Frozen Planet II

In this series,

we have explored

the Earth's frozen frontiers.

We have celebrated the astonishing array

of animals that are found there...

...and revealed

the extraordinary ways

by which they manage to survive.

At a time when our icecaps are melting

faster than ever before...

...we will meet the scientists

and people who are dedicating their lives

to protecting our frozen planet better...

...and striving to turn things around

while there is still time to do so.

It won't be easy, but it's doable.

It's crucial that we try to understand

what the impact will be,

not just for the wildlife and the people that live there,

but for you and for me.

We start our journey in the High Arctic,

and the vast frozen expanse of Greenland.

This huge island is blanketed by the largest store of ice

in the northern hemisphere.

But now it's shrinking.

Professor Alun Hubbard is a glaciologist,

and he's spent over 30 years

studying the movement of ice along Greenland's coastline.

It is quite a beast of a glacier.

It's just growling constantly.

Thundering... in the background.

Ooh. There we go - bit of activity.

Calving icebergs Is a natural process,

but what we've seen in the last 20 years is

there's been much more melt,

and much more ice calving off,

producing huge icebergs...

...So it's quite an intimidating place

to be hanging out.

One thing in particular

has caused this increase in melting and calving.

We put this weather station here in 2010.

And the hottest temperature was...

...two days ago...

...at 22.37 degrees centigrade.

That is very, very hot

for Greenland.

As the ice falls into the ocean,

it raises sea levels globally.

These are now rising

by an average of four millimetres a year.

A quarter of that comes from the Greenland ice sheet,

and scientists fear that this figure could increase rapidly.

To investigate, Alun has travelled 70 miles inland

to the top of the ice sheet,

where the glaciers start their lives as compacted snow

more than a mile thick.

Here, the effects of a warming climate

are only too clear.

There are thousands

of these beautiful azure-blue lakes

littered across the surface of the ice sheet.

The surface has always melted in the summer,

but not on this scale...

...and Alun wants to know

what effect the increase in meltwater

is having on the ice sheet as a whole.

The sheer quantity of water...

...shifting through this system is crazy!

Powerful torrents of meltwater are boring shafts -

known as moulins - into the ice sheet.

This is nuts.

This is a moulin actively being formed,

a moulin in genesis.

As we speak, that water is finding

the path of least resistance,

sculpting this shaft that's going deep into the ice.

And here it is,

just toppling over a waterfall edge

and dropping into the ice sheet.

But where is all this meltwater is going?

And what impact is it having

on the structure of the ice sheet?

To find out,

Alun decides to climb inside a dried-up moulin.

I think I must be 15, 20 metres down here,

but I'm going to go down a bit further.

It's a very narrow shaft here.

It's always been assumed that the meltwater

drains straight down and out of the bottom of the ice sheet,

but what Alun discovers is very different.

- (GUSHING) - I can hear

a big amount of water moving in this system,

and the water's starting to spread sideways, laterally,

so the drainage system is obviously complex.

It's interlinked.

These observations suggest that the meltwater

is branching out in every direction,

causing this once-rigid structure to destabilise.

Whoa.

It's a bit rotten.

Everything's rotting here.

The implications of this are frightening.

Alun believes that as the ice sheet begins to thaw,

it's sliding towards the ocean at a much faster rate.

And he's now confirmed that using time-lapse photography.

The ice at the front can be moving

in excess of 20 metres a day,

which is fast.

That is a huge quantity of ice straight into the ocean.

Some of Greenland's glaciers are moving

three times faster today than they were 30 years ago.

As the climate's warming,

the rate at which this ice sheet flows

is absolutely critical.

So whereas, at the moment,

we're thinking this thing is going to take

thousands of years to melt and disintegrate,

if it does move faster and accelerate,

it means centuries.

That is a really contentious and very important question -

because this ice sheet has enough water in it

to raise global sea level by over seven metres,

and that's a total disaster for humanity.

Calculations predict

that nearly half a billion people

living in coastal communities around the world

will be displaced by flooding by the end of the century.

But if the Greenland ice sheet

slips into the ocean more rapidly,

this could all happen far sooner.

Greenland isn't the only large body of ice in the Arctic.

In winter, the ocean here freezes over,

creating a cover of ice

larger than the entire United States.

This sea ice has always got smaller in summer,

but today it's rapidly disappearing.

Hotter temperatures are melting it at an unprecedented rate...

...with worrying consequences

for the wildlife that depends on it.

For harp seals, the sea ice is an excellent place

for giving birth out of the water.

It provides the defenceless newborn pups

with a safe space for their first six weeks,

until they're big enough to swim proficiently.

But with the sea ice

disappearing increasingly fast...

...will they be able to adapt?

Coastguard 432.

Coastguard radio. Coastguard 432. Check out.

In Canada's Gulf of Saint Lawrence,

a group of seal biologists are trying to find out.

It's a pretty dangerous, pretty inhospitable place, but...

...it's the perfect environment for these seals

to spend the first few weeks of their lives.

There's a group just down here to the right now.

But the fragile sea ice

is a challenging place in which to work.

Here... Let's go a little further out.

To support a two-tonne helicopter, the ice must be

at least 30 centimetres thick,

and the only way to find out if that's so is with a drill.

It's just not safe here.

There's a couple just down here below us now.

We've got a pretty short window here.

The team are trying to discover

where the seals go when they become independent.

So, this is a juvenile harp seal.

This is exactly what we've been out on the ice trying to find.

Hey, little guy.

They're absolutely beautiful.

We'll be putting a satellite transmitter

on the top of this animal's head

so that every time the animal comes to the surface,

we can get a location estimate for where he is at sea.

It won't harm them in any way, and, in return,

the amount of information we get from them is invaluable.

It'll be really interesting to see where these animals go

as the ice starts to break up over the coming months.

The results from the study so far

do not look encouraging.

Despite migrating huge distances,

when the time comes to have pups of their own,

harp seals almost always return to the area

where they themselves were born.

But as the sea ice shrinks,

so does its suitability as a nursery.

The problem really comes about if the only ice available

in the traditional areas is very thin.

They'll still use that ice, and then you get

an increased mortality.

In short, the pups risk drowning

if the ice isn't thick enough.

And the bigger question is,

will the ice continue to exist at all?

In my lifetime, we've lost about two-thirds

of the summer sea ice in the Arctic.

And it's likely that in the next 30 years

we're going to end up with an ice-free Arctic in the summer.

I think one of the issues with climate change