Paleoventilation Studies of the North Pacific Ocean

根据这一奖项，PIS将使用底栖生物和浮游有孔虫样本对的放射性碳含量来确定最近一次冰川消融期间关键时间间隔北太平洋的通风状态。这些估计将有助于理解过去100,000年来北太平洋沉积发生最戏剧性变化的时间及其之间的联系。东太平洋大陆边缘沉积物的组成(有机含量、层理)与气候有关的变化有很好的记录，但很难确定这些变化的原因。一些研究暗示了上层海洋生产力的变化，而另一些研究则认为西北太平洋露头地区中等深度底层水的通风变化起着主导作用。重要的是要确定这两种机制各自的贡献，因为它们各自意味着不同的气候强迫。以生产力为基础的对富有机/叠层沉积物的解释意味着整个太平洋东部边缘表层海洋的物理和生物条件(风场、层化、营养物质)发生了变化。相比之下，基于通风的解释意味着控制高纬度北太平洋致密水形成的因素(风、层化、海冰形成)发生了变化。支持者将从西北太平洋和鄂霍次克海1至4公里水深的一组沉积物岩芯，以及类似深度范围内的一组新的白令海岩心，确定关键去冰期段的底栖-浮游14C年龄差异。为了补充这些基于放射性碳的通风估计，他们将使用共存的底栖有孔虫对之间的d13C差异来估计相同深度范围和时间间隔内的底层水氧浓度，并将使用底栖有孔虫的累积率来估计有机物质流入海底的流量。这三组数据(B-P.14C、D13C和BFAR)将记录通风率、底水化学和从末次冰期到消冰期的碳通量之间的关系。这些数据可能有助于解决长期以来的争论，即生产力与底水通风在控制整个东太平洋中等深度富含有机的沉积物和层状沉积物的积累方面所起的作用。该项目将提供为期两年的半日制博士后支持。

Under this award the PIs will use the radiocarbon content of paired samples of benthic and planktonic foraminifera to determine the ventilation state of the North Pacific Ocean at key intervals during the most recent deglaciation. These estimates will help to understand the timing of and the connections between some of the most dramatic changes in North Pacific sedimentation in the past 100,000 years. Climate-linked changes in the composition of sediments from the eastern Pacific continental margin (organic content, lamination) are well documented, but it has been difficult to determine the cause of these changes. Some studies have implicated changes in upper ocean productivity, while others assign a dominant role to changes in ventilation of the intermediate-depth bottom waters in their northwest Pacific outcrop regions. It is important to determine the contributions from each of these two mechanisms because they each imply different climate forcing. Productivity-based explanations for organic rich / laminated sediments imply changes in the physical and biological conditions of the surface ocean (wind field, stratification, nutrients) all along the eastern margin of the Pacific. In contrast, ventilation-based explanations imply changes in the factors that control dense water formation in the high-latitude North Pacific (winds, stratification, sea ice formation). The proponents will determine benthic-planktonic 14C age differences on key deglacial intervals from a set of sediment cores from water depths ranging between 1 and 4 km in the northwest Pacific and the Okhotsk Sea and from a new set of Bering Sea cores over a similar depth range. To complement these radiocarbon-based ventilation estimates, they will use the d13C difference between pairs of co-existing benthic foraminifera to estimate bottom water oxygen concentrations over the same depth range and time intervals, and they will use the accumulation rate of benthic foraminifera to estimate the flux of organic matter to the sea floor. These three sets of data (B-P .14C, d 13C, and BFAR) will document the relationships between ventilation rate, bottom water chemistry, and carbon flux from the LGM through the deglacial. The data may help resolve the long-standing debate about the role of productivity versus the role of bottom water ventilation in controlling the accumulation of organic-rich sediments and laminated sediments at intermediate depths throughout the eastern Pacific. The project will provide half-time postdoctoral support for two years.