New study suggests North Atlantic is close to ‘tipping point’

The results suggest that before the Little Ice Age, the North Atlantic climate system lost its resilience and perturbed, potentially forcing it to “flip” into a new, cooler state.

Study of the Little Ice Age reveals new information about the North Atlantic climate system.

Scientists have examined centuries-old oyster shells to determine how the North Atlantic climate system reached a “tipping point” before the Little Ice Age. The Little Ice Age, the period of regional cooling particularly pronounced in the North Atlantic, lasted for several centuries and ended around 1850.

A long-standing theory asserts that the initial cooling of this period was maintained by “sea ice to oceanic reactions”. As sea ice expanded, ocean currents slowed, which in turn reduced the flow of warm water from the south.

The University of Exeter has conducted a new study that examined how the ocean has changed and its response to external changes over the past few centuries using oyster shells, which can live for several hundred years.

Ocean Quahog Clam

Ocean Quahog Clam. Credit: Paul Kay

The results show that the North Atlantic climate system lost elasticity (the ability to recover from external changes) and perturbed before the Little Ice Age, which could have caused the “flip” to a new, colder state. In addition, according to experts, a new tipping point in the North Atlantic may be near, which will have serious consequences for the climate of the region.

The work is aiding our understanding of how and when tipping points are triggered, which is important given that scientists have warned that many tipping points may now be approaching worldwide due to human-driven climate change.

“One way to tell that a system is approaching an abrupt transformation is that it becomes slow to respond to perturbations (external changes),” said lead author Beatrice Arellano-Nava of the World Systems Institute in Exeter. In other words, the system loses the ability to return to its normal state, and can instead ‘tend’ to a new state.

said Dr. Paul Halloran, who co-led the research.

The new study warns that the vulnerability of the North Atlantic system is a critical issue today, with recent analysis indicating that it has destabilized over the past century and may be approaching a tipping point.

“Our latest analysis indicates that the ocean currents system in the North North Atlantic could now be at risk of overturning again due to global warming, again triggering abrupt climate change over Europe,” said Professor Tim Linton, Director of the World Systems Institute.

Analysis of the clam shells focused on oxygen, carbon isotopes, and shell growth – all of which can be used as measures of environmental change.

Reference: “Disstabilization of the Arctic Atlantic before the Little Ice Age” by Beatrice Arellano-Nava, and Paul R. Halloran, and Chris A. Bolton, James Scores, Paul J. Butler, David J. Reynolds, and Timothy M. Linton, August 25, 2022, Available here.

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