Development and Validation of a Tipping Element Emulator Integrated into a Simplified Climate Model to Simulate the AMOC Collapse

Despite its potential future collapse and profound impacts, assessing the tipping dynamics of the Atlantic Meridional Overturning Circulation (AMOC) remains a significant challenge. Complex models such as Earth System Models (ESMs) and Earth System Models of Intermediate Complexity (EMICs) introduce substantial uncertainties in identifying tipping points. To address this, recent research has focused on developing conceptual models based on non-linear dynamics to capture the tipping behavior of the system. However, existing conceptual models typically simulate the AMOC response to a single temperature forcing, whereas it is well established that the AMOC is also influenced by freshwater flux.

In this study, we develop and validate an AMOC Tipping Calibration module that incorporates two forcing parameters: global mean temperature and freshwater flux. This module is designed as an emulator for the AMOC response within cGenie, an EMIC. Following validation, the emulator is integrated into SURFER, a simplified climate model that enables rapid and efficient simulations of AMOC trajectories under various scenario-based pathways. Our results show that incorporating both forcing parameters improves the accuracy of AMOC trajectory predictions. The methodology used to develop the two-parameter emulator is generalizable and can be applied to other tipping elements. By facilitating a greater number of simulations than complex models while maintaining calibration to them, this tool represents a significant advancement in exploring and understanding the potential future behaviour of the AMOC and other tipping elements.