Is Climate Change Slowing Down the Ocean? | Susan Lozier | TED

Summary

The video script discusses the importance of understanding and monitoring the 'ocean overturning circulation,' a vital process that redistributes heat on our planet and plays a significant role in our climate. It explains how the process works, starting from the sinking of cold, dense waters at high latitudes to their eventual upwelling and warming, completing the cycle. The script highlights concerns over the potential slowing or collapse of this circulation due to climate change, which could lead to severe disruptions in climate and weather patterns. It emphasizes the need for global measurements and collective action to reduce carbon dioxide emissions to mitigate these risks. The speaker also underscores the urgency of addressing climate change within the next nine years, calling for a unified effort to protect our oceans and planet.

Takeaways

• 📚 Adelard of Bath, a 12th-century philosopher, listed 76 unanswered questions about nature, including those relevant to oceanographers.
• 🌊 Oceanographers today are concerned with how climate change impacts navigation, marine ecosystems, and the potential collapse of ocean overturning circulation.
• 🔄 The ocean overturning circulation is a large-scale current system that redistributes heat on Earth, maintaining a 30-degree-Celsius difference between the equator and the poles.
• ❄️ In winter, cold winds convert warm surface waters to cold, dense waters that sink and spread across the globe, eventually upwelling and warming again.
• 🌡️ The overturning circulation also affects climate by carrying carbon dioxide absorbed from the atmosphere, which has increased ocean acidity and impacted marine life.
• 📈 The ocean has absorbed 30% of CO2 released by humans since the Industrial Revolution, but this carbon uptake is causing ocean acidification.
• 🌞 As the ocean warms and ice melts, surface waters may become less dense, potentially slowing the overturning circulation and leading to climate disruptions.
• ⏳ Oceanographers once believed overturning changed slowly, but evidence suggests it could change rapidly, within decades or even years.
• 📉 Climate models project a decline in overturning circulation by between 11% and 34% this century, which could cause significant climate disruptions.
• 🌍 Observations are crucial for improving predictions; the longer we measure, the better our understanding of the overturning circulation and its impacts.
• 🔬 International efforts like OSNAP are essential for global ocean measurements, providing data to understand and mitigate the effects of climate change.
• ⛵️ Advances in technology, such as autonomous gliders, enable more efficient data collection and monitoring of ocean conditions, even for those prone to seasickness.

Q & A

What was Adelard of Bath known for in the 12th century?

Adelard of Bath was a natural philosopher known for compiling a list of unanswered questions about the natural world, including phenomena related to the ocean.

Why are the waters of the sea salty, according to the script?

The script does not directly answer why the sea is salty, as this was one of the questions listed by Adelard of Bath that remained unanswered in his time.

What is the significance of the ocean overturning circulation in climate regulation?

The ocean overturning circulation is crucial for redistributing heat across the planet. It works in tandem with atmospheric circulation to maintain a significant temperature difference between the equator and the poles, which would otherwise be much more extreme.

How does the ocean overturning circulation affect carbon dioxide levels?

The ocean overturning circulation helps sequester carbon dioxide by carrying surface waters, which have absorbed atmospheric CO2, to deeper parts of the ocean. This process is essential for controlling atmospheric CO2 levels and mitigating global warming.

What are the potential impacts of a slowdown in the ocean overturning circulation?

A slowdown in the ocean overturning circulation could lead to reduced carbon uptake by the ocean, more extreme weather patterns, stronger hurricanes, and more intense precipitation.

Why might the ocean overturning circulation slow down?

The script suggests that as global warming continues and polar ice melts, the surface waters may become less dense and not sink during winter as they currently do, potentially causing a slowdown in the overturning circulation.

What role does the OSNAP monitoring system play in oceanographic research?

The OSNAP (Overturning in the Subpolar North Atlantic Program) system plays a crucial role by providing data on ocean currents, temperature, and salinity across the North Atlantic, helping scientists monitor and understand changes in the ocean overturning circulation.

How does modern technology enhance oceanographic studies?

Modern technology, like autonomous gliders and satellite communication, allows for more efficient and extensive data collection from remote parts of the ocean, aiding in real-time monitoring and research without the need for constant human presence.

What is the urgency of addressing oceanic and atmospheric changes mentioned in the script?

The script emphasizes the urgency of acting within the next nine years to mitigate adverse changes in the ocean and atmosphere, highlighting the critical time window to avert severe climate and ecological disruptions.

What is the main solution proposed to reduce the risk of an overturning circulation slowdown or shutdown?

The primary solution proposed in the script is a global effort to reduce atmospheric carbon dioxide levels, which involves collective action to address the root cause of climate change and its impacts on oceanic systems.

Outlines

00:00

🌊 Oceanographic Mysteries and Climate Change

The first paragraph introduces Adelard of Bath, a 12th-century philosopher who compiled a list of unanswered questions, some of which are still relevant to oceanographers today. It discusses the salinity of the sea, the tide's ebb and flow, and the ocean's volume relative to river influx. The paragraph then transitions to modern concerns such as the impact of melting ice on navigation, the state of marine ecosystems in warming waters, and the potential collapse of the ocean overturning circulation. This circulation, also known as the 'conveyor belt' of the ocean, is a critical component of Earth's climate system, redistributing heat and maintaining temperature differences between the equator and the poles. The paragraph also touches on the ocean's role in carbon dioxide uptake, which, while beneficial for reducing atmospheric CO2 levels, increases ocean acidity and poses a threat to marine life.

05:03

📉 Projecting the Future of Ocean Overturning

The second paragraph delves into the future projections of the ocean overturning circulation using climate models. It presents the good news that a collapse of the overturning is unlikely before the year 2100, but warns that the overturning is expected to weaken by 11 to 34 percent over the current century, which could lead to significant climate disruptions. The paragraph highlights the importance of observations in refining these predictions. It introduces the OSNAP (Overturning in the Subpolar North Atlantic Program), an international observing system that measures the ocean currents, temperature, and salinity in the subpolar North Atlantic. The use of technology such as autonomous gliders for data collection is also mentioned, emphasizing the multinational effort and the need for global measurements to understand the interconnectedness of the ocean's various phenomena.

10:06

🌍 Collective Action for Climate Stability

The final paragraph emphasizes the urgency of collective action to reduce atmospheric carbon dioxide levels in order to mitigate the effects of climate change, including the potential slowdown of ocean overturning. It acknowledges that while answers to questions posed by historical figures like Adelard took centuries to develop, the timeline for addressing the current environmental crisis is much shorter, with approximately nine years to make significant changes. The paragraph calls for a united effort, or 'all hands on deck,' to address the challenges posed by climate change and protect the health of the planet's oceans and overall climate.

Keywords

💡Natural philosopher

A natural philosopher is a person who investigates the phenomena of the natural world, similar to what we now call a scientist. In the video, Adelard of Bath is described as a 12th-century natural philosopher who compiled a list of unanswered questions, which reflects the historical context of scientific inquiry.

💡Oceanography

Oceanography is the study of the ocean, including its physical, chemical, biological, geological, and atmospheric properties. The video discusses how modern oceanographers are asking complex questions about the ocean's role in climate change and its future state, which is central to the video's theme.

💡Ocean overturning circulation

Ocean overturning circulation refers to the large-scale system of deep-water circulation driven by differences in water density. It is a critical component of the Earth's climate system, as it redistributes heat and nutrients. The video explains how this circulation is threatened by climate change and its potential collapse is a significant concern.

💡Carbon dioxide (CO2)

Carbon dioxide is a greenhouse gas that is released through natural processes such as respiration and volcano eruptions, and through human activities such as deforestation and burning fossil fuels. The video discusses how the ocean absorbs CO2 from the atmosphere, which contributes to ocean acidification and is a key factor in climate change.

💡Climate change

Climate change refers to long-term shifts in temperatures, precipitation, and how natural systems function. The video emphasizes the impact of climate change on the ocean, including the potential for altering ocean currents and causing more extreme weather events.

💡Marine ecosystems

Marine ecosystems are communities of marine life that interact with each other and their environment. The video highlights concerns about how warming waters and ocean acidification, both consequences of increased CO2, are affecting these ecosystems and the species that build skeletons and shells.

💡Sea ice melt

Sea ice melt refers to the process by which ice in the ocean, particularly at the poles, melts due to rising temperatures. The video discusses how the melting of sea and land ice can affect ocean circulation and navigation routes, as well as contribute to sea level rise.

💡Ocean acidification

Ocean acidification is the ongoing decrease in the pH of the Earth's oceans, caused by the uptake of CO2 from the atmosphere. The video explains that this process is harmful to marine species and ecosystems, as it affects the chemistry of the water and makes it more difficult for organisms to form shells and skeletons.

💡Global measurement system

A global measurement system refers to the network of instruments and platforms that collect data on a worldwide scale. In the video, it is mentioned that such a system is crucial for monitoring the health of the oceans and understanding the complex interactions within the Earth's climate system.

💡OSNAP (Overturning in the Subpolar North Atlantic Program)

OSNAP is an international observing system that measures the ocean currents, temperature, and salinity in the subpolar North Atlantic. The video describes how this program contributes to our understanding of the ocean overturning circulation and its potential changes due to climate change.

💡Autonomous glider

An autonomous glider is an unmanned underwater vehicle that can travel a pre-programmed course, taking measurements at different depths. The video mentions the use of such technology in oceanographic research, which allows for the collection of data in a more efficient and less labor-intensive manner.

💡Carbon uptake

Carbon uptake refers to the process by which the ocean absorbs carbon dioxide from the atmosphere. The video discusses the implications of this process, including the positive aspect of reducing atmospheric CO2 levels and the negative aspect of increasing ocean acidity.

Highlights

Adelard of Bath, a 12th-century natural philosopher, compiled a list of 76 unanswered questions about nature, including those relevant to oceanography.

Modern oceanographers are concerned with how climate change will affect navigation routes, marine ecosystems, and the ocean overturning circulation.

The ocean overturning circulation is a large-scale movement of water that redistributes heat on the planet, maintaining a 30-degree-Celsius difference between the equator and the poles.

The ocean's carbon uptake has been increasing with atmospheric CO2 concentrations, now storing 30 percent of carbon dioxide released since the Industrial Revolution.

Ocean acidification, a result of increased carbon dioxide absorption, is harmful to marine species that build skeletons and shells.

Warming and melting ice could lead to a slowing of the overturning circulation, impacting carbon uptake and causing major disruptions to climate and weather patterns.

Oceanographers once believed the overturning changed slowly over tens of thousands of years, but recent studies suggest it could change within decades.

Climate modeling has improved our understanding of the risk of an abrupt collapse of the overturning circulation due to human-induced warming.

The overturning is unlikely to collapse before 2100, but it is expected to weaken by 11 to 34 percent over this century.

Observations are crucial for improving predictions; the longer we measure, the better our predictions become.

OSNAP is an international observing system in the subpolar North Atlantic that measures ocean currents, temperature, and salinity.

New technology like autonomous gliders allows for continuous and remote data collection on ocean conditions.

OSNAP data cannot yet determine the current direction of the overturning's change due to the inherent 'noise' in oceanic data.

Global measurement systems are essential for understanding the interconnectedness of the ocean and the impacts of climate change.

NOAA buoys and a vast global measurement network are part of the multinational effort in 21st-century oceanography.

Reducing atmospheric carbon dioxide is the collective solution to mitigate the effects of climate change on the ocean and the planet.

The urgency of addressing climate change is emphasized, with a timeline of approximately nine years to make significant changes.

The need for a collective effort, 'all hands on deck,' is highlighted to address the challenges posed by climate change.

Transcripts

I'm going to start this morning

by telling you about a 12th century natural philosopher

named Adelard of Bath.

Adelard compiled a list of unanswered questions

near the end of his long life.

Among the 76 questions in his treatise on nature

were those that interest an oceanographer like me:

Why are the waters of the sea salty?

Whence comes the ebb and flow of the tide?

And why does the ocean not increase from the influx of the rivers?

Nine centuries later,

oceanographers are asking questions unfathomable to Adelard.

How will navigation routes change as sea and land ice continue to melt?

How are marine ecosystems faring in these warming waters?

And, will climate change cause the collapse

of the ocean overturning circulation?

If that last one puzzles you, let me explain.

Ocean waters are constantly on the move.

Many of the ocean waters are local,

like the surface currents of the North Atlantic you see here.

But the ocean is also home to large currents

that travel from one ocean basin to the next,

often thousands of kilometers away.

The largest of these is referred to as the “ocean overturning circulation.”

This current originates at high latitudes.

In the winter,

when cold winds blow across the ocean,

warm surface waters are converted to cold waters.

That's the orange arrow turning blue.

These cold waters are now denser than the waters underneath,

and so they sink and then spread at depth to distant parts of the globe

following that ribbon of blue.

Eventually these waters upwell,

meaning they return to the surface where they warm.

And so now the blue ribbon turns back to orange,

and they return to where they started completing the ocean overturning.

Now, this ocean overturning redistributes heat on our planet.

In partnership with the atmospheric circulation,

this fluid movement maintains a 30-degree-Celsius difference

between the equator and the poles.

Without these fluid motions,

that temperature difference would be 110 degrees Celsius

and not just over the ocean,

inland as well.

Polar latitudes would be completely frozen,

and the tropics, well the tropics would be even more sweltering.

But this overturning also impacts our climate

because when those waters sink,

they carry with them the carbon dioxide they've gained

by exchange with the atmosphere.

And so as a result of this, as the decades have progressed,

the amount of carbon taken up or fluxed into the ocean

has been increasing

in tandem with the increasing concentrations of carbon dioxide

in the atmosphere.

In fact, the ocean now stores 30 percent of the carbon dioxide

released by humanity

since the start of the Industrial Revolution.

Now, this does mean that the levels of carbon dioxide in the atmosphere

are less than they would be otherwise, which is good news.

But that carbon uptake by the ocean increases ocean acidity,

which is not good news for marine species that build skeletons and shells.

And it is certainly not good news for marine ecosystems in general.

Now, as our ocean continues to warm and as ice continues to melt,

both of which cause surface waters to become less dense,

we fully expect that at some point, in winter,

those surface waters will not get dense enough to sink.

And at that point, we expect the overturning to slow.

And if the overturning slows,

well, there will be less carbon uptake by the ocean.

But there will also be even more major disruptions to our climate

and weather patterns; we can expect stronger hurricanes,

even more intense precipitation.

Just about now, you might be wondering,

how quickly might the overturning change?

Well, for decades, oceanographers assumed that the overturning changed slowly

on the time scales of tens of thousands of years, in concert with the ice ages.

But a study in the 1990s of ice sheets,

which hold bubbles of air from past climates,

well, that study suggested that the overturning could change quickly,

within decades, maybe even within years.

And with that, the possibility of an abrupt collapse

of the overturning circulation brought about by human-induced warming?

Well, at that point it became a very real possibility.

Thankfully, advances in climate modeling

give us a much better idea today of that risk.

The black and gray lines that you see on this graph

are the model reconstructions of the past relatively steady overturning changes.

The lines of various colors show you the future projections

of the overturning, based on different climate models

and different climate scenarios.

I'm going to start with the good news.

And the good news is that the overturning is unlikely to collapse

before 2100.

Now, before anybody breathes a sigh of relief,

I will remind you that our children, our grandchildren, will likely see 2100.

And really, none of us are out of the woods

because the overturning is likely to weaken over this century

by between 11 percent and 34 percent.

And that weakening is enough to cause the disruptions that I mentioned earlier.

Now back to those various lines of color.

All future projections show a decline,

but they differ in how fast and by how much that decline will be.

And this is exactly where observations come in,

because the longer we measure, the better our predictions will be.

If Adelard had started measuring nine centuries ago,

we would be way ahead of the game.

Unfortunately, we only started measuring in this century

when we had the resources

and, frankly, the motivation to do so.

One of those efforts is an international observing system

in the subpolar North Atlantic.

OSNAP stretches from the Labrador coast to one side of Greenland,

and then again from the other side of Greenland,

all the way over to the Scottish coast.

Those red ribbons depict the surface currents,

and those dark blue ribbons depict the deep currents

of the ocean overturning circulation.

Every black vertical line you see is the mooring that stretches

from the sea surface to the sea floor,

upon which instruments, shown as red dots,

those instruments are on those moorings, and they're measuring the ocean currents,

the temperature and the salinity.

Every other summer since 2014,

research vessels like this one have traced the OSNAP line,

deploying instruments and taking measurements.

Dozens of oceanographers from many different countries

have been on these cruises.

Here's a former student of mine off the coast of Greenland,

bringing in a rosette of bottles that have captured water samples

in the deep ocean.

OSNAP also allows us to use new technology,

like this autonomous glider that, once deployed,

will set off on a programmed course,

taking measurements at depth.

Every now and again,

this glider will pop to the surface and relay its information

to a passing satellite.

You could be sitting in a cafe, enjoying your latte,

all the while downloading data from this glider,

which, for a seasick-prone oceanographer like me, is a godsend.

(Laughter)

However, it is true

that conditions on these cruises are sometimes challenging.

But I must admit that the views are almost always worth it.

Now, you can tell from a glance

that our OSNAP data to date

do not tell us whether the overturning in this part of the ocean

is currently increasing or decreasing.

And the reason for that is the same reason

that you cannot tell what the stock market will do in a year

by looking at the Dow Jones Industrial Index for a week.

There is noise in the market, and there is noise in the ocean.

But just as we have confidence that stocks are a good bet in the long run,

we have confidence that in the long run,

the overturning will decline if our climate continues to warm.

And with that confidence, we know that it's not enough for us to study

the overturning in isolation.

We need to understand how the overturning is impacting

and being impacted by everything else going on in the ocean.

I just told you, the ocean is noisy.

Well, the ocean is also connected.

What's happening in one part of the ocean

affects what's going on in another part.

And so to understand and to improve our estimates of the overturning,

the warming, the freshening, the acidification,

we need to measure globally.

And we are.

This NOAA buoy is out there,

measuring the exchange of carbon between the ocean and the atmosphere.

This one buoy is but a small part of a vast global measurement system

that looks like this.

Every line or dot you see on this map is where there is a ship,

a mooring or buoy out in the ocean, taking measurements.

This multinational effort is the backbone of 21-century oceanography.

But we can do all those measurements of many things in many places.

But to stem the warming, the freshening,

the acidification, the sea level rise

and to reduce the very real risk of an overturning slowdown or shutdown,

there's one solution.

We must work collectively

to reduce the carbon dioxide in our atmosphere.

Adelard did not have everything figured out in the 12th century,

and we certainly don't here in the 21st.

Answers to Adelard's questions were centuries in the making.

But to figure everything out on our end,

we don't have nine centuries.

We don't have nine decades.

We probably have about nine years to get it right.

And to get it right,

it's just like everyone says,

we need all hands on deck.

Thank you.

(Applause)