53903
2018
2018
eng
169
187
19
1
12
article
Copernicus
Göttingen
1
--
--
--
On the similarity and apparent cycles of isotopic variations in East Antarctic snow pits
Stable isotope ratios delta O-18 and delta D in polar ice provide a wealth of information about past climate evolution. Snow-pit studies allow us to relate observed weather and climate conditions to the measured isotope variations in the snow. They therefore offer the possibility to test our understanding of how isotope signals are formed and stored in firn and ice. As delta O-18 and delta D in the snowfall are strongly correlated to air temperature, isotopes in the near-surface snow are thought to record the seasonal cycle at a given site. Accordingly, the number of seasonal cycles observed over a given depth should depend on the accumulation rate of snow. However, snow-pit studies from different accumulation conditions in East Antarctica reported similar isotopic variability and comparable apparent cycles in the delta O-18 and delta D profiles with typical wavelengths of similar to 20 cm. These observations are unexpected as the accumulation rates strongly differ between the sites, ranging from 20 to 80mmw.e.yr(-1) (similar to 6-21 cm of snow per year). Various mechanisms have been proposed to explain the isotopic variations individually at each site; however, none of these are consistent with the similarity of the different profiles independent of the local accumulation conditions. Here, we systematically analyse the properties and origins of delta O-18 and delta D variations in high-resolution firn profiles from eight East Antarctic sites. First, we confirm the suggested cycle length (mean distance between peaks) of similar to 20 cm by counting the isotopic maxima. Spectral analysis further shows a strong similarity between the sites but indicates no dominant periodic features. Furthermore, the appar-ent cycle length increases with depth for most East Antarctic sites, which is inconsistent with burial and compression of a regular seasonal cycle. We show that these results can be explained by isotopic diffusion acting on a noise-dominated isotope signal. The firn diffusion length is rather stable across the Antarctic Plateau and thus leads to similar power spectral densities of the isotopic variations. This in turn implies a similar distance between isotopic maxima in the firn profiles. Our results explain a large set of observations discussed in the literature, providing a simple explanation for the interpretation of apparent cycles in shallow isotope records, without invoking complex mechanisms. Finally, the results underline previous suggestions that isotope signals in single ice cores from low-accumulation regions have a small signal-to-noise ratio and thus likely do not allow the reconstruction of interannual to decadal climate variations.
The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
10.5194/tc-12-169-2018
1994-0416
1994-0424
wos:2018
WOS:000422885300001
Laepple, T (reprint author), Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, Telegrafenberg A43, D-14473 Potsdam, Germany., thomas.laepple@awi.de
Initiative and Networking Fund of the Helmholtz Association grant Seventh Framework Programme (FP7)/RC grant [306045]; ERC under the
2022-02-14T16:35:01+00:00
sword
importub
filename=package.tar
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<a href="https://doi.org/10.25932/publishup-44605">Zweitveröffentlichung in der Schriftenreihe Postprints der Universität Potsdam : Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe ; 932 </a>
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CC-BY - Namensnennung 4.0 International
Thomas Laepple
Thomas Münch
Mathieu Casado
Maria Hoerhold
Amaelle Landais
Sepp Kipfstuhl
Geografie, Reisen
Institut für Geowissenschaften
Import
44605
2018
2020
eng
169
187
21
932
postprint
1
2020-06-02
2020-06-02
--
On the similarity and apparent cycles of isotopic variations in East Antarctic snow pits
Stable isotope ratios delta O-18 and delta D in polar ice provide a wealth of information about past climate evolution. Snow-pit studies allow us to relate observed weather and climate conditions to the measured isotope variations in the snow. They therefore offer the possibility to test our understanding of how isotope signals are formed and stored in firn and ice. As delta O-18 and delta D in the snowfall are strongly correlated to air temperature, isotopes in the near-surface snow are thought to record the seasonal cycle at a given site. Accordingly, the number of seasonal cycles observed over a given depth should depend on the accumulation rate of snow. However, snow-pit studies from different accumulation conditions in East Antarctica reported similar isotopic variability and comparable apparent cycles in the delta O-18 and delta D profiles with typical wavelengths of similar to 20 cm. These observations are unexpected as the accumulation rates strongly differ between the sites, ranging from 20 to 80mmw.e.yr(-1) (similar to 6-21 cm of snow per year). Various mechanisms have been proposed to explain the isotopic variations individually at each site; however, none of these are consistent with the similarity of the different profiles independent of the local accumulation conditions.
Here, we systematically analyse the properties and origins of delta O-18 and delta D variations in high-resolution firn profiles from eight East Antarctic sites. First, we confirm the suggested cycle length (mean distance between peaks) of similar to 20 cm by counting the isotopic maxima. Spectral analysis further shows a strong similarity between the sites but indicates no dominant periodic features. Furthermore, the appar-ent cycle length increases with depth for most East Antarctic sites, which is inconsistent with burial and compression of a regular seasonal cycle. We show that these results can be explained by isotopic diffusion acting on a noise-dominated isotope signal. The firn diffusion length is rather stable across the Antarctic Plateau and thus leads to similar power spectral densities of the isotopic variations. This in turn implies a similar distance between isotopic maxima in the firn profiles. Our results explain a large set of observations discussed in the literature, providing a simple explanation for the interpretation of apparent cycles in shallow isotope records, without invoking complex mechanisms. Finally, the results underline previous suggestions that isotope signals in single ice cores from low-accumulation regions have a small signal-to-noise ratio and thus likely do not allow the reconstruction of interannual to decadal climate variations.
Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
10.25932/publishup-44605
urn:nbn:de:kobv:517-opus4-446052
1866-8372
The Cryosphere 12 (2018) 169–187 DOI: 10.5194/tc-12-169-2018
<a href="http://publishup.uni-potsdam.de/53903">Bibliographieeintrag der Originalveröffentlichung/Quelle</a>
CC-BY - Namensnennung 4.0 International
Thomas Laepple
Thomas Münch
Mathieu Casado
Maria Hoerhold
Amaelle Landais
Sepp Kipfstuhl
Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
932
eng
uncontrolled
Dronning-Maud-Land
eng
uncontrolled
ice-core
eng
uncontrolled
climate variability
eng
uncontrolled
surface snow
eng
uncontrolled
stable-isotopes
eng
uncontrolled
water-isotopes
eng
uncontrolled
oxygen-isotope
eng
uncontrolled
south-pole
eng
uncontrolled
athmospheric circulation
eng
uncontrolled
mathematical-analysis
Geografie, Reisen
open_access
Mathematisch-Naturwissenschaftliche Fakultät
Referiert
Open Access
Universität Potsdam
https://publishup.uni-potsdam.de/files/44605/pmnr932.pdf
52876
2018
2018
eng
1745
1766
22
5
12
article
Copernicus
Göttingen
1
2018-05-24
2018-05-24
--
Archival processes of the water stable isotope signal in East Antarctic ice cores
The oldest ice core records are obtained from the East Antarctic Plateau. Water isotopes are key proxies to reconstructing past climatic conditions over the ice sheet and at the evaporation source. The accuracy of climate reconstructions depends on knowledge of all processes affecting water vapour, precipitation and snow isotopic compositions. Fractionation processes are well understood and can be integrated in trajectory-based Rayleigh distillation and isotope-enabled climate models. However, a quantitative understanding of processes potentially altering snow isotopic composition after deposition is still missing. In low-accumulation sites, such as those found in East Antarctica, these poorly constrained processes are likely to play a significant role and limit the interpretability of an ice core's isotopic composition.
By combining observations of isotopic composition in vapour, precipitation, surface snow and buried snow from Dome C, a deep ice core site on the East Antarctic Plateau, we found indications of a seasonal impact of metamorphism on the surface snow isotopic signal when compared to the initial precipitation. Particularly in summer, exchanges of water molecules between vapour and snow are driven by the diurnal sublimation-condensation cycles. Overall, we observe in between precipitation events modification of the surface snow isotopic composition. Using high-resolution water isotopic composition profiles from snow pits at five Antarctic sites with different accumulation rates, we identified common patterns which cannot be attributed to the seasonal variability of precipitation. These differences in the precipitation, surface snow and buried snow isotopic composition provide evidence of post-deposition processes affecting ice core records in low-accumulation areas.
The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
10.5194/tc-12-1745-2018
1994-0416
1994-0424
wos:2018
WOS:000433005400002
Casado, M (reprint author), CEA CNRS UVSQ UPS, Lab Sci Climat & Environm IPSL, UMR 8212, Gif Sur Yvette, France.; Casado, M (reprint author), Univ Grenoble Alpes, CNRS, LIPHY, F-38000 Grenoble, France., mathieu.casado@gmail.com
Programme (FP7)/RC grant [306045]; Initiative and Networking Fund of the Helmholtz Association Grant [VG-NH900]; LGGE; LIPHY
2021-11-30T08:51:58+00:00
sword
importub
filename=package.tar
00053b082b6a5226149448b531bb306c
Casado, Mathieu
<a href="https://doi.org/10.25932/publishup-42705">Zweitveröffentlichung in der Schriftenreihe Postprints der Universität Potsdam : Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe ; 716 </a>
CC-BY - Namensnennung 4.0 International
Mathieu Casado
Amaelle Landais
Ghislain Picard
Thomas Münch
Thomas Laepple
Barbara Stenni
Giuliano Dreossi
Alexey Ekaykin
Laurent Arnaud
Christophe Genthon
Alexandra Touzeau
Valerie Masson-Delmotte
Jean Jouzel
Geowissenschaften
Institut für Geowissenschaften
Referiert
Import
Gold Open-Access
DOAJ gelistet
42705
2018
2019
eng
22
716
postprint
1
2019-05-28
2019-05-28
--
Archival processes of the water stable isotope signal in East Antarctic ice cores
The oldest ice core records are obtained from the East Antarctic Plateau. Water isotopes are key proxies to reconstructing past climatic conditions over the ice sheet and at the evaporation source. The accuracy of climate reconstructions depends on knowledge of all processes affecting water vapour, precipitation and snow isotopic compositions. Fractionation processes are well understood and can be integrated in trajectory-based Rayleigh distillation and isotope-enabled climate models. However, a quantitative understanding of processes potentially altering snow isotopic composition after deposition is still missing. In low-accumulation sites, such as those found in East Antarctica, these poorly constrained processes are likely to play a significant role and limit the interpretability of an ice core's isotopic composition.
By combining observations of isotopic composition in vapour, precipitation, surface snow and buried snow from Dome C, a deep ice core site on the East Antarctic Plateau, we found indications of a seasonal impact of metamorphism on the surface snow isotopic signal when compared to the initial precipitation. Particularly in summer, exchanges of water molecules between vapour and snow are driven by the diurnal sublimation-condensation cycles. Overall, we observe in between precipitation events modification of the surface snow isotopic composition. Using high-resolution water isotopic composition profiles from snow pits at five Antarctic sites with different accumulation rates, we identified common patterns which cannot be attributed to the seasonal variability of precipitation. These differences in the precipitation, surface snow and buried snow isotopic composition provide evidence of post-deposition processes affecting ice core records in low-accumulation areas.
Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
urn:nbn:de:kobv:517-opus4-427054
1866-8372
10.25932/publishup-42705
online registration
The Cryosphere 12 (2018) 5, S. 1745–1766 DOI: 10.5194/tc-12-1745-2018
<a href="http://publishup.uni-potsdam.de/52876">Bibliographieeintrag der Originalveröffentlichung/Quelle</a>
CC-BY - Namensnennung 4.0 International
Mathieu Casado
Amaelle Landais
Ghislain Picard
Thomas Münch
Thomas Laepple
Barbara Stenni
Giuliano Dreossi
Alexey Ekaykin
Laurent Arnaud
Christophe Genthon
Alexandra Touzeau
Valerie Masson-Delmotte
Jean Jouzel
Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
716
eng
uncontrolled
dronning maud-land
eng
uncontrolled
shallow firn cores
eng
uncontrolled
near-surface snow
eng
uncontrolled
Dome C
eng
uncontrolled
Kohnen station
eng
uncontrolled
South Pole
eng
uncontrolled
climate varibility
eng
uncontrolled
Vostok station
eng
uncontrolled
deuterium content
eng
uncontrolled
GCM analysis
Geografie, Reisen
open_access
Mathematisch-Naturwissenschaftliche Fakultät
Referiert
Open Access
Copernicus
Universität Potsdam
https://publishup.uni-potsdam.de/files/42705/pmnr716.pdf