On the observed connection between Arctic sea ice and Eurasian snow in relation to the winter North Atlantic Oscillation

María Santolaria-Otín,Javier García-Serrano,Martin Ménégoz,Joan Bech

doi:10.1088/1748-9326/abad57

Abstract

Sea ice concentration (SIC) in the eastern Arctic and snow cover extent (SCE) over central Eurasia in late autumn have been proposed as potential predictors of the winter North Atlantic Oscillation (NAO). Here, maximum covariance analysis is used to further investigate the links between autumn SIC in the Barents-Kara Seas (BK) and SCE over Eurasia (EUR) with winter sea level pressure (SLP) in the North Atlantic-European region over 1979-2019. As shown by previous studies, the most significant covariability mode of SIC/BK is found for November. Similarly, the covariability with SCE/EUR is only statistically significant for November, not for October. Changes in temperature, specific humidity, SIC/BK and SCE/EUR in November are associated with a circulation anomaly over the Ural-Siberian region that appears as a precursor of the winter NAO; where the advection of climatological temperature/humidity by the anomalous flow is related to SCE/EUR and SIC/BK anomalies.

Highlights

The North Atlantic Oscillation (NAO) is the most prominent pattern of atmospheric circulation variability in the Euro-Atlantic sector and has a strong influence on the regional surface climate (e.g., ?, ?)
The downward response decelerates the westerlies in the North Atlantic sector shifting the storm-tracks southward, which is tied to a negative NAO phase (e.g., ?, ?)
maximum covariance analysis (MCA) mode based on November sea ice concentration (SIC)/BK anomalies explains 82% of scf (p-value 2%), with a sc of 3.35 × 107 (p-value 0%) and yields a cor of 0.63 (p-value 1%)(Table 1)

Summary

Introduction

The North Atlantic Oscillation (NAO) is the most prominent pattern of atmospheric circulation variability in the Euro-Atlantic sector and has a strong influence on the regional surface climate (e.g., ?, ?). Many recent studies have stressed the potential predicting role of eastern Arctic sea ice and continental snow over Eurasia in autumn, with a reduction of sea ice concentration (SIC) in the Barents-Kara Seas and an increase of snow cover extent (SCE) across Siberia that would favor a negative. (e.g., ?, ?, ?, ?) and coupled climate models (e.g., ?, ?) have found that an anomalous anticyclone over northern Eurasia related to low SIC/BK in late-autumn tends to evolve into a negative NAO-like pattern in winter through a lagged stratospheric pathway. The downward response decelerates the westerlies in the North Atlantic sector shifting the storm-tracks southward, which is tied to a negative NAO phase (e.g., ?, ?). Causality in this chain of processes has to be confirmed (?, ?, ?)

Objectives

Results

Conclusion