Heat advection processes leading to El Nino events as depicted by an ensemble of ocean assimilation products
Heat advection processes leading to El Nino events as depicted by an ensemble of ocean assimilation products
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DOI：
10.1002/2016jc011718
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发表时间：
2016-06-01
影响因子：
3.6
通讯作者：
Rodo, Xavier
中科院分区：
文献类型：
--
作者：
Ballester, Joan;Bordoni, Simona;Rodo, Xavier
厄尔尼诺-南方涛动的振荡性质是海洋和大气之间的近平衡平衡和异相不平衡过程的复杂叠加的结果。本工作的主要目标是进行详尽的时空分析的上层海洋热收支的国家的最先进的海洋同化产品的合奏。我们把具体的重点放在海洋热平流机制，其代表性的个人合奏成员和ENSO振荡的不同阶段，导致EN事件。我们的分析一致表明，在赤道西太平洋的初始次表层变暖平流到太平洋中部的赤道潜流，这与赤道平流与异常的纬向温度梯度和环流在温跃层的水平，解释了热量积累在太平洋中部的补给阶段。我们还发现，补给阶段的特点是增加的温跃层的纬向倾斜，以及一个向南的上层海洋跨赤道质量输送所造成的埃克曼引起的异常垂直运动在离赤道地区。虽然数据集之间的差异一般很小，异常往往有相同的符号，在幅值的差异的纬向项被认为是关键的解释不同的传播速度的地下变暖趋势沿着温跃层。唯一的例外是GECCO，它不产生赤道表面Ekman辐散（次表层Sverdrup辐合）的模式在赤道太平洋西部和中部。
The oscillatory nature of El Nino-Southern Oscillation results from an intricate superposition of near-equilibrium balances and out-of-phase disequilibrium processes between the ocean and the atmosphere. The main objective of the present work is to perform an exhaustive spatiotemporal analysis of the upper ocean heat budget in an ensemble of state-of-the-art ocean assimilation products. We put specific emphasis on the ocean heat advection mechanisms, and their representation in individual ensemble members and in the different stages of the ENSO oscillation leading to EN events. Our analyses consistently show that the initial subsurface warming in the western equatorial Pacific is advected to the central Pacific by the equatorial undercurrent, which, together with the equatorward advection associated with anomalies in both the meridional temperature gradient and circulation at the level of the thermocline, explains the heat buildup in the central Pacific during the recharge phase. We also find that the recharge phase is characterized by an increase of meridional tilting of the thermocline, as well as a southward upper-ocean cross-equatorial mass transport resulting from Ekman-induced anomalous vertical motion in the off-equatorial regions. Although differences between data sets are generally small, and anomalies tend to have the same sign, the differences in the magnitude of the meridional term are seen to be key for explaining the different propagation speed of the subsurface warming tendency along the thermocline. The only exception is GECCO, which does not produce the patterns of meridional surface Ekman divergence (subsurface Sverdrup convergence) in the western and central equatorial Pacific.