Plantagenet wrote:Here it comes......glacier on Antarctica has sped up by 10% and is dumping huge amounts of ice into ocean.
This glacier is the single largest source of sea level rise on the planet.....
And its going to get worse....
Pine Island Glacier in Antarctica is going to collapse soonHere comes a rapid foot-and-a-half of sea level rise.....just from one huge glacier......and the show starts in just a few years
Cheers!
This statement right at the end of the article is what drives me batty;
But if ice shelves can shift quickly and decisively, so too can humanity. Healing the ozone hole and taking swift action against climate change will alter the conditions in Antarctica’s atmosphere and oceans and help stabilize the continent’s glaciers.
“The future is still open to change," Davies said — if people do what is needed to change it.
This statement shows 100% lack of understanding of dynamic tipping point behavior. Humanity could just disappear today and thereby stop consuming fossil fuels and it would not do a thing to change the fate of Pine Island Glacier.It has long been known that climate lags anywhere from 20-50 years behind the changes in CO2 and other GHG levels because large complex systems do not change overnight.
The behavior exhibited by Pine Island Glacier 2016-2021 was set in motion by GHG emissions from 1996 or earlier, not what we did in 2016. As far as that goes healing the ozone hole over Antarctica is actually adding to the GHG conditions over Pine Island Glacier because stratospheric ozone is a GHG trapping heat in the atmosphere. That is science, not myself advocating leaving the Ozone problem in place or making it worse, just stating a known scientific fact. Pine Island Glacier is doomed and saying its loss will add 50 cm of sea level rise barely touches on the reality of the situation.
A decade ago Dr. Richard Alley and his team determined that if any of the big West Antarctic sea terminating glaciers move off their underwater sills and become floating ice masses the stability of that whole region falls apart. The reason is basic physics, floating ice can only rise so far above the water line before the sheer forces break it up and lower its ultimate height. This number is around 75 meters or 240 feet. This physics fact is why those huge tabular icebergs like the one that just calved off of Pine Island Glacier look like a flat mesa floating on the sea. The West Antarctic basin is a deep region filled with ice as much as 2000-3500 meters thick. This deep basin is mostly surrounded by mountains and buried peaks that protect the interior ice from the surrounding ocean. In multiple places including Pine Island Glacier the edge of the deep basin forms a submerged ridge known as a sill in oceanography. Think of the sill as being like the lip of a plate.
Here is a science experiment you can do at home to see what this matters. Put a plate in the middle of a kiddie wading pool and pour a bag of ice cubes on it so that they stack high on the plate and surround it on all sides in the pool. Then slowly add water to the pool. Once you have around an inch or 25 mm of water in the pool the edge of the plate buried under the ice is reached. The loose ice cubes that didn't fit on the plate will start floating and moving randomly which will disperse them from around the plate. As you keep adding water it will move under the ice on the plate and the edges of the mound will start eroding, dropping more and more ice cubes into the water where they will disperse just like the earlier loose cubes did. Before long the whole mound becomes unstable and all the ice disperses into floating cubes in the much larger kiddie pool.
That is the behavior the paleoclimate record shows takes place when West Antarctica passes its tipping point. Once the "cork" breaks out of the bottle the effect is basically unstoppable as the mass of ice in the deep basin will start shedding into the opening with a great deal more speed than people intuitively expect. In the plate and pool example the water never gets close to submerging the entire pile of cubes before buoyancy tears the pile apart from edge to center. In West Antarctica when the ice retreats behind the sill the very high pile becomes exposed to the open ocean. Not only does sea water carry vast reservoirs of heat to the contact face of the glacier, the 12 hour tidal cycle creates a buoyancy cycle that stresses the edge of the vast ice sheet with sheer forces up and down without ever stopping. For floating tabular icebergs the tides matter little as the entire berg bobs up and down, but for ice fixed to a large unyielding mass this is not the case. This cycle and the strength of natural ice even very very cold ice the flexing leads to calving in the face meeting the sea. Once it is off the sill the forces erode their way in ward meter by meter until the entire basin is emptied of ice.
Once the process passes the tipping point, which recent reports indicate may be the case, the process will continue until there is no more ice that can be easily destabilized. When the huge Larsen B ice shelf collapsed in 2003 it as the author puts it, took the cork out of the bottle holding back several completely above sea level glacier in the Antarctic Peninsula. Without the ice shelf putting resistance on their movement towards the sea every single exposed glacier accelerated its forward movement thinning each and every one of them in the process and dumping a flurry of icebergs into the sea from where the glaciers crossed the shore line. Pine Island Glacier has its own ice shelf which has been keeping it from moving faster and thinning where it meets the sea. What we are observing now is that shelf eroding strongly, four to six times faster starting in 2017 than it was during the earlier part of the observationa record.
Pine Island Glacier's ice shelf is ripping apart, speeding up key Antarctic glacier
Pine Island Glacier ends in an ice shelf that floats in the Amundsen Sea. These crevasses are near the grounding line, where the glacier makes contact with the Antarctic continent. The photo was taken in January 2010 from the east side of the glacier, looking westward. This ice shelf lost one-fifth of its area from 2017 to 2020, causing the inland glacier to speed up by 12%.
For decades, the ice shelf helping to hold back one of the fastest-moving glaciers in Antarctica has gradually thinned. Analysis of satellite images reveals a more dramatic process in recent years: From 2017 to 2020, large icebergs at the ice shelf's edge broke off, and the glacier sped up.
Since floating ice shelves help to hold back the larger grounded mass of the glacier, the recent speedup due to the weakening edge could shorten the timeline for Pine Island Glacier's eventual collapse into the sea. The study from researchers at the University of Washington and British Antarctic Survey was published June 11 in the open-access journal Science Advances.
"We may not have the luxury of waiting for slow changes on Pine Island; things could actually go much quicker than expected," said lead author Ian Joughin, a glaciologist at the UW Applied Physics Laboratory. "The processes we'd been studying in this region were leading to an irreversible collapse, but at a fairly measured pace. Things could be much more abrupt if we lose the rest of that ice shelf."
Pine Island Glacier contains approximately 180 trillion tons of ice—equivalent to 0.5 meters, or 1.6 feet, of global sea level rise. It is already responsible for much of Antarctica's contribution to sea-level rise, causing about one-sixth of a millimeter of sea level rise each year, or about two-thirds of an inch per century, a rate that's expected to increase. If it and neighboring Thwaites Glacier speed up and flow completely into the ocean, releasing their hold on the larger West Antarctic Ice Sheet, global seas could rise by several feet over the next few centuries.
These glaciers have attracted attention in recent decades as their ice shelves thinned because warmer ocean currents melted the ice's underside. From the 1990s to 2009, Pine Island Glacier's motion toward the sea accelerated from 2.5 kilometers per year to 4 kilometers per year (1.5 miles per year to 2.5 miles per year). The glacier's speed then stabilized for almost a decade.
Results show that what's happened more recently is a different process, Joughin said, related to internal forces on the glacier.
From 2017 to 2020, Pine Island's ice shelf lost one-fifth of its area in a few dramatic breaks that were captured by the Copernicus Sentinel-1 satellites, operated by the European Space Agency on behalf of the European Union. The researchers analyzed images from January 2015 to March 2020 and found that the recent changes on the ice shelf were not caused by processes directly related to ocean melting.
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