Is the Mediterranean Sean Outflow conditioning cold water corals in the North Atlantic?

posterWithin the context of the UE project ATLAS, in September - October 2016 on board RV Sarmiento de Gamboa, the MEDWAVES (MEDiterranean out flow WAter and Vulnerable EcosystemS) targeted areas under the potential influence of the MOW (Mediterranean Water Outflow) within the Mediterranean and Atlantic realms. These include seamounts where cold-water corals (CWC) have been reported, they may act as essential “stepping stones” connecting fauna of seamounts in the Mediterranean with those of seamounts in the continental shelf of Portugal, the Azores and the Mid‐ Atlantic Ridge. During MEDWAVES sampling was conducted through several seamounts: Formigas (Azores), Ormonde & Gazul (North Atlantic) and Seco de los Olivos (Alboran Sea). High quality CO2 measurements were conducted in the 500 meters above the bottom in order to characterize the water masses and detect the MOW spreading. MOW is warm and salty, but also high in alkalinity and pH. Is MOW conditioning CWC

The CARIMED (CARbon IN the MEDiterranean Sea) data synthesis initiative: overview and quality control procedures

posterIn this work we present the data synthesis project CARIMED (CARbon in the MEDiterranean Sea), we aim to create a uniformly formatted consistent quality controlled public database for carbon relevant variables from hydrographic cruises covering the whole water column and the different basins in the MedSea. Both primary and secondary quality control (QC) of the data has been performed following the experience gathered in CARINA and GLODAPv2. The motivation for this initiative stemmed from two CIESM (Mediterranean Science Commission) workshops, the first one in Menton (France) October 2008 (CIESM, 2008) focused on the impact of OA on biological, chemical and physical systems in the MedSea, and the second one in Supetar (Croatia) May 2011 (CIESM, 2012) focused on designing the Mediterranean Sea repeat hydrography program (MED-SHIP). The unresolved issues regarding the CO2 system in the MedSea were summarized in Malanotte-Rizzoli et al. (Oc Sc, 2014), one of them the temporal and spatial variability of the interior CO2 system, clearly justifies the need for CARIMED. Independently two projects focused on compiling CO2 water column data in the MedSea, an initiative within the EU MedSeA project (Gemayel et al., ESD 2015) called MEDICA (T. Lovato personal communication) and the one here presented lead by the Spanish IEO and partially funded by SanLeón-Bartolomé 's PhD project. We hope a product like this will be much welcome by the oceanographic community, both observationist and modellers, as it was the release of the Meteor cruise M84/3 data in CDIAC used in several publications (Palmieri et al., BG 2015; Cossarini et al., BG 2015; Hassoun et al., DSR 2015 & JWROS 2015; Lovato & Vichi, DSR 2015; Gemayel et al., ESD 2015)

Is Deep Sea Cold Water Corals distribution constrained by CO2 distinct signatures?

conferenceObjectThe MEDWAVESThe MEDWAVES (MEDiterranean out flow WAter and Vulnerable EcosystemS) cruise was developed in the framework of the ATLAS project, with the main objective of determining areas under the influence of the Mediterranean Overflow Water within the Mediterranean and Atlantic areas. MEDWAVES cruise (LEG 1: Cadiz – Punta Delgada and LEG 2: Punta Delgada – Málaga) was completed between September-October 2016 on board the Spanish R/V Sarmiento de Gamboa. Within the specific aim of evaluating the biogeochemichal role of the Mediterranean Water, over and around the Formigas, Ormonde and Seco de los Olivos seamounts, and the Gazul Mud volcano, some CO2 system variables were measured on board (pH, total alkalinity and carbonate ion concentration) together with dissolved oxygen samples. The chemistry of the CO2 in the Mediterranean Sea is very particular, characterised by warm, salty and high alkalinity waters [1]. The Mediterranean Water goes into the Atlantic Ocean through the strait of Gibraltar, being clearly identified as the most saline water of the water column located at approximately 1000 dbar [2]. Apart from the water mass characteristic, other properties and organism characteristics of the Mediterranean Sea are spilt into the Atlantic. According to the objectives of MEDWAVES cruise and taking into account the fine scale sampling made over the 400m above the bottom, we will characterise the CO2 system of the four different areas, trying to distinguish the signature of the Mediterranean Water in each seamount. The presence of depth cold water coral in those seamounts is poorly known and we would like to connect those of Mediterranean Sea with those of the continental shelf of Portugal, the Azores and the Mid-Atlantic Ridge with the CO2 variables. Hence, a second step will be to evaluate the connexion between the cold water corals and the CO2 system

Spectrophotometric Measurement of Carbonate Ion in Seawater over a Decade: Dealing with Inconsistencies

The spectrophotometric methodology for carbonate ion determination in seawater was first published in 2008 and has been continuously evolving in terms of reagents and formulations. Although being fast, relatively simple, affordable, and potentially easy to implement in different platforms and facilities for discrete and autonomous observations, its use is not widespread in the ocean acidification community. This study uses a merged overdetermined CO2 system data set (carbonate ion, pH, and alkalinity) obtained from 2009 to 2020 to assess the differences among the five current approaches of the methodology through an internal consistency analysis and discussing the sources of uncertainty. Overall, the results show that none of the approaches meet the climate goal (± 1 % standard uncertainty) for ocean acidification studies for the whole carbonate ion content range in this study but usually fulfill the weather goal (± 10 % standard uncertainty). The inconsistencies observed among approaches compromise the consistency of data sets among regions and through time, highlighting the need for a validated standard operating procedure for spectrophotometric carbonate ion measurements as already available for the other measurable CO2 variables.4,84

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

Decadal acidification in the water masses of the Atlantic Ocean

Global ocean acidification is caused primarily by the ocean's uptake of CO2 as a consequence of increasing atmospheric CO2 levels. We present observations of the oceanic decrease in pH at the basin scale (50°S-36°N) for the Atlantic Ocean over two decades (1993-2013). Changes in pH associated with the uptake of anthropogenic CO2 (ΔpHCant) and with variations caused by biological activity and ocean circulation (ΔpHNat) are evaluated for different water masses. Output from an Institut Pierre Simon Laplace climate model is used to place the results into a longer-term perspective and to elucidate the mechanisms responsible for pH change. The largest decreases in pH (ΔpH) were observed in central, mode, and intermediate waters, with a maximum ΔpH value in South Atlantic Central Waters of -0.042 ± 0.003. The ΔpH trended toward zero in deep and bottom waters. Observations and model results show that pH changes generally are dominated by the anthropogenic component, which accounts for rates between -0.0015 and -0.0020/y in the central waters. The anthropogenic and natural components are of the same order of magnitude and reinforce one another in mode and intermediate waters over the time period. Large negative ΔpHNat values observed in mode and intermediate waters are driven primarily by changes in CO2 content and are consistent with (i) a poleward shift of the formation region during the positive phase of the Southern Annular Mode in the South Atlantic and (ii) an increase in the rate of the water mass formation in the North Atlantic

Gaining insights into the seawater carbonate system using discrete fCO2 measurements

Understanding the ocean carbon sink and its future acidification-derived changes requires accurate and precise measurements with good spatiotemporal coverage. In addition, a deep knowledge of the thermodynamics of the seawater carbonate system is key to interconverting between measured and calculated variables. To gain insights into the remaining inconsistencies in the seawater carbonate system, we assess discrete water column measurements of carbon dioxide fugacity (fCO2), dissolved inorganic carbon (DIC), total alkalinity (TA), and pH measured with unpurified indicators, from hydrographic cruises in the Atlantic, Pacific, and Southern Oceans included in GLODAPv2.2020 (19,013 samples). An agreement of better than ±3% between fCO2 measured and calculated from DIC and pH is obtained for 94% of the compiled dataset, while when considering fCO2 measured and calculated from DIC and TA, the agreement is better than ±4% for 88% of the compiled dataset, with a poorer internal consistency for high-CO2 waters. Inspecting all likely sources of uncertainty from measured and calculated variables, we conclude that the seawater carbonate system community needs to (i) further refine the thermodynamic model of the seawater carbonate system, especially K2, including the impact of organic compounds and other acid-base systems on TA; (ii) update the standard operating procedures for the seawater carbonate system measurements following current technological and analytical advances, paying particular attention to the pH methodology that is the one that evolved the most; (iii) encourage measuring discrete water column fCO2 to further check the internal consistency of the seawater carbonate system, especially given the new era of sensor-based seawater measurements; and (iv) develop seawater Certified Reference Materials (CRMs) for fCO2 and pH together with seawater CRMs for TA and DIC over the range of values encountered in the global ocean. Our conclusions also suggest the need for a re-evaluation of the adjustments applied by GLODAPv2 to pH, which were based on DIC and TA consistency checks but not supported by fCO2 and DIC consistency

Ocean Circulation over Formigas and Ormonde Seamounts

Seamounts constitute an obstacle to the free ocean flow, modifying the patter of circulation. As a result of these alterations, a variety of hydrodynamical processes and phenomena may take place in seamounts, among others, Taylor columns/caps. These oceanographic effects may turn seamounts into very productive ecosystems with high biodiversity. Under these conditions seamounts provide a particularly good environment for the settle of some organisms, acting as stepping stones and contributing to its dispersal. In this study, we verify if these oceanographic effects explain the presence of cold-water corals of Mediterranean origin in the Atlantic. To achieve this, three seamounts in the path of the Mediterranean Outflow Water (MOW) through the Eastern North Atlantic were selected: the Gazul mud volcano, and the Ormonde and Formigas seamounts. In order to determine the hydrographic and dynamical conditions in each one of the three locations, CTD, LADPC and biochemical observations were carried out. Taylor columns were not observed in any of the three sampled areas. Although we found suggestions of upwelling/downwelling systems, their effect was barely noticed in the circulation pattern. The oceanographic processes in those areas are more influenced by the vertical distribution of water masses, which determine the stability of the water column. Moreover, the high values of the Brunt-Väisälä frequency around the MOW halocline can lead to the formation of internal waves. These perturbations in the water column can enhance the vertical mixing, producing suspension, which, in turn, could affect the vertical distribution of cold-water corals

Ocean Circulation over North Atlantic underwater features in the path of the Mediterranean Outflow Water: Ormonde and Formigas seamounts, and the Gazul mud volcano

Seamounts constitute an obstacle to the ocean circulation, modifying it. As a result, a variety of hydrodynamical processes and phenomena may take place over seamounts, among others, flow intensification, current deflection, upwelling, Taylor caps, and internal waves. These oceanographic effects may turn seamounts into very productive ecosystems with high species diversity, and in some cases, are densely populated by benthic organisms, such corals, gorgonians, and sponges. In this study, we describe the oceanographic conditions over seamounts and other underwater features in the path of the Mediterranean Outflow Water (MOW), where populations of benthic suspensions feeders have been observed. Using CTD, LADPC and biochemical measurements carried out in the Ormonde and Formigas seamounts and the Gazul mud volcano (Northeast Atlantic), we show that Taylor caps were not observed in any of the sampled features. However, we point out that the relatively high values of the Brunt–Väisälä frequency in the MOW halocline, in conjunction with the slope of the seamount flanks, set up conditions for the breakout of internal waves and amplification of the currents. This may enhance the vertical mixing, resuspending the organic material deposited on the seafloor and, therefore, increasing the food availability for the communities dominated by benthic suspension feeders. Thus, we hypothesize that internal waves could be improving the conditions for benthic suspension feeders to grow on the slope of seamounts.En prens

North Atlantic CO2 sink variability revealed by the Go-Ship A25-OVIDE section

EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022.-- This work is distributed under the Creative Commons Attribution 4.0 LicenseAbout 30% of the carbon dioxide derived from human activities (CANTH) has been absorbed by the ocean (DeVries, 2014; Gruber et al., 2019; Friedlingstein et al., 2021), with the North Atlantic (NA) being one of the largest CANTH sinks per unit area (Khatiwala et al., 2013; Sabine et al., 2004). In the NA, oceanic CANTH uptake strongly relies on the meridional overturning circulation and the associated regional winter deep convection. In fact, the formation and deep spreading of Labrador Sea Water stands as a critical CANTH gateway to intermediate and abyssal depths. The NA CANTH uptake has fluctuated over the years according to changes in the North Atlantic Oscillation. Biennial observation of the marine carbonate system along the Go-Ship A25-OVIDE section has allowed us assessing the decadal and interannual variability of the CANTH storage in the subpolarNA from 2002 to 2021. In this study, we investigate 1) the trend of CANTH and 2) the relationship between the CANTH saturation, the apparent oxygen utilization, and the ventilation of the water masses between the A25-OVIDE section and the Greenland-Iceland-Scotland sills during 2002-2021. We divided the A25-OVIDE section into three main basins (Irminger, Iceland, and Eastern NA). Our results show that the Irminger Basin presents a more homogenous CANTH profile and higher CANTH saturation values at depth than the other two basins, which is related to the pronounced convective activity in the Irminger Basin. In contrast, the Eastern NA Basin has higher CANTH values at the surface due to its higher surface temperature, but its deep water masses show the lowest CANTH values since they are the less ventilated in the section. Our analysis also reveals that, overall, the NA CANTH storage has increased during 2002-2021, but varied according to the ventilation changes. While the Eastern NA water masses experienced a relatively constant, although shallower, average ventilation, the Irminger and Iceland Basins underwent a less steady CANTH uptake pattern characterized by alternating periods of strong and weak CANTH storageN