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Swart S, du Plessis MD, Nicholson SA, Monteiro PMS, Dove LA, Thomalla S, Thompson AF, Biddle LC, Edholm JM, Giddy I, Heywood KJ, Lee C, Mahadevan A, Shilling G, de Souza RB. The Southern Ocean mixed layer and its boundary fluxes: fine-scale observational progress and future research priorities. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2023; 381:20220058. [PMID: 37150200 PMCID: PMC10164470 DOI: 10.1098/rsta.2022.0058] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 03/03/2023] [Indexed: 05/09/2023]
Abstract
Interactions between the upper ocean and air-ice-ocean fluxes in the Southern Ocean play a critical role in global climate by impacting the overturning circulation and oceanic heat and carbon uptake. Remote and challenging conditions have led to sparse observational coverage, while ongoing field programmes often fail to collect sufficient information in the right place or at the time-space scales required to constrain the variability occurring in the coupled ocean-atmosphere system. Only within the last 10 years have we been able to directly observe and assess the role of the fine-scale ocean and rapidly evolving atmospheric marine boundary layer on the upper limb of the Southern Ocean's overturning circulation. This review summarizes advances in mechanistic understanding, arising in part from observational programmes using autonomous platforms, of the fine-scale processes (1-100 km, hours-seasons) influencing the Southern Ocean mixed layer and its variability. We also review progress in observing the ocean interior connections and the coupled interactions between the ocean, atmosphere and cryosphere that moderate air-sea fluxes of heat and carbon. Most examples provided are for the ice-free Southern Ocean, while major challenges remain for observing the ice-covered ocean. We attempt to elucidate contemporary research gaps and ongoing/future efforts needed to address them. This article is part of a discussion meeting issue 'Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities'.
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Affiliation(s)
- Sebastiaan Swart
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
- Department of Oceanography, University of Cape Town, Rondebosch, South Africa
| | | | | | | | - Lilian A. Dove
- Environmental Science and Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Sandy Thomalla
- Southern Ocean Carbon-Climate Observatory, CSIR, Cape Town, South Africa
| | - Andrew F. Thompson
- Environmental Science and Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Louise C. Biddle
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Johan M. Edholm
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Isabelle Giddy
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
- Southern Ocean Carbon-Climate Observatory, CSIR, Cape Town, South Africa
| | - Karen J. Heywood
- Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, UK
| | - Craig Lee
- Applied Physics Laboratory, University of Washington, Seattle, WA, USA
| | | | - Geoff Shilling
- Applied Physics Laboratory, University of Washington, Seattle, WA, USA
| | - Ronald Buss de Souza
- Earth System Numerical Modeling Division, National Institute for Space Research (INPE), Cachoeira Paulista, Brazil
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Tamisiea ME, Hughes CW, Williams SDP, Bingley RM. Sea level: measuring the bounding surfaces of the ocean. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:rsta.2013.0336. [PMID: 25157196 PMCID: PMC4150292 DOI: 10.1098/rsta.2013.0336] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The practical need to understand sea level along the coasts, such as for safe navigation given the spatially variable tides, has resulted in tide gauge observations having the distinction of being some of the longest instrumental ocean records. Archives of these records, along with geological constraints, have allowed us to identify the century-scale rise in global sea level. Additional data sources, particularly satellite altimetry missions, have helped us to better identify the rates and causes of sea-level rise and the mechanisms leading to spatial variability in the observed rates. Analysis of all of the data reveals the need for long-term and stable observation systems to assess accurately the regional changes as well as to improve our ability to estimate future changes in sea level. While information from many scientific disciplines is needed to understand sea-level change, this review focuses on contributions from geodesy and the role of the ocean's bounding surfaces: the sea surface and the Earth's crust.
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Affiliation(s)
- Mark E Tamisiea
- National Oceanography Centre, Joseph Proudman Building, 6 Brownlow Street, Liverpool L3 5DA, UK
| | - Chris W Hughes
- National Oceanography Centre, Joseph Proudman Building, 6 Brownlow Street, Liverpool L3 5DA, UK School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, UK
| | - Simon D P Williams
- National Oceanography Centre, Joseph Proudman Building, 6 Brownlow Street, Liverpool L3 5DA, UK
| | - Richard M Bingley
- Nottingham Geospatial Institute and Department of Civil Engineering, University of Nottingham, Nottingham NG7 2TU, UK
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Gille ST. Meridional displacement of the Antarctic Circumpolar Current. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130273. [PMID: 24891396 PMCID: PMC4032512 DOI: 10.1098/rsta.2013.0273] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Observed long-term warming trends in the Southern Ocean have been interpreted as a sign of increased poleward eddy heat transport or of a poleward displacement of the entire Antarctic Circumpolar Current (ACC) frontal system. The two-decade-long record from satellite altimetry is an important source of information for evaluating the mechanisms governing these trends. While several recent studies have used sea surface height contours to index ACC frontal displacements, here altimeter data are instead used to track the latitude of mean ACC transport. Altimetric height contours indicate a poleward trend, regardless of whether they are associated with ACC fronts. The zonally averaged transport latitude index shows no long-term trend, implying that ACC meridional shifts determined from sea surface height might be associated with large-scale changes in sea surface height more than with localized shifts in frontal positions. The transport latitude index is weakly sensitive to the Southern Annular Mode, but is uncorrelated with El Niño/Southern Oscillation.
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Affiliation(s)
- Sarah T Gille
- Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, Mail Code 0230, La Jolla, CA 92093-0230, USA
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Palter JB, Marinov I, Sarmiento JL, Gruber N. Large-Scale, Persistent Nutrient Fronts of the World Ocean: Impacts on Biogeochemistry. THE HANDBOOK OF ENVIRONMENTAL CHEMISTRY 2013. [DOI: 10.1007/698_2013_241] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Hansen MW, Johannessen JA, Dagestad KF, Collard F, Chapron B. Monitoring the surface inflow of Atlantic Water to the Norwegian Sea using Envisat ASAR. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2011jc007375] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Falco P, Zambianchi E. Near-surface structure of the Antarctic Circumpolar Current derived from World Ocean Circulation Experiment drifter data. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010jc006349] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Herraiz-Borreguero L, Rintoul SR. Subantarctic Mode Water variability influenced by mesoscale eddies south of Tasmania. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2008jc005146] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Swart S, Speich S. An altimetry-based gravest empirical mode south of Africa: 2. Dynamic nature of the Antarctic Circumpolar Current fronts. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009jc005300] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Sokolov S, Rintoul SR. Circumpolar structure and distribution of the Antarctic Circumpolar Current fronts: 1. Mean circumpolar paths. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008jc005108] [Citation(s) in RCA: 244] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Thompson AF. The atmospheric ocean: eddies and jets in the Antarctic Circumpolar Current. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2008; 366:4529-4541. [PMID: 18818151 DOI: 10.1098/rsta.2008.0196] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Although the Antarctic Circumpolar Current (ACC) is the longest and the strongest oceanic current on the Earth and is the primary means of inter-basin exchange, it remains one of the most poorly represented components of global climate models. Accurately describing the circulation of the ACC is made difficult owing to the prominent role that mesoscale eddies and jets, oceanic equivalents of atmospheric storms and storm tracks, have in setting the density structure and transport properties of the current. The successes and limitations of different representations of eddy processes in models of the ACC are considered, with particular attention given to how the circulation responds to changes in wind forcing. The dynamics of energetic eddies and topographically steered jets may both temper and enhance the sensitivity of different aspects of the ACC's circulation to changes in climate.
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Affiliation(s)
- Andrew F Thompson
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK.
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Swart S, Speich S, Ansorge IJ, Goni GJ, Gladyshev S, Lutjeharms JRE. Transport and variability of the Antarctic Circumpolar Current south of Africa. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007jc004223] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hughes CW, Meredith MP. Coherent sea-level fluctuations along the global continental slope. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2006; 364:885-901. [PMID: 16537146 DOI: 10.1098/rsta.2006.1744] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Signals in sea-level or, more properly, sub-surface pressure (SSP; sea-level corrected for the inverse barometer effect) are expected to propagate rapidly along the continental slope due to the effect of sloping topography on wave modes, resulting in strongly correlated SSP over long-distances. Observations of such correlations around the Arctic and Antarctic are briefly reviewed, and then extended using satellite altimetry to the rest of the global continental slope. It is shown that such long-distance correlations are common, especially in extra-tropical regions. Simple correlations from altimetry cannot, however, establish the wave speed, or whether waves are responsible for the correlations as opposed to large-scale coherence in the forcing. A case study around South America is used to highlight some of the complications, and is found to strengthen the case for the importance of wave modes in such long-distance SSP coherence, although more detailed in situ data are required to resolve the cause of the correlations.
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Affiliation(s)
- Chris W Hughes
- Proudman Oceanographic Laboratory, Joseph Proudman Building, 6 Brownlow Street, Liverpool L3 5DA, UK.
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