Seasonal Variation in Water Circulations and Its Impact on Thermal Environment in a Coral Reef Area of Southwest Japan

Abstract

Summer and wintertime observations were conducted through deploying horizontal oceanographic time series sensors in a coral reef region of Southwest Japan to assess the existing hydrodynamic and thermal environments in relation to seasonal changes. A significant variation in water circulation and temperature distribution pattern was recorded in Shiraho reef area between two different seasons. During winter, a strong inflow of oceanic water was recorded inside the reef on a semidiurnal pattern that led to significant water temperature rising while in summer, considerable amount of sea water entered the reef area with a diurnal frequency causing water temperature slightly lower. Outside the reef, current was found to flow nearly parallel in direction to the north-south stretch of the reef.