Record-breaking Barents Sea Ice Loss Favors to the Unprecedented Summertime Extreme Heatwave in 2021 over Western North America by Enhancing Rossby Wave Ridge

Abstract

AbstractA record-setting extreme heatwave occurred over western North America (WNA) in the summer of 2021, which was associated with an extreme atmospheric Rossby wave ridge (ARR) over WNA and a minimum record event of the pre-winter Barents Sea ice concentration. We identify the temporal-spatial remote effect and investigate how the sea ice loss in the Barents Sea modulates the intensity of the ARR and extreme heatwaves by analyzing the reanalysis data. Our results suggest that atmospheric wave activity flux associated with Barents Sea ice loss (BSIL) in pre-winter transferred wave energy towards the circumglobal teleconnection (CGT)-like wave trains, increasing the wave amplitude and enhancing the ARR over WNA. Meanwhile, the weakening of the jet streams drives atmospheric subsidence and increases the shortwave radiation, leading to anticyclonic anomalies over WNA and the enhancement of the ARR. Both the CGT-like wave trains and the weakened jet streams contribute to the synergistic effect of the enhancing ARR and more frequent extreme heatwaves. And the BSIL serves as a pioneer predictor for the predictions of extreme heatwaves 6 months in advance. The above analysis can improve the prediction skills of extreme heatwaves over WNA, possibly predicting more precisely.