Swindles, G.T., Patterson, R.T., Roe, H.M., Galloway, J.M., 2012. Evaluating periocidities in peat-based climate proxy records. Quanternary Science Reviews. v. 41, p. 94-103.
Proxy records derived from ombrotrophic peatlands provide important insights into climate change over decadal to millennial timescales. We present mid- to late- Holocene humification data and testate amoebae-derived water table records from two peatlands in Northern Ireland. We examine the replication of periodicities in these proxy climate records which have been precisely linked through tephrochronology. Age-depth models were constructed using a Bayesian piece-wise linear accumulation model and chronological errors were calculated for each profile. A Lomb-Scargle Fourier transform-based spectral analysis is used to test for statistically significant periodicities in the data. Periodicities of c. 130, 180, 260, 540 and 1160 years are present in at least one proxy records in each site. The replication of these periodicities provides persuasive evidence that they are a product of allogenic climate controls, rather than internal peatland dynamics. A technique to estimate the possible level of red noise in the data is applied and demonstrates that these periodicities cannot be explained by a first-order autoregressive model. We evaluate the periodicities with a review of those reported previously from marine and terrestrial climate proxy data and put into the context of climate forcing parameters.