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首页> 外文期刊>Ocean Dynamics >Spatial trend patterns in the Pacific Ocean sea level during the altimetry era: the contribution of thermocline depth change and internal climate variability
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Spatial trend patterns in the Pacific Ocean sea level during the altimetry era: the contribution of thermocline depth change and internal climate variability

机译：高空时代太平洋海平面的空间趋势模式：跃层深度变化和内部气候变化的贡献

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摘要

This study investigates the spatial trend patterns and variability of observed sea level and upper ocean thermal structure in the Pacific Ocean during the altimetry era (1993-2012), and the role of thermocline depth changes. The observed sea level trend pattern in this region results from the superposition of two main signals: (1) a strong broad-scale Ⅴ-shaped positive trend anomaly extending to mid-latitudes in the central Pacific and (2) another very strong positive trend anomaly located in the western tropical Pacific within about 120° E-160° E and 20° S-20° N latitude. In this study, we focus on the tropical Pacific (20° N-20° S) where the strongest trends in sea level are observed. By making use of in situ observational data, we study the impact of thermocline depth changes on steric sea level between the surface and 700 m and its relation with the altimetry-based observed sea level changes. This is done by calculating the time-varying thermocline depth (using the 20 ℃ isotherm depth as a proxy) and estimating the sea level trend patterns of the thermocline-attributed individual steric components. We show that it is essentially the vertical movement of the thermocline that governs most of the observed sea level changes and trends in the tropical Pacific. Furthermore, we also show that in the equatorial band, the changes in the upper ocean thermal structure are in direct response to the zonal wind stress. Away from the equatorial band (say, within 5°-15° latitude), the changes in the upper ocean thermal structure are consistent with the wind stress-generated Rossby waves. We also estimate the contribution of the Interdecadal Pacific Oscillation (IPO) on the vertical thermal structure of the tropical Pacific Ocean. Removing the IPO contribution to the upper layer steric sea level provides a non-negligible residual pattern, suggesting that IPO-related internal ocean variability alone cannot account for the observed trend patterns in the Pacific sea level. It is likely that the residual signal may also reflect non-linear interactions between different natural modes like El Nino Southern Oscillation (ENSO), IPO, etc.
机译：这项研究调查了高空时代（1993-2012年）期间太平洋观测到的海平面和上层海洋热结构的空间趋势模式和变化，以及温跃层深度变化的作用。在该区域观测到的海平面趋势模式是由两个主要信号叠加而成的：（1）强烈的大规模Ⅴ型正趋势异常延伸到中太平洋中纬度，（2）另一个非常强的正趋势该异常位于热带西太平洋的大约120°E-160°E和20°S-20°N纬度内。在这项研究中，我们重点关注热带太平洋（20°N-20°S），那里观测到最强烈的海平面趋势。利用原位观测数据，我们研究了跃层深度变化对地表和700 m之间空间海平面的影响及其与基于测高仪的观测海平面变化的关系。这是通过计算随时间变化的温跃层深度（使用20℃等温线深度作为替代）并估算由温跃层归因的单个空间成分的海平面趋势图来完成的。我们表明，本质上是温跃层的垂直运动控制着热带太平洋大部分观测到的海平面变化和趋势。此外，我们还表明，在赤道带，上层海洋热力结构的变化直接响应于纬向风应力。远离赤道带（例如在纬度5°-15°之内），上层海洋热结构的变化与风应力产生的Rossby波一致。我们还估计了年代际太平洋涛动（IPO）对热带太平洋垂直热结构的贡献。去除IPO对上层空间海平面的贡献提供了不可忽略的残留模式，这表明仅与IPO相关的内部海洋变化并不能解释太平洋海平面观测到的趋势模式。残留信号也可能反映了不同自然模式（如厄尔尼诺南方涛动（ENSO），IPO等）之间的非线性相互作用。

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