SOIL-TEMPERATURE VARIATIONS ON A TIDAL FLAT IN MINAS BASIN, BAY OF FUNDY, CANADA

The thermal features of the air (and water) over a tidal flat and within the sediments are described. Data were collected at Starrs Point, Minas Basin, Bay of Fundy in July 1989 as part of a multidisciplinary study of sediment properties. Temperature in the intertidal sediments exhibits rapid changes which occur principally during tidal inundation. Vertical gradients of 0·5 10-2 °C m-1 were found in the upper 0·25 m layer. Thermal diffusivity were calculated by two methods, the amplitude equation and a numerical approach. Observed rates of temperature change were compared with theoretical rates. The results show that, if sufficient data is available the numerical method is preferred. The presence of large populations of Corophium Volutator increases thermal diffusivity because of their vertical migrations. Therefore, the heat is distributed faster and through a greater depth. FFT analysis of air-water temperatures time series presented spectrum peaks at 24, 6, 2·7 and 1·8 h. Sediment temperature spectra show peaks at 24 and 6 h, confirming that radiation and tides are the driving mechanisms of the thermal behaviour over and within the tidal flat. An empirical orthogonal function analysis was performed on the temperature time series over the tidal flats. Modes 1 and 2 explain about 99·6% of the total variance. Mode 1 reflects the mean pattern of the temperature and mode 2 shows the abrupt changes produced when the water arrives or leaves the flat. © 1993 Academic Press. All rights reserved.