Possible contribution of Arctic sea ice decline to intense warming over Siberia in June

Abstract

Siberia experienced intense heat waves in 2020, and this unusual warming may have caused more wildfires and losses of permafrost than normal, both of which can be devastating to ecosystems. Based on observational data, this paper shows that there was an intense warming trend over Siberia (60°–75°N, 70°–130°E) in June during 1979–2020. The linear trend of the June surface air temperature is 0.90°C/10 yr over Siberia, which is much larger than the area with the same latitudes (60°–75°N, 0°–360°, trend of 0.46°C/10 yr). The warming over Siberia extends from the surface to about 300 hPa. Increased geopotential height in the mid-to-upper troposphere plays an important role in shaping the Siberian warming, which favors more shortwave radiation reaching the surface and further heating the overlying atmosphere via upward turbulent heat flux and longwave radiation. The Siberian warming is closely related to Arctic sea-ice decline, especially the sea ice over northern Barents Sea and Kara Sea. Numerical experiments carried out using and atmospheric general circulation model (IAP-AGCM4.1) confirmed the contribution of the Arctic sea-ice decline to the Siberian warming and the related changes in circulations and surface fluxes.摘要西伯利亚地区异常的升温可能会给生态系统带来灾难性的影响. 本文从气候角度分析西伯利亚地区初夏升温的特征以及北极海冰减小的可能贡献. 观测和再分析资料表明, 1979–2020年间西伯利亚地区6月地表气温有很强的升温趋势 (0.9°C/10年), 明显高于同纬度地区平均的升温趋势 (0.46°C/10年) . 升温从地表延伸至300hPa左右. 环流场的分析表明该区域对流层中高层位势高度场的增加对升温有重要贡献. 位势高度场的正异常有利于更多太阳辐射到达地表, 并通过湍流和长波辐射加热大气. 相关分析表明, 北极海冰减少与西伯利亚升温有密切联系. 同时, 大气模式IAP4.1模拟试验的结果也验证了海冰对西伯利亚升温的贡献. 相应的环流场以及表面辐射和湍流通量的变化也能在模拟试验中得到体现.