, at the end of our simulation net transfer of nutrients to the deep ocean was still taking place, which suggests that ecosystem productivity and potential fisheries catch would decline even further beyond 2300. 随着海洋生态系统中的养分越来越少，全球大部分海洋中浮游植物的生长和净初级生产都会下降，我们估计，随着这些影响逐渐波及食物链，到2030年，全球鱼类捕捞量可能会减少23%，北大西洋和其他几个地区将减少50%以上。此外，在模拟即将结束时，营养物质净迁移到深海的现象仍在发生，这就告诉我们生态系统的生产力和潜在的渔业捕捞量将进一步下降，远不如2030年的捕捞量。 Eventually, after more than a thousand years, most of the carbon dioxide that human activities have added to the atmosphere will be absorbed by the oceans, and the Earth’s climate will cool back down. Sea ice will return to polar oceans, suppressing phytoplankton growth around Antarctica and allowing more upwelled nutrients to flow north once again to lower latitudes. But even then, it will take centuries more for ocean circulation to fully replenish nutrients in the upper ocean. 最终，一千多年以后，人类活动释放到大气中的大部分二氧化碳将被海洋吸收，地球的温度将变得凉爽。极地海洋重新出现了海冰，抑制了南极周围浮游植物的生长，使得更多的营养物质上升流再次流向北部的低纬度地区。但即便如此，海洋环流仍然需要花费几百年的时间才能充分补充海洋上层的养分。  Phytoplankton are critical to life on Earth. Climate change is interfering with ocean mixing processes that promote phytoplankton growth. 浮游植物对地球上的生命至关重要。气候变化干扰了促进浮游植物生长的海洋混合过程。 Ocean resources are already stressed today. About 90 percent of the world’s marine fisheries are fully fished or overfished. World population is projected to increase from 7.3 billion in 2015 to 11 billion in 2100. The impacts that we found in our study would have serious implications for global food security. Expanding aquaculture, or even more drastic steps such as directly fertilizing the oceans to spur plankton growth, would not even come close to making up for the loss of nutrients to the deep ocean driven by sustained global warming. 今天，海洋资源面临巨大压力。世界上大约90%的海洋渔业都已经出现了完全捕捞或过度捕捞的现象。世界人口预计将从2015年的73亿增长到2100年的110亿。我们在研究中发现的影响可能会对全球粮食安全带来严重威胁。就算我们扩大水产养殖，或者是采取更激烈的手段，如直接给海洋施肥以促进浮游生物的生长，我们都无法弥补持续的全球变暖导致的深海养分流失。 Our simulation was based on a strong climate warming scenario. More research is needed to explore just how warm the climate has to get to melt sea ice and initiate Southern Ocean nutrient trapping. But clearly this is a tipping point that we don’t want to cross. 我们的模拟以较强的气候变暖情景为基础。需要通过更多的研究，来探索气候变暖到什么程度就能使海冰融化，并导致南大洋的营养捕获。很明显，这是一个我们并不想跨越的临界点。 April 19, 2018 6.50am EDT |
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