Along with the high spectral resolution of the recent and upcoming spaceborne imaging spectrometers described above, hyperspectral sensors mounted on UAVs may be able to detect subtle spectral features such as algae absorption in snow. Current and upcoming spaceborne imaging spectroscopy missions, such as the Italian Space Agency’s PRecursore IperSpettrale della Missione Applicativa, Hyperspectral PRecursor of the Application Mission (PRISMA), the German hyperspectral Environmental Mapping and Analysis Program (EnMAP) and NASA’s Surface Biology and Geology (SBG) mission, feature instruments with high spectral resolution, such as 30 m ground sampling distance, which is sufficient to detect algae in snow 47. However, satellite images are less likely to have closely corresponding ground validation data and usually have limited spectral or spatial resolutions sufficient to capture the snow algae. The Takeuchi index has been applied to other satellites, including Landsat 46 and Sentinel-2A 44. One of the most prevalent indices developed thus far is the red (610–680 nm) to green (500–590 nm) SPOT satellite reflectance ratio developed by Takeuchi et al. The current research on the remote detection of snow algae has largely been focused on using satellite images 40, 41, 42, 43, 44, 45. One of the first studies to remotely estimate snow algae was conducted by the National Air and Space Administration/Jet Propulsion Laboratory Airborne Visible Infrared Imaging Spectrometer (AVIRIS) flown on a twin otter in the Sierras 40. While there have been studies that use the UAV to study glacier algae on the Greenland Ice Sheet 38, 39, the remote detection of snow algal blooms in mid-latitudes using UAVs have received little attention. This approach has been applied as a means to evaluate snow and glacier ablation 21, 22, 23, 24, assess glacier dynamics 25, 26, 27, 28, 29, and retrieve snow depth 30, 31, 32, 33, 34, 35, 36, 37. The advances in Structure-from-Motion (SfM) technology allow researchers to construct high-resolution digital elevation models (DEMs) from UAV imagery. Previous studies have utilized UAVs to evaluate a variety of research questions in the cryosphere. With the increasing capabilities of uncrewed aerial vehicles (UAV), we can evaluate the prevalence and albedo influence of snow algae across large, inaccessible areas. ![]() Quantifying the impacts of this reduced albedo across glaciers and snowfields would be prohibitive with in situ studies. These photoprotective pigments, primarily astaxanthin, color the snow red where they bloom and cause the albedo of the snow to decrease by around 20% 18, 19, 20. They develop colored photoprotective pigments to protect the cells from intense solar radiation present at the surface of the snowpack 15, 16, 17. Snow algae bloom on the surface of the snowpack during the summer months when there is sufficient interstitial water to provide the necessary habitat for the algae. Even a small-scale reduction in snow cover extent or snow albedo will drastically reduce the protective properties of the cryosphere and contribute to a warming climate 2, 3.Ī variety of microorganisms grow in snowpacks across the cryosphere, including bacteria 4, 5, annelids 6, 7, chytrids 8, fungi 9, and algae 10, 11, 12, 13, 14. ![]() Clean snow surfaces reflect as much as 99% of incoming solar radiation, protecting our atmosphere from warming 1. The highly reflective snow surfaces of the world contribute substantially to maintaining the energy balance of the earth.
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