With warmer than average temperatures, sea ice appears to be melting faster than scientists ever predicted. But the latest study suggests Earth's internal heat may be enhancing rapid ice flow and subglacial melting of the Greenland Ice Sheet, too.
In other words, the ice sheet may be melting from the inside out.
An international team of researchers recently discovered that about half of the ice covered area in north-central Greenland actually rests on a thawed bed. What's more is meltwater from the famed ice sheet is routed to the ocean through a dense underlying hydrological network.
"The strength of this paper is that many different lines of reasoning about data lead to the same conclusion," said Jesse Johnson, a University of Montana researcher and ice sheet modeler. "I was able to demonstrate that the ice velocities observed by satellite are nearly impossible to explain without the geothermal anomaly discovered here. Glaciologists have long suspected the anomaly exists, but this work quantifies its location and degree and explains why it is there."
While numerous studies have examined the rapid melting of the Greenland Ice Sheet, this is the first to prove that geothermal processes deep in the Earth's interior are directly related to ice flow dynamics.
These deep hot spots, so to speak, are believed to have originated between 35 million and 85 million years ago, when tectonic processes shifted Greenland over an area of abnormally hot mantle material now responsible for the volcanic activity of Iceland.
Specifically, researchers identified unusually high heat in a west to east zone of northern Greenland. The intense heat radiating from this region causes Greenland's ice to melt from below and flow rapidly.
"This ancient and sustained source of heat has created a region having warmer, softer ice and abundant subglacial meltwater, lubricating the base of the ice and making it flow rapidly," Johnson added.
This anomaly helps explain the widespread melting originally recorded from radar observations and ice core drilling. It also accounts for increased sliding at the base of the ice, which facilitates rapid ice flow over a distance of 750 kilometers from the summit area of the Greenland ice sheet to the North Atlantic Ocean - an area of active plate tectonics.
"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 sheet and for the high flow-rate of the ice," added Irina Rogozhina, co-researcher from the GFZ German Research Centre for Geosciences. "This, in turn, broadly influences the dynamic behavior of ice masses and must be included in studies of the future response to climate change."
These findings not only shed light on Greenland ice melt, but also reveal an unexpected link between Earth's deep geothermal history and ice sheet dynamics.
Their study was recently published in the journal Nature Geoscience.
