Temporal and spatial variabilities in the sediment temperature on the Baeksu tidal flat, Korea

The vertical structure of the sediment temperature on the Baeksu tidal flat of western Korea was measured and analyzed. Five stations were established, and the temperatures measured at six different sediment levels from the surface to a depth of 40 cm, on 14 days for each season. The sediment temperature was found to be closely related with solar radiation and the tides. The temperatures were found to decrease with depth in spring and summer, and then increase with depth during autumn and winter. The mean temperature increased with increasing exposure-time ratio of the tidal flat during the 14 days of observation during both spring and summer, and then decreased in the autumn, by a ratio of 0.02-0.03 °C/% at most depths. The temperature variability increased greatly with increases in the exposure-time ratio. High peaks in the sediment temperatures were found at 24-, 8- and 6-h periods from spectral analyses. The peaks at the 24- and 6-h periods could be explained by the day-night change and the tide, respectively. The high energy at the 8-h period could be the result of the unequal duration of day and night. The spectral density was found to decrease with increasing depth and inundation time.