From April to July is the peak hunting season for bears when they eat almost ninety percent of their yearly diet.
四月到六月是北极熊的捕猎高峰期，它们在此期间的捕食量几乎占全年总量的百分之九十。
They need the ice to hunt their seaborne prey and they must build enough fat preserve to see them through the ice free summer months.
它们需要冰层才能捕食生活在海里的猎物，而且它们必须积累足够的体内脂肪来熬过冰层融化的夏季时光。
Death is swift with a bite to the head.
被一口咬住头部，猎物很快就死了。
A seal pup full of its mother's milk is a nutritious, energy rich meal.
一头体内充满母乳的小海豹就是一顿富含营养和能量的美餐。
Hunting seal is never easy, but for a mother bear accompany by noisy cubs, the challenging is even greater.
捕猎海豹向来都不容易，而对带着吵闹小熊的母熊来说这就更为艰难了。
The cubs will stay with their mother for over two years learning everything they need to know to survive.
小熊们将与妈妈呆在一起两年多，学习求生所需要的一切东西。
This cub is eager to get stuck in.
这头小熊急切地想钻进去。
The cubs copy the techniques their mother uses to hunt.
小熊们模仿着妈妈捕猎时采用的动作。
But out on the ice, the mother bear is careful to keep her cubs close to her at all times.
不过在冰面上母熊谨慎地时刻使孩子们围绕在自己身边。
A large male bear would kill the cubs given the opportunity. For a male, the cubs are simply food.
体型庞大的公熊一旦有时机就会杀死小熊。对公熊来说，小熊只是食物而已。
Male bears are much larger than females and the mother bear must avoid any encounters if her cubs are to survive.
公熊的体型比母熊大得多，因此母熊必须尽力避免与公熊相遇以保证小熊能够存活下来。
By late April, the high Arctic has daylight around the clock.
到了四月末高纬度的北极地区已是通宵白昼了。
For the next six months, the sun won't sink below the horizon and its nonstop warmth begins to melt the ice
在未来六个月里，太阳将不会落至地平线以下，它所持续释放的热量开始融化。
The vast island of Greenland is covered with a gigantic ice sheet, in places the ice is more than three kilometers thick, making it the largest body of ice in the northern hemisphere.
冰雪广阔的格陵兰岛被巨大的冰原覆盖，某些地方的冰厚度超过了三公里，使它成为了整个北半球最大的冰体。
As the surface of the ice sheet begins to melt, water is on the move everywhere as drips turn to waterfalls and streams flow into roaring rivers,
随着冰原的表面开始融化，冰融水在到处流动滴水变成了瀑布，溪流变成了咆哮的大河。
Vertical shafts swallow entire rivers as water plunges down to the base of the icecap.
竖井般的冰洞吞没了整个河流，冰融水冲到冰盖底部。
The sound of the melt is deafening.
冰块融化的声音震耳欲聋。