Yesterday Gary K drew my attention to this:
Multiple NASA Studies Confirm Bedrock Heat Flow Behind Melting Polar Ice, Not Global Warming
I have some interest in this because for the past 18 months I’ve been building heat flow models in which ice sheets are melted by bedrock heat flow.
The article above is dated August 2018, so it seems there’s currently a bit of an argument going on between one bunch of (NASA?) scientists and another bunch of Global Warming alarmists as to what is melting the ice.
The argument seems to have been getting a bit heated:
The evidence for geologically induced geothermal heat flow on the Greenland continent shows that recent reports from NASA on Greenland ice melt from global warming are premature and ill informed based on the following observations;
Glaciers do not melt uniformly as would be expected from atmospheric global warming, rather the melting and advancing of the glacial is complex and therefore more likely associated with geological forces.
The most significant and most recent glacial melting occurs in what is likely a geologically faulted linear valley that is theorized to have increased heat flow.
Sub-glacial freshwater lakes have been identified.
Newly released research by other scientists agree that geothermal forces are active in Greenland
In my own simulation models I’ve seen ice sheets being melted both from the top and the bottom, and sometimes by both at the same time. But in general they melt at the bottom, for the simple reason that heat flows from the centre of the Earth out through the surface and into the atmosphere, and there’s a descending temperature gradient all the way along this path: the atmosphere is generally colder than the surface of the Earth beneath it. But sometimes, on hot summer days, the atmosphere above some locality may be hotter than Earth’s surface, and the heat flow will reverse.
The argument between these scientists is a rather important one because if it is ever proved that the Greenland and Antarctic ice sheets are being melted by geothermal heat sources beneath them and not by a warming of the atmosphere above then, that’ll be the end of Global Warming alarmism. After all, the whole global warming scare is essentially that CO2-induced rising air temperatures will melt the Greenland and Antarctic ice sheets, and raise global sea levels by 70 metres, causing coastal cities all round the world to become uninhabitable.
And lots of people are very worried about this, including Pink Floyd guitarist David Gilmour:
Pink Floyd star David Gilmour sells guitar collection for nearly £17m at auction to fight climate change
The British musician said the current climate emergency was the “greatest challenge that humanity will ever face” and warned against the “irreversible” effects of climate change.
He said: “The choice really is that simple, and I hope that the sale of these guitars will help ClientEarth in their cause to use the law to bring about real change”
If it should emerge that ice sheets are not being melted by rising atmospheric air temperatures, he will have just wasted £17 million.
However, while I’m inclined to agree that the ice sheets are most likely being melted from below rather than from above, I tend to disagree about the source of that geological heat.
For the geological heat sources that the researchers invoke seem to be mantle plumes:
The presence of Greenland bedrock geologically induced heat flow actually comes as no surprise because geologists and collaborating scientists have known for many years that an ancient mantle plume (shallow earth hotspot) was present beneath Greenland’s ice sheet.
A mantle plume is a convective upwelling of molten rock in the liquid mantle of the Earth. The Earth’s mantle begins at the Mohorovičić discontinuity 20 – 90 km beneath the continental crust of the Earth. And so the heat from a mantle plume has to get through a lot of rock in order to melt overlying ice sheets in Greenland.
My explanation for the heating does not invoke any mantle plumes or volcanoes or rifts in or thinning of the Earth’s crust. My explanation for subglacial bedrock warming is that wherever there is deep snow or ice lying on the surface of the Earth, it acts as a layer of thermal insulation, and causes the rock beneath to slowly warm up over many thousands of years. The rocks to warm up in the exact same way that people warm up when they don quilted jackets in winter.
This heating is greatest where snow and ice is thickest. And in Greenland it seems that this is exactly what is found:
Greenland’s coasts are mountainous, but not its interior:
The Greenland ice sheet is 3 kilometers (1.9 mi) thick and broad enough to blanket an area the size of Mexico. The ice is so massive that its weight presses the bedrock of Greenland below sea level
This means that the deepest ice in Greenland is likely to be at those places in its interior furthest below sea level, and it will be beneath this deep layer of thermal insulation that the bedrock temperatures will rise highest.
It could of course be that Greenland ice sheet melting could be caused by a combination of both geological and atmospheric influences, For no doubt atmospheric warming will be causing some degree of melting of its ice sheets. But it could well be that less than 5% of Greenland’s ice melt has atmospheric causes.