Collaborative Research: Beyond the Instrumental Record---The Ocean Circulation at the Last Glacial Maximum and the Deglacial sequence

合作研究：超越仪器记录——末次盛冰期的海洋环流和冰消期序列

• 批准号: 1060735
• 负责人: Carl Wunsch
• 金额: $ 33.58万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-04-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1060735&HistoricalAwards=false
• 关键词: Collaborative; Research; Beyond; Instrumental; Record

This project is directed at a quantitative understanding of the ocean circulation during the last glacial maximum, a period during which the climate was a radically different state from today with an ocean inferred to also have behaved quite differently. The central approach is to combine an ocean general circulation model found to be useful in the modern world, with the paleo-oceanographic proxy data for the North Atlantic during the last glacial maximum. The numerical technique for combining the two is based upon the least squared method of Lagrange multipliers as implemented using an adjoint model. Proxy data will be individually weighted according to best estimates of the relative errors. Calculation of the oceanic state involves adjusting "first-guess" initial and boundary conditions that are then modified to reduce the model-proxy-data misfits. The most abundant useful proxy data include isotopic oxygen and carbon, inferred pore water salinities and various sea surface temperature reconstructions. Estimates will be of an assumed perpetual yearly cycle. Supporting work is directed at inferences, mainly global ones, of circulation properties in the modern ocean that can most readily be compared to the much more poorly constrained last glacial maximum period.Intellectual Merit: At one level, determination of the ocean circulation is a fundamental intellectual challenge in the earth sciences - apart from any practical applications. Determination in the modern world is very difficult, even given the comparatively large data sets available. The circulation of the last glacial maximum presents a far greater intellectual challenge, dependent as it is on indirect data sets (called "proxies") and which are sparse in space and time. In addition to this scientific curiosity aspect, the ocean is widely regarded as a major contributor in determining past and future climate states differing radically from the present one. As long as the oceanic state during the last glacial maximum remains as obscure as it is, it will be extremely difficult to claim understanding how the climate system works, and it will undermine predictions of what the future might bring as anthropogenic forcing increases.Broader Impacts: This project is a part of a wide community effort aimed at understanding the very different climate state known to have occurred in the past, including periods of full glaciation and ones of essentially no ice. A consensus exists that the influence of the ocean in bring about these different states and/or sustaining them for extended periods of time is very important, but extremely poorly understood. This effort is unique in attempting to understand the ocean of the last glacial maximum by the fully quantitative use of all the proxy data plus a general circulation model thought to well describe the modern world. With a successfully outcome, this approach could be used to the deglacial periods as well as other intervals in the past, perhaps inter-glacial, where an adequate data exists. Most to the proposed research will be done by a graduate student as part of her Ph.D. thesis.

该项目旨在定量了解末次极大冰期的海洋环流，这一时期的气候与今天截然不同，据推测海洋的行为也大不相同。核心方法是将一个在现代世界有用的海洋环流模型与末次盛冰期北大西洋的古海洋学替代数据结合起来。结合两者的数值技术是基于拉格朗日乘子的最小二乘法，并使用伴随模型实现。代理数据将根据相对误差的最佳估计单独加权。海洋状态的计算包括调整“第一猜测”的初始条件和边界条件，然后修改这些条件以减少模型-代理数据的不匹配。最有用的代用数据包括同位素氧和碳、推断孔隙水盐度和各种海面温度重建。估计将是一个假定的永恒的年循环。支持的工作是针对现代海洋环流特性的推断，主要是全球性的推断，这些推断最容易与约束更差的末次极大冰期进行比较。知识价值：在一个层面上，海洋环流的确定是地球科学中一个基本的知识挑战——除了任何实际应用之外。在现代世界，即使有相对较大的可用数据集，也很难确定。末次盛冰期的环流带来了更大的智力挑战，因为它依赖于间接数据集（称为“代理”），而这些数据集在空间和时间上都很稀疏。除了这一令人好奇的科学方面，海洋还被广泛认为是决定过去和未来与现在截然不同的气候状态的主要因素。只要最后一次冰期极大期的海洋状态仍然像现在这样模糊不清，就很难宣称理解气候系统是如何运作的，而且随着人为强迫的增加，它将破坏对未来可能带来什么的预测。更广泛的影响：该项目是广泛的社区努力的一部分，旨在了解过去已知发生过的非常不同的气候状态，包括完全冰期和基本上没有冰的时期。人们一致认为，海洋的影响带来了这些不同的状态，并（或）使它们在较长时间内保持下去，这是非常重要的，但人们对这一点知之甚少。这项工作是独一无二的，它试图通过充分定量地利用所有代理数据，加上一个被认为能很好地描述现代世界的一般环流模式，来了解末次冰期极大期的海洋。有了成功的结果，这种方法可以用于去冰期以及过去的其他间隔，也许是间冰期，在那里有足够的数据存在。大部分拟议的研究将由研究生完成，作为她博士论文的一部分。