THE SECRET OF ANTARCTICA

 Almost three miles of ice buries most of Antarctica, cloaking a continent half again as large as the United States. But when an Antarctic ice shelf the size of Manhattan collapsed in less than a month in 2002, it shocked scientists and raised the alarming possibility that Antarctica may be headed for a meltdown. Even a 10 percent loss of Antarctica's ice would cause catastrophic flooding of coastal cities unlike any seen before in human history. What are the chances of a widespread melt? "Secrets Beneath the Ice" explores whether Antarctica's climate past can offer clues to what may happen. NOVA follows a state-of-the-art expedition that is drilling three-quarters of a mile into the Antarctic seafloor. The drill is recovering rock cores that reveal intimate details of climate and fauna from a time in the distant past when the Earth was just a few degrees warmer than it is today. As researchers grapple with the harshest conditions on the planet, they discover astonishing new clues about Antarctica's past — clues that carry ominous implications for coastal cities around the globe.

It’s a mystery continent at the bottom of the earth of the world And the largest single mass of ice on Earth. for longer than humans have walked the planet. ice has dominated Antarctica but what about the future. ice melts from this continent......Sea Level goes up. as earth gets warmer what will happen to Antarctica. We’re going into uncertain lands uncertain future. how will the earth respond?  Today a pioneering team is searching for answers, with a bold new plan and a revolutionary new machine no one has ever drove through an  ice (unintelligible) and I present these challenges they must drill down nearly a mile and more than 20 million years deep into Antarctica’s ancient history in this unforgiving place it’s never been done before its quite amazing when you think about where we are and what we’re doing anything can go wrong at any minute the stakes are high because the secret to Earths future lies buried in Antarctica’s past right now on nova secrets beneath the ice it’s the coldest windiest driest and most desolate landscape on the planet with few permanent residents except penguins and seals. This frosty continent appears locked in  perpetual Ice Age a colossal cloak of ice covers almost every inch of land and in some places the ice is so thick and so heavy it depresses the Earth’s crust almost half a mile Simple for call it Earths freezer but scientists call Antarctica the ice Antarctica plays a fundamental role in the way the earth functions for polar researchers Antarctica is a giant laboratory more than one and a half times the size of the United States and home to 90% of all the ice in the world anything that happens down here anything that changes will affect the rest of the world most people don't think that change in Antarctica matters to them but when we look at New York City and we looked at it in front of the ocean it matters what would happen if all of Antarctica’s ice were to melts Antarctica melts sea level goes up twelve stories in New York City sea levels would rise by more than 150 feet flooding coastal cities displacing hundreds of millions of people that would be a change that you could see from space earth would look different in any case even a loss of just 10% of Antarctica’s ice would be catastrophic it would raise the sea level over there in Manhattan about 19 feet right up along the edge big sections of Brooklyn would be underwater certainly the Mediterranean some of my favorite cities like Venice would look very different tens of millions of people would have to be relocated to be almost different planet if sea level changes in the climate around the coastal regions change its going to affect the climate where you live it’s going to affect the things you can you can grow is going to affect how you have you live there may be a list of things in store that come as a result of raising sea levels that we haven’t even thought about yet could this be our fate is Antarctica heading for a major meltdown if so it may happen over centuries but it could already be starting because the climate is changing and it’s changing because burning fossil fuels has increased the level of carbon dioxide in the atmosphere today we have something that’s completely man-made and that is the addition of carbon dioxide and put into the atmosphere by humanity by us carbon dioxide is a greenhouse gas it prevents the suns heat from escaping I’m in the Brooklyn Botanic Garden in a greenhouse greenhouses there are basically like heat motels where the sun’s rays can come in and they get trapped inside the greenhouse they can’t get out so like glass in a greenhouse gases like carbon dioxide trap solar energy in our atmosphere but now those levels are increasing the result is our earth is now warming up and the ice is melting both in Antarctica and the Arctic in the north there’s two clear signals in the Arctic Ocean you have lots of floating ice and not sticking around through the summer that’s one sign of it getting warmer the other side the edges of the Greenland ice sheet are changing and the loss of Greenland’s ice is now speeding up in August 2010 and iceberg four times the size of Manhattan broke off the edge of Greenland but Antarctica has nearly ten times as much ice as Greenland and in the past decade alone rising temperatures have caused giant pieces of coastal ice to shrink or crumble polar researchers fear that this could be just the beginning of a chain reaction but have Antarctica’s ice sheets ever collapsed before that’s what an international team of geo detectives wants to find out here we actually have some running water some melt water coming out of the ice to get a more precise picture of Antarctica’s future they plan to dig deep for answers in the past with a giant drill by drilling into areas around the Erika were able to perceive a history that has an impact for where were headed as a planet Antarctica was not always locked in a deep freeze 160 million years ago it was part of an enormous supercontinent closer to the equator at the time earth was much warmer than today and fossil evidence suggests this giant landmass was a tropical habitat teeming with Dinosaurs eventually the supercontinent broke apart and Antarctica drifted south as Earth was getting colder falling carbon dioxide levels and powerful ocean currents cooled the isolated continent even further and then around 34 million years ago ice slowly began to form it would take millions of years for Antarctica to finally lock into a deep freeze and during that time it remained warm enough for plant life to survive evidence of that was recently unearthed in a relatively ice-free Valley in the interior here geologist Alan Ashworth and Adam Lewis find a remarkable fossil oh wait is that a leaf there’s a leaf right there that leaf fell into the mud maybe 20 million years ago suddenly do the best is yet that’s a sweet leaf and then they find something extraordinary this is like a peat moss and then if we take T some of this out there flight freeze-dried under the microscope these brittle mosses are in pristine condition moss fossils are not rock but actual plant tissue the last vestiges of vegetation from a time when Antarctica was still warm they were found under a layer of volcanic ash that dates back millions of years this is the original moss tissue and even the cells are preserved in these fossils these plants were flash-frozen when an article plummeted into a deep freeze that preserved them until today it’s mind-boggling the only way is to say the climate remained very  cold it remained very dry and it did not warm up for even relatively short periods of time in this location otherwise these things are gone now as Earth is heating up what will happen to Antarctica will it melt raising sea levels all over the planet how sensitive is this frozen land to the temperature changes we currently face but before researchers can investigate in Antarctica.

Last-minute testing is taking place here over 2,000 miles away in the countryside of New Zealand, with a brand new drill. Yeah, it’s a shake down. we’ve got a few leaking connections and things that don't quite fit as well as I need to a little bit of modifications required pretty common with a brand new piece of equipment weighing in at a whopping 40 tonnes this mechanized marvel is as heavy as a humpback whale and just as large towering some 5 stories high the giant rig will soon dwarf everything in sight except the ice this will be the largest Rorick in Antarctica that’s used on land in this mammoth rig can drill in more than one place that’s because its mounted on a sled I think it probably is unusual all of the equipment is on sledges so in Antarctica we pull it all with pygmy bulldozers it’s been specially designed to drill from the ice in order to extract hidden secrets from beneath Antarctica itself this unique multinational enterprise is called an drill the Antarctic drilling project for team leader David Harwood it’s a dream come true as a scientist there’s a passion there’s a passion that comes in trying to figure it out trying to identify what has been the past history of the ice sheet and wondering what the future might hold soon the giant drill will be dismantled and ready for a long sea voyage this will get you to take your extreme cold weather days off but now the and rill team gathers at Christchurch New Zealand for the six-hour flight to Antarctica in a c-17 cargo plane jam-packed with people and gear their flight passes over the Transantarctic mountains which divide the continent into two regions with colossal glaciers called ice sheets blanketing both The giant East Antarctica Ice Sheet is ten times the size of the West its frozen firmly to bedrock high above the sea and in some places the ice towers almost three miles into the sky the smaller West Antarctic Ice Sheet is less stable that’s because it rests on land well below sea level and it extends hundreds of miles over the ocean in floating ice shelves its likely East and West Antarctica will respond very differently to a warming world the and real team touches down in the West on an icy runway at McMurdo Station the largest US research base in Antarctica.

As David Harwood and Richard Levy stepped out of the ice, the first thing they notice is the weather. It is a bit chilly but it’s beautiful. It is good to be back. It’s October springtime and its minus 20 degrees the earliest I’ve ever been down to Antarctica and its very cold when the wind picks up its rather an unpleasant place to be working when the wind isn’t blowing and the sun shining it’s actually really quite nice but very cold. but even a sunny afternoon can turn nasty in a moment’s notice. It’s a beautiful day. Come on guys!

McMurdo Station has been a vital hub of research for over half a century. what began as a tiny outpost as over the years grown into a small town McMurdo houses a population of 200 people year round but during the research season it becomes home base for over a thousand Every year Mc Murdo supports scores of research projects providing lab facilities food and supplies . and survival training of scientists who will head out to remote field camps. this season, those numbers include the and rill team of over 50 technicians and researchers From the U.S.. New Zealand Germany and Italy and An drill is funded by their governments and the National Science Foundation There’s probably a week at least of work in McMurdo where we have to get all of our gear sorted out getting everything we need in order to be able to work and survive on the field as they gather supplies for more than a month on the ice one item is in high demand. sugar actually heats your body it gives you a quick energy especially if you’re like freezing and we expect to be very cold we don’t really know how much chocolate is enough we can take up to 560 candy bars but I’m looking at this and I’m already getting queasy I’m like oh I don’t know if I can eat this or not.

Hey David. As An drill researchers prepare for life in the field they join hundreds of other scientists fanning out across Antarctica and many are focused on the same question could Antarctica be headed for a meltdown.  Over here is Mount Boreas were gonna have a lot of scientists working together there is a little bit of volcanic ash and you know challenge each other’s theories challenging what we know. Look at that. As a community we are gonna find the answers. But the continent won’t give up its secrets, easily. The star beauty of Antarctica masks a treacherous nature more than seventy percent of all the fresh water in the world is harbored here. But most of that water is frozen and with less precipitation than the Sahara Antarctica is the driest desert on Earth. Raging winds of up to 200 miles per hour sometimes blasts the frozen terrain. where temperatures can drop to a hundred degrees below zero. Only during the short Antarctic summer can most researchers gather precious scientific data from this giant mystery continent. 

A four hour flight and 400 miles for McMurdo is the center of the West Antarctic Ice sheet. And for one team, this is This is the best way to find out about the past. This is the side of a snow pit it’s a thin wall between two pits the other side is open so that can light can shine through and you can really see the different layers in the pit. So this is one years’ worth of  snow accumulation and there’s a second years’ worth of snow accumulation here below it. Two years of record right here in the snow pit.

Of course, you want to go back a lot further in time with that. In order to do that we can’t just use shovels and chainsaws like we did here. so we have to use a drill ken Taylors team is drilling through ice their goal is to gather samples from the nearly two mile thick West Antarctic Ice Sheet and the deeper they go the further back in time they travel. Here about 480 meters deep right now this is right around the time when Jesus lived its right about zero ad right when BC year turned into 80 years. These ice cores contain tiny bubbles of ancient atmosphere that were trapped each year as the snow was compressed into ice. Ice bubbles in this one its ancient area there when we crush samples like this I don’t get the cows out there and we can sample the ancient atmosphere we can also get a record of how things like temperature and sea ice changed in the past by combining these different records we can understand how the climate system is operating the past but the ice work valuable as it is only goes back about eight hundred thousand years a tiny fraction of geologic time to get a more complete picture of Antarctica’s climate history you have to drill farther back in time and that’s what the An drill team is trying to did.

They want to paint a picture of Antarctica as it changed from warm to cold millions of years ago in order to do that An drill will have to drill deep into the earth but finding the right location is a major challenge on a continent covered by ice and even in those few places where the ice has receded it’s still not easy An drills David Harwood and Richard levy are searching for places to drill but as they fly over a field of rubble they see the gathering evidence for a chronological history is not possible here. something has stirred things up and that something is the ice itself that’s because ice moves for tens of millions of years glaciers have slowly scoured the land gobbling up rocks and debris and spreading them all across the landscape in random order this we call glacial paleontology some call it garbage pile paleontology because were looking and sorting through these Marines to try to get pieces of information that the ice sheet has brought to us.

A marine is the chaotic accumulation of rocks and debris deposited by glacial movement this one here she has abundant shell fossils this shell brought here by a glacier comes from a time when the continent was warmer and water ran through these valleys.

This landscape is a treasure trove of a Nordica’s climate history but the ice has scrambled all the clues we’re looking at a jigsaw puzzle yet there’s one place where the evidence remains intact that’s in the seafloor beneath the Antarctic ice shelf where the glacial movement has also deposited layer after layer in chronological order drilling gives us an opportunity to get a serial history in time each layer goes back in time and we know that a rock was younger than a rock below so we could put it into history . The An drill team aims to drill through the Antarctic ice and the sea below then like a straw thrust through a layer cake they’ll bore deep into the ocean floor in order to recover millions of years of rock and mud the trace Antarctica’s climate history.

Even after ice began to form in Antarctica around 34 million years ago the continent remained warm enough for plant life to survive a lot like areas of New Zealand today where ice can be found bordered by trees and plants but when di Antarctica plunge into a solid deep freeze and how did it happen was it gradual or abrupt will the story of how Antarctica changed from green house to ice house reveal new clues about the continents climate future and our own. Charlie, Charlie, I am David  Harwood The An drill team will spend the next few weeks searching for drilling locations from the surface of the ice. But David Harwood remains focused on what lies below when I’m driving across there I’m always thinking about what’s beneath this I’m over about 15 feet of ice and over that I’m over about 1,500 feet of water and then the sediments below that here at the bottom of the world the Sun never sets in the summer and his night blends in today the work begins in earnest. The team heads out to McMurdo South. A place where the ocean freezes annually creating a precarious platform of floating sea ice that will only last a few months we’re standing right now in the southern part of the proto Sound seasonally this region will break out the sea ice that are standing on the melt out its now strong enough perhaps 20 feet beneath us is a thickness of ice and then 15 hundred feet of water beneath us as well just to be sure they’re in the right place fire in the hole the team blasts powerful sound waves through the sea ice and into the sea floor below the result is a sonic street map of layer after layer of rock and mud each one representing a different era of the past by looking in the past we can may be projecting to the future how dynamic has been the behavior of the ice sheets have they been static and slowly changing act of a player have they been Finally it’s time to tow the giant drill out onto the ice to ensure that the weight of the rig isn’t supported by the sea ice alone divers attach flotation devices to the drill pipe and at the end of that pipe is a whirling tool with a unique cutting edge a drill bit made of diamonds that can bore through almost everything in its path the diamond core system that we have it’s almost like melting the core down through the rocks just cuts through whatever’s there if you hit a big boulder you’ll just end up with a cylinder of that Boulder but it just keep going.

Now, the real drilling begins. there’s not a minute to waste because the Antarctic research season is so short the crews work around the clock to recover cores of rock the trace Antarctica’s ancient past the powerful drill bores down over three-quarters of a mile bringing up 12 feet of core at a time each foot averaging a thousand years of climate history it’s an astonishing feat its quite amazing when you think about where we are and what we’re doing we’ve got a drill rig a 60 ton 290 ton with all the equipment on a drill rig sitting behind us here on eight meters of sea ice above 380 meters of water and then were drilling down into the sea floor below there with a three to four inch diameter pipe that’s turning round and round like a piece of spaghetti hanging down through the water and into the ground and its wobbling around a bit and were turning around and bringing Cora from deep within the earth anything can go wrong at any minute with this process and all too soon it does sometimes even a drill bit made of diamonds can run into trouble we haven’t been getting particularly good quality core and were suspecting that the drill bit has been damaged in places it’s a little bit narrower it should be for the size of the diamond bits and that means we have to pull our pipe out about 1700 meters and replace a bit right back down the hole and that’s going to take us about 24 hours to 36 hours removing and replacing nearly a mile of pipe is no easy task especially when it’s your job to change it all out piece by piece but for other members of the Andrill team it’s a welcome break in an extreme environment like Antarctica nobody’s on a die your body is working so hard to stay warm packing away 6,000 calories or more a day is not an indulgence it’s a necessity and because Antarctica is drier than the hottest desert dehydration is a constant concern and keeping the drill up and running is another finally after a day and a half of hard work the new bid is in place and drilling is back on track they recover a 12-foot length of core wrapped in a protective cover workers carefully carry it back to the lab to be examined when they crack it open its in perfect condition this mud and rock is more valuable than gold because each core is a time machine were currently down to the depth of body 440 meters that’s about a quarter mile down corresponding to a time at least 15 million years ago when Antarctica was still warm as the cores are recovered each section is sliced lengthwise x-rayed and scanned in labs at the drill site and back at McMurdo this course came out of the ground three days ago they were split yesterday they were imaged yesterday sedimentology stew worked the night shift 12 hours describing these pours millimeter by millimeter looking at the color size ratios any kind of structure they see in a core trying to understand how these sediments were deposited each core tells a story depending on its texture color and contents and some of those stories are spectacular were seeing some macro fossils some large shells these shells are evidence of warmer times even as Antarctica is icing up this is one the most particular fossil found within and really decision this is a scallop now this kind of scalloped simply do not live in extreme polar waters and there are other clues some of them nearly invisible hidden inside these cores are shells of microscopic algae called diatoms for Andrew climate detectives these tiny diatoms create a highly revealing picture of the past because not all diatoms are alike some species are adapted to colder conditions while others flourish in warmer waters we use them as biological markers index of different environmental conditions cold or warm frozen waters or open ocean waters again the andrill team examines cores from around 15 million years ago they find smooth green sands containing diatoms that thrived in relatively warm water confirming this was a time before Antarctica finally froze over this is very well-defined warm period iceberg free waters open waters where diatoms are growing and thriving you can see this persistent for quite some time a picture is beginning to form of a long period of transition starting 34 million years ago when a cooling climate led to the formation of ice but even so conditions remained relatively mild but when did Antarctica finally slip into a deep freeze the answer lies in cores from around 14 million years ago instead of smooth and green these cores are rocky and gray and some contain diatoms that thrived in cold glacial waters this amazing discovery reveals a rapid change from cool to frozen it fills in what has always been a blank page in Antarctica’s climate history next season they’ll attack another crucial question after Antarctica froze 14 million years ago did the ice ever melt or has it remained a frozen wilderness right up until today that answer will have to wait cracks in the sea-ice tell the team its time to return to base we’ve seen the ice break in quite a bit in the last month but it’s not broken in anywhere further south than it is right now we can only be on this site for so long before the sea ice starts to melt before the conditions change and for safety reasons we have to get off the sea ice the precarious sea ice of West Antarctica may come and go with the seasons but what about the giant East Antarctic Ice Sheet a mountain of ice so high it covers mountains this is like an MRI of the ice sheet some places its really thick two miles thick and pretty flat and boring but then there are other places where what we discovered were hidden mountain ranges the size of the Appalachians but totally hidden by the huge you said Artic ice sheet there’s ten times as much ice in the east as in the west but a small portion of the East has almost no ice at all it’s an unearthly location that defies the very image of Antarctica these are the Dry Valleys cold barren and except for a few scientists almost completely devoid of life the landscape is so alien NASA has used it as a test site for space programs it’s a fantastic place you can’t find this anywhere else on earth its closest analogue is the surface of Mars. Mullen’s valley is the ultimate remote field camp.

It serves as home base for a pioneering band of glaciologists led by Dave Marchland Marsh aunt and his team are conducting research the rugged old-fashioned way they’ll live in tents and won’t be picked up for two months they need to be self-sufficient and for the most part they like it that way Burritos. The good thing about working out here is its actually double-edged sword you come out here you have no contact with the outside world no email no real telephone contacts so you can totally immerse yourself in the science and that allows you to think 24 hours a day about what you’re doing the other  side of that is you have no idea what’s going on outside right beginning of the season I didn’t like it when there you would breathe and the frost would form on the outside of the sleeping bag but it hold up now and it’s a little more comfortable and a lot easier small setups like we have which are helicopter supported are isolated they’re among the most isolated in the region and as a result we have to check in daily with McMurdo I’ll try to heat the batteries up so that we can get a signal out right now there appears to be no satellite coverage and the batter is a little bit cold so I’m trying to warm it up sometimes you have to contort your body in various ways to get the signal no not we don’t have enough signal yet well here we go we’ve got something that might work Mac ops this is gone for Mullin Valley we have seven on board and all as well over are we lost transmission this valley holds an incredible record this area is so dry and so cold that the landscape is pristine the rocks we see here are millions of years old more shock believes that little has changed here for millions of years what to me is exciting is that were walking on an ancient landscape imagine living ten million years ago in Antarctica this is what you’d see exactly as it is today hardly modified at all but when marsh awns team drilled beneath this rubble they found something totally unexpected a hidden glacier that extends hundreds of feet below the surface this is in my opinion the oldest dated berry glacier on earth the evidence comes from volcanic ash the dry valleys are surrounded by extinct volcanoes that erupted millions of years ago were finding ash deposits on top of ice ash dates are coming back as old as 8 million years and according to more shot this volcanic ash shows this hidden glacier once frozen has never melted this volcanic ash that erupted from a volcano and has been sitting there for millions of years it shows no chemical alteration which you’d expect if there were any amount of liquid melt water over that duration the fact that its dry and pristine tells me it’s always been here which is incredible equally astonishing and just three hundred miles away there appears to be a completely different picture exploring East Antarctica closer to the South Pole and riyals David Harwood found leaf fossils and pieces of wood surprisingly according to Harwood these date to a relatively recent time when Antarctica was not only warmer than  today there were plants and trees this is a piece of southern beach this wood is not fossilized in the sense that it is petrified it could still burn to find the wood and leaves together it is pretty phenomenal its really phenomenal for Antarctica particularly for Antarctica in the in this time period about 4 million years ago this season the drill is setup to find evidence of what happened in Antarctica during this period three to five million years ago it’s a time known as the Pliocene now what’s important about that is that the Pliocene was globally warmer than today the same temperatures as our earth may be headed for at the end of the century if climate change predictions are correct if we go back three to five million years into the geological past we know that there was a time when Earth’s climate was warmer than it is today perhaps by 3 to 4 degrees so it’s the best example we have of where the climate is heading in the next hundred years the drills new location is on the giant Ross Ice Shelf which extends out and over the ocean it’s the largest ice shelf in the world and it helps hold back the massive Antarctic Ice Sheet from flowing into the sea these ice shelves are very important what they do is hold back the flow of ice that’s actually trying to flow out into the ocean we call that buttressing if warming oceans cause the Ross Ice Shelf to break up and melt into the sea the West Antarctic Ice Sheet would eventually follow right behind the andrel team is looking for the answer to a critical question when Earth was warming during the Pliocene what happened to the ice did the Ross Ice Shelf melt taking the giant ice sheets with it drilling on an ice shelf brings with it a unique set of technological challenges including constant problems with mud and water unlike drilling through sea ice which is just 26 feet thick the ice shelf here is 400 feet were looking at least doubling or trying to double our capability below the sea floor and penetrate 2,000 meters or better into the sea floor but that’s only the beginning no one has ever drilled through an ice shelf and they present these challenges the ice shelves they float up and down with the tide so you’ve got to deal with this vertical elevation change they move sideways they flow so eventually your drill pipe is going to get bent can the drill bore through a thick layer of ice that’s constantly moving without breaking or getting yanked out of the sea floor to confront this unique challenge head-on the Android team invents a new tool a hot-water drill this marvel of engineering is a moving ring of heat that blasts jets of steaming water to melt a wide hole so the drill can operate freely through four hundred feet of shifting ice and once again time is so precious the team must work around the clock not only retrieving cores but also analyzing them its 2:00 a.m. but you wouldn’t know it geologists are busy logging cores like its early afternoon we’re laying out the cores and a proper sequence from top grade highest point in the core all the way to the very slowest point of the quarter an 80-foot core that dates back about three million years is closely examined it contains micro fossils of single-celled animals known as forums they’re from the crucial warm period called the Pliocene and these tiny shells are precise indicators of ocean temperature these guys are about the size of a grain of sand because the same species lived through time we can use the chemistry of modern examples to allow us to calibrate if you like the chemistry of the ancient examples what Gibes doing here is he’s measuring the amount of two metals magnesium and calcium that are in the ocean and get incorporated into the shell of the 4m when its growing in that ocean and that process is dependent on the temperature of the ocean so if we know the magnesium.

We know the calcium we can determine the temperature of the ocean at the time that forum lived and because of that Andrew researchers can now calculate Antarctic water temperatures during the Pliocene what this is telling us as temperatures were three to four perhaps five degrees above prison even just one degree rise notion temperatures in the waters surrounding Antarctica will attack and begin to melt the ice shelves from below very quickly the air temperatures will stay cold enough to keep things frozen at the surface but what were worried about is the ice being attacked from beneath not from above and the cores revealed that this is what happened during the Pliocene when global climate was warming but they display even more change than expected revealing not only a patchwork of glacial rubble but also smooth mud from open seas indicating that ice both froze and then melted many times there’s a really important change right here this involves us quite a dramatic change in the environment there was ice and then there was no ice the ice shade has gone backwards and forwards its advanced and its retreated as they examine core after core from the Pliocene they continue to see surprising signs of change the results of the drilling are simply spectacular they give us a picture of a dynamic ice sheet coming and going regularly more than 60 times what we’re seeing and this record is telling us that Antarctica’s not just a benign spectator it’s a playa what this means is while it was generally warm during the Pliocene there were also brief periods of cooling and the ice was exquisitely sensitive to even small changes in climate just a few degrees could tip the scale from ice to no ice so what’s in store for our future as Earth continues to warm how much Antarctic ice will melt and how high will sea levels rise and An drill scientists turned to computer models by Rob de canto and Dave Pollard we developed these climate models based on our best understanding of the physics of the climate system and in this case ice sheets and now information from anvil is added to the climate model this is a computer model simulation of the Antarctic Ice Sheet over the last several million years and covers a good chunk of the interval that was recovered by the an drill sediment core so were looking for the same kind of behavior in our models that were seeing in the geological record as the model simulates the warming periods of the Pliocene all of the ice shelves disappear followed by the entire West Antarctic Ice Sheet and edges of the east and as temperatures change the ice refreezes and melts again and again and that’s important because the changes in the ice sheet that were seeing here reflect pretty significant changes in sea level according to the cantos model sea levels rose about 23 feet during the Pliocene temperatures back then were three to five degrees higher than now just what’s projected to take place by the end of the century but there is a lag time in the way ice responds that may delay the impact for hundreds if not thousands of years regardless coastal cities all over the world would be at risk potentially displacing millions we would be remapping places like Boston in New York the Bay Area not to mention of course places like Louisiana Miami New Orleans of course but even that might not be the worst-case scenario things were very similar to today in terms of our climate Tim Nations robbed a Kanto to New Zealand to look at a possibility that’s even more frightening this is the first time I’ve seen the actual direct evidence for what the models are doing you seeing a deepening syllable rise up through here were going to look at some rocks set at the same age as rocks look drilled and Antarctica that give us the record of global sea level changes here along the ranga tiki river tectonic forces have raised the land and the river has cut into the earth to expose layer after layer of sediment that once was the sea floor what they find our shells dated to the warming era of the Pliocene these shells provide a way to chart sea level in the past because some of these species still exist today many of these Shoals you see in here actually live today so they live around the coastline and we know the water depth they live in today so by breaking them out of these rocks and identifying them we can say the depth they were living here over three million years ago because these shellfish live on the seafloor and can only survive in water at specific depths they suggest that sea levels in the Pliocene were much higher than even the computer models predict this is really a troll this is where we would say we had the evidence for sea level being up to as much as 20 meters about Britain that’s over 60 feet in order for sea level to arisen that high an enormous amount of ice must have melted and this raises a startling possibility that a large part of the vast East Antarctic Ice Sheet melted along with the West and if it melted once could it melt again?

Could be a very bad thing because that would actually produce a contribution to future sea level change that we really haven’t been thinking about this presents an even more dangerous and unpredictable picture of Antarctica what’s been surprising is even geologists thought that glaciers and ice sheets were these large static features which we would never really see change in our lifetime but glacial processes are no longer quite as glacial things are moving faster than we had thought what’s driving these changes are rising levels of greenhouse gases in the next five years greenhouse gas levels will be like they were in the Pliocene but were not just going back to the Pliocene some of the projections put co2 levels at twice the concentrations of the Pliocene by the end of the next century were essentially going back to the time of the dinosaurs when there was very little ice on the planet and there were forests covering Antarctica and signs of change are already here.

Scientists were completely caught by surprise when in 2002 the Larsen Ice Shelf shattered apart without warning in just a few weeks. And today the Wilkins Ice Shelf a block of ice approximately the size of Connecticut barely hangs on.

I would say it’s inevitable that Western occur will disappear. How long it will take you start occur to engage is something  that’s not yet known in the coming years the An drill team will continue to explore Antarctica’s climate history in order to gain valuable insight into Earths future with each new core we gain new knowledge about a continent that always been shrouded in mystery but its faith remains very much tied to our own this nova program is available on DVD at Shaw PBS org or call 1-800 play PBS you.