Impurity controlled firn densification
Models of firn densification are a necessary requisite for dating air inclusions in polar ice cores. Previous densification models assume a homogenous firn column where densification is mainly dependent on accumulation rate, temperature and surface density. From measured density profiles with a vert...
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ftawi:oai:epic.awi.de:33830 2023-05-15T13:40:26+02:00 Impurity controlled firn densification Freitag, Johannes Kipfstuhl, Sepp Hörhold, Maria Wegner, Anna Wilhelms, Frank Bigler, Matthias 2012-04-23 https://epic.awi.de/id/eprint/33830/ https://hdl.handle.net/10013/epic.42161 unknown Freitag, J. orcid:0000-0003-2654-9440 , Kipfstuhl, S. , Hörhold, M. , Wegner, A. , Wilhelms, F. orcid:0000-0001-7688-3135 and Bigler, M. (2012) Impurity controlled firn densification , EGU Meeting, Vienna, 22 April 2012 - 27 April 2012 . hdl:10013/epic.42161 EPIC3EGU Meeting, Vienna, 2012-04-22-2012-04-27 Conference notRev 2012 ftawi 2021-12-24T15:38:56Z Models of firn densification are a necessary requisite for dating air inclusions in polar ice cores. Previous densification models assume a homogenous firn column where densification is mainly dependent on accumulation rate, temperature and surface density. From measured density profiles with a vertical resolution of millimetres it is known that firn is a layered medium with considerable porosity variations at the firn-ice transition (sometimes more than 50 percent in adjacent layers). Very recently it turned out that the density (porosity) variations in deep firn are linked to variations of the Ca++ concentration which points to an impurity effect on densification. In our contribution we will present the first densification model for layered firn that accounts for the impurity effect. In the model the impurity effect is parameterized by the Ca++ concentration. The impurities are assumed to act like a catalyst: they increase the densification rate by reducing the activation energy. The model is applied to firn from Greenland (B26) and Antarctica (B36, EDML, EDC). The simulations are fitted on measured density profiles to find reasonable model input parameters for the impurity effect in recent firn. The derived parameterization is used to simulate the densification in Glacial periods in Antarctica and Greenland. Applying our model to Glacial conditions on the Antarctic plateau the firn column is reduced as it is suggested by d15N measurements without assuming convective zones of several tens of meters. Conference Object Antarc* Antarctic Antarctica Greenland Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) Antarctic Greenland The Antarctic |
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Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) |
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Models of firn densification are a necessary requisite for dating air inclusions in polar ice cores. Previous densification models assume a homogenous firn column where densification is mainly dependent on accumulation rate, temperature and surface density. From measured density profiles with a vertical resolution of millimetres it is known that firn is a layered medium with considerable porosity variations at the firn-ice transition (sometimes more than 50 percent in adjacent layers). Very recently it turned out that the density (porosity) variations in deep firn are linked to variations of the Ca++ concentration which points to an impurity effect on densification. In our contribution we will present the first densification model for layered firn that accounts for the impurity effect. In the model the impurity effect is parameterized by the Ca++ concentration. The impurities are assumed to act like a catalyst: they increase the densification rate by reducing the activation energy. The model is applied to firn from Greenland (B26) and Antarctica (B36, EDML, EDC). The simulations are fitted on measured density profiles to find reasonable model input parameters for the impurity effect in recent firn. The derived parameterization is used to simulate the densification in Glacial periods in Antarctica and Greenland. Applying our model to Glacial conditions on the Antarctic plateau the firn column is reduced as it is suggested by d15N measurements without assuming convective zones of several tens of meters. |
format |
Conference Object |
author |
Freitag, Johannes Kipfstuhl, Sepp Hörhold, Maria Wegner, Anna Wilhelms, Frank Bigler, Matthias |
spellingShingle |
Freitag, Johannes Kipfstuhl, Sepp Hörhold, Maria Wegner, Anna Wilhelms, Frank Bigler, Matthias Impurity controlled firn densification |
author_facet |
Freitag, Johannes Kipfstuhl, Sepp Hörhold, Maria Wegner, Anna Wilhelms, Frank Bigler, Matthias |
author_sort |
Freitag, Johannes |
title |
Impurity controlled firn densification |
title_short |
Impurity controlled firn densification |
title_full |
Impurity controlled firn densification |
title_fullStr |
Impurity controlled firn densification |
title_full_unstemmed |
Impurity controlled firn densification |
title_sort |
impurity controlled firn densification |
publishDate |
2012 |
url |
https://epic.awi.de/id/eprint/33830/ https://hdl.handle.net/10013/epic.42161 |
geographic |
Antarctic Greenland The Antarctic |
geographic_facet |
Antarctic Greenland The Antarctic |
genre |
Antarc* Antarctic Antarctica Greenland |
genre_facet |
Antarc* Antarctic Antarctica Greenland |
op_source |
EPIC3EGU Meeting, Vienna, 2012-04-22-2012-04-27 |
op_relation |
Freitag, J. orcid:0000-0003-2654-9440 , Kipfstuhl, S. , Hörhold, M. , Wegner, A. , Wilhelms, F. orcid:0000-0001-7688-3135 and Bigler, M. (2012) Impurity controlled firn densification , EGU Meeting, Vienna, 22 April 2012 - 27 April 2012 . hdl:10013/epic.42161 |
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1766133662906056704 |