In an illustration of the Amundsen Sea Embayment in West Antarctica, a cutaway reveals the foundation beneath the ice, as well as the earth’s crust (the brown layer), the bottom of the lithosphere (the red area) and the mantle (yellow) underneath. Credit: Planetary Visions/ESA
Foundation under Antarctica is rising faster than ever recorded — approximately 1.6 inch (41 mm) upward per year. And thinning ice in Antarctica may be responsible.
Because if the ice melts, the weight on the rock below lighter. And after some time, when the enormous quantities of ice are gone, the base rises in response, driven by the flow of the viscous mantle below the earth’s surface, scientists reported in a new study.
These uplifting findings are both bad news and good news for the frozen continent.
The good news is that the refueling of the support of the rock of the remaining ice caps more stable. The bad news is that in recent years, the rising earth has probably skewed satellite measurements of ice loss, leading researchers to underestimate the speed of the disappearance of the ice by as much as 10 percent of the scientists reported. [Images of Melt: Earth’s Vanishing Ice]
An incomplete picture
Interaction between the base and the shell in Antarctica is just one of the many geological processes that take place on our dynamic planet. Under the earth’s crust to cover the molten mantle extends about 1,796 miles (2,890 kilometers) down to Earth’s core. Mantle motion is known to wrinkle-up and influence on the crust of the tectonic plates, as these plates, drive convection currents in the mantle of the outer part, known as the lithosphere.
But while the computer models give scientists an idea of how the mantle of the earth behaves, the picture is incomplete, lead study author, Valentina Barletta, a postdoctoral researcher at DTU Space, National Space Institute at the Technical University of Denmark, told Science.
“The study of the distribution of the viscosity in the mantle — is still in its infancy,” Barletta said. “We know where the Earth is getting warmer-and cooler — more or less. However, the viscosity of the mantle depends not only on the temperature, but also on the water content.” The estimate of the temperature of the mantle in a particular area may therefore give an inaccurate view of how fast to move is — to a cooler patch with a high water content can be as syrupy as a warmer zone that use less water, Barletta explained.
Major changes, such as those of the researchers observed in Antarctica’s bedrock — and pushed up by the mantle below — were supposed to happen in the course of thousands, or even tens of thousands of years. Their new findings show that this shift in response to the disappearance of the ice can take place much faster, in the course of centuries, or decades. This suggests that the mantle under Antarctica, which is lifting the rock up, it can be more fluid, flows faster than was previously suspected, the study authors reported.
The measure of the rebound
Antarctica is the rock, is difficult to study, because most of it is covered by thick layers of ice; the continent’s ice sheet coverage, about 90 percent of all the ice on Earth, containing enough water to raise sea levels worldwide by about 200 feet (61 meters), according to NASA. To measure how it was changing, the researchers installed six GPS stations at locations around the Amundsen Sea Embayment (ASE), a region of the ice sheet about the size of Texas, which flows into the Amundsen Sea. They place the GPS monitors in the places where the base was exposed, the collection of data with a spatial resolution of 0.6 miles (1 km), higher than any recorded in previous studies.
The scientists expect to see some evidence of a slow increase of the rock over time, which can be linked to historical ice loss — because “when the ice melts, the earth rebounds elastically,” Barletta said. Instead, they observed that the rate of recovery was approximately four times faster than expected ice loss of data. The speed of the rebound in the ASE — 1.6 inches (41 mm) per year — was “one of the fastest rates ever recorded in glaciated areas,” study co-author Abbas Khan, an associate professor at DTU Space, said in a statement.
Their findings suggest that the mantle underneath is a fast and flowing, responding quickly as the heavy weight of the ice is removed, push the rock to the top very quickly, Barletta said. [Icy Images: Antarctica Will Amaze You in Incredible Aerial view]
An uncertain future for Antarctica’s ice
The foundation uplift is a result of ice loss of the last century, but ice cream continues to disappear from parts of Antarctica at a dramatic rate, fueled by human-induced climate change. An estimated 3 billion tons of ice have disappeared from the continent since 1992, the cause of about 0.3 inch (about 8 mm) of sea level rise. And scientists recently predicted that the West Antarctic ice sheet (WAIS) could collapse completely within the next 100 years, what leads to increase of the sea level up to almost 10 feet (3 meters).
But the researchers suggest that there may be a glimmer of hope for the weakening of the WAIS. The deformation of the rock under Antarctica, supported by a liquid mantle, it could provide an unexpected source of support for the WAIS, scientists have discovered. In fact, the foundation of the uplift can stabilize the WAIS enough to prevent a complete collapse, even under a strong pressure of a warming world.
There is a down side to their findings. Estimates of ice loss in Antarctica depend on satellite measurements of gravity in localized areas, which can be affected by significant changes in the mass. If the foundation under Antarctica is rapidly adapting in response to ice loss, hair uplift would register in the gravity measurements, to compensate for what ice loss and blackout how much ice is really gone by about 10 percent, according to the study.
Hopefully now that scientists are aware of this difference can be addressed in future models of the disappearing ice, Barletta said.
The findings are published online today (21 June) in the journal Science.
Original article on Live Science.