The influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice
Air bubbles found in polar ice cores preserve a record of past atmospheric composition up to 800 kyr back in time. The composition of the bubbles is not identical to the ancient atmosphere, as it is influenced by processes prior to trapping, within the ice sheet itself, and during sampling and stora...
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Niels Bohr Institutet
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Online Access: | https://curis.ku.dk/portal/da/publications/the-influence-of-firn-air-transport-processes-and-radiocarbon-production-on-gas-records-from-polar-firn-and-ice(5f7dc4c3-6a0f-4b69-89bb-61ee9e0b4c42).html https://curis.ku.dk/ws/files/40868858/Buizert.pdf |
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ftcopenhagenunip:oai:pure.atira.dk:publications/5f7dc4c3-6a0f-4b69-89bb-61ee9e0b4c42 2023-05-15T16:30:33+02:00 The influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice Buizert, Christo 2012 application/pdf https://curis.ku.dk/portal/da/publications/the-influence-of-firn-air-transport-processes-and-radiocarbon-production-on-gas-records-from-polar-firn-and-ice(5f7dc4c3-6a0f-4b69-89bb-61ee9e0b4c42).html https://curis.ku.dk/ws/files/40868858/Buizert.pdf eng eng Niels Bohr Institutet info:eu-repo/semantics/restrictedAccess Buizert , C 2012 , The influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice . Niels Bohr Institutet , Center for Ice & Climate . book 2012 ftcopenhagenunip 2021-09-23T17:17:03Z Air bubbles found in polar ice cores preserve a record of past atmospheric composition up to 800 kyr back in time. The composition of the bubbles is not identical to the ancient atmosphere, as it is influenced by processes prior to trapping, within the ice sheet itself, and during sampling and storage. Understanding of these processes is essential for a correct interpretation of ice core gas records. In this work we focus on transport processes in the porous firn layer prior to bubble trapping, and in situ cosmogenic radiocarbon ( 14 C) production in ice. First, we present a review of firn air studies. We describe the firn air sampling process, the relevant physical characteristics of firn, the different mechanisms of air transport, and the effects of firn air transport on gas records. Second, we present a characterization of the firn air transport properties of the NEEM deep drilling site in Northern Greenland (77.45 o N 51.06 o W). The depthdiffusivity relationship needs to be reconstructed using reference tracers of known atmospheric history. We present a novel method of characterizing the firn transport using ten tracers simultaneously, thus constraining the effective diffusivity better than the commonly used single-tracer method would. A comparison between two replicate boreholes drilled 64m apart shows differences in measured mixing ratio profiles that exceed the experimental error, which we attribute to lateral inhomogeneities in firn stratigraphy. We find evidence that diffusivity does not vanish completely in the lock-in zone, as is commonly assumed. Six state-of-the-art firn air transport models are tuned to the NEEM site; all models successfully reproduce the data within a 1 Gaussian distribution. We present the first intercomparison study of firn air models, where we introduce diagnostic scenarios designed to probe speciffc aspects of the model physics. Our results show that there are major di erences in the way the models handle advective transport, and that dffusive fractionation of isotopes in the firn is poorly constrained by the models. Book Greenland ice core Ice Sheet University of Copenhagen: Research Greenland |
institution |
Open Polar |
collection |
University of Copenhagen: Research |
op_collection_id |
ftcopenhagenunip |
language |
English |
description |
Air bubbles found in polar ice cores preserve a record of past atmospheric composition up to 800 kyr back in time. The composition of the bubbles is not identical to the ancient atmosphere, as it is influenced by processes prior to trapping, within the ice sheet itself, and during sampling and storage. Understanding of these processes is essential for a correct interpretation of ice core gas records. In this work we focus on transport processes in the porous firn layer prior to bubble trapping, and in situ cosmogenic radiocarbon ( 14 C) production in ice. First, we present a review of firn air studies. We describe the firn air sampling process, the relevant physical characteristics of firn, the different mechanisms of air transport, and the effects of firn air transport on gas records. Second, we present a characterization of the firn air transport properties of the NEEM deep drilling site in Northern Greenland (77.45 o N 51.06 o W). The depthdiffusivity relationship needs to be reconstructed using reference tracers of known atmospheric history. We present a novel method of characterizing the firn transport using ten tracers simultaneously, thus constraining the effective diffusivity better than the commonly used single-tracer method would. A comparison between two replicate boreholes drilled 64m apart shows differences in measured mixing ratio profiles that exceed the experimental error, which we attribute to lateral inhomogeneities in firn stratigraphy. We find evidence that diffusivity does not vanish completely in the lock-in zone, as is commonly assumed. Six state-of-the-art firn air transport models are tuned to the NEEM site; all models successfully reproduce the data within a 1 Gaussian distribution. We present the first intercomparison study of firn air models, where we introduce diagnostic scenarios designed to probe speciffc aspects of the model physics. Our results show that there are major di erences in the way the models handle advective transport, and that dffusive fractionation of isotopes in the firn is poorly constrained by the models. |
format |
Book |
author |
Buizert, Christo |
spellingShingle |
Buizert, Christo The influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice |
author_facet |
Buizert, Christo |
author_sort |
Buizert, Christo |
title |
The influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice |
title_short |
The influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice |
title_full |
The influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice |
title_fullStr |
The influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice |
title_full_unstemmed |
The influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice |
title_sort |
influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice |
publisher |
Niels Bohr Institutet |
publishDate |
2012 |
url |
https://curis.ku.dk/portal/da/publications/the-influence-of-firn-air-transport-processes-and-radiocarbon-production-on-gas-records-from-polar-firn-and-ice(5f7dc4c3-6a0f-4b69-89bb-61ee9e0b4c42).html https://curis.ku.dk/ws/files/40868858/Buizert.pdf |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland ice core Ice Sheet |
genre_facet |
Greenland ice core Ice Sheet |
op_source |
Buizert , C 2012 , The influence of firn air transport processes and radiocarbon production on gas records from polar firn and ice . Niels Bohr Institutet , Center for Ice & Climate . |
op_rights |
info:eu-repo/semantics/restrictedAccess |
_version_ |
1766020285437313024 |