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Madagascar corals reveal a multidecadal signature of rainfall and river runoff since 1708
Version 2 2020-06-11, 11:08
Version 1 2019-10-24, 15:29
journal contribution
posted on 2020-06-11, 11:08 authored by CA Grove, J Zinke, F Peeters, W Park, T Scheufen, S Kasper, B Randriamanantsoa, MT McCulloch, G-JA BrummerPacific 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 Nino 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 rainfallinduced 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.
Funding
This work was supported as part of the SINDOCOM grant under the Dutch NWO program “Climate Variability”, grant 854.00034/035. Additional support comes from the NWO ALW project CLIMATCH, grant 820.01.009, and the Western Indian Ocean Marine Science Association through the Marine Science for Management programme under grant MASMA/CC/2010/02. We thank the Wildlife Conservation Society (WCS) Madagascar, especially Heriliala Randriamahazo and the WCS/ANGAP team in Maroantsetra, for their support in fieldwork logistics and in the organisation of the research permits. We would also like to thank CAF/CORE Madagascar for granting the CITES permit and ANGAP Madagascar for support of our research activities in the vicinity of the marine and forest nature parks. Furthermore, we would like to thank Bob Koster and Rineke Gieles for their continuous development and maintenance of the XRF-Core Scanner, and Rik Tjallingii and Thomas Richter for their fruitful discussions concerning the manuscript. We are grateful to the ARC Centre of Excellence in Coral Reef Studies and ANU Research School of Earth Sciences for support of the Laser-Ablation analysis. JZ was supported by a collaborative UWA/AIMS/CSIRO postdoctoral fellowship.
History
Citation
Climate of the Past Discussions, 2013, 8 (2), pp. 787-817Author affiliation
/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/School of Geography, Geology and the EnvironmentVersion
- VoR (Version of Record)