Articles | Volume 13, issue 4
https://doi.org/10.5194/os-13-551-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/os-13-551-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Research article
| 
06 Jul 2017
Research article |
| 06 Jul 2017
Decadal oxygen change in the eastern tropical North Atlantic
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Peter Brandt
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Christian-Albrechts-Universität zu Kiel, Kiel, Germany
Sunke Schmidtko
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Gerd Krahmann
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Related authors
Gerd Krahmann, Damian L. Arévalo-Martínez, Andrew W. Dale, Marcus Dengler, Anja Engel, Nicolaas Glock, Patricia Grasse, Johannes Hahn, Helena Hauss, Mark Hopwood, Rainer Kiko, Alexandra Loginova, Carolin R. Löscher, Marie Maßmig, Alexandra-Sophie Roy, Renato Salvatteci, Stefan Sommer, Toste Tanhua, and Hela Mehrtens
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2020-308, https://doi.org/10.5194/essd-2020-308, 2021
Preprint withdrawn
Short summary
Short summary
The project "Climate-Biogeochemistry Interactions in the Tropical Ocean" (SFB 754) was a multidisciplinary research project active from 2008 to 2019 aimed at a better understanding of the coupling between the tropical climate and ocean circulation and the ocean's oxygen and nutrient balance. On 34 research cruises, mainly in the Southeast Tropical Pacific and the Northeast Tropical Atlantic, 1071 physical, chemical and biological data sets were collected.
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.
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.
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.
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.
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.
Pierre L'Hégaret, Florian Schütte, Sabrina Speich, Gilles Reverdin, Dariusz B. Baranowski, Rena Czeschel, Tim Fischer, Gregory R. Foltz, Karen J. Heywood, Gerd Krahmann, Rémi Laxenaire, Caroline Le Bihan, Philippe Le Bot, Stéphane Leizour, Callum Rollo, Michael Schlundt, Elizabeth Siddle, Corentin Subirade, Dongxiao Zhang, and Johannes Karstensen
Earth Syst. Sci. Data, 15, 1801–1830, https://doi.org/10.5194/essd-15-1801-2023, https://doi.org/10.5194/essd-15-1801-2023, 2023
Short summary
Short summary
In early 2020, the EUREC4A-OA/ATOMIC experiment took place in the northwestern Tropical Atlantic Ocean, a dynamical region where different water masses interact. Four oceanographic vessels and a fleet of autonomous devices were deployed to study the processes at play and sample the upper ocean, each with its own observing capability. The article first describes the data calibration and validation and second their cross-validation, using a hierarchy of instruments and estimating the uncertainty.
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.
Lothar Stramma and Sunke Schmidtko
Ocean Sci., 17, 833–847, https://doi.org/10.5194/os-17-833-2021, https://doi.org/10.5194/os-17-833-2021, 2021
Short summary
Short summary
Six tropical areas in the Pacific, Atlantic and Indian oceans were investigated for trends for the years since 1950 for temperature, salinity, oxygen and nutrients at 50 to 300 m and 300 to 700 m depth. Generally, temperature increases, oxygen decreases and nutrients often increase. Overlain variability on the trends seem to be related to climate modes. Different trends indicate that oxygen and nutrient trends cannot by completely explained by local warming.
Jaard Hauschildt, Soeren Thomsen, Vincent Echevin, Andreas Oschlies, Yonss Saranga José, Gerd Krahmann, Laura A. Bristow, and Gaute Lavik
Biogeosciences, 18, 3605–3629, https://doi.org/10.5194/bg-18-3605-2021, https://doi.org/10.5194/bg-18-3605-2021, 2021
Short summary
Short summary
In this paper we quantify the subduction of upwelled nitrate due to physical processes on the order of several kilometers in the coastal upwelling off Peru and its effect on primary production. We also compare the prepresentation of these processes in a high-resolution simulation (~2.5 km) with a more coarsely resolved simulation (~12 km). To do this, we combine high-resolution shipboard observations of physical and biogeochemical parameters with a complex biogeochemical model configuration.
Gerd Krahmann, Damian L. Arévalo-Martínez, Andrew W. Dale, Marcus Dengler, Anja Engel, Nicolaas Glock, Patricia Grasse, Johannes Hahn, Helena Hauss, Mark Hopwood, Rainer Kiko, Alexandra Loginova, Carolin R. Löscher, Marie Maßmig, Alexandra-Sophie Roy, Renato Salvatteci, Stefan Sommer, Toste Tanhua, and Hela Mehrtens
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2020-308, https://doi.org/10.5194/essd-2020-308, 2021
Preprint withdrawn
Short summary
Short summary
The project "Climate-Biogeochemistry Interactions in the Tropical Ocean" (SFB 754) was a multidisciplinary research project active from 2008 to 2019 aimed at a better understanding of the coupling between the tropical climate and ocean circulation and the ocean's oxygen and nutrient balance. On 34 research cruises, mainly in the Southeast Tropical Pacific and the Northeast Tropical Atlantic, 1071 physical, chemical and biological data sets were collected.
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.
Jan Lüdke, Marcus Dengler, Stefan Sommer, David Clemens, Sören Thomsen, Gerd Krahmann, Andrew W. Dale, Eric P. Achterberg, and Martin Visbeck
Ocean Sci., 16, 1347–1366, https://doi.org/10.5194/os-16-1347-2020, https://doi.org/10.5194/os-16-1347-2020, 2020
Short summary
Short summary
We analyse the intraseasonal variability of the alongshore circulation off Peru in early 2017, this circulation is very important for the supply of nutrients to the upwelling regime. The causes of this variability and its impact on the biogeochemistry are investigated. The poleward flow is strengthened during the observed time period, likely by a downwelling coastal trapped wave. The stronger current causes an increase in nitrate and reduces the deficit of fixed nitrogen relative to phosphorus.
Lothar Stramma, Sunke Schmidtko, Steven J. Bograd, Tsuneo Ono, Tetjana Ross, Daisuke Sasano, and Frank A. Whitney
Biogeosciences, 17, 813–831, https://doi.org/10.5194/bg-17-813-2020, https://doi.org/10.5194/bg-17-813-2020, 2020
Short summary
Short summary
The influence of climate signals in the Pacific, especially the Pacific Decadal Oscillation and the North Pacific Gyre Oscillation, as well as El Niño–La Niña and an 18.6-year nodal tidal cycle on oxygen and nutrient trends is investigated. At different locations in the Pacific Ocean different climate signals dominate. Hence, not only trends related to warming but also the influence of climate signals need to be investigated to understand oxygen and nutrient changes in the ocean.
Marie Maßmig, Jan Lüdke, Gerd Krahmann, and Anja Engel
Biogeosciences, 17, 215–230, https://doi.org/10.5194/bg-17-215-2020, https://doi.org/10.5194/bg-17-215-2020, 2020
Short summary
Short summary
Little is known about the rates of bacterial element cycling in oxygen minimum zones (OMZs). We measured bacterial production and rates of extracellular hydrolytic enzymes at various in situ oxygen concentrations in the OMZ off Peru. Our field data show unhampered bacterial activity at low oxygen concentrations. Meanwhile bacterial degradation of organic matter substantially contributed to the formation of the OMZ.
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.
Yonss Saranga José, Lothar Stramma, Sunke Schmidtko, and Andreas Oschlies
Biogeosciences Discuss., https://doi.org/10.5194/bg-2019-155, https://doi.org/10.5194/bg-2019-155, 2019
Revised manuscript accepted for BG
Short summary
Short summary
In situ observations along the Peruvian and Chilean coasts have exhibited variability in the water column oxygen concentration. This variability, which is attributed to the El Niño Southern Oscillation (ENSO), might have implication on the vertical extension of the Eastern Tropical South Pacific (ETSP) oxygen minimum zone. Here using a coupled physical-biogeochemical model, we provide new insights into how ENSO variability affects the vertical extension of the oxygen-poor waters of the ETSP.
Soeren Thomsen, Johannes Karstensen, Rainer Kiko, Gerd Krahmann, Marcus Dengler, and Anja Engel
Biogeosciences, 16, 979–998, https://doi.org/10.5194/bg-16-979-2019, https://doi.org/10.5194/bg-16-979-2019, 2019
Short summary
Short summary
Physical and biogeochemical observations from an autonomous underwater vehicle in combination with ship-based measurements are used to investigate remote and local drivers of the oxygen and nutrient variability off Mauritania. Beside the transport of oxygen and nutrients characteristics from remote areas towards Mauritania also local remineralization of organic material close to the seabed seems to be important for the distribution of oxygen and nutrients.
Jürgen Fischer, Johannes Karstensen, Marilena Oltmanns, and Sunke Schmidtko
Ocean Sci., 14, 1167–1183, https://doi.org/10.5194/os-14-1167-2018, https://doi.org/10.5194/os-14-1167-2018, 2018
Short summary
Short summary
Based on nearly 17 years of profiling (Argo) float data, high-resolution (~ 25 km grid) maps of mean flow and eddy kinetic energy (EKE) were constructed for the intermediate to deep subpolar North Atlantic. Robust boundary currents along topographic slopes, mid-basin advective pathways, and stagnation regimes were identified. The ratio of mean flow vs. the square root of EKE indicates regions dominated by advection, and large regions in which eddy diffusion prevails.
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.
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.
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: In situ Observations | Depth range: Thermocline | Geographical range: Deep Seas: North Atlantic | Phenomena: Current Field
The flow field of the upper hypoxic eastern tropical North Atlantic oxygen minimum zone
Stability and forcing of the Iceland-Faroe inflow of water, heat, and salt to the Arctic
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.
B. Hansen, H. Hátún, R. Kristiansen, S. M. Olsen, and S. Østerhus
Ocean Sci., 6, 1013–1026, https://doi.org/10.5194/os-6-1013-2010, https://doi.org/10.5194/os-6-1013-2010, 2010
Cited articles
Argo: Argo float data and metadata from Global Data Assembly Centre (Argo GDAC), SEANOE, 2000, available at: http://doi.org/10.17882/42182, last access: March 2016.
Ascani, F., Firing, E., Dutrieux, P., McCreary, J. P., and Ishida, A.: Deep Equatorial Ocean Circulation Induced by a Forced-Dissipated Yanai Beam, J. Phys. Oceanogr., 40, 1118–1142, https://doi.org/10.1175/2010jpo4356.1, 2010.
Ascani, F., Firing, E., McCreary, J. P., Brandt, P., and Greatbatch, R. J.: The Deep Equatorial Ocean Circulation in Wind-Forced Numerical Solutions, J. Phys. Oceanogr., 45, 1709–1734, https://doi.org/10.1175/jpo-d-14-0171.1, 2015.
Aviso, MADT-H-UV: Maps of Absolute Dynamic Topography & absolute geostrophic velocities, available at: https://www.aviso.altimetry.fr/index.php?id=1271, last access: July 2016.
Banyte, D., Tanhua, T., Visbeck, M., Wallace, D. W. R., Karstensen, J., Krahmann, G., Schneider, A., Stramma, L., and Dengler, M.: Diapycnal diffusivity at the upper boundary of the tropical North Atlantic oxygen minimum zone, J. Geophys. Res.-Ocean., 117, C09016, https://doi.org/10.1029/2011jc007762, 2012.
Biastoch, A., Böning, C. W., Schwarzkopf, F. U., and Lutjeharms, J. R. E.: Increase in Agulhas leakage due to poleward shift of Southern Hemisphere westerlies, Nature, 462, 495–498, https://doi.org/10.1038/nature08519, 2009.
Bopp, L., Le Quéré, C., Heimann, M., Manning, A. C., and Monfray, P.: Climate-induced oceanic oxygen fluxes: Implications for the contemporary carbon budget, Global Biogeochem. Cy., 16, 6-1–6-13, https://doi.org/10.1029/2001gb001445, 2002.
Brandt, P., Hormann, V., Bourlès, B., Fischer, J., Schott, F. A., Stramma, L., and Dengler, M.: Oxygen tongues and zonal currents in the equatorial Atlantic, J. Geophys. Res.-Ocean., 113, C04012, https://doi.org/10.1029/2007jc004435, 2008.
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.
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.-Ocean., 117, C12015, https://doi.org/10.1029/2012jc008118, 2012.
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.
Bunge, L., Provost, C., Hua, B. L., and Kartavtseff, A.: Variability at intermediate depths at the equator in the Atlantic ocean in 2000–06: Annual cycle, equatorial deep jets, and intraseasonal meridional velocity fluctuations, J. Phys. Oceanogr., 38, 1794–1806, https://doi.org/10.1175/2008jpo3781.1, 2008.
Cabre, A., Marinov, I., Bernardello, R., and Bianchi, D.: Oxygen minimum zones in the tropical Pacific across CMIP5 models: mean state differences and climate change trends, Biogeosciences, 12, 5429–5454, https://doi.org/10.5194/bg-12-5429-2015, 2015.
Chang, P., Yamagata, T., Schopf, P., Behera, S. K., Carton, J., Kessler, W. S., Meyers, G., Qu, T., Schott, F., Shetye, S., and Xie, S. P.: Climate fluctuations of tropical coupled systems – The role of ocean dynamics, J. Clim., 19, 5122–5174, https://doi.org/10.1175/jcli3903.1, 2006.
Chang, P., Zhang, R., Hazeleger, W., Wen, C., Wan, X. Q., Ji, L., Haarsma, R. J., Breugem, W. P., and Seidel, H.: Oceanic link between abrupt changes in the North Atlantic Ocean and the African monsoon, Nat. Geosci., 1, 444–448, https://doi.org/10.1038/ngeo218, 2008.
Czeschel, R., Stramma, L., and Johnson, G. C.: Oxygen decreases and variability in the eastern equatorial Pacific, J. Geophys. Res.-Ocean., 117, C11019, https://doi.org/10.1029/2012jc008043, 2012.
Doi, T., Tozuka, T., and Yamagata, T.: The Atlantic Meridional Mode and Its Coupled Variability with the Guinea Dome, J. Clim., 23, 455–475, https://doi.org/10.1175/2009jcli3198.1, 2010.
Duteil, O., Böning, C. W., and Oschlies, A.: Variability in subtropical-tropical cells drives oxygen levels in the tropical Pacific Ocean, Geophys. Res. Lett., 41, 8926–8934, https://doi.org/10.1002/2014gl061774, 2014a.
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, 2014b.
Eden, C. and Dengler, M.: Stacked jets in the deep equatorial Atlantic Ocean, J. Geophys. Res.-Ocean., 113, C04003, https://doi.org/10.1029/2007jc004298, 2008.
Fischer, T., Banyte, D., Brandt, P., Dengler, M., Krahmann, G., Tanhua, T., and Visbeck, M.: Diapycnal oxygen supply to the tropical North Atlantic oxygen minimum zone, Biogeosciences, 10, 5079–5093, https://doi.org/10.5194/bg-10-5079-2013, 2013.
Foltz, G. R., McPhaden, M. J., and Lumpkin, R.: A Strong Atlantic Meridional Mode Event in 2009: The Role of Mixed Layer Dynamics, J. Clim., 25, 363–380, https://doi.org/10.1175/jcli-d-11-00150.1, 2012.
Frölicher, T. L., Joos, F., Plattner, G. K., Steinacher, M., and Doney, S. C.: Natural variability and anthropogenic trends in oceanic oxygen in a coupled carbon cycle-climate model ensemble, Global Biogeochem. Cy., 23, 15, GB1003, https://doi.org/10.1029/2008gb003316, 2009.
Garzoli, S. L. and Katz, E. J.: The Forced Annual Reversal of the Atlantic North Equatorial Countercurrent, J. Phys. Oceanogr., 13, 2082–2090, https://doi.org/10.1175/1520-0485(1983)013<2082:tfarot>2.0.co;2, 1983.
Garzoli, S. L. and Richardson, P. L.: Low-frequency meandering of the Atlantic North Equatorial Countercurrent, J. Geophys. Res.-Ocean., 94, 2079–2090, https://doi.org/10.1029/JC094iC02p02079, 1989.
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.
Hahn, J., Brandt, P., Schmidtko, S., and Krahmann, G.: Oxygen, hydrography and velocity in the eastern tropical North Atlantic (1999–2015), Pangaea, https://doi.pangaea.de/10.1594/PANGAEA.869568, 2016.
Helly, J. J. and Levin, L. A.: Global distribution of naturally occurring marine hypoxia on continental margins, Deep-Sea Res. Pt. I, 51, 1159–1168, https://doi.org/10.1016/j.dsr.2004.03.009, 2004.
Helm, K. P., Bindoff, N. L., and Church, J. A.: Observed decreases in oxygen content of the global ocean, Geophys. Res. Lett., 38, L23602, https://doi.org/10.1029/2011gl049513, 2011.
Hormann, V., Lumpkin, R., and Foltz, G. R.: Interannual North Equatorial Countercurrent variability and its relation to tropical Atlantic climate modes, J. Geophys. Res.-Ocean., 117, C04035, https://doi.org/10.1029/2011jc007697, 2012.
Hummels, R., Brandt, P., Dengler, M., Fischer, J., Araujo, M., Veleda, D., and Durgadoo, J. V.: Interannual to decadal changes in the western boundary circulation in the Atlantic at 11° S, Geophys. Res. Lett., 42, 7615–7622, https://doi.org/10.1002/2015gl065254, 2015.
Johns, W. E., Brandt, P., Bourlès, B., Tantet, A., Papapostolou, A., and Houk, A.: Zonal structure and seasonal variability of the Atlantic Equatorial Undercurrent, Clim. Dynam., 43, 3047–3069, https://doi.org/10.1007/s00382-014-2136-2, 2014.
Joyce, T. M., Frankignoul, C., Yang, J. Y., and Phillips, H. E.: Ocean response and feedback to the SST dipole in the tropical Atlantic, J. Phys. Oceanogr., 34, 2525–2540, https://doi.org/10.1175/jpo2640.1, 2004.
Kamenkovich, I., Berloff, P., and Pedlosky, J.: Anisotropic Material Transport by Eddies and Eddy-Driven Currents in a Model of the North Atlantic, J. Phys. Oceanogr., 39, 3162–3175, https://doi.org/10.1175/2009jpo4239.1, 2009.
Karstensen, J., Stramma, L., and Visbeck, M.: Oxygen minimum zones in the eastern tropical Atlantic and Pacific oceans, Prog. Oceanogr., 77, 331–350, https://doi.org/10.1016/j.pocean.2007.05.009, 2008.
Karstensen, J., Fiedler, B., Schütte, F., Brandt, P., Körtzinger, A., Fischer, G., Zantopp, R., Hahn, J., Visbeck, M., and Wallace, D.: Open ocean dead zones in the tropical North Atlantic Ocean, Biogeosciences, 12, 2597–2605, https://doi.org/10.5194/bg-12-2597-2015, 2015.
Keeling, R. F. and Garcia, H. E.: The change in oceanic O2 inventory associated with recent global warming, P. Natl. Acad. Sci. USA, 99, 7848–7853, https://doi.org/10.1073/pnas.122154899, 2002.
Kirchner, K., Rhein, M., Hüttl-Kabus, S., and Böning, C. W.: On the spreading of South Atlantic Water into the Northern Hemisphere, J. Geophys. Res.-Ocean., 114, C05019, https://doi.org/10.1029/2008jc005165, 2009.
Köllner, M., Visbeck, M., Tanhua, T., and Fischer, T.: Diapycnal diffusivity in the core and oxycline of the tropical North Atlantic oxygen minimum zone, J. Mar. Syst., 160, 54–63, https://doi.org/10.1016/j.jmarsys.2016.03.012, 2016.
Kolodziejczyk, N., Reverdin, G., Gaillard, F., and Lazar, A.: Low-frequency thermohaline variability in the Subtropical South Atlantic pycnocline during 2002–2013, Geophys. Res. Lett., 41, 6468–6475, https://doi.org/10.1002/2014gl061160, 2014.
Liu, L. L. and Huang, R. X.: The Global Subduction/Obduction Rates: Their Interannual and Decadal Variability, J. Clim., 25, 1096–1115, https://doi.org/10.1175/2011jcli4228.1, 2012.
Lübbecke, J. F., Durgadoo, J. V., and Biastoch, A.: Contribution of Increased Agulhas Leakage to Tropical Atlantic Warming, J. Clim., 28, 9697–9706, https://doi.org/10.1175/jcli-d-15-0258.1, 2015.
Luyten, J. R., Pedlosky, J., and Stommel, H.: The Ventilated Thermocline, J. Phys. Oceanogr., 13, 292–309, https://doi.org/10.1175/1520-0485(1983)013<0292:tvt>2.0.co;2, 1983.
Marshall, J., Kushner, Y., Battisti, D., Chang, P., Czaja, A., Dickson, R., Hurrell, J., McCartney, M., Saravanan, R., and Visbeck, M.: North Atlantic climate variability: Phenomena, impacts and mechanisms, Int. J. Climatol., 21, 1863–1898, https://doi.org/10.1002/joc.693, 2001.
Matear, R. J. and Hirst, A. C.: Long-term changes in dissolved oxygen concentrations in the ocean caused by protracted global warming, Global Biogeochem. Cy., 17, 1125, https://doi.org/10.1029/2002gb001997, 2003.
Maximenko, N. A., Bang, B., and Sasaki, H.: Observational evidence of alternating zonal jets in the world ocean, Geophys. Res. Lett., 32, L12607, https://doi.org/10.1029/2005gl022728, 2005.
McCreary, J. P. and Lu, P.: Interaction between the Subtropical and Equatorial Ocean Circulations: The Substropical Cell, J. Phys. Oceanogr., 24, 466–497, 1994.
Ollitrault, M. and de Verdiere, A. C.: The Ocean General Circulation near 1000-m Depth, J. Phys. Oceanogr., 44, 384–409, https://doi.org/10.1175/jpo-d-13-030.1, 2014.
Oschlies, A., Schulz, K. G., Riebesell, U., and Schmittner, A.: Simulated 21st century's increase in oceanic suboxia by CO2-enhanced biotic carbon export, Global Biogeochem. Cy., 22, GB4008, https://doi.org/10.1029/2007gb003147, 2008.
Pena-Izquierdo, J., van Sebille, E., Pelegri, J. L., Sprintall, J., Mason, E., Llanillo, P. J., and Machin, F.: Water mass pathways to the North Atlantic oxygen minimum zone, J. Geophys. Res.-Ocean., 120, 3350–3372, https://doi.org/10.1002/2014jc010557, 2015.
Perez, R. C., Lumpkin, R., Johns, W. E., Foltz, G. R., and Hormann, V.: Interannual variations of Atlantic tropical instability waves, J. Geophys. Res.-Ocean., 117, C03011, https://doi.org/10.1029/2011jc007584, 2012.
Plattner, G. K., Joos, F., and Stocker, T. F.: Revision of the global carbon budget due to changing air-sea oxygen fluxes, Global Biogeochem. Cy., 16, 12, 1096, https://doi.org/10.1029/2001gb001746, 2002.
Qiu, B., Chen, S. M., and Sasaki, H.: Generation of the North Equatorial Undercurrent Jets by Triad Baroclinic Rossby Wave Interactions, J. Phys. Oceanogr., 43, 2682–2698, https://doi.org/10.1175/jpo-d-13-099.1, 2013.
Rabe, B., Schott, F. A., and Kohl, A.: Mean circulation and variability of the tropical Atlantic during 1952–2001 in the GECCO assimilation fields, J. Phys. Oceanogr., 38, 177–192, https://doi.org/10.1175/2007jpo3541.1, 2008.
Rhein, M., Kirchner, K., Mertens, C., Steinfeldt, R., Walter, M., and Fleischmann-Wischnath, U.: Transport of South Atlantic water through the passages south of Guadeloupe and across 16° N, 2000–2004, Deep-Sea Res. Pt. I, 52, 2234–2249, https://doi.org/10.1016/j.dsr.2005.08.003, 2005.
Richardson, P. L., Arnault, S., Garzoli, S., and Bruce, J. G.: Annual cycle of the Atlantic North Equatorial Countercurrent, Deep-Sea Res. Pt. A, 39, 997–1014, https://doi.org/10.1016/0198-0149(92)90036-s, 1992.
Roemmich, D., Johnson, G. C., Riser, S., Davis, R., Gilson, J., Owens, W. B., Garzoli, S. L., Schmid, C., and Ignaszewski, M.: The Argo Program Observing the Global Ocean with Profiling Floats, Oceanography, 22, 34–43, https://doi.org/10.5670/oceanog.2009.36, 2009.
Rosell-Fieschi, M., Pelegri, 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.
Schmidtko, S. and Johnson, G. C.: Multidecadal Warming and Shoaling of Antarctic Intermediate Water, J. Clim., 25, 207–221, https://doi.org/10.1175/jcli-d-11-00021.1, 2012.
Schmidtko, S., Johnson, G. C., and Lyman, J. M.: Monthly Isopycnal & Mixed-layer Ocean Climatology, available at: https://www.pmel.noaa.gov/mimoc/, 2013.
Schmidtko, S., Johnson, G. C., and Lyman, J. M.: MIMOC: A global monthly isopycnal upper-ocean climatology with mixed layers, J. Geophys. Res.-Ocean., 118, 1658–1672, https://doi.org/10.1002/jgrc.20122, 2013.
Schmidtko, S., Stramma, L., and Visbeck, M.: Decline in global oceanic oxygen content during the past five decades, Nature, 542, 335–339, https://doi.org/10.1038/nature21399, 2017.
Schmittner, A., Oschlies, A., Matthews, H. D., and Galbraith, E. D.: Future changes in climate, ocean circulation, ecosystems, and biogeochemical cycling simulated for a business-as-usual CO2 emission scenario until year 4000 AD, Global Biogeochem. Cy., 22, GB1013, https://doi.org/10.1029/2007gb002953, 2008.
Schott, F. A., Dengler, M., Brandt, P., Affler, K., Fischer, J., Bourlès, B., Gouriou, Y., Molinari, R. L., and Rhein, M.: The zonal currents and transports at 35° W in the tropical Atlantic, Geophys. Res. Lett., 30, 1349, https://doi.org/10.1029/2002gl016849, 2003.
Schott, F. A., McCreary, J. P., and Johnson, G. C.: Shallow Overturning Circulations of the Tropical-Subtropical Oceans, in: Earth's Climate, edited by: Wang, C., S. P., X., and J. A., Carton, American Geophysical Union, Washington, DC, 261–304, 2004.
Schott, F. A., Dengler, M., Zantopp, R., Stramma, L., Fischer, J., and Brandt, P.: The shallow and deep western boundary circulation of the South Atlantic at 5°–11° S, J. Phys. Oceanogr., 35, 2031–2053, https://doi.org/10.1175/jpo2813.1, 2005.
Schütte, F., Karstensen, J., Krahmann, G., Hauss, H., Fiedler, B., Brandt, P., Visbeck, M., and Körtzinger, A.: Characterization of dead-zone eddies in the eastern tropical North Atlantic, Biogeosciences, 13, 5865–5881, https://doi.org/10.5194/bg-13-5865-2016, 2016.
Servain, J.: Simple climatic indices for the tropical Atlantic Ocean and some applications, J. Geophys. Res.-Ocean., 96, 15137–15146, https://doi.org/10.1029/91jc01046, 1991.
Stendardo, I. and Gruber, N.: Oxygen trends over five decades in the North Atlantic, J. Geophys. Res.-Ocean., 117, C11004, https://doi.org/10.1029/2012jc007909, 2012.
Stramma, L. and Schott, F.: The mean flow field of the tropical Atlantic Ocean, Deep-Sea Res. Pt. II, 46, 279–303, https://doi.org/10.1016/s0967-0645(98)00109-x, 1999.
Stramma, L., Hüttl, S., and Schafstall, J.: Water masses and currents in the upper tropical northeast Atlantic off northwest Africa, J. Geophys. Res.-Ocean., 110, C12006, https://doi.org/10.1029/2005jc002939, 2005.
Stramma, L., Johnson, G. C., Sprintall, J., and Mohrholz, V.: Expanding oxygen-minimum zones in the tropical oceans, Science, 320, 655–658, https://doi.org/10.1126/science.1153847, 2008.
Stramma, L., Visbeck, M., Brandt, P., Tanhua, T., and Wallace, D.: Deoxygenation in the oxygen minimum zone of the eastern tropical North Atlantic, Geophys. Res. Lett., 36, L20607, https://doi.org/10.1029/2009gl039593, 2009.
Stramma, L., Schmidtko, S., Levin, L. A., and Johnson, G. C.: Ocean oxygen minima expansions and their biological impacts, Deep-Sea Res. Pt. I, 57, 587–595, https://doi.org/10.1016/j.dsr.2010.01.005, 2010.
Stramma, L., Oschlies, A., and Schmidtko, S.: Mismatch between observed and modeled trends in dissolved upper-ocean oxygen over the last 50 yr, Biogeosciences, 9, 4045–4057, https://doi.org/10.5194/bg-9-4045-2012, 2012.
Thomsen, S., Kanzow, T., Colas, F., Echevin, V., Krahmann, G., and Engel, A.: Do submesoscale frontal processes ventilate the oxygen minimum zone off Peru?, Geophys. Res. Lett., 43, 8133–8142, https://doi.org/10.1002/2016gl070548, 2016.
Wallace, D. W. R. and Bange, H. W.: Introduction to special section: Results of the Meteor 55: Tropical SOLAS expedition, Geophys. Res. Lett., 31, L23S01, https://doi.org/10.1029/2004gl021014, 2004.
Wyrtki, K.: The oxygen minima in relation to ocean circulation, Deep-Sea Res., 9, 11–23, https://doi.org/10.1016/0011-7471(62)90243-7, 1962.
Zhang, D. X., McPhaden, M. J., and Johns, W. E.: Observational evidence for flow between the subtropical and tropical Atlantic: The Atlantic subtropical cells, J. Phys. Oceanogr., 33, 1783–1797, https://doi.org/10.1175/2408.1, 2003.
Zhu, J. S., Huang, B. H., and Wu, Z. H.: The Role of Ocean Dynamics in the Interaction between the Atlantic Meridional and Equatorial Modes, J. Clim., 25, 3583–3598, https://doi.org/10.1175/jcli-d-11-00364.1, 2012.
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.
Recent studies have shown that the eastern tropical North Atlantic is subject to a strong...
