0:00:04 > 0:00:06Travel so far north,
0:00:06 > 0:00:08the summer sun never sets.
0:00:11 > 0:00:14Here is one of the last great wildernesses -
0:00:14 > 0:00:17the vast ice sheet of Greenland.
0:00:20 > 0:00:23It's the birthplace of the most massive and spectacular objects
0:00:23 > 0:00:25on the planet -
0:00:25 > 0:00:27icebergs.
0:00:30 > 0:00:34Up to 20 billion tonnes in weight and the height of a skyscraper,
0:00:34 > 0:00:37these monsters of the ocean have long fascinated us.
0:00:42 > 0:00:43Now, in this series,
0:00:43 > 0:00:48an international team of scientists and adventurers
0:00:48 > 0:00:51wants to explore these wonders of the natural world.
0:00:52 > 0:00:54Wow! Look at that!
0:00:54 > 0:00:57I knew it was going to be big, but this is massive.
0:00:57 > 0:00:58Just phenomenal.
0:00:59 > 0:01:03They hope to discover the secret life of icebergs,
0:01:03 > 0:01:05from spectacular birth,
0:01:05 > 0:01:07to watery death.
0:01:07 > 0:01:10This is a dream come true.
0:01:10 > 0:01:13A polar bear on OUR iceberg.
0:01:13 > 0:01:17They'll be risking their lives in one of the most unpredictable
0:01:17 > 0:01:19and violent environments on Earth.
0:01:19 > 0:01:22- It's falling here. - This whole bit's coming off.
0:01:23 > 0:01:26Look at the wave! Look at the wave!
0:01:26 > 0:01:27Look at the wave!
0:01:27 > 0:01:31That's one of the biggest bits of natural destruction
0:01:31 > 0:01:33I've ever seen in my life.
0:01:33 > 0:01:38In this programme, the team will be exploring an arctic glacier,
0:01:38 > 0:01:42to try to answer how icebergs are born,
0:01:42 > 0:01:46from blocks of ice of just a thousand tonnes,
0:01:46 > 0:01:48to giant mega-bergs.
0:01:48 > 0:01:51That, to me, looks like one great big, white mystery.
0:01:51 > 0:01:55Every measurement counts because this is like a knowledge void, a data void.
0:01:55 > 0:02:01We've been trying to measure these things in St Paul's Cathedrals, but I wouldn't know where to start.
0:02:01 > 0:02:06If you think icebergs are nothing more than floating chunks of ice,
0:02:06 > 0:02:07prepare to think again.
0:02:28 > 0:02:30Greenland's glaciers.
0:02:31 > 0:02:35Each year, they pump out 20,000 icebergs,
0:02:35 > 0:02:3995% of all icebergs in the northern hemisphere.
0:02:41 > 0:02:44The iceberg that sank the Titanic came from here.
0:02:48 > 0:02:52And one of the mightiest of all Greenland glaciers is Store.
0:02:56 > 0:03:00A group of two dozen scientists, divers and camera crew
0:03:00 > 0:03:04has now come to investigate this remote glacier.
0:03:07 > 0:03:11Store glacier is on the west coast of Greenland,
0:03:11 > 0:03:14a 400-kilometre river of ice.
0:03:14 > 0:03:18It meets the sea with an ice cliff eight kilometres wide.
0:03:21 > 0:03:24The team's base camp will be on a high peninsula,
0:03:24 > 0:03:27overlooking this glacier front.
0:03:30 > 0:03:34It's the expedition of a lifetime for naturalist Chris Packham.
0:03:37 > 0:03:40All my life I've been fascinated by the natural world,
0:03:40 > 0:03:42understanding how it works.
0:03:42 > 0:03:47I remember as a kid opening my childhood encyclopaedias
0:03:47 > 0:03:50and looking in there and seeing glaciers.
0:03:52 > 0:03:55This is Store glacier.
0:03:55 > 0:03:57It's magnificent.
0:03:57 > 0:04:03If you can suffer landscape culture shock, then I'm in it.
0:04:07 > 0:04:09It's a logistical nightmare -
0:04:09 > 0:04:13five tonnes of scientific and filming equipment,
0:04:13 > 0:04:15and enough supplies for three weeks.
0:04:21 > 0:04:26Ocean expert Helen Czerski is also fascinated by Store.
0:04:26 > 0:04:29I'm a physicist and I study this stuff all around us.
0:04:29 > 0:04:31And so looking at that, that's just
0:04:31 > 0:04:35one big jigsaw puzzle to solve from a physicist's point of view.
0:04:37 > 0:04:41Andy Torbet used to be an underwater bomb disposal specialist.
0:04:43 > 0:04:48Here, he'll be helping the scientists reach places they wouldn't normally get to.
0:04:49 > 0:04:52Every morning when I wake up,
0:04:52 > 0:04:54that is what I see,
0:04:54 > 0:04:56and that is what it's all about.
0:04:57 > 0:05:00The medic is Dr Chris Van Tulleken.
0:05:02 > 0:05:04This is the kind of injury I absolutely love.
0:05:04 > 0:05:07- You're going to have a nice scar... - Marvellous!
0:05:07 > 0:05:09..makes me look a tiny bit heroic,
0:05:09 > 0:05:10no-one's actually hurt.
0:05:12 > 0:05:15As well as treating the injured,
0:05:15 > 0:05:21Chris is keen on finding out how the team copes in this harsh environment.
0:05:21 > 0:05:22Right, good news.
0:05:22 > 0:05:27I've got another painful experiment, and I need a volunteer.
0:05:27 > 0:05:32They've been joined by a group of ice experts from around the world.
0:05:34 > 0:05:36We've got three weather stations going in here
0:05:36 > 0:05:38so it's nice to see that they've made it.
0:05:39 > 0:05:45They're all here to try to understand the birth of icebergs
0:05:45 > 0:05:49and, particularly, why glaciers like Store create so many.
0:05:49 > 0:05:54All of this ice is moving. It's creeping downwards all the time
0:05:54 > 0:05:58and, partly, that's happening because of gravity pulling the ice downwards
0:05:58 > 0:06:02towards the sea, down here to where icebergs calve off the front.
0:06:02 > 0:06:05But if that was the only thing that's going on,
0:06:05 > 0:06:08we wouldn't see as many icebergs as we do.
0:06:08 > 0:06:10So there's something else.
0:06:15 > 0:06:21This restless glacier releases 15 billion tonnes of ice
0:06:21 > 0:06:25into the sea every year, peaking now in summer.
0:06:29 > 0:06:32Day one and polar cameraman Doug Allan is filming
0:06:32 > 0:06:35the birth of a small iceberg.
0:06:35 > 0:06:38It's a process called calving.
0:06:38 > 0:06:42But it's nothing to what the team hopes to observe -
0:06:42 > 0:06:45a multi-million tonne mega-berg.
0:06:45 > 0:06:51The problem with calving, as far as I can see, is its unpredictability.
0:06:51 > 0:06:53Is there a point on the glacier
0:06:53 > 0:06:57where it's more or less likely to happen?
0:06:57 > 0:07:00There's a lot of minor activity in this embayment.
0:07:00 > 0:07:01It's kinda carved in that way,
0:07:01 > 0:07:04but we'll see the big ones out by these peninsulas.
0:07:04 > 0:07:06I so, so want to see it.
0:07:06 > 0:07:10I'm quite prepared to put up with being eaten alive by mosquitoes
0:07:10 > 0:07:11if, at the end of it,
0:07:11 > 0:07:14I can see one of these things happening. It'll be great!
0:07:14 > 0:07:18We've just got to keep our fingers crossed that someone's
0:07:18 > 0:07:21got a camera running when it happens. If it happens.
0:07:21 > 0:07:23All right, Doug, would you like a biscuit?
0:07:23 > 0:07:24I'll bring you a biscuit.
0:07:24 > 0:07:27A chocolate biscuit, thank you very much.
0:07:27 > 0:07:29That's what I like about that man.
0:07:36 > 0:07:37Like all glaciers,
0:07:37 > 0:07:42Store is a constantly moving river of frozen fresh water.
0:07:42 > 0:07:45I'm pretty good at that kind of thing!
0:07:45 > 0:07:47I mean, Jason's a dab hand, too.
0:07:47 > 0:07:51The team's first task is to discover how fast it flows.
0:07:55 > 0:07:59British glaciologist Alun Hubbard wants to helicopter in
0:07:59 > 0:08:05to plant a GPS tracker to measure its fastest point - the very front.
0:08:05 > 0:08:08You think there's a spot we can get down there?
0:08:08 > 0:08:12Not to land. I'll just jump out, is the idea.
0:08:12 > 0:08:14A quick game is a good game.
0:08:14 > 0:08:18OK. So three minutes, GPS on, right at the headland.
0:08:24 > 0:08:26It's extremely hazardous.
0:08:26 > 0:08:31This part of the glacier will be the next to collapse into the sea.
0:08:31 > 0:08:33He's calculated that if we put this device on,
0:08:33 > 0:08:36during the time we're here, it will break free
0:08:36 > 0:08:39and we'll get all the measurements up to that point,
0:08:39 > 0:08:43and that's cutting edge. I mean, you know, that's science at the edge.
0:08:45 > 0:08:48There's no room for a full camera crew.
0:08:48 > 0:08:51Chris himself will have to film Alun.
0:09:11 > 0:09:12Can you get on that?
0:09:14 > 0:09:18He needs to secure his GPS to the ice.
0:09:19 > 0:09:21But he must be quick.
0:09:21 > 0:09:24OK. Two, three minutes, OK?
0:09:36 > 0:09:39Oh, my goodness me!
0:09:39 > 0:09:41Just look at where he is!
0:09:44 > 0:09:46Frankly, that is astonishing.
0:09:48 > 0:09:52From where Alun is perched on top of this part of the glacier,
0:09:52 > 0:09:54there has to be a 100-metre drop,
0:09:54 > 0:09:58and he's got a couple of minutes to get that drill,
0:09:58 > 0:10:00and get that material in,
0:10:00 > 0:10:03and, frankly, if there's any movement on the ice,
0:10:03 > 0:10:07there is no chance of him making it off of there.
0:10:10 > 0:10:14It's just a pillar with this enormous crack down one side of it.
0:10:14 > 0:10:18- If I was to bet on the next pillar of ice...- The next thing to go, it'd be that one.
0:10:18 > 0:10:20The pinnacle has to topple soon.
0:10:20 > 0:10:24Alun's instinct tells him it won't be today.
0:10:24 > 0:10:25But he cannot know for sure.
0:10:27 > 0:10:29Oh, that is astonishing!
0:10:29 > 0:10:31He's putting the pole in.
0:10:33 > 0:10:35OK, he's ready to go.
0:10:35 > 0:10:40OK, take us in, he's got it fixed. He wants to get out of there.
0:10:43 > 0:10:46Four minutes, 30 seconds.
0:10:46 > 0:10:47The device is secure.
0:10:52 > 0:10:56No wonder so little's known about the birth of icebergs.
0:10:56 > 0:11:02It's always quite a thrill to be in such a spectacular place.
0:11:02 > 0:11:05And, you know, it's a weird space-time thing, isn't it?
0:11:05 > 0:11:09Am I here at the right time or the wrong time?
0:11:17 > 0:11:20If all goes to plan, the GPS will beam back to camp
0:11:20 > 0:11:23the speed at the very front of the glacier.
0:11:26 > 0:11:29I tell you something, though, I hope the machine works.
0:11:29 > 0:11:32- If it malfunctions now and we have to go back...- Exactly!
0:11:32 > 0:11:33Oh, no, no, no!
0:11:39 > 0:11:41The rate the glacier flows
0:11:41 > 0:11:44undoubtedly affects the number of icebergs formed.
0:11:44 > 0:11:47But how does the glacier,
0:11:47 > 0:11:51a four thousand million-tonne slab of ice, move at all?
0:11:53 > 0:11:56There's a theory Helen wants to investigate.
0:11:56 > 0:11:58Something is helping it along.
0:11:58 > 0:12:01The icebergs form mostly in the summer,
0:12:01 > 0:12:05so the glacier is flowing fastest in the summer.
0:12:05 > 0:12:10And we think there are some clues to why that happens right up ahead.
0:12:19 > 0:12:2115 kilometres up the glacier
0:12:21 > 0:12:27is a shimmering expanse of water over a kilometre wide.
0:12:27 > 0:12:29It's known as a blue lake.
0:12:30 > 0:12:33As we're coming in over the top of it,
0:12:33 > 0:12:36it looks like someone's poured blue food dye in there.
0:12:39 > 0:12:42Store has half a dozen of these temporary lakes.
0:12:42 > 0:12:45They form in spring as the temperature rises
0:12:45 > 0:12:47and water begins to pool.
0:12:47 > 0:12:51One theory claims water from these lakes drains
0:12:51 > 0:12:53to the bottom of the glacier,
0:12:53 > 0:12:56and helps it slide across the bedrock.
0:13:00 > 0:13:04But is there really enough water in the lake
0:13:04 > 0:13:07to move a four billion-tonne glacier?
0:13:08 > 0:13:10That's what the team hopes to discover.
0:13:11 > 0:13:13Oh, wow! Here's a really nice overlook.
0:13:13 > 0:13:16You can really see the colour. That's fantastic.
0:13:16 > 0:13:21Canadian glaciologist Michele Koppes believes these blue lakes
0:13:21 > 0:13:23help create icebergs.
0:13:23 > 0:13:27So what we're really trying to do is figure out where this water goes,
0:13:27 > 0:13:29and is it contributing to more calving
0:13:29 > 0:13:31at the terminus of the glacier?
0:13:31 > 0:13:34So what's happening from here, all the way to the end.
0:13:34 > 0:13:37At any moment, the ice below could crack open
0:13:37 > 0:13:40and drain the lake, like water pouring down a plughole.
0:13:40 > 0:13:45The team want to see how much water collects before it empties.
0:13:45 > 0:13:48So if I go in straight for a bit and then turn it sideways?
0:13:48 > 0:13:50- Yeah, that's great.- So about there?
0:13:53 > 0:13:58Climatologist Jason Box has been tracking Store's blue lakes.
0:14:00 > 0:14:03Satellite images from recent years tells him
0:14:03 > 0:14:05that this lake should already have drained.
0:14:05 > 0:14:10So this lake's now two days past the average time when it would drain.
0:14:10 > 0:14:11It could go at any moment,
0:14:11 > 0:14:15so I'm glad that we're here getting this done.
0:14:15 > 0:14:19Before it drains, the team will track the rise in water level
0:14:19 > 0:14:24using a time-lapse camera and a depth sensor.
0:14:24 > 0:14:27We want to get as much information as we can.
0:14:27 > 0:14:30Every measurement counts because this is
0:14:30 > 0:14:32like a knowledge void, a data void.
0:14:34 > 0:14:37A rock acts as an anchor for the depth sensor.
0:14:37 > 0:14:42But it needs to be positioned on a stable surface ten metres down.
0:14:42 > 0:14:46It's a job for the two most experienced divers - Doug and Andy.
0:14:48 > 0:14:50I've never dived anywhere like this.
0:14:50 > 0:14:53And I've never dived in a location as remote,
0:14:53 > 0:14:54or as wild, or as dynamic as this,
0:14:54 > 0:14:58and certainly nowhere where, at any point during the dive,
0:14:58 > 0:15:02the water could all just drain under your feet.
0:15:02 > 0:15:06It looks fairly benign at the moment, and I think we can kit up,
0:15:06 > 0:15:10get in fairly quickly, do the job, put in the sensors where necessary,
0:15:10 > 0:15:13and then we'll get out and everything will be fine.
0:15:13 > 0:15:16Famous last words!
0:15:23 > 0:15:26No-one has ever dived a blue lake.
0:15:26 > 0:15:28If the lake unexpectedly drains,
0:15:28 > 0:15:31they could be sucked down into the glacier.
0:15:31 > 0:15:36The safety team would then attempt to haul them back on lifelines.
0:15:36 > 0:15:39Three, two, one, jump!
0:15:58 > 0:16:01It's absolutely beautiful down here.
0:16:01 > 0:16:05All these shades of white and blue.
0:16:15 > 0:16:21I'm going to...try and place this sensor here.
0:16:23 > 0:16:25The sensor will now record any change in depth.
0:16:28 > 0:16:31Let's have a bit of an explore,
0:16:31 > 0:16:35see if we can find where this plughole is, eh?
0:16:36 > 0:16:41Andy is keen to try to track down the opening through which the lake could drain.
0:16:43 > 0:16:46The bottom of the crevasse is deepening off here,
0:16:46 > 0:16:51as we push further out into the middle of the lake.
0:16:58 > 0:17:02But there are worrying signs the lake bed is unstable.
0:17:02 > 0:17:04Out into the middle of the lake
0:17:04 > 0:17:07and it's very, very calm water conditions,
0:17:07 > 0:17:10we've spotted a rising column of bubbles in the deep water.
0:17:10 > 0:17:13And that's obviously going to give us cause for concern.
0:17:14 > 0:17:15Oh!
0:17:15 > 0:17:17HE CHUCKLES
0:17:17 > 0:17:21Doug, there's a big cave here going straight down.
0:17:25 > 0:17:28I'm just going to have a look.
0:17:28 > 0:17:30This could be the lake's plughole.
0:17:30 > 0:17:33For Andy, it's a challenge he can't resist.
0:17:37 > 0:17:39Getting pretty dark in here.
0:17:39 > 0:17:43It's definitely getting narrower.
0:17:50 > 0:17:54No way. It's getting too tight.
0:17:54 > 0:17:56It's getting way too tight.
0:17:58 > 0:18:01I'm still...nowhere near the bottom.
0:18:06 > 0:18:10That's 40 minutes on the dive now, 41 now,
0:18:10 > 0:18:12so it's getting to be a long dive.
0:18:12 > 0:18:16The maximum dive length we agreed on wasn't much longer than this,
0:18:16 > 0:18:19and it's cold, and they'll be using air quickly,
0:18:19 > 0:18:22so they'll be out very soon, whatever they're doing.
0:18:26 > 0:18:29But something more urgent threatens Andy.
0:18:31 > 0:18:33HE BREATHES RAPIDLY
0:18:33 > 0:18:35I need to surface.
0:18:36 > 0:18:39I think this air hose is freezing up.
0:18:43 > 0:18:45Ice is blocking Andy's air supply.
0:18:48 > 0:18:51In this sort of environment,
0:18:51 > 0:18:55you can only do so much about trying to fix your kit underwater.
0:18:55 > 0:18:59There comes a point when you need to sack it and go home.
0:18:59 > 0:19:01In one piece.
0:19:02 > 0:19:08But the time-lapse camera is now in position and the depth sensor will track the water level.
0:19:13 > 0:19:17The team will return in a few days to see how much melt water
0:19:17 > 0:19:19has accumulated in the lake.
0:19:33 > 0:19:39Meanwhile, Chris is joining Alun and his crew on the research yacht Gambo.
0:19:43 > 0:19:44At the glacier front,
0:19:44 > 0:19:48Store has eight kilometres of ice in contact with the sea.
0:19:48 > 0:19:51The team suspects the ocean might also play
0:19:51 > 0:19:54a role in the creation of icebergs.
0:19:54 > 0:19:58But getting to the front isn't straightforward.
0:20:02 > 0:20:05Could you go up front and just tell me left or right, please?
0:20:07 > 0:20:11The Gambo is dwarfed by the towering ice front.
0:20:15 > 0:20:19I mean, it's difficult to get a sense of scale from here,
0:20:19 > 0:20:21but how high, 100 metres?
0:20:21 > 0:20:22Yeah, just under.
0:20:27 > 0:20:30To understand how the sea affects the glacier,
0:20:30 > 0:20:32Alun wants to map its front.
0:20:32 > 0:20:37He uses a powerful tool - side-scanning sonar.
0:20:37 > 0:20:41It reveals the hidden part of the glacier that's underwater.
0:20:43 > 0:20:46That's the actual equipment that sends out the sound wave,
0:20:46 > 0:20:50the acoustic wave, which bounces off the glacier and we pick it up.
0:20:50 > 0:20:54So we, hopefully, will be able to scan the whole face of the glacier
0:20:54 > 0:20:56and its toe.
0:20:57 > 0:21:01In charge of gathering data is Nolwenn.
0:21:01 > 0:21:03Happy with the speed, skipper?
0:21:03 > 0:21:06Yeah, yeah. I just have to restart the software.
0:21:06 > 0:21:08It's just crashed at the moment.
0:21:08 > 0:21:09Yeah, OK.
0:21:10 > 0:21:14To get a detailed scan, Gambo needs to be right up close
0:21:14 > 0:21:17to the ice front, just where the icebergs calve.
0:21:21 > 0:21:24They're playing Russian roulette with a glacier.
0:21:27 > 0:21:28Just a little bit.
0:21:28 > 0:21:30Just a little bit!
0:21:30 > 0:21:33We're 150 metres now. I would like to keep 200 or 300.
0:21:33 > 0:21:35Yeah, OK.
0:21:36 > 0:21:38How are we for bergs, Johannes?
0:21:38 > 0:21:42You have to go a bit starboard, I think.
0:21:43 > 0:21:49It's the first attempt by any research team to map the entire underwater ice front
0:21:49 > 0:21:51of a glacier as big as this.
0:21:51 > 0:21:53If they succeed,
0:21:53 > 0:21:57the scan could explain how the sea helps to trigger calving.
0:21:59 > 0:22:04But just then, the giant glacier reminds them of the risks.
0:22:08 > 0:22:09Woah, woah, woah!
0:22:11 > 0:22:13Over there.
0:22:44 > 0:22:46What happened?
0:22:46 > 0:22:49We have a calving event and what it triggered off
0:22:49 > 0:22:52was a large lump from under the water
0:22:52 > 0:22:56that shot up really high out of the water.
0:22:56 > 0:23:01That is quite a minor calving event, I hate to say, Chris.
0:23:01 > 0:23:02Minor it may be,
0:23:02 > 0:23:05but if the berg had calved minutes earlier,
0:23:05 > 0:23:08Gambo would've been crushed.
0:23:08 > 0:23:11But they've already got results.
0:23:11 > 0:23:12What can you see there?
0:23:12 > 0:23:16OK, here we've got a 2D slice of the glacier.
0:23:16 > 0:23:20So we've got the glacier front here and the sea bed here.
0:23:20 > 0:23:22That's the boat here.
0:23:22 > 0:23:24And looking at this top section here then,
0:23:24 > 0:23:28how deep is it now from the boat to the bottom?
0:23:28 > 0:23:33So the bottom of the fjord at the moment is about 400 metres here.
0:23:33 > 0:23:37So we're looking at cliffs outside that are about 80 to 100 metres tall
0:23:37 > 0:23:40at their highest, but there's 400 metres beneath the water.
0:23:40 > 0:23:44Yeah, yeah, at least. It will be even deeper in some places.
0:23:44 > 0:23:47- Even deeper? - Yeah, we went down to 500 metres.
0:23:47 > 0:23:49And the ice was still touching the bottom?
0:23:49 > 0:23:50Still touching the bottom, yeah.
0:23:50 > 0:23:53- Wow!- Yeah, clearly, it's touching the bottom.
0:23:53 > 0:23:59There is four times as much ice cliff below the water than above.
0:23:59 > 0:24:02And a scan reveals another surprise -
0:24:02 > 0:24:06the bottom of the glacier is undercut.
0:24:07 > 0:24:10Now, what's the distance between the front of the cliff
0:24:10 > 0:24:13and the back, how deep is that undercut?
0:24:13 > 0:24:17- At the moment it's about 150 metres. At least.- 150 metres?- At least.
0:24:17 > 0:24:20It might be deeper but we can't see it
0:24:20 > 0:24:22because of the kind of angle we are.
0:24:24 > 0:24:29The huge undercut means the glacier above is unstable.
0:24:29 > 0:24:34It could explain why the ice front is so prone to collapsing.
0:24:38 > 0:24:42It's the end of a long day and the team will need to return to find out
0:24:42 > 0:24:45how this undercut has been formed.
0:24:52 > 0:24:54The expedition has been under way for a week.
0:24:54 > 0:24:58The team came prepared for the dangers of the glacier,
0:24:58 > 0:25:01but no-one bargained for a far more maddening threat.
0:25:01 > 0:25:03BUZZING
0:25:04 > 0:25:06Mosquitoes.
0:25:06 > 0:25:08During the short Arctic summer,
0:25:08 > 0:25:12the mosquitoes survive on nectar from plants.
0:25:12 > 0:25:16But they much prefer the blood of mammals, any they can find.
0:25:16 > 0:25:20Let's look at this. There are quite proper bites, actually, aren't they?
0:25:20 > 0:25:23Dr Chris is an expert in tropical medicine.
0:25:23 > 0:25:27He didn't expect to be using those skills here.
0:25:27 > 0:25:31He wants to find out if some people are especially attractive to mosquitoes.
0:25:31 > 0:25:35Good news, everyone! I've developed another experiment.
0:25:35 > 0:25:38It's going to be painful and I need a volunteer.
0:25:38 > 0:25:40Andy Torbet, thank you.
0:25:40 > 0:25:42LAUGHTER
0:25:42 > 0:25:44- I hate you!- Let's go.
0:25:44 > 0:25:46With friends like these...
0:25:47 > 0:25:51- So what's the plan?- We're going to sit here with our shirts off,
0:25:51 > 0:25:53no insect repellent on, and see who gets more bites.
0:25:53 > 0:25:57- I like straightforward experimental protocols.- You're a genius(!)
0:25:59 > 0:26:02So, obviously, there is a competitive element to this.
0:26:02 > 0:26:05Whoever gets bitten more loses blatantly.
0:26:05 > 0:26:09Hmm. So what they'll be doing is smelling us,
0:26:09 > 0:26:12and they're first of all attracted to our carbon dioxide.
0:26:12 > 0:26:15They'll be following the carbon dioxide trail in,
0:26:15 > 0:26:16and when they get close,
0:26:16 > 0:26:18they start to smell sweat and body odour.
0:26:18 > 0:26:22Some people have chemicals in their sweat that mosquitoes really like.
0:26:22 > 0:26:24- Argh!- There.
0:26:24 > 0:26:28They're all females, and this one is swollen with blood.
0:26:31 > 0:26:34The person bitten most will be producing
0:26:34 > 0:26:37more of the chemicals that attract mosquitoes.
0:26:39 > 0:26:43There's absolutely nothing on you. So how are we doing?
0:26:43 > 0:26:45- I've got one there.- Two, three.
0:26:45 > 0:26:48- Four.- Four.- Five.- Five.
0:26:48 > 0:26:53- My go.- 8, 9, 10, 11, 12, 13, 14, 15, 16, 17.
0:26:53 > 0:26:55So why have you got 32 on your right side
0:26:55 > 0:26:57and only two on your left side?
0:26:57 > 0:26:58I think it's the down-wind side.
0:26:58 > 0:27:01They're attracted to the CO2 from there,
0:27:01 > 0:27:03and they're not getting blown away.
0:27:03 > 0:27:06So they're more attracted to you. You're getting bitten more.
0:27:06 > 0:27:09My sweat is more appealing to mosquitoes than yours.
0:27:09 > 0:27:11So if I had these chemicals like Octanol in my sweat,
0:27:11 > 0:27:13mosquitoes really like that.
0:27:13 > 0:27:14Hence, I've won!
0:27:14 > 0:27:17- All I've won is more mosquito bites. - Correct.
0:27:45 > 0:27:49It's been several days since the team were at the blue lake
0:27:49 > 0:27:53to set up the time-lapse camera and the depth sensor.
0:27:53 > 0:27:56So, what's happened?
0:27:57 > 0:28:00The lake is quite definitely still there.
0:28:00 > 0:28:03It hasn't drained and the lake's got bigger,
0:28:03 > 0:28:07so it looks as though it's been rising. It's filled up.
0:28:07 > 0:28:11It was full of ice islands before and it's not any more.
0:28:13 > 0:28:15The lake has risen so much,
0:28:15 > 0:28:19the camera is centimetres away from being drowned.
0:28:30 > 0:28:34The equipment was supposed to be retrieved from the shore.
0:28:37 > 0:28:40Andy will have to improvise.
0:28:41 > 0:28:43I just want him out of the water as quickly as possible.
0:28:43 > 0:28:44I'm finding it like...
0:28:44 > 0:28:47I'm finding it a bit stressful watching him.
0:28:47 > 0:28:49I know he's good and I know he's a good swimmer and he knows what
0:28:49 > 0:28:51he's doing in the water, but...
0:28:51 > 0:28:54this water is not a human habitat. Erm...
0:28:56 > 0:28:57Yeah.
0:28:57 > 0:29:01Give it to me. Oh, good man! Success!
0:29:01 > 0:29:03It's getting a bit cold now, though.
0:29:03 > 0:29:05Right. Cup of tea, I think!
0:29:10 > 0:29:13But for Helen and Jason, it was worth it.
0:29:13 > 0:29:15The time-lapse footage
0:29:15 > 0:29:19and the data from the sensor reveal what's been happening.
0:29:20 > 0:29:23- It's so smooth and still on top... - It's so glassy!
0:29:23 > 0:29:27..but you can see it's just creeping, creeping up the sides of the ice.
0:29:27 > 0:29:29It's just filling up.
0:29:29 > 0:29:31I love the way you can see the bits blown by the wind.
0:29:31 > 0:29:35Because they're speeded up, they just zoom across the field of view.
0:29:35 > 0:29:36Yeah, we call those speed-bergs.
0:29:36 > 0:29:39- Did you see that one? Nyerrrrm! - SHE LAUGHS
0:29:40 > 0:29:43But more precise is Jason's depth sensor.
0:29:45 > 0:29:48It shows exactly how much the lake's risen.
0:29:48 > 0:29:50- It filled up fairly smoothly.- Yeah.
0:29:50 > 0:29:53It just kept going, kept going, kept topping up,
0:29:53 > 0:29:55- and then slowed down a bit at the end.- Yeah.
0:29:55 > 0:29:58It looks like it filled on... You can see on this axis,
0:29:58 > 0:30:02let's call that, like, 18 to 25.
0:30:02 > 0:30:04- Seven metres. - Yeah, that's impressive.
0:30:04 > 0:30:06- That's a lot of water.- Right!
0:30:07 > 0:30:10The team calculates just this one lake now contains
0:30:10 > 0:30:14over five million cubic metres of water.
0:30:14 > 0:30:17That's 2,000 Olympic swimming pools.
0:30:19 > 0:30:21A staggering quantity.
0:30:24 > 0:30:29Together with the other blue lakes and melt water on Store,
0:30:29 > 0:30:32that's easily enough water to help the glacier
0:30:32 > 0:30:35slide towards the sea and create more icebergs.
0:30:39 > 0:30:43Glaciologists believe the water drains down shafts
0:30:43 > 0:30:45into the heart of the glacier.
0:30:45 > 0:30:49At the bottom, it spreads across the bedrock,
0:30:49 > 0:30:54and it's this lubricating water that allows the ice to slide quickly.
0:30:57 > 0:31:01So just how fast does the glacier travel?
0:31:04 > 0:31:08The GPS Alun set up at the ice front should give them the answer.
0:31:12 > 0:31:15But at four o'clock in the morning,
0:31:15 > 0:31:19when only the unmanned cameras are watching, this happens.
0:31:19 > 0:31:21CRACKING
0:31:25 > 0:31:28Not just the ice pillar that Alun stood on,
0:31:28 > 0:31:32but a whole section of the glacier front collapses,
0:31:32 > 0:31:34taking the GPS with it.
0:31:37 > 0:31:40It's the biggest calving the team has seen so far.
0:31:43 > 0:31:46But before the GPS took the plunge,
0:31:46 > 0:31:49it sent back data about the glacier's speed.
0:31:52 > 0:31:57It's quite revealing. Its mean velocity is about 25 metres a day.
0:31:57 > 0:32:01That's just under 10km a year right at the ice front,
0:32:01 > 0:32:06and you can see it's varied from something down at ten metres a day
0:32:06 > 0:32:08and just before it toppled in,
0:32:08 > 0:32:12you can see it's moving at over 50 metres a day.
0:32:12 > 0:32:15It's a lovely idea cos we've been looking at this thing
0:32:15 > 0:32:18and in my head I'd imagined it was almost steady movement and it isn't.
0:32:18 > 0:32:23You're saying it speeds up and slows down, and it speeds up and slows down, as the days go on.
0:32:24 > 0:32:29That average of 25 metres a day is the length of two buses.
0:32:29 > 0:32:32It makes Store one of the fastest glaciers in the world.
0:32:34 > 0:32:37So the fact that the front of Store glacier
0:32:37 > 0:32:40is moving at such a high speed
0:32:40 > 0:32:42means there's lots and lots of ice coming through,
0:32:42 > 0:32:45and that's generating lots and lots of icebergs.
0:32:45 > 0:32:48Of course. It is an iceberg-producing machine.
0:32:52 > 0:32:57This speed is only possible thanks to the lubrication by melt water.
0:32:59 > 0:33:02But the team still wants to find out how the ocean
0:33:02 > 0:33:04drives the creation of icebergs.
0:33:08 > 0:33:11The Gambo has returned to the glacier front.
0:33:12 > 0:33:18They're back to investigate why there's such a severe undercut at the base.
0:33:18 > 0:33:21Yeah, try to get it somewhere like here.
0:33:21 > 0:33:24Nolwenn suspects the temperature of the water could be responsible,
0:33:24 > 0:33:28and lowers a probe to the sea bed.
0:33:28 > 0:33:33Much of the Gambo's kit has been ingeniously lashed together.
0:33:33 > 0:33:35Where did this come from?
0:33:35 > 0:33:38The top pulley is actually a pram wheel.
0:33:38 > 0:33:43- What on earth is going on here, Nolwenn?!- That's a brake.
0:33:43 > 0:33:46Look at that! Depth is spelt incorrectly!
0:33:46 > 0:33:48It says D-E-P-H-T! There's no P in "Speed".
0:33:48 > 0:33:50LAUGHTER
0:33:50 > 0:33:52Keep winching!
0:33:52 > 0:33:55Marvellous(!) It's a contraption without...
0:33:55 > 0:33:58It's a grade ten contraption, without a shred of a doubt.
0:34:00 > 0:34:02But it works.
0:34:02 > 0:34:06And the temperature readings are a revelation.
0:34:06 > 0:34:09So here we've got the temperature against the depth,
0:34:09 > 0:34:12so here we've got the depth, surfaces here, 800 metres here.
0:34:12 > 0:34:15- Yeah.- That's zero degrees and that's six degrees here,
0:34:15 > 0:34:18so what we can see is that on the surface
0:34:18 > 0:34:22we get relatively warm water that's cooling down pretty quickly,
0:34:22 > 0:34:26and after that, it's warming as we go further down,
0:34:26 > 0:34:29with a maximum at 2.7 degrees.
0:34:29 > 0:34:35This water, from 300 metres to the bottom at 800, is at 2.4 degrees.
0:34:36 > 0:34:39The water of the sea bed is unexpectedly warm,
0:34:39 > 0:34:41well above freezing.
0:34:43 > 0:34:47The impact of such water is dramatic.
0:34:47 > 0:34:51It's melting the undercut at the glacier's base,
0:34:51 > 0:34:54weakening the ice front,
0:34:54 > 0:34:56creating icebergs.
0:34:57 > 0:35:00- Hmm, top data! - Yeah, really great! Yep.
0:35:00 > 0:35:03- Terrible winch. - Yeah, terrible winch.
0:35:03 > 0:35:04Can't win 'em all.
0:35:08 > 0:35:12The team believe the warm water that's undercutting the glacier
0:35:12 > 0:35:16might get even warmer due to climate change.
0:35:19 > 0:35:22Across the Greenland ice sheet itself,
0:35:22 > 0:35:25warmer spring temperatures are leading to a dramatic increase
0:35:25 > 0:35:29in the amount of ice and melt water draining into the sea.
0:35:31 > 0:35:36It's something that particularly concerns Jason Box.
0:35:36 > 0:35:40There's a net loss of ice from Greenland in the last decade
0:35:40 > 0:35:44of about 300 billion tonnes per year.
0:35:44 > 0:35:49That's producing approaching 1mm per year of sea level rise,
0:35:49 > 0:35:52so in ten years, that adds up to a centimetre.
0:35:52 > 0:35:55But then it's not a linear increase.
0:35:55 > 0:35:57By the end of the century,
0:35:57 > 0:36:00this should produce a global sea level rise
0:36:00 > 0:36:03between one and two metres.
0:36:03 > 0:36:06Sea level rise is something, which I think
0:36:06 > 0:36:08is...frightening lots of people.
0:36:08 > 0:36:12It could have a massive effect on the way that we live on this planet.
0:36:12 > 0:36:15Yeah, that's a colossal problem
0:36:15 > 0:36:18for hundreds of large cities around the world.
0:36:21 > 0:36:24Climate change is likely to accelerate the mechanisms
0:36:24 > 0:36:27the team has witnessed at Store.
0:36:31 > 0:36:33So far, they've seen how melt water lubricates
0:36:33 > 0:36:37the base of the glacier, speeding it towards the sea.
0:36:39 > 0:36:41And they've also revealed how the sea weakens
0:36:41 > 0:36:43the bottom of the glacier front.
0:36:45 > 0:36:48ALL: Cheers! Kasuutta!
0:36:48 > 0:36:49- ALUN:- Iechyd da!
0:36:49 > 0:36:52Together, it solves the mystery of how Store,
0:36:52 > 0:36:56and glaciers like it, create icebergs.
0:37:00 > 0:37:04But if the team think they've now cracked all the forces at play,
0:37:04 > 0:37:06they're in for a shock.
0:37:14 > 0:37:16Can we get this stuff out of the water?
0:37:16 > 0:37:18I'm sorry, I want to get out of here.
0:37:23 > 0:37:25Wow! Look at that!
0:37:25 > 0:37:28A wall of ice is splitting from the glacier.
0:37:28 > 0:37:34Compared to anything the team has seen so far, this is vast.
0:37:35 > 0:37:38It's made a new embayment in one go.
0:37:38 > 0:37:40That is a major calving event.
0:37:40 > 0:37:42What are we doing, Nolwenn, are we out of here?
0:37:42 > 0:37:45Yeah, yeah, we're escaping.
0:37:45 > 0:37:47Look at the wave! Look at the wave!
0:37:47 > 0:37:49Look at the wave!
0:37:49 > 0:37:51It's a ten-metre wave.
0:37:51 > 0:37:53Is that going to be a monster?
0:37:53 > 0:37:55It looks big. It was massive on the front.
0:37:55 > 0:37:58It hasn't reached us yet, but it looks really big.
0:38:01 > 0:38:04Up at base camp, the rest of the team look on anxiously.
0:38:04 > 0:38:06The Gambo - where is the Gambo?
0:38:06 > 0:38:09They're right down there, next to it.
0:38:09 > 0:38:11She was on this side of the fjord.
0:38:11 > 0:38:13I think they're down here.
0:38:13 > 0:38:16Which way are these big ones?
0:38:18 > 0:38:21It's the calving...of a mega-berg.
0:38:22 > 0:38:25That is absolutely enormous.
0:38:25 > 0:38:28140 million tonnes of ice,
0:38:28 > 0:38:32travelling so fast it could outrun the Gambo.
0:38:33 > 0:38:36It's a huge surge of water,
0:38:36 > 0:38:40a massive wave that rose up the side of the front of the glacier,
0:38:40 > 0:38:45and, quite clearly, is going to slowly spread out towards us here.
0:38:45 > 0:38:47Major event, Alun?
0:38:48 > 0:38:51If we'd been there, Nolwenn, we'd have been wiped out.
0:38:51 > 0:38:54- I don't want to think about it! - We'd have been wiped out, man.
0:38:54 > 0:38:57Yeah, we would have been wiped out.
0:38:57 > 0:39:01It's calving on a scale far bigger than the team has yet witnessed.
0:39:04 > 0:39:08The forces they've seen so far don't explain these mega-bergs.
0:39:08 > 0:39:13To understand them, they'll need a new theory.
0:39:13 > 0:39:18Those are the lumps of ice, which break off the front intact
0:39:18 > 0:39:22and drift out to sea as huge icebergs.
0:39:22 > 0:39:26There's another mechanism helping those icebergs calve,
0:39:26 > 0:39:28and I want to find out what it is.
0:39:33 > 0:39:36The team's focus returns to the upper glacier.
0:39:36 > 0:39:40They know melt water from here lubricates the base of the glacier.
0:39:42 > 0:39:46But could some water also be helping create the mega-bergs?
0:39:48 > 0:39:51I'm a little bit sceptical that all the water can get
0:39:51 > 0:39:55all the way from the surface all the way down to the bottom.
0:39:57 > 0:40:01Michele wants to explore the many holes that riddle the glacier.
0:40:02 > 0:40:06Melt water from a blue lake once ran down this one.
0:40:06 > 0:40:07It's called a moulin.
0:40:09 > 0:40:11Moulin is a grinder in French,
0:40:11 > 0:40:16so think of the water grinding its way through the ice down to the bed.
0:40:16 > 0:40:18So these are like big drainpipes going down
0:40:18 > 0:40:21- and the question is how far down they go?- Exactly.
0:40:21 > 0:40:26Andy is going to climb down into the heart of the glacier.
0:40:26 > 0:40:28Andy's very excited about this.
0:40:28 > 0:40:31I think that a lot of people would say he's brave.
0:40:31 > 0:40:32I think he might be being a bit foolish.
0:40:32 > 0:40:34It's very dangerous, I think.
0:40:34 > 0:40:37How far do you think you'll be able to get into this?
0:40:37 > 0:40:39I have no idea where it stops.
0:40:39 > 0:40:42What would be great to find out from you, Andy,
0:40:42 > 0:40:44is as you go down, what do you see?
0:40:46 > 0:40:51The moulin's big and - at the moment - dry,
0:40:51 > 0:40:54giving Andy the best chance of exploring.
0:40:58 > 0:41:01But the glacier is constantly moving.
0:41:04 > 0:41:07There was a big rumble just then.
0:41:07 > 0:41:08All the walls are pretty unstable,
0:41:08 > 0:41:11with all these big icicles and big, like, snowflakes,
0:41:11 > 0:41:13so the quicker we get down and out the better.
0:41:16 > 0:41:19As team medic, Dr Chris is nervous.
0:41:19 > 0:41:21I feel fairly redundant,
0:41:21 > 0:41:24because of all the things that can happen to him,
0:41:24 > 0:41:26there are very few I'm going to be able to fix.
0:41:28 > 0:41:32We know very little about what happens to water below the surface.
0:41:32 > 0:41:35I mean, we know more about what's going on
0:41:35 > 0:41:39on the surface of the moon than what happens inside the ice.
0:41:47 > 0:41:50You can see the floor beneath me.
0:41:52 > 0:41:54There's these huge blocks of ice.
0:41:54 > 0:41:57Things as big as cars are lying down there,
0:41:57 > 0:42:01and they weigh tonnes, and they've all peeled off from up above me.
0:42:01 > 0:42:05So if that was to happen while I was hanging here, that'd be it.
0:42:10 > 0:42:11Woah!
0:42:11 > 0:42:17There's a massive, absolutely enormous side passage.
0:42:19 > 0:42:21You could drive a double-decker bus,
0:42:21 > 0:42:24with another double-decker bus on top of it,
0:42:24 > 0:42:26and it would still fit through there quite easily.
0:42:28 > 0:42:32It's a remarkable discovery, on a massive scale.
0:42:33 > 0:42:35When this tunnel was active,
0:42:35 > 0:42:39it would've channelled vast amounts of water.
0:42:39 > 0:42:42Not downwards, but sideways.
0:42:42 > 0:42:46And there's been no-one down here before us and the chances are
0:42:46 > 0:42:48there'll never be anyone down here again.
0:42:48 > 0:42:49This is proper exploration.
0:42:49 > 0:42:51This is all completely virgin territory.
0:42:51 > 0:42:52And this...
0:42:52 > 0:42:55This is the crowning glory,
0:42:55 > 0:42:59this immense cathedral-like tunnel.
0:43:03 > 0:43:07The team lowers a camera crew down to explore.
0:43:07 > 0:43:11But just as they're preparing to enter the tunnel...
0:43:11 > 0:43:12CRACKING
0:43:15 > 0:43:18- I think we should get out.- Yeah.
0:43:18 > 0:43:21OK. We've got to get out of here. That stuff up top is not good.
0:43:21 > 0:43:23CRACKING
0:43:23 > 0:43:25The tunnel roof has started to crack.
0:43:25 > 0:43:29If it collapsed, it could bury the team.
0:43:47 > 0:43:48Glad to be out of there.
0:43:48 > 0:43:51It was huge, absolutely massive.
0:43:51 > 0:43:53And we got out, which is even better!
0:43:53 > 0:43:54Which is always nice.
0:43:54 > 0:43:58Having said that, the footage is still at the bottom of the hole. Will I get it out?
0:43:58 > 0:44:01Yeah, the camera is yet to be lifted up.
0:44:01 > 0:44:03So let's not celebrate too soon!
0:44:09 > 0:44:12While some melt water flows to the bottom of the glacier,
0:44:12 > 0:44:16other water appears to take an alternative route.
0:44:21 > 0:44:25The glacier has a hidden plumbing system,
0:44:25 > 0:44:26a vast network of tunnels
0:44:26 > 0:44:30carrying melt water through the ice, horizontally.
0:44:32 > 0:44:33Now that we've seen this moulin,
0:44:33 > 0:44:36we've seen that it's not a simple picture.
0:44:36 > 0:44:39It's not straight down the plughole to the bottom.
0:44:39 > 0:44:40It's much more complex.
0:44:40 > 0:44:43Water goes down a little way and then maybe it goes sideways,
0:44:43 > 0:44:45and then maybe it falls down a bit more.
0:44:45 > 0:44:48Eventually, all going towards the sea,
0:44:48 > 0:44:52but getting there by a huge variety of different routes.
0:44:55 > 0:44:58The team wonders if these side channels
0:44:58 > 0:45:00could be linked to the creation of mega-bergs.
0:45:10 > 0:45:14While the science team devise their next experiment,
0:45:14 > 0:45:17Chris is making friends with a local.
0:45:19 > 0:45:23This little arctic fox has been coming in to our camp
0:45:23 > 0:45:27almost every day, on the scrounge for food, of course.
0:45:27 > 0:45:31But then things aren't easy up here, there's not a lot of food about.
0:45:31 > 0:45:33They feed on young birds they find them in their nest.
0:45:33 > 0:45:37Ptarmigan, hare - that'd be a pretty special day,
0:45:37 > 0:45:41but I'm just tempting him in with some of this pasta.
0:45:41 > 0:45:44I have to say, a lot of people haven't taken a shine to the fox.
0:45:44 > 0:45:46They come up with these stories about them
0:45:46 > 0:45:49breaking into the tents, chewing all the cables.
0:45:49 > 0:45:50I can't see it myself.
0:45:52 > 0:45:54In the winter, he'd be bright white,
0:45:54 > 0:45:57and they have an amazing winter coat,
0:45:57 > 0:45:59cos they are a bit different than our foxes.
0:45:59 > 0:46:04Much smaller of course, blunter nose, smaller ears, shorter legs.
0:46:04 > 0:46:09That's all about conserving heat when it's cold here.
0:46:10 > 0:46:11(Oi!)
0:46:13 > 0:46:15You're going to get me into trouble.
0:46:15 > 0:46:18I'm going to get told off for encouraging you into the camp.
0:46:18 > 0:46:19I don't care, though.
0:46:19 > 0:46:22I'd rather have the fox than the food.
0:46:28 > 0:46:30Back on the upper glacier,
0:46:30 > 0:46:33the team has cooked up an ambitious experiment.
0:46:33 > 0:46:36They want to try to trace the route of melt water
0:46:36 > 0:46:40through the horizontal tunnels and out the glacier front.
0:46:41 > 0:46:46We've found a moulin that's about 8km up from the ice front,
0:46:46 > 0:46:50and it looks like the water that's flowing down into this moulin
0:46:50 > 0:46:54is making a direct connection down to the north side of the ice front.
0:46:56 > 0:46:59They're going to throw 30 plastic balls,
0:46:59 > 0:47:02called cryospheres, into a moulin.
0:47:02 > 0:47:04They may look home-made,
0:47:04 > 0:47:07but they're packed with sophisticated electronics.
0:47:08 > 0:47:12It looks reasonably likely that the water flowing past us here
0:47:12 > 0:47:14will, at some point, flow out of the glacier front
0:47:14 > 0:47:17that we've been watching for the past week or so.
0:47:17 > 0:47:20Exactly. It's the "at some point" that is the big question.
0:47:20 > 0:47:23- So if we can find these at the other end...- Big if!
0:47:23 > 0:47:26- ..lots of useful information is going to come out of them.- Yeah.
0:47:26 > 0:47:28That's it. Looking good!
0:47:28 > 0:47:29If the team's lucky,
0:47:29 > 0:47:32some cryospheres may travel from this moulin
0:47:32 > 0:47:35all the way to the glacier front,
0:47:35 > 0:47:37without getting stuck inside the ice.
0:47:37 > 0:47:42Michele, number 19 is going at 5.56.
0:47:49 > 0:47:53The cryospheres will measure the speed and pressure of the water...
0:47:53 > 0:47:56- Off it goes.- ..and, crucially, reveal where the tunnels come out.
0:47:58 > 0:47:59Woo-hoo!
0:48:00 > 0:48:03You know, glaciology is an experimental science.
0:48:03 > 0:48:05We've gotta try new stuff.
0:48:05 > 0:48:09That's why I've got one left and I'm going to wish it...
0:48:11 > 0:48:12..happy returns.
0:48:12 > 0:48:14Mwah!
0:48:21 > 0:48:25Electronics expert Mark Neal designed the cryospheres.
0:48:27 > 0:48:31He'll stake out the fjord from a mountain top.
0:48:36 > 0:48:41Meanwhile, Chris, back on the Gambo, also has his eyes peeled.
0:48:44 > 0:48:49The terms wild, goose and chase, and needle, haystack come to mind.
0:48:49 > 0:48:54What's we're looking for is about, you know, 30 ping pong-size balls
0:48:54 > 0:48:57in amongst all of this ice bobbing on the surface.
0:48:57 > 0:49:00I mean, I've spent some crazy evenings in my life
0:49:00 > 0:49:04but this adds up to another one of them, you know.
0:49:04 > 0:49:07Chris is relying on his bird-spotter's training.
0:49:07 > 0:49:10But Mark takes a hi-tech approach.
0:49:10 > 0:49:13We should have the image from the telescope on the screen here,
0:49:13 > 0:49:15and then I can activate my filtering software
0:49:15 > 0:49:18which will tell us if we can see any orange dots.
0:49:23 > 0:49:25- Hello.- Just have a look up the mast for you.
0:49:25 > 0:49:28Well, good luck. My eyes are bleeding down here,
0:49:28 > 0:49:31and I'm prepared to offer you a South American country,
0:49:31 > 0:49:33a front-engine racing Ferrari,
0:49:33 > 0:49:35and a night with a supermodel of your choice,
0:49:35 > 0:49:37if you spot one of these balls.
0:49:37 > 0:49:39That's generous of you.
0:49:39 > 0:49:42It's a generous offer but I'm confident that I won't be exposed.
0:49:46 > 0:49:49Mark is also finding it tricky.
0:49:50 > 0:49:52No sign of any orange things.
0:49:52 > 0:49:55If they've come out or if they are going to come out,
0:49:55 > 0:49:56they probably have come out by now.
0:49:59 > 0:50:02I'm not going to tell you how many hours we've been out here now,
0:50:02 > 0:50:05looking for these tiny orange ping pong balls,
0:50:05 > 0:50:09which are packed full of this...scientific paraphernalia,
0:50:09 > 0:50:11but we haven't found them.
0:50:12 > 0:50:15The experiment has been less than successful.
0:50:18 > 0:50:20But, during the search, Chris spotted something which
0:50:20 > 0:50:24might give a clue about the route of melt water to the ice front.
0:50:24 > 0:50:28This body of water here is very different than everywhere else.
0:50:28 > 0:50:31There's brash ice everywhere and yet this is open, it's turbid,
0:50:31 > 0:50:33and parts of it are boiling.
0:50:33 > 0:50:37Well, not boiling, but there's a lot of Jacuzzi action.
0:50:37 > 0:50:39Jacuzzi action! That's a pretty cool word for it.
0:50:39 > 0:50:43The upwelling plumes - these Jacuzzis - I suspect,
0:50:43 > 0:50:47are absolutely fundamental to the processes going on at the ice front.
0:50:51 > 0:50:55The team wonders whether the Jacuzzis could have
0:50:55 > 0:50:58anything to do with the hidden tunnels within the glacier.
0:51:02 > 0:51:05To find out, they've flown in a secret weapon -
0:51:05 > 0:51:08imaging expert Richard Bates.
0:51:10 > 0:51:14He's turning the entire underwater scan into a 3D world.
0:51:14 > 0:51:15Richard, what have we got, then?
0:51:15 > 0:51:19This is the side-scanning sonar results,
0:51:19 > 0:51:23but you've transformed them with some software in to something?
0:51:23 > 0:51:26Yeah, that's right. If I put that into 3D, you can start to see now.
0:51:26 > 0:51:28Ooh! So that's just the sea floor, no ice?
0:51:28 > 0:51:31- That's just the sea floor we're looking at here.- Right, OK.
0:51:31 > 0:51:34We can put the ice back into that and there you can see the ice
0:51:34 > 0:51:38stretching from the north side to the south side of the glacier.
0:51:38 > 0:51:40Look at that!
0:51:40 > 0:51:44But then round the corner, into that embayment - huge cave.
0:51:44 > 0:51:46And this on the south side, here -
0:51:46 > 0:51:48that's where the plume's coming from.
0:51:48 > 0:51:53Exactly. These places match where all that water's coming out.
0:51:54 > 0:52:00Seen for the first time, they're the mouths of the horizontal tunnels,
0:52:00 > 0:52:05spewing out millions of litres of fresh melt water into the sea.
0:52:05 > 0:52:08These are the source of the Jacuzzis.
0:52:08 > 0:52:11Most tunnels are at the base of the ice,
0:52:11 > 0:52:13but not all.
0:52:14 > 0:52:17Is that a cave in the face of the glacier, then?
0:52:17 > 0:52:19Yes, it is a hole or a cave,
0:52:19 > 0:52:23or at least a heavily fractured zone in there.
0:52:23 > 0:52:26That's coming out within the face and that's something very new.
0:52:26 > 0:52:29What an astonishing view!
0:52:29 > 0:52:30It's lovely, isn't it?
0:52:30 > 0:52:33You can really visualise the fact that
0:52:33 > 0:52:36this glacier front is not just a big flat wall.
0:52:36 > 0:52:39- This is the best data we've got. - Is this the money shot?
0:52:39 > 0:52:41This, for me, is it.
0:52:41 > 0:52:44Our time on the Gambo has been very well spent.
0:52:44 > 0:52:46Look at that!
0:52:48 > 0:52:52But it's the effect of the plumes that most intrigues Alun.
0:52:52 > 0:52:56He believes they melt the glacier front at particular locations,
0:52:56 > 0:52:58forming a series of deep bays,
0:53:00 > 0:53:02with powerful consequences.
0:53:04 > 0:53:10What we're seeing is the embayments are generally cutting back.
0:53:10 > 0:53:13That's leaving these very exposed promontories,
0:53:13 > 0:53:17these massive headlands, with towering ice above the water line.
0:53:17 > 0:53:20They're 100, 120 metres high in places,
0:53:20 > 0:53:24and that's where we're getting the really big mega-bergs forming.
0:53:28 > 0:53:33For the team, it means all the pieces have finally come together.
0:53:33 > 0:53:38We've seen that huge amounts of melt water are produced at the surface,
0:53:38 > 0:53:43and they percolate down into the ice through moulins and crevasses,
0:53:43 > 0:53:45and one theory was that all of that water
0:53:45 > 0:53:48flowed down to the bedrock and underneath the ice,
0:53:48 > 0:53:52lubricating the movement of the glacier as it surges forward.
0:53:53 > 0:53:57But we've also seen that there's a new theory that water could be
0:53:57 > 0:54:01taking a different route, through a small number of huge tunnels,
0:54:01 > 0:54:05and that helps melt away the ice where the tunnels are formed,
0:54:05 > 0:54:07and so we get these bays,
0:54:07 > 0:54:11and in between the bays there are headlands,
0:54:11 > 0:54:14and those seem to be the bits that break off intact,
0:54:14 > 0:54:17and that form the huge lumps of ice
0:54:17 > 0:54:22that carry on out to the open ocean as icebergs.
0:54:25 > 0:54:28The team's packing up.
0:54:30 > 0:54:32I believe I've got a cake!
0:54:34 > 0:54:39They're leaving the glacier that's been part of their lives for three weeks.
0:54:39 > 0:54:40It has started to feel like home,
0:54:40 > 0:54:43although I'm definitely ready for a shower!
0:54:46 > 0:54:50But Store has one last surprise for Operation Iceberg -
0:54:50 > 0:54:53the culmination of everything they've discovered.
0:54:54 > 0:54:56Wow!
0:54:56 > 0:54:57HE LAUGHS
0:54:58 > 0:55:01- Oh, wow, look!- Wow!
0:55:01 > 0:55:03That is massive.
0:55:03 > 0:55:07Just as Alun predicted, an entire headland is collapsing.
0:55:11 > 0:55:14It's the biggest and most violent calving they've seen.
0:55:17 > 0:55:19Just phenomenal!
0:55:19 > 0:55:23The mega-berg to end all mega-bergs.
0:55:36 > 0:55:38That iceberg is a kilometre across.
0:55:45 > 0:55:49We talk about glaciers as like a metaphor for slowness and tedium,
0:55:49 > 0:55:51but this thing's completely alive.
0:55:53 > 0:55:56There's a wave of kind of fractures going along the top end of it,
0:55:56 > 0:56:01so all the stuff that was the cliff is now just crumbling.
0:56:02 > 0:56:05And that's the first time the water in that
0:56:05 > 0:56:08has seen the light of day for thousands of years.
0:56:24 > 0:56:25It's great!
0:56:25 > 0:56:30You know how we're all kids at heart and love a really good car crash?
0:56:30 > 0:56:35Well, that was a really, really good car crash.
0:56:36 > 0:56:39That's one of the biggest bits of natural destruction
0:56:39 > 0:56:42I've ever seen in my life. It was fantastic!
0:56:52 > 0:56:56But from this destruction, a new iceberg is born.
0:56:57 > 0:56:58And what's more,
0:56:58 > 0:57:04the team has come to understand the forces that led to this moment.
0:57:04 > 0:57:08And now that I've seen all of what's going on to produce just one iceberg,
0:57:08 > 0:57:12all of the things that happen behind the scenes, if you like,
0:57:12 > 0:57:16watching an iceberg calve is a much richer event.
0:57:18 > 0:57:21We've been trying to measure these things in St Paul's cathedrals,
0:57:21 > 0:57:23but I wouldn't know where to start.
0:57:25 > 0:57:27I wonder where that iceberg will end up.
0:57:27 > 0:57:30Where's it going to drift to? Where's it going to finally melt?
0:57:30 > 0:57:33Where's it going to be when the last little piece,
0:57:33 > 0:57:37the size of a golf ball, melts and becomes part of the ocean?
0:57:39 > 0:57:41Makes you wonder, doesn't it?
0:57:46 > 0:57:48Next on Operation Iceberg,
0:57:48 > 0:57:52the team is on the hunt for one of the largest icebergs in the whole Arctic.
0:57:53 > 0:57:55- Happy?- Yep. Let's go!
0:57:55 > 0:57:57They've seen how an iceberg is born.
0:57:57 > 0:58:01Now they hope to follow its life - and death - out at sea.
0:58:05 > 0:58:10But to succeed, they'll need to confront the Arctic's most dangerous predator.
0:58:10 > 0:58:12It's all my Christmases come at once!
0:58:12 > 0:58:16I really, really hoped to see one but I never thought that we would.
0:58:16 > 0:58:18And it's a world where the ice beneath them
0:58:18 > 0:58:20can collapse at any time.
0:58:20 > 0:58:24This is a new crack forming. This whole bit's coming off.
0:58:47 > 0:58:50Subtitles by Red Bee Media Ltd