Kinematic response of ice-rise divides to changes in oceanic and atmospheric forcing

Abstract

Abstract. The majority of Antarctic ice shelves are bounded by grounded ice rises. These ice rises exhibit local flow regimes that partially oppose the flow of the surrounding ice shelves. Formation of such ice rises is accompanied by a characteristic upward arching internal stratigraphy (Raymond arches), archiving potential past divide migration and the onset of divide flow. Information about past ice-sheet conditions can therefore be retrieved in areas where other archives are missing. However, the quantitative interpretation of the stratigraphy requires modelling and radar observations. Hitherto, ice-rise modelling has been restricted to 2D and excluded the coupling between ice shelf and ice rise. This presents a major limitation for the interpretation of ice rises as ice-dynamic archive. Here we present an improved modelling framework to study ice-rise evolution using a calibrated, isothermal, and isotropic 3D Full-Stokes model including grounding-line dynamics at the required mesh resolution (<500 m). We apply the model to the Ekström Ice Shelf catchment containing two ice rises. Our results show that changes in the surface mass balance result in immediate and sustained divide migration (>2.0 m/yr) of up to 3.5 km. In contrast, instantaneous ice-shelf disintegration causes a short-lived and delayed (by 60–100 years) response of smaller magnitude (<0.75 m/yr). The model tracks migration of a triple junction and synchronous ice-divide migration in both ice rises with similar magnitude but differing rates. The model is suitable for glacial/interglacial simulations on the catchment scale, providing the next step forward to unravel the ice-dynamic history stored in ice rises all around Antarctica.

Characteristics of ice rises and ice rumples in Dronning Maud Land and Enderby Land, Antarctica

“…Basal melt rates obtained using a steady state input–output method applied to the ice-shelf mass balance reveals values up to ~1.1 m a −1 near the grounding zone and at the calving front north of western side of Halvfarryggen (Neckel and others, 2012). Model simulations of the catchment of the Ekström Ice Shelf reveal that SMB perturbations result in immediate and sustained divide migration of up to 3.5 km at a speed >2 m a −1 of the Halvfarryggen and Søråsen promontories (Schannwell and others, 2019). Whereas simulations show that instantaneous ice-shelf disintegration results in small (<0.75 m a −1 ) divide migration, which is short-lived and delayed.…”

Parameter sensitivity analysis of dynamic ice sheet models-Numerical computations

“…The stationary basal friction coefficients have been derived from satellite data in this way for many glaciers and continental ice sheets using velocity data in e.g. Gillet-Chaulet et al (2016); Isaac et al (2015); Schannwell et al (2019); Sergienko and Hindmarsh (2013). The sensitivity to changes at the base increases closer to the grounding line in the coastal regions in Durand et al (2011).…”

“…The difficulty in separating the topography from the sliding properties at base in the inversion is also addressed in [14,32]. Considerable differences in the friction coefficient in the FS and SSA models are found after inversion in [26]. By linearization of the model equations, a transfer operator is derived in [7,8] and it is shown in [9] how the topography and the friction coefficients are affected by measurement errors at the surface.…”

Sensitivity of ice sheet surface velocity and elevation to variations in basal friction and topography in the Full Stokes and Shallow Shelf Approximation frameworks

“…Shallow shelf/stream approximation (SSA) model, see Sect. 2), has an impact on the values of the friction parameters obtained from the solution of the corresponding inverse problem (Gudmundsson, 2008;Schannwell et al, 2019).…”