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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Creator Hendricks, Stefan ORCID logo; Itkin, Polona ORCID logo; Ricker, Robert ORCID logo; Webster, Melinda ORCID logo; von Albedyll, Luisa ORCID logo; Rohde, Jan; Raphael, Ian ORCID logo; Jaggi, Matthias; Arndt, Stefanie ORCID logo
Publisher PANGAEA
Publication Year 2022
Funding Reference Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven Crossref Funder ID AFMOSAiC-1_00 Multidisciplinary drifting Observatory for the Study of Arctic Climate; Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven Crossref Funder ID AWI_PS122_00 Multidisciplinary drifting Observatory for the Study of Arctic Climate / MOSAiC; German Research Foundation Crossref Funder ID 404680418 Der Einfluss von gegensätzlichen Schnee-Charakteristika auf die Entwicklung des Meereises; German Research Foundation Crossref Funder ID 5472008 Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; Horizon 2020 Crossref Funder ID 730965 doi:10.3030/730965 Arctic Research Icebreaker Consortium: A strategy for meeting the needs for marine-based research in the Arctic (ARICE); National Aeronautics and Space Administration Crossref Funder ID 80NSSC20K0658 Assessing and improving the seasonal capability of ICESat-2 data for sea ice research; National Science Foundation Crossref Funder ID 1735862 Chemical, Physical and Biological processes linking snow and sea ice to the Arctic Ocean mixed layer: Improving models through the MOSAiC platform; National Science Foundation Crossref Funder ID 1820927 Parameterizing sub-grid Arctic snow-on-sea-ice processes in Earth System Models using MOSAiC field observations and realistic-resolution process models; The Research Council of Norway Crossref Funder ID 287871 Sea Ice Deformation and Snow for an Arctic in Transition (SIDRiFT)
Rights Creative Commons Attribution 4.0 International;
OpenAccess true
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