The decline of Arctic sea ice has been revealed to instigate Eurasian cold and snowy winters. In spring, Eurasia has experienced significant warming, accompanied by frequent extreme heat events (EHE). Whether the Arctic sea ice has contributed to the spring Eurasian EHE variation is still unclear. Here, Principal Scientist Judah Cohen and his Chinese colleagues demonstrate that the winter sea ice concentration (SIC) anomalies over the Barents-Kara Seas (BK) dominate the leading mode of spring EHE interannual variation over mid-to-high latitude Eurasia in the recent two decades. With a faster decline rate and larger variability, the winter BK SIC anomalies significantly enhance the tropospheric-stratospheric interactions and further exert influence on the spring atmospheric circulations that favors the formation of Eurasian EHE. Consequently, winter BK sea ice affects the interannual variation of spring Eurasian EHE in the recent two decades. Cross-validated hindcasts of the spring EHE dipole mode index using winter BK SIC anomalies yield a correlation skill of 0.71 over 2001–2018, suggesting that nearly 50% of its variance could be predicted one season in advance.
Fig. The linkage between interannual variations of winter Barents-Kara (BK) sea ice and spring extreme heat events (EHE) over mid-to-high latitude Eurasia. The modes of common variability for a spring (MAM(0)) EHE (units: %) over mid-to-high latitude Eurasia (35°-80°N, 10°W-180°E) and b preceding winter (DJF(-1)) sea ice concentration (SIC) over the BK region (67°-84°N, 0°-90°E) during 2001-2018, which are obtained by regressing the SIC and EHE onto the normalized two time series of SVD1, respectively. Dotted areas in a and b denote anomalies significant at the 90% confidence level. The red and blue boxes in a denote the regions of positive and negative EHE anomalies (P1: 35°-57°N, 20°-120°E, P2: 50°-70°N, 125°-165°E, and N: 60°-76°N, 20°-120°E) used for constructing the spring EHE mode index, and the blue box in b denotes region of BK SIC anomalies (76°-83°N, 11°-75°E, and 68°-76°N, 50°-75°E) used for constructing the BK SIC index. c Normalized two time series of common mode of variability. The explained covariance by the SVD1 and the correlation (R) between the two time series are shown in the top of c. d Cross wavelet transform (XWT) of the indices of winter BK sea ice and spring EHE dipole mode. In d, the thick black contour denotes the 95% significance level and lighter shade indicate the cone of influence where edge effects might distort the picture.
Sun, S. Liu, J. Cohen, S. Yu
Communications Earth & Environment, 3:172, .2022. https://doi.org/10.1038/s43247-022-00503-9