GEM-2 quicklook total thickness measurements from the 2019-2020 MOSAiC expedition


The total snow and ice thickness (distance from the snow surface to the ice-ocean interface) was measured by the electromagnetic induction (EM) method. On MOSAiC transects, we used a broad-band EM instrument sensor (GEM-2 by Geophex Ltd) towed on a small sled (Hunkeler et al, 2015; Hunkeler et al, 2016). The instrument includes a real-time data processing unit including a GPS receiver which communicates with a pocket PC that is operates the sensor and records the EM and GPS data streams.The GEM-2 is a broadband sensor that can transmit multiple configurable frequencies in the kHz range simultaneously. The sensor setup during MOSAiC used 5 frequencies with an approximately logarithmic spacing throughout the frequency range of the sensor (1.525 kHz, 5.325 kHz, 18.325 kHz, 63.025 kHz, and 93.075 kHz).The transect measurements are based on an empirical approach based on a sensor calibration, where the GEM-2 was placed at known heights above the sea ice surface using a wooden ladder on top of level ice with a known thickness determined by 5 drill holes. An exponential function was then fitted to the frequency components as function of distance of the sensor to the ice/ocean interface and then applied to the transect data. The closest-in-time calibration result was used when a GEM-2 survey could not be accompanied with a calibration.The total thickness retrieval with the GEM-2 calibration and survey data was done on-board shortly after each profile. The dataset is therefore labeled as GEM-2 quickview data but has been subject to manual quality control. Using a direct relationship between total thickness and frequency component implies the assumption that the sea ice conductivity is negligible and the ice/water interface constant within the GEM-2 footprint. While this is a reasonable assumption for level ice, the peak thicknesses of ridges are known to be underestimated by as much as 50 % (Pfaffing et al, 2007) and will be subject of further processing.To estimate the snow depth and then subtract its thickness from the total thickness we rely on direct measurements of snow depth with Magnaprobe. The co-inciding snow depth measurements on MOSAiC transect can be found here: every GEM-2 transect has complimentary snow depth measurements. An overview of all transect measurements at MOSAiC is given in the attached table.For more details we refer to the MOSAiC transect paper by Itkin et al, 2022: Sea ice and snow mass balance from transects in the MOSAiC Central Observatory, in review at Elementa – Science of Anthropocene.

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Metadata Access
Creator Hendricks, Stefan; Itkin, Polona; Ricker, Robert; Webster, Melinda; von Albedyll, Luisa; Rohde, Jan; Raphael, Ian; Jaggi, Matthias; Arndt, Stefanie
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 2022
Funding Reference Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, AFMOSAiC 1_00; Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, AWI_PS122_00; German Science Foundation, 404680418; German Science Foundation, 5472008; Horizon 2020, 730965; National Aeronautics and Space Administration, 80NSSC20K0658; National Science Foundation, 1735862; National Science Foundation, 1820927; The Research Council of Norway, 287871
Rights Data access is restricted (moratorium, sensitive data, license constraints)
OpenAccess false
Language English
Resource Type Dataset
Format application/zip
Size 415.3 MBytes
Discipline Earth System Research
Spatial Coverage (-2.691W, 79.353S, 129.250E, 89.141N); Arctic Ocean
Temporal Coverage Begin 2019-10-24T05:15:00Z
Temporal Coverage End 2020-09-30T13:23:16Z