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13. High-alpine Glacier Record Influenced by Melting

Author

Huber, Carla, primary, Eichler, Anja, additional, Mattea, Enrico, additional, Brütsch, Sabina, additional, Jenk, Theo, additional, Gabrieli, Jacopo, additional, Barbante, Carlo, additional, and Schwikowski, Margit, additional

Published
2022
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14. Multimillennial synchronization of low and polar latitude ice cores by matching a time constrained Alpine record with an accurate Arctic chronology

Author

Gabrielli, Paolo, primary, Jenk, Theo Manuel, additional, Bertó, Michele, additional, Dreossi, Giuliano, additional, Festi, Daniela, additional, Kofler, Werner, additional, Winstrup, Mai, additional, Oeggl, Klaus, additional, Schwikowski, Margit, additional, Stenni, Barbara, additional, and Barbante, Carlo, additional

Published
2022
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15. Supplementary material to "Multimillennial synchronization of low and polar latitude ice cores by matching a time constrained Alpine record with an accurate Arctic chronology"

Author

Gabrielli, Paolo, primary, Jenk, Theo Manuel, additional, Bertó, Michele, additional, Dreossi, Giuliano, additional, Festi, Daniela, additional, Kofler, Werner, additional, Winstrup, Mai, additional, Oeggl, Klaus, additional, Schwikowski, Margit, additional, Stenni, Barbara, additional, and Barbante, Carlo, additional

Published
2022
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16. Early Holocene ice on the Begguya plateau (Mt. Hunter, Alaska) revealed by ice core 14C age constraints.

Author

Ling Fang, Jenk, Theo M., Winski, Dominic, Kreutz, Karl, Brooks, Hanna L., Erwin, Emma, Osterberg, Erich, Campbell, Seth, Wake, Cameron, and Schwikowski, Margit

Abstract

Investigating North Pacific climate variability during warm intervals prior to the Common Era can improve our understanding of the behavior of ocean-atmosphere teleconnections between low latitudes and the Arctic under future warming scenarios. However, most of the existing ice core records from the Alaska/Yukon region only allow access to climate information covering the last few centuries. Here we present a surface-to-bedrock age scale for a 210-meter long ice core recovered in 2013 from the summit plateau of Begguya (Mt. Hunter; Denali National Park, Central Alaska). Combining dating by annual layer counting with absolute dates from micro28 radiocarbon dating, a continuous chronology for the entire ice core archive was established using an ice flow model. Calibrated 14C ages from the deepest section (209.1 m, 7.7 to 9.0 ka cal BP) indicate that basal ice on Begguya is at least of early Holocene origin. A series of samples from a shallower depth interval (199.8 to 206.6 m) were dated with near uniform 14C ages (3 to 5 ka cal BP). Our results suggest this may be related to an increase in annual net snow accumulation rates over this period following the Northern Hemisphere Holocene Climate Optimum (around 8 to 5 ka BP). With absolute dates constraining the timescale for the last > 8 ka, this paleo archive will allow future investigations of Holocene climate and the regional evolution of spatial and temporal changes in atmospheric circulation and hydroclimate in the North Pacific. [ABSTRACT FROM AUTHOR]

Published
2023
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18. Significant mass loss in the accumulation area of the Adamello glacier indicated by the chronology of a 46 m ice core

Author

Festi, D, Schwikowski, M, Maggi, V, Oeggl, K, Jenk, T, Festi, Daniela, Schwikowski, Margit, Maggi, Valter, Oeggl, Klaus, Jenk, Theo Manuel, Festi, D, Schwikowski, M, Maggi, V, Oeggl, K, Jenk, T, Festi, Daniela, Schwikowski, Margit, Maggi, Valter, Oeggl, Klaus, and Jenk, Theo Manuel

Abstract

Dating glaciers is an arduous yet essential task in ice core studies, which becomes even more challenging when dating glaciers suffering from mass loss in the accumulation zone as result of climate warming. In this context, we dated a 46 m deep ice core from the Central Italian Alps retrieved in 2016 from the Adamello glacier in the locality Pian di Neve (3100 m a.s.l.). Here we present a timescale for the core obtained by integrating results from the analyses of the radionuclides 210Pb and 137Cs with annual layer counting derived from pollen and refractory black carbon concentrations. Our results clearly indicate that the surface of the glacier is older than the drilling date of 2016 by about 20 years and that the 46 m ice core reaches back to around 1944. Despite the severe mass loss affecting this glacier even in the accumulation zone, we show that it is possible to obtain a reliable timescale for such a temperate glacier. Our results are therefore very encouraging and open new perspectives on the potential of such glaciers as informative palaeoarchives.

Published
2021

33. Multimillennial synchronization of low and polar latitude ice cores by matching a time constrained Alpine record with an accurate Arctic chronology.

Author

Gabrielli, Paolo, Jenk, Theo Manuel, Bertó, Michele, Dreossi, Giuliano, Festi, Daniela, Kofler, Werner, Winstrup, Mai, Oeggl, Klaus, Schwikowski, Margit, Stenni, Barbara, and Barbante, Carlo

Abstract

We present a novel application of empirical methodologies that significantly reduce the chronological uncertainty of a low latitude-high altitude Alpine ice core record obtained in 2011 from the glacier Alto dell'Ortles (3859 m, Eastern Alps, Italy). A preliminary absolute timescale based on a peak in ³H activity, and 210Pb and 14C analyses on carbonaceous particles and organic remains provided evidence of one of the oldest Alpine ice core records spanning the last ~7000 years, back to the last Northern Hemisphere Climatic Optimum. Here we combine three empirical methods that provide an additional number of time markers that corroborate the multimillennial nature of the Alto dell'Ortles ice cores while significantly decreasing the uncertainty of the chronology. First, 14C analysis of an additional organic fragment (a charred spruce needle) discovered next to the basal ice provides an age (232 ± 126 BCE) which agrees with previous 14C dates in the oldest part of the record. Second, a new millennial-scale high resolution atmospheric Pb depositional record was used to synchronize the Alto dell'Ortles cores with an accurately-dated (±5 years) Pb record from an array of Arctic ice cores during the ~200 BCE to ~1900 CE time period. This match resulted in a shift of the initial Alto dell'Ortles timescale ~200 years earlier, but still within the initial time uncertainty. Third, novel seasonally resolved pollen records from the upper firn/ice portion of the Alto dell'Ortles cores were combined with δ18O and dust annual variations to refine the dating for the 20th century by means of an automatic algorithm (Straticounter; between 2011 and 1927 CE) and visual counting (1926-1900 CE). The time markers obtained by these three methods were combined in a continuous timescale by running a Montecarlo based fit (COPRA model). This Alto dell'Ortles revised chronology shows a significantly reduced uncertainty, between ±1 and ±4 years after 1927 CE, and between a maximum of ±100 years to a minimum of ±5 years between 1927 CE and 200 BCE by conservative estimates. An investigation of the revised chronology by means of a simple 1-D flow model suggests that non-steady-state conditions (e.g., changes in past snow accumulation rate) need to be considered to provide a full physical explanation of the age-depth relationship obtained. The new revised chronology will allow the constraint of the Holocene climatic and environmental histories emerging from this high-altitude glacial archive of Central Europe. The novel methodologies may also be adopted to build or improve the chronologies of other ice cores extracted from-low latitude/high-altitude glaciers that typically suffer from larger dating uncertainties compared with well dated polar records. [ABSTRACT FROM AUTHOR]

Published
2022
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34. Apparent discrepancy of Tibetan ice core δ18O records may be attributed to misinterpretation of chronology

Author

Hou, Shugui, Zhang, Wangbin, Pang, Hongxi, Wu, Shuang-Ye, Jenk, Theo M., Schwikowski, Margit, and Wang, Yetang

Abstract

Ice cores from the Tibetan Plateau (TP) are widely used for reconstructing past climatic and environmental conditions that extend beyond the instrumental period. However, challenges in dating and interpreting ice core records often lead to inconsistent results. The Guliya ice core drilled from the northwestern TP suggested a cooling trend during the mid-Holocene based on its decreasing δ18O values, which is not observed in other Tibetan ice cores. Here we present a new high-resolution δ18O record of the Chongce ice cores drilled to bedrock ∼30 km away from the Guliya ice cap. Our record shows a warming trend during the mid-Holocene. Based on our results as well as previously published ice core data, we suggest that the apparent discrepancy between the Holocene δ18O records of the Guliya and the Chongce ice cores may be attributed to a possible misinterpretation of the Guliya ice core chronology.

Published
2019

39. Application of the radionuclide 210Pb in glaciology – an overview.

Author

Gäggeler, Heinz W., Tobler, Leonhard, Schwikowski, Margit, and Jenk, Theo M.

Subjects
SUBLIMATION (Chemistry), RADIOACTIVE decay, RADIOISOTOPES, ICE cores, CRUST of the earth, SNOW accumulation
Abstract

210Pb is an environmental radionuclide with a half-life of 22.3 years, formed in the atmosphere via radioactive decay of radon (222Rn). 222Rn itself is a noble gas with a half-life of 3.8 days and is formed via radioactive decay of uranium (238U) contained in the Earth crust from where it constantly emanates into the atmosphere. 210Pb atoms attach to aerosol particles, which are then deposited on glaciers via scavenging with fresh snow. Due to its half-life, ice cores can be dated with this radionuclide over roughly one century, depending on the initial 210Pb activity concentration. Optimum 210Pb dating is achieved for cold glaciers with no – or little – influence by percolating meltwater. This paper presents an overview which not only includes dating of cold glaciers but also some special cases of 210Pb applications in glaciology addressing temperate glaciers, glaciers with negative mass balance, sublimation processes on glaciers in arid regions, determination of annual net snow accumulation as well as glacier flow rates. [ABSTRACT FROM AUTHOR]

Published
2020
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43. Age of the Tibetan ice cores

Author

Hou, Shugui, primary, Zhang, Wangbin, additional, Wang, Chaomin, additional, Wu, Shuangye, additional, Wang, Yetang, additional, Pang, Hongxi, additional, Jenk, Theo M., additional, and Schwikowski, Margit, additional

Published
2018
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45. 19th century glacier retreat in the Alps preceded the emergence of industrial black carbon deposition on high-alpine glaciers

Author

Sigl, Michael, Abram, Nerilie, Gabrieli, Jacopo, Jenk, Theo M, Osmont, Dimitri, Schwikowski, Margit, Sigl, Michael, Abram, Nerilie, Gabrieli, Jacopo, Jenk, Theo M, Osmont, Dimitri, and Schwikowski, Margit

Abstract

Light absorbing aerosols in the atmosphere and cryosphere play an important role in the climate system. Their presence in ambient air and snow changes the radiative properties of these systems, thus contributing to increased atmospheric warming and snowmelt. High spatio-temporal variability of aerosol concentrations and a shortage of long-term observations contribute to large uncertainties in properly assigning the climate effects of aerosols through time.

Published
2018

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