[ Envirowatchers ] [ Main Menu ]
18842
From: ryan, [DNS_Address]
Subject: Antarctica’s glaciers are melting from beneath, speeding sea-level ris
|
Antarctica’s glaciers are melting from beneath, speeding sea-level rise by Saul Elbein - 10/27/23 2:00 PM ET This 2020 photo provided by the British Antarctic Survey shows the Thwaites glacier in Antarctica. (David Vaughan/British Antarctic Survey via AP) Hidden rivers of meltwater are decaying Antarctica’s glaciers from beneath, a new study has found — meaning sea levels are likely rising faster than scientists had feared. The faster melting rates are also changing the balance of freshwater and saltwater in the oceans, affecting both ocean circulation and global weather in unknown ways, according to findings published Friday in Science Advances. The study focused on two Antarctic glaciers — which collectively hold enough water to raise global sea levels by 5 feet. Scientists have long known that Antarctica’s Denman glacier — like many across the once-vast icelands of the polar regions — was melting from beneath. But what was less clear was whether that would have an impact on sea level rise, scientists from the University of California, Irvine, said. In 2021, the research team realized that Denman was melting much faster than the neighboring Scott glacier, despite the fact that both jutted out into oceans of virtually identical temperatures and levels of salinity. The reason for the change, they found, was that Denman was thawing from beneath at rates faster than unexpected. As that process accelerates — and begins to take hold in the neighboring Scott glacier — the study found that it will drive global sea levels up by 15 percent more than anticipated. That’s equivalent to about a sixth of an inch by 2300, in what researchers called a “conservative estimate.” That may not sound like much on its own — but it comes on top of the melting from fossil fuel burning, which will lead to about three-quarters of an inch of sea-level rise from the Denman and Scott glaciers alone. All told, the scientists estimated that in a world where fossil fuel burning isn’t controlled, total rise from just these glaciers would be 0.86 inches. Denman isn’t the only glacier melting from both sides. For example, the massive Thwaites glacier — an Antarctic glacier the size of Florida whose precarious state has earned it the nickname of “the doomsday glacier” — is also melting from beneath, according to a study published in February. Scientists have long known that reasons for the slow collapse of all these glaciers differ between their tops and bottoms. Up top, the glacial melt is occurring for a familiar reason: global heating caused by the uncontrolled burning of fossil fuels. This is the key factor in ice sheet loss, emphasized study coauthor Jamin Greenbaum, a researcher at the Scripps Institution of Oceanography. “If there is a doomsday story here it isn’t subglacial discharge,” Greenbaum said. “The real doomsday story is still emissions, and humanity is still the one with its finger on the button.” But that doomsday story is being swept along by a very different process of thawing from beneath the ice. Where the ice meets the bedrock, it can be warmed by the geothermal heat put out by the Earth itself, which only needs to be a hair more than 32 F to cause ice to dissolve. Then there is friction, as the grinding of slow moving ice against rock generates heat that melts the ice. This melting is particularly significant where the rivers of meltwater have a chance to reach the sea, where they churn up warmer saltwater and accelerate the process of glacial collapse. That’s a particular concern when this melting river mouth spills out beneath an ice sheet — the floating part of a glacier that extends out to sea — potentially creating a feedback loop of collapse that will lead to sea levels rising at even faster rates than those anticipated in the study published Friday. Researchers said that such feedback loops were beyond their ability to model. “We can’t yet say how much sea-level rise will be accelerated by this process,” Greenbaum said. |
Responses:
[18843]
18843
From: ryan, [DNS_Address]
Subject: Re: Antarctica’s glaciers are melting from beneath, speeding...
URL: https://www.counterpunch.org/2023/10/27/roaming-charges-104/
|
“It is a curious situation that the sea, from which life first arose should now be threatened by the activities of one form of that life. But the sea, though changed in a sinister way, will continue to exist; the threat is rather to life itself.” – Rachel Carson, The Sea Around Us + A report by the British Antarctic Survey concludes that the melting of the West Antarctic ice sheet is now inevitable. Even under the best possible scenario of reductions in greenhouse gas emissions, the ice sheet will continue to melt, at a speed three times faster than during the 20th century, causing global sea levels to rise by 3.9 feet by 2100. The melting of the entire ice sheet would raise sea levels worldwide by 17 feet. + For 223 straight days, Earth’s sea surface temperatures have been at record warm levels. + As of mid-October, 78% of the global oceans were experiencing a marine heatwave. + A new study in Nature asserts that these changes in ocean temperature and the associated loss of oxygen are causing a centuries-long irreversible loss in the habitable zone of the upper 1000 meters of the world’s oceans: “These results suggest that the combined effect of warming and deoxygenation will have profound and long-lasting impacts on the viability of marine ecosystems, well after global temperatures have peaked.” + North Pacific marine heatwaves – super-charged by climate change – killed 10 billion snow crabs, largely through starvation. + We have the clearest evidence to date that the Gulf Stream is weakening and may ultimately collapse, with catastrophic implications for the marine life of the Atlantic and the global climate. According to research conducted by the Woods Hole Oceanographic Institute, over the past four decades, the flow of warm ocean water through the straits of Florida has slowed by four percent. Not only does the Gulf Stream distribute oxygen, nutrients, carbon, and heat around the Atlantic, but its sweeping currents also regulate sea levels, keeping near-shore water levels as much as up to 5 feet lower than the ocean farther off-shore. + Hurricane Otis, which seemed to materialize almost full-grown out of the eastern Pacific, is one of the fastest-intensifying hurricanes in history, growing from a tropical storm to a Category 5 hurricane in just 12 hours. It made landfall at Acapulco, Mexico as a Category 5 storm with sustained winds of 165 mph and gusts to nearly 200 mph. + Fishing boats that trawl the ocean floor with heaving nets release more than a gigaton of carbon dioxide every year, roughly much as the entire airline industry, according to a study published in Nature. + By 2035, the steel, cement and chemical industries will overtake both transportation and electricity generation to become the largest sources of U.S. greenhouse gas emissions. + 41 percent of the land base in the continental US is consigned for the production of meat, dairy, and eggs. + In 2020 wind was usually the cheapest energy source. By 2030, solar will be the cheapest nearly everywhere, even in Greenland. + In response to a story about the toxic nitrate discharges from his family farms, Nebraska Governor Jim Pillen, smeared Yanqi Xu, the Guangzhou-born journalist who wrote the story: “The author is from communist China. What more do you need to know?” + Wild mammals account for only about 4% of biomass compared to livestock (62%) and humans (34%), and global poultry weighs more than twice that of wild birds. + Climate Brink: “Nearly every single day since mid-June 2023 has been warmer than any prior days since the JRA-55 record began in 1958 – and, potentially, much further into the past.” + One in three children worldwide–roughly 815 million–suffered lead poisoning, a condition linked to heart and kidney disorders, impaired intelligence, violent behavior and premature death. A recent paper in Lancet Planetary Health estimated that in 2019, 5.5 million people died because of cardiovascular disease caused by lead poisoning, about three times the number killed by lung cancer: “More than 90% of those born between 1950 and 1980 experienced [blood lead levels] in excess of 5 µg/dL, the threshold considered ‘safe’ for children. The legacy of early life lead exposure will stay in the United States for decades to come.” + We still haven’t eliminated lead from fuels. In 2023, more than 170,000 smaller planes still use leaded gasoline and, predictably, a study found high levels of lead in children who lived near a general aviation airport. + Half of the world’s economies (107 countries) are already five years past a peak in fossil power generation. + In both the US and Canada, methane leaks were roughly 50 percent higher than reported. In Mexico, they were double. + There has been a dramatic increase in the number and intensity of bushfires across Australia since August, producing the highest smoke emissions for August through October in the last 10 years. + The five-year average of US annual wildfire acres burned has nearly tripled in the past 20 years. + Brazil’s July through September precipitation was the lowest in 50 years. And the recent trend is getting worse. Much of the moisture source for Amazon precipitation is from plant transpiration. A shrinking rainforest means less transpiration; which leads to less precipitation. + In 2010, oil giant Occidental Petroleum opened the world’s largest carbon-capture plant. It never operated at more than a third of its capacity. In 2022, Oxy quietly sold the plant for a fraction of the cost of its construction. + Malte Meinshausen, Professor in climate science at the University of Melbourne: “The high cost of carbon capture and storage technology makes it very clear that avoiding the emissions in the first place is economically the wisest thing to do.” + A 1980 law prohibits rural Arizona communities from controlling their groundwater. However, mining companies, many of them owned by foreign corporations, can extract as much groundwater as they want, and they do. + More than 80% of the wild macadamia trees that existed when European settlement started in Australia have been lost. Fewer 8,800 trees remain inside isolated remnants of sub-tropical rainforest in Queensland and New South Wales. + Alaska authorized a mass slaughter of 99 bears (including 20 cubs) from a helicopter gunship in order to increase the population of a Caribou herd the bears weren’t threatening… + 2.08 billion gallons: amount of water per year used to keep golf courses in the US green. |
Responses:
None
[ Envirowatchers ] [ Main Menu ]