Wind-driven Surface Currents Research Articles

The Pelagic Phase of Spiny Lobster Development

A reappraisal of the pelagic phase of development in palinurid lobsters, in conjunction with recent oceanographic data, shows that the ontogenetic changes in the vertical migratory behaviour of phyllosoma larvae operate as a biological strategy to effect larval recruitment. Wind-driven surface currents can transport the larvae in the opposite direction to the general circulation of the upper 300 m water layer. Ocean circulation charts are unreliable indicators of likely paths of larval transport because of their gross scale, lack of seasonal information, and the absence of indications of wind-driven surface currents. The majority of larvae are transported beyond the continental shelf to areas greater than 100 km offshore. This appears to be the principal source of larval recruitment to benthic populations, although some local recruitment from coastal areas may occur. Larval transport between populations of Jasus sp. in the Southern Ocean appears likely but is unconfirmed. For some insular populations this may be the sole, or major, source of recruitment. Delayed development of phyllosomata, or of pueruli, may account for year-round settlement in some species. Salinity changes are implicated as a factor stimulating metamorphosis from the final phyllosoma larval stage. The pelagic phase is completed by the nektonic, puerulus stage which swims (possibly directionally) across the continental shelf before settling and metamorphosing into the benthic stage.

Deep-sea erosional unconformity in the southeastern Gulf of Mexico

Multichannel seismic data and Deep Sea Drilling Project (DSDP) well information reveal a prominent erosional unconformity in the deep southeastern Gulf of Mexico. Corresponding to a 44 to 38.5 m.y. B.P. hiatus (middle to late Eocene) at DSDP site 540 (Leg 77), the unconformity was apparently produced by the bottom effects of wind-driven surface currents (paleo-Florida Current) and gravitational mass movements capable of scouring the slope. Intensification of these sedimentary processes may have been related to global cooling and a reported drop in sea level in the late Eocene, but it may also have been part of a complex global response to a postulated Paleogene meteorite impact.

Dispersal and deposition of eolian and fluvial sediments off Peru and northern Chile

Research Article| February 01, 1982 Dispersal and deposition of eolian and fluvial sediments off Peru and northern Chile KENNETH F. SCHEIDEGGER; KENNETH F. SCHEIDEGGER 1School of Oceanography, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar LAWRENCE A. KRISSEK LAWRENCE A. KRISSEK 1School of Oceanography, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar Author and Article Information KENNETH F. SCHEIDEGGER 1School of Oceanography, Oregon State University, Corvallis, Oregon 97331 LAWRENCE A. KRISSEK 1School of Oceanography, Oregon State University, Corvallis, Oregon 97331 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1982) 93 (2): 150–162. https://doi.org/10.1130/0016-7606(1982)93<150:DADOEA>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation KENNETH F. SCHEIDEGGER, LAWRENCE A. KRISSEK; Dispersal and deposition of eolian and fluvial sediments off Peru and northern Chile. GSA Bulletin 1982;; 93 (2): 150–162. doi: https://doi.org/10.1130/0016-7606(1982)93<150:DADOEA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Relative abundances of quartz and feldspar in fine-grained terrigenous sediments have been used to recognize specific continental sediment sources along northwestern South America and to trace the dispersal of specific grain size fractions from these sources to adjacent continental margin and deep-sea sedimentary environments. Quartz/feldspar ratios are low (∼0.6) for all fractions of sediments derived from southern Peru and northern Chile, but such ratios increase systematically in central and northern Peru as the importance of granitic and related intrusives increases relative to more basaltic extrusives and gabbroic equivalents. Limited published analyses of dusts collected offshore (Prospero and Bonatti, 1969) are also consistent with a latitudinally varying continental sediment source. We find that clay (<4 µm) and fine silt (8–11 µm) dispersal patterns are coincident with offshore wind-driven surface currents, whereas nearly all coarser sedimentary components (32–62 µm particles) exhibit limited dispersal normal to the shoreline on the continental margin. Because of the coincidence of wind and surface current patterns, transport of clay and fine silt away from the South American continent could be caused by either mechanism. However, on crossing to the seaward side of the Peru-Chile Trench, sedimentation rates decrease dramatically, silt/clay ratios are higher than expected, and clay mineral assemblages change abruptly. We argue that the trench is an imposing physiographic barrier to the seaward near-bottom advection of suspended particulates, thereby limiting the major influence of hemipelagic sedimentation to the continental margin. Deposition of terrigenous eolian components is clearly dominant seaward of the trench. Regardless of the mechanism responsible for the horizontal transport, rapid settling is required once a terrigenous particle leaves the surface mixed layer. We propose that coarse silt particles settle out of the water column rapidly over the shelf and continental slope, while finer components are incorporated into fecal pellets by large populations of zooplankton and nekton. Our observations that planktonic organisms ingest quartz and feldspar grains in proportions similar to those found on the underlying sea floor and that fecal pellets are ubiquitous in bottom sediments where an oxygen minimum impinges on the continental slope suggest the predominance of fecal pellet transport for these components. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A Numerical Case Study of the Development of Large-Scale Thermal Anomalies in the Central North Pacific Ocean

Abstract A 10-level primitive equation ocean circulation model is used to investigate the formation and evolution of large-scale thermal anomalies in the central North Pacific Ocean during the fall and winter of 1976–77. A simplified parameterization of the effects of turbulent vertical mixing produced by wind stirring and surface cooling is included in the model. The numerical experiments consist of prescribed change experiments in which monthly mean ocean temperature anomalies, observed down to 400 m by the North Pacific Experiment (NORPAX), are used to define the prescribed changes (anomalies) in the initial conditions and observed monthly mean anomalies of surface winds, and surface heat fluxes are used to define the prescribed changes in the atmospheric forcing. Oceanic processes are investigated by comparing several prescribed change experiments with observations. With anomalous wind forcing, horizontal advection by anomalous wind-driven surface (Ekman) currents and anomalous wind mixing contribute ...

Carbonate Sediment Drifts in Northern Straits of Florida

High-resolution, air-gun seismic reflection profiles from the northern Straits of Florida (water depths < 800 m) have revealed the presence of large (up to 3,000 sq km) carbonate sediment drifts off the northwest corners of both Little Bahama and Great Bahama Banks. These drifts are hemiconical bodies of carbonate sands up to 600 m thick that have prograded north in response to an intensification of the Florida Current since the middle Miocene. Deposition of the sediment drifts occurred along the Bahama Banks on the lee side of the present oceanic circulation pattern, where there appears to be a convergence of bottom currents having velocities of up to 60 cm/sec. However, depositional rates may have been episodic, with the greatest rates correlating with intensified ci culation patterns during glacial events. Because of widespread submarine cementation, piston coring of these sediment drifts was difficult. Most cores contained less than 1 m of sand and angular rock fragments, suggesting that a thin veneer of sand overlays hardgrounds. In one 5-m-long core, granule-size material constitutes up to 40% of the total sediment (average of 3.9%), sands 50 to 80% (average of 60.4%), silts 5 to 35% (average of 25.0%), and clays 5 to 20% (average of 10.7%). Mean grain size ranges from 0.0 to 3.0 ^phgr (coarse to fine sand) and the sediments are moderately to poorly sorted. The granules are mostly submarine-lithified intraclasts; the fine sands are mostly planktonic Foraminifera; and the coarser sands consist of pteropods and shallow-water material such as Halimeda, peneropolid Foraminifera, fragment of coralline algae, ooids, or micritized mollusk debris. Off-bank sediment transport along the west side of the Bahama Banks and subsequent along-slope transport by the Florida Current appear responsible for the supply of bank-derived sediment to the drifts. Rocks recovered by dredging and in-situ sampling from submersibles are mostly grain-supported biomicrites, biomicrudites, and intramicrudites cemented by submicrocrystalline, amorphous to peloidal high-Mg calcite. Preliminary bulk-rock C14 dates suggest a late Pleistocene or older age. Porosities of up to 40% are common within these rocks, consisting of both primary intergranular and intragranular pores and secondary macroborings and microborings produced by endolithic organisms. In the rock record, sandy sediment drifts formed at relatively shallow depths (< ~ 1 km) by strong bottom currents associated with wind-driven surface currents may be attractive hydrocarbon reservoirs. In contrast, sediment drifts formed at abyssal depths (3 to 5 km) by relatively sluggish thermohaline bottom currents would probably contain too much impermeable muddy sediment to be potential reservoirs.

A Dynamical-Numerical Study of the Formation and Evolution of Large-Scale Ocean Anomalies

To identify oceanic processes responsible for the formation and evolution of large-scale thermal anomalies, a series of initial-value model simulations are carried out using a 10-level primitive equation model in a closed rectangular basin. The model contains time-dependent seasonal forcing by the atmosphere, a parameterization of surface-generated wind stirring and convective overturning, and nonlinear lateral eddy viscosity based on two-dimensional turbulence theory. A “model climatology” is first generated by integrating the model over 240 years of simulated time using climatological atmospheric forcing which varies on the seasonal time scale. This model-generated ocean climatology is shown to compare qualitatively with the large-scale circulation in the North Pacific Ocean. The model is used to simulate oceanic thermal anomalies using both anomalous and climatological atmospheric forcing. The initial conditions for the simulations are obtained by combining a particular temperature anomaly with the climatological temperatures generated by the model for the given time of year. The anomalous part of the initial vertical shear current is geostrophic while that of the vertical mean current is zero. Using climatological atmospheric forcing, the free evolution of an initial sea surface temperature (SST) anomaly is shown to be dependent on its depth of penetration. Using anomalous atmospheric wind forcing derived from the first empirical orthogonal function of monthly mean sea level pressure anomalies (Davis, 1976), realistic SST anomalies develop in a period of 30 days. The mechanism responsible for the anomaly development is horizontal advection of mean temperature by anomalous surface (Ekman) currents. Two simulation experiments are made using observed anomaly data from the atmosphere and the ocean. In one case (fall–winter 1971–72) the temperature anomaly is known only at the surface where in the other case (fall–winter 1976–77) it is mapped from observations down to 400 m by a NORPAX ships-of-opportunity program. Both experiments utilize climatological heating and anomalous wind forcing derived from monthly mean sea level pressure anomalies. In both cases horizontal advection of mean temperature by anomalous wind-driven surface (Ekman) currents is able to explain a large fraction of the observed anomaly development in the upper layers. In the 1976–77 case the model simulation below 100 m is less successful. It is pointed out that improved simulations can be expected from an inclusion of anomalous surface heat fluxes and a more realistic treatment of anomalous wind mixing but these are left for a future study.

On Planetary Voltages, Ocean Tides, and Electrical Conductivity below the Pacific

Voltages observed between the ends of various underwater telegraph cables up to 9660 km long are analyzed in terms of planetary electric fields, deep ocean tides, wind driven surface currents, and geomagnetic induction.It is concluded that the average planetary electric field, which may originate from the internal processes generating the geomagnetic field, is not more than 0.038 mv/km ± 20% between Fiji and Vancouver Island. This is almost an order of magnitude less than previously reported.The average resistivity of the sea bed to a scale depth of 130 ± 20 km, treated as a single homogeneous plane layer, is 37 ± 5 ?m off the coast of Vancouver Island. This is similar to what is observed below the adjacent land.No statistically significant model was found relating the voltages on the 9660 km cable to tide heights at the shore, and geomagnetic field changes. However, it was found that the geomagnetically induced voltages between the ends of the 85 and 23 km cables were larger than the tidally induced voltages. A satisfactory model of these cable voltages was developed in terms of tidal heights, measured at the shore, and geomagnetic fields measured at a nearby observatory.All the cables were broken at sea, and the data are therefore of special interest because it is unlikely they will ever be duplicated.

Depositional Anticlines of Deep Environments--Past Success and Future Exploration: ABSTRACT

As the energy quest probes deeper into the oceanic environment, enormous depositional anticlines formed by deep current action are being documented, and certain of these with favorable rock properties beckon to the explorationist. Wind-driven surface currents, such as the Gulf Stream, can shape these anticlines at the outer edges of detrital sedimentation where such high-velocity currents End_Page 1842------------------------------ sweep the bases of continental slopes. Similarly, the "bottom" currents which are moving at slower velocities deeper on the continental rises will form varied anticlinal profiles characteristic of particular bottom conditions. Redistributed terrigenous materials which in great part compose these anticlines are carried into both current systems by intermittent gravity sliding and turbidity currents. A striking example of wind-driven current deposition occurs in the Florida Strait where calcareous sands from the Florida reef vicinity are swept along a trough by the Gulf Stream, then onto a broad anticlinal rise. Examples typifying "bottom" current anticlines are numerous in the North Atlantic, and deep-water coring programs have partly revealed their sedimentary sequences. A wind-driven current origin can plausibly explain the Poza Rica trend in Mexico. As the Golden Lane Reef contributed its Tamabra talus downslope into swift currents of the Chicontepec foredeep, anticlines were shaped at the base of the slope. Similar origins are suggested for other examples in the geologic record. Significant reserves in anticlines formed by current action will be found beyond the reefs and laterally away from the deltas in the deep environment where the subtle character of these features must come to be recognized. Reservoirs such as Poza Rica attest to the excellent rock properties and trap conditions which can be realized in an inspired search for such targets. End_of_Article - Last_Page 1843------------

Depositional Anticlines of Deep Environments--Past Success and Future Exploration: ABSTRACT

As the energy quest probes deeper into the oceanic environment, enormous depositional anticlines formed by deep current action are being documented, and certain of these with favorable rock properties beckon to the explorationist. Wind-driven surface currents, such as the Gulf Stream, can shape these anticlines at the outer edges of detrital sedimentation where such high-velocity currents End_Page 1842------------------------------ sweep the bases of continental slopes. Similarly, the currents which are moving at slower velocities deeper on the continental rises will form varied anticlinal profiles characteristic of particular bottom conditions. Redistributed terrigenous materials which in great part compose these anticlines are carried into both current systems by intermittent gravity sliding and turbidity currents. A striking example of wind-driven current deposition occurs in the Florida Strait where calcareous sands from the Florida reef vicinity are swept along a trough by the Gulf Stream, then onto a broad anticlinal rise. Examples typifying current anticlines are numerous in the North Atlantic, and deep-water coring programs have partly revealed their sedimentary sequences. A wind-driven current origin can plausibly explain the Poza Rica trend in Mexico. As the Golden Lane Reef contributed its Tamabra talus downslope into swift currents of the Chicontepec foredeep, anticlines were shaped at the base of the slope. Similar origins are suggested for other examples in the geologic record. Significant reserves in anticlines formed by current action will be found beyond the reefs and laterally away from the deltas in the deep environment where the subtle character of these features must come to be recognized. Reservoirs such as Poza Rica attest to the excellent rock properties and trap conditions which can be realized in an inspired search for such targets. End_of_Article - Last_Page 1843------------

Specification of Sea Surface Temperature Anomaly Patterns in the Eastern North Pacific

Observed changes in sea surface temperature anomaly patterns on monthly and seasonal time scales are related to anomalous circulation patterns in the overlying atmosphere using data collected from the eastern North Pacific over a 10-year period (1961–70). Three monthly (November 1969, December 1969, January 1970) and four seasonal (fall 1969, winter 1969–70, spring 1970, summer 1970) case studies are described which show that the observed anomalous temperature changes can be explained quite well by relating them to anomalous heat transfer across the air-sea interface and heat advection by anomalous wind-driven ocean surface currents. These interactions are documented by charts showing the anomaly patterns of sea surface temperature change, sea level pressure, types of heat transfer across the air-sea interface, and wind drift currents. In addition, correlations computed between the anomaly patterns for each of the periods studied show that the interactions hypothesized have statistical significance. Although only seven case studies are described, the results are representative of those for most of the other months and seasons in the 10-year period. An analysis of several years of data from Station PAPA (50N,145W), which included observed mixed layer depth values, indicates that between-year fluctuations in mixed layer depths can have a large effect in determining anomalous sea surface temperature changes, particularly when new seasonal thermoclines are forming. These effects should he included in any method used to specify (or predict) anomaly changes in order to avoid the relatively large errors that can occur from using long-term mean values.

A note on the growth of small-scale Langmuir circulations

The processes responsible for the generation of the vorticity in Langmuir circulations are unknown. Perhaps the most elementary and attractive proposition suggests that longitudinal vorticity is produced by the distortion of the cross-wind vorticity of the mean wind-driven surface currents by Reynold's stresses due to short-crested gravity waves. This suggestion, made by Ichiye (1967), and by Kraus (1967) in a somewhat different proposal, is the heart of a recent theory proposed by Craik (1970). In this paper, Craik's assumptions concerning the relative magnitudes of the waves and current are criticized, and it is shown that for Langmuir circulations the interaction between the two should occur at a higher order. By concentrating on vortex line deformations the necessary modifications are calculated. Viewed in this way, the proposed mechanism is so simple that its consequences can be easily explored. The principal consequence is that no inviscid mechanism by which the cross-stream vorticity is distorted (by waves or any other means) to produce longitudinal vorticity appears to be consistent with the observed facts. Langmuir circulations are therefore likely to be more intricate than Craik supposed.