Hidden Antarctic Lake Drains 78 Billion Liters, Causing Deep Surface Ice Subsidence

Between 2016 and 2017, a 61-square-kilometer patch of ice near East Antarctica's Amery Ice Shelf began to sink at a rate of 2.54 meters per year. By 2021, the center of this seemingly featureless white expanse had dropped by a total of 6.37 meters.[2][4]

The ice itself was not melting from above. Instead, the bedrock below was effectively giving way as a hidden reservoir, the Kronshtadskiy subglacial lake, rapidly emptied 78 billion liters of water into the continent's dark plumbing system.[1][2][3]

Antarctica is not a static block of frozen freshwater. Hundreds of lakes lie trapped between the bottom of the ice sheet and the continental bedrock. These reservoirs exist because the immense pressure of the overlying ice lowers the melting point of water, while geothermal heat radiating from the Earth's interior warms the base.[2]

Friction from the grinding movement of the glacier generates additional heat, allowing liquid water to pool in bedrock depressions even when surface temperatures remain far below freezing. When these pressurized subglacial lakes breach their confines, they do not evaporate; they drain into interconnected channels beneath the ice sheet.[3]

Radar interferometry isolates the signal

Because researchers cannot see this water move through kilometers of solid ice, they must track the physical response of the surface above it. As a lake empties, the ice roof subsides like a slow-motion piston. Conversely, when a lake refills, the surface bulges upward.[2]

Cataloging this hidden hydrology has historically relied on airborne radio-echo sounding and satellite altimetry. Instruments like those on the ICESat and CryoSat missions bounce laser or radar pulses off the ice to track height changes over time.[2]

However, these altimeters sample the ground in narrow tracks. A lake spanning a few dozen square kilometers that empties over a matter of months can easily slip between the orbital paths of a global observing system.[2]

To capture the Kronshtadskiy collapse, researchers Jihyun Moon and Hoonyol Lee from South Korea's Kangwon National University turned to a different tool. They analyzed imagery from the European Space Agency's Sentinel-1 radar satellites, which revisit the exact same polar coordinates every 24 days.[2]

Cross-checking the collapse

The team employed a technique called double-differential interferometric synthetic aperture radar, or DDInSAR, to process the data acquired between 2016 and 2021. Standard interferometry compares the phase of radar signals returned on successive satellite passes to measure tiny changes in surface distance.[2][4]

Double-differential interferometry takes the difference between two of those interferograms. This mathematical subtraction cancels out long-wavelength errors and the broad, rapid flow of the glacier itself, isolating the localized, vertical deformation signal produced exclusively by the draining lake.[2]

The resulting stack of 77 interferograms revealed a burst of rapid water loss that tapered off over five years. After the initial plunge in 2016 and 2017, the subsidence slowed sharply to 0.88 meters in 2018. The rate fell below 0.30 meters per year between 2019 and 2021.[2]

This long tail of diminishing movement indicates the lake emptied its primary inventory and then stabilized, rather than vanishing in a single catastrophic blowout. Translating the measured surface deformation into a physical water volume, the researchers calculated that the drainage removed 78.0 million cubic meters of subglacial water.[2][3]

Downstream consequences

That volume is equivalent to more than 31,000 Olympic swimming pools moving through a plumbing system sealed beneath the ice. The sheer scale of the displacement confirms that the Amery Ice Shelf sector hosts a highly active hydrological landscape.[2]

The radar findings were independently corroborated by point measurements from NASA's ICESat-2 and the European CryoSat-2 altimeters. While the altimeters provided sparse spatial coverage, their precise height data matched the overall subsidence trend observed in the interferograms, giving researchers high confidence that the 6.37-meter drop is a genuine hydrological event.[2]

The location of the Kronshtadskiy lake adds particular weight to the findings. This sector of East Antarctica feeds one of the largest ice shelf systems on the continent. The ice here flows relatively quickly compared to the sluggish interior, which normally degrades the coherence of radar images and blurs the exact signals researchers want to isolate.[2]

Where exactly the 78 billion liters of water went remains unmapped. Satellite radar tracks the sinking roof of the lake, but it cannot trace the liquid as it moves downstream. Adjacent areas of slight surface uplift suggest the water may have flowed into neighboring subglacial reservoirs, but the precise routing through the basal channels is still a matter of interpretation.[2]

Understanding this hidden network is critical for modeling ice sheet stability. Water at the bed of a glacier acts as a lubricant, and changes in its distribution and pressure modulate how fast the ice slides toward the ocean. Sudden drainage events can send pulses of water downstream, altering basal conditions and potentially accelerating the velocity of the overlying ice.[2]

If these subglacial floods consistently speed up the movement of outlet glaciers, they directly influence the rate at which Antarctica discharges mass into the sea. East Antarctica is often viewed as more stable than the rapidly melting West Antarctic Ice Sheet, making dynamic events here crucial for accurate global sea-level predictions.[2]

"The drainage of Kronshtadskiy lake is a vivid reminder that Antarctica is not a frozen still life but an active hydrological landscape," notes the scientific outlet BIOENGINEER.ORG in its review of the findings. "One that satellites are now equipped to watch in fine detail."[2]