Impact of internal variability on recent opposite trends in wintertime temperature over the Barents–Kara Seas and central Eurasia

Sai Wang,Wen Chen

doi:10.1007/s00382-021-06077-0

Abstract

The large ensembles of the IPSL-CM6A-LR model output for the historical forcing experiment were employed to investigate the role of internal variability in the formation of the recent “warm Arctic–cold Eurasia” trend pattern in winter surface air temperature (SAT). The ensemble-mean SAT shows a positive trend over Arctic during 1990–2014, indicating a positive contribution of anthropogenic forcing to the warming Arctic. Over the region of central Eurasia, the ensemble-mean SAT trend is opposite to the observed trend. The winter SAT trends display remarkable inter-member diversity over the Barents–Kara Seas (BKS) region and central Eurasia, suggesting an important role played by internal variability. In addition to anthropogenic forcing, the results suggest that the barotropic anticyclone over northern Eurasia arising from internal variability can also contribute positively to the warming anomalies over the BKS region. On the other hand, through a fingerprint pattern matching method, it is found that the observed cooling trend over central Eurasia tends to be predominantly due to the internal variability. Finally, the results estimate that the internal variability can contribute to about 50–60% of the observed warming trend over the BKS region.

Highlights

Since the 1990s, rapid surface warming has occurred over the Arctic region (Polyakov et al 2002; Johannessen et al 2004; Serreze et al 2008; Screen and Simmonds 2010b; Screen and Simmonds 2010a; Serreze and Barry 2011)
Adopting the methodology formulated by Deser et al (2012), we examine the influence of internal variability on the winter surface air temperature (SAT) trends over the Barents–Kara Seas and central Eurasia, separately, and reveal whether the warming trend over the Barents–Kara Seas and cooling trend over central Eurasia are caused by a common internal driver or independent ones
In this paper we have investigated the role of internal variability in the formation of the opposite trends in winter SAT over the Barents–Kara Seas and central Eurasia during 1991–2014 through analysis of large ensembles of fully coupled climate model simulations with historical radiative forcing

Summary

Introduction

Since the 1990s, rapid surface warming has occurred over the Arctic region (Polyakov et al 2002; Johannessen et al 2004; Serreze et al 2008; Screen and Simmonds 2010b; Screen and Simmonds 2010a; Serreze and Barry 2011). Over the same period, cooling trends have been observed in mid-latitudes, especially over central Eurasia (Wu et al 2011; Cohen et al 2012a; Cohen et al 2012b; Liu et al 2012) The pattern of this Northern Hemisphere temperature signal has been referred to as the “warm Arctic–cold continents” pattern (Overland et al 2010; Cohen et al 2013; Cohen et al 2014). The internally generated variability can be extracted using a given climate model with large ensemble simulations forced by the same external forcing (Deser et al 2012) This methodology has been adopted to study the impact of internally generated variability on regional climate changes over periods of several decades (Deser et al 2016; Wang et al 2018; Ding et al 2019; Hu et al 2019).

Data And Methods

Trend analysis

Physical processes for internally driven Arctic SAT trends

Internal drivers of a warm Arctic and cold Eurasia

Causes of the observed trend pattern of SAT and circulation anomalies

Summary And Discussion