29 Sep 2020

Doomsday Glacier and sea level rise

From Nine To Noon, 9:20 am on 29 September 2020

An Antarctic glacier the size of Great Britain is melting at an alarming rate, according to new research.

Nicknamed the Doomsday glacier, the Thwaites glacier flows off the west of the Antarctic and is dumping billions of tonnes of ice into the ocean.

The melt has increased from 10 billion tonnes of ice a year in the 1990s, to 80 billion tonnes a year now. 

The British Antarctic Survey (BAS) has been mapping warm seawater cavities eroding the glacier, some of which are half the size of the Grand Canyon. 

Dr Kelly Hogan from the British Antarctic Survey is one of the team surveying Thwaites, whose research has been published in the Cryosphere journal.

She told Kathryn Ryan the scale of the glacier is immense. It is  a150km long cliff of ice, 25m above sea level and 300m below water.

The glacier is 2000km from the nearest research base, meaning it’s a four-day voyage to reach it.

She says the glacier is melting from underneath.

“One of the biggest causes of the retreat and this accelerated melting there is the warm ocean water getting right up under the floating parts of the glacier where it sits on the sea bed and it actually does the melting underneath.

“There is some melting on the surface but by far the largest factor causing the melt is that warm ocean water getting in there and melting underneath the ice and weakening the structure of the glacier as well.”

The danger is the melting could become “runaway”, she says.

“Because it gets thicker and thicker as it goes down towards the centre of Antarctica the more you melt into it the more ice you expose to that warm water, so the more you will increase the rate at which you melt.

“And eventually that could lead to the collapse of the glacier where it is just too thick to be stable anymore and that could lead to a runaway retreat.

“In that situation if the whole glacier melted then you would raise global sea levels by about 65 centimetres or 25 inches.”

The timeframe for that could be two centuries, she says.

“The problem is with something like Thwaites and the processes we see going on, is that once you begin this sort of runaway retreat there’s no chance of reversing it.”

At the moment a kind of plug of ice is protecting the front of the glacier.

“As you melt off the front of it you are exposing more and more to the warm water.

“If it loses that plug it’s like releasing the cork of a bottle it could allow much greater acceleration of ice loss and acceleration of melting.”

The glacier also has huge cavities and channels which could be channelling warm water, Dr Hughes says.

The next phase of the research will look at the impact of those cavities, she says.