Articles | Volume 19, issue 3
https://doi.org/10.5194/os-19-923-2023
© 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-19-923-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
28 Jun 2023
Research article |
| 28 Jun 2023
| 28 Jun 2023
Factors influencing the meridional width of the equatorial deep jets
Swantje Bastin
CORRESPONDING AUTHOR
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
now at: Climate Variability Department, Max Planck Institute for Meteorology, Hamburg, Germany
Martin Claus
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Faculty of Mathematics and Natural Sciences, Kiel University, Kiel, Germany
Richard J. Greatbatch
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Faculty of Mathematics and Natural Sciences, Kiel University, Kiel, Germany
Peter Brandt
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Faculty of Mathematics and Natural Sciences, Kiel University, Kiel, Germany
Related authors
Swantje Bastin, Aleksei Koldunov, Florian Schütte, Oliver Gutjahr, Marta Agnieszka Mrozowska, Tim Fischer, Radomyra Shevchenko, Arjun Kumar, Nikolay Koldunov, Helmuth Haak, Nils Brüggemann, Rebecca Hummels, Mia Sophie Specht, Johann Jungclaus, Sergey Danilov, Marcus Dengler, and Markus Jochum
EGUsphere, https://doi.org/10.5194/egusphere-2024-2281, https://doi.org/10.5194/egusphere-2024-2281, 2024
Short summary
Short summary
Vertical mixing is an important process e.g. for tropical sea surface temperature, but cannot be resolved by ocean models. Comparisons of mixing schemes and settings have usually been done with a single model, sometimes yielding conflicting results. We systematically compare two widely used schemes, TKE and KPP, with different parameter settings, in two different ocean models, and show that most effects from mixing scheme parameter changes are model dependent.
Cathy Hohenegger, Peter Korn, Leonidas Linardakis, René Redler, Reiner Schnur, Panagiotis Adamidis, Jiawei Bao, Swantje Bastin, Milad Behravesh, Martin Bergemann, Joachim Biercamp, Hendryk Bockelmann, Renate Brokopf, Nils Brüggemann, Lucas Casaroli, Fatemeh Chegini, George Datseris, Monika Esch, Geet George, Marco Giorgetta, Oliver Gutjahr, Helmuth Haak, Moritz Hanke, Tatiana Ilyina, Thomas Jahns, Johann Jungclaus, Marcel Kern, Daniel Klocke, Lukas Kluft, Tobias Kölling, Luis Kornblueh, Sergey Kosukhin, Clarissa Kroll, Junhong Lee, Thorsten Mauritsen, Carolin Mehlmann, Theresa Mieslinger, Ann Kristin Naumann, Laura Paccini, Angel Peinado, Divya Sri Praturi, Dian Putrasahan, Sebastian Rast, Thomas Riddick, Niklas Roeber, Hauke Schmidt, Uwe Schulzweida, Florian Schütte, Hans Segura, Radomyra Shevchenko, Vikram Singh, Mia Specht, Claudia Christine Stephan, Jin-Song von Storch, Raphaela Vogel, Christian Wengel, Marius Winkler, Florian Ziemen, Jochem Marotzke, and Bjorn Stevens
Geosci. Model Dev., 16, 779–811, https://doi.org/10.5194/gmd-16-779-2023, https://doi.org/10.5194/gmd-16-779-2023, 2023
Short summary
Short summary
Models of the Earth system used to understand climate and predict its change typically employ a grid spacing of about 100 km. Yet, many atmospheric and oceanic processes occur on much smaller scales. In this study, we present a new model configuration designed for the simulation of the components of the Earth system and their interactions at kilometer and smaller scales, allowing an explicit representation of the main drivers of the flow of energy and matter by solving the underlying equations.
Yawouvi Dodji Soviadan, Miriam Beck, Joelle Habib, Alberto Baudena, Laetitia Drago, Alexandre Accardo, Remi Laxenaire, Sabrina Speich, Peter Brandt, Rainer Kiko, and Lars Stemmann
EGUsphere, https://doi.org/10.5194/egusphere-2024-3302, https://doi.org/10.5194/egusphere-2024-3302, 2024
Short summary
Short summary
Key parameters representing the gravity flux in global models are the sinking speed and the vertical attenuation of the exported material. We calculate for the first time, these parameters in situ for 6 intermittent blooms followed by export events using high-resolution (3 days) time series of 0–1000 m depth profiles from imaging sensor mounted on an Argo float. We show that sinking speed depends not only on size but also on the morphology of the particles, density being an important property.
Joelle Habib, Lars Stemmann, Alexandre Accardo, Alberto Baudena, Franz Philip Tuchen, Peter Brandt, and Rainer Kiko
EGUsphere, https://doi.org/10.5194/egusphere-2024-3365, https://doi.org/10.5194/egusphere-2024-3365, 2024
Short summary
Short summary
This study investigates how carbon moves from the ocean surface to the depths in the equatorial Atlantic, contributing to long-term carbon storage. Using an Argo float equipped with a camera, we captured two periods with major carbon export events. By identifying particle types and their sinking behaviors, we found that smaller, compact particles are key drivers of carbon transport. Our findings underscore the value of using imaging tools on autonomous platforms in tracking carbon sequestration.
Léo C. Aroucha, Joke F. Lübbecke, Peter Brandt, Franziska U. Schwarzkopf, and Arne Biastoch
EGUsphere, https://doi.org/10.5194/egusphere-2024-3320, https://doi.org/10.5194/egusphere-2024-3320, 2024
Short summary
Short summary
The West African coastal region sustains highly productive fisheries and marine ecosystems influenced by sea surface temperature. We use oceanic models to show that the freshwater input from land to ocean strengthens a surface northward (southward) coastal current north (south) of the Congo river mouth, promoting a transfer of cooler (warmer) waters to north (south) of the Congo discharge location. We highlight the significant impact of river discharge on ocean temperatures and circulation.
Eike E. Köhn, Richard J. Greatbatch, Peter Brandt, and Martin Claus
Ocean Sci., 20, 1281–1290, https://doi.org/10.5194/os-20-1281-2024, https://doi.org/10.5194/os-20-1281-2024, 2024
Short summary
Short summary
The latitudinally alternating zonal jets are a ubiquitous feature of the ocean. We use a simple model to illustrate the potential role of these jets in the formation, maintenance, and multidecadal variability in the oxygen minimum zones, using the eastern tropical North Atlantic oxygen minimum zone as an example.
Swantje Bastin, Aleksei Koldunov, Florian Schütte, Oliver Gutjahr, Marta Agnieszka Mrozowska, Tim Fischer, Radomyra Shevchenko, Arjun Kumar, Nikolay Koldunov, Helmuth Haak, Nils Brüggemann, Rebecca Hummels, Mia Sophie Specht, Johann Jungclaus, Sergey Danilov, Marcus Dengler, and Markus Jochum
EGUsphere, https://doi.org/10.5194/egusphere-2024-2281, https://doi.org/10.5194/egusphere-2024-2281, 2024
Short summary
Short summary
Vertical mixing is an important process e.g. for tropical sea surface temperature, but cannot be resolved by ocean models. Comparisons of mixing schemes and settings have usually been done with a single model, sometimes yielding conflicting results. We systematically compare two widely used schemes, TKE and KPP, with different parameter settings, in two different ocean models, and show that most effects from mixing scheme parameter changes are model dependent.
Kristin Burmeister, Franziska U. Schwarzkopf, Willi Rath, Arne Biastoch, Peter Brandt, Joke F. Lübbecke, and Mark Inall
Ocean Sci., 20, 307–339, https://doi.org/10.5194/os-20-307-2024, https://doi.org/10.5194/os-20-307-2024, 2024
Short summary
Short summary
We apply two different forcing products to a high-resolution ocean model to investigate their impact on the simulated upper-current field in the tropical Atlantic. Where possible, we compare the simulated results to long-term observations. We find large discrepancies between the two simulations regarding the wind and current fields. We propose that long-term observations, once they have reached a critical length, need to be used to test the quality of wind-driven simulations.
Peter Brandt, Gaël Alory, Founi Mesmin Awo, Marcus Dengler, Sandrine Djakouré, Rodrigue Anicet Imbol Koungue, Julien Jouanno, Mareike Körner, Marisa Roch, and Mathieu Rouault
Ocean Sci., 19, 581–601, https://doi.org/10.5194/os-19-581-2023, https://doi.org/10.5194/os-19-581-2023, 2023
Short summary
Short summary
Tropical upwelling systems are among the most productive ecosystems globally. The tropical Atlantic upwelling undergoes a strong seasonal cycle that is forced by the wind. Local wind-driven upwelling and remote effects, particularly via the propagation of equatorial and coastal trapped waves, lead to an upward and downward movement of the nitracline. Turbulent mixing results in upward supply of nutrients. Here, we review the different physical processes responsible for biological productivity.
Jufen Lai, Richard J. Greatbatch, and Martin Claus
Ocean Sci., 19, 421–430, https://doi.org/10.5194/os-19-421-2023, https://doi.org/10.5194/os-19-421-2023, 2023
Short summary
Short summary
The El Niño Southern Oscillation (ENSO) has a global influence on weather and climate. Over most of the equatorial Pacific, where ENSO is focused, variations in sea surface height, such as measured by satellite, are strongly influenced by vertical displacements of the ocean thermocline. We show that linearly removing this influence leads to a time series of sea surface height that capture ENSO dynamics in the central Pacific, where ENSO variability has become more active in recent decades.
Cathy Hohenegger, Peter Korn, Leonidas Linardakis, René Redler, Reiner Schnur, Panagiotis Adamidis, Jiawei Bao, Swantje Bastin, Milad Behravesh, Martin Bergemann, Joachim Biercamp, Hendryk Bockelmann, Renate Brokopf, Nils Brüggemann, Lucas Casaroli, Fatemeh Chegini, George Datseris, Monika Esch, Geet George, Marco Giorgetta, Oliver Gutjahr, Helmuth Haak, Moritz Hanke, Tatiana Ilyina, Thomas Jahns, Johann Jungclaus, Marcel Kern, Daniel Klocke, Lukas Kluft, Tobias Kölling, Luis Kornblueh, Sergey Kosukhin, Clarissa Kroll, Junhong Lee, Thorsten Mauritsen, Carolin Mehlmann, Theresa Mieslinger, Ann Kristin Naumann, Laura Paccini, Angel Peinado, Divya Sri Praturi, Dian Putrasahan, Sebastian Rast, Thomas Riddick, Niklas Roeber, Hauke Schmidt, Uwe Schulzweida, Florian Schütte, Hans Segura, Radomyra Shevchenko, Vikram Singh, Mia Specht, Claudia Christine Stephan, Jin-Song von Storch, Raphaela Vogel, Christian Wengel, Marius Winkler, Florian Ziemen, Jochem Marotzke, and Bjorn Stevens
Geosci. Model Dev., 16, 779–811, https://doi.org/10.5194/gmd-16-779-2023, https://doi.org/10.5194/gmd-16-779-2023, 2023
Short summary
Short summary
Models of the Earth system used to understand climate and predict its change typically employ a grid spacing of about 100 km. Yet, many atmospheric and oceanic processes occur on much smaller scales. In this study, we present a new model configuration designed for the simulation of the components of the Earth system and their interactions at kilometer and smaller scales, allowing an explicit representation of the main drivers of the flow of energy and matter by solving the underlying equations.
Mareike Körner, Peter Brandt, and Marcus Dengler
Ocean Sci., 19, 121–139, https://doi.org/10.5194/os-19-121-2023, https://doi.org/10.5194/os-19-121-2023, 2023
Short summary
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.
Rainer Kiko, Marc Picheral, David Antoine, Marcel Babin, Léo Berline, Tristan Biard, Emmanuel Boss, Peter Brandt, Francois Carlotti, Svenja Christiansen, Laurent Coppola, Leandro de la Cruz, Emilie Diamond-Riquier, Xavier Durrieu de Madron, Amanda Elineau, Gabriel Gorsky, Lionel Guidi, Helena Hauss, Jean-Olivier Irisson, Lee Karp-Boss, Johannes Karstensen, Dong-gyun Kim, Rachel M. Lekanoff, Fabien Lombard, Rubens M. Lopes, Claudie Marec, Andrew M. P. McDonnell, Daniela Niemeyer, Margaux Noyon, Stephanie H. O'Daly, Mark D. Ohman, Jessica L. Pretty, Andreas Rogge, Sarah Searson, Masashi Shibata, Yuji Tanaka, Toste Tanhua, Jan Taucher, Emilia Trudnowska, Jessica S. Turner, Anya Waite, and Lars Stemmann
Earth Syst. Sci. Data, 14, 4315–4337, https://doi.org/10.5194/essd-14-4315-2022, https://doi.org/10.5194/essd-14-4315-2022, 2022
Short summary
Short summary
The term
marine particlescomprises detrital aggregates; fecal pellets; bacterioplankton, phytoplankton and zooplankton; and even fish. Here, we present a global dataset that contains 8805 vertical particle size distribution profiles obtained with Underwater Vision Profiler 5 (UVP5) camera systems. These data are valuable to the scientific community, as they can be used to constrain important biogeochemical processes in the ocean, such as the flux of carbon to the deep sea.
Josefine Herrford, Peter Brandt, Torsten Kanzow, Rebecca Hummels, Moacyr Araujo, and Jonathan V. Durgadoo
Ocean Sci., 17, 265–284, https://doi.org/10.5194/os-17-265-2021, https://doi.org/10.5194/os-17-265-2021, 2021
Short summary
Short summary
The Atlantic Meridional Overturning Circulation (AMOC) is an important component of the climate system. Understanding its structure and variability is a key priority for many scientists. Here, we present the first estimate of AMOC variations for the tropical South Atlantic from the TRACOS array at 11° S. Over the observed period, the AMOC was dominated by seasonal variability. We investigate the respective mechanisms with an ocean model and find that different wind-forced waves play a big role.
Tim Fischer, Annette Kock, Damian L. Arévalo-Martínez, Marcus Dengler, Peter Brandt, and Hermann W. Bange
Biogeosciences, 16, 2307–2328, https://doi.org/10.5194/bg-16-2307-2019, https://doi.org/10.5194/bg-16-2307-2019, 2019
Short summary
Short summary
We investigated air–sea gas exchange in oceanic upwelling regions for the case of nitrous oxide off Peru. In this region, routine concentration measurements from ships at 5 m or 10 m depth prove to overestimate surface (bulk) concentration. Thus, standard estimates of gas exchange will show systematic error. This is due to very shallow stratified layers that inhibit exchange between surface water and waters below and can exist for several days. Maximum bias occurs in moderate wind conditions.
Yao Fu, Johannes Karstensen, and Peter Brandt
Ocean Sci., 14, 589–616, https://doi.org/10.5194/os-14-589-2018, https://doi.org/10.5194/os-14-589-2018, 2018
Short summary
Short summary
Hydrographic analysis in the Atlantic along 14.5° N and 24.5° N shows that between the periods of 1989/92 and 2013/15, the Antarctic Intermediate Water became warmer and saltier at 14.5° N, and that the Antarctic Bottom Water became lighter at both latitudes. By applying a box inverse model, the Atlantic Meridional Overturning Circulation (AMOC) was determined. Comparison among the inverse solution, GECCO2, RAPID, and MOVE shows that the AMOC has not significantly changed in the past 20 years.
Fabrice Ardhuin, Yevgueny Aksenov, Alvise Benetazzo, Laurent Bertino, Peter Brandt, Eric Caubet, Bertrand Chapron, Fabrice Collard, Sophie Cravatte, Jean-Marc Delouis, Frederic Dias, Gérald Dibarboure, Lucile Gaultier, Johnny Johannessen, Anton Korosov, Georgy Manucharyan, Dimitris Menemenlis, Melisa Menendez, Goulven Monnier, Alexis Mouche, Frédéric Nouguier, George Nurser, Pierre Rampal, Ad Reniers, Ernesto Rodriguez, Justin Stopa, Céline Tison, Clément Ubelmann, Erik van Sebille, and Jiping Xie
Ocean Sci., 14, 337–354, https://doi.org/10.5194/os-14-337-2018, https://doi.org/10.5194/os-14-337-2018, 2018
Short summary
Short summary
The Sea surface KInematics Multiscale (SKIM) monitoring mission is a proposal for a future satellite that is designed to measure ocean currents and waves. Using a Doppler radar, the accurate measurement of currents requires the removal of the mean velocity due to ocean wave motions. This paper describes the main processing steps needed to produce currents and wave data from the radar measurements. With this technique, SKIM can provide unprecedented coverage and resolution, over the global ocean.
Yao Fu, Johannes Karstensen, and Peter Brandt
Ocean Sci., 13, 531–549, https://doi.org/10.5194/os-13-531-2017, https://doi.org/10.5194/os-13-531-2017, 2017
Short summary
Short summary
Meridional Ekman transport in the tropical Atlantic was estimated directly by using observed ageostrophic velocity, and indirectly by using wind stress data. The direct and indirect methods agree well with each other. The top of the pycnocline represents the Ekman depth better than the mixed layer depth and a constant depth. The Ekman heat and salt fluxes calculated from sea surface temperature and salinity or from high-resolution temperature and salinity profile data differ only marginally.
Johannes Hahn, Peter Brandt, Sunke Schmidtko, and Gerd Krahmann
Ocean Sci., 13, 551–576, https://doi.org/10.5194/os-13-551-2017, https://doi.org/10.5194/os-13-551-2017, 2017
Short summary
Short summary
Recent studies have shown that the eastern tropical North Atlantic is subject to a strong decrease of the oceanic oxygen concentration in the upper 1000 m from the 1960s to today. By analyzing a broad observational data set, this study found an even stronger oxygen decrease in the upper 400 m throughout the past decade, whereas oxygen increase was found below (400–1000 m). Changes in the strength of the zonal currents are the most likely reason for the observed decadal oxygen changes.
Rafael Abel, Claus W. Böning, Richard J. Greatbatch, Helene T. Hewitt, and Malcolm J. Roberts
Ocean Sci. Discuss., https://doi.org/10.5194/os-2017-24, https://doi.org/10.5194/os-2017-24, 2017
Revised manuscript not accepted
Short summary
Short summary
In coupled global atmosphere ocean models a feedback from ocean surface currents to atmospheric winds was found. Surface winds are energized by about 30 % of the ocean currents. We were able to implement this feedback in uncoupled ocean models which results in a realistic surface flux coupling. Due to changes in the dissipation the kinetic energy of the time-variable flow is increased up to 10 % when this feedback is implemented. Implementation in other models should be straightforward.
Florian Schütte, Johannes Karstensen, Gerd Krahmann, Helena Hauss, Björn Fiedler, Peter Brandt, Martin Visbeck, and Arne Körtzinger
Biogeosciences, 13, 5865–5881, https://doi.org/10.5194/bg-13-5865-2016, https://doi.org/10.5194/bg-13-5865-2016, 2016
Short summary
Short summary
Mesoscale eddies with very low–oxygen concentrations at shallow depth have been recently discovered in the eastern tropical North Atlantic. Our analysis shows that low oxygen eddies occur more frequent than expected and are found even close to the equator (8° N). From budget calculations we show that an oxygen reduction of 7 µmol/kg in the depth range of 50–150 m in the eastern tropical North Atlantic (peak reduction is 16 µmol/kg at 100 m depth) can be associated with the dispersion of these eddies.
Florian Schütte, Peter Brandt, and Johannes Karstensen
Ocean Sci., 12, 663–685, https://doi.org/10.5194/os-12-663-2016, https://doi.org/10.5194/os-12-663-2016, 2016
Short summary
Short summary
We want to examine the characteristics of mesoscale eddies in the tropical northeastern Atlantic. They serve as transport agents, exporting water from the coast into the open ocean. Traditionally eddies are categorized with respect to their rotation: cyclonic and anticyclonic. But we could identify, with a combination of different satellite products, a third type called "anticyclonic mode-water eddy" transporting much larger anomalies. We propose a distinction into three classes for further studies.
L. Stramma, R. Czeschel, T. Tanhua, P. Brandt, M. Visbeck, and B. S. Giese
Ocean Sci., 12, 153–167, https://doi.org/10.5194/os-12-153-2016, https://doi.org/10.5194/os-12-153-2016, 2016
Short summary
Short summary
The subsurface circulation in the eastern tropical North Atlantic OMZ is derived from velocity, float and tracer data and data assimilation results, and shows a cyclonic flow around the Guinea Dome reaching into the oxygen minimum zone. The stronger cyclonic flow around the Guinea Dome in 2009 seem to be connected to a strong Atlantic Meridional Mode (AMM) event.
A continuous deoxygenation trend of the low oxygen layer was confirmed.
Eddy influence is weak south of the Cape Verde Islands.
J. Karstensen, B. Fiedler, F. Schütte, P. Brandt, A. Körtzinger, G. Fischer, R. Zantopp, J. Hahn, M. Visbeck, and D. Wallace
Biogeosciences, 12, 2597–2605, https://doi.org/10.5194/bg-12-2597-2015, https://doi.org/10.5194/bg-12-2597-2015, 2015
Short summary
Short summary
This study is the first report of the formation of dead zones in the open ocean. A combination of multiple ocean observing system elements (mooring, floats, satellites, ships) allowed us to reconstruct the generation of the dead zones and to connect the formation to enhanced respiration within mesoscale ocean eddies. The dead zones present specific threats to the ecosystem, such as the interruption of the diurnal migration of zooplankters.
P. Brandt, H. W. Bange, D. Banyte, M. Dengler, S.-H. Didwischus, T. Fischer, R. J. Greatbatch, J. Hahn, T. Kanzow, J. Karstensen, A. Körtzinger, G. Krahmann, S. Schmidtko, L. Stramma, T. Tanhua, and M. Visbeck
Biogeosciences, 12, 489–512, https://doi.org/10.5194/bg-12-489-2015, https://doi.org/10.5194/bg-12-489-2015, 2015
Short summary
Short summary
Our observational study looks at the structure of the eastern tropical North Atlantic (ETNA) oxygen minimum zone (OMZ) in comparison with the less-ventilated, eastern tropical South Pacific OMZ. We quantify the OMZ’s oxygen budget composed of consumption, advection, lateral and vertical mixing. Substantial oxygen variability is observed on interannual to multidecadal timescales. The deoxygenation of the ETNA OMZ during the last decades represents a substantial imbalance of the oxygen budget.
M. Thoma, R. Gerdes, R. J. Greatbatch, and H. Ding
Geosci. Model Dev., 8, 51–68, https://doi.org/10.5194/gmd-8-51-2015, https://doi.org/10.5194/gmd-8-51-2015, 2015
T. Fischer, D. Banyte, P. Brandt, M. Dengler, G. Krahmann, T. Tanhua, and M. Visbeck
Biogeosciences, 10, 5079–5093, https://doi.org/10.5194/bg-10-5079-2013, https://doi.org/10.5194/bg-10-5079-2013, 2013
Cited articles
Bastin, S., Claus, M., Brandt, P., and Greatbatch, R. J.: Equatorial Deep Jets
and Their Influence on the Mean Equatorial Circulation in an Idealized Ocean
Model Forced by Intraseasonal Momentum Flux Convergence, Geophys. Res.
Lett., 47, e2020GL087808, https://doi.org/10.1029/2020gl087808, 2020. a, b, c, d, e, f, g, h, i, j, k
Bastin, S., Claus, M., Greatbatch, R. J., and Brandt, P.: Supplementary dataset and scripts to Bastin et al.: Factors influencing the meridional width of the equatorial deep jets (Ocean Science) (2.0), Zenodo [data set], https://doi.org/10.5281/zenodo.7940306, 2023. a
Bourlès, B., Andrié, C., Gouriou, Y., Eldin, G., du Penhoat, Y.,
Freudenthal, S., Dewitte, B., Gallois, F., Chuchla, R., Baurand, F., Aman,
A., and Kouadio, G.: The deep currents in the Eastern Equatorial Atlantic
Ocean, Geophys. Res. Lett., 30, 8002, https://doi.org/10.1029/2002gl015095, 2003. a
Brandt, P., Funk, A., Hormann, V., Dengler, M., Greatbatch, R. J., and Toole,
J. M.: Interannual atmospheric variability forced by the deep equatorial
Atlantic Ocean, Nature, 473, 497–500, https://doi.org/10.1038/nature10013, 2011. a
Brandt, P., Greatbatch, R. J., Claus, M., Didwischus, S.-H., Hormann, V., Funk,
A., Hahn, J., Krahmann, G., Fischer, J., and Körtzinger, A.: Ventilation of
the equatorial Atlantic by the equatorial deep jets, J. Geophys. Res.-Oceans, 117, C12015, https://doi.org/10.1029/2012jc008118, 2012. a
Brandt, P., Bange, H. W., Banyte, D., Dengler, M., Didwischus, S.-H., Fischer, T., Greatbatch, R. J., Hahn, J., Kanzow, T., Karstensen, J., Körtzinger, A., Krahmann, G., Schmidtko, S., Stramma, L., Tanhua, T., and Visbeck, M.: On the role of circulation and mixing in the ventilation of oxygen minimum zones with a focus on the eastern tropical North Atlantic, Biogeosciences, 12, 489–512, https://doi.org/10.5194/bg-12-489-2015, 2015. a
Bunge, L., Provost, C., Lilly, J. M., d'Orgeville, M., Kartavtseff, A., and
Melice, J.-L.: Variability of the Horizontal Velocity Structure in the Upper
1600 m of the Water Column on the Equator at 10∘ W, J. Phys. Ocean., 36, 1287–1304, https://doi.org/10.1175/jpo2908.1, 2006. a
Cane, M. A. and Moore, D. W.: A Note on Low-Frequency Equatorial Basin Modes,
J. Phys. Ocean., 11, 1578–1584,
https://doi.org/10.1175/1520-0485(1981)011<1578:anolfe>2.0.co;2, 1981. a, b, c, d
Claus, M., Greatbatch, R. J., and Brandt, P.: Influence of the Barotropic Mean
Flow on the Width and the Structure of the Atlantic Equatorial Deep Jets,
J. Phys. Ocean., 44, 2485–2497,
https://doi.org/10.1175/jpo-d-14-0056.1, 2014. a, b
Claus, M., Greatbatch, R. J., Brandt, P., and Toole, J. M.: Forcing of the
Atlantic Equatorial Deep Jets Derived from Observations, J. Phys. Ocean., 46, 3549–3562, https://doi.org/10.1175/jpo-d-16-0140.1, 2016. a, b
Crameri, F., Shephard, G. E., and Heron, P. J.: The misuse of colour in science
communication, Nat. Commun., 11, 5444, https://doi.org/10.1038/s41467-020-19160-7,
2020. a
Dengler, M. and Quadfasel, D.: Equatorial Deep Jets and Abyssal Mixing in the
Indian Ocean, J. Phys. Ocean., 32, 1165–1180,
https://doi.org/10.1175/1520-0485(2002)032<1165:edjaam>2.0.co;2, 2002. a, b
Dietze, H. and Loeptien, U.: Revisiting “nutrient
trapping” in global coupled biogeochemical ocean
circulation models, Global Biogeochem. Cy., 27, 265–284,
https://doi.org/10.1002/gbc.20029, 2013. a
d'Orgeville, M., Hua, B. L., and Sasaki, H.: Equatorial deep jets triggered by
a large vertical scale variability within the western boundary layer, J.
Mar. Res., 65, 1–25, https://doi.org/10.1357/002224007780388720, 2007. a, b
Eriksen, C. C.: Geostrophic equatorial deep jets, J.
Mar. Res.,
40, 143–156, 1982. a
Firing, E., Fernandes, F., Barna, A., and Abernathey, R.: TEOS-10/GSW-Python:
v3.3.1,
https://github.com/TEOS-10/GSW-Python/releases/tag/v3.3.1 (last access: 17 February 2020),
2019. a
Getzlaff, J. and Dietze, H.: Effects of increased isopycnal diffusivity
mimicking the unresolved equatorial intermediate current system in an earth
system climate model, Geophys. Res. Lett., 40, 2166–2170,
https://doi.org/10.1002/grl.50419, 2013. a
Gill, A. E.: Atmosphere-Ocean Dynamics, Academic Press, International
Geophysics Series Volume 30, ISBN-13 978-0-12-283520-9, 1982. a
Gouriou, Y., Andrié, C., Bourlès, B., Freudenthal, S., Arnault, S.,
Aman, A., Eldin, G., du Penhoat, Y., Baurand, F., Gallois, F., and Chuchla,
R.: Deep circulation in the equatorial Atlantic Ocean, Geophys. Res. Lett., 28, 819–822, https://doi.org/10.1029/2000gl012326, 2001. a
Greatbatch, R. J., Claus, M., Brandt, P., Matthießen, J.-D., Tuchen, F. P.,
Ascani, F., Dengler, M., Toole, J., Roth, C., and Farrar, J. T.: Evidence for
the Maintenance of Slowly Varying Equatorial Currents by Intraseasonal
Variability, Geophys. Res. Lett., 45, 1923–1929,
https://doi.org/10.1002/2017gl076662, 2018. a, b, c, d, e, f, g
Gregg, M. C., Sanford, T. B., and Winkel, D. P.: Reduced mixing from the
breaking of internal waves in equatorial waters, Nature, 422, 513–515,
https://doi.org/10.1038/nature01507, 2003. a, b
Hayes, S. P. and Milburn, H. B.: On the Vertical Structure of Velocity in the
Eastern Equatorial Pacific, J. Phys. Ocean., 10, 633–635,
https://doi.org/10.1175/1520-0485(1980)010<0633:otvsov>2.0.co;2, 1980. a
Hua, B. L., d'Orgeville, M., Fruman, M. D., Ménesguen,
C., Schopp, R., Klein, P., and Sasaki, H.: Destabilization of mixed Rossby
gravity waves and the formation of equatorial zonal jets, J. Fluid
Mech., 610, 311–341, https://doi.org/10.1017/s0022112008002656, 2008. a
Hunter, J. D.: Matplotlib: A 2D Graphics Environment, Comput. Sci. Eng., 9, 90–95, https://doi.org/10.1109/mcse.2007.55, 2007. a
Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D., Gandin, L.,
Iredell, M., Saha, S., White, G., Woollen, J., Zhu, Y., Chelliah, M.,
Ebisuzaki, W., Higgins, W., Janowiak, J., Mo, K. C., Ropelewski, C., Wang,
J., Leetmaa, A., Reynolds, R., Jenne, R., and Joseph, D.: The NCEP/NCAR
40-Year Reanalysis Project, B. Am. Meteorol. Soc.,
77, 437–471, https://doi.org/10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2, 1996. a
Kistler, R., Collins, W., Saha, S., White, G., Woollen, J., Kalnay, E.,
Chelliah, M., Ebisuzaki, W., Kanamitsu, M., Kousky, V., van den Dool, H.,
Jenne, R., and Fiorino, M.: The NCEP-NCAR 50-Year
Reanalysis: Monthly Means CD-ROM and Documentation, B. Am. Meteorol. Soc., 82, 247–267,
https://doi.org/10.1175/1520-0477(2001)082<0247:tnnyrm>2.3.co;2, 2001. a
Krahmann, G. and Mehrtens, H.: SFB754 LADCP data,
https://doi.org/10.1594/PANGAEA.926517, 2021. a, b
Krahmann, G., Arévalo-Martínez, D. L., Dale, A. W., Dengler, M., Engel, A.,
Glock, N., Grasse, P., Hahn, J., Hauss, H., Hopwood, M. J., Kiko, R.,
Loginova, A. N., Löscher, C. R., Maßmig, M., Roy, A.-S., Salvatteci, R.,
Sommer, S., Tanhua, T., and Mehrtens, H.: Climate-Biogeochemistry
Interactions in the Tropical Ocean: Data Collection and Legacy, Front. Mar. Sci., 8, 723304, https://doi.org/10.3389/fmars.2021.723304, 2021. a
Kundu, P. K., Cohen, I. M., and Dowling, D. R.: Fluid Mechanics, Academic
Press, 5th edn., ISBN 978-0-521-72169-1, 2012. a
Körner, M., Claus, M., Brandt, P., and Tuchen, F. P.: Sources and Pathways of
Intraseasonal Meridional Kinetic Energy in the Equatorial Atlantic Ocean,
J. Phys. Ocean., 52, 2445–2462,
https://doi.org/10.1175/JPO-D-21-0315.1, 2022. a, b
Leetmaa, A. and Spain, P. F.: Results from a Velocity Transect Along the
Equator from 125 to 159∘ W, J. Phys. Ocean., 11, 1030–1033,
https://doi.org/10.1175/1520-0485(1981)011<1030:rfavta>2.0.co;2, 1981. a
Locarnini, R. A., Mishonov, A. V., Baranova, O. K., Boyer, T. P., Zweng, M. M., Garcia, H. E., Reagan, J. R., Seidov, D., Weathers, K. W., Paver, C. R., and Smolyar, I. V.: World Ocean Atlas 2018, Volume 1: Temperature. A. Mishonov, Technical Editor. NOAA Atlas NESDIS 81, 52 pp., 2019. a
Luyten, J. R. and Swallow, J.: Equatorial undercurrents, Deep Sea Res., 23, 999–1001, https://doi.org/10.1016/0011-7471(76)90830-5,
1976. a
MacLachlan, C., Arribas, A., Peterson, K. A., Maidens, A., Fereday, D., Scaife,
A. A., Gordon, M., Vellinga, M., Williams, A., Comer, R. E., Camp, J.,
Xavier, P., and Madec, G.: Global Seasonal forecast system version 5
(GloSea5): a high-resolution seasonal forecast system, Q. J. Roy. Meteor. Soc., 141, 1072–1084, https://doi.org/10.1002/qj.2396,
2015. a
Madec, G., Bourdallé-Badie, R., Bouttier, P.-A., Bricaud, C., Bruciaferri, D.,
Calvert, D., Chanut, J., Clementi, E., Coward, A., Delrosso, D., Ethé, C.,
Flavoni, S., Graham, T., Harle, J., Iovino, D., Lea, D., Lévy, C., Lovato,
T., Martin, N., Masson, S., Mocavero, S., Paul, J., Rousset, C., Storkey, D.,
Storto, A., and Vancoppenolle, M.: NEMO ocean engine, Notes du Pôle
de modélisation de l'Institut Pierre-Simon Laplace (IPSL),
https://doi.org/10.5281/ZENODO.3248739, 2017. a
Matthießen, J.-D., Greatbatch, R. J., Brandt, P., Claus, M., and
Didwischus, S.-H.: Influence of the equatorial deep jets on the north
equatorial countercurrent, Ocean Dynam., 65, 1095–1102,
https://doi.org/10.1007/s10236-015-0855-5, 2015.
a, b
Matthießen, J.-D., Greatbatch, R. J., Claus, M., Ascani, F., and Brandt,
P.: The emergence of equatorial deep jets in an idealised primitive equation
model: an interpretation in terms of basin modes, Ocean Dynam., 67,
1511–1522, https://doi.org/10.1007/s10236-017-1111-y, 2017. a, b
Ménesguen, C., Hua, B. L., Fruman, M. D., and Schopp, R.: Intermittent
layering in the Atlantic equatorial deep jets, J. Mar. Res.,
67, 347–360, https://doi.org/10.1357/002224009789954748, 2009. a
Ménesguen, C., Delpech, A., Marin, F., Cravatte, S., Schopp, R., and
Morel, Y.: Observations and Mechanisms for the Formation of Deep Equatorial
and Tropical Circulation, Earth Space Sci., 6, 370–386,
https://doi.org/10.1029/2018ea000438, 2019. a
Pacanowski, R. C. and Philander, S. G. H.: Parameterization of Vertical Mixing
in Numerical Models of Tropical Oceans, J. Phys. Ocean., 11,
1443–1451, https://doi.org/10.1175/1520-0485(1981)011<1443:povmin>2.0.co;2, 1981. a
Tuchen, F. P., Brandt, P., Claus, M., and Hummels, R.: Deep Intraseasonal
Variability in the Central Equatorial Atlantic, J. Phys. Ocean., 48, 2851–2865, https://doi.org/10.1175/jpo-d-18-0059.1, 2018. a, b
Tuchen, F. P., Brandt, P., Hahn, J., Hummels, R., Krahmann, G., Bourlès,
B., Provost, C., McPhaden, M. J., and Toole, J. M.: Two Decades of Full-Depth
Current Velocity Observations From a Moored Observatory in the Central
Equatorial Atlantic at 0∘ N, 23∘ W, Front. Mar.
Sci., 9, 910979, https://doi.org/10.3389/fmars.2022.910979, 2022a. a
Tuchen, F. P., Brandt, P., Hahn, J., Hummels, R., Krahmann, G.,
Bourlès, B., Provost, C., McPhaden, M. J., and Toole, J. M.:
Data product of full-depth current velocity observations at 0∘ N,
23∘ W from 2001–2021 (v1.0), https://doi.org/10.1594/PANGAEA.941042, 2022b. a
von Schuckmann, K., Brandt, P., and Eden, C.: Generation of tropical
instability waves in the Atlantic Ocean, J. Geophys., Res.,
113, C08034, https://doi.org/10.1029/2007jc004712, 2008. a
Yamagata, T. and Philander, S. G. H.: The role of damped equatorial waves in
the oceanic response to winds, J. Ocean. Soc. Jpn., 41, 345–357, https://doi.org/10.1007/BF02109241, 1985. a, b
Zweng, M., Reagan, J., Seidov, D., Boyer, T., Locarnini, R., Garcia, H.,
Mishonov, A., Baranova, O., Weathers, K., Paver, C., and Smolyar, I.: World Ocean Atlas 2018, Volume 2: Salinity. A. Mishonov, Technical Editor, NOAA Atlas NESDIS 82, 50 pp., 2019. a
Short summary
Equatorial deep jets are ocean currents that flow along the Equator in the deep oceans. They are relevant for oxygen transport and tropical surface climate, but their dynamics are not yet entirely understood. We investigate different factors leading to the jets being broader than theory predicts. Mainly using an ocean model, but corroborating the results with shipboard observations, we show that loss of momentum is the main factor for the broadening but that meandering also contributes.
Equatorial deep jets are ocean currents that flow along the Equator in the deep oceans. They are...
