The Agulhas Current, giant swirling whirlpools at the crossroads of three oceans

The Agulhas Current runs along the East African coast descending after Madagascar and running along the Mozambique Channel. And just before the Cape of Good Hope, it diverges from the coast and then makes a 180-degree turn, a big reversal off the tip of the African continent. At this point, it generates whirlpools with very strong currents (up to 2.5 knots). These are the rings of the Agulhas Current, well known to sailors.

The Vendée Globe sailors pass far from the Cape of Good Hope, much further south where they catch the edge of the reversal of the Agulhas Current to be helped on their way eastwards.

But it is an important current in terms of biodiversity. The water is marked by horizontal movements on the surface but also by vertical movements that promote life below the surface. Indeed, whirlpools bring nutrients, present in deep and opaque waters, to the surface where light promotes the growth of plankton, the first link in the trophic (food) chain. In addition, whirlpools also carry floating waste.

Sensors, satellites and digital models help us understand ocean currents

The oceans are in motion. The wind generates waves, the Moon and the Sun cause the tides, the rotation of the Earth generates whirlpools. And to add the vertical dimension, cold and salty water sinks. A vast oceanic conveyor belt thus transports each drop of water around the world, from the surface to the bottom and from the bottom to the surface. Clément Vic tells us more about the scientific questions he still asks about this mechanics of currents: 

Why is it important today to better understand these dynamics of ocean currents? 

Because they have a decisive impact on our climate. The best-known current, which is actually not the strongest is the Gulf Stream, whose extension, the North Atlantic Current, brings mild weather and humidity towards Europe. 

However, climate change disrupts ocean currents. For example, the melting of ice increases and accelerates the flow of fresh water at the poles with less salty, lighter surface water. How will our conveyor belt react in the coming decades? Is it at risk of seizing up? To answer this question, scientists are deploying measuring devices in all the world's oceans, for example with the Argo float network. They also use surface observations made using satellites equipped with sensors. Finally, they solve the equations that govern the movements of the oceans using computer calculations. This is a way of predicting what may happen in future climates by 2050 or 2100. Because the ocean is a significant heat reservoir compared to the atmosphere. Water has a capacity a thousand times greater than air to absorb energy. The ocean thus functions like a sponge that absorbs excess heat from the atmosphere as well as 25% of the CO2 emitted by human activities.