Lake bigger than Sydney Harbour drains under Antarctic ice

A lake bigger than Sydney Harbour has suddenly drained under an Antarctic ice shelf, prompting worry among scientists.

The drainage took place in 2019, but a study of the event was only recently published in the Geophysical Research Letters journal.

Researchers believe that up to 750 gigalitres (0.75 cubic kilometres) was lost when the lake under the 1.4km-thick Amery Ice Shelf in the continent's east suddenly drained away.

READ MORE: Aussies in Antarctica celebrate mid-winter with icy dip

For comparison, Sydney Harbour holds about 500 gigalitres of water.

The disappearance of the lake left an 80m-deep ice-filled crater behind covering about 11 square kilometres.

Meanwhile, the pressure of the ocean beneath the floating ice sheet increased, lifting the ice around the crater more than 30m.

University of Tasmania glaciologist Roland Warner, the study's lead author, told Columbia University the weight of the water in the lake was believed to have opened a crack in the ice shelf below, giving it a means of draining.

READ MORE: World's largest iceberg breaks off from Antarctica

Similar examples of the process, known as hydrofracturing, have been seen on other ice shelves, but not usually on one so large.

"The flow into the ocean beneath would have been like the flow over Niagara Falls, so it would have been an impressive sight," Dr Warner said.

The study authors said surface melting over Antarctica's floating ice shelves was predicted to increase "significantly" during the coming decades.

This could lead to the collapse of the ice shelves and a rise in ocean levels.

You can find out more details about how to book your vaccine through the Federal Government health site here.