Gas isotope thermometry in the South Pole and Dome Fuji ice cores provides evidence for seasonal rectification of ice core gas records
Gas isotope thermometry using the isotopes of molecular nitrogen and argon has been used extensively to reconstruct past surface temperature change from Greenland ice cores. The gas isotope ratios δ 15 N and δ 40 Ar in the ice core are each set by the amount of gravitational and thermal fractionatio...
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Copernicus Publications
2022
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Online Access: | https://doi.org/10.5194/tc-16-2947-2022 https://doaj.org/article/bdaef5e5e2634fdc97006d6eac08b603 |
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ftdoajarticles:oai:doaj.org/article:bdaef5e5e2634fdc97006d6eac08b603 2023-05-15T13:58:34+02:00 Gas isotope thermometry in the South Pole and Dome Fuji ice cores provides evidence for seasonal rectification of ice core gas records J. D. Morgan C. Buizert T. J. Fudge K. Kawamura J. P. Severinghaus C. M. Trudinger 2022-07-01T00:00:00Z https://doi.org/10.5194/tc-16-2947-2022 https://doaj.org/article/bdaef5e5e2634fdc97006d6eac08b603 EN eng Copernicus Publications https://tc.copernicus.org/articles/16/2947/2022/tc-16-2947-2022.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-16-2947-2022 1994-0416 1994-0424 https://doaj.org/article/bdaef5e5e2634fdc97006d6eac08b603 The Cryosphere, Vol 16, Pp 2947-2966 (2022) Environmental sciences GE1-350 Geology QE1-996.5 article 2022 ftdoajarticles https://doi.org/10.5194/tc-16-2947-2022 2022-12-30T23:17:40Z Gas isotope thermometry using the isotopes of molecular nitrogen and argon has been used extensively to reconstruct past surface temperature change from Greenland ice cores. The gas isotope ratios δ 15 N and δ 40 Ar in the ice core are each set by the amount of gravitational and thermal fractionation in the firn. The gravitational component of fractionation is proportional to the firn thickness, and the thermal component is proportional to the temperature difference between the top and bottom of the firn column, which can be related to surface temperature change. Compared to Greenland, Antarctic climate change is typically more gradual and smaller in magnitude, which results in smaller thermal fractionation signals that are harder to detect. This has hampered application of gas isotope thermometry to Antarctic ice cores. Here, we present an analytical method for measuring δ 15 N and δ 40 Ar with a precision of 0.002 ‰ per atomic mass unit, a two-fold improvement on previous work. This allows us to reconstruct changes in firn thickness and temperature difference at the South Pole between 30 and 5 kyr BP. We find that variability in firn thickness is controlled in part by changes in snow accumulation rate, which is, in turn, influenced strongly by the along-flowline topography upstream of the ice core site. Variability in our firn temperature difference record cannot be explained by annual-mean processes. We therefore propose that the ice core gas isotopes contain a seasonal bias due to rectification of seasonal signals in the upper firn. The strength of the rectification also appears to be linked to fluctuations in the upstream topography. As further evidence for the existence of rectification, we present new data from the Dome Fuji ice core that are also consistent with a seasonal bias throughout the Holocene. Our findings have important implications for the interpretation of ice core gas records. For example, we show that the effects of upstream topography on ice core records can be significant at flank sites ... Article in Journal/Newspaper Antarc* Antarctic Greenland Greenland ice cores ice core South pole South pole The Cryosphere Directory of Open Access Journals: DOAJ Articles Antarctic Dome Fuji ENVELOPE(39.700,39.700,-77.317,-77.317) Greenland South Pole The Cryosphere 16 7 2947 2966 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental sciences GE1-350 Geology QE1-996.5 |
spellingShingle |
Environmental sciences GE1-350 Geology QE1-996.5 J. D. Morgan C. Buizert T. J. Fudge K. Kawamura J. P. Severinghaus C. M. Trudinger Gas isotope thermometry in the South Pole and Dome Fuji ice cores provides evidence for seasonal rectification of ice core gas records |
topic_facet |
Environmental sciences GE1-350 Geology QE1-996.5 |
description |
Gas isotope thermometry using the isotopes of molecular nitrogen and argon has been used extensively to reconstruct past surface temperature change from Greenland ice cores. The gas isotope ratios δ 15 N and δ 40 Ar in the ice core are each set by the amount of gravitational and thermal fractionation in the firn. The gravitational component of fractionation is proportional to the firn thickness, and the thermal component is proportional to the temperature difference between the top and bottom of the firn column, which can be related to surface temperature change. Compared to Greenland, Antarctic climate change is typically more gradual and smaller in magnitude, which results in smaller thermal fractionation signals that are harder to detect. This has hampered application of gas isotope thermometry to Antarctic ice cores. Here, we present an analytical method for measuring δ 15 N and δ 40 Ar with a precision of 0.002 ‰ per atomic mass unit, a two-fold improvement on previous work. This allows us to reconstruct changes in firn thickness and temperature difference at the South Pole between 30 and 5 kyr BP. We find that variability in firn thickness is controlled in part by changes in snow accumulation rate, which is, in turn, influenced strongly by the along-flowline topography upstream of the ice core site. Variability in our firn temperature difference record cannot be explained by annual-mean processes. We therefore propose that the ice core gas isotopes contain a seasonal bias due to rectification of seasonal signals in the upper firn. The strength of the rectification also appears to be linked to fluctuations in the upstream topography. As further evidence for the existence of rectification, we present new data from the Dome Fuji ice core that are also consistent with a seasonal bias throughout the Holocene. Our findings have important implications for the interpretation of ice core gas records. For example, we show that the effects of upstream topography on ice core records can be significant at flank sites ... |
format |
Article in Journal/Newspaper |
author |
J. D. Morgan C. Buizert T. J. Fudge K. Kawamura J. P. Severinghaus C. M. Trudinger |
author_facet |
J. D. Morgan C. Buizert T. J. Fudge K. Kawamura J. P. Severinghaus C. M. Trudinger |
author_sort |
J. D. Morgan |
title |
Gas isotope thermometry in the South Pole and Dome Fuji ice cores provides evidence for seasonal rectification of ice core gas records |
title_short |
Gas isotope thermometry in the South Pole and Dome Fuji ice cores provides evidence for seasonal rectification of ice core gas records |
title_full |
Gas isotope thermometry in the South Pole and Dome Fuji ice cores provides evidence for seasonal rectification of ice core gas records |
title_fullStr |
Gas isotope thermometry in the South Pole and Dome Fuji ice cores provides evidence for seasonal rectification of ice core gas records |
title_full_unstemmed |
Gas isotope thermometry in the South Pole and Dome Fuji ice cores provides evidence for seasonal rectification of ice core gas records |
title_sort |
gas isotope thermometry in the south pole and dome fuji ice cores provides evidence for seasonal rectification of ice core gas records |
publisher |
Copernicus Publications |
publishDate |
2022 |
url |
https://doi.org/10.5194/tc-16-2947-2022 https://doaj.org/article/bdaef5e5e2634fdc97006d6eac08b603 |
long_lat |
ENVELOPE(39.700,39.700,-77.317,-77.317) |
geographic |
Antarctic Dome Fuji Greenland South Pole |
geographic_facet |
Antarctic Dome Fuji Greenland South Pole |
genre |
Antarc* Antarctic Greenland Greenland ice cores ice core South pole South pole The Cryosphere |
genre_facet |
Antarc* Antarctic Greenland Greenland ice cores ice core South pole South pole The Cryosphere |
op_source |
The Cryosphere, Vol 16, Pp 2947-2966 (2022) |
op_relation |
https://tc.copernicus.org/articles/16/2947/2022/tc-16-2947-2022.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-16-2947-2022 1994-0416 1994-0424 https://doaj.org/article/bdaef5e5e2634fdc97006d6eac08b603 |
op_doi |
https://doi.org/10.5194/tc-16-2947-2022 |
container_title |
The Cryosphere |
container_volume |
16 |
container_issue |
7 |
container_start_page |
2947 |
op_container_end_page |
2966 |
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1766266931072991232 |