Miguel Bartolomé

Hydrological change in Southern Europe responding to increasing North Atlantic overturning during Greenland Stadial 1

Significance This study presents robust evidence of two hydrological phases within the Greenland Stadial 1 (GS-1) cold event (12.8−11.7 ka B.P.) in Southern Europe. We present a well-dated high-resolution speleothem record (Seso Cave, Central Pyrenees) where temperature and hydrological signals are independently reconstructed. Detailed interpretation of stable isotopes and trace elements allow characterizing a first dry period followed, after 12,500 y before 2000 A.D., by more humid conditions. Our findings point to the resumption of the Atlantic overturning circulation as the main mechanism behind the hydrological response in Europe during this mid–GS-1 transition. The second phase, cold in Greenland but humid in Western Europe, represents a new paradigm in the well-established model of dry, cold stadials during the last glacial period. Greenland Stadial 1 (GS-1) was the last of a long series of severe cooling episodes in the Northern Hemisphere during the last glacial period. Numerous North Atlantic and European records reveal the intense environmental impact of that stadial, whose origin is attributed to an intense weakening of the Atlantic Meridional Overturning Circulation in response to freshening of the North Atlantic. Recent high-resolution studies of European lakes revealed a mid–GS-1 transition in the climatic regimes. The geographical extension of such atmospheric changes and their potential coupling with ocean dynamics still remains unclear. Here we use a subdecadally resolved stalagmite record from the Northern Iberian Peninsula to further investigate the timing and forcing of this transition. A solid interpretation of the environmental changes detected in this new, accurately dated, stalagmite record is based on a parallel cave monitoring exercise. This record reveals a gradual transition from dry to wet conditions starting at 12,500 y before 2000 A.D. in parallel to a progressive warming of the subtropical Atlantic Ocean. The observed atmospheric changes are proposed to be led by a progressive resumption of the North Atlantic convection and highlight the complex regional signature of GS-1, very distinctive from previous stadial events.

Speleothem formation in Northeastern Iberian Peninsula under the influence of different climatic conditions over last glacial cycles

Speleothem growing is closely linked to warm climates with a positive hydrological balance. Mild temperatures and hydrological availability are conditions that tend to stimulate soil CO 2 production due to denser vegetation cover and higher microbial activity. In such situations, waters enriched with dissolved carbonate are common and can infiltrate in the karstic system. This study compiles 158 dates from 34 speleothems collected in nine caves in the Northeastern Iberia to distinguish the time intervals with speleothem formation. A clear connection of speleothem growth and interglacial periods is established but

Abrupt climate changes during Termination III in Southern Europe

Significance We present an outstanding speleothem record that reconstructs the vegetation activity and hydrological availability during Termination III (T-III) in Southern Europe throughout δ13C, δ18O, and Mg/Ca variations. The results reveal for the North Atlantic region the sequence of abrupt stadial events during T-III, in close analogy to the Asian Monsoon changes reconstructed from Chinese speleothems. The two stadials identified in this record (S8.1 and S8.2) have similarities with Heinrich 1 and Heinrich 2 events in Termination I in terms of changes in the phasing of benthic δ18O, rise of semidesert pollen taxa, and ice-rafted debris release. The Late Quaternary glacial–interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of events and feedbacks at Termination III (T-III), including potential abrupt climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ13C, δ18O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium–thorium dates provide a solid chronology for two millennial-scale events (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I).

Ice Caves in Spain

Abstract In Spain there are at least 156 ice caves inventoried in the Pyrenees, Cantabrian Mountains, and Teide. In the Pyrenees there are ice caves in at least seven different massifs and in the Cantabrian Mountains are concentrated mainly in the Picos de Europa. In eight ice caves there have been applied techniques such as endoclimatic survey, geochronology, CCC analysis, mapping, ice structure, mass balances, TLS surveys, orthothermography and GPR surveys from the last 8 years. The ice volume has a significant interannual variation together with a regressive trend during the last decades, and the ice has ages ranging from centuries to a few millennia. In Spain Ice there are all kinds of possible ice caves, from the static to the dynamic, with metamorphic and congelation ice. Due to their risk of disappearance in the short medium term, it is very important to understand the ice cave systems and their past dynamics.

Ice cave reveals environmental forcing of long-term Pyrenean tree line dynamics

Tree lines are supposed to react sensitively to the current global change. However, the lack of a long‐term (millennial) perspective on tree line shifts in the Pyrenees prevents understanding the underlying ecosystem dynamics and processes. We combine multiproxy palaeoecological analyses (fossil pollen, spores, conifer stomata, plant macrofossils, and ordination) from an outstanding ice cave deposit located in the alpine belt c. 200 m above current tree line (Armena‐A294 Ice Cave, 2,238 m a.s.l.), to assess for the first time in the Pyrenees, tree line dynamics, and ecosystem resilience to climate changes 5,700–2,200 (cal.) years ago. The tree line ecotone was located at the cave altitude from 5,700 to 4,650 cal year bp, when vegetation consisted of open Pinus uncinata Ramond ex DC and Betula spp. Woodlands and timberline were very close to the site. Subsequently, tree line slightly raised and timberline reached the ice cave altitude, exceeding its todays uppermost limit by c. 300–400 m during more than four centuries (4,650 and 4,200 cal year bp) at the end of the Holocene Thermal Maximum. After 4,200 cal year bp, alpine tundra communities dominated by Dryas octopetala L. expanded while tree line descended, most likely as a consequence of the Neoglacial cooling. Prehistoric livestock raising likely reinforced climate cooling impacts at 3,450–3,250 cal year bp. Finally, a tree line ecotone developed around the cave that was on its turn replaced by alpine communities during the past 2,000 years. Synthesis. The long‐term Pyrenean tree line ecotone sensitivity suggests that rising temperatures will trigger future P. uncinata and Betula expansions to higher elevations, replacing arctic–alpine plant species. Climate change is causing the rapid melting of the cave ice; rescue investigations would be urgently needed to exploit its unique ecological information.