From NASA’s Jet propulsion Laboratory and the “inconvenient science” department comes this study that dashes hopes of pinning melting in Antarctica entirely on human activity.
NASA’s satellite and airborne observations have proposed that a hot ‘mantle plume’, a collection of scorching hot rocks which rise from beneath the earth, is responsible for the ice loss. The suggestion—that a mantle plume exists beneath the glacier—was first made 30 years ago by Wesley E LeMasurier, a scientist from the University of Colorado. The NASA survey has now offered concrete evidence to support the claim.
A new NASA study adds evidence that a geothermal heat source called a mantle plume lies deep below Antarctica’s Marie Byrd Land, explaining some of the melting that creates lakes and rivers under the ice sheet. Although the heat source isn’t a new or increasing threat to the West Antarctic ice sheet, it may help explain why the ice sheet collapsed rapidly in an earlier era of rapid climate change, and why it is so unstable today.
The project, by Edinburgh University researchers, has revealed almost 100 volcanoes – with the highest as tall as the Eiger, which stands at almost 4,000 meters in Switzerland.
Geologists say this huge region is likely to dwarf that of east Africa’s volcanic ridge, currently rated the densest concentration of volcanoes in the world.
The stability of an ice sheet is closely related to how much water lubricates it from below, allowing glaciers to slide more easily. Understanding the sources and future of the meltwater under West Antarctica is important for estimating the rate at which ice may be lost to the ocean in the future.
Some 30 years ago, a scientist at the University of Colorado Denver suggested that heat from a mantle plume under Marie Byrd Land might explain regional volcanic activity and a topographic dome feature. Very recent seismic imaging has supported this concept. When Hélène Seroussi of NASA’s Jet Propulsion Laboratory in Pasadena, California, first heard the idea, however, “I thought it was crazy,” she said. “I didn’t see how we could have that amount of heat and still have ice on top of it.”
To assure the model was realistic, the scientists drew on observations of changes in the altitude of the ice sheet surface made by NASA’s IceSat satellite and airborne Operation IceBridge campaign. “These place a powerful constraint on allowable melt rates — the very thing we wanted to predict,” Ivins said. Since the location and size of the possible mantle plume were unknown, they tested a full range of what was physically possible for multiple parameters, producing dozens of different simulations.
The Marie Byrd Land mantle plume formed 50 to 110 million years ago, long before the West Antarctic ice sheet came into existence. At the end of the last ice age around 11,000 years ago, the ice sheet went through a period of rapid, sustained ice loss when changes in global weather patterns and rising sea levels pushed warm water closer to the ice sheet — just as is happening today. Seroussi and Ivins suggest the mantle plume could facilitate this kind of rapid loss.