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Observing and modeling the influence of layering on bubble trapping in polar firn
- Source :
- Journal of Geophysical Research: Atmospheres, vol 120, iss 6, Journal of Geophysical Research: Atmospheres, Journal of Geophysical Research: Atmospheres, American Geophysical Union, 2015, 120 (6), pp.2558-2574. ⟨10.1002/2014JD022766⟩, Journal of Geophysical Research: Atmospheres, 2015, 120 (6), pp.2558-2574. ⟨10.1002/2014JD022766⟩, Journal of Geophysical Research, vol 120, iss 6
- Publication Year :
- 2015
- Publisher :
- American Geophysical Union (AGU), 2015.
-
Abstract
- International audience; Interpretation of ice core trace gas records depends on an accurate understanding of the processes that smooth the atmospheric signal in the firn. Much work has been done to understand the processes affecting air transport in the open pores of the firn, but a paucity of data from air trapped in bubbles in the firn-ice transition region has limited the ability to constrain the effect of bubble closure processes. Here we present high-resolution measurements of firn density, methane concentrations, nitrogen isotopes, and total air content that show layering in the firn-ice transition region at the West Antarctic Ice Sheet (WAIS) Divide ice core site. Using the notion that bubble trapping is a stochastic process, we derive a new parameterization for closed porosity that incorporates the effects of layering in a steady state firn modeling approach. We include the process of bubble trapping into an open-porosity firn air transport model and obtain a good fit to the firn core data. We find that layering broadens the depth range over which bubbles are trapped, widens the modeled gas age distribution of air in closed bubbles, reduces the mean gas age of air in closed bubbles, and introduces stratigraphic irregularities in the gas age scale that have a peak-to-peak variability of~10 years at WAIS Divide. For a more complete understanding of gas occlusion and its impact on ice core records, we suggest that this experiment be repeated at sites climatically different from WAIS Divide, for example, on the East Antarctic plateau.
- Subjects :
- Atmospheric Science
Bubble
Antarctic ice sheet
F800
firn
Physical Geography and Environmental Geoscience
Methane
Atmospheric Sciences
Physics::Geophysics
layering
chemistry.chemical_compound
Ice core
Earth and Planetary Sciences (miscellaneous)
Meteorology & Atmospheric Sciences
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Porosity
Physics::Atmospheric and Oceanic Physics
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere
methane
firn density
Firn
Geophysics
total air content
Trace gas
Climate Action
chemistry
13. Climate action
Space and Planetary Science
Climatology
Layering
ice core
Geology
Subjects
Details
- ISSN :
- 2169897X and 21698996
- Volume :
- 120
- Database :
- OpenAIRE
- Journal :
- Journal of Geophysical Research: Atmospheres
- Accession number :
- edsair.doi.dedup.....17c91c5592b045c1c11de4a7f6bc5604