New Crack Found in Delaware-Sized Chunk of Larsen C Ice Shelf as it Heads Toward Southern Ocean

A 2,000 square mile section of the Larsen C Ice Shelf is hanging by a thread as it continues to drift toward the Weddell Sea.

(A second crack develops in Larsen C Ice Shelf. Image source: Project MIDAS.)

The break-off section represents fully 10 percent of all the ice contained in the Larsen C system. It has been divided from the larger ice shelf by a 180 kilometer long crack that began to develop in 2009 and that swiftly lengthened during recent years. Now only a 10 kilometer wide bridge links the breaking section to the larger ice shelf. And considering the enormous stresses now being placed on this break-off section it is expected to go at any time.

Since January, according to researchers at Project MIDAS, the large crack has been widening but its length growth has stalled. However, recent reports out this week from MIDAS found that a new crack had developed at the ice-bridge end of the break-off section. The new crack appears to be rounding the corner of the bridge to begin a quicker path to segmenting the massive ice berg away from Larsen C. A testament to the powerful forces that are inevitably forcing this enormous section of ice to relinquish its hold.

(Large section of Larsen C is moving far faster than the rest of the ice shelf toward the Southern Ocean. Image source: Project MIDAS.)

At issue is the fact that the break-off section is moving toward the Weddell Sea considerably faster than the rest of the Larsen C ice shelf. Much of this large section of ice is proceeding away from the Antarctic mainland at 3 meters per day. Surrounding sections of Larsen C are moving at only 1-2 meters per day. As a result, the toe end of the break-off mass is tipping out into Weddell’s waters and the crack separating it from Larsen C is widening.

It’s not really a question of if this massive block of ice will separate from Larsen C. More an issue of how soon.

Loss of so large a section of ice from Larsen C threatens the entire ice shelf’s stability. And some scientists are questioning whether the whole ice shelf will destabilize and eventually splinter — as happened to Larsen A and Larsen B during recent years.

(Rapid loss of buttressing ice shelves like Larsen C lock in higher and higher ranges for sea level rise. A worrying risk for rapid sea level rise occurs as global temperatures warm to between 1.5 and 2.5 C. A level we are fast approaching. Scientists like James Hansen identify a significant risk for multi-meter sea level rise this Century if 2 C warming thresholds are breached. Video Source: Carbon Freeze.)

Warming ocean waters due to human-forced climate change are the primary driver for loss of ice shelves around the world. These ice shelves hold back land glaciers — preventing them from more rapidly sliding into the world’s oceans. Larsen C alone holds back glaciers capable of lifting global ocean levels by 4 inches. But there are numerous such ice shelves and many are now facing thinning and increasing instability due to warming ocean waters. As a result, a growing number of scientists are concerned about the possibility for multi-meter sea level rise this Century if fossil fuel burning is not swiftly halted.

Links:

Project MIDAS

Carbon Freeze

Second Giant Crack Appears on Larsen C

Crack in Larsen C Forks

Larsen C Destabilization Could Trigger 4 Inch Sea Level Rise

Hat tip to June

Hat tip to Andy in San Diego

Antarctica is About to Lose a 2,000 Square Mile Chunk of Ice — And it Could Mean the End of the Larsen C Ice Shelf

It’s happened before. Ice shelves on the northern Antarctic Peninsula released large chunks of ice into the Southern Ocean as the world warmed up. They developed a concave shape which became unstable. Then they collapsed.

The ultimate collapse of Larsen A occurred in 1995. In 2002, further up the Antarctic Peninsula, the larger Larsen B Ice Shelf succumbed to the same fate. And it is thought that such losses haven’t happened to this section of Antarctica in at least 11,000 years and possibly as long ago as 100,000 years.

(NASA’s Jet Propulsion Laboratory provides this narrative describing the collapse of the Larsen B Ice Shelf in 2002. Video source: JPL.)

But in the present world, one where human fossil fuel emissions have forced global temperatures above 1 C hotter than 1880s averages, the stability of many of the great great ice shelves is now endangered.

Larsen C Ice Shelf to Calve 2,000 Square Mile Ice Berg

Today, a huge rift has nearly bisected a large frontal section of the Larsen C Ice shelf — an ice system many times the size of its now deceased companions Larsen A and Larsen B. And during December — a period when Antarctica was warming into Austral Summer — this massive crack grew by 18 kilometers.

When, and not if, the crack reaches the ocean, a 2,000 square mile ice berg will float away from Larsen C. It will be one of the largest ice bergs ever to form in human memory. One the size of the state of Delaware. It will tower hundreds of feet above the ocean surface. And it will last for years before ultimately melting.

larsen-c-ice-rift-length-and-width

(The Larsen C is rift grew considerably — both lengthening and widening during December of 2016. It was an indication that a massive ice berg was about to break off. Image source: MIDAS.)

This event will change the geography of our world. And for this alteration alone, it has great consequence. But, as Chris Mooney notes in this excellent Washington Post article on the subject, it’s what happens afterward that really counts.

Event Could Presage Total Collapse

Of concern is the fact that once this massive ice berg calves off of Larsen C, the great ice sheet may become unstable. It will take on a concave form. This form will make it more vulnerable to further melt by warming waters running in toward the shelf. Furthermore, the large ice berg will take a chunk of Larsen C’s compressive arch with it. Such a compressive arch — like the arch of a flying buttress — helps to bear the weight of the shelf and keep it from smashing into thousands of tiny pieces. If too much of the arc is lost, the shelf can’t survive for long.

larsen-c-ice-rift-midas

(Researchers at The MIDAS Project have projected that a 2,000 square mile section of the Larsen C Ice Shelf is about to break off. This section represents 10 percent of the Larsen C system. Its loss risks destabilization of the entire ice shelf. If Larsen C does disintegrate, it will release glaciers capable of increasing global sea level by another 4 inches. Image source: MIDAS.)

Glaciologist Eric Rignot notes in The Washington Post:

“We studied the current rift in the past few years, it has been progressing rather ‘normally,’ the recent acceleration in the rift progression is ‘expected’ in my opinion. The consequences on the rest of the ice shelf are not clear at this point. If the calving continues and goes past the compressive arch … then the ice shelf will break up.”

Scientists are currently divided over the issue of whether or not Larsen C’s near-term demise is imminent. However, the loss of such a massive ice berg from Larsen C, the present human-forced warming of the Antarctic land and ocean environment, and the presently observed thinning of the ice shelf all point toward a rising risk of destabilization or disintegration.

As with most things geological, you can’t really say that such an event is certain until after the fact. But as for Larsen C’s prospects of long term survival, things aren’t looking too great at the moment.

Links/Credits

The MIDAS Project

Antarctica is Set to Lose an Enormous Piece of Ice

An Ice Berg the Size of Delaware is About to Break off From Antarctica

NASA’s Jet Propulsion Laboratory

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