Ancient, Deep-Earth Heat Sources Cause Greenland’s Ice Sheet to Melt FasterMelting rates below ice sheets are small, relative to those at the surface, but they disproportionally influence ice transport toward the ocean

4 April 2016

New research conducted by an international team of geoscientists has indicated that ancient heat sources in the Earth’s crust are responsible for making Greenland’s ice sheet melt and flow faster.

The team has, for the first time, proved that processes deep in Earth’s mantle are coupled with the flow dynamics and subglacial hydrology of large ice sheets.

Critically, the finding confirms that climate change assessments based on ice sheet movement must take into account the possibility that important factors may be at work miles below the surface.

Research Fellow in Geology in the School of Natural Sciences at Trinity College Dublin, Dr Alan Vaughan, was a co-author on the paper that has just been published in leading international journal Nature Geoscience.

Dr Vaughan said: “This study demonstrates an unexpected link between hotspot history and ice sheet behaviour."

"It shows that the influences on ice sheets span a huge range of timescales from the month by month changes of the ice cover to the multi-million year epochs over which the Earth’s mantle and tectonic plates evolve.”

The North Atlantic Ocean is an area of active plate tectonics on the Earth. Between 80 and 35 million years ago these processes moved Greenland over an area of abnormally hot mantle material, which is now responsible for the volcanic activity of Iceland.

This mantle material heated and thinned Greenland at depth creating a zone 1200 km long and 400 km wide where the present day flow of heat from the Earth’s interior is elevated.

This ancient, long-lived source of heat has created a region where subglacial meltwater is more abundant, lubricating the base of the ice and making it flow more rapidly. These secrets of Greenland’s past have been hidden until now by the 3 km thick ice sheet covering the landmass.

Irina Rogozhina, team leader, from the GFZ German Research Centre for Geosciences, said: “The geothermal anomaly which resulted from the Icelandic mantle-plume tens of millions of years ago is an important motor for today’s hydrology under the ice sheets and for the flow-rate of the ice. This, in turn, broadly influences the dynamic behaviour of the large ice sheets and must be included in studies of the future response to climate change.”

The location and orientation of the zone of elevated heat flow shows where Greenland moved over the mantle plume and provides an independent test for models of the opening of the North Atlantic that will revitalise a three-decade-long debate.

The size and location of the newly identified anomaly zone explains observations of widespread rapid melting beneath the ice sheet from radar and ice core drilling data.

The study results suggest that 50% of the ice-covered area in central-northern Greenland is melting from below and that the meltwater is routed to the ocean through a dense hydrological network beneath the ice.

Increased sliding at the base of the ice in the zone of elevated heat flow has created an area of rapid ice flow over a distance of 750 km, which transports ice from the summit area of the Greenland ice sheet to the North Atlantic Ocean.

The research team used sophisticated computer models to combine data from seismology, gravity measurements, ice core drilling campaigns, and radar sounding, as well as both airborne, satellite and ground-based measurements on the thickness of the ice cover.

The journal article can be viewed here.

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