Collaborative Research: Quantifying Abyssal Circulation and Its Variability

GSTDTAP

项目编号	1850772
	Collaborative Research: Quantifying Abyssal Circulation and Its Variability
	Sarah Purkey (Principal Investigator)
主持机构	University of California-San Diego Scripps Inst of Oceanography
项目开始年	2019
	2019-03-15
项目结束日期	2022-02-28
资助机构	US-NSF
项目类别	Standard Grant
项目经费	364923(USD)
国家	美国
语种	英语
英文摘要	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.
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/213175
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Sarah Purkey .Collaborative Research: Quantifying Abyssal Circulation and Its Variability.2019.