North Atlantic patterns of primary production and phenology in two Earth System Models

Abstract. Uniquely long datasets, spanning 1750–2100, of daily output from two fully coupled CMIP6 Earth System Models, EC-Earth3-CC and NorESM2-LM, have been used to investigate the historical and future (under SSP5-8.5 scenario) evolution of marine net primary production and its phenology in a North Atlantic region (30–60° N). We compared the data to estimates of net primary production (NPP) derived from the CAFE satellite data and found significant differences between the Earth System Model simulations and the CAFE model. The low spatial resolution of the earth system models can explain much of such difference. However, the two models well represent both the magnitude of NPP and the seasonal cycles. The daily output made it possible to detect change points in peak NPP. Two major change points in peak NPP, of an amplitude not present in the PI-Control or the historical simulation, were detected in both Earth System Models in the first decade of the 21st century. The results clearly indicate a shift towards an earlier peak NPP with a clear inflection point in the beginning of the 21st century, at the end of the historical simulation. The early timing of the detected shifts in both models suggests that similar shifts could already have been initiated or start in the near future. This highlights the need for long term monitoring campaigns in the North Atlantic.