Optimum multiparameter analysis of the water mass structure in the Atlantic Ocean thermocline

Poole, Robert K.; Tomczak, Matthias

doi:10.1016/s0967-0637(99)00025-4

Cited by 184 publications

(196 citation statements)

References 27 publications

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“…Near-surface isopycnals show some indication of downwelling and upwelling: during austral summer; these isopycnals bend downward toward the shore, suggesting downwelling, while during austral winter, the same isopycnals tilt upward as they approach the shore, indicating upwelling. SACW is formed in the subtropical convergence of the Brazil-Malvinas confluence zone (Poole and Tomczak 1999). On its way following the South Atlantic subtropical gyre circulation and the equatorial current system toward the Angola Gyre, the properties of SACW are constantly altered.…”

Section: Angolan Capacitybuilding Con Textmentioning

confidence: 99%

Eastern Boundary Circulation and Hydrography Off Angola: Building Angolan Oceanographic Capacities

Tchipalanga

Dengler

Brandt

et al. 2018

Bulletin of the American Meteorological Society

123

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The eastern boundary region off Angola encompasses a highly productive ecosystem important for the food security of the coastal population. The fish-stock distribution, however, undergoes large variability on intraseasonal, interannual, and longer time scales. These fluctuations are partly associated with large-scale warm anomalies that are often forced remotely from the equatorial Atlantic and propagate southward, reaching the Benguela upwelling off Namibia. Such warm events, named Benguela Niños, occurred in 1995 and in 2011. Here we present results from an underexplored extensive in situ dataset that was analyzed in the framework of a capacity-strengthening effort. The dataset was acquired within the Nansen Programme executed by the Food and Agriculture Organization of the United Nations and funded by the Norwegian government. It consists of hydrographic and velocity data from the Angolan continental margin acquired biannually during the main downwelling and upwelling seasons over more than 20 years. The mean seasonal changes of the Angola Current from 6° to 17°S are presented. During austral summer the southward Angola Current is concentrated in the upper 150 m. It strengthens from north to south, reaching a velocity maximum just north of the Angola Benguela Front. During austral winter the Angola Current is weaker, but deeper reaching. While the southward strengthening of the Angola Current can be related to the wind forcing, its seasonal variability is most likely explained by coastally trapped waves. On interannual time scales, the hydrographic data reveal remarkable variability in subsurface upper-ocean heat content. In particular, the 2011 Benguela Niño was preceded by a strong subsurface warming of about 2 years’ duration.

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Section: Angolan Capacitybuilding Con Textmentioning

confidence: 99%

Eastern Boundary Circulation and Hydrography Off Angola: Building Angolan Oceanographic Capacities

Tchipalanga

Dengler

Brandt

et al. 2018

Bulletin of the American Meteorological Society

123

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“…Based on this 0-20ºC temperature range equations (1) Consequently, the determination of A T º and C dis where  <5 ºC should be ideally estimated via an extended OMP (eOMP) analysis (Poole and Tomczak, 1999;Álvarez et al, 2004) to avoid important biases. The eOMP analysis is a method used to estimate the mixing proportions (and thus tracer concentrations) from a set of endmembers that make up a particular water sample (Poole and Tomczak, 1999). Unlike the classical OMP, it accounts for the biogeochemical changes that cannot be disregarded in large scale mixing processes and have to be included in the analysis.…”

Section: A C C E P T E Dmentioning

confidence: 99%

The subsurface layer reference to calculate preformed alkalinity and air–sea CO2 disequilibrium in the Atlantic Ocean

Vázquez-Rodríguez

Pad́ın

Pardo

et al. 2012

Journal of Marine Systems

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The subsurface ocean layer (100-200 m deep) is suggested as a reference to parameterize preformed alkalinity (A T º) and air-sea CO 2 disequilibrium (C dis ) in the Atlantic. Results suggest that this domain retains the memory of water mass formation (WMF) conditions over annual periods and avoids the large, short-term variability of the uppermost layers. Its thermohaline variability also encompasses and represents all water masses that outcrop in the Atlantic. Subsurface data also avoids the scarcity of late wintertime surface observations and benefit from the larger availability of yearround measurements, thus enhancing their representativeness and application coverage.This last feature is most relevant in high Atlantic latitudes, where WMF typically occurs and the widespread ice sheets often preclude surface pCO 2 sampling during wintertime.The obtained A T º and C dis parameterizations achieve uncertainties of 4.6 and 5.6 mol kg -1 , respectively, improving significantly the estimates in previous works, particularly in the high latitudes. The A T º parameterization is well correlated with observations and is coherent with the latitudinal subsurface distribution of silicate, particularly in the northern subpolar region, where previous studies showed discrepancies. The C dis estimates in the upper layers are coherent with air-sea ∆pCO 2 data from Takahashi´s climatology, thus tackling known important shortcomings and biases of anthropogenic CO 2 estimates in Atlantic waters.

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“…6b). The relative age, defined by AOU (μmol kg -1 ) divided by oxygen utilization rate (OUR; μmol kg -1 yr -1 ), is a way to obtain the information on the time scale of accumulating denitrification readings taken from the bottom layer (Poole and Tomczak 1999;Karstensen et al 2008;Kim et al 2010a). It is assumed that the relative age increases with depth and the horizontal advection is small within these two regions.…”

Section: Estimation Of Denitrification Ratesmentioning

confidence: 99%

Deep Nitrate Deficit Observed in the Highly Oxygenated East/Japan Sea and Its Possible Cause

Kim¹,

Min²,

Lee³

2012

Terr. Atmos. Ocean. Sci.

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We present evidence of denitrification on the continental slopes of the Ulleung Basin (UB) and the Eastern Japan Basin (EJB) near the Tatar Strait (TtS) in the East/Japan Sea (EJS), despite its high water column dissolved oxygen concentrations. Some nutrient concentration data deviate significantly from the fitted regression line of nitrate (N) vs. phosphate (P) in deep waters, indicating a loss of nitrate in the region. The EJS has a lower N/P ratio (ca. 12.4 below 300 dbar) than a traditional Redfield ratio (16). The N/P ratio and oxygen concentration are substantially lower at several locations whose depths are close to the sediment-water interface, near TtS (500 -1100 dbar) and in UB (1100 -2200 dbar). The decreased nitrate concentration is smaller than the expected nitrate level (a low N/P ratio of < 12.4), and a secondary nitrite peak near the bottom of these two regions: taken collectively, both indicate the presence of denitrification in the bottom layer. It is speculated that active re-mineralization and denitrification may occur simultaneously along the rich organic matter bottom layer on the slope environment. Denitrification rates are estimated at ~3 -33 μmol N m -2 d -1 . Current estimates do not support the previous idea of basin-wide denitrification in EJS, although the N/P ratio is low like in other hypoxic/anoxic seas. A better understanding of the denitrification process is necessary for predicting future changes of nitrogen cycle in the well-oxygenated EJS considering the decadal-scale physical and biogeochemical changes that have occurred.

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Optimum multiparameter analysis of the water mass structure in the Atlantic Ocean thermocline

Cited by 184 publications

References 27 publications

Eastern Boundary Circulation and Hydrography Off Angola: Building Angolan Oceanographic Capacities

Eastern Boundary Circulation and Hydrography Off Angola: Building Angolan Oceanographic Capacities

The subsurface layer reference to calculate preformed alkalinity and air–sea CO2 disequilibrium in the Atlantic Ocean

Deep Nitrate Deficit Observed in the Highly Oxygenated East/Japan Sea and Its Possible Cause

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