Figure 14. A time series of imagery extending over 
many years will be required to quantitatively deter- 
mine the coupling between upwelling and large- 
scale patterns in ocean basins. 
Seasonal Phytoplankton Blooms 
During the vertical mixing process in winter, 
deep waters rich in plant nutrients are mixed with 
near-surface waters that are depleted of nutrients. 
The net effect is fertilization of the upper layers of 
the ocean and stimulation of rapid phytoplankton 
growth as the daily sunlight increases in the spring. 
Figure 14. 
Plumes of chlo- 
rophyll-rich wa- 
ters extend 
many kilometers 
off the U.S. 
West Coast. 
(Courtesy of M. 
Abbott) 
This period of rapid growth and accumulation of 
phytoplankton biomass in the mixed layer is called 
a "spring phytoplankton bloom" and is illustrated 
in Figure 15. The spring bloom is one of the ma- 
jor events in the sea and is a time when the flux 
of dissolved carbon dioxide into phytoplankton bi- 
omass is very rapid. Thus, spring blooms in the 
global ocean may play an important role in the 
global carbon cycle. Satellite ocean-color meas- 
urements provide the only means of answering 
questions concerning the large-scale distribution 
and timing of spring blooms in the global ocean. 
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