Comparing age model techniques for the last glacial cycle: A case study of ten Iberian Margin sediment cores

Abstract

Because interpretations of paleoclimate records from ocean sediment cores rely on age models to estimate age as a function of core depth, age model uncertainty can affect the conclusions drawn from paleoclimate data. To assess the age model uncertainty associated with three methods, we compare the age models they generate over the last glacial cycle for high-resolution data from ten western and southern Iberian Margin cores. The first method uses radiocarbon data and the Bayesian statistical software Bacon [Blaauw and Christen, 2011]. The second method aligns benthic δ18O to a target core using the probabilistic alignment algorithm HMM-Match [Lin et al., 2014]. The third method is alignment of planktonic δ18O or sea surface temperature (SST) using the deterministic alignment software Match [Lisiecki and Lisiecki, 2002]. Where three or more age model types overlap in a core, the average range of age estimates is 1.7 kyr, and 90% of age ranges are less than 3 kyr. For the two probabilistic methods, HMM-Match and Bacon, age estimates agree to within uncertainty, and the highest resolution records yield 95% confidence interval widths of 1–2 kyr. However, HMM-Match appears to underestimate alignment uncertainty near gaps in benthic δ18O data in one core, as indicated by disagreement with the core's planktonic δ18O and SST alignments. Planktonic δ18O appears to provide the most precise age models for Iberian Margin cores due to strong millennial-scale variability and good correlation between aligned cores. Probabilistic alignment algorithms should be developed for planktonic δ18O and SST proxies to improve estimates of the age uncertainty for these alignments.