Explicit Oceanic Tides in the Energy Exascale Earth System Model

Oceanic tides are seldom represented in Earth System Models (ESMs) owing to the need for high horizontal resolution to accurately represent the associated barotropic wave close to coasts. This poster presents first results of tides implemented in the Energy Exascale Earth System Model (E3SM) that circumvents this limitation using unstructured global meshing. We are at this stage simulating the largest semidiurnal (M2, S2, N2, K2) and diurnal (K1, O1, Q1 and P1) tidal constituents in a single layer version of the ocean component of E3SM, the Model for Prediction Across Scales or MPAS-O. We show the effects of implementing the topographic-wave and bottom-layer drag on the global solution. In particular, we show that the tidal constituents calculated using E3SM closely agree with TPXO8 results when suitably tuned topographic wave drag and bottom drag coefficients are employed. The effect of ice shelves on the amplitude and phase of tidal constituents are also presented. Lower values of complex errors (with respect to TPX08 results) for the M2 tidal constituents are observed when ice shelf is added in the simulations. Finally, we present our first results of sea ice-tide coupling in E3SM, illustrating the impact of non-levitating coupling and spatially-varying ice strength on tidal phase and amplitude. Our work points towards future research with varying ice shelf geometries and sea ice coupling that might lead to better comparison and prediction of tides, and thus better prediction of sea-level rise and also the future climate variability.