A Little Ice Age study reveals new insights into the North Atlantic climate system.
Scientists have examined centuries-old clam shells to determine how the North Atlantic climate system reached a “tipping point” before the Little Ice Age. The Little Ice Age, a period of particularly pronounced regional cooling in the North Atlantic, lasted several centuries and ended around 1850.
A long-standing theory holds that the period’s initial cooling was maintained by “sea ice-to-ocean feedbacks”; as the sea ice expanded, ocean currents slowed, which in turn decreased the flow of warm water from the south.
The University of Exeter has conducted a new study that looked at how the ocean has changed and responded to external changes over the past few centuries using the shells of clams, which can survive for hundreds of years.
The results demonstrate that the North Atlantic climate system lost its resilience (the ability to recover from external changes) and destabilized before the Little Ice Age, which may have ‘tipped’ it to a new colder state. Moreover, according to experts, a new tipping point in the North Atlantic could be near, which has major consequences for the region’s climate.
The work helps us understand how and when tipping points are triggered, which is important given that scientists have warned that many tipping points could now be approaching around the world due to human-induced climate change.
“One way to tell that a system is approaching a sudden transition is that it is becoming slow to react to perturbations (external changes),” said lead author Beatriz Arellano-Nava, of the Global Systems Institute in Exeter. “In other words, a system loses the ability to revert to its mean state and can instead ‘tip’ into a new state.”
“In the case of the North Atlantic before the Little Ice Age, this loss of resilience made the system vulnerable to abrupt change, potentially heralding the transition to Little Ice Age conditions,” said Dr Paul Halloran, who co-directed the research.
The new study warns that the vulnerability of the North Atlantic system is a critical issue today, with recent analysis suggesting it has destabilized over the past century and could be approaching a tipping point.
“Our latest analysis suggests that the system of ocean currents in the northern North Atlantic could once again be at risk of reaching a tipping point due to global warming, once again leading to abrupt climate change in Europe,” said said Professor Tim Lenton, director of the Global Systems Institute.
Analysis of clam shells has focused on oxygen and carbon isotopes and shell growth – all of which can be used as measures of environmental variability.
Reference: “Subpolar North Atlantic destabilization before the Little Ice Age” by Beatriz Arellano-Nava, Paul R. Halloran, Chris A. Boulton, James Scourse, Paul G. Butler, David J. Reynolds and Timothy M. Lenton, August 25, 2022,
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