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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >On the structure, paths, and fluxes associated with Agulhas rings
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On the structure, paths, and fluxes associated with Agulhas rings

机译:关于Agulhas环的结构,路径和通量

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In January 1993, two Agulhas rings were sampled in the eastern South Atlantic during the World Ocean Circulation Experiment one-time hydrographic section All. The first of these, Ring 1, was sampled at 36 deg S, 4 deg E in the Subtropical Frontal Zone and was smaller and less energetic than other, more typical Agulhas rings, owing partly to its interactions with the North Subtropical Front. The other, Ring 2, was sampled at 33 deg S, 10 deg E in the subtropics. This ring was average in size and reasonably representative of the rings observed in the southeast Atlantic during the early 1990s. The path of the rings is found to be dominated by advection in the mean flow rather than self-induced velocities of eddies under the #beta# effect. We observe significant differences in reduced gravity and available heat and salt anomalies in the rings; from these we infer temporal variability in the stratification of rings upon their formation at the Agulhas Retroflection. This temporal variability in the structure of rings will affect the fluxes associated with them. Data collected within Ring 2 show that neglecting consideration of the water beneath the 10 deg C isotherm underestimates the volume flux by half and the potential temperature and salinity flux by in excess of one third and one half, respectively. Using a base of the 3.5 deg C isotherm and including the high-salinity intermediate water from the Indian Ocean is found to be more appropriate. With these conditions, six Agulhas rings per year entering the subtropical South Atlantic would equate to a volume flux of 9 Sv and an absolute potential temperature and salinity flux of 84 Sv deg C and 322 Sv psu (1 Sv psu approx= 16~6 kg s~(-1)). The significant flux of intermediate water from the Indian Ocean may be as important in the return path of the thermohaline circulation as the intermediate water that enters the South Atlantic through Drake Passage. Further, the water associated with Agulhas rings and cooler than 10 deg C potentially contributes a larger volume flux to the warm water return path than the corresponding surface and upper thermocline water.
机译:1993年1月,在世界海洋环流试验一次水文剖面All期间,在南大西洋东部采样了两个Agulhas环。其中第一个,即环1,在亚热带锋区中以36度,东4度采样,比其他更典型的Agulhas环更小且能量更低,部分是由于其与北亚热带锋的相互作用。另一个环2在亚热带以33度S,10度E采样。该环的大小平均,可以合理地代表1990年代初在东南大西洋观察到的环。发现在#beta#效应下,环的路径主要由平流控制,而不是涡流的自感应速度。我们观察到重力降低以及环中可用热和盐异常的显着差异。从这些推论中,我们推断出环的分层在Agulhas Retroflection形成时的时间变异性。环结构的时间变化会影响与其相关的通量。在第2圈中收集的数据表明,忽略对等温线在10摄氏度以下的水的考虑,将体积通量低估了一半,将潜在的温度和盐度通量分别低估了三分之一和一半以上。发现使用3.5摄氏度等温线的基准并包括来自印度洋的高盐度中间水更为合适。在这些条件下,每年进入亚热带南大西洋的六个Agulhas环相当于9 Sv的体积通量,84 Sv摄氏度和322 Sv psu的绝对势能温度和盐度通量(1 Sv psu约等于16〜6 kg s〜(-1))。来自印度洋的大量中间水在热盐环流的返回路径中与通过德雷克通道进入南大西洋的中间水一样重要。此外,与Agulhas环相关联且温度低于10摄氏度的水可能比相应的地表水和上层热跃层水对暖水返回路径的体积通量贡献更大。

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