Dispersion in deep polar firn driven by synoptic-scale surface pressure variability
Commonly, three mechanisms of firn air transport are distinguished: molecular diffusion, advection, and near-surface convective mixing. Here we identify and describe a fourth mechanism, namely dispersion driven by synoptic-scale surface pressure variability (or barometric pumping). We use published...
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Copernicus Publications
2016
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fttriple:oai:gotriple.eu:oai:doaj.org/article:3bdf094c4fae4b8bac3896c1fd0b7d51 2023-05-15T18:32:17+02:00 Dispersion in deep polar firn driven by synoptic-scale surface pressure variability C. Buizert J. P. Severinghaus 2016-09-01 https://doi.org/10.5194/tc-10-2099-2016 https://www.the-cryosphere.net/10/2099/2016/tc-10-2099-2016.pdf https://doaj.org/article/3bdf094c4fae4b8bac3896c1fd0b7d51 en eng Copernicus Publications doi:10.5194/tc-10-2099-2016 1994-0416 1994-0424 https://www.the-cryosphere.net/10/2099/2016/tc-10-2099-2016.pdf https://doaj.org/article/3bdf094c4fae4b8bac3896c1fd0b7d51 undefined The Cryosphere, Vol 10, Pp 2099-2111 (2016) geo envir Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2016 fttriple https://doi.org/10.5194/tc-10-2099-2016 2023-01-22T18:03:49Z Commonly, three mechanisms of firn air transport are distinguished: molecular diffusion, advection, and near-surface convective mixing. Here we identify and describe a fourth mechanism, namely dispersion driven by synoptic-scale surface pressure variability (or barometric pumping). We use published gas chromatography experiments on firn samples to derive the along-flow dispersivity of firn, and combine this dispersivity with a dynamical air pressure propagation model forced by surface air pressure time series to estimate the magnitude of dispersive mixing in the firn. We show that dispersion dominates mixing within the firn lock-in zone. Trace gas concentrations measured in firn air samples from various polar sites confirm that dispersive mixing occurs. Including dispersive mixing in a firn air transport model suggests that our theoretical estimates have the correct order of magnitude, yet may overestimate the true dispersion. We further show that strong barometric pumping, such as at the Law Dome site, may reduce the gravitational enrichment of δ15N–N2 and other tracers below gravitational equilibrium, questioning the traditional definition of the lock-in depth as the depth where δ15N enrichment ceases. Last, we propose that 86Kr excess may act as a proxy for past synoptic activity (or paleo-storminess) at the site. Article in Journal/Newspaper The Cryosphere Unknown Law Dome ENVELOPE(112.833,112.833,-66.733,-66.733) The Cryosphere 10 5 2099 2111 |
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language |
English |
topic |
geo envir |
spellingShingle |
geo envir C. Buizert J. P. Severinghaus Dispersion in deep polar firn driven by synoptic-scale surface pressure variability |
topic_facet |
geo envir |
description |
Commonly, three mechanisms of firn air transport are distinguished: molecular diffusion, advection, and near-surface convective mixing. Here we identify and describe a fourth mechanism, namely dispersion driven by synoptic-scale surface pressure variability (or barometric pumping). We use published gas chromatography experiments on firn samples to derive the along-flow dispersivity of firn, and combine this dispersivity with a dynamical air pressure propagation model forced by surface air pressure time series to estimate the magnitude of dispersive mixing in the firn. We show that dispersion dominates mixing within the firn lock-in zone. Trace gas concentrations measured in firn air samples from various polar sites confirm that dispersive mixing occurs. Including dispersive mixing in a firn air transport model suggests that our theoretical estimates have the correct order of magnitude, yet may overestimate the true dispersion. We further show that strong barometric pumping, such as at the Law Dome site, may reduce the gravitational enrichment of δ15N–N2 and other tracers below gravitational equilibrium, questioning the traditional definition of the lock-in depth as the depth where δ15N enrichment ceases. Last, we propose that 86Kr excess may act as a proxy for past synoptic activity (or paleo-storminess) at the site. |
format |
Article in Journal/Newspaper |
author |
C. Buizert J. P. Severinghaus |
author_facet |
C. Buizert J. P. Severinghaus |
author_sort |
C. Buizert |
title |
Dispersion in deep polar firn driven by synoptic-scale surface pressure variability |
title_short |
Dispersion in deep polar firn driven by synoptic-scale surface pressure variability |
title_full |
Dispersion in deep polar firn driven by synoptic-scale surface pressure variability |
title_fullStr |
Dispersion in deep polar firn driven by synoptic-scale surface pressure variability |
title_full_unstemmed |
Dispersion in deep polar firn driven by synoptic-scale surface pressure variability |
title_sort |
dispersion in deep polar firn driven by synoptic-scale surface pressure variability |
publisher |
Copernicus Publications |
publishDate |
2016 |
url |
https://doi.org/10.5194/tc-10-2099-2016 https://www.the-cryosphere.net/10/2099/2016/tc-10-2099-2016.pdf https://doaj.org/article/3bdf094c4fae4b8bac3896c1fd0b7d51 |
long_lat |
ENVELOPE(112.833,112.833,-66.733,-66.733) |
geographic |
Law Dome |
geographic_facet |
Law Dome |
genre |
The Cryosphere |
genre_facet |
The Cryosphere |
op_source |
The Cryosphere, Vol 10, Pp 2099-2111 (2016) |
op_relation |
doi:10.5194/tc-10-2099-2016 1994-0416 1994-0424 https://www.the-cryosphere.net/10/2099/2016/tc-10-2099-2016.pdf https://doaj.org/article/3bdf094c4fae4b8bac3896c1fd0b7d51 |
op_rights |
undefined |
op_doi |
https://doi.org/10.5194/tc-10-2099-2016 |
container_title |
The Cryosphere |
container_volume |
10 |
container_issue |
5 |
container_start_page |
2099 |
op_container_end_page |
2111 |
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1766216388574183424 |