Coast Of Angola Research Articles

A Southeast Atlantic deep‐ocean observatory: first experiences and results

The DELOS (Deep‐ocean Environmental Long‐term Observatory System) project is a long‐term research program focused on understanding the impacts of oil and gas extraction on deep‐sea ecosystems. We have installed two seafloor observation platforms, populated with ROV‐serviced sensor modules, at 1400 m water depth in the Southeast Atlantic off the coast of Angola. The ‘impact’ Near‐Field platform is located 50 m from subsea oil production facilities. The ‘control’ Far‐Field platform is 16 km distant from any industry seafloor activity. Each platform includes oceanographic, acoustic, and camera sensor modules. The latter carries two still cameras providing close‐up and wide‐angle views of the seabed. The Far‐Field platform is also equipped with a sediment trap that deploys to 100 m above the seafloor. The instrumented platforms were installed in Feb 2009, and the sensor modules subsequently serviced in Aug 2009, Feb 2010, and Aug 2010. Here, we report on our first experiences of operating the observatories and present some of the first data. The oceanographic data (temperature, salinity, oxygen concentration) and biological observations (demersal fish and benthic invertebrates) suggest that the two study sites have near identical environmental characteristics. We, therefore, believe that these sites are appropriate as control and impact locations for long‐term monitoring of potential anthropogenic effects referenced to natural background environmental variation. We suggest that DELOS‐type observatories, particularly operated as pairs (or in networks), are a highly effective means of appropriately monitoring deep‐water resource exploitation—both hydrocarbon extraction and mineral mining.

Classification of warm and cold water events in the eastern tropical Atlantic Ocean

AbstractFor the tropical Atlantic Ocean two phenomena showing anomalous sea surface temperature (SST) warming have been described: the Atlantic Niño in the equatorial Atlantic and the Benguela Niño off the Angolan coast. In this study, both Niño types are integrated into a new set of SST regions and the definition of a robust standardized index for the long‐term period 1870–2011. Comparisons of these regions and indices show a close connection between anomalous warming and cooling in the equatorial Atlantic and the Benguela region. Therefore, instead of considering equatorial Atlantic and Benguela warm and cold events separately, we propose to classify them into three subtypes of one comprehensive Atlantic Niño. Copyright © 2013 Royal Meteorological Society

High-field NMR spectroscopy and FTICR mass spectrometry: powerful discovery tools for the molecular level characterization of marine dissolved organic matter

Abstract. High-performance, non-target, high-resolution organic structural spectroscopy was applied to solid phase extracted marine dissolved organic matter (SPE-DOM) isolated from four different depths in the open South Atlantic Ocean off the Angola coast (3° E, 18° S; Angola Basin) and provided molecular level information with extraordinary coverage and resolution. Sampling was performed at depths of 5 m (Angola Current; near-surface photic zone), 48 m (Angola Current; fluorescence maximum), 200 m (still above Antarctic Intermediate Water, AAIW; upper mesopelagic zone) and 5446 m (North Atlantic Deep Water, NADW; abyssopelagic, ~30 m above seafloor) and produced SPE-DOM with near 40% carbon yield and beneficial nuclear magnetic resonance (NMR) relaxation properties, a crucial prerequisite for the acquisition of NMR spectra with excellent resolution. 1H and 13C NMR spectra of all four marine SPE-DOM showed smooth bulk envelopes, reflecting intrinsic averaging from massive signal overlap, with a few percent of visibly resolved signatures and variable abundances for all major chemical environments. The abundance of singly oxygenated aliphatics and acetate derivatives in 1H NMR spectra declined from surface to deep marine SPE-DOM, whereas C-based aliphatics and carboxyl-rich alicyclic molecules (CRAM) increased in abundance. Surface SPE-DOM contained fewer methyl esters than all other samples, likely a consequence of direct exposure to sunlight. Integration of 13C NMR spectra revealed continual increase of carboxylic acids and ketones from surface to depth, reflecting a progressive oxygenation, with concomitant decline of carbohydrate-related substructures. Aliphatic branching increased with depth, whereas the fraction of oxygenated aliphatics declined for methine, methylene and methyl carbon. Lipids in the oldest SPE-DOM at 5446 m showed a larger share of ethyl groups and methylene carbon than observed in the other samples. Two-dimensional NMR spectra showed exceptional resolution and depicted resolved molecular signatures in excess of a certain minimum abundance. Classical methyl groups terminating aliphatic chains represented ~15% of total methyl in all samples investigated. A noticeable fraction of methyl (~2%) was bound to olefinic carbon. Methyl ethers were abundant in surface marine SPE-DOM, and the chemical diversity of carbohydrates was larger than that of freshwater and soil DOM. In all samples, we identified sp2-hybridized carbon chemical environments with discrimination of isolated and conjugated olefins and α,β-unsaturated double bonds. Olefinic proton and carbon atoms were more abundant than aromatic ones; olefinic unsaturation in marine SPE-DOM will be more directly traceable to ultimate biogenic precursors than aromatic unsaturation. The abundance of furan, pyrrol and thiophene derivatives was marginal, whereas benzene derivatives, phenols and six-membered nitrogen heterocycles were prominent; a yet unassigned set of six-membered N-heterocycles with likely more than one single nitrogen occurred in all samples. Various key polycyclic aromatic hydrocarbon substructures suggested the presence of thermogenic organic matter at all water depths. Progressive NMR cross-peak attenuation from surface to deep marine SPE-DOM was particularly strong in COSY NMR spectra and indicated a continual disappearance of biosignatures as well as entropy gain from an ever increased molecular diversity. Nevertheless, a specific near-seafloor SPE-DOM signature of unsaturated molecules recognized in both NMR and Fourier transform ion cyclotron mass spectrometry (FTICR/MS) possibly originated from sediment leaching. The conformity of key NMR and FTICR/MS signatures suggested the presence of a large set of identical molecules throughout the entire ocean column even though the investigated water masses belonged to different oceanic regimes and currents. FTICR/MS showed abundant CHO, CHNO, CHOS and CHNOS molecular series with slightly increasing numbers of mass peaks and average mass from surface to bottom SPE-DOM. The proportion of CHO and CHNO negative ions increased from surface to depth, whereas CHOS and especially CHNOS molecular series markedly declined. While certain rather aliphatic CHOS and CHNOS ions were observed solely in the surface, deep marine SPE-DOM was enriched in unique unsaturated and rather oxygenated CHO and CHNO molecular series. With the exception of abyssopelagic SPE-DOM at 5446 m, which showed a peculiar CHOS chemistry of unsaturated carbon and reduced sulphur (black sulphur), CHO and CHNO molecular series contributed ~87% to total positive electrospray ionization FTICR mass peak integral, with a near constant ratio of CHNO / CHO molecular compositions near 1.13 ± 0.05. In case of all four marine SPE-DOM, remarkably disparate average elemental compositions as determined from either MS and NMR spectra were observed, caused by a pronounced ionization selectivity in electrospray ionization FTICR/MS. The study demonstrates that the exhaustive characterization of complex unknowns in marine DOM will enable a meaningful classification of individual marine biogeosignatures. Future in-depth functional biodiversity studies with a clear understanding of DOM structure and function might eventually lead to a novel, unified perception of biodiversity and biogeochemistry.

The Relationship of Rainfall Variability in Western Equatorial Africa to the Tropical Oceans and Atmospheric Circulation. Part II: The Boreal Autumn

Abstract This paper examines the mechanisms controlling the year-to-year variability of rainfall over western equatorial Africa during the rainy season of October–December. Five regions with distinct behavior are analyzed separately. Only two show strong associations with the ocean and atmospheric features in the global tropics. These two regions, in the east (the eastern Zaire basin) and west (Angolan coast) of the study area, respectively, demonstrate strikingly opposite relationships with the anomalies of sea surface temperatures (SSTs), sea level pressure (SLP), and east–west atmospheric circulation. The wet (dry) conditions in the eastern Zaire basin are associated with El Niño(La Niña)–like phases. The inverse pattern is apparent for the Angolan coast. The other three regions, lying between these two poles of variability, represent a transition zone with a weak linear relationship to the circulation features. The vital impact of the east–west circulation cells on rainfall variability results in a stronger association with zonal wind than with SSTs or SLP. In addition to the zonal shift, changes in intensity of the zonal cells also play a crucial role. Variability in both magnitude and location of the circulation cells appear to be modulated by the remote forcing from the Pacific via an atmospheric bridge. However, the eastern sector is impacted mainly when synchronous changes occur in the Indian Ocean, and the western sector is impacted mainly when synchronous changes occur in the Atlantic Ocean.

Response of the Benguela upwelling systems to spatial variations in the wind stress

In this paper we combine field observations, numerical modeling and an idealized analytical theory to study some features of the Benguela upwelling system. The current system can be established through a combination of observations and realistic simulations with an advanced numerical model. The poleward undercurrent below the equator-ward coastal jet is often found as a countercurrent that reaches the sea surface seaward of the coastal jet. The coastal band of cold upwelled water appears to broaden from south to north and at the northern edge of the wind band an offshore flow is often detected, which deflects the coastal Angola current to the west. These features can be explained and understood with an idealized analytical model forced by a spatially variable wind.A crucial role is played by the wind stress curl, which shapes the oceanic response through Ekman-pumping. The interplay of the curl driven effects and the coastal Ekman upwelling together with the coastal jet, Kelvin waves, and the undercurrent is the key to understand the formation of the three-dimensional circulation patterns in the Benguela system. While the numerical model is based on the full set of primitive equations, realistic topography and forcing, the analytic model uses a linear, flat-bottomed f-plane ocean, where the coast is a straight wall and the forcing is represented by an alongshore band of dome-shaped wind stress. Although the analytical model is highly idealized it is very useful to grasp the basic mechanisms leading to the response patterns.

Convective Squalls over the Eastern Equatorial Atlantic

Abstract The Congo Basin and the adjacent equatorial eastern Atlantic are among the most active regions of the world in terms of intense deep moist convection, leading to frequent lightning and severe squalls. Studying the dynamics and climatology of this convection is difficult due to a very sparse operational network of ground-based observations. Here, a detailed analysis of recently available high temporal resolution meteorological observations from three oil platforms off the coast of Angola spanning the three wet seasons from 2006/07 to 2008/09 is presented. The annual cycle of squall days as identified from wind data closely follows that of convective available potential energy (CAPE) and therefore mirrors the cycle of wet and dry seasons. The diurnal cycle of squall occurrence varies from station to station, most likely related to local features such as coastlines and orography, which control the initiation of storms. An attempt to classify squalls based on the time evolution of the station meteorology and satellite imagery suggests that microbursts account for at least one-third of the strong gusts, while mesoscale squall lines appear to be quite rare. On a daily basis the probability of squall occurrence increases with increasing values of CAPE, downdraft CAPE, and 925–700-hPa wind shear, and decreases for high convective inhibition, all calculated from vertical profiles of temperature and humidity at the nearest grid point in the NCEP–NCAR and ECMWF reanalysis datasets. Both the climatological results and the stability indices can be used for local forecasting to avoid squalls impacting on operations on the offshore platforms.

Influence of Different Factors on Abundance Estimates Obtained from Simultaneous Sonar and Echo Sounder Recordings

Use of horizontal guided sonar in addition to vertical echo sounder may improve biomass estimation of pelagic fish schooling near the surface. But proportions of horizontal guided sonar to vertical echo integration estimates have been shown to be very variable, and it is necessary to provide better knowledge on factors that influence acoustic recordings of fish near surface before a reliable method of combining sonar and echo integration estimates can be established. To explore factors that influence horizontal sonar recordings of fish biomass near surface, we collected and analysed data from two acoustic surveys on Norwegian spring-spawning herring (Clupea harengus L.) in the Norwegian Sea in 1997 and 1998, and two acoustic surveys off the southwest coast of Africa, investigating pilchard (Sardinops sagax), anchovy (Engraulis capensis) and round herring (Etrumeus whiteheadi) off the coast of Namibia in 1994, and sardinella (Sardinella sp.) off the coast of Angola in 1995. The ratios of fish densities obtained by sonar to those obtained by echo sounder varied both with respect to location and between different years within a specific location. For three of the four surveys, the biomass estimated by sonar was significantly higher than the estimates by echo sounder, whereas in the remaining survey there was no significant difference in estimated biomass. Periods of bad weather, shallow, or low- density patchy fish distributions and mixture of the target species with other species contributed to the higher and more variable sonar estimates. Still a goal should be to improve knowledge about the factors that contributes to variations between simultaneously recorded echo sounder and sonar data. An aim should be to combine the recordings from both methods in the biomass estimations, or at least assess which of the estimates that are less biased under the prevailing environmental conditions and actual school distribution.

Pelagic Fish Behaviour During Trawl Sampling Off Angola

Large sardinella (Sardinella maderensis and Sardinella aurita) in warm waters off the coast of Africa are known to be a challenge for pelagic trawl sampling, for example during acoustic surveys for abundance estimation. We observed the swimming behaviour of sardinella mixed with other pelagic species, mainly Cunene horse mackerel (Trachurus trecae), during sampling with a pelagic trawl in the course of a study of swimming behaviour and endurance in the trawl belly and escape behaviour during hauling. The study consisted of two pelagic trawl surveys with R/V Dr. Fridtjof Nansen off the coast of Angola. We observed the fish with a trawl sonde in the trawl mouth, from a towed vehicle with sonar and camera positioned above the trawl belly or the trawl mouth, and finally with a camera with video recorder in the trawl belly. The behaviour of the fish was quantified from the video recordings by observing the swimming speed of the fish relative to the trawl and by recording the frequency of different behaviours. Two different reactions of schools were observed. We defined a fright reaction as a sudden reaction, where individuals swam in different directions and the collective school organisation collapsed for a few seconds. The second type of school reaction, the adjust reaction, did not cause the school organisation to disintegrate, but caused the whole school to gradually change its swimming direction by moving closer to one of the sides or the bottom of the trawl. The fish were also observed to swim along within the trawl for tens of minutes, possibly for up to around an hour. The main conclusion of this study is that pelagic species in warm water have the potential to actively swim forward in the trawl and escape during hauling. This could have substantial consequences for trawl sampling during surveys in terms of species- and size- dependent selectivity.

Latitude and psoriasis prevalence

Latitude and psoriasis prevalence

Evaluation of Model-Predicted Top-of-Atmosphere Radiation and Cloud Parameters over Africa with Observations from GERB and SEVIRI

Abstract This study compared the Regional Atmospheric Climate Model version 2 (RACMO) with satellite data by simultaneously looking at cloud properties and top-of-atmosphere (TOA) fluxes. This study used cloud properties retrieved from Spinning Enhanced Visible and Infrared Imager (SEVIRI) data and TOA shortwave and longwave outgoing radiative fluxes measured by one of the Geostationary Earth Radiation Budget (GERB) sensors. Both SEVIRI and GERB resolve the diurnal cycle extremely well with 96 images per day. To test the physical parameterizations of the model, RACMO was run for a domain-enclosing Africa and part of the surrounding oceans. Simulations for July 2006, forced at the lateral boundaries by ERA-Interim reanalyses, show generally accurate positioning of the various cloud regimes but also some important model–observation differences, which the authors tried to reduce by altering model parameterizations. These differences are as follows: 1) TOA albedo differences in clear-sky regions like the Sahara and southern Africa. These differences were considerably reduced by prescribing the surface albedo from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. 2) A considerable overestimation of outgoing longwave radiation within the continental ITCZ caused by the fact that modeled cirrus clouds are far too thin. 3) Underestimation by the model of cloud cover, condensed water path and albedo of the stratocumulus fields off the coast of Angola. The authors reduced these underestimations by suppressing the amount of turbulent mixing above the boundary layer, by prescribing droplet radii derived from SEVIRI data, and by assuming in-cloud horizontal homogeneity for the radiation calculations. 4) Overestimation by the model of the albedo of the trade wind cumulus fields over the Atlantic Ocean. This study argues that this overestimation is likely caused by a model overestimation of condensed water path. In general, the analyses demonstrate the power of the simultaneous evaluation of the TOA fluxes and cloud properties.

A supressão do tráfico de escravos em Angola (ca. 1830-ca. 1860)

Th is article deals with the process of abolishing the transatlantic slave trade in Angola in the fi rst half of the nineteenth century. It breaks down the Angolan slave trade into three macro-regions: Luanda, Benguela, and “northern Angola” (Cabinda and Ambriz). It argues that in order to understand the impact of abolitionism on the ground, scholars need to take into account local conditions, such as the supply of slaves to the coast, the participation of local elites in the business of slaving, and Angola’s close ties to Brazil. Th e article demonstrates that abolitionism policies only became eff ective with the participation of Portugal in the 1840s and the naval operations that ended shipments of slaves from Luanda, the largest slave port in Angola. Th is development signifi cantly increased risks associated with the Angolan slave trade and provided further momentum to the process of spread of shipments of slaves to other parts of the Angolan coast. Key words: Angola, Slave Trade, Abolitionism, Atlantic.

A New Genus and Species of Harpactirinae from Coastal Angola (Araneae, Theraphosidae)

Summary A distinctive new monotypic African theraphosid spider genus is described from coastal Angola and diagnosed from the other Harpactirinae genera. The type species of the new genus represents a new species.

Two NewPterinochilusSpecies from Kenya (Araneae, Theraphosidae, Harpactirinae)

The African theraphosid spider genus Pterinochilus Pocock, 1897 was revised by Gallon (2002), reducing the number of species within the genus from 23 to 6, by synonymy and transfers to other genera. Schmidt (2002a, b) added an additional species, Pterinochilus leetzi Schmidt, 2002, but Gallon (2008) considered this species to be a junior synonym of Pterinochilus murinus Pocock, 1897. In the same publication Gallon described Pterinochilus cryptus Gallon, 2008 from coastal Angola. Whilst working through unidentified and unsorted African theraphosids at the Natural History Museum, London, I came across two hitherto undescribed Pterinochilus species from Kenya. The description of these two species here brings the total number of Pterinochilus species to nine.

Atypical profiles of paralytic shellfish poisoning toxins in shellfish from Luanda and Mussulo bays, Angola

Currently Angola does not possess a monitoring programme for shellfish contamination with marine biotoxins. Among other potentially toxic microalgae, the presence of Gymnodinium catenatum and Pyrodinium bahamense has been reported at the Angola coast, two species associated worldwide with production of paralytic shellfish poisoning toxins (PSTs). A preliminary assessment of contamination with PSTs was carried out by HPLC with pre-column derivatization in samples of Semele proficua from Luanda Bay and samples of Senilia senilis from Mussulo Bay, collected between June 2007 and February 2008. An unusual profile was found, not matching any of the 10 oxidation products expected from the known hydrophilic PSTs normally reported in marine dinoflagellates: the N-sulfocarbamoyl, the decarbamoyl or the carbamoyl analogues of saxitoxin (STX). Four major compounds were noted, and designated A through D. These were not autofluorescent, additionally A and D presented much stronger response after peroxide oxidation than after periodate oxidation. Fluorescence emission and ultraviolet absorption maxima were similar to oxidation products of STX analogues. Separation carried out in two different C18 columns clearly showed the retention times did not match the oxidation products of standards. In the period of August through October 2007, samples of S. proficua from Luanda Bay presented a strong cross-reaction with a commercial antibody towards STX, in the range of 2600–5800 STX equiv./kg, while for the same period levels in the samples of S. senilis from Mussulo Bay ranged between <30 and 340 STX equiv./kg. This reaction was directly proportional to the presence of the four unknown fluorescent peaks. The presence of these compounds was very persistent throughout the studied period, in particular in Luanda Bay. This contamination might not be characteristic of a dinoflagellate blooming, but could be related to a persistent cyanobacterial contamination, due to the strong sewage pollution of the area.

Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)

Abstract. ODP Site 1078 situated under the coast of Angola provides the first record of the vegetation history for Angola. The upper 11 m of the core covers the past 30 thousand years, which has been analysed palynologically in decadal to centennial resolution. Alkenone sea surface temperature estimates were analysed in centennial resolution. We studied sea surface temperatures and vegetation development during full glacial, deglacial, and interglacial conditions. During the glacial the vegetation in Angola was very open consisting of grass and heath lands, deserts and semi-deserts, which suggests a cool and dry climate. A change to warmer and more humid conditions is indicated by forest expansion starting in step with the earliest temperature rise in Antarctica, 22 thousand years ago. We infer that around the period of Heinrich Event 1, a northward excursion of the Angola Benguela Front and the Congo Air Boundary resulted in cool sea surface temperatures but rain forest remained present in the northern lowlands of Angola. Rain forest and dry forest area increase 15 thousand years ago. During the Holocene, dry forests and Miombo woodlands expanded. Also in Angola globally recognised climate changes at 8 thousand and 4 thousand years ago had an impact on the vegetation. During the past 2 thousand years, savannah vegetation became dominant.

Physical Processes Associated with the Tropical Atlantic SST Gradient during the Anomalous Evolution in the Southeastern Ocean

Abstract This work is focused on the evolution of the dominant air–sea coupled mode in the equatorial and southeastern tropical Atlantic and the associated physical processes. It is shown that in June–August (JJA) the evolution of the dominant mode is mainly dynamically driven and displays a coherent warming or cooling pattern extending from the Angola coast toward the equator in the Gulf of Guinea. For anomalies peaking in JJA, the warming (cooling) is initiated near the Angola coast in March–May. It is suggested that SST anomalies along the coast and near the equator are physically connected. The air–sea interaction along the coast may be a major factor in triggering the development of SST anomalies near the equator, which is intensified by local positive feedbacks that may include Bjerknes and Ekman processes. In return, the warming or cooling near the equator weaken the SST anomalies along the coast by changing the direction of anomalous wind. Slow westward Rossby wave propagation may also play a role in stimulating the equatorial feedback. The thermodynamic processes affect the evolution of this mode. On average, the net surface latent heat flux anomalies are the leading damping factor, and the net surface sensible heat flux plays the same role on a smaller scale, while the net surface shortwave (longwave) radiation heating has a negative (positive) contribution to the SST variation. However, although on average the surface heat flux damps the SST anomalies, the role played by the heat flux varies with regions and components. Spatially, the latent and sensible heat flux as well as the longwave radiation damp air–sea coupling in the eastern South Atlantic near the Gulf of Guinea and amplify the coupling in the western equatorial ocean. The situation is opposite for the solar radiation.

Tropical cyclone Dera, the unusual 2000/01 tropical cyclone season in the South West Indian Ocean and associated rainfall anomalies over Southern Africa

Austral summer 2000/01 in the southern African region was unusual in several respects. Tropical cyclone activity in the southwest Indian Ocean was substantially less than average despite large areas of this region showing anomalously warm sea surface temperatures (SST) for much of the season. Many areas of southern Africa experienced above average rainfall with local flooding in parts of Mozambique. In the tropical southeast Atlantic, a large warm SST anomaly evolved off the coast of Angola and northern Namibia in late summer suggesting a Benguela Nino event. During the late summer (February–April 2001), three particularly widespread and intense wet spells occurred over tropical southern Africa, one of which coincided with tropical cyclone Dera. This study considers the generation and evolution of the middle wet spell of late summer 2001 and its relationship with tropical cyclone Dera. This storm was generated in the northwestern part of the Mozambique Channel and then tracked more or less due south through the Channel and into the subtropical southwest Indian Ocean. Rainfall associated with Dera contributed to the ongoing floods over central Mozambique that arose from rains earlier in the season. Dera occurred in early March following a relatively long period of no tropical cyclone activity in the southwest Indian Ocean. A build up of favorable conditions during the preceding weeks contributed towards the storm whereas an anticyclonic anomaly east of Madagascar led to the northerly steering current and the southward track of tropical cyclone Dera out of the Mozambique Channel.

LOWELL J. SATRE. Chocolate on Trial: Slavery, Politics, and the Ethics of Business. Athens, Ohio: Ohio University Press. 2005. Pp. xi, 308. Cloth $55.00, paper $24.95

Cadbury has long been associated in Britain with ethics and progressive social policy, both because of the antislavery position associated with its Quaker founders and because of its model village of Bournville, which housed some company workers at the end of the nineteenth century in exemplary conditions. Lowell J. Satre challenges this image through a detailed examination of Cadbury's use of cocoa beans farmed by slaves in the Portuguese island colonies of São Tomé and Princípe off the coast of Angola between the years 1901 and 1909. Although Portugal had abolished slavery in all of its colonies by 1870, it allowed contract labor. Natives could sign agreements of their own free will by which they committed themselves to five years' labor at a set wage. Under this system by 1900 Angola shipped about 4,000 serviçais a year to São Tomé and Princípe to work on cocoa plantations. In reality, the workers were coerced, repatriation was all but impossible, and the death rate was as high as twelve percent. Cadbury, Satre shows, was one of the main customers for the crop farmed by this de facto slave labor. By 1900 Cadbury purchased forty-five percent of its cocoa beans from São Tomé. By 1907, long after the labor practices in the Portuguese colonies had come to light, Cadbury still imported 7.4 million pounds of cocoa beans from São Tomé, about thirteen percent of the island's total exports (p. 80).

Through thick and thin: early pottery in southern Africa

Conventional wisdom has it that ceramic technology reached southernmost Africa with or just ahead of the so-called Iron Age, Bantu migrations of ca 2000 years ago. A review of the evidence suggests that the earliest ceramics in the subcontinent are thin-walled and smooth surfaced vessels, technologically quite distinct from the first thick-walled, coarse surfaced “Iron Age” ware of the subcontinent, and predating the latter by two to four centuries. There is no published evidence of a thin-walled ware to the north of the Zambezi, although undated examples are known from coastal Angola. It seems unlikely that the thin-walled wares in southernmost Africa represent a residue of some mass human migration in the distant past. It is more likely that the art of making fired clay pots reached the subcontinent through archaeologically invisible infiltrations by small groups, perhaps peripatetic artisans; or it may have been invented locally.

Physical Processes Associated with the Tropical Atlantic SST Meridional Gradient

Abstract The major modes of seasonal sea surface temperature (SST) meridional gradient and their connection with some regional mean SST indices in the Atlantic Ocean are examined using reanalysis data. The focus of the work is on the evolution of the dominant mode of the meridional SST gradient in boreal spring and the associated physical processes. The spatial distribution of the dominant mode in boreal spring is a seesaw pattern, reflecting the opposite variation of the meridional SST gradient between the subtropical and tropical North Atlantic, which resulted from a coherent warming or cooling with maxima along 10°–15°N. It is confirmed that this mode is dominated by the wind–evaporation–SST feedback. The feedback persists a longer time in the western Atlantic than in the eastern. The contribution to the SST variation is mainly from latent heat flux. The surface longwave and shortwave cloud radiative forcings are mainly determined by low cloud cover variations. The authors also found that the thermodynamic mode that peaked in boreal spring becomes weak in the following boreal summer. A similar thermodynamic mode appears in a northward position in boreal autumn, and its life cycle is shorter than the one in boreal spring. In contrast to the leading mode in boreal spring, it is shown that the leading mode in boreal summer is a dynamical air–sea feedback mode, reflecting a coherent warming or cooling pattern extending from the Angolan coast toward the equator in the Gulf of Guinea. The thermodynamic processes act as a negative feedback. The net surface latent heat flux anomalies are the leading damping factor, while the sensible heat flux plays the same role on a smaller scale.