The secrets I find on the mysterious ocean floor

Well, I'm an ocean chemist. I look at
the chemistry of the ocean today.

I look at the chemistry
of the ocean in the past.

The way I look back in the past
is by using the fossilized remains

of deepwater corals.

You can see an image of
one of these corals behind me.

It was collected from close to Antarctica,

thousands of meters below the sea,

so very different than the kinds of corals
that you may have been lucky enough

to see if you've had a tropical holiday.

So I'm hoping that this talk will give you
a four-dimensional view of the ocean.

Two dimensions, such as this
beautiful two-dimensional image

of the sea surface temperature.

This was taken using satellites,
so it's got tremendous spatial resolution.

The overall features are
extremely easy to understand.

The equatorial regions are warm
because there's more sunlight.

The polar regions are cold
because there's less sunlight.

And that allows big icecaps
to build up on Antarctica

and up in the Northern Hemisphere.

If you plunge deep into the sea,
or even put your toes in the sea,

you know it gets colder as you go down,

and that's mostly because the deep waters
that fill the abyss of the ocean

come from the cold polar regions
where the waters are dense.

If we travel back in time
20,000 years ago,

the Earth looked very much different.

And I've just given you a cartoon version
of one of the major differences

you would have seen
if you went back that long.

The icecaps were much bigger.

They covered lots of the continent,
and they extended out over the ocean.

Sea level was 120 meters lower.

Carbon dioxide were very much
lower than they are today.

So the Earth was probably about
three to five degrees colder overall,

and much, much colder
in the polar regions.

What I'm trying to understand,

and what other colleagues of mine
are trying to understand,

is how we moved
from that cold climate condition

to the warm climate condition
that we enjoy today.

We know from ice core research

that the transition from these
cold conditions to warm conditions

wasn't smooth, as you might predict
from the slow increase in solar radiation.

And we know this from ice cores,
because if you drill down into ice,

you find annual bands of ice,
and you can see this in the iceberg.

You can see those blue-white layers.

Gases are trapped in the ice cores,
so we can measure CO2.

That's why we know CO2
was lower in the past,

and the chemistry of the ice
also tells us about temperature

in the polar regions.

And if you move in time
from 20,000 years ago to the modern day,

you see that temperature increased.

It didn't increase smoothly.

Sometimes it increased very rapidly,
then there was a plateau,

then it increased rapidly.

It was different in the two polar regions,
and CO2 also increased in jumps.

So we're pretty sure that the ocean
has a lot to do with this.

The ocean stores huge amounts of carbon,

about 60 times more
than is in the atmosphere.

It also acts to transport heat
across the equator,

and the ocean is full is nutrients
and it controls primary productivity.

So if we want to find out
what's going on down in the deep sea,

we really need to get down there,
see what's there,

and start to explore.

This is some spectacular footage
coming from a seamount

about a kilometer deep
in international waters

in the equatorial Atlantic, far from land.

You're amongst the first people
to see this bit of the seafloor,

along with my research team.

You're probably seeing new species.

We don't know.
You'd have to collect the samples

and do some very intense taxonomy.

You can see beautiful bubblegum corals.

There are brittlestars
growing on these corals.

Those are things that look like tentacles
coming out of the corals.

There are corals made of different forms
of calcium carbonate

growing off the basalt of this
massive undersea mountain,

and the dark sort of stuff,
those are fossilized corals,

and we're going to talk
a little more about those

as we travel back in time.

To do that, we need
to charter a research boat.

This is the James Cook,
an ocean class research vessel

moored up in Tenerife.
Looks beautiful, right?

Great if you're not a great mariner.

Sometimes it looks
a little more like this.

This is us trying to make sure
that we don't lose precious samples,

and everyone's scurrying around,
and I get terribly seasick,

so it's not always a lot of fun,
but overall it is.

So we've got to become
a really good mapper to do this.

You don't see that kind of spectacular
coral abundance everywhere.

It is global, and it is deep,

but we need to really find
the right places.

We just saw a global map,
and overlaid was our cruise passage

from last year.

This was a seven-week cruise,
and this is us having made

our own map of about 75,000 square
kilometers of the seafloor in seven weeks,

but that's only a tiny fraction
of the seafloor.

We're traveling from west to east,

over part of the ocean that would
look featureless on a big scale map

but actually some of these mountains
are as big as Everest.

So with the maps that we make on board,

we get about 100 meter resolution,

enough to pick out areas
to deploy our equipment,

but not enough to see very much.
To do that, we need to fly

remotely-operated vehicles
about five meters off the seafloor,

and if we do that, we can get maps
that are one-meter resolution

down thousands of meters.

Here is a remotely-operated vehicle,

a research grade vehicle.

You can see an array
of big lights on the top.

There are high-definition cameras,
manipulator arms,

and lots of little boxes and things
to put your samples.

Here we are on our first dive
of this particular cruise,

plunging down into the ocean.

We go pretty fast to make sure
the remotely operated vehicles

are not affected by any other ships.

And we go down,

and this is the kinds of things you see.

These are deep sea sponges, meter scale.

This is a swimming holothurian.
It's a small sea slug, basically.

This is slowed down.

Most of the footage I'm showing you
is speeded up,

because all of this takes a lot of time.

This is a beautiful holothurian as well.

And this animal you're going to see
coming up was a big surprise.

I've never seen anything like this,
and it took us all a bit surprised.

This was after about 15 hours of work,
and we were all a bit trigger-happy,

and suddenly this giant sea monster
started rolling past.

It's called a pyrosome,
or colonial tunicate, if you'd like.

This wasn't what we were looking for.

We were looking for corals,
deep sea corals.

You're going to see a little picture
of one in a moment.

It's a small, about five centimeters high.

It's made of calcium carbonate,
so you can see its tentacles there

moving in the ocean currents.

An organism like this probably lives
for about a hundred years,

and as it grows, it takes in
chemicals from the ocean.

And the chemicals,
or the amount of chemicals,

depends on the temperature.

It depends on the pH.

It depends on the nutrients,

and we can understand how
these chemicals get into the skeleton,

we can then go back,
collect fossil specimens,

and reconstruct what the ocean
used to look like in the past.

And here you can see us collecting
that coral with a vacuum system,

and we put it into a sampling container.

We can do this very carefully,
I should add.

Some of these organisms live even longer.

This is a black coral called Leiopathes,

an image taken by my colleague
Brendan Roark

about 500 meters below Hawaii.

Four thousand years is a long time.

Now, if you take a branch
from one of these corals

and polish it up,

this is about 100 microns across,

and Brendan took some analyses
across this coral --

you can see the marks --

and he's been able to show that these
are actual annual bands.

So even at 500 meters deep in the ocean,
corals can record seasonal changes,

which is pretty spectacular.

But 4,000 years is not enough to get us
back to our last glacial maximum.

So what do we do?
We go in for these fossil specimens.

This is what makes me really unpopular
with my research team.

So going along,
there's giant sharks everywhere,

there are pyrosomes,
there are swimming holothurians,

there's giant sponges,

but I make everyone go down
to these dead fossil areas

and spend ages kind of
shoveling around on the seafloor.

And we pick up all these corals,
bring them back,

we sort them out.

Each one of these is a different age,
and if we can find out how old they are,

and then we can measure
those chemical signals,

this helps us to find out
what's been going on

in the ocean in the past.

So on the lefthand image here,

I've taken a slice through a coral,
polished it very carefully,

and taken an optical image.

On the righthand side,
we've taken that same piece of coral,

put it in a nuclear reactor,
induced fission,

and every time there's some decay,

you can see that marked out in the coral,
so you can see the uranium distribution.

Why are we doing this?

Uranium is a very poorly regarded element,

but I love it.

The decay helps us find out
about the rates and dates

and what's going on in the ocean.

And if you remember from the beginning,

that's what we want to get at
when we're thinking about climate.

So we use a laser to analyze uranium

and one of its daughter products,
thorium, in these corals,

and that tells us exactly
how old the fossils are.

This beautiful animation
of the Southern Ocean

I'm just going to use illustrate
how we're using these corals

to get at some of
the ancient ocean feedbacks.

You can see the density
of the surface water

in this animation by Ryan Abernathey.

It's just one year of data,

but you can see how dynamic
the Southern Ocean is.

The intense mixing,
particularly the Great Passage,

which is shown by the box,

is really one of the strongest
currents in the world

coming through here,
flowing from west to east.

It's very turbulently mixed,
because it's moving over

those great big undersea mountains,

and this allows CO2 and heat to exchange
with the atmosphere in and out.

And essentially, the oceans are breathing
through the Southern Ocean.

We've collected corals from back and forth
across this Antarctica passage,

and we've found quite a surprising thing
from my uranium dating.

The corals migrated from south to north

during this transition from the glacial
to the interglacial.

We don't really know why,
but we think it's something

to do with the food source,
and maybe the oxygen in the water.

So here we are. I'm going to illustrate
what I think we've found

about climate from those corals
in the Southern Ocean.

We went up and down sea mountains.

We collected little fossil corals.

This is my illustration of that.

We think back in the glacial,

from the analysis
we've made in the corals,

that the deep part of the Southern Ocean
was very rich in carbon,

and there was a low-density layer
sitting on top.

That stops carbon dioxide
coming out of the ocean.

We then found corals that are
of an intermediate age,

and they show us that the ocean mixed
partway through that climate transition.

That allows carbon to come out
of the deep ocean.

And then if we analyze corals
closer to the modern day,

or indeed if we go down there
today anyway

and measure the chemistry of the corals,

we see that we move to a position
where carbon can exchange in and out.

So this is the way
we can use fossil corals

to help us learn about the environment.

So I want to leave you
with this last slide.

It's just a still taken out of that first
piece of footage that I showed you.

This is a spectacular coral garden.

We didn't even expect
to find things this beautiful.

It's thousands of meters deep.

There are new species.

It's just a beautiful place.

There are fossils in amongst,
and now I've trained you

to appreciate the fossil corals
that are down there.

So next time you're lucky enough

to fly over the ocean
or sail over the ocean,

just think, there are massive
sea mountains down there

that nobody's ever seen before,
and there are beautiful corals.

Thank you.

(Applause)