Abstract:
The SWAIS2C project is an international partnership of 10 countries and the International Continental Scientific Drilling Program (ICDP) that aims to investigate the stability of the West Antarctic Ice Sheet in a warmer-than-present world from geological archives.
Here we present the initial scientific findings from the SWAIS2C project’s 217 m-long drill core recovered during the 2025/26 field season from beneath Crary Ice Rise (CIR), West Antarctica (83° 1.6002’S, 172° 37.5546’W). Drilling at CIR represented a significant technical challenge, requiring melting a ~523 m deep access hole through the ice and then rock drilling into the frozen bedrock below with the Antarctic Intermediate Depth Drill (AIDD) system. The AIDD system successfully cored to 228.12 m below seafloor (mbsf) with 96% core recovery. We divide the core into five lithostratigraphic units (LSU) based on the abundance of varying amounts of mud, sand, gravel and biogenic content as well as the stacking patterns of lithologies. We interpret the facies succession within our core in terms of advance and retreat of the ice sheet. Natural gamma ray downhole logging data supports the placement of these unit boundaries. Initial biostratigraphic age estimates from the lowermost lithostratigraphic unit suggests a maximum age of middle Mio-cene (~17 Ma). The entire record appears to represent discrete intervals of time separated by unconformities evident in seismic profiles that spans from the middle Miocene to Holocene, although this requires verification. The sedimentary packages provide the first direct evidence, recovered below the modern WAIS, for a dynamic, climate sensitive, WAIS from the mid-Miocene onwards. Successful integration of hot water drilling and the AIDD system provides a basis for future subglacial drilling endeavors in the Antarctic deep field where observations are lacking but are urgently needed to better constrain the likely response of WAIS to future warming.