• American Meteorological Society, 2017: Thermally indirect. Glossary of Meteorology, http://glossary.ametsoc.org/wiki/thermally_indirect.

  • Badin, G., R. G. Williams, Z. Jing, and L. Wu, 2013: Water mass transformations in the Southern Ocean diagnosed from observations: Contrasting effects of air–sea fluxes and diapycnal mixing. J. Phys. Oceanogr., 43, 14721484, doi:10.1175/JPO-D-12-0216.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Belcher, S. E., and Coauthors, 2012: A global perspective on Langmuir turbulence in the ocean surface boundary layer. Geophys. Res. Lett., 39, L18605, doi:10.1029/2012GL052932.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cerovečki, I., L. D. Talley, M. R. Mazloff, and G. Maze, 2013: Subantarctic Mode Water formation, destruction, and export in the eddy-permitting Southern Ocean state estimate. J. Phys. Oceanogr., 43, 14851511, doi:10.1175/JPO-D-12-0121.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Danabasoglu, G., R. Ferrari, and J. C. McWilliams, 2008: Sensitivity of an ocean general circulation model to a parameterization of near-surface eddy fluxes. J. Climate, 21, 11921208, doi:10.1175/2007JCLI1508.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dong, S., S. T. Gille, and J. Sprintall, 2007: An assessment of the Southern Ocean mixed layer heat budget. J. Climate, 20, 44254442, doi:10.1175/JCLI4259.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dong, S., J. Sprintall, S. T. Gille, and L. Talley, 2008: Southern Ocean mixed-layer depth from Argo float profiles. J. Geophys. Res., 113, C06013, doi:10.1029/2006JC004051.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Downes, S. M., A. S. Budnick, J. L. Sarmiento, and R. Farneti, 2011: Impacts of wind stress on the Antarctic Circumpolar Current fronts and associated subduction. Geophys. Res. Lett., 38, L11605, doi:10.1029/2011GL047668.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ferrari, R., J. C. McWilliams, V. M. Canuto, and M. Dubovikov, 2008: Parameterization of eddy fluxes near oceanic boundaries. J. Climate, 21, 27702789, doi:10.1175/2007JCLI1510.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hanawa, K., and L. D. Talley, 2001: Mode waters. Ocean Circulation and Climate, International Geophysical Series, Vol. 77, Academic Press, 373–386.

    • Crossref
    • Export Citation
  • Herraiz-Borreguero, L., and S. R. Rintoul, 2011: Subantarctic mode water: Distribution and circulation. Ocean Dyn., 61, 103126, doi:10.1007/s10236-010-0352-9.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hogg, A. McC., 2010: An Antarctic Circumpolar Current driven by surface buoyancy forcing. Geophys. Res. Lett., 37, L23601, doi:10.1029/2010GL044777.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Holte, J., and L. Talley, 2009: A new algorithm for finding mixed layer depths with applications to Argo data and Subantarctic Mode Water formation. J. Atmos. Oceanic Technol., 26, 19201939, doi:10.1175/2009JTECHO543.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Holte, J., L. Talley, T. K. Chereskin, and B. M. Sloyan, 2012: The role of air–sea fluxes in Subantarctic Mode Water formation. J. Geophys. Res., 117, C03040, doi:10.1029/2011JC007798.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Holte, J., J. Gilson, L. Talley, and D. Roemmich, 2016: Argo mixed layers. Scripps Institution of Oceanography, http://mixedlayer.ucsd.edu.

  • Jones, D. C., A. J. S. Meijers, E. Shuckburgh, J. B. Sallée, P. Haynes, E. K. McAufield, and M. R. Mazloff, 2016: How does Subantarctic Mode Water ventilate the Southern Hemisphere subtropics? J. Geophys. Res. Oceans, 121, 65586582, doi:10.1002/2016JC011680.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77, 437471, doi:10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kuo, A., R. A. Plumb, and J. Marshall, 2005: Transformed Eulerian-mean theory. Part II: Potential vorticity homogenization and the equilibrium of a wind- and buoyancy-driven zonal flow. J. Phys. Oceanogr., 35, 175187, doi:10.1175/JPO-2670.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kuo, H.-L., 1956: Forced and free meridional circulations in the atmosphere. J. Meteor., 13, 561568, doi:10.1175/1520-0469(1956)013<0561:FAFMCI>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Large, W. G., and S. G. Yeager, 2009: The global climatology of an interannually varying air–sea flux data set. Climate Dyn., 33, 341364, doi:10.1007/s00382-008-0441-3.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Large, W. G., J. C. McWilliams, and S. C. Doney, 1994: Oceanic vertical mixing: A review and a model with a nonlocal boundary layer parameterization. Rev. Geophys., 32, 363403, doi:10.1029/94RG01872.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Large, W. G., G. Danabasoglu, S. C. Doney, and J. C. McWilliams, 1997: Sensitivity to surface forcing and boundary layer mixing in a global ocean model: Annual-mean climatology. J. Phys. Oceanogr., 27, 24182447, doi:10.1175/1520-0485(1997)027<2418:STSFAB>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lee, M. M., A. J. G. Nurser, I. Stevens, and J. B. Sallée, 2011: Subduction over the Southern Indian Ocean in a high-resolution atmosphere–ocean coupled model. J. Climate, 24, 38303849, doi:10.1175/2011JCLI3888.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Li, Qian, S. Lee, and A. Griesel, 2016: Eddy fluxes and jet-scale overturning circulations in the Indo–western Pacific Southern Ocean. J. Phys. Oceanogr., 46, 29432959, doi:10.1175/JPO-D-15-0241.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Li, Qing, A. Webb, B. Fox-Kemper, A. Craig, G. Danabasoglu, W. G. Large, and M. Vertenstein, 2016: Langmuir mixing effects on global climate: WAVEWATCH III in CESM. Ocean Modell., 103, 145160, doi:10.1016/j.ocemod.2015.07.020.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Li, Qing, B. Fox-Kemper, ∅. Breivik, and A. Webb, 2017: Statistical modeling of global Langmuir mixing. Ocean Modell., 113, 95114, doi:10.1016/j.ocemod.2017.03.016.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Maltrud, M. E., F. Bryan, and S. Peacock, 2010: Boundary impulse response functions in a century-long eddying global ocean simulation. Environ. Fluid Mech., 10, 275295, doi:10.1007/s10652-009-9154-3.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Mazloff, M., P. Heimbach, and C. Wunsch, 2010: An eddy-permitting Southern Ocean state estimate. J. Phys. Oceanogr., 40, 880899, doi:10.1175/2009JPO4236.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McCartney, M. S., 1977: Subantarctic mode water. A Voyage of Discovery, M. Angel, Ed., Elsevier, 103–119.

  • McCartney, M. S., 1982: The subtropical recirculation of Mode Water. J. Mar. Res., 40, 427464.

  • Morrison, A. K., O. A. Saenko, A. M. Hogg, and P. Spence, 2013: The role of vertical eddy flux in Southern Ocean heat uptake. Geophys. Res. Lett., 40, 54455450, doi:10.1002/2013GL057706.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pfeffer, R. L., 1981: Wave-mean flow interactions in the atmosphere. J. Atmos. Sci., 38, 13401359, doi:10.1175/1520-0469(1981)038<1340:WMFIIT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Phillips, H. E., and S. R. Rintoul, 2000: Eddy variability and energetics from direct current measurements in the Antarctic Circumpolar Current south of Australia. J. Phys. Oceanogr., 30, 30503076, doi:10.1175/1520-0485(2000)030<3050:EVAEFD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ribbe, J., 1999: On wind-driven mid-latitude convection in ocean general circulation models. Tellus, 51A, 517525, doi:10.3402/tellusa.v51i4.14116.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rintoul, S. R., and M. H. England, 2002: Ekman transport dominates local air–sea fluxes in driving variability of Subantarctic Mode Water. J. Phys. Oceanogr., 32, 13081321, doi:10.1175/1520-0485(2002)032<1308:ETDLAS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Robinson, W. A., 2006: On the self-maintenance of midlatitude jets. J. Atmos. Sci., 63, 21092122, doi:10.1175/JAS3732.1.

  • Sabine, C. L., and Coauthors, 2004: The oceanic sink for anthropogenic CO2. Science, 305, 367371, doi:10.1126/science.1097403.

  • Sallée, J. B., N. Wienders, K. Speer, and R. Morrow, 2006: Formation of subantarctic mode water in the southeastern Indian Ocean. Ocean Dyn., 56, 525542, doi:10.1007/s10236-005-0054-x.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sallée, J. B., K. Speer, and S. Rintoul, 2010: Zonally asymmetric response of the Southern Ocean mixed-layer depth to the Southern Annular Mode. Nat. Geosci., 3, 273279, doi:10.1038/ngeo812.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sallée, J. B., R. Matear, S. R. Rintoul, and A. Lenton, 2012: Localized subduction of anthropogenic carbon dioxide in the Southern Hemisphere oceans. Nat. Geosci., 5, 579584, doi:10.1038/ngeo1523.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sarmiento, J. L., N. Gruber, M. A. Brzezinski, and J. P. Dunne, 2004: High-latitude controls of thermocline nutrients and low latitude biological productivity. Nature, 427, 5660, doi:10.1038/nature02127.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schiller, A., and K. R. Ridgway, 2013: Seasonal mixed-layer dynamics in an eddy-resolving ocean circulation model. J. Geophys. Res. Oceans, 118, 33873405, doi:10.1002/jgrc.20250.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schmitz, W. J., Jr., 1996: On the eddy field in the Agulhas retroflection, with some global considerations. J. Geophys. Res., 101, 16 25916 271, doi:10.1029/96JC01143.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Smith, R. D., J. K. Dukowicz, and R. C. Malone, 1992: Parallel ocean general circulation modeling. Physica D, 60, 3861, doi:10.1016/0167-2789(92)90225-C.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Treguier, A. M., I. M. Held, and V. D. Larichev, 1997: Parameterization of quasigeostrophic eddies in primitive equation ocean models. J. Phys. Oceanogr., 27, 567580, doi:10.1175/1520-0485(1997)027<0567:POQEIP>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Weller, R. A., P. W. Furey, M. A. Spall, and R. E. Davis, 2004: The large-scale context for oceanic subduction in the northeast Atlantic. Deep-Sea Res., 51, 665699, doi:10.1016/j.dsr.2004.01.003.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wenegrat, J. O., and M. J. McPhaden, 2016: Wind, waves, and fronts: Frictional effects in a generalized Ekman model. J. Phys. Oceanogr., 46, 371394, doi:10.1175/JPO-D-15-0162.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Williams, R. G., C. Wilson, and C. W. Hughes, 2007: Ocean and atmosphere storm tracks: The role of eddy vorticity forcing. J. Phys. Oceanogr., 37, 22672289, doi:10.1175/JPO3120.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 204 118 8
PDF Downloads 126 80 2

A Mechanism of Mixed Layer Formation in the Indo–Western Pacific Southern Ocean: Preconditioning by an Eddy-Driven Jet-Scale Overturning Circulation

View More View Less
  • 1 Department of Meteorology and Atmospheric Science, The Pennsylvania State University, University Park, Pennsylvania
Restricted access

Abstract

The formation of a narrow band of the deep winter mixed layer (hereinafter “mixed layer wedge”) in the Indo–western Pacific Southern Ocean is examined using an eddy-resolving Parallel Ocean Program (POP) model simulation. The mixed layer wedge starts to deepen in June, centered at 47.5°S, with a meridional scale of only ~2° latitude. Its center is located ~1° north of the model’s Subantarctic Front (SAF). The Argo-based observed mixed layer is similarly narrow and occurs adjacent to the observed SAF. In the small sector of 130°–142°E, where the SAF is persistent and the mixed layer is deepest, the formation of the narrow mixed layer wedge coincides with destratification underneath the mixed layer. This destratification can be attributed primarily to the downwelling branch of a jet-scale overturning circulation (JSOC). The JSOC, which was reported in an earlier study by the authors, is driven by eddy momentum flux convergence and is therefore thermally indirect: its descending branch occurs on the warmer equatorward flank of the SAF, promoting destratification during the warm season. The model-generated net air–sea heat flux reveals a similar wedge-like feature, indicating that the flux contributes to the mixed layer depth wedge, but again this feature is preconditioned by the JSOC. Ekman advection contributes to the formation of the mixed layer, but it occurs farther north of the region where the mixed layer initially deepens. These findings suggest that the eddy-driven JSOC associated with the SAF plays an important role in initiating the narrow, deep mixed layer wedge that forms north of the SAF.

Publisher’s Note: This article was revised on 22 November 2017 to correct an error in the presentation of Eq. (1) when originally published.

© 2017 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Qian Li, qvl5065@psu.edu

Abstract

The formation of a narrow band of the deep winter mixed layer (hereinafter “mixed layer wedge”) in the Indo–western Pacific Southern Ocean is examined using an eddy-resolving Parallel Ocean Program (POP) model simulation. The mixed layer wedge starts to deepen in June, centered at 47.5°S, with a meridional scale of only ~2° latitude. Its center is located ~1° north of the model’s Subantarctic Front (SAF). The Argo-based observed mixed layer is similarly narrow and occurs adjacent to the observed SAF. In the small sector of 130°–142°E, where the SAF is persistent and the mixed layer is deepest, the formation of the narrow mixed layer wedge coincides with destratification underneath the mixed layer. This destratification can be attributed primarily to the downwelling branch of a jet-scale overturning circulation (JSOC). The JSOC, which was reported in an earlier study by the authors, is driven by eddy momentum flux convergence and is therefore thermally indirect: its descending branch occurs on the warmer equatorward flank of the SAF, promoting destratification during the warm season. The model-generated net air–sea heat flux reveals a similar wedge-like feature, indicating that the flux contributes to the mixed layer depth wedge, but again this feature is preconditioned by the JSOC. Ekman advection contributes to the formation of the mixed layer, but it occurs farther north of the region where the mixed layer initially deepens. These findings suggest that the eddy-driven JSOC associated with the SAF plays an important role in initiating the narrow, deep mixed layer wedge that forms north of the SAF.

Publisher’s Note: This article was revised on 22 November 2017 to correct an error in the presentation of Eq. (1) when originally published.

© 2017 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Qian Li, qvl5065@psu.edu
Save