Located in the heart of Patagonia's Los Glaciares National Park, Perito Moreno has long stood out for defying global trends of glacial retreat. But since 2018, researchers say, that stability has given way to a steady and accelerating decline.
Over the past seven years, the glacier has lost nearly 2 square kilometres of surface area, and its thickness is now decreasing by up to 8 metres annually — double the rate recorded just two years ago.
"It's too large for the climate it now finds itself in," says Dr Lucas Ruiz, a glaciologist with the Argentine Institute of Nivology, Glaciology and Environmental Sciences. "It simply cannot withstand the current heat."
A Shift After More Than a Century of Stability
For decades, Perito Moreno remained an anomaly — gaining as much snow in its upper reaches as it lost through melting and dramatic icefalls at its front. Tourists from around the world travelled to witness its towering wall of ice calve into Lago Argentino, a breathtaking and seemingly eternal spectacle.
But scientists now say that equilibrium has been broken. The first signs of net retreat were observed in 2022. It happened again in 2023, 2024, and now 2025.
Most concerning is the glacier's northern margin, which lies over the deepest part of Lago Argentino — and is now thinning so rapidly that ice once grounded on the lakebed is beginning to float. This loss of contact with the lake bottom acts like a pulled anchor, allowing the glacier's front to accelerate and deform.
"This sliding process creates a feedback loop," Ruiz explains. "The more the front moves, the more the glacier destabilises — a process that could be impossible to reverse."
A Heatwave-Driven Collapse?
The summer of 2023-24 saw record high temperatures of 11.2°C in the region. Over the past three decades, the average summer temperature has risen by 1.2°C, a shift that glaciologists say is sufficient to significantly increase melt rates.
"We're now seeing giant calving events — louder, more frequent, and far larger than what's historically been recorded," says Dr Ruiz. In April, local guides described witnessing the collapse of an ice tower the height of a 20-storey building.
New Monitoring Technology Confirms the Loss
To better understand the glacier's retreat, researchers led by Professor Xabier Blanch Gorriz at the Polytechnic University of Catalonia have deployed automated photogrammetry systems that take images every 30 minutes. Early comparisons from just six months apart show stark ice loss at the glacier's front.
Satellite data echoes these findings, revealing clear signs of retreat across a 100-day period.
Blanch Gorriz is cautious about calling the process "irreversible" but admits that current trends point in that direction. "Glaciers are dynamic systems, yes. But what we're seeing now is an accelerating collapse."
Losing the Magallanes Buttress
The most dramatic change may still be ahead. Perito Moreno currently rests against the Magallanes Peninsula, a landmass that has acted as a natural stabiliser, slowing its retreat. But researchers believe the glacier could soon detach from this buttress.
"When that happens," says Ruiz, "the glacier will likely retreat rapidly into a narrow valley behind it — reaching a configuration never seen before, even by the first explorers in the 1800s."
Unlike the peninsula, the valley offers no firm ground to hold the glacier in place, potentially triggering a new phase of rapid, sustained retreat.
A Global Pattern of Loss
Perito Moreno's decline mirrors that of nearby glaciers like Upsala and Viedma, which have retreated drastically over the past 20 years. It is also emblematic of a larger global trend.
"What we're seeing here," says Ruiz, "is humanity digging the grave of the world's glaciers."
Designated a UNESCO World Heritage Site, Perito Moreno has long stood as a symbol of resilience in a fragile climate. That symbol is now slipping away — not with a sudden collapse, but with the slow and relentless force of warming air, rising temperatures, and an accelerating loss of ice.