Imaging a Polygonal Network of Ice-Wedge Casts with an Electromagnetic Induction Sensor

• Published in: Soil Science Society of America journal Vol. 75; no. 6; pp. 2095 - 2100
• Main Authors: Meerschman, Eef, Meirvenne, Marc Van, Smedt, Philippe de, Saey, Timothy, Islam, Mohammad Monirul, Meeuws, Fun, Vijver, Ellen van de, Ghysels, Gunther
• Format: Journal Article
• Language: English
• Published: Madison Soil Science Society of America 01.11.2011; The Soil Science Society of America, Inc; American Society of Agronomy
• Subjects: Aerial photography; Agricultural land; Agricultural production; Clay; Coastal plains; Data processing; electrical conductivity; electromagnetic induction techniques; Eocene; Heterogeneity; Ice; image analysis; Marine sediments; Moisture content; paleoclimatology; Permafrost; precision agriculture; Precision farming; Quaternary; sensors (equipment); Soils; Subsoils; surveys; texture
• ISSN: 0361-5995; 1435-0661
• DOI: 10.2136/sssaj2011.0063

Images of the morphology of a polygonal network of ice-wedge casts are a valuable aid to paleoclimatological reconstructions. Usually such images are obtained by aerial photography showing polygonal crop marks reflecting textural differences between wedge filling and host material. Our objective was to investigate an alternative method by measuring the soil apparent electrical conductivity (ECa) with an electromagnetic induction (EMI) sensor. Based on an aerial photograph showing polygonal crop marks in an agricultural field in Belgium, a test area of 0.63 ha was selected. A small part of the test area (6 by 6 m) was excavated revealing a clear pattern of ice-wedge casts. The wedges penetrated clay-rich Tertiary marine sediments, covered by a 0.6-m layer of eolian sandy sediments, and were associated with the permafrost during the last glacial period. We took 94 subsoil (0.6–0.8 m) samples distributed over the test area and analyzed their texture. The results showed a clear difference between the Eocene host material (on average 21% clay) and the Quaternary wedge filling (on average 6% clay). The test area was surveyed with an EMI sensor (we used an EM38DD) which resulted in an accurate image of the polygonal network. We concluded that an EMI survey is an appropriate technique to image the morphology of a polygonal network of subsoil ice-wedge casts. A final perspective comprises the strong heterogeneity of the subsoil, since nearly half of the subsoil consists of ice-wedge material. This might open perspectives for precision agriculture in such landscapes.