Seasonal evolution of an ice-shelf influenced fast-ice regime, derived from an autonomous thermistor chain

Mario.Hoppmann [ at ]


Ice shelves strongly interact with coastal Antarctic sea ice and the associated ecosystem by creating conditions favorable to the formation of a sub-ice platelet layer. The close investigation of this phenomenon and its seasonal evolution remains a challenge due to logistical constraints and a lack of suitable methodology. In this study, we characterize the seasonal cycle of Antarctic fast ice adjacent to the Ekstr€om Ice Shelf in the eastern Weddell Sea. We used a thermistor chain with the additional ability to record the temperature response induced by cyclic heating of resistors embedded in the chain. Vertical sea-ice temperature and heating profiles obtained daily between November 2012 and February 2014 were analyzed to determine sea-ice and snow evolution, and to calculate the basal energy budget. The residual heat flux translated into an ice-volume fraction in the platelet layer of 0.18+-0.09, which we reproduced by a independent model simulation and agrees with earlier results. Manual drillings revealed an average annual platelet-layer thickness increase of at least 4 m, and an annual maximum thickness of 10 m beneath second-year sea ice. The oceanic contribution dominated the total sea-ice production during the study, effectively accounting for up to 70% of second-year sea-ice growth. In summer, an oceanic heat flux of 21 Wm-2 led to a partial thinning of the platelet layer. Our results further show that the active heating method, in contrast to the acoustic sounding approach, is well suited to derive the fast-ice mass balance in regions influenced by ocean/ice-shelf interaction, as it allows subdiurnal monitoring of the platelet-layer thickness.

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DOI 10.1002/2014JC010327

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Hoppmann, M. , Nicolaus, M. , Hunkeler, P. , Heil, P. , Behrens, L. K. , König-Langlo, G. and Gerdes, R. (2015): Seasonal evolution of an ice-shelf influenced fast-ice regime, derived from an autonomous thermistor chain , Journal of Geophysical Research: Oceans, 120 , pp. 1703-1724 . doi: 10.1002/2014JC010327

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