North Atlantic Oscillation in winter is largely insensitive to autumn Barents-Kara sea ice variability.

Peter Yu Feng Siew,Camille Li,Mingfang Ting,Yutian Wu,Xiaodan Chen,Stefan P Sobolowski

doi:10.1126/sciadv.abg4893

Abstract

Arctic sea ice extent in autumn is significantly correlated with the winter North Atlantic Oscillation (NAO) in the satellite era. However, questions about the robustness and reproducibility of the relationship persist. Here, we show that climate models are able to simulate periods of strong ice-NAO correlation, albeit rarely. Furthermore, we show that the winter circulation signals during these periods are consistent with observations and not driven by sea ice. We do so by interrogating a multimodel ensemble for the specific time scale of interest, thereby illuminating the dynamics that produce large spread in the ice-NAO relationship. Our results support the importance of internal variability over sea ice but go further in showing that the mechanism behind strong ice-NAO correlations, when they occur, is similar in longer observational records and models. Rather than sea ice, circulation anomalies over the Urals emerge as a decisive precursor to the winter NAO signal.

Highlights

Autumn Arctic sea ice loss, especially over the Barents-Kara Sea, is associated with a negative North Atlantic Oscillation (NAO) the following winter (Fig. 1)
The statistical relationship between autumn sea ice and the late- winter NAO is, at first glance, very weak in coupled climate models compared to reality
The climate models, show very weak NAO correlations in winter when calculated from the long control simulations, which range in length from 451 to 2000 years

Summary

Introduction

Autumn Arctic sea ice loss, especially over the Barents-Kara Sea, is associated with a negative North Atlantic Oscillation (NAO) the following winter (Fig. 1). Historical simulations do show lagged relationships between the Barents-Kara sea ice reduction and a negative NAO, but the timing varies across models and is generally inconsistent with observations [18] While these studies indicate that ice-NAO linkages exist in some form in coupled models, these linkages seem not to set the long-term trends in European climate under future warming scenarios [19]. The simulated ice-NAO relationship may be unrealistically weak because of model deficiencies, especially those related to near-surface heat fluxes in the stable boundary layers that are found at high latitudes during winter [20,21,22].

Methods

Results

Conclusion