The most advanced Earth-observing laser ever launched by Nasa has spotted two more subglacial lakes under the ice of Antarctica.
The finding could help scientists understand a hidden "plumbing system" under the ice-bound continent that could hold secrets about its future.
From above the Antarctic Ice Sheet looks like a calm, perpetual ice blanket – but it hides hundreds of meltwater lakes where the ice sheet meets the continent’s bedrock, Nasa said.
The space agency's Ice, Cloud and land Elevation Satellite 2, or ICESat-2, allowed scientists to precisely map the subglacial lakes.
The satellite measures the height of the ice surface, which, despite its enormous thickness, rises or falls as lakes fill or empty under the ice sheet.
Hydrology systems under the Antarctic ice sheet have been a mystery for decades.
That began to change in 2007, when Helen Amanda Fricker, a glaciologist at Scripps Institution of Oceanography at the University of California San Diego, made a breakthrough that helped update classical understanding of subglacial lakes in Antarctica.
Using data from the original ICESat in 2007, Fricker found for the first time that under Antarctica’s fast flowing ice streams, an entire network of lakes connects with one another, filling and draining actively over time.
Before, these lakes were thought to hold meltwater statically, without filling and draining.
Matthew Siegfried, assistant professor of geophysics at Colorado School of Mines in Golden, Colorado, and lead investigator in the new study, said: "The discovery of these interconnected systems of lakes at the ice-bed interface that are moving water around, with all these impacts on glaciology, microbiology, and oceanography – that was a big discovery from the ICESat mission.
"ICESat-2 is like putting on your glasses after using ICESat, the data are such high precision that we can really start to map out the lake boundaries on the surface."
To study the regions where subglacial lakes fill and drain more frequently with satellite data, Siegfried worked with Fricker, who played a key role in designing the way the ICESat-2 mission observes polar ice from space.
Siegfried and Fricker’s research shows that a group of lakes, including the Conway and Mercer lakes under the Mercer and Whillans ice streams in West Antarctica, are experiencing a draining period for the third time since the original ICESat mission began measuring elevation changes on the ice sheet’s surface in 2003.
The two newly-found lakes also sit in this region.
In addition to providing vital data, the study revealed that the outlines or boundaries of the lakes can change gradually as water enters and leaves the reservoirs.
"We're really mapping out any height anomalies that exist at this point," Siegfried said. "If there are lakes filling and draining, we will detect them with ICESat-2."
Precise measurements of basal meltwater are crucial if scientists want to gain a better understanding of Antarctica’s subglacial plumbing system, and how all that freshwater might alter the speed of the ice sheet above or the circulation of the ocean into which it ultimately flows.
Fricker said: "These are processes that are going on under Antarctica that we wouldn't have a clue about if we didn't have satellite data.
"We've been struggling with getting good predictions about the future of Antarctica, and instruments like ICESat-2 are helping us observe at the process scale."
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