WHATS GOING ON WITH GLACIERS?
First, glaciers move forward under the weight of the large ice sheets behind them. A typical speed is 10 inches (25 cm) per day.
Second, glaciers are retreating all over the world and are a dramatic sign of global warming. It’s quite simple. As the earth’s atmosphere warms up, the ice in the glaciers melts faster, so a long glacier shortens in length and this is what is meant by glacier retreat. Such glaciers occur in the Himalayas, Greenland, and New Zealand, for example.
Now it turns out that Antarctica has glaciers too – absolutely enormous ones that can be two miles thick. One of these is called Thwaites glacier and it is retreating too. And from time to time the ice-cliffs at the front of the glacier break off huge icebergs, which cause sea level to rise a bit when they melt.
THE DOOMSDAY GLACIER.
Thwaites is a massive glacier – roughly the size of Britain. It already accounts for 4% of world sea level rise each year – a huge figure for a single glacier – and satellite data show that it is melting increasingly rapidly.
There is enough water locked up in it to raise world sea level by more than half a meter if the glacier completely melted.
It’s sometimes called the Doomsday glacier — because its retreating faster all the time and calving larger and larger icebergs. So its contribution to sea level rise is growing and could eventually get scary.
Note: The ice in Antarctica is so thick that it holds 90% of the world’s fresh water.
HOW WE MIGHT BE AFFECTED.
The front of the Thwaites glacier is almost 100 miles wide (160km) and is collapsing into the sea at up to two miles (3km) a year. This is why Thwaites is such an important part of world sea level rise — it already accounts for 4% of world sea level rise each year and this is growing.
Now average sea level has a huge effect on the severity of storm surges, says Prof David Vaughan, the director of science at the British Antarctic Survey.
In London, for instance, an increase in sea level of half a meter (about 1.5 ft) would mean the storm surge that used to come every thousand years will now come every 100 years. If you increase that to one meter (about 3 ft) then the storm surge is likely to come once every 10 years.
POST-SCRIPT: HOW THWAITES GLACIER IS MELTING.
Scientists think that warm ocean water flows to the Antarctic coast all the way from Greenland, believe it or not. Then it flows under the ice front, melting the glacier (see the double-figure).
As the glacier retreats, yet more ice is exposed because the glacier gets thicker as you go inland. This means larger icebergs.
Also, the weight of the vast quantity of ice in a glacier slowly pushes it forward (but very very slowly). It wants to “smoosh out,” explains Dr Riverman. The higher the ice cliff, she says, the more “smooshing” the glacier wants to do.
So, the more the glacier melts, the more quickly the ice in it is likely to move toward the sea.
“The fear is these processes will just accelerate,” she says. “It is a feedback loop, a vicious cycle.”
Much of the above is adapted from BBC News:
Justin Rowlatt, Antarctica melting: Journey to the ‘doomsday glacier’, BBC News, 28 January 2020.
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