Role of Ural blocking in Arctic sea ice loss and its connection with Arctic warming in winter

Dong-Jae Cho,Kwang-Yul Kim

doi:10.1007/s00382-020-05545-3

Abstract

Ural blocking (UB) is suggested as one of the contributors to winter sea ice loss in the Barents–Kara Seas (BKS). This study compares UB with Arctic warming (AW) in order to delineate the role of UB on winter sea ice loss and its potential link with AW. A detailed comparison reveals that UB and AW are partly linked on sub-seasonal scales via a two-way interaction; circulation produced by AW affects UB and advection induced by UB affects temperature in AW. On the other hand, the long-term impacts of AW and UB on the sea ice concentration in the BKS are distinct. In AW, strong turbulent flux from the sea surface warms the lower troposphere, increases downward longwave radiation, and broadens the open sea surface. This feedback process explains the substantial sea ice reduction observed in the BKS in association with long-term accelerating trend. Patterns of turbulent flux, net evaporation, and net longwave radiation at surface associated with UB are of opposite signs to those associated with AW, which implies that moisture and heat flux is suppressed as warm and moist air is advected from mid-latitudes. As a result, vertical feedback process is hindered under UB. The qualitative and quantitative differences arise in terms of their impacts on sea ice concentrations in the BKS, because strong turbulent flux from the open sea surface is a main driving force in AW whereas heat and moisture advection is a main forcing in UB.

Highlights

Growing concerns over the recent changes of rapid sea ice loss and atmospheric warming in the Arctic, known as Arctic warming (AW), have led to major debates on its linkage to mid-latitude weather in winter (Cohen et al 2020)
A number of studies suggested a connection between AW and harsh mid-latitude winters, which is often referred as “warm Arctic–cold Eurasia (WACE)” (Overland et al 2011; Francis and Vavrus 2012; Mori et al 2014; Kug et al 2015)
Significant winter sea ice loss in the Barents–Kara Seas (BKS) drew a strong attention, due to its distinctive nature compared with other regions in the Arctic (Petoukhov and Semenov 2010; Comiso 2012; Kim et al 2016)

Summary

Introduction

Growing concerns over the recent changes of rapid sea ice loss and atmospheric warming in the Arctic, known as Arctic warming (AW), have led to major debates on its linkage to mid-latitude weather in winter (Cohen et al 2020). A number of studies suggested a connection between AW and harsh mid-latitude winters, which is often referred as “warm Arctic–cold Eurasia (WACE)” (Overland et al 2011; Francis and Vavrus 2012; Mori et al 2014; Kug et al 2015). Despite that the connection between AW and WACE is inconclusive, a consensus has been reached on a rapid sea ice loss and its importance on Arctic climate change (Screen and Simmonds 2010; Stroeve et al 2011; Cohen et al 2014). Several mechanisms have been suggested for winter sea ice loss, including meridional transports of heat (Graversen et al 2008; Screen et al 2012) and moisture (Park et al 2015), increased cloud cover (Francis and Hunter 2006), and the temperature feedbacks including

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