The Blood Falls in the Antarctica were discovered in 1911 by geologist Griffith Taylor. For more than a century, scientists have wondered why the waterfall is mysteriously tinted red. In 2006, a group of scientists said red algae gave the flowing water its red color. A new study has traced the origin to a large source of briny seawater trapped under a glacier. Findings of the study were described in the Journal of Glaciology.

Blood Falls Antarctica
Image Source: Wikimedia Commons / National Science Foundation / Peter Rejcek

What gives the Blood Falls its reddish tint?

Scientists at the University of Alaska, Fairbanks and Colorado College explained that the Blood Falls is fed by a source of saltwater trapped under the glacier for more than a million years. The Blood Falls is located in the McMurdo Dry Valleys of Antarctica. It flows out from the Taylor Glacier to the West Lake Bonney. The flow of red water had long been a mystery because the mean temperature is negative 17 degrees Celsius and there is little glacial melting on the surface.

The makeup of the brine helps explain why it flows rather than freezing. Scientists said the saltwater remains liquid in the englacial and subglacial environments because of the heat generated by water when it freezes. The high salt content also helps keep it in the liquid state because saltwater has a lower freezing point than pure water. The iron-rich brine in the subglacial water gives the Blood Falls its reddish tint.

Jessica Badgeley, the lead author of the study, said in a statement that the saltwater comes to the surface on the northern side of Taylor Glacier. The red color results when the iron-rich brine comes in contact with atmospheric oxygen. The red tint remained a mystery until now due to the lack of evidence for the flow of englacial saltwater from the subglacial source.

Yes, liquid water can exist inside a glacier

Jessica Badgeley said the discovery was made possible by the high salt content because the salts amplified the contrast with the fresh glacier ice. Scientists used the radio-echo sounding to track the brine. The technique involved using two antennas to study glaciers and ice sheets in the Antarctica. One antenna transmits electrical pulses and the other one receives signals.

Researchers moved the antennas in “grid-like patterns” around Taylor Glacier to see what was under the ice. They were surprised to find large rivers and lakes with flowing water. Many previously believed that liquid water cannot exist inside the glacier. The new study shows that liquid water can indeed exist inside a cold glacier. Scientists said the Taylor Glacier was now the “coldest known glacier” to have persistently flowing water. Brine content and water temperature were found to be related to each other.