Watermelon snow, also called red snow, has been a fascination and a puzzle for a long time. Aristotle’s writings first mentioned it, explorers and mountain climbers marveled at it. But no one knew what it was exactly… This changed in 1818.
In 1818, Captain John Ross was the leader of a British Expedition to the Arctic region. The main goal was to find the Northwest Passage, which is a sea route connecting the northern Atlantic and Pacific Oceans through the Arctic Ocean. He did not succeed because of stormy weather, forcing him to go back. But he did not leave empty-handed.
While he was exploring the coast of Greenland, he noticed patches of red snow. Being as fascinated as every man before him has been, John and his crew decided to take samples and take them back for study.
The first conclusion was that the reddish coloration was caused by meteoric iron deposits. Seems like an plausible explanation, but not every place where watermelon snow has been found also has iron deposits. So the iron deposit theory does not hold up.
When John Ross published an account of his expedition later that year, it contained a botanical appendix by Robert Brown. In it, Robert Brown mentioned his thoughts on the watermelon snow. He thought the red color might be of organic origin, most likely algae. Later research would would prove him correct.
The microscopic creature responsible for the red color is Chlamydomonas Nivalis, a green algae. No mistake here, the algae is green, it only turns red when it’s comes to the surface and comes into contact with the sun’s UV-light.
The algae have a large number of UV-absorbing pigments, carotenoids. The pigments serve as protection for the sun’s UV radiation. The pigment also absorb heat, causing the ice around the algae to melt, providing it with liquid water. To give you an idea of the color, carotenoids are also found in carrots.
These algae may have an impact on climate change. The algae turn red when exposed to the surface. Lately, arctic ice is melting at a faster rate. This exposes more algae to the sun. Red snow doesn’t reflect sunlight as normal snow would. Instead, it absorbs more sunlight and heat from the sun, causing the ice to melt faster. The more ice is melting, the more algae will be exposed. This creates a snowball effect, increasing the velocity at which the ice is melting.
What does it taste like?
If it’s called watermelon ice, does it taste like a watermelon? Well, it’s said to smell a bit like a watermelon. Maybe it tastes like one too? But before you try it, let me tell you it’s known the have a laxative effect, so I’ll pass :).