Calcite dissolution kinetics and solubility in Na-Ca-Mg-Cl brines of geologically relevant composition at 0.1 to 1 bar pCO2 and 25 to 80°C

Sedimentary basins can contain close to 20% by volume pore fluids that are commonly classified as brines. These fluids can become undersaturated with respect to calcite as a result of processes such as migration, dispersive mixing, or anthropogenic injection of CO2. This study measured calcite solubility and dissolution rates in geologically relevant Na-Ca-Mg-Cl synthetic brines (35 to 200 g L-1 TDS). In brines 0.2 in these calcium-rich brines. These findings offer important implications to reaction-transport models in carbonate-bearing saline reservoirs

Time of Emergence of Surface Ocean Carbon Dioxide Trends in the North American Coastal Margins in Support of Ocean Acidification Observing System Design

Time of Emergence (ToE) is the time when a signal emerges from the noise of natural variability. Commonly used in climate science for the detection of anthropogenic forcing, this concept has recently been applied to geochemical variables, to assess the emerging times of anthropogenic ocean acidification (OA), mostly in the open ocean using global climate and Earth System Models. Yet studies of OA variables are scarce within costal margins, due to limited multidecadal time-series observations of carbon parameters. ToE provides important information for decision making regarding the strategic configuration of observing assets, to ensure they are optimally positioned either for signal detection and/or process elicitation and to identify the most suitable variables in discerning OA-related changes. Herein, we present a short overview of ToE estimates on an OA variable, CO2 fugacity f(CO2,sw), in the North American ocean margins, using coastal data from the Surface Ocean CO2 Atlas (SOCAT) V5. ToE suggests an average theoretical timeframe for an OA signal to emerge, of 23(±13) years, but with considerable spatial variability. Most coastal areas are experiencing additional secular and/or multi-decadal forcing(s) that modifies the OA signal, and such forcing may not be sufficiently resolved by current observations. We provide recommendations, which will help scientists and decision makers design and implement OA monitoring systems in the next decade, to address the objectives of OceanObs19 (http://www.oceanobs19.net) in support of the United Nations Decade of Ocean Science for Sustainable Development (2021–2030) (https://en.unesco.org/ocean-decade) and the Sustainable Development Goal (SDG) 14.3 (https://sustainabledevelopment.un.org/sdg14) target to “Minimize and address the impacts of OA.

Projecting ocean acidification impacts for the Gulf of Maine to 2050: new tools and expectations

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Siedlecki, S. A., Salisbury, J., Gledhill, D. K., Bastidas, C., Meseck, S., McGarry, K., Hunt, C. W., Alexander, M., Lavoie, D., Wang, Z. A., Scott, J., Brady, D. C., Mlsna, I., Azetsu-Scott, K., Liberti, C. M., Melrose, D. C., White, M. M., Pershing, A., Vandemark, D., Townsend, D. W., Chen, C,. Mook, W., Morrison, R. Projecting ocean acidification impacts for the Gulf of Maine to 2050: new tools and expectations. Elementa: Science of the Anthropocene, 9(1), (2021): 00062, https://doi.org/10.1525/elementa.2020.00062.Ocean acidification (OA) is increasing predictably in the global ocean as rising levels of atmospheric carbon dioxide lead to higher oceanic concentrations of inorganic carbon. The Gulf of Maine (GOM) is a seasonally varying region of confluence for many processes that further affect the carbonate system including freshwater influences and high productivity, particularly near the coast where local processes impart a strong influence. Two main regions within the GOM currently experience carbonate conditions that are suboptimal for many organisms—the nearshore and subsurface deep shelf. OA trends over the past 15 years have been masked in the GOM by recent warming and changes to the regional circulation that locally supply more Gulf Stream waters. The region is home to many commercially important shellfish that are vulnerable to OA conditions, as well as to the human populations whose dependence on shellfish species in the fishery has continued to increase over the past decade. Through a review of the sensitivity of the regional marine ecosystem inhabitants, we identified a critical threshold of 1.5 for the aragonite saturation state (Ωa). A combination of regional high-resolution simulations that include coastal processes were used to project OA conditions for the GOM into 2050. By 2050, the Ωa declines everywhere in the GOM with most pronounced impacts near the coast, in subsurface waters, and associated with freshening. Under the RCP 8.5 projected climate scenario, the entire GOM will experience conditions below the critical Ωa threshold of 1.5 for most of the year by 2050. Despite these declines, the projected warming in the GOM imparts a partial compensatory effect to Ωa by elevating saturation states considerably above what would result from acidification alone and preserving some important fisheries locations, including much of Georges Bank, above the critical threshold.This research was financially supported by the Major Special Projects of the Ministry of Science and Technology of China (2016YFC020600), the Young Scholars Science Foundation of Lanzhou Jiaotong University (2018033), and the Talent Innovation and Entrepreneurship Projects of Lanzhou (2018-RC-84)

Ocean and coastal acidification off New England and Nova Scotia

Author Posting. © The Oceanography Society, 2015. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 28, no. 2 (2015): 182-197, doi:10.5670/oceanog.2015.41.New England coastal and adjacent Nova Scotia shelf waters have a reduced buffering capacity because of significant freshwater input, making the region’s waters potentially more vulnerable to coastal acidification. Nutrient loading and heavy precipitation events further acidify the region’s poorly buffered coastal waters. Despite the apparent vulnerability of these waters, and fisheries’ and mariculture’s significant dependence on calcifying species, the community lacks the ability to confidently predict how the region’s ecosystems will respond to continued ocean and coastal acidification. Here, we discuss ocean and coastal acidification processes specific to New England coastal and Nova Scotia shelf waters and review current understanding of the biological consequences most relevant to the region. We also identify key research and monitoring needs to be addressed and highlight existing capacities that should be leveraged to advance a regional understanding of ocean and coastal acidification.This project was supported in part by an appointment to the Internship/Research Participation Program at the Office of Water, US Environmental Protection Agency (EPA), administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and the EPA. JS acknowledges support from NASA grant from NNX14AL84G NASA-CCS

Taking the Metabolic Pulse of the World\u27s Coral Reefs

Worldwide, coral reef ecosystems are experiencing increasing pressure from a variety of anthropogenic perturbations including ocean warming and acidification, increased sedimentation, eutrophication, and overfishing, which could shift reefs to a condition of net calcium carbonate (CaCO3) dissolution and erosion. Herein, we determine the net calcification potential and the relative balance of net organic carbon metabolism (net community production; NCP) and net inorganic carbon metabolism (net community calcification; NCC) within 23 coral reef locations across the globe. In light of these results, we consider the suitability of using these two metrics developed from total alkalinity (TA) and dissolved inorganic carbon (DIC) measurements collected on different spatiotemporal scales to monitor coral reef biogeochemistry under anthropogenic change. All reefs in this study were net calcifying for the majority of observations as inferred from alkalinity depletion relative to offshore, although occasional observations of net dissolution occurred at most locations. However, reefs with lower net calcification potential (i.e., lower TA depletion) could shift towards net dissolution sooner than reefs with a higher potential. The percent influence of organic carbon fluxes on total changes in dissolved inorganic carbon (DIC) (i.e., NCP compared to the sum of NCP and NCC) ranged from 32% to 88% and reflected inherent biogeochemical differences between reefs. Reefs with the largest relative percentage of NCP experienced the largest variability in seawater pH for a given change in DIC, which is directly related to the reefs ability to elevate or suppress local pH relative to the open ocean. This work highlights the value of measuring coral reef carbonate chemistry when evaluating their susceptibility to ongoing global environmental change and offers a baseline from which to guide future conservation efforts aimed at preserving these valuable ecosystems

Climate Science Special Report: Fourth National Climate Assessment (NCA4), Volume I

New observations and new research have increased our understanding of past, current, and future climate change since the Third U.S. National Climate Assessment (NCA3) was published in May 2014. This Climate Science Special Report (CSSR) is designed to capture that new information and build on the existing body of science in order to summarize the current state of knowledge and provide the scientific foundation for the Fourth National Climate Assessment (NCA4)

Vulnerability and adaptation of US shellfisheries to ocean acidification

Ocean acidification is a global, long-term problem whose ultimate solution requires carbon dioxide reduction at a scope and scale that will take decades to accomplish successfully. Until that is achieved, feasible and locally relevant adaptation and mitigation measures are needed. To help to prioritize societal responses to ocean acidification, we present a spatially explicit, multidisciplinary vulnerability analysis of coastal human communities in the United States. We focus our analysis on shelled mollusc harvests, which are likely to be harmed by ocean acidification. Our results highlight US regions most vulnerable to ocean acidification (and why), important knowledge and information gaps, and opportunities to adapt through local actions. The research illustrates the benefits of integrating natural and social sciences to identify actions and other opportunities while policy, stakeholders and scientists are still in relatively early stages of developing research plans and responses to ocean acidification.This is the publisher’s final pdf. The published article is copyrighted by the Nature Publishing Group and can be found at: http://www.nature.com/nclimate/index.html

Sulfur geochemistry of thermogenic gas hydrate and associated sediment from the Texas-Louisiana continental slope

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 64-70).Issued also on microfiche from Lange Micrographics.Thermogenic gas hydrate and associated sediment were recovered from the northern Gulf of Mexico east of the Mississippi Canyon to investigate the interactions between gas hydrate and sedimentary sulfides. Sediment solid phase analyses included total reduced sulfide (TRS), acid volatile sulfide, and citrate-dithionate and HCl extractable iron. Pore-fluid measurements included []H₂S, chloride, sulfate, ammonia and total dissolved inorganic carbon. Gas hydrate hydrogen sulfide and carbon dioxide content were measured using a new wet chemical technique. The []³⁴S relative to Vienna Canyon Diablo troilite was determined for TRS and hydrate H₂S. Extensive (>95%) reduction of pore-fluid sulfate occurred, resulting in exceptionally high []H₂S concentrations (up to ~10 mM) and TRS concentrations (271 ± 50 []mole/g). However, the mole fraction of H₂S within the gas hydrate was too low (~0.3%) to significantly influence hydrate stability. This appears related to high reactive iron concentrations which average 256 ± 66 []mol/g (pyrite iron + HCl extractable iron). These iron-rich sediments are thus capable of sequestering much of the generated sulfide in the form of TRS minerals, thereby making it unavailable for incorporation by gas hydrate. The TRS concentrations are about an order of magnitude greater than expected for sites at similar water depths in the northern Gulf of Mexico. Steep dissolved []H₂S concentration gradients were observed both above and below the gas hydrate indicating diffusion of sulfide from the surrounding system into the gas hydrate. The gradients were used to estimate an incorporation rate of ~1 []mol H₂S/yr-cm² assuming molecular diffusion. TRS in close proximity to the hydrate was depleted in ³⁴S by ~10[0/00] relative to TRS remote to the hydrate. The precise mechanism responsible for this relative depletion in ³⁴S is not clear, but may prove an important geochemical indicator of sediments in which gas hydrate is or has been present. Studies at other sites will be necessary to confirm the generality of these observations

Observing Ocean Acidification from Space

Space-based observations provide synoptic coverage of surface ocean temperature, winds, sea surface height, and color useful to a wide range of oceanographic applications. These measurements are increasingly applied to monitor large-scale environmental and climate processes that can have an impact on important managed marine resources. From observing the development of harmful algal blooms using ocean color, to tracking regions of thermal stress that can induce coral bleaching, satellites are routinely used for environmental monitoring. Here, we demonstrate an approach to monitoring changes in sea surface ocean chemistry in response to ocean acidification as applied to the Greater Caribbean Region. It is based on establishing regional empirical algorithms that combine parameters measured in situ and remotely sensed observables and then using the high-resolution remotely sensed products. This tool is important for exploring regional to basinwide trends in ocean acidification on seasonal to interannual time scales

Caco 3 precipitation kinetics in waters from the great Bahama bank: : Implications for the relationship between bank hydrochemistry and whitings

The source of whitings on the Great Bahama Bank and their relationship to major changes in the chemistry of Bank waters have been among the longest and most hotly debated topics in carbonate geochemistry. In this paper, we demonstrate that the reaction kinetics of calcite with Bank waters for a given saturation state are similar to, but somewhat slower (2 to 3 times) than with Gulf Stream water. The interpretation of the reaction kinetics of suspended Bank sediment with Bank water requires that the precipitating phase be about twice as soluble as aragonite. Good agreement at equivalent saturation states was found between experimental precipitation rates and those calculated for the rate of change of Bank water chemistry in the region of whitings. These results indicate that the dominant mode of carbonate removal is via precipitation on resuspended sediments rather than the rapid pseudo-homogeneous precipitation of calcium carbonate in the water column resulting in the formation of a whiting. Estimates indicate that single aragonite needles may be resuspended many times over a period of decades during which they experience repeated overgrowth. A major portion (>98%) of suspended calcium carbonate is outside the visually dramatic whitings. Thus, as visually spectacular as they are, whitings do not represent a short-term locally massive precipitation of carbonate on the Great Bahama Bank, nor are they even likely to be the dominant sites of carbonate removal in this region. Although future refinements are needed that include seafloor processes, we have at this point arrived at a mechanistic kinetic model that provides a reasonably quantitative explanation for the hydrochemistry of the carbonate system on the northern Great Bahama Bank