Largest iceberg in 50 years breaks off of Greenland

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An enormous ice berg has broken off of Greenland in what could be an ominous portent for future climate change. That part of the world has been suffering the worst heat wave on record. New records are being set everyday in Russia, where persistent heat could eventually kill more than the 40,000 who perished during the great European heat wave of 2003. This hunk of ice could be another clear symptom, and size does matter:

A giant chunk of ice four times the size of Manhattan has broken off from one of Greenland's two biggest glaciers, creating the largest Arctic iceberg since 1962. The new ice island has a surface area of about 100 square miles and a thickness of about half the height of the Empire State Building. "The freshwater stored in this ice island could keep the Delaware or Hudson rivers flowing for more than two years," University of Delaware researcher Andreas Muenchow said in a statement on the school's website. "It could also keep all U.S. public tap water flowing for 120 days."

No one heat wave or giant ice berg is the smoking gun for global warming. But these phenomena are predicted to become the norm rather than the exception as the planet heats up. In the case of Greenland, this could be the beginning of the end. There are a dozen or so outlet glaciers on the coast of Greenland that drain the interior ice sheet in a slow motion version of creeks draining a rain swollen pond. But warmer weather produces moulins, illustrated above via the Wikipedia, holes in the surface of the ice that allows meltwater to pour down and build up at the base of the glacier.

As illustrated above courtesy of Karen Wehrstein, a normal glacier on the left is in contact with the ground and slowly grinds along. But shown right, when enough water builds up below, the ice is buoyed up, the water acts like lubricant for the outlet glacier to slide along faster. As the ice moves faster, structural weakness quickly bloom into rifts, rifts join up and expand becoming deep crevasses, crevasses widen into gullies and ice bergs calve off. This may be what's going in Greenland now, and other cracks further upstream are said to be forming that could cause more calving. Over time, the process could eventually turn the slow moving outlet glaciers into ice choked rivers, at which point these natural, glacial dams would effectively collapse. Massive amounts of ice and water would then be released, as if from a dike, and thousands of cubic miles of fresh water and giant chunks of ice could pour into the ocean every year for decades.

Scientists can only estimate how fast it would take for enough of the Greenland ice layers to melt before it would raise sea levels significantly. It might be centuries, or decades. But if those glaciers collapse rapidly, it could happen frighteningly fast. If only half the ice were to melt, it would raise global sea levels more than ten feet. And long before the process was complete, that much fresh water pouring into the North Atlantic could threaten the Atlantic conveyor, a critical piece of the global ocean circulation system that keeps much of western Europe warmer than it would otherwise be. The last time a similar event happened, it resulted in a brutal cold snap and mini extinction event along the western European coast called the Younger Dryas. If something like that happened again, with a global population of seven billion almost half of which live near coasts, cities from Florida to India could be inundated creating hundreds of millions of refugees.