Spring Thermal Transition Date
Phenology is the climate influence on the timing between plant and animal production cycles. Many marine organisms time their reproductive cycles to best utilize seasonal phytoplankton blooms, like the spring bloom, and in turn temperature plays a role in the development of the spring bloom. One measure to characterize the change in the timing of thermal forcing is the date of arrival of a spring transition temperature, which will vary by region and is meant to mark the average temperature between winter and summer. The date of arrival of the spring thermal transition temperature has been relative constant since 1982 to approximately 2006 for the Northeast Shelf as a whole and its constituent ecoregions (see figure). Since 2006, spring transition date has advanced on the order of two weeks. The 2017 spring transition dates reflect the moderate temperature conditions observed this past spring and for many areas are more in line with the long term trend.