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461.
Hey-Jin Kim Arthur J. Miller John McGowan Melissa L. Carter 《Progress in Oceanography》2009,82(2):137-147
Surface chlorophyll (CHL) measured at the Scripps Pier in the Southern California Bight (SCB) for 18 years (1983–2000) reveals that the spring bloom occurs with irregular timing and intensity each year, unlike sea-surface temperature (SST), which is dominated by a regular seasonal cycle. In the 1990s, the spring bloom occurred earlier in the year and with larger amplitudes compared to those of the 1980s. Seasonal anomalies of the Pier CHL have no significant correlation with local winds, local SST, or upwelling index, which implies that classical coastal upwelling is not directly responsible for driving chlorophyll variations in nearshore SCB.The annual mean Pier CHL exhibits an increasing trend, whereas the Pier SST has no evident concomitant trend during the CHL observation period. The interannual variation of the Pier CHL is not correlated with tropical El Niño or La Niña conditions over the entire observing period. However, the Pier CHL was significantly influenced by El Nino/Southern Oscillation during the 1997/1998 El Niño and 1998/1999 La Niña transition period. The Pier CHL is highly coherent at long periods (3–7 years) with nearby offshore in situ surface CHL at the CalCOFI (California Cooperative Fisheries Investigations) station 93.27. 相似文献
462.
3-D reconstruction of coastal bathymetry from AIRSAR/POLSAR data 总被引:1,自引:0,他引:1
This paper introduces a new method for reconstructing three-dimensional (3D) coastal bathymetry changes from Airborne AIRSAR/POLSAR synthetic aperture data. The new method is based on integration between fuzzy B-spline and Volterra algorithm. Volterra algorithm is used to simulate the ocean surface current from AIRSAR/POLSAR data. Then, the ocean surface current information used as input for continuity equation to estimate the water depths from AIRSAR/POLSAR data. This study shows that 3D ocean bathymetry can be reconstructed from AIRSAR/POLSAR data with root mean square error of ±0.03 m. 相似文献
463.
Arthur Horowitz 《Marine Geology》1974,17(2):103-122
Samples from the active Reykjanes Ridge and the inactive Iceland—Faroes Ridge have been investigated sedimentologically, mineralogically, and geochemically. The sediments display polymodal grain-size distributions and are poorly sorted, indicating deposition by various mechanisms and contributions from numerous sources. The mineralogy is fairly typical for the region and strongly reflects the large input of volcanic ash and ice-rafted material.Bulk chemical analyses indicate that the Reykjanes Ridge sediments appear to be enriched in Fe, Mn, Cu, Cr, and Zn as has been reported for other active ridges while the inactive Iceland—Faroes Ridge does not display such enrichments. The enriched metals in the ridge sediments do not show a particular affinity for any one size class. Partition studies indicate that the enriched Fe and Mn are held in separate phases while the other metals are present in all phases. Adsorption is not a major concentrating mechanism for the enhanced elements.Li distributions are apparently unaffected by active ridges and Pb seems to be partially concentrated biologically. There are indications that other criteria must be used in conjunction with bulk chemical analyses, in order to establish the presence of active ridge metal contributions. 相似文献
464.
To investigate the influence of compression, Poisson effect and turbulence on the fluid flow process and the inversion for fracture surface geometries, we simulate two sets of fractures: one with a defined fracture height standard deviation σ constant and a varying autocorrelation length λ and another with a fixed λ and a changing σ. Under compression, the normal stress closes fractures with a large aperture and thus reduces the effective permeability. However, the Poisson effect, which is induced by the compression, has little influence on the fluid flow properties and does not affect the inversion for fracture height standard deviation or the autocorrelation length. When introducing turbulence, we observe a significant difference between the performance of the Navier–Stokes equation and the local cubic law; compared with the Navier–Stokes equation, the local cubic law overestimates the peak value of the breakthrough time curve and effective permeability, thereby underestimating the mean fracture aperture. 相似文献
465.
Cordero-Quirós Nathalí Miller Arthur J. Pan Yunchun Balitaan Lawrence Curchitser Enrique Dussin Raphael 《Ocean Dynamics》2022,72(1):21-36
Ocean Dynamics - We analyze the bottom-up El Niño/Southern Oscillation (ENSO) driven physical-biological response of the California Current System (CCS) in a high-resolution,... 相似文献
466.
This paper presents a new approach for modeling shoreline change due to wave energy effects from remotely sensed data. The
airborne AIRSAR and POLSAR data were employed to extract wave spectra information and integrate them with historical remotely
sensed data such as aerial photography data to model the rate of change of the shoreline. A partial differential equation
(PDE) of the wave conversion model was applied to investigate the wave refraction patterns. The volume of sediment transport
at several locations was estimated based on the wave refraction patterns. The shoreline change model developed was designed
to cover a 14-km stretch of shoreline of Kuala Terengganu in Peninsular Malaysia. The model utilized data from aerial photographs,
AIRSAR, POLSAR, ERS-2, and in situ wave data. The results show that the shoreline rate of change modeled from the quasi-linear
wave spectra algorithm has a significant relationship with one estimated from historical vector layers of aerial photography,
AIRSAR, and POLSAR data. With the quasi-linear algorithm, an error of ±0.18 m/year in shoreline rate of change determination
was obtained with C
vv band. 相似文献
467.
Ya-Mei Yang Mitchell J. Small Brian Junker Grant S. Bromhal Brian Strazisar Arthur Wells 《Environmental Earth Sciences》2011,64(3):787-798
Proper characterizations of background soil CO2 respiration rates are critical for interpreting CO2 leakage monitoring results at geologic sequestration sites. In this paper, a method is developed for determining temperature-dependent
critical values of soil CO2 flux for preliminary leak detection inference. The method is illustrated using surface CO2 flux measurements obtained from the AmeriFlux network fit with alternative models for the soil CO2 flux versus soil temperature relationship. The models are fit first to determine pooled parameter estimates across the sites,
then using a Bayesian hierarchical method to obtain both global and site-specific parameter estimates. Model comparisons are
made using the deviance information criterion (DIC), which considers both goodness of fit and model complexity. The hierarchical
models consistently outperform the corresponding pooled models, demonstrating the need for site-specific data and estimates
when determining relationships for background soil respiration. A hierarchical model that relates the square root of the CO2 flux to a quadratic function of soil temperature is found to provide the best fit for the AmeriFlux sites among the models
tested. This model also yields effective prediction intervals, consistent with the upper envelope of the flux data across
the modeled sites and temperature ranges. Calculation of upper prediction intervals using the proposed method can provide
a basis for setting critical values in CO2 leak detection monitoring at sequestration sites. 相似文献
468.
Sorted bedforms on the inner shelf off northeastern New Zealand: spatiotemporal relationships and potential paleo-environmental implications 总被引:1,自引:1,他引:0
Sorted bedforms are heterogeneous shelf seabed features found ubiquitously on the inner shelf of New Zealand and around the
world. In this study we examine the shallow stratigraphy of sorted bedforms using diver-collected short cores together with
the textural analysis of the associated surface sediments in the Tairua-Pauanui embayment on the northeast coast of the North
Island of New Zealand. Combining sonar and textural analysis together with the local oceanographic conditions provides new
insight into the interpretation of sorted bedform features. In this regional case study, sorted bedforms are found to have
a stratigraphic signature characterized by alternating fine and coarse sequences that does not reflect alternating calm (low-energy)
and storm (high-energy) cycles. Instead, the core sequences suggest the signature of a heterogeneous inner shelf sedimentary
facies developed from morphodynamic feedback mechanisms operating at the scale of the bottom boundary layer. The resulting
sedimentary sequence (alternating coarse and fine units) found throughout this study site is the result of contemporaneous
sorting processes. 相似文献
469.
Accurate benthic habitat maps are critical for resource management in coastal waters with competing uses. We used a 500 kHz
phase-measuring bathymetric sonar (PMBS) and 900 kHz side-scan sonar to acquire seafloor data in estuarine and shelf environments.
Grab samples and remotely operated vehicle video created geological and biological classifications for segmented maps produced
by a backscatter clustering program. PMBS improves regional map resolution (<1 m), reduces the need for direct sampling, extends
information on sediment–biological relationships to larger areas, and allows measurements of bedforms. Auto-segmentation was
successful in environments with highly contrasting acoustic signatures and meters-scale homogeneity. Patchier communities
are identifiable in PMBS data. Species preferences for sediment (i.e., tubeworm preference for sediment without shell hash)
allowed us to determine potential habitat without identifying individual organisms in acoustic data. PMBS with sufficient
ground-truthing offers an efficient way to map seafloor characteristics, which is critical in marine spatial planning efforts. 相似文献
470.
Arthur J. Askew 《水文科学杂志》2013,58(1):195-196
Abstract A snowmelt runoff model is derived for relatively small rivers. The model involves the main components of the catchment water budget, physiographical and some other factors: water equivalent of snow cover, precipitation, antecedent moisture content, daily snowmelt, non-uniformity of snow cover, retention capacity of the basin, and percentage of forest area. The model structure includes calculations of the daily values of snowmelt excess and the transformation of these values into discharges at the outlet of the basin based on meteorological observations and appropriate distribution functions. Both calculations are made separately for open and forest areas. The parameters of the model were derived by optimization methods. The linear model based on the superposition principle is used to transform the discharges of a small river into total inflow into a large reservoir. The combined model was used to forecast for five days in advance daily mean inflows into the Gorky and Kuibyshev reservoirs (on the River Volga), using the observed and forecast discharges of the small rivers as input. 相似文献