Life and Death of a 'Berg Operation Iceberg

Travel up into the North Atlantic,

so far north the summer sun never sets,

and you will find an island the size of a city,

but made of ice.

A huge Arctic iceberg.

And now, an international team of scientists and explorers

are on the ultimate expedition,

to investigate this wonder of the natural world.

That is absolutely beautiful.

They have already seen how icebergs are born

as they calve off the front of their mother glacier.

That's one of the biggest bits of natural destruction I've ever seen.

Now the team's attention is turning

to one of the biggest icebergs in the world.

This is super-super-hard ice.

They want to discover what happens to it out at sea.

Beautiful.

And, above all, the forces that will cause its ultimate destruction.

This whole bit's coming off.

They will face huge challenges...

It's falling here.

..from confronting the largest land predator...

Oh, eyes on... It's just there.

..to surviving one of the most unpredictable environments on earth.

The Operation Iceberg team has swapped its glacier camp

in Greenland for the research vessel Neptune.

23 scientists, adventurers and camera crew

are setting off on an ambitious two-week expedition.

I think we need to think through that plan now...

They're heading across these waters in search of a massive Arctic berg.

Helen Czerski is a physicist and oceanographer.

She's interested in what's happening to the ice itself.

I'm fascinated by the mechanisms -

what's going on and why it's happening - inside this iceberg.

And how it lasts so long.

When you look at the photos, you can see the algae actually on the ice.

Naturalist Chris Packham wants to understand the role icebergs play

in the environment of the polar seas.

Icebergs carry with them an almost mythical aura.

We think we know them but we don't.

They're still very, very much of a mystery.

Joining the Iceberg team is a group of renowned ice scientists.

This is a very rare opportunity

because you very seldom get a large Arctic berg.

When you do see them, it's very hard to get to work on them.

The team has identified their target.

In 2010, in the northwest corner of Greenland...

..a vast piece of ice calved off the Petermann Glacier.

Over two years, it's drifted south on ocean currents.

Four times, vast chunks have broken off.

Now, over a thousand kilometres from its mother-glacier,

the largest piece is stuck just off the coast of Canada's Baffin Island.

We were trying to make measurements

where we knew most dynamic things were happening.

Remarkably, one of the scientists, Richard Bates,

already knows this ice.

So you've stood on this piece of ice before?

That's right, yeah, back in 2009, we were up there.

So, before it actually broke off,

we were there doing measurements on it, around it.

This crack carried on around the back here

and this crack worked its way towards it

and broke that off as one chunk

and that is the iceberg that is working its way south.

For the team, there's one key mystery they want to solve.

What are the physical forces slowly destroying this vast chunk of ice?

The ocean has a huge amount of energy

pushing and pulling and twisting,

and I'm really interested to see how the iceberg stands up

to all of those stresses.

After 36 hours at sea, looming out of the fog,

an almost unimaginable wall of ice.

The team has found their goal.

There it is!

I knew it was going to be big, but this is massive!

Good to be back here.

First Arctic iceberg for me. First ANY iceberg for me, actually.

It looks very frightening to me, it's full of cracks

and fissures, and cliffs and rivers. There's a huge river coming off.

And it looks entirely without life -

an inhospitable lump of freezing fresh water floating in sea water.

It's just a stunning sight.

I've never seen a single piece of ice that is this big....

One molecule...

Billions and billions and billions of it in a single lump,

floating on the ocean. It's an absolutely amazing sight.

This is the iceberg the team plan to board and explore.

It is criss-crossed with crevasses and melt-rivers.

For two years, it's been the largest single object

floating in Arctic seas.

It even has a name.

The Petermann Iceberg.

As soon as the team arrive, it's action stations.

RADIO: 'We've lost full signal on the iceberg.'

We've got the funny angles that we've re-set the transducers at.

First task - to scan the berg.

Richard and his colleague, Max, want to know exactly how large it is.

We've clearly we've got an echo off the bottom.

This equipment will reveal its dimensions,

both above and below water.

RADIO: Do you need it closer in, Max,

or do you think this distance is a good offset?

To scan the berg, they'll need to circumnavigate it,

and the nearer the ship is, the better the data.

Will the ping-rate go up at that?

But it's a game of careful negotiation

with the ship's skipper, Raggi Ellison.

50 metres towards the iceberg, if the captain's happy with that?

We are 50 metres away from the iceberg, so...

I'm not going to climb on board it!

THEY LAUGH

Raggi is cautious for good reason.

He knows icebergs are notoriously unstable.

Smaller ones can suddenly roll over.

And, without warning, can completely shatter.

Boarding one of these smaller ones would be suicidal.

Which is why the team picked the Petermann Berg -

it's bigger, flatter and, they hope, more stable.

It's one of the remotest spots in the world.

But they're not the only visitor.

There's a polar bear swimming, what, 50 metres off the ship.

Really close, and he's just hanging out.

We were debating whether we'd ever see one out here.

I'm actually shaking. Wow.

This is all my Christmases come at once.

A polar bear.

Now, I really, really, really, hoped to see one,

but I never thought that we would.

But then, you know, these are marine mammals.

They can cover great distances in the sea,

and they frequently do, swimming between the ice floes.

Look, it's about 20 metres off, now.

How exciting though, honestly.

Polar bears hunt on the sea ice for most of the year.

But now it's summer, the sea ice has melted,

and the team's berg is the last remaining ice in the area.

And it's not alone.

There's another bear on the berg itself.

A polar bear on our iceberg.

Hold on a moment, hold on - can we have the binoculars?

Can we get the binoculars, please?

-Turn over, Keith. Turn over.

-I am turning over.

Oh, I don't believe it. I really don't.

There's actually another bear over here on the ice.

You can see it...

..through my binoculars, there, as a little speck.

So, in the space of just half an hour, we've seen three polar bears.

One in the water, just off the iceberg...

There's one here happy, smiling.

And about 500 metres over there is a third bear on our iceberg.

It's Bear-tastic!

It's Bear City.

Even experienced Polar cameraman Doug Allan is excited.

Look at him - he's just lovely!

Lovely, lovely bear.

Don't they just look so completely at home?

I know, I know.

You know, they totally epitomise the Arctic and ice.

That's what I like about polar bears.

Bears will stay on ice as long as possible,

they don't like going ashore, they'll stay on ice.

So, in as much as this is by far the biggest bit of ice

for miles and miles around, perhaps it's not so surprising

that they should be found here.

Despite the team's enthusiasm,

these predators pose a real problem for the science mission.

Highly curious, polar bears are very capable

of attacking anything - or anyone - that enters their domain.

The intention is to go on that iceberg.

But three bears in 15 minutes...

Well, it adds a bit of excitement to the whole thing.

You need to change the scale to make it move.

It's much more obvious above that.

The scientists have two different theories

about which forces are slowly breaking up the berg.

The melt team believes sea water is melting it over time.

So, that's the main sea...

The wave team argues the ocean waves

are rocking and flexing the ice, snapping it into smaller chunks.

And that's ocean swell, which has come a huge distance.

This is Peter Wadhams' theory.

Waves do have a big effect, and we need to understand

that relationship between waves and icebergs

as part of understanding the relationship

between waves and ice in general.

Working with Peter is Till Wagner.

He's the wave team's tech-head.

And this is the beautiful green antenna.

It's just all green, and shiny, and concentric...

I think it's beautiful.

To measure the size and frequency of the waves,

they deploy a hi-tech buoy.

Till, are you sad to see this go?

Well, I do feel quite attached to it.

It's always funny watching these instruments go out,

cos they look so tiny. And we're just going to let this drift,

we're going to have to find it again afterwards,

and it looks so small out there...

But it's recording exactly the data we need.

Left to ride the ocean waves,

it'll beam this information back to the ship.

Here's the outside edge of it...

Richard has completed his survey.

Nine tenths of the iceberg is underwater.

But the scan still allows Richard

to make an accurate estimate of its size.

The result is extraordinary.

OK, so we've measured the circumference,

it's about 27km around here.

We've measured the thickness all around,

and we've got about an average of, say, 70-75 metres of thickness.

Gives us a volume of about two billion metres cubed

of ice in there.

Two billion metres cubed?

You can roughly say two billion tons of ice in there or...

Two trillion litres of water, OK?

So you've got about maybe 200-odd days of consumption for the UK.

So this water would last the UK domestic consumption for 200 days?

Something like that.

If we towed her back up the Thames

and, you know, tapped it in to Thames Water, and there you go.

That's amazing.

But the scan has also revealed a problem.

Strangely, the position of the ship in relation to the iceberg

seems to be constantly changing.

According to your diagram we're in the middle of the iceberg,

which can only mean one thing to me,

-and that is that it's moved.

-Exactly.

-It's complicated life for you a little bit, hasn't it?

-Yes.

-I'm really sorry about that.

-Thank you.

It's a shock.

The iceberg was chosen

because the team thought it had gone aground and was stationary.

Instead, it looks like it's on the move.

Richard will need to deploy additional equipment

onto the ice to track its shifting position.

And he's not the only one with difficulties.

Raggi has 30 years' experience of these waters.

Even so, he is cautious about landing the team on a moving target.

You should always take the worst scenario

and work out for that.

Prepare for the worst.

It's not often you land against an iceberg, you know.

It's very exciting.

There's a lot of inertia in a ship like this

so it's very easy, very quickly, to do some damage.

CONVERSATION INAUDUBLE

The berg's behaviour is unpredictable.

It's hard to avoid collisions.

RADIO CHATTER

And there's another unexpected problem.

The team discovers a huge ledge of ice jutting out,

just beneath the waterline.

That's 13 from the deck.

This "ice-ram", as it's known, is right under the ship.

-RAGGI ON RADIO:

-'No problem. I will move forward. I'm moving forward.

'Thank you.'

There's several hundred thousand tons of ice down there in that ram

and we're on top of it.

If a crack opened and it broke off,

the buoyancy would bring the whole thing up above sea level

and we'd be tipped over one way or the other.

It looks like a nice, neat place to moor

but actually it's quite dangerous.

Raggi insists they search for a safer landing site.

-RADIO:

-'Are we above or over?'

And as if that weren't enough...

..in a single day they've seen five more bears, eight in total.

The safety officer calls an emergency briefing.

So there are going to be a few simple rules here,

which I think all of us can just get into our minds very early on.

Number one - nobody wandering around off the ship on their own.

Number two - we got to make sure that there are watchers out.

Number three - you're going to need some equipment with you

to make sure that you can fend off if a bear comes too close.

Having seen bears stalking the seals on ice similar to this,

they're very clever. They'll see a seal from a long way away

and they will take advantage of the dips and hollows

to stay out of sight.

Just, sort of, try to be super-bear-aware.

But if a bear did suddenly... You know, you found one very close.

Then drop a piece of clothing on the ice.

Put a pair of dirty socks in your pocket,

something nice and smelly so you've got a couple of things to drop.

It'll buy you vital seconds if you're backing off.

The Inuit have a great saying,

which says, "It's not the bear you can see that's going to get you".

RADIO CHATTER

It's the next morning

and Raggi has found a possible mooring spot.

The bear risk calls for additional precautions.

-Here is the rifle.

-Thank you, Captain.

Aqqaluk will be on guard.

A native Greenlander,

he's used to living with the threat of polar bears.

There should be some cartridges in there, which we need to confirm with the captain.

Let's hope we don't have to use them.

It's well over a kilometre away. Perhaps 1,200...

The man leading the shore party is Andy Torbet,

a specialist in extreme environments.

They need to secure the boat to the ice.

We're about to get the gangway across at the iceberg

and take those first few steps. We'll recce sites,

that we can get these big ship anchors in.

The point of all this is to get the scientists on there safely

and they can carry on and do the science.

Let's go.

Argh!

SHE LAUGHS

That's why we need crampons.

-First on the iceberg.

-It is.

-How does it feel?

-Done mate, this is awesome!

-This is where the adventure properly starts.

-Yeah, it is.

This is how you imagine big lumps of ice. This is fabulous.

-Yeah, yeah feel it on the top.

-It's just like marble, isn't it?

There's nothing, there's no give in that at all.

-RADIO: 'The ice looks very solid here.'

-Good, good.

That's fine, go for it there.

They need ice that's hard and stable enough to attach mooring ropes.

But before long...

they've got company.

Yeah, he does seem to be moving a little bit towards the left.

-Doesn't he?

-He is, he's walking left, right?

-Yeah, exactly.

Whoa, eyes on. He's just there.

-Here he is.

-Aqqaluk!

He's very close, very close to us.

-RADIO:

-'Could you give us an update please on the situation?'

-RADIO:

-'Still moving left to right.'

'OK, very good, thank you.'

As long as the bear keeps its distance, the team can continue.

-Beautiful.

-Yeah, through, through.

It's a good motivator for quick work.

Another couple. One more.

Awesome - done.

First step on the iceberg.

First person to fall over on the iceberg!

First person... Yeah. I think, yeah, a rather unceremoniously

"first step for man, giant leap for mankind" - that one, yeah.

It's taken two days to find the spot,

just an hour to moor up.

For the moment, the bears have disappeared,

so the scientists can finally board.

It's late...

but, because they're in the High Arctic,

it is still light enough to work.

All right.

Till and Peter are first to deploy their kit.

This is it.

This SATICE GPS will, they hope,

measure the flexing of the iceberg as it's rocked by waves.

Finally. I've been waiting for this moment.

Now we've got these high-resolution SATICE GPS which tells us,

to a centimetre, how the iceberg is moving.

Beautiful.

But one GPS isn't enough.

They need to get Richard's base station deep into the interior

to track how the whole iceberg is moving.

Yeah, I think we're far enough away

from any immediate calving, breaking.

I mean, there's still big crevasses, cracks going through here,

but I think we could walk to the other side of the iceberg

-and we'd still find them.

-They're all over the place.

But bears are known to use the cover of fog to hunt

and the weather is deteriorating.

The mist is coming in fairly rapidly,

-a little bit of haste would be good.

-Yeah, five minutes, less than that.

This is where it does all the magic.

-RADIO:

-'We're losing visibility very fast with this approaching.'

RADIO: 'OK, understood. Understood.'

Once that really freezes in,

we should get a nice record of what it's doing.

OK, guys, let's go, come on.

Back on the Neptune,

there's a sense of relief to have finally got out onto the berg.

THEY ALL LAUGH

The following morning,

with all the instruments in place,

the team puts the ice science on hold.

Instead...

they decide to do an Arctic experiment...with a difference.

The expedition doctor is Chris van Tulleken.

He's fascinated by the body's physiological reactions to extreme cold.

He's cooked up a simple experiment for himself and Andy.

When you jump in very, very cold water, you have this shock response.

And you have two different problems -

you have, from your skin, a huge number of nerves

sending adrenalin to your heart, which speeds it up.

But from the nerves in your face you have a dive response,

which actually wants to slow your heart down.

So you have two conflicting nerves going into your heart

and we think that's what gives people heart attacks

when they jump into water.

Chris is interested in whether these responses can be controlled

using the power of the mind.

Andy was in the army, where he did regular cold-water training.

Chris wonders if that conditioning allows him to cope better.

You can increase your chances of survival,

if you fall into cold water, by being psychologically prepared

and also by being physically prepared.

I think this will be fun, this'll be interesting - pioneering work.

-Fun would not be the word I would use but let's just get it done.

-OK.

Doug's looking out for the guys' safety

but he has the luxury of a dry suit.

Look at Doug, he is dressed up like a seal, isn't he?

-That kit works.

-Does it?

I know that kit works, whereas your pants do not.

You haven't seen my pants, mate.

I'm getting a little bit nervous now.

Waterproof heart monitors

will record their pulse and breathing rates throughout

and any differences between the two of them.

HE PUFFS

That is very, very impressive.

-How are you feeling? Can you talk to me?

-Yeah.

OK.

-Just about, can you give me your name?

-Yeah.

ANDY COUGHS AND SPLUTTERS

Can you even swear?

ANDY GASPS

The big key there is to prepare your mind.

Genuinely, I don't want to sound all airy fairy,

but you just get in your head that it's going to be cold, it's going to hurt.

Accept it and just take charge of yourself.

Now Chris' turn.

Cold hands, cold hands, Tim!

Sorry.

Ready?

Three, two, one...

CHRIS SHRIEKS

HE GASPS

How is it, mate?

-GASPING:

-Painful-ful! Your head...

It hurts, it hurts.

CHRIS GROANS

Ice cream headache...

The worst ice-cream headache I've ever had!

Let's get back to the warm boat and download the data,

because I think my heart went completely bananas.

So the results here are really good, actually.

When we get in the water, your heart rate is 145, mine is 175.

So much, much higher than yours. Breathing rate -

your breathing rate goes up to 30, my breathing rate goes up to 40.

So...

In all senses, my panic cold-shock response

is much, much more extreme than yours.

That, for me, is the key thing -

if you're psychologically prepared and relaxed

and keep your head together for that 30 seconds like you did,

then you're much more likely to survive.

And you'd be better able to survive longer in cold water

because you're carrying a bit of excess...insulation.

That's exactly right. I mean this, this is my survival strategy.

If I can't stay calm, I'll do that.

Later that day, the weather has cleared enough to re-board the berg.

Peter and Till are desperate

to get the first results from the ice itself.

Could the waves make this massive chunk of ice break up?

The data's working and we're collecting data

on how the iceberg is moving up and down and sideways

and how it's responding to the swell.

I can see the data files. We've actually been measuring

the exact movement of the berg for the last 12 hours,

so this is exactly what we wanted.

Got about 12 files, it's going to be about 15 seconds.

Peter's all ready excited by the initial readings.

Because it's a very big iceberg,

it's tilting in a kind of resonant oscillation.

We've seen other bergs doing that.

DISTANT EXPLOSION

And so by having a tiltmeter on the edge, it's really going up and down.

RUMBLING

-What's just happened there, Till?

-OK, we just had a massive...

A massive part of the iceberg just collapsed back there

but I think we're fine, I'm just going to disconnect this.

-Peter, you've got the adaptor for the other...

-Yeah.

In fact, this will be recording that event, probably, we hope.

But what they haven't noticed is a 200 metre fault-line

opening-up behind them.

ICE CRACKS

Is that a new crack?

That is a new crack forming. That's definitely a new crack.

-RADIO:

-'Say again. I missed that last...'

We can feel cracking under our feet.

So it's probably... And it's falling here.

CRASHING Right, we should go...

Just go.

I've done the download now, here.

Run, Peter. Run, run, run.

They have to get out of there.

We've had a major breakout down there,

we've had a major breakout over there,

people on the ice felt cracking under their feet,

so no-one's taking any chances.

And for good reason.

It's not just a crack -

a huge block is actually beginning to separate from the main berg.

ICE CRACKS

-RADIO:

-'A massive crack 150 metres back, the whole thing is going,

'the whole thing is coming loose.'

The detached piece will have a new centre of gravity,

which could easily make it roll over.

-RADIO:

-'The whole side of the berg is giving way.'

With the Neptune tied to the ice,

there's a danger the ship will be dragged underwater.

-RADIO:

-'I suggest we cut the lines.'

Understood. Understood.

-ANDREW ON RADIO:

-'Are we ready to let go of the lines? Let go?'

It's crazy, that's the craziest thing I've ever seen.

For most of the team, evacuating the ice is a major setback.

But Peter thinks they've got the results they need.

We're very pleased to have got this equipment out,

because the data we have got was, very luckily,

right from the time when an iceberg broke up underneath us,

so that we...we...we now have some data that tells us

what happens when a berg separates from a bigger berg, so that's great.

Peter and Till have unique data...

..but the other scientists are frustrated.

No-one knows if they'll be able to moor again.

For Chris...it's an opportunity.

Now's the time to study the wildlife.

He wants to know how so many bears can survive on the iceberg.

There's a group of four seals here.

They are bear burgers.

They're exactly what the bears are here for

and the seals wouldn't be here

unless there was seal food here - fish, krill, other crustaceans.

So this iceberg is supporting an entire ecosystem.

That's very exciting. This is like a little lost world

we might be able to study in some detail.

Doug and Andy are helping Chris investigate this lost world.

They want to find out if the sea close to the berg

is richer in life than other parts of the ocean.

But their immediate concern...

is the animal at the very top of the food chain.

-Hello, bear.

-He's on the move.

-He's seen us.

-There's no way...

We're could have a diving buddy, mate.

Let's just see what this bear does.

Would you still dive, Andy, if he jumped in?

Um, If he jumped in?

I think that would be a bold move.

They have been recorded diving to 24 metres.

I wouldn't like to go in the water with him hanging around, no.

-This sort of...

-HE MAKES A CHOMPING NOISE

-..not a good sign.

What's that?

It's usually what they do when they're a little bit...

-Hungry?

-Yeah, getting ready to do something.

Oh, look. He's looking. He's like, "Can I do it?"

I can't believe he'll go in from there.

-But he's thinking about it.

-He is.

Their sense of smell is absolutely astonishing.

So they'll smell people from some way away - maybe they heard it too

and if it was just over the back of that rise,

the sound of the engines and talking, it would've heard it and come over.

Well, I say it's come over to have a look but it's just run off.

But then, the first time I saw Doug Allan,

I looked at him and I ran off as well.

So, to be quite honest with you, I'm not surprised!

This closed? OK?

Doug and Andy now feel it's safe enough to go ahead.

-Clear to go when you want.

-Yep?

-Yep, clear to go.

-Yep.

-Go when ready.

-Go when ready.

This place is stunning.

I've never seen walls of ice...

..and the colours of blue and of white, it's absolutely beautiful.

On the surface, this ice wall -

it looks like tiny little dimples all across it.

Just the whole surface looks like a golf ball.

I can't believe how much plankton is down here.

The size of these things!

Andy's amazed at how rich the waters are around the berg.

Is that a lion's mane?

These creatures form part of a complex food chain

that feeds the fish...

that feed the seals...

..and ultimately feed the polar bears.

That's a sample for Chris.

That should keep him happy.

OK, let's go up.

Moment of truth.

Whatever's in here, it's unlikely that I've ever seen it before

and meeting a new animal is always very, very exciting.

They've filled it to the top so it's a little bit messy.

Some of these things are very, very fragile.

So I'm going to do my best to pour it in.

Oh, my goodness!

Look at these!

Look at them! They may as well be from another planet.

Absolutely fantastic.

Guys, come and look at this! Come and look at it.

I know you've seen it already,

but you might be able to see it more clearly here

than you were through your masks.

Aren't they beautiful?

Who needs science fiction when you've got this?

Absolutely. I agree.

The common name for these things is sea gooseberries.

Look at the cilia going! Can you see it?

It's covered in tiny, beating cells,

rippling there with the light going through them.

But, frankly, it's nothing compared to this other thing down here.

The common name for these is sea angels.

This is very closely related to the slug and the snail

that you'll find in your back garden.

They're very bonny animals. They're very handsome.

Is that his gut that you can see?

It's his gut and those beating wings are its modified foot.

Because it's a mollusc and that equates to the foot -

the bit a snail or a slug moves around on

and, in this animal, it's divided it into two

and it uses them to literally fly through the water.

-And I love the fact it's see-through.

-Yeah.

I've got to tell you, this is the highlight of my entire trip so far.

I've seen two-two animals the likes of which I've never seen before.

They're extraordinary. They're beautiful

and obviously very important in the ecosystem around the ice.

Get your suits back on.

Get these two back in, we're done with these - I want more!

I mean, it's a significant peak,

but it's not a great peak in the energy.

In the scanning room,

the wave team has analysed the results of the SATICE GPS.

What do they reveal about the big break-up of the iceberg?

The red line is where we actually went on to the iceberg

to download the data.

And, as we go on there, the berg breaks up.

And we see this huge jump of 60cm,

so the box that was sitting on the iceberg just was moved upwards,

shifted upwards by 60cm, by the whole iceberg moving

after it cracked off of the main berg.

That's something quite astonishing and it's...

I mean, we were really lucky to be actually on there

with our sensor as the break-up happened.

That's never been achieved before.

Next, Till compares results from the wave buoy

to see if ocean swell caused the cracking.

This is the day when the break up happened.

The exact point of the break up was where this blue square is

and what we can see from this

is that there is nothing remarkable going on.

Swell is really small, there's no peak of wave height

or anything of this sort prior to the break-up.

So we can pretty conclusively say that this particular break-up

was not in any way caused by ocean waves or by bending due to waves.

It's official - waves didn't cause the big break-up.

In this case, the wave team has proved their own theory wrong.

Now it's time for the other group of scientists to step in.

The melt team believes Arctic waters surrounding the berg

are warm enough to thaw away significant amounts of ice.

They're headed by Keith Nicholls from the British Antarctic survey.

In recent years, we've been seeing a lot more big tabular icebergs

come off the Greenland ice sheet

and they've...they're now ending up in Baffin Bay.

That's a change and the only reason it can change

is that the climate around Greenland is changing.

And Keith believes it will get more extreme.

I think it's a warning for all of us, really, that things are changing.

Things are going to look very different in 20 years' time,

50 years' time.

And I think it should be a concern for everyone.

The first thing the melt team wants to investigate

is the temperature of the ice deep inside the berg.

To do this, they'll need to drill into the ice...

..which means they'll have to get back on the berg.

Raggi's not prepared to moor again.

This time, he'll hold position just next to the iceberg.

In its own way, just as treacherous.

RADIO CHATTER

Helen joins them. It's her first time on the ice.

She's been waiting for this moment for eight days.

I'm here!

We have fought so many battles - with the weather,

with ship logistics, with fog, with polar bears. Not literally.

So the fact that I'm standing here at all

is honestly astonishing to me and it makes me appreciate

so much more the difficulties of studying what we're standing on.

Now that we're here, the thing is to drill down into the ice

and measure the temperature in the middle,

and the reason that matters

is that ever since this iceberg broke off the glacier,

it's been gaining heat from the environment and heating up.

From measurements taken back in Greenland,

the team knows the iceberg's temperature

was around -15 degrees Celsius when it first calved.

So what we're keen to do is to find out what the temperature

in the middle of the ice is because that will help us understand

how fast it's melting, and why it's melting at the speed it is.

They're drilling into the very heart of the berg.

It feels like we're going to be here for a long time, doing this,

but it is going down. The drill is going down

and we are drilling into a fantastically tough material.

If this was easy, the iceberg wouldn't still be here.

When the core comes out, it's still holding onto

the temperature it had when it was in the ice itself.

Later, we can put the thermistor to the bottom of the borehole,

once we've made it,

and get another measurement from within the borehole,

but this gives us a first good approximation

to the borehole temperature.

While they drill, Chris is on bear watch.

What's that there?

That's a bear.

-It is a bear, isn't it.

-See it? There.

It's miles away. We've got no problem, it's miles away.

But it's not just one bear.

RADIO: 'David, we've clocked them. They seem quite close. Over.'

It's a mother and her two cubs.

The likelihood is she'll take a look at us

because she's curious and then lead them away.

I mean, people aren't nice to bears,

she doesn't want to expose her cubs, which are very valuable to her.

So the likelihood of her coming close to us is pretty small.

But the bears keep approaching.

At 80 metres, they're too close for comfort.

-RADIO: 'Yes, coming towards us.

-OK.'

They've only managed to drill down two metres,

but Keith thinks that's enough.

RADIO: 'The group is gradually walking back to us.'

RADIO: 'All personnel on board ship. We're clear of gangway.'

And it's been a unique experience.

I'm not used to being interrupted by bears.

I mean, we come from the British Antarctic Survey

and we don't allow polar bears anywhere near us.

We may have the odd irate penguin, but that's about it to contend with.

The melt team have their results.

The iceberg is -6.16 degrees Celsius two metres down.

From this, they estimate that, at its coldest point,

it'll be -13 degrees.

It's surprisingly cold.

The ice is just two degrees warmer

than when it split off the glacier two years earlier.

But why is it still so cold?

The melt team knows the main regulator

of the iceberg's temperature is the water around it.

So they turn their attention to the sea.

They use a device called a CTD.

It measures how cold or warm the surrounding water is,

as well as its saltiness.

We want to look at the ocean temperature, salinity,

all around the iceberg,

so we can think about whether the iceberg is melting.

Keith sees a chance to take the best measurements of all,

right next to the berg.

Once again, Doug and Andy help out.

For years, we've guessed at what really happens

in that boundary layer between the ocean and the ice.

And we simply can't get close to it

because ships simply can't get in there.

But when you've got divers,

the divers can take the instrument right up to the wall.

It's very exciting to see the data we're going to get back.

All set up and ready to go.

-It's all switched on.

-OK.

Straight to 30 now. All the way down.

No-one has recorded sea temperature and salinity like this before.

I'm going to try and keep it as close to the edge as possible.

This flat edge here.

As well as taking these unique readings,

Keith has given the divers another experiment.

This bottle contains a tracer dye.

It will reveal whether powerful currents

are moving up and down the sides of the berg.

That is absolutely beautiful.

It's like some kind of huge, ruffled, velvet blanket.

What a bizarre shape.

It doesn't appear to be moving much,

it's just kind of hanging there.

The results are surprising.

If there were strong currents,

the dye would spread rapidly through the water.

But this isn't happening.

Appears to be very little water disturbance right at the ice edge.

The dye shows the waters around the berg are still and settled.

This is brilliant. Real science in action.

Not a bad day at the office.

So what about the temperature of the water?

Back on the ship, Alon has his results.

And a revealing insight.

As you can see, the ocean is separated into two layers.

So this is the surface and this is the bottom.

We've drawn in what looks like an iceberg in the middle

just to give us a bit of an orientation.

And what you see is the ocean is separated into two layers.

The bottom layer, which is most of the ocean, is cold and salty.

It's like -1.5 degrees,

which means it's actually not doing that much melting to the iceberg.

The deeper seawater here is incredibly cold.

Below normal freezing.

This cocoons the ice underwater,

and explains why the heart of the berg is so cold.

But the melt team has discovered something else.

The top ten metres of the sea are very different.

Here, there's a much warmer layer,

which will sit on top of the cold deeper water.

And this layer is warm enough to have a major impact on the berg.

What's really melting the iceberg is the top layer,

which is really, really warm.

That's eroding at the iceberg, which is exactly what we've seen outside.

While they've been here, the scientists have noticed

a surprising feature - a notch in the ice where it meets the sea.

And now they know what makes it.

The warm water on the sea-surface is melting this narrow band of ice.

Chiselling a groove around the berg.

-That's four or five metres.

-Really?

-It goes a long way back.

The reason this iceberg is breaking up really fast in front of us

is all about what's happening at the wave-cut

in the warm water layer, right at the surface.

The team are realising this seemingly insignificant notch

is closely linked to the crumbling of the ice above it,

and the underwater ram they saw earlier.

The pieces of the puzzle have come together.

The warm surface water melts the notch.

The ice above is unsupported and collapses.

This leaves the large ice-foot, or ram,

which is protected from melting by deep, cold water.

As this ice foot enlarges, it becomes more buoyant.

And, finally...

..the upward pressure is just too much.

The ice snaps off.

Only by seeing it happen in front of their eyes,

could the team have had this insight.

There are these enormous stresses on the ice

and the place where the damage will happen is at the weaknesses.

And I thought that was a fabulous excuse to get some chocolate.

This is our ice shelf sticking out like this.

And what we're saying is that the foot is pushing on it here

and if I push on it enough...

it breaks.

It's actually creating this huge lever,

which is forcing the front edge of the iceberg up

and causing it to crack along the line of weakness.

Now I think we probably ought to eat your experiment.

I think that's a very important part of this experiment. Have a bit.

Thank you very much. I think that's a good few thousand tons.

SHE LAUGHS

The team have discovered a completely new way

in which icebergs can break up.

Throughout the expedition,

the team has constantly faced the threat of polar bears.

Although they've made life difficult, they fascinate Chris.

He wants to know how many bears the berg can support.

As his last job, he wants to do a census.

We've got the chopper,

and we're going to go out and take a look round.

I'm really excited to be a part of this.

I've waited a long time to be able to do this.

So I'm hoping we'll find some bears.

So far, they've only been able to observe bears

around the edge of the iceberg.

But there are 40 square kilometres of ice.

And, by flying over the interior,

Chris can get a more accurate estimate of the total number of bears.

We've got one just here down here now.

It's on the side of a small lake.

A single adult bear.

It's cream-coloured against the white snow,

which means that we can see it.

I'm going to grab a couple of shots of it with my still camera.

The presence of these additional bears in the interior

confirms the ones on the edge

must be just a fraction of the population.

So, in total, looking at the circumference,

which was around 27 kilometres, and how frequently we saw them,

I'd go for mid teens to 20 bears on this berg.

What there is there for them is security

and I think they're taking advantage of that.

So I think they're hanging out on this berg basically to stay safe

and just wait for that sea ice to come back in.

Then they can just charge out and hunt.

With the Arctic spring temperatures becoming warmer,

there's far less sea ice.

It's making it harder for polar bears to survive.

It's why Chris' survey is so valuable.

This is the first time a large population of polar bears

has been recorded on a tabular iceberg, using it as a sanctuary.

It's time to leave. Despite the hardships,

the team accomplished far more in the ten days than they dared hope.

I suppose this is it then, the end of Operation Iceberg,

and what an expedition it's been. What an expedition it's been

Seriously, I never thought we'd get on here

and now it's time to get off.

I can't think I'll ever be on another one.

It's been amazing, absolutely amazing.

Just one last question now -

what's going to happen to it after we've left?

Where's it going to end up? Where's it going to melt?

Where's the last molecule of this mass of ice

going to drip into that sea?

I hope we find out.

And we will, because the team has left a tracking device.

It will send back the location of the iceberg over the coming months,

revealing its future journey.

It's been a remarkable adventure.

The team have seen how huge icebergs are born

as they split from a glacier.

And what happens to an iceberg out at sea.

They'll continue to track the Petermann Berg

as it floats south, out into the Atlantic.

And over time, perhaps in as little as a year,

the berg will disappear altogether, back into the water.

Subtitles by Red Bee Media Ltd