0:00:02 > 0:00:05Travel up into the North Atlantic,
0:00:05 > 0:00:09so far north the summer sun never sets,
0:00:09 > 0:00:13and you will find an island the size of a city,
0:00:13 > 0:00:16but made of ice.
0:00:16 > 0:00:18A huge Arctic iceberg.
0:00:19 > 0:00:23And now, an international team of scientists and explorers
0:00:23 > 0:00:26are on the ultimate expedition,
0:00:26 > 0:00:30to investigate this wonder of the natural world.
0:00:31 > 0:00:34That is absolutely beautiful.
0:00:35 > 0:00:38They have already seen how icebergs are born
0:00:38 > 0:00:41as they calve off the front of their mother glacier.
0:00:43 > 0:00:47That's one of the biggest bits of natural destruction I've ever seen.
0:00:48 > 0:00:50Now the team's attention is turning
0:00:50 > 0:00:53to one of the biggest icebergs in the world.
0:00:53 > 0:00:56This is super-super-hard ice.
0:00:56 > 0:00:59They want to discover what happens to it out at sea.
0:01:00 > 0:01:01Beautiful.
0:01:02 > 0:01:06And, above all, the forces that will cause its ultimate destruction.
0:01:06 > 0:01:08This whole bit's coming off.
0:01:08 > 0:01:11They will face huge challenges...
0:01:11 > 0:01:12It's falling here.
0:01:14 > 0:01:17..from confronting the largest land predator...
0:01:17 > 0:01:19Oh, eyes on... It's just there.
0:01:19 > 0:01:24..to surviving one of the most unpredictable environments on earth.
0:01:42 > 0:01:44The Operation Iceberg team has swapped its glacier camp
0:01:44 > 0:01:47in Greenland for the research vessel Neptune.
0:01:51 > 0:01:5423 scientists, adventurers and camera crew
0:01:54 > 0:01:57are setting off on an ambitious two-week expedition.
0:01:59 > 0:02:01I think we need to think through that plan now...
0:02:02 > 0:02:07They're heading across these waters in search of a massive Arctic berg.
0:02:09 > 0:02:12Helen Czerski is a physicist and oceanographer.
0:02:15 > 0:02:18She's interested in what's happening to the ice itself.
0:02:19 > 0:02:22I'm fascinated by the mechanisms -
0:02:22 > 0:02:26what's going on and why it's happening - inside this iceberg.
0:02:26 > 0:02:29And how it lasts so long.
0:02:29 > 0:02:32When you look at the photos, you can see the algae actually on the ice.
0:02:32 > 0:02:35Naturalist Chris Packham wants to understand the role icebergs play
0:02:35 > 0:02:38in the environment of the polar seas.
0:02:39 > 0:02:43Icebergs carry with them an almost mythical aura.
0:02:43 > 0:02:46We think we know them but we don't.
0:02:46 > 0:02:48They're still very, very much of a mystery.
0:02:50 > 0:02:56Joining the Iceberg team is a group of renowned ice scientists.
0:02:57 > 0:02:59This is a very rare opportunity
0:02:59 > 0:03:02because you very seldom get a large Arctic berg.
0:03:02 > 0:03:05When you do see them, it's very hard to get to work on them.
0:03:09 > 0:03:11The team has identified their target.
0:03:14 > 0:03:17In 2010, in the northwest corner of Greenland...
0:03:20 > 0:03:24..a vast piece of ice calved off the Petermann Glacier.
0:03:24 > 0:03:28Over two years, it's drifted south on ocean currents.
0:03:29 > 0:03:33Four times, vast chunks have broken off.
0:03:34 > 0:03:38Now, over a thousand kilometres from its mother-glacier,
0:03:38 > 0:03:43the largest piece is stuck just off the coast of Canada's Baffin Island.
0:03:46 > 0:03:48We were trying to make measurements
0:03:48 > 0:03:52where we knew most dynamic things were happening.
0:03:52 > 0:03:56Remarkably, one of the scientists, Richard Bates,
0:03:56 > 0:03:59already knows this ice.
0:03:59 > 0:04:01So you've stood on this piece of ice before?
0:04:01 > 0:04:04That's right, yeah, back in 2009, we were up there.
0:04:04 > 0:04:06So, before it actually broke off,
0:04:06 > 0:04:09we were there doing measurements on it, around it.
0:04:09 > 0:04:12This crack carried on around the back here
0:04:12 > 0:04:15and this crack worked its way towards it
0:04:15 > 0:04:17and broke that off as one chunk
0:04:17 > 0:04:20and that is the iceberg that is working its way south.
0:04:23 > 0:04:26For the team, there's one key mystery they want to solve.
0:04:27 > 0:04:32What are the physical forces slowly destroying this vast chunk of ice?
0:04:35 > 0:04:37The ocean has a huge amount of energy
0:04:37 > 0:04:39pushing and pulling and twisting,
0:04:39 > 0:04:41and I'm really interested to see how the iceberg stands up
0:04:41 > 0:04:43to all of those stresses.
0:04:47 > 0:04:52After 36 hours at sea, looming out of the fog,
0:04:52 > 0:04:55an almost unimaginable wall of ice.
0:04:59 > 0:05:02The team has found their goal.
0:05:03 > 0:05:04There it is!
0:05:06 > 0:05:09I knew it was going to be big, but this is massive!
0:05:11 > 0:05:13Good to be back here.
0:05:14 > 0:05:18First Arctic iceberg for me. First ANY iceberg for me, actually.
0:05:19 > 0:05:22It looks very frightening to me, it's full of cracks
0:05:22 > 0:05:26and fissures, and cliffs and rivers. There's a huge river coming off.
0:05:26 > 0:05:28And it looks entirely without life -
0:05:28 > 0:05:33an inhospitable lump of freezing fresh water floating in sea water.
0:05:34 > 0:05:37It's just a stunning sight.
0:05:37 > 0:05:41I've never seen a single piece of ice that is this big....
0:05:42 > 0:05:43One molecule...
0:05:44 > 0:05:47Billions and billions and billions of it in a single lump,
0:05:47 > 0:05:51floating on the ocean. It's an absolutely amazing sight.
0:05:54 > 0:05:58This is the iceberg the team plan to board and explore.
0:06:00 > 0:06:03It is criss-crossed with crevasses and melt-rivers.
0:06:06 > 0:06:09For two years, it's been the largest single object
0:06:09 > 0:06:11floating in Arctic seas.
0:06:13 > 0:06:15It even has a name.
0:06:15 > 0:06:17The Petermann Iceberg.
0:06:24 > 0:06:28As soon as the team arrive, it's action stations.
0:06:28 > 0:06:30RADIO: 'We've lost full signal on the iceberg.'
0:06:30 > 0:06:34We've got the funny angles that we've re-set the transducers at.
0:06:34 > 0:06:35First task - to scan the berg.
0:06:35 > 0:06:38Richard and his colleague, Max, want to know exactly how large it is.
0:06:38 > 0:06:41We've clearly we've got an echo off the bottom.
0:06:41 > 0:06:45This equipment will reveal its dimensions,
0:06:45 > 0:06:48both above and below water.
0:06:50 > 0:06:52RADIO: Do you need it closer in, Max,
0:06:52 > 0:06:54or do you think this distance is a good offset?
0:06:54 > 0:06:59To scan the berg, they'll need to circumnavigate it,
0:06:59 > 0:07:01and the nearer the ship is, the better the data.
0:07:03 > 0:07:05Will the ping-rate go up at that?
0:07:05 > 0:07:07But it's a game of careful negotiation
0:07:07 > 0:07:09with the ship's skipper, Raggi Ellison.
0:07:09 > 0:07:1350 metres towards the iceberg, if the captain's happy with that?
0:07:13 > 0:07:16We are 50 metres away from the iceberg, so...
0:07:16 > 0:07:18I'm not going to climb on board it!
0:07:18 > 0:07:20THEY LAUGH
0:07:22 > 0:07:24Raggi is cautious for good reason.
0:07:25 > 0:07:29He knows icebergs are notoriously unstable.
0:07:32 > 0:07:34Smaller ones can suddenly roll over.
0:07:35 > 0:07:38And, without warning, can completely shatter.
0:07:42 > 0:07:46Boarding one of these smaller ones would be suicidal.
0:07:48 > 0:07:52Which is why the team picked the Petermann Berg -
0:07:52 > 0:07:56it's bigger, flatter and, they hope, more stable.
0:07:57 > 0:08:00It's one of the remotest spots in the world.
0:08:01 > 0:08:02But they're not the only visitor.
0:08:06 > 0:08:09There's a polar bear swimming, what, 50 metres off the ship.
0:08:09 > 0:08:11Really close, and he's just hanging out.
0:08:13 > 0:08:16We were debating whether we'd ever see one out here.
0:08:17 > 0:08:19I'm actually shaking. Wow.
0:08:23 > 0:08:25This is all my Christmases come at once.
0:08:25 > 0:08:27A polar bear.
0:08:27 > 0:08:29Now, I really, really, really, hoped to see one,
0:08:29 > 0:08:31but I never thought that we would.
0:08:31 > 0:08:34But then, you know, these are marine mammals.
0:08:34 > 0:08:36They can cover great distances in the sea,
0:08:36 > 0:08:40and they frequently do, swimming between the ice floes.
0:08:40 > 0:08:43Look, it's about 20 metres off, now.
0:08:45 > 0:08:47How exciting though, honestly.
0:08:52 > 0:08:55Polar bears hunt on the sea ice for most of the year.
0:08:56 > 0:08:59But now it's summer, the sea ice has melted,
0:08:59 > 0:09:03and the team's berg is the last remaining ice in the area.
0:09:04 > 0:09:06And it's not alone.
0:09:08 > 0:09:11There's another bear on the berg itself.
0:09:14 > 0:09:17A polar bear on our iceberg.
0:09:17 > 0:09:20Hold on a moment, hold on - can we have the binoculars?
0:09:20 > 0:09:21Can we get the binoculars, please?
0:09:21 > 0:09:24- Turn over, Keith. Turn over. - I am turning over.
0:09:25 > 0:09:29Oh, I don't believe it. I really don't.
0:09:29 > 0:09:32There's actually another bear over here on the ice.
0:09:32 > 0:09:34You can see it...
0:09:35 > 0:09:37..through my binoculars, there, as a little speck.
0:09:39 > 0:09:43So, in the space of just half an hour, we've seen three polar bears.
0:09:43 > 0:09:46One in the water, just off the iceberg...
0:09:46 > 0:09:49There's one here happy, smiling.
0:09:49 > 0:09:54And about 500 metres over there is a third bear on our iceberg.
0:09:54 > 0:09:56It's Bear-tastic!
0:09:56 > 0:09:58It's Bear City.
0:10:00 > 0:10:04Even experienced Polar cameraman Doug Allan is excited.
0:10:05 > 0:10:08Look at him - he's just lovely!
0:10:08 > 0:10:11Lovely, lovely bear.
0:10:11 > 0:10:13Don't they just look so completely at home?
0:10:13 > 0:10:15I know, I know.
0:10:15 > 0:10:18You know, they totally epitomise the Arctic and ice.
0:10:18 > 0:10:21That's what I like about polar bears.
0:10:22 > 0:10:24Bears will stay on ice as long as possible,
0:10:24 > 0:10:27they don't like going ashore, they'll stay on ice.
0:10:27 > 0:10:31So, in as much as this is by far the biggest bit of ice
0:10:31 > 0:10:33for miles and miles around, perhaps it's not so surprising
0:10:33 > 0:10:35that they should be found here.
0:10:40 > 0:10:42Despite the team's enthusiasm,
0:10:42 > 0:10:46these predators pose a real problem for the science mission.
0:10:48 > 0:10:52Highly curious, polar bears are very capable
0:10:52 > 0:10:56of attacking anything - or anyone - that enters their domain.
0:10:59 > 0:11:02The intention is to go on that iceberg.
0:11:02 > 0:11:05But three bears in 15 minutes...
0:11:05 > 0:11:08Well, it adds a bit of excitement to the whole thing.
0:11:15 > 0:11:17You need to change the scale to make it move.
0:11:17 > 0:11:19It's much more obvious above that.
0:11:19 > 0:11:22The scientists have two different theories
0:11:22 > 0:11:25about which forces are slowly breaking up the berg.
0:11:26 > 0:11:30The melt team believes sea water is melting it over time.
0:11:32 > 0:11:35So, that's the main sea...
0:11:35 > 0:11:37The wave team argues the ocean waves
0:11:37 > 0:11:42are rocking and flexing the ice, snapping it into smaller chunks.
0:11:42 > 0:11:45And that's ocean swell, which has come a huge distance.
0:11:45 > 0:11:47This is Peter Wadhams' theory.
0:11:49 > 0:11:52Waves do have a big effect, and we need to understand
0:11:52 > 0:11:55that relationship between waves and icebergs
0:11:55 > 0:11:58as part of understanding the relationship
0:11:58 > 0:12:01between waves and ice in general.
0:12:03 > 0:12:05Working with Peter is Till Wagner.
0:12:07 > 0:12:09He's the wave team's tech-head.
0:12:10 > 0:12:13And this is the beautiful green antenna.
0:12:13 > 0:12:17It's just all green, and shiny, and concentric...
0:12:18 > 0:12:20I think it's beautiful.
0:12:23 > 0:12:26To measure the size and frequency of the waves,
0:12:26 > 0:12:28they deploy a hi-tech buoy.
0:12:34 > 0:12:36Till, are you sad to see this go?
0:12:36 > 0:12:39Well, I do feel quite attached to it.
0:12:40 > 0:12:42It's always funny watching these instruments go out,
0:12:42 > 0:12:45cos they look so tiny. And we're just going to let this drift,
0:12:45 > 0:12:47we're going to have to find it again afterwards,
0:12:47 > 0:12:50and it looks so small out there...
0:12:50 > 0:12:53But it's recording exactly the data we need.
0:12:55 > 0:12:57Left to ride the ocean waves,
0:12:57 > 0:12:59it'll beam this information back to the ship.
0:13:02 > 0:13:05Here's the outside edge of it...
0:13:05 > 0:13:07Richard has completed his survey.
0:13:10 > 0:13:12Nine tenths of the iceberg is underwater.
0:13:12 > 0:13:14But the scan still allows Richard
0:13:14 > 0:13:17to make an accurate estimate of its size.
0:13:18 > 0:13:22The result is extraordinary.
0:13:22 > 0:13:24OK, so we've measured the circumference,
0:13:24 > 0:13:27it's about 27km around here.
0:13:27 > 0:13:29We've measured the thickness all around,
0:13:29 > 0:13:34and we've got about an average of, say, 70-75 metres of thickness.
0:13:34 > 0:13:37Gives us a volume of about two billion metres cubed
0:13:37 > 0:13:38of ice in there.
0:13:38 > 0:13:41Two billion metres cubed?
0:13:41 > 0:13:46You can roughly say two billion tons of ice in there or...
0:13:46 > 0:13:48Two trillion litres of water, OK?
0:13:48 > 0:13:54So you've got about maybe 200-odd days of consumption for the UK.
0:13:54 > 0:13:59So this water would last the UK domestic consumption for 200 days?
0:13:59 > 0:14:01Something like that.
0:14:01 > 0:14:03If we towed her back up the Thames
0:14:03 > 0:14:06and, you know, tapped it in to Thames Water, and there you go.
0:14:06 > 0:14:08That's amazing.
0:14:12 > 0:14:15But the scan has also revealed a problem.
0:14:15 > 0:14:19Strangely, the position of the ship in relation to the iceberg
0:14:19 > 0:14:22seems to be constantly changing.
0:14:22 > 0:14:25According to your diagram we're in the middle of the iceberg,
0:14:25 > 0:14:28which can only mean one thing to me,
0:14:28 > 0:14:30- and that is that it's moved.- Exactly.
0:14:31 > 0:14:34- It's complicated life for you a little bit, hasn't it?- Yes.
0:14:34 > 0:14:36- I'm really sorry about that. - Thank you.
0:14:39 > 0:14:40It's a shock.
0:14:40 > 0:14:42The iceberg was chosen
0:14:42 > 0:14:46because the team thought it had gone aground and was stationary.
0:14:46 > 0:14:49Instead, it looks like it's on the move.
0:14:50 > 0:14:53Richard will need to deploy additional equipment
0:14:53 > 0:14:56onto the ice to track its shifting position.
0:14:58 > 0:15:01And he's not the only one with difficulties.
0:15:04 > 0:15:08Raggi has 30 years' experience of these waters.
0:15:08 > 0:15:12Even so, he is cautious about landing the team on a moving target.
0:15:15 > 0:15:18You should always take the worst scenario
0:15:18 > 0:15:20and work out for that.
0:15:20 > 0:15:21Prepare for the worst.
0:15:31 > 0:15:34It's not often you land against an iceberg, you know.
0:15:34 > 0:15:35It's very exciting.
0:15:35 > 0:15:37There's a lot of inertia in a ship like this
0:15:37 > 0:15:40so it's very easy, very quickly, to do some damage.
0:15:43 > 0:15:46CONVERSATION INAUDUBLE
0:15:46 > 0:15:48The berg's behaviour is unpredictable.
0:15:50 > 0:15:53It's hard to avoid collisions.
0:15:53 > 0:15:54RADIO CHATTER
0:15:57 > 0:15:59And there's another unexpected problem.
0:16:01 > 0:16:05The team discovers a huge ledge of ice jutting out,
0:16:05 > 0:16:07just beneath the waterline.
0:16:07 > 0:16:09That's 13 from the deck.
0:16:10 > 0:16:15This "ice-ram", as it's known, is right under the ship.
0:16:15 > 0:16:19- RAGGI ON RADIO:- 'No problem. I will move forward. I'm moving forward.
0:16:19 > 0:16:20'Thank you.'
0:16:20 > 0:16:25There's several hundred thousand tons of ice down there in that ram
0:16:25 > 0:16:26and we're on top of it.
0:16:27 > 0:16:29If a crack opened and it broke off,
0:16:29 > 0:16:33the buoyancy would bring the whole thing up above sea level
0:16:33 > 0:16:36and we'd be tipped over one way or the other.
0:16:39 > 0:16:43It looks like a nice, neat place to moor
0:16:43 > 0:16:45but actually it's quite dangerous.
0:16:50 > 0:16:54Raggi insists they search for a safer landing site.
0:16:56 > 0:16:58- RADIO:- 'Are we above or over?'
0:17:01 > 0:17:03And as if that weren't enough...
0:17:04 > 0:17:09..in a single day they've seen five more bears, eight in total.
0:17:12 > 0:17:15The safety officer calls an emergency briefing.
0:17:19 > 0:17:21So there are going to be a few simple rules here,
0:17:21 > 0:17:24which I think all of us can just get into our minds very early on.
0:17:24 > 0:17:28Number one - nobody wandering around off the ship on their own.
0:17:28 > 0:17:31Number two - we got to make sure that there are watchers out.
0:17:31 > 0:17:34Number three - you're going to need some equipment with you
0:17:34 > 0:17:38to make sure that you can fend off if a bear comes too close.
0:17:38 > 0:17:44Having seen bears stalking the seals on ice similar to this,
0:17:44 > 0:17:47they're very clever. They'll see a seal from a long way away
0:17:47 > 0:17:50and they will take advantage of the dips and hollows
0:17:50 > 0:17:51to stay out of sight.
0:17:51 > 0:17:55Just, sort of, try to be super-bear-aware.
0:17:55 > 0:17:59But if a bear did suddenly... You know, you found one very close.
0:17:59 > 0:18:03Then drop a piece of clothing on the ice.
0:18:03 > 0:18:04Put a pair of dirty socks in your pocket,
0:18:04 > 0:18:07something nice and smelly so you've got a couple of things to drop.
0:18:07 > 0:18:10It'll buy you vital seconds if you're backing off.
0:18:10 > 0:18:12The Inuit have a great saying,
0:18:12 > 0:18:16which says, "It's not the bear you can see that's going to get you".
0:18:22 > 0:18:23RADIO CHATTER
0:18:25 > 0:18:27It's the next morning
0:18:27 > 0:18:29and Raggi has found a possible mooring spot.
0:18:32 > 0:18:35The bear risk calls for additional precautions.
0:18:37 > 0:18:39- Here is the rifle. - Thank you, Captain.
0:18:39 > 0:18:41Aqqaluk will be on guard.
0:18:41 > 0:18:42A native Greenlander,
0:18:42 > 0:18:44he's used to living with the threat of polar bears.
0:18:46 > 0:18:50There should be some cartridges in there, which we need to confirm with the captain.
0:18:50 > 0:18:52Let's hope we don't have to use them.
0:18:55 > 0:18:58It's well over a kilometre away. Perhaps 1,200...
0:18:58 > 0:19:01The man leading the shore party is Andy Torbet,
0:19:01 > 0:19:04a specialist in extreme environments.
0:19:05 > 0:19:09They need to secure the boat to the ice.
0:19:09 > 0:19:12We're about to get the gangway across at the iceberg
0:19:12 > 0:19:15and take those first few steps. We'll recce sites,
0:19:15 > 0:19:18that we can get these big ship anchors in.
0:19:18 > 0:19:20The point of all this is to get the scientists on there safely
0:19:20 > 0:19:23and they can carry on and do the science.
0:19:24 > 0:19:25Let's go.
0:19:36 > 0:19:37Argh!
0:19:38 > 0:19:40SHE LAUGHS
0:19:40 > 0:19:42That's why we need crampons.
0:19:48 > 0:19:50- First on the iceberg.- It is.
0:19:50 > 0:19:53- How does it feel? - Done mate, this is awesome!
0:19:53 > 0:19:57- This is where the adventure properly starts.- Yeah, it is.
0:20:04 > 0:20:07This is how you imagine big lumps of ice. This is fabulous.
0:20:07 > 0:20:10- Yeah, yeah feel it on the top. - It's just like marble, isn't it?
0:20:10 > 0:20:13There's nothing, there's no give in that at all.
0:20:13 > 0:20:18- RADIO: 'The ice looks very solid here.'- Good, good.
0:20:18 > 0:20:19That's fine, go for it there.
0:20:22 > 0:20:26They need ice that's hard and stable enough to attach mooring ropes.
0:20:30 > 0:20:32But before long...
0:20:32 > 0:20:34they've got company.
0:20:34 > 0:20:38Yeah, he does seem to be moving a little bit towards the left.
0:20:38 > 0:20:42- Doesn't he?- He is, he's walking left, right?- Yeah, exactly.
0:20:42 > 0:20:45Whoa, eyes on. He's just there.
0:20:46 > 0:20:49- Here he is.- Aqqaluk!
0:20:49 > 0:20:52He's very close, very close to us.
0:20:52 > 0:20:56- RADIO:- 'Could you give us an update please on the situation?'
0:20:56 > 0:20:58- RADIO:- 'Still moving left to right.'
0:21:00 > 0:21:01'OK, very good, thank you.'
0:21:01 > 0:21:06As long as the bear keeps its distance, the team can continue.
0:21:06 > 0:21:09- Beautiful.- Yeah, through, through.
0:21:09 > 0:21:12It's a good motivator for quick work.
0:21:15 > 0:21:16Another couple. One more.
0:21:18 > 0:21:19Awesome - done.
0:21:21 > 0:21:22First step on the iceberg.
0:21:23 > 0:21:25First person to fall over on the iceberg!
0:21:25 > 0:21:28First person... Yeah. I think, yeah, a rather unceremoniously
0:21:28 > 0:21:33"first step for man, giant leap for mankind" - that one, yeah.
0:21:36 > 0:21:38It's taken two days to find the spot,
0:21:38 > 0:21:41just an hour to moor up.
0:21:45 > 0:21:47For the moment, the bears have disappeared,
0:21:47 > 0:21:50so the scientists can finally board.
0:21:52 > 0:21:54It's late...
0:21:54 > 0:21:56but, because they're in the High Arctic,
0:21:56 > 0:21:58it is still light enough to work.
0:22:01 > 0:22:02All right.
0:22:02 > 0:22:05Till and Peter are first to deploy their kit.
0:22:05 > 0:22:06This is it.
0:22:06 > 0:22:09This SATICE GPS will, they hope,
0:22:09 > 0:22:13measure the flexing of the iceberg as it's rocked by waves.
0:22:16 > 0:22:20Finally. I've been waiting for this moment.
0:22:22 > 0:22:26Now we've got these high-resolution SATICE GPS which tells us,
0:22:26 > 0:22:29to a centimetre, how the iceberg is moving.
0:22:30 > 0:22:32Beautiful.
0:22:38 > 0:22:40But one GPS isn't enough.
0:22:42 > 0:22:45They need to get Richard's base station deep into the interior
0:22:45 > 0:22:47to track how the whole iceberg is moving.
0:22:58 > 0:23:00Yeah, I think we're far enough away
0:23:00 > 0:23:02from any immediate calving, breaking.
0:23:02 > 0:23:06I mean, there's still big crevasses, cracks going through here,
0:23:06 > 0:23:08but I think we could walk to the other side of the iceberg
0:23:08 > 0:23:10- and we'd still find them. - They're all over the place.
0:23:15 > 0:23:19But bears are known to use the cover of fog to hunt
0:23:19 > 0:23:21and the weather is deteriorating.
0:23:21 > 0:23:23The mist is coming in fairly rapidly,
0:23:23 > 0:23:27- a little bit of haste would be good. - Yeah, five minutes, less than that.
0:23:27 > 0:23:29This is where it does all the magic.
0:23:30 > 0:23:34- RADIO:- 'We're losing visibility very fast with this approaching.'
0:23:34 > 0:23:36RADIO: 'OK, understood. Understood.'
0:23:36 > 0:23:37Once that really freezes in,
0:23:37 > 0:23:41we should get a nice record of what it's doing.
0:23:41 > 0:23:44OK, guys, let's go, come on.
0:23:53 > 0:23:55Back on the Neptune,
0:23:55 > 0:23:59there's a sense of relief to have finally got out onto the berg.
0:24:00 > 0:24:02THEY ALL LAUGH
0:24:14 > 0:24:15The following morning,
0:24:15 > 0:24:17with all the instruments in place,
0:24:17 > 0:24:20the team puts the ice science on hold.
0:24:21 > 0:24:23Instead...
0:24:23 > 0:24:26they decide to do an Arctic experiment...with a difference.
0:24:30 > 0:24:33The expedition doctor is Chris van Tulleken.
0:24:33 > 0:24:37He's fascinated by the body's physiological reactions to extreme cold.
0:24:41 > 0:24:44He's cooked up a simple experiment for himself and Andy.
0:24:47 > 0:24:52When you jump in very, very cold water, you have this shock response.
0:24:52 > 0:24:53And you have two different problems -
0:24:53 > 0:24:55you have, from your skin, a huge number of nerves
0:24:55 > 0:24:58sending adrenalin to your heart, which speeds it up.
0:24:58 > 0:25:00But from the nerves in your face you have a dive response,
0:25:00 > 0:25:02which actually wants to slow your heart down.
0:25:02 > 0:25:05So you have two conflicting nerves going into your heart
0:25:05 > 0:25:08and we think that's what gives people heart attacks
0:25:08 > 0:25:10when they jump into water.
0:25:14 > 0:25:17Chris is interested in whether these responses can be controlled
0:25:17 > 0:25:19using the power of the mind.
0:25:21 > 0:25:25Andy was in the army, where he did regular cold-water training.
0:25:25 > 0:25:29Chris wonders if that conditioning allows him to cope better.
0:25:30 > 0:25:33You can increase your chances of survival,
0:25:33 > 0:25:36if you fall into cold water, by being psychologically prepared
0:25:36 > 0:25:38and also by being physically prepared.
0:25:38 > 0:25:42I think this will be fun, this'll be interesting - pioneering work.
0:25:42 > 0:25:45- Fun would not be the word I would use but let's just get it done.- OK.
0:25:47 > 0:25:49Doug's looking out for the guys' safety
0:25:49 > 0:25:52but he has the luxury of a dry suit.
0:25:53 > 0:25:55Look at Doug, he is dressed up like a seal, isn't he?
0:25:57 > 0:25:59- That kit works.- Does it?
0:25:59 > 0:26:01I know that kit works, whereas your pants do not.
0:26:01 > 0:26:03You haven't seen my pants, mate.
0:26:03 > 0:26:05I'm getting a little bit nervous now.
0:26:09 > 0:26:11Waterproof heart monitors
0:26:11 > 0:26:14will record their pulse and breathing rates throughout
0:26:14 > 0:26:17and any differences between the two of them.
0:26:29 > 0:26:31HE PUFFS
0:26:33 > 0:26:36That is very, very impressive.
0:26:36 > 0:26:39- How are you feeling? Can you talk to me?- Yeah.
0:26:39 > 0:26:40OK.
0:26:40 > 0:26:42- Just about, can you give me your name?- Yeah.
0:26:42 > 0:26:43ANDY COUGHS AND SPLUTTERS
0:26:43 > 0:26:45Can you even swear?
0:26:45 > 0:26:46ANDY GASPS
0:26:48 > 0:26:52The big key there is to prepare your mind.
0:26:52 > 0:26:54Genuinely, I don't want to sound all airy fairy,
0:26:54 > 0:26:57but you just get in your head that it's going to be cold, it's going to hurt.
0:26:57 > 0:26:59Accept it and just take charge of yourself.
0:27:01 > 0:27:02Now Chris' turn.
0:27:04 > 0:27:07Cold hands, cold hands, Tim!
0:27:07 > 0:27:08Sorry.
0:27:14 > 0:27:15Ready?
0:27:15 > 0:27:17Three, two, one...
0:27:18 > 0:27:20CHRIS SHRIEKS
0:27:20 > 0:27:22HE GASPS
0:27:22 > 0:27:24How is it, mate?
0:27:25 > 0:27:27- GASPING:- Painful-ful! Your head...
0:27:29 > 0:27:32It hurts, it hurts.
0:27:34 > 0:27:37CHRIS GROANS
0:27:37 > 0:27:39Ice cream headache...
0:27:39 > 0:27:42The worst ice-cream headache I've ever had!
0:27:42 > 0:27:46Let's get back to the warm boat and download the data,
0:27:46 > 0:27:50because I think my heart went completely bananas.
0:27:54 > 0:27:57So the results here are really good, actually.
0:27:57 > 0:28:00When we get in the water, your heart rate is 145, mine is 175.
0:28:00 > 0:28:03So much, much higher than yours. Breathing rate -
0:28:03 > 0:28:06your breathing rate goes up to 30, my breathing rate goes up to 40.
0:28:06 > 0:28:08So...
0:28:08 > 0:28:11In all senses, my panic cold-shock response
0:28:11 > 0:28:13is much, much more extreme than yours.
0:28:13 > 0:28:15That, for me, is the key thing -
0:28:15 > 0:28:17if you're psychologically prepared and relaxed
0:28:17 > 0:28:20and keep your head together for that 30 seconds like you did,
0:28:20 > 0:28:23then you're much more likely to survive.
0:28:23 > 0:28:26And you'd be better able to survive longer in cold water
0:28:26 > 0:28:30because you're carrying a bit of excess...insulation.
0:28:30 > 0:28:34That's exactly right. I mean this, this is my survival strategy.
0:28:34 > 0:28:36If I can't stay calm, I'll do that.
0:28:45 > 0:28:49Later that day, the weather has cleared enough to re-board the berg.
0:28:50 > 0:28:52Peter and Till are desperate
0:28:52 > 0:28:55to get the first results from the ice itself.
0:28:57 > 0:29:00Could the waves make this massive chunk of ice break up?
0:29:02 > 0:29:07The data's working and we're collecting data
0:29:07 > 0:29:09on how the iceberg is moving up and down and sideways
0:29:09 > 0:29:12and how it's responding to the swell.
0:29:13 > 0:29:17I can see the data files. We've actually been measuring
0:29:17 > 0:29:19the exact movement of the berg for the last 12 hours,
0:29:19 > 0:29:22so this is exactly what we wanted.
0:29:22 > 0:29:25Got about 12 files, it's going to be about 15 seconds.
0:29:28 > 0:29:31Peter's all ready excited by the initial readings.
0:29:32 > 0:29:35Because it's a very big iceberg,
0:29:35 > 0:29:38it's tilting in a kind of resonant oscillation.
0:29:38 > 0:29:39We've seen other bergs doing that.
0:29:39 > 0:29:40DISTANT EXPLOSION
0:29:40 > 0:29:43And so by having a tiltmeter on the edge, it's really going up and down.
0:29:45 > 0:29:47RUMBLING
0:29:48 > 0:29:51- What's just happened there, Till? - OK, we just had a massive...
0:29:51 > 0:29:54A massive part of the iceberg just collapsed back there
0:29:54 > 0:29:57but I think we're fine, I'm just going to disconnect this.
0:29:57 > 0:30:00- Peter, you've got the adaptor for the other...- Yeah.
0:30:01 > 0:30:05In fact, this will be recording that event, probably, we hope.
0:30:07 > 0:30:11But what they haven't noticed is a 200 metre fault-line
0:30:11 > 0:30:13opening-up behind them.
0:30:13 > 0:30:15ICE CRACKS
0:30:15 > 0:30:17Is that a new crack?
0:30:17 > 0:30:20That is a new crack forming. That's definitely a new crack.
0:30:21 > 0:30:24- RADIO:- 'Say again. I missed that last...'
0:30:24 > 0:30:27We can feel cracking under our feet.
0:30:27 > 0:30:30So it's probably... And it's falling here.
0:30:30 > 0:30:33CRASHING Right, we should go...
0:30:33 > 0:30:34Just go.
0:30:38 > 0:30:40I've done the download now, here.
0:30:40 > 0:30:42Run, Peter. Run, run, run.
0:30:44 > 0:30:46They have to get out of there.
0:30:48 > 0:30:51We've had a major breakout down there,
0:30:51 > 0:30:53we've had a major breakout over there,
0:30:53 > 0:30:55people on the ice felt cracking under their feet,
0:30:55 > 0:30:57so no-one's taking any chances.
0:30:58 > 0:31:00And for good reason.
0:31:00 > 0:31:01It's not just a crack -
0:31:01 > 0:31:05a huge block is actually beginning to separate from the main berg.
0:31:07 > 0:31:09ICE CRACKS
0:31:09 > 0:31:12- RADIO:- 'A massive crack 150 metres back, the whole thing is going,
0:31:12 > 0:31:13'the whole thing is coming loose.'
0:31:13 > 0:31:17The detached piece will have a new centre of gravity,
0:31:17 > 0:31:20which could easily make it roll over.
0:31:21 > 0:31:23- RADIO:- 'The whole side of the berg is giving way.'
0:31:25 > 0:31:26With the Neptune tied to the ice,
0:31:26 > 0:31:29there's a danger the ship will be dragged underwater.
0:31:30 > 0:31:32- RADIO:- 'I suggest we cut the lines.'
0:31:32 > 0:31:33Understood. Understood.
0:31:35 > 0:31:38- ANDREW ON RADIO:- 'Are we ready to let go of the lines? Let go?'
0:31:39 > 0:31:41It's crazy, that's the craziest thing I've ever seen.
0:31:56 > 0:32:00For most of the team, evacuating the ice is a major setback.
0:32:01 > 0:32:04But Peter thinks they've got the results they need.
0:32:05 > 0:32:07We're very pleased to have got this equipment out,
0:32:07 > 0:32:11because the data we have got was, very luckily,
0:32:11 > 0:32:15right from the time when an iceberg broke up underneath us,
0:32:15 > 0:32:19so that we...we...we now have some data that tells us
0:32:19 > 0:32:23what happens when a berg separates from a bigger berg, so that's great.
0:32:28 > 0:32:32Peter and Till have unique data...
0:32:33 > 0:32:35..but the other scientists are frustrated.
0:32:35 > 0:32:39No-one knows if they'll be able to moor again.
0:32:39 > 0:32:43For Chris...it's an opportunity.
0:32:44 > 0:32:47Now's the time to study the wildlife.
0:32:48 > 0:32:52He wants to know how so many bears can survive on the iceberg.
0:32:57 > 0:32:59There's a group of four seals here.
0:32:59 > 0:33:01They are bear burgers.
0:33:01 > 0:33:03They're exactly what the bears are here for
0:33:03 > 0:33:05and the seals wouldn't be here
0:33:05 > 0:33:10unless there was seal food here - fish, krill, other crustaceans.
0:33:10 > 0:33:14So this iceberg is supporting an entire ecosystem.
0:33:14 > 0:33:18That's very exciting. This is like a little lost world
0:33:18 > 0:33:20we might be able to study in some detail.
0:33:23 > 0:33:28Doug and Andy are helping Chris investigate this lost world.
0:33:28 > 0:33:31They want to find out if the sea close to the berg
0:33:31 > 0:33:34is richer in life than other parts of the ocean.
0:33:36 > 0:33:38But their immediate concern...
0:33:38 > 0:33:40is the animal at the very top of the food chain.
0:33:42 > 0:33:45- Hello, bear.- He's on the move.
0:33:45 > 0:33:47- He's seen us.- There's no way...
0:33:47 > 0:33:50We're could have a diving buddy, mate.
0:33:51 > 0:33:54Let's just see what this bear does.
0:33:54 > 0:33:57Would you still dive, Andy, if he jumped in?
0:33:57 > 0:33:59Um, If he jumped in?
0:33:59 > 0:34:01I think that would be a bold move.
0:34:02 > 0:34:06They have been recorded diving to 24 metres.
0:34:06 > 0:34:09I wouldn't like to go in the water with him hanging around, no.
0:34:09 > 0:34:12- This sort of... - HE MAKES A CHOMPING NOISE - ..not a good sign.
0:34:12 > 0:34:13What's that?
0:34:13 > 0:34:16It's usually what they do when they're a little bit...
0:34:16 > 0:34:18- Hungry?- Yeah, getting ready to do something.
0:34:18 > 0:34:21Oh, look. He's looking. He's like, "Can I do it?"
0:34:21 > 0:34:23I can't believe he'll go in from there.
0:34:23 > 0:34:27- But he's thinking about it.- He is.
0:34:27 > 0:34:29Their sense of smell is absolutely astonishing.
0:34:29 > 0:34:33So they'll smell people from some way away - maybe they heard it too
0:34:33 > 0:34:35and if it was just over the back of that rise,
0:34:35 > 0:34:39the sound of the engines and talking, it would've heard it and come over.
0:34:39 > 0:34:41Well, I say it's come over to have a look but it's just run off.
0:34:41 > 0:34:43But then, the first time I saw Doug Allan,
0:34:43 > 0:34:44I looked at him and I ran off as well.
0:34:44 > 0:34:48So, to be quite honest with you, I'm not surprised!
0:34:48 > 0:34:49This closed? OK?
0:34:51 > 0:34:54Doug and Andy now feel it's safe enough to go ahead.
0:34:54 > 0:34:58- Clear to go when you want.- Yep? - Yep, clear to go.
0:34:58 > 0:35:01- Yep.- Go when ready.- Go when ready.
0:35:13 > 0:35:15This place is stunning.
0:35:19 > 0:35:22I've never seen walls of ice...
0:35:23 > 0:35:29..and the colours of blue and of white, it's absolutely beautiful.
0:35:32 > 0:35:35On the surface, this ice wall -
0:35:35 > 0:35:39it looks like tiny little dimples all across it.
0:35:39 > 0:35:43Just the whole surface looks like a golf ball.
0:35:52 > 0:35:55I can't believe how much plankton is down here.
0:35:59 > 0:36:00The size of these things!
0:36:06 > 0:36:09Andy's amazed at how rich the waters are around the berg.
0:36:15 > 0:36:17Is that a lion's mane?
0:36:21 > 0:36:23These creatures form part of a complex food chain
0:36:23 > 0:36:26that feeds the fish...
0:36:26 > 0:36:27that feed the seals...
0:36:28 > 0:36:31..and ultimately feed the polar bears.
0:36:33 > 0:36:35That's a sample for Chris.
0:36:36 > 0:36:39That should keep him happy.
0:36:39 > 0:36:40OK, let's go up.
0:36:49 > 0:36:51Moment of truth.
0:36:51 > 0:36:55Whatever's in here, it's unlikely that I've ever seen it before
0:36:55 > 0:36:59and meeting a new animal is always very, very exciting.
0:36:59 > 0:37:02They've filled it to the top so it's a little bit messy.
0:37:02 > 0:37:04Some of these things are very, very fragile.
0:37:04 > 0:37:06So I'm going to do my best to pour it in.
0:37:06 > 0:37:08Oh, my goodness!
0:37:09 > 0:37:12Look at these!
0:37:12 > 0:37:16Look at them! They may as well be from another planet.
0:37:16 > 0:37:19Absolutely fantastic.
0:37:21 > 0:37:23Guys, come and look at this! Come and look at it.
0:37:23 > 0:37:25I know you've seen it already,
0:37:25 > 0:37:27but you might be able to see it more clearly here
0:37:27 > 0:37:28than you were through your masks.
0:37:28 > 0:37:30Aren't they beautiful?
0:37:30 > 0:37:32Who needs science fiction when you've got this?
0:37:32 > 0:37:33Absolutely. I agree.
0:37:35 > 0:37:39The common name for these things is sea gooseberries.
0:37:39 > 0:37:41Look at the cilia going! Can you see it?
0:37:41 > 0:37:45It's covered in tiny, beating cells,
0:37:45 > 0:37:48rippling there with the light going through them.
0:37:49 > 0:37:52But, frankly, it's nothing compared to this other thing down here.
0:37:56 > 0:37:59The common name for these is sea angels.
0:37:59 > 0:38:02This is very closely related to the slug and the snail
0:38:02 > 0:38:05that you'll find in your back garden.
0:38:05 > 0:38:08They're very bonny animals. They're very handsome.
0:38:08 > 0:38:11Is that his gut that you can see?
0:38:11 > 0:38:15It's his gut and those beating wings are its modified foot.
0:38:15 > 0:38:19Because it's a mollusc and that equates to the foot -
0:38:19 > 0:38:21the bit a snail or a slug moves around on
0:38:21 > 0:38:25and, in this animal, it's divided it into two
0:38:25 > 0:38:28and it uses them to literally fly through the water.
0:38:28 > 0:38:30- And I love the fact it's see-through.- Yeah.
0:38:30 > 0:38:33I've got to tell you, this is the highlight of my entire trip so far.
0:38:33 > 0:38:38I've seen two-two animals the likes of which I've never seen before.
0:38:38 > 0:38:41They're extraordinary. They're beautiful
0:38:41 > 0:38:45and obviously very important in the ecosystem around the ice.
0:38:45 > 0:38:46Get your suits back on.
0:38:46 > 0:38:49Get these two back in, we're done with these - I want more!
0:38:51 > 0:38:54I mean, it's a significant peak,
0:38:54 > 0:38:56but it's not a great peak in the energy.
0:38:56 > 0:38:58In the scanning room,
0:38:58 > 0:39:02the wave team has analysed the results of the SATICE GPS.
0:39:04 > 0:39:08What do they reveal about the big break-up of the iceberg?
0:39:12 > 0:39:16The red line is where we actually went on to the iceberg
0:39:16 > 0:39:17to download the data.
0:39:17 > 0:39:21And, as we go on there, the berg breaks up.
0:39:21 > 0:39:23And we see this huge jump of 60cm,
0:39:23 > 0:39:29so the box that was sitting on the iceberg just was moved upwards,
0:39:29 > 0:39:33shifted upwards by 60cm, by the whole iceberg moving
0:39:33 > 0:39:36after it cracked off of the main berg.
0:39:36 > 0:39:38That's something quite astonishing and it's...
0:39:38 > 0:39:41I mean, we were really lucky to be actually on there
0:39:41 > 0:39:45with our sensor as the break-up happened.
0:39:45 > 0:39:46That's never been achieved before.
0:39:49 > 0:39:53Next, Till compares results from the wave buoy
0:39:53 > 0:39:55to see if ocean swell caused the cracking.
0:39:59 > 0:40:01This is the day when the break up happened.
0:40:01 > 0:40:07The exact point of the break up was where this blue square is
0:40:07 > 0:40:10and what we can see from this
0:40:10 > 0:40:13is that there is nothing remarkable going on.
0:40:13 > 0:40:18Swell is really small, there's no peak of wave height
0:40:18 > 0:40:20or anything of this sort prior to the break-up.
0:40:20 > 0:40:25So we can pretty conclusively say that this particular break-up
0:40:25 > 0:40:30was not in any way caused by ocean waves or by bending due to waves.
0:40:35 > 0:40:38It's official - waves didn't cause the big break-up.
0:40:39 > 0:40:43In this case, the wave team has proved their own theory wrong.
0:40:45 > 0:40:50Now it's time for the other group of scientists to step in.
0:40:50 > 0:40:53The melt team believes Arctic waters surrounding the berg
0:40:53 > 0:40:57are warm enough to thaw away significant amounts of ice.
0:40:59 > 0:41:04They're headed by Keith Nicholls from the British Antarctic survey.
0:41:04 > 0:41:07In recent years, we've been seeing a lot more big tabular icebergs
0:41:07 > 0:41:09come off the Greenland ice sheet
0:41:09 > 0:41:13and they've...they're now ending up in Baffin Bay.
0:41:13 > 0:41:16That's a change and the only reason it can change
0:41:16 > 0:41:18is that the climate around Greenland is changing.
0:41:20 > 0:41:23And Keith believes it will get more extreme.
0:41:25 > 0:41:29I think it's a warning for all of us, really, that things are changing.
0:41:29 > 0:41:31Things are going to look very different in 20 years' time,
0:41:31 > 0:41:3350 years' time.
0:41:33 > 0:41:36And I think it should be a concern for everyone.
0:41:43 > 0:41:46The first thing the melt team wants to investigate
0:41:46 > 0:41:49is the temperature of the ice deep inside the berg.
0:41:49 > 0:41:54To do this, they'll need to drill into the ice...
0:41:55 > 0:41:57..which means they'll have to get back on the berg.
0:42:00 > 0:42:02Raggi's not prepared to moor again.
0:42:02 > 0:42:06This time, he'll hold position just next to the iceberg.
0:42:06 > 0:42:08In its own way, just as treacherous.
0:42:13 > 0:42:15RADIO CHATTER
0:42:16 > 0:42:21Helen joins them. It's her first time on the ice.
0:42:21 > 0:42:24She's been waiting for this moment for eight days.
0:42:26 > 0:42:27I'm here!
0:42:30 > 0:42:34We have fought so many battles - with the weather,
0:42:34 > 0:42:36with ship logistics, with fog, with polar bears. Not literally.
0:42:36 > 0:42:40So the fact that I'm standing here at all
0:42:40 > 0:42:44is honestly astonishing to me and it makes me appreciate
0:42:44 > 0:42:48so much more the difficulties of studying what we're standing on.
0:42:52 > 0:42:55Now that we're here, the thing is to drill down into the ice
0:42:55 > 0:42:57and measure the temperature in the middle,
0:42:57 > 0:42:59and the reason that matters
0:42:59 > 0:43:02is that ever since this iceberg broke off the glacier,
0:43:02 > 0:43:05it's been gaining heat from the environment and heating up.
0:43:08 > 0:43:10From measurements taken back in Greenland,
0:43:10 > 0:43:12the team knows the iceberg's temperature
0:43:12 > 0:43:16was around -15 degrees Celsius when it first calved.
0:43:18 > 0:43:21So what we're keen to do is to find out what the temperature
0:43:21 > 0:43:24in the middle of the ice is because that will help us understand
0:43:24 > 0:43:27how fast it's melting, and why it's melting at the speed it is.
0:43:28 > 0:43:31They're drilling into the very heart of the berg.
0:43:35 > 0:43:38It feels like we're going to be here for a long time, doing this,
0:43:38 > 0:43:41but it is going down. The drill is going down
0:43:41 > 0:43:45and we are drilling into a fantastically tough material.
0:43:46 > 0:43:49If this was easy, the iceberg wouldn't still be here.
0:43:54 > 0:43:56When the core comes out, it's still holding onto
0:43:56 > 0:43:59the temperature it had when it was in the ice itself.
0:43:59 > 0:44:01Later, we can put the thermistor to the bottom of the borehole,
0:44:01 > 0:44:03once we've made it,
0:44:03 > 0:44:07and get another measurement from within the borehole,
0:44:07 > 0:44:09but this gives us a first good approximation
0:44:09 > 0:44:11to the borehole temperature.
0:44:12 > 0:44:16While they drill, Chris is on bear watch.
0:44:16 > 0:44:19What's that there?
0:44:19 > 0:44:20That's a bear.
0:44:22 > 0:44:25- It is a bear, isn't it. - See it? There.
0:44:26 > 0:44:30It's miles away. We've got no problem, it's miles away.
0:44:32 > 0:44:34But it's not just one bear.
0:44:35 > 0:44:39RADIO: 'David, we've clocked them. They seem quite close. Over.'
0:44:39 > 0:44:41It's a mother and her two cubs.
0:44:43 > 0:44:46The likelihood is she'll take a look at us
0:44:46 > 0:44:49because she's curious and then lead them away.
0:44:49 > 0:44:51I mean, people aren't nice to bears,
0:44:51 > 0:44:54she doesn't want to expose her cubs, which are very valuable to her.
0:44:54 > 0:44:57So the likelihood of her coming close to us is pretty small.
0:45:01 > 0:45:03But the bears keep approaching.
0:45:03 > 0:45:06At 80 metres, they're too close for comfort.
0:45:08 > 0:45:10- RADIO: 'Yes, coming towards us.- OK.'
0:45:12 > 0:45:15They've only managed to drill down two metres,
0:45:15 > 0:45:17but Keith thinks that's enough.
0:45:18 > 0:45:21RADIO: 'The group is gradually walking back to us.'
0:45:24 > 0:45:26RADIO: 'All personnel on board ship. We're clear of gangway.'
0:45:26 > 0:45:29And it's been a unique experience.
0:45:29 > 0:45:32I'm not used to being interrupted by bears.
0:45:32 > 0:45:35I mean, we come from the British Antarctic Survey
0:45:35 > 0:45:38and we don't allow polar bears anywhere near us.
0:45:38 > 0:45:42We may have the odd irate penguin, but that's about it to contend with.
0:45:45 > 0:45:47The melt team have their results.
0:45:47 > 0:45:53The iceberg is -6.16 degrees Celsius two metres down.
0:45:55 > 0:46:00From this, they estimate that, at its coldest point,
0:46:00 > 0:46:02it'll be -13 degrees.
0:46:04 > 0:46:06It's surprisingly cold.
0:46:06 > 0:46:08The ice is just two degrees warmer
0:46:08 > 0:46:12than when it split off the glacier two years earlier.
0:46:12 > 0:46:14But why is it still so cold?
0:46:19 > 0:46:21The melt team knows the main regulator
0:46:21 > 0:46:26of the iceberg's temperature is the water around it.
0:46:26 > 0:46:29So they turn their attention to the sea.
0:46:29 > 0:46:32They use a device called a CTD.
0:46:33 > 0:46:37It measures how cold or warm the surrounding water is,
0:46:37 > 0:46:39as well as its saltiness.
0:46:43 > 0:46:47We want to look at the ocean temperature, salinity,
0:46:47 > 0:46:48all around the iceberg,
0:46:48 > 0:46:51so we can think about whether the iceberg is melting.
0:46:57 > 0:47:00Keith sees a chance to take the best measurements of all,
0:47:00 > 0:47:02right next to the berg.
0:47:04 > 0:47:06Once again, Doug and Andy help out.
0:47:09 > 0:47:12For years, we've guessed at what really happens
0:47:12 > 0:47:16in that boundary layer between the ocean and the ice.
0:47:16 > 0:47:17And we simply can't get close to it
0:47:17 > 0:47:19because ships simply can't get in there.
0:47:19 > 0:47:22But when you've got divers,
0:47:22 > 0:47:24the divers can take the instrument right up to the wall.
0:47:24 > 0:47:27It's very exciting to see the data we're going to get back.
0:47:29 > 0:47:31All set up and ready to go.
0:47:31 > 0:47:32- It's all switched on.- OK.
0:47:45 > 0:47:48Straight to 30 now. All the way down.
0:47:56 > 0:48:01No-one has recorded sea temperature and salinity like this before.
0:48:04 > 0:48:06I'm going to try and keep it as close to the edge as possible.
0:48:06 > 0:48:08This flat edge here.
0:48:17 > 0:48:20As well as taking these unique readings,
0:48:20 > 0:48:22Keith has given the divers another experiment.
0:48:26 > 0:48:29This bottle contains a tracer dye.
0:48:30 > 0:48:32It will reveal whether powerful currents
0:48:32 > 0:48:34are moving up and down the sides of the berg.
0:48:41 > 0:48:44That is absolutely beautiful.
0:48:48 > 0:48:55It's like some kind of huge, ruffled, velvet blanket.
0:48:57 > 0:49:00What a bizarre shape.
0:49:00 > 0:49:03It doesn't appear to be moving much,
0:49:03 > 0:49:04it's just kind of hanging there.
0:49:08 > 0:49:10The results are surprising.
0:49:13 > 0:49:15If there were strong currents,
0:49:15 > 0:49:18the dye would spread rapidly through the water.
0:49:19 > 0:49:20But this isn't happening.
0:49:27 > 0:49:31Appears to be very little water disturbance right at the ice edge.
0:49:34 > 0:49:38The dye shows the waters around the berg are still and settled.
0:49:39 > 0:49:42This is brilliant. Real science in action.
0:49:43 > 0:49:45Not a bad day at the office.
0:49:48 > 0:49:50So what about the temperature of the water?
0:49:54 > 0:49:57Back on the ship, Alon has his results.
0:49:58 > 0:50:01And a revealing insight.
0:50:01 > 0:50:04As you can see, the ocean is separated into two layers.
0:50:04 > 0:50:08So this is the surface and this is the bottom.
0:50:08 > 0:50:10We've drawn in what looks like an iceberg in the middle
0:50:10 > 0:50:12just to give us a bit of an orientation.
0:50:12 > 0:50:16And what you see is the ocean is separated into two layers.
0:50:16 > 0:50:20The bottom layer, which is most of the ocean, is cold and salty.
0:50:20 > 0:50:24It's like -1.5 degrees,
0:50:24 > 0:50:27which means it's actually not doing that much melting to the iceberg.
0:50:29 > 0:50:32The deeper seawater here is incredibly cold.
0:50:32 > 0:50:34Below normal freezing.
0:50:34 > 0:50:38This cocoons the ice underwater,
0:50:38 > 0:50:41and explains why the heart of the berg is so cold.
0:50:44 > 0:50:47But the melt team has discovered something else.
0:50:48 > 0:50:51The top ten metres of the sea are very different.
0:50:51 > 0:50:54Here, there's a much warmer layer,
0:50:54 > 0:50:57which will sit on top of the cold deeper water.
0:50:58 > 0:51:03And this layer is warm enough to have a major impact on the berg.
0:51:04 > 0:51:07What's really melting the iceberg is the top layer,
0:51:07 > 0:51:09which is really, really warm.
0:51:09 > 0:51:13That's eroding at the iceberg, which is exactly what we've seen outside.
0:51:18 > 0:51:21While they've been here, the scientists have noticed
0:51:21 > 0:51:28a surprising feature - a notch in the ice where it meets the sea.
0:51:28 > 0:51:30And now they know what makes it.
0:51:30 > 0:51:35The warm water on the sea-surface is melting this narrow band of ice.
0:51:35 > 0:51:38Chiselling a groove around the berg.
0:51:42 > 0:51:45- That's four or five metres.- Really? - It goes a long way back.
0:51:47 > 0:51:51The reason this iceberg is breaking up really fast in front of us
0:51:51 > 0:51:53is all about what's happening at the wave-cut
0:51:53 > 0:51:55in the warm water layer, right at the surface.
0:51:56 > 0:52:00The team are realising this seemingly insignificant notch
0:52:00 > 0:52:03is closely linked to the crumbling of the ice above it,
0:52:03 > 0:52:07and the underwater ram they saw earlier.
0:52:09 > 0:52:12The pieces of the puzzle have come together.
0:52:12 > 0:52:14The warm surface water melts the notch.
0:52:17 > 0:52:21The ice above is unsupported and collapses.
0:52:22 > 0:52:25This leaves the large ice-foot, or ram,
0:52:25 > 0:52:29which is protected from melting by deep, cold water.
0:52:31 > 0:52:36As this ice foot enlarges, it becomes more buoyant.
0:52:36 > 0:52:37And, finally...
0:52:39 > 0:52:42..the upward pressure is just too much.
0:52:42 > 0:52:44The ice snaps off.
0:52:53 > 0:52:56Only by seeing it happen in front of their eyes,
0:52:56 > 0:52:58could the team have had this insight.
0:53:00 > 0:53:02There are these enormous stresses on the ice
0:53:02 > 0:53:05and the place where the damage will happen is at the weaknesses.
0:53:05 > 0:53:08And I thought that was a fabulous excuse to get some chocolate.
0:53:08 > 0:53:11This is our ice shelf sticking out like this.
0:53:11 > 0:53:14And what we're saying is that the foot is pushing on it here
0:53:14 > 0:53:16and if I push on it enough...
0:53:16 > 0:53:18it breaks.
0:53:18 > 0:53:21It's actually creating this huge lever,
0:53:21 > 0:53:24which is forcing the front edge of the iceberg up
0:53:24 > 0:53:27and causing it to crack along the line of weakness.
0:53:27 > 0:53:30Now I think we probably ought to eat your experiment.
0:53:30 > 0:53:32I think that's a very important part of this experiment. Have a bit.
0:53:32 > 0:53:36Thank you very much. I think that's a good few thousand tons.
0:53:36 > 0:53:38SHE LAUGHS
0:53:48 > 0:53:51The team have discovered a completely new way
0:53:51 > 0:53:54in which icebergs can break up.
0:54:07 > 0:54:09Throughout the expedition,
0:54:09 > 0:54:13the team has constantly faced the threat of polar bears.
0:54:13 > 0:54:18Although they've made life difficult, they fascinate Chris.
0:54:18 > 0:54:21He wants to know how many bears the berg can support.
0:54:22 > 0:54:25As his last job, he wants to do a census.
0:54:27 > 0:54:29We've got the chopper,
0:54:29 > 0:54:32and we're going to go out and take a look round.
0:54:32 > 0:54:33I'm really excited to be a part of this.
0:54:33 > 0:54:35I've waited a long time to be able to do this.
0:54:35 > 0:54:37So I'm hoping we'll find some bears.
0:54:50 > 0:54:53So far, they've only been able to observe bears
0:54:53 > 0:54:55around the edge of the iceberg.
0:54:56 > 0:55:00But there are 40 square kilometres of ice.
0:55:00 > 0:55:03And, by flying over the interior,
0:55:03 > 0:55:06Chris can get a more accurate estimate of the total number of bears.
0:55:10 > 0:55:12We've got one just here down here now.
0:55:12 > 0:55:14It's on the side of a small lake.
0:55:15 > 0:55:17A single adult bear.
0:55:19 > 0:55:21It's cream-coloured against the white snow,
0:55:21 > 0:55:24which means that we can see it.
0:55:24 > 0:55:27I'm going to grab a couple of shots of it with my still camera.
0:55:32 > 0:55:36The presence of these additional bears in the interior
0:55:36 > 0:55:38confirms the ones on the edge
0:55:38 > 0:55:41must be just a fraction of the population.
0:55:43 > 0:55:47So, in total, looking at the circumference,
0:55:47 > 0:55:52which was around 27 kilometres, and how frequently we saw them,
0:55:52 > 0:55:59I'd go for mid teens to 20 bears on this berg.
0:55:59 > 0:56:02What there is there for them is security
0:56:02 > 0:56:05and I think they're taking advantage of that.
0:56:05 > 0:56:08So I think they're hanging out on this berg basically to stay safe
0:56:08 > 0:56:10and just wait for that sea ice to come back in.
0:56:10 > 0:56:12Then they can just charge out and hunt.
0:56:16 > 0:56:19With the Arctic spring temperatures becoming warmer,
0:56:19 > 0:56:21there's far less sea ice.
0:56:21 > 0:56:24It's making it harder for polar bears to survive.
0:56:26 > 0:56:29It's why Chris' survey is so valuable.
0:56:29 > 0:56:33This is the first time a large population of polar bears
0:56:33 > 0:56:38has been recorded on a tabular iceberg, using it as a sanctuary.
0:56:49 > 0:56:52It's time to leave. Despite the hardships,
0:56:52 > 0:56:57the team accomplished far more in the ten days than they dared hope.
0:57:00 > 0:57:06I suppose this is it then, the end of Operation Iceberg,
0:57:06 > 0:57:09and what an expedition it's been. What an expedition it's been
0:57:09 > 0:57:12Seriously, I never thought we'd get on here
0:57:12 > 0:57:14and now it's time to get off.
0:57:14 > 0:57:17I can't think I'll ever be on another one.
0:57:17 > 0:57:20It's been amazing, absolutely amazing.
0:57:20 > 0:57:21Just one last question now -
0:57:21 > 0:57:24what's going to happen to it after we've left?
0:57:24 > 0:57:27Where's it going to end up? Where's it going to melt?
0:57:27 > 0:57:30Where's the last molecule of this mass of ice
0:57:30 > 0:57:33going to drip into that sea?
0:57:35 > 0:57:36I hope we find out.
0:57:40 > 0:57:44And we will, because the team has left a tracking device.
0:57:44 > 0:57:48It will send back the location of the iceberg over the coming months,
0:57:48 > 0:57:50revealing its future journey.
0:57:51 > 0:57:54It's been a remarkable adventure.
0:57:55 > 0:57:58The team have seen how huge icebergs are born
0:57:58 > 0:58:01as they split from a glacier.
0:58:01 > 0:58:04And what happens to an iceberg out at sea.
0:58:05 > 0:58:07They'll continue to track the Petermann Berg
0:58:07 > 0:58:11as it floats south, out into the Atlantic.
0:58:17 > 0:58:21And over time, perhaps in as little as a year,
0:58:21 > 0:58:26the berg will disappear altogether, back into the water.
0:58:34 > 0:58:37Subtitles by Red Bee Media Ltd