Shifts in rain-on-snow occurrence in northwestern Eurasia and their connection to Arctic sea ice loss

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Abstract. This study explores precipitation, rain-on-snow (ROS) events and subsequent refreezing across northwestern Eurasia, and their relationship with Arctic sea ice. Daily outputs from nine CMIP6 models were analysed for 2015−2100 under three emission scenarios. ROS events were detected using precipitation, temperature, and snow cover after bias correction, and refreezing was identified when sub-freezing temperatures were found within four days after ROS. We find increasing winter precipitation across northwestern Eurasia, dominated by a shift towards more rainfall. The shift from snow to rainfall is more pronounced where temperatures remain near 0 °C, leading to changes in ROS frequency and timing under higher emissions. ROS events followed by refreezing occur less frequently than the total ROS events but indicate conditions favourable for ice-layer formation within the snowpack. The greatest changes occur between 55° N and 70° N, while northern regions remain less affected. ROS timing shifts from spring peaks towards later winter and early spring; at lower latitudes, the spring peak weakens as snow cover becomes less persistent. The Barents-Kara sea ice concentration anomalies are negatively correlated with accumulated precipitation and rainfall. Detrending of the correlations shows that the common long-term trend partly drives this relationship, but negative correlations between sea ice concentration anomalies and rainfall remain in several cases. Future ROS changes are driven mainly by increased rainfall rather than by total precipitation alone, while subsequent refreezing remains dependent on sub-freezing conditions following rainfall. The projected shifts in ROS timing and refreezing may affect snow conditions, socio-ecological systems, and infrastructure across northwestern Eurasia.

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