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Recent years have seen growing interest in improving seasonal predictions of Arctic sea ice conditions, including the timing of ice melt onset and retreat, especially on the regional scale. This paper investigates potential links between regional sea ice melt onset and retreat in the southern Laptev Sea and retreat of terrestrial snow cover. Past studies have shown that variability of snow extent over Eurasia can substantially impact regional atmospheric circulation patterns over the North Pacific and Arctic Oceans. It is shown here that for the Laptev Sea, earlier melt onset and retreat of sea ice are encouraged by earlier retreat of snow cover over the West Siberian Plain. Earlier snow retreat in spring encourages greater ridging (e.g., at 500 hPa) over the East Siberian Sea through the summer. This results in more frequently southerly flow of warm, moist air over the Laptev Sea. This relationship could provide modest improvements to predictive skill for sea ice melt onset and retreat in the southern Laptev Sea at lead times of approximately 50 and 90 days, respectively. The detrended time series of snow retreat in the West Siberian Plain explains 26 and 29% of the detrended variance of the timing of sea ice melt onset and retreat in southern Laptev Sea, respectively.

Plain Language Summary Over the past several decades, decreasing in the amount of Arctic sea ice have allowed human activities, like shipping and tourism, to increase. Even though less sea ice exists in summer, plenty still forms in winter. Therefore, being able to forecast when the winter sea ice will disappear and Arctic waters will open up each summer is valuable to human activities. This study focuses on the Laptev Sea, which is part of the Northern Sea Route along the Russian Arctic coast. We show that by knowing when snow retreats from the West Siberian Plain, we can improve forecasts of when sea ice will retreat from the Laptev Sea later in the year. Especially valuable for forecasting, the snow retreat in the West Siberian Plain occurs about 90 days before the sea ice disappears in the Laptev Sea, so there is ample time to act on such forecasts. The physical link between these two regions is through the atmosphere. If snow melts away earlier than normal in the West Siberian Plain, the Laptev Sea experiences more winds blowing from south to north than normal. This brings more warm, wet air than normal, which helps melt the sea ice faster.