The Tides, Internal Waves, Mixing and Climate

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ABSTRACTPI/Institution: Jayne / WHOI Proposal No: OCE-0241061The overall objective of this proposal is to work toward understanding the connections between the ocean's tides, the conversion of the tide's energy into internal waves, the vertical mixing that results from the breaking internal waves, and the impact of that mixing on Earth's climate. Evidence linking this chain of processes together has only recently been found and this topic is rife with important implications for the ocean's role in climate. Breaking internal waves are the main cause of turbulent mixing in the ocean. Recent studies have implicated the internal tides as a major source of mechanical energy for mixing, with up to 1 terawatt of tidal power being dissipated in the interior of the deep ocean, away from the continental shelves of the major land masses. This power is extracted from the ocean's tides through generation of internal waves in the ocean's interior in regions of rough seafloor topography. The mixing supported by the dissipating internal wave energy influences the thermohaline structure of the deep ocean and provides buoyancy forcing for driving circulation in the abyss. However, none of the state-of-the-art ocean general circulation models take into account this tidally driven enhanced vertical mixing, and this lack of correct physics begs the question of how reliable these models are at predicting the present ocean circulation. These models are also an important part of climate models, and their ability to predict future climate change is brought into serious question. This highlights the need for improved parameterizations of mixing in ocean general circulation models used to study the Earth's climate. The intellectual merit of this proposal is addressing some of the outstanding questions concerning the parameterization of the dynamics of enhanced tidal dissipation and mixing over rough topography and its relation to Earth's climate. Further it seeks to understand the physical linkages between the cycles in tidal forcing and changes in the earth's climate. The broader impact of this work will be the societal benefit of improved climate forecasts through more realistic climate models (in particular the Community Climate System Model) which lead to more accurate forecasts of naturally-occurring and anthropogenically-forced changes in earth's climate.