Pulses in the eastern margin current and warmer water off the north west European shelf linked to North Sea ecosystem changes

The North Sea ecosystem has recently undergone dramatic changes, observed a s altered biomass of individual species spanning a range of life forms from algae to birds, with evidence for an approximate doubling in the abundance of both phytoplankton and benthos as part of a regime shift after 1987. Re markably, these changes, in part recorded in the Phytoplankton Colour Index of the Continuous Plankton Recorder (CPR) survey, are notable as episodic shifts occurring in 1988/89 and 1998 imposed on a gradual decadal trend. Th ese biological events are shown to be a response to coincident changes in o ceanic input and water temperature. Geostrophic transports have been calcul ated from a hydrographic section across the Rockall Trough, and a time seri es of sea-surface temperature derived from satellite observations. The 2 pu lses of oceanic incursion into the North Sea in circa 1988 and 1998 coincid ed with strong northward advection of anomalously warm water at the edge of the continental shelf.