Evaluation of annual and interannual trends of marine Chlorophyll concentration

Since 1997, remote sensing of the ocean colour has routinely documented ecosystems health and productivity on a global scale. Therefore, these observations, especially chlorophyll-a concentration, are particularly important not only for the management of living marine resources but also for climate studies as the ocean might act as a sink or a source of carbon for the atmosphere. In such a context, reliable evaluations of trends, whether seasonal, annual, or especially interannual variations, are critical.

There are several products of surface chlorophyll concentrations derived from ocean colour sensing available through the Copernicus Marine Service. Some of them are more adapted to specific regional seas and use adapted algorithms for chlorophyll retrieval. There also exist chlorophyll products at global scale that are built with different assumptions each of them aiming at building the best time series (from 1997 up to now) for climate analysis. Moreover, some products offer uncertainty estimates and/or quality indicators that are useful for trend computations. We will present an intercomparison of trend evaluations made with these different products at different time scales (annual and interannual). Differences will be commented on and explained.