Time series observations of bio-optical properties in the upper layer of the Sargasso Sea

Measurements were taken from a mooring in order to address questions concerning variability of bio-optical and physical properties in the upper ocean. The measurements are relevant to questions involving: 1) the identification of bio-optical processes and their time scales; 2) relationships between bio-optical variability and physical forcing; and 3) the development and testing of coupled bio-optical and physical models. The concurrent measurements provide time series of beam attenuation coefficient, chlorophyll fluorescence, photosynthetically available radiation, and dissolved oxygen along with horizontal currents and temperature. Data were obtained during three consecutive mooring periods in the upper 160m from 7 to 8 depths in the Sargasso Sea (34N 70W). Sampling was done at 4 minute intervals during a nine month period in 1987. Here, data obtained from the first deployment (March 1 through May 10) are described. Some of the primary observations include: 1) the abrupt onset of springtime stratification and episodic changes in the beam attenuation coefficient and chlorophyll fluorescence; 2) advective water mass variations associated with a cold core ring and warm Gulf Stream outbreak waters in the vicinity of the mooring; and 3) diurnal variations in the near surface beam attenuation coefficient and chlorophyll fluorescence which are associated with daily cycles of biological primary productivity. The present in situ, high frequency, long-term observations provide an impetus for similar future observations relevant to studies of optical property variability, primary productivity, and particulate fluxes.