The thermal regime in salt marsh peat at Barnstable, Massachusetts

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Abstract
The major features of the thermal regime in the peat of a salt marsh at Barnstable, Massachusetts, are described by the theory of heat flow in a homogeneous noncon-vective medium subjected to an annual sinusoidal change in temperature having an amplitude of 12°C at the surface. The thermal diffusivity of the peat is 1.57 × 10−3 cm2 sec−1. Departures, attributed to meteorological effects, consist of a long term trend during the two-year period of observation, which may be approximated by a biennial sinusoidal component of 1°C amplitude, and of somewhat irregular perturbations occurring at intervals of about three months. The average effects attributed to the latter attenuate with depth at the rate expected for a component of one quarter year period. In the deeper layers of peat residuals remain after these components are eliminated from the observed data which are accounted for by the movement of ground water from the upland, a condition evidenced by the low chloride content of the peat at these depths. The mean temperature of the peat increases downward at a rate which indicates, when combined with the thermal diffusivity and volumetric heat capacity, that heat is moving upward through the peat layer at an average rate of 1.58 × 10−6 cal. cm−2 sec−1. This value agrees with previous determinations of the geothermal heat flux. The march of temperature at the marsh surface agrees closely in amplitude and epoch with that of the air over the upland. The mean temperature of the marsh is 0.9° cooler than the air, an effect attributed to evaporation. The effect of spring tides which flood the marsh is examined and it is concluded that the principal effect is to keep the peat moist and thus increase evaporation. DOI: 10.1111/j.2153-3490.1965.tb01416.x

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