INVESTIGATING THE SPATIAL AND TEMPORAL PERSISTENCE OF THE EL NIÑO SOUTHERN OSCILLATION AND SOUTH ATLANTIC OCEANIC DIPOLE SYSTEMS USING SEDIMENTOLOGICAL EVIDENCE FROM MARINE CORES

Observed teleconnections, such as El Niño–Southern Oscillation (ENSO) and other oceanic dipole systems, are globally important factors in today's climate dynamics; however, their directly measured record is relatively short. These regional teleconnections, oscillating on multi-annual to –decadal time periods, are likely coupled to global synchronizations on millennial-scale variabilities. The observation (periodicity, local effect, indices, etc.) of these teleconnections are primarily from instrumental records, ice cores, and annually resolve biological proxies from the Late Holocene. Annually resolved proxy records from bivalves, wood, and algal mats indicate that Cenozoic deposits (Eocene) preserve evidence of climate variations on similar periodicities to modern teleconnections. However, there is also evidence that the coupled sea surface temperature (SST) patterns that are indicative of modern teleconnection/oceanic dipole system (strong, regional thermohaline gradients) are neither stable nor permanent features throughout the Cenozoic. The purpose of this research study was to gather and synthesize lower temporal resolution sedimentological evidence to determine the persistence of the strong SST gradients indicative of modern ENSO and South Atlantic oceanic dipole systems.

The two modern dipole systems were identified using inverse correlation of SST records and then characterized using modern instrument records and coupled ocean-atmospheric models. Geochemical, paleontological, and sedimentological data from Cenozoic deep sea sediment cores available from online data repositories were used to compile and synthesize sedimentological records of SST across dipole regions through geologic time. Correlation of the synthesized core records indicate that the present-day ~5ºC thermal gradient across the South Atlantic dipole region is relatively constant throughout the Neogene. In comparison, of the three ENSO end members, only the southwestern Pacific's regional ~4ºC thermal gradient remained consistent. Evidence from the ENSO equatorial dipole indicate changes in thermal gradients over time while the northeastern systems pattern remains inconclusive due to lack of spatial and temporal records recovered by sediment coring.