The Blue Planet (2001): Season 1, Episode 4 - Frozen Seas - full transcript

The frozen seas are worlds
unto themselves

Beneath their ceiling of ice
they have an eerie,

almost magical stillness, cut off
from the storms that rage above

In the winter, the feeble slanting
rays of the sun bring little warmth

and the temperature seldom rises
above minus fifty degrees Centigrade

For much of the year,
it is dark and cripplingly cold

Yet, there is life here
- at both ends of the earth...

the Arctic and the Antarctic

For most animals, whether they
live in or out of water,

the winters, when much of the sea
is frozen, bring the greatest challenge

The Northern hemisphere



It's February, and as the Earth
tilts on its axis,

the sun's rays creep
slowly northwards

and the Arctic emerges
from its harsh winter

The Arctic is a frozen ocean
surrounded by continents

- and when the surface of the sea
between the continents freezes

from shore to shore, land predators
walk out onto it - to hunt

It's early March and the sea
is still covered with ice

But there are patches of open water
- polynyas - that never freeze over

Here, where tidal currents
are squeezed between islands,

the water movement is so strong
that ice cannot form

Walruses spend the
winter in polynyas

Here they have permanent
access to the air,

but they can also retreat to
the sea to shelter to hunt

Other sea mammals overwinter
in the polynyas as well



- in this one, a young bowhead whale

Here the current is really fast
and the shifting ice is dangerous

This whale became trapped when
ice encircled it last autumn

There is no food here, but a whale
must breathe and the only place

that it can do so, for miles around,
is in this tiny hole

It's living entirely on its reserves
of fat, but now they are dangerously low

It will be some months yet,
before it can escape

Elsewhere, other whales
have also been trapped

These are belugas

Their tiny hole in the ice
has been kept open,

not by currents but by
the belugas' continuous movements

as they rise to breathe

Open water is now some
twenty miles away

It will be two months yet
before the ice melts

The belugas are extremely thin
- and most of them are horribly scarred

But their wounds were not
inflicted by the ice

A whale would be a huge prize for
any meat-eating hunter and these belugas,

trapped by the ice,
are within reach of polar bears

Well aware of the danger, the belugas
stay submerged as long as they can

But they can only hold their breath
for about twenty minutes

Catching a four-metre long whale
that weighs one ton is no easy task

- even if that whale is
weakened by starvation

But a beluga is well
worth waiting for

Day by day, as the hole
gets bigger,

it becomes increasingly difficult
for the bear to land a whale

Keeping its fur in good condition and
free from salt is important for warmth

- and the bear uses snow
like blotting paper

These belugas have been attacked by many
bears over the last six months

- and some have been caught

It may have taken a long time and
a lot of patience, but a catch,

when it's made, brings abundant
rewards of energy rich blubber

Gulls rely on bear-kills
at this time of the year

- and the colour of blood staining the
ice attracts them from a long way away

The remaining belugas still have
a long wait before they are released

from their prison and
the threat of slaughter

Arctic foxes also rely on the
polar bears to hunt on their behalf

They're the jackals of the north and
scavenge from bear kills whenever they can

In winter and early spring,
they are wholly dependent on bears

Only in the summer,
when the sea ice melts,

will they regularly
catch prey for themselves

They are not strong enough
to tackle adult seals,

but can certainly take
new-born pups or birds

This canny individual
is going to bury its prize

- it may need it during
the uncertain times ahead

The presence of bears
affects the behaviour of almost

all the animals here
- big and small

The bears tend to avoid the fringe of
fragmented ice bordering open water

- where travelling can
be very laborious

But that very fact makes
this area - the pack ice

- a particularly good place
for seals to pup

Harp seals breed here

Their pups are born with white
coats which camouflage them

very effectively against the snow

Harp seals have a very
short nursing period

- a necessity on this
unstable pack ice

But suckling is intensive

The pup feeds for just twelve days
on milk that is 45 percent fat

Then it is abandoned
and has to fend for itself

A male hooded seal

This impressive nasal display is used
to warn away other males...

...and to win a mate
Hooded seals also breed on pack ice

Their pups suckle for only four days

- the shortest nursing period
known for any mammal

- and all because the
threat of polar bears

caused them to breed
on the unstable ice

Another Arctic seal opts
for the solid ice further north

Because it's easy for
bears to hunt here,

these ringed seals must be particularly
vigilant and have to hide their pups

Ringed seals are comparatively small,
so they can give birth

to their pups in little caves,
or lairs, under the snow

Here, a pup is out of sight
and protected from bad weather

In late March and into April,
female bears emerge from winter

dens with their new cubs

The mother has not eaten for at least
five months and she's hungry - very hungry

If she doesn't succeed in catching
a regular supply of seals,

her milk will fail and
her cub will die

Bears have an extraordinarily
sensitive sense of smell

and can detect seal pups hidden in
the snow from two kilometres away

But a female ringed seal
uses several lairs

and a bear will almost certainly
have to break into a number

before it finds one
that is occupied

This is a crucial time
for the cub

By watching its mother hunt
and by copying her actions,

it's beginning to acquire the
rudiments of its own hunting skills

Play is also important for developing
muscles and improving co-ordination

As the days go by,
the sun rises higher

and remains above the
horizon even at night

The female bear continues to hunt

until her cub is too tired
and can't keep up

She has smelt something

The pup escapes through a hole in
its lair that leads to the sea below

Only one in twenty hunts
is successful

But this mother must find a seal pup soon
if her cub is not to starve to death

As spring turns into summer, the sun's
heat begins to melt the sea ice

Now the ocean is accessible and
the Arctic's summer visitors return

Migrating birds arrive
from the south to nest

and feed on the seafood
that's now within their reach

Brunnich's guillemots are the
northern equivalent of penguins

But they have retained
the power of flight,

for they need to
reach cliff ledges

where their nests will be safe
from predatory bears and foxes

Nonetheless, they are as at home
in the water as in the air

They dive down to a depth of fifty
metres or more to catch fish

In June, the ice begins
to fracture

The cracks - or leads
- form useful corridors

of open water for
air-breathing animals

Belugas, migrating to
their feeding grounds,

use these leads to penetrate
the ice-covered seas

and reach areas where
their preferred food,

Arctic cod, has spent the winter

The males regularly dive to about
five hundred metres to find fish

The females and young, which have
smaller lungs, only go to about 350

In late June and July,
narwhals arrive

The females, who usually lack tusks,
come first with their new calves

The males follow a little later

They also move up the leads in
search of fresh feeding grounds

Bowheads. Up to 18 metres long
and weighing a hundred tonnes,

these are the only large whales
that stay in the Arctic all year round

They are not after fish
They are seeking smaller prey

Despite having the largest mouths
in the animal kingdom,

the size of a small garage,
they eat tiny crustaceans

- copepods - straining them from the
water with the four-metre long strips

of baleen that hang from
their upper jaws

In the summer they store
enough energy to last them

through the following winter,
when food will be less abundant

As the ice melts away, the polar
bears are forced to head for land

They are excellent swimmers
and can cover a hundred miles

of continuous open water
if need be

Off east Greenland,
there is little ice left by August,

so walruses haul out
to rest on land

At this time of the year
they are moulting,

getting rid of their old scarred
and parasite-ridden skin

A bathe in the cold water brings
some relief from the itching

But even there,
the odd scratch is irresistible

They make daily excursions
out to deeper water

Down at 20 metres, they root
around in the sediment,

using their sensitive bristles
to search out soft-shelled clams

Once they find a clam,
they suck its flesh from the shell

with their powerful,
muscular mouths

Walruses can feed for about
five minutes at this depth

before they have to return
to the surface to breathe

Elsewhere in the Arctic, belugas are
gathering in their thousands

They congregate in just
a few large estuaries

Belugas of all ages
and sizes come here

There are even young calves

Some are so young - born only a week or
so ago - that they need help

They swim on their mothers' backs so
that they can breathe more easily

As the tide moves up the estuary,
the belugas follow,

swimming into surprisingly
shallow water

Like walruses,
they also need to moult

A combination of warm fresh water
and vigorous rubbing

against the gravel does the trick

They remain here for days,
or even weeks,

so it's likely that socialising
is also important to them

After moulting, they head back
out to sea to feed

It's now autumn and the sea
begins to freeze over, once again

Thin sheets of ice form at
the surface and pile up,

layer upon layer, gradually
creating an impenetrable barrier

By late November, the Arctic Ocean
is sealed once again by ice

The lights of the aurora play
in the winter sky

At the other end of the planet
- in the Antarctic

- there is the southern aurora

Antarctica is now emerging
from winter

This is the coldest,
windiest place in the world

Temperatures are still hovering
at a numbing minus 50

and the returning sun has
virtually no warmth

Very few animals can survive
such extreme conditions

But emperor penguins can

Standing on the frozen sea, they endure
the full force of the Antarctic storms

Only by huddling together can they can
survive the appalling winter months

They take it in turns to bear
the brunt of the gales

They can only live here at all because
Antarctica is surrounded

by the Great Southern Ocean and no land
predators have been able to reach it,

so unlike Arctic animals,
they're not threatened by polar bears

The sea is still frozen

But one seal, nonetheless,
manages to stay here,

even throughout the winter...

... the Weddell seal

Underwater, it's protected
from the storms above

But it must have access to the air
all year - in order to breathe

And they keep their breathing holes open
- with their teeth

Only by continually scraping away at the
ice can they maintain access to the air

But that means that their teeth
get badly worn down

Then they can no longer hunt
and eat effectively

Weddell seals die young

The continent of Antarctica
is so isolated

and so high - almost five
thousand metres in places

- that it's considerably colder
than the Arctic

Ice slides slowly down from its centre
towards its rim in immense glaciers

During winter, the continent effectively
doubles in size as the sea freezes over

Ice forms around its shores
and extends outwards

for hundreds of miles around
the entire land mass

Under the sea-ice live small
shrimp-like creatures - krill

They have been here all winter

During these dark months, they feed by
scraping algae from the ice

Remarkably, they also
shrink in size

and revert to their juvenile
form to save energy

As the temperature
rises in spring,

the ice begins to melt and little air
bubbles trapped within it are released

Microscopic algae grow around these
bubbles and the krill now graze on them,

gathering them up with
their beating legs

As the sun's rays grow stronger
and penetrate deeper into the water,

floating algae begin to
flourish and krill leave

the dwindling ice and gather in swarms
as they harvest this new crop

Far to the north, beyond the
blanket of sea ice,

chinstrap penguins have been
overwintering in the open ocean

The occasional iceberg gives
them the chance of a rest

- if they can get onto it

But at this time of year, where they
really want to be is on land

It's just getting there
that's tricky

It's spring and the penguins
are returning to breed

Their need to get ashore is now
urgent and imperative

Doing so is all a matter of timing
- and picking the right wave

But their journey has
only just begun

Most of them will have to walk many miles
before they can find a nest site

This is Zavodovski Island, which has the
largest penguin colony in the world

About two million chinstraps
breed here

- and they come to this island
for a good reason

It's an active volcano

The heat from the crater
and the fumeroles

keeps the slopes free from
the ice and snow,

allowing these chinstraps to start
breeding earlier than those further south

But then again, living on an active
volcano is not without its risks

Unlike the emperors, these penguins are
able to lay their eggs on the bare ground

Little wonder so many
of them choose to brave

the mountainous waves
in order to get here

Further south, near the continent,

the blanket of sea ice
is beginning to break up

Icebergs are gigantic fragments
of ice that have broken away

into the sea from the
front of glaciers

During the winter they
were frozen into the sea ice,

but now they are set
adrift once more

As the bergs break up,
they form brash ice

It litters the backwaters
of the Antarctic Peninsula

Minke whales make their way into
these placid waters in summer

This is the most abundant whale
in the Southern Ocean

Minkes are one of the smallest
of all the baleen whales

And like all others,
they come here to feed

The majestic humpback whales
are also summer visitors

They have travelled thousands of miles
from their winter

breeding grounds in the
tropics to gather the food

that becomes available
here in summer

In just four months,
they accumulate enough fat

to provide them with energy for
the whole of the rest of the year

All these animals have come here
in search of one thing - the krill

Krill is the mainstay of
the Antarctic food web

It occurs in phenomenal quantity

- billions of individuals
in a single swarm,

and swarms can stretch for miles

Fur seals also collect this
rich superabundant food

Krill swarms are very patchy,
but once found, feeding is easy

Humpbacks engulf hundreds of thousands of
them in a single gargantuan mouthful

When the going is good,
the whales feed continuously,

each eating up to two tonnes
of krill in twenty-four hours

Further south, near the continent,
the sea ice is still sound

Here, where the ice remains
for most of the summer,

emperor penguins make their home

These have been feeding out
at sea and are now ready

to make their way back to the
colony to feed their chicks

Instead of heading straight
for the ice edge,

the penguins hesitate
some distance from it

They're nervous

They dive down and
investigate the ice edge

And for good reason
Leopard seals patrol this border

Leopard seals are the Antarctic's
equivalent of polar bears

They are the top predators

But they hunt most successfully
in the water,

so by and large, the animals they prey
on are safer out on the ice

They have a lazy grace that belies
their ferocious nature

Confident that the coast is clear,
the emperor penguins head for the ice

But they certainly don't linger

Now they have a long walk
back to the colony

Emperor penguin colonies are some
way back from the ice edge

In winter they may be as much as
a hundred miles from it,

but as the summer progresses
and the ice melts,

the edge comes ever
closer to the colony

So by the time the chicks are fledged
and ready to take their first swim,

the water is close by

This colony is in the lee
of a headland

and that prevents the ice from
being broken up by ocean currents

The returning adults are so full
of food that they can barely walk

But with no predator to threaten
them now, they can take their time

Somehow, in this melee of sixty
thousand or so penguins,

a parent has to find its chick

It returns to the place where it last
left its chick in the hope that

it might still be close by

But chicks tend to wander,
so the adult has to call to it

The chick responds - and they slowly
home in on one another

The plaintive entreaties
of the chick stimulates

the adult to regurgitate
a mouthful of fish

With the return of one parent,

the other is free to go
to sea to feed for itself

Aware of the leopard
seal's presence,

the penguins press
together at the ice edge,

unwilling to be the
first to risk diving in

Occasionally, the seal comes out
onto the ice and attempts to grab one

But its most successful strategy
by far is to lie in wait

It hides behind a corner of ice

The emperors gain confidence
and make a dash for it

The first wave of penguins escape

Once in open water,
they will be safe

But the seal is alerted by the noise,
and through the mass of bubbles,

it makes its attack

Almost invariably,
it makes a kill

Encouraged by the absence
of the seal,

the remaining penguins
make a break for the open sea

In time, their chicks will fledge

And when the Antarctic
autumn is near its end,

these adults will walk across
the newly formed ice,

to endure yet another winter
on the frozen sea