Antarctic Waters: Warmer with More Acidity and Less Oxygen

Antarctic Waters: Warmer with More Acidity and Less Oxygen

SOURCE: University of Arizona News DATE: January 6, 2020 SNIP: The increased freshwater from melting Antarctic ice sheets plus increased wind has reduced the amount of oxygen in the Southern Ocean and made it more acidic and warmer, according to new research led by University of Arizona geoscientists. The researchers found Southern Ocean waters had changed by comparing shipboard measurements taken from 1990 to 2004 with measurements taken by a fleet of microsensor-equipped robot floats from 2012 to 2019. The observed oxygen loss and warming around the Antarctic coast is much larger than predicted by a climate model, which could have implications for predictions of ice melt. “It’s the first time we’ve been able to reproduce the new changes in the Southern Ocean with an Earth system model,” said co-author Joellen Russell, a professor of geosciences. The research is the first to incorporate the Southern Ocean’s increased freshwater plus additional wind into a climate change model, she said. The team used the National Oceanic and Atmospheric Administration’s ESM2M model. Previously, global climate change models did not predict the current physical and chemical changes in the Southern Ocean, said Russell, who holds the Thomas R. Brown Distinguished Chair in Integrative Science. “We underestimated how much influence that added freshwater and wind would have. When we add these two components to the model, we can directly and beautifully reproduce what has happened over the last 30 years,” she said. Now, models will be able to do a better job of predicting future environmental changes in and around Antarctica, she said, adding that the Southern Ocean takes up most of the heat...
Why Rising Acidification Poses a Special Peril for Warming Arctic Waters

Why Rising Acidification Poses a Special Peril for Warming Arctic Waters

SOURCE: Yale Environment 360 DATE: October 24, 2019 SNIP: From the deck of a Norwegian research ship, the ravages of climate change in the Arctic are readily apparent. In the Fram Strait, the ocean passageway between Norway’s Arctic islands and the east coast of Greenland, seas that should be ice-covered in early September shimmer in the sunlight. Glaciers that muscled across mountains a decade ago are now in rapid retreat, leaving behind walls of glacial till. Rivers of meltwater gush off the Greenland Ice Sheet. But some of the biggest changes taking place in these polar seas are invisible. Under disappearing ice cover, these waters are rapidly growing more acidic as decades of soaking up humanity’s carbon emissions take their toll on ocean chemistry. “Warm, fresh, and sour,” says Colin Stedmon, a chemical oceanographer from the Technical University of Denmark, of the changes sweeping Arctic seas, which, along with the Southern Ocean surrounding Antarctica, are acidifying faster than any other marine waters on the planet. He and the rest of the crew of researchers from across Europe are trying to decipher how a warming Arctic is, as Stedmon puts it, “melting ice, freshening seawater, and reducing its ability to resist acidification.” The Arctic is a bellwether for acidification, oceanographers say. Since the Industrial Age, the planet’s oceans have stored up to 30 percent of human CO2 output, with cold polar waters, in which the gas is the most soluble, absorbing the lion’s share. Those same cold waters and unique environmental conditions make the Arctic especially susceptible to the rapidly shifting ocean chemistry wrought by that excess carbon. The result:...
‘Precipitous’ fall in Antarctic sea ice since 2014 revealed

‘Precipitous’ fall in Antarctic sea ice since 2014 revealed

SOURCE: The Guardian DATE: July 2, 2019 SNIP: The vast expanse of sea ice around Antarctica has suffered a “precipitous” fall since 2014, satellite data shows, and fell at a faster rate than seen in the Arctic. The plunge in the average annual extent means Antarctica lost as much sea ice in four years as the Arctic lost in 34 years. The cause of the sharp Antarctic losses is as yet unknown and only time will tell whether the ice recovers or continues to decline. But researchers said it showed ice could disappear much more rapidly than previously thought. Unlike the melting of ice sheets on land, sea ice melting does not raise sea level. But losing bright white sea ice means the sun’s heat is instead absorbed by dark ocean waters, leading to a vicious circle of heating. Sea ice spreads over enormous areas and has major impacts on the global climate system, with losses in the Arctic strongly linked to extreme weather at lower latitudes, such as heatwaves in Europe. Antarctic sea ice had been slowly increasing during the 40 years of measurements and reached a record maximum in 2014. But since then sea ice extent has nosedived, reaching a record low in 2017. “There has been a huge decrease,” said Claire Parkinson, at Nasa’s Goddard Space Flight Center in the US. In her study, published in the journal Proceedings of the National Academy of Sciences, she called the decline precipitous and a dramatic reversal. “The Arctic has become a poster child for global warming,” Parkinson said, but the recent sea ice falls in Antarctica have been...
‘Extraordinary thinning’ of ice sheets revealed deep inside Antarctica

‘Extraordinary thinning’ of ice sheets revealed deep inside Antarctica

SOURCE: The Guardian DATE: May 16, 2019 SNIP: Ice losses are rapidly spreading deep into the interior of the Antarctic, new analysis of satellite data shows. The warming of the Southern Ocean is resulting in glaciers sliding into the sea increasingly rapidly, with ice now being lost five times faster than in the 1990s. The West Antarctic ice sheet was stable in 1992 but up to a quarter of its expanse is now thinning. More than 100 metres of ice thickness has been lost in the worst-hit places. A complete loss of the West Antarctic ice sheet would drive global sea levels up by about five metres, drowning coastal cities around the world. The current losses are doubling every decade, the scientists said, and sea level rise are now running at the extreme end of projections made just a few years ago. “From a standing start in the 1990s, thinning has spread inland progressively over the past 25 years – that is rapid in glaciological terms,” said Prof Andy Shepherd, of Leeds University in the UK, who led the study. “The speed of drawing down ice from an ice sheet used to be spoken of in geological timescales, but that has now been replaced by people’s...
Climate change: Warning from ‘Antarctica’s last forests’

Climate change: Warning from ‘Antarctica’s last forests’

SOURCE: BBC DATE: April 3, 2019 SNIP: Scramble across exposed rocks in the middle of Antarctica and it’s possible to find the mummified twigs of shrubs that grew on the continent some three to five million years ago. This plant material isn’t much to look at, but scientists say it should serve as a warning to the world about where climate change could take us if carbon emissions go unchecked. The time period is an epoch geologists call the Pliocene, 2.6-5.3 million years ago. It was marked by temperatures that were significantly warmer than today, perhaps by 2-3 degrees globally. These were conditions that permitted plant growth even in the middle of the White Continent. Higher, too, were sea-levels. It’s uncertain by how much, but possibly in the region of 10-20m above the modern ocean surface. What’s really significant, though, is that the amount of carbon dioxide in the atmosphere was very similar to what it is today – at around 400 CO2 molecules for every million molecules of air. Indeed, the Pliocene was the last time in Earth history that the air carried this same concentration of the greenhouse gas. And it tells you where we’re heading if we don’t get serious about addressing the climate problem. Temperatures may currently be lower than in the Pliocene, but that’s only because there is a lag in the system. Prof Jane Francis, the director of the British Antarctic Survey, pulled her fossilised shrub material from rocks just 500km from the South Pole. “These are twigs similar to southern beech,” she told BBC News. “I like to call them the remnants...