Comparison of the Atlantic Meridional Overturning Circulation behaviors in HYCOM and POP within the CESM

For the Coordinated Ocean-ice Reference Experiment (CORE), the HYbrid Coordinate Ocean Model (HYCOM) had been implemented in, what was then, the Community Climate System Model (CCSM3). While the results were reasonable when using the CORE-I climatology as an atmospheric forcing, they showed an almost collapse of the Atlantic Meridional Overturning Circulation (AMOC) when using the CORE-II interannual atmospheric forcing. To understand that behavior, extensive tests were performed using a HYCOM-CICE stand-alone configuration and a more suitable set of parameters was found to improve the AMOC strength.

As part of the Earth System Prediction Capability (ESPC), the newest version of HYCOM has been (re-)introduced as an alternative ocean component to POP2 in the latest version of the Community Earth System Model (CESM). The response of HYCOM and POP identically configured (bathymetry, grid and CORE-I forcing) is described in 500-year simulations. Special attention is given to the AMOC strength and variability.