Nonstationary Relationship Between Autumn Arctic Sea Ice and the Winter North Atlantic Oscillation

Abstract

The North Atlantic Oscillation (NAO) has a dominating influence on wintertime weather in the North Atlantic region, and therefore, it is of great interest to predict the NAO several months ahead. While state-of-the-art dynamical forecast models appear to be increasingly skillful in predicting the NAO, statistical methods with comparable or higher predictive skill are still often used. An inherent problem with statistical methods is that any empirical relationship between predictors and the NAO may be valid for some periods but subject to change over time. Here we use a set of new centennial reanalyses and large-ensemble simulations with multiple climate models to discover clear evidence of nonstationarity in the lagged correlation between autumn Barents-Kara sea ice and the winter NAO. This nonstationarity leads us to question the causality and/or robustness of the ice-NAO link. We caution against indiscriminately using Barents-Kara sea ice to predict the NAO.