Browsing by Author "Garçon, Véronique"
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Item Open Access A global ocean oxygen database and atlas for assessing and predicting deoxygenation and ocean health in the open and coastal ocean(Frontiers Media, 2021-12-21) Grégoire, Marilaure; Garçon, Véronique; Garcia, Hernan; Breitburg, Denise; Isensee, Kirsten; Oschlies, Andreas; Telszewski, Maciej; Barth, Alexander; Bittig, Henry C.; Carstensen, Jacob; Carval, Thierry; Chai, Fei; Chavez, Francisco; Conley, Daniel; Coppola, Laurent; Crowe, Sean; Currie, Kim; Dai, Minhan; Deflandre, Bruno; Dewitte, Boris; Diaz, Robert; Garcia-Robledo, Emilio; Gilbert, Denis; Giorgetti, Alessandra; Glud, Ronnie; Gutierrez, Dimitri; Hosoda, Shigeki; Ishii, Masao; Jacinto, Gil; Langdon, Chris; Lauvset, Siv K.; Levin, Lisa A.; Limburg, Karin E.; Mehrtens, Hela; Montes Torres, Ivonne; Naqvi, Wajih; Paulmier, Aurélien; Pfeil, Benjamin; Pitcher, Grant; Pouliquen, Sylvie; Rabalais, Nancy; Rabouille, Christophe; Recape, Virginie; Roman, Michaël; Rose, Kenneth; Rudnick, Daniel; Rummer, Jodie; Schmechtig, Catherine; Schmidtko, Sunke; Seibel, Brad; Slomp, Caroline; Sumalia, U. Rashid; Tanhua, Toste; Thierry, Virginie; Uchida, Hiroshi; Wanninkhof, Rik; Yasuhara, MoriakiIn this paper, we outline the need for a coordinated international effort toward the building of an open-access Global Ocean Oxygen Database and ATlas (GO₂DAT) complying with the FAIR principles (Findable, Accessible, Interoperable, and Reusable). GO₂DAT will combine data from the coastal and open ocean, as measured by the chemical Winkler titration method or by sensors (e.g., optodes, electrodes) from Eulerian and Lagrangian platforms (e.g., ships, moorings, profiling floats, gliders, ships of opportunities, marine mammals, cabled observatories). GO₂DAT will further adopt a community-agreed, fully documented metadata format and a consistent quality control (QC) procedure and quality flagging (QF) system. GO₂DAT will serve to support the development of advanced data analysis and biogeochemical models for improving our mapping, understanding and forecasting capabilities for ocean O₂ changes and deoxygenation trends. It will offer the opportunity to develop quality-controlled data synthesis products with unprecedented spatial (vertical and horizontal) and temporal (sub-seasonal to multi-decadal) resolution. These products will support model assessment, improvement and evaluation as well as the development of climate and ocean health indicators. They will further support the decision-making processes associated with the emerging blue economy, the conservation of marine resources and their associated ecosystem services and the development of management tools required by a diverse community of users (e.g., environmental agencies, aquaculture, and fishing sectors). A better knowledge base of the spatial and temporal variations of marine O₂ will improve our understanding of the ocean O₂ budget, and allow better quantification of the Earth’s carbon and heat budgets. With the ever-increasing need to protect and sustainably manage ocean services, GO₂DAT will allow scientists to fully harness the increasing volumes of O₂ data already delivered by the expanding global ocean observing system and enable smooth incorporation of much higher quantities of data from autonomous platforms in the open ocean and coastal areas into comprehensive data products in the years to come. This paper aims at engaging the community (e.g., scientists, data managers, policy makers, service users) toward the development of GO₂DAT within the framework of the UN Global Ocean Oxygen Decade (GOOD) program recently endorsed by IOC-UNESCO. A roadmap toward GO₂DAT is proposed highlighting the efforts needed (e.g., in terms of human resources).Item Restricted Boundaries of the Peruvian oxygen minimum zone shaped by coherent mesoscale dynamics(Nature Research, 2015) Bettencourt, Joao; López, Cristobal; Hernández-García, Emilio; Montes Torres, Ivonne; Sudre, Joël; Dewitte, Boris; Paulmier, Aurélien; Garçon, VéroniqueDissolved oxygen in sea water is a major factor affecting marine habitats and biogeochemical cycles. Oceanic zones with oxygen deficits represent significant portions of the area and volume of the oceans and are thought to be expanding. The Peruvian oxygen minimum zone is one of the most pronounced and lies in a region of strong mesoscale activity in the form of vortices and frontal regions, whose effect in the dynamics of the oxygen minimum zone is largely unknown. Here, we study this issue from a modeling approach and a Lagrangian point of view, using a coupled physical-biogeochemical simulation of the Peruvian oxygen minimum zone and finite-size Lyapunov exponent fields to understand the link between mesoscale dynamics and oxygen variations. Our results show that, at depths between 380 and 600 meters, mesoscale structures have a relevant dual role. First, their mean positions and paths delimit and maintain the oxygen minimum zone boundaries. Second, their high frequency fluctuations entrain oxygen across these boundaries as eddy fluxes that point towards the interior of the oxygen minimum zone and are one order of magnitude larger than mean fluxes. We conclude that these eddy fluxes contribute to the ventilation of the oxygen minimum zone.Item Restricted Declining oxygen in the global ocean and coastal waters(American Association for the Advancement of Science, 2018-01-05) Breitburg, Denise; Levin, Lisa A.; Oschlies, Andreas; Grégoire, Marilaure; Chavez, Francisco P.; Conley, Daniel J.; Garçon, Véronique; Gilbert, Denis; Gutiérrez, Dimitri; Isensee, Kirsten; Jacinto, Gil S.; Limburg, Karin E.; Montes Torres, Ivonne; Naqvi, S. W. A.; Pitcher, Grant C.; Rabalais, Nancy N.; Roman, Michael R.; Rose, Kenneth A.; Seibel, Brad A.; Telszewski, Maciej; Yasuhara, Moriaki; Zhang, JingOxygen is fundamental to life. Not only is it essential for the survival of individual animals, but it regulates global cycles of major nutrients and carbon. The oxygen content of the open ocean and coastal waters has been declining for at least the past half-century, largely because of human activities that have increased global temperatures and nutrients discharged to coastal waters. These changes have accelerated consumption of oxygen by microbial respiration, reduced solubility of oxygen in water, and reduced the rate of oxygen resupply from the atmosphere to the ocean interior, with a wide range of biological and ecological consequences. Further research is needed to understand and predict long-term, global- and regional-scale oxygen changes and their effects on marine and estuarine fisheries and ecosystems.Item Open Access Emergent constraint on oxygenation of the upper South Eastern Pacific oxygen minimum zone in the twenty-first century(Nature Research, 2024-05-28) Almendra, Ivan; Dewitte, Boris; Garçon, Véronique; Muñoz, Praxedes; Parada, Carolina; Montes Torres, Ivonne; Duteil, Olaf; Paulmier, Aurélien; Pizarro, Oscar; Ramos, Marcel; Koeve, Wolfgang; Oschlies, AndreasThe erosion of marine sediments is a pressing issue for coastal areas worldwide. Established methods to mitigate coastal erosion fail to provide lasting and sustainable solutions to protect marine ecosystems. Here we demonstrate the application of mild electrical stimulations to precipitate calcareous mineral binders from seawater in the pores of marine soils via electrodeposition, an alternative approach to mitigating coastal erosion. Results of electrochemical laboratory experiments unveil that the polymorphs, precipitation sites, intrusion mechanisms, and effects of electrodeposited minerals in marine sands vary as a function of the magnitude and duration of applied voltage, soil relative density, and electrolyte ionic concentration. Surprisingly, in addition to the precipitation of calcium carbonate and magnesium hydroxide, the formation of hydromagnesite is also observed due to electrically driven fluctuations in the local pH. These electrodeposits lead to enhanced mechanical and hydraulic properties of the marine sands, indicating that electrodeposition routes could be developed to reinforce marine soils in coastal areas that more closely mimic natural systems.Item Open Access ENSO diversity driving low-frequency change in mesoscale activity off Peru and Chile(Nature Research, 2020-10-21) Conejero, Carlos; Dewitte, Boris; Garçon, Véronique; Sudre, Joël; Montes Torres, IvonneTransient mesoscale oceanic eddies in Eastern Boundary Upwelling Systems are thought to strongly affect key regional scale processes such as ocean heat transport, coastal upwelling and productivity. Understanding how these can be modulated at low-frequency is thus critical to infer their role in the climate system. Here we use 26 years of satellite altimeter data and regional oceanic modeling to investigate the modulation of eddy kinetic energy (EKE) off Peru and Chile by ENSO, the main mode of natural variability in the tropical Pacific. We show that EKE tends to increase during strong Eastern Pacific (EP) El Niño events along the Peruvian coast up to northern Chile and decreases off central Chile, while it is hardly changed during Central Pacific El Niño and La Niña events. However the magnitude of the EKE changes during strong EP El Niño events is not proportional to their strength, with in particular the 1972/1973 El Niño event standing out as an extreme event in terms of EKE increase off Peru reaching an amplitude three times as large as that during the 1997/1998 El Niño event, and the 2015/2016 El Niño having instead a weak impact on EKE. This produces decadal changes in EKE, with a similar pattern than that of strong EP El Niño events, resulting in a significant negative (positive) long-term trend off Peru (central Chile).Item Open Access Evaluating future climate change exposure of marine habitat in the South East Pacific based on metabolic constraints(Frontiers Media, 2023-01-05) Parouffe, Alexandra; Garçon, Véronique; Dewitte, Boris; Paulmier, Aurélien; Montes Torres, Ivonne; Parada, Carolina; Mecho, Ariadna; Veliz, DavidOn-going climate change is now recognized to yield physiological stresses on marine species, with potentially detrimental effects on ecosystems. Here, we evaluate the prospect of using climate velocities (CV) of the metabolic index (Φ) for assessing changes in habitat in the South East Pacific. Our approach is based on a species with mean ecophysiotype (i.e. model species) and the use of a global Earth System Model simulation (CESM-LE) under RCP 8.5 scenario. The SEP is chosen as a case study as it hosts an Oxygen Minimum Zone and seamounts systems sustaining local communities through artisanal fisheries. Our results indicate that CVΦ pattern is mainly constrained by the oxygen distribution and that its sign is affected by contrasting oxygen trends (including a re-oxygenation in the upper OMZ) and warming. We further show that CVΦ is weakly dependent on physiological traits composing Φ, which conveys to this metrics some value for inferring the projected mean displacement and potential changes in viability of metabolic habitat in a region where physiological data are scarce. Based on sensitivity experiments to physiological traits and natural variability, we propose a general method for inferring broad areas of climate change exposure regardless of species-specific Φ. We show in particular that for the model used here, the upper OMZ region can be considered a “safe” area for the species with ecophysiotype close to that of 71 species used to derive the model species. Limitations of the approach and perspectives of this work are also discussed.Item Open Access High‐resolution modeling of the Eastern Tropical Pacific oxygen minimum zone: sensitivity to the tropical oceanic circulation(American Geophysical Union (AGU), 2014-08) Montes Torres, Ivonne; Dewitte, Boris; Gutknecht, Elodie; Paulmier, Aurélien; Dadou, Isabelle; Oschlies, Andreas; Garçon, VéroniqueThe connection between the equatorial mean circulation and the oxygen minimum zone (OMZ) in the Eastern Tropical Pacific is investigated through sensitivity experiments with a high‐resolution coupled physical‐biogeochemical model. A validation against in situ observations indicates a realistic simulation of the vertical and horizontal oxygen distribution by the model. Two sets of climatological open‐boundary conditions for the physical variables, which differ slightly with respect to the intensity and vertical structure of the Equatorial Current System, are shown to lead to contrasting characteristics of the simulated OMZ dynamics. From a Lagrangian perspective, the mean differences near the coast originate to a large extent from the different transport of deoxygenated waters by the secondary Tsuchiya Jet (secondary Southern Subsurface Countercurrent, sSSCC). The O₂ budget further indicates a large difference in the balance between tendency terms, with advection exhibiting the largest difference between both simulations, which is shown to result from both linear and nonlinear advection. At regional scale, we also find that the variability of the physical contribution to the rate of O₂ change is one order of magnitude larger than the variability associated with the biogeochemical contribution, which originates from internal high‐frequency variability. Overall our study illustrates the large sensitivity of the OMZ dynamics to the equatorial circulation.Item Open Access Modulation of the vertical particle transfer efficiency in the oxygen minimum zone off Peru(European Geosciences Union (EGU), 2018) Bretagnon, Marine; Paulmier, Aurélien; Garçon, Véronique; Dewitte, Boris; Illig, Seréna; Leblond, Nathalie; Coppola, Laurent; Campos, Fernando; Velazco, Federico; Panagiotopoulos, Christos; Oschlies, Andreas; Hernandez-Ayon, J. Martin; Maske, Helmut; Vergara, Oscar; Montes Torres, Ivonne; Martinez, Philippe; Carrasco, Edgardo; Grelet, Jacques; Desprez-De-Gesincourt, Olivier; Maes, Christophe; Scouarnec, LionelThe fate of the organic matter (OM) produced by marine life controls the major biogeochemical cycles of the Earth's system. The OM produced through photosynthesis is either preserved, exported towards sediments or degraded through remineralisation in the water column. The productive eastern boundary upwelling systems (EBUSs) associated with oxygen minimum zones (OMZs) would be expected to foster OM preservation due to low O₂ conditions. But their intense and diverse microbial activity should enhance OM degradation. To investigate this contradiction, sediment traps were deployed near the oxycline and in the OMZ core on an instrumented moored line off Peru. Data provided high-temporal-resolution O₂ series characterising two seasonal steady states at the upper trap: suboxic ([O₂] < 25µmolkg−1) and hypoxic–oxic (15 < [O₂] < 160µmolkg−1) in austral summer and winter–spring, respectively. The OMZ vertical transfer efficiency of particulate organic carbon (POC) between traps (Teff) can be classified into three main ranges (high, intermediate, low). These different Teff ranges suggest that both predominant preservation (high Teff > 50%) and remineralisation (intermediate Teff 20 < 50% or low Teff < 6%) configurations can occur. An efficient OMZ vertical transfer (Teff > 50%) has been reported in summer and winter associated with extreme limitation in O₂ concentrations or OM quantity for OM degradation. However, higher levels of O₂ or OM, or less refractory OM, at the oxycline, even in a co-limitation context, can decrease the OMZ transfer efficiency to below 50%. This is especially true in summer during intraseasonal wind-driven oxygenation events. In late winter and early spring, high oxygenation conditions together with high fluxes of sinking particles trigger a shutdown of the OMZ transfer (Teff < 6%). Transfer efficiency of chemical elements composing the majority of the flux (nitrogen, phosphorus, silica, calcium carbonate) follows the same trend as for carbon, with the lowest transfer level being in late winter and early spring. Regarding particulate isotopes, vertical transfer of δ15N suggests a complex pattern of 15N impoverishment or enrichment according to Teff modulation. This sensitivity of OM to O₂ fluctuations and particle concentration calls for further investigation into OM and O₂-driven remineralisation processes. This should include consideration of the intermittent behaviour of OMZ towards OM demonstrated in past studies and climate projections.Item Open Access Multidisciplinary observing in the World Ocean’s Oxygen Minimum Zone regions: from climate to fish-The VOICE initiative(Frontiers Media, 2019-12-05) Garçon, Véronique; Karstensen, Johannes; Palacz, Artur; Telszewski, Maciej; Aparco Lara, Tony; Breitburg, Denise; Chavez, Francisco; Coelho, Paulo; Cornejo-D’Ottone, Marcela; Santos, Carmen; Fiedler, Björn; Gallo, Natalya D.; Grégoire, Marilaure; Gutierrez, Dimitri; Hernandez-Ayon, Martin; Isensee, Kirsten; Koslow, Tony; Levin, Lisa; Marsac, Francis; Maske, Helmut; Mbaye, Baye C.; Montes Torres, Ivonne; Naqvi, Wajih; Pearlman, Jay; Pinto, Edwin; Pitcher, Grant; Pizarro, Oscar; Rose, Kenneth; Shenoy, Damodar; Van der Plas, Anja; Vito, Melo R.; Weng, KevinMultidisciplinary ocean observing activities provide critical ocean information to satisfy ever-changing socioeconomic needs and require coordinated implementation. The upper oxycline (transition between high and low oxygen waters) is fundamentally important for the ecosystem structure and can be a useful proxy for multiple observing objectives connected to eastern boundary systems (EBSs) that neighbor oxygen minimum zones (OMZs). The variability of the oxycline and its impact on the ecosystem (VOICE) initiative demonstrates how societal benefits drive the need for integration and optimization of biological, biogeochemical, and physical components of regional ocean observing related to EBS. In liaison with the Global Ocean Oxygen Network, VOICE creates a roadmap toward observation-model syntheses for a comprehensive understanding of selected oxycline-dependent objectives. Local to global effects, such as habitat compression or deoxygenation trends, prompt for comprehensive observing of the oxycline on various space and time scales, and for an increased awareness of its impact on ecosystem services. Building on the Framework for Ocean Observing (FOO), we present a first readiness level assessment for ocean observing of the oxycline in EBS. This was to determine current ocean observing design and future needs in EBS regions (e.g., the California Current System, the Equatorial Eastern Pacific off Ecuador, the Peru–Chile Current system, the Northern Benguela off Namibia, etc.) building on the FOO strategy. We choose regional champions to assess the ocean observing design elements proposed in the FOO, namely, requirement processes, coordination of observational elements, and data management and information products and the related best practices. The readiness level for the FOO elements was derived for each EBS through a similar and very general ad hoc questionnaire. Despite some weaknesses in the questionnaire design and its completion, an assessment was achievable. We found that fisheries and ecosystem management are a societal requirement for all regions, but maturity levels of observational elements and data management and information products differ substantially. Identification of relevant stakeholders, developing strategies for readiness level improvements, and building and sustaining infrastructure capacity to implement these strategies are fundamental milestones for the VOICE initiative over the next 2–5 years and beyond.Item Open Access On the interpretation of changes in the subtropical oxygen minimum zone volume off Chile during two La Niña events (2001 and 2007)(Frontiers Media, 2023-07-04) Pizarro-Koch, Matías; Pizarro, Oscar; Dewitte, Boris; Montes Torres, Ivonne; Paulmier, Aurélien; Garçon, Véronique; Sepulveda, Hector Hito; Corredor-Acosta, Andrea; Aguirre, Catalina; Ramos, MarcelOxygen minimum zones (OMZs) are extended oceanic regions for which dissolved oxygen concentration is extremely low. They are suspected to be expanding in response to global warming. However, currently, the mechanisms by which OMZ varies in response to climate variability are still uncertain. Here, the variability of the subtropical OMZ off central Chile of a regional coupled physical–biogeochemical regional model simulation was analyzed for the period 2000–2008, noting that its fluctuations were significant despite the relatively weak amplitude of the El Niño/Southern Oscillation (ENSO). In particular, the interannual variability in the OMZ volume (OMZVOL, defined as the volume with dissolved oxygen concentration (DO) ≤ 45μM) was approximately 38% larger than that of the seasonal cycle, with maximum and minimum anomalies of OMZVOL taking place during two cold La Niña (LN) years (2001 and 2007). The model analyses further reveal that these anomalies resulted from a combined effect of changes in (1) the oxygen-poor waters poleward transport by the Peru–Chile undercurrent (PCUC), (2) the intensity of quasi-zonal jets influencing the transport of water to and from the OMZ, and (3) the zonal DO transport related to mesoscale eddy activity. Specifically, the interannual variability of the PCUC modulated primarily the DO contents of the OMZ core [(DO) ≤ 20μM] and secondarily the OMZVOL, while cross-shore DO transport by the zonal jets and the eddy fluxes played a major role in ventilating and shaping the offshore extent of the OMZ. When the OMZVOL was maximum (minimum), the PCUC transport was slightly increased (reduced), which was associated with a reduction (increase) in the ventilation of the OMZ through negative (positive) anomalies of zonal advection and DO eddy fluxes. Our results demonstrate that significant natural interannual variability in the subtropical OMZ off Chile originates from the interplay between oceanic equatorial teleconnection (PCUC transport) and local non-linear dynamics (the zonal jets and mesoscale eddies).Item Open Access Seasonal variability of the Southern tip of the Oxygen Minimum Zone in the Eastern South Pacific (30°‐38°S): a modeling study(American Geophysical Union (AGU), 2019-12) Pizarro‐Koch, Matias; Pizarro, Oscar; Dewitte, Boris; Montes Torres, Ivonne; Ramos, Marcel; Paulmier, Aurélien; Garçon, VéroniqueWe investigate the seasonal variability of the southern tip (30°–38°S) of the eastern South Pacific oxygen minimum zone (OMZ) based on a high horizontal resolution (1/12°) regional coupled physical‐biogeochemical model simulation. The simulation is validated by available in situ observations and the OMZ seasonal variability is documented. The model OMZ, bounded by the contour of 45 μM, occupies a large volume (4.5x10⁴ km³) during the beginning of austral winter and a minimum (3.5x10⁴ km³) at the end of spring, just 1 and 2 months after the southward transport of the Peru‐Chile Undercurrent (PCUC) is maximum and minimum, respectively. We showed that the PCUC significantly impacts the alongshore advection of dissolved oxygen (DO) modulating the OMZ seasonal variability. However, zonal transport of DO by meridionally alternating zonal jets and mesoscale eddy fluxes play also a major role in the seasonal and spatial variability of the OMZ. Consistently, a DO budget analysis reveals a significant contribution of advection terms to the rate of change of DO and the prominence of mesoscale variability within the seasonal cycle of these terms. Biogeochemical processes and horizontal and vertical mixing, associated with subgrid scale processes, play only a secondary role in the OMZ seasonal cycle. Overall, our study illustrates the interplay of mean and (mesoscale) eddy‐induced transports of DO in shaping the OMZ and its seasonal cycle off Central Chile.Item Restricted System controls of coastal and open ocean oxygen depletion(Elsevier, 2021-09-09) Pitcher, Grant C.; Aguirre-Velarde, Arturo; Breitburg, Denise; Cardich, Jorge; Carstensen, Jacob; Conley, Daniel J.; Dewitte, Boris; Engel, Anja; Espinoza-Morriberón, Dante; Flores, Georgina; Garçon, Véronique; Graco, Michelle; Grégoire, Marilaure; Gutiérrez, Dimitri; Hernandez-Ayon, José Martin; Huang, Huai-Hsuan May; Isensee, Kirsten; Jacinto, María Elena; Levin, Lisa; Lorenzo, Alberto; Machu, Eric; Merma, Lander; Montes Torres, Ivonne; Naqvi, S. W. A.; Paulmier, Aurelien; Roman, Michael; Rose, Kenneth; Hood, Raleigh; Rabalais, Nancy N.; Salvanves, Anne Gro V.; Salvatteci, Renato; Sánchez, Sonia; Sifeddine, Abdelfettah; Tall, Abdoul Wahab; van der Plas, Anja K.; Yasuhara, Moriaki; Zhang, Jing; Zhu, Z. Y.The epoch of the Anthropocene, a period during which human activity has been the dominant influence on climate and the environment, has witnessed a decline in oxygen concentrations and an expansion of oxygen-depleted environments in both coastal and open ocean systems since the middle of the 20th century. This paper provides a review of system-specific drivers of low oxygen in a range of case studies representing marine systems in the open ocean, on continental shelves, in enclosed seas and in the coastal environment. Identification of similar and contrasting responses within and across system types and corresponding oxygen regimes is shown to be informative both in understanding and isolating key controlling processes and provides a sound basis for predicting change under anticipated future conditions. Case studies were selected to achieve a balance in system diversity and global coverage. Each case study describes system attributes, including the present-day oxygen environment and known trends in oxygen concentrations over time. Central to each case study is the identification of the physical and biogeochemical processes that determine oxygen concentrations through the tradeoff between ventilation and respiration. Spatial distributions of oxygen and time series of oxygen data provide the opportunity to identify trends in oxygen availability and have allowed various drivers of low oxygen to be distinguished through correlative and causative relationships. Deoxygenation results from a complex interplay of hydrographic and biogeochemical processes and the superposition of these processes, some additive and others subtractive, makes attribution to any particular driver challenging. System-specific models are therefore required to achieve a quantitative understanding of these processes and of the feedbacks between processes at varying scales.