Abstract Sea spray, originating from wave breaking under high wind conditions, can significantly affect turbulent heat fluxes at the air–sea interface. Even though polar lows (PLs) can become extreme weather features with gale-force wind, the impact of sea spray on their development has rarely been investigated and is not considered in operational forecast models. In this study, the impact of sea spray on the development of two PLs over the Barents Sea is studied based on sensitivity experiments with an atmosphere–wave coupled model, where the spray-mediated heat fluxes are parameterized. The results show that the impact of sea-spray-mediated heat fluxes on PL development is sensitive to the surface wind speed. In the case of the stronger PL, the higher surface wind speed results in significantly higher spray-mediated heat fluxes. Consequently, these spray-mediated heat fluxes intensify the convection and diabatic heating of the PL, resulting in its intensification. In comparison, the case with a weaker PL experiences less sea spray production and lower spray-mediated heat fluxes due to its weaker surface wind speeds. Overall, we find that spray-mediated sensible heat fluxes play an important role in the development of PLs, while the latent heat fluxes induced by sea spray have a relatively minor impact.

Sea surface temperature anomaly (SSTA) associated with mesoscale oceanic processes, which are prevalent throughout the ocean, can significantly influence the atmospheric boundary layer and consequently atmospheric systems. While its influences on tropical and extratropical cyclones have been well-documented, the influence of mesoscale SSTA on polar lows (PLs) remains unexplored. To bridge this knowledge gap, we conducted a series of sensitivity numerical experiments with different SST configurations. The simulation results indicate that, over the lifespan of a PL, SSTA does not significantly influence PL intensity but does enhance latent heat release. On a longer time scale, based on simulations of five winter seasons over the Nordic Sea, we found that the accumulated impact of mesoscale SSTA creates favorable environments for PL intensification, characterized by higher moisture levels and lower static stability. These results highlight the importance of considering high-resolution SST boundary conditions, i.e. resolving mesoscale SST, in climate simulations of PLs.

Polar lows (PLs) are intense mesoscale cyclones that form over polar oceans during colder months. Characterized by high wind speeds and heavy precipitation, they profoundly impact coastal communities, shipping, and offshore activities. Amid the substantial environmental changes in polar regions due to global warming, PLs are expected to undergo noteworthy transformations. In this study, we investigate the response of PL development in the Barents Sea to climate warming based on two representative PLs. Sensitivity experiments were conducted including the PLs in the present climate and the PLs in a pseudo–global warming scenario projected by the late twenty-first century for Shared Socioeconomic Pathway (SSP) 2-4.5 and SSP 3-7.0 scenarios from phase 6 of the Coupled Model Intercomparison Project (CMIP6). In both warming climate scenarios, there is an anticipated decrease in PL intensity, in terms of the maximum surface wind speed and minimum sea level pressure. Despite the foreseen increase in latent heat release in the future climate, contributing to the enhancement of PL intensity, other primary factors such as decreased baroclinic instability, heightened atmospheric static stability, and reduced overall surface heat fluxes play pivotal roles in the overall decrease in PL intensity in the Barents Sea under warming conditions. The augmentation of surface latent heat flux, however, results in increased precipitation associated with PLs by enhancing the latent heat release. Furthermore, the regional steering flow shifts in the warming climate can influence the trajectory of PLs during their development.