Yet Another Antarctic Ice Shelf Breaking up Faster Than Expected
The time is fast approaching when we will have to acknowledge that scientist’s projections of the rate at which climate change is impacting the environment is simply too conservative. It may be that the rate of climate change is faster or the impacts are greater. Or both.
Image courtesy British Antarctic Survey
While monitoring satellite images of the shelf, glaciologist Ted Scambos, of the University of Colorado noticed a 41 km x 2.5 km (25.5 by 1.5 miles) iceberg had broken away from the Wilkins Ice Shelf at the end of February 2008. He alerted the British Antarctic Survey (BAS) team who investigated the ice shelf first hand.
The BAS reports that the edge of the shelf proceeded to crumble and disintegrate in a pattern that has become characteristic of climate-caused ice shelf retreats throughout the northern Peninsula, leaving a sky-blue patch spreading across the ocean surface compose of hundreds of large blocks of exposed old glacier ice.
By 8 March 2008, the ice shelf had lost just over 570 km2 (220 sq. miles), and the patch of disintegrated Antarctic ice had spread over 1400km2. As of mid-March, only a narrow 6km (3.7 miles)wide thread of shelf ice between two small islands that support part of the shelf was protecting several thousand kilometres of potential further break-up.
Scambos said that it’s not just ice breaking off the shelf, but rather massive sections shattering, and that if the thread of ice collapses, half of the ice shelf could be lost within a few years.
In 1993, Professor David Vaughan of the BAS predicted that the Wilkins Ice Shelf would likely disappear within 30 years if climate change continued at the same rate as in 1993.
There’s now a good chance the Wilkins Ice Shelf will dissappear long before 2023, which will come as no surprise for those who are following closely the recent evidence of the impact of climate change. This discovery follows the recent UNEP report that the world’s glaciers are continuing to melt away. Data from 30 reference glaciers in nine mountain ranges show that between the years 2004-2005 and 2005-2006 the average rate of melting and thinning has more than doubled.
Professor Vaughan said: “Wilkins is the largest ice shelf on the Antarctic Peninsula yet to be threatened. I didn’t expect to see things happen this quickly. The ice shelf is hanging by a thread – we’ll know in the next few days or weeks what its fate will be.
“Climate warming in the Antarctic Peninsula has pushed the limit of viability for ice shelves further south – setting some of them that used to be stable on a course of retreat and eventual loss. The Wilkins breakout won’t have any effect on sea-level because it is floating already, but it is another indication of the impact that climate change is having on the region.”
Ice shelves float in the sea and already displace water volume. When they break up and melt, they do not raise sea level. However, ice shelves restrain the flow of glaciers behind them from sliding into the sea. When the ice shelves disintegrate, glaciers can slide quicker towards the sea, melt and raise the sea level. The collapse of ice shelves can therefore precede a faster rise in sea level. Melting sheets also increase feedback in the climate system by reducing the reflectivity of that part of the earth’s surface, enabling sunlight to be converted to ocean heat which in turn accelerates melting of the floating ice.
Fortunately, few glaciers flow into Wilkins Ice Sheet, but if the trend continues and other sheets are affected, sea levels will eventually be impacted.
The Antarctic has warmed at three times the global average – and, along with Alaska, faster than any other region on the planet – over the past half century and six Antarctic ice shelves have already disappeared over recent decades, including Prince Gustav Channel, Larsen Inlet, Larsen A, Wordie, Muller, Jones and the 3,250 sq. km, 220 metres thick Larsen B Ice Shelf, which fell apart over several months in 2002 – 720 billion tonnes of ice gone. Again, an unexpected event.
Science magazine reported that the Ross and Ronne ice shelves may be instrumental in retaining the glaciers behind them and that if those two shelves were to collapse, the entire land-based western ice sheet could flow into the ocean, with the potential to raise sea levels by 5 metres.
And still we keep pumping out more and more greenhouse gases and argue over what action to take, when the solutions are already available.
For more Antarctic images see Polar View
Note: Ice sheet – is the huge mass of ice, up to 4 km thick, that covers Antarctica’s bedrock. It flows from the centre of the continent towards the coast where it feeds ice shelves.
Ice shelf – is the floating extension of the grounded ice sheet. It is composed of freshwater ice that originally fell as snow, either in situ or inland and brought to the ice shelf by glaciers. As they are already floating any disintegration (like Larsen B) will have no impact on sea level. Sea level will rise only if the ice held back by the ice shelf flows into the sea. By Christo Norden-Powers © 2008 Spandah
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