scholarly journals The fate of pelagic CaCO<sub>3</sub> production in a high CO<sub>2</sub> ocean: A model study

2007 ◽  
Vol 4 (1) ◽  
pp. 533-560 ◽  
Author(s):  
M. Gehlen ◽  
R. Gangstø ◽  
B. Schneider ◽  
L. Bopp ◽  
O. Aumont ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Inorganic Carbon ◽  
Emiliania Huxleyi ◽  
Atmospheric Co2 ◽  
Saturation State ◽  
Carbonate Production ◽  
Model Simulations ◽  
Carbon Production ◽  
Model Study ◽  
Organic And Inorganic Carbon

Abstract. This model study addresses the change in pelagic calcium carbonate production (CaCO3, as calcite in the model) and dissolution in response to rising atmospheric CO2. The parameterization of CaCO3 production includes a dependency on the saturation state of seawater with respect to calcite. It was derived from laboratory and mesocosm studies on particulate organic and inorganic carbon production in Emiliania huxleyi as a function of pCO2. The model predicts values of CaCO3 production and dissolution in line with recent estimates. The effect of rising pCO2 on CaCO3 production and dissolution was quantified by means of model simulations forced with atmospheric CO2 increasing at a rate of 1% per year from 286 ppm to 1144 ppm. The simulation predicts a decrease of CaCO3 production by 27%. The combined change in production and dissolution of CaCO3 yields an excess uptake of CO2 from the atmosphere by the ocean of 5.9 GtC.

scholarly journals The fate of pelagic CaCO<sub>3</sub> production in a high CO<sub>2</sub> ocean: a model study

2007 ◽  
Vol 4 (4) ◽  
pp. 505-519 ◽  
Author(s):  
M. Gehlen ◽  
R. Gangstø ◽  
B. Schneider ◽  
L. Bopp ◽  
O. Aumont ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Inorganic Carbon ◽  
Atmospheric Co2 ◽  
Saturation State ◽  
Carbonate Production ◽  
Model Simulations ◽  
Carbon Production ◽  
Model Study ◽  
Time Period ◽  
Organic And Inorganic Carbon

Abstract. This model study addresses the change in pelagic calcium carbonate production (CaCO3, as calcite in the model) and dissolution in response to rising atmospheric CO2. The parameterization of CaCO3 production includes a dependency on the saturation state of seawater with respect to calcite. It was derived from laboratory and mesocosm studies on particulate organic and inorganic carbon production in Emiliania huxleyi as a function of pCO2. The model predicts values of CaCO3 production and dissolution in line with recent estimates. The effect of rising pCO2 on CaCO3 production and dissolution was quantified by means of model simulations forced with atmospheric CO2 increasing at a rate of 1% per year from 286 ppm to 1144 ppm over a 140 year time-period. The simulation predicts a decrease of CaCO3 production by 27%. The combined change in production and dissolution of CaCO3 yields an excess uptake of CO2 from the atmosphere by the ocean of 5.9 GtC over the period of 140 years.

scholarly journals Temporal changes in surface partial pressure of carbon dioxide and carbonate saturation state in the eastern equatorial Indian Ocean during the 1962–2012 period

2014 ◽  
Vol 11 (22) ◽  
pp. 6293-6305 ◽  
Author(s):  
L. Xue ◽  
W. Yu ◽  
H. Wang ◽  
L.-Q. Jiang ◽  
L. Feng ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Indian Ocean ◽  
Partial Pressure ◽  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Equatorial Indian Ocean ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Saturation State ◽  
Eastern Equatorial Indian Ocean

Abstract. Information on changes in the oceanic carbon dioxide (CO2) concentration and air–sea CO2 flux as well as on ocean acidification in the Indian Ocean is very limited. In this study, temporal changes of the inorganic carbon system in the eastern equatorial Indian Ocean (EIO, 5° N–5° S, 90–95° E) are examined using partial pressure of carbon dioxide (pCO2) data collected in May 2012, historical pCO2 data since 1962, and total alkalinity (TA) data calculated from salinity. Results show that sea surface pCO2 in the equatorial belt (2° N–2° S, 90–95° E) increased from ∼307 μatm in April 1963 to ∼373 μatm in May 1999, ∼381 μatm in April 2007, and ∼385 μatm in May 2012. The mean rate of pCO2 increase in this area (∼1.56 μatm yr−1) was close to that in the atmosphere (∼1.46 μatm yr−1). Despite the steady pCO2 increase in this region, no significant change in air–sea CO2 fluxes was detected during this period. Ocean acidification as indicated by pH and saturation states for carbonate minerals has indeed taken place in this region. Surface water pH (total hydrogen scale) and saturation state for aragonite (Ωarag), calculated from pCO2 and TA, decreased significantly at rates of −0.0016 ± 0.0001 and −0.0095 ± 0.0005 yr−1, respectively. The respective contributions of temperature, salinity, TA, and dissolved inorganic carbon (DIC) to the increase in surface pCO2 and the decreases in pH and Ωarag are quantified. We find that the increase in DIC dominated these changes, while contributions from temperature, salinity, and TA were insignificant. The increase in DIC was most likely associated with the increasing atmospheric CO2 concentration, and the transport of accumulated anthropogenic CO2 from a CO2 sink region via basin-scale ocean circulations. These two processes may combine to drive oceanic DIC to follow atmospheric CO2 increase.

scholarly journals Carbonate chemistry in sediment pore waters of the Rhône River delta driven by early diagenesis (NW Mediterranean)

2016 ◽  
Author(s):  
Jens Rassmann ◽  
Bruno Lansard ◽  
Lara Pozzato ◽  
Christophe Rabouille
Keyword(s):  
Calcium Carbonate ◽  
Inorganic Carbon ◽  
Early Diagenesis ◽  
Carbonate Precipitation ◽  
Pore Waters ◽  
Calcium Carbonate Precipitation ◽  
Rhône River ◽  
Saturation State ◽  
Rhone River ◽  
Aerobic And Anaerobic

Abstract. The Rhône River is the largest source of terrestrial organic and inorganic carbon for the Mediterranean Sea, and a large fraction thereof is buried or mineralized in the sediments close to the river mouth. The mineralization follows aerobic and anaerobic pathways with varying impacts on the carbonate chemistry in the sediment pore waters. This study focused on the production of dissolved inorganic carbon (DIC) and total alkalinity (TA) by early diagenesis at the sediment water-interface, consequential pH variations and the effect on calcium carbonate precipitation or dissolution. The sediment pore water chemistry was investigated during the DICASE cruise along a transect from the Rhône River outlet to the continental shelf. The concentrations of DIC, TA, SO42− and Ca2+ were analyzed on bottom waters and extracted pore waters, whereas pH and oxygen concentrations were measured in situ using microelectrodes. The average oxygen penetration depth into the sediment was 1.7 ± 0.4 mm in the proximal domain and 8.2 ± 2.6 mm in the distal domain, indicating intense aerobic respiration rates. Diffusive oxygen fluxes through the sediment water interface range between 3 and 13 mmol O2 m−2 d−1. The DIC and TA concentrations increased with depth in the sediment pore waters up to 48 mmol L−1 near the river outlet and up to 7 mmol L−1 on the shelf as a result of aerobic and anaerobic mineralization processes. Due to oxic processes, the pH decreased by 0.6 pH units in the oxic layer of the sediment accompanied by a decrease of the saturation state regarding calcium carbonate. In the anoxic part of the sediments, sulfate reduction was seen to be the dominant mineralization process and was associated to an increase of pore water saturation state regarding calcium carbonate. Ultimately anoxic mineralization of organic matter caused calcium carbonate precipitation as shown by large decrease in Ca2+ concentration with depth in the sediment. The saturation state and carbonate precipitation decreased in offshore direction, together with the carbon turnover and sulfate consumption in the sediments.

scholarly journals Calcium carbonate production response to future ocean warming and acidification

2011 ◽  
Vol 8 (6) ◽  
pp. 11863-11897
Author(s):  
A. J. Pinsonneault ◽  
H. D. Matthews ◽  
E. D. Galbraith ◽  
A. Schmittner
Keyword(s):  
Calcium Carbonate ◽  
Co2 Emissions ◽  
Climate Model ◽  
Surface Air Temperature ◽  
Ocean Warming ◽  
Total Carbon ◽  
Global Ocean ◽  
Saturation State ◽  
Carbonate Production ◽  
The Impact

Abstract. Anthropogenic carbon dioxide (CO2) emissions are acidifying the ocean, affecting calcification rates in pelagic organisms and thereby modifying the oceanic alkalinity cycle. However, the responses of pelagic calcifying organisms to acidification vary widely between species, contributing uncertainty to predictions of atmospheric CO2 and the resulting climate change. Meanwhile, ocean warming caused by rising CO2 is expected to drive increased growth rates of all pelagic organisms, including calcifiers. It thus remains unclear whether anthropogenic CO2 will ultimately increase or decrease the globally-integrated pelagic calcification rate. Here, we assess the importance of this uncertainty by introducing a variable dependence of calcium carbonate (CaCO3) production on calcite saturation state (ΩCaCO3) in the University of Victoria Earth System Climate Model, an intermediate complexity coupled carbon-climate model. In a series of model simulations, we examine the impact of this parameterization on global ocean carbon cycling under two CO2 emissions scenarios, both integrated to the year 3500. The simulations show a significant sensitivity of the vertical and surface horizontal alkalinity gradients to the parameterization, as well as the removal of alkalinity from the ocean through CaCO3 burial. These sensitivities result in an additional oceanic uptake of carbon when calcification depends on ΩCaCO3 (of up to 13 % of total carbon emissions), compared to the case where calcification is insensitive to acidification. In turn, this response causes a reduction of global surface air temperature of up to 0.4 °C in year 3500, a 13 % reduction in the amplitude of warming. Narrowing these uncertainties will require better understanding of both temperature and acidification effects on pelagic calcifiers. Preliminary examination suggests that alkalinity observations can be used to constrain the range of uncertainties and may exclude large sensitivities of CaCO3 production on ΩCaCO3.

scholarly journals Lateral, Vertical, and Temporal Variability of Seawater Carbonate Chemistry at Hog Reef, Bermuda

2021 ◽  
Vol 8 ◽  
Author(s):  
Ariel K. Pezner ◽  
Travis A. Courtney ◽  
Heather N. Page ◽  
Sarah N. Giddings ◽  
Cory M. Beatty ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Organic Carbon ◽  
Water Column ◽  
Temporal Variability ◽  
Current Flow ◽  
Biogeochemical Processes ◽  
Carbonate Chemistry ◽  
Carbonate Production ◽  
Carbon Production ◽  
Seawater Carbonate Chemistry

Spatial and temporal carbonate chemistry variability on coral reefs is influenced by a combination of seawater hydrodynamics, geomorphology, and biogeochemical processes, though their relative influence varies by site. It is often assumed that the water column above most reefs is well-mixed with small to no gradients outside of the benthic boundary layer. However, few studies to date have explored the processes and properties controlling these multi-dimensional gradients. Here, we investigated the lateral, vertical, and temporal variability of seawater carbonate chemistry on a Bermudan rim reef using a combination of spatial seawater chemistry surveys and autonomous in situ sensors. Instruments were deployed at Hog Reef measuring current flow, seawater temperature, salinity, pHT, pCO2, dissolved oxygen (DO), and total alkalinity (TA) on the benthos, and temperature, salinity, DO, and pCO2 at the surface. Water samples from spatial surveys were collected from surface and bottom depths at 13 stations covering ∼3 km2 across 4 days. High frequency temporal variability in carbonate chemistry was driven by a combination of diel light and mixed semi-diurnal tidal cycles on the reef. Daytime gradients in DO between the surface and the benthos suggested significant water column production contributing to distinct diel trends in pHT, pCO2, and DO, but not TA. We hypothesize these differences reflect the differential effect of biogeochemical processes important in both the water column and benthos (organic carbon production/respiration) vs. processes mainly occurring on the benthos (calcium carbonate production/dissolution). Locally at Hog Reef, the relative magnitude of the diel variability of organic carbon production/respiration was 1.4–4.6 times larger than that of calcium carbonate production/dissolution, though estimates of net organic carbon production and calcification based on inshore-offshore chemical gradients revealed net heterotrophy (−118 ± 51 mmol m–2 day–1) and net calcification (150 ± 37 mmol CaCO3 m–2 day–1). These results reflect the important roles of time and space in assessing reef biogeochemical processes. The spatial variability in carbonate chemistry parameters was larger laterally than vertically and was generally observed in conjunction with depth gradients, but varied between sampling events, depending on time of day and modifications due to current flow.

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