Lectures on Thermodynamics and Ocean Mixing (September 2018)

• Main Author: McDougall, Trevor
• Format: Course Material
• Language: English
• Published: Trevor McDougall 2018
• Subjects: Ice Shelves
• Online Access: https://oceanrep.geomar.de/id/eprint/44343/; https://oceanrep.geomar.de/id/eprint/44343/1/Thermo_Lect_A_2018.pdf; https://oceanrep.geomar.de/id/eprint/44343/2/Thermo_Lect_B_2018.pdf; https://oceanrep.geomar.de/id/eprint/44343/3/Thermo_Lect_C_2018.pdf; https://oceanrep.geomar.de/id/eprint/44343/4/Thermo_Lect_D_2018.pdf; https://oceanrep.geomar.de/id/eprint/44343/5/Thermo_Lect_E_2018.pdf; https://oceanrep.geomar.de/id/eprint/44343/6/Thermo_Lect_F_2018.pdf; https://oceanrep.geomar.de/id/eprint/44343/7/Thermo_Lect_G_2018.pdf; https://oceanrep.geomar.de/id/eprint/44343/8/Thermo_Lect_H_2018.pdf; https://oceanrep.geomar.de/id/eprint/44343/9/Thermo_Lect_I_2018.pdf

Course Outline The aim of these lectures is to present the fundamentals of thermodynamics in the context of fluid flow and mixing in the ocean and the interaction of seawater and ice. The course will develop thermodynamic concepts that are needed to account for the flow of heat in the coupled atmosphere-ocean-ice system of planet earth. The thermophysical quantities in the ocean are functions of three variables, namely salinity, temperature and pressure, and this functional dependence complicates what is even meant by seemingly simple concepts such as "specific volume", "specific heat" and "heat content per unit mass". For example, what is a meaningful definition of an “isopycnal surface”? The ocean and atmosphere are in a continuous state of turbulent motion, and the course will derive the appropriate theoretical framework in which these time varying motions should be examined. This course introduces the conservation laws that govern the fluid dynamics the ocean, in particular concentrating on what variables should be carried in ocean models given that the ocean is subject to turbulent fluxes rather than simply molecular fluxes of heat and salt. The distinctions between variables that are conservative versus those that are non-conservative are emphasized. Several new results on the interaction of seawater and ice, and particularly of frazil ice, will be introduced. These results add thermodynamic rigor to existing practices. This rigor is now possible because the thermodynamic properties of seawater, ice and humid air have been redefined in 2010, as adopted by the Intergovernmental Oceanographic Commission. Frazil ice is the name used when small crystals of ice form in cold seawater such as occurs at the underside of ice shelves near the poles. The course will explore some of the implications of this thermodynamic knowledge for how oceanic data should be analyzed. For example, it is possible to developed a closed expression for the mean absolute velocity in the ocean, but it seems to depend on the local value ...