By developing a special method, scientists from the Oban-based Scottish Association for Marine Science (SAMS) have reconstructed data from the past 120 years to show the link between strong ocean currents, better known as the Atlantic Meridional Overturning Circulation (AMOC) and sea surface temperature – a major influence on our climate and weather. And while doing so, they have come up with the longest reconstructed AMOC time series derived from ocean observations. Previously, the AMOC has only been continuously measured for 17 years even though it is such an important component of our climate.
Ocean currents heavily influence the weather and climate as they transport warm and cold water around the globe. The AMOC, for example, is known to transport warm surface waters from the topics towards the subpolar and Arctic regions where the water cools down, becomes denser and sinks in the water column before returning southward in the deeper ocean. This water movement heavily dictates global temperature distribution, regional sea level changes, and the ocean’s absorption of carbon, making it a vital component in the measuring of global climate change.
The SAMS scientists used temperature and salinity data from the past 120 years to showcase the AMOC’s strength. As seen in the graph below, since the start of the 20th century, the AMOC (shown in blue here) was found to correlate with the North Atlantic surface temperature (shown in red here).
The study published on Monday, 20 September in Geophysical Research Letters, underlines the dominant role of the AMOC in climate and, since changes in the AMOC precede sea surface temperature change by two to five years, this may provide a means for predicting sea surface temperature in the short-to-medium term.
“This is important because devastating European summer heatwaves have been linked to Atlantic surface temperature patterns,” explains lead author Dr Neil Fraser. “We want to know how warm the Atlantic is going to be because it has such a great influence on air temperatures, rainfall and storms over the surrounding continents.
“However, the role of AMOC in governing sea surface temperature is something that has long been debated, with previous studies, usually reliant on ocean simulations, seeing a range of different behaviours. Since our study uses only direct ocean measurements, and finds that the AMOC strength dominates surface temperature change, I think this debate is now effectively over.”
The study by Dr Neil Fraser and Prof Stuart Cunningham can be found here.
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Photography courtesy of Thomas Horig/Ocean Image Bank and Unsplash.