Some Three-Dimensional Characteristics of Low-Frequency Current Fluctuations near the Oregon Coast

Kundu, Pijush K.; Allen, J. S.

doi:10.1175/1520-0485(1976)006<0181:stdcol>2.0.co;2

Cited by 284 publications

(172 citation statements)

References 11 publications

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“…In general, alongshore correlation length scales are much longer than cross-shelf correlation length scales. For instance, Kundu and Allen (1976), using moored velocity data, find alongshore and cross-shelf correlation scales of at least 30 km, i.e. about the same distance as our between-track spacing and 7 times the size of the bins into which we combined our data (see below).…”

Section: Methodsmentioning

confidence: 71%

Physical and biological variables affecting seabird distributions during the upwelling season of the northern California Current

Ainley

Spear

Tynan

et al. 2005

Deep Sea Research Part II: Topical Studies in Oceanography

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As a part of the GLOBEC-Northeast Pacific project, we investigated variation in the abundance of marine birds in the context of biological and physical habitat conditions in the northern portion of the California Current System (CCS) during cruises during the upwelling season 2000. Continuous surveys of seabirds were conducted simultaneously in June (onset of upwelling) and August (mature phase of upwelling) with ocean properties quantified using a towed, undulating vehicle and a multi-frequency bioacoustic instrument (38-420 kHz). Twelve species of seabirds contributed 99% of the total community density and biomass. Species composition and densities were similar to those recorded elsewhere in the CCS during earlier studies of the upwelling season. At a scale of 2-4 km, physical and biological oceanographic variables explained an average of 25% of the variation in the distributions and abundance of the 12 species. The most important explanatory variables (among 14 initially included in each multiple regression model) were distance to upwelling-derived frontal features (center and edge of coastal jet, and an abrupt, inshore temperature gradient), sea-surface salinity, acoustic backscatter representing various sizes of prey (smaller seabird species were associated with smaller prey and the reverse for larger seabird species), and chlorophyll concentration. We discuss the importance of these variables in the context of what factors may be that seabirds use to find food. The high seabird density in the Heceta Bank and Cape Blanco areas indicate them to be refuges contrasting the low seabird densities currently found in most other parts of the CCS, following decline during the recent warm regime of the Pacific Decadal Oscillation.

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Section: Methodsmentioning

confidence: 71%

Physical and biological variables affecting seabird distributions during the upwelling season of the northern California Current

Ainley

Spear

Tynan

et al. 2005

Deep Sea Research Part II: Topical Studies in Oceanography

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“…In this region, the upwelling front generally lies inshore of the shelf-break (Mooers et al, 1976). The baroclinic coastal jet flows equatorward along the mid-shelf and current fluctuations tend to be aligned with isobaths (Kundu and Allen, 1976). The cross-shelf circulation tends to be nearly two-dimensional and in reasonable agreement with the Ekman transport estimated from the wind (Smith, 1981).…”

Section: Introductionmentioning

confidence: 62%

Two coastal upwelling domains in the northern California Current system

et al. 2005

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A pair of hydrographic sections, one north and one south of Cape Blanco at 42.9N, was sampled in five summers (1998 -2000 and 2002-2003). The NH line at 44.6N lies about 130 km south of the Columbia River, and spans a relatively wide shelf off Newport, Oregon. The CR line at 41.9N off Crescent City, California, lies 300 km farther south and spans a narrower shelf. Summer winds are predominantly southward in both locations but the southward winds are stronger on the CR line. Sampling included CTD/rosette casts (to measure temperature, salinity, dissolved oxygen, nutrients, chlorophyll), zooplankton net tows and continuous operation of an Acoustic Doppler Current Profiler. We summarize and compare July-August observations from the two locations. We find significant summer-season differences in the coastal upwelling domains north and south of Cape Blanco. Compared to the domain off Newport, the domain off Crescent City has a more saline, cooler, denser and thicker surface mixed layer, a wider coastal zone inshore of the upwelling front and jet, higher nutrient concentrations in the photic zone and higher phytoplankton biomass. The southward coastal jet lies near the coast (about 20 -30 km offshore, over the shelf) on the NH line, but far from shore (about 120 km) on the CR line; a weak secondary jet lies near the shelf-break (35 km from shore) off Crescent City. Phytoplankton tend to be light-limited on the CR line and nutrientlimited on the NH line. Copepod biomass is high (15 mg C m Ϫ3 ) inshore of the mid-shelf on both NH and CR lines, and is also high in the core of the coastal jet off Crescent City. The CR line shows evidence of deep chlorophyll pockets that have been subducted from the surface layer. We attribute these significant differences to stronger mean southward wind stress over the southern domain, to strong small-scale wind stress curl in the lee of Cape Blanco, and to the reduced influence of the Columbia River discharge in this region.

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“…The method is similar to conventional EOFs except that it is applied to the complex field obtained from a pair of associated variables such as the zonal and meridional components u and v of the wind field U = (u, v) (Kundu and Allen, 1976;Hardy and Walton, 1978;Salstein et al, 1983;Brink and Muench, 1986;von Storch and Zwiers, 1999;Preisendorfer, 1988). The wind field U tl = U(t, s l ), defined at each location s l , l = 1, .…”

Section: Conventional Complex Eofsmentioning

confidence: 99%

“…The phase and amplitude at each grid are obtained using the real and imaginary parts of the loadings. This method of doing CEOFs seems to have been originally applied by Kundu and Allen (1976) to the velocity field of the Oregon coastal current. The conventional CEOFs are similar to conventional EOFs in the sense that time ordering is irrelevant, and hence the method is mostly useful to capture covarying spatial patterns between the two fields.…”

Section: Conventional Complex Eofsmentioning

confidence: 99%

Empirical orthogonal functions and related techniques in atmospheric science: A review

Hannachi

Jolliffe

Stephenson

2007

Intl Journal of Climatology

942

637

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Abstract:Climate and weather constitute a typical example where high dimensional and complex phenomena meet. The atmospheric system is the result of highly complex interactions between many degrees of freedom or modes. In order to gain insight in understanding the dynamical/physical behaviour involved it is useful to attempt to understand their interactions in terms of a much smaller number of prominent modes of variability. This has led to the development by atmospheric researchers of methods that give a space display and a time display of large space-time atmospheric data.Empirical orthogonal functions (EOFs) were first used in meteorology in the late 1940s. The method, which decomposes a space-time field into spatial patterns and associated time indices, contributed much in advancing our knowledge of the atmosphere. However, since the atmosphere contains all sorts of features, e.g. stationary and propagating, EOFs are unable to provide a full picture. For example, EOFs tend, in general, to be difficult to interpret because of their geometric properties, such as their global feature, and their orthogonality in space and time. To obtain more localised features, modifications, e.g. rotated EOFs (REOFs), have been introduced. At the same time, because these methods cannot deal with propagating features, since they only use spatial correlation of the field, it was necessary to use both spatial and time information in order to identify such features. Extended and complex EOFs were introduced to serve that purpose.Because of the importance of EOFs and closely related methods in atmospheric science, and because the existing reviews of the subject are slightly out of date, there seems to be a need to update our knowledge by including new developments that could not be presented in previous reviews. This review proposes to achieve precisely this goal. The basic theory of the main types of EOFs is reviewed, and a wide range of applications using various data sets are also provided.

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Some Three-Dimensional Characteristics of Low-Frequency Current Fluctuations near the Oregon Coast

Cited by 284 publications

References 11 publications

Physical and biological variables affecting seabird distributions during the upwelling season of the northern California Current

Physical and biological variables affecting seabird distributions during the upwelling season of the northern California Current

Two coastal upwelling domains in the northern California Current system

Empirical orthogonal functions and related techniques in atmospheric science: A review

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