Sea level variability over the Northwest European Shelf across different timescales

We examine the sea level variability over the Northwest European Shelf (NWES) across different timescales and its underlying drivers. Using a basin-scale Atlantic Ocean model that accurately reproduces the NWES sea level variability compared with observations, we separate the sea level change into interannual, seasonal, intraseasonal, and high-frequency (less than 10 days) components. The seasonal, intraseasonal, and high-frequency variabilities exhibit comparable magnitudes, whereas interannual variability contributes a smaller fraction of the total sea level variation. We further decompose the shelf sea level change into contributions from mass and steric (density) changes. Our analysis shows that the steric change only contributes to the seasonal cycle of the NWES sea level variability, primarily driven by surface heat transport rather than lateral one. In contrast, lateral mass transport induced by winds onto the shelf accounts for most of the variability on seasonal, intraseasonal, and high-frequency timescales. The mass transport contribution is strongly correlated with regional wind stresses across all timescales, which is explained by the Ekman transport mechanism. These correlations, however, exhibit distinct spatial patterns depending on the timescale considered.