Earth’s Gulf Stream System at its weakest in over a millennium 

A new study involving researchers from UCL has found consistent evidence of a decline in ocean currents, with the Gulf Stream System, also known as the Atlantic Meridional Overturning Circulation (AMOC), at its weakest in over 1,000 years. Published today in Nature Geoscience, the team found that the Gulf Stream's slowdown in the 20th century is unprecedented and is likely linked to human-induced climate change. A major mechanism for heat redistribution and crucial to the world's climate, an abrupt slowdown of the AMOC could trigger disruptions around the globe - including a sudden rise in regional sea levels, changes in the position of major rainfall and arid climate zones. The international research team made up of scientists from Ireland, Britain and Germany were able to reconstruct the flow history of the AMOC over the last 1600 years by using a range of several different and largely independent proxy indicators including data from tree rings, ice cores, ocean sediments, and corals, as well as from historical data, such as ship logs. Analysis of the collated data indicates that whilst AMOC has been relatively stable until the 19th century, the system of ocean currents began to decline by the end of the Little Ice Age after around 1850, with a second, more drastic decline following since the mid-20th century. The study findings build upon, and are consistent with, previous research led by study co-author Dr David Thornalley (UCL Geography). A 2018 Nature study by Dr Thornalley used the size of sediment grains in marine cores to reconstruct the strength of important deep sea currents, and alongside data used to reconstruct past surface ocean temperatures, it provided the first ocean evidence for the unprecedented nature of recent changes in the AMOC.