Miguel Bartolomé

Climate models predict an increase in extreme hydrological events (droughts and floods) as global temperatures respond to anthropogenic increases in greenhouse gases. This change in the pattern of extreme events due to global climate change raises uncertainties in assessing the risk of future droughts and floods. Conventionally, this problem has been addressed from a “top-down” approach based on downscaling of climate models. The development of this approach generates a high uncertainty that, in practice, does not allow determining in a reasonable and operational manner the magnitude of the change. Recently, it has been proposed to move towards a “bottom-up” approach of progressive adaptation to change based on the experience of recent events. It is assumed that future climate change will not create entirely new types of extreme weather events that have never before occurred on the planet. In this work, we review the main paleo-records (geological and botanical), which allow us to characterize and quantify hydrological extremes and their relation to climate variability at multi-decadal and secular time scales. This information is relevant to advance in the adaptation to extreme events in the context of climate change, particularly in the design of infrastructures, urbanism and territorial planning.

Ice caves are understudied environments within the cryosphere, hosting unique ice deposits valuable for paleoclimate studies. Recently, many of these deposits have experienced accelerated retreat due to global warming, threatening their existence. The A294 cave contains the world's known oldest firn cave deposit (6100 yr cal BP), which is progressively waning. This study presents 12 years (2009–2021) of monitoring of A294 cave, including temperature measurements both outside and inside the cave, meteoric precipitation, and ice loss measurements by comparing historical cave surveys (1978, 2012, 2019), photographs, and ice measurements within the cave. Our findings indicate a continuous increase in cave air temperature (∼ 1.07 to 1.56 °C over 12 years), increases in the Thaw Index, and a decrease in the number of freezing days (i.e., days below 0 °C) as well as in the Freezing Index. Calculated melting rates based on cave surveys and measurements show significant variations depending on the cave sector, ranging from ∼ 15 to ∼ 192 cm per year. The retreat of the ice body is primarily driven by an increase in winter temperatures, more rainfall during the warm season, and a decrease in snowfall and snow cover duration. The ice stratigraphy and local paleoclimate records suggest unprecedented melting conditions since this ice began to form about 6100 years ago. This study highlights the urgent need to recover all possible information from these unique subterranean ice deposits before they disappear.

Climate change is profoundly affecting mountain areas. While glacier retreat is highly visible, the underground cryosphere, including cave ice deposits, faces less apparent but equally concerning threats. These ice deposits serve as exceptional frozen archives. The analysis of environmental proxies such as stable isotopes, pollen, plant macrofossils and cryogenic cave minerals offers valuable insights into past environmental and climate dynamics. Research on ice caves in the Pyrenees has uncovered unique and novel information about past climatic conditions, treeline shifts, microbial communities and the dynamics of mountain permafrost. However, these fragile ice masses are rapidly diminishing due to raising temperatures, underscoring their critical role as palaeoenvironmental archives and sentinels of ongoing climate change.

Els canvis en el règim de precipitacions, impulsats pel canvi climàtic, estan intensificant els fenòmens de pluges extremes i inundacions, i plantegen reptes socials, ecològics i econòmics. Comprendre i predir la variabilitat de les inundacions en el temps i l’espai és crucial, però el registre instrumental és massa curt i no permet fer anàlisis precises a llarg termini. Els registres geològics, sobretot els que es troben en coves, ofereixen informació valuosa per la seua cronologia precisa, el seu ampli rang temporal i la seua conservació. A pesar del seu potencial, les estalagmites i els reblerts detrítics de les coves continuen sent infrautilitzats en l’estudi de les inundacions. L’anàlisi d’aquests registres, juntament amb els models hidràulics de les coves i el monitoratge del nivell d’aigua, pot millorar el que sabem sobre la relació entre les inundacions i el clima, i millorar les prediccions de la variabilitat de les inundacions en un context d’escalfament global.

Ice caves are understudied environments within the cryosphere, hosting unique ice deposits valuable for paleoclimate studies. Recently, many of these deposits have experienced accelerated retreat due to global warming, threatening their existence. The A294 cave contains the world’s known oldest firn cave deposit (6100 years cal. BP), which is progressively waning. This study presents 12 years (2009–2021) of monitoring data from A294, including temperature measurements both outside and inside the cave, meteoric precipitation, and ice loss measurements by comparing historical cave surveys (1978, 2012, 2019), photographs, and ice measurements within the cave. Our findings indicate a continuous increase in cave air temperature (~1.07 to 1.56 °C over 12 years), increases in the Thaw Index, and a decrease in the number of freezing days (i.e., days below 0 °C) as well as in the Freezing Index. Calculated melting rates based on cave surveys and measurements show significant variations depending on the cave sector, ranging from ~15 to ~192 cm per year. The retreat of the ice body is primarily driven by an increase in winter temperatures, the rise in rainfall during the warm seasons, and the decrease in snowfall and snow cover duration. The ice stratigraphy and local paleoclimate records suggest unprecedented melting conditions since this ice began to form 6100 years ago. This study highlights the urgent need to recover all possible information from these unique subterranean ice deposits before they disappear.

Ice caves are understudied environments within the cryosphere, hosting unique ice deposits valuable for paleoclimate studies. Recently, many of these deposits have experienced accelerated retreat due to global warming, threatening their existence. The A294 cave contains the world’s known oldest firn cave deposit (6100 years cal. BP), which is progressively waning. This study presents 12 years (2009–2021) of monitoring data from A294, including temperature measurements both outside and inside the cave, meteoric precipitation, and ice loss measurements by comparing historical cave surveys (1978, 2012, 2019), photographs, and ice measurements within the cave. Our findings indicate a continuous increase in cave air temperature (~1.07 to 1.56 °C over 12 years), increases in the Thaw Index, and a decrease in the number of freezing days (i.e., days below 0 °C) as well as in the Freezing Index. Calculated melting rates based on cave surveys and measurements show significant variations depending on the cave sector, ranging from ~15 to ~192 cm per year. The retreat of the ice body is primarily driven by an increase in winter temperatures, the rise in rainfall during the warm seasons, and the decrease in snowfall and snow cover duration. The ice stratigraphy and local paleoclimate records suggest unprecedented melting conditions since this ice began to form 6100 years ago. This study highlights the urgent need to recover all possible information from these unique subterranean ice deposits before they disappear.

In the Northern Hemisphere, the last 16.5 kyr was characterized by abrupt temperature transitions during stadials, interstadials, and the onset of the Holocene. These changes are closely linked to large-scale variations in the extent of continental ice sheets, greenhouse gas concentrations, and ocean circulation. Speleothems and their fluid inclusions serve as valuable proxies, offering high-resolution chronologies and quantitative records of past temperature changes for understanding global and regional climate mechanisms in the past. Here, we present a record based on five speleothems from two caves on the northeastern Iberian Peninsula (Ostolo and Mendukilo caves). Using hydrogen isotopic composition of fluid inclusions and rainfall samples, we developed a δ2H/T transfer function in order to reconstruct regional temperatures over the past 16.5 kyr (Ostolo–Mendukilo Fluid Inclusion Temperature record, OM-FIT). Our novel findings reveal abrupt temperature changes in SW Europe during the last deglaciation and Early Holocene, at millennial and centennial scales, anchored by a precise chronology. At the onset of Greenland Interstadial 1, the OM-FIT record shows an increase of 6.7 ± 2.8 °C relative to the cold conditions of the preceding Greenland Stadial 2.1a. During the early phase of Greenland Stadial 1, OM-FIT records a temperature decline of 6.1 ± 2.8 °C. The end of this cold phase and the onset of the Holocene are marked by a rapid warming of about 5 °C, reaching a maximum at 11.66 ± 0.03 kyr BP. The OM-FIT record also exhibits abrupt events during the Holocene (e.g., the 8.2 kyr event), which are also reflected in the δ ¹⁸ O values of the calcite. These abrupt temperature changes during the last deglaciation and the Holocene correspond to variations seen in paleotemperature records across Europe and in Greenland ice cores. This clearly and quantitatively illustrates the influence of changes in the Atlantic Meridional Overturning Circulation, driven by subarctic freshening, on the climate of southern Europe.

We explore the potential of various caves and karst systems of the Central Pyrenees (Lecherines-Collarada-Monte Perdido-Escuaín-Vignemale-Cotiella-Aneto-Maladeta) that could host speleothems that grew in karstic caves under glaciated areas. The requirements for the formation of speleothems in caves under areas covered by ice are: i) warm-based glaciers and ii) the presence of sulfides in the host rock. Springs and drip water were analysed to measure the presence of sulfates. Also, the presence of gypsum speleothems, pyrite, or other sulfides in the caves has been explored. Speleological observations, geological descriptions, and hydrochemical analyses have allowed the identification of caves and karst systems that may host these types of subglacial cave speleothems.

Ice caves are understudied environments within the cryosphere, hosting unique ice deposits valuable for paleoclimate studies. Recently, many of these deposits have experienced accelerated retreat due to global warming, threatening their existence. The A294 cave contains the world’s known oldest firn cave deposit (6100 years cal. BP), which is progressively waning. This study presents 12 years (2009–2021) of monitoring data from A294, including temperature measurements both outside and inside the cave, meteoric precipitation, and ice loss measurements by comparing historical cave surveys (1978, 2012, 2019), photographs, and ice measurements within the cave. Our findings indicate a continuous increase in cave air temperature (~1.07 to 1.56 °C over 12 years), increases in the Thaw Index, and a decrease in the number of freezing days (i.e., days below 0 °C) as well as in the Freezing Index. Calculated melting rates based on cave surveys and measurements show significant variations depending on the cave sector, ranging from ~15 to ~192 cm per year. The retreat of the ice body is primarily driven by an increase in winter temperatures, the rise in rainfall during the warm seasons, and the decrease in snowfall and snow cover duration. The ice stratigraphy and local paleoclimate records suggest unprecedented melting conditions since this ice began to form 6100 years ago. This study highlights the urgent need to recover all possible information from these unique subterranean ice deposits before they disappear.