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Impurity-controlled densification: a new model for stratified polar firn

  • Johannes Freitag (a1), Sepp Kipfstuhl (a1), Thomas Laepple (a1) and Frank Wilhelms (a1)
Abstract
Abstract

A 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. Motivated by recent observations, the impurity effect is formulated on an empirical basis using the seasonally varying Ca2+ ion concentration. Excellent agreement between simulated and measured high-resolution density profiles confirms the new approach. The same parameterization applies for Greenland and Antarctica despite the one order of magnitude difference in impurity concentration. The new models allow us, for the first time, to simulate the density layering in firn down to the firn–ice transition. Our results emphasize the importance of impurities and density layering for the air entrapment and for dating gas records of deep ice cores, in particular for glacial climate conditions where the impurity concentrations are 10–100-fold higher than in modern firn.

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References
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Arnaud L, Barnola JM and Duval P (2000) Physical modeling of the densification of snow/firn and ice in the upper part of polar ice sheets. In Hondoh T ed. Physics of ice core records. Hokkaido University Press, Sapporo, 285305
Arthern RJ, Vaughan DG, Rankin AM, Mulvaney R and Thomas ER (2010) In situ measurements of Antarctic snow compaction compared with predictions of models. J. Geophys. Res., 115(F3), F03011 (doi: 10.1029/2009JF001306)
Barnola JM, Pimienta P, Raynaud D and Korotkevich Y (1991) CO2 climate relationship as deduced from the Vostok ice core: a re-examination based on new measurements and on a re-evaluation of the air dating. Tellus B, 43(2), 8390 (doi: 10.1034/j.1600-0889.1991.t01-1-00002.x)
EPICA Community Members (2004) Eight glacial cycles from an Antarctic ice core. Nature, 429(6992), 623628 (doi: 10.1038/nature02599)
Freitag J, Wilhelms F and Kipfstuhl S (2004) Microstructure-dependent densification of polar firn derived from X-ray microtomography. J. Glaciol., 50(169), 243250 (doi: 10.3189/172756504781830123)
Freitag J, Kipfstuhl S and Laepple T (2013) Core-scale radioscopic imaging: a new method reveals density–calcium link in Antarctic firn. J. Glaciol. 59(218), 10091014 (doi: 10.3189/2013JoG13J028)
Gerland S, Oerter H, Kipfstuhl J, Wilhelms F, Miller H and Miners WD (1999) Density log of a 181 m long ice core from Berkner Island, Antarctica. Ann. Glaciol., 29, 215219 (doi: 10.3189/172756499781821427)
Goujon C, Barnola JM and Ritz C (2003) Modeling the densification of polar firn including heat diffusion: application to close-off characteristics and gas isotopic fractionation for Antarctica and Greenland sites. J. Geophys. Res., 108(D24), 4792 (doi: 10.1029/2002JD003319)
Herron MM and Langway CC Jr (1980) Firn densification: an empirical model. J. Glaciol., 25(93), 373385
Hörhold MW, Kipfstuhl S, Wilhelms F, Freitag J and Frenzel A (2011) The densification of layered polar firn. J. Geophys. Res., 116(F1), F01001 (doi: 10.1029/2009JF001630)
Hörhold MW, Laepple T, Freitag J, Bigler M, Fischer Hand Kipfstuhl S (2012) On the impact of impurities on the densification of polar firn. Earth Planet. Sci. Lett., 325–326, 9399 (doi: 10.1016/j.epsl.2011.12.022)
Hori A and 11 others (1999) A detailed density profile of the Dome Fuji (Antarctica) shallow ice core by X-ray transmission method. Ann. Glaciol., 29, 211214 (doi: 10.3189/172756499781821157)
Landais A and 15 others (2006) Firn-air δ15N in modern polar sites and glacial–interglacial ice: a model–data mismatch during glacial periods in Antarctica? Quat. Sci. Rev., 25(1–2), 4962 (doi: 10.1016/j.quascirev.2005.06.007)
Oerter H and 6 others (2000) Accumulation rates in Dronning Maud Land, Antarctica, as revealed by dielectric-profiling measurements of shallow firn cores. Ann. Glaciol., 30, 2734 (doi: 10.3189/172756400781820705)
Rempel AW, Waddington ED, Wettlaufer JS and Worster MG (2001) Possible displacement of the climate signal in ancient ice by premelting and anomalous diffusion. Nature, 411(6837), 568571 (doi: 10.1038/35079043)
Sommer S (1996) Hochauflösende Spurenstoffuntersuchungen an Eisbohrkernen aus Nord-Grönland. (Diploma thesis, Universität Bern)
Sommer S, Wagenbach D, Mulvaney R and Fischer H (2000) Glacio-chemical study spanning the past 2 kyr on three ice cores from Dronning Maud Land, Antarctica. 2. Seasonally resolved chemical records. J. Geophys. Res., 105(D24), 2942329433 (doi: 10.1029/2000JD900450)
Wilhelms F (1996) Leitfähigkeits- und Dichtemessung an Eisbohrkernen. Ber. Polarforsch/Rep. Pol. Res. 191
Wilkinson DS and Ashby MF (1975) Pressure sintering by power law creep. Acta Metall., 23(11), 12771285 (doi: 10.1016/0001-6160(75)90136-4)
Zwally HJ and Li J (2002) Seasonal and interannual variations of firn densification and ice-sheet surface elevation at Greenland summit. J. Glaciol., 48(161), 199207 (doi: 10.3189/172756502781831403)
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Journal of Glaciology
  • ISSN: 0022-1430
  • EISSN: 1727-5652
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