Ocean Upwelling Research Articles

Effects of Streamflow and Upwelling on Yield of Wild Coho Salmon (Oncorhynchus kisutch) in Oregon

To investigate the dependence of coho salmon (Oncorhynchus kisutch) yield on streamflow and oceanic upwelling, I regressed catch by the Oregon commercial troll fishery from 1942 to 1962 against indices of offshore upwelling the previous spring and measurements of streamflow from five Oregon coastal rivers during the freshwater rearing phase. A highly significant positive relation was found between total streamflows during the freshwater residency of the fish for the five rivers combined and the weight of the annual catch of coho salmon from 1942 to 1962. There was also a significant positive relation between total combined annual (January–December) flows for these rivers and the catch 2 yr later. Conversely, I found no significant relation between the 60 consecutive days of lowest flow during summer and catch 2 yr later. High flows during freshwater rearing probably provide more habitat and better conditions for growth and survival. I also found a significant positive relation between April through June upwelling at two stations and catch of coho salmon the following year from 1947 to 1962. Fifty-six percent of the variation in catch from 1947 to 1962 was explained by the total flows during freshwater residency, 60 consecutive days of lowest flow, plus combined April through June upwelling at both stations. It is suggested that some stocks of coho salmon smolts may move southward or remain in local offshore waters after they enter the ocean to take advantage of the production of invertebrates resulting from upwelling.Key words: streamflow, upwelling, coho salmon, Oregon coast

Modeling sound propagation through a coastal ocean upwelling

Coastal ocean upwellings occur throughout the world's seas; many are regions of high marine productivity. Two factors associated with these features could significantly effect sound propagation: Abrupt temperature changes and a sloping topography. An analysis is made utilizing a range dependent propagation model and environmental data from upwelling areas off the coast of California and Brazil. The effect on sound propagation is compared with adjacent open ocean conditions for various source and receiver depths over a frequency range of 10–5000 Hz.

A Numerical Study of Tropical Large-Scale Air-Sea Interaction

Abstract In a series of numerical experiments using a simplified, domain-averaged, coupled air-sea model, some aspects of the low-latitude large-scale interaction between the atmosphere and the ocean are investigated. Experiments are designed with a view toward elucidating basic mechanisms involved in the coupled processes. In this paper, we focus on the response of coupled system to 1) steady forcing, 2) seasonal variations and 3) large perturbations and continuous short-period random forcings. Results indicated that the sea surface temperature (SST) distribution, which is strongly controlled by the oceanic upwelling, is the primary factor in determining the location and transition of the tropical rainbelt. The strongest convective activities in the ITCZ, however, depend mainly on the moisture supply from horizontal convergence and the static stability of lower atmosphere, and do not necessarily coincide with the occurrence of maximum SST. It is also demonstrated that the positive feedback processes betw...

A contribution to the dynamic climatology of Arabia

Maps and transects are presented for January, April, July, and October. The uppertropospheric wind regime is dominated by Westerlies during winter, and the Tropical Easterly Jet in summer; seasonal reversals being related to the meridional gradient in the tropospheric thickness pattern. The relation between the kinematics of flow and the surface climate is most readily apparent during the extreme seasons. In winter, winds from northerly directions prevail over the Arabian Peninsula. Highest speeds are found in the Northeast monsoon flow over the open Arabian Sea. A confluence zone between winds from westerly and northerly directions extends from Ethiopia to the Southern part of the Red Sea, broadly coincident with a band of convergence. Cloudiness and sea surface temperature decrease from the equatorial seas northward. In summer a prominent core of maximum speed is found within the Southwest monsoon over the Western Arabian Sea. Divergence prevails upstream and convergence downstream from this speed maximum. Marked cyclonic vorticity is characteristic for the area to the left of the high speed core, that is along the Southeast coast of Arabia. The concomitant positive curl of wind stress is conducive to oceanic upwelling and cold coastal waters. Concurrently, the increase of surface friction from the open sea to the continent, that is towards the left of the flow core, favors atmospheric subsidence along the Southeast coast of Arabia. The gradient of cloudiness across the coast is also particularly steep in summer. The relative abundance of rainfall along the coasts of the Southern Red Sea seems at least in part to be related to the presence of a confluence zone during much of the year.

Meristic Variation of Lycodapus mandibularis (Pisces: Zoarcidae) and Oceanic Upwelling on the West Coast of North America

Total vertebral counts of Lycodapus mandibularis populations in Georgia Strait, British Columbia, are significantly lower than those of southern populations off Oregon and California. The highest temperatures and lowest salinities at 200 m or deeper, where the species is most abundant, are also in Georgia Strait and correlate with the lowest counts. The Strait's deep water originates from tidal mixing of intermediate and estuarine surface waters of lower salinities and higher temperatures, whereas the mechanism in southern latitudes, which instead provides unmixed cooler and saline deep waters, is oceanic up-welling. It is suggested that differences in environment associated with different degrees of upwelling and mixing may cause the lower counts in the Strait of Georgia. Key words: Lycodapus mandibularis, Zoarcidae, meristic variation, inlets, upwelling, temperature, salinity, northeast Pacific Ocean, zoogeography

The development of planktonic biogeography in the Southern Ocean during the Cenozoic

The development of planktonic biogeography in the Southern Ocean during the Cenozoic

Experiment with a Simple Ocean-Atmosphere Climate Model: The Role of the Ocean in the Global Climate

A study of the seasonal variation of the climatic states of the atmosphere and the ocean is made using a coupled atmosphere-ocean model. The “domain-averaged” nature of the model enables the inclusion of effects due to continent-ocean-ice distribution in a quasi-two-dimensional framework. While the atmosphere is described by simplified “domain-average” primitive equations, the ocean is represented as simple advective mixed layer. Large-scale circulation and upwelling in the ocean are modeled in terms of a wind-driven and a thermally driven component. Integration is carried out for the coupled model until a repeatable annual cycle is observed in the mean climatic states. Results of the experiment show that large differences in the time scale and amplitude of the response exist between the land and ocean domains. Features of the mean atmospheric circulation such as the Hadley cell, the Ferrel cell, tropical easterly jet and monsoon transition are well simulated. In the model ocean the domain-averaged spatial and temporal response of sea surface temperature and mixed layer depth are simulated fairly realistically. The large-scale circulation in the ocean shows some interesting features such as the gyre circulation, the western boundary transports, and a decrease in sea surface temperature in eastern and equatorial oceans as a result of oceanic upwelling. In the overall heat budget of the combined system, the ocean is found to dominate in energy storage. Between 20 and 30°S, the maximum oceanic poleward heat transport is computed in February and March and is as large as or larger than the corresponding atmospheric heat transport at the same latitudes.

Uranium-series disequilibrium studies in phosphorite nodules from the west coast of South America

Sedimentary phosphorites occurring on the sea floor off Peru and Chile have been analyzed for U and Th isotopes, to establish their ages and hence obtain clues for their mode of formation. Fission-track distribution studies indicate that the U is primarily associated with the apatite fraction. Uranium-series disequilibrium methods, therefore, should be applicable, if the U incorporation is syngenetic with the apatite. The fractionation of U isotopes between oxidation states in the relatively young phosphorites from South America is low compared to that in older deposits. This supports the contention of Kolodny and Kaplan (1970) that the major mechanism of 234U 238U fractionation is displacement of 234U atoms into sites where they are more ‘oxidizable’ than the 238U parent. Age estimates based on 234U(IV) and 230Th contents are internally consistent and range from late Pleistocene to Recent. The results indicate that marine phosphorites are currently forming in this area of intense oceanic upwelling. The age pattern during the last 150,000 yr suggests a correlation with eustatic high sea level stands and implies that conditions were more favorable for apatite genesis in this area during interglacials rather than during glacial times.

Geographical Coincidence of High Heat Flow, High Seismicity, and Upwelling, with Hydrocarbon Deposits, Phosphorites, Evaporites, and Uranium Ores

Oil deposits occur in deep sediments, and appear to be organic matter that has been transformed through the action of geothermal heat and pressure. Deep sediments, rich in biological remains, are created by ocean upwelling, caused in part by high geothermal heat flow through the sea bottom. Such regions correlate with enhanced seismic activity. We look for correlations of seismicity, high heat flux, petroleum, uranium, phosphates, and salts, deposited from abundant plant life. These may be useful in discovering more petroleum and coal. We estimate that the known world reserves of petroleum and coal are about 10(-4) of the total of buried biogenic carbon.

A note on the origin of Mussoorie phosphorite in the Lower Himalaya, India, and its palaeogeographic implications

An indirect role of organisms whose productivity was supported during the oceanic upwelling is recognised for the deposition of the Mussoorie phosphorites which are associated with black-shale-chert-carbonate-pyrite facies in the Lower Himalaya. The lithological gradation and textural variation of these sediments are described. Bone and teeth beds or rich fossiliferous beds are absent within these sediments forming the base of the Tal Formation. This occurrence of phosphorites is already within the 40 parallel and therefore still warmer palaeolatitudes are not considered to be necessary. However, if the Lower Himalayan region drifted northwards as a part of the Indian Shield, the post-Cambrian Lower Himalayan rocks may also represent sediments of the Tethys sea. Contrary to the current practice, the southern limit of the Tethys may have to be moved still southwards from “the line of high snow peaks” to a lithologically better defined zone, i.e. the northern fringes of the Indian Shield. The criteria speaking for this opinion are presented.

Upwelling and Coastal Jets in a Continuously Stratified Ocean

A simple, linear, two-dimensional, f-plane model of coastal upwelling in a continuously stratified ocean is investigated. The transient response of the fluid to an impulsively applied alongshore wind stress, the nature of the approach to a steady state, and the final steady state flow are studied. Particular attention is given here to an examination, in the continuously stratified case, of the interrelation of upwelling and the phenomenon of a baroclinic coastal jet. The coastal jet is a feature which has appeared in studies of the transient response of two-layer fluid models near a coast. The stratification parameter S = (δN/f)2, where δ = II/L is the aspect ratio, H the depth, L a characteristic horizontal scale, N the Brunt-Väisälä frequency, and f the Coriolis parameter, is assumed to lie in the range O(Ev½)<S≤O(1), where λ = Ev/EH and where EH and Ev are respectively the horizontal and vertical Ekman numbers. It is also assumed that L is large enough that S≪1 and λ≫1. These are the conditions for which, during the transient flow, a baroclinc coastal jet is present in an inviscid upwelling layer of width O(S½). It also appears that these conditions are reasonable for oceanic upwelling regions. The jet development is initiated on a time scale of O(Ev−½). A steady state is reached in the O(S½) upwelling layer on a longer diffusive time scale of O(SEH−1). For Sλ<O(1), the alongshore current outside the O(S½) layer increases in magnitude with time, by diffusive spreading of the boundary effects, in an additional boundary layer of width O(λ−½). It reaches a steady state on a yet longer time scale of O(Ev−1). For Sλ = O(1), the two boundary layers merge and adjust on the same time scale. The final steady state is characterized by a coastal current which is confined to the O(S½) and O(λ−½) boundary layers.

Minor Metal Contents of Recent Organic-rich Sediments off South West Africa

BRONGERSMA-SAUNDERS has recently proposed1,2 that the extreme metal enrichment of many bituminous shales is brought about by the supply of metals by plankton in areas of oceanic upwelling. This model has been applied1,2 to the well known Permian Kupferschiefer of northern Germany, where the concentrations of Cu, Pb and Zn are exceptionally high3. A modern environment of organic-rich sedimentation with metal enrichment is supposedly found on the continental shelf off South West Africa2, especially the region in and around Walvis Bay. The area lies beneath the Benguela Current, a site of intensive upwelling4 and very high primary organic production5. Information on the bottom sediments accumulating here is meagre, although they are known to be organic and sulphide-rich6–8.

Primary production, isotopes, extinctions and the atmosphere

Phytoplankton photosynthesis has controlled the atmospheric carbon dioxide-oxygen balance since the early Precambrian when algal abundance became sufficient to convert the reducing atmosphere to an oxygenic one. Later phytoplankton maxima indicated in the geologic record coincide with and are here suggested to have caused extensive biogenic calcareous deposition, and evolutionary diversification of the contemporaneous biota. In contrast, the onset of decreased productivity in the geologic past triggered a general biotic turnover on both land and sea. Times of phytoplankton extinctions coincide with similar periods affecting animal taxa rather than terrestrial plants. These periods of severely reduced microfloras and low productivity resulted in atmospheric oxygen depletion and increased pCO 2, 12C enriched limestones, formation of 32S enriched sulfates, and submarine dissolution of carbonates. Selective extinctions of animal taxa were due to quantitative variations in the interrelated processes of carbon fixation (the food source for the marine environment), and the photosynthetic consumption of carbon dioxide and production of oxygen. The phytoplankton abundance may have been controlled by contemporaneous continental physiography, through its effect on climate, atmospheric circulation and oceanic upwelling. Low continents, equable climates, little influx of land-derived materials and lessened effectiveness of upwelling allowed the sinking of nutrients to exceed their renewal, resulting in marked reduction of phytoplankton, with the attendant effects of the decreased productivity and oxygen depletion crossing ecologic and systematic boundaries. Continental rejuvenation with resultant climatic changes and increased oceanic circulation stimulated renewed phytoplankton diversification and growth, and allowed a renewed expansion of dependent animal taxa.