A three-dimensional theory of wind pumping
Abstract Quantitative understanding of the processes that couple the lower atmosphere to the upper surface of ice sheets is necessary for interpreting ice-core records. Of special interest are those processes that involve the exchange of energy or atmospheric constituents. One such process, wind pum...
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Language: | English |
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Cambridge University Press (CUP)
1991
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Online Access: | http://dx.doi.org/10.1017/s0022143000042830 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000042830 |
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crcambridgeupr:10.1017/s0022143000042830 2024-04-28T08:11:53+00:00 A three-dimensional theory of wind pumping Clarke, Garry K. C. Waddington, Edwin D. 1991 http://dx.doi.org/10.1017/s0022143000042830 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000042830 en eng Cambridge University Press (CUP) Journal of Glaciology volume 37, issue 125, page 89-96 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1991 crcambridgeupr https://doi.org/10.1017/s0022143000042830 2024-04-09T06:55:43Z Abstract Quantitative understanding of the processes that couple the lower atmosphere to the upper surface of ice sheets is necessary for interpreting ice-core records. Of special interest are those processes that involve the exchange of energy or atmospheric constituents. One such process, wind pumping, entails both possibilities and provides a possible mechanism for converting atmospheric kinetic energy into a near-surface heat source within the firn layer. The essential idea is that temporal and spatial variations in surface air pressure, resulting from air motion, can diffuse into permeable firn by conventional Darcy flow. Viscous friction between moving air and the solid firn matrix leads to energy dissipation in the firn that is equivalent to a volumetric heat source. Initial theoretical work on wind pumping was aimed at explaining anomalous near-surface temperatures measured at sites on Agassiz Ice Cap, Arctic Canada. A conclusion of this preliminary work was that, under highly favourable conditions, anomalous warming of as much as 2°C was possible. Subsequent efforts to confirm wind-pumping predictions suggest that our initial estimates of the penetration depth for pressure fluctuations were optimistic. These observations point to a deficiency of the initial theoretical formulation — the surface-pressure forcing was assumed to vary temporally, but not spatially. Thus, within the firn there was only a surface-normal component of air flow. The purpose of the present contribution is to advance a three-dimensional theory of wind pumping in which air flow is driven by both spatial and temporal fluctuations in surface pressure. Conclusions of the three-dimensional analysis are that the penetration of pressure fluctuations, and hence the thickness of the zone of frictional interaction between air and permeable firn, is related to both the frequency of the pressure fluctuations and to the spatial coherence length of turbulence cells near the firn surface. Article in Journal/Newspaper Arctic Ice cap ice core Journal of Glaciology Cambridge University Press Journal of Glaciology 37 125 89 96 |
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Open Polar |
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Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Clarke, Garry K. C. Waddington, Edwin D. A three-dimensional theory of wind pumping |
topic_facet |
Earth-Surface Processes |
description |
Abstract Quantitative understanding of the processes that couple the lower atmosphere to the upper surface of ice sheets is necessary for interpreting ice-core records. Of special interest are those processes that involve the exchange of energy or atmospheric constituents. One such process, wind pumping, entails both possibilities and provides a possible mechanism for converting atmospheric kinetic energy into a near-surface heat source within the firn layer. The essential idea is that temporal and spatial variations in surface air pressure, resulting from air motion, can diffuse into permeable firn by conventional Darcy flow. Viscous friction between moving air and the solid firn matrix leads to energy dissipation in the firn that is equivalent to a volumetric heat source. Initial theoretical work on wind pumping was aimed at explaining anomalous near-surface temperatures measured at sites on Agassiz Ice Cap, Arctic Canada. A conclusion of this preliminary work was that, under highly favourable conditions, anomalous warming of as much as 2°C was possible. Subsequent efforts to confirm wind-pumping predictions suggest that our initial estimates of the penetration depth for pressure fluctuations were optimistic. These observations point to a deficiency of the initial theoretical formulation — the surface-pressure forcing was assumed to vary temporally, but not spatially. Thus, within the firn there was only a surface-normal component of air flow. The purpose of the present contribution is to advance a three-dimensional theory of wind pumping in which air flow is driven by both spatial and temporal fluctuations in surface pressure. Conclusions of the three-dimensional analysis are that the penetration of pressure fluctuations, and hence the thickness of the zone of frictional interaction between air and permeable firn, is related to both the frequency of the pressure fluctuations and to the spatial coherence length of turbulence cells near the firn surface. |
format |
Article in Journal/Newspaper |
author |
Clarke, Garry K. C. Waddington, Edwin D. |
author_facet |
Clarke, Garry K. C. Waddington, Edwin D. |
author_sort |
Clarke, Garry K. C. |
title |
A three-dimensional theory of wind pumping |
title_short |
A three-dimensional theory of wind pumping |
title_full |
A three-dimensional theory of wind pumping |
title_fullStr |
A three-dimensional theory of wind pumping |
title_full_unstemmed |
A three-dimensional theory of wind pumping |
title_sort |
three-dimensional theory of wind pumping |
publisher |
Cambridge University Press (CUP) |
publishDate |
1991 |
url |
http://dx.doi.org/10.1017/s0022143000042830 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000042830 |
genre |
Arctic Ice cap ice core Journal of Glaciology |
genre_facet |
Arctic Ice cap ice core Journal of Glaciology |
op_source |
Journal of Glaciology volume 37, issue 125, page 89-96 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000042830 |
container_title |
Journal of Glaciology |
container_volume |
37 |
container_issue |
125 |
container_start_page |
89 |
op_container_end_page |
96 |
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1797579047693189120 |