Structure of the Atlantic Meridional Overturning Circulation in Three Generations of Climate Models

Through a large meridional transport of heat and freshwater, the Atlantic overturning circulation (AMOC) plays fundamental role in earth climate system. Yet, there exist significant biases representing AMOC structures models it is unclear whether or to what extent have reduced through different generations models. To address this question, study compared represented three phases Coupled Model Intercomparison Project (CMIP) with similar horizontal resolution: CMIP3, CMIP5, CMIP6. We found that (a) although model spread large, multi-model ensemble each CMIP reproduced magnitude depth are reasonable agreement observations; (b) CMIP, smaller temperature salinity difference between northward flowing top limb southward second AMOC, which lead systematic bias weaker freshwater; (c) these generally CMIP5 CMIP6 significantly improved from CMIP3.