About 115,000 years ago, Homo sapiens still lived in groups of hunters, largely restricted to Africa. We still shared the globe with the Neanderthals, although it is unclear that we have met them yet.
Although these different hominids did not know it, the Earth comes to the end of a great warm period. It was very close to our current climate, but with a great inconsistency – the seas at that time were 6 to 9 meters high.
During this ancient period, sometimes called Emese, the oceans were last month, interesting new studies emerged, suggesting that the glaciers in the Northern Hemisphere had already retreated just as much as in the Emese, driven by dramatic warming in the Arctic regions .
arose when a team of researchers working on the island of Baffin in northeastern Canada took samples of the remains of ancient plants that emerged under the fast-moving mountain glaciers.
They found that the plants were really old and probably passed
This is the last time the areas were not actually covered with ice, scientists say.
"It is very difficult to think of another explanation except that at least in this area we work in … the last century is as warm as any century in the past 1
But if Miller is right there is a big problem. We have geological data on the sea levels of the Earth. And oceans, scientists say, were 20 to 30 feet (6 to 9 meters) high.
Some additional water is likely to come from Greenland, whose ice currently contains over 6 feet (6 meters) of potential rise in sea level. But it could not be just Greenland, because the entire ice layer did not melt at that time.
This is why researchers also suspect a collapse of the most vulnerable part of Antarctica, Western Antarctic Coating. This region could easily deliver another 3 feet (3 meters) of sea level rise or more.
"There is no way to raise tens of meters at sea level without getting tens of meters from rising sea levels from Antarctica," said Rob DeConto, an Antarctic expert at the University of Massachusetts. Trying to Understand How Antarctic Will Fall
Scientists are now intensively debating exactly which processes they could play then – and how soon they will "play again." After all, Western Antarctica has already
Some researchers, including DeConto, believe they have found a key process called the collapse of the sea-rock that can release a lot of sea level from rising from the West Antarctic in a hurry
But they are being challenged by another group whose members suspect (19659003) In order to understand the dispute, consider the vulnerability of the West Antarctic itself
This is a huge block of ice that is most often immersed in very cold water Its glaciers face the ocean in all directions, and the bottom of the ice climbs the bottom of the sea, even when the surface of the ice sheet itself grows thicker to a total depth of two miles.
] A mile and a half of this ice is below sea level, but there is still plenty of ice on it.
So if the gates of the glaciers begin to move backward – especially a glacier called the Thwaites, far away the largest – the ocean would have access to much thicker ice quickly.
The idea is that during Emian, this whole area was not a block of ice at all, not an unnamed sea. Somehow the ocean came in, took off the outer glacial forts, and gradually put the entire West Antarctica on the surface and on the road of melting.
DeConto, along with his colleague David Pollard, built a model that watched Eemian and another ancient warm period called Pliocene to understand how this could happen.
In particular, they involved two processes that can remove the glaciers. One of these, called "ice shelf life instability," describes a situation where a partially submerged glacier changes deeper and thicker as you move to its center.
In this configuration, warm water can cause a glacier to move back and forth, exposing any thicker ice to the ocean – and thicker ice flowing out faster.
So the loss goes to yourself.
The instability of sea ice is already under way in Western Antarctica, but the model is not enough. DeConto and Pollard also added another process they think is currently being played in Greenland, on a large glacier called Jakobshavn.
Jakobshavn moves back down the slope of the underwater hill, just as he is afraid of drifting. But Jakobshavn also does something else. He constantly tears thick pieces at the front, almost like bread, cutting a piece after a piece.
This is because Jakobshavn no longer has a icy shelf floating extension that has been used to grow over the ocean in front of the glacier and stabilize it. Over the last two decades, the shelf collapsed when Greenland warmed up.
As a result, Jakobshavn is now a steep vertical front to the sea. Most of the ice ice is under water, but over 100 meters (330 feet) extend over it – and for DeConto and Pollard, that's the problem.
The ice is not steel. It collapses. And interrupts.
This additional process, called "collapse of a sea ice rock," causes a final disaster if you apply it to Thwaites. If one day Thwaites loses its own ice shelf and finds a vertical front to the ocean, you would have ice cliffs hundreds of meters above the surface of the water
DeConto and Pollard say that such rocks will continually fall into the sea. And when they add this calculation, it not only recreates the rise of Emian's sea level, but also increases the projection of how much ice Antarctica can bring in this century – more than three feet. like Greenland, it means we can see up to six feet in total this century, roughly twice before forecasts. And in the next century the loss of ice will worsen even more.
"What we pointed out was if the kind of calving we see today in Greenland begins to engage in analogous conditions in Antarctica, then Antarctica has a way of thicker ice, that's bigger ice, the consequences would be potentially truly monumental for rising sea levels, "DeConto said.
"We can not recreate a six-meter rise in sea level early in the Eames, without taking into account some fragile fractures in the ice sheet pattern," said DeConto.
Mass Debate on Marine Rocks
Tamsin Edwards is not convinced. A journalist at Kings College London, she is the lead author, with a number of other Antarctic experts, a study published on Wednesday Nature (the same magazine that publishes DeConto and Pollard in 2016), challenging their model,
Using a statistical technique to study the results, Edwards and her associates find that removing ice rocks is not necessary to reproduce the last warm months. Antarctica this century. If they are right, the worst case is back to about 40 centimeters, or slightly over the leg, not three to four feet. "Things may not be as terrible as predicted the latest study," Edwards. said. "But they are still bad."
This is a new science, she said, and without more modeling, it is unclear how the ice rocks will ultimately affect the rise in sea level.
But then, what happened in the Emema? Edwards thinks it takes a long time to lose West Antarctica. That it was not fast. After all, the entire geological period is thousands of years long.
"We are very impatient, people and ice sheets do not react after a decade, they are slow beasts," she said. DeConto says he has learned something from criticism.
The Edwards study illustrates the need for deeper statistical data than we originally applied to our model for 2016, but the models are evolving rapidly and have changed significantly since 2016, "he said in a written statement.
But he does not retreat to the sea ice rocks. The new criticism, says DeConto, suggests that "these processes are not important for the future rise of the sea level, and I think this is a dangerous message."
He certainly has his allies. Richard Ali, a well-known scholar of the Penn State University who published with DeConto and Pollard, wrote in an e-mail that "the retreat of the rocks is not a strange and unexpected physical process; it is happening now in some places, it happened in the past, is expected when high temperatures occur in the ocean or in the air around the ice that flows into the ocean.
The Emian – but worse? Atmospheric carbon dioxide is far lower than it is today. Instead, the event is provoked by changes in Earth's orbit around the Sun, resulting in more sunlight in the northern hemisphere.
The big difference this time is that people warm up things much faster than it is believed
And that's a key difference, said Ted Scambos, a researcher from Antarctica, leading the US side of an international multi-million-dollar mission to explore the Glacier Travis and who is a senior researcher at the National Snow and Ice Data Center in Colorado.
"The current rate of climate change is very rapid," says Skambos, and the rate of warming can lead to glacier behavior in a different way than in the past.
Accordingly, Scambos says he sees the present debate as fruitful – "this is the discussion that must happen" – but that does not reduce his worries about the fate of Glacier Taylats if she goes far enough.
"There is no pattern that says glaciation – it will not accelerate if it falls into those conditions," said Scambos. "It just has to."
People were nowhere near Antarctica in the Emians – and in the modern times never we have seen such a large glacier as it has retreated.We may have something that we do not have a precedent or prophecy.As only last week, for example, scientists have reported that much of the hole under one part of the glacier – according to them, the models could not predict
Now there is a huge share that at least trying to figure out what could happen – before doing so – it will help to determine if people who are now organized and industrialized and fossil fuel masters are ready to repeat our own geological history
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