by Goddard Space Flight Center

More articles in Satellites

A NASA satellite penetrates the blue waters off the west coast to reveal a spectacular image of a 700-mile long phytoplankton bloom stretching from southern California to the middle of Oregon. Phytoplankton represents the bottom rung of the ocean food chain and consists of many diverse species of microscopic free-floating ocean plants. The bloom was fed by an upwelling that brought cold nutrient rich water to the ocean surface. Upwellings occur regularly and often spawn large phytoplankton blooms that nourish an incredible diversity of creatures.


The upwelling around the California coast was brought on by winds blowing southward along the west coast of the United States. Friction and the effects of the 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, replacing it. This upwelling fuel the growth of marine phytoplankton which, along with larger seaweeds, nourishes the incredible diversity of creatures found along the northern and central California coast.

Sea-viewing Wide Field-of-view Sensor (SeaWiFS) on board the Orbview 2 satellite captured the phytoplankton bloom October 6, 2002 (Images 1 and 2 above). Red represents high concentration of chlorophyll, follow by orange, yellow and green. Land and cloud portions of the image are presented in natural color. SeaWiFS monitors ocean plant life by measuring the amount of chlorophyll in the ocean.

Large phytoplankton blooms tend to coincide with natural phenomena that drive that nutrient rich water to the surface. The process is called upwelling. Here's what's happening: winds coming off principal land masses push surface layers of water away from the shore. Into the resulting wind-driven void deeper water underneath the surface layers rushes in toward the coast, bringing with it nutrients for life to bloom.

It's different on the equator. There, water currents on either side of the hemispheric dividing line are generally moving in opposite directionsUagain due to planetary rotation and the Coriolis effect. As those currents rush past each other they ostensibly "peel back" the surface of the ocean, creating a void for deeper water to rush in and take its place.