Tracking Holocene climate change using peat bog stable isotopes

Category Geochemistry
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Daley, Tim۱; Street-Perrott, F. Alayne۱; Loader, Neil۱; Barber, Keith۲
Holding Date 08 September 2008

Precipitation-fed peatlands are an abundant source of Sphagnum moss in temperate climates. Sphagnum moss is an ideal recorder of the isotopic composition of precipitation by virtue of the simplicity of the biosynthetic pathway by which oxygen and hydrogen are incorporated into cellulose. It is also highly resistant to decay and undergoes minimal diagenetic alteration with incorporation into peat sediments. Stable-isotopic analyses of Sphagnum moss remains from these sediments, often extending back throughout the Holocene period, therefore provide a very direct link to variations in the isotopic composition of palaeo-precipitation. Peatland sediments contain a mixture of plant species. Previous work in the 1980s and early 1990s was limited by technological constraints to the analysis of large bulk sediment samples. The changing proportions of key plant components (mosses, sedges, ericaceous shrubs, etc.) in these samples amplified the isotopic signal, thereby exaggerating the range of past climatic variability. Recent technological developments now allow for the determination of both oxygen- and hydrogen-isotope ratios from just a few mg of genus-specific Sphagnum alpha-cellulose. The small sample sizes required also offer the possibility of achieving sub-decadal resolution throughout the Holocene. Here, we report how combined modern and palaeo data reveal a dynamically simple isotope system, leading to new interpretations of the palaeoecological evidence traditionally derived from peatlands and challenging our understanding of palaeo-atmospheric circulation over North Atlantic region during the Holocene.