18O Concentrations in Sea Ice of the Weddell Sea, Antarctica
Abstract:We present data an ice texture, salinity, and 18O obtained from identical sections of ice cares during the Winter Weddell Sea Project 1986 an RV Polarstern fram July through August 1986, in the longitude range between 5 °W. and 7°E. We find no. uniquely definable relationship between 18O values and ice texture in a particular section. However, most of the snow ice as well as same sections of frazil ice are found to. have negative 18O concentrations. This is due to varying degrees of admixtures of meteoric ice (snow) and sea-water during formation of snow ice. In contrast to common assumptions, our results seem to. indicate that a snow caver contributes positively to sea-ice growth rather than slowing down the overall growth rate. Based an a simple model, we have estimated the contributions of meteoric ice (mean of 3 ± 3%) and the combined meteoric ice/sea-water fraction (a minimum of 7 ± 6%) to the total ice thickness far the majority of the sampled f1aes. Although this is only a moderate contribution to the overall mass balance, in the absence of congelation growth it nevertheless enhances ice growth in general. This hypothesis is independently supported by our snow- and ice-thickness data (Wadhams and others, 1987), which demonstrate that the depression of the snow/ice interface below the water line (i.e. a negative freeboard) and the formation of snow ice is a common occurrence in the Weddell Sea. Therefore, we hypothesize that the major part of the observed apparent increase in ice thickness between our inbound and outbound tracks of WWSP'86 may not be derived from “regular”, thermodynamically driven congelation growth, but rather from the snow-ice component in f1oes of the Weddell Sea.
Document Type: Research Article
Publication date: January 1, 1990
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