Microstructure of West Antarctic Firn and its Effect on Air Permeability
The microstructure of snow and firn has a great impact on the transport of chemical species from the atmosphere to the underlying firn. For improved ice core interpretation, it is important to understand air-snow interactions within the firs layers and how they are affected by snow microstructure. P...
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ftdtic:ADA426837 2023-05-15T13:38:48+02:00 Microstructure of West Antarctic Firn and its Effect on Air Permeability Rick, Ursula Albert, Mary ENGINEER RESEARCH AND DEVELOPMENT CENTER HANOVER NH COLD REGIONS RESEARCH AND ENGINEERING LAB 2004-09 text/html http://www.dtic.mil/docs/citations/ADA426837 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA426837 en eng http://www.dtic.mil/docs/citations/ADA426837 APPROVED FOR PUBLIC RELEASE DTIC AND NTIS Snow Ice and Permafrost *MICROSTRUCTURE *ICE FORMATION *SNOW THICKNESS LOW TEMPERATURE PERMEABILITY HIGH RATE WEATHER GRAIN SIZE SEASONAL VARIATIONS TEMPERATURE GRADIENTS CLIMATE MEAN ACCUMULATION GRAIN GROWTH DIURNAL VARIATIONS METAMORPHOSIS *WEST ANTARTIC FIRN *AIR PERMEABILITY ANTARTICA ICE CORES ICE STRUCTURES GLACIAL FIRN ICE VEINS AIR SNOW INTERACTIONS SNOW MICROSTRUCTURE ITASE(INTERNATIONAL TRANS ANTARCTIC SCIENCE EXPEDITION) METAMORPHISM Text 2004 ftdtic 2016-02-21T09:02:08Z The microstructure of snow and firn has a great impact on the transport of chemical species from the atmosphere to the underlying firn. For improved ice core interpretation, it is important to understand air-snow interactions within the firs layers and how they are affected by snow microstructure. Permeability and thick-section microstructure measurements have been made from snowpit and firn core samples retrieved during the U.S.-International Trans-Antarctic Science Expedition (ITASE) 1999-2001 field seasons. Our measurements have shown that the permeability of the snow at all of the sites generally increases with depth into the firn to about 3 m, then decreases due to microstructure changes, although at several sites there were areas of increased permeability at depth because of local changes in weather and climate. Thick-section microstructure measurements show that the grain size generally increases with depth, and the specific surface decreases with depth. Rapid grain growth is caused by diurnal and seasonal temperature gradients near the surface. Deeper in the core, the grain growth slows as the firn temperature gradients become small. The grain growth and specific surface trends do not follow those of the permeability. Pore size correlates well with the permeability of the snow samples; a formula was developed that predicts the firs permeability from pore characteristics. in addition to variation with depth in the core, the permeability and microstructure vary greatly from site to site, revealing that meteorological-effects, such as accumulation rate and mean annual temperature, are important factors in shaping the firn micro structure. High accumulation rates or low mean annual temperatures will result in low permeability due to little or no metamorphism in the firn, although accumulation rate seems to be the dominant factor. Text Antarc* Antarctic antartic* Ice ice core permafrost Defense Technical Information Center: DTIC Technical Reports database Antarctic |
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Open Polar |
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Defense Technical Information Center: DTIC Technical Reports database |
op_collection_id |
ftdtic |
language |
English |
topic |
Snow Ice and Permafrost *MICROSTRUCTURE *ICE FORMATION *SNOW THICKNESS LOW TEMPERATURE PERMEABILITY HIGH RATE WEATHER GRAIN SIZE SEASONAL VARIATIONS TEMPERATURE GRADIENTS CLIMATE MEAN ACCUMULATION GRAIN GROWTH DIURNAL VARIATIONS METAMORPHOSIS *WEST ANTARTIC FIRN *AIR PERMEABILITY ANTARTICA ICE CORES ICE STRUCTURES GLACIAL FIRN ICE VEINS AIR SNOW INTERACTIONS SNOW MICROSTRUCTURE ITASE(INTERNATIONAL TRANS ANTARCTIC SCIENCE EXPEDITION) METAMORPHISM |
spellingShingle |
Snow Ice and Permafrost *MICROSTRUCTURE *ICE FORMATION *SNOW THICKNESS LOW TEMPERATURE PERMEABILITY HIGH RATE WEATHER GRAIN SIZE SEASONAL VARIATIONS TEMPERATURE GRADIENTS CLIMATE MEAN ACCUMULATION GRAIN GROWTH DIURNAL VARIATIONS METAMORPHOSIS *WEST ANTARTIC FIRN *AIR PERMEABILITY ANTARTICA ICE CORES ICE STRUCTURES GLACIAL FIRN ICE VEINS AIR SNOW INTERACTIONS SNOW MICROSTRUCTURE ITASE(INTERNATIONAL TRANS ANTARCTIC SCIENCE EXPEDITION) METAMORPHISM Rick, Ursula Albert, Mary Microstructure of West Antarctic Firn and its Effect on Air Permeability |
topic_facet |
Snow Ice and Permafrost *MICROSTRUCTURE *ICE FORMATION *SNOW THICKNESS LOW TEMPERATURE PERMEABILITY HIGH RATE WEATHER GRAIN SIZE SEASONAL VARIATIONS TEMPERATURE GRADIENTS CLIMATE MEAN ACCUMULATION GRAIN GROWTH DIURNAL VARIATIONS METAMORPHOSIS *WEST ANTARTIC FIRN *AIR PERMEABILITY ANTARTICA ICE CORES ICE STRUCTURES GLACIAL FIRN ICE VEINS AIR SNOW INTERACTIONS SNOW MICROSTRUCTURE ITASE(INTERNATIONAL TRANS ANTARCTIC SCIENCE EXPEDITION) METAMORPHISM |
description |
The microstructure of snow and firn has a great impact on the transport of chemical species from the atmosphere to the underlying firn. For improved ice core interpretation, it is important to understand air-snow interactions within the firs layers and how they are affected by snow microstructure. Permeability and thick-section microstructure measurements have been made from snowpit and firn core samples retrieved during the U.S.-International Trans-Antarctic Science Expedition (ITASE) 1999-2001 field seasons. Our measurements have shown that the permeability of the snow at all of the sites generally increases with depth into the firn to about 3 m, then decreases due to microstructure changes, although at several sites there were areas of increased permeability at depth because of local changes in weather and climate. Thick-section microstructure measurements show that the grain size generally increases with depth, and the specific surface decreases with depth. Rapid grain growth is caused by diurnal and seasonal temperature gradients near the surface. Deeper in the core, the grain growth slows as the firn temperature gradients become small. The grain growth and specific surface trends do not follow those of the permeability. Pore size correlates well with the permeability of the snow samples; a formula was developed that predicts the firs permeability from pore characteristics. in addition to variation with depth in the core, the permeability and microstructure vary greatly from site to site, revealing that meteorological-effects, such as accumulation rate and mean annual temperature, are important factors in shaping the firn micro structure. High accumulation rates or low mean annual temperatures will result in low permeability due to little or no metamorphism in the firn, although accumulation rate seems to be the dominant factor. |
author2 |
ENGINEER RESEARCH AND DEVELOPMENT CENTER HANOVER NH COLD REGIONS RESEARCH AND ENGINEERING LAB |
format |
Text |
author |
Rick, Ursula Albert, Mary |
author_facet |
Rick, Ursula Albert, Mary |
author_sort |
Rick, Ursula |
title |
Microstructure of West Antarctic Firn and its Effect on Air Permeability |
title_short |
Microstructure of West Antarctic Firn and its Effect on Air Permeability |
title_full |
Microstructure of West Antarctic Firn and its Effect on Air Permeability |
title_fullStr |
Microstructure of West Antarctic Firn and its Effect on Air Permeability |
title_full_unstemmed |
Microstructure of West Antarctic Firn and its Effect on Air Permeability |
title_sort |
microstructure of west antarctic firn and its effect on air permeability |
publishDate |
2004 |
url |
http://www.dtic.mil/docs/citations/ADA426837 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA426837 |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic antartic* Ice ice core permafrost |
genre_facet |
Antarc* Antarctic antartic* Ice ice core permafrost |
op_source |
DTIC AND NTIS |
op_relation |
http://www.dtic.mil/docs/citations/ADA426837 |
op_rights |
APPROVED FOR PUBLIC RELEASE |
_version_ |
1766111313847648256 |