Probability Estimates of a 21st Century AMOC Collapse

TL;DR

This study provides observationally based probability estimates for a potential AMOC collapse within this century, suggesting a 59% chance before 2050, based on reanalysis data and optimal observation regions.

Contribution

It introduces a novel method using reanalysis data to estimate AMOC collapse probabilities, improving upon previous conceptual and proxy-based estimates.

Findings

Estimated collapse between 2037-2064 with a mean of 2050.

Probability of collapse before 2050 is 59% ± 17%.

Salinity data near the southern Atlantic boundary are key indicators.

Abstract

There is increasing concern that the Atlantic Meridional Overturning Circulation (AMOC) may collapse this century with a disrupting societal impact on large parts of the world. Preliminary estimates of the probability of such an AMOC collapse have so far been based on conceptual models and statistical analyses of proxy data. Here, we provide observationally based estimates of such probabilities from reanalysis data. We first identify optimal observation regions of an AMOC collapse from a recent global climate model simulation. Salinity data near the southern boundary of the Atlantic turn out to be optimal to provide estimates of the time of the AMOC collapse in this model. Based on the reanalysis products, we next determine probability density functions of the AMOC collapse time. The collapse time is estimated between 2037-2064 (10-90% CI) with a mean of 2050 and the probability of an AMOC collapse before the year 2050 is estimated to be 59 +/- 17%.