Ocean dynamics associated with rapid J2 fluctuations: Importance of circumpolar modes and identification of a coherent Arctic mode
Ocean dynamics associated with rapid J2 fluctuations: Importance of circumpolar modes and identification of a coherent Arctic mode
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与快速 J2 波动相关的海洋动力学：环极模式的重要性和相干北极模式的识别
DOI：
10.1029/2003jc002176
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发表时间：
2004
影响因子：
--
通讯作者：
V. Stepanov
中科院分区：
文献类型：
--
作者：
C. Hughes;V. Stepanov
[1]地球动力扁率J₂的波动是衡量赤道和极地地区之间质量全球再分布的一个指标，对关于赤道对称的分量很敏感。考克斯和赵最近发表了一个基于卫星定轨的J₂月值时间序列，该序列显示出逐月的快速波动，以及1997/1998年J₂的大幅变化。我们在此利用一个由大气风应力和气压驱动的正压海洋模型来研究与这些快速波动相关的海洋动力学。我们发现该模型在重现观测结果方面有显著能力，尽管不能重现1997/1998年的变化。模型的大部分变异性与北极和南极底部压力的连贯环极波动有关，尽管它们表面上对称，但却是由截然不同的机制驱动的。南极模式是由环极风驱动的，而北极模式是由极地海入口处的北向风驱动的。与现场观测的比较表明，该模型在重现极地模式方面有能力。北极验潮仪记录证实了在短周期以及至少在欧亚北极陆架的长周期存在一个连贯模式。如果是正压的且能代表整个北极，这将足以对测量到的J₂波动做出重大贡献，但不能解释1997/1998年的事件。
[1] Fluctuations of the Earth's dynamic oblateness J2 are a measure of global redistributions of mass between equatorial and polar regions, sensitive to the component which is symmetric about the equator. Cox and Chao recently published a time series of monthly values of J2 based on satellite orbit determination, which showed rapid fluctuations from month to month, as well as a large change in J2 in 1997/1998. We here investigate the ocean dynamics associated with these rapid fluctuations using a barotropic ocean model forced by atmospheric wind stress and pressure. We find that the model has significant skill in reproducing the observations, though not the change in 1997/1998. Much of the model variability is related to coherent circumpolar fluctuations in Arctic and Antarctic bottom pressure which, despite their apparent symmetry, are forced by quite different mechanisms. The Antarctic mode is forced by circumpolar winds, whereas the Arctic mode is forced by northward winds over the entrances to the polar sea. Comparison with in situ observations shows that the model has skill in reproducing the polar modes. Arctic tide gauge records confirm the presence of a coherent mode at short periods, and at long periods over at least the Eurasian Arctic shelf. If barotropic, and representative of the whole Arctic, this would be large enough to make a major contribution to measured J2 fluctuations, but does not account for the 1997/1998 event.