Climatic and geological long-term prognosis for a salt structure in northern Germany

A climatic and geological long-term prognosis is relevant in order to predict the future development of a potential site for radioactive waste disposal independently of the repository. This long-term prognosis for a salt diapir in the Subercynian Basin in northern Germany first analyzes the climatic development, geological processes and then, in particular, the interactions between climate and geology. Geological processes are divided into climatically influenced and non-climatically influenced. Following the Doctrine of Uniformity and the uncertainties involved in predicting future climate developments, one can assume that there will be another ice age at the site in the next 100,000 years with the corresponding processes, i.e. permafrost formation, inland glaciation, formation of subglacial channels and stress changes due to ice loading. We consider these processes in the cold period scenario as well as the retreat of the ice sheet after 110,000 years and associated processes. Isostatic rebound of the lithosphere, which can lead to earthquakes and the reactivation of faults in the cap rock and overburden as well as in the subsalinar. The anthropogenic influence is playing an increasingly important role in the development of the climate (Talento & Ganopolski 2021). Therefore we consider a warm period scenario where the actually expected cold period will weaken considerably or even will not taking place in the next 100,000 years. The consideration of a cold and a warm period scenario thus fully covers two opposing developments. Depending on the intensity of arid or wet conditions in the warm period scenario, groundwater recharge is affected. Changed precipitation affects the processes of sedimentation and erosion.

Overall, processes associated with a glacial period have a greater impact on the site conditions than warm-period processes. The climatically influenced geological processes are of greater importance than the non-climatically influenced processes because the site is located in a tectonically quiet area. We assume that a succession of cold periods and warm periods will characterize the climate for the next 1 million years, assuming that the anthropogenic effect on the climate will no longer play a role on the long term. Based on this, the normal sequence of cold and warm periods will return and up to ten cold periods will affect the location. In particular, the associated inland glaciation, glacial erosion and subglacial channels can reshape the overburden significantly.

 

Talento, S. & Ganopolski, A. (2021): Reduced-complexity model for the impact of anthropogenic CO₂ emissions on future glacial cycles. Earth Syst. Dynam., 12: 1275 – 1293.