Holocene climate variability revealed by oxygen isotope analysis of Sphagnum cellulose from Walton Moss, northern England

Stable isotope analyses of Sphagnum alpha-cellulose, precipitation and bog water from three sites across northwestern Europe (Raheenmore, Ireland, Walton Moss, northern England and Dosenmoor, northern Germany) over a total period of 26 months were used to investigate the nature of the climatic signal recorded by Sphagnum moss. The delta O-18 values of modern alpha-cellulose tracked precipitation more closely than bog water, with a mean isotopic fractionation factor alpha(cellulose-precipitation) of 1.0274 +/- 0.001 (1 sigma) (approximate to 27 parts per thousand). Sub-samples of isolated Sphagnum alpha-cellulose were subsequently analysed from core WLM22, Walton Moss, northern England yielding a Sphagnum-specific isotope record spanning the last 4300 years. The palaeo-record, calibrated using the modern data, provides evidence for large amplitude variations in the estimated oxygen Isotope composition of precipitation during the mid-to late Holocene. Estimates of palaeotemperature change derived from statistical relationships between modern surface precipitation values for the British Isles give unrealistically large variation in air temperatures and delta O-18(precipitation) comparison to proxies from other archives. We conclude that use of such relationships to calibrate mid-latitude palaeo-data must be undertaken with caution. The delta O-18 record from Sphagnum cellulose was highly correlated with a palaeoecologically-derived index of bog surface wetness (BSW), suggesting a common climatic driver. (C) 2009 Elsevier Ltd. All rights reserved.