Original subtitles

DAVID ATTENBOROUGH: In winter, at the top of the planet

lies an icy wilderness...

...not of land but of frozen water.

The Arctic Ocean.

Its surface forms an almost solid platform

that is bigger than the whole of the United States.

(WIND HOWLS)

Its presence and condition

dominates the lives of all the many and varied animals

that live both on it...

...and beneath it.

In the coming months, the sun's warmth

will melt much of it and expose the rich waters beneath.

(ICE CRACKLING)

To survive here, life must adapt to this world

that alternates between ice and water.

(CRACKLING)

After three months of winter darkness,

the sun rises across Arctic Norway.

A newly emerged polar bear mother

encourages her cubs

to take their first tentative steps on the sea ice.

Cubs will stay with their mothers for two years,

learning the skills needed to survive out here.

(GRUNTS)

But thereafter, they will be on their own.

Further out on the sea ice...

(GRUNTS)

...this young female bear, less than six years old,

is already fully independent.

She's superbly adapted to life

on the frozen ocean,

protected from the cold by thick, insulating fat

and a double layer of fur.

This time of year is the best time for feeding.

The ringed seals on which she depends

feed on fish,

and are swimming 40 metres beneath her.

But after ten minutes down there,

they must return to the few gaps in the ice

to take a breath and rest.

She has acute hearing

and one of the most sensitive noses in nature.

(SNIFFS)

She can detect a seal's lair beneath two metres

of snow and ice.

Timing is everything.

Only one in ten attempts is successful...

...So for a young bear, each meal is very important.

But a male has picked up the scent of the Kill.

Large males pose a real threat...

...and could inflict fatal injuries in a fight.

But she stands her ground.

Remarkably, rather than fight...

(GRUNTS)

...they start to play.

And then,

they set off to explore together.

Well fed and still young,

these two seem to be forming a friendship.

She shows off the swimming skills

that enable her to move with ease between water and ice.

(GROWLING)

She's behind you!

Dancing on ice...

...apparently just for the joy of it.

After three hours together, they part company...

(GRUNTS)

...and return once again to their solitary lives.

(GRUNTS)

Polar bears thrive at this time of year

thanks to the huge platform of sea ice on which they can hunt.

The Arctic Ocean lies

across the top of the northern hemisphere

and over the North Pole itself...

...and is surrounded by three continents -

Europe, North America and Asia.

In winter, the sea ice extends

across an area of over five million square miles.

But off the coast of Arctic Russia,

a tiny pocket of water has been kept open...

...by the continuous stirring of 30 trapped beluga whales.

These four-metre-long arctic whales are superbly adapted

for hunting far beneath the surface of the sea ice.

(BUZZING)

Nonetheless, being mammals,

they must return to the surface to breathe

every 15 minutes or so.

But this cold spell is exceptionally severe.

And there's not another breathing hole within 20 miles.

(WHISTLING)

Nearby fish and squid disappeared long ago.

These emaciated whales have been imprisoned by the ice

for five months, and they're now starving.

Their only chance of escape will come

when there is a change in the season.

As spring finally reaches the north of the planet,

air temperatures creep above freezing.

(CRACKLING)

The impenetrable ice ceiling begins to fracture.

Small life-saving channels open up...

...bringing freedom.

But spring is a dangerous time for beluga.

As tides and currents pull ice apart,

the beluga find themselves

in a labyrinth of shifting ice floes

that could close their breathing holes

at any point, and so drown them.

(WHISTLING)

(BUZZING)

Using their sophisticated sonar,

they try to find a way through the icy maze...

...and eventually reach a patch of open water.

They're not the only whales here.

Narwhal,

the unicorns of the sea,

are closely related to beluga.

In a rarely seen encounter,

these two kinds of whales appear to socialise.

Who knows what's going on between them?

But soon, they set off together

through the shifting fields of ice...

...a journey of up to 1,000 miles...

(BUZZING)

...before they reach ice-free waters,

where they can rear their young.

As the spring sunshine strengthens,

the broken pack ice off the coast of Greenland

becomes a nursery.

A harp seal pup...

...born just a week ago.

He has little fat.

(TRILLS)

His thick fur

is his only protection from the arctic chill.

In between dozes, he waits for his mother to return.

(MOTHER GRUNTS)

She has only one pup a year...

(PUP SQUEALS)

...and will produce milk for only 12 days,

one of the shortest nursing periods in nature.

That is just long enough

for him to develop a thick layer of blubber...

...thanks to his mother's milk, which is 50% fat.

And his mother stays alongside

while he learns an important survival skill

for any seal...

(SQUEALS)

(MOTHER GRUNTS)

(SQUEALS)

...how to swim.

He may not be keen to take the plunge.

The salt water is minus two degrees Celsius, after all.

Pups start with a doggy paddle.

Mum stays reassuringly close.

Still developing his insulating blubber,

a pup is at risk of hypothermia,

So needs to rest

and warm up.

Each day,

he puts on another two kilos...

(SQUEALS)

...and practises swimming

for just a little longer.

Since birth, this pup has tripled in weight,

and he's now at ease in this curious other world.

12 days gone by.

A mother's work is done.

(GRUNTS)

In producing milk, she's lost a third of her body weight.

Now she must return to her feeding grounds.

(SQUEALS)

She will never see her pup again.

The next four weeks he spends alone,

sticking close to the ice platform...

...surviving on his fat reserves

as his downy fleece is replaced by a sleek coat

more suited to swimming.

(SQUEALS)

But temperatures in the Arctic are now

rising faster than ever before...

...creating storms that break up the ice floes

earlier each spring.

(SQUEALS)

Harp seal pups are being tipped into freezing waters

before they're ready to endure long periods at sea.

In some pupping areas,

almost none survive.

As spring turns to summer,

life on the sea ice suddenly begins to proliferate.

The daylight increases,

and algae that had remained dormant

within the ice all winter

begin to bloom.

This upside-down meadow is now cropped

by plankton.

For a little skeleton shrimp

living at the bottom of a towering forest of kelp,

the best way to get a share of the food...

...Is to climb.

If you're only two centimetres long...

...this is like scaling a skyscraper.

And yet it's not alone.

Hundreds of fellow shrimps

are attempting the same ascent.

A new mother

has parked her brood halfway up.

And she's not about to give way.

This one is a determined commuter.

But the mother's drive to protect her young

is now causing a traffic jam.

At last...

...many have made it to the topmost branches

of this underwater forest.

And it's been well worth the effort.

The prize...

...is a plankton feast...

...raining down from above.

By midsummer, arctic waters are filled

with food...

...making them into one of the richest of all oceans...

...feeding billions of microscopic mouths,

as well as...

...the biggest mouth on the planet...

...the bow head whale.

Its four-metre-long baleen plates

enable it to sieve out

up to six tonnes of plankton a day.

And it grows swiftly into an 18-metre 100-tonne giant.

In summer, the bow heads are so well fed

they head for an annual get-together.

After a year of wear and tear,

their skin needs reconditioning.

(BOOMING)

This is a whale health spa.

(BOOMING)

Rocks and sand in the shallows are used like pumice stones

with which to rub off dead skin and parasites.

Such places can become very popular.

This bay, off the coast of Russia,

attracts an immense gathering

of over 50 bow heads.

They are the longest-lived of all mammals.

Some are 200 years old

and have been coming here for many decades.

Suddenly, their peace is shattered.

Killer whales have arrived from the south.

Nine metres long,

weighing nine tonnes...

...and renowned for their exceptional intelligence...

...this particular pack specialises in hunting

bow head whales.

The bow heads retreat into the shallows...

...where it will be harder

for killer whales to launch an attack.

But the killers can swim much faster than the bow heads.

The group tries to close ranks.

But the killers attempt to separate them.

They look for individual signs of weakness.

In the shallows, the bow heads lash out...

...with their seven-metre-wide tails.

But in the confusion, some run aground.

Others try to reach deeper water.

This youngster, half the size of an adult,

is extremely vulnerable.

The Killer whales

take turns to ram into its sides...

...cracking its ribs so that it struggles to breathe.

Then they push the youngster down until, finally...

...it drowns.

The battle is over.

It lasted an hour.

Yet now the Killer whales eat only one part of their prey...

...the young bow head's soft, fatty tongue.

Today, more and more bow heads

are falling prey to killer whales,

as the warming climate

causes the protective barrier of sea ice

to melt earlier each year.

By midsummer, millions of migratory sea birds,

having flown thousands of miles to get here,

are feeding in the Arctic's rich waters.

(BIRDS CALL)

Over a million

crested auklets, no bigger than puffins,

now descend on Alaska's Saint Lawrence Island

and are preparing to breed.

To win a mate, a male must try to stand out from the crowd.

And auditions are already under way.

(CHEEPING)

Males and females, unusually, look very similar,

each adorned with an Elvis-like crest.

But it's the size of the crest that matters.

And this male's headgear seems to be

no more than adequate.

(SCREECHES)

A position on the ground is also important.

(SCREECHES)

One large male wants this particular perch...

...and having got it, he breaks into song.

(WHOOPS)

He now releases a potent tangerine scent

from the back of his neck...

...and a mob of fans go wild.

This male, however,

seems to have nothing to offer.

But a gaggle of groupies can be a dangerous distraction.

An arctic fox.

(BIRDS SCREECH)

It's found an egg.

With the stage cleared,

the highest perch has become vacant.

This is a moment to shine.

(WHOOPS)

His display doesn't go unnoticed.

And his tangerine perfume attracts an admirer.

And not just one.

Now it's down to the females to impress him.

In auklet society, both sexes

have a say when it comes to choosing a mate.

At the height of summer,

with 24 hours of sunlight a day,

over half the sea ice melts away.

(BIRDS CALL)

The beaches of Svalbard

provide safe places to haul out

for one of the Arctic's special residents...

...walruses.

They forage for shellfish

for up to 17 hours at a stretch.

Now...

(GRUNTS)

...it's time for a rest.

Each adult male weighs more than a tonne.

And heaving oneself over the sand...

...without the support of water

is very hard work.

This male has a particular sunbathing spot in mind...

...right in the middle

of the 50-strong huddle.

(GRUNTING)

A prod helps in parting the crowd.

Almost in.

At last, he can settle down for a snooze...

...swaddled on all sides

by the bodies of his neighbours.

(GRUNTS)

But it's not a peaceful spot.

(BELLOWING GRUNTS)

Sleep isn't easy when a fidgety bedfellow

decides that he has an itch

that needs scratching.

This is the time to moult,

to get rid of one's old fur with all its parasites,

and expose the healthy new coat beneath.

These days, Svalbard's summer temperatures

can soar to 22 degrees Celsius.

Flushing red by bringing blood close to the skin

helps them to keep cool.

But some overheating is unavoidable...

...especially for a big male.

Enough is enough.

Getting up here...

...was a slog.

But this male has found a better way of getting down.

Let gravity do the work.

Now, that...is cool.

Ahhh!

Everyone is doing it.

It saves both time and energy.

But walruses will need all the tricks they can find.

The Arctic is warming,

and these cold-loving animals are facing

a precarious future.

For millennia, the Arctic Ocean has frozen over in the winter

and then gradually melted

throughout the spring and summer.

But in the last 40 years,

the extent of the summer sea ice has declined by 50%.

Some predict that it will be ice free

as early as 2035.

This profound change...

...is already having an impact

on the Arctic Ocean's highly specialised wildlife.

With less summer sea ice from which to hunt seals,

some polar bears are now travelling up to 400 miles...

...swimming continuously for up to ten days

in search of land.

Wrangel Island, off Arctic Russia...

...the only land for almost 100 miles.

Each summer, more and more polar bears come ashore here.

This newly arrived mother

needs to find food for her family...

(GRUNTS)

...but knows not to approach other adult bears.

A full-grown male

can Kill and eat a cub,

and will do so if other food is in short supply.

There are over 1,000 bears on this one island.

It's the greatest concentration of polar bears on the planet.

But there is food to be had on these remote shores.

A walrus colony...

...2,000 strong.

The walruses panic.

And there are casualties.

(GROWLS)

Fights break out.

This is no place for a young family.

The mother calls her cubs away.

(CHUFFS)

They must search elsewhere.

Grass is a poor meal for a growing cub...

...and starvation in summer is a real threat.

But this opportunity to feed...

...is one she cannot afford to ignore.

It's time to gamble.

Her cubs follow her.

(GROWLS)

She urges them to stay back.

(BRAYS)

The males are twice her size...

...but, preoccupied with feeding,

they tolerate her presence.

(WHIMPERS)

The distress calls of her cubs, however...

(GROWLS)

...attract unwelcome attention.

(WHIMPERS)

(WHIMPERS)

Their mother rushes to shield them with her body.

(GROWLS)

But she seems torn between guarding her family

and feeding herself.

Cubs left by themselves

are easy prey for a hungry male bear.

But now her maternal instincts take over.

(GROWLING)

Faced with a mother's fury,

the dominant male backs down.

(BRAYS)

Having fought her way in...

...her cubs can now feed

for the first time in weeks.

Polar bears were once

the supreme hunters

on the sea ice.

Now, each summer,

more and more of them

have to come to land

in search of food.

Whether the ice bear survives into the next century

depends on what happens to the sea ice on which they rely.

As with all of the Arctic Ocean's remarkable wildlife,

it's how the climate changes over the coming years

that will determine their future.