Hidden world of Antarctic

Scientists have produced the most detailed map yet of the White Continent's underbelly - its rock bed.

Called simply BEDMAP, this startling view of the landscape beneath the ice incorporates decades of survey data acquired by planes, satellites, ships and even people on dog-drawn sleds. It is remarkable to think that less than 1% of this rock base projects above the continent's frozen veil.

In the map at the top of this page, the highest elevations are marked in red/black. The light blue colour shows the extent of the continental shelf.

The lowest elevations are dark blue. You will note the deep troughs within the interior of the continent that are far below today's sea level.

The map is a fascinating perspective but it is more than just a pretty picture - it represents critical knowledge in the quest to understand how Antarctica might respond to a warming world.

Scientists are currently reporting significant changes at the margins of the continent, with increasing volumes of ice now being lost to the ocean, raising global sea levels. The type of information contained in BEDMAP will help researchers forecast the pace of future events.

The Antarctic ice sheet is constantly supplied by falling snow, and the ice flows down to the coast where great bergs calve into the ocean or it melts. It's a big, slow-speed hydrological cycle.

This is actually the second generation of the digital BEDMAP. The first version, which was produced in 2001, incorporated 1.9 million measurement points. For BEDMAP2, the sampling has been raised to more than 27 million points on a grid spacing of 5km.

The source data comes from a range of international partners. The project has benefited greatly from the large number of airborne radar surveys that have been flown in recent years.

Unlike rock, ice is transparent to radar. So by firing microwave pulses through the overlying sheet and recording the return echoes, scientists can plot both the depth of the rock bed and - by definition - the thickness of the ice covering.

Instrumented planes, guided by GPS, will now fly back and forth across the ice in campaigns that can last weeks at a time. 

Perhaps the most publicised of these recent efforts was the multinational expedition in 2007/2008 to map the Gamburtsev mountains. This range is the size of the European Alps with the tallest peaks reaching 3,000m above sea-level - and yet they are still hidden below more than a 1,000m of ice.

It is clear from BEDMAP2 that there are still two big areas of the continent that need improved coverage. One of these lies between the Gamburtsevs and the coast; the other runs south of the Shackleton mountain range towards the South Pole.

         An animated view revealing great mountains and deepest depressions