Could the world be facing the next deluge—a catastrophic rise in sea levels—as a result of the rapid break-up of the huge Antarctic ice sheets? The ice sheets hold 70% of the world's fresh water in a deep freeze cold enough to shatter steel, but now scientists are racing to understand whether the recent calving of a Connecticut sized iceberg signals the beginning of a giant meltdown.
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00:00Tonight on NOVA, is Antarctica melting?
00:05A mountain of ice is on the move, and its fate could spell disaster.
00:09It does matter to everybody in the world what that ice sheet is doing.
00:15Are we on the verge of the next ice age, or a great flood that may consume the world's
00:20coastlines?
00:21The race for answers sparks a NOVA expedition to the ends of the earth.
00:28The bottom of the world is a beautiful but unforgiving place.
00:58An entire continent cloaked in ice.
01:08Antarctica, just over 700 miles from South America, yet it's so isolated its existence
01:20was a myth until the 19th century.
01:28For over 20 million years, Antarctica has been the coldest place on earth.
01:35But recently, things have been heating up.
01:40In 1995, an iceberg the size of Rhode Island broke off from the Larson ice shelf along the
01:48Antarctic coast.
01:52And a large portion of the ice shelf disintegrated in a matter of days.
02:01Over the last half century, the coastal ice on the Antarctic peninsula has been gradually disappearing.
02:11What does it mean?
02:13Is Antarctica melting?
02:15What would happen if all this ice were unleashed into the oceans?
02:27What does it mean?
02:28What does it mean?
02:31Kevin Costner's epic film Waterworld depicts Hollywood's version of the disaster, a future
02:38where dry earth is rare and precious.
02:41What does it mean?
02:46Beneath the waves, civilization lies destroyed, drowned by melted polar ice caps.
03:01Is this a science fiction, fantasy, or could Waterworld really happen?
03:14To find out, scientists are heading south to Antarctica.
03:22Their first stop is New Zealand, where they gear up to battle the elements.
03:29Even it's an eight-hour flight in a military cargo plane.
03:34The LC-130 Hercules, affectionately known as the Herc, is not designed for comfort.
03:45But it's one of the few planes tough enough to do the job.
03:56Every summer, Herc deliver hundreds of scientists to Antarctica.
04:01They have just a few short weeks to unload supplies, set up camp, and collect crucial data before the dark polar winter sets in.
04:15These are the ice experts.
04:18They're on a mission to unlock the secrets of Antarctic ice.
04:25Is it melting?
04:27Is it moving?
04:29Most importantly, how will it affect the rest of the world?
04:37Taking the pulse of Antarctica is a daunting task.
04:42The continent is one and a half times the size of the U.S. and is covered with seven million cubic miles of ice.
04:53The giant ice sheet in the east is probably more than 15 million years old.
05:00But the West Antarctic ice sheet is younger, and scientists fear much less stable.
05:10While the ice on the eastern side of the continent rests on dry land, most of the West Antarctic ice sheet sits precariously on bedrock that lies below sea level.
05:25Part of the ice sheet is in direct contact with seawater, which is much warmer than the air, and that means the ice can melt much faster.
05:38The West Antarctic ice sheet is as big as Mexico.
05:43If it broke up and fell into the ocean, sea level would rise by almost 20 feet.
05:51That's enough to redraw the world's coastlines, flooding Bangladesh and Florida, London and New Orleans.
06:03The deluge would wipe out entire cities and render millions of people homeless.
06:10Many experts believe the West Antarctic ice sheet is doomed to collapse.
06:17The question is, how long will it take?
06:21Two thousand years or a few decades?
06:25The answer may lie in the nature of the ice itself.
06:34The ice sheet is made up of layers of snow that piled higher and higher over the millennia and then compacted under their own weight into ice.
06:46In some areas, the ice sheet is almost three miles deep.
06:53And when ice gets this thick, it can't sit still.
06:59Antarctic ice is constantly on the move.
07:06When the ice sheet reaches the mountains, it squeezes through the ridges, forming valley glaciers.
07:21Across the continent, scientists are trying to track the movements of the ice.
07:27On the eastern side, one research team is probing the depths of the Masurve glacier.
07:36A year ago, chainsaws carved this 200-foot tunnel into the heart of the ice.
07:43A tunnel provides one with a spatial picture that you can look at the geometry of these features in a way that's unique.
07:50You can't do it any other way.
07:53Charles Raymond is trying to understand how ice moves.
08:00We put these bolts in vertical lines about a year ago.
08:04And we lined those lines up so that these figures were actually squares.
08:08And what's happened in the meantime over the intervening year is that the top up there has moved this way,
08:15and this down here has stayed relatively fixed in place.
08:19And so there's been this kind of motion, which we call shearing, that deformed these lines into inclined lines,
08:27from vertical to inclined, and the little squares are now parallelograms.
08:31The bolts reveal that the ice at the bottom of the glacier only moved about a fifth of an inch in the last year.
08:39But the ice above it flowed much faster.
08:43The top of the Masurve glacier moved about six feet.
08:48What we have to remember first is that the ice moves. It flows.
08:53And if you think about taking pancake batter and pouring it onto a plate, it will spread.
08:59Gravity pulls it down, it flumps out, and so it flows. Ice does exactly the same thing.
09:04It snows on top of the glacier, the weight of the ice pushes it down and it spreads out,
09:10and so you have moving ice.
09:13The ice in Antarctica is so thick, gravity forces it to spread out towards its edges.
09:23Eventually, there's only one place for the ice sheet to go, into the sea.
09:40As it pushes off the coast, the ice thins out and begins to float.
09:45It is now called an ice shelf.
09:50Above the water, the ice shelves look like towering cliffs,
09:54but they are actually just the tops of enormous floating ledges of ice
10:00that extend hundreds of feet beneath the surface.
10:04As the shelves break apart, colossal icebergs are launched into the Southern Oceans.
10:20Antarctic icebergs are famous for their extraordinary size, often several miles long.
10:33Floating among the majestic icebergs is a less glamorous type of ice,
10:38but one that's extremely important for Antarctic wildlife.
10:50Sea ice forms when ocean water freezes.
10:53Just a few feet thick, sea ice is the perfect platform for marine mammals like seals.
11:07And for birds, especially penguins.
11:14In the water, penguins hunt for krill, fish, and squid.
11:27But they mate and breed on land, or on the shifting sea ice itself.
11:33During the winter, as air temperatures drop, the sea ice freezes into sheets and expands outward from the coast.
11:50This image produced by microwaves shows how sea ice grows and shrinks with the seasons.
11:58At the height of winter, the thin veneer of ice stretches almost a thousand miles across the ocean,
12:05in effect doubling the size of the continent.
12:13Sea ice protected Antarctica from human invasion for thousands of years.
12:19When sailors finally did venture south, the floating ice tormented them.
12:28In 1914, the British ship Endurance headed for Antarctica.
12:35Explorer Ernest Shackleton was hoping to march across the entire continent.
12:41But he never made it ashore.
12:44Sea ice closed in around the Endurance and carried it in an aimless drift for nine months.
12:58Documenting their ordeal with a film camera, the crew struggled to cut the boat free, but failed.
13:06Finally, they were forced to abandon ship, and could only watch helplessly,
13:17as the mighty Endurance was broken and crushed by the shifting ice.
13:22Civilization was more than a thousand miles away, and Shackleton was left with just three small lifeboats.
13:39He spent nearly a year battling, crushing ice flows and hurricane seas, but overcame the odds.
13:48With one of the boats, he was able to reach a small whaling station in the South Atlantic.
13:56Two years after they'd set out, the crew of the Endurance was rescued.
14:03Amazingly, all 28 men survived.
14:11Antarctic exploration has come a long way in the last 85 years.
14:16Today, 13,000-ton steel-hulled icebreakers slice their way to the coast.
14:28One of the early camps has exploded into a scientific boomtown.
14:34McMurdo Station is headquarters for the U.S. Antarctic Program, supported by the National Science Foundation.
14:41Hundreds of scientists are based here.
14:47Many of them study the crucial relationship between ice and climate.
14:55In the last century, global temperatures have risen about one degree Fahrenheit,
15:01possibly as a result of industrial activity.
15:06But on the Antarctic Peninsula, it's warmed up more than four degrees during the same period.
15:14Here, large chunks of the floating ice shelf are breaking away.
15:20And native plants are thriving along the rocky coast.
15:28Scientists do not blame global warming for the massive meltdown.
15:34Instead, they believe it's part of a natural, local climate shift.
15:39Looking back in time, it's clear that climate has undergone some major changes,
15:49with direct impact on the size of the ice sheets.
15:53In the last million years, the glaciers have grown and shrunk about ten times.
16:00And they typically spend about 90,000 years growing, and 10,000 years melting,
16:04and 90,000 years growing, and 10,000 years melting, and so on.
16:09Ice ages. Each lasting 100,000 years have come and gone again and again.
16:16At the height of the last ice age, 21,000 years ago,
16:21much of North America was frozen under a giant ice sheet.
16:27And temperatures were about 20 degrees colder than they are now.
16:36Today, we are in one of the shorter warm periods between the ice ages,
16:41called interglacials, when much of the ice melts.
16:47As it melts, more and more water flows into the oceans, and sea level goes up.
16:55Sea level is ultimately controlled by how much water is in the ocean,
16:59and by how hot that water is.
17:01If we take water out of the ocean and put it in an ice sheet,
17:05then the ocean gets lower.
17:07If we take water out of the ice sheet and put it back in the ocean,
17:10sea level comes up.
17:12During the ice ages, water accumulated in the expanding ice sheets,
17:18and global sea level went down.
17:21But for the last 20,000 years, the ice has been melting,
17:26and the oceans are getting bigger.
17:28Over the last 20,000 years, sea level has been rising.
17:33Over the last 4,000 years, it's been rising about 2 millimeters a year.
17:38And so the concern is whether that rate is going to continue,
17:42or whether it's going to accelerate, or whether it might even decelerate.
17:46So far, the collapsing ice shelves haven't raised sea level at all,
17:53because they were already floating and displacing water long before they broke up.
18:03For sea level to rise significantly, ice from a grounded ice sheet
18:08has to flow rapidly into the sea.
18:11And that's most likely to happen in West Antarctica,
18:16where the ice sits on bedrock below sea level.
18:25To find out how vulnerable this ice sheet is,
18:28scientists like Bob Binschatler are heading out into the Antarctic wilderness.
18:33We're out there trying to understand how the ice sheet works.
18:40What are the forces that make the ice move?
18:43And if those forces change,
18:44how is the ice sheet going to respond to those changes?
18:50But tracking the West Antarctic ice sheet isn't easy.
18:56Even during the summer months, conditions can be brutal.
18:59The team's only protection is an insulated box
19:04that serves as a traveling base camp.
19:08It's a kitchen, lab,
19:14and dormitory squeezed into a ten-foot-by-ten-foot room.
19:19When the winds die down, team members set out in pairs across the surface of the ice.
19:38Their mission is to locate and map hundreds of marker poles spread out across 4,000 square miles of the West Antarctic ice sheet.
19:55We use global positioning satellite receivers, which tell us our precise location.
20:03So we go to a site and we put the receiver antenna on top of the pole,
20:09measure its position, and then come back a year later and re-measure its position.
20:14And then that tells us how far it's moved in that year.
20:27Pole by pole, and day after day, the team collects the data.
20:32Every few days, base camp moves on, and the process repeats itself until something breaks down.
20:47With the wind chill plunging to 50 below, equipment repair is a challenge.
20:52Fixing the skidoo in the cold is really difficult.
20:57One of the problems is that your tools have been outside, probably.
21:01So they're very cold.
21:03So you're not going to be able to work with bare hands, fingers.
21:07So trying to put a socket on a nut can be difficult.
21:13Maneuvering some of the tools in tight spaces can be difficult.
21:17And you'll drop things.
21:18You'll drop things, and it'll go into the snow, and you won't be able to find it,
21:21and you'll just be fishing around for half an hour just trying to find the nut that just fell.
21:28So those kinds of frustrations just limit your ability to move and do the things that you're accustomed to being able to do.
21:40As they make their daily rounds, the scientists face more than frustration and cold.
21:46The movement of the ice sheet can open up gaping cracks called crevasses.
21:57Crevasses can be 50 feet wide and more than 100 feet deep.
22:03Worst of all, sometimes they're invisible, covered by fragile bridges formed by blowing snow.
22:11Walking along the surface, a researcher would never see the giant chasms until it's too late.
22:24This was a demonstration, but Bob Binschadler knows firsthand the terror of an unexpected plunge.
22:37It's just like having a rug pulled out from underneath you.
22:40You're walking on something that you think is a firm surface, and all of a sudden it disappears, and you just shoot downward.
22:45Bob must be all the more vigilant because he spends much of his time driving a heavy skidoo across the ice.
22:55The skidoo makes it even more hazardous because you have something that is about five times your weight,
23:02and if the two of you fall into a hole, you don't want to be anywhere close to that machine.
23:08Over the years, crevasses have killed several explorers and scientists.
23:16In this case, the driver survived, but his bulldozer is lost forever.
23:27The data that Bob's team is collecting may help to explain why parts of the ice sheet are riddled with crevasses.
23:34Measurements reveal that some of the poles have moved almost half a mile in a single year.
23:43They are riding on a 200-mile-long ribbon of rapidly flowing ice called an ice stream.
23:52The ice stream is probably best described as just a river of ice contained within the ice sheet.
23:59Ice sheets, in general, are thought to be very slow-moving features,
24:04slow-moving meaning just a few feet per year.
24:08But these ice streams, these faster rivers, rapid currents, will go about a few hundred meters per year,
24:15up to 700 meters per year in the case of the ice streams that we're studying.
24:19The ice streams move so fast, friction at the sides splits open the ice, creating enormous crevasse fields.
24:30The ice streams are so large, their true size and shape can only be appreciated from space.
24:37Satellite imagery of West Antarctica reveals several areas where rapid movement has occurred.
24:47Through these ice streams, highlighted in blue, ice is flowing from the heart of the West Antarctic ice sheet,
24:55out into the huge, floating Ross ice shelf.
24:58Ice streams are 50 to 100 kilometers wide, about a kilometer thick.
25:05They go 10 to 100 times faster than the interior ice.
25:09So they're capable of moving vast amounts of material into the oceans.
25:13But why are the ice streams moving so fast?
25:18Geologist Don Blankenship believes the answers lie beneath the ice, in the rocks that support it.
25:25The problem of understanding the dynamics of the West Antarctic ice sheet in the context of the geology is that the geology is largely unknown.
25:35It's covered with ice.
25:37If something sticks up through the ice to study, to get a piece of, to get a rock, it's probably an anomaly.
25:43It's not telling us what's really going on. What's really going on is a secret.
25:47To see the rocks beneath the ice, Don Blankenship would need X-ray vision.
25:55Thanks to this airplane, he has it.
25:58This twin otter is scanning the ice sheet with a slew of high-tech remote sensors, including radar that can see right through the ice.
26:08The ice-penetrating radar gives us the bed. The laser altimeter gives us the nuances of the surface to within a fraction of a meter.
26:18And there are instruments that measure the magnetism of the rocks, as well as the gravitational pull of the Earth.
26:27The radar will be in 20 nanoseconds, 250 millivolts range.
26:34With the aircraft, we can fly around and get at least indirect indications of where the rocks are dense, where the volcanic rocks are, where the vaults are.
26:43All kinds of things that we can put together to understand the geology.
26:47Flying over the ice sheet, the sensors detected rocks that were less dense, a characteristic of sedimentary layers, which form at the bottom of oceans.
27:04Okay, start of segment.
27:07In another experiment, sound waves revealed evidence of a layer of soft, wet mud directly below the ice streams.
27:18Don believed that this mud was making the ice streams flow so fast.
27:27But to prove this idea would take a more direct approach.
27:31Our approach is to get access to the base, where the action is, where we believe the action is.
27:38And we do that by drilling.
27:42One, two, three.
27:45Barkley Cam is part of a team that's drilling a hole straight down through an ice stream to take samples from the bed below.
27:54If there's mud down there, he's going to find it.
27:59The normal methods of drilling, it takes a year or so to drill a hole deep enough to serve the purpose.
28:06We have to do it to get an appreciable amount of information.
28:09We have to do it much faster than that.
28:11Okay, we're ready.
28:13So we have a hot water jet that melts its way rapidly down into the ice.
28:21Finding water to supply the jet was no problem.
28:24But producing and maintaining enough heat was a bigger challenge.
28:30To do the job, the team converted eight car wash heaters into industrial strength ice melters.
28:37The temperature of the ice is minus 25 degrees centigrade.
28:43And the air temperature is always below freezing.
28:47The near boiling water is pumped through almost a mile of rubber hose.
28:50And pressurized to 1,500 pounds per square inch.
29:04The resulting jet easily cuts through the rock hard ice.
29:08Okay, Airborne, shut it off.
29:14The biggest single challenge of the cold to our operation is the hazard that some part of this system will freeze up, or all of it will freeze up.
29:22To avoid freezing, the drill must operate continuously until it reaches the bottom, more than half a mile down.
29:30Okay, it's ready to go down now.
29:31We can drill a hole at roughly 3,000 feet deep within a time less than a day.
29:41And then we can get to the bottom and then put down instruments that will reveal something about what goes on down there.
29:48Just as Don Blankenship had predicted, the team found mud directly under the ice stream.
29:58When they pulled up their probe, it was coated with a thick, gooey mixture of wet clay, sand, and pebbles.
30:07Under the microscope, they found these diatons, the tiny fossils of prehistoric algae.
30:20Together, the evidence points to one conclusion.
30:24Where there is now an ice sheet, there once was an ocean.
30:29One thing we all agree on is that the West Antarctic ice sheet does disappear during the interglacial periods, which happen about every 100,000 years.
30:40It may not disappear in this one, the current one that we're in, but it does disappear.
30:46The question that's really important is, what triggers the disappearance?
30:51The ice streams are key to solving the puzzle.
30:54By carrying large amounts of ice quickly into the sea, they are gradually eating away at the ice sheet.
31:03But what's driving the ice streams forward?
31:07Is it just the underlying mud?
31:10Barclay Cam's drill turned up some intriguing evidence that something else might be going on.
31:17A half a mile down, he found signs of a very thin layer of water, possibly less than a millimeter thick, flowing between the mud and the ice.
31:32We learned there that the base of the ice is at the melting point.
31:36And we learned that the pressure of water at the base of the ice is very high.
31:41It's almost high enough to float the glacier off its bed.
31:46And that is a physical driving phenomenon which allows the rapid motion, this near flotation of the ice.
31:55But where is the water coming from?
31:58Why is the base of the ice melting?
32:01We had our high tension coming up.
32:06Port Ashtack and TCG are up.
32:09While flying over the ice sheet, Don Blanken ship's sensors picked up evidence of magnetic rock and a cone-shaped mountain beneath the ice.
32:20And it looks good. We're reading five, nine, eight, four, six.
32:23At the surface, there was a round depression four miles wide.
32:27Ice flows downhill.
32:31And whenever you have a depression, that means that ice on one side is flowing in, and ice on the other side is flowing in.
32:38And it has to go someplace. Mass is conserved.
32:41And so what turns out that the only way for that mass to go someplace is to be melting away at the bottom,
32:47for that ice to be flowing into essentially depression on the bottom that's formed by very high heat flow.
32:52It was an active volcano melting the bottom of the ice.
32:59Even a volcano isn't enough to destroy an entire ice sheet.
33:04But it is evidence of some major geological activity.
33:09Don made his discovery just west of the Trans-Antarctic Mountains.
33:14Here, two continental plates have moved apart.
33:21In the middle, the Earth's crust is very thin, allowing heat to flow up from below.
33:28This could be contributing water to the base of the ice streams.
33:34But scientists worry there could be an additional source of heat.
33:38We have these fast-moving ice streams, which are lubricated on the bed, and between them are ridges of slow-moving ice, which are probably frozen to their beds.
33:49The temperature at the bed depends on a number of things.
33:53It depends on how hot the Earth is underneath and how much heat comes up.
33:57But it also depends on how hot the atmosphere is.
33:59The atmosphere above the ice sheet is extremely cold.
34:05But during the last ice age, it was even colder.
34:10The bed doesn't notice immediately when the temperature at the surface changes.
34:16In the same way that if you take the Thanksgiving turkey out of the freezer and put it in the oven,
34:21the center of the turkey takes a while to notice that it's in the oven.
34:24It remains frozen for a while.
34:27When the air warmed at the end of the last ice age, the bed of the glacier is just now realizing that.
34:35It takes that long for the heat to get down.
34:37So there is some concern that the warming at the end of the last ice age would now be causing melting at the bottom,
34:43and that as more melts, it goes faster.
34:46That makes friction, which makes heat, which melts more, which goes faster.
34:50And same thing, disaster.
34:55If the ice streams are speeding up, disaster could come sooner rather than later.
35:03But it's hard for scientists to identify any long-term trends
35:08when they've been tracking the icy rivers for such a short time.
35:15To forecast the future of the ice sheet, they'll need a better picture of the past.
35:25Kendrick Taylor is one of the detectives trying to decipher the climate history of Antarctica.
35:32He's looking for clues embedded in the ice itself.
35:36When I look out here across the surface here, I see, of course, a small portion of the West Antarctic ice sheet.
35:43This is really a small little teeny portion of it.
35:45But I know that underneath there, there's just a series of layers stacked up one on top of each other.
35:50And those layers contain a record of what the climate has been in the past.
35:54The layers are obvious just beneath the surface.
35:58This is the surface of the snow right up here.
36:02This is a winter sequence, this dense, darker snow up here.
36:06That's snow that fell last winter.
36:08This very light layer, it's a surface hoarfrost layer, which formed last summer when it was warm out.
36:13This is a dense layer here, another winter layer sequence in here.
36:17And then this is a summer sequence right in here.
36:19Now, what's really interesting about this is just by looking at this, I can tell you certain things about what the weather used to be like here.
36:23First off, this winter, it snowed a lot more than this winter it did. You can tell that simply because it's thicker.
36:29And during this summer, this summer was particularly warm. You can tell that because of this ice layer right in there.
36:34That happens when the snow gets very warm, it gets kind of slushy, and that surface layer refreezes and forms a very hard ice crust.
36:42What's going to happen here is more snow is going to fall on the surface, and this whole sequence here is going to get compacted and compacted down until it becomes solid ice.
36:49Ken's job is to retrieve the compacted layers in an ice core.
37:06Each meter-long cylinder of ice represents about 10 to 20 years of snowfall.
37:13And this ice core is going to give us a window on what's happened in the past.
37:16By looking at this ice, we're going to be able to pull up ice that's over 100,000 years old.
37:22We can make measurements on that ice, and we can determine what the climate has been for 100,000 years,
37:26and we can determine the general nature of this ice sheet during that 100,000-year period.
37:33So for some of the ice cores, we have to be very careful about how we collect them.
37:36We have to wear special suits and handle them very carefully to make sure that we don't contaminate the core in the process of working with it.
37:45Scientists have been collecting ice cores for decades, but small rigs like this one can only drill about 450 feet.
37:58The ice at that level is only about 1,800 years old.
38:08At this site, the really old ice is more than a half mile down.
38:14Reaching those depths requires a very long drill.
38:18This is the biggest ice core drill rig in the world.
38:29Ken's team will use it to drill through Seipal Dome, a ridge of ice that rises up between two ice streams.
38:37The ice core they collect will provide important clues about the history of the West Antarctic ice sheet.
38:48That is, if they can get the drill to work.
38:52Greg LaMaurie is one of the managers on the project.
38:57We broke one of the couplings that connects the shaft to the inner core barrel that does the actual drilling.
39:02They don't have this particular coupling in McMurdo.
39:06They're able to machine it up for us in a couple of hours because it's not a very hard part to make.
39:12They have a very good machine shot there.
39:14But now we're really waiting on the weather.
39:16And around here, the weather can sock you in for over a week sometimes.
39:21And they just can't get the Herc flights in.
39:24And so until we can get that part in off the Herc, we're kind of held up.
39:33For the crew at Seipal Dome, sitting out a summer blizzard is frustrating but not life-threatening.
39:42More than 50 people live here at one time.
39:46And they have shelter, heat and food to weather the storm.
39:51But this wasn't always the case.
39:54Frozen in time by the dry Antarctic air, the supply hut of Robert Falcon Scott has sat undisturbed for almost a century.
40:13A British naval officer, Scott led two high-profile expeditions to the frozen continent.
40:20In 1911, he set out for the Holy Grail of Antarctic exploration, the South Pole.
40:30The journey would take him across almost a thousand miles of icy terrain, deep into the heart of the continent.
40:40He rejected the use of sled dogs to haul provisions, instead relying on Manchurian ponies.
40:50They were soon hobbled by the extreme cold, and Scott and his four companions were left to drag their supplies on foot.
41:06After ten weeks of exhausting labor, they arrived at the pole, where they found an empty tent.
41:16A Norwegian team had beaten them by one month.
41:21Scott recorded his feelings in a diary.
41:24It is a terrible disappointment, and I am very sorry for my loyal companions.
41:32It will be a wearisome return.
41:36Great God, this is an awful place.
41:42Malnourished and depressed, the British headed for home, but they never made it.
41:48A relentless windstorm stops Scott in his tracks, just eleven miles from a supply depot.
41:58We shall stick it out to the end.
42:01But we are getting weaker, of course.
42:05It seems a pity, but I do not think I can write more.
42:10Eight months later, rescuers found Scott and his companions frozen in their sleeping bags.
42:20They covered the site with a monument of snow, and Scott's tent became his grave.
42:29Today, visitors are better prepared for the unforgiving Antarctic weather.
42:34When we are out here in Antarctica, it can be relatively benign weather sometimes, and then sometimes it can get violent.
42:42It can change pretty violently for the worse in a relatively short period of time.
42:47Steve Dunbar teaches scientists how to survive the worst Antarctica has to offer.
42:53Including winds that can reach a hundred miles an hour,
42:58and winter temperatures that plunge to more than 70 below zero.
43:02I was out here one time doing a search and rescue exercise with some people, and the weather ended up closing in.
43:07I watched it from about three miles away. There's a good landmark.
43:10And I watched it come in, and in less than two minutes, we had less than 20-foot visibility.
43:16You darn well better get a camp up and get out of the elements, or you're not going to last very long out in this sort of weather.
43:21The shelter is probably the most important thing that you need to do, and you need to get that up first.
43:28Once again, break it free.
43:30And carefully lift it out.
43:40Most scientists come in the summer, but even then, they face the threat of sudden storms.
43:47Calories are gold, and all the calories that you have on board, all that food that you've eaten, all the fats that you have stored, you only have so many of them.
43:57And when you run into a situation here where you find yourself stressed by the weather or stressed by the environment, you need to go ahead and hang on to all those calories and spend them wisely.
44:05So you want to go ahead and build your snow shelter as quickly and as efficiently as possible.
44:11Stronger than any tent, the best protection from the biting winds is a shelter made from blocks of snow.
44:18And it's really dramatic. The second you get into your shelter, you just feel that much warmer.
44:27Safety is always an issue in Antarctica, especially in the isolated research camps like Seipal Dome, where Ken Taylor's team has been waiting patiently for a replacement part for the big drill.
44:44Finally, the weather has cleared, and the new coupling has flown in from McMurdo, almost 600 miles away.
45:00Bigger one?
45:03No.
45:05Left-right, down.
45:13With time running out on their work season,
45:16the crew has only drilled about 25 feet, with 3,000 more to go.
45:23In all, it will take three or four summers to reach the bottom.
45:28Yeah.
45:29Done.
45:31The drillers are weathered veterans of ice sheet research.
45:34Before coming to Antarctica, many of them investigated the ice
45:39on the opposite side of the planet, in Greenland.
45:44Like Antarctica, much of Greenland is covered with an
45:49enormous ice cap, the last of the great northern ice sheets.
45:55The ice is over two miles deep, and the bottom is made from
46:01snow that fell about 250,000 years ago.
46:13American and European teams collected ice cores here that have
46:17revolutionized our vision of climate.
46:24The ice cores were sliced up, and every aspect was scrutinized in detail.
46:30From their crystalline structure, to chemical content, and electrical conductivity.
46:42In this test, two electrodes are dragged across a clean surface of the ice core.
46:48The readout reveals fluctuations in atmospheric dust content.
46:54A dip on the graph indicates more dust and a drier, colder climate.
47:06Climate experts used to believe that the warm-up after the last ice age was slow and steady.
47:12But the Greenland ice cores told a very different story.
47:19Instead of gradual warming occurring over thousands of years,
47:25the end of the ice age 11,000 years ago came suddenly and swiftly.
47:31When you look at the long record, the warm-up from the ice age to today was not a smooth process.
47:42It jumped.
47:43It'd be coming along, and then, boing, the world changed.
47:46The world changed.
47:47And the boing may have taken 50 years.
47:50It may have taken 20 years.
47:52Some of the boings, one to three years.
47:56And the change is something a third to a half of the whole warming from the ice age.
48:02Just the world changed.
48:03Looking back in time, the last 10,000 years have been marked by dramatic changes.
48:12Century-long cold spells and decades of drought.
48:19But these were nothing compared to what came before.
48:23The average yearly temperature has fluctuated wildly, creating climate shifts within a human lifetime that are nearly unimaginable.
48:39If we remember the Dust Bowl, it got dry, and the fields blew away, and the crops died, and people starved, or they moved.
48:47The Dust Bowl was a change in the weather, a change in the climate that would be barely a blip in the climate records we're seeing.
48:56So if you think of the impact of the Dust Bowl on the people living in Oklahoma when that happened, that was a small change.
49:03That was not a big change.
49:06This is the crucial distinction between climate and weather.
49:13The natural disasters we've known, including hurricanes, tornadoes, and floods, are weather events taking place in a climate that is basically stable and predictable.
49:34But if the climate changed, if the average temperature suddenly went up or down by even a few degrees, it could radically disrupt life as we know it.
49:49One way to think of these large changes in climates is as if the climate that you find up in the Midwest, in Iowa or something like that, was suddenly occurring down in Texas.
50:01The cause of such rapid shifts is a mystery.
50:06But some scientists fear there are critical thresholds in our climate that once crossed, could trigger the sudden change.
50:17What it means is that there may be sort of triggers or thresholds in the climate system so that you can be in this one climate state and you can be changing something, perhaps greenhouse gases, perhaps other aspects of the climate system, and you won't see any change or very much change in climate.
50:32And then once you cross a critical threshold or you sort of trip a trigger, if you will, the climate abruptly changes to another state and it catches you by surprise.
50:40So you can be sort of monitoring climate and you can be saying, well, there's nothing going on, there's no real changes, we don't have anything to worry about.
50:47And then all of a sudden, boom, you've got a problem and it's there and it's sort of too late to do anything about it.
50:53When it comes to global warming, popular fears usually focus on the water world disaster, melting polar ice caps and devastating floods.
51:08But now there's concern that if the world gets too warm, high temperatures could help trip a climate trigger and plunge us into a colder and icier age.
51:32If the ice teaches anything, it's that there is no room for complacency.
51:37This is a volatile world.
51:41If climate shifted abruptly in the past, not just once, but repeatedly, it's inevitable it will happen again.
51:53The question is, when?
51:57Ultimately, we would like to know what faces us in the future.
52:01Will the climate do this again?
52:03Should we get ready for it?
52:05Will our actions affect it?
52:07If we humans do this, will the climate change?
52:10Can we change it so that it's nice to us or might we change it so it's very bad for us?
52:15The ice core at Seipal Dome is one piece in a giant puzzle.
52:26If researchers can date the ice at the bottom, they may find out when the West Antarctic ice sheet last collapsed.
52:34And the ice core itself could help solve the mystery of rapid climate change.
52:47slowly, the ice is surrendering its secrets.
52:50Here in Antarctica, they're hoping it will answer some important questions about our future before it's too late.
53:04Where would your favorite stretch of coastline be if the West Sheet melted?
53:21It wouldn't be.
53:22On NOVA's website, see for yourself what such a catastrophe could do.
53:28To order this show for $19.95 plus shipping and handling, call 1-800-255-9424.
53:49And to learn more about how science can solve the mysteries of our world, ask about our many other NOVA videos.
54:04Next time on NOVA, frightening power, lightning speed, and amazing drive for survival.
54:13Brave a close encounter, Crocodile.
54:18NOVA is a production of WGBH Boston.
54:35NOVA is a production of WGBH Boston.
54:38NOVA is a production of WGBH Boston.