- 18 minutes ago
Antarctica is the fifth-largest continent, being about 40% larger than Europe, and has an area of 14,200,000 km 2 (5,500,000 sq mi). Population 1,300 (winter) ...
南极洲位于地球最南端，总面积约1424.5万平方公里，其中大陆面积1239.3万平方千米，比欧洲面积还要大 。全境是平均海拔2350米的大高原，是世界上平均海拔最高的洲，冰层平均厚度约2千米，最厚处可达4750米以上
南极洲位于地球最南端，总面积约1424.5万平方公里，其中大陆面积1239.3万平方千米，比欧洲面积还要大 。全境是平均海拔2350米的大高原，是世界上平均海拔最高的洲，冰层平均厚度约2千米，最厚处可达4750米以上
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00:05It's a mystery continent at the bottom of the world.
00:10And the largest single mass of ice on Earth.
00:18For longer than humans have walked the planet,
00:24ice has dominated Antarctica.
00:31But what about the future?
00:34Ice melts from this continent, sea level goes up.
00:42As Earth gets warmer, what will happen to Antarctica?
00:47We're going into uncertain lands, uncertain future.
00:50How will the Earth respond?
00:52Today, a pioneering team is searching for answers
00:56with a bold new plan and a revolutionary new machine.
01:01No one has ever drilled through an ice shelf.
01:03And they present these challenges.
01:07They must drill down nearly a mile and more than 20 million years
01:11deep into Antarctica's ancient history.
01:14In this unforgiving place, it's never been done before.
01:20It's quite amazing when you think about where we are and what we're doing.
01:25Anything can go wrong at any minute.
01:28The stakes are high because the secret to Earth's future
01:33lies buried in Antarctica's past.
01:36Right now on NOVA.
01:39Secrets beneath the sky.
01:55Secrets beneath the sky.
02:00It's the coldest, windiest, driest, and most desolate landscape on the planet.
02:08With few permanent residents except penguins and seals.
02:15This frosty continent appears locked in a perpetual ice age.
02:20A colossal cloak of ice covers almost every inch of land.
02:25And in some places, the ice is so thick and so heavy,
02:29it depresses the Earth's crust almost half a mile.
02:37Some people call it Earth's freezer.
02:40But scientists call Antarctica the ice.
02:47Antarctica plays a fundamental role in the way the Earth functions.
02:51For polar researchers, Antarctica is a giant laboratory
02:55more than one and a half times the size of the United States.
02:59And home to 90% of all the ice in the world.
03:03Anything that happens down here, anything that changes,
03:05will affect the rest of the world.
03:07Most people don't think that change in Antarctica matters to them.
03:11But when we look at New York City, and we look that it's in front of the ocean,
03:16it matters.
03:19What would happen if all of Antarctica's ice were to melt?
03:25If Antarctica melts, sea level goes up 12 stories in New York City.
03:31Sea levels would rise by more than 150 feet.
03:39Flooding coastal cities, displacing hundreds of millions of people.
03:44That would be a change that you could see from space.
03:46Earth would look different.
03:48In any case, even a loss of just 10% of Antarctica's ice would be catastrophic.
03:56It would raise the sea level over there in Manhattan, about 19 feet.
04:02Right up along the edge.
04:04Big sections of Brooklyn would be underwater.
04:07Certainly the Mediterranean, some of my favorite cities like Venice,
04:10would look very different.
04:13Tens of millions of people would have to be relocated.
04:16It would be almost a different planet.
04:18If sea level changes and the climate around the coastal regions change,
04:23it's going to affect the climate where you live.
04:25It's going to affect the things you can grow.
04:27It's going to affect how you live.
04:30There may be a list of things in store that come as a result of raising sea levels
04:37that we haven't even thought about yet.
04:40Could this be our fate?
04:42Is Antarctica heading for a major meltdown?
04:46If so, it may happen over centuries.
04:50But it could already be starting, because the climate is changing.
04:56And it's changing because burning fossil fuels
04:59has increased the level of carbon dioxide in the atmosphere.
05:03Today, we have something that's completely man-made,
05:06and that is the addition of carbon dioxide being put into the atmosphere by humanity, by us.
05:12Carbon dioxide is a greenhouse gas.
05:15It prevents the sun's heat from escaping.
05:18I'm in the Brooklyn Botanic Garden, in a greenhouse.
05:21Greenhouses, they're basically like heat motels,
05:24where the sun's rays can come in and they get trapped inside the greenhouse.
05:28They can't get out.
05:30So like glass in a greenhouse,
05:32gases like carbon dioxide trap solar energy in our atmosphere.
05:37But now, those levels are increasing.
05:40The result is, our Earth is now warming up.
05:45And the ice is melting.
05:49Both in Antarctica and the Arctic.
05:54In the North, there's two clear signals.
05:58In the Arctic Ocean, you have lots of floating ice,
06:01and not sticking around through the summer.
06:03That's one sign of it getting warmer.
06:05The other sign, the edges of the Greenland ice sheet are changing.
06:10And the loss of Greenland's ice is now speeding up.
06:13In August 2010, an iceberg four times the size of Manhattan broke off the edge of Greenland.
06:22But Antarctica has nearly ten times as much ice as Greenland.
06:27And in the past decade alone,
06:29rising temperatures have caused giant pieces of coastal ice to shrink or crumble.
06:36Polar researchers fear that this could be just the beginning of a chain reaction.
06:41But have Antarctica's ice sheets ever collapsed before?
06:46That's what an international team of geodetectives wants to find out.
06:50Here we actually have some running water, some melt water coming out of the ice.
06:55To get a more precise picture of Antarctica's future,
06:58they plan to dig deep for answers in the past with a giant drill.
07:03By drilling into areas around Antarctica,
07:05we're able to perceive a history that has an impact for where we're headed as a planet.
07:11Antarctica was not always locked in a deep freeze.
07:15160 million years ago, it was part of an enormous supercontinent closer to the equator.
07:21At the time, Earth was much warmer than today,
07:25and fossil evidence suggests this giant landmass was a tropical habitat teeming with dinosaurs.
07:33Eventually, the supercontinent broke apart, and Antarctica drifted south.
07:38As Earth was getting colder, falling carbon dioxide levels and powerful ocean currents cooled the isolated continent even further.
07:46And then, around 34 million years ago, ice slowly began to form.
07:53It would take millions of years for Antarctica to finally lock into a deep freeze.
07:59And during that time, it remained warm enough for plant life to survive.
08:04Evidence of that was recently unearthed in a relatively ice-free valley in the interior.
08:10Here, geologists Alan Ashworth and Adam Lewis find a remarkable fossil.
08:20Oh, a leaf, is that a leaf? There's a leaf, right there.
08:23Hey!
08:25That leaf fell into the mud maybe 20 million years ago.
08:29That may be the best leaf yet.
08:31That's a sweet leaf.
08:32And then, they find something extraordinary.
08:36This is like a peat, peat moss.
08:39And then, if we, you know, take, tease some of this out, they're, like, freeze-dried.
08:46Under the microscope, these brittle mosses are in pristine condition.
08:51These moss fossils are not rock, but actual plant tissue.
08:56The last vestiges of vegetation from a time when Antarctica was still warm.
09:01They were found under a layer of volcanic ash that dates back millions of years.
09:06This is the original moss tissue.
09:09And even the cells are preserved in these fossils.
09:12These plants were flash-frozen when Antarctica plummeted into a deep freeze
09:17that preserved them until today.
09:21It's mind-boggling.
09:22The only way is to say the climate remained very, very cold,
09:27it remained very, very dry, and it did not warm up
09:30for even relatively short periods of time in this location.
09:34Otherwise, these things are gone.
09:38Now, as Earth is heating up, what will happen to Antarctica?
09:43Will it melt, raising sea levels all over the planet?
09:47How sensitive is this frozen land to the temperature changes we currently face?
09:53But before researchers can investigate in Antarctica,
09:59last-minute testing is taking place here,
10:02over 2,000 miles away, in the countryside of New Zealand,
10:08with a brand-new drill.
10:14Yeah, it's a shakedown.
10:16We've got a few leaking connections and things that don't quite fit as well as they need to,
10:21a little bit of modifications required.
10:23They're pretty common with a brand-new piece of equipment.
10:26Weighing in at a whopping 40 tons, this mechanized marvel is as heavy as a humpback whale,
10:33and just as large.
10:36Towering some five stories high, the giant rig will soon dwarf everything in sight, except the ice.
10:43This will be the largest drill rig in Antarctica that's used on land.
10:48And this mammoth rig can drill in more than one place.
10:52That's because it's mounted on a sled.
10:55I think it probably is unusual.
10:57All of the equipment is on sledges, so in Antarctica we pull it all with big bulldozers.
11:02It's been specially designed to drill from the ice,
11:05in order to extract hidden secrets from beneath Antarctica itself.
11:11This unique multinational enterprise is called Andrill, the Antarctic Drilling Project.
11:18For team leader David Harwood, it's a dream come true.
11:23As a scientist, there's a passion.
11:25There's a passion that comes in trying to figure this out,
11:28trying to identify what has been the past history of the ice sheet,
11:31and wondering what the future might hold.
11:34Soon, the giant drill will be dismantled and ready for a long sea voyage.
11:39We'll then start the final screening process,
11:42and that's, we'll get you to take your extreme cold weather jackets off.
11:46But now, the Andrill team gathers at Christchurch, New Zealand,
11:49for the six-hour flight to Antarctica in a C-17 cargo plane,
11:54jam-packed with people and gear.
11:57Their flight passes over the Trans-Antarctic Mountains,
12:00which divide the continent into two regions,
12:03with colossal glaciers, called ice sheets, blanketing both.
12:08The giant East Antarctic ice sheet is ten times the size of the West.
12:13It's frozen firmly to bedrock, high above the sea,
12:16and in some places, the ice towers almost three miles into the sky.
12:22The smaller West Antarctic ice sheet is less stable.
12:27That's because it rests on land well below sea level,
12:31and it extends hundreds of miles over the ocean in floating ice shelves.
12:36It's likely East and West Antarctica will respond very differently to a warming world.
12:45The Andrill team touches down in the West, on an icy runway at McMurdo Station,
12:50the largest U.S. research base in Antarctica.
12:59As David Harwood and Richard Levy step out onto the ice,
13:03the first thing they notice is the weather.
13:07The breeze is a bit chilly, but it's beautiful.
13:09It's good to be back.
13:17It's October, springtime, and it's minus 20 degrees.
13:23It's the earliest I've ever been down to Antarctica, and it's very cold.
13:26When the wind picks up, it's rather an unpleasant place to be working.
13:29When the wind isn't blowing and the sun's shining,
13:31it's actually really quite nice, but very cold.
13:34But even a sunny afternoon can turn nasty at a moment's notice.
13:43It's a beautiful day!
13:47Come on, guys!
13:55McMurdo Station has been a vital hub of research for over half a century.
14:00What began as a tiny outpost has, over the years, grown into a small town.
14:08McMurdo houses a population of 200 people year-round.
14:12But during the research season, it becomes home base for over a thousand.
14:19Every year, McMurdo supports scores of research projects,
14:23providing lab facilities, food and supplies,
14:27and survival training for teams of scientists who will head out to remote field camps.
14:34This season, those numbers include the Andrel team of over 50 technicians and researchers
14:40from the U.S., New Zealand, Germany and Italy.
14:45Andrel is funded by their governments and the National Science Foundation.
14:51There's probably a week at least of work in McMurdo where we have to get all of our gear sorted
14:56out,
14:57getting everything we need in order to be able to work and survive out in the field.
15:01As they gather supplies for more than a month on the ice,
15:05one item is in high demand.
15:08Sugar actually heats your body. It gives you quick energy,
15:10especially if you're, like, freezing, and we expect to be very cold.
15:15We don't really know how much chocolate is enough.
15:18We can take up to 560 candy bars.
15:21But I'm looking at this, and I'm already getting queasy.
15:24I'm like, oh, I don't know if I can eat this or not.
15:26Hey, save it!
15:28As Andrel researchers prepare for life in the field,
15:32they join hundreds of other scientists fanning out across Antarctica.
15:36And many are focused on the same question.
15:39Could Antarctica be headed for a meltdown?
15:42Over here is Mount Boreas.
15:44We're going to have a lot of scientists working together.
15:46There is a little bit of volcanic ash.
15:48And, you know, challenging each other's theories, challenging what we know.
15:52Look at that.
15:54As a community, we're going to find the answers.
16:00But the continent won't give up its secrets easily.
16:05The stark beauty of Antarctica masks a treacherous nature.
16:10More than 70% of all the fresh water in the world is harbored here.
16:17But most of that water is frozen.
16:21And with less precipitation than the Sahara, Antarctica is the driest desert on Earth.
16:29Raging winds of up to 200 miles per hour sometimes blast the frozen terrain,
16:35where temperatures can drop to 100 degrees below zero.
16:39Only during the short Antarctic summer can most researchers gather precious scientific data
16:44from this giant mystery continent.
16:56A four-hour flight, and 400 miles from McMurdo, is the center of the West Antarctic ice sheet.
17:05And for one team, this is the best way to find out about the past.
17:15This is the side of a snow pit. It's a thin wall between two pits.
17:18The other side is open so the light can shine through.
17:21And you can really see the different layers in the pit.
17:25So this is one year's worth of snow accumulation.
17:27And there's a second year's worth of snow accumulation here below it.
17:31Two years of record right here in the snow pit.
17:34Of course, we want to go back a lot further in time than that.
17:37In order to do that, we can't just use shovels and chainsaws like we did here, so we have to
17:41use a drill.
17:48Ken Taylor's team is drilling through ice.
17:51Their goal is to gather samples from the nearly two-mile-thick West Antarctic ice sheet.
17:56And the deeper they go, the further back in time they travel.
18:02Here, we're at about 480 meters deep right now.
18:05This is right around the time when Jesus lived.
18:07It's right about 0 A.D., right when B.C. years turned into A.D. years.
18:12These ice cores contain tiny bubbles of ancient atmosphere that were trapped each year as the snow was compressed into
18:20ice.
18:21Nice bubbles in this one.
18:23That's ancient air in there.
18:24When we crush samples like this, that'll get the gas out of there and we can sample the ancient atmosphere.
18:31We can also get a record of how things like temperature and sea ice changed in the past.
18:35And by combining these different records, we can understand how the climate system has operated in the past.
18:45But the ice record, valuable as it is, only goes back about 800,000 years, a tiny fraction of geologic
18:53time.
18:54To get a more complete picture of Antarctica's climate history, you have to drill farther back in time.
19:01And that's what the Andrel team is trying to do.
19:04They want to paint a picture of Antarctica as it changed from warm to cold millions of years ago.
19:11In order to do that, Andrel will have to drill deep into the Earth.
19:15But finding the right location is a major challenge on a continent covered by ice.
19:20And even in those few places where the ice has receded, it's still not easy.
19:26Andrel's David Harwood and Richard Levy are searching for places to drill.
19:31But as they fly over a field of rubble, they see that gathering evidence for a chronological history is not
19:37possible here.
19:38Something has stirred things up.
19:41And that something is the ice itself.
19:44That's because ice moves.
19:47For tens of millions of years, glaciers have slowly scoured the land, gobbling up rocks and debris, and spreading them
19:54all across the landscape in random order.
19:57This we call glacial paleontology, some call it garbage pile paleontology, because we're looking and sorting through these moraines to
20:03try to get pieces of information that the ice sheet has brought to us.
20:07A moraine is the chaotic accumulation of rocks and debris deposited by glacial movement.
20:12This one here actually has abundant shell fossils.
20:16This shell, brought here by a glacier, comes from a time when the continent was warmer, and water ran through
20:23these valleys.
20:25This landscape is a treasure trove of Antarctica's climate history.
20:29But the ice has scrambled all the clues.
20:33We're looking at a jigsaw puzzle.
20:35Yet there's one place where the evidence remains intact.
20:38That's in the sea floor beneath the Antarctic ice shelf, where the glacial movement has also deposited layer after layer
20:46in chronological order.
20:48Drilling gives us an opportunity to get a serial history in time.
20:53Each layer goes back in time.
20:55And we know that a rock above was younger than a rock below, so we can put it into a
20:59history.
21:00The Andrill team aims to drill through the Antarctic ice and the sea below.
21:05Then, like a straw thrust through a layer cake, they'll bore deep into the ocean floor in order to recover
21:12millions of years of rock and mud that trace Antarctica's climate history.
21:19Even after ice began to form in Antarctica around 34 million years ago, the continent remained warm enough for plant
21:27life to survive.
21:28A lot like areas of New Zealand today, where ice can be found bordered by trees and plants.
21:35But when did Antarctica plunge into a solid deep freeze?
21:39And how did it happen?
21:41Was it gradual or abrupt?
21:45Will the story of how Antarctica changed from greenhouse to ice house reveal new clues about the continent's climate future
21:52and our own?
22:08The Andrill team will spend the next few weeks searching for drilling locations from the surface of the ice.
22:16But David Harwood remains focused on what lies below.
22:20When I'm driving across there, I'm always thinking about what's beneath this.
22:24I'm over about 15 feet of ice, and over that I'm over about 1,500 feet of water, and then
22:30the sediments below that.
22:34Here at the bottom of the world, the sun never sets in the summer.
22:38And as night blends into day, the work begins in earnest.
22:43The team heads out to McMurdo Sound, a place where the ocean freezes annually, creating a precarious platform of floating
22:52sea ice that will only last a few months.
22:55We're standing right now in the southern part of McMurdo Sound. Seasonally, this region will break out. The sea ice
23:04that we're standing on will melt out.
23:06It's now strong enough, perhaps 20 feet beneath us is the thickness of ice, and then 1,500 feet of
23:13water beneath us as well.
23:16Just to be sure they're in the right place, the team blasts powerful sound waves through the sea ice and
23:27into the sea floor below.
23:29The result is a sonic street map of layer after layer of rock and mud, each one representing a different
23:37era of the past.
23:41By looking into the past, you can maybe project into the future how dynamic has been the behavior of the
23:48ice sheets.
23:49Have they been static and slowly changing? How active a player have they been?
24:01Finally, it's time to tow the giant drill out onto the ice.
24:07To ensure that the weight of the rig isn't supported by the sea ice alone.
24:15Divers attach flotation devices to the drilled pipe.
24:18And at the end of that pipe is a whirling tool with a unique cutting edge.
24:24A drill bit made of diamonds that can bore through almost everything in its path.
24:30The diamond core system that we have, it's almost like melting the core down through the rocks.
24:35It just cuts through whatever's there.
24:37If you hit a big boulder, you'll just end up with a cylinder of that boulder.
24:41And it'll just keep going.
24:44Now the real drilling begins.
24:52There's not a minute to waste because the Antarctic research season is so short.
25:00The crews work around the clock to recover cores of rock that trace Antarctica's ancient past.
25:15The powerful drill bores down over three quarters of a mile, bringing up twelve feet of core at a time.
25:23Each foot averaging a thousand years of climate history.
25:29It's an astonishing feat.
25:31It's quite amazing when you think about where we are and what we're doing.
25:36We've got a drill rig, a 60 ton to 90 ton with all the equipment on a drill rig,
25:41sitting behind us here on eight metres of sea ice, above 380 metres of water.
25:46And then we're drilling down into the sea floor below that with a three to four inch diameter pipe
25:50that's turning round and round like a piece of spaghetti hanging down through the water and into the ground.
25:54And it's wobbling around a bit and we're turning around and bringing core up from deep within the earth.
26:01Anything can go wrong at any minute with this process.
26:04And all too soon, it does.
26:09Sometimes even a drill bit made of diamonds can run into trouble.
26:13We haven't been getting particularly good quality core and we're suspecting that the drill bit has been damaged.
26:20In places it's a little bit narrower than it should be for the size of the diamond bits.
26:27And that means we have to pull all of our pipe out.
26:29It's about 1,700 metres and replace the bit and then put the pipe back down the hole.
26:36And that's going to take us about 24 hours to 36 hours.
26:41Removing and replacing nearly a mile of pipe is no easy task, especially when it's your job to change it
26:48all out, piece by piece.
26:52But for other members of the Andrill team, it's a welcome break.
27:07In an extreme environment like Antarctica, nobody's on a diet.
27:13Your body is working so hard to stay warm, packing away 6,000 calories or more a day is not
27:20an indulgence.
27:21It's a necessity.
27:22Is there coffee on the stove?
27:25And because Antarctica is drier than the hottest desert, dehydration is a constant concern.
27:34And keeping the drill up and running is another.
27:45Finally, after a day and a half of hard work, the new bid is in place.
27:50And drilling is back on track.
27:55They recover a 12-foot length of core, wrapped in a protective cover.
28:01Workers carefully carry it back to the lab to be examined.
28:04When they crack it open, it's in perfect condition.
28:09This mud and rock is more valuable than gold because each core is a time machine.
28:16We're currently down at a depth of about 440 meters.
28:20That's about a quarter mile down, corresponding to a time at least 15 million years ago when Antarctica was still
28:28warm.
28:32As the cores are recovered, each section is sliced lengthwise, x-rayed, and scanned in labs at the drill site
28:42and back at McMurdo.
28:46These cores came out of the ground three days ago, they were split yesterday, they were imaged yesterday.
28:50Sedimentologists worked the night shift, 12 hours, describing these cores millimeter by millimeter,
28:56looking at the color, size ratios, any kind of structure they see in a core, trying to understand how these
29:01sediments were deposited.
29:04Each core tells a story, depending on its texture, color, and contents.
29:10And some of those stories are spectacular.
29:13We're seeing some macro fossils, some large shells.
29:16These shells are evidence of warmer times, even as Antarctica is icing up.
29:21This is one of the most spectacular fossils found within Andriel this season.
29:25This is a scallop.
29:27Now this kind of scallop simply do not live in extreme polar waters.
29:36And there are other clues, some of them nearly invisible.
29:41Hidden inside these cores are shells of microscopic algae called diatoms.
29:46For Andriel climate detectives, these tiny diatoms create a highly revealing picture of the past.
29:54Because not all diatoms are alike.
29:57Some species are adapted to colder conditions, while others flourish in warmer waters.
30:04We use them as biological markers, index of different environmental conditions, cold or warm, frozen waters or open ocean waters.
30:12Again, the Andriel team examines cores from around 15 million years ago.
30:18They find smooth green sands containing diatoms that thrived in relatively warm water.
30:24Confirming this was a time before Antarctica finally froze over.
30:29This is a very well-defined warm period.
30:33Iceberg-free waters, open waters where diatoms are growing and thriving.
30:38You can see this persisted for quite some time.
30:40A picture is beginning to form of a long period of transition, starting 34 million years ago, when a cooling
30:48climate led to the formation of ice.
30:51But even so, conditions remained relatively mild.
30:55But when did Antarctica finally slip into a deep freeze?
31:01The answer lies in cores from around 14 million years ago.
31:07Instead of smooth and green, these cores are rocky and gray.
31:11And some contain diatoms that thrived in cold glacial waters.
31:16This amazing discovery reveals a rapid change from cool to frozen.
31:24It fills in what has always been a blank page in Antarctica's climate history.
31:31Next season, they'll attack another crucial question.
31:35After Antarctica froze 14 million years ago, did the ice ever melt?
31:41Or has it remained a frozen wilderness right up until today?
31:46That answer will have to wait.
31:52Cracks in the sea ice tell the team it's time to return to base.
31:57We've seen the ice break in quite a bit in the last month, but it's not broken in anywhere further
32:03south than it is right now.
32:05We can only be on this site for so long before the sea ice starts to melt, before the conditions
32:11change.
32:11And for safety reasons, we have to get off the sea ice.
32:16The precarious sea ice of West Antarctica may come and go with the seasons.
32:22But what about the giant East Antarctic ice sheet?
32:26A mountain of ice so high, it covers mountains.
32:31This is like an MRI of the ice sheet.
32:34Some places it's really thick, two miles thick and pretty flat and boring.
32:38But then there are other places where what we discovered were hidden mountain ranges the size of the Appalachians.
32:46But totally hidden by the huge East Antarctic ice sheet.
32:51There's ten times as much ice in the East as in the West.
32:56But a small portion of the East has almost no ice at all.
33:05It's an unearthly location that defies the very image of Antarctica.
33:17These are the dry valleys.
33:20Cold.
33:21Barren.
33:23And except for a few scientists, almost completely devoid of life.
33:29The landscape is so alien, NASA has used it as a test site for space programs.
33:39It's a fantastic place.
33:41You can't find this anywhere else on Earth.
33:44Its closest analog is the surface of Mars.
33:51Mullins Valley is the ultimate remote field camp.
33:55It serves as home base for a pioneering band of glaciologists, led by Dave Marchant.
34:10Marchant and his team are conducting research the rugged, old-fashioned way.
34:16They'll live in tents and won't be picked up for two months.
34:21They need to be self-sufficient, and for the most part, they like it that way.
34:26Good day.
34:28Burritos.
34:34The good thing about working out here, it's actually a double-edged sword.
34:38You come out here, you have no contact with the outside world, no email, no real telephone contact.
34:43So you can totally immerse yourself in the science.
34:45And that allows you to think 24 hours a day about what you're doing.
34:48The other side of that is, you have no idea what's going on outside.
34:51Hi.
34:52At the beginning of the season, I didn't like it when you would breathe and the frost would form on
34:56the outside of the sleeping bag.
34:58But it's warmed up now, and it's a little more comfortable in the morning.
35:03Small setups like we have, which are helicopter-supported, are isolated.
35:07They're among the most isolated in the region.
35:09And as a result, we have to check in daily with McMurdo.
35:15I'm trying to heat the batteries up so that we can get a signal out.
35:18Right now, there appears to be no satellite coverage, and the batteries are a little bit cold, so I'm trying
35:25to warm it up.
35:27Sometimes you have to contort your body in various ways to get the signal.
35:34Nah, we don't have enough signal yet.
35:40Well, here we go. We've got something that might work.
35:43Mac Ops, this is Gulf 054 Mullins Valley.
35:46We have seven on board, and all is well. Over.
35:51Ah, we lost transmission.
35:56This valley holds an incredible record.
35:59This area is so dry and so cold that the landscape is pristine.
36:02The rocks we see here are millions of years old.
36:08Marchant believes that little has changed here for millions of years.
36:14What, to me, is exciting is that we're walking on an ancient landscape.
36:19Imagine living 10 million years ago in Antarctica.
36:21This is what you'd see, exactly as it is today, hardly modified at all.
36:30But when Marchant's team drilled beneath this rubble, they found something totally unexpected.
36:40A hidden glacier that extends hundreds of feet below the surface.
36:46This is, in my opinion, the oldest dated buried glacier on Earth.
36:50Is it all out? Yep, it's all out.
36:52Are you getting it? Yeah.
36:53The evidence comes from volcanic ash.
36:57The dry valleys are surrounded by extinct volcanoes that erupted millions of years ago.
37:03We're finding ash deposits on top of ice.
37:06Ash dates are coming back as old as 8 million years.
37:09And according to Marchant, this volcanic ash shows this hidden glacier, once frozen, has never melted.
37:18This is volcanic ash that erupted from a volcano and has been sitting there for millions of years.
37:23It shows no chemical alteration, which you'd expect if there were any amount of liquid meltwater over that duration.
37:30The fact that it's dry and pristine tells me it's always been here, which is incredible.
37:38Equally astonishing and just 300 miles away, there appears to be a completely different picture.
37:46Exploring East Antarctica, closer to the South Pole,
37:50Andrill's David Harwood found leaf fossils and pieces of wood.
37:56Surprisingly, according to Harwood, these date to a relatively recent time, when Antarctica was not only warmer than today, there
38:05were plants and trees.
38:06This is a piece of southern beach.
38:09This wood is not fossilized in the sense that it is petrified. It could still burn.
38:15To find the wood and leaves together is pretty phenomenal.
38:18It's really phenomenal for Antarctica, particularly for Antarctica in this time period about 4 million years ago.
38:29This season, the drill is set up to find evidence of what happened in Antarctica during this period.
38:353 to 5 million years ago.
38:38It's a time known as the Pliocene.
38:41Now what's important about that is that the Pliocene was globally warmer than today.
38:48The same temperatures as our Earth may be headed for at the end of the century, if climate change predictions
38:54are correct.
38:55If we go back 3 to 5 million years into the geological past, we know that there was a time
39:01when Earth's climate was warmer than it is today.
39:03Perhaps by 3 to 4 degrees.
39:06So it's the best example we have of where the climate's heading in the next hundred years.
39:11The drill's new location is on the giant Ross ice shelf, which extends out and over the ocean.
39:18It's the largest ice shelf in the world.
39:22And it helps hold back the massive Antarctic ice sheet from flowing into the sea.
39:29These ice shelves are very important.
39:31What they do is hold back the flow of ice that's actually trying to flow out into the ocean.
39:37We call that buttressing.
39:38If warming oceans cause the Ross ice shelf to break up and melt into the sea, the West Antarctic ice
39:46sheet would eventually follow right behind.
39:53The andrel team is looking for the answer to a critical question.
39:57When Earth was warming during the Pliocene, what happened to the ice?
40:03Did the Ross ice shelf melt, taking the giant ice sheets with it?
40:09Drilling on an ice shelf brings with it a unique set of technological challenges.
40:20Including constant problems with mud and water.
40:25Unlike drilling through sea ice, which is just 26 feet thick, the ice shelf here is 400 feet.
40:33We're looking at at least doubling or trying to double our capability below the sea floor and penetrate to 1
40:42,000 metres or better into the sea floor.
40:44But that's only the beginning.
40:47No one has ever drilled through an ice shelf.
40:49And they present these challenges.
40:51The ice shelves, they float up and down with the tide.
40:54So you've got to deal with this vertical elevation change.
40:57They move sideways, they flow.
40:59So eventually your drill pipe's going to get bent.
41:03Can the drill bore through a thick layer of ice that's constantly moving without breaking or getting yanked out of
41:10the sea floor?
41:11To confront this unique challenge head on, the andrel team invents a new tool.
41:17A hot water drill.
41:19This marvel of engineering is a moving ring of heat that blasts jets of steaming water to melt a wide
41:26hole so the drill can operate freely through 400 feet of shifting ice.
41:31And once again, time is so precious, the team must work around the clock, not only retrieving cores, but also
41:39analyzing them.
41:41It's 2 a.m. but you wouldn't know it.
41:44Geologists are busy logging cores like it's early afternoon.
41:48We're laying out the cores in a proper sequence from the top to the highest point of the core all
41:53the way to the very slowest point of the core here.
41:55An 80-foot core that dates back about 3 million years is closely examined.
42:01It contains microfossils of single celled animals known as forums.
42:10They're from the crucial warm period called the Pliocene.
42:14And these tiny shells are precise indicators of ocean temperature.
42:19These guys are about the size of a grain of sand.
42:22Because the same species lived through time, we can use the chemistry of modern examples to allow us to calibrate,
42:30if you like, the chemistry of the ancient examples.
42:42What Gav's doing here is he's measuring the amount of two metals, magnesium and calcium, that are in the ocean
42:49and get incorporated into the shell of the forearm when it's growing in that ocean.
42:54And that process is dependent on the temperature of the ocean.
42:58So if we know the magnesium, we know the calcium, we can determine the temperature of the ocean at the
43:03time that forearm lived.
43:04And because of that, Andrel researchers can now calculate Antarctic water temperatures during the Pliocene.
43:11What this is telling us is temperatures were 3 to 4, perhaps 5 degrees above present.
43:18Even just one degree rise in ocean temperatures in the waters surrounding Antarctica will attack and begin to melt the
43:27ice shelves from below very quickly.
43:30The air temperatures will stay cold enough to keep things frozen at the surface, but what we're worried about is
43:35the ice being attacked from beneath, not from above.
43:40And the cores reveal that this is what happened during the Pliocene, when global climate was warming.
43:46But they display even more change than expected, revealing not only a patchwork of glacial rubble, but also smooth mud
43:55from open seas, indicating that ice both froze and then melted many times.
44:00There's a really important change right here. This interval shows us quite a dramatic change in the environment.
44:09There was ice, and then there was no ice.
44:11The ice sheet has gone backwards and forwards. It's advanced and it's retreated.
44:16As they examine core after core from the Pliocene, they continue to see surprising signs of change.
44:22The results of the drilling are simply spectacular. They give us a picture of a dynamic ice sheet coming and
44:31going regularly more than 60 times.
44:36What we're seeing in this record is telling us that Antarctica is not just a benign spectator. It's a player.
44:44What this means is while it was generally warm during the Pliocene, there were also brief periods of cooling.
44:51And the ice was exquisitely sensitive to even small changes in climate.
44:56Just a few degrees could tip the scale from ice to no ice.
45:02So what's in store for our future?
45:05As Earth continues to warm, how much Antarctic ice will melt? And how high will sea levels rise?
45:14Andrel scientists turned to computer models by Rob DeCanto and Dave Pollard.
45:23We developed these climate models based on our best understanding of the physics of the climate system, and in this
45:31case ice sheets.
45:33And now, information from Andrel is added to the climate model.
45:37This is a computer model simulation of the Antarctic ice sheet over the last several million years,
45:43and covers a good chunk of the interval that was recovered by the Andrel sediment core.
45:48So we're looking for the same kind of behavior in our models that we're seeing in the geological record.
45:54As the model simulates the warming periods of the Pliocene, all of the ice shelves disappear.
46:02Followed by the entire west Antarctic ice sheet, and edges of the east.
46:08And as temperatures change, the ice refreezes and melts again and again.
46:14And that's important because the changes in the ice sheet that we're seeing here reflect pretty significant changes in sea
46:22level.
46:25According to DeCanto's model, sea levels rose about 23 feet during the Pliocene.
46:31Temperatures back then were 3 to 5 degrees higher than now.
46:35Just what's projected to take place by the end of the century.
46:41But there's a lag time in the way ice responds that may delay the impact for hundreds, if not thousands,
46:48of years.
46:50Regardless, coastal cities all over the world would be at risk, potentially displacing millions.
46:57We would be remapping places like Boston and New York, the Bay Area.
47:04Not to mention, of course, places like Louisiana, Miami, New Orleans, of course.
47:10But even that might not be the worst case scenario.
47:20Things were very similar to today in terms of our climate.
47:24Tim Naish brings Rob DeCanto to New Zealand to look at a possibility that's even more frightening.
47:30This is the first time I've seen the actual direct evidence for what the models are doing.
47:36You're seeing a deepening sea level rise up through here.
47:42We're going to look at some rocks that are the same age as rocks we've drilled in Antarctica that give
47:48us the record of global sea level changes.
47:55Here along the Rangitiki River, tectonic forces have raised the land and the river has cut into the earth to
48:03expose layer after layer of sediment that once was the sea floor.
48:10What they find are shells dated to the warming era of the Pliocene.
48:15These shells provide a way to chart sea level in the past because some of these species still exist today.
48:22Many of these shells you see in here actually live today.
48:25So they live around the coastline and we know the water depth they live in today.
48:29So by breaking them out of these rocks and identifying them, we can say the depth they were living here
48:36over three million years ago.
48:38Because these shellfish live on the sea floor and can only survive in water at specific depths, they suggest that
48:46sea levels in the Pliocene were much higher than even the computer models predict.
48:52This is really it, Rob.
48:54This is where we would say we have the evidence for sea level being up to as much as 20
48:59meters above present.
49:01That's over 60 feet.
49:04In order for sea level to have risen that high, an enormous amount of ice must have melted.
49:11And this raises a startling possibility that a large part of the vast East Antarctic ice sheet melted along with
49:19the West.
49:21And if it melted once, could it melt again?
49:26That could be a very bad thing because that would actually produce a contribution to future sea level change that
49:33we really haven't been thinking about.
49:37This presents an even more dangerous and unpredictable picture of Antarctica.
49:47What's been surprising is even geologists thought that glaciers and ice sheets were these large static features, which we would
49:55never really see change in our lifetime.
49:57But glacial processes are no longer quite as glacial. Things are moving faster than we had thought.
50:06What's driving these changes are rising levels of greenhouse gases.
50:11In the next five years, greenhouse gas levels will be like they were in the Pliocene.
50:17But we're not just going back to the Pliocene.
50:20Some of the projections put CO2 levels at twice the concentrations of the Pliocene.
50:26By the end of the next century, we're essentially going back to the time of the dinosaurs when there was
50:32very little ice on the planet and there were forests covering Antarctica.
50:38And signs of change are already here.
50:42Scientists were completely caught by surprise when in 2002, the Larson Ice Shelf shattered apart without warning in just a
50:51few weeks.
50:53And today, the Wilkins Ice Shelf, a block of ice approximately the size of Connecticut, barely hangs on.
51:01I would say it's inevitable that Western Antarctica will disappear.
51:04How long it will take East Antarctica to engage is something that's not yet known.
51:11In the coming years, the Andro team will continue to explore Antarctica's climate history in order to gain valuable insight
51:19into Earth's future.
51:20With each new core, we gain new knowledge about a continent that's always been shrouded in mystery.
51:27But its fate remains very much tied to our own.
51:31therefore, it is possible.
51:56The λ scale is over 38.
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