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

## TL;DR

The Gulf Stream's sudden path changes can signal an upcoming collapse of the Atlantic Meridional Overturning Circulation, based on simulations and observations.

## Contribution

The study identifies abrupt Gulf Stream shifts as an early warning indicator for AMOC tipping.

## Key findings

- A 219 km abrupt northward Gulf Stream shift occurs decades before simulated AMOC collapse.
- Satellite and subsurface data confirm a significant northward Gulf Stream trend near Cape Hatteras.
- Gulf Stream shifts serve as an indirect early warning of AMOC weakening.

## 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.

The northward shift and rapid displacement of the Gulf Stream provide an indirect early warning of Atlantic Meridional Overturning Circulation weakening and collapse, revealed by both high-resolution ocean simulations and historical observations.