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Scientists have seen once again just how dynamic a place the underside of the Antarctic ice sheet can be.
Survey data collected from the middle of the White Continent shows liquid water is being frozen on to the bottom of the sheet in huge quantities.
In places, this deeply buried add-on layer is hundreds of metres thick and represents about half of the entire ice column, researchers say.
The discovery is reported online in the journal Science.
Project leaders confess to being astonished by the findings.
"It's jaw-dropping, I have to say," said Professor Robin Bell from Columbia University's Lamont-Doherty Earth Observatory.
"The first time I showed the data to colleagues, there was an audible gasp," she told BBC News.
The new data will add to the understanding of how the ice sheet expands and moves, which in turn will inform researchers as they try to grasp how Antarctica might change in a warmer world.
- Two camps (N & S) were established deep in the Antarctic interior around the plateau region known as Dome A
- Aircraft used radar to detect ice thickness and layering, and mapped the shape of the deeply buried bedrock
- The planes also conducted gravity and magnetic surveys to glean more information about the mountains' structure
- By listening to seismic waves passing through the range, scientists could probe rock properties deep in the Earth
- The Gamburtsev range is totally hidden by ice. In some places that ice covering is more than 4,000m thick
- A key quest was to find a location to drill ancient ice - ice made from snow that has accumulated over a million years
- The oldest ice drilled so far comes from a location known as Dome C. It records climate conditions 800,000 years into the past
As well as the ice-penetrating radar, other instruments measured the local gravitational and magnetic fields.
Some 120,000km were flown in total, the equivalent of three trips around the globe.
More than 20% of the East Antarctic Ice Sheet was explored.
An International Polar Year aerogeophysical investigation of the high interior of East Antarctica reveals widespread freeze-on that drives significant mass redistribution at the bottom of the ice sheet. While surface accumulation of snow remains the primary mechanism for ice sheet growth, beneath Dome A 24% of the base by area is frozen-on ice.
In some places, up to half the ice thickness has been added from below. These ice packages result from conductive cooling of water ponded near the Gamburtsev Subglacial Mountain ridges and supercooling of water forced up steep valley walls. Persistent freeze-on thickens the ice column, alters basal ice rheology and fabric and upwarps the overlying ice sheet, including the oldest atmospheric climate archive, and drives flow behavior not captured in present models.
In all, refrozen meltwater may be responsible for as much as half the thickness of the ice sheet over large areas, the team reports online today in Science. (Bell says clues suggest the same process occurs in Greenland and on the west side of the Antarctic ice sheet.)
Originally posted by Xcathdra
This is intresting. It makes me wonder about the whole melting issues the Earth seems to be having. Is this natures way of "exfoliating", for lack of a better term.
If the Ice is building from the bottom, which is something we did not expect, is it replacing ice at the same level its been loosing it on the top?