Two Modes of Gulf Stream Variability Revealed in the Last Two Decades of Satellite Altimeter Data
Two Modes of Gulf Stream Variability Revealed in the Last Two Decades of Satellite Altimeter Data
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DOI：
10.1175/jpo-d-13-0136.1
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发表时间：
2014-01
影响因子：
3.5
通讯作者：
M. Pérez-Hernández;T. Joyce
中科院分区：
文献类型：
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作者：
M. Pérez-Hernández;T. Joyce
西北大西洋经向紧邻oftheGulfStream(GS)separationpointrevealaleadingmodeinwhichthepathshiftsapproximately下游100公里、名义纬度为398N的区域的月图海平面异常，产生了从728W到508W的相干海平面异常。这种模式可以通过使用简单的16点指数来捕捉，该指数基于沿338-468N和458-758W区域中观测到的变异性的最大值获取的SLA数据。2010至2012年间的GS变化是过去十年中最大的，相当于整个记录中最大的。第二组EOF模式描述了标准EOFs中的GSmeanders、whichpropagatemainlywestwardinterruptedbybriefperiodsof eastwardorstationarymeanders.Thesemeandershavewavelengthsofapproximately400kmandcanbeseen，它是通过SLA数据中站立曲折模式的空间相移来描述的。这些模式的光谱特性表明，第一个模式的年际和较长周期具有很强的变异性，而曲折模式的周期为几个月到几个月。虽然前者与以前高度计在GS路径上的使用非常相似，但简单指数是一种有用的测量GS路径中大范围移动的指标，可以快速估计和更新，而不会与以前的估计不同。时间尺度的分离使低通滤波的16点指数能够反映GS路径中的大尺度相干位移。
Monthly mapped sea level anomalies (MSLAs) of the NW Atlantic in the region immediately downstream oftheGulfStream(GS)separationpointrevealaleadingmodeinwhichthepathshiftsapproximately 100km meridionally about a nominal latitude of 398N, producing coherent sea level anomaly (SLA) variability from 728 to 508W. This mode can be captured by use of a simple 16-point index based on SLA data taken along the maximum of the observed variability in the region 338–468N and 458–758W. The GS shifts between 2010 and 2012 are the largest of the last decade and equal to the largest of the entire record. The second group of EOF modesofvariabilitydescribesGSmeanders,whichpropagatemainlywestwardinterruptedbybriefperiodsof eastwardorstationarymeanders.Thesemeandershavewavelengthsofapproximately400kmandcanbeseen in standard EOFs by spatial phase shifting of a standing meander pattern in the SLA data. The spectral properties of these modes indicate strong variability at interannual and longer periods for the first mode and periods of a few to several months for the meanders. While the former is quite similar to a previous use of the altimeter for GS path, the simple index is a useful measure of the large-scale shifts in the GS path that is quickly estimatedand updatedwithoutchangesin previous estimates. Thetime-scaleseparationallows alowpass filtered 16-point index to be reflective of large-scale, coherent shifts in the GS path.