Winds blowing southward along the west coast of the United States -- because of friction and the effects of Earth's rotation -- cause the surface layer of the ocean to move away from the coast. As the surface water moves offshore, cold, nutrient-rich water upwells from below to replace it. This upwelling fuels the growth of marine phytoplankton which, along with larger seaweeds, in turn nourish the incredible diversity of creatures found along the northern and central California coast.

Sensors such as SeaWiFS can "see" the effects of this upwelling-related productivity because the chlorophyll-bearing phytoplankton reflect predominantly green light back into space as opposed to the water itself which reflects predominantly blue wavelengths back to space.

The ocean areas of the above image (collected on 6 October 2002) are color coded to show chlorophyll concentrations. Land and cloud portions of the image are presented in quasi-natural color.

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Sea-viewing Wide Field-of-view Sensor (SeaWiFS) on board TERRA and AQUA POES satellites