Poised to Hindcast and Earthcast the Effect of Climate on the Critical Zone

Abstract

One goal in critical zone (CZ) science is to project the response of Earth's near-surface fluxes of water, sediments, and nutrients to perturbations in climate and human actions, an approach that is increasingly known as earthcasting. However, earthcasting requires knowledge of the present and a deep understanding of the past and, more importantly, a validation through collection of data and simulations of past processes. This so-called hindcasting pairs past climate and present-day critical zone structure to understand how the function of Earth's living skin has evolved with time. The combined approach of hindcasting and earthcasting illuminates strategies for managing the critical zone and generates new hypotheses to be tested in the field and laboratory. Here we: (a) present a road map to earthcasting and hindcasting, (b) review several examples of these projections, and (c) explore a recent earthcast and hindcast of the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) where aspect was used to explore the effect of increased temperature and enhanced evapotranspiration rates on soil water solute fluxes. We conclude by discussing opportunities, challenges, and future directions for earthcasting and hindcasting, with the intent to inspire more simulations that simultaneously project water, sediments, and solute fluxes and their effect on CZ architecture.