This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Glaciers are often thought of as unyielding blocks of ice that slowly carve out the landscape as they move downhill by gravity. But sometimes their slow crawl becomes a surge that sees them move orders of magnitude faster than their usual speed.
Such events can have dramatic effects on the environment, acting like a bulldozer to erode valleys, shattering the glacier's surface into crevasses, blocking side valleys to create ice dams with temporary lakes behind, or causing catastrophic flooding when these ice dams burst. And as glaciers move toward the sea, increased ice calving and melting have considerable impacts on rising sea levels. Understanding the mechanisms behind these aggressive advances is therefore vital for scientists to monitor instabilities in the world's glaciers and their wider implications for climate change conversations.
Parker Wilkerson, of Boise State University, and colleagues turned to the steep, highly crevassed Sít' Kusá (Turner Glacier) in Alaska to explore how rain can induce glacier surges. Using GPS measurements from instruments installed around the glacier, the researchers recorded its position every 15 seconds to monitor speed changes in the short term compared to the glacier's longer-term movement. These were then associated with rain estimates validated by measurements taken at the weather station of the nearby Yakutat Airport to identify if there was a correlation between rainfall events and glacier surges.
The results, published in The Cryosphere, show that there is. Comparing a period of surge (2020–2021) to slow flow (2022–2024), the team found that over half of the rainfall events caused speed-ups, with the maximum reaching 7.5 meters (24.6 feet) in a single day—that's equivalent to a 116% increase in speed, or more than double. This surge also lasted twice as long (66 hours) as any occurring during the quiescent flow period and tended to begin 12 hours after the start of the rainfall event when precipitation reached at least 20 mm (0.79 inches).
The glacier returned to a stable state three days later. However, while rain-induced speed-ups were less frequent during quiescence, when they did occur, they required 60 mm (2.4 inches) of rain since the start of the event and resulted in a much bigger percentage increase (251%) in speed, peaking on average 32 hours later. Despite this speed increase only being 1.5 meters (4.9 feet) per day, it is proportionately larger given the glacier is moving at such a slow background speed.
And during both phases, glacier acceleration was greatest in the downhill parts compared to those higher in the valley, likely a combination of landscape topography, gravity and meltwater aiding movement. The researchers explain that the surge phenomenon is a consequence of the efficiency of the glacier's drainage system. An efficient one has linked channels running on top of, through and beneath the glacier that allow rainwater and meltwater to drain away quickly, meaning the glacier sits on the underlying bedrock and continues its slow, steady advance.
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