Aug 22, 2016

A huge crack is spreading across one of Antarctica’s biggest ice shelves

Larsen C Ice Shelf
by
Chris Mooney
,
Washington Post
The Larsen B ice shelf on March 7, 2002, after it shattered into thousands of smaller icebergs. Photo: NASA / Goddard Space Flight Center Scientific Visualization Studio
The Larsen B ice shelf on March 7, 2002, after it shattered into thousands of smaller icebergs. Photo: NASA / Goddard Space Flight Center Scientific Visualization Studio

For some time, scientists who focus on Antarctica have been watching the progression of a large crack in one of the world’s great ice shelves — Larsen C, the most northern major ice shelf of the Antarctic peninsula, and the fourth largest Antarctic ice shelf overall.

Larsen C, according to the British Antarctic Survey, is “slightly smaller than Scotland.” It’s called an ice “shelf” because the entirety of this country-sized area is covered by 350 meter thick ice that is floating on top of deep ocean waters.

The crack in Larsen C grew around 30 kilometers (18.6 miles) in length between 2011 and 2015. And as it grew, also became wider — by 2015, yawning some 200 meters in length. Since then, growth has only continued — and now, a team of researchers monitoring Larsen C say that with the intense winter polar night over Antarctica coming to an end, they’ve been able to catch of glimpse of what happened to the crack during the time when it could not be observed by satellite.

The result was astonishing.

The rift had grown another 22 kilometers (13.67 miles) since it was last observed in March 2016, and has widened to about 350 meters, report researchers from Project MIDAS, a British Antarctic Survey funded collaboration of researchers from Swansea and Aberystwyth Universities in Wales, and other institutions. The full length of the rift is now 130 km, or over 80 miles.

What this means is that it may be only a matter of time before we see the loss of an enormous chunk of Larsen C — an historic event that would bring to mind the losses of the Larsen A ice shelf in 1995 and the sudden breakup of Larsen B in 2002. When that last event happened, the National Snow and Ice Data Center remarked that the Earth had lost a major feature that had “likely existed since the end of the last major glaciation 12,000 years ago.”

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The Larsen C ice shelf is the fourth largest in Antarctica, but all of the continent’s shelves pale in comparison to the Ross and Ronne-Filchner ice shelves, each of which is over 400,000 square kilometers in area.

When ice shelves lose large chunks, it does not raise sea level because these bodies are already afloat. However, the loss of an ice shelf can speed up the seaward flow of the non-floating glacial ice behind it, and this ice can in turn contribute to sea-level rise. Researchers have estimated that the loss of all the ice that the Larsen C ice shelf currently holds back would raise global sea levels by 10 centimeters, or just under 4 inches