The Bransfield current system     

Pablo Sangrà  Carmen GordoMónica Hernández-Arencibia  Angeles Marrero-DíazAngel Rodríguez-Santana  Alexander Stegner  Antonio Martínez-MarreroJosep L. Pelegrí  Thierry Pichon 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(4):390-402

We use hydrographic data collected during two interdisciplinary cruises, CIEMAR and BREDDIES, to describe the mesoscale variability observed in the Central Basin of the Bransfield Strait (Antarctica). The main mesoscale feature is the Bransfield Front and the related Bransfield Current, which flows northeastward along the South Shetland Island Slope. A laboratory model suggests that this current behaves as a gravity current driven by the local rotation rate and the density differences between the Transitional Zonal Water with Bellingshausen influence (TBW) and the Transitional Zonal Water with Weddell Sea influence (TWW). Below the Bransfield Front we observe a narrow (10 km wide) tongue of Circumpolar Deep Water all along the South Shetland Islands Slope. At the surface, the convergence of TBW and TWW leads to a shallow baroclinic front close to the Antarctic Peninsula (hereafter Peninsula Front). Between the Bransfield Front and the Peninsula Front we observe a system of TBW anticyclonic eddies, with diameters about 20 km that can reach 300 m deep. This eddy system could be originated by instabilities of the Bransfield Current. The Bransfield Current, the anticyclonic eddy system, the Peninsula Front and the tongue of Circumpolar Deep Water, are the dynamically connected components of the Bransfield Current System.  相似文献   

Vertical Distribution of Radiation and Energy Balance Partitioning Within and Above a Lodgepole Pine Stand Recovering from a Recent Insect Attack   总被引：1，自引：0，他引：1  

Carmen Emmel  Eugenie Paul-Limoges  Thomas Andrew Black  Andreas Christen 《Boundary-Layer Meteorology》2013,149(2):133-163

The current outbreak of mountain pine beetle (MPB) that started in the late 1990s in British Columbia, Canada, is the largest ever recorded in the north American native habitat of the beetle. The killing of trees is expected to change the vertical distribution of net radiation ( $Q^*$ Q ? ) and the partitioning of latent ( $Q_\mathrm{E}$ Q E ) and sensible ( $Q_\mathrm{H}$ Q H ) heat fluxes in the different layers of an attacked forest canopy. During an intensive observation period in the summer of 2010, eddy-covariance flux and radiation measurements were made at seven heights from ground level up to 1.34 times the canopy height in an MPB-attacked open-canopy forest stand $(\hbox {leaf area index} = 0.55~\mathrm{{m}}^{2}\ \mathrm{{m}}^{-2})$ ( leaf area index = 0.55 m 2 m - 2 ) in the interior of British Columbia, Canada. The lodgepole pine dominated stand with a rich secondary structure (trees and understorey not killed by the beetle) was first attacked by the MPB in 2003 and received no management. In this study, the vertical distribution of the energy balance components and their sources and sinks were analyzed and energy balance closure (EBC) was determined for various levels within the canopy. The low stand density resulted in approximately 60 % of the shortwave irradiance and 50 % of the daily total $Q^*$ Q ? reaching the ground. Flux divergence calculations indicated relatively strong sources of latent heat at the ground and where the secondary structure was located. Only very weak sources of latent heat were found in the upper part of the canopy, which was mainly occupied by dead lodgepole pine trees. $Q_\mathrm{H}$ Q H was the dominant term throughout the canopy, and the Bowen ratio ( $Q_\mathrm{H}/Q_\mathrm{E}$ Q H / Q E ) increased with height in the canopy. Soil heat flux ( $Q_\mathrm{G}$ Q G ) accounted for approximately 4 % of $Q^*$ Q ? . Sensible heat storage in the air ( $\Delta Q_\mathrm{S,H}$ Δ Q S , H ) was the largest of the energy balance storage components in the upper canopy during daytime, while in the lower canopy sensible heat storage in the boles ( $\Delta Q_\mathrm{S,B}$ Δ Q S , B ) and biochemical energy storage ( $\Delta Q_\mathrm{S,C}$ Δ Q S , C ) were the largest terms. $\Delta Q_\mathrm{S,H}$ Δ Q S , H was almost constant from the bottom to above the canopy. $\Delta Q_\mathrm{S,C}$ Δ Q S , C , $\Delta Q_\mathrm{S,B}$ Δ Q S , B and latent heat storage in the air ( $\Delta Q_\mathrm{S,E}$ Δ Q S , E ) varied more than $\Delta Q_\mathrm{S,H}$ Δ Q S , H throughout the canopy. During daytime, energy balance closure was high in and above the upper canopy, and in the lowest canopy level. However, where the secondary structure was most abundant, ${\textit{EBC}} \le 66\,\%$ EBC ≤ 66 % . During nighttime, the storage terms together with $Q_\mathrm{G}$ Q G made up the largest part of the energy balance, while $Q_\mathrm{H}$ Q H and $Q_\mathrm{E}$ Q E were relatively small. These radiation and energy balance measurements in an insect-attacked forest highlight the role of secondary structure in the recovery of attacked stands.  相似文献   

Extension′s role in disseminating information about climate change to agricultural stakeholders in the United States     

Linda Stalker Prokopy  J. Stuart Carlton  J. Gordon Arbuckle Jr.  Tonya Haigh  Maria Carmen Lemos  Amber Saylor Mase  Nicholas Babin  Mike Dunn  Jeff Andresen  Jim Angel  Chad Hart  Rebecca Power 《Climatic change》2015,130(2):261-272

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Variations in cereal crop phenology in Spain over the last twenty-six years (1986–2012)     

Jose Oteros  Herminia García-Mozo  Roser Botey  Antonio Mestre  Carmen Galán 《Climatic change》2015,132(4):545-558

Over recent years, the Iberian Peninsula has witnessed an increase both in temperature and in rainfall intensity, especially in the Mediterranean climate area. Plant phenology is modulated by climate, and closely governed by water availability and air temperature. Over the period 1986–2012, the effects of climate change on phenology were analyzed in five crops at 26 sites growing in Spain (southern Europe): oats, wheat, rye, barley and maize. The phenophases studied were: sowing date, emergence, flag leaf sheath swollen, flowering, seed ripening and harvest. Trends in phenological response over time were detected using linear regression. Trends in air temperature and rainfall over the period prior to each phenophase were also charted. Correlations between phenological features, biogeographical area and weather trends were examined using a Generalized Lineal Mixed Model approach. A generalized advance in most winter-cereal phenophases was observed, mainly during the spring. Trend patterns differed between species and phenophases. The most noticeable advance in spring phenology was recorded for wheat and oats, the “Flag leaf sheath swollen” and “Flowering date” phenophases being brought forward by around 3 days/year and 1 day/year, respectively. Temperature changes during the period prior to phenophase onset were identified as the cause of these phenological trends. Climate changes are clearly prompting variations in cereal crop phenology; their consequences could be even more marked if climate change persists into the next century. Changes in phenology could in turn impact crop yield; fortunately, human intervention in crop systems is likely to minimize the negative impact.  相似文献   

Dechlorinating and Iron Reducing Bacteria Distribution in a TCE-Contaminated Aquifer     

Carmen Lourdes Yupanqui Zaa  Joan E. McLean  R. Ryan Dupont  Jeanette M. Norton  Darwin L. Sorensen 《Ground Water Monitoring & Remediation》2010,30(1):46-57

Dehalorespiration bioremediation has been considered for chlorinated compound removal from two trichloroethene contaminated groundwater plumes in the OU 5 area of Hill Air Force Base, Utah. The distributions and population densities of the 16S rRNA genes of Bacteria, Dehalococcoides ethenogenes, Desulfuromonas michiganensis, Geobacter spp. and Rhodoferax ferrireducens -like bacteria, as well as the functional genes trichloroethene reductive dehalogenase ( tce A) and vinyl chloride reductase ( vcr A) were determined in contaminated aquifer material samples. The influence of aquifer physical and chemical properties, including iron availability, on these distributions was evaluated. Twenty aquifer cores were collected. DNA was extracted and analyzed using real-time quantitative polymerase chain reaction (RT-qPCR) to quantify the gene densities. Dehalococcoides population densities were low and unevenly distributed. D. michiganensis was found in 12 cores while Geobacter spp. were found in 8 cores. Rhodoferax ferrireducens -like bacteria were widely distributed. The vcr A gene distribution was relatively uniform and broad but the tce A gene was detectable in only 2 cores. Gene distribution was not related to core clusters derived from physical/chemical characteristics.  相似文献   

Shell architecture,element composition,and stable isotope signature of the giant deep-sea oyster Neopycnodonte zibrowii sp. n. from the NE Atlantic     

Max Wisshak  Matthias López Correa  Serge Gofas  Carmen Salas  Marco Taviani  Joachim Jakobsen  André Freiwald 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(3):374-407

A conspicuous new deep-sea oyster, Neopycnodonte zibrowii sp. n., is described from the Azores Archipelago, where it thrives in 420 to >500 m water depth in high densities concealed underneath overhangs. The new species reaches a relatively large size, which may exceed 20 cm, and is characterised by a very unusual hinge line morphology, straight without a bulge of the resilium. It is compared to the extant Indo-Pacific Empressostrea kostini Huber and Lorenz, 2007 and to the cosmopolitan Neopycnodonte cochlear (Poli, 1791), which has a broadly sympatric distribution at shallower depths in the Azores and Bay of Biscay. Radiocarbon dating reveals that individuals reach an impressive lifespan of one to more than five centuries, placing them among the longest-lived molluscs known to date. They often grow on top of each other, forming stacks that resemble dish piles—an effective measure to optimise shell stability with minimal biomineralisation effort, but with the drawback of increased bioerosion ultimately leading to detachment.Three microstructure types are developed in N. zibrowii: (1) the cross-foliated, calcitic, dorsal to central endostracum and aragonitic ligostracum, (2) the porous vesicular structure of the calcitic ventral endostracum, and (3) the simple prismatic aragonitic myostracum. Foliated and vesicular shell portions show sub-millimetre-scale first-order increments delineated by conchiolin-rich growth breaks (interpreted as reproductive cyclicity), and less distinct second-order increments (interpreted as annual in nature). This pattern is clearly reflected by the elemental composition with the primary growth breaks lacking Ca and Sr but including Mg and S as organic matrix constituents. The second-order increments within the calcite are mirrored by moderately co-varying Mg/Ca and S/Ca fluctuations at stable Sr concentrations, reflecting varying proportions of organic matrix. Dorsal and central endostracum transects reveal a low inter-valve, but considerable inter-specimen variability with high Mg/Ca molar ratios and fluctuations (22.5±17.6 mmol/mol), low Sr/Ca values (0.2±0.1 mmol/mol), and a typical to high S/Ca content (6.9±2.2 mmol/mol), when compared to other calcitic bivalves.Unlike short-lived, shallow-water oysters, N. zibrowii thrives under very stable environmental conditions. Minimal temperature fluctuations and stable open marine salinity provide an optimal basis to recognise biological fractionation processes. Strong Mg/Ca fluctuations indicate a physiological control related to metabolism and biomineralisation, prohibiting the use of this ratio as a temperature or ocean chemistry proxy. Low Sr/Ca ratios indicate rather constant and low long-term accretion rates, while short-scale fluctuations may be attributed to short-term variations in growth rate and Mg incorporation. Oxygen isotopes yield a considerable spread of 1.8‰ with a mean of 2.0±0.3‰ δ¹⁸O V-PDB, and low correlation between different contemporaneous parts of the shell and between specimens. These values surprisingly exceed expected equilibrium conditions, calculated from in situ temperature data (annual mean 12.3±0.3 °C) and seawater isotopic composition (0.5±0.1‰ δ¹⁸O SMOW), by 0.5‰ on average. Such positively shifting vital effects, previously reported for limpets and barnacles, are often overlooked in high-temperature and high-amplitude settings and may be more common than is currently believed. Carbon isotopes range from 0.2 to 3.5‰ δ¹³C V-PDB (mean 1.8±0.7‰) and show an ontogenetic decrease, but may incorporate an environmental signal in adult portions, indicated by a strong correspondence of peaks between specimens. This signal is likely driven by a complex interplay of different factors, such as primary production, current-based food supply and metabolism.  相似文献   

Groundwater Monitoring on Guam: Management Responses to Recent Water Quality Violations     

Gary R.W. Denton  Carmen M. Sian-Denton 《Ground Water Monitoring & Remediation》2010,30(2):127-133

Guam has one of the finest limestone aquifers in the world. Located in the northern half of the island, this vital underground resource supplies the local community with about 80% of its drinking water needs. The majority of the island’s approximately 180,000 inhabitants live in the northern half of the island where significant economic growth and urban development have occurred over the last 30 years. The U.S. military has also occupied large tracts of land in this region for the past 60 years. The risks of groundwater contamination are, therefore, very real considering the population density in northern Guam and the rapid recharge rates to the underlying aquifer. Since April 1996, Guam Waterworks Authority (GWA) has regularly monitored the island’s drinking water resources for chemical and biological contaminants in accordance with the U.S. Safe Drinking Water Act requirements. This report summarizes and compares the groundwater data sets for two discrete time intervals: 1996 through 2001 and 2002 through 2007 for chemicals, and 1997(8) through 2002 and 2003 through 2007 for bacteria. Adaptive management strategies that evolved to deal with contaminant violations over this time frame are critically discussed. Overall, 95% of all GWA’s drinking water production wells were considered to be in relatively good shape from a chemical standpoint. Identified chemicals of concern were chlordane, ethylene dibromide, perchloroethylene, trichloroethylene, and nitrate. The microbiological integrity of Guam’s groundwater was, by comparison, less impressive prior to 2003 because of numerous wastewater spills, leaks, and overflows. Improved management practices introduced shortly afterward have significantly reduced the incidence of Escherichia coli contamination in recent years.  相似文献   

A study of a possible lunar batholith     

Carmen J. Villella 《Earth, Moon, and Planets》1976,15(3-4):479-484

The author suggests that a particular foothills feature located northwest of, but nearly parallel to, the Apennine Mountains of the moon is a batholith which was generated deep beneath the Apennines as a result of the Imbrium impact. Confirmation of this theory depends upon whether batholiths can be generated on the moon. The Apollo 11 rock samples apparently originated by a small degree of partial melting at depths between 200 and 600 km. The lava produced by the melt was chemically different from the anorthositic highlands. Once the lunar crust had congealed, any magmatic flow from the interior would find movement toward the surface increasingly hampered by the continually thickening and hardening crust. Though faulting caused by meteorite impact would result in easier access locally through the crust by the migrating magma, that access would be blocked off once the lava reached the surface and congealed over the fault. It is suggested that the lava collected in a series of secondary magma chambers located closer and closer to the surface. As the continuing lava stream fed the original secondary chamber, pressure build-up on the roof caused brecciation and cracking. The stream then migrated through the new cracks upward to a point where it could not proceed further, so that another secondary chamber was established. This process continued until the lava reached the surface or until the radioactive heat source cooled.  相似文献   

A reappraisal of the significance of obstacle clasts in cluster bedform dispersal     

Carmen De Jong 《地球表面变化过程与地形》1991,16(8):737-744

The dispersal of cluster bedforms is examined in a short, partially braided reach of the River Quoich, northeast Scotland, after minor flood events in 1989 and 1990. In all cases, the eventual dispersal of clusters occurred without prior removal of the obstacle clast. Since none of the obstacle clasts was dispersed in 1989 and only two-thirds by 1990, obstacle clasts probably form a less significant delay to sediment entrainment than previously assumed and represent a relatively immobile component of bed sediment.  相似文献   

Temporal dynamics of shallow subtidal meiobenthos from a beach in Tenerife (Canary Islands, northeast Atlantic Ocean)     

Rodrigo Rier  Jorge N&#;&#;ez  Mar&#;a del Carmen Brito 《海洋学报(英文版)》2013,32(8):44-54

A shallow subtidal (3 m deep) meiofaunal assemblage in Los Abrigos Bay, Tenerife, Canary Islands was sampled during May 2000-April 2001. Themain aims were to (1) find temporal variations inmeiofaunal assemblage structure and overall abundance, as well as in the most abundant meiofaunal species throughout the study period, and (2) identify environmental variables (sedimentary composition, organic matter content, and total nitrogen) that better explain meiofaunal assemblage structure during the study year. The most abundant species were the nematodes Siphonolaimus sp. 2 and Catanema sp., which represented 46.2% of the overall meiofaunal abundances and varied significantly throughout the study duration. Overall meiofaunal abundance and the most abundant taxonomic groups (nematodes, copepods, and oligochaetes) showed significant temporal variations during the study period. Nematodes overwhelmingly dominated during the study period, ranging from 78% in May to 97.34% in February. Multivariate analyses showed seasonality inmeiofaunal community structure during the study year, with the lowest abundances in May.  相似文献