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

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Hoppmann, Mario, Nicolaus, Marcel, Hunkeler, Priska, Heil, Petra, Behrens, Lisa Katharina, König-Langlo, Gert, Gerdes, Rüdiger
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 2015
• Subjects: Antarc*; Antarctic; Ice Shelf; Ice Shelves; Sea ice; Weddell Sea
• Online Access: https://epic.awi.de/id/eprint/37394/; https://epic.awi.de/id/eprint/37394/1/Hoppmann_JGR_2015.pdf; https://hdl.handle.net/10013/epic.46331; https://hdl.handle.net/10013/epic.46331.d001

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.