Tidal Influences on Temperature Dynamics and Heat Exchange in Coastal Wetlands

Abstract

Soil temperature is crucial for the ecological functions of coastal wetlands. While the impact of tides on porewater flow is well recognized, their effect on soil temperature, which is also closely related to hydrodynamic processes, has not been sufficiently explored. This study investigates how dynamic tidal and atmospheric conditions interact to drive temperature variations in coastal wetlands, based on both laboratory experiments and numerical simulations. The results reveal that temperature plumes develop near creek banks, where the annual mean soil temperature closely correlates with tidal temperature. Tide-induced water circulation enhances local heat transfer and mixing, leading to moderate annual temperature ranges in areas close to creeks. In contrast, surface soil temperatures across the wetland platform are closer to atmospheric conditions in both annual mean values and ranges. At the field scale, tide-induced advective heat exchange is apparent, particularly near creeks. However, its net impact on the overall heat balance is relatively limited compared to the conductive heat flux at the sediment-water interface. The study also highlights the role of macropores in enhancing local temperature fluctuations by augmenting advective heat exchange and increasing heat capacity. Additionally, increased hydraulic and thermal conductivities in wetland sediments could result in more efficient temperature transfer and larger temperature ranges in deeper soil layers. These findings advance our understanding of the hydrodynamic and thermal processes in coastal wetlands coupled with benthic bioturbation.