Watermelon Snow Spreads Across North America, Threatens Future of Frozen Glaciers

Pink-tinted snow has become more widespread than previously thought. A study suggests that this phenomenon can be found all over the glaciers of North America.

What is Watermelon Snow?

Watermelon snow refers to a phenomenon where the snow on the ground is tinged with a red and pinkish hue. Also known as 'glacier blood,' it is caused by the blooming of pink-colored algae called Chlamydomonas nivalis.

This species of green algae contains a secondary red carotenoid pigment in addition to chlorophyll. Unlike most species of fresh-water algae, Chlamydomonas nivalis appears to be cold-loving (cryophilic) and thrives in freezing water.

Watermelon snow and its effects on shrinking glaciers are observed worldwide. Captain John Ross first followed it in the Arctic in 1818 when he led four English ships sent to the Arctic Circle for the first North-West Passage expedition.

Growing Threat to Glaciers

According to a study entitled "Satellite mapping of red snow on North American glaciers," it was discovered that this phenomenon has crept across 5% of the total glacier area in northwestern North America. This includes British Columbia, Idaho, Washington State, Alberta, Alaska, and Montana mountains.

Some individual glaciers were found to have 65% of their area covered in pink algae during a single season. The researchers estimate that this caused as much melting as a 1.2-inch (3 centimeters) average meltwater, equivalent across the glacier's surface.

According to Simon Fraser University molecular biology and biochemistry professor Lynne Quarmby, ice is melting by absorbing dark colors. As the glacier turns pink, it becomes much more prone to melting since the colored algae cause sunlight to be absorbed rather than reflected, heating the surrounding ice. Aside from this, liquid water is also darker than the white color of snow and ice, so it is also very good at reflecting the incoming energy out into space.

The algae under study grow on the snow overlying frozen lakes, rocks, and glaciers. Since their cells need liquid water to grow, this rapid melting stimulates more growth, darkening, and absorption of incoming energy from the Sun.

Researchers discovered this using thousands of satellite images captured between 2019 and 2022. Out of 8,700 glaciers examined in this study, 4,552 showed presence of Chlamydomonas nivalis algae.

Compared to the impacts of climate change and global warming, the effect of the algae on the glacier and snowpack is considered mild. The glaciers are melting rapidly because of climate change, causing the algae to disappear altogether.

Watermelon snow is not exclusive to the Arctic since it can also be found in New Zealand, the Alps, Mount Olympus, and Antarctica. As the glaciers shrink further, the melting effect of the remaining watermelon snow algae may damage the snow and ice more. As the snowpack decreases, the algal blooms become increasingly concentrated and smaller, according to Utah State University ecologist Scott Hotaling.