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  • 1
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    Association for the Sciences of Limnology and Oceanography
    In:  Limnology and Oceanography, 46 . pp. 964-970.
    Publication Date: 2014-01-30
    Description: Redfield ratios of remineralization are calculated based on chemical data analysis on isopycnal surfaces. The concentrations of dissolved inorganic carbon used in this study were corrected for the anthropogenic CO2 content as estimated with a back-calculation technique. The corrections increased the apparent carbon remineralization by 25-30%, thus proving important for the reliable estimation of Redfield carbon ratios in the presence of anthropogenic CO2. Best estimates from this study largely confirm the more recently published Redfield ratios of remineralization. The following results were obtained for the latitude range 3-41°N along 20-29°W in the Northeast Atlantic Ocean: Corg: P ratio = 123 ± 10; Corg : N ratio = 7.2 ± 0.8; -O2 :Corg ratio = 1.34 ± 0.06; -O2 : P ratio = 165 ± 15; N: P ratio = 17.5 ± 2.0. These ratios are in close agreement with the average composition of phytoplankton and represent respiration of organic matter consisting on average of 52% protein, 36% polysaccharide, and 12% lipid.
    Type: Article , PeerReviewed
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  • 2
    Publication Date: 2018-03-16
    Description: The results of 1 year of automated pCO2 measurements in 2002/2003 onboard the car carrier M/V Falstaff are presented and analyzed with regard to the driving forces that change the seawater pCO2 in the midlatitude North Atlantic Ocean. The pCO2 in surface seawater is controlled by thermodynamics, biology, air-sea gas exchange, and physical mixing. Here we estimate the effects on the annual cycle of pCO2 and relate this property to parameters like SST, nitrate, and chlorophyll. On the basis of the amplitude in seawater pCO2 for all 4° × 5° grid boxes, this region can be separated into an eastern and western basin. The annual pCO2 cycle in the eastern basin (10°W–35°W) is less variable, which can be related to the two counteracting effects of temperature and biology; air-sea gas exchange plays a minor role when using climatological MLD. In the western basin (36°W–70°W) the pCO2 amplitude is more variable and strongly follows the thermodynamic forcing, since the biological forcing (as derived from nitrate concentrations) is decreased. Biology and air-sea exchange strongly depend on the MLD and therefore also include physical mixing effects. The pCO2 data of the analyzed region between 34°N and 52°N compare well to the Takahashi et al. [2002] climatology except for regions north of 45°N during the wintertime where the bias is significant.
    Type: Article , PeerReviewed
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  • 3
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    DWD
    In:  Promet - Meteorologische Fortbildung, 28 (1/2). pp. 64-70.
    Publication Date: 2016-10-04
    Type: Article , NonPeerReviewed
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  • 4
    Publication Date: 2017-07-12
    Description: We show the distribution of nutrients, oxygen, total dissolved inorganic carbon (CT) and total alkalinity (AT) along three sections close to the Canary Islands, between 18°W and the African coast during Meteor 37/2 cruise (January 1997). From the thermohaline properties of Eastern North Atlantic Central Water (ENACW), Mediterranean Water (MW), Antarctic Intermediate Water (AAIW) and North Atlantic Deep Water (NADW), a mixing model has been established based on the water mass description. It can explain most of the variabilities found in the distribution of the chemical variables, including the carbon system, and it is validated through the use of conservative chemical variables like ‘NO.’ From nutrients, oxygen, AT and CT, the chemical characterisation of the water masses was performed by calculating the concentration of these variables in the previously defined thermohaline end-members. The relative variation of nutrient concentrations, resulting from the regeneration of organic matter, was estimated. Close to the African shelf-break, a poleward undercurrent conveying as much as a 11% of AAIW was observed only in the southern section (28.5°N). From the chemical and thermohaline properties of the end-members, a comparison with data from other oceanic regions was made in respect to conservative chemical variables (‘NO’). In addition, a north–south gradient in the ventilation pattern of water masses is observed from the residuals of the model.
    Type: Article , PeerReviewed
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  • 5
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    American Society of Limnology and Oceanography
    In:  Limnology and Oceanography: Methods, 2 . pp. 126-136.
    Publication Date: 2018-08-14
    Description: A newly designed system for high quality discrete spectrophotometric measurements of pHT using a low-cost CCD detector is described. Considerations and requirements for the choice of spectrophotometers with a CCD detector instead of scanning spectrophotometers with photomultiplier detector are elucidated. The presented system is evaluated in the laboratory for system accuracy and short-term precision and at-sea for long-term precision and at-sea capability. Derived system characteristics are a (1s) short-term precision of ± 0.0012 pH units and a (1s) long-term precision at-sea of ± 0.0032 pH units based on Certified Reference Materials (CRM). Such long-term precision is equivalent to a deviation of ± 1.1 to 2.2 µmol kg-1 in total dissolved inorganic carbon (TCO2) and ± 1.4 to 2.1 µmol kg-1 in total alkalinity (TA), depending on temperature and the TCO2/TA ratio. Over-determination of the CO2 system (TCO2, TA, pHT) from surface-to-deep water profiles support the accuracy and precision assessment in comparison to earlier data. With careful design and testing low-cost CCD spectrophotometers can be used for high accuracy pH-measurements.
    Type: Article , PeerReviewed
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  • 6
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    Instituto de Investigaciones Oceanologicas de la Universidad Autonoma de Baja
    In:  Ciencias Marinas, 26 (1). pp. 23-37.
    Publication Date: 2019-01-21
    Description: Seawater was sampled from different depths in the North Atlantic Ocean (Canary Islands region) and distributed among three different labs for the determination of titration alkalinity. Analysis was performed by potentiometric methods, involving titration in a closed cell, titration in an open cell and a two end-point acid addition method. The precision, which is the sample reproducibility taken from the mean standard deviation for replicate measurements, was between 0.45 and 0.90 µmol kg(-1) for the individual labs. Accuracy, here taken as the deviation for the values of a lab from the mean of all three, was mostly below 1 µmol kg(-1) and never exceeded 0.1% of the sample value. Mean standard deviation for all labs and all samples was 0.87 µmol kg(-1), once the individual methods were calibrated using certified reference material (CRM). Without CRM calibration, the mean standard deviation would increase to 2.8 µmol k(-1). The conclusion is that current high precision methods for alkalinity measurements calibrated with CRMs are able to reach similar accuracy as the measurement of total dissolved inorganic carbon by coulometry and therefore allow for the precise determination of the oceanic carbon dioxide system by using the two measured parameters.
    Type: Article , PeerReviewed
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  • 7
    Publication Date: 2018-02-20
    Description: During Meteor cruise 55 a strong undersaturation of surface seawater with respect to atmospheric CO2 was found in the Amazon River plume which is advected into the surface circulation of the tropical Atlantic. A conservative estimate of the plume-related CO2 sink in the tropical Atlantic yields a net air-sea flux of 0.014 ± 0.005 Pg C yr−1. The corresponding average CO2 flux density of 1.35 mmol m−2 d−1 is of similar magnitude but opposite sign as found elsewhere in the slightly supersaturated tropical Atlantic illustrating the significant impact of the Amazon on the biogeochemistry of large ocean areas. The dramatic change of the CO2 saturation state from highly supersaturated river waters to markedly undersaturated surface waters in the plume can be explained by a combination of the effects of CO2 outgassing from river water, of mixing between river and ocean water on the CO2 system properties, and of strong biological carbon drawdown in the plume.
    Type: Article , PeerReviewed
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  • 8
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    American Association for the Advancement of Science (AAAS)
    In:  Science, 306 (5700). p. 1377.
    Publication Date: 2016-09-08
    Type: Article , PeerReviewed
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  • 9
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    AGU
    In:  Geophysical Research Letters, 30 . pp. 1085-1088.
    Publication Date: 2018-02-20
    Description: Normalization to a constant salinity (S) is widely used for the adjustment of marine inorganic carbon chemistry data such as total alkalinity (AT) and total dissolved inorganic carbon (CT). This procedure traces back to the earliest studies in marine chemistry, but ignores the influence of riverine input of alkalinity and of dissolution of biogenic carbonates in the ocean. We tested different adjustment possibilities for AT and conclude that in most parts of the surface ocean the normalization concept does not reflect relationships which represent reality. In this paper, we propose a salinity adjustment based on a constant and region-specific term for S = 0, which expresses river run off, upwelling from below the lysocline, calcification, and lateral sea surface water exchange. One application of the normalization concept is its extension to AT and also CT predictions and implementation in models. We give a brief discussion on the usage of such extensions.
    Type: Article , PeerReviewed
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  • 10
    Publication Date: 2017-02-14
    Description: Recent measurements and model studies have consistently identified a decreasing trend in the concentration of dissolved O2 in the ocean over the last several decades. This trend has important implications for our understanding of anthropogenic climate change. First, the observed oceanic oxygen changes may be a signal of the beginning of a reorganization of large-scale ocean circulation in response to anthropogenic radiative forcing. Second, the repartitioning of oxygen between the ocean and the atmosphere requires a revision of the current atmospheric carbon budget and the estimates of the terrestrial and oceanic carbon sinks as calculated by the Intergovernmental Panel on Climate Change (IPCC) from measurements of atmospheric O2/N2.
    Type: Article , NonPeerReviewed
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