Poleward shift of subtropical highs drives Patagonian glacier mass loss.

Noël, Brice; Lhermitte, Stef; Wouters, Bert; Fettweis, Xavier · Nat Commun · 2025

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Abstract

Patagonian glaciers have been rapidly losing mass in the last two decades, but the driving processes remain poorly known. Here we use two state-of-the-art regional climate models to reconstruct long-term (1940-2023) glacier surface mass balance (SMB), i.e., the difference between precipitation accumulation, surface runoff and sublimation, at about 5 km spatial resolution, further statistically downscaled to 500 m. High-resolution SMB agrees well with in-situ observations and, combined with solid ice discharge estimates, captures recent GRACE/GRACE-FO satellite mass change. Glacier mass loss coincides with a long-term SMB decline (-0.35 Gt yr<sup>-2</sup>), primarily driven by enhanced surface runoff (+0.47 Gt yr<sup>-2</sup>) and steady precipitation. We link these trends to a poleward shift of the subtropical highs favouring warm northwesterly air advections towards Patagonia (+0.14°C dec<sup>-1</sup> at 850 hPa). Since the 1940s, Patagonian glaciers have lost 1350  ± 449 Gt of ice, equivalent to 3.7  ± 1.2 mm of global mean sea-level rise.