Vostok Ice Core Research Articles

Gigatonne Carbon Dioxide Removal Can Reverse Global Heating Trend

It is a surprising realization to many that a changing temperature tightly correlates with the carbon dioxide (CO2) levels worldwide in a linear, lockstep manner with a reversible but very short temporal feedback loop of only a few decades. A mapping of the past 400,000 years of earth’s climate history by Hansen, based on the Vostok ice core sampling, offers a glimpse into this remarkably tight relationship between CO2 and global temperature levels but also the average sea level over four ice ages that are clearly delineated in his historic depiction of all three quantities. As his Table accompanying the graph is analyzed, an equation linking the three variables has now been generated, yielding a fresh view into how past decades of hundreds of gigatons of atmospheric increase will continue to affect a worldwide temperature rise, also called “global warming.” The implication that is inescapable from such an analysis is that the presently stored CO2 level, far surpassing by over 40% those present in 1950, is the real cause of the physics “heat-trapping effect” seen worldwide. (Note: US tons are 0.907 of metric tonnes and both are used in this article.) Research accomplished in this review point to the heat-trapping property of CO2 as the major contributor to increasing heat worldwide and lead to the prediction of how much higher global temperature will rise if left unchecked, with the level of CO2 over 40% higher than it has ever been in more than 400,000 years. The proposed solution offered in this review is to initiate a 40 gigatonne carbon dioxide removal (CDR) annually in order to stabilize atmospheric CO2, to be followed by an expanded CDR effort toward a goal of 100 gigatonnes/year to begin reversing and lowering global temperature.

Asynchronous student engagement in analysis of climate data achieves learning objectives related to climate change understanding, statistical competence, and climate anxiety

Learning in asynchronous online environments has gained importance over the last several decades, and educational environment shifts from the COVID-19 pandemic appear to have increased this need. Science educators and students need information about which approaches work in the asynchronous environment where informal feedback tends to be reduced, compared to other teaching modalities. In this study, we asynchronously implemented a learning module across 5 institutions that guided students (N = 199) from prescriptive data analysis through guided inquiry and eventually to open inquiry. The module focuses on the science behind climate change. Students work with the same authentic data sets used by professional scientists to examine geologic history and causes of climate change. By analyzing contemporary atmospheric carbon dioxide and temperature data and then using the 800,000-year record available from the Vostok ice core proxy record of atmospheric properties, students identify the causes of climate change and discover the unprecedented nature of recent atmospheric changes. Using a pre/post-module assessment, we demonstrate improvement in students’ understanding of climate change processes and statistical methods used to analyze data. However, there was no evidence that the module develops students’ scientific reasoning about the relationship between causation and correlation. Students maintained that correlation is not causation, even when a robust causal mechanism (i.e., the greenhouse effect) explains the link between atmospheric carbon dioxide and temperature. Finally, our analysis indicated that generally, anxiety about climate change was reduced during the module, such that students become less anxious about the climate change the more they learn about it. However, science-denying students experienced much higher anxiety about climate change than students who accepted the scientific consensus about climate change. Climate science-dissenting students were so few in this study that a statistical comparison was not possible, but this intriguing finding warrants further investigation of the role of anxiety in science denial. Mainly, this study demonstrates how asynchronous online learning environments can indeed support the achievement of learning objectives related to conducting authentic science, such as increasing understanding of climate change and statistical concepts, all while not provoking anxiety about climate change.

3He flux obtained from South Pole air and snow‐ice and its connection to interplanetary dust particles

AbstractResearchers have characterized extraterrestrial (ET) helium, likely carried by interplanetary dust particles (IDPs), in deep‐sea sediments spanning more than the last 100 Myr. Here we complement those low resolution and deep time studies by measuring He in modern Antarctic air and recent ice. We analyzed 180 air filter samples collected in 2017 and 2018 at the South Pole and detected 3He above blank levels in 178. The filters collected during the austral springs had elevated 3He in multiple subsamples indicating the presence of many individual IDPs and potentially, a temporal variation in the ET small particle flux. Our calculated mean 3He flux of 1.4 ± 1.2 × 10−12 cc STP cm−2 ka−1 is the first such measurement from air samples. We also melted, filtered, and analyzed one hundred and forty‐one 1 m‐long ice sections from a ˜2000‐yr‐old South Pole core. We detected 3He above blank levels in 139 of the 141 ice core samples and calculated an average flux of 1.2 ± 0.3 × 10−12 cc STP cm−2 ka−1. Our two flux values are within a factor of two of those calculated from stratospheric IDP concentrations, those previously measured for sections of the GISP2 and Vostok ice cores, and from sediment cores from different locations and ages. The similarity of these flux values over disparate time scales (1–108 yr) and geographic locations (90° S to equator) indicates modest temporal variability and remarkable agreement among diverse IDP archives. These data provide a compelling link from IDPs collected in the stratosphere to those recorded in deep time sedimentary archives.

Sea-ice, primary productivity and ocean temperatures at the Antarctic marginal zone during late Pleistocene

While Pleistocene glacial-interglacial cycles are commonly associated with strong waxing and waning of Northern Hemisphere ice sheets, the response of the Antarctic ice sheet and regional changes in oceanographic and environmental conditions to Pleistocene climate dynamics remain poorly constrained. We present a reconstruction of sea-ice cover, sea surface temperature and primary productivity off the Ross Sea margin (Adare Basin at the slope of the Drygalski Basin) during the marine isotope stages (MIS) 9 to 5 (350–70 thousands years ago, encompassing Terminations IV to II). Our multiproxy study relies on micropaleontology (diatoms, dinoflagellate cysts, benthic foraminifers), organic and inorganic geochemistry proxies (carbon and nitrogen isotopes, lipid biomarkers, XRF-data), and sedimentology (IRD) obtained from deep-sea core AS05-10. For each glacial-interglacial transition a clear succession of events can be observed: (near-)permanent sea ice cover during glacial stages is followed by ice-shelf break-up with episodic ice-free areas and surface water stratification. Notably, ice-shelf break-up precedes the increase in air temperature as measured in the Vostok ice core for each glacial-interglacial transition. Generally, air temperature over Vostok starts rising once sea-ice cover at site AS05-10 has significantly decreased, becoming seasonal, as indicated by the diatom species composition. This is also reflected by the high diatom productivity and increased water mixing at site AS05-10, which is indicative of its proximity to the Marginal Ice Zone. At the onset of Termination II (MIS6 to 5), high export productivity and dysoxic bottom water conditions occurred, while water temperature increased about 5 °C. During each interglacial spring/summer sea-ice cover is most reduced, and highest productivity occurs. Following each interglacial, the warm and cold fluctuations match the sawtooth character of the temperatures over Vostok. This record illustrates that at the Ross Sea margin, sea surface conditions and (export) productivity were strongly influenced by the natural climate variability of the Pleistocene. In light of this, current global warming may lead to increased ice-shelf break-up, water column stratification and shifts in the position/size of the Marginal Ice Zone with implications for algal species composition and diversity, and for primary productivity.

The Influence of Dust Levels on Atmospheric Carbon Dioxide and Global Temperature

The purpose of this paper is to examine the causality between DUST, CO2 and temperature for the Vostok ice core data series [Vostok Data Series], dating from 420 000 years ago, and the EPICA C Dome data going back 800 000 years. In addition, the time-varying volatility and coefficient of variation in the CO2, dust and temperature is examined, as well as their dynamic correlations and interactions. We find a clear link between atmospheric C02 levels, dust and temperature, together with a bi-directional causality effects when applying both Granger Causality Tests (1969) and multi-directional Non-Linear analogues, i.e. Generalized Correlation. We apply both parametric and non-parametric statistical measures and testing. Linear interpolation with 100 years and 1000 years is applied to the three variables, in order to solve the problem of data points mismatch among them. The visualizations and descriptive statistics of the interpolated variables (using the two periods) show robustness in the results. The data analysis points out that variables are volatile, but their respective rolling mean and standard deviation remain stable. Additionally, 1000 years interpolated data suggests positive correlation between temperature and CO2, while dust is negatively correlated with both temperature and CO2. The application of the non-parametric Generalized Measure of Correlation to our data sets, in a pairwise fashion suggested that CO2 better explains temperature than temperature does CO2, that temperature better explains dust than dust does temperature, and finally that CO2 better explains dust than vice -versa. The latter two pairs of relationships are negative. The summary of the paper presents some avenues for further research, as well as some policy relevant suggestions.

Linear Global Temperature Correlation to Carbon Dioxide Level, Sea Level, and Innovative Solutions to a Projected 6°C Warming by 2100

Too many climate committees, conferences, articles and publications continue to suggest a one and a half (1.5°C) to two degrees (2°C) Celsius as an achievable global limit to climate changes without establishment of any causal link to the proposed anti-warming mechanism. A comprehensive review has found instead that observationally informed projections of climate science underlying climate change offer a different outlook of five to six-degree (5°C - 6°C) increase as “most accurate” with regard to present trends, climate history and models, yielding the most likely outcome for 2100. The most causative triad for the present warming trend from 1950 to the present is identified in this paper: 1) the tripling (3×) of world population; 2) the quadrupling (4×) of carbon emissions; and 3) the quintupling (5×) of the world energy consumption. This paper presents a quantitative, linear global temperature correlation to carbon dioxide levels that has great predictive value, a short temporal feedback loop, and the finding that it is also reversible. The Vostok ice core temperature and CO2 values for the past 400,000 years, with past sea level estimates have produced the sufficiently evidential “Hansen’s Graph”. Detailed analysis results in an equation for global average temperature change and an indebted, long-term sea level rise, from even a 20 ppm of CO2 change above 290 ppm, commonly taken as a baseline for levels before 1950. Comparison to the well-known 800,000 year old Dome C ice core is also performed. The best-performing climate change models and observational analysis are seen to project more warming than the average model often relied upon. World atmosphere, temperature, and sea level trends for 2100 and beyond are analyzed. A laboratory experiment proves the dramatic heat-entrapment capability of CO2 compared to pure air, which yields insights into the future global atmospheric system. Policy-relevant climate remediation, including gigaton carbon capture, zero and negative emissions and positive individual action, are reviewed and updated, with recommendations.

Insight Into Provenance and Variability of Atmospheric Dust in Antarctic Ice Cores During the Late Pleistocene From Magnetic Measurements

We measured saturation isothermal remanent magnetization (SIRM), coercivity of remanence (Hcr) and insoluble dust concentration (IDC) of 52 ice samples from Vostok and EPICA Dome-C ice cores (Antarctica) as a measure of magnetic properties of the aerosol dust entrapped in the ice. Samples range in age from marine isotopic stage (MIS) 7 to 19 in EPICA Dome-C ice core and from MIS 1 to 11 in Vostok ice core. Data from ice samples were compared with 86 samples from possible source areas (PSA) from East Antarctica, and 10 samples from South America and New Zealand. Previous results from MIS 1 to MIS 6 found that magnetic properties of aerosol dust could be divided in two distinct groups characterized by high-Hcr and low-SIRMdust for glacial samples, and low-Hcr and high-SIRMdust, for interglacial samples. The new data from older ice samples highlighted several discrepancies from this expectation with significant differences between Vostok and Dome-C sites. Magnetic properties of Antarctic PSA sample show a large variability, however PSA samples from Victoria Land and few other, have magnetic properties compatible with that of the glacial dust, or more precisely with samples characterized by high dust flux. The new data from Pleistocene ice and from PSA samples confirm the South American and Antarctic provenance of the largest atmospheric dust load typical of glacial stages. On the other hand, we did not found any PSA sample with properties compatible with the highly magnetic samples (mostly from interglacial stages), which are characterized by low IDC. These samples from the oldest and deepest part of the cores revealed a more complex picture than previously outlined from the analysis of MIS 1–6, and show unusual magnetic properties which can be tentatively attributed to chemical.

Metatranscriptomic and Metagenomic Analysis of Biological Diversity in Subglacial Lake Vostok (Antarctica).

A combined metatranscriptomic and metagenomic study of Vostok (Antarctica) ice core sections from glacial, basal, and lake water accretion ice yielded sequences that indicated a wide variety of species and possible conditions at the base of the glacier and in subglacial Lake Vostok. Few organisms were in common among the basal ice and accretion ice samples, suggesting little transmission of viable organisms from the basal ice meltwater into the lake water. Additionally, samples of accretion ice, each of which originated from water in several locations of the shallow embayment, exhibit only small amounts of mixing of species. The western-most portion of the embayment had very low numbers of organisms, likely due to biologically challenging conditions. Increasing numbers of organisms were found progressing from west to east, up to approximately 7 km into the embayment. At that point, the numbers of unique sequences and sequence reads from thermophilic, thermotolerant, psychrophilic, and psychrotolerant organisms increased dramatically, as did sequences from alkaliphilic, alkalitolerant, acidophilic, and acidotolerant sequences. The number of unique and total sequences were positively associated with increases in concentrations of Na+, Ca2+, Mg2+, SO42−, Cl−, total amino acids, and non-purgeable organic carbon. The numbers of unique sequences from organisms reported from soil, sediment, ice, aquatic, marine, animal, and plant (probably pollen) sources also peaked in this region, suggesting that this was the most biologically active region. The confluence of the high numbers of organisms, physiologies, and metabolic capabilities suggests the presence of energy and nutrient sources in the eastern half of the embayment. Data from the main basin suggested a cold oligotrophic environment containing fewer organisms. In addition to bacteria, both the basal ice and accretion ice contained sequences from a diverse assemblage of eukaryotes, as well as from bacteria that are known to be associated with multicellular eukaryotes.

On the possibility to restore the climatic signal in the disturbed record of stable water isotope content in the old (0.4–1.2 Ma) Vostok ice (Central Antarctica)

In this work we have presented new detailed (with the resolution of 10 cm) stable water isotope (δD and δ 18 O) profile measured in the central Antarctic Vostok ice core section that contains old ice with the age from 0.4 to 1.2 million years. To interpret these data we have developed a model of molecular diffusion in ice and determined the value of so-called «diffusion length». We have demonstrated that the climatic signal in this ice interval is disturbed by a combination of two processes, ice layer folding (that is accompanied by layer overturning and mixing) and molecular diffusion. The whole old ice interval can be divided in 5 zones that differ in terms of character and intensity of these two processes. In three of these zones the climatic signal is partly preserved and could be restored to some extent. However, in the most interesting and old zone 5 (0.75–1.2 Ma) the climatic signal is nearly completely erased and could hardly be reconstructed. At the same time, the isotopic records obtained from the Vostok old ice have preserved the information on the mean level of the isotopic content of ice in glacial and interglacial stages. This gives an opportunity to reveal and study long-term climatic trends with typical duration longer than main climatic cycles (40–100 ka).

Predictive Connection for 2100 between Atmospheric Carbon, Global Warming and Ocean Height Based on Climate History

Many recent climate panels and committees have predicted a one and a half (1.5°C) to two degrees (2°C) Celsius as an achievable global limit to climate change [1]. Instead, this review has found that observationally informed projections of climate science underlying climate change offer a different outlook for the most likely outcome for 2100 of five to six-degree (5-6°C) increase as “most accurate” with regard to present trends, climate history and models [2]. The most significant result from the review is a quantitative, linear global temperature link to carbon dioxide levels, which has a short temporal feedback loop. The Vostok ice core temperature and CO2 values for the past 420,000 years, with sea level estimates have produced “Hansen’s Graph” [3]. Analysis results in an equation for global average temperature change and an indebted sea level rise, from any CO2 change. The best-performing climate change models and observational analysis project more warming than the average model often relied upon [4]. World atmosphere, temperature, and sea level trends for 2100 and beyond are examined. A CO2 experimental analysis proves its dramatic heat-entrapment versus air which relates to the global atmospheric system. Policy-relevant climate adaptation, including carbon capture, positive individual action, zero and negative emissions are reviewed, including Hansen (1988) projected temperature increase for 2019.

Time and frequency analysis of Vostok ice core climate data

The periodicity of Vostok ice core climate temperature and gas concentration data indicate inherent long term past regularity of Earth’s climate, with a period of around 100,000 years, warming around 15,000 and cooling of around 85,000 years. At this point we are at the top of one of the warming periods. Vostok data cover around 430,000 years, ie 4 climate cycles (warming-cooling), of similar but not quite the same duration. In this paper we perform a detailed time and frequency analysis of these data for each of the cycles as well as their various combinations, including a full tested period of 430,000 years. Time correlation analysis allows for more accurate time lag estimate in each cycle already noted between temperature change and carbon dioxide content. We estimate these lags to lie between 1000-2500 years, longer than previously concluded. On the frequency side we perform Fast Fourier Analysis and identify full spectrum of harmonics for various cycles, and then perform energy analysis to identify which of the harmonics contributes the most. The idea is to reduce the computational load for further modeling and analysis using Kalman Filter based prediction method. Once the prediction model is defined (a follow up paper) data will be split into two segments, Learning and Testing, in preparation of a Machine Learning fine tunning methodology. We can use last three or last two or even just last cycle to learn on, and then the current on going cycle to test on. This will result in real time prediction of relevant climate data. Assuming causal time regularity, more of these cycles are employed in training, more the prediction error for the next cycle should be reduced. Hence it is critical to perform very detailed time and frequency analysis of Vostok data as a solid data base for the prediction model to follow.

Radar isochronic layer dating for a deep ice core at Kunlun Station, Antarctica

The ages and accumulation rates of ice are important boundary conditions for paleoclimatic ice models. Radar-detected isochronic layers can be used to date the ice column beneath the ice surface and infer past accumulation rates. A Deep Ice-Core Drilling Project has been carried out at Kunlun station in the Dome A region, East Antarctica. Radio echo sounding data are collected during the 2004/2005 Chinese National Research Expedition and the 2007/2008 Dome Connection East Antarctica project of the Alfred Wegener Institute (Germany). Radar isochronic layers from the dataset were linked to compare a new deep ice core site from Kunlun station and the Vostok ice core site. Ten visible layers, accounting for ∼50% ice thickness at the Kunlun station ice core site, were dated based on the Vostok ice core chronology. At 1,640 m depth below surface, an age of ∼160,400 yr was determined, corresponding to a bright layer at Kunlun station. These layers provided geometric information on the past surface of the ice sheet around the ice core site through the Wisconsin glacial stage, Eemian interglacial and Marine Isotope Stage 6. Based on a simple ice flow model and the age-depth relationship, we concluded that the region around the Kunlun ice core site had lower past accumulation rates, consistent with the present pattern. The age-depth relationship would thus be expected to correlate and constrain the chronology of the deep ice core at Kunlun station in the future.

New Estimates of Ice and Oxygen Fluxes Across the Entire Lid of Lake Vostok From Observations of Englacial Radio Wave Attenuation

AbstractOver deep Antarctic subglacial lakes, spatially varying ice thickness and the pressure‐dependent melting point of ice result in distinct areas of melting and freeze‐on at the ice‐water interface, that is, at the lake lid. These ice mass fluxes drive lake circulation and, because basal Antarctic ice contains air clathrate, affect the input of oxygen to the lake, with implications for subglacial life. Inferences of rates of melting and freeze‐on, that is, accretion rates, from radar layer tracking and geodesy are limited in spatial coverage and resolution. Here we develop a new method to estimate accretion rate, and the resulting oxygen input at a lake lid, using airborne radar data over Lake Vostok together with ice‐temperature and chemistry data from the Vostok ice core. Because the lake lid is a coherent reflector of known reflectivity (at our radar frequency), we can infer depth‐averaged radio wave attenuation in the ice, with a spatial resolution of ~1 km along flight lines. Spatial variation in attenuation depends mostly on variation in ice temperature near the lid, which in turn varies strongly with ice mass flux at the lid. We model ice temperature versus depth with ice mass flux as a parameter, thus linking that flux to observed depth‐averaged attenuation. The resulting map of melt and accretion rates independently reproduces features known from earlier studies but now covers the entire lid. We find that freeze‐on is dominant when integrated over the lid, with an ice imbalance of 0.05 to 0.07 km3/year, which is robust against uncertainties.

Unknown Widespread Iron- and Sulfur-Oxidizing Bacteria beneath the East Antarctic Ice Sheet

Comparative analysis of the Vostok ice core (Central East Antarctica; one horizon, three boreholes) and D10 ice core (shoreline nearby the French Dumont d’Urville station) has reliably revealed three phylotypes (species) of aerobic iron-oxidizing betaproteobacteria of the family Gallionellaceae (closely related at the genus level to Sideroxydans lithotrophicus and Ferriphaselus amnicola), one of which has been detected from both the Vostok (borehole 5G-3) and D10 cores. In addition, the phylotype related to sulfur-oxidizing bacteria Tumebacillus sp. has been detected from both the Vostok (borehole 5G-2) and D10 cores. The both ice cores are almost equal in age, about 20 000 years; however, they differ in origin: the ice from Dumont d’Urville is atmospheric, while that from Vostok is a lake ice. The ice samples greatly vary in the storage time before treatment in the laboratory (from 0.5 to 40 years) and in intervals between treatments (from 1 to 5 years). The drilling sites are more than 1000 km apart. No evident hydrological links (the transfer of water beneath the ice sheet) between the Lake Vostok and Dumont D’Urville station have been found. This coincidence can be explained by the fact that minerals from the bedrock under the glacier, containing ferrous iron and reduced sulfur compounds, as well as physical and chemical conditions in both sites, liquid fresh water at a temperature near the freezing point, are similar. These and other assumptions are considered in the present article.

New CO2 Concentration Predictions and Spectral Estimation Applied to the Vostok Ice Core

The Vostok ice core provides measurements of the CO2 concentration during the last $414\times 10^{3}$ years (yr). Estimations of power spectra show peaks, with the strongest one corresponding to a time period of around $100\times 10^{3}$ yr. In this paper, a new reconstruction method from irregular sampling is used, allowing more accurate estimation of spectral peaks. This method intrinsically decomposes the analyzed signal as a sum of sines, providing amplitudes but also phase measurements of periodic tendencies (due to the nature of the studied phenomena). This decomposition can be conducted with noisy and inaccurate measurements of the sampling instants and the concentrations. The widely used Vostok data were chosen as an example, but the method could also be applied to data from other places (e.g., dome C, Antarctica) or to study other phenomena as nitrogen dioxide NO2, methane CH4, oxygen isotope 18O (closely linked to temperature), deuterium 2H, or dust concentrations.

Summit of the East Antarctic Ice Sheet underlain by thick ice-crystal fabric layers linked to glacial–interglacial environmental change

Abstract Ice cores in Antarctica and Greenland reveal ice-crystal fabrics that can be softer under simple shear compared with isotropic ice. Owing to the sparseness of ice cores in regions away from the ice divide, we currently lack information about the spatial distribution of ice fabrics and its association with ice flow. Radio-wave reflections are influenced by ice-crystal alignments, allowing them to be tracked provided reflections are recorded simultaneously in orthogonal orientations (polarimetric measurements). Here, we image spatial variations in the thickness and extent of ice fabric across Dome A in East Antarctica, by interpreting polarimetric radar data. We identify four prominent fabric units, each several hundred metres thick, extending over hundreds of square kilometres. By tracing internal ice-sheet layering to the Vostok ice core, we are able to determine the approximate depth–age profile at Dome A. The fabric units correlate with glacial–interglacial cycles, most noticeably revealing crystal alignment contrasts between the Eemian and the glacial episodes before and after. The anisotropy within these fabric layers has a spatial pattern determined by ice flow over subglacial topography.

Identification of inorganic and organic inclusions in the subglacial antarctic Lake Vostok ice with Raman spectroscopy

The investigation of inclusions entrapped into the accretion ice of the subglacial Lake Vostok in Antarctica gives an insight into former times of the Antarctic history. Terrestrial (of biological and geologically mineralogical origin) as well as extraterrestrial (meteorites) materials are hermetically embedded in the Vostok ice core and provide information about the conditions and events on Earth existed/occurred during last million years. Confocal Raman spectroscopy is well suited for the analysis of the inclusions without melting the ice and, therefore, preventing undesirable contamination with present‐day material. It is a nondestructive method for material identification with depth resolving capability. It permits a locally precise statement about the chemical–mineralogical composition and allows the context information preservation of several side by side inclusions.Here, we present first results of our Raman measurements of the inclusion embedded in the Lake Vostok ice sample 5G‐3 3607‐4 (3607‐m depth). The results obtained confirm that Raman spectroscopy is a very useful method for the exploration of inclusions entrapped into lattice of any natural ice. As Raman spectroscopy is already planned to be applied in upcoming missions in space research (ExoMars, Mars 2020, to the icy moons), a co‐operation of the space science community with the Antarctica–Lake Vostok community is suggested to test the space instrumentation under the extreme environment of the Central East Antarctica and conditions of the subglacial Lake Vostok. Copyright © 2017 John Wiley & Sons, Ltd.

An improved north–south synchronization of ice core records around the 41 kyr <sup>10</sup>Be peak

Abstract. Using new high-resolution 10Be measurements in the NGRIP, EDML and Vostok ice cores, together with previously published data from EDC, we present an improved synchronization between Greenland and Antarctic ice cores during the Laschamp geomagnetic excursion ∼ 41 kyr ago. We estimate the precision of this synchronization to be ±20 years, an order of magnitude better than previous work. We discuss the implications of this new synchronization for making improved estimates of the depth difference between ice and enclosed gas of the same age (Δdepth), difference between age of ice and enclosed gas at the same depth (Δage) in the EDC and EDML ice cores, spectral properties of the 10Be profiles and phasing between Dansgaard–Oeschger-10 (in NGRIP) and AIM-10 (in EDML and EDC).

Spatio-temporal variability of past accumulation rates inferred from isochronous layers at Dome A, East Antarctica

ABSTRACTStudies of palaeo-accumulation rates at Dome A, East Antarctica, are entirely absent. Here, spatio-temporal variations in ice accumulation rates for the past ~161 ka are calculated from isochronous internal layering, traced from radio-echo sounding (RES) data collected by the Polar Research Institute of China (PRIC) during the 21st CHINARE. The layers are dated by linking them to the site of Vostok ice core along an RES profile, which was flown by the Alfred-Wegener-Institut (AWI) in the Dome Connection East Antarctica (DoCo) project. The Dansgaard-Johnsen model is used to determine the spatial and temporal pattern of ice accumulation in Dome A region. The results show that there is a slight increasing pattern of ice accumulation from south to north along the 216 km radar profile at Dome A. The lowest ice accumulation rates were calculated around the Dome A zone. In the past ~90 ka, there were relatively high accumulation rates during the time period 34–47 ka (Marine Isotope Stage 3) at Dome A.

Modelling directionality for paleoclimatic time series

The ice core time series from Vostok Station in Antarctica and the North Greenland Ice Core Project have seasonal variation corresponding to the Milankovitch cycles. After removing these cycles, and interpolating to equal time intervals, stationary time series models are fitted. The series show clear directionality and this feature is modelled by either non-Gaussian errors or non-linear time series models. Threshold autoregressive models are fitted by penalized least squares and compared with non-threshold autoregressive models. Since both ice core time series are reasonably modelled as first order autoregressive series with parameters close to one, directionality will arise from non-symmetric error distributions. However, two regime threshold autoregressive models, of order one and two for Greenland and Vostok, respectively, give an improved match to the observed directionality and a reduced sum of squared residuals. Realizations from the threshold autoregressive models are noticeably different from the non-threshold models. Since the non-threshold models are a restricted case of the threshold models, and the threshold models are a better fit to the observed time series, threshold models should provide more realistic realizations. References C. Chatfield. The Analysis of Time Series: An Introduction . CRC Press, 2004. https://www.crcpress.com/The-Analysis-of-Time-Series-An-Introduction-Sixth-Edition/Chatfield/p/book/9781584883173 A. J. Lawrance. Directionality and reversibility in time series. Int. Stat. Rev. 59(1):67–79, 1991. doi:10.2307/1403575 M. M. Mansor, M. E. Glonek, D. A. Green and A. V. Metcalfe. Threshold autoregressive models for directional time series. In I. Rojas and H. Pomares (Eds.), Time Series Analysis and Forecasting Selected Contributions from the ITISE Conference (ITISE 2015) . pp. 13–25, 2016. doi:10.1007/978-3-319-28725-6 M. M. Mansor, M. E. Glonek, D. A. Green and A. V. Metcalfe. Modelling directionality in stationary geophysical time series. International work-conference on Time Series (ITISE 2015) . http://www.researchgate.net/publication/281835075 M. M. Mansor, D. A. Green and A. V. Metcalfe. Modelling and simulation of directional financial time series. Proceedings of the 21st International Congress on Modelling and Simulation (MODSIM 2015) , pp. 1022–1028, 2015. http://www.mssanz.org.au/modsim2015/E4/mansor.pdf M. M. Mansor, D. A. Green and A. V. Metcalfe. Directionality and volatility in electroencephalogram time series. Proceedings of the 2nd International Conference on Mathematical Sciences and Statistics (ICMSS 2016), AIP Conf. Proc. 1739:020080, 2016. doi:10.1063/1.4952560 North Greenland Ice Core Project members. High-resolution record of Northern Hemisphere climate extending into the last interglacial period. Nature , 431:147–151, 2004. doi:10.1038/nature02805 J. R. Petit, J. Jouzel, D. Raynaud, N. I. Barkov, J.-M. Barnola, I. Basile, M. Bender, J. Chappellaz, M. Davis, G. Delaygue, M. Delmotte, V. M. Kotlyakov, M. Legrand, V. Y. Lipenkov, C. Lorius, L. Pepin, C. Ritz, E. Saltzman and M. Stievenard. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature , 399:429–436, 1999. doi:10.1038/20859 S. Soubeyrand, C. E. Morris and E. K. Bigg. Analysis of fragmented time directionality in time series to elucidate feedbacks in climate data. Environ. Modell. Softw. 61:78–86, 2014. doi:10.1016/j.envsoft.2014.07.003