Articles | Volume 20, issue 2
https://doi.org/10.5194/os-20-307-2024
© Author(s) 2024. 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-20-307-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
15 Mar 2024
Research article |
| 15 Mar 2024
| 15 Mar 2024
Dependency of simulated tropical Atlantic current variability on the wind forcing
Kristin Burmeister
CORRESPONDING AUTHOR
SAMS Scottish Association for Marine Science, University of the Highlands and Islands, Oban, Scotland, UK
Franziska U. Schwarzkopf
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Willi Rath
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Arne Biastoch
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
Joke F. Lübbecke
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Mark Inall
SAMS Scottish Association for Marine Science, University of the Highlands and Islands, Oban, Scotland, UK
Related authors
No articles found.
Swantje Bastin, Martin Claus, Richard J. Greatbatch, and Peter Brandt
Ocean Sci., 19, 923–939, https://doi.org/10.5194/os-19-923-2023, https://doi.org/10.5194/os-19-923-2023, 2023
Short summary
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.
Jake W. Casselman, Joke F. Lübbecke, Tobias Bayr, Wenjuan Huo, Sebastian Wahl, and Daniela I. V. Domeisen
Weather Clim. Dynam., 4, 471–487, https://doi.org/10.5194/wcd-4-471-2023, https://doi.org/10.5194/wcd-4-471-2023, 2023
Short summary
Short summary
El Niño–Southern Oscillation (ENSO) has remote effects on the tropical North Atlantic (TNA), but the connections' nonlinearity (strength of response to an increasing ENSO signal) is not always well represented in models. Using the Community Earth System Model version 1 – Whole Atmosphere Community Climate Mode (CESM-WACCM) and the Flexible Ocean and Climate Infrastructure version 1, we find that the TNA responds linearly to extreme El Niño but nonlinearly to extreme La Niña for CESM-WACCM.
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.
Roy Dorgeless Ngakala, Gaël Alory, Casimir Yélognissè Da-Allada, Olivia Estelle Kom, Julien Jouanno, Willi Rath, and Ezinvi Baloïtcha
Ocean Sci., 19, 535–558, https://doi.org/10.5194/os-19-535-2023, https://doi.org/10.5194/os-19-535-2023, 2023
Short summary
Short summary
Surface heat flux is the main driver of the heat budget in the Senegal, Angola, and Benguela regions but not in the equatorial region. In the Senegal and Benguela regions, freshwater flux governs the salt budget, while in equatorial and Angola regions, oceanic processes are the main drivers. Results from numerical simulation show the important role of mesoscale advection for temperature and salinity variations in the mixed layer. Nonlinear processes unresolved by observations play a key role.
Sam C. Jones, Neil J. Fraser, Stuart A. Cunningham, Alan D. Fox, and Mark E. Inall
Ocean Sci., 19, 169–192, https://doi.org/10.5194/os-19-169-2023, https://doi.org/10.5194/os-19-169-2023, 2023
Short summary
Short summary
Warm water is transported from the tropical Atlantic towards western Europe and the Arctic. It loses heat to the atmosphere on the way, which strongly influences the climate. We construct a dataset encircling the North Atlantic basin north of 47° N. We calculate how and where heat enters and leaves the basin and how much cooling must happen in the interior. We find that cooling in the north-eastern Atlantic is a crucial step in controlling the conversion of water to higher densities.
Torge Martin and Arne Biastoch
Ocean Sci., 19, 141–167, https://doi.org/10.5194/os-19-141-2023, https://doi.org/10.5194/os-19-141-2023, 2023
Short summary
Short summary
How is the ocean affected by continued Greenland Ice Sheet mass loss? We show in a systematic set of model experiments that atmospheric feedback needs to be accounted for as the large-scale ocean circulation is more than twice as sensitive to the meltwater otherwise. Coastal winds, boundary currents, and ocean eddies play a key role in redistributing the meltwater. Eddy paramterization helps the coarse simulation to perform better in the Labrador Sea but not in the North Atlantic Current region.
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.
Alan D. Fox, Patricia Handmann, Christina Schmidt, Neil Fraser, Siren Rühs, Alejandra Sanchez-Franks, Torge Martin, Marilena Oltmanns, Clare Johnson, Willi Rath, N. Penny Holliday, Arne Biastoch, Stuart A. Cunningham, and Igor Yashayaev
Ocean Sci., 18, 1507–1533, https://doi.org/10.5194/os-18-1507-2022, https://doi.org/10.5194/os-18-1507-2022, 2022
Short summary
Short summary
Observations of the eastern subpolar North Atlantic in the 2010s show exceptional freshening and cooling of the upper ocean, peaking in 2016 with the lowest salinities recorded for 120 years. Using results from a high-resolution ocean model, supported by observations, we propose that the leading cause is reduced surface cooling over the preceding decade in the Labrador Sea, leading to increased outflow of less dense water and so to freshening and cooling of the eastern subpolar North Atlantic.
Jörg Fröhle, Patricia V. K. Handmann, and Arne Biastoch
Ocean Sci., 18, 1431–1450, https://doi.org/10.5194/os-18-1431-2022, https://doi.org/10.5194/os-18-1431-2022, 2022
Short summary
Short summary
Three deep-water masses pass the southern exit of the Labrador Sea. Usually they are defined by explicit density intervals linked to the formation region. We evaluate this relation in an ocean model by backtracking the paths the water follows for 40 years: 48 % densify without contact to the atmosphere, 24 % densify in contact with the atmosphere, and 19 % are from the Nordic Seas. All three contribute to a similar density range at 53° N with weak specific formation location characteristics.
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.
Benjamin R. Loveday, Timothy Smyth, Anıl Akpinar, Tom Hull, Mark E. Inall, Jan Kaiser, Bastien Y. Queste, Matt Tobermann, Charlotte A. J. Williams, and Matthew R. Palmer
Earth Syst. Sci. Data, 14, 3997–4016, https://doi.org/10.5194/essd-14-3997-2022, https://doi.org/10.5194/essd-14-3997-2022, 2022
Short summary
Short summary
Using a new approach to combine autonomous underwater glider data and satellite Earth observations, we have generated a 19-month time series of North Sea net primary productivity – the rate at which phytoplankton absorbs carbon dioxide minus that lost through respiration. This time series, which spans 13 gliders, allows for new investigations into small-scale, high-frequency variability in the biogeochemical processes that underpin the carbon cycle and coastal marine ecosystems in shelf seas.
Takaya Uchida, Julien Le Sommer, Charles Stern, Ryan P. Abernathey, Chris Holdgraf, Aurélie Albert, Laurent Brodeau, Eric P. Chassignet, Xiaobiao Xu, Jonathan Gula, Guillaume Roullet, Nikolay Koldunov, Sergey Danilov, Qiang Wang, Dimitris Menemenlis, Clément Bricaud, Brian K. Arbic, Jay F. Shriver, Fangli Qiao, Bin Xiao, Arne Biastoch, René Schubert, Baylor Fox-Kemper, William K. Dewar, and Alan Wallcraft
Geosci. Model Dev., 15, 5829–5856, https://doi.org/10.5194/gmd-15-5829-2022, https://doi.org/10.5194/gmd-15-5829-2022, 2022
Short summary
Short summary
Ocean and climate scientists have used numerical simulations as a tool to examine the ocean and climate system since the 1970s. Since then, owing to the continuous increase in computational power and advances in numerical methods, we have been able to simulate increasing complex phenomena. However, the fidelity of the simulations in representing the phenomena remains a core issue in the ocean science community. Here we propose a cloud-based framework to inter-compare and assess such simulations.
Jens Zinke, Takaaki K. Watanabe, Siren Rühs, Miriam Pfeiffer, Stefan Grab, Dieter Garbe-Schönberg, and Arne Biastoch
Clim. Past, 18, 1453–1474, https://doi.org/10.5194/cp-18-1453-2022, https://doi.org/10.5194/cp-18-1453-2022, 2022
Short summary
Short summary
Salinity is an important and integrative measure of changes to the water cycle steered by changes to the balance between rainfall and evaporation and by vertical and horizontal movements of water parcels by ocean currents. However, salinity measurements in our oceans are extremely sparse. To fill this gap, we have developed a 334-year coral record of seawater oxygen isotopes that reflects salinity changes in the globally important Agulhas Current system and reveals its main oceanic drivers.
Ioana Ivanciu, Katja Matthes, Arne Biastoch, Sebastian Wahl, and Jan Harlaß
Weather Clim. Dynam., 3, 139–171, https://doi.org/10.5194/wcd-3-139-2022, https://doi.org/10.5194/wcd-3-139-2022, 2022
Short summary
Short summary
Greenhouse gas concentrations continue to increase, while the Antarctic ozone hole is expected to recover during the twenty-first century. We separate the effects of ozone recovery and of greenhouse gases on the Southern Hemisphere atmospheric and oceanic circulation, and we find that ozone recovery is generally reducing the impact of greenhouse gases, with the exception of certain regions of the stratosphere during spring, where the two effects reinforce each other.
Arne Biastoch, Franziska U. Schwarzkopf, Klaus Getzlaff, Siren Rühs, Torge Martin, Markus Scheinert, Tobias Schulzki, Patricia Handmann, Rebecca Hummels, and Claus W. Böning
Ocean Sci., 17, 1177–1211, https://doi.org/10.5194/os-17-1177-2021, https://doi.org/10.5194/os-17-1177-2021, 2021
Short summary
Short summary
The Atlantic Meridional Overturning Circulation (AMOC) quantifies the impact of the ocean on climate and climate change. Here we show that a high-resolution ocean model is able to realistically simulate ocean currents. While the mean representation of the AMOC depends on choices made for the model and on the atmospheric forcing, the temporal variability is quite robust. Comparing the ocean model with ocean observations, we able to identify that the AMOC has declined over the past two decades.
Christina Schmidt, Franziska U. Schwarzkopf, Siren Rühs, and Arne Biastoch
Ocean Sci., 17, 1067–1080, https://doi.org/10.5194/os-17-1067-2021, https://doi.org/10.5194/os-17-1067-2021, 2021
Short summary
Short summary
We estimate Agulhas leakage, water flowing from the Indian Ocean to the South Atlantic, in an ocean model with two different tools. The mean transport, variability and trend of Agulhas leakage is simulated comparably with both tools, emphasising the robustness of our method. If the experiments are designed differently, the mean transport of Agulhas leakage is altered, but not the trend. Agulhas leakage waters cool and become less salty south of Africa resulting in a density increase.
Ioana Ivanciu, Katja Matthes, Sebastian Wahl, Jan Harlaß, and Arne Biastoch
Atmos. Chem. Phys., 21, 5777–5806, https://doi.org/10.5194/acp-21-5777-2021, https://doi.org/10.5194/acp-21-5777-2021, 2021
Short summary
Short summary
The Antarctic ozone hole has driven substantial dynamical changes in the Southern Hemisphere atmosphere over the past decades. This study separates the historical impacts of ozone depletion from those of rising levels of greenhouse gases and investigates how these impacts are captured in two types of climate models: one using interactive atmospheric chemistry and one prescribing the CMIP6 ozone field. The effects of ozone depletion are more pronounced in the model with interactive chemistry.
Josefine Maas, Susann Tegtmeier, Yue Jia, Birgit Quack, Jonathan V. Durgadoo, and Arne Biastoch
Atmos. Chem. Phys., 21, 4103–4121, https://doi.org/10.5194/acp-21-4103-2021, https://doi.org/10.5194/acp-21-4103-2021, 2021
Short summary
Short summary
Cooling-water disinfection at coastal power plants is a known source of atmospheric bromoform. A large source of anthropogenic bromoform is the industrial regions in East Asia. In current bottom-up flux estimates, these anthropogenic emissions are missing, underestimating the global air–sea flux of bromoform. With transport simulations, we show that by including anthropogenic bromoform from cooling-water treatment, the bottom-up flux estimates significantly improve in East and Southeast Asia.
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.
Katja Matthes, Arne Biastoch, Sebastian Wahl, Jan Harlaß, Torge Martin, Tim Brücher, Annika Drews, Dana Ehlert, Klaus Getzlaff, Fritz Krüger, Willi Rath, Markus Scheinert, Franziska U. Schwarzkopf, Tobias Bayr, Hauke Schmidt, and Wonsun Park
Geosci. Model Dev., 13, 2533–2568, https://doi.org/10.5194/gmd-13-2533-2020, https://doi.org/10.5194/gmd-13-2533-2020, 2020
Short summary
Short summary
A new Earth system model, the Flexible Ocean and Climate Infrastructure (FOCI), is introduced, consisting of a high-top atmosphere, an ocean model, sea-ice and land surface model components. A unique feature of FOCI is the ability to explicitly resolve small-scale oceanic features, for example, the Agulhas Current and the Gulf Stream. It allows to study the evolution of the climate system on regional and seasonal to (multi)decadal scales and bridges the gap to coarse-resolution climate models.
Sam Jones, Mark Inall, Marie Porter, Jennifer A. Graham, and Finlo Cottier
Ocean Sci., 16, 389–403, https://doi.org/10.5194/os-16-389-2020, https://doi.org/10.5194/os-16-389-2020, 2020
Short summary
Short summary
The ocean is an important source of nutrients and organisms to coastal waters, but it is not clear what controls current flow between the deep ocean and the coast. We contrasted ocean flow pathways and coastal water properties between summer 2013 and a series of intense storms in December 2013. Further, we assessed the likelihood of storms occurring over the North Atlantic during each winter. We found that local weather patterns exert a strong influence on coastal water properties and origins.
Nele Tim, Eduardo Zorita, Kay-Christian Emeis, Franziska U. Schwarzkopf, Arne Biastoch, and Birgit Hünicke
Earth Syst. Dynam., 10, 847–858, https://doi.org/10.5194/esd-10-847-2019, https://doi.org/10.5194/esd-10-847-2019, 2019
Short summary
Short summary
Our study reveals that the latitudinal position and intensity of Southern Hemisphere trades and westerlies are correlated. In the last decades the westerlies have shifted poleward and intensified. Furthermore, the latitudinal shifts and intensity of the trades and westerlies impact the sea surface temperatures around southern Africa and in the South Benguela upwelling region. The future development of wind stress depends on the strength of greenhouse gas forcing.
Franziska U. Schwarzkopf, Arne Biastoch, Claus W. Böning, Jérôme Chanut, Jonathan V. Durgadoo, Klaus Getzlaff, Jan Harlaß, Jan K. Rieck, Christina Roth, Markus M. Scheinert, and René Schubert
Geosci. Model Dev., 12, 3329–3355, https://doi.org/10.5194/gmd-12-3329-2019, https://doi.org/10.5194/gmd-12-3329-2019, 2019
Short summary
Short summary
A family of nested global ocean general circulation model configurations, the INALT family, has been established with resolutions of 1/10°, 1/20° and 1/60° in the South Atlantic and western Indian oceans, covering the greater Agulhas Current (AC) system. The INALT family provides a consistent set of configurations that allows to address eddy dynamics in the AC system and their impact on the large-scale ocean circulation.
Josefine Maas, Susann Tegtmeier, Birgit Quack, Arne Biastoch, Jonathan V. Durgadoo, Siren Rühs, Stephan Gollasch, and Matej David
Ocean Sci., 15, 891–904, https://doi.org/10.5194/os-15-891-2019, https://doi.org/10.5194/os-15-891-2019, 2019
Short summary
Short summary
In a large-scale analysis, the spread of disinfection by-products from oxidative ballast water treatment is investigated, with a focus on Southeast Asia where major ports are located. Halogenated compounds such as bromoform (CHBr3) are produced in the ballast water and, once emitted into the environment, can participate in ozone depletion. Anthropogenic bromoform is rapidly emitted into the atmosphere and can locally double around large ports. A large-scale impact cannot be found.
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.
Siren Rühs, Franziska U. Schwarzkopf, Sabrina Speich, and Arne Biastoch
Ocean Sci., 15, 489–512, https://doi.org/10.5194/os-15-489-2019, https://doi.org/10.5194/os-15-489-2019, 2019
Short summary
Short summary
We revisit the sources for the upper limb of the overturning circulation in the South Atlantic by tracking fluid particles in a high-resolution ocean model. Our results suggest that the upper limb’s transport is dominantly supplied by waters with Indian Ocean origin, but the contribution of waters with Pacific origin is substantially larger than previously estimated with coarse-resolution models. Yet, a large part of upper limb waters obtains thermohaline properties within the South Atlantic.
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.
Robert Marsh, Ivan D. Haigh, Stuart A. Cunningham, Mark E. Inall, Marie Porter, and Ben I. Moat
Ocean Sci., 13, 315–335, https://doi.org/10.5194/os-13-315-2017, https://doi.org/10.5194/os-13-315-2017, 2017
Short summary
Short summary
To the west of Britain and Ireland, a strong ocean current follows the steep slope that separates the deep Atlantic and the continental shelf. This “Slope Current” exerts an Atlantic influence on the North Sea and its ecosystems. Using a combination of computer modelling and archived data, we find that the Slope Current weakened over 1988–2007, reducing Atlantic influence on the North Sea, due to a combination of warming of the subpolar North Atlantic and weakening winds to the west of Scotland.
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.
T. J. Sherwin, D. Aleynik, E. Dumont, and M. E. Inall
Ocean Sci., 11, 343–359, https://doi.org/10.5194/os-11-343-2015, https://doi.org/10.5194/os-11-343-2015, 2015
Short summary
Short summary
The Rockall Trough feeds warm salty water to Polar regions and the European Shelf. Detailed observations from an underwater glider show that a) the meandering surface current field in the central trough is driven by deep eddies; b) chance circulations deflect the eastern slope current and warm the western side; c) and altimeter observations omit the mean flow in the narrow slope current. There are wider implications for satellite altimeter observations, ocean monitoring and ocean model results.
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.
D. Le Bars, J. V. Durgadoo, H. A. Dijkstra, A. Biastoch, and W. P. M. De Ruijter
Ocean Sci., 10, 601–609, https://doi.org/10.5194/os-10-601-2014, https://doi.org/10.5194/os-10-601-2014, 2014
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
Related subject area
Approach: Numerical Models | Properties and processes: Overturning circulation, gyres and water masses
Altered Weddell Sea warm- and dense-water pathways in response to 21st-century climate change
Assessing the drift of fish aggregating devices in the tropical Pacific Ocean
Assessment of Indonesian Throughflow transports from ocean reanalyses with mooring-based observations
Persistent Climate Model Biases in the Atlantic Ocean's Freshwater Transport
Surface factors controlling the volume of accumulated Labrador Sea Water
Cara Nissen, Ralph Timmermann, Mathias van Caspel, and Claudia Wekerle
Ocean Sci., 20, 85–101, https://doi.org/10.5194/os-20-85-2024, https://doi.org/10.5194/os-20-85-2024, 2024
Short summary
Short summary
The southeastern Weddell Sea is important for global ocean circulation due to the cross-shelf-break exchange of Dense Shelf Water and Warm Deep Water, but their exact circulation pathways remain elusive. Using Lagrangian model experiments in an eddy-permitting ocean model, we show how present circulation pathways and transit times of these water masses on the continental shelf are altered by 21st-century climate change, which has implications for local ice-shelf basal melt rates and ecosystems.
Philippe F. V. W. Frankemölle, Peter D. Nooteboom, Joe Scutt Phillips, Lauriane Escalle, Simon Nicol, and Erik van Sebille
Ocean Sci., 20, 31–41, https://doi.org/10.5194/os-20-31-2024, https://doi.org/10.5194/os-20-31-2024, 2024
Short summary
Short summary
Tuna fisheries in the Pacific often use drifting fish aggregating devices (dFADs) to attract fish that are advected by subsurface flow through underwater appendages. Using a particle advection model, we find that virtual particles advected by surface flow are displaced farther than virtual dFADs. We find a relation between El Niño–Southern Oscillation and circular motion in some areas, influencing dFAD densities. This information helps us to understand processes that drive dFAD distribution.
Magdalena Fritz, Michael Mayer, Leopold Haimberger, and Susanna Winkelbauer
Ocean Sci., 19, 1203–1223, https://doi.org/10.5194/os-19-1203-2023, https://doi.org/10.5194/os-19-1203-2023, 2023
Short summary
Short summary
The interaction between the Indonesian Throughflow (ITF) and regional climate phenomena indicates the high relevance for monitoring the ITF. Observations remain temporally and spatially limited; hence near-real-time monitoring is only possible with reanalyses. We assess how well ocean reanalyses depict the intensity of the ITF via comparison to observations. The results show that reanalyses agree reasonably well with in situ observations; however, some aspects require higher-resolution products.
René M. van Westen and Henk A. Dijkstra
EGUsphere, https://doi.org/10.5194/egusphere-2023-1502, https://doi.org/10.5194/egusphere-2023-1502, 2023
Short summary
Short summary
The Atlantic Meridional Overturning Circulation (AMOC) is an important component in the global climate system. Observations of the present-day AMOC indicate that it may weaken or collapse under global warming, with profound disruptive effects on future climate. However, AMOC weakening is not correctly represented because an important feedback is underestimated due to biases in the Atlantic's freshwater budget. Here we address these biases in several state-of-the-art climate model simulations.
Yavor Kostov, Marie-José Messias, Herlé Mercier, David P. Marshall, and Helen L. Johnson
EGUsphere, https://doi.org/10.5194/egusphere-2023-1564, https://doi.org/10.5194/egusphere-2023-1564, 2023
Short summary
Short summary
We examine factors affecting variability in the volume of Labrador Sea Water (LSW), a deep watermass that is important for the uptake and storage of heat and carbon in the Atlantic Ocean. We find that LSW accumulated in the Labrador Sea exhibits a lagged response to remote conditions: surface wind stress, heat flux, and freshwater flux anomalies, especially along the pathways of the North Atlantic Current branches. We use our results to reconstruct and attribute historical changes in LSW volume.
Cited articles
Arhan, M., Treguier, A. M., Bourlès, B., and Michel, S.: Diagnosing the Annual Cycle of the Equatorial Undercurrent in the Atlantic Ocean from a General Circulation Model, J. Phys. Oceanogr., 36, 1502–1522, https://doi.org/10.1175/JPO2929.1, 2006. a, b, c, d
Ascani, F., Wang, D., and Firing, E.: Equatorial deep jets in a simple ocean generation circulation model, Eos, Trans. Amer. Geophys. Union, 87, Ocean Sci. Meeting Suppl., Abstract OS33C-05, 2006. a
Assene, F., Morel, Y., Delpech, A., Aguedjou, M., Jouanno, J., Cravatte, S., Marin, F., Ménesguen, C., Chaigneau, A., Dadou, I., Alory, G., Holmes, R., Bourlès, B., and Koch-Larrouy, A.: From mixing to the large scale circulation: how the inverse cascade is involved in the formation of the subsurface currents in the gulf of guinea, Fluids, 5, 1–34, https://doi.org/10.3390/fluids5030147, 2020. a, b, c, d, e, f, g, h
Athie, G. and Marin, F.: Cross-equatorial structure and temporal modulation of intraseasonal variability at the surface of the Tropical Atlantic Ocean, J. Geophys. Res.-Oceans, 113, 1–17, https://doi.org/10.1029/2007JC004332, 2008. a
Barnier, B., Madec, G., Penduff, T., Molines, J.-M., Treguier, A.-M., Sommer, J. L., Beckmann, A., Biastoch, A., Böning, C., Dengg, J., Derval, C., Durand, E., Gulev, S., Remy, E., Talandier, C., Theetten, S., Maltrud, M., McClean, J., and Cuevas, B. D.: Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution, Ocean Dynam., 56, 543–567, https://doi.org/10.1007/s10236-006-0082-1, 2006. a
Behrens, E., Våge, K., Harden, B., Biastoch, A., and Böning, C. W.: Composition and variability of the Denmark Strait Overflow Water in a high-resolution numerical model hindcast simulation, J. Geophys. Res.-Oceans, 122, 2830–2846, https://doi.org/10.1002/2016JC012158, 2017. a
Bourlès, B., Gouriou, Y., and Chuchla, R.: On the circulation in the upper layer of the western equatorial Atlantic, J. Geophys. Res.-Oceans, 104, 21151–21170, https://doi.org/10.1029/1999JC900058, 1999. a, b
Bourlès, B., D'Orgeville, M., Eldin, G., Gouriou, Y., Chuchla, R., DuPenhoat, Y., and Arnault, S.: On the evolution of the thermocline and subthermocline eastward currents in the Equatorial Atlantic, Geophys. Res. Lett., 29, 32-1–32-4, https://doi.org/10.1029/2002GL015098, 2002. a
Brandt, P., Schott, F. A., Provost, C., Kartavtseff, A., Hormann, V., Bourlès, B., and Fischer, J.: Circulation in the central equatorial Atlantic: Mean and intraseasonal to seasonal variability, Geophys. Res. Lett., 33, 1–4, https://doi.org/10.1029/2005GL025498, 2006. a
Brandt, P., Hormann, V., Körtzinger, A., Visbeck, M., Krahmann, G., Stramma, L., Lumpkin, R., and Schmid, C.: Changes in the Ventilation of the Oxygen Minimum Zone of the Tropical North Atlantic, J. Phys. Oceanogr., 40, 1784–1801, https://doi.org/10.1175/2010JPO4301.1, 2010. a
Brandt, P., Funk, A., Tantet, A., Johns, W. E., and Fischer, J.: The Equatorial Undercurrent in the central Atlantic and its relation to tropical Atlantic variability, Clim. Dynam., 43, 2985–2997, https://doi.org/10.1007/s00382-014-2061-4, 2014. a, b, c, d
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, b
Brandt, P., Claus, M., Greatbatch, R. J., Kopte, R., Toole, J. M., Johns, W. E., and Böning, C. W.: Annual and Semiannual Cycle of Equatorial Atlantic Circulation Associated with Basin-Mode Resonance, J. Phys. Oceanogr., 46, 3011–3029, https://doi.org/10.1175/JPO-D-15-0248.1, 2016. a, b, c, d, e, f, g
Brandt, P., Hahn, J., Schmidtko, S., Tuchen, F. P., Kopte, R., Kiko, R., Bourlès, B., Czeschel, R., and Dengler, M.: Atlantic Equatorial Undercurrent intensification counteracts warming-induced deoxygenation, Nat. Geosci., 14, 278–282, https://doi.org/10.1038/s41561-021-00716-1, 2021. a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q
Burmeister, K.: Kristin-2002/Wind_forcing_public: Supplementary code to: Dependency of simulated tropical Atlantic current variability on the wind forcing (v.1.0.1), Zenodo [code], https://doi.org/10.5281/zenodo.10814849, 2024. a
Burmeister, K. and Schwarzkopf, F. U.: Supplementary data to: Dependency of simulated tropical Atlantic current variability on the wind forcing, GEOMAR Helmholtz Centre for Ocean Research Kiel [data set], https://data.geomar.de/downloads/20.500.12085/77c0d676-1933-4f17-9849-5ea2161736eb/ (last access: 14 March 2024), 2023. a
Böning, C. W., Behrens, E., Biastoch, A., Getzlaff, K., and Bamber, J. L.: Emerging impact of Greenland meltwater on deepwater formation in the North Atlantic Ocean, Nat. Geosci., 9, 523–527, https://doi.org/10.1038/ngeo2740, 2016. a
Cane, M. A. and Moore, D. W.: A Note on Low-Frequency Equatorial Basin Modes, J. Phys. Oceanogr., 11, 1578–1584, https://doi.org/10.1175/1520-0485(1981)011<1578:ANOLFE>2.0.CO;2, 1981. a
Carton, J. A., Cao, X., Giese, B. S., and Silva, A. M. D.: Decadal and Interannual SST Variability in the Tropical Atlantic Ocean, J. Phys. Oceanogr., 26, 1165–1175, https://doi.org/10.1175/1520-0485(1996)026<1165:DAISVI>2.0.CO;2, 1996. a
Chang, P., Ji, L., and Li, H.: A decadal climate variation in the tropical Atlantic Ocean from thermodynamic air-sea interactions, Nature, 385, 516–518, https://doi.org/10.1038/385516a0, 1997. a
Claus, M., Greatbatch, R. J., Brandt, P., and Toole, J. M.: Forcing of the Atlantic equatorial deep jets derived from observations, J. Phys. Oceanogr., 46, 3549–3562, https://doi.org/10.1175/JPO-D-16-0140.1, 2016. a, b, c
Debreu, L., Vouland, C., and Blayo, E.: AGRIF: Adaptive grid refinement in Fortran, Comput. Geosci., 34, 8–13, https://doi.org/10.1016/j.cageo.2007.01.009, 2008. a
Delworth, T. L. and Greatbatch, R. J.: Multidecadal Thermohaline Circulation Variability Driven by Atmospheric Surface Flux Forcing, J. Climate, 13, 1481–1495, https://doi.org/10.1175/1520-0442(2000)013<1481:MTCVDB>2.0.CO;2, 2000. a
Ding, H., Keenlyside, N. S., and Latif, M.: Seasonal cycle in the upper equatorial Atlantic Ocean, J. Geophys. Res., 114, C09016, https://doi.org/10.1029/2009JC005418, 2009. a
Doi, T., Tozuka, T., Sasaki, H., Masumoto, Y., and Yamagata, T.: Seasonal and interannual variations of oceanic conditions in the Angola Dome, J. Phys. Oceanogr., 37, 2698–2713, https://doi.org/10.1175/2007JPO3552.1, 2007. a, b
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. Marine Res., 65, 1–25, https://doi.org/10.1357/002224007780388720, 2007. a
Duteil, O., Schwarzkopf, F. U., Böning, C. W., and Oschlies, A.: Major role of the equatorial current system in setting oxygen levels in the eastern tropical Atlantic Ocean: A high-resolution model study, Geophys. Res. Lett., 41, 2033–2040, https://doi.org/10.1002/2013GL058888, 2014. a, b
Fichefet, T. and Maqueda, M. A. M.: Sensitivity of a global sea ice model to the treatment of ice thermodynamics and dynamics, J. Geophys. Res.-Oceans, 102, 12609–12646, https://doi.org/10.1029/97JC00480, 1997. a
Fiorino, M.: The impact of the satellite observing system on low-frequency temperature variability in the ECMWF and NCEP reanalyses, Proceedings of the Second WCRP International Conference on Reanalyses, Wokefield Park, Nr. Reading, UK, 23–27 August 1999, WCRP-109, https://library.wmo.int/idurl/4/44372 (last access: 14 March 2024), 2000. a
Fischer, J., Brandt, P., Dengler, M., Müller, M., and Symonds, D.: Surveying the upper ocean with the ocean surveyor: A new phased array Doppler current profiler, J. Atmos. Ocean. Tech., 20, 742–751, https://doi.org/10.1175/1520-0426(2003)20<742:STUOWT>2.0.CO;2, 2003. a
Fischer, J., Hormann, V., Brandt, P., Schott, F. A., Rabe, B., and Funk, A.: South Equatorial Undercurrent in the western to central tropical Atlantic, Geophys. Res. Lett., 35, 1–5, https://doi.org/10.1029/2008GL035753, 2008. a
Frajka-Williams, E., Beaulieu, C., and Duchez, A.: Emerging negative Atlantic Multidecadal Oscillation index in spite of warm subtropics, Sci. Rep., 7, 11224, https://doi.org/10.1038/s41598-017-11046-x, 2017. a
Fratantoni, D. M., Johns, W. E., Townsend, T. L., and Hurlburt, H. E.: Low-Latitude Circulation and Mass Transport Pathways in a Model of the Tropical Atlantic Ocean, J. Phys. Oceanogr., 30, 1944–1966, https://doi.org/10.1175/1520-0485(2000)030<1944:LLCAMT>2.0.CO;2, 2000. a
Furue, R., McCreary, J. P., Yu, Z., and Wang, D.: Dynamics of the Southern Tsuchiya Jet, J. Phys. Oceanogr., 37, 531–553, https://doi.org/10.1175/JPO3024.1, 2007. a, b
Furue Jr., R., J. P. M., and Yu, Z.: Dynamics of the Northern Tsuchiya Jet, J. Phys. Oceanogr., 39, 2024–2051, https://doi.org/10.1175/2009JPO4065.1, 2009. a, b
Greatbatch, R. J., Brandt, P., Claus, M., Didwischus, S.-H., and Fu, Y.: On the Width of the Equatorial Deep Jets, J. Phys. Oceanogr., 42, 1729–1740, https://doi.org/10.1175/JPO-D-11-0238.1, 2012. a
Griffies, S. M., Biastoch, A., Böning, C., Bryan, F., Danabasoglu, G., Chassignet, E. P., England, M. H., Gerdes, R., Haak, H., Hallberg, R. W., Hazeleger, W., Jungclaus, J., Large, W. G., Madec, G., Pirani, A., Samuels, B. L., Scheinert, M., Gupta, A. S., Severijns, C. A., Simmons, H. L., Treguier, A. M., Winton, M., Yeager, S., and Yin, J.: Coordinated Ocean-ice Reference Experiments (COREs), Ocean Model., 26, 1–46, https://doi.org/10.1016/j.ocemod.2008.08.007, 2009. a, b, c
Hahn, J., Brandt, P., Greatbatch, R. J., Krahmann, G., and Körtzinger, A.: Oxygen variance and meridional oxygen supply in the Tropical North East Atlantic oxygen minimum zone, Clim. Dynam., 43, 2999–3024, https://doi.org/10.1007/s00382-014-2065-0, 2014. a
Hahn, J., Brandt, P., Schmidtko, S., and Krahmann, G.: Decadal oxygen change in the eastern tropical North Atlantic, Ocean Sci., 13, 551–576, https://doi.org/10.5194/os-13-551-2017, 2017. a, b, c
He, Y. C., Drange, H., Gao, Y., and Bentsen, M.: Simulated Atlantic Meridional Overturning Circulation in the 20th century with an ocean model forced by reanalysis-based atmospheric data sets, Ocean Model., 100, 31–48, https://doi.org/10.1016/j.ocemod.2015.12.011, 2016. a
Heukamp, F. O., Brandt, P., Dengler, M., Tuchen, F. P., McPhaden, M. J., and Moum, J. N.: Tropical Instability Waves and Wind-Forced Cross-Equatorial Flow in the Central Atlantic Ocean, Geophys. Res. Lett., 49, 1–10, https://doi.org/10.1029/2022GL099325, 2022. a, b
Hormann, V. and Brandt, P.: Atlantic Equatorial Undercurrent and associated cold tongue variability, J. Geophys. Res.-Oceans, 112, 1–18, https://doi.org/10.1029/2006JC003931, 2007. a, b, c
Hormann, V., Lumpkin, R., and Foltz, G. R.: Interannual North Equatorial Countercurrent variability and its relation to tropical Atlantic climate modes, J. Geophys. Res.-Oceans, 117, 1–17, https://doi.org/10.1029/2011JC007697, 2012. a, b
Hsin, Y. C. and Qiu, B.: Seasonal fluctuations of the surface North Equatorial Countercurrent (NECC) across the Pacific basin, J. Geophys. Res.-Oceans, 117, 1–17, https://doi.org/10.1029/2011JC007794, 2012. a, b
Hua, B. L., Marin, F., and Schopp, R.: Three-Dimensional Dynamics of the Subsurface Countercurrents and Equatorial Thermostad. Part II: Influence of the Large-Scale Ventilation and of Equatorial Winds, J. Phys. Oceanogr., 33, 2588–2609, https://doi.org/10.1175/1520-0485(2003)033<2610:TDOTSC>2.0.CO;2, 2003. a
Hurrell, J. W. and Trenberth, K. E.: Difficulties in obtaining reliable temperature trends: reconciling the surface and satellite microwave sounding unit records, J. Climate, 11, 945–967, https://doi.org/10.1175/1520-0442(1998)011<0945:DIORTT>2.0.CO;2, 1998. a
Ishida, A., Mitsudera, H., Kashino, Y., and Kadokura, T.: Equatorial Pacific subsurface countercurrents in a high-resolution global ocean circulation model, J. Geophys. Res.-Oceans, 110, 1–21, https://doi.org/10.1029/2003JC002210, 2005. a
Jochum, M., Malanotte-Rizzoli, P., and Busalacchi, A.: Tropical instability waves in the Atlantic Ocean, Ocean Model., 7, 145–163, https://doi.org/10.1016/S1463-5003(03)00042-8, 2004. a, b
Johns, W. E., Zantopp, R. J., and Goni, G.: Cross-gyre transport by North Brazil Current rings, Elsevier, 68, 411–441, https://doi.org/10.1016/S0422-9894(03)80156-3, 2003. a
Johnson, G. C. and Moore, D. W.: The Pacific Subsurface Countercurrents and an Inertial Model, J. Phys. Oceanogr., 27, 2448–2459, https://doi.org/10.1175/1520-0485(1997)027<2448:TPSCAA>2.0.CO;2, 1997. a
Kessler, W. S., Johnson, G. C., and Moore, D. W.: Sverdrup and nonlinear dynamics of the Pacific equatorial currents, J. Phys. Oceanogr., 33, 994–1008, https://doi.org/10.1175/1520-0485(2003)033<0994:SANDOT>2.0.CO;2, 2003. a
Kobayashi, S., Ota, Y., Harada, Y., Ebita, A., Moriya, M., Onoda, H., Onogi, K., Kamahori, H., Kobayashi, C., Endo, H., Miyaoka, K., and Kiyotoshi, T.: The JRA-55 reanalysis: General specifications and basic characteristics, J. Meteorol. Soc. Jpn., 93, 5–48, https://doi.org/10.2151/jmsj.2015-001, 2015. a
Kopte, R., Brandt, P., Claus, M., Greatbatch, R. J., and Dengler, M.: Role of Equatorial Basin-Mode Resonance for the Seasonal Variability of the Angola Current at 11S, J. Phys. Oceanogr., 48, 261–281, https://doi.org/10.1175/JPO-D-17-0111.1, 2018. a
Large, W. G. and Yeager, S. G.: The global climatology of an interannually varying air – Sea flux data set, Climate Dynamics, 33, 341–364, https://doi.org/10.1007/s00382-008-0441-3, 2009. a, b
Lee, T., Lagerloef, G., Kao, H. Y., McPhaden, M. J., Willis, J., and Gierach, M. M.: The influence of salinity on tropical Atlantic instability waves, J. Geophys. Res.-Oceans, 119, 8375–8394, https://doi.org/10.1002/2014JC010100, 2014. a, b
Levitus, S., Boyer, T. P., Conkright, M. E., O'Brien, T., Antonov, J., Stephens, C., Stathoplos, L., Johnson, D., and Gelfeld, R.: World ocean database 1998. Volume 1, Introduction, National Environmental Satellite, Data, and Information Service., Washington, D.C., US and National Oceanographic Data Center, Ocean Climate Laboratory, Silver Spring, MD, US, NOAA Atlas NESDIS, 18, 346 pp., https://repository.library.noaa.gov/view/noaa/49345 (last access: 14 March 2024), 1998. a
Madec, G. and the NEMO System Team: NEMO ocean engine, in: Notes du Pôle de modélisation de l'Institut Pierre-Simon Laplace (IPSL), v3.6-patch, Number 27, Zenodo [data set], https://doi.org/10.5281/zenodo.3248739, 2017. a
Marin, F., Hua, B. L., and Wacongne, S.: The equatorial thermostad and subsurface countercurrents in the light of the dynamics of atmospheric Hadley cells, J. Marine Res., 58, 405–437, https://doi.org/10.1357/002224000321511098, 2000. a
Marin, F., Schopp, R., and Hua, B. L.: Three-dimensional dynamics of the subsurface countercurrents and equatorial thermostad. Part II: Influence of the large-scale ventilation and of equatorial winds, J. Phys. Oceanogr., 33, 2610–2626, https://doi.org/10.1175/1520-0485(2003)033<2610:TDOTSC>2.0.CO;2, 2003. a
McCreary, J. P. and Lu, P.: Interaction between the subtropical and equatorial ocean circulations: The subtropical cell, J. Phys. Oceanogr., 24, 466–497, https://doi.org/10.1175/1520-0485(1994)024<0466:IBTSAE>2.0.CO;2, 1994. a
McCreary, J. P., Lu, P., and Yu, Z.: Dynamics of the Pacific Subsurface Countercurrents, J. Phys. Oceanogr., 32, 2379–2404, https://doi.org/10.1175/1520-0485(2002)032<2379:DOTPSC>2.0.CO;2, 2002. a, b
McPhaden, M. J.: On the Dynamics of Equatorial Subsurface Countercurrents, J. Phys. Oceanogr., 14, 1216–1225, https://doi.org/10.1175/1520-0485(1984)014<1216:OTDOES>2.0.CO;2, 1984. a
Molinari, R. L., Bauer, S., Snowden, D., Johnson, G. C., Bourles, B., Gouriou, Y., and Mercier, H.: A comparison of kinematic evidence for tropical cells in the Atlantic and Pacific oceans, Elsevier Oceanography Series, 68, 269–286, https://doi.org/10.1016/S0422-9894(03)80150-2, 2003. a
Olivier, L., Reverdin, G., Hasson, A., and Boutin, J.: Tropical Instability Waves in the Atlantic Ocean: Investigating the Relative Role of Sea Surface Salinity and Temperature From 2010 to 2018, J. Geophys. Res.: Oceans, 125, https://doi.org/10.1029/2020JC016641, 2020. a, b
Pedlosky, J.: An Inertial Theory of the Equatorial Undercurrent, J. Phys. Oceanogr., 17, 1978–1985, https://doi.org/10.1175/1520-0485(1987)017<1978:AITOTE>2.0.CO;2, 1987. a, b
Perez, R. C., Lumpkin, R., Johns, W. E., Foltz, G. R., and Hormann, V.: Interannual variations of Atlantic tropical instability waves, J. Geophys. Res.-Oceans, 117, 1–13, https://doi.org/10.1029/2011JC007584, 2012. a, b
Perez, R. C., Hormann, V., Lumpkin, R., Brandt, P., Johns, W. E., Hernandez, F., Schmid, C., and Bourlès, B.: Mean meridional currents in the central and eastern equatorial Atlantic, Clim. Dynam., 43, 2943–2962, https://doi.org/10.1007/s00382-013-1968-5, 2014. a, b, c
Peterson, R. G. and Stramma, L.: Upper-level circulation in the South Atlantic Ocean, Prog. Oceanogr., 26, 1–73, https://doi.org/10.1016/0079-6611(91)90006-8, 1991. a
Philander, S. G. H.: Instabilities of zonal equatorial currents, 2, J. Geophys. Res., 83, 3679, https://doi.org/10.1029/JC083iC07p03679, 1978. a
Rosell-Fieschi, M., Pelegrí, J. L., and Gourrion, J.: Zonal jets in the equatorial Atlantic Ocean, Prog. Oceanogr., 130, 1–18, https://doi.org/10.1016/j.pocean.2014.08.008, 2015. a
Rühs, S., Getzlaff, K., Durgadoo, J. V., Biastoch, A., and Böning, C. W.: On the suitability of North Brazil Current transport estimates for monitoring basin-scale AMOC changes, Geophys. Res. Lett., 42, 8072–8080, https://doi.org/10.1002/2015GL065695, 2015. a
Schott, F. A., Fischer, J., and Stramma, L.: Transports and Pathways of the Upper-Layer Circulation in the Western Tropical Atlantic, J. Phys. Oceanogr., 28, 1904–1928, https://doi.org/10.1175/1520-0485(1998)028<1904:TAPOTU>2.0.CO;2, 1998. a
Schubert, R., Schwarzkopf, F. U., Baschek, B., and Biastoch, A.: Submesoscale Impacts on Mesoscale Agulhas Dynamics, J. Adv. Model. Earth Sy., 11, 2745–2767, https://doi.org/10.1029/2019MS001724, 2019. a
Schwarzkopf, F. U., Biastoch, A., Böning, C. W., Chanut, J., Durgadoo, J. V., Getzlaff, K., Harlaß, J., Rieck, J. K., Roth, C., Scheinert, M. M., and Schubert, R.: The INALT family – a set of high-resolution nests for the Agulhas Current system within global NEMO ocean/sea-ice configurations, Geosci. Model Dev., 12, 3329–3355, https://doi.org/10.5194/gmd-12-3329-2019, 2019. a
Small, R. J., Curchitser, E., Hedstrom, K., Kauffman, B., and Large, W. G.: The Benguela Upwelling System: Quantifying the Sensitivity to Resolution and Coastal Wind Representation in a Global Climate Model, J. Climate, 28, 9409–9432, https://doi.org/10.1175/JCLI-D-15-0192.1, 2015. a
Steele, M., Morley, R., and Ermold, W.: PHC: A Global Ocean Hydrography with a High-Quality Arctic Ocean, J. Climate, 14, 2079–2087, https://doi.org/10.1175/1520-0442(2001)014<2079:PAGOHW>2.0.CO;2, 2001. a
Stewart, K. D., Hogg, A. M. C., Griffies, S. M., Heerdegen, A. P., Ward, M. L., Spence, P., and England, M. H.: Vertical resolution of baroclinic modes in global ocean models, Ocean Model., 113, 50–65, https://doi.org/10.1016/J.OCEMOD.2017.03.012, 2017. a
Stramma, L., Hüttl, S., and Schafstall, J.: Water masses and currents in the upper tropical northeast Atlantic off northwest Africa, J. Geophys. Res.-Oceans, 110, 1–18, https://doi.org/10.1029/2005JC002939, 2005. a, b, c, d
Stramma, L., Brandt, P., Schafstall, J., Schott, F., Fischer, J., and Körtzinger, A.: Oxygen minimum zone in the North Atlantic south and east of the Cape Verde Islands, J. Geophys. Res.-Oceans, 113, 1–15, https://doi.org/10.1029/2007JC004369, 2008. a
Stramma, L., Czeschel, R., Tanhua, T., Brandt, P., Visbeck, M., and Giese, B. S.: The flow field of the upper hypoxic eastern tropical North Atlantic oxygen minimum zone, Ocean Sci., 12, 153–167, https://doi.org/10.5194/os-12-153-2016, 2016. a
Sverdrup, H. U.: Wind-Driven Currents in a Baroclinic Ocean; with Application to the Equatorial Currents of the Eastern Pacific, P. Natl. Acad. Sci. USA, 33, 318–326, https://doi.org/10.1073/pnas.33.11.318, 1947. a
Thierry, V., Treguier, A. M., and Mercier, H.: Numerical study of the annual and semi-annual fluctuations in the deep equatorial Atlantic Ocean, Ocean Model., 6, 1–30, https://doi.org/10.1016/S1463-5003(02)00054-9, 2004. a
Tsujino, H., Urakawa, S., Nakano, H., Small, R. J., Kim, W. M., Yeager, S. G., Danabasoglu, G., Suzuki, T., Bamber, J. L., Bentsen, M., Böning, C. W., Bozec, A., Chassignet, E. P., Curchitser, E., Dias, F. B., Durack, P. J., Griffies, S. M., Harada, Y., Ilicak, M., Josey, S. A., Kobayashi, C., Kobayashi, S., Komuro, Y., Large, W. G., Sommer, J. L., Marsland, S. J., Masina, S., Scheinert, M., Tomita, H., Valdivieso, M., and Yamazaki, D.: JRA-55 based surface dataset for driving ocean–sea-ice models (JRA55-do), Ocean Model., 130, 79–139, https://doi.org/10.1016/j.ocemod.2018.07.002, 2018. a, b, c, d
Tuchen, F. P., Lübbecke, J. F., Schmidtko, S., Hummels, R., and Böning, C. W.: The Atlantic Subtropical Cells inferred from observations, J. Geophys. Res.-Oceans, 124, 7591–7605, https://doi.org/10.1029/2019JC015396, 2019. a, b, c, d
Tuchen, F. P., Perez, R. C., Foltz, G. R., Brandt, P., and Lumpkin, R.: Multidecadal Intensification of Atlantic Tropical Instability Waves, Geophys. Res. Lett., 49, e2022GL101073, https://doi.org/10.1029/2022gl101073, 2022b. a, b, c
Urbano, D. F., Jochum, M., and da Silveira, I. C.: Rediscovering the second core of the Atlantic NECC, Ocean Model., 12, 1–15, https://doi.org/10.1016/j.ocemod.2005.04.003, 2006. a
Urbano, D. F., Almeida, R. A. D., and Nobre, P.: Equatorial undercurrent and North equatorial countercurrent at 38W: A new perspective from direct velocity data, J. Geophys. Res.-Oceans, 113, 1–16, https://doi.org/10.1029/2007JC004215, 2008. a, b
von Schuckmann, K., Brandt, P., and Eden, C.: Generation of tropical instability waves in the Atlantic Ocean, J. Geophys. Res.-Oceans, 113, 1–12, https://doi.org/10.1029/2007JC004712, 2008. a
Wacongne, S.: Dynamical regimes of a fully nonlinear stratified model of the Atlantic equatorial undercurrent, J. Geophys. Res., 94, 4801, https://doi.org/10.1029/JC094iC04p04801, 1989. a, b, c
Wang, C.: Subthermocline tropical cells and equatorial subsurface countercurrents, Deep-Sea Res. Pt. I, 52, 123–135, https://doi.org/10.1016/j.dsr.2004.08.009, 2005. a
Weisberg, R. H. and Weingartner, T. J.: Instability Waves in the Equatorial Atlantic Ocean, J. Phys. Oceanogr., 18, 1641–1657, https://doi.org/10.1175/1520-0485(1988)018<1641:IWITEA>2.0.CO;2, 1988. a
Xie, S. and Carton, J.: Tropical Atlantic variability: Patterns, mechanisms, and impacts, Geophysical Monograph Series, 147, 121–142, https://doi.org/10.1029/147GM07, 2004. a
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.
We apply two different forcing products to a high-resolution ocean model to investigate their...
