Basal freeze-on generates complex ice-sheet stratigraphy

• Published in: Nature Communications
• Main Authors: Leysinger Vieli, GJ-MC, Martin, Carlos, Hindmarsh, Richard, Lüthi, MP
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2018
• Subjects: Greenland; Antarc*; Antarctica; ice core; Ice Sheet
• Online Access: http://nora.nerc.ac.uk/id/eprint/521446/; https://nora.nerc.ac.uk/id/eprint/521446/1/10.1038_s41467-018-07083-3.pdf; https://doi.org/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.