Zinke14_CLIDY-D-13-00156.pdf (7.66 MB)
Seychelles coral record of changes in sea surface temperature bimodality in the western Indian Ocean from the Mid-Holocene to the present
journal contributionposted on 2019-10-21, 15:00 authored by J Zinke, M Pfeiffer, W Park, B Schneider, L Reuning, W-C Dullo, GF Camoin, A Mangini, A Schroeder-Ritzrau, D Garbe-Schoenberg, GR Davies
We report fossil coral records from the Seychelles comprising individual time slices of 14–20 sclerochronological years between 2 and 6.2 kyr BP to reconstruct changes in the seasonal cycle of western Indian Ocean sea surface temperature (SST) compared to the present (1990–2003). These reconstructions allowed us to link changes in the SST bimodality to orbital changes, which were causing a reorganization of the seasonal insolation pattern. Our results reveal the lowest seasonal SST range in the Mid-Holocene (6.2–5.2 kyr BP) and around 2 kyr BP, while the highest range is observed around 4.6 kyr BP and between 1990 and 2003. The season of maximum temperature shifts from austral spring (September to November) to austral autumn (March to May), following changes in seasonal insolation over the past 6 kyr. However, the changes in SST bimodality do not linearly follow the insolation seasonality. For example, the 5.2 and 6.2 kyr BP corals show only subtle SST differences in austral spring and autumn. We use paleoclimate simulations of a fully coupled atmosphere–ocean general circulation model to compare with proxy data for the Mid-Holocene around 6 kyr BP. The model results show that in the Mid-Holocene the austral winter and spring seasons in the western Indian Ocean were warmer while austral summer was cooler. This is qualitatively consistent with the coral data from 6.2 to 5.2 kyr BP, which shows a similar reduction in the seasonal amplitude compared to the present day. However, the pattern of the seasonal SST cycle in the model appears to follow the changes in insolation more directly than indicated by the corals. Our results highlight the importance of ocean–atmosphere interactions for Indian Ocean SST seasonality throughout the Holocene. In order to understand Holocene climate variability in the countries surrounding the Indian Ocean, we need a much more comprehensive analysis of seasonally resolved archives from the tropical Indian Ocean. Insolation data alone only provides an incomplete picture.
This research was funded by the European Union Research and Training Network STOPFEN. We thank the Seychelles Centre for Marine Research and Technology for support in fieldwork logistics and for organising the CITES permit. We thank the two anonymous reviewers for their very constructive comments. We also thank the team of the EU-TESTREEF programme who sampled the corals La Digue. Saskia Kaars produced and processed the SEM pictures processed at the VU University Amsterdam (NL). Uwe Wollenberg and Jean-Marie Nachtigal are thanked for XRD-analyses at RWTH Aachen University, and Karin Kissling for help with ICP-OES analyses at CAU Kiel (Germany). We thank the M. Joachimski from the University of Erlangen (Germany) for the oxygen isotope analysis of the La Digue coral. We thank the Seychelles Centre for Marine Research and Technology for logistical support during fieldwork in 2003. The climate model simulations are contributions from the Cluster of Excellence ‘The Future Ocean’ (EXC-80/1) and the SFB754 ‘Climate-Biogeochemistry Interactions in the Tropical Ocean’, funded by the German Science Foundation (DFG). JZ was supported by an IOMRC AIMS/CSIRO/UWA post-doctoral fellowship.
CitationClimate Dynamics, 2014, 43 (3-4), pp. 689-708 (20)
Author affiliation/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/School of Geography, Geology and the Environment
- AM (Accepted Manuscript)
Published inClimate Dynamics
PublisherSpringer (part of Springer Nature)
NotesThe online version of this article (doi: 10.1007/s00382-014-2082-z) contains supplementary material, which is available to authorized users.