By Kimberly Mann Bruch and Sneha Lele
Algae that grows on snow in the Pacific Northwest have now been linked to increasing snowmelt, according to research conducted on Mount Baker in the North Cascades, Washington. The role of algae in snowmelt has previously been overlooked due to a lack of evidence to support correlations between the two. However, Alia Khan and her team at Western Washington University have found that algae are now linked to significantly more snow melt when compared to clean snow.
Alia Khan and her team collect snow samples to test specific albedos on large lands of algae covered snow.
Credit: Mauri Pelto
Often a red color, algae in the Pacific Northwest generally bloom on snow in the summer - causing it to be a central driver of snowmelt - absorbing large amounts of solar radiation in visible wavelengths. This, in turn, causes the albedo (reflectivity) of the snow to decrease.
“Algae biomass in the snow and albedo reduction are well-correlated across the visible spectrum,” said Khan, a professor at Western Washington University and research affiliate at the National Snow and Ice Data Center (NSIDC). “Relative to clean snow, visibly green patches reduce snow albedo by around 40 percent and red patches by 20 percent.”
Khan said that as snow cover decreases, the bare ice of glaciers are exposed earlier in the summer. She said that meltwater from snow and glaciers are important for stream and river temperature regulation, which greatly impact the health of downstream ecosystems and wildlife.
“Changes to the timing and magnitude of spring snowmelt, as well as summer ice melt, have negative consequences for salmon spawning habitat,” Khan said. “which greatly impacts downstream communities such as the Nooksack Tribe and Lummi Nation, for whom salmon hold great cultural and subsistence importance..”
To conduct their research, Khan and her team used uncrewed aerial vehicles (UAVs) affixed with multispectral cameras to help them detect snow algae across large, inaccessible areas. She described the UAVs as “game changers” for mapping snow algae and hard to access parts of the cryosphere, stating that their methods are applicable to additional hard-to-reach sites - such as snow on glaciers that are heavily crevassed.
“Understanding the impact of snow algae on snowmelt timing is important in order to improve melt and water resource models,” Khan said. “Not only are our techniques applicable to other watersheds in the Pacific Northwest, but also other regions of the cryosphere where snow algae are also prevalent.”
The scientists’ study, titled Albedo change from snow algae blooms can contribute substantially to snow melt in the North Cascades, USA, was published in Nature’s Communications Earth and Environment journal.