0:00:02 > 0:00:04BOTH: We are Dr Chris and Dr Xand van Tulleken.
0:00:04 > 0:00:07- And we're tracking down the most awesome...- Incredible...
0:00:07 > 0:00:11BOTH: And epic things in the universe!
0:00:21 > 0:00:25Come with us and discover unbelievable things...
0:00:25 > 0:00:28that will blow your mind!
0:00:28 > 0:00:31Blow Your Mind will be bringing you loads of top experts
0:00:31 > 0:00:35and scientists to help you find out more about some amazing stuff
0:00:35 > 0:00:38from the Arctic to elephants, spaceships to sharks,
0:00:38 > 0:00:43and this week, it's all about ice. Yes, frozen water.
0:00:43 > 0:00:45So, hold on to your brains.
0:00:45 > 0:00:46Cos here's what's coming up!
0:00:48 > 0:00:52We'll find out exactly what makes a glacier move,
0:00:52 > 0:00:55find the plughole deep inside a blue lake,
0:00:55 > 0:00:58and watch some super speed-bergs on the move.
0:00:59 > 0:01:02So, Chris, you've kept me waiting all day to find out more
0:01:02 > 0:01:03about what you and the scientists
0:01:03 > 0:01:05got up to on the Store Glacier in Greenland.
0:01:05 > 0:01:08You're not going to keep me waiting any longer, are you?
0:01:08 > 0:01:09Xand, would I do that to you?
0:01:09 > 0:01:11Yes, you probably would, actually.
0:01:11 > 0:01:15It was absolutely incredible to see the new iceberg forming,
0:01:15 > 0:01:17and you said the glacier you were on
0:01:17 > 0:01:20was the size of 4,000 football pitches
0:01:20 > 0:01:22and yet it's actually moving
0:01:22 > 0:01:24the length of two double-decker buses every day.
0:01:24 > 0:01:27So what I want to know is, how? How does it move?
0:01:27 > 0:01:30It's so huge, you'd think it would be difficult to move at all.
0:01:30 > 0:01:33Well, it is moving and we showed how the experts discovered
0:01:33 > 0:01:35that it is moving very fast.
0:01:35 > 0:01:38There are different theories about how it moves, so check this out.
0:01:42 > 0:01:47Today's team of intrepid explorers and scientists are...
0:01:47 > 0:01:49Chris Packham, wildlife and nature expert.
0:01:51 > 0:01:54Dr Helen Czerski, physicist and oceanographer.
0:01:55 > 0:02:00Andy Torbet, extreme explorer and glacial diver.
0:02:00 > 0:02:05Doug Allan, polar cameraman and glacial diver.
0:02:05 > 0:02:10Jason Box and Michelle Koppes, glaciologists and ice experts.
0:02:13 > 0:02:15The team headed to the centre of the glacier
0:02:15 > 0:02:18to carry out experiments to prove Helen's theory
0:02:18 > 0:02:20about how the glacier moves.
0:02:20 > 0:02:23Something is helping it along.
0:02:23 > 0:02:26The icebergs form mostly in the summer,
0:02:26 > 0:02:29so the glacier is flowing fastest in the summer.
0:02:29 > 0:02:33And we think there are some clues to why that happens right up ahead.
0:02:34 > 0:02:37This is what is known as a blue lake.
0:02:37 > 0:02:41It's a lake that's formed 15km into the glacier
0:02:41 > 0:02:45and it's a sensational, beautiful area of water
0:02:45 > 0:02:47more than a kilometre wide.
0:02:47 > 0:02:50There were half a dozen of these blue lakes on Store Glacier
0:02:50 > 0:02:53and they appeared in the spring when some of the ice melts
0:02:53 > 0:02:56and the water begins to form pools which become blue lakes.
0:03:00 > 0:03:03There is a theory that eventually the water from the blue lake
0:03:03 > 0:03:04drains to the bottom of the glacier,
0:03:04 > 0:03:07causing it to slide along the bedrock.
0:03:16 > 0:03:18So what we're really trying to do is try to figure out,
0:03:18 > 0:03:19where does this water go
0:03:19 > 0:03:21and is it contributing to more calving
0:03:21 > 0:03:23at the terminus of the glacier?
0:03:23 > 0:03:25So what's happening from here all the way to the end.
0:03:25 > 0:03:29So what Michelle was saying was that the water in this lake
0:03:29 > 0:03:31might drain to the front of the glacier,
0:03:31 > 0:03:35causing calving events or icebergs to break off.
0:03:35 > 0:03:37The team wanted to find out how much water was in the lake
0:03:37 > 0:03:39before it drained.
0:03:39 > 0:03:42The danger of doing an experiment at a blue lake
0:03:42 > 0:03:45is that no-one knew when it might crack open and empty.
0:03:47 > 0:03:50Ice expert Jason Box has been studying this blue lake
0:03:50 > 0:03:53and his results show it should have drained already.
0:03:56 > 0:04:00So this lake's now two days past the average time when it would drain.
0:04:00 > 0:04:01It could go at any moment.
0:04:01 > 0:04:03The team set up a time-lapse camera
0:04:03 > 0:04:06to see what happened on the surface of the lake
0:04:06 > 0:04:11and a depth sensor to record how much water melts into it daily.
0:04:11 > 0:04:12- Got it?- Yup.
0:04:12 > 0:04:15The depth sensor had to be attached to something heavy,
0:04:15 > 0:04:18as it needed to be positioned ten metres down, deep in the lake.
0:04:20 > 0:04:22And expert glacial diver, Andy Torbet,
0:04:22 > 0:04:26had to dive down with it to put it in place.
0:04:26 > 0:04:28I've never dived anywhere like this.
0:04:28 > 0:04:31And certainly nowhere where, at any point during the dive,
0:04:31 > 0:04:34the water can all just drain under your feet.
0:04:34 > 0:04:36I think we can kit up and get in fairly quickly.
0:04:36 > 0:04:41Do the job, put in the sensors where necessary and we'll get out
0:04:41 > 0:04:43and everything will be fine.
0:04:43 > 0:04:44Famous last words.
0:04:44 > 0:04:47HE CHUCKLES
0:04:47 > 0:04:48Um, why is he laughing?
0:04:48 > 0:04:50He's about to go into a blue lake
0:04:50 > 0:04:53that at any time could empty like a giant bathtub
0:04:53 > 0:04:55with him getting flushed down the plughole!
0:04:55 > 0:04:57I know. It's bonkers.
0:04:57 > 0:04:59But that's the kind of guy you need on an expedition like this.
0:04:59 > 0:05:01Someone fearless, like me.
0:05:01 > 0:05:04Actually, he is really incredibly safety conscious
0:05:04 > 0:05:07and he's made sure everything is being done as safely as possible.
0:05:07 > 0:05:09I'm glad to hear it.
0:05:09 > 0:05:10Now, how are these blue lakes
0:05:10 > 0:05:13supposed to help the glacier move towards the sea?
0:05:13 > 0:05:14Well, this is how it works.
0:05:14 > 0:05:17Now, imagine these ice cubes are a glacier
0:05:17 > 0:05:20weighing billions and billions of tonnes.
0:05:20 > 0:05:22- Hmm. - HE GROANS
0:05:22 > 0:05:23Not like that!
0:05:23 > 0:05:26Now, they're stuck on the bedrock, but if I pour water on it
0:05:26 > 0:05:28so it flows under the glacier...
0:05:28 > 0:05:30- Like the water draining from the blue lake?- Exactly.
0:05:30 > 0:05:33Watch what happens.
0:05:33 > 0:05:34- Oh, yeah.- Yes.
0:05:35 > 0:05:37Oh, there we go. It's moving.
0:05:37 > 0:05:40And now they slip down the dish and move easily into the sea.
0:05:40 > 0:05:43What an amazing demonstration. It was just like being there!
0:05:45 > 0:05:47Believe me, it wasn't.
0:05:47 > 0:05:49Diving into a blue lake is really dangerous
0:05:49 > 0:05:52because the water could drain at any time.
0:05:52 > 0:05:55If that happened when Andy and Doug were in there,
0:05:55 > 0:05:57they would have been sucked right down with it.
0:05:57 > 0:05:59Three, two, one... Jump.
0:06:01 > 0:06:05You should never, ever dive into any icy water.
0:06:05 > 0:06:08Only experts with experienced safety teams
0:06:08 > 0:06:10should ever attempt anything like this.
0:06:14 > 0:06:18It's absolutely beautiful down here. All these shades of...
0:06:18 > 0:06:19white...
0:06:19 > 0:06:20and blue.
0:06:27 > 0:06:28I'm going to...
0:06:29 > 0:06:33..try and place this...sensor here.
0:06:33 > 0:06:36When the ice melts, the water level in the lake rises
0:06:36 > 0:06:40and this device will tell the team exactly by how much.
0:06:41 > 0:06:43To push further out...
0:06:44 > 0:06:46..into the middle.
0:06:49 > 0:06:51Let's have a bit of an explore
0:06:51 > 0:06:54and see if you can find where this plughole is, eh?
0:06:57 > 0:06:58Despite the dangers,
0:06:58 > 0:07:01Andy couldn't help himself from exploring to find the plughole.
0:07:03 > 0:07:06Chris, that does look really amazing, but really,
0:07:06 > 0:07:10this thing could go at any time and he's swimming merrily further down.
0:07:10 > 0:07:12- Is he mad?- Far from it, Xand.
0:07:12 > 0:07:16He's an explorer, like me, and his instinct is to find things out.
0:07:16 > 0:07:18Remember, there's a full safety team above him
0:07:18 > 0:07:21and, of course, cameraman Doug is down there too.
0:07:21 > 0:07:24Wow, I mean, what Doug is doing is really impressive.
0:07:24 > 0:07:28He's swimming around too and he's having to operate a massive camera.
0:07:28 > 0:07:31The thing is, I just can't get the sound
0:07:31 > 0:07:33of a massive toilet flushing out of my head.
0:07:33 > 0:07:36I'd hate to see these guys getting washed away.
0:07:36 > 0:07:40- Imagine how worrying it was at the time.- Oh!
0:07:41 > 0:07:42Doug...
0:07:43 > 0:07:47There's a big...big cave here going straight down.
0:07:47 > 0:07:51- Andy's found the lake's giant plughole...- Let's go have a look.
0:07:51 > 0:07:54..and decided to go down it.
0:07:57 > 0:07:58It's pretty dark in here.
0:08:01 > 0:08:03It's definitely getting narrower.
0:08:03 > 0:08:07This was incredibly dangerous as he could have got stuck.
0:08:10 > 0:08:12No way.
0:08:12 > 0:08:14It's getting too tight.
0:08:14 > 0:08:16It's getting way too tight.
0:08:18 > 0:08:21I'm still...nowhere near the bottom.
0:08:24 > 0:08:2840 minutes on the dive now. 41, now.
0:08:28 > 0:08:30It's cold and they'll be using air quickly,
0:08:30 > 0:08:32so they'll be out very soon, whatever they're doing.
0:08:33 > 0:08:36Andy couldn't get further into the plughole and, thankfully,
0:08:36 > 0:08:38decided to come out.
0:08:38 > 0:08:43But the extreme cold started to cause a much more urgent problem.
0:08:43 > 0:08:46HE BREATHES HEAVILY I need to surface.
0:08:47 > 0:08:50I think this air hose is freezing up.
0:08:50 > 0:08:54Ice was blocking Andy's air supply, making it harder for him to breathe.
0:08:54 > 0:08:56It was time to get him out.
0:09:00 > 0:09:03In this sort of environment,
0:09:03 > 0:09:06you can only do so much about trying to fix your kit under water.
0:09:06 > 0:09:10There comes a point where you just need to sack it and go home.
0:09:10 > 0:09:11In one piece.
0:09:13 > 0:09:15Absolutely. But what a successful dive.
0:09:15 > 0:09:18Not only did Andy position the sensor deep in the glacier,
0:09:18 > 0:09:21he also located the entrance to the plughole.
0:09:21 > 0:09:23So, with all the equipment set up,
0:09:23 > 0:09:27the team decided to head back to base camp for a few days.
0:09:35 > 0:09:37That is mind-blowing.
0:09:37 > 0:09:40I can't believe that something, or somewhere actually,
0:09:40 > 0:09:44can be so, so beautiful and so scary at the same time.
0:09:44 > 0:09:47I mean, at any point, that lake could have drained
0:09:47 > 0:09:50and sucked the divers through its massive plughole,
0:09:50 > 0:09:51never to be seen again.
0:09:51 > 0:09:53You're right. It's terrifyingly beautiful.
0:09:53 > 0:09:57But the question is, did the sensor do its job?
0:09:57 > 0:10:00And do they get the results for their water depth test?
0:10:00 > 0:10:01Do you want to find out?
0:10:01 > 0:10:03Of course I want to find out! That's why I'm here.
0:10:03 > 0:10:06- And that's why we're watching. - All right. Well, watch, then.
0:10:08 > 0:10:10The team didn't know what they'd find
0:10:10 > 0:10:12when they headed back a few days later.
0:10:12 > 0:10:14The entire lake could have drained and disappeared,
0:10:14 > 0:10:16taking all their equipment with it.
0:10:22 > 0:10:26The lake is quite definitely still there. It hasn't drained.
0:10:26 > 0:10:30And it... The lake's got bigger so it looks as though it's been rising.
0:10:30 > 0:10:32- It's filled up.- Helen was right.
0:10:32 > 0:10:33The lake had risen so much
0:10:33 > 0:10:36that the time-lapse camera they left behind
0:10:36 > 0:10:37was almost underwater.
0:10:37 > 0:10:40This meant that Andy had to get back in the lake,
0:10:40 > 0:10:42just to get to the equipment.
0:10:45 > 0:10:47And Helen was really worried about him.
0:10:49 > 0:10:51I just want him out of the water as quickly as possible.
0:10:51 > 0:10:52I'm finding, like...
0:10:52 > 0:10:54Finding it a bit stressful watching him.
0:10:54 > 0:10:56I know he's good, and I know he's a good swimmer,
0:10:56 > 0:10:59and he knows what he's doing in the water, but...
0:11:00 > 0:11:02..this water is not a human habitat.
0:11:07 > 0:11:09Cup of tea, I think.
0:11:12 > 0:11:13Andy's bravery paid off
0:11:13 > 0:11:16and the footage from the time-lapse camera was amazing.
0:11:18 > 0:11:21I love the way that you can see the little bits blown by the wind.
0:11:21 > 0:11:22Because they're speeded up,
0:11:22 > 0:11:25they're just zooming across the field of view.
0:11:25 > 0:11:26Yeah, we call those speed-bergs.
0:11:26 > 0:11:28See that one? Nee-ow...
0:11:29 > 0:11:31Speed-bergs. Wow!
0:11:31 > 0:11:33But it's the results from the depth sensor
0:11:33 > 0:11:35that they'd left deep in the lake
0:11:35 > 0:11:37that gave them an accurate measurement
0:11:37 > 0:11:39of how much the water level has risen.
0:11:39 > 0:11:42It looks like it filled on... You can see on this axis, it's...
0:11:42 > 0:11:46Let's call that, like, 18 to 25.
0:11:46 > 0:11:48- Seven metres.- Yeah. That's impressive.
0:11:48 > 0:11:49- That's a lot of water.- Right.
0:11:51 > 0:11:53The results show that in one part of the lake,
0:11:53 > 0:11:57the water had risen by seven metres, which is loads.
0:11:57 > 0:11:59About as high as a three-storey building.
0:11:59 > 0:12:02The scientists calculated that this lake
0:12:02 > 0:12:05held over five million cubic metres of water,
0:12:05 > 0:12:06which is a mind-blowing amount.
0:12:06 > 0:12:07To give you an idea,
0:12:07 > 0:12:11that's roughly the same as 2,000 Olympic swimming pools.
0:12:15 > 0:12:16The team had come to the blue lake
0:12:16 > 0:12:19to find out if it held enough water to move a glacier.
0:12:19 > 0:12:22These results showed that the combined amount of water
0:12:22 > 0:12:24from all the blue lakes on Store
0:12:24 > 0:12:27would definitely be enough to move it towards the sea,
0:12:27 > 0:12:29where it creates icebergs.
0:12:36 > 0:12:41That was amazing stuff. So now, we know how an iceberg is made.
0:12:41 > 0:12:44Gravity is pulling the glacier down towards the sea anyway,
0:12:44 > 0:12:46but the lakes on the glacier's surface
0:12:46 > 0:12:49are draining to the bottom of the glacier,
0:12:49 > 0:12:50which helps it slide along faster.
0:12:50 > 0:12:54And when it gets to the sea, chunks break off to form icebergs.
0:12:54 > 0:12:56Science made simple.
0:12:56 > 0:12:58Simple? Are you kidding?
0:12:58 > 0:13:02That expedition and those experiments took for ever to plan.
0:13:02 > 0:13:05The amazing results took a lot of blood, sweat and tears
0:13:05 > 0:13:09and the team faced a lot of danger in very difficult conditions.
0:13:11 > 0:13:15- Anyway, that is our journey over for today, Xand.- I hate this moment.
0:13:15 > 0:13:19It's all so exciting. I want to find out more, more, more about icebergs.
0:13:19 > 0:13:22Well, there is plenty more, more, more to see.
0:13:22 > 0:13:23So join us next, next, next time
0:13:23 > 0:13:25when we will bring you much, much, much
0:13:25 > 0:13:27more brilliant stuff that will...
0:13:27 > 0:13:29BOTH: Blow, blow, blow your mind.