Quantifying dating uncertainties in layer-counted paleoclimate proxy archives

• Main Authors: Myrvoll-Nilsen, Eirik, Riechers, Keno, Rypdal, Martin Wibe, Boers, Niklas
• Format: Text
• Language: English
• Published: 2021
• Subjects: Greenland; Dansgaard-Oeschger events; Greenland ice core; Greenland ice cores; ice core
• Online Access: https://doi.org/10.5194/cp-2021-176; https://cp.copernicus.org/preprints/cp-2021-176/

Paleoclimate proxy records have non-negligible uncertainties that arise from both the proxy measurement and the dating processes. Knowledge of the dating uncertainties is important for a rigorous propagation to further analyses; for example for identification and dating of stadial-interstadial transitions in Greenland ice core records during glacial intervals, for comparing the variability in different proxy archives, and for model-data comparisons in general. In this study we develop a statistical framework to quantify and propagate dating uncertainties in layer-counted proxy archives using the example of the Greenland Ice Core Chronology 2005 (GICC05). We express the number of layers per depth interval as the sum of a structured component that represents both underlying physical processes and biases in layer counting, described by a regression model, and a noise component that represents the fluctuations of the underlying physical processes, as well as unbiased counting errors. The age-depth relationship of the joint dating uncertainties can then be described by a multivariate Gaussian process from which realizations of the chronology can be sampled. We show how the effect of an unknown counting bias can be incorporated in our framework and present refined estimates of the occurrence times of Dansgaard-Oeschger events evidenced in Greenland ice cores together with a complete uncertainty quantification of these timings.