Oxygen-Isotopic Variability Across the 8.2ka Cold Event in an Ombrotrophic Peat bog on the Bonavista Peninsula, Newfoundland

Ombrotrophic (precipitation-fed) peatlands are well established as sources of proxy-climate information through the Holocene (Aaby, 1974; Barber, 1981; Barber et al., 1994, 1998; Hughes et al., 2000; Charman, 2002). Over the past decade, innovative methodological developments have resulted in the production of multi-proxy records where co-registered signals are used to establish the response of bogs to climatic forcing (Blundell & Barber, 2005, Langdon & Barber, in press; Hughes et al., in press). These techniques have utilised changes in the relative abundance of bog taxa, combined with knowledge of their ecology and the degree of decomposition of the peat, to infer the nature of past environmental changes. Despite the success of this methodology, there remains a need for an approach that is better able to quantify the magnitude of observed climatic changes and which is directly comparable with records from lakes, ice cores and marine sediments. Analysis of the stable isotopes of oxygen and hydrogen in the cellulose of Sphagnum moss offers additional environmentally-sensitive proxies with which to reconstruct isotopic variations in source water (palaeo-precipitation), and hence changes in climate and atmospheric circulation. Sphagnum moss is particularly suited to isotopic analysis by virtue of the comparatively simple pathway that leads from precipitation to cellulose synthesis. We present an oxygen-isotope time series developed from a 2m section of a peat core from Newfoundland (latitude, 49°.150 N, longitude, 53°.583 W). The location of the site on the North east coast of the island makes it particularly sensitive to the atmospheric impact of changes in the nature of the Inner Labrador current, thought to be the conduit that carried the meltwater plume from the Lake Agassiz megaflood (e.g. Keigwin, et al., 2005). The results will be compared with existing multi-proxy data on plant macrofossils, peat humification and testate amoebae derived from the same core (Hughes et al., in press), and also with published marine and ice-core isotopic records that span the 8.2ka event.