Professor Jens Zinke adn Dr Arnoud Boom
Indian Ocean sea surface temperatures (SST) play an important role in determining the location of precipitation over the tropics and the Indian Monsoon regions. Future global warming on land and ocean is thought to increase the land-ocean temperature gradient driving Indian Ocean circulation, leading to droughts or floods in adjacent biodiversity hotspots in Africa. Indian Ocean SST, precipitation and circulation anomalies also show a remote response to El Niño-Southern Oscillation (ENSO) events originating in the tropical Pacific. Atmospheric and oceanic teleconnections between the Indian Ocean and the Pacific are thought to vary on interannual to multidecadal time scales. A better knowledge of past SST and hydroclimate variability over the Indian Ocean and their interaction with the tropical Pacific over long time scales is needed to characterize natural climate variability. Such information is crucial in addressing the effects of anthropogenic climate change in light of such natural forcing factors.
Therefore, the aim of this project is to produce several centuries long climate records from and nearby Madagascar with bimonthly temporal resolution in order to unravel natural changes in the teleconnectivity with the tropical Pacific (abundant ENSO archives). Coral records dating back several centuries will be used for the reconstruction of past surface ocean variability under different boundary conditions, such as during the Little Ice Age (1600-1850). We therefore propose to build a 300-400 year modern climate and a Holocene (snapshots from fossil corals) data base for the western Indian Ocean biodiversity hotspot Madagascar and nearby islands through a seasonally resolved multi-proxy geochemical study of corals complimented by instrumental climate data analysis.
The coral data will be compared to terrestrial climate archives and instrumental climate data from Sub-Saharan Africa and Madagascar to assess past and present land-ocean climate teleconnections. Here, we collaborate with colleagues in Germany, South Africa and the USA who simultaneously work on tree ring, speleothem and lake level records. Furthermore, the paleoclimate data will be assessed in the context of newly discovered archaeological sites in Madagascar to shed light on the influence of climate variability and early human impact on megafaunal extinctions in Madagascar since the Little Ice Age.
1. Zinke, J., Loveday, B., Reason, C., Dullo, W.-C., Kroon, D. (2014) Madagascar corals track sea surface temperature variability in the Agulhas Current core region over the past 334 years. Scientific Reports 4, 4393; DOI:10.1038/srep04393.
2. Zinke, J., D’Olivo, J. P., Gey, C. J., McCulloch, M. T., Bruggemann, J. H., Lough, J. M., Guillaume, M. M. M. (2019) Multi-trace element sea surface temperature coral reconstruction for the southern Mozambique Channel reveals teleconnections with the tropical Atlantic. Biogeosciences 16, 697-712.
3. Hennekam, R., Zinke, J., ten Have, M., Brummer, G.J.A. and Reichart, G.-J. (2018) ‘Cocos (Keeling) corals reveal 200 years of multi-decadal modulation of southeast Indian Ocean hydrology by Indonesian Throughflow’, Paleoceanography and Paleoclimatology, 33, doi: 10.1002/2017PA003181.
4. Zinke, J., Hoell, A., Lough, J., Feng, M., Kuret, A., Clarke, H., Ricca, V., McCulloch, M.T. (2015) ‘Coral record of southeastern Indian Ocean marine heatwaves with intensified Western Pacific temperature gradient’, Nature Communications, 6, doi: 10.1038/ncomms9562.
5. Zinke, J., Timm, O., Pfeiffer, M., Dullo, W.-Chr., Kroon, D. and Thomassin, B. A. (2008) ‘Mayotte coral reveales hydrological changes in the western Indian between 1865 to 1994’, Geophysical Research Letters, 35, L23707, doi:10.1029/2008GL035634.