Impacts of IOD and ENSO on the phytoplankton’s vertical variability in the Northern Indian Ocean
The Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO) are the primary climatic modes that profoundly impact physical and biological processes in the Northern Indian Ocean (NIO). IOD- and ENSO-related vertical phytoplankton anomalies, however, remain poorly understood. Using the three...
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Frontiers Media S.A.
2025-01-01
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fmars.2025.1523434/full |
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| author | Qiwei Hu Xiaoyan Chen Xianqiang He Yan Bai Tingchen Jiang Yu Huan Zhanlin Liang |
| author_facet | Qiwei Hu Xiaoyan Chen Xianqiang He Yan Bai Tingchen Jiang Yu Huan Zhanlin Liang |
| author_sort | Qiwei Hu |
| collection | DOAJ |
| description | The Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO) are the primary climatic modes that profoundly impact physical and biological processes in the Northern Indian Ocean (NIO). IOD- and ENSO-related vertical phytoplankton anomalies, however, remain poorly understood. Using the three-dimensional Chlorophyll a concentration dataset generated by a machine learning model, this study examines IOD- and ENSO-linked vertical phytoplankton anomalies over the entire euphotic layer (0–100 m) in the NIO during 2000–2019. Results reveal that IOD and ENSO trigger significant opposite changes in phytoplankton at 0–50 m and 50–100 m. The effects of IOD and ENSO on the vertical structure of phytoplankton are generally asymmetric, with anomalies at 0–50 m being significantly larger than that at 50–100 m. During summer and fall, the significant vertical phytoplankton anomalies in the Central Arabian Sea (CAS), Southern Tip of India (STI), and the Eastern Equatorial Indian Ocean (EEIO), are primarily related to IOD forcing. IOD-linked negative (positive) phytoplankton anomalies at 0–50 m (50–100 m) are driven by the westward propagating downwelling Rossby waves. During winter and spring, due to the local wind anomalies and shallower thermocline, the Seychelles–Chagos Thermocline Ridge (SCTR) is the only region where ENSO exhibits greater positive effects on phytoplankton at 50–100 m than IOD. Different from IOD, the ENSO-related wind reversal impedes subsurface upwelling in the STI and EEIO, thereby constraining vertical biological activity. These findings could shed light on how phytoplankton will respond to changing ocean dynamics under global warming. |
| format | Article |
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| institution | Kabale University |
| issn | 2296-7745 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | Frontiers Media S.A. |
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| series | Frontiers in Marine Science |
| spelling | doaj-art-f66d4f73b09845639522c569b65a33b82025-01-31T05:10:24ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452025-01-011210.3389/fmars.2025.15234341523434Impacts of IOD and ENSO on the phytoplankton’s vertical variability in the Northern Indian OceanQiwei Hu0Xiaoyan Chen1Xianqiang He2Yan Bai3Tingchen Jiang4Yu Huan5Zhanlin Liang6School of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang, ChinaState Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaState Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaState Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaSchool of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang, ChinaSchool of Marine Technology and Geomatics, Jiangsu Ocean University, Lianyungang, ChinaState Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, ChinaThe Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO) are the primary climatic modes that profoundly impact physical and biological processes in the Northern Indian Ocean (NIO). IOD- and ENSO-related vertical phytoplankton anomalies, however, remain poorly understood. Using the three-dimensional Chlorophyll a concentration dataset generated by a machine learning model, this study examines IOD- and ENSO-linked vertical phytoplankton anomalies over the entire euphotic layer (0–100 m) in the NIO during 2000–2019. Results reveal that IOD and ENSO trigger significant opposite changes in phytoplankton at 0–50 m and 50–100 m. The effects of IOD and ENSO on the vertical structure of phytoplankton are generally asymmetric, with anomalies at 0–50 m being significantly larger than that at 50–100 m. During summer and fall, the significant vertical phytoplankton anomalies in the Central Arabian Sea (CAS), Southern Tip of India (STI), and the Eastern Equatorial Indian Ocean (EEIO), are primarily related to IOD forcing. IOD-linked negative (positive) phytoplankton anomalies at 0–50 m (50–100 m) are driven by the westward propagating downwelling Rossby waves. During winter and spring, due to the local wind anomalies and shallower thermocline, the Seychelles–Chagos Thermocline Ridge (SCTR) is the only region where ENSO exhibits greater positive effects on phytoplankton at 50–100 m than IOD. Different from IOD, the ENSO-related wind reversal impedes subsurface upwelling in the STI and EEIO, thereby constraining vertical biological activity. These findings could shed light on how phytoplankton will respond to changing ocean dynamics under global warming.https://www.frontiersin.org/articles/10.3389/fmars.2025.1523434/fullIODENSOphytoplanktonvertical structurethe Northern Indian Ocean |
| spellingShingle | Qiwei Hu Xiaoyan Chen Xianqiang He Yan Bai Tingchen Jiang Yu Huan Zhanlin Liang Impacts of IOD and ENSO on the phytoplankton’s vertical variability in the Northern Indian Ocean Frontiers in Marine Science IOD ENSO phytoplankton vertical structure the Northern Indian Ocean |
| title | Impacts of IOD and ENSO on the phytoplankton’s vertical variability in the Northern Indian Ocean |
| title_full | Impacts of IOD and ENSO on the phytoplankton’s vertical variability in the Northern Indian Ocean |
| title_fullStr | Impacts of IOD and ENSO on the phytoplankton’s vertical variability in the Northern Indian Ocean |
| title_full_unstemmed | Impacts of IOD and ENSO on the phytoplankton’s vertical variability in the Northern Indian Ocean |
| title_short | Impacts of IOD and ENSO on the phytoplankton’s vertical variability in the Northern Indian Ocean |
| title_sort | impacts of iod and enso on the phytoplankton s vertical variability in the northern indian ocean |
| topic | IOD ENSO phytoplankton vertical structure the Northern Indian Ocean |
| url | https://www.frontiersin.org/articles/10.3389/fmars.2025.1523434/full |
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