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首页> 外文期刊>Journal of Physical Oceanography >Kuroshio Extension Variability and Forcing of the Pacific Decadal Oscillations: Responses and Potential Feedback
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Kuroshio Extension Variability and Forcing of the Pacific Decadal Oscillations: Responses and Potential Feedback

机译：黑潮扩展变异性和太平洋年代际振荡的强迫：响应和潜在的反馈

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摘要

A forcing mechanism is sought for the large-scale circulation changes in the Kuroshio Extension region of the western North Pacific Ocean as inferred by TOPEX/Poseidon sea surface height (SSH) data. The low-frequency signal of the Kuroshio Extension over the last decade was characterized by a modulation in its zonal mean flow intensity: the mean Kuroshio Extension jet weakened progressively from 1993 to 1996 and this trend reversed after 1997. The ability to simulate the major trends in the observed SSH signals with linear vorticity dynamics leads the authors to conclude that the modulation in the zonal mean jet was remotely forced by wind stress curl anomalies in the eastern North Pacific Ocean related to the Pacific decadal oscillations (PDOs). To be specific, the weakening (strengthening) trend in 1993―96 (1997―2001) was caused by westward expansions of negative (positive) SSH anomalies south of the Kuroshio Extension and positive (negative) SSH anomalies north of the Kuroshio Extension. Emergence of oppositely signed SSH anomalies on the two sides of the Kuroshio Extension jet is due to the different propagating speeds of the baroclinic Rossby waves, which carry the wind-induced SSH anomalies generated in the eastern North Pacific at different phases of the PDOs. Hindcasting the Kuroshio Extension jet strength over the last 45 years reveals that the jet modulation has a dominant timescale of ～12 yr. Given the location of the Kuroshio Extension jet relative to the maximum atmospheric forcing, it is found that this dominant timescale is consistent with the preferred timescale under a stochastic white-noise atmospheric forcing. It is hypothesized that this connection between the Kuroshio Extension strength and the latitudinally dependent baroclinic adjustment contributes to an increase in variance and persistence of the North Pacific midlatitude coupled system on the decadal timescale.
机译：根据TOPEX / Poseidon海面高度（SSH）数据推断，正在寻找一种强迫机制，用于北太平洋西部黑潮扩展区的大规模环流变化。在过去的十年中，黑潮扩展的低频信号的特征在于其纬向平均流强度的调节：从1993年到1996年，黑潮扩展的平均射流逐渐减弱，1997年之后这种趋势发生了逆转。模拟主要趋势的能力在观测到的具有线性涡旋动力学的SSH信号中，作者得出的结论是，与太平洋年代际振荡（PDO）有关的北太平洋东部风应力卷曲异常是对纬向平均射流的调制强加了强迫。具体来说，1993年至96年（1997年至2001年）的减弱（增强）趋势是由黑潮扩展以南的负（正）SSH异常向西扩展和黑潮扩展以北的正（负）SSH异常向西扩展所致。黑潮扩展喷气机两侧出现符号相反的SSH异常是由于斜压Rossby波的传播速度不同，它们携带了在PDO不同阶段在北太平洋东部产生的风致SSH异常。在过去的45年中对黑潮扩展射流强度进行了后播，发现射流调制的主要时标约为12年。给定黑潮扩展射流相对于最大大气强迫的位置，发现该主导时标与随机白噪声大气强迫下的首选时标一致。据推测，黑潮延伸强度与纬度依赖的斜度调节之间的这种联系导致了北太平洋中纬度耦合系统在年代际尺度上的变化和持续性的增加。

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  • 来源
    《Journal of Physical Oceanography》 |2003年第12期|p.2465-2482|共18页
  • 作者

    Bo Qiu;

  • 作者单位

    Department of Oceanography, University of Hawaii at Manoa, 1000 Pope Road, Honolulu, HI 96822;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 海洋学;
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