French scientists investigate rise in Alpine snow turning red, dubbed ‘glacial blood’ by locals

© Jean-Gabriel VALAY/JARDIN DU LAUTARET/UGA/CNRS
Leah Sinclair15 June 2021

French scientists have reported a rise in Alpine snow turning from white to pinkish red, warning the colour change could indicate accelerating climate change.

The Alps are covered with a thick blanket of white snow from winter to spring but as summer approaches, the slopes warm and some turn various shades of orange and red.

While it’s been dubbed by locals as “sang de glacier” or “glacier blood” and has been observed for centuries, French researchers say they change in colour to protect themselves from ultraviolet light and that they may be proliferating due to global warming.

Eric Maréchal the head of a plant physiology lab at Grenoble Alpes University and a leader of the project told the Telegraph: “When you ski, you slide over these micro-algae but you don’t notice them because they are green and less numerous.

“It’s when the sun’s rays become very strong, starting in May, that they create a shield of red molecules that play the same role as sun cream.”

Alongside experts from CNRS, CEA, Meteo France and Inrae, Mr Maréchal decided to assess how they survive and why blood glaciers have flourished in recent years.

To do so, they took samples from soil found in five peaks at different altitudes to create a snow bloom map.

After studying their DNA, they found a variety of algae including one key blood-red type appropriately named Sanguina, which only grows above 2,000m (6,500ft).

Here, the experts believe that the snow algae may be a marker of climate change.

"The first is that the algae are photosynthetic and live off carbon dioxide, which is positive for them but causes an imbalance in nature," Mr Maréchal told the paper.

"Second, all other blooms in nature, such as algae in lakes, are linked to human activity and emissions of nitrates and phosphates. We believe this is the case here and that they reach the snow in high altitude rather like acid rain."

"The third reason is that all mountain residents have noticed that whereas these blooms were pretty rare in the past, they are now observable every year."

The red algae’s rise could also accelerate the shrinking of glaciers and snow caps, he said.

“Unfortunately, the red coloration favours the melting of glaciers by getting rid of the snow’s ‘albedo’ effect; it reflects the sun’s rays less, and heats up and melts more quickly,” said Mr Maréchal.

“In areas without glaciers, it shortens periods of snow cover with cascading consequences on (water) supply to dams, farming irrigation in the plains.

"Climate change is underway and as scientists, there is no point crying about it,” he said.

“Our job is to try and understand it as we are observing huge change in our lifetimes. I personally find these red blooms marvellous as it’s nature’s way of adapting."

The researchers, who have just had their preliminary findings published in Frontiers in Plant Science, have taken some species back to the lab to develop their investigation into what causes the blood-red blooms.

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