Figure F3. North-south cross section of water masses, characterized by dissolved oxygen concentrations in the southeast Pacific (Ocean Climate Laboratory, 1999). Southward-spreading middepth waters (PCW = Pacific Central Water) are characterized by relatively low oxygen and salinity and high nutrients. Northward-spreading Antarctic Intermediate Water (AAIW), ~400-1000 m depth, is high in oxygen but is low in both salinity and nutrients. The Gunther Undercurrent (GUC) flows southward between 100 and 400 m water depth and is characterized by relatively low oxygen and high nutrients. Vertical tails on site locations indicate likely changes in position relative to water masses associated with ~130-m sea level lowering at the Last Glacial Maximum.