Basal freeze-on generates complex ice-sheet stratigraphy

• Published in: Nature communications Vol. 9; no. 1; pp. 4669 - 13
• Main Authors: Leysinger Vieli, G. J.-M. C., Martín, C., Hindmarsh, R. C. A., Lüthi, M. P.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07.11.2018; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/189; 704/106/125; Computer simulation; Fluctuations; Flux; Heat; Humanities and Social Sciences; Hypotheses; Ice; Ice cover; Ice sheets; Ice thickness; Mathematical models; multidisciplinary; Radar; Radar imaging; Science; Science (multidisciplinary); Stratigraphy; Structure-function relationships; Topography; Water availability; Water flow; Greenland
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-07083-3

Large, plume-like internal ice-layer-structures have been observed in radar images from both Antarctica and Greenland, rising from the ice-sheet base to up to half of the ice thickness. Their origins are not yet understood. Here, we simulate their genesis by basal freeze-on using numerical ice-flow modelling and analyse the transient evolution of the emerging ice-plume and the surrounding ice-layer structure as a function of both freeze-on rate and ice flux. We find good agreement between radar observations, modelled ice-plume geometry and internal layer structure, and further show that plume height relates primarily to ice-flux and only secondarily to freeze-on. An in-depth analysis, performed for Northern Greenland of observed spatial plume distribution related to ice flow, basal topography and water availability supports our findings regarding ice flux and suggests freeze-on is controlled by ascending subglacial water flow. Our results imply that widespread basal freeze-on strongly affects ice stratigraphy and consequently ice-core interpretations. Subsurface ice-sheet radar images reveal large plume-shaped bodies rising from the base, with their origin not yet understood. Here, the authors show that freeze-on of water at the ice-sheet base combined with ice-flux explains the vertical extent, shape and structure of the observed plumes.