The existence of a deep countercurrent in the subtropical northwest Pacific, named Subtropical Deep Countercurrent (STDCC), has been revealed by moored current-meter data obtained from a buoy system (∼21.6°N, ∼132.8°E) during 4 years (2010–2014). The climatological average of Argo-based absolute geostrophic velocities and ocean reanalyzes have further confirmed the spatial picture of the eastward-flowing STDCC. STDCC is identified as a time-mean feature in the latitudinal range of 19°–25°N with a meridional scale of 200–300 km that persistently appears from 125° to 180°E and slightly shifts to the north as it goes east. Vertically, STDCC is mostly found below 1,000 m with its core located between the depths of 1,250 and 2,000 m, which corresponds to the undercurrent's meridional pattern with increasing depth northward and a meridional space of 2°–4°. Nevertheless, STDCC is distinctive where it lies along ∼27.6 − , which is deeper than the North Equatorial Undercurrent's density layer (∼27.0 − ). The mean velocity of STDCC at 2,000 m observed by mooring measurements was approximately 0.2 ± 0.15 cm s⁻¹ with a maximum speed of approximately 5.59 cm s⁻¹. The ocean reanalyzes also support the existence of STDCC with mean velocity of approximately 0.2–0.6 cm s⁻¹ west of 145°E and can be as large as 1.6 cm s⁻¹ at the eastern region. The results show that STDCC is closely related to the westward-propagating eddies. Our finding emphasizes that the convergence of the cyclonic and anticyclonic eddies possibly generates time-mean zonally elongated eastward flows forming STDCC feature.

中文翻译：

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新观测到的亚热带西北太平洋深部逆流

4 年（2010 年）从浮标系统（~21.6°N，~132.8°E）获得的系泊电流计数据揭示了在副热带西北太平洋存在深逆流，称为亚热带深逆流（STDCC） –2014）。基于 Argo 的绝对地转速度和海洋再分析的气候平均值进一步证实了向东流动的 STDCC 的空间图。STDCC 被确定为纬度范围为 19°–25°N 的时间平均特征，子午尺度为 200–300 km，持续出现在 125°至 180°E 并随着向东移动而略微向北移动。垂直方向，STDCC 多位于 1,000 m 以下，其核心位于 1,250 至 2,000 m 深度之间，对应于暗流' s 子午线模式，向北深度增加，子午线空间为 2°–4°。尽管如此，STDCC 是独特的，它位于 ∼27.6 - ，比北赤道暗流的密度层（~27.0 - ）更深 。通过系泊测量观测到的 STDCC 在 2,000 m 处的平均速度约为 0.2 ± 0.15 cm s ^-1，最大速度约为 5.59 cm s ^-1。海洋重新分析也支持 STDCC 的存在，其平均速度在145°E 以西约为 0.2-0.6 cm s ^-1并且在东部地区可能高达 1.6 cm s ^-1。结果表明，STDCC与向西传播的涡流密切相关。我们的发现强调气旋和反气旋涡旋的会聚可能会产生时均纬向拉长的向东流动，形成 STDCC 特征。