Reconstructing the evolution of the Gulf Stream system

As one of its most important heat transport systems, the Gulf Stream system has a significant influence on the Earth’s climate. The system is predicted to weaken under global warming, and scientists have wondered for years whether this slowdown has already begun. As direct measurements of the system are rare, one has to look at indirect, so-called proxy data, to answer this question. One promising proxy data set of the Gulf Stream system is the sea surface temperatures of the North Atlantic: they are highly affected by the northward heat transport associated with the Gulf Stream system and reach back as far as 1870. And indeed, a unique region of cooling temperatures south of Greenland provides evidence that the system has weakened by about 15 percent since the middle of the 20th century. This is in line with the trends found in other proxy data like the grain sizes or the composition of coral shells found in ocean sediments, that all indicate that the Gulf Stream system in recent decades has been weaker than ever before in at least 1600 years.