RELATIONSHIPS BETWEEN SURFACE CHLOROPHYLL AND SOLAR IRRADIANCE IN THENORTH-ATLANTIC

In 1979 the sea surface light distribution at 490 nanometers (nm) in t he North Atlantic is shown to have influenced chlorophyll pigment conc entration. Results show the importance of solar irradiance on the deve lopment of the monthly chlorophyll bloom. Seasonal changes in ocean ch lorophyll are believed to be closely associated with the global carbon budget. Photosynthesis, which is responsible for the majority of the oceans' carbon fixation, is stimulated by light (irradiance) and nutri ent availability. The photosynthetic process in the surface waters is represented by the chlorophyll pigment concentration that can be obtai ned from ocean color. The North Atlantic mean monthly chlorophyll pigm ent concentration is computed from the Coastal Zone Color Scanner at a resolution of 20 km for 1979. Spatially and temporally coincident mea n monthly surface irradiance at 490 nm is modeled in hourly steps usin g atmospheric inputs of (a) aerosol optical depth, (b) ozone optical d epth, and (c) percentage of cloud cover. Different ocean regions were analyzed representing the equatorial, Northern Atlantic, Sargasso, Afr ican upwelling and U.S. shelf waters. The solar irradiance intensity i s shown to be related to chlorophyll pigment concentration in specific ocean regions. Spring and fall chlorophyll pigment blooms develop in regions where a strong seasonal cycle of irradiance is observed. This research illustrates the application of satellite ocean color for char acterizing the ocean's biological dependence on solar irradiance and p rovides an initial understanding of the seasonal carbon distribution a t the sea surface.