The sub-ice platelet layer and its influence on freeboard to

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TitleThe sub-ice platelet layer and its influence on freeboard to thickness conversion of Antarctic sea iceAbstractThis is an investigation to quantify the influence of the sub-ice platelet layer on satellite measurements of total freeboard and their conversion to thickness of Antarctic sea ice. The sub-ice platelet layer forms as a result of the seaward advection of supercooled ice shelf water from beneath ice shelves. This ice shelf water provides an oceanic heat sink promoting the formation of platelet crystals which accumulate at the sea ice-ocean interface. The build-up of this porous layer increases sea ice freeboard, and if not accounted for, leads to overestimates of sea ice thickness from surface elevation measurements. In order to quantify this buoyant effect, the solid fraction of the sub-ice platelet layer must be estimated. An extensive in situ data set measured in 2011 in McMurdo Sound in the southwestern Ross Sea is used to achieve this. We use drill-hole measurements and the hydrostatic equilibrium assumption to estimate a mean value for the solid fraction of this sub-ice platelet layer of 0.16. This is highly dependent upon the uncertainty in sea ice density. We test this value with independent Global Navigation Satellite System (GNSS) surface elevation data to estimate sea ice thickness. We find that sea ice thickness can be overestimated by up to 19 with a mean deviation of 12% as a result of the influence of the sub-ice platelet layer. It is concluded that within 100 km of an ice shelf this influence might need to be considered when undertaking sea ice thickness investigations using remote sensing surface elevation measurements. Copyright 2014 Author(s).AcknowledgementsThe authors would like to acknowledge the K063 2011 fieldwork team including J. Beckers, A. Gough and K. Hughes and further the Scott Base staff of 2011. We would like to thank J.-F. Baure of Icam School of Engineering, Toulouse, France for processing GNSS data during a University of Canterbury supported internship. We are grateful for the logistics support of Antarctica New Zealand. Envisat ASAR data were received through CryoSat cal/val project 4512. This work was carried out at Gateway Antarctica, University of Canterbury, Christchurch, New Zealand.

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1st AuthorPrice, D.AuthorPrice, D.Rack, W.Langhorne, P.Haas, C.Leonard, G.Barnsdale, K.Year2014JournalCryosphereVolume8Number3Pages1031-1039DOI10.5194/tc-8-1031-2014URLhttps://www.scopus.com/inward/recor.....deab367f3af573b3a9cb2a8a9KeywordsGNSSice shelfice thicknessice-ocean interactionin situ measurementmeasurement methodremote sensingsatellite imagerysea ice, AntarcticaEast AntarcticaMcMurdo SoundRoss SeaSouthern Ocean, rank5ProgrammeK131 - Sea Ice and Southern Ocean Processes

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TypeArticleCitationPrice, D., Rack, W., Langhorne, P., Haas, C., Leonard, G. and Barnsdale, K. (2014) The sub-ice platelet layer and its influence on freeboard to thickness conversion of Antarctic sea ice. Cryosphere, 8(3): 1031-1039 doi:10.5194/tc-8-1031-2014