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<p><span lang="EN-US">The dynamic and thermohaline characteristics of the Atlantic Ocean linked to the Atlantic Meridional Overturning Circulation (AMOC) give it a specific role in the accumulation of heat and CO<sub>2</sub>, either of natural or anthropogenic origin (Cant), from the surface layer to the deep waters, significantly mitigating the impacts of anthropogenic climate change. Here, we evaluate the annual mean, long-term trends, seasonal cycle and interannual variability of net sea-air CO<sub>2</sub> fluxes (FCO<sub>2</sub>) between 1985 and 2018 based on observation products (pCO<sub>2</sub>-products) and global ocean biogeochemical models (GOBMs) for the Atlantic from 30ºS to the Nordic Seas (~79ºN) and the Mediterranean. The mean contemporary FCO<sub>2 </sub>(sum of anthropogenic and natural components) is estimated to be 0.362 ± 0.067 and 0.47 ± 0.15 Pg C yr<sup>-1</sup> using pCO<sub>2</sub>-products and GOBMs, respectively. The GOBMs show consistent growth trends in CO<sub>2</sub> uptake with rates similar to the atmospheric CO<sub>2 </sub>growth, however trends obtained from CO<sub>2</sub>-products show a sharp increase from the pre-2000 period to the post-2000 period. There is overall agreement between pCO<sub>2</sub>-products and GOBMs results for mean values, seasonal cycle and interannual variability in all biomes, except for the North Atlantic subpolar biome, where pCO<sub>2</sub>-products show lower mean values, larger trends, and a different seasonal cycle than GOBMs. The GOBMs and pCO<sub>2</sub>-products show very concordant values in equatorial and subtropical regions, where CO<sub>2</sub> variability is strongly determined by temperature. For the period 1994-2007, GOBMs show concordant values in annual Cant storage rate with carbonate marine system observations (Gruber et al., 2019) with values of 0.506 ± 0.106 Pg C yr<sup>-1</sup> vs 0.673 ± 0.066 Pg C yr<sup>-1</sup>, respectively. The Cant storage rate agreement between GOBMs and </span><span lang="EN-US">observations are</span><span lang="EN-US"> also registered in the different biomes, although in both permanently stratified subtropical in North and South Atlantic biomes, the storage rates in GOBMs show a larger spread with their mean values 30 and 40% lower than those estimated from observations. In general, the Atlantic accumulates more Cant than that inferred from the cumulative </span><span lang="EN-US">FCO<sub>2</sub></span><span lang="EN-US"> changes, partly due to a significant lateral Cant transport from the Southern Ocean (about 30%).</span></p>

<p>Since 1750s human industrial activities have emitted large amounts of CO<sub>2</sub> into the atmosphere, increasing the atmospheric CO<sub>2</sub> content to unprecedent levels. About a quarter of this exccess of carbon (namely anthropogenic carbon, C<sub>ant</sub>) is absorbed by the ocean, which acts as a major net C<sub>ant</sub> sink. Changes in the inorganic carbon chemistry of sea water due to the invasion of C<sub>ant</sub> - increasing (decreasing) concentration of hydrogen ions, H<sup>+</sup> (carbonate ions, CO<sub>3</sub><sup>2−</sup>) - are referred to as ocean acidification (OA). The North Atlantic is the oceanic region with the highest storage of C<sub>ant </sub>per area, closely linked to the Atlantic meridional overturning circulation and subpolar winter deep convection. As a result, it is also the main region where both upper-ocean C<sub>ant</sub> and fast OA signals are tranferred to deeper levels. Yet, it is still uncertain how much of this signal originates (locally) at these high latitudes or is conveyed (remotely) from the subtropics; or what are the driving mechanisms regulating its lateral vs vertical transfer at different temporal scales. Here we present the preliminary data and results of the CARING (Carbon irrigation in the Noth Atlantic by the gulf Stream) project to <em>i)</em> provide a contemporary assessment of the OA rates conveyed poleward by the Gulf Stream, and to <em>ii)</em> elucidate its role as far-field control to the North Atlantic OA. Our results of <em>i</em><em>n situ</em> pH data over the first 2000 dbar of the water-column, in combination with historical GLODAP data, show the pH decline to be the highest at the surface (subtropical waters down to</p>

<p>About 30% of the carbon dioxide derived from human activities (C<sub>ANTH</sub>) 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 C<sub>ANTH </sub>sinks per unit area (Khatiwala et al., 2013; Sabine et al., 2004). In the NA, oceanic C<sub>ANTH</sub> 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 C<sub>ANTH</sub> gateway to intermediate and abyssal depths. The NA C<sub>ANTH </sub>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 C<sub>ANTH</sub> storage in the subpolar NA from 2002 to 2021. In this study, we investigate 1) the trend of C<sub>ANTH</sub> and 2) the relationship between the C<sub>ANTH</sub> 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 C<sub>ANTH</sub> profile and higher C<sub>ANTH </sub>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 C<sub>ANTH</sub> values at the surface due to its higher surface temperature, but its deep water masses show the lowest C<sub>ANTH</sub> values since they are the less ventilated in the section. Our analysis also reveals that, overall, the NA C<sub>ANTH</sub> 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 C<sub>ANTH</sub> uptake pattern characterized by alternating periods of strong and weak C<sub>ANTH</sub> storage.</p>

<p><span>Since the industrial revolution, human activities have emitted large amount of anthropogenic carbon (C</span><span><sub>ant</sub></span><span>) into the atmosphere through the burning of fossil fuel, the production of cement and land-use change. Via air-sea gas exchange, the ocean absorbs roughly a third of C</span><span><sub>ant</sub></span><span>, meaning that C</span><span><sub>ant</sub></span><span> is an additional source of carbon for the ocean. In particular, the North Atlantic is known to be a region with a high storage capacity of C</span><span><sub>ant</sub></span><span>. Whereas the distribution of C</span><span><sub>ant</sub></span><span> in the upper layers of the North Atlantic is well documented, its transport to the abyssal ocean and the mechanisms behind its deep redistribution remain scarcely described. To shed light on this research gap, we use a database provided by ~70 Deep-Argo floats equipped with oxygen sensors and located in the North Atlantic that allow us to explore the deep pathways of C</span><span><sub>ant</sub></span><span>. First, the macronutrients and carbon variables (pH, total alkalinity, total inorganic carbon and pCO</span><span><sub>2</sub></span><span>) are estimated with bayesian neural networks (CANYON-B and CONTENT) from the temperature, salinity and oxygen data of the floats. Second, C</span><span><sub>ant </sub></span><span>concentrations in the water column are then estimated with back-calculation methods. Here we present the first results of our study. <span>   </span></span></p>