scholarly journals An automated approach for annual layer counting in ice cores

2012 ◽  
Vol 8 (4) ◽  
pp. 2519-2555 ◽  
Author(s):  
M. Winstrup ◽  
A. M. Svensson ◽  
S. O. Rasmussen ◽  
O. Winther ◽  
E. J. Steig ◽  
...  
Keyword(s):  
Markov Models ◽  
Ice Core ◽  
Ice Cores ◽  
Detection Algorithm ◽  
Data Series ◽  
Probabilistic Uncertainty ◽  
Annual Layer ◽  
Multiple Data ◽  
Ice Core Record ◽  
Paleoclimate Records

Abstract. A novel method for automated annual layer counting in seasonally-resolved paleoclimate records has been developed. It relies on algorithms from the statistical framework of Hidden Markov Models (HMMs), which originally was developed for use in machine speech-recognition. The strength of the layer detection algorithm lies in the way it is able to imitate the manual procedures for annual layer counting, while being based on statistical criteria for annual layer identification. The most likely positions of multiple layer boundaries in a section of ice core data are determined simultaneously, and a probabilistic uncertainty estimate of the resulting layer count is provided, ensuring an objective treatment of ambiguous layers in the data. Furthermore, multiple data series can be incorporated and used simultaneously. In this study, the automated layer counting algorithm has been applied to an ice core record from Greenland. The algorithm shows high skill in reproducing the results from manual layer counts.

scholarly journals An automated approach for annual layer counting in ice cores

2012 ◽  
Vol 8 (6) ◽  
pp. 1881-1895 ◽  
Author(s):  
M. Winstrup ◽  
A. M. Svensson ◽  
S. O. Rasmussen ◽  
O. Winther ◽  
E. J. Steig ◽  
...  
Keyword(s):  
Markov Models ◽  
Ice Core ◽  
Ice Cores ◽  
Detection Algorithm ◽  
Data Series ◽  
Probabilistic Uncertainty ◽  
Annual Layer ◽  
Statistical Framework ◽  
Multiple Data ◽  
Paleoclimate Records

Abstract. A novel method for automated annual layer counting in seasonally-resolved paleoclimate records has been developed. It relies on algorithms from the statistical framework of hidden Markov models (HMMs), which originally was developed for use in machine speech recognition. The strength of the layer detection algorithm lies in the way it is able to imitate the manual procedures for annual layer counting, while being based on statistical criteria for annual layer identification. The most likely positions of multiple layer boundaries in a section of ice core data are determined simultaneously, and a probabilistic uncertainty estimate of the resulting layer count is provided, ensuring an objective treatment of ambiguous layers in the data. Furthermore, multiple data series can be incorporated and used simultaneously. In this study, the automated layer counting algorithm has been applied to two ice core records from Greenland: one displaying a distinct annual signal and one which is more challenging. The algorithm shows high skill in reproducing the results from manual layer counts, and the resulting timescale compares well to absolute-dated volcanic marker horizons where these exist.

scholarly journals Extracting the annual signal from Greenland ice-core chemistry and isotopic records

2002 ◽  
Vol 35 ◽  
pp. 131-135 ◽  
Author(s):  
Sune Olander Rasmussen ◽  
Katrine Krogh Andersen ◽  
Marie-Louise Siggaard-Andersen ◽  
Henrik B. Clausen
Keyword(s):  
Annual Variation ◽  
Ice Core ◽  
Ice Cores ◽  
Original Data ◽  
Data Series ◽  
Simple Method ◽  
Annual Cycles ◽  
Annual Layer ◽  
Isotopic Records ◽  
Set Up

AbstractStratigraphic dating of ice cores by identification and counting of annual cycles in, for example, chemical measurements requires skill and experience. the work presented here investigates a method of data enhancement which is a first step towards an automated and more objective method of annual-layer counting. the method of dynamical decorrelation is briefly introduced and is applied to data from Site D and NorthGRIP in central Greenland. With this method the measured data series are decomposed into a number of independent source series, one of which exhibits a more pronounced annual variation than the input data themselves. the annual variation is more regular in that (1) some double and triple peaks in the measured series are replaced by single peaks in the extracted signal, and (2) the resulting annual peaks have a much more uniform height. A simple method of determining the number of annual peaks in a series is set up. Using this method, it is shown that it is easier to determine the number of annual peaks in the series produced by dynamical decorrelation than in the original data series. Dynamical decorrelation may thus be used to improve data series prior to dating.

scholarly journals South Pole glacial climate reconstruction from multi-borehole laser particulate stratigraphy

2013 ◽  
Vol 59 (218) ◽  
pp. 1117-1128 ◽  
Author(s):  
Keyword(s):  
Particle Physics ◽  
Volcanic Ash ◽  
Ice Core ◽  
Hot Water ◽  
Radiometric Dating ◽  
South Pole ◽  
Last Glacial Period ◽  
Annual Layer ◽  
Paleoclimate Records ◽  
The Last Glacial

AbstractThe IceCube Neutrino Observatory and its prototype, AMANDA, were built in South Pole ice, using powerful hot-water drills to cleanly bore >100 holes to depths up to 2500 m. The construction of these particle physics detectors provided a unique opportunity to examine the deep ice sheet using a variety of novel techniques. We made high-resolution particulate profiles with a laser dust logger in eight of the boreholes during detector commissioning between 2004 and 2010. The South Pole laser logs are among the most clearly resolved measurements of Antarctic dust strata during the last glacial period and can be used to reconstruct paleoclimate records in exceptional detail. Here we use manual and algorithmic matching to synthesize our South Pole measurements with ice-core and logging data from Dome C, East Antarctica. We derive impurity concentration, precision chronology, annual-layer thickness, local spatial variability, and identify several widespread volcanic ash depositions useful for dating. We also examine the interval around ∼74 ka recently isolated with radiometric dating to bracket the Toba (Sumatra) supereruption.

A novel high-resolution laser-melting sampler for discrete analyses of ion concentrations and stable water isotopic compositions in firn and ice cores

2021 ◽  
Author(s):  
Yuko Motizuki ◽  
Yoichi Nakai ◽  
Kazuya Takahashi ◽  
Junya Hirose ◽  
Yu Vin Sahoo ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Depth Resolution ◽  
Climatic Changes ◽  
Accumulation Rates ◽  
Laser Melting ◽  
Ion Concentrations ◽  
Annual Layer ◽  
Annual Resolution ◽  
High Depth

<p>Ice cores preserve past climatic changes and, in some cases, astronomical signals. Here we present a newly developed automated ice-core sampler that employs laser melting. A hole in an ice core approximately 3 mm in diameter is melted and heated well below the boiling point by laser irradiation, and the meltwater is simultaneously siphoned by a 2 mm diameter movable evacuation nozzle that also holds the laser fiber. The advantage of sampling by laser melting is that molecular ion concentrations and stable water isotope compositions in ice cores can be measured at high depth resolution, which is advantageous for ice cores with low accumulation rates. This device takes highly discrete samples from ice cores, attaining depth resolution as small as ~3 mm with negligible cross contamination; the resolution can also be set at longer lengths suitable for validating longer-term profiles of various ionic and water isotopic constituents in ice cores. This technique allows the detailed reconstruction of past climatic changes at annual resolution and the investigation of transient ionic and isotopic signals within single annual layers in low-accumulation cores, potentially by annual layer counting.</p>

scholarly journals Synchronizing the Greenland ice core and radiocarbon timescales over the Holocene – Bayesian wiggle-matching of cosmogenic radionuclide records

2016 ◽  
Vol 12 (1) ◽  
pp. 15-30 ◽  
Author(s):  
F. Adolphi ◽  
R. Muscheler
Keyword(s):  
Statistical Approach ◽  
Ice Core ◽  
Ice Cores ◽  
The Holocene ◽  
Counting Error ◽  
Climate Reconstructions ◽  
Uncertainty Measurement ◽  
Uncertainty Estimates ◽  
Paleoclimate Records ◽  
Cosmogenic Radionuclide

Abstract. Investigations of past climate dynamics rely on accurate and precise chronologies of the employed climate reconstructions. The radiocarbon dating calibration curve (IntCal13) and the Greenland ice core chronology (GICC05) represent two of the most widely used chronological frameworks in paleoclimatology of the past  ∼  50 000 years. However, comparisons of climate records anchored on these chronologies are hampered by the precision and accuracy of both timescales. Here we use common variations in the production rates of 14C and 10Be recorded in tree-rings and ice cores, respectively, to assess the differences between both timescales during the Holocene. Compared to earlier work, we employ a novel statistical approach which leads to strongly reduced and yet, more robust, uncertainty estimates. Furthermore, we demonstrate that the inferred timescale differences are robust independent of (i) the applied ice core 10Be records, (ii) assumptions of the mode of 10Be deposition, as well as (iii) carbon cycle effects on 14C, and (iv) in agreement with independent estimates of the timescale differences. Our results imply that the GICC05 counting error is likely underestimated during the most recent 2000 years leading to a dating bias that propagates throughout large parts of the Holocene. Nevertheless, our analysis indicates that the GICC05 counting error is generally a robust uncertainty measurement but care has to be taken when treating it as a nearly Gaussian error distribution. The proposed IntCal13-GICC05 transfer function facilitates the comparison of ice core and radiocarbon dated paleoclimate records at high chronological precision.

scholarly journals A 60 000 year Greenland stratigraphic ice core chronology

2008 ◽  
Vol 4 (1) ◽  
pp. 47-57 ◽  
Author(s):  
A. Svensson ◽  
K. K. Andersen ◽  
M. Bigler ◽  
H. B. Clausen ◽  
D. Dahl-Jensen ◽  
...  
Keyword(s):  
North Atlantic ◽  
Time Scale ◽  
Ice Core ◽  
Ice Cores ◽  
The North ◽  
Annual Layer ◽  
Zone Ii ◽  
Absolute Age ◽  
Age Estimates ◽  
New Time

Abstract. The Greenland Ice Core Chronology 2005 (GICC05) is a time scale based on annual layer counting of high-resolution records from Greenland ice cores. Whereas the Holocene part of the time scale is based on various records from the DYE-3, the GRIP, and the NorthGRIP ice cores, the glacial part is solely based on NorthGRIP records. Here we present an 18 ka extension of the time scale such that GICC05 continuously covers the past 60 ka. The new section of the time scale places the onset of Greenland Interstadial 12 (GI-12) at 46.9±1.0 ka b2k (before year AD 2000), the North Atlantic Ash Zone II layer in GI-15 at 55.4±1.2 ka b2k, and the onset of GI-17 at 59.4±1.3 ka b2k. The error estimates are derived from the accumulated number of uncertain annual layers. In the 40–60 ka interval, the new time scale has a discrepancy with the Meese-Sowers GISP2 time scale of up to 2.4 ka. Assuming that the Greenland climatic events are synchronous with those seen in the Chinese Hulu Cave speleothem record, GICC05 compares well to the time scale of that record with absolute age differences of less than 800 years throughout the 60 ka period. The new time scale is generally in close agreement with other independently dated records and reference horizons, such as the Laschamp geomagnetic excursion, the French Villars Cave and the Austrian Kleegruben Cave speleothem records, suggesting high accuracy of both event durations and absolute age estimates.

Dating of ice cores from temperate glaciers - Significant mass loss in the accumulation area of the Adamello glacier indicated by the chronology of a 46 m ice core

2021 ◽  
Author(s):  
Theo Jenk ◽  
Daniela Festi ◽  
Margit Schwikowski ◽  
Valter Maggi ◽  
Klaus Oeggl
Keyword(s):  
Mass Loss ◽  
Ice Core ◽  
Ice Cores ◽  
Italian Alps ◽  
Accumulation Zone ◽  
The Core ◽  
Annual Layer ◽  
Significant Mass Loss ◽  
Carbon Concentrations ◽  
Significant Mass

<p>Dating glaciers is an arduous yet essential task in ice core studies, which becomes even more challenging for the dating of glaciers suffering from mass loss in the accumulation zone as result of climate warming. In this context, we present the dating of a 46 m deep ice core from the Central Italian Alps retrieved in 2016 from the Adamello glacier (Pian di Neve, 3100 m a.s.l.). We will show how the timescale for the core could be obtained by integrating results from the analyses of the radionuclides <sup>210</sup>Pb and <sup>137</sup>Cs 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. These results are very encouraging and open new perspectives on the potential of such glaciers as informative palaeoarchives. We thus consider it important to present our dating approach to a broader audience.</p>

On the relationship between stable isotopes and major impurity species as inferred from a two-dimensional firn sampling approach at EDML, East Antarctica

2021 ◽  
Author(s):  
Thomas Münch ◽  
Maria Hörhold ◽  
Johannes Freitag ◽  
Melanie Behrens ◽  
Thomas Laepple
Keyword(s):  
Isotopic Composition ◽  
Interannual Variability ◽  
Ice Core ◽  
Ice Cores ◽  
Temperature Changes ◽  
Impurity Species ◽  
Intermittent Precipitation ◽  
Ice Core Record ◽  
Stable Oxygen ◽  
Atmospheric Variations

<p>Ice cores constitute a major palaeoclimate archive by recording, among many others, the atmospheric variations of stable oxygen and hydrogen isotopic composition of water and of soluble ionic impurities. While impurities are used as proxies for, e.g., variations in sea ice, marine biological activity and volcanism, stable isotope records are the main source of information for the reconstruction of polar temperature changes.</p><p>However, such reconstruction efforts are complicated by the fact that temperature is by far not the only driver of isotopic composition changes. A single isotopic ice-core record will comprise variations caused by a multitude of processes, from variable atmospheric circulation and moisture pathways to the intermittency of precipitation and finally to the mixing and re-location of surface snow by wind drift (stratigraphic noise). Under the assumption that specific trace components are originally deposited with the precipitated snow and its isotopic composition, the retrieved impurity records should display a similar spatial and seasonal to interannual variability as the isotope records, caused by local stratigraphic noise as well as the time-variable and intermittent precipitation patterns, respectively.</p><p>In this contribution, we investigate the possible relationship between isotope and impurity data at the East Antarctic low-accumulation site EDML. We sampled and analysed isotopic composition and major impurity species on a four metre deep and 50 metre long trench. This enables us (1) to study the spatial (horizontal times vertical) relationship in the data, and (2) to analyse and compare the seasonal and interannual variability after removing the strong contribution of local stratigraphic noise. By this, the study improves our understanding of the depositional mechanisms that play an important role for the formation of ice-core records, and it offers to investigate the potential of using impurities to correct isotopic variability in order to improve temperature reconstructions.</p>

scholarly journals The magnitude and impact of the 431 CE Tierra Blanca Joven eruption of Ilopango, El Salvador

2020 ◽  
Vol 117 (42) ◽  
pp. 26061-26068 ◽  
Author(s):  
Victoria C. Smith ◽  
Antonio Costa ◽  
Gerardo Aguirre-Díaz ◽  
Dario Pedrazzi ◽  
Andrea Scifo ◽  
...  
Keyword(s):  
High Resolution ◽  
El Salvador ◽  
Central America ◽  
State Of The Art ◽  
Ice Core ◽  
Ice Cores ◽  
Ash Layer ◽  
Ice Core Record ◽  
Climatic Impacts ◽  
Eruption Magnitude

The Tierra Blanca Joven (TBJ) eruption from Ilopango volcano deposited thick ash over much of El Salvador when it was inhabited by the Maya, and rendered all areas within at least 80 km of the volcano uninhabitable for years to decades after the eruption. Nonetheless, the more widespread environmental and climatic impacts of this large eruption are not well known because the eruption magnitude and date are not well constrained. In this multifaceted study we have resolved the date of the eruption to 431 ± 2 CE by identifying the ash layer in a well-dated, high-resolution Greenland ice-core record that is >7,000 km from Ilopango; and calculated that between 37 and 82 km3of magma was dispersed from an eruption coignimbrite column that rose to ∼45 km by modeling the deposit thickness using state-of-the-art tephra dispersal methods. Sulfate records from an array of ice cores suggest stratospheric injection of 14 ± 2 Tg S associated with the TBJ eruption, exceeding those of the historic eruption of Pinatubo in 1991. Based on these estimates it is likely that the TBJ eruption produced a cooling of around 0.5 °C for a few years after the eruption. The modeled dispersal and higher sulfate concentrations recorded in Antarctic ice cores imply that the cooling would have been more pronounced in the Southern Hemisphere. The new date confirms the eruption occurred within the Early Classic phase when Maya expanded across Central America.

scholarly journals Black carbon variability since preindustrial times in Eastern part of Europe reconstructed from Mt Elbrus, Caucasus ice cores

2016 ◽  
Author(s):  
Saehee Lim ◽  
Xavier Faïn ◽  
Patrick Ginot ◽  
Vladimir Mikhalenko ◽  
Stanislav Kutuzov ◽  
...  
Keyword(s):  
Black Carbon ◽  
20Th Century ◽  
Biomass Burning ◽  
Mass Concentration ◽  
Ice Core ◽  
Ice Cores ◽  
Anthropogenic Emissions ◽  
Ice Core Record ◽  
Summer Time ◽  
Mass Concentrations

Abstract. Black carbon (BC), emitted by fossil fuel combustion and biomass burning, is the second largest man-made contributor to global warming after carbon dioxide (Bond et al., 2013). However, limited information exists on its past emissions and atmospheric variability. In this study, we present the first high-resolution record of refractory BC (rBC, including mass concentration and size) reconstructed from ice cores drilled at a high-altitude Eastern European site in Mt. Elbrus (ELB), Caucasus (5115 m a.s.l.). The ELB ice core record, covering the period 1825–2013, reflects the atmospheric load of rBC particles at the ELB site transported from the European continent with a larger rBC input from sources located in the Eastern part of Europe. In the first half of the 20th century, European anthropogenic emissions resulted in a 1.5-fold increase in the ice core rBC mass concentrations as respect to its level in the preindustrial era (before 1850). The rBC mass concentrations increased by a 5-fold in 1960–1980, followed by a decrease until ~ 2000. Over the last decade, the rBC signal for summer time slightly increased. We have compared the signal with the atmospheric BC load simulated using past BC emissions (ACCMIP and MACCity inventories) and taken into account the contribution of different geographical region to rBC distribution and deposition at the ELB site. Interestingly, the observed rBC variability in the ELB ice core record since the 1960s is not in perfect agreement with the simulated atmospheric BC load. Similar features between the ice core rBC record and the best scenarios for the atmospheric BC load support that anthropogenic BC increase in the 20th century is reflected in the ELB ice core record. However, the peak in BC mass concentration observed in ~ 1970 in the ice core is estimated to occur a decade later from past inventories. BC emission inventories for the period 1960s–1970s may be underestimating European anthropogenic emissions. Furthermore, for summer time snow layers of the last 2000s, the slightly increasing trend of rBC deposition likely reflects recent changes in anthropogenic and biomass burning BC emissions in the Eastern part of Europe. Our study highlights that the past changes in BC emissions of Eastern Europe need to be considered in assessing on-going air quality regulation.

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