Nearly 20 years of continuous data tracking the behaviour of a major system of ocean currents that underpins Western Europe’s mild climate is now available from the UK’s National Oceanography Centre (NOC).
The data from the international RAPID programme, which has been observing the Atlantic Meridional Overturning Circulation (AMOC) since 2004, now covers up to 2023, helping scientists to improve climate models and predications.
A weakening of the AMOC, which plays a fundamental role in transporting heat northwards to western Europe, is predicted by climate models this century. If this happens, it could dramatically impact weather systems all around the Atlantic.
So far, observations made by the RAPID array – an ocean observatory strung out across the Atlantic at 26 degrees north to track the AMOC – have not been made for long enough to differentiate between decadal variability and long-term decline.
The latest RAPID data, which is sent out to nearly 1,000 climate and ocean scientists and freely available, will help identify what influences any changes in the AMOC, the impact those changes have on the climate and how they might change in the future.
Unanswered questions about the AMOC
Dr Ben Moat, Physical Oceanographer at NOC and Co-Chief Scientist of the project, says, “Prior to starting the RAPID project in 2004, changes in large scale ocean circulation were thought to happen very slowly, perhaps on time scales of 100 years.
“Observations made within the first year of the RAPID array showed the ocean circulation changed on hourly and daily time scales. The results made fundamental changes in the way we understand how the ocean circulates heat around the planet.
“While we have made some revolutionary steps already, the big unanswered questions are about the predicted weakening of the AMOC. We think it will weaken, but by how much and when is still uncertain.
“So it’s critical that we continue to observe the AMOC with the RAPID array at 26 degrees north, as well as the Overturning in the Subpolar North Atlantic Programme (UK-OSNAP), which observes the AMOC at 57 degrees north, between Canada and Scotland.
“Sustained, long-term observations are fundamental to better understand the predicted slowdown of the AMOC, and benchmarking and improving climate models to better equip decision makers to be able to make appropriate climate change mitigation and adaptation measures.”
A jointly-funded international programme
The RAPID programme is jointly UK-US funded (Natural Environment Research Council and US National Science Foundation) and led by NOC in collaboration with the University of Miami and the US National Oceanic and Atmospheric Administration (NOAA).
It uses one of the longest running, continual deep-ocean observation arrays in the world. This is an array of permanently installed instruments measuring key ocean variables, from the sea surface to the seafloor. They are positioned on moorings across the full width of the Atlantic, from Florida to Morocco, all at 26 degrees north.
The instruments on the array are serviced annually by scientists and technicians, with the most recent 20th year of the RAPID array milestone expedition carried out onboard the NOC-operated RRS Discovery.
The data can be access from the Rapid website.
Learn more: The Florida Current: New insights from 40 years of observations