Preprints
https://doi.org/10.5194/egusphere-2024-1865
https://doi.org/10.5194/egusphere-2024-1865
25 Jun 2024
 | 25 Jun 2024
Status: this preprint is open for discussion.

Modulating surface heat flux through sea ice leads improves Arctic sea ice simulation in the coupled EC-Earth3

Tian Tian, Richard Davy, Leandro Ponsoni, and Shuting Yang

Abstract. In this study, we address a persistent positive bias in Arctic sea ice (concentration and thickness) in the global climate model EC-Earth3 (ECE3) by including a modulating factor to the surface sensible heat flux over regions with sea ice concentrations above 70 %, so-called ECE3L. We performed two pairs of 50-year simulations with repeated seasonal cycles: one pair replicating a cold climate and the other a warmer climate, with the latter characterised by thinner ice and weaker atmospheric boundary layer stability during winter. We show that modified heat flux can significantly alter surface air temperatures in the Arctic, with no substantial impact on lower latitudes. The changes are more pronounced in the cold climate, particularly during Arctic winter. We extended our comparison to two CMIP6 historical ensembles in a transient climate (1980–2014). We found that the mean sea ice states in the changing climate for the ECE3 (ECE3L) ensemble mean closely resembled the mean states in the cold-climate experiment. However, the reduction in sea ice area and volume achieved by ECE3L was nearly four times greater in the cold climate experiment than in the transient climate, reflecting the diminishing role of sea ice leads in a changing climate with decreasing occurrences of stable stratification in winter. Finally, our comparisons with satellite observations and reanalysis datasets demonstrated that ECEL3 significantly improves the local amplification ratio in the marginal ice zone of the Arctic, underscoring the importance of atmospheric stability shaped by central Arctic pack ice and its impact on Arctic amplification.

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Tian Tian, Richard Davy, Leandro Ponsoni, and Shuting Yang

Status: open (until 28 Aug 2024)

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Tian Tian, Richard Davy, Leandro Ponsoni, and Shuting Yang
Tian Tian, Richard Davy, Leandro Ponsoni, and Shuting Yang

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Short summary
We introduced a modulating factor to the surface heat flux in the EC-Earth3 model to address the lack of parameterization for turbulent exchange over sea ice leads and correct the bias in Arctic sea ice. Three pairwise experiments showed that the amplified heat flux effectively reduces the overestimated sea ice, especially during cold periods, thereby improving agreement with observed and reanalysis data for sea ice area, volume, and ice edge, particularly in the North Atlantic Sector.