Figure 4 shows the difference between relative wind stress and resting ocean wind stress. Data for relative wind stress is obtained from scatterometers. These accurately represent the relative wind stress as they measure backscatter from small-scale structures on the ocean surface, which respond to the sea surface-air interface and not to wind speed.   
Overestimations of power input into the ocean in models have been identified when using wind stress calculated from zonal mean wind instead of relative wind stress, ranging between 20-35%. In regions where wind speeds are relatively low and current speeds relatively high this effect is the greatest. An example is the tropical Pacific ocean where trade winds blow with 5-9m/s and the ocean current velocities can exceed 1m/s. In this region, depending on if it is an El Niño or La Niña state, the wind stress difference (resting ocean wind stress minus relative wind stress) can vary between negative and positive, respectively.