Warming and circulation change in the eastern South Pacific Ocean

Deep-ocean temperature, salinity and dissolved oxygen observations in the eastern South Pacific Ocean collected during the late austral fall in 1995 are compared with observations made there 28 years earlier during the same season and similar El Nino-Southern Oscillation phase. Warming observed above 800 m at 43°S reflects the production of warmer Subantarctic Mode Water in recent decades. Warming observed above 1600 m at 28°S is due to downward isotherm displacement and southward movement of water masses by 100-200 km, as revealed by joint analysis of temperature and oxygen data. Such changes would be expected for a weaker subtropical gyre in the South Pacific. An observed oxygen decrease between about 1800 m and 2900 m at 28°S may indicate enhanced southward, boundary current flow at mid-depths off Chile.