New Coupling Capabilities in the Energy Exascale Earth System Model (E3SM)

To improve the computational efficiency and scientific productivity, efforts have been made to transition the coupling infrastructure of the current E3SM model from the Model Coupling Toolkit (MCT) to a topology-aware library, the Mesh Oriented datABase (MOAB). Unlike MCT, MOAB provides a comprehensive description of the topology for each submodel in E3SM and exposes interfaces to seamlessly query and serialize field data directly on mesh entities.  With complete mesh representations, the new E3SM coupler can now compute and apply optimal decompositions, generate traditional conservative (first and high-order) mapping weights using TempestRemap and apply the weights to compute field projections that are essential in coupled simulations.  MOAB's purely local memory model without the use of O(p) data structures, provides good scaling and its C++ code base provides multiple avenues to exploit fine-grained parallelism with GPUs.   Simultaneously, E3SM is adding new coupling pathways for dynamic ice sheets and surface wave models.  We will present the new infrastructure and its performance in comparison to MCT for representative cases.