The loss of the lake is especially unusual considering that it was supported by a relatively sturdy part of Amery Ice Shelf, which is about 4,590 feet thick.
While hydrofractures have been implicated in the collapse of more fragile ice sheets, a drainage event of this size and speed has never been observed in detail before. As the water levels rapidly fell, an ice lid that perennially covered the lake collapsed some 260 feet and then flexed upwards about half that distance, creating the distinctive doline structure that first tipped Warner off to the lake’s disappearance. Warner and his colleagues think that the weight of the lakewater exceeded what the ice could bear, sparking a process called “hydrofracture” in which burst fissures allow water to flow through the ice shelf and out into the ocean. It held an estimated 21 to 26 billion cubic feet of water, equivalent to twice the volume of San Diego Bay. Indeed, data from NASA’s ICESat-2 captured during the southern winter revealed that there was a huge intact lake consisting of meltwater at the site of the doline on June 9, 2019. “Without the satellite data we pulled together we would not have achieved such a quantitative assessment of the scale and size of the disruption caused by the lake draining.” “It was bringing together the expertise of the team that made this more than just an ‘Oh! Look what I found’ paper,” he said. Warner checked his findings with researchers who study surface meltwater patterns on Amery Ice Shelf, and who became co-authors of the study. With the help of sophisticated satellites such as NASA’S WorldView and the European Space Agency’s Sentinel constellation, he was able to look back in time and pinpoint when the vast lake emptied out through channels that burst open in the ice below it. Warner thought the structure might be a doline, or sinkhole, that could point to a dramatic and recent drainage event. “The collapsed surface feature caught my eye.” “Looking down to Antarctica, for a break from watching the destruction, I noticed a spell of several clear days on Amery Ice Shelf and decided to see how the summer surface melt season was progressing,” he said in an email. Roland Warner, a glaciologist with the Australian Antarctic Program Partnership at the University of Tasmania, first noticed signs of the missing lake while examining satellite imagery captured in January 2020, which “serendipitously revealed a striking collapsed surface structure” at Amery Ice Shelf, according to the study, which was published last Wednesday in Geophysical Research Letters.Īt this time, Australia was gripped by an intense bushfire season, and Warner had been regularly checking satellite images of the damage.