Modelled fracture and calving on the Totten Ice Shelf

Abstract

Abstract. The Totten Ice Shelf (IS) has a large drainage basin, much of which is grounded below sea level, leaving the glacier vulnerable to retreat through the Marine Ice Shelf Instability mechanism. The ice shelf has also been shown to be sensitive to changes in calving rate, as a very small retreat of the calving front from its current position is predicted to cause a change in flow at the grounding line. Therefore understanding the processes behind calving on the Totten IS is key to predicting its future sea level rise contribution. Here we use the Helsinki Discrete Element Model (HiDEM) to show that calving on the Totten IS 15 is controlled not only by locally produced fractures at the calving front, but is also influenced by basal fractures which are likely produced at the grounding line. Our model results show that regrounding points may be key areas of basal crevasse production, and can produce basal crevasses in both an along and across flow orientation. As well as affecting calving, along flow basal crevasses at the grounding line may be a possible precursor to basal channels. We use two additional models to examine the evolution of basal fractures as they advect downstream, demonstrating that both strain and ocean melt have the 20 potential to deform narrow fractures into the broad basal features observed near the calving front. The wide range of factors which influence fracture patterns and calving on this glacier will be a challenge for predicting its future mass loss.

Marine ice-cliff instability modeling shows mixed-mode ice-cliff failure and yields calving rate parameterization

“…Brittle failure, after viscous deformation in Elmer/Ice, is simulated with the standard brittle-elastic implementation of the 3D Helsinki Discrete Element Model (HiDEM be ) 17,18,38 . HiDEM be replicates a wide range of calving styles 19 and successfully reproduced observed calving events at Kronebreen, Svalbard 22 , Totten Ice Shelf, Antarctica 21 and Bowdoin Glacier, Greenland 20 . The fracture properties used in this study are informed by those used to model Bowdoin Glacier 20 and Store Glacier (Joe Todd, pers.…”

“…This suggests that some degree of viscous deformation or shear localisation is a necessary pre-condition for the failure of ice cliffs with such characteristics over this topography. We therefore assess ice-cliff failure via interacting viscous deformation and brittle failure through a one-way offline coupling of Elmer/Ice and HiDEM be 21,22 . Elmer/Ice is employed to simulate the viscous deformation of initially vertical ice faces, and output from successive time-steps is used to initialize the domain of HiDEM be simulations that test the evolved geometry for brittle failure.…”

Effective Rheology Across the Fragmentation Transition for Sea Ice and Ice Shelves

“…The height, h , distributions of these ridges and keels have been observed to follow exponentials, n ( h ) ∝ exp(− const * h ) (Rothrock & Thorndike, ; Tan et al, ; Wadhams, ). HiDEM results for glacier and shelf calving can be found in Åström et al (), Benn et al (), and Cook et al ().…”

“…Figure d shows the spatial power spectrum of fracture patterns such as those as displayed in Figure a. Results are displayed for sea ice and Totten ice shelf (Cook et al, ). It is evident from these plots that the HiDEM model can consistently reproduce observed behavior of sea ice and ice shelves.…”

Calving glaciers and ice shelves

“…The third example we present here focuses on fracturing of the Totten ice shelf in eastern Antarctica [115]. Figure 10 shows a comparison of observed fracture patterns with HiDEM results using the present-day shelf thickness and location of grounded zones as boundary conditions.…”