Sensivity of the West Antarctic Ice Sheet to 2° Celsius of Warming. The SWAIS2C project

The West Antarctic Ice Sheet (WAIS) is currently experiencing accelerated mass loss. It contains enough ice to raise global sea levels by up to five meters if completely melted. Yet we do not know under which environmental conditions a total collapse will occur.

Here we present an overview of the SWAIS2C (Sensivity of the West Antarctic Ice Sheet to 2 Degrees Celsius of Warming)  project. The project aims to unravel past and present factors influencing WAIS dynamics and to reconstruct WAIS response to warmer temperatures, including those exceeding the +2°C target outlined in the Paris Climate Agreement. SWAIS2C (ICDP project 5072) targets two sites, chosen to obtain geological data close to the centre of the WAIS to improve model-based projections of future sea level contributions from Antarctica. The first site is close to the grounding line of the Kamb Ice Stream site (KIS3) and sensitive to ocean forcing of ice shelf and ice sheet collapse. The second site on the Crary Ice Rise (CIR) demarks a pinning point of the ice shelf and offers a complementary view on processes that can (de)stabilise the WAIS. Data obtained at these sites will enable us to answer the overarching question under which climatic conditions we will lose the WAIS.

 In the first two field seasons of the SWAIS2C project in 2023/24 and 2024/25, equipment was traversed more than 800 km across the Ross Ice Shelf to the remote KIS3 field site. Hot water drilling was successfully completed in both years and penetrated ~580 m of ice to provide access to the 55 m deep ocean cavity and seafloor beneath. Oceanographic measurements were made beneath the ice shelf,  videos of the seafloor and ice shelf were recorded, and a long-term oceanographic mooring was installed. Gravity and hammer coring during both seasons yielded a total of 9.5 m of unconsolidated diamict sediment, including the longest sediment core from the Siple Cost, measuring 1.92 m. All of the cored material was x-rayed in the field. During each drilling season, one or two cores were extruded in a sterile environment and sampled for microbiology, geochemistry, pore water or ancient DNA work.

Deep drilling was attempted in both years using the Antarctic Intermediate Depth Drill (AIDD). In our first season, Glass Reinforced Epoxy (GRE) formed part of our sea riser. It was chosen for its light weight and thermal properties, but deployment proved challenging. In our second season, we replaced the GRE sea riser with HRQ steel pipe. We successfully lowered the sea riser to the sea floor, which marked a major project milestone. After deploying 450 m of NQ drill string inside the riser, we had to call off operations, just a couple of hours short of retrieving our first sediment core. Our next drilling attempt will be at Crary Ice Rise in 2025/26, where we hope to recover 200 m of sediment core, and perform a range of geophysical surveys.

Deep field work in Antarctica is challenging, but the questions we are trying to answer for humanity are worth it.