Articles | Volume 8, issue 4
Clim. Past, 8, 1153–1167, 2012

Special issue: Advances in understanding and applying speleothem climate...

Clim. Past, 8, 1153–1167, 2012

Research article 11 Jul 2012

Research article | 11 Jul 2012

Millennial-length forward models and pseudoproxies of stalagmite δ18O: an example from NW Scotland

A. Baker1,6, C. Bradley2, S. J. Phipps3, M. Fischer4, I. J. Fairchild2, L. Fuller2, C. Spötl7, and C. Azcurra5,6 A. Baker et al.
  • 1Connected Waters Initiative Research Centre, University of New South Wales, Water Research Laboratory, 110 King St., Manly Vale, Australia
  • 2School of Geography, Earth and Environmental Sciences, University of Birmingham, UK
  • 3Climate Change Research Centre and ARC Centre of Excellence for Climate System Science, University of New South Wales, Sydney, Australia
  • 4Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia
  • 5Connected Waters Initiative Research Centre, University of New South Wales, School of Civil and Environmental Engineering, Kensington, Australia
  • 6National Centre for Groundwater Research and Training, Australia
  • 7Department of Geology and Palaeontology, University of Innsbruck, Innrain 52, Innsbruck, 6020, Austria

Abstract. The stable oxygen isotope parameter δ18O remains the most widely utilised speleothem proxy for past climate reconstructions. Uncertainty can be introduced into stalagmite δ18O from a number of factors, one of which is the heterogeneity of groundwater flow in karstified aquifers. Here, we present a lumped parameter hydrological model, KarstFor, which is capable of generating monthly simulations of surface water – ground water – stalagmite δ18O for more than thousand-year time periods. Using a variety of climate input series, we use this model for the first time to compare observational with modelled (pseudoproxy) stalagmite δ18O series for a site at Assynt, NW Scotland, where our knowledge of δ18O systematics is relatively well understood. The use of forward modelling allows us to quantify the relative contributions of climate, peat and karst hydrology, and disequilibrium effects in stalagmite δ18O, from which we can identify potential stalagmite δ18O responses to climate variability. Comparison of the modelled and actual stalagmite δ18O for two stalagmites from the site demonstrates that, for the period of overlapping growth, the two series do not correlate with one another, but forward modelling demonstrates that this falls within the range explicable by differences in flow routing to the stalagmites. Pseudoproxy δ18O stalagmite series highlight the potential significance of peat hydrology in controlling stalagmite δ18O over the last 1000 yr at this site.