Role of strong subsurface mode on the anomalous basin-wide surface warming of the Tropical Indian Ocean in 2019–2020

IF 1.3 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Earth System Science Pub Date : 2024-07-20 DOI:10.1007/s12040-024-02360-w

C Gnanaseelan, Rashmi Kakatkar, Sebastian Anila, Sandeep Mohapatra, Anant Parekh, J S Chowdary

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引用次数: 0

Abstract

2019 witnessed one of the strongest positive Indian Ocean Dipole. A very strong positive subsurface mode (pSSM) co-evolved in the Tropical Indian Ocean (TIO) during September–October–November 2019, which strengthened further during December–January–February (DJF) 2019–2020. This is the first occurrence of such a very strong pSSM in the recent decades, which strengthened during DJF without any favourable forcing from the Pacific. The TIO further displayed anomalous basin-wide surface warming from winter 2019 to summer 2020. It is found from both observations and model experiments that ocean dynamics associated with pSSM played a major role in the TIO basin-wide warming during 2020. The subsurface–surface interaction along the downwelling Rossby wave path from boreal winter to spring, the reflected Kelvin waves and surface currents have contributed to the basin-wide surface warming of the TIO from DJF (2019–2020) onwards. The mixed layer heat budget analysis reveals that the surface heat fluxes were not favourable for the basin-wide surface warming, thereby undermining the role of any Pacific forcing through atmospheric pathways. The ocean model sensitivity experiments further highlight the importance of Indian Ocean dynamics in the co-evolution of subsurface temperature and sea surface temperature over TIO, especially during the 2019–2020 event.

Research highlights

A strong subsurface dipole mode evolved in the Tropical Indian Ocean temperature during 2019–2020.
Indian Ocean basin-wide surface warming persisted up to summer 2020, highlighting the role of ocean dynamics.
Indian Ocean dynamics associated with the subsurface mode is responsible for the evolution of basin-wide surface warming.
Ocean model experiments support the role of ocean dynamics in the evolution of basin-wide surface warming.

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强次表层模式对 2019-2020 年热带印度洋全海盆表层异常变暖的影响

摘要 2019 年见证了最强的正印度洋偶极子。2019年9月-10月-11月期间，热带印度洋（TIO）共同演化出一个非常强的正次表层模式（pSSM），并在2019年12月-1月-2月（DJF）期间进一步加强。这是近几十年来首次出现如此强烈的 pSSM，它在 DJF 期间在没有任何来自太平洋的有利强迫的情况下得到加强。从 2019 年冬季到 2020 年夏季，TIO 进一步显示出异常的全流域地表变暖。通过观测和模式实验发现，与 pSSM 相关的海洋动力学在 2020 年期间太极IO 全流域变暖中发挥了重要作用。从寒冬到春季，沿下沉罗斯比波路径的次表层-表层相互作用、反射的开尔文波和表层流对从 DJF（2019-2020 年）开始的 TIO 全流域表层变暖起到了推动作用。混合层热量预算分析表明，地表热通量不利于全流域地表变暖，从而削弱了太平洋通过大气途径产生的任何强迫作用。海洋模式敏感性实验进一步突出了印度洋动力学在热带印度洋次表层温度和海面温度共同演变中的重要性，尤其是在 2019-2020 年期间。印度洋全海盆表面变暖一直持续到2020年夏季，凸显了海洋动力学的作用。海洋模式实验支持海洋动力学在全海盆表面变暖演变中的作用。

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来源期刊

Journal of Earth System Science Earth and Planetary Sciences-General Earth and Planetary Sciences

CiteScore

3.20

自引率

5.30%

发文量

226

期刊介绍： The Journal of Earth System Science, an International Journal, was earlier a part of the Proceedings of the Indian Academy of Sciences – Section A begun in 1934, and later split in 1978 into theme journals. This journal was published as Proceedings – Earth and Planetary Sciences since 1978, and in 2005 was renamed ‘Journal of Earth System Science’. The journal is highly inter-disciplinary and publishes scholarly research – new data, ideas, and conceptual advances – in Earth System Science. The focus is on the evolution of the Earth as a system: manuscripts describing changes of anthropogenic origin in a limited region are not considered unless they go beyond describing the changes to include an analysis of earth-system processes. The journal''s scope includes the solid earth (geosphere), the atmosphere, the hydrosphere (including cryosphere), and the biosphere; it also addresses related aspects of planetary and space sciences. Contributions pertaining to the Indian sub- continent and the surrounding Indian-Ocean region are particularly welcome. Given that a large number of manuscripts report either observations or model results for a limited domain, manuscripts intended for publication in JESS are expected to fulfill at least one of the following three criteria. The data should be of relevance and should be of statistically significant size and from a region from where such data are sparse. If the data are from a well-sampled region, the data size should be considerable and advance our knowledge of the region. A model study is carried out to explain observations reported either in the same manuscript or in the literature. The analysis, whether of data or with models, is novel and the inferences advance the current knowledge.