The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations
Water mass transformation in the Southern Ocean is vital for driving the large-scale overturning circulation, which transports heat from the surface to the ocean interior. Using profiling gliders, this study investigates the role of summertime buoyancy forcing and wind-driven processes on the intras...
Published in: | Journal of Geophysical Research: Oceans |
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Main Authors: | , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
2022
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Subjects: | |
Online Access: | http://hdl.handle.net/10204/12728 https://doi.org/10.1029/2021JC017760 |
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ftcsir:oai:researchspace.csir.co.za:10204/12728 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
Council for Scientific and Industrial Research (South Africa): CSIR Research Space |
op_collection_id |
ftcsir |
language |
English |
topic |
Buoyancy Marginal Ice Zone Polar Frontal Zone Regional glider missions Sea-ice impacted Southern Ocean Storms suppresses Subantarctic |
spellingShingle |
Buoyancy Marginal Ice Zone Polar Frontal Zone Regional glider missions Sea-ice impacted Southern Ocean Storms suppresses Subantarctic Du Plessis, MD Swart, S Biddle, LC Giddy, IS Monteiro, Pedro M Reason, CJC Thompson, AF Nicholson, Sarah-Anne The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations |
topic_facet |
Buoyancy Marginal Ice Zone Polar Frontal Zone Regional glider missions Sea-ice impacted Southern Ocean Storms suppresses Subantarctic |
description |
Water mass transformation in the Southern Ocean is vital for driving the large-scale overturning circulation, which transports heat from the surface to the ocean interior. Using profiling gliders, this study investigates the role of summertime buoyancy forcing and wind-driven processes on the intraseasonal (1–10 days) mixed layer thermohaline variability in three Southern Ocean regions southwest of Africa important for water mass transformation—the Subantarctic Zone (SAZ), Polar Frontal Zone (PFZ), and Marginal Ice Zone (MIZ). At intraseasonal time scales, heat flux was shown as the main driver of buoyancy gain in all regions. In the SAZ and MIZ, shallow mixed layers and strong stratification enhanced mixed layer buoyancy gain by trapping incoming heat, while buoyancy loss resulted primarily from the entrainment of cold, salty water from below. In the PFZ, rapid mixing linked to Southern Ocean storms set persistently deep mixed layers and suppressed mixed layer intraseasonal thermohaline variability. In the polar regions, lateral stirring of meltwater from seasonal sea-ice melt dominated daily mixed layer salinity variability. We propose that these meltwater fronts are advected to the PFZ during late summer, indicating the potential for seasonal sea-ice freshwater to impact a region where the upwelling limb of overturning circulation reaches the surface. This study reveals a regional dependence of how the mixed layer thermohaline properties respond to small spatiotemporal processes, emphasizing the importance of surface forcing occurring between 1 and 10 days on the mixed layer water mass transformation in the Southern Ocean. 21 © 2022 The Authors.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Smart Places Ocean Systems and Climate |
format |
Article in Journal/Newspaper |
author |
Du Plessis, MD Swart, S Biddle, LC Giddy, IS Monteiro, Pedro M Reason, CJC Thompson, AF Nicholson, Sarah-Anne |
author_facet |
Du Plessis, MD Swart, S Biddle, LC Giddy, IS Monteiro, Pedro M Reason, CJC Thompson, AF Nicholson, Sarah-Anne |
author_sort |
Du Plessis, MD |
title |
The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations |
title_short |
The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations |
title_full |
The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations |
title_fullStr |
The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations |
title_full_unstemmed |
The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations |
title_sort |
daily-resolved southern ocean mixed layer: regional contrasts assessed using glider observations |
publishDate |
2022 |
url |
http://hdl.handle.net/10204/12728 https://doi.org/10.1029/2021JC017760 |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
Sea ice Southern Ocean |
genre_facet |
Sea ice Southern Ocean |
op_source |
Journal of Geophysical Research: Oceans, 127(4) |
op_relation |
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JC017760 Du Plessis, M., Swart, S., Biddle, L., Giddy, I., Monteiro, P.M., Reason, C., Thompson, A. & Nicholson, S. et al. 2022. The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations. Journal of Geophysical Research: Oceans, 127(4). http://hdl.handle.net/10204/12728 2169-9275 2169-9291 https://doi.org/10.1029/2021JC017760 http://hdl.handle.net/10204/12728 Du Plessis, M., Swart, S., Biddle, L., Giddy, I., Monteiro, P. M., Reason, C., . Nicholson, S. (2022). The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations. Journal of Geophysical Research: Oceans, 127(4) , http://hdl.handle.net/10204/12728 Du Plessis, MD, S Swart, LC Biddle, IS Giddy, Pedro M Monteiro, CJC Reason, AF Thompson, and Sarah-Anne Nicholson "The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations." Journal of Geophysical Research: Oceans, 127(4) (2022) http://hdl.handle.net/10204/12728 Du Plessis M, Swart S, Biddle L, Giddy I, Monteiro PM, Reason C, et al. The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations. Journal of Geophysical Research: Oceans, 127(4). 2022; http://hdl.handle.net/10204/12728. 26535 |
op_doi |
https://doi.org/10.1029/2021JC017760 |
container_title |
Journal of Geophysical Research: Oceans |
container_volume |
127 |
container_issue |
4 |
_version_ |
1766193098439786496 |
spelling |
ftcsir:oai:researchspace.csir.co.za:10204/12728 2023-05-15T18:17:48+02:00 The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations Du Plessis, MD Swart, S Biddle, LC Giddy, IS Monteiro, Pedro M Reason, CJC Thompson, AF Nicholson, Sarah-Anne 2022-04 Fulltext application/pdf http://hdl.handle.net/10204/12728 https://doi.org/10.1029/2021JC017760 en eng https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021JC017760 Du Plessis, M., Swart, S., Biddle, L., Giddy, I., Monteiro, P.M., Reason, C., Thompson, A. & Nicholson, S. et al. 2022. The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations. Journal of Geophysical Research: Oceans, 127(4). http://hdl.handle.net/10204/12728 2169-9275 2169-9291 https://doi.org/10.1029/2021JC017760 http://hdl.handle.net/10204/12728 Du Plessis, M., Swart, S., Biddle, L., Giddy, I., Monteiro, P. M., Reason, C., . Nicholson, S. (2022). The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations. Journal of Geophysical Research: Oceans, 127(4) , http://hdl.handle.net/10204/12728 Du Plessis, MD, S Swart, LC Biddle, IS Giddy, Pedro M Monteiro, CJC Reason, AF Thompson, and Sarah-Anne Nicholson "The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations." Journal of Geophysical Research: Oceans, 127(4) (2022) http://hdl.handle.net/10204/12728 Du Plessis M, Swart S, Biddle L, Giddy I, Monteiro PM, Reason C, et al. The daily-resolved Southern Ocean mixed layer: Regional contrasts assessed using glider observations. Journal of Geophysical Research: Oceans, 127(4). 2022; http://hdl.handle.net/10204/12728. 26535 Journal of Geophysical Research: Oceans, 127(4) Buoyancy Marginal Ice Zone Polar Frontal Zone Regional glider missions Sea-ice impacted Southern Ocean Storms suppresses Subantarctic Article 2022 ftcsir https://doi.org/10.1029/2021JC017760 2023-04-11T23:50:18Z Water mass transformation in the Southern Ocean is vital for driving the large-scale overturning circulation, which transports heat from the surface to the ocean interior. Using profiling gliders, this study investigates the role of summertime buoyancy forcing and wind-driven processes on the intraseasonal (1–10 days) mixed layer thermohaline variability in three Southern Ocean regions southwest of Africa important for water mass transformation—the Subantarctic Zone (SAZ), Polar Frontal Zone (PFZ), and Marginal Ice Zone (MIZ). At intraseasonal time scales, heat flux was shown as the main driver of buoyancy gain in all regions. In the SAZ and MIZ, shallow mixed layers and strong stratification enhanced mixed layer buoyancy gain by trapping incoming heat, while buoyancy loss resulted primarily from the entrainment of cold, salty water from below. In the PFZ, rapid mixing linked to Southern Ocean storms set persistently deep mixed layers and suppressed mixed layer intraseasonal thermohaline variability. In the polar regions, lateral stirring of meltwater from seasonal sea-ice melt dominated daily mixed layer salinity variability. We propose that these meltwater fronts are advected to the PFZ during late summer, indicating the potential for seasonal sea-ice freshwater to impact a region where the upwelling limb of overturning circulation reaches the surface. This study reveals a regional dependence of how the mixed layer thermohaline properties respond to small spatiotemporal processes, emphasizing the importance of surface forcing occurring between 1 and 10 days on the mixed layer water mass transformation in the Southern Ocean. 21 © 2022 The Authors.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Smart Places Ocean Systems and Climate Article in Journal/Newspaper Sea ice Southern Ocean Council for Scientific and Industrial Research (South Africa): CSIR Research Space Southern Ocean Journal of Geophysical Research: Oceans 127 4 |