Water mass pathways to the <scp>N</scp>orth <scp>A</scp>tlantic oxygen minimum zone

Peña-Izquierdo, Jesús; Sebille, Erik van; Pelegrí, Josep Lluís; Sprintall, Janet; Mason, Evan; Llanillo, P. J.; Machín, Francisco

doi:10.1002/2014jc010557

Cited by 48 publications

(75 citation statements)

References 66 publications

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“…It intensified during the relaxation season. The observed opposing flow regimes in the two central water layers compare well with the results obtained by Peña‐Izquierdo et al () who suggested by analyzing hydrographic data and the output of an assimilation model opposing circulation cells in the upper and lCW layers. Equatorward flow below the poleward eastern boundary currents was also observed in the upwelling region off Peru (e.g., Chaigneau et al, ) and off Angola (Tchipalanga et al, ), suggesting that it is a common feature of EBC.…”

Section: Discussionsupporting

confidence: 90%

“…Meridional sections taken during two successive upwelling/relaxation cruises further suggest that ventilation of the uCW and lCW layers occurs from the south and north, respectively. This has previously been proposed through modeling studies by Elmoussaoui et al () and Peña‐Izquierdo et al () and was inferred from observed hydrographic properties and oxygen distributions by Voituriez and Chuchla (). Waters high in SACW concentration advected from the south in the uCW layer, and waters high in NACW concentration from the north in the lCW layer were both higher in oxygen concentrations with respect to ambient waters.…”

Section: Discussionsupporting

confidence: 67%

“…This method aids in describing the central water mass distribution at the continental slope during the individual cruises and its connection to seasonal EBC variability. The linear potential temperature‐salinity ( θ ‐S ) relationship of the SACW and NACW allowed for a composition analysis of individual water parcels (e.g., Johns et al, ; Peña‐Izquierdo et al, , ). Lower and upper potential density bounds used are 25.8 and 27.1 kg/m 3 (Stramma et al, ), further divided by the 26.8‐kg/m 3 isopycnal into a lower Central Water (lCW) and upper Central Water (uCW; e.g., Elmoussaoui et al, ; Fischer et al, ; Peña‐Izquierdo et al, , ).…”

Section: Methodsmentioning

confidence: 99%

“…Upwelling‐favorable winds in the MUR are largely controlled by the seasonal migration of the intertropical convergence zone, and the main upwelling season lasts from December to April (Barton et al, ; Brandt et al, ; Mittelstaedt, , ). During this period, the MUR exhibits elevated biological productivity in the surface layer due to the supply of cold, nutrient‐rich waters of predominantly South Atlantic origin to the continental slope and shelf region (Mittelstaedt, , ; Peña‐Izquierdo et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Seasonal Variability of the Mauritania Current and Hydrography at 18°N

2018

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Extensive field campaigns in the Mauritanian upwelling region between 2005 and 2016 provide the database for analyzing the seasonal variability of the eastern boundary circulation (EBC) and associated water mass distribution at 18°N. The data set includes shipboard upper ocean current, hydrographic, and oxygen measurements from nine research cruises conducted during upwelling (December to April) and relaxation (May to July) seasons. During the upwelling season, the EBC closely resembles a classical eastern boundary current regime, with a poleward undercurrent flowing beneath an equatorward coastal jet. In contrast, elevated poleward flow exceeding 30 cm/s and extending from the surface down to 250‐m depth is observed during the relaxation season. The pronounced seasonal variability of the across‐shore structure of the EBC can be related to local wind forcing and is in general agreement with Sverdrup balance. The EBC transport is correlated to the wind stress curl leading the transport by 7 days. The short lead time suggests a fast response of locally forced waves adjusting the EBC to wind forcing. The seasonal and vertical water mass distribution is presented based on hydrographic observations. The meridional oxygen distribution and corresponding water mass partitioning into South and North Atlantic Central Water masses reveal a possible northerly ventilation pathway in the deeper layers of the central water stratum. Our results suggest that the poleward surface flow and the poleward undercurrent both are a consequence of the cyclonic wind stress curl forcing and thus propose to name it the Mauritania Current.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 67%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Seasonal Variability of the Mauritania Current and Hydrography at 18°N

2018

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“…7 and S2 in supplemental materials). The anomaly linear regression is set predominantly by the data in the eastern basin, influenced by the African upwelling where major remineralization processes take place (Peña-Izquierdo et al 2015). The data from the western basin shows little dependence of the F(340/440) anomalies on NO 3 and AOU, probably as a consequence of input of humic-organic-matter sediments.…”

Section: Discussionmentioning

confidence: 99%

A Simple Nonlinear and End-Member-Free Approach for Obtaining Ocean Remineralization Patterns

Fuente

Pelegrí

Canepa

et al. 2017

Journal of Atmospheric and Oceanic Technology

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The variability of a biogeochemical property in the ocean is the outcome of both nonconservative (such as respiration and photosynthesis) and conservative (mixing of water masses with distinct concentrations at origin) processes. One method to separate both contributions is based on a multiple regression of the biogeochemical property in terms of temperature u and salinity S as conservative proxies of water masses. This regression delivers the variability related to the conservative fraction and hence allows for identifying the residual as the biogeochemical anomaly. Here, the standard multiple linear regression (MLR) method, which assumes that water masses mix locally and linearly, is compared with a nonlinear polynomial regression (PR) over the entire (u, S) space. The PR method has two important advantages over MLR: allows for simultaneous nonlinear mixing of all water masses and does not require knowing the end-member water types. Both approaches are applied to data along 7.58N in the equatorial Atlantic Ocean, and the biogeochemical anomalies are calculated for humic-like fluorescent dissolved organic matter, apparent oxygen utilization, and nitrate-all of them related through in situ remineralization processes. The goodness of both approaches is assessed by analyzing the linear dependence and the coefficient of correlation between the anomalies. The results show that the PR method can be applied over the entire water column and yet retains the local variability associated with nonconservative processes. The potential of the PR approach is also illustrated by calculating the oxygen-nitrate stoichiometric ratio for the entire 7.58N transatlantic section.

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Oxygen Pathways and Budget for the Eastern South Pacific Oxygen Minimum Zone

Llanillo

Pelegrí²,

Talley

et al. 2018

JGR Oceans

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Ventilation of the eastern South Pacific Oxygen Minimum Zone (ESP‐OMZ) is quantified using climatological Argo and dissolved oxygen data, combined with reanalysis wind stress data. We (1) estimate all oxygen fluxes (advection and turbulent diffusion) ventilating this OMZ, (2) quantify for the first time the oxygen contribution from the subtropical versus the traditionally studied tropical‐equatorial pathway, and (3) derive a refined annual‐mean oxygen budget for the ESP‐OMZ. In the upper OMZ layer, net oxygen supply is dominated by tropical‐equatorial advection, with more than one‐third of this supply upwelling into the Ekman layer through previously unevaluated vertical advection, within the overturning component of the regional Subtropical Cell (STC). Below the STC, at the OMZ's core, advection is weak and turbulent diffusion (isoneutral and dianeutral) accounts for 89% of the net oxygen supply, most of it coming from the oxygen‐rich subtropical gyre. In the deep OMZ layer, net oxygen supply occurs only through turbulent diffusion and is dominated by the tropical‐equatorial pathway. Considering the entire OMZ, net oxygen supply (3.84 ± 0.42 µmol kg−1 yr−1) is dominated by isoneutral turbulent diffusion (56.5%, split into 32.3% of tropical‐equatorial origin and 24.2% of subtropical origin), followed by isoneutral advection (32.0%, split into 27.6% of tropical‐equatorial origin and 4.4% of subtropical origin) and dianeutral diffusion (11.5%). One‐quarter (25.8%) of the net oxygen input escapes through dianeutral advection (most of it upwelling) and, assuming steady state, biological consumption is responsible for most of the oxygen loss (74.2%).

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Water mass pathways to the North Atlantic oxygen minimum zone

Cited by 48 publications

References 66 publications

Seasonal Variability of the Mauritania Current and Hydrography at 18°N

Seasonal Variability of the Mauritania Current and Hydrography at 18°N

A Simple Nonlinear and End-Member-Free Approach for Obtaining Ocean Remineralization Patterns

Oxygen Pathways and Budget for the Eastern South Pacific Oxygen Minimum Zone

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