Royal Society Wolfson Fellow Prof. Jens Zinke from the Centre of Palaeobiology Research at the University of Leicester together with Prof. Bruggemann from the University of La Réunion (France) recently led a research team on board the French research vessel Marion Dufresne II in April.
The research cruise was organised by French research organisation TAAF and Prof. Zinke and three researchers from the UK, France and Germany joined the team of more than 70 scientists from all over the world and from multiple disciplines in the Esparses Islands in the SW Indian Ocean to collect living and fossil coral cores at four remote coral reef islands.
The coral collected from the Islands, located between Mozambique and Madagascar, will be used to reconstruct the sea surface temperature, salinity and nutrient cycles and analyse how they affect Sub-Saharan and global climate and regional environmental variability. The area is one of the most important surface routes of the global ocean feeding the water exchange between the Indian Ocean and the Atlantic south of Southern Africa.
The heat and salt exported from this region into the Atlantic will eventually feed the Gulf Stream a few decades later, and therefore influence climate in North America and Europe. With their research, the scientists hope to decipher how the climate in the past 6000 years has changed in the aftermath of the sea level rise following the last Ice Age.
Of particular interest will be the changes in seasonality brought about by the changes in incoming solar radiation during slow movements in the position of the Earth to the Sun. The scientists will also study the changing impact of El Niño on ocean temperatures, heat transport and the balance of rainfall and evaporation over the past 6000 years to the present.
Prof. Zinke said, “We know that El Niño led to severe coral bleaching and mortality in the western Indian Ocean in the past three decades. With our new cores, we aim to shed light on the unknown thermal stress history of the remote Eparses Islands”,
Strong trade winds create large swells which occasionally throw large coral boulders on the beach. The team spent up to four days on four islands and successfully collected more than 23 metres of fossil coral material.
A powerful drill enabled coring of 5cm in diameter cores from the fossil corals scattered along the beach. A similarly large collection of modern coral cores covering the past 200 years complements the research material. Over the coming four years the multinational team will analyse the geochemical composition of the corals.
The researchers will read the unique climatic and environmental information archived in the skeletons of annually banded reef corals prior to the start of instrumental observations and the establishment of world-wide systematic reef monitoring.
Coral reconstructions extending back for centuries provide a crucial link between the observational period and lower-resolution sediment archives from our oceans. This is of high relevance for comparisons of natural recorders of climate variability and model simulations of reef ecosystem dynamics and global and regional climate – on the time scales most relevant to human societies.
Prof. Zinke’s goal is to ‘take the pulse’ of the tropical ocean with the help of these corals, which due to their long multi-century life span act as natural sensors of past and current tropical climate and environmental change.
[Photo: Profs. Zinke and Bruggemann collecting a core from a fossil Porites coral which had grown a few thousand years ago along the shores of Europa, a small island which is home to large bird colonies, turtle nesting grounds and colourful coral reefs.]