References

The Cryosphere

1994-0424

Copernicus GmbH

Göttingen, Germany

10.5194/tc-5-809-2011

An improved semi-empirical model for the densification of Antarctic firn

Ligtenberg

S. R. M.

¹ Helsen

M. M.

¹ van den Broeke

M. R.

Institute for Marine and Atmospheric research Utrecht (IMAU) P.O. Box 80000, 3508 TA Utrecht, The Netherlands

12 10 2011

5 4 809 819

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A firn densification model is presented that simulates steady-state Antarctic firn density profiles, as well as the temporal evolution of firn density and surface height. The model uses an improved firn densification expression that is tuned to fit depth-density observations. Liquid water processes (meltwater percolation, retention and refreezing) are also included. Two applications are presented. First, the steady-state model version is used to simulate the strong spatial variability in firn layer thickness across the Antarctic ice sheet. Second, the time-dependent model is run for 3 Antarctic locations with different climate conditions. Surface height changes are caused by a combination of accumulation, melting and firn densification processes. On all 3 locations, an upward trend of the surface during autumn, winter and spring is present, while during summer there is a more rapid lowering of the surface. Accumulation and (if present) melt introduce large inter-annual variability in surface height trends, possibly hiding ice dynamical thickening and thinning.

References 1

Arthern, R J., Vaughan, D G., Rankin, A M., Mulvaney, R., and Thomas, E R.: In situ measurements of Antarctic snow compaction compared with predictions of models, J. Geophys. Res., 115, (F03011), http://dx.doi.org/10.1029/2009JF001306doi:10.1029/2009JF001306, 2010.

Barnola, J.-M., Pimienta, P., Raynaud, D., and Korotkevich, Y S.: CO<sub>2</sub>-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, 43B, 83–90, 1991.

Coléou, C. and Lesaffre, B.: Irreducible water saturation in snow: experimental results in a cold laboratory, Ann. Glaciol., 26, 64–68, 1998.

Davis, C H., Li, Y., McConnell, J R., Frey, M M., and Hanna, E.: Snowfall-driven growth in East Antarctic ice sheet mitigates recent sea-level rise, Science, 308, 1898–1901, http://dx.doi.org/10.1126/science.1110662doi:10.1126/science.1110662, 2005.

Helsen, M., M R. van~den Broeke, R S W. van~de Wal, W J. van~de Berg, E van Meijgaard, C H. Davis, Y Li, and I Goodwin (2008), Elevation changes in Antarctica mainly determined by accumulation variability, Science, 320, 1626–1628, http://dx.doi.org/10.1126/science.1153894doi:10.1126/science.1153894.

Herron, M. and Langway, C.:Firn densification: an empirical model, J. Glaciol., 25, 373–385, 1980.

Holland, P R., Corr, H F J., Pritchard, H D., Vaughan, D G., Arthern, R J., Jenkins, A., and Tedesco, M.: The air content of Larsen C ice shelf, Geophys. Res. Lett., 38, L10503, http://dx.doi.org/10.1029/2011GL047245doi:10.1029/2011GL047245, 2011.

Kaspers, K. A., van de Wal, R. S. W., van den Broeke, M. R., Schwander, J., van Lipzig, N. P. M., and Brenninkmeijer, C. A. M.: Model calculations of the age of firn air across the Antarctic continent, Atmos. Chem. Phys. Discuss., 4, 1817–1853, http://dx.doi.org/10.5194/acpd-4-1817-2004doi:10.5194/acpd-4-1817-2004, 2004.

Kuipers Munneke, P., van~den Broeke, M R., Lenaerts, J T M., Flanner, M G., Gardner, A S., and van~de Berg, W J.: A new albedo parameterization for use in climate models over the Antarctic ice sheet, J. Geophys. Res., 116, D05114, http://dx.doi.org/10.1029/2010JD015113doi:10.1029/2010JD015113, 2011.

Lenaerts, J. T M. and van~den Broeke, M R.: Modeling snowdrift in Antarctica with a regional climate model, Part II: Results, J. Geophys. Res., in review, 2011.

Lenaerts, J. T M., van~den Broeke, M R., van~de Berg, W J., van Meijgaard, E., and Munneke, P K.: A new, high resolution surface mass balance map of antarctica (1979–2009) based on regional climate modeling, Geophys. Res. Lett., in review, (2011a).

Lenaerts, J T M., van~den Broeke, M R., Déry, S J., van Meijgaard, E., van~de Berg, W J., Palm, S P., and Rodrigo, J S.: Modeling snowdrift in Antarctica with a regional climate model, Part I: Methods and model evaluation, J. Geophys. Res., in review, (2011b).

Li, J. and Zwally, H J.: Modeling the density variation in the shallow firn layer, Ann. Glaciol., 38, 303–313, 2004.

Lythe, M B., Vaughan, D G., and the BEDMAP~Consortium BEDMAP: A new ice thickness and subglacial topographic model of Antarctica, J. Geophys. Res., 106, 11335–11352, http://dx.doi.org/10.1029/2000JB900449doi:10.1029/2000JB900449, 2001.

McConnell, J R., Arthern, R J., Mosley-Thompson, E., Davis, C H., Bales, R C., Thomas, R., Burkhart, J F., and Kyne, J D.: Changes in Greenland ice sheet elevation attributed primarily to snow accumulation variability, Nature, 406, 877–879, 2000.

Paterson, W. S B.:The physics of glaciers, 3~Edn., Pergamon, 1994.

Pimienta, M. and Duval, P.: Rate controlling processes in the creep of polar glacier ice, J. Phys., 48, 243–248, 1987.

Rignot, E., Bamber, J L., van~den Broeke, M R., Davis, C., Li, Y., van~de Berg, W J., and van Meijgaard, E.: Recent Antarctic ice mass loss from radar interferometry and regional climate modelling, Nat. Geosci., 1, 106–110, http://dx.doi.org/10.1038/ngeo102doi:10.1038/ngeo102, 2008.

van~de Berg, W J., van~den Broeke, M R., Reijmer, C H., and van Meijgaard, E.: Reassessment of the Antarctic surface mass balance using calibrated output of a regional atmospheric climate model, J. Geophys. Res., 111, (D11104), http://dx.doi.org/10.1029/2005JD006495doi:10.1029/2005JD006495, 2006.

van~den Broeke, M R.: Depth and density of the Antarctic firn layer, Arctic, Antarct. Alp. Res., 40, 432–438, doi:10.1657/1523-0430(07-021)[BROEKE]2.0.CO;2, 2008.

van~den Broeke, M R., van~de Berg, W J., and van Meijgaard, E.: Firn depth correction along the Antarctic grounding line, Antarct. Sci., 20, 513–517, http://dx.doi.org/10.1017/S095410200800148Xdoi:10.1017/S095410200800148X, 2008.

Vaughan, D G., Marshall, G J., Connolley, W M., Parkinson, C., Mulvaney, R., Hodgson, D A., King, J C., Pudsey, C J., and Turner, J.: Recent rapid regional climate warming on the Antarctic Peninsula, Clim. Change, 60(3), 243–274, http://dx.doi.org/10.1023/A:1026021217991doi:10.1023/A:1026021217991, 2003.

Wilkinson, D S.: A pressure-sintering model for the densification of polar firn and glacier ice, J. Glaciol., 34, 40–45, 1988.

Wingham, D J., Wallis, D W., and Sheperd, A.: Spatial and temporal evolution of Pine Island Glacier thinning, Geophys. Res. Lett., 36, L17501, http://dx.doi.org/10.1029/2009GL039126doi:10.1029/2009GL039126, 2009.

Winther, J.-G., Jespersen, M N., and Liston, G E.: Blue-ice areas in Antarctica derived from NOAA AVHRR satellite data, J. Glaciol., 47, 325–334, 2001.

Zwally, H J. and Li, J.: Seasonal and interannual variations of firn densification and ice-sheet surface elevation at the Greenland Summit, J. Glaciol., 48, 199–207, http://dx.doi.org/10.3189/172756502781831403doi:10.3189/172756502781831403, 2002.