scholarly journals Aragonite saturation states and pH in western Norway fjords: seasonal cycles and controlling factors, 2005–2009

2016 ◽  
Author(s):  
A. M. Omar ◽  
I. Skjelvan ◽  
S. R. Erga ◽  
A. Olsen
Keyword(s):  
Coastal Water ◽  
Surface Waters ◽  
Spring Bloom ◽  
Dissolved Inorganic Carbon ◽  
Vertical Mixing ◽  
Late Summer ◽  
Early Spring ◽  
Saturation State ◽  
Aragonite Saturation ◽  
Western Norway

Abstract. The uptake of anthropogenic CO2 by the ocean leads to a process known as ocean acidification (OA) which lowers aragonite saturation state (ΩAr) and pH, and this is poorly documented in coastal environments including fjords due to lack of appropriate observations. Here we use weekly underway data from Voluntary Observing Ships (VOS) covering the period 2005–2009 combined with data from research cruises to estimate ΩAr and pH values in several adjacent western Norwegian fjords, and to evaluate how seawater CO2 chemistry drives their variations in response to physical and biological factors. The OA parameters in the surface waters of the fjords are characterized by strong seasonal and spatially coherent variations. These changes are governed by the seasonal changes in temperature, salinity, formation and decay of organic matter, and vertical mixing with deeper, carbon rich coastal water. Annual mean pH and ΩAr values were 8.13 and 2.21, respectively. The former varies from minimum values (≈ 8.05) in late December – early January to maximum values of around 8.2 during early spring (March–April) as a consequence of the phytoplankton spring bloom, which reduces Dissolved Inorganic Carbon (DIC). In the following months, pH decreases in response to warming. This thermodynamic decrease in pH is reinforced by the deepening of the mixed layer, which brings up carbon rich coastal water to the surface, and this trend continues until the low winter values are reached again. ΩAr, on the other hand, reaches its seasonal maximum (> 2.5) in mid to late summer (July–Sept), when the spring bloom is over and pH is decreasing. The lowest ΩAr values (≈ 1.3–1.6) occur during winter (Jan–Mar), when both pH and Sea Surface Temperature (SST) are low and DIC is highest. Consequently, seasonal ΩAr variations align with those of SST and salinity normalized DIC. We demonstrate that underway measurements of fugacity of CO2 in seawater (fCO2), SST, and SSS from VOS lines combined with high frequency observations of the complete carbonate system at strategically placed fixed stations provide an approach to interpolate OA parameters over large areas in the fjords of western Norway.

scholarly journals Aragonite saturation states and pH in western Norwegian fjords: seasonal cycles and controlling factors, 2005–2009

Ocean Science ◽  
2016 ◽  
Vol 12 (4) ◽  
pp. 937-951 ◽  
Author(s):  
Abdirahman M. Omar ◽  
Ingunn Skjelvan ◽  
Svein Rune Erga ◽  
Are Olsen
Keyword(s):  
Coastal Water ◽  
Spring Bloom ◽  
Dissolved Inorganic Carbon ◽  
Vertical Mixing ◽  
Late Summer ◽  
Early Spring ◽  
Saturation State ◽  
Aragonite Saturation ◽  
Anthropogenic Carbon ◽  
Carbon Dioxide Co2

Abstract. The uptake of anthropogenic carbon dioxide (CO2) by the ocean leads to a process known as ocean acidification (OA), which lowers the aragonite saturation state (ΩAr) and pH, and this is poorly documented in coastal environments including fjords due to lack of appropriate observations.Here we use weekly underway data from the Voluntary Observing Ships (VOS) program covering the period 2005–2009 combined with data from research cruises to estimate ΩAr and pH values in several adjacent western Norwegian fjords, and to evaluate how seawater CO2 chemistry drives their variations in response to physical and biological factors.The OA parameters in the surface waters of the fjords are subject to strong seasonal and spatially coherent variations. These changes are governed by the seasonal changes in temperature, salinity, formation and decay of organic matter, and vertical mixing with deeper, carbon-rich coastal water. Annual mean pH and ΩAr values were 8.13 and 2.21, respectively. The former varies from minimum values ( ≈  8.05) in late December – early January to maximum values of around 8.2 during early spring (March–April) as a consequence of the phytoplankton spring bloom, which reduces dissolved inorganic carbon (DIC). In the following months, pH decreases in response to warming. This thermodynamic decrease in pH is reinforced by the deepening of the mixed layer, which enables carbon-rich coastal water to reach the surface, and this trend continues until the low winter values of pH are reached again. ΩAr, on the other hand, reaches its seasonal maximum (> 2.5) in mid- to late summer (July–September), when the spring bloom is over and pH is decreasing. The lowest ΩAr values ( ≈  1.3–1.6) occur during winter (January–March), when both pH and sea surface temperature (SST) are low and DIC is its highest. Consequently, seasonal ΩAr variations align with those of SST and salinity normalized DIC (nDIC).We demonstrate that underway measurements of fugacity of CO2 in seawater (fCO2) and SST from VOS lines combined with high frequency observations of the complete carbonate system at strategically placed fixed stations provide an approach to interpolate OA parameters over large areas in the fjords of western Norway.

scholarly journals Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation

2015 ◽  
Vol 12 (11) ◽  
pp. 8429-8465 ◽  
Author(s):  
H. B. DeJong ◽  
R. B. Dunbar ◽  
D. A. Mucciarone ◽  
D. A. Koweek
Keyword(s):  
Southern Ocean ◽  
Surface Waters ◽  
Ross Sea ◽  
Polar Front ◽  
Early Spring ◽  
Total Alkalinity ◽  
Saturation State ◽  
System Data ◽  
Algal Photosynthesis ◽  
Carbon System

Abstract. Predicting when surface waters of the Ross Sea and Southern Ocean will become undersaturated with respect to biogenic carbonate minerals is challenging in part due to the lack of baseline high resolution carbon system data. Here we present ~ 1700 surface total alkalinity measurements from the Ross Sea and along a transect between the Ross Sea and southern Chile from the austral autumn (February–March 2013). We calculate the saturation state of aragonite (ΩAr) and calcite (ΩCa) using measured total alkalinity and pCO2. In the Ross Sea and south of the Polar Front, variability in carbonate saturation state (Ω) is mainly driven by algal photosynthesis. Freshwater dilution and calcification have minimal influence on Ω variability. We estimate an early spring surface water ΩAr value of ~ 1.2 for the Ross Sea using a total alkalinity–salinity relationship and historical pCO2 measurements. Our results suggest that the Ross Sea is not likely to become undersaturated with respect to aragonite until the year 2070.

scholarly journals A regional hindcast model simulating ecosystem dynamics, inorganic carbon chemistry, and ocean acidification in the Gulf of Alaska

2020 ◽  
Vol 17 (14) ◽  
pp. 3837-3857
Author(s):  
Claudine Hauri ◽  
Cristina Schultz ◽  
Katherine Hedstrom ◽  
Seth Danielson ◽  
Brita Irving ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Seasonal Cycle ◽  
Bottom Water ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Gulf Of Alaska ◽  
Saturation State ◽  
Aragonite Saturation ◽  
Carbon Chemistry ◽  
Seward Line

Abstract. The coastal ecosystem of the Gulf of Alaska (GOA) is especially vulnerable to the effects of ocean acidification and climate change. Detection of these long-term trends requires a good understanding of the system’s natural state. The GOA is a highly dynamic system that exhibits large inorganic carbon variability on subseasonal to interannual timescales. This variability is poorly understood due to the lack of observations in this expansive and remote region. We developed a new model setup for the GOA that couples the three-dimensional Regional Oceanic Model System (ROMS) and the Carbon, Ocean Biogeochemistry and Lower Trophic (COBALT) ecosystem model. To improve our conceptual understanding of the system, we conducted a hindcast simulation from 1980 to 2013. The model was explicitly forced with temporally and spatially varying coastal freshwater discharges from a high-resolution terrestrial hydrological model, thereby affecting salinity, alkalinity, dissolved inorganic carbon, and nutrient concentrations. This represents a substantial improvement over previous GOA modeling attempts. Here, we evaluate the model on seasonal to interannual timescales using the best available inorganic carbon observations. The model was particularly successful in reproducing observed aragonite oversaturation and undersaturation of near-bottom water in May and September, respectively. The largest deficiency in the model is its inability to adequately simulate springtime surface inorganic carbon chemistry, as it overestimates surface dissolved inorganic carbon, which translates into an underestimation of the surface aragonite saturation state at this time. We also use the model to describe the seasonal cycle and drivers of inorganic carbon parameters along the Seward Line transect in under-sampled months. Model output suggests that the majority of the near-bottom water along the Seward Line is seasonally undersaturated with respect to aragonite between June and January, as a result of upwelling and remineralization. Such an extensive period of reoccurring aragonite undersaturation may be harmful to ocean acidification-sensitive organisms. Furthermore, the influence of freshwater not only decreases the aragonite saturation state in coastal surface waters in summer and fall, but it simultaneously decreases the surface partial pressure of carbon dioxide (pCO2), thereby decoupling the aragonite saturation state from pCO2. The full seasonal cycle and geographic extent of the GOA region is under-sampled, and our model results give new and important insights for months of the year and areas that lack in situ inorganic carbon observations.

scholarly journals Seasonal variation in physiology and shell condition of the pteropod Limacina retroversa in the Gulf of Maine relative to life cycle and carbonate chemistry

2020 ◽  
Author(s):  
Amy E. Maas ◽  
Gareth L. Lawson ◽  
Alexander J. Bergan ◽  
Zhaohui A. Wang ◽  
Ann M. Tarrant
Keyword(s):  
Life Cycle ◽  
Spring Bloom ◽  
Gulf Of Maine ◽  
Late Summer ◽  
Carbonate Chemistry ◽  
Pelagic Ecosystem ◽  
Saturation State ◽  
Reproductive Events ◽  
Lipid Stores ◽  
Natural Cycles

AbstractNatural cycles in the seawater partial pressure of carbon dioxide (CO2) in the Gulf of Maine, which vary from ∼250-550 µatm seasonally, provide an opportunity to observe how the life cycle and phenology of the shelled pteropod Limacina retroversa responds to changing food, temperature and carbonate chemistry conditions. Distributional, hydrographic, and physiological sampling suggest that pteropod populations are located in the upper portion of the water column (0-150 m) with a maximum abundance above 50 m, allowing them to generally avoid aragonite undersaturation. Gene expression and shell condition measurements show, however, that the population already experiences biomineralization stress in the winter months even when aragonite is slightly oversaturated, reinforcing the usefulness of this organism as a bio-indicator for pelagic ecosystem response to ocean acidification. There appear to be two reproductive events per year with one pulse timed to coincide with the spring bloom, the period with highest respiration rate, fluorescence, and pH, and a second more extended pulse in the late summer and fall. During the fall there is evidence of lipid storage for overwintering, allowing the second generation to survive the period of low food and aragonite saturation state. Based on these observations we predict that in the future pteropods will likely be most vulnerable to changing CO2 regionally during the fall reproductive event when CO2 concentration already naturally rises and there is the added stress of generating lipid stores.

scholarly journals Isotopic Analysis and Cycling of Dissolved Inorganic Carbon at Lake Biwa, Central Japan

Radiocarbon ◽  
1997 ◽  
Vol 40 (2) ◽  
pp. 933-944 ◽  
Author(s):  
Toshio Nakamura ◽  
Sadao Kojima ◽  
Tomoko Ohta ◽  
Hirotaka Oda ◽  
Akiko Ikeda ◽  
...  
Keyword(s):  
Inorganic Carbon ◽  
Lake Biwa ◽  
Dissolved Inorganic Carbon ◽  
Seasonal Pattern ◽  
Vertical Mixing ◽  
Isotopic Analysis ◽  
Early Spring ◽  
Central Japan ◽  
Depth Profiles ◽  
Carbon Isotopic

This paper reports on concentrations and carbon isotopic results of dissolved inorganic carbon (DIC) in water samples collected at four locations and from several depths in Lake Biwa, central Japan, covering every season of the year, starting in the spring of 1995. Depth profiles of DIC concentration and DIC δ13C showed a strong seasonal pattern, as a result of vertical mixing of the lake water in winter and early spring, or lack of mixing in the other seasons. No seasonal change in DIC ∆14C depth profiles was recognizable, mainly owing to the wide scatter of DIC ∆14C. Values typically ranged from 0.47 to 0.65 mmol kg-1 for DIC concentration, and from -4 to -8‰ and from +10 to +80‰ for DIC ∆13C and DIC ∆14C, respectively, for the Lake Biwa water.

scholarly journals Seasonal variation in aragonite saturation in surface waters of Puget Sound – a pilot study

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Gregory Pelletier ◽  
Mindy Roberts ◽  
Mya Keyzers ◽  
Simone R. Alin
Keyword(s):  
Pilot Study ◽  
Surface Waters ◽  
Puget Sound ◽  
Phytoplankton Production ◽  
Carbonate System ◽  
Saturation State ◽  
Aragonite Saturation ◽  
Spatially Distributed ◽  
Long Term Trends

A pilot study of sampling, using monthly marine flights over spatially distributed stations, was conducted with the aim to characterize the carbonate system in Puget Sound over a full year-long period. Surface waters of Puget Sound were found to be under-saturated with respect to aragonite during October–March, and super-saturated during April–September. Highest pCO2 and lowest pH occurred during the corrosive October–March period. Lowest pCO2 and highest pH occurred during the super-saturated April–September period. The monthly variations in pCO2, pH, and aragonite saturation state closely followed the variations in monthly average chlorophyll a. Super-saturated conditions during April–September are likely strongly influenced by photosynthetic uptake of CO2 during the phytoplankton growing season. The relationship between phytoplankton production, the carbonate system, and aragonite saturation state suggests that long-term trends in eutrophication processes may contribute to trends in ocean acidification in Puget Sound.

scholarly journals Impact of rapid sea-ice reduction in the Arctic Ocean on the rate of ocean acidification

2011 ◽  
Vol 8 (5) ◽  
pp. 10617-10644
Author(s):  
A. Yamamoto ◽  
M. Kawamiya ◽  
A. Ishida ◽  
Y. Yamanaka ◽  
S. Watanabe
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Surface Waters ◽  
Co2 Concentration ◽  
The Arctic ◽  
Saturation State ◽  
Aragonite Saturation ◽  
The Arctic Ocean ◽  
Arctic Surface ◽  
Sea Ice Reduction

Abstract. The largest pH decline and widespread undersaturation with respect to aragonite in this century due to uptake of anthropogenic carbon dioxide in the Arctic Ocean have been projected. The reductions in pH and aragonite saturation state have been caused primarily by an increase in the concentration of atmospheric carbon dioxide. However, in a previous study, simulations with and without warming showed that these reductions in the Arctic Ocean also advances due to the melting of sea ice caused by global warming. Therefore, future projections of pH and aragonite saturation in the Arctic Ocean will be affected by how rapidly the reduction in sea ice occurs. In this study, the impact of sea-ice reduction rate on projected pH and aragonite saturation state in the Arctic surface waters was investigated. Reductions in pH and aragonite saturation were calculated from the outputs of two versions of an earth system model (ESM) with different sea-ice reduction rates under similar CO2 emission scenarios. The newer model version projects that Arctic summer ice-free condition will be achieved by the year 2040, and the older version predicts ice-free condition by 2090. The Arctic surface water was projected to be undersaturated with respect to aragonite in the annual mean when atmospheric CO2 concentration reached 480 (550) ppm in year 2040 (2048) in new (old) version. At an atmospheric CO2 concentration of 520 ppm, the maximum differences in pH and aragonite saturation state between the two versions were 0.08 and 0.15, respectively. The analysis showed that the decreases in pH and aragonite saturation state due to rapid sea-ice reduction were caused by increases in both CO2 uptake and freshwater input. Thus, the reductions in pH and aragonite saturation state in the Arctic surface waters are significantly affected by the difference in future projections for sea-ice reduction rate. The critical CO2 concentration, at which the Arctic surface waters become undersaturated with respect to aragonite on annual mean bias, would be lower by 70 ppm in the version with the rapid sea-ice reduction.

scholarly journals An initial study on ocean acidification in Southern waters of Vietnam

2021 ◽  
Vol 21 (1) ◽  
pp. 47-55
Author(s):  
Phu Le Hung ◽  
Tuan Linh Vo Tran ◽  
Ngoc Pham Hong
Keyword(s):  
Ocean Acidification ◽  
Dissolved Inorganic Carbon ◽  
Initial Study ◽  
The State ◽  
Total Alkalinity ◽  
Saturation State ◽  
Aragonite Saturation ◽  
Mean Values ◽  
Co2 Partial Pressure ◽  
Average Value

Ocean acidification (OA) refers to the increase of dissolved CO2 and the reduction in the pH of seawater as a consequence of the absorption of large amounts of carbon dioxide (CO2) by the oceans. This process is the result of large quantities of CO2, produced by vehicles and industrial and agricultural activities. Over the past decades there have been many worldwide studies focusing on potential impacts of OA. However, researches regarding this issue remain scarce in Vietnam. In this paper, data of pH, total alkalinity (TA), dissolved inorganic carbon (HCO3-, CO32-, CO2), partial pressure of CO2 (pCO2) and the state of aragonite saturation (Ωar) measured in Southern waters of Vietnam in 2018 were used to: (1) Provide the initial data of OA parameters in Southern waters of Vietnam; (2) Compare the current situation of OA in Southern waters of Vietnam with the situation of world oceans. The results showed that mean values of pH, TA and CO32- concentrations were 8.04 (7.92–8.11), 2300.28 µmol/kgSW (2,144.10–2,523.15), 218.83 µmol/kgSW (151.32–262.83), respectively. These values were higher in offshore areas than in coastal areas, especially at the estuaries. The average value of pCO2 was 414.47 µatm (327.93–568.59), higher when compared with that of other areas (370 µatm). On the other hand, the state of aragonite saturation of the studied area had the similar patterns of TA and CO32- concentrations. Most of values were always greater than 3, with this saturation state, the marine calcifiers are more likely to survive and reproduce.

scholarly journals Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation

2015 ◽  
Vol 12 (23) ◽  
pp. 6881-6896 ◽  
Author(s):  
H. B. DeJong ◽  
R. B. Dunbar ◽  
D. Mucciarone ◽  
D. A. Koweek
Keyword(s):  
Southern Ocean ◽  
Surface Waters ◽  
Ross Sea ◽  
Polar Front ◽  
Early Spring ◽  
Total Alkalinity ◽  
Saturation State ◽  
System Data ◽  
Algal Photosynthesis ◽  
Carbon System

Abstract. Predicting when surface waters of the Ross Sea and Southern Ocean will become undersaturated with respect to biogenic carbonate minerals is challenging in part due to the lack of baseline high-resolution carbon system data. Here we present ~ 1700 surface total alkalinity measurements from the Ross Sea and along a transect between the Ross Sea and southern Chile from the austral autumn (February–March 2013). We calculate the saturation state of aragonite (ΩAr) and calcite (Ω Ca) using measured total alkalinity and pCO2. In the Ross Sea and south of the Polar Front, variability in carbonate saturation state (Ω) is mainly driven by algal photosynthesis. Freshwater dilution and calcification have minimal influence on Ω variability. We estimate an early spring surface water ΩAr value of ~ 1.2 for the Ross Sea using a total alkalinity–salinity relationship and historical pCO2 measurements. Our results suggest that the Ross Sea is not likely to become undersaturated with respect to aragonite until the year 2070.

scholarly journals The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

2017 ◽  
Author(s):  
Benjamin L. Moore-Maley ◽  
Debby Ianson ◽  
Susan E. Allen
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Coupled Model ◽  
Ph Sensitivity ◽  
Total Alkalinity ◽  
Low Flow ◽  
Saturation State ◽  
Aragonite Saturation ◽  
Strait Of Georgia ◽  
River Chemistry ◽  
The Impact

Abstract. Ocean acidification threatens to reduce pH and aragonite saturation state (ΩA) in estuaries, potentially damaging their ecosystems. However, the impact of highly variable river total alkalinity (TA) and dissolved inorganic carbon (DIC) on pH and ΩA in these estuaries is unknown. We assess the sensitivity of estuarine surface pH and ΩA to river chemistry using a 1-dimensional, biogeochemical-coupled model of the Strait of Georgia on the Canadian Pacific coast and generalize the results in the context of global rivers. The productive Strait of Georgia estuary has a large, seasonally variable freshwater input from the glacially fed, undammed Fraser River. Analyzing TA and pH observations from this river and its estuary, we find that the Fraser is moderately alkaline (TA 500–1350 μmol kg−1) but relatively DIC-rich, especially during winter (low flow). Model results show that estuarine pH and ΩA, while sensitive to freshwater DIC and TA, do not vary in synchrony. Instead, rivers with high DIC and TA produce lower estuarine pH due to an increased estuarine DIC : TA ratio, but higher estuarine ΩA because of DIC contributions to the carbonate ion. This estuarine pH sensitivity decreases with increasing mean river TA, but the zone of maximum pH sensitivity also moves to higher salinity which could impact a larger areal extent of the estuary. Many temperate rivers, such as the Fraser, are expected to experience weaker freshets and stronger winter flows under climate change, reducing the extent of the river plume and the impact of river chemistry in much of the estuary. However, increasing carbon in rivers will move the highest sensitivity zone to higher salinities that cover larger areas under present-day flow regimes.

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