Observations on the effects of frost on beach sediments at Rimouski, lower St. Lawrence Estuary, Québec
Freezing of beach sediment during exposure to cold air and subsequent thawing upon immersion have been analyzed in a strong tidal environment, near Rimouski in the St. Lawrence Estuary (Quebec). Temperature data, recorded at different depths in the sediment over a 25-h period above the high water mark and following a sudden drop of air temperature to −6 °C, indicate that temperatures in the top 15 cm of the beach dropped below the freezing point of seawater (<−1.36 °C). At the mid-tide level station, which was alternately exposed to air and immersed, freezing temperatures were observed to a depth of approximately 5 cm. Observations show that the surface sediment became ice-cemented to a corresponding depth. Temperature changes on exposure to air and immersion were rapid in the surface sandy layer (about 5 cm) and slower in the underlying coarser sediment. Temperature changes were barely perceptible at low tide level and no ice-cemented sediment was observed. Observations on the frozen beach showed that wa...