Patagonia Is Losing Its Glaciers Due to Circulation Shifts Near South Pole

Located between Chile and Argentina in the southern Andes, Patagonia is home to the largest area of ​​glaciers—including the wettest—in the Southern Hemisphere, second only to Antarctica. “The Southern Andes act as a kind of natural barrier that blocks the moisture brought by westerly winds crossing the Pacific Ocean,” explains Brice Noël, a climatologist at ULiège. “As a result, glaciers locally receive more than fifteen meters of snow each year, particularly on the western flank of the Andes.” While glaciers grow through snow accumulation in higher regions, they also melt very quickly at lower altitudes. “Glacier can extend all the way down to sea level, where warmer air leads to a strong summer melt. This meltwater flows down to the ocean and causes a rise in sea level.” "Scientists have estimated that since the 1940s, Patagonia's glaciers have lost more than a quarter of their total volume, raising sea levels by 3.7 mm.

High-resolution climate models

The team of scientists from the universities of Liège, Leuven, and Delft estimated the surface mass balance of these glaciers since 1940—that is, the difference between winter snowfall and summer surface runoff. “We used the MAR, our regional atmospheric model developed here at the University of Liège,” adds Xavier Fettweis, a climatologist at ULiège. The MAR is a polar climate model that represents snow and ice processes on a five-kilometer spatial grid, which is insufficient to represent the small glaciers of Patagonia. “High spatial resolution is essential for studying the surface mass balance of Patagonian glaciers, so we refined our model to achieve a more detailed 500-meter grid,” continues Brice Noël. Low-resolution models can neither represent the narrow, rapidly melting glacier tongues * nor estimate realistic precipitation across the rugged terrain of the Andes. "Due to its higher spatial resolution, our model aligns very well with melt observations measured in the field or by satellite," confirms Bert Wouters of Delft University.

What factors explain melting?

This continuous mass loss from glaciers since 1940 is explained by the long-term increase in meltwater runoff to the ocean, a consequence of atmospheric warming in Patagonia. “We identify increased meltwater runoff as the main factor behind the glacier mass loss, as snowfall has remained stable since the 1940s,” explains Brice Noël. Surface runoff increases when the firn, the porous, persistent snow layer that covers the highest areas of the glacier, melts to expose the underlying open ice. “Open ice is darker than the surrounding firn layer. It therefore absorbs more solar energy, which promotes melting and thus causes increased runoff,” explains Stef Lhermitte of KU Leuven.

Poleward movement of subtropical anticyclones

In addition to the effect of global warming, researchers link the rapid temperature increase in Patagonia to a large-scale change in atmospheric circulation, shifting subtropical high-pressure systems toward the South Pole. This shift has been observed over the past forty years and is bringing more warm air toward Patagonia, amplifying mass loss. The ocean-atmosphere interactions driving this circulation change are due to global warming and will likely persist into the future. "The complete melting of Patagonia's glaciers could result in an additional rise in sea level of about one centimeter," worries Brice Noël.

"Their disappearance would endanger many South American communities dependent on summer meltwater." At the current rate of melting, researchers estimate that Patagonia's glaciers could disappear within 250 years.

* The glacier tongue is the part of the glacier that extends downstream, like a sort of "arm" of ice that descends into a valley or onto flatter terrain.

Reference: Noël B, Lhermitte S, Wouters B and Fettweis X. Poleward shift of subtropical highs drives Patagonian glacier mass loss. Nat Com. 2025. doi:10.1038/s41467-025-58974-1

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