scholarly journals Current CaCO3 dissolution at the seafloor caused by anthropogenic CO2

2018 ◽  
Vol 115 (46) ◽  
pp. 11700-11705 ◽  
Author(s):  
Olivier Sulpis ◽  
Bernard P. Boudreau ◽  
Alfonso Mucci ◽  
Chris Jenkins ◽  
David S. Trossman ◽  
...  
Keyword(s):  
North Atlantic ◽  
Deep Sea ◽  
Hot Spots ◽  
Ion Concentration ◽  
Rate Model ◽  
Saturation State ◽  
Calcite Dissolution ◽  
Carbonate Ion ◽  
Anthropogenic Component ◽  
Compensation Depth

Oceanic uptake of anthropogenic CO2 leads to decreased pH, carbonate ion concentration, and saturation state with respect to CaCO3 minerals, causing increased dissolution of these minerals at the deep seafloor. This additional dissolution will figure prominently in the neutralization of man-made CO2. However, there has been no concerted assessment of the current extent of anthropogenic CaCO3 dissolution at the deep seafloor. Here, recent databases of bottom-water chemistry, benthic currents, and CaCO3 content of deep-sea sediments are combined with a rate model to derive the global distribution of benthic calcite dissolution rates and obtain primary confirmation of an anthropogenic component. By comparing preindustrial with present-day rates, we determine that significant anthropogenic dissolution now occurs in the western North Atlantic, amounting to 40–100% of the total seafloor dissolution at its most intense locations. At these locations, the calcite compensation depth has risen ∼300 m. Increased benthic dissolution was also revealed at various hot spots in the southern extent of the Atlantic, Indian, and Pacific Oceans. Our findings place constraints on future predictions of ocean acidification, are consequential to the fate of benthic calcifiers, and indicate that a by-product of human activities is currently altering the geological record of the deep sea.

scholarly journals Natural variability in the surface ocean carbonate ion concentration

2015 ◽  
Vol 12 (21) ◽  
pp. 6321-6335 ◽  
Author(s):  
N. S. Lovenduski ◽  
M. C. Long ◽  
K. Lindsay
Keyword(s):  
Interannual Variability ◽  
North Atlantic ◽  
North Pacific ◽  
Tropical Pacific ◽  
Ion Concentration ◽  
Saturation State ◽  
Surface Ocean ◽  
The North ◽  
Carbonate Ion ◽  
The Tropical Pacific

Abstract. We investigate variability in the surface ocean carbonate ion concentration ([CO32−]) on the basis of a~long control simulation with an Earth System Model. The simulation is run with a prescribed, pre-industrial atmospheric CO2 concentration for 1000 years, permitting investigation of natural [CO32−] variability on interannual to multi-decadal timescales. We find high interannual variability in surface [CO32−] in the tropical Pacific and at the boundaries between the subtropical and subpolar gyres in the Northern Hemisphere, and relatively low interannual variability in the centers of the subtropical gyres and in the Southern Ocean. Statistical analysis of modeled [CO32−] variance and autocorrelation suggests that significant anthropogenic trends in the saturation state of aragonite (Ωaragonite) are already or nearly detectable at the sustained, open-ocean time series sites, whereas several decades of observations are required to detect anthropogenic trends in Ωaragonite in the tropical Pacific, North Pacific, and North Atlantic. The detection timescale for anthropogenic trends in pH is shorter than that for Ωaragonite, due to smaller noise-to-signal ratios and lower autocorrelation in pH. In the tropical Pacific, the leading mode of surface [CO32−] variability is primarily driven by variations in the vertical advection of dissolved inorganic carbon (DIC) in association with El Niño–Southern Oscillation. In the North Pacific, surface [CO32−] variability is caused by circulation-driven variations in surface DIC and strongly correlated with the Pacific Decadal Oscillation, with peak spectral power at 20–30-year periods. North Atlantic [CO32−] variability is also driven by variations in surface DIC, and exhibits weak correlations with both the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation. As the scientific community seeks to detect the anthropogenic influence on ocean carbonate chemistry, these results will aid the interpretation of trends calculated from spatially and temporally sparse observations.

scholarly journals Natural variability in the surface ocean carbonate ion concentration

2015 ◽  
Vol 12 (15) ◽  
pp. 13123-13157
Author(s):  
N. S. Lovenduski ◽  
M. C. Long ◽  
K. Lindsay
Keyword(s):  
Interannual Variability ◽  
North Atlantic ◽  
North Pacific ◽  
Tropical Pacific ◽  
Ion Concentration ◽  
Saturation State ◽  
Surface Ocean ◽  
The North ◽  
Carbonate Ion ◽  
The Tropical Pacific

Abstract. We investigate variability in the surface ocean carbonate ion concentration ([CO32−]) on the basis of a long control simulation with a fully-coupled Earth System Model. The simulation is run with a prescribed, pre-industrial atmospheric CO2 concentration for 1000 years, permitting investigation of natural [CO32−] variability on interannual to multi-decadal timescales. We find high interannual variability in surface [CO32−] in the tropical Pacific and at the boundaries between the subtropical and subpolar gyres in the Northern Hemisphere, and relatively low interannual variability in the centers of the subtropical gyres and in the Southern Ocean. Statistical analysis of modeled [CO32−] variance and autocorrelation suggests that significant anthropogenic trends in the saturation state of aragonite (Ωaragonite) are already or nearly detectable at the sustained, open-ocean timeseries sites, whereas several decades of observations are required to detect anthropogenic trends in Ωaragonite in the tropical Pacific, North Pacific, and North Atlantic. The detection timescale for anthropogenic trends in pH is shorter than that for Ωaragonite, due to smaller noise-to-signal ratios and lower autocorrelation in pH. In the tropical Pacific, the leading mode of surface [CO32−] variability is primarily driven by variations in the vertical advection of dissolved inorganic carbon (DIC) in association with El Niño–Southern Oscillation. In the North Pacific, surface [CO32−] variability is caused by circulation-driven variations in surface DIC and strongly correlated with the Pacific Decadal Oscillation, with peak spectral power at 20–30 year periods. North Atlantic [CO32−] variability is also driven by variations in surface DIC, and exhibits weak correlations with both the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation. As the scientific community seeks to detect the anthropogenic influence on ocean carbonate chemistry, these results will aid the interpretation of trends calculated from spatially- and temporally-sparse observations.

scholarly journals Changes in calcification of coccoliths under stable atmospheric CO<sub>2</sub>

2014 ◽  
Vol 11 (4) ◽  
pp. 929-944 ◽  
Author(s):  
C. Berger ◽  
K. J. S. Meier ◽  
H. Kinkel ◽  
K.-H. Baumann
Keyword(s):  
Environmental Factors ◽  
North Atlantic ◽  
Ion Concentration ◽  
Average Weight ◽  
Natural Environments ◽  
Weight Changes ◽  
The Holocene ◽  
The North ◽  
Carbonate Ion ◽  
The North Atlantic

Abstract. The response of coccolithophore calcification to ocean acidification has been studied in culture experiments as well as in present and past oceans. The response, however, is different between species and strains, and for the relatively small carbonate chemistry changes observed in natural environments, a uniform response of the entire coccolithophore community has not been documented so far. Moreover, previous palaeo-studies basically focus on changes in coccolith weight due to increasing CO2 and the resulting changes in the carbonate system, and only few studies focus on the influence of other environmental factors. In order to untangle changes in coccolithophore calcification due to environmental factors such as temperature and/or productivity from changes caused by increasing pCO2 and decreasing carbonate ion concentration, we here present a study on coccolith calcification from the Holocene North Atlantic Ocean. The pre-industrial Holocene, with its predominantly stable atmospheric CO2, provides the conditions for such a comprehensive analysis. For an analysis on changes in major components of Holocene coccolithophores under natural conditions, the family Noelaerhabdaceae was selected, which constitutes the main part of the assemblage in the North Atlantic. Records of average coccolith weights from three Holocene sediment cores along a north–south transect in the North Atlantic were analysed. During the Holocene, mean weight (and therefore calcification) of Noelaerhabdaceae (Emiliania huxleyi and Gephyrocapsa) coccoliths decreased at the Azores (Geofar KF 16) from around 7 to 6 pg, but increased at the Rockall Plateau (ODP site 980) from around 6 to 8 pg, and at the Vøring Plateau (MD08-3192) from 7 to 10 pg. The amplitude of average weight variability is within the range of glacial–interglacial changes that were interpreted to be an effect of decreasing carbonate ion concentration. By comparison with SEM assemblage counts, we show that weight changes are not only partly due to variations in the coccolithophore assemblage but also an effect of a change in calcification and/or morphotype variability within single species. Our results indicate that there is no single key factor responsible for the observed changes in coccolith weight. A major increase in coccolith weight occurs during a slight decrease in carbonate ion concentration in the late Holocene at the Rockall Plateau and Vøring Plateau. Here, more favourable productivity conditions apparently lead to an increase in coccolith weight, either due to the capability of coccolithophore species, especially E. huxleyi, to adapt to decreasing carbonate ion concentration or due to a shift towards heavier calcifying morphotypes.

scholarly journals Changes in coccolith calcification under stable atmospheric CO<sub>2</sub>

2013 ◽  
Vol 10 (6) ◽  
pp. 9415-9450 ◽  
Author(s):  
C. Bauke ◽  
K. J. S. Meier ◽  
H. Kinkel ◽  
K.-H. Baumann
Keyword(s):  
Environmental Factors ◽  
North Atlantic ◽  
Ion Concentration ◽  
Average Weight ◽  
Weight Changes ◽  
Carbonate System ◽  
The Holocene ◽  
The North ◽  
Carbonate Ion ◽  
The North Atlantic

Abstract. Coccolith calcification is known to respond to ocean acidification in culture experiments as well as in present and past oceans. Previous studies basically focus on changes in coccolith weight due to increasing CO2 and the resulting changes in the carbonate system but pay little attention to the influence of other environmental factors. In order to untangle changes in coccolithophore calcification due to environmental factors such as temperature and/or productivity from changes caused by increasing pCO2 and carbonate ion concentration we here present a study on coccolith calcification from the Holocene North Atlantic Ocean. The pre-industrial Holocene with its predominantly stable carbonate system provides the conditions for such a comprehensive analysis. For a realistic analysis on changes in major components of Holocene coccolithophores, the family Noelaerhabdaceae was selected, which constitutes the main part of the assemblage in the North Atlantic. Records of average coccolith weights from three Holocene sediment cores along a North–South transect in the North Atlantic were analysed. During the Holocene mean weight (and therefore calcification) of Noelaerhabdaceae (E. huxleyi and Gephyrocapsa) coccoliths decreases at the Azores (Geofar KF 16) from around 7 to 5.5 pg, but increases at the Rockall Plateau (ODP Site 980) from around 6 to 8 pg and at the Vøring Plateau (MD08-3192) from 7 to 10.5 pg. This amplitude of average weight variability is within the range of glacial/interglacial changes that were interpreted to be an effect of decreasing carbonate ion concentration. By comparison with SEM assemblage counts, we show that weight changes are partly due to variations in the coccolithophore assemblage, but also an effect of a change in calcification and/or morphotype variability within single species. Our results indicate that there is no single key factor responsible for the observed changes in coccolith weight. A major increase in coccolith weight occurs during a slight decrease in carbonate ion concentration in the Late Holocene at the Rockall Plateau and Vøring Plateau. Here, more favourable productivity conditions apparently lead to an increase in coccolith weight, either due to the capability of coccolithophore species, especially E. huxleyi, to adapt to decreasing carbonate ion concentration, or due to a shift towards heavier calcifying morphotypes.

scholarly journals The effect of ocean alkalinity and carbon transfer on deep-sea carbonate ion concentration during the past five glacial cycles

2017 ◽  
Vol 471 ◽  
pp. 42-53 ◽  
Author(s):  
Joanna Kerr ◽  
Rosalind Rickaby ◽  
Jimin Yu ◽  
Henry Elderfield ◽  
Aleksey Yu. Sadekov
Keyword(s):  
Deep Sea ◽  
Ion Concentration ◽  
Glacial Cycles ◽  
The Past ◽  
Carbonate Ion ◽  
Carbon Transfer

scholarly journals Sensitivity of pelagic CaCO<sub>3</sub> dissolution to ocean acidification in an ocean biogeochemical model

2013 ◽  
Vol 10 (7) ◽  
pp. 11343-11373
Author(s):  
A. Regenberg ◽  
B. Schneider ◽  
R. Gangst&amp;oslash;
Keyword(s):  
Ocean Acidification ◽  
Ion Concentration ◽  
Biogeochemical Model ◽  
Saturation State ◽  
Saturation Concentration ◽  
Carbonate Ion ◽  
Biogeochemical Models ◽  
Wide Range ◽  
The Impact

Abstract. In ocean biogeochemical models pelagic CaCO3 dissolution is usually calculated as R = k * Sn, where k is the dissolution rate constant transforming S, the degree of (under-) saturation of seawater with respect to CaCO3, into a time dependent rate R, and n is the reaction rate order. Generally, there are two ways to define the saturation state of seawater with respect to CaCO3: (1) Δ[CO32−], which reflects the difference between the in-situ carbonate ion concentration and the saturation concentration, and (2) Ω, which is approximated by the ratio of in-situ carbonate ion concentration over the saturation concentration. Although describing the same phenomenon, the deviation from equilibrium, both expressions are not equally applicable for the calculation of CaCO3 dissolution in the ocean across pressure gradients, as they differ in their sensitivity to ocean acidification (change of [CO32−]) over depth. In the present study we use a marine biogeochemical model to test the sensitivity of pelagic CaCO3 dissolution to ocean acidification (1–4 × CO2 + stabilization), exploring the possible parameter space for CaCO3 dissolution kinetics as given in the literature. We find that at the millennial time scale there is a wide range of CaCO3 particle flux attenuation into the ocean interior (e.g. a reduction of −55 to −85% at 1000 m depth), which means that there are significant differences in the impact on particle ballasting, depending on the kinetic expression applied.

scholarly journals Effects of ocean acidification on calcification of symbiont-bearing reef foraminifers

2011 ◽  
Vol 8 (1) ◽  
pp. 1809-1829 ◽  
Author(s):  
K. Fujita ◽  
M. Hikami ◽  
A. Suzuki ◽  
A. Kuroyanagi ◽  
H. Kawahata
Keyword(s):  
Coral Reefs ◽  
Ocean Acidification ◽  
Ion Concentration ◽  
Saturation State ◽  
Benthic Foraminifers ◽  
Carbonate Ion ◽  
Algal Symbiont ◽  
Coral Reef Ecosystems ◽  
Flow Through ◽  
Carbonate Species

Abstract. Ocean acidification (decreases in carbonate ion concentration and pH) in response to rising atmospheric pCO2 is generally expected to reduce rates of calcification by reef calcifying organisms, with potentially severe implications for coral reef ecosystems. Large, algal symbiont-bearing benthic foraminifers, which are important primary and carbonate producers in coral reefs, produce high-Mg calcite shells, whose solubility can exceed that of aragonite produced by corals, making them the "first responder" in coral reefs to the decreasing carbonate saturation state of seawater. Here we report results of culture experiments performed to assess the effects of ongoing ocean acidification on the calcification of symbiont-bearing reef foraminifers using a high-precision pCO2 control system. Living clone individuals of three foraminiferal species (Baculogypsina sphaerulata, Calcarina gaudichaudii, and Amphisorus hemprichii) were subjected to seawater at five pCO2 levels from 260 to 970 μatm. Cultured individuals were maintained for about 12 weeks in an indoor flow-through system under constant water temperature, light intensity, and photoperiod. After the experiments, the shell diameter and weight of each cultured specimen were measured. Net calcification of Baculogypsina and Calcarina, which secrete a hyaline shell and host diatom symbionts, increased under intermediate levels of pCO2 (580 and/or 770 μatm) and decreased at a higher pCO2 level (970 μatm). Net calcification of Amphisorus, which secretes a porcelaneous shell and hosts dinoflagellate symbionts, tended to decrease at elevated pCO2. These different responses among the three species are possibly due to differences in calcification mechanisms (in particular, the specific carbonate species used for calcification) between hyaline and porcelaneous taxa, and to links between calcification by the foraminiferal hosts and photosynthesis by the algal endosymbionts. Our findings suggest that ongoing ocean acidification might favor symbiont-bearing reef foraminifers with hyaline shells at intermediate pCO2 levels (580 to 770 μatm) but be unfavorable to those with either hyaline or porcelaneous shells at higher pCO2 levels (near 1000 μatm).

scholarly journals On CO<sub>2</sub> pertubation experiments: over-determination of carbonate chemistry reveals inconsistencies

2010 ◽  
Vol 7 (2) ◽  
pp. 1707-1726 ◽  
Author(s):  
C. J. M. Hoppe ◽  
G. Langer ◽  
S. D. Rokitta ◽  
D. A. Wolf-Gladrow ◽  
B. Rost
Keyword(s):  
Perturbation Methods ◽  
Input Parameter ◽  
Ion Concentration ◽  
Carbonate Chemistry ◽  
Carbonate System ◽  
Saturation State ◽  
Carbonate Ion ◽  
Input Parameters ◽  
Seawater Carbonate Chemistry

Abstract. Seawater carbonate chemistry is typically calculated from two measured parameters. Depending on the choice of these input parameters, discrepancies in calculated pCO2 have been recognized by marine chemists, but the significance of this phenomenon for CO2 perturbation experiments has so far not been determined. To mimic different pCO2 scenarios, two common perturbation methods for seawater carbonate chemistry (changing either DIC or TA) were applied using state-of-the-art protocols and equipment. The carbonate system was over-constrained by measuring DIC, TA, pH, and pCO2. Calculated pCO2 matched measured pCO2 if pH and TA or pH and DIC were chosen as input parameters, whereas pCO2 calculated from TA and DIC was considerably lower than measured values. This has important implications for CO2 perturbation experiments. First, calculated pCO2 values may not be comparable if different input parameters were used. Second, responses of organisms to acidification may be overestimated when using TA and DIC for calculations. This is especially troublesome for experiments with calcifiers, as carbonate ion concentration and thus calcite or aragonite saturation state are overestimated. We suggest refraining from measuring TA and DIC only and rather include pH as input parameter for carbonate chemistry calculations.

Large Plastic Debris Dumps: New Biodiversity Hot Spots Emerging on the Deep-Sea Floor

2021 ◽  
Author(s):  
Xikun Song ◽  
Mingxin Lyu ◽  
Xiaodi Zhang ◽  
Bernhard Ruthensteiner ◽  
In-Young Ahn ◽  
...  
Keyword(s):  
Deep Sea ◽  
Hot Spots ◽  
Plastic Debris ◽  
Sea Floor
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