This study presents data from field experiments that focus on the influence of coral reef geometry on wave transformation in the Metropolitan Area of Recife (MAR) on the northeast coast of Brazil. First, a detailed bathymetric survey was conducted, revealing a submerged reef bank, measuring 18 km long by 1 km wide, parallel to the coastline with a quasi-horizontal top that varies from 0.5 m to 4 m in depth at low tide. Cluster similarity between 180 reef profiles indicates that in 75% of the area, the reef geometry has a configuration similar to a platform reef, whereas in 25% of the area it resembles a fringing reef. Measurements of wave pressure fluctuations were made at two stations (experiments E1 and E2) across the reef profile. The results indicate that wave height was tidally modulated at both experimental sites. Up to 67% (E1) and 99.9% (E2) of the incident wave height is attenuated by the reef top at low tide. This tidal modulation is most apparent at E2 due to reef geometry. At this location, the reef top is only approximately 0.5 m deep during mean low spring water, and almost all incident waves break on the outer reef edge. At E1, the reef top depth is 4 m, and waves with height ratios smaller than the critical breaking limit are free to pass onto the reef and are primarily attenuated by bottom friction. These results highlight the importance of reef geometry in controlling wave characteristics of the MAR beaches and demonstrate its effect on the morphology of the adjacent coast. Implications of differences in wave attenuation and the level of protection provided by the reefs to the adjacent shoreline are discussed.

Estuaries comprise broad spectra of systems whose morphology often rule theirs hydrodynamics. The Itamaracá estuarine system (NE-Brazil) is formed by the Santa Cruz Channel (SCC), connecting to the Atlantic Ocean through two inlets. Water level and in depth current measurements were used to evaluate an analytical approach for representing its tidal circulation. Depth-averaged currents were analytically predicted with 11% error (δ1 = 0.11). Currents measurements for five different sampling stations and depths were compared to model responses for various values of eddy viscosity (ν) and bottom friction parameter (r). The best-fit quadratic error δ2 = 0.155 was obtained with ν = 6.3×10−3m2s−1 and r = 6.5×10−3ms−1. Model improvements, considering bottom friction and eddy diffusivity formulations, indicated a boundary layer depth of 0.10H (H=channel depth), and a large (6.1×10−3m) mean roughness length of the sea-bed to couple with the intricate roots system of red mangroves along the SCC. Simulations were also used to test Taylor’s (1954) scale analysis, yielding c = 0.080 as best value (c = ν/u*H constant; u* =bottom friction velocity) and a mean eddy viscosity of 5.8×10−3 m2s−1). The low sensibility of momentum distribution to changes in eddy viscosity verified suggests that stronger viscosity dumping may be compensated by higher bottom shear stress. This simple analytical approach could also be used to predict spatial and temporal distribution of pollutants and other materials at SSC and at similar systems as advection of those components could easily be simulated combining modelled currents with measurements of theirs concentrations.

This paper presents a study about wave climate acting on the Northeast coast of Brazil (Recife, Pernambuco) from the use of X-band nautical radar, which runs through the emission of electromagnetic waves and receives the signal by backscattering the sea surface. The main objective of this work is to obtain information about the wave acting on this coast, by analyzing significant height, period and direction of the incident waves, which will be helpful to generate a solid database for future coastal measures, engineering works of contention for coastal and marine protection. Data were obtained from polar images of X-band nautical radar, from April 2010 to April 2011. By analysing the results, it was possible to observe the joint occurrence of waves wind sea and swell in the region of study. Wind sea waves occur predominantly at 90° – 135°, with higher values at the end of September (3.9 m). Swell waves were more frequent during June, October and December 2010, and February and March 2011. Moreover, we observed a change in direction of the waves and decrease in wave heights along the inner shelf of the coast, caused by variation in bathymetry and the presence of sandstone reefs. The results of this study demonstrated great efficiency in acquiring the physical parameters of waves through the X-band nautical radar system, proving to be an efficient tool for measuring physical parameters of waves in coastal regions.

The Rocas Atoll Biological Reserve is located in the Atlantic Ocean, at 3º 51′ S and 33º 49′ W. It lies 143 nautical miles from the City of Natal, Rio Grande do Norte (Brazil). The purpose of this study was to analyze the hydrology, water masses, currents and chlorophyll a content to determine the dynamics of phytoplankton biomass around the Rocas Atoll. Samples were collected in July 2010 in the area around the Atoll, using the Research Vessel Cruzeiro do Sul of the Brazilian Navy. Two transects were established according to the surface currents, one of which at the southeast of the Atoll (SE) and the other at norwest (NW). Three collection points were determined on each of these transects. Samples were collected at different depths (surface and DCM – Deep Chlorophyll Maximum) and different times (day and night). According to PCA (Principal Component Analysis), the nutrients analyzed, DIN (dissolved inorganic nitrogen), DIP (dissolved inorganic phosphorus) and silicate, were inversely correlated with temperature and dissolved oxygen. Most environmental variables showed a significant increase due to the turbulence on the Northwest transect. There was an increase in the concentration of chlorophyll a and nutrients when the temperature and oxygen in the mixed layer was reduced due to the influence of the SACW (South Atlantic Central Water). Despite the increase observed in some variables such as nutrient salts and chlorophyll a, the temperature in the mixed layer attained a mean value of 23.23 ºC due to the predominance of Tropical Water. The increase of the phytoplankton biomass on the NW transect was, therefore, caused by the “island effect” and not by upwelling.

The thermodynamics of the seasonal evolution of the Southwestern Tropical Atlantic Warm Pool (hereafter SWTAWP), which is delimited by the 28 °C isotherm, is investigated using the Regional Ocean Modeling System (ROMS). Results indicate that the net heat flux is responsible for the appearance and extinction of the SWTAWP. From March to May, the SWTAWP attains its maximum development and sometimes merges with equatorial warm waters towards the African continent, whose development follows the same period. Along the equator, the combination of oceanic terms (i.e., advection and diffusion) is important to promote the separation – when it occurs – of equatorial warm waters from southwestern tropical waters, which develops off the Brazilian coast. An analysis of the relative contribution of the temperature tendency terms of the mixed layer (ML) heat budget over the appearance, development and extinction of the SWTAWP is also done. The most important term for warming and cooling inside of the ML is the net heat flux at the sea surface. The ML is heated by the atmosphere between October and April, whereas the upper ocean cools down between May and September. The highest heat content values occur during the lower-temperature period (August to October), which is linked to the deepening of the ML during this time period. The horizontal advection along the equator is important, particularly at the eastern domain, which is influenced by the cold tongue. In this area, the vertical diffusive term is also significant; however, it presents values near zero outside the equator. These results contribute to a better understanding of the behavior of the heat budget within the tropical Atlantic, as previous studies over this region focused along the equator only.

The thermodynamics of the seasonal evolution of the Southwestern Tropical Atlantic Warm Pool (hereafter SWTAWP), which is delimited by the 28 °C isotherm, is investigated using the Regional Ocean Modeling System (ROMS). Results indicate that the net heat flux is responsible for the appearance and extinction of the SWTAWP. From March to May, the SWTAWP attains its maximum development and sometimes merges with equatorial warm waters towards the African continent, whose development follows the same period. Along the equator, the combination of oceanic terms (i.e., advection and diffusion) is important to promote the separation – when it occurs – of equatorial warm waters from southwestern tropical waters, which develops off the Brazilian coast. An analysis of the relative contribution of the temperature tendency terms of the mixed layer (ML) heat budget over the appearance, development and extinction of the SWTAWP is also done. The most important term for warming and cooling inside of the ML is the net heat flux at the sea surface. The ML is heated by the atmosphere between October and April, whereas the upper ocean cools down between May and September. The highest heat content values occur during the lower-temperature period (August to October), which is linked to the deepening of the ML during this time period. The horizontal advection along the equator is important, particularly at the eastern domain, which is influenced by the cold tongue. In this area, the vertical diffusive term is also significant; however, it presents values near zero outside the equator. These results contribute to a better understanding of the behavior of the heat budget within the tropical Atlantic, as previous studies over this region focused along the equator only.

Nine surface water surveys were performed in the Formoso estuary (Brazil) during 2012-2013 mainly in summer and winter periods and during spring tide. Temporal variations of temperature, salinity, phosphate, silicate, total alkalinity, dissolved inorganic carbon, partial pressure of CO2 (pCO2) and water-air CO2 fluxes were analyzed. Low rates of water-air CO2 fluxes (4.7 ± 8.0 mmol C m-2 d-1) were estimated despite the different climate conditions. pCO2 values ranged from 190 to 988 matm. These values are lower than those observed in other tropical estuaries. CO2 fluxes presented in this study contribute to the characterization of humid tropical estuarine systems, thus filling an important geographical information gap.

Many nations need information on the Atlantic Ocean. Several of them already share the burden of supporting scientific observations as well as maritime operations. While space-based observations are better coordinated, the in- situ observing networks are still somewhat fragmented. More effective international coordination on requirements, observing system design, implementation, data management arrangements, and information products delivery, hold significant potential to increase efficiency. Some existing in- situ observing networks are built on internationally coordinated strategic scientific requirements, design and implementation plans, while others are voluntary communities of practice that promote common standards and best practice. The newly launched Horizon 2020 AtlantOS project (http:// www.atlantos-h2020.eu) brings together scientists, stakeholders and industry from around the Atlantic to provide a multinational framework for more and better-coordinated efforts in observing, understanding and predicting the Atlantic Ocean. The overarching objective of AtlantOS is to achieve a transition from a loosely coordinated set of existing ocean observing activities producing fragmented, often mono- disciplinary data, towards a sustainable, efficient, and fit- for-purpose integrated Atlantic Ocean Observing System. To this end, the project builds on complementary observing systems that have emerged to meet the needs of particular research disciplines (physical, chemical, biological) and stakeholders; specifically, the existing elements of the Global Ocean Observing System (GOOS) and in support of the GEO Blue Planet Initiative. AtlantOS takes strategic guidance from the “Framework of Ocean Observing” (FOO; see Lindstrom and Visbeck, in this special issue of CLIVAR Exchanges). The vision of AtlantOS is to create a more systematic, cost effective, user-driven and international coordinated Atlantic observing system. This requires a better identification of key requirements as well as the identification and filling of targeted gaps in the in-situ observing system networks. Data accessibility and data usability, including standard formatting, storage and exploration services, are key aspects of AtlantOS. Thus, the scope of the existing Atlantic observing networks will be extended to more fully include underrepresented disciplines such as ocean biogeochemistry and biology. The integration of in-situ and remotely sensed Earth observations will produce information products supporting a wide range of sectors.

CO2 fugacities obtained from a merchant ship sailing from France to French Guyana were used to explore the seasonal and interannual variability of the sea-air CO2 exchange in the western tropical North Atlantic (TNA; 5–14°N, 41–52°W). Two distinct oceanic water masses were identified in the area associated to the main surface currents, i.e., the North Brazil Current (NBC) and the North Equatorial Current (NEC). The NBC was characterized by permanent CO2 oversaturation throughout the studied period, contrasting with the seasonal pattern identified in the NEC. The NBC retroflection was the main contributor to the North Equatorial Counter Current (NECC), thus spreading into the central TNA, the Amazon River plume, and the CO2-rich waters probably originated from the equatorial upwelling. Strong CO2 undersaturation was associated to the Amazon River plume. Total inorganic carbon drawdown due to biological activity was estimated to be 154 µmol kg−1 within the river plume. As a consequence, the studied area acted as a net sink of atmospheric CO2 (from −72.2 ± 10.2 mmol m−2 month−1 in February to 14.3 ± 4.5 mmol m−2 month−1 in May). This contrasted with the net CO2 efflux estimated by the main global sea-air CO2 flux climatologies. Interannual sea surface temperature changes in the TNA caused by large-scale climatic events could determine the direction and intensity of the sea-air CO2 fluxes in the NEC. Positive temperature anomalies observed in the TNA led to an almost permanent CO2 outgassing in the NEC in 2010.

The western boundary current system off Brazil is a key region for diagnosing variations of the Atlantic meridional overturning circulation (AMOC) and the southern subtropical cell. In July 2013 a mooring array was installed off the coast at 11°S similar to an array installed between 2000 and 2004 at the same location. Here we present results from two research cruises and the first 10.5 months of moored observations in comparison to the observations a decade ago. Average transports of the North Brazil Undercurrent and the Deep Western Boundary Current (DWBC) have not changed between the observational periods. DWBC eddies that are predicted to disappear with a weakening AMOC are still present. Upper layer changes in salinity and oxygen within the last decade are consistent with an increased Agulhas leakage, while at depths water mass changes are likely related to changes in the North Atlantic as well as tropical circulation changes.

The western boundary current system off Brazil is a key region for diagnosing variations of the Atlantic meridional overturning circulation (AMOC) and the southern subtropical cell. In July 2013 a mooring array was installed off the coast at 11°S similar to an array installed between 2000 and 2004 at the same location. Here we present results from two research cruises and the first 10.5 months of moored observations in comparison to the observations a decade ago. Average transports of the North Brazil Undercurrent and the Deep Western Boundary Current (DWBC) have not changed between the observational periods. DWBC eddies that are predicted to disappear with a weakening AMOC are still present. Upper layer changes in salinity and oxygen within the last decade are consistent with an increased Agulhas leakage, while at depths water mass changes are likely related to changes in the North Atlantic as well as tropical circulation changes.

The Sub-middle São Francisco Valley (SMSF), Northeast Brazil, is known for its great potential for viticulture, as it is one of the few regions in the world with two to three harvests per year. Results presented here establish the influence of remote Sea Surface Temperature (SST) on the rainfall variability and wine chemical compounds in the SMSF. Cross-correlation analyses show that the rainfall in the SMSF is negatively correlated with the SST at the North Tropical Atlantic, and positively correlated with the SST at Southwestern Atlantic. Cross-wavelet analyses identify that, in addition to the annual signal, intermittent signals in rainfall at the SMSF respond to remote influences of the SST with 3-4 months of periodicity at interannual timescales (~36-month band). Coherence analyses identify that the SST in Southwestern Atlantic affects the rainfall in the SMSF at the 3-4-month periodicity band. Principal Component Analysis indicated different influences between wet and dry meteorological seasons on the chemical wine samples produced at SMSF. Extreme rainfalls observed during 2009, are linked to northward displacement of the South Atlantic Convergence Zone, when strong rainfall and high relative humidity at SMSF contributed to reduce Free Sulfur Dioxide (FSO2) in grapes. During dry seasons the northward displacement of Intertropical Convergence Zone (ITCZ) is correlated to lower rainfall and relative humidity (RH) in SMSF region, resulting in higher Sulfur Dioxide (TSO2, FSO2), alcohol and higher acidity (VOL. AC) wines.