Collaborative Research: Quantifying Abyssal Circulation and its Variability

合作研究：量化深海环流及其变化

• 批准号: 1850753
• 负责人: Geoffrey Gebbie
• 金额: $ 20.7万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-03-15 至 2023-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1850753&HistoricalAwards=false
• 关键词: Collaborative; Research; Quantifying; Abyssal; Circulation

The global ocean has absorbed over 90% of the excess anthropogenic heat between 1971 and 2010, with about 10% of that going into the deep ocean and contributing to global and local sea level rise. Despite these broad societal implications, the mechanisms driving the deep warming are still poorly understood. This project aims to improve our understanding of these mechanisms through a global study using a new method to utilize chemical tracers (in this case chlorofluorocarbons; CFCs) to overcome previous obstacles due to limitations from sparse data. The analysis will capitalize on a growing data set of detectable CFC concentrations throughout the deep ocean as anthropogenic tracers enter and circulate along the bottom limb of the overturning circulation of the ocean. This data set allows for both defining new pathways that bring new waters into the deep ocean and assessment of the variability in deep water formation rates. The variability will allow for correlations with surface conditions to evaluate driving mechanisms so that they can be included in climate models. In addition, this work will update decadal trends in abyssal warming, anthropogenic carbon uptake, and deep steric sea level rise annually through the end of the project in 2021. The results will help to close current global energy, carbon, and sea level budgets and advance our understanding of the physical mechanisms forcing the distribution of anthropogenic heat and carbon throughout the ocean. This work will demonstrate and explain modes of deep variability previously unknown for use in climate models leading to improved long-term climate projections under increased CO2 emissions, therefore enabling better societal adaptability to changes to come. The project will support a third year graduate student for his PhD work at SIO. In addition, smaller summer projects will be made available for undergraduate summer students through the Scripps Institution of Oceanography Undergraduates Research Fellowship (SURF) program. The project will produce gridded global CFC, deep ocean warming, and steric sea level rise data products that will be made available to the broader scientific and educational communities.The overall objective of this proposal is to understand the variability in the bottom limb of the Meridional Overturning Circulation (MOC) in order to quantify, explain, and forecast the role that the deep ocean plays in ocean heat and carbon uptake. The deep ocean is warming at a significant rate with important climatic implications for sea level rise and ocean heat absorption. Despite these broad societal implications, the mechanism driving this deep warming is still poorly understood and difficult to simulate in climate models, decreasing our ability to predict how the climate will change under increased CO2 emissions . One hypothesis is the warming is driven by a decrease in deep water formation around Antarctica. The deep CFC data will be used to produce annual gridded maps within neutral density surfaces around the globe by modeling the oceanic subsurface response and fitting the data within its uncertainty. The gridded CFC dataset will allow for inference of deep circulation, ventilation, and assessment of any interdecadal change in locations with multiple decades of data. It will validate any observed interdecadal variability by comparing to changes in tracer age, oxygen, and volume of deep water along repeated hydrographic sections. The decadal variability will be compared to observed deep warming trends in order to identify if these changes are causing the recent accumulation of heat in the abyssal ocean and explore any mechanisms driving the variability. This work will allow better characterization of the mean and variability of the deep transport along the bottom limb of the MOC and how it has affected deep-ocean temperatures. The new method to find tracer transport from CFCs to provide an improved estimate of deep ocean circulation, ventilation, and variability will also lay the groundwork for future monitoring of global deep-ocean warming.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.

在1971年至2010年之间，全球海洋吸收了超过90％的过量人为热量，其中约有10％进入深海，并促进了全球和当地的海平面上升。尽管有这些广泛的社会意义，但推动深度变暖的机制仍然很少理解。该项目旨在通过一项全球研究来利用一种新方法来利用化学示踪剂（在这种情况下为氯氟氯众； CFCS）通过全球研究来提高我们对这些机制的理解，以克服由于稀疏数据的限制而引起的先前障碍。当人为示踪剂进入并沿着海洋倾覆的底肢进入并循环时，该分析将利用不断增长的可检测到CFC浓度的数据集。该数据集允许定义将新水域带入深海的新途径，并评估深水形成率的变异性。可变性将允许与表面条件的相关性评估驾驶机制，从而将它们包括在气候模型中。此外，这项工作将在2021年的项目结束之前每年都会更新深渊变暖，人为碳吸收和深层海平面上升的衰落趋势。结果将有助于关闭当前的全球能源，碳和海平面预算，并促进我们对迫使人类热量热量和碳整个海洋分布的物理机制的理解。这项工作将证明和解释在二氧化碳排放量增加的情况下，在气候模型中未知的深层可变性模式，从而改善了长期气候预测，因此可以更好地对社会适应性进行更改的变化。该项目将为他在SIO的博士学位工作提供第三年的研究生。此外，较小的夏季项目将通过Scripps海洋学大学生研究奖学金（SURF）计划为本科夏季学生提供。该项目将生产网格的全球CFC，深海变暖以及将提供给更广泛的科学和教育社区的空间海平面上升数据产品。该提案的总体目的是了解子午倒闭循环（MOC）底肢的可变性（MOC）的可变性，以量化，并在海洋中进行量化，并在海洋中量化，并在海洋中进行深海的热量和Carbon plays plays plays and Carbon。深海以显着的速度变暖，对海平面上升和海洋热量吸收的重要影响。 尽管有这些广泛的社会意义，但在气候模型中，推动这种深度变暖的机制仍然很难理解，很难模拟，从而降低了我们预测气候如何在增加的二氧化碳排放下会改变的能力。一个假设是温暖是由南极周围深水形成的减少驱动的。 CFC数据将用于通过对海洋地下响应进行建模并将数据拟合到其不确定性之内，以在全球中性密度表面产生年度网格图。网格的CFC数据集将允许对具有数十年数据的位置中的任何次数变化进行深度循环，通风和评估。它将通过与沿重复的水文切片的示踪剂年龄，氧气和深水体积的变化进行比较，从而验证任何观察到的跨际变异性。将际变异性与观察到的深度变暖趋势进行比较，以确定这些变化是否导致了深渊海洋中热量的近期积累，并探索了推动变异性的任何机制。 这项工作将可以更好地表征沿MOC底部的深层运输的平均值和变异性，以及它如何影响深海温度。找到从CFC进行示踪剂运输的新方法提供了对深海循环，通风和可变性的改进估计，这也将为未来监测全球深向海洋升温的监测奠定基础。该奖项反映了NSF的法定任务，并通过使用该基金会的智力功能和广泛的影响来评估CRITERIA CRITERIA CRITERIA。