Satellite-derived ocean climatology around Santo Antão Island: 20 years of surface and near-surface observations

• SST, PAR, and PIC remained stable over 20 years. • Chl a , POC, and K 490 showed positive trends with time. • Stable SST conditions tied to regional increases in near-surface Chl a levels. • New ocean seasons proposed for the Santo Antão region. Understanding the implications of climate change is especially critical for the Cape Verde Islands, which are acutely vulnerable to climate variability and its associated impacts. This study characterised the temporal variability of surface and near-surface biophysical properties around Santo Antão using 20 years of MODIS-Aqua Level-2 imagery at 1 km resolution for Ocean Colour and Thermal Infrared parameters. The results of this study show that the waters around this island exhibited stable Sea Surface Temperature conditions with a pronounced seasonal cycle and no long-term warming over two decades, contrasting with global trends. Bio-optical parameters (Chlorophyll a , Diffuse Attenuation Coefficient and Particulate Organic Carbon) reflected the oligotrophic nature of the waters, with slight positive trends hinting at increasing concentrations of primary productivity. Consistently high levels of Photosynthetically Available Radiation affirmed light is not a limiting factor, with nutrient dynamics likely playing a dominant role. Particulate Inorganic Carbon displayed distinct variability, with no significant trends, underscoring the need for further research into its unique drivers. Based on ocean surface temperature cycles, the newly proposed seasonal classification successfully captured the dynamics of key parameters and demonstrated the value of satellite-derived data for long-term ecosystem monitoring. These findings enhanced the understanding of Santo Antão’s oceanographic dynamics and highlight the importance of regionally specific studies to complement global assessments. The results also provide a valuable baseline to support future research and inform conservation strategies and sustainable marine resource management in the Cape Verde region.