Watermelon snow is a striking natural phenomenon where vast expanses of pristine white snow are tinged with an unexpected splash of color, resembling a spilled fruit drink. Often appearing as patches of pink, red, or orange, this unusual coloration can cover significant areas of snowfields, capturing the attention of hikers and explorers. It sparks curiosity about its origin and implications.
What is Watermelon Snow?
Watermelon snow is a natural phenomenon characterized by snow that has turned pink, red, or sometimes orange. This vibrant coloration often comes with a faint, sweet aroma, reminiscent of fresh watermelon. Despite the name and scent, it is not flavored snow. Walking on this colored snow can even leave bright red soles on shoes. This striking appearance happens when certain conditions are met in melting snowfields, and the color is not due to mineral deposits or pollution, but rather to microscopic life within the snow itself.
The Algal Origin
The vibrant coloration of watermelon snow stems from Chlamydomonas nivalis, a single-celled green alga. This alga contains chlorophyll, which gives most plants their green color, and a red carotenoid pigment called astaxanthin. These microscopic organisms are cryophilic, meaning they thrive in freezing water and extreme cold environments.
Chlamydomonas nivalis spends much of its life cycle dormant beneath the snow. As spring and summer arrive and the snow begins to melt, these algae become active. The red pigment, astaxanthin, acts as a natural sunscreen, protecting the algae from intense ultraviolet (UV) radiation present at high altitudes. This protective mechanism allows the algae to photosynthesize and survive in harsh conditions, giving the snow its characteristic pink or red hue.
Assessing the Danger
Consuming watermelon snow is not advised. While the algae themselves are not typically harmful in small amounts, the snow can collect various environmental contaminants like dust, bacteria, and pollutants. Ingesting these could cause digestive upset or other health issues.
The environmental impact of watermelon snow is a more significant concern. The dark pigment of the algae reduces the snow’s albedo, which is its ability to reflect sunlight. Clean, white snow reflects solar radiation, helping to keep the snowpack cool.
However, the dark red algae cause the snow to absorb more solar energy. This increased absorption of heat accelerates the rate at which snow and glaciers melt. This accelerated melting contributes to the overall decline of snowpacks and glaciers. This decline potentially impacts water resources for human use and contributes to rising sea levels.
Studies have shown that red algae patches can reduce snow albedo by approximately 20%. Green algae patches can reduce it by an even greater 40%.
Where It’s Found
Watermelon snow predominantly appears in high-altitude mountain ranges across the globe and in polar regions. It is observed in environments such as the Rocky Mountains, the Alps, and the Himalayas, as well as in the Arctic and Antarctic.
These cold-loving algae thrive in melting snowfields during warmer months, typically spring and summer, when there is sufficient sunlight and moisture. The phenomenon is common in areas where snow lingers at altitudes between 10,000 to 12,000 feet (3,000–3,600 m).