Like many good scientific discoveries, Heriniaina Juliano Dani Ramanantsoa’s was made somewhat by accident.
While studying the variability of a coastal upwelling, in which deep, cold, nutrient-rich water rises towards the surface, nourishing marine wildlife and fisheries off the south-west coast of Madagascar, he stumbled across an unknown coastal current. This warm, salty and newly-described Southwest Madagascar Coastal Current flows poleward off the south-west coast of Madagascar.
“By defining the forces generating this upwelling, I’ve found unusual warm water flowing toward the southern tip of Madagascar. Therefore, I was faced with an undefined ocean current,” says Ramanantsoa.
“Advances in different technologies have helped us to describe and confirm this new ocean current, such as in-situ measurements (cruise measurement), satellite observations and ocean simulations.
“To describe an ocean current for the first time is really rare because we (are) taught that we have enough knowledge about our ocean circulation, but a lot still needs to be explored.”
The findings of the five-member South African, Malagasy and French research team of oceanographic experts from the CSIR, University of Cape Town (UCT), the University of Western Brittany in France and the French Institute for Research and Development have now been published in the scientific journal, Geophysical Research Letters.
For Ramanantsoa and his team of South African, Malagasy and French researchers, they had to provide strong evidence for the find to be accepted in a peer-reviewed journal. “It’s a rare opportunity to discover a new current in the 21st century,” says his supervisor, Dr Marjolaine Krug, a senior researcher at the Council for Scientific and Industrial Research (CSIR).
For Ramanantsoa, of the Nansen-Tutu Centre for Marine Environmental Research at UCT, the discovery is deeply personal.
“I’ve realised that my life makes way more sense because this new current was uncovered based on the indigenous knowledge that I have, as a Malagasy son of fisherman, and my skills as a physical oceanographer. It’s fantastic how the combination made a discovery.”
The CSIR says a thorough understanding of the coastal current will help scientists understand ocean circulation in the region, and the discovery will have direct implications for the management of local fisheries south of Madagascar.
The current, it says, is relatively shallow (<300m) and narrow (<100km wide) with a transport volume comparable to that of the Leeuwin current, near Australia, a warm, poleward-flowing current off its west and south coasts.
Krug explains how the southern waters off Madagascar are highly productive and support a wide range of migratory species, including sea birds and cetacean species, and “that therefore there is a direct biological link between the oceanic regions of Madagascar and South Africa".
“There’s a genetic connectivity between the material that is transported between Madagascar and South Africa - fish, sharks and turtles migrate and move between the oceans because there is no border. The current is what they use to move them around.”
The ocean, she says, is a major mitigator of climate change. “We need to understand how this water is transported polewards to balance the Earth’s climate system.”
For Ramanantsoa, the discovery will unlock several oceanographic questions that remain unsolved in the south-west Indian Ocean region. “The presence of this new ocean current will redefine the geographical structure of the global ocean circulation atlas.
“For Madagascar, this also will help to redefine coastal governance, such as the marine spatial planning, or an eventual insertion of a marine protected area. It will also attract international organisations and scientists to invest and undertake ocean studies around Madagascar."