Landscape evolution and ice-sheet behaviour in a semi-arid polar environment: James Ross Island, NE Antarctic Peninsula

This study of landscape evolution presents both new modern and palaeo process-landform data, and analyses the behaviour of the Antarctic Peninsula Ice Sheet through the Last Glacial Maximum (LGM), the Holocene and to the present day. Six sediment-landform assemblages are described and interpreted for Ulu Peninsula, James Ross Island, NE Antarctic Peninsula: (1) the Glacier Ice and Snow Assemblage; (2) the Glacigenic Assemblage, which relates to LGM sediments and comprises both erratic-poor and erratic-rich drift, deposited by cold-based and wet-based ice and ice streams respectively; (3) the Boulder Train Assemblage, deposited during a Mid-Holocene glacier readvance; (4) the Ice-cored Moraine Assemblage, found in front of small cirque glaciers; (5) the Paraglacial Assemblage including scree, pebble-boulder lags, and littoral and fluvial processes; and (6) the Periglacial Assemblage including rock glaciers, protalus ramparts, blockfields, solifluction lobes and extensive patterned ground. The interplay between glacial, paraglacial and periglacial processes in this semi-arid polar environment is important in understanding polygenetic landforms. Crucially, cold-based ice was capable of sediment and landform genesis and modification. This landsystem model can aid the interpretation of past environments, but also provides new data to aid the reconstruction of the last ice sheet to overrun James Ross Island.

Long-term drift of the coronal source magnetic flux and the total solar irradiance

We test the method of Lockwood et al. [1999] for deriving the coronal source flux from the geomagnetic aa index and show it to be accurate to within 12% for annual means and 4.5% for averages over a sunspot cycle. Using data from four solar constant monitors during 1981-1995, we find a linear relationship between this magnetic flux and the total solar irradiance. From this correlation, we show that the 131% rise in the mean coronal source field over the interval 1901-1995 corresponds to a rise in the average total solar irradiance of {\Delta}I = 1.65 +/- 0.23 Wm^{-2}.

Auroral bright spot sequence near 1400 MLT: Coordinated optical and ion drift observations

Optical observations of a dayside auroral brightening sequence, by means of all-sky TV cameras and meridian scanning photometers, have been combined with EISCAT ion drift observations within the same invariant latitude-MLT sector. The observations were made during a January 1989 campaign by utilizing the high F region ion densities during the maximum phase of the solar cycle. The characteristic intermittent optical events, covering ∼300 km in east-west extent, move eastward (antisunward) along the poleward boundary of the persistent background aurora at velocities of ∼1.5 km s−1 and are associated with ion flows which swing from eastward to westward, with a subsequent return to eastward, during the interval of a few minutes when there is enhanced auroral emission within the radar field of view. The breakup of discrete auroral forms occurs at the reversal (negative potential) that forms between eastward plasma flow, maximizing near the persistent arc poleward boundary, and strong transient westward flow to the south. The reported events, covering a 35 min interval around 1400 MLT, are embedded within a longer period of similar auroral activity between 0830 (1200 MLT) and 1300 UT (1600 MLT). These observations are discussed in relation to recent models of boundary layer plasma dynamics and the associated magnetosphere-ionosphere coupling. The ionospheric events may correspond to large-scale wave like motions of the low-latitude boundary layer (LLBL)/plasma sheet (PS) boundary. On the basis of this interpretation the observed spot size, speed and repetition period (∼10 min) give a wavelength (the distance between spots) of ∼900 km in the present case. The events can also be explained as ionospheric signatures of newly opened flux tubes associated with reconnection bursts at the magnetopause near 1400 MLT. We also discuss these data in relation to random, patchy reconnection (as has recently been invoked to explain the presence of the sheathlike plasma on closed field lines in the LLBL). In view of the lack of IMF data, and the existing uncertainty on the location of the open-closed field line boundary relative to the optical events, an unambiguous discrimination between the different alternatives is not easily obtained.

Fast adaptive real-time classification for data streams with concept drift

An important application of Big Data Analytics is the real-time analysis of streaming data. Streaming data imposes unique challenges to data mining algorithms, such as concept drifts, the need to analyse the data on the fly due to unbounded data streams and scalable algorithms due to potentially high throughput of data. Real-time classification algorithms that are adaptive to concept drifts and fast exist, however, most approaches are not naturally parallel and are thus limited in their scalability. This paper presents work on the Micro-Cluster Nearest Neighbour (MC-NN) classifier. MC-NN is based on an adaptive statistical data summary based on Micro-Clusters. MC-NN is very fast and adaptive to concept drift whilst maintaining the parallel properties of the base KNN classifier. Also MC-NN is competitive compared with existing data stream classifiers in terms of accuracy and speed.

Drift from the use of handheld knapsack pesticide sprayers in Boyacá (Colombian Andes)

Offsite pesticide losses in tropical mountainous regions have been little studied. One example is measuring pesticide drift soil deposition, which can support pesticide risk assessment for surface water, soil, bystanders, off target plants and fauna. This is considered a serious gap, given the evidence of pesticide-related poisoning in those regions. Empirical data of drift deposition of a pesticide surrogate, Uranine tracer, within one of the highest potato producing regions in Colombia, characterized by small plots and mountain orography, is presented. High drift values encountered in our study reflect the actual spray conditions using handled knapsack sprayers. Comparison between measured and predicted drift values using three existing empirical equations showed important underestimation. However, after their optimization based on measured drift information, the equations showed a strong predictive power for this study area and the study conditions. The most suitable curve to assess mean relative drift was the IMAG calculator after optimization.

Impact of a Fram Strait cyclone on ice edge, drift, divergence, and concentration: Possibilities and limits of an observational analysis

This study aims at the determination of a Fram Strait cyclone track and of the cyclone’s impact on ice edge, drift, divergence, and concentration. A 24 h period on 13–14 March 2002 framed by two RADARSAT images is analyzed. Data are included from autonomous ice buoys, a research vessel, Special Sensor Microwave Imager (SSM/I) and QuikSCAT satellite, and the operational European Centre for Medium-Range Weather Forecasts (ECMWF) model. During this 24 h period the cyclone moved northward along the western ice edge in the Fram Strait, crossed the northern ice edge, made a left-turn loop with 150 km diameter over the sea ice, and returned to the northern ice edge. The ECMWF analysis places the cyclone track 100 km too far west over the sea ice, a deviation which is too large for representative sea ice simulations. On the east side of the northward moving cyclone, the ice edge was pushed northward by 55 km because of strong winds. On the rear side, the ice edge advanced toward the open water but by a smaller distance because of weaker winds there. The ice drift pattern as calculated from the ice buoys and the two RADARSAT images is cyclonically curved around the center of the cyclone loop. Ice drift divergence shows a spatial pattern with divergence in the loop center and a zone of convergence around. Ice concentration changes as retrieved from SSM/I data follow the divergence pattern such that sea ice concentration increased in areas of divergence and decreased in areas of convergence.

Evaluation of directional microphone drift in digital hearing aids

The occurrence of directional microphone drift following hearing aid use has been infrequently examined. This study uses the front-to-side ratio to evaluate changes in directional microphone output from new behind-the-ear hearing aids and following approximately three months of hearing aid use. Results indicate no overall significant differences in the front-to-side ratio between initial and follow-up measurements.

Comparing performance of instrumental drift correction by linear and quadratic adjusting in inductive electromagnetic data

Electromagnetic induction (EMI) method results are shown for vertical magnetic dipole (VMD) configuration by using the EM38 equipment. Performance in the location of metallic pipes and electrical cables is compared as a function of instrumental drift correction by linear and quadratic adjusting under controlled conditions. Metallic pipes and electrical cables are buried at the IAG/USP shallow geophysical test site in Sao Paulo City. Brazil. Results show that apparent electrical conductivity and magnetic susceptibility data were affected by ambient temperature variation. In order to obtain better contrast between background and metallic targets it was necessary to correct the drift. This correction was accomplished by using linear and quadratic relation between conductivity/susceptibility and temperature intending comparative studies. The correction of temperature drift by using a quadratic relation was effective, showing that all metallic targets were located as well deeper targets were also improved. (C) 2010 Elsevier B.V. All rights reserved.

Sediment-contact fish embryo toxicity assay with Danio rerio to assess particle-bound pollutants in the Tiete River Basin (Sao Paulo, Brazil)

The Tiete River and its tributary Pinheiros River receive a highly complex organic and inorganic pollutants load from sanitary sewage and industrial sources, as well as agricultural and agroindustrial activities. The aim of the present study was to evaluate the embryotoxic and teratogenic effects of sediments from selected locations in the Tiete River Basin by means of the sediment contact embryo toxicity assay with Danio rerio, in order to provide a comprehensive and realistic insight into the bioavailable hazard potential of these sediment samples. Lethal and sub-lethal effects were recorded, and high embryo toxicity could be found in the samples not only in the vicinity of the megacity Sao Paulo (Billings reservoir and Pinheiros River samples), but also downstream (in the reservoirs Barra Bonita, Promissao and Tres Irmaos). Results confirm that most toxicity is due to the discharges of the metropolitan area of Sao Paulo. However, they also indicate additional sources of pollutants along the river course, probably from industrial, agricultural and agroindustrial residues, which contribute to the degradation of each area. The sediment contact fish embryo test showed to be powerful tool to detect embryo toxicity in sediments, not only by being a sensitive method, but also for taking into account bioavailability. This test provides an ecological highly realistic and relevant exposure scenario, and should therefore be added in ecotoxicological sediment quality assessments. (C) 2011 Elsevier Inc. All rights reserved.

Potentially bioavailable metals in sediment from a tropical polymictic environment-Rio Grande Reservoir, Brazil

Background, aim and scope Although many recent studies have focused on sediment potential toxicity, few of them were performed in tropical shallow aquatic environments. Those places can suffer short-time variations, especially due to water column circulations generated by changes in temperature and wind. Rio Grande reservoir is such an example; aside from that, it suffers various anthropogenic impacts, despite its multiple uses. Materials and methods This work presents the first screening step for understanding sediment quality from Rio Grande reservoir by comparing metal content using three different sediment quality guidelines. We also aimed at verifying any possible spatial heterogeneity. Results and discussion We found spatial heterogeneity varying according to the specific metal. Results showed a tendency for metals to remain as insoluble as metal sulfide (potentially not bioavailable), since sulfide was in excess and sediment physical-chemical characteristics contribute to sulfide maintenance (low redox potential, neutral pH, low dissolved oxygen, and high organic matter content). On the other hand, metal concentrations were much higher than suggested by Canadian guidelines and regional background values, especially Cu, which raises the risk of metal remobilization in cases of water circulation. Further study steps include the temporal evaluation of AVS/SEM, a battery of bioassays and the characterization of organic compounds.

Characterization of organic matter in sediment cores of the Todos os Santos Bay, Bahia, Brazil, by elemental analysis and (13)C NMR

The impact of human activity on the sediments of Todos os Santos Bay in Brazil was evaluated by elemental analysis and (13)C Nuclear Magnetic Resonance ((13)C NMR). This article reports a study of six sediment cores collected at different depths and regions of Todos os Santos Bay. The elemental profiles of cores collected on the eastern side of Frades Island suggest an abrupt change in the sedimentation regime. Auto-regressive Integrated Moving Average (ARIMA) analysis corroborates this result. The range of depths of the cores corresponds to about 50 years ago, coinciding with the implantation of major onshore industrial projects in the region. Principal Component Analysis of the (13)C NMR spectra clearly differentiates sediment samples closer to the Subae estuary, which have high contents of terrestrial organic matter, from those closer to a local oil refinery. The results presented in this article illustrate several important aspects of environmental impact of human activity on this bay. (C) 2011 Elsevier Ltd. All rights reserved.

Sediment deformation in Miocene and post-Miocene strata, Northeastern Brazil: Evidence for paleoseismicity in a passive margin

Stratigraphic intervals characterized by varied and complex styles of soft-sediment deformation structures are well preserved in Miocene and Late Pleistocene to Holocene deposits of a sedimentary basin located in Northeastern Brazil. The Miocene strata, represented by the Barreiras Formation, record only brittle structures, including numerous faults and fractures with straight and high angle-dipping planes that are often filled with sands derived from overlying beds. Folds consisting of broad anticlines and synclines are also present in this unit. The late Pleistocene to Holocene deposits, named Post-Barreiras Sediments, contain an indurated sandy package with a large variety of ductile and brittle deformation structures (i.e., massive sandstones with isolated sand fragments and breccias, undulatory strata, sand dykes and diapirs, sinks and bowls, pebbly pockets, plunged sediment mixtures, fitted sand masses, cone-shaped cracks, fault grading and sedimentary enclaves). These features, confined to sharp-based stratigraphic horizons that progressively grade downward into undisturbed deposits, are related to seismic shocks of high surface-wave magnitude (i.e., Ms>5 or 6). Amalgamated seismites suggest that previously formed seismites were affected by subsequent seismic-wave propagation. Seismic waves caused by activity along one, or most likely, several tectonic structures would have propagated throughout the depositional environment, producing laterally extensive seismites. The close proximity to earthquake epicenters would have promoted pervasive re-sedimentation due to pore overpressure, resulting high volumes of massive sandstones and breccia. The similarity between deposits with correlatable strata from many other areas along the Brazilian coast allows raise the hypothesis that the seismic episodes might have affected sedimentation patterns in a large (i.e., extension of several hundreds of kilometers) geographic area. Thus, the modern seismicity recorded along Northeastern Brazil was recurrent during the Quaternary and, perhaps, also in the Pliocene. The estimated high magnitude of the seismic events and the great regional extent of the affected area demonstrate that the Brazilian coast experienced tectonic stress through the last geological episodes of its evolution, which would have favored sediment accumulation and penecontemporaneous re-sedimentation. This geological context is unexpected in a passive margin, inducing to revisit the debate on how active is a passive margin. (C) 2010 Elsevier B.V. All rights reserved.

THE SOUTHERN BRAZILIAN SHELF: GENERAL CHARACTERISTICS, QUATERNARY EVOLUTION AND SEDIMENT DISTRIBUTION

Extending from latitude 34 degrees S to 22 degrees S the Southern Brazilian shelf constitutes the only part of the Brazilian shelf with a subtropical to temperate environment. The studies on the different geological aspects of the area began in the 1960`s and have recently been reassessed after studies related to the determination of the Economic Exclusive Zone. In terms of morphology, the Southern Brazilian shelf may be divided into three sectors, the Sao Paulo Bight, the Florianopolis-Mostardas Sector and the Rio Grande Cone, characterized by conspicuous differences in terms of geological determining factors, bathymetry, declivities and the presence of canyons and channels. Despite the existence of hundreds of radiocarbon datings the sea level changes curve of southern Brazil during the Last Glacial Cycle is still a matter of debate. A recent controversy on the Middle and late Holocene sea level changes curve raised the question of the amplitude of the oscillations which occurred in the period. Also, a few but relatively consistent radiocarbon datings suggest the occurrence of a high sea level during Isotope Stage 3. In terms of sedimentary cover the Southern Brazilian shelf exhibits a very strong hydrodynamic control, both latitudinal and bathymetrical. The sector southward from 25 degrees S is characterized by the influence of the plume of water carrying sediments originating from the Rio de La Plata. Actually its presence is conspicuous up to 28 degrees S, with the area between this latitude and 25 degrees S constituting a transitional zone. In terms of bathymetry the outer shelf is marked by the ""floor-polisher"" effect of the Brazil Current, which is responsible for the maintenance of a relict facies in areas deeper than 100 meters.

Nd and Pb isotope signatures on the Southeastern South American upper margin: Implications for sediment transport and source rocks

Neodymium and lead isotope values in sediment samples were used to interpret sediment transport and source rocks on the Southeastern South American upper margin. The sediments of the Argentinian margin exhibit an average epsilon(Nd) value of -1.9, indicating the influence of the Andean rocks as sediment sources. Sediments from the Rio de La Plata estuary show an average epsilon(Nd) value of -9.6 which is similar to that of the Southern Brazilian Upper Margin. Finally, sediments of Southeastern Brazil, which are associated with the transport of the Brazil Current exhibit an average epsilon(Nd) of -13.0. The Pb isotope signatures also confirm the differentiation of source rocks in the sedimentation of the study area. In addition, Pb isotopes helped to establish the extent of the influence of the Rio de La Plata on the sedimentation of the Southern Brazilian margin. In terms of Pb isotopes the sediments from the Rio de La Plata estuary and Southern Brazil are more radiogenic than those of Southeastem Brazil and the Argentinian margin. (c) 2007 Elsevier B.V. All rights reserved.