New research reveals that the Gulf Stream, a crucial ocean current that warms Europe, was stronger during the last ice age than it is today. This discovery, led by scientists at University College London (UCL), suggests the current might be more sensitive to climate change than previously thought, potentially impacting Europe’s future climate.
The study, published in Nature, found that about 20,000 years ago, when much of the northern hemisphere was covered in ice, stronger winds in the subtropical North Atlantic led to a more powerful Gulf Stream. This finding challenges our understanding of how ocean currents respond to climate shifts and raises concerns about future changes.
Dr. Jack Wharton, lead author from UCL Geography, explains: “We found that during the last ice age, the Gulf Stream was much stronger because of stronger winds across the subtropical North Atlantic. As a result, the Gulf Stream was still moving lots of heat northwards, despite the rest of the planet being far colder. Our work also highlights the Gulf Stream’s potential sensitivity to future changes in wind patterns.”
A Complex System of Currents
The Gulf Stream is part of a larger system called the Atlantic Meridional Overturning Circulation (AMOC). This system is driven by both wind patterns and the formation of deep water in the North Atlantic, where cooling surface waters become dense and sink.
Climate change could weaken the AMOC in two ways. First, melting glacial water from Greenland could disrupt deep water formation. Second, changing wind patterns could affect the Gulf Stream directly. The combined effect could significantly cool Europe.
Professor Mark Maslin, co-author from UCL Geography, notes: “It’s not always recognised how much ocean currents are responsible for transferring heat around the planet and shaping our climate. Paradoxically, the warming of the climate could cool down much of Europe by disrupting the AMOC.”
New Insights from Ancient Oceans
To measure the prehistoric Gulf Stream’s strength, researchers analyzed fossil remains of tiny organisms called foraminifera from ocean sediment cores. These cores, taken off the coasts of North Carolina and Florida, provided a window into past ocean conditions.
The analysis revealed that during the last ice age, the Gulf Stream was twice as deep and flowed twice as fast compared to today. This dramatic difference highlights the current’s sensitivity to climate conditions.
Professor David Thornalley, co-author from UCL Geography, suggests a new way of thinking about these ocean currents: “Rather than the established conveyor belt metaphor, perhaps it is better to think of the AMOC as a series of interconnected loops. There is the subtropical loop—that the Gulf Stream is part of—and a subpolar loop, which carries heat further northwards into the Arctic.”
This research underscores the complexity of ocean currents and their potential responses to climate change. If future climate change weakens the winds driving the Gulf Stream, as some initial studies suggest, it could lead to cooler temperatures in Europe and higher sea levels in North America.
While the exact magnitude of these potential changes remains unclear, this study highlights the need for continued research into ocean currents and their role in shaping our planet’s climate. As we face an uncertain climate future, understanding these complex systems becomes increasingly crucial for predicting and preparing for potential changes.
