Ice physical properties, structural characteristics and stratigraphy in Hobson’s Choice Ice Island and implications for the growth history of East Ward Hunt Ice Shelf, Canadian High Arctic

• Published in: Journal of Glaciology
• Main Authors: Jeffries, Martin O., Serson, Harold V., Krouse, H. Roy, Sackinger, William M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1991
• Subjects: Earth-Surface Processes; Arctic; Canada; Ward Hunt Ice Shelf; Disraeli Fiord; Ice Shelf; Iceberg*; Journal of Glaciology; Sea ice
• Online Access: http://dx.doi.org/10.1017/s0022143000007267; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000007267

Abstract Hobson’s Choice Ice Island is a tabular iceberg that calved in 1982-83 from East Ward Hunt Ice Shelf, N.W.T., Canada. Four ice cores have been analyzed for ice-crystal size, structure and fabric, bulk density, liquid electrical conductivity, δ 18 O and tritium. This has enabled a complete characterization of the physical properties and the structural characteristics of the ice-shelf component of Hobson’s Choice Ice Island and the first ever study of the stratigraphy and growth history of East Ward Hunt Ice Shelf. The δ 18 O values range from -34.6 to and indicate that all the ice is derived directly and/or indirectly from precipitation. High tritium values occur only in the lowermost 5 m of the ice shelf in a layer named stratum B. The tritium is anthropogenic and indicates bottom accretion of fresh-water ice since 1952, most likely from fresh water flowing out of Disraeli Fiord below the eastern ice shelf. Above this deepest and youngest ice layer is a 35-38 m thick, unconformable layer (stratum A) comprising three ice types: iced-firn, slush ice and lake ice. This depositional-superimposed ice represents past surface accumulation, which, according to δ 18 O and ice-crystal structure and size variations, occurred in three major periods, each interrupted by major ablation periods. Fresh water flowing out of Disraeli Fiord below the ice shelf during those warm intervals was the most likely agent responsible for the ablation and eventual complete loss of the original sea-ice platform on which stratum A initially accumulated. The three sub-strata of stratum A vary in thickness from core to core and suggest that there has been an inversion of relief during each ablation period. The different properties and occurrences of the three superimposed ice types are due primarily to past topographic variability.