Observed winter near-surface air temperature anomalies in the Northern Hemisphere have exhibited a warm Arctic-cold Eurasia (WACE) pattern in recent decades, but the exact mechanism behind this WACE pattern is still unclear. AER scientist Judah Cohen collaborated with Chinese colleagues to reanalyze observational data and climate model simulations to investigate the decadal variations of the WACE pattern, as well as the role of the atmospheric circulation over the twentieth century. It is found that the second mode of atmospheric variability over the North Atlantic-Arctic region, known as the Barents Oscillation (BO), played a dominant role in regulating the decadal-scale variability of the WACE pattern. The atmospheric circulation associated with the positive phase of the BO corresponds to an anomalous enhancement of the anticyclone (high pressure) near the southern Barents-Kara Seas (BKS) and the North Atlantic, as well as a weakening of the mid-latitude jet stream. This atmospheric circulation anomaly favors the northward transport of atmospheric heat and moisture to the BKS from the mid-latitudes, resulting in warmer air temperature. Concurrently cold air is transported from the polar region to Central Eurasia (CE), cooling air temperatures over CE. The temperature anomaly dipole magnifies the WACE pattern. The atmospheric circulation anomalies related to the negative phase of the BO are the opposite, which in turn leads to the decadal dampening of the WACE pattern.
Figure 1. Interdecadal variation characteristics of the WACE pattern. (a-d) First two EOFs of winter (DJF) surface air temperature anomalies in the Arctic-Eurasian region from 1910 to 2014 and their corresponding principal components (PCs). The black lines represent the 21-year moving average. The red and blue bars at the bottom in (d) represent the positive and negative phases, respectively. (e) Scatterplot of the relationships between the WACE index, Barents-Kara Sea (BKS) averaged near-surface air temperature (BKS_TAS) anomaly, and Central Eurasia (CE) averaged near-surface air temperature (CE_TAS) anomaly. The WACE index is defined as PC2 in (d). (f) Power spectral analysis of the 11-year running mean WACE index (solid blue line). The black and red dashed lines indicate the corresponding red noise spectra and 95% confidence levels for power spectra. The gray shade indicates interdecadal timescales (10–30 years)
Citation: Interdecadal variability of the warm Arctic-cold Eurasia pattern linked to the Barents Oscillation
Z. Cai, Q. You, H. W. Chen, R. Zhang, Z. Zuo, G. Dai, D. Chen, J. Cohen, O. Zolina, S. K. Gulev
Atmospheric Research, 287, 106712, 2023