Variability in the modelled and observed spring bloom in the North Atlantic: Variability in the modelled and observed spring bloom in the North Atlantic

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When projecting biogeochemical models into the future, it is important to be able to capture both the seasonal cycle and the interannual variability. In-situ and satellite measurements from the North Atlantic indicate that both timing and magnitude of phytoplankton blooms as well as the primary production vary considerably between years. Modelled chlorophyll and primary production produce a reasonable seasonal cycle, but the result show less interannual variability than the observations. The underlying assumptions behind these coupled physical-biological models is that the variability at the lower trophic levels is controlled by the variability in the climate system, it is therefore surprising that this variability is absent when the model is forced with an atmospheric reanalysis product that inherently contains this climatic variability. To pinpoint the reason behind the lack of variability we explore two different hypotheses for the model uniformity: (1) the observed variability occurs because of lack of representativity of the measurements (statistical sampling effects). (2) The variability stems from internal processes in the biological model. In this extended abstract, results from investigating only hypothesis (1) is presented