Before beginning a voyage, we usually try to learn about the places we will
visit. We look at maps and we consult travel guides. In this book, our guide will
be the papers and books published by oceanographers. We begin with a brief
overview of what is known about the ocean. We then proceed to a description
of the ocean basins, for the shape of the seas influences the physical processes
in the water. Next, we study the external forces, wind and heat, acting on
the ocean, and the ocean’s response. As we proceed, I bring in theory and
observations as necessary.
By the time we reach chapter 7, we will need to understand the equations
describing dynamic response of the ocean. So we consider the equations of
motion, the influence of earth’s rotation, and viscosity. This leads to a study of
wind-driven ocean currents, the geostrophic approximation, and the usefulness
of conservation of vorticity.
Toward the end, we consider some particular examples: the deep circulation,
the equatorial ocean and El Ni˜no, and the circulation of particular areas of the
ocean. Next we look at the role of numerical models in describing the ocean.
At the end, we study coastal processes, waves, tides, wave and tidal forecasting,
tsunamis, and storm surges.

The ocean is one part of the earth system. It mediates processes in the
atmosphere by the transfers of mass, momentum, and energy through the sea
surface. It receives water and dissolved substances from the land. And, it lays
down sediments that eventually become rocks on land. Hence an understanding
of the ocean is important for understanding the earth as a system, especially for
understanding important problems such as global change or global warming. At
a lower level, physical oceanography and meteorology are merging. The ocean
provides the feedback leading to slow changes in the atmosphere.
As we study the ocean, I hope you will notice that we use theory, observations, and numerical models to describe ocean dynamics. None is sufficient by
itself.