Articles | Volume 13, issue 4
https://doi.org/10.5194/os-13-531-2017
© 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-13-531-2017
© 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
On the meridional ageostrophic transport in the tropical Atlantic
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Invited contribution by Yao Fu, recipient of the EGU Ocean Sciences Outstanding Student Poster Award 2015.
Johannes Karstensen
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
Related authors
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.
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.
Léa Olivier, Jacqueline Boutin, Gilles Reverdin, Nathalie Lefèvre, Peter Landschützer, Sabrina Speich, Johannes Karstensen, Matthieu Labaste, Christophe Noisel, Markus Ritschel, Tobias Steinhoff, and Rik Wanninkhof
Biogeosciences, 19, 2969–2988, https://doi.org/10.5194/bg-19-2969-2022, https://doi.org/10.5194/bg-19-2969-2022, 2022
Short summary
Short summary
We investigate the impact of the interactions between eddies and the Amazon River plume on the CO2 air–sea fluxes to better characterize the ocean carbon sink in winter 2020. The region is a strong CO2 sink, previously underestimated by a factor of 10 due to a lack of data and understanding of the processes responsible for the variability in ocean carbon parameters. The CO2 absorption is mainly driven by freshwater from the Amazon entrained by eddies and by the winter seasonal cooling.
Jannes Koelling, Dariia Atamanchuk, Johannes Karstensen, Patricia Handmann, and Douglas W. R. Wallace
Biogeosciences, 19, 437–454, https://doi.org/10.5194/bg-19-437-2022, https://doi.org/10.5194/bg-19-437-2022, 2022
Short summary
Short summary
In this study, we investigate oxygen variability in the deep western boundary current in the Labrador Sea from multiyear moored records. We estimate that about half of the oxygen taken up in the interior Labrador Sea by air–sea gas exchange during deep water formation is exported southward the same year. Our results underline the complexity of the oxygen uptake and export in the Labrador Sea and highlight the important role this region plays in supplying oxygen to the deep ocean.
Gerhard Fischer, Oscar E. Romero, Johannes Karstensen, Karl-Heinz Baumann, Nasrollah Moradi, Morten Iversen, Götz Ruhland, Marco Klann, and Arne Körtzinger
Biogeosciences, 18, 6479–6500, https://doi.org/10.5194/bg-18-6479-2021, https://doi.org/10.5194/bg-18-6479-2021, 2021
Short summary
Short summary
Low-oxygen eddies in the eastern subtropical North Atlantic can form an oasis for phytoplankton growth. Here we report on particle flux dynamics at the oligotrophic Cape Verde Ocean Observatory. We observed consistent flux patterns during the passages of low-oxygen eddies. We found distinct flux peaks in late winter, clearly exceeding background fluxes. Our findings suggest that the low-oxygen eddies sequester higher organic carbon than expected for oligotrophic settings.
Bjorn Stevens, Sandrine Bony, David Farrell, Felix Ament, Alan Blyth, Christopher Fairall, Johannes Karstensen, Patricia K. Quinn, Sabrina Speich, Claudia Acquistapace, Franziska Aemisegger, Anna Lea Albright, Hugo Bellenger, Eberhard Bodenschatz, Kathy-Ann Caesar, Rebecca Chewitt-Lucas, Gijs de Boer, Julien Delanoë, Leif Denby, Florian Ewald, Benjamin Fildier, Marvin Forde, Geet George, Silke Gross, Martin Hagen, Andrea Hausold, Karen J. Heywood, Lutz Hirsch, Marek Jacob, Friedhelm Jansen, Stefan Kinne, Daniel Klocke, Tobias Kölling, Heike Konow, Marie Lothon, Wiebke Mohr, Ann Kristin Naumann, Louise Nuijens, Léa Olivier, Robert Pincus, Mira Pöhlker, Gilles Reverdin, Gregory Roberts, Sabrina Schnitt, Hauke Schulz, A. Pier Siebesma, Claudia Christine Stephan, Peter Sullivan, Ludovic Touzé-Peiffer, Jessica Vial, Raphaela Vogel, Paquita Zuidema, Nicola Alexander, Lyndon Alves, Sophian Arixi, Hamish Asmath, Gholamhossein Bagheri, Katharina Baier, Adriana Bailey, Dariusz Baranowski, Alexandre Baron, Sébastien Barrau, Paul A. Barrett, Frédéric Batier, Andreas Behrendt, Arne Bendinger, Florent Beucher, Sebastien Bigorre, Edmund Blades, Peter Blossey, Olivier Bock, Steven Böing, Pierre Bosser, Denis Bourras, Pascale Bouruet-Aubertot, Keith Bower, Pierre Branellec, Hubert Branger, Michal Brennek, Alan Brewer, Pierre-Etienne Brilouet, Björn Brügmann, Stefan A. Buehler, Elmo Burke, Ralph Burton, Radiance Calmer, Jean-Christophe Canonici, Xavier Carton, Gregory Cato Jr., Jude Andre Charles, Patrick Chazette, Yanxu Chen, Michal T. Chilinski, Thomas Choularton, Patrick Chuang, Shamal Clarke, Hugh Coe, Céline Cornet, Pierre Coutris, Fleur Couvreux, Susanne Crewell, Timothy Cronin, Zhiqiang Cui, Yannis Cuypers, Alton Daley, Gillian M. Damerell, Thibaut Dauhut, Hartwig Deneke, Jean-Philippe Desbios, Steffen Dörner, Sebastian Donner, Vincent Douet, Kyla Drushka, Marina Dütsch, André Ehrlich, Kerry Emanuel, Alexandros Emmanouilidis, Jean-Claude Etienne, Sheryl Etienne-Leblanc, Ghislain Faure, Graham Feingold, Luca Ferrero, Andreas Fix, Cyrille Flamant, Piotr Jacek Flatau, Gregory R. Foltz, Linda Forster, Iulian Furtuna, Alan Gadian, Joseph Galewsky, Martin Gallagher, Peter Gallimore, Cassandra Gaston, Chelle Gentemann, Nicolas Geyskens, Andreas Giez, John Gollop, Isabelle Gouirand, Christophe Gourbeyre, Dörte de Graaf, Geiske E. de Groot, Robert Grosz, Johannes Güttler, Manuel Gutleben, Kashawn Hall, George Harris, Kevin C. Helfer, Dean Henze, Calvert Herbert, Bruna Holanda, Antonio Ibanez-Landeta, Janet Intrieri, Suneil Iyer, Fabrice Julien, Heike Kalesse, Jan Kazil, Alexander Kellman, Abiel T. Kidane, Ulrike Kirchner, Marcus Klingebiel, Mareike Körner, Leslie Ann Kremper, Jan Kretzschmar, Ovid Krüger, Wojciech Kumala, Armin Kurz, Pierre L'Hégaret, Matthieu Labaste, Tom Lachlan-Cope, Arlene Laing, Peter Landschützer, Theresa Lang, Diego Lange, Ingo Lange, Clément Laplace, Gauke Lavik, Rémi Laxenaire, Caroline Le Bihan, Mason Leandro, Nathalie Lefevre, Marius Lena, Donald Lenschow, Qiang Li, Gary Lloyd, Sebastian Los, Niccolò Losi, Oscar Lovell, Christopher Luneau, Przemyslaw Makuch, Szymon Malinowski, Gaston Manta, Eleni Marinou, Nicholas Marsden, Sebastien Masson, Nicolas Maury, Bernhard Mayer, Margarette Mayers-Als, Christophe Mazel, Wayne McGeary, James C. McWilliams, Mario Mech, Melina Mehlmann, Agostino Niyonkuru Meroni, Theresa Mieslinger, Andreas Minikin, Peter Minnett, Gregor Möller, Yanmichel Morfa Avalos, Caroline Muller, Ionela Musat, Anna Napoli, Almuth Neuberger, Christophe Noisel, David Noone, Freja Nordsiek, Jakub L. Nowak, Lothar Oswald, Douglas J. Parker, Carolyn Peck, Renaud Person, Miriam Philippi, Albert Plueddemann, Christopher Pöhlker, Veronika Pörtge, Ulrich Pöschl, Lawrence Pologne, Michał Posyniak, Marc Prange, Estefanía Quiñones Meléndez, Jule Radtke, Karim Ramage, Jens Reimann, Lionel Renault, Klaus Reus, Ashford Reyes, Joachim Ribbe, Maximilian Ringel, Markus Ritschel, Cesar B. Rocha, Nicolas Rochetin, Johannes Röttenbacher, Callum Rollo, Haley Royer, Pauline Sadoulet, Leo Saffin, Sanola Sandiford, Irina Sandu, Michael Schäfer, Vera Schemann, Imke Schirmacher, Oliver Schlenczek, Jerome Schmidt, Marcel Schröder, Alfons Schwarzenboeck, Andrea Sealy, Christoph J. Senff, Ilya Serikov, Samkeyat Shohan, Elizabeth Siddle, Alexander Smirnov, Florian Späth, Branden Spooner, M. Katharina Stolla, Wojciech Szkółka, Simon P. de Szoeke, Stéphane Tarot, Eleni Tetoni, Elizabeth Thompson, Jim Thomson, Lorenzo Tomassini, Julien Totems, Alma Anna Ubele, Leonie Villiger, Jan von Arx, Thomas Wagner, Andi Walther, Ben Webber, Manfred Wendisch, Shanice Whitehall, Anton Wiltshire, Allison A. Wing, Martin Wirth, Jonathan Wiskandt, Kevin Wolf, Ludwig Worbes, Ethan Wright, Volker Wulfmeyer, Shanea Young, Chidong Zhang, Dongxiao Zhang, Florian Ziemen, Tobias Zinner, and Martin Zöger
Earth Syst. Sci. Data, 13, 4067–4119, https://doi.org/10.5194/essd-13-4067-2021, https://doi.org/10.5194/essd-13-4067-2021, 2021
Short summary
Short summary
The EUREC4A field campaign, designed to test hypothesized mechanisms by which clouds respond to warming and benchmark next-generation Earth-system models, is presented. EUREC4A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic – eastward and southeastward of Barbados. It was the first campaign that attempted to characterize the full range of processes and scales influencing trade wind clouds.
Josefine Herrford, Peter Brandt, Torsten Kanzow, Rebecca Hummels, Moacyr Araujo, and Jonathan V. Durgadoo
Ocean Sci., 17, 265–284, https://doi.org/10.5194/os-17-265-2021, https://doi.org/10.5194/os-17-265-2021, 2021
Short summary
Short summary
The Atlantic Meridional Overturning Circulation (AMOC) is an important component of the climate system. Understanding its structure and variability is a key priority for many scientists. Here, we present the first estimate of AMOC variations for the tropical South Atlantic from the TRACOS array at 11° S. Over the observed period, the AMOC was dominated by seasonal variability. We investigate the respective mechanisms with an ocean model and find that different wind-forced waves play a big role.
Tim Fischer, Annette Kock, Damian L. Arévalo-Martínez, Marcus Dengler, Peter Brandt, and Hermann W. Bange
Biogeosciences, 16, 2307–2328, https://doi.org/10.5194/bg-16-2307-2019, https://doi.org/10.5194/bg-16-2307-2019, 2019
Short summary
Short summary
We investigated air–sea gas exchange in oceanic upwelling regions for the case of nitrous oxide off Peru. In this region, routine concentration measurements from ships at 5 m or 10 m depth prove to overestimate surface (bulk) concentration. Thus, standard estimates of gas exchange will show systematic error. This is due to very shallow stratified layers that inhibit exchange between surface water and waters below and can exist for several days. Maximum bias occurs in moderate wind conditions.
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.
Mochamad Furqon Azis Ismail, Joachim Ribbe, Johannes Karstensen, and Vincent Rossi
Ocean Sci. Discuss., https://doi.org/10.5194/os-2018-142, https://doi.org/10.5194/os-2018-142, 2019
Publication in OS not foreseen
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.
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.
Johannes Karstensen, Florian Schütte, Alice Pietri, Gerd Krahmann, Björn Fiedler, Damian Grundle, Helena Hauss, Arne Körtzinger, Carolin R. Löscher, Pierre Testor, Nuno Vieira, and Martin Visbeck
Biogeosciences, 14, 2167–2181, https://doi.org/10.5194/bg-14-2167-2017, https://doi.org/10.5194/bg-14-2167-2017, 2017
Short summary
Short summary
High-resolution observational data from underwater gliders and ships are used to investigate drivers and pathways of nutrient upwelling in high-productive whirling ecosystems (eddies). The data suggest that the upwelling is created by the interaction of wind-induced internal waves with the local rotation of the eddy. Because of differences in nutrient and oxygen pathways, a low-oxygen core is established at shallow depth in the high-productive eddies.
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.
Björn Fiedler, Damian S. Grundle, Florian Schütte, Johannes Karstensen, Carolin R. Löscher, Helena Hauss, Hannes Wagner, Alexandra Loginova, Rainer Kiko, Péricles Silva, Toste Tanhua, and Arne Körtzinger
Biogeosciences, 13, 5633–5647, https://doi.org/10.5194/bg-13-5633-2016, https://doi.org/10.5194/bg-13-5633-2016, 2016
Short summary
Short summary
Oxygen-depleted mesoscale features in the open eastern tropical North Atlantic, which are formed in the Mauritanian upwelling region, were discovered recently. This study examines biogeochemical structure and magnitudes of related processes within these isolated water masses. We found very low oxygen concentrations and strongly enhanced acidity at near-surface depth. Oxygen utilization and downward carbon export were found to exceed known values for this ocean region.
Gerhard Fischer, Johannes Karstensen, Oscar Romero, Karl-Heinz Baumann, Barbara Donner, Jens Hefter, Gesine Mollenhauer, Morten Iversen, Björn Fiedler, Ivanice Monteiro, and Arne Körtzinger
Biogeosciences, 13, 3203–3223, https://doi.org/10.5194/bg-13-3203-2016, https://doi.org/10.5194/bg-13-3203-2016, 2016
Short summary
Short summary
Particle fluxes at the Cape Verde Ocean Observatory in the eastern tropical North Atlantic for the period December 2009 until May 2011 are discussed based on deep sediment trap time-series data collected at 1290 and 3439 m water depths. The typically open-ocean flux pattern with weak seasonality is modified by the appearance of a highly productive and low oxygen eddy in winter 2010. The eddy passage was accompanied by high biogenic and lithogenic fluxes, lasting from December 2009 to May 2010.
Marcela Cornejo D'Ottone, Luis Bravo, Marcel Ramos, Oscar Pizarro, Johannes Karstensen, Mauricio Gallegos, Marco Correa-Ramirez, Nelson Silva, Laura Farias, and Lee Karp-Boss
Biogeosciences, 13, 2971–2979, https://doi.org/10.5194/bg-13-2971-2016, https://doi.org/10.5194/bg-13-2971-2016, 2016
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.
Helena Hauss, Svenja Christiansen, Florian Schütte, Rainer Kiko, Miryam Edvam Lima, Elizandro Rodrigues, Johannes Karstensen, Carolin R. Löscher, Arne Körtzinger, and Björn Fiedler
Biogeosciences, 13, 1977–1989, https://doi.org/10.5194/bg-13-1977-2016, https://doi.org/10.5194/bg-13-1977-2016, 2016
Short summary
Short summary
In a low-oxygen eddy in the tropical Atlantic, total zooplankton biomass was increased. Larger plankton avoided the oxygen minimum zone (OMZ, < 20 µmol O2 kg−1). We identified four strategies by different plankton groups: (i) shallow OMZ avoidance and compression at surface, (ii) migration to shallow OMZ core during daytime, migration to surface at nighttime, (iii) residing in shallow OMZ day and night and (iv) migration through the shallow OMZ from oxygenated depths to surface and back.
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.
C. R. Löscher, M. A. Fischer, S. C. Neulinger, B. Fiedler, M. Philippi, F. Schütte, A. Singh, H. Hauss, J. Karstensen, A. Körtzinger, S. Künzel, and R. A. Schmitz
Biogeosciences, 12, 7467–7482, https://doi.org/10.5194/bg-12-7467-2015, https://doi.org/10.5194/bg-12-7467-2015, 2015
Short summary
Short summary
The waters of the tropical Atlantic Open Ocean usually contain comparably high concentrations of oxygen. Now, it became clear that there are watermasses related to eddies that are nearly anoxic. We surveyed one of those eddies and found a biosphere that largely differed from the usual biosphere present in this area with a specific community responsible for primary production and for degradation processes. Further, we found the very first indication for active nitrogen loss in the open Atlantic.
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.
J. Karstensen, T. Liblik, J. Fischer, K. Bumke, and G. Krahmann
Biogeosciences, 11, 3603–3617, https://doi.org/10.5194/bg-11-3603-2014, https://doi.org/10.5194/bg-11-3603-2014, 2014
P. J. Llanillo, J. Karstensen, J. L. Pelegrí, and L. Stramma
Biogeosciences, 10, 6339–6355, https://doi.org/10.5194/bg-10-6339-2013, https://doi.org/10.5194/bg-10-6339-2013, 2013
T. Fischer, D. Banyte, P. Brandt, M. Dengler, G. Krahmann, T. Tanhua, and M. Visbeck
Biogeosciences, 10, 5079–5093, https://doi.org/10.5194/bg-10-5079-2013, https://doi.org/10.5194/bg-10-5079-2013, 2013
Cited articles
Alford, M. H.: Improved global maps and 54-year history of wind-work on ocean inertial motions, Geophys. Res. Lett., 30, 1424, https://doi.org/10.1029/2002GL016614, 2003.
Chereskin, T. K.: Direct evidence for an Ekman balance in the California Current, J. Geophys. Res., 100, 18261–18269, https://doi.org/10.1029/95JC02182, 1995.
Chereskin, T. K. and Roemmich, D.: A Comparison of Measured and Wind-derived Ekman Transport at 11° N in the Atlantic Ocean, J. Phys. Oceanogr., 21, 869–878, 1991.
Chereskin, T. K., Wilson, W. D., Bryden, H. L., Ffield, A., and Morrison, J.: Observations of the Ekman balance at 8°30′ N in the Arabian Sea during the 1995 southwest monsoon, Geophys. Res. Lett., 24, 2541, https://doi.org/10.1029/97GL01057, 1997.
Chereskin, T. K., Wilson, W. D., and Beal, L. M.: The Ekman temperature and salt fluxes at 8°30′ N in the Arabian Sea during the 1995 southwest monsoon, Deep-Sea Res. Pt. II, 49, , 1211–1230, https://doi.org/10.1016/S0967-0645(01)00168-0, 2002.
Cunningham, S. A., Kanzow, T., Rayner, D., Baringer, M. O., Johns, W. E., Marotzke, J., Longworth, H. R., Grant, E. M., Hirschi, J. J., Beal, L. M., Meinen, C. S., and Bryden, H. L.: Temporal Variability of the Atlantic Meridional Overturning Circulation at 26.5° N, 317, 935–938, 2007.
Ekman, V. W.: On the influence of the earth's rotation on ocean-currents, Arkiv för matematik, astronomi och fysik, Bd. 2, no. 11., 68 pp., 1905.
Elipot, S. and Gille, S. T.: Estimates of wind energy input to the Ekman layer in the Southern Ocean from surface drifter data, J. Geophys. Res. Ocean., 114, 1–14, https://doi.org/10.1029/2008JC005170, 2009.
EU Copernicus: Wind: The L4 near-real-time wind stress data from Copernicus Marine Environment Monitoring Service, EU Commission, available at: https://marine.copernicus.eu, last access: 20 September 2016.
Fairall, C. W., Bradley, E. F., Hare, J. E., Grachev, A. A., and Edson, J. B.: Bulk parameterization of air-sea fluxes: Updates and verification for the COARE algorithm, J. Climate, 16, 571–591, https://doi.org/10.1175/1520-0442(2003)016<0571:BPOASF>2.0.CO;2, 2003.
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.
Friedrichs, M. A. M. and Hall, M. M.: Deep circulation in the tropical North Atlantic, J. Mar. Res., 51, 697–736, https://doi.org/10.1357/0022240933223909, 1993.
Fu, Y., Karstensen, J., and Brandt, P.: Physical oceanography and meteorology during METEOR cruises M96, M97 and M98, https://doi.org/10.1594/PANGAEA.870516, 2017.
Ganachaud, A. and Wunsch, C.: Large-Scale Ocean Heat and Freshwater Transports during the World Ocean Circulation Experiment, J. Climate, 16, 696–705, https://doi.org/10.1175/1520-0442(2003)016<0696:LSOHAF>2.0.CO;2, 2003.
Garzoli, S. L. and Molinari, R. L.: Ageostrophic transport in the upper layers of the tropical Atlantic Ocean, Geophys. Res. Lett., 28, 4619–4622, https://doi.org/10.1029/2001GL013473, 2001.
Hood, E. M., Sabine, C. L., and Sloyan, B. M.: GO-SHIP Repeat Hydrography Manual: A Collection of Expert Reports and Guidelines, IOCCP Report No. 14, ICPO Publication Series No. 134, available at: http://www.go-ship.org/HydroMan.html (last access: 8 August 2016), 2010.
Kanzow, T., Cunningham, S. A., Johns, W. E., Hirschi, J. J.-M., Marotzke, J., Baringer, M. O., Meinen, C. S., Chidichimo, M. P., Atkinson, C., Beal, L. M., Bryden, H. L. and Collins, J.: Seasonal Variability of the Atlantic Meridional Overturning Circulation at 26.5° N, J. Climate, 23, 5678–5698, https://doi.org/10.1175/2010JCLI3389.1, 2010.
Klein, B., Molinari, R. L., Müller, T. J., and Siedler, G.: A transatlantic section at 14.5N: Meridional volume and heat fluxes, J. Mar. Res., 53, 929–957, https://doi.org/10.1357/0022240953212963, 1995.
Köhl, A.: Evaluation of the GECCO2 ocean synthesis: transports of volume, heat and freshwater in the Atlantic, Q. J. Roy. Meteor. Soc., 141, 166–181, https://doi.org/10.1002/qj.2347, 2015.
Large, W. G. and Pond, S.: Open ocean momentum flux measurements in moderate to strong winds, J. Phys. Oceanogr., 11, 324–336, https://doi.org/10.1175/1520-0485(1981)011<0324:OOMFMI>2.0.CO;2, 1981.
Large, W. G. and Yeager, S. G.: Diurnal to decadal global forcing for ocean and sea-ice models: The data sets and flux climatologies, NCAR Technical Note NCAR/TN-460+STR, https://doi.org/10.5065/D6KK98Q6, 2004.
Larson, N. and Pedersen, A. M.: Temperature measurements in flowing water: Viscous heating of sensor tips, Proceedings of 1st IGHEM Meeting, Montreal, QC, Canada, June 1996, available at: http://www.seabird.com/viscous-heating-sensor-tips (last access: 8 August 2016), 1996.
Lenn, Y. and Chereskin, T. K.: Observations of Ekman Currents in the Southern Ocean, J. Phys. Oceanogr., 39, 768–779, https://doi.org/10.1175/2008JPO3943.1, 2009.
Levitus, S.: Meridional Ekman Heat Fluxes for the World Ocean and Individual Ocean Basins, J. Phys. Oceanogr., 17, 1484–1492, https://doi.org/10.1175/1520-0485(1987)017<1484:MEHFFT>2.0.CO;2, 1987.
Locarnini, R. A., Mishonov, A. V., Antonov, J. I., Boyer, T. P., Garcia, H. E., Baranova, O. K., Zweng, M. M., Paver, C. R., Reagan, J. R., Johnson, D. R., Hamilton, M., and Seidov, D.: World Ocean Atlas 2013, Volume 1: Temperature, edited by: Levitus, S., technically edited by: Mishonov, A., NOAA Atlas NESDIS 73, 40 pp., 2013.
Lueck, R. G. and Picklo, J. J.: Thermal Inertia of Conductivity Cells: Observations with a Sea-Bird Cell, J. Atmos. Ocean. Tech., 7, 756–768, https://doi.org/10.1175/1520-0426(1990)007<0756:TIOCCO>2.0.CO;2, 1990.
Mason, E., Colas, F., Molemaker, J., Shchepetkin, A. F., Troupin, C., McWilliams, J. C., and Sangrà, P.: Seasonal variability of the Canary Current: A numerical study, J. Geophys. Res., 116, C06001, https://doi.org/10.1029/2010JC006665, 2011.
McCarthy, G., Frajka-Williams, E., Johns, W. E., Baringer, M. O., Meinen, C. S., Bryden, H. L., Rayner, D., Duchez, A., Roberts, C., and Cunningham, S. A.: Observed interannual variability of the Atlantic meridional overturning circulation at 26.5° N, Geophys. Res. Lett., 39, 1–5, https://doi.org/10.1029/2012GL052933, 2012.
McCarthy, G. D., Smeed, D. A., Johns, W. E., Frajka-Williams, E., Moat, B. I., Rayner, D., Baringer, M. O., Meinen, C. S., Collins, J., and Bryden, H. L.: Measuring the Atlantic Meridional Overturning Circulation at 26° N, Prog. Oceanogr., 130, 91–111, https://doi.org/10.1016/j.pocean.2014.10.006, 2015.
McDonagh, E. L., King, B. A., Bryden, H. L., Courtois, P., Szuts, Z., Baringer, M., Cunningham, S. A., Atkinson, C., and McCarthy, G.: Continuous estimate of Atlantic oceanic freshwater flux at 26.5° N, J. Climate, 28, 8888–8906, https://doi.org/10.1175/JCLI-D-14-00519.1, 2015.
McDougall, T. J. and Barker, P. M.: Getting started with TEOS-10 and the Gibbs Seawater (GSW) Oceanographic Toolbox, SCOR/IAPSO WG127, 28 pp., available at: http://www.teos-10.org/pubs/Getting_Started.pdf (last access: 10 August 2016), 2011.
Montgomery, R. B.: Comments on “Seasonal variability of the Florida Current”, by Niiler and Richardson, J. Mar. Res., 32, 533–535, 1974.
National Centers for Environmental Prediction/National Weather Service/NOAA/U.S. Department of Commerce: NCEP/NCAR Reanalysis Monthly Mean Subsets (from DS090.0), 1948-continuing, Research Data Archive at the National Center for Atmospheric Research, Computational and Information Systems Laboratory, available at: http://rda.ucar.edu/datasets/ds090.2/ (last access: 20 September 2016), 1996 (updated monthly).
Pérez-Hernández, M. D., McCarthy, G. D., Vélez-Belchí, P., Smeed, D. A., Fraile-Nuez, E., and Hernández-Guerra, A.: The Canary Basin contribution to the seasonal cycle of the Atlantic Meridional Overturning Circulation at 26° N, J. Geophys. Res.-Oceans, 120, 7237–7252, https://doi.org/10.1002/2015JC010969, 2015.
Price, J. F., Weller, R. A., and Schudlich, R. R.: Wind-Driven Ocean Currents and Ekman Transport, Science, 238, 1534–1538, https://doi.org/10.1126/science.238.4833.1534, 1987.
Rabe, B., Schott, F. A., and Köhl, 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.
Roemmich, D. and Gilson, J.: The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program, Prog. Oceanogr., 82, 81–100, https://doi.org/10.1016/j.pocean.2009.03.004, 2009.
Rudnick, D. L. and Klinke, J.: The underway conductivity-temperature-depth instrument, J. Atmos. Ocean. Tech., 24, 1910–1923, https://doi.org/10.1175/JTECH2100.1, 2007.
Saha, S., Moorthi, S., Pan, H.-L., Wu, X., Wang, J., Nadiga, S., Tripp, P., Kistler, R., Woollen, J., Behringer, D., Liu, H., Stokes, D., Grumbine, R., Gayno, G., Wang, J., Hou, Y.-T., Chuang, H.-Y., Juang, H.-M. H., Sela, J., Iredell, M., Treadon, R., Kleist, D., Van Delst, P., Keyser, D., Derber, J., Ek, M., Meng, J., Wei, H., Yang, R., Lord, S., van den Dool, H., Kumar, A., Wang, W., Long, C., Chelliah, M., Xue, Y., Huang, B., Schemm, J.-K., Ebisuzaki, W., Lin, R., Xie, P., Chen, M., Zhou, S., Higgins, W., Zou, C.-Z., Liu, Q., Chen, Y., Han, Y., Cucurull, L., Reynolds, R. W., Rutledge, G., and Goldberg, M.: NCEP Climate Forecast System Reanalysis (CFSR) 6-hourly Products, January 1979 to December 2010, Research Data Archive at the National Center for Atmospheric Research, Computational and Information Systems Laboratory, https://doi.org/10.5065/D69K487J, 2010.
Sato, O. T. and Polito, P. S.: Comparison of the Global Meridional Ekman Heat Flux Estimated from Four Wind Sources, J. Phys. Oceanogr., 35, 94–108, https://doi.org/10.1175/JPO-2665.1, 2005.
Schott, F. A., Dengler, M., Zantopp, R., Stramma, S., 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.
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., Xie, S. P., and Carton, J. A., American Geophysical Union, Washington, D.C., 261–304, https://doi.org/10.1029/147GM15, 2004.
Smith, S. D.: Coefficients for sea surface wind stress, heat flux, and wind profiles as a function of wind speed and temperature, J. Geophys. Res., 93, 15467–15472, https://doi.org/10.1029/JC093iC12p15467, 1988.
Smyth, W. D., Durland, T. S., and Moum, J. N.: Energy and heat fluxes due to vertically propagating Yanai waves observed in the equatorial Indian Ocean, J. Geophys. Res.-Oceans, 120, 1–15, https://doi.org/10.1002/2014JC010152, 2015.
Talley, L. D., Pickard, G. L., Emery, W. J., and Swift, J. H.: Descriptive Physical Oceanography: an introduction, 6th Edn., Elsevier, 555 pp., 2011.
Ullman, D. S. and Hebert, D.: Processing of underway CTD data, J. Atmos. Ocean. Tech., 31, 984–998, https://doi.org/10.1175/JTECH-D-13-00200.1, 2014.
Wang, W. and Huang, R.: Wind Energy Input to the Ekman Layer*, J. Phys. Oceanogr., 34, 1267–1275, https://doi.org/10.1175/1520-0485(2004)034<1267:WEITTE>2.0.CO;2, 2004.
Watanabe, M. and Hibiya, T.: Global estimates of the wind-induced energy flux to inertial motions in the surface mixed layer, Geophys. Res. Lett., 29, 1239, https://doi.org/10.1029/2001GL014422, 2002.
Wijffels, S., Firing, E., and Bryden, H.: Direct Observations of the Ekman Balance at 10° N in the Pacific, J. Phys. Oceanogr., 24, 1666–1679, https://doi.org/10.1175/1520-0485(1994)024<1666:DOOTEB>2.0.CO;2, 1994.
Wijffels, S. E., Toole, J., and Bryden, H.: The water masses and circulation at 10° N in the Pacific, Deep-Sea Res. Pt. I, 43, 501–544, https://doi.org/10.1016/0967-0637(96)00006-4, 1996.
Wunsch, C. and Heimbach, P.: Estimated Decadal Changes in the North Atlantic Meridional Overturning Circulation and Heat Flux 1993–2004, J. Phys. Oceanogr., 36, 2012–2024, https://doi.org/10.1175/JPO2957.1, 2006.
Zhang, J. and Rothrock, D.: Modeling Arctic sea ice with an efficient plastic solution, J. Geophys. Res., 105, 3325, https://doi.org/10.1029/1999JC900320, 2000.
Zweng, M. M., Reagan, J. R., Antonov, J. I., Locarnini, R. A., Mishonov, A. V., Boyer, T. P., Garcia, H. E., Baranova, O. K., Johnson, D. R., Seidov, D., and Biddle, M. M.: World Ocean Atlas 2013, Volume 2: Salinity, edited by: Levitus, S., technically edited by: Mishonov, A., NOAA Atlas NESDIS 74, 39 pp., 2013.
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.
Meridional Ekman transport in the tropical Atlantic was estimated directly by using observed...
