Report by Paridhi Agarwal
People in the Utah mountains have been noticing pink and red colors in the snow for the past week. People have started calling this pink snow “watermelon snow”. This type of snow has been commonly observed during the summers in coastal polar regions of Western United States including Sierra Nevada in California, Utah, Montana, Wyoming, Washington, and Oregon. It has also emerged in Alaska.
How is it caused?
Scientists have found that “watermelon snow” is caused by a green alga called Chlamydomonas nivalis that contains a red pigment in addition to chlorophyll.
These algae live and bloom in colder environments of snow or ice.
Blooming, a part of the algae’s reproductive stage, is the process in which a red or secondary pigment gets generated which darkens the algae’s cells. This pigment shields the cells from the sun’s ultraviolet rays and serves as an ultraviolet ray blocker. There are many types of algae which live in the snow and ice and turn it into various colours such as purple, orange, and green.
How is pink snow a threat to the environment?
The harmful effect of watermelon snow on glacial regions has been termed “bio-albedo feedback”. Albedo is the fraction of sunlight that is reflected by a body. This pink-coloured snow reduces the albedo of the snow (ability of snow to reflect light). This makes the snow heat up more quickly and may contribute to faster melting of snow and glaciers.
References:
Lutz, S., Anesio, A., Raiswell, R. et al. The biogeography of red snow microbiomes and their role in melting arctic glaciers. Nat Commun 7, 11968 (2016). https://doi.org/10.1038/ncomms11968
Image credit: Image tweeted by @hmvncbzc4