Climatic controls on the spring phytoplankton growing season in a temperate shelf sea

Abstract The Northwest European Shelf is positioned directly beneath the North Atlantic Storm Track, within which frequency and intensity of transient storms are modulated by large‐scale climatic oscillations. In temperate shelf seas, impact on physical environment has received considerable attention, but effect biogeochemistry less studied. Here, we use output from a multidecadal (1982–2015) coupled physical‐biogeochemical model supported observations ocean gliders to investigate phytoplankton growth throughout winter‐spring transition. We define two separate events: spring bloom, defined as exponential following seasonal stratification, prebloom, occurring before accounting for up 22% total growth. Our results support paradigm that light first‐order control, with bloom initiating 22 days after stratification onset should levels be too low trigger bloom. prebloom heavily influenced phase Multidecadal Oscillation (AMO), demonstrated an acceleration in rate increase chlorophyll concentrations (±90% confidence limit) 7.6 ± 2.8 mg m −2 d −1 (during positive AMO) 13.1 4.3 (negative AMO), due modulation periods ephemeral occur between successive storms. propose events might help buffer lag supply larval recruitment, particularly during years when delayed.