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

该项目旨在定量了解上一次冰川盛期期间的海洋环流，这段时期的气候与今天截然不同，据推测，海洋的行为也完全不同。中心方法是将在现代世界中被发现有用的海洋环流模型与最后一次冰川盛期北大西洋的古海洋学替代数据结合起来。将两者结合的数值技术是基于拉格朗日乘子的最小二乘法，该方法是使用伴随模型实现的。代理数据将根据对相对误差的最佳估计进行单独加权。海洋状态的计算包括调整“第一次猜测”的初始和边界条件，然后对这些条件进行修改以减少模型-代理-数据的不匹配。最丰富的有用替代数据包括氧和碳同位素、推断的孔隙水盐度和各种海洋表面温度重建。估计将假设为一个永久的年度周期。支持工作主要针对现代海洋环流特性的推论，这些推论最容易与约束更差的上一次冰川盛期相比较。智力上的优点：在一个层面上，确定海洋环流是地球科学中一项基本的智力挑战--除了任何实际应用。在现代世界中，即使有相对较大的数据集，确定也是非常困难的。最后一次冰川盛期的循环是一个更大的智力挑战，因为它依赖于间接数据集(称为“代理人”)，而且在空间和时间上都是稀疏的。除了科学上的好奇心，海洋被广泛认为是决定过去和未来气候状态的主要因素，这些气候状态与现在的气候状态截然不同。只要上一次冰川盛期的海洋状态仍然如此模糊，就很难声称理解气候系统是如何工作的，这将破坏对未来可能会带来什么的预测，因为人为强迫增加。广泛的影响：这个项目是一个广泛的社区努力的一部分，旨在了解过去发生的非常不同的气候状态，包括完全冰川时期和基本上没有冰川的时期。一个共识是，海洋对这些不同状态的产生和/或长期维持的影响是非常重要的，但人们对此知之甚少。这一努力的独特之处在于，试图通过完全定量地使用所有替代数据加上一个被认为能够很好地描述现代世界的一般环流模型来理解最后一次冰川盛期的海洋。如果取得了成功的结果，这种方法可以用于过去的退冰期以及其他有足够数据的时期，也许是间冰期。大部分拟议的研究将由一名研究生完成，作为她的博士论文的一部分。

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.