Structure and Transport of the Agulhas Current and Its Temporal Variability     

Harry?L.?BrydenEmail author  Lisa?M.?Beal  Louise?M.?Duncan 《Journal of Oceanography》2005,61(3):479-492

Using a year-long moored array of current meters and well-sampled synoptic sections, we define the variability and mean structure and transport of the Agulhas current. Nineteen current meter records indicate that time scales for the temporal variability in the alongshore and offshore velocities are 10.2 and 5.4 days, respectively. Good vertical correlation exists between the alongshore or onshore velocity fluctuations, excluding the Agulhas Undercurrent. The lateral scale for the thermocline Agulhas current is about 60 km and the onshore velocity correlations are positive throughout the Agulhas Current system. Mean velocities from the array determine that the offshore edge of the Agulhas Current lies at 203 km and the penetration depth is 2200 m offshore of the Undercurrent. Hence, daily averaged velocity sections, determined by interpolation and extrapolation of current meter locations, for a 267-day period, from the surface to 2400 m depth and from the coast out to 203 km offshore encompass the main features of the Agulhas Current system. The Agulhas current is generally found close to the continental slope, within 31 km of the coast for 211 of 267 days. There are only five days when the core of the current is found offshore at 150 km. Total transport is always poleward, varying from −121 to −9 Sv, with maximum transport occurring when the core is 62 km from the coast. Average total transport for the 267 day period is −69.7 Sv; the standard deviation in daily transport values is 21.5 Sv; and the mean transport has an estimated standard error of 4.3 Sv. The Agulhas Undercurrent, which hugs the continental slope below the zero velocity isotach, has an average equatorward transport of 4.2 Sv, standard deviation of 2.9 Sv and an estimated standard error of 0.4 Sv. Transports from the moored array are in reasonable agreement with transport results from synoptic sections. Based on time series measurements at about 30° latitude in each ocean basin, the Agulhas Current is the largest western boundary current in the world ocean.  相似文献   

Surficial Hydrocarbon Seep Infauna from the Blake Ridge (Atlantic Ocean, 2150 m) and the Gulf of Mexico (690–2240 m)     

Christie A. Robinson  Joan M. Bernhard  Lisa A. Levin  Guillermo F. Mendoza  & Jessica K. Blanks 《Marine Ecology》2004,25(4):313-336

Abstract.  Infauna, including foraminifera and metazoans, were enumerated and identified from five types of seep habitats and two adjacent non-seep habitats. Collections were made with the deep submergence research vessel 'Alvin' from three areas of active seepage in the Gulf of Mexico (Alaminos Canyon [2220 m], Atwater Canyon [1930 m], and Green Canyon lease block 272 [700 m]) and on the Blake Ridge Diapir [2250 m], which is located off the southeastern coast of the United States. The seep habitats sampled included four types of microbial mats ( Beggiatoa , Thioploca , thin and thick Arcobacter ) and the periphery of a large mussel bed. Sediments under large rhizopod protists, xenophyophores, were sampled adjacent to the mussel bed periphery. A non-seep site, which was >1 km away from active seeps, was also sampled for comparison. Densities of most taxa were higher in the Gulf of Mexico seeps than in Blake Ridge samples, largely because densities in the thick microbial mats of Blake Ridge were significantly lower. Diversity was higher in the Thioploca mats compared to other microbial-mat types. Within an ocean basin ( i.e. , Atlantic, Gulf of Mexico) we did not observe significant differences in meiofaunal or macrofaunal composition in Beggiatoa versus Thioploca mats or thin versus thick Arcobacter mats. Foraminifera represented up to 16% of the seep community, a proportion that is comparable to their contribution at adjacent non-seep communities. In general, the observed densities and taxonomic composition of seep sites at the genus level was consistent with previous observations from seeps ( e.g. , the foraminifers Bolivina and Fursenkoina , the dorvilleid polychaete Ophryotrocha ).  相似文献   

Understanding the dynamics of sustainability transitions: the Home Insulation Program     

Lisa Smoleniec  Elizabeth Duncan 《The Australian geographer》2017,48(4):497-517

The Home Insulation Program (HIP) in Australia is an outstanding example of a contemporary attempt to intervene in a socio-technical regime. The program, implemented in 2009 under the then Australian Labor Party government led by Kevin Rudd, was targeted at stimulating the retrofit insulation industry. The objective was to both improve the energy efficiency of homes and thereby contribute to Australia’s emissions reduction targets by reducing greenhouse gas emissions and to stimulate the Australian economy at the time of the global financial crisis. The program ended early following a number of economic issues and health and safety concerns. Despite previous investigation into the HIP reviewing its design and implementation, the focus has been on economic issues and health and safety concerns. To date there has been no investigation of the HIP as a sustainability transition. This article integrates socio-technical transition theory (STTT) and political ecology (PE) approaches to analyse the HIP and identify lessons for future sustainability transition initiatives. This is achieved by illustrating the effect of regime management (RM) on the orientation of niche governance (NG) which highlights the importance of considering the RM and NG aspects of STTT with a PE approach in symmetry, in order to adequately account for political and economic contest and power relations, which are ubiquitous in environmental management governance.  相似文献   

Differential gene expression in mummichogs (Fundulus heteroclitus) following treatment with pyrene: comparison to a creosote contaminated site     

Roling JA  Bain LJ  Baldwin WS 《Marine environmental research》2004,57(5):377-395

Mummichogs, Fundulus heteroclitus, an estuarine fish with a relatively small home range found along the eastern coast of the United States are well-suited to monitoring contaminant effects, including those of polycyclic aromatic hydrocarbons (PAHs). One of the common PAHs in estuaries is pyrene. We report here on efforts to develop multiple biomarkers of pyrene exposure in this species. Adult male mummichogs were exposed in the laboratory to the weak aryl hydrocarbon receptor (AhR) agonist pyrene at 0, 30, or 50 microg/L in 7-day static renewal exposures. The RNA was extracted from livers and alterations in mRNA expression were assessed by subtractive hybridization and differential display in order to produce multiple biomarkers of pyrene exposure. Genes demonstrating differential expression were confirmed by quantitative-PCR (Q-PCR) and include cytochrome P-450 1A (CYP1A), a putative hepatocyte growth factor activator, a X-ray inducible retrotransposon, and several expressed sequenced tags (ESTs). Some of these genes represent new biomarkers of pyrene exposure and potential biomarkers of PAH exposure. Therefore, similar changes were investigated at a Superfund site in Charleston, SC. Mummichogs from a creosote contaminated site and from a reference site (North Inlet National Estuarine Research Reserve near Georgetown, SC) were trapped, RNA extracted from the livers, and Q-PCR performed. Many of the genes differentially expressed following pyrene exposure were not altered at the creosote contaminated site in comparison to the reference site. However, CYP1A and an EST were induced. CYP1A induction at Diesel Creek indicates that this population of fish does not demonstrate refractory CYP1A phenotypes observed at several sites with high levels of AhR agonists. Ultimately, we anticipate that the use of multiple biomarkers of PAH exposure will provide useful information on the potential effects of toxicants.  相似文献   

'Back to the future'     

Maria Cristina Gambi  Lisa Ann Levin 《Marine Ecology》2005,26(1):1-2

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Age-related differences in the recovery of lysosomes from stress-induced pathological reactions in marine mussels     

Lisa M. Hole  Michael N. Moore  Denis Bellamy 《Marine environmental research》1992,34(1-4)

This study was conducted to investigate the adaptability of marine mussels Mytilus edulis of increasing age to induced stress and subsequent recovery. Lysosomes, present in large numbers in the molluscan digestive gland, play a major role in intracellular digestion, and the stability of their membranes provides a sensitive biomarker for generalised cell injury which is correlated with the stress response of the whole animal. Lysosomal stability was measured in mussels of three age groups (2–4, 6–8 and ≥ 10 years) during exposure to hypoxia/hyperthermia and, in a separate experiment, to copper (50 ppb: where billion = 10⁹). The lysosomal reactions of all three age groups to both experimental stressors were similar. However, recovery from the induced pathological reactions was most pronounced in the youngest animals and least apparent in the oldest group. These findings indicate that the stress reaction is independent of age but that the potential for recovery of lysosomal integrity is age-related.  相似文献   

“The Corner of Avenue A and Twenty-Third Street”: Geographies of Street Numbering in the United States     

Reuben Rose-Redwood  Lisa Kadonaga 《The Professional geographer》2016,68(1):39-52

The designation of streets by number is one of the hallmarks of North American urbanism, yet very few studies have examined the geographies of street numbering in U.S. cities and towns. This article provides one of the first comprehensive, nationwide assessments of the spatial distribution of street numbering and lettering practices across the United States. Drawing on data collected from Google Maps, census records, state almanacs, and related sources, we analyze the proportion of incorporated places in all fifty U.S. states that have adopted some form of street numbering or lettering; the regional variation in the prevalence of alphanumerical systems of street designation and the relationships between the occurrence of street numbering, population size, and date of incorporation. In doing so, the broader aim of this study is to undertake the empirical groundwork needed to develop a more nuanced critical theory of the social production of calculable space.  相似文献   

Temporal variation and the effect of rainfall on metals flux from the historic Beatson mine,Prince William Sound,Alaska, USA     

Lisa L. Stillings  Andrea L. Foster  Randolph A. Koski  LeeAnn Munk  Wayne C. Shanks III 《Applied Geochemistry》2008

Several abandoned Cu mines are located along the shore of Prince William Sound, AK, where the effect of mining-related discharge upon shoreline ecosystems is unknown. To determine the magnitude of this effect at the former Beatson mine, the largest Cu mine in the region and a Besshi-type massive sulfide ore deposit, trace metal concentration and flux were measured in surface run-off from remnant, mineralized workings and waste. Samples were collected from seepage waters; a remnant glory hole which is now a pit lake; a braided stream draining an area of mineralized rock, underground mine workings, and waste piles; and a background location upstream of the mine workings and mineralized rock. In the background stream pH averaged ∼7.3, specific conductivity (SC) was ∼40 μS/cm, and the aqueous components indicative of sulfide mineral weathering, SO₄ and trace metals, were at detection limits or lower. In the braided stream below the mine workings and waste piles, pH usually varied from 6.7 to 7.1, SC varied from 40 to 120 μS/cm, SO₄ had maximum concentrations of 32 mg/L, and the trace metals Cu, Ni, Pb, and Zn showed maximum total acid extractable concentrations of 186, 5.9, 6.2 and 343 μg/L, respectively.  相似文献   

Zonal winds and southeast Australian rainfall in global and regional climate models     

Acacia S. Pepler  Lisa V. Alexander  Jason P. Evans  Steven C. Sherwood 《Climate Dynamics》2016,46(1-2):123-133

Southeast Australia is a region of high rainfall variability related to major climate drivers, with a long-term declining trend in cool-season rainfall. Projections of future rainfall trends are uncertain in this region, despite projected southward shifts in the subtropical ridge and mid-latitude westerlies. This appears to be related to a poor representation of the spatial relationships between rainfall variability and zonal wind patterns across southeast Australia in the latest Coupled Model Intercomparison Project ensemble, particularly in the areas where weather systems embedded in the mid-latitude westerlies are the main source of cool-season rainfall. Downscaling with regional climate models offers improvements in the mean rainfall climatology, and shows some ability to correct for poor modelled relationships between rainfall and zonal winds along the east coast of Australia. However, it provides only minor improvements to these relationships in southeast Australia, despite the improved representation of topographic features. These results suggest that both global and regional climate models may fail to translate projected circulation changes into their likely rainfall impacts in southeast Australia.  相似文献   

Long-lead ENSO predictability from CMIP5 decadal hindcasts     

Paula L. M. Gonzalez  Lisa Goddard 《Climate Dynamics》2016,46(9-10):3127-3147

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