Description: We use a coupled physical–biogeochemical model to investigate the drivers and mechanisms responsible for the spatiotemporal variability of the partial pressure of carbon dioxide in seawater (pCO2) and associated air–sea CO2 fluxes in the Northern Humboldt Current System (NHCS). Simulated pCO2 is in good agreement with available observations with an average absolute error of, approximately, 24 µatm. The highly productive upwelling region, 300 km from the shore and between 5 and 17 °S, is shown to be a strong CO2 source with an averaged flux of 5.60  ±  2.94 mol C m year which represents an integrated carbon flux of 0.028  ±  0.015 Pg C year. Through a series of model experiments we show that the high pCO2 is primarily the result of coastal upwelling, which is incompletely compensated by biology. Specifically, the supply of dissolved inorganic carbon (DIC)-rich waters to the surface pushes pCO2 up to levels around 1100 µatm. Even though biological production is high, it reduces pCO2 only by about 300 µatm. We show that this relatively low degree of biological compensation, which implies an inefficient biological pump in the nearshore domain, results from a spatiotemporal decoupling between the counteracting effects of biological production and the transport and mixing of DIC. The contribution of the outgassing and the processes affecting CO2 solubility, associated with the seasonal cycle of heating and cooling, are minor. Across the whole domain, the balance of mechanisms is similar, but with smaller amplitudes. We demonstrate that seawater pCO2 is more sensitive to changes in DIC and sea surface temperature, while alkalinity plays a minor role.

Description: Cruise M160 is part of concerted MOSES/REEBUS Eddy Study featuring three major research expeditions (M156, M160, MSM104). It aims to develop both a qualitative and quantitative understanding of the role of physical-chemical-biological coupling in eddies for the biological pump. The study is part of the MOSES “Ocean Eddies” event chain, which follows three major hypotheses to be addressed by the MOSES/REEBUS field campaigns: (1) Mesoscale and sub-mesoscale eddies play an important role in transferring energy along the energy cascade from the large-scale circulation to dissipation at the molecular level. (2) Mesoscale and sub-mesoscale eddies are important drivers in determining onset, magnitude and characteristics of biological productivity in the ocean and contribute significantly to global primary production and particle export and transfer to the deep ocean. (3) Mesoscale and sub-mesoscale eddies are important for shaping extreme biogeochemical environments (e.g., pH, oxygen) in the oceans, thus acting as a source/sink function for greenhouse gases. In contrast to the other two legs, MOSES Eddy Study II during M160 did not include any benthic work but focused entirely on the pelagic dynamics within eddies. It accomplished a multi-disciplinary, multi-parameter and multi-platform study of two discrete cyclonic eddies in an unprecedented complexity. The pre-cruise search for discrete eddies suitable for detailed study during M160 had already started a few months prior to the cruise. Remote sensing data products (sea surface height, sea surface temperature, ocean color/chlorophyll a) were used in combination with eddy detection algorithms and numerical modelling to identify and track eddies in the entire eddy field off West Africa. In addition, 2 gliders and 1 waveglider had been set out from Mindelo/Cabo Verde for pre-cruise mapping of the potential working area north of the Cabo Verdean archipelago. At the start of M160, a few suitable eddies – mostly of cyclonic type – had been identified, some of which were outside the safe operation range of the motorglider plane. As technical problems delayed the flight operations, the first eddy (center at 14.5°N/25°W) for detailed study was chosen to the southwest of the island of Fogo. It was decided to carry out a first hydrographic survey there followed by the deployment of a suite of instruments (gliders, waveglider, floats, drifter short-term mooring). Such instrumented, we left this first eddy and transited – via a strong anticyclonic feature southwest of the island of Santiago – to the region northeast of the island of Sal, i.e. in the working range of the glider plane. During the transit, a full suite of underway measurements as well as CTD/RO section along 22°W (16°-18.5°N) were carried in search for sub-surface expressions of anticyclonic eddy features. In the northeast, we had identified the second strong cyclonic eddy (center at 18°N/22.5°W) which was chosen for detailed study starting with a complete hydrographic survey (ADCP, CTD/RO, other routine station work). After completion of the mesoscale work program, we identified a strong frontal region at the southwestern rim of the cyclonic eddy, which was chosen for the first sub-mesoscale study with aerial observation component. There, the first dye release experiment was carried out which consisted of the dye release itself followed by an intense multi-platforms study of the vertical and horizontal spreading of the initial dye streak. This work was METEOR-Berichte, Cruise M160, Mindelo – Mindelo, 23.11.2019 4 – 20.12.2019 supported and partly guided by aerial observation of the research motorglider Stemme, which was still somewhat compromised by technical issues and meteorological conditions (high cloud cover, Saharan dust event). Nevertheless, this first dye release experiment was successful and showed rapid movement of the dynamic meandering front. After completion of work on this second eddy and execution of a focused sampling program at the Cape Verde Ocean Observation, RV METEOR returned to the first eddy for continuation of the work started there in the beginning of the cruise. This was accompanied by a relocation of the airbase of Stemme from the international airport of Sal to the domestic airport of Fogo. The further execution of the eddy study at this first eddy, which again included a complete hydrographic survey followed by a mesoscale eddy study with dye release, was therefore possible with aerial observations providing important guidance for work on RV METEOR. Overall, M160 accomplished an extremely intense and complex work program with 212 instrument deployments during station work, 137 h of observation with towed instruments and a wide range of underway measurements throughout the cruise. Up to about 30 individually tracked platforms (Seadrones, glider, wavegliders, drifters, floats) were in the water at the same time providing unprecedented and orchestrated observation capabilities in an eddy. All planned work components were achieved and all working groups acquired the expected numbers of instrument deployments and sampling opportunities.

Description: The Argo Program has been implemented and sustained for almost two decades, as a global array of about 4000 profiling floats. Argo provides continuous observations of ocean temperature and salinity versus pressure, from the sea surface to 2000 dbar. The successful installation of the Argo array and its innovative data management system arose opportunistically from the combination of great scientific need and technological innovation. Through the data system, Argo provides fundamental physical observations with broad societally-valuable applications, built on the cost-efficient and robust technologies of autonomous profiling floats. Following recent advances in platform and sensor technologies, even greater opportunity exists now than 20 years ago to (i) improve Argo's global coverage and value beyond the original design, (ii) extend Argo to span the full ocean depth, (iii) add biogeochemical sensors for improved understanding of oceanic cycles of carbon, nutrients, and ecosystems, and (iv) consider experimental sensors that might be included in the future, for example to document the spatial and temporal patterns of ocean mixing. For Core Argo and each of these enhancements, the past, present, and future progression along a path from experimental deployments to regional pilot arrays to global implementation is described. The objective is to create a fully global, top-to-bottom, dynamically complete, and multidisciplinary Argo Program that will integrate seamlessly with satellite and with other in situ elements of the Global Ocean Observing System (Legler et al., 2015). The integrated system will deliver operational reanalysis and forecasting capability, and assessment of the state and variability of the climate system with respect to physical, biogeochemical, and ecosystems parameters. It will enable basic research of unprecedented breadth and magnitude, and a wealth of ocean-education and outreach opportunities.

Description: Ocean boundary current systems are key components of the climate system, are home to highly productive ecosystems, and have numerous societal impacts. Establishment of a global network of boundary current observing systems is a critical part of ongoing development of the Global Ocean Observing System. The characteristics of boundary current systems are reviewed, focusing on scientific and societal motivations for sustained observing. Techniques currently used to observe boundary current systems are reviewed, followed by a census of the current state of boundary current observing systems globally. The next steps in the development of boundary current observing systems are considered, leading to several specific recommendations.

Description: Mesoscale eddies in the ocean strongly impact the distribution of planktonic particles, mediating carbon fluxes over ~1/3 of the world ocean. However, mechanisms controlling particle transport through eddies are complex and challenging to measure in situ. Here we show the subsurface distribution of eddy particles funneled into a wineglass shape down to 1000 m, leading to a sevenfold increase of vertical carbon flux in the eddy center versus the eddy flanks, the “wineglass effect”. We show that the slope of the wineglass (R) is the ratio of particle sinking velocity to the radially inward velocity, such that R represents a tool to predict radial particle movement (here 0.05ms�1). A simple model of eddy spindown predicts such an ageostrophic flow concentrating particles in the eddy center. We explore how size-specific particle flux toward the eddy center impacts eddies' biogeochemistry and export fluxes.

Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 12 (2015): 5793-5809, doi:10.5194/bg-12-5793-2015.

Description: We use an eddy-resolving, regional ocean biogeochemical model to investigate the main variables and processes responsible for the climatological spatio-temporal variability of pCO2 and the air-sea CO2 fluxes in the southwestern Atlantic Ocean. Overall, the region acts as a sink of atmospheric CO2 south of 30° S, and is close to equilibrium with the atmospheric CO2 to the north. On the shelves, the ocean acts as a weak source of CO2, except for the mid/outer shelves of Patagonia, which act as sinks. In contrast, the inner shelves and the low latitude open ocean of the southwestern Atlantic represent source regions. Observed nearshore-to-offshore and meridional pCO2 gradients are well represented by our simulation. A sensitivity analysis shows the importance of the counteracting effects of temperature and dissolved inorganic carbon (DIC) in controlling the seasonal variability of pCO2. Biological production and solubility are the main processes regulating pCO2, with biological production being particularly important on the shelves. The role of mixing/stratification in modulating DIC, and therefore surface pCO2, is shown in a vertical profile at the location of the Ocean Observatories Initiative (OOI) site in the Argentine Basin (42° S, 42° W).

Description: P. H. R. Calil acknowledges support from the Brazilian agencies Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), grants 483112/2012-7 and 307385/2013-2, and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES Process 23038.004299/2014-53). R. Arruda acknowledges support from a CAPES scholarship. S. C. Doney and I. Lima acknowledge support from the National Science Foundation (NSF AGS-1048827). N. Gruber and G. Turi received support from ETH Zurich and from the EU FP7 project CarboChange (264879).

Description: Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(12), (2019): 3127-3143, doi: 10.1175/JPO-D-19-0011.1.

Description: The Intermediate Western Boundary Current (IWBC) transports Antarctic Intermediate Water across the Vitória–Trindade Ridge (VTR), a seamount chain at ~20°S off Brazil. Recent studies suggest that the IWBC develops a strong cyclonic recirculation in Tubarão Bight, upstream of the VTR, with weak time dependency. We herein use new quasi-synoptic observations, data from the Argo array, and a regional numerical model to describe the structure and variability of the IWBC and to investigate its dynamics. Both shipboard acoustic Doppler current profiler (ADCP) data and trajectories of Argo floats confirm the existence of the IWBC recirculation, which is also captured by our Regional Oceanic Modeling System (ROMS) simulation. An “intermediate-layer” quasigeostrophic (QG) model indicates that the ROMS time-mean flow is a good proxy for the IWBC steady state, as revealed by largely parallel isolines of streamfunction ψ⎯ and potential vorticity Q⎯; a ψ⎯−Q⎯ scatter diagram also shows that the IWBC is potentially unstable. Further analysis of the ROMS simulation reveals that remotely generated, westward-propagating nonlinear eddies are the main source of variability in the region. These eddies enter the domain through the Tubarão Bight eastern edge and strongly interact with the IWBC. As they are advected downstream and negotiate the local topography, the eddies grow explosively through horizontal shear production.

Description: We thank Frank O. Smith for copy editing and proofreading this manuscript. This study was financed in part by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—CAPES, Brazil—Finance Code 001 and by Projeto REMARSUL (Processo CAPES 88882.158621/2014-01), Projeto VT-Dyn (Processo FAPESP 2015/21729-4) and Projeto SUBMESO (Processo CNPq 442926/2015-4). Rocha was supported by a WHOI Postdoctoral Scholarship.

Description: 2020-06-06

Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Todd, R. E., Chavez, F. P., Clayton, S., Cravatte, S., Goes, M., Greco, M., Ling, X., Sprintall, J., Zilberman, N., V., Archer, M., Aristegui, J., Balmaseda, M., Bane, J. M., Baringer, M. O., Barth, J. A., Beal, L. M., Brandt, P., Calil, P. H. R., Campos, E., Centurioni, L. R., Chidichimo, M. P., Cirano, M., Cronin, M. F., Curchitser, E. N., Davis, R. E., Dengler, M., deYoung, B., Dong, S., Escribano, R., Fassbender, A. J., Fawcett, S. E., Feng, M., Goni, G. J., Gray, A. R., Gutierrez, D., Hebert, D., Hummels, R., Ito, S., Krug, M., Lacan, F., Laurindo, L., Lazar, A., Lee, C. M., Lengaigne, M., Levine, N. M., Middleton, J., Montes, I., Muglia, M., Nagai, T., Palevsky, H., I., Palter, J. B., Phillips, H. E., Piola, A., Plueddemann, A. J., Qiu, B., Rodrigues, R. R., Roughan, M., Rudnick, D. L., Rykaczewski, R. R., Saraceno, M., Seim, H., Sen Gupta, A., Shannon, L., Sloyan, B. M., Sutton, A. J., Thompson, L., van der Plas, A. K., Volkov, D., Wilkin, J., Zhang, D., & Zhang, L. Global perspectives on observing ocean boundary current systems. Frontiers in Marine Science, 6, (2010); 423, doi: 10.3389/fmars.2019.00423.

Description: Ocean boundary current systems are key components of the climate system, are home to highly productive ecosystems, and have numerous societal impacts. Establishment of a global network of boundary current observing systems is a critical part of ongoing development of the Global Ocean Observing System. The characteristics of boundary current systems are reviewed, focusing on scientific and societal motivations for sustained observing. Techniques currently used to observe boundary current systems are reviewed, followed by a census of the current state of boundary current observing systems globally. The next steps in the development of boundary current observing systems are considered, leading to several specific recommendations.

Description: RT was supported by The Andrew W. Mellon Foundation Endowed Fund for Innovative Research at WHOI. FC was supported by the David and Lucile Packard Foundation. MGo was funded by NSF and NOAA/AOML. XL was funded by China’s National Key Research and Development Projects (2016YFA0601803), the National Natural Science Foundation of China (41490641, 41521091, and U1606402), and the Qingdao National Laboratory for Marine Science and Technology (2017ASKJ01). JS was supported by NOAA’s Global Ocean Monitoring and Observing Program (Award NA15OAR4320071). DZ was partially funded by the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement NA15OAR4320063. BS was supported by IMOS and CSIRO’s Decadal Climate Forecasting Project. We gratefully acknowledge the wide range of funding sources from many nations that have enabled the observations and analyses reviewed here.

Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Roemmich, D., Alford, M. H., Claustre, H., Johnson, K., King, B., Moum, J., Oke, P., Owens, W. B., Pouliquen, S., Purkey, S., Scanderbeg, M., Suga, T., Wijffels, S., Zilberman, N., Bakker, D., Baringer, M., Belbeoch, M., Bittig, H. C., Boss, E., Calil, P., Carse, F., Carval, T., Chai, F., Conchubhair, D. O., d'Ortenzio, F., Dall'Olmo, G., Desbruyeres, D., Fennel, K., Fer, I., Ferrari, R., Forget, G., Freeland, H., Fujiki, T., Gehlen, M., Greenan, B., Hallberg, R., Hibiya, T., Hosoda, S., Jayne, S., Jochum, M., Johnson, G. C., Kang, K., Kolodziejczyk, N., Kortzinger, A., Le Traon, P., Lenn, Y., Maze, G., Mork, K. A., Morris, T., Nagai, T., Nash, J., Garabato, A. N., Olsen, A., Pattabhi, R. R., Prakash, S., Riser, S., Schmechtig, C., Schmid, C., Shroyer, E., Sterl, A., Sutton, P., Talley, L., Tanhua, T., Thierry, V., Thomalla, S., Toole, J., Troisi, A., Trull, T. W., Turton, J., Velez-Belchi, P. J., Walczowski, W., Wang, H., Wanninkhof, R., Waterhouse, A. F., Waterman, S., Watson, A., Wilson, C., Wong, A. P. S., Xu, J., & Yasuda, I. On the future of Argo: A global, full-depth, multi-disciplinary array. Frontiers in Marine Science, 6, (2019): 439, doi:10.3389/fmars.2019.00439.

Description: The Argo Program has been implemented and sustained for almost two decades, as a global array of about 4000 profiling floats. Argo provides continuous observations of ocean temperature and salinity versus pressure, from the sea surface to 2000 dbar. The successful installation of the Argo array and its innovative data management system arose opportunistically from the combination of great scientific need and technological innovation. Through the data system, Argo provides fundamental physical observations with broad societally-valuable applications, built on the cost-efficient and robust technologies of autonomous profiling floats. Following recent advances in platform and sensor technologies, even greater opportunity exists now than 20 years ago to (i) improve Argo’s global coverage and value beyond the original design, (ii) extend Argo to span the full ocean depth, (iii) add biogeochemical sensors for improved understanding of oceanic cycles of carbon, nutrients, and ecosystems, and (iv) consider experimental sensors that might be included in the future, for example to document the spatial and temporal patterns of ocean mixing. For Core Argo and each of these enhancements, the past, present, and future progression along a path from experimental deployments to regional pilot arrays to global implementation is described. The objective is to create a fully global, top-to-bottom, dynamically complete, and multidisciplinary Argo Program that will integrate seamlessly with satellite and with other in situ elements of the Global Ocean Observing System (Legler et al., 2015). The integrated system will deliver operational reanalysis and forecasting capability, and assessment of the state and variability of the climate system with respect to physical, biogeochemical, and ecosystems parameters. It will enable basic research of unprecedented breadth and magnitude, and a wealth of ocean-education and outreach opportunities.

Description: DR, MS, and NZ were supported by the US Argo Program through the NOAA Grant NA15OAR4320071 (CIMEC). WO, SJ, and SWi were supported by the US Argo Program through the NOAA Grant NA14OAR4320158 (CINAR). EuroArgo scientists were supported by the two grants: (1) AtlantOS funding by the European Union’s Horizon 2020 Research and Innovation Programme under the Grant Agreement No. 633211 and (2) Monitoring the Oceans and Climate Change with Argo (MOCCA) Co-funded by the European Maritime and Fisheries Fund (EMFF) Project No. SI2.709624. This manuscript represents a contribution to the following research projects for HC, CaS, and FD: remOcean (funded by the European Research Council, grant 246777), NAOS (funded by the Agence Nationale de la Recherche in the frame of the French “Equipement d’avenir” program, grant ANR J11R107-F), AtlantOS (funded by the European Union’s Horizon 2020 Research and Innovation Programme, grant 2014-633211), and the BGC-Argo project funded by the CNES. DB was funded by the EU RINGO project (730944 H2020-INFRADEV-2016-1). RF was supported by the AGS-1835576. GCJ was supported by the Global Ocean Monitoring and Observing Program, National Oceanic and Atmospheric Administration (NOAA), U.S., and the Department of Commerce and NOAA Research. LT was funded under the SOCCOM Grant No. NSF PLR-1425989. VT’s contribution was supported by the French National Research Agency (ANR) through the EQUIPEX NAOS (Novel Argo Observing System) under the reference ANR-10-EQPX-40 and by the European H2020 Research and Innovation Programme through the AtlantOS project under the reference 633211. WW was supported by the Argo Poland program through the Ministry of Sciences and Higher Education Grant No. DIR/WK/2016/12. AmW was funded by the NSF-OCE1434722. K-RK is funded by the National Institute of Meteorological Sciences’ Research and Development Program “Development of Marine Meteorology Monitoring and Next-generation Ocean Forecasting System” under the grant KMA2018-00421. CSchmid is funded by NOAA/AOML and the US Argo Program through NOAA/OOMD. MBa is funded by NOAA/AOML.

Description: Eastward zonal jets at intermediate depths of 300–800 m connect the oxygen‐rich western boundary of the Atlantic basin with the oxygen minimum zones (OMZs) on the eastern boundary. They are not well represented in climate models because the low horizontal resolution of these models yields excessive viscosity. We use two physical‐biogeochemical model configurations of the Tropical Atlantic to show that the increase in resolution results in more robust intermediate zonal jets and a better representation of the OMZs. The OMZ structure is distorted at low‐resolution as surface, westward jets advect low‐oxygen waters from the eastern boundary much further west than in the climatology. The emergence of robust eastward jets in the high‐resolution run alleviate this problem and reproduce the Atlantic OMZs more accurately. The asymmetry between westward and eastward jets occurs because the former are associated with homogenous potential vorticity regions originating in the eastern boundary while the latter are associated with potential vorticity gradients. Intermediate, eastward jets constrain the westward expansion of the OMZs by supplying oxygen to their western edge. Within the OMZs, higher resolution allows a better representation of the boundary current system and eddying processes at depth which redistribute of low oxygen values from the productive eastern boundary. Basin‐scale, high‐resolution simulations reproduce more accurately the transfer of energy across scales that results in robust zonal jets as well as their impact on the ocean biogeochemistry. Accurate model predictions provide a pathway to disentangle natural and anthropogenic causes of ocean deoxygenation.

Description: Plain Language Summary: Long‐term averages of ocean velocities reveal the existence of east‐west, alternating currents along multiple latitudes. These currents are difficult to observe and model because of their small speeds at great depths. Despite their low intensity, in the long‐term they can transport tracers across the ocean basins with oxygen being a very important one as it provides conditions for aerobic respiration in so‐called oxygen minimum zones (OMZs) on the eastern side of the basin. Long‐term measurements show that oxygen concentrations are decreasing in various regions of the ocean and that OMZs are expanding, which can be a problem as these regions may become inhospitable for aerobic life. That is why we need to understand the processes that supply oxygen to OMZs and are important for their evolution with time. Models can be used as tools for testing hypotheses regarding the expansion or contraction of OMZs in the future. However, models must be shown to correctly simulate the dynamics and biogeochemistry of the region as a whole. Our results show that these intermediate east‐west current systems are important in structuring the OMZs and that higher‐resolution, basin‐scale simulations are necessary to correctly simulate their impact on oxygen concentrations in the ocean.

Description: Key Points: Intermediate, eastward zonal jets are an important oxygen supply route to the oxygen minimum zones and modulate their westward extent. Robust, intermediate zonal jets emerge in a high‐resolution (3 km), basin‐scale simulation with robust eddying motions at depth. A correct representation of the zonal jets in climate models is key for reliable, long‐term forecasts of ocean deoxygenation.

Description: Changing Earth ‐ Helmholtz Association

Description: https://doi.org/10.5281/zenodo.7229219

Description: https://doi.org/10.5281/zenodo.7081664

Description: https://doi.org/10.5281/zenodo.7234366