Thermal impact of Heinrich stadials in cave temperature and speleothem oxygen isotope records

Abstract

During each Heinrich stadial (HS), temperatures in southern Europe typically dropped several degrees during several hundred to few thousand years. We have developed a one-dimensional thermal conduction model that transfers the typical surface temperature anomaly of a HS to a series of hypothetical underlying caves. The results show that with increasing depth, the thermal anomaly is attenuated, the lag time increases, and the signal structure experiences larger modifications. The model suggests that in most cases, it is not acceptable to assume a synchronous thermal variability and similar average temperature values between the surface atmosphere and the cave interior at millennial timescales. We also simulated the thermal impact of the modeled HS on speleothem δ18O records. The outputs of most model scenarios suggest that temperature changes associated with the HS produce δ18O anomalies capable of contributing significantly or even decisively to the speleothem isotope variability. Therefore, despite controls other than temperature often being considered more important when interpreting Pleistocene speleothem δ18O records in temperate climates, this research suggests that temperature is expected to be one of the major controls of δ18O values in most cave sites outside the tropics and should be included as a significant parameter affecting Pleistocene speleothem δ18O records.

Variable Phase Relationship Between Monsoon and Temperature in East Asia During Termination II Revealed by Oxygen and Clumped Isotopes of a Northern Chinese Stalagmite

“…As mentioned in Section 2.1, the cave air temperature with negligible seasonal variations is ∼3.6°C higher than MAAT outside due to the unshaded land over the cave (Domínguez‐Villar et al., 2013, 2021). Because the slope of bedrock is too steep (∼65°) for soil formation (Osman, 2018), it is plausible that the rock above Xinglong cave was also bare and unshaded during T‐II, similar to today.…”

“…The overlying vegetation is limited to scattered shrubs and grasses, and thus most parts of the rock are bare. Accordingly, compared with the shaded weather station, the bare rock over the cave would allow the ground surface to get more direct heating from sunlight, and thus make cave temperature higher than the MAAT outside (Domínguez‐Villar et al., 2013, 2021).…”

Modeling Heat Transfer for Assessing the Convection Length in Ventilated Caves

“…Understanding heat transfer in karst systems is a key issue for underground biota (Mammola et al., 2019), preservation of cave art (Bourges et al., 2014), speleothem growth rates (Banner et al., 2007; Spötl et al., 2005), or paleoclimate reconstruction (Borsato et al., 2016; Casteel & Banner, 2015; Domínguez‐Villar et al., 2021). However, heat transfer in karst results from an intricate coupling between several mechanisms, including heat conduction in the rock mass (Quindos et al., 1987), convection due to water or air flow in caves (Cropley, 1965), or radiative transfer between cave walls (Guerrier et al., 2019).…”