Overview

Understanding how the AMOC has changed in the past is important for understanding the AMOC’s role in climate and how it might change in the future. However, as direct observations of the AMOC only exist since 2004, we have to rely on other lines of evidence to understand how AMOC has changed over the 20th Century. Unfortunately, those other lines of evidence have significant disagreements on how the AMOC evolved over the 20th Century (see figure). However, they also have significant uncertainties. For example, low-resolution coupled climate models (including those used in the CMIP6) have known limitations and struggle to represent the variability of AMOC volume, heat and freshwater transports. Observationally, a range of proxies have been used to diagnose past AMOC variability (e.g., SST, sea level, western boundary velocities, upper ocean heat content), but a robust systematic evaluation of their utility has yet to be performed.

Therefore, in EPOC we will use high resolution historical simulations, compared with low resolution simulations, to evaluate the utility and robustness of different proxies of AMOC variability to reduce uncertainty on past AMOC variability (1850-present). Furthermore, we will perform new simulations with high-resolution coupled models in order to identify, and evaluate, the multivariate fingerprint of how greenhouse gas forcing impacts on the AMOC.

For the recent past (1993 – present), we will compare the best available modern oceanographic observations of AMOC variability to high resolution paleo proxies in order to assess their utility to reconstruct deep ocean circulation over the period 1850 – present.