Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores
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)....
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ftunicolboulder:oai:scholar.colorado.edu:geol_facpapers-1011 2023-05-15T13:49:40+02:00 Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores Jones, Tyler R. White, James W C Steig, Eric J. Vaughn, Bruce H. Morris, Valerie Gkinis, Vasileios Markle, Bradley R. Schoenemann, Spruce W. 2017-02-01T08:00:00Z application/pdf https://scholar.colorado.edu/geol_facpapers/8 https://scholar.colorado.edu/cgi/viewcontent.cgi?article=1011&context=geol_facpapers unknown CU Scholar https://scholar.colorado.edu/geol_facpapers/8 https://scholar.colorado.edu/cgi/viewcontent.cgi?article=1011&context=geol_facpapers http://creativecommons.org/licenses/by/3.0/ CC-BY Geological Sciences Faculty Contributions text 2017 ftunicolboulder 2018-10-07T09:10:52Z 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 ∼ 1m × 1.3cm2 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. Text Antarc* Antarctic Greenland Greenland ice core ice core Ice Sheet South pole South pole University of Colorado, Boulder: CU Scholar Antarctic West Antarctic Ice Sheet Greenland South Pole |
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University of Colorado, Boulder: CU Scholar |
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ftunicolboulder |
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description |
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 ∼ 1m × 1.3cm2 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. |
format |
Text |
author |
Jones, Tyler R. White, James W C Steig, Eric J. Vaughn, Bruce H. Morris, Valerie Gkinis, Vasileios Markle, Bradley R. Schoenemann, Spruce W. |
spellingShingle |
Jones, Tyler R. White, James W C Steig, Eric J. Vaughn, Bruce H. Morris, Valerie Gkinis, Vasileios Markle, Bradley R. Schoenemann, Spruce W. Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores |
author_facet |
Jones, Tyler R. White, James W C Steig, Eric J. Vaughn, Bruce H. Morris, Valerie Gkinis, Vasileios Markle, Bradley R. Schoenemann, Spruce W. |
author_sort |
Jones, Tyler R. |
title |
Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores |
title_short |
Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores |
title_full |
Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores |
title_fullStr |
Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores |
title_full_unstemmed |
Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores |
title_sort |
improved methodologies for continuous-flow analysis of stable water isotopes in ice cores |
publisher |
CU Scholar |
publishDate |
2017 |
url |
https://scholar.colorado.edu/geol_facpapers/8 https://scholar.colorado.edu/cgi/viewcontent.cgi?article=1011&context=geol_facpapers |
geographic |
Antarctic West Antarctic Ice Sheet Greenland South Pole |
geographic_facet |
Antarctic West Antarctic Ice Sheet Greenland South Pole |
genre |
Antarc* Antarctic Greenland Greenland ice core ice core Ice Sheet South pole South pole |
genre_facet |
Antarc* Antarctic Greenland Greenland ice core ice core Ice Sheet South pole South pole |
op_source |
Geological Sciences Faculty Contributions |
op_relation |
https://scholar.colorado.edu/geol_facpapers/8 https://scholar.colorado.edu/cgi/viewcontent.cgi?article=1011&context=geol_facpapers |
op_rights |
http://creativecommons.org/licenses/by/3.0/ |
op_rightsnorm |
CC-BY |
_version_ |
1766251940343185408 |