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Variability of the Shallow Overturning Circulation in the Indian Ocean
Author(s) -
Meng Lingsheng,
Zhuang Wei,
Zhang Weiwei,
Yan Chi,
Yan XiaoHai
Publication year - 2020
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2019jc015651
Subject(s) - geostrophic wind , zonal and meridional , equator , ekman transport , geology , climatology , ocean current , oceanography , ekman layer , environmental science , atmospheric sciences , latitude , boundary layer , upwelling , physics , geodesy , thermodynamics
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.