Kinematic response of ice-rise divides to changes in ocean and atmosphere forcing

Abstract

Abstract. The majority of Antarctic ice shelves are bounded by grounded ice rises. These ice rises exhibit local flow fields that partially oppose the flow of the surrounding ice shelves. Formation of ice rises is accompanied by a characteristic upward-arching internal stratigraphy (“Raymond arches”), whose geometry can be analysed to infer information about past ice-sheet changes in areas where other archives such as rock outcrops are missing. Here we present an improved modelling framework to study ice-rise evolution using a satellite-velocity calibrated, isothermal, and isotropic 3-D full-Stokes model including grounding-line dynamics at the required mesh resolution (<500 m). This overcomes limitations of previous studies where ice-rise modelling has been restricted to 2-D and excluded the coupling between the ice shelf and ice rise. We apply the model to the Ekström Ice Shelf, Antarctica, containing two ice rises. Our simulations investigate the effect of surface mass balance and ocean perturbations onto ice-rise divide position and interpret possible resulting unique Raymond arch geometries. Our results show that changes in the surface mass balance result in immediate and sustained divide migration (>2.0 m yr−1) 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−1). 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.

Impact of coastal East Antarctic ice rises on surface mass balance: insights from observations and modeling

“…In fact, there is observational evidence for an increase in erosion with snowfall. For example a recent study by Souverijns et al (2018), who used a set of remote-sensing instruments at a study site close to PEA station, found that snowfall events only led to accumulation 60 % of the time, while leading to ablation 40 % of the time due to the erosion of the freshly fallen snow, and confirmed earlier studies in that the availability of fresh snow is more important for erosion to occur than high wind speeds (Gallée et al, 2001).…”

Quantifying the effect of ocean bed properties on ice sheet geometry over 40 000 years with a full-Stokes model

“…The location of the EDML ice core is about 700 km to the south-east of the modelling domain on the Antarctic plateau. The Ekström catchment also contains two ice rises (Schannwell et al, 2019;Drews et al, 2013) with ice flow centres independent from the main ice sheet. Ice rises archive the regional ice sheet history in their internal stratigraphy.…”

“…The risk involved is that the matching may overcompensate for the simplified model physics, leading to higher uncertainties in future predictions where model constraints are absent. Due to the high computational demands, in terms of both mesh resolution and the physics required to solve for a freely evolving grounding line (Gillet-Chaulet et al, 2012;Seddik et al, 2012;Favier et al, 2014;Schannwell et al, 2019), FS models up to now have been restricted to individual simulations and simulation lengths of < 1000 years for real-world geometries. Therefore, there is a need to extend the applicability of regional FS ice sheet models to timescales longer than 1000 years so that uncertainties due to physical approximations in the force balance can be quantified and reduced in the near future.…”

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), and Sergienko and Hindmarsh (2013).…”

“…In an ill-conditioned problem, the sensitivity at the surface to perturbations at the base is low. This matrix can also be used to quantify the uncertainty in the ice flow due to uncertainties in the model parameters (see, e.g., Bulthuis et al, 2019;Schlegel et al, 2018;Smith, 2014). Perturbations at the ice base with short wavelength are propagated to the surface with a weaker effect on the height and velocity compared to long wavelengths in Gudmundsson (2003Gudmundsson ( , 2008.…”