Research Shows A Revived CO2 Uptake By The Southern Ocean

 

Research Shows A Revived CO2 Uptake By The Southern Ocean

A research vessel ploughs through the waves, braving the strong westerly winds of the Roaring Forties in the Southern Ocean in order to measure levels of dissolved carbon dioxide in the surface ocean. Photo: Nicolas Metzl, LOCEAN/IPSL Laboratory.

Like a giant lung, the Southern Ocean seasonally absorbs vast amounts of carbon dioxide (CO2) from the atmosphere and releases some of it back later in the year — but not all.

 

The end result: The ocean removes a large part of the CO2 that human activities emit, slowing down the growth of greenhouse gas in the atmosphere.

Although the Southern Ocean represents no more than a quarter of the total surface of the world’s oceans, it accounts for 40 percent of the global oceanic uptake of that man-made CO2.

A decade ago scientists thought the Southern Ocean carbon sink was beginning to saturate, as models suggested the amount of carbon absorbed had not increased since the late 1980s. This was unexpected since the assumption was that the higher the concentration of CO2 in the air, the greater the amount of CO2 the ocean would absorb.

But new research published in Science this week indicates the Southern Ocean carbon sink has become much stronger since 2002 — roughly doubling to 1.2 billion tonnes in 2011 (equivalent to the European Union’s annual man-made greenhouse gas emissions).

Nicolas Gruber, a professor of environmental physics at ETH Zurich who led the study, says the results suggest that the strength of the Southern Ocean carbon sink fluctuates strongly, possibly in periodic cycles, rather than increasing monotonically in response to the growth in atmospheric CO2.

“We were surprised to see such large variations in this ocean’s net carbon uptake,” he says.

“A strong carbon sink in the Southern Ocean helps to mitigate climate change for the moment, as otherwise even more CO2 would have stayed in the atmosphere, but we cannot conclude that this will continue forever,” Gruber told the Guardian.

“One has to recognise that despite this remarkable increase in the Southern Ocean carbon sink, emissions have gone up even more.”

Blame the weather

Gruber and colleagues attribute the reinvigoration of the carbon sink above all to changes in the prevailing weather patterns in the studied region.

Since the turn of the millennium, the dominant atmospheric pressure systems have exhibited an increasingly asymmetrical distribution. A powerful high-pressure system has built up above the Atlantic sector of the Southern Ocean, while a distinct area of low pressure has formed over the Pacific sector.

Winds now tend to blow in an undulating pattern, whereas in the 1990s they mainly blew straight from the west to the east.

The air pressure gradient between these regions of high and low air pressure has caused wind patterns to change. Winds now tend to blow in an undulating pattern, whereas in the 1990s they mainly blew straight from the west to the east. In the 1990s these winds were also stronger over much of the Southern Ocean, causing more water to be upwelled to the surface from depth.

Since these deeper waters contain higher concentrations of dissolved CO2, this upwelling led to an anomalous release of this greenhouse gas into the atmosphere, resulting in a stagnation or even a decrease in the ocean’s net carbon uptake.

Can’t predict the future

Since the turn of the millennium, upwelling has generally subsided in all sectors apart from the Pacific, stopping the release of stored CO2 into the atmosphere. But the winds have also changed the temperature of the surface water.

By bringing warm air from subtropical latitudes into the South Atlantic, they have warmed the surface waters of the South Atlantic substantially. At the same time, the anomalous low-pressure system in the South Pacific brought exceptionally cold air from the interior of the Antarctic continent to this sector of the Southern Ocean, leading to a strong cooling there.

Together, the wind and temperature changes explain much of the reinvigoration of the Southern Ocean carbon sink.

The cooling of surface waters in the Pacific sector enables them to absorb more CO2. In the Atlantic sector, on the other hand, changes in the wind-driven circulation patterns are likely responsible for the higher oceanic uptake of atmospheric CO2.

The reinvigoration of the ocean’s carbon sink has occurred during a period when global air temperatures have changed very little, which is possibly related to a stronger heat uptake by the ocean.

Peter Landschützer, a postdoctoral researcher involved in the study, says the model can’t predict how the pattern will change in the future, “so it is very critical to continue measuring the surface ocean CO2 concentrations in the Southern Ocean”.

“This is particularly important since current models are not able to reproduce the observed variations,” adds Gruber. Hence, longterm datasets are the only reliable means for determining the future evolution of the ocean’s sink for carbon.

Another factor that is not yet fully understood is the effect of large-scale climate phenomena such as El Niño and La Niña on the Southern Ocean carbon sink. It is particularly noticeable that the reinvigoration of the carbon sink coincides with a period of prevalent La Niña conditions — i.e., relatively cool sea surface temperatures in the Pacific.

The reinvigoration of the ocean’s carbon sink also occurred during a period when global air temperatures have changed very little — the so-called climate warming hiatus, possibly related to a stronger heat uptake by the ocean.

About The Author

Peter Rüegg is part of the communications team at ETH Zurich.

Related Books

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook-icontwitter-iconrss-icon

 Get The Latest By Email

{emailcloak=off}

EVIDENCE

How Climate Change Affects Wildfires
by NBC News
NYU environmental studies professor David Kanter explains how climate change is creating the perfect conditions for…
Warning of 'Untold Human Suffering,' Over 11,000 Scientists From Around the World Declare Climate Emergency
Warning of Untold Human Suffering, Over 11,000 Scientists From Around the World Declare Climate Emergency
by Julia Conley
"Scientists have a culture of reticence when it comes to making statements like this, but the emergency is rapidly…
New Land Height Metric Raises Sea Level Rise Risk
New Land Height Metric Raises Sea Level Rise Risk
by Tim Radford
Millions of us now live in danger: we could be at risk from future high tides and winds, says a new approach to…
The Science Of Drought Is Complex But The Message On Climate Change Is Clear
The Science Of Drought Is Complex But The Message On Climate Change Is Clear
by Ben Henley, et al
The issue of whether Australia’s current drought is caused by climate change has been seized on by some media…
Understanding Natural Climate Cycles
by NOVA PBS
The climate has changed on a schedule for millennia.
"Climate Predictions and Projections" by Jim Hurrell (Climate Change Symposium)
by Jim Hurrell
Professor Jim Hurrell presents "Climate Predictions and Projections in the Coming Decades: Uncertainty due to Natural…
Understanding Climate Change Science On Oceans And The Cryosphere
by CBC Nova Scotia
The United Nations panel dedicated to reviewing the science of climate change recently released a dense new report…
Where's The Proof In Science?
Where's The Proof In Science?
by Geraint Lewis
One word is rarely spoken or printed in science and that word is “proof”. In fact, science has little to do with…

LATEST VIDEOS

How Supercharged Trash Gas Could Produce More Green Energy
by InnerSelf Staff
Synthetic compounds called “siloxanes” from everyday products like shampoo and motor oil are finding their way into…
300 Million Face Severe Risk of Climate-Fueled Coastal Flooding by 2050
by Democracy Now!
As a shocking new report finds that many coastal cities will be flooded by rising sea levels by 2050, Chile’s President…
Climate Warning: California Continues To Burn, Data Estimates Of Global Flooding
by MSNBC
Ben Strauss, CEO and Chief Scientist of Climate Central joins MTP Daily to discuss alarming new information about…
Stanford Climate Solutions
by Stanford
Climate change has brought us to a defining moment in human history.
Buying Renewable Energy From Your Neighbor
by NBC News
Brooklyn Microgrid, a project of parent company LO3 Energy, is looking to disrupt the more than 100-year-old energy…
Debate Over Pipelines Clouds Concern For Climate Change
by Global News
Climate experts are warning that Canada shouldn't ignore the wildfire crisis in California
How Climate Change Affects Wildfires
by NBC News
NYU environmental studies professor David Kanter explains how climate change is creating the perfect conditions for…
Rice Bowl Of Malaysia Threatened By Climate Change
by The Star Online
Kedah is known as the country’s “Rice Bowl,” and it is especially suitable for the growing of the grain.

LATEST ARTICLES

Building With Bamboo Can Cool The Climate
Building With Bamboo Can Cool The Climate
by Kieran Cooke
If you want to cut global temperatures try building with bamboo, say UK-based researchers studying its thermal…
To Win A Climate Election, Parties Need Ambition, Not Compromise With The Fossil Fuel Industry
To Win A Climate Election, Parties Need Ambition, Not Compromise With The Fossil Fuel Industry
by Marc Hudson
The UK will go to the polls on December 12 for the third time in four years. Climate change didn’t make waves in…
3 Ways Cities Can Prepare For Climate Emergencies
3 Ways Cities Can Prepare For Climate Emergencies
by Ryan Plummer, et al
Cities are on the front line of climate change. While their footprints cover a mere two per cent of the Earth’s…
How Green Roofs Can Protect City Streets From Flooding
How Green Roofs Can Protect City Streets From Flooding
by Catherine Howell, et al
Spring and summer 2017 have been among the wettest on record in eastern North America.
How Supercharged Trash Gas Could Produce More Green Energy
by InnerSelf Staff
Synthetic compounds called “siloxanes” from everyday products like shampoo and motor oil are finding their way into…
Climate Change Will Magnify Weather Blocking Events
How Climate Change Will Magnify Weather Blocking Events
by InnerSelf Staff
“Blocking events” have produced some of the 21st century’s deadliest heat waves. These stalled high-pressure weather…
Arctic Sea Ice Loss Opens Marine Mammals To Deadly Virus
Arctic Sea Ice Loss Opens Marine Mammals To Deadly Virus
by InnerSelf Staff
Scientists have linked Arctic sea ice loss to a deadly virus that could threaten marine mammals in the North Pacific,…
Scientists’ Climate Gap Is Narrowing
Scientists’ Climate Gap Is Narrowing
by Alex Kirby
A poll shows scientists’ climate gap is shrinking − between their work on climate change and their own response to it.