Global analysis of seasonality

Introduction Conclusions References Tables Figures Back Close Full Screen / Esc This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Abstract Shell fluxes of planktonic foraminifera species vary intra-annually in a pattern that appears to follow the seasonal cycle. However, the variation in the timing and prominence of seasonal flux maxima in space and among species remain poorly constrained. Thus, although changing seasonality may result in a flux-weighted temperature off-5 set of more than 5 • C within a species, this effect is often ignored in the interpretation of foraminifera-based paleoceanographic records. Here we present an analysis of the intra-annual pattern of shell flux variability in 37 globally distributed time series. The existence of a seasonal component in flux variability was objectively characterised using periodic regression. This analysis yielded estimates of the number, timing and promi-10 nence of seasonal flux maxima. Over 80 % of the flux series across all species showed a statistically significant periodic component, indicating that a considerable part of the intra-annual flux variability is predictable. Temperature appears to be a powerful pre-dictor of flux seasonality, but its effect differs among species. Three different modes of seasonality are distinguishable. Tropical and subtropical species (G. ruber (white and 15 pink varieties), appear to have a less predictable flux pattern with random peak timing in warm waters. In colder waters, sea-sonality is more prevalent: peak fluxes occur shortly after summer temperature maxima and peak prominence increases. This tendency is stronger in species with a narrower 20 temperature range, implying that warm-adapted species find it increasingly difficult to reproduce outside their optimum temperature range and that with decreasing mean temperature, their flux is progressively focussed into the warm season. The second group includes the temperate to cold-water species Globigerina bulloides, G. glutinata, 25 uvula. These species show a highly predictable seasonal pattern with one to two peaks a year, which occur earlier in warmer waters. Peak prominence in this group is independent of temperature. The earlier-when-warmer pattern in this group is related to 1328 Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc the timing of productivity maxima. Finally, the deep dwelling G. truncatulinoides and G. inflata show a regular and pronounced peak in winter/spring. The remarkably low flux outside the …