Researchers have suggested that the Gulf Stream, a major Atlantic current with wide-ranging effects on climate may have shifted centuries ago based on testing of a stalagmite in Leamington Caves.

A scientific paper, published late last month in Communications Earth and Climate, sought to create a temperature record dating back to 1449 using the chemical breakdown of the slow-growing formation, which rises from a cave’s floor.

Edward Foreman, Professor of Earth Sciences at Durham University and the lead author of the paper, said: “The stalagmites record the chemical signals of the drip water that formed them.

“Cold weather tends to be windier, for example, leading to more sea spray and more seawater in the drip water. Analysing the chemistry of one of these stalagmites has thus enabled us to indirectly reconstruct past sea surface temperatures.”

He said that, based on their findings, sea surface temperatures around Bermuda cooled substantially for more than a century after 1720, while at the same time records along the East Coast of North America showed the opposite trend.

Mr Foreman said the shift suggested that the Atlantic Meridional Overturning Circulation, a system of ocean currents including the Gulf Stream, may have begun to weaken earlier than previously believed.

“This indicates that the system may be more sensitive than previously thought, because it responded to natural melting of ice sheets earlier than expected,” he said.

“It could also mean the current AMOC is closer to a tipping point than expected. If a tipping point is crossed, the weakening would become self-perpetuating and lead to a near-complete shutdown of these vital ocean currents.”

According to the paper, the researchers found that sea surface temperatures were fairly stable until the 18th century.

However, a cooling trend began in about 1720 and continued until about 1850, near the end of the “Little Ice Age”.

The writers theorised that the change occurred because the Gulf Stream migrated northward as the Little Ice Age abated as part of a wider shift in ocean currents, potentially helping researchers better gauge future impacts of climate change.

“The system of ocean currents collectively known as the AMOC are a major driver of climate variability,” the paper said.

“The AMOC is a highly non-linear system, and some climate models suggest that it will cross a tipping point this century due to additional external forcing from increasing greenhouse gas concentrations.

“A substantial AMOC slowdown would have serious ramifications for regional climates, such as up to ~15C mean annual temperature reductions in Northwest Europe. Thus, understanding its response to climate forcing is critical.”

The paper noted that the Gulf Stream transports warm water from the Gulf of Mexico to Northern Europe, allowing much of Western Europe to be as much as 10C warmer than other regions at the same latitude.

However, a weaker AMOC could potentially cause temperatures in Northern Europe to fall by as much as 15C and intensifying weather conditions in the tropics.

“The Little Ice Age represents a key time interval for understanding how Gulf Stream positioning and dynamics respond to climate change because it was characterised by extended Northern Hemisphere cold intervals.

“Proxy evidence suggests the Little Ice Age featured a Gulf Stream that was approximately 10 per cent weaker and positioned further south, likely due to a stronger Labrador Current and enhanced recirculation gyre.

“The lack of instrumental records from the Little Ice Age means that palaeoclimate reconstructions are crucial for inferring Gulf Stream state and position.”

Mr Foreman said the study provided additional historical context and suggested that even small changes in ocean circulation could come with significant consequences for the region.

“Even if the AMOC does not cross a tipping point soon, our research shows the weakening could still have a significant impact on regional climate patterns,” he said.

“The record does not just tell us about the past — it’s a warning that any amount of slowing down could have serious effects.”