Blood Falls may sound like the title of a thriller novel, but it's actually an Antarctic mystery that has puzzled scientists for over a century. The origin of the blood-red water that flows from Taylor Glacier in East Antarctica has puzzled explorers since it was first seen in 1911, but researchers from the University of Alaska Fairbanks and Colorado College say that they have discovered the source.

Discovered by Australian geologist Griffith Taylor, Blood falls is one of the more spectacular, if not a trifle gruesome, features of the frozen continent. Pouring out of the face of the 54 km (34 mi) long glacier, the contrast between the bluish-white ice and the blood-red water flowing out makes it look as if there's some Lovecraftian monster embedded in the ice that had better be left where it is.

In fact, the reddish color is due to the salt water that make up the falls being tainted with iron minerals. As the water reaches the surface periodically and is exposed to air, the iron turns into iron oxide, giving it that crimson hue. The question is, where is this iron-rich saltwater coming from?

To find out, a research team led by University of Alaska Fairbanks glaciologist Erin Pettit carried out a radar survey of Taylor Glacier. Since saltwater has a different radar profile from freshwater ice, the contrast would make the geophysical survey relatively easy.

For the survey, one team carried a transmitter over the glacier in a grid pattern while a second team followed with a receiver antenna. As the signals bounced off whatever was below, an accurate map was gradually built up.

It was found that the saltwater came from a deposit inside the ice that had been trapped there for a million years. More surprisingly, that saltwater was actually flowing through the ice in subzero antarctic temperatures instead of freezing solid. This is because the freshwater ice is heating the saltwater.

"While it sounds counterintuitive, water releases heat as it freezes, and that heat warms the surrounding colder ice," says Pettit. "Taylor Glacier is now the coldest known glacier to have persistently flowing water."

The research was published in the Journal of Glaciology.

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