Wired Magazine recently reported that an area of Antarctica the size of France and Germany combined is channeling meltwater into a nearly 300-mile-long river at the base of Antarctica that empties into the sea. Scientists have been aware of a vast network of water in the ice of Antarctica for years.
The highly pressurized freshwater systems play a significant role in the fast flow of the ice shelf above — "the water exits the ice sheet at specific locations, appearing to drive ice-shelf melting in these areas critical for the ice-sheet stability."
The study published in Nature GeoScience found that "high-pressure distributed drainage plays a key role in Antarctic fast flow, yet variability in ice-shelf topography at the grounding line, along with our modeling, provides strong evidence of large focused channels exiting many ice streams10,11"
The research turns what science has believed for thirty years to be that the ice is frozen at the bed, adds new complexity to an already complex system of ice and water on its head. London glaciologist Martin Siegert stated, "Now we're in a position that we've just never been in before, to understand the whole of the Antarctic ice sheet."
From Wired Magazine:
As the scientists found out, it moves very weirdly. Because there can be miles of ice resting on Antarctica’s land, and because the region isn’t warming as fast as the Arctic, the ice doesn’t melt the way you might think, from the sun striking the surface. That’s the way it works in places like Greenland, where ever-warming temperatures are creating lakes on the surface of the ice, and that water then leaks down through crevasses, known as moulins.
But in Antarctica, the basal melt instead comes from the land warming the ice. While it’s not volcanically boisterous, Antarctica has enough geothermal heat to get melt going. Further heat is provided by friction, as the ice grinds across bedrock. That means that instead of the melt happening top down, it happens at the bottom.
It’s not a tremendous amount of melt per square foot. But over an area that’s the size of two large European countries, that scales up. “What we concluded is the melting is really small—it's like a millimeter per year,” says Siegert. “But the catchment is enormous, so you don't need much melting. That all funnels together into this river, which is several hundred kilometers long, and it's three times the rate of flow of the river Thames in London.
That water is under extreme pressure, both because there’s a lot of ice pressing down from above and because there isn’t much room between the ice and the bedrock for the liquid to move around. “And because it's under high pressure, it can act to lift the ice off its bed, which can reduce friction,” Siegert says. “And if you reduce that basal friction, the ice can flow much quicker than it would do otherwise.” Think of that ice like a puck sliding across an air hockey table, only instead of riding on air, the ice is riding on pressurized water.
The story's lead author, Christine Dow of Waterloo University, notes that in Antarctica, the meltwater is held back by the massive marine extensions of land glaciers which act like a cork holding the river water back from entering the sea. The problem is that the marine glacial extensions are carved into cavities near the grounding line by warm ocean upwelling. As a result, Dow says, "So anything that is going to change where that grounding line rests is going to have significant control on how much sea level rise we have in the future."
Exhibit A for the cavities that decay the underbellies of Antarctic glaciers such as Thwaites, a/ka the Doomsday glacier, rapidly breaking into fragments on both the eastern and western tongues. It is likely to shatter within three to five years (not collapse), raising sea levels worldwide by two feet when the failure occurs. But Thwaites has the potential to take the entire West Antarctica ice sheet down, raising the sea level by ten and a half feet.
The warm ocean upwelling is battering the grounding line due to tidal pumping. "When tides go in and out, they heave the ice shelf up and down, allowing warm seawater to rush inland and melt the underside of the ice. This new research shows that pressurized meltwater comes from the other direction, flowing from inland to the grounding line." The potential for a significant sea level rise is that the grounded ice displaces salt water and instantly threatens the coastline worldwide.
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