image: (a) geographical distribution of the annual average of ∆R ; (b) the monthly variations of ∆CRE at the TOA and the SFC, with the error bars representing the standard deviation; (c) the monthly average trends of SIC and SA (histogram) and the variation of ∆R (gray line), with the shadow representing the standard deviation of ∆R .
Credit: ©Science China Press
The rate of Arctic surface warming has reached 2 to 4 times the global average—a phenomenon known as "Arctic amplification." Traditional theories suggest that snow and ice melt reduce surface albedo, leading to greater absorption of solar radiation and forming a positive "ice-albedo feedback" loop. However, a research team led by Professor Chuanfeng Zhao from Peking University has uncovered a key regulatory role played by clouds in this process, based on CERES satellite data from 2000 to 2020 and simulations from the CMIP6 climate models. The study found that even when cloud properties remain unchanged, the melting of snow and ice can trigger an enhancement in the cloud short-wave cooling effect. “This, in turn, partially slows down further melting of snow and ice, offering a new perspective on the self-regulating mechanisms of the climate system”, says Mr. Annan Chen, a PhD candidate at Peking University.
Based on satellite observations from 2000 to 2020 and CMIP6 climate model data, the analysis shows that Arctic snow and ice coverage decreased by 0.016 per decade. This triggered an increase in the cloud short-wave radiative cooling effect, leading to radiative cooling at the top of the atmosphere and surface reaching -1.25 ± 0.49 and -0.21 ± 0.20 W/m² per decade, respectively. As a result, the average annual sea ice melting rate got slowed by 3.45 cm, with localized reductions up to 10 cm per year (Figure 1). This effect peaks during the polar day in June and July. Model projections show that under the SSP585 scenario, Arctic sea ice coverage will decrease by 83% by the year 2100, with the cloud cooling effect continuing to intensify (Figure 2). The study reveals the co-evolution mechanism between clouds, snow/ice coverage, and surface albedo. At the same time, it highlights that under the influence of Arctic amplification, the trend of snow and ice loss remains irreversible.
Professor Chuanfeng Zhao from Peking University is the corresponding author of the study. The first author is PhD candidate Annan Chen. Co-authors include Professors Jing Li and Qinghong Zhang, Assistant Professor Yan Yu, postdoctoral researchers Haotian Zhang and Yikun Yang, and PhD candidate Jiefeng Li.
See the article:
Weakened snow and ice melting by enhanced cloud short-wave cooling effect in the Arctic
https://doi.org/10.1093/nsr/nwaf116
Journal
National Science Review