Seasonal temperature variations controlling cave ventilation processes in Cueva Larga, Puerto Rico

Authors

Rolf Vieten, University of Puerto RicoFollow
Amos Winter, University of Puerto RicoFollow
Sophie Friederike Warken, Johannes Gutenberg-University MainzFollow
Andrea Schrӧder-Ritzrau, Ruprecht-Karls-University HeidelbergFollow
Thomas E. Miller, University of Puerto RicoFollow
Denis Scholz, Johannes Gutenberg-University MainzFollow

Highlights

• Seasonal temperature variations control cave ventilation processes in a tropical cave.
• Cave air pCO₂ in varies between 600 ppm in winter and 1800 ppm in summer.
• The cave air exchange time is estimated to be 36 ± 5 days.
• Minor pCO₂ variations are related to atmospheric pressure changes.
• Cave morphology is a key parameter of ventilation processes.

Abstract

Two years of cave monitoring investigate ventilation processes in Cueva Larga, a tropical cave in Puerto Rico. The cave is 1,440 m long with a large main passage (about 120,000 m³). Cave air pCO₂ in the main passage varies seasonally, between 600 ppm in winter and 1,800 ppm in summer. The seasonal variability in cave pCO₂ permits the estimation of a cave air exchange time of 36 ± 5 days and a winter ventilation rate of 3,300 ± 1,000 m³/day for the main cave passage. Calculations of virtual temperature and differences between cave and surface temperature indicate that the seasonal temperature cycle is the main driver of the alternation between a well-ventilated winter mode and a near-stagnant summer mode. The winter mode is characterized by a positive buoyancy contrast at night leading to maximal cave ventilation, while cave ventilation is at a minimum during summer. Between winter and summer, a transitional mode of partial cave ventilation is observed. On shorter time scales (diurnal to weekly), cave pCO₂ is also influenced by atmospheric pressure but this variation is one order of magnitude lower than the seasonal pCO₂ change. The cave morphology of Cueva Larga including its large volume, tubular shape and the obstructed cave entrance geometry are important boundary conditions for the observed ventilation patterns. Our findings emphasize that cave systems with varying morphology have to be studied individually in order to correctly describe ventilation processes.

DOI

http://dx.doi.org/10.5038/1827-806X.45.3.1983

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

Recommended Citation

Vieten, Rolf; Amos Winter; Sophie Friederike Warken; Andrea Schrӧder-Ritzrau; Thomas E. Miller; and Denis Scholz. 2016. Seasonal temperature variations controlling cave ventilation processes in Cueva Larga, Puerto Rico. International Journal of Speleology, 45: 259-273.
Available at: https://digitalcommons.usf.edu/ijs/vol45/iss3/7