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A New Estimate of Marine Ice Under Amery Ice Shlef

AJAS · 2020 Earth and Environmental Sciences (inferred)

Madeleine Maylath · South Carolina Academy of Science

Overview

Accreted marine ice is present under East Antarctica’s Amery Ice Shelf (AIS). The distribution of marine ice under the AIS was previously mapped by Fricker et al. (2001) using Russian airborne ice-penetrating radar (IPR) measurements acquired between 1986 and 1995 and a digital elevation model (DEM) of the ice shelf surface generated from data from ERS-1 (European Remote Sensing satellite). The study provides a new estimate of accreted marine ice thickness under the outer AIS, derived from IPR measurements and laser ranging data collected jointly by China, Australia, and the US during the 2016-2017 and 2017-2018 austral summers. It was hypothesized that both the distribution and properties of the marine ice layer are a signal of ocean forcing beneath the ice shelf and can be resolved using IPR measurements of the meteoric-marine ice interface. Conditions at the ice-ocean interface, including the presence of marine ice, make AIS a compelling analog for Jupiter’s icy moon, Europa. Due to the presence of water ice and specific energy and chemistry phenomena, Europa has been identified as a potential site for life in the solar system, and NASA's Europa Clipper will travel there in the 2020s to further investigate properties of Europa and its icy crust. This study follows the approach of Fricker et al. (2001) to estimate the distribution of marine ice by applying the hydrostatic equation. Ellipsoid height is obtained using aircraft GPS elevation and laser ranging data. To obtain orthometric height, the geoid height is subtracted from the ellipsoid height. The orthometric height is then compared to the height calculated using the ice thickness from IPR data and the modeled densities of meteoric ice and sea water. The difference between the orthometric height and IPR-derived height is called the hydrostatic height anomaly. Where the hydrostatic height anomaly is high, the ice is expected to be grounded or for marine present. Where marine ice is present, orthometric height is used with a new density model that accounts for the presence of marine ice, to estimate the total ice thickness. The difference between the IPR-derived thickness and the revised total ice thickness gives an estimate of the thickness of marine ice. The hypothesis that IPR measurements of the meteoric-marine ice interface can be used to resolve both the distribution and properties of a marine ice layer was proven valid. A map of marine ice was successfully created using hydrostatic calculations and radar measurements for ice elevation and thickness. This map, showing marine ice accreting towards the front of the ice shelf, was consistent with previous estimates of marine ice and known ocean processes occurring under the ice shelf.

Competition history

  • AJAS 2020 Category not listed

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Source: AAAS Annual Meeting (Confex) / American Junior Academy of Science

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