在南北极的海底，有时能见到从海面一直延伸到海底的细长冰柱，神话故事经常把死神白色的手指描写成这样，只要生命与它轻轻触碰，就会瞬间被冰封在原地！由于人们惊叹于海底冰柱对海底生物的巨大杀伤力，形象地把它称作“死亡冰柱”。这样让动物心生恐怖的“死亡冰柱”如何形成的呢？为什么只在南、北极地区现身？

      At the bottom of the Arctic regions and Antarctic regions, a long and thin icicle that stretches from the surface to the bottom of the sea can sometimes be seen, which is often depicted as the white finger of death that any creature will be instantly frozen as long as he or she touches it in myths. As people marvel at the great lethality of the submarine icicles to the underwater creatures, they tend to call them “icicles of death”. However, how are the “icicles of death” formed and why can they only be found in the Arctic and Antarctic regions?

      原来，在南、北极地区的冬季，海面上遍布海冰。海冰上下的温度是有区别的，海面通常低于-20°C，海水有海冰保温温度仅为-1.9°C左右。当海面气温过低，海水开始结冰时，由于盐分析出，导致冰块周围的海水盐度增加。这些高盐度的海水，冰点更低，密度更大，在冰块周围温度降到普通海水的冰点以下时仍不结冰，又因为密度大的关系不断下沉，使下方的海水温度降到冰点以下，从而凝固。这一过程不断发生，从而形成了快速向下生长的冰柱。

       It turns out that the sea surfaces in the Antarctic regions and Arctic regions are covered with ice in winter. At that time, the temperature of the sea surface is usually below -20 ° C but that of the sea water is about -1.9 ° C because of the insulation work of the sea water. When the temperature of the sea surface is too low and seawater begins to freeze, the salinity of the seawater around the ice increases due to the separation of salt. The seawater with high salinity still does not freeze for its lower freezing point and greater density. Furthermore, such seawater sinks constantly because of its great density so that the seawater below freezes when its temperature reaches its freezing point. When this process mentioned above occurs continuously, the icicles can be formed.

       由此可见，南、北极海面上极度寒冷的气温，是“死亡冰柱”主要形成的原因。不断向海底延伸生长的“死亡冰柱”，必须从海面有源源不断的低温传导，这才是维持“死亡冰柱”势力范围的关键。当海面回暖后，冷能来源慢慢减弱，冰柱也逐渐被海水融化直到消失。

      Therefore, the extremely cold temperatures on the seawater surfaces of the Antarctic regions and Arctic regions are the main reasons for the formation of the “icicles of death”. And the constant low-temperature heat conduction from the seawater surface is the key to the expansion of them. When the sea warms up, the source of cold energy slowly decreases, which leads to the melting and disappearance of the icicles.

本文来源：南海海洋资源利用国家重点实验室