Environment

Rising beaches suggest Antarctic glaciers are melting faster than ever

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Thwaites glacier, pictured here, is almost the size of Great Britain
NASA
Researchers on Antarctica's Edwards Island beach collect sea shells and penguin bones
James Kirkham, British Antarctic Survey
Thwaites glacier, pictured here, is almost the size of Great Britain
NASA

According to a new study, two of the main glaciers that make up the Antarctic ice sheet are now melting faster than they have over the past 5,500 years. Ironically, the conclusion is based on how sea levels have seemingly dropped in the region over time.

The study was conducted by scientists from the University of Maine and the British Antarctic Survey.

It involved the radiocarbon-dating of seashells and penguin bones found in what were at one time beaches near the present-day Thwaites and Pine Island glaciers. Given the rate at which the two glaciers are presently melting, it is hypothesized that global sea levels could rise by as much as 3.4 meters (11.2 ft) over the next few centuries.

That said, 5,500 years ago, the much slower melting process actually caused relative sea levels in the area to drop. This is due to the fact that when a heavy glacier is lying on the earth, its weight compresses the land downward. As that glacier melts and gets lighter, the land beneath it "bounces" back up accordingly. It's not unlike the fashion in which a coiled spring jumps up after being loaded and then unloaded.

As a result, glacier-adjacent beaches which were initially at sea level gradually moved upward, being replaced by new beaches below (this happened even though on a global basis, the melting of the glaciers was causing sea levels to rise slightly).

Therefore, by determining the age of shells and bones in each beach level, the scientists were able to determine the rate at which the land was moving up, and thus the rate at which the glaciers were melting. And while that rate remained slow and steady over almost all of the 5,500-year period, it has reportedly increased by a factor of five in modern times, due to global warming.

Researchers on Antarctica's Edwards Island beach collect sea shells and penguin bones
James Kirkham, British Antarctic Survey

"These currently elevated rates of ice melting may signal that those vital arteries from the heart of the West Antarctic Ice Sheet have been ruptured, leading to accelerating flow into the ocean that is potentially disastrous for future global sea level in a warming world," said Dr. Dylan Rood of Imperial College London, which is part of the British Antarctic Survey.

The scientists are now planning to drill through the glaciers to take samples of the rock underneath, which may provide clues as whether or not the present accelerated melting rate is reversible.

A paper on the research was recently published in the journal Nature.

Source: Imperial College London

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3 comments
aksdad
Post glacial rebound is happening even now in Alaska, northern Canada and northern Europe. Search for "sea level trends noaa tides & currents" to see how sea level rises or falls at different rates around the world. Interestingly, if global sea level rise continues at the current satellite-measured rate of 3.3 mm per year, the oceans will be 3.4 meters higher in about 1,000 years, not far off the prediction of "several hundred years". But it will still be lower than it was 125,000 years ago during the peak warming of the previous interglacial period, when it was up to 6 meters higher than today.
A.L.
“The much slower melting process actually caused relative sea levels in the area to drop. This is due to the fact that when a heavy glacier is lying on the earth, its weight compresses the land downward. As that glacier melts and gets lighter, the land beneath it "bounces" back up accordingly. It's not unlike the fashion in which a coiled spring jumps up after being loaded and then unloaded.”

Not just that, but the melting of trillions of tons of solid ice that had been locked up at high latitudes flowing into the oceans is migrating to the equator due to centrifugal force from the earth’s rotation. This is also causing a redistribution of both mass and gravitation to the equatorial regions.
ljaques
I heard nothing about the previously known volcanoes, nor of the 90 newest volcanoes in Antarctica, and how they could change the sea level. Hmm, could be a plot.