Coupled ice shelf‐ocean modeling and complex grounding line retreat from a seabed ridge

Abstract

Recent observations and modeling work have shown a complex mechanical coupling betweenAntarctica's floating ice shelves and the adjacent grounded ice sheet. A prime example is Pine Island Glacier, West Antarctica, which has a strong negative mass balance caused by a recent increase in ocean-induced melting of its ice shelf. The mass loss coincides with the retreat of the grounding line from a seabed ridge, on which it was at least partly grounded until the 1970s. At present, it is unclear what has caused the onset of this retreat and how feedback mechanisms between the ocean and ice shelf geometry have influenced the ice dynamics. To address these questions, we present the first results from an offline coupling between a state-of-the-art shallow-ice flow model with grounding line resolving capabilities and a three-dimensional ocean general circulation model with a static implementation of the ice shelf. A series of idealized experiments simulate the retreat from a seabed ridge in response to changes in the ocean forcing, and we show that the retreat becomes irreversible after 20 years of warm ocean conditions. A comparison to experiments with a simple depth-dependent melt rate parameterization demonstrates that such parameterizations are unable to capture the details of the retreat process, and they overestimate mass loss by more than 40% over a 50 year timescale.

Projections of Future Sea Level Contributions from the Greenland and Antarctic Ice Sheets: Challenges Beyond Dynamical Ice Sheet Modeling

“…The first studies relying on coupled ice-ocean models show that simulations performed with parameterizations of ice shelf melt tend to overestimate glacier changes and mass loss compared to simulations performed with coupled ice-ocean models (De Rydt and Gudmundsson, 2016;Seroussi et al, 2017). The coupled models agree better with observations of real glacier changes and grounding line retreat, in particular .…”

Five decades of strong temporal variability in the flow of Brunt Ice Shelf, Antarctica

“…Numerical modelling has shown how ocean-induced ice shelf melting can lead to enhanced ice flow through loss in buttressing (e.g Gagliardini and others, 2010;De Rydt and Gudmundsson, 2016), and observations point to dynamical thinning of glaciers being caused by changes in thicknesses over abutting ice shelves (e.g. Wouters and others, 2015;Wuite and others, 2015).…”

Progress in Numerical Modeling of Antarctic Ice-Sheet Dynamics

“…Gladstone et al [52] coupled a 1D time-dependent flow-line model to a box model for ice-shelf cavity circulation and made centennial predictions for Pine Island Glacier. 2D plan-view coupling with ice-sheet models has been realized for ideal cases [30,57], and more recently for Pine Island Glacier [116]. The time steps employed by both models differ by few orders of magnitude, making the coupling asynchronous.…”