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