Water vapor fuels the release of heat that can strengthen storms and influence weather far downstream, but we know less about how this moisture is supplied. By tracing air backward for 43 winters over the North Atlantic, we show that its moisture is built up over several preceding days as air moves through earlier weather systems. Storms therefore inherit a memory of past weather that helps determine their potential to release heat and affect the atmosphere.

Saharan dust can reach the high Arctic within only a few days, but it was unclear whether such rapid transport occurs regularly. Using atmospheric models, satellite observations, and 21 years of air-mass trajectories, we identify a recurrent pathway across the North Atlantic. This pathway becomes increasingly important at higher Arctic latitudes and efficiently carries large dust particles northward, with potential consequences for Arctic clouds and climate.