Predicting the steady-state isochronal stratigraphy of ice shelves using observations and modeling

• Published in: The Cryosphere
• Main Authors: Višnjević, Vjeran, Drews, Reinhard, Schannwell, Clemens, Koch, Inka, Franke, Steven, Jansen, Daniela, Eisen, Olaf
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: article; Verlagsveröffentlichung; Antarctic; East Antarctica; Roi Baudouin; The Antarctic; Antarc*; Antarctica; Ice Sheet; Ice Shelf; Ice Shelves; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-16-4763-2022; https://noa.gwlb.de/receive/cop_mods_00063609; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00062614/tc-16-4763-2022.pdf; https://tc.copernicus.org/articles/16/4763/2022/tc-16-4763-2022.pdf

Ice shelves surrounding the Antarctic perimeter moderate ice discharge towards the ocean through buttressing. Ice-shelf evolution and integrity depend on the local surface accumulation, basal melting and on the spatially variable ice-shelf viscosity. These components of ice-shelf mass balance are often poorly constrained by observations and introduce uncertainties in ice-sheet projections. Isochronal radar stratigraphy is an observational archive for the atmospheric, oceanographic and ice-flow history of ice shelves. Here, we predict the stratigraphy of locally accumulated ice on ice shelves with a kinematic forward model for a given atmospheric and oceanographic scenario. This delineates the boundary between local meteoric ice (LMI) and continental meteoric ice (CMI). A large LMI to CMI ratio hereby marks ice shelves whose buttressing strength is more sensitive to changes in atmospheric precipitation patterns. A mismatch between the steady-state predictions of the kinematic forward model and observations from radar can highlight inconsistencies in the atmospheric and oceanographic input data or be an indicator for a transient ice-shelf history not accounted for in the model. We discuss pitfalls in numerical diffusion when calculating the age field and validate the kinematic model with the full Stokes ice-flow model Elmer/Ice. The Roi Baudouin Ice Shelf (East Antarctica) serves as a test case for this approach. There, we find a significant east–west gradient in the LMI / CMI ratio. The steady-state predictions concur with observations on larger spatial scales (>10 km), but deviations on smaller scales are significant, e.g., because local surface accumulation patterns near the grounding zone are underestimated in Antarctic-wide estimates. Future studies can use these mismatches to optimize the input data or to pinpoint transient signatures in the ice-shelf history using the ever growing archive of radar observations of internal ice stratigraphy.