The Atlantic Meridional Overturning Circulation in High-Resolution Models
The Atlantic Meridional Overturning Circulation (AMOC) is a circulation pattern in the Atlantic Ocean that is a critical element of the global climate system. Its behavior has almost exclusively been studied using low-resolution models that do not resolve critical meso-scale processes like eddies and narrow boundary currents. This study reviews the literature on high-resolution model representations of the AMOC. It is shown that the higher resolution improves critical aspects of the AMOC, hence reducing biases that are still plaguing low-resolution models. High-resolution models also display higher levels of variability, more consistent with the decades-long observations provided by the trans-Atlantic RAPID, SAMBA, and OSNAP arrays.
With the ever-increasing power of high-performance computing platforms, high-resolution ocean climate models can now represent the AMOC in configurations in which mesoscale eddies and narrow boundary currents are explicitly and realistically represented. This will allow us to test whether our intuition of AMOC behavior, built on decades of experience with low-resolution, eddy-parameterized models, carries over to a strongly eddying ocean.
The Atlantic Meridional Overturning Circulation (AMOC) is a critical element of the global climate system, as it redistributes heat globally. Its fate under continued anthropogenic forcing is uncertain, and our understanding is almost exclusively based on models in which mesoscale eddies are parameterized. The availability of high-resolution models, and the computational facilities available to run them, will finally allow us to test the basic paradigms of AMOC behavior that the science community has developed in the last half-century or so. This paper reviews the literature on the AMOC in strongly eddying ocean models. One main conclusion is that eddying models generally represent the circulation pathways better than low-resolution models, leading to a background state that is much closer to observations. With reduced biases and dynamics that are better grounded in fundamental hydrodynamics, it is expected that the AMOC in eddying models is a better representation of the AMOC in the real world. Further studies are needed to understand the implications of this for predictability, and for our understanding of the role of the AMOC in climate variability.