PrefaceMarine paleoclimatic proxies: A shift from qualitative to quantitative estimation of seawater parameters

Understanding past climate during contrasting boundary conditions can help in assessing imminent climate changes. Marine sediments offer a vast archive of past climate. Various indirect methods called proxies are used to infer principal climate parameters like temperature, salinity, productivity, monsoon intensity, ocean circulation, seawater pH, and others, from the marine sediments. The relationship between a climate parameter and marine paleoclimate proxy may vary from region to region. Additionally, the marine proxies are often affected by more than one climate parameter, thus making it difficult to assess the change in any particular parameter from a single proxy. Diagenetic alteration can also significantly affect the parameter-proxy relationship. A growing emphasis now is on quantifying changes in key climatic parameters in the past. Proxies for quantitative estimation of seawater temperature, runoff, sea-level and pH are now fairly well established. Similar robust quantitative proxies for dissolved oxygen concentration and productivity are, however, still being developed. Additionally, the uncertainty associated with quantitative estimation of past climate has to be reduced. Therefore, continuous efforts are being made to develop novel paleoclimate proxies and to evaluate existing proxies in different regions of the world oceans.