Antarctica’s 4th Largest Ice Shelf is About to Melt Back to its Smallest Area Ever Recorded

These days, there’s a big debate raging in the sciences over the issue of Antarctic melt. On the one side, you have a growing flood of data indicating that many ice shelves are thinning, that surface melt is more prevalent than previously thought, and that glaciers are threatening to destabilize at faster than previously expected rates. On the other side, we still have a number of hold-outs who rightly claim that ice shelves have always calved and that many of the processes we now observe have always been in place.

The scientific messengers sending these various indicators of Antarctic destabilization are cautious not to draw too many conclusions. But the data itself is pretty stark — which has been enough to produce some qualified, if very appropriate, warnings that Antarctica could be tipping toward instability far faster than previously imagined.

(The northern end of a massive rift in the Larsen C Ice Shelf is spawning numerous smaller ice bergs off a larger, Delaware-sized monstrosity. Now, only 3 miles of ice connect this emerging berg to the Larsen C ice mass. Once the berg separates, Larsen C will break back to its smallest area ever recorded. Image source: Project MIDAS.)

Of course the ice shelves named Larsen A and Larsen B existed throughout human times until they were only recently melted by warmth creeping up the along the Antarctic Peninsula in both the air and the water. Meanwhile, the Larsen C ice shelf is about to shatter off a very large 5,800 square kilometer ice berg even as several smaller ice bergs also appear ready to form. This event, which is now imminent in the coming days, weeks, or at most, months, will break the Larsen C ice shelf back to its smallest area ever recorded even as it marks a period of increased instability and risk of ice shelf loss.

For recent scientific assessments show that Larsen C is lowering in the water — an indication that the shelf is thinning. Furthermore, when the gigantic, Delaware-sized, ice berg and its smaller siblings break off they will take with them outer sections of a stabilizing compression arch. The compression arch, somewhat like the arch of a flying buttress, helps to balance structural stresses for the ice shelf. If it were to be compromised in total, according to glacier scientists like Dr. Eric Rignot, Larsen C would soon be adding its name to the list of various ice shelves around the world that have already fallen due to the warming airs and waters produced by human-caused climate change.

(The large ice berg that is presently breaking away from Larsen C appears to have bisected both southern and northern sections of the ice shelf’s stabilizing compression arch [indicated in the upper images by a solid gray line]. Loss of parts of the compression arch are an indication that Larsen C could become considerably less stable in the near future. However, some science indicates that the ice berg presently breaking off from Larsen C does not compromise key stability features. The nearer term future for the greatly reduced Larsen C Ice Shelf is therefore uncertain. Image source: Marine Ice Regulates Future Stability of Large Antarctic Ice Shelf.)

As with most predictive measures, however, the present trend isn’t perfectly clear with regards to the ultimate fate of Larsen C in the near future. Some studies have indicated that the section of ice breaking off is not crucial to the ice shelf’s stability. And the sections of the compression arch that are being taken out are closer to the outer edge of the ice shelf — not representing the key central arch region.

Overall, however, this story for Larsen C isn’t a good one. The shelf is thinning, it is about to reach its smallest area ever recorded, and even the loss of some outer sections of the compression arch are enough for a number scientists to express qualified concern. Larsen C didn’t show this level of instability back in the 90s or 2000s, so the overall trend here is more toward melt and instability for this 4th largest ice shelf in Antarctica.

UPDATE:

As of 7/10/2017 through 7/12/2017, rift formation had finally met open water and the large ice berg breaking away from Larsen C had finally calved. From the Project MIDAS website:

A one trillion tonne iceberg – one of the biggest ever recorded – has calved away from the Larsen C Ice Shelf in Antarctica. The calving occurred sometime between Monday 10th July and Wednesday 12th July 2017, when a 5,800 square km section of Larsen C finally broke away. The iceberg, which is likely to be named A68, weighs more than a trillion tonnes.  Its volume is twice that of Lake Erie, one of the Great Lakes.

Links:

Project MIDAS (and associated scientists)

Antarctica is About to Lose an Enormous Piece of Ice

Marine Ice Regulates Future Stability of a Large Antarctic Ice Shelf

Maximum Buttressing of Larsen C Ice Shelf

Antarctica’s Ice Shelves Thin — Threaten Significant Sea Level Rise

Scientific Hat tip to Dr. Eric Rignot

Scientific Hat tip to Dr. Richard Alley

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