scholarly journals Water mass pathways to the North Atlantic oxygen minimum zone

2015 ◽  
Vol 120 (5) ◽  
pp. 3350-3372 ◽  
Author(s):  
Jesús Peña-Izquierdo ◽  
Erik van Sebille ◽  
Josep L. Pelegrí ◽  
Janet Sprintall ◽  
Evan Mason ◽  
...  
Keyword(s):  
North Atlantic ◽  
Water Mass ◽  
Oxygen Minimum Zone ◽  
The North ◽  
Minimum Zone ◽  
The North Atlantic ◽  
Oxygen Minimum

scholarly journals Oxygen minimum zone in the North Atlantic south and east of the Cape Verde Islands

2008 ◽  
Vol 113 (C4) ◽  
Author(s):  
Lothar Stramma ◽  
Peter Brandt ◽  
Jens Schafstall ◽  
Friedrich Schott ◽  
Jürgen Fischer ◽  
...  
Keyword(s):  
North Atlantic ◽  
Oxygen Minimum Zone ◽  
Cape Verde ◽  
Cape Verde Islands ◽  
The North ◽  
Minimum Zone ◽  
The North Atlantic ◽  
Oxygen Minimum

scholarly journals Isopycnal Mixing in the North Atlantic Oxygen Minimum Zone Revealed by RAFOS Floats

2019 ◽  
Vol 124 (9) ◽  
pp. 6478-6497 ◽  
Author(s):  
Donald Rudnickas ◽  
Jaime Palter ◽  
David Hebert ◽  
H. Thomas Rossby
Keyword(s):  
North Atlantic ◽  
Oxygen Minimum Zone ◽  
The North ◽  
Minimum Zone ◽  
The North Atlantic ◽  
Oxygen Minimum ◽  
Isopycnal Mixing

scholarly journals Madrepora oculata forms large frameworks in hypoxic waters off Angola (SE Atlantic)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Covadonga Orejas ◽  
Claudia Wienberg ◽  
Jürgen Titschack ◽  
Leonardo Tamborrino ◽  
André Freiwald ◽  
...  
Keyword(s):  
North Atlantic ◽  
Environmental Conditions ◽  
Coral Community ◽  
Hypoxic Conditions ◽  
The North ◽  
Minimum Zone ◽  
The North Atlantic ◽  
Age Range ◽  
Local Oxygen ◽  
Oxygen Minimum

AbstractThis study aims to map the occurrence and distribution of Madrepora oculata and to quantify density and colony sizes across recently discovered coral mounds off Angola. Despite the fact that the Angolan populations of M. oculata thrive under extreme hypoxic conditions within the local oxygen minimum zone, they reveal colonies with remarkable heights of up to 1250 mm—which are the tallest colonies ever recorded for this species—and average densities of 0.53 ± 0.37 (SD) colonies m−2. This is particularly noteworthy as these values are comparable to those documented in areas without any oxygen constraints. The results of this study show that the distribution pattern documented for M. oculata appear to be linked to the specific regional environmental conditions off Angola, which have been recorded in the direct vicinity of the thriving coral community. Additionally, an estimated average colony age of 95 ± 76 (SD) years (total estimated age range: 16–369 years) indicates relatively old M. oculata populations colonizing the Angolan coral mounds. Finally, the characteristics of the Angolan populations are benchmarked and discussed in the light of the existing knowledge on M. oculata gained from the North Atlantic and Mediterranean Sea.

scholarly journals Diapycnal oxygen supply to the tropical North Atlantic oxygen minimum zone

2012 ◽  
Vol 9 (10) ◽  
pp. 14291-14325 ◽  
Author(s):  
T. Fischer ◽  
D. Banyte ◽  
P. Brandt ◽  
M. Dengler ◽  
G. Krahmann ◽  
...  
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Oxygen Supply ◽  
Water Layer ◽  
Oxygen Minimum Zone ◽  
Depth Interval ◽  
Diapycnal Mixing ◽  
Tropical North Atlantic ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. The replenishment of consumed oxygen in the open ocean oxygen minimum zone (OMZ) off West Africa in the tropical North Atlantic Ocean is studied, with a focus on oxygen transport across density surfaces (diapycnal flux). The latter is obtained from a large observational set of oxygen profiles and diapycnal mixing data from years 2008 to 2010. Diapycnal mixing is inferred from different sources: a large scale tracer release experiment, microstructure profiles, and shipboard acoustic current measurements plus density profiles. The average diapycnal diffusivity in the study area is 1 × 10−5 m2 s−1. No significant vertical gradient of average diapycnal diffusivities exists in the depth interval from 150 to 500 m. The diapycnal flux is found to contribute substantially to the oxygen supply of the OMZ. Within the OMZ core, 1.5 µmol kg−1 a−1 of oxygen is supplied via diapycnal mixing, contributing about a third of the total demand. The oxygen that is contributed via diapycnal mixing originates from oxygen that has been laterally supplied within the overlying Central Water layer by advective and eddy fluxes. Due to the existence of a separate shallow oxygen minimum at about 100 m depth throughout most of the study area, there is no direct net vertical oxygen flux from the surface layer of the study area into the Central Water layer. Thus all oxygen supply of the OMZ is associated with remote pathways.

scholarly journals Water mass distributions and transports for the 2014 GEOVIDE cruise in the North Atlantic

2018 ◽  
Vol 15 (7) ◽  
pp. 2075-2090 ◽  
Author(s):  
Maribel I. García-Ibáñez ◽  
Fiz F. Pérez ◽  
Pascale Lherminier ◽  
Patricia Zunino ◽  
Herlé Mercier ◽  
...  
Keyword(s):  
North Atlantic ◽  
Water Mass ◽  
Water Levels ◽  
Water Masses ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Intermediate Water ◽  
North East ◽  
The North ◽  
The North Atlantic

Abstract. We present the distribution of water masses along the GEOTRACES-GA01 section during the GEOVIDE cruise, which crossed the subpolar North Atlantic Ocean and the Labrador Sea in the summer of 2014. The water mass structure resulting from an extended optimum multiparameter (eOMP) analysis provides the framework for interpreting the observed distributions of trace elements and their isotopes. Central Waters and Subpolar Mode Waters (SPMW) dominated the upper part of the GEOTRACES-GA01 section. At intermediate depths, the dominant water mass was Labrador Sea Water, while the deep parts of the section were filled by Iceland–Scotland Overflow Water (ISOW) and North-East Atlantic Deep Water. We also evaluate the water mass volume transports across the 2014 OVIDE line (Portugal to Greenland section) by combining the water mass fractions resulting from the eOMP analysis with the absolute geostrophic velocity field estimated through a box inverse model. This allowed us to assess the relative contribution of each water mass to the transport across the section. Finally, we discuss the changes in the distribution and transport of water masses between the 2014 OVIDE line and the 2002–2010 mean state. At the upper and intermediate water levels, colder end-members of the water masses replaced the warmer ones in 2014 with respect to 2002–2010, in agreement with the long-term cooling of the North Atlantic Subpolar Gyre that started in the mid-2000s. Below 2000 dbar, ISOW increased its contribution in 2014 with respect to 2002–2010, with the increase being consistent with other estimates of ISOW transports along 58–59° N. We also observed an increase in SPMW in the East Greenland Irminger Current in 2014 with respect to 2002–2010, which supports the recent deep convection events in the Irminger Sea. From the assessment of the relative water mass contribution to the Atlantic Meridional Overturning Circulation (AMOC) across the OVIDE line, we conclude that the larger AMOC intensity in 2014 compared to the 2002–2010 mean was related to both the increase in the northward transport of Central Waters in the AMOC upper limb and to the increase in the southward flow of Irminger Basin SPMW and ISOW in the AMOC lower limb.

scholarly journals Changes in the Ventilation of the Oxygen Minimum Zone of the Tropical North Atlantic

2010 ◽  
Vol 40 (8) ◽  
pp. 1784-1801 ◽  
Author(s):  
Peter Brandt ◽  
Verena Hormann ◽  
Arne Körtzinger ◽  
Martin Visbeck ◽  
Gerd Krahmann ◽  
...  
Keyword(s):  
North Atlantic ◽  
Oxygen Minimum Zone ◽  
Time Interval ◽  
Depth Range ◽  
Oxygen Levels ◽  
The Core ◽  
Zonal Jets ◽  
Tropical North Atlantic ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract Changes in the ventilation of the oxygen minimum zone (OMZ) of the tropical North Atlantic are studied using oceanographic data from 18 research cruises carried out between 28.5° and 23°W during 1999–2008 as well as historical data referring to the period 1972–85. In the core of the OMZ at about 400-m depth, a highly significant oxygen decrease of about 15 μmol kg−1 is found between the two periods. During the same time interval, the salinity at the oxygen minimum increased by about 0.1. Above the core of the OMZ, within the central water layer, oxygen decreased too, but salinity changed only slightly or even decreased. The scatter in the local oxygen–salinity relations decreased from the earlier to the later period suggesting a reduced filamentation due to mesoscale eddies and/or zonal jets acting on the background gradients. Here it is suggested that latitudinally alternating zonal jets with observed amplitudes of a few centimeters per second in the depth range of the OMZ contribute to the ventilation of the OMZ. A conceptual model of the ventilation of the OMZ is used to corroborate the hypothesis that changes in the strength of zonal jets affect mean oxygen levels in the OMZ. According to the model, a weakening of zonal jets, which is in general agreement with observed hydrographic evidences, is associated with a reduction of the mean oxygen levels that could significantly contribute to the observed deoxygenation of the North Atlantic OMZ.

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