Simulating the Thermal Response of Tidal Sediments by Integrating Numerical Modeling and Field Measurements

Abstract

Tidal flat ecosystems hold significant socio-economic value but are vulnerable to increasingly frequent extreme climate events such as heatwaves. Predicting temperature effects on intertidal sediment ecology and biogeochemistry requires a high-resolution mechanistic model to simulate sediment thermal responses to weather conditions. Here, we develop an open-source model that captures sediment temperature dynamics over vertical distances up to 10 m, with sub-millimeter resolution near the sediment surface. Calibrated with field data from intertidal sediments (muds and sands) in the Oosterschelde tidal bay, the Netherlands, the model successfully reproduces temperature fluctuations from minutes to seasons at depths between 0.05 and 1 m. Key controlling parameters include sediment porosity, thermal properties of the dry sediment, and albedo. Simulated sediment temperatures show pronounced seasonal dynamics in the upper 2–3 m but stay relatively stable at depths between 6 and 10 m. Hence, the sediment seasonally alternates between states of being a heat source (September–March) and a heat sink (March–September) for the overlying water. Muddy sediments exhibit higher temperature than sandy sediments, and longer inundation periods yield more stable sediment surface temperatures. Fine-scale simulations identified March as the most dynamic month, with sediment surface temperature changing at rates up to 0.68°C min−1 and −0.71°C min−1, and temperature gradients in the top 1 cm reaching up to 4.8°C cm−1 and −8.4°C cm−1. Overall, our model offers a valuable analytical tool for studying estuarine and coastal biogeochemistry, particularly the impacts of climate change on tidal flat ecosystems.