Development, structure and composition of land-fast sea ice in the northern Baltic Sea

The structural and stable-oxygen-isotopic properties of sea-ice samples collected on land-fast sea ice in the northern Baltic Sea, at 60.2-65.7degreesN, 21.3-26.9degreesE, were used to estimate the contribution of snow ice to the total sea-ice thickness, and the fraction of snow in the snow-ice layers and in the total sea-ice thickness. The textural analysis of the sea-ice cores revealed a general structure of a granular surface layer and a columnar basal layer. Using different isotopic criteria to distinguish snow-ice layers, we estimate that snow-ice layers contributed on average 24-32% of the total ice thickness in the study region. Transition ice (intermediate granular-columnar ice) also contributed significantly to the total ice thickness. The snow in the snow-ice layers contributed on average 18-21% of the total sea-ice thickness (by mass), a significant contribution when compared to other regions with sea-ice cover. The methods used could be improved to give more accurate estimates, especially by improving knowledge of the temporal variability of the isotopic properties of the snow incorporated into the sea-ice cover. However, our results can be regarded as plausible estimates for the contribution of snow ice and snow to sea-ice growth in the study area.