1 00:00:08,200 --> 00:00:15,400 Ice is one of the most mesmerising and beguiling substances in the world. 2 00:00:15,400 --> 00:00:20,400 It's very familiar and yet never ceases to be other-worldly. 3 00:00:20,400 --> 00:00:23,400 Always a little bit strange. 4 00:00:27,080 --> 00:00:29,240 Ice is full of contradictions. 5 00:00:29,240 --> 00:00:31,320 It's transparent 6 00:00:31,320 --> 00:00:34,120 but it can glow with colour like nothing on earth. 7 00:00:34,120 --> 00:00:37,080 It's powerful enough to shatter rock and sink ships. 8 00:00:38,480 --> 00:00:41,880 But can just melt away in the blink of an eye. 9 00:00:48,200 --> 00:00:51,360 I'm Dr Gabrielle Walker. 10 00:00:51,360 --> 00:00:55,560 I trained as a chemist, but now I'm a science writer. 11 00:00:55,560 --> 00:00:58,960 And for a long time, I've been obsessed by ice. 12 00:01:00,000 --> 00:01:02,480 Ever since I first set foot on Arctic sea ice, 13 00:01:02,480 --> 00:01:04,520 I've been drawn back year after year. 14 00:01:06,680 --> 00:01:11,680 I've been trying to discover the secrets hidden deep within ice. 15 00:01:11,800 --> 00:01:15,560 I think the ice crystal has something extraordinary to reveal 16 00:01:15,560 --> 00:01:17,560 about how the world works. 17 00:01:17,560 --> 00:01:20,280 How it does that 18 00:01:20,280 --> 00:01:23,760 and what it tells us is what I want to explore in this programme. 19 00:01:23,760 --> 00:01:26,560 This is it. Wow! 20 00:01:26,560 --> 00:01:29,880 Welcome to Nigarsbreen. It's magnificent! 21 00:01:29,880 --> 00:01:34,920 I'm going to find out how something so ephemeral is powerful enough to carve solid rock. 22 00:01:38,240 --> 00:01:43,320 How ice has led to the evolution of some of the most extraordinary creatures on our planet. 23 00:01:44,000 --> 00:01:46,040 This is a really small one. 24 00:01:47,560 --> 00:01:52,160 How ice in space might lead us to discover extra-terrestrial life. 25 00:01:52,160 --> 00:01:56,880 If we've got an ocean underneath the surface of the moon, 26 00:01:56,880 --> 00:01:59,280 that's a place to search for life. 27 00:01:59,280 --> 00:02:03,200 And how its astonishing ability to store ancient atmospheres 28 00:02:03,200 --> 00:02:06,240 is helping us understand our climate. 29 00:02:07,680 --> 00:02:11,320 When they invaded Britain in 1066, this is the air they were breathing! 30 00:02:11,320 --> 00:02:12,920 Do your worst! 31 00:02:14,240 --> 00:02:17,800 And I reveal how its power to preserve our past 32 00:02:17,800 --> 00:02:19,400 and inform our future 33 00:02:19,400 --> 00:02:22,600 lies deep within the ice crystal. 34 00:02:36,840 --> 00:02:39,920 First of all, I've come to southern Norway... 35 00:02:41,360 --> 00:02:45,200 ..to visit an enormous glacier called Jostedalsbreen. 36 00:02:49,480 --> 00:02:52,520 It's the biggest piece of ice in continental Europe. 37 00:02:54,160 --> 00:02:57,600 It covers nearly 500 square kilometres of mountain. 38 00:03:04,720 --> 00:03:08,200 Glaciers are one of the most powerful forces in nature. 39 00:03:08,200 --> 00:03:13,240 They turn fragile ice into enormous grinding machines 40 00:03:13,480 --> 00:03:15,280 that can erode mountains. 41 00:03:19,160 --> 00:03:24,200 I'm going to explore one of Jostedalsbreen's many glacial tongues, Nigardsbreen. 42 00:03:26,560 --> 00:03:30,000 I'm meeting local glaciologist, Evan Lowe. 43 00:03:30,000 --> 00:03:31,760 Hello, Evan! 44 00:03:31,760 --> 00:03:34,560 Hello. Welcome to Jostedalsbreen. Thank you. 45 00:03:34,560 --> 00:03:36,680 Gosh, it's gorgeous! 46 00:03:36,680 --> 00:03:39,640 We have a kayak to take us across the lake. 47 00:03:48,720 --> 00:03:51,960 I want to find out exactly what makes glaciers so powerful. 48 00:03:53,120 --> 00:03:55,480 How something as malleable as ice 49 00:03:55,480 --> 00:03:58,800 can carve out such a spectacular landscape. 50 00:03:58,800 --> 00:04:01,400 From the sculpted walls of the valley 51 00:04:01,400 --> 00:04:03,520 to the colour of the lake. 52 00:04:11,400 --> 00:04:14,440 And full speed onto land. Full speed. 53 00:04:19,600 --> 00:04:23,720 Even though it's just ten per cent of the Jostedalsbreen's glacier, 54 00:04:23,720 --> 00:04:27,800 Nigardsbreen covers nearly 50 square kilometres of mountain. 55 00:04:27,800 --> 00:04:32,160 It rises steeply to almost two kilometres above sea level. 56 00:04:35,840 --> 00:04:40,640 Down here in the valley, where the temperatures are warmer than in the high mountains, 57 00:04:40,640 --> 00:04:43,560 the glacier melts abruptly in a ragged wall. 58 00:04:45,720 --> 00:04:50,440 It's only when you get this much ice that you can witness something spectacular. 59 00:04:50,440 --> 00:04:52,520 This is it! Wow! 60 00:04:52,520 --> 00:04:54,400 'Its full range of colours.' 61 00:04:54,400 --> 00:04:59,320 It's magnificent! The blue colour is absolutely amazing. 62 00:04:59,320 --> 00:05:02,160 It's like looking into the heart of the glacier. 63 00:05:02,160 --> 00:05:07,200 Yes, it goes from completely white and all the way to very dark blue, 64 00:05:07,440 --> 00:05:10,480 depending on how the light hits the surface 65 00:05:10,480 --> 00:05:13,680 and how far into the ice the light penetrates 66 00:05:13,680 --> 00:05:16,080 before it's reflected to us. 67 00:05:20,840 --> 00:05:23,160 The surface of the glacier looks white 68 00:05:23,160 --> 00:05:27,200 because its jagged crystals are deflecting sunlight in all directions. 69 00:05:29,640 --> 00:05:32,560 Close up, the ice seems transparent. 70 00:05:32,560 --> 00:05:34,680 But it's not. 71 00:05:34,680 --> 00:05:38,960 Pure ice crystals absorb light at the red end of the spectrum. 72 00:05:40,760 --> 00:05:43,480 So as sunlight travels deeper into the ice, 73 00:05:43,480 --> 00:05:46,320 a new blue light is reflected back. 74 00:05:51,280 --> 00:05:55,080 When it's in a huge chunk like a glacier, it looks blue. 75 00:05:55,080 --> 00:05:59,840 But if you grab a chunk of it, it's just white, ordinary boring ice! 76 00:05:59,840 --> 00:06:02,000 Ice is never boring. Never, ever! 77 00:06:05,680 --> 00:06:09,920 The ice in this front wall is at the end of its journey down the mountain. 78 00:06:09,920 --> 00:06:13,040 It's now at the point of melting away. 79 00:06:13,040 --> 00:06:16,320 Every moment it's changing, 80 00:06:16,320 --> 00:06:18,480 like a moving sculpture. 81 00:06:22,760 --> 00:06:25,480 Melt water is raining down on me 82 00:06:25,480 --> 00:06:28,080 and it's making the most amazing shapes. 83 00:06:28,080 --> 00:06:31,280 You can see it's eating into the walls here 84 00:06:31,280 --> 00:06:34,400 and making all these curves and round parts 85 00:06:34,400 --> 00:06:39,040 and that's why it looks like the moon outside with all those incredible curves. 86 00:06:39,040 --> 00:06:40,560 It's beautiful. 87 00:06:46,800 --> 00:06:48,840 Although glacial ice is a solid, 88 00:06:48,840 --> 00:06:51,400 it actually flows like a river. 89 00:06:51,400 --> 00:06:54,200 It's incredible to think that this much ice 90 00:06:54,200 --> 00:06:56,120 is constantly on the move. 91 00:06:57,800 --> 00:07:01,160 I've been climbing up to see what drives the glacier. 92 00:07:03,600 --> 00:07:06,840 And it's the phenomenal weight of this enormous ice pack, 93 00:07:06,840 --> 00:07:08,680 over nine kilometres long, 94 00:07:08,680 --> 00:07:11,440 and up to 500 metres deep. 95 00:07:11,440 --> 00:07:15,760 Millions of tonnes of ice crammed into this valley. 96 00:07:18,840 --> 00:07:21,720 Built up from layer upon layer of snow, 97 00:07:21,720 --> 00:07:25,760 this monumental river of ice is constantly being topped up 98 00:07:25,760 --> 00:07:27,480 by fresh snowfall. 99 00:07:27,480 --> 00:07:30,160 And that keeps it flowing downhill. 100 00:07:31,240 --> 00:07:35,800 It makes very slow progress. But there is a way to see it move. 101 00:07:46,560 --> 00:07:50,560 A time-lapse camera shows that Nigardsbreen's surface ice 102 00:07:50,560 --> 00:07:53,960 travels at around 275 metres per year, 103 00:07:53,960 --> 00:07:57,400 carving away the rock as it goes. 104 00:08:04,160 --> 00:08:07,960 When you're here, the only clues you see of the glacier's movement 105 00:08:07,960 --> 00:08:09,800 are crevasses. 106 00:08:10,880 --> 00:08:14,640 Deep gashes that split open the surface of the ice. 107 00:08:16,520 --> 00:08:18,600 These open up at the top of the ice. 108 00:08:18,600 --> 00:08:22,400 One of the reasons is the top of the ice is brittle and tough. 109 00:08:22,400 --> 00:08:26,080 Further down, where it's been squeezed, it's plastic and soft. 110 00:08:26,080 --> 00:08:29,400 But as the glacier moves, the brittle part breaks open 111 00:08:29,400 --> 00:08:31,720 and creates these great crevasses. 112 00:08:34,800 --> 00:08:38,560 When a crevasse has opened up in the ice, melt water can gather in it 113 00:08:38,560 --> 00:08:41,720 and start hollowing its way down towards the bedrock. 114 00:08:44,160 --> 00:08:49,200 Here, it carves out a hidden world of icy caverns deep within the glacier. 115 00:08:52,680 --> 00:08:57,680 I'm going to try to abseil right into the heart of the glacier 116 00:08:58,040 --> 00:09:00,160 to see for myself how it moves. 117 00:09:10,760 --> 00:09:12,960 That was amazing! 118 00:09:18,760 --> 00:09:21,360 We're in the engine room of the glacier. 119 00:09:21,360 --> 00:09:25,800 You can see just down here right where the ice melts the ground. 120 00:09:25,800 --> 00:09:29,400 And this is where everything important happens. 121 00:09:29,400 --> 00:09:31,760 I'm getting wet with the melting water, 122 00:09:31,760 --> 00:09:35,000 but it's that that helps the glacier slide on its belly, 123 00:09:35,000 --> 00:09:38,400 one of the things that makes it so dynamic. 124 00:09:39,960 --> 00:09:42,680 Nigardsbreen's temperate mountain climate 125 00:09:42,680 --> 00:09:47,720 means the ice at the lower end of the glacier exists very close to melting point. 126 00:09:49,560 --> 00:09:52,360 As well as the melt water flowing beneath the ice, 127 00:09:52,360 --> 00:09:56,160 which helps lubricate the glacier on its journey down the mountain, 128 00:09:56,160 --> 00:09:59,520 there's melt water within the ice itself, 129 00:09:59,520 --> 00:10:01,960 seeping out of these walls. 130 00:10:03,600 --> 00:10:08,320 That melting water also makes this cave, and other caves like it all around. 131 00:10:08,320 --> 00:10:12,520 I bet this cave wasn't here last year and it probably won't be here next. 132 00:10:12,520 --> 00:10:17,200 It's transient, part of the signs that the glacier is dynamic 133 00:10:17,200 --> 00:10:19,760 and moving and changing all the time. 134 00:10:27,760 --> 00:10:31,000 When you look at the slick blue ice in these caves, 135 00:10:31,000 --> 00:10:34,480 it's hard to imagine it began its life as snowflakes. 136 00:10:35,720 --> 00:10:37,920 But hundreds of years of compression 137 00:10:37,920 --> 00:10:42,560 have gradually turned it into this glittering mass of ice crystals. 138 00:10:48,440 --> 00:10:49,960 Look at that! 139 00:10:49,960 --> 00:10:53,560 The sides of the ice here are just like they were in the cave. 140 00:10:53,560 --> 00:10:58,520 They really look like solid squashed together lumps and cubes. 141 00:10:58,600 --> 00:11:01,080 And here you can really see that. 142 00:11:01,080 --> 00:11:04,880 Like someone's taken a bunch of cubes and squeezed them together. 143 00:11:06,640 --> 00:11:10,560 And that's what I'm walking on. Like walking on a giant Slushie! 144 00:11:17,560 --> 00:11:21,120 Every single one of these ice crystals has an unusual property. 145 00:11:22,720 --> 00:11:25,960 If you throw them into water, they float. 146 00:11:27,480 --> 00:11:30,600 That's something we take completely for granted. 147 00:11:30,600 --> 00:11:33,000 But it's incredibly rare in nature. 148 00:11:35,400 --> 00:11:38,440 It's what helps to make ice special. 149 00:11:38,440 --> 00:11:42,680 And what gives it the power to transform our world. 150 00:11:47,000 --> 00:11:50,480 The secret lies at the heart of the ice crystal. 151 00:11:51,640 --> 00:11:55,240 I'm going to witness the very instant it forms, 152 00:11:55,240 --> 00:12:00,240 with chemist and fellow ice enthusiast, Dr Andrea Sella. 153 00:12:02,360 --> 00:12:05,840 Ice breaks all the rules that we learn. 154 00:12:05,840 --> 00:12:10,880 Andrea believes this moment is key to understanding the mysterious world of the ice crystal 155 00:12:11,720 --> 00:12:16,760 because of the curious way that water turns from liquid to solid ice. 156 00:12:17,920 --> 00:12:20,360 Let me show you something really amazing. 157 00:12:20,360 --> 00:12:24,120 We've got some mineral water here that we've been cooling for a bit. 158 00:12:24,120 --> 00:12:26,800 I want you to take these bottles quite gingerly. 159 00:12:26,800 --> 00:12:30,120 Take this and bang it on the table. Just bang it? Bang it. 160 00:12:31,680 --> 00:12:34,640 There it goes! Look at that! Instant ice! 161 00:12:34,640 --> 00:12:38,400 It's spreading out these fingers and shards of ice all the way down. 162 00:12:38,400 --> 00:12:42,600 It's quite amazing. You can see the crystals growing before your very eyes! 163 00:12:46,440 --> 00:12:50,680 Ice is a crystal in which the water molecules are very carefully arranged. 164 00:12:50,680 --> 00:12:53,200 If you think of guards on parade, 165 00:12:53,200 --> 00:12:58,240 all lined up in neat rows, that's what a crystal is, and that's what ice is. 166 00:13:01,360 --> 00:13:06,040 Like any crystal, ice doesn't form spontaneously, 167 00:13:06,040 --> 00:13:08,400 even in this super-cooled water, 168 00:13:08,400 --> 00:13:11,040 which is well below zero degrees centigrade. 169 00:13:11,040 --> 00:13:14,480 It needs a seed, a template. 170 00:13:17,120 --> 00:13:19,920 You need someone to kind of blow the whistle 171 00:13:19,920 --> 00:13:23,040 and provide an initial point, saying start here. 172 00:13:24,720 --> 00:13:29,720 So I bang it, you get bubbles and each of those bubbles is a place for the crystals to form. Absolutely. 173 00:13:31,600 --> 00:13:34,040 You can do it in other ways, too. 174 00:13:34,040 --> 00:13:37,080 Take another bottle, and this time what we'll do 175 00:13:37,080 --> 00:13:40,240 is try dropping another piece of ice into it. 176 00:13:40,240 --> 00:13:41,800 Just pop it in. 177 00:13:41,800 --> 00:13:44,120 Ready, steady... 178 00:13:46,320 --> 00:13:49,840 It's really the ice which is acting as the initial starting point 179 00:13:49,840 --> 00:13:51,880 on which the rest of the ice grows. 180 00:14:00,720 --> 00:14:05,160 It's the way the ice crystal forms that is the key to why it floats. 181 00:14:08,080 --> 00:14:11,280 Water molecules are loosely held together by bonds 182 00:14:11,280 --> 00:14:14,280 which are constantly making and breaking. 183 00:14:14,280 --> 00:14:17,080 When the temperature drops to zero, 184 00:14:17,080 --> 00:14:19,960 these bonds begin to hold. Fast. 185 00:14:19,960 --> 00:14:24,280 Creating a hexagonal lattice, an ice crystal. 186 00:14:28,600 --> 00:14:31,880 In the lattice, the bonds hold the molecules far apart. 187 00:14:32,920 --> 00:14:34,960 It's that sudden opening out 188 00:14:34,960 --> 00:14:39,080 that makes ice lighter, less dense, than liquid water. 189 00:14:41,800 --> 00:14:44,360 In water, the approaches are quite close. 190 00:14:44,360 --> 00:14:47,640 When we get to ice, suddenly it expands a bit. 191 00:14:47,640 --> 00:14:52,560 And we end up with a strangely spacious open structure 192 00:14:52,560 --> 00:14:55,720 which is less dense and therefore it floats. 193 00:14:55,720 --> 00:14:57,720 It's really quite miraculous. 194 00:14:57,720 --> 00:15:01,200 That's all down to the structure of the crystal? Absolutely. 195 00:15:01,200 --> 00:15:03,280 Ice is incredibly special. 196 00:15:03,280 --> 00:15:06,560 The irony is that to us it's completely common. 197 00:15:06,560 --> 00:15:10,280 We take an ice cube and drop it into a drink and it floats. 198 00:15:10,280 --> 00:15:12,760 Well, it is almost unique 199 00:15:12,760 --> 00:15:17,040 in the enormous, the millions of compounds and materials that we know about, 200 00:15:17,040 --> 00:15:20,400 in being a solid that floats on its melt. 201 00:15:27,400 --> 00:15:31,760 If ice didn't float, the world would be a very different place. 202 00:15:33,520 --> 00:15:36,360 Instead of forming on the surface of the ocean, 203 00:15:36,360 --> 00:15:39,920 allowing marine life to survive beneath, 204 00:15:39,920 --> 00:15:43,240 ice would form on the sea bed, 205 00:15:43,240 --> 00:15:46,440 oceans would freeze from the bottom up 206 00:15:46,440 --> 00:15:50,080 and life as we know it might never have evolved at all. 207 00:15:54,200 --> 00:15:59,280 We also wouldn't have developed an elegant British pastime 208 00:15:59,280 --> 00:16:02,720 that began on frozen lakes and rivers hundreds of years ago. 209 00:16:10,760 --> 00:16:14,760 Every Sunday morning, members of the Royal Skating Club 210 00:16:14,760 --> 00:16:19,840 meet at Guildford ice rink to skate in what is called "the English style". 211 00:16:24,480 --> 00:16:28,400 Once considered England's highest form of skating art, 212 00:16:28,400 --> 00:16:32,600 "the English style" originates from the early 19th century. 213 00:16:32,600 --> 00:16:36,400 It combines a Victorian sense of elegance and understatement 214 00:16:36,400 --> 00:16:39,320 with a high level of skill. 215 00:16:39,320 --> 00:16:42,720 Around a centre marked by an orange, 216 00:16:42,720 --> 00:16:46,600 the skaters perform perfectly-shaped geometric figures 217 00:16:46,600 --> 00:16:51,640 in absolute unison, holding their bodies stiff and straight. 218 00:16:53,160 --> 00:16:56,160 Centre change, sub circle. 219 00:16:59,600 --> 00:17:03,160 In keeping with the Victorian horror of showing off, 220 00:17:03,160 --> 00:17:07,080 the challenge is to make these complex manoeuvres look graceful 221 00:17:07,080 --> 00:17:08,720 and effortless. 222 00:17:12,960 --> 00:17:14,720 These are lovely. 223 00:17:14,720 --> 00:17:19,120 Elaine Hooper, historian for the National Ice Skating Association, 224 00:17:19,120 --> 00:17:22,320 has some Victorian pictures of the English Style. 225 00:17:22,320 --> 00:17:27,320 It was very much a more polite style of skating. It was very dignified. 226 00:17:27,640 --> 00:17:32,680 The ladies had long dresses and big hats on and the men had top hats in Victorian times. 227 00:17:33,160 --> 00:17:35,760 That was the style of skating 228 00:17:35,760 --> 00:17:38,440 that evolved on the frozen lakes and rivers 229 00:17:38,440 --> 00:17:40,480 as early as the 1600s. 230 00:17:40,480 --> 00:17:45,560 Over the years, different moves were added when people wanted to make it more difficult. 231 00:17:48,240 --> 00:17:51,440 The English Style developed amongst the upper classes 232 00:17:51,440 --> 00:17:55,720 while Britain was experiencing what became known as "the little ice age". 233 00:17:55,720 --> 00:18:00,480 From the 13th century to the middle of the 19th century, 234 00:18:00,480 --> 00:18:04,320 British winters were up to two degrees cooler. 235 00:18:04,320 --> 00:18:07,280 Many lakes and rivers regularly froze over. 236 00:18:09,360 --> 00:18:13,400 Pepys himself talks about skating with Nell Gwyn on the Thames 237 00:18:13,400 --> 00:18:18,000 in one of the great frost fairs where they would roast hogs and skate. 238 00:18:18,000 --> 00:18:21,520 It was just a way of life then. It was much colder. 239 00:18:21,520 --> 00:18:25,400 The Thames doesn't tend to freeze over now so we can't have that again. 240 00:18:30,800 --> 00:18:33,480 We can skate because of another quality of ice. 241 00:18:33,480 --> 00:18:35,320 Its slipperiness. 242 00:18:40,120 --> 00:18:44,320 This may seem completely normal, but it's actually very rare for a solid. 243 00:18:48,360 --> 00:18:53,400 The reason we can skate is to do with what happens when ice is squeezed by a blade. 244 00:18:54,800 --> 00:18:56,960 The way it reacts to pressure. 245 00:19:01,840 --> 00:19:06,320 So Andrea Sella and I are going to put ice under a lot of pressure 246 00:19:06,320 --> 00:19:08,360 in a classic experiment. 247 00:19:10,800 --> 00:19:15,800 OK, we need to lift it up and get it onto our platform. 248 00:19:16,000 --> 00:19:18,680 It is pretty heavy. I'm strong, don't worry! 249 00:19:18,680 --> 00:19:20,560 Good. There we are. 250 00:19:20,560 --> 00:19:22,760 So now we need to unpack things. 251 00:19:25,040 --> 00:19:27,440 Ooh, that's lovely! Gorgeous! 252 00:19:29,480 --> 00:19:31,280 I'll lift it and you pull. 253 00:19:31,280 --> 00:19:32,560 That's great. 254 00:19:33,760 --> 00:19:37,960 What we're going to do is sling this wire over the top 255 00:19:37,960 --> 00:19:43,000 and hang these two really rather heavy weights, 256 00:19:45,920 --> 00:19:47,520 There we go. 257 00:19:47,520 --> 00:19:50,240 It's now suspended. 258 00:19:50,240 --> 00:19:54,040 What we have to do is wait for the pressure of the wire 259 00:19:54,040 --> 00:19:56,160 to work its magic on the ice. 260 00:20:01,800 --> 00:20:05,040 As we wait, the wire works its way through the ice. 261 00:20:05,040 --> 00:20:07,040 Almost cutting it in two. 262 00:20:08,920 --> 00:20:12,360 And behind the wire, the ice is sealing up again. 263 00:20:12,360 --> 00:20:15,480 Something very strange is going on. 264 00:20:20,240 --> 00:20:22,120 It's amazing. Look at it! 265 00:20:22,120 --> 00:20:24,600 So how's it gone through the ice like this? 266 00:20:24,600 --> 00:20:29,680 Of course, the wire has the weight on it. And because the wire's very thin, 267 00:20:29,840 --> 00:20:33,120 what it does is apply really quite a large pressure 268 00:20:33,120 --> 00:20:35,320 on a local area of the ice. 269 00:20:35,320 --> 00:20:38,360 We know that ice expands when it freezes 270 00:20:38,360 --> 00:20:43,440 so if you squeeze it, you can drive it back towards that molten state. 271 00:20:43,440 --> 00:20:46,520 So when you put pressure on it, it turns it back to water. 272 00:20:46,520 --> 00:20:48,520 You can re-melt it back to water. 273 00:20:52,400 --> 00:20:55,280 That's one of the key reasons we can skate. 274 00:20:55,280 --> 00:20:59,840 The pressure of the blades is enough to melt the top layer of ice into water 275 00:20:59,840 --> 00:21:03,400 which lubricates the skates. 276 00:21:05,480 --> 00:21:08,000 Friction can also help melt the ice. 277 00:21:10,240 --> 00:21:14,360 In our experiment, as the wire passed through the block, 278 00:21:14,360 --> 00:21:16,920 the ice sealed up behind. 279 00:21:16,920 --> 00:21:21,680 This shows how ice can engulf something solid 280 00:21:21,680 --> 00:21:24,440 leaving barely a trace. 281 00:21:26,120 --> 00:21:31,080 I was expecting the wire to cut through it. And it's completely sealed. 282 00:21:31,080 --> 00:21:36,080 It looks as though it ought to fall apart. It's an extraordinary process. 283 00:21:36,160 --> 00:21:40,520 Effectively, underneath the wire, the ice melts 284 00:21:40,520 --> 00:21:42,800 and then behind it, it re-freezes again. 285 00:21:42,800 --> 00:21:45,440 So this whole process is making the ice 286 00:21:45,440 --> 00:21:49,600 move between those two points on that knife-edge between liquid and solid. 287 00:21:49,600 --> 00:21:51,800 The pressure squeezes it, 288 00:21:51,800 --> 00:21:55,000 take the pressure off and it freezes again. Absolutely. 289 00:21:59,080 --> 00:22:02,880 This formidable ability to swallow up another solid 290 00:22:02,880 --> 00:22:06,640 is a real insight into just how peculiar ice is. 291 00:22:06,640 --> 00:22:11,640 It also explains how ice can do seemingly impossible things 292 00:22:12,400 --> 00:22:14,000 in nature. 293 00:22:20,880 --> 00:22:24,280 In Norway, at the foot of Nigardsbreen, 294 00:22:24,280 --> 00:22:28,080 glaciologist Evan Lowe has some local stories to tell 295 00:22:28,080 --> 00:22:33,120 of how glaciers can engulf things much bigger than a thin metal wire. 296 00:22:34,360 --> 00:22:39,400 From where we're sitting now we can see a place where a farm used to be, 250 years ago. 297 00:22:41,240 --> 00:22:45,880 Until it was knocked down by this glacier behind us 298 00:22:45,880 --> 00:22:50,320 and all the buildings and farm were just swallowed by the glacier. 299 00:22:50,320 --> 00:22:53,160 If something goes into the ice, what happens to it? 300 00:22:53,160 --> 00:22:57,680 A bit further south, there's a plane with a pilot who crashed in the '70s 301 00:22:57,680 --> 00:22:59,520 on top of the glacier. 302 00:22:59,520 --> 00:23:04,480 Before the rescuers could get there, the whole thing was covered by snow. 303 00:23:04,480 --> 00:23:07,080 And it never appeared again. 304 00:23:07,080 --> 00:23:11,520 Some guy calculated that it should come out of the glacier 305 00:23:11,520 --> 00:23:16,400 some 25 years later, but they're still waiting for it. 306 00:23:16,400 --> 00:23:21,440 No-one's seen any trace of it. So there's a plane, body and everything. 307 00:23:21,680 --> 00:23:22,760 Somewhere! 308 00:23:22,760 --> 00:23:26,360 That's a spooky ghost story to tell just before bed! 309 00:23:37,800 --> 00:23:40,560 When it comes to a glacier shaping the landscape, 310 00:23:40,560 --> 00:23:42,840 this ability of ice to absorb things 311 00:23:42,840 --> 00:23:45,560 is a real secret to its strength. 312 00:23:48,160 --> 00:23:53,080 Ice on its own is far too fragile to leave any mark on solid rock. 313 00:23:53,080 --> 00:23:56,680 It can only carve out a valley by picking up tools. 314 00:23:59,640 --> 00:24:04,640 The ice engulfs rocks and boulders as it moves down the mountainside. 315 00:24:05,200 --> 00:24:09,600 They pass through the ice and get dragged along in its underbelly. 316 00:24:09,600 --> 00:24:13,880 Together they scrape and chip away at the rock beneath. 317 00:24:17,440 --> 00:24:22,360 It's easy to imagine that this was once just one big mountain. 318 00:24:22,360 --> 00:24:26,080 And now all this space that we are in now 319 00:24:26,080 --> 00:24:28,520 is the result of the glacier 320 00:24:28,520 --> 00:24:32,960 taking its bites like this during thousands of years. 321 00:24:32,960 --> 00:24:37,840 I like the way you say, "taking bites". The rocks are the teeth of the glacier 322 00:24:37,840 --> 00:24:40,080 and that's what it's using to grind away. 323 00:24:40,080 --> 00:24:44,960 It's still doing it up there, making the valley bigger and wider. 324 00:24:44,960 --> 00:24:49,400 If it were some other solid like steel or rock, 325 00:24:49,400 --> 00:24:51,840 it would just sit there. It couldn't do this. 326 00:24:51,840 --> 00:24:53,880 That's one of the secrets of the ice 327 00:24:53,880 --> 00:24:57,520 that it's strong enough to carry big rocks to work on the surface 328 00:24:57,520 --> 00:25:00,560 but it's also soft enough to move. 329 00:25:09,360 --> 00:25:14,400 Over the thousands of years that Nigardsbreen has been advancing and retreating, 330 00:25:15,120 --> 00:25:17,160 it's been grinding down the rock 331 00:25:17,160 --> 00:25:19,400 like an enormous sheet of sand paper. 332 00:25:21,640 --> 00:25:26,400 Gradually, it's turned boulders and bedrock into dust so fine 333 00:25:26,400 --> 00:25:28,480 that when it's washed into the lake, 334 00:25:28,480 --> 00:25:30,600 it remains suspended there. 335 00:25:30,600 --> 00:25:32,960 And it's the minerals in this dust 336 00:25:32,960 --> 00:25:35,720 that give the lake its colour. 337 00:25:47,760 --> 00:25:50,360 So that piece of ice there has done everything. 338 00:25:50,360 --> 00:25:52,800 It's shaped and smoothed these rocks 339 00:25:52,800 --> 00:25:55,560 and it's made these scrape marks and teeth marks 340 00:25:55,560 --> 00:26:00,520 and down there, the bigger boulders and the pebbles and the silt 341 00:26:01,160 --> 00:26:03,560 all the way through to the colour of the lake, 342 00:26:03,560 --> 00:26:05,320 even the shape of the valley, 343 00:26:05,320 --> 00:26:09,440 everything about everything I see has been dictated and defined by the ice. 344 00:26:17,520 --> 00:26:20,240 But ice itself is ruled by temperature. 345 00:26:21,440 --> 00:26:25,080 That's what determines everything from how long it lasts 346 00:26:25,080 --> 00:26:27,560 to how and where it forms. 347 00:26:27,560 --> 00:26:31,600 And nowhere is this more true than in the sky, 348 00:26:31,600 --> 00:26:34,480 where ice is at its most unpredictable. 349 00:26:37,480 --> 00:26:39,760 Clouds are usually made of water vapour. 350 00:26:39,760 --> 00:26:43,800 But if it's cold enough, you can get clouds entirely made of ice crystals. 351 00:26:43,800 --> 00:26:47,640 When you get ice in the sky, that can cause havoc with the weather. 352 00:26:51,000 --> 00:26:53,720 One of the most treacherous forms of icy weather 353 00:26:53,720 --> 00:26:56,160 is an ice storm. 354 00:26:59,360 --> 00:27:03,120 11 Canadians have been killed and two million are without electricity 355 00:27:03,120 --> 00:27:06,040 after devastating ice storms swept the country. 356 00:27:06,040 --> 00:27:11,080 In 1998, eastern Canada was hit by a massive ice storm, 357 00:27:11,400 --> 00:27:13,600 its worst on record. 358 00:27:16,280 --> 00:27:20,920 Over five days, freezing rain turned into a slick glaze of ice 359 00:27:20,920 --> 00:27:24,680 and built up to 7.5 centimetres thick in some places. 360 00:27:28,360 --> 00:27:32,840 It became heavy enough to bring down trees and power lines. 361 00:27:35,880 --> 00:27:40,840 The ice storm forced the government to declare a state of emergency. 362 00:27:49,640 --> 00:27:53,840 Ice storms can begin high in the atmosphere. 363 00:27:55,800 --> 00:28:00,200 Here, ice crystals grow into delicate snowflakes 364 00:28:00,200 --> 00:28:03,120 with stunningly symmetrical branches. 365 00:28:08,120 --> 00:28:11,720 If snowflakes fall into a warmer band of air, 366 00:28:11,720 --> 00:28:14,840 they'll melt away into rain. 367 00:28:14,840 --> 00:28:19,480 But in the unusual circumstances that lead to an ice storm, 368 00:28:19,480 --> 00:28:22,920 there's much colder air beneath this warm layer 369 00:28:22,920 --> 00:28:25,200 and it's very close to the ground. 370 00:28:27,800 --> 00:28:30,360 As the rain falls through this cold air, 371 00:28:30,360 --> 00:28:32,440 it becomes super-cooled, 372 00:28:32,440 --> 00:28:35,000 ready to freeze again in an instant. 373 00:28:36,200 --> 00:28:39,200 It crystallises as soon as it touches something, 374 00:28:39,200 --> 00:28:43,920 creating layer upon hazardous layer of ice. 375 00:28:46,200 --> 00:28:49,520 MAN: Millions of people here in Montreal are affected. 376 00:28:49,520 --> 00:28:52,400 WOMAN: It's like a war scene, almost. 377 00:28:52,400 --> 00:28:57,440 We're going round house to house suggesting to people that it'll be a while before the power's back 378 00:28:58,560 --> 00:29:01,800 and it might be wise to relocate to a shelter. 379 00:29:05,960 --> 00:29:08,680 The damage cost the country $3 billion. 380 00:29:08,680 --> 00:29:12,480 In some areas, the ice didn't melt for three months. 381 00:29:22,880 --> 00:29:25,760 Temperature is truly the master of ice. 382 00:29:25,760 --> 00:29:30,120 And there's a mysterious phenomenon called hot ice, 383 00:29:30,120 --> 00:29:33,240 which freezes at room temperature. 384 00:29:35,440 --> 00:29:40,000 Hot ice is created by putting water under enormous pressure, 385 00:29:40,000 --> 00:29:43,680 far greater than any glacier on our planet. 386 00:29:44,880 --> 00:29:48,480 This is ice that we wouldn't normally find anywhere on Earth. 387 00:29:53,120 --> 00:29:58,160 Professor Paul Macmillan is going to show me how to make this high-pressure ice. 388 00:29:58,160 --> 00:30:01,880 What we've got is a little drop of liquid water 389 00:30:01,880 --> 00:30:04,680 and it's placed between two diamonds. 390 00:30:04,680 --> 00:30:09,760 Inside here we've got two tiny diamonds that are pressing together. 391 00:30:10,080 --> 00:30:13,480 You're going to turn this knob here very gently. 392 00:30:13,480 --> 00:30:18,360 Because otherwise you'll force the two diamonds together too fast and they'll break. 393 00:30:18,360 --> 00:30:20,360 I'll be very careful. 394 00:30:21,880 --> 00:30:25,640 I'm about to put a tiny drop of water under more pressure 395 00:30:25,640 --> 00:30:28,840 than occurs naturally anywhere on the Earth's surface. 396 00:30:28,840 --> 00:30:31,560 When this gets to around 12, 397 00:30:31,560 --> 00:30:33,920 I want you to start to watch the screen. OK. 398 00:30:33,920 --> 00:30:36,760 Nine and a half now. Yes. 399 00:30:36,760 --> 00:30:39,480 So what's happening is the pressure is going on 400 00:30:39,480 --> 00:30:42,760 and the diamonds are squeezing that drop of water. Yes. 401 00:30:42,760 --> 00:30:46,240 It's close to 12. I would slow it down just a wee bit. 402 00:30:46,240 --> 00:30:51,280 At the moment this is liquid water, but it's really squeezed now. 403 00:30:51,880 --> 00:30:53,960 The pressure's going up... 404 00:30:53,960 --> 00:30:55,800 Look at that! 405 00:30:55,800 --> 00:30:57,600 It's crystals! 406 00:30:57,600 --> 00:31:01,960 Yeah. Oh, that is cool. You've just made ice crystals in there. 407 00:31:01,960 --> 00:31:04,640 They're growing as well, not just sitting there. 408 00:31:04,640 --> 00:31:06,960 It's a whole faceful of tiny crystals. 409 00:31:08,840 --> 00:31:12,800 The ice has formed even though it's way above zero degrees. 410 00:31:14,000 --> 00:31:17,800 See the room temperature is 25 degrees. 411 00:31:17,800 --> 00:31:20,840 So we've made water freeze at 25 degrees C? Yes. 412 00:31:20,840 --> 00:31:24,720 These are icebergs floating in dense water. 413 00:31:26,840 --> 00:31:30,720 'The hot ice is at a pressure of 15,000 atmospheres. 414 00:31:30,720 --> 00:31:34,280 'That's 15 times more pressure 415 00:31:34,280 --> 00:31:38,080 'than you find at the bottom of the deepest ocean on Earth.' 416 00:31:38,080 --> 00:31:41,800 What would it be like, then? I know we can't take it out and look at it 417 00:31:41,800 --> 00:31:44,720 or do things with it because it's under that pressure. 418 00:31:44,720 --> 00:31:47,400 But how is it different from real, normal ice? 419 00:31:47,400 --> 00:31:52,360 The first thing is that it doesn't melt at normal temperatures. 420 00:31:52,640 --> 00:31:57,640 This one here, you'd have to take this up to well over 100 degrees centigrade 421 00:31:58,960 --> 00:32:01,360 for it even to start to melt. 422 00:32:01,360 --> 00:32:04,320 So you can go above boiling point and it doesn't melt? 423 00:32:04,320 --> 00:32:07,120 Exactly. This is a high-density form of ice. 424 00:32:07,120 --> 00:32:11,040 The structure is very like a little cube. 425 00:32:11,040 --> 00:32:15,480 You would never get the hexagon snowflake shapes 426 00:32:15,480 --> 00:32:18,160 that you get with normal ice. 427 00:32:18,160 --> 00:32:22,960 'This kind of ice might occur naturally out in space.' 428 00:32:24,640 --> 00:32:28,920 We think that it probably does exist in the solar system, 429 00:32:28,920 --> 00:32:33,320 deep inside some of the icy moons out there 430 00:32:33,320 --> 00:32:36,760 like Titan, which is the large moon of Saturn. 431 00:32:36,760 --> 00:32:39,760 And we know that the pressure inside 432 00:32:39,760 --> 00:32:42,520 gets to these pressure values. 433 00:32:42,520 --> 00:32:46,960 So it's like having a telescope to look into the heart of Saturn's moon. Exactly. 434 00:32:50,480 --> 00:32:54,640 We know already that the surfaces of some of the moons of Jupiter and Saturn 435 00:32:54,640 --> 00:32:58,800 are covered in more normal ice, the type we're familiar with on Earth. 436 00:33:01,880 --> 00:33:05,200 Recently, we've been able to get close enough to see it 437 00:33:05,200 --> 00:33:06,840 in more detail. 438 00:33:06,840 --> 00:33:10,160 And that's revealed something startling. 439 00:33:10,160 --> 00:33:15,200 It might be protecting oceans of liquid water out in space. 440 00:33:18,680 --> 00:33:23,520 Professor Michele Dougherty is a space physicist who explores these outerplanets. 441 00:33:28,200 --> 00:33:30,640 It was Jupiter's moon, Europa, 442 00:33:30,640 --> 00:33:32,920 that first attracted her attention 443 00:33:32,920 --> 00:33:36,880 thanks to a surprising photograph taken by the Galileo spacecraft. 444 00:33:40,640 --> 00:33:43,840 This image shows us what looks like an ice shelf 445 00:33:43,840 --> 00:33:46,560 which is floating on a liquid. 446 00:33:46,560 --> 00:33:50,320 We could almost say it was the Antarctic or Greenland. 447 00:33:50,320 --> 00:33:55,400 What you can clearly see are these icebergs which look as if they're moving around on the surface. 448 00:33:56,200 --> 00:34:00,200 The only way for that to happen is for there to be liquid underneath 449 00:34:00,200 --> 00:34:03,440 that's helping shift them around on the icy surface. 450 00:34:06,800 --> 00:34:09,000 By studying data from Galileo, 451 00:34:09,000 --> 00:34:12,880 scientists reckon that Europa's ice is covering an ocean 452 00:34:12,880 --> 00:34:14,560 of liquid water. 453 00:34:17,800 --> 00:34:21,200 If true, this will be an amazing discovery. 454 00:34:21,200 --> 00:34:26,200 But frustratingly, there's no way yet of penetrating the surface 455 00:34:26,720 --> 00:34:28,480 to confirm it. 456 00:34:35,160 --> 00:34:37,320 However, in 1997, 457 00:34:37,320 --> 00:34:40,240 an unmanned probe called Cassini 458 00:34:40,240 --> 00:34:41,800 was sent into space. 459 00:34:43,360 --> 00:34:48,400 Its mission, to explore Saturn, 700 million miles from Earth. 460 00:34:51,400 --> 00:34:56,280 When it flew by a tiny ice-covered moon called Enceladus, 461 00:34:56,280 --> 00:35:01,080 it gave a reading that Michele and her team simply couldn't explain. 462 00:35:02,640 --> 00:35:07,680 So she asked the mission planners if Cassini could make a closer fly-by. 463 00:35:08,880 --> 00:35:10,560 And this revealed a spectacle 464 00:35:10,560 --> 00:35:12,800 that had never been seen before 465 00:35:12,800 --> 00:35:15,080 anywhere in the solar system. 466 00:35:17,120 --> 00:35:21,080 This is the image we took when we went really close to Enceladus. 467 00:35:21,080 --> 00:35:24,320 You can clearly see this large plume of water vapour 468 00:35:24,320 --> 00:35:27,080 coming off from the south pole. A gorgeous image! 469 00:35:27,080 --> 00:35:32,160 As Cassini has shown us that water definitely exists under Enceladus's ice, 470 00:35:32,960 --> 00:35:37,960 that makes it a fantastic place to search for evidence of extra-terrestrial life. 471 00:35:40,640 --> 00:35:43,760 The reason that this discovery is so amazing 472 00:35:43,760 --> 00:35:48,760 is that it's telling us there's water under the surface of Enceladus 473 00:35:48,960 --> 00:35:52,080 and in the plume itself there is water vapour, 474 00:35:52,080 --> 00:35:53,960 there are ice crystals 475 00:35:53,960 --> 00:35:57,640 and there are organic compounds - nitrogen, carbon, hydrogen - 476 00:35:57,640 --> 00:36:01,280 all the things that you need for the basic building blocks of life. 477 00:36:03,280 --> 00:36:08,160 Michele and her colleagues are currently working on building much smaller probes 478 00:36:08,160 --> 00:36:12,400 that will be able to analyse the plumes jetting out from Enceladus. 479 00:36:13,800 --> 00:36:16,160 They'll look for more evidence of life. 480 00:36:17,680 --> 00:36:22,160 Ice in space may bring us one step closer to finding out 481 00:36:22,160 --> 00:36:25,520 if other life forms have evolved in our solar system. 482 00:36:41,040 --> 00:36:44,000 Although icy environments even on our own planet 483 00:36:44,000 --> 00:36:46,520 seem too hostile to support life, 484 00:36:46,520 --> 00:36:51,160 in fact they can be a very favourable place for life to flourish. 485 00:36:54,560 --> 00:36:58,120 Under the sea ice around the edges of the Antarctic continent, 486 00:36:58,120 --> 00:37:01,560 at temperatures that would kill most living things, 487 00:37:01,560 --> 00:37:04,560 live some of the most intriguing creatures on Earth. 488 00:37:06,160 --> 00:37:09,240 In total, I've been to the Antarctic 13 times. 489 00:37:09,240 --> 00:37:13,480 'At the laboratories of the British Antarctic Survey, 490 00:37:13,480 --> 00:37:16,920 'Professor Lloyd Peck studies these creatures to find out 491 00:37:16,920 --> 00:37:18,640 'just how they survive 492 00:37:18,640 --> 00:37:22,920 'and what makes the icy ocean so advantageous for some forms of life.' 493 00:37:24,040 --> 00:37:26,000 If we move down here, 494 00:37:26,000 --> 00:37:28,560 we can see some of our really special animals. 495 00:37:28,560 --> 00:37:31,120 These little fish are called the plunder fish. 496 00:37:31,120 --> 00:37:33,280 I haven't seen this. 497 00:37:33,280 --> 00:37:37,400 That's a beauty! Is it all right? Yeah, they're fine. 498 00:37:37,400 --> 00:37:41,800 If a predator comes along, they open their mouth, push their gill cases out 499 00:37:41,800 --> 00:37:44,400 and push their spines out to stop being eaten. 500 00:37:44,400 --> 00:37:49,400 They breed in our tank. They're one of the classic types of Antarctic fish. 501 00:37:49,880 --> 00:37:52,960 How cold is it? The water is below zero degrees. 502 00:37:52,960 --> 00:37:55,240 But it's sea water so it doesn't freeze. 503 00:37:55,240 --> 00:37:58,000 What you see here is, those animals living there 504 00:37:58,000 --> 00:38:01,160 are permanently living below zero degrees. 505 00:38:01,160 --> 00:38:04,280 Why don't they freeze? Well, the fish would freeze 506 00:38:04,280 --> 00:38:09,280 except for the fact they've got antifreeze in their blood, their tissues and their bodies. 507 00:38:09,360 --> 00:38:12,520 They need antifreeze to live in these temperatures. 508 00:38:12,520 --> 00:38:17,560 They have antifreeze in their blood? They make their own antifreeze. They have antifreeze proteins. 509 00:38:18,640 --> 00:38:21,560 There's antifreeze everywhere because without it, 510 00:38:21,560 --> 00:38:25,360 ice crystals would grow inside their cells and inside their blood 511 00:38:25,360 --> 00:38:27,400 and it would rip their tissues apart. 512 00:38:29,200 --> 00:38:31,960 OK. I've got another animal here to show you. 513 00:38:31,960 --> 00:38:33,800 This is a sea spider. 514 00:38:33,800 --> 00:38:35,920 Oh, look at him! 515 00:38:35,920 --> 00:38:39,720 In Antarctica, the sea spiders get really big. 516 00:38:39,720 --> 00:38:43,000 The biggest ones are 40 centimetres from leg tip to leg tip. 517 00:38:43,000 --> 00:38:46,240 So that's twice the size of this one? About twice the size. 518 00:38:46,240 --> 00:38:48,840 And the biggest sea spiders in the Antarctic 519 00:38:48,840 --> 00:38:52,640 are a thousand, maybe two thousand, three thousand times heavier 520 00:38:52,640 --> 00:38:56,240 than the biggest sea spiders in Europe. Why do they get so big? 521 00:38:56,240 --> 00:39:00,600 Well, the reason they get big is because it's cold! 522 00:39:00,600 --> 00:39:03,160 Two things happen when sea water gets cold. 523 00:39:03,160 --> 00:39:07,680 One is that the amount of oxygen you get in the water goes up. 524 00:39:07,680 --> 00:39:12,120 There's nearly twice as much oxygen in the sea in Antarctica as in the tropics. 525 00:39:12,120 --> 00:39:17,000 Because it's cold, their metabolic rates run much slower than animals elsewhere. 526 00:39:17,000 --> 00:39:19,400 So it's like live cheaper, grow bigger? 527 00:39:19,400 --> 00:39:22,920 Live cheaper, grow bigger. And it's not just the sea spiders. 528 00:39:22,920 --> 00:39:26,160 This is a 40-arm starfish. 529 00:39:26,160 --> 00:39:30,160 Its Latin name is Labidiaster. Oh, my God! 530 00:39:30,160 --> 00:39:32,000 Have a hold of that. 531 00:39:32,000 --> 00:39:34,520 OK? This is a really small one. 532 00:39:34,520 --> 00:39:39,520 The big ones get up to 70, 80 centimetres across. They're huge. 533 00:39:40,320 --> 00:39:43,880 They're one of the big predators in the Antarctic on the sea bed. 534 00:39:43,880 --> 00:39:48,920 There's his stomach. They crawl over the top of animals, put their stomachs out and eatthem. 535 00:39:50,320 --> 00:39:54,960 What is it about the ice that makes all these weird adaptations and strange animals? 536 00:39:54,960 --> 00:39:58,600 The ice helps keep the temperature constant in the seas. 537 00:39:58,600 --> 00:40:02,360 What it's done is kept that temperature low and constant 538 00:40:02,360 --> 00:40:04,640 for maybe 25 million years. 539 00:40:04,640 --> 00:40:07,000 So it's not just cold, it's also steady. 540 00:40:07,000 --> 00:40:12,000 It is. The Antarctic Ocean is possibly the most constant temperature place on Earth. 541 00:40:12,520 --> 00:40:16,920 And it's been there for such a long time that animals have been able to adapt to it 542 00:40:16,920 --> 00:40:21,440 in a very fine-scaled way, in a way that hasn't happened anywhere else on Earth. 543 00:40:25,240 --> 00:40:28,600 These creatures are the product of a unique eco-system 544 00:40:28,600 --> 00:40:30,880 that revolves around ice. 545 00:40:32,720 --> 00:40:36,080 By studying how they managed not just to adapt, but to thrive, 546 00:40:36,080 --> 00:40:38,920 we can learn about the impact of cold 547 00:40:38,920 --> 00:40:42,240 and how well icy environments can support life. 548 00:40:51,480 --> 00:40:56,160 Antarctica is the coldest, windiest continent on the planet. 549 00:40:57,360 --> 00:41:02,000 It's covered by the largest single mass of ice on Earth. 550 00:41:17,680 --> 00:41:19,800 Back in the 1950s, 551 00:41:19,800 --> 00:41:23,760 a team of scientists set out with a seemingly impossible dream, 552 00:41:23,760 --> 00:41:27,560 to discover how thick the Antarctic ice sheet was 553 00:41:27,560 --> 00:41:30,360 and what might be lying beneath. 554 00:41:33,480 --> 00:41:38,000 Part of that team was glaciologist, Dr Charles Swithinbank. 555 00:41:40,120 --> 00:41:43,040 He's a legend in the world of Antarctic science. 556 00:41:43,040 --> 00:41:47,160 He's spent a lifetime exploring the heart of the white continent. 557 00:41:49,320 --> 00:41:51,400 That's it. That's you? 558 00:41:51,400 --> 00:41:54,600 That's me. I was mad keen and always have been. 559 00:41:54,600 --> 00:41:59,520 Here was a chance of real adventure and real exploring 560 00:41:59,520 --> 00:42:03,560 in a really unknown part of the Antarctic. 561 00:42:06,880 --> 00:42:10,280 It was Charles' job to try to measure the depth of the ice. 562 00:42:11,640 --> 00:42:15,640 Taking a sled loaded with dynamite out onto the ice, 563 00:42:15,640 --> 00:42:20,080 he and his colleagues set off an explosion at the surface. 564 00:42:21,800 --> 00:42:25,440 They measured how long it took for its echo to bounce back. 565 00:42:25,440 --> 00:42:29,520 From this, they could work out how far it had travelled 566 00:42:29,520 --> 00:42:32,160 and how thick the ice sheet was. 567 00:42:34,760 --> 00:42:38,600 We found thicknesses up to 2,500 metres. 568 00:42:38,600 --> 00:42:43,120 That's nothing nowadays. People have found a lot deeper. 569 00:42:43,120 --> 00:42:45,000 But it staggered us 570 00:42:45,000 --> 00:42:48,600 because here we were, walking over solid ice 571 00:42:48,600 --> 00:42:51,440 without any idea how thick it was. 572 00:42:53,480 --> 00:42:56,640 But as it took a day to make one single measurement, 573 00:42:56,640 --> 00:43:00,160 mapping the whole continent was going to take decades. 574 00:43:03,080 --> 00:43:08,120 Until another ice secret was unlocked by American army engineer, Amory Waite. 575 00:43:12,200 --> 00:43:17,200 In the 1950s, experienced pilots were crashing into the Antarctic ice sheet and no-one knew why. 576 00:43:20,920 --> 00:43:25,960 Waite knew the planes' altimeters used radar to measure how high they were above the ground. 577 00:43:27,680 --> 00:43:32,320 He started hitting ice with different frequencies of radio waves 578 00:43:32,320 --> 00:43:36,480 and realised some of them were going straight through the ice. 579 00:43:36,480 --> 00:43:40,600 This could have given the pilots a false reading of their height. 580 00:43:42,680 --> 00:43:45,040 Waite realised that despite being a solid, 581 00:43:45,040 --> 00:43:47,920 ice was transparent to radar. 582 00:43:50,320 --> 00:43:53,440 Once this was known, planes stopped crashing, 583 00:43:53,440 --> 00:43:55,120 saving countless lives. 584 00:43:56,320 --> 00:44:00,280 But it also revolutionised Charles Swithinbank's job 585 00:44:00,280 --> 00:44:04,080 of surveying the Antarctic ice sheet and the land beneath. 586 00:44:06,720 --> 00:44:10,200 His team could now criss-cross the continent in a plane, 587 00:44:10,200 --> 00:44:13,320 using radar to see through the ice 588 00:44:13,320 --> 00:44:16,200 by bouncing radio waves off the bedrock below. 589 00:44:16,200 --> 00:44:21,040 And he could now take hundreds of readings every second. 590 00:44:25,880 --> 00:44:27,760 It was staggeringly exciting 591 00:44:27,760 --> 00:44:31,600 because we were getting a cross-section of the ice sheet as we flew over it. 592 00:44:31,600 --> 00:44:36,640 We went to a number of places where I'd worked on the ground 593 00:44:36,920 --> 00:44:39,600 and dreamed and wondered how thick the ice was. 594 00:44:39,600 --> 00:44:41,840 And in the matter of a minute - 595 00:44:41,840 --> 00:44:45,040 pow! - we'd measured how thick it was. 596 00:44:45,040 --> 00:44:47,160 It was very, very exciting. 597 00:44:48,840 --> 00:44:51,720 Beneath the white and pristine Antarctic surface, 598 00:44:51,720 --> 00:44:54,560 an entire new world was uncovered. 599 00:44:55,640 --> 00:44:59,480 A world made of valleys, mountains and plateaus 600 00:44:59,480 --> 00:45:03,320 hidden in parts by ice more than four kilometres thick. 601 00:45:06,040 --> 00:45:10,600 And all laid bare thanks to discovering another secret of the ice crystal. 602 00:45:20,160 --> 00:45:23,040 While the Antarctic lies on mountainous bedrock, 603 00:45:23,040 --> 00:45:27,320 on the other side of the world, the Arctic is a treacherous ocean 604 00:45:27,320 --> 00:45:29,440 of floating sea ice, 605 00:45:29,440 --> 00:45:33,200 where exploration has often been driven by commerce. 606 00:45:43,080 --> 00:45:48,120 For hundreds of years, sailors searched for a short and lucrative trade route through these waters 607 00:45:48,600 --> 00:45:51,600 between Europe and the Pacific. 608 00:45:51,600 --> 00:45:55,680 One that would be cheaper than the long route via India and China. 609 00:45:55,680 --> 00:45:59,400 The elusive North-West Passage. 610 00:46:04,200 --> 00:46:08,880 For the expedition that found it, there was a prize of thousands of pounds. 611 00:46:10,280 --> 00:46:14,120 I'm interested in the story of one particular expedition. 612 00:46:14,120 --> 00:46:17,520 It was led by a celebrated naval officer, Sir John Franklin. 613 00:46:17,520 --> 00:46:22,600 But it turned out to be the worst disaster in the history of British polar exploration. 614 00:46:25,880 --> 00:46:27,640 What draws me to this story 615 00:46:27,640 --> 00:46:30,440 is that it plays out like a detective mystery 616 00:46:30,440 --> 00:46:32,840 with ice as the key witness. 617 00:46:33,880 --> 00:46:38,920 And some of the clues are here, at the Scott Polar Research Institute. 618 00:46:41,240 --> 00:46:44,600 This is the leader of the expedition, Sir John Franklin. 619 00:46:44,600 --> 00:46:48,000 In 1845, he was already 59 years old. 620 00:46:48,000 --> 00:46:50,920 He'd fought with Nelson at the Battle of Trafalgar. 621 00:46:50,920 --> 00:46:54,560 He'd been to the Arctic three times and mapped thousands of miles of coastline. 622 00:46:54,560 --> 00:46:58,560 The British public had been captivated by stories of how he and his men 623 00:46:58,560 --> 00:47:01,680 staved off hunger by eating their own leather boots. 624 00:47:04,800 --> 00:47:07,080 Franklin was clearly the man for the job. 625 00:47:08,480 --> 00:47:13,480 Before he set off, he arranged to have portraits taken of himself and his senior officers 626 00:47:13,880 --> 00:47:16,320 with the very latest technology. 627 00:47:18,760 --> 00:47:23,040 Curator Heather Lane has these precious early daguerreotypes 628 00:47:23,040 --> 00:47:24,720 for me to see. 629 00:47:24,720 --> 00:47:27,720 If you'd like to pick it up and open it. I'd love to. 630 00:47:27,720 --> 00:47:29,600 Very happy. 631 00:47:29,600 --> 00:47:32,240 And there he is. 632 00:47:32,240 --> 00:47:37,280 Quite extraordinary to think you're seeing him on the day they set off. 633 00:47:40,560 --> 00:47:45,600 'Franklin had assembled a team of experienced officers to sail with him to the Arctic, 634 00:47:48,280 --> 00:47:52,920 They all look quite sure of themselves. Franklin had been sensible. 635 00:47:52,920 --> 00:47:56,520 He's pulled together a team he knows will actually obey orders 636 00:47:56,520 --> 00:47:59,920 in what are likely to be quite difficult circumstances. 637 00:48:04,040 --> 00:48:08,160 In total, 133 men set sail with Franklin from Kent 638 00:48:08,160 --> 00:48:12,080 in two sturdy ships, the Erebus and the Terror, 639 00:48:12,080 --> 00:48:15,760 both of which had seen service in the Polar regions before. 640 00:48:18,360 --> 00:48:21,200 They were expecting to sail from the Atlantic Ocean 641 00:48:21,200 --> 00:48:24,200 through the ice-bound islands of Northern Canada 642 00:48:24,200 --> 00:48:28,720 to the Pacific Ocean, and return within three years. 643 00:48:32,000 --> 00:48:37,040 They'd refitted these ships with state-of-the-art equipment. They were steam-powered, 644 00:48:40,920 --> 00:48:45,400 They really put a huge amount of effort into ensuring 645 00:48:45,400 --> 00:48:50,440 that this was the expedition that was going to make it all the way through the North-West Passage. 646 00:48:51,200 --> 00:48:53,960 Then suddenly, they disappear. 647 00:48:53,960 --> 00:48:56,800 The ice has swallowed this expedition whole. 648 00:48:56,800 --> 00:49:01,800 And it's the beginning of a great Victorian mystery - what has happened to Franklin andhis men? 649 00:49:04,400 --> 00:49:06,480 Over the next few years, 650 00:49:06,480 --> 00:49:10,840 more than 30 rescue missions searched the icy Arctic for survivors 651 00:49:10,840 --> 00:49:12,640 but failed to find any. 652 00:49:15,320 --> 00:49:20,240 It wasn't until 1858 that the likely fate of Franklin's men was confirmed 653 00:49:20,240 --> 00:49:25,280 by a message discovered in a can on a small uninhabited island. 654 00:49:29,400 --> 00:49:31,280 Written by two senior officers, 655 00:49:31,280 --> 00:49:35,920 it announced that Sir John Franklin had died in 1847, 656 00:49:35,920 --> 00:49:37,960 two years after he'd set sail. 657 00:49:39,920 --> 00:49:43,440 Both ships had been abandoned in the ice 658 00:49:43,440 --> 00:49:48,520 and second-in-command Captain Crozier was attempting to lead 105 survivors tosafety. 659 00:49:51,400 --> 00:49:55,840 But why had an expedition with experienced Polar navigators 660 00:49:55,840 --> 00:49:57,760 in state-of-the-art ships, 661 00:49:57,760 --> 00:49:59,680 ended up like this? 662 00:50:00,960 --> 00:50:03,560 Well, although the records end here, 663 00:50:03,560 --> 00:50:06,000 the detective story doesn't. 664 00:50:06,000 --> 00:50:09,840 What I find fascinating about the Franklin story 665 00:50:09,840 --> 00:50:14,080 is it doesn't seem to die. Clues keep on showing up in the ice. 666 00:50:16,560 --> 00:50:20,680 And eventually, it would be the ice that would provide the answer. 667 00:50:28,720 --> 00:50:32,720 In 1986, a team of forensic archaeologists 668 00:50:32,720 --> 00:50:35,840 travelled to Beachy Island in northern Canada. 669 00:50:35,840 --> 00:50:38,640 This was where, in 1850, 670 00:50:38,640 --> 00:50:41,960 a search party had found empty food cans, 671 00:50:41,960 --> 00:50:44,680 evidence that the expedition had wintered here. 672 00:50:47,400 --> 00:50:51,240 And not far from them, three graves. 673 00:50:56,320 --> 00:50:59,640 Over two intense weeks, Dr Owen Beatty and his team 674 00:50:59,640 --> 00:51:02,320 exhumed the bodies of able seaman John Hartnell 675 00:51:02,320 --> 00:51:04,200 and Private William Brain 676 00:51:04,200 --> 00:51:06,680 to try to find out how they'd died. 677 00:51:08,840 --> 00:51:13,440 The forensic team had no idea what to expect. What condition the bodies would be in. 678 00:51:13,440 --> 00:51:16,680 They had to pick-axe their way through the frozen ground 679 00:51:16,680 --> 00:51:21,720 which is what the grave-diggers must have had to do when they buried the bodies in the Arctic winter. 680 00:51:26,440 --> 00:51:30,200 They found that the ice had preserved the bodies almost perfectly. 681 00:51:30,200 --> 00:51:34,360 When they released them, using warm water, 682 00:51:34,360 --> 00:51:39,040 there was so little decay, it was relatively easy to investigate how they'd died. 683 00:51:41,400 --> 00:51:46,400 John Hartnell had had tuberculosis, but he was also incredibly thin. 684 00:51:47,440 --> 00:51:50,760 He had no food in his stomach or intestines. 685 00:51:53,960 --> 00:51:58,960 Scattered around the camp, Beatty had found empty cans that had been soldered with lead. 686 00:51:59,120 --> 00:52:01,920 He put two and two together. 687 00:52:01,920 --> 00:52:04,360 He tested the men's bodies 688 00:52:04,360 --> 00:52:07,600 and found dangerously high levels of lead 689 00:52:07,600 --> 00:52:10,600 in their hair, bones and soft tissue. 690 00:52:13,200 --> 00:52:16,320 To date, about 17 more of Franklin's men 691 00:52:16,320 --> 00:52:19,800 have been found to have had toxic levels of lead in their bones. 692 00:52:22,960 --> 00:52:27,360 New research suggest the lead might not have come from the cans at all 693 00:52:27,360 --> 00:52:32,400 but is more likely to have leeched out of the new lead piping in the ship's water system 694 00:52:32,800 --> 00:52:35,120 and contaminated their water. 695 00:52:41,360 --> 00:52:43,880 Lead poisoning is a horrible way to die. 696 00:52:43,880 --> 00:52:48,480 It paralyses your muscles and eats away at your brain and central nervous system. 697 00:52:48,480 --> 00:52:52,560 So then what you get is disorientation and anorexia. 698 00:52:52,560 --> 00:52:56,680 The worst things that can happen if you're trying to survive an Arctic winter. 699 00:53:10,200 --> 00:53:13,520 We know so much about the tragic fate of Franklin and his men 700 00:53:13,520 --> 00:53:16,560 because of the miraculous ability of ice to preserve. 701 00:53:16,560 --> 00:53:20,680 But it doesn't just preserve history by slowing down decomposition. 702 00:53:20,680 --> 00:53:25,120 It also has the ability to preserve something much more delicate than bodies. 703 00:53:25,120 --> 00:53:28,920 And one that might prove even more valuable. 704 00:53:36,040 --> 00:53:40,680 In the Antarctic, teams of scientists have been reaching back into history. 705 00:53:43,560 --> 00:53:47,000 They've been drilling thousands of metres into the ice sheet 706 00:53:47,000 --> 00:53:51,000 to remove columns of ice that can bear witness to our past. 707 00:53:54,720 --> 00:53:59,720 These ice cores preserve air from hundreds of thousands of years ago. 708 00:54:02,720 --> 00:54:06,920 They're helping us understand one of the most complex aspects of nature, 709 00:54:06,920 --> 00:54:08,600 our climate. 710 00:54:13,680 --> 00:54:16,040 I'm with Dr Robert Mulvaney 711 00:54:16,040 --> 00:54:19,760 at the British Antarctic Survey's ice core freezer in Cambridge 712 00:54:19,760 --> 00:54:21,720 where he studies this ancient ice. 713 00:54:27,800 --> 00:54:29,480 So if I take a piece of this out. 714 00:54:29,480 --> 00:54:31,880 Let's put that down on here. 715 00:54:35,760 --> 00:54:38,800 You can probably make out the tiny air balls in there. 716 00:54:38,800 --> 00:54:42,920 It's the magic of the ice that it's able to take these air molecules 717 00:54:42,920 --> 00:54:47,960 into its matrix without altering them, and release them back to us later. A storage box. Yes. 718 00:54:48,240 --> 00:54:52,440 What we'll do is cut a piece off and see if we can see the air bubbles. 719 00:54:53,440 --> 00:54:56,240 The deeper you go, the older the ice gets. 720 00:54:56,240 --> 00:54:59,440 Scientists are able to date each layer of ice 721 00:54:59,440 --> 00:55:02,440 from chemical markers within the ice crystal itself. 722 00:55:03,840 --> 00:55:08,400 It's starting to clear. I think you can see the air bubbles in that. 723 00:55:08,400 --> 00:55:11,000 Fantastic, isn't it? 724 00:55:11,000 --> 00:55:13,200 This air is about 1,000 years old! 725 00:55:13,200 --> 00:55:16,280 So when they were invading Britain in 1066, 726 00:55:16,280 --> 00:55:18,960 this is the air they would have been breathing! 727 00:55:18,960 --> 00:55:21,320 The Saxons and Normans. Saxons and Normans. 728 00:55:21,320 --> 00:55:23,120 That is wild! It is, isn't it? 729 00:55:25,120 --> 00:55:27,720 This is quite a long way down in the ice sheet. 730 00:55:27,720 --> 00:55:32,240 This is about 80,000 years old. You can probably see the air in that. 731 00:55:32,240 --> 00:55:35,840 So this is before... This fell as snow and trapped air 732 00:55:35,840 --> 00:55:38,080 before human civilisation? 733 00:55:38,080 --> 00:55:40,920 That's right. Fascinating, isn't it? 734 00:55:43,120 --> 00:55:45,600 As well as preserving past atmospheres, 735 00:55:45,600 --> 00:55:49,000 the ice crystals preserve another important secret. 736 00:55:49,000 --> 00:55:52,280 Tiny variations in their chemistry 737 00:55:52,280 --> 00:55:56,120 reveal the temperature of the climate when they originally formed. 738 00:55:56,120 --> 00:55:59,840 This has allowed us to see in more detail than ever before 739 00:55:59,840 --> 00:56:02,880 how our climate has changed throughout history. 740 00:56:05,320 --> 00:56:07,880 It's also enabled us to explore a link 741 00:56:07,880 --> 00:56:11,520 between temperature and levels of atmospheric carbon dioxide. 742 00:56:14,280 --> 00:56:18,320 Our oldest ice core goes back 800,000 years. 743 00:56:18,320 --> 00:56:21,400 In that period, we've been in and out of an ice age eight times. 744 00:56:21,400 --> 00:56:26,400 And all through that period, the atmosphere and the temperature have been very closelylinked. 745 00:56:26,880 --> 00:56:31,920 So as we go into an ice age, the levels of carbon dioxide, greenhouse gases, decrease, 746 00:56:31,960 --> 00:56:34,960 and as come out of an ice age they start to increase. 747 00:56:34,960 --> 00:56:40,040 The ice core record shows that there was a strong relationship between temperature and carbondioxide. 748 00:56:42,200 --> 00:56:47,120 They've moved in tandem throughout history for 800,000 years. 749 00:56:49,840 --> 00:56:54,880 To many scientists, this historical record supports current theories of global warming, 750 00:56:55,280 --> 00:56:59,680 suggesting that if carbon dioxide levels rise, as they're doing today, 751 00:56:59,680 --> 00:57:02,440 temperatures will also rise. 752 00:57:02,440 --> 00:57:06,600 It's a warning from the past that many find hard to ignore. 753 00:57:06,600 --> 00:57:10,080 And all because of the unique ability of ice 754 00:57:10,080 --> 00:57:12,680 to capture air and preserve it. 755 00:57:21,720 --> 00:57:25,760 Ice is one of the most enigmatic substances in nature. 756 00:57:25,760 --> 00:57:30,000 A solid can pass through it, without leaving a trace. 757 00:57:32,280 --> 00:57:35,280 It can shatter rock and sculpt our planet. 758 00:57:38,360 --> 00:57:42,000 In space, its protective shell may conceal life forms 759 00:57:42,000 --> 00:57:44,040 just waiting to be discovered. 760 00:57:46,200 --> 00:57:48,760 It can last for millions of years 761 00:57:48,760 --> 00:57:51,480 or just melt in an instant. 762 00:57:54,840 --> 00:57:57,680 I'm drawn to ice because of its contradictions. 763 00:57:57,680 --> 00:58:02,720 Although is seems so fragile, it's capable of carving out landscapes and preserving histories, 764 00:58:03,080 --> 00:58:06,200 even giving us warnings about the future of our world. 765 00:58:06,200 --> 00:58:09,280 But what's really struck me about making this programme 766 00:58:09,280 --> 00:58:11,960 is discovering where all that power comes from. 767 00:58:11,960 --> 00:58:16,360 Because actually, the very thing that makes ice seem fragile and vulnerable, 768 00:58:16,360 --> 00:58:19,400 the fact that it's always on the point of disappearing 769 00:58:19,400 --> 00:58:22,360 turns out to be the source of all its strength.