Reconstruction of the End Member Contributions to and Ventilation Rate of Glacial-Age Lower Atlantic Deep Water

冰期下大西洋深水端元贡献和通风率的重建

• 批准号: 0221979
• 负责人: Wallace Broecker
• 金额: $ 22.86万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0221979&HistoricalAwards=false
• 关键词: Reconstruction; End; Member; Contributions; Ventilation

ABSTRACTOCE-0221979Reorganizations of large-scale ocean circulation very likely triggered the large and abrupt climate changes which punctuated the glacial world. Hence, as part of our preparation to deal with the ongoing greenhouse gas buildup, we must learn as much as possible regarding the nature of the ocean's alternate modes of operation. This project is aimed toward doing just this.Two paleo observations for the glacial deep Atlantic fail to jibe. One is the difference between the 14 C to C ages for coexisting benthic and planktonic foraminifera, which was greater than that for pre-industrial time but still far less than that for the deep Pacific. This suggests that the conveyor circulation was operating at a somewhat reduced but still significant rate. The other is the tilt of density horizons across the Florida Straits reconstructed from 18O measurements on benthic foraminifera which suggest that the strength of conveyor circulation was far less than today's.In the absence of a clear way to reconcile these observations with one another and also with the nutrient content reconstructed for glacial age lower deep water, researchers at the Lamont Dougherty Eart Observatory of Columbia University will attempt to improve upon both the paleonutrient reconstruction and the estimates of benthic-planktonic age difference. To do so, they have identified 21 cores in the LDEO collection forming a traverse sampling along the western flank of the Mid Atlantic Ridge extending from 45'N to 45'S (water depth 3.6 + 0.4 km). They will establish the stratigraphy in each core by 14C and 18O measurements on planktonic foraminifera and also attempt to quantify the extent to which Holocene foraminifera have been mixed downward into the late glacial section by analyzing single benthic foraminifera for 18O. They will then do d18O, d13C, Cd, and Zn measurements on benthic foraminifera, and neodymium isotope measurements on dispersed ferromanganese coatings on fine silicate debris, in late glacial sections for all cores. Additionally they will measure benthic-planktonic 14C age differences on late glacial samples from the cores with the highest sedimentation rate.

大规模海洋环流的重组很可能引发了大规模的突然气候变化，这些变化使冰川世界中断。因此，作为我们准备应对持续的温室气体积累的一部分，我们必须尽可能多地了解海洋交替运作模式的性质。这个项目的目标就是要做到这一点。大西洋冰川深处的两个古观测结果并不一致。一是底栖有孔虫与浮游有孔虫共存的14 C ~ C年龄之差，大于工业化前时期，但远小于深太平洋时期。这表明输送机循环的运行速度有所降低，但仍然很大。另一个是根据对底栖有孔虫的18 O测量重建的横跨佛罗里达海峡的密度层位的倾斜，这表明输送环流的强度远小于今天的。在缺乏明确的方法来使这些观测相互一致的情况下，也使这些观测与冰川时代较低深水的营养物含量相一致，哥伦比亚大学的拉蒙道格拉斯-厄特天文台的研究人员将试图改进古营养素重建和底栖生物-浮游生物年龄差的估计。为此，他们确定了LDEO收集的21个岩心，形成了沿大西洋中脊西侧从北纬45 '延伸至南纬45'（水深3.6 + 0.4 km）的沿着取样的导线。他们将通过对南极有孔虫的14 C和18 O测量来建立每个岩心的地层学，并试图通过分析单个底栖有孔虫的18 O来量化全新世有孔虫向下混合到晚冰期部分的程度。 然后，他们将对底栖有孔虫进行d18 O、d13 C、Cd和Zn测量，并对所有岩心的晚冰期部分的细硅酸盐碎片上分散的锰铁涂层进行钕同位素测量。 此外，他们还将测量沉积速率最高的冰芯中晚冰期样品的底栖-浮游14 C年龄差异。