Abrupt Gulf Stream path changes are a precursor to a collapse of the Atlantic Meridional Overturning Circulation.

Abstract

The Gulf Stream is part of the Atlantic Meridional Overturning Circulation (AMOC). The AMOC is a tipping element and may collapse under changing forcing. However, the role of the Gulf Stream in such a tipping event is unknown. Here, we investigate the link between the AMOC and Gulf Stream using a high-resolution (0. 1°) stand-alone ocean simulation, in which the AMOC collapses under a slowly-increasing freshwater forcing. AMOC weakening gradually shifts the Gulf Stream near Cape Hatteras northward, followed by an abrupt northward displacement of 219 km within 2 years. This rapid shift occurs a few decades before the simulated AMOC collapse. Satellite altimetry shows a significant (1993-2024, p < 0.05) northward Gulf Stream trend near Cape Hatteras, which is also confirmed in subsurface temperature observations (1965-2024, p < 0.01). These findings provide indirect evidence for present-day AMOC weakening and demonstrate that abrupt Gulf Stream shifts can serve as early warning indicator for AMOC tipping.