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

E W Kolstad,J A Screen

doi:10.1029/2019gl083059

E W Kolstad, J A Screen

Open Access

https://doi.org/10.1029/2019gl083059

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Abstract

AbstractThe 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.

Highlights

Skillful forecasting of wintertime weather anomalies several months in advance appears attainable
We have shown that the interannual correlation between autumn BK sea ice and the winter North Atlantic Oscillation (NAO) is nonstationary and displays considerabledecadal variability
The strong positive correlation observed in recent decades is a rare occurrence in the historical record, but it is within the range of internal variability as simulated by climate models

Summary

Introduction

Skillful forecasting of wintertime weather anomalies several months in advance appears attainable. In a recent study by Wang et al (2017), anomalies of sea ice concentration, sea surface temperature (SST), and snow cover were used to predict the NAO (and surface variables) several months ahead In their empirical model, autumn Barents‐Kara (BK) sea ice was the strongest predictor of the winter NAO. It is worth noting that in the analyses of Wang et al (2017) and Hall et al (2017), the skill of NAO predictions was highly sensitive to the inclusion, or not, of the large downward trend in sea ice, with higher skill when using detrended time series This sensitivity raises potential concerns about the robustness of the ice‐NAO link

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