The incredible photos of an Antarctic lake that suddenly disappeared | Between 600 and 750 million cubic meters of water have been lost

A study by scientists from various universities around the world determined that a large, deep, ice-covered lake quickly disappeared to the surface of an Antarctic pack ice, probably because of the weight of the water itself.

According to research published in the journal Geophysical Research Letters, this event occurred during the Antarctic winter of 2019 on the Amery Ice Shelf, located in East Antarctica, which produced loss of 600 to 750 million cubic meters of water.

The study authors used images from a radar satellite that records what is happening during the polar night to set the time of the event to a week or less in June.

After drainage, instead of the lake, there was a crater-shaped depression on the surface of the pack ice that covered about eleven square kilometers.. This surface depression, known as the ice sink, contained the fractured remains of the ice cap.

“We believe that the weight of the water accumulated in this deep lake has opened a crack in the pack ice below the lake, a process known as hydrofracture, which causes the water to flow into the ocean below, ”said lead author of the study, Roland Warner, a glaciologist with the Australian Antarctic Program at the University of Tasmania.

The hydrofracture process has also been implicated in the collapse of small ice shelves in the Antarctic Peninsula, where meltwater forms on the surface of the ice shelves during the austral summer. However, it is not common in this region for this process to take place in ice that is 1,400 meters thick.

The southern winter was in turn captured by a green light laser instrument from NASA’s ICESat-2 satellite. This tool transmits pulses of photons that precisely locate the point of reflection of each photon it receives from Earth.

Repeating the ICESat-2 orbits on the exact ground tracks before and after the lake drained revealed the vertical scale of the disturbance. The ice surface has dropped to 80 meters in the chasm and the immediate surroundings of the lake have fallen to 36 meters. All of this happened despite the loss of water head, which resulted in the floating ice shelf becoming lighter and the pressure of the ocean causing it to flex upward.

In recent decades, with increasing air temperature, some ice shelves have experienced more surface melt. This trend not only continues, but produces more melt lakes, based on the most recent model projections for future warming.

This increases the risk of widespread hydrofracture that would cause ice shelves to collapse, which in turn would allow faster flow of ice from land-bound ice caps and sea level rise.

As a result of this study, its authors argued that the possible increase in flows in deep ice-covered lakes and hydrofracture from thick ice shelves should be taken into account in projections of future warming.

The science team also used surface elevation maps generated by the University of Minnesota’s Polar Geospatial Center (PGC) to show that the disturbance altered the regional landscape of 60 square kilometers.

The amount of water lost to the ocean was calculated using the volume of the cavity and the extent of uplift. While the Amery Ice Shelf has many lakes and melt streams during the southern summer, the amount of water lost when the lake emptied was several times greater than the annual influx of water. of cast iron.

The elevation of the lake created a new lake from a shallow arm of the original. In the ensuing thaw season, this lake filled in a few days to over a million cubic meters per day and overflowed into the sinkhole cavity.

When ICESat-2 re-crossed the sinkhole a few days later, the team was able to measure a 20-meter-wide meltwater channel, freshly dug into the sinkhole, detecting the surface of the water at a depth of three meters and photons scattered from the bottom of the chasm, the bed of the stream still three meters lower.

Finally, the study authors acknowledged that it is not yet possible to determine that the drainage of this meltwater lake is linked to broader trends such as the warming of the climate around Antarctica. .

“This brutal event was apparently the culmination of decades of meltwater accumulating and storing under this insulating ice cap,” said co-author Jonathan Kingslake, professor at the Lamont Doherty Earth Observatory of the Columbia University.