Algal blooms, which are rapid proliferations of tiny photosynthetic organisms known as algae, are intensifying as a result of human-driven climate change. While most of these blooms occur in balmy freshwater or marine environments, there’s a special type of algal bloom that thrives in cold snowy conditions atop mountain peaks and in glaciers.
Known as “red snow” or “blood snow” because of its distinctive color, these algae species dye their habitats a darker hue, causing snow to absorb more sunlight and melt faster. This accelerated snow melt reduces the reflectivity, or albedo, of the snow, which can exacerbate climate change. In this way, red snow is potentially both a beneficiary of global warming and a catalyst of it, which is why scientists want to better understand the global distribution of these algae and their impact on Earth’s declining frozen regions, called the “cryosphere.”
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Now, scientists led by Yukihiko Onuma, a researcher at the University of Tokyo, have created an updated model that links the appearance of red snow to specific snowmelt and snowfall patterns and simulates where this algae is most likely to appear in the cryosphere. The team’s work has the “potential to be used for global prediction of future red snow phenomena, which are likely to synchronize with global climate change,” according to a new study published in the Journal of Geophysical Research: Biogeosciences.
In an email, Onuma said that scientists are not yet sure of the exact correlations between red snow and climate change, but that “we imagine that the distribution of the red snow will change under global warming in the future.”
“Accordingly, the ecosystem in the cryosphere may change in the future too although further study is necessary,” he added.
The new study attempts to constrain this question, among others, by improving an existing model of red snow and testing out its performance using real-world data from 15 polar to alpine areas across the globe. The team then used that data to generate a global map that predicted where this algae was likely to appear, and linked it to specific snow and weather conditions.
The results revealed that the growth of red snow on the surface of snow or ice was disrupted by new snowfall that covered the blooms. As a result, the success of these algal populations was heavily influenced both by the duration of time that snowy habitats existed for it to thrive in, and by the patterns of new snow falling on top of it.
“Red snow phenomena worldwide have been often reported in summer when such snow conditions are more likely to occur,” said Onuma. “In addition to that, the snowfall amount during winter may be an important factor to control the duration of the red snow phenomenon because the duration of the remaining snow is highly related to it.”
Earth’s frozen habitats are among the most vulnerable to disruption as a result of human-driven climate change, so it’s essential to understand the full scope of the changes these cold places are currently undergoing. While red snow is a blossoming of life, it also signals the onset of a new normal that may affect many other species in these cold regions.
“We are currently interested in a future projection of the effects of biological activity on the cryosphere using our model proposed in this study,” Onuma concluded. “For example, we plan to evaluate the decrease in snow albedo and the increase in organic carbon caused by snow algal blooming on climate. Of course, we are interested in the inter-annual change in the red snow distribution worldwide too.”
