LIST WATER LECTURES on Critical Zone Sciences Seminar Series #2

 

The Critical Zone of the Earth

The Critical Zone (CZ) denotes the fine pellicle at the surface of the Earth in which water circulates; life has developed and humans live. In all the countries, it is studied by a large number of disconnected disciplines, funded by a large number of research institutions over the last decades and monitored by a impressive number of long-term Critical Zone Observatories (CZO). However, today, we still lack a systemic approach to this particularly heterogeneous and complex layer of the globe whose behavior is particularly critical for our future. We still have to deal with very fragmented, non-interoperable observation chronicles, a wide variety of scientific approaches and of models and no systemic approach of the CZ. The challenge of Critical Zone sciences is to better articulate the different disciplines and representations of the CZ around common questions and instrumental and modeling tools. It is also to better incorporate life processes into the system.

While keeping the wealth of each disciplinary approach, the challenge is now to better understand how water, soils, visible and invisible biomass, as well as humans are connected and interact. Particularly difficult is to connect timescales -ranging from the meteorological or biological timescale to the geological timescale- and understand how rapid or extreme sudden events may influence the CZ trajectory for thousands and millions of years.

Originally proposed by geochemists, the CZ initiative is developing rapidly in the different countries in parallel to critical zone observatory programs and infrastructure and is now encompassing a wide range of disciplines. The CZ initiative is a unique opportunity to decompartmentalise Earth Sciences and couple timescales at the local scale of territories. It is also a unique opportunity to reconcile biological and geological sciences by focusing on local –territorial- observatories. CZ appears to be a crucial component of the terrestrial ESS.

Prof. Jérôme GAILLARDET, Institut de Physique du Globe, Paris France