Elevation Slope Research Articles

Storm‐induced sediment gravity flows at the head of the Eel submarine canyon, northern California margin

As part of the STRATAFORM program, a bottom‐boundary layer (BBL) tripod was deployed at 120 m depth in the northern thalweg of the Eel Canyon during winter 2000. Increases of the near‐bottom suspended‐sediment concentrations (SSC) recorded at the canyon head were not directly related to the Eel River discharge, but were clearly linked to the occurrence of storms. BBL measurements revealed that during intensifications of the wave orbital velocity, sediment transport at the head of the canyon occurred as sediment gravity flows directed down‐canyon. Observational evidence for near‐bed sediment gravity‐flow transport included an increase toward the bed of the down‐canyon component of wave‐averaged velocity and high estimated SSC. At higher sampling frequencies (1 Hz), the current components during these events fluctuated at the same periodicity as the pressure, reflecting a clear influence of the surface‐wave activity on the generation and maintenance of the sediment gravity flows. The origin of such flows is not related to the formation of fluid muds on the shelf or to intense wave‐current sediment resuspension around the canyon head region. Rather, liquefaction of sediment deposited at the head of the canyon (induced by wave‐load excess pore water pressures during storms) combined with elevated slopes around the canyon head appear to be the mechanisms initiating sediment transport. The resulting fluidized‐sediment layer can easily be eroded, entrained into the water column, and transported down‐canyon as a sediment gravity flow. Results from this study reveal that storm‐induced sediment gravity flows occur periodically in the Eel Canyon head, and suggest that this kind of sediment transport process can occur in other submarine canyons more frequently than previously expected.

Mapping the climate of Puerto Rico, Vieques and Culebra

AbstractSpatially explicit climate data contribute to watershed resource management, mapping vegetation type with satellite imagery, mapping present and hypothetical future ecological zones, and predicting species distributions. The regression‐based parameter–elevation regressions on independent slopes model (PRISM) uses spatial data sets, a knowledge base and expert interaction to generate grids of climate variables that are compatible with geographical information systems. This study applied PRISM to generate maps of mean monthly and annual precipitation and minimum and maximum temperature for the Caribbean islands of Puerto Rico, Vieques and Culebra over the 1963–95 averaging period. PRISM was run under alternative parameterizations that simulated simpler interpolation methods as well as the full PRISM model. For temperature, the standard PRISM parameterization was compared with a hypsometric method (HYPS), in which the temperature–elevation slope was assumed to be −6.5 °C/km. For precipitation, the standard PRISM parameterization was compared with an inverse‐distance weighting interpolation (IDW). Spatial temperature patterns were linked closely to elevation, topographic position, and coastal proximity. Both PRISM and HYPS performed well for July maximum temperature, but HYPS performed relatively poorly for January minimum temperature, due primarily to lack of a spatially varying temperature–elevation slope, vertical atmospheric layer definition, and coastal proximity guidance. Mean monthly precipitation varied significantly throughout the year, reflecting seasonally differing moisture trajectories. Spatial precipitation patterns were associated most strongly with elevation, upslope exposure to predominant moisture‐bearing winds, and proximity to the ocean. IDW performed poorly compared with PRISM, due largely to the lack of elevation and moisture‐availability information. Overall, the full PRISM approach resulted in greatly improved performance over simpler methods for precipitation and January minimum temperature, but only a small improvement for July maximum temperature. Comparisons of PRISM mean annual temperature and precipitation maps with previously published hand‐drawn maps showed similar overall patterns and magnitudes, but the PRISM maps provided much more spatial detail. Copyright © 2003 Royal Meteorological Society

Discretization of Integral Equations Describing Flow in Nonprismatic Channels with Uneven Beds

Application of the finite-volume method in one dimension for open channel flow predictions mandates the direct discretization of integral equations for mass conservation and momentum balance. The integral equations include source terms that account for the forces due to changes in bed elevation and channel width, and an exact expression for these source term integrals is presented for the case of a trapezoidal channel cross section whereby the bed elevation, bottom width, and inverse side slope are defined at cell faces and assumed to vary linearly and uniformly within each cell, consistent with a second-order accurate solution. The expressions may be used in the context of any second-order accurate finite-volume scheme with channel properties defined at cell faces, and it is used here in the context of the Monotone Upwind Scheme for Conservation Laws (MUSCL)-Hancock scheme which has been adopted by many researchers. Using these source term expressions, the MUSCL-Hancock scheme is shown to preserve stationarity, accurately converge to the steady state in a frictionless flow test problem, and perform well in field applications without the need for upwinding procedures previously reported in the literature. For most applications, an approximate, point-wise treatment of the bed slope and nonprismatic source terms can be used instead of the exact expression and, in contrast to reports on other finite-volume-based schemes, will not cause unphysical oscillations in the solution.

Visualização 3D de uma imagem digital: metodologia e potencial cartográfico

This article presents a methodology for 3D visualization of a digital image and discusses its cartographic potential. Assuming that a regular DTM (Digital Terrain Model) is available, whose points are connected to form a triangular mesh, a shading methodology is applied triangle-by-triangle. This requires the computation of gray levels of image points corresponding to the pixels of 3D visualization plane, what in turn requires the modeling of the sensor used to acquire the image. Next, a shading model may be used to add artificially an extra effect of shading to the gray levels previously obtained, generating, e.g., shadows along the most elevated slopes opposed to the artificial light source. Finally, a projection model is used to obtain the 3D perception on the visualization plane. Results obtained were sufficient, showing that the 3D visualization methodology has the potential to be used in several cartographic application, as, e.g., in the cartographic revision.

Is the elevated slope relating ventilation to carbon dioxide production in chronic heart failure a consequence of slow metabolic gas kinetics?

Patients with heart failure have slow metabolic gas exchange kinetics, which may contribute to the elevated slope of the relationship between ventilation and carbon dioxide production (Ve/Vco(2) slope). A tertiary referral centre for cardiology. Eleven patients with stable chronic heart failure and 11 age-matched controls. Each subject underwent maximal bicycle-based peak exercise testing with metabolic gas exchange analysis and three further repeated tests at 15%, 25% and 50% of the load achieved at peak exercise. The ventilation and carbon dioxide production from each of these steady-state tests was used to re-calculate the Ve/Vco(2) slope and compared with the Ve/Vco(2) slope derived from the maximal test. Peak oxygen consumption [mean (S.D.)] was lower in heart failure patients [18.2 (4.0) vs. 31.2 (6.3) ml/kg per min; P<0.001] than in controls. The Ve/Vco(2) slope was steeper in patients than controls [32.7 (8.3) vs. 27.1 (1.6); P<0.05]. There was no difference between the Ve/Vco(2) slope reconstructed from the three steady state tests and resting data and that gained from the maximal test [35.3 (7.8) vs. 25.9 (3.2); P=0.43]. The elevated slope of the relationship between ventilation and carbon dioxide production is not a consequence of the short stages of a standard incremental exercise test combined with delayed metabolic gas kinetics in heart failure patients.

Does Kleptoparasitism by Glaucous-Winged Gulls Limit the Reproductive Success of Tufted Puffins?

AbstractInterspecific kleptoparasitism (food stealing) occurs in many seabird species and can sometimes significantly affect host individuals and populations. We investigated effects of kleptoparasitism by Glaucous-winged Gulls (Larus glaucescens) on a population of Tufted Puffins (Fratercula cirrhata) in which almost all chicks die before fledging in some years. Rates of kleptoparasitism were estimated during two seasons and compared with several spatial and temporal factors that have been predicted to influence kleptoparasitism rates both within and among seasons. Kleptoparasitism rates increased from 2% in the first year to 19% in the second, whereas puffin fledging success declined precipitously from 81% in the first year to 11% in the second. Within years, kleptoparasitism rates increased with number of puffins returning with fish, decreased during fair weather, and were unaffected by tidal height. Spatially, those rates increased with puffin burrow density and declined with angle of the nesting slope. Gull kleptoparasitism success increased during foul weather and at higher puffin nesting elevations. Despite those associations, survival of puffin chicks was not influenced by kleptoparasitism activity near their nests although it increased with a combination of low elevation and high slope at the nesting burrow. Neither kleptoparasitism nor predation by gulls were exceptional relative to other seabird colonies and they were unlikely to cause reproductive failures that characterize puffins at that site. Other factors, particularly food shortages at sea, merit further attention in explaining those failures.

Observations of the wind-induced exchange at the entrance to Chesapeake Bay

Water density and velocity data from two ;75-day deployments across the entrance to the Chesapeake Bay were used in conjunction with wind velocity and sea level records to describe the transverse structure of wind-induced subtidal exchange. Acoustic Doppler current proe lers, electromagnetic current meters, and conductivity-temperature-depth recorders were deployed at the entrance to the bay from mid-April to early July of 1999 and from early September to mid-November of 1999. Three main scenarios of wind-induced exchange were identie ed: (1) Northeasterly (NE) winds consistently drove water from the coast toward the lower Chesapeake Bay as well as water from the upper bay to the lower bay, which was indicated by the surface elevation slopes across the lower bay and along the bay. This resulted in water piling up against the southwestern corner of the bay. The subtidal e ow over the southern portion of the bay entrance was directed to the left of the wind direction, likely the result of the ine uence of Coriolis and centripetal accelerations on the adjustment of the sea level gradients. Over the northern shallow half of the entrance, the subtidal e ows were nearly depth-independent and in the same direction as the wind. (2) Southwesterly (SW) winds caused opposite sea level gradients (relative to NE winds), which translated into near-surface oute ows throughout the entrance and near-bottom ine ows restricted to the channels. This windinduced circulation enhanced the two-way exchange between the estuary and the adjacent ocean. (3) Northwesterly winds produced the same exchange pattern as NE winds. Water piled up against the southwestern corner of the bay causing net oute ow in the deep, southern area and downwind e ow over the shallow areas. Northwesterly winds greater than 12 m/s caused the most efe cient e ushing of the bay, driving water out over the entire mouth of the estuary.

Methods for Controlling Stresses and Distortions in Stage-Constructed Steel Bridges

Widening and staged construction of steel bridges are becoming more frequent with today’s heavy traffic demands, right-of-way restrictions, and environmental constraints. Both construction practices require the addition of new girders to an existing structure. When new girders are added to an existing structure, inherent constructibility problems arise. The completed structure requires that the new girders, after placement of the new concrete deck, be aligned in both elevation and cross slope with the existing structure. Problems occur when the loading over the new girders is unbalanced, causing a torsional moment and twisting of the bridge. The twisting of the new girders may add undesirable vertical and horizontal displacements. Six design and construction methodologies for staged construction or widening of straight, steel girders are discussed. Research was initiated in response to construction problems experienced by the Washington State Department of Transportation (WSDOT). Several state highway agencies were surveyed, and the survey revealed that the problems experienced by WSDOT were not unique. The six methods are presented and the advantages, disadvantages, and applicable situations are discussed. A finite-element model was developed and used to compare calculated deflections with actual WSDOT case study field measurements. The model was then used to investigate the stresses and deformations for the six methods. A design paradigm is also presented for use in determining the appropriate method to be used for each particular situation.

Spring habitat selection of sables in Daxing’an Mountains

This paper studies the habitat selection of sables (Martes. zibellina) in spring adopting radio-tracking and GPS (Global Positioning System) in Daxing’an Mountains of China. Sables liked mature and elder forest, but it avoided uncovered and young growth land. In spring sables had strong selection to medium cover-degree forest, but it avoided widen ground and especial high cover-degree forest. On the contrary sables didn’t have the strong selection to shrubs cover-degree, but strong selection to dominant tree species, slope degree and slope direction, especially sable liked medium and lower slope. At the same time, sables had the strong selection to the log’s density and the crown’s cover-degree. Generally it avoided high elevation and lower slope land.

Usefulness of the presenting electrocardiogram in predicting successful reperfusion with Streptokinase in acute myocardial infarction

The presenting electrocardiogram may contain information indicating the probability of successful reperfusion. The relation between 3 parameters in the presenting electrocardiogram (pathologic Q waves, T-wave inversion, and the slope of ST elevation) and Thrombolysis in Myocardial Infarction trial (TIMI) grade 3 flow in the infarct-related artery was assessed angiographically 90 minutes after beginning streptokinase in 362 patients. TIMI grade 3 flow was more common in patients without Q waves (55%) than in those with Q waves (35%; p <0.001), and more common in patients without T-wave inversion (50%) than in those with T-wave inversion (30%; p <0.002). There was no relation between the slope of the ST segment or the magnitude of its deviation and the achievement of TIMI grade 3 flow. Only 20% of the 59 patients with both Q waves and T-wave inversion had TIMI grade 3 flow, compared with 50% of the remaining patients (p <0.0001). Among patients treated within 3 hours, TIMI grade 3 flow was seen in 68% of those without versus 44% of those with Q waves (p <0.01), and in 62% of those without versus 43% of those with T-wave inversion (p = 0.06). Among patients treated after 3 hours, TIMI grade 3 flow was seen in 38% of those without versus 30% of those with Q waves (p = NS), and in 38% of those without versus 23% of those with T-wave inversion (p <0.05). On multivariate analysis, the absence of Q waves, the time from the onset of chest pain to treatment, and age were independent predictors of TIMI grade 3 flow. Pathologic Q waves in the presenting electrocardiogram provide valuable information as to the probability of achieving successful reperfusion following administration of streptokinase, and may be helpful for triage of patients to alternative reperfusion strategies, including percutaneous revascularization.

Orientation tuning of the spatial-frequency-tuned mechanisms of the red-green channel.

Significant orthogonal masking for color stimuli [Invest. Ophthalmol. Visual Sci. 34, 782 (No. 405-54) (1993)] but not for achromatic stimuli [J. Opt. Soc. Am. A 1, 226 (1984)] under sustained presentation led us to investigate the orientation tuning of the spatial-frequency- (SF-) tuned color mechanisms. The Red-Green channel was isolated from the achromatic channel by the minimum flicker technique and from the Yellow-Blue channel by the hue cancellation technique. Contrast sensitivity functions, threshold elevation versus mask orientation curves (measured by orientation masking), and threshold elevation versus mask contrast curves were measured by the method of constant stimuli and a two-interval forced-choice technique on two normal observers. Test targets were spatially localized (D6), vertical color patterns, and masks were sinusoidal color patterns oriented 15 degrees-90 degrees from the vertical in 15 degrees steps and had the same SF's as those of test patterns. Mask contrasts were varied between 1.2% and 60%. The orientation tuning curves of the SF-tuned color mechanisms were extracted by obtaining the best fit to contrast sensitivity and threshold elevation data simultaneously at a given SF with use of the masking model. Results show that threshold elevations depend on test SF, mask SF, mask orientation, and mask contrast. Half-bandwidths at half-height (with respect to 15 degrees from the vertical) of threshold elevation versus mask orientation curves range from 90 degrees to 29 degrees depending on SF's. The slopes of threshold elevation versus mask contrast curves range from 0.76 to 0.29 on octave-octave coordinates depending on SF's. Orientation half-bandwidths at half-height of orientation tuning curves of the SF-tuned color mechanisms (1) range from 79 degrees to 28 degrees and (2) average from 68 degrees to 30 degrees for SF's 0.063-8 cycles per degree (cpd). Data suggest that the orientation tuning curves of the SF-tuned chromatic mechanisms are broader (except at 2 cpd) than those of the achromatic mechanisms (orientation half-bandwidths: 32 degrees-15 degrees for 0.5-11.3 cpd [J. Opt. Soc. Am. A 1, 226 (1984)]); moreover, the orientation bandwidths are SF dependent.

Modelling runoff using optical satellite remote sensing data in a high mountainous alpine catchment of Italy

Development of hydrological models for seasonal and real-time runoff forecast in rivers of high alpine catchments is useful for management of water resources. The conceptual models for this purpose are based on a temperature index and/or energy budget and can be either lumped or distributed over the catchment area. Remote sensing satellite data are most useful to acquire near real-time geophysical parameters in order to input to the distributed forecasting models. In the present study, integration of optical satellite remote sensing-derived information was made with ground meteorological and hydrological data, and predetermined catchment morphological parameters, to study the feasibility of application of a distributed temperature index snowmelt runoff model to one of the high mountainous catchments in the Italian Alps, known as Cordevole River Basin. Five sets of Landsat Multispectral Scanning System (MSS) and Thematic Mapper (TM) computer-compatible tapes (CCTs) were processed using digital image processing techniques in order to evaluate the snow cover variation quantitatively. Digital elevation model, slope and aspect parameters were developed and used during satellite data processing. The satellite scenes were classified as snow, snow under transition and snow free areas. A second-order polynomial fit has been attempted to approximate the snow depletion and to estimate daily snow cover areal extent for three elevation zones of the catchment separately. Model performance evaluation based on correlation coefficient, Nash–Sutcliffe coefficient and percentage volume deviation indicated very good simulation between measured and computed discharges for the entire snowmelt period. The use of average temperature values computed from the maximum and minimum temperatures into the model was studied and a suitable algorithm was proposed. © 1997 John Wiley & Sons, Ltd.

Age-related differences in temporal scaling of postural EMG activity.

Electromyographical (EMG) burst onset times for postural muscles were compared in young and elderly male and female subjects performing a forceful abrupt pull with the right arm against a load cell apparatus while standing. EMG activity was collected via surface electrodes from the posterior deltoid, and right and left hamstring and quadriceps muscles. Pulls were performed at varying force levels from 100% to approximately 50% of a maximum effort. Regression equations were developed for each postural muscle for each group, using force production values as the independent variable, and postural muscle onset latencies (relative to deltoid onset) as the dependent variable. Regression slopes for postural muscles of elderly subjects ranged from 0.59 to 0.33, while slopes for the young subjects ranged from 0.72 to 0.63. Less elevated slopes for the elderly may indicate a reduced ability to temporally scale postural muscle onset latencies to variations in the force of the upper-limb task; a reduction in this ability may constitute a possible contributing factor to instability in the elderly.

Lichen Diversity and Stand Continuity in the Northern Hardwoods and Spruce-Fir Forests of Northern New England and Western New Brunswick

ME 04743 Abstract. The continuity of33 northern hardwoods and spruce-fir stands in Maine, New Hamp- shire, Vermont, and western New Brunswick is assessed using indices of ecological continuity (IEC) that are based upon the percentage occurrence of ancient forest indicator lichen species found at each site. Stands are ranked according to decreasing IEC value, with results confirming the ancient forest status of 12 ofthe 15 previously investigated old-growth forest sites included in the investigation. The data also show that epiphytic lichen floras become richer over time, with older stands harboring more rare species, and suggest that the total number of Caliciales species collected at a site may, in itself be an indicator of continuity. Lying within a transition zone between the boreal forests of Canada and the eastern deciduous forests to the south, northern New England and western New Brunswick are approximately 85% forested, occupied principally by forest types in the spruce- fir and northern hardwoods groups. Spruce-fir stands dominated by Picea spp. and Abies balsamea are found on poorly- to moderately well-drained flat to low-lying areas and on well-drained steep, shallow to bedrock upper elevation slopes. Acer saccharum, Betula alleghaniensis, and Fagus grandifolia dom- inate the northern hardwoods stands which gener- ally occur on well- to moderately well-drained sites and are best developed on fertile soils at low to middle elevations (Eyre 1980; Kasmer, unpubl. data). Three hundred and fifty years of logging in the region have left few of these areas undisturbed, with most of the forests having been cut from one to six times (Lull 1968). By one estimate, almost all soft- wood of commercial value had been removed from the White Mountains by 1890, while the northern

Trench and slope basin deposits in an Archean metasedimentary belt, Superior Province, Canadian Shield

The identification of a late Archean arc–trench assemblage in northwestern Ontario provides the opportunity to compare depositional systems developed in a Precambrian convergent setting with Cenozoic examples. Two types of sedimentary associations exist in the accretionary complex. Medium- to thick-bedded Bouma A, AB, and ABC felsic turbidites dominate the belt. These are primarily organized into unstructured sequences and reflect deposition in a ramp-like environment with multiple feed points supplying sediment from a forearc basin. Mafic turbidites with possible shallow water reworked intervals form isolated pods within the metasedimentary belt. Erosion of upthrust blocks of sedimentary strata containing ultramafic masses supplied this sediment to elevated slope basins. These types of depositional systems are similar in many respects to those developed in Cenozoic and Holocene arc–trench settings.

Interstitial meiofauna of Namib sandy beaches

Interstitial meiofauna were sampled across the intertidal zone and into the sublittoral region on two exposed sandy beaches on the Namibian coast, Langstrand and Cape Cross. A transverse barrip beach configuration at Langstrand allowed a comparison between the distribution and abundance patterns at the horn and within the bay of the cusp formation on this beach. Of the eight major meiofauna groups, nematodes were widely distributed and always dominant. The crustaceans, harpacticoid copepods and mystacocarids, were prominent in the mid-shore at Cape Cross but occurred in low numbers at Langstrand , where archiannelids were abundant at mid-tide level. Notably high numbers of gastrotrichs (> 1000 per 100 cm3) were found sublittorally at both beaches. Non-selective deposit feeders accounted for at least 58% of those nematodes examined from all stations, suggesting an abundant particulate food supply in coastal waters off South West Africa. Cape Cross supported the highest total meiofauna biomass followed by the Langstrand cusp horn and then cusp bay. A slightly elevated slope over a wide beach face, promoting rapid drainage and optimal oxygenation and food input, appeared as characteristics promoting meiofaunal colonization. These Namibian beaches could mark a zone of decline in the abundance of interstitial meiofauna which, from published work, appears to reach a maximum farther to the south.

THE INTERACTION OF IRON DEFICIENCY AND LEAD POISONING IN NORMAL CHILDREN. AN EPIDMIOLGICAL STUDY

In children the levels of erythrocyte porphyrins (EP) increase exponentially with the blood lead (BPb) above a threshold of 18 μg/dl (P.N.A.S. 79: 3335, 1982). The EP levels are also elevated by iron deficiency. This study was directed to assess the response of normal and Fe deficient children to low levels of Pb. In addition to BPb and EP, serum ferritin (SF) and mean corpuscular volume (MCV) were measured in 3459 children age 1 to 6 years. The normal range for SF and MCV were first established for each year of age. Children with SF 1 σ below the mean were considered certainly Fe sufficient. Children who did not fulfill any of these criteria were left unclassified and excluded from the analysis. The threshold BPb for EP elevation was established by the segmented line technique. The threshold BPb for the entire group of 3459 children was 18 μg/dl; for the 331 Fe deficient children it was 12.5 μg/dl and for the 2314 Fe sufficient children it was 20.3 μg/dl; all slopes of elevation were parallel. Because of the lower threshold BPb, Fe deficient children have a greater increase in EP in response to Pb than Fe sufficient children. These findings demonstrate the greater sensitivity of Fe deficient children to the effect of Pb, probably mediated by the competitive inhibition between Pb and Fe at the ferrochelatase step (Blood 66: 47a, 1985). Fe deficiency increases the sensitivity of children to Pb; Fe supplementation may protect them from the adverse effects of Pb on heme synthesis.

A comparison of relict versus equilibrium models for insular mammals of the Gulf of Maine

For the mammalian faunas of 24 landbridge islands in the Gulf of Maine (0.003–279 km2 in size), area accounts for 86% of variance in species richness. The slope, z, of the species-area curve is 0.247. For the seven largest islands (>10km2), the non-equilibrium hypothesis of relaxation following saturation in the post-Pleistocene is suggested by (1) elevated slope of the species-area curve (0.353), (2) correlation of species richness with island age (r=- 0.81) and water depth to mainland (r= -0.70), (3) highly non-random nested subsets of species ranked by island area, and (4) discontinuity with the extremely depauperate faunas of oceanic islands of the eastern North Atlantic. The alternative hypothesis of a dynamic equilibrium determined by recurrent immigration and extinction is supported by (1) documented turnover in 16 species, (2) correlation of species-area residuals with distance (r= - 0.90), (3) distribution dependent upon vagility with reduction or absence of hibernators and other poor dispersers, (4) low levels of endemism, and (5) congruence of community structure with that of mainland fauna for both trophic level and body size. I conclude that while some insular populations may be relictual, the faunal composition of most of these islands is dependent on recurrent colonization, much of which takes place over ice bridges. However, true equilibrium is perturbed by climatic shifts, range expansions, and human disturbance.

The seasonal alongshore pressure gradient on the West Coast of the United States

The long‐term mean steric height (0/500 dbar) data of Reid and Mantyla (1976) are added to relative monthly mean adjusted sea level data to obtain a seasonal time series of “quasi‐absolute” large‐scale (&gt;300 km) sea surface elevation along the west coast of the United States from 48°N to 33°N. North of 38°N, the elevation slope reverses sign seasonally so that the resulting pressure gradient force is southward from October to June and northward from July to September. South of 38°N, the pressure gradient force is northward except during January at all latitudes and during February in the interval from 38°N to 35°N. Maximum northward force occurs during August and September at all latitudes. The relative contributions to sea level elevation slope by seasonal heating and cooling, freshwater effluent effects, the alongshore component of coastal wind stress, and deep‐ocean currents are investigated. Both seasonal heating and cooling and freshwater contributions to large‐scale elevation slope are relatively insignificant (&lt;10% in every month) at all latitudes. Wind stress forcing (determined with the barotropic, steady, frictional model of Csanady (1978)) is significant north of Point Conception (35°N) for both the long‐term mean slope and its seasonal oscillation. Remote contributions are particularly important in the Pacific Northwest. South of San Francisco (38°N), empirical evidence suggests that deep‐ocean currents contribute significantly to coastal elevation slope in summer and fall and in the mean. Deep‐ocean currents may also affect elevation slope along the whole coast during spring, causing elevated sea level toward the north.

The spectral characteristics of wind-generated capillary waves

An experimental study of wind-generated capillary waves has been carried out in a laboratory wind-wave tunnel. In this tunnel it was possible to generate a stationary homogeneous wave field and to vary the wind over a range of speeds. A technique which makes use of a Preston tube has been used to measure the shear stress at the air-water boundary. Measurements of surface elevation and wave slope spectra in the capillary range of frequencies were obtained. Equations describing the wave spectra equilibrium range under the action of wind shear, surface tension and viscosity are derived. For frequencies beyond 15 hertz the measured spectra are in satisfactory agreement with the derived equations. Comparisons with other existing data have also been made.