CLIMATE CHANGE TAKES ITS TOLL ON THE ANTARCTIC
CLIMATE CHANGE TAKES ITS TOLL ON THE ANTARCTIC
Sea ice surrounding and linked to the Antarctic continent is melting, vanishing and leaving long burried land in plain sight. This can sound astonishing for scientific expeditions – that can now unravel mysteries of the most off reach part of Earth – but for human and animal life as we know it, it’s no good news at all.
New study reports that as greenhouse gases rise and warm the planet, the ice in Antarctica is to become more vulnerable to astronomical cycles. With CO2 going beyond 400 parts per million (ppm), Earth’s climate becomes more sensitive to its tilt, as it spins around its axis. It may not seem much, but over a 30 million years, this only happened when CO2 levels peaked to what research predicts for the end of the century.
The Antarctic melting is happening six times faster than a few decades ago, so the continent lost an average of 252 gigatons of ice per year, compared to the loss of 40 gigatons per year, between 1979 and 1990. So, a total loss of sea ice seems imminent. That is, if countries all over the planet don’t reduce greenhouse gas emissions.
NO SEA ICE MAKES THE EARTH TILT
The research, published in the Nature Geoscience on January 14, says that the Earth’s tilt matters, because sunlight hits it differently – so it influences overall climate. To get a broad vision about this, study co-author and paleo-climatologist Stephen Meyers explained that over 40,000 years, the planet goes back and forth, literally “like a rocking chair”, between 22.1 and 24.5 degrees – while currently it’s at about 23.4 degrees.
Reconstructing the Earth’s past, Meyers and his colleagues used two sources of information: the calcium carbonate from the ocean’s bottom – left behind by micro-organisms called benthic foraminifera – and the sediment records from around Antarctica. Drilled in long, columnar cores from the bottom of the ocean, they hold a record of the past, as a glacier dumps a specific mixture of sand, gravel and mud. So, scientists got a detailed picture of where the ice once was.
They discovered that 34 million years ago, CO2 levels were as high as 800 ppm. And Antarctica lacked sea ice.
WHEN CARBON DIOXIDE CHANGES EVERYTHING WE KNOW
The unveiled history of Antarctica means trouble for the future, as carbon dioxide in the Earth’s atmosphere went past 400 ppm. And the last time this happened in the planet’s history, there was no year-round sea ice in Antarctica.
Paleo-climatologist Richard Levy of GNS Science thinks that soon “we will jump back to a world that hasn’t existed for a million years,” if greenhouse gas emissions continue to rise. He added that “Antarctica’s vulnerable marine-based ice sheets will feel the effect of our current relatively high tilt, and ocean warming at Antarctica’s margins will be amplified.”
Geologically speaking, the year-round sea ice became the norm only about 3 million years ago, just when CO2 levels went below 400 ppm. Before that, 34 to 25 million years ago, CO2 levels were above 600 ppm and the Antarctic’s ice was only land-based – so the advances and retreats were quite insensitive to the planet’s tilt. Between 24.5 and 14 million years ago, CO2 dropped below 600 ppm and the ice sheets started to advance into the sea. And this when climate became sensitive to the tilt of Earth’s axis.
When carbon dioxide levels dropped at about 200 ppm, 13 million to 5 million years ago, floating ice engulfed the Antarctic sea and its sensitivity to the planet’s tilt decreased.
TO BE OR NOT TO BE?
Sensitivity seems to involve contact between the ice and the ocean, though it’s still unclear why. Until now, research tells us that at times of high tilt, polar regions warm and climate differences between the poles and the equator become less extreme. And this severely alters wind and current patterns, increasing the flow of warm ocean waters to the Antarctic.
This flow of warm water matters a lot, because ice sheets are grounded on the bottom of the ocean, being in contact with the currents. Sea ice seems to block some of the flow, decreasing the chance of melting ice sheets. But with CO2 levels high enough, nothing stands against the warm currents and that’s when Earth’s tilt matters the most.
Now we can see how many million years it took the planet to naturally drop CO2 levels. But as our scientific knowledge and technological skills increased, why not make it happen faster, by using everything we know to create a green and clean future for us and our planet?
