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Tropical free‐tropospheric humidity plays a crucial role for the Earth's radiative balance and climate sensitivity. In addition to atmospheric humidity, stable water isotopes can provide important information about the hydrological cycle. We use the isotope‐ and water tagging‐enabled version of the COSMOiso model to determine isotopic fingerprints of diagnosed moisture pathways over the western tropical Atlantic (WTA). A convection‐permitting, high‐resolution (5 km) nudged simulation is performed for January–February 2020. During this period, the target region is characterized by alternating large‐scale circulation regimes with different humidity and isotope signatures. Moist conditions in the middle troposphere (300–650 hPa) are associated with moisture transport from the south, east, southeast, as well as evaporation from the North Atlantic, while dry conditions correspond to extratropical transport from the north and west. To predict the contribution of different moisture sources, we used a statistical model based on the local specific humidity and temperature as predictors and obtained an R‐squared (R2) of 0.52. Adding water isotopes improved the prediction (R2 = 0.73), showing that isotopes provide unique information on moisture sources and transport patterns beyond conventional local observations. [ABSTRACT FROM AUTHOR]

N2 fixation is a central process of the marine nitrogen cycle, yet little is known about how this process varies from year‐to‐year. Here, we investigate this variability in the Western Tropical Atlantic (WTA), a region where N2 fixation is prevalent, fueled, in part, by the nutrient input from the Amazon River. We use hindcast simulations from 1983 through 2019 with the Regional Oceanic Modeling System (ROMS) coupled to the Biogeochemical Elemental Cycling (BEC) model expanded to include Diatom‐Diazotroph Assemblages (DDAs). Throughout the WTA, we find a substantial level of interannual variability of N2 fixation, altering it by up to 33%, and locally by up to nearly 60%. Part of this interannual variability is driven by variations in the Amazon River discharge, which during high discharge events leads to reduced rates in the upper parts of the plume and strongly enhanced rates in the downstream part. This dipole pattern is a consequence of the riverine inputs of phosphorus and the competition with non‐diazotrophs for this limiting resource. Another part of the N2 fixation variability is driven by the Atlantic Meridional Mode (AMM), and the El Niño‐Southern Oscillation (ENSO). These processes alter N2 fixation primarily through the supply of the limiting nutrients phosphorus and iron by vertical mixing, while the role of top‐down control through grazing is relatively limited in our model. The high, and so far not well recognized interannual N2 fixation variability can lead to erroneous extrapolation of field measurements and inaccuracies in the marine nitrogen budget, if unaccounted for. Plain Language Summary: Nitrogen fixation is a vital biological process in which dinitrogen is transformed into bioavailable nitrogen, which supports phytoplankton growth and ultimately maintains oceanic food webs. The amount of nitrogen fixed in this way can vary substantially due to a complex interplay of changes in environmental conditions, but this variability remains poorly constrained. Here, we focus on the year‐to‐year variability of nitrogen fixation that occurs in the Western Tropical Atlantic, where nitrogen fixation rates are particularly high due to the input of nutrients from the Amazon River. We use a regional ocean model that includes two types of nitrogen‐fixing organisms and analyze the variability from 1983 through 2019. We find that nitrogen fixation in the Western Tropical Atlantic deviates up to a third from the mean. These deviations are related to Amazon River discharge fluctuations and climate variability, in particular the El Niño—Southern Oscillation and the Atlantic Meridional Mode. Discharge and climate variability impact the availability of nutrients, which controls the growth and activity of nitrogen‐fixing organisms. In contrast, zooplankton predation does not drive variations in nitrogen fixation. These findings have implications for the marine nitrogen cycle and underscore the importance of better constraining interannual variability in nitrogen fixation. Key Points: Marine N2 fixation in the Western Tropical Atlantic varies substantially from year‐to‐year, up to a third of the mean rateIn the Amazon River plume, variability is primarily caused by variations in Amazon River discharge, altering the supply of phosphorusIn most of the Western Tropical Atlantic, the Atlantic Meridional Mode and ENSO drive variability by altering the upward nutrient mixing [ABSTRACT FROM AUTHOR]

The western tropical North Atlantic (WTNA) is a very complex region, with the influence of intense western boundary currents in connection with equatorial zonal currents, important atmospheric forcings (e.g Intertropical Convergence Zone), mesoscale activities (e.g NBC rings), and the world’s largest river discharge as the Amazon River runoff. The volume discharge is equivalent to more than one-third of the Atlantic river freshwater input, with a plume that spreads over the region reaching the northwestward Caribbean Sea and eastward longitudes of 30°W, and influencing from physical to biological structures. Therefore, in order to enable and encourage more understanding of the region, here we present a dataset based on an idealized scenario of no river runoff of the Amazon River and Par ́a River in the WTNA. The numerical simulations were conducted with a regional oceanic modeling system (ROMS) model and three pairs of files were generated with the model outputs: (i) ROMS-files, with the parameters of the ROMS-outputs raw data in a NetCDF format and monthly and weekly frequencies; (ii) MATLAB-files, which contain oceanographic parameters also in monthly and weekly frequencies; and (iii) NetCDF-files, with oceanographic parameters again in monthly and weekly frequencies. For each file, we present the coordinates and variable names, descriptions, and correspondent units. The dataset is available in the Science Data Bank repository (doi: https://doi.org/10.57760/sciencedb.02145)

The killer whale (Orcinus orca) is a cosmopolitan cetacean distributed worldwide. Extensive studies have described its ecology and behavior across multiple polar and temperate regions. On the other hand, there is limited information on the distribution, ecological roles, and abundance of killer whales in tropical and subtropical regions. Herein, we build on previous work to update information on the spa-tiotemporal distribution, exploitation, and natural history of killer whales in the Caribbean Sea. We also document new records on their interaction with other species and human activities. We collated 385 records from the literature, online biodiversity information systems, the Internet (social networks and video-hosting websites), and citizen science-based initiatives. Records included sightings (87.3%), intentional captures (10.6%), bycatch (0.3%), and strandings (1.8%). Data primarily originated from research projects/activities (57%) and citizen science-based initiatives (43%). Records were distributed in the eastern Caribbean (39.5%), the southern Caribbean (19.7%), the Greater Antilles (19.2%), the Bahamian Region (13.0%), Central America (6.8%), and eastern Florida (1.8%). Killer whales were recorded year-round, but most data were reported between March and August (59.6%). The scarcity of records in Central America could reflect true lower densities in the region, lower observation effort, or a combination of the two. Because of the paucity of data, this study supports the growing importance of citizen-science initiatives to document the occurrence and ecology of this species in the Caribbean. Our dataset also confirms the occasional and widespread occurrence of killer whales throughout the Caribbean Sea. Potential low densities and limited predictability of their occurrence hinder dedicated research on this species. [ABSTRACT FROM AUTHOR]

Marine fisheries and seafood provide important economic and social benefits for communities in the Western Tropical Atlantic Region, including food security, livelihoods, and tourist activities. However, these resources have experienced a global decline due to overfishing, pollution, and warming oceans. To help halt and reverse this decline, interventions should prioritize the threats that are identified as most severe. The UN Decade of Ocean Science for Sustainable Development (2021-2030) presents itself as an opportunity to enhance ocean sustainability with “A sustainably harvested and productive ocean ensuring the provision of food supply and ocean resources” as one of its seven major societal outcomes. This paper addresses the proposed research priorities identified during the workshop for the UN Decade Working Group V which agree with the findings from two previous workshops conducted during 2017 and 2019 by the Gulf and Caribbean Fisheries Institute (GCFI) and the Environmental Defense Fund (EDF). Over 300 scientists, policymakers, managers, government officials, representatives from tourism, maritime sector and communicators discussed regional priorities, and recognized the urgent need to expand stakeholder and partnership engagement. The respondents generally agreed on the major gaps within science and governance; however, managers and stakeholders view science as a critical source of information for the decision-making process. Respondents recommended that science should be inclusive of various knowledge types across sectors, including community and traditional knowledge. Furthermore, science quality assurance requires review processes that are impartial, reliable, and transparent. Ultimately, science-based management and policies require effective scientific input which must be achievable. There are good opportunities over the next decade to improve the sustainability and governance of the region’s fisheries resources. However, ensuring that fishers, resource users, civil society, and scientists work together with national and regional government resource management agencies will be the key for the development of successful governance structures overseeing these resources.

The frequency and intensity of ocean related hazards and its overlapping and cascading effects are escalating with devastating and unsustainable impact on life and livelihoods in the Western Tropical Atlantic. From the Bahamas to Brazil, from Mexico and Central America to the Lesser Antilles, coastal and maritime communities have been impacted by hurricanes, storm surges, earthquakes, sargassum and oil spills along with other climate, weather and human induced events. In addition to the coastal impacts, ocean hazards also have affected the safe and timely delivery of goods and services in a region that is extremely dependent on maritime transport. COVID-19 has compounded even more the situation of millions of people in the region and put extreme pressure on government officials, including disaster management and health professionals as well as the maritime industry. Climate change will only exacerbate the situation. The UN Decade of Ocean Science for Sustainable Development (2021-2030) presents itself as a once-in-a-lifetime opportunity to stop the cycle of disasters with “A Safe Ocean” as one of its seven major societal outcomes. The Western Tropical Atlantic Safe Ocean Working Group was established to co-design and co-deliver with local, national and regional partners transformative strategies that will facilitate and inspire actions to reduce and mitigate the ocean related threats while creating resilient and safer coastal communities and maritime activities. At the core is an Integrated Multi Hazard Ocean Data and Forecast System. Its services would be linked to education, outreach, readiness and communication that empowers and recognizes national and local policy decisions and includes individual response for the

Using current, hydrographic and satellite observations collected off Northeast Brazil around the Fernando de Noronha Archipelago and Rocas Atoll during two oceanographic cruises (spring 2015 and fall 2017), we investigated the general oceanic circulation and its modifications induced by the islands. In spring 2015, the area was characterized by lower SST (26.6°C) and deep mixed-layer (∼90 m). At this depth, a strong current shear was observed between the central branch of the eastward flowing near-surface South Equatorial Current and the westward flowing South Equatorial Undercurrent. In contrast, in fall 2017, SST was higher (∼28.8°C) and the mixed-layer shallower (∼50 m). The shear between the central South Equatorial Current and the South Equatorial Undercurrent was weaker during this period. Interestingly, no oxygen-rich water from the south (retroflection of the North Brazil undercurrent) was observed in the region in fall 2017. In contrast, we revealed the presence of an oxygen-rich water entrained by the South Equatorial Undercurrent reaching Rocas Atoll in spring 2015. Beside these global patterns, island wake effects were noted. The presence of islands, in particular Fernando de Noronha, strongly perturbs central South Equatorial Current and South Equatorial Undercurrent features, with an upstream core splitting and a reorganization of single current core structures downstream of the islands. Near islands, flow disturbances impact the thermohaline structure and biogeochemistry, with a negative anomaly in temperature (−1.3°C) and salinity (−0.15) between 200 and 400 m depth in the southeast side of Fernando Noronha (station 5), where the fluorescence peak (>1.0 mg m–3) was shallower than at other stations located around Fernando de Noronha, reinforcing the influence of flow-topography. Satellite maps of sea-surface temperature and chlorophyll-a confirmed the presence of several submesoscale features in the study region. Altimetry data suggested the presence of a cyclonic mesoscale eddy around Rocas Atoll in spring 2015. A cyclonic vortex (radius of 28 km) was actually observed in subsurface (150–350 m depth) southeast of Rocas Atoll. This vortex was associated with topographically induced South Equatorial Undercurrent flow separation. These features are likely key processes providing an enrichment from the subsurface to the euphotic layer near islands, supplying local productivity.

In the tropics, the marine sponge Dysidea janiae lives in obligatory symbiosis with the red macroalga Jania adhaerens. However, how this symbiosis is achieved, and how it influences the reproduction of the sponge is still unknown. We analysed the influence of environmental variables on the gametogenesis and embryogenesis of the sponge. We also investigated the histology of the reproductive propagules of the sponge over 3 years, aiming to understand how this symbiosis is established. Dysidea janiae is viviparous and gonochoristic, with a continuous but small reproductive effort. The reproductive dynamics of gametes and embryos were explained by different sets of environmental variables. Although the temperature was not directly related to the reproduction of the sponge in general, there was an increase in the density of spermatic cysts during the year when the El Niño occurred. The day length was related to the embryo dynamics, which were interpreted as an indirect effect of the increase in photosynthetic rates of the symbiont on the energetic budget of the sponge. As no algal propagules were found associated with the eggs or larvae of the sponge, the acquisition of the algae by the sponge is probably a ‘trial-and-error’ relationship after larval release. We propose that the symbiosis increases the fitness of the adult sponge, forcing the larvae to seek new macroalgae to settle on and start a new symbiosis all over again. [ABSTRACT FROM AUTHOR]

New data on the taxonomic composition and distribution of rare deep-sea species of the Bathylagidae, Microstomatidae, and Opisthoproctidae (Argentiniformes) collected off northeastern Brazil, including the Rocas Atoll, the Fernando de Noronha Archipelago, and seamounts off Rio Grande do Norte State are provided. Collections were made by the French RV Antea during the ABRACOS 2 (Acoustics along the BRAzilian COaSt) expedition, between April 9 and May 6, 2017. Among the six species of argentiniforms identified, three are reported for the first time in Brazilian waters: Xenophthalmichthys danae (Microstomatidae), Opisthoproctus soleatus and Rhynchohyalus natalensis (Opisthoproctidae). Three additional species previously recorded off Brazil have their geographic distributions extended to the northeastern region of the country: Dolicholagus longirostris, Melanolagus bericoides (Bathylagidae), and Winteria telescopa (Opisthoproctidae). Remarks on other species of the Argentiniformes reported in the Brazilian Exclusive Economic Zone are also provided. A total of 11 genera and 14 species of the order are confirmed to occur in the region. [ABSTRACT FROM AUTHOR]

Marine bioinvasions are potential threats to biodiversity and ecosystems services, being one of the major environmental, human health and socio-economic problems throughout the world. In 2005, a sponge species never reported before to the Atlantic Ocean was detected in Rio de Janeiro (Brazil). This species was initially considered new to science and in less than a decade its populations became very abundant and widespread in the Brazilian coast. In the present work, we performed detailed morphological and molecular analyses of this supposedly new species and found out that it is in fact the Indo-Pacific calcareous sponge Heteropia glomerosa (Bowerbank, 1873). Heteropia glomerosa is the third alien species of calcareous sponge reported in the Atlantic and the second one that allegedly came from the Indo-Pacific. To confirm the taxonomic identification of the Atlantic specimens, we used morphological and molecular tools and re-described the holotypes of H. glomerosa and Uteopsis argentea (Poléjaeff, 1883). We discuss the possibility that biofouling is the introduction source for sponges and present the known distribution of H. glomerosa. Moreover, we verified that H. glomerosa fits seven out of 10 criteria proposed for recognizing alien species. Although this species can be recognized as introduced in the Atlantic Ocean, studies on population genetics, phylogeography, reproduction strategies, larval behaviour, and ecology will be necessary to allow a better evaluation of its invasive potential. [ABSTRACT FROM AUTHOR]

The propagule pressure exerts an important role during the bioinvasion process. However, this biological characteristic of invasive species is still poorly understood for marine invertebrates. Here, we investigated aspects of the propagule pressure of the cryptogenic calcareous sponge Heteropia cf. glomerosa in the northeastern coast of Brazil. The investigated population was continuously reproductively active. Oocytes were present mainly during the rainy season, while embryos and larvae only during the dry season. The reproductive effort of this species was among the highest observed for sponges. The wet weight of the species did not influence on the reproductive output, but the number of tubes with apical osculum comprising the sponge was related to the number of oocytes. The reproduction of H. cf. glomerosa seemed to be driven by temperature, tides, and photoperiod. Our findings indicate that this species presents an opportunistic life history strategy enabling it to reproduce early in its life cycle with abundant propagules. As photoperiod is one of the drivers of its reproduction, it is expected that in higher latitudes (where this species has been found), the reproductive effort may exert an even higher pressure for the establishment and dispersion of the species. If H. cf. glomerosa is confirmed as a non-native in the study area, our results indicate that the best time to apply field efforts to avoid the expansion and establishment of the species is during the rainy period, when fewer larvae are found. [ABSTRACT FROM AUTHOR]

The long-term orbital-scale sea surface temperature (SST) variability in the tropics is thought to be mainly driven by greenhouse gases (GHG) forcing. However, few studies have investigated the drivers of such variability in the tropical Atlantic. Given the evidence of orbital-scale changes in Atlantic Meridional Overturning Circulation (AMOC) strength, one can hypothesize that AMOC variability also modulates the long-term tropical Atlantic SST through the bipolar seesaw mechanism. According to this mechanism, under weak [strong] AMOC conditions, the Southern Hemisphere is expected to warm up [cool down], while the Northern Hemisphere cools down [warms up]. Here, we investigate the long-term SST variability of the western tropical South Atlantic (WTSA), i.e., along the main pathway of the upper AMOC branch towards the equator, using a new 300 thousand years (kyr)-long Mg/Ca-based SST record. Our SST record shows glacial-interglacial variability superimposed by four remarkable long-term warm events during the three recorded glacial periods. These glacial warm events occurred between ca. 280–260, 160–143, 75–60, and 40–24 ka before present. Our results support the notion that atmospheric GHG plays a leading role in modulating the glacial-interglacial SST variability in the WTSA. However, it does not explain the occurrence of glacial warm events. Our study supports that the glacial warm events were caused by an orbital-scale bipolar seesaw mechanism operating in the Atlantic due to changes in the AMOC strength. These warm events may have been amplified by annual mean insolation driven by obliquity. Finally, we suggest that the long-term bipolar seesaw warmed the western tropical (South) Atlantic during the MIS 5/4 transition when the Earth's climate was cooling off. • The western tropical South Atlantic SST was reconstructed for the last 300 kyr. • Greenhouse gases control the glacial-interglacial SST variability. • Four long-term warm events were identified during glacial conditions. • The warm events were caused by an orbital-scale bipolar seesaw in the Atlantic. [ABSTRACT FROM AUTHOR]

Although the Orton’s rule was already questioned for several invertebrate lineages, it remains unchallenged in sponges. To assess its validity in Porifera, we investigated the reproductive cycle of five species of Demospongiae on a tropical rocky shore, aiming to determine the effect of some environmental variables (EVs) on the periodicity, density of reproductive elements, and population engagement in reproduction. All species reproduced continuously, with low percentage of reproductive individuals and low fecundity. Each species presented a set of models containing different EVs to explain their reproductive traits. In general, the relationship of the EVs on the percentage of reproductive individuals and density of gametes and embryos was delayed in 1-3 months. Temperature was amongst the factors that best explained the species reproduction, with a delay of 1 month being the factor most consistently found amongst the models. In addition, we carried out a meta-analysis and discovered that in temperate regions most species reproduced periodically, whilst in the tropics, a small percentage reproduced continuously. Our findings suggest that Orton’s Rule is partially sustained, as species reproduced continuously, but challenge the lack of the influence of the temperature and other EVs in the reproduction of tropical marine invertebrates. [ABSTRACT FROM AUTHOR]

To reduce uncertainty regarding the contribution of continental shelf areas in low latitude regions to the air-sea CO 2 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 CO 2 (fCO 2 ) 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 CO 2 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 fCO 2 are observed during the wet season when the winds are the weakest. As a result, the CO 2 flux does not show a clear seasonal pattern. Further offshore, fCO 2 is significantly lower than on the continental shelf. However, the oceanic CO 2 flux, with an annual mean of 2.32±1.09 mmol m −2 d −1 , is not statistically different from the CO 2 flux at the continental shelf because the wind is stronger in the open ocean. [ABSTRACT FROM AUTHOR]

The western tropical North Atlantic (WTNA) is a very complex region, with the influence of intense western boundary currents in connection with equatorial zonal currents, important atmospheric forcings (e.g Intertropical Convergence Zone), mesoscale activities (e.g NBC rings), and the world's largest river discharge as the Amazon River runoff. The volume discharge is equivalent to more than one-third of the Atlantic river freshwater input, with a plume that spreads over the region reaching the northwestward Caribbean Sea and eastward longitudes of 30°W, and influencing from physical to biological structures. Therefore, in order to enable and encourage more understanding of the region, here we present a dataset based on an idealized scenario of no river runoff of the Amazon River and Par ´a River in the WTNA. The numerical simulations were conducted with a regional oceanic modeling system (ROMS) model and three pairs of files were generated with the model outputs: (i) ROMS-files, with the parameters of the ROMS-outputs raw data in a NetCDF format and monthly and weekly frequencies; (ii) MATLAB-files, which contain oceanographic parameters also in monthly and weekly frequencies; and (iii) NetCDF-files, with oceanographic parameters again in monthly and weekly frequencies. For each file, we present the coordinates and variable names, descriptions, and correspondent units. The dataset is available in the Science Data Bank repository (doi: https://doi.org/10.57760/sciencedb.02145)., Competing Interests: No competing interests were disclosed., (Copyright: © 2023 Varona HL et al.)

The variability of sea surface Total Alkalinity (TA) and sea surface Total Inorganic Carbon (C T ) is examined using all available data in the western tropical Atlantic (WTA: 20°S-20°N, 60°W-20°W). Lowest TA and C T 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 C T are linked to the CO 2 –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 C T of 0.9 ± 0.3 μmol kg −1 yr −1 has been observed in the SEC region and is consistent with previous published estimates. A revised C T -Sea Surface Salinity (SSS) relationship is proposed for the WTA to take into account the variability of C T at low salinities. This new C T -SSS relationship together with a published TA-SSS relationship allow to calculate p CO 2 values that compare well with observed p CO 2 (R 2 = 0.90). [ABSTRACT FROM AUTHOR]

Abstract: A two-year long record from a triangular mooring array between the Lesser Antilles islands Tobago, Barbados, and St. Lucia is used to investigate the inflow into the Caribbean Sea, the amount of South Atlantic Water (SAW) carried with the inflow, and the role of North Brazil Current (NBC) rings in the observed variability. The data set consists of time series from temperature/conductivity recorders and current meters in the moorings, bottom-mounted inverted echo sounders at the Tobago and St. Lucia mooring positions, and supplementary shipboard measurements. The acoustic travel time measurements of the inverted echo sounders and the conductivity/temperature time series are used for continuous estimation of dynamic height profiles and geostrophic currents between the surface and 1000dbar as well as the amount of SAW found at the mooring positions. The observations show a domination of intraseasonal variability between 0 and 15Sv, superimposed on the long-term fluctuations. With time scales of one to three months, these represent the signature of the NBC rings. The baroclinic transport time series shows nine periods of increased variability, indicative of the rings interacting with the Lesser Antilles island arc; with the exception of one, these periods were associated with corresponding sea surface height anomalies. No marked seasonality was observed in the transport variability or the ring frequency. The arrival of individual rings leads to a weakening of the inflow into the Caribbean. Nevertheless, the rings carry large amounts of SAW into the area, and the immediate increase of the transport towards the end of a ring event suggests a subsequent flow of this SAW-rich water into the Caribbean. At St. Lucia, rings sometimes cause a short-term decrease of SAW content, indicative of an influx of northern hemispheric water and a blocking situation. The average transport of SAW into the Caribbean south of St. Lucia during the observations amounted to 5.5Sv, with no significant seasonal cycle, but a small positive trend in SAW fraction as well as in transport of about 15% and 1Sv, respectively; a corresponding trend in the baroclinic volume transport was not observed. [Copyright &y& Elsevier]

Abstract: A sediment core from the western tropical Atlantic covering the last 21,000 yr has been analysed for centennial scale reconstruction of sea surface temperature (SST) and ice volume-corrected oxygen isotopic composition of sea water (δ 18Oivc-sw) using Mg/Ca and δ 18O of the shallow dwelling planktonic foraminifer Globigerinoides ruber (white). At a period between 15.5 and 17.5 kyr BP, the Mg/Ca SST and δ 18Oivc-sw, a proxy for sea surface salinity (SSS), reveals a warming of around 2.5 °C along with an increase in salinity. A second period of pronounced warming and SSS increase occurred between 11.6 and 13.5 kyr BP. Within age model uncertainties, both warming intervals were synchronous with air temperature increase over Antarctica and ice retreat in the southern South Atlantic and terminated with abrupt centennial scale SSS decrease and slight SST cooling in conjunction with interglacial reactivation of the meridional overturning circulation (MOC). We suggest that during these warm intervals, production of saline and warm water of the North Brazil Current resulted in pronounced heat and salt accumulation, and was associated with warming in the southern Atlantic, southward displacement of the intertropical convergence zone and weakened MOC. At the termination of the Younger Dryas and Heinrich event 1, intensification of cross-equatorial heat and salt transport caused centennial scale cooling and freshening of the western tropical Atlantic surface water. This study shows that the western tropical Atlantic served as a heat and salt reservoir during deglaciation. The sudden release of accumulated heat and salt at the end of Younger Drays and Heinrich event 1 may have contributed to the rapid reinvigoration of the Atlantic MOC. [Copyright &y& Elsevier]

Abstract: CTD, vessel-mounted ADCP and LADCP measurements in the Caribbean passages south of Guadeloupe (three repeats) and along 16°N (five repeats) were carried out between December 2000 and July 2004. The CTD data were used to calculate the contribution of South Atlantic water (SAW) in the upper 1200m between the isopycnals and 27.6. Northern and southern source water masses are defined and an isopycnal mixing approach is applied. The SAW fractions are then combined with the ADCP flow field to calculate the transport of SAW into the Caribbean and across 16°N. The SAW inflow into the Caribbean through the passages south of Guadeloupe ranges from 7.6 to 11.6Sv, which is 50–75% of the total inflow. The mean (9.1±2.2Sv) is in the range of previous estimates. Ambiguities in the northern and southern source water masses of the salinity maximum water permitted us only to calculate the contribution of SAW from the eastern source in this water mass. We estimated the additional SAW transport by the western source to be of the order of 1.9±0.7Sv. The calculation of the SAW transport across 16°N was hampered by the presence of several anticyclonic rings from the North Brazil Current (NBC) retroflection region, some of the rings were subsurface intensified. Provided that the rings observed at 16°N are typical rings and that all rings which are annually produced in the NBC retroflection area (6.5–8.5 per year) reach 16°N, the SAW ring transport across 16°N is calculated to 5.3±0.7Sv. From the 5 repeats at 16°N, only two showed a net northward flow, suggesting that the mean northward SAW transport is dominated by ring advection. The joint SAW transports of the Caribbean inflow (9.1Sv) and the flow across 16°N (5.3Sv) sum up to 14.4Sv. The transport increases to 16.3Sv if the additional SAW transport from the western source of SMW (1.9±0.7Sv) is included. These transport estimates and the following implications depend strongly on the assumption that the surface water in the Caribbean inflow is of South Atlantic origin. The transport estimates are, however, in the range of the inverse model calculations for the net cross-hemispheric flow. About 30–40% of this transport is intermediate water from the South Atlantic, presumably supporting studies which found the contributions of intermediate and upper warm water to be of a comparable magnitude. For the upper warm water (), the Caribbean inflow seems to be the major path (7.9±1.6Sv), the ring induced transport across 16°N is about 30% of that value. The intermediate water transport across 16°N was calculated to be 2.3–3.6Sv, the inflow into the Caribbean is slightly smaller (1.5–2.4Sv). [Copyright &y& Elsevier]

Abstract: The upper ocean large-scale circulation of the western tropical Atlantic from 11.5°S to the Caribbean in November and December 2000 is investigated from a new type of shipboard ADCP able to measure accurate velocities to 600m depth, combined with lowered ADCP measurements. Satellite data and numerical model output complement the shipboard measurements to better describe the large-scale circulation. In November 2000 the North Brazil Undercurrent (NBUC) was strongly intensified between 11 and 5°S by inflow from the east, hence the NBUC was formed further to the north than in the mean. The NBUC was transporting 23.1Sv northward at 5°S, slightly less than the mean of six cruises (Geophysical Research Letters (2002) 29 (7) 1840). At 35°W the North Brazil Current (NBC) transported 29.4Sv westward, less than the mean of 13 cruises (Geophysical Research Letters (2003) 30 (7) 1349). A strong retroflection ring had just pinched off the NBC retroflection according to the satellite information. The inflow into the Caribbean south of 16.5°N originated in part of a leakage from the NBC retroflection zone and in part from the North Equatorial Current. A thermocline intensified ring with a transport of about 30Sv was located off Guadeloupe carrying South Atlantic Central Water towards the north. Observed deviations of the November/December 2000 flow field from the November long-term mean flow field were related to an enhanced Intertropical Convergence Zone (ITCZ) associated with an increased North Equatorial Countercurrent (NECC), as well as to boundary current rings and Rossby waves with zonal wavelength of the order of 1000km. At 44°W the presence of a Rossby wave associated with an anticyclonic circulation led to a strongly enhanced NBC of 65.0Sv as well as to a combined NECC and Equatorial Undercurrent transport of 52.4Sv, much stronger than during earlier cruises. While the 1/3°-FLAME model is unable to reproduce details of the vertical distribution of the observed horizontal flow at 44°W for November 2000 as well as the horizontal distribution of some of the observed permanent current bands, a climatological simulation with the 1/12°-FLAME agrees much better with the observations and provides information on the spreading path between the sections. E.g., the interpretation that the widening in the Antarctic Intermediate Water layer of the westward flowing NBC at 44°W in November was caused by water from the Equatorial Intermediate Current was further supported by the model results. [Copyright &y& Elsevier]

The western tropical Atlantic is strongly influenced by the Amazon, receiving the full discharge from the largest river basin of the world. In order to ascertain the coastal-oceanic gradient in abundance and composition of planktonic decapod communities along the Amazon River Plume (ARP) and its retroflection, 33 plankton samples were obtained along three sampling transects: Coastal and oceanic area influenced by the ARP (Coastal IARP and Ocean IARP , respectively), and oceanic waters without ARP influence (Ocean). A total of 13,117 specimens, belonging to 33 taxa, were analyzed. The distribution of planktonic decapod communities was strongly influenced by the Amazon discharge, showing the following patterns: (1) The coastal-oceanic gradients in decapod abundance are similar to other shelf areas of eastern South America, with higher abundance in the area under ARP influence, (2) meroplanktonic decapods dominate in coastal and some oceanic areas due to the offshore transport of coastal organisms along the ARP retroflection, and (3) the ARP is clearly responsible for the observed differences in community structure between the three transects. Furthermore, this study highlights the importance of coastal and shelf environments as main sources of planktonic decapods for pelagic ecosystems in the tropical Atlantic during the period of strong North Brazil Current retroflection. • A total of 13,117 specimens, belonging to 33 taxa, were analyzed. • Planktonic decapod distributions were strongly influenced by the Amazon discharge. • Higher abundance of decapods in the area under plume influence • Larval forms dominate in coastal and oceanic plume areas. • Coastal areas are sources of planktonic decapods for offshore pelagic ecosystems. [ABSTRACT FROM AUTHOR]

The western tropical Atlantic (WTA) supplies warm and saline waters to the upper-limb of the Atlantic Meridional Overturning Circulation (AMOC) and may store excess heat and salinity during periods of AMOC slowdown. Since previous sea surface temperature (SST) reconstructions from the WTA typically focus on the Last Glacial Maximum and the last deglaciation, additional long-term records spanning multiple glacial-interglacial transitions are needed in order to elucidate the drivers of long-term WTA SST variability. We performed Mg/Ca analyses on the surface-dwelling planktic foraminifera Globigerinoides ruber (pink) from a sediment core raised from the southern WTA to reconstruct SST changes over the past 322 kyr. We evaluate the relative importance of atmospheric p CO 2 , AMOC strength and trade-wind intensity in driving the thermal evolution of the WTA across three glacial-interglacial cycles. Our results indicate a lack of pronounced glacial-interglacial variability in the SST record, prompting us to exclude atmospheric p CO 2 as a direct driver of SST variations in the southern WTA. Similarly, we conclude that variations in AMOC strength also likely did not have a strong influence on long-term WTA SST, based on the low and relatively stable interhemispheric SST gradient over the past 322 kyr. Our results reveal high-amplitude variability in zonal SST gradients within the (sub)tropical South Atlantic and similarities between the long-term patterns of the intrahemispheric meridional SST gradient and our SST record. Based on these findings, we propose that changes in the intrahemispheric meridional SST gradient modulate southeast trade wind intensity, which in turn drives variations in zonal SST gradients and southern WTA SSTs. • Trade wind intensity drives western tropical Atlantic sea surface temperature. • Low and stable cross-equatorial temperature gradient over the past 322 kyr • Prolonged western tropical Atlantic surface warming during Marine Isotope Stage 6 [ABSTRACT FROM AUTHOR]