Natural acid rock drainage in alpine catchments: A side effect of climate warming

A historical series of aerial photographs spanning more than 70 years (1945–2018) revealed that natural acid rock drainage (ARD) has experienced an intensification in the Noguera de Vallferrera alpine catchment (Central Pyrenees) due to climate change during last decade. ARD manifests by precipitation whitish aluminum-compounds strikingly cover beds some gullies and streams high-mountain catchments. The total length affected increased from ca. 5 km (1945) 35 (2018). Up 68 water samples were collected three main areas determine spatial variation acidity concentration dissolved metals, representative surface subsurface waters. Concentration aluminum clearly correlates with Aluminum occurs where acidic waters, enriched metals related oxidation sulfides, mix non-acidic In addition aluminum, other potentially toxic trace are present at concentrations well above quality standards for Here, we show warming severe droughts recorded decade most plausible causes observed intensification. This result is supported a good correlation between regional ascending rate periglacial limits (ca. 46 m-height/decade) rising maximum elevations which 45 55 m-height/decade). climatic control, also local geomorphology playing major role. distribution deposits (rock glaciers, protalus ramparts, cones talus slopes) deep-seated gravitational slope deformations exert strong control on patterns hydrodynamics ARD. better understanding phenomenon monitoring its evolution can provide clues these side effects warming, here many catchments worldwide.