Calibrating peat-based palaeoclimate reconstructions with instrumental climate data
by
Dan Charman
Department of Geographical Sciences, University of Plymouth, UK
Coauthors: Dawn Hendon (Department of Geography, University of Exeter, UK)

Peat deposits occur throughout mid-high latitudes in Europe and also in alpine areas further south on the PEPIII transect. They provide a source of Holocene palaeoclimate information with approximately decadal resolution. The most widely used techniques reconstruct surface wetness changes as a proxy for climate change. However, an inadequate understanding of the relationship between peat surface wetness and climate hampers these palaeoclimate reconstructions. Fluctuations in mire surface wetness have been interpreted as general directional changes from wet/cold to warm/dry and have not been expressed in more ‘meaningful’ climatic parameters such as precipitation and temperature. Here, we calibrate a peat record against instrumental climate data from NW England in an attempt to help solve this problem. Mean annual water table changes were inferred from changes in testate amoebae assemblages using a transfer function approach, for two cores from Butterburn Flow, an ombrotrophic mire in northern England. A temporal resolution of 2-10 years per sample over the past 300 years was achieved. The chronology is based on pollen markers, spheroidal carbonaceous particles (SCPs) and ²¹⁰Pb, supplemented by AMS ¹⁴C analyses. Correlations between the water table record and a variety of annual and seasonal temperature and precipitation variables show a strong relationship between water table and summer temperature, with summer precipitation of secondary importance. Regression analyses suggest the reconstructed water table values are dependent on the summer (JJA) temperatures of a considerable preceding period (50-70 years). R-squared values for this relationship are in the range 0.50 to 0.75 (p<0.01), depending on the length of the preceding period used. The water table record can therefore be used as a proxy for low frequency summer temperature variability. The approach will provide new quantitative estimates of past summer temperature on centennial to millennial timescales for the mid- to late-Holocene for the UK. Further work will use a similar approach to test the peat surface wetness -climate relationship for other regions of PEPIII where suitable peat deposits are found.

Date received: April 2, 2001

Copyright © 2001 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cagc-89.