Mid-summer snow-free albedo across the Arctic tundra was mostly stable or increased over the past two decades

• Published in: Environmental Research Letters
• Main Authors: Elena Plekhanova, Jin-Soo Kim, Jacqueline Oehri, Angela Erb, Crystal Schaaf, Gabriela Schaepman-Strub
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publishing 2022
• Subjects: albedo; Arctic; tundra; vegetation; spectral albedo; climate models; Environmental technology. Sanitary engineering; TD1-1066; Environmental sciences; GE1-350; Science; Q; Physics; QC1-999; Tundra
• Online Access: https://doi.org/10.1088/1748-9326/aca5a1; https://doaj.org/article/3802875c974a4a5fbe12ebea53b84b63

Arctic vegetation changes, such as increasing shrub-cover, are expected to accelerate climate warming through increased absorption of incoming radiation and corresponding decrease in summer shortwave albedo. Here we analyze mid-summer shortwave land-surface albedo and its change across the pan-Arctic region based on MODerate resolution Imaging Spectroradiometer satellite observations over the past two decades (2000–2021). In contrast to expectations, we show that terrestrial mid-summer shortwave albedo has not significantly changed in 82% of the pan-Arctic region, while 14% show an increase and 4% a decrease. The total median significant change was 0.014 over the past 22 years. By analyzing the visible and near-/shortwave-infrared range separately, we demonstrate that the slight increase arises from an albedo increase in the near-/shortwave infrared domain while being partly compensated by a decrease in visible albedo. A similar response was found across different tundra vegetation types. We argue that this increase in reflectance is typical with increasing biomass as a result of increased multiple reflection in the canopy. However, CMIP6 global land surface model albedo predictions showed the opposite sign and different spatial patterns of snow-free summer albedo change compared to satellite-derived results. We suggest that a more sophisticated vegetation parametrization might reduce this discrepancy, and provide albedo estimates per vegetation type.