首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
The barrier coast of north Yucatan has been evolving into a beachfront recreational landscape since the introduction of passenger rail service between Mérida and Progreso in 1881. Beginning in the 1950's, middle-class vacation home construction spread laterally outward from Progreso, and even distal fishing and salt-gathering villages became engulfed by a recreational landuse overlay. In spite of geomorphic evidence of marine transgression, such as dune scarps and washover fans, the focus of recreational urbanization has been the beachfront. And although attempts at retarding shore erosion have taken place since the 1960s, hazard perception has remained generally low until the late 1980s. When Hurricane Gilbert blew across the Yucatan peninsula in 1988, damage to beachfront structures, highways, boats, and salt ponds was extensive. The barrier environment exhibited extensive overwashing and breaching, especially in areas of human modification, and the lagoon ecosystem experienced considerable ecologic disruption. Because the north Yucatan coast is a locus of domestic tourism, and the thousands of uninsured summer homes are owned largely by members of Mérida's middle class, reconstruction since Gilbert has been slow. Incipient trends of international tourism development have slowed since 1988.  相似文献   

2.
Climate change on the Yucatan Peninsula during the Little Ice Age   总被引：1，自引：0，他引：1  
We studied a 5.1-m sediment core from Aguada X'caamal (20° 36.6′N, 89° 42.9′W), a small sinkhole lake in northwest Yucatan, Mexico. Between 1400 and 1500 A.D., oxygen isotope ratios of ostracod and gastropod carbonate increased by an average of 2.2‰ and the benthic foraminifer Ammonia beccarii parkinsoniana appeared in the sediment profile, indicating a hydrologic change that included increased lake water salinity. Pollen from a core in nearby Cenote San José Chulchacá showed a decrease in mesic forest taxa during the same period. Oxygen isotopes of shell carbonate in sediment cores from Lakes Chichancanab (19° 53.0′N, 88° 46.0′W) and Salpeten (16° 58.6′N, 89° 40.5′W) to the south also increased in the mid-15th century, but less so than in Aguada X'caamal. Climate change in the 15th century is also supported by historical accounts of cold and famine described in Maya and Aztec chronicles. We conclude that climate became drier on the Yucatan Peninsula in the 15th century A.D. near the onset of the Little Ice Age (LIA). Comparison of results from the Yucatan Peninsula with other circum-Caribbean paleoclimate records indicates a coherent climate response for this region at the beginning of the LIA. At that time, sea surface temperatures cooled and aridity in the circum-Caribbean region increased.  相似文献   

3.
The Yucatan Peninsula is a coastal plain underlain by permeable limestone and receives abundant rainfall. Such hydrogeologic conditions should provide major supplies of water; however, factors of climate and hydrogeology have combined to form a hydrologic system with chemical boundaries that limits the amount of fresh water available. Management of water resources has long had a major influence on the cultural and economic development of the Yucatan. The Mayan culture of the northern Yucatan developed on extensive use of groundwater. The religion was water oriented and the Mayan priests prayed to Chac, the water god, for assistance in water management, primarily to decrease the severity of droughts. The Spaniards arrived in 1517 and augmented the supply by digging wells, which remained the common practice for more than 300 years. Many wells now have been abandoned because of serious problems of pollution. A historical perspective of a paper such as this provides insight into the attitudes concerning water of early people and perhaps provides insight into current attitudes concerning water. Hydrogeologists possess the expertise to generate relevant information required by water managers to arrive at management programs to achieve sustainable development.  相似文献   

4.
Geometry and connectivity of high-permeability zones determine groundwater flow in karst aquifers. Efficient management of karst aquifers requires regional mapping of preferential flow paths. Remote-sensing technology provides tools to efficiently map the subsurface at such scales. Multi-spectral remote sensing imagery, shuttle radar topography data and frequency-domain airborne electromagnetic (AEM) survey data were used to map karst-aquifer structure on the Yucatan Peninsula, Mexico. Anomalous AEM responses correlated with topographic features and anomalous spectral reflectance of the terrain. One known preferential flow path, the Holbox fracture zone, showed lower bulk electrical resistivity than its surroundings in the AEM surveys. Anomalous structures delineated inland were sealed above by a low-resistivity layer (resistivity: 1–5 Ωm, thickness: 5–6?m). This layer was interpreted as ejecta from the Chicxulub impact (Cretaceous/Paleogene boundary), based on similar resistivity signatures found in borehole logs. Due to limited sensitivity of the AEM survey, the subsurface configuration beneath the low-resistivity layer could not be unambiguously determined. AEM measurements combined with remote-sensing data analysis provide a potentially powerful multi-scale methodology for structural mapping in karst aquifers on the Yucatan Peninsula and beyond.  相似文献   

5.
Natural Hazards - In this study, the first ever Sea, Lake, Overland Surges from Hurricanes (SLOSH) grid was built for the Yucatan Peninsula. The SLOSH model was used to simulate storm surges in the...  相似文献   

6.
Groundwater-flow modeling in the Yucatan karstic aquifer, Mexico   总被引：1，自引：0，他引：1  
The current conceptual model of the unconfined karstic aquifer in the Yucatan Peninsula, Mexico, is that a fresh-water lens floats above denser saline water that penetrates more than 40 km inland. The transmissivity of the aquifer is very high so the hydraulic gradient is very low, ranging from 7–10 mm/km through most of the northern part of the peninsula. The computer modeling program AQUIFER was used to investigate the regional groundwater flow in the aquifer. The karstified zone was modeled using the assumption that it acts hydraulically similar to a granular, porous medium. As part of the calibration, the following hypotheses were tested: (1) karstic features play an important role in the groundwater-flow system; (2) a ring or belt of sinkholes in the area is a manifestation of a zone of high transmissivity that facilitates the channeling of groundwater toward the Gulf of Mexico; and (3) the geologic features in the southern part of Yucatan influence the groundwater-flow system. The model shows that the Sierrita de Ticul fault, in the southwestern part of the study area, acts as a flow barrier and head values decline toward the northeast. The modeling also shows that the regional flow-system dynamics have not been altered despite the large number of pumping wells because the volume of water pumped is small compared with the volume of recharge, and the well-developed karst system of the region has a very high hydraulic conductivity. Electronic Publication  相似文献   

7.
Natural Hazards - Principal characteristics of summer mesoscale convective systems in the Yucatan Peninsula, Mexico, were studied using three years of radar imagery. MCSs occurred almost daily in...  相似文献   

8.
Hurricane Gilbert has been labelled the storm of the century because of the many meteorological records it set. These include size, straightness of track, atmospheric pressure, precipitation, and total energy. After ravaging Jamaica as a Force 3 storm, Gilbert made landfall in Yucatan as a Force 5, one of only three hurricanes of such magnitude to do so in North America this century. In spite of a death toll of 318 and property damage in the billions of dollars, Gilbert's impacts were eclipsed by the extensive publicity that accompanied Hurricane Hugo's landfall in South Carolina the following year (1989).  相似文献   

9.
Global controls on the oceanographic influences on the nature of carbonate factories are broadly understood. The details of the influences of changes in temperature and nutrients across individual carbonate shelves are less well constrained, however. This study explores spatial and temporal variations in chemical oceanography along and across the Yucatan Shelf, a modern carbonate ramp, and how these factors relate to variable bottom character, sediment and sediment geochemistry. In‐situ sensors and remote‐sensing data indicate the sporadic presence of cool, upwelled water with low dissolved oxygen and elevated Chlorophyll‐a. This current‐driven, westward flow of upwelled water is most evident in a zone just offshore of the northern peninsular shoreline, but its influence wanes ca 75 km offshore and as the shore turns southward. The impacts of this water mass include a transitional photozoan–heterozoan assemblage with biosiliceous components, relict grains and common thin Holocene sediment accumulations nearshore; further offshore are coralgal reefs and expansive sand plains. Geochemical proxies of bulk sediment, including high δ18O and elevated HREE/LREE (heavy rare‐earth element/light rare‐earth element) ratios near, and downcurrent of, the upwelling source, are interpreted to represent the signal of nearshore, westward movement of the cool and nutrient‐rich, upwelled water. Collectively, these data emphasize how local processes such as upwelling and longshore transport can variably influence carbonate sediment accumulations and their geochemical signatures, both along and across individual shelves. These data and insights provide an analogue for the influences of spatial variability of water masses in the geological record, and for accurate interpretation of stratigraphic changes of sedimentary and geochemical proxy data in carbonate archives.  相似文献   

10.
Lindsey Carte  Erin Daley 《Geoforum》2010,41(5):700-710
In response to a growing body of literature encouraging geographers to present textured, regional case studies that demonstrate how neoliberalism functions at diverse scales, this article presents a nuanced account of neoliberalism in Mexico’s Yucatan peninsula. The study seeks to illustrate how neoliberal reforms to agriculture and ongoing neoliberal tourism development in the Yucatecan state of Quintana Roo intersect to create a unique regional context for migration between the state’s rural areas and Mexico’s largest planned tourism development zone in Cancun. The research presented is based on a series of in-depth qualitative interviews that took place in 2003 with rural residents and regional migrants working in Cancun. Through the employment of an experiential definition of neoliberalism, grounded in the lived experiences and perceptions of study participants, the article suggests that rural-urban tourist pole migration is the result of a complex negotiation of the region’s neoliberal landscape. The article argues that rural residents’ and migrants’ perceptions of the failure of agriculture as a livelihood is shaped relative to the perceived success of the tourism industry and better livelihood opportunities in Cancun. These widespread perceptions of agricultural failure in the Yucatan peninsula are constructed not solely in response to local conditions but rather in response to the overall regional outcome of neoliberal economic restructuring initiatives which have negatively affected traditional agriculture in the rural sphere while privileging tourism development in the urban sphere centered in Cancun.  相似文献   

11.
The application of agrochemicals in crops can cause pollution of aquifers, especially those with a shallow water table and covered by thin soils; such is the case of Yucatan, Mexico. Information about the requirements and application of fertilizers to major irrigation and rainfed crops as well as the volume of water consumed in growing were used to determine the potential amount of nitrate delivered to groundwater. The research reported in this paper was conducted in the metropolitan area of the city of Merida, in Yucatán, Mexico, where groundwater plays an important role since it is the main source of supply, due to the lack of surface water in the region. In addition, the vulnerability of this aquifer is threatened by the various activities taking place in the municipalities, which emphasize agriculture, located within the groundwater basin. This activity is analyzed as a source of contamination given the concentration of NO3 ? present in groundwater intended for human consumption. The results show that the contribution of farming that enriches the presence of nitrates in the aquifer is different for each municipality in the study area. For the ZMM, the average nutrient leaching is 44 % of the original mass applied; it could be diluted approximately 12 times, in the groundwater.  相似文献   

12.
 The nitrate concentration in 12 water-supply wells were monitored for the period April 1992 to March 1993. Each water-supply well was sampled once a month. The nitrate concentrations in the 12 wells ranged from 7 to 156 mg/l. Two water-supply wells (Chacsinkin and Peto) showed concentrations that reached 3.5 times the maximum permissible limit for the Drinking Water Standard (45 mg/l). A third water-supply well (Akil) exceeds the norm for 7 out of 12 months. The use of nitrogen-rich fertilizers are responsible for high nitrate concentrations in groundwater in the southern part of Yucatan, Mexico where intensive agricultural practices exist. Received: 14 December 1999 · Accepted: 2 May 2000  相似文献   

13.
Effects of urbanization on groundwater resources of Merida, Yucatan, Mexico   总被引：3，自引：0，他引：3  
 Groundwater quality in the city of Merida, Yucatan, Mexico, where dependence on groundwater supply is 100%, is affected by urbanization. Data from the sampling of shallow wells and boreholes along with water level records are used to study the aquifer. Chemical changes in time of the bottom and top half of the freshwater zone are the basis for hydrogeochemistry. The comparison of 1970 data (which represent information prior to urbanization) to 1991, suggests that the most affected (contaminated) areas coincide with that of urbanization. Received: 1 October 1997 · Accepted: 23 February 1998  相似文献   

14.
A hydraulic analysis of the interface between freshwater–saltwater behavior was done in the Merida Yucatan zone, two machines that constantly register the groundwater levels were installed, and three electric conductivity logs were taken from wells. When comparing the measured results with the ones obtained using theoretical equations developed to calculate the freshwater–saltwater interface position, it was proved that in some cases these equations can be applied, and in others not. Two effects that rule the behavior of karst aquifers in extraordinary conditions were found.  相似文献   

15.
Pensacola Bay, Florida, was in the strong northeast quadrant of Hurricane Ivan when it made landfall on September 16, 2004 as a category 3 hurricane on the Saffir-Simpson scale. We present data describing the timeline and maximum height of the storm surge, the extent of flooding of coastal land, and the magnitude of the freshwater inflow pulse that followed the storm. We computed the magnitude of tidal flushing associated with the surge using a tidal prism model. We also evaluated hurricane effects on water quality using water quality surveys conducted 20 and 50 d after the storm, which we compared with a survey 14 d before landfall. We evaluated the scale of hurricane effects relative to normal variability using a 5-yr monthly record. Ivan's 3.5 m storm surge inundated 165 km2 of land, increasing the surface area of Pensacola Bay by 50% and its volume by 230%. The model suggests that 60% of the Bay's volume was flushed, initially increasing the average salinity of Bay waters from 23 to 30 and lowering nutrient and chlorophylla concentrations. Additional computations suggest that wind forcing was sufficient to completely mix the water column during the storm. Freshwater discharge from the largest river increased twentyfold during the subsequent 4 d, stimulating a modest phytoplankton bloom (chlorophyll up to 18 μg l−1) and maintaining hypoxia for several months. Although the immediate physical perturbation was extreme, the water quality effects that persisted beyond the first several days were within the normal range of variability for this system. In terms of water quality and phytoplankton productivity effects, this ecosystem appears to be quite resilient in the face of a severe hurricane effect.  相似文献   

16.
In this work, geographic information systems (GIS) and multi-criteria decision analysis (MCDA) were used in order to identify the appropriate location for hazardous waste (HW) treatment facilities and final disposal sites in the State of Yucatan, Mexico. For HW-treatment facilities, in addition to the distance to generators and treatment facilities, geographic conditions of the site, such as vegetation, soil type, accessibility, distance to urban or rural communities, and all the boundary elements as agricultural or livestock areas, were considered in GIS and MCDA. Final disposal was taken into account only for those HW that could not be avoided or treated. In order to find the most suitable areas, the Mexican Official Norm NOM-055-SEMARNAT-2003 criteria were observed too. It was found that the most suitable zones for HW-treatment facilities were at the centre of the State, whereas the most recommended areas for HW final disposal sites were at the south.  相似文献   

17.
Although hurricane disturbance is a natural occurrence in mangrove forests, the effect of widespread human alterations on the resiliency of estuarine habitats is unknown. The resiliency of mangrove forests in southwest Florida to the 2004 hurricane season was evaluated by determining the immediate response of mangroves to a catastrophic hurricane in areas with restricted and unrestricted tidal connections. The landfall of Hurricane Charley, a category 4 storm, left pronounced disturbances to mangrove forests on southwest Florida barrier islands. A significant and negative relationship between canopy loss and distance from the eyewall was observed. While a species-specific response to the hurricane was expected, no significant differences were found among species in the size of severely impacted trees. In the region farthest from the eyewall, increases in canopy density indicated that refoliation and recovery occurred relatively quickly. There were no increases or decreases in canopy density in regions closer to the eyewall where there were complete losses of crown structures. In pre-hurricane surveys, plots located in areas of management concern (i.e., restricted connection) had significantly lower stem diameter at breast height and higher stem densities than plots with unrestricted connection. These differences partially dictated the severity of effect from the hurricane. There were also significantly lower red mangrove (Rhizophora mangle) seedling densities in plots with restricted connections. These observations suggest that delays in forest recovery are possible in severely impacted areas if either the delivery of propagules or the production of seedlings is reduced by habitat fragmentation.  相似文献   

18.
《第四纪科学杂志》2017,32(8):1112-1120
Chemical composition, magnetic susceptibility and texture of sediments in a swamp from the Los Petenes Biosphere Reserve provide information about late Holocene hydrological variations on the western margin of the Yucatan Peninsula, Mexico. Periods of lower than average amounts of K‐bearing clastics during 2580–2050, 1100–825 and 700–160 cal a BP represent drought intervals. Magnetic minerals were better preserved during these arid intervals, as the swamp was not perennially anoxic. Hydroclimate was unstable during 2580–2050 cal a BP, as several storm‐surge events occurred within an overall arid interval. The drought of 1100–825 cal a BP was contemporary with the Terminal Classic Period and the drought of 700–160 cal a BP was characterized by the lowest erosion as well as highest abundance of authigenic carbonate. Comparison with other climate proxy records from the region suggests that droughts had different geographic coverage. We attribute the different geographic coverage of droughts to variable strengths of polar continental air masses as well as dynamics of the Caribbean Low Level Jet and tropical cyclones that brought precipitation into different parts of the peninsula.
  相似文献   

19.
《Atmósfera》2014,27(1):77-89
Wind power density, vertical velocity profiles, and other wind characteristics were established using a 51 m meteorological mast located very close to the shoreline on the northwest of the Yucatan peninsula in the Gulf of Mexico. A comparative study of the wind power density was carried out using information obtained between September 2010 and September 2011. The wind speed probability density function was found to be bimodal due to sea-land breezes, a characteristic that becomes less evident as the vertical distance to the ground increases. The distinction between these two wind regimes was used to fit the Weibull-Weibull curve using a linear least-squares criterion in the parameters. In addition, numerical simulations from a mesoscale model are in close agreement with measurements above z = 50 m (z is the vertical distance to the ground). This result suggests that some mesoscale simulations may serve as a preliminary wind energy assessment tool in coastal zones with extended low-lying areas.  相似文献   

20.
Three sequential hurricanes made landfall over the South Florida peninsula in August and September 2004. The storm systems passed north of the Everglades wetlands and northeastern Florida Bay, but indirect storm effects associated with changes in freshwater discharge during an otherwise drought year occurred across the wetland–estuary transition area. To assess the impacts of the 2004 hurricane series on hydrology, nutrients, and microbial communities in the Everglades wetlands to Florida Bay transition area, results are presented in the context of a seasonal cycle without hurricane activity (2003). Tropical activity in 2004 increased rainfall over South Florida and the study area, thereby temporarily relieving drought conditions. Not so much actual rainfall levels at the study site but more so water management practices in preparation of the hurricane threats, which include draining of an extensive freshwater canal system into the coastal ocean to mitigate inland flooding, rapidly reversed hypersalinity in the wetlands-estuary study area. Although annual discharge was comparable in both years, freshwater discharge in 2004 occurred predominantly during the late wet season, whereas discharge was distributed evenly over the 2003 wet season. Total organic carbon (TOC), ammonium ( \operatornameNH + 4 \operatorname{NH} ^{ + }_{4} ), and soluble reactive phosphorus (SRP) concentrations increased during the hurricane series to concentrations two to five times higher than long-term median concentrations in eastern Florida Bay. Spatiotemporal patterns in these resource enrichments suggest that TOC and SRP originated from the Everglades mangrove ecotone, while \operatornameNH + 4 \operatorname{NH} ^{ + }_{4} originated from the bay. Phytoplankton biomass in the bay increased significantly during storm-related freshwater discharge, but declined at the same time in the wetland mangrove ecotone from bloom conditions during the preceding drought. In the bay, these changes were associated with increased nanophytoplankton and decreased picophytoplankton biomass. Heterotrophic bacterial production increased in response to freshwater discharge, whereas bacterial abundance decreased. Hydrochemical and microbial changes were short-lived, and the wetland–bay transition area reverted to more typical oligotrophic conditions within 3 months after the hurricanes. These results suggest that changes in freshwater discharge after drought conditions and during the hurricane series forced the productivity and P-enriched characteristics of the wetland’s mangrove ecotone, although only briefly, to the south into Florida Bay.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号