ISOTOPES IN WATER

Abstract

The study of isotopic proxies has two different though related basic aims: an understanding of the way in which the water cycle is linked to alterations in climate, and how the carbon cycle has responded to these changes. This necessarily requires the study of oxygen, hydrogen and carbon stable isotope ratios. Water plays a vital role in the growth or formation of all proxies whether animal, vegetable or mineral; while water molecules consist of oxygen and hydrogen isotopes alone, they are also a solvent for several different forms of carbon. There are of course stable isotopes of other elements encountered in dissolved form, for example boron, chlorine, nitrogen and sulphur, but none of these has yet achieved more than a niche role in the study of proxies. This chapter therefore concentrates exclusively on the well-established trio of O, H and C. Note that the dating of water by carbon-14 or other radio-isotope methods is not included as direct dating of proxies provides much higher resolution. Water dating and allied information is extensively reviewed in books by Clark and Fritz (1997) and Cook and Herczeg (1999).