For decades, Glaciar Perito Moreno stood out as a stubborn exception. While neighboring ice masses in Patagonia shrank year after year, the 250-square-kilometer glacier in southern Argentina’s Los Glaciares National Park kept advancing, calving enormous icebergs into Lago Argentino in a well-documented advance-rupture cycle that drew tourists and reassured scientists. That exception is over.
A peer-reviewed study published in April 2026 in Communications Earth & Environment, part of the Nature Portfolio, documents that Perito Moreno has entered a phase of accelerated retreat. Led by glaciologist Luciano Gelos of Argentina’s National Scientific and Technical Research Council (CONICET), the research team used direct ice-flow measurements and newly mapped bedrock topography beneath the glacier to show that the glacier’s front is pulling back faster than at any point in the modern observational record. “We expected Perito Moreno to remain stable for at least another decade,” Gelos said in a statement accompanying the paper. “The bedrock geometry we mapped tells us that once retreat begins here, it is very difficult to reverse.” The finding removes one of the last reassuring data points in a region where ice loss has become the norm, and it sharpens an urgent question: what happens to the millions of people downstream who depend on meltwater they have long taken for granted?
A glacier that defied the trend, until now
Perito Moreno sits within the Southern Patagonian Ice Field, the largest temperate ice mass in the Southern Hemisphere. Most of the ice field’s outlet glaciers have been retreating for decades, a pattern consistent with rising temperatures across Patagonia that have averaged roughly 0.5 to 1.0 degrees Celsius above mid-20th-century baselines. Perito Moreno’s periodic advances, driven by a unique geometry that allowed it to dam a side channel of Lago Argentino and build pressure until a spectacular rupture, made it a scientific outlier and a symbol of glacial resilience. That advance-rupture cycle, last observed in 2018, now appears to have ended.
The new study upends that narrative. Bedrock data reveal that the glacier’s base sits in a configuration that makes sustained retreat more likely once it begins. The researchers note that the transition from stability to retreat appears linked to warming surface temperatures and changing precipitation patterns, both consistent with broader climate trends identified by the Intergovernmental Panel on Climate Change.
The IPCC’s Sixth Assessment Report, in its Cross-Chapter Paper on mountains, synthesizes evidence from thousands of studies showing that glacier retreat worldwide is reducing water availability in mountain catchments. The assessment attributes these losses to human-caused warming with high confidence and traces clear hydrological pathways from shrinking ice to diminished river flows. While the IPCC operates at a global and regional scale rather than isolating individual Argentine basins, Argentina’s own National Institute of Snow, Ice, and Environmental Glaciology Research (IANIGLA) provides basin-level glacier data that fills that gap. Together, the two sources confirm that the pattern carries material consequences for a country where Andean meltwater feeds rivers supplying agriculture, hydropower, and drinking water to cities hundreds of kilometers from the mountains.
Water on the line
Argentina’s arid western provinces, from Mendoza to San Juan to Neuquen, rely on snowmelt and glacier-fed rivers for irrigation that sustains vineyards, orchards, and row crops. Hydroelectric dams on Andean tributaries generate a significant share of the country’s electricity. Farther south, communities around Lago Argentino and the Santa Cruz River basin draw water from systems fed in part by the Southern Patagonian Ice Field.
IANIGLA has cataloged more than 16,000 ice bodies across the Andes as part of the country’s glacier inventory, mandated under Law 26.639, the 2010 Glacier Protection Law. That inventory provides baseline data, but translating glacier-area losses into specific water-supply shortfalls for individual cities or irrigation districts requires hydrological modeling that remains incomplete in public records. “We know the ice is disappearing, but we still lack the models to tell a mayor exactly when her city’s tap water will be affected,” said Marcela Gonzalez, a hydrologist at the University of Cuyo in Mendoza who studies Andean water systems. The gap means policymakers are working with strong directional signals, glaciers are shrinking and flows will decline, but without precise timelines for when shortages will hit specific communities.
What is not in doubt is the direction. The IPCC assessment makes clear that as glaciers lose mass, they initially release more meltwater before eventually delivering less. Many Andean basins may already be past that peak, meaning river flows could decline even as ice loss continues. For downstream users, the practical effect is a future with less predictable and less abundant water during the dry summer months when demand is highest.
A new law loosens protections
Against this backdrop, Argentina’s congress in early 2025 approved legislation backed by President Javier Milei that weakens the legal framework protecting glaciers and periglacial zones. The measure, which modifies provisions of Law 26.639, was included as part of the administration’s broader deregulation package. According to reporting by the Associated Press, the bill modifies how glacier inventories are used in regulation and narrows the geographic scope of areas where industrial activity, including mining, is restricted. The law effectively opens high-mountain zones previously shielded under Law 26.639 to new resource-extraction projects.
Supporters of the measure argue it will attract investment and create jobs in economically struggling Andean provinces where mining is a major employer. Critics, including environmental organizations and opposition lawmakers, contend that the short-term economic logic ignores the glaciers’ irreplaceable role as natural water reservoirs. “You cannot replace a glacier with a desalination plant,” said Enrique Viale, an environmental lawyer and co-founder of the Argentine Association of Environmental Lawyers. “This law trades permanent water infrastructure built over millennia for a few decades of lithium and copper.” Periglacial zones, the rocky, ice-rich terrain surrounding glaciers, act as buffers that store and release meltwater gradually, smoothing seasonal supply for downstream users. Removing protections from those zones, opponents warn, risks disrupting water systems that millions of people depend on.
The AP reported that the bill’s passage followed a contentious congressional debate marked by protests. Environmental groups have signaled they will challenge the law through legal and political channels, but as of May 2026, the legislation stands.
What remains unclear
Several important questions do not yet have firm answers. The Perito Moreno study establishes that retreat has begun but does not publish a specific forecast for how far or how fast the glacier’s front will pull back over the next decade. Bedrock mapping will improve future models, yet precise projections for downstream river flows tied to this glacier’s losses have not been released.
On the policy side, the full regulatory details of the new law, including which zones will be opened, what environmental review processes will remain, and how existing mining concessions will be affected, are still being worked out through implementation rules and agency guidelines. No peer-reviewed study has yet quantified the hydrological effects of expanded mining in periglacial areas under the new framework. The concern is scientifically grounded: mining activity in cold mountain environments is known to disturb permafrost and alter drainage patterns. But measured outcomes specific to Argentina’s new regulatory reality do not yet exist.
Voices from affected communities are also largely absent from the public record. News coverage has documented protests in Buenos Aires and provincial capitals, but direct testimony from farmers, ranchers, and residents in glacier-fed valleys about how they are already experiencing changes in seasonal water flows has not surfaced in the primary sources reviewed for this report.
Extraction vs. the ice: a policy collision with no easy exit
The convergence of these developments, a flagship glacier shifting into retreat, global science confirming that such losses reduce water availability, and a government choosing to loosen protections over the landscapes that store and release that water, creates a tension that will define environmental policy in Argentina for years to come.
The Perito Moreno findings and the IPCC synthesis represent strong, independently verified warning signals. The new glacier law represents a political bet that extraction and ice preservation can coexist. Whether that bet pays off, or whether it accelerates the very losses scientists are documenting, will depend on monitoring, enforcement, and decisions that have not yet been made. For the communities downstream, the stakes are not abstract. They are measured in the rivers that water their crops, power their cities, and flow from ice that is no longer holding steady.
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*This article was researched with the help of AI, with human editors creating the final content.
