Posts Tagged 'globalmodeling'

Using the Health Belief Model to explore the impact of environmental empathy on behavioral intentions to protect ocean health

We examine psychological mediating mechanisms to promote ocean health among the U.S. public. Ocean acidification (OA) was chosen as the focus, as experts consider it as important as climate change with the same cause of humanity’s excessive carbon dioxide (CO2) emissions, but it is lesser known. Empathy is a multi-dimensional concept that includes cognitive and emotional aspects. Previous literature argues that environmental empathy can facilitate positive behaviors. We tested the hypothesis that empathy affects beliefs and behavioral intentions regarding ocean health using the Health Belief Model. We found that higher empathy toward ocean health led to higher perceived susceptibility and severity from OA, greater perceived benefits of CO2 emissions reduction, greater perceived barriers, and keener attention to the media. Beliefs and media attention positively influenced behavioral intentions (e.g., willingness to buy a fuel efficient car). Theoretical and practical implications regarding audience targeting and intervention design are discussed.

Continue reading ‘Using the Health Belief Model to explore the impact of environmental empathy on behavioral intentions to protect ocean health’

Irreversibility of marine climate change impacts under carbon dioxide removal

Artificial carbon dioxide removal (CDR) from the atmosphere has been proposed as a measure for mitigating climate change and restoring the climate system to a target state after exceedance (“overshoot”). This research investigates to what extent overshoot and subsequent recovery of a given cumulative CO2 emissions level by CDR leaves a legacy in the marine environment using an Earth system model. We use RCP2.6 and its extension to year 2300 as the reference scenario and design a set of cumulative emissions and temperature overshoot scenarios based on other RCPs. Our results suggest that the overshoot and subsequent return to a reference cumulative emissions level would leave substantial impacts on the marine environment. Although the changes in sea surface temperature, pH and dissolved oxygen are largely reversible, global mean values and spatial patterns of these variables differ significantly from those in the reference scenario when the reference cumulative emissions are attained.

Continue reading ‘Irreversibility of marine climate change impacts under carbon dioxide removal’

Towards an understanding of the Ca isotopic signal related to ocean acidification and alkalinity overshoots in the rock record

In this contribution, we explore the idea that the Ca isotope proxy has utility as an indicator of carbonate authigenesis (i.e., post-depositional precipitation of CaCO3 within the sedimentary package). Given the strong contrast in isotopic fractionation factor between the formational and diagenetic environments, Ca isotopes have the potential to fingerprint carbonate authigenesis when it occurs close to the seawater-sediment interface. We demonstrate that Ca isotopes are particularly applicable to exploring ocean acidification events, and potentially ocean anoxic events, and focus our attention on ocean acidification related to the Paleocene-Eocene Thermal Maximum (PETM). We present three scenarios that vary in magnitude and duration of carbon fluxes simulated using an Earth System model of intermediate complexity (cGENIE) and use the cGENIE output to constrain the upper boundary conditions of 1-D reactive transport models of authigenesis and recrystallization in the sedimentary section. Along with simple mixing calculations, the models inform our exploration of the hypothesis that authigenic carbonate induced by a saturation state overshoot during the PETM explains recently published Ca isotope records, and perhaps bulk carbonate records over Ocean Anoxic Event (OAE) 2. Our simulations suggest that fractionation factor variability does not explain the PETM δ44Ca records, and we propose a δ44Ca-CaCO3 space framework to assist with the elucidation of authigenic additions over time scales that are short relative to the residence time of Ca in the ocean (~1 Ma). Ultimately, we find that the ‘authigenic zone’ generated in the sedimentary column may be influenced by alkalinity overshoots or redox state; the CaCO3 produced in this zone can overprint temporal signals with depth-dependent signals that reflect lithology and sedimentation rate and need not be spatially uniform, even when driven by a global event. Ultimately, we demonstrate the utility of Ca isotopes for exploring short time scale climatic events and a quantitative framework to guide interpretations.

Continue reading ‘Towards an understanding of the Ca isotopic signal related to ocean acidification and alkalinity overshoots in the rock record’

Dissolved inorganic carbon pump in methane-charged shallow marine sediments: state of the art and new model perspectives

Methane transport from subsurface reservoirs to shallow marine sediment is characterized by unique biogeochemical interactions significant for ocean chemistry. Sulfate-Methane Transition Zone (SMTZ) is an important diagenetic front in the sediment column that quantitatively consumes the diffusive methane fluxes from deep methanogenic sources toward shallow marine sediments via sulfate-driven anaerobic oxidation of methane (AOM). Recent global compilation from diffusion-controlled marine settings suggests methane from below and sulfate from above fluxing into the SMTZ at an estimated rate of 3.8 and 5.3 Tmol year–1, respectively, and wider estimate for methane flux ranges from 1 to 19 Tmol year–1. AOM converts the methane carbon to dissolved inorganic carbon (DIC) at the SMTZ. Organoclastic sulfate reduction (OSR) and deep-DIC fluxes from methanogenic zones contribute additional DIC to the shallow sediments. Here, we provide a quantification of 8.7 Tmol year–1 DIC entering the methane-charged shallow sediments due to AOM, OSR, and the deep-DIC flux (range 6.4–10.2 Tmol year–1). Of this total DIC pool, an estimated 6.5 Tmol year–1 flows toward the water column (range: 3.2–9.2 Tmol year–1), and 1.7 Tmol year–1 enters the authigenic carbonate phases (range: 0.6–3.6 Tmol year–1). This summary highlights that carbonate authigenesis in settings dominated by diffusive methane fluxes is a significant component of marine carbon burial, comparable to ∼15% of carbonate accumulation on continental shelves and in the abyssal ocean, respectively. Further, the DIC outflux through the SMTZ is comparable to ∼20% of global riverine DIC flux to oceans. This DIC outflux will contribute alkalinity or CO2 in different proportions to the water column, depending on the rates of authigenic carbonate precipitation and sulfide oxidation and will significantly impact ocean chemistry and potentially atmospheric CO2. Settings with substantial carbonate precipitation and sulfide oxidation at present are contributing CO2 and thus to ocean acidification. Our synthesis emphasizes the importance of SMTZ as not only a methane sink but also an important diagenetic front for global DIC cycling. We further underscore the need to incorporate a DIC pump in methane-charged shallow marine sediments to models for coastal and geologic carbon cycling.

Continue reading ‘Dissolved inorganic carbon pump in methane-charged shallow marine sediments: state of the art and new model perspectives’

Potential predictability of marine ecosystem drivers

Climate variations can have profound impacts on marine ecosystems and the socioeconomic systems that may depend upon them. Temperature, pH, oxygen (O2) and net primary production (NPP) are commonly considered to be important marine ecosystem drivers, but the potential predictability of these drivers is largely unknown. Here, we use a comprehensive Earth system model within a perfect modeling framework to show that all four ecosystem drivers are potentially predictable on global scales and at the surface up to 3 years in advance. However, there are distinct regional differences in the potential predictability of these drivers. Maximum potential predictability (>10 years) is found at the surface for temperature and O2 in the Southern Ocean and for temperature, O2 and pH in the North Atlantic. This is tied to ocean overturning structures with “memory” or inertia with enhanced predictability in winter. Additionally, these four drivers are highly potentially predictable in the Arctic Ocean at the surface. In contrast, minimum predictability is simulated for NPP (<1 years) in the Southern Ocean. Potential predictability for temperature, O2 and pH increases with depth below the thermocline to more than 10 years, except in the tropical Pacific and Indian oceans, where predictability is also 3 to 5 years in the thermocline. This study indicating multi-year (at surface) and decadal (subsurface) potential predictability for multiple ecosystem drivers is intended as a foundation to foster broader community efforts in developing new predictions of marine ecosystem drivers.

Continue reading ‘Potential predictability of marine ecosystem drivers’

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

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, cumulative 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 reinjected 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 habitats, i.e., the volume of the global upper ocean (0 to 130 m depth) with omega aragonite > 3.4 and ocean temperatures between 21 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 levels, 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.

Continue reading ‘Meeting climate targets by direct CO2 injections: what price would the ocean have to pay? (update)’

A global assessment of the vulnerability of shellfish aquaculture to climate change and ocean acidification

Human‐induced climate change and ocean acidification (CC‐OA) is changing the physical and biological processes occurring within the marine environment, with poorly understood implications for marine life. Within the aquaculture sector, molluskan culture is a relatively benign method of producing a high‐quality, healthy, and sustainable protein source for the expanding human population. We modeled the vulnerability of global bivalve mariculture to impacts of CC‐OA over the period 2020–2100, under RCP8.5. Vulnerability, assessed at the national level, was dependent on CC‐OA‐related exposure, taxon‐specific sensitivity and adaptive capacity in the sector. Exposure risk increased over time from 2020 to 2100, with ten nations predicted to experience very high exposure to CC‐OA in at least one decade during the period 2020–2100. Predicted high sensitivity in developing countries resulted, primarily, from the cultivation of species that have a narrow habitat tolerance, while in some European nations (France, Ireland, Italy, Portugal, and Spain) high sensitivity was attributable to the relatively high economic value of the shellfish production sector. Predicted adaptive capacity was low in developing countries primarily due to governance issues, while in some developed countries (Denmark, Germany, Iceland, Netherlands, Sweden, and the United Kingdom) it was linked to limited species diversity in the sector. Developing and least developed nations (n = 15) were predicted to have the highest overall vulnerability. Across all nations, 2060 was identified as a tipping point where predicted CC‐OA will be associated with the greatest challenge to shellfish production. However, rapid declines in mollusk production are predicted to occur in the next decade for some nations, notably North Korea. Shellfish culture offers human society a low‐impact source of sustainable protein. This research highlights, on a global scale, the likely extent and nature of the CC‐OA‐related threat to shellfish culture and this sector enabling early‐stage adaption and mitigation.

Continue reading ‘A global assessment of the vulnerability of shellfish aquaculture to climate change and ocean acidification’

Year of emergence of ocean acidification in the global ocean

Year of emergence (YoE) is the year when an environment and the organisms within begin to experience significant different conditions (two times of natural variability) from the pre-industrial conditions (~1770 C.E.). This study calculates the global surface ocean YoEs for pH, partial pressure of CO(CO) and aragonite saturation (Ω) from a recent calculated surface ocean carbonate chemistry data product. The data product is calculated from the Surface Ocean CO Atlas version 6 (SOCATv6) with modeled CO changes in the global surface ocean from the ESM2M model. We find that CO, pH and Ω generally emerged from preindustrial conditions in the open ocean by the year 1950, while these properties have still not yet emerged along many ocean margins. We also find that Ω had a significantly delayed YoE compared to pH and CO. The delayed YoE for Ω is caused by its lasting sensitivity to temperature variability, which increases the natural variability experienced by organisms, and a partial cancellation of the long term acidification trend by the global warming. Together, YoEs presented here highlight that there are hotspots (open ocean) and coldspots (ocean margins that were impacted by boundary currents) for the emergence of anthropogenic signals. Continuous data collection and synthesis are needed to further examine the impact of ocean acidification on ecosystem health.

Continue reading ‘Year of emergence of ocean acidification in the global ocean’

Processes driving global interior ocean pH distribution

Ocean acidification evolves on the background of a natural ocean pH gradient that is the result of the interplay between ocean mixing, biological production and remineralization, calcium carbonate cycling, and temperature and pressure changes across the water column. While previous studies have analyzed these processes and their impacts on ocean carbonate chemistry, none have attempted to quantify their impacts on interior ocean pH globally. Here we evaluate how anthropogenic changes and natural processes collectively act on ocean pH, and how these processes set the vulnerability of regions to future changes in ocean acidification. We use the mapped data product from the Global Ocean Data Analysis Project version 2, a novel method to estimate preformed total alkalinity based on a combination of a total matrix intercomparison and locally interpolated regressions, and a comprehensive uncertainty analysis. We find that the largest contribution to the interior ocean pH gradient comes from organic matter remineralization, with CaCO3 cycling being the second most important process. The estimates of the impact of anthropogenic CO2 changes on pH reaffirm the large and well‐understood anthropogenic impact on pH in the surface ocean, and put it in the context of the natural pH gradient in the interior ocean. We also show that in the depth layer 500–1,500 m natural processes enhance ocean acidification by on average 28 ± 15%, but with large regional gradients.

Continue reading ‘Processes driving global interior ocean pH distribution’

Increase in ocean acidity variability and extremes under increasing atmospheric CO2

Ocean acidity extreme events are short-term periods of extremely high [H+] concentrations. The uptake of anthropogenic CO2 emissions by the ocean is expected to lead to more frequent and intense ocean acidity extreme events, not only due to mean ocean acidification, but also due to increases in ocean acidity variability. Here, we use daily output from ensemble simulations of a comprehensive Earth system model under a low and high CO2 emission scenario to isolate and quantify the impact of changes in variability on changes in ocean acidity extremes. We show that the number of days with extreme [H+] conditions for surface waters is projected to increase by a factor of 14 by the end of the 21st century under a high CO2 emission scenario relative to preindustrial levels. The duration of individual events is projected to triple, and the maximal intensity and the volume extent in the upper 200 m to quintuple. Similar changes are projected in the thermocline. At surface, the changes are mainly driven by increases in [H+] seasonality, whereas changes in interannual variability are also important in the thermocline. Increases in [H+] variability and extremes arise predominantly from increases in the sensitivity of [H+] to variations in its drivers. In contrast to [H+] extremes, the occurrence of short-term extremes in low aragonite saturation state due to changes in variability is projected to decrease. An increase in [H+] variability and an associated increase in extreme events superimposed onto the long-term ocean acidification trend will enhance the risk of severe and detrimental impacts on marine organisms, especially for those that are adapted to a more stable environment.

Continue reading ‘Increase in ocean acidity variability and extremes under increasing atmospheric CO2’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,356,543 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book