TY - JOUR
T1 - Controls on cave drip water temperature and implications for speleothem-based paleoclimate reconstructions
AU - Rau, Gabriel C.
AU - Cuthbert, Mark O.
AU - Andersen, Martin S.
AU - Baker, Andy
AU - Rutlidge, Helen
AU - Markowska, Monika
AU - Roshan, Hamid
AU - Marjo, Christopher E.
AU - Graham, Peter W.
AU - Acworth, R. Ian
PY - 2015/11/1
Y1 - 2015/11/1
N2 - While several studies explore cave climate and thermal regimes, little is known about the controls on cave drip water temperature. Yet water temperature significantly influences biogeochemical processes associated with cave drips. To identify the processes that control the cave drip water temperature, we measured the temperatures at multiple locations along a speleothem flow path and drip sources (stalactites) concurrently with the drip rates in Cathedral Cave, Wellington, Australia. We monitored long-term drip water temperature, drip rates, surface and cave climate and in-cave evaporation rates and conducted 3 infiltration experiments with different flow, temperature and isotopic conditions. Our results show that the drip water temperature is controlled by multiple superimposed heat transport mechanisms that act upon the infiltrating water in the epikarst, the water film after it enters the cave and before it becomes a drip. The two main heat sources/sinks for drip water are the cave air and the surrounding rock. The subsurface temperature is coupled to the surface temperature by conduction through the soil and rock mass, but the cave climate is also coupled to the surface climate by venting. On a regional scale, drip temperatures are mainly driven by the annual ground surface temperature signal but damped with depth and shifted in time compared to the surface. On a local scale, the drip water temperature can differ significantly from cave air and speleothem temperature due to the latent heat exchange of evaporation and localised water film convection. The main controls are ground surface temperature, subsurface depth, air density induced ventilation, distance from entry and drip rate. We present a conceptual model that explains drip water temperature signals and provide signal driven guidance on best type and location for speleothem sampling. We anticipate that our results will significantly improve the understanding of temperature-dependent paleoclimate signals from speleothem archives.
AB - While several studies explore cave climate and thermal regimes, little is known about the controls on cave drip water temperature. Yet water temperature significantly influences biogeochemical processes associated with cave drips. To identify the processes that control the cave drip water temperature, we measured the temperatures at multiple locations along a speleothem flow path and drip sources (stalactites) concurrently with the drip rates in Cathedral Cave, Wellington, Australia. We monitored long-term drip water temperature, drip rates, surface and cave climate and in-cave evaporation rates and conducted 3 infiltration experiments with different flow, temperature and isotopic conditions. Our results show that the drip water temperature is controlled by multiple superimposed heat transport mechanisms that act upon the infiltrating water in the epikarst, the water film after it enters the cave and before it becomes a drip. The two main heat sources/sinks for drip water are the cave air and the surrounding rock. The subsurface temperature is coupled to the surface temperature by conduction through the soil and rock mass, but the cave climate is also coupled to the surface climate by venting. On a regional scale, drip temperatures are mainly driven by the annual ground surface temperature signal but damped with depth and shifted in time compared to the surface. On a local scale, the drip water temperature can differ significantly from cave air and speleothem temperature due to the latent heat exchange of evaporation and localised water film convection. The main controls are ground surface temperature, subsurface depth, air density induced ventilation, distance from entry and drip rate. We present a conceptual model that explains drip water temperature signals and provide signal driven guidance on best type and location for speleothem sampling. We anticipate that our results will significantly improve the understanding of temperature-dependent paleoclimate signals from speleothem archives.
KW - Drip water temperature
KW - Paleoclimate archive
KW - Speleology heat transport
KW - Speleometeorology
UR - http://www.scopus.com/inward/record.url?scp=84935033481&partnerID=8YFLogxK
U2 - 10.1016/j.quascirev.2015.03.026
DO - 10.1016/j.quascirev.2015.03.026
M3 - Article
AN - SCOPUS:84935033481
SN - 0277-3791
VL - 127
SP - 19
EP - 36
JO - Quaternary Science Reviews
JF - Quaternary Science Reviews
ER -