Glaciology: Salt beneath Antarctica's dry valleys

A new airborne instrument has detected vast aquifers of salty groundwater beneath Antarctica's dry valleys, the coldest desert on Earth. It may harbour a microbial ecosystem of creatures adapted to live in brine at temperatures well below the normal freezing point of water.

A US team made the discovery by flying a Danish electromagnetic mapping sensor called SkyTem, suspended from a helicopter, over the McMurdo Dry Valleys - the largest ice-free region of Antarctica. The results appear in the journal Nature Communications.

The aquifers are quite distinct from the well-known subglacial lakes, such as Lake Ellsworth and Lake Vostok, which are trapped more than 3km below the Antarctic ice cap. The new discoveries are much closer to the surface - less than 400m deep.

"These unfrozen materials appear to be relics of past surface ecosystems and our findings provide compelling evidence that they now provide deep subsurface habitats for microbial life despite extreme environmental conditions," says lead author Jill Mikucki of the University of Tennessee.

The brines form an extensive system of interconnected aquifers, which flow slowly beneath the dry valleys from about 20km inland to the Ross Sea coastline. Their dissolved salts may be an important source of minerals for marine life.

Some of the brine also seeps out of the Taylor Glacier at the head of the dry valleys, where dissolved iron stains the ice red at a bizarre site known as Blood Falls. This seepage hosts an active microbial community that scientists believe may be representative of the entire subsurface ecosystem.

Photograph: Karen Hilton

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