Heavy rainfall can accelerate the speed of Alaska’s Turner Glacier (Sít’ Kusá) by up to 251 percent during its slow-flow phase, Interesting Engineering reported, revealing how precipitation directly drives glacial movement.
Boise State University researchers analyzed GPS measurements from the glacier to track these shifts. They compared rainfall-driven speed changes during a surge between 2020 and 2021 with a slower-flow quiescence period from 2022 to 2024.
Surge-type glaciers undergo periodic order-of-magnitude increases in flow speed. To investigate these variations, researchers compared 10 GPS-derived glacier surface speed records with modeled rainfall estimates.
GPS instruments installed around the glacier recorded its position every 15 seconds. Researchers compared these data with rainfall measurements from a weather station at nearby Yakutat Airport.
During the 2020–2021 surge, 56 percent of large rainfall events recorded speed anomalies. The glacier reached speeds of 24.6 feet per day, representing a 116 percent increase that lasted an average of 66.5 hours.
Between 2022 and 2024, rainfall-induced acceleration occurred during 46 percent of 37 monitored rainfall events. These events produced smaller absolute speed changes of approximately 1.5 meters per day and lasted around 33 hours. However, the relative percentage increase reached 251 percent.
Glacier drainage efficiency influences how water moves beneath the ice. Inefficient drainage allows water pressure to build underneath a glacier, which reduces friction between the ice and the ground.
Differences in acceleration characteristics indicated more efficient drainage during quiescence. Yet, because precipitation-triggered speed-ups were observed in both periods, it appears that a poorly draining element remained active across all stages of the surge cycle.
Particularly large and prolonged rainfall events could temporarily slow the glacier during its surge. Within under a fortnight, velocities dropped back to normal as the subglacial network resumed its ineffective drainage configuration.
Acceleration during the surge generally began about 12 hours after rainfall started. Speed increases during quiescence peaked approximately 32 hours after rainfall began.
Across both periods, the most pronounced increases in velocity occurred in the lower portions of the glacier rather than higher up in the valley. The findings demonstrate that rainfall affects the movement of both fast- and slow-flowing glaciers, helping scientists understand how glacier speeds respond to precipitation.
