共查询到20条相似文献，搜索用时 656 毫秒
1.
E.S. Van Vleet W.M. Sackett S.B. Reinhardt M.E. Mangini 《Marine pollution bulletin》1984,15(3):106-110
Pelagic tar was monitored over a two-year period in the Eastern Gulf of Mexico. A total of 416 surface and subsurface samples were collected during monthly cruises. Concentrations of pelagic tar found in the Eastern Gulf of Mexico were substantially higher than values reported for other areas around the world. Tar is primarily associated with the Gulf Loop Current, whereas continental shelf areas are relatively uncontaminated. Grounding of significant amounts of tar occurs primarily along the south-east coast of Florida, between Key West and Fort Pierce. Approximately 10–50% of the tar in the eastern Gulf is transported in from the Caribbean Sea via the Yucatan Straits. The remainder originates within the Gulf. Approximately half of the pelagic tar samples collected during the study appeared to have originated from tanker operations. 相似文献
2.
George R. HalliwellJr Alexander Barth Robert H. Weisberg Patrick Hogan Ole Martin Smedstad James Cummings 《Ocean Dynamics》2009,59(1):139-155
Nested non-assimilative simulations of the West Florida Shelf for 2004–2005 are used to quantify the impact of initial and
boundary conditions provided by Global Ocean Data Assimilation Experiment ocean products. Simulations are nested within an
optimum interpolation hindcast of the Atlantic Ocean, the initial test of the US Navy Coupled Ocean Data Assimilation system
for the Gulf of Mexico, and a global ocean hindcast that used the latter assimilation system. These simulations are compared
to one that is nested in a non-assimilative Gulf of Mexico model to document the importance of assimilation in the outer model.
Simulations are evaluated by comparing model results to moored Acoustic Doppler Current Profiler measurements and moored sea
surface temperature time series. The choice of outer model has little influence on simulated velocity fluctuations over the
inner and middle shelf where fluctuations are dominated by the deterministic wind-driven response. Improvement is documented
in the representation of alongshore flow variability over the outer shelf, driven in part by the intrusion of the Loop Current
and associated cyclones at the shelf edge near the Dry Tortugas. This improvement was realized in the simulation nested in
the global ocean hindcast, the only outer model choice that contained a realistic representation of Loop Current transport
associated with basin-scale wind-driven gyre circulation and the Atlantic Meridional Overturning Circulation. For temperature,
the non-assimilative outer model had a cold bias in the upper ocean that was substantially corrected in the data-assimilative
outer models, leading to improved temperature representation in the simulations nested in the assimilative outer models. 相似文献
3.
Dirk Nürnberg Martin Ziegler Cyrus Karas Ralf Tiedemann Matthew W. Schmidt 《Earth and Planetary Science Letters》2008,272(1-2):278-289
The Loop Current mediating the oceanic heat and salt flux from the Caribbean Sea into the Atlantic Ocean and its interference with the Mississippi River discharge are critical for both the regional climate in the Gulf of Mexico area and the water vapor transport towards high northern latitudes. We present a 400-kyr record of sea surface temperature and local surface salinity from the northeastern Gulf of Mexico (IMAGES core MD02-2575) approximated from combined planktonic foraminiferal δ18O and Mg/Ca, which reflects the temporal dynamics of the Loop Current and its relationship to both varying Mississippi discharge and evolution of the Western Hemisphere Warm pool. The reconstructed sea surface temperature and salinity reveal glacial/interglacial amplitudes that are significantly larger than in the Western Hemisphere Warm pool. Sea surface freshening is observed during the extreme cool periods of Marine Isotope Stages 2, 8, and 10, caused by the strengthened Mississippi discharge which spread widely across the Gulf favored by the less established Loop Current. Interglacial and interstadial sea-surface conditions, instead, point to a strengthened, northward flowing Loop Current in line with the northward position of the Intertropical Convergence Zone, allowing northeastern Gulf of Mexico surface hydrographic conditions to approach those of the Caribbean. At these times, the Mississippi discharge was low and deflected westward, promoted by the extended Loop Current. Previously described deglacial megadischarge events further to the west did not affect the northeastern Gulf of Mexico hydrography, implying that meltwater routing from the Laurentide Ice Sheet via the Mississippi River is unlikely to have affected Atlantic Meridional Overturning Circulation. 相似文献
4.
Muhling BA Roffer MA Lamkin JT Ingram GW Upton MA Gawlikowski G Muller-Karger F Habtes S Richards WJ 《Marine pollution bulletin》2012,64(4):679-687
The 2010 Deepwater Horizon oil spill impacted the northern Gulf of Mexico (GOM) during the spring spawning season of Atlantic bluefin tuna (BFT). Overlap between BFT spawning habitat and surface oil in the northern GOM was examined using satellite-derived estimates of oil coverage, and spawning habitat models. Results suggested that although eggs and larvae were likely impacted by oil-contaminated waters in the eastern GOM, high abundances of larvae were located elsewhere, especially in the western GOM. Overall, less than 10% of BFT spawning habitat was predicted to have been covered by surface oil, and less than 12% of larval BFT were predicted to have been located within contaminated waters in the northern GOM, on a weekly basis. Our results provide preliminary but important initial estimates of the effects of the spill on larval BFT mortality, as concern continues over the appropriate management responses to impacts of the spill. 相似文献
5.
《Continental Shelf Research》1987,7(8):883-894
The release times of five buoys, which broke free of moorings on the Alabama inner shelf, are known. The locations of subsequent sightings or recoveries of the buoys gave estimated trajectories of the buoys. These results show that the inner-shelf circulation is strongly wind-driven. When the Loop Current penetrates deeply into the northeastern Gulf of Mexico, outer shelf waters are often entrained by the Loop Current. 相似文献
6.
《Continental Shelf Research》1999,19(9):1221-1245
This paper presents some recent results of drifters released on the West Florida Shelf during 1996–1997 and compares with the numerical model results of the wind-driven circulation. Using satellite tracked surface drifters during the one year period from February 1996 to February 1997, a drifter free region, called the “forbidden zone”, is found over the southern portion of the West Florida Shelf. This finding is consistent with historical drift bottle data and with a recent numerical model study of the West Florida Shelf circulation response to climatological wind forcing. Direct drifter simulations by numerical model during March 1996 show a good agreement with both the in situ ADCP current observation and drifter observation. Three mechanisms are proposed for the observed Lagrangian features. The primarily dynamic mechanism is the along-shore wind forcing, which induces a coastal jet that tends to leave the coast and the bottom onshore and near surface offshore transports. The second one is the convergent coastal geometry and bottom topography for the southward flow in central shelf near Tampa Bay that enforces the coastal jet and the bottom and near surface transport. The last is a kinematic one, simply due to the short along-shore Lagrangian excursion, driven by the typical synoptic weather systems. Thus near surface shelf waters over the north may not reach the southern coast of the West Florida. Implication is that surface hazard such as oil spill that may occur outside of the southern West Florida shelf may not greatly impact the southern coastal region except Florida Keys. However, the biological and chemical patches over the north that may occur in the water column such as red tides still can easily reach the southern coastal region through the subsurface and bottom waters. 相似文献
7.
Predicting summer hypoxia in the northern Gulf of Mexico: redux 总被引：1，自引：0，他引：1
We report on the evolution and accuracy of a model used to predict the mid-summer area of hypoxia (oxygen ≤2 mg l(-1)) in the northern Gulf of Mexico, use it to test for impacts from the Deepwater Horizon oil spill (2010), and estimate the N loading that would meet a management goal. The prediction since 2000 were 100%±6% (μ±1 SE) of the actual value. The predicted in 2010 was 99% of that actual value, suggesting that the net effect of the 2010 oil spill on the hypoxic zone size was negligible. A tropical storm, however, may have reduced the potential size of the hypoxic zone. Lowering the May nitrogen load to about 70,000 mton N nitrate+nitrite would bring the model's predicted hypoxic zone size down to the management goal of 5000 km(2) and restore hypoxic waters to normoxic conditions. 相似文献
8.
It has been established that idealized western boundary currents, which encounter a gap in their supporting boundary, will assume one of two dominant steady states: a loop current state and a gap leaping state, and that transitions between these states display hysteresis. However, a question of whether the idealized geometries considered to date apply to the Gulf of Mexico Loop Current (LC) remained. Here, the nonlinear potential vorticity advection-diffusions equations are solved, for Gulf of Mexico topography, using Newton’s method. We demonstrate that, in application to the LC in the Gulf of Mexico, the original conclusions do hold and additionally describe peculiarities of the more realistic steady states. The existence of our numerically calculated steady LC states in the actual Gulf of Mexico are supported through analysis of historical sea surface height data, and implications of our results for LC modeling and forecasting are discussed.
相似文献9.
The rapid expansion of urbanization along the world’s coastal areas requires a more comprehensive and accurate understanding of the coastal ocean. Over the past several decades, numerical ocean circulation models have tried to provide such insight, based on our developing understanding of physical ocean processes. The systematic establishment of coastal ocean observation systems adopting cutting-edge technology, such as high frequency (HF) radar, satellite sensing, and gliders, has put such ocean model predictions to the test, by providing comprehensive observational datasets for the validation of numerical model forecasts. The New York Harbor Observing and Prediction System (NYHOPS) is a comprehensive system for understanding coastal ocean processes on the continental shelf waters of New York and New Jersey. To increase confidence in the system’s ocean circulation predictions in that area, a detailed validation exercise was carried out using HF radar and Lagrangian drifter-derived surface currents from three drifters obtained between March and October 2010. During that period, the root mean square (RMS) differences of both the east–west and north–south currents between NYHOPS and HF radar were approximately 15 cm s?1. Harmonic analysis of NYHOPS and HF radar surface currents shows similar tidal ellipse parameters for the dominant M2 tide, with a mean difference of 2.4 cm s?1 in the semi-major axis and 1.4 cm s?1 in the semi-minor axis and 3° in orientation and 10° in phase. Surface currents derived independently from drifters along their trajectories showed that NYHOPS and HF radar yielded similarly accurate results. RMS errors when compared to currents derived along the trajectory of the three drifters were approximately 10 cm s?1. Overall, the analysis suggests that NYHOPS and HF radar had similar skill in estimating the currents over the continental shelf waters of the Middle Atlantic Bight during this time period. An ensemble-based set of particle tracking simulations using one drifter which was tracked for 11 days showed that the ensemble mean separation generally increases with time in a linear fashion. The separation distance is not dominated by high frequency or short spatial scale wavelengths suggesting that both the NYHOPS and HF radar currents are representing tidal and inertial time scales correctly and resolving some of the smaller scale eddies. The growing ensemble mean separation distance is dominated by errors in the mean flow causing the drifters to slowly diverge from their observed positions. The separation distance for both HF radar and NYHOPS stays below 30 km after 5 days, and the two technologies have similar tracking skill at the 95 % level. For comparison, the ensemble mean distance of a drifter from its initial release location (persistence assumption) is estimated to be greater than 70 km in 5 days. 相似文献
10.
This paper proposes a numerical method to simulate oil spill trajectories, which are affected by the combination of advection, turbulent diffusion and mechanical spreading process, based on a particle tracking algorithm. Recent studies have shown that the trajectories of drifters on the ocean surface have a fractal structure that is far from being described using ordinary Brownian motion. Thus, in modeling the diffusion process, a discrete method has been employed for the generation of fractional Brownian motion (fBm) to illustrate superdiffusive transport. The algorithm is implemented to predict oil slick trajectories following the “Arteaga” oil spill accident that occurred near the Dalian coastal region in 2005. When compared with the observed data and the results of traditional diffusion modeling, the numerical results based on the fBm model are encouraging. 相似文献
11.
Hurricanes produce mixing and flow divergences (and convergences) that alter the upper-ocean heat content (OHC), which in turn affects the storm. Ocean observations under a hurricane are rare, making it difficult to validate forecast models. Past research have mainly focused on OHC-changes by vertical mixing and tacitly assumed that horizontal transports are slowly varying. Moreover, effects of coastal boundaries on ocean responses to hurricanes are generally omitted. This work uses satellite data to detect and verify forecast isopycnal motions under hurricane Wilma (Oct/16–26/2005) in the Caribbean Sea and the Gulf of Mexico. The model is then used to show that Wilma-induced convergences in northwestern Caribbean Sea produce increased Yucatan-Channel transport into the Gulf ahead of the storm, and the Yucatan–Loop Current front diverts most of this heat around the Loop. This response is distinct from that of an ocean without the Loop, for which warming is widespread north of the channel. These intricate ocean responses can impact hurricane predictions. 相似文献
12.
Previous investigations have suggested that wind stress curl, the balance of influx- and outflux-induced upwelling, as well
as a positive vorticity source fed from the left flank of the Kuroshio are all possible mechanisms that contribute to a persistent
cyclonic gyre in the South China Sea (SCS). Studies have also suggested that the loop current that forms from the Kuroshio
intrusion in the Luzon Strait, similar to the Loop Current in the Gulf of Mexico (GOM), has rarely been observed in the northern
SCS. In this research, an idealized numerical model driven by annual mean wind stress was adopted to investigate the relative
importance of dynamic processes that control the mean flow pattern of Kuroshio in the Luzon Strait and regulate circulation
in the SCS. An analysis of results drawn from numerical experiments suggests that the three mechanisms are of approximately
equal importance in the formation of the persistent cyclonic gyre in the northern SCS. Unlike the Gulf Stream which enters
the Gulf of Mexico through the Yucatan Channel, the two topographic ridges that align nearly meridionally in the Luzon Strait
keep the Kuroshio flowing roughly northward without distinct intrusion into the SCS. Unsurprisingly, an anticyclonic loop
current similar to the Gulf Stream pathway in the GOM was barely observed in the northern SCS. 相似文献
13.
Variation of the Kuroshio intrusion pathways northeast of Taiwan using the Lagrangian method 总被引：1，自引：0，他引：1
The seasonal variations of the Kuroshio intrusion pathways northeast of Taiwan were investigated using observational data from satellite-tracked sea surface drifters and a numerical particle-tracking experiment based on a high-resolution numerical ocean model. The results of sea surface drifter data observed from 1989 to 2013 indicate that the Kuroshio surface intrusion follows two distinct pathways: one is a northwestward intrusion along the northern coast of Taiwan Island, and the other is a direct intrusion near the turn of the shelf break. The former occurs primarily in the winter, while the latter exists year round. A particle-tracking experiment in the high-resolution numerical model reproduces the two observed intrusion paths by the sea surface drifters. The three-dimensional structure of the Kuroshio intrusion is revealed by the model results. The pathways, features and possible dynamic mechanisms of the subsurface intrusion are also discussed. 相似文献
14.
Hybrid-polarimetric SAR (synthetic aperture radar) is a new SAR mode, with relatively simple architecture, low cost, and wide swath, which will be carried by several Earth-observing systems from now to the near future. Here, we show how the second Stokes parameter of hybrid-polarimetric SAR can be employed to detect oil on the ocean surface using the classic well-known Otsu threshold methodology, in relation to contributions from different polarizations and dampening effects on backscatter intensity, neglecting the specific scattering mechanisms and oil types for an oil-covered surface. The detection methodology is demonstrated to be reliable in three example cases: oil-on-water experiments conducted by the Norwegian Clean Seas Association, natural oil seeps from the Gulf of Mexico, and observations from the Deep Water Horizon oil spill disaster in 2010. 相似文献
15.
Several studies have provided evidence for the enrichment of trace elements in coastal waters, particularly for copper. These enrichments have been attributed to diffusion from continental shelf sediments and to an influx of river water. We attempted to resolve between these sources by undertaking an extensive suite of measurements of trace metals (Cu, Ni, Cd), 226Ra and 228Ra in the surface waters of the Gulf of Mexico, along with trace metal profiles at 6 stations (April 1981 and December 1982). These data establish that enrichments of copper, nickel and cadmium occur in the shallow waters of the Gulf of Mexico. On the Mississippi continental shelf, high trace element concentrations (Cu, Ni: ～ 9 nmol/kg; Cd: ～ 200 pmol/kg) in lower-salinity waters (26‰) are similar to those observed in the Mississippi plume at the same salinity. This evidence suggests a river water source. On the other hand, trace element enrichments are also observed in the northern Gulf (Cu: +0.4 nmol/kg; Ni: +0.5 nmol/kg; Cd: +20 pmol/kg) which coincide with an increase in 228Ra but are not accompanied by decreased salinity. The excess of evaporation over precipitation in this region makes it possible that this water could be evaporated estuarine water; therefore, hydrographic observations cannot distinguish readily between river and shelf sources. A regional flux balance shows that most of the excess copper in the surface waters of the Florida Current can be supplied by the river-borne dissolved copper flux. Within the uncertainties of such calculations, the continental shelf copper flux must be less than or equal to the river flux. 相似文献
16.
On the processes that influence the transport and fate of Mississippi waters under flooding outflow conditions 总被引：1，自引：1，他引：0
The Mississippi River (MR) freshwater outflow is a major circulation forcing mechanism for the Northern Gulf of Mexico. We investigate the transport and fate of the brackish waters under flood conditions. The largest outflow in history (45,000 m3/s in 2011) is compared with the second largest outflow in the last 8 years (41,000 m3/s in 2008). Realistically forced simulations reveal the synergistic effect of enhanced discharge, winds, stratification of ambient shelf waters, and offshore circulation over the transport of plume waters. The strongest impact is attributed to the evolution of the Loop Current (LC) and associated frontal cyclonic eddies and anticyclonic rings, which exhibited distinctly different influence during the two study periods. The northward LC intrusion in the summer of 2011 weakened and blocked the buoyancy-driven downstream (westward) transport of brackish waters. The 2011 flood was thus characterized by upstream (eastward) flow and an extensive coverage of the Mississippi–Alabama–Florida shelf. An immediate response between the LC and the brackish offshore eastward spreading is computed during and after this historic event. The absence of a LC northward intrusion during the 2008 flood, in combination with wind effects, promotes downstream advection of MR waters towards the Louisiana–Texas shelf; large amounts of buoyant waters are also retained near the Delta, subject to local offshore advection under the synergistic action of LC-associated counter-rotating eddies. 相似文献
17.
Jorge Zavala-Hidalgo Artemio Gallegos-García Benjamín Martínez-López Steven L. Morey James J. O’Brien 《Ocean Dynamics》2006,56(3-4):333-338
An 8-year database of sea surface temperature (SST), 7 years of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color images, wind fields, and numerical model results are analyzed to identify regions and periods of coastal upwelling on the western and southern shelves of the Gulf of Mexico. On the seasonal scale, it is found that on the Tamaulipas, Veracruz, and southwestern Texas–Louisiana shelves there are upwelling favorable winds from April to August, when southeasterly winds are dominant and cold SST anomalies associated with upwelling are observed along their coasts. However, during summer, values of chlorophyll-a concentration are lower than those in autumn and winter, which are high due to advection of old bloom biological material from upstream. During winter, there is a cold front on the Tamaulipas shelf produced by advection of cold water from the Texas–Louisiana shelf and not due to upwelling. On the eastern Campeche Bank, persistent upwelling is observed due to favorable winds throughout the year with cold SST and large chlorophyll-a content along the inner shelf from May to September. On the Tamaulipas shelf, the summer upwelling delays the annual SST peak until September, while in most of the Gulf SST peaks in August. This difference is due to the end of the upwelling favorable wind conditions and the September seasonal current reversal. 相似文献
18.
Transport properties in small-scale coastal flows: relative dispersion from VHF radar measurements in the Gulf of La Spezia 总被引：2，自引：2，他引：0
Angelique C. Haza Tamay M. Özgökmen Annalisa Griffa Anne Molcard Pierre-Marie Poulain Germana Peggion 《Ocean Dynamics》2010,60(4):861-882
Lagrangian transport characteristics in the Gulf of La Spezia, a 5 × 10-km area along the western coast of Italy, are investigated
using data collected from a very high frequency (VHF) radar system with 250 m and 30-min resolution and two clusters of Coastal
Dynamics Experiment surface drifters during 2 weeks in the summer of 2007. The surface drifters are found to follow the temporal
and spatial evolution of the finite-scale Lyapunov exponents (FSLEs) computed by the VHF radar, indicating the precision of
both the radar measurements and the diagnostic FSLE in mapping accurately the transport pathways. In light of this agreement,
an analysis of the relative dispersion is conducted. It is found that the average FSLE value varies within a narrow range
of 4 day-1 ￡ l ￡ 7 day-14 \;\mbox{day}^{-1} \leq \lambda \leq 7 \;\mbox{day}^{-1} and displays an exponential regime over the entire extent of the measurements. The dynamical implication is that relative
dispersion is controlled nonlocally, namely by slow, persistent, energetic mesoscale structures as opposed to the rapidly
evolving high-gradient small-scale turbulent features. The value of the exponent is about an order of magnitude larger than
those found in previous modeling studies and analysis of SCULP data in the Gulf of Mexico but somewhat smaller than that estimated
from CLIMODE drifters in the Gulf Stream region. Scaling of the FSLE using a metric of resolved gradients of the Eulerian
fields in the form of a positive Okubo–Weiss criterion is useful, but not as precise as in modeling studies. The horizontal
flow convergence is found to have a small yet tangible effect on relative dispersion. 相似文献
19.
Based on an empirical orthogonal function analysis of satellite altimeter data, guidance from numerical model results, and CANEK transport estimates, we propose an index, based on differences in satellite-measured sea surface height anomalies, for measuring the influence of Gulf of Mexico Loop Current intrusion on vertically integrated transport variability through the Yucatan Channel. We show that the new index is significantly correlated at low frequencies (cut-off 120 days) with the cable estimates of transport between Florida and the Bahamas. We argue that the physical basis for the correlation is the geometric connectivity between the Yucatan Channel and the Straits of Florida. 相似文献
20.
Oil spill detection with fully polarimetric UAVSAR data 总被引：3，自引：0，他引：3
In this study, two ocean oil spill detection approaches based on four scattering matrices measured by fully polarimetric synthetic aperture radar (SAR) are presented and compared. The first algorithm is based on the co-polar correlation coefficient, ρ, and the scattering matrix decomposition parameters, Cloud entropy (H), mean scattering angle (α) and anisotropy (A). While each of these parameters has oil spill signature in it, we find that combining these parameters into a new parameter, F, is a more effective way for oil slick detection. The second algorithm uses the total power of four polarimetric channels image (SPAN) to find the optimal representation of the oil spill signature. Otsu image segmentation method can then be applied to the F and SPAN images to extract the oil slick features. Using the L-band fully polarimetric Uninhabited Aerial Vehicle – synthetic aperture radar (UAVSAR) data acquired during the 2010 Deepwater Horizon oil spill disaster event in the Gulf of Mexico, we are able to successfully extract the oil slick information in the contaminated ocean area. Our result shows that both algorithms perform well in identifying oil slicks in this case. 相似文献