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

• Main Authors: Plekhanova, Elena, Kim, Jin-Soo, Oehri, Jacqueline, Erb, Angela, Schaaf, Crystal, Schaepman-Strub, Gabriela
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publishing 2022
• Subjects: Institute of Evolutionary Biology and Environmental Studies; Global Change and Biodiversity; 570 Life sciences; biology; 590 Animals (Zoology); Public Health; Environmental and Occupational Health; General Environmental Science; Renewable Energy; Sustainability and the Environment; Arctic; albedo; Tundra
• Online Access: https://www.zora.uzh.ch/id/eprint/223775/; https://www.zora.uzh.ch/id/eprint/223775/1/Plekhanova_et_al_2022_Environ._Res._Lett._10.1088_1748_9326_aca5a1.pdf; https://doi.org/10.5167/uzh-223775; https://doi.org/10.1088/1748-9326/aca5a1

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 MODIS 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 cumulative 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 climate 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.