US Climate Variability and Predictability Program

The Sensitivity of Regional Coupled Ocean-Atmosphere Simulations over the Intra-Americas Seas to the Prescribed Bathymetry

Florida State University
Florida State University
Session V: Identifying sources of model biases for the IAS in both coupled and ocean or atmospheric models
This study highlights the importance of the ocean circulation in the maintenance upper ocean heat content of the Intra-Americas Seas (IAS; comprising of the Gulf of Mexico and the Caribbean Sea). Two multi-decadal, high-resolution (15km grid interval), regional coupled ocean-atmosphere model integrations centered over the IAS are compared that differ only in their bathymetry. Both of these model integrations are forced by identical global atmospheric and oceanic reanalysis at the lateral boundaries. It is observed that the model integration with a smoother and coarser bathymetry in the region (EXP) results in more widespread SST bias across the IAS. These differences in the climatological SST between the model integrations are also associated with changes in the prevalent upper ocean currents, especially that related to the flow through the Yucatan Channel. Furthermore, the upper ocean heat content in large portions of the IAS is underestimated in EXP relative to the CTL integration that uses a higher resolution bathymetry. The EXP integration uses a bathymetry with a shallower Yucatan Channel, which tends to produce unrealistically weak flow through the Yucatan Channel and a weak Loop Current. In addition the EXP integration grossly underestimates the surface eddy kinetic energy in the IAS relative to corresponding observations. These results illuminate the important role of the prescribed bathymetry in high resolution regional models to simulate the IAS upper ocean climate and its variations.
Presentation file