Saturday, 21 July, 2018

Fire Down Below: Mantle Plume Supervolcano Melting Antarctic Ice

Theresa Hayes | 09 November, 2017, 14:07

NASA researchers have found new evidence that an ancient geothermal heat source might help explain how rivers and lakes form beneath the West Antarctic ice sheet. Study lead author Helene Seroussi of NASA's Jet Propulsion Laboratory thought it was "crazy" that it would be there: "I didn't see how we could have that amount of heat and still have ice on top of it", she said.

The underground mantle plume is thought to be driving some of the melting seen beneath the ice, giving rise to lakes and rivers. The JPL researchers created a model that accounted for the physics of the ice sheets, sources of heat in the region and how heat is transported, changes in the altitude of the ice sheet surface, among other factors.

While the mantle plume is not a new discovery, the recent research indicates it may explain why the ice sheet collapsed in a previous era of rapid climate change 11,000 years ago and why the sheet is breaking up so quickly now. A scientist at the University of Colorado Denver was the first to suggest that a mantle plume under Marie Byrd Land might explain these observations.

Scientists in June published a report saying a 300,000-square-mile portion of the West Antarctica Ice sheet's perimeter was melting, and that it was caused by an unusually strong El Nino event around January 2016. The measurement of this phenomenon helps scientists to estimate the volume of water at the bottom of the ice sheaths.

Mantle plumes are believed to be narrow streams of hot, molten rock which erupts through Earth's mantle and forms a mushroom cap-like structure under the crust.

Earlier studies and images show that there are a lot of rivers and lakes adjacent to Antarctica's bedrock.

In the past, researchers had observed volcanic activity and a topographic dome feature in this region.

As the material is buoyant, it pushes the crust upward.

After that, they simulated a number of different scenarios for the size and location of a possible mantle plume, since both those factors were unknown, and compared the effects with observations of Antarctic melting, as recorded by satellites in space.

For 30 years, scientists have suggested that a mantle plume may exist under Marie Byrd Land.

'These place a powerful constraint on allowable melt rates - the very thing we wanted to predict, ' said Erik Ivins of JPL. Whereas, the Yellowstone National Park in the United States which is well known as a geothermal hotspot has an average heat flux of 200 milliwatts per square meter over the entire park, even though individual geothermal features like geysers will be much hotter.

Sea ice is seen from NASA's Operation IceBridge research aircraft in the Antarctic Peninsula region, on November 4, 2017, above Antarctica.