High Resolution Studies of Late Quaternary Climate and Oceanographic Change, Santa Barbara Basin

9529839 Kennett基金被要求对加利福尼亚州圣巴巴拉盆地的一个非常优质的晚第四纪沉积层序（厚度200 m） 893站点（水深588 m）进行高分辨率的古气候和古海洋调查。最初的年代学、氧同位素和有孔虫组合研究揭示了一个完整到近乎完整的气候记录，代表了近160年来~15 cm/100年的近线性沉积速率。该序列的位置很好，可以监测与北太平洋温盐环流变化模式相关的上升流中间水域的变化。沉积物序列记录了低氧条件下（以沉积物层状和低氧耐受性底栖有孔虫为代表）和高氧条件下（以非层状生物扰动沉积物和喜爱氧气的底栖有孔虫为代表）之间的多次振荡。我们对最近20天间隔的相对详细的研究表明，有孔虫18O和浮游有孔虫组合记录的盆地通风开关与全球气候变化密切相关。在较冷的时期（新仙女木期和末次盛冰期），氧合条件占优势。相反，在较温暖的时间间隔（Bolling/Allerod和全新世），缺氧条件发生，在较冷的时间间隔，浮游和底栖有孔虫对之间的放射性碳年龄差异较小（约90年）；在暖期较大（约470年）。我们对沉积物相和放射性碳年龄的这些振荡进行了解释，以反映中间水域的变化，在较冷的时间间隔内，相对于较暖的时间间隔（包括今天），来自相对近端的来源的比例更大。我们的初步研究表明，在过去的20年里，通风和气候变化之间没有任何明显的滞后。这表明影响圣巴巴拉盆地的环流变化与气候之间存在紧密耦合。圣巴巴拉盆地层序是一个对全球气候变化高度敏感的不稳定环境系统。我们最近还发现，893站点的层状沉积物层序与格陵兰冰盖记录的几乎整个冰川间冰期序列（Dansgaard-Oeschger事件）密切相关，并间接与北大西洋沉积物层序相关。我们建议进行研究来检验几个假设：1。在过去70年里，圣巴巴拉盆地的通风变化与全球气候变化密切相关；2. 过去70年的通风变化与北大西洋深海沉积物记录有关，通过海洋传送带环流的变化，或通过全球气候变化引起的太平洋中间水域的温盐变化，或两者同时发生；和3。最后一次间冰期（5e或Eemian亚阶段，125-115 ka）变暖高峰期间的气候与全新世的气候差异很大，足以影响太平洋中水深温盐环流的重大变化，进而导致我们在圣巴巴拉盆地记录的盆地环境条件的根本变化。

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.