Name: How Antarctica Froze Over
Uploaded: 2020-03-30T02:21:25.000Z
Duration: 6 min 59 s
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which is covered in floating sea ice, Antarctica is a true continent.

It's twice the size of Australia, with mountains, valleys, and other landforms

-- but it's almost completely covered in ice sheets

In fact, Antarctica's current icy state wasn't exactly inevitable.

It was sort of in the wrong place at the wrong time sort of thing.

Scientists have spent many years and many studies examining the questions of

how, why, and when Antarctica froze over.

If you go back about 100 million years, for example,

Antarctica was home to vast coniferous forests populated with all sorts of animals,

This was possible because Antarctica was farther north back then,

but also because the world was a warmer place.

meaning there were no permanent polar ice caps.

It wasn't until much later that our planet transitioned to a more familiar condition:

an icehouse - a world with perpetually frozen north and south poles.

Geologists generally agree that Antarctica's ice sheets began to form around 34 million

during the transition between the Eocene and Oligocene Epochs.

Antarctica was going through a lot of changes at the time.

While the early Jurassic was overall warmer and wetter everywhere,

Antarctica was still cooler than the other continents,

and was already starting to suffer from the occasional cold and dark winter.

And although Antarctica was located further north than it is today,

tectonic forces were gradually sliding the continent southward.

But on top of that, Antarctica got lonely.

It was around this time that Antarctica lost its last lingering connections

This gave rise to one of the South Pole's most famous features:

This is an ocean current that surrounds Antarctica.

like the Gulf Stream, carry warm and cold water to new places.

Many researchers believe the Antarctic current keeps cold water flowing around Antarctica,

keeping warmer water out and making sure everything stays chilly.

But that's still an active area of study, and not everyone believes that's the case.

Some scientists have referred to this time period as “The Big Chill.”

scientists have pinned this major climate shift on fluctuations in carbon dioxide.

Ancient fossils and sediments capture chemical evidence that atmospheric and ocean compositions

were changing at this time in ways that suggest CO2 levels around the world were dropping.

See, those shifting continents created a bunch of mountains.

Around the time Antarctica started freezing,

India collided with Asia and began the uplift of the Himalayas.

This created a lot of exposed rock, which is subject to chemical weathering --

and chemical weathering takes up carbon from the atmosphere.

CO2 reacts with rainwater to make carbonic acid,

The dissolved rock gets washed downriver into the ocean, where marine organisms like plankton

to make their shells, locking away even more CO2.

In fact, plankton are a seriously potent force

for climate change, for multiple reasons.

These tiny floating organisms leave behind a lot of fossil evidence,

and geologists have observed a rise in fossilized plankton

remains at the same time Antarctica was splitting off from the other continents.

This leads some scientists to suspect that as the Antarctic Circumpolar Current grew

the movement of cold, nutrient-rich water from the deep ocean up to the surface.

Upwelling acts as a fertilizer for shallow waters,

providing fuel for blooms of ocean plankton.

the more carbon dioxide they incorporate in their skeletons.

When they die and sink to the ocean floor,

those shells become incorporated into limestone,

And some experts say these oceanic changes weren't just in the south.

As the continents shifted, ocean currents around the globe were changing.

by plugging these ancient conditions into the same sort of computer models

that scientists use to study climate and oceans today.

What they found is that changes in the flow of the Antarctic Current,

like the opening of the Drake Passage between Antarctica and South America,

That would have led to an overall slowdown of the currents

that bring deep-water carbon up to the surface, keeping more of that carbon stuck underwater.

helped global CO2 decline over the past 40 million years or so.

and things started getting chilly at the South Pole.