New research reveals that the Gulf Stream was stronger during the last ice age due to stronger winds. Could future climate change weaken the current and affect European climate and North American sea level?
A new study suggests that the Gulf Stream was stronger during the last ice age due to stronger winds, indicating that future changes in wind patterns may weaken the Gulf Stream, affecting the climate in Europe and sea level in North America. This study deepens our understanding of the Atlantic Overturning Circulation (AMOC) and its vulnerability to climate change.
Stronger winds during the last ice age strengthened the Gulf Stream, but it flowed deep in the ocean and not near the surface, preventing Europe from warming. These findings point to future risks of a cooler Europe and rising sea levels as a result of changes in wind caused by climate change.
Researchers at University College London found that the Gulf Stream was stronger during the last ice age, about 20,000 years ago, due to stronger winds in the subtropical North Atlantic. Their research, recently published in Nature, suggests that a future decrease in these winds due to climate change could weaken the Gulf Stream. Such a change would reduce the flow of tropical heat to Europe, which could cool the continent and raise sea levels in North America.
Historical insights into Gulf Stream dynamics
The Gulf Stream is a surface current that flows along the east coast of the USA and then crosses the Atlantic Ocean to Europe, carrying with it warm tropical water. This water releases heat into the atmosphere and warms Europe.
The researchers found that during the last ice age, when ice sheets covered much of the Northern Hemisphere, stronger winds in the region made the Gulf Stream stronger and deeper. However, even though the Gulf Stream was stronger, the planet was still much colder than it is today.
The role of winds in the dynamics of the Gulf Stream
"We found that during the last ice age, the Gulf Stream was much stronger because of stronger winds in the subtropical North Atlantic. As a result, the Gulf Stream still carried a lot of heat north, Although the rest of the planet was much colder, our work also highlights the potential for the Gulf Stream to be sensitive to future changes in wind patterns, for example, if the winds become weaker in the future, as research shows Current through climate models, this may result in a weaker Gulf Stream and a cooler Europe," said Dr Jack Wharton (UCL), lead author.
The Gulf Stream is also part of the massive Atlantic Overturning Circulation (AMOC), which is driven both by the formation of deep water in the subpolar North Atlantic, where cooling causes the surface water to become dense and sinking, and by winds. Scientists have previously raised concerns about how climate change could weaken the AMOC as glacial water melting from Greenland glaciers could disrupt deep water formation, preventing warm tropical water from reaching Europe and cooling the continent.
The possible consequences of disrupting the AMOC current system
Together, the combined effect of weakening winds and decreased deep water formation can significantly weaken the Gulf Stream. If the AMOC were to collapse—which is considered an unlikely but possible future scenario—temperatures in Europe would cool by 10 to 15 degrees Celsius, causing severe damage to inland agriculture and weather patterns, and the decline in the wind-driven part of the Gulf Stream would make this even worse.
Although the AMOC and its component currents, including the Gulf Stream, are sometimes described as a "giant conveyor belt," this study highlights the complexity of the system, where each part of the current can respond uniquely to climate change.
Research methods and findings
To assess the strength of the prehistoric Gulf Stream, the researchers analyzed the fossil remains of foraminifera – microorganisms that live on the bottom of the ocean – taken from sediment cores collected off the coasts of North Carolina and Florida, in collaboration with researchers from the Woods Hole Oceanographic Institution in Massachusetts.
The researchers found that foraminifera taken from layers dating to the last ice age and sediment cores from various locations beneath the Gulf Stream had isotopic signatures (the ratio of oxygen-18 to oxygen-16, controlled by a combination of temperature and salinity) that indicated the Gulf Stream was twice as deep and flowed twice as fast. Two faster than today.
More of the topic in Hayadan:
