Status: this preprint was under review for the journal CP. A revision for further review has not been submitted.
A modelling approach to assessing the timescale uncertainties in proxy series with chronological errors
D. V. Divine,F. Godtliebsen,and H. Rue
D. V. Divine
Department of Mathematics and Statistics, Faculty of Science, University of Tromsø, 9037, Norway
F. Godtliebsen
Department of Mathematics and Statistics, Faculty of Science, University of Tromsø, 9037, Norway
Norwegian Polar Institute, FRAM Centre, 9296 Tromsø, Norway
H. Rue
Department of Mathematical Sciences, Norwegian University of Science and Technology, Trondheim, 7491, Norway
Abstract. The paper proposes an approach to assessment of timescale errors in proxy-based series with chronological uncertainties. The method relies on approximation of the physical process(es) forming a proxy archive by a random Gamma process. Parameters of the process are partly data-driven and partly determined from prior assumptions. For a particular case of a linear accumulation model and absolutely dated tie points an analytical solution is found suggesting the Beta-distributed probability density on age estimates along the length of a proxy archive. In a general situation of uncertainties in the ages of the tie points the proposed method employs MCMC simulations of age-depth profiles yielding empirical confidence intervals on the constructed piecewise linear best guess timescale. It is suggested that the approach can be further extended to a more general case of a time-varying expected accumulation between the tie points. The approach is illustrated by using two ice and two lake/marine sediment cores representing the typical examples of paleoproxy archives with age models based on tie points of mixed origin.
Received: 06 Dec 2011 – Discussion started: 03 Jan 2012