SST is derived by compositing data from three sources: the Advanced Very-High Resolution Radiometer onboard the Polar Orbiting Environmental Satellite (AVHRR-POES); and the MODIS Terra and MODIS Aqua sensors. The data represents the near-surface ocean temperature, not the temperature of the entire water column.
Synoptic views of surface concentrations of chlorophyll a are derived from the Sea-viewing Wide Field of View Sensors (SeaWiFS) and MODIS Aqua ocean color sensors. SeaWiFS data was used during the period 1998-2007; the sensor was out of service during most of the first half of 2008. MODIS Aqua data was used to represent trends in chlorophyll during 2008; however, there are known discrepancies between the two sensors. The MODIS data was transformed to reduce the bias between the two sensors, but the data should only be used qualitatively until an upcoming data reprocessing can be completed. Chlorophyll a is considered to be an index of the amount of phytoplankton biomass present in surface water.
Zooplankton biomass is derived from shipboard surveys of the U.S. Northeast Shelf ecosystem – these small animals provide the link from primary production to higher trophic levels. From 1977-1987, the MArine Resources Monitoring, Assessment, & Prediction (MARMAP) program conducted intensive surveys from Cape Hatteras, North Carolina to Nova Scotia. These efforts continued at a reduced level through the 1990s and are ongoing today as the Ecosystem Monitoring program (EcoMon). Currently, 30 plankton samples are taken 6 times a year in each of the four ecosystem subareas: Middle Atlantic Bight, Southern New England, Georges Bank, and Gulf of Maine (resulting in approximately 720 measures of zooplankton biomass annually). Zooplankton are identified to the lowest taxonomic level possible resulting in taxa specific abundances and distributions.