The datasets of two Ocean Model Intercomparison Project (OMIP) simulation experiments from the LASG/IAP Climate Ocean Model, version 3 (LICOM3), forced by two different sets of atmospheric surface data, are described in this paper. The experiment forced by CORE-II (Co-ordinated Ocean-Ice Reference Experiments, Phase II) data ) is called OMIP1, and that forced by JRA55-do (surface dataset for driving ocean-sea-ice models based on Japanese 55-year atmospheric reanalysis) data is called OMIP2. First, the improvement of LICOM from CMIP5 to CMIP6 and the configurations of the two experiments are described. Second, the basic performances of the two experiments are validated using the climatological-mean and interannual time scales from observation. We find that the mean states, interannual variabilities, and long-term linear trends can be reproduced well by the two experiments. The differences between the two datasets are also discussed. Finally, the usage of these data is described. These datasets are helpful toward understanding the origin system bias of the fully coupled model.Citation: Lin, P. F., and Coauthors, 2020: LICOM model datasets for the CMIP6 Ocean Model Intercomparison Project. Adv. Atmos. Sci., 37(3), 239−249, https://doi.org/10.1007/s00376-019-9208-5.Article Highlights:• The OMIP1 and OMIP2 simulation datasets produced by LICOM3 are described. • The mean states, interannual variabilities, and long-term linear trends can be reproduced well by the two experiments.

The Atlantic Multidedal Oscillation (AMO) is a prominent mode of sea surface temperature variability in the Atlantic and incurs significant global influence. Most coupled models failed to reproduce the observed 50-80-year AMO, but were overwhelmed by a 10-30-year AMO. Here we show that the 50-80-year AMO and 10-30-year AMO represent two different AMO regimes. The key differences are: (1) the 50-80-year AMO involves transport of warm and saline Atlantic water into the Greenland-Iceland-Norwegian (GIN) Seas prior to reaching its maximum positive phase, while such a transport is weak for the 10-30-year AMO; (2) the zonality of atmospheric variability associated with the 50-80 year AMO favors the transport of warm and saline water into the GIN Seas; (3) the disappearance of Pacific variability weakens the zonality of atmospheric variability and the transport of warm and saline water into the GIN Seas, leading to the weakening of the 50-80-year AMO. In contrast, the 10-30-year AMO does not show dependence on the variability in Pacific and in the GIN Seas and may be an Atlantic-intrinsic mode. Our results suggest that differentiating these AMO regimes and a better understanding of the cross-basin connections are essential to reconcile the current debate on the nature of AMO and hence to its reliable prediction, which is still lacking in most of coupled models.

A 61-year (1958–2018) global eddy-resolving dataset for phase 2 of the Ocean Model Intercomparison Project has been produced by the version 3 of Chinese Academy of Science, the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics (LASG/IAP) Climate system Ocean Model (CAS-LICOM3). The monthly and a part of the surface daily data in this study can be accessed on the Earth System Grid Federation (ESGF) node. Besides the details of the model and experiments, the evolutions and spatial patterns of large-scale and mesoscale features are also presented. The mesoscale features are reproduced well in the high-resolution simulation, as the mesoscale activities can contribute up to 50% of the total SST variability in eddy-rich regions. Also, the large-scale circulations are remarkably improved compared with the low-resolution simulation, such as the climatological annual mean SST (the RMSE is reduced from 0.59°C to 0.47°C, globally) and the evolution of Atlantic Meridional Overturning Circulation. The preliminary evaluation also indicates that there are systematic biases in the salinity, the separation location of the western boundary currents, and the magnitude of eddy kinetic energy. All these biases are worthy of further investigation.