On-board measurements of noble gases in the Amundsen Sea, Antarctica, using a membrane inlet mass spectrometer (MIMS)

Abstract

Remote sensing approaches based on satellite observations have been widely conducted to investigate the retreat of Antarctic ice sheets. However, most of the satellite-based studies have following limitations; i) they cannot capture the short-term variability of basal melting rate due to the relatively lower temporal resolutions from several years to decades, and ii) they cannot give an insights to pathways or distributions of glacial meltwater (GMW) in the water columns. Recently, Kim et al. (2016) presented the distributions of GMW in the water column of Amundsen Sea revealed by light noble gas tracers, helium (He) and neon (Ne). The study shows that there were significant spatio-temporal variations between each ice shelves and (inter-annual) sampling periods. However, the conventional method to determine noble gases is dependent on shore-based mass spectrometric system and very time-consuming processes. Thus, the main objective of this study is i) to make on-board measurements of 5 noble gases (4He, 22Ne, 38Ar, 84Kr, and 132,136Xe) in seawater, for the first time, ii) to get a broader understandings of GMW distribution in the Amundsen Sea. Recently, Visser et al. (2013) developed a quicker and more efficient noble gas analysis for laboratory experiments using a membrane inlet mass spectrometer (MIMS) with a semi permeable membrane and simplified gas extraction line. Based on this method, we conducted a intensive noble gas observation covering entire Amundsen Sea region, (Jan.～Feb. 2016) on the Korean icebreaker R/V Araon. Here, we will present the detailed method and preliminary results as a beginning of our effort to observe GMW distributions with a larger spatial coverage of polar oceans in future.