Stormier mid-Holocene southwest Indian Ocean due to poleward trending tropical cyclones

A.N. Green, Andrew Cooper, Carlos Loureiro, Shannon Dixon, Annette Hahn, Mattias Zabel

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Abstract

Geological evidence of past storminess is fundamental for contextualizing long-term climate variability and investigating future climate. Unlike the Atlantic and Pacific basins, robust storminess reconstructions do not exist for most of the Indian Ocean, despite the hazard that tropical cyclones pose to the SE African margin. Here we combine seismic stratigraphy with analysis of marine sediment cores to look for regionally representative storm-related sediment deposits (tempestites) intercalated in shoreface sediments from the SW Indian Ocean off South Africa. Tempestites, represented by hummocky seismic units, whose sediments have clear marine geochemical signatures, are found to have been deposited between 7.0 and 4.8 cal kyr BP, when sea level was between 0 and +3 m above present. Deposition and preservation of the tempestites reflect unprecedented tropical cyclone impacts, associated with periods of strongly positive Indian Ocean Dipole anomalies and linked to warmer sea surface temperatures. Future climate projections suggest stronger positive IOD anomalies and further intensification and poleward migration of tropical cyclones, like their mid-Holocene predecessors. Given the rarity of tropical cyclone landfalls in South Africa, this urges a revaluation of hazards in areas along the SE African coast likely to become more vulnerable to landfalling tropical cyclones in the future.
Original languageEnglish
Article number15
Pages (from-to)60-66
Number of pages7
JournalNature Geoscience
Issue number1
DOIs
Publication statusPublished (in print/issue) - 23 Dec 2021

Bibliographical note

Funding Information:
This work was financially supported by the Bundesministerium für Bildung und Forschung (BMBF, Germany) within the project Regional Archives for Integrated Investigations (RAiN, 03G0840A) (M.Z.). We thank the captain, crew and scientists of the METEOR M102 cruise for facilitating the recovery of the studied material, and eThekwini Municipality for access to multibeam bathymetry.

Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer Nature Limited.

Keywords

  • Indian Ocean
  • South Africa
  • Indian Ocean (Southwest)
  • coast
  • Dipole
  • marine sediment
  • sea level
  • sea surface
  • sea surface temperature
  • seismic stratigraphy
  • tropical cyclone

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