<p>A regionally adapted one-dimensional model of Shelf Sea Physics and Primary Production (or S2P3) was tuned based on satellite and in-situ observations of sea surface temperature in the western English Channel over the period 2002–2014. Key parameters governing mixing and light attenuation were adjusted. Comparisons between default and tuned simulations revealed significant differences in interannual variability of stratification and the associated distributions of chlorophyll and dissolved inorganic nitrate. In the tuned simulation, stronger stratification leads to an approximately 10 d earlier occurrence of spring bloom, with an average 15% reduction in peak chlorophyll concentration, aligning more closely with satellite observations. The summer subsurface chlorophyll maxima were found deeper and up to 50% weaker in response to the deepening of the thermocline. Additionally, the tuned simulation exhibited more distinct subsurface chlorophyll maxima, which is in better qualitative agreement with the observations. Overall, our results demonstrate the capability of a computationally efficient one-dimensional model to capture the temporal variability of stratification and associated biological processes in a shelf sea.</p>