Implications of land surface thaw on moisture transport into the Arctic

In this study, we investigate moisture sources from the high-latitude land surface in the context of summer cyclone activity and attendant moisture transport into the Arctic using atmospheric reanalysis and high-resolution model simulations. In ERA-5 reanalysis, we find that cyclones (50-90⁰N, 1999-2018) account for 74% of the annual average poleward moisture flux into the Arctic. For summer, this percentage is 81%. Summer cyclones primarily enter the Arctic from the North Atlantic and track along the north coast of Eurasia or develop over the continental interior before they collect over the central Arctic. This propagation pathway positions the cyclone’s warm sector circulation either overtop or adjacent to the Eurasian landmass which in summer is snow-free and undergoing various stages of subsurface thaw. High-resolution numerical experiments, conducted with the Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS^®), for two cyclone cases with modulated regional soil moisture show that cyclone-induced moisture transport into the Arctic is augmented by as much as 20% due to the regional land-surface moisture flux. Back trajectories were used to identify moisture source regions and to quantify moisture uptake from numerical experiments. The sensitivity of land-surface moisture uptake has implications for differences in the low-level moisture, moisture transport, and Arctic clouds.