INTERANNUAL VARIABILITY IN GLOBAL PHYTOPLANKTON PHENOLOGY

Harriet Cole will be presenting a practice talk for the ASLO conference this week.

INTERANNUAL VARIABILITY IN GLOBAL PHYTOPLANKTON PHENOLOGY

Harriet Cole, Stephanie Henson, Adrian Martin & Andrew Yool

Large areas of the world's oceans experience a significant seasonal cycle in phytoplankton biomass. The timing of the bloom affects ecosystem dynamics with implications for biogeochemical cycles and higher trophic levels. Phenological changes may additionally indicate climate change, as the physical processes that control timing alter in a warming world.

However, to understand future phenological changes we must first determine variability in timing and what drives it.

Here, phytoplankton phenology metrics such as bloom initiation and peak are calculated globally using satellite ocean colour data. The impact of gaps in the time-series is investigated using a global biogeochemical model that assimilates SeaWiFS data. We find that the missing data significantly alter estimations of bloom timing. This uncertainty is seen to vary spatially and between different methods of calculating the same metric.

We choose the most reliable metric based on this analysis to explore the relationships between interannual variability in phenology and underlying physical drivers, such as mixed layer depth and climate oscillation indices. Relating phenology to indicators of ocean variability offers new insights on the mechanisms that control bloom dynamics.