New research has indicated that a ‘big freeze’ that Europe went through almost 13,000 years ago, plunging it into an ice age, happened over the course of a few months, and could happen again in the future.
According to a report in European Science Foundation, William Patterson, from the University of Saskatchewan in Canada, and his colleagues have shown that switching off the North Atlantic circulation can force the Northern hemisphere into a mini ‘ice age’ in a matter of months. Around 12,800 years ago the northern hemisphere was hit by a mini ice-age, known by scientists as the Younger Dryas, and nicknamed the ‘Big Freeze’, which lasted around 1300 years.
Geological evidence shows that the Big Freeze was brought about by a sudden influx of freshwater, when the glacial Lake Agassiz in North America burst its banks and poured into the North Atlantic and Arctic Oceans.
This vast pulse, a greater volume than all of North America’s Great Lakes combined, diluted the North Atlantic conveyor belt and brought it to a halt. Without the warming influence of this ocean circulation temperatures across the Northern hemisphere plummeted, ice sheets grew and human civilisation fell apart.
Previous evidence from Greenland ice cores has indicated that this sudden change in climate occurred over the space of a decade or so. Now, new data shows that the change was amazingly abrupt, taking place over the course of a few months, or a year or two at most. Patterson and his colleagues have created the highest resolution record of the ‘Big Freeze’ event to date, from a mud core taken from an ancient lake, Lough Monreach, in Ireland.
Carbon isotopes in each slice reveal how productive the lake was, while oxygen isotopes give a picture of temperature and rainfall.
At the start of the ‘Big Freeze’, their new record shows that temperatures plummeted and lake productivity stopped over the course of just a few years.
Looking ahead to the future, Patterson said that there is no reason why a ‘Big Freeze’ shouldn’t happen again. “If the Greenland ice sheet melted suddenly, it would be catastrophic,” he said.