共查询到20条相似文献，搜索用时 31 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.
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
3.
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
4.
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
5.
David F. Reid Willard S. Moore William M. Sackett 《Earth and Planetary Science Letters》1979,43(2):227-236
The Mn-fiber technique for extracting radium from seawater has proved useful for studying the marine geochemistry of228Ra. In the Gulf of Mexico, this technique was used to measure the surface and near-surface distribution of226Ra and228Ra. The observed surface distribution of228Ra, and particularly the radium activity ratio (228/226) can be explained by known circulation patterns, or, when local surface currents are not well understood, may provide insight into their general characteristics.The radium activity ratio has increased from 0.5 in 1968 to 0.7 in 1973 in the surface Gulf of Mexico. This observed increase cannot be attributed to known anthropogenic or natural source perturbations within the Caribbean Sea-Gulf of Mexico system. Possible causes include a change in the residence time for near-surface water, or variations in the relative dominance of the two sources for water entering the eastern Caribbean; the North Equatorial Current and the Guiana Current.The temporal distribution of228Ra is unstable and naturally variable over a time period less than or equal to five years in the Gulf of Mexico and by extrapolation, the Caribbean Sea. Therefore, its usefulness in calculations of eddy diffusion coefficients for these regions is greatly diminished. 相似文献
6.
The long-term variability of sea level and surface flows in the Gulf of Mexico (GOM) is studied using global monthly sea level reconstruction (RecSL) for 1900–2015. The study explored the long-term relation between the dynamics of the GOM and inflows/outflows through the Yucatan Channel (YC) and the Florida Straits (FS). The results show a century-long trend of increased mean velocity and variability in the Loop Current (LC); however, no significant upward trend was found in the YC and FS flows, only increased variability. Empirical orthogonal function (EOF) analysis of sea surface height found spatial patterns dominated by variations in the LC and temporal variations on time scales ranging from a few months to multidecadal. The time evolution of each EOF mode of sea level is correlated with the velocity of either the LC, the YC, or the FS or some combination of the different flows. The mean sea level difference between the GOM and the northwestern Caribbean Sea was found to be influenced by the North Atlantic Oscillation (NAO), with unusually high differences during the 1970s when the NAO index was low and the Atlantic Ocean circulation was weak. Extreme peaks in SL difference coincide with the extension of the LC and the seasonal eddy shedding pattern. The observed seasonal cycle in the extension area of the LC as obtained from 20 years of altimeter data is significantly correlated (R = 0.63; confidence level = 98%) with the seasonal YC flow obtained from 116 years of the RecSL data. However, the same LC extension record had lower correlation (R = 0.45; confidence level = 90%) with the observed YC transport obtained from direct moored measurements over ~ 5 years, indicating the need for much longer measurements, since the LC extension and the YC flow are strongly affected by interannual and decadal variations. The study demonstrates the usefulness of even a coarse-resolution reconstruction for studies of regional ocean variability and climate change over longer time scales than current direct observations allow.
相似文献7.
An accurate method for long-term (weeks to months) projections of oil spill trajectories based on multi-year ensemble analyses
of simulated surface and subsurface (z = −800 m) drifters released at the northern Gulf of Mexico spill site is demonstrated during the 2010 oil spill. The simulation
compares well with satellite images of the actual oil spill which show that the surface spread of oil was mainly confined
to the northern shelf and slope of the Gulf of Mexico, with some (more limited) spreading over the north/northeastern face
of the Loop Current, as well as northwestward toward the Louisiana–Texas shelf. At subsurface, the ensemble projection shows
drifters spreading south/southwestward, and this tendency agrees well with ADCP current measurements near the spill site during
the months of May–July, which also show southward mean currents. An additional model analysis during the spill period (Apr–Jul/2010)
confirms the above ensemble projection. The 2010 analysis confirms that the reason for the surface oil spread to be predominantly
confined to the northern Gulf shelf and slope is because the 2010 wind was more southerly compared to climatology and also
because a cyclone existed north of the Loop Current which moreover was positioned to the south of the spilled site. 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.
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
10.
11.
Reverdin Gilles Friedman Andrew Ronald Chafik Léon Holliday Naomi Penny Szekely Tanguy Valdimarsson Héðinn Yashayaev Igor 《Ocean Dynamics》2019,69(3):385-403
We present a binned annual product (BINS) of sea surface temperature (SST), sea surface salinity (SSS), and sea surface density (SSD) observations for 1896–2015 of the subpolar North Atlantic between 40° N and 70° N, mostly excluding the shelf areas. The product of bin averages over spatial scales on the order of 200 to 500 km, reproducing most of the interannual variability in different time series covering at least the last three decades or of the along-track ship monitoring. Comparisons with other SSS and SST gridded products available since 1950 suggest that BINS captures the large decadal to multidecadal variability. Comparison with the HadSST3 SST product since 1896 also indicates that the decadal and multidecadal variability is usually well-reproduced, with small differences in long-term trends or in areas with marginal data coverage in either of the two products. Outside of the Labrador Sea and Greenland margins, interannual variability is rather similar in different seasons. Variability at periods longer than 15 years is a large part of the total interannual variability, both for SST and SSS, except possibly in the south-western part of the domain. Variability in SST and SSS increases towards the west, with the contribution of salinity variability to density dominating that of temperature in the western Atlantic, except close to the Gulf Stream and North Atlantic Current in the southwest area. Weaker variability and larger relative temperature contributions to density changes are found in the eastern part of the gyre and south of Iceland.
相似文献12.
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
13.
Jing Lu Fangli Qiao Xiaohua Wang Yong Teng Kyung Tae Jung Yanguang Liu 《Ocean Dynamics》2013,63(6):709-722
A numerical sediment transport model was embedded into a coupled wave-tide-circulation model to quantitatively estimate the suspended sediment fluxes (SSF) and distribution in different areas for the Yellow River derived sediment. The model is validated by comparing model simulated sediment deposition rates with those from observations. Simulated results show that the SSF of the Yellow River across two major sections (the Bohai Strait and the 37° N section) are highest during September and October, whereas for the 32° N section the flux is negligibly small (less than 0.1 kg/s). We demonstrate that the sediment flux is primarily driven by the buoyancy forcing of the Yellow River freshwater discharge and modulated by the wind-driven surface wave and circulation patterns in this region. The SSF across the Bohai Strait is about 30 % of the Yellow River discharge, while across the 37° N section it is 15.8 %. Therefore, about 70 % of the total discharged Yellow River sediments are deposited in the Bohai Sea, 14.1 % in the North Yellow Sea, and 13.9 % in the South Yellow Sea. There are two deposition branches in the Yellow Sea. The primary one is located off the eastern tip of the Shandong Peninsula and extends to the southwest off the coastline, which is consistent with the observed “Ω”-shape deposition pattern. This simulated tongue shape deposition pattern is isolated from the north by the strong resuspension off the eastern tip of Shandong Peninsula. The secondary branch extends to the middle of the South Yellow Sea and has been strengthened by resuspension process. The two deposition branches are separated by the wintertime Yellow Sea Warm Current in the bottom layer. 相似文献
14.
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
15.
The regional ocean model system (ROMS) is used to downscale a 26-year period of the twentieth century 20C3M experiment from
the global coupled Bergen climate model (BCM) for the North Sea. Compared to an observational-based climatology, BCM have
good results on the mean temperature, except for too low winter temperature. This is connected to a too weak inflow of Atlantic
water. The downscaling gives added value to the BCM results by providing regional details, doubling the Atlantic inflow, and
improving the mean winter temperature. For mean salinity, BCM has values very close to the climatology, whereas the downscaling
becomes too fresh. The downscaling, however, improves the sea surface salinity, the vertical structure, and the Norwegian
Coastal Current. It is concluded that the downscaling procedure as presented here is a suitable tool for assessing the future
Atlantic inflow and sea temperature in the North Sea based on a global climate projection. 相似文献
16.
Priyadarsi D. Roy Guillermo Vera-Vera Jason H. Curtis José L. Sánchez-Zavala Jesús David Quiroz-Jiménez Gowrappan Muthu Sankar 《地球表面变化过程与地形》2019,44(11):2211-2222
Anthropogenic global warming might cause expansion of the drylands and trigger socio-economic challenges in the water-deficit subtropical regions. Changes in hydroclimate during the intervals of variable global temperature over the recent geological past, however, could provide useful information about the possible responses of these arid ecosystems to the near future warmer conditions. We evaluated hydroclimates of two different parts of subtropical North America by generating new records of surface processes and regional vegetation from drought-prone northeast Mexico and subsequently compared them with the paleoclimate of the central-southern United States. Our study suggests that congruent changes occurred in both parts during ~13.5–9.5 cal ka BP, an interval with no warm pool in the northern Gulf of Mexico. The precipitation and erosion responded to temperature-modulated variations in positions of the Inter-Tropical Convergence Zone (ITCZ). Conditions were wetter than today in the subsequent warmer interval (~9.5–8.2 cal ka BP) with generally stable ITCZ and the highest summer insolation. Hydroclimate changes of both parts lacked congruency during ~8.2–6.8 cal ka BP as the northern Gulf of Mexico began hosting a warm pool. Similar to the modern conditions, this warm pool might have modified trajectories of the tropical storms. Erosion and abundance of C3 plants decreased in northeast Mexico. Higher wetness in the Mississippi River Basin and the southern Great Plains during this interval suggested that the storms made landfall more frequently in the central-southern United States. © 2019 John Wiley & Sons, Ltd. 相似文献
17.
18O/16O and14C analysis of deep-sea cores from the Gulf of Mexico revealed a 2.4% isotopic anomaly between 12,000 and 11,000 years ago. This value, together with estimates of the oxygen isotopic composition of ice meltwater and rates of mixing within the Gulf of Mexico indicates that the average yearly discharge of the Mississippi River was between 100,000 and 230,000 m3/s (as compared to 57,000 m3/s for the peak flood of February 17, 1937), with probable yearly peak floods twice as large. Corresponding sea-level rise was between 1 and 2 m per century. 相似文献
18.
In June 2003, we conducted a two-part field exercise to examine biogeochemical characteristics of water in the lower Mississippi river during the 4 days prior to discharge and in the Mississippi river plume over 2 days after discharge. Here we describe the fates of materials immediately after their discharge through Southwest Pass of the Mississippi delta into the northern Gulf of Mexico. Changes in surface water properties immediately after discharge were much larger and more rapid than changes prior to discharge. Total suspended matter (TSM) declined, probably due to sinking, dissolved macronutrients were rapidly diminished by mixing and biological uptake, and phytoplankton populations increased dramatically, and then declined. This decline appeared to begin at salinities of approximately 10 and was nearly complete by 15. A large increase in dissolved organic carbon (DOC) occurred over approximately the same salinity range. Weak winds (<2 m s−1) during and preceding this cruise apparently led to the formation of an extensive but thin freshwater lens from the river. This lens spread widely without much mixing, and the bloom of phytoplankton that occurred between discharge and a salinity of 10 was probably a freshwater community seeded from the lower river. Phytoplankton bloomed for a period of about 1–2 days, then declined dramatically, apparently releasing large amounts of DOC. Macronutrients from the river were utilized by the river phytoplankton community in the extensive freshwater lens. This contrasted with the more typical situation in which river nutrients stimulate a marine phytoplankton bloom at salinities in the mid-20s. We concluded that the direct effects of dissolved and particulate bio-reactive materials discharged by the Mississippi river were spatially restricted at this time to low-salinity water, at least as surface phenomena. After being transported through the lower river essentially unaltered, these materials were biogeochemically processed within days and tens of km. More generally, the mixing rate of plume water with receiving oceanic water has profound effects on the food web structure and biogeochemical cycling in the plume. 相似文献
19.
Ntaganou Nektaria Kourafalou Vassiliki Le Hénaff Matthieu Androulidakis Yannis 《Ocean Dynamics》2022,72(1):49-78
Ocean Dynamics - The evolution of the Loop Current (LC) system under the interaction with the complex topography of the Gulf of Mexico (GoM) is examined. Focusing on the eastern GoM, we study the... 相似文献
20.
IndoTROPICS studies on the plume of the Mamberamo river into the Bismarck Sea, West Papua, Indonesia
The tropical river ocean processes in coastal settings (TROPICS) program in Indonesia (Indotropics) was carried out in the Mamberamo estuary on May–June 1999 and August 2000. The Mamberamo River flows northward from the high mountains of West Papua to the narrow and steep continental slope of the Pacific Ocean. The data for the 1999 Mamberamo estuary cruises show the dispersal of fresh water coming out of the Mamberamo River into the Bismarck Sea, and the plume is clearly defined by the pattern of salinity, turbidity, and nutrient distribution. The Mamberamo River and other nearby rivers supply high concentrations of phosphate and nitrate to the New Guinea Coastal Current, so that nutrient concentrations are higher in the surface estuarine plume, compared to offshore areas. The distribution of fishes and benthic animals were also sampled over this area. 相似文献