Articles | Volume 19, issue 1
https://doi.org/10.5194/os-19-121-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-19-121-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
27 Jan 2023
Research article |
| 27 Jan 2023
| 27 Jan 2023
Seasonal cycle of sea surface temperature in the tropical Angolan Upwelling System
Physical Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Peter Brandt
Physical Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Faculty of Mathematics and Natural Sciences, Kiel University, Kiel,
Germany
Marcus Dengler
Physical Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
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Cited articles
Awo, F. M., Rouault, M., Ostrowski, M., and Tomety, F. S.: Seasonal Cycle of
Sea Surface Salinity in the Angola Upwelling System, J. Geophys. Res.-Oceans, 127, e2022JC018518, https://doi.org/10.1029/2022JC018518, 2022.
Bachèlery, M. Lou, Illig, S., and Dadou, I.: Interannual variability in
the South-East Atlantic Ocean, focusing on the Benguela Upwelling System:
Remote versus local forcing, J. Geophys. Res.-Oceans, 121, 284–310,
https://doi.org/10.1002/2015JC011168, 2016.
Davis, R. E.: Sampling Turbulent Dissipation, J. Phys. Oceanogr., 26,
341–358, 1996.
Deppenmeier, A. L., Haarsma, R. J., van Heerwaarden, C., and Hazeleger, W.:
The southeastern tropical atlantic sst bias investigated with a coupled
atmosphere-ocean single-column model at a pirata mooring site, J. Climate, 33,
6255–6271, https://doi.org/10.1175/JCLI-D-19-0608.1, 2020.
ESR: OSCAR third deg. Ver. 1. PO.DAAC, CA, USA, NASA Earthdata [data set],
https://doi.org/10.5067/OSCAR-03D01, 2009.
ESSO – Indian National Centre for Ocean Information Services: Overview, https://incois.gov.in/tropflux/index.jsp, last access: 20 January 2023.
FAO: Fishery and aquaculture country profiles: Republic of Angola, report, https://www.fao.org/figis/pdf/fishery/facp/AGO/en?title=FAO Fisheries & Aquaculture - Fishery and Aquaculture Country Profiles - The Republic of Angola (last access: 23 January 2023), 2018.
Farneti, R., Stiz, A., and Ssebandeke, J. B.: Improvements and persistent
biases in the southeast tropical Atlantic in CMIP models, npj Clim. Atmos.
Sci., 5, 42, https://doi.org/10.1038/s41612-022-00264-4, 2022.
Foltz, G. R., Grodsky, S. A., Carton, J. A., and McPhaden, M. J.: Seasonal
mixed layer heat budget of the tropical Atlantic Ocean, J. Geophys. Res.,
108, 3146, https://doi.org/10.1029/2002jc001584, 2003.
Foltz, G. R., Schmid, C., and Lumpkin, R.: Seasonal cycle of the mixed layer
heat budget in the northeastern tropical atlantic ocean, J. Climate, 26,
8169–8188, https://doi.org/10.1175/JCLI-D-13-00037.1, 2013.
Foltz, G. R., Brandt, P., Richter, I., Rodriguez-fonseca, B., Hernandez, F.,
Dengler, M., Rodrigues, R. R., Schmidt, J. O., Yu, L., Lefevre, N., Da
Cunha, L. C., McPhaden, M. J., Araujo Filho, M. C., Karstensen, J., Hahn,
J., Martín-Rey, M., Patricola, C. M., Poli, P., Zuidema, P., Hummels,
R., Perez, R. C., Hatje, V., Luebbecke, J., Polo, I., Lumpkin, R.,
Bourlès, B., Asuquo, F. E., Lehodey, P., Conchon, A., Chang, P., Dandin,
P., Schmid, C., Sutton, A. J., Giordani, H., Xue, Y., Illig, S., Losada, T.,
Grodsky, S., Gasparin, F., Lee, T., Mohino, E., Nobre, P., Wanninkhof, R.,
Keenlyside, N. S., Garcon, V., Sanchez-Gomez, E., Nnamchi, H. C., Drevillon,
M., Storto, A., Remy, E., Lazar, A., Speich, S., Goes, M. P., Dorrington,
T., Johns, W. E., Moum, J. N., Robinson, C., Perruche, C., Souza, R. B.,
Gaye, A., Lopez-Parages, J., Monerie, P. A., Castellanos, P., Benson, N. U.,
Hounkonnou, M. N., and Duha, J. T.: The tropical atlantic observing system,
Front. Mar. Sci., 6, 1–36, https://doi.org/10.3389/fmars.2019.00206, 2019.
Global Modeling and Assimilation Office (GMAO): tavgM_2d_ocn_Nx: MERRA 2D IAU Ocean Surface
Diagnostic, Monthly Mean V5.2.0, Greenbelt, MD, USA, Goddard Earth Sciences
Data and Information Services Center (GES DISC) [data set],
https://doi.org/10.5067/LH0VEHYM7Y8Z, 2008.
Good, S., Fiedler, E., Mao, C., Martin, M. J., Maycock, A., Reid, R.,
Roberts-Jones, J., Searle, T., Waters, J., While, J., and Worsfold, M.: The
current configuration of the OSTIA system for operational production of
foundation sea surface temperature and ice concentration analyses, Remote
Sens., 12, 1–20, https://doi.org/10.3390/rs12040720, 2020.
Gregg, M. C., D'Asaro, E. A., Riley, J. J., and Kunze, E.: Mixing Efficiency
in the Ocean, Annu. Rev. Mar. Sci., 10, 443–473,
https://doi.org/10.1146/annurev-marine-121916-063643, 2018.
Good, S., Fiedler, E., Mao, C., Martin, M. J., Maycock, A., Reid, R., Roberts-Jones, J., Searle, T., Waters, J., While, J., and Worsfold, M.: Global Ocean OSTIA Sea Surface Temperature and Sea Ice Reprocessed, Copernicus [data set], https://doi.org/10.48670/moi-00168, 2020.
Hourdin, F., Găinusă-Bogdan, A., Braconnot, P., Dufresne, J. L., Traore, A.
K., and Rio, C.: Air moisture control on ocean surface temperature, hidden
key to the warm bias enigma, Geophys. Res. Lett., 42, 10885–10893,
https://doi.org/10.1002/2015GL066764, 2015.
Huang, B., Hu, Z. Z., and Jha, B.: Evolution of model systematic errors in
the tropical atlantic basin from coupled climate hindcasts, Clim. Dynam., 28,
661–682, https://doi.org/10.1007/s00382-006-0223-8, 2007.
Hummels, R., Dengler, M., Brandt, P., and Schlundt, M.: Diapycnal heat flux
and mixed layer heat budget within the Atlantic Cold Tongue, Clim. Dynam., 43,
3179–3199, https://doi.org/10.1007/s00382-014-2339-6, 2014.
Illig, S., Bachèlery, M. Lou, and Cadier, E.: Subseasonal
Coastal-Trapped Wave Propagations in the Southeastern Pacific and Atlantic
Oceans: 2. Wave Characteristics and Connection With the Equatorial
Variability, J. Geophys. Res.-Oceans, 123, 3942–3961,
https://doi.org/10.1029/2017JC013540, 2018.
Kopte, R., Brandt, P., Tchipalanga, P. C. M., Macueria, M., and Ostrowski,
M.: The Angola Current: Flow and hydrographic characteristics as observed at
11∘ S, J. Geophys. Res.-Oceans, 122, 1177–1189,
https://doi.org/10.1002/2016JC012374, 2017.
Körner M., Brandt, P., and Dengler M.: Upper-ocean microstructure data from the tropical Angolan upwelling system, PANGAEA [data set], https://doi.org/10.1594/PANGAEA.953869, 2023.
Kumar, B. P., Vialard, J., Lengaigne, M., Murty, V. S. N., and McPhaden, M.
J.: TropFlux: Air-sea fluxes for the global tropical oceans-description and
evaluation, Clim. Dynam., 38, 1521–1543,
https://doi.org/10.1007/s00382-011-1115-0, 2012.
Kurian, J., Li, P., Chang, P., Patricola, C. M., and Small, J.: Impact of
the Benguela coastal low-level jet on the southeast tropical Atlantic SST
bias in a regional ocean model, Clim. Dynam., 56, 2773–2800,
https://doi.org/10.1007/s00382-020-05616-5, 2021.
Legg, S. and Adcroft, A.: Internal wave breaking at concave and convex
continental slopes, J. Phys. Oceanogr., 33, 2224–2246,
https://doi.org/10.1175/1520-0485(2003)033<2224:IWBACA>2.0.CO;2, 2003.
Lellouche, J.-M., Greiner, E., Bourdallé Badie, R., Garric, G., Melet,
A., Drévillon, M., Bricaud, C., Hamon, M., Le Galloudec, O., Regnier,
C., Candela, T., Testut, C.-E., Gasparin, F., Ruggiero, G., Benkiran, M.,
Drillet, Y., and Le Traon, P.-Y.: The Copernicus Global 1/12∘
Oceanic and Sea Ice GLORYS12 Reanalysis, Front. Earth Sci., 9, 1–27,
https://doi.org/10.3389/feart.2021.698876, 2021a.
Lellouche, J.-M., Greiner, E., Bourdallé Badie, R., Garric, G., Melet, A., Drévillon, M., Bricaud, C., Hamon, M., Le Galloudec, O., Regnier, C., Candela, T., Testut, C.-E., Gasparin, F., Ruggiero, G., Benkiran, M., Drillet, Y., and Le Traon, P.-Y.: Global Ocean Physics Reanalysis, Copernicus [data set], https://doi.org/10.48670/moi-00021, 2021b.
Lübbecke, J. F., Brandt, P., Dengler, M., Kopte, R., Lüdke, J.,
Richter, I., Sena Martins, M., and Tchipalanga, P. C. M.: Causes and
evolution of the southeastern tropical Atlantic warm event in early 2016,
Clim. Dynam., 53, 261–274, https://doi.org/10.1007/s00382-018-4582-8, 2019.
Moisan, J. R. and Niiler, P. P.: the seasonal heat budget of the North
Pacific: Net heat flux and heat storage rates (1950–1990), J. Phys.
Oceanogr., 28, 401–421, https://doi.org/10.1175/1520-0485(1998)028<0401:TSHBOT>2.0.CO;2, 1998.
Morel, A. and Antoine, D.: Heating Rate within the Upper Ocean in Relation
to Irs Bio-Optical State, J. Phys. Oceanogr., 24, 1652–1665, 1994.
National Oceanic and
Atmospheric Administration
United States Department of Commerce: Global Tropical Moored Buoy Array, https://www.pmel.noaa.gov/gtmba/, last access: 20 January 2023.
Nielsen-Englyst, P., Høyer, J. L., Alerskans, E., Pedersen, L. T., and
Donlon, C.: Impact of channel selection on SST retrievals from passive
microwave observations, Remote Sens. Environ., 254, 112252,
https://doi.org/10.1016/j.rse.2020.112252, 2021.
Ocean Productivity: Online Data: Eppley VGPM, http://orca.science.oregonstate.edu/1080.by.2160.8day.hdf.eppley.m.chl.m.sst.php, last access: 20 January 2023.
Osborn, T. R.: Estimates of the Local Rate of Vertical Diffusion from
Dissipation Measurements, J. Phys. Oceanogr., 10, 83–89,
https://doi.org/10.1175/1520-0485(1980)010<0083:eotlro>2.0.co;2, 1980.
Ostrowski, M., Da Silva, J. C. B., and Bazik-Sangolay, B.: The response of
sound scatterers to El Ninõ- and La Niña-like oceanographic regimes
in the southeastern Atlantic, ICES J. Mar. Sci., 66, 1063–1072,
https://doi.org/10.1093/icesjms/fsp102, 2009.
Perlin, A., Moum, J. N., and Klymak, J. M.: Response of the bottom boundary
layer over a sloping shelf to variations in alongshore wind, J. Geophys.
Res.-Oceans, 110, C10S09, https://doi.org/10.1029/2004JC002500, 2005.
Ricciardulli, L. and Wentz, F. J.: Remote Sensing Systems ASCAT C-2015 Daily Ocean Vector Winds on 0.25 deg grid, Version 02.1, Remote Sensing Systems [data set], Santa Rosa, CA, https://www.remss.com/missions/ascat/ (last access: 24 January 2023), 2016.
Ricciardulli, L., Wentz, F. J., and Smith, D. K.: Remote Sensing Systems QuikSCAT Ku-2011 Monthly Ocean Vector Winds on 0.25 deg grid, Version 4, Remote Sensing Systems [data set], Santa Rosa, CA, https://www.remss.com/missions/qscat/ (last access: 24 January 2023), 2011.
Richter, I.: Climate model biases in the eastern tropical oceans: Causes,
impacts and ways forward, Wiley Interdiscip. Rev. Clim. Chang., 6, 345–358,
https://doi.org/10.1002/wcc.338, 2015.
Richter, I. and Tokinaga, H.: An overview of the performance of CMIP6 models
in the tropical Atlantic: mean state, variability, and remote impacts, Clim.
Dynam., 55, 2579–2601, https://doi.org/10.1007/s00382-020-05409-w, 2020.
Rouault, M.: Bi-annual intrusion of tropical water in the northern Benguela
upwelling, Geophys. Res. Lett., 39, L12606,
https://doi.org/10.1029/2012GL052099, 2012.
Scannell, H. A. and McPhaden, M. J.: Seasonal Mixed Layer Temperature
Balance in the Southeastern Tropical Atlantic, J. Geophys. Res.-Oceans, 123,
5557–5570, https://doi.org/10.1029/2018JC014099, 2018.
Schafstall, J., Dengler, M., Brandt, P., and Bange, H.: Tidal-induced mixing
and diapycnal nutrient fluxes in the Mauritanian upwelling region, J.
Geophys. Res.-Oceans, 115, C10014, https://doi.org/10.1029/2009JC005940,
2010.
Shannon, L. V., Agenbag, J. J., and Buys, M. E. L.: Large- and mesoscale
features of the Angola-Benguela front, South African J. Mar. Sci., 5,
11–34, https://doi.org/10.2989/025776187784522261, 1987.
Siegfried, L., Schmidt, M., Mohrholz, V., Pogrzeba, H., Nardini, P.,
Böttinger, M., and Scheuermann, G.: The tropical-subtropical coupling in
the Southeast Atlantic from the perspective of the northern Benguela
upwelling system, PLOS ONE, 14, e0210083, https://doi.org/10.1371/journal.pone.0210083,
2019.
Sowman, M. and Cardoso, P.: Small-scale fisheries and food security
strategies in countries in the Benguela Current Large Marine Ecosystem
(BCLME) region: Angola, Namibia and South Africa, Mar. Policy, 34,
1163–1170, https://doi.org/10.1016/j.marpol.2010.03.016, 2010.
Stevenson, J. W. and Niiler, P. P.: Upper Ocean Heat Budget During the
Hawaii-to-Tahiti Schuttle Experiment, J. Phys. Oceanogr., 13, 1894–1907,
1983.
Tchipalanga, P., Dengler, M., Brandt, P., Kopte, R., Macuéria, M.,
Coelho, P., Ostrowski, M., and Keenlyside, N. S.: Eastern boundary
circulation and hydrography off Angola building Angolan oceanographic
capacities, B. Am. Meteorol. Soc., 99, 1589–1605,
https://doi.org/10.1175/BAMS-D-17-0197.1, 2018.
Thomsen, S., Capet, X., and Echevin, V.: Competition between baroclinic
instability and Ekman transport under varying buoyancy forcings in upwelling
systems: An idealized analog to the Southern Ocean., J. Phys. Oceanogr., 51,
3347–3364, https://doi.org/10.1175/jpo-d-20-0294.1, 2021.
Voldoire, A., Exarchou, E., Sanchez-Gomez, E., Demissie, T., Deppenmeier, A.
L., Frauen, C., Goubanova, K., Hazeleger, W., Keenlyside, N., Koseki, S.,
Prodhomme, C., Shonk, J., Toniazzo, T., and Traoré, A. K.: Role of wind
stress in driving SST biases in the Tropical Atlantic, Clim. Dynam., 53,
3481–3504, https://doi.org/10.1007/s00382-019-04717-0, 2019.
Wolk, F., Yamazaki, H., Seuront, L., and Lueck, R. G.: A new free-fall
profiler for measuring biophysical microstructure, J. Atmos. Ocean.
Tech., 19, 780–793, https://doi.org/10.1175/1520-0426(2002)019<0780:ANFFPF>2.0.CO;2, 2002.
Xu, Z., Chang, P., Richter, I., Kim, W., and Tang, G.: Diagnosing southeast
tropical Atlantic SST and ocean circulation biases in the CMIP5 ensemble,
Clim. Dynam., 43, 3123–3145, https://doi.org/10.1007/s00382-014-2247-9, 2014.
Zeng, Z., Brandt, P., Lamb, K. G., Greatbatch, R. J., Dengler, M., Claus,
M., and Chen, X.: Three-Dimensional Numerical Simulations of Internal Tides
in the Angolan Upwelling Region, J. Geophys. Res.-Oceans, 126, e2020JC016460,
https://doi.org/10.1029/2020JC016460, 2021.
Zhang, S., Alford, M. H., and Mickett, J. B.: Characteristics, generation
and mass transport of nonlinear internal waves on the Washington continental
shelf, J. Geophys. Res.-Oceans, 120, 741–758,
https://doi.org/10.1002/2014JC010393, 2015.
Zuidema, P., Chang, P., Medeiros, B., Kirtman, B. P., Mechoso, R.,
Schneider, E. K., Toniazzo, T., Richter, I., Small, R. J., Bellomo, K.,
Brandt, P., De Szoeke, S., Farrar, J. T., Jung, E., Kato, S., Li, M.,
Patricola, C., Wang, Z., Wood, R., and Xu, Z.: Challenges and prospects for
reducing coupled climate model sst biases in the eastern tropical atlantic
and pacific oceans: The U.S. Clivar eastern tropical oceans synthesis
working group, B. Am. Meteorol. Soc., 97, 2305–2327,
https://doi.org/10.1175/BAMS-D-15-00274.1, 2016.
Short summary
The coastal waters off Angola host a productive ecosystem. Surface waters at the coast are colder than further offshore. We find that surface heat fluxes warm the coastal region more strongly than the offshore region and cannot explain the differences. The influence of horizontal heat advection is minor on the surface temperature change. In contrast, ocean turbulence data suggest that cooling associated with vertical mixing is an important mechanism to explain the near-coastal cooling.
The coastal waters off Angola host a productive ecosystem. Surface waters at the coast are...
