Surface Melting Drives Fluctuations in Airborne Radar Penetration in West Central Greenland

[en] Greenland Ice Sheet surface melting has increased since the 1990s, affecting the rheology and scattering properties of the near‐surface firn. We combine firn cores and modelled firn densities with seven years of CryoVEx airborne Ku‐band (13.5 GHz) radar profiles to quantify the impact of melting on microwave radar penetration in West‐Central Greenland. Although annual layers are present in the Ku‐band radar profiles to depths up to 15 m below the ice sheet surface, fluctuations in summer melting strongly affect the degree of radar penetration. The extreme melting in 2012, for example, caused an abrupt 6.2 ± 2.4 m decrease in Ku‐band radar penetration. Nevertheless, retracking the radar echoes mitigates this effect, producing surface heights that agree to within 13.9 cm of coincident airborne laser measurements. We also examine two years of Ka‐band (34.5 GHz) airborne radar data and show that the degree of penetration is half that of coincident Ku‐band.

Disciplines :

Earth sciences & physical geography

Author, co-author :

Otosaka, I.

Shepherd, A.

Casal, T.

Coccia, A.

Davidson, M.

Di Bella, A.

Fettweis, Xavier ; Université de Liège - ULiège > Département de géographie > Climatologie et Topoclimatologie

Forsberg, R.

Forsberg, V.

Hogg, A.

More authors (8 more)

Language :

English

Title :

Surface Melting Drives Fluctuations in Airborne Radar Penetration in West Central Greenland

Publication date :

24 August 2020

Journal title :

Geophysical Research Letters

ISSN :

0094-8276

eISSN :

1944-8007

Publisher :

Wiley, Washington, United States - District of Columbia

Volume :

Peer reviewed :

Peer Reviewed verified by ORBi

Tags :

CÉCI : Consortium des Équipements de Calcul Intensif

Additional URL :

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL088293

Funders :

F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
CÉCI - Consortium des Équipements de Calcul Intensif [BE]

Commentary :

Radar waves emitted by satellites can be used to measure changes in surface elevation of the Greenland Ice Sheet. However, they do not reflect off the ice sheet surface itself, but penetrate into the snow to a depth of about 15 m for radar wavelengths of 2.3 cm. When the snow melts, meltwater can percolate into the snow or refreeze at the surface. Layers of refrozen ice sharply reduce the degree of radar penetration and may be mistaken for an elevation increase in radar measurements. Here, we combine firn cores and modelled firn densities with seven years of airborne radar data collected during field campaigns in West Central Greenland to quantify this effect. We identify internal layers corresponding to annual stratigraphy within the snowpack and we show that more melt means less radar penetration into the firn. The unprecedented surface melting which occurred across Greenland in 2012 caused a sharp reduction in the degree of radar penetration, from 11.5 m to 5.3 m. However, if the effects of penetration are corrected for, radar altimeters can accurately measure the surface elevation of the ice sheet.

Available on ORBi :

since 26 August 2020

Statistics

Number of views

42 (4 by ULiège)

Number of downloads

2 (2 by ULiège)

More statistics

Scopus citations^®

Scopus citations^®
without self-citations

OpenCitations

Bibliography

van Angelen, J. H., van den Broeke, M. R., Wouters, B., & Lenaerts, J. T. M. (2014). Contemporary (1960–2012) evolution of the climate and surface mass balance of the Greenland ice sheet. Surveys in Geophysics, 35(5), 1155–1174. https://doi.org/10.1007/s10712-013-9261-z
Benson, C. S. (1996). Stratigraphic studies in the snow and firn of the Greenland ice sheet (No. SIPRE-RR-70). Wilmette, IL: U.S. Army Snow, Ice and Permafrost Research Establishment.
Brown, J., Bradford, J., Harper, J., Pfeffer, W. T., Humphrey, N., & Mosley-Thompson, E. (2012). Georadar-derived estimates of firn density in the percolation zone, western Greenland ice sheet. Journal of Geophysical Research, 117, F01011. https://doi.org/10.1029/2011JF002089
Brun, E., David, P., Sudul, M., & Brunot, G. (1992). A numerical model to simulate snow-cover stratigraphy for operational avalanche forecasting. Journal of Glaciology, 38(128), 13–22. https://doi.org/10.1017/S0022143000009552
Cullen, R. (2010). CryoVEx airborne data products description. Noordwijk, The Netherlands: European Space Agency, ESTEC.
Davis, C. H. (1997). A robust threshold retracking algorithm for measuring ice-sheet surface elevation change from satellite radar altimeters. IEEE Transactions on Geoscience and Remote Sensing, 35(4), 974–979. https://doi.org/10.1109/36.602540
de la Peña, S., Howat, I. M., Nienow, P. W., van den Broeke, M. R., Mosley-Thompson, E., Price, S. F., Mair, D., Noël, B., & Sole, A. J. (2015). Changes in the firn structure of the western Greenland Ice Sheet caused by recent warming. The Cryosphere, 9(3), 1203–1211. https://doi.org/10.5194/tc-9-1203-2015
de la Peña, S., Nienow, P., Shepherd, A., Helm, V., Mair, D., Hanna, E., Huybrechts, P., Guo, Q., Cullen, R., & Wingham, D. (2010). Spatially extensive estimates of annual accumulation in the dry snow zone of the Greenland Ice Sheet determined from radar altimetry. The Cryosphere, 4(4), 467–474. https://doi.org/10.5194/tc-4-467-2010
Enderlin, E. M., Howat, I. M., Jeong, S., Noh, M.-J., van Angelen, J. H., & van den Broeke, M. R. (2014). An improved mass budget for the Greenland ice sheet. Geophysical Research Letters, 41(3), 866–872. https://doi.org/10.1002/2013gl059010
Fettweis, X., Box, J. E., Agosta, C., Amory, C., Kittel, C., Lang, C., van As, D., Machguth, H., & Gallée, H. (2017). Reconstructions of the 1900–2015 Greenland Ice Sheet surface mass balance using the regional climate MAR model. The Cryosphere, 11(2), 1015–1033. https://doi.org/10.5194/tc-11-1015-2017
Fettweis, X., Hofer, S., Krebs-Kanzow, U., Amory, C., Aoki, T., Berends, C. J., Born, A., Box, J. E., Delhasse, A., Fujita, K., Gierz, P., Goelzer, H., Hanna, E., Hashimoto, A., Huybrechts, P., Kapsch, M.-L., King, M. D., Kittel, C., Lang, C., Langen, P. L., Lenaerts, J. T. M., Liston, G. E., Lohmann, G., Mernild, S. H., Mikolajewicz, U., Modali, K., Mottram, R. H., Niwano, M., Noël, B., Ryan, J. C., Smith, A., Streffing, J., Tedesco, M., van de Berg, W. J., van den Broeke, M., van de Wal, R. S. W., van Kampenhout, L., Wilton, D., Wouters, B., Ziemen, F., & Zolles, T. (2020). GrSMBMIP: Intercomparison of the modelled 1980–2012 surface mass balance over the Greenland Ice Sheet. The Cryosphere Discussions. https://doi.org/10.5194/tc-2019-321, in review
Hall, D. K., Comiso, J. C., Digirolamo, N. E., Shuman, C. A., Box, J. E., & Koenig, L. S. (2013). Variability in the surface temperature and melt extent of the Greenland Ice Sheet from MODIS. Geophysical Research Letters, 40, 2114–2120. https://doi.org/10.1002/grl.50240
Hawley, R. L., Morris, E. M., Cullen, R., Nixdorf, U., Shepherd, A. P., & Wingham, D. J. (2006). ASIRAS airborne radar resolves internal annual layers in the dry-snow zone of Greenland. Geophysical Research Letters, 33, L04502. https://doi.org/10.1029/2005GL025147
Helm, V., Humbert, A., & Miller, H. (2014). Elevation and elevation change of Greenland and Antarctica derived from CryoSat-2. The Cryosphere, 8(4), 1539–1559. https://doi.org/10.5194/tc-8-1539-2014
Helm, V., Rack, W., Cullen, R., Nienow, P., Mair, D., Parry, V., & Wingham, D. J. (2007). Winter accumulation in the percolation zone of Greenland measured by airborne radar altimeter. Geophysical Research Letters, 34, L06501. https://doi.org/10.1029/2006GL029185
Koenig, L. S., Ivanoff, A., Alexander, P. M., MacGregor, J. A., Fettweis, X., Panzer, B., Paden, J. D., Forster, R. R., Das, I., Mcconnell, J. R., Tedesco, M., & Leuschen, C. (2016). Annual Greenland accumulation rates (2009–2012) from airborne snow radar. The Cryosphere, 10(4), 1739–1752. https://doi.org/10.5194/tc-10-1739-2016
Kuipers Munneke, P., Ligtenberg, S. R. M., Noël, B. P. Y., Howat, I. M., Box, J. E., Mosley-Thompson, E., Mcconnell, J. R., Steffen, K., Harper, J. T., Das, S. B., & van den Broeke, M. R. (2015). Elevation change of the Greenland Ice Sheet due to surface mass balance and firn processes, 1960-2014. The Cryosphere, 9(6), 2009–2025. https://doi.org/10.5194/tc-9-2009-2015
Ligtenberg, S., Helsen, M., & van den Broeke, M. (2011). An improved semi-empirical model for the densification of Antarctic firn. The Cryosphere, 5(4), 809–819. https://doi.org/10.5194/tc-5-809-2011
Ligtenberg, S. R. M., Kuipers Munneke, P., Noël, B. P. Y., & van den Broeke, M. R. (2018). Brief communication: Improved simulation of the present-day Greenland firn layer (1960–2016). The Cryosphere, 12(5), 1643–1649. https://doi.org/10.5194/tc-12-1643-2018
MacFerrin, M., Machguth, H., As, D. V., Charalampidis, C., Stevens, C. M., Heilig, A., Vandecrux, B., Langen, P. L., Mottram, R., Fettweis, X., van den Broeke, M. R. V. D., Pfeffer, W. T., Moussavi, M. S., & Abdalati, W. (2019). Rapid expansion of Greenland's low-permeability ice slabs. Nature, 573(7774), 403–407. https://doi.org/10.1038/s41586-019-1550-3
MacGregor, J. A., Fahnestock, M. A., Catania, G. A., Paden, J. D., Prasad Gogineni, S., Young, S. K., Rybarski, S. C., Mabrey, A. N., Wagman, B. M., & Morlighem, M. (2015). Radiostratigraphy and age structure of the Greenland Ice Sheet. Journal of Geophysical Research: Earth Surface, 120, 212–241. https://doi.org/10.1002/2014JF003215
Machguth, H., MacFerrin, M., van As, D., Box, J. E., Charalampidis, C., Colgan, W., Fausto, R. S., Meijer, H. A. J., Mosley-Thompson, E., & van de Wal, R. S. W. (2016). Greenland meltwater storage in firn limited by near-surface ice formation. Nature Climate Change, 6(4), 390–393. https://doi.org/10.1038/nclimate2899
McMillan, M., Leeson, A., Shepherd, A., Briggs, K., Armitage, T. W. K., Hogg, A., Kuipers Munneke, P., van den Broeke, M., Noël, B., van de Berg, W. J., Ligtenberg, S., Horwath, M., Groh, A., Muir, A., & Gilbert, L. (2016). A high-resolution record of Greenland mass balance: High-resolution Greenland mass balance. Geophysical Research Letters, 43, 7002–7010. https://doi.org/10.1002/2016GL069666
Medley, B., Joughin, I., Das, S. B., Steig, E. J., Conway, H., Gogineni, S., Criscitiello, A. S., Mcconnell, J. R., Smith, B. E., van den Broeke, M. R., Lenaerts, J. T. M., Bromwich, D. H., & Nicolas, J. P. (2013). Airborne-radar and ice-core observations of annual snow accumulation over Thwaites Glacier, West Antarctica confirm the spatiotemporal variability of global and regional atmospheric models. Geophysical Research Letters, 40, 3649–3654. https://doi.org/10.1002/grl.50706
Miège, C., Forster, R. R., Box, J. E., Burgess, E. W., Mcconnell, J. R., Pasteris, D. R., & Spikes, V. B. (2017). Southeast Greenland high accumulation rates derived from firn cores and ground-penetrating radar. Annals of Glaciology, 54(63), 322–332.
Montgomery, L., Koenig, L., Lenaerts, J. T. M., & Kuipers Munneke, P. (2020). Accumulation rates (2009–2017) in Southeast Greenland derived from airborne snow radar and comparison with regional climate models. Annals of Glaciology, 1–9. https://doi.org/10.1017/aog.2020.8
Morris, E. M., & Wingham, D. J. (2011). The effect of fluctuations in surface density, accumulation and compaction on elevation change rates along the EGIG line, central Greenland. Journal of Glaciology, 57(203), 416–430. https://doi.org/10.3189/002214311796905613
Mosley-Thompson, E., Mcconnell, J., Bales, R., Lin, P. N., Steffen, K., Thompson, L., Edwards, R., & Bathke, D. (2001). Local to regional-scale variability of annual net accumulation on the Greenland Ice Sheet from PARCA cores. Journal of Geophysical Research, 106(D24), 33,839–33,851. https://doi.org/10.1029/2001JD900067
Nghiem, S. V., Hall, D. K., Mote, T. L., Tedesco, M., Albert, M. R., Keegan, K., Shuman, C. A., DiGirolamo, N. E., & Neumann, G. (2012). The extreme melt across the Greenland Ice Sheet in 2012. Geophysical Research Letters, 39, L20502. https://doi.org/10.1029/2012GL053611
Nilsson, J., Vallelonga, P., Simonsen, S. B., Sørensen, L. S., Forsberg, R., Dahl-Jensen, D., Hirabayashi, M., Goto-Azuma, K., Hvidberg, C. S., Kjaer, H. A., & Satow, K. (2015). Greenland 2012 melt event effects on CryoSat-2 radar altimetry: Effect of Greenland melt on Cryosat-2. Geophysical Research Letters, 42, 3919–3926. https://doi.org/10.1002/2015GL063296
Noël, B., van de Berg, W. J., van Wessem, J. M., van Meijgaard, E., van As, D., Lenaerts, J. T. M., Lhermitte, S., Kuipers Munneke, P., Smeets, C. J. P. P., van Ulft, L. H., van de Wal, R. S. W., & van den Broeke, M. R. (2018). Modelling the climate and surface mass balance of polar ice sheets using RACMO2—Part 1: Greenland (1958–2016). The Cryosphere, 12(3), 811–831. https://doi.org/10.5194/tc-12-811-2018
Overly, T. B., Hawley, R. L., Helm, V., Morris, E. M., & Chaudhary, R. N. (2016). Greenland annual accumulation along the EGIG line, 1959-2004, from ASIRAS airborne radar and neutron-probe density measurements. The Cryosphere, 10(4), 1679–1694. https://doi.org/10.5194/tc-10-1679-2016
Parry, V., Nienow, P., Mair, D., Scott, J., Hubbard, B., Steffen, K., & Wingham, D. (2007). Investigations of meltwater refreezing and density variations in the snowpack and firn within the percolation zone of the Greenland Ice Sheet. Annals of Glaciology, 46, 61–68. https://doi.org/10.3189/172756407782871332
Rémy, F., Flament, T., Michel, A., & Blumstein, D. (2015). Envisat and SARAL/AltiKa observations of the Antarctic ice sheet: A comparison between the Ku-band and Ka-band. Marine Geodesy, 38(sup1), 510–521. https://doi.org/10.1080/01490419.2014.985347
Renaud, A., Schumacher, E., Hughes, B., Oeschgerand, H., & Mühlemann, C. (1963). Tritium variations in Greenland ice. Journal of Geophysical Research, 68(13), 3783–3783. https://doi.org/10.1029/JZ068i013p03783
Ridley, J. K., & Partington, K. (1988). A model of satellite radar altimeter return from ice sheets. Remote Sensing, 9(4), 601–624. https://doi.org/10.1080/01431168808954881
Scott, J. B. T., Nienow, P., Mair, D., Parry, V., Morris, E., & Wingham, D. J. (2006). Importance of seasonal and annual layers in controlling backscatter to radar altimeters across the percolation zone of an ice sheet. Geophysical Research Letters, 33, L24502. https://doi.org/10.1029/2006GL027974
Shepherd, A., Gilbert, L., Muir, A. S., Konrad, H., Mcmillan, M., Slater, T., Briggs, K. H., Sundal, A. V., Hogg, A. E., & Engdahl, M. (2019). Trends in Antarctic Ice Sheet elevation and mass. Geophysical Research Letters, 46, 8174–8183. https://doi.org/10.1029/2019GL082182
Simonsen, S. B., & Sørensen, L. S. (2017). Implications of changing scattering properties on Greenland Ice Sheet volume change from Cryosat-2 altimetry. Remote Sensing of Environment, 190, 207–216. https://doi.org/10.1016/j.rse.2016.12.012
Simonsen, S. B., Stenseng, L., Ađalgeirsdóttir, G., Fausto, R. S., Hvidberg, C. S., & Lucas-Picher, P. (2013). Assessing a multilayered dynamic firn-compaction model for Greenland with ASIRAS radar measurements. Journal of Glaciology, 59(215), 545–558. https://doi.org/10.3189/2013JoG12J158
Skourup, H., Olesen, A. V., Sandberg Sørensen, L., Simonsen, S., Hvidegaard, S. M., Hansen, N., Olsesen, A. F., Coccia, A., Helm, V., Ladkin, R. S., Forsberg, R., Hogg, A. E., Otosaka, I., Shepherd, A., Haas. C., & Wilkinson, J. (2019). ESA CryoVEx/EU ICE-ARC 2017
Slater, T., Shepherd, A., Mcmillan, M., Armitage, T. W. K., Otosaka, I., & Arthern, R. J. (2019). Compensating changes in the penetration depth of pulse-limited radar altimetry over the Greenland Ice Sheet. IEEE Transactions on Geoscience and Remote Sensing, 57(12), 9633–9642. https://doi.org/10.1109/TGRS.2019.2928232
van de Wal, R. S. W., Boot, W., van den Broeke, M. R., Smeets, C. J. P. P., Reijmer, C. H., Donker, J. J. A., & Oerlemans, J. (2008). Large and rapid melt-induced velocity changes in the ablation zone of the Greenland Ice Sheet. Science, 321(5885), 111–113. https://doi.org/10.1126/science.1158540
van den Broeke, M. R., Enderlin, E. M., Howat, I. M., Kuipers Munneke, P., Noel, B. P. Y., van de Berg, W. J., van Meijgaard, E., & Wouters, B. (2016). On the recent contribution of the Greenland Ice Sheet to sea level change. The Cryosphere, 10(5), 1933–1946. https://doi.org/10.5194/tc-10-1933-2016
Vandecrux, B., Fausto, R. S., Langen, P. L., As, D., MacFerrin, M., Colgan, W. T., Ingeman-Nielsen, T., Steffen, K., Jensen, N. S., Møller, M. T., & Box, J. E. (2018). Drivers of firn density on the Greenland ice sheet revealed by weather station observations and modeling. Journal of Geophysical Research: Earth Surface, 123, 2563–2576. https://doi.org/10.1029/2017JF004597
Verjans, V., Leeson, A. A., Stevens, C. M., MacFerrin, M., Noël, B., & van den Broeke, M. R. (2019). Development of physically based liquid water schemes for Greenland firn-densification models. The Cryosphere, 13(7), 1819–1842. https://doi.org/10.5194/tc-13-1819-2019
Wingham, D., Rapley, C., & Griffiths, H. (1986). New techniques in satellite altimeter tracking systems. Proceedings of IEEE International Geoscience & Remote Sensing Symposium, 1339–1344.