81756 - Physical Oceanography

Learning outcomes

The course aims at giving the basic understanding of ocean dynamics solving the classical problems of the wind driven ocean circulation for the world open ocean areas, starting from the Ekman and ending with the quasigeostrophic vorticity dynamics. Planetary gravity and Rossby wave motion is discussed in details ending with a short introduction to the overturning climatic circulation of the oceans.

Course contents

Governing equations and dominant balances

Overview and physical interpretation of the Primitive Equations, including their relationship to the Navier–Stokes equations. Hydrostatic and Boussinesq approximations, scaling arguments, non-dimensional parameters, geostrophic balance, beta-plane dynamics, and Rossby radius of deformation.

Shallow-water dynamics and ocean waves

Derivation of the shallow-water equations and their use as a reduced model for rotating ocean dynamics. Vorticity and potential-vorticity conservation, inertia-gravity waves, Kelvin waves, Rossby waves, and their role in ocean adjustment.

Wind-driven circulation and boundary currents

Vertically integrated vorticity balance, wind-stress forcing, Ekman pumping, Sverdrup balance, and classical theories of western intensification. Stommel and Munk models, frictional boundary layers, and western boundary currents.

Quasi-geostrophic dynamics

Scaling and derivation of the quasi-geostrophic approximation. Streamfunction formulation, quasi-geostrophic potential vorticity, Rossby-wave dynamics, basin-scale adjustment, and balanced large-scale ocean motion.

Barotropic and baroclinic instability

Instability of geophysical flows in one-layer and two-layer quasi-geostrophic models. Barotropic instability, baroclinic modes, internal deformation radius, vertical shear, baroclinic instability, Eady and Charney models, and energy conversion mechanisms.

Abyssal circulation, eddies, internal waves, and mixing

Selected advanced topics including abyssal circulation, overturning, deep western boundary currents, topographic effects, diapycnal mixing, eddy-mean flow interaction, geostrophic turbulence, internal waves, internal tides, and the connection between mixing and large-scale circulation.

Readings/Bibliography

Cushman-Roisin, B., Introduction to Geophysical Fluid Dynamics, Academic Press.

Pond, S. and Pickard, G. L., Introductory Dynamical Oceanography, 2nd edition, Pergamon Press.

Stewart, R. H., Introduction to Physical Oceanography, online textbook.

Vallis, G. K., Atmospheric and Oceanic Fluid Dynamics, Cambridge University Press.

Gill, A. E., Atmosphere-Ocean Dynamics, Academic Press, 1982.

Pedlosky, J., Geophysical Fluid Dynamics, Springer-Verlag.

Oddo, P., Notes in Physical Oceanography, lecture notes distributed through Virtuale.

Teaching methods

All lectures and exercises are carried out in the classroom. The course is based on frontal lectures, blackboard derivations, guided discussion of physical mechanisms, and analytical development of classical problems in dynamical physical oceanography. Exercises are integrated into the lectures and are used to connect mathematical derivations with physical interpretation and oceanographic applications.

Assessment methods

The assessment will be carried out by an oral exam. The exam will assess the student’s understanding of the physical principles, mathematical derivations, and oceanographic interpretation of the topics covered in the course.

The first topic will be chosen by the student. The following questions will be chosen by the teacher and will cover different parts of the programme, with particular attention to the ability to derive the relevant equations, identify the dominant balances, explain the physical meaning of the results, and connect reduced theoretical models with ocean circulation processes. The exam normally lasts about 45 minutes.

Teaching tools

Lectures are given mainly at the blackboard. Additional material, including lecture notes and supporting documents, is distributed through the “Teaching material” section on Virtuale.

Office hours

See the website of Paolo Oddo