Theory 017/Earth & Space /Glaciology
Surges Happen at a Storage Threshold
Surges are timed by the melt year. The trigger may be a filled reservoir.
Glacier surges occur when subglacial water storage reaches a threshold rather than when melt peaks, so surge timing should be predicted from storage rather than from the melt season.
01The evidence
Surges are observed to occur after periods of accumulation of subglacial water, and the timing is not locked to peak melt.
02The tension
Surge models often link onset to melt season intensity, which predicts surge in the warmest year and fails when surges occur in average years.
03The mechanism
A glacier stores water at its bed until the drainage system can no longer evacuate it. When storage passes a threshold, the effective pressure rises and the glacier slides.
That makes surge timing a threshold crossing, which can occur in any year once storage is near the limit.
04What this is not
Melt models predict surges in warm years. This predicts them when storage crosses a threshold, which can be any year.
05Predictions
- P1Surge timing should track storage rather than melt.
- P2Surges should occur in average melt years near threshold.
- P3Drainage improvements should delay surges.
06Refutation
Surges locked to peak melt years would restore melt triggering.
07What it changes
It would change surge forecasting and hazard planning.