ALBERT

Description: In this paper we present a paleoceanographic reconstruction of the southwestern South Atlantic for the past 13 kyr based on faunal and isotopic analysis of planktonic foraminifera from a high-resolution core retrieved at the South Brazil Bight continental slope. Our record indicates that oceanographic changes in the southwestern South Atlantic during the onset of the Holocene were comparable in strength to those that occurred during the Younger Dryas. Full interglacial conditions started abruptly after 8.2 kyr BP with a sharp change in faunal composition and surface hydrography (SST and SSS). Part of the observed events may be explained in terms of changes in thermohaline circulation while the other part suggests a dominant role of winds. Our data indicate that during the Early Holocene upwelling was significantly strengthened in the South Brazil Bight promoting high productivity and preventing the establishment of the typically interglacial menardiiform species. In general terms, oceanographic changes recorded by core KF02 occurred in synchrony with Antarctica's climate.

Description: Repeated automated runs of signal alignment were used both to obtain an average fit (age model) and confidence intervals (uncertainties) for two marine sediment records from the southwest South Atlantic. A global and regional δ18O stack (LR04 and SL14, respectively) were used to transfer ages to the two records employing calibrated radiocarbon ages as chronological control points using the automated Match algorithm. A similar correlation between the two records is found both when the two records are correlated using the age model obtained and using δ18O correlation, validating the age models obtained by repeated automated tuning. The use of Termination I and Biozone Y/Z as chronological control points for the last deglaciation on high-resolution records is discussed here. The availability of uncertainties allowed more accurate interpretations. It is possible to observe that Biozone Y/Z is diachronous even on regional scale. Meanwhile Termination I is approximately synchronous on the regional scale but it is diachronous on the global scale. Although the stratigraphic events considered in this investigation are not globally synchronous and therefore not ideal control points for age models of high-resolution records, timing stratigraphic events in different locations has great relevance for investigations on triggering and propagation of climatic events and detailed understanding of climatic change mechanisms.

Description: This paper introduces an integrated Neogene microfossil biostratigraphic chart developed within post-merger BP for the Gulf of Mexico Basin and is the first published industrial framework "fully-tuned" to orbital periodicities. Astronomical-tuning was accomplished through a 15-year research program on ODP Leg 154 sediments (offshore NE Brazil) with sampling resolution for calcareous nannofossils and planktonic foraminifera about 20 k.y. and 40 k.y. (thousand year), respectively. This framework extends from the Late Oligocene (25.05 Ma) to Recent at an average Chart Horizon resolution for the Neogene of 144 k.y., approximately double that of published Gulf of Mexico biostratigraphic charts and a five-fold increase over the highest resolution global calcareous microfossil biozonation. Such resolution approximates that of 4th to 5th order parasequences and is a critical component in the verification of seismic correlations between mini-basins in the deep-water Gulf of Mexico. Its utility in global time-scale construction and correlation has been proven, in part, by application of the scheme in full to internal research for the Oligocene-Miocene boundary interval on the Global Boundary Stratotype Section and Point (GSSP) in northern Italy and offshore wells in the eastern Mediterranean Sea. This step change in Neogene resolution, now at the level of cyclostratigraphy (the orbital periodicity of eccentricity) and the magnetostratigraphic chron, demonstrates the potential for calcareous microfossil biostratigraphy to more consistently reinforce correlations of these time scale parameters. The integration of microfossil disciplines, consistent taxonomies, and rigorous analytical methodologies are all critical to obtaining and reproducing this new level of biostratigraphic resolution.

Description: Paleoceanographic reconstructions from the Brazil Current are scarce and lack the required temporal resolution to appropriately represent its variability during key periods of the last glacial-interglacial cycles. Here, we present the first high-temporal resolution multiproxy reconstruction of the Brazil Current at 24 °S covering the last 185 ka. During the last and penultimate glacial periods, our Mg/Ca-derived sea surface temperature (SST) record shows a strong cooling at ca. 47 and ca. 156 ka, respectively, that is followed by a warming trend from late-Marine Isotope Stage (MIS) 3 to MIS 1 and from late-MIS 6 to MIS5e, respectively. Importantly, the Brazil Current warmed uninterruptedly towards Termination I (II) after the low SST at ca. 47 and ca. 156 ka, with no SST minima during the Last Glacial Maximum or penultimate glacial maximum. The reason for the strong cooling and the warming trend during late-MIS 3 and late-MIS 6 could reside in the favorable obliquity configuration. However, this mechanism is not sufficient to sustain the warming observed for the rest of the last and penultimate glacial periods. We propose that the change in the Atlantic meridional overturning circulation (AMOC), as described in the literature, from a 'warm' to a 'cold mode' for MIS 2 and MIS 6 is responsible for the accumulation of warm waters in the subtropical western South Atlantic, preventing SST minima during the last and penultimate glacial maxima in the region. Change in benthic d13C corroborates that a fundamental modification in the AMOC mode might have triggered the heat accumulation. Our data also show a sudden increase in SST and surface salinity during the last glacial descent (MIS 4), indicating that the western portion of the subtropical gyres may have acted as a heat and salt reservoir, while higher latitude climates transited to a glacial background. Our findings imply that the AMOC 'cold mode' induces heat storage in the subtropical western South Atlantic and, because of that, the last two regional SST minima occurred out-of-phase with the glacial maxima of higher latitudes.

Description: This study was designed to assess the concentration of heavy metals in water, two fish species (Clarias gariepinus and Oreochromis niloticus), and three different vegetables (Spinach, Rosella, and Jute mallow) which were grown around the riverbank of River Benue. A laboratory-based study was adopted. Fish, water samples, and vegetables were collected monthly at different locations named points A, B, and C from River Benue for five consecutive months between October 2019 and February 2020 and analyzed for physicochemical parameters. The parameters included pH, dissolved oxygen (DO), temperature, conductivity, lead, cadmium, manganese, zinc, Iron, and copper.

Description: During glacial/interglacial cycles, changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) modified the intermediate and deep-water mass proportions and high latitude productivity in the Atlantic Ocean. These factors influence the distribution and geochemical partitioning of trace metals in the ocean. Mercury is a redox and productivity-sensitive trace metal, making it a potential proxy of paleoenvironmental changes. Therefore, this work examines the effect of Atlantic Ocean circulation changes during the last two glacial/interglacial cycles on the biogeochemistry of Hg. For this, a high-resolution record of the total Hg concentration was determined in core GL-1090 collected from the Southwestern Subtropical Atlantic that represents the last 185 thousand years. During the reported glacial/interglacial cycles, Hg showed a distinct trend throughout Marine Isotope Stages with higher concentrations during periods of enhanced penetration of northern component water into the southwestern Atlantic. This is supported by the similarity of mercury variability with benthic foraminifera δ¹³C, suggesting a strong influence of deep ocean circulation on the availability and accumulation of this metal in deep-sea sediments. Mercury geochemistry and particle scavenging were correlated with organic matter (OM) input at the core site. We also noted that mercury responded to redox variation in sediment after Termination II, which can be explained by the increase in deep ocean ventilation due to AMOC strengthening. This hypothesis was confirmed by the antiphase behavior of Hg and Total Organic Carbon when compared with Mn/Al ratios and CaCO3. Our work, therefore, allows for a better understanding of the processes leading to long-term mercury removal to sediments.

Description: Expansions of coastal upwelling spots along the Brazilian coast were previously reported for Marine Isotope Stage (MIS) 5, but open questions remain regarding the climatic mechanisms and the periodicity of such changes. Based on two marine sediment cores, we provide evidence for multiple intensifications of the upwelling regime off the Southeast Brazilian margin (SBM) during several interglacials and highlight the major role of eccentricity as the responsible forcing. In addition, we show a two-step change in the upwelling regime across the Mid-Brunhes Event (MBE) and an increase in the amplitude of upwelling variability after this climatic transition. Our findings point to substantial modifications of the upwelling regions during several glacial-interglacial transitions that probably altered the regional marine productivity regime and the carbon budget.

Description: The presence of snow on sea-ice can have dramatic effects on the photosynthetically available radiation (PAR) that reaches the ice algae. To better quantify this effect in the high Arctic, an experiment was conducted in Kangerlussuaq, west Greenland, throughout March 2013 where snow was cleared off the sea-ice and measured parameters were compared to a control area. Samples of under-ice algae were then taken to analyse the species composition. The bottom 30 mm of the sampled ice cores were used to determine the stress on the photosystems of the sea ice algae as they experienced the rapid irradiance via the variable fluorescence of photosystem II (PSII). PSII was measured using pulse amplitude modulated (PAM) fluorometry (Walz Imaging-PAM fluorometer). This provides the effective quantum yield of PSII (Φ_PSII), which is a unitless ratio of ambient (F) and maximum (F_m) fluorescence yields. These measurements were taken every 3 hours over the final day of the study. Periodically over the week of the study, similar measurements were taken (in triplicate) with a Phyto-PAM System II Emitter-Detector (Phyto-ED) to determine how F and F_m values changed at a courser temporal resolution. Also measured were rapid light curves (RLCs), which allowed for the derivation of the relative electron transfer rate (rETR and rETR_max; µmol é/m²/s), the slope of the light-limited portion of the RLC (α; mol é /mol photons), and the irradiance at which rETR was light-saturated (E_k; µmol photon/m²/s). 100 ml samples of thawed sea-ice were also collected and stored in the dark to be used for species identification. This was done by first enumerating the ice algae to the Utermöhl method. A Zeiss Axiovert 135M (40×) inverted microscope was used to identify and count species/morphological groups via a total of four diagonals per sample. Relative abundances of algae were estimated as percent of total count, and the biomass was calculated according to the ALGESYS protocol. Throughout the experiment the following variables were collected at 5 minute intervals: Air temperature (°C; sun-screened Campbell 107 temperature probe), upwelling and downwelling PAR (µmol photons/m²s; Li-COR Li-191 PAR sensor) at 0.5 m above the sea-ice surface, and under-ice PAR (µmol photon/m²/s; Li-COR –Li-192 submersible PAR sensor). From these data, transmittance (τ) was calculated as the ratio between under-ice PAR and downwelling PAR at the surface, and albedo (0-1 scale) was calculated as the ratio between upwelling and downwelling PAR at the surface.

Description: Core MVSEIS08-TG-2 was acquired during the Euromargin-MVSEIS08 cruise on the Moroccan margin, south of the Gulf of Cadiz. This site was targeted to discuss the possibility of the saline upper branch of the Mediterranean Outflow Water (MOW) diverging southwards along the Moroccan margin, in addition to the well-established northern MOW current. The southern TG-2 is a 2.12 m gravity core. Contourite records cover the time interval from the last deglaciation starting at HS1 (18.6 ka) to the Holocene. New datasets of current velocity (sortable silt) and water mass origin (O and C isotopes of benthic foraminifera) define the intensity of the MOW as contourite deposits, together with element ratios (XRF-scan) and physical properties of the sediment. O and C isotopes of planktonic foraminifera, foraminiferal species and sea surface temperature (simmax.28 transfer function) were used to determine millennial climate changes during the last deglaciation.

Description: Core GC-01A was collected during the Contouriber-I cruise in the northern Gulf of Cadiz, bathed by the well-established northern Mediterranean Outflow Water (MOW) current along the Iberian margin; this site was a contrasting reference site to discuss the possibility of the saline upper branch of the MOW diverging southwards along the Moroccan margin (core MVSEIS08-TG-2). GC-01A-TC (0.87 m) and GC-01A-PC (5.21 m) consist of trigger and gravity cores from the same site, with both sections connected by a time gap at 8-9 ka. The contourite records cover the time interval from the Last Glacial Maximum (22 ka) through the last deglaciation to the Holocene (GC-01A). New datasets of current velocity (sortable silt) and water mass origin (O and C isotopes of benthic foraminifera) define the intensity of the MOW as contourite deposits, together with element ratios (XRF-scan) and physical properties of the sediment. O and C isotopes of planktonic foraminifera, foraminiferal species and sea surface temperature (simmax.28 transfer function) were used to determine millennial climate changes during the last deglaciation.