Melting of the Greenland and West Antarctic ice sheets have been blamed on global warming, but both have a geologic origin. The “Blob” a recent warm ocean area off the Oregon coast, responsible in part for the hot weather and drought in California, has been blamed on global warming, but that too may have a geologic cause.
My article Greenland surprises (Feb. 2014) reported on research that posited “The Greenland ice sheet is melting from below, caused by a high heat flow from the mantle into the lithosphere. [Lithosphere: The solid part of the earth consisting of the crust and outer mantle.] The Greenland lithosphere is 2.8 to 1.7 billion years old and is only about 70 to 80 kilometers thick under Central Greenland.”
A recent paper (April, 2016) published in Nature Geoscience supports the hypothesis of a geologic cause of metling: Melting at the base of the Greenland ice sheet explained by Iceland hotspot history.
The paper abstract says:
Ice-penetrating radar and ice core drilling have shown that large parts of the north-central Greenland ice sheet are melting from below. It has been argued that basal ice melt is due to the anomalously high geothermal flux that has also influenced the development of the longest ice stream in Greenland. Here we estimate the geothermal flux beneath the Greenland ice sheet and identify a 1,200-km-long and 400-km-wide geothermal anomaly beneath the thick ice cover. We suggest that this anomaly explains the observed melting of the ice sheet’s base, which drives the vigorous subglacial hydrology and controls the position of the head of the enigmatic 750-km-long northeastern Greenland ice stream. Our combined analysis of independent seismic, gravity and tectonic data implies that the geothermal anomaly, which crosses Greenland from west to east, was formed by Greenland’s passage over the Iceland mantle plume between roughly 80 and 35 million years ago. We conclude that the complexity of the present-day subglacial hydrology and dynamic features of the north-central Greenland ice sheet originated in tectonic events that pre-date the onset of glaciation in Greenland by many tens of millions of years.
Geology – not global warming.
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