Tidal mixing around Indonesia and the Maritime continent: Implications for paleoclimate simulations

Tidal mixing provides an important source of mechanical energy for the ocean circulation and as such is being incorporated into state‐of‐the‐art climate models. Calculation of the tidal energy flux depends on high‐resolution topographic datasets, not available for paleoclimate simulations. In this study we demonstrate that changes in the tidal mixing may have significant impacts on ocean circulation, sea surface temperatures, and hence climate. Using a coupled climate model, we test the system's sensitivity to perturbations in the tidal mixing surrounding the Maritime continent and show that an increase in such mixing could cause significant changes in the ocean thermal structure, including a ∼1°C warming of the ocean surface in the eastern equatorial Pacific and a similar cooling in the west. The mechanism of these changes involves mixing the relatively cold waters of the Equatorial undercurrent with warmer surface waters. The reduction of the zonal temperature gradient is amplified by ocean–atmosphere interactions associated with a weakening of the atmospheric Walker circulation. Potential implications of this study concern the Pliocene (an epoch characterized by a reduced zonal temperature contrast along the equator) and other past climates. While the actual strength of tidal mixing during the Pliocene is uncertain, our study assesses the bounds on how much tidal mixing may have contributed to maintaining its climate state. We conclude that, on geological timescales, changes in tidal mixing may be an important dynamical factor together with ocean bathymetry and continental configuration. Key Points Tidal mixing within the Maritime continent helps determine climate properties Changes in tidal mixing may have changed climate on geological timescales Changes in tidal mixing could be the most important aspect of bathymetry changes