Shells found in Scotland rewrite our understanding of climate change

27 Apr 2018

Rannoch Moor in the central Scottish Highlands was the epicentre of the last ice cap in Scotland. Radiocarbon ages from plant remains were preserved in lake sediments and show the ice cap disappeared around 12,500 years ago. Image: Gordon Bromley

An international team of scientists has found evidence that physical alterations in climate change are different to what we thought.

Following a spate of unseasonable temperatures experienced in Ireland – notably March’s major snow deluge – fears that climate change is drastically altering our temperate climate have grown substantially.

Now, new evidence obtained by a team of researchers from NUI Galway and the University of Maine in the US suggests that the physical impact of abrupt climate change in Ireland, Britain and maritime Europe may be markedly different to what we once thought.

In a paper published to Paleoceanography and Paleoclimatology, the team wanted to investigate how abrupt climate changes, such as high-magnitude shifts in average climate, have impacted maritime Europe at the close of the last ice age.

While once believed to have been gradual, recent findings suggest that the development of the ice age was anything but slow and constant – after its peak 20,000 years ago, the planet still experienced rapid returns in as little as a few years to decades.

The most recent of these events was the ‘Younger Dryas’, occurring between 11,600 and 12,900 years ago, prior to the onset of our current warm Holocene climate 11,000 years ago.

By analysing ancient shells found in Scotland, the team’s data challenges the idea that the period was an abrupt return to an ice age climate in the North Atlantic, by showing that the last glaciers there were actually decaying rapidly during that period.

The shells were found in glacial deposits, and one in particular was dated as being the first organic matter to colonise the newly ice-free landscape, helping to provide a minimum age for the glacial advance. While all of these shell species are still in existence in the North Atlantic, many are extinct in Scotland, where ocean temperatures are too warm.

‘This finding is controversial’

This means that although winters in Britain and Ireland were extremely cold, summers were a lot warmer than previously thought, more in line with the seasonal climates of central Europe.

“There’s a lot of geologic evidence of these former glaciers, including deposits of rubble bulldozed up by the ice, but their age has not been well established,” said Dr Gordon Bromley, lead author of the study, from NUI Galway’s School of Geography and Archaeology.

“It has largely been assumed that these glaciers existed during the cold Younger Dryas period, since other climate records give the impression that it was a cold time.”

He continued: “This finding is controversial and, if we are correct, it helps rewrite our understanding of how abrupt climate change impacts our maritime region, both in the past and potentially into the future.”

These findings raise the significant possibility of a future weakening of warm ocean currents in the North Atlantic and a return to a harsher seasonal climate in the British Isles.

Colm Gorey was a senior journalist with Silicon Republic