The Experts below are selected from a list of 21471 Experts worldwide ranked by ideXlab platform
Jeremy T Mathis - One of the best experts on this subject based on the ideXlab platform.
-
storm induced upwelling of high pco2 waters onto the continental shelf of the western arctic ocean and implications for carbonate mineral saturation states
Geophysical Research Letters, 2012Co-Authors: Jeremy T Mathis, Robert S Pickart, Robert H Byrne, Craig Mcneil, G W K Moore, Laurie W Juranek, Xuewu Liu, Regina A Easley, Matthew M Elliot, Jessica N CrossAbstract:[1] The carbon system of the western Arctic Ocean is undergoing a rapid transition as sea ice extent and thickness decline. These processes are dynamically forcing the region, with unknown consequences for CO2 fluxes and carbonate mineral saturation states, particularly in the coastal regions where sensitive ecosystems are already under threat from multiple stressors. In October 2011, persistent wind-driven upwelling occurred in open water along the continental shelf of the Beaufort Sea in the western Arctic Ocean. During this time, cold ( 32.4) halocline water—supersaturated with respect to atmospheric CO2 (pCO2 > 550 μatm) and undersaturated in Aragonite (ΩAragonite < 1.0) was transported onto the Beaufort shelf. A single 10-day event led to the outgassing of 0.18–0.54 Tg-C and caused Aragonite undersaturations throughout the water column over the shelf. If we assume a conservative estimate of four such upwelling events each year, then the annual flux to the atmosphere would be 0.72–2.16 Tg-C, which is approximately the total annual sink of CO2 in the Beaufort Sea from primary production. Although a natural process, these upwelling events have likely been exacerbated in recent years by declining sea ice cover and changing atmospheric conditions in the region, and could have significant impacts on regional carbon budgets. As sea ice retreat continues and storms increase in frequency and intensity, further outgassing events and the expansion of waters that are undersaturated in carbonate minerals over the shelf are probable.
-
coupling primary production and terrestrial runoff to ocean acidification and carbonate mineral suppression in the eastern bering sea
Journal of Geophysical Research, 2011Co-Authors: Jeremy T Mathis, Jessica N Cross, Nicholas R BatesAbstract:Water column pH and carbonate mineral saturation states were calculated from dissolved inorganic carbon (DIC) and total alkalinity data collected over the eastern Bering Sea shelf in the spring and summer of 2008. The saturation states (?) of the two most important carbonate minerals, calcite (?calcite) and Aragonite (?Aragonite) were strongly coupled to terrestrial runoff from the Yukon and Kuskokwim rivers, primary production in the surface waters, and remineralization of organic matter at depth over the shelf. In spring, before ice melt occurred, pH over the shelf was largely confined to a range of 7.9–8.1 and ?calcite and ?Aragonite ranged from 1.5 to 3.0 and 0.8 to 2.0, respectively. At the stations closest to river outflows, Aragonite was undersaturated in the water column from the surface to the bottom. During the summer sea ice retreat, high rates of primary production consumed DIC in the mixed layer, which increased pH and ?calcite and ?Aragonite. However, ?calcite and ?Aragonite decreased by ?0.3 in the bottom waters over the middle and outer shelf. Over the northern shelf, where export production is highest, ?Aragonite decreased by ?0.35 and became highly undersaturated. The observed suppression and undersaturation of ?calcite and ?Aragonite in the eastern Bering Sea are correlated with anthropogenic carbon dioxide uptake into the ocean and will likely be exacerbated under business-as-usual emission scenarios. Therefore, ocean acidification could threaten some benthic and pelagic calcifying organisms across the Bering Sea shelf in the coming decades.
-
ocean acidification and biologically induced seasonality of carbonate mineral saturation states in the western arctic ocean
Journal of Geophysical Research, 2009Co-Authors: Nicholas R Bates, Jeremy T Mathis, Lee W CooperAbstract:Calcium carbonate (CaCO3) mineral saturation states for Aragonite (?Aragonite) and calcite (?calcite) are calculated for waters of the Chukchi Sea shelf and Canada Basin of the western Arctic Ocean during the Shelf-Basin Interactions project from 2002 to 2004. On the Chukchi Sea shelf, a strong seasonality and vertical differentiation of Aragonite and calcite saturation states was observed. During the summertime sea ice retreat period, high rates of phytoplankton primary production and net community production act to increase the ?Aragonite and ?calcite of surface waters, while subsurface waters become undersaturated with respect to Aragonite due primarily to remineralization of organic matter to CO2. This seasonal “phytoplankton-carbonate saturation state” interaction induces strong undersaturation of Aragonite (?Aragonite = 10%). The seasonal Aragonite undersaturation of waters observed on the Chukchi Sea shelf is likely a recent phenomenon that results from the uptake of anthropogenic CO2 and subsequent ocean acidification, with seasonality of saturation states superimposed by biological processes. These undersaturated waters are potentially highly corrosive to calcifying benthic fauna (e.g., bivalves and echinoderms) found on the shelf, with implications for the food sources of large benthic feeding mammals (e.g., walrus, gray whales, and bearded seals). The benthic ecosystem of the Chukchi Sea (and other Arctic Ocean shelves) is thus potentially vulnerable to future ocean acidification and suppression of CaCO3 saturation states.
Jessica N Cross - One of the best experts on this subject based on the ideXlab platform.
-
storm induced upwelling of high pco2 waters onto the continental shelf of the western arctic ocean and implications for carbonate mineral saturation states
Geophysical Research Letters, 2012Co-Authors: Jeremy T Mathis, Robert S Pickart, Robert H Byrne, Craig Mcneil, G W K Moore, Laurie W Juranek, Xuewu Liu, Regina A Easley, Matthew M Elliot, Jessica N CrossAbstract:[1] The carbon system of the western Arctic Ocean is undergoing a rapid transition as sea ice extent and thickness decline. These processes are dynamically forcing the region, with unknown consequences for CO2 fluxes and carbonate mineral saturation states, particularly in the coastal regions where sensitive ecosystems are already under threat from multiple stressors. In October 2011, persistent wind-driven upwelling occurred in open water along the continental shelf of the Beaufort Sea in the western Arctic Ocean. During this time, cold ( 32.4) halocline water—supersaturated with respect to atmospheric CO2 (pCO2 > 550 μatm) and undersaturated in Aragonite (ΩAragonite < 1.0) was transported onto the Beaufort shelf. A single 10-day event led to the outgassing of 0.18–0.54 Tg-C and caused Aragonite undersaturations throughout the water column over the shelf. If we assume a conservative estimate of four such upwelling events each year, then the annual flux to the atmosphere would be 0.72–2.16 Tg-C, which is approximately the total annual sink of CO2 in the Beaufort Sea from primary production. Although a natural process, these upwelling events have likely been exacerbated in recent years by declining sea ice cover and changing atmospheric conditions in the region, and could have significant impacts on regional carbon budgets. As sea ice retreat continues and storms increase in frequency and intensity, further outgassing events and the expansion of waters that are undersaturated in carbonate minerals over the shelf are probable.
-
coupling primary production and terrestrial runoff to ocean acidification and carbonate mineral suppression in the eastern bering sea
Journal of Geophysical Research, 2011Co-Authors: Jeremy T Mathis, Jessica N Cross, Nicholas R BatesAbstract:Water column pH and carbonate mineral saturation states were calculated from dissolved inorganic carbon (DIC) and total alkalinity data collected over the eastern Bering Sea shelf in the spring and summer of 2008. The saturation states (?) of the two most important carbonate minerals, calcite (?calcite) and Aragonite (?Aragonite) were strongly coupled to terrestrial runoff from the Yukon and Kuskokwim rivers, primary production in the surface waters, and remineralization of organic matter at depth over the shelf. In spring, before ice melt occurred, pH over the shelf was largely confined to a range of 7.9–8.1 and ?calcite and ?Aragonite ranged from 1.5 to 3.0 and 0.8 to 2.0, respectively. At the stations closest to river outflows, Aragonite was undersaturated in the water column from the surface to the bottom. During the summer sea ice retreat, high rates of primary production consumed DIC in the mixed layer, which increased pH and ?calcite and ?Aragonite. However, ?calcite and ?Aragonite decreased by ?0.3 in the bottom waters over the middle and outer shelf. Over the northern shelf, where export production is highest, ?Aragonite decreased by ?0.35 and became highly undersaturated. The observed suppression and undersaturation of ?calcite and ?Aragonite in the eastern Bering Sea are correlated with anthropogenic carbon dioxide uptake into the ocean and will likely be exacerbated under business-as-usual emission scenarios. Therefore, ocean acidification could threaten some benthic and pelagic calcifying organisms across the Bering Sea shelf in the coming decades.
Nicholas R Bates - One of the best experts on this subject based on the ideXlab platform.
-
coupling primary production and terrestrial runoff to ocean acidification and carbonate mineral suppression in the eastern bering sea
Journal of Geophysical Research, 2011Co-Authors: Jeremy T Mathis, Jessica N Cross, Nicholas R BatesAbstract:Water column pH and carbonate mineral saturation states were calculated from dissolved inorganic carbon (DIC) and total alkalinity data collected over the eastern Bering Sea shelf in the spring and summer of 2008. The saturation states (?) of the two most important carbonate minerals, calcite (?calcite) and Aragonite (?Aragonite) were strongly coupled to terrestrial runoff from the Yukon and Kuskokwim rivers, primary production in the surface waters, and remineralization of organic matter at depth over the shelf. In spring, before ice melt occurred, pH over the shelf was largely confined to a range of 7.9–8.1 and ?calcite and ?Aragonite ranged from 1.5 to 3.0 and 0.8 to 2.0, respectively. At the stations closest to river outflows, Aragonite was undersaturated in the water column from the surface to the bottom. During the summer sea ice retreat, high rates of primary production consumed DIC in the mixed layer, which increased pH and ?calcite and ?Aragonite. However, ?calcite and ?Aragonite decreased by ?0.3 in the bottom waters over the middle and outer shelf. Over the northern shelf, where export production is highest, ?Aragonite decreased by ?0.35 and became highly undersaturated. The observed suppression and undersaturation of ?calcite and ?Aragonite in the eastern Bering Sea are correlated with anthropogenic carbon dioxide uptake into the ocean and will likely be exacerbated under business-as-usual emission scenarios. Therefore, ocean acidification could threaten some benthic and pelagic calcifying organisms across the Bering Sea shelf in the coming decades.
-
ocean acidification and biologically induced seasonality of carbonate mineral saturation states in the western arctic ocean
Journal of Geophysical Research, 2009Co-Authors: Nicholas R Bates, Jeremy T Mathis, Lee W CooperAbstract:Calcium carbonate (CaCO3) mineral saturation states for Aragonite (?Aragonite) and calcite (?calcite) are calculated for waters of the Chukchi Sea shelf and Canada Basin of the western Arctic Ocean during the Shelf-Basin Interactions project from 2002 to 2004. On the Chukchi Sea shelf, a strong seasonality and vertical differentiation of Aragonite and calcite saturation states was observed. During the summertime sea ice retreat period, high rates of phytoplankton primary production and net community production act to increase the ?Aragonite and ?calcite of surface waters, while subsurface waters become undersaturated with respect to Aragonite due primarily to remineralization of organic matter to CO2. This seasonal “phytoplankton-carbonate saturation state” interaction induces strong undersaturation of Aragonite (?Aragonite = 10%). The seasonal Aragonite undersaturation of waters observed on the Chukchi Sea shelf is likely a recent phenomenon that results from the uptake of anthropogenic CO2 and subsequent ocean acidification, with seasonality of saturation states superimposed by biological processes. These undersaturated waters are potentially highly corrosive to calcifying benthic fauna (e.g., bivalves and echinoderms) found on the shelf, with implications for the food sources of large benthic feeding mammals (e.g., walrus, gray whales, and bearded seals). The benthic ecosystem of the Chukchi Sea (and other Arctic Ocean shelves) is thus potentially vulnerable to future ocean acidification and suppression of CaCO3 saturation states.
Jaroslaw Stolarski - One of the best experts on this subject based on the ideXlab platform.
-
diagenetic alteration of triassic coral from the Aragonite konservat lagerstatte in alakir cay turkey implications for geochemical measurements
PALAIOS, 2013Co-Authors: Katarzyna Frankowiak, Maciej Mazur, Anne M Gothmann, Jaroslaw StolarskiAbstract:ABSTRACT Skeletons of Norian corals from the Aragonite Konservat-Lagerstatte in Alakir Cay, Turkey are commonly considered to be exceptionally preserved. However, one example of Pachysolenia cylindrica shows that although Aragonite is the dominant mineral phase (about 86.2%), the distribution of microscale diagenetic features in the skeleton complicate its usage as a paleoenvironmental archive. We used a density separation technique to isolate Aragonite-enriched powders of skeletal material, which compared to powders of bulk skeleton (∼8.3% more calcite than Aragonite-enriched powders), exhibit higher Sr/Ca (by an average of 0.27 mmol/mol), lower Mg/Ca (by an average of 1.34 mmol/mol), and lower δ18O (by an average of 0.28‰). In addition, paleo-sea surface temperatures calculated using values from bulk measurements are 1.1–3.4 °C colder (3.3–3.4 °C for Sr/Ca and 1.1–2.0 °C for δ18O) than temperatures calculated from the density-separated, Aragonite-enriched powders. These data suggest that the presence of...
-
diagenetic alteration of triassic coral from the Aragonite konservat lagerstatte in alakir cay turkey implications for geochemical measurements
PALAIOS, 2013Co-Authors: Katarzyna Frankowiak, Maciej Mazur, Anne M Gothmann, Jaroslaw StolarskiAbstract:Skeletons of Norian corals from the Aragonite Konservat-Lagerstatte in Alakir Cay, Turkey are commonly considered to be exceptionally preserved. However, one example of Pachysolenia cylindrica shows that although Aragonite is the dominant mineral phase (about 86.2%), the distribution of microscale diagenetic features in the skeleton complicate its usage as a paleoenvironmental archive. We used a density separation technique to isolate Aragonite-enriched powders of skeletal material, which compared to powders of bulk skeleton (∼8.3% more calcite than Aragonite-enriched powders), exhibit higher Sr/Ca (by an average of 0.27 mmol/mol), lower Mg/Ca (by an average of 1.34 mmol/mol), and lower δ18O (by an average of 0.28‰). In addition, paleo-sea surface temperatures calculated using values from bulk measurements are 1.1–3.4 °C colder (3.3–3.4 °C for Sr/Ca and 1.1–2.0 °C for δ18O) than temperatures calculated from the density-separated, Aragonite-enriched powders. These data suggest that the presence of about 13.8% of secondary calcite can influence the robustness of geochemical proxies and that density separation is an effective tool for recovering the original geochemical signal from diagenetically altered samples.
-
high resolution synchrotron radiation studies on natural and thermally annealed scleractinian coral biominerals
Journal of Applied Crystallography, 2007Co-Authors: Jaroslaw Stolarski, Maciej Mazur, R Przenioslo, Michela BrunelliAbstract:The structural phase transition from Aragonite to calcite in biogenic samples extracted from the skeletons of selected scleractinian corals has been studied by synchrotron radiation diffraction. Biogenic Aragonite samples were extracted en bloc without pulverization from two ecologically different scleractinian taxa: Desmophyllum (deep-water, solitary and azooxanthellate) and Favia (shallow-water, colonial, zooxanthellate). It was found that natural (not pulverized) samples contribute to narrow Bragg peaks with Δd/d values as low as 1 × 10−3, which allows the exploitation of the high resolution of synchrotron radiation diffraction. A precise determination of the lattice parameters of biogenic scleractinian coral Aragonite shows the same type of changes of the a, b, c lattice parameter ratios as that reported for Aragonite extracted from other invertebrates [Pokroy, Quintana, Caspi, Berner & Zolotoyabko (2004). Nat. Mater. 3, 900–902]. It is believed that the crystal structure of biogenic samples is influenced by interactions with organic molecules that are initially present in the biomineralization hydrogel. The calcite phase obtained by annealing the coral samples has a considerably different unit-cell volume and lattice parameter ratio c/a as compared with reference geological calcite and annealed synthetic Aragonite. The internal strain in the calcite structure obtained by thermal annealing of the biomineral samples is about two times larger than that found in the natural Aragonite structure. This effect is observed despite slow heating and cooling of the sample.
Alfonso Mucci - One of the best experts on this subject based on the ideXlab platform.
-
phosphoric acid fractionation factors for calcite and Aragonite between 25 and 75 c revisited
Chemical Geology, 2007Co-Authors: Alfonso Mucci, Bruce E TaylorAbstract:This paper reports the results of an investigation to re-determine the phosphoric acid fractionation factor for calcite and Aragonite in order to improve the accuracy and limit the uncertainty of this very important quantity. The 18 O/ 16 O ratio of 100% of the oxygen in calcite and Aragonite was determined directly by combining data from a two-step procedure involving thermal decomposition of the carbonate, followed by fluorination of the residual CaO using BrF5. The oxygen isotope composition of the CO2 released upon the thermal decarbonation of calcite and Aragonite is enriched in 18 O relative to that of the remaining CaO. Reproducibility of the oxygen isotope composition of the CO2 derived from each of the decarbonation and fluorination steps was 0.55‰ (1σ). Nevertheless, statistically reliable acid fractionation factors for calcite (se=0.07) and Aragonite (se=0.10) were determined on the basis of a large set of combined data from conventional phosphoric acid reactions at three different temperatures, plus the decarbonation/fluorination procedure. The acid fractionation factors (αCO2(ACID)-carbonate) determined in this study for calcite (αCO2(ACID)–Calcite=1.01030) and Aragonite (αCO2(ACID)–Aragonite=1.01063) at 25 °C, differ slightly from previously published values. On the basis of our new determinations at 25, 50, and 75 °C, revised expressions for the temperature dependence of the acid fractionation factors for calcite and Aragonite are proposed for the temperature range of 25–75 °C:
-
oxygen isotope fractionation between synthetic Aragonite and water influence of temperature and mg2 concentration
Geochimica et Cosmochimica Acta, 2007Co-Authors: Sangtae Kim, James R Oneil, Claude Hillairemarcel, Alfonso MucciAbstract:Aragonite was precipitated in the laboratory at 0, 5, 10, 25, and 40 C to determine the temperature dependence of the equilibrium oxygen isotope fractionation between Aragonite and water. Forced CO2 degassing, passive CO2 degassing, and constant addition methods were employed to precipitate Aragonite from supersaturated solutions, but the resulting Aragonite–water oxygen isotope fractionation was independent of the precipitation method. In addition, under the experimental conditions of this study, the effect of precipitation rate on the oxygen isotope fractionation between Aragonite and water was almost within the analytical error of ±� 0.13‰ and thus insignificant. Because the presence of Mg 2+ ions is required to nucleate and precipitate Aragonite from Na–Ca–Cl–HCO3 solutions under these experimental conditions, the influence of the total Mg 2+ concentration (up to � 0.9 molal) on the Aragonite–water oxygen isotope fractionation was examined at 25 C. No significant Mg 2+ ion effect, or oxygen isotope salt effect, was detected up to 100 mmolal total Mg 2+ but a noticeable isotope salt effect was observed at � 0.9 molal total Mg 2+ . On the basis of results of the laboratory synthesis experiments, a new expression for the Aragonite–water fractionation is