Alpine permafrost thawing during the Medieval Warm Period identified from cryogenic cave carbonates (original) (raw)

First alpine evidence of in situ coarse cryogenic cave carbonates (CCCCOARSE)

2017

A layer of coarse cryogenic cave carbonate (CCCcoarse) is documented within a subsurface ice outcrop (in-situ) in a cave of the Julian Alps (southeastern Alps). This original finding, representing the first alpine evidence of in-situ CCCcoarseand the first occurrence from the southern side of the Alps, provides a unique opportunity to better understand the processes associated with the formation of CCCcoarsewith respect to the cave ice mass balance. Here, we discuss first considerations on the shape and characteristics of CCCcoarsesamples and their potential for palaeoclimate reconstructions in the southern Alps. In the light of accelerated climate change, we emphasize the need for scientific actions to exploit the available physical, chemical, isotopic and biological records from still untapped and fragile cryospheric archives such as ice caves

Cryogenic cave carbonates from the Cold Wind Cave, Nízke Tatry Mountains, Slovakia: Extending the age range of cryogenic cave carbonate formation to the Saalian

International Journal of Speleology, 2009

orvosova@ smopaj.sk 4. Czech Geological Survey, Klárov 3, 118 21 Praha 1, Czech Republic; ivana.jackova@geology.cz Žák K., Hercman H., Orvošová M. and Jačková I. 2009. Cryogenic cave carbonates from the Cold Wind Cave, Nízke Tatry Mountains, Slovakia: Extending the age range of cryogenic cave carbonate formation to the Saalian. International Journal of Speleology, 38(2), 139-152. Bologna (Italy). ISSN 0392-6672.

Cryogenic cave calcite from several Central European caves: age, carbon and oxygen isotopes and a genetic model

Chemical Geology, 2004

Cryogenic cave calcite (CCC), formed by segregation of solutes during water freezing, was found in three Central European caves. This calcite type forms accumulations of loose calcite grains on cave floor. The calcite grains are of highly variable crystal morphology, and of sizes ranging from less than 1 mm to over 1 cm. The most typical feature is their accumulation as loose (uncemented) crystals. U-series dating indicates the formation of CCC in the studied caves during several climatic oscillations of the Weichselian (between 61 and 36 ka BP in the Chelsiowa Jama -Jaskinia Jaworznicka cave system in Poland, between 34 and 26 ka BP in the BUML Cave in the Czech Republic, and between 26 and 21 ka BP in the Stratenská Jaskyňa cave system, Slovakia). At the time of CCC formation, the studied caves were lying in a periglacial zone.

Cryogenic carbonates in cave environments: A review

Quaternary International, 2008

Cryogenic cave carbonate (CCC) represents a specific type of speleothem. Its precipitation proceeds at the freezing point and is triggered by freezing-induced concentration of solutes. Compared to classical speleothems (stalagmites, flowstones), CCC occurs as accumulations of loose uncemented aggregates. The grain sizes range from less than 1 mm to over 1 cm in diameter. Karst groundwater chemistry and its freezing rate upon entering the cave are responsible for highly variable grain morphology. Rapid freezing of water results in the formation of CCC powders with grain size typically below 50 mm. Slow freezing of water in caves (usually in systems where the CO 2 escape is partly restricted; e.g., ice covered water pools) results in the formation of large mineral grains, with sizes from less than 1 mm to about 20 mm. The range of carbon and oxygen stable isotope compositions of CCC is larger than for a typical carbonate speleothem. Rapid freezing of water accompanied by a quick kinetic CO 2 degassing results in large ranges of d 13 C of the CCC powders (between -10% and +18% PDB). Slow freezing of water, with a restricted CO 2 escape results in gradual increase of d 13 C values (from À9% to +6% PDB; data ranges in individual caves are usually much more restricted), accompanied by a d 18 O decrease of the precipitated carbonate (overall range from À10% to À24% PDB). These unusual trends of the carbonate d 18 O evolution reflect incorporation of the heavier 18 O isotope into the formed ice. New isotope data on CCC from three Romanian ice caves allow better understanding of the carbon and oxygen isotope fingerprint in carbonates precipitated from freezing of bulk water. CCCs are proposed as a new genetic group of speleothems. r

Permafrost occurrence during the Last Permafrost Maximum in the Western Carpathian Mountains of Slovakia as inferred from cryogenic cave carbonate

Boreas, 2013

Coarse crystalline cryogenic cave carbonate (CCC) forms during the slow freezing of standing water pools and represents indirect proof of freezing temperature in the past. The dating by U-series of CCC deposits from nine caves in the Western Carpathians Mountains of Slovakia suggests that freezing conditions, and possible permafrost conditions, occurred during the Last Permafrost Maximum (LPM, c. 20-18 ka BP). The CCC deposits occur in caves at elevations of between 800 and 1800 m a.s.l. They point to widespread alpine permafrost, the lower limit of discontinuous/sporadic permafrost being approximately 800 m a.s.l. The thickness of permafrost probably varied between 30 and 180 m. In the Vysoké Tatry Mountains at altitudes of ∼1800 m a.s.l., one occurrence of CCC suggests that subzero temperatures may have penetrated to a depth of over 285 m.

First investigations of an ice core from Eisriesenwelt cave (Austria

The Cryosphere Discussions, 2010

Investigations into the genesis and dynamical properties of cave ice are essential for assessing the climate significance of these underground glaciers. We drilled an ice core through a 7.1 m-thick ice body filling a large cavern of the dynamic ice cave Eisenriesenwelt (Austria). In addition to visual core inspections, quasi-continuous measurements at 2 cm resolution comprised particulate matter, stable water isotope (δ 18 O, δD) and electrolytic conductivity profiles supplemented by specifically selected samples analyzed for tritium and radiocarbon. We found that recent ablation led to an almost complete loss of bomb-derived tritium removing any ice accumulated since, at least, the early fifties leaving the actual ice surface even below the natural tritium level. The small particulate organic masses rendered radiocarbon dating inconclusive, though a crude estimate gave a basal ice age in the order of several thousand years. The visual stratigraphy and all investigated parameters showed a clear dichotomy between the upper 2 m and the bottom 3 m of the core, which points to a substantial change in the ice formation process. Main features of the core comprise the changing appearance and composition of distinct cryocalcite layers, extremely low total ion content and a surprisingly high variability of the isotope signature. Co-isotope evaluation (δD versus δ 18 O) of the core in comparison with data from precipitation and karst spring water clearly indicate that ice formation is governed by (slow) freezing of dripping water.

Multi-centennial mass balance of perennial ice deposits in Alpine caves mirrors the evolution of glaciers during the Late Holocene

Scientific Reports

Mid-latitude alpine caves preserve a record of past solid precipitation during winter, locally spanning several centuries to millennia. Dating organic macro-remains trapped in ice layers allows the determination of timing and duration of past periods of positive and negative ice mass balance. We present here the largest comparative study of ice cave sites yet published, using Bayesian age-modelling on a database comprising 107 radiocarbon dates, spread over eight caves in the Austrian Alps. We show that periods of positive mass balance coincide with past glacier advances. We find organic and macro-remain rich layers dated to the Medieval Climate Anomaly (between 850 and 1200 CE) marking widespread ice retreat. We demonstrate positive ice mass balance at all studied sites for the Little Ice Age, coinciding with the largest glacier advances in the Holocene between 1400 and 1850 CE. At the sites with records spanning over 2000 years, positive mass balance is also observed during the pe...

Cryogenic cave carbonates from the Ural Mountains (Russia)

2018

Coarsely crystalline cryogenic cave carbonates (CCCcoarse) are widely used indicators of past permafrost conditions. Nevertheless, details of their formation with respect to macroscopic morphology, stable isotope evolution and potential metastable precursor phases are poorly understood. CCCcoarse were found in 5 caves located along a north-south transect of the Ural Mountains, Russia. A comprehensive data set was generated including results of carbonate stable isotope composition, stable isotopic composition of fluid inclusion water, stable oxygen isotope thermometry, trace element composition, X-ray diffraction and transmission properties and U/Th disequilibrium dating. Detailed petrographic characterization of the samples allows for the proposal of a morphological classification scheme for CCCcoarse. Non-crystallographic branching of crystallites, also referred to as crystal splitting, is identified as the mechanism enabling morphological variety in CCCcoarse. Splitting propensity...

Clumped isotope thermometry of cryogenic cave carbonates

Geochimica et Cosmochimica Acta, 2014

Freezing of cave pool water that is increasingly oversaturated with dissolved carbonate leads to precipitation of a very specific type of speleothems known as cryogenic cave carbonates (CCC). At present, two different environments for their formation have been proposed, based on their characteristic carbon and oxygen isotope ratios. Rapidly freezing thin water films result in the fast precipitation of fine-grained carbonate powder (CCC fine ). This leads to rapid physicochemical changes including CO 2 degassing and CaCO 3 precipitation, resulting in significantly 13 C-enriched carbonates. Alternatively, slow carbonate precipitation in ice-covered cave pools results in coarse crystalline CCC (CCC coarse ) yielding strongly 18 O-depleted carbonate. This is due to the formation of relatively 18 O-enriched ice causing the gradual depletion of 18 O in the water from which the CCC precipitates.

Age Estimates on the Deposition of the Cave Ice Block in the Saarhalle Dachstein-Mammoth Cave (Mammuthöhle, Austria) based on 3H and 14C

Radiocarbon, 2018

ABSTRACTMeasurements of the radiocarbon (14C) and tritium (3H) activity in a 5.8-m-long ice core from the Saarhalle, Dachstein-Mammoth Cave allowed a substantial revision of previous opinions concerning the age of the ice block, and provide useful experience that may be applied to future 14C dating of cave ice deposits. The stepped combustion technique results in a remarkably older radiocarbon age for the 800°C than for the 400°C fractions of the carbonaceous matter from ice layer samples. The highest tritium activity (37.2±1.2 TU) can be linked to the period of anthropogenically increased tritium activity of atmospheric precipitation at the mid-1960s, providing a well-dated radiochemical reference horizon. Compared the 3H-based extrapolated ages of two shallow samples to the expected atmospheric signal an average 14C reservoir bias of ~1500 BP was obtained for the insoluble organic fraction combusted at 400°C. The conventional 14C age measured for the 400°C fraction of the deeper s...