On Thin Ice Frozen Planet

This white wilderness, this emptiness, is the North Pole.

I'm standing in the middle of a frozen ocean.

Beneath my feet and for over 500 miles in every direction,

there are several metres of ice.

But something significant is likely to happen here,

at the North Pole, soon.

Chances are that some time, within the next few decades,

perhaps even as soon as 2020, there will be open water here

for the first time in human recorded history.

The Arctic and Antarctic are changing.

Enormous masses of ice that have been frozen for thousands of years

are breaking apart and melting away.

Ice scientists are going to extremes to find out exactly

what's going on.

For them, these are exciting times.

But the transformation that's being seen here will be felt

far beyond the polar wilderness.

In this programme,

I'll be trying to understand what these changes mean, not just to the

wildlife and people that live around the Poles, but for the whole planet.

I'm starting my journey in the Arctic, the far north of our planet.

It's still very cold outside by most people's standards,

but the Arctic has been warming fast,

twice as fast as the rest of our planet.

My first mission is to find out what effect

that's having on the animals.

Although first, we have to find them.

It's April in Svalbard.

We are 1,000 miles north of the Arctic Circle,

in search of the region's top predator.

We need to travel away from the land and out over the frozen sea.

There's some tracks right beneath us.

Over there.

I'm with a Norwegian team,

which is giving the polar bears of Svalbard their yearly health check.

She's under us now.

I'll come round for a clean shot.

The team works together to give an anaesthetic injection

from a dart gun without hurting the bear.

It takes tremendous skill.

Ah, you've got it.

I'll just back off until she's asleep.

Nobody likes to see a magnificent

animal like a polar bear lolling about unconscious on the ice,

but it's only by darting them

in this way and keeping check on them

year after year, that we can be sure we know

what is happening to them and the population of polar bears as a whole.

Over the last 30 years, many teams have been seeing

the condition of their local bears deteriorate.

Although not every bear is suffering.

-How much?

-96, there.

And 102 here, so that's 197, yeah.

Is that good?

It's not too bad, it's a bit above average.

So she's a bear in a good condition for Svalbard.

The trouble is that if this was underweight, she would be in trouble.

Not only from her own point of view, but from the point of her cubs,

because an underweight female gives birth to underweight cubs

and underweight cubs have a great problem of surviving

their difficult first year in these circumstances.

It can be minus 40 degrees Centigrade when polar bear cubs emerge

at the start of the Arctic spring,

from their dens where they were born.

This mother hasn't eaten for half a year.

She and her cubs need to fatten up fast over the next few months and

their chances of survival depend on what's happening beneath their feet.

These polar bears aren't walking on land.

They're roaming across the frozen surface of the sea.

And the bear's food lives under the ice.

Ringed seals are hunted by polar bears.

In fact, in some parts, polar bears eat almost nothing else.

So, it's very understandable that this mother ringed seal...

..who's looking at me now, should be a little apprehensive.

That pup of hers is only about three or four days old...

..and the pup won't be able to swim for another two or three days.

Seals have good reason to be nervous around their holes.

They need the holes to breathe when the sea is frozen,

but this makes them easy to find.

Polar bears can sniff out seal holes, even if they're covered in snow.

Spring is the best hunting season.

This mother's found a food store under the snow

that was probably made by an Arctic fox.

It's a time of plenty now,

but the bear family need to make the best of it

because the good times are about to come to an end.

As the weather warms,

the ice beneath the bears' feet starts to break up and then melt.

And as the ice dwindles, so do the bears' chances of a successful hunt.

Most of the ice is lost over these shallow coastal waters,

where most of the seals live.

It's now summer and these bears have a choice - take their chances

on the shrinking ice floes, or make for the safety of the land.

It's a case of sink or swim.

Bears have always gone hungry in the summer,

but the length of time when there's enough ice for them

to go hunting is getting shorter and shorter, across much of the Arctic.

This is hitting cubs particularly hard,

because they can't survive for as long without feeding as their mother.

Cubs that were born underweight are at the greatest risk.

This mother and her cubs may well not get another meal

until the sea freezes again in winter.

There's not much to eat on land and the fact is that the longer the cubs

have to wait until the ice returns, the more likely they are to die.

Longer summers with no ice are probably the main reason why

many polar bear populations are dropping.

To help monitor bears into the future, this female is being fitted

with a radio collar to track her movements.

It's an extraordinary sensation to be

so close to such a powerful animal.

With luck, carrying that collar,

she will have more years to go yet...

..and be telling us a great deal

about herself and the rest

of the race of polar bears, as they

face this very uncertain future.

The future of the ice cover on the sea isn't just

an issue for the animals.

It's a big concern for the people

who live in the Arctic

and travel across the ice every day.

David Iqaqrialu is an Inuit from the village of Clyde River

in the Canadian Far North.

There are very few roads up here, so David and his community,

like most Inuit people, have always travelled across the frozen sea.

Dog sleds are the safest way to get around because the dogs feel

thin ice underfoot and won't lead travellers into trouble.

Old-timers, like David, know the ice is as well as we know

the streets in our local neighbourhood.

Every spring,

cracks have always formed in the same places at the same time.

It's going to be big very soon. After two weeks maybe...

..it will be more open.

But now, cracks are appearing where they never did before.

So, David and his friend, Laimikie, have taken on a new job.

They are using special GPS units to record the position

of new cracks or weak ice.

These findings will be used

by locals for their own safety,

but they're also being studied by ice scientists,

who want to predict how the ice will change in years to come.

THEY SPEAK THEIR NATIVE LANGUAGE

The Inuit are keen to know what the future holds too

because they've seen with their own eyes the changes

that the scientists have seen from space.

This satellite photo from 1980 shows the Arctic Ocean

at the end of the summer, when ice cover is at its minimum.

Since then, there's been a 30% drop in the area covered by ice.

But these images can't tell us about changes to the most important factor,

the thickness of the ice.

Measuring thickness across the whole ocean

was beyond scientists for many years,

until help came from an unexpected source.

The Arctic Ocean is of huge military importance, as it's the shortest

route between North America and Russia.

Since the late 1950s, British, US and Russian submarines

have been patrolling the Arctic Ocean.

But as well as looking out for enemy activity,

they've also been measuring the thickness of the ice,

critical when looking for a place to surface.

When scientists got permission to look at the submarine crew's records,

they discovered that the ice has been thinning fast.

In fact, it's nearly halved in thickness since 1980.

Across most of the Arctic Ocean,

there are now just a couple of metres of ice.

It's so thin that it could melt away almost entirely in the summertime,

and that includes the ice at the North Pole.

If current trends continue, then there will be

open ocean here by summer's end,

some time within the next few decades.

So, the days of the Arctic Ocean being covered

by a continuous sheet of ice seem to have passed.

Whether or not that's a good or bad thing, of course,

depends on your point of view.

Nobody has had a better view of the changes to the Arctic Ocean

than the people of Barrow, the most northerly town in Alaska.

The people here have always survived by hunting on the frozen sea

and they celebrate this at a festival every year.

The blanket toss was once the best way to spot distant animals to hunt,

as lifelong resident Lewis Brower explains.

When we throw ourselves up into the blanket, you know,

you get that much more of an 'Ahh' of seeing further and further out,

so sometimes, you'll jump 15-20 feet in the air,

and hopefully, you're being caught right back into the blanket.

-I'm OK!

-THEY LAUGH

But the old way of life is under threat.

When Lewis was young, the sea stayed frozen to the horizon until July,

and some ice remained off-shore all summer.

But now, it's breaking up in June

and melting away completely for two or three months.

I used to go out on the ice all the time at this time of the year,

but we can't do that any more, cos there's no more ice.

Lewis can also see that the loss of sea ice is affecting

the animals he hunts for a living.

Since 2007, something very strange has been happening

on this stretch of coastline, close to Barrow.

Mother walruses, confused by the lack of ice, are crowding onto the land

with their pups.

This very tight crowding isn't normal

and it's caused many youngsters to be crushed to death.

Many Arctic animals are threatened by the changing conditions

and that's also bad news for the traditional hunters.

But the ice loss could be good news for some people.

There are trillions of dollars' worth of oil

and gas under the Arctic Ocean.

But the only way to get to them,

until now, has been by building expensive artificial islands,

like this.

But if the sea ice goes,

it will be much easier to drill for the huge riches below.

So, the countries that surround the Arctic are scrambling

to stake their claims.

This daring attempt by the Russians to claim the disputed seabed

at the North Pole in 2007 caused fury among the competing countries

and it's unlikely to be the last such dispute.

The Arctic has never been so important

and not just because of its resources.

The North-West Passage,

a legendary sea route around the north of Canada and Alaska, cleared

of ice in the summer of 2007 for the first time since records began.

This promises a much faster

and cheaper shipping route between the Atlantic and Pacific Oceans.

And some wildlife could benefit from an ice-free Arctic too.

Bowhead whales are one of just a few whales that can live

year-round in the Arctic because they have no dorsal fin.

This means they can come up for air in small spaces

and travel easily under the ice.

Their unique body shape used to mean that the Arctic whales had

the seas to themselves for most of the year.

But now, some cousins from down south are moving in.

Killer whales are now a much more common sight in the Arctic.

Their tall fins make it difficult for them to travel under ice,

but the longer summers mean they can travel much further north

and make the most of the rich Arctic seas.

For animals and people,

it will be those that can adapt who will thrive in a changing Arctic.

But the loss of sea ice isn't just an issue for the Arctic,

because the state of the ice affects the climate of the whole planet.

Because it's white, the ice reflects up to 90% of the Sun's energy.

This is called the albedo effect and it's why

we often see heat haze in the Arctic, even when the air feels cold.

The frozen Arctic Ocean acts as a huge reflector,

bouncing back the Sun's heat into space.

Throughout history, that has helped to cool the planet,

but when the ice melts, it's a different story.

Because sea water is dark, it absorbs most of the Sun's heat.

In the Arctic, this can trigger a chain reaction, as the warming

water melts more ice, exposing more water to the Sun's heat.

This cycle of warming, as huge areas start to absorb rather than

reflect heat, is the main reason why the Arctic, a region the size

of North America, is warming twice as fast as the rest of the Earth.

So, melting sea ice is a big issue.

But there's another kind of ice that could have an even more

dramatic impact on our world.

The ice that is found on land.

This is fresh water ice,

formed from thousands of years of accumulated snowfall.

This is the front of a glacier, quite a small one, believe it or not.

Glaciers are like rivers of frozen

fresh water flowing across the surface of the land.

This one, like most polar glaciers,

is flowing down from a vast inland ice sheet.

And it's what happens to those ice sheets

that could radically alter the face of the planet.

The Greenland ice sheet is by far the largest in the Arctic.

It's two miles thick in places

and six times the size of the United Kingdom.

Every summer, some of the surface of the ice sheet melts,

forming sapphire-blue lakes of melt water.

More and more of these lakes have been forming

as Greenland has warmed over the last 20 years.

This lake has grown over several weeks and now it's overflowing,

carving a deep channel through the ice.

A network of channels criss-crosses the ice sheet,

but many of them come to an abrupt end.

Huge holes, like this, can open up quite suddenly,

draining the melt water away.

Alun Hubbard is a glaciologist, studying the enormous power

of these waterfalls, which are known as moulins.

We've got this amazing moulin going off here today.

The water's overflowing from the lake, which is beginning to drain.

Tonnes of water cascading down this pipe that is, effectively,

plummeting to the depths of the ice sheet through

over a kilometre of vertical ice.

Alun is here to study where the melt water goes

and what effect it has on the remaining ice.

To do that, he needs to find a moulin that has recently run dry.

Just a week ago, there was a three-mile long,

ten-metre deep lake here.

The weight of all that water cracked the ice beneath

and the late drained in just a few hours with incredible force.

Thousand-tonne ice boulders were tossed about like dice.

Alun's team have found the hole down which the lake disappeared

and they want to have a closer look.

It's not a job for anyone with a fear of heights.

As you can see, it's dry up here, but if you listen,

you can hear the thunder of,

there's a lot of water entering it at some depth.

Alun wants to place a sensor deep into the moulin to discover

how much water is flowing through the ice.

As they drop, they travel back in time.

30 metres down and they reach ice formed from snow that fell

10,000 years ago, in the last Ice Age.

When this lake drained and the plug got pulled and the whole lot

flushed down through here, this ice sheet, it rose by a metre

as that water accessed the bed and forced, jacked up the ice sheet.

So, we know that the water

in this whole plumbing cavity system, down here,

we know that shoots straight through that ice

and actually hits the bed of the ice sheet.

We've hit the water, I can see the water now.

Great. Nice work.

This daring experiment is measuring how the water flowing under

the ice sheet affects the speed with which the glaciers

flow from it, down to the sea.

The theory is that the water is acting as a lubricant.

So, the more water there is, the faster the glacier flows.

To the naked eye, glaciers don't appear to move at all.

But move they do.

These unique time-lapse images were captured over the last four years.

Through long observations, we now know that Greenland's ice

is flowing down to the sea twice as quickly as it was 20 years ago.

The speed of the glaciers affects our sea levels

because when they reach the water, they break apart into icebergs.

Occasionally, a real mega-berg is born.

This is the Store Glacier in May 2010.

75 million tonnes of ice, that had been sitting on land

for thousands of years, has broken away.

Events like this have become increasingly common,

as Greenland's glaciers flow faster into the sea.

Every single one of these icebergs raises the sea level a small amount.

Scientists monitoring the ice sheet predict that Greenland might add

as much as a half metre to world sea levels by the end of the century,

enough to swamp many of the world's low-lying islands.

99% of the Arctic's fresh water ice is in Greenland.

It's a staggeringly big ice sheet, but it's just a drop in the ocean

compared to that at the southern end of our planet.

In Antarctica, there is ten times more ice,

by far the largest concentration of ice on Earth.

Our exploration of the Antarctic only began

a little over 100 years ago.

The study of ice retreat here was unwittingly begun

on an expedition led by the great early explorer Ernest Shackleton.

In 1916, after their expedition boat was crushed and sunk by ice,

Shackleton and two companions set off to summon help in a tiny boat.

They sailed over 800 miles across the Southern Ocean

to the island of South Georgia, on the edge of the Antarctic.

Near starving and dressed in rags, the three men

walked across the ice sheet at the centre of the island, knowing there

was a whaling base on the opposite coast where they could summon help.

This team of Royal Marines is re-tracing the steps

of that journey in tribute to Shackleton and his men.

But for all their efforts, they can't exactly copy the great walk

because the ice is not as it was.

A number of South Georgia's glaciers

were photographed

by Shackleton's cameraman.

Frozen Planet saw a dramatic change

when they returned 94 years later.

Most of South Georgia's glaciers have shrunk since Shackleton's time

and most of that has happened

since I first went to the Antarctic 30 years ago.

I've been to South Georgia several times

and seen how greatly the glaciers there have changed.

This photograph of a glacier

reaching right down to the sea

was taken just six years

before I first visited in 1981.

Now, that glacier has retreated by 400 metres away from the beach.

Temperatures in South Georgia have risen sharply, but the Southern

Hemisphere's most dramatic warming has happened a little further south.

In recent years, stronger winds blowing over the Southern Ocean

have brought warmer air to the 800- mile-long finger of land that forms

the northern extremity of the Antarctic continent.

Here, on the Antarctic Peninsula, the changing wind patterns have driven

temperatures up by nearly three degrees Centigrade

over the last 50 years.

Ten times the average rate of the rest of the planet.

The rapid warming is having a big effect on the birdlife.

The Adelie penguin is the most southerly nesting of all penguins.

And like the polar bear up in the north,

their lives are dependent on the sea ice.

Adelies spend their whole lives near ice.

These birds have spent the winter feeding at the ice edge,

but now it's spring

and they've started a long trek over the frozen sea towards land.

They're heading for areas of exposed rock, where they gather

to breed, in colonies that can be over 100,000 strong.

But it seems that Adelies don't find the conditions

on the peninsula to their liking any more.

17 years ago, when I was last in the Antarctic, there were

large colonies of Adelie penguins all along the Antarctic Peninsula.

Now, warming temperatures have meant less sea ice

and Adelie penguin numbers are in decline.

Many colonies have been emptying fast.

It may be that penguins are starving,

or it may be that they're heading south to colder climes

where there's still plenty of ice on the sea.

But, as in the Arctic, while ice-loving animals are feeling

the heat, animals that like it a bit more cosy are moving in.

The bright orange beaks of Gentoo penguins are a much more common sight

on the peninsula these days.

I always used to know them as residents

of the slightly warmer islands north of the Antarctic.

But they've moved south in numbers.

There are thought to be ten times more Gentoos on the peninsula now

than just 30 years ago.

The peninsula has warmed a great deal,

but the same is not true further south.

The Antarctic continent is smothered by the world's greatest ice sheet.

One and half times the size of Australia

and up to three miles thick.

A staggering 75% of the Earth's fresh water is locked up in this ice.

Global sea levels would rise by some 60 metres if all this was to melt.

But what chance is there of that happening here in the coldest,

most hostile place on Earth?

The ice beneath me, up here on top of the ice cap, is so thick

that I am short of breath, simply because of the altitude.

This is midsummer

and the average temperature is some 20 degrees below freezing.

And I can tell you it feels much lower than that.

And even the worst predictions don't suggest

that the air is going to warm enough to melt the ice.

But now, scientists are asking a different question.

Could the speed at which the Antarctic ice flows off the land

be increased by a warmer ocean?

Where the ice sheet meets the sea,

scientists are going to extreme lengths to find out.

Firing!

Andy Smith works for the British Antarctic Survey.

What we have here is one kilogramme of pentolite explosive.

We're going to use this to generate a shockwave

and record the echoes that come back from underneath the ice.

Firing.

Andy is particularly interested in mapping

the underside of the ice around the coast.

Because here, it isn't resting on land.

It's floating on sea water, so if sea temperatures rise

just a little, it can be melted from below.

Around the coast of Antarctica,

the glaciers have flowed out across the sea to form immense masses

of floating fresh water ice, called ice shelves.

These freeze to the land around them, sticking fast and acting

like bathplugs, holding back the flow of the glaciers into the sea.

On the Antarctic Peninsula, a one-degree sea temperature rise

has helped to break apart seven major ice shelves in the last 30 years.

This is the Larsen B ice shelf,

three times the size of Greater London, breaking apart in 2002.

Afterwards, the glaciers it had been holding back

started flowing up to six times faster.

In 2008, a much larger ice shelf at the southern end

of the peninsula started to break up.

It's an enormous event that's never been filmed before.

Andy Smith is flying down the peninsula to study

this phenomenon first hand.

We're flying to a place called Wilkins Ice Shelf.

It's an ice shelf that, over the last couple of years,

has shown a very sudden and dramatic break-up.

The Wilkins Ice Shelf is a two-hour long flight south

from his research base, but Andy can start to see

the evidence of ice shelf break-up a long way before he gets there.

As we're heading further south,

we can see more and more icebergs in the ocean.

And most of the big ones will be ones

that have broken off the ice shelves in this area.

Once we cross the mountains, we should be able to see

Wilkins Ice Shelf and then it's not far then to the ice front, here,

where it's collapsing.

As Andy's team reaches their destination,

the scale of what's been happening soon becomes clear.

Here, for thousands of years, an area the size of Yorkshire

has been covered by a sheet of ice 200 metres thick.

But now, over half of that has broken apart.

Andy has been studying Antarctic ice for 25 years,

but even he is blown away by what he's seeing.

Now, that is pretty awesome. That is remarkable.

The edge of the ice shelf has just, kind of, disintegrated.

Some of the big pieces look like

they could be a mile or more in size.

It's almost like a, sort of, a slow motion explosion.

It all pushes outwards very quickly.

Every one of these huge icebergs will slowly drift out to sea.

To study how fast that happens, Andy needs to get closer to the action.

We're going to look around and see if we can find a place where

we can land. And if we can, we'll be able to put down an instrument

that will help us monitor the big icebergs that are breaking off

as the ice shelf breaks up.

Landing on an iceberg is another first for Andy's team.

This satellite transmitter will help to track the continued break-up

of this colossal ice shelf.

The remainder of the Wilkins looks set to break apart soon.

It's the latest ice shelf to disintegrate in a wave that's been

travelling southwards,

playing a major role in the loss of ice from the peninsula.

Next in line, and already weakening in places, are the ice shelves

that hold back Antarctica's gigantic continental ice sheet.

And it would only take a small corner of this to slide into the sea

to have major global consequences.

We've only started to see changes in the Arctic and Antarctic recently.

So, it's hard to predict exactly what impact these changes will have.

But we can see for ourselves that these places are changing

and on a scale that is hard to ignore.

The Poles, North and South, may seem very remote,

but what is happening here is likely to have a greater effect upon us

than any other aspect of global warming.

If the Arctic sea ice continues to disappear,

it will drive up the planet's temperature more quickly.

And the melting ice sheets could contribute to a sea level rise

of a metre, enough to threaten the homes of millions of people

around the world's coasts by the end of the century.

We've seen that the animals are already adapting to these changes,

but can WE respond to what is happening now to the frozen planet?

The increasing unpredictability of the ice was a big issue

for the Frozen Planet team, who spent three years working on top of it.

Whether on sea, land, lake or river,

the state of the ice was the first concern for most filming crews.

Unexpected break-ups left many a cameraman in need of a swift rescue.

Sometimes, help came by boat, and sometimes by air.

I had a chance to see the changing ice conditions for myself,

when I visited the North Pole.

I flew with the team to a temporary camp that is set up every year in

the centre of the frozen Arctic Ocean to support expeditions to the Pole.

I had never visited the North Pole before,

so this was a great highlight for me.

But it was hard going in temperatures of minus 40,

so as soon as filming finished, we flew south.

Little did we know that we had made it out just in time.

We got back from the Pole camp last night and I've just bumped into

the Russian Commander, who's just heard from the camp.

And the news is that a little crack, which I'd seen in the ice

between our tent and the airstrip, which was no more than an inch

or so wide, has, overnight, widened to 20 metres.

Temporary break-ups, caused by stormy weather

and strong winds, have happened before, but they've been getting

more and more frequent over recent years as the ice has got weaker.

It was only swift action by the staff that prevented

a lot of valuable equipment going in the drink.

The biggest concern was that the ice airstrip might break apart,

but, luckily, it held and everyone was able to evacuate

when the weather improved.

The Frozen Planet team's clearest demonstration of the power

and unpredictability of breaking ice

came when they went to film the melting of a frozen Canadian river.

Producer Mark Linfield

and researcher Matt Swarbrick have travelled to the far North of Canada.

Matt, when was the last time we saw a car?

I don't know, about three hours ago.

They've driven through the vast Northwest Territory on a mission

to film the moment when this frozen waterfall breaks apart.

The break-up, when the frozen river above the waterfall thaws

and masses of water start to flow again, can be a spectacular event.

But predicting exactly when it's going to break

is the big challenge, if Mark and Matt want to get the best shots.

And they're not the only ones who want to know.

When the waterfall breaks, it can flood the town of Hay River,

just downstream, with millions of tonnes of water and ice.

Mark is taking advice from scientist Fay Hicks,

who studies the break-up of Canada's frozen rivers.

What happens is, you get ice jams form upstream and they start to dam

up the water and it builds

and builds and builds, and that can let go,

and that's a much bigger wave of water, you know,

than just the normal flow.

So, it just depends upon how dramatically it unfolds.

Every spring, Fay travels to Northern Canada

to study the way that breaking ice can jam rivers.

The spring break-up is of great significance to the people of the far north.

When the upper reaches of these rivers melt, huge amounts of water can build up

behind dams of ice.

When these dams burst, a surge of ice and water

can cause devastation to settlements along the banks.

Ground-penetrating radar provides information about the thickness of the ice,

crucial to the study of the break-up.

But predicting the date of the big day is notoriously hard.

Fay has warned the team that events could unfold very quickly

if conditions continue to warm.

The crew start to prepare. The waterfall appears to be waking.

There's a lot of work to do if they're to cover the break-up with as many cameras as possible.

The weather continues to warm, but nothing happens.

Far upstream, there's been a snowstorm, which is slowing down the break-up.

The team waits and waits and waits.

Mark is concerned that the crew have to return home soon, so

he heads into town to get the advice

of long-term resident Red McBrian.

We just have to live with it and take whatever evasive action we can.

Red has had 50 years of witnessing the power of the river.

Well, we're hoping that she may break up in two or three days.

Oh, no, no, no, that's too soon. Oh, no, no.

Boys, you're looking at seven or eight days

before she breaks of any significance.

And if she breaks, she can jam and hold up. She can be...

She'd be down here probably around the 5th or 6th May.

The snowstorm has derailed the team's plans,

and another week goes by before the river starts to move.

Finally, it seems that things might be happening.

We've just heard some cracks from upstream,

so, if we're lucky, we might get some action.

-Seven o'clock, which gives us two hours of light.

-Two hours.

If it happens at night, we're going to miss the whole thing.

Sure enough, the town is put on red alert

that the river is about to break in the middle of the night.

They've just called a full evacuation of the Eye Inn,

where we're staying, and if we don't move now, we're all going to be

underwater and possibly get trapped here for a few days.

The team have to move out and get up to the waterfall,

hoping that it doesn't break before it's light enough to film.

Luckily, the sun is up before the main event begins.

That is a serious amount of ice coming around the corner.

After weeks of waiting, the sleeping giant of a river,

we thought nothing was go to happen and suddenly, look at this!

This is what we're here for. Unbelievable.

-Absolutely unbelievable. Holy

-BLEEP!

The team is used to handling multiple cameras,

but they don't usually have to dodge ten-tonne ice floes at the same time.

As you can see, it's racing over at unbelievable speed.

The power, I just, if you were here to feel this, it's a deep rumbling

sound of the river, I can feel it up through my feet.

The power, I just can't imagine. That could crush a house in no time.

The team takes to the air to witness the destruction that's unleashed.

Huge ice blocks are pushed downstream on the wave of water

released by the breaking waterfall.

This could devastate the town.

But, this year, the residents are lucky.

There was no serious flooding,

as the ice blocks didn't badly jam the river near to the town.

As for the date of the break-up, 6th May,

Red is right on the nose.

I don't use any of these here gauges and mechanical assistance,

I just go by what I see on the river as I walk it down.

And I say I walk it down, back and forth every day on the river to see

what's happening, and from that, I gauge when it's going to hit here

and what the situation is going to be like when it does get here.

You know, when it went this morning,

I said to my students, "Guess what the date is?"

Red told us it was the 6th May and we were, you know, I'm not

surprised, because we've been here a couple of times and that's happened.

Ten days, two weeks out and he just looks around and goes "5th May."

How does he know that?

It's incredible.

It's because he just has lived on this river

and lived this break-up for 50 years.

Ice scientists are improving the accuracy of their predictions

all the time, but in the meantime,

the people of Hay River have a remarkable guardian.

Red, you were completely right this year. Are you right every year?

No, I'm...

I miss the odd one. Yes, 1985, I missed it.

Subtitles by Red Bee Media Ltd