Airborne mapping of the sub-ice platelet layer under fast ice in McMurdo Sound, Antarctica

Basal melting of ice shelves can result in the outflow of supercooled ice shelf water, which can lead to the formation of a sub-ice platelet layer (SIPL) below adjacent sea ice. McMurdo Sound, located in the southern Ross Sea, Antarctica, is well known for the occurrence of a SIPL linked to ice shel...

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Bibliographic Details
Main Authors: Haas, Christian, Langhorne, Patricia J., Rack, Wolfgang, Leonard, Greg H., Brett, Gemma M., Price, Daniel, Beckers, Justin F., Gough, Alex J.
Format: Text
Language:English
Published: 2020
Subjects:
McMurdo Ice Shelf
McMurdo Sound
Ross Sea
Antarc*
Antarctica
Ice Shelf
Ice Shelves
Sea ice
Online Access:https://doi.org/10.5194/tc-2020-268
https://tc.copernicus.org/preprints/tc-2020-268/
Description
Summary:Basal melting of ice shelves can result in the outflow of supercooled ice shelf water, which can lead to the formation of a sub-ice platelet layer (SIPL) below adjacent sea ice. McMurdo Sound, located in the southern Ross Sea, Antarctica, is well known for the occurrence of a SIPL linked to ice shelf water outflow from under the McMurdo Ice Shelf. Airborne, single frequency, frequency-domain electromagnetic induction (AEM) surveys were performed in November of 2009, 2011, 2013, 2016, and 2017 to map the thickness and spatial distribution of the landfast sea ice and underlying, porous SIPL. We developed a simple method to retrieve the thickness of the consolidated ice and SIPL from the EM inphase and quadrature components, supported by EM forward modeling, and calibrated and validated by drill-hole measurements. Linear regression of EM inphase measurements of apparent SIPL thickness and drill-hole measurements of <q>true</q> SIPL thickness yields a scaling factor of 0.3 to 0.4, and rms error of 0.47 m. EM forward modeling suggests that this corresponds to SIPL conductivities between 900 and 1800 mS/m, with associated SIPL solid fractions between 0.09 and 0.47. The AEM surveys showed the spatial distribution and thickness of the SIPL well, with SIPL thicknesses of up to 8 m near the ice shelf front. They indicate interannual SIPL thickness variability of up to 2 m. In addition, they reveal high-resolution spatial information about the small-scale SIPL thickness variability, and indicate the presence of persistent peaks in SIPL thickness that may be linked to the geometry of the outflow from under the ice shelf.

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