International attention focuses on a climate change 'trigger'
The Agulhas Current off the coast of South Africa is said to stimulate the so-called overturning circulation of the Atlantic that plays a significant role in the northward flow of the Gulf Stream and hence climate of Northwest Europe and beyond. At regional scales the Agulhas influences extreme weather events while annual rainfall variations in southern Africa are correlated with warm and cold anomalies in the Agulhas system, in turn associated with several Indian Ocean climate modes.
However, despite its crucial role, the Agulhas system has largely been ignored as a potential trigger of climate variability. That is until the arrival of the Marie-Curie Actions project GATEWAYS ('Multi-level Assessment of Ocean-Climate Dynamics: A Gateway to Interdisciplinary Training and Analysis').
Professor Rainer Zahn, the project coordinator, from the Institute of Environmental Science & Technology at the Universitat Autònoma de Barcelona, says; 'The project is innovative because it combines new and established analytical methodologies not normally available in single research projects.
It links modern ocean and climatic processes with the analysis of materials collected from water column sampling and sediment traps in order to verify the degree to which the collected materials represent ocean processes,' he explains.
Using cutting-edge high-resolution modelling, the GATEWAYS team has discovered that the atmosphere can impact oceanography in the Indian-Atlantic Ocean corridor south of Africa in a way not intuitively expected. The strong winds in one direction can generate a surface ocean current going against the wind, hence directly driving the water transports from the Indian to the Atlantic Ocean. This discovery was an unexpected outcome of the project, and heavily influenced the way the team now look at wind-driven ocean currents, including strong surges of the water exchange between the two oceans.
'While this is hypothetical, it is a physically plausible result which reveals that the suggested circulation patterns fitted the database that the marine palaeoclimatiology community compiled in the project. Hence this is a true highlight and a new area of scientific knowledge,' reveals Professor Zahn.
The GATEWAYS consortium, consisting of scientists from Spain, Germany, Israel, The Netherlands, the UK and South Africa, formed an interdisciplinary partnership including expertise in physical oceanography, meteorology, ocean and atmospheric numerical modelling, and marine and terrestrial palaeoclimatology.
The latter enabled the research to apply analytical protocols on a wide range of materials linking marine with terrestrial palaeoclimatic expertise to perform the often postulated, but rarely conducted, land-ocean palaeoclimatic linking, the professor suggests.
He believes that it is due to this cross-disciplinary collaboration that the project has been so successful.
'It took pains, time, patience and, above all, "out-of-the-box" thinking by all sides to make progress with our collaboration. And it has to be said, that we made substantial steps forward. But it is clear that the learning has to continue long after our project has come to an end,' Prof. Zahn concludes.