The finding that the Greenland ice sheet is melting from the bottom up is totally unsurprising given what we know about subsurface vulcanisn in Greenland Having a volcano underneath you can give you a pretty warm bottom. But it totally undermines the Warmist gospel that atmospheric warming is at work. Warmists frequently point to global warming as the cause of melting in the Arctic.
Widespread awareness of subsurface vulcanism would however take away from Warmists one of their favorite claims. It would confiscate one of their toys. So they had to come up with an explanstion for the anomalous warming that did not refer to vulcanism.
And what they have come up with is a lulu. They say that meltwater from the top of the glacier has trickled down through cracks in the glacier and delivered its higher temperature to the bottom of the glacier
But that is pretty mad. Surely water trickling down through cracks would rapidly refreeze long before it got to the botton of the glacier. Do they think that the meltwater wears little furry coats as it trickled down?
Greenland's Ice Sheet is melting from the bottom up and is now the largest single contributor to global sea level rise, a new study has warned.
Researchers have observed 'unprecedented' rates of melting at the bottom of the ice sheet, caused by huge quantities of meltwater falling from the surface to the base.
As the meltwater falls, energy is converted into heat in a similar way to how hydroelectric power is generated by large dams.
This effect is by far the largest heat source beneath the world's second-largest ice sheet, an international team of scientists led by the University of Cambridge found, leading to phenomenally high rates of melting at its base.
The lubricating effect of meltwater has a strong effect on the movement of glaciers and the quantity of ice discharged into the ocean, but directly measuring conditions beneath more than half a mile (1 km) of ice to the bottom is a challenge, especially in Greenland where glaciers are among the world's fastest moving.
Experts say this makes it difficult to understand the dynamic behaviour of the Greenland Ice Sheet and predict future changes
Each summer, thousands of meltwater lakes and streams form on the surface of the ice sheet as temperatures rise and daily sunlight increases.
But many of these lakes quickly drain to the bottom, falling through cracks and large fractures which form in the ice.
With a continued supply of water from streams and rivers, connections between surface and bed often remain open.
Professor Poul Christoffersen from Cambridge's Scott Polar Research Institute has been studying these meltwater lakes, how and why they drain so quickly, and the effect that they have on the overall behaviour of the ice sheet as global temperatures continue to rise.
The current work, which includes researchers from Aberystwyth University, is the culmination of a seven-year study focused on Store Glacier, one of the largest outlets from the Greenland Ice Sheet.
'When studying basal melting of ice sheets and glaciers, we look at sources of heat like friction, geothermal energy, latent heat released where water freezes and heat losses into the ice above,' said Christoffersen.
'But what we hadn't really looked at was the heat generated by the draining meltwater itself.
'There's a lot of gravitational energy stored in the water that forms on the surface and when it falls, the energy has to go somewhere.'
To measure melt rates at the base of the ice sheet, the researchers used radio-echo sounding, a technique developed at the British Antarctic Survey and used previously on floating ice sheets in Antarctica.
'We weren't sure that the technique would also work on a fast-flowing glacier in Greenland,' said fellow author Dr Tun Jan Young, who installed the radar system on Store Glacier as part of his PhD at Cambridge.
'Compared to Antarctica, the ice deforms really fast and there is a lot of meltwater in summer, which complicates the work.'
The melt rates at the base were found to be as high as those measured on the surface with a weather station.
This is despite the fact that the surface receives heat from the sun while the base does not.
To explain the results, the Cambridge researchers teamed up with scientists at the University of California Santa Cruz and the Geological Survey of Denmark and Greenland.
The researchers calculated that as much as 82 million cubic metres of meltwater was transferred to the bed of Store Glacier every day during the summer of 2014.
They estimated that the power produced by the falling water during peak melt periods was comparable to the power produced by the Three Gorges Dam in China, the world's largest hydroelectric power station.
With a melt area that expands to nearly a million square kilometres at the height of summer, the Greenland Ice Sheet produces more hydropower than the world's ten largest hydroelectric power stations combined, the researchers found.
'Given what we are witnessing at the high latitudes in terms of climate change, this form of hydropower could easily double or triple, and we're still not even including these numbers when we estimate the ice sheet's contribution to sea level rise,' said Christoffersen.
The researchers compared temperature measurements from sensors installed in a nearby borehole to verify the melt rates recorded by the radar.
At the base, they found the temperature of water to be as high as 33°F (0.88°C), which is unexpectedly warm for an ice sheet base with a melting point of 31°F (-0.40°C).
'The borehole observations confirmed that the meltwater heats up when it hits the bed,' said Christoffersen.
'The reason is that the basal drainage system is a lot less efficient than the fractures and conduits that bring the water through the ice. The reduced drainage efficiency causes frictional heating within the water itself.
'When we took this heat source out of our calculations, the theoretical melt rate estimates were a full two orders of magnitude out.
'The heat generated by the falling water is melting the ice from the bottom up, and the melt rate we are reporting is completely unprecedented.'
Researchers said their study provides the first concrete evidence of an ice-sheet mass-loss mechanism, which is not yet included in projections of global sea level rise.
While the high melt rates are specific to heat produced in subglacial drainage paths carrying surface water, the volume of surface water produced in Greenland is huge and growing, and nearly all of it drains to the bed.
The study has been published in the journal Proceedings of the National Academy of Sciences.
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