Search

Oceans Sciences Meeting, 28 February-4 March 2022, virtual event, Despite covering only 15% of the global oceanic area, the North Atlantic (NA) accumulates one of the highest contents of anthropogenic CO2 (CANTH) in the ocean, storing 23% of the oceanic CANTH (Sabine et al., 2004). In terms of CANTH increase, large regions of the NA recorded average rates of 1.2 ± 0.1 mol m-2 yr-1 during 1994-2007, doubling the global oceanic rate of CANTH increase of 0.65 ± 0.08 mol m-2 yr-1 (Gruber et al., 2019). In the NA, high CANTH concentrations penetrate to mid and abyssal depths as a result of the formation and deep spreading of Labrador Sea Water. These processes are linked to the meridional overturning circulation and winter convection occurring in the NA subpolar gyre. Differences in CANTH storage rates have been observed between different phases of the NA Oscillation (NAO), attributed to both changes in CANTH concentration and decreases in volumetric water mass census (Fröb et al., 2018). There has been a 50% slowdown in the rate of CANTH increase in the NA subpolar gyre between 1994 and 2007, coinciding with a period of low NAO. Biennial observation of the marine carbonate system along the GOSHIP A25-OVIDE section has allowed assessing the long-term and interannual variability of the CANTH storage in the subpolar NA from 2002 to 2018. In this research, we determined the increases of CANTH in the water masses present between the OVIDE section and the Nordic sills. The average accumulation rate CANTH in the water column between the A25-OVIDE section and the sills was 0.90 ± 0.08 mol m-2 yr-1 (0.041 ± 0.003 Pg-C yr-1) for 2002-2021, being 61% higher than the 0.54 ± 0.06 mol m-2 yr-1 observed for 1997-2006 (low NAO). The increase in the CANTH accumulation rate during 2002-2021 is mainly found in the Irminger and Iceland basins and is mainly associated with the period of high NAO that occurred after 2014. In these two basins, the CANTH accumulation rates during the high NAO double those found during the low NAO

XX Seminario Ibérico de Química Marina, SIQUIMAR 2020, Barcelona (Spain), 1st-3rd July 2020, Ocean acidification decreases the excess carbonate, that is, the amount of carbonate available for marine calcifiers. Here, the chemical status of the Northeast Atlantic and its cold-water corals (CWC) communities is examined by means of a high-quality database of carbon variables based on the GO-SHIP A25 section. The database covers a two-decade period (1997-2018), where the mean annual atmospheric carbon dioxide (CO2) increased from 364 to 409 parts per million of volume. The running out of excess carbonate, that is, the progression of undersaturation with respect to aragonite, could compromise the conservation of the habitats and ecosystem services developed by CWC communities. We find that the anthropogenic perturbation in the ocean carbon cycle is significantly decreasing the concentration of excess carbonate in the waters surrounding CWC communities at a rate of -0.17±0.02 μmol kg-1·ppm-1. The optimal chemical conditions for development of CWC communities in the Northeast Atlantic are maintained by the interplay between the northward spreading of recently conveyed Mediterranean Water with excess of carbonate available and the arrival of subpolar-origin waters close to undersaturation. Given the current acidification rate, the living CWC communities would be exposed to undersaturated waters before the end of the century, if atmospheric CO2 concentration reached ~700 ppm. Therefore, the future of the CWC communities in the Northeast Atlantic is closely linked to the accomplishment of global climate policies to limit global warming below 1.5-2ºC, which would preserve chemically optimal conditions of CWC growth in this particular oceanic region, For this work M. Fontela was funded by the Spanish Ministry of Economy and Competitiveness (BES-2014-070449) supported by the Spanish Government and co-funded by the Fondo Europeo de Desarrollo Regional 2007–2012 (FEDER) and by Portuguese national funds from FCT - Foundation for Science and Technology through project UIDB/04326/2020 and CEECINST/00114/2018. F.F. Pérez were supported by the BOCATS Project (CTM2013-41048-P) and ARIOS project (CTM2016-76146-C3-1-R) both co-funded by the Spanish Government and the Fondo Europeo de Desarrollo Regional (FEDER). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 820989 (project COMFORT, Our common future ocean in the Earth system – quantifying coupled cycles of carbon, oxygen, and nutrients for determining and achieving safe operating spaces with respect to tipping points).”

Report on Tracers, Carbon and ADCPs: Report on transient tracer, carbonate system variables and ADCP data from hydrographic sections and a system to sustain these observations past AtlantOS on key hydrographic sections

Refined description from AtlantOS work of the societal imperatives for sustained Atlantic Ocean observations, the phenomena to observe, EOVs, and contributing observing networks.

OVIDE 2018 cruise focused on the 9th repetition of the OVIDE section. OVIDE cruises have been run biennially since 2002, always in June-July, and the section is labelled as a high-resolution reference section in the international program GO-SHIP. OVIDE 2018 started in Brest on June 11 and ended in Brest on July 14 on the N/O Thalassa. The 98 stations of the OVIDE section, from Portugal to the tip of Greenland, were cast within 3 weeks, and 6 stations were added afterwards in the Bight Fracture Zone. The core of the work consisted in acquiring surface-to-bottom hydrographic profiles of pressure, temperature, salinity and dissolved oxygen, and analyzing 20 physical and biogeochemical tracers from 17500 samples drawn from the Niskin bottles of the CTD frame. We report here an overview of the cruise operations and team, followed by a focus on the acquisition and calibration steps of the physical variables measured specifically by the hydrographic CTD-O2 probe. After calibration, we find precisions for pressure, temperature, salinity and dissolved oxygen that fit the GO-SHIP international quality requirements. Pressure and temperature were calibrated at the laboratory before and after the cruise, leading to a precision of 1 dbar and 0.001 ��C respectively. The calibration of salinity and dissolved oxygen data is obtained by applying polynomial correcting functions that are calculated to statistically minimize the differences between the probe data and the sample data analyzed on board in the chemistry container. These chemical data are also evaluated by the comparison of replicates. After calibration, the differences in salinity and oxygen follow a zero-centered Gaussian-like distribution which standard deviation is used to evaluate the probe precision for each variable. For salinity, we find a standard deviation of 0.001, and for oxygen, 0.03 ml/l (or 1.3 ��mol/kg). The oxygen uncertainty could be reduced to 1 ��mol/kg after correcting for isopycnal heave. Those numbers correspond to a 68 % confidence interval and must be doubled to obtain the precision within a 95 % confidence interval., La campagne OVIDE 2018 portait sur la 9��me r��p��tition de la section OVIDE. Les campagnes OVIDE ont lieu tous les deux ans depuis 2002, toujours en juin-juillet, et la section est labellis��e comme section de r��f��rence �� haute r��solution dans le programme international GO-SHIP. OVIDE 2018 a d��but�� �� Brest le 11 juin et s'est termin��e �� Brest le 14 juillet sur le N/O Thalassa. Les 98 stations de la section OVIDE, du Portugal �� la pointe du Groenland, ont ��t�� effectu��es en 3 semaines, et 6 stations ont ensuite ��t�� ajout��es ensuite dans la zone de fracture Bight. L'essentiel du travail a consist�� �� acqu��rir des profils hydrographiques surface-fond de pression, temp��rature, salinit�� et oxyg��ne dissous, et �� analyser 20 traceurs physiques et biog��ochimiques �� partir de 17500 ��chantillons pr��lev��s dans les bouteilles Niskin. Nous pr��sentons ici un aper��u des op��rations de la campagne et de l'��quipe, puis nous nous concentrons sur les ��tapes d'acquisition et d'ajustage des variables physiques mesur��es sp��cifiquement par la sonde hydrographique CTD-O2. Apr��s ��talonnage, nous trouvons des pr��cisions pour la pression, la temp��rature, la salinit�� et l'oxyg��ne dissous qui correspondent aux exigences de qualit�� internationales de GO-SHIP. La pression et la temp��rature ont ��t�� calibr��es au laboratoire avant et apr��s la campagne, conduisant �� une pr��cision de 1 dbar et 0,001 ��C respectivement. L'��talonnage des donn��es de salinit�� et d'oxyg��ne dissous est obtenu en appliquant des fonctions de correction polynomiales qui sont calcul��es pour minimiser statistiquement les diff��rences entre les donn��es de la sonde et les donn��es de l'��chantillon analys�� �� bord dans le conteneur de chimie. Ces donn��es chimiques sont ��galement ��valu��es par la comparaison de r��plicats. Apr��s ajustage, les diff��rences de salinit�� et d'oxyg��ne suivent une distribution de type gaussienne centr��e sur z��ro dont l'��cart-type est utilis�� pour ��valuer la pr��cision de la sonde pour chaque variable. Pour la salinit��, nous trouvons un ��cart-type de 0,001, et pour l'oxyg��ne, 0,03 ml/l (ou 1,3 ��mol/kg). L'incertitude sur l'oxyg��ne pourrait ��tre r��duite �� 1 ��mol/kg d'apr��s la correction de la profondeur des isopycnes. Ces chiffres correspondent �� un intervalle de confiance de 68 % et doivent ��tre doubl��s pour obtenir la pr��cision dans un intervalle de confiance de 95 %.

The distribution of dissolved aluminium (dAl) in the water column of the North Atlantic and Labrador Sea was studied along GEOTRACES section GA01 to unravel the sources and sinks of this element. Surface water dAl concentrations were low (median of 2.5 nM) due to low aerosol deposition and removal by phytoplankton. However, surface water dAl concentrations were enhanced on the Iberian and Greenland shelves (up to 30.9 nM) due to continental inputs (rivers, glacial flour and ice melt). A negative correlation was observed between dAl in surface waters and primary production, phytoplankton community structure and biogenic opal production. The abundance of diatoms exerted a significant (p 0.76) west of the Iberian Basin, suggesting net release of dAl at depth during remineralization of sinking biogenic opal containing particles. Enrichment of dAl at near-bottom depths was observed due to resuspension of sediments near the sediment-water interface. The highest dAl (up to 38.7 nM) concentrations were observed in Mediterranean Overflow Waters which act as a major source of dAl to mid depth waters of the eastern North Atlantic. This study clearly shows that the vertical and lateral distribution of dAl in the North Atlantic differs when compared to other regions of the North Atlantic and global ocean due to the large spatial differences both in the main source of Al, atmospheric deposition, and the main sink for Al, particle scavenging, between different oceanic regions.

1 poster.-- 2018 Ocean Sciences Meeting, 11-16 February, Portland, Oregon, USA, From 2002 to 2016, a biennial transoceanic section from Portugal to Greenland (Ovide section/GO-SHIP-A25 line, Fig. 1) was performed as part of the CLIVAR and GOSHIP programs. The marine CO2 system parameters were measured to study their temporal variability due to natural and anthropogenic drivers. The rather deep Aragonite Saturation Horizon (ASH) in the Irminger Sea has been experiencing a very rapid shoaling mainly due to the rapid penetration of the anthropogenic CO2. From 1991 to 2016, the ASH shoaled 12-14 m year-1 for the intermediate waters in the Irminger Sea. The deep-convection events occurred during severe winters (1991-1994 and 2015-2106) fostered the fast addition of more acidified water into the deep layers of the North Atlantic. We calculated the increase in anthropogenic CO2 during the last two decades (2002-2016) and its concomitant decrease in the excess of calcium carbonate over the aragonite saturation levels. We found a reduction of about 1/3 in the transport of ion carbonate excess over the saturation levels with respect to the natural CO2 cycle for the period 2002-2016. The projection of these results to a future scenario where the atmospheric CO2 is 500±20 ppm indicates that the export of the aragonite saturated waters to the deep Atlantic associated with the thermohaline circulation would be reduced in nearly 2/3, which will have a negative impact in the deep habitats based in carbonate structures

The GEOVIDE cruise was carried out in the subpolar North Atlantic (SPNA) along the OVIDE section and across the Labrador Sea in May–June 2014. It was planned to clarify the distribution of the trace elements and their isotopes in the SPNA as part of the GEOTRACES international program. This paper focuses on the state of the circulation and distribution of thermohaline properties during the cruise. In terms of circulation, the comparison with the 2002–2012 mean state shows a more intense Irminger Current and also a weaker North Atlantic Current, with a transfer of volume transport from its northern to its central branch. However, those anomalies are compatible with the variability already observed along the OVIDE section in the 2000s. In terms of properties, the surface waters of the eastern SPNA were much colder and fresher than the averages over 2002–2012. In spite of negative temperature anomalies in the surface waters, the heat transport across the OVIDE section estimated at 0.56 ± 0.06 PW was the largest measured since 2002. This relatively large value is related to the relatively strong Meridional Overturning Circulation measured across the OVIDE section during GEOVIDE (18.7 ± 3.0 Sv). By analyzing the air–sea heat and freshwater fluxes over the eastern SPNA in relation to the heat and freshwater content changes observed during 2013 and 2014, we concluded that on a short timescale these changes were mainly driven by air–sea heat and freshwater fluxes rather than by ocean circulation.

Poster presentado en la European Geosciences Union General Assembly 2014 (Viena, Austria, 27 Abril–02 Mayo), The water mass structure, mixing and spreading in the North Atlantic Subpolar Gyre (SPG) were analyzed by means of an extended Optimum MultiParameter (eOMP) approach over the six repeats of the WOCE A25 hydrographic line located at the southern boundary of this gyre. The data includes the Fourex (4x) line taken in 1997 and the five repeat sections of the OVIDE line taken every other year from 2002 to 2010. We proposed 10 water masses, defined by their thermohaline properties (potential temperature and salinity), oxygen and nutrients (nitrate, phosphate and silicate), to resolve the water mass structure of the SPG. The eOMP enables to decompose the transports by water mass quantitatively. Our model provides water mass distributions that are able to reproduce the input data of potential temperature, salinity and silicate with r2>0.997 and of oxygen, nitrate and phosphate with r2>0.96. By combining the velocity field and the water mass structure across each section we provide the relative contribution of each water mass to the Meridional Overturning Circulation (MOC) and we evaluate the water mass transformation in the North Atlantic. The MOC upper limb during OVIDE (2002-2010) is constituted by the northward transports of the central waters (9.4 Sv; 1 Sv = 106 m3 s-1), the Subarctic Intermediate Water (SAIW, 2.8 Sv) and the Subpolar Mode Water (SPMW) of the Iceland Basin (2.1 Sv). The MOC lower limb is constituted by the southward transports of the Iceland-Scotland Overflow Water (ISOW, 2.9 Sv), the Denmark Strait Overflow Water (DSOW, 2.5 Sv), the Polar Intermediate Water (PIW, 0.8 Sv), the Labrador Sea Water (LSW, 3.6 Sv) and the SPMW of the Irminger Sea (4.7 Sv). These results contrast with those obtained for the 1997, cruise developed after a period of high NAO index. The greater MOC strength in 1997 resulted in greater northward transports of central waters (17.5 Sv), while the SAIW transports remained approximately unchanged. The increase of the northward transports of the MOC upper limb is partially balanced by a greater southward export of the SPMW of the Irminger Sea (8.2 Sv) and the LSW (4.6 Sv). The transport of all the waters from the Arctic and Nordic seas (PIW, ISOW and DSOW) remained equal in both periods.

99 páginas.-- Aida F. Ríos ... et al., The objectives of the CATARINA project are a) to quantify the Meridional Overturning Circulation and water mass ventilation changes and their effect on the changes in the anthropogenic carbon ocean uptake and storage capacity, and b) to evaluate the effect of present CO2 emissions and past atmospheric CO2 concentrations in the production and preservation of CaCO3, both in the North Atlantic To can achieve these objectives, the CATARINA cruise was organized in two phases according to the two main activities of the project: “Circulation and anthropogenic CO2”, and “Past and recent acidification impacts”. LEG 1: Section OVIDE 2012 including Labrador: 103 stations. Chief Scientist: Aida F. Ríos. LEG 2: Paleoacid: 6 areas of sampling. Chief Scientist: Guillermo Frances. This report is organized in two parts: Leg 1 (pages 2-61) and Leg 2 (pages 62-91), and finishing with a Miscellany (pages 92-98) that covers common issues on internationalization, outreach, incidences during the cruise and acknowledgements., Project funded by MICINN, Ref. CTM2010-17141 and co-funded by FEDER

41 páginas, 19 figuras.-- Pascale Lherminier ... et al.-- Merian Cruise N. 2, Leg. 1, Lisbon (Portugal) - Thorshavn (Faroes), May 21 to June 28, 2006, Cruise MSM02/1 is the third occurrence of the Ovide hydrological section that was performed in 2002 and 2004, as part of the CLIVAR programme under the name of A25. The Ovide Principal Investigator is Herlé Mercier. A Greenland-Portugal section was previously performed in 1997 under the leadership of S. Bacon (NOCS), slightly south of the Ovide path. The Ovide route crosses Reykjanes Ridge 300 miles north of Charlie-Gibbs Fracture Zone and runs through the West European Basin without having to sample on top of the complex Mid-Atlantic Ridge. The objective of this repeated hydrological section is to monitor the variability of water mass properties and main current transports in the basin, complementing the international observation array relevant for climate studies. The western part of the Ovide section is redundant with AR7E (called also A1) which was done on the odd years and will allow a better analysis of the inter annual variability. The hydrological section includes a hundred surface-bottom stations from coast to coast, collecting profiles of temperature, salinity, oxygen and currents. From the 28 bottles closed at various depth at each stations, samples of sea water are used for salinity and oxygen calibration, and for measurements of biogeochemical components, including tracers, isotopes, nutrients and carbon. From the thermal wind equations, geostrophic transports are deduced from temperature and salinity. Then, direct current observations, preferentially those measured by the ship ADCP, are used to constrain the velocity at the chosen reference level. This is particularly important in the Irminger Sea, where bottom currents are very energetic. This way, the contribution in heat and fresh water of the major currents crossed (mostly perpendicularly) by the Ovide line can be estimated. From north to south, the major currents are the East Greenland/Irminger Current (about 20 Sv southward, 1 Sv = 106 m3s-1), the Deep Western Boundary Current (about 10 Sv southward), the Irminger Current (about 10 Sv northward), and the North Atlantic Current (about 20 Sv northward). Between 1997 and 2004, we already observed a significative variability of these transports (about 30%), The Meridional Overturning Circulation reflects the equilibrium between the warm and salty waters flowing poleward near surface and the cold and relatively fresh water flowing equatorward near the bottom. Measured across Ovide, it is mainly the balance between the North Atlantic Current and the Deep Western Boundary Current. The simple sketch is however complicated by the export into the Labrador Sea and around the Subpolar Gyre of part of the highly variable East Greenland Current. This is why an array of four currentmeter moorings and one ADCP lander was deployed on the East Greenland slope and shelf in 2004, for two year. While temperature and salinity are often the basic parameters to identify water masses, it is useful to use tracers like CFCs to determine when they were ventilated. Oxygen is also a good indicator near the sources, but not conservative. Combining oxygen with nutrients gives useful information on the biological activity and on the remineralization processes. CFCs and nutrients are analysed by the Roscoff team led by Pascal Morin (LCM). The measurements and analyses of pH, alkalinity and pCO2 are performed by a Fiz Perez and Aida Rios from Vigo (IIMV) at every Ovide cruise. In 2006, it was officially part of the CARBO-OCEAN international program, and the objective is to better quantify the role of the North Atlantic in the storage and transport of anthropogenic carbon accumulated in the atmosphere. In 2006, samples were taken to measure isotopes of oxygen (18) and carbon (13) after the cruise. Oxygen isotopes are very useful to determine the proportion of fresh water from different origin (rain/snow, runoff, sea ice).

The highest anthropogenic CO2 (Cant) inventories of all the oceans are found in the subpolar North Atlantic (SPNA). The OVIDE section crosses the SPNA from Greenland to Portugal and is repeated biennially since 2002. Therefore, OVIDE data allow evaluating the evolution of inventories of anthropogenic CO2 (Cant) in the SPNA. This oceanic region is known to host water formation and ventilation processes that change the water mass volumetric census year by year. Changes in the volumetric census cause differences in the Cant inventory estimates (Pérez et al., 2008). Consequently, Pérez et al. (2010) proposed a method for computing Cant inventory in the SPNA taking into account the volumetric census variability and a bathymetric adjustment. This method has been recently revised. The initial methodology and the recent improvements are detailed in this report., Les inventaires de CO2 anthropique (Cant) les plus hauts de tous les océans sont trouvés en Atlantique Nord subpolaire. La section OVIDE traverse l’Atlantique Nord Subpolaire du Groenland au Portugal ; elle est visitée tous les deux ans depuis 2002. Les données acquises pendant les campagnes OVIDE sont donc un outil très intéressant pour étudier l’évolution des inventaires de Cant dans l’Atlantique Nord subpolaire. Dans cette région océanique il y a des processus de ventilation et de formation de masses d’eau qui provoquent des changements de volume de masses d’eau d’une année à l’autre, et ces derniers causent des différences sur le calcul d’inventaires de Cant (Pérez et al., 2008). Donc Pérez et al. (2010) ont proposé une méthode pour calculer des inventaires de Cant en corrigeant la variabilité du volume des masses d’eau et en tenant compte de la bathymétrie du bassin. Cette méthode a était récemment révisée, et les améliorations de la méthode initiale sont détaillées et quantifiées dans ce rapport.

The BOCATS cruise (Biennial Observation of Carbon, Acidification, Transport and Sedimentation) was carried out in the North Atlantic from Vigo (June 18) to Reykjavik (July 31). It was composed of 2 main sections: the OVIDE section coast to coast between Portugal and the south tip of Greenland, followed by the Reykjanes Ridge section, from 55 °N to Iceland. The classical hydrographic rosette was cast 137 times along the route. While the CTD-O2 probe acquired continuous profiles of the “physical” variables (pressure, temperature, salinity and dissolved oxygen), 28 Niskin bottles were closed at different levels during the upcast to provide samples for biogeochemical analysis. We report here an overview of the cruise operations and team, followed by a focus on the acquisition and calibration steps of the physical variables measured by the hydrographic CTD-O2 probe. After calibration, we find precisions for pressure, temperature, salinity and dissolved oxygen that fit the GO-SHIP international quality requirements. Pressure and temperature were calibrated at the laboratory before and after the cruise, leading to a precision of 1 dbar and 0.002°C respectively. The calibration of salinity and dissolved oxygen data is obtained by applying polynomial correcting functions that are calculated to statistically minimize the differences between the probe data and the sample data analyzed on board in the chemistry container. These chemical data are also evaluated by the comparison of replicates. After calibration, the differences in salinity and oxygen follow a zero-centered Gaussian-like distribution which standard deviation is used to evaluate the probe precision for each variable. For salinity, we find a standard deviation of 0.001, and for oxygen, 0.027 ml/l (or 1.3 μmol/kg). Those numbers correspond to a 68 % confidence interval and must be doubled to reach a precision with a 95 % confidence interval., La campagne BOCATS s’est déroulée en Atlantique Nord, de Vigo (18 juin) à Reykjavik (31 juillet). Elle se compose de 2 sections principales: la section OVIDE du Portugal à la pointe sud du Groenland, suivie de la section sur la Ride de Reykjanes, de 55 °N à l’Islande. La rosette hydrographique a été mise à l’eau à 137 stations sur cette route. Alors que la sonde CTD-O2 enregistrait en continu les variables dites « physique » (pression, température, salinité et oxygène dissous), 28 bouteilles Niskin étaient fermées à la remontée à différentes profondeurs afin de disposer d’échantillons d’eau de mer pour les analyses biogéochimiques. Ce rapport expose tout d’abord une présentation des opérations et de l’équipe de la campagne, suivie par les étapes d’acquisition et d’ajustage des variables physiques mesurés par la sonde CTD-O2. Après ajustage, la précision estimée pour la pression, la température, la salinité et l’oxygène dissous est conforme aux exigences internationales des campagnes GO-SHIP. La pression et la température ont été ajustées grâce à une vérification au laboratoire de métrologie avant et après la campagne, et les précisions de 1 dbar et 0.002°C sont obtenues respectivement. L’ajustage des données de salinité et oxygène dissous se fait par application de polynômes de correction calculés pour statistiquement minimiser l’écart entre les données de la sonde et les analyses chimiques faites sur les prélèvements, ces dernières étant validées par l’analyse régulière de doublons. La différence entre les données de la sonde après ajustage et les données de chimie suit une distribution quasi gaussienne centrée sur zéro pour les deux variables, et la précision des données est estimée par le calcul de l’écart-type de cette distribution, qui donne une valeur de 0.001 en salinité et 0.027 ml/l (soit 1.3 μmol/kg) en oxygène, correspondant à un intervalle de confiance de 68%. Une précision à 95 % nécessite de doubler la valeur de l’écart-type.