Calculating uncertainty for the RICE ice core continuous flow analysis water isotope record

Abstract. We describe a systematic approach to the calibration and uncertainty estimation of a high-resolution continuous flow analysis (CFA) water isotope (δ2H, δ18O) record from the Roosevelt Island Climate Evolution (RICE) Antarctic ice core. Our method establishes robust uncertainty estimates for CFA δ2H and δ18O measurements, comparable to those reported for discrete sample δ2H and δ18O analysis. Data were calibrated using a time-weighted two-point linear calibration with two standards measured both before and after continuously melting 3 or 4 m of ice core. The error at each data point was calculated as the quadrature sum of three factors: Allan variance error, scatter over our averaging interval (error of the variance) and calibration error (error of the mean). Final mean total uncertainty for the entire record is δ2H=0.74 ‰ and δ18O=0.21 ‰. Uncertainties vary through the data set and were exacerbated by a range of factors, which typically could not be isolated due to the requirements of the multi-instrument CFA campaign. These factors likely occurred in combination and included ice quality, ice breaks, upstream equipment failure, contamination with drill fluid and leaks or valve degradation. We demonstrate that our methodology for documenting uncertainty was effective across periods of uneven system performance and delivered a significant achievement in the precision of high-resolution CFA water isotope measurements.

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Calculating uncertainty for the RICE ice core continuous flow analysis water isotope record

10.5194/amt-2017-387 ◽

2018 ◽

Cited By ~ 2

Author(s):

Elizabeth D. Keller ◽

W. Troy Baisden ◽

Nancy A. N. Bertler ◽

B. Daniel Emanuelsson ◽

Silvia Canessa ◽

...

Keyword(s):

High Resolution ◽

Continuous Flow ◽

Total Error ◽

Ice Core ◽

Flow Analysis ◽

Analysis Data ◽

Linear Calibration ◽

Continuous Flow Analysis ◽

Uncertainty Estimates ◽

Water Isotope

Abstract. We describe a novel approach to the calibration and uncertainty estimation of a high-resolution continuous flow analysis (CFA) water isotope (δ2H, δ18O) record from the Roosevelt Island Climate Evolution (RICE) Antarctic ice core. Our method establishes robust uncertainty estimates for CFA δ2H and δ18O measurements, comparable to those reported for discrete sample δ2H and δ18O analysis. Data were calibrated using a time-weighted two-point linear calibration with two standards measured both before and after continuously melting three or four meters of ice core. The error at each data point was calculated as the quadrature sum of three factors: Allan variance, scatter over the averaging interval, and general calibration accuracy. Final mean total error for the entire record is δ2H = 0.74 ‰ and δ18O = 0.21 ‰. The quality over the length of the dataset is variable, likely due to a combination of poorer ice quality at lower depths, interruptions in the CFA measurements due to ice breaks and equipment failure, the build-up over time of residual drill fluid, and leaks or valve degradation in the system. Despite the somewhat uneven system performance, this represents a significant achievement in precision of high-resolution CFA water isotope measurement.

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Forty years later: High resolution continuous flow analysis of the Dye3 ice core

10.5194/egusphere-egu21-11820 ◽

2021 ◽

Author(s):

Helle Astrid Kjær ◽

Margaret Harlan ◽

Paul Vallelonga ◽

Anders Svensson ◽

Thomas Blunier ◽

...

Keyword(s):

High Resolution ◽

Forest Fires ◽

Continuous Flow ◽

Ice Core ◽

Flow Analysis ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Cores ◽

The Core ◽

Continuous Flow Analysis

<div>The Dye-3 ice core was drilled to bedrock at the Southern part of the central Greenland ice sheet (65&#176;11'N, 43&#176;50'W) in 1979-1981. The southern location is characterized by high accumulation rates compared to more central locations of the ice sheet. Since its drilling, numerous analyses of the core have been performed, and the ice has since been in freezer storage both in the USA and in Denmark.</div><div>In October and November 2019, the remaining ice, two mostly complete sections covering the depths of 1753&#8211;1820m and 1865&#8211;1918m of the Dye-3 core, were melted during a continuous flow analysis (CFA) campaign at the Physics of Ice, Climate, and Earth (PICE) group at the University of Copenhagen. The data represents both Holocene, Younger Dryas and Glacial sections (GS 5 to 12).</div><div>&#160;</div><div>The measured data consist chemistry and impurities contained in the ice, isotopes, as well as analysis of methane and other atmospheric gases.&#160;</div><div>The chemistry measurements include NH4+, Ca2+, and Na+&#160;ions, which besides being influenced by transport, provide information about forest fires, wind-blown dust, and sea ice, respectively, as well as acidity, which aids in the identification of volcanic events contained in the core. The quantity and grain size distribution of insoluble particles was analyzed by means of an Abakus laser particle counter.</div><div>&#160;</div><div>We compare the new high-resolution CFA record of dye3 with previous analysis and thus evaluate the progress made over 40 years. Further we compare overlapping time periods with other central Greenland ice cores and discuss spatial patterns in relation to the presented climate proxies.</div>

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Review Keller et al: Calculating uncertainty for the RICE ice core continuous flow analysis water isotope record

10.5194/amt-2017-387-rc1 ◽

2018 ◽

Author(s):

Anonymous

Keyword(s):

Continuous Flow ◽

Ice Core ◽

Flow Analysis ◽

Continuous Flow Analysis ◽

Isotope Record ◽

Water Isotope

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A novel approach to process brittle ice for continuous flow analysis of stable water isotopes

Journal of Glaciology ◽

10.1017/jog.2018.19 ◽

2018 ◽

Vol 64 (244) ◽

pp. 289-299 ◽

Cited By ~ 5

Author(s):

REBECCA L. PYNE ◽

ELIZABETH D. KELLER ◽

SILVIA CANESSA ◽

NANCY A. N. BERTLER ◽

ALEX R. PYNE ◽

...

Keyword(s):

Continuous Flow ◽

Ice Core ◽

Flow Analysis ◽

Ice Cores ◽

Water Isotopes ◽

Stable Water Isotopes ◽

Climate History ◽

Continuous Flow Analysis ◽

Isotope Measurements ◽

Water Isotope

ABSTRACTBrittle ice, which occurs in all intermediate-depth and deep ice cores retrieved from high-latitude regions, presents a challenge for high-resolution measurements of water isotopes, gases, ions and other quantities conducted with continuous flow analysis (CFA). We present a novel method of preserving brittle ice for CFA stable water isotope measurements using data from a new ice core recovered by the Roosevelt Island Climate Evolution (RICE) project. Modest modification of the drilling technique and the accommodation of non-horizontal fractures (‘slanted breaks’) in processing led to a substantial improvement in the percentage of brittle ice analyzed with CFA (87.8%). Whereas traditional processing methods remove entire fragmented pieces of ice, our method allowed the incorporation of a total of 3 m of ice (1% of the 261 m of brittle ice and ~1300 years of climate history) that otherwise would not have been available for CFA. Using the RICE stable water isotope CFA dataset, we demonstrate the effect of slanted breaks and analyze the resulting smoothing of the data with real and simulated examples. Our results suggest that retaining slanted breaks are a promising technique for preserving brittle ice material for CFA stable water isotope measurements.

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High resolution aerosol concentration data from the Greenland NorthGRIP and NEEM deep ice cores

10.5194/essd-2021-324 ◽

2021 ◽

Author(s):

Tobias Erhardt ◽

Matthias Bigler ◽

Urs Federer ◽

Gideo Gfeller ◽

Daiana Leuenberger ◽

...

Keyword(s):

High Resolution ◽

Continuous Flow ◽

Ice Core ◽

Historical Context ◽

Flow Analysis ◽

Ice Cores ◽

Deposition Flux ◽

Concentration Data ◽

Continuous Flow Analysis ◽

North Greenland

Abstract. Records of chemical impurities from ice cores enable us to reconstruct the past deposition of aerosols onto the polar ice sheets and alpine glaciers. Through that, they allow us to gain insight into changes of the source, transport and deposition processes that ultimately determine the deposition flux at the coreing location. However, the low concentrations of the aerosol species in the ice and the resulting high risk of contamination poses a formidable analytical challenge, especially if long, continuous and highly resolved records are needed. Continuous Flow Analysis, CFA, the continuous melting, decontamination and analysis of ice-core samples has mostly overcome this issue and has quickly become the de-facto standard to obtain high-resolution aerosol records from ice cores after its inception at the University of Bern in the mid 90s. Here we present continuous records of calcium (Ca2+), sodium (Na+), ammonium (NH4+), nitrate (NO3−1) and electrolytic conductivity at 1 mm depth resolution from the NGRIP (North Greenland Ice Core Project) and NEEM (North Greenland Eemian Ice Drilling) ice cores produced by the Bern Continuous Flow Analysis group in the years 2000 to 2011. Both of the records have previously been used in a number of studies but have never been published in the full 1 mm resolution. Alongside the 1 mm datasets we provide decadal averages, a detailed description of the methods, relevant references, an assessment of the quality of the data and its usable resolution. Along the way we will also give some historical context on the development of the Bern CFA system.

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Continuous flow analysis of the Mount Brown South ice core

10.5194/egusphere-egu21-15782 ◽

2021 ◽

Author(s):

Margaret Harlan ◽

Helle Astrid Kjær ◽

Tessa Vance ◽

Paul Vallelonga ◽

Vasileios Gkinis ◽

...

Keyword(s):

Indian Ocean ◽

Size Distribution ◽

Continuous Flow ◽

Ice Core ◽

Flow Analysis ◽

East Antarctica ◽

Southern Indian Ocean ◽

Indian Ocean Region ◽

Continuous Flow Analysis ◽

Ocean Region

The Mount Brown South (MBS) ice core is an approximately 300-meter-long ice core, drilled in 2016-2017 to the south of Mount Brown, Wilhelm II Land, East Antarctica. This location in East Antarctica was chosen as it produces an ice core with well-preserved sub-annual records of both chemistry and isotope concentrations, spanning back over 1000 years. MBS is particularly well suited to represent climate variations of the Indian Ocean sector of Antarctica, and to provide information about regional volcanism in the Southern Indian Ocean region.A section of ice spanning the length of the MBS core was melted as part of the autumn 2019 continuous flow analysis (CFA) campaign at the Physics of Ice, Climate, and Earth (PICE) group at the University of Copenhagen. During this campaign, measurements were conducted for chemistry and impurities contained in the ice, in addition to water isotopes. The data measured in Copenhagen include measurements of H2O2, pH, electrolytic conductivity, and NH4+, Ca2+, and Na+&#160;ions, in addition to insoluble particulate concentrations and size distribution measured using an Abakus laser particle counter.Here, we present an overview of the CFA chemistry and impurity data, as well as preliminary investigations into the size distribution of insoluble particles and the presence of volcanic material within the ice. These initial chemistry and particulate size distribution data sets are useful in order to identify sections of the MBS core to subject to further analysis to increase our understanding of volcanic activity in the Southern Indian Ocean region.

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High-resolution glacial and deglacial record of atmospheric methane by continuous-flow and laser spectrometer analysis along the NEEM ice core

Climate of the Past ◽

10.5194/cp-9-2579-2013 ◽

2013 ◽

Vol 9 (6) ◽

pp. 2579-2593 ◽

Cited By ~ 37

Author(s):

J. Chappellaz ◽

C. Stowasser ◽

T. Blunier ◽

D. Baslev-Clausen ◽

E. J. Brook ◽

...

Keyword(s):

High Resolution ◽

Continuous Flow ◽

Ice Core ◽

Rate Of Change ◽

Atmospheric Methane ◽

Data Set ◽

Rate Of Increase ◽

Concentration Changes ◽

Cross Dating ◽

Laser Spectroscopic

Abstract. The Greenland NEEM (North Greenland Eemian Ice Drilling) operation in 2010 provided the first opportunity to combine trace-gas measurements by laser spectroscopic instruments and continuous-flow analysis along a freshly drilled ice core in a field-based setting. We present the resulting atmospheric methane (CH4) record covering the time period from 107.7 to 9.5 ka b2k (thousand years before 2000 AD). Companion discrete CH4 measurements are required to transfer the laser spectroscopic data from a relative to an absolute scale. However, even on a relative scale, the high-resolution CH4 data set significantly improves our knowledge of past atmospheric methane concentration changes. New significant sub-millennial-scale features appear during interstadials and stadials, generally associated with similar changes in water isotopic ratios of the ice, a proxy for local temperature. In addition to the midpoint of Dansgaard–Oeschger (D/O) CH4 transitions usually used for cross-dating, sharp definition of the start and end of these events brings precise depth markers (with ±20 cm uncertainty) for further cross-dating with other palaeo- or ice core records, e.g. speleothems. The method also provides an estimate of CH4 rates of change. The onsets of D/O events in the methane signal show a more rapid rate of change than their endings. The rate of CH4 increase associated with the onsets of D/O events progressively declines from 1.7 to 0.6 ppbv yr−1 in the course of marine isotope stage 3. The largest observed rate of increase takes place at the onset of D/O event #21 and reaches 2.5 ppbv yr−1.

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Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores

Atmospheric Measurement Techniques ◽

10.5194/amt-10-617-2017 ◽

2017 ◽

Vol 10 (2) ◽

pp. 617-632 ◽

Cited By ~ 14

Author(s):

Tyler R. Jones ◽

James W. C. White ◽

Eric J. Steig ◽

Bruce H. Vaughn ◽

Valerie Morris ◽

...

Keyword(s):

Continuous Flow ◽

Ice Core ◽

Flow Analysis ◽

Ice Cores ◽

Isotope Ratio Mass Spectrometry ◽

Absorption Spectrometry ◽

Isotopic Analysis ◽

Water Isotopes ◽

Stable Water Isotopes ◽

Continuous Flow Analysis

Abstract. Water isotopes in ice cores are used as a climate proxy for local temperature and regional atmospheric circulation as well as evaporative conditions in moisture source regions. Traditional measurements of water isotopes have been achieved using magnetic sector isotope ratio mass spectrometry (IRMS). However, a number of recent studies have shown that laser absorption spectrometry (LAS) performs as well or better than IRMS. The new LAS technology has been combined with continuous-flow analysis (CFA) to improve data density and sample throughput in numerous prior ice coring projects. Here, we present a comparable semi-automated LAS-CFA system for measuring high-resolution water isotopes of ice cores. We outline new methods for partitioning both system precision and mixing length into liquid and vapor components – useful measures for defining and improving the overall performance of the system. Critically, these methods take into account the uncertainty of depth registration that is not present in IRMS nor fully accounted for in other CFA studies. These analyses are achieved using samples from a South Pole firn core, a Greenland ice core, and the West Antarctic Ice Sheet (WAIS) Divide ice core. The measurement system utilizes a 16-position carousel contained in a freezer to consecutively deliver ∼  1 m  ×  1.3 cm2 ice sticks to a temperature-controlled melt head, where the ice is converted to a continuous liquid stream and eventually vaporized using a concentric nebulizer for isotopic analysis. An integrated delivery system for water isotope standards is used for calibration to the Vienna Standard Mean Ocean Water (VSMOW) scale, and depth registration is achieved using a precise overhead laser distance device with an uncertainty of ±0.2  mm. As an added check on the system, we perform inter-lab LAS comparisons using WAIS Divide ice samples, a corroboratory step not taken in prior CFA studies. The overall results are important for substantiating data obtained from LAS-CFA systems, including optimizing liquid and vapor mixing lengths, determining melt rates for ice cores with different accumulation and thinning histories, and removing system-wide mixing effects that are convolved with the natural diffusional signal that results primarily from water molecule diffusion in the firn column.

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Sulphate record from a northeast Greenland ice core over the last 1200 years based on continuous flow analysis

Annals of Glaciology ◽

10.3189/172756402781817158 ◽

2002 ◽

Vol 35 ◽

pp. 250-256 ◽

Cited By ~ 40

Author(s):

Matthias Bigler ◽

Dietmar Wagenbach ◽

Hubertus Fischer ◽

Josef Kipfstuhl ◽

Heinrich Miller ◽

...

Keyword(s):

Continuous Flow ◽

Ice Core ◽

Flow Analysis ◽

Depth Resolution ◽

The Novel ◽

Small Shift ◽

Annual Layer ◽

Continuous Flow Analysis ◽

Clear Identification ◽

Relative Errors

AbstractA 150 m deep ice core from the low-accumulation area of northeast Greenland was analyzed for sulphate, calcium, sodium and electrolytical meltwater conductivity at a depth resolution of approximately 1 cm by continuous flow analysis (CFA). the calcium and sodium profiles are used to establish a relatively precise ice-core chronology by annual-layer counting back to AD 830. Inspection of the novel CFA method for sulphate revealed relative errors typically around 15%, but at least ±20 ng g–1, for concentrations 5130 ng g–1, and a current detection limit for routine ice-core analyses of 40 ng g–1. Annual sulphate peaks are shown to occur over almost the entire core, with only a small shift in seasonality between the modern and pre-industrial sections. Inspection of volcanic horizons allowed more accurate timing of these peaks and clear identification of calcium-rich events. Disregarding clear volcanic peaks, significant long-term changes of sulphate are only seen over the industrial period. However, a higher frequency of important volcanic inputs was identified around AD 1200.

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Improved Methodologies for Continuous Flow Analysis of Stable Water Isotopes in Ice Cores

10.5194/amt-2016-118 ◽

2016 ◽

Cited By ~ 2

Author(s):

Tyler R. Jones ◽

James W. C. White ◽

Eric J. Steig ◽

Bruce H. Vaughn ◽

Valerie Morris ◽

...

Keyword(s):

Continuous Flow ◽

Ice Core ◽

Flow Analysis ◽

Ice Cores ◽

Isotope Ratio Mass Spectrometry ◽

Isotopic Analysis ◽

Water Isotopes ◽

Mixing Length ◽

Stable Water Isotopes ◽

Continuous Flow Analysis

Abstract. Water isotopes in ice cores are used as a climate proxy for local temperature and regional atmospheric circulation as well as evaporative conditions in moisture source regions. Traditional measurements of water isotopes have been achieved using magnetic sector isotope ratio mass spectrometry (IRMS). However, a number of recent studies have shown that laser absorption spectrometers (LAS) perform as well or better than IRMS. The new LAS technology has been combined with continuous flow analysis (CFA) to improve data density and sample throughput in numerous prior ice coring projects. Here, we present a comparable semi-automated LAS-CFA system for measuring high-resolution water isotopes of ice cores. We outline new methods for partitioning both system uncertainty and system mixing length into liquid and vapor components – useful measures for defining and improving the overall performance of the system. Critically, our methods take into account the uncertainty of depth registration that is not present in IRMS nor fully accounted for in other CFA studies. We also explain a method for introducing consecutive sections of isotopically distinct ice at the melt head to define the system-wide mixing length. These analyses are achieved using samples from a South Pole firn core, a Greenland ice core, and the WAIS Divide ice core. The measurement system utilizes a 16-position carousel contained in a freezer to consecutively deliver ~ 1 m × 1.3 cm2 ice sticks to a temperature controlled melt head, where the ice is converted to a continuous liquid stream, and eventually vaporized using a concentric nebulizer for isotopic analysis. An integrated delivery system for water isotope standards is used for calibration to the VSMOW-SLAP scale and depth registration is achieved using a precise overhead laser distance device with an uncertainty of ±0.2 mm. As an added check on our system, we perform inter-lab LAS comparisons using WAIS Divide ice samples, a corroboratory step not taken in prior CFA studies. The overall results are important for substantiating data obtained from LAS-CFA systems, including optimizing liquid and vapor mixing lengths, determining melt rates for ice cores with different accumulation and thinning histories, and removing system-wide mixing effects that are convolved with the natural diffusional signal that results primarily from water molecule diffusion in the firn column.

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