Characterising recent terrestial influence on coastal Antarctic air masses using radon-222 and physiochemical properties

• Main Author: Saeed, Daniel
• Format: Text
• Language: unknown
• Published: School of Earth, Atmospheric and Life Sciences 2021
• Subjects: casey; davis; Mawson; Mercury; bromine; Ozone; Fetch Winds; RV Aurora Australis; troposphere; Antarctic; The Antarctic; Antarc*; Antarctica; aurora australis
• Online Access: https://ro.uow.edu.au/thsci/193; https://ro.uow.edu.au/cgi/viewcontent.cgi?article=1197&context=thsci

Antarctica exhibits near pristine conditions to study natural chemical processes that occur under extreme temperatures and radiation conditions. As such, Antarctica provides an ideal location to observe the long-term hemispheric-scale trends in atmospheric trace gases. Air mass observations at three coastal Antarctic stations (Casey, Davis, and Mawson) during 2018/19 resupply voyages aboard the RV Aurora Australis were classified according to their recent fetch history, and their degree of terrestrial influence characterised via radon-222 (radon) observations. Fetch classification categories were based on absolute water content, with oceanic being the wettest and katabatic being the driest (i.e., originating from the Antarctic interior). The fetch separation technique was most successful when a wide representation of meteorological conditions was present. Casey showed the clearest separation of air mass fetch categories, with each fetch category also having observable differences in trace gas composition. Casey corresponded to the longest study period (14 days) followed by Mawson (9 days) and Davis (8 Days). Davis showed the highest degree of mixing with most observed air masses correlating to mixed/coastal fetch. Air mass observations at Mawson were almost completely synoptically forced down slope winds/katabatic flow. Radon observations at all three sites was proven to be a reliable indicator of terrestrial influence, however all three sites could have benefited from a deeper understanding of (radon) source mechanisms and better-established baseline concentrations. The use of radon observations as a marker for terrestrial influence was also shown to be dependent on the success of the fetch classification technique.