Characteristics of spectrum gamma radiation (SGR) data from geophysical downhole logging in the SWAIS2C project – West Antarctica

The West Antarctic Ice Sheet (WAIS) is currently experiencing accelerated mass loss and contains enough ice to raise global sea levels by up to five meters if it were to melt completely. The objective of the international and interdisciplinary SWAIS2C project (Sensivity of the West Antarctic Ice Sheet to 2 Degrees Celsius of Warming) is to understand 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.

In its third season, the SWAIS2C project targeted the second drilling location Crary Ice Rise Site 1 (CIR), a grounded ice sheet upstream the Ross Ice Shelf. After hot water drilling through ~516 m of ice, rotary coring retrieved a sediment succession of 228 m length comprising different lithological units.

The LIAG Institute for Applied Geophysics and the German Helmholtz Centre for Geosciences (GFZ) are in charge of geophysical downhole logging operations and retrieved the first such dataset below grounded ice. The spectrum gamma radiation (SGR) tool records the natural radiation and its components – the K-, Th-, and U-concentration – of the surrounding sediments. The data indicate distinct boundaries between the main lithological units, but minor variations and ratios of the measured elements indicate smaller differences within the units. Particularly in transitions between major units, patterns in the data may reflect changing paleo-environmental conditions. This data set will be valuable for the ongoing project as it is an in-situ, continuous record of drilled sediment succession with high accuracy depth measurements.

We give a brief overview of the SWAIS2C project, focus on the downhole logging data measured as part of the project and relate the results to other data sets from below/around the Ross Ice Shelf.