Parameterized internal wave mixing in three ocean general circulation models

• Main Authors: Brueggemann, Nils, Losch, Martin, Scholz, Patrick, Pollmann, Friederike, Danilov, Sergey, Gutjahr, Oliver, Jungclaus, Johann H, Koldunov, Nikolay V., Korn, Peter, Olbers, Dirk, Eden, Carsten
• Format: Other/Unknown Material
• Language: unknown
• Published: Authorea, Inc. 2023
• Subjects: Pacific; Southern Ocean; Weddell; Weddell Sea; North Atlantic
• Online Access: http://dx.doi.org/10.22541/essoar.168286764.45506774/v1

The parameterization IDEMIX for vertical mixing by breaking internal gravity waves is evaluated in three different non-eddy resolving ocean models. Three different products of wave forcing by tidal flow over topography, representing the current uncertainty, are applied and compared to reference simulations without IDEMIX, allowing the model-independent effects of the new closure to be assessed. Common to all models is larger interior mixing work with stronger horizontal structure due to the inhomogeneous forcing functions in all simulations using IDEMIX, in better agreement to observations. Coherent model responses to the stronger mixing work are changes in the thermocline depth including IDEMIX related to stronger shallow overturning cells in the Indo-Pacific Ocean. Furthermore, deeper mixed layer depths in the subpolar North Atlantic are related to an increase of the Atlantic overturning circulation which brings the model closer to observations, coming along with an increase in northward heat transport. In the Southern Ocean, excessive energy input by one of the forcing products leads to unrealistic deep convection in the Weddell Sea in one of the models. The deep Indo-Pacific overturning circulation and the bottom cell of the Atlantic feature an incoherent model response, which may point towards the importance of excessive numerical mixing in the models.