Antinuclear

Australian news, and some related international items

Antarctic melting could raise sea levels by up to 30 feet

At this rate, Earth risks sea level rise of 20 to 30 feet, historical analysis shows  New research finds that a vast area of Antarctica retreated when Earth’s temperatures weren’t much warmer than they are now, WP  Chris Mooney, September 20  2018

Temperatures not much warmer than the planet is experiencing now were sufficient to melt a major part of the East Antarctic ice sheet in Earth’s past, scientists reported Wednesday, including during one era about 125,000 years ago when sea levels were as much as 20 to 30 feet higher than they are now.

“It doesn’t need to be a very big warming, as long as it stays 2 degrees warmer for a sufficient time, this is the end game,” said David Wilson, a geologist at Imperial College London and one of the authors of the new research, which was published in Nature. Scientists at institutions in Australia, New Zealand, Japan and Spain also contributed to the work.

The research concerns a little-studied region called the Wilkes Subglacial Basin, which is roughly the size of California and Texas combined and contains more than 10 feet of potential sea-level rise. Fronted by three enormous glaciers named Cook, Mertz and Ninnis, the Wilkes is known to be vulnerable to fast retreat because the ice here is not standing on land and instead is rising up from a deep depression in the ocean floor.

Moreover, that depression grows deeper as you move from the current icy coastline of the Wilkes farther inland toward the South Pole, a downhill slope that could facilitate rapid ice loss.

What the new science adds is that during past warm periods in Earth’s history, some or all of the ice in the Wilkes Subglacial Basin seems to have gone away. That’s an inference researchers made by studying the record of sediments in the seafloor just off the coast of the current ice front……..

Humans have caused about 1 degree Celsius (1.8 degrees Fahrenheit) of warming above the preindustrial planetary temperatures experienced before the year 1880 or so. The world has pledged to avoid a warming above 2 degrees Celsius, and even hopes to hold the warming to 1.5 degrees, but current promises made by countries are not nearly enough to prevent these outcomes.

n other words, we are already on a course that could heat the planet enough to melt some or all of the Wilkes Basin.

“We say 2 degrees beyond preindustrial, and we’re already beyond preindustrial,” Wilson said. “So this is potentially the kinds of temperatures we could see this century.”

The study cannot reveal, however, just how quickly ice emptied out of the Wilkes Basin. The past warm periods in question are thought to have been driven by slight variations in Earth’s orbit as it rotates around the sun, leading to stronger summer heat. That warmth was maintained for thousands of years.

…….. The new research “contributes to the mounting pile of evidence that East Antarctica is not as stable as we thought,” Isabella Velicogna, a glaciologist at the University of California at Irvine, said by email. Velicogna was not directly involved in the paper…….https://www.washingtonpost.com/energy-environment/2018/09/20/antarctica-warming-could-fuel-disastrous-sea-level-rise-study-finds/?utm_term=.7c426ea2a985

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September 21, 2018 - Posted by | General News

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