Papers by Andre Luiz Belem
Minerals and elements are important proxies that can provide information about variations in the ... more Minerals and elements are important proxies that can provide information about variations in the delivery and deposition of coastal ocean sediments associated with past climate changes. In this study, postglacial changes in the accumulation of sediments on the upper shelf of southeastern Brazil are linked to the evolution of regional paleoceanographic and continental paleoclimatic conditions during the last 14.4 kyr CAL BP. Mineralogical and major and trace element analyses of a 14 C-dated sediment core identify three main lithostratigraphic units of this core that reveal a succession of changes in sediment delivery and accumulation as postglacial sea level rose and Holocene climate on land evolved. The depositional setting has transitioned in response to the large sea level rise prior to 9.9 kyr CAL BP from being a shallow water high energy environment to a deeper water one. This location has since then been a lower energy environment that has persisted into modern times. Due to the high marine productivity associated with the Cabo Frio upwelling system in an oxygenated water column, the sediments have shown a complex and dynamic redox condition, making variations in redox-sensitive trace elements indicative of changes in primary production and organic matter diagenesis at this location. After sea level stabilized ~9 kyr CAL BP, variations in fluxes of Al, Fe, Ca, and minerals were small, indicating that climate driven changes had only secondary controls on delivery of detrital sediment components to the Cabo Frio shelf. Modern coastal upwelling conditions and the onset of mid-shelf organic-rich sediment deposition were established after 9.9 CAL kyr BP.
Continental Shelf Research, 2014
Organic sediments 210 Pb and 239 þ 240 Pu geochronology δ 13 C TOC/TN molar ratio Lateral transpo... more Organic sediments 210 Pb and 239 þ 240 Pu geochronology δ 13 C TOC/TN molar ratio Lateral transport a b s t r a c t
Most of the global organic carbon (nearly 90%) stored in modern marine sediments is accumulated a... more Most of the global organic carbon (nearly 90%) stored in modern marine sediments is accumulated at continental margins. Continental shelves are dynamic regions that receive inputs of organic carbon derived from both terrestrial and marine sources. Organic carbon originated by vascular plant can potentially represent a substantial fraction of the total organic carbon preserved in sediments on continental margins and plays an important role in global marine systems. Besides, it can provide further information about climatic variables, such as wind strength, continental rainfall, etc. Major terrestrial inputs to Cabo Frio upwelling system come from both Guanabara Bay and Paraíba do Sul River, which shows different properties. In this context, we used lignin phenols as a tool to understand the distribution and early diagenetic patterns of terrigenous organic matter in two sediments boxcores collected from inner (~12 km from the coast, 80 m depth) and outer (~62 km offshore, 110 m depth) Cabo Frio continental shelf, southeastern Brazilian coast. Results show higher lignin concentration in the coastal
Marine Micropaleontology, 2014
The distribution of planktonic foraminifera in box-core tops under the influence of a western bou... more The distribution of planktonic foraminifera in box-core tops under the influence of a western boundary upwelling system along the southeastern Brazilian continental margin was examined to evaluate the similarity percentage (SIMPER) and to create a biofacies model for paleoenvironmental applications. Species associated with warm and oligotrophic water were distributed in the Rio de Janeiro sector of the Campos Basin, while productive water species were most abundant in the Rio de Janeiro sector of the Santos Basin, and cold-water species were most abundant in the Cabo Frio Upwelling System (CFUS). Four major biofacies are associated with the oceanographic setting of the CFUS: one from the Campos Basin (A -Brazil Current front), one from the Santos Basin (Bmixture of coastal and oceanic waters), and two associated with the Cabo Frio High in the northern biofacies (C) and southern biofacies (D). The distribution of biofacies C and D was associated with temperature differences. Biofacies C represents a mixture of upwelling and tropical waters, while biofacies D represents a mixture of cold, nutrient-rich and Santos Basin waters. These biofacies were also defined in core CF10-01B, in which six main paleoceanographic phases were characterized during the last 9 cal kyr, predominantly showing alternating dominance between biofacies C and D. From 9.0 to 5.0 cal kyr before the present (BP), the system was dominated by biofacies C. Between 4.0 and 3.5 cal kyr BP, biofacies D was dominant. Between 3.5 and 2.5 cal kyr BP, a strong influence of coastal waters and weakened upwelling activity were indicated by the dominance of biofacies B + C + D. The last 2.5 cal kyr was dominated by biofacies D. The SST in this core was reconstructed using the Modern Analog Technique (MAT), which revealed 0.35°C of variability, indicating no SST changes during the Holocene. The weak sensitivity of the MAT was due to the interplay among different oceanographic features.
14 We assessed trace element evidence for changes in the delivery and deposition of sediments to ... more 14 We assessed trace element evidence for changes in the delivery and deposition of sediments to the upper shelf of southeast Brazil, which can be linked to the evolution of regional oceanic and continental conditions during the last 17.1 cal kyr. Mineralogical and major and trace elements analyses of a Cdated sediment core have identifiedchanges in the compositions of the two lithologic units of this core that reveal a succession of changes in sediment delivery and accumulation at this location as postglacial sea level rose and the Holocene climate on land evolved. The results imply that depositional conditions have changed from a high energy environment under the strong influence of sea level rise before 9.1 kyr cal BP to conditions indicative of progressive sealevel stabilization until ~3 kyr cal BP. This location then became a deepwater lower energy environment that has persisted to modern times. Despite their proximity to the high organic matter productivity associated with t...
Monthy Multichannel Sea Surface Temperature (MCSST) images derived from the Advanced Very High Re... more Monthy Multichannel Sea Surface Temperature (MCSST) images derived from the Advanced Very High Resolution Radiometer (AVHRR) during the 1981-1991 period are examined in conjunction with sea surface temperature (ShipSST) data obtained by ships of opportunity over 30 years (1950-1979) in the Southern Brazilian coastal waters (28°S - 35°S). The satellite and ship datasets were supplied by the Jet Propulsion Laboratory (JPL) and US National Climate Center, respectively. Each image has a spatial resolution of 18 km. The remote sensing data has shown a dominant 1-year period in the area. To compare both datasets, the mean differences (MCSST-ShipSST) were computed for 114 months using the monthly averaged ShipSST (over 30 years). The mean differences varied from -2.176°C to 2.939°C, having an average of 0.52°C. An discussion about the variability of the MCSST signal is also presented in this work. Pages: 72-78
The calibration procedures for the Advanced Very High Resolution Radiometer (AVHRR) infrared chan... more The calibration procedures for the Advanced Very High Resolution Radiometer (AVHRR) infrared channels is examined in this work. The AVHRR literature states that the linear calibration used to convert radiometric count to radiance is satisfactory for channel 3, but is only approximately correct for channels 4 and 5 because they have a slight curvature in their response functions. So the nonlinearity correction is applied to verify the diference in temperature between the data calibrated only linearly and with nonlinearity correction. The standard National Environmental Satellite, Data, and Information Service (NESDIS) linear calibration is used and the nonlinear corrections are made over the radiance as suggested by Steyn-Ross et al. (1992). Sea Surface Temperatures (SST) are calculated using published split-window algorithms revised by Pearce et al. (1989) and that given by NESDIS/NOAA. The diferences between SST using both methods can vary from 1.10oC (Deschamps e Phulpin, 1980) to...
Quaternary International, 2015
To improve the efficiency of upwelling to control nitrogen dynamic in the ocean, better understan... more To improve the efficiency of upwelling to control nitrogen dynamic in the ocean, better understanding of the occurring processes is necessary. This research explores δ N of nitrate and sinking particles on a western boundary upwelling System (Cabo Frio, Brazil). The Continental Shelf of southeastern Brazil is dominated by the oligotrophic Brazil Current, whose instabilities promote the coastal upwelling of South Atlantic Central Water (SACW), and consequently increases of primary productivity. The coastal upwelling system plays an important role in the nitrogen dynamics on the Cabo Frio Upwelling System (CFUS). However, the interactions between biological induced processes, including biological Nfixation and nitrate inputs from upwelled waters in CFUS still have not been well explored. Then, this study aims clarify Ndynamics on CFUS based on a crossshelf approach. δ Nnitrate was characterized for each water masses present on the shelf (South Atlantic Central Water, Tropical Wate...
14 We assessed trace element evidence for changes in the delivery and deposition of sediments to ... more 14 We assessed trace element evidence for changes in the delivery and deposition of sediments to the upper shelf of southeast Brazil, which can be linked to the evolution of regional oceanic and continental conditions during the last 17.1 cal kyr. Mineralogical and major and trace elements analyses of a Cdated sediment core have identifiedchanges in the compositions of the two lithologic units of this core that reveal a succession of changes in sediment delivery and accumulation at this location as postglacial sea level rose and the Holocene climate on land evolved. The results imply that depositional conditions have changed from a high energy environment under the strong influence of sea level rise before 9.1 kyr cal BP to conditions indicative of progressive sealevel stabilization until ~3 kyr cal BP. This location then became a deepwater lower energy environment that has persisted to modern times. Despite their proximity to the high organic matter productivity associated with t...
Continental shelf is the final destination of terrigenous sediments drained by rivers and estuari... more Continental shelf is the final destination of terrigenous sediments drained by rivers and estuaries, forming a mass of water drifting over the shelf due to its differential density from underlaying salty oceanic waters, forming a coastal plume. On the Southeastern Brazilian Continental Shelf, Cabo Frio region represents the limit between Santos and Campos basin oil reserves. The continental drainage in this area is not expressive, nevertheless presents a complex interaction between the western boundary Brazil Current (BC) and shelf border mechanisms providing amidshelf intrusion and a coastal upwelling of South Atlantic Central Water (SACW) over the shelf. Satellite images of the region shows expressive shelf plumes with sedimentary contributions from Paraiba do Sul river located approximately 180 km northward of Cabo Frio, as well as from Guanabara bay, located 150 km westward of Cabo Frio. In order to understand the role of plumes in sedimentary processes over the continental she...
The general conclusions emerging from Southeastern Brazilian continental margin over the past dec... more The general conclusions emerging from Southeastern Brazilian continental margin over the past decade is in general in agreement that the current dynamics, sea level coupled with climate system developed over the Pleistocene suggest changing in dynamics closely follow the precession-driven insolation cycle. The physical mechanism invoked by most authors involves the intensification of trade NE wind, which are linked principally with the southward migration of the Intertropical Convergence Zone (ITCZ) and the intensification of the South American Monsoon. This model yields several hypotheses about the nature of sedimentation along the Southeastern Brazilian margin that are yet to be regionally tested. Here, we provide high-resolution sedimentation data from 16 cores distributed along the Cabo Frio upwelling zone, off the southeastern coast of Brazil (23°11'24"S, 41°47'59.9"W). The first results show low sedimentation rate during late glacial, an increase during the m...
Boletim de Geociencias - Petrobras
v. 20, n. 1/2, p. 193-210, nov.2011/nov.2012 | resumo A Região Costeira de Cabo Frio é caracteriz... more v. 20, n. 1/2, p. 193-210, nov.2011/nov.2012 | resumo A Região Costeira de Cabo Frio é caracterizada por peculiaridades geomorfológicas e hidrodinâmicas que contribuem para a complexidade dos processos sedimentares na plataforma. Dentre as peculiari dades da região, destaca-se a ocorrência de um depósito lamoso. Este depósito constitui o principal objeto de estudo do Projeto Ressurgência, que visa esta-belecer modelos de produção, transformação, acu-mulação e transporte de material orgânico através de uma abordagem em multiescalas temporais. A caracterização geofísica demonstrou ecocarac-teres com feições distintas em diferentes partes da plataforma, confirmando a complexidade na for-mação deste depósito. Ecocaracteres interpretados como beach-rock e como paleolagunas demonstram o potencial da região como análogo moderno. A análise de processos geoquímicos na interface água-sedimento mostrou que os sedimentos na plataforma são essencialmente subóxicos, com a sul-fato redução dominan...
Physical and biogeochemical processes in continental shelves act synergistically in both transpor... more Physical and biogeochemical processes in continental shelves act synergistically in both transporting and transforming suspended material, and ocean dynamics control the dispersion of particles by the coastal zone and their subsequent mixing and dilution within the shelf area constrained by oceanic boundary currents, followed by their gradual settling in a complex sedimentary scenario. One of these regions is the Cabo Frio Upwelling System located in a significantly productive area of Southeastern Brazil, under the control of the nutrient-poor western boundary Brazil Current but also with a wind-driven coastal upwelling zone, inducing cold-water intrusions of South Atlantic Central Water on the shelf. To understand these synergic interactions among physical and biogeochemical processes in the Cabo Frio shelf, a series of four experiments with a total of 98 discrete samples using sediment traps was performed from November 2010 to March 2012, located on the 145 m isobath on the edge of the continental shelf. The results showed that lateral transport might be relevant in some cases, especially in deep layers, although no clear seasonal cycle was detected. Two main physical-geochemical coupling scenarios were identified: singular downwelling events that can enhance particles fluxes and are potentially related to the Brazil Current oscillations; and events of significant fluxes related to the intrusion of the 18°C isotherm in the euphotic zone. The particulate matter settling in the Cabo Frio shelf area seems to belong to multiple marine and terrestrial sources, in which both Paraiba do Sul River and Guanabara Bay could be potential land-sources, although the particulate material might subject intense transformation (diagenesis) during its trajectory to the shelf edge.
Journal of Marine Systems, 2014
Stable isotopic composition (δ 18 O and δD of water, δ 13 C DIC ) of the water column in the open... more Stable isotopic composition (δ 18 O and δD of water, δ 13 C DIC ) of the water column in the open ocean is related to the origin of water masses. Due to the recent increase of paleoceanographic studies on continental shelves, it is also important to understand their distribution and variability in those systems. To examine the influence of continental shelves internal processes on isotopic composition of water masses, we present data of stable isotopes and phosphate content from a western boundary upwelling system located on the Southeastern Brazilian coast and compare them with offshore observations. High mixing of the main water masses (SSW, TW and SACW) was observed in the majority of the samples collected during different seasons in 2011 and 2012. A mixing triangle approach was used to separate the water masses contribution and characterize their isotopic composition. In addition, an isotopic three end-member model was established, proposing it as a paleoceanographic tool to reconstruct relative contribution of these water masses in sediment records. Variations of δ 18 O values are linked to oceanographic dynamics, mixing, continental runoff and upwelling processes on the shelf. Differently the δ 13 C DIC variations in the middle and inner parts of the shelf are related to the productivity of the upwelling system. Seasonal variability of the δ 13 C DIC values may be also related to changes in the upwelling intensity.
Anais da Academia Brasileira de Ciências, 2014
Physical and biogeochemical processes in continental shelves act synergistically in both transpor... more Physical and biogeochemical processes in continental shelves act synergistically in both transporting and transforming suspended material, and ocean dynamics control the dispersion of particles by the coastal zone and their subsequent mixing and dilution within the shelf area constrained by oceanic boundary currents, followed by their gradual settling in a complex sedimentary scenario. One of these regions is the Cabo Frio Upwelling System located in a significantly productive area of Southeastern Brazil, under the control of the nutrient-poor western boundary Brazil Current but also with a wind-driven coastal upwelling zone, inducing cold-water intrusions of South Atlantic Central Water on the shelf. To understand these synergic interactions among physical and biogeochemical processes in the Cabo Frio shelf, a series of four experiments with a total of 98 discrete samples using sediment traps was performed from November 2010 to March 2012, located on the 145 m isobath on the edge of the continental shelf. The results showed that lateral transport might be relevant in some cases, especially in deep layers, although no clear seasonal cycle was detected. Two main physical-geochemical coupling scenarios were identified: singular downwelling events that can enhance particles fluxes and are potentially related to the Brazil Current oscillations; and events of significant fluxes related to the intrusion of the 18°C isotherm in the euphotic zone. The particulate matter settling in the Cabo Frio shelf area seems to belong to multiple marine and terrestrial sources, in which both Paraiba do Sul River and Guanabara Bay could be potential land-sources, although the particulate material might subject intense transformation (diagenesis) during its trajectory to the shelf edge.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2013
We performed δ 18 O C (Globigerinoides ruber, 250-300 μm white) and SST (modern analogue techniqu... more We performed δ 18 O C (Globigerinoides ruber, 250-300 μm white) and SST (modern analogue technique) paleoceanographic reconstructions for the western tropical South Atlantic Ocean at the northeast Brazilian margin to assess millennial-to centennial-scale climatic shifts that may be propagated by the thermohaline circulation. The results show a progressive SST increase (~1°C) over the Holocene, with a prominent shift occurring during the mid-Holocene that may be linked to changes in insolation distribution. Furthermore, spectral and coherency analyses reveal several centennial-to millennial-scale modes of variability that are similar in both proxy records (4.1-3.8 kyr, 1.5-1.0 kyr,~700 yr, 570-560 yr,~390 yr,~350 yr and~330 yr). Such variability could be the result of (1) solar-induced atmospheric changes at northern high latitudes (possibly propagated southward by the meridional overturning circulation and hence inducing shifts in tropical δ 18 O c and sea surface temperature), and/or (2) salinity anomalies propagated from the Southern Atlantic Ocean and transmitted to the study site through the Agulhas Leakage. These climate oscillations may have had substantive effects on the Holocene climate system, especially over the tropical western South Atlantic Ocean and the South American continent. Our data show that the western tropical South Atlantic may respond to multi-centennial to millennial oscillations that are possibly triggered by external (solar) and internal (northern and southern high latitudes) climate forcing. Further investigations are necessary to illuminate the role of the western tropical South Atlantic in interhemispheric heat transfer.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2014
The North Brazil Current in the western equatorial Atlantic is the main route for poleward heat t... more The North Brazil Current in the western equatorial Atlantic is the main route for poleward heat transfer and therefore is a key component of the climate system. To understand the parameters that influence this region, we present a paleoceanographic reconstruction of the last 40 kyr based on study of sediment core MC 10/3. This reconstruction is based on: i) the oxygen isotope composition of the planktonic foraminifer Globigerinoides ruber (white); ii) census counts of the planktonic foraminifera assemblage to estimate sea surface temperature (SST) via the Modern Analogue Technique (SST MAT ) and to deduce characteristics of the water column; and iii) values of δ 18 O ivc-sw (a proxy for sea surface salinity (SSS)). The oxygen isotope composition of G. ruber showed a strong shift of greater than 1‰ after 21 cal kyr BP. Such a change can be attributed mainly to a salinity reduction of two units, as well as a slight SST increase (~1°C), between 21 and 17.5 kyr BP. This change may be related to a southward displacement of the Intertropical Convergence Zone (ITCZ) and its belt of convective activity, which would have increased precipitation over the region and diminished surface salinity. The structure of the planktonic foraminiferal assemblage also indicates such conditions. The productive/thermocline-dwelling Globigerinita glutinata showed higher abundance prior to 21 cal kyr BP. Other productive/deep-dwellers, i.e., Neogloboquadrina dutertrei, Globorotalia truncatulinoides (left-and right-coiling) and Globorotalia inflata, were slightly more abundant prior to 21 cal kyr BP and became less frequent with the development of low-salinity surface water that created more stratified and oligotrophic conditions in the water column. However, the warm/oligotrophic surface-dwellers (G. ruber, Globigerinoides sacculifer and Globigerinella siphonifera) became more abundant after 21 cal kyr BP. The species Globorotalia menardii was nearly absent during the Last Glacial Maximum (LGM), and its growth in abundance, mainly after 17.5 cal kyr BP, may indicate the resumption of the Agulhas leakage, which would have reached the study area via the South Equatorial Current (SEC). The return of high salinity values synchronous with the G. menardii increase also denotes the influence of Agulhas leakage into the western equatorial Atlantic.
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Papers by Andre Luiz Belem