Hindcast of the timing of the spring phytoplankton bloom in the Strait of Georgia, 1968-2010

Using a one-dimensional coupled bio-physical model, the spring phytoplankton bloom in the Strait of Georgia was hindcast for years 1968 to 2010. Relative to the long term mean (March 25), the timing of the bloom was later in the early 1970s (about April 2), earlier in the early 1990s (about March 18) and later again in recent years (about March 30). These long term shifts are related to shifts in the intensity of winter storms and cloudiness. A more dramatic shift is seen in the interannual variation in timing with the standard deviation over seven consecutive years doubling during the timeseries. Since the early 1990s there have been a few, very early blooms leading to a large interannual spread in bloom times. We show that this change is related to warming and therefore we project that this level of variation may continue under climate change.