Located in the southernmost region of South America, Patagonia hosts the largest glacial system in the Southern Hemisphere outside of Antarctica. Its three main ice fields — the Northern (NPI), Southern (SPI), and Darwin Range (CDI) — contain approximately 4,772 gigatons of ice, which, if completely melted, would raise global sea levels by about 13 millimetres. Although these glaciers represent only 3% of the planet’s non-polar ice volume, they have contributed disproportionately to sea level rise, accounting for 10% of the increase between 2002 and 2016.
The study, led by Brice Noël and an international team of researchers and published in Nature Communications, reconstructs the evolution of the surface mass balance (SMB) of Patagonian glaciers between 1940 and 2023 using state-of-the-art regional climate models (MAR and RACMO), refined to a spatial resolution of up to 500 metres. The SMB balance measures the difference between accumulation from precipitation and mass loss due to runoff and sublimation.
The results are striking: since 1940, the glaciers have lost 1,350 ± 499 gigatons of ice, equivalent to a sea level rise of 3.7 ± 1.2 millimetres. The loss has been continuous, with a marked decline over the past two decades, coinciding with rising atmospheric temperatures and a sustained increase in surface melting.
Climate change and atmospheric patterns: the true driver of melting
Contrary to previous assumptions, the study shows that a decrease in precipitation is not the main cause of glacial collapse, but rather a significant increase in surface melt, which has risen by 0.47 Gt per year since 1940. This phenomenon is closely linked to a steady rise in near-surface air temperature, at about 0.10 °C per decade.
Long-term average of (a) total precipitation, (b) surface runoff and (c) surface mass balance (SMB) as modelled by MAR, statistically downscaled to 500 m, for the period 1940-2023. d–f same as a–c but for long-term trends (1940-2023). / Noël, B., Lhermitte, S., Wouters, B. et al. Poleward shift of subtropical highs drives Patagonian glacier mass loss. Nat Commun 16, 3795 (2025). https://doi.org/10.1038/s41467-025-58974-1
According to the study, this warming is not merely a reflection of global climate change, but rather the result of a large-scale atmospheric reconfiguration: the southward migration of the South Pacific subtropical highs. This shift has brought warm air masses from the northwest, intensifying melting across the Patagonian Andes.
The dynamics of melting: beyond temperature
Researchers identified three key processes that amplify runoff: the expansion of ablation zones (areas where ice is lost), an increased ratio of rain to snow, and the progressive loss of firn (compacted snow) capacity to retain meltwater. These factors act in synergy, accelerating the flow of water to the oceans and reducing the glaciers’ ability to temporarily “store” water as ice.
The study contradicts previous research that attributed SMB variability primarily to precipitation. Thanks to more precise and detailed modelling, along with the use of satellite data (such as GRACE and GRACE-FO), this new research achieves an almost perfect correlation between simulations and observations, reinforcing its reliability.
The projections are alarming. If the current rate of mass loss (around 24 gigatons per year) continues, Patagonian glaciers could disappear within the next 220 years. Under moderate (RCP2.6) or extreme (RCP8.5) climate change scenarios, an additional 22% to 27% of ice volume could be lost by 2050, further contributing to sea level rise.
