PERITO GLACIER: The deep cracking sound bursting from within the ice signals the dramatic fall about to happen. Seconds later, a block of ice some 70 metres tall — the size of a 20-story building — collapses from the face of the Perito Moreno glacier into the aquamarine water below.

The sight has attracted visitors to Argentina’s most famous glacier for years. Standing on platforms facing the ice, they wait for the next crack to split the cool Patagonian air. But recently the size of the ice chunks breaking off — a process called “calving” — has been starting to alarm local guides and glaciologists, already anxious at a prolonged retreat by Perito Moreno, which had bucked the trend in recent decades by maintaining its mass even as warmer climates spurred faster glacial melting worldwide.

“Ice calving events of this size haven’t been very common at the Perito Moreno glacier over the past 20 years,” said Pablo Quinteros, an official tourist guide at Los Glaciares National Park in the southern province of Santa Cruz. “It’s only in the last four to six years that we’ve started to see icebergs this big,” he said during a visit in April. The face of the glacier, which flows down from Andean peaks to end in the waters of Lake Argentina, had for decades held more or less steady, some years advancing and others retreating. But in the last five years, there’s been a firmer retreat.

“It had been in more or less the same position for the past 80 years. And that’s unusual,” said Argentine glaciologist Lucas Ruiz.

Published in Dawn, May 16th, 2025