Mechanisms of Regional Winter Sea-Ice Variability in a Warming Arctic

Jakob Dörr,Marius Årthun,Erica Madonna,Tor Eldevik

doi:10.1175/jcli-d-21-0149.1

Jakob Dörr, Marius Årthun + Show 2 more

Open Access

https://doi.org/10.1175/jcli-d-21-0149.1

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Abstract

AbstractThe Arctic winter sea ice cover is in retreat overlaid by large internal variability. Changes to sea ice are driven by exchange of heat, momentum, and freshwater within and between the ocean and the atmosphere. Using a combination of observations and output from the Community Earth System Model Large Ensemble, we analyze and contrast present and future drivers of the regional winter sea ice cover. Consistent with observations and previous studies, we find that for the recent decades ocean heat transport though the Barents Sea and Bering Strait is a major source of sea ice variability in the Atlantic and Pacific sectors of the Arctic, respectively. Future projections show a gradually expanding footprint of Pacific and Atlantic inflows highlighting the importance of future Atlantification and Pacification of the Arctic Ocean. While the dominant hemispheric modes of winter atmospheric circulation are only weakly connected to the sea ice, we find distinct local atmospheric circulation patterns associated with present and future regional sea ice variability in the Atlantic and Pacific sectors, consistent with heat and moisture transport from lower latitudes. Even if the total freshwater input from rivers is projected to increase substantially, its influence on simulated sea ice is small in the context of internal variability.

Highlights

Over the last decades, the sea ice in the Arctic has significantly declined in all seasons (Notz and Stroeve 2016; Onarheim et al 2018)
We have assessed the connection of the regional winter sea ice variability in the Arctic to the oceanic and atmospheric circulation variability in the present and the future, using a combination of available observations and CESM-LE
In agreement with previous studies, we find that ocean heat transport has been a major driver of recent sea ice variability in the Atlantic (Årthun et al 2012; Lien et al 2017) and Pacific sector (Woodgate et al 2012; Serreze et al 2016)

Summary

Introduction

The sea ice in the Arctic has significantly declined in all seasons (Notz and Stroeve 2016; Onarheim et al 2018). The potential drivers of sea ice variability assessed in this study include ocean heat transport (OHT) into the Arctic Ocean, large-scale atmospheric circulation, and river runoff. To assess the different drivers of winter sea ice variability, we use a combination of observations and simulations from the Community Earth System Model Large Ensemble (CESMLE; Kay et al 2015), which has been widely used and extensively evaluated for Arctic sea ice variability (Barnhart et al 2016; Jahn et al 2016; England et al 2019; Desmarais and Tremblay 2021), ocean heat transport (Auclair and Tremblay 2018; Årthun et al 2019), and atmospheric circulation variability (Wettstein and Deser 2014; Ding et al 2017; Wang et al 2019a). This forced increase is similar to the 30% increase projected by the CMIP5 multimodel mean (Nummelin et al 2016)

The role of ocean heat transport in winter sea ice variability

Influence of river runoff

Interannual variability versus trends

Findings

Discussion and conclusions