What Happened the Last Time Antarctica Melted?


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The JOIDES staff snapped this picture on their transit by the ice close to Antarctica. (Credit score: JOIDES Decision/Twitter)

Earlier this week, a global staff of geologists and local weather scientists parked their ship off the coast of West Antarctica and began drilling. Their mission: To search out out why glaciers right here melted thousands and thousands of years in the past and what that may inform us about what’s occurring at the moment.

Over the following couple months, their ship, the Worldwide Ocean Discovery Program’s JOIDES Decision, will drill not less than 5 core samples reaching hundreds of ft beneath the Ross Sea. These cores will let scientists learn layers within the rock report like pages of a e book, unraveling local weather and ice situations stretching again tens of thousands and thousands of years.

Amelia Shevenell is the venture’s mastermind. The College of South Florida knowledgeable in historic climates has labored for years on proposing and planning the expedition.

“This expedition is admittedly thrilling, and significantly to me as a result of I’ve been engaged on it for 10 years,” says Shevenell.

In that point, scientists have develop into more and more assured that heat ocean water from extra northern climes is washing up towards the coast of Antarctica and discovering its means beneath these ice sheets, melting them from beneath. That’s inflicting coastal glaciers, like Pine Island in West Antarctica, to retreat irreversibly, dropping lots of of ft every year. And these glaciers act like a stopper, holding again inland glaciers. As soon as they soften, the entire West Antarctic Ice Sheet is liable to collapsing.

The IODP drilling expedition goals to higher perceive what made these ice sheets soften previously. Was it warming ocean waters again then, too? If scientists can be taught extra about these historic climates, they may higher perceive what the long run holds.

Day by day from now by early March, Shevenell and her colleagues will work a 12-hour shift. Drill employees will pull up cores from the ocean depths and hand them off to scientists for examination within the ship’s laboratory.

Because the cores are available, Shevenell says she’ll be searching for altering rock sizes. Pebbles and gravel are deposited close to a glacier’s grounding line — the purpose the place it meets the ocean. So when scientists see layers of these small rocks, they’ll know glaciers reached their drill location at that time in historical past.

Layers of grey clays point out the sediments fashioned beneath a big floating ice shelf. And when Shevenell sees tiny marine creatures by the microscope, she is aware of the area was open ocean at that time at the moment — devoid of ice. These microscopic marine animals may reveal particulars in regards to the setting, like temperature.

“We will mix all that knowledge and attempt to perceive occasions the place ocean temperatures have been heat, and we will take a look at occasions the place oceans weren’t as heat,” she says.

She’ll even be searching for pollen, as a result of earlier than the ice sheets, Antarctica was a giant rain forest lined in tree ferns. Ice overtook the continent between 50 and 34 million years in the past. Scientists are nonetheless debating why that occurred.

About 34 million years in the past, Tasmania and South America broke away from Antarctica, leaving the continent remoted. That kick-started what’s known as the Antarctic Circumpolar Present — an unlimited present of chilly waters that walled the continent off from extra tropical warmth.

However atmospheric carbon dioxide ranges have been additionally altering across the similar time, main some to consider that greenhouse gases have been the principle reason for Antarctica’s icy shift.

Shevenell suspects each modifications performed a job, however she’s hoping so as to add extra proof to the scientific debate.

Nonetheless, probably the most intriguing time — the interval that issues most to us at the moment — scientists hope to discover within the rock report is between 7 and 14 million years in the past. It’s a interval geologists name the Miocene. Earth’s temperature and atmospheric CO2 ranges have been much like what we’re experiencing at the moment, and but Antarctica was going by vital modifications.

“At the moment in Antarctica, the ices retreated fairly considerably and brought on sea stage rise,” Shevenell says. Scientists don’t totally perceive what drove these modifications. However Shevenell has a hunch.

“I’ve a sneaking suspicion that this ice variability will probably be associated to ocean modifications,” she says.

The IODP staff ought to have a greater concept later this yr. As soon as the collections efforts are over, the staff will deliver the cores again to land for extra intensive examine.

This one journey can’t present all of the solutions, however Shevenell says it’s one in all a handful of drilling expeditions set to occur across the continent over the following a number of years. By combining snapshots of historic ocean temperatures and glacier areas over time, scientists can higher map out the continent’s icy historical past — and get a fuller image of why its glaciers retreat and develop.

“We’re going to start to grasp much more about Antarctic ice sheets and the way they reply to atmospheric and oceanic modifications,” she says.

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