Figure 9.20 Coastal upwelling. Wind from north Oregon- Califomia 20° 18° 16° Ekman transport To the west Thermocline Offshore current, Upwelling Continental shelf Chlorophyll Concentration b A satellite view of the U.S. west coast shows (in artificial In the Northern Hemisphere, coastal upwelling can be caused by winds from the north blowing along the west coast of a continent. Water moved offshore by Ekman transport is replaced by cold, deep, nutrient- laden water. In this diagram, temperature of the ocean surface is shown in degrees Celsius. (Vertical exaggeration ~100x.) color) the growth of small plantlike organisms stimu- lated by upwelled nutrients. The color bar indicates the concentration of chlorophyll in milligrams per cubic meter of seawater. Notice that chlorophyll concentration-and biological productivity-is highest near the coast. James Acker, Goddard Space Flight Center

What season of the year results in the greatest upwelling—thus the greatest growth of small, plantlike organisms, off the coast of California?