text: The following panels show sea surface concentrations of fields prepared by GLODAPv1.1. The "pre-industrial" is the 18th century, while "present-day" is approximately the 1990s.
  The following panels show sea surface concentrations of fields prepared by GLODAPv2. The "pre-industrial" is the 18th century, while "present-day" is normalised to 2002. Note that these properties are shown in mass units (per kilogram of seawater) rather than the volume units (per cubic metre of seawater) used in the GLODAPv1.1 panels.