NASA image acquired March 14, 2010
Pine Island Bay is tucked into a corner of the West Antarcticâs Walgreen Coast. The bay, which opens to the Amundsen Sea, is typically filled with sea ice at this time of year, but when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASAâs Aqua satellite passed overhead on March 14, 2010, the bay was largely ice-free.
Acquired at the end of the Antarctic summer, the image is illuminated by fairly low-angled sunlight, which highlights raised and textured areas, including ice-covered peninsulas and the corrugated surface of iceberg B-22A. B-22A broke from the Mertz Glacier Tongue several thousand miles to the west; it may be grounded on a submarine shoal. Northwest of the iceberg is a combination of sea ice and grounded icebergs. This sea ice/iceberg feature has been larger in recent Antarctic summers than it appears in this image.
The coast of Antarctica not only has sea ice that comes and goes from year to year, but also longer-lasting ice shelves (thick slabs of ice attached to the coastline that partially float on the ocean surface). Among the ice shelves on the Walgreen Coast is Dotson Ice Shelf. Although most of the surface appears smooth, several long cracks appear to trace the leading edge of the shelf, hinting that the margin may calve some long, narrow icebergs in coming summers.
The presence or absence of sea ice affects both ocean surface waters and ice shelves. Thanks to its light color, sea ice reflects much of the Sunâs energy back into space, keeping underlying ocean waters cool. Without a cover of sea ice, the surface waters of the ocean warm. The exposure to sunlight also makes it possible for phytoplankton to bloom. West of the line of grounded icebergs, the ice floating in the Amundsen Sea takes on a greenish color; this may be due to phytoplankton or algae. When it comes to ice shelves, a sea-ice cap on the ocean surface dampens wave energy that might otherwise trigger ice-shelf retreat.
NASA image courtesy Jeff Schmaltz, MODIS Rapid Response Team at NASA GSFC. Caption by Michon Scott and Rebecca Lindsey, based on image interpretation by Ted Scambos, National Snow and Ice Data Center.
Instrument:Â Aqua - MODIS
To learn more about this image go to: http://earthobservatory.nasa.gov/IOTD/view.php?id=43499
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A UK team of climate scientists has discovered a rift in the Antarctic rock as deep as the Grand Canyon, which they believe is increasing the rate ice melt from the continent. With the recent news that an iceberg twice the size of Manhattan has broken away from Greenland, it seems that both of the planet’s ice caps may be in significant trouble.
The Antarctic chasm, known as the Ferrigno rift, was discovering using ice-penetrating radar and was revealed to be about 1.5km (1 mile) deep. The team believe that the sheer depth of the canyon is bringing warmer sea water into the ice sheet, which is speeding up the rate of melting.
Describing their discovery in the journal Nature, the team, led by Dr Bingham from the University of Aberdeen, said: “What we found is that lying beneath the ice there is a large valley, parts of which are approximately a mile deeper than the surrounding landscape. If you stripped away all of the ice here today, you’d see a feature every bit as dramatic as the huge rift valleys you see in Africa and in size as significant as the Grand Canyon. This is at odds with the flat ice surface that we were driving across – without these measurements we would never have known that it was there.
“What’s particularly important is that this spectacular valley aligns perfectly with the recordings of ice-surface lowering and ice loss that we have witnessed with satellite observations over this area for the last 20 years.”
The team also discovered that present-day ice loss is greater here than in other parts of Antarctica, where some glaciers are shrinking by more than a metre per year. The study was conducted in partnership with the British Antarctic Survey. Co-author Dr Fausto Feraccioli from the organization said: “The newly discovered Ferrigno Rift is part of a huge and yet poorly understood rift system that lies beneath the West Antarctic Ice Sheet. What this study shows is that this ancient rift basin, and the others discovered under the ice that connect to the warming ocean can influence contemporary ice flow and may exacerbate ice losses by steering coastal changes further inland.”
Ice loss from West Antarctica is believed to contribute about 10% to global sea level rise, but it is still unknown how the planet’s ice sheets are responding to the rising temperatures. What is known that if either the Arctic or Antarctic ice sheets were to completely melt, then the sea levels would rise by several metres.
+ University of Aberdeen
via Press Association/BBC News
Images: University of Aberdeen, NASA Goddard Photo and Video