276 results found
Silva M, Araujo M, Geber F, et al., 2021, Ocean Dynamics and Topographic Upwelling Around the Aracati Seamount - North Brazilian Chain From in situ Observations and Modeling Results, Frontiers in Marine Science, Vol: 8
The hydrodynamics and the occurrence of topographic upwelling around the northern Brazilian seamount chain were investigated. Meteorological and physical oceanographic data collected under the REVIZEE-NE Program cruises around the Aracati Bank, the major and highly productive seamount in the area, were analyzed and used to force and validate simulations using the 3D Princeton Ocean Model (3D POM). The Tropical Water mass in the top 150-m layer and the South Atlantic Central Water (SACW) beneath it and down to a depth of 670 m was present. The thickness of the barrier layer varied seasonally, being thinner (2 m) during the austral spring (October–December) and thicker (20 m) during the austral autumn (April–June) when winds were stronger. The surface mixed and isothermal layers in the austral winter (July–September) were located at depths of 84 and 96 m, respectively. During the austral spring, those layers were located at depths of 6 and 8 m, respectively. The mean wind shear energy was 9.8 × 10–4 m2 s–2, and the energy of the surface gravity wave break was 10.8 × 10–2 m2 s–2, and both served to enhance vertical mixing in the area. A permanent thermocline between the 70- and 150-m depths was present throughout the year. The isohaline distribution followed an isotherm pattern of variation, but at times, the formation of low-salinity eddies was verified on the bank slope. The 3D POM model reproduced the thermohaline structure accurately. Temperature and salinity profiles indicated the existence of vertical water displacements over the bank and along the direction of the North Brazil Current, which is the strongest western boundary current crossing the equatorial Atlantic. The kinematic structure observed in the simulations indicated vertical velocities of O (10–3 m.s–1) in the upstream region of the bank during austral winter and summer seasons. During the summer, the most important vertical velocities
Noriega C, Medeiros C, Araujo M, et al., 2021, Long-term water quality conditions and trends in 12 tropical coastal rivers in Northeast Brazil., Environ Monit Assess, Vol: 193
The water quality and trends in 12 tropical rivers in northeastern Brazil over a 27-year period (1990-2016; N = 39,008 samples) were evaluated. The analyzed parameters included temperature, conductivity, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrogen (NH4+), total phosphorus (P), and fecal coliforms. Densely populated basins (> 1000 inhab km-2) presented lower DO values (average 3.4 mg l-1; 43% DO saturation), while those with low demographic density (< 100 inhab km-2) presented values that aligned well with the recommendations of environmental legislation (average 5.8 mg l-1; 75% DO saturation). The NH4+ and P compound concentrations were typical of water bodies affected by urban inputs. The average p values were above the allowable limit (< 0.1 mg l-1) at all stations. The NH4+ values were high at the stations showing low DO concentrations, which suggested that due to reducing conditions after NH4+ accumulation was favored in those aquatic systems. In densely populated basins, the average fecal coliform concentrations were > 40,000 MPN 100 ml-1, indicating the input of improperly treated domestic/industrial liquid wastes. For the period from 1990 to 2016, 45% of the stations (N = 19) showed a rate of DO reduction that ranged from 0.01 to 0.17 mg l-1.O2 year-1. An increase in NH4+ concentrations was observed in 33% of the stations (N = 14), with an estimated average increase rate from 0.013 to 1.8 mg l-1 NH4+ year-1. These results demonstrated that the rates of increase in anthropogenic factors were significant (p < 0.05), while the natural factors remained constant.
Costa da Silva A, Chaigneau A, Dossa AN, et al., 2021, Surface Circulation and Vertical Structure of Upper Ocean Variability Around Fernando de Noronha Archipelago and Rocas Atoll During Spring 2015 and Fall 2017, FRONTIERS IN MARINE SCIENCE, Vol: 8
Taheri S, Naimi B, Rahbek C, et al., 2021, Improvements in reports of species redistribution under climate change are required, SCIENCE ADVANCES, Vol: 7, ISSN: 2375-2548
Silva NBA, Flores-Montes M, Guennes M, et al., 2021, Phytoplankton cell size in an urban tropical estuarine system in Northeast Brazil, Regional Studies in Marine Science, Vol: 43
The variability of the phytoplankton community structure and cell size classes was quantitatively studied at an urban hypereutrophic tropical estuarine system to assess responses to inorganic nutrient levels. Samplings were carried out in three stations during the dry and wet seasons in 2015. Seasonal variability of temperature, salinity, phosphate, and ammonia levels was statistically significant, with higher values found in the dry season. Total chlorophyll a varied from 4.76 to 79.69 mg m−3 and the fractionated chlorophyll a (pico–nanophytoplankton) from 1.28 to 28.35 mg m−3. Cell density ranged from 172 x 10 3 to 8.1 × 10 6 cells L −1 with higher values during the dry season. The community structure was dominated by the nanophytoplankton (< 20μm fraction) with cyanobacteria being particularly abundant. Pico–nanophytoplankton contributed to 47% of the total biomass, representing 65% at point 1, 55% at point 3, and 38% at point 2. Thalassiosira sp 1, Melosira sp. and Chroococcus sp. were the dominant species in number of cells. The largest cell size variation occurred in the cyanobacteria and diatoms, which dominated the area and were favored by the increase of temperature, salinity, ammonia and phosphate during the dry season. The high values of nutrients demonstrated that the environment is hypereutrophic as a consequence of the release of domestic effluents from a highly urbanized area. Salinity and nutrients (nitrate and ammonia) were influential factors for the quantity and size of phytoplankton cells, leading to changes in community structure. The availability of ammonia in the study area favored the selection and dominance of species of the fraction < 20μm. However, the fraction > 20μm had a greater contribution to total chlorophyll a and biomass in the studied region.
Bennett JM, Sunday J, Calosi P, et al., 2021, The evolution of critical thermal limits of life on Earth, NATURE COMMUNICATIONS, Vol: 12
Herrford J, Brandt P, Kanzow T, et al., 2021, Seasonal variability of the atlantic meridional overturning circulation at 11°&thinsp;s inferred from bottom pressure measurements, Ocean Science, Vol: 17, Pages: 265-284, ISSN: 1812-0784
Bottom pressure observations on both sides of the Atlantic basin, combined with satellite measurements of sea level anomalies and wind stress data, are utilized to estimate variations of the Atlantic Meridional Overturning Circulation (AMOC) at 11? S. Over the period 2013 2018, the AMOC and its components are dominated by seasonal variability, with peak-to-peak amplitudes of 12 Sv for the upper-ocean geostrophic transport, 7 Sv for the Ekman and 14 Sv for the AMOC transport. The characteristics of the observed seasonal cycles of the AMOC and its components are compared to results from an ocean general circulation model, which is known to reproduce the variability of the Western Boundary Current on longer timescales. The observed seasonal variability of zonally integrated geostrophic velocity in the upper 300 m is controlled by pressure variations at the eastern boundary, while at 500 m depth contributions from the western and eastern boundaries are similar. The model tends to underestimate the seasonal pressure variability at 300 and 500 m depth, especially at the western boundary, which translates into the estimate of the upper-ocean geostrophic transport. In the model, seasonal AMOC variability at 11? S is governed, besides the Ekman transport, by the geostrophic transport variability in the eastern basin. The geostrophic contribution of the western basin to the seasonal cycle of the AMOC is instead comparably weak, as transport variability in the western basin interior related to local wind curl forcing is mainly compensated by the Western Boundary Current. Our analyses indicate that while some of the uncertainties of our estimates result from the technical aspects of the observational strategy or processes not being properly represented in the model, uncertainties in the wind forcing are particularly relevant for the resulting uncertainties of AMOC estimates at 11<S.
Taheri S, Garcia-Callejas D, Araujo MB, 2021, Discriminating climate, land-cover and random effects on species range dynamics, GLOBAL CHANGE BIOLOGY, Vol: 27, Pages: 1309-1317, ISSN: 1354-1013
Dossa AN, Silva AC, Chaigneau A, et al., 2021, Near-surface western boundary circulation off Northeast Brazil, PROGRESS IN OCEANOGRAPHY, Vol: 190, ISSN: 0079-6611
de Santana CS, Lira SMDA, Varona HL, et al., 2020, Amazon river plume influence on planktonic decapods in the tropical Atlantic, Journal of Marine Systems, Vol: 212, ISSN: 0924-7963
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.
Aroucha LC, Veleda D, Lopes FS, et al., 2020, Intra- and Inter-Annual Variability of North Brazil Current Rings Using Angular Momentum Eddy Detection and Tracking Algorithm: Observations From 1993 to 2016, Journal of Geophysical Research: Oceans, Vol: 125, ISSN: 2169-9275
In order to investigate intra- and inter-annual variability of North Brazil Current (NBC) rings, angular momentum eddy detection and tracking algorithm (AMEDA) was used for identification of their occurrence, trajectories, and parameters. Based on 24 years (1993–2016) of geopotential height and geostrophic current fields reanalysis data from ARMOR 3D (¼°), we identified an average rate of five NBC rings shed by year. The rings present an average lifetime of 15.3 (±5.4) weeks, average speed-based radius (Rmax) of 139.8 (±23.6) km, and mean sea surface height anomaly (SSHa) of 9.4 (±4.0) cm. The mean observed maximum azimuthal velocity (Vmax) was 0.27 (±0.08) m/s, while the averaged Rossby number (Ro) value was 0.08 (±0.04) and averaged kinetic energy (KE) was of 255.3 (±154.8) cm2/s2. NBC rings have larger dimensions, rotate faster, live less, and transfer more energy in boreal winter months. In contrast, those shed during boreal summer and early fall last longer, have smaller diameters and carry less energy. Besides, the analysis of ring merging pointed that the interaction between NBC rings generated a significantly increase in ring energy (52%), and velocity (22%). Finally, we observed the vertical anomalies temperature and salinity profiles, which indicated a thermocline deepening and sinking of coastal and tropical waters due to NBC rings downwelling. This study emphasizes the robustness and efficiency of AMEDA for studying rings in the ocean and further theorizes possible impacts of NBC ring on ocean physical and biogeochemical features in the Western Tropical North Atlantic.
Assuncao R, Silva AC, Roy A, et al., 2020, 3D characterisation of the thermohaline structure in the southwestern tropical Atlantic derived from functional data analysis of in situ profiles, PROGRESS IN OCEANOGRAPHY, Vol: 187, ISSN: 0079-6611
Araujo MB, Mestre F, Naimi B, 2020, Ecological and epidemiological models are both useful for SARS-CoV-2, NATURE ECOLOGY & EVOLUTION, Vol: 4, Pages: 1153-1154, ISSN: 2397-334X
Foltz GR, Hummels R, Dengler M, et al., 2020, Vertical Turbulent Cooling of the Mixed Layer in the Atlantic ITCZ and Trade Wind Regions, Journal of Geophysical Research: Oceans, Vol: 125, ISSN: 2169-9275
The causes of the seasonal cycle of vertical turbulent cooling at the base of the mixed layer are assessed using observations from moored buoys in the tropical Atlantic Intertropical Convergence Zone (ITCZ) (4°N, 23°W) and trade wind (15°N, 38°W) regions together with mixing parameterizations and a one-dimensional model. At 4°N the parameterized turbulent cooling rates during 2017–2018 and 2019 agree with indirect estimates from the climatological mooring heat budget residual: both show mean cooling of 25–30 W m (Formula presented.) during November–July, when winds are weakest and the mixed layer is thinnest, and 0–10 W m (Formula presented.) during August–October. Mixing during November–July is driven by variability on multiple time scales, including subdiurnal, near-inertial, and intraseasonal. Shear associated with tropical instability waves (TIWs) is found to generate mixing and monthly mean cooling of 15–30 W m (Formula presented.) during May–July in 2017 and 2019. At 15°N the seasonal cycle of turbulent cooling is out of phase compared to 4°N, with largest cooling of up to 60 W m (Formula presented.) during boreal fall. However, the relationships between wind speed, mixed layer depth, and turbulent mixing are similar: weaker mean winds and a thinner mixed layer in the fall are associated with stronger mixing and turbulent cooling of SST. These results emphasize the importance of seasonal modulations of mixed layer depth at both locations and shear from TIWs at 4°N.
Herrando-Perez S, Monasterio C, Beukema W, et al., 2020, Heat tolerance is more variable than cold tolerance across species of Iberian lizards after controlling for intraspecific variation, FUNCTIONAL ECOLOGY, Vol: 34, Pages: 631-645, ISSN: 0269-8463
Mendoza M, Araujo MB, 2019, Climate shapes mammal community trophic structures and humans simplify them, NATURE COMMUNICATIONS, Vol: 10, ISSN: 2041-1723
Ribeiro J, Reino L, Schindler S, et al., 2019, Trends in legal and illegal trade of wild birds: a global assessment based on expert knowledge, BIODIVERSITY AND CONSERVATION, Vol: 28, Pages: 3343-3369, ISSN: 0960-3115
Ortega JCG, Machado N, Felizola Diniz-Filho JA, et al., 2019, Meta-analyzing the likely cross-species responses to climate change, ECOLOGY AND EVOLUTION, Vol: 9, Pages: 11136-11144, ISSN: 2045-7758
Garcia-Callejas D, Molowny-Horas R, Araujo MB, et al., 2019, Spatial trophic cascades in communities connected by dispersal and foraging, ECOLOGY, Vol: 100, ISSN: 0012-9658
Norberg A, Abrego N, Blanchet FG, et al., 2019, A comprehensive evaluation of predictive performance of 33 species distribution models at species and community levels, ECOLOGICAL MONOGRAPHS, Vol: 89, ISSN: 0012-9615
Araujo M, Ometto J, Rodrigues-Filho S, et al., 2019, The socio-ecological Nexus+ approach used by the Brazilian Research Network on Global Climate Change, Current Opinion in Environmental Sustainability, Vol: 39, Pages: 62-70, ISSN: 1877-3435
The Brazilian Research Network on Global Climate Change (Rede CLIMA) is an interdisciplinary network composed of 16 research groups, which interact in different levels and programs. This work aims at building climate change cause–effect research from a ‘Nexus+’ perspective, considering the added value of flexibility and adaptability of the concept. The article draws on the Nexus literature alongside a case study in São Francisco River Basin, Northeast Brazil. An additional pillar to the Nexus approach is proposed here, the socio-ecological security, which can be defined as a political-territorial dimension of coupled social and ecological systems. A collaborative research-practice frame was applied to the study region, a hotspot of climate vulnerability in Brazil. Our results highlight the need for this fourth component to address socio-ecological sustainability into context.
Araujo MB, Svenning J-C, Tuomisto H, 2019, Ecography's flip to a pay-to-publish model, ECOGRAPHY, Vol: 42, Pages: 1456-1457, ISSN: 0906-7590
Hounsou-Gbo GA, Servain J, Araujo M, et al., 2019, SST Indexes in the Tropical South Atlantic for Forecasting Rainy Seasons in Northeast Brazil, ATMOSPHERE, Vol: 10, ISSN: 2073-4433
Orselli IBM, Goyet C, Kerr R, et al., 2019, The effect of Agulhas eddies on absorption and transport of anthropogenic carbon in the South Atlantic Ocean, Climate, Vol: 7
The South Atlantic Ocean is currently undergoing significant alterations due to climate change. This region is important to the global carbon cycle, but marine carbon data are scarce in this basin. Additionally, this region is influenced by Agulhas eddies. However, their effects on ocean biogeochemistry are not yet fully understood. Thus, we aimed to model the carbonate parameters in this region and investigate the anthropogenic carbon (Cant) content in 13 eddies shed by the Agulhas retroflection. We used in situ data from the CLIVAR/WOCE/A10 section to elaborate total dissolved inorganic carbon (CT) and total alkalinity (AT) models and reconstruct those parameters using in situ data from two other Brazilian initiatives. Furthermore, we applied the Tracer combining Oxygen, inorganic Carbon, and total Alkalinity (TrOCA) method to calculate the Cant, focusing on the 13 identified Agulhas eddies. The CT and AT models presented root mean square errors less than 1.66 and 2.19 μmol kg-1, indicating Global Ocean Acidification Observing Network climate precision. The Cant content in the Agulhas eddies was 23% higher than that at the same depths of the surrounding waters. We observed that Agulhas eddies can play a role in the faster acidification of the South Atlantic CentralWater.
Noriega C, Araujo M, Flores-Montes M, et al., 2019, Trophic dynamics (Dissolved Inorganic Nitrogen-DIN and Dissolved Inorganic Phosphorus-DIP) in tropical urban estuarine systems during periods of high and low river discharge rates., An Acad Bras Cienc, Vol: 91
This paper focused on the use of the biogeochemical LOICZ (Land Ocean Interactions in the Coastal Zone) to investigate the dynamics of DIN and DIP nutrients among three highly urbanized tropical estuaries (Barra das Jangadas (BJ), Recife (RE) and Timbó (TB)), located in the northeastern region of Brazil. The input data were obtained through in situ measurements (2007) and governmental agency databases (2001-2007). The balances of the non-conservative elements showed that the RE and TB systems alternated between sources and sinks during the observation periods (0.2-0.8 mmoles DIP m-2 d-1 and 0.1-10 mmoles DIN m-2 d-1). The metabolism rates in the systems indicated that the BJ system was autotrophic during the two observation periods (10-26 mmoles C m-2 d-1), while the RE system was heterotrophic (9-12 mmoles C m-2 d-1). The river discharge rates observed during the period 2001-2007 showed averages ranging from 9.4±3.8 to 18.4±7.7 m3s-1. Measurements of the trophic status in the RE system during 2007 characterized the system as eutrophic, thereby demonstrating high levels of chlorophyll-a and inorganic nutrients. The applications of balance sheets modeling proved to be very useful toward understanding the dynamics of estuarine systems dominated by large urban centers.
Kanagaraj R, Araujo MB, Barman R, et al., 2019, Predicting range shifts of Asian elephants under global change, DIVERSITY AND DISTRIBUTIONS, Vol: 25, Pages: 822-838, ISSN: 1366-9516
Bourles B, Araujo M, McPhaden MJ, et al., 2019, PIRATA: A Sustained Observing System for Tropical Atlantic Climate Research and Forecasting, EARTH AND SPACE SCIENCE, Vol: 6, Pages: 577-616
Varona HL, Veleda D, Silva M, et al., 2019, Amazon River plume influence on Western Tropical Atlantic dynamic variability, Dynamics of Atmospheres and Oceans, Vol: 85, Pages: 1-15, ISSN: 0377-0265
This study focuses on analysing the potential impact of the Amazon and Pará Rivers on the salinity, temperature and hydrodynamics of the Western Tropical North Atlantic (WTNA) region between 60.5°–24 °W and 5 °S–16 °N. The Regional Ocean Model System (ROMS) was used to simulate ocean circulation with 0.25° horizontal resolution and 32 vertical levels. Two numerical experiments were performed considering river discharge and river input. Temperature and salinity distributions obtained numerically were compared with Simple Ocean Data Assimilation (SODA) and in situ observations from the Prediction Research Moored Array in the Tropical Atlantic (PIRATA) buoys located at 38 °W8 °N and 38 °W12 °N. Surface currents were compared with Surface Currents from Diagnostic model (SCUD). Once we verified that model results agreed with observations, scenarios with and without river discharges were compared. The difference between both simulations in the Sea Surface Temperature distribution was smaller than 2 °C, whereas the Sea Surface Salinity (SSS) changed by approximately 8 psu in the plume area close to the coast from August to December and reaching SSS differences of approximately 4 psu in the region of the North Equatorial Counter Current (NECC). The surface current velocities are stronger in the experiment with river discharge, mainly in the NECC area from September to December and close to the coast in June to August. The results show that river discharges also cause a phase shift in the zonal currents, anticipating the retroflection of the North Brazil Current by two months and enhancing eastward NECC transport, which is in agreement with observations. The Mixed Layer Depth and Isothermal Layer Depth in the presence of river discharge is 20–50 m shallower over the entire extension of the Amazon plume compared with the situation without continental inflows. As a consequence, stronger Barrier Layers develop in
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