Connecting the Great Lakes in MOM6: sub-grid scale topography and hydraulic control

"Many current earth system models suffer from biases in the North America regional climate. It has been speculated that these biases partly stem from the absence of the Great Lakes in current simulations. In this work, we aim to use MOM6 as a hydrodynamics model for the Great Lakes system, as a first step to integrate and connect the Great Lakes in the global simulations.
Simulating the Great Lakes presents challenges to the ocean models, particularly in preserving their staircase-like water levels, which relies on properly connecting individual lakes. The Great Lakes are connected by narrow rivers and waterfalls (e.g. the Niagara Falls). The rivers (around ~1 km wide at maximum) cannot be fully resolved by resolutions used in global configurations. The waterfalls cannot be simulated by most of the ocean models, as they are often inherently incapable of simulating discontinuities.
To tackle these challenges, we explore two complementary approaches. Firstly, we employ sub-grid scale topography to represent the narrow rivers. Secondly, we adopt a hydraulic control theory-based parameterization to effectively represent the dynamics of waterfalls."