Ice composition has until now been mostly used for reconstructing the environment of the past. A great research effort is made today to model the climate system in which the ice cover at the earth sur­ face plays a prominent role. To obtain a correct model of the ice sheets, due attention must be paid to the physical processes operating at the interfaces, i. e. the boundary conditions. The idea behind the title of this book is that the study of ice composition can shed some light on the various processes operating at the ice­ bedrock and ice-ocean interfaces and more generally on glacier dy­ namics. The book is not intended as a treatise on some specialized topic of glaciology. It is mainly the product of the experience of the two authors gained over several years research on the subject. The two authors are both members of the same university department and personal friends. The book was prepared in the following way. After a first draft of the complete book had been written by the first author, it was put in the hands of the second. The final version sent to the publishers is therefore the result of ex­ tended discussion, while at the same time preserving the unity of style that would have been lost had the two authors written selected chapters of the book individually. The book is organized into two distinct parts.