Precipitation over eastern South America and the South Atlantic Sea surface temperature during neutral ENSO periods     

Rodrigo J. Bombardi  Leila M. V. Carvalho  Charles Jones  Michelle S. Reboita 《Climate Dynamics》2014,42(5-6):1553-1568

The dominant mode of coupled variability over the South Atlantic Ocean is known as “South Atlantic Dipole” (SAD) and is characterized by a dipole in sea surface temperature (SST) anomalies with centers over the tropical and the extratropical South Atlantic. Previous studies have shown that variations in SST related to SAD modulate large-scale patterns of precipitation over the Atlantic Ocean. Here we show that variations in the South Atlantic SST are associated with changes in daily precipitation over eastern South America. Rain gauge precipitation, satellite derived sea surface temperature and reanalysis data are used to investigate the variability of the subtropical and tropical South Atlantic and impacts on precipitation. SAD phases are assessed by performing Singular value decomposition analysis of sea level pressure and SST anomalies. We show that during neutral El Niño Southern Oscillation events, SAD plays an important role in modulating cyclogenesis and the characteristics of the South Atlantic Convergence Zone. Positive SST anomalies over the extratropical South Atlantic (SAD negative phase) are related to increased cyclogenesis near southeast Brazil as well as the migration of extratropical cyclones further north. As a consequence, these systems organize convection and increase precipitation over eastern South America.  相似文献   

First record of sea snake (Hydrophis elegans, Hydrophiinae) entrapped in marine debris     

Vinay Udyawer  Mark A. Read  Mark Hamann  Colin A. Simpfendorfer  Michelle R. Heupel 《Marine pollution bulletin》2013

Entanglement in derelict fishing gear and other marine debris is a major threat to the survival of large marine wildlife like cetaceans, seabirds and sea turtles. However, no previous reports of entanglement or entrapment have been recorded in sea snakes (Hydrophiinae). We report here on a sea snake (Hydrophis elegans) found with a ceramic washer encircling its body captured from the north-east coast of Queensland, Australia. The ring had constricted the body and over time caused extensive damage to the underlying tissues. A post-mortem examination showed the snake was severely emaciated as the ring restricted the passage of food to the stomach and intestine. This is the first record of mortality due to marine debris entrapment in sea snakes.  相似文献   

The orbital period and negative superhumps of the nova-like cataclysmic variable V378 Pegasi     

F.A. Ringwald  Kenia VelascoJonathan J. Roveto  Michelle E. Meyers 《New Astronomy》2012,17(4):433-437

A radial velocity study is presented of the cataclysmic variable V378 Pegasi (PG 2337 + 300). It is found to have an orbital period of 0.13858 ± 0.00004 d (3.32592 ± 0.00096 h). Its spectrum and long-term light curve suggest that V378 Peg is a nova-like variable, with no outbursts. We use the approximate distance and position in the Galaxy of V378 Peg to estimate E(B − V) = 0.095, and use near-infrared magnitudes to calculate a distance of 680 ± 90 pc and M_V = 4.68 ± 0.70, consistent with V378 Peg being a nova-like. Time-resolved photometry taken between 2001 and 2009 reveals a period of 0.1346 ± 0.0004 d (3.23 ± 0.01 h). We identify this photometric variability to be negative superhumps, from a precessing, tilted accretion disk. Our repeated measurements of the photometric period of V378 Peg are consistent with this period having been stable between 2001 and 2009, with its negative superhumps showing coherence over as many as hundreds or even thousands of cycles.  相似文献   

From Kerala to Dubai and back again: Construction migrants and the global economic crisis     

Michelle Buckley 《Geoforum》2012,43(2):250-259

As a crisis that was precipitated in part by risky forms of investment in the built environment, construction workers, and particularly migrants employed in the industry have been at the forefront of job-losses worldwide since 2008. I offer a reading of construction unemployment through David Harvey’s theorisation of the secondary circuit of capital, arguing that these trends reflect the industry’s immanent connections to the built environment and to volatile, debt-fuelled urbanisation strategies which have played a crucial role in absorbing global capital surpluses in recent years. I ground this international perspective through a case study on the crisis experiences of a group of migrant construction workers from the south Indian state of Kerala who lost their jobs in Dubai in 2009. Based on interviews with migrants who returned home following the collapse of the emirate’s construction sector, I explore how a number of place-specific relationships that transect the Kerala–Dubai construction labour market served to compound these workers’ economic insecurity following the crisis. These include the immense migration debts that migrants shouldered, the insecure and exploitative character of employment in Dubai’s building trades, and the particular vulnerability of Dubai’s construction markets to the retreat of finance capital from the Gulf region in 2008. Workers’ accounts offer insights into the uneven and trans-local geometries of risk that define contemporary construction work in Dubai. More broadly, they provide a key perspective on the precarious producer geographies that underpin the secondary circuit of capital.  相似文献   

Seagrass population dynamics and water quality in the Great Barrier Reef region: a review and future research directions   总被引：6，自引：0，他引：6  

Waycott M  Longstaff BJ  Mellors J 《Marine pollution bulletin》2005,51(1-4):343-350

Seagrasses in the Great Barrier Reef region, particularly in coastal habitats, act as a buffer between catchment inputs and reef communities and are important habitat for fisheries and a food source for dugong and green turtle. Within the Great Barrier Reef region there are four different seagrass habitat types now recognised. The spatial and temporal dynamics of the different types of seagrass habitat is poorly understood. In general seagrass growth is limited by light, disturbance and nutrient supply, and changes to any or all of these limiting factors may cause seagrass decline. The capacity of seagrasses to recover requires either recruitment via seeds or through vegetative growth. The ability of seagrass meadows to recover from large scale loss of seagrass cover observed during major events such as cyclones or due to anthropogenic disturbances such as dredging will usually require regeneration from seed bank. Limited research into the role of pollutants on seagrass survival suggests there may be ongoing impacts due to herbicides, pesticides and other chemical contaminants. Further research and monitoring of seagrass meadow dynamics and the influence of changing water quality on these is needed to enhance our ability to manage seagrasses on the Great Barrier Reef.  相似文献   

Descent into the Abyss     

Enrico Bonatti 《地学学报》1995,7(6):578-579

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Climate change, ambient ozone, and health in 50 US cities   总被引：2，自引：1，他引：2  

Michelle L. Bell  Richard Goldberg  Christian Hogrefe  Patrick L. Kinney  Kim Knowlton  Barry Lynn  Joyce Rosenthal  Cynthia Rosenzweig  Jonathan A. Patz 《Climatic change》2007,82(1-2):61-76

We investigated how climate change could affect ambient ozone concentrations and the subsequent human health impacts. Hourly concentrations were estimated for 50 eastern US cities for five representative summers each in the 1990s and 2050s, reflecting current and projected future climates, respectively. Estimates of future concentrations were based on the IPCC A2 scenario using global climate, regional climate, and regional air quality models. This work does not explore the effects of future changes in anthropogenic emissions, but isolates the impact of altered climate on ozone and health. The cities’ ozone levels are estimated to increase under predicted future climatic conditions, with the largest increases in cities with present-day high pollution. On average across the 50 cities, the summertime daily 1-h maximum increased 4.8 ppb, with the largest increase at 9.6 ppb. The average number of days/summer exceeding the 8-h regulatory standard increased 68%. Elevated ozone levels correspond to approximately a 0.11% to 0.27% increase in daily total mortality. While actual future ozone concentrations depend on climate and other influences such as changes in emissions of anthropogenic precursors, the results presented here indicate that with other factors constant, climate change could detrimentally affect air quality and thereby harm human health.  相似文献   

Investigation of the Andrew Bain transform fault zone (African-Antarctic region)     

A. A. Peyve  S. G. Skolotnev  M. Ligi  N. N. Turko  E. Bonatti  S. Yu. Kolodyazhnyi  N. P. Chamov  N. V. Tsukanov  Yu. E. Baramykov  A. E. Eskin  N. Grindlay  J. G. Sclater  D. Brunelly  A. N. Pertsev  A. Cipriani  G. Bortoluzzi  R. Mercuri  E. Paganelli  F. Muccini  Ch. Takeuchi  F. Zaffagnini  K. O. Dobrolyubova 《Doklady Earth Sciences》2007,416(1):991-994

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Distribution and habitat partitioning of immature bull sharks (Carcharhinus leucas) in a Southwest Florida estuary     

Colin A. Simpfendorfer  Garin G. Freitas  Tonya R. Wiley  Michelle R. Heupel 《Estuaries and Coasts》2005,28(1):78-85

The distribution and salinity preference of immature bull sharks (Carcharhinus leucas) were examined based on the results of longline surveys in three adjacent estuarine habitats in southwest Florida: the Caloosahatchee River, San Carlos Bay, and Pine Island Sound. Mean sizes were significantly different between each of these areas indicating the occurrence of size-based habitat partitioning. Neonate and young-of-the-year animals occurred in the Caloosahatchee River and juveniles older than 1 year occurred in the adjacent embayments. Habitat partitioning may reduce intraspecific predation risk and increase survival of young animals. Classification tree analysis showed that both temperature and salinity were important factors in determining the occurrence and catch per unit effort (CPUE) of immatureC. leucas. The CPUE of <1 year oldC. leucas was highest at temperatures over 29°C and in areas with salinities between 7‰ and 17.5‰ Although they are able to osmoregulate in salinities from fresh to fully marine, youngC. leucas may have a salinity preference. Reasons for this preference are unknown, but need to be further investigated.  相似文献   

Statistical analysis of modern seed assemblages from the San Francisco Bay: applications for the reconstruction of paleo-salinity and paleo-tidal inundation     

Michelle Goman 《Journal of Paleolimnology》2001,26(4):393-409

The feasibility of developing a seed calibration data set to infer environmental constraints was examined by studying modern seed and vegetation assemblages from 53 stations at three distinct tidal marshes within the San Francisco Bay (salt, brackish and freshwater). Pearson's correlation indicates autochthonous derivation of seeds at the marsh sites. Multivariate statistical analysis of the vegetation and seed data indicates discrete assemblages, which can be used as a proxy for modern salinity and tidal inundation within the estuary. Canonical discriminant analysis indicates that the vegetation and seed assemblages of the three marsh types are statistically distinct. Cluster analysis suggests that marsh vegetation is zoned at the mean higher high water mark at all the sites. The calibration set was then applied to stratigraphic seed data from the estuary to infer changes in paleo-salinity and -tidal inundation during the Holocene. The results of the calibration are compared to earlier reconstructions within the estuary. While the calibrated reconstruction broadly compares to previous reconstructions, a period of inferred lower salinity within the estuary between 3800–2000 cal yr B.P. is calibrated as brackish and not fresh by the calibration model.  相似文献