9529839 Kennett Funds are requested to conduct high resolution paleoclimatic and paleoceanographic investigations of Site 893 (588 m water depth), a late Quaternary sediment sequence (200 m thickness) of very high quality from Santa Barbara Basin, California. Initial chronological, oxygen isotopic and foraminiferal assemblage investigations reveal a complete to near-complete climate record representing near-linear sedimentation rates at ~15 cm/100 years for the last 160 kyrs. The sequence is well located to monitor changes in upwelled intermediate waters associated with changing modes of thermohaline circulation in the north Pacific. The sediment sequence records many oscillations between low oxygen conditions, represented by sediment laminations and low oxygen tolerant benthic foraminifers, and higher oxygen conditions, represented by non-laminated bioturbated sediments and oxygen-loving benthic forminifers. Our relatively detailed studies for the last 20 ky interval suggests close coincidence between switches in basinal ventilation and global climate changes as recorded by foraminiferal 18O and planktonic forminiferal assemblages. Oxygenated conditions prevailed during colder intervals (Younger Dryas and last glacial maximum). Conversely, suboxic conditions occurred during warmer intervals (Bolling/Allerod and Holocene), Radiocarbon age differences between planktonic and benthic foraminiferal pairs are smaller (av. 90 yrs) during cool intervals; larger (av. 470 yrs) during warm intervals. We have interpreted these oscillations in sediment facies and radiocarbon ages to reflect changes in intermediate waters with a greater proportion originating from a relatively proximal source during cooler intervals compared with a distal source during warmer intervals, including the present day. Our initial studies suggest an absence of any significant lags between the ventilation and climate changes during the last 20 kyrs. This suggest that a tight coupling existed between changes i n circulation influencing Santa Barbara Basin and climate. The Santa Barbara Basin sequence has been an inherently unstable environmental system that is highly sensitive to global climate change. We have also recently discovered that the sequence of laminated sediment intervals in Site 893 closely correlated with almost the entire sequence of glacial interstadials (Dansgaard-Oeschger events) as recorded in the Greenland ice sheet and indirectly in sediment sequences in the north Atlantic. We proposed to conduct studies to test several hypotheses: 1. that the changes in ventilation in Santa Barbara Basin are intimately linked with global climate change during the last 70 kyrs; 2. that the changes in ventilation during the last 70 kyrs were linked to the north Atlantic deep sea sediment record through changes in oceanic conveyor circulation, or through thermohaline changes in Pacific intermediate waters resulting from global climate change, or to both in unison; and 3. that climate during peak-warming of the last interglacial episode (substage 5e or Eemian; 125-115 ka) was sufficiently different from that of the Holocene to affect major change in Pacific thermohaline circulation at intermediate water depths that, in turn, caused fundamental changes in basinal environmental conditions that we record in Santa Barbara Basin.
