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Analysis of the climate signal contained within d18O and growth rate parameters in two Ethiopian stalagmites.

Research output: Contribution to journalJournal article

Published

  • Andy Baker
  • Asfawossen Asrat
  • Ian J. Fairchild
  • Melanie J. Leng
  • Peter M. Wynn
  • Charlotte Bryant
  • Dominique Genty
  • Mohammed Umer
Journal publication date15/06/2007
JournalGeochimica et Cosmochimica Acta
Journal number12
Volume71
Number of pages14
Pages2975-2988
Original languageEnglish

Abstract

We combine surface and cave climate monitoring with multiple stalagmite parameters to help understand and calibrate the climate records contained within stalagmites from a region with strong rainfall seasonality. Two actively growing stalagmites from Ethiopia were analysed in order to investigate the climate signal contained within d18O and growth rate parameters. The d18O and growth rate of the two stalagmites give different responses to surface climate due to variations in the climate signal transfer. Both stalagmites (Merc-1 and Asfa-3) have a climate response that is seasonal; however this signal is subsequently smoothed by the mixing of event and storage water within the aquifer. Merc-1 responds more to high frequency (‘event’) climate, due to a greater ratio of event to storage water in this sample, whereas Asfa-3 responds more to low frequency (‘storage’) climate. In addition, different parameters respond to different seasons. For example, stalagmite Asfa-3, from greater depth from the surface and with a slow drip rate, has a growth rate that responds to the amount of summer rain. In contrast, Merc-1, closer to the surface and with a faster drip rate, exhibits no clear response to surface climate, probably due to a more complex climate signal transfer. d18O response varies with stalagmite due to the interplay between rainfall forcing factors (amount, seasonality) and disequilibrium kinetics, with opposing correlations between seasonal rainfall and d18O between the samples. Our results demonstrate that analysis of seasonal climate forcing, and transfer functions reflecting the mixing of event and storage water, may be the most appropriate approach to develop of transfer functions appropriate for highresolution, stalagmite climate reconstruction.