Beneath the frozen expanse of West Antarctica, water has been quietly moving in the dark, filling and emptying hidden basins in ways scientists had not fully imagined. Between 2003 and 2006, NASA's ICESat satellite, tracing the height of the ice with pulses of light, caught a patch near the Whillans and Mercer Ice Streams sinking by about nine metres, a change too large and too distant from the coast to be explained by tides. The sinking traced back to a previously unknown lake, now called Subglacial Lake Engelhardt, which lost roughly two cubic kilometres of water as it drained toward the sea
Satellite Lasers Revealed Hidden Water Moving Beneath West Antarctica's Ice in 2007
Even beneath one of Earth's most frozen landscapes, the ground is anything but still
Mark
Start me off. What did the satellite actually see?
Mimi
A surface that moved. Near the Whillans and Mercer Ice Streams, one area dropped about 9 metres between October 2003 and November 2005, and it was too big and too far inland to be tides.
Mark
And that pointed to a lake nobody knew about?
Mimi
Yes, later named Subglacial Lake Engelhardt. It lost an estimated 2 cubic kilometres of water in about three years.
Luke
I'd flag that word, estimated. Nobody looked at the lake. The volume is inferred from how the surface changed, so it's a calculation from effects, not a measurement of the water itself.
Mark
Fair. But there were 14 regions in total, right?
Mimi
Fourteen areas where the ice rose or sank between 2003 and 2006. Some sank as lakes drained, others rose as water collected.
Luke
Careful there too. The source says the changes suggest lakes filling and draining. It doesn't say each of the 14 was individually confirmed as a lake.
Mark
Why does it matter for sea level?
Mimi
Ice streams move ice toward the ocean, and water underneath may change their speed. But the Whillans Ice Stream actually slowed while water was stored elsewhere.
Luke
Which means the link between subglacial water and ice speed isn't settled. And the researchers didn't say climate change drained this lake. Anyone reading that into it is adding something the reporting doesn't carry.
Mimi
Right. What it does show is a system that moves and that models need to include.
O Pulso
- A nine-metre drop in the ice surface appeared where no one expected it, and it could not be dismissed as the ordinary rise and fall of the tides.
- A hidden lake that no map had recorded was draining, losing about two cubic kilometres of water in roughly three years.
- Researchers scrambled to confirm the vanishing surface with satellite images, checking shifting shadows and slopes to prove the ice had truly sunk.
- Across the continent, fourteen regions were found rising or sinking, suggesting a connected plumbing system of water that fills and drains over short spans.
- The puzzle deepens because the Whillans Ice Stream slowed even as water was being stored elsewhere, leaving models of ice speed in need of refinement.
Beneath the frozen expanse of West Antarctica, water has been quietly moving in the dark, filling and emptying hidden basins in ways scientists had not fully imagined. Between 2003 and 2006, NASA's ICESat satellite, tracing the height of the ice with pulses of light, caught a patch near the Whillans and Mercer Ice Streams sinking by about nine metres, a change too large and too distant from the coast to be explained by tides. The sinking traced back to a previously unknown lake, now called Subglacial Lake Engelhardt, which lost roughly two cubic kilometres of water as it drained toward the sea. The discovery reminds us that the great ice sheets are not static monuments but living systems whose inner workings still hold surprises, and that the pace at which their hidden waters move remains an open question for the future.
Between October 2003 and November 2005, a stretch of ice in West Antarctica near the Whillans and Mercer Ice Streams dropped roughly nine metres. NASA's ICESat satellite caught the change, and it was far too large, and too far inland, to be blamed on tides. Helen Amanda Fricker, a geophysicist who had been using the satellite's laser pulses to track tiny shifts in the height of the ice, saw that this one did not fit.
Further work traced the sinking to a subglacial lake that no one had known existed, later named Subglacial Lake Engelhardt. To make sure the change was real, the team compared the elevation readings with satellite images taken at different times, and the shifting shadows and slopes backed up the case. The lake had lost an estimated two cubic kilometres of water in about three years, draining toward the ocean. Other patches were rising, hinting that water was gathering beneath them. In all, fourteen regions changed between 2003 and 2006.
The findings suggested that hidden lakes are not isolated pools but can fill and drain over fairly short periods, linked by a connected system. Water under an ice stream can reduce friction and change how fast the ice moves, yet the Whillans Ice Stream slowed during the very years large volumes were being stored elsewhere. That contradiction showed how much remains unclear. The researchers did not blame climate change for the drainage; they treated it as a natural process that models of the Antarctic ice sheet must account for.
Between October 2003 and November 2005, a patch of ice in West Antarctica, near the Whillans and Mercer Ice Streams, dropped by roughly 9 metres. The change was caught by NASA's ICESat satellite, and it was far too large, and too far from the coast, to be blamed on tides.
The person who noticed was Helen Amanda Fricker, a geophysicist who had been using ICESat to track small shifts in the height of Antarctica's ice surface. The satellite carried a laser instrument that sent pulses toward the ground and timed their return. By passing over the same places again and again, it let scientists tell whether a surface had risen or fallen. In the Whillans and Mercer region, Fricker saw something that did not fit.
Further work traced the sunken area to the draining of a subglacial lake no one had known about. It was later named Subglacial Lake Engelhardt. To confirm that the surface had really changed over a wide area, the researchers paired the ICESat elevation readings with satellite images taken at different times. Shifts in shadows and surface slopes in those images backed up the case that the ice had sunk. The lake had lost an estimated 2 cubic kilometres of water in about three years, with the water draining toward and ultimately into the ocean.
Other spots showed the reverse. Their surfaces were rising, which suggested water was collecting beneath them. In all, the team identified 14 regions where surface elevation changed between 2003 and 2006. The findings were published in 2007 in the journal Science and later explained by NASA's Earth Observatory. They suggested that at least some of Antarctica's hidden lakes were not isolated pools but could fill and drain over fairly short periods, linked by a connected system of water.
Liquid water can exist there because conditions under a thick ice sheet differ from those at the surface. Heat from Earth's interior and friction from ice sliding over the ground can warm the base, while the pressure of the ice above lowers the melting point. That pressure also shapes where water flows and collects, so it can move between basins, emptying one lake while filling another. As the water level shifts, the ice above rises or sinks. Scientists cannot see the lakes through the ice, but they can measure these surface effects from orbit.
The result complicated the picture of how water affects ice motion. Water under an ice stream can reduce friction with the ground and potentially change how fast the ice travels. But according to NASA, during the period studied the Whillans Ice Stream was slowing even as large volumes of water were being stored elsewhere under the ice. That apparent contradiction showed how much remained unclear about the way subglacial water, pressure and ice movement interact.
The stakes lie in the ice streams themselves, which carry enormous quantities of ice from the continent toward the sea. Changes in their speed affect how much ice reaches the ocean and, over longer periods, can contribute to sea-level change. The researchers did not claim that climate change caused the lake to drain. They presented it as a natural process that has to be accounted for when modelling the future of Antarctic ice sheets.
Later research using ICESat data found many more active subglacial lakes across the continent. The open question is how that plumbing system connects to ice speed, and models of the West Antarctic Ice Sheet still need refinement to capture it.
Citações Notáveis
During the period studied, the Whillans Ice Stream was slowing even as substantial volumes of water were being stored elsewhere beneath the ice.— NASA, as reported by the Times of India
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