@incollection{opel_ancient_2025,
	title = {Ancient permafrost and past permafrost in the {Northern} {Hemisphere}},
	copyright = {https://www.elsevier.com/tdm/userlicense/1.0/},
	isbn = {978-0-443-29997-1},
	url = {https://linkinghub.elsevier.com/retrieve/pii/B9780323999311002580},
	language = {en},
	urldate = {2025-01-14},
	booktitle = {Encyclopedia of {Quaternary} {Science}},
	publisher = {Elsevier},
	author = {Opel, Thomas and Bertran, Pascal and Grosse, Guido and Jones, Miriam and Luetscher, Marc and Schirrmeister, Lutz and Stadelmaier, Kim H. and Veremeeva, Alexandra},
	year = {2025},
	doi = {10.1016/B978-0-323-99931-1.00258-0},
	pages = {16--33},
}

@article{bartolome_extreme_2024,
	title = {Extreme flood events in the western {Mediterranean}: integrating numerical {MODelling} and flood records in {KARST} systems ({MODKARST} project)},
	volume = {75},
	copyright = {https://creativecommons.org/licenses/by-nc-sa/4.0},
	issn = {2173-6545, 0213-683X},
	shorttitle = {Extreme flood events in the western {Mediterranean}},
	url = {https://recyt.fecyt.es/index.php/geogaceta/article/view/100997},
	doi = {10.55407/geogaceta100997},
	abstract = {Changes in rainfall patterns are a direct consequence of the current climate change. Climate projections indicate an intensification of extreme rainfall events, which will directly affect social, ecological, and economic systems. One of the greatest challenges of climate science is to understand, model, and predict the variability of floods. The uncertainties in projected rainfall are still high, and even higher in Mediterranean areas where the climate is characterized by extreme and sudden rainfall events. The instrumental record is too short to correctly estimate flood return periods. Thus, geological records are required to better understand the long term variability, at millennial to decadal scales, of natural extreme flood events. MODKARST is a MSCA-GF project awarded by the European Union, to develop a quantitative flood database for the Western Mediterranean realm based on speleothems. The action plans to infer past flood events from the last 18 ka based on detrital layers recorded in stalagmites from 5 different caves in the north of Spain, in combination with karst hydraulic models and water-level monitoring. MODKARST will help to better disentangle the relation between flood recurrence and climate changes, and will shed light on how to better predict the variability of floods in the context of present-day global warming.},
	urldate = {2025-01-14},
	journal = {Geogaceta},
	author = {Bartolomé, Miguel and Luetscher, Marc and Stoll, Heather and Moreno, Ana and Benito, Gerardo},
	month = jun,
	year = {2024},
	pages = {95--98},
}

Changes in rainfall patterns are a direct consequence of the current climate change. Climate projections indicate an intensification of extreme rainfall events, which will directly affect social, ecological, and economic systems. One of the greatest challenges of climate science is to understand, model, and predict the variability of floods. The uncertainties in projected rainfall are still high, and even higher in Mediterranean areas where the climate is characterized by extreme and sudden rainfall events. The instrumental record is too short to correctly estimate flood return periods. Thus, geological records are required to better understand the long term variability, at millennial to decadal scales, of natural extreme flood events. MODKARST is a MSCA-GF project awarded by the European Union, to develop a quantitative flood database for the Western Mediterranean realm based on speleothems. The action plans to infer past flood events from the last 18 ka based on detrital layers recorded in stalagmites from 5 different caves in the north of Spain, in combination with karst hydraulic models and water-level monitoring. MODKARST will help to better disentangle the relation between flood recurrence and climate changes, and will shed light on how to better predict the variability of floods in the context of present-day global warming.

@article{calvet_valley_2024,
	title = {Valley incision chronologies from alluvium-filled cave systems},
	volume = {258},
	doi = {https://doi.org/10.1016/j.earscirev.2024.104963},
	number = {104963},
	journal = {Earth-Science Reviews},
	author = {Calvet, Marc and Gunnell, Yanni and Delmas, Magali and Braucher, Régis and Jaillet, Stéphane and Häuselmann, Philipp and Delunel, Romain and Sorriaux, Patrick and Valla, Pierre G. and Audra, Philippe},
	year = {2024},
	pages = {40 p.},
}

@article{gimenez_mitigating_2024,
	title = {Mitigating flood risk and environmental change in show caves: {Key} challenges in the management of the {Las} {Güixas} cave ({Pyrenees}, {Spain})},
	volume = {370},
	issn = {03014797},
	shorttitle = {Mitigating flood risk and environmental change in show caves},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0301479724022710},
	doi = {10.1016/j.jenvman.2024.122285},
	language = {en},
	urldate = {2024-09-10},
	journal = {Journal of Environmental Management},
	author = {Giménez, Reyes and Moreno, Ana and Luetscher, Marc and Ezquerro, Lope and Delgado-Huertas, Antonio and Benito, Gerardo and Bartolomé, Miguel},
	month = nov,
	year = {2024},
	pages = {122285},
}

@article{klaba_multi-scale_2024,
	title = {Multi-scale hydrostructural approach for karst environment. {Application} to the {Arcier} hydrosystem (eastern {France})},
	volume = {184},
	issn = {0191-8141},
	url = {https://www.sciencedirect.com/science/article/pii/S0191814124001068},
	doi = {10.1016/j.jsg.2024.105154},
	abstract = {Based on a multi-scale and hydrostructural approach, this study presents the most relevant methodology to be applied to a karst hydrosystem in order to get a full understanding of underground water flow. It implies a complete structural analysis, from the hydrosystem scale to the outcrop scale, including the intermediate scale of the major geological structures. We illustrate the method in the Arcier hydrosystem, in the northwestern border of the Jura fold-and-thrust belt (Eastern France). Field mapping and structural analysis allow to update the geological vision of the hydrosystem with two kink-type fault propagation folds, including a trishear kinematic model, on either side of a plateau presenting a hollow-and-dome configuration. Fracturing analysis reveals a fault-fracture network that we infer governs the entire hydrosystem. A Riedel pattern is highlighted, characterized by a N–S-striking (N355° ± 5), sinistral strike-slip, regional shear zone. Then, two 3D geological models, at different scales, constructed with MOVE and Visual Karsys softwares are combined with water levels and artificial tracer tests. It reveals a multilayer aquifer and a redefinition of groundwater circulations for the Arcier hydrosystem. The results demonstrate a strong geological control of karstic hydrosystems on groundwater circulations, proving that classical hydrogeological methods, such as natural and/or artificial tracers, must be combined with rigorous geological analysis. Moreover, the multi-scale approach provides an explanation of groundwater circulation based on the intersection between 3D geometry of impervious layers delimiting the aquifers and their base water level, instead of the 2D view (section or map) requiring systematic recourse to inferred vertical faults to cross permeability barriers vertically or laterally. This study also brings a new vision to the local protection of the water resource.},
	urldate = {2024-05-27},
	journal = {Journal of Structural Geology},
	author = {Klaba, V. and Celle, H. and Trap, P. and Choulet, F. and Smeraglia, L. and Malard, A. and Carry, N.},
	month = jul,
	year = {2024},
	keywords = {3D model, Groundwater, Jura mountains, Karst, Structural geology},
	pages = {105154},
}

Based on a multi-scale and hydrostructural approach, this study presents the most relevant methodology to be applied to a karst hydrosystem in order to get a full understanding of underground water flow. It implies a complete structural analysis, from the hydrosystem scale to the outcrop scale, including the intermediate scale of the major geological structures. We illustrate the method in the Arcier hydrosystem, in the northwestern border of the Jura fold-and-thrust belt (Eastern France). Field mapping and structural analysis allow to update the geological vision of the hydrosystem with two kink-type fault propagation folds, including a trishear kinematic model, on either side of a plateau presenting a hollow-and-dome configuration. Fracturing analysis reveals a fault-fracture network that we infer governs the entire hydrosystem. A Riedel pattern is highlighted, characterized by a N–S-striking (N355° ± 5), sinistral strike-slip, regional shear zone. Then, two 3D geological models, at different scales, constructed with MOVE and Visual Karsys softwares are combined with water levels and artificial tracer tests. It reveals a multilayer aquifer and a redefinition of groundwater circulations for the Arcier hydrosystem. The results demonstrate a strong geological control of karstic hydrosystems on groundwater circulations, proving that classical hydrogeological methods, such as natural and/or artificial tracers, must be combined with rigorous geological analysis. Moreover, the multi-scale approach provides an explanation of groundwater circulation based on the intersection between 3D geometry of impervious layers delimiting the aquifers and their base water level, instead of the 2D view (section or map) requiring systematic recourse to inferred vertical faults to cross permeability barriers vertically or laterally. This study also brings a new vision to the local protection of the water resource.

@article{pastore_monitoring_2024,
	title = {Monitoring air fluxes in caves using digital flow metres},
	volume = {53},
	issn = {0392-6672, 1827-806X},
	url = {https://digitalcommons.usf.edu/ijs/vol53/iss1/7},
	doi = {10.5038/1827-806X.53.1.2500},
	abstract = {Precise measurements of airflow within caves are increasingly demanded to assess heat and mass transfers and their impacts on the karst environment, including subsurface ecosystems, hydrochemistry of karst water and secondary mineral precipitates. In this study, we introduce a new, low-cost and lightweight device adapted to monitoring air fluxes in caves which addresses the need for reliable measurements, low power consumption, durability and affordability. The device was calibrated in a wind tunnel, showing the high accuracy and precision of the device. Field-related uncertainties were further investigated in a ventilated cave to determine the effect of local airflow conditions on the inferred mass flux. Comparing measured values with a 3-D air velocity distribution modelled on a surveyed cave section suggests that most of the uncertainties in estimating the airflow result from the relative position of the instrument in the streamlines rather than from the accuracy of the device.},
	number = {1},
	urldate = {2025-01-14},
	journal = {International Journal of Speleology},
	author = {Pastore, Claudio and Sedaghatkish, Amir and Weber, Eric and Schmid, Nicolas and Jeannin, Pierre-Yves and Luetscher, Marc},
	month = jun,
	year = {2024},
	pages = {63--73},
}

Precise measurements of airflow within caves are increasingly demanded to assess heat and mass transfers and their impacts on the karst environment, including subsurface ecosystems, hydrochemistry of karst water and secondary mineral precipitates. In this study, we introduce a new, low-cost and lightweight device adapted to monitoring air fluxes in caves which addresses the need for reliable measurements, low power consumption, durability and affordability. The device was calibrated in a wind tunnel, showing the high accuracy and precision of the device. Field-related uncertainties were further investigated in a ventilated cave to determine the effect of local airflow conditions on the inferred mass flux. Comparing measured values with a 3-D air velocity distribution modelled on a surveyed cave section suggests that most of the uncertainties in estimating the airflow result from the relative position of the instrument in the streamlines rather than from the accuracy of the device.

@article{pastore_dispersion_2024,
	title = {Dispersion of artificial tracers in ventilated caves},
	volume = {53},
	issn = {0392-6672, 1827-806X},
	url = {https://digitalcommons.usf.edu/ijs/vol53/iss1/6},
	doi = {10.5038/1827-806X.53.1.2497},
	abstract = {Artificial CO2 was used as a tracer along ventilated karst conduits to infer airflow and investigate tracer dispersion. In the karst vadose zone, cave ventilation is an efficient mode of transport for heat, gases and aerosols and thus drives the spatial distribution of airborne particles. Modelling this airborne transport requires geometrical and physical parameters of the conduit system, including the cross-sectional areas, the airflow and average air speed, as well as the longitudinal dispersion coefficient which describes the spreading of a solute. Four gauging tests were carried out in one mine (artificial conduit) and two ventilated caves (natural conduits). In this paper, we demonstrate that it is possible to gain reliable airflow rates and geometric information of ventilated karst conduits using CO2 as a tracer. Airflow was gauged along two caves and one mine and compared with punctual measurements made with a hot-wire anemometer. Cross-sectional areas estimated with CO2 tests were compared with those measured in situ. Moreover, breakthrough curve (BTC) analysis displayed an accentuated tailing along the investigated natural conduits due to the presence of dispersive singularities which possibly enable aerosol deposition. The long tailing observed in Milandre and Longeaigue Caves is probably due to cross-section variations. A 1-D advection-dispersion model tested for these sites was unable to fit BTC tailing in natural conduits. In Baulmes artificial conduit, where long tailing is not observed, the dispersion coefficient has been estimated using Chatwin’s method, and compared with the prediction of Taylor’s theory. Despite the regular geometry of Baulmes Mine, Taylor’s correlation significantly underestimates the dispersion coefficient deduced from field data, showing the need for more theoretical work on turbulent dispersion in mines. This paper gives a first insight into air motion and matter dispersion along ventilated karst conduits, preparing for proper aerosol dispersion modelling.},
	number = {1},
	urldate = {2024-04-12},
	journal = {International Journal of Speleology},
	author = {Pastore, Claudio and Weber, Eric and Doumenc, Frédéric and Jeannin, Pierre-Yves and Luetscher, Marc},
	month = apr,
	year = {2024},
	pages = {51--62},
}

Artificial CO2 was used as a tracer along ventilated karst conduits to infer airflow and investigate tracer dispersion. In the karst vadose zone, cave ventilation is an efficient mode of transport for heat, gases and aerosols and thus drives the spatial distribution of airborne particles. Modelling this airborne transport requires geometrical and physical parameters of the conduit system, including the cross-sectional areas, the airflow and average air speed, as well as the longitudinal dispersion coefficient which describes the spreading of a solute. Four gauging tests were carried out in one mine (artificial conduit) and two ventilated caves (natural conduits). In this paper, we demonstrate that it is possible to gain reliable airflow rates and geometric information of ventilated karst conduits using CO2 as a tracer. Airflow was gauged along two caves and one mine and compared with punctual measurements made with a hot-wire anemometer. Cross-sectional areas estimated with CO2 tests were compared with those measured in situ. Moreover, breakthrough curve (BTC) analysis displayed an accentuated tailing along the investigated natural conduits due to the presence of dispersive singularities which possibly enable aerosol deposition. The long tailing observed in Milandre and Longeaigue Caves is probably due to cross-section variations. A 1-D advection-dispersion model tested for these sites was unable to fit BTC tailing in natural conduits. In Baulmes artificial conduit, where long tailing is not observed, the dispersion coefficient has been estimated using Chatwin’s method, and compared with the prediction of Taylor’s theory. Despite the regular geometry of Baulmes Mine, Taylor’s correlation significantly underestimates the dispersion coefficient deduced from field data, showing the need for more theoretical work on turbulent dispersion in mines. This paper gives a first insight into air motion and matter dispersion along ventilated karst conduits, preparing for proper aerosol dispersion modelling.

@article{spotl_speleothems_2024,
	title = {Speleothems in subglacial caves: {An} emerging archive of glacial climate history and mountain glacier dynamics},
	volume = {333},
	issn = {02773791},
	shorttitle = {Speleothems in subglacial caves},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379124001859},
	doi = {10.1016/j.quascirev.2024.108684},
	language = {en},
	urldate = {2024-05-07},
	journal = {Quaternary Science Reviews},
	author = {Spötl, Christoph and Baker, Jonathan L. and Skiba, Vanessa and Honiat, Alexandre and Fohlmeister, Jens and Luetscher, Marc and Trüssel, Martin},
	month = jun,
	year = {2024},
	pages = {108684},
}

@article{sedaghatkish_modelling_2024,
	title = {Modelling the effect of free convection on permafrost melting rates in frozen rock clefts},
	volume = {18},
	copyright = {https://creativecommons.org/licenses/by/4.0/},
	issn = {1994-0424},
	url = {https://tc.copernicus.org/articles/18/4531/2024/},
	doi = {10.5194/tc-18-4531-2024},
	abstract = {Abstract. This research develops a conceptual model of a karst system subject to mountain permafrost. The transient thermal response of a frozen rock cleft after the rise in the atmospheric temperature above the melting temperature of water is investigated using numerical simulations. Free convection in liquid water (i.e. buoyancy-driven flow) is considered. The density increase in water from 0 to 4 °C causes warmer meltwater to flow downwards and colder upwards, resulting in significant enhancement of the heat transferred from the ground surface to the melting front. Free convection increases the melting rate by approximately an order of magnitude compared to a model based on thermal conduction in stagnant water. The model outcomes are compared qualitatively with field data from the Monlesi ice cave (Switzerland) and confirm the agreement between real-world observations and the proposed model when free convection is considered.},
	language = {en},
	number = {10},
	urldate = {2024-10-10},
	journal = {The Cryosphere},
	author = {Sedaghatkish, Amir and Doumenc, Frédéric and Jeannin, Pierre-Yves and Luetscher, Marc},
	month = oct,
	year = {2024},
	pages = {4531--4546},
}

Abstract. This research develops a conceptual model of a karst system subject to mountain permafrost. The transient thermal response of a frozen rock cleft after the rise in the atmospheric temperature above the melting temperature of water is investigated using numerical simulations. Free convection in liquid water (i.e. buoyancy-driven flow) is considered. The density increase in water from 0 to 4 °C causes warmer meltwater to flow downwards and colder upwards, resulting in significant enhancement of the heat transferred from the ground surface to the melting front. Free convection increases the melting rate by approximately an order of magnitude compared to a model based on thermal conduction in stagnant water. The model outcomes are compared qualitatively with field data from the Monlesi ice cave (Switzerland) and confirm the agreement between real-world observations and the proposed model when free convection is considered.

@article{sedaghatkish_modeling_2024,
	title = {Modeling {Heat} {Transfer} for {Assessing} the {Convection} {Length} in {Ventilated} {Caves}},
	volume = {129},
	issn = {2169-9003, 2169-9011},
	url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JF007646},
	doi = {10.1029/2024JF007646},
	abstract = {Abstract
            The present study focuses on heat transfer in ventilated caves for which the airflow is driven by the temperature contrast between the cave and the external atmosphere. We use a numerical model that couples the convective heat transfer due to the airflow in a single karst conduit with the conductive heat transfer in the rock mass. Assuming dry air and a simplified geometry, we investigate the propagation of thermal perturbations inside the karst massif. We perform a parametric study to identify general trends regarding the effect of the air flowrate and conduit size on the amplitude and spatial extent of thermal perturbations. Numerical results support the partition of a cave into three regions: (a) a short (few meters) diffusive region, where heat mainly propagates from the external atmosphere by conduction in the rock mass; (b) a convective region where heat is mainly transported by the air flow; (c) a deep karst region characterized by quasi‐constant temperatures throughout the year. Numerical simulations show that the length of the convective region is approximately proportional to the amplitude of the flowrate annual fluctuations divided by the square root of the cave radius. This result is tested against field data from a mine tunnel and two caves. Our study provides first estimates to identify climate sensitive regions for speleothem science and/or ecosystemic studies.
          , 
            Plain Language Summary
            Karsts are landscapes formed from the dissolution of soluble rocks. The chemical erosion due to rainwater results in the formation of an extensive network of caves traversed by air and water flows. Understanding heat transfer in karst is a key issue in many fields, as diverse as study of underground biota or paleoclimate reconstruction. The present work focuses on heat transfer in ventilated caves for which the airflow is driven by the temperature contrast between the cave and the external atmosphere. In winter, the air inside the massif is hotter (and thus lighter) than the air outside. This situation results in an upward airflow as in a chimney. The airflow is reversed in summer (colder and thus heavier air inside the massif). Assuming a simplified geometry, we investigate by numerical simulations the propagation of thermal perturbations inside a single ventilated conduit. The results of the numerical simulations are tested against field data from a mine and two caves. We show that in ventilated caves, the airflow can propagate the annual temperature fluctuations over distances from the entrance ranging from a few tens to a few hundreds of meters. In extreme cases, it could go up to kilometers. Our study provides first estimates to identify climate sensitive regions for speleothem science and/or ecosystemic studies.
          , 
            Key Points
            
              
                
                  A numerical model was developed to investigate heat transfer inside ventilated caves driven by chimney effect
                
                
                  The airflow can propagate annual temperature fluctuations over a few tens to a few hundreds of meters from the cave entrance (over kilometers in extreme cases)
                
                
                  The distance of propagation (the convection length) is approximately proportional to the airflow rate and inversely proportional to the square root of the cave diameter},
	language = {en},
	number = {6},
	urldate = {2024-05-30},
	journal = {Journal of Geophysical Research: Earth Surface},
	author = {Sedaghatkish, Amir and Pastore, Claudio and Doumenc, Frédéric and Jeannin, Pierre‐Yves and Luetscher, Marc},
	month = jun,
	year = {2024},
	pages = {e2024JF007646},
}

Abstract The present study focuses on heat transfer in ventilated caves for which the airflow is driven by the temperature contrast between the cave and the external atmosphere. We use a numerical model that couples the convective heat transfer due to the airflow in a single karst conduit with the conductive heat transfer in the rock mass. Assuming dry air and a simplified geometry, we investigate the propagation of thermal perturbations inside the karst massif. We perform a parametric study to identify general trends regarding the effect of the air flowrate and conduit size on the amplitude and spatial extent of thermal perturbations. Numerical results support the partition of a cave into three regions: (a) a short (few meters) diffusive region, where heat mainly propagates from the external atmosphere by conduction in the rock mass; (b) a convective region where heat is mainly transported by the air flow; (c) a deep karst region characterized by quasi‐constant temperatures throughout the year. Numerical simulations show that the length of the convective region is approximately proportional to the amplitude of the flowrate annual fluctuations divided by the square root of the cave radius. This result is tested against field data from a mine tunnel and two caves. Our study provides first estimates to identify climate sensitive regions for speleothem science and/or ecosystemic studies. , Plain Language Summary Karsts are landscapes formed from the dissolution of soluble rocks. The chemical erosion due to rainwater results in the formation of an extensive network of caves traversed by air and water flows. Understanding heat transfer in karst is a key issue in many fields, as diverse as study of underground biota or paleoclimate reconstruction. The present work focuses on heat transfer in ventilated caves for which the airflow is driven by the temperature contrast between the cave and the external atmosphere. In winter, the air inside the massif is hotter (and thus lighter) than the air outside. This situation results in an upward airflow as in a chimney. The airflow is reversed in summer (colder and thus heavier air inside the massif). Assuming a simplified geometry, we investigate by numerical simulations the propagation of thermal perturbations inside a single ventilated conduit. The results of the numerical simulations are tested against field data from a mine and two caves. We show that in ventilated caves, the airflow can propagate the annual temperature fluctuations over distances from the entrance ranging from a few tens to a few hundreds of meters. In extreme cases, it could go up to kilometers. Our study provides first estimates to identify climate sensitive regions for speleothem science and/or ecosystemic studies. , Key Points A numerical model was developed to investigate heat transfer inside ventilated caves driven by chimney effect The airflow can propagate annual temperature fluctuations over a few tens to a few hundreds of meters from the cave entrance (over kilometers in extreme cases) The distance of propagation (the convection length) is approximately proportional to the airflow rate and inversely proportional to the square root of the cave diameter

@article{fohlmeister_role_2023,
	title = {The role of {Northern} {Hemisphere} summer insolation for millennial-scale climate variability during the penultimate glacial},
	volume = {4},
	issn = {2662-4435},
	url = {https://www.nature.com/articles/s43247-023-00908-0},
	doi = {10.1038/s43247-023-00908-0},
	abstract = {Abstract
            Previous glacial intervals were punctuated by abrupt climate transitions between cold (stadial) and warm (interstadial) conditions. Many mechanisms leading to stadial-interstadial variability have been hypothesized with ice volume being a commonly involved element. Here, we test to which extent insolation modulated stadial-interstadial oscillations occurred during the penultimate glacial. We present a replicated and precisely dated speleothem record covering the period between 200 and 130 ka before present from caves located in the European Alps known to be sensitive to millennial-scale variability. We show that the widely proposed relationship between sea level change and stadial-interstadial variability was additionally modulated by solar insolation during this time interval. We find that interstadials occurred preferentially near maxima of Northern Hemisphere summer insolation, even when sea level remained close to its minimum during peak glacial periods. We confirm these observations with model simulations that accurately reproduce the frequency and duration of interstadials for given sea-level and insolation forcing. Our results imply that summer insolation played an important role in modulating the occurrence of stadial-interstadial oscillations and highlight the relevance of insolation in triggering abrupt climate changes.},
	language = {en},
	number = {1},
	urldate = {2024-06-06},
	journal = {Communications Earth \& Environment},
	author = {Fohlmeister, Jens and Luetscher, Marc and Spötl, Christoph and Schröder-Ritzrau, Andrea and Schröder, Birgit and Frank, Norbert and Eichstädter, René and Trüssel, Martin and Skiba, Vanessa and Boers, Niklas},
	month = jul,
	year = {2023},
	pages = {245},
}

Abstract Previous glacial intervals were punctuated by abrupt climate transitions between cold (stadial) and warm (interstadial) conditions. Many mechanisms leading to stadial-interstadial variability have been hypothesized with ice volume being a commonly involved element. Here, we test to which extent insolation modulated stadial-interstadial oscillations occurred during the penultimate glacial. We present a replicated and precisely dated speleothem record covering the period between 200 and 130 ka before present from caves located in the European Alps known to be sensitive to millennial-scale variability. We show that the widely proposed relationship between sea level change and stadial-interstadial variability was additionally modulated by solar insolation during this time interval. We find that interstadials occurred preferentially near maxima of Northern Hemisphere summer insolation, even when sea level remained close to its minimum during peak glacial periods. We confirm these observations with model simulations that accurately reproduce the frequency and duration of interstadials for given sea-level and insolation forcing. Our results imply that summer insolation played an important role in modulating the occurrence of stadial-interstadial oscillations and highlight the relevance of insolation in triggering abrupt climate changes.