Blood Falls

Blood Falls is an outflow of an iron oxide-tainted plume of saltwater, flowing from the tongue of Taylor Glacier onto the ice-covered surface of West Lake Bonney in the Taylor Valley of the McMurdo Dry Valleys in Victoria Land, East Antarctica.

The water is sourced from a brine lake beneath the Taylor Glacier, which over time has picked up iron from the underlying bedrock. The iron rich brine, which is under high pressures due to the overlying glacier, is injected through fissures in the glacier as it attempts to make its way toward lower pressures.

One would initially assume the water should be frozen in place as it sits below a thick column of ice. However, several factors allow the water to remain as a liquid. One is the release of latent heat associated with water freezing, this low amount of heat contributes to keep the water above freezing temperature. 

 In addition, water super-saturated in salt freezes at a lower temperature than fresh water. This is the exact reason cities salt roads in preparation for a winter storm. Lastly, the high pressures at the base of the glacier will have a small impact in reducing the temperature at which water freezes.

Sources : Google Images & wikipedia