Seasonal variability of isotopes and chemistry in a coastal firn core from the Amundsen Sea, West Antarctica

Abstract

The West Antarctic Ice Sheet (WAIS) is undergoing significant ice loss, causing global sea level rise and posing a critical threat to coastal communities worldwide (Shepherd et al. 2018; Rignot et al. 2019). We analyzed stable isotopes, major ions, and hydrogen peroxide (H2O2) in a 10.11 m shallow ice core from Moore Dome, West Antarctica, to provide a basis for future deep ice-core studies. Seasonal peaks in H2O2, methanesulfonic acid (MSA, CH3SO3-), and non-sea-salt sulphate (nss-SO42-) served as annual layer markers, yielding a chronology from austral spring/summer 2012 to 2016 and a mean accumulation rate of 1.25 m w.e. yr(-)(1). The delta D-delta O-1(8) slope of 7.93 closely matches the Global Meteoric Water Line (GMWL, slope = 8; Dansgaard 1964), indicating minimal post-depositional alteration. Comparisons with IsoGSM model output confirm that delta O-1(8) reliably reflects regional climate variability. Variations in sea-salt ions (Na+, Cl-, K+, Mg-2(+), Ca-2(+)) and biogenic sulphate (MSA, nss-SO42-) reflect seasonal marine influences, including winter sea spray and summer phytoplankton blooms. These findings highlight Moore Dome's capacity to preserve high-resolution climate signals and demonstrate the value of integrating observational records with models to improve understanding of long-term WAIS instability.