A modelling approach to assessing the timescale uncertainties in proxy series with chronological errors
D. V. Divine1, F. Godtliebsen1,2, and H. Rue31Department of Mathematics and Statistics, Faculty of Science, University of Tromsø, 9037, Norway 2Norwegian Polar Institute, FRAM Centre, 9296 Tromsø, Norway 3Department of Mathematical Sciences, Norwegian University of Science and Technology, Trondheim, 7491, Norway
Received: 06 Dec 2011 – Accepted for review: 17 Dec 2011 – Discussion started: 03 Jan 2012
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.
Divine, D. V., Godtliebsen, F., and Rue, H.: A modelling approach to assessing the timescale uncertainties in proxy series with chronological errors, Clim. Past Discuss., 8, 31-61, doi:10.5194/cpd-8-31-2012, 2012.