Abstract
Blue ice areas (BIAs) allow for the collection of large-sized old ice samples in a cost-effective way because deep ice outcrops and make old ice samples available close to the surface. However, most chronostratigraphy studies on blue ice are complicated due to fold and fault structures. Here, we report a simple stratigraphy of ice from the Larsen BIA, Antarctica, making the area valuable for paleoclimate studies. Ice layers defined by dust bands and ground penetration radar (GPR) surveys indicate a monotonic increase in age along the ice flow direction on the downstream side, while the upstream ice exhibits a potential repetition of ages on scales of tens of meters, as shown in the complicated fold structure. Stable water isotopes (δ18Oice and δ2Hice) and components of the occluded air (i.e., CO2, N2O, CH4, δ15N-N2, δ18Oatm (= δ18O-O2), δO2/N2, δAr/N2, 81Kr and 85Kr) were analyzed for surface ice and shallow ice core samples. Correlating δ18Oice, δ18Oatm, and CH4 records of Larsen ice with existing ice core records indicates that the gas age at shallow coring sites ranges between 9.2–23.4 ka BP and ice age for entire surface sampling sites between 5.6–24.7 ka BP. Absolute radiometric 81Kr dating for the two cores confirms the ages within acceptable levels of analytical uncertainty. Our study demonstrates that BIA in northern Victoria Land may help researchers obtain high-quality records for paleoclimate and atmospheric greenhouse gas compositions through the last deglaciation.
Highlights
30 Ice cores serve as very useful archives for paleoclimate records, such as ancient atmospheric greenhouse gas composition, surface temperature, and aerosols
Ice layers defined by dust bands and ground penetration radar (GPR) surveys 20 indicate a monotonic increase in age along the ice flow direction on the downstream side, while the upstream ice exhibits a potential repetition of ages on scales of tens of meters, as shown in the complicated fold structure
4 Conclusions 405 Based on the dust bands, GPR profile, and no significant anomaly of chemical results (δ18Oatm, δ2Hice, and CH4) we conclude that the ages of the downstream ice in Larsen Blue ice areas (BIAs) monotonically increase along the ice flow direction
Summary
30 Ice cores serve as very useful archives for paleoclimate records, such as ancient atmospheric greenhouse gas composition, surface temperature, and aerosols. Coring in blue ice areas (BIAs) has emerged as an alternative to obtain large ice samples in a cost-effective manner (Folco et al, 2006; Petrenko et al, 2006; Schaefer et al, 2006; Sinisalo et al, 2007; Korotkikh et 40 al., 2011; Turney et al, 2013; Bauska et al, 2016; Aarons et al, 2017; Baggenstos et al, 2017; Yan et al, 2019; Fogwill et al, 2020). The stratigraphy of the blue ice is complicated, as shown by the fold and fault structures on the surface (Folco et al, 2006; Petrenko et al, 2006; Curzio et al, 2008; Schaefer et al, 2009; Baggenstos et al, 2017) and stratigraphy is discontinuous at deep depths 55 near the bedrock where ice ages are similar to or older than the MPT (Higgins et al, 2015; Yan et al, 2019). Studies on the Taylor Glacier and Allan Hills BIA have constrained the age of the blue ice along several transects and cores.
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