Marine outlet glacier dynamics, steady states and steady-state stability

Abstract

Laterally confined marine outlet glaciers exhibit a diverse range of behaviours. This study investigates time-evolving and steady configurations of such glaciers. Using simplified analytic models, it determines conditions for steady states, their stability and expressions for the rate of the calving-front migration for three widely used calving rules. It also investigates the effects of ice mélange when it is present. The results show that ice flux at the terminus is an implicit function of ice thickness that depends on the glacier geometric and dynamic parameters. As a consequence, stability of steady-state configurations is determined by a complex combination of these parameters, specifics of the calving rule and the details of mélange stress conditions. The derived expressions of the rate of terminus migration suggest a non-linear feedback between the migration rate and the calving-front position. A close agreement between the obtained analytic expressions and numerical simulations suggests that these expressions can be used to gain insights into the observed behaviour of the glaciers and also to use observations to improve understanding of calving conditions.

No general stability conditions for marine ice-sheet grounding lines in the presence of feedbacks

“…While several studies 14 , 15 , 18 have considered the effects of a feedback between the surface elevation and behavior of land-based ice sheets, all existing studies of stability of marine ice sheets 5 , 10 – 12 , 19 – 21 did not take into account feedbacks between the external conditions and the ice-sheet characteristics. It is, thus, not a priori clear whether the results of these studies remain valid in the presence of feedbacks.…”

Ocean‐Forcing and Glacier‐Specific Factors Drive Differing Glacier Response Across the 69°N Boundary, East Greenland

“…However, reverse bed slopes were associated with a range of changes in terminus position, including glaciers that underwent the most retreat and advance (Table 2). Thus, the impact of a reverse bed slope on glacier dynamics is variable within our study area, as has been observed elsewhere in Greenland (e.g., Bunce et al, 2018), and cannot alone account for observed differences in glacier dynamics across 69°N (e.g., Schoof et al, 2017;Sergienko, 2022).…”

Migration of the Shear Margins at Thwaites Glacier: Dependence on Basal Conditions and Testability Against Field Data

“…One of the reasons for a potential disconnect between models and paleo field observations is our incomplete understanding of the physical processes that could alter the MISI by breaking the monotonic increase of ice flux with ice thickness at the grounding line (Schoof, 2007; Weertman, 1974). Several processes could alter the monotonic relationship between ice flux and ice thickness including basal topography (Sergienko & Wingham, 2022), as well as different calving laws and the presence of ice melange (Sergienko, 2022). Large scale, 3D ice sheet models have attempted holistic modeling of the marine ice sheet at Thwaites Glacier accounting for many factors, including glacier widening, basal rheology, and solid earth feedbacks, among others and also predict MISI style collapse at Thwaites Glacier (Book et al., 2022; Joughin etal., 2014; Waibel et al., 2018).…”