The variability of tidewater-glacier calving: origin of event-size and interval distributions

TL;DR

This study analyzes calving activity at tidewater glaciers, showing that event sizes follow power-law distributions influenced by glacier susceptibility, and introduces a model explaining the variability and transition to self-sustained calving.

Contribution

The paper presents a simple calving model that reproduces observed size and interval distributions, linking glacier stability to calving susceptibility and transition points.

Findings

Event sizes follow power-law distributions over several orders of magnitude.

Inter-event intervals are broad but less tail-heavy, insensitive to calving susceptibility.

High calving susceptibility leads to self-sustained calving activity and rapid glacier retreat.

Abstract

Calving activity at the termini of tidewater glaciers produces a wide range of iceberg sizes at irregular intervals. We present calving-event data obtained from continuous observations of the termini of two tidewater glaciers on Svalbard, and show that the distributions of event sizes and inter-event intervals can be reproduced by a simple calving model focusing on the mutual interplay between calving and the destabilization of the glacier terminus. The event-size distributions of both the field and the model data extend over several orders of magnitude and resemble power laws. The distributions of inter-event intervals are broad, but have a less pronounced tail. In the model, the width of the size distribution increases with the calving susceptibility of the glacier terminus, a parameter measuring the effect of calving on the stress in the local neighborhood of the calving region. Inter-event interval distributions, in contrast, are insensitive to the calving susceptibility. Above a critical susceptibility, small perturbations of the glacier result in ongoing self-sustained calving activity. The model suggests that the shape of the event-size distribution of a glacier is informative about its proximity to this transition point. Observations of rapid glacier retreats can be explained by supercritical self-sustained calving.