How a grain of sand rewrote our ocean’s history | Andrew Wheeler | TEDxDublin

How a grain of sand rewrote our ocean’s history | Andrew Wheeler | TEDxDublin


Translator: Hiroko Kawano
Reviewer: Cristina Bufi-Pöcksteiner This is our planet. This is planet Earth. What a curious name for a planet! I mean, there’s very little earth on it. Only 29% of the surface of this planet
is actually earth, land. (Laughter) We need to challenge our human-centric
perspective of where we live. This is an oceanic planet. The oceans is where most
of the life on this planet lives. The oceans control our weather. The oceans control our climate. When ocean circulation changes,
the climate changes. The oceans are present absorbing
excess CO2 and heat from our atmosphere. Yet, we know very little about our oceans. So what I want to do is
I want to tell you about some discoveries that me and my research team and some
colleagues have made in the ocean. I want to tell you a story
about climate change. And I want to tell you a story
about a grain of sand, a grain of sand that was discovered
in the deep ocean, and a grain of sand
that was actually discovered deep below the seabed in the deep ocean. When I was a boy
I was a lot cuter than I am today. (Laughter) Now I have a distinct memory
of standing on a beach and looking out to sea and thinking, “I wonder what it’d be like
if I just kept walking.” “I wonder what it would be like
if I walk down across the bay.” “If I walked out across the shelf
and down into the deep abyss, I wonder what it’s like down there.” As a boy, I had a dream that one day man would walk
upon not the moon but the seabed, because the seabed,
the deep ocean is our final frontier. We haven’t explored it properly yet. We’ve hardly started. Well, I’m a little bit more grown-up
and I was following my dreams. I am a marine geologist. And that means
I’m passionate about finding out what rocks and sediments can tell us
about how the Earth functions. We live on a very dynamic planet,
a planet that’s constantly changing. And as sediments accumulate
on the seabed, sand and mud, they record changes in the ocean. And geologists can look back
through those sediments and discover what’s been going on. I’m not interested in what happened
hundreds of millions of years ago. I’m interested in what’s happening now. And I’m interested in what processes
have brought us to where we are now, and where we’re going to go in the future. I’m also an ocean explorer. I’m interested in discovering
bits of the ocean that no one’s looked at before. I’ve seen many places for the first time
that anyone’s ever seen. And I’m going there and finding
what’s down there, what’s going on. And to do that, it involves going out on research vessels, and we might go out to sea
for maybe a week. We may even go out for a month. It’s a big place out there,
you’ve got to get out there. And that means
that if a storm comes along, well, maybe you just have
to ride out that storm, and when it calms down,
you can get on working. Although I’d say that the most dangerous
thing out there is not really the weather, it’s being stuck on a small boat
with a bunch of crazy scientists and succumbing to cabin fever. (Laughter) No, seriously. The depths of water
I’m interested in exploring are deep. Scuba divers go down 40 meters,
50 meters, maybe a little bit more. I’m interested in what happens
in the deep ocean, maybe 1,000 meters down,
maybe 5,000 meters down. And at those kind of depths
humans simply implode, so we use robotic instruments
like the one behind me, that become our arms to take samples, and the cameras on these
become our eyes to look around. So this is our oceanic planet. And this map of our ocean is
the kind of standard public-domain map that you get on your smartphones
through Google Earth. And it’s fairly state-of-the-art. It depicts actually the resolution
that we know most of our oceans at. We have spent centuries mapping our land. We’ve mapped our countries,
we’ve mapped our towns, our streets, We even have plans of our own houses. Yet, less than 10% of our ocean seabed
is properly mapped. That means 90% of our ocean
is very poorly mapped, or simply undiscovered. I want to tell you the story
about this grain of sand which we discovered here. And if we zoom into that area, this is what the map of that bit
of seabed looks like. A one pixel here. You could fit Central Park
of Manhattan in that pixel. That’s how poor that map is. And that’s pretty much standard
for most of our ocean. Now, this bit of seabed
has been mapped in detail by scientists who’ve bothered
to go out there and have a look. If you do that – We’re going to view it from this direction
because it just looks a little bit better. If you do that, it looks like this. There’s a whole landscape down there. There’s a series of channels
that go into a bigger channel that goes off even deeper off of the map. That red square there
is our Central Park size pixel, and there are hills down here. And these hills are a 100 meters tall. They’re as big as office blocks. And if we take camera systems,
we dive down and we look at those hills and find out what’s on the surface, we find they’re covered
in cold-water coral reefs. So if we bother to look at west of Ireland
about a kilometer below the surface, we have coral existing at about 4 ℃
in the perpetual darkness. Now, in 1998 I was fortunate
in being one of the first people to see these coral reefs in Irish waters as a collaboration
with Russian scientists. And since then I have been
very very interested in this habitat. And I’m interested in it not so much because of the organisms
that live there that are very important. But what fascinated me was: if these coral reefs sit
on top of these 100-meter-tall hills, does that mean all of that hill
is made by coral reef? And if so, what record
do they contain of our Earth’s past? So the most significant discovery
that I think I’ve made here is this grain of sand. And we didn’t discover this grain of sand
from on top of one of those reefs. We discovered it right
at the very, very base of one of those 100-meter-plus mounds. And to do that, we needed to get
out there, we needed to drill. And we collected a continuous core
all the way down through that mound. At the very bottom of it, there was
a very interesting layer of sand. The sand grains on the left are what you usually expect to find
in the marine environment. They’re kind of rounded, they’ve been rolling around on the seabed
they’ve had the corners knocked off. The layer of sand that we found
is over on the right. And to a geologist’s eye
this looks very different. This sand is really quite angular, and it shows evidence
of being crushed or shattered. This sand has been in a glacier. It’s been in ice and
it’s been crushed in a glacier, and somehow found its way out and deposited on this coral reef
deep on the seabed. That’s not so fanciful
because this happens all the time today. And if glaciers exit down
to sea level, they break apart, and they produce dirty icebergs
that float out across the ocean, and as they melt, they drop all this sand
and mud down on the seabed and look very much
like that grain down there. So that’s okay. So we had an iceberg floating out
into the deep ocean long time ago, and depositing sediment
in this coral reef. But how old is that layer of sand? It’s 145 meters down, it must be quite old. But if we took that core – it’s full of coral, it’s all coral reef – we could date
the individual bits of coral. And it looks something like this. On the vertical axis, you see depth below the seabed
going down through that mound. On the bottom, there’s age
in millions of years. This shows triangles that have a date
from this bit of coral. And at 145 meters down
where a layer of sand is, it comes out at 2.5 million years, which is a very, very interesting time. Sorry to throw graphs at you,
this is another graph. On the vertical axis we have
mean global temperature, the average temperature of our planet. And on the bottom is
five million years to present. So, you can see our global
temperature on our planet has been going up and down quite a bit. And in the last five million years,
it’s been slowly cooling down. Our planet has been cooling down, okay? And if you look at the far side
at zero, that’s present-day, we’ve just come out of a glaciation,
and we’ve gone up, and that’s present-day temperature there. We worry that it might be
going up even more. When you get to this temperature here,
as our planet cools down, something interesting happens. Snow that falls in winter
doesn’t melt in summer because it gets too cool
up in northern latitudes. And this is the start of glaciation. This is when glaciers
first started forming in the northern hemisphere
in the relatively recent time. And that is 2.5 million years ago. Now, we didn’t get widespread glaciation into Europe and into Britain and Ireland
and from Canada into North America till about 1.4 million years ago. And you can see after that,
our climate curve really yo-yos, and we get these really cold periods,
these big full glaciations. So what we’re saying is, 2.5 million years ago, there was a glacier
that liberated some icebergs, and they floated all the way down
from Scandinavia or Canada all the way south to west of Ireland. That’s a long long way to go. Is that realistic? Uh, perhaps. So we wanted to find out
where did this grain of sand come from. And this is where
the real forensics kicks in because we could isotopically
fingerprint this grain of sand and match it to the rocks
that it eroded from. So if you take a rock made of crystals
and you erode it, you break it up, you create grains of sand
made of individual crystals, and they are made of a regular
arrangement of elements, and elements are made of electrons
with protons and neutrons, and some elements can carry
slightly more neutrons in them. They’re called the isotopes. If we look at the ratio of isotopes, we can get really quite a unique
isotopic signature for different rocks depending on how old they are,
or where they come from. So if we look to the isotopic signature
of strontium and neodymium for our rock, we can distinguish Iceland and Greenland
from Canada, from the British Irish Isles, from the gulfs and lands
from Scandinavia. And our layer of sand,
2.5 million years ago, plots right in the middle
of the British Irish Isles, perhaps a little bit close
to the Scandinavia domain. But if you look at lead isotopes, well, it’s pretty convincing,
it comes from Northwest Ireland. Now, that’s really quite surprising. What we’re saying is,
2.5 million years ago, when we had the very,
very start of glaciation, the very first icebergs
floating around in the Atlantic, when they should have been way up
in Scandinavia or northern Canada, we’ve got glaciers in Ireland, a million years too early, so big
that they’re actually exiting at sea level and floating out and then melting
a deposit of this sand in this early reef that eventually gets buried. That’s really quite surprising,
and is that feasible? Well, maybe, because if you look
at the west coast of Ireland today, it’s pretty mountainous. It’s pretty rugged. And 2.5 million years of glaciation,
or even 1.4 for that matter, those mountains would have been
considerably higher before those glaciers eroded them down. So right at the side of glaciation, with really, really tall mountains
on the west of Ireland, we may have had permanent snow caps getting those lovely wet westerlies
that we loved in Ireland, falling as permanent snowfall
and getting so much snowfall that they were producing glaciers
that pumped down to sea level, rather like Patagonia today
in southern Chile and Argentina. Okay, well, that’s an interesting
bit of detective work. It’s a story about the Earth’s past. And it’s important
that we understand the past if we’re to understand
what’s possible in the future. It’s a story of a radical rewrite
of our understanding of glaciation in the northern hemisphere. It’s a story about sensitivity
of ice caps to climate change, in this case, global cooling. But we’re very worried today
about what ice caps are doing with global warming. It’s only part of a jigsaw of trying to understand
how this planet works. But the message that I want
to leave you with today is if we can learn so much
from one small grain of sand, what could we do if we bothered
to explore 90% of our oceans that we haven’t really looked at? And I really, really think we should. Thank you. (Applause)

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10 thoughts on “How a grain of sand rewrote our ocean’s history | Andrew Wheeler | TEDxDublin

  1. To call it an Oceanic planet is the more anthropocentric – the oceans give life and weather which is good for us humans and all other life-but the oceans, lakes and rivers comprise only 0.04 percent of this Planet Earth.

  2. Keep looking, but considering the numerous changes in thinking, and the abysmal human ability to predict, It seems foolish to upend the world for trendy beliefs. Shouldn't we work on ensuring worldwide access to food, water, and peace? Indeed since the world is so cold, and co2 so close to flora starvation levels should we not welcome and increase in both temperature and co2?

  3. Quite an interesting talk, and the man is obviously passionate about his work. However…

    Five million years is nothing in relation to the age of the planet (it's about 90 seconds in relation to a day) so don't draw any conclusions about global warming from his graph.

    And, as a frivolous comment – don't wear a suit jacket over jeans (it makes it look like you buy your clothes in charity shops) and lose the silly little lip-beard.

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