Fjords are both an interface and a buffer between glaciated continents and the oceans. They exhibit a very wide range in environmental conditions, both in dynamics and geography. Some are truly wonders of the world with their dizzying mountain slopes rising sharply from the ocean edge. Others represent some of the harshest conditions on earth, with hurricane winds, extremes in temperature, and catastrophic earth and ice movements. Fjords are unique estuaries and represent a large portion of the earth's coastal zone. Yet they are not very well known, given the increasing population and food pressures, and their present industrial and strategic importance. Temperate­ zone estuaries have had many more years of intense study, with multiyear data available. Most fjords have not been impacted by man but, if history repeats itself, that condition will not last long. Fjords present some unique environmental problems, such as their usually slow flushing time, a feature common to many silled environments. Thus there is presently a need for management guidelines, which can only be based on a thorough knowledge of the way fjords work. Fjords are, in many respects, perfect natural oceanographic and geologic lab­ oratories. Source inputs are easily identified and their resulting gradients are well developed. Throughout this book, we emphasize the potential of modeling pro­ cesses in fjords, with comparisons to other estuary, lake, shelf and slope, and open ocean environments.