A new study from NASA has provided evidence that there is a geothermal source of heat with the name of a mantle plume lying deep under West Antarctica’s Marie Byrd Land.
HEAT SOURCE COULD BE REASON FOR LAKES AND RIVERS UNDER THE ICE
The heat source would explain why there has been ice melting that has created rivers and lakes underneath the ice sheet. While the heat source is not something that is new and it is not a threat that is increasing to the ice sheet in West Antarctica, it does go a long way to explain why the sheet of ice had collapsed so fast during an earlier era during rapid climate change and why it has remained unstable.
The ice sheets stability has been related to how much of the water below it lubricating and allowing the ice glaciers to be able to slide along easily. Being able to understand the sources along with the future of West Antarctica’s meltwater is extremely important for scientists to be able to estimate the rate of ice that might end up back in the ocean in the future.
The bedrock of Antarctica has many lakes and rivers, and one of the biggest is said to be the same size as that of Lake Erie. A lot of the lakes drain along with filling quickly and this force the surface of the ice many thousands of feet above them to rise and then fall by as much as 6 meters. Scientists have been able to use that motion to provide estimation about how much of the water and where that water has to exist at the base.
HEAT SOURCE FROM MANTLE PLUME HAD BEEN SUGGESTED 30 YEARS AGO
The University of Colorado suggested thirty years ago that a heat source from a mantle plume that was underneath the Marie Byrd Land explained a lot of the volcanic activity in the region along with a topographic dome feature. Recent seismic imaging taken has gone to support the concept of the University of Colorado. Helene Seroussi from the Jet Propulsion Laboratory of NASA in California said that when the idea was first mentioned it was thought of as being crazy. She went on to say that she did not know how such an amount of heat would be able to have ice sitting on top of it.
NUMERICAL MODELLING IS BEST WAY TO STUDY MANTLE PLUME
Direct measurements have been taken from underneath the ice, and Erik Ivins from JPL said that the best way of studying the mantle plume idea is by using numerical modeling. The Ice Sheet System Model is a numerical depiction of the ice sheets physics that was developed by JPL and the University of California scientists. The ISSM was enhanced by Seroussi and this captured the natural sources of the heating and the transport of heat from the water that is freezing, melting and liquid, friction, and any other processes. To make sure that the model was realistic the scientists took the ice sheet surface altitude that had been made by the IceSat satellite of NASA and the Operation IceBridge airborne campaign. Ivins said that they placed a powerful constraint on the melt rates that were allowable, which was the single thing that they wanted to be able to predict. Ivins went on to say that as the size and location of the possible mantle plume were not known, the scientists had to test the whole range of might have been physically possible for a number of parameters and therefore produced simulations by the dozens.
The scientists found that the mantle plumes flux of energy had to be not more than 150 milliwatts for each square meter. In comparison for regions in the US that do not have a volcanic activity the heat flux from the mantle of the Earth is between 40 and 60 milliwatts. Underneath Yellowstone National Park in the United States, which is a region that is a geothermal hotspot, the heat that comes from under the ground is 200 milliwatts for each square meter throughout the whole of the park. However, scientists said that the individual geothermal features, for instance, the geysers, did get a lot hotter.
The simulations of Ivins and Seroussi made use of a heat flow that was higher than 150 milliwatts for each square meter and showed that there was too much melting for it to be compatible with the space-based data, other than in one location, an inland region of the Ross Sea. The region of the Ross Sea needed a heat flow of about 150 to 180 milliwatts for each square meter for it to live up to the observations. The seismic imaging revealed that the mantle heat in that region could reach the sheet of ice by a rift, a fracture occurring in the crust of the Earth, not unlike the one in the African Great Rift Valley.
MANTLE PLUMES CAME TO LIGHT DURING THE 70S
The mantle plumes are said to be narrow hot rock streams that rise up through the mantle of the Earth and then spread out the same way as a mushroom cap under the crust of the Earth. The materials buoyancy, with some of this being molten, then causes the crust to bulge up. The theory about the mantle plumes first came to light in the 70s to explain the geothermal activity that occurred a long way from the boundary of the tectonic plate, such as that in Yellowstone and Hawaii. The mantle plume at Marie Byrd Land was said to have formed around 50 to 110 million years ago, and this would have been a long time before the ice sheet in West Antarctica existed. Towards the end of the ice age about 11,000 years ago, the sheet of ice happened to go through a period of sustained and rapid ice loss thanks to global weather changes and sea levels rising, which pushed water that had warmed closer to the sheet of ice. This is something that is continuing to happen today. Ivins and Seroussi have suggested that the mantle plume might help with that kind of huge loss.