A high-resolution Antarctic grounding zone product from ICESat-2 laser altimetry

Tian Li,Stephen J Chuter,Jonathan L Bamber,Geoffrey J Dawson

doi:10.5194/essd-14-535-2022

Abstract

Abstract. The Antarctic grounding zone, which is the transition between the fully grounded ice sheet to freely floating ice shelf, plays a critical role in ice sheet stability, mass budget calculations, and ice sheet model projections. It is therefore important to continuously monitor its location and migration over time. Here we present the first ICESat-2-derived high-resolution grounding zone product of the Antarctic Ice Sheet, including three important boundaries: the inland limit of tidal flexure (Point F), inshore limit of hydrostatic equilibrium (Point H), and the break in slope (Point Ib). This dataset was derived from automated techniques developed in this study, using ICESat-2 laser altimetry repeat tracks between 30 March 2019 and 30 September 2020. The new grounding zone product has a near-complete coverage of the Antarctic Ice Sheet with a total of 21 346 Point F, 18 149 Point H, and 36 765 Point Ib locations identified, including the difficult-to-survey grounding zones, such as the fast-flowing glaciers draining into the Amundsen Sea embayment. The locations of newly derived ICESat-2 landward limit of tidal flexure agree well with the most recent differential synthetic aperture radar interferometry (DInSAR) observations in 2018, with a mean absolute separation and standard deviation of 0.02 and 0.02 km, respectively. By comparing the ICESat-2-derived grounding zone with the previous grounding zone products, we find a grounding line retreat of up to 15 km on the Crary Ice Rise of Ross Ice Shelf and a pervasive landward grounding line migration along the Amundsen Sea embayment during the past 2 decades. We also identify the presence of ice plains on the Filchner–Ronne Ice Shelf and the influence of oscillating ocean tides on grounding zone migration. The product derived from this study is available at https://doi.org/10.5523/bris.bnqqyngt89eo26qk8keckglww (Li et al., 2021) and is archived and maintained at the National Snow and Ice Data Center.

Highlights

With a global sea level rise equivalent of 58 m (Fretwell et al, 2013), the Antarctic Ice Sheet has been losing ice at an accelerated pace (Shepherd et al, 2018)
Using the GZ mapping techniques developed in this study, we produced a new high-resolution GZ product (Li et al, 2021) by identifying 21 346 Point F (Fig. 5a), 18 149 Point H (Fig. 5b), and 36 765 Point Ib (Fig. 5c) locations over the Antarctic Ice Sheet from 18 months of ICESat-2 repeat tracks
It is able to recover the GZ of the fast-flowing glaciers that are difficult to map with the dynamic method, including Pine Island, Thwaites, Kohler, Smith, and Pope glaciers located in the Amundsen Sea embayment as well as the mountainous regions in Victoria Land

Summary

Introduction

With a global sea level rise equivalent of 58 m (Fretwell et al, 2013), the Antarctic Ice Sheet has been losing ice at an accelerated pace (Shepherd et al, 2018). This mass loss is largely driven by the ice dynamics of the marine ice sheet due to sustained and accelerated thinning of the ice shelves (Bamber et al, 2009; Paolo et al, 2015; Pattyn and Morlighem, 2020; Favier et al, 2014; Gardner et al, 2018) and rapid retreat of the grounding line (hereinafter referred to as the GL) (Point G in Fig. 1) (Christie et al, 2018; Milillo et al, 2019; Rignot et al, 2014; Scheuchl et al, 2016), which is the boundary between the grounded ice sheet and the floating ice shelves (Rignot et al, 2011a). Continuous long-term monitoring of the GL location and its temporal migration is crucial for understanding ice sheet stability and assessing the Antarctic Ice Sheet’s contribution to future sea level rise.

Results

Discussion

Conclusion