PLANET EARTH Ice Worlds

Flocks forty thousand strong sweep across the frozen wastes. They all have the same goal a polinear, a permanent hole in the sea ice kept open throughout the winter by strong ocean currents. This unusual duck pond provides an overnight sanctuary（庇护所） and when day breaks a rare chance to feed. Just ten meters beneath the ice, the sea floor is carpeted with dense mussel beds（贻贝床）. These can only be reached during a brief lull in the currents. The ducks must quickly prise the mussels free before the tide starts to turn.



The window of opportunity is short. As the current begins to build it's up and away. These permanent holes in the ice provide seafood throughout winter. The diners attract others. In the Arctic, any breach in the icy barrier can be a lifeline. Musk oxen create their own. These giants have the strength to smash through the frozen crust to graze on the vegetation below.



These icebreakers create an opening for other over winterers. Flocks of ptarmigan（松鸡） make unusual grazing companions for the musk oxen whose entourage（随行人员） grows throughout the day. This odd assembly of vegetarians doesn't go unnoticed. An arctic fox. The musk oxen have recently given birth. For the fox, it's a chance to scavenge but half a ton of mad hairy cow is not to be trifled（轻视） with.