Indian Ocean mixed layer depth changes under global warming
The surface ocean mixed layer (OML) is critical for climate and biological systems. Changes in ocean mixed layer depth (MLD) of the Indian Ocean under global warming are examined utilizing outputs from 24 climate models in the Coupled Model Intercomparison Project phase 6 (CMIP6) models and the Comm...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2023-01-01
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| Series: | Frontiers in Climate |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fclim.2023.1112713/full |
| _version_ | 1797943917834928128 |
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| author | Zhen Gao Zhen Gao Zhen Gao Shang-Min Long Shang-Min Long Shang-Min Long Jia-Rui Shi Lijing Cheng Gen Li Gen Li Jun Ying |
| author_facet | Zhen Gao Zhen Gao Zhen Gao Shang-Min Long Shang-Min Long Shang-Min Long Jia-Rui Shi Lijing Cheng Gen Li Gen Li Jun Ying |
| author_sort | Zhen Gao |
| collection | DOAJ |
| description | The surface ocean mixed layer (OML) is critical for climate and biological systems. Changes in ocean mixed layer depth (MLD) of the Indian Ocean under global warming are examined utilizing outputs from 24 climate models in the Coupled Model Intercomparison Project phase 6 (CMIP6) models and the Community Earth System Model 1.0 with Community Atmosphere Model version 5 (CESM1–CAM5). The results show that the MLD generally decreases in low- and high-emissions Shared Socioeconomic Pathway (SSP) scenarios (ssp126 and ssp585). In ssp126 and ssp585, the multi-model ensemble-mean OML, respectively shoals about 5 and 10% over both the northern tropics and southern subtropics, with high model consistency. This robust OML shoaling appears in the 1980s and is closely associated with increased surface buoyancy forcing and weakened winds. In contrast, the OML in the south equatorial Indian Ocean slightly deepens and displays large intermodel differences in the sign and magnitude of the changes. The effects of direct CO2 increase and wind changes on OML changes are further quantified by CESM1–CAM5 partially coupled experiments. The results show that the increased surface net heat flux from direct CO2 increase dominates OML shoaling in the northern tropics. In the southern subtropics, the increased surface heat flux, reduced wind speed, and wind-driven divergence all facilitate the OML shoaling. In the south equatorial Indian Ocean, wind changes generally deepen the OML, consistent with the CMIP6 results. Moreover, the OML shoaling-related upper ocean stratification changes are contributed by both temperature and salinity changes in the northern tropics but dominated by temperature changes south of 10°S. These results highlight the regional differences in MLD changes and their forcing, which is important for understanding regional climate changes and corresponding changes in extreme events and biological systems under global warming. |
| first_indexed | 2024-04-10T20:30:41Z |
| format | Article |
| id | doaj.art-61f949bdb4054587a0a0adeacef12eda |
| institution | Directory Open Access Journal |
| issn | 2624-9553 |
| language | English |
| last_indexed | 2024-04-10T20:30:41Z |
| publishDate | 2023-01-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Climate |
| spelling | doaj.art-61f949bdb4054587a0a0adeacef12eda2023-01-25T06:10:11ZengFrontiers Media S.A.Frontiers in Climate2624-95532023-01-01510.3389/fclim.2023.11127131112713Indian Ocean mixed layer depth changes under global warmingZhen Gao0Zhen Gao1Zhen Gao2Shang-Min Long3Shang-Min Long4Shang-Min Long5Jia-Rui Shi6Lijing Cheng7Gen Li8Gen Li9Jun Ying10Key Laboratory of Marine Hazards Forecasting, Ministry of Natural Resources, Hohai University, Nanjing, ChinaState Key Laboratory of Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaCollege of Oceanography, Hohai University, Nanjing, ChinaKey Laboratory of Marine Hazards Forecasting, Ministry of Natural Resources, Hohai University, Nanjing, ChinaState Key Laboratory of Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaCollege of Oceanography, Hohai University, Nanjing, ChinaWoods Hole Oceanographic Institution, Woods Hole, MA, United StatesInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, ChinaKey Laboratory of Marine Hazards Forecasting, Ministry of Natural Resources, Hohai University, Nanjing, ChinaCollege of Oceanography, Hohai University, Nanjing, ChinaState Key Laboratory of Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, ChinaThe surface ocean mixed layer (OML) is critical for climate and biological systems. Changes in ocean mixed layer depth (MLD) of the Indian Ocean under global warming are examined utilizing outputs from 24 climate models in the Coupled Model Intercomparison Project phase 6 (CMIP6) models and the Community Earth System Model 1.0 with Community Atmosphere Model version 5 (CESM1–CAM5). The results show that the MLD generally decreases in low- and high-emissions Shared Socioeconomic Pathway (SSP) scenarios (ssp126 and ssp585). In ssp126 and ssp585, the multi-model ensemble-mean OML, respectively shoals about 5 and 10% over both the northern tropics and southern subtropics, with high model consistency. This robust OML shoaling appears in the 1980s and is closely associated with increased surface buoyancy forcing and weakened winds. In contrast, the OML in the south equatorial Indian Ocean slightly deepens and displays large intermodel differences in the sign and magnitude of the changes. The effects of direct CO2 increase and wind changes on OML changes are further quantified by CESM1–CAM5 partially coupled experiments. The results show that the increased surface net heat flux from direct CO2 increase dominates OML shoaling in the northern tropics. In the southern subtropics, the increased surface heat flux, reduced wind speed, and wind-driven divergence all facilitate the OML shoaling. In the south equatorial Indian Ocean, wind changes generally deepen the OML, consistent with the CMIP6 results. Moreover, the OML shoaling-related upper ocean stratification changes are contributed by both temperature and salinity changes in the northern tropics but dominated by temperature changes south of 10°S. These results highlight the regional differences in MLD changes and their forcing, which is important for understanding regional climate changes and corresponding changes in extreme events and biological systems under global warming.https://www.frontiersin.org/articles/10.3389/fclim.2023.1112713/fullocean mixed layer depthIndian Oceanglobal warmingCMIP6ocean stratificationbuoyancy forcing |
| spellingShingle | Zhen Gao Zhen Gao Zhen Gao Shang-Min Long Shang-Min Long Shang-Min Long Jia-Rui Shi Lijing Cheng Gen Li Gen Li Jun Ying Indian Ocean mixed layer depth changes under global warming Frontiers in Climate ocean mixed layer depth Indian Ocean global warming CMIP6 ocean stratification buoyancy forcing |
| title | Indian Ocean mixed layer depth changes under global warming |
| title_full | Indian Ocean mixed layer depth changes under global warming |
| title_fullStr | Indian Ocean mixed layer depth changes under global warming |
| title_full_unstemmed | Indian Ocean mixed layer depth changes under global warming |
| title_short | Indian Ocean mixed layer depth changes under global warming |
| title_sort | indian ocean mixed layer depth changes under global warming |
| topic | ocean mixed layer depth Indian Ocean global warming CMIP6 ocean stratification buoyancy forcing |
| url | https://www.frontiersin.org/articles/10.3389/fclim.2023.1112713/full |
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