The Antarctic ice cap forms the largest body of fresh water in the world. Ninety percent of our fresh water supply is locked up in 7.25 million cubic miles (30 million cubic kilometres) of glacial ice on the southern continent. If all of this ice were to melt, the height of the earth's oceans - sea level - would rise 160-200 feet (50-60 metres). Islands and coastal cities around the world, including Boston, would be completely submerged.
Scientists at NASA have generated a computer model depicting changes in the Antarctic ice sheet since the peak of the last ice age nearly 20,000 years ago. The West Antarctic ice sheet has lost nearly two-thirds of its mass during this period, a volume sufficient to raise sea level 33 feet (10 metres).
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ICE CORE RESEARCH
The study of the ice sheet, ice streams, ice shelves and sea ice of Antarctica is a fascinating and puzzling one for scientists. Much is known but much remains to be discovered. Your own reading has likely revealed many facts about the ice: e.g. 98% of the continent is covered with ice; it is the largest single mass of ice on earth; the ice is up to 4700 metres thick; perhaps 70% of the world's fresh water is contained in the ice sheet; much of our planet's history has been revealed through the analysis of ice cores drilled deep into the Antarctic ice-cap. These facts only scratch the surface of the amazing ice world being revealed by present day research. In East Antarctica the ice sheet rests on a major landmass, while in West Antarctica it lies on the sea bed which is as much as 2500 metres below sea level. Interestingly, this monumental ice sheet is very active and portions of it are in constant motion. The surface of the ice is below 0 degrees Celsius all year long so frost, snow and ice crystals continually build up year after year, and exert a tremendous force on the dense ice mass below. The ice sheet is forced by this pressure to flow toward the sea. Picture a huge conveyor belt taking precipitation from the atmosphere, creating this dense and impermeable ice mass, and slowly delivering it back to the sea.
The base of the ice sheet tends to be warmer. This creates a lubricating effect that creates fast moving areas of ice called ice streams. Some of the images captured by the Canadian Space Agency's RADARSAT II show ice streams in startling detail. As you learn more you might become familiar with truncated spurs, shear margins and tributary glaciers.
Coastal ice sheets rest on the seabed below sea level. Ice is lighter than water and therefore floats. Eventually, portions of these ice sheets become ice shelves, either attached to the ice sheet or breaking away to become tabular icebergs. The Ross Ice Shelf, alone, is roughly the size of France so you can imagine the immensity of ice covering areas of the Southern Sea.
The sea lies just beyond the ice shelves and when this sea freezes it covers a huge area with sea ice. This area is estimated to cover around 3 million square kilometres in February and 20 million square kilometres in October. The Antarctic actually doubles in size every winter with the surrounding frozen ocean! This will provide another clue as to why our expedition is slated for January. The amount of sea ice is directly related to the magnitude of energy transfer between the ocean and the atmosphere and is a critical factor in both the climate of Antarctica and the marine ecosystem beneath the ice.
Antarctica is a huge 'iceberg factory', larger than the continental United States and Mexico combined, that is estimated to create over 250,000 icebergs in an average year. As we approach Antarctica you will see icebergs that defy description. Some are tabular icebergs and have been known to exceed 100 kilometres in length and be greater in size than the smallest American states and even some countries. As icebergs melt, roll over and erode, nature creates sculptures of breath taking beauty. Their colours range from aquamarine to navy blue, with every hue and shade in between. No two icebergs are ever the same.
You have known for some time that about 80% of floating ice is below the water. When your ship comes alongside an immense iceberg, (the tip of the iceberg) towering above you and shimmering in the blazing Antarctic sun (or engulfed in an Antarctic blizzard), you will finally begin to understand what an unbelievable fact this is.
TYPES OF ICE ... ICE SHEETS, ICE SHELVES, ICE STREAMS, SEA ICE
GLACIER ICE http://nsidc.org/glaciers/
STUDENTS ON ICE: EDUCATION PROGRAM - ANTARCTICA
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