Evidence for substantial accumulation rate variability in Antarctica during the Holocene, through synchronization of CO2 in the Taylor Dome, Dome C and DML ice cores

doi:10.1016/j.epsl.2004.05.007

Earth and Planetary Science Letters

Volume 224, Issues 1–2, 30 July 2004, Pages 45-54

https://doi.org/10.1016/j.epsl.2004.05.007 Get rights and content

Abstract

High resolution records of atmospheric CO₂ concentration during the Holocene are obtained from the Dome Concordia and Dronning Maud Land (Antarctica) ice cores. These records confirm that the CO₂ concentration varied between 260 and 280 ppmv in the Holocene as measured in the Taylor Dome ice core. However, there are differences in the CO₂ records most likely caused by mismatches in timescales. Matching the Taylor Dome timescale to the Dome C timescale by synchronization of CO₂ indicates that the accumulation rate at Taylor Dome increased through the Holocene by a factor two and bears little resemblance to the stable isotope record used as a proxy for temperature. This result shows that different locations experienced substantially different accumulation changes, and casts doubt on the often-used assumption that accumulation rate scales with the saturation vapor pressure as a function of temperature, at least for coastal locations.

Introduction

For the interpretation of information obtained from ice cores, an accurate timescale is a prerequisite. There exist many different approaches for dating ice cores, such as counting annual layers or modelling of ice flow. Another approach is to determine the age by comparing concentrations of trace gases that, due to their long atmospheric residence time, should be essentially identical in all cores. For some purposes, an absolute timescale may not be needed but reliable cross-dating between two records is sufficient. One successfully applied method is the matching of methane among Antarctic and Greenland ice cores [1], [2]. Methane is well suited for timescale synchronization through the last glacial because it is globally well mixed and exhibits rapid and large changes. For the Holocene, methane synchronization between ice cores is less suitable because this is a time period where methane shows a limited number of significant sharp changes [3].

CO₂, which is also a well-mixed trace gas, shows variations during the Holocene with similar relative amplitudes and similar rates of change as methane but at different times [4], [5]. CO₂ variations can therefore be used as an additional tool to synchronize timescales. In this paper, we use this method to synchronize the timescales of the Dome C, DML and the Taylor Dome ice cores from Antarctica, as high resolution CO₂ records of good quality measured in the same lab with the same procedure are available for each of these cores.

Section snippets

Measurements

Here we present records from the Dome C (75°06′S, 123°21′E) and DML (Dronning Maud Land, 75°00′S, 00°04′E), ice cores, both drilled in the framework of the “European Project for Ice Coring in Antarctica” (EPICA). We increased the resolution of the Dome C data published in Flückiger et al. [5] by measuring CO₂ on an additional 498 samples at 83 different depth intervals, between 99 and 416 m depth, covering the period from 0 to 11.2 ky BP (thousand years before present, where present is chosen

Potential artefacts

One problem concerning the CO₂ measurements is the possibility of CO₂ enrichment by chemical reactions between impurities in the ice cores. The most likely sources are acid-carbonate reactions and the oxidation of organic compounds [8], [9], [10]. Generally, it is assumed that artefacts are more likely in relatively warm ice. Detailed high resolution measurements over a full 55 cm length of Dome C ice (mean annual surface temperature: −54.5°C) showed that in the Holocene, the scattering of the

Chronologies

We are now interested in cross-dating both the gas and the ice timescales for the Dome C and Taylor Dome cores. For the Dome C ice core a timescale (EDC1) was constructed by Schwander et al. [13]. The absolute uncertainty of the timescale for the ice is estimated to ±10 years back to 700 years and ±200 years back to 10 ky BP. Back to 700 years, the timescale was matched with historically documented and other well-dated volcanic signals. Between 700 and 7100 years, the volcanic signals were

Synchronization of the CO₂ records

We begin by adjusting the gas timescale for Taylor Dome to that of Dome C using CO₂. As the CO₂ record in the Holocene does not often show very distinct features but rather stepwise increases of a few ppmv, we used three different methods for the synchronization to test the consistency of the results. The first synchronization was done by matching the entire record visually. For the second synchronization, we visually matched control points at areas with prominent features and interpolated with

Ice timescale and accumulation rate calculations

To obtain an ice age timescale from the new gas ages for Taylor Dome, calculation of the Δage value is needed. Δage values can be calculated with a firn densification model, if the temperature and snow accumulation rate are known. Because snow accumulation rates are not known a priori, this poses a difficulty that is usually resolved by inferring accumulation rate from some other measurement. Here we use an alternative approach, which minimizes the mismatch between accumulation rates obtained

Conclusions

Detailed measurements of the CO₂ concentration on the Dome C and DML ice cores exhibit differences up to 6 ppmv to the measurements of Indermühle et al. [4] from Taylor Dome. We attribute this disagreement to differences in the respective timescales. A new chronology for the Taylor Dome ice core established through CO₂ synchronization reveals that the accumulation has changed substantially during the Holocene, with a long-term increase that shows little relation with the temperature history.

Acknowledgements

We thank E.J. Brook, T. Blunier, M. Hutterli, G. Raisbeck and M. L. Bender for the fruitful discussions. This work is a contribution to the “European Project for Ice Coring in Antarctica” (EPICA), a joint ESF (European Science Foundation)/EC scientific programme, funded by the European Commission and by national contributions from Belgium, Denmark, France, Germany, Italy, The Netherlands, Norway, Sweden, Switzerland and the United Kingdom. This is EPICA publication No. 103. The measurements

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Evidence for substantial accumulation rate variability in Antarctica during the Holocene, through synchronization of CO2 in the Taylor Dome, Dome C and DML ice cores

Abstract

Introduction

Section snippets

Measurements

Potential artefacts

Chronologies

Synchronization of the CO2 records

Ice timescale and accumulation rate calculations

Conclusions

Acknowledgements

Asynchrony of Antarctica and Greenland climate change during the last glacial period

Nature

Synchronous climate changes in Antarctica and the North Atlantic

Science

Changes in the atmospheric CH4 gradient between Greenland and Antarctica during the Holocene

J. Geophys. Res.

Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica

Nature

High resolution Holocene N2O ice core record and its relationship with CH4 and CO2

Glob. Biogeochem. Cycles

Atmospheric concentrations over the last glacial termination

Science

Processes affecting the CO2 concentrations measured in Greenland ice

Tellus

The CO2 concentration of air trapped in Greenland Ice Sheet Project 2 ice formed during periods of rapid climate change

J. Geophys. Res.

Reconstructing the past atmospheric CO2 concentration based on ice core analyses: open questions due to in situ production of CO2 in the ice

J. Glaciol.

Discussion of the reliability of CO2, CH4, N2O, and records from polar ice cores

Wisconsian and Holocene climate history from an ice core at Taylor Dome, western Ross Embayment, Antarctica

Geogr. Ann.

A tentative chronology of the EPICA Dome Concordia ice core

Geophys. Res. Lett.

Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica

Nature

Absolute dating of the last 7000 years of the Vostok ice Core using 10Be

Min. Mag.

Timing of the Antarctic Cold Reversal and the atmospheric CO2 increase with respect to the Younger Dryas event

Geophys. Res. Lett.

Evidence for substantial accumulation rate variability in Antarctica during the Holocene, through synchronization of CO₂ in the Taylor Dome, Dome C and DML ice cores

Synchronization of the CO₂ records

Changes in the atmospheric CH₄ gradient between Greenland and Antarctica during the Holocene

Holocene carbon-cycle dynamics based on CO₂ trapped in ice at Taylor Dome, Antarctica

High resolution Holocene N₂O ice core record and its relationship with CH₄ and CO₂

Processes affecting the CO₂ concentrations measured in Greenland ice

The CO₂ concentration of air trapped in Greenland Ice Sheet Project 2 ice formed during periods of rapid climate change

Reconstructing the past atmospheric CO₂ concentration based on ice core analyses: open questions due to in situ production of CO₂ in the ice

Discussion of the reliability of CO₂, CH₄, N₂O, and records from polar ice cores

Absolute dating of the last 7000 years of the Vostok ice Core using ¹⁰Be

Timing of the Antarctic Cold Reversal and the atmospheric CO₂ increase with respect to the Younger Dryas event