Cryptotephra in the East Antarctic Mount Brown South ice core

Abstract

Ice cores contain stratified layers of impurities scavenged from the atmosphere, which are a vital tool for investigating the Earth system. Reconstructing past eruption records by way of ice core tephrochronology can help us understand ash dispersal, atmospheric circulation processes, and the impacts of volcanic eruptions on climate. This study presents the coastal East Antarctic Mount Brown South (MBS, 69.11° S, 86.31° E; 2084 meter above sea level (m a.s.l.)) ice core as an untapped tephrochronological archive. We utilize a customized cryptotephra sampling plan, integrating ice core data, HYSPLIT air parcel trajectories, and known eruption records, and identify two distinct cryptotephra horizons at ∼13.3 and ∼17.9m depth in the MBS-Alpha ice core. We also find sparse cryptotephra grains from various unidentified sources throughout the core. Through geochemical characterization with electron probe microanalysis (EPMA), we correlate the two cryptotephra horizons with the 1991 eruption of Cerro Hudson and the continuous eruptions of Mt. Erebus throughout the mid-1980s. The volcanic horizons identified here underscore the role of MBS in extending the regional volcanic record, helping to constrain ice core dating efforts, and enhancing understanding of volcanic ash dispersal to East Antarctica.