Alpine Ice Core Research Articles

Review of recent advances in Continuous Flow Analysis (CFA) technique for polar and alpine ice cores

Continuous Flow Analysis (CFA) systems, originally designed for field analyses of trace chemical species in ice cores, have seen significant innovations over the past decade, particularly through the integration of new spectrometric (Inductively Coupled Plasma Mass Spectrometers, Laser Absorption Spectrometers) and chromatographic techniques (Ionic Chromatography, Gas Chromatography and Liquid Chromatography). This paper reviews recent technical and methodological advances in CFA adopted by leading laboratories worldwide for the high-resolution detection of trace elements, major ions, isotopic and gaseous species in polar and alpine ice cores, exploring the strengths and limitations of different couplings, and discussing potential future enhancements.

A customizable digital holographic microscope

We propose a compact, portable, and low-cost holographic microscope designed for the characterization of micrometric particles suspended in a liquid. This system is built around a commercial optical microscope by substituting its illumination source (a light-emitting diode) with a collimated laser beam. Similarly, a quartz flow cell replaces the microscope glass slide using a 3D-printed custom mount. With the hardware presented in this paper, the holographic imaging of the electromagnetic fields emitted by the particles that intercept the laser beam achieves a resolution close to that of optical microscopes but with a greater depth of field. Several morphological and optical features can be extracted from the holograms, including particle projected section, aspect ratio, and extinction cross-section. Additionally, we introduce a remote system control that enables users to process the acquired holograms on a remote computational device. This work provides a comprehensive description of the methodology of image processing in holographic microscopy and a series of validation measurements conducted using calibrated particles. This technique is suitable for the characterization of airborne particles found in snow, firn, and ice; here we report experimental results obtained from Alpine ice cores.

Preservation of chemical and isotopic signatures within the Weißseespitze millennial old ice cap (Eastern Alps), despite the ongoing ice loss

Alpine ice core research has long focused on a few suitable drilling sites at high elevation in the Western European Alps, assuming that the counterparts at lower elevation in the eastern sector are unsuitable for paleoenvironmental studies, due to the presence of melting and temperate basal conditions. However, it has been demonstrated that even in the Eastern Alpine range, below 4,000 m a.s.l., cold ice frozen to bedrock can exist. In fact, millennial-old ice has been found at some locations, such as at the Weißseespitze (WSS) summit ice cap (Ӧtztal Alps, 3,499 m a.s.l.), where about 6 kyrs appear locked into 10 m of ice. In this work, we present a full profile of the stable water isotopes (δ18O, δ2H), major ions (Na+, K+, Mg2+, Ca2+, NH4+, Cl−, NO3−, SO42−), levoglucosan, and microcharcoal for two parallel ice cores drilled at the Weißseespitze cap. We find that, despite the ongoing ice loss, the chemical and isotopic signatures appear preserved, and may potentially offer an untapped climatic record. This is especially noteworthy considering that chemical signals of other archives at similar locations have been partially or full corrupted by meltwater (i.e., Silvretta glacier, Grand Combin glacier, Ortles glacier). In addition, the impurity concentration near the surface shows no signs of anthropogenic contamination at WSS, which constrains the age at the surface to fall within the pre-industrial age.

Tropical mountain ice core δ18O: A Goldilocks indicator for global temperature change.

Very high tropical alpine ice cores provide a distinct paleoclimate record for climate changes in the middle and upper troposphere. However, the climatic interpretation of a key proxy, the stable water oxygen isotopic ratio in ice cores (δ18Oice), remains an outstanding problem. Here, combining proxy records with climate models, modern satellite measurements, and radiative-convective equilibrium theory, we show that the tropical δ18Oice is an indicator of the temperature of the middle and upper troposphere, with a glacial cooling of -7.35° ± 1.1°C (66% CI). Moreover, it severs as a "Goldilocks-type" indicator of global mean surface temperature change, providing the first estimate of glacial stage cooling that is independent of marine proxies as -5.9° ± 1.2°C.Combined with all estimations available gives the maximum likelihood estimate of glacial cooling as -5.85° ± 0.51°C.

A Two‐Fold Increase of Phosphorus in Alpine Ice Over the Twentieth Century: Contributions From Dust, Primary Biogenic Emissions, Coal Burning, and Pig Iron Production

AbstractPhosphorus (P) is a key nutrient for many organisms but its global atmospheric budget is largely unconstrained. Estimates of major emissions sources such as fossil‐fuel combustion range from ∼0.02 to 1.1 Tg yr−1, and primary biogenic emissions range from 0.16 to 1.0 Tg yr−1. Here we used detailed measurements of phosphorus in Alpine ice cores extracted from the Col du Dôme (CDD) glacier located near the Mont Blanc summit and atmospheric model simulations to evaluate changes in western European emissions from pre‐industrial (PI) to modern times. The ice‐core records show that P concentrations during the PI were about 0.9 ng g−1, of which one third was of crustal origin and two thirds the result of primary biogenic emissions. Concentrations were higher throughout the 20th century, reaching 2.5 ng g−1 in the 1980s. Analysis of source tracers measured in the same ice, commodity productions statistics, and other information suggest that the increase in P throughout the 20th century was caused by enhanced emissions from natural and anthropogenic sources. Coal burning and steel industry represented the main anthropogenic sources during the first and second half of the century, respectively. After 1950, the increase in P was also caused by enhanced dust emissions, with increased biogenic emissions caused by recent changes of use‐land also contributing. These findings provide important constraints on the atmospheric P budget at the scale of western Europe during the recent centuries.

Radiocarbon dating of alpine ice cores

Radiocarbon dating of alpine ice cores

Rapid vegetation responses over the last seven decades revealed by an alpine ice core and land-cover patterns

ContextSyntheses of vegetation responses over the last century are rare for the Alps, and limited in chronological and taxonomical resolution. We propose that pollen records from glaciers can be used to fill this gap.ObjectivesOur aim is to evaluate the reliability of glacier pollen records as historical archives of biodiversity to obtain plant diversity data and landscape changes. In detail, we aim at reconstructing taxa and vegetation trends in central sector of the Italian Alps over the last century integrating pollen-inferred vegetation trends with drifts in spatially explicit land-cover.MethodsOur study area is the Lombardy region (Italy). We performed pollen analyses of Adamello glacier cores, and reconstructed trends of single taxa and main vegetation types since the 1950s. Pollen-inferred vegetation trends were calculated using pollen indicators obtained from a database of vegetation-plot observations. The reliability of these trends is evaluated by comparison with spatially explicit tendencies reconstructed with a time-series of land-cover maps.ResultsPollen records well represent the natural vegetation types as the temperate and the riverine forests, and the anthropic vegetation as crops and alien species. From the 1980s a thermophilisation took place, and warm-demanding native and alien species expanded. The contraction of cultivated land since the 1970s, and the decline of the riverine forest appear driven by socio-economic factors.ConclusionsWe conclude that pollen-inferred vegetation trends from glaciers can be used to obtain large scale biodiversity information. This is relevant also for areas where biodiversity data are scarce but needed for landscape management planning.

An upgraded CFA – FLC – MS/MS system for the semi-continuous detection of levoglucosan in ice cores

A new Continuous Flow Analysis (CFA) system coupled with Fast Liquid Chromatography – tandem Mass Spectrometry (FLC-MS/MS) has been recently developed for determining organic markers in ice cores. In this work we present an upgrade of this innovative technique, optimized for the detection of levoglucosan in ice cores, a crucial tracer for reconstructing past fires. The upgrade involved a specific optimization of the chromatographic and mass spectrometric parameters, allowing for a higher sampling resolution (down to 1 cm) and the simultaneous collection of discrete samples, for off-line analysis of water stable isotopes and additional chemical markers. The robustness and repeatability of the method has been tested by the analysis of multiple sticks of ice cut from the same shallow alpine ice core, and running the system for several hours on different days. The results show similar and comparable trends between the ice sticks. With this upgraded system, a higher sensitivity and a lower limit of detection (LOD) was achieved compared to discrete analysis of alpine samples for levoglucosan measurements. The new LOD was as low as 66 ng L−1, a net improvement over the previous LOD of 600 ng L−1.

Consistent histories of anthropogenic western European air pollution preserved in different Alpine ice cores

Abstract. Individual high-Alpine ice cores have been proven to contain a well-preserved history of past anthropogenic air pollution in western Europe. The question of how representative one ice core is with respect to the reconstruction of atmospheric composition in the source region has not been addressed so far. Here, we present the first study systematically comparing longer-term ice-core records (1750–2015 CE) of various anthropogenic compounds, such as major inorganic aerosol constituents (NH4+, NO3-, SO42-), black carbon (BC), and trace species (Cd, F−, Pb). Depending on the data availability for the different air pollutants, up to five ice cores from four high-Alpine sites located in the European Alps analysed by different laboratories were considered. Whereas absolute concentration levels can partly differ depending on the prevailing seasonal distribution of accumulated precipitation, all seven investigated anthropogenic compounds are in excellent agreement between the various sites for their respective, species-dependent longer-term concentration trends. This is related to common source regions of air pollution impacting the four sites less than 100 km away including western European countries surrounding the Alps. For individual compounds, the Alpine ice-core composites developed in this study allowed us to precisely time the onset of pollution caused by industrialization in western Europe. Extensive emissions from coal combustion and agriculture lead to an exceeding of pre-industrial (1750–1850) concentration levels already at the end of the 19th century for BC, Pb, exSO42- (non-dust, non-sea salt SO42-), and NH4+, respectively. However, Cd, F−, and NO3- concentrations started surpassing pre-industrial values only in the 20th century, predominantly due to pollution from zinc and aluminium smelters and traffic. The observed maxima of BC, Cd, F−, Pb, and exSO42- concentrations in the 20th century and a significant decline afterwards clearly reveal the efficiency of air pollution control measures such as the desulfurization of coal, the introduction of filters and scrubbers in power plants and metal smelters, and the ban of leaded gasoline improving the air quality in western Europe. In contrast, NO3- and NH4+ concentration records show levels in the beginning of the 21th century which are unprecedented in the context of the past 250 years, indicating that the introduced abatement measures to reduce these pollutants were insufficient to have a major effect at high altitudes in western Europe. Only four ice-core composite records (BC, F−, Pb, exSO42-) of the seven investigated pollutants correspond well with modelled trends, suggesting inaccuracies of the emission estimates or an incomplete representation of chemical reaction mechanisms in the models for the other pollutants. Our results demonstrate that individual ice-core records from different sites in the European Alps generally provide a spatially representative signal of anthropogenic air pollution trends in western European countries.

Humic Like Substances (HULIS): Contribution to Global Warming and Stratospheric Ozone Depletion

The authors have previously provided compelling evidence that coal fly ash particles, not chlorofluorocarbons (CFC’s), are the primary cause of stratospheric ozone depletion. Coal burning and coal fly ash aerosols utilized in covert tropospheric geoengineering have already severely damaged the stratospheric ozone layer, leading to deadly ultraviolet radiation UV-B and UV-C penetrating to Earth’s surface. Coal burning and biomass burning are primary sources of a particular organic aerosol, humic-like substances, referred to collectively as HULIS. HULIS, like coal fly ash, plays a key role in climate change due to its ubiquity in biogenic and anthropogenic aerosols, its ability to absorb solar ultraviolet radiation and to transfer that heat to atmospheric gases, which reduces the temperature difference relative to the near-surface air, which reduces atmospheric convection, and which concomitantly reduces heat loss from the surface, causing regional and global warming. HULIS affects human and environmental health by production of reactive oxygen species and environmentally persistent free radicals. Stratospheric ozone was apparently depleted during the Permian Extinction by coal and biomass combustion aerosols produced by massive volcanic activity. A spike in sea and land temperature during World War II, associated with particulate pollution, also is correlated with a spike in HULIS obtained from Alpine ice cores. Recently, large forest fires have also been shown to deplete stratospheric ozone. Since HULIS is common to both coal and biomass burning, and ozone is taken up by submicron HULIS particles, it follows that HULIS aerosols are another cause of stratospheric ozone depletion. Our time is short to end all geoengineering activities and reduce or eliminate anthropogenic coal fly ash and HULIS-type aerosols.

Thallium Pollution in Europe Over the Twentieth Century Recorded in Alpine Ice: Contributions From Coal Burning and Cement Production

AbstractEmission inventories indicate that thallium, a highly toxic metal, is emitted during coal burning and cement production. These estimates have been established only for the 1980s and 1990s but up to now they have not been compared to long‐term observations. Here we used alpine ice cores to document thallium pollution over Europe since ∼1850. Ice‐core thallium concentrations increased from 1890 to 1910, and decreased after 1965 to concentrations that were half 1890 levels. Comparison of ice‐core trends, estimated past emissions, and state‐of‐the‐art atmospheric aerosol transport modeling suggest that coal burning was responsible for thallium pollution in Europe, particularly from 1920 to 1965 because of high coal consumption at that time. The subsequent decline resulted from decreased coal consumption and reduced emissions following technological improvements. The ice‐core data suggest that the rapid growth of cement production that took place in Europe after 1950 had a limited impact on thallium pollution.

Optically enhanced discharge excitation and trapping of Ar39

We report on a two-fold increase of the $^{39}Ar$ loading rate in an atom trap by enhancing the generation of metastable atoms in a discharge source. Additional atoms in the metastable $1s_5$ level (Paschen notation) are obtained via optically pumping both the $1s_4$ - $2p_6$ transition at 801 nm and the $1s_2$ - $2p_6$ transition at 923 nm. By solving the master equation for the corresponding six-level system, we identify these two transitions to be the most suitable ones and encounter a transfer process between $1s_2$ and $1s_4$ when pumping both transitions simultaneously. We calculate the previously unknown frequency shifts of the two transitions in $^{39}Ar$ and confirm the results with trap loading measurements. The demonstrated increase in the loading rate enables a corresponding decrease in the required sample size, uncertainty and measurement time for $^{39}Ar$ dating, a significant improvement for applications such as dating of ocean water and alpine ice cores.

A quantitative method of resolving annual precipitation for the past millennia from Tibetan ice cores

Abstract. Net accumulation records derived from alpine ice cores provide the most direct measurement of past precipitation. However, quantitative reconstruction of accumulation for past millennia remains challenging due to the difficulty in identifying annual layers in the deeper sections of ice cores. In this study, we propose a quantitative method to reconstruct annual accumulation from alpine ice cores for past millennia, using as an example an ice core drilled at the Chongce ice cap in the northwestern Tibetan Plateau (TP). First, we used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) technology to develop ultra-high-resolution trace element records in three sections of the ice core and identified annual layers in each section based on seasonality of these elements. Second, based on nine 14C ages determined for this ice core, we applied a two-parameter flow model to established the thinning parameter of this ice core. Finally, we converted the thickness of annual layers in the three sample sections to past accumulation rates based on the thinning parameter derived from the ice flow model. Our results show that the mean annual accumulation rates for the three sample sections are 109 mm yr−1 (2511–2541 years BP), 74 mm yr−1 (1682–1697 years BP), and 68 mm yr−1 (781–789 years BP), respectively. For comparison, the Holocene mean precipitation is 103 mm yr−1. This method has the potential to reconstruct continuous high-resolution precipitation records covering millennia or even longer time periods.

Fast Liquid Chromatography Coupled with Tandem Mass Spectrometry for the Analysis of Vanillic and Syringic Acids in Ice Cores.

The development of new analytical systems and the improvement of the existing ones to obtain high-resolution measurements of chemical markers in samples from ice cores, is one of the main challenges the paleoclimatic scientific community is facing. Different chemical species can be used as markers for tracking emission sources or specific environmental processes. Although some markers, such as methane sulfonic acid (a proxy of marine productivity), are commonly used, there is a lack of data on other organic tracers in ice cores, making their continuous analysis analytically challenging. Here, we present an innovative combination of fast liquid chromatography coupled with tandem mass spectrometry (FLC-MS/MS) to continuously determine organic markers in ice cores. After specific optimization, this approach was applied to the quantification of vanillic and syringic acids, two specific markers for biomass burning. Using the validated method, detection limits of 3.6 and 4.6 pg mL–1 for vanillic and syringic acids, respectively, were achieved. Thanks to the coupling of FLC-MS/MS with the continuous flow analytical system, we obtained one measurement every 30 s, which corresponds to a sampling resolution of a sample every 1.5 cm with a melting rate of 3.0 cm min–1. To check the robustness of the method, we analyzed two parallel sticks of an alpine ice core over more than 5 h. Vanillic acid was found with concentrations in the range of picograms per milliliter, suggesting the combustion of coniferous trees, which are found throughout the Italian Alps.

Firn changes at Colle Gnifetti revealed with a high-resolution process-based physical model approach

Abstract. Our changing climate is expected to affect ice core records as cold firn progressively transitions to a temperate state. Thus, there is a need to improve our understanding and to further develop quantitative process modeling, to better predict cold firn evolution under a range of climate scenarios. Here we present the application of a distributed, fully coupled energy balance model, to simulate cold firn at the high-alpine glaciated saddle of Colle Gnifetti (Swiss–Italian Alps) over the period 2003–2018. We force the model with high-resolution, long-term, and extensively quality-checked meteorological data measured in the closest vicinity of the firn site, at the highest automatic weather station in Europe (Capanna Margherita, 4560 m a.s.l.). The model incorporates the spatial variability of snow accumulation rates and is calibrated using several partly unpublished high-altitude measurements from the Monte Rosa area. The simulation reveals a very good overall agreement in the comparison with a large archive of firn temperature profiles. Our results show that surface melt over the glaciated saddle is increasing by 3–4 mm w.e. yr−2 depending on the location (29 %–36 % in 16 years), although with large inter-annual variability. Analysis of modeled melt indicates the frequent occurrence of small melt events (<4 mm w.e.), which collectively represent a significant fraction of the melt totals. Modeled firn warming rates at 20 m depth are relatively uniform above 4450 m a.s.l. (0.4–0.5 ∘C per decade). They become highly variable at lower elevations, with a marked dependence on surface aspect and absolute values up to 2.5 times the local rate of atmospheric warming. Our distributed simulation contributes to the understanding of the thermal regime and evolution of a prominent site for alpine ice cores and may support the planning of future core drilling efforts. Moreover, thanks to an extensive archive of measurements available for comparison, we also highlight the possibilities of model improvement most relevant to the investigation of future scenarios, such as the fixed-depth parametrized routine of deep preferential percolation.

Causes of Enhanced Bromine Levels in Alpine Ice Cores During the 20th Century: Implications for Bromine in the Free European Troposphere

AbstractTotal bromine (Br) was investigated in seasonally resolved alpine ice cores covering the 20th century. Results revealed increased Br concentrations in summer (from 0.7 ng g−1 in the late 1940s to 1.6 ng g−1 in the mid 1970s), followed by a slight decrease to 1.25 ng g−1 during the last decade of the 20th century. In winter, a more moderate increase was observed from before 1950 (0.35 ng g−1) to the 1970–2000 period (∼0.50 ng g−1). Measurements of lead suggest that ∼75% of the bromine increase in summer alpine ice between 1930–1950 and 1965–1985 was from bromine‐containing aerosol (PbBrCl) emitted during the combustion of leaded gasoline. This contribution decreased to ∼27% in 2000 following the large decrease of lead additive content in gasoline used in western Europe. Summer ice bromine concentrations, not related to PbBrCl aerosol (denoted Bry*), increased by 40% from the late 1940s to the 1990–2000 decade. In winter, the contribution of leaded‐gasoline aerosol to total bromine levels was weaker than in summer, with the winter bromine trend mainly caused by enhanced Bry* levels (∼40%) after 1950. These Bry* variations in glacial ice are discussed in terms of past atmospheric reactive bromine (Bry) changes in the European troposphere, including anthropogenic CH3Br emissions and transport from the stratosphere.

Radiocarbon dating of alpine ice cores with the dissolved organic carbon (DOC) fraction

Abstract. High-alpine glaciers are valuable archives of past climatic and environmental conditions. The interpretation of the preserved signal requires a precise chronology. Radiocarbon (14C) dating of the water-insoluble organic carbon (WIOC) fraction has become an important dating tool to constrain the age of ice cores from mid-latitude and low-latitude glaciers. However, in some cases this method is restricted by the low WIOC concentration in the ice. In this work, we report first 14C dating results using the dissolved organic carbon (DOC) fraction, which is present at concentrations of at least a factor of 2 higher than the WIOC fraction. We evaluated this new approach by comparison to the established WIO14C dating based on parallel ice core sample sections from four different Eurasian glaciers covering an age range of several hundred to around 20 000 years; 14C dating of the two fractions yielded comparable ages, with WIO14C revealing a slight, barely significant, systematic offset towards older ages comparable in magnitude with the analytical uncertainty. We attribute this offset to two effects of about equal size but opposite in direction: (i) in-situ-produced 14C contributing to the DOC resulting in a bias towards younger ages and (ii) incompletely removed carbonates from particulate mineral dust (14C-depleted) contributing to the WIOC fraction with a bias towards older ages. The estimated amount of in-situ-produced 14C in the DOC fraction is smaller than the analytical uncertainty for most samples. Nevertheless, under extreme conditions, such as very high altitude and/or low snow accumulation rates, DO14C dating results need to be interpreted cautiously. While during DOC extraction the removal of inorganic carbon is monitored for completeness, the removal for WIOC samples was so far only assumed to be quantitative, at least for ice samples containing average levels of mineral dust. Here we estimated an average removal efficiency of 98±2 %, resulting in a small offset of the order of the current analytical uncertainty. Future optimization of the removal procedure has the potential to improve the accuracy and precision of WIO14C dating. With this study we demonstrate that using the DOC fraction for 14C dating not only is a valuable alternative to the use of WIOC but also benefits from a reduced required ice mass of typically ∼250 g to achieve comparable precision of around ±200 years. This approach thus has the potential of pushing radiocarbon dating of ice forward even to remote regions where the carbon content in the ice is particularly low.

The Impact of a Six-Year Climate Anomaly on the "Spanish Flu" Pandemic and WWI.

The H1N1 “Spanish influenza” pandemic of 1918–1919 caused the highest known number of deaths recorded for a single pandemic in human history. Several theories have been offered to explain the virulence and spread of the disease, but the environmental context remains underexamined. In this study, we present a new environmental record from a European, Alpine ice core, showing a significant climate anomaly that affected the continent from 1914 to 1919. Incessant torrential rain and declining temperatures increased casualties in the battlefields of World War I (WWI), setting the stage for the spread of the pandemic at the end of the conflict. Multiple independent records of temperature, precipitation, and mortality corroborate these findings.

Time marker of 137Cs fallout maximum in lake sediments of Northwest China

Caesium-137 (137Cs) has no natural source and is commonly employed in establishing the chronology of recent lake sediments in the Anthropocene epoch. Because of their location in the northern mid-latitude Westerlies circulation region, downwind of the Chernobyl accident and their proximity to the Lop Nur Chinese Nuclear Testing (CNT) site, lake sediments in NW China record a137Cs fallout maximum of global atmospheric thermonuclear weapon tests (GTWT) in 1963–1964 Common Era (CE), with probably local fallout subpeaks due to the Chernobyl accident in 1986 CE and CNT in 1976 CE. This complexity means that the use of 137Cs fallout maximum in lake sediments as a time marker in NW China is thus far not well constrained, impeding assessment of recent and future changes in paleoclimate and human activities. To identify the 137Cs time marker and provide a reliable chronology of surface lake sediments for investigating paleoclimatic changes and for defining the Anthropocene epoch in NW China during the last 50–100 years, here we describe chronologies of 6 near-surface sediment cores from NW China based on 137Cs and 210Pb activities, and review the chronology of 23 lake sediments and 10 ice cores from NW China and central Asia based on 137Cs, 210Pb, 239+240Pu, 3H, 241Am, and beta-activity dating methods, and annual layer counting, as well as 240Pu/239Pu isotopic ratios. Based on the potential influence of radioactivity transport from the Chernobyl accident and CNT, and the comparison with deposition records of 26 European lake sediments and 5 Alpine ice cores, we propose that the 137Cs fallout maximum of lake sediments in NW China and central Asia is primarily attributable to GTWT and that there is no unambiguous evidence to confirm the Chernobyl- and CNT-derived 137Cs local-fallout subpeaks. Taking into account the approximately one-year delay between injection of 137Cs into the atmosphere and its incorporation in lake sediment records, we conclude that the 137Cs fallout maximum in lake sediments of NW China provides a reliable GTWT time marker for 1964 CE.

Dating of an alpine ice core from the interior of the Tibetan Plateau

Accurate archive-based paleoclimate reconstruction requires precise dating. However, the dating of mid- and low-latitude alpine ice cores is in challenge, in particular for the lower parts of ice cores. Here, we present a new dating work for a 109 m ice core collected to bedrock from the Qiangtang No. 1 glacier, central Tibetan Plateau. Annual layer counting based on seasonal indicators, in combination with absolute dating of radioactivity peaks, indicates that the upper part (0–79 m) captures a period of 678 years from 1334–2011 AD, with an uncertainty of ±20 years at 79 m. In the lower part (79–109 m), we dated by visible annual layer thickness-depth relationships and found the lower ice core captures 665 years of deposition and can be dated back to 669 ± 66 AD at 109 m. This new method reduces the ambiguity of utilizing glacier flow models that have been widely used in previous study. On the presence of observable optical annual layers, the polynomial fitting method based on annual layer thickness-depth relationships is a superior method to obtain reliable chronology in the lower parts. Furthermore, this method has the potential to improve the dating of other alpine ice cores with similar settings.