Trends in anthropogenic CO2 in water masses of the Subtropical North Atlantic Ocean

12 páginas, 4 figuras,1 tabla.-- Proyecto CarbochangeThe variability in the storage of the oceanic anthropogenic CO2 (Cant) on decadal timescales is evaluated within the main water masses of the Subtropical North Atlantic along 24.5°N. Inorganic carbon measurements on five cruises of the A05 section are used to assess the changes in Cant between 1992 and 2011, using four methods (ΔC∗, TrOCA, φCT0, TTD). We find good agreement between the Cant distribution and storage obtained using chlorofluorocarbons and CO2 measurements in both the vertical and horizontal scales. Cant distribution shows higher concentrations and greater decadal storage rates in the upper layers with both values decreasing with depth. The greatest enrichment is obserbed in the central water masses, with their upper limb showing a mean annual accumulation of about 1 μmol kg−1 yr−1 and the lower limb showing, on average, half that value. We detect zonal gradients in the accumulation of Cant. This finding is less clear in the upper waters, where greater variability exists between methods. In accordance with data from time series stations, greater accumulation of Cant is observed in the upper waters of the western basin of the North Atlantic Subtropical Gyre. In intermediate and deep layers, the zonal gradient in the storage of Cant is more robust between methods. The much lower mean storage rates found along the section (<0.25 μmol kg−1 yr−1) become more obvious when longitudinal differences in the Cant accumulation are considered. In particular, west of 70°W the ventilation by the Labrador Sea Water creates a noticeable accumulation rate up to ∼0.5 μmol kg−1 yr−1 between 1000 and 2500 dbar. If a Transient Stationary State of the Cant distributions is considered, significant bi-decadal trends in the Cant storage rates in the deepest North Atlantic waters are detected, in agreement with recent estimations.We acknowledge funding from the Spanish Ministry of Economy and Competitiveness through Grants CSD2008-00077 (Circumnavigation Expedition MALASPINA 2010 Project), CTM2009-08849 (ACDC Project) and CTM2012-32017 (MANIFEST Project). We also acknowledge funding from the EU FP7 project CARBOCHANGE under Grant Agreement No. 264879 and by the Marine Biogeochemistry and Global Change research group (Generalitat de Catalunya, 2014SGR1029). E.F. Guallart was funded through a JAE-Pre grant that was financed by the Spanish National Research Council Agency (Consejo Superior de Investigaciones Científicas, CSIC) and by the European Social Fund.Peer reviewe

Coccolithophore calcification is independent of carbonate chemistry in the tropical ocean

Marañón, Emilio ... et al.-- 13 pages, 7 figures, 1 table, supporting information https://dx.doi.org/10.1002/lno.10295Short-term experiments indicate that seawater acidification can cause a decrease in the rate of calcification by coccolithophores, but the relationship between carbonate chemistry and coccolithophore calcification rate in natural assemblages is still unclear. During the Malaspina 2010 circumnavigation, we measured primary production, calcification, coccolithophore abundance, particulate inorganic carbon (PIC) concentration, and the parameters of the carbonate system, along basin-scale transects in the tropical Atlantic, Indian and Pacific oceans. Euphotic layer-integrated calcification and mean cell-specific calcification in the euphotic layer ranged between 2–10 mgC m−2 d−1 and 5–20 pgC cell−1 d−1, respectively. We found a significant relationship between primary production and calcification, such that the calcification to primary production (CP/PP) ratio was relatively invariant among ocean basins, with an overall mean value of 0.05 ± 0.04. Extrapolating this value to the entire ocean would result in a global pelagic calcification rate of 2.4 PtC yr−1. The mean PIC concentration in surface waters was 1.8 ± 1.6 mgC m−3 and its turnover time averaged 20 d. We combined our data of calcification, primary production, and carbonate chemistry from Malaspina 2010 with those obtained during two previous cruises in the northern Arabian Sea. Both the CP/PP ratio and cell-specific calcification were largely constant across a wide range of calcite saturation state (1.5–6.5), [ inline image]/[H+] (0.08–0.24; mol: μmol), and pH (7.6–8.1), which indicates that calcification by natural coccolithophore assemblages was independent of carbonate chemistry. Our results suggest that coccolithophore calcification, at least in tropical regions, may not be decreasing in the currently acidifying oceanFunding for this study was provided by the Spanish Ministry of Science and Innovation through research projects Malaspina 2010 (grant no. CSD2008-00077), PERSEO (CTM2007-28925-E/MAR), MANIFEST (CTM2012-32017) and TERRIFIC (CTM2014-53582-R). Funding for W.M.B. came from the NSF (OCE-0961660; OCE1220068), NASA (NNX11AO72G; NNX11AL93G; NNX14AQ41G; NNX14AQ43A; NNX14AL92G; NNX14AM77G) and NOAA (NA11OAR4310055).Peer Reviewe

Variability and Trends in Physical and Biogeochemical Parameters of the Mediterranean Sea during a Cruise with RV MARIA S. MERIAN in March 2018

The last few decades have seen dramatic changes in the hydrography and biogeochemistry of the Mediterranean Sea. The complex bathymetry and highly variable spatial and temporal scales of atmospheric forcing, convective and ventilation processes contribute to generate complex and unsteady circulation patterns and significant variability in biogeochemical systems. Part of the variability of this system can be influenced by anthropogenic contributions. Consequently, it is necessary to document details and to understand trends in place to better relate the observed processes and to possibly predict the consequences of these changes. In this context we report data from an oceanographic cruise in the Mediterranean Sea on the German research vessel Maria S. Merian (MSM72) in March 2018. The main objective of the cruise was to contribute to the understanding of long-term changes and trends in physical and biogeochemical parameters, such as the anthropogenic carbon uptake and to further assess the hydrographical situation after the major climatological shifts in the eastern and western part of the basin, known as the Eastern and Western Mediterranean Transients. During the cruise, multidisciplinary measurements were conducted on a predominantly zonal section throughout the Mediterranean Sea, contributing to the Med-SHIP and GO-SHIP long-term repeat cruise section that is conducted at regular intervals in the Mediterranean Sea to observe changes and impacts on physical and biogeochemical variables. The data can be accessed at https://doi.org/10.1594/PANGAEA.905902 (Hainbucher et al., 2019), https://doi.org/10.1594/PANGAEA.913512 (Hainbucher, 2020a) https://doi.org/10.1594/PANGAEA.913608, (Hainbucher, 2020b) https://doi.org/10.1594/PANGAEA.913505, (Hainbucher, 2020c) https://doi.org/10.1594/PANGAEA.905887 (Tanhua et al., 2019) and https://doi.org/10.25921/z7en-hn85 (Tanhua et al, 2020)

Spatiotemporal variability of the carbonate system in the North Atlantic Ocean

Memoria de tesis doctoral presentada por Elisa Fernández Guallart para obtener el título de Doctora en Oceanografía por la Universidad de las Palmas de Gran Canaria (ULPGC), realizada bajo la dirección del Dr. Carles Pelejero Bou del Institut de Ciències del Mar (ICM-CSIC) y del Dr. Fiz Fernández Pérez del Instituto de Investigaciones Marinas (IIM-CSIC).-- 279 pages[EN] The ocean carbon sink contributes to mitigate global warming. However, the resulting anthropogenic CO2 (C ant) oceanic invasion affects the chemical balances of the CO system in seawater, which translates into a decrease in surface ocean pH. The North Atlantic Ocean presents the largest Cant storage rate of all oceans. The key mechanism contributing to this high value is the northward transport of warm tropical and subtropical waters that contain high Cant concentrations from low latitudes poleward into the regions of deep water formation, through the upper limb of the Atlantic Meridional Overturning Circulation. These deep waters return southward into the Deep Western Boundary Current (DWBC) containing moderate but increasing Cant levels. Given the predominant part of the (sub)tropical North Atlantic region in the uptake of atmospheric Cant , the anthropogenically derived acidification and taking into account the role of ocean circulation on the distribution of the absorbed Cant between basins, this thesis assesses de decadal changes and trends in some parameters of the carbonate system along two oceanographic sections located at 24.5°N and at 7.5°N of latitude, occurred between the early 1990s and the early 2010s. We assessed the interactions between ocean circulation and the carbonate system, in particular regarding the processes that control and modulate the storage rates of Cant and the associated acidification. This was accomplished by splitting the water masses present in each of the two sections into separated zonal regions that were defined following oceanographic criteria. This methodological approach showed that the spatiotemporal variability in the storage of Cant along the two sections is strongly related with the deep Cant signal conveyed by the main circulation current (i.e. DWBC) that spreads across the two sections. The deconvolution of the temporal pH differences into anthropogenic and non-anthropogenic (natural) components revealed that these are of similar magnitudes but have different representations with depth and longitude. Our results emphasize the need to provide more insight into natural variability of the parameters of the carbonate system, with the aim of providing further insight on the predictability of the observed trends for time periods over decadal timescales.[ES] El sumidero oceánico de carbono contribuye a mitigar el calentamiento global. Pero la entrada al océano de este CO2 de origen antropogénico (Cant) tiene consecuencias sobre los balances químicos del sistema del carbónico en agua de mar, que se traducen en una reducción del pH superficial del océano. El Océano NortAtlántico tiene la tasa de acumulación de Cant más alta de todos los océanos. El mecanismo clave para explicar este hecho es el transporte de aguas cálidas tropicales y subtropicales enriquecidas en Cant hasta las zonas de formación de agua profunda, a través de la circulación de retorno. Estas aguas profundas vuelven hacia el sur dentro de la corriente profunda de frontera oeste, transportando cantidades moderadas pero crecientes de Cant. Teniendo en cuenta el papel predominante del Atlántico (sub)tropical en la captación de Cant atmosférico, la acidificación oceánica asociada a esta captación y considerando también el papel de la circulación en la distribución del Cant absorbido entre distintas cuencas, esta tesis evalúa los cambios decenales y tendencias en algunos parámetros del sistema del carbónico a lo largo de dos secciones oceanográficas situadas a 24.5°N y 7.5°N de latitud, ocurridos desde principios de 1990s a principios de 2010s. Hemos evaluado la interacción entre la circulación oceánica y el sistema del carbónico, en concreto respecto a los mecanismos que controlan y condicionan las tasas de acumulación de Cant y la acidificación asociada. Esto se consiguió estudiando las masas de agua presentes en cada una de las dos secciones separadamente en distintas zonas o regiones que se definieron de acuerdo a criterios oceanográficos. Esta metodología mostró que la variabilidad espaciotemporal en la acumulación de Cant a lo largo de las dos secciones está fuertemente relacionada con la señal de Cant transportada dentro de la corriente principal (la corriente profunda de frontera oeste) que atraviesa las dos secciones. La separación de las diferencias de pH encontradas en los componentes antropogénico y no-antropogénico (natural) mostró que estos tienen una magnitud similar pero muestran diferente distribución en profundidad y en longitud. Nuestros resultados sugieren que todavía es necesario describir de una forma más completa cuál es la variabilidad natural de los parámetros del sistema del carbónico, para definir con más claridad la capacidad de predicción de las tendencias observadas más allá de la escala de tiempo decenalPeer Reviewe

High spatial resolution Alkalinity and pH measurements by IIM-CSIC group along 24.5°N during the R/V Hesperides WOCE Section A05 cruise (July 14 - August 15, 1992)

Dataset contributed to the Project Carbochange.-- More information in http://hdl.handle.net/10261/93331This dataset gathers discrete measurements of CO2 (pH and alkalinity) and hydrographic variables (salinity, temperature, dissolved oxygen, nitrate, phosphate and silicate) obtained during the cruise WOCE Section A05 carried out from 14 July to 15 August 1992. The pH was measured potentiometrically in the NBS scale with a combined glass electrode associated to a thermo-compensator and referred to 15ºC (Perez and Fraga, 1987a). The method had a shipboard precision of 0.005 units, based on 184 replicate analysis corresponding to two different oceanographic bottles fired at the same depth at each station (Ríos and Rosón, 1996). AT measurements were made by titration of seawater with potentiometric endpoint detection (Perez and Fraga, 1987b), reaching a precision of ±1 µmol kg-1. Dissolved oxygen was analyzed following the widely applied Winkler method. Determinations of nitrate, phosphate and silicate were carried out following methods described by Hansen and Grassoff (1983) Salinity and Temperature were recorded with a CTD probeInstituto Español de Oceanografía y Comisión Interministerial de Ciencia y Tecnología (CICYT)N

High spatial resolution alkalinity and pH measurements by IIm-CSIC group along 24.5ºN durinf the R/V Hespérides WOCE Section A05 cruise (July 14-August 15, 1992)

23 páginas, 8 figuras, 3 tablasPeer reviewe

Calcium distribution in the subtropical Atlantic Ocean: Implications for calcium excess and saturation horizons

7 páginas, 1 tabla, 4 figurasThis study constituted the first attempt to measure dissolved calcium ([Ca2 +]meas) in the subtropical North Atlantic, during a zonal transoceanic cruise along 24.5°N (WOCE A05 section), in summer 1992. [Ca2 +]meas was obtained in 20 full-depth equidistant stations along the section, showing that their gradients are rather sensitive to horizontal and vertical water mass distribution. Deep waters along 24.5°N systematically show a positive calcium excess of 20 ± 14 μmol·kg− 1, i.e., more [Ca2 +] than expected by CaCO3 dissolution and organic matter oxidation (estimated by total alkalinity and nitrate). CaCO3 settling and benthic dissolution accounts for 70% and the North Atlantic plus Arctic riverine inputs of HCO3− for the remaining 30%. Combining [Ca2 +]meas and CO2 data sets, carbonate mineral saturation states distributions for aragonite and calcite can be obtained. The two solubility ratios resulted, on average, 0.5% smaller than if conservative behavior for Ca2 + was assumed (an approach widely followed when [Ca2 +]meas is unknown). As a result, shallower saturation horizon depths for both carbonate states (19 dbar for aragonite and 10 dbar for calcite) are yielded if [Ca2 +]meas is taken into account instead than estimated from salinityThis work has been performed under the project BOCATS (CTM2013-41048-P) supported by the Spanish Government and co-founded by the European Regional Development Fund (FEDER)Peer reviewe

Transports and budgets of anthropogenic CO2 in the tropical North Atlantic in 1992–1993 and 2010–2011

17 páginas, 8 figuras, 5 tablasThe meridional transport of anthropogenic CO2 (Cant) in the tropical North Atlantic (TNA) is investigated using data from transoceanic sections along 7.5°N and 24.5°N, carried out in the early 1990s and 2010s. The net Cant transport across both sections is northward. At 7.5°N, this transport increased from 315 ± 47 kmol s−1 in 1993 to 493 ± 51 kmol s−1 in 2010; similarly, across 24.5°N it grew from 530 ± 46 kmol s−1 in 1992 to 662 ± 49 kmol s−1 in 2011. These changes result from modifications in the intermediate and deep circulation patterns, as well as from Cant increase within the thermocline waters. In deep waters, lateral advection causes a net Cant input of 112 ± 60 kmol s−1 (234 ± 65 kmol s−1) in 1992–1993 (2010–2011); within these deep waters, the storage rate of Cant is not statistically different from the net Cant input, 139 ± 21 kmol s−1 (188 ± 21 kmol s−1) in 1992–1993 (2010–2011). The Cant increase in deep waters is due to the large injection of Cant across the 24.5°N by the Deep Western Boundary Current and the northward recirculation of North Atlantic Deep Water along 7.5°N. In contrast, a large net Cant output in the upper layer is caused by the Florida Current. Despite this net Cant output, the Cant accumulates at a rate of 215 ± 24 kmol s−1 (291 ± 24 kmol s−1) referenced to year 1993 (2010). From the two Cant budgets, we infer a Cant air-sea flux of 0.23 ± 0.02 Pg yr−1in the TNA, much larger than previous estimatesThe first author received a grant from the Tricontinental Atlantic Campus spending a 6 month period at the Universidad de Las Palmas de Gran Canaria where this study was carried out. This work has been performed under the projects MOC2 (CTM2008- 06438), Malaspina (CSD2008-00077), BOCATS (CTM2013-41048-P), and TIC-MOC (CTM2011-28867) supported by the Spanish Government and cofounded by the European Regional Development Fund (FEDER)Peer reviewe

Anthropogenic CO2 changes in the Equatorial Atlantic Ocean

15 páginas, 4 tablas, 5 figuras, 3 apéndices.-- Proyecto CarbochangeMethods based on CO2 and chlorofluorocarbon (CFC) data are used to describe and evaluate the anthropogenic CO2 (Cant) concentrations, Cant specific inventories, and Cant storage rates in the Equatorial Atlantic Ocean. The Cant variability in the water masses is evaluated from the comparison of two hydrographic sections along 7.5°N carried out in 1993 and 2010. During both cruises, high Cant concentrations are detected in the upper layers, with values decreasing progressively towards the deep layers. Overall, the Cant concentrations increase from 1993 to 2010, with a large increment in the upper North Atlantic Deep Water layer of about 0.18 ± 0.03 μmol kg−1 y−1. In 2010, the Cant inventory along the whole section amounts to 58.9 ± 2.2 and 45.1 ± 2.0 mol m−2 using CO2 and CFC based methods, respectively, with most Cant accumulating in the western basin. Considering the time elapsed between the two cruises, Cant storage rates of 1.01 ± 0.18 and 0.75 ± 0.17 mol m−2 y−1 (CO2 and CFC based methods, respectively) are obtained. Below ∼1000 m, these rates follow the pace expected from a progressive increase of Cant at steady state; above ∼1000 m, Cant increases faster, mainly due to the retreat of the Antarctic Intermediate WatersThis work was funded by the 7th Framework Programme (EU FP7 CARBOCHANGE, under grand agreement no. 264879) and by the Spanish Ministry of Economy and Competitiveness through Projects GHGMOC (CTM2009-07574-E), MOC2 (CTM2008-06438-C02-01/MAR) and ESCLAT (CTM2009-07405-E/MAR) and by the Deutsche Forschungsgemeinschaft (DFG) (M. Rhein, grant Rh25/36-1). FFP and AFR were supported by the Spanish Government and co-founded by the European Regional Development Fund (CTM2013-41048-P).Peer reviewe