Three subtropical fronts in the North Pacific: Observational evidence for mode water-induced subsurface frontogenesis
Three subtropical fronts in the North Pacific: Observational evidence for mode water-induced subsurface frontogenesis
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DOI：
10.1029/2006jc003479
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发表时间：
2006-09-26
影响因子：
3.6
通讯作者：
Xie, Shang-Ping
中科院分区：
文献类型：
--
作者：
Kobashi, Fumiaki;Mitsudera, Humio;Xie, Shang-Ping
通过建立高分辨率的温度气候系统，研究了北太平洋副热带地区的次表层锋。根据相对地理位置的不同，将其划分为南、北方和东三个亚热带锋区。南、北方、东热带气旋分别位于副热带环流西部和中部的沿着21 -24 ° N和26 ° N，南热带气旋沿沿着19 - 21 ° N分布。我们的分析表明，这些STFs都与大的负纬向位涡（PV）梯度的温跃层以下的前面。北方STF位于黑潮环流的南部边缘，在那里，负PV梯度发生在一个狭窄的密度范围内，并由副热带模态水（STMW）的低PV核心维持。另一方面，在东部和南部的STFs的负PV梯度跨越一个广泛的密度范围。东部STF形成于副热带环流的中心轴附近，在其以北，中央模态水（CMW）的上部和下部汇合，形成一个厚的低位涡池，维持锋面的负位涡梯度。同样，在南部的STF，负的PV梯度是由于一个低的PV池的北部，与STMW的最南端的部分堆叠在上层CMW平流从中央副热带环流。结果表明，模态沃茨是北太平洋STFs的重要组成部分。
Subsurface fronts in the subtropical North Pacific were investigated by constructing a high-resolution temperature climatology. Three distinct subtropical fronts (STFs) are identified, which are the southern, northern and eastern STFs according to their relative geographical locations. The southern STF extends along 19 degrees-21 degrees N west of the dateline, while the northern and eastern STFs appear along 21 degrees-24 degrees N and 26 degrees N in the western and central subtropical gyre, respectively. Our analysis showed that each of these STFs is associated with large negative meridional potential vorticity (PV) gradient in the thermocline below the front. The northern STF is located on the southern edge of the Kuroshio recirculation, where the negative PV gradient occurs within a narrow density range and is maintained by the low PV core of the subtropical mode water (STMW). On the other hand, the negative PV gradient at the eastern and southern STFs spans over a wide density range. The eastern STF forms near the center axis of the subtropical gyre, north of which the upper and lower portions of the central mode water (CMW) converge, forming a thick low PV pool that maintains the negative PV gradient on the front. Similarly, at the southern STF, the negative PV gradient is due to a low PV pool to the north, with the southernmost portion of the STMW stacked above the upper CMW advected from the central subtropical gyre. It is concluded that the mode waters are essential for the North Pacific STFs.