Abstract
AbstractHydraulically forced crevassing is thought to reduce the stability of ice shelves and ice sheets, affecting structural integrity and providing pathways for surface meltwater to the bed. It can cause ice shelves to collapse and ice sheets to accelerate into the ocean. However, direct observations of the hydraulically forced crevassing process remain elusive. Here we report a novel method and observations that use icequakes to directly observe crevassing and determine the role of hydrofracture. Crevasse icequake depths from seismic observations are compared to a theoretically derived maximum dry crevasse depth. We observe icequakes below this depth, suggesting hydrofracture. Furthermore, icequake source mechanisms provide insight into the fracture process, with predominantly opening cracks observed, which have opening volumes of hundredths of a cubic meter. Our method and findings provide a framework for studying a critical process that is key for the stability of ice shelves and ice sheets and, therefore, future sea level rise projections.
Highlights
Forced surface crevassing, referred to as hydrofracture, has the potential to significantly influence the stability of glaciers, ice sheets, and ice shelves (Lai et al, 2020)
On glaciers and ice sheets, hydraulically forced crevassing provides a potential pathway for surface meltwater to reach and lubricate the bed (Das et al, 2008; Van Der Veen, 1998; Weertman, 1973), enhancing basal sliding of ice into the ocean (Rignot & Kanagaratnam, 2006), accelerating sea level rise
Forced surface crevassing on ice shelves can result in catastrophic failure, with melt ponds promoting fracture that can lead to the collapse of the ice shelf (Hughes, 1983; Mcgrath et al, 2012; Scambos et al, 2000, 2003)
Summary
Forced surface crevassing, referred to as hydrofracture, has the potential to significantly influence the stability of glaciers, ice sheets, and ice shelves (Lai et al, 2020). On glaciers and ice sheets, hydraulically forced crevassing provides a potential pathway for surface meltwater to reach and lubricate the bed (Das et al, 2008; Van Der Veen, 1998; Weertman, 1973), enhancing basal sliding of ice into the ocean (Rignot & Kanagaratnam, 2006), accelerating sea level rise. We present icequake observations from Skeidararjökull, an outlet glacier of the Vatnajökull Ice Cap, Iceland This glacier is an ideal environment for studying potential hydraulically forced crevassing due to the high levels of surface melt present. Our results provide for the first time direct evidence of hydrofracture, offering insights into this previously elusive process
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