Worst ice age for 10,000 years actually triggered by global warming

By Mark Waghorn via SWNS

The worst ice age for 10,000 years that hit 600 years ago devastating Europe was actually triggered by global warming, according to new research.

Sea currents responsible for keeping the UK temperate strengthened dramatically - melting Arctic ice.

Over the course of a few decades in the late 1300s and 1400s, vast amounts were flushed out into the North Atlantic.

It cooled the water, diluted its saltiness - and ultimately crashed the AMOC (Atlantic Meridional Overturning Circulation).

Northern Europe was plunged into the 'Little Ice Age' lasting from the 15th to the 19th Centuries.

And it could happen again, warn scientists. Disaster movie "The Day After Tomorrow" was based on the phenomenon.

AMOC drives the gulf stream - and has been likened to a planetary conveyor belt.

It carries warm surface water from the equator - returning it cold to the ocean depths.

The findings in Science Advances have implications for climate change today - despite there now being much less sea ice.

"We have to keep an eye on the build-up of freshwater in the Beaufort Sea north of Alaska,"said lead author Dr. Francois Lapointe.

"It has increased by 40 percent in the past two decades. Its export to the subpolar North Atlantic could have a strong impact on oceanic circulation.

"Also, persistent periods of high pressure over Greenland in summer have been much more frequent over the past decade and are linked with record-breaking ice melt.

"Climate models do not capture these events reliably and so we may be underestimating future ice loss from the ice sheet.

"More freshwater is entering the North Atlantic - potentially leading to a weakening or collapse of the AMOC."

Dr. Lapointe and co-author Professor Raymond Bradley say there is an urgent need to address these uncertainties.

The Little Ice Age was one of the coldest periods of the past 10,000 years - and Britain bore the brunt.

The Thames turned to ice, gales flattened communities and famine killed peasants in their thousands.

Frost fairs were held in the heart of London, crop failures ruined farms and cattle and sheep froze to death in the fields.

Pandemics occurred throughout Europe - resulting in misery and death for millions.

Now the University of Massachusetts Amherst team have found the calamities were sparked by an unusually warm episode.

The paradox was discovered after they analyzed 3,000 years of North Atlantic sea surface temperatures.

The reconstructions identified spikes in the late 1300s followed by unprecedented drops in the early 1400s - only 20 years later.

Using detailed marine records, the researchers also discovered an abnormally strong northward transfer of warm water in the late 1300s.

It peaked around 1380 - resulting in waters south of Greenland and the Nordic Seas becoming much warmer than usual.

"No one has recognized this before," saidDr. Lapointe.

Normally, AMOC transports warm water from the tropics to the coast of Northern Europe.

It loses heat and becomes denser when it reaches higher latitudes and meets colder arctic waters - sinking to the bottom of the ocean.

This deep-water formation then flows south along the coast of North America and continues on to circulate around the world.

But in the late 1300s, the system gathered pace. Far more warm water than usual moved north - causing rapid ice loss. AMOC crashed.

Fast-forwarding to modern times to our own time, between the 1960s and 1980s we have also seen a rapid strengthening of AMOC.

It has been linked with persistently high pressure in the atmosphere over Greenland.

The researchers think the same atmospheric situation occurred just prior to the Little Ice Age.

Clues can be found in tree rings. Radiocarbon isotopes show unusually high solar activity during the late 1300s.

It led to high atmospheric pressure over Greenland. At the same time, fewer volcanic eruptions were happening on Earth.

Less ash meant the air was cleaner and the planet more responsive to changes in solar output.

"Hence the effect of high solar activity on the atmospheric circulation in the North-Atlantic was particularly strong,"Dr. Lapointe said.

Earlier this year a study found AMOC is now at its weakest point in 1,000 years.

Scientists said Britain and the rest of Europe could be facing a 'big freeze' - like in "The Day After Tomorrow."