Alfred Wegener Institute and University of Alberta
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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Authors |
Dr. Christian Haas and Dr. Stefan Hendricks |
Principal contacts |
Dr Christian Haas, email: Christian.Haas at ualberta.ca Dr. Stefan Hendricks, email: stefan.hendricks 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 |
2001-2015 |
Data processing notes |
Data were processed and calibrated by Dr. Haas. 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 |
5123374 point measurements, 455 cluster averages, 24 campaigns |
Versions |
V20160513: added PAM-ARCMIP 2015, 47 clusters |
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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): Other citations: Ark 17, 20, 22, NP_07: GreenICE 2004 2005: Ark 19: SEDNA: The Sea Ice Experiment: Dynamic Nature of the Arctic BREA: Beaufort Region Environmental Assessment SIZONet & PAM-ARCMIP: 2007-2015 Transdrift: |
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German Federal Ministry of Education and Research National Science Foundation |
Diagram of airborne electromagnetic induction measurement system
Map of the location of each cluster from each campaign
Campaigns mapped individually (click to enlarge)
Date of each campaign
Boxplots of ice thickness for each cluster for each campaign
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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.