In this study, we proposed an 88% match-up threshold method to determine phenological parameters
of marine phytoplankton spring bloom (timing, duration, and intensity). That madе it possible to estimate
their interannual variability for the period of 1998–2022 in the North European Basin (Barents, Norwegian, and
Greenland Seas). According to the results, over the past 25 years the spring bloom intensity in the area has
increased with a small trend of 0.02 mg m–3 year–1. However, there were no considerable shifts in the timing.
The zonal variability of the phenological characteristics shows that the spring bloom began later at high latitudes.