The African continental divide: Indian versus Atlantic Ocean spreading during Gondwana dispersal

ABSTRACT It is well established that plate-tectonic processes operate on a global scale and that spatially separate but temporally coincident events may be linked. However, identifying such links in the geological record and understanding the mechanisms involved remain speculative. This is particularly acute during major geodynamic events, such as the dispersal of supercontinents, where multiple axes of breakup may be present as well as coincidental collisional events. To explore this aspect of plate tectonics, we present a detailed analysis of the temporal variation in the mean half rate of seafloor spreading in the Indian and Atlantic Oceans, as well as plate-kinematic attributes extracted from global plate-tectonic models during the dispersal of Gondwana since ca. 200 Ma. Our analysis shows that during the ~20 m.y. prior to collision between India and Asia at ca. 55 Ma, there was an increase in the mean rate of seafloor spreading in the Indian Ocean. This manifests as India rapidly accelerating toward Asia. This event was then followed by a prompt deceleration in the mean rate of Indian Ocean seafloor spreading after India collided with Asia at ca. 55 Ma. Since inception, the mean rate of seafloor spreading in the Indian Ocean has been generally greater than that in the Atlantic Ocean, and the period of fastest mean half spreading rate in the Indian Ocean was coincident with a slowdown in mean half seafloor spreading rate in the competing Atlantic Ocean. We hypothesize that faster and hotter seafloor spreading in the Indian Ocean resulted in larger ridge-push forces, which were transmitted through the African plate, leading to a slowdown in Atlantic Ocean spreading. Following collision between India and Asia, and a slowdown of Indian Ocean spreading, Atlantic spreading rates consequently increased again. We conclude that the processes in the Indian and Atlantic Oceans have likely remained coupled throughout their existence, that their individual evolution has influenced each other, and that, more generally, spreading in one basin inevitably influences proximal regions. While we do not believe that ridge push is the main cause of plate motions, we consider it to have played a role in the coupling of the kinematic evolution of these oceans. The implication of this observation is that interaction and competition between nascent ocean basins and ridges during supercontinent dispersal exert a significant control on resultant continental configuration.

Joint Boost to Super El Niño from the Indian and Atlantic Oceans

Super El Niño has been a research focus since the first event occurred. Based on observations and models, we propose that a super El Niño emerges if El Niño is an early-onset type coincident with the distribution of an Atlantic Niña (AN) in summer and a positive Indian Ocean Dipole (IOD) in autumn which is called Indo-Atlantic Booster (IAB). The underlying physical mechanisms refer to three-ocean interactions with seasonality. Early onset endows super El Niño with adequate strength in summer to excite wind-driven responses over the Indian and Atlantic Oceans, which further facilitate IAB formation by coupling with the seasonal cycle. In return, IAB alternately produces additional zonal winds over the Pacific (U), augmenting super El Niño via the Bjerknes feedback. Adding AN and IOD indices into the regression model of U leads to a better performance than the single Niño3.4 model, with a rise in the total explained variances by 10–20% and a reduction in the misestimations of super El Niños by 50%. Extended analyses using Coupled Model Intercomparison Project models further confirm the sufficiency and necessity of early onset and IAB on super El Niño formation. Approximately, 70% of super El Niños are early-onset types accompanied by IAB and 60% of early-onset El Niños with IAB finally grow into extreme events. These results highlight the super El Niño as an outcome of pantropical interactions, so including both the Indian and Atlantic Oceans and their teleconnections with the Pacific will greatly improve super El Niño prediction.

Interactions of temperature fluctuations of the Pacific, Indian and Atlantic oceans with Global atmospheric oscillation

<p>The predictability of El Niño and La Niña is investigated. In this case, the recently discovered so-called Global Atmospheric Oscillation (GAO) is considered (Serykh et al., 2019). Assuming GAO to be the main mode of short-term climatic variability, this study defines an index that characterizes the dynamics and relationships of the extratropical components of the GAO and El Niño – Southern Oscillation (ENSO). Due to the general propagation of the GAO’s spatial structure from west to east, another index – predictor of ENSO is defined. The cross-wavelet analysis between both of these indices and the Oceanic Niño Index (ONI) is performed. This analysis reveals a range of timescales within which the closest relationship between the GAO and ONI takes place. Using this relationship, it is possible to predict El Niño and La Niña with a lead-time of approximately 12 months (Serykh and Sonechkin, 2020a).</p><p>Using data on the distribution of temperatures in the Pacific, Indian, and Atlantic Oceans, large-scale structures of spatial and temporal variations of these temperatures are investigated (Serykh and Sonechkin, 2020b). A structure is found which is almost identical to the spatial and temporal sea surface temperature (SST) structure that is characteristic of the GAO. Variations in water temperature in a near-equatorial zone of the Pacific Ocean at depths up to about 150 meters behave themselves in the same way as variations in sea surface height and SST. At even greater depths, variations in water temperature reveal a "striped" structure, which is, however, overall similar to that of SST variations. Variations of water temperature at depths in all three oceans spread from east to west along the equator with a period of 14 months. This makes it possible to think that the dynamics of these temperatures are controlled by the so-called Pole tides. The surface North Pacific Pole Tide was found previously responsible for excitation of El Niño (Serykh and Sonechkin, 2019). The deep Pole tides in the Southern Atlantic and Southern Indian Ocean appear to be triggers of the Atlantic El Niño and Indian Ocean Dipole (IOD). Thus, IOD manifests itself at the depth of the thermocline more clearly than on the surface of the Indian Ocean. The out-of-phase behavior of El Niño and IOD is explained by the 180-degree difference in the longitudes of these phenomena.</p><p> </p><p><strong>References</strong></p><p>Serykh I.V., Sonechkin D.M. Nonchaotic and globally synchronized short-term climatic variations and their origin // Theoretical and Applied Climatology. 2019. Vol. 137. No. 3-4. pp 2639–2656. https://doi.org/10.1007/s00704-018-02761-0</p><p>Serykh I.V., Sonechkin D.M., Byshev V.I., Neiman V.G., Romanov Yu.A. Global Atmospheric Oscillation: An Integrity of ENSO and Extratropical Teleconnections // Pure and Applied Geophysics. 2019. Vol. 176. pp 3737–3755. https://doi.org/10.1007/s00024-019-02182-8</p><p>Serykh I.V., Sonechkin D.M. El Niño forecasting based on the global atmospheric oscillation // International Journal of Climatology. 2020a. https://doi.org/10.1002/joc.6488</p><p>Serykh I.V., Sonechkin D.M. Interrelations between temperature variations in oceanic depths and the Global atmospheric oscillation // Pure and Applied Geophysics. 2020b. Vol. 177. pp 5951–5967. https://doi.org/10.1007/s00024-020-02615-9</p>

Rapsodia Ibero-Indiana: Transoceanic creolization and the mando of Goa

The mando is a secular song-and-dance genre of Goa whose archival attestations began in the 1860s. It is still danced today, in staged rather than social settings. Its lyrics are in Konkani, their musical accompaniment combine European and local instruments, and its dancing follows the principles of the nineteenth-century European group dances known as quadrilles, which proliferated in extra-European settings to yield various creolized forms. Using theories of creolization, archival and field research in Goa, and an understanding of quadrille dancing as a social and memorial act, this article presents the mando as a peninsular, Indic, creolized quadrille. It thus offers the first systematic examination of the mando as a nineteenth-century social dance created through processes of creolization that linked the cultural worlds of the Indian and Atlantic Oceans—a manifestation of what early twentieth-century Goan composer Carlos Eugénio Ferreira called a ‘rapsodia Ibero-Indiana’ (‘Ibero-Indian rhapsody’). I investigate the mando's kinetic, performative, musical, and linguistic aspects, its emergence from a creolization of mentalités that commenced with the advent of Christianity in Goa, its relationship to other dances in Goa and across the Indian and Atlantic Ocean worlds, as well as the memory of inter-imperial cultural encounters it performs. I thereby argue for a new understanding of Goa through the processes of transoceanic creolization and their reverberation in the postcolonial present. While demonstrating the heuristic benefit of theories of creolization to the study of peninsular Indic culture, I bring those theories to peninsular India to develop further their standard applications.

Distribution of methane fluxes on the water–atmosphere interface in different regions of the World Ocean

For the first time, methane fluxes at the water-atmosphere interface were calculated for the water area of Pacific, Indian, and Atlantic oceans (for the area about 30,000 miles) on the basis of the expeditionary measurements of methane concentrations in the surface layer of water and subsurface layer of the atmosphere along the entire course of the vessel. Methane fluxes at the water-atmosphere interface were calculated for the water areas of the Pacific, Indian and Atlantic oceans. In the result of the studies carried out in various regions of the World Ocean, an uneven spatial distribution of methane fluxes from strong absorption to emission of anomalous intensity was observed. The article presents the results of a detailed study for the deepwater area of the Indian Ocean open waters in the northern part of the Ninetyeast Ridge. Both supersaturation and undersaturation of seawater respectively to its concentrations in the atmosphere have been revealed on the basis of the direct measurements of methane concentrations in the ocean surface water layer. The distribution of dissolved methane in the water column of the Indian Ocean has been considered.

Occurrence of Omura’s whale, Balaenoptera omurai (Cetacea: Balaenopteridae), in the Equatorial Atlantic Ocean based on Passive Acoustic Monitoring

The current known distribution of Omura’s whale includes the tropical and warm temperate waters of the western Pacific, Indian, and Atlantic Oceans. Evidence of their presence in the Atlantic Ocean is based on beach cast specimens found on the coasts of Mauritania (North Atlantic) and Northeastern Brazil (South Atlantic). The present study characterizes the occurrence of this species in the São Pedro and São Paulo Archipelago (SPSPA), on the mid-Atlantic ridge between South America and Africa, based on autonomous recording systems. Acoustic signals were similar, but not identical, to B. omurai vocalizations recorded off the coast of Madagascar. Although these signals were recorded for only 11 months, there are peaks in vocal activity between May and June in the vicinities of SPSPA, suggesting either a shift in distribution within the Atlantic equatorial waters or seasonality in the species’ vocal behavior in this region. The first acoustic records of Omura’s whales in the Equatorial Atlantic suggest that these animals may also use deep-water habitats, in addition to the shallow-water habitat use observed in other regions.

History of Mozambique

The peoples of early-21st-century Mozambique underwent different historical experiences which, to a certain extent, were homogenized when Portuguese colonialism encompassed the entire territory from the late 19th century onward. However, all of them had common origins, rooted in successive Bantu migrations. These peoples were organized into small chiefdoms based on lineages, but those located in the central region of Mozambique were integrated into states with some level of centralization, created by the Karanga south of the Zambezi and by the Maravi to the north. The interior regions were articulated into mercantile networks with the Indian Ocean through Swahili coastal entrepôts, exporting gold and ivory. From 1505 onward, the Portuguese sought to control this commerce from some settlements along the coast, particularly Mozambique Island, their capital. During the last decades of the 16th century, projects emerged for territorial appropriation in the Zambezi Valley, where a Luso-Afro-Indian Creole society developed. From the mid-18th century onward the slave trade to the Indian and Atlantic Oceans became increasingly important, with different impacts in the respective regions. Modern Portuguese colonialism was established by means of military campaigns: having limited capital, Portugal granted concessions for part of the territory to companies. When these concessions ended in 1942, the colonial state developed a direct administration throughout the territory, headquartered in Lourenço Marques (Maputo). Nationalist ideals developed during the 1950s among various movements, of which three organizations united to form the Mozambique Liberation Front (FRELIMO) in 1962. From 1964 onward, FRELIMO unleashed an anticolonial war in northern and central Mozambique. After the 1974 revolution in Portugal, negotiations resulted in the recognition of Mozambique’s independence on June 25, 1975, and a FRELIMO government. Armed opposition to the Marxist-Leninist government and the civil war continued until 1992. During the 1990s, Mozambique adopted a multiparty system and liberalized its economy.