Results 21 to 30 of about 7,958 (231)
Pore morphology of polar firn around closure revealed by X-ray tomography [PDF]
The Cryosphere, 2018 Understanding the slow densification process of polar firn into ice is essential in order to constrain the age difference between the ice matrix and entrapped gases.
A. Burr +7 more
doaj +3 more sources
Annals of Glaciology, 2019 We compared elastic moduli in polar firn derived from diving wave refraction seismic velocity analysis, firn-core density measurements and microstructure modelling based on firn-core data.
Rebecca Schlegel +8 more
doaj +3 more sources
Gas diffusivity and permeability through the firn column at Summit, Greenland: measurements and comparison to microstructural properties [PDF]
The Cryosphere, 2014 The physical structure of polar firn plays a key role in the mechanisms by which glaciers and ice sheets preserve a natural archive of past atmospheric composition. This study presents the first measurements of gas diffusivity and permeability along with
A. C. Adolph, M. R. Albert
doaj +6 more sources
Impurity-controlled densification: a new model for stratified polar firn [PDF]
Journal of Glaciology, 2013 AbstractA new densification model, which simulates the effect of impurities on the densification of polar firn, is presented. The classical densification models of Herron and Langway (1980) and Pimienta and Barnola (Barnola and others, 1991) are modified by assuming that the activation energy for deformation is reduced by the impurities.
Johannes Freitag +3 more
openalex +3 more sources
On the impact of impurities on the densification of polar firn [PDF]
Earth and Planetary Science Letters, 2012 Abstract Understanding polar firn densification is crucial for reconstructing the age of greenhouse gas concentrations extracted from ice cores, and for the interpretation of air in ice as a dating tool or as a climate proxy. Firn densification is generally modeled as a steady burial and sintering process of defined layers, where the structure of the
Hörhold, Maria +5 more
openaire +4 more sources
Thermal fractionation of air in polar firn by seasonal temperature gradients [PDF]
Geochemistry, Geophysics, Geosystems, 2001 Air withdrawn from the top 5–15 m of the polar snowpack (firn) shows anomalous enrichment of heavy gases during summer, including inert gases. Following earlier work, we ascribe this to thermal diffusion, the tendency of a gas mixture to separate in a temperature gradient, with heavier molecules migrating toward colder regions.
Severinghaus, Jeffrey P. +2 more
openaire +3 more sources
Modeling enhanced firn densification due to strain softening [PDF]
The Cryosphere, 2022 In the accumulation zone of glaciers and ice sheets snow is transformed into glacial ice by firn densification. Classically, this process is assumed to solely depend on temperature and overburden pressure, which is controlled by the accumulation rate ...
F. M. Oraschewski +2 more
doaj +1 more source
Chlorine isotope composition in chlorofluorocarbons CFC-11, CFC-12 and CFC-113 in firn, stratospheric and tropospheric air [PDF]
, 2014 The stratospheric degradation of chlorofluorocarbons (CFCs) releases chlorine, which is a major contributor to the destruction of stratospheric ozone (O3).
Allin, S. J. +14 more
core +22 more sources
The Community Firn Model (CFM) v1.0 [PDF]
Geoscientific Model Development, 2020 Models that simulate the evolution of polar firn are important for several applications in glaciology, including converting ice-sheet elevation change measurements to mass change and interpreting climate records in ice cores.
C. M. Stevens +8 more
doaj +1 more source
Pure rotational Raman spectroscopy applied to N2/O2 analysis of air bubbles in polar firn
Journal of Glaciology, 2021 Earlier gas measurements of firn air (atmosphere in open pore channels) at polar sites have revealed the occurrence of gas fractionation phenomena during bubble close-off, in addition to well-known thermal and gravitational gas separation.
Hiroshi Ohno +2 more
doaj +1 more source