To most observers, Antarctica is a barren wasteland, a frozen continent best known for its endless icescapes and harrowing stories of survival. But when flying over the white continent, John Priscu sees something different: a rich network of raging rivers and enormous lakes, an entire hydrological system that just happens to be covered by ice.
Through the magic of radar imagery, scientists have been able to see through the ice -- which can reach thicknesses of several thousand of meters -- to the dramatic landscape of craggy peaks and deep valleys beneath the glaciers. There, sandwiched between the ice and rock, river systems that rival the Amazon in spatial extent feed lakes and, possibly, fuel an entire hidden biosphere.
In a presentation to the Center for Dark Energy Biosphere Investigation, Priscu, a Professor of Ecology at Montana State University, highlighted a few of his favorite subglacial lakes, sites where exotic chemical mixtures and unique physical realities converge to create bizarre environments.
At the foot of Taylor Glacier, an icefall several stories tall is streaked with orange and red bands, earning the name Blood Falls. “Taylor glacier used to be well above an ancient coastline,” Priscu notes, “and when the climate changed, the ocean water receded, the glacier advanced, and it trapped salty marine water under the ice.” Over time, the subglacial water lost its oxygen and got saltier, creating a viscous brine that is liquid -- and thus more available to enterprising microbes -- down to -10°C. Water emerging from the base of the glacier contains abundant Fe2+ due to anaerobic microbial metabolism; when the solution emerges, it’s quickly oxidized, painting the icefall red with rust. But mysteries remain: “We don’t understand why the water comes out at this spot,” concedes Priscu. “And where did all of the iron come from? What kinds of metabolism occur underneath the glacier? There’s got to be something going on.”
Satellite imagery also provides evidence of an active hydrologic cycle. At Adventurer Trench, the ice has moved up and down as subglacial lakes fill and drain. Photos taken two years apart reveal a nine-meter elevation change of the ice. The flat surface indicates a lake far below (“anything less than a 10-degree angle of ice on the surface strongly suggests you’ve got a lake,” according to Priscu), and the elevation change points to an enormous flood that swelled the lake’s volume.
To Priscu, the detection of microbes in glacier outflow and the first forays into subglacial lakes is just the tip of the proverbial iceberg. “The whole bottom of the Antarctic ice sheet is wet,” he explains. “It’s our planet’s largest wetland, and it’s got all of the biogeochemistry to go along with that.” Life could even exist throughout the glaciers themselves, inhabiting microscopic niches between crystals of frozen water, where thin films of liquid persist. It’s been shown before, after all, but the pervasiveness of the phenomenon in the world’s largest ice sheet remains to be seen.
Priscu has been conducting research in Antarctica for 29 years, and he's begun to think differently about the world's highest, coldest continent. "Growing up, you’re indoctrinated as a scientist into thinking that Antarctica is just a big benign block of ice,” Priscu recalls. “We wanted to change that paradigm; it just doesn’t make sense, that we can have so much real estate on our planet and so much fresh water, that it couldn’t have life.”
