Seasonal Cycle of the Mixed Layer Heat Budget in the Northeastern Tropical Atlantic Ocean

Gregory R. Foltz NOAA/Atlantic Oceanographic and Meteorological Laboratory, Miami, Florida

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Claudia Schmid NOAA/Atlantic Oceanographic and Meteorological Laboratory, Miami, Florida

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Rick Lumpkin NOAA/Atlantic Oceanographic and Meteorological Laboratory, Miami, Florida

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Abstract

The seasonal cycle of the mixed layer heat budget in the northeastern tropical Atlantic (0°–25°N, 18°–28°W) is quantified using in situ and satellite measurements together with atmospheric reanalysis products. This region is characterized by pronounced latitudinal movements of the intertropical convergence zone (ITCZ) and strong meridional variations of the terms in the heat budget. Three distinct regimes within the northeastern tropical Atlantic are identified. The trade wind region (15°–25°N) experiences a strong annual cycle of mixed layer heat content that is driven by approximately out-of-phase annual cycles of surface shortwave radiation (SWR), which peaks in boreal summer, and evaporative cooling, which reaches a minimum in boreal summer. The surface heat-flux-induced changes in the mixed layer heat content are damped by a strong annual cycle of cooling from vertical turbulent mixing, estimated from the residual in the heat balance. In the ITCZ core region (3°–8°N) a weak seasonal cycle of mixed layer heat content is driven by a semiannual cycle of SWR and damped by evaporative cooling and vertical turbulent mixing. On the equator the seasonal cycle of mixed layer heat content is balanced by an annual cycle of SWR that reaches a maximum in October and a semiannual cycle of turbulent mixing that cools the mixed layer most strongly during May–July and November. These results emphasize the importance of the surface heat flux and vertical turbulent mixing for the seasonal cycle of mixed layer heat content in the northeastern tropical Atlantic.

Corresponding author address: Gregory Foltz, NOAA/Atlantic Oceanographic and Meteorological Laboratory, 4301 Rickenbacker Causeway, Miami, FL 33149. E-mail: gregory.foltz@noaa.gov

Abstract

The seasonal cycle of the mixed layer heat budget in the northeastern tropical Atlantic (0°–25°N, 18°–28°W) is quantified using in situ and satellite measurements together with atmospheric reanalysis products. This region is characterized by pronounced latitudinal movements of the intertropical convergence zone (ITCZ) and strong meridional variations of the terms in the heat budget. Three distinct regimes within the northeastern tropical Atlantic are identified. The trade wind region (15°–25°N) experiences a strong annual cycle of mixed layer heat content that is driven by approximately out-of-phase annual cycles of surface shortwave radiation (SWR), which peaks in boreal summer, and evaporative cooling, which reaches a minimum in boreal summer. The surface heat-flux-induced changes in the mixed layer heat content are damped by a strong annual cycle of cooling from vertical turbulent mixing, estimated from the residual in the heat balance. In the ITCZ core region (3°–8°N) a weak seasonal cycle of mixed layer heat content is driven by a semiannual cycle of SWR and damped by evaporative cooling and vertical turbulent mixing. On the equator the seasonal cycle of mixed layer heat content is balanced by an annual cycle of SWR that reaches a maximum in October and a semiannual cycle of turbulent mixing that cools the mixed layer most strongly during May–July and November. These results emphasize the importance of the surface heat flux and vertical turbulent mixing for the seasonal cycle of mixed layer heat content in the northeastern tropical Atlantic.

Corresponding author address: Gregory Foltz, NOAA/Atlantic Oceanographic and Meteorological Laboratory, 4301 Rickenbacker Causeway, Miami, FL 33149. E-mail: gregory.foltz@noaa.gov
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  • Balaguru, K., P. Chang, R. Saravanan, and C. J. Jang, 2012: Barrier layers of the Atlantic warm pool: Formation mechanism and influence on the mean climate. Tellus, 64, 18 162–18 179, doi:10.3402/tellusa.v64i0.18162.

    • Search Google Scholar
    • Export Citation
  • Bates, S. C., 2010: Seasonal influences on coupled ocean–atmosphere variability in the tropical Atlantic Ocean. J. Climate, 23, 582604.

    • Search Google Scholar
    • Export Citation
  • Bonjean, F., and G. S. E. Lagerloef, 2002: Diagnostic model and analysis of the surface currents in the tropical Pacific Ocean. J. Phys. Oceanogr., 32, 29382954.

    • Search Google Scholar
    • Export Citation
  • Bourlès, B., and Coauthors, 2008: The PIRATA program: History, accomplishments, and future directions. Bull. Amer. Meteor. Soc., 89, 11111125.

    • Search Google Scholar
    • Export Citation
  • Brandt, P., F. A. Schott, C. Provost, A. Kartavtseff, V. Hormann, B. Bourlès, and J. Fischer, 2006: Circulation in the central equatorial Atlantic: Mean and intraseasonal to seasonal variability. Geophys. Res. Lett., 33, L07609, doi:10.1029/2005GL025498.

    • Search Google Scholar
    • Export Citation
  • Caniaux, G., H. Giordani, J. L. Redelsperger, F. Guichard, E. Key, and M. Wade, 2011: Coupling between the Atlantic cold tongue and the West African monsoon in boreal spring and summer. J. Geophys. Res., 116, C04003, doi:10.1029/2010JC006570.

    • Search Google Scholar
    • Export Citation
  • Carton, J. A., and B. H. Huang, 1994: Warm events in the tropical Atlantic. J. Phys. Oceanogr., 24, 888903.

  • Carton, J. A., and Z. X. Zhou, 1997: Annual cycle of sea surface temperature in the tropical Atlantic Ocean. J. Geophys. Res., 102 (C13), 27 81327 824.

    • Search Google Scholar
    • Export Citation
  • Chang, P., and S. G. Philander, 1994: A coupled ocean–atmosphere instability of relevance to the seasonal cycle. J. Atmos. Sci., 51, 36273648.

    • Search Google Scholar
    • Export Citation
  • Chang, P., L. Ji, and H. Li, 1997: A decadal climate variation in the tropical Atlantic Ocean from thermodynamic air-sea interactions. Nature, 385, 516518.

    • Search Google Scholar
    • Export Citation
  • Chang, P., L. Ji, and R. Saravanan, 2001: A hybrid coupled model study of tropical Atlantic variability. J. Climate, 14, 361390.

  • Chiang, J. C. H., and D. J. Vimont, 2004: Analogous Pacific and Atlantic meridional modes of tropical atmosphere–ocean variability. J. Climate, 17, 41434158.

    • Search Google Scholar
    • Export Citation
  • Chiang, J. C. H., Y. Kushnir, and A. Giannini, 2002: Deconstructing Atlantic intertropical convergence zone variability: Influence of the local cross-equatorial sea surface temperature gradient and remote forcing from the eastern equatorial Pacific. J. Geophys. Res., 107, 4004, doi:10.1029/2000JD000307.

    • Search Google Scholar
    • Export Citation
  • Czaja, A., P. Van der Vaart, and J. Marshall, 2002: A diagnostic study of the role of remote forcing in tropical Atlantic variability. J. Climate, 15, 32803290.

    • Search Google Scholar
    • Export Citation
  • Doi, T., T. Tozuka, and T. Yamagata, 2010: The Atlantic meridional mode and its coupled variability with the Guinea Dome. J. Climate, 23, 455475.

    • Search Google Scholar
    • Export Citation
  • Doi, T., G. A. Vecchi, A. J. Rosati, and T. L. Delworth, 2012: Biases in the Atlantic ITCZ in seasonal–interannual variations for a coarse- and a high-resolution coupled climate model. J. Climate, 25, 54945511.

    • Search Google Scholar
    • Export Citation
  • Fairall, C. W., E. F. Bradley, J. E. Hare, A. A. Grachev, and J. B. Edson, 2003: Bulk parameterization of air–sea fluxes: Updates and verification for the COARE algorithm. J. Climate, 16, 571591.

    • Search Google Scholar
    • Export Citation
  • Foltz, G. R., and M. J. McPhaden, 2009: Impact of barrier layer thickness on SST in the central tropical North Atlantic. J. Climate, 22, 285299.

    • Search Google Scholar
    • Export Citation
  • Foltz, G. R., S. A. Grodsky, J. A. Carton, and M. J. McPhaden, 2003: Seasonal mixed layer heat budget of the tropical Atlantic Ocean. J. Geophys. Res., 108, 3146, doi:10.1029/2002JC001584.

    • Search Google Scholar
    • Export Citation
  • Foltz, G. R., J. Vialard, B. P. Kumar, and M. J. McPhaden, 2010: Seasonal mixed layer heat balance of the southwestern tropical Indian Ocean. J. Climate, 23, 947965.

    • Search Google Scholar
    • Export Citation
  • Foltz, G. R., M. J. McPhaden, and R. Lumpkin, 2012: A strong Atlantic meridional mode event in 2009: The role of mixed layer dynamics. J. Climate, 25, 363380.

    • Search Google Scholar
    • Export Citation
  • Foltz, G. R., A. T. Evan, H. P. Freitag, S. Brown, and M. J. McPhaden, 2013: Dust accumulation biases in PIRATA shortwave radiation records. J. Atmos. Oceanic Technol., 30, 14141432.

    • Search Google Scholar
    • Export Citation
  • Giordani, H., G. Caniaux, and A. Voldoire, 2013: Intraseasonal mixed layer heat budget in the equatorial Atlantic during the cold tongue development in 2006. J. Geophys. Res., 118, 650671, doi:10.1029/2012JC008280.

    • Search Google Scholar
    • Export Citation
  • Gregg, M. C., T. B. Sanford, and D. P. Winkel, 2003: Reduced mixing from the breaking of internal waves in equatorial waters. Nature, 422, 513515.

    • Search Google Scholar
    • Export Citation
  • Grodsky, S. A., J. A. Carton, C. Provost, J. Servain, J. A. Lorenzzetti, and M. J. McPhaden, 2005: Tropical instability waves at 0°N, 23°W in the Atlantic: A case study using Pilot Research Moored Array in the Tropical Atlantic (PIRATA) mooring data. J. Geophys. Res., 110, C08010, doi:10.1029/2005JC002941.

    • Search Google Scholar
    • Export Citation
  • Hayes, S. P., P. Chang, and M. J. McPhaden, 1991: Variability of the sea surface temperature in the eastern equatorial Pacific during 1986–88. J. Geophys. Res., 96 (C8), 10 55310 566.

    • Search Google Scholar
    • Export Citation
  • Hummels, R., M. Dengler, and B. Bourles, 2013: Seasonal and regional variability of upper ocean diapycnal heat flux in the Atlantic cold tongue. Prog. Oceanogr., 111, 5274, doi:10.1016/j.pocean.2012.11.001.

    • Search Google Scholar
    • Export Citation
  • Jouanno, J., F. Marin, Y. du Penhoat, J. Sheinbaum, and J. M. Molines, 2011: Seasonal heat balance in the upper 100 m of the equatorial Atlantic Ocean. J. Geophys. Res., 116, C09003, doi:10.1029/2010JC006912.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77, 437471.

  • Kaufman, Y. J., I. Koren, L. A. Remer, D. Tanr, P. Ginoux, and S. Fan, 2005: Dust transport and deposition observed from the Terra-Moderate Resolution Imaging Spectroradiometer (MODIS) spacecraft over the Atlantic Ocean. J. Geophys. Res., 110, D10S12, doi:10.1029/2003JD004436.

    • Search Google Scholar
    • Export Citation
  • Keenlyside, N. S., and M. Latif, 2007: Understanding equatorial Atlantic interannual variability. J. Climate, 20, 131142.

  • Klein, S. A., and D. L. Hartmann, 1993: The seasonal cycle of low stratiform clouds. J. Climate, 6, 15871606.

  • Kraus, E. B., and J. S. Turner, 1967: A one-dimensional model of the seasonal thermocline. Tellus, 19, 98105.

  • Kumar, B. P., J. Vialard, M. Lengaigne, V. S. N. Murty, and M. J. McPhaden, 2012: TropFlux: Air-sea fluxes for the global tropical oceans—Description and evaluation. Climate Dyn., 38, 15211543, doi:10.1007/s00382-011-1115-0.

    • Search Google Scholar
    • Export Citation
  • Lumpkin, R., and G. J. Johnson, 2013: Global ocean surface velocities from drifters: Mean, variance, ENSO response, and seasonal cycle. J. Geophys. Res., 118, 29923006, doi:10.1002/jgrc.20210.

    • Search Google Scholar
    • Export Citation
  • McClain, C. R., and J. Firestone, 1993: An investigation of Ekman upwelling in the North Atlantic. J. Geophys. Res., 98 (C7), 12 32712 339.

    • Search Google Scholar
    • Export Citation
  • Mignot, J., A. Lazar, and M. Lacarra, 2012: On the formation of barrier layers and associated vertical temperature inversions: A focus on the northwestern tropical Atlantic. J. Geophys. Res., 117, C02010, doi:10.1029/2011JC007435.

    • Search Google Scholar
    • Export Citation
  • Mitchell, T. P., and J. M. Wallace, 1992: The annual cycle in equatorial convection and sea surface temperature. J. Climate, 5, 11401156.

    • Search Google Scholar
    • Export Citation
  • Moisan, J. R., and P. P. Niiler, 1998: The seasonal heat budget of the North Pacific: Net heat flux and heat storage rates (1950–1990). J. Phys. Oceanogr., 28, 401421.

    • Search Google Scholar
    • Export Citation
  • Morel, A., and D. Antoine, 1994: Heating rate within the upper ocean in relation to its biooptical state. J. Phys. Oceanogr., 24, 16521665.

    • Search Google Scholar
    • Export Citation
  • Muñoz, E., W. Weijer, S. A. Grodsky, S. C. Bates, and I. Wainer, 2012: Mean and variability of the tropical Atlantic Ocean in the CCSM4. J. Climate, 25, 48604882.

    • Search Google Scholar
    • Export Citation
  • Niiler, P. P., and E. B. Kraus, 1977: One-dimensional models of the upper ocean. Modelling and Prediction of the Upper Layers of the Ocean, E. B. Kraus, Ed., Pergamon, 143–172.

  • Nobre, C., and J. Shukla, 1996: Variation of sea surface temperature, wind stress, and rainfall over the tropical Atlantic and South America. J. Climate, 9, 24642479.

    • Search Google Scholar
    • Export Citation
  • Owens, W. B., and A. P. S. Wong, 2009: An improved calibration method for the drift of the conductivity sensor on autonomous CTD profiling floats by theta-S climatology. Deep-Sea Res. I, 56, 450457.

    • Search Google Scholar
    • Export Citation
  • Pailler, K., B. Bourles, and Y. Gouriou, 1999: The barrier layer in the western tropical Atlantic Ocean. Geophys. Res. Lett., 26, 20692072.

    • Search Google Scholar
    • Export Citation
  • Payne, R. E., 1972: Albedo of the sea surface. J. Atmos. Sci., 29, 959970.

  • Peter, A. C., M. Le Henaff, Y. Du Penhoat, C. E. Menkes, F. Marin, J. Vialard, G. Caniaux, and A. Lazar, 2006: A model study of the seasonal mixed layer heat budget in the equatorial Atlantic. J. Geophys. Res., 111, C06014, doi:10.1029/2005JC003157.

    • Search Google Scholar
    • Export Citation
  • Rienecker, M. M., and Coauthors, 2011: MERRA: NASA's Modern-Era Retrospective Analysis for Research and Applications. J. Climate, 24, 36243648.

    • Search Google Scholar
    • Export Citation
  • Siedler, G., N. Zangenberg, and R. Onken, 1992: Seasonal changes in the tropical Atlantic circulation: Observation and simulation of the Guinea Dome. J. Geophys. Res., 97 (C1), 703715.

    • Search Google Scholar
    • Export Citation
  • Stramma, L., S. Hüttl, and J. Schafstall, 2005: Water masses and currents in the upper tropical northeast Atlantic off northwest Africa. J. Geophys. Res., 110, C12006, doi:10.1029/2005JC002939.

    • Search Google Scholar
    • Export Citation
  • Sweeney, C., A. Gnanadesikan, S. M. Griffies, M. J. Harrison, A. J. Rosati, and B. L. Samuels, 2005: Impacts of shortwave penetration depth on large-scale ocean circulation and heat transport. J. Phys. Oceanogr., 35, 11031119.

    • Search Google Scholar
    • Export Citation
  • Tanguy, Y., S. Arnault, and P. Lattes, 2010: Isothermal, mixed, and barrier layers in the subtropical and tropical Atlantic Ocean during the ARAMIS experiment. Deep-Sea Res. I, 57, 501517.

    • Search Google Scholar
    • Export Citation
  • Wang, W. M., and M. J. McPhaden, 1999: The surface-layer heat balance in the equatorial Pacific Ocean. Part I: Mean seasonal cycle. J. Phys. Oceanogr., 29, 18121831.

    • Search Google Scholar
    • Export Citation
  • Xie, S.-P., and S. G. H. Philander, 1994: A coupled ocean-atmosphere model of relevance to the ITCZ in the eastern Pacific. Tellus, 46, 340350.

    • Search Google Scholar
    • Export Citation
  • Yamagata, T., and S. Iizuka, 1995: Simulation of the tropical thermal domes in the Atlantic: A seasonal cycle. J. Phys. Oceanogr., 25, 21292140.

    • Search Google Scholar
    • Export Citation
  • Yu, L. S., X. Z. Jin, and R. A. Weller, 2006: Role of net surface heat flux in seasonal variations of sea surface temperature in the tropical Atlantic Ocean. J. Climate, 19, 61536169.

    • Search Google Scholar
    • Export Citation
  • Zebiak, S. E., 1993: Air–sea interaction in the equatorial Atlantic region. J. Climate, 6, 15671586.

  • Zhang, Y., W. B. Rossow, A. A. Lacis, V. Oinas, and M. I. Mishchenko, 2004: Calculation of radiative fluxes from the surface to top of atmosphere based on ISCCP and other global data sets: Refinements of the radiative transfer model and the input data. J. Geophys. Res., 109, D19105, doi:10.1029/2003JD004457.

    • Search Google Scholar
    • Export Citation
  • Zhu, J., B. Huang, and M. A. Balmaseda, 2012: An ensemble estimation of the variability of upper-ocean heat content over the tropical Atlantic Ocean with multi-ocean reanalysis products. Climate Dyn., 39, 10011020.

    • Search Google Scholar
    • Export Citation
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