Ocean circulation rethink solves climate conundrum

September 28, 2015, University of Exeter
Credit: Tiago Fioreze / Wikipedia

Researchers from the University of Exeter believe they have solved one of the biggest puzzles in climate science. The new study, published in Nature Geoscience, explains the synchrony observed during glacial periods when low temperatures in the Southern Ocean correspond with low levels of atmospheric carbon dioxide (CO2).

The interdisciplinary study, carried out in collaboration with the University of Tasmania, demonstrates how a reconfiguration of ocean circulation can result in more carbon being stored in the deep ocean that previously thought.

The researchers used a computer model representing the physics of the ocean along with a biogeochemical model of ocean chemistry to show how the so far neglected aspect of changed water buoyancy can make a major contribution to atmospheric CO2.

During an ice age, the on Antarctica mean that the water near to the continent is colder and so less buoyant. The upwelling of warmer water - during which CO2 is lost to the atmosphere - occurs further away from Antarctica enabling carbon dioxide to be drawn down into the ocean, and also producing a larger volume of deep cold water in the Southern Ocean in which carbon can be stored.

Professor Andrew Watson from Geography at the University of Exeter said: "Our study offers a new explanation for a problem that has occupied oceanographers and climate scientists for more than 30 years - what caused atmospheric CO2 to increase and decrease in near-perfect synchrony with the series of glacial cycles that have occurred over the last million years?

"This is a major advance in our understanding of the natural carbon cycle that comes from applying new ideas about how the 'overturning circulation' of the Southern Ocean works."

Professor Geoffrey Vallis from Mathematics at the University of Exeter said: "We combined a model of the with a model of the carbon cycle and obtained a rather striking result, hopefully throwing some new light on an old problem."

The new mechanism provides an explanation for the positive feedback that occurs during an ice age. As the temperature drops, more CO2 is absorbed into the resulting in less atmospheric CO2 and so a reduction in the greenhouse effect, meaning that it gets colder still. And so the cycle continues.

Scientists had previously presumed that the reduced levels of CO2 in the atmosphere during an meant that more CO2 was being stored in the oceans but this new mechanism explains how this can actually occur and why it is that temperatures in a specific region of the world - Antarctica - are so closely linked to the atmospheric CO2 concentration.

Explore further: Carbon release from ocean helped end the Ice Age

More information: Southern Ocean buoyancy forcing of ocean ventilation and glacial atmospheric CO2, Nature Geoscience, DOI: 10.1038/ngeo2538

Related Stories

How fossil corals can shed light on the Earth's past climate

September 24, 2015

In a paper published today in Science, researchers from the University of Bristol describe how they used radiocarbon measured in deep-sea fossil corals to shed light on carbon dioxide (CO2) levels during the Earth's last ...

Research shows revived oceanic CO2 uptake

September 10, 2015

Breathe in, breathe out, in, out... Like a giant lung, the Southern Ocean seasonally absorbs vast amounts of carbon dioxide (CO2) from the atmosphere and releases it back later in the year. But on an annual average the seas ...

The last ice age

July 3, 2014

A team of scientists has discovered that a giant 'burp' of carbon dioxide (CO2) from the North Pacific Ocean helped trigger the end of last ice age, around 17,000 years ago.

Recommended for you

Corals light the way to a healthy partnership

January 22, 2019

Corals know how to attract good company. New research finds that corals emit an enticing fluorescent green light that attracts the mobile microalgae, known as Symbiodinium, that are critical to the establishment of a healthy ...

For zombie microbes, deep-sea buffet is just out of reach

January 22, 2019

Far below the ocean floor, sediments are teeming with bizarre zombie-like microbes. Although they're technically alive, they grow in slow motion, and can take decades for a single cell to divide—something their cousins ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.