Ocean Passages Research Articles

Prepaid tickets to the New World: the New York Continental Conference and transatlantic steerage Fares 1885–1895

RESUMENEste artículo examina la situación de los cárteles del transporte naviero (conferencias) que regularon el transporte migratorio transatlántico del continente europeo a los Estados Unidos. El objetivo del artículo es identificar las presiones internas y externas subyacentes a estos acuerdos, así como las estrategias empleadas para neutralizar estas presiones. El autor llega a la conclusión de que un acuerdo sobre la división del mercado en quatos (market shares) era esencial para la eficacia de la Conferencia, que era al mismo tiempo una forma de integración horizontal que regulaban la competencia entre las compañías de transporte naviero, así como una integración vertical para obtener el control sobre la red de agentes transatlánticos de venta de billetes a la emigración. El autor correlaciona también la eficacia de los acuerdos con las tarifas para emigrantes y los costes de la migración.

Responses of algal communities to gradients in herbivore biomass and water quality in Marovo Lagoon, Solomon Islands

Settlement tiles were used to characterise and quantify coral reef associated algal communities along water quality and herbivory gradients from terrestrial influenced near shore sites to oceanic passage sites in Marovo Lagoon, the Solomon Islands. After 6 months, settlement tile communities from inshore reefs were dominated by high biomass algal turfs (filamentous algae and cyanobacteria) whereas tiles located on offshore reefs were characterised by a mixed low biomass community of calcareous crustose algae, fleshy crustose algae and bare tile. The exclusion of macrograzers, via caging of tiles, on the outer reef sites resulted in the development of an algal turf community similar to that observed on inshore reefs. Caging on the inshore reef tiles had a limited impact on community composition or biomass. Water quality and herbivorous fish biomass were quantified at each site to elucidate factors that might influence algal community structure across the lagoon. Herbivore biomass was the dominant driver of algal community structure. Algal biomass on the other hand was controlled by both herbivory and water quality (particularly dissolved nutrients). This study demonstrates that algal communities on settlement tiles are an indicator capable of integrating the impacts of water quality and herbivory over a small spatial scale (kilometres) and short temporal scale (months), where other environmental drivers (current, light, regional variability) are constant.

Effect of ocean gateways on the global ocean circulation in the late Oligocene and early Miocene

We investigate the effect of changes in the tectonic boundary conditions on global ocean circulation patterns. Using a fully coupled climate model in an idealized setup, we compare situations corresponding to the late Oligocene, the early Miocene, and present day. The model results show the existence of a flow reversal through the Panama Seaway between the Oligocene and Miocene. This flow reversal is induced by global tectonic changes related to the widening of the Southern Ocean passages and the closing of the Tethys Seaway. It mainly involves the wind‐driven ocean circulation, in agreement with previous model studies. The global thermohaline circulation in the Oligocene and Miocene simulations is significantly different from the present‐day conveyor circulation, as there is deepwater formation in both the North Atlantic and the North Pacific oceans. In particular, in the Oligocene simulation the salinity contrast between the Atlantic and Pacific oceans is reduced because of water mass exchange through the low‐latitude connections between the two oceans.

Diapycnal mixing associated with an overflow in a deep submarine canyon

Abstract In order to close the global overturning circulation the buoyancy loss to the atmosphere associated with the formation of deep and bottom water at high latitudes must be balanced by buoyancy gain elsewhere. In case of water that is not in contact with the atmosphere except in its formation region the required buoyancy gain is accomplished primarily by diapycnal mixing. Recent observations suggest that a significant portion of the diapycnal buoyancy fluxes in the abyss is associated with overflows in submarine valleys or canyons, especially on the flanks of slow-spreading mid-ocean ridges. In the present study, hydrographic and velocity data from an overflow across a sill rising 1000 m above the floor of the rift valley of the Mid-Atlantic Ridge near 36°N were used to infer the associated diapycnal mixing. The cross-sill density gradients are characterized by a vertical dipole, with an upper layer of streamwise density increase overlying a lower layer where the density decreases along the flow. This is qualitatively consistent with the effects of diapycnal mixing transferring buoyancy from the upper into the lower layer. Hydrographic and velocity profiles provide evidence for strong mixing associated with the overflow across the sill: in addition to thick layers that are susceptible to shear instability, there are numerous density overturns indicating a spatially averaged diffusivity of order 10 - 2 m 2 s - 1 . Inversions of the density equation reveal that the cross-sill gradients can be accounted for either by adiabatic vertical advection or by vertical eddy diffusion, although the adiabatic solutions are considered energetically implausible because they require upwelling in the layer of cross-sill density increase. Eddy-diffusive solutions, both with and without adiabatic downwelling, are characterized by diffusivity profiles attaining local maxima of order 10 - 2 m 2 s - 1 ≈ 250 m above the sill depth. The vertical structure of the inversion-derived diffusivities is consistent with the Thorpe-scale based estimates and with observations from overflows in major ocean passages, which also are often characterized by local diffusivity maxima of order 10 - 2 m 2 s - 1 a few 100 m above sill depth. Combining the diffusivity profiles near the sill with budget-derived bulk estimates for 150 km of rift valley implies that ≈ 50 % of the mixing in the rift valley is associated with overflows, while the remainder is caused by other processes, including the breaking of tidally forced internal waves.

Effect of potential vorticity on flow rate through a gap

Mathematical solutions for constant potential vorticity critically controlled flow through ocean passages are complicated and not available in simple form. Therefore, to provide formulas for numerical circulation and ocean climate models, two simple formulas for volume flux are developed here. They are fitted to numerical values of the critical flux for constant potential vorticity flow over a flat bottom through a constriction. The two formulas of increasing complexity agree with the numerical values to better than 6% and 1.4%. These flux values are up to 24% less than the values of flux from zero potential vorticity formulas presently applied to ocean passages. The most precise new formula is used to predict flux magnitude through nine ocean passages that have current meter measurements. The size of the revisions compared to zero potential vorticity predictions is a few percent in the direction of better agreement. For further improvement between prediction and observation, other factors such as realistic bottom topography, friction, mixing, waves, and eddies must be included.

Westerly wind events and precipitation in the eastern Indian Ocean as predictors for El Niño: Climatology and case study for the 2002–2003 El Niño

This study expands on recent work linking intraseasonal‐to‐seasonal variability in observed precipitation and wind from September to March in the eastern Indian Ocean with the initiation of El Niño events during the last 25 years. First, westerly wind burst (WWB) events are defined as days when westerly wind speeds averaged over 5°–15°S and 70°–100°E were greater than 1.5 standard deviations from the mean. The number of WWB days from September to March was high before the onset of the 1982–1983, 1991–1992, 1997–1998, and 2002–2003 El Niño events, but not the 1986–1987 El Niño. This study suggests that for the 1979–2002 period, variations in precipitation in the eastern Indian Ocean is a more robust predictor of El Niño onset than analyzed winds. On the basis of the work of Curtis et al. [2002], a real‐time precipitation‐based El Niño Onset Index is presented, which during the austral summer of 2001–2002 successfully predicted the 2002–2003 El Niño. The index focuses on the magnitude of 30–60 day oscillations and mean conditions in the precipitation field. Case studies of high‐resolution satellite‐based data sets of precipitation, wind, and sea surface temperature (SST) for the 2001–2002 season are examined to better understand how events in the Indian Ocean are linked to Pacific Ocean wind disturbances and SST changes. Twice during this season maxima in precipitation and zonal winds propagated eastward, the first near the equator and the second to the south. For the southern case, warm waters preceded heavy precipitation in the eastern Indian Ocean, which preceded strong westerly winds. A cooling of the sea surface followed the wind‐rain system. This sequence of events moved through the ocean passage between Indonesia and Australia, suggesting a coupling of convection, wind, and sea surface temperatures on the timescale of days. These case studies provide a basis for how the east Indian Ocean variations are linked to subsequent events in the Pacific Ocean, including the initiation of El Niño events.

Mid-depth calcareous contourites in the latest Cretaceous of Caravaca (Subbetic Zone, SE Spain). Origin and palaeohydrological significance

Deep marine carbonates of Late Campanian to Early Maastrichtian age that crop out in the Subbetic Zone near Caravaca (SE Spain) contain a thick succession of dm-scale levels of calcareous contourites, alternating with fine-grained pelagites/hemipelagites. These contourites, characterised by an abundance and variety of traction structures, internal erosive surfaces and inverse and normal grading at various scales, were interpreted as having been deposited under the influence of relatively deep ocean currents. Based on these contourites, a new facies model is proposed.The subsurface currents that generated the contourites of Caravaca were probably related to the broad circumglobal, equatorial current system, the strongest oceanic feature of Cretaceous times. These deposits were formed in the mid-depth (200–600 m), hemipelagic environments at the ancient southern margin of Iberia. This palaeogeographic setting was susceptible to the effects of these currents because of its position close to the narrowest oceanic passage, through which the broad equatorial current system flowed in the westernmost area of the Tethys Seaway. Regional uplift, related to the onset of convergence between Iberia and Africa, probably favoured the generation of the contourites during the Late Campanian to the Early Maastrichtian.

THE HISTORICAL BIOGEOGRAPHY OF TWO CARIBBEAN BUTTERFLIES (LEPIDOPTERA: HELICONIIDAE) AS INFERRED FROM GENETIC VARIATION AT MULTIPLE LOCI

Mitochondrial DNA and allozyme variation was examined in populations of two Neotropical butterflies, Heliconius charithonia and Dryas iulia. On the mainland, both species showed evidence of considerable gene flow over huge distances. The island populations, however, revealed significant genetic divergence across some, but not all, ocean passages. Despite the phylogenetic relatedness and broadly similar ecologies of these two butterflies, their intraspecific biogeography clearly differed. Phylogenetic analyses of mitochondrial DNA sequences revealed that populations of D. iulia north of St. Vincent are monophyletic and were probably derived from South America. By contrast, the Jamaican subspecies of H. charithonia rendered West Indian H. charithonia polyphyletic with respect to the mainland populations; thus, H. charithonia seems to have colonized the Greater Antilles on at least two separate occasions from Central America. Colonization velocity does not correlate with subsequent levels of gene flow in either species. Even where range expansion seems to have been instantaneous on a geological timescale, significant allele frequency differences at allozyme loci demonstrate that gene flow is severely curtailed across narrow ocean passages. Stochastic extinction, rapid (re)colonization, but low gene flow probably explain why, in the same species, some islands support genetically distinct and nonexpanding populations, while nearby a single lineage is distributed across several islands. Despite the differences, some common biogeographic patterns were evident between these butterflies and other West Indian taxa; such congruence suggests that intraspecific evolution in the West Indies has been somewhat constrained by earth history events, such as changes in sea level.

THE HISTORICAL BIOGEOGRAPHY OF TWO CARIBBEAN BUTTERFLIES (LEPIDOPTERA: HELICONIIDAE) AS INFERRED FROM GENETIC VARIATION AT MULTIPLE LOCI

Mitochondrial DNA and allozyme variation was examined in populations of two Neotropical butterflies, Heliconius charithonia and Dryas iulia. On the mainland, both species showed evidence of considerable gene flow over huge distances. The island populations, however, revealed significant genetic divergence across some, but not all, ocean passages. Despite the phylogenetic relatedness and broadly similar ecologies of these two butterflies, their intraspecific biogeography clearly differed. Phylogenetic analyses of mitochondrial DNA sequences revealed that populations of D. iulia north of St. Vincent are monophyletic and were probably derived from South America. By contrast, the Jamaican subspecies of H. charithonia rendered West Indian H. charithonia polyphyletic with respect to the mainland populations; thus, H. charithonia seems to have colonized the Greater Antilles on at least two separate occasions from Central America. Colonization velocity does not correlate with subsequent levels of gene flow in either species. Even where range expansion seems to have been instantaneous on a geological timescale, significant allele frequency differences at allozyme loci demonstrate that gene flow is severely curtailed across narrow ocean passages. Stochastic extinction, rapid (re)colonization, but low gene flow probably explain why, in the same species, some islands support genetically distinct and nonexpanding populations, while nearby a single lineage is distributed across several islands. Despite the differences, some common biogeographic patterns were evident between these butterflies and other West Indian taxa; such congruence suggests that intraspecific evolution in the West Indies has been somewhat constrained by earth history events, such as changes in sea level.Corresponding Editor: S. Karl

The Ordovician Sebree Trough: An oceanic passage to the Midcontinent United States

The Sebree Trough is a relatively narrow, shale-filled sedimentary feature extending for several hundred kilometers across the Middle and Late Ordovician carbonate platform of the Midcontinent United States. The dark graptolitic shales within the trough stand in contrast to the coeval bryozoan-brachiopod-echinoderm– rich limestones on the flanking platforms. We infer from regional stratal patterns, thickness and facies trends, and temporal relations established by biostratigraphy and K-bentonite stratigraphy that the Sebree Trough initially began to develop during late Turinian to early Chatfieldian time (Mohawkian Series) as a linear bathymetric depression situated over the failed late Precambrian–Early Cambrian Reelfoot Rift. Rising sea level and positioning of a subtropical convergence zone along the southern margin of Laurentia caused the rift depression to descend into cool, oxygen-poor, phosphate-rich oceanic waters that entered the southern reaches of the rift from the Iapetus Ocean. The trough apparently formed in a system of epicontinental estuarine circulation marked by a density- stratified water column. Trough formation was accompanied by cessation of carbonate sedimentation, deposition of graptolitic shales, development of hardground omission surfaces, substrate erosion, and local phosphogenesis. The carbonate platforms on either side of the trough are dominated by bryozoan-brachiopod- echinoderm grainstones and packstones that were deposited in zones of mixing where cool, nutrient-rich waters encountered warmer shelf waters. Concurrently, lime mudstone and wackestone were deposited shoreward (northern Illinois, Wisconsin, Iowa, Minnesota, Michigan) in warmer, more tropical shallow seas. Coeval upward growth of the flanking carbonate platforms sustained and enhanced development of the trough shale facies. Five widespread diachronous late Mohawkian and Cincinnatian omission surfaces are present in the carbonate facies of the Midcontinent. These surfaces include sub-Deicke K-bentonite, DS1; top of Black River Limestone, DS2; base and top of the Guttenberg Limestone Member of the Decorah Formation, DS3 and DS4; and top of the Trenton Limestone, DS5. Some of the surfaces correspond to previously described depositional sequence boundaries. All five surfaces, which embody deepening phases on top of highstand-systems tracts, converge in the Sebree Trough, indicating that the trough was a long-lived feature and was the source of eutrophic waters that episodically spread across the adjacent platforms, terminating carbonate production. Late Turinian and early Chatfieldian incipient drowning episodes were followed by a final drowning event that began in the Sebree Trough during the late Chatfieldian ( Climacograptus spiniferus Zone) and reached southernmost Minnesota and other regions far within the platform interior by Richmondian time ( Amorphognathus ordovicicus Zone).

Size-fractionated biomass and productivity of phytoplankton and particulate organic carbon in the Southern Ocean

During the austral summer of 1989/1990, surface samples were obtained of size-fractionated biomass, and the productivity of phytoplankton, its cell abund ance, the composition of the dominant species, the concentration of particulate organic carbon (POC) and the related environmental surface parameters were measured in a large-scale survey primarily of the Atlantic and Indian Sectors. The results showed that the southern atlantic sector is the most fertile; chlorophylla (Chl a) concentration averaged over 2 μg l−1, average cell abundance was about 41.0×103 cell l−1, and average POC concentration was also the highest (> 100 μg l−1), but was lower in the Drake Passage and the southern Indian sector. The results for size fractionated Chla showed that netplankton (> 20μm) in the South Atlantic Ocean, having abundant nutrients, accounted for the highest proportion (average 65%) of biomass. In the infertile South Indian Ocean, picoplankton (< 2 μm) accounted for the highest proportion, averaging 47%. The results for size-fractionated productivity showed that the contribution of picoplankton to total productivity was the largest in the South Atlantic Ocean and Drake Passage, those of nanoplankton (2–20 μm) and netplankton being about equal. The relatively high photosynthesis assimilation number of picoplankton demonstrates their importance in the marine ecosystems of Antarctic water. In comparison with the Antarctic water, the subantarctic and subtropical waters are infertile.

European Women and the Second British Empire. Margaret Strobel

Previous articleNext article No AccessBook ReviewsEuropean Women and the Second British Empire. Margaret Strobel Susan GeigerSusan Geiger Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Modern History Volume 66, Number 1Mar., 1994 Article DOIhttps://doi.org/10.1086/244795 Views: 11Total views on this site Citations: 1Citations are reported from Crossref Copyright 1994 The University of ChicagoPDF download Crossref reports the following articles citing this article:Ayodeji Olukoju “The service had to come first”: leave and ocean passages of British officials and their dependants in inter-war West Africa, Canadian Journal of African Studies / Revue canadienne des études africaines 54, no.33 (Feb 2020): 541–556.https://doi.org/10.1080/00083968.2020.1717563

Towards Global Marine Traffic Control — the Need, the Technical Feasibility and the Social and Political Impediments

1. Introduction. Active MTC (Marine Traffic Control), in its various forms, is at present mainly confined to port areas and canals and their approaches, whereas all other areas are mainly subject to passive MTC measures; that is, the Collision Regulations, including traffic separation schemes, areas to be avoided by certain classes of vessels, deep water routes, etc. The Collision Regulations, however, despite many attempts to improve them, are fundamentally flawed by specious logic sanctioned, unfortunately, by legislation which is supported in turn by the well-meaning connivance of the courts. This paper highlights some of the insoluble problems of the Collision Regulations and looks at the planning of ocean passages, weather routeing, search and rescue, and fishery protection; and shows that there is already a measure of active MTC in these areas of activity. The future possibility of a comprehensive global active MTC system to deal with avoidance of collisions and strandings, in addition to those other activities, is considered with respect to technical feasibility and to social and political impediments.

Geographical Variations in Precipitation Yields and Circulation Types in Britain and Ireland

The geographical distribution of daily precipitation with each of the Lamb-classification circulation types is examined for 65 locations in Britain and Ireland. Substantial differences in spatial receipt are related to exposure at the location concerned and length of ocean passage for the air mass involved. Airflow contrasts occurring at regional scales are also instrumental in producing geographical variability in receipt. Cyclonic south westerlies are identified as the most prolific precipitation-producing synoptic type for the area as a whole, while anticyclonic northerlies and north easterlies are the driest. Changes in the frequency of the 27 categories identified by Lamb are then examined over 130 years of record. A significant change in the make-up of the synoptic circulation is seen to have occurred in recent decades. Declining westerlies and increasing cyclonic and anticyclonic airflows are suggested as being primarily responsible for recent changes in precipitation geography. Future precipitation will be determined partly by such changes in airflow types.

Internal hydraulic control in rotating fluids—applications to oceans

Abstract Laboratory experiments and analysis of shallow water equations in a rotating fluid show that channel flow is governed by the ratio of the width of the channel to the Rossby radius of deformation R= √[gΔρH/ρf 2]. Flows through narrow ocean openings exhibit blocking and clear evidence of hydraulic control. These imply that formulae can be derived for width, volume flux, and velocity scales of the currents. A new version of the constant potential vorticity problem is solved, and it is shown to predict volume flux within 22% of the zero potential vorticity results. Next a systematic method of predicting volume flux through ocean passages is described. Some examples are given from the Denmark Straits overflow and the flow of Antarctic Bottom Water into the western Atlantic Ocean. Two-layer flows and counter-flows with rotation in a narrow passage, the so-called lock exchange flow problem, duplicate flows at a number of important straits and openings to bays. A potential vorticity formulation is ...

The Early History of Great Circle Sailing

The least spherical distance between two points on the surface of a sphere is that along the minor arc of the great circle on which the two points lie. It is an easy matter to demonstrate this using a cord stretched between two points on a small globe; noting that the circle whose plane coincides with that of the cord contains the centre of the sphere and that it is, therefore, a great circle. It is a little more difficult to prove the fact analytically. The practice of sailing along the shortest route on an ocean passage—sometimes known as ‘orthodromic’ as opposed to rhumbline or ‘loxodromic’ sailing—would require the course to be continually changed (except, of course, in cases in which the rhumb-line and great circle arc coincide). This would clearly be impossible; the term ‘approximate great circle sailing’ is sometimes used to describe the techniques of following a great circle route as closely as practicable.

Transmission of microseisms across North America and the western North Atlantic

A comparison of microseisms recorded at Bermuda and North American stations indicates that the North Atlantic between the continent and Bermuda has a relatively high absorption rate for microseisms having periods of ten seconds or less. If the source area is on the margin of the continent and the period on the continent is 6.5 to nine seconds, energy absorption over a 1000‐km oceanic path is probably at least an order greater than over an equal continental path, and absorption rates of the longer periods are relatively less. The oceanic passage is accompanied by a slight increase in period. All four‐ to five‐second microseisms recognizable on the Bermuda Milne‐Shaw records are believed to have local sources.

Excursion to International Medical Congress.

St. Joseph, Mo., Sept. 23, 1902. <h3>To the Editor:</h3> —I have just made arrangements for conducting a party to Madrid to the International Medical Congress at the expense of $265.00 minimum. The trip can be made in a little over four weeks. This amount will cover all expenses, including first-class ocean passage each way, first-class railway travel, hotel accommodations for fourteen days in Spain, all transfers of baggage, several days sight seeing in Madrid, all fees for hotel service, etc., including the services of a first-class conductor and interpreter. Side trips, of course, can be taken, and the stay extended indefinitely by those who wish to remain longer in foreign countries. The trip will be a most enjoyable one at that season of the year, going and coming via Gibraltar. If you will kindly call attention to this matter in your columns, I shall be under many obligations, stating that