A statistical approach to construct composite climate records of dated archives

Proxy records of dated environmental archives like stalagmites are used for reconstruction of past climate and therefore are of fundamental interest for the paleoclimate community. However, dating conditions are often not perfect to obtain precise ages with small uncertainties. On this matter, the use of statistical approaches applied to reproduced climate signals of several nearby situated specimens, like stalagmites from one cave, can help to reduce age uncertainties. A new method implemented in MATLAB uses a Monte Carlo approach on absolute age determinations to find the best correlation between climate proxies of several signal reproducing adjacent archives. Therefore, the program is able to combine climatic proxies to construct a composite record. This intra-site correlation age modelling (iscam) approach offers great advantages. The age uncertainty can be significantly reduced within the overlapping time intervals and it can be tested if the signal of interest is indeed similar in both records. Additionally, iscam allows to enlarge the time span of a single record while at the same time the signal to noise ratio of the combined record improves in periods where replicates exist. Significance levels of the correlation can be calculated against the red-noise background from a first order autoregressive process (AR1), which allows to determine adequate age uncertainties. The method was designed to synchronize time series of nearby locations, where changes in the climate signal occur simultaneously. Applying this method to geographically dispersed locations might not be appropriate due to unknown leads and lags in the climate system. (c) 2012 Elsevier B.V. All rights reserved.