scholarly journals Carbonate system distribution, anthropogenic carbon and acidification in the Western Tropical South Pacific (OUTPACE 2015 transect)

2018 ◽  
Author(s):  
Thibaut Wagener ◽  
Nicolas Metzl ◽  
Mathieu Caffin ◽  
Jonathan Fin ◽  
Sandra Helias Nunige ◽  
...  
Keyword(s):  
Surface Waters ◽  
Inorganic Carbon ◽  
South Pacific ◽  
Total Alkalinity ◽  
Total Inorganic Carbon ◽  
Saturation State ◽  
Anthropogenic Carbon ◽  
Derived Properties ◽  
Intermediate Waters ◽  
South Pacific Gyre

Abstract. The western tropical South Pacific was sampled along a longitudinal 4000 km transect (OUTPACE cruise, 18 Feb., 3 Apr. 2015) for measurement of carbonates parameters (total alkalinity and total inorganic carbon) between the Melanesian Archipelago (MA) and the western part of the South Pacific gyre (WGY). This manuscript reports this new dataset and derived properties: pH on the total scale (pHT) and the CaCO3 saturation state with respect to calcite (Ωcal) and aragonite (Ωara). We also estimate anthropogenic carbon (CANT) distribution in the water column using the TrOCA method (Tracer combining Oxygen, inorganic Carbon and total Alkalinity). Along the OUTPACE transect, CANT inventories of 37–43 mol m−2 were estimated with higher CANT inventories in MA waters (due to a deeper penetration of CANT in the intermediate waters) than in the WGY waters although highest CANT concentrations were detected in the sub-surface waters of WGY. By combining our OUTPACE dataset with data available in GLODAPv2 (1974–2009), temporal changes in oceanic inorganic carbon were evaluated. An increase of 1.3 to 1.6 µmol kg−1 a−1 for total inorganic carbon in the upper thermocline waters is estimated whereas CANT increases of 1.1 to 1.2 µmol kg−1 a−1. In the MA intermediate waters (27 kg m−3 < σθ < 27.2 kg m−3) an increase of 0.4 µmol kg−1 a−1 of CANT is detected. Our results suggest a clear progression of ocean acidification in the western tropical South Pacific with a decrease of the oceanic pH of up to −0.0027 a−1 and a shoaling of the saturation depth for aragonite of up to 200 m since the pre-industrial period.

scholarly journals Carbonate system distribution, anthropogenic carbon and acidification in the western tropical South Pacific (OUTPACE 2015 transect)

2018 ◽  
Vol 15 (16) ◽  
pp. 5221-5236 ◽  
Author(s):  
Thibaut Wagener ◽  
Nicolas Metzl ◽  
Mathieu Caffin ◽  
Jonathan Fin ◽  
Sandra Helias Nunige ◽  
...  
Keyword(s):  
Inorganic Carbon ◽  
South Pacific ◽  
Total Alkalinity ◽  
Total Inorganic Carbon ◽  
Saturation State ◽  
Anthropogenic Carbon ◽  
Subsurface Waters ◽  
Derived Properties ◽  
Intermediate Waters ◽  
South Pacific Gyre

Abstract. The western tropical South Pacific was sampled along a longitudinal 4000 km transect (OUTPACE cruise, 18 February, 3 April 2015) for the measurement of carbonate parameters (total alkalinity and total inorganic carbon) between the Melanesian Archipelago (MA) and the western part of the South Pacific gyre (WGY). This paper reports this new dataset and derived properties: pH on the total scale (pHT) and the CaCO3 saturation state with respect to aragonite (Ωara). We also estimate anthropogenic carbon (CANT) distribution in the water column using the TrOCA method (Tracer combining Oxygen, inorganic Carbon and total Alkalinity). Along the OUTPACE transect a deeper penetration of CANT in the intermediate waters was observed in the MA, whereas highest CANT concentrations were detected in the subsurface waters of the WGY. By combining our OUTPACE dataset with data available in GLODAPv2 (1974–2009), temporal changes in oceanic inorganic carbon were evaluated. An increase of 1.3 to 1.6 µmol kg−1 a−1 for total inorganic carbon in the upper thermocline waters is estimated, whereas CANT increases by 1.1 to 1.2 µmol kg−1 a−1. In the MA intermediate waters (27 kg m−3 <σθ<27.2 kg m−3) an increase of 0.4 µmol kg−1 a−1 CANT is detected. Our results suggest a clear progression of ocean acidification in the western tropical South Pacific with a decrease in the oceanic pHT of up to −0.0027 a−1 and a shoaling of the saturation depth for aragonite of up to 200 m since the pre-industrial period.

scholarly journals Climatological variations of total alkalinity and total inorganic carbon in the Mediterranean Sea surface waters

2015 ◽  
Vol 6 (2) ◽  
pp. 1499-1533 ◽  
Author(s):  
E. Gemayel ◽  
A. E. R. Hassoun ◽  
M. A. Benallal ◽  
C. Goyet ◽  
P. Rivaro ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Surface Waters ◽  
Inorganic Carbon ◽  
World Ocean ◽  
Sea Surface ◽  
Total Alkalinity ◽  
Total Inorganic Carbon ◽  
Eastern Basin ◽  
Marginal Seas ◽  
The Mediterranean

Abstract. A compilation of several cruises data from 1998 to 2013 was used to derive polynomial fits that estimate total alkalinity (AT) and total inorganic carbon (CT) from measurements of salinity and temperature in the Mediterranean Sea surface waters. The optimal equations were chosen based on the 10-fold cross validation results and revealed that a second and third order polynomials fit the AT and CT data respectively. The AT surface fit showed an improved root mean square error (RMSE) of ±10.6 μmol kg−1. Furthermore we present the first annual mean CT parameterization for the Mediterranean Sea surface waters with a RMSE of ±14.3 μmol kg−1. Excluding the marginal seas of the Adriatic and the Aegean, these equations can be used to estimate AT and CT in case of the lack of measurements. The seven years averages (2005–2012) mapped using the quarter degree climatologies of the World Ocean Atlas 2013 showed that in surface waters AT and CT have similar patterns with an increasing eastward gradient. The surface variability is influenced by the inflow of cold Atlantic waters through the Strait of Gibraltar and by the oligotrophic and thermohaline gradient that characterize the Mediterranean Sea. The summer-winter seasonality was also mapped and showed different patterns for AT and CT. During the winter, the AT and CT concentrations were higher in the western than in the eastern basin, primarily due to the deepening of the mixed layer and upwelling of dense waters. The opposite was observed in the summer where the eastern basin was marked by higher AT and CT concentrations than in winter. The strong evaporation that takes place in this season along with the ultra-oligotrophy of the eastern basin determines the increase of both AT and CT concentrations.

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 Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

2017 ◽  
Author(s):  
Jacoba Mol ◽  
Helmuth Thomas ◽  
Paul G. Myers ◽  
Xianmin Hu ◽  
Alfonso Mucci
Keyword(s):  
Sea Ice ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Beaufort Sea ◽  
Total Alkalinity ◽  
The Arctic ◽  
Surface Mixed Layer ◽  
Saturation State ◽  
Carbon Transfer ◽  
Mackenzie Shelf

Abstract. The Mackenzie Shelf in the southeastern Beaufort Sea is a region that has experienced large changes in the past several decades as warming, sea-ice loss, and increased river discharge have altered carbon cycling. Upwelling and downwelling events are common on the shelf, caused by strong, fluctuating along-shore winds, resulting in cross-shelf Ekman transport, and an alternating estuarine and anti-estuarine circulation. Downwelling carries inorganic carbon and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world oceans. Upwelling carries dissolved inorganic carbon (DIC) and nutrient-rich waters from the Pacific-origin upper halocline layer (UHL) onto the shelf. Profiles of DIC and total alkalinity (TA) taken in August and September of 2014 are used to investigate the cycling of inorganic carbon on the Mackenzie Shelf. The along-shore transport of water and the cross-shelf transport of inorganic carbon are quantified using velocity field output from a simulation of the Arctic and Northern Hemisphere Atlantic (ANHA4) configuration of the Nucleus of European Modelling of the Ocean (NEMO) framework. A strong upwelling event prior to sampling on the Mackenzie Shelf is analyzed and the resulting influence on the carbonate system, including the saturation state of waters with respect to aragonite and pH, is investigated. TA and the oxygen isotope ratio of water (δ18O) are used to examine water-mass distributions in the study area and to investigate the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air-sea fluxes of carbon dioxide (CO2) in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key to quantify the importance of Arctic shelf regions to the global carbon cycle and provide a basis for understanding how it will respond to the aforementioned climate-induced changes.

scholarly journals CO<sub>2</sub> perturbation experiments: similarities and differences between dissolved inorganic carbon and total alkalinity manipulations

2009 ◽  
Vol 6 (10) ◽  
pp. 2145-2153 ◽  
Author(s):  
K. G. Schulz ◽  
J. Barcelos e Ramos ◽  
R. E. Zeebe ◽  
U. Riebesell
Keyword(s):  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Total Alkalinity ◽  
Calcium Carbonate Precipitation ◽  
Carbonate Chemistry ◽  
Carbonate System ◽  
Experimental Conditions ◽  
Saturation State ◽  
Basic Approaches

Abstract. Increasing atmospheric carbon dioxide (CO2) through human activities and invasion of anthropogenic CO2 into the surface ocean alters the seawater carbonate chemistry, increasing CO2 and bicarbonate (HCO3−) at the expense of carbonate ion (CO32−) concentrations. This redistribution in the dissolved inorganic carbon (DIC) pool decreases pH and carbonate saturation state (Ω). Several components of the carbonate system are considered potential key variables influencing for instance calcium carbonate precipitation in marine calcifiers such as coccolithophores, foraminifera, corals, mollusks and echinoderms. Unravelling the sensitivities of marine organisms and ecosystems to CO2 induced ocean acidification (OA) requires well-controlled experimental setups and accurate carbonate system manipulations. Here we describe and analyse the chemical changes involved in the two basic approaches for carbonate chemistry manipulation, i.e. changing DIC at constant total alkalinity (TA) and changing TA at constant DIC. Furthermore, we briefly introduce several methods to experimentally manipulate DIC and TA. Finally, we examine responses obtained with both approaches using published results for the coccolithophore Emiliania huxleyi. We conclude that under most experimental conditions in the context of ocean acidification DIC and TA manipulations yield similar changes in all parameters of the carbonate system, which implies direct comparability of data obtained with the two basic approaches for CO2 perturbation.

scholarly journals Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

2016 ◽  
Vol 10 (5) ◽  
pp. 2173-2189 ◽  
Author(s):  
Nicolas-Xavier Geilfus ◽  
Ryan J. Galley ◽  
Brent G. T. Else ◽  
Karley Campbell ◽  
Tim Papakyriakou ◽  
...  
Keyword(s):  
Sea Ice ◽  
Water Column ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Carbon Dynamics ◽  
Total Alkalinity ◽  
Main Process ◽  
Saturation State ◽  
Ice Growth ◽  
Ice Melt

Abstract. The precipitation of ikaite and its fate within sea ice is still poorly understood. We quantify temporal inorganic carbon dynamics in sea ice from initial formation to its melt in a sea ice–seawater mesocosm pool from 11 to 29 January 2013. Based on measurements of total alkalinity (TA) and total dissolved inorganic carbon (TCO2), the main processes affecting inorganic carbon dynamics within sea ice were ikaite precipitation and CO2 exchange with the atmosphere. In the underlying seawater, the dissolution of ikaite was the main process affecting inorganic carbon dynamics. Sea ice acted as an active layer, releasing CO2 to the atmosphere during the growth phase, taking up CO2 as it melted and exporting both ikaite and TCO2 into the underlying seawater during the whole experiment. Ikaite precipitation of up to 167 µmolkg−1 within sea ice was estimated, while its export and dissolution into the underlying seawater was responsible for a TA increase of 64–66 µmolkg−1 in the water column. The export of TCO2 from sea ice to the water column increased the underlying seawater TCO2 by 43.5 µmolkg−1, suggesting that almost all of the TCO2 that left the sea ice was exported to the underlying seawater. The export of ikaite from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased vertical connectivity in sea ice due to the upward percolation of seawater and meltwater flushing during sea ice melt. Based on the change in TA in the water column around the onset of sea ice melt, more than half of the total ikaite precipitated in the ice during sea ice growth was still contained in the ice when the sea ice began to melt. Ikaite crystal dissolution in the water column kept the seawater pCO2 undersaturated with respect to the atmosphere in spite of increased salinity, TA and TCO2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper the effect of oceanic acidification on the aragonite saturation state (Ωaragonite) in fall and in winter in ice-covered areas, at the time when Ωaragonite is smallest.

scholarly journals Ocean carbonate system variability in the North Atlantic Subpolar surface water (1993–2017)

2019 ◽  
Author(s):  
Coraline Leseurre ◽  
Claire Lo Monaco ◽  
Gilles Reverdin ◽  
Nicolas Metzl ◽  
Jonathan Fin ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
North Atlantic ◽  
Surface Waters ◽  
Total Alkalinity ◽  
Subpolar Gyre ◽  
Saturation State ◽  
The North ◽  
Anthropogenic Co2 ◽  
North Atlantic Subpolar Gyre ◽  
The North Atlantic

Abstract. The North Atlantic is one of the major sinks for anthropogenic CO2. In this study, we investigate the evolution of CO2 uptake and ocean acidification in the North Atlantic Subpolar Gyre (50° N–64° N) using repeated observations collected over the last three decades in the framework of the long-term monitoring program SURATLANT (SURveillance de l'ATLANTique). Data obtained between 1993 and 1997 suggest an important reduction in the capacity of the ocean to absorb CO2 from the atmosphere during summer, due to a rapid increase in the fugacity of CO2 (fCO2) in surface waters (5 times faster than the increase in the atmosphere). This was associated with a rapid decrease in surface pH (of the order of −0.014/yr) and was mainly driven by a significant warming and increase in DIC. Similar trends are observed between 2001 and 2007 during both summer and winter with a mean decrease of pH between −0.006/yr and −0.013/yr. These rapid trends are mainly explained by a significant warming of surface waters, a decrease in alkalinity during summer and an increase in DIC during winter. On the contrary, data obtained during the last decade (2008–2017) show a stagnation of surface fCO2 (increasing the ocean sink for CO2) and pH. These recent trends are explained by the cooling of surface waters, a small decrease of total alkalinity and the near-stagnation of dissolved inorganic carbon. Overall our results show that the uptake of CO2 and ocean acidification in the North Atlantic Subpolar Gyre is substantially impacted by multi-decadal variability, in addition to the accumulation of anthropogenic CO2. As a consequence, the future evolution of air-sea CO2 fluxes, pH and the saturation state of surface waters with regards to aragonite and calcite remain highly uncertain in this region.

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