Airborne thickness and freeboard measurements over the McMur

Details of Research

TitleAirborne thickness and freeboard measurements over the McMurdo Ice Shelf, Antarctica, and implications for ice densityAbstractWe present airborne measurements to investigate the thickness of the western McMurdo Ice Shelf in the western Ross Sea, Antarctica. Because of basal accretion of marine ice and brine intrusions conventional radar systems are limited in detecting the ice thickness in this area. In November 2009, we used a helicopter-borne laser and electromagnetic induction sounder (EM bird) to measure several thickness and freeboard profiles across the ice shelf. The maximum electromagnetically detectable ice thickness was about 55 m. Assuming hydrostatic equilibrium, the simultaneous measurement of ice freeboard and thickness was used to derive bulk ice densities ranging from 800 to 975 kg m-3. Densities higher than those of pure ice can be largely explained by the abundance of sediments accumulated at the surface and present within the ice shelf, and are likely to a smaller extent related to the overestimation of ice thickness by the electromagnetic induction measurement related to the presence of a subice platelet layer. The equivalent thickness of debris at a density of 2800 kg m-3 is found to be up to about 2 m thick. A subice platelet layer below the ice shelf, similar to what is observed in front of the ice shelf below the sea ice, is likely to exist in areas of highest thickness. The thickness and density distribution reflects a picture of areas of basal freezing and supercooled Ice Shelf Water emerging from below the central ice shelf cavity into McMurdo Sound. Key Points EM and laser measurements for ice shelf Freeboard and thickness used to derive bulk densities High bulk densities a result of glacial sediments and sub-ice platelet layer Ã‚Copyright2013. American Geophysical Union. All Rights Reserved.AcknowledgementsThe field work was supported by Antarctica New Zealand event K053. Envisat ASAR satellite imagery was received through CryoSat cal/val project 4512. Participation in the 2009 field validation by A. Gough and W. Clavano is greatly acknowledged. Thanks to N. Glasser and one anonymous reviewer for very constructive comments on the manuscript.

Details

1st AuthorRack, W.AuthorRack, W.Haas, C.Langhorne, P.Year2013JournalJournal of Geophysical Research: OceansVolume118Number11Pages5899-5907DOI10.1002/2013JC009084URLhttps://www.scopus.com/inward/recor.....74e6f098bee2b00fb6085931eKeywordsBirdsElectromagnetic inductionRadar systemsSea ice, Airborne measurementsBulk densityDensity distributionsfreeboardHydrostatic equilibriumMcmurdo ice shelvesSimultaneous measurementthickness, Platelets, accretionairborne surveybulk densityelectromagnetic fieldglacial depositice thicknessradar imagery, AntarcticaEast AntarcticaMcMurdo Ice ShelfRoss SeaSouthern Ocean, Aves, rank5Author Keywordsbulk densityelectromagnetic inductionEM birdfreeboardMcMurdo Ice Shelfthickness

Other

TypeArticleCitationRack, W., Haas, C. and Langhorne, P. (2013) Airborne thickness and freeboard measurements over the McMurdo Ice Shelf, Antarctica, and implications for ice density. Journal of Geophysical Research: Oceans, 118(11): 5899-5907 doi:10.1002/2013JC009084 IdentifierRack2013Relevancerank5