Progress and Challenges in Representing Tropical Pacific Ocean Dynamics in A Global Operational System

The tropical Pacific region is a place of strong air-sea interactions, where the ocean exchanges heat, moisture and carbon dioxide with the atmosphere. Given its role in the global climate variability, we present progress and new challenges for the operational Mercator Ocean systems combining both model and observation information in representing mean ocean dynamics in that particular region. Based on a series of global 1/12° ocean state estimates with different data-assimilated data sets, the strength and limitations of the operational system to represent key processes are investigated. A focus is made on the representation of the thermocline, the intensity of tropical cells, and the horizontal and vertical structures of surface and subsurface zonal currents. A particular focus on vertical physics, based on an analysis of the zonal momentum balance, will help to understand the impact of data assimilation on equatorial dynamics, which is suspected to strongly influence biogeochemical model solutions. New challenges for further model and assimilation development of the Mercator Ocean systems associated with atmospheric forcing, parameterisation of physical processes and assimilation techniques are discussed.