Decadal changes in the South Pacific western boundary current system revealed in observations and ocean state estimates
Decadal changes in the South Pacific western boundary current system revealed in observations and ocean state estimates
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DOI：
10.1029/2009jc005926
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发表时间：
2011-01-20
影响因子：
3.6
通讯作者：
Oke, P. R.
中科院分区：
文献类型：
--
作者：
Hill, K. L.;Rintoul, S. R.;Oke, P. R.
利用观测和海洋状态估计来研究东澳大利亚流（EAC）系统和南太平洋副热带环流的年代际变化的性质和机制。塔斯马尼亚大陆架62年的记录显示温度和盐度的年代际变化，以及长期趋势，这与EAC向极地延伸的风驱动变化有关。过去15年的重复深海温度测量线表明，东太平洋外延和塔斯曼锋的低频传输变化是反相关的，但时间序列太短，无法得出确切的结论。本文利用近50年的两个海洋状态估计，诊断了南太平洋副热带环流年代际变化的物理机制和空间结构。观测和状态估计描绘了一幅关于环流和EAC系统年代际变化的一致图景。全盆地风应力旋度的增强驱动副热带环流向南扩展。当环流向南移动时，EAC扩展路径以牺牲塔斯曼锋为代价而得到支持，导致观测到这两个主要气流的反相关。结果表明：副热带环流和西边界流响应了海盆尺度风应力旋度的年代际变化，符合岛律动力学；南太平洋环流强烈的年代际变化使从短期记录推断趋势的努力复杂化；南太平洋盆地的风应力旋度变化驱动了EAC系统的变化，这可能对海洋生态系统和区域气候产生影响。
Observations and ocean state estimates are used to investigate the nature and mechanism of decadal variability in the East Australian Current (EAC) system and South Pacific subtropical gyre. A 62 year record on the Tasmanian continental shelf shows decadal variations of temperature and salinity, as well as a long-term trend, which has been related to wind-driven variations in the poleward extension of the EAC. Repeat expendable bathythermograph lines spanning the last 15 years suggest that low-frequency variations in the transport of the EAC extension and Tasman Front are anticorrelated, but the time series are too short to draw firm conclusions. Here we use two ocean state estimates spanning the past 50 years to diagnose the physical mechanisms and spatial structure of the decadal variability of the South Pacific subtropical gyre. The observations and state estimates paint a consistent picture of the decadal variability of the gyre and EAC system. Strengthening of the basin-wide wind stress curl drives a southward expansion of the subtropical gyre. As the gyre shifts south, the EAC extension pathway is favored at the expense of the Tasman Front, resulting in the observed anticorrelation of the these two major currents. The results suggest that the subtropical gyre and western boundary current respond to decadal variability in basin-scale wind stress curl, consistent with Island Rule dynamics; that strong decadal variability of the South Pacific gyre complicates efforts to infer trends from short-term records; and that wind stress curl changes over the South Pacific basin drive changes in the EAC system that are likely to have implications for marine ecosystems and regional climate.