Heat exchanges in the heterothermic zone of a karst system: Monlesi cave, Swiss Jura Mountains

Abstract

[1] Subsurface ice accumulations in temperate karst environments are assumed to be highly sensitive to external climate forcing and therefore represent a favorable setting for studying processes controlling heat exchanges in the heterothermic zone of a karst system. Air, rock, water, and ice temperatures were measured and complemented by airflow, water discharge, and cave air humidity data during a case study carried out between 2001 and 2006 at Monlesi ice cave in the Swiss Jura Mountains. The energy balance of the system could be quantified for an annual cycle, and results demonstrate that forced convection, which is controlled by the temperature difference between the cave air and the external atmosphere, is a driving force for the heat exchange between the cave and the surrounding environment. Therefore compared to the external mean annual conditions, major thermal anomalies are to be expected in the entrance zone of a cave system. Since this heterothermic zone may extend over several hundreds of meters, a better understanding of the mechanisms controlling the subsurface deposition environment represents a major prerequisite for high-resolution paleoenvironmental reconstructions from cave deposits.

Variances in airflows during different ventilation modes in a dynamic U-shaped cave

“…In spite of the same temperature difference |T exterior -T cave | = 20 °C, the differences between air densities are distinct, ∆ρ = 0.082 kg m -3 and ∆ρ = 0.095 kg m -3 in cases (a) and (b), respectively. Actually, temperatures of the cave air near the entrances are influenced by external temperature, which lead to formation of a heterothermic zones (see, Wigley & Brown, 1971;de Freitas & Littlejohn, 1987;Luetscher et al, 2008). This effect predominates near the entrance, through which the external air enters a cave (see Table 1).…”

“…Airflow is plotted against the temperature difference, ∆T = T external -T cave (Fig. 2), assumed generally as the airflow driving force (e.g., Christoforou et al, 1996;Luetscher et al, 2008;Fernández-Cortés et al, 2009;Kowalczk & Froelich, 2010;Boch et al, 2011). Note that the positive airflows correspond to the direction into the cave (inflowing air) and the negative ones to the direction from the cave (outflowing air) (Jernigan & Swift, 2001).…”

The mass and energy balance of ice within the Eisriesenwelt cave, Austria

“…The authors also note a prevalence of sublimation during winter, a decrease of ice thickness (−5 cm yr −1 from 1989 to 1992) and a considerable variability in different parts of the cave. Luetscher et al (2008) investigated the energy and mass balance of perennial ice in Monlesi cave (Switzerland). This cave experiences similar outside temperatures as ERW and due to its sag-like topography there is weak oscillating air flow during summer and unidirectional ventilation during winter.…”

“…Saar, 1956;Pavuza and Mais, 1999;Mais, 1999). Even less is known about the energy and mass balance of cave ice deposits (Ohata et al, 1994a, b;Luetscher et al, 2008) indicating a lack on process-oriented investigations.…”

Caracterização Do Espeleoclima Da Gruta Do Mateus (Bonito-Ms) E Aplicações No Manejo Espeleológico E Na Gestão Do Espeleoturismo

“…Apresenta também processos físico-químicos de transferência e conservação de energia e massa semelhantes aos encontrados em sistemas atmosféricos da superfície terrestre, mas em intensidades atenuadas na maioria dos casos (LUETSCHER et al, 2008). A reposição energética ocorre a partir de fluxos gasosos e hídricos de troca com o ambiente externo, o qual recebe incidência direta da radiação solar, bem como sob influência geotermal (STOEVA; STOEV, 2005;LUETSCHER et al, 2008). Estas e outras características diferem as cavernas de outros ambientes de pequena circulação atmosférica, particularizando-as dentre os microclimas e caracterizando-as como espeleoclimas (LOBO, 2012).…”