Structure, salinity and isotopic composition of multi-year landfast sea ice in Nella Fjord, Antarctica

The structural, salinity and stable oxygen-isotopic properties of multi-year landfast sea-ice samples collected from Nella Fjord, East Antarctica were used to determine the ice formation process and the fractional contribution of snow, in both snow ice and superimposed ice, to the total sea-ice thickness. The textural analysis of the sea-ice cores revealed a general structure of a granular surface layer, horizontal c-axis in the columnar ice and, in some cases, a “buried” granular-ice layer at depth between two columnar-ice layers. The textural and isotopic properties of the ice core samples indicate that thermodynamic mechanisms alone are responsible for the development of the multi-year fast ice in the region investigated. Superimposed ice contributed 5% to the ice thickness at some sites. Using a mid-range isotopic criterion to distinguish between snow ice and frazil ice in the granular layers, we estimate that snow-ice layers contributed 38% of the total ice thickness in the samples. The actual fraction of snow in the granular-ice layers in different cores was from 1% to 24% of the total sea-ice thickness.