Crack. After a nearly 20 mile rift formed over Antarctica's returning Pine Island glacier in early September, about 115 square…
After a nearly 20 mile rift formed over Antarctica’s returning Pine Island glacier in early September, about 115 square miles of ice – an area more than five times as large as Manhattan – has now broken
The single largest ice cubes are four times as big as Manhattan.
This iceberging event reinforces a continuing history of melting and retreat of Antarctic glaciers, especially because of relatively hot oceans eating on the ice from below.
“This retreat and weakening is almost entirely driven by a thinning run by bottom meltdown,” says Stef Lhermitte, a geoscience specialist on remote sensing at Delft University of Technology in Holland. 1
9659002] This recent calving – while significant – was the sixth largest event of its kind from Pine Island Glacier since 2001.
Ice shelves – the ends of massive Antarctic glaciers floating on the ocean – break into the ocean regularly.
But today, with ice thinning from below, ice goes faster in the ocean than it can be replenished naturally.
Relatively warm sea water thin an ice shelf from below.
“At the beginning of the 2000s it was about every sixth year but the calf rate has increased since 2013,” said Lhermitte.
“The resulting isbergen also decays faster, as was already the case with yesterday’s iceberg.”
These ice shelves are very important.
Specifically, they act as plugs that are often stuck to the seabed and hold back Antarctica’s formidable ice sheets flow unrestrictedly in the sea.
With more ice recession, like this latest instance, the ice shelter loses its foot and becomes increasingly vulnerable to collapse.
In short, the plug can break into the sea, which can ultimately release laps – not feet – of sea level elevation.
Such major collapse is relatively new and to a large extent never before seen in human history, so it is unknown how fast this might happen – maybe this century or soon after.
“We really do not know how fast they will collapse,” said NASA oceanographer Josh Willis in September.