盛夏北极边缘海冰与来年冬季NAO之联系

摘要

许多研究认为, 只有北大西洋涛动 (NAO) 是一种具有物理意义的模态, 而北极涛动 (AO) 则是EOF分解得到的一种统计假象模态.为了从一个新的角度进一步探讨二者的差别, 我们运用附条件的最大协方差分析 (CMCA) 统计了前期北极边缘海冰密集度 (MSCI) 与来年冬季NAO之间的跨季节遥相关关系, 其中的ENSO信号和线性趋势已经在分析之前被去除.统计显著性结果表明:冬季负位相的NAO信号可以追溯到6个月前自盛夏开始至早冬季节北极MSCI异常的逐步演变.然而根据先前的研究, 北极海冰异常仅可以超前冬季AO大概4个月表现出显著信号.这表明盛夏北极MSCI的持续异常对来年冬季NAO的影响比对AO更强, 同时也从另一个角度证实了AO与NAO确实存在差异.进一步分析还表明, 前期MSCI异常的逐步演变主要与海表面热通量及气温异常有关.此外, 我们还重新审视了负位相的NAO对北半球冬季气候异常的影响以及可能的物理机制.%Many studies pointed out that the North Atlantic Oscillation (NAO) is a physically meaningful mode but the Arctic Oscillation (AO) likes a statistical artifact mode from EOF analysis.To further explore their difference from a new perspective, here we applied a conditional maximum covariance analysis (CMCA) to capture the cross-seasonal teleconnection between preceding Arctic marginal sea ice concentration (MSIC) and the following wintertime NAO, from which the ENSO signals and the linear trends were removed.Statistically significant results showed that the dominant Ocean-Atmosphere interaction was the atmospheric effect on the MSIC anomalies, with a peak occurring when atmosphere leading MSCI by 0-1 month.However, the most eye-catching phenomenon was that the wintertime negative NAO could be significantly linked to the gradual evolution of preceding Arctic MSIC anomalies from high-summer to early-winter, with lead-times up to 6months.However, according to previous studies, Arctic sea ice anomalies could only show significant precursory signals for winter AO about 4 months, suggesting that Arctic MSIC has a stronger impact on the following winter NAO than AO.And it also confirmed that there was a difference between AO and NAO from a new perspective.Further analysis showed that the gradual evolution of changes in Arctic MSIC was mainly driven by sea surface heat fluxes and surface temperature anomalies.Besides, we also reinvestigated the effect of negative NAO on the boreal winter climate anomalies and the corresponding possible physical mechanisms.