T18 Sea Level and Ice-Sheet Changes, Glacial Isostatic Adjustment, and Landscape Evolution I

Monday, 26 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

A NEW METHOD TO SIMULATE THE ANTARCTIC ICE SHEET OVER THE LAST GLACIAL CYCLE USING A COUPLED 3D GIA – ICE DYNAMIC MODEL

Paper number: T18-9
Program: Technical Sessions
Time: 3:10 PM – 3:25 PM

Authors

Abstract

It is projected that the contribution of the Antarctic Ice Sheet to future global sea level rise can reach up to 30 centimeters in 2100, but the uncertainty of the projections is high. To better predict the future of the Antarctic Ice Sheet (AIS), more accurate simulations of the evolution of the AIS are needed. It has been shown that Glacial Isostatic Adjustment (GIA) is an important process to consider when simulating the AIS over glacial-interglacial cycles. GIA has a stabilizing feedback effect on the evolution of the ice sheet in two ways. First, vertical bedrock deformation due to a changing ice load alters ice-sheet surface elevation. Second, bedrock deformation will change the location of the ice sheet grounding line. GIA is mainly determined by the viscosity of the mantle underneath the AIS, with relatively low viscosities in West Antarctica and higher viscosities in East Antarctica. Most ice-dynamic models consider radial or lateral viscosity variations underneath the AIS but do not take into account the stabilizing GIA feedback effects when simulating the evolution of the AIS.

This study presents a new method to investigate 3D GIA feedback effects in detail at short timescales of thousands of years at any chosen period during the last glacial cycle. The method is applied using an ice-sheet-shelf model called ANICE combined with a 3D GIA FEM model. This led to the development of a fully coupled ice dynamic-3D GIA model with coupling timesteps of 1000 and 5000 years. The model computations alternate between the ice-sheet model and a 3D Finite Element Method model until convergence of the Earth’s surface deformation occurs at each timestep. We simulate the evolution of the AIS from 120,000 years ago to present day, considering 1D and non-linear 3D rheologies.

Preliminary results show a maximum difference of deformation of the Earth’s surface between the uncoupled and the coupled model of 8 mm per year using a radially and laterally varying Earth structure. The increase of deformation is highest at the Siple Coast, the Ronne Ice Shelf, and several other locations along the grounding line of the AIS. The grounding line position differs up to 160 kilometers over 5000 years close to areas with high changes in ice thickness when comparing the coupled model to the uncoupled model.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-359854

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