Poleward shift of the subtropical highs drives Patagonian ice fields mass loss

The Patagonian ice fields have been rapidly losing mass in the last decades, but little is known about the driving processes. Here we use state-of-the-art regional climate models to reconstruct the contemporary climate and glacier surface mass balance (SMB), i.e., the difference between snowfall accumulation and meltwater runoff, in the Southern Andes at 5 km spatial resolution for the period 1940-2022. Model outputs are further statistically downscaled to a 500 m grid that resolves SMB processes in high spatial detail. Our high-resolution SMB products show good agreement with both in-situ observations and GRACE/GRACE-FO satellite mass change measurements, when combined to solid ice discharge. We link recent glacier mass loss to an ongoing poleward shift of the subtropical highs that warms the ocean and atmosphere nearby Patagonian ice fields, in turn enhancing meltwater runoff.