Agulhas rings pathways and the resulting MOC control

厄加勒斯环通路和由此产生的 MOC 控制

• 批准号: 0752225
• 负责人: Doron Nof
• 金额: $ 41.75万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2011-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0752225&HistoricalAwards=false
• 关键词: Agulhas; rings; pathways; resulting; MOC

Intellectual merit: The study will improve the understanding of nonlinear climatic processes as they relate to retroflecting currents and eddy formation. In particular, the relationship between eddy generation and coastline inclination, bottom topography, and upstream potential vorticity will be examined. A theoretical and numerical modeling approached will be used to achieve those goals.The study focus on a problem critical to the Meridional Overturning Cell (MOC): Agulhas rings injection that forces large amounts of salt into the South Atlantic and is thus critical for maintaining the Atlantic relatively high salinity. A recent analysis of paleoceanographic proxies reveals that the injection of salty Agulhas rings into the South Atlantic during the Younger Dryas (when the MOC was not operational) was dramatically reduced compared to today's injection levels. The increase to today's levels occurred toward the end of the Younger Dryas and it has been suggested that the associated increase in salt influx into the Atlantic re-started the, then-collapsed, MOC. Given that the salt anomaly that the rings inject into the Atlantic is presently roughly five times that of the Mediterranean Sea and the Bering Strait, the above MOC restart idea appears plausible. It has been hypothesized that the injection variability is due to the slanting of the South African coastline (relative to the east-west direction) at the location where the retroflection occurs. This slanting varies widely with latitude"it is almost zero near the southernmost edge of the continent and nearly 90' at lower latitudes off Madagascar. In this scenario, the rings are able to propagate freely away from the generation area in the small slant case but not in the large slant case. This is because the long-shore migration is just the open-ocean westward migration times the cosine of the slant so that there is a significant long-shore migration component in the small slant case but not in the large slant case. The approach will be to employ nonlinear analytical methods as well as process oriented studies and high-resolution numerical experiments to investigate processes associated with various configurations of the above problems. Broader Impacts: The Indian-Atlantic ocean basin exchange affects the MOC whose functioning is critical to the world climate. The proposed studies are pertinent to ocean variability on long time scales, and are thus important to the significant societal question of global climate change and predictability. One graduate Ph.D. student will be supported in this research area where new graduates are needed. The project will also enhance our outreach program of exposing underprivileged kids (boys and girls) housed and educated in the Florida Sheriffs Youths Ranches (FSYR) to science. These ranches house several hundred underprivileged girls and boys, identified by the Florida sheriffs to have a potential criminal future unless steered away from their immediate social environment and housed elsewhere. A similar outreach program will be conducted at the Federal prison in Tallahassee.

学术价值：这项研究将提高对非线性气候过程的理解，因为它们与逆流和涡流形成有关。特别是，将研究涡旋的产生与海岸线倾角、海底地形和上游位涡之间的关系。为了实现这些目标，将使用理论和数值模拟方法。这项研究的重点是对子午线倾覆单元(MOC)至关重要的一个问题：阿古拉斯环注入，迫使大量盐分进入南大西洋，因此对维持大西洋相对较高的盐度至关重要。最近对古海洋学指标的分析表明，与今天的注入水平相比，年轻仙女座时期(MOC没有运行时)向南大西洋注入的咸水阿古拉环大大减少了。上升到今天的水平发生在年轻的仙女座末期，有人认为，与之相关的流入大西洋的盐分增加重新启动了后来崩溃的MOC。考虑到环带注入大西洋的盐分异常目前大约是地中海和白令海峡的五倍，上述MOC重启的想法似乎是可信的。据推测，注入变化是由于南非海岸线(相对于东西方向)在发生后向反射的位置倾斜所致。这种倾斜度随着纬度的不同而变化很大。“在大陆最南端附近几乎为零，在马达加斯加附近的较低纬度地区接近90度。在这种情况下，在小倾斜的情况下，环能够自由地传播到远离产生区的地方，但在大倾斜的情况下，环不能自由传播。这是因为长岸迁移只是公海向西的迁移乘以倾斜余弦，所以在小倾斜的情况下存在显着的长岸迁移分量，而在大倾斜的情况下则不存在。该方法将采用非线性分析方法以及面向过程的研究和高分辨率的数值实验来研究与上述问题的各种构型相关的过程。更广泛的影响：印度洋-大西洋海盆交换影响到对世界气候至关重要的交通部的运作。拟议的研究涉及长时间尺度上的海洋变异性，因此对全球气候变化和可预测性这一重大社会问题具有重要意义。在这个需要应届毕业生的研究领域，一名研究生博士生将得到支持。该项目还将加强我们的外展计划，让居住在佛罗里达州警长青年牧场(FSYR)并接受教育的贫困儿童(男孩和女孩)接触科学。这些牧场收容了数百名贫困女孩和男孩，佛罗里达州的警长发现，除非他们离开直接的社会环境，转而安置在其他地方，否则他们可能会有潜在的犯罪未来。类似的外展计划将在塔拉哈西的联邦监狱进行。