Nature, 15 February 2023<\/p>\n
Glacial lake outburst floods (GLOFs) now occur at higher altitudes and six weeks earlier than they did a century ago; their declining volume provides a clear message that worldwide glaciers are disappearing at an alarming rate. GLOFs release an outpouring of meltwater that can travel hundreds of kilometers, raising local river levels by several meters and triggering landslides that destabilize surrounding hilltops. This study consolidates more than one hundred years of data to understand long-term trends in GLOFs across six major mountain regions. They found that glaciers in the Himalayas and European Alps can now produce massive floods even at the highest elevations, which were previously stabilized by snowfall and cooler temperatures. Glacier lakes form in \u201cablation\u201d zones, traditionally low-altitude areas of a glacier where ice loss dominates. Over the past century, rising global temperatures have expanded these ablation zones to encompass entire glaciers at high altitudes, increasing the formation of meltwater pools at unprecedented heights. The instability of these lakes worsens as the ice thins and temperatures rise.<\/p>\n
The ice dams restraining glacier lakes in High Mountain Asia now burst open eleven weeks earlier than they did in 1900, followed by the European Alps at ten weeks and northwestern North America at seven weeks earlier. Under a mid to high emission scenario, authors predict that GLOFs will diminish, and by 2100 eventually disappear with the glaciers themselves in regions such as the European Alps, Scandinavia, and British Columbia. Other regions with larger glaciers, such as Patagonia and Alaska, will likely endure intense high elevation GLOFs as new high-altitude areas begin losing ice, endangering downstream communities. This study underscores the importance of reducing emissions to preserve these delicate ice-covered mountain regions across the world, and emphasizes the need for monitoring high-risk regions to better anticipate flooding and reduce damage to local infrastructure, farmland, and transportation systems.<\/p>\n