Regionalization and Multidecadal Change in the Southern Canary Current Large Marine Ecosystem

Abstract

The current delineation of the southern Canary Current Large Marine Ecosystem fisheries management zones responds only to political divisions rather than ecological features or a combination of both. In this paper, we implemented three time series analysis techniques on spatially explicit daily and monthly resolved data sets from satellite and reanalysis. Methods are based on climatologies, wavelet analysis and clusters and seasonal regression models, thus covering different aspects of the upwelling dynamics. Due to the overall convergence of the outputs of the analysis, by describing the spatiotemporal dynamics of oceanographic processes and biogeochemical features, we delineate distinct robust subregions and examine their recent trends. Our results identified four subregions: (a) a tropical subregion (12–18–21°N), (b) a Western Sahara (18–21°N to 25°N), (c) a South Morocco (26–28°N) and (d) a North Morocco subregion (29–35°N). The tropical subregion continues to exhibit a highly seasonal upwelling pattern with decreasing duration of winter upwelling events, in contrast with the other subregions that show slight variations in their seasonality. Although wind-driven upwelling has intensified in Western Sahara, leading to a cooling trend in sea surface temperature, chlorophyll-a does not show a concomitant increase. The North Morocco subregion is experiencing an increase in both the intensity and duration of the upwelling, making it more closely resemble the permanent upwelling zone of Western Sahara. This revisited subdivision provides a robust framework for ecosystem-based management by incorporating current ecological variability. Monitoring of hydrographic and biological trends is essential to adapt boundaries to future conditions.