A PRELIMINARY ASSESSMENT OF HEMISPHERIC CLIMATE SYMMETRY DURING THE PLIOCENE: INSIGHTS FROM ODP 1088

The Pliocene (5.3-2.7Mya) was the most recent interval of sustained warmth (~3°C warmer on average globally than pre-industrial) and the most recent interval that the atmospheric concentration of carbon dioxide was comparable to modern at ~400ppm. As a result, the Pliocene has been studied as a possible analog for future climate change. Previous studies suggest fairly hemispherically symmetric responses to forcing on long-time scales (millions of years). Here, we explore the coordination of the climate system on orbital (10,000 year) timescales by presenting a ~3kyr resolution, alkenone-derived, sea surface temperature (SST) record from Ocean Drilling Program (ODP) Site 1088 (41°S, 13.5°E, 2082m water depth) in the South Atlantic Ocean. We examine the hemispheric and interbasin symmetry of SST on orbital timescales. Our Site 1088 SST and productivity records demonstrate no long-term trend but strong glacial-interglacial variations (~3ºC in magnitude on average) from 3.8-2.4Ma. Additionally, novel pronounced coolings (~5-6°C) are evident in this record antecedent to the start of Northern Hemisphere Glaciation (NHG) (2.7 Ma). One of these excursions corresponds to Marine Isotope Stage (MIS) M2, long considered a first failed attempt at NHG. We compare our SST record from Site 1088 with another S. Atlantic site (ODP 1090), a N. Atlantic site (Deep Sea Drilling Program (DSDP) 607), a S. Pacific site (ODP 1125), a tropical Atlantic site (ODP 662), and a tropical Pacific site (ODP 846). We find significantly different absolute temperatures, but quite similar variance in records from similar latitudes. Relatable features between the 1088 record and those from other localities demonstrate the viability of this site for paleoclimate reconstructions. These comparisons between records in different hemispheres and ocean basins indicate a broadly global response to changes in forcing on orbital timescales, despite a significant difference in glacial extent between hemispheres.