The secrets I find on the mysterious ocean floor Laura Robinson
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
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 satellite,
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 [levels] 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 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 of 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 brittle stars
growing on these corals.
Those are things that look
like tentacles coming out of 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.
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 maps
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 these are 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 like.
This wasn’t what we were looking for.
We were looking for corals,
deep sea corals.
You’re going to see a picture
of one in a moment.
It’s 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 if 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.
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.
But 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 left-hand image here,
I’ve taken a slice through a coral,
polished it very carefully
and taken an optical image.
On the right-hand 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 we 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
of 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 Drake 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 Antarctic 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)