Satellite Ocean Color Imagery Research Articles

Study ofA Recurring Anticyclonic Eddy Off The Northeast Korean Coast Using Satellite Ocean Color and Sea Surface Temperature Imagery

Study ofA Recurring Anticyclonic Eddy Off The Northeast Korean Coast Using Satellite Ocean Color and Sea Surface Temperature Imagery

Episodic inputs of atmospheric nitrogen to the Sargasso Sea: Contributions to new production and phytoplankton blooms

Atmospheric wet deposition rates of nitrate and ammonia on Bermuda collected in the Atmosphere Ocean Chemistry Experiment (AEROCE) are compared with the synoptic measurements of carbon and nitrogen cycling from the U.S. Joint Global Ocean Flux Study (JGOFS) Bermuda Atlantic Time Series Study (BATS) station, 75 km southeast of Bermuda. Measurable deposition events were found on 23.8% of the days between October 1, 1988 and June 30, 1991. However, only a few of these events significantly contributed to the standing stocks of nitrogen and phytoplankton or rates of primary production. For 1.7% of the days each year, the atmospheric nitrogen deposition would have equaled the sinking particulate nitrogen flux as estimated by sediment traps. For only 0.2% of the time, would adequate nitrogen be deposited to a 20 m mixed layer to change the surface concentrations of particulate organic nitrogen by 10%. The results are dramatically different if all of the deposition remains confined to the upper l m of the water column enabling intense, surface phytoplankton blooms to occur. The occurrence of these near‐surface blooms may be an important signal in the interpretation of satellite ocean color imagery, particularly when the satellite data are used to infer whole water‐column phytoplankton stocks or productivity. Numerical simulations of the evolution of the near‐surface mixed layer after a rainfall event indicate that low salinity surface waters would be mixed to the upper 10 m or so within 2‐4 hours, except for wind speeds less than approximately 5m s−1. Thus, wet deposition induced surface algae blooms should only be observed under relatively calm meteorological conditions. In summary, wet deposition of nitrogen is a relatively unimportant process in affecting upper ocean nitrogen cycling for the Sargasso Sea off Bermuda, although in oceans with lower productivity and areas where deposition may increase with future industrial development, episodic deposition events may eventually have some short‐term impacts on the local nitrogen cycle. To assess the total impact of atmospheric deposition of nitrogen will require additional information on dry deposition and the organic nitrogen content of rainwater.

Bio‐optical provinces of the Northeast Pacific Ocean: A provisional analysis.

A provisional analysis of satellite ocean color imagery and in situ profiles of spectral irradiance and Chl a fluorescence partitions the Northeast Pacific Ocean into four geographically and bio‐optically distinct provinces: the California Current system, the Alaskan gyre, the east central North Pacific central gyre, and the subarctic front. Within each province in a given 2‐month period (June– July 1985 and October–November 1982), a family of regression equations was found to accurately predict the vertical profiles of irradiance attenuation and normalized Chl a fluorescence from K490—the surface diffuse attenuation coefficient which can be estimated from remotely sensed ocean color. The irradiance attenuation profile (to the depth where irradiance is 0.1% of the surface value) is predicted directly from the reciprocal of K490. Prediction of the Chl a fluorescence profile is based on a log‐linear photoadaptive profile of fluorescence over diffuse optical depth—a conceptual model which robustly fit the entire sample analyzed. Given K490, the profile is determined from four regression models predicting the depth in meters of the fluorescence maximum, the optical depth of the deep background fluorescence minimum, the surface intercept of the profile, and the slope of the profile between the surface and maximum.