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|Title:||Petrographic and salinity characteristics of brackish water ice in the Bay of Bothnia|
|Authors:||Institute of Marine Research (Finland)|
Radarsat Project Office. (Ottowa, Canada)
NASA Oceanic Processes Program.
United States. Office of Naval Research.
Gow, Anthony Jack.
Weeks, W. F.
|Keywords:||Bay of Bothnia|
|Publisher:||Cold Regions Research and Engineering Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||CRREL report ; 92-13.|
Abstract: Field observations made during the March 1988 BEPERS (Bothnian Experiment in Preparation for ERS-1) remote sensing experiment included measurements of the snow and ice thickness, temperature, salinity and crystal structure profiles of the different types of brackish ice that form in the Bay of Bothnia. Both undeformed fast ice and ice that had formed under more disturbed conditions were sampled. Ice thicknesses varied from 36 to 64 cm in the bay to the east of Umeá, Sweden, with somewhat thicker ice (76 cm) occurring in the northernmost, nearly fresh water areas of the Bay of Bothnia. Three major ice crystal types or textures were identified—granular, transition and columnar ice—with the amount of each depending on the level of disturbance in the water column. At seven of the sixteen sites investigated, granular (mainly frazil) ice was the dominant component. At six of the remaining nine sites, columnar-congelation ice was the predominant ice crystal type. A mix of transition and transitioncongelation ice types dominated the structure of the remaining three sites. At all but two sites the bottom ice consisted of congelation ice, which in many instances exhibited the ice plate and brine layer substructure so typical of arctic sea ice. A variety of c-axis fabrics were observed in the columnar-congelation ice, including random, vertical and horizontal (planar) orientations. Aligned c-axes were observed at several locations, but in most cases there was no obvious pattern to the geographic arrangement of these fabrics. Surface water salinities ranged from 3.6 to 4.1 % except at the northernmost sites near Tornio, where essentially riverine fresh water was present. Bulk salinities ranged from 1.21-0.58% in the area of the main experiment to as low as 0.06% o near Tornio. Ice temperatures were usually higher than -3.5°C. Brine volume profiles were used to estimate representative ice property profiles for comparison with those of more typical sea ice of similar thicknesses from the Arctic Ocean. A variety of structural factors contributing to specific areas of high and low radar return from ice in the Bay of Bothnia are also discussed.
|Appears in Collections:||CRREL Report|