The tritium-helium age (in years) on the 26.5 kg m-3 density horizon in the Pacific. horizon corresponds to water masses slightly less dense, and hence shallower than the Intermediate Waters in the Pacific. Please remember that the age must not be interpreted literally. However, note the invasion of younger water (red) from the sub-polar outcrops (to the southeast in the South Pacific and the northwest in the North Pacific). The blue region denotes the older, poorly ventilated eastern equatorial zone that is also characterized by low oxygen and high nutrients on this horizon.