According to glaciologist David Vaughn at the British Antarctic Survey, the Wilkins Ice Shelf in Antarctica is now connected to the continent by just a narrow ridge of ice. The threat level, in terms of potential sea-level rise, is rather like having two kilos of enriched uranium go missing from a military base in the Middle East. If you're not concerned, perhaps you should be.

The observation was made during a recent flyover and landing - a landing which Vaughn suggests may be the last, coming as it did near the narrow ice bridge holding the Wilkins, a floating berg covering about 5,282 square miles and jutting 65 feet up from the sea, to the continent of Antarctica.

The shelf, located due south of the tip of South America, is currently hanging on by a rapidly diminishing 25-mile wide strip of ice which has narrowed to 1,640 feet at its narrowest point.

Another victim of climate change, the shelf was more than 62 miles wide as recently as 1950 and covered 6,000 square miles, or slightly larger than the U.S. state of Connecticut. As it breaks up, and pieces break free, the sea around the Shelf is fraught with icebergs as big as football fields.

 In its demise, Wilkins follows in the footsteps of nine other shelves which have gone the same route in the past half-century; the three sections of Filchner (1986), the Larsen A (1995), several portions of the Ross A (2000), the Larsen B (2002), the Ayles (2005), and the Markham (2008). In total, Antarctic ice loss since 1950 exceeds 9,652 square miles, an area the size of Vermont, changing the face of a continent which has endured, intact (prior to the advent of the Industrial Revolution) for at least 10,000 years.

The loss of ice shelves like the Wilkins (named after Australian aviator George Hubert Wilkins) doesn't raise sea levels all that much because the greater part of an iceberg is already under water, displacing more as ice than it would if it melted. The top part of an iceberg represents only about one-tenth the total mass.

The real worry is that removing ice shelves allows the continental landmass of ice trapped in glaciers to flow faster, and that flow is inevitably toward the ocean. Exacerbating that likelihood is the fact that temperatures in Antarctica have risen faster than in any other area in the southern hemisphere - a rise that translates to more than five degrees Fahrenheit since the middle of the last century.

When the United Nations Climate Panel calculated, in 2007, that world sea levels were liable to rise between 7 and 23 inches in this century, their estimate didn't factor in added ice loss from Antarctica, whose ice sheets contain enough water to raise sea levels by an additional 187 feet.

Now, to make matters worse, geophysicists from the University of Toronto warn that the increasingly unstable West Antarctic Ice Sheet (WAIS) could lead to significantly higher sea level rises, and such changes will be highly variable as well, affecting primarily North American and nations in and along the southern Indian Ocean (Indonesia, the Maldives, and Madagascar).

Estimates suggest rises up to 16.5 feet, which is the value of the total volume of water locked up in the WAIS. However, warns study author and geophysicist Jerry X. Mitrovica, the estimate may fall shy because it ignores three significant effects: sea levels fall near a melting ice sheet, but rise progressively at greater distances; earth rebounds when an ice sheet melts, pushing more water into the ocean, and; melting of an ice sheet as large as the WAIS may cause the earth's rotational axis to shift, potentially as much as 1,640 feet from its present location - an alteration in the earth's geophysical plane that could shift water from the southern oceans to the Indian Ocean and northward toward North America.

These estimates of instability and potential melting are supported by a January, 2006 UK government-commissioned report headed by Chris Rapley, the head of the British Antarctic Survey.

"The last IPCC report characterized Antarctica as a slumbering giant in terms of climate change," Rapley noted at the time. "I would say it is now an awakened giant. There is real concern, since parts of the Antarctic ice sheet that rest on bedrock below sea level have begun to discharge ice fast enough to make a significant contribution to sea level rise. Current computer models do not include the effect of liquid water on ice sheet sliding and flow, and so provide only conservative estimates of future behavior."

James Hansen, senior NASA scientist and the climate change prophet who warned President Barack Obama that he had four years to save earth, agrees the study results are troubling.

"Once a sheet starts to disintegrate, it can reach a tipping point beyond which break-up is explosively rapid," Hansen agreed.

It's hard to imagine Hansen as an alarmist when he uses the word ‘troubling' to describe a sea-level rise of 16 feet in New York or San Diego. Of course, climate change skeptics have a vocabulary all their own. Hopefully, they have a world equally as remote from reality when the waves start lapping at their doorsteps.

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Our Climate: What We're Still Working On

Image Credit:
NASA Earth Observatory