1.4: The Big Picture

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.

1. Ocean processes are nonlinear and turbulent. Yet we don’t really understand the theory of non-linear, turbulent flow in complex basins. Theories used to describe the ocean are much simplified approximations to reality.
2. Observations are sparse in time and space. They provide a rough description of the time-averaged flow, but many processes in many regions are poorly observed.
3. Numerical models include much more realistic theoretical ideas, they can help interpolate oceanic observations in time and space, and they are used to forecast climate change, currents, and waves. Nonetheless, the numerical equations are approximations to the continuous analytic equations that describe fluid flow, they contain no information about flow between grid points, and they cannot yet be used to describe fully the turbulent flow seen in the ocean.

By combining theory and observations in numerical models we avoid some of the difficulties associated with each approach used separately (figure \(\PageIndex{1}\)). Continued refinements of the combined approach are leading to ever-more-precise descriptions of the ocean. The ultimate goal is to know the ocean well enough to predict the future changes in the environment, including climate change or the response of fisheries to overfishing.

Figure \(\PageIndex{1}\): Data, numerical models, and theory are all necessary to understand the ocean. Eventually, an understanding of the ocean-atmosphere-land system will lead to predictions of future states of the system.

The combination of theory, observations, and computer models is relatively new. Four decades of exponential growth in computing power has made available desktop computers capable of simulating important physical processes and oceanic dynamics.

“All of us who are involved in the sciences know that the computer has become an essential tool for research …scientific computation has reached the point where it is on a par with laboratory experiment and mathematical theory as a tool for research in science and engineering.”
—Langer (1999)

The combination of theory, observations, and computer models also implies a new way of doing oceanography. In the past, an oceanographer would devise a theory, collect data to test the theory, and publish the results. Now, the tasks have become so specialized that few can do it all. Few excel in theory, collecting data, and numerical simulations. Instead, the work is done more and more by teams of scientists and engineers.