The Gulf Stream ocean current shifted northward during a global cold snap nearly 13,000 years ago. This shift temporarily disrupted eastern Canada's oceanic ecosystems. Researchers at University College London (UCL) found this direct evidence. This process could happen again as the climate changes.
The study, published in Nature Communications, reconstructed the ocean current's history. Researchers used marine sediments from off Canada's East Coast. They found that during the Younger Dryas, about 12,900 years ago, the Gulf Stream moved hundreds of miles north. It came closer to the coast of Nova Scotia.
Previous modeling studies predicted this northward shift. The sediment cores provide the first empirical evidence of it during a major abrupt climate event. This research offers insight into potential shifts in Atlantic currents due to climate change. This could provide earlier warnings of significant changes.
The Gulf Stream transports warm tropical waters northward. It plays a major role in regulating the North Atlantic's climate. The ancient shift would have initially warmed waters near Nova Scotia by four to five degrees Celsius. This likely disrupted local marine ecosystems. This effect lasted for the first few hundred years of the Younger Dryas. Cold freshwater from growing sea ice then covered the warmer current. This insulated it from the land and atmosphere.
The Younger Dryas was an abrupt cold snap. It occurred as Earth's climate and oceans warmed after the last Ice Age. Climate models predict that current warming could lead to similar tipping points. Researchers analyzed tiny fossil shells, called foraminifera, in mud on the ocean floor. These microfossils recorded the temperature and salinity of the ancient seawater. Chemical signals in these shells helped estimate past ocean temperatures.
Scientists are concerned about a similar abrupt change in the Atlantic Meridional Overturning Circulation (AMOC). Climate models predict that warming North Atlantic waters will become less dense. This will reduce the AMOC's strength. If the AMOC weakens, the Gulf Stream is expected to shift northward again. This would have a similarly disruptive effect on the region's climate and ecosystems.
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