Preformed and regenerated phosphate in ocean general circulation models: can right total concentrations be wrong?

Duteil, Olaf; Koeve, Wolfgang; Oschlies, Andreas; Aumont, Olivier; Bianchi, Daniele; Bopp, Laurent; Galbraith, Eric D.; Matear, Richard J.; Moore, J. Keith; Sarmiento, Jorge L.; Segschneider, Joachim

doi:10.5194/bg-9-1797-2012

Cited by 65 publications

(92 citation statements)

References 33 publications

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“…The model simulates particulate inorganic carbon (PIC) production as a function of particulate organic carbon (POC) production via the rain ratio (9 %) following Yamanaka and Tajika (1996). This ocean biogeochemical model was shown to simulate the observed distributions of total carbon and alkalinity in the ocean (Matear and Lenton, 2014) and phosphate (Duteil et al, 2012).…”

Section: Model Descriptionmentioning

confidence: 99%

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

et al. 2018

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Abstract. Atmospheric carbon dioxide (CO 2 ) levels continue to rise, increasing the risk of severe impacts on the Earth system, and on the ecosystem services that it provides. Artificial ocean alkalinization (AOA) is capable of reducing atmospheric CO 2 concentrations and surface warming and addressing ocean acidification. Here, we simulate global and regional responses to alkalinity (ALK) addition (0.25 PmolALK yr −1 ) over the period 2020-2100 using the CSIRO-Mk3L-COAL Earth System Model, under high (Representative Concentration Pathway 8.5; RCP8.5) and low (RCP2.6) emissions. While regionally there are large changes in alkalinity associated with locations of AOA, globally we see only a very weak dependence on where and when AOA is applied. On a global scale, while we see that under RCP2.6 the carbon uptake associated with AOA is only ∼ 60 % of the total, under RCP8.5 the relative changes in temperature are larger, as are the changes in pH (140 %) and aragonite saturation state (170 %). The simulations reveal AOA is more effective under lower emissions, therefore the higher the emissions the more AOA is required to achieve the same reduction in global warming and ocean acidification. Finally, our simulated AOA for 2020-2100 in the RCP2.6 scenario is capable of offsetting warming and ameliorating ocean acidification increases at the global scale, but with highly variable regional responses.

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Section: Model Descriptionmentioning

confidence: 99%

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

et al. 2018

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“…3a and b). In analogy to the concept of preformed nutrients or preformed oxygen (Redfield et al, 1963;Duteil et al, 2012Duteil et al, , 2013, preformed alkalinity (in the following denoted TA 0 ) refers to the alkalinity which a water mass had when last in contact with the atmosphere before being subducted (Chen and Millero, 1979). In the ocean interior TA 0 is a strictly conservative tracer, whereas TA is variable due to transformations of CaCO 3 and organic matter.…”

Section: Ta Distribution and Caco 3 Transformationsmentioning

confidence: 99%

Methods to evaluate CaCO<sub>3</sub> cycle modules in coupled global biogeochemical ocean models

et al. 2014

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Abstract. The marine CaCO 3 cycle is an important component of the oceanic carbon system and directly affects the cycling of natural and the uptake of anthropogenic carbon. In numerical models of the marine carbon cycle, the CaCO 3 cycle component is often evaluated against the observed distribution of alkalinity. Alkalinity varies in response to the formation and remineralization of CaCO 3 and organic matter. However, it also has a large conservative component, which may strongly be affected by a deficient representation of ocean physics (circulation, evaporation, and precipitation) in models. Here we apply a global ocean biogeochemical model run into preindustrial steady state featuring a number of idealized tracers, explicitly capturing the model's CaCO 3 dissolution, organic matter remineralization, and various preformed properties (alkalinity, oxygen, phosphate). We compare the suitability of a variety of measures related to the CaCO 3 cycle, including alkalinity (TA), potential alkalinity and TA * , the latter being a measure of the time-integrated imprint of CaCO 3 dissolution in the ocean. TA * can be diagnosed from any data set of TA, temperature, salinity, oxygen and phosphate. We demonstrate the sensitivity of total and potential alkalinity to the differences in model and ocean physics, which disqualifies them as accurate measures of biogeochemical processes. We show that an explicit treatment of preformed alkalinity (TA 0 ) is necessary and possible. In our model simulations we implement explicit model tracers of TA 0 and TA * . We find that the difference between modelled true TA * and diagnosed TA * was below 10 % (25 %) in 73 % (81 %) of the ocean's volume. In the Pacific (and Indian) Oceans the RMSE of A * is below 3 (4) mmol TA m −3 , even when using a global rather than regional algorithms to estimate preformed alkalinity. Errors in the Atlantic Ocean are significantly larger and potential improvements of TA 0 estimation are discussed. Applying the TA * approach to the output of three state-of-the-art ocean carbon cycle models, we demonstrate the advantage of explicitly taking preformed alkalinity into account for separating the effects of biogeochemical processes and circulation on the distribution of alkalinity. In particular, we suggest to use the TA * approach for CaCO 3 cycle model evaluation.

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“…We use the terms "preformed" 14 C-DIC and "preformed" 14 C-age (Emerson and Hedges, 2008) in analogy to preformed components of other ocean tracers such as nutrients, oxygen or alkalinity (Redfield et al, 1963, Najjar et al, 2007, Koeve et al, 2014. The common feature of bulk tracers is that their distribution within the ocean's interior is a combination of a preformed component entering the ocean interior via physical transport processes (subduction, downwelling), a component related to processes (sources or sinks) within the ocean (respiration, remineralisation, mineral dissolution, radioactive decay), and the mixing of both components as water masses mix (Duteil et al, 2012(Duteil et al, , 2013Koeve et al, 2014). Note that the term "reservoir age" is used in the radiocarbon and palaeo-climatological literature in a similar way in which "preformed age" is used in this paper.…”

Section: W Koeve Et Almentioning

confidence: 99%

<sup>14</sup>C-age tracers in global ocean circulation models

et al. 2015

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Abstract. The natural abundance of 14 C in total CO 2 dissolved in seawater (DIC) is a property applied to evaluate the water age structure and circulation in the ocean and in ocean models. In this study we use three different representations of the global ocean circulation augmented with a suite of idealised tracers to study the potential and limitations of using natural 14 C to determine water age, which is the time elapsed since a body of water has been in contact with the atmosphere. We find that, globally, bulk 14 C-age is dominated by two equally important components, one associated with ageing, i.e. the time component of circulation, and one associated with a "preformed 14 C-age". The latter quantity exists because of the slow and incomplete atmosphere-ocean equilibration of 14 C particularly in high latitudes where many water masses form. In the ocean's interior, preformed 14 Cage behaves like a passive tracer. The relative contribution of the preformed component to bulk 14 C-age varies regionally within a given model, but also between models. Regional variability in the Atlantic Ocean is associated with the mixing of waters with very different end members of preformed 14 Cage. Here, variations in the preformed component over space and time mask the circulation component to an extent that its patterns are not detectable from bulk 14 C-age. Between models, the variability of preformed 14 C-age can also be considerable (factor of 2), related to the combination of physical model parameters, which influence circulation dynamics or gas exchange. The preformed component was found to be very sensitive to gas exchange and moderately sensitive to ice cover. In our model evaluation, the choice of the gasexchange constant from within the currently accepted range of uncertainty had such a strong influence on preformed and bulk 14 C-age that if model evaluation would be based on bulk 14 C-age, it could easily impair the evaluation and tuning of a model's circulation on global and regional scales. Based on the results of this study, we propose that considering preformed 14 C-age is critical for a correct assessment of circulation in ocean models.

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Preformed and regenerated phosphate in ocean general circulation models: can right total concentrations be wrong?

Cited by 65 publications

References 33 publications

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

Methods to evaluate CaCO<sub>3</sub> cycle modules in coupled global biogeochemical ocean models

<sup>14</sup>C-age tracers in global ocean circulation models

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Preformed and regenerated phosphate in ocean general circulation models: can right total concentrations be wrong?

Cited by 65 publications

References 33 publications

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

Methods to evaluate CaCO&lt;sub&gt;3&lt;/sub&gt; cycle modules in coupled global biogeochemical ocean models

&lt;sup&gt;14&lt;/sup&gt;C-age tracers in global ocean circulation models

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Methods to evaluate CaCO<sub>3</sub> cycle modules in coupled global biogeochemical ocean models

<sup>14</sup>C-age tracers in global ocean circulation models