Accomplished Based Renewal: A Glacial Age Synthesis of Western North Atlantic Hydrography

在今天，墨西哥湾流起源的温暖和咸的近地表水被输送到高纬度地区，在那里它们放弃了热量，温暖了欧洲东北部。与此同时，地表水变得更稠密，流出北欧（格陵兰、冰岛和挪威）海，并在大约1000年的时间里扩散到海洋的其他部分。这个过程在冰河时期被打断了，因为北欧海被附近冰盖的水净化了，欧洲的气候更像今天的格陵兰岛。因此，人们通常认为，深海环流在冰期是“关闭”的，而在间冰期是“开启”的。考虑到深海环流的大小和对气候的影响，深海的采样很差。例如，直到最近才发现，在水深5000米以上的地方，有一种稠密的咸水，一定是在冰川时期在北欧或拉布拉多海产生的。所以现在可以说，冰川环流可能从来没有“停止”过。该项目将把北大西洋副热带西部冰川时代沉积物特性的现有数据库增加约30%，进而将形成冰川海洋“状态”的第一张三维图像，从而可以对热量、盐、营养物质和二氧化碳的输出进行建模和量化。为了准确地重建过去深水循环的变化，需要广泛分布的稳定同位素（d18O和d13C）测量和来自不同位置和深度的深海沉积物岩心的微观化石壳的放射性碳测年。这些核心是由首席研究员在1994年、1998年、2004年、2010年、2017年、2019年和2021年的研究巡航中收集的，其中12个将开发新的数据。稳定同位素是深海温度、盐度和二氧化碳含量的代用物，来自浮游生物的放射性碳数据将用于确定末次冰期高峰（约2万年前），并作为海底微化石壳中深水年龄的示踪剂。此外，冰川最大值数据汇编将包括来自北大西洋西部上部2km的岩心，那里的数据很少，但古性质的非常强的梯度指示了北大西洋冰川中间水的盐度、温度、营养和运输。这些综合数据将有助于研究海洋储存和运输热量、盐和营养物质的能力，并将用于验证气候模型。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。

In the present day, warm and salty near surface waters of Gulf Stream origin are transported to high latitudes where they give up their heat and warm northeast Europe. At the same time the surface waters become denser and exit the Nordic (Greenland, Iceland, and Norwegian) Seas and over about 1000 years spread to other parts of the ocean. This process was interrupted during glacial times because the Nordic Seas were freshened by water from nearby ice sheets, and climate in Europe was more like Greenland today. As a result, it is often thought that deep ocean circulation was “off” during glaciation, and “on” during interglacial climate. Considering the size and climate impact of deep ocean circulation, the deep ocean is poorly sampled. For example, only recently it was found that at depths greater than 5000 m there was a dense, salty water that must have been produced in the Nordic or Labrador Seas during glacial times. So now it can be stated that the glacial circulation was probably never “off.” This project will increase the existing database of glacial-age sediment properties from the western subtropical North Atlantic by about 30 percent, and that in turn will lead to a first three-dimensional picture of the “state” of the glacial ocean where the export of heat, salt, nutrients, and carbon dioxide can be modeled and quantified.To accurately reconstruct past changes in deep water circulation requires a wide distribution of stable isotope (d18O and d13C) measurements and radiocarbon dates on microscopic fossil shells from deep sea sediment cores at various locations and depths. These cores were collected by the Principal Investigator on research cruises from 1994, 1998, 2004, 2010, 2017, 2019, and 2021 and new data will be developed for a dozen of them. The stable isotopes are proxies for deep ocean temperature, salinity and CO2 content, and radiocarbon data from plankton will be used to identify the last glacial maximum (about 20,000 years ago) as well as act as a tracer for the age of the deep water in shells of bottom dwelling microfossils. In addition, the glacial maximum data compilation will include cores from the upper 2 km of the western North Atlantic, where there are few data, but very strong gradients in paleo properties are indicative of salinity, temperature, nutrients, and transport in Glacial North Atlantic Intermediate Water. The synthesis data will be useful for studying the ocean’s capacity to store and transport heat, salt, and nutrients and will be used to validate climate models.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.