南极长年冰天雪地,人迹罕至,不少奇怪异象都是世人从未见过,英国广播公司( BBC)摄制队,早前首次在南极海底拍摄到“死亡冰柱”( icicle of death),冰柱下沉到海床后,所到之处周遭的海水都会凝结,海胆、海星全被冻死,蔚为奇观。
其实这种死亡冰柱自 1960年代已开始存在,通常当南极海洋混入了带盐份的水后就会出现,不过今次还是首度有人拍摄到这个奇景。拍摄当日,海底水温只得-2℃, BBC摄影师米勒( Hugh Miller)及安德森( Doug Anderson)在南极罗斯群岛( Ross Archipelago)的小剃刀背岛( Little Razorback Island)海中,亲眼目击死亡冰柱的形成过程。
由于冰柱的密度较海水高,因此一直朝海床沉下,并迅速扩张,周遭接触到冰柱的海水随即变冷凝固,但看上去像海绵状多过普通海冰,而附近的海洋生物,如海胆及海星等,因冰柱的温度太低而全被冻死。
米勒忆述当日亲眼目击冰柱沉下并迅速扩张,仍感到有点难以置信,“这情况有点像与时间竞赛,因为没有人真正知道它们形成得有多快。我们一星期前看到的那条冰柱,在我们面前迅速扩张变长,整个过程只用了5、6小时。”
Remarkable broadcast moment: The ice begins to expand outwards. The brine is a lot more dense than seawater so sinks to the bottom. It is also a lot colder - causing the freezing
Touchdown: The brinicle reaches the ocean floor. Starfish can be seen. Often the brinicles break up before they become so large
Killer: The ice floods outwards across the ocean surface rapidly, destroying everything in its wake
Destruction: The starfish are frozen by the ice as it expands outwards
Broadcasting feat: Although the existence of brinicles has long been known it is the first time they have ever been caught on camera
Seabed spread: When the seawater freezes as it comes into contact with the brinicle it is a lot more spongelike than normal ice