Crevasse advection increases glacier calving

Abstract

Iceberg calving, the process where icebergs detach from glaciers, remains poorly understood. Moreover, few parameterizations of the calving process can easily be integrated into numerical models to accurately capture observations, resulting in large uncertainties in projected sea level rise. Recent efforts have focused on estimating crevasse depths assuming tensile failure occurs when crevasses fully penetrate the glacier thickness. However, these approaches often ignore the role of advecting crevasses on calculations of crevasse depth. Here, we examine a more general crevasse depth calving model that includes crevasse advection. We apply this model to idealized prograde and retrograde bed geometries as well as a prograde geometry with a sill. Neglecting crevasse advection results in steady glacier advance and ice tongue formation for all ice temperatures, sliding law coefficients and constant slope bed geometries considered. In contrast, crevasse advection suppresses ice tongue formation and increases calving rates, leading to glacier retreat. Furthermore, crevasse advection allows a grounded calving front to stabilize on top of sills. These results suggest that crevasse advection can radically alter calving rates and hint that future parameterizations of fracture and failure need to more carefully consider the lifecycle of crevasses and the role this plays in the calving process.

Basal hydrofractures near sticky patches

“…If an ice shelf extends seaward from the grounding line, the basal crevasses will weaken the shelf to lateral shear stresses associated with buttressing and vertical shear associated with calving (Bassis and Ma, 2015). The recent numerical model developed by Berg and Bassis (2022) suggests that the advection of crevasses could increase the calving rate and promote glacier retreat.…”

Increased crevassing across accelerating Greenland Ice Sheet margins

“…Changes in crevasse morphology and extent reflect changes in ice dynamics: specifically, the surface stress regime 1,37,38 . We used records of total ice flux through outlet glacier termini, termed discharge, as a proxy for the bulk dynamic change of ice sectors and basins.…”

“…pre-existing weaknesses that can promote calving and instability at glacier fronts 1 , whilst accumulated damage can soften the large-scale rheology of ice 2 . As key hydrological pathways [3][4][5] , crevasses transfer up to half of Greenland's seasonal surface runoff to the bed 6 .…”

“…By modulating the rate of meltwater transport to the ocean, further influence is exerted on terminus melt, fjord circulation, and fjord biogeochemistry [11][12][13] . These crevasse-dependent processes hold the potential to induce significant feedbacks between ice flow acceleration and mass loss 4,14 , making them a key source of uncertainty in projections of future Greenland Ice Sheet behaviour 1,15 .…”

Coupled 3-D full-Stokes modelling of tidewater glaciers

“…Unless the damage can be modelled as part of the viscous evolution of the ice and stress concentrations accounted for, a stress multiplier would need to be used that would likely end up being a tunable parameter, varying between glaciers, so would be far from ideal. Alternatively, using a Lagrangian approach, crevasse history could be explicitly tracked, something already implemented in 2-D modelling, which has been shown to lead to an increase in modelled calving compared to not including crevasse history (Berg and Bassis, 2022). Another possibility is to use computationally expensive models that explicitly model fracture dynamics to attempt to directly determine new calving laws or, at least, diagnostic stress states for calving (Åström and others, 2013;Benn and Åström, 2018).…”