Increase of the energy available for snow ablation in the Pyrenees (1959–2020) and its relation to atmospheric circulation

Mid-latitude mountain snowpacks are highly vulnerable to climate warming. Past and future hydroclimate changes require a thorougout knowledge of snow ablation physical processes the associate drivers. In this work we provide first spatio-temporal characteritzation energy available for (Qm) in Pyrenees period 1959–2020, during main season (March June) low (1200 m), mid (1800 m) high (2400 elevations. We analyze role Circulation Weather Types (CTs) Qm components entire range. Finally, train tune machine learning algorithm, Random Forest, with atmospheric data (Surface Level Pressure 500 hPa Geopotential Height) as an independent variable dependent one, order determine how much observed can be related circulation variability. The largest contribution is Net Radiation (Rn), increasing elevation. has shown statistically significant increase since 1980s. comparison between 1959–1980 2000–2020 revealed that positive fluxes have been anticipated 22 12 days at elevations, respectively, showing evidence advance timing faster high-elevation areas Pyrenees. principally driven by Rn prevailing antyciclonic situations, characterized extension high-pressure systems, low-barometric gradients SE advection hot dry air masses. frequency these anticyclonic CTs explains majority (75%) variability, upward trends earlier onset