Somewhere off Greenland, a bright yellow robotic probe is sinking silently beneath the waves. Roughly the size of a person, with a tough metal body and packed sensors, the Argo float is part of a global effort to solve one of the great mysteries of the ocean: how its hidden movements shape the climate above.
There is no crew, no one steering it. It drifts with the currents, measuring temperature, salt and pressure. When it rises, it breaks the surface briefly and sends data home by satellite. Dive, drift, measure, surface, transmit – then it does it all again.
“Scientists investigate whether a changing Atlantic current could bring more extreme weather to the UK.”
The question these floats are helping investigate is one of the most important – and most contested – in climate science: whether the Atlantic Meridional Overturning Circulation, or AMOC – a vast north-south system of currents that carries warm surface water towards the Arctic – is beginning to change.
Scientists say the AMOC is under pressure. Most agree it is likely to weaken as the planet warms. The UK government has described it as “a key component within the Earth's climate system”, contributing to the UK’s long-term climate risks. The disagreement is over how much and how fast the current could change, and what that would mean for the weather – whether the seasons we know today could begin to shift.
The UK sits in the middle of the heat exchange that the AMOC drives. Heat released from the Atlantic feeds into the air above it, helping fuel storms, steer winds and influence pressure systems that reach north-west Europe. If the ocean changes, the weather can change too.
That includes a possibility that might seem bizarre in a warming world: changes in the Atlantic could bring more extreme swings in the UK’s weather, including colder winters, even as average global temperatures continue to rise.
For Britain, the stakes could not be higher: the same ocean that has long kept the country mild may now be the source of its most dramatic weather shifts.