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  • 1
    Online Resource
    Online Resource
    N〈sub〉2〈/sub〉 fixation in eddies of the eastern tropical South Pacific Ocean
    Copernicus GmbH ; 2016
    In:  Biogeosciences Vol. 13, No. 10 ( 2016-05-18), p. 2889-2899
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 13, No. 10 ( 2016-05-18), p. 2889-2899
    Abstract: Abstract. Mesoscale eddies play a major role in controlling ocean biogeochemistry. By impacting nutrient availability and water column ventilation, they are of critical importance for oceanic primary production. In the eastern tropical South Pacific Ocean off Peru, where a large and persistent oxygen-deficient zone is present, mesoscale processes have been reported to occur frequently. However, investigations into their biological activity are mostly based on model simulations, and direct measurements of carbon and dinitrogen (N2) fixation are scarce.We examined an open-ocean cyclonic eddy and two anticyclonic mode water eddies: a coastal one and an open-ocean one in the waters off Peru along a section at 16° S in austral summer 2012. Molecular data and bioassay incubations point towards a difference between the active diazotrophic communities present in the cyclonic eddy and the anticyclonic mode water eddies.In the cyclonic eddy, highest rates of N2 fixation were measured in surface waters but no N2 fixation signal was detected at intermediate water depths. In contrast, both anticyclonic mode water eddies showed pronounced maxima in N2 fixation below the euphotic zone as evidenced by rate measurements and geochemical data. N2 fixation and carbon (C) fixation were higher in the young coastal mode water eddy compared to the older offshore mode water eddy. A co-occurrence between N2 fixation and biogenic N2, an indicator for N loss, indicated a link between N loss and N2 fixation in the mode water eddies, which was not observed for the cyclonic eddy. The comparison of two consecutive surveys of the coastal mode water eddy in November 2012 and December 2012 also revealed a reduction in N2 and C fixation at intermediate depths along with a reduction in chlorophyll by half, mirroring an aging effect in this eddy. Our data indicate an important role for anticyclonic mode water eddies in stimulating N2 fixation and thus supplying N offshore.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    URL: Article
    DOI: 10.5194/bg-13-2889-2016
    DOI: 10.5194/bg-13-2889-2016-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
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  • 2
    Online Resource
    Online Resource
    Oxygen decreases and variability in the eastern equatorial Pacific : OXYGEN DECREASES IN EQUATORIAL PACIFIC
    American Geophysical Union (AGU) ; 2012
    In:  Journal of Geophysical Research: Oceans Vol. 117, No. C11 ( 2012-11), p. n/a-n/a
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 117, No. C11 ( 2012-11), p. n/a-n/a
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2012JC008043
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2012
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    detail.hit.zdb_id: 3094181-7
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    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
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    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    Transport, properties, and life cycles of mesoscale eddies in the eastern tropical South Pacific
    Copernicus GmbH ; 2018
    In:  Ocean Science Vol. 14, No. 4 ( 2018-07-31), p. 731-750
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 14, No. 4 ( 2018-07-31), p. 731-750
    Abstract: Abstract. The influence of mesoscale eddies on the flow field and the water masses, especially the oxygen distribution of the eastern tropical South Pacific, is investigated from a mooring, float, and satellite data set. Two anticyclonic (ACE1/2), one mode-water (MWE), and one cyclonic eddy (CE) are identified and followed in detail with satellite data on their westward transition with velocities of 3.2 to 6.0 cm s−1 from their generation region, the shelf of the Peruvian and Chilean upwelling regime, across the Stratus Ocean Reference Station (ORS; ∼20∘ S, 85∘ W) to their decaying region far west in the oligotrophic open ocean. The ORS is located in the transition zone between the oxygen minimum zone and the well oxygenated South Pacific subtropical gyre. Velocity, hydrographic, and oxygen measurements at the mooring show the impact of eddies on the weak flow region of the eastern tropical South Pacific. Strong anomalies are related to the passage of eddies and are not associated with a seasonal signal in the open ocean. The mass transport of the four observed eddies across 85∘ W is between 1.1 and 1.8 Sv. The eddy type-dependent available heat, salt, and oxygen anomalies are 8.1×1018 J (ACE2), 1.0×1018 J (MWE), and -8.9×1018 J (CE) for heat; 25.2×1010 kg (ACE2), -3.1×1010 kg (MWE), and -41.5×1010 kg (CE) for salt; and -3.6×1016 µmol (ACE2), -3.5×1016 µmol (MWE), and -6.5×1016 µmol (CE) for oxygen showing a strong imbalance between anticyclones and cyclones for salt transports probably due to seasonal variability in water mass properties in the formation region of the eddies. Heat, salt, and oxygen fluxes out of the coastal region across the ORS region in the oligotrophic open South Pacific are estimated based on these eddy anomalies and on eddy statistics (gained out of 23 years of satellite data). Furthermore, four profiling floats were trapped in the ACE2 during its westward propagation between the formation region and the open ocean, which allows for conclusions on lateral mixing of water mass properties with time between the core of the eddy and the surrounding water. The strongest lateral mixing was found between the seasonal thermocline and the eddy core during the first half of the eddy lifetime.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    URL: Article
    DOI: 10.5194/os-14-731-2018
    DOI: 10.5194/os-14-731-2018-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
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  • 4
    Online Resource
    Online Resource
    Atlantic Equatorial Undercurrent intensification counteracts warming-induced deoxygenation
    Springer Science and Business Media LLC ; 2021
    In:  Nature Geoscience Vol. 14, No. 5 ( 2021-05), p. 278-282
    Details
    In: Nature Geoscience, Springer Science and Business Media LLC, Vol. 14, No. 5 ( 2021-05), p. 278-282
    Type of Medium: Online Resource
    ISSN: 1752-0894 , 1752-0908
    URL: Article
    DOI: 10.1038/s41561-021-00716-1
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
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    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Eddies and an extreme water mass anomaly observed in the eastern south Pacific at the Stratus mooring
    American Geophysical Union (AGU) ; 2014
    In:  Journal of Geophysical Research: Oceans Vol. 119, No. 2 ( 2014-02), p. 1068-1083
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 119, No. 2 ( 2014-02), p. 1068-1083
    Abstract: Anticyclonic eddy carried low oxygen water from the Chilean shelf to ∼20°S, 85.5°W Water mass in the eddy was isolated for about 11 months Sea surface height anomaly is not sufficient to specify eddy strength
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Issue
    URL: Article
    DOI: 10.1002/jgrc.v119.2
    DOI: 10.1002/2013JC009470
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2014
    detail.hit.zdb_id: 2016804-4
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    SSG: 16,13
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  • 6
    Online Resource
    Online Resource
    Middepth circulation of the eastern tropical South Pacific and its link to the oxygen minimum zone
    American Geophysical Union (AGU) ; 2011
    In:  Journal of Geophysical Research Vol. 116, No. C1 ( 2011-01-21)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 116, No. C1 ( 2011-01-21)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2010JC006565
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2011
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    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Seasonal variability of the Arabian Sea intermediate circulation and its impact on seasonal changes of the upper oxygen minimum zone
    Copernicus GmbH ; 2020
    In:  Ocean Science Vol. 16, No. 6 ( 2020-11-27), p. 1459-1474
    Details
    In: Ocean Science, Copernicus GmbH, Vol. 16, No. 6 ( 2020-11-27), p. 1459-1474
    Abstract: Abstract. Oxygen minimum zones (OMZs) in the open ocean occur below the surface in regions of weak ventilation and high biological productivity with associated sinking organic matter. Very low levels of dissolved oxygen alter biogeochemical cycles and significantly affect marine life. One of the most intense though poorly understood OMZs in the world ocean is located in the Arabian Sea between 300 and 1000 m of depth. An improved understanding of the physical processes that have an impact on the OMZ in the Arabian Sea is expected to increase the reliability of assessments of its future development. This study uses reanalysis velocity fields from the ocean model HYCOM (Hybrid Coordinate Ocean Model), which are verified with observational data, to investigate advective pathways of Lagrangian particles into the Arabian Sea OMZ at intermediate depths between 200 and 800 m. In the eastern basin, the vertical expansion of the OMZ is strongest during the winter monsoon, revealing a core thickness 1000 m deep and oxygen values below 5 µmol kg−1. The minimum oxygen concentration might be favoured by a maximum water mass advection that follows the main advective pathway of Lagrangian particles along the perimeter of the basin into the eastern basin of the Arabian Sea during the winter monsoon. These water masses pass regions of high primary production and respiration, contributing to the transport of low-oxygenated water into the eastern part of the OMZ. The maximum oxygen concentration in the western basin of the Arabian Sea in May coincides with a maximum southward water mass advection in the western basin during the spring intermonsoon, supplying the western core of the OMZ with high-oxygenated water. The maximum oxygen concentration in the eastern basin of the Arabian Sea in May might be associated with the northward inflow of water across 10∘ N into the Arabian Sea, which is highest during the spring intermonsoon. The Red Sea outflow of advective particles into the western and eastern basin starts during the summer monsoon associated with the northeastward current during the summer monsoon. On the other hand, waters from the Persian Gulf are advected with little variation on seasonal timescales. As the weak seasonal cycle of oxygen concentration in the eastern and western basin can be explained by seasonally changing advection of water masses at intermediate depths into the Arabian Sea OMZ (ASOMZ), the simplified backward-trajectory approach seems to be a good method for prediction of the seasonality of advective pathways of Lagrangian particles into the ASOMZ.
    Type of Medium: Online Resource
    ISSN: 1812-0792
    URL: Article
    URL: Article
    DOI: 10.5194/os-16-1459-2020
    DOI: 10.5194/os-16-1459-2020-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
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  • 8
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    Ocean cross-validated observations from R/Vs L'Atalante , Maria S. Merian , and Meteor and related platforms as part of the EUREC 4 A-OA/ATOMIC campaign
    Copernicus GmbH ; 2023
    In:  Earth System Science Data Vol. 15, No. 4 ( 2023-04-25), p. 1801-1830
    Details
    In: Earth System Science Data, Copernicus GmbH, Vol. 15, No. 4 ( 2023-04-25), p. 1801-1830
    Abstract: Abstract. The northwestern Tropical Atlantic Ocean is a turbulent region, filled with mesoscale eddies and regional currents. In this intense dynamical context, several water masses with thermohaline characteristics of different origins are advected, mixed, and stirred at the surface and at depth. The EUREC4A-OA/ATOMIC experiment that took place in January and February 2020 was dedicated to assessing the processes at play in this region, especially the interaction between the ocean and the atmosphere. For that reason, four oceanographic vessels and different autonomous platforms measured properties near the air–sea interface and acquired thousands of upper-ocean (up to 400–2000 m depth) profiles. However, each device had its own observing capability, varying from deep measurements acquired during vessel stations to shipboard underway near-surface observations and measurements from autonomous and uncrewed systems (such as Saildrones). These observations were undertaken with a specific sampling strategy guided by near-real-time satellite maps and adapted every half day, based on the process that was investigated. These processes were characterized by different spatiotemporal scales, from mesoscale eddies, with diameters exceeding 100 km, to submesoscale filaments of 1 km width. This article describes the datasets gathered from the different devices and how the data were calibrated and validated. In order to ensure an overall consistency, the platforms' datasets are cross-validated using a hierarchy of instruments defined by their own specificity and calibration procedures. This has enabled the quantification of the uncertainty in the measured parameters when different datasets are used together, e.g., https://doi.org/10.17882/92071 (L'Hégaret et al., 2020a).
    Type of Medium: Online Resource
    ISSN: 1866-3516
    URL: Article
    DOI: 10.5194/essd-15-1801-2023
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2023
    detail.hit.zdb_id: 2475469-9
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