WACSWAIN Project: Developing a High-Accuracy Total Air Content Setup for Reconstructing the Palaeoelevation History of Skytrain Ice Rise, Antarctica

Abstract:

Modelling studies and sea level reconstructions suggest the loss of the West Antarctic Ice Sheet (WAIS) during the Last Interglacial (LIG) about 120’000 years ago, but direct evidence for a collapse of the WAIS is lacking. The WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial (WACSWAIN) project aims at providing direct evidence allowing for a comprehensive assessment of whether or not the WAIS collapsed during the LIG. One of the expected consequences of such massive ice mass loss is the rise of land masses in close proximity of the WAIS due to isostatic adjustments. This process should have lifted the Skytrain Ice Rise by approximately 200 m. Such major altitude changes should be imprinted in the Total Air Content (TAC) based on simple barometric considerations. Here we present a new experimental setup of a high-accuracy TAC measurement system under development at the British Antarctic Survey. We are planning to reconstruct the palaeoelevation history at Skytrain Ice Rise using discrete samples from the recently drilled Skytrain Ice Rise ice core. Our experimental setup is dedicated to and optimised for the measurement of TAC and is based on a vacuum extraction principle. Here, the air is extracted by melting an approximately 100 g ice sample by thermal radiation. The released air is directly dried and expanded into a large expansion chamber. State-of-the-art pressure gauges and thorough temperature control allow for high-accuracy measurements. In addition, we continuously recorded the air-to-water ratio of the main melt line within the scope of the Skytrain Ice Rise Continuous Flow Analysis campaign based on a non-invasive ultrasonic bubble detector. We will try to calibrate this ratio using the discretely measured TAC data from the same ice core.