Sensitivity of the Atlantic Meridional Overturning Circulation to Model Resolution in CMIP6 HighResMIP Simulations
<p>The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the three-dimensional ocean circulation that transports warm and salty water northward, and exports cold and dense water from the Arctic southward.</p><p>The simulated AMOC in Coupled Model Intercomparison Project models (both coupled and ocean-only) has been studied extensively. However, correctly simulating the AMOC with these models remains a challenge for the climate modelling community. One model aspect that can affect the AMOC representation is the model&#160;resolution (i.e. grid spacing).</p><p>Here, we examine key aspects of the North Atlantic Ocean circulation using a multi-model, multi-resolution ensemble based on the CMIP6 HighResMIP coupled experiments.&#160;The AMOC and associated heat transport tend to become stronger as&#160;model resolution increases, particularly when the ocean resolution changes from non-eddying to eddy-present and eddy-rich. However, the circulation remains too&#160;shallow compared to observations for most models, and this, together with temperature biases, cause the northward&#160;heat transport to be too low for a given overturning&#160;strength.</p><p>In the period 2015-2050, the overturning circulation tends to decline more rapidly in the higher&#160;resolution models by more than 20% compared to the control state, which is related to both themean state and to the subpolar gyre contribution to deep water formation. The main part of the&#160;decline comes from the Florida Current component of the circulation.</p>