Published On: Sun, Oct 30th, 2016

A Mystery Solved: Why Does Our Planet Experience an Ice Age Every 100, 000 Years?

Up until now, scientists have been unable to explain why this happens.

snowball_earth-ice-age

 

Why our planet began to move in and out of ice ages every 100, 000 years? Researchers from Cardiff University have offered up an explanation for this mysterious dubbed the ‘100, 000 year problem’.

The history of our planet phenomena has been occurring for the past million years leaving North America, Europe, and Asia swallowed in ice, and the last one ended roughly 11, 000 years ago.

Up until now, scientists have been unable to explain why this happens.

Our planet’s ice ages used to occur at intervals of every 40, 000 years, which made sense to scientists as the Earth’s seasons vary in a predictable way, with colder summers occurring at these intervals.

However there was a point, about a million years ago, called the ‘Mid-Pleistocene Transition’, in which the ice age intervals changed from every 40, 000 years to every 100, 000 years.

The New research has suggested the oceans may be responsible for this change, specifically in the way that they suck carbon dioxide (CO2) out of the atmosphere.

By studying the chemical make-up of tiny fossils at the bottom of the ocean, the reseteam discovered that there was more CO2 stored in the deep ocean during the ice age periods at regular intervals every 100, 000 years.

 

This suggests that extra carbon dioxide was being pulled from the atmosphere and into the oceans at this time, subsequently lowering the temperature on Earth and enabling vast ice sheets to engulf the Northern Hemisphere.

 

Iceberg in Antarctic sea ice. photo Caitlin Gionfriddo,   University of Melbourne

 

 

Lead author of the research Professor Carrie Lear, from the School of Earth and Ocean Sciences, said: “We can think of the oceans as inhaling and exhaling carbon dioxide, so when the ice sheets are larger, the oceans have inhaled carbon dioxide from the atmosphere, making the planet colder. When the ice sheets are small, the oceans have exhaled carbon dioxide, so there is more in the atmosphere which makes the planet warmer.

“By looking at the fossils of tiny creatures on the ocean floor, we showed that when ice sheets were advancing and retreating every 100, 000 years the oceans were inhaling more carbon dioxide in the cold periods, suggesting that there was less left in the atmosphere.”

Marine algae play a key role in removing CO2 from the atmosphere as it is an essential ingredient of photosynthesis.

CO2 is put back into the atmosphere when deep ocean water rises to the surface through a process called upwelling, but when a vast amount of sea ice is present this prevents the CO2 from being exhaled, which could make the ice sheets bigger and prolong the ice age.

“If we think of the oceans inhaling and exhaling carbon dioxide, the presence of vast amounts of ice is like a giant gobstopper.” Prof Lear said, “It’s like a lid on the surface of the ocean.”

Today, the Earth’s climate is in a warm spell between glacial periods. Temperatures and sea levels both on the rise since the end of the last ice age about 11, 000 years ago and ice caps have retreated back to the poles.

And, yes, in addition to these natural cycles, human caused carbon emissions have accelerated the warming effect.

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