Acceleration of western Arctic sea ice loss linked to the Pacific North American pattern

Zhongfang Liu,Gabriel J Bowen,Camille Risi,Sha Li,Francis Codron,Dong Chen,Xiaogang He,Christopher J Poulsen,Zhongwang Wei

doi:10.1038/s41467-021-21830-z

Abstract

Recent rapid Arctic sea-ice reduction has been well documented in observations, reconstructions and model simulations. However, the rate of sea ice loss is highly variable in both time and space. The western Arctic has seen the fastest sea-ice decline, with substantial interannual and decadal variability, but the underlying mechanism remains unclear. Here we demonstrate, through both observations and model simulations, that the Pacific North American (PNA) pattern is an important driver of western Arctic sea-ice variability, accounting for more than 25% of the interannual variance. Our results suggest that the recent persistent positive PNA pattern has led to increased heat and moisture fluxes from local processes and from advection of North Pacific airmasses into the western Arctic. These changes have increased lower-tropospheric temperature, humidity and downwelling longwave radiation in the western Arctic, accelerating sea-ice decline. Our results indicate that the PNA pattern is important for projections of Arctic climate changes, and that greenhouse warming and the resultant persistent positive PNA trend is likely to increase Arctic sea-ice loss.

Highlights

Recent rapid Arctic sea-ice reduction has been well documented in observations, reconstructions and model simulations
The Pacific North American (PNA) pattern has had a positive trend throughout the satellite era and the spatial pattern of Arctic sea ice concentration (SIC) change that is correlated with PNA change (Fig. 1b) is very similar to the overall pattern of the SIC trends (Fig. 1a), with the fastest sea-ice decline over the western Arctic
Lead-lag correlations indicate that the western Arctic SIC is strongly correlated with the simultaneous (ASO) and 1-month leading (JAS) PNA index, and correlates more weakly with the 1-month lagging (SON) PNA index (Supplementary Fig. 2), suggesting that the PNA pattern acts as a precursor to western Arctic SIC changes

Summary

Introduction

Recent rapid Arctic sea-ice reduction has been well documented in observations, reconstructions and model simulations. These changes have increased lower-tropospheric temperature, humidity and downwelling longwave radiation in the western Arctic, accelerating sea-ice decline. We combine observational satellite data of Arctic SIC, ERA-Interim atmospheric reanalysis, and numerical simulations (see “Methods” section) to demonstrate the importance of the PNA as a driver of western Arctic sea ice loss on both interannual and decadal timescales, and diagnose the associated physical mechanisms

Methods

Results

Conclusion