Published online by Cambridge University Press: 05 June 2012
In this chapter we consider the powerful forces that drive the shelf seas, and supply the large amounts of energy which are dissipated within them. We shall see that these forces act mainly through the transfer of properties (momentum, heat, freshwater, etc.) at the sea surface and through the lateral boundary where the shelf seas meet the deep ocean. Together the various forcing mechanisms produce an energetic regime which, in most shelf seas, maintains a high level of energy dissipation far greater than that of the deep ocean. We begin by identifying the principal energy and momentum sources and then consider, in turn, the forcing mechanisms involved and the extent to which the resultant inputs are known and can be related to measurable parameters.
Energy sources
Perhaps the most obvious and striking form of mechanical energy input to the sea arises from surface wind stresses and pressure gradients imposed by the atmosphere. These forces drive ocean currents and generate surface waves whose impact at the coast can be dramatic and is often seen as symbolic of the ocean's power. In many shelf seas, however, energy input through tidal forcing is a more consistent and more powerful source of mechanical energy. Most tidal energy is delivered to the shelf in the form of energy fluxes in tidal waves which originate in the deep ocean, although there is also a (usually small) contribution arising from tidal body forces acting directly on the waters of the shelf seas. Both winds and tides inject very large amounts of kinetic energy to the ocean as a whole; total inputs have been estimated recently as ~1 and ~3.5 TW for wind and tidal inputs respectively (Munk and Wunsch, 1998).
To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.