【经济学人】海水有多热？ | 2016.12.17 | 总第769期

“NOBODY really knows” was Donald Trump’s assessment of man-made global warming, in an interview on December 11th. As far as the atmosphere is concerned, that puts him at odds with most scientists who have studied the matter. They do know that the atmosphere is warming, and they also know by how much. But turn to the sea and Mr Trump has a point. Though the oceans are warming too, climatologists readily admit that they have only a rough idea how much heat is going into them, and how much is already there.

唐纳德·特朗普在12月11日的一次访谈中，发表了对人为原因造成全球变暖一事的看法，他的评价是“天晓得它变没变暖”。鉴于这关系到大气，此事使得唐纳德·特普与研究此问题的大多数科学家起了争执。因为这些科学家清楚地知道大气正在变暖以及变暖的确切数值。但说道海水变暖一事，特朗普先生的观点更能站得住脚。虽然海洋也在变暖，但是气候学家们爽快地承认道目前只能粗略地估计海洋温度未来会升高多少度，以及目前已经升高了多少度。

Many suspect that the heat capacity of seawater explains the climate pause of recent years, in which the rate of atmospheric warming has slowed. But without decent data, it is hard to be sure to what extent the oceans are acting as a heat sink that damps the temperature rise humanity is visiting upon the planet—and, equally important, how long they can keep that up.

许多人怀疑近几年来气候停止变暖的原因是海水的热容量，是它减缓了大气变暖速率。（期待您的翻译，明天会有针对这句话的长难句解析呦~）

This state of affairs will change, though, if a project described by Robert Tyler and Terence Sabaka to a meeting of the American Geophysical Union, held in San Francisco this week, is successful. Dr Tyler and Dr Sabaka, who work at the Goddard Space Flight Centre, in Maryland, observe that satellites can detect small changes in Earth’s magnetic field induced by the movement of water. They also observe that the magnitude of such changes depends on the water’s temperature all the way down to the ocean floor.

但如果本周在旧金山召开的美国地球物理学会上，罗伯特·泰勒和特伦斯·沙巴卡博士所演讲的课题成功的话，那么整个事态将改变。泰勒博士和沙巴卡博士任职于马里兰州的戈达德太空飞行中心，他们负责观测那些能够检测海水流动引起的地球磁场的微小变化的卫星。他们还发现地球磁场变化的幅度取决于从海水表面一路下降到海底的温度变化。

美国地球物理学会

That, they think, opens a window into the oceans which has, until now, been lacking. To measure things in the deep sea almost always requires placing instruments there—either by lowering them from a ship or by putting them on board submarine devices. The supply of oceanographic research vessels, though, is limited, and even the addition in recent years of several thousand “Argo” probes (floating robots that roam the oceans and are capable of diving to a depth of 2,000 metres) still leaves ocean temperatures severely under-sampled.

因此他们认为，这一发现为海洋研究领域开启了一扇全新的大门。此前若要在深海中测量数据，必须在海底安置测量仪器，要么利用船只或潜水装置将其放到海底。但海洋科学研究船的数量十分有限。虽然近年来“Argo”探测器（一种能在海中漫游并能下潜至海下2000米深处的可漂浮机器人）的数量已达数千只。但海洋温度数据的采样仍然不足。

Satellites, however, can look at the whole ocean—and, if they are properly equipped, can plot ways in which Earth’s magnetic field is deflected by seawater. This deflection happens because seawater is both electrically conductive and always on the move. Such a moving conductor will deflect any magnetic field that passes through it. Crucially, saltwater’s conductivity increases with its temperature. This means the deflection increases, too. And since the magnetic field originates from within Earth, it penetrates the whole ocean, from bottom to top. So any heat, whether in the deepest troughs or near the surface, contributes to the deflection.

相比探测器，卫星能够俯瞰整个海洋。并且如果经过适当调配，可以绘制出海水使地球磁场发生偏移的方式。由于海水本身导电，而且总是处于流动状态，因此磁场偏移是一直存在的。海水这一流动导体能致使任何经过的电磁场发生偏移。最重要的一点是，盐水的电导率会随着自身温度的升高而提高。这意味着磁场偏移也会随之增大。而地球磁场源于地球内部，贯穿整个海洋的。因此海水内部的所有热量，无论在海底波谷处或是近海表面，都会使该偏移量增大。

地球磁场

All this means that, if you know where and how ocean water is displaced, the changes in the magnetic field, as seen from a satellite, will tell you the heat content of that water. Dr Tyler and Dr Sabaka therefore built a computer model which tried this approach on one reasonably well-understood form of oceanic displacement, the twice-daily tidal movement caused by the gravitational attraction of the moon.

所有这一切意味着，如果你知道海水发生位移的位置和过程的话，那么利用卫星观测到的磁场变化，即可得到海水的热容量。因此泰勒博士和沙巴卡博士构建了一个计算机模型，并用了一个合理易懂的海洋位移（即月球引力造成的每天两次的潮汐运动）来验证此方法。

Sadly, when they had crunched all the numbers, they found that with the available magnetic data, understanding the tides alone is not enough to calculate the oceans’ heat content. That requires one or both of two things to happen: adding the effects of other water movements, such as ocean currents and solar (as opposed to lunar) tides to the calculation, and collecting better magnetic data. The second approach, at least, is already in hand. Three recently launched European satellites, known collectively as Swarm, are busy gathering just the sort of data required. So if Dr Tyler and Dr Sabaka can upgrade their model of ocean movement appropriately to receive Swarm’s data, they may yet answer the questions of how much heat there is in the sea, and how much more it might reasonably be expected to absorb.

可惜的是，他们发现在得到相关数据之后，仅靠潮汐运动，根本无法计算出海洋的热含量。这还需要以下一两个条件：第一，还需了解其他海水运动的影响，例如：洋流和日潮（相对于月潮来说）的计算以及更详尽的磁场数据；第二点便是至少目前已经可以利用的数据。欧洲最近发射的三颗“Swarm”计划项下的卫星正在紧锣密鼓地收集上文提到的必要数据。所以如果泰勒博士和沙巴卡博士能够对其海洋运动模式进行适当升级使其能够接收Swarms数据的话，他们或许还能够计算出海洋热容量，并且还有可能计算出未来海洋还能够容纳的热量的合理数值。

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