0:00:02 > 0:00:04TOGETHER: We are Dr Chris and Dr Xand van Tulleken.
0:00:04 > 0:00:06And we're tracking down the most awesome,
0:00:06 > 0:00:10incredible and epic things in the universe!
0:00:21 > 0:00:24TOGETHER: Come with us and discover unbelievable things...
0:00:25 > 0:00:28..that 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 > 0:00:41and this week, it's all about ice.
0:00:41 > 0:00:43Yes, frozen water.
0:00:43 > 0:00:45So, hold on to your brains...
0:00:45 > 0:00:47BOTH: Here's what's coming up!
0:00:47 > 0:00:49Chris Packham has mighty polar bears in his sights,
0:00:49 > 0:00:52but how many are there on the berg?
0:00:52 > 0:00:54The team have a decision to make,
0:00:54 > 0:00:57should they dive when polar bears are around?
0:00:57 > 0:01:00We get a fascinating glimpse of the underside of an iceberg
0:01:00 > 0:01:03and the weird stuff that lives there.
0:01:04 > 0:01:07This morning we saw loads more amazing icy stuff
0:01:07 > 0:01:10when the team finally made it onto the iceberg despite terrifying
0:01:10 > 0:01:11polar bear danger.
0:01:11 > 0:01:13Yeah, that was all amazing,
0:01:13 > 0:01:16but I think my favourite bit was watching Andy fall on his behind.
0:01:16 > 0:01:17Look.
0:01:20 > 0:01:21Brilliant.
0:01:21 > 0:01:23Chris, do you think he learned to break his fall
0:01:23 > 0:01:25- when he was in the army? - I'm sure he did learn that,
0:01:25 > 0:01:28along with how to deal with people that take the mickey out of him.
0:01:28 > 0:01:29Anyway, back to those polar bears.
0:01:29 > 0:01:32Chris Packham was in his element on this expedition.
0:01:32 > 0:01:34He's fascinated by polar bears
0:01:34 > 0:01:37and how an iceberg can support a population of them.
0:01:37 > 0:01:40I wondered that too. I mean, what do they eat?
0:01:40 > 0:01:42There isn't anything growing there,
0:01:42 > 0:01:45there doesn't seem to be much other wildlife around,
0:01:45 > 0:01:47and there isn't a burger joint for a few thousand miles.
0:01:47 > 0:01:49Maybe they eat ice-berg-ers.
0:01:54 > 0:01:57Actually, Xand, they're more likely to eat you.
0:01:57 > 0:02:00Here are the team of icy explorers you're going to meet today.
0:02:00 > 0:02:02That's a bear.
0:02:02 > 0:02:04Chris Packham, wildlife and nature expert.
0:02:06 > 0:02:09Andy Torbet, extreme explorer and glacial diver.
0:02:11 > 0:02:14Doug Allan, polar cameraman and glacial diver.
0:02:15 > 0:02:19Peter Wadhams, ocean physicist and ice expert.
0:02:24 > 0:02:28Chris wanted to study the wildlife on and around the berg.
0:02:28 > 0:02:32He wanted to know how so many bears could survive on the iceberg.
0:02:33 > 0:02:35There's a group of four seals here.
0:02:35 > 0:02:39They are bear burgers, they are exactly what the bears are here for.
0:02:40 > 0:02:44And the seals wouldn't be here unless there was seal food here.
0:02:44 > 0:02:47Fish, krill, other crustaceans.
0:02:47 > 0:02:50So, this iceberg is supporting an entire ecosystem.
0:02:52 > 0:02:54That's very exciting. This is like a little lost world
0:02:54 > 0:02:57we might be able to study in some detail.
0:03:00 > 0:03:05Divers Doug and Andy were helping Chris investigate this lost world.
0:03:05 > 0:03:08They were hoping to find out if the sea nearest the berg
0:03:08 > 0:03:10supports more life than the rest of the ocean.
0:03:13 > 0:03:15But their biggest concern at that moment
0:03:15 > 0:03:18was the animal at the very top of the food chain.
0:03:19 > 0:03:22- Hello, bear.- He's on the move, he's seen you.
0:03:24 > 0:03:25No way!
0:03:25 > 0:03:27We could have a diving buddy, mate.
0:03:28 > 0:03:31Let's just see what this bear does.
0:03:31 > 0:03:34So, would you still dive, Andy, if it jumped in?
0:03:34 > 0:03:38Erm, if he jumped in, I think that would be a bold move.
0:03:39 > 0:03:42They have been recorded diving to 24 metres.
0:03:42 > 0:03:46I wouldn't like to go in the water with him hanging around, no.
0:03:47 > 0:03:49- Not a good sign.- What's that?
0:03:50 > 0:03:53It's usually what they do when they're a little bit, you know...
0:03:53 > 0:03:55- Hungry?- Yeah, getting ready to do something.
0:03:55 > 0:03:59Look, he's looking. He's like, "Can I do it?"
0:03:59 > 0:04:01It might be easier going from there.
0:04:01 > 0:04:04- He's thinking about it. - He is thinking.
0:04:04 > 0:04:06Their sense of smell is absolutely astonishing,
0:04:06 > 0:04:10so they'll smell people from some way away. Maybe they heard it, too.
0:04:10 > 0:04:12And if it was just over the back of that rise,
0:04:12 > 0:04:15the sound of the engines and them talking, it would have heard it.
0:04:15 > 0:04:16And it's just come over.
0:04:16 > 0:04:19Well, I say it has come over to have a look, it's just run off.
0:04:19 > 0:04:21But then, the first time I saw Doug Allan,
0:04:21 > 0:04:23I looked at him and I ran off as well!
0:04:23 > 0:04:25So, to be quite honest with you, I'm not surprised.
0:04:25 > 0:04:27Is this closed? OK.
0:04:27 > 0:04:30Doug and Andy were now happy to dive, as the bear had gone.
0:04:30 > 0:04:33We all hoped it didn't return and fancy a swim.
0:04:34 > 0:04:37- Yep.- Clear to go. Go when ready.
0:04:51 > 0:04:53This place is stunning.
0:04:58 > 0:05:02I've never seen walls of ice, the colours of blue and white.
0:05:06 > 0:05:07It's absolutely beautiful.
0:05:10 > 0:05:12From the surface,
0:05:12 > 0:05:16this ice wall looks like tiny little dimples all across it,
0:05:16 > 0:05:18it is the whole surface.
0:05:20 > 0:05:21It looks like a golf ball.
0:05:24 > 0:05:27I have to say, I don't think I would have jumped into that water at all.
0:05:27 > 0:05:28It looks absolutely freezing
0:05:28 > 0:05:30and there are polar bears prowling around.
0:05:30 > 0:05:33I think I'd have been back in my cabin, tucked up safe and warm.
0:05:33 > 0:05:36These guys are either very brave or very crazy.
0:05:36 > 0:05:39I suspect probably a bit of both, Xand.
0:05:39 > 0:05:41But doesn't it look stunning down there?
0:05:41 > 0:05:44But imagine you're swimming around in that beautiful blue water
0:05:44 > 0:05:47and suddenly, there's a splash above you and you look up
0:05:47 > 0:05:51and there's a huge polar bear popped in, and he's looking for lunch.
0:05:51 > 0:05:54Yeah, I think I would suddenly become a much, much faster swimmer.
0:05:54 > 0:05:56Faster than a polar bear, I hope.
0:05:56 > 0:05:58I can't wait to see what the guys found
0:05:58 > 0:06:00down in that enchanting underwater world.
0:06:00 > 0:06:02Well, they saw some really amazing-looking creatures
0:06:02 > 0:06:05and came back with some rather interesting samples
0:06:05 > 0:06:06for Chris Packham to examine.
0:06:06 > 0:06:07Take a look at this.
0:06:09 > 0:06:12Andy was amazed at how rich the waters were around the berg.
0:06:14 > 0:06:17I can't believe how much plankton there is down here.
0:06:18 > 0:06:20The size of these things.
0:06:20 > 0:06:23And I was really amazed at just how weird these things looked.
0:06:23 > 0:06:25What was that?
0:06:26 > 0:06:27Is that a lion's mane?
0:06:29 > 0:06:33These creatures formed part of an intricate food chain that feeds
0:06:33 > 0:06:37the fish, that feeds the seals, that feeds the polar bears.
0:06:39 > 0:06:41That's that sample, for Chris.
0:06:43 > 0:06:45That should keep him happy.
0:06:45 > 0:06:47OK, let's go up.
0:06:51 > 0:06:52Moment of truth.
0:06:53 > 0:06:56Whatever's in here, it's unlikely that I've ever seen it before.
0:06:56 > 0:06:59And meeting a new animal is always very, very exciting.
0:07:01 > 0:07:02Oh my goodness.
0:07:04 > 0:07:07Look at them, they may as well be from another planet.
0:07:07 > 0:07:09Absolutely fantastic.
0:07:11 > 0:07:12Guys, come and look at this.
0:07:12 > 0:07:15I know you've seen it already but you might be able to see it more
0:07:15 > 0:07:18- clearly here than you were through your masks.- Oh, yeah.
0:07:18 > 0:07:20Aren't they beautiful?
0:07:20 > 0:07:24- Who needs science-fiction when you've got this?- Absolutely, I agree.
0:07:24 > 0:07:28The common name for these things is sea gooseberries.
0:07:28 > 0:07:31Look at the cilia going, can you see it?
0:07:31 > 0:07:35It's covered in tiny beating cells, rippling there,
0:07:35 > 0:07:37with the light going through them.
0:07:39 > 0:07:42But frankly, it's nothing compared to this other thing down here.
0:07:45 > 0:07:48The common name for these is sea angels.
0:07:48 > 0:07:51This is very closely related to the slug
0:07:51 > 0:07:54and the snail that you'll find in your back garden.
0:07:54 > 0:07:57They're very bonny animals, very handsome.
0:07:59 > 0:08:01Is that his gut that you can see?
0:08:01 > 0:08:06It is his gut and those beating wings are its modified foot.
0:08:06 > 0:08:07Because it's a mollusc
0:08:07 > 0:08:09and that equates to the foot,
0:08:09 > 0:08:11the bit that a snail or a slug moves around on.
0:08:11 > 0:08:14And in this animal, it has divided it into two
0:08:14 > 0:08:17and it uses them to literally fly through the water.
0:08:17 > 0:08:19- And I love the fact it is see-through.- Yeah.
0:08:19 > 0:08:23I've got to tell you, this is the highlight of my entire trip so far.
0:08:23 > 0:08:28I've seen two animals the likes of which I've never seen before.
0:08:28 > 0:08:31They are extraordinary, they are beautiful
0:08:31 > 0:08:35and obviously very important in the ecosystem around the ice.
0:08:35 > 0:08:37Get your suits back on, get these two back in.
0:08:37 > 0:08:39We're done with these, and I want some more.
0:08:41 > 0:08:43These little creatures really do look like something
0:08:43 > 0:08:45from another planet, don't they?
0:08:45 > 0:08:48It's almost like they have Christmas tree lights all around them.
0:08:48 > 0:08:51True, but what's really interesting is that there seems to be
0:08:51 > 0:08:53no shortage of life around the berg.
0:08:53 > 0:08:56The plankton that we just saw are food for fish that then
0:08:56 > 0:09:00become food for seals, that then become food for the polar bears.
0:09:00 > 0:09:02That's why we call it a food chain, because it's all linked.
0:09:02 > 0:09:05Oh, I get it. So, if you lose one link in the chain,
0:09:05 > 0:09:07- it's disastrous for every link after that?- Exactly.
0:09:07 > 0:09:10So, the number of bears there are will be dependent
0:09:10 > 0:09:12on the number of these little creatures there are
0:09:12 > 0:09:14- swimming around the berg. - Absolutely.
0:09:14 > 0:09:17OK, so how many polar bears are on the berg?
0:09:17 > 0:09:19Well, I'm glad you asked because that gives us
0:09:19 > 0:09:21an excuse to watch this brilliant bit of film
0:09:21 > 0:09:23that Chris Packham made when we were there.
0:09:23 > 0:09:25Check this out.
0:09:27 > 0:09:31Throughout the expedition, we faced a constant threat from polar bears.
0:09:31 > 0:09:32Although they made life difficult,
0:09:32 > 0:09:35Chris was completely fascinated by them.
0:09:35 > 0:09:38He wanted to work out how many bears the berg could support,
0:09:38 > 0:09:42so he decided to do a count of how many were living there.
0:09:45 > 0:09:47We've got the chopper.
0:09:47 > 0:09:49Now we're going to go out and take a look round.
0:09:49 > 0:09:51I'm really excited to be a part of it.
0:09:51 > 0:09:53I've waited a long time to be able to do this,
0:09:53 > 0:09:55so I'm hoping we'll find some bears.
0:09:57 > 0:09:59So far, they'd only been able to see bears
0:09:59 > 0:10:01around the edge of the iceberg.
0:10:01 > 0:10:06But there was also a gigantic inland area, 40 square kilometres of ice,
0:10:06 > 0:10:09about the same as 5,000 football pitches.
0:10:09 > 0:10:11By flying over all of this ice,
0:10:11 > 0:10:13Chris would get a more accurate estimate
0:10:13 > 0:10:15of how many bears lived there.
0:10:18 > 0:10:22We've got one just down here now. It's on the side of a small lake.
0:10:24 > 0:10:25A single adult bear.
0:10:28 > 0:10:32It's cream-coloured against the white snow, which means that we can see it.
0:10:33 > 0:10:36I'm just going to grab a couple of shots of it with my still camera.
0:10:36 > 0:10:39The presence of even more bears, which Chris saw on his flight,
0:10:39 > 0:10:43had confirmed the bears seen at the edge of the berg must have
0:10:43 > 0:10:45just been a small part of the population.
0:10:47 > 0:10:50So, in total, looking at the circumference,
0:10:50 > 0:10:54which was around 27km, and how frequently we saw them,
0:10:54 > 0:11:00I'd go for mid-teens to 20 bears on this berg.
0:11:02 > 0:11:04What there is there for them is a security
0:11:04 > 0:11:07and I think they are taking advantage of that.
0:11:07 > 0:11:10So I think they are hanging out on this berg, basically,
0:11:10 > 0:11:13to stay safe and just wait for that sea ice to come back in,
0:11:13 > 0:11:16and then they can all charge out and hunt.
0:11:17 > 0:11:20Chris' count of the bears was really valuable
0:11:20 > 0:11:23because it was the first time that a population of polar bears had
0:11:23 > 0:11:27been counted on one of these big bergs.
0:11:27 > 0:11:29With the Arctic spring temperatures becoming warmer,
0:11:29 > 0:11:31there was far less sea ice,
0:11:31 > 0:11:34which was making it harder for polar bears to survive,
0:11:34 > 0:11:37which is why they use the megaberg to keep themselves safe.
0:11:40 > 0:11:43Sometimes it's hard to believe they're such fierce hunters,
0:11:43 > 0:11:46because they just look so cute and cuddly, I want to give them a hug.
0:11:46 > 0:11:49But I don't think it's a cuddle that Mr Bear would be looking for
0:11:49 > 0:11:53- if you bumped into him on your way home across an iceberg.- Fair enough.
0:11:53 > 0:11:56So, we have seen what Chris Packham was up to with the wildlife.
0:11:56 > 0:11:58What else was happening on the berg?
0:11:58 > 0:12:01Well, the scientists were trying to work out what happens to bergs
0:12:01 > 0:12:03once they're out at sea and they hope to learn
0:12:03 > 0:12:06from this berg about the forces that eventually lead to it disappearing.
0:12:06 > 0:12:08Like ice melting in a glass of water?
0:12:08 > 0:12:11Well, yes, like that, but it's also more complicated than that.
0:12:11 > 0:12:14Because there are all sorts of other things at work on an iceberg
0:12:14 > 0:12:16like waves, wind and current.
0:12:16 > 0:12:17And so they wanted to find out
0:12:17 > 0:12:20what effects these forces have on the berg.
0:12:23 > 0:12:26- So, you need to change the scale... - It's much more if it's above that.
0:12:26 > 0:12:30The scientists had two different ideas about what was helping
0:12:30 > 0:12:32to slowly break up the berg.
0:12:32 > 0:12:36The melt team believed that sea water was melting it over time.
0:12:40 > 0:12:42So, that's the main...
0:12:42 > 0:12:45The wave team thought the ocean's waves were rocking
0:12:45 > 0:12:48and bending the ice, snapping it into smaller chunks.
0:12:50 > 0:12:53Waves do have a big effect and we need to understand that
0:12:53 > 0:12:57relationship between waves and icebergs as part
0:12:57 > 0:13:01of understanding the relationship between waves and ice in general.
0:13:03 > 0:13:05Aha! It's the battle of the glaciologists.
0:13:05 > 0:13:09Two competing theories about the fate of the berg.
0:13:09 > 0:13:13Only one can triumph. So, come on, Chris, which team do you support?
0:13:13 > 0:13:15I support them both, Xand.
0:13:15 > 0:13:18Science is like that, competing theories are good.
0:13:18 > 0:13:20It makes everyone think much harder to work stuff out.
0:13:20 > 0:13:22I'd be interested to see how they get on, then.
0:13:22 > 0:13:25I reckon there is probably a bit of truth in both camps.
0:13:25 > 0:13:28Well, you're going to have to wait a bit to find out, though,
0:13:28 > 0:13:29because we're out of time again.
0:13:29 > 0:13:31Why are you teasing us, showing us that clip, then?
0:13:31 > 0:13:33I wasn't teasing you.
0:13:33 > 0:13:36I just wanted you to see how fascinating it is that although they
0:13:36 > 0:13:40are really clever scientists, they don't all agree on the same thing.
0:13:40 > 0:13:42And to show you there is lots more interesting stuff to come.
0:13:42 > 0:13:44So, remember to join us later
0:13:44 > 0:13:47to find out more stuff that will blow your mind.