Regional variability of diatoms in ice cores from the Antarctic Peninsula and Ellsworth Land, Antarctica

Abstract

Abstract. The presence of marine microfossils (diatoms) in glacier ice and ice cores has been documented from numerous sites in Antarctica, Greenland, as well as from sites in the Andes and the Altai mountains, and attributed to entrainment and transport by winds. However, their presence and diversity in snow and ice, especially in polar regions, are not well documented and still poorly understood. Here we present the first data to resolve the regional and temporal distribution of diatoms in ice cores, spanning a 20-year period across four sites in the Antarctic Peninsula and Ellsworth Land, Antarctica. We assess the regional variability in diatom composition and abundance at annual and sub-annual resolution across all four sites. These data corroborate the prevalence of contemporary marine diatoms in Antarctic Peninsula ice cores, reveal that the timing and amount of diatoms deposited vary between low- and high-elevation sites, and support existing evidence that marine diatoms have the potential to yield a novel palaeoenvironmental proxy for ice cores in Antarctica.

Regional validation of the use of diatoms in ice cores from the Antarctic Peninsula as a Southern Hemisphere westerly wind proxy

“…The diatom abundance parameter includes all diatoms and diatom remains identified on each sample, regardless of their potential source. As reported by Tetzner et al (2022a), the diatom assemblages at all ice core sites presented in this study are primarily comprised of Fragilariopsis cylindrus, Fragilariopsis pseudonana, Pseudonitzschia spp., Shionodiscus gracilis and Cyclotella group., with the exclusive presence of other diatom species at each site (Appendix A -Table A1).…”

“…The Sky-Blu firn core (SKBL, 21.8 m) from the vicinity of Sky-Blu Field Station, southern AP, and the Sherman Island firn core (SHIC, 21.3 m) from Eights Coast were drilled using a Kovacs hand auger during the austral summer 2019-2020; hereafter, for practical reasons, firn cores will be referred to as ice cores. For JUR, SKBL and SHIC, an ice core chronology was established (Tetzner et al, 2022a) based on their hydrogen peroxide (H 2 O 2 ) annual cycle that is assumed to peak during the austral summer solstice and to exhibit its minimum during the austral winter (Frey et al, 2006;Thomas et al, 2008). Ice core chronologies were corroborated using the annual cycle of the non-sea-salt component of major ions, such as nonsea-salt sulfate (nssSO 2− 4 ) (Piel et al, 2006), that is assumed to peak between November and January in this region (Pasteris et al, 2014;Thoen et al, 2018).…”

“…Diatom samples from each ice core site were previously analysed and reported by Tetzner et al (2022a). All diatom samples were extracted by filtration.…”

“…The MPC record from JUR covers the interval 1992-2011 CE; therefore, correlations calculated using this parameter at JUR are calculated over a 19-year period. Since diatom concentrations at SHIC peak during the austral summer (Tetzner et al, 2022a), spatial correlations for the SHIC diatom record were also calculated over a 6-month period covering the austral spring and summer season (September-February).…”

“…Once in the atmosphere, they can be transported by winds over long distances (Chalmers et al, 1996;Elster et al, 2007;Harper and McKay, 2010;Budgeon et al, 2012;Marks et al, 2019;Allen et al, 2020). Diatom records have been evaluated at multiple ice core sites in the AP and Ellsworth Land (EL) regions (Tetzner et al, 2022a) to reveal consistent spatial variations and increases in the diatom concentration during the past 3 decades. Despite the potential the diatom record has shown to reconstruct past wind strength, this proxy requires evaluation against more established ice core wind and atmospheric circulation proxies.…”