Articles | Volume 9, issue 2
Clim. Past, 9, 641–656, 2013
Clim. Past, 9, 641–656, 2013

Research article 13 Mar 2013

Research article | 13 Mar 2013

Madagascar corals reveal a multidecadal signature of rainfall and river runoff since 1708

C. A. Grove1, J. Zinke1,2, F. Peeters3, W. Park4, T. Scheufen1,5,*, S. Kasper1, B. Randriamanantsoa6, M. T. McCulloch7, and G.-J. A. Brummer1 C. A. Grove et al.
  • 1NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Geology, P.O. Box 59, 1790 AB Den Burg, Texel, the Netherlands
  • 2School of Earth and Environment, The University of Western Australia and the UWA Oceans Institute, 35 Stirling Highway, Crawley WA 6009, Australia and the Australian Institute of Marine Science, 39 Fairway, Nedlands WA 6009, Australia
  • 3Vrije Universiteit Amsterdam, Faculty of Earth and Life Sciences, De Boelelaan 1105, 1081 HV Amsterdam, the Netherlands
  • 4GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, Duesternbrooker Weg 20, 24105 Kiel, Germany
  • 5University of Amsterdam, Institute for Biodiversity and Ecosystem Dynamics (IBED), Nieuwe Achtergracht 127, 1018 WS Amsterdam, the Netherlands
  • 6Wildlife Conservation Society (WCS), B.P. 8500 Soavimbahoaka, Antananarivo 101, Madagascar
  • 7The University of Western Australia and the UWA Oceans Institute, School of Earth and Environment, M004 and ARC Centre of Excellence in Coral Studies, Crawley, Western Australia 6009, Australia
  • *now at: Unidad Académica de Sistemas Arrecifales, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Apdo. Postal 1152, Cancún, Quintana Roo 77500, Mexico

Abstract. Pacific Ocean sea surface temperatures (SST) influence rainfall variability on multidecadal and interdecadal timescales in concert with the Pacific Decadal Oscillation (PDO) and Interdecadal Pacific Oscillation (IPO). Rainfall variations in locations such as Australia and North America are therefore linked to phase changes in the PDO. Furthermore, studies have suggested teleconnections exist between the western Indian Ocean and Pacific Decadal Variability (PDV), similar to those observed on interannual timescales related to the El Niño Southern Oscillation (ENSO). However, as instrumental records of rainfall are too short and sparse to confidently assess multidecadal climatic teleconnections, here we present four coral climate archives from Madagascar spanning up to the past 300 yr (1708–2008) to assess such decadal variability. Using spectral luminescence scanning to reconstruct past changes in river runoff, we identify significant multidecadal and interdecadal frequencies in the coral records, which before 1900 are coherent with Asian-based PDO reconstructions. This multidecadal relationship with the Asian-based PDO reconstructions points to an unidentified teleconnection mechanism that affects Madagascar rainfall/runoff, most likely triggered by multidecadal changes in North Pacific SST, influencing the Asian Monsoon circulation. In the 20th century we decouple human deforestation effects from rainfall-induced soil erosion by pairing luminescence with coral geochemistry. Positive PDO phases are associated with increased Indian Ocean temperatures and runoff/rainfall in eastern Madagascar, while precipitation in southern Africa and eastern Australia declines. Consequently, the negative PDO phase that started in 1998 may contribute to reduced rainfall over eastern Madagascar and increased precipitation in southern Africa and eastern Australia. We conclude that multidecadal rainfall variability in Madagascar and the western Indian Ocean needs to be taken into account when considering water resource management under a future warming climate.