Abstract
The only low latitude pathway of heat and salt from the Pacific Ocean to the Indian Ocean, known as Indonesian Throughflow (ITF), has been suggested to modulate Global Mean Surface Temperature (GMST) warming through redistribution of surface Pacific Ocean heat. ITF observations are only available since ~1990s, and thus, its multidecadal variability on longer time scales has remained elusive. Here we present a 200 year bimonthly record of geochemical parameters (δ18O-Sr/Ca) measured on Cocos (Keeling) corals tracking sea surface temperature (SST; Sr/Ca) and sea surface salinity (SSS; seawater-δ18O═δ18Osw) in the southeastern tropical Indian Ocean (SETIO). Our results show that SETIO SSS and δ18Osw were impacted by ITF transport over the past 60 years, and therefore, reconstructions of Cocos δ18Osw hold information on past ITF variability on longer time spans. Over the past 200 years ITF leakage into SETIO is dominated by the interannual climate modes of the Pacific Ocean (El Niño—Southern Oscillation) and Indian Ocean (Indian Ocean Dipole). Pacific decadal climate variability (represented by the Pacific Decadal Oscillation) significantly impacted ITF strength over the past 200 years determining the spatiotemporal SST and SSS advection into the Indian Ocean on multidecadal time scales. A comparison of our SETIO δ18Osw record to GMST shows that ITF transport varied in synchrony with global warming rate, being predominantly high/low during GMST warming slowdown/acceleration, respectively. This hints toward an important role for the ITF in global warming rate modulation.
| Original language | English |
|---|---|
| Pages (from-to) | 48-60 |
| Number of pages | 13 |
| Journal | Paleoceanography and Paleoclimatology |
| Volume | 33 |
| Issue number | 1 |
| Early online date | 3 Jan 2018 |
| DOIs | |
| Publication status | Published - Jan 2018 |
Funding
We acknowledge the constructive comments by three anonymous reviewers, which were helpful to improve the original manuscript. We thank the VPRO, Royal NIOZ, and NWO for funding the coral drilling campaign as part of the Beagle program during the Darwin year (2009) and the people of Cocos Keeling Islands for assistance throughout the fieldwork and help with permits. We thank Gerrit van den Bergh (University of Wollongong) and Roel Nagtegaal for their help during retrieval and initial analysis of the coral cores. UV-luminescence analysis was supported through the SCAN2 program (NWO project 834.11.003). Analytical assistance of Piet van Gaever during oxygen isotope analyses was greatly appreciated. We thank Dieter Garbe-Schönberg from the Chistian Albrechts University Kiel (Germany) for assistance with the ICP-OES measurements and quality checks. Bouke Lacet and Wynanda Koot (VU University Amsterdam) helped cut the core slabs. The TROPAC01 model was developed within the framework of the DFG pro ject SFB754 and integrated at the North-German Supercomputing Alliance (HLRN). EvS was supported by the Australian Research Council via grant DE130101336. A Senior Curtin Fellowship in Western Australia and an Honorary Fellowship with the University of the Witwatersrand in South Africa supported J.Z. R.H. is supported through NWO open competition project “SCANALOGUE” (ALWOP.2015.113). This work was partly carried out under the program of Netherlands Earth System Science Centre (NESSC), financially supported by the Dutch Ministry of Education, Culture and Science (OCW). The published data are archived in the PANGAEA data repository (https://doi. pangaea.de/10.1594/ PANGAEA.883837).
| Funders | Funder number |
|---|---|
| VPRO | |
| Australian Research Council | DE130101336 |
| Nederlandse Organisatie voor Wetenschappelijk Onderzoek | ALWOP.2015.113, 834.11.003 |
| Koninklijk Nederlands Instituut voor Onderzoek der Zee |
Keywords
- Cocos (Keeling)
- Coral paleoclimate
- global warming rate
- Indonesian throughflow
- PDO
- seawater &δ18O
