Field measurements of the atmosphere, ocean, sea ice and sub-ice platelet layer at Atka Bay in 2013

• Main Authors: Hoppmann, Mario, Nicolaus, Marcel, Hunkeler, Priska A, König-Langlo, Gert
• Format: Dataset
• Language: English
• Published: PANGAEA 2015
• Subjects: AWI_SeaIce; Sea Ice Physics @ AWI; Antarctic; Atka; Ekström Ice Shelf; Weddell; Weddell Sea; Antarc*; Ice Shelf; Ice Shelves; Sea ice
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.833978; https://doi.org/10.1594/PANGAEA.833978

Ice shelves strongly interact with coastal Antarctic sea ice and the associated ecosystem by creating conditions favourable to the formation of a sub-ice platelet layer. The close investigation of this phenomenon and its seasonal evolution remain 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 Ekström 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 4m, and an annual maximum thickness of 10m 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 W/m**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 sub-diurnal monitoring of the platelet-layer thickness.