Author(s): T. Kawamura; M. A. Granskog; J. Ehn; T. Martma; A. Lindfors; N. Ishikawa; K. Shirasawa; M. Lepparanta; R. Vaikmae
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Abstract: Two winter observations have been performed along a 20-km transect from the mouth of the Gulf of Finland to the inner parts of the Pojo Bay. We collected ice samples together with snow and under-ice water samples at four sites in the area in March 1999 and several times in 2000. The ice samples from the outermost site, whose surface water salinity was1.3–3.3 psu (practical salinity unit), had a characteristic sea ice structure, while at the three inner sites, where the water salinity was 0.1–0.5 psu, structure similar to lake iceappeared. Thus the fresh water-sea ice boundary was at about 1 psu of water salinity, consistent with previous studies. The ice was two-layered. The δ O values suggest that the upper ice with granular structure is snow ice, while the lower layer is congelation ice. Snow contributed significantly to the sea ice growth in the area. The δ O values in thebottom ice layers are 1–2‰higher than in the water, which strongly suggests isotopic fractionation during freezing.
Year: 2002