Climate Change hazards to social-ecological systems are well-documented and the time to act is now. The IPCC-SROCC used the best available scientific knowledge to identify paths for effective adaptation and mitigation of climate change impacts on the ocean and cryosphere. Despite all the evidence highlighted by SROCC and the key role of the ocean and cryosphere for climate change at all levels, Latin America (LA) faces challenges to take effective action mostly due to socio-economic vulnerability, political instability and overall technical capacities. Countries have adopted diverse actions as the information needed by policy makers has been made available, not necessarily in accessible and inclusive ways. Regional imbalance in economic development, technological level, capacity development, societal involvement, and governmental oversight have contributed to skewed geographical and technological gaps of knowledge on key ecosystems and specific areas preventing effective climate actions/solutions. We analyze the Nationally Determined Contributions (NDCs) from the region as proxies to the incorporation of IPCC recommendations. The gaps and opportunities for the uptake of ocean and climate science to political decision making is discussed as five key aspects: (i) climate assessment information and regional policies, (ii) knowledge production, (iii) knowledge accessibility, (iv) knowledge impact to policy, and (v) long term monitoring for decision making. We advocate that the uptake of SROCC findings in LA policies can be enhanced by: (a) embracing local realities and incorporating local, traditional and indigenous knowledge; (b) empowering locals to convey local knowledge to global assessments and adapt findings to local realities; (c) enhancing regional research capabilities; and (d) securing long-term sustainable ocean observations. Local and regional participation in knowledge production and provision enhances communication pathways, climate literacy and engagement which are key for effective action to be reflected in governance. Currently, the lack of accessible and inclusive information at the local level hampers the overall understanding, integration and engagement of the society to mitigate climate effects, perpetuates regional heterogeneity and threatens the efforts to reverse the course of climate change in LA. Local researchers should be empowered, encouraged, rewarded and better included in global climate-ocean scientific assessments.

Pacific and Atlantic sea surface temperature (SST) variability strongly influences rainfall changes in the Amazon River basin, which impacts on the river discharge and consequently the sea surface salinity (SSS) in the Amazon plume. An Empirical Orthogonal Function (EOF) analysis was performed using 46 years of SST, rainfall, and SSS datasets, in order to establish the relationship between these variables. The first three modes of SST/rainfall explained 87.83% of the total covariance. Pacific and Atlantic SSTs led Amazon basin rainfall events by 4 months. The resultant SSS in the western tropical North Atlantic (WTNA) lagged behind basin rainfall by 3 months, with 75.04% of the total covariance corresponding to the first four EOF modes. The first EOF mode indicated a strong SSS pattern along the coast that was connected to negative rainfall anomalies covering the Amazon basin, linked to El Niño events. A second pattern also presented positive SSS anomalies, when the rainfall was predominantly over the northwestern part of the Amazon basin, with low rainfall around the Amazon River mouth. The pattern with negative SSS anomalies in the WTNA was associated with the fourth mode, when positive rainfall anomalies were concentrated in the northwest part of South America. The spatial rainfall structure of this fourth mode was associated with the spatial rainfall distribution found in the third EOF mode of SST vs. rainfall, which was a response to La Niña Modoki events. A statistical analysis for the 46 year period and monthly anomaly composites for 2008 and 2009 indicated that La Niña Modoki events can be used for the prediction of low SSS patterns in the WNTA.

The Amazon generates the world’s largest offshore river plume, which covers extensive areas of the tropical Atlantic. The data and samples in this study were obtained during the oceanographic cruise Camadas Finas III in October 2012 along the Amazon River-Ocean Continuum (AROC). The cruise occurred during boreal autumn, when the river plume reaches its maximum eastward extent. In this study, we examine the links between physics, biogeochemistry and plankton community structure along the AROC. Hydrographic results showed very different conditions, ranging from shallow well-mixed coastal waters to offshore areas, where low salinity Amazonian waters mix with open ocean waters. Nutrients, mainly NO3− and SiO2−, were highly depleted in coastal regions, and the magnitude of primary production was greater than that of respiration (negative apparent oxygen utilization). In terms of phytoplankton groups, diatoms dominated the region from the river mouth to the edge of the area affected by the North Brazil Current (NBC) retroflection (with chlorophyll a concentrations ranging from 0.02 to 0.94 mg m−3). The North Equatorial Counter Current (NECC) region, east of retroflection, is fully oligotrophic and the most representative groups are Cyanobacteria and dinoflagellates. Additionally, in this region, blooms of cyanophyte species were associated with diatoms and Mesozooplankton (copepods). A total of 178 zooplankton taxa were observed in this area, with Copepoda being the most diverse and abundant group. Two different zooplankton communities were identified: a low-diversity, high-abundance coastal community and a high-diversity, low-abundance oceanic community offshore. The CO2 fugacity (fCO2sw), calculated from total alkalinity (1,450 < TA < 2,394 μmol kg−1) and dissolved inorganic carbon (1,303 < DIC < 2,062 μmol kg−1) measurements, confirms that the Amazon River plume is a sink of atmospheric CO2 in areas with salinities <35 psu, whereas, in regions with salinities >35 and higher-intensity winds, the CO2 flux is reversed. Lower fCO2sw values were observed in the NECC area. The ΔfCO2 in this region was less than 5 μatm (−0.3 mmol m−2 d−1), while the ΔfCO2 in the coastal region was approximately 50 μatm (+3.7 mmol m−2 d−1). During the cruise, heterotrophic and autotrophic processes were observed and are indicative of the influences of terrestrial material and biological activity, respectively.

Hourly data of CO2 fugacity (fCO2) at 8°N-38°W were analyzed from 2008 to 2011. Analyses of wind, rainfall, temperature and salinity data from the buoy indicated two distinct seasonal periods. The first period (January to July) had a mean fCO2 of 378.9 μatm (n = 7512). During this period, in which the study area was characterized by small salinity variations, the fCO2 is mainly controlled by sea surface temperature (SST) variations (fCO2 = 24.4*SST-281.1, r2 = 0.8). During the second period (August-December), the mean fCO2 was 421.9 μatm (n = 11571). During these months, the region is subjected to the simultaneous action of (a) rainfall induced by the presence of the Intertropical Convergence Zone (ITCZ); (b) arrival of fresh water from the Amazon River plume that is transported to the east by the North Equatorial Countercurrent (NECC) after the retroflection of the North Brazil Current (NBC); and (c) vertical input of CO2-rich water due to Ekman pumping. The data indicated the existence of high-frequency fCO2 variability (periods less than 24 h). This high variability is related to two different mechanisms. In the first mechanism, fCO2 increases are associated to rapid increases in SST and are attributed to the diurnal cycle of solar radiation. In addition, low wind speed contributes to SST rising by inhibiting vertical mixing. In the second mechanism, fCO2 decreases are associated to SSS decreases caused by heavy rainfall.

To reduce uncertainty regarding the contribution of continental shelf areas in low latitude regions to the air-sea CO2 exchange, more data are required to understand the carbon turnover in these regions and cover gaps in coverage. For the first time, inorganic carbon and alkalinity were measured along a cross-shelf transect off the coast of Maranhão (North Brazil) in 9 cruises spawning from April 2013 to September 2014. On the last 4 transects, dissolved organic matter and nutrients were also measured. The highest inorganic and organic carbon concentrations are observed close to land. As a result of low productivity and significant remineralization, heterotrophy dominates along the transect throughout the year. Although the temporal variability is significantly reduced at the offshore station with carbon concentrations decreasing seaward, the fugacity of CO2 (fCO2) at this station remains significantly higher, especially during the wet season, than the open ocean values measured routinely by a merchant ship further west. Overall, the continental shelf is a weak source of CO2 to the atmosphere throughout the year with an annual mean flux of 1.81±0.84 mmol m−2 d−1. The highest magnitudes of fCO2 are observed during the wet season when the winds are the weakest. As a result, the CO2 flux does not show a clear seasonal pattern. Further offshore, fCO2 is significantly lower than on the continental shelf. However, the oceanic CO2 flux, with an annual mean of 2.32±1.09 mmol m−2 d−1, is not statistically different from the CO2 flux at the continental shelf because the wind is stronger in the open ocean.

Observational data and numerical modeling were used to investigate oceanic current wakes surrounding Fernando de Noronha Island (3°51′S–32°25′W) and Rocas Atoll (3°52′S–33°49′W). These two Brazilian systems are located in the western tropical Atlantic region and are under the influence of the westward flow of the central South Equatorial Current (cSEC). In order to highlight the effects of wakes on ocean dynamics, two different numerical simulations were performed, using the Regional Oceanic Modeling System (ROMS): the first one including Fernando de Noronha Island and Rocas Atoll (Scenario I) and the second one with artificial removal of the island and atoll (Scenario NI). Simulations are validated through the Scenario I that well reproduces the wakes that give rise to the development of eddies downstream of FN and AR. These mesoscale structures have a strong influence on the thermodynamic properties surrounding the Island and the Atoll. Scenario NI allows evidence of the presence of an Island and Atoll shoaling mixed layer throughout the year, primarily on the western side of the Island and the Atoll. Mixing at the base of the mixed layer, inducing a subsurface cooling, is also enhanced in the downstream portion of the Island and Atoll, particularly when the cSEC is strengthened. These simulations support the “island mass effect” on the high productivity of subsurface waters generally observed on the western side of these islands.

Multiple biotic and abiotic drivers regulate the balance between CO2 assimilation and release in surface waters. In the present study, we compared in situ measurements of plankton carbon metabolism (primary production and respiration) to calculated air–water CO2 fluxes (based on abiotic parameters) during 1 year (2008) in a hypereutrophic tropical estuary (Recife Harbor, NE Brazil – 08°03′S, 34°52′W) to test the hypothesis that high productivity leads to a net CO2 flux from the atmosphere. The calculated CO2 fluxes through the air–water interface (FCO2) were negative throughout the year (FCO2: –2 to –9 mmol C·m−2·day−1), indicating that Recife Harbor is an atmospheric CO2 sink. Respiration rates of the plankton community ranged from 2 to 45 mmol C·m−2·hr−1. Gross primary production ranged from 0.2 to 281 mmol C·m−2·hr−1, exceeding respiration during most of the year (net autotrophy), except for the end of the wet season, when the water column was net heterotrophic. The present results highlight the importance of including eutrophic tropical shallow estuaries in global air–water CO2 flux studies, in order to better understand their role as a sink of atmospheric CO2.

No ambiente marinho uma equação inversa entre a alcalinidade total e a salinidade, denominada de alcalinidade total normalizada (ATN) para mostrar uma relação linear entre esses parâmetros. O objetivo deste trabalho foi avaliar a distribuição superficial e vertical da ATN ao longo da Zona Econômica Exclusiva-ZEE da região Norte do Brasil, com os dados obtidos nas Operações Norte III e Norte IV, dentro do âmbito do Programa de Avaliação do Potencial Sustentável de Recursos Vivos na Zona Econômica Exclusiva (REVIZEE). Os dados demonstraram que o sistema do dióxido de carbono ao longo da ZEE Norte mantém o pH dentro da faixa esperada para o ambiente marinho. Os menores valores de pH (7,48 Norte III e 7,38 Norte IV), de AT (1971µmol kg-1, Norte III e 1878 µmol kg-1 Norte IV) e de ATN (2295 µmol kg-1 Norte III, 2293 µmol kg-1 Norte IV) na camada superficial, foram observados na área com influência da descarga do rio Amazonas, ou seja, com baixos valores de salinidade (28,31 Norte III e 24,00 Norte IV). As massas de águas na coluna de água, encontradas na região, tiveram diferenças na concentração de ATN. Essas diferenças podem ser associadas aos processos de degradação da matéria orgânica, e a formação ou dissolução do carbonato de cálcio. Pesquisas futuras englobando outras formas do sistema do dióxido de carbono, e também com a utilização de métodos mais precisos, irão servir para explicar a dinâmica desse sistema de forma mais precisa.

A relationship between oceanic conditions in the northwestern equatorial Atlantic (NWEA) and the seasonal rainfall over the northern part of Brazilian Northeast (NNEB) allows large climate events to be forecasted with a delay of a few months. Observed sea surface variables (sea surface temperature, wind stress and latent heat flux) and reanalyzed temperature and salinity profiles at depths of 0 – 150 m are used during 1974-2008. Perturbations in the Wind-Evaporation-SST mechanism over the NWEA during the last months of the year and the first months of the following year are of primary importance in evaluating the risk that strong climate events will affect the subsequent seasonal rainfall (in March-April) over the NNEB. Especially interesting are the Barrier Layer Thickness (BLT) and Ocean Heat Content (OHC) in the NWEA region from August-September through the subsequent months, during which a slow and steady evolution is apparent, with the highest signal occurring in October-November. Through their relationship with the local surface dynamic conditions, such BLT and OHC perturbations during the last months of the year can be used as a valuable indicator for forecasting wet or dry events over the NNEB during the subsequent rainfall season. A proposal is discussed to deploy additional temperature/conductivity sensors down to a depth of 140 m at three PIRATA moorings located in the NWEA region. That will be necessary if the BLT and other parameters of energy exchange between the ocean and atmosphere are to be estimated in real time and with a sufficiently high vertical resolution.

Hourly fCO2 is recorded at a time series at the PIRATA buoy located at 6°S 10°W in the eastern tropical Atlantic since June 2006. This site is located south and west of the seasonal Atlantic cold tongue and is affected by its propagation from June to September. Using an alkalinity–salinity relationship determined for the eastern tropical Atlantic and the observed fCO2, pH and the inorganic carbon concentration are calculated. The time series is investigated to explore the intraseasonal, seasonal and interannual timescales for these parameters, and to detect any long-term trends. At intraseasonal timescales, fCO2 and pH are strongly correlated. On seasonal timescales, the correlation still holds between fCO2 and pH and their variations are in agreement with those of sea surface salinity. At interannual timescales, some important differences appear in 2011–2012: lower fCO2 and fluxes are observed from September to December 2011 and are explained by higher advection of salty waters at the mooring, in agreement with the wind. In early 2012, the anomaly is still present and associated with lower sea surface temperatures. No significant long-term trend is detected over the period 2006–2013 on CO2 and any other physical parameter. However, as atmospheric fCO2 is increasing over time, the outgassing of CO2 is reduced over the period 2006–2013 as the flux is mainly controlled by the difference of fCO2 between the ocean and the atmosphere. A longer time series is required to determine if any significant trend exists in this region.

The intense rainfall in the tropical Atlantic spatially overlaps with the spread of the Amazon plume. Based on remote-sensed sea surface salinity and rainfall, we removed the contribution of rainfall to the apparent Amazon plume area, thus refining the quantification of its extension (0.84 ± 0.06 × 106 km2 to 0.89 ± 0.06 × 106 km2). Despite the previous overestimation of the Amazon plume area due to the influence of rainfall (>16%), our calculated annual CO2 flux based on rainfall-corrected sea surface CO2 fugacity confirms that the Amazon River plume is an atmospheric CO2 sink of global importance (−7.61 ± 1.01 to −7.85 ± 1.02 Tg C yr−1). Yet we show that current sea-air CO2 flux assessments for the tropical Atlantic could be overestimated in about 10% by neglecting the CO2 sink associated to the Amazon plume. Thus, including the Amazon plume, the sea-air CO2 exchange for the tropical Atlantic is estimated to be 81.1 ± 1.1 to 81.5 ± 1.1 Tg C yr−1.

The variability of sea surface Total Alkalinity (TA) and sea surface Total Inorganic Carbon (CT) is examined using all available data in the western tropical Atlantic (WTA: 20°S-20°N, 60°W-20°W). Lowest TA and CT are observed for the region located between 0°N-15°N/60°W-50°W and are explained by the influence of the Amazon plume during boreal summer. In the southern part of the area, 20°S-10°S/40°W-60°W, the highest values of TA and CT are linked to the CO2–rich waters due to the equatorial upwelling, which are transported by the South Equatorial Current (SEC) flowing from the African coast to the Brazilian shore. An increase of CT of 0.9 ± 0.3 μmol kg−1yr−1 has been observed in the SEC region and is consistent with previous published estimates. A revised CT-Sea Surface Salinity (SSS) relationship is proposed for the WTA to take into account the variability of CT at low salinities. This new CT-SSS relationship together with a published TA-SSS relationship allow to calculate pCO2 values that compare well with observed pCO2 (R2 = 0.90).