In the past nearly two decades, the Argo Program has created an unprecedented global observing array with continuous in situ salinity observations, providing opportunities to extend our knowledge on the variability and effects of ocean salinity. In this study, we utilize the Argo data during 2004–2017, together with the satellite observations and a newly released version of ECCO ocean reanalysis, to explore the decadal salinity variability in the Southeast Indian Ocean (SEIO) and its impacts on the regional sea level changes. Both the observations and ECCO reanalysis show that during the Argo era, sea level in the SEIO and the tropical western Pacific experienced a rapid rise in 2005–2013 and a subsequent decline in 2013–2017. Such a decadal phase reversal in sea level could be explained, to a large extent, by the steric sea level variability in the upper 300 m. Argo data further show that, in the SEIO, both the temperature and salinity changes have significant positive contributions to the decadal sea level variations. This is different from much of the Indo-Pacific region, where the halosteric component often has minor or negative contributions to the regional sea level pattern on decadal timescale. The salinity budget analyses based on the ECCO reanalysis indicate that the decadal salinity change in the upper 300 m of SEIO is mainly caused by the horizontal ocean advection. More detailed decomposition reveals that in the SEIO, there exists a strong meridional salinity front between the tropical low-salinity and subtropical high salinity waters. The meridional component of decadal circulation changes will induce strong cross-front salinity exchange and thus the significant regional salinity variations.

中文翻译：

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Argo时代东南亚洋盐度变化对印度洋年代际海平面变化的影响

在过去的近二十年中，Argo计划创造了前所未有的全球观测阵列连续原位盐度观测，提供了扩展我们对海洋盐度变化和影响的认识的机会。在这项研究中，我们利用2004-2017年期间的Argo数据，卫星观测数据和ECCO海洋再分析的最新版本，来探索东南亚印度洋（SEIO）的年代际盐度变化及其对区域海洋的影响级别变化。观测和ECCO重新分析都表明，在Argo时代，SEIO和热带西太平洋的海平面在2005-2013年迅速上升，而在2013-2017年随后下降。这种海平面年代际逆转可以在很大程度上由上部300 m的空间海平面变化来解释。Argo数据进一步表明，在SEIO中，温度和盐度的变化都对年代际海平面变化具有显着的正贡献。这与印度-太平洋地区的大部分地区不同，后者的年代际尺度上，晕船成分通常对该地区的海平面模式贡献较小或负面影响。基于ECCO再分析的盐度预算分析表明，SEIO上部300 m的年代际盐度变化主要是由水平海洋平流引起的。更详细的分解表明，在SEIO中，热带低盐度水与亚热带高盐度水之间存在强子午线盐度锋。年代际环流变化的子午分量将引起强烈的跨前盐度交换，从而引起明显的区域盐分变化。