Sensitivity of the West Antarctic Ice Sheet to +2 °C (SWAIS 2C)

Jae Il Lee,David M Harwood,David Try,Christian Ohneiser,Molly O Patterson,Denise K Kulhanek,Johann Philipp Klages ,J Paul Winberry ,Gavin B Dunbar,Alex Pyne,Jeanine L Ash ,Darcy Mandeno,Francisco J Jiménez‐Espejo ,Andreas Läufer,Rachel Kirkman,Daleen Koch,Timothy R Naish,José-Abel Flores,Kyu‐Cheul Yoo ,Paolo Stocchi,Fabio Florindo,Osamu Seki,Huw Horgan,R H Levy ,Yûsuke Suganuma ,Tina Van De Flierdt,Edward Gasson,Florence Colleoni

doi:10.5194/sd-30-101-2022

Abstract

Abstract. The West Antarctic Ice Sheet (WAIS) presently holds enough ice to raise global sea level by 4.3 m if completely melted. The unknown response of the WAIS to future warming remains a significant challenge for numerical models in quantifying predictions of future sea level rise. Sea level rise is one of the clearest planet-wide signals of human-induced climate change. The Sensitivity of the West Antarctic Ice Sheet to a Warming of 2 ∘C (SWAIS 2C) Project aims to understand past and current drivers and thresholds of WAIS dynamics to improve projections of the rate and size of ice sheet changes under a range of elevated greenhouse gas levels in the atmosphere as well as the associated average global temperature scenarios to and beyond the +2 ∘C target of the Paris Climate Agreement. Despite efforts through previous land and ship-based drilling on and along the Antarctic margin, unequivocal evidence of major WAIS retreat or collapse and its causes has remained elusive. To evaluate and plan for the interdisciplinary scientific opportunities and engineering challenges that an International Continental Drilling Program (ICDP) project along the Siple coast near the grounding zone of the WAIS could offer (Fig. 1), researchers, engineers, and logistics providers representing 10 countries held a virtual workshop in October 2020. This international partnership comprised of geologists, glaciologists, oceanographers, geophysicists, microbiologists, climate and ice sheet modelers, and engineers outlined specific research objectives and logistical challenges associated with the recovery of Neogene and Quaternary geological records from the West Antarctic interior adjacent to the Kamb Ice Stream and at Crary Ice Rise. New geophysical surveys at these locations have identified drilling targets in which new drilling technologies will allow for the recovery of up to 200 m of sediments beneath the ice sheet. Sub-ice-shelf records have so far proven difficult to obtain but are critical to better constrain marine ice sheet sensitivity to past and future increases in global mean surface temperature up to 2 ∘C above pre-industrial levels. Thus, the scientific and technological advances developed through this program will enable us to test whether WAIS collapsed during past intervals of warmth and determine its sensitivity to a +2 ∘C global warming threshold (UNFCCC, 2015).

Highlights

Human activities are estimated to have caused an increase in average surface temperature of ∼ 1.0 ◦C above pre-industrial levels (IPCC, 2018, 2021)
The range of estimates is partly due to uncertainty regarding glacial processes including marine ice cliff instability (Pollard et al, 2015; DeConto and Pollard, 2016; Edwards et al, 2019; DeConto et al, 2021; Bassis et al, 2021; Golledge and Lowry, 2021; Crawford et al, 2021) and mantle and ice sheet grounding zone dynamics associated with glacial isostatic adjustment (Catania et al, 2012; Gomez et al, 2015; Kingslake et al, 2018; Whitehouse et al, 2019)
Efforts to improve our knowledge of glacial processes and dynamics from modern observations and reconstructions of past ice sheet behavior aim to reduce uncertainty in future projections and are a major objective of the Sensitivity of the

Summary

Introduction

Human activities are estimated to have caused an increase in average surface temperature of ∼ 1.0 ◦C above pre-industrial levels (IPCC, 2018, 2021). Response of the West Antarctic Ice Sheet (WAIS) to climate warming is the focus of several major national and international science programs including the International Thwaites Glacier Collaboration (https://thwaitesglacier.org/ about/itgc, last access: 10 February 2022), the Subglacial Antarctic Lakes Scientific Access (SALSA) Project (Priscu et al, 2021), and SWAIS 2C This focus on the WAIS is due, in part, to satellite observations that demonstrate the WAIS is losing mass at an accelerating rate (e.g., Bamber et al, 2018; Shepherd et al, 2018; IMBIE team, 2018), with the potential for future melt to contribute 4.3 m to global sea level (Fretwell et al, 2013). The SWAIS 2C Project proposes to quantify the Antarctic ice sheet (AIS) contribution to past (with drilling) and future (with modeling) sea level change, through an improved understanding of climate, ocean, cryosphere, biosphere, and solid Earth interactions and feedbacks, so that decisionmakers can better anticipate and assess risk associated with SLR and make more informed decisions around mitigation pathways.

Drill sites

New capabilities in drilling subglacial sediment

Findings

The SWAIS 2C Project approach and challenges