Airflow dynamics in Wind Cave and Jewel Cave: How do barometric caves breathe?

Abstract

Recent research on air pressure propagation through barometric caves has revealed various speleoclimatological processes, which cause a more complex relationship between surface air pressure changes and resulting pressure gradients between cave and surface air than previously assumed. So far, however, studies on barometric cave airflow have only been based on surface air pressure measurements. Thus, this study investigates and compares airflow at the openings of Wind Cave and Jewel Cave – two major barometric cave systems in South Dakota, USA – as a response to surface air pressure changes and air pressure gradients. Based on high-resolution long-term air pressure measurements from the surfaces and several locations inside the caves, as well as ultra-sonic airflow measurements at the openings, the analysis proves that for both caves, cave airflow velocity can be predicted more accurately by air pressure gradients than by previous surface air pressure changes. An inter-cave comparison also reveals substantial differences in cave airflow dynamics between Wind Cave and Jewel Cave, with the relevant period of surface air pressure variations for cave airflow velocity and the cave reaction times being significantly longer at Jewel Cave compared to Wind Cave. Therefore, the findings of this study demonstrate the effects of cave morphology on airflow and significantly contribute to a better understanding of the speleoclimatological mechanisms and dynamics of compensating airflow at the openings of barometric caves.