As the sea ice melts away from Greenland shores, massive icebergs fall from the island's coastal glaciers.
随着格陵兰沿岸的海冰不断融化，大量的冰山从这座岛屿沿岸的冰川崩落。
Greenland produces tens of thousands of icebergs each year. Some stretching up to a kilometer across.
每年格陵兰岛都会产生成千上万的冰山。有些冰山绵延长达一公里。
Over the next few months more than three hundred billion tons of ice will be released into the Arctic Ocean.
在未来几个月里，超过三千亿吨崩离的冰体将会进入北冰洋。
All around the Arctic Circle, the sea ice is beginning to break up.
整个北极圈沿线，海冰都开始破裂。
By September, two thirds of the ice will have melted away.
到了九月份三分之二的冰体都会融化。
This massive seasonal change governs the lives of all the animals that live in the Arctic, especially the polar bears.
这种剧烈的季节更替主宰了北极圈内所有动物的命运，特别是北极熊。
In spring, the sea ice covering the Arctic Ocean is melting.
春季里，覆盖北冰洋的海冰在融化。
Whales return to the warmth of western Greenland, amongst them are narwhals.
鲸类纷纷回到温暖的西格陵兰海岸。其中的一种是角鲸。
These narwhals have spent the winter further south on the edge of the pack ice.
这些角鲸在南方的浮冰区的边缘度过冬季的。
Now as the ice melts, the whales follow pathways that grow to extend many hundreds of kilometers north into the frozen Arctic Ocean.
现在随着冰层融化，它们就沿着向北延伸几百公里的水路游动直达冰冻的北冰洋。
They are heading for their summer feeding grounds.
它们的目的地是夏季的进食区。
Narwhals are famous for their single spiral tusk which centuries ago, inspired the myth of the unicorn.
角鲸以独一无二的螺旋状尖角著称几世之前，人们对神话中独角兽的遐想就来自于它。
It's actually a huge oversize tooth and in mature adults, it can grow up to three meters long.
那实际上是一只超大号的牙齿，而成年角鲸的尖角可以长到三米长。
Some females grow a small tusk, but it's never as prominent as that of the males.
有些雌性角鲸长着稍小的尖角，但远不如雄性角鲸的那么显眼。
The purpose of the tusk remained something of a mystery, but it's thought it may help establish status between males.
这种尖角的作用始终是一个谜团，不过有人认为它可能有助于雄性角鲸确立它们的地位。
Groups of males often duel with each other using their sword-like tusks.
成群的角鲸经常用它们剑一般的尖角相互决斗。
Scientists believe these contests are a way of sizing up rival males before mating takes place.
科学家们认为这种角逐是雄性角鲸在交配前估量对手实力的一种方式。
The narwhals are swiftly followed up to coast of Greenland by pods of beluga whales.
白鲸动作迅速地尾随在角鲸群后来到格陵兰海岸。
Like the narwhals, the belugas are heading for the Northwest Passage.
与角鲸一样白鲸也打算游往西北航道。
This is a legendary pathway through the Arctic Ocean across the top of Canada, leading from the Atlantic to the Pacific Ocean.
这条著名航道穿过北冰洋，横越加拿大北端，从大西洋通往太平洋。
The melting sea ice is unpredictable and constantly on the move.
融化中的海冰行踪难测而且在不断移动。
If the weather turns bad, it can refreeze at speed.
如果天气变坏，它就会很快又冻结。
These treacherous waters brought ruin to many early European explorers and the belugas can also fall foul of the ice.
这些及其危险的水域给很多早期的欧洲探险者带来了灾难，而白鲸也同样有可能与浮冰相撞。
If the sea refreezes, they can become trapped, unable to feed or reach the surface to breathe.
如果海面再次冻结，它们就会被困住无法进食以及探出水面进行呼吸。
Traveling in groups, they use the sophisticated sonar system to navigate through the ice.
它们成群航行，利用体内复杂的声纳系统在浮冰间进行导航。
Early sailors called belugas "sea canaries".
早期的水手们称白鲸为“海洋高音”。
By squeezing air out of their blow holes, they fill the ocean with an incredible repertoire of sound.
通过将空气挤压出自己的喷水孔，大海中充满了这种奇异的歌声。
These vocalizations bounce off the ice and help the belugas to find open water.
这种发声遇到冰层就会反弹回来从而帮助白鲸找到开阔水域。
The rich larger food that awaits the whales makes the journey well worth the risk.
等待着它们的大量丰富的食物使得它们的冒险之旅物有所值。