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，生活在小粒沙子大小的碳酸钙壳中。每一种有孔虫都有自己的生活偏好——表层或深海，温水或冷水，食物的数量或光线的可用性。在海底沉积物中，有孔虫的壳变成了化石；它们提供了上面水域生活条件的记录。其中一种叫做Globorolatia truncatulinoides，从右边或左边看起来就像用卷纸做成的小聚会帽。左边的卷筒喜欢温暖。它们喜欢生活在从表面延伸到水深达300米的温水层的地区，包括今天在佛罗里达海岸的墨西哥湾流中发现的水域。它们的化石记录告诉科学家气候的一个方面——在一个特定的地方存在温暖的海水。该项目将研究墨西哥湾流从北美东海岸向东转向欧洲，然后向北经过爱尔兰的路径上这些遗留的卷鱼化石遗骸的丰富程度的变化。想象一下，在遥远的爱尔兰北部的海洋沉积物中发现一大堆这样的左旋派对帽！这意味着过去的海洋环境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，以隔离有孔虫，在有孔虫中可以识别和计数聚会帽。实验室工作将为两所学院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，包括划分采样位置和时间间隔，以便每个学生都可以“拥有”一部分数据。然后，学生们将负责解释他们关于过去海洋和气候变化的数据。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。该项目还将支持特拉华大学的一名研究生。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。该研究将验证一个假设，即副热带环流的向极地延伸和北大西洋暖水输送的增强对过去5个间冰期的变暖，特别是它们的最大值（MIS 15,5e, 7a-c, 7e, 9e, 11c， PAGES等，2016）做出了贡献。每个间冰期极大值对应不同的边界条件（例如日照、CO2、冰体积，PAGES等，2016），但变暖程度与强迫幅度之间没有关系（PAGES等，2016）。提出的研究提供了另一个气候参数，即暖水平流，它可能在这些时间间隔内放大高纬度温度方面发挥了作用。为了重建暖流平流，本研究将使用圆弧藻（Globorolatia truncatulinoides）的盘绕方向作为过去450 kyr北大西洋三个地点上层水柱结构的代表。它将重点关注海洋同位素阶段（MIS） 1、5、7、9和11，以解决可能与这些时间间隔重建的相对温暖有关的上层海洋水文的差异。三个建议的研究地点（U1313、U1308和Site 980）提供了北大西洋副热带和亚极地之间的空间样带，已发表的轨道尺度年龄模型提供了时间相关性的手段。相对于总truncatulinoides（左偏侧加右偏侧）的G. truncatulinoides（左偏侧）丰度反映了永久温跃层的相对深度，从而反映了副热带至亚极地北大西洋上层海洋热储的相对大小。在U1313，偏侧型与总型的比值增加反映了副热带环流向北扩展。U1308的左旋试验增加表明北大西洋洋流的暖水输送增强，如果该洋流在亚极站点980的影响很大，则那里的左旋试验也会增加。所提出的记录将具有0.5 kyr的时间分辨率，以便监测间冰期北环流和北大西洋洋流的暖流平流的相对稳定性。拟议中的项目是一所面向女性和非二元性别学生的西班牙裔小型文理学院（米尔斯）和一所主要研究型大学（特拉华大学）的教授之间的合作。该项目将为来自米尔斯的两名本科生提供具体的研究经验，让他们参加特拉华大学的NSF赞助的REU网站。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大学的一名研究生和一名本科生助理。该奖项反映了美国国家科学基金会的法定使命，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.