Bleeding Glacier

Antarctica's Dry Valleys are the most arid places on Earth, but underneath their icy soils lays a vast and ancient network of salty, liquid water filled with life, a new study finds.

Now, for the first time, scientists have traced the water underneath Taylor Glacier to learn more about the mysterious Blood Falls. In the process, the researchers discovered that briny water underlies much of Taylor Valley. The subsurface network connects the valley's scattered lakes, revealing that they're not as isolated as scientists once thought. The findings were published today (April 28) in the journal Nature Communication.

Why it is happened?

There is different reason or idea….  But I found main 2 reasons

Microbial ecosystem

Chemical and microbial analyses both indicate that a rare sub glacial ecosystem of autotrophic bacteria developed that metabolizes sulfate and ferric ions. According to geomicrobiologist Jill Mikucki at the University of Tennessee, water samples from Blood Falls contained at least 17 different types of microbes, and almost no oxygen. An explanation may be that the microbes use sulfate as a catalyst to respire with ferric ions and metabolize the trace levels of organic matter trapped with them. Such a metabolic process had never before been observed in nature.

A puzzling observation is the coexistence of Fe2+ and SO42− ions under anoxic conditions. No sulfide anions (HS−) are found in the system. This suggests an intricate and poorly understood interaction between the sulfur and the iron biochemical cycles.

In December 2014, scientists and engineers led by Mikucki returned to Taylor Glacier and used a probe called Ice Mole, designed by a German collaboration, to melt into the glacier and directly sample the brine that feeds Blood Falls.

Geochemistry

Poorly soluble hydrous ferric oxides are deposited at the surface of ice after the ferrous ions present in the unfrozen saltwater are oxidized in contact with atmospheric oxygen. The more soluble ferrous ions initially are dissolved in old seawater trapped in an ancient pocket remaining from the Antarctic Ocean when a fjord was isolated by the glacier in its progression during the Miocene period, some 5 million years ago when the sea level was higher than today.

Unlike most Antarctic glaciers, the Taylor glacier is not frozen to the bedrock, probably, because of the presence of salts concentrated by the crystallization of the ancient seawater imprisoned below it. Salt cryo-concentration occurred in the deep relict seawater when pure ice crystallized and expelled its dissolved salts as it cooled down because of the heat exchange of the captive liquid seawater with the enormous ice mass of the glacier. As a consequence, the trapped seawater was concentrated in brines with salinity two to three times that of the mean ocean water. A second mechanism sometimes also explaining the formation of hyper saline brines is the water evaporation of surface lakes directly exposed to the very dry polar atmosphere in the McMurdo Dry Valleys. The analyses of stable isotopes of water allow, in principle, to distinguish between both processes as long as there is no mixing between differently formed brines.

Hyper saline fluid, sampled fortuitously through a crack in the ice, was oxygen-free and rich in sulfate and ferrous ion. Sulfate is a remnant geochemical signature of marine conditions while soluble divalent iron likely was liberated under reducing conditions from the sub glacial bedrock minerals weathered by microbial activity.

see the video of bleeding glacier