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Ocean quahog clam. Credit Paul Kay |
Scientists have used centuries-old clam shells to see how the North Atlantic climate system reached a "tipping point" before the Little Ice Age.
The Little Ice Age – a period of regional cooling, especially in the North Atlantic – lasted several centuries, ending in about 1850.
A long-standing theory suggests initial cooling in this period was sustained by "sea-ice to ocean feedbacks" – sea ice expanded and this slowed ocean currents which in turn reduced the flow of warm water from the south.
The new study, by the University of Exeter, used the shells of quahog clams – which can live for several hundred years – to understand how the ocean has evolved and responded to external changes over recent centuries.
The findings show that the North Atlantic climate system destabilized and lost resilience (the ability to recover from external changes) prior to the Little Ice Age, possibly causing it to "tip" into a new, colder state.
And the researchers say the North Atlantic could be approaching a new tipping point, with major consequences for the region's climate.