Origins of mesoscale mixed-layer depth variability in the Southern Ocean
<p>Mixed-layer depth (MLD) exhibits significant variability, which is important for atmosphere–ocean exchanges of heat and atmospheric gases. The origins of the mesoscale MLD variability in the Southern Ocean are studied here in an idealised regional ocean–atmosphere model (ROAM). The main con...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-05-01
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| Series: | Ocean Science |
| Online Access: | https://os.copernicus.org/articles/19/615/2023/os-19-615-2023.pdf |
| _version_ | 1797829270086615040 |
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| author | Y. Gao Y. Gao I. Kamenkovich N. Perlin |
| author_facet | Y. Gao Y. Gao I. Kamenkovich N. Perlin |
| author_sort | Y. Gao |
| collection | DOAJ |
| description | <p>Mixed-layer depth (MLD) exhibits significant variability, which is important for atmosphere–ocean exchanges of heat and atmospheric gases. The origins of the mesoscale MLD variability in the Southern Ocean are studied here in an idealised regional ocean–atmosphere model (ROAM). The main conclusion from the analysis of the upper-ocean buoyancy budget is that, while the atmospheric forcing and oceanic vertical mixing, on average, induce the mesoscale variability of MLD, the three-dimensional oceanic advection of buoyancy counteracts and partially balances these atmosphere-induced vertical processes. The relative importance of advection changes with both season and average MLD. From January to May, when the mixed layer is shallow, the atmospheric forcing and oceanic mixing are the most important processes, with the advection playing a secondary role. From June to December, when the mixed layer is deep, both atmospheric forcing and oceanic advection are equally important in driving the MLD variability. Importantly, buoyancy advection by mesoscale ocean current anomalies can lead to both local shoaling and deepening of the mixed layer. The role of the atmospheric forcing is then directly addressed by two sensitivity experiments in which the mesoscale variability is removed from the atmosphere–ocean heat and momentum fluxes. The findings confirm that mesoscale atmospheric forcing predominantly controls MLD variability in summer and that intrinsic oceanic variability and surface forcing are equally important in winter. As a result, MLD variance increases when mesoscale anomalies in atmospheric fluxes are removed in winter, and oceanic advection becomes a dominant player in the buoyancy budget. This study highlights the importance of oceanic advection and intrinsic ocean dynamics in driving mesoscale MLD variability and underscores the importance of MLD in modulating the effects of advection on upper-ocean dynamics.</p> |
| first_indexed | 2024-04-09T13:18:49Z |
| format | Article |
| id | doaj.art-58a218448a7b40c2a647149b3bcd29be |
| institution | Directory Open Access Journal |
| issn | 1812-0784 1812-0792 |
| language | English |
| last_indexed | 2024-04-09T13:18:49Z |
| publishDate | 2023-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Ocean Science |
| spelling | doaj.art-58a218448a7b40c2a647149b3bcd29be2023-05-11T11:32:13ZengCopernicus PublicationsOcean Science1812-07841812-07922023-05-011961562710.5194/os-19-615-2023Origins of mesoscale mixed-layer depth variability in the Southern OceanY. Gao0Y. Gao1I. Kamenkovich2N. Perlin3Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USARosenstiel School of Marine, Atmospheric and Earth Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USARosenstiel School of Marine, Atmospheric and Earth Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USARosenstiel School of Marine, Atmospheric and Earth Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA<p>Mixed-layer depth (MLD) exhibits significant variability, which is important for atmosphere–ocean exchanges of heat and atmospheric gases. The origins of the mesoscale MLD variability in the Southern Ocean are studied here in an idealised regional ocean–atmosphere model (ROAM). The main conclusion from the analysis of the upper-ocean buoyancy budget is that, while the atmospheric forcing and oceanic vertical mixing, on average, induce the mesoscale variability of MLD, the three-dimensional oceanic advection of buoyancy counteracts and partially balances these atmosphere-induced vertical processes. The relative importance of advection changes with both season and average MLD. From January to May, when the mixed layer is shallow, the atmospheric forcing and oceanic mixing are the most important processes, with the advection playing a secondary role. From June to December, when the mixed layer is deep, both atmospheric forcing and oceanic advection are equally important in driving the MLD variability. Importantly, buoyancy advection by mesoscale ocean current anomalies can lead to both local shoaling and deepening of the mixed layer. The role of the atmospheric forcing is then directly addressed by two sensitivity experiments in which the mesoscale variability is removed from the atmosphere–ocean heat and momentum fluxes. The findings confirm that mesoscale atmospheric forcing predominantly controls MLD variability in summer and that intrinsic oceanic variability and surface forcing are equally important in winter. As a result, MLD variance increases when mesoscale anomalies in atmospheric fluxes are removed in winter, and oceanic advection becomes a dominant player in the buoyancy budget. This study highlights the importance of oceanic advection and intrinsic ocean dynamics in driving mesoscale MLD variability and underscores the importance of MLD in modulating the effects of advection on upper-ocean dynamics.</p>https://os.copernicus.org/articles/19/615/2023/os-19-615-2023.pdf |
| spellingShingle | Y. Gao Y. Gao I. Kamenkovich N. Perlin Origins of mesoscale mixed-layer depth variability in the Southern Ocean Ocean Science |
| title | Origins of mesoscale mixed-layer depth variability in the Southern Ocean |
| title_full | Origins of mesoscale mixed-layer depth variability in the Southern Ocean |
| title_fullStr | Origins of mesoscale mixed-layer depth variability in the Southern Ocean |
| title_full_unstemmed | Origins of mesoscale mixed-layer depth variability in the Southern Ocean |
| title_short | Origins of mesoscale mixed-layer depth variability in the Southern Ocean |
| title_sort | origins of mesoscale mixed layer depth variability in the southern ocean |
| url | https://os.copernicus.org/articles/19/615/2023/os-19-615-2023.pdf |
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