CZ-Tope: Using Measurements of Multiple Isotopes in One Setting to Understand Critical Zone Processes Occurring over Different Timescales

Critical Zone (CZ) science includes the study of the inter-related chemical, physical, and biological processes happening at the earth surface. CZ science differs from watershed science or other similar initiatives in that it not only incorporates many disciplinary approaches and crosses spatial scales, but it also aims to understand processes occurring at timescales varying from those characterizing fast chemical reactions to the slow responses of surficial systems to tectonic change. Isotope systems are an important tool that can be used to assess processes at different timescales. Some isotopic systems are used as chronometers. Synthesizing isotopic data from different elemental systems to understand processes as complex as weathering at a ridgetop, hillslope transformation, or watershed evolution is a difficult task but is essential toward deciphering the complex coupling that characterizes surficial systems.

A good example where isotopes are elucidating CZ processes is the analysis of weathering at ridgetops, along hillslopes, and in watersheds. Targetting these three types of study sites at the Susquehanna Shale Hills Critical Zone Observatory, we have used Mg, Fe, Li, Ca, Be, Sr, U and other isotopes to understand the effects of weathering in one-dimension (1D), 2D and 3D, respectively. Some of the systems such as Fe yield information about elemental losses due to biogeochemical weathering. Other isotopes such as U yield information about the development of particles from bedrock. In this talk I will synthesize data from many different researchers working at the CZO to show how disparate isotopic data for one set of sites can answer questions of how landforms develop and change. This effort to use many isotopes on the same CZ setting -- which we call "CZ-tope" science -- requires sharing of sites, samples, and data in team research. CZ-tope science delineates which processes control which features at each timescale of interest.