Result of in situ measurements across the river plume front. (a) Path of the survey ship through the river mouth and the river plume front 24 July, 2008, 12:00–12:30. Times in the panel denote moments of the crossings of the front. “Plume” is the area under the influence of the river water, where the salinity is relatively low and the turbidity is high compared to those of “ocean.” (b) Picture photographed from offshore of the river mouth looking towards the north-northeast. The left side of the front is ocean and the right side is plume. Time histories of (c) salinity, turbidity, and (d) vertical water temperature distribution observed in the vicinity of the river plume front.