TIMCOM model datasets for the CMIP6 Ocean Model Intercomparison Project

Abstract

The participation of the Taiwan Multi-scale Community Ocean Model (TIMCOM) in the Ocean Model Intercomparison Project (OMIP) experiments is introduced here, as part of phase 6 of the Coupled Model Intercomparison Project (CMIP6). Two ocean–sea ice model experiments are compared: (a) OMIP1, forced by the Coordinated Ocean-Ice Reference Experiments Phase II data (1948–2009), and (b) OMIP2, forced by JRA55-do data (1958–2018). The observed annual means and the interannual variability of physical states are reasonably captured in both experiments, but improved mean temperatures and salinities are found in OMIP2. The weaker winds and stronger freshwater discharge in the OMIP2 forcing contribute to some simulated differences between OMIP1 and OMIP2. Many patterns and biases are similar to those found in other modeling efforts, confirming the common systematic biases. However, a few unique features are found in this study, including the recent increase of the Atlantic Meridional Overturning Circulation (AMOC) that has been observed in the last decade and a generally higher Drake Passage transport. The enhanced AMOC can be explained by the recent cooling event over the North Atlantic, which thermally increased the surface density flux. The higher Drake Passage transport compared to observations is possibly linked to a stronger bottom cell of meridional circulation and a smaller Antarctic sea-ice extent.