A statistical fracture model for Antarctic ice shelves and glaciers

Veronika Emetc,Malcolm Sambridge,Paul Tregoning,Chris Borstad,Mathieu Morlighem

doi:10.5194/tc-12-3187-2018

Abstract

Abstract. Antarctica and Greenland hold enough ice to raise sea level by more than 65 m if both ice sheets were to melt completely. Predicting future ice sheet mass balance depends on our ability to model these ice sheets, which is limited by our current understanding of several key physical processes, such as iceberg calving. Large-scale ice flow models either ignore this process or represent it crudely. To model fractured zones, an important component of many calving models, continuum damage mechanics as well as linear fracture mechanics are commonly used. However, these methods have a large number of uncertainties when applied across the entire Antarctic continent because the models were typically tuned to match processes seen on particular ice shelves. Here we present an alternative, statistics-based method to model the most probable zones of the location of fractures and demonstrate our approach on all main ice shelf regions in Antarctica, including the Antarctic Peninsula. We can predict the location of observed fractures with an average success rate of 84 % for grounded ice and 61 % for floating ice and a mean overestimation error rate of 26 % and 20 %, respectively. We found that Antarctic ice shelves can be classified into groups based on the factors that control fracture location.

Highlights

In recent years, increased positive-temperature anomalies have been observed in Antarctica (Jansen et al, 2007; Vaughan et al, 2003; Johanson and Fu, 2007; Steig et al, 2009), and future climate change in this area may be even more pronounced (Vaughan et al, 2003)
Understanding the factors that control the mass balance of the Antarctic Ice Sheet is crucial if we want to better understand the future impact of climate change and contribution of Antarctic ice mass loss to global sea level rise (SLR)
We applied the logistic regression algorithm (LRA) method combined with the randomwalk method to 45 ice shelf regions, including both ice shelves and surrounding grounded ice

Summary

Introduction

In recent years, increased positive-temperature anomalies have been observed in Antarctica (Jansen et al, 2007; Vaughan et al, 2003; Johanson and Fu, 2007; Steig et al, 2009), and future climate change in this area may be even more pronounced (Vaughan et al, 2003). A number of studies have shown that increased calving can lead to destabilization of ice shelves and to a loss of the supporting mechanism (known as the “buttressing effect” or “back stress”) they provide to inland ice in Antarctica (Jezek, 1984; De Angelis and Skvarca, 2003; Dupont and Alley, 2005; Goldberg et al, 2009; Katz and Worster, 2010; Gudmundsson, 2013; Borstad et al, 2013) This support can be crucial for the overall stability of the West Antarctic Ice Sheet as strong basal melting and reduced ice shelf buttressing can make the ice sheet unstable (Miles et al, 2013). More explicit simulations have been performed using discrete element models describing short-term calving events (Åström et al, 2013)

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