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enough area in a sufficiently short period of time 
to synoptically sample at ocean-basin or global 
scales. In the future, oceanographers will be 
able to use SeaWiFS imagery to solve large-scale 
problems, such as the role of phytoplankton pro- 
duction in the global carbon cycle. It is possible 
to consider such ambitious goals for the future 
partly because of the successful integration of 
CZCS imagery into studies of relatively small-scale 
systems. 
The remainder of this section consists of a 
brief review of some of the scientific uses of 
CZCS imagery, a description of how SeaWiFS im- 
agery will be used in the early 1990s, and a dis- 
cussion of scientific research requirements for 
the SeaWiFS system. 
Studies of Small-scale 
Processes 
Small-scale ocean features, i.e., features en- 
compassing less than about 10,000 km? of ocean 
area, generally form and dissipate within relatively 
short periods of time (days to weeks). The pre- 
dominant use of CZCS imagery has been in con- 
ducting studies of small-scale features in the 
ocean because, until recently, small-scale fea- 
tures were of greatest interest to biological and 
chemical oceanographers. The dimensions of 
these features are clearly visible in satellite imag- 
ery. In contrast, mapping small-scale features 
from oceanographic research vessels is difficult, 
if not impossible, because the features change 
faster than the ships can map them. Small-scale 
studies will continue to be an important applica- 
tion for satellite-acquired ocean-color imagery, 
since the results of such studies are the building 
blocks upon which programs to study large-scale 
processes are built. 
River Plumes 
Riverine and estuarine plumes contain rela- 
tively high concentrations of suspended organic 
and inorganic material that are highly reflective in 
the visible spectrum. This high reflectance is 
easily observed by satellite-borne color scanners, 
such as the CZCS. An issue currently being de- 
bated is the fate of fluvial nutrients and their pos- 
sible effect on carbon budgets. Simply stated, 
"Do the nitrates and phosphates produced from 
agricultural and urban sources and injected via 
freshwater discharge into the coastal zone result 
in a significant enhancement in primary produc- 
tion?" To answer this question requires an un- 
derstanding of the sedimentation and circulation 
processes that control the exchange of material 
across the continental shelf. Ocean-color imag- 
ery is beginning to provide answers to such 
questions by providing time-series imagery of 
plume formation and dissipation on continental 
shelves and insight into other processes that af- 
fect the rate at which river and ocean water in- 
termix. 
Coastal Upwelling 
Vertical movement, or upwelling, of deep, 
cold, nutrient-rich water is an important process 
in the marine ecosystem. Upwelling areas tend 
to be highly productive and are often the site of 
important fisheries, such as the anchovy fishery 
off the Peruvian coast. Upwelling is largely 
caused by wind stress and may occur in the 
coastal ocean and deep sea. Winds favorable 
for upwelling are episodic, varying on time scales 
of 3 to 5 days and on length scales from a few 
tens to several hundreds of kilometers. In freshly 
upwelled waters, phytoplankton grow faster than 
zooplankton can consume them, and, as a result, 
a large fraction of the phytoplankton may sink to 
the bottom. Thus, sites of wind-driven upwelling 
are important in understanding the ocean's role 
in the global carbon cycle. 
Studies of wind-driven upwelling systems off 
the U.S. West Coast revealed that their extreme 
variability is difficult to resolve using traditional 
ship sampling. Hence, satellite imagery is a ne- 
cessary tool for resolving upwelling dynamics 
and, perhaps more importantly, for determining 
the large-scale effect of these systems. For in- 
stance, CZCS and AVHRR imagery showed for 
the first time that plumes of upwelled, productive 
waters extend hundreds of kilometers seaward 
off the U.S. West Coast, as illustrated in 
