Scientists descended into Greenland’s perilous ice caverns — and came back with a worrying message
https://www.washingtonpost.com/climate-environment/2020/12/23/climate-moulins-greenland/
Source: By Chris Mooney, The Washington Post.
Source: By Chris Mooney, The Washington Post.
Excerpt: The scientists ...created two intersecting holes into the bed of a now frozen-over ice river.... The hole, scientists believe, ultimately penetrates more than a half-kilometer into the ice, joining a network of channels extending all the way to the base of the ice sheet. ...Covington and his colleague Jason Gulley, ...were motivated by a scientific question with enormous implications as the climate warms. Just how vast are these moulins, these ice caves found by the thousands across Greenland’s surface? How much are they undermining the integrity of the second-largest sheet of ice on the planet? And how much worse will it get as melting, and moulins, begin to extend farther and farther toward the airy center of Greenland, where the ice is well over a mile thick? ...As the climate warms — with the Arctic warming fastest of all — more and more of Greenland’s surface is melting in the summer. More lakes are forming and at higher, colder elevations on the ice sheet. The ice sheet has lost some 4 trillion tons of mass just since 1992, and scientists estimate that surface melting makes up about half of those losses, with the rest being driven by huge icebergs calving into the sea. ...The first results of these moulin descents have been published in the journal Geophysical Research Letters. ,,,The key finding: Moulins can be huge. In particular, the Phobos moulin in western Greenland, which Gulley and Gadd explored in 2018, was not simply a narrow hole penetrating downward. Instead, it opened into a vast cavern that reached nearly 100 meters in depth before the water level began, and extended horizontally outward as well. The group calculated that, at the water’s surface, the spatial area of the cave was some 5,000 square feet, or the size of several houses next to one another.This volume is much larger than previous models assumed. And it suggests that the moulin can store much more water than previously thought. This, in turn, might mean that the water in the moulins can exert more pressure on the surrounding ice and cause it to slide faster — which would be bad for sea level rise, and Greenland’s future....