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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)