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Mid- to late Holocene Indian Ocean Monsoon variability recorded in four speleothems from Socotra Island, Yemen
Van Rampelbergh, M.; Fleitmann, D; Verheyden, S.; Cheng, H; Edwards, L; De Geest, P; De Vleeschouwer, D.; Burns, J; Matter, A; Claeys, P.; Keppens, E. (2013). Mid- to late Holocene Indian Ocean Monsoon variability recorded in four speleothems from Socotra Island, Yemen. Quat. Sci. Rev. 65: 129-142. dx.doi.org/10.1016/j.quascirev.2013.01.016
In: Quaternary Science Reviews. Pergamon Press: Oxford; New York. ISSN 0277-3791, more
Peer reviewed article  

Available in  Authors 
    VLIZ: Open Repository 274914 [ OMA ]

Keyword
    Marine
Author keywords
    Speleothems; Indian Ocean Monsoon; Socotra; Paleoclimate; Stableisotopes; Trace elements

Authors  Top 
  • Van Rampelbergh, M., more
  • Fleitmann, D
  • Verheyden, S., more
  • Cheng, H
  • Edwards, L
  • De Geest, P
  • De Vleeschouwer, D., more
  • Burns, J
  • Matter, A
  • Claeys, P., more
  • Keppens, E., more

Abstract
    Four stalagmites covering the last 7.0 ka were sampled on Socotra, an island in the northern Indian Ocean to investigate the evolution of the northeast Indian Ocean Monsoon (IOM) since the mid Holocene. On Socotra, rain is delivered at the start of the southwest IOM in May–June and at the start of the northeast IOM from September to December. The Haggeher Mountains act as a barrier forcing precipitation brought by the northeast winds to fall preferentially on the eastern side of the island, where the studied caves are located. d18O and d13C and Mg/Ca and Sr/Ca signals in the stalagmites reflect precipitation amounts brought by the northeast winds. For stalagmite STM6, this amount effect is amplified by kinetic effects during calcite deposition. Combined interpretation of the stalagmites' signals suggest a weakening of the northeast precipitation between 6.0 and 3.8 ka. After 3.8 ka precipitation intensities remain constant with two superimposed drier periods, between 0 and 0.6 ka and from 2.2 to 3.8 ka. No link can be established with Greenland ice cores and with the summer IOM variability.In contrast to the stable northeast rainy season suggested by the records in this study, speleothem records from western Socotra indicate a wettening of the southwest rainy season on Socotra after 4.4 ka. The local wettening of western Socotra could relate to a more southerly path (more over the Indian Ocean) taken by the southwest winds. Stalagmite STM5, sampled at the fringe between both rain areas displays intermediate d18O values. After 6.2 ka, similar precipitation changes are seen between eastern Socotra and northern Oman indicating that both regions are affected similarly by the monsoon. Different palaeoclimatologic records from the Arabian Peninsula currently located outside the ITCZ migration pathway display an abrupt drying around 6 ka due to their disconnection from the southwest rain influence. Records that are nowadays still receiving rain by the southwest winds, suggest a more gradual drying reflecting the weakening of the southwest monsoon.

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