The Advent of the Spring Bloom in the Eastern Subarctic Pacific Ocean

The spring phytoplankton bloom in the eastern subarctic Pacific Ocean was described from estimations of the critical depth and the depth of the mixed layer. The results suggested that the spring bloom begins during February in the area south of 45°N and east of 135°W. During March the bloom area advances in a northwesterly direction to 50°N at 125°W and 45°N at 135°W. A net increase in primary production is also possible during March near 55°N and 155°W. During April, the spring bloom is generally well established throughout the region except in a central area where suitable conditions are not firmly established until May. This description is supported by the distribution of copepods in the region during April.