The Humboldt current, occupying the upper ocean, flows equatorward carrying fresh, cold Sub-Antarctic surface water northward, along the outskirts of the subtropical gyre. The main flow of the current veers offshore in southern Peru, as a weaker limb continues to flow equatorward. Around 18th parallel south the fresh, cold waters begin to mix with the warm, high salinity Subtropical Surface waters. This collision causes partial subductions. Within this region, the equatorial undercurrent (EUC) flows eastward along the equator, feeding the Peru-Chile undercurrent (PCU) that moves poleward.