Firn Densification: An Empirical Model

Herron, Michael M.; Langway, Chester C.

doi:10.3189/s0022143000015239

Cited by 288 publications

(461 citation statements)

References 13 publications

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“…The observed mean density profiles agree well with the density profiles predicted by the firn densification model most commonly used in the literature (Herron and Langway, 1980). However, the analysis of the density variability revealed a paradoxical behavior (Freitag et al, 2004;Gerland et al, 1999;Hörhold et al, 2011).…”

Section: Introductionsupporting

confidence: 76%

On the impact of impurities on the densification of polar firn

Hörhold

Laepple

Freitag

et al. 2012

Earth and Planetary Science Letters

153

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Editor: P. DeMenocalKeywords: polar firn density densification impurity density variability 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 layering is maintained along the whole firn and ice column. However, available high-resolution density data, as well as firn air samples, question this picture and point to a lack of understanding of firn densification. Based on analysis of high-resolution density and calcium concentration records from Antarctic and Greenland ice cores, we show for the first time that also impurities may have a significant impact on the densification. Analysis of firn cores shows a correlation between density and the calcium ion (Ca++) concentration, and this correlation increases with depth. The existence of this relationship is independent of the local climatic conditions at the core sites analyzed. The strong positive correlation between the density and the logarithm of Ca++ concentration indicates that impurities induce softening and lead to faster densification over a wide range of concentrations. In one core, the impurity effect manifests itself so strongly that the density develops a seasonal cycle closely following the seasonal cycle of Ca++. Our results clearly show that the structure of the firn layering changes with depth and suggest that the increased variability in density observed in deep firn, recently described as a universal feature of polar firn, may arise from the influence of Ca++ and/or other impurities. The impurity effect is likely to have direct implications on our understanding of glacial firn densification and on glacial gas age estimates.

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Section: Introductionsupporting

confidence: 76%

On the impact of impurities on the densification of polar firn

Hörhold

Laepple

Freitag

et al. 2012

Earth and Planetary Science Letters

153

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“…7). The latter is calculated according to [8], based on mean annual air temperature (corrected for recent warming) and precipitation, assuming no melt. The total pore space available for melt storage is derived to p HL = ∫ ρ i − ρ HL dℎ Supplementary Table 2).…”

Section: Fraction Of Relict Pore Spacementioning

confidence: 99%

“…In Greenland's accumulation area, porous firn up to 80 meters thick underlies the ice sheet surface 8 .…”

mentioning

confidence: 99%

Greenland meltwater storage in firn limited by near-surface ice formation

et al. 2016

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“…[9] The derivation of the firn compaction follows Sørensen et al [2011], where the change in the air space of the top firn (top 15 annual layers) is estimated from a dynamic firn model based on the description of firn compaction by Herron and Langway [1980] and Arthern et al [2010]. The dynamical firn model is forced by interpolated output fields from the HIRHAM5 regional climate model at a resolution of 5 Â 5 km [Lucas-Picher et al, 2012].…”

Section: Density Determinationmentioning

confidence: 99%

Mass loss of Greenland's glaciers and ice caps 2003–2008 revealed from ICESat laser altimetry data

Bolch

Sørensen²,

Simonsen

et al. 2013

Geophysical Research Letters

131

136

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The recently finalized inventory of Greenland's glaciers and ice caps (GIC) allows for the first time to determine the mass changes of the GIC separately from the ice sheet using space‐borne laser altimetry data. Corrections for firn compaction and density that are based on climatic conditions are applied for the conversion from volume to mass changes. The GIC which are clearly separable from the icesheet (i.e., have a distinct ice divide or no connection) lost 27.9 ± 10.7 Gt a−1 or 0.08 ± 0.03 mm a−1 sea‐level equivalent (SLE) between October 2003 and March 2008. All GIC (including those with strong but hydrologically separable connections) lost 40.9 ± 16.5 Gt a−1 (0.12 ± 0.05 mm a−1 SLE). This is a significant fraction (~14 or 20%) of the reported overall mass loss of Greenland and up to 10% of the estimated contribution from the world's GIC to sea level rise. The loss was highest in southeastern and lowest in northern Greenland.

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Firn Densification: An Empirical Model

Cited by 288 publications

References 13 publications

On the impact of impurities on the densification of polar firn

On the impact of impurities on the densification of polar firn

Greenland meltwater storage in firn limited by near-surface ice formation

Mass loss of Greenland's glaciers and ice caps 2003–2008 revealed from ICESat laser altimetry data

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