An international team of scientists from Ireland, Great Britain and Germany has recorded an unprecedented weakening of the warm Gulf Stream in the Atlantic Ocean over the past thousand years. This is reported in an article published in the journal Nature Geoscience.
Researchers analyzed so-called proxy data: tree rings, ocean sediment samples, ice cores and records in old ship’s logs to reconstruct changes in the Gulf Stream (also known as the Atlantic Meridional Circulation or AMOS). Although proxy data individually are subject to strong uncertainties, their combination yielded statistically significant results. It turned out that in the 20th century it slowed down more than ever in the second millennium AD, which scientists associate with anthropogenic climate change.
The Gulf Stream carries warm water from the equator to the north, where it cools and sinks into the depths, from where it goes south again. It is estimated that the current carries 20 million cubic tons of water per second, but since the middle of the 20th century, it has weakened by 15 percent. At the same time, until the end of the 19th century, AMOC was relatively stable. With the end of the Little Ice Age in 1850, ocean currents began to weaken, and from the middle of the 20th century, a second, stronger weakening followed.
In Europe, a further slowdown in AMOC could contribute to more extreme weather events, including worsening winter storms, summer droughts and heatwaves. The US east coast will become more prone to flooding by mitigating the effect that large volumes of water in the Gulf Stream are deflected eastward by the Coriolis force. The Gulf Stream is projected to weaken 34-45 percent by 2100, making it even more volatile.