Representation of Arctic winter atmospheric boundary layer stability over sea ice in CMIP6 models

Duffey, Alistair, Mallett, Robbie, Dutch, Victoria R., Steckling, Julia, Hermant, Antoine, Day, Jonathan and Pithan, Felix (2025) Representation of Arctic winter atmospheric boundary layer stability over sea ice in CMIP6 models. Journal of Geophysical Research: Atmospheres, 130 (11). ISSN 2169-897X

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Abstract

The Arctic winter atmospheric boundary layer often features strong and persistent low-level stability (LLS), which arises from longwave radiative cooling of the surface during the polar night. This stable stratification results in a positive lapse rate feedback, which is a major contributor to Arctic amplification. A second state, with cloudy conditions, weaker stability, and near-zero net surface longwave flux is also observed. Previous work has shown that many CMIP5 models fail to appropriately partition water between liquid and ice phases in mixed-phase clouds, leading to a lack of this cloudy state. In this study, we assess the representation of the Arctic winter atmospheric boundary layer over sea ice in global climate models contributing to the latest phase of the Coupled Model Intercomparison Project (CMIP6). We compare boundary layer process relationships in these models to those in surface-based and radiosonde observations collected during the MOSAiC (2019–2020) and SHEBA (1997–1998) expeditions, and by North Pole drifting stations (1955–1991). The majority of CMIP6 models fail to realistically represent the cloudy state over winter Arctic sea ice. Despite this, CMIP6 multimodel mean LLS falls within the observational range, and models mostly capture the observed dependence of LLS on near-surface air temperature and wind speed. CMIP6 models predict a decline in winter LLS with Arctic warming, with mean stability falling below zero by 2100 under the SSP2-4.5 scenario. Our results highlight the failure to accurately simulate mixed-phase clouds as an important limitation on representing a realistic Arctic winter boundary layer in many CMIP6 models.

Item Type:	Article
Additional Information:	Data Availability Statement: All data used in this work are publically available. The CMIP6 data can be accessed from the Earth System Grid Federation CMIP6 archive (https://esgf-index1.ceda.ac.uk/search/cmip6-ceda/). The North Pole drifting stations observations are available to download online from the National Snow and Ice Data Centre, (Colony & Thorndike, 1984). MOSAiC data are available from Pangea (Maturilli et al., 2021) and MOSAiC tower radiation data (Reynolds & Riihimaki, 2019) can be downloaded from https://www.arm.gov. SHEBA data can be downloaded at https://atmos.uw.edu/~roode/SHEBA.html. Code to perform all analysis and plotting is available on Zenodo at https://zenodo.org/records/13763472 (Duffey, 2024). Funding information: AD acknowledges funding from the London Natural Environment Research Council (NERC) Doctoral Training Partnership (DTP) Grant NE/S007229/1. RM acknowledges funding from the Canada 150 Research Chairs Program via Julienne Stroeve, which supported some of this work at the University of Manitoba. FP acknowledges funding from the European Union's Horizon 2020 research and innovation program under grant agreement no. 101003826 via project CRiceS (Climate Relevant interactions and feedbacks: the key role of sea ice and Snow in the polar and global climate system). VRD was supported by a Research Development Fund (RDF) studentship from Northumbria University and the Northern Water Futures project.
Uncontrolled Keywords:	sdg 13 - climate action ,/dk/atira/pure/sustainabledevelopmentgoals/climate_action
Faculty \ School:	Faculty of Science > School of Environmental Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Depositing User:	LivePure Connector
Date Deposited:	09 Jun 2025 15:30
Last Modified:	16 Jun 2025 03:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99414
DOI:	10.1029/2024JD041412

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