Posts Tagged 'modeling'



Linking social preferences and ocean acidification impacts in mussel aquaculture

Ocean Acidification (OA) has become one of the most studied global stressors in marine science during the last fifteen years. Despite the variety of studies on the biological effects of OA with marine commercial species, estimations of these impacts over consumers’ preferences have not been studied in detail, compromising our ability to undertake an assessment of market and economic impacts resulting from OA at local scales. Here, we use a novel and interdisciplinary approach to fill this gap. We experimentally test the impact of OA on commercially relevant physical and nutritional attributes of mussels, and then we use economic discrete choice models to assess the marginal effects of these impacts over consumers’ preferences and wellbeing. Results showed that attributes, which were significantly affected by OA, are also those preferred by consumers. Consumers are willing to pay on average 52% less for mussels with evidences of OA and are willing to increase the price they pay to avoid negative changes in attributes due to OA. The interdisciplinary approach developed here, complements research conducted on OA by effectively informing how OA economic impacts can be analyzed under the lens of marginal changes in market price and consumer’ welfare. Thereby, linking global phenomena to consumers’ wellbeing, and shifting the focus of OA impacts to assess the effects of local vulnerabilities in a wider context of people and businesses.

Continue reading ‘Linking social preferences and ocean acidification impacts in mussel aquaculture’

Particulate inorganic to organic carbon production as a predictor for coccolithophorid sensitivity to ongoing ocean acidification

Ocean acidification (OA) can induce shifts in plankton community composition, with coccolithophores being mostly negatively impacted. This is likely to change particulate inorganic and organic carbon (PIC and POC, respectively) production, with impacts on the biological carbon pump. Hence, assessing and, most importantly, understanding species‐specific sensitivities of coccolithophores is paramount. In a multispecies comparison, spanning more than two orders of magnitude in terms of POC and PIC production rates, among Calcidiscus leptoporus, Coccolithus pelagicus subsp. braarudii, Emiliania huxleyi, Gephyrocapsa oceanica, and Scyphosphaera apsteinii, we found that cellular PIC : POC was a good predictor for a species’ OA sensitivity. This is likely related to the need for cellular pH homeostasis, which is challenged by the process of calcification producing protons internally, especially when seawater pH decreases in an OA scenario. With higher PIC : POC, species and strains being more sensitive to OA coccolithophores may shift toward less calcified varieties in the future.

Continue reading ‘Particulate inorganic to organic carbon production as a predictor for coccolithophorid sensitivity to ongoing ocean acidification’

The oceanic sink for anthropogenic CO2 from 1994 to 2007

We quantify the oceanic sink for anthropogenic carbon dioxide (CO2) over the period 1994 to 2007 by using observations from the global repeat hydrography program and contrasting them to observations from the 1990s. Using a linear regression–based method, we find a global increase in the anthropogenic CO2 inventory of 34 ± 4 petagrams of carbon (Pg C) between 1994 and 2007. This is equivalent to an average uptake rate of 2.6 ± 0.3 Pg C year−1 and represents 31 ± 4% of the global anthropogenic CO2 emissions over this period. Although this global ocean sink estimate is consistent with the expectation of the ocean uptake having increased in proportion to the rise in atmospheric CO2, substantial regional differences in storage rate are found, likely owing to climate variability–driven changes in ocean circulation.

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Sudden emergence of a shallow aragonite saturation horizon in the Southern Ocean

Models project that with current CO2 emission rates, the Southern Ocean surface will be undersaturated with respect to aragonite by the end of this century1,2,3,4. This will result in widespread impacts on biogeochemistry and ocean ecosystems5,6,7, particularly the health of aragonitic organisms, such as pteropods7, which can dominate polar surface water communities6. Here, we quantify the depth of the present-day Southern Ocean aragonite saturation horizon using hydrographic and ocean carbon chemistry observations, and use a large ensemble of simulations from the Community Earth System Model (CESM)8,9 to track its evolution. A new, shallow aragonite saturation horizon emerges in many Southern Ocean locations between now and the end of the century. While all ensemble members capture the emergence, internal climate variability may affect the year of emergence; thus, its detection may have been overlooked by ensemble average analysis in the past. The emergence of the new horizon is driven by the slow accumulation of anthropogenic CO2 in the Southern Ocean thermocline, where the carbonate ion concentration exhibits a local minimum and approaches undersaturation. The new horizon is also apparent under an emission-stabilizing scenario indicating an inevitable, sudden decrease in the volume of suitable habitat for aragonitic organisms.

Continue reading ‘Sudden emergence of a shallow aragonite saturation horizon in the Southern Ocean’

The internal consistency of the marine carbon dioxide system for high latitude shipboard and in situ monitoring

Highlights
• Best calculations from combination of T,P-dependent and non-dependent parameters

• The dissociation constants of M73 and L yielded the best internal consistency

• Monte Carlo simulation of uncertainty propagation shows combined uncertainty to be more dependent on input parameters, less on dissociation constants

• Internal consistency study for deep ocean conditions is required

Abstract
Deep convection in the Labrador Sea supplies large amounts of anthropogenic carbon to the ocean’s interior. We use measurements of all four measurable CO2 system parameters made along AR7W (across Labrador Sea) between 2013 and 2015 to assess the internal consistency of the carbonate system, including, as appropriate, conversion to in situ temperature (T) and pressure (P). The best agreement between measured and calculated values was obtained through combination of T,P-dependent (pH or pCO2) and non-dependent (TA or DIC) parameters. Use of the dissociation constants of Mehrbach et al. (1973) as refit by Dickson and Millero (1987) and Lueker et al. (2000) yielded the best internal consistency irrespective of the input parameters used. A Monte Carlo simulation demonstrated that the propagated uncertainty (i.e. combined standard uncertainty) of calculated parameters of the carbonate system is (a) always larger than the analytical precision of the measurements themselves; (b) strongly dependent on the choice of input parameters and uncertainties; (c) less dependent on choice of the specific set of constants. For calculation of other parameters of the carbonate system from TA and DIC measurements made throughout the Labrador Sea time-series, the estimated combined standard uncertainty of calculated pCO2 and pH based on the Monte Carlo simulation is ~ 13 μatm and ~ 0.012 pH units respectively, with accuracy relative to laboratory-based measurement estimated to be between −3 and − 13 μatm and 0.002 and 0.007 pH units. Internal consistency especially at in situ temperature and pressure conditions is important for rapidly developing sensor-based monitoring programs in the region, including measurement of pH and/or pCO2 from gliders, profiling floats and moorings. We highlight uncertainty associated with the large pressure effect on pH and pCO2, and recommend a study of carbonate system internal consistency under deep ocean conditions that addresses pressure effects on calculations.

Continue reading ‘The internal consistency of the marine carbon dioxide system for high latitude shipboard and in situ monitoring’

Meeting climate targets by direct CO2 injections: what price would the ocean have to pay?

We investigate the climate mitigation potential and collateral effects of direct injections of captured CO2 into the deep ocean as a possible means to close the gap between an intermediate CO2 emissions scenario and a specific temperature target, such as the 1.5 °C target aimed for by the Paris Agreement. For that purpose, a suite of approaches for controlling the amount of direct CO2 injections at 3000 m water depth are implemented in an Earth System Model of intermediate complexity.

Following the representative concentration pathway RCP4.5, which is a medium mitigation CO2 emissions scenario, cumula-tive CO2 injections required to meet the 1.5 °C climate goal are found to be 390 Gt C by the year 2100 and 1562 Gt C at the end of simulations, by the year 3020. The latter includes a cumulative leakage of 602 Gt C that needs to be re-injected in order to sustain the targeted global mean temperature.

CaCO3 sediment and weathering feedbacks reduce the required CO2 injections that comply with the 1.5 °C target by about 13 % in 2100 and by about 11 % at the end of the simulation.

With respect to the injection-related impacts we find that average pH values in the surface ocean are increased by about 0.13 to 0.18 units, when compared to the control run. In the model, this results in significant increases in potential coral reef habi-tats, i.e., the volume of the global upper ocean (0 to 130 m depth) with omega aragonite > 3.4 and ocean temperatures be-tween 21 °C and 28 °C, compared to the control run. The potential benefits in the upper ocean come at the expense of strongly acidified water masses at depth, with maximum pH reductions of about −2.37 units, relative to preindustrial, in the vicinity of the injection sites. Overall, this study demonstrates that massive amounts of CO2 would need to be injected into the deep ocean in order to reach and maintain the 1.5 °C climate target in a medium mitigation scenario on a millennium timescale, and that there is a trade-off between injection-related reductions in atmospheric CO2 levels accompanied by reduced upper-ocean acidification and adverse effects on deep ocean chemistry, particularly near the injection sites.

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Ecological-economic sustainability of the Baltic cod fisheries under ocean warming and acidification

Highlights
• Ocean warming and acidification (OAW) will drastically decrease cod fishing opportunities in the Baltic.

• Ecological-economic modeling shows high losses in catch, and profits due to OAW.

• There is a high risk of cod stock collapse under mid-term climate change.

• Improved management could temporarily counteract OAW stressors.

• Adaptation includes a reduction in fishing mortality, and increased mesh size.

Abstract
Human-induced climate change such as ocean warming and acidification, threatens marine ecosystems and associated fisheries. In the Western Baltic cod stock socio-ecological links are particularly important, with many relying on cod for their livelihoods. A series of recent experiments revealed that cod populations are negatively affected by climate change, but an ecological-economic assessment of the combined effects, and advice on optimal adaptive management are still missing. For Western Baltic cod, the increase in larval mortality due to ocean acidification has experimentally been quantified. Time-series analysis allows calculating the temperature effect on recruitment. Here, we include both processes in a stock-recruitment relationship, which is part of an ecological-economic optimization model. The goal was to quantify the effects of climate change on the triple bottom line (ecological, economic, social) of the Western Baltic cod fishery. Ocean warming has an overall negative effect on cod recruitment in the Baltic. Optimal management would react by lowering fishing mortality with increasing temperature, to create a buffer against climate change impacts. The negative effects cannot be fully compensated, but even at 3 °C warming above the 2014 level, a reduced but viable fishery would be possible. However, when accounting for combined effects of ocean warming and acidification, even optimal fisheries management cannot adapt to changes beyond a warming of +1.5° above the current level. Our results highlight the need for multi-factorial climate change research, in order to provide the best available, most realistic, and precautionary advice for conservation of exploited species as well as their connected socio-economic systems.

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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

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