Structural characteristics of the halocline in shallow brackish Lake Obuchi.

概要

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In order to elucidate the structural characteristics of the halocline in shallow Brackish Lake Obuchi, located virtually in the center of the Shimokita Peninsula in Aomori Prefecture, continuous observations were made of the salinity, current velocity, wind, meteorological tide and water level from April 1998 to December 2000. The results showed that in the center of the lake at a water depth of 4.5 m, the mean salinity was 15, 17 and 25 psu at a depth of 0, 2 and 4 m, respectively. Almost throughout the observation period a halocline formation could be seen at the lake center. The depth of the maximum density gradient tended to be deeper from summer to spring. From calculation of the Richardson number (Ri), an indicator of halocline structural stability, the halocline was clearly very stable at the center because Ri indicated approximately>10 (maximum 4.0×105, minimum 1.0×10-1). By analyzing the relationships of the halocline disappearance to the wind direction and speed, the salinity tended to become uniform at a depth from 0 m to 3 m with a wind speed of 6-8 m s-1 in an east-west direction. However, when winds higher than 10 m s-1 continued to blow for over 3 h, the water churned and mixed so that the halocline obviously disappeared. Nevertheless, the halocline rapidly reappeared after the wind subsided.
日本陸水学会の論文