Time-Scale Reliability and Climate Features in a Network of East Antarctic Water Isotope Records

Abstract:

Stable water isotope ratio records (δD and δ¹⁸O) from ice cores are used for investigating historical climate variations, predominantly fluctuations in site temperature. Due to the ability of ice cores to archive information in high temporal resolution, it is tempting to interpret raw isotope measurements directly. However, records contain post-depositional and stratigraphically-derived noise in addition to the climate signal. Furthermore, regional variation in accumulation leads to vastly differing temporal reliability of the signal in different cores. Trench, snow-pit and firn-core studies in low accumulation areas show that single cores do not accurately represent local short term changes. They reveal the need to combine records to sufficiently determine sub-decadal climate variations. On orbital and millennial time-scales, records from multiple sites (within hemispheres) show variations are in general agreement for continental spatial scales. The finer extent to which climatic conclusions can be drawn from isotope records of deep ice cores, spatially and temporally, is uncertain.

Here we present δD and δ¹⁸O records from the BE-OI candidate site at Little Dome C, East Antarctica, drilled in the 2017/18 Austral summer using the British Antarctic Survey’s Rapid Access Isotope Drill (RAID). Using a network of four local (< 50 km apart) sites around the Dome C region, water isotope records from up to the Last Glacial Maximum to present are compared. Records were synchronised without the isotope records themselves to preserve independence of variability, avoiding circularity. With a simple statistical method, the climate signal common to the network’s records is extracted. We demonstrate that approximately centennial-scale isotopic variations can reliably represent climatic changes, increasing possibly to multi-decadal scale through direct comparison of increasingly proximal cores. Using these time-scales, the climatic variations are compared and contrasted spatially.