Search

Trotz ihrer enormen Bedeutung für zahlreiche wissenschaftliche und gesellschaftliche Fragestellungen ist die Klimatologie von Höhlen bisher unzureichend erforscht. Deshalb untersucht diese Dissertation wie sich Luftdruckwellen innerhalb barometrischer Höhlen ausbreiten, durch welche klimatologischen Prozesse Luftdruckgradienten zwischen der Höhlen- und Außenluft entstehen und wie durch diese Ausgleichsströmungen induzieren werden. Dabei werden vier systematische Unterschiede zwischen Höhlen- und Außenluftdruck sowie die zugehörigen klimatologischen Prozesse identifiziert und modelliert, wodurch der Einfluss der Morphologie auf das Höhlenklima nachgewiesen und die Strömungsdynamik an der Höhleneingängen erklärt werden kann. Die Ergebnisse zeigen eine bisher unbekannte Komplexität der Klimatologie barometrischer Höhlen und tragen wesentlich zu einem besseren Verständnis speläoklimatologischer Mechanismen der Druckausbreitung sowie der Dynamik barometrischer Ausgleichsströmungen bei.

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.

Recent speleoclimatological research has shed new light on air pressure dynamics inside barometric caves by identifying pressure-modifying processes and resulting systematic differences between cave and surface air pressure. Based on these new findings, a multi- step quantitative model is developed and explored to predict air pressure inside Wind Cave and Jewel Cave – two major barometric cave systems in the Black Hills of South Dakota, USA – from external surface measurements. Therefore, each identified speleoclimatological pressure process is translated into a mathematical operation. Model evaluation based on Pearson correlation and mean (absolute) deviation between model outputs and control measurements yields good to excellent results: Depending on the location, the presented model predicts 99.2% to 99.7% of measured air pressure inside Wind Cave compared to 90.3% and 99.4% inside Jewel Cave, thus proving that the previously identified and now modeled processes adequately and comprehensively describe the speleoclimatological pressure dynamics inside barometric caves. Slightly weaker model performance is observed at the lower elevator level inside Wind Cave and at Deep Camp inside Jewel Cave due to irregular pressure disturbances caused by elevator operation and unique morphological features in the deeper parts of Jewel Cave, respectively. Comparative spatial analyses of model constants and model accuracies at all investigated locations reveal significant differences in pressure patterns between the caves, thus demonstrating the effect of morphological characteristics on air pressure propagation and resulting modifications. The findings also support earlier research in Wind Cave and Jewel Cave as they provide speleoclimatological background for previously observed differences in airflow dynamics between both caves. Therefore, this study presents an important contribution to understanding the complex speleoclimatology of barometric caves.

In barometric caves, air pressure gradients between the outside atmosphere and the cave induce strong bidirectional compensating currents, which control almost all elements of speleoclimatology, including air temperature, humidity, and CO\(_2\) dynamics. Therefore, this study set out to investigate air pressure propagation through Wind Cave and Jewel Cave – two major barometric cave systems in the Black Hills of South Dakota, USA. Based on high-resolution air pressure data from both the surface and several measurement sites inside the caves, four systematic changes of pressure waves during their journey through the caves and their related speleoclimatological processes were identified and discussed: Compared to the outside atmosphere, the pressure signals within Wind Cave and Jewel Cave showed (1) an absolute displacement due to different altitudes of the measuring sites, (2) a delay related to the travel times of the pressure wave to the measuring sites, (3) a smoothing effect, and (4) a damping effect due to long response times of the caves to external pressure changes. The spatial distribution of the changes observed in this study shows that for Wind Cave, the cave opening and the narrow entrance area represent the main obstacle for pressure propagation, while for Jewel Cave, the deep areas have the greatest influence on the development of air pressure gradients. Our analyses provide completely new insights into the processes and mechanisms inside barometric caves, which will significantly contribute to the understanding of pressure-related airflow dynamics and all related elements of speleoclimatology.