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# Physics-based early warning signal shows that AMOC is on tipping course

## Details

**Authors** René M. van Westen, Michael Kliphuis, Henk A. Dijkstra

**Year** 2024

**Publisher** Science Advances

**Kind of work** article

**Discipline** Oceanography

**Secondary disciplines** Climatology

**Applied** false

[Read it at the publisher](https://doi.org/10.1126/sciadv.adk1189) 
10.1126/sciadv.adk1189

## In authors' words

### Abstract

One of the most prominent climate tipping elements is the Atlantic meridional overturning circulation (AMOC), which can potentially collapse because of the input of fresh water in the North Atlantic. Although AMOC collapses have been induced in complex global climate models by strong freshwater forcing, the processes of an AMOC tipping event have so far not been investigated. Here, we show results of the first tipping event in the Community Earth System Model, including the large climate impacts of the collapse. Using these results, we develop a physics-based and observable early warning signal of AMOC tipping: the minimum of the AMOC-induced freshwater transport at the southern boundary of the Atlantic. Reanalysis products indicate that the present-day AMOC is on route to tipping. The early warning signal is a useful alternative to classical statistical ones, which, when applied to our simulated tipping event, turn out to be sensitive to the analyzed time interval before tipping.

### What they set out to do (purpose)

To investigate the physical mechanism of an AMOC collapse ('tipping') event and to develop a physics-based, observable early-warning indicator for it.

### Who or what was studied (sample)

Output of the Community Earth System Model, a coupled ocean-atmosphere global climate model, run under slowly increasing North Atlantic freshwater forcing until a full AMOC collapse occurred, validated against present-day oceanographic reanalysis and observational datasets.

### How they did it (methods)

Numerical climate-model simulation combined with diagnostic time-series and threshold analysis, benchmarked against classical statistical early-warning-signal methods.

### What they found (results)

A full AMOC collapse was simulated for the first time in a complex global climate model, and a physics-based precursor, the minimum in AMOC-induced freshwater transport at the Atlantic's southern boundary, was identified and applied to present-day reanalysis data, indicating the real-world AMOC is currently moving toward its collapse threshold.

## Commentary

### In short

The AMOC's shift from a circulating to a collapsed state is a system-level regime boundary driven by a causal freshwater-forcing relationship, with the collapse itself an emergent property of the whole circulation system rather than any single local measurement.

**Patterns it shows** D, S, R

**Added** 2026-09-22

**How to cite this** René M. van Westen, Michael Kliphuis, Henk A. Dijkstra (2024). Physics-based early warning signal shows that AMOC is on tipping course. Science Advances.