The Impact of Mechanical Ablation on the Mass Balance of Hailuogou Glacier, Southeastern Tibetan Plateau

Sustained negative mass balance leads to glacier retreat and thinning, which can compromise the structural strength of the ice. This, in turn, impacts glacier stability, giving rise to mechanical ablation processes such as frontal ice collapse and subglacial channel collapse; however, such events are poorly quantified and characterized. We quantify mechanical ablation events occurring around the terminus of Hailuogou Glacier in the southeastern Tibetan Plateau. We use previous data describing frontal ice collapse events to establish an area-volume relationship, and approximate their contribution to glacier mass balance. ASTER stereo-derived geodetic data show that the glacier experienced enhanced negative mass balance from 2002 to 2021. Frontal mechanical ablation processes dominated the geomorphological changes around the glacier terminus during this period. Despite the relatively minor contribution of mechanical ablation events to glacier-scale mass balance, these events altered the dominance of ice loss from melting to collapsing in the lowermost part of the glacier. This finding suggests that, for glacier termini susceptible to frontal collapse, mass loss during periods of strongly negative balance may not be characterized by a constant melting rate. Instead, the response is often a rapid frontal collapse, followed by adjustment and subsequent mass loss through melting, ultimately reaching a new dynamic equilibrium. Given projected warming, the glacier is expected to enter a phase of enhanced recession, leading to an increased magnitude and frequency of mechanical failures. This advances our understanding of ablation during periods of rapid deglaciation, which is highly relevant for other similar glaciers on the Tibetan Plateau.