0:00:06 > 0:00:10There's an ocean where giants gather to feast.
0:00:13 > 0:00:16Where people battle the planet's roughest seas.
0:00:19 > 0:00:24It stretches nearly 10,000 miles from Arctic to Antarctic...
0:00:29 > 0:00:31..from tropical shallows...
0:00:33 > 0:00:35..to mysterious depths.
0:00:41 > 0:00:43It's an ocean of extremes...
0:00:45 > 0:00:49..engine room for storms 1,000 miles across...
0:00:51 > 0:00:54..yet also a sanctuary for the vulnerable.
0:00:57 > 0:01:00People and animals brave this unpredictable ocean...
0:01:02 > 0:01:05..risking it all for rich rewards.
0:01:07 > 0:01:10This is the Atlantic,
0:01:10 > 0:01:13the wildest ocean on Earth.
0:01:32 > 0:01:35It's January in the far north of the Atlantic,
0:01:35 > 0:01:38off the coast of Arctic Norway.
0:01:42 > 0:01:45The air temperature is ten degrees below freezing.
0:01:49 > 0:01:52The land is lifeless, locked in ice.
0:01:58 > 0:02:03But, beneath the surface of the ocean, the water is stirring.
0:02:08 > 0:02:13Billions of herring have arrived from the open ocean to spawn.
0:02:16 > 0:02:19And their presence attracts giants.
0:02:21 > 0:02:23Humpback whales.
0:02:26 > 0:02:29Massive fin whales.
0:02:36 > 0:02:39Hundreds of orcas.
0:02:48 > 0:02:52Animals travel hundreds, even thousands of miles,
0:02:52 > 0:02:54for this once a year event,
0:02:54 > 0:02:57a feast that will last for just a few weeks.
0:03:04 > 0:03:07This extraordinary gathering is only possible because of
0:03:07 > 0:03:11one of the planet's most powerful forces,
0:03:11 > 0:03:13a force whose origin lies half a world away
0:03:13 > 0:03:16from these Norwegian waters...
0:03:17 > 0:03:18..the Gulf Stream...
0:03:20 > 0:03:24..an underwater current of warm water 50 miles wide
0:03:24 > 0:03:27that cuts through the ocean for thousands of miles.
0:03:29 > 0:03:33The Gulf Stream shapes all life in the North Atlantic,
0:03:33 > 0:03:36from the Arctic to the Caribbean.
0:03:50 > 0:03:54The Gulf Stream is driven by winds and it begins here,
0:03:54 > 0:03:57where the open ocean meets the reefs of the Caribbean Sea.
0:04:01 > 0:04:04Sheltering here are animals that will soon travel
0:04:04 > 0:04:07to the Arctic, on the same journey as the great current.
0:04:13 > 0:04:15WHALE SONG
0:04:15 > 0:04:18Every winter, these reefs, north of the Dominican Republic,
0:04:18 > 0:04:22are filled with the song of humpback whales.
0:04:22 > 0:04:24WHALE SONG
0:04:33 > 0:04:36WHALE SONG CONTINUES
0:04:37 > 0:04:41This female humpback came here this time last year to mate.
0:04:44 > 0:04:4811 months later, she's returned because these waters are warm
0:04:48 > 0:04:52and calm, sheltered by the surrounding reefs.
0:04:56 > 0:04:59The perfect place to have her baby.
0:05:15 > 0:05:19This calf was born just a few days ago,
0:05:19 > 0:05:23weighing in at a healthy one tonne.
0:05:31 > 0:05:35For now, while his mother rests,
0:05:35 > 0:05:37the calf explores his new world.
0:05:48 > 0:05:51But he's so young that he tires easily.
0:05:53 > 0:05:55He'll need to be a much stronger swimmer
0:05:55 > 0:05:57before he can leave this sanctuary.
0:06:02 > 0:06:06His mother lifts him to the surface to breathe.
0:06:17 > 0:06:20There's very little food here for the mother to eat,
0:06:20 > 0:06:23so she won't be able to produce milk for much longer.
0:06:25 > 0:06:27Soon they will have to leave.
0:06:32 > 0:06:35There are many dangers ahead -
0:06:35 > 0:06:38orca attack, collisions with ships.
0:06:41 > 0:06:45His mother's back is lined with scars from a boat propeller.
0:06:46 > 0:06:50But the young calf faces an even more immediate threat
0:06:50 > 0:06:52from a very dangerous animal.
0:06:54 > 0:06:58Male humpbacks come here every year, looking for a chance to mate.
0:06:58 > 0:07:02They compete amongst themselves for access to the females.
0:07:04 > 0:07:07Their rivalry can be very dangerous.
0:07:10 > 0:07:13Some females in these waters are looking for a mate,
0:07:13 > 0:07:16but not this mother, with her vulnerable young calf.
0:07:19 > 0:07:23If she doesn't shake off the testosterone charged males,
0:07:23 > 0:07:27the calf could be crushed to death in a scrum of 30-tonne bodies.
0:07:35 > 0:07:38The males chase her down, jostling to get into position
0:07:38 > 0:07:40to try and mate with her.
0:07:40 > 0:07:42The calf struggles to keep up.
0:07:48 > 0:07:51The mother guides her calf up for a breath
0:07:51 > 0:07:54and uses her body as a block to protect him from the males.
0:08:01 > 0:08:05The males become more aggressive as they battle for access.
0:08:08 > 0:08:12Five metre long fins, edged with sharp barnacles,
0:08:12 > 0:08:15are swung like clubs.
0:08:18 > 0:08:21Their bodies can be weapons too.
0:08:23 > 0:08:27A breach can severely wound a rival,
0:08:27 > 0:08:30or crush a calf caught up in the fight.
0:08:36 > 0:08:38The calf is exhausted.
0:08:49 > 0:08:53But finally his mother, who's bigger and stronger than the males,
0:08:53 > 0:08:55gets her message across.
0:09:08 > 0:09:10The males move on.
0:09:19 > 0:09:22The calf is now six weeks old.
0:09:22 > 0:09:24His mother has done well to keep him safe this far
0:09:24 > 0:09:27but her energy supplies are dwindling.
0:09:27 > 0:09:30She needs to leave the breeding grounds and head north.
0:09:35 > 0:09:40Fortunately, her baby's diet of around 200 litres of milk a day,
0:09:40 > 0:09:43coupled with lots of play time, have built his strength.
0:09:53 > 0:09:56Now he, too, is strong enough to breach.
0:10:08 > 0:10:10He's ready to face the open ocean.
0:10:15 > 0:10:18His mother leads him away from the nursery.
0:10:22 > 0:10:25They're headed to the fertile waters of Norway's distant shores.
0:10:29 > 0:10:32It's a journey they must embark on.
0:10:34 > 0:10:37The great Gulf Stream will help carry them on their way.
0:10:44 > 0:10:48The Gulf Stream is driven by winds which blow across the ocean,
0:10:48 > 0:10:50pushing water before them.
0:10:52 > 0:10:56From the Caribbean and the Gulf of Mexico, the winds blow north,
0:10:56 > 0:10:58driving the current towards the United States.
0:11:00 > 0:11:02Off the Florida coast,
0:11:02 > 0:11:05the Gulf Stream grows in strength as it's squeezed against the land.
0:11:09 > 0:11:12Just offshore from the beaches of Miami flows a current
0:11:12 > 0:11:16100 times greater than all the world's rivers combined.
0:11:17 > 0:11:20And it's a busy highway, packed with giants.
0:11:23 > 0:11:26Thousands of three-metre long bluefin tuna
0:11:26 > 0:11:28hitch a ride every spring,
0:11:28 > 0:11:30travelling north from the Gulf of Mexico
0:11:30 > 0:11:32to their summer hunting grounds.
0:11:35 > 0:11:40Swordfish, marlin and their cousins sailfish also jump on board.
0:11:48 > 0:11:51The sailfishes' thousand-mile summer migration
0:11:51 > 0:11:52takes about a month.
0:11:54 > 0:11:57But unlike the whales, they find something to eat along the way.
0:12:02 > 0:12:05This floating mat of sargassum seaweed
0:12:05 > 0:12:07is a perfect place to find food.
0:12:09 > 0:12:13Sargassum gives its name to a nearby sea, the Sargasso -
0:12:13 > 0:12:15a huge region at the heart of the Atlantic...
0:12:17 > 0:12:18..where sailors fear to travel
0:12:18 > 0:12:22because of stories of ships trapped forever in huge mats of the weed.
0:12:27 > 0:12:30In reality, these floating islands provide food and shelter
0:12:30 > 0:12:32for hundreds of small fish...
0:12:34 > 0:12:36..and that makes them a rich hunting ground.
0:12:38 > 0:12:42Sailfish can sprint at up to 60mph,
0:12:42 > 0:12:44able to chase down the fastest prey.
0:13:02 > 0:13:06How they catch their prey has only recently been discovered.
0:13:07 > 0:13:11The sailfish uses its long bill to flick a fish out from the shore...
0:13:12 > 0:13:15..throwing it off balance before striking.
0:13:26 > 0:13:28The Gulf Stream and the winds that blow it
0:13:28 > 0:13:30aren't just relied upon by wildlife.
0:13:30 > 0:13:32CREW SHOUT
0:13:32 > 0:13:36People have used the Gulf Stream winds for hundreds of years.
0:13:36 > 0:13:38We're going home!
0:13:41 > 0:13:46When Christopher Columbus set foot on the New World in 1492,
0:13:46 > 0:13:48he opened up a world of opportunities.
0:13:52 > 0:13:53For hundreds of years,
0:13:53 > 0:13:56treasures and natural riches were shipped back and forth
0:13:56 > 0:13:57across the Atlantic,
0:13:57 > 0:14:00driving the colonisation of America
0:14:00 > 0:14:02and changing the course of human history.
0:14:05 > 0:14:09And none of that could have happened without the Gulf Stream winds...
0:14:18 > 0:14:21From the Caribbean, the winds push the current north
0:14:21 > 0:14:23and then east towards Europe
0:14:23 > 0:14:26with such consistency that sailors could rely on them
0:14:26 > 0:14:28to cross thousands of miles of ocean.
0:14:33 > 0:14:36Even today, sailors use this ancient trading route.
0:14:36 > 0:14:38CREW SHOUT
0:14:42 > 0:14:45The crew of this Dutch ship use the winds to ship rum,
0:14:45 > 0:14:48chocolate and coffee beans from the Caribbean back to Amsterdam.
0:14:57 > 0:15:00The Tres Hombres has no engine.
0:15:00 > 0:15:02She's entirely reliant on winds and currents,
0:15:02 > 0:15:05so the crew have to respond to every change in the breeze.
0:15:05 > 0:15:06Everybody ready?
0:15:08 > 0:15:10Standby on the breakers.
0:15:10 > 0:15:11Standby on the main.
0:15:21 > 0:15:23The crew work in shifts,
0:15:23 > 0:15:2412 hours out of every 24.
0:15:26 > 0:15:27It's hard work,
0:15:27 > 0:15:29but it has its rewards...
0:15:33 > 0:15:35You feel very connected to nature
0:15:35 > 0:15:38because you constantly feel the waves on the ship...
0:15:38 > 0:15:40You feel the wind when you're on deck.
0:15:43 > 0:15:44It's the dolphins visiting you.
0:15:46 > 0:15:49You feel exactly what your ancestors felt.
0:15:50 > 0:15:53The same waves, the same winds.
0:15:53 > 0:15:55So it's beautiful.
0:16:00 > 0:16:01CREW SHOUT
0:16:03 > 0:16:05But as in ancient times,
0:16:05 > 0:16:07harnessing the Atlantic's natural power
0:16:07 > 0:16:10means putting your life on the line.
0:16:10 > 0:16:12WAVES CRASH
0:16:17 > 0:16:18Over the centuries,
0:16:18 > 0:16:20more than 600 ships have been wrecked
0:16:20 > 0:16:23along just one short stretch of America's Atlantic coast,
0:16:23 > 0:16:27where the Gulf Stream flows perilously close to land.
0:16:30 > 0:16:34The treacherous sand banks off the barrier islands of North Carolina
0:16:34 > 0:16:36are known as the graveyard of the Atlantic.
0:16:40 > 0:16:43But there may have been some survivors from the wrecks here...
0:16:43 > 0:16:45No-one's certain how they got here,
0:16:45 > 0:16:48but many believe that their ancestors made it to shore
0:16:48 > 0:16:51from shipwrecked galleons of Spanish conquistadors.
0:16:57 > 0:17:00HORSE NEIGHS
0:17:00 > 0:17:02For the last 500 years,
0:17:02 > 0:17:04horses descended from Spanish stock
0:17:04 > 0:17:07have lived completely wild on these islands.
0:17:24 > 0:17:28Today, the fertile grasses of the salt marshes
0:17:28 > 0:17:30support over 100 horses...
0:17:41 > 0:17:43..once domesticated, now completely wild.
0:17:45 > 0:17:48They live in small groups of mares and foals,
0:17:48 > 0:17:51over which stallions battle for access.
0:18:11 > 0:18:13But these horses face a critical challenge.
0:18:15 > 0:18:18The water that surrounds them is too salty to drink.
0:18:21 > 0:18:24To quench their thirst, they must first dig.
0:18:29 > 0:18:30HORSES LAP UP WATER
0:18:34 > 0:18:35NEIGHING
0:18:36 > 0:18:39These horses are survivors.
0:18:39 > 0:18:43They'll even swim between islands in search of fresh grazing.
0:18:57 > 0:19:01Marooned for centuries on this Atlantic outpost,
0:19:01 > 0:19:03these Spanish horses are a living reminder
0:19:03 > 0:19:06of the role the Gulf Stream's played in human history.
0:19:12 > 0:19:15Offshore from the barrier islands,
0:19:15 > 0:19:17the Gulf Stream's helped to carry these humpbacks
0:19:17 > 0:19:20for over a thousand miles from the Caribbean.
0:19:27 > 0:19:30This mother and calf have joined forces with a male,
0:19:30 > 0:19:32perhaps to give them some protection
0:19:32 > 0:19:35against the increasing threat from orcas.
0:19:35 > 0:19:36HISSING
0:19:40 > 0:19:43They have done well to make it this far,
0:19:43 > 0:19:46but the mother may not have eaten for six months
0:19:46 > 0:19:48and her milk won't last much longer.
0:19:53 > 0:19:57Luckily, the Atlantic is about to deliver salvation.
0:20:02 > 0:20:05As the Gulf Stream passes the northern United States,
0:20:05 > 0:20:07a meeting of the waters
0:20:07 > 0:20:10helps to drive an extraordinary transformation.
0:20:13 > 0:20:17A cold current pushes down from the Arctic along the coast,
0:20:17 > 0:20:19carrying icebergs with it.
0:20:19 > 0:20:21DRAMATIC MUSIC
0:20:24 > 0:20:25The mingling of the two currents
0:20:25 > 0:20:27helps to bring nutrients to the surface,
0:20:27 > 0:20:30sowing the seeds for an explosion of life.
0:20:36 > 0:20:39Bluefin tuna are one of many Gulf Stream travellers
0:20:39 > 0:20:42that end their summer migration off New England and eastern Canada...
0:20:44 > 0:20:46..some of the richest seas on earth.
0:20:52 > 0:20:56This rich stretch of ocean also supports seabirds in their millions
0:20:56 > 0:20:58and huge numbers of marine mammals.
0:20:58 > 0:20:59GULLS CRY
0:21:01 > 0:21:04Harp seals travel together on the hunt for fish.
0:21:09 > 0:21:13Every spring, these fertile seas turn into a rich green soup
0:21:13 > 0:21:14across hundreds of miles
0:21:14 > 0:21:17as billions of tiny plants burst into life.
0:21:19 > 0:21:20A plankton bloom.
0:21:22 > 0:21:26Individually, these plants are too small for the naked eye to see,
0:21:26 > 0:21:27but in such huge numbers,
0:21:27 > 0:21:30they are the basis for these incredibly rich seas.
0:21:33 > 0:21:35Tiny animals feed on the tiny plants.
0:21:37 > 0:21:40These in turn are preyed on by even larger animals...
0:21:40 > 0:21:43and so on, up the food chain.
0:21:55 > 0:21:58Any animal or plant that can't swim against the current
0:21:58 > 0:22:00is called plankton.
0:22:00 > 0:22:03Most of these are tiny...
0:22:03 > 0:22:06but this fertile region can provide enough food
0:22:06 > 0:22:08for the colossus of the plankton world...
0:22:10 > 0:22:12This is a lion's mane...
0:22:14 > 0:22:16..the largest jellyfish in the world.
0:22:18 > 0:22:21Its body alone can be wider than a man is tall.
0:22:23 > 0:22:27Its stinger-covered tentacles can be longer than a blue whale,
0:22:27 > 0:22:31catching anything from tiny shrimps to fish to other jellyfish.
0:22:38 > 0:22:42This is a creature most would go out of their way to avoid...
0:22:47 > 0:22:51..but one remarkable animal swims all the way from the Caribbean
0:22:51 > 0:22:54to southern Canada in search of it.
0:22:57 > 0:23:00In the waters off the island of Nova Scotia,
0:23:00 > 0:23:04people are on the lookout for these mysterious ocean predators.
0:23:05 > 0:23:09Zoologist Mike James and boatman Blair Fricker
0:23:09 > 0:23:12have worked to study and protect these animals for 16 years.
0:23:12 > 0:23:16But to study them, they first have to find them.
0:23:16 > 0:23:19We start watching, just start looking.
0:23:19 > 0:23:22Sometimes we see one of them on a nice day, never see them again.
0:23:23 > 0:23:25You can't believe that he got away from you.
0:23:27 > 0:23:30Blair and Mike are searching for a giant of its kind.
0:23:32 > 0:23:34But just because it's giant,
0:23:34 > 0:23:37doesn't make it easy to find.
0:23:37 > 0:23:39I think I just saw him. Two o'clock.
0:23:39 > 0:23:42Right there. See where I'm pointing?
0:23:42 > 0:23:43- Yep.- Definitely him.
0:23:49 > 0:23:51Yes, get your net ready.
0:23:51 > 0:23:54Oh, she's taking a pretty good turn, there. There she goes.
0:23:54 > 0:23:55The problem is they're not staying,
0:23:55 > 0:23:58they're just coming up for breath and really trucking along.
0:23:58 > 0:24:00- A few jellies, eh?- All done?
0:24:02 > 0:24:04'Have you seen any more?'
0:24:04 > 0:24:06Nah, it's been a while.
0:24:10 > 0:24:14There he is, just under the surface. He's come up again, I think.
0:24:18 > 0:24:20Success at last.
0:24:20 > 0:24:22This is an animal that takes a lot of skill
0:24:22 > 0:24:25and strength to bring on board without doing it harm.
0:24:26 > 0:24:30- The best to do is get her in head first.- Hang on!
0:24:30 > 0:24:32The leatherback turtle.
0:24:33 > 0:24:36At up to 900kg in weight,
0:24:36 > 0:24:38this is the largest sea turtle in the world.
0:24:40 > 0:24:43Mike estimates that over 1,000 turtles
0:24:43 > 0:24:44come to Canadian waters every year.
0:24:46 > 0:24:48He's tagged over 300
0:24:48 > 0:24:50so they can be identified if they're caught again.
0:24:50 > 0:24:51She's really big.
0:24:53 > 0:24:55Every turtle gets measured.
0:24:57 > 0:24:59148.2.
0:24:59 > 0:25:02The longest ever recorded is nearly twice as long as this one.
0:25:02 > 0:25:05So that's a metre plus around the neck.
0:25:08 > 0:25:11Leatherbacks have a crucial advantage over other,
0:25:11 > 0:25:12smaller sea turtles.
0:25:14 > 0:25:15Unusually for reptiles,
0:25:15 > 0:25:17they can generate body heat
0:25:17 > 0:25:20which their huge bulk helps them to retain.
0:25:20 > 0:25:23That means they can swim beyond the warm Gulf Stream
0:25:23 > 0:25:25and deep into the bountiful northern seas.
0:25:31 > 0:25:33And Mike has recently revealed
0:25:33 > 0:25:36what the leatherbacks get up to in the murky depths.
0:25:37 > 0:25:41He's fitted small cameras to the backs of some of his turtles.
0:25:41 > 0:25:42SPLASHING
0:25:48 > 0:25:50Leatherbacks have excellent eyesight,
0:25:50 > 0:25:54helping them track down the lion's manes in the green plankton soup.
0:26:00 > 0:26:02But jellyfish are mostly water.
0:26:04 > 0:26:07A big animal needs to eat a lot of them to survive
0:26:07 > 0:26:11and Mike has discovered that turtles feed from dawn to dusk,
0:26:11 > 0:26:14eating nearly three quarters of their own body weight in jellyfish
0:26:14 > 0:26:16every day all through the summer.
0:26:19 > 0:26:21These giant reptiles thrive here
0:26:21 > 0:26:23because of the incredibly fertile seas
0:26:23 > 0:26:26that the Gulf Stream has helped to create.
0:26:30 > 0:26:33And that fertility also sustains huge numbers
0:26:33 > 0:26:35of a more familiar sea creature.
0:26:39 > 0:26:41The waters off New England
0:26:41 > 0:26:44and eastern Canada are incredibly rich in fish.
0:26:45 > 0:26:48But today, these sand eels are in the wrong place
0:26:48 > 0:26:50at the wrong time...
0:26:55 > 0:26:57Out of the murk,
0:26:57 > 0:27:00a stream of bubbles begins to surround the shoal.
0:27:01 > 0:27:04The panicking fish gather even tighter together.
0:27:09 > 0:27:10Beneath the shoal,
0:27:10 > 0:27:13a scream louder than a jet engine
0:27:13 > 0:27:14pierces the water,
0:27:14 > 0:27:17- driving the fish upwards. - PIERCING UNDERWATER SCREAM
0:27:20 > 0:27:22The net of bubbles draws tighter
0:27:22 > 0:27:25as the predator rises around the fish in a spiral.
0:27:25 > 0:27:26SCREAM CONTINUES
0:27:39 > 0:27:40It's the humpbacks.
0:27:42 > 0:27:44After up to six months of fasting,
0:27:44 > 0:27:46they're making the most of their chance to feed.
0:27:53 > 0:27:56Humpbacks are the only animal that traps its prey in a bubble net.
0:28:02 > 0:28:05The whales have a mouth full of giant strips of baleen...
0:28:07 > 0:28:09..a fingernail-like material.
0:28:12 > 0:28:15They gulp in huge mouthfuls of seawater and fish...
0:28:19 > 0:28:22..then force the water back out through the baleen sieve,
0:28:22 > 0:28:24trapping the fish inside.
0:28:26 > 0:28:27WHALES SNORT
0:28:35 > 0:28:37Across a huge stretch of the ocean,
0:28:37 > 0:28:40hundreds of whales gather to gorge themselves.
0:28:42 > 0:28:44There is so much to eat here
0:28:44 > 0:28:47that the whales can put on enough fat over the summer months
0:28:47 > 0:28:49to last them the whole year.
0:28:52 > 0:28:55But not all of the humpbacks that set off from the Caribbean
0:28:55 > 0:28:58end their migration off the North American coast.
0:29:02 > 0:29:06Some swim much further, heading for even greater riches
0:29:06 > 0:29:08on the far side of the Atlantic,
0:29:08 > 0:29:10where the Gulf Stream is also heading.
0:29:17 > 0:29:19Off the northern coasts of America,
0:29:19 > 0:29:21the winds begin to blow due east.
0:29:21 > 0:29:25That pushes the Gulf Stream across the Atlantic towards Europe.
0:29:27 > 0:29:30As it leaves America, the Gulf Stream is up to ten degrees warmer
0:29:30 > 0:29:32than the sea just to the north.
0:29:32 > 0:29:35The warm current warms the air above it,
0:29:35 > 0:29:37which creates a difference in air pressure,
0:29:37 > 0:29:39leading to even stronger winds.
0:29:41 > 0:29:45This helps whip up the notorious rough seas of the North Atlantic.
0:29:55 > 0:29:57As well as creating turbulent weather,
0:29:57 > 0:30:00the Gulf Stream once again drives life.
0:30:02 > 0:30:05The flow of the current churns nutrients up from the seafloor
0:30:05 > 0:30:08and enriches the North Atlantic,
0:30:08 > 0:30:09creating a feast for seabirds.
0:30:14 > 0:30:17Gannets fly hundreds of miles on their fishing trips.
0:30:19 > 0:30:22They hit the water at up to 50mph.
0:30:22 > 0:30:25They swim down as much as 20 metres in pursuit of their prey.
0:30:27 > 0:30:30GANNETS CRY
0:30:34 > 0:30:36There are rich rewards to be had in this fertile ocean...
0:30:38 > 0:30:40..but misjudge the conditions out here
0:30:40 > 0:30:43and the Atlantic's power can destroy you.
0:30:46 > 0:30:49And that goes for everything
0:30:49 > 0:30:50and everyone.
0:30:55 > 0:30:56WAVES CRASH
0:31:03 > 0:31:05All around the ocean,
0:31:05 > 0:31:08from Canada, Iceland, France and the British Isles...
0:31:09 > 0:31:11..men and women brave the elements
0:31:11 > 0:31:13and head out to harvest the seas.
0:31:15 > 0:31:18Scottish skipper Davie Milne has been fishing the Atlantic
0:31:18 > 0:31:20for 35 years
0:31:20 > 0:31:21and is still in awe of its power.
0:31:23 > 0:31:25I've a great respect for the sea.
0:31:27 > 0:31:30We're in just like a bath tub, really,
0:31:30 > 0:31:31compared with the Atlantic Ocean.
0:31:31 > 0:31:32It's massive.
0:31:34 > 0:31:38Davie is skippering his bath tub into waters he knows well,
0:31:38 > 0:31:40but he still makes use of the latest sonar and radar
0:31:40 > 0:31:42to help find the fish
0:31:42 > 0:31:44and keep an eye on what the elements have in store.
0:31:47 > 0:31:50The weather comes from the west, brought by the same winds that blow
0:31:50 > 0:31:53the warm Gulf Stream waters over from the Americas.
0:31:57 > 0:32:00Davie and his crew of six seek out the places where the current
0:32:00 > 0:32:03drives the nutrients most strongly to the surface,
0:32:03 > 0:32:06creating the most fertile fishing grounds.
0:32:11 > 0:32:15But fishing these rich waters is a very dangerous job.
0:32:15 > 0:32:16MEN SHOUT
0:32:18 > 0:32:21Trawlermen lose their lives every year out here.
0:32:25 > 0:32:27For Davie and his crew,
0:32:27 > 0:32:28it's a daily battle
0:32:28 > 0:32:31with one of the most hostile environments on earth.
0:32:32 > 0:32:35Go, go, go, go!
0:32:35 > 0:32:36WIND DROWNS OUT SHOUTING
0:32:51 > 0:32:54Winds blowing over 2,000 miles of ocean
0:32:54 > 0:32:57build up towering Atlantic swirls,
0:32:57 > 0:32:58taller than a house.
0:33:06 > 0:33:07But for these fishermen,
0:33:07 > 0:33:10this is just a typical day at the office.
0:33:11 > 0:33:13WIND HOWLS
0:33:18 > 0:33:20Davie fights to keep the boat steady...
0:33:22 > 0:33:26..while a massive net, filled with up to 15 tonnes of fish,
0:33:26 > 0:33:27is hauled in by the men on deck.
0:33:32 > 0:33:36The catch is mostly haddock, with the occasional huge cod.
0:33:43 > 0:33:46Trawlermen have to work to strict quotas,
0:33:46 > 0:33:49while arguments rage about how much fish they should be taking.
0:33:51 > 0:33:54Today, though, they'll be lucky to take any more fish at all.
0:33:58 > 0:33:59Off the cast of Canada,
0:33:59 > 0:34:01a storm has swept down from the Arctic.
0:34:04 > 0:34:07The spiral of storm clouds has been blown towards Europe,
0:34:07 > 0:34:08whipping up the seas.
0:34:24 > 0:34:26As the swell builds,
0:34:26 > 0:34:29the skipper starts to monitor the western horizon more closely.
0:34:30 > 0:34:34Davie will soon have a decision to make.
0:34:34 > 0:34:37When do conditions get too dangerous to carry on fishing?
0:34:39 > 0:34:42You've always to be mindful you've men's lives in your hands basically.
0:34:45 > 0:34:48It only takes one bad lump of sea and you're gone.
0:34:56 > 0:34:59Stronger winds mean bigger waves.
0:35:00 > 0:35:03Seamen have a way to describe how rough the sea is -
0:35:03 > 0:35:06they call it the sea state.
0:35:06 > 0:35:09You'll usually get rough, very rough or high
0:35:09 > 0:35:11and then you get phenomenal.
0:35:11 > 0:35:13And phenomenal's phenomenal! HE LAUGHS
0:35:17 > 0:35:19The storm has grown very quickly,
0:35:19 > 0:35:23the winds reaching hurricane strength by mid-Atlantic.
0:35:26 > 0:35:29Powerful storms that form this fast are called weather bombs
0:35:29 > 0:35:32and they can catch fishermen off-guard.
0:35:32 > 0:35:34WAVE CRASHES
0:35:37 > 0:35:39This is rough even by trawlermen standards.
0:36:10 > 0:36:14Davie knows there are masses of fish right beneath him,
0:36:14 > 0:36:16but he has to weigh up the risks of staying out.
0:36:22 > 0:36:23He decides to turn back.
0:36:30 > 0:36:33Turning side-on to the waves is just about the most dangerous
0:36:33 > 0:36:35manoeuvre a boat can make.
0:36:49 > 0:36:52And that's when your seamanship comes in - you make a decision,
0:36:52 > 0:36:55and you make the decision and it's got to be right
0:36:55 > 0:36:57because there's no room for error.
0:37:01 > 0:37:03Davie's ship isn't the only one heading home
0:37:03 > 0:37:05through the gathering storm.
0:37:40 > 0:37:43As the trawlermen make it to the shelter of their harbour,
0:37:43 > 0:37:47the storm crashes into the coastline.
0:37:47 > 0:37:49WAVES CRASH
0:38:02 > 0:38:05Through autumn and winter, storms batter Europe.
0:38:07 > 0:38:10Nowhere feels their force more than the coast of Ireland.
0:38:13 > 0:38:16Reaching up to over 200 metres, the Cliffs of Moher are pummelled
0:38:16 > 0:38:20by over 1,000 tonnes of water in every wave.
0:38:34 > 0:38:37If you could harness the energy of just one storm,
0:38:37 > 0:38:39it could power the whole of the UK for the winter.
0:38:46 > 0:38:48But no-one's come close to harnessing this.
0:39:19 > 0:39:22Storms bring destruction on a huge scale,
0:39:22 > 0:39:26but churning seas bring up nutrients which drive huge summer
0:39:26 > 0:39:30plankton blooms, crucial for the marine life of the British Isles.
0:39:33 > 0:39:37Ten metre-long basking sharks swim up from the depths of the ocean.
0:39:37 > 0:39:41The second largest fish in the world, they feed on nothing
0:39:41 > 0:39:43but tiny plankton.
0:39:45 > 0:39:48Seabirds thrive, breeding in their millions.
0:39:54 > 0:39:56Puffins flock in from the open ocean,
0:39:56 > 0:39:58where they've spent the winter.
0:40:01 > 0:40:03They raise their young on cliff-top burrows,
0:40:03 > 0:40:06fishing by day in the fertile seas.
0:40:06 > 0:40:08PUFFINS PEEP
0:40:16 > 0:40:19Today's meal is a beakful of sprats.
0:40:24 > 0:40:28And there's plenty of food, too, for travellers who brave
0:40:28 > 0:40:29the stormy Atlantic crossing.
0:40:31 > 0:40:34Some of the humpback whales that spent the winter in the Caribbean
0:40:34 > 0:40:38feed off the coast of Ireland in the summer.
0:40:41 > 0:40:43The Gulf Stream helps to whip up the storms
0:40:43 > 0:40:46that makes these waters so rich,
0:40:46 > 0:40:48but the great current also brings warmth.
0:40:55 > 0:40:59As it approaches Europe, the Gulf Stream splits.
0:40:59 > 0:41:02Part of the warm water flows south towards Africa
0:41:02 > 0:41:05but the rest, now known as the North Atlantic Current,
0:41:05 > 0:41:08flows north, past the shores of Europe.
0:41:14 > 0:41:17The sea off the British Isles is ten degrees warmer
0:41:17 > 0:41:20than at the same latitude on the other side of the Atlantic.
0:41:23 > 0:41:27So animals thrive here that are usually more at home further south.
0:41:31 > 0:41:32Like the pink sea fan
0:41:32 > 0:41:35and the European cuttlefish.
0:41:40 > 0:41:42These close relatives of squid
0:41:42 > 0:41:46and octopus breed in the waters off Southern England every summer.
0:41:50 > 0:41:53The warm current is now thought to have less influence on land
0:41:53 > 0:41:57temperatures in the British Isles than people used to believe,
0:41:57 > 0:42:02adding, perhaps, just a degree or two to winter temperatures,
0:42:02 > 0:42:05but further north, it has a significant effect.
0:42:07 > 0:42:10Norway is five to ten degrees warmer than other places at the same
0:42:10 > 0:42:14latitude because of a combination of the ocean current
0:42:14 > 0:42:16and the warm westerly winds that have blown with it
0:42:16 > 0:42:17across the Atlantic.
0:42:22 > 0:42:25Those winds are no longer the only thing driving the current as it
0:42:25 > 0:42:27flows on even further north,
0:42:27 > 0:42:31far beyond the Arctic Circle to the edge of the frozen Arctic Ocean.
0:42:37 > 0:42:38At the edge of the ice,
0:42:38 > 0:42:42a strange process takes place that draws the current up here.
0:42:46 > 0:42:50As the seawater freezes, it squeezes out its salt,
0:42:50 > 0:42:53making the unfrozen water around it extremely saline.
0:43:01 > 0:43:05This super salty water is heavier, so it sinks towards the seabed,
0:43:05 > 0:43:08setting up a circulation as the warmer water from the Gulf
0:43:08 > 0:43:10Stream is sucked in to replace it.
0:43:14 > 0:43:18Everywhere else in the Arctic, the sea freezes over in winter,
0:43:18 > 0:43:21but here the Gulf Stream's warmth keeps a vast
0:43:21 > 0:43:25expanse of the North Atlantic ice-free all year round.
0:43:34 > 0:43:39This combination of nutrient-rich water and unfrozen sea creates
0:43:39 > 0:43:42the arena for one of the earth's great wildlife spectacles.
0:43:45 > 0:43:48It's January and over a billion herring have gathered to
0:43:48 > 0:43:50spawn off the coast of Norway.
0:43:57 > 0:44:00It's a feast for any predator that can reach it.
0:44:08 > 0:44:12For the humpback whales, it's a reward for their 5,000-mile
0:44:12 > 0:44:14swim across the Atlantic.
0:44:18 > 0:44:21Humpbacks can't get to most of the Arctic at winter.
0:44:23 > 0:44:27They can't travel beneath the ice because they need to breathe.
0:44:33 > 0:44:36Here, the Gulf Stream has opened up rich hunting grounds,
0:44:36 > 0:44:39though catching the fish isn't easy.
0:44:42 > 0:44:46The whales struggle to surround and bubble net such a huge mass of fish.
0:44:47 > 0:44:52And now, the humpbacks' deadliest enemy enters the fray.
0:44:54 > 0:44:58Hundreds of orcas swim in from the open ocean,
0:44:58 > 0:45:01moving in pods up to 30 strong.
0:45:10 > 0:45:14But these deadly predators are not here to eat humpbacks.
0:45:15 > 0:45:17They're after the fish.
0:45:17 > 0:45:19ORCAS WHISTLE
0:45:19 > 0:45:22And they have an extraordinary technique for catching them.
0:45:25 > 0:45:27First, they must work as a team,
0:45:27 > 0:45:30coordinating their movements using clicks and whistles.
0:45:30 > 0:45:31ORCAS CLICK
0:45:31 > 0:45:34They break off a section of the mega-shoal
0:45:34 > 0:45:36into a more manageable ball.
0:45:36 > 0:45:39Some whales circle the herring,
0:45:39 > 0:45:41herding them together,
0:45:41 > 0:45:43while others swim deep and push
0:45:43 > 0:45:46the ball of fish up towards the surface.
0:46:00 > 0:46:04The water boils with herring, desperate to escape their fate.
0:46:04 > 0:46:08It's now the orcas deploy their heavy weaponry.
0:46:14 > 0:46:18A six-tonne orca slaps its tail with awesome destructive power.
0:46:24 > 0:46:27Under the water, tail slaps are used to stun the herring.
0:46:42 > 0:46:45Some fish come too quickly and escape back
0:46:45 > 0:46:46to the safety of the shoal.
0:46:49 > 0:46:52But most are picked off by the orcas one-by-one.
0:47:05 > 0:47:08Soon the water glitters with fish scales as the orcas
0:47:08 > 0:47:10methodically consume the ball of fish.
0:47:19 > 0:47:22By breaking up the herring into a smaller shoal,
0:47:22 > 0:47:24the orcas have done the humpbacks a favour,
0:47:24 > 0:47:28turning the usual relationship between the animals on its head.
0:47:31 > 0:47:34Everywhere else on earth, orcas are the humpbacks' biggest enemy,
0:47:34 > 0:47:40but here, the humpbacks cash in on the colossal fish supper.
0:47:52 > 0:47:55And the humpbacks aren't the only ones to gatecrash the orcas' party.
0:48:00 > 0:48:04Massive fin whales, 80 foot long,
0:48:04 > 0:48:06can swallow 3,000 herring in a single gulp.
0:48:22 > 0:48:24Deadly enemies feed side-by-side.
0:48:26 > 0:48:29A unique scene only possible here
0:48:29 > 0:48:31because of the warmth of the Gulf Stream.
0:48:46 > 0:48:47For just a few weeks,
0:48:47 > 0:48:51the humpbacks will eat their fill before the herring move on.
0:48:59 > 0:49:03It's a wonderful spectacle but its future is hard to predict.
0:49:05 > 0:49:07As our climate warms, more
0:49:07 > 0:49:11and more fresh water flows into the Atlantic from Greenland's ice caps.
0:49:12 > 0:49:14This makes the sea less salty.
0:49:18 > 0:49:21And there are signs that the salinity-driven circulation
0:49:21 > 0:49:25which draws the warm current north may be slowing down.
0:49:34 > 0:49:38But for now, at the end of the feeding season,
0:49:38 > 0:49:43the whales begin their long journey south back to the Caribbean
0:49:43 > 0:49:45and the cycle of their lives will begin again.
0:49:48 > 0:49:53Lives that are shaped by the awesome power of the Gulf Stream.
0:49:57 > 0:50:00A driving force for life throughout the rich
0:50:00 > 0:50:03northern seas of the Atlantic.
0:50:24 > 0:50:28It's January in the Norwegian town of Andenes,
0:50:28 > 0:50:30far above the Arctic Circle.
0:50:33 > 0:50:36Offshore, one of nature's great spectacles is about to
0:50:36 > 0:50:40unfold as hundreds of whales gather to gorge themselves.
0:50:42 > 0:50:44But as the camera team test their equipment,
0:50:44 > 0:50:48they realise just how hard it's going to be to operate here.
0:50:49 > 0:50:53Director Lucy Wells is particularly worried about the lack of light.
0:50:53 > 0:50:58Actual filming time, we may get an hour a day at the moment, um...
0:50:58 > 0:51:02which isn't very much and potentially could be quite frustrating
0:51:02 > 0:51:05because if there's lots going on and it's too dark, there is
0:51:05 > 0:51:07nothing we can do, we can't film anything.
0:51:09 > 0:51:11The other big challenge will be the cold.
0:51:13 > 0:51:15With temperatures well below freezing,
0:51:15 > 0:51:19hypothermia and freezing scuba equipment are very real dangers.
0:51:22 > 0:51:25The team are particularly keen to film orcas feeding.
0:51:26 > 0:51:28And within an hour of leaving shore,
0:51:28 > 0:51:31they get lucky and make first contact.
0:51:34 > 0:51:37The orcas are herding the herring shoal into a ball,
0:51:37 > 0:51:38exactly what the team were after.
0:51:40 > 0:51:41Wow.
0:51:44 > 0:51:48With just an hour's daylight, the crew rush to get in the water.
0:51:48 > 0:51:50- Go in. - Go?- Yes.
0:51:52 > 0:51:55Wow! They're everywhere!
0:52:02 > 0:52:08Day one, and already the team have their first shots of the orcas.
0:52:12 > 0:52:15And soon, the orcas have company.
0:52:17 > 0:52:20Oh, this humpback's just... coming close, look how close he is.
0:52:22 > 0:52:25Here you get two whale species for the price of one.
0:52:27 > 0:52:31And it looks like the humpbacks are following the orcas around.
0:52:38 > 0:52:40The team are thrilled.
0:52:42 > 0:52:44This has never been filmed before.
0:52:46 > 0:52:50The humpbacks seem to take advantage of the orcas' herding skills.
0:53:03 > 0:53:04Whoo!
0:53:04 > 0:53:06A great start.
0:53:06 > 0:53:09But the team soon realise that the humpbacks' presence might not
0:53:09 > 0:53:11be such a good thing after all.
0:53:15 > 0:53:17Their main goal is to film the amazing herding
0:53:17 > 0:53:21and tail-slapping behaviour that the orcas here use to catch herring.
0:53:28 > 0:53:32But every time the team find feeding orcas...
0:53:32 > 0:53:33the humpbacks soon turn up...
0:53:36 > 0:53:38..and drive the orcas away.
0:53:42 > 0:53:46Despite the team's best efforts, the humpbacks have become a pest
0:53:46 > 0:53:47and show up again...
0:53:51 > 0:53:52..and again.
0:53:55 > 0:53:57It's a challenge for cameraman, David Reichert.
0:53:57 > 0:54:01We're seeing humpbacks going back and forth all the time down there
0:54:01 > 0:54:04but just not seeing the feeding event.
0:54:05 > 0:54:08This soon becomes a big problem for the team.
0:54:08 > 0:54:11Any moment, the herring could leave, followed by the orcas,
0:54:11 > 0:54:13and the team's mission will be a failure.
0:54:15 > 0:54:211:10. I reckon the latest we can go is probably 1:45.
0:54:21 > 0:54:23So that's not really much time at all,
0:54:23 > 0:54:26and so far today we haven't got anything.
0:54:26 > 0:54:30With morale already low, something happens that reminds the team
0:54:30 > 0:54:33just how dangerous it can be to dive here in midwinter.
0:54:37 > 0:54:40One of the divers gives the signal to be picked up.
0:54:40 > 0:54:42Something is very wrong.
0:54:44 > 0:54:47It's PB, the second underwater cameraman.
0:54:47 > 0:54:49And he's clearly struggling.
0:54:50 > 0:54:51Ow.
0:54:53 > 0:54:56It's every diver's worst fear.
0:54:56 > 0:54:59His breathing equipment has frozen, starving him of air.
0:54:59 > 0:55:02If that had happened deeper underwater,
0:55:02 > 0:55:03it could have been fatal.
0:55:07 > 0:55:10The problem is quickly sorted out but the team is shaken.
0:55:16 > 0:55:18The only camera that is getting close to the orcas
0:55:18 > 0:55:20is the team's mini helicopter.
0:55:28 > 0:55:30But with the team's current run of bad luck,
0:55:30 > 0:55:32they should have foreseen some trouble.
0:55:35 > 0:55:39Thomas, the pilot, skilfully flies the helicopter
0:55:39 > 0:55:41straight into the smallest sign in the harbour.
0:55:46 > 0:55:48He is mortified.
0:55:48 > 0:55:51Luckily, the rest of the team see the funny side...
0:55:51 > 0:55:53THEY LAUGH
0:55:55 > 0:55:58..and mount a rescue mission.
0:55:58 > 0:56:00You can see the propellers moving around.
0:56:04 > 0:56:07I don't want to find out.
0:56:07 > 0:56:08We will have a nice funeral!
0:56:08 > 0:56:11SHE LAUGHS
0:56:11 > 0:56:13It was my toy!
0:56:13 > 0:56:15I'm going home.
0:56:17 > 0:56:20Morale is good but the team have now lost the only camera
0:56:20 > 0:56:22that was filming any orcas.
0:56:26 > 0:56:28The divers are going to need some luck.
0:56:32 > 0:56:35Quite a lot of action in front of us, guys.
0:56:40 > 0:56:43We have just come across a group of orcas,
0:56:43 > 0:56:45no humpbacks, which is a good thing.
0:56:45 > 0:56:48It's... Dare I say it?
0:56:48 > 0:56:51..looking encouraging, but so far every kind of good situation
0:56:51 > 0:56:55we've come across that, on the top side, we thought is amazing,
0:56:55 > 0:56:58they've come up, and it hasn't been good for them.
0:56:59 > 0:57:00It's a tense wait.
0:57:02 > 0:57:03Come on!
0:57:06 > 0:57:09But today, everything happens on cue.
0:57:12 > 0:57:16The cameras start rolling and finally the team capture the amazing
0:57:16 > 0:57:18behaviour they came here to film.
0:57:18 > 0:57:19It is magical.
0:57:23 > 0:57:26The herring ball powers above you.
0:57:26 > 0:57:28The scales of the herring catch the light
0:57:28 > 0:57:30and they just flicker like diamonds.
0:57:34 > 0:57:37And then the orcas move up to them and push them, gently
0:57:37 > 0:57:40nudge this ball up to the surface...
0:57:42 > 0:57:46..where they kind of pin it up there and then they come in and attack.
0:57:49 > 0:57:55This is one of the most spectacular natural events I've ever seen.
0:57:59 > 0:58:00Good.
0:58:00 > 0:58:01Job done.
0:58:01 > 0:58:03Yes!
0:58:03 > 0:58:04Thank God!
0:58:04 > 0:58:07They've had to overcome some very tough conditions,
0:58:07 > 0:58:11but through perseverance and a bit of good luck, they've managed to
0:58:11 > 0:58:15document one of the most remarkable scenes in the whole of the Atlantic.
0:58:27 > 0:58:31From a surface feeding frenzy to the crushing depths of the abyss,
0:58:31 > 0:58:35meet the strange animals of the world's longest mountain range,
0:58:35 > 0:58:37far beneath the surface,
0:58:37 > 0:58:41and discover the origin of the world's youngest ocean.