The origin, pathway, and destination of Nino-3 water estimated by a simulated passive tracer and its adjoint
The origin, pathway, and destination of Nino-3 water estimated by a simulated passive tracer and its adjoint
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DOI：
10.1175/2515.1
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发表时间：
2004-03-01
影响因子：
3.5
通讯作者：
Menemenlis, D
中科院分区：
文献类型：
--
作者：
Fukumori, I;Lee, T;Menemenlis, D
本文研究了太平洋亚热带-热带水团交换的性质，着重于赤道东太平洋（Nino-3区; 5 ° S-5 ° N，150 °-90 ° W）表层水的来源、路径和去向。模拟被动示踪剂和它们的伴随物被用来明确地跟踪特定水团的环流，解释平流和扩散效应及其时间变化。前向被动示踪剂和伴随被动示踪剂的演变可以被识别为分别描述示踪剂标记的水团去哪里和来自哪里。平均10年来，Nino-3区域的水团可追溯到北方（27%）和南半球（39%）的东亚热带温跃层沃茨。随后，Nino-3水返回到上层海洋的这些亚热带纬度。然而，与假设的“亚热带环流”相反，这种环流是一个开放的回路，水返回两个半球的西部地区（亚热带环流）和印度洋，而不是返回其起源。代表性的过境时间尺度是10 - 15年。时间变率导致从时间平均状态推断的热带环流与平均环流有显著差异。特别是，搅拌由于非季节性，年内变化显着增强了所谓的内部路径相对于迂回的低纬度西部边界路径的运输量。这种在亚热带-热带交换中的短路可能有助于更好地解释示踪剂的分布，例如在赤道太平洋观测到的中盆氚最大值。还确定了与厄尔尼诺和拉尼娜事件相关的环流路径的显着差异。据估计，1990年代，亚热带-热带水团交换的强度有所减弱。
The nature of subtropical - tropical water mass exchange in the Pacific Ocean is investigated, focusing on the origin, pathway, and destination of water occupying the surface layer of the eastern equatorial Pacific Ocean (Nino-3 region; 5degreesS - 5degreesN, 150degrees - 90degreesW). Simulated passive tracers and their adjoint are employed to explicitly follow the circulation of specific water masses accounting for advective and diffusive effects and their time variabilities. The evolution of the forward passive tracer and adjoint passive tracer can be identified as describing where the tracer-tagged water mass goes and from where it comes, respectively. Over 10 years on average, water mass of the Nino-3 region can be traced back to eastern subtropical thermocline waters of the Northern (27%) and Southern Hemispheres (39%). The Nino-3 water subsequently returns to these subtropical latitudes in the upper ocean. In contrast to the hypothesized "subtropical cell,'' however, this circulation is an open circuit with water returning to the western regions of the two hemispheres ( subtropical gyres) and to the Indian Ocean, instead of returning to its origins. The representative transit time scale from the subtropics to the Tropics is 10 15 yr. Temporal variability causes the tropical circulation inferred from a time-mean state to differ significantly from the average circulation. In particular, stirring due to nonseasonal, intra-annual variability significantly enhances the transport magnitude of the so-called interior pathways relative to that of the circuitous low-latitude western boundary pathways. Such short-circuit in the subtropical - tropical exchange may help better to explain tracer distributions, such as the observed midbasin tritium maximum in the equatorial Pacific Ocean. Significant differences in circulation pathways are also identified that are associated with El Nino and La Nina events. The strength of the subtropical - tropical water mass exchange is estimated to have weakened during the 1990s.