Revealed: how Scotland must have looked 16,000 years ago…

Published on Saturday 3 May 2008 19:43

HIGHS of –7°C and lows of –20°C: welcome to the long-range weather forecast circa 10,000 BC.

Scotland as it looked during the last ice age has been revealed by a stunning new set of computer-generated images.

An ice sheet spreading 100 kilometres wide and 200 kilometres north from near Glasgow to Sutherland would have blanketed the country around 12,000 years ago.

The size of the current Iceland ice sheet, it would have ranged in depth from tens of metres near the coast to hundreds of metres inland, where it helped create glens such as Glencoe.

Most of western and northern Scotland above Loch Lomond would have been in its icy grip, with isolated glaciers on mountainous islands such as Skye.

Lowland Scotland would have been largely ice-free by this time, as would eastern mountain ranges such as the Cairngorms, which, despite their height, have less rainfall.

Winter temperatures would have been around a steady and bone-chilling –7C, although warmer summers would have hastened ice-cap melting. Scotland is believed to have been ice-free by around 11,000 years ago.

Meanwhile, the bottom right image shows the extent of the ice sheet as it would have been around 25,000 years ago when it reached out into the North Sea off Orkney and Shetland towards Scandinavia.

It shows in detail the glacial ridges and valleys left under the sea after the gigantic ice sheet melted and slowly retreated towards the Scottish mainland, allowing sea levels to rise. The deeper areas are depicted in darker blue and are now some of the richest fishing grounds in Europe.

Geologists say the map reveals that the British ice sheet melted much quicker than previously thought, providing clues as to how the current melting of the Antarctic ice sheet in the southern hemisphere will unfold.

Dr Tom Bradwell, head of the quaternary period (last ice age) at the Edinburgh-based British Geological Survey, said: "We used to think the British ice sheet was a very stable block of ice that grew and receded very slowly.

"Now we see it was made of fast-flowing dynamic ice sheets – and that it collapsed in the same way that the Antarctic ice sheet is collapsing now.

"So this has happened before on a continental scale in our history. There is no difference to what happened then to what is happening now. Obviously, it still took thousands of years for the British ice sheet to melt but in geological time that is not very long."

At its full extent, the British ice sheet would have almost joined up with the Scandinavian ice sheet covering what is now Norway and stretched down to a line from South Wales to East Anglia. Areas to the south would have been largely ice-free.

The map of the extent of the ice sheet, published in the scientific journal Science Review, has been compiled from data provided by North Sea fishing boats equipped with echo sounders. The readings have enabled geologists to compile the best picture yet of what lies under the surface.

It reveals an underwater landscape of tunnel valleys and glacial debris – moraines – carved and deposited as the ice flowed from the southeast to the northwest across what is now the North Sea Basin to the edge of the Continental Shelf.

The features show how far the ice sheet extended at its maximum and at various stages during its retreat.

"By getting access to this data, we have for the first time put together a model of the last British ice sheet and properly reconstructed its true extent," Bradwell said. "We have a clear picture of the seabed of the North Sea off Shetland and Orkney and it was really eye-opening.

"We have found these stunning valleys and big glacial ridges. There are phenomenal shelf-edge moraines, which chart the recession of the last ice sheet. They show the positions as the ice sheet fluctuates. As it pushes forward it pushes up a moraine. Then it retreats, then it pushes again.

"The big story is that the British ice sheet collapsed very rapidly and it is very similar to the situation in Antarctica today. Marine-based ice sheets, those that terminate in the sea, are very susceptible to collapse as sea levels rise, and the British ice sheet collapsed in a very similar way to what we are seeing in Antarctica now."

The current North Sea seabed was a legacy of what happened during the last ice age, Bradwell added.

"The channels, such as the Devil's Deeps, are tunnel valleys formed under a fast-flowing ice sheet," he said. "Now they are the best grounds for shrimp and lobster in Europe. It is fascinating that what we now eat is a direct result of what happened all those thousands of years ago."

At the full extent of the ice sheet, most of Scotland would have been under a kilometre of ice and snow, with temperatures falling to around –20C. As global warming progressed, a glacier would still have been flowing in the Loch Lomond area, about 10 miles north of Glasgow. Further north a clean ice shelf would have marked the coast of northwest Scotland, as shown in the image above.

Animals such as the lynx, Arctic hare and polar bear are likely to have been roaming the frigid landscape, although little is known about any human presence at that time.

What happened to the vanishing British ice sheet could shed light on what will happen in Antarctica this century if global warming continues to gather pace.

Measurements of the western Antarctic ice sheet show the balance of snowfall and melting has shifted and it is now shrinking. According to a study, a local warming of more than 5C could trigger uncontrollable melting.