Frozen Planet

Our journey begins on the frozen Arctic Ocean. We follow a pair of courting polar bears revealing a surprisingly tender side. Next stop is the giant Greenland ice cap where waterfalls plunge into the heart of the ice. Further south, the tree-line marks the start of the Taiga forest, containing one third of all trees on earth. Here 25 of the world's largest wolves take on formidable bison prey.

The Antarctic begins in the Southern Ocean where teams of orcas create giant waves to wash seals from ice floes - a filming first. Below the ice we discover prehistoric giants. Above ground, crystal caverns ring the summit of Erebus, the most southerly volcano on earth. From here we retrace the routes of early explorers on their quest to be the first humans to reach the South Pole.

Spring brings the appearance of the sun after an absence of five months; warmth and life return to these magical ice worlds - the greatest seasonal transformation on our planet is underway. Male Adelie penguins arrive in Antarctica to build their nests, but these early birds face the fiercest storms on the planet. In the Arctic, a polar bear mother is hunting with her cubs.

As the transformation of the Arctic reaches completion, it teams with life, migrating from the south. In Antarctica vast numbers of seabirds arrive on South Georgia joining the giant albatross and king penguins that have been there all winter. Elephant seals fight furious battles over females on a beach and, finally, the female Adelie penguins arrive, chased from the water by killer whales.

It's high summer and the sun never sets. Vast hordes of summer visitors cram a lifetime of drama into one long, magical day; they must feed, fight and rear their young in this brief window. Summer is a tough time for the polar bear family as their ice world melts away. But summer also brings surprises as a huge colony of 400,000 king penguins cope with an unlikely problem - heat.

On the Island of South Georgia, a bull fur seal is prepared to fight to the death with a rival. Further south, a minke whale is hunted amongst the ice floes by a family of killer whales in a dramatic chase that has never been filmed before. Finally, comical Adelie penguins waddle back to their half a million strong colony.

Autumn means dramatic battles and epic journeys. Time is running out - the Arctic Ocean is freezing over. Polar bears gather on the Arctic coast as they wait for the return of the ice. Meanwhile two thousand beluga whales head for one special estuary, to thrash their snow-white bodies against the gravel and exfoliate. Inland, the tundra undergoes a dramatic transformation from green to fiery red.

Down in Antarctica, as the sea ice advances 2.5 miles a day, Adelie penguin chicks huddle together in crèches. When a parent returns from fishing, it leads its twins on a comical steeplechase - sadly there's only enough for one so the winner gets the meal. As winter approaches, and everyone has left, the giant Emperor penguin arrives and makes an epic trek inland to breed.

There is no greater test for life than winter as temperatures plummet to 70 below and winds reach 200kph. Darkness and ice extend and only a few remarkable survivors gamble on remaining. Arctic forests transform into a wonderland of frost and snow - scene to a desperate and bloody battle between wolf and bison, but also where a remarkable alliance between raven and wolverine is made.

In Antarctica, we join male emperor penguins in their darkest hour, battling to protect precious eggs from fierce polar storms. The sun finally returns, and with it comes the female emperor penguins, sleek and fat, ready to deliver the first meal to their precious chick. The adelies flood back and as the ice edge bustles with life, male emperor penguins can finally return to the sea.

We reveal the extraordinary riches and wonders that have kept people coming to the Polar Regions for thousands of years. Most Arctic people live in Siberia. On the coast, traditional people still hunt walrus from open boats, but today's settlers are drawn to the Arctic by its abundant minerals. Above, the spectacular Northern lights can disrupt power supplies so scientists monitor it constantly.

Today science is the only significant human activity allowed in Antarctica: robot submarines are sent deep beneath the ice in search of new life-forms, which may also be found in a labyrinth of ice caves high up on an active volcano. Above, colossal balloons are launched into the purest air on earth to detect cosmic rays.