Collaborative Research: Importance of the subtropical gyre and North Atlantic Current in interglacial warmth

被称为有孔虫的微生物生活在海洋中，在碳酸钙的外壳中，大小如一颗小沙粒。每一种有孔虫都有自己的生活偏好--海面或深海、温水或冷水、食物的数量或光线的可用性。在海底沉积物中，有孔虫的外壳变成化石;它们提供了上覆水中生活条件的记录。其中一种叫做Globorolatia truncatulinoides的物种看起来像是用卷纸制成的派对小帽子，要么在右边，要么在左边。左卷取器喜欢它温暖。它们更喜欢生活在温暖的水层从表面延伸到水深达300米的地区，包括今天在墨西哥湾流中的佛罗里达海岸发现的沃茨。它们的化石记录告诉科学家气候的一个方面--在一个特定的位置存在温暖的沃茨。该项目将研究这些左卷取器的化石遗骸丰度的变化，这些化石遗骸沿着墨西哥湾流的路径从北美东海岸向东转向欧洲，然后向北经过爱尔兰。想象一下，在遥远的北部爱尔兰的海洋沉积物中发现一大堆这样的左盘绕派对帽子！这意味着过去的海洋条件和气候可能与佛罗里达相似。找到这些化石遗骸需要实验室工作，包括筛选深海泥浆以分离有孔虫，其中可以识别和计数派对帽子。实验室工作将为PI学校的本科生提供本科生研究经验。它将给学生一个在实验室环境中动手工作的机会，包括划分采样地点和时间间隔，以便每个学生都可以“拥有”一部分数据。然后，学生将负责解释他们的数据与过去的海洋和气候变化。通过这种方式，每个学生都可以发展自己的成功故事，并在专业会议上展示他们的成果。该项目还将资助特拉华州大学的一名研究生。 该项目旨在提供全球变暖期间低纬度到高纬度海洋学联系的记录。这项研究将检验这样一个假设，即亚热带环流的向极延伸和北大西洋洋流中增强的暖水输送促成了过去五个间冰期的温暖，特别是它们的最大值（MIS 1，5e，7a-c，7 e，9 e，11 c，PAGES等人，2016）。每个间冰期极大值对应于不同的边界条件（例如，日射量，CO2，冰量，PAGES等，2016年），但变暖的程度和强迫的幅度之间没有关系（PAGES等人，2016）。拟议的研究提供了另一个气候参数，温水平流，可能在这些时间间隔内放大高纬度温暖方面发挥了作用。为了重建暖水平流，该研究将使用Globorolatia truncatulinoides的螺旋方向作为北大西洋三个地点过去450 kyr的上层水柱结构的代表。它将侧重于海洋同位素阶段（MIS）1，5，7，9和11，以解决上层海洋水文的差异，可能与这些时间间隔重建的相对温暖。三个拟议的研究地点提供了一个空间断面之间的北方亚热带和副极地北大西洋（U1313，U1308，和网站980），和公布的轨道尺度的年龄模型提供了一种手段的时间相关性。G. truncatulinoides（左旋）与总G. truncatulinoides（左旋加右旋）反映了永久温跃层的相对深度，因此也反映了北大西洋亚热带至亚极地上层海洋热库的相对大小。左侧G占总G的比例增加。U1313的truncatulinoides测试反映了副热带环流的北向扩展。在U1308的左旋测试的这种增加表明北大西洋洋流的暖水输送增强，如果这种电流的影响在副极地站点980是显着的，左旋测试也会增加。拟议的记录将具有0.5 kyr的时间分辨率，以监测间冰期期间北方环流和北大西洋洋流中暖水平流的相对稳定性。拟议的项目是一个西班牙裔服务的妇女和性别非二元学生的小型文科学院（米尔斯）和一个主要的研究型大学（特拉华州大学）的教授之间的合作。该项目将提供一个具体的研究经验，两名本科生从米尔斯，让他们参加特拉华州的NSF赞助REU网站的大学。实验室工作旨在为本科生提供有意义的研究经验，目的是巩固他们对STEM相关职业的兴趣。该项目还将支持特拉华州大学的一名研究生和一名本科生助理。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Microscopic organisms called foraminifera live in the ocean, in shells of calcium carbonate the size of a small grain of sand. Every foraminifer has its own living preferences - surface or deep ocean, warm or cold water, the amount of food or the availability of light. In seafloor sediments the foraminifers’ shells become fossils; they provide a record of the living conditions in the overlying water. One such species called Globorolatia truncatulinoides looks like little party hats made from coiling paper either to the right or the left. The left coilers like it warm. They prefer to live in areas where a layer of warm water extends from the surface to a water depth as deep as 300 m, including waters that today are found off the coast of Florida in the Gulf Stream. Their fossil record tells scientist about one aspect of climate - the presence of warm waters in a particular location. This project will study changes in the abundance of fossil remains of these left coilers along the path of the Gulf Stream from the east coast of North America, turning east toward Europe, and then traveling north past Ireland. Imagine finding a whole bunch of these left coiling party hats in ocean sediments as far north as Ireland! It would mean that oceanic conditions and hence climate in the past may have been similar to Florida. Finding these fossil remains requires laboratory work involving sieving deep-sea mud to isolate foraminifera, in which the party hats can be identified and counted. The laboratory work will provide undergraduate research experience to undergraduates at both PI’s schools. It will give the students an opportunity for hands-on work in a laboratory setting, including dividing up the sampling locations and time intervals so that each student can “own” a portion of the data. The students will then be responsible for interpreting their data with respect to past oceanic and climate change. In this manner each student can develop their own success story and present their results at a professional meeting. The project will also support a graduate student at the University of Delaware. This project aims to provide a record of low to high latitude oceanographic links during intervals of global warmth. The study will test the hypothesis that poleward extension of the subtropical gyre and enhanced warm water transport in the North Atlantic Current contributed to the warmth of the past five interglacial intervals, and in particular, their maxima (MIS 1, 5e, 7a-c, 7e, 9e, 11c, PAGES et al., 2016). Each of the interglacial maxima corresponds to different boundary conditions (e.g., insolation, CO2, ice volume, PAGES et al., 2016), yet there is no relationship between the degree of warming and the amplitude of the forcing (PAGES et al., 2016). The proposed study contributes another climate parameter, warm water advection, that may have played a role in amplifying high latitude warmth during these intervals of time. To reconstruct warm water advection, the study will use the coiling direction of Globorolatia truncatulinoides as a proxy for upper water column structure at three sites in the North Atlantic Ocean spanning the past 450 kyr. It will focus on Marine Isotope Stages (MIS) 1, 5, 7, 9, and 11 in order to resolve differences in upper ocean hydrography that may relate to the relative warmth reconstructed for these intervals of time. Three proposed study sites provide a spatial transect between the northern subtropical and subpolar North Atlantic Ocean (U1313, U1308, and Site 980), and published orbital-scale age models provide a means for temporal correlations. The abundance of G. truncatulinoides (sinistral) in relation to total G. truncatulinoides (sinistral plus dextral) reflects the relative depth of the permanent thermocline and hence the relative size of the heat reservoir in the upper ocean of the subtropical to subpolar North Atlantic. An increase in the ratio of sinistral to total G. truncatulinoides tests at U1313 would reflect a northward expansion of the subtropical gyre. Such an increase in sinistral tests at U1308 would suggest enhanced warm water transport in the North Atlantic Current, and if the influence of this current is significant at subpolar Site 980, sinistral tests will increase there as well. The proposed records will have a temporal resolution of 0.5 kyr in order to monitor the relative stability of warm water advection in the northern gyre and the North Atlantic Current during the interglacial intervals. The proposed project is a collaboration between professors at a Hispanic serving small liberal arts college for women and gender nonbinary students (Mills) and a major research University (University of Delaware). The project will provide a concrete research experience to two undergraduate students from Mills by having them participate in the University of Delaware’s NSF sponsored REU site. The laboratory work is designed to provide the undergraduates with a meaningful research experience, with the goal of solidifying their interest in a STEM related career. The project will also support a graduate student and an undergraduate student assistant at the University of Delaware.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.