Moulins are near-vertical conduits that capture and funnel meltwater runoff from the ice surface during summer. There are many thousands of them across Greenland, and they grow to substantial sizes because of the thickness of the ice coupled with the exceptionally high surface melt rates experienced. These gaping holes can be as large as tennis courts at the surface, with chambers hidden in the ice beneath that could swallow cathedrals.
A new study demonstrates that ice sheets are littered with millions of tiny hairlike cracks that are forced open by the meltwater from the rivers and streams that intercept them.
Because glacier ice is so brittle at the surface, such cracks are common across the melt zones of all glaciers, ice sheets and ice shelves. However, because they are so tiny, they can’t be detected by satellite remote sensing.
As the water rushes in, it damages the ice sheet structure and releases its latent heat. The ice fabric warms and softens and thus flows and melts faster.
The stream-driven hydrofractures damage the ice and transfer heat into the heart of the ice sheet, destabilizing if from the inside. Ultimately, the internal structure of ice sheets is becoming more vulnerable to climate warming.
The ice sheet is also flowing and releasing icebergs much faster. It has lost roughly 270 billion metric tons of ice per year since 2002.
According to the study, the current generation of ice sheet models used to assess how Greenland and Antarctica will respond to warming in the future don’t account for amplification processes that are being discovered. That means that the models’ sea-level rise estimates, used to inform Intergovernmental Panel on Climate Change (IPCC) reports and policymakers worldwide, are conservative and lowballing the rates of global sea rise in a warming world.
https://phys.org/news/2023-06-meltwater-hydro-fracking-greenland-ice-sheet.html