Variability of the Shallow Overturning Circulation in the Indian Ocean
Variability of the Shallow Overturning Circulation in the Indian Ocean
复制标题
印度洋浅层翻转环流的变化
DOI：
10.1029/2019jc015651
复制
发表时间：
2020
影响因子：
3.6
通讯作者：
Xiao-Hai Yan
中科院分区：
文献类型：
--
作者：
Meng Lingsheng;Zhuang Wei;Zhang Weiwei;Yan Chi;Xiao-Hai Yan
研究了1958-2017年印度洋浅层翻转环流的变化特征，该环流由跨赤道环流圈（CEC）和南副热带环流圈（SSTC）组成。利用最新发布的海洋再分析系统5（Ocean Reanalysis System 5）数据集，通过流速剖面和输运流函数图对这些浅元的结构进行了研究，结果表明，浅元次表层回流主要出现在西边界，而在海洋内部则没有。然后根据年平均纬向流函数剖面确定IO浅胞的强度。1958-2017年，CEC和SSTC在年际到年代际尺度上均表现出明显的变化，这种变化主要是由上层纬向Ekman输送和纬向地转流的变化引起的，并且在某些年份，这两个分量都可以主导浅层环流的变化。地转流的浅细胞的贡献可能是相反的Ekman运输在南印度洋的几年时，后者达到了极端。CEC与SSTC在研究期间呈负相关。2000-2015年，CEC呈明显的年代际减弱趋势，对IO热含量的年代际增加有贡献，而SSTC仅经历了很小的增强。本文综合研究了IO浅环流的年际和年代际变化及其原因和影响，并试图将这些变化与IO的其它变化联系起来。研究海洋环流对了解海洋和大气的变化和过程具有重要意义。经向流在平衡海洋热量方面起着重要的作用，因此，经向流的变化对气候变化有着重要的影响。浅层翻转环流是指沿着南北方向的上层几百米的风驱动环流。本文研究了印度洋浅水翻转环流的结构和时间序列，结果表明在不同的时间尺度上有明显的变化。本文进一步探讨了这种变化的原因及其对海洋热量再分布的影响。我们的发现促进了对海洋环流及其在海-气系统和气候变化中的作用的理解。
Variability of the Indian Ocean (IO) shallow overturning circulation during 1958-2017 was investigated, which consisted of a cross-equator cell (CEC) and a southern subtropical cell (SSTC). Structures of these shallow cells were examined through the velocity sections and the transport steamfunction patterns based on the newly released Ocean Reanalysis System 5 data set, and the results showed that the returning flows, at the subsurface, of the shallow cells mainly presented at the western boundary while absented in the ocean interior. Strengths of the IO shallow cells were then determined according to the annual-mean meridional streamfunction profiles. Both the CEC and the SSTC exhibited significant variability on interannual to decadal timescales during 1958-2017, and this variability mainly resulted from changes in both meridional Ekman transports and meridional geostrophic flows in the upper layer, and each component could dominate the shallow cells' variations in certain years. Contributions of the geostrophic currents to the shallow cells were likely opposite to that of the Ekman transport in the South Indian Ocean during years when the latter reached the extremes. The CEC and the SSTC were negatively correlated during the research period. The CEC exhibited a decadal weakening during 2000-2015, contributing to the decadal increasing of the IO heat content, while the SSTC only experienced very little strengthening. Here this paper presents a comprehensively study of the interannual to decadal variability of the IO shallow cells and the corresponding reasons and influences and tried to link these variations with other variations in the IO. Plain Language Summary Studying ocean circulation is of great importance in understanding the changes and processes of the ocean and atmosphere. Meridional flows play an important role in balancing the heat in the ocean, and thus, their changes have great influences on climate change. The shallow overturning circulation is the wind-driven circulation in the upper few hundred meters along the north-south direction. This work examined the structure and time series of the Indian Ocean shallow overturning circulation and the results shown obvious variability on different timescales. This paper further explored the reasons for this variability and its influences on ocean heat redistributions. Our findings promote the understanding of the oceanic circulation and its role in the sea-atmosphere system and climate changes.