1 00:00:06,527 --> 00:00:07,960 DAVID ATTENBOROUGH: The power of the sun 2 00:00:08,047 --> 00:00:11,403 drives the seasons, transforming our planet. 3 00:00:12,967 --> 00:00:16,403 Vast movements of ocean and air currents 4 00:00:16,487 --> 00:00:19,638 bring dramatic change throughout the year. 5 00:00:23,687 --> 00:00:27,600 And in a few special places, these seasonal changes 6 00:00:27,687 --> 00:00:31,999 create some of the greatest wildlife spectacles on Earth. 7 00:00:35,687 --> 00:00:40,602 Here in the Arctic each summer, the sun begins to melt the winter ice. 8 00:00:43,007 --> 00:00:47,046 Nearly three million square miles of ice will disappear, 9 00:00:50,607 --> 00:00:55,840 opening up a narrow window of opportunity for millions of animals. 10 00:01:04,647 --> 00:01:08,959 For many, it's their best chance to feed and breed. 11 00:01:13,207 --> 00:01:18,076 But for polar bears, it's the hardest time of the year. 12 00:01:18,167 --> 00:01:23,195 They have to survive the greatest seasonal change on the planet. 13 00:01:44,927 --> 00:01:47,441 Winter in the Arctic. 14 00:01:48,327 --> 00:01:51,603 The northern lights flicker across the sky. 15 00:01:55,127 --> 00:01:57,721 It's a land of continuous night 16 00:01:58,087 --> 00:02:00,965 where temperatures plummet to minus 40. 17 00:02:10,647 --> 00:02:13,639 Polar bears are in their element, 18 00:02:13,727 --> 00:02:16,844 hunting for seals on the frozen sea. 19 00:02:18,647 --> 00:02:21,605 But the long night is coming to an end. 20 00:02:21,687 --> 00:02:24,326 In February the sun rises 21 00:02:24,407 --> 00:02:27,205 for the first time in four months. 22 00:02:34,767 --> 00:02:37,565 In the coming weeks the strength of the sun 23 00:02:37,647 --> 00:02:40,605 will power an enormous change. 24 00:02:40,687 --> 00:02:44,396 But for now its rays offer only a little warmth. 25 00:02:57,087 --> 00:03:02,241 Despite the sun's return, six million square miles of the planet's far north 26 00:03:02,327 --> 00:03:04,716 is still cloaked in ice. 27 00:03:08,367 --> 00:03:10,756 Deep snow covers the mountains. 28 00:03:21,207 --> 00:03:25,883 Even the sea is frozen solid, many metres deep. 29 00:03:37,167 --> 00:03:41,399 Groups of ringed seals haul out through holes in the ice 30 00:03:41,487 --> 00:03:43,682 to bask in the weak sunlight. 31 00:03:43,767 --> 00:03:45,803 (YELPING) 32 00:03:45,887 --> 00:03:48,924 But they are vulnerable and have to keep a lookout. 33 00:03:49,007 --> 00:03:53,125 With the sea still frozen, it's easier for predators to get close, 34 00:03:53,207 --> 00:03:56,324 and the seal's greatest enemy is the polar bear. 35 00:04:02,527 --> 00:04:06,406 A mother bear and her four-month-old cub are hunting. 36 00:04:08,487 --> 00:04:11,877 Seals make up most of the bear's diet, 37 00:04:11,967 --> 00:04:15,562 and to find them she must lead her youngster out onto the ice 38 00:04:15,647 --> 00:04:17,603 for the first time. 39 00:04:22,967 --> 00:04:27,279 Scientists, looking at how a changing climate is affecting bears, 40 00:04:27,367 --> 00:04:30,882 have fitted the female with a radio collar. 41 00:04:32,327 --> 00:04:34,124 The ice here is thinner, 42 00:04:34,207 --> 00:04:37,802 and she must spread her weight to avoid breaking through. 43 00:04:42,087 --> 00:04:44,920 For her cub, it's all just a game. 44 00:05:04,727 --> 00:05:09,198 By sticking close to Mum, he'll learn how she hunts for seals, 45 00:05:09,287 --> 00:05:12,120 a critical lesson for his future survival. 46 00:05:17,807 --> 00:05:22,039 At this time of year the frozen Arctic is empty of life 47 00:05:22,127 --> 00:05:25,358 and only a few hardy residents can survive. 48 00:05:26,927 --> 00:05:31,398 For a female arctic fox, the winter has been a time of hunger. 49 00:05:31,487 --> 00:05:34,843 Food is scarce and she's had to wander far and wide, 50 00:05:34,927 --> 00:05:37,725 scavenging from the remains of bear kills. 51 00:05:43,807 --> 00:05:45,081 (YELPING) 52 00:05:50,567 --> 00:05:53,286 But her fortunes are changing. 53 00:05:53,367 --> 00:05:56,484 A dead reindeer is a lucky find. 54 00:05:58,287 --> 00:06:00,562 If no other scavengers come along, 55 00:06:00,647 --> 00:06:03,923 this could sustain her for the rest of the winter. 56 00:06:20,767 --> 00:06:25,045 With the sea frozen, polar bears are busy hunting. 57 00:06:26,287 --> 00:06:28,596 This bear has caught a seal. 58 00:06:28,687 --> 00:06:31,804 He waited for it to surface through a hole in the ice 59 00:06:31,887 --> 00:06:34,447 and his patience has been rewarded. 60 00:06:36,287 --> 00:06:41,315 He must catch a seal about once a week, and this is the best hunting season. 61 00:06:41,407 --> 00:06:43,967 As long as there is sea ice the bears won't go hungry, 62 00:06:44,047 --> 00:06:48,802 as walking on the ice is the easiest way for a bear to get close to a seal. 63 00:06:55,327 --> 00:07:00,037 But the ice will soon start to break up and hunting will get harder. 64 00:07:00,127 --> 00:07:02,277 The calories the bear takes in now 65 00:07:02,367 --> 00:07:05,359 will have to see him through hard times ahead. 66 00:07:08,767 --> 00:07:12,840 For polar bears it's the survival of the fattest. 67 00:07:16,527 --> 00:07:20,281 At this time of year there are still only five hours of daylight. 68 00:07:20,367 --> 00:07:25,395 But as the sun rises higher, each day lasts 40 minutes longer. 69 00:07:32,807 --> 00:07:35,685 It's March, and with increasing sunlight 70 00:07:35,767 --> 00:07:39,840 the first in a huge wave of migrants are arriving. 71 00:07:49,447 --> 00:07:54,441 Millions of seabirds are travelling north to reach the frozen coast. 72 00:08:01,167 --> 00:08:04,398 Huge flocks of little auks and guillemots 73 00:08:04,487 --> 00:08:08,560 fly across many miles of ice from the nearest open water. 74 00:08:17,247 --> 00:08:21,718 Their destination is the still-frozen sea cliffs. 75 00:08:21,807 --> 00:08:24,241 It's an inhospitable place, 76 00:08:24,327 --> 00:08:28,036 but in a few weeks everything here will change. 77 00:08:37,167 --> 00:08:41,718 It pays to be early, even though the snow has yet to melt. 78 00:08:41,807 --> 00:08:46,483 The first arrivals get the best nesting ledges and a head start. 79 00:08:46,567 --> 00:08:47,636 (SQUAWKING) 80 00:08:47,727 --> 00:08:53,165 They have just 50 days from laying their eggs to raise their chicks. 81 00:08:54,927 --> 00:08:56,440 (SQUAWKING) 82 00:09:00,767 --> 00:09:05,124 The Arctic's silent wilderness is coming to life. 83 00:09:16,487 --> 00:09:21,561 It's three months since the sun's return and its power is growing daily. 84 00:09:23,527 --> 00:09:26,963 The air temperature rises slowly 85 00:09:27,047 --> 00:09:32,360 and once above zero, at long last, the melt begins. 86 00:09:52,807 --> 00:09:58,404 Melting snow feeds freshwater streams which pour off the land. 87 00:09:59,527 --> 00:10:04,999 In just a few short days, the melt unveils a whole new landscape. 88 00:10:32,127 --> 00:10:36,040 The coastal cliffs now teem with nesting seabirds, 89 00:10:36,127 --> 00:10:40,518 and it's not long before they attract unwelcome attention. 90 00:10:41,687 --> 00:10:45,760 The fox's white winter coat has disappeared with the snow. 91 00:10:46,807 --> 00:10:51,927 Her new camouflage will allow her to change from scavenger to hunter. 92 00:10:52,207 --> 00:10:56,359 The short summer will be her best chance to raise a family. 93 00:11:10,967 --> 00:11:14,118 The snow may be disappearing from the land, 94 00:11:15,847 --> 00:11:19,283 but the sea ice has yet to melt. 95 00:11:27,047 --> 00:11:30,517 The coastline is still locked in ice. 96 00:11:36,327 --> 00:11:37,919 The islands of the Arctic 97 00:11:38,007 --> 00:11:42,398 are surrounded by thousands of miles of white frozen ocean. 98 00:11:44,367 --> 00:11:47,803 Because the sea ice is so thick, it won't begin to break up 99 00:11:47,887 --> 00:11:51,960 until the temperature stays above zero for a number of days. 100 00:11:52,927 --> 00:11:57,284 Until then, few creatures can penetrate this icy barrier. 101 00:12:03,567 --> 00:12:07,446 The sun reflects from the white frozen sea, 102 00:12:07,527 --> 00:12:10,837 creating a desert of icy mirage. 103 00:12:24,767 --> 00:12:28,476 The bear can still walk on the ice to hunt for seals, 104 00:12:28,567 --> 00:12:30,558 but not for much longer. 105 00:12:30,647 --> 00:12:33,605 It's getting warmer by the day. 106 00:12:55,007 --> 00:12:59,285 The bear's world is about to melt away. 107 00:13:13,447 --> 00:13:18,601 It's now June and the sun beats down 24 hours a day. 108 00:13:18,887 --> 00:13:22,880 The temperature remains constant above zero degrees. 109 00:13:22,967 --> 00:13:25,401 The frozen sea begins to melt. 110 00:13:27,647 --> 00:13:32,198 Pools form across the surface, absorbing more of the sun's heat, 111 00:13:32,287 --> 00:13:34,198 speeding the thaw. 112 00:13:42,847 --> 00:13:46,237 Sunlight penetrates the frozen surface, 113 00:13:46,327 --> 00:13:50,161 illuminating a strange world beneath the ice. 114 00:13:56,607 --> 00:13:59,519 The frozen barrier has split. 115 00:14:07,087 --> 00:14:11,683 Mysterious voices echo against the icy ceiling. 116 00:14:16,607 --> 00:14:21,635 Giant cracks, or leads, form at weak points, 117 00:14:21,727 --> 00:14:25,720 creating a pathway for new arrivals. 118 00:14:37,247 --> 00:14:38,885 Narwhal. 119 00:14:55,407 --> 00:15:00,481 Known as the arctic unicorn because of their strange spiral tusks, 120 00:15:00,567 --> 00:15:03,957 narwhal are some of the most secretive and elusive animals 121 00:15:04,047 --> 00:15:06,607 in the world's oceans. 122 00:15:06,687 --> 00:15:11,761 The leads provide passage for thousands of these mysterious whales. 123 00:15:13,647 --> 00:15:16,639 Each summer they travel 600 miles north, 124 00:15:16,727 --> 00:15:21,403 navigating through the ice to reach rich fishing grounds. 125 00:15:24,167 --> 00:15:28,445 More whales travel along the edge of the ice where it meets the open sea, 126 00:15:28,527 --> 00:15:31,166 to search for the openings of leads. 127 00:15:44,767 --> 00:15:49,363 It's a hazardous journey. As mammals, they need air to breath 128 00:15:49,447 --> 00:15:53,201 and if the ice closes above them they could suffocate. 129 00:16:22,847 --> 00:16:26,317 They're looking for holes in the ice where they can surface. 130 00:16:26,407 --> 00:16:29,877 A single breath will last them for 1 5 minutes. 131 00:16:32,207 --> 00:16:37,361 The further they travel, the harder it becomes to find holes in the ice. 132 00:16:45,807 --> 00:16:49,163 They snatch a breath and then travel on. 133 00:16:55,567 --> 00:17:00,004 But ahead, the ice forms an impenetrable barrier. 134 00:17:14,847 --> 00:17:17,964 The narwhal use their heads and their long tusks 135 00:17:18,047 --> 00:17:21,642 to break the ice and enlarge the breathing holes. 136 00:17:29,367 --> 00:17:33,758 For now they've reached a dead end and must wait. 137 00:17:33,847 --> 00:17:37,476 The ice will need to melt further if they are to continue. 138 00:17:39,047 --> 00:17:42,881 All across the Arctic the sea ice is beginning to retreat. 139 00:17:45,247 --> 00:17:48,239 The leads widen, forming tracts of open water. 140 00:17:48,327 --> 00:17:52,605 Wind and ocean currents shift the loosening ice, breaking it up. 141 00:17:56,647 --> 00:18:01,801 As the ice melts, thousands of miles of open ocean become accessible, 142 00:18:01,887 --> 00:18:05,721 providing a bonanza for millions of seabirds. 143 00:18:14,887 --> 00:18:18,118 In just four weeks a colony of guillemots 144 00:18:18,207 --> 00:18:22,758 can devour one and a half million tonnes of arctic fish. 145 00:18:29,407 --> 00:18:33,764 As the ice melts, their journey to their feeding grounds in the open sea 146 00:18:33,847 --> 00:18:36,156 shortens by the day. 147 00:18:41,767 --> 00:18:44,406 They gather at the edge of the retreating ice 148 00:18:44,487 --> 00:18:47,604 and dive to hunt for arctic cod and capelin. 149 00:19:02,607 --> 00:19:06,600 The shoals are found 80 metres down in the murky depths, 150 00:19:06,687 --> 00:19:10,919 and the guillemots must hold their breath for nearly two minutes. 151 00:19:21,007 --> 00:19:24,716 With their crops stuffed with fish, they return to the colony 152 00:19:24,807 --> 00:19:27,162 to feed their hungry youngsters. 153 00:19:28,527 --> 00:19:29,846 (YELPING) 154 00:19:35,807 --> 00:19:40,835 With 24 hours of daylight, they go on fishing around the clock. 155 00:19:53,287 --> 00:19:57,166 Warmed by the sun and driven by winds and currents, 156 00:19:57,247 --> 00:19:59,841 the sea ice is now fragmenting. 157 00:20:04,967 --> 00:20:08,437 That is a big problem if you need the ice to hunt from. 158 00:20:12,087 --> 00:20:16,524 A polar bear can smell a seal from over a mile away. 159 00:20:17,727 --> 00:20:18,955 (SNIFFS) 160 00:20:20,607 --> 00:20:23,360 But the prey he depends on is hard to find 161 00:20:23,447 --> 00:20:25,961 in this constantly moving landscape. 162 00:20:33,887 --> 00:20:38,199 He must take to the water to navigate through the drifting maze of ice. 163 00:20:39,607 --> 00:20:43,919 Bears are excellent swimmers, but he's no match for a seal. 164 00:20:46,087 --> 00:20:49,841 As the ice melts, finding seals gets harder 165 00:20:49,927 --> 00:20:54,125 and with more open water, it's easier for a seal to escape. 166 00:21:08,967 --> 00:21:12,198 The melt has caused a shift in power. 167 00:21:12,287 --> 00:21:15,006 Now it's ''advantage seal''. 168 00:21:24,767 --> 00:21:29,761 The bear's chance has slipped away, and his hunger grows. 169 00:21:39,847 --> 00:21:41,644 The ice barrier broken, 170 00:21:41,727 --> 00:21:45,561 strange marine visitors begin to arrive. 171 00:22:03,327 --> 00:22:08,003 They've swum 600 miles to get here, and with the ice gone 172 00:22:08,087 --> 00:22:12,239 they can make their way into the shallows of freshwater estuaries. 173 00:22:24,287 --> 00:22:25,720 (CLICKING) 174 00:22:25,807 --> 00:22:27,798 Beluga whales. 175 00:22:35,167 --> 00:22:37,727 As more and more belugas arrive, 176 00:22:37,807 --> 00:22:40,799 a strange annual ritual begins. 177 00:22:43,407 --> 00:22:47,082 For belugas, this is a very special event. 178 00:22:56,447 --> 00:23:00,998 The violent thrashing against the river bed loosens their year-old skin 179 00:23:01,087 --> 00:23:02,998 and rids them of unwelcome parasites 180 00:23:03,087 --> 00:23:05,885 they may have picked up on their journey. 181 00:23:18,367 --> 00:23:21,837 In freshwater, warmed by the strengthening sun 182 00:23:21,927 --> 00:23:25,078 and with the smooth pebbles in the shallows to rub against, 183 00:23:25,167 --> 00:23:27,601 the whales whistle with pleasure. 184 00:23:34,127 --> 00:23:36,846 (ALL WHISTLING) 185 00:23:52,007 --> 00:23:55,363 But the ice-free summer will be short. 186 00:23:55,447 --> 00:24:00,237 The whales can only enjoy their arctic spa for two weeks. 187 00:24:01,327 --> 00:24:04,000 Soon the belugas must leave the shallows 188 00:24:04,087 --> 00:24:06,442 and make the most of what's left of the summer 189 00:24:06,527 --> 00:24:09,280 to hunt the shoals of arctic fish. 190 00:24:16,127 --> 00:24:17,765 It's early July, 191 00:24:17,847 --> 00:24:22,045 and at the bird cliff the fox has caught a nesting fulmar. 192 00:24:27,207 --> 00:24:30,836 She has a family now, eight tiny mouths to feed, 193 00:24:30,927 --> 00:24:33,760 and one bird is not enough to go round. 194 00:24:44,767 --> 00:24:46,917 The cubs bicker over their dinner. 195 00:24:47,007 --> 00:24:50,363 They're only three weeks old and in just another two weeks 196 00:24:50,447 --> 00:24:53,200 they'll have to be ready to fend for themselves. 197 00:24:57,487 --> 00:24:58,636 (YELPING) 198 00:24:58,727 --> 00:25:03,676 The winter ahead will be so harsh that only two of these eight cubs 199 00:25:03,767 --> 00:25:07,442 are likely to gain enough weight to survive. 200 00:25:07,527 --> 00:25:10,519 Their lives depend on every mouthful. 201 00:25:12,407 --> 00:25:13,681 (YELPING) 202 00:25:14,887 --> 00:25:18,721 When food is scarce the most dominant cub will feed. 203 00:25:20,167 --> 00:25:22,635 And the smallest will go hungry. 204 00:25:32,327 --> 00:25:36,479 The seabirds have been working round the clock to keep their chicks fed 205 00:25:36,567 --> 00:25:40,606 and to prepare them for the first big challenge of their lives. 206 00:25:40,687 --> 00:25:42,359 If they are to escape the winter, 207 00:25:42,447 --> 00:25:46,759 they'll have to leave the cliffs right away, and get far out to sea. 208 00:25:48,687 --> 00:25:51,724 But it's only been 20 days since they hatched 209 00:25:51,807 --> 00:25:55,197 and their wings are still too weak for them to fly. 210 00:25:55,887 --> 00:25:58,355 So far their feet have never left the ground 211 00:25:58,447 --> 00:26:02,042 and there is only one way down to the safety of the sea, 212 00:26:03,127 --> 00:26:05,436 300 metres below. 213 00:26:20,607 --> 00:26:26,125 Reluctantly, the chicks take a few nervous steps towards the edge. 214 00:26:33,607 --> 00:26:36,440 Encouraged by a gentle nudge, 215 00:26:38,287 --> 00:26:40,847 he leaps into the unknown. 216 00:26:51,647 --> 00:26:56,562 Dad follows right behind him, reassuringly calling to his chick. 217 00:26:57,447 --> 00:26:58,960 (SQUAWKING) 218 00:27:08,487 --> 00:27:09,920 Made it. 219 00:27:32,447 --> 00:27:37,157 The landings may not be stylish, but at least they're on target. 220 00:27:45,807 --> 00:27:47,320 (SQUAWKING) 221 00:27:52,367 --> 00:27:57,521 It's easy to misjudge the distance and some fall short of the water. 222 00:27:58,007 --> 00:28:01,124 But even now, Dad sticks close by. 223 00:28:05,487 --> 00:28:08,718 He encourages his chick to take the last few steps 224 00:28:08,807 --> 00:28:11,719 towards the safety of the waves. 225 00:28:11,807 --> 00:28:15,641 But some chicks land a long way from the water. 226 00:28:23,407 --> 00:28:26,365 They're sturdy enough to survive the fall, 227 00:28:26,447 --> 00:28:29,519 but this is no place to be left alone. 228 00:28:41,247 --> 00:28:44,876 For the mother fox it's easy pickings. 229 00:28:55,327 --> 00:28:58,399 With so many free meals falling from the sky, 230 00:28:58,487 --> 00:29:01,604 she runs from one kill to the next. 231 00:29:18,047 --> 00:29:21,084 The chicks will be jumping for only three days, 232 00:29:21,167 --> 00:29:24,204 so she must make the most of this bonanza. 233 00:29:24,287 --> 00:29:27,438 The survival of her own family depends on it. 234 00:29:56,847 --> 00:30:00,396 With more chicks than she can possibly carry, 235 00:30:00,487 --> 00:30:02,955 the mother fox has to be clever. 236 00:30:07,247 --> 00:30:10,557 What her family can't eat now, she buries. 237 00:30:10,647 --> 00:30:13,559 For the days ahead she'll have a well-stocked larder, 238 00:30:13,647 --> 00:30:16,400 enough for all eight of her cubs. 239 00:30:25,127 --> 00:30:29,803 Their bellies now full at last, the cubs can relax in the sun. 240 00:30:42,847 --> 00:30:47,921 For the guillemot chicks that survive, the ordeal has only just begun. 241 00:30:48,007 --> 00:30:53,001 They must retreat south 600 miles, beyond the reach of winter. 242 00:30:53,687 --> 00:30:57,521 But the youngsters can't fly yet, their wings aren't strong enough. 243 00:30:57,607 --> 00:31:01,964 So, led by their parents, they'll have to swim. 244 00:31:02,047 --> 00:31:03,480 (SQUAWKING) 245 00:31:15,407 --> 00:31:19,161 At the height of summer even the permanent ice caps 246 00:31:19,247 --> 00:31:21,807 are touched by the power of the sun. 247 00:31:26,247 --> 00:31:30,001 Melt-water, channelled down from high on these ice caps, 248 00:31:30,087 --> 00:31:33,841 pours over a precipice where the ice meets the ocean. 249 00:31:35,247 --> 00:31:37,807 Along this 200-mile wall of ice, 250 00:31:37,887 --> 00:31:42,085 a thousand freshwater cascades plummet into the sea. 251 00:32:00,287 --> 00:32:05,042 As July draws on, the great melt reaches its peak. 252 00:32:11,527 --> 00:32:16,237 The greatest seasonal change on the planet has taken place. 253 00:32:29,807 --> 00:32:33,720 The sea ice that once extended all the way to the horizon 254 00:32:33,807 --> 00:32:35,957 is now open ocean. 255 00:32:38,847 --> 00:32:44,001 In just three months, the sun has won its battle with the ice. 256 00:32:46,727 --> 00:32:51,118 Over two and a half million square miles of ice has melted away, 257 00:32:51,207 --> 00:32:55,883 uncovering thousands of islands surrounded by open ocean. 258 00:32:55,967 --> 00:33:00,324 But in recent years, the scale of this melt has been growing. 259 00:33:02,407 --> 00:33:06,286 And for one animal this is a critical issue. 260 00:33:22,767 --> 00:33:25,804 A mother bear and her adolescent cub 261 00:33:25,887 --> 00:33:28,765 rest on a fragment of sea ice. 262 00:33:29,447 --> 00:33:33,201 With the melt, they're forced to swim ever-greater distances 263 00:33:33,287 --> 00:33:35,243 to hunt for seals. 264 00:33:39,167 --> 00:33:43,763 Their arctic home is increasingly vulnerable to a changing climate, 265 00:33:43,847 --> 00:33:47,476 and this year there has been even less ice than normal. 266 00:33:53,487 --> 00:33:56,684 If future melts are as extreme as this one, 267 00:33:56,767 --> 00:34:01,761 bears like these may starve or drown, lost at sea. 268 00:34:08,967 --> 00:34:14,200 This is one of the last pieces of ice now adrift in the open ocean. 269 00:34:14,887 --> 00:34:19,085 The polar bear's icy world has melted away. 270 00:34:29,687 --> 00:34:34,807 For many others the open water provides the greatest feast of the year. 271 00:34:35,887 --> 00:34:38,321 The narwhal have made it through the ice. 272 00:34:38,407 --> 00:34:42,798 They gather in bays where they can hunt for arctic cod and squid. 273 00:34:56,367 --> 00:34:59,723 Here they are joined by other ocean migrants. 274 00:35:03,767 --> 00:35:05,723 Bowhead whales. 275 00:35:06,967 --> 00:35:11,916 These 1 00-tonne giants feed on millions of tiny plankton 276 00:35:12,007 --> 00:35:14,646 that flourish in the sunlit waters. 277 00:35:25,687 --> 00:35:28,406 Belugas have come for the rich fishing 278 00:35:28,487 --> 00:35:31,604 and rest on the surface between dives. 279 00:35:39,767 --> 00:35:43,362 Even on the sea bed there is plenty on the menu. 280 00:35:53,767 --> 00:35:57,043 Two tonnes of pulsating blubber 281 00:35:57,127 --> 00:35:59,960 forages for clams in the sediment. 282 00:36:00,047 --> 00:36:02,959 Walrus are year-round residents of the Arctic, 283 00:36:03,047 --> 00:36:05,686 following the ebb and flow of the ice. 284 00:36:07,047 --> 00:36:11,438 In the open summer waters they can reach huge areas of the ocean floor, 285 00:36:11,527 --> 00:36:14,803 rich feeding grounds for these giant seals. 286 00:36:17,207 --> 00:36:20,756 They hoover up clams with their rubbery lips. 287 00:36:20,847 --> 00:36:26,160 A single walrus can eat up to 4,000 clams in one 1 0-minute dive. 288 00:36:34,647 --> 00:36:37,559 Bellies full, they come up for air. 289 00:36:52,087 --> 00:36:56,877 With the sea ice gone, the walrus haul out on dry land to rest. 290 00:36:57,807 --> 00:37:00,241 (BELLOWING) 291 00:37:00,327 --> 00:37:03,160 They're used to huddling together to keep warm, 292 00:37:03,247 --> 00:37:06,796 and even now that it's 1 2 degrees above freezing, 293 00:37:06,887 --> 00:37:09,685 they prefer to stick close together. 294 00:37:09,767 --> 00:37:13,760 In the warmth of the sun, the walrus begin to shed their old skin, 295 00:37:13,847 --> 00:37:16,236 and they spend hours scratching. 296 00:37:19,367 --> 00:37:22,803 Some places are harder to reach than others. 297 00:37:26,087 --> 00:37:27,076 (GRUNTING) 298 00:37:27,167 --> 00:37:32,116 These irritations make them bad-tempered and arguments often break out. 299 00:37:32,207 --> 00:37:34,482 (BELLOWING) 300 00:37:40,007 --> 00:37:41,918 (SNORTING) 301 00:37:45,247 --> 00:37:49,718 Spitting, stabbing and bellowing iron out any disagreements. 302 00:37:51,607 --> 00:37:53,996 (SNORTING) 303 00:37:55,407 --> 00:38:00,356 All disputes settled, a peace of sorts returns once more. 304 00:38:06,967 --> 00:38:11,358 Digesting a belly full of clams generates a lot of wind, 305 00:38:11,447 --> 00:38:16,043 making walrus colonies very fragrant places. 306 00:38:17,447 --> 00:38:20,519 (FARTING) 307 00:38:35,207 --> 00:38:38,404 Fed by the abundant supply of guillemot chicks, 308 00:38:38,487 --> 00:38:42,958 all eight fox cubs seem to have boundless energy. 309 00:38:43,047 --> 00:38:46,960 Soon they will be ready to face the world without their mother. 310 00:38:57,207 --> 00:39:00,199 In just five weeks she's raised her cubs, 311 00:39:00,287 --> 00:39:02,926 making the most of the short summer. 312 00:39:09,327 --> 00:39:13,206 The mother fox has won her race against time. 313 00:39:18,167 --> 00:39:23,287 Between June and July, the Arctic is the land of the midnight sun. 314 00:39:23,567 --> 00:39:26,957 An empty wilderness has been transformed. 315 00:39:31,807 --> 00:39:34,162 (CHIRPING) 316 00:39:52,527 --> 00:39:56,645 The once-frozen ocean is now bursting with life, 317 00:39:56,727 --> 00:39:59,685 as all the animals enjoy the summer feast. 318 00:40:05,007 --> 00:40:06,804 (CLICKING) 319 00:40:30,487 --> 00:40:34,241 But polar bears aren't so fortunate. 320 00:40:36,447 --> 00:40:41,362 With no sea ice to hunt on, they're now trapped on dry land. 321 00:40:44,087 --> 00:40:48,285 A hungry bear will eat any food it can get its paws on, 322 00:40:48,367 --> 00:40:53,202 but for a meat-eater a few scraps of dry lichen won't go far. 323 00:40:58,487 --> 00:41:02,480 It may have been four months since his last kill 324 00:41:02,567 --> 00:41:05,001 and he won't find any seals here. 325 00:41:07,767 --> 00:41:11,555 If the yearly increase in the scale of the melt continues, 326 00:41:11,647 --> 00:41:14,081 more bears will starve. 327 00:41:14,167 --> 00:41:19,321 Two thirds of the world's polar bears could vanish by 2050. 328 00:41:22,367 --> 00:41:25,518 The great melt has always been difficult for bears, 329 00:41:25,607 --> 00:41:29,759 but soon surviving the summer may become impossible. 330 00:41:32,927 --> 00:41:37,205 The scale of the summer melt has changed over the last 30 years. 331 00:41:37,287 --> 00:41:41,678 2007's melt broke all records. 332 00:41:42,647 --> 00:41:46,765 400,000 extra square miles of ice disappeared, 333 00:41:46,847 --> 00:41:50,237 the greatest melt ever recorded. 334 00:41:50,327 --> 00:41:55,640 The latest predictions suggest that the Arctic may be entirely ice-free 335 00:41:55,727 --> 00:41:58,799 in summertime within 20 to 40 years. 336 00:42:04,287 --> 00:42:07,643 By September, the sun's power begins to ebb. 337 00:42:07,727 --> 00:42:12,039 The summer comes to an end and the Arctic empties of life. 338 00:42:13,207 --> 00:42:16,040 The last seabirds begin their long journey south, 339 00:42:16,127 --> 00:42:19,517 leaving only a few hardy residents behind. 340 00:42:24,167 --> 00:42:28,763 The fox cubs now face the changing season alone. 341 00:42:35,167 --> 00:42:38,523 Already, the first snow is beginning to fall. 342 00:42:38,607 --> 00:42:42,885 The full Arctic winter is just six weeks away. 343 00:42:54,487 --> 00:42:59,197 For hungry bears, six weeks may be too long to wait. 344 00:43:01,167 --> 00:43:05,638 The sea ice will not freeze properly till it reaches minus 2 degrees. 345 00:43:05,727 --> 00:43:08,366 For now, it's still too warm. 346 00:43:10,447 --> 00:43:15,601 This ice is no use to the bears. They can't walk on it to hunt. 347 00:43:25,207 --> 00:43:28,597 The normally unsocial bears gather in groups, 348 00:43:28,687 --> 00:43:31,042 trapped on the shoreline. 349 00:43:35,087 --> 00:43:39,478 This is the time of year the male bears spar. 350 00:43:41,007 --> 00:43:42,565 (GROWLING) 351 00:43:42,647 --> 00:43:46,435 Only the biggest bears have the energy reserves to fight. 352 00:43:46,527 --> 00:43:51,078 After a summer without food, the bear's systems are in low gear. 353 00:43:51,167 --> 00:43:53,601 These aerobics help warm them up, 354 00:43:53,687 --> 00:43:56,485 in readiness for the winter hunting ahead. 355 00:43:58,447 --> 00:44:00,278 (GROWLING) 356 00:44:46,287 --> 00:44:51,202 It's late October, but still the sea hasn't frozen. 357 00:44:51,287 --> 00:44:54,279 For every degree rise in the average temperature, 358 00:44:54,367 --> 00:44:57,962 the summer melt is extended by a whole week. 359 00:44:58,047 --> 00:45:00,880 That's more bad news for polar bears. 360 00:45:10,247 --> 00:45:15,037 Smaller, younger bears don't have the energy of the big males. 361 00:45:15,127 --> 00:45:19,917 Each day they are without food, they lose nearly a kilo. 362 00:45:20,007 --> 00:45:22,760 Some have lost half of their body weight. 363 00:45:25,047 --> 00:45:30,075 These hungry bears must now rest in the snow and conserve energy. 364 00:45:30,767 --> 00:45:32,803 All they can do is wait. 365 00:45:45,087 --> 00:45:47,965 At last the wind changes, 366 00:45:48,047 --> 00:45:51,357 blowing from the cold north across the sea. 367 00:45:51,447 --> 00:45:55,156 The air temperature plummets to 20 degrees below. 368 00:45:56,287 --> 00:46:00,326 It's now cold enough for ice crystals to form in the ocean. 369 00:46:00,407 --> 00:46:05,117 They knit together forming a greasy layer of surface ice. 370 00:46:06,567 --> 00:46:08,398 This thickens into plates 371 00:46:08,487 --> 00:46:12,878 which bump and collide in the swell, forming pancake ice. 372 00:46:18,927 --> 00:46:23,557 These pancakes lock together to form a continuous surface. 373 00:46:29,767 --> 00:46:33,077 At long last the sea has frozen. 374 00:46:37,527 --> 00:46:42,999 Only now can the bears head out onto the sea ice to hunt for seals. 375 00:46:44,207 --> 00:46:47,165 But the new ice has a surprise in store. 376 00:46:47,247 --> 00:46:48,839 (ICE CRACKING) 377 00:47:03,767 --> 00:47:07,476 This season, for the first time ever recorded, 378 00:47:07,567 --> 00:47:10,206 even the winter ice is thinner. 379 00:47:15,487 --> 00:47:18,763 The ice here is too thin to climb out on 380 00:47:19,047 --> 00:47:21,436 and he struggles to free himself. 381 00:48:03,527 --> 00:48:06,564 At last, safely on the firmer ice, 382 00:48:06,647 --> 00:48:09,719 he rolls in the snow to dry his fur. 383 00:48:23,647 --> 00:48:28,357 In November, the sun sets over the frozen north. 384 00:48:28,447 --> 00:48:31,598 It will not appear again for four months. 385 00:48:36,687 --> 00:48:40,919 The summer melt provides opportunities for millions of animals, 386 00:48:41,007 --> 00:48:45,398 but has now become a threat to the polar bear's very survival. 387 00:48:48,047 --> 00:48:52,996 This season, the bear has survived the greatest melt yet recorded 388 00:48:53,487 --> 00:48:56,923 and made it through to the Arctic winter. 389 00:49:19,887 --> 00:49:24,597 The frozen Arctic sea is one of the most demanding of all environments, 390 00:49:24,687 --> 00:49:27,759 and the location for a rarely seen spectacle. 391 00:49:29,127 --> 00:49:31,516 The Nature's Great Events team 392 00:49:31,607 --> 00:49:36,522 wanted to film the annual migration of the elusive arctic narwhal. 393 00:49:37,527 --> 00:49:42,681 To do so, they would have to live on, dive beneath and fly over the ice 394 00:49:42,967 --> 00:49:45,925 during the climax of the great melt. 395 00:49:55,527 --> 00:49:59,839 The quest for the narwhal started at the height of the melt, in July, 396 00:49:59,927 --> 00:50:02,839 when the sea ice was at its most dangerous. 397 00:50:02,927 --> 00:50:07,205 This made the task of first finding the whales a tough prospect. 398 00:50:12,167 --> 00:50:16,763 This is rough ice. And we're stuck. 399 00:50:18,487 --> 00:50:19,761 ATTENBOROUGH: Narwhal are so elusive 400 00:50:19,847 --> 00:50:22,407 and the conditions working on the ice so difficult, 401 00:50:22,487 --> 00:50:26,924 that the crew allowed a month to track them down. 402 00:50:27,007 --> 00:50:29,646 The plan was to get to the edge of the ice 403 00:50:29,727 --> 00:50:34,039 in the hope of finding the whales at the beginning of their migration. 404 00:50:38,047 --> 00:50:42,563 The melt was in full swing and the team were in the thick of it. 405 00:50:44,607 --> 00:50:48,805 With 24-hour sunlight, the leads along which the narwhal migrate 406 00:50:48,887 --> 00:50:51,162 were getting wider every day. 407 00:51:00,167 --> 00:51:01,919 After three weeks of searching, 408 00:51:02,007 --> 00:51:05,556 the whales were living up to their secretive reputation. 409 00:51:14,167 --> 00:51:16,442 The crew couldn't see the narwhal, 410 00:51:16,527 --> 00:51:19,087 but there was evidence that they were not far away. 411 00:51:19,167 --> 00:51:22,955 A sensitive hydrophone enabled them to eavesdrop on the whales 412 00:51:23,047 --> 00:51:24,526 under the ice. 413 00:51:29,527 --> 00:51:33,281 I am hearing what could be sedation whistles and clicks. 414 00:51:33,367 --> 00:51:35,198 So it could be narwhal. 415 00:51:39,207 --> 00:51:42,199 It's very distant and sound travels a long way under water, 416 00:51:42,287 --> 00:51:45,404 so these guys are probably still far away, but it's a good sign. It's good. 417 00:51:46,687 --> 00:51:48,405 ATTENBOROUGH: They could hear the whales, 418 00:51:48,487 --> 00:51:51,001 but would they be able to see them? 419 00:51:52,047 --> 00:51:56,837 By now the cracks had opened wide enough for them to dive to search for them. 420 00:51:59,727 --> 00:52:02,560 Ice diving is dangerous at the best of times, 421 00:52:02,647 --> 00:52:06,686 but in such a remote location, days away from the nearest help, 422 00:52:06,767 --> 00:52:09,235 they had to be especially careful. 423 00:52:13,047 --> 00:52:15,038 Even though it was the height of the summer, 424 00:52:15,127 --> 00:52:19,325 the icy sea water was still a chilly minus 1 .6 degrees. 425 00:52:20,407 --> 00:52:23,638 So the team needed not only specialist equipment 426 00:52:23,727 --> 00:52:25,922 but specialist attitude. 427 00:52:27,167 --> 00:52:28,646 You're very quiet there, Tom. 428 00:52:28,727 --> 00:52:31,639 Well, I was just thinking we don't really want the ice to close up 429 00:52:31,727 --> 00:52:33,763 while we're underneath it. 430 00:52:34,927 --> 00:52:36,485 No, closing up would be a bad thing. 431 00:52:36,567 --> 00:52:37,556 -It would be a bummer. -Yes. 432 00:52:38,367 --> 00:52:43,282 ATTENBOROUGH: And Tom from Florida was taking no chances against the cold. 433 00:52:44,127 --> 00:52:47,597 Ah, that feels really good. 434 00:52:47,687 --> 00:52:48,881 (CHUCKLING) 435 00:52:50,367 --> 00:52:51,766 Sam, we gotta do this more often. 436 00:52:51,847 --> 00:52:53,166 Wha-hey! 437 00:53:04,247 --> 00:53:07,444 ATTENBOROUGH: Now they were in the whales' realm. 438 00:53:09,487 --> 00:53:12,365 A vast underworld of frigid water 439 00:53:12,447 --> 00:53:15,325 enclosed beneath a ceiling of ice. 440 00:53:18,767 --> 00:53:21,361 This is a world we rarely see. 441 00:53:21,447 --> 00:53:25,440 Sinister, but at the same time uniquely beautiful. 442 00:53:31,367 --> 00:53:34,200 As the melting ice runs into the open cracks, 443 00:53:34,287 --> 00:53:36,517 it creates an underwater mirage 444 00:53:36,607 --> 00:53:41,442 as the layer of freshwater mixes with the denser saltwater beneath it. 445 00:53:47,767 --> 00:53:51,965 If the ice were to close in on them now they could get trapped. 446 00:53:53,967 --> 00:53:57,880 As they ventured deeper, the crew carried a lifeline to the surface 447 00:53:57,967 --> 00:54:01,004 to guide them back to their opening in the ice. 448 00:54:22,727 --> 00:54:25,799 Sadly, there were no narwhal to be seen, 449 00:54:25,887 --> 00:54:29,516 but it was a unique glimpse of the whale's world. 450 00:54:30,207 --> 00:54:33,916 Sometimes it's a little bit spooky to have a ceiling above your head, 451 00:54:34,007 --> 00:54:37,636 and then when the tank starts breaking through a little bit 452 00:54:37,727 --> 00:54:38,921 once in a while you think, 453 00:54:39,007 --> 00:54:42,317 ''Is this really an intelligent thing to be doing?'' 454 00:54:43,927 --> 00:54:46,805 But the shot looked cool, so I think it was worth it. 455 00:54:49,247 --> 00:54:53,160 ATTENBOROUGH: They had spent over a month on and under the sea ice. 456 00:54:53,247 --> 00:54:57,957 But with still no shots of narwhal, time and ice were running out. 457 00:54:59,967 --> 00:55:03,357 The edge of the ice was now only 1 5 centimetres thick, 458 00:55:03,447 --> 00:55:08,077 barely enough to support the weight of a man, let alone a camera team. 459 00:55:11,367 --> 00:55:15,519 You can feel the swell just coming up underneath this ice, it's pretty trippy. 460 00:55:15,607 --> 00:55:18,360 It's just a gentle undulation all around. 461 00:55:19,407 --> 00:55:21,284 This won't be here tomorrow. 462 00:55:25,647 --> 00:55:28,480 ATTENBOROUGH: But just as the ice was getting too thin, 463 00:55:28,567 --> 00:55:30,637 their effort was rewarded. 464 00:55:31,487 --> 00:55:34,479 -What do you see, Sam? -Narwhal. 465 00:55:34,567 --> 00:55:38,446 See where the five guillemots are out there on the water, six guillemots? 466 00:55:54,367 --> 00:55:57,245 ATTENBOROUGH: Tom and his team had found the narwhal. 467 00:55:57,327 --> 00:56:00,080 The whales had arrived at long last. 468 00:56:00,167 --> 00:56:03,762 But sadly, the ice was now too dangerous to film from. 469 00:56:05,807 --> 00:56:09,356 If they were to stand any chance of continuing to film, 470 00:56:09,447 --> 00:56:12,678 it was time to call for reinforcements. 471 00:56:21,447 --> 00:56:24,678 After being stranded for seven days due to bad weather, 472 00:56:24,767 --> 00:56:28,760 the helicopter crew finally arrived, just in time. 473 00:56:31,807 --> 00:56:36,756 There was now one last chance to film the narwhal, from the air. 474 00:56:37,767 --> 00:56:40,804 Armed with an advanced aerial camera system, 475 00:56:40,887 --> 00:56:44,482 they could zoom in on the action from a long distance away. 476 00:56:44,567 --> 00:56:46,876 This would enable them to find the whales 477 00:56:46,967 --> 00:56:50,323 and even get close-up shots without disturbing them. 478 00:56:55,247 --> 00:56:59,923 As the ice team headed home, the helicopter team took over. 479 00:57:03,647 --> 00:57:07,606 The helicopter could only carry enough fuel for a few hours' flying, 480 00:57:07,687 --> 00:57:11,965 and finding the whales in this vast landscape was a daunting task. 481 00:57:13,687 --> 00:57:17,839 But at last they caught up with the magical arctic unicorn. 482 00:57:18,687 --> 00:57:21,520 PILOT: Yeah, there they are. They're kind of 1 0 o'clock from me. 483 00:57:21,607 --> 00:57:23,245 Just coming under us now. 484 00:57:48,887 --> 00:57:51,924 ATTENBOROUGH: Unaware of the helicopter flying high above, 485 00:57:52,007 --> 00:57:55,363 the whales carried on their journey through the ice. 486 00:57:57,767 --> 00:58:01,760 This is the first time the narwhal migration has been filmed 487 00:58:01,847 --> 00:58:04,725 from this incredible aerial perspective. 488 00:58:12,767 --> 00:58:16,396 The plan had worked. It had taken over six weeks, 489 00:58:16,487 --> 00:58:20,480 but the team had managed to film the amazing journey of the narwhal 490 00:58:20,567 --> 00:58:24,355 in this most harsh and testing of landscapes. 491 00:58:24,447 --> 00:58:27,007 It was a rare and magical insight 492 00:58:27,087 --> 00:58:31,797 into the life of one of our planet's most mysterious creatures.