The secrets I find on the mysterious ocean floor | Laura Robinson

128,179 views ・ 2016-03-30

TED


Please double-click on the English subtitles below to play the video.

00:12
Well, I'm an ocean chemist.
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I look at the chemistry of the ocean today.
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I look at the chemistry of the ocean in the past.
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The way I look back in the past
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is by using the fossilized remains of deepwater corals.
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You can see an image of one of these corals behind me.
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It was collected from close to Antarctica, thousands of meters below the sea,
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so, very different than the kinds of corals
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you may have been lucky enough to see if you've had a tropical holiday.
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So I'm hoping that this talk will give you
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a four-dimensional view of the ocean.
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Two dimensions, such as this beautiful two-dimensional image
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of the sea surface temperature.
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This was taken using satellite, so it's got tremendous spatial resolution.
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The overall features are extremely easy to understand.
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The equatorial regions are warm because there's more sunlight.
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The polar regions are cold because there's less sunlight.
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And that allows big icecaps to build up on Antarctica
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and up in the Northern Hemisphere.
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If you plunge deep into the sea, or even put your toes in the sea,
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you know it gets colder as you go down,
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and that's mostly because the deep waters that fill the abyss of the ocean
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come from the cold polar regions where the waters are dense.
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If we travel back in time 20,000 years ago,
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the earth looked very much different.
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And I've just given you a cartoon version of one of the major differences
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you would have seen if you went back that long.
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The icecaps were much bigger.
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They covered lots of the continent, and they extended out over the ocean.
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Sea level was 120 meters lower.
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Carbon dioxide [levels] were very much lower than they are today.
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So the earth was probably about three to five degrees colder overall,
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and much, much colder in the polar regions.
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What I'm trying to understand,
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and what other colleagues of mine are trying to understand,
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is how we moved from that cold climate condition
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to the warm climate condition that we enjoy today.
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We know from ice core research
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that the transition from these cold conditions to warm conditions
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wasn't smooth, as you might predict from the slow increase in solar radiation.
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And we know this from ice cores, because if you drill down into ice,
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you find annual bands of ice, and you can see this in the iceberg.
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You can see those blue-white layers.
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Gases are trapped in the ice cores, so we can measure CO2 --
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that's why we know CO2 was lower in the past --
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and the chemistry of the ice also tells us about temperature
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in the polar regions.
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And if you move in time from 20,000 years ago to the modern day,
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you see that temperature increased.
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It didn't increase smoothly.
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Sometimes it increased very rapidly,
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then there was a plateau,
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then it increased rapidly.
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It was different in the two polar regions,
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and CO2 also increased in jumps.
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So we're pretty sure the ocean has a lot to do with this.
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The ocean stores huge amounts of carbon,
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about 60 times more than is in the atmosphere.
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It also acts to transport heat across the equator,
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and the ocean is full of nutrients and it controls primary productivity.
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So if we want to find out what's going on down in the deep sea,
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we really need to get down there,
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see what's there
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and start to explore.
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This is some spectacular footage coming from a seamount
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about a kilometer deep in international waters
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in the equatorial Atlantic, far from land.
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You're amongst the first people to see this bit of the seafloor,
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along with my research team.
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You're probably seeing new species.
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We don't know.
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You'd have to collect the samples and do some very intense taxonomy.
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You can see beautiful bubblegum corals.
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There are brittle stars growing on these corals.
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Those are things that look like tentacles coming out of corals.
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There are corals made of different forms of calcium carbonate
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growing off the basalt of this massive undersea mountain,
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and the dark sort of stuff, those are fossilized corals,
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and we're going to talk a little more about those
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as we travel back in time.
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To do that, we need to charter a research boat.
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This is the James Cook, an ocean-class research vessel
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moored up in Tenerife.
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Looks beautiful, right?
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Great, if you're not a great mariner.
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Sometimes it looks a little more like this.
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This is us trying to make sure that we don't lose precious samples.
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Everyone's scurrying around, and I get terribly seasick,
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so it's not always a lot of fun, but overall it is.
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So we've got to become a really good mapper to do this.
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You don't see that kind of spectacular coral abundance everywhere.
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It is global and it is deep,
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but we need to really find the right places.
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We just saw a global map, and overlaid was our cruise passage
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from last year.
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This was a seven-week cruise,
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and this is us, having made our own maps
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of about 75,000 square kilometers of the seafloor in seven weeks,
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but that's only a tiny fraction of the seafloor.
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We're traveling from west to east,
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over part of the ocean that would look featureless on a big-scale map,
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but actually some of these mountains are as big as Everest.
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So with the maps that we make on board,
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we get about 100-meter resolution,
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enough to pick out areas to deploy our equipment,
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but not enough to see very much.
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To do that, we need to fly remotely-operated vehicles
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about five meters off the seafloor.
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And if we do that, we can get maps that are one-meter resolution
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down thousands of meters.
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Here is a remotely-operated vehicle,
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a research-grade vehicle.
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You can see an array of big lights on the top.
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There are high-definition cameras, manipulator arms,
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and lots of little boxes and things to put your samples.
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Here we are on our first dive of this particular cruise,
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plunging down into the ocean.
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We go pretty fast to make sure the remotely operated vehicles
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are not affected by any other ships.
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And we go down,
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and these are the kinds of things you see.
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These are deep sea sponges, meter scale.
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This is a swimming holothurian -- it's a small sea slug, basically.
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This is slowed down.
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Most of the footage I'm showing you is speeded up,
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because all of this takes a lot of time.
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This is a beautiful holothurian as well.
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And this animal you're going to see coming up was a big surprise.
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I've never seen anything like this and it took us all a bit surprised.
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This was after about 15 hours of work and we were all a bit trigger-happy,
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and suddenly this giant sea monster started rolling past.
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It's called a pyrosome or colonial tunicate, if you like.
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This wasn't what we were looking for.
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We were looking for corals, deep sea corals.
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You're going to see a picture of one in a moment.
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It's small, about five centimeters high.
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It's made of calcium carbonate, so you can see its tentacles there,
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moving in the ocean currents.
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An organism like this probably lives for about a hundred years.
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And as it grows, it takes in chemicals from the ocean.
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And the chemicals, or the amount of chemicals,
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depends on the temperature; it depends on the pH,
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it depends on the nutrients.
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And if we can understand how these chemicals get into the skeleton,
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we can then go back, collect fossil specimens,
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and reconstruct what the ocean used to look like in the past.
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And here you can see us collecting that coral with a vacuum system,
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and we put it into a sampling container.
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We can do this very carefully, I should add.
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Some of these organisms live even longer.
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This is a black coral called Leiopathes, an image taken by my colleague,
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Brendan Roark, about 500 meters below Hawaii.
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Four thousand years is a long time.
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If you take a branch from one of these corals and polish it up,
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this is about 100 microns across.
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And Brendan took some analyses across this coral --
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you can see the marks --
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and he's been able to show that these are actual annual bands,
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so even at 500 meters deep in the ocean,
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corals can record seasonal changes,
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which is pretty spectacular.
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But 4,000 years is not enough to get us back to our last glacial maximum.
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So what do we do?
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We go in for these fossil specimens.
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This is what makes me really unpopular with my research team.
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So going along,
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there's giant sharks everywhere,
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there are pyrosomes, there are swimming holothurians,
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there's giant sponges,
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but I make everyone go down to these dead fossil areas
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and spend ages kind of shoveling around on the seafloor.
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And we pick up all these corals, bring them back, we sort them out.
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But each one of these is a different age,
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and if we can find out how old they are
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and then we can measure those chemical signals,
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this helps us to find out
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what's been going on in the ocean in the past.
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So on the left-hand image here,
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I've taken a slice through a coral, polished it very carefully
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and taken an optical image.
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On the right-hand side,
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we've taken that same piece of coral, put it in a nuclear reactor,
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induced fission,
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and every time there's some decay,
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you can see that marked out in the coral,
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so we can see the uranium distribution.
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Why are we doing this?
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Uranium is a very poorly regarded element,
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but I love it.
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The decay helps us find out about the rates and dates
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of what's going on in the ocean.
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And if you remember from the beginning,
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that's what we want to get at when we're thinking about climate.
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So we use a laser to analyze uranium
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and one of its daughter products, thorium, in these corals,
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and that tells us exactly how old the fossils are.
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This beautiful animation of the Southern Ocean
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I'm just going to use illustrate how we're using these corals
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to get at some of the ancient ocean feedbacks.
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You can see the density of the surface water
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in this animation by Ryan Abernathey.
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It's just one year of data,
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but you can see how dynamic the Southern Ocean is.
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The intense mixing, particularly the Drake Passage,
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which is shown by the box,
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is really one of the strongest currents in the world
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coming through here, flowing from west to east.
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It's very turbulently mixed,
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because it's moving over those great big undersea mountains,
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and this allows CO2 and heat to exchange with the atmosphere in and out.
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And essentially, the oceans are breathing through the Southern Ocean.
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We've collected corals from back and forth across this Antarctic passage,
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and we've found quite a surprising thing from my uranium dating:
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the corals migrated from south to north
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during this transition from the glacial to the interglacial.
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We don't really know why,
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but we think it's something to do with the food source
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and maybe the oxygen in the water.
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So here we are.
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I'm going to illustrate what I think we've found about climate
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from those corals in the Southern Ocean.
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We went up and down sea mountains. We collected little fossil corals.
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This is my illustration of that.
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We think back in the glacial,
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from the analysis we've made in the corals,
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that the deep part of the Southern Ocean was very rich in carbon,
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and there was a low-density layer sitting on top.
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That stops carbon dioxide coming out of the ocean.
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We then found corals that are of an intermediate age,
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and they show us that the ocean mixed partway through that climate transition.
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That allows carbon to come out of the deep ocean.
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And then if we analyze corals closer to the modern day,
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or indeed if we go down there today anyway
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and measure the chemistry of the corals,
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we see that we move to a position where carbon can exchange in and out.
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So this is the way we can use fossil corals
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to help us learn about the environment.
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So I want to leave you with this last slide.
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It's just a still taken out of that first piece of footage that I showed you.
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This is a spectacular coral garden.
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We didn't even expect to find things this beautiful.
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It's thousands of meters deep.
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There are new species.
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It's just a beautiful place.
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There are fossils in amongst,
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and now I've trained you to appreciate the fossil corals
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that are down there.
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So next time you're lucky enough to fly over the ocean
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or sail over the ocean,
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just think -- there are massive sea mountains down there
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that nobody's ever seen before,
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and there are beautiful corals.
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Thank you.
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(Applause)
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