0:00:34 > 0:00:38Over one third of our planet is frozen,
0:00:38 > 0:00:41and yet, the icy worlds of the Arctic and Antarctic
0:00:41 > 0:00:44are as alien to most of us as the surface
0:00:44 > 0:00:46of another planet.
0:00:48 > 0:00:51They are places of superlatives.
0:00:51 > 0:00:55From ice caps that hold nearly 80% of our planet's fresh water
0:00:55 > 0:01:00to frozen forests that encircle the entire globe.
0:01:04 > 0:01:07These are places that feed our imaginations,
0:01:07 > 0:01:10places that seem to be borrowed from fairy tales.
0:01:12 > 0:01:15They're dominated and shaped by the ice...
0:01:17 > 0:01:20..both by its coming and by its going.
0:01:23 > 0:01:28This is our planet's last true wilderness
0:01:28 > 0:01:32and one that is changing just as we're beginning to understand it.
0:01:35 > 0:01:39In this series, we'll be travelling to all parts of these lonely lands,
0:01:39 > 0:01:41both north and south,
0:01:41 > 0:01:44to witness its wonders perhaps for the last time
0:01:44 > 0:01:47and to discover some extraordinary examples
0:01:47 > 0:01:50of survival against all the odds,
0:01:50 > 0:01:53as can be found anywhere on the planet.
0:02:16 > 0:02:20The poles are permanently capped with ice.
0:02:20 > 0:02:24Nowhere is colder, windier or more hostile to life.
0:02:29 > 0:02:35I'm standing at the North Pole - the very top of the Earth.
0:02:35 > 0:02:41Up here, it's easy to see why the polar regions are so cold.
0:02:41 > 0:02:47The sun never rises high enough in the sky to warm my back
0:02:47 > 0:02:50and those rays that do strike the surface
0:02:50 > 0:02:55are mostly reflected back from this great whiteness.
0:02:55 > 0:03:01But the fundamental problem is that there's no sun here at all
0:03:01 > 0:03:03for half the year.
0:03:03 > 0:03:07The polar winter is unrivalled in its harshness.
0:03:07 > 0:03:11A night that lasts for months.
0:03:11 > 0:03:13Only the toughest stay,
0:03:13 > 0:03:18as temperatures plunge to minus 70 degrees centigrade.
0:03:18 > 0:03:22And yet, the greatest challenge to life here is not the cold,
0:03:22 > 0:03:26but the extreme swings between the seasons.
0:03:28 > 0:03:30When the sun finally returns,
0:03:30 > 0:03:33an extraordinary transformation begins.
0:03:33 > 0:03:38This frozen world begins to melt away.
0:03:42 > 0:03:46The polar spring brings a brief opportunity for life.
0:03:49 > 0:03:52By summer, the sun no longer sets
0:03:52 > 0:03:55and works its magic for 24 hours a day.
0:03:59 > 0:04:04Now it's a race to breed before the sun departs.
0:04:08 > 0:04:12By autumn, all but the hardiest abandon the poles
0:04:12 > 0:04:15and the ice extends its grip.
0:04:20 > 0:04:26Land and sea close down for the long, polar winter,
0:04:26 > 0:04:30until, once again, the sun returns.
0:04:38 > 0:04:40It's spring in the High Arctic
0:04:40 > 0:04:43and the sun illuminates a giant frozen ocean,
0:04:43 > 0:04:45the first stop on our journey.
0:04:50 > 0:04:53The most powerful land predator is on the prowl.
0:04:59 > 0:05:03A male polar bear is searching for a mate.
0:05:07 > 0:05:10Willing females are few and far between
0:05:10 > 0:05:14and the sea ice on which he travels will soon melt and vanish.
0:05:16 > 0:05:22He's running out of time to find a mate in this vast, frozen desert.
0:05:38 > 0:05:43Ten miles ahead, a single female without cubs -
0:05:43 > 0:05:45exactly what the male is seeking.
0:05:47 > 0:05:52He seems to relish her scent, even though she's miles away.
0:05:54 > 0:05:56This is an exciting prospect.
0:05:58 > 0:06:01She's clearly giving off the right signals.
0:06:04 > 0:06:09He locks onto her tracks, eager not to lose her trail.
0:06:09 > 0:06:13It's easier to tread in the compacted snow of her footprints.
0:06:13 > 0:06:17This pursuit could last for days.
0:06:22 > 0:06:25The female eventually comes into view.
0:06:27 > 0:06:29The search is finally over.
0:06:43 > 0:06:45For the female, only half his weight,
0:06:45 > 0:06:48this must be a nerve-racking encounter.
0:06:48 > 0:06:51The male could kill her if he chooses.
0:06:55 > 0:06:57But he has other intentions...
0:06:59 > 0:07:01..and she is ready and willing.
0:07:04 > 0:07:07She leads him to higher ground.
0:07:12 > 0:07:16It seems that courting polar bears prefer privacy,
0:07:16 > 0:07:19often leaving the sea ice and heading for the hills
0:07:19 > 0:07:21to avoid the prying eyes
0:07:21 > 0:07:24of rival males who might disturb them.
0:07:27 > 0:07:30Few have witnessed this moment.
0:07:32 > 0:07:33For the male,
0:07:33 > 0:07:38his only tender encounter in an otherwise solitary life.
0:07:41 > 0:07:44But it doesn't last long -
0:07:44 > 0:07:47a rival suitor has also caught the female's scent.
0:07:49 > 0:07:54Courtship has to be put on hold. He must fight for his rights.
0:07:54 > 0:07:59THEY ROAR
0:08:04 > 0:08:10He sees off this first challenger without injury to either party,
0:08:10 > 0:08:13but bloodier battles are to come.
0:08:21 > 0:08:27THEY ROAR
0:08:39 > 0:08:45Another battle won, though he has been slightly injured.
0:08:45 > 0:08:47He hurries back to his mate,
0:08:47 > 0:08:50but now she seems to have lost her enthusiasm.
0:08:52 > 0:08:56Female polar bears are high-maintenance.
0:09:11 > 0:09:15Wherever she goes, he will follow, mating with her when she allows
0:09:15 > 0:09:17and guarding her at all times.
0:09:30 > 0:09:34Over the next two weeks, the male sees off many rivals
0:09:34 > 0:09:36but the battles take their toll on him.
0:09:42 > 0:09:45He is almost spent,
0:09:45 > 0:09:49but he has ensured that no other bears have mated with his female.
0:09:54 > 0:09:55It's time for the couple
0:09:55 > 0:09:58to go their separate ways.
0:09:58 > 0:10:03She will give birth to his cubs, alone, in nine months' time
0:10:03 > 0:10:06and he may never see her again.
0:10:08 > 0:10:10He returns to the frozen ocean,
0:10:10 > 0:10:14no doubt relieved to resume his solitary ways,
0:10:14 > 0:10:16and just in time.
0:10:16 > 0:10:20The ice beneath his feet will soon be gone.
0:10:23 > 0:10:26Each spring, the Arctic Ocean undergoes
0:10:26 > 0:10:29an extraordinary transformation.
0:10:29 > 0:10:33An area of sea ice the size of Europe melts,
0:10:33 > 0:10:35exposing the rich waters beneath.
0:10:38 > 0:10:41Short-tailed shearwaters have travelled 10,000 miles
0:10:41 > 0:10:43from Australia to be here.
0:10:51 > 0:10:5518 million visitors darken the skies,
0:10:55 > 0:10:58the largest gathering of sea birds on the planet.
0:11:13 > 0:11:17Humpback whales have come all the way from the Equator
0:11:17 > 0:11:19to feed in these rich, polar waters.
0:11:26 > 0:11:30Their giant tails are five metres across.
0:11:32 > 0:11:34Simply raising them above the surface
0:11:34 > 0:11:37gives the whales enough downward momentum
0:11:37 > 0:11:40to reach the great swarms of krill and herring below.
0:11:55 > 0:11:59The shearwaters follow the giants' lead.
0:12:19 > 0:12:22For those who can get here, in summer,
0:12:22 > 0:12:26these waters provide a feast of epic proportions.
0:12:26 > 0:12:29But the good times will be very short -
0:12:29 > 0:12:32a problem that faces all life in the polar regions.
0:12:35 > 0:12:38Journeying south across the Arctic Ocean,
0:12:38 > 0:12:41the first land you reach is Greenland,
0:12:41 > 0:12:43the largest island in the world.
0:12:45 > 0:12:48Despite its name, Greenland is mostly white,
0:12:48 > 0:12:50covered by a giant ice sheet
0:12:50 > 0:12:53six times the size of the United Kingdom.
0:12:57 > 0:13:01In the middle of the island, the ice is nearly two miles thick.
0:13:01 > 0:13:03It's a bleak, quiet world.
0:13:10 > 0:13:12Sapphire-blue melt lakes
0:13:12 > 0:13:17are the first sign that a dynamic process is underway.
0:13:20 > 0:13:25Each lake forms in a matter of days, expanding until it's miles across
0:13:25 > 0:13:27and starts to overflow.
0:13:29 > 0:13:33The spill water then carves its way through the ice.
0:13:44 > 0:13:47The water courses through an icy delta
0:13:47 > 0:13:52like blood along the arteries of a cold-blooded monster,
0:13:52 > 0:13:54a monster that is stirring.
0:14:06 > 0:14:11And without warning, the water suddenly plunges down an open shaft,
0:14:11 > 0:14:16falling a vertical mile into the heart of the ice sheet.
0:14:40 > 0:14:43This meltwater has a surprising effect -
0:14:43 > 0:14:45it lubricates the junction
0:14:45 > 0:14:48between the ice and the rock floor beneath,
0:14:48 > 0:14:52so the entire ice sheet is now on the move,
0:14:52 > 0:14:55sliding downhill into the ocean.
0:14:57 > 0:15:01This, Jakobshavn Isbrae,
0:15:01 > 0:15:03is the fastest-flowing glacier on our planet,
0:15:03 > 0:15:06moving as much as 40 metres a day.
0:15:09 > 0:15:14As it advances, it destroys everything in its path,
0:15:14 > 0:15:18even cutting its way through Greenland's great mountain ranges
0:15:18 > 0:15:21on its drive downwards towards the sea.
0:15:24 > 0:15:25When speeded up,
0:15:25 > 0:15:30these solid rivers of ice seem to flow just like liquid rivers.
0:15:36 > 0:15:38This is the titanic force
0:15:38 > 0:15:42that cuts down mountains and levels the surface of continents.
0:16:00 > 0:16:05The ice is now entering the last stage of its descent.
0:16:07 > 0:16:08As it gains speed,
0:16:08 > 0:16:12huge crevasses open that extend down to its very core.
0:16:18 > 0:16:20It's reached the ocean,
0:16:20 > 0:16:24and millions of tonnes of ice have lost the support of their rocky bed.
0:16:28 > 0:16:31Something must give.
0:16:31 > 0:16:33CREAKING
0:16:51 > 0:16:55These icefalls are an ominous sign of what is about to happen...
0:16:56 > 0:16:59..a rupture deep within the glacier.
0:17:26 > 0:17:29A colossal iceberg is born.
0:17:54 > 0:17:56This single block of ice,
0:17:56 > 0:17:58many hundreds of metres across,
0:17:58 > 0:18:01would dwarf the biggest of mankind's buildings.
0:18:08 > 0:18:10Every year,
0:18:10 > 0:18:14tens of thousands of icebergs are spawned by Greenland's glaciers,
0:18:14 > 0:18:16and their number is steadily increasing
0:18:16 > 0:18:19as the climate continues to warm.
0:18:30 > 0:18:34The break-up of the bergs fills the bays of the Arctic
0:18:34 > 0:18:36with exquisite ice sculptures.
0:18:37 > 0:18:42It also releases great volumes of cold, fresh water into the sea.
0:18:44 > 0:18:49Greenland's meltwater influences the course of the ocean currents,
0:18:49 > 0:18:54which, in turn, has an effect on the weather around the world.
0:19:02 > 0:19:06The Arctic is closer to home than many of us realise.
0:19:06 > 0:19:09It includes the northernmost parts of the three continents
0:19:09 > 0:19:14on which most of us live - Europe, Asia and North America.
0:19:17 > 0:19:20The first bare land we reach on our journey south
0:19:20 > 0:19:24is a bleak treeless wilderness known as tundra.
0:19:26 > 0:19:29Each spring, animals travel up from the south,
0:19:29 > 0:19:32to be ready for the rich grazing
0:19:32 > 0:19:35that will be unveiled by the spring melt.
0:19:36 > 0:19:38For the caribou,
0:19:38 > 0:19:39the timing is critical.
0:19:39 > 0:19:42Arrive early and a winter storm could kill you.
0:19:42 > 0:19:45Delay too long and you may fail to lay down the fat
0:19:45 > 0:19:47needed to survive a polar winter.
0:19:56 > 0:19:58Further south still,
0:19:58 > 0:20:04and stooped, shrouded figures end the flat monotony of the tundra.
0:20:07 > 0:20:11This is the tree line, the first place on our journey
0:20:11 > 0:20:13with sufficient warmth and liquid water
0:20:13 > 0:20:15to enable a tree to grow.
0:20:17 > 0:20:20Surviving here is so crushingly difficult,
0:20:20 > 0:20:23that it can take hundreds of years for a seedling
0:20:23 > 0:20:25to grow into a stunted shrub.
0:20:34 > 0:20:36But even small trees
0:20:36 > 0:20:38can provide cover for a predator.
0:20:40 > 0:20:43Wolves. These, in northern Canada,
0:20:43 > 0:20:46are the largest and most powerful in the world
0:20:46 > 0:20:48and they are setting out to hunt.
0:20:52 > 0:20:55The pack is 25 strong,
0:20:55 > 0:20:58a sign that the prey they are seeking is formidable.
0:21:06 > 0:21:10These bison are even bigger than their southern cousins
0:21:10 > 0:21:12and the largest land animals in North America.
0:21:12 > 0:21:17For generations, wolves and bison here
0:21:17 > 0:21:19have been shaped by their battles with each other,
0:21:19 > 0:21:23making each the most impressive of its kind.
0:21:25 > 0:21:28The bison will not stay long among the trees.
0:21:28 > 0:21:30They're not safe here.
0:21:36 > 0:21:38The wolves are closing in,
0:21:38 > 0:21:42but their chance of ambushing the bison in the woods has passed.
0:21:42 > 0:21:46Their prey are now in the open and grouped together for safety.
0:21:48 > 0:21:52The wolves will need to work as a team
0:21:52 > 0:21:53if they are to make a kill.
0:21:56 > 0:22:00They circle the herd, trying to unsettle it
0:22:00 > 0:22:01and split it up.
0:22:01 > 0:22:04But the bison are armed and dangerous.
0:22:04 > 0:22:07They will be safe as long as they stick together.
0:22:12 > 0:22:15The wolves up their game, harrying the herd,
0:22:15 > 0:22:17a ploy to trigger a stampede
0:22:17 > 0:22:19and split away one of the smaller ones.
0:22:22 > 0:22:26The bison form a defensive circle around their young,
0:22:26 > 0:22:28horns pointing outwards.
0:22:32 > 0:22:36The wolves need a bison to break rank.
0:22:42 > 0:22:46But the tables are turning and now the wolves have to retreat.
0:22:49 > 0:22:53The pack focus their attention on the rear of the herd
0:22:53 > 0:22:54and the bison begin to panic.
0:23:29 > 0:23:32A young bison falls behind.
0:23:38 > 0:23:41Even this yearling dwarfs the wolves.
0:23:49 > 0:23:52Running head-down, the herd's only thought is escape.
0:23:57 > 0:24:00A stroke of luck for the wolves.
0:24:13 > 0:24:16The kill will feed the pack for several days.
0:24:16 > 0:24:20But then they will have to resume the chase.
0:24:20 > 0:24:22At the frozen ends of our planet,
0:24:22 > 0:24:25the struggle for survival never eases.
0:24:36 > 0:24:39South of the tree line, the winters are shorter,
0:24:39 > 0:24:45so trees grow faster and taller and forests begin to appear.
0:24:45 > 0:24:51As the warm, humid air from the south meets the cold, arctic air,
0:24:51 > 0:24:57the moisture it carries crystallises and snowflakes fall from the sky.
0:25:00 > 0:25:03Each crystal forms around a particle of dust.
0:25:09 > 0:25:11All have a six-fold symmetry
0:25:11 > 0:25:15but no two have ever been found with exactly the same shape.
0:25:23 > 0:25:27Their variety and complexity is breathtaking.
0:25:33 > 0:25:38Each snowflake is water waiting to be released in spring.
0:25:38 > 0:25:39For this reason,
0:25:39 > 0:25:42snow is the lifeblood of these silent forests
0:25:42 > 0:25:46and all that live here depend on it in one way or another.
0:25:53 > 0:25:59Some, like the great grey owl, appear in spring for the boom times,
0:25:59 > 0:26:02then vanish like phantoms.
0:26:05 > 0:26:07Others, like their lemming prey,
0:26:07 > 0:26:12are here year-round beneath the snow, insulated from the cold air above.
0:26:33 > 0:26:36The northern forests are a crossroads
0:26:36 > 0:26:39for seasonal visitors and arctic specialists.
0:26:41 > 0:26:43But they are so much more than this.
0:26:43 > 0:26:47Together, they make up the taiga, an unbroken belt of forest
0:26:47 > 0:26:51that stretches 7,000 miles around our planet
0:26:51 > 0:26:55and contains one third of all the trees on Earth.
0:27:05 > 0:27:09The taiga forest marks the end of our journey through the Arctic,
0:27:09 > 0:27:13from the frozen ocean down across the lands that surround it.
0:27:22 > 0:27:27The other end of our planet, the Antarctic, is starkly different.
0:27:27 > 0:27:31A frozen continent completely surrounded by ocean.
0:27:33 > 0:27:36Icebergs here are so large
0:27:36 > 0:27:39that they're measured in miles not metres.
0:27:39 > 0:27:43They're the only obstacles in the path of giant waves,
0:27:43 > 0:27:46which circle around the continent unchecked by other lands.
0:28:01 > 0:28:05These seas may be cold and storm-racked
0:28:05 > 0:28:07but they're bursting with life.
0:28:35 > 0:28:38No bird is more at home in water
0:28:38 > 0:28:42and they are masterful surfers.
0:28:46 > 0:28:51Penguins are found only in the Southern Hemisphere.
0:28:51 > 0:28:56They can't fly, but they don't need to.
0:28:56 > 0:28:58There are no polar bears here.
0:29:07 > 0:29:09These are Gentoo Penguins.
0:29:09 > 0:29:14Each spring, they come ashore to lay their eggs and rear their young.
0:29:14 > 0:29:17Their hungry chicks demand so much seafood
0:29:17 > 0:29:20that both parents have to go fishing.
0:29:24 > 0:29:27And fishing can be dangerous.
0:29:43 > 0:29:45A southern sea lion.
0:29:49 > 0:29:54It uses the speed of a breaking wave to catch up with the Gentoos.
0:30:09 > 0:30:11Sea lions normally eat fish,
0:30:11 > 0:30:14so he's used to catching streamlined swimmers,
0:30:14 > 0:30:19but the Gentoos seem more than his match out at sea.
0:30:19 > 0:30:20He must change tactics.
0:30:24 > 0:30:28Perhaps it will be easier in the shallows.
0:30:50 > 0:30:54But no! It seems penguins are uncatchable in water.
0:31:01 > 0:31:02How about on land?
0:31:03 > 0:31:07The penguin's wings, so powerful for swimming,
0:31:07 > 0:31:10are of no help when it comes to running.
0:31:10 > 0:31:12Now, surely, the sea lion has a chance.
0:31:18 > 0:31:21But on the beach, both are like fish out of water.
0:31:44 > 0:31:48Rarely do hunter and hunted play their roles with so little skill.
0:31:48 > 0:31:50The outcome is anyone's guess.
0:32:26 > 0:32:28Every summer,
0:32:28 > 0:32:32over 40 million penguins take to the Southern Ocean to feed.
0:32:38 > 0:32:41They're joined by thousands of whales.
0:32:41 > 0:32:43Minkes are the most numerous.
0:32:46 > 0:32:49They all come here to harvest the richest ocean on Earth.
0:32:52 > 0:32:57Carrying on south, we get our first glimpse of the frozen continent.
0:33:12 > 0:33:17Southern humpbacks, after travelling 4,000 miles from the equator,
0:33:17 > 0:33:20are finally arriving in Antarctica.
0:33:25 > 0:33:28Humans have long felt the lure of this mysterious world,
0:33:28 > 0:33:31yet it was only a hundred years ago
0:33:31 > 0:33:35that the first explorers walked inland and were confronted by
0:33:35 > 0:33:39the highest, driest and coldest territory on Earth.
0:33:45 > 0:33:48Every year, the continent is transformed
0:33:48 > 0:33:51as the sea ice that surrounds it begins to disappear.
0:34:00 > 0:34:04This melt halves the size of Antarctica.
0:34:06 > 0:34:09It's the most spectacular seasonal change occurring
0:34:09 > 0:34:12anywhere on our planet.
0:34:15 > 0:34:19The remnants of the sea ice are occupied by sunbathing seals
0:34:19 > 0:34:21that have been here all winter.
0:34:24 > 0:34:28But new arrivals are following the retreating ice edge
0:34:28 > 0:34:31and they have come here to hunt.
0:34:38 > 0:34:41Killer whales, the ocean's top predator.
0:34:43 > 0:34:45Killers are like wolves,
0:34:45 > 0:34:48for they will hunt animals far larger than themselves.
0:34:48 > 0:34:52But even smaller prey are a problem if you can't reach them.
0:34:58 > 0:35:00The solution is teamwork.
0:35:01 > 0:35:05Swimming in perfect formation, they flick their tails in unison
0:35:05 > 0:35:09and create a wave that cracks the ice.
0:35:18 > 0:35:22They regroup and assess the damage. A more powerful wave is needed.
0:35:28 > 0:35:31The ice floe is breaking up.
0:35:32 > 0:35:36Now they are close enough to get a good look at their target.
0:35:36 > 0:35:40The seal is a crabeater, sharp-toothed and feisty.
0:35:40 > 0:35:42Not their favourite.
0:35:46 > 0:35:50The wolves of the sea move on in search of easier quarry.
0:35:55 > 0:35:58A Weddell seal. That's better.
0:35:58 > 0:36:01These are more docile and easier to tackle.
0:36:04 > 0:36:08The pod stays close together and travels silently.
0:36:10 > 0:36:13This time, they unleash a far more powerful wave,
0:36:13 > 0:36:16and with astonishing accuracy.
0:36:22 > 0:36:26These big waves are not intended to break the ice,
0:36:26 > 0:36:30but to knock the prey into the water, and they rarely fail.
0:37:16 > 0:37:18The seal is now where the killers want it,
0:37:18 > 0:37:23but the hunt is far from over.
0:37:25 > 0:37:28They need to grab their prey by the tail
0:37:28 > 0:37:29while avoiding its snapping jaws.
0:37:29 > 0:37:34Only then will they be able to pull it down and drown it.
0:37:38 > 0:37:42Sideswipes create violent underwater turbulence, a new tactic.
0:37:49 > 0:37:54Blowing bubbles gives cover for others to lunge at the seal's tail.
0:38:03 > 0:38:06Somehow, the seal manages to reach a tiny ice floe.
0:38:11 > 0:38:13The killers could easily grab it,
0:38:13 > 0:38:16but now this seems to have become a game.
0:38:18 > 0:38:22The seal's life hangs on a roll of the ice.
0:38:34 > 0:38:38Yet again, the pod joins forces to dislodge the seal.
0:38:55 > 0:38:58The seal sees a chance to escape.
0:39:03 > 0:39:07Exhausted, it no longer has the energy to pull itself to safety
0:39:07 > 0:39:10and the killers are moving in.
0:39:18 > 0:39:20Game over.
0:39:32 > 0:39:37Although such team hunts are rarely seen, scientists believe
0:39:37 > 0:39:41they may be the most complex ever documented in the natural world.
0:39:41 > 0:39:45They were first witnessed by Captain Scott and his men
0:39:45 > 0:39:48when they came to explore Antarctica 100 years ago.
0:39:52 > 0:39:56Journeying further south, the fragmenting ice is replaced
0:39:56 > 0:40:00by a permanent sheet that doesn't melt even at the height of summer.
0:40:02 > 0:40:06It's a barrier that many creatures find impassable.
0:40:08 > 0:40:11It repels even powerful minke whales.
0:40:11 > 0:40:12They have to turn back
0:40:12 > 0:40:16if they can no longer reach the air they need to breathe.
0:40:23 > 0:40:29Under the ice, life has to be extremely specialised to survive.
0:40:30 > 0:40:36Few of us will ever experience this strangely-still world,
0:40:36 > 0:40:38and, as yet, no-one knows much about it.
0:40:44 > 0:40:47The crystalline surface of the ice stalactites
0:40:47 > 0:40:51provides a home for ice fish whose bodies are full of anti-freeze.
0:40:56 > 0:40:59The ceiling of ice shields those living below it
0:40:59 > 0:41:04from the violent polar weather that rages above.
0:41:04 > 0:41:07Little here has changed for millions of years.
0:41:10 > 0:41:15The cold allows animals to grow very slowly and become giants.
0:41:31 > 0:41:36A relative of the woodlouse is the size of a dinner plate.
0:41:37 > 0:41:43And this so-called "sea spider" has legs that span half a metre.
0:41:45 > 0:41:49Now explorers are revealing other worlds
0:41:49 > 0:41:52that lie hidden beneath the ice on land.
0:41:56 > 0:42:00These smoking towers are the gateway to a network of caves.
0:42:03 > 0:42:07Each contains an extraordinary assembly of ice crystals,
0:42:07 > 0:42:09unlike any other on Earth.
0:42:17 > 0:42:22Like snowflakes, every crystal is unique.
0:42:22 > 0:42:25Some are taller than a man.
0:42:28 > 0:42:31Others are thought to harbour life,
0:42:31 > 0:42:35seeded by strange bacteria that thrive in these extreme conditions.
0:42:37 > 0:42:40The breeze that gently sways these crystals
0:42:40 > 0:42:43is responsible for making them.
0:42:43 > 0:42:46It's steam from the molten heart of Mount Erebus,
0:42:46 > 0:42:49the most southerly volcano on our planet.
0:43:01 > 0:43:05It's now thought that the ice caves fringing this crater
0:43:05 > 0:43:09may even be a home for hitherto-unknown life forms.
0:43:13 > 0:43:17From this oasis of warmth at the edge of the continent,
0:43:17 > 0:43:21our journey continues inland towards the South Pole.
0:43:22 > 0:43:24The first great hurdle
0:43:24 > 0:43:28is the formidable Transantarctic mountain range.
0:43:30 > 0:43:33We are following the route taken by Scott and Amundsen
0:43:33 > 0:43:36as they struggled to become the first humans
0:43:36 > 0:43:37to reach the South Pole.
0:43:42 > 0:43:44They were travelling on foot
0:43:44 > 0:43:47and their first sight of these mountains
0:43:47 > 0:43:49must have been daunting indeed.
0:43:49 > 0:43:52In front of them stretched one of the world's longest ranges,
0:43:52 > 0:43:57spanning 2,000 miles from one side of the continent to the other.
0:44:01 > 0:44:04The winds up here are the fastest on Earth.
0:44:04 > 0:44:06They reach speeds of 200 miles an hour.
0:44:10 > 0:44:14An ice-capped mountain bears the scars of the gales,
0:44:14 > 0:44:17bizarre sculptures carved from solid ice.
0:44:29 > 0:44:31It's not only the ice that yields.
0:44:32 > 0:44:36This sculptured spire is the remnant of a mountain,
0:44:36 > 0:44:40eroded from all sides by the ferocious elements.
0:44:44 > 0:44:49Beyond, a wholly unexpected landscape - the dry valleys.
0:44:56 > 0:44:59Only 1% of Antarctica is free of ice,
0:44:59 > 0:45:02and most of that bare rock is here.
0:45:09 > 0:45:12The Dry Valleys are more like the surface of Mars
0:45:12 > 0:45:14than is any other place on Earth.
0:45:23 > 0:45:27The floor is covered with extraordinary natural sculptures,
0:45:27 > 0:45:32created by the same winds that help to keep these valleys free of snow.
0:45:35 > 0:45:40Over time, entire boulders are weathered from the inside out,
0:45:40 > 0:45:42until just a shell remains.
0:45:47 > 0:45:51At the head of these valleys, the ice is making a breakthrough.
0:45:55 > 0:45:59Millions of tons are tumbling in slow motion into the valley.
0:46:10 > 0:46:15These ice blocks are the size of skyscrapers.
0:46:21 > 0:46:24And this is the Beardmore Glacier,
0:46:24 > 0:46:29which Scott and his men somehow traversed on foot.
0:46:31 > 0:46:34It's over 100 miles long
0:46:34 > 0:46:37and one of the largest glaciers on Earth.
0:46:42 > 0:46:46But nothing could have prepared those early explorers
0:46:46 > 0:46:49for what they were about to encounter.
0:46:56 > 0:47:00The Antarctic ice cap, the largest expanse of ice on the planet.
0:47:02 > 0:47:04It's three miles thick in places
0:47:04 > 0:47:09and imprisons 70% of the world's fresh water.
0:47:12 > 0:47:16From here to the South Pole 700 miles away,
0:47:16 > 0:47:18there is nothing but ice.
0:47:30 > 0:47:34I'm at the South Pole at the end of my journey.
0:47:34 > 0:47:39Although it's midsummer, the temperature here
0:47:39 > 0:47:43is a bone-chilling 35 degrees below freezing.
0:47:43 > 0:47:46It's exactly a hundred years almost to the day
0:47:46 > 0:47:50that the first human beings stood right here,
0:47:50 > 0:47:52Amundsen followed by Scott.
0:47:54 > 0:47:56In those days, reaching the poles
0:47:56 > 0:48:02was regarded as the ultimate in human endeavour and endurance,
0:48:02 > 0:48:04and a source of great national pride.
0:48:05 > 0:48:10Today, the polar regions have a rather different significance,
0:48:10 > 0:48:15because now we've come to understand that what happens here
0:48:15 > 0:48:19and in the north affects every one of us,
0:48:19 > 0:48:23no matter where we live on this planet.
0:48:51 > 0:48:54The greatest challenge for the team making Frozen Planet
0:48:54 > 0:48:58was the extreme remoteness of their locations.
0:48:58 > 0:49:00Many of the shoots lasted months at a time
0:49:00 > 0:49:03and needed a number of crews to join forces.
0:49:06 > 0:49:10One location that would require such siege tactics
0:49:10 > 0:49:14was Mount Erebus, Antarctica's most active volcano.
0:49:14 > 0:49:18This magical mountain does not give up her secrets easily.
0:49:24 > 0:49:27To capture the full story of Mount Erebus from top to bottom
0:49:27 > 0:49:31required four different film crews.
0:49:33 > 0:49:36The cave team is dropped off at 12,000 feet,
0:49:36 > 0:49:37close to the crater.
0:49:42 > 0:49:44In howling winds and thin oxygen,
0:49:44 > 0:49:48their challenge is to find a way into the volcano itself.
0:49:49 > 0:49:52They are venturing into the unknown.
0:49:52 > 0:49:58Somewhere below are spectacular ice caves, melted out by volcanic steam.
0:49:58 > 0:50:01Getting the team safely underground
0:50:01 > 0:50:03is a relief for director Chadden Hunter.
0:50:03 > 0:50:07Excellent, it's much warmer down here, it's freezing up there.
0:50:07 > 0:50:09Minus 29.
0:50:09 > 0:50:11With him is cameraman Gavin Thurston.
0:50:11 > 0:50:16You sort of forget being in here, you are actually inside a volcano.
0:50:16 > 0:50:19You know, above us and below us, there's bubbling lava
0:50:19 > 0:50:22and you've got all these gases seeping up through here,
0:50:22 > 0:50:23which is how these caves are made,
0:50:23 > 0:50:26so there's also increased carbon dioxide in here.
0:50:27 > 0:50:29As the cave team head deeper,
0:50:29 > 0:50:32dangerous volcanic gases make breathing difficult.
0:50:32 > 0:50:34The clock is ticking.
0:50:34 > 0:50:37They will not have long to find the caves of crystals.
0:50:40 > 0:50:45Above ground, the aerial team is pushing for the summit of Erebus.
0:50:46 > 0:50:50Series producer Vanessa Berlowitz directs from the front seat,
0:50:50 > 0:50:52while aerial cameraman Michael Kelem
0:50:52 > 0:50:55controls the camera attached to the nose.
0:50:55 > 0:50:57We're going to be around 14,000 feet,
0:50:57 > 0:51:00on the performance limits of this aircraft.
0:51:00 > 0:51:01Any bad weather comes in up there
0:51:01 > 0:51:04and you're pretty much screwed, really,
0:51:04 > 0:51:06you've got to get off the mountain fast.
0:51:06 > 0:51:09Above 10,000 feet, the pilot must breathe oxygen
0:51:09 > 0:51:11through a plastic tube in his nostrils.
0:51:11 > 0:51:16Approaching the crater, conditions do not look good.
0:51:16 > 0:51:19Today, Erebus is belching out steam and gases,
0:51:19 > 0:51:22making flying extremely risky.
0:51:22 > 0:51:25Up here, the air is so thin, the helicopter can't hover
0:51:25 > 0:51:27and must keep moving.
0:51:28 > 0:51:33This is aerial filming at its most extreme.
0:51:33 > 0:51:35They struggle to get a clear view.
0:51:38 > 0:51:41We're just coming up to 14,000 feet,
0:51:41 > 0:51:44you can actually look right into the lava lake.
0:51:45 > 0:51:48Oh, that's looking really good, Mike, just hold that there.
0:51:48 > 0:51:52The cameraman captures a rare shot of the molten lava,
0:51:52 > 0:51:54but it's soon obscured again.
0:51:57 > 0:52:00The volcano is temperamental.
0:52:00 > 0:52:02The team have seized a rare opportunity
0:52:02 > 0:52:07to see into its molten heart, but now they must descend to safety.
0:52:09 > 0:52:14As the weather closes in above, the cave team are making progress below.
0:52:21 > 0:52:24It's Christmas Day and the crew are dressed for the occasion.
0:52:28 > 0:52:31Just watch my back on these icicles,
0:52:31 > 0:52:33I don't want to snap that top one off.
0:52:35 > 0:52:39How strong are these pillars of ice?
0:52:39 > 0:52:42It's about... Round about five...
0:52:42 > 0:52:45So if I squeeze past, it's not going to snap it?
0:52:47 > 0:52:50Gavin is reassured by advice from the scientist.
0:52:54 > 0:52:55Oh!
0:52:55 > 0:52:58Ohhh! Gavin!
0:52:58 > 0:53:00I'm sorry.
0:53:01 > 0:53:05That's terrible. Oh, look, it fits perfectly, look. Look at that.
0:53:09 > 0:53:12Fortunately, these crystals are made of frozen water
0:53:12 > 0:53:14and can grow back in weeks.
0:53:14 > 0:53:18You've got these beautiful, clear, glass-like pillars
0:53:18 > 0:53:21and right next to it, this really delicate...
0:53:21 > 0:53:24Look how thin that filament is there.
0:53:26 > 0:53:28As the cave team explore deeper,
0:53:28 > 0:53:31each chamber reveals ice crystals
0:53:31 > 0:53:34more strange and spectacular than the last.
0:53:37 > 0:53:41No-one on the team imagined a single Antarctic mountain
0:53:41 > 0:53:43could house so many wonders.
0:53:47 > 0:53:50Down at the foot of Mount Erebus, a third crew, the dive team,
0:53:50 > 0:53:53plan to explore the volcano's lower slopes,
0:53:53 > 0:53:56which extend beneath the frozen sea.
0:53:56 > 0:54:00On board is underwater cameraman Hugh Miller.
0:54:00 > 0:54:04The problem is, we don't actually know what's under the ice here.
0:54:04 > 0:54:07So who knows, it's a bit of an adventure.
0:54:07 > 0:54:11Old-fashioned tools still work best.
0:54:11 > 0:54:13First, a hand chisel to create an opening,
0:54:13 > 0:54:16then a saw to widen the hole.
0:54:17 > 0:54:20Ice-diving in the coldest waters on the planet
0:54:20 > 0:54:22should be taken extremely seriously.
0:54:22 > 0:54:28This dive's going to be a lot of things and warm is not on that list.
0:54:28 > 0:54:32Insulated suits will keep them alive under the ice for only 60 minutes.
0:54:32 > 0:54:38Once the helicopter departs, there's no margin for error.
0:54:41 > 0:54:45The dive team begin to explore the lower slopes of Erebus,
0:54:45 > 0:54:49discovering a hidden world rarely seen by humans.
0:54:51 > 0:54:55Patrolling the icy shores of the volcano are killer whales,
0:54:55 > 0:54:57the most southerly in the world.
0:54:59 > 0:55:02Tracking them from above is the orca team.
0:55:04 > 0:55:07They need a helicopter to get ahead of the whales
0:55:07 > 0:55:10and to land them on the fragile sea ice.
0:55:12 > 0:55:15Cameraman Jamie McPherson must pick his spot carefully.
0:55:15 > 0:55:18His aim is to get the cameras
0:55:18 > 0:55:22as close to the killer whales as possible without disturbing them.
0:55:24 > 0:55:28He uses a film camera to capture the action in slow motion.
0:55:37 > 0:55:39And the orcas come right by him.
0:55:41 > 0:55:42Even in the extreme cold,
0:55:42 > 0:55:46a film camera proves to be rugged and reliable...
0:55:46 > 0:55:49provided there's enough film in the camera.
0:55:51 > 0:55:53- End of the run.- No!
0:55:56 > 0:55:59I've got him coming out, I just didn't get him going back in.
0:56:01 > 0:56:03All right!
0:56:07 > 0:56:12Below the sea ice, the dive team is setting up an underwater studio.
0:56:12 > 0:56:15Using a range of waterproof lights and time-lapse cameras,
0:56:15 > 0:56:20they hope to capture the growth of bizarre underwater ice formations.
0:56:28 > 0:56:30Over the coming weeks,
0:56:30 > 0:56:32the dive team would go below the ice over 100 times
0:56:32 > 0:56:35to film the extraordinary secret world
0:56:35 > 0:56:37on the lower flanks of Mount Erebus.
0:56:40 > 0:56:43On top of the ice, the orca team has repositioned.
0:56:43 > 0:56:46Their new goal is to get underwater shots of the whales.
0:56:46 > 0:56:49They don't dare to get IN the water with orcas.
0:56:49 > 0:56:52Attaching a camera to a pole is a safer option,
0:56:52 > 0:56:55provided the whales aren't put off by it.
0:57:01 > 0:57:05No-one is prepared for what happens next.
0:57:05 > 0:57:07Tell her what you just saw.
0:57:08 > 0:57:10HE LAUGHS
0:57:10 > 0:57:13The entire pod arrives.
0:57:32 > 0:57:34Eyeball to eyeball,
0:57:34 > 0:57:39this is about as close to killer whales as it's possible to get.
0:57:39 > 0:57:42By using multiple crews and cameras, the Frozen Planet team
0:57:42 > 0:57:46have been able to capture the full Erebus story, from the fire
0:57:46 > 0:57:50at its crater down to the whales that patrol its frozen shores.
0:57:51 > 0:57:56It's quite a privilege to feel whale breath on your face.
0:58:11 > 0:58:14Subtitles by Red Bee Media Ltd
0:58:14 > 0:58:17E-mail subtitling@bbc.co.uk