Clam shells sound warning of Atlantic ‘tipping point’

A study of clam shells suggests Atlantic Ocean currents could also be approaching a “tipping point”.

Scientists studied data of quahog clams (which may reside for over 500 years) and canine cockles – as a result of shell layers present an annual file of ocean situations.

They studied these pure archives to know long-term patterns in Atlantic Ocean currents such because the Atlantic Meridional Overturning Circulation (AMOC) and the subpolar gyre (SPG).

Recent research have debated attainable AMOC and SPG tipping factors – transitions that will remodel local weather patterns. For instance, AMOC collapse would have far-reaching world results, from harsher winters in north-west Europe to shifts in world rainfall patterns, whereas a weakening of the SPG could be much less catastrophic however nonetheless convey substantial impacts, together with extra frequent excessive climate within the North Atlantic area.

The new examine, led by the University of Exeter, finds proof of “stability loss” which suggests the area is “moving towards a tipping point”.

“Anticipating a tipping point requires good data, covering a long period with no gaps,” mentioned Dr Beatriz Arellano Nava.

“We don’t have ocean observations going back into the distant past, but the bands in clam shells give us an unbroken annual record covering hundreds of years.”

The annual distinction in shell progress doesn’t reveal particular particulars of the previous local weather, as progress is dependent upon a number of components, however it offers an general image of ocean situations from 12 months to 12 months.

“When a system is stable, there will still be variations – but we would typically see a rapid return to the normal state after a change,” mentioned Professor Paul Halloran, from Exeter’s Global Systems Institute.

“When a system destabilises, it doesn’t recover as quickly – and this could be a sign of an approaching tipping point.”

The examine reveals two “destabilisation episodes” during the last 150 years.

The first – doubtless involving the SPG – occurred within the early 20^th Century, and should have performed a job in a documented warming of the Arctic and North Atlantic within the Twenties.

The second, stronger destabilisation started round 1950 and continues to the current.

“Although we cannot yet say which part of the system is losing stability, or what may be causing it, our results provide independent evidence that the North Atlantic has lost stability – suggesting that a tipping point could be approaching,” Dr Arellano Nava mentioned.

“Because these circulation techniques are interconnected, it isn’t clear whether or not the AMOC, the SPG, or each are driving the alerts we see – however any tipping level would have main implications for the local weather.

“Melting of polar ice due to climate change is certainly contributing to the weakening of ocean currents and pushing them closer to a tipping point, so rapidly reducing greenhouse gas emissions is the best way to prevent tipping points in the Atlantic Ocean.”

The examine was funded by European Union’s Horizon 2020 COMFORT and the ARIA AdvanTip tasks.

The paper, printed within the journal Science Advances, is entitled: “Recent and early twentieth century destabilization of the subpolar North Atlantic recorded in bivalves.”