Preprints
https://doi.org/10.5194/cp-2021-172
https://doi.org/10.5194/cp-2021-172
 
19 Jan 2022
19 Jan 2022
Status: this discussion paper is a preprint. It has been under review for the journal Climate of the Past (CP). The manuscript was not accepted for further review after discussion.

Mid-Holocene rainfall changes in the southwestern Pacific

Cinthya Esther Nava Fernandez1, Tobias Braun2, Bethany Fox3, Adam Hartland4, Ola Kwiecien5, Chelsea Pederson1, Sebastian Hoepker4, Stefano Bernasconi6, Madalina Jaggi6, John Hellstrom7, Fernando Gázquez8,9, Amanda French4, Norbert Marwan2, Adrian Immenhauser1,10, and Sebastian Franz Martin Breitenbach5 Cinthya Esther Nava Fernandez et al.
  • 1Sediment- and Isotope Geology, Institute for Geology, Mineralogy and Geophysics, Ruhr-Universität Bochum, Universitätsstr. 150, 44801 Bochum, Germany
  • 2Potsdam Institute for Climate Impact Research (PIK), Member of the Leibniz Association, Potsdam, Germany
  • 3Department of Biological and Geographical Sciences, School of Applied Sciences, University of Huddersfield, Queensgate, Huddersfield, UK
  • 4Environmental Research Institute, School of Science, Faculty of Science and Engineering, University of Waikato, Hamilton, Waikato, New Zealand
  • 5Department of Geography and Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK
  • 6Department of Earth Sciences, ETH Zurich, Sonneggstrasse 5, 8092 Zurich, Switzerland
  • 7School of Earth Sciences, The University of Melbourne, Australia
  • 8Department of Biology and Geology, Universidad de Almería, Almería, 04120, Spain
  • 9Andalusian Centre for the Monitoring and Assessment of Global Change (CAESCG), University of Almería, Spain
  • 10Fraunhofer Research Institution for Energy Infrastructures and Geothermal Systems IEG, Am Hochschulcampus 1, 44801 Bochum, Germany

Abstract. A better understanding of ENSO dynamics is essential for modelling future climate change and its impacts on the ecosystems and lives of the inhabitants of the tropical Pacific islands, which face considerable environmental risk in the coming decades. This study reconstructs past ENSO dynamics using a multi-proxy approach applied to a stalagmite from Niue Island that covers the period 6.4–5.4 ka BP. δ18O and δ13C, trace-element concentrations and image analysis are linked to an age-depth model constrained by eight U/Th dates and a complete lamina count.

Principal component analysis of the proxy time series reveals hydrological changes at seasonal scale that are expressed in differential stalagmite lamina growth and geochemical characteristics. Increased concentrations of host-rock derived elements (Mg/Ca and U/Ca) and higher δ18O and δ13C values are observed in the dark, dense calcite laminae that are deposited during the dry season, whereas during the wet season higher concentrations of soil derived elements (Zn/Ca, Mn/Ca) and higher δ18O and δ13C values are found in pale, porous calcite laminae. Greyscale intensity values measured along the stalagmite growth axis are used here as an indicator of colour and density changes of the alternating laminae, allowing for the construction of a further seasonality record which expresses the contrast between wet and dry seasons. The multi-proxy record from Niue shows seasonal cycles associated with hydrological changes controlled by the South Pacific convergence zone. Wavelet analysis of the greyscale record reveals that ENSO was continuously active during the depositional period, with two weaker intervals at 6–5.9 and 5.6–5.5 ka BP. ENSO activity is also observed in the seasonality record, but muted periods are more prolonged, and intervals of significant ENSO-band power are more episodic. Recurrence analysis of nonlinear behaviour shows the influence that ENSO activity exerts on seasonality patterns and allows us to quantify the predictability of the climate system. Our results suggest that recurrence in the seasonal cycle of rainfall was reduced during periods when ENSO activity was stronger, pushing the system towards stochastic conditions. The tipping points from stochastic to predictable conditions may represent transitions in the Tropical Pacific mean state.

Cinthya Esther Nava Fernandez et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-172', Anonymous Referee #1, 12 Apr 2022
  • RC2: 'Comment on cp-2021-172', Anonymous Referee #2, 12 May 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-172', Anonymous Referee #1, 12 Apr 2022
  • RC2: 'Comment on cp-2021-172', Anonymous Referee #2, 12 May 2022

Cinthya Esther Nava Fernandez et al.

Cinthya Esther Nava Fernandez et al.

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Short summary
We provide a ca. 1000 year long (6.4–5.4 ka BP) stalagmite-based reconstruction of mid-Holocene rainfall variability in the tropical western Pacific. The annually laminated multi-proxy (δ13C, δ18O, X/Ca, gray values) record comes from Niue island and informs on El Nino-Southern Oscillation and South Pacific Convergence Zone dynamics. Our data suggest that ENSO was active and influenced rainfall seasonality over the covered time interval. Rainfall seasonality was subdued during active ENSO phases