• Abernathey, R. P., I. Cerovecki, P. R. Holland, E. Newsom, M. Mazloff, and L. D. Talley, 2016: Water-mass transformation by sea ice in the upper branch of the Southern Ocean overturning. Nat. Geosci., 9, 596601, https://doi.org/10.1038/ngeo2749.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Adler, R., and et al. , 2016: The new version 2.3 of the Global Precipitation Climatology Project (GPCP) monthly analysis product. University of Maryland, 8 pp., http://apdrc.soest.hawaii.edu/doc/GPCPmonthlyV2.3.pdf.

  • Arbic, B. K., and W. Brechner Owens, 2001: Climatic warming of Atlantic intermediate waters. J. Climate, 14, 40914108, https://doi.org/10.1175/1520-0442(2001)014<4091:CWOAIW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Banks, H., R. Wood, and J. Gregory, 2002: Changes to Indian Ocean subantarctic mode water in a coupled climate model as CO2 forcing increases. J. Phys. Oceanogr., 32, 28162827, https://doi.org/10.1175/1520-0485(2002)032<2816:CTIOSM>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bindoff, N. L., and J. A. Church, 1992: Warming of the water column in the southwest Pacific Ocean. Nature, 357, 5962, https://doi.org/10.1038/357059a0.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bindoff, N. L., and T. J. McDougall, 1994: Diagnosing climate change and ocean ventilation using hydrographic data. J. Phys. Oceanogr., 24, 11371152, https://doi.org/10.1175/1520-0485(1994)024<1137:DCCAOV>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bryden, H. L., M. J. Griffiths, A. M. Lavin, R. C. Millard, G. Parrilla, and W. M. Smethie, 1996: Decadal changes in water mass characteristics at 24°N in the subtropical North Atlantic Ocean. J. Climate, 9, 31623186, https://doi.org/10.1175/1520-0442(1996)009<3162:DCIWMC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bryden, H. L., E. L. McDonagh, and B. A. King, 2003: Changes in ocean water mass properties: Oscillations or trends? Science, 300, 20862088, https://doi.org/10.1126/science.1083980.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bye, J. A. T. 1972: Oceanic circulation south of Australia. Antarctica Oceanology II: The Australian–New Zealand Sector, D. E. Hayes, Ed., Antarctic Research Series, Vol. 19, Amer. Geophys. Union, 95–100, https://doi.org/10.1029/AR019p0095.

    • Crossref
    • Export Citation
  • Bye, J. A. T., 1983: The general circulation in a dissipative ocean basin with longshore wind stresses. J. Phys. Oceanogr., 13, 15531563, https://doi.org/10.1175/1520-0485(1983)013<1553:TGCIAD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cerovečki, I., and M. R. Mazloff, 2016: The spatiotemporal structure of diabatic processes governing the evolution of subantarctic mode water in the Southern Ocean. J. Phys. Oceanogr., 46, 683710, https://doi.org/10.1175/JPO-D-14-0243.1.

    • 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, https://doi.org/10.1175/JPO-D-12-0121.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Clément, L., E. L. McDonagh, A. Marzocchi, and A. J. G. Nurser, 2020: Signature of ocean warming at the mixed layer base. Geophys. Res. Lett., 47, e2019GL086269, https://doi.org/10.1029/2019GL086269.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • de Boyer Montégut, C., G. Madec, A. S. Fischer, A. Lazar, and D. Iudicone, 2004: Mixed layer depth over the global ocean: An examination of profile data and a profile-based climatology. J. Geophys. Res., 109, C12003, https://doi.org/10.1029/2004JC002378.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Desbruyères, D., E. L. McDonagh, B. A. King, and V. Thierry, 2017: Global and full-depth ocean temperature trends during the early twenty-first century from Argo and repeat hydrography. J. Climate, 30, 19851997, https://doi.org/10.1175/JCLI-D-16-0396.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • DeVries, T., M. Holzer, and F. Primeau, 2017: Recent increase in oceanic carbon uptake driven by weaker upper-ocean overturning. Nature, 542, 215218, https://doi.org/10.1038/nature21068.

    • 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, https://doi.org/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, https://doi.org/10.1029/2006JC004051.

    • Search Google Scholar
    • Export Citation
  • Downes, S. M., N. L. Bindoff, and S. R. Rintoul, 2009: Impacts of climate change on the subduction of mode and intermediate water masses in the Southern Ocean. J. Climate, 22, 32893302, https://doi.org/10.1175/2008JCLI2653.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Downes, S. M., N. L. Bindoff, and S. R. Rintoul, 2010: Changes in the subduction of Southern Ocean water masses at the end of the twenty-first century in eight IPCC models. J. Climate, 23, 65266541, https://doi.org/10.1175/2010JCLI3620.1.

    • 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, https://doi.org/10.1029/2011GL047668.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Downes, S. M., C. Langlais, J. P. Brook, and P. Spence, 2017: Regional impacts of the westerly winds on Southern Ocean mode and intermediate water subduction. J. Phys. Oceanogr., 47, 25212530, https://doi.org/10.1175/JPO-D-17-0106.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Eyring, V., S. Bony, G. A. Meehl, C. A. Senior, B. Stevens, R. J. Stouffer, and K. E. Taylor, 2016: Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization. Geosci. Model Dev., 9, 19371958, https://doi.org/10.5194/gmd-9-1937-2016.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fine, R. A., 1993: Circulation of Antarctic intermediate water in the South Indian Ocean. Deep-Sea Res. I, 40, 20212042, https://doi.org/10.1016/0967-0637(93)90043-3.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fine, R. A., W. M. Smethie, J. L. Bullister, M. Rhein, D.-H. Min, M. J. Warner, A. Poisson, and R. F. Weiss, 2008: Decadal ventilation and mixing of Indian Ocean waters. Deep-Sea Res. I, 55, 2037, https://doi.org/10.1016/j.dsr.2007.10.002.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gao, L. B., S. R. Rintoul, and W. D. Yu, 2018: Recent wind-driven change in Subantarctic Mode Water and its impact on ocean heat storage. Nat. Climate Change, 8, 5863, https://doi.org/10.1038/s41558-017-0022-8.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Garabato, A. C., K. L. Polzin, B. A. King, K. J. Heywood, and M. Visbeck, 2004: Widespread intense turbulent mixing in the Southern Ocean. Science, 303, 210213, https://doi.org/10.1126/science.1090929.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Häkkinen, S., P. B. Rhines, and D. L. Worthen, 2016: Warming of the global ocean: Spatial structure and water-mass trends. J. Climate, 29, 49494963, https://doi.org/10.1175/JCLI-D-15-0607.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hall, A., and M. Visbeck, 2002: Synchronous variability in the Southern Hemisphere atmosphere, sea ice, and ocean resulting from the annular mode. J. Climate, 15, 30433057, https://doi.org/10.1175/1520-0442(2002)015<3043:SVITSH>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hanawa, K., and L. D. Talley, 2001: Mode waters. Int. Geophys. Series, 77, 373386, https://doi.org/10.1016/S0074-6142(01)80129-7.

  • Hartmann, D. L., and F. Lo, 1998: Wave-driven zonal flow vacillation in the Southern Hemisphere. J. Atmos. Sci., 55, 13031315, https://doi.org/10.1175/1520-0469(1998)055<1303:WDZFVI>2.0.CO;2.

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

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Holte, J. W., L. D. 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, https://doi.org/10.1029/2011JC007798.

    • Search Google Scholar
    • Export Citation
  • Hong, Y., Y. Du, T. Qu, Y. Zhang, and W. Cai, 2020: Variability of the subantarctic mode water volume in the South Indian Ocean during 2004–2018. Geophys. Res. Lett., 47, e2020GL087830, https://doi.org/10.1029/2020GL087830.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hu, S., and et al. , 2019: Interannual to decadal variability of upper-ocean salinity in the southern Indian Ocean and the role of the Indonesian Throughflow. J. Climate, 32, 64036421, https://doi.org/10.1175/JCLI-D-19-0056.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., and A. H. Orsi, 1997: Southwest Pacific Ocean water-mass changes between 1968/69 and 1990/91. J. Climate, 10, 306316, https://doi.org/10.1175/1520-0442(1997)010<0306:SPOWMC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 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, https://doi.org/10.1002/2016JC011680.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Karstensen, J., and M. Tomczak, 1997: Ventilation processes and water mass ages in the thermocline of the southeast Indian Ocean. Geophys. Res. Lett., 24, 27772780, https://doi.org/10.1029/97GL02708.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Karstensen, J., and M. Tomczak, 1998: Age determination of mixed water masses using CFC and oxygen data. J. Geophys. Res., 103, 18 59918 609, https://doi.org/10.1029/98JC00889.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Karstensen, J., and D. Quadfasel, 2002a: Water subducted into the Indian Ocean subtropical gyre. Deep-Sea Res. II, 49, 14411457, https://doi.org/10.1016/S0967-0645(01)00160-6.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Karstensen, J., and D. Quadfasel, 2002b: Formation of Southern Hemisphere thermocline waters: Water mass conversion and subduction. J. Phys. Oceanogr., 32, 30203038, https://doi.org/10.1175/1520-0485(2002)032<3020:FOSHTW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Koch-Larrouy, A., R. Morrow, T. Penduff, and M. Juza, 2010: Origin and mechanism of Subantarctic Mode Water formation and transformation in the Southern Indian Ocean. Ocean Dyn., 60, 563583, https://doi.org/10.1007/s10236-010-0276-4.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kolodziejczyk, N., W. Llovel, and E. Portela, 2019: Interannual variability of upper ocean water masses as inferred from Argo array. J. Geophys. Res. Oceans, 124, 60676085, https://doi.org/10.1029/2018JC014866.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lange, M., and E. van Sebille, 2017: Parcels v0.9: Prototyping a Lagrangian ocean analysis framework for the petascale age. Geosci. Model Dev., 10, 41754186, https://doi.org/10.5194/gmd-10-4175-2017.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lee, D. Y., M. R. Petersen, and W. Lin, 2019: The Southern Annular Mode and Southern Ocean surface westerly winds in E3SM. Earth Space Sci., 6, 26242643, https://doi.org/10.1029/2019EA000663.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Li, Q., and S. Lee, 2017: A mechanism of mixed layer formation in the Indo–Western Pacific Southern Ocean: Preconditioning by an eddy-driven jet-scale overturning circulation. J. Phys. Oceanogr., 47, 27552772, https://doi.org/10.1175/JPO-D-17-0006.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Li, Y., and F. Wang, 2015: Thermocline spiciness variations in the tropical Indian Ocean observed during 2003–2014. Deep-Sea Res. I, 97, 5266, https://doi.org/10.1016/j.dsr.2014.12.004.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Li, Y., F. Wang, and F. Zhai, 2012: Interannual variations of subsurface spiciness in the Philippine Sea: Observations and mechanism. J. Phys. Oceanogr., 42, 10221038, https://doi.org/10.1175/JPO-D-12-06.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Liu, W., J. Lu, S.-P. Xie, and A. Fedorov, 2018: Southern Ocean heat uptake, redistribution, and storage in a warming climate: The role of meridional overturning circulation. J. Climate, 31, 47274743, https://doi.org/10.1175/JCLI-D-17-0761.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Llovel, W., and L. Terray, 2016: Observed southern upper-ocean warming over 2005–2014 and associated mechanisms. Environ. Res. Lett., 11, 124023, https://doi.org/10.1088/1748-9326/11/12/124023.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lovenduski, N. S., 2005: Impact of the Southern Annular Mode on Southern Ocean circulation and biology. Geophys. Res. Lett., 32, L11603, https://doi.org/10.1029/2005GL022727.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lumpkin, R., and K. Speer, 2007: Global ocean meridional overturning. J. Phys. Oceanogr., 37, 25502562, https://doi.org/10.1175/JPO3130.1.

  • Luo, Y., 2005: On the connection between South Pacific subtropical spiciness anomalies and decadal equatorial variability in an ocean general circulation model. J. Geophys. Res., 110, C10002, https://doi.org/10.1029/2004JC002655.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Luyten, J. R., J. Pedlosky, and H. Stommel, 1983: The ventilated thermocline. J. Phys. Oceanogr., 13, 292309, https://doi.org/10.1175/1520-0485(1983)013<0292:TVT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Marsh, R., A. G. Nurser, A. P. Megann, and A. L. New, 2000a: Water mass transformation in the Southern Ocean of a global isopycnal coordinate GCM. J. Phys. Oceanogr., 30, 10131045, https://doi.org/10.1175/1520-0485(2000)030<1013:WMTITS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Marsh, R., A. J. G. Nurser, A. P. Megann, and A. L. New, 2000b: Water mass transformation in the Southern Ocean of a global isopycnal coordinate GCM. J. Phys. Oceanogr., 30, 10131045, https://doi.org/10.1175/1520-0485(2000)030<1013:WMTITS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Marshall, D., and J. Marshall, 1995: On the thermodynamics of subduction. J. Phys. Oceanogr., 25, 138151, https://doi.org/10.1175/1520-0485(1995)025<0138:OTTOS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Marshall, G. J., 2003: Trends in the southern annular mode from observations and reanalyses. J. Climate, 16, 41344143, https://doi.org/10.1175/1520-0442(2003)016<4134:TITSAM>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Marshall, J. C., R. G. Williams, and A. J. G. Nurser, 1993: Inferring the subduction rate and period over the North Atlantic. J. Phys. Oceanogr., 23, 13151329, https://doi.org/10.1175/1520-0485(1993)023<1315:ITSRAP>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McCartney, M., 1979: Subantarctic mode water. Woods Hole Oceanographic Institution Contribution 3773, 103119.

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

  • McDougall, T. J., 1989: Streamfunctions for the lateral velocity vector in a compressible ocean. J. Mar. Res., 47, 267284, https://doi.org/10.1357/002224089785076271.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDougall, T. J., and O. A. Krzysik, 2015: Spiciness. J. Mar. Res., 73, 141152, https://doi.org/10.1357/002224015816665589.

  • Middleton, J. F., and J. A. T. Bye, 2007: A review of the shelf-slope circulation along Australia’s southern shelves: Cape Leeuwin to Portland. Prog. Oceanogr., 75, 141, https://doi.org/10.1016/j.pocean.2007.07.001.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Montgomery, R. B., 1937: A suggested method for representing gradient flow in isentropic surfaces. Bull. Amer. Meteor. Soc., 18, 210212, https://doi.org/10.1175/1520-0477-18.6-7.210.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nagura, M., and S. Kouketsu, 2018: Spiciness anomalies in the upper South Indian Ocean. J. Phys. Oceanogr., 48, 20812101, https://doi.org/10.1175/JPO-D-18-0050.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nonaka, M., and H. Sasaki, 2007: Formation mechanism for isopycnal temperature–salinity anomalies propagating from the eastern South Pacific to the equatorial region. J. Climate, 20, 13051315, https://doi.org/10.1175/JCLI4065.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nurser, A. J. G., and J. C. Marshall, 1991: On the relationship between subduction rates and diabatic forcing of the mixed layer. J. Phys. Oceanogr., 21, 17931802, https://doi.org/10.1175/1520-0485(1991)021<1793:OTRBSR>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Portela, E., N. Kolodziejczyk, C. Maes, and V. Thierry, 2020: Interior water-mass variability in the Southern-Hemisphere oceans during the last decade. J. Phys. Oceanogr., 50, 361381, https://doi.org/10.1175/JPO-D-19-0128.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Qu, T., I. Fukumori, and R. A. Fine, 2019: Spin-up of the southern hemisphere super gyre. J. Geophys. Res. Oceans, 124, 154170, https://doi.org/10.1029/2018JC014391.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Qu, T., S. Gao, and R. A. Fine, 2020: Variability of the sub-antarctic mode water subduction rate during the Argo period. Geophys. Res. Lett., 47, e2020GL088248, https://doi.org/10.1029/2020GL088248.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rintoul, S. R., 2018: The global influence of localized dynamics in the Southern Ocean. Nature, 558, 209218, https://doi.org/10.1038/s41586-018-0182-3.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rintoul, S. R., and S. Sokolov, 2001: Baroclinic transport variability of the Antarctic Circumpolar Current south of Australia (WOCE repeat section SR3). J. Geophys. Res., 106, 28152832, https://doi.org/10.1029/2000JC900107.

    • 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, https://doi.org/10.1175/1520-0485(2002)032<1308:ETDLAS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rintoul, S. R., and A. C. N. Garabato, 2013: Dynamics of the Southern Ocean circulation. Ocean Circulation and Climate: A 21st Century Perspective, International Geophysics Series, Vol. 103, Academic Press, 471–492, https://doi.org/10.1016/B978-0-12-391851-2.00018-0.

    • Crossref
    • Export Citation
  • Roemmich, D., and J. Gilson, 2009: The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Prog. Oceanogr., 82, 81100, https://doi.org/10.1016/j.pocean.2009.03.004.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Roemmich, D., J. Church, J. Gilson, D. Monselesan, P. Sutton, and S. Wijffels, 2015: Unabated planetary warming and its ocean structure since 2006. Nat. Climate Change, 5, 240245, https://doi.org/10.1038/nclimate2513.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sabine, C. L., and et al. , 2004: The oceanic sink for anthropogenic CO2. Science, 305, 367371, https://doi.org/10.1126/science.1097403.

  • Sallée, J. B., and S. R. Rintoul, 2011: Parameterization of eddy-induced subduction in the Southern Ocean surface-layer. Ocean Modell., 39, 146153, https://doi.org/10.1016/j.ocemod.2011.04.001.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 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, https://doi.org/10.1007/s10236-005-0054-x.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sallée, J. B., R. Morrow, and K. Speer, 2008a: Eddy heat diffusion and subantarctic mode water formation. Geophys. Res. Lett., 35, L05607, https://doi.org/10.1029/2007GL032827.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sallée, J. B., K. G. Speer, and R. Morrow, 2008b: Response of the Antarctic Circumpolar Current to atmospheric variability. J. Climate, 21, 30203039, https://doi.org/10.1175/2007JCLI1702.1.

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

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sallée, J. B., K. G. Speer, S. R. Rintoul, and S. Wijffels, 2010b: Southern Ocean thermocline ventilation. J. Phys. Oceanogr., 40, 509529, https://doi.org/10.1175/2009JPO4291.1.

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

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

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schneider, N., 2000: A decadal spiciness mode in the tropics. Geophys. Res. Lett., 27, 257260, https://doi.org/10.1029/1999GL002348.

  • Sloyan, B. M., and S. R. Rintoul, 2001a: The Southern Ocean limb of the global deep overturning circulation. J. Phys. Oceanogr., 31, 143173, https://doi.org/10.1175/1520-0485(2001)031<0143:TSOLOT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sloyan, B. M., and S. R. Rintoul, 2001b: Circulation, renewal, and modification of Antarctic mode and intermediate water. J. Phys. Oceanogr., 31, 10051030, https://doi.org/10.1175/1520-0485(2001)031<1005:CRAMOA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sloyan, B. M., L. D. Talley, T. K. Chereskin, R. Fine, and J. Holte, 2010: Antarctic intermediate water and subantarctic mode water formation in the southeast Pacific: The role of turbulent mixing. J. Phys. Oceanogr., 40, 15581574, https://doi.org/10.1175/2010JPO4114.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Speer, K., S. Rintoul, and B. Sloyan, 1997: Subantarctic mode water formation by air–sea fluxes. International WOCE Newsletter, No. 27, WOCE International Project Office, Southampton, United Kingdom, 2931.

  • Speer, K. G., and G. Forget, 2013: Global distribution and formation of mode waters. Ocean Circulation and Climate: A 21st Century Perspective, G. Siedler et al., Eds., International Geophysics, Vol. 103, Elsevier, 211–226, https://doi.org/10.1016/B978-0-12-391851-2.00009-X.

    • Crossref
    • Export Citation
  • Talley, L. D., 1999: Some aspects of ocean heat transport by the shallow, intermediate and deep overturning circulations. Geophys. Mono. Ser, 112, 122, https://doi.org/10.1029/GM112p0001.

    • Search Google Scholar
    • Export Citation
  • Talley, L. D., 2013: Closure of the global overturning circulation through the Indian, Pacific, and Southern Oceans: Schematics and transports. Oceanography, 26, 8097, https://doi.org/10.5670/oceanog.2013.07.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thompson, D. W. J., and J. M. Wallace, 2000: Annular modes in the extratropical circulation. Part I: Month-to-Month variability. J. Climate, 13, 10001016, https://doi.org/10.1175/1520-0442(2000)013<1000:AMITEC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thompson, R. O., and R. Edwards, 1981: Mixing and water-mass formation in the Australian subantarctic. J. Phys. Oceanogr., 11, 13991406, https://doi.org/10.1175/1520-0485(1981)011<1399:MAWMFI>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wong, A. P. S., 2005: Subantarctic mode water and Antarctic intermediate water in the South Indian Ocean based on profiling float data 2000–2004. J. Mar. Res., 63, 789812, https://doi.org/10.1357/0022240054663196.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wong, A. P. S., N. L. Bindoff, and J. A. Church, 1999: Large-scale freshening of intermediate waters in the Pacific and Indian Oceans. Nature, 400, 440443, https://doi.org/10.1038/22733.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yang, H., G. Lohmann, W. Wei, M. Dima, M. Ionita, and J. Liu, 2016: Intensification and poleward shift of subtropical western boundary currents in a warming climate. J. Geophys. Res. Oceans, 121, 49284945, https://doi.org/10.1002/2015JC011513.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yeager, S. G., and W. G. Large, 2004: Late-winter generation of spiciness on subducted isopycnals. J. Phys. Oceanogr., 34, 15281547, https://doi.org/10.1175/1520-0485(2004)034<1528:LGOSOS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yeager, S. G., and W. G. Large, 2007: Observational evidence of winter spice injection. J. Phys. Oceanogr., 37, 28952919, https://doi.org/10.1175/2007JPO3629.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • You, Y., 1996: Dianeutral mixing in the thermocline of the Indian Ocean. Deep-Sea Res. I, 43, 291320, https://doi.org/10.1016/0967-0637(96)00007-6.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yu, L., X. Jin, and R. A. Weller, 2008: Multidecade global flux datasets from the Objectively Analyzed Air-Sea Fluxes (OAFlux) Project: Latent and sensible heat fluxes, ocean evaporation, and related surface meteorological variables. Woods Hole Oceanographic Institution OAFlux Project Tech. Rep. OA-2008-01, 64 pp.

  • Zhang, Y., M. Feng, Y. Du, H. E. Phillips, N. L. Bindoff, and M. J. McPhaden, 2018: Strengthened Indonesian Throughflow drives decadal warming in the southern Indian Ocean. Geophys. Res. Lett., 45, 61676175, https://doi.org/10.1029/2018GL078265.

    • Search Google Scholar
    • Export Citation
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Changes in the Subantarctic Mode Water Properties and Spiciness in the Southern Indian Ocean based on Argo Observations

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  • 1 a State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
  • | 2 b Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, China
  • | 3 c College of Marine Science, University of Chinese Academy of Sciences, Beijing, China
  • | 4 d Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, Los Angeles, California
  • | 5 e National Oceanography Centre, Southampton, United Kingdom
  • | 6 f Centre of Excellence for Climate Extremes, Australian Research Council, Hobart, Tasmania, Australia
  • | 7 g Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
  • | 8 h CSIRO Oceans and Atmosphere, Crawley, Western Australia, Australia
  • | 9 i Centre for Southern Hemisphere Oceans Research, Hobart, Tasmania, Australia
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Abstract

The Subantarctic Mode Water (SAMW) plays an essential role in the global heat, freshwater, carbon, and nutrient budgets. In this study, decadal changes in the SAMW properties in the southern Indian Ocean (SIO) and associated thermodynamic and dynamic processes are investigated during the Argo era. Both temperature and salinity of the SAMW in the SIO show increasing trends during 2004–18. A two-layer structure of the SAMW trend, with more warm and salty light SAMW but less cool and fresh dense SAMW, is identified. The heaving and spiciness processes are important but have opposite contributions to the temperature and salinity trends of the SAMW. A significant deepening of isopycnals (heaving), peaking at σθ = 26.7–26.8 kg m−3 in the middle layer of the SAMW, expands the warm and salty light SAMW and compresses the cool and fresh dense SAMW corresponding to the change in subduction rate during 2004–18. The change in the SAMW subduction rate is dominated by the change in the mixed layer depth, controlled by the changes in wind stress curl and surface buoyancy fluxes. An increase in the mixed layer temperature due to weakening northward Ekman transport of cool water leads to a lighter surface density in the SAMW formation region. Consequently, density outcropping lines in the SAMW formation region shift southward and favor the intrusion and entrainment of the cooler and fresher Antarctic surface water from the south, contributing to the cooling/freshening trend of isopycnals (spiciness). Subsequently, the cooler and fresher SAMW spiciness anomalies spread in the SIO via the subtropical gyre.

Significance Statement

Subantarctic Mode Water is a distinct water mass with vertically uniform properties in the Southern Hemisphere’s subtropical gyres. Climate change is imprinted in the SAMW through the ventilation at the base of the winter mixed layer. The ocean modulation associated with wind-forced large-scale waves and circulation also plays an essential role in heat, salinity, and water mass redistribution. A net increase in volume-weighted potential temperature and salinity of the SAMW is found during the Argo era since 2004, resulting from a combination of climate change and ocean modulation through opposite heaving and spiciness processes. This study improves our understanding of the dynamics and thermodynamics involved in the SAMW formation during rapid climate change.

© 2021 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: Yan Du, duyan@scsio.ac.cn

Abstract

The Subantarctic Mode Water (SAMW) plays an essential role in the global heat, freshwater, carbon, and nutrient budgets. In this study, decadal changes in the SAMW properties in the southern Indian Ocean (SIO) and associated thermodynamic and dynamic processes are investigated during the Argo era. Both temperature and salinity of the SAMW in the SIO show increasing trends during 2004–18. A two-layer structure of the SAMW trend, with more warm and salty light SAMW but less cool and fresh dense SAMW, is identified. The heaving and spiciness processes are important but have opposite contributions to the temperature and salinity trends of the SAMW. A significant deepening of isopycnals (heaving), peaking at σθ = 26.7–26.8 kg m−3 in the middle layer of the SAMW, expands the warm and salty light SAMW and compresses the cool and fresh dense SAMW corresponding to the change in subduction rate during 2004–18. The change in the SAMW subduction rate is dominated by the change in the mixed layer depth, controlled by the changes in wind stress curl and surface buoyancy fluxes. An increase in the mixed layer temperature due to weakening northward Ekman transport of cool water leads to a lighter surface density in the SAMW formation region. Consequently, density outcropping lines in the SAMW formation region shift southward and favor the intrusion and entrainment of the cooler and fresher Antarctic surface water from the south, contributing to the cooling/freshening trend of isopycnals (spiciness). Subsequently, the cooler and fresher SAMW spiciness anomalies spread in the SIO via the subtropical gyre.

Significance Statement

Subantarctic Mode Water is a distinct water mass with vertically uniform properties in the Southern Hemisphere’s subtropical gyres. Climate change is imprinted in the SAMW through the ventilation at the base of the winter mixed layer. The ocean modulation associated with wind-forced large-scale waves and circulation also plays an essential role in heat, salinity, and water mass redistribution. A net increase in volume-weighted potential temperature and salinity of the SAMW is found during the Argo era since 2004, resulting from a combination of climate change and ocean modulation through opposite heaving and spiciness processes. This study improves our understanding of the dynamics and thermodynamics involved in the SAMW formation during rapid climate change.

© 2021 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: Yan Du, duyan@scsio.ac.cn

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