An automated approach for annual layer counting in ice cores

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.

Download Full-text

An automated approach for annual layer counting in ice cores

Climate of the Past Discussions ◽

10.5194/cpd-8-2519-2012 ◽

2012 ◽

Vol 8 (4) ◽

pp. 2519-2555 ◽

Cited By ~ 1

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.

Download Full-text

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

Annals of Glaciology ◽

10.3189/172756402781817310 ◽

2002 ◽

Vol 35 ◽

pp. 131-135 ◽

Cited By ~ 7

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.

Download Full-text

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

Journal of Glaciology ◽

10.3189/2013jog13j068 ◽

2013 ◽

Vol 59 (218) ◽

pp. 1117-1128 ◽

Cited By ~ 14

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.

Download Full-text

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

10.5194/egusphere-egu21-7935 ◽

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

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.

Download Full-text

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

Climate of the Past ◽

10.5194/cp-12-15-2016 ◽

2016 ◽

Vol 12 (1) ◽

pp. 15-30 ◽

Cited By ~ 38

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.

Download Full-text

A 60 000 year Greenland stratigraphic ice core chronology

Climate of the Past ◽

10.5194/cp-4-47-2008 ◽

2008 ◽

Vol 4 (1) ◽

pp. 47-57 ◽

Cited By ~ 697

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.

Download Full-text

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

10.5194/egusphere-egu21-7473 ◽

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

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 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. 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.

Download Full-text

Temperature and mineral dust variability recorded in two low-accumulation Alpine ice cores over the last millennium

Climate of the Past ◽

10.5194/cp-14-21-2018 ◽

2018 ◽

Vol 14 (1) ◽

pp. 21-37 ◽

Cited By ~ 13

Author(s):

Pascal Bohleber ◽

Tobias Erhardt ◽

Nicole Spaulding ◽

Helene Hoffmann ◽

Hubertus Fischer ◽

...

Keyword(s):

Time Series ◽

Mineral Dust ◽

Ice Core ◽

Ice Cores ◽

Temperature Reconstruction ◽

Relative Increase ◽

Ice Age ◽

European Alps ◽

Stable Water Isotopes ◽

Annual Layer

Abstract. Among ice core drilling sites in the European Alps, Colle Gnifetti (CG) is the only non-temperate glacier to offer climate records dating back at least 1000 years. This unique long-term archive is the result of an exceptionally low net accumulation driven by wind erosion and rapid annual layer thinning. However, the full exploitation of the CG time series has been hampered by considerable dating uncertainties and the seasonal summer bias in snow preservation. Using a new core drilled in 2013 we extend annual layer counting, for the first time at CG, over the last 1000 years and add additional constraints to the resulting age scale from radiocarbon dating. Based on this improved age scale, and using a multi-core approach with a neighbouring ice core, we explore the time series of stable water isotopes and the mineral dust proxies Ca2+ and insoluble particles. Also in our latest ice core we face the already known limitation to the quantitative use of the stable isotope variability based on a high and potentially non-stationary isotope/temperature sensitivity at CG. Decadal trends in Ca2+ reveal substantial agreement with instrumental temperature and are explored here as a potential site-specific supplement to the isotope-based temperature reconstruction. The observed coupling between temperature and Ca2+ trends likely results from snow preservation effects and the advection of dust-rich air masses coinciding with warm temperatures. We find that if calibrated against instrumental data, the Ca2+-based temperature reconstruction is in robust agreement with the latest proxy-based summer temperature reconstruction, including a “Little Ice Age” cold period as well as a medieval climate anomaly. Part of the medieval climate period around AD 1100–1200 clearly stands out through an increased occurrence of dust events, potentially resulting from a relative increase in meridional flow and/or dry conditions over the Mediterranean.

Download Full-text

1000 year ice-core records from Berkner Island, Antarctica

Annals of Glaciology ◽

10.3189/172756402781817176 ◽

2002 ◽

Vol 35 ◽

pp. 45-51 ◽

Cited By ~ 39

Author(s):

Robert Mulvaney ◽

Hans Oerter ◽

David A. Peel ◽

Wolfgang Graf ◽

Carol Arrowsmith ◽

...

Keyword(s):

Decadal Variability ◽

Ice Core ◽

Ice Cores ◽

Aerosol Deposition ◽

Climate History ◽

Joint Project ◽

The Past ◽

Annual Layer ◽

History Of ◽

Field Season

AbstractTwo medium-depth ice cores were retrieved from Berkner Island by a joint project between the Alfred-Wegener-Institut and the British Antarctic Survey in the 1994/95 field season. A 151m deep core from the northern dome (Reinwarthhöhe) of Berkner Island spans 700 years, while a 181 m deep core from the southern dome (Thyssenhöhe) spans approximately 1200 years. Both cores display clear seasonal cycles in electrical conductivity measurements, allowing dating by annual-layer counting and the calculation of accumulation profiles. Stable-isotope measurements (both δ18O and δD), together with the accumulation data, allow us to estimate changes in climate for most of the past millennium: the data show multi-decadal variability around a generally stable long-termmean. In addition, a full suite of major chemistry measurements is available to define the history of aerosol deposition at these sites: again, there is little evidence that the chemistry of the sites has changed over the past six centuries. Finally, we suggest that the southern dome, with an ice thickness of 950 m, is an ideal site from which to gain a climate history of the late stages of the last glacial and the deglaciation for comparison with the records from the deep Antarctic ice cores, and with other intermediate-depth cores such as Taylor Dome and Siple Dome.

Download Full-text

A multiproxy approach to identify the Tambora volcanic fallout in 1810s from the Styx glacier in Victoria Land, Antarctica

10.5194/egusphere-egu2020-3262 ◽

2020 ◽

Author(s):

Changhee Han ◽

Songyi Kim ◽

Yeongcheol Han ◽

Jangil Moon ◽

Sang-Bum Hong ◽

...

Keyword(s):

Inner Core ◽

Major Ions ◽

Ice Core ◽

Ice Cores ◽

Isotope Ratios ◽

Depth Interval ◽

Additional Time ◽

Aerosol Composition ◽

Annual Layer ◽

Victoria Land

Ice cores provide records of past aerosol composition and have been used to reconstruct the relative contribution of different emission sources changing in time. A precise age scale is essential to achieve this goal, for which annual layer counting of seasonal cycles in water stable isotope ratios (&#948;18O and &#948;D) and major ion concentrations have been basically utilized. Introducing additional time markers are helpful for reducing the uncertainty of the depth-age scale, and the fallout of volcanic products has offered useful time markers when they are well-dated. Here, we report lead isotope ratios (206Pb/207Pb and 208Pb/207Pb) and concentrations of thallium (Tl) and major ions in a shallow ice core from the Styx Glacier (73&#176;51 S, 163&#176;41 E) in the Victoria Land, Antarctica, analyzed for discriminating volcanic products of the 1815 AD Tambora eruption, Indonesia from local volcanic inputs. Mechanically decontaminated 19 inner core pieces between the depth interval 40.8 &#8211; 42.4 m were analyzed. The results show that the increases of volcanic SO42- input are accompanied by either (1) input of more-radiogenic lead (higher 206Pb/207Pb) and Tl or (2) relatively 208Pb enriched lead. These results suggest that the Tambora volcanic input is overprinted by local volcanic aerosol input and that the isotope-based assessment of the Pb sources can help to discriminate between remote and local components of the volcanic input signals recorded in Victoria Land glaciers.

Download Full-text