Heavy rainfall can accelerate the speed of Turner Glacier in Alaska by as much as 251 percent, according to a new study.
Researchers from Boise State University analyzed GPS measurements from the glacier, also known as Sít’ Kusá. They evaluated precipitation impacts during two distinct operating phases. The team compared data from a surge period between 2020 and 2021 against a slower quiescent period spanning from 2022 to 2024.
GPS Tracking During the 2020–2021 Surge Phase
During the 2020 to 2021 surge, nine out of 16 large rainfall events recorded speed anomalies, representing 56 percent of those storms.
The ice reached movement rates of 24.6 feet per day, which marked a 116 percent increase. These surges lasted an average of 66.5 hours.
Contrasting Speeds in the 2022–2024 Quiescent Window
Between 2022 and 2024, rainfall-triggered acceleration happened less frequently. Out of 37 monitored rainfall episodes, 17 showed speed-ups, translating to 46 percent.
These events generated smaller movements of approximately 4.9 feet per day over roughly 33 hours. Despite the smaller absolute movement, the percentage increase reached 251 percent.
Sub-Glacial Drainage Pressures and Temporal Lags
Surge acceleration typically began about 12 hours after rainfall commenced. Speed increases during quiescence peaked around 32 hours after precipitation started. Lower sections of the glacier experienced the most substantial acceleration during both phases.
The investigation examined how sub-glacial drainage systems react to water influx. Inefficient drainage allows pressure to accumulate beneath the ice, lowering friction against the ground. The differences in speed characteristics point to more efficient drainage during quiescence. However, the presence of rainfall-induced acceleration in both phases indicates that an inefficient drainage component remains active throughout the surge cycle.
Particularly heavy and prolonged storms could temporarily decelerate the ice during active surges. Speeds subsequently recovered to pre-event levels in less than two weeks as drainage networks reverted to their inefficient states.
Earlier coverage: Barnes Ice Cap Growth Halted by Human-Driven Climate Change