Classic CZCS Scenes Chapter 5: Orinoco River Plume in the Caribbean
In the previous chapter, the seasonal changes in the Arabian
Sea that are associated with the monsoon winds were discussed,
along with the corresponding shifts in the primary productivity in
the region. In this chapter, a different kind of seasonal effect is
illustrated.
In the equatorial rain forests of South America, the primary
seasonal change is apparent in the amount of rainfall. These tropical rain
forests experience a "dry" season in the winter and a "rainy" season
in the summer. The larger amount of rainfall in the rainy season causes a
significant increase in the flow and discharge of the major rivers
draining the South American continent.
CZCS composite image of the
eastern Caribbean Sea for October 1979, showing the spatial extent of the
Orinoco River plume of induced high productivity that occurs during the summer
rainy season. (Image courtesy of Dr. Frank Muller-Karger, University
of South Florida Remote Sensing Laboratory.)
The Orinoco River delta is located along the coast of
Venezuela, where the river flows into the southern Caribbean Sea
just east of Trinidad and Tobago. The drainage basin of the Orinoco
comprises most of the countries of Venezuela and Colombia, and part
of the northern region of Brazil.
During the rainy season, the fresh water of the Orinoco flowing
into the Caribbean Sea is carried to the northeast by the
predominant currents flowing along the South American coast. The river
outflow is enriched in nutrients, and because it is less dense
than seawater, the fresh water remains at the surface, breaking up into lenses of
less saline water. The nutrients in the river waters
stimulate phytoplankton growth, so that a plume of higher
productivity waters can be observed emanating from the Orinoco
delta into the Caribbean Sea.
The image shown here illustrates the extent of the Orinoco
River plume. It is evident from this image that the seasonal
productivity increase due to the discharge of the river extends over
much of the southern Caribbean Basin. Near Venezuela, some of
this productivity is carried over the Cariaco Trench, which due to a high
input of organic matter, is an anoxic ("no oxygen") basin. The anoxic
characteristics of the Cariaco Trench make it ideal for the
preservation of organic material, so that the seasonal changes in
productivity due to the Orinoco River discharge are recorded in the
sediments of the Cariaco Trench. The study of the sediments in the
basin, and the seasonal variation in the flux of organic matter,
allows detailed research into the climatic history of this region of the
ocean. (see References and related sites)
Chapter 6: The Gulf Stream
Chapter 4: Seasonal upwelling in the Arabian Sea
Index: Classic CZCS scenes
|
Atmos Composition
