Alfred Wegener Institute
Airborne EM ice thickness
Airborne Electromagnetic Induction Estimates of Ice plus Snow Thickness
Organizations |
Alfred Wegener Institute for Polar and Marine Research and York University |
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Providers |
Christian Haas, Stefan Hendricks, Thomas Krumpen and collaborators for various research campaigns. |
Principal contacts |
Dr Christian Haas, email: chaas at awi.de Dr. Stefan Hendricks, email: stefan.hendricks at awi.de Dr.Thomas Krumpen thomas.krumpen at awi.de |
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Airborne electromagnetic induction measures snow+ice thickness EM sounding is a classical geophysical method to detect the distance between an EM instrument and the boundary between the resistive sea ice and the conductive sea water, i.e. its altitude above the ice/water-interface. The method is based on measurements of the amplitude and phase of a secondary EM field induced in the seawater by a primary field transmitted by the EM instrument. Surveys are usually performed with a towed sensor package, which is operated some tens of meters below the aircraft and 20 m above the ice. The Bird’s altitude above the snow or ice surface is measured with a laser altimeter. Ice-plus-snow thickness results from the difference between the altitude above the ice/water-interface and above the snow or ice surface [Haas et al., 2009]. The accuracy of EM measurements is ±0.1 m over level ice [Pfaffling et al., 2007; Haas et al., 2009]. However, the maximum thickness of pressure ridges is generally underestimated due to their porosity and the EM footprint diameter of up to 3.7 times the instrument altitude [Reid et al., 2006]. The measured thickness of unconsolidated ridges can be less than 50% of the “true” thickness [e.g., Haas and Jochmann, 2003]. Therefore, the measured thickness distributions are most accurate with respect to their modal thickness, while mean ice thickness can still be used for relative comparisons between regions and campaigns. |
Location |
Arctic Ocean and Fram Strait |
Time interval |
2001-2025 |
Data processing notes |
Data were either provided by investigators directly to Ron Lindsay or Axel Schweiger or downloaded from the Pangaea archive. Data were processed and calibrated by the data set Author. Statistical summaries and PDFs for 50-km clusters were computed and by R. Lindsay and Axel Schweiger, PSC, from the point data. Where the tracks overlap or bend, more than 50 km of track is included in many clusters. When flights spaned a few days in a small region, the flights were combined when the clusters were formed. |
Number of samples |
11542954 point measurements, 1395 cluster averages, 53 campaigns |
Versions |
V20250930: Updated and added multiple campaigns that had been missing from previous versions. |
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Some of the point data were reformated so that the formats are uniform for the different files and missing values are removed. There are 11 columns of data, the variables are ['year','mth','dom','yday','hour','lat','lon', 'fid', 'dist', 'alt','thick'], and the format is '(4i5,3f11.5,i7, f9.1, 2f9.3 )'.
Some variables are set to constants in some of the files.
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Method (use this one as a general reference if you use the data): AWI EM IceBird program info https://www.awi.de/en/science/climate-sciences/sea-ice-physics/projects/ice-bird.html Documenation Individual Campaigns with AWI designation corresponding Thickness CDR abbreviation, duration and info can be found in this table (Excel spread sheet, csv file) Other citations: Pfaffling, A., Haas, C., Reid, J. E. (2007). A direct helicopter EM sea ice thickness inversion, assessed with synthetic and field data, Geophysics, 72, F127-F137. Krumpen, T., von Albedyll, L., Bünger, H.J. et al. Smoother sea ice with fewer pressure ridges in a more dynamic Arctic. Nat. Clim. Chang. 15, 66–72 (2025). https://doi.org/10.1038/s41558-024-02199-5 von Albedyll, Luisa; Haas, Christian; Grodofzig, Raphael (2021): EM-Bird ice thickness measurements in the Transpolar Drift during MOSAiC 2019/2020, part 1. PANGAEA, https://doi.org/10.1594/PANGAEA.934578
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German Federal Ministry of Education and Research, National Science Foundation, NSERC Canada (Natural Sciences and Engineering Research Council), Canada Research Chair Program CRC, York University, University of Alberta |
Diagram of airborne electromagnetic induction measurement system
Map of the location of each cluster from each campaign
Campaigns mapped individually
Date of each campaign
Boxplots of ice thickness for each cluster for each campaign (incomplete for recent updates)
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Box plots show the median (black) and the 5th, 25th, 75th, and 95th percentile values for each cluster of each campaign. The star marks the mode. Click on an image to see an enlarged view.