What’s really in Antarctica’s mysterious blood falls

Blood
Falls^[1], named for its ruddy
color, is not in fact a gush of blood from some unseen
wound.

The color was initially chalked
up^[2] to red algae, but a
study^[3] in the Journal of
Glaciology has uncovered its true origin using radar to scan the
layers of ice from which the river pours.

The discovery came at the hands of a team of scientists,
including National Geographic emerging explorer Erin C
Pettit^[4].

Located in Antarctica’s McMurdo Dry Valleys, the falls pour
forth from Taylor Glacier, and the liquid bubbles up from fissures
in the glacier^[5]’s surface. The flow was
previously a mystery, as the mean temperature is 1.4 degrees
Fahrenheit (-17 degrees Celsius) and little glacial melting can be
seen at the surface.

Imaging from underneath the glacier helped solve the mystery,
revealing a complex network of subglacial rivers and a subglacial
lake—all filled with brine high in iron, giving the falls its
reddish tint.

According to the study, the makeup of the brine explains the
fact that it flows instead of freezes.

“The brine remains liquid within the subglacial and englacial
environments through latent heat of freezing coupled with elevated
salt content,” the study explains.

The lake under the glacier has an unusually salty consistency,
and because saltwater has a lower freezing point than pure water
and releases heat as it freezes, it melts the ice, enabling the
rivers to flow.

This means that the glacier can support flowing water and also
that this is the coldest glacier on Earth with constantly flowing
water—though this water is so filled with iron that it looks like
something else entirely.

The study also measured the amount of iron-rich brine in the
river water and found the brine content increased as the
measurements drew closer to the falls.

Water temperature and brine content were also found to be
related: Cracks of various sizes in the glacier let brine into the
glacier. Then the brine (pictured here in red to represent the
amount of iron present in the water) begins to freeze, and the
latent heat warms the ice around it, upping the brine concentration
in the center of the cracks.