Analysis of the climate signal contained within σ18O and growth rate parameters in two Ethiopian stalagmites

Research output: Contribution to journalArticle

Authors

  • A Asrat
  • MJ Leng
  • C Bryant
  • D Genty
  • M Umer

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 delta O-18 and growth rate parameters. The delta O-18 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. delta O-18 response varies with stalagmite due to the interplay between rainfall forcing factors (amount, seasonality) and disequilibrium, kinetics, with opposing correlations between seasonal rainfall and delta O-18 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 high-resolution, stalagmite climate reconstruction. (c) 2007 Elsevier Ltd. All rights reserved.

Details

Original languageEnglish
Pages (from-to)2975-2988
Number of pages14
JournalGeochimica et Cosmochimica Acta
Volume71
Publication statusPublished - 15 Jun 2007