• Abraham, J. P., and et al. , 2013: A review of global ocean temperature observations: Implications for ocean heat content estimate and climate change. Rev. Geophys., 51, 450483, https://doi.org/10.1002/rog.20022.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Anderson, D. L. T., and A. Gill, 1975: Spin-up of a stratified ocean with application to upwelling. Deep-Sea Res., 22, 583596, https://doi.org/10.1016/0011-7471(75)90046-7.

    • Search Google Scholar
    • Export Citation
  • Berloff, P., 2016: Dynamically consistent parameterization of mesoscale eddies-part II: Eddy fluxes and diffusivity from transient impulses. Fluids, 1, 22, https://doi.org/10.3390/fluids1030022.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Berloff, P., 2018: Dynamically consistent parameterization of mesoscale eddies. Part III: Deterministic approach. Ocean Modell., 127, 115, https://doi.org/10.1016/j.ocemod.2018.04.009.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Biastoch, A., C. W. Böning, J. Getzlaff, J. M. Molines, and G. Madec, 2008: Causes of interannual-decadal variability in the meridional overturning circulation of the midlatitude North Atlantic Ocean. J. Climate, 21, 65996615, https://doi.org/10.1175/2008JCLI2404.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bingham, R. J., C. W. Hughes, V. Roussenov, and R. G. Williams, 2007: Meridional coherence of the North Atlantic meridional overturning circulation. Geophys. Res. Lett., 34, L23606, https://doi.org/10.1029/2007GL031731.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bryan, K., 1982: Seasonal variation in meridional overturning and poleward heat transport in the Atlantic and Pacific Oceans. J. Mar. Res., 40, 3953.

    • Search Google Scholar
    • Export Citation
  • Buckley, M. W., R. M. Ponte, G. Foget, and P. Heimbach, 2015: Determining the origins of advective heat transport convergence variability in the North Atlantic. J. Climate, 28, 39433956, https://doi.org/10.1175/JCLI-D-14-00579.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Evans, D. G., J. Toole, G. Forget, J. D. Zika, A. C. N. Garabato, A. J. Nurser, and L. Yu, 2017: Recent wind-driven variability in Atlantic water mass distribution and meridional overturning circulation. J. Phys. Oceanogr., 47, 633647, https://doi.org/10.1175/JPO-D-16-0089.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Frajka-Williams, E., and et al. , 2016: Compensation between meridional flow components of the Atlantic MOC at 26°N. Ocean Sci., 12, 481493, https://doi.org/10.5194/os-12-481-2016.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Grist, J. P., and et al. , 2010: The roles of surface heat flux and ocean heat transport convergence in determining Atlantic Ocean temperature variability. J. Phys. Oceanogr., 60, 771790, https://doi.org/10.1007/s10236-010-0292-4.

    • Search Google Scholar
    • Export Citation
  • Häkkinen, S., P. B. Rhines, and D. L. Worthen, 2015: Heat content variability in the North Atlantic Ocean in ocean reanalysis. Geophys. Res. Lett., 42, 29012909, https://doi.org/10.1002/2015GL063299.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Huang, R. X., 2015: Heaving modes in the world oceans. Climate Dyn., 45, 35633591, https://doi.org/10.1007/s00382-015-2557-6.

  • Jayne, S. R., and J. Marotzke, 2001: The dynamics of ocean heat transport variability. Rev. Geophys., 39, 385411, https://doi.org/10.1029/2000RG000084.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kanzow, T., and et al. , 2010: Seasonal variability of the Atlantic meridional overturning circulation at 26.5°N. J. Climate, 23, 56785698, https://doi.org/10.1175/2010JCLI3389.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Karabasov, S. A., P. S. Berloff, and V. M. Goloviznin, 2009: CABARET in the ocean gyres. Ocean Modell., 30, 155168, https://doi.org/10.1016/j.ocemod.2009.06.009.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Knight, J. R., R. J. Allan, C. K. Folland, M. Vellinga, and M. E. Mann, 2005: A signature of persistent natural thermohaline circulation cycles in observed climate. Geophys. Res. Lett., 32, L20708, https://doi.org/10.1029/2005GL024233.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Latif, M., C. Böning, J. Willebrand, A. Biastoch, J. Dengg, N. Keenlyside, G. Madec, and U. Schweckendiek, 2006: Is the thermohaline circulation changing? J. Climate, 19, 46314637, https://doi.org/10.1175/JCLI3876.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Levitus, S., and et al. , 2012: World ocean heat content and thermosteric sea level change (0–2000 m), 1955–2010. Geophys. Res. Lett., 39, L10603, https://doi.org/10.1029/2012GL051106.

    • Search Google Scholar
    • Export Citation
  • Lozier, M. S., S. Leadbetter, R. G. Williams, V. Roussenov, M. S. C. Reed, and N. J. Moore, 2008: The spatial pattern and mechanisms of heat-content change in the North Atlantic. Science, 319, 800803, https://doi.org/10.1126/science.1146436.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McCarthy, G., and et al. , 2012: Observed interannual variability of the Atlantic meridional overturning circulation at 26.5°N. Geophys. Res. Lett., 39, L19609, https://doi.org/10.1029/2012GL052933.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McCarthy, G. D., and et al. , 2015: Measuring the Atlantic meridional overturning circulation at 26.5°N. Prog. Oceanogr., 130, 91111, https://doi.org/10.1016/j.pocean.2014.10.006.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pillar, H., P. Heimbach, H. Johnson, and D. Marshall, 2016: Dynamical attribution of recent variability in Atlantic overturning. J. Climate, 29, 33393352, https://doi.org/10.1175/JCLI-D-15-0727.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Polo, I., J. Robson, R. Sutton, and M. A. Balmaseda, 2014: The importance of wind and buoyancy forcing for the boundary density variations and the geostrophic component of the AMOC at 26°N. J. Phys. Oceanogr., 44, 23872408, https://doi.org/10.1175/JPO-D-13-0264.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Roemmich, D., and C. Wunsch, 1985: Two transatlantic sections: Meridional circulation and heat flux in the subtropical North Atlantic Ocean. Deep-Sea Res., 32, 619664, https://doi.org/10.1016/0198-0149(85)90070-6.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Spall, M. A., and D. Nieves, 2020: Wind-forced variability of the remote overturning circulation. J. Phys. Oceanogr., 50, 455469, https://doi.org/10.1175/JPO-D-19-0190.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Tandon, N. F., O. A. Saenko, M. A. Kane, and P. J. Kushner, 2020: Interannual variability of the global meridional overturning dominated by the Pacific Ocean. J. Phys. Oceanogr., 3, 559574, https://doi.org/10.1175/JPO-D-19-0129.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • White, W. B., 1977: Annual forcing of baroclinic long waves in the tropical North Pacific Ocean. J. Phys. Oceanogr., 7, 5061, https://doi.org/10.1175/1520-0485(1977)007<0050:AFOBLW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Williams, R. G., V. Roussenov, D. Smith, and M. S. Lozier, 2014: Decadal evolution of ocean thermal anomalies in the North Atlantic: The effects of Ekman, overturning, and horizontal transport. J. Climate, 27, 698719, https://doi.org/10.1175/JCLI-D-12-00234.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yang, J., 2015: Local and remote wind-stress forcing of the seasonal variability of the Atlantic Meridional Overturning Circulation (AMOC) transport at 26.5°N. J. Geophys. Res., 120, 24882503, https://doi.org/10.1002/2014JC010317.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yeager, S., and G. Danabasoglu, 2014: The origins of late twentieth-century variations in the large-scale North Atlantic circulation. J. Climate, 27, 32223247, https://doi.org/10.1175/JCLI-D-13-00125.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhao, J., and W. Johns, 2014a: Wind-driven seasonal cycle of the Atlantic meridional overturning circulation. J. Phys. Oceanogr., 44, 15411562, https://doi.org/10.1175/JPO-D-13-0144.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhao, J., and W. Johns, 2014b: Wind-forced interannual variability of the Atlantic Meridional Overturning Circulation at 26.5°N. J. Geophys. Res., 119, 24032419, https://doi.org/10.1002/2013JC009407.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zou, S., M. S. Lozier, and M. Buckley, 2019: How is meridional coherence maintained in the lower limb of the Atlantic meridional overturning circulation? Geophys. Res. Lett., 46, 244252, https://doi.org/10.1029/2018GL080958.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zou, S., M. S. Lozier, and X. Xu, 2020: Latitudinal structure of the meridional overturning circulation variability on interannual to decadal time scales in the North Atlantic Ocean. J. Climate, 33, 38453862, https://doi.org/10.1175/JCLI-D-19-0215.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 307 307 44
Full Text Views 94 94 14
PDF Downloads 121 121 23

An Idealized Modeling Study of the Midlatitude Variability of the Wind-Driven Meridional Overturning Circulation

View More View Less
  • 1 a Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

The frequency and latitudinal dependence of the midlatitude wind-driven meridional overturning circulation (MOC) is studied using theory and linear and nonlinear applications of a quasigeostrophic numerical model. Wind forcing is varied either by changing the strength of the wind or by shifting the meridional location of the wind stress curl pattern. At forcing periods of less than the first-mode baroclinic Rossby wave basin crossing time scale, the linear response in the middepth and deep ocean is in phase and opposite to the Ekman transport. For forcing periods that are close to the Rossby wave basin crossing time scale, the upper and deep MOC are enhanced, and the middepth MOC becomes phase shifted, relative to the Ekman transport. At longer forcing periods the deep MOC weakens and the middepth MOC increases, but eventually for long enough forcing periods (decadal) the entire wind-driven MOC spins down. Nonlinearities and mesoscale eddies are found to be important in two ways. First, baroclinic instability causes the middepth MOC to weaken, lose correlation with the Ekman transport, and lose correlation with the MOC in the opposite gyre. Second, eddy thickness fluxes extend the MOC beyond the latitudes of direct wind forcing. These results are consistent with several recent studies describing the four-dimensional structure of the MOC in the North Atlantic Ocean.

Significance Statement

The purpose of this study is to better understand how large-scale winds at midlatitudes move water northward or southward, even in the deep ocean that is not in direct contact with the atmosphere. This is important because winds can shift where heat is stored and whether it might be released into the atmosphere. Our results provide a guide on what controls this motion and highlight the importance of large-scale ocean waves and smaller-scale ocean turbulence on the water movement and heat storage.

© 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: Michael A. Spall, mspall@whoi.edu

Abstract

The frequency and latitudinal dependence of the midlatitude wind-driven meridional overturning circulation (MOC) is studied using theory and linear and nonlinear applications of a quasigeostrophic numerical model. Wind forcing is varied either by changing the strength of the wind or by shifting the meridional location of the wind stress curl pattern. At forcing periods of less than the first-mode baroclinic Rossby wave basin crossing time scale, the linear response in the middepth and deep ocean is in phase and opposite to the Ekman transport. For forcing periods that are close to the Rossby wave basin crossing time scale, the upper and deep MOC are enhanced, and the middepth MOC becomes phase shifted, relative to the Ekman transport. At longer forcing periods the deep MOC weakens and the middepth MOC increases, but eventually for long enough forcing periods (decadal) the entire wind-driven MOC spins down. Nonlinearities and mesoscale eddies are found to be important in two ways. First, baroclinic instability causes the middepth MOC to weaken, lose correlation with the Ekman transport, and lose correlation with the MOC in the opposite gyre. Second, eddy thickness fluxes extend the MOC beyond the latitudes of direct wind forcing. These results are consistent with several recent studies describing the four-dimensional structure of the MOC in the North Atlantic Ocean.

Significance Statement

The purpose of this study is to better understand how large-scale winds at midlatitudes move water northward or southward, even in the deep ocean that is not in direct contact with the atmosphere. This is important because winds can shift where heat is stored and whether it might be released into the atmosphere. Our results provide a guide on what controls this motion and highlight the importance of large-scale ocean waves and smaller-scale ocean turbulence on the water movement and heat storage.

© 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: Michael A. Spall, mspall@whoi.edu
Save