A new study by NASA scientists has proved that a geothermal heat source, called a mantle plume, deep underground in Marie Byrd in Antarctica, explains the rapid thawing that creates lakes and rivers under the ice cover. Although the source of heat is not a new or increasing threat to the West Antarctic ice sheet, this can help explain why the ice cover is unstable today.
The stability of the ice shield is closely related to how much water is washing it from below, which facilitates the glacier glide. Understanding the sources and future of thawed water in West Antarctica is important in assessing the rate at which ice can melt and increase the water level in the ocean.
The glaciers of Antarctica are unstable and filled with rivers and lakes, the largest of which is Lake Erie. Many lakes quickly fill and drain, causing a surface of ice thousands of feet above them to rise and fall as much as 6 meters. The movement allows scientists to assess where and how much water should exist.
About 30 years ago, a scientist from the University of Colorado Denver suggested that the heat from the mantle plume under the earth Marie Bird can explain the regional volcanic activity and the topographical function of the dome. Very recent seismic visualization supported this concept.
With small direct measurements existing up to the ice, the scientists from the JPL have come to a better way of studying the idea of mantle plume by numerical simulation. They used the Ice Sheet (ISSM) model, a numerical description of the physics of ice sheets developed by JPL scientists and the University of California at Irvine.
To ensure that the model was realistic, scientists conducted observations of changes in the height of the surface of the ice cover, using data from the NASA IceSat satellite and the Operation IceBridge air campaign.
Since the location and size of the possible mantle plume were unknown, they tested the full range of what was physically possible for several parameters, producing dozens of different simulations.
They found that the flow of energy from the mantle loop should not be more than 150 milliwatts per square meter. For comparison, in the US regions without volcanic activity, the heat flux from the Earth’s mantle is from 40 to 60 milliwatts.
In Yellowstone National Park – a famous geothermal hot spot – the heat from below is about 200 milliwatts per square meter, averaged throughout the park, although individual geothermal properties, such as geysers, are much hotter.
Simulation of scientists, Serusi and Ivins using a heat flux above 150 milliwatts per square meter showed too much melting to be compatible with data based on outer space, with the exception of one place: an area in the depths of the Ross Sea known for intense water flows. This area required a heat flux of at least 150-180 milliwatts per square meter. However, seismic visualization has shown that the heat of the mantle in this region can reach the ice sheet through a split, that is, a break in the earth’s crust, such as appeared in the Great Rift Valley in Africa.
It is believed that mantle plumes are narrow streams of rock that rise through the mantle of the earth and spread like a mushroom cap beneath the earth’s crust. The buoyancy of the material, part of which is melted, causes the bark to heave upward. The theory of mantle plumes was proposed in the 1970s to explain geothermal activity that occurs far from the boundary of a tectonic plate such as Hawaii and Yellowstone.
The mantle plume of the Mari Bird land was formed from 50 to 110 million years ago, long before the appearance of the glacial cover of West Antarctica. At the end of the last ice age, about 11,000 years ago, the ice sheet passed through a period of rapid, steady loss of ice, when changes in global weather conditions and sea level rise pushed warm water closer to the ice cover – just like today.
“The presence of this mantle plume is important, as it suggests that the ice of Antarctica is more vulnerable in this area: this additional heat heats the ice, which indicates greater weakness in the face of future and past changes in the environment,” the researchers say.