A new study led by UCL researchers has found new evidence that the Gulf Stream changed during the last ice age, suggesting it may be more sensitive to future climate change.
This study was published in: nature, They found that during the last ice age, about 20,000 years ago, the Gulf Current was stronger than it is today due to stronger winds blowing across the subtropical North Atlantic.
This means that, according to early research, climate change could lead to a decline in subtropical winds and a weakening of the Gulf Stream in the future.
Subtropical
This would limit the amount of tropical heat reaching Europe, cooling the continent and raising sea levels in North America, but the magnitude of these potential effects is still uncertain.
The Gulf Stream is a surface current that flows along the eastern coast of the United States across the Atlantic Ocean to Europe, carrying warm tropical waters with it. This warm water releases heat into the atmosphere, warming Europe.
Researchers found that during the last Ice Age, when most of the Northern Hemisphere was covered by an ice sheet, stronger winds in the region led to a stronger and deeper Gulf Stream. But despite the stronger Gulf Stream, the planet was still much colder overall than it is today.
Dr Jack Wharton, from UCL’s Department of Geography and lead author, said: “We found that during the last Ice Age the Gulf Stream became much stronger due to stronger winds across the subtropical North Atlantic. As a result, the Gulf Stream still carried a lot of heat northwards, even though the rest of the planet was much colder.
“Our study also highlights that the Gulf Stream may be sensitive to future changes in wind patterns. For example, if winds weaken in the future, as recent studies using climate models have shown, the Gulf Stream could weaken and Europe could become colder.”
weakening
The Gulf Stream is also part of the broader Atlantic Overturning Circulation (AMOC), which is caused by winds and the formation of deep waters in the subpolar North Atlantic, which cause surface waters to become denser and sink.
Scientists have previously raised concerns that climate change could weaken the AMOC, as meltwater from Greenland could disrupt deep ocean formation and prevent warm tropical waters from reaching Europe, cooling the continent.
The combined effects of weakening winds and reduced deep-water formation could significantly weaken the Gulf Stream. If the AMOC were to collapse (a low probability but considered a possible future scenario), European temperatures would drop by 10-15 degrees Celsius, with significant damage to continental agriculture and weather patterns, and a reduction in the wind-driven portion of the Gulf Stream would make this even worse.
“It is not always recognised how big a role ocean currents play in transporting heat around the planet and shaping climate,” said co-author Professor Mark Maslin, from UCL’s Department of Geography.
