Coloree chall
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They control the balance of the Earth's ice sheets and are acutely sensitive to climate change.
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Their quantification facilitates predictions of meltwater runoff as well as distribution and availability of fresh water. Snow and ice melt processes are a key in Earth's energy-balance and hydrological cycle. We expect that the study of LAPs in snow and ice will grow in the future, and more data and models will be developed in order to describe the hydrological and climatic effect of LAPs in the cryosphere. We divided these methods in proximal (field spectroscopy) and remote (aerial surveys and satellite data) sensing. Lastly, we described different observation approaches for studying LAPs impact on snow and ice. We divided LAPs in non-carbonaceous (mineral dust) and carbonaceous (biogenic particles and cryoconite), and we created a set of radiative transfer simulations for each category. Later in the chapter, we provide a classification of LAPs based on their optical features. We show that snow and ice albedo reduction due to LAPs deposition or resurfacing is a global phenomenon with regional characteristics. In this chapter, we review the different processes occurring at middle latitudes, tropical areas, and polar regions. Worldwide, snow and ice can be polluted with impurities also referred as Light-Absorbing Particles (LAPs). Our results suggest that the extent, duration, and radiative forcing of snow algal blooms are sufficient to enhance glacial melt rates. This is equivalent to an average snow algal radiative forcing of 8.25 ± 1.6 W/m² through July and August. Snow algae caused an additional 5.25 ± 1.0 × 10⁷ J/m² of solar energy to be absorbed by the snowpack in July–August, which is enough energy to melt 31.5 cm of snow. At their peak in late July the blooms reduced albedo by 0.04 ± 0.01 on average. Algal abundance increased through July, after which the red snow algal bloom area decreased due to snow cover loss. Blooms were first detected following the onset of above-freezing temperatures in early July and persisted for about two months. The maximum extent of snow algal bloom cover was 1.4 and 2.0 km² respectively, about one third of the total surface area of the two glaciers, making these among the largest contiguous bloom areas yet reported. We applied the field calibrated index to Sentinel-2, Landsat-8, and MODIS/Terra images to monitor snow algae on the Vowell and Catamount Glaciers (Purcells, British Columbia) in summer 2020. We calibrated an established index by comparing snow algal field spectroradiometer measurements with direct counts of algal cell abundance in British Columbia, Canada. Red snow algal blooms reduce albedo and increase snowmelt, but little is known of their extent, duration, and radiative forcing.