A strange episode of the so-called “watermelon snow” in the Alps this year certainly seems picaresque. Unfortunately, the salmon-tinged landscape is actually a bad omen for Earth’s climate.
Watermelon snow, which takes on a reddish-pink hue, is caused by snow algae. While most freshwater algae thrive in warmer temperatures, watermelon snow is cryophilic, which means that organisms thrive in cold temperatures. Algae are red due to their carotenoid pigment.
Scientific concern about the increasing presence of algae in the Alps arises because the red color increases the absorption of sunlight in snows, which means that they will melt earlier and exacerbate the impact of climate change. Biagio Di Mauro, researcher at the Institute of Polar Sciences of the National Research Council of Italy, explained to Earther that the algal blooms in question here are Chlamydomonas nivalis, It is found not only in the Alps but also in both polar regions, including Greenland and Antarctica.
“A classic reminder of how uncertainty is not our friend,” Dr. Michael E. Mann, a distinguished professor of atmospheric science at Penn State University, told Salon by email. “In this case, we are seeing amplifying feedback in which the biological darkening (due to the growth of algae on the surface of the melted ice) leads to greater solar absorption by the ice and even faster melting. To this We call it ‘positive feedback’ but it is anything but positive. It reflects a process that is leading to faster melting of glaciers than our simple models predict. “
Ken Caldeira, an atmospheric scientist in the Department of Global Ecology at the Carnegie Institution for Science, expressed similar thought by email and commented that “photosynthetic organisms are designed to absorb sunlight. A small fraction of the energy of sunlight It is used to make carbohydrates, but most go into warming the body and its local environment. If that body lives in the snow, the snow is likely to melt. “
He also described how he and other scientists wanted to experiment with how black carbon influences melting rates, but had to abandon the project because the experiments are difficult to do.
“You need a lot of control parcels and a lot of experimental parcels, and you need the parcels and the snow on them to be as uniform as possible, and then you have to be uniform when spreading the particles in the snow,” said Caldeira Salón. “And they need similar conditions of light and temperature, etc. Then you have to measure many things: amount of incoming light, amount of reflected light, amount of melting, snow temperature, air temperature, etc. Surprisingly, few experiments have done everything. this.”
Kevin Trenberth, a distinguished senior scientist in the Climate Analysis Section of the National Center for Atmospheric Research, referred to his own research among penguin colonies in Antarctica.
“I was surprised when I went down there by the snowy snow resulting from hundreds of thousands of guano penguins,” Trenberth explained. “Pink certainly changes the albedo (reflectivity). This source or the source of algae is not unique either. Dust in the northern hemisphere deposited in Greenland and ice also decreases albedo and probably contributes to faster melting. However, this is a very small effect overall. but it sure doesn’t help. “
This is not the first time that climate change appears to be related to changes in snow color. In May, researchers from the University of Cambridge and the British Antarctic Survey discovered that green snow algae are turning most of the snow in Antarctica green.
