bluuebunny/crossref_metadata_2025 huggingface dataset:
Lipase‐Catalyzed Irreversible Transesterification of Jatropha Curcas L. Seed Oil to Fatty Acid Esters: An Optimization Study
Authors: Su Erzheng , Du Liqin , Gong Xiangyu , Wang Pixiang
Published: December 2010

In this work, fatty acid ethyl esters were produced from the lipase‐catalyzed irreversible transesterification reaction between Jatropha oil and diethyl carbonate (DEC). Response surface methodology (RSM) based on central composite design (CCD) was used to optimize the five important reaction variables for the irreversible transesterification of Jatropha oil in a solvent‐free system. The optimum conditions for the transesterification were a reaction time of 13.3 h, a temperature of 44.5 °C, a lipase amount of 13.7% (w/w), a DEC to Jatropha oil molar ratio of 3.75:1 and no need for adding water. The optimal predicted yield of fatty acid esters was 97.7% and the actual value was 96.2%. The results showed that the RSM based on CCD was adaptable for a fatty acid esters yield study for the current transesterification system.
5S for Healthcare
Authors: Collins Susan J.
Published: December 2010

5S for Healthcare Thomas L. Jackson 2009, Productivity Press 120 $28.95 softcover
Health Care Waste Management and Environmentally Preferable Purchasing
Authors: Brusco Jennifer M. , Ogg Mary
Published: December 2010

The nation's health care system produces a large amount of waste, both hazardous and nonhazardous; however, there are simple steps that any health care professional can take to minimize the effects of health care waste on the environment and human health. Not only can health care professionals reduce, reuse, and recycle, but they can also make smarter, “green” purchasing decisions. AORN J 92 (December 2010) XX‐XX. © AORN, Inc, 2010.
Provenance of loess from the Spanish central region: chemometric interpretation
Authors: GARCÍA R. , PETIT-DOMÍNGUEZ M. D. , RUCANDIO M. I. , GONZÁLEZ J. A.
Published: December 2010

In this work our purposes are (1) geochemical characterization of loess (‘primary loess’ or ‘true loess’ and ‘secondary loess’ or ‘loess-like deposits’) located in the centre of the Iberian Peninsula, (2) systematic study of element behaviour during pedogenesis and (3) evaluation of the suitability of using the geochemistry of loess to establish the average composition of these discontinuous aeolian sedimentary covers in central Spain. Several analyses were carried out on the bulk sample and on the sandy and clay fractions (mineralogical composition by X-ray diffraction, mineralogical studies of heavy minerals by petrographical microscopy and chemical composition by flame atomic absorption spectrometry). Loess from the Spanish central region has a local origin. The presence of gypsum in the ‘loess-like’ deposits reaches values two times higher than in ‘true loess’, and ‘true loess’ has a higher concentration of quartz, calcite and kaolinite. Regarding chemical composition, similar concentrations of Ca, K, Mg and Na were found, although it is important to note the higher concentration of Na in some of the samples.
The loss, discovery, and rediscovery of the crew of U.S. Navy LA-9 at Kronborg Glacier, east Greenland
Authors: Brooks Kent
Published: December 2010

In January 1962, a US Navy aircraft patroling the Denmark Stait mysteriously disappeared. In spite of an international search continuing over several weeks, the crash was first found accidentally 4.5 years later by geologists, but subsequently it was discovered that all the bodies had not been returned. It was not until 2009 that the story was brought to a close with a ceremony at the naval air base in Jacksonville, Florida.
Captain Scott's last camp, Ross Ice Shelf
Authors: Headland R. K.
Published: December 2010

On 19 March 1912, Captain R.F. Scott, Dr E.A. Wilson, and Lt H.R Bowers reached a latitude of 79° 40ʹS during their return journey from the South Pole. There they camped and were fatally delayed by a blizzard. The date of Scott's last diary entry is 29 March 1912 and he died on, or shortly after, that date, with his two companions, of starvation and cold. They had left their base at Cape Evans in stages from 24 October 1911 with a party of 16. Relay parties returned on 11 and 21 December 1911, and on 4 January 1912. Five men attained the South Pole on 17 January 1912 where they found that an expedition, led by R.E.G. Amundsen from Norway, has preceded them on 14 December 1911. 33 days had elapsed between the departure of the Norwegian party from the pole and Scott's arrival there. During the return journey over the Ross Ice Shelf, roughly along the 169°E meridian, two of the party of five died: E. Evans on 17 February 1912 and L.E.G. Oates on, or shortly after, 16 March 1912.
Sovereignty watch: claimant states, resources, and territory in contemporary Antarctica
Authors: Dodds Klaus J.
Published: December 2010

This article is concerned with the contemporary Antarctic and the kinds of sovereignty performances undertaken by claimant states such as Australia. Notwithstanding the entry into force of the Antarctic Treaty, claimant states have used, what this article terms, ‘treaty sovereignty’ further to entrench their sovereign rights, especially within public culture. Using Australia as a detailed example, the article considers how a range of activities including anti-whaling developments alongside contemporary public commentary has on the one hand stressed ‘sovereign rights’ and yet on the other hand, revealed a sense of anxiety and fear regarding the role of others; what one might term overall a form of ‘sovereignty watch’. In conclusion, the paper speculates on whether the treaty parties are entering an unstable phase of Antarctic co-existence precisely because of the kinds of behaviours that ‘treaty sovereignty’ encourages.
The ‘American supply trail’: archaeological notes on the remains of the Ziegler polar expedition in Zemlya Frantsa-Iosifa, 1903–1905
Authors: Capelotti P.J.
Published: December 2010

Between 1898 and 1905, three American expeditions attempted to reach the geographical North Pole from the archipelago of Zemlya Frantsa-Iosifa [Franz Josef Land] and each went to extraordinary and expensive lengths to stage their work. The third of these, the Ziegler polar expedition (1903–1905), led by Anthony Fiala and funded by the American baking soda tycoon William Ziegler, set up numerous camps and caches of supplies along its various expedition routes through the islands. The papers of Anton Vedoe and Ernest Leffingwell at the Rauner Special Collections Library at Dartmouth College reveal both the locations and contents of the caches Fiala ordered to be established in spring 1905, as he made his second and final attempt to reach the pole. These caches extend from the expedition base camp (Camp Abruzzi) at Bukhta Teplitsa [Teplitz Bay] on Ostrov Rudol'fa [Rudolf Island] to the main base of the preceding 1901–1902 Baldwin-Ziegler expedition (Camp Ziegler) on Ostrov Aldzher [Alger Island]. Little is known of the condition of these sites, especially the main cache site of Kane Lodge on Ostrov Grili [Greely Island]. As such, they hold the potential to provide new sources of archaeological data to study American polar ambitions at the turn of the 20th century. While these sites remain unexplored, increasing tourism in the islands necessitates informed planning and field research to establish the nature and stability of these remains so that they may be preserved and the potential effects of tourism mitigated.
Dominant diatom species in the Canada Basin in summer 2003, a reported serious melting season
Authors: Zheng Shuxian , Wang Guizhong , Zhang Fang , Cai Minghong , He Jianfeng
Published: December 2010

During the second Chinese National Arctic Research Expedition in summer 2003, sea ice cores and the underlying water were sampled from seven stations in the pack ice zone of the Canada Basin and were examined with a phase contrast microscope. A total of 102 and 78 algal species were identified for the ice cores and the underlying water, respectively, ranking in the middle range among the surveys of the Arctic Ocean up to the present despite seasonal variability. The Shannon-Wiener indices ranged from 1.40 to 4.88 with an average of 3.58 ± 0.68. Diatom species, especially pennate species, dominated in all the samples. A large number of algal spores were contained in every layer (abundance percentage > 1%). The microalgal abundances ranged from 1.4 × 104 to 8.73 × 105 cells L−1 and the biomass ranged from 0.56 to 89.49 μg L−1. They were correlated with the number of algal species (P < 0.05) but not with the diversity index (P > 0.05). Ice algal maxima were observed in various layers (bottom, interior and near the surface of the ice floes). The phytoplankton biomass in the ice-water interface was one order of magnitude lower than that in the bottom ice (P < 0.05). The species number and the diversity index in water samples, with much less biomass (P < 0.01), were comparative with the ice samples (P > 0.05). Spatial heterogeneity in both horizontal and vertical directions was the main characteristic of the algal community structure, which was demonstrated by the cluster analysis result and the distribution patterns.
The elastic contact influences on passive walking gaits
Authors: Qi Feng , Wang Tianshu , Li Junfeng
Published: December 2010

This paper presents a new planar passive dynamic model with contact between the feet and the ground. The Hertz contact law and the approximate Coulomb friction law were introduced into this human-like model. In contrast to McGeer's passive dynamic models, contact stiffness, contact damping, and coefficients of friction were added to characterize the walking model. Through numerical simulation, stable period-one gait and period-two gait cycles were found, and the contact forces were derived from the results. After investigating the effects of the contact parameters on walking gaits, we found that changes in contact stiffness led to changes in the global characteristics of the walking gait, but not in contact damping. The coefficients of friction related to whether the model could walk or not. For the simulation of the routes to chaos, we found that a small contact stiffness value will lead to a delayed point of bifurcation, meaning that a less rigid surface is easier for a passive model to walk on. The effects of contact damping and friction coefficients on routes to chaos were quite small.
Public decisions on animal species: does body size matter?
Authors: KNEGTERING EDO , VAN DER WINDT HENNY J. , SCHOOT UITERKAMP ANTON J. M.
Published: December 2010

Systematic knowledge about factors affecting the willingness of societies to conserve biodiversity is still scarce. This study investigates the role of body size in national decisions on wild animal species by analysing the average body sizes of the animal species subject to species-specific legislation in the Netherlands over the period 1857–1995. Three legal objectives were distinguished, namely ‘control’, ‘use’ and ‘protection’. For most taxa, average body sizes of species were found to differ significantly between legal objectives within a substantial number of subperiods analysed. Throughout the entire period examined, protected bird, mammal, fish and mollusc species were of smaller average body size than those subject to use legislation and protected bird, mammal and mollusc species were also smaller than those subject to control legislation most of the time. Protected insects were generally larger than those subject to control or use. For vertebrate taxa, average sizes of protected species increased over the time period selected for examination, suggesting that legislation initially excluded larger vertebrates from protection, possibly partly owing to demands to maintain use of these species. The results emphasize that conservation context is important, as other studies suggest that conservation policy generally favours larger species.
Latitudinal variation of demersal fish assemblages in the western Ross Sea
Authors: Clark Malcolm R. , Dunn Matthew R. , McMillan Peter J. , Pinkerton Matthew H. , Stewart Andrew , Hanchet Stuart M.
Published: December 2010

Demersal fishes were sampled using a large fish trawl during two surveys carried out in February and March 2004 and 2008 in the Ross Sea, and around seamounts and islands just to the north at 66°S. The distribution and abundance of 65 species collected in these surveys were examined to determine if demersal fish communities varied throughout the area, and what environmental factors might influence this. Species accumulation with sample frequency did not reach an asymptote, but the rate of new species was low suggesting data were adequate for describing the main components of the communities. Three broad assemblages were identified, in the southern Ross Sea (south of 74°S), central–northern Ross Sea (between latitudes 71°–74°S), and the seamounts further north (65°–68°S) where some species more typical of sub-Antarctic latitudes were observed. Multivariate analyses indicated that environmental factors of seafloor rugosity (roughness), temperature, depth, and current speed were the main variables determining patterns in demersal fish communities.
Diverse hypolithic refuge communities in the McMurdo Dry Valleys
Authors: Cowan Don A. , Khan Nuraan , Pointing Stephen B. , Cary S. Craig
Published: December 2010

Hyper-arid deserts present extreme challenges to life. The environmental buffering provided by quartz and other translucent rocks allows hypolithic microbial communities to develop on sub-soil surfaces of such rocks. These refuge communities have been reported, for many locations worldwide, to be predominantly cyanobacterial in nature. Here we report the discovery in Antarctica’s hyper-arid McMurdo Dry Valleys of three clearly distinguishable types of hypolithic community. Based on gross colonization morphology and identification of dominant taxa, we have classified hypolithic communities as Type I (cyanobacterial dominated), Type II (fungal dominated) and Type III (moss dominated). This discovery supports a growing awareness of the high biocomplexity in Antarctic deserts, emphasizes the possible importance of cryptic microbial communities in nutrient cycling and provides evidence for possible successional community processes within a cold arid landscape.
Latitudinal distribution and mitochondrial DNA (COI) variability of Stereotydeus spp. (Acari: Prostigmata) in Victoria Land and the central Transantarctic Mountains
Authors: Demetras Nicholas J. , Hogg Ian D. , Banks Jonathan C. , Adams Byron J.
Published: December 2010

We examined mitochondrial DNA (COI) variability and distribution of Stereotydeus spp. in Victoria Land and the Transantarctic Mountains, and constructed Neighbour Joining (NJ) and Maximum Likelihood (ML) phylogenetic trees using all publicly available COI sequences for the three Stereotydeus species present (S. belli, S. mollis and S. shoupi). We also included new COI sequences from Miers, Marshall and Garwood valleys in southern Victoria Land (78°S), as well as from the Darwin (79°S) and Beardmore Glacier (83°S) regions. Both NJ and ML methods produced trees which were similar in topology differing only in the placement of the single available S. belli sequence from Cape Hallett (72°S) and a S. mollis haplotype from Miers Valley. Pairwise sequence divergences among species ranged from 9.5–18.1%. NJ and ML grouped S. shoupi from the Beardmore Glacier region as sister to those from the Darwin with pairwise divergences of 8%. These individuals formed a monophyletic clade with high bootstrap support basal to S. mollis and S. belli. Based on these new data, we suggest that the distributional range of S. shoupi extends northward to Darwin Glacier and that a barrier to dispersal for Stereotydeus, and possibly other arthropods, exists immediately to the north of this area.
Cytogenetic diversity in the Antarctic plunderfishes (Notothenioidei: Artedidraconidae)
Authors: Ghigliotti Laura , Near Thomas J. , Ferrando Sara , Vacchi Marino , Pisano Eva
Published: December 2010

Antarctic plunderfishes (Notothenioidei, Artedidraconidae) are important components of the Southern Ocean fish fauna. As a contribution to the Victoria Land Transect Project, we performed a cytogenetic analysis of six species from three of the four artedidraconid genera,Artedidraco glareobarbatus,A. orianae,A. skottsbergi,A. shackletoni,Histiodraco velifer, andPogonophrynesp. We investigated the species-specific cytogenetic features and highlighted patterns of chromosomal evolutionary change using a molecular phylogeny based on mitochondrial and nuclear genes. Despite a conserved diploid number, some important karyotypic traits account for major differences among artedidraconid species. Specific cytogenetic features, including the chromosomal organization of ribosomal genes and the occurrence of sex chromosomes, are characteristics ofA. skottsbergi, making this species distinct among those studied. These chromosomal peculiarities are consistent with the phylogenetic hypothesis resolvingA. skottsbergias the sister lineage of all other Artedidraconidae. A karyological similarity was found betweenA. glareobarbatusandA. shackletoniconsistent with their inferred sister species relationship in the phylogeny. The results indicate that artedidraconids are not conservative in their genomic organization at the chromosomal level and provide new evidence for the degree of biological diversity in this notothenioid group.
Characterization of active layer water contents in the McMurdo Sound region, Antarctica
Authors: Seybold C.A. , Balks M.R. , Harms D.S.
Published: December 2010

The liquid soil water contents in the seasonally thawed layer (active layer) were characterized from seven soil climate monitoring sites - four coastal sites from south to north (Minna Bluff, Scott Base, Marble Point and Granite Harbour), and inland sites from low to high altitude (Wright Valley, Victoria Valley and Mount Fleming). Mean water contents ranged from 0.013 m3 m-3 near the surface at Victoria Valley to 0.33 m3 m-3 near the ice-cemented layer at Granite Harbour. The coastal sites have greater soil water contents than the McMurdo Dry Valley and Mount Fleming sites, and moisture contents increase with depth in the active layer. The Wright Valley site receives very little infiltration from snowmelt, with none in most years. All other sites, except Mount Fleming, received between one and four wetting events per summer, and infiltrated water moved to greater depths (≈ 10–25 cm). The Scott Base and Granite Harbour sites are on sloping ground and receive a subsurface flow of water along the ice-cemented permafrost. Our findings indicate that water contents are low with very little recharge, are greatly influenced by the local microclimate and topography, and show no significant increasing or decreasing trend over 10 years of monitoring.
Spatial variations in the geochemistry of glacial meltwater streams in the Taylor Valley, Antarctica
Authors: Welch Kathleen A. , Lyons W. Berry , Whisner Carla , Gardner Christopher B. , Gooseff Michael N. , McKnight Diane M. , Priscu John C.
Published: December 2010

Streams in the McMurdo Dry Valleys, Antarctica, flow during the summer melt season (4–12 weeks) when air temperatures are close to the freezing point of water. Because of the low precipitation rates, streams originate from glacial meltwater and flow to closed-basin lakes on the valley floor. Water samples have been collected from the streams in the Dry Valleys since the start of the McMurdo Dry Valleys Long-Term Ecological Research project in 1993 and these have been analysed for ions and nutrient chemistry. Controls such as landscape position, morphology of the channels, and biotic and abiotic processes are thought to influence the stream chemistry. Sea-salt derived ions tend to be higher in streams that are closer to the ocean and those streams that drain the Taylor Glacier in western Taylor Valley. Chemical weathering is an important process influencing stream chemistry throughout the Dry Valleys. Nutrient availability is dependent on landscape age and varies with distance from the coast. The streams in Taylor Valley span a wide range in composition and total dissolved solids and are surprisingly similar to a wide range of much larger temperate and tropical river systems.
Relationships between periglacial features and vegetation development in Victoria Land, continental Antarctica
Authors: Cannone N. , Guglielmin M.
Published: December 2010

The relationships between vegetation patterns and periglacial features and their underlying ecology are still poorly understood and lack specific investigations in Antarctica. Here we present the results of vegetation colonization of different types of sorted patterned ground and gelifluction features (lobes and terracettes) at four sites in northern Victoria Land. This paper aims to understand the relationships between vegetation and the most widespread periglacial features in Victoria Land, discuss the role of periglacial features and vegetation in determining the ground surface temperature, and assess whether periglacial features provide ecological niches for vegetation colonization and development. Vegetation patterns are influenced by the feature type, mainly relating to patterned ground and debris island versus gelifluction features. The relations between vegetation and the periglacial features investigated in continental Antarctic are similar to those described for the Arctic, although in this part of the Antarctic vegetation is exclusively composed of cryptogams. Frost heave, ground texture and relief associated with different types of periglacial features provide a range of ecological niches sustaining vegetation biodiversity. Our data confirm the importance of periglacial features in shaping flora and vegetation biodiversity, as previously assessed only for the soil fauna in continental Antarctic.
Cosmogenic nuclide exposure age constraints on the glacial history of the Lake Wellman area, Darwin Mountains, Antarctica
Authors: Storey B.C. , Fink D. , Hood D. , Joy K. , Shulmeister J. , Riger-Kusk M. , Stevens M.I.
Published: December 2010

We present direct terrestrial evidence of ice volume change of the Darwin and Hatherton glaciers which channel ice from the Transantarctic Mountains into the Ross Ice Shelf. Combining glacial geomorphology with cosmogenic exposure ages from 25 erratics indicates a pre-LGM ice volume at least 600 m thicker than current Hatherton ice elevation was established at least 2.2 million years ago. In particular, five erratics spread across a drift deposit at intermediate elevations located below a prominent moraine feature mapped previously as demarcating the LGM ice advance limits, give a well-constrained single population with mean 10Be age of 37.0 ± 5.5 ka (1σ). At lower elevations of 50–100 m above the surface of Lake Wellman, a further five samples from within a younger drift deposit range in exposure age from 1 to 19 ka. Our preferred age model interpretation, which is partly dependent on the selection of a minimum or maximum age-elevation model, suggests that LGM ice volume was not as large as previously estimated and constrains LGM ice elevation to be within ± 50 m of the modern Hatherton Glacier ice surface, effectively little different from what is observed today.
The formal ball model for -categories
Authors: KOSTANEK MATEUSZ , WASZKIEWICZ PAWEŁ
Published: December 2010

We generalise the construction of the formal ball model for metric spaces due to A. Edalat and R. Heckmann in order to obtain computational models for separated-categories. We fully describe-categories that are

(a)

Yoneda complete

(b)

continuous Yoneda complete

via their formal ball models. Our results yield solutions to two open problems in the theory of quasi-metric spaces by showing that:

(a)

a quasi-metric spaceXis Yoneda complete if and only if its formal ball model is a dcpo, and

(b)

a quasi-metric spaceXis continuous and Yoneda complete if and only if its formal ball modelBXis a domain that admits a simple characterisation of approximation.
Does learning Spanish grammatical gender change English-speaking adults' categorization of inanimate objects?
Authors: KURINSKI ELENA , SERA MARIA D.
Published: December 2010

Second language acquisition studies can contribute to the body of research on the influence of language on thought by examining cognitive change as a result of second language learning. We conducted a longitudinal study that examined how the acquisition of Spanish grammatical gender influences categorization in native English-speaking adults. We asked whether learning the grammatical gender of Spanish affects adult native English speakers' attribution of gender to inanimate objects. College students enrolled in beginning Spanish participated in two tasks repeatedly (four times) throughout one academic year. One task examined their acquisition of grammatical gender. The other examined their categorization of inanimate objects. We began to observe changes in participants' grammatical gender acquisition and in categorization after ten weeks of Spanish instruction. Results indicate that learning a second language as an adult can change the way one categorizes objects. However, the effect of Spanish grammatical gender was more limited in Spanish learners than in native Spanish speakers; it was not observed for all kinds of objects nor did it increase with learners' proficiency, suggesting that adults learning Spanish reach a plateau beyond which changes in categorization do not occur.
Senior Chinese high school students' awareness of thematic and taxonomic relations in L1 and L2
Authors: LI DEGAO , ZHANG XIANNV , WANG GUOYING
Published: December 2010

In the development of their semantic networks, bilinguals can be influenced by the levels of proficiency they have in their second language (L2) and by the age at which they acquired the language. Two exercises, one in word association and one in forced-choice decision-making, were used to test whether the pattern of relative awareness of thematic and taxonomic relations that senior Chinese high school students had in L2 differed from the pattern they had in their first language (L1). The results consistently indicated that (i) the participants appeared as aware of taxonomic relations in L2 as they were in L1; and (ii) they were more readily aware of thematic than of taxonomic relations in L1 but less readily aware of thematic than of taxonomic relations in L2. It was concluded that with taxonomic relations, low-proficiency bilinguals could have a common set of conceptual representations for both L2 and L1, as they are assumed in the revised hierarchical model (RHM) to have. With thematic associations, they might have more difficulty gaining access to their representations in L2 than they might have in L1.
Gender Attribution in Online Video Games
Authors: Eden Allison , Maloney Erin , Bowman Nicholas David
Published: December 2010

Demographic research and anecdotal evidence suggest that, historically, games have been dominated by male players. However, newer research shows gains by female players, especially in online games. Therefore, how gamers perceive the masculinity of other gamers in game has become relevant. Two experiments examine how two variables – game genre and player skill – inform gender perception in online games. Results from both studies show that game genre is a salient cue for gender perception, but that perception of player skill is not. A number of gender differences in perceptions of player skill and the relationship between genre and perceptions of player masculinity are also identified. These findings are an important first step in understanding the perception of others in online entertainment environments.
Heterogeneity and anisotropy of the lithosphere of SE Tibet from surface wave array tomography
Authors: Yao Huajian , van der Hilst Robert D. , Montagner Jean‐Paul
Published: December 2010

Understanding the geotectonic evolution of the southeastern Tibetan plateau requires knowledge about the structure of the lithosphere. Using data from 77 broadband stations in SW China, we invert Rayleigh wave phase velocity dispersion curves from ambient noise interferometry (T = 10–40 s) and teleseismic surface waves (T = 20–150 s) for 3‐D heterogeneity and azimuthal anisotropy in the lithosphere to ∼150 km depth. Our surface wave array tomography reveals (1) deep crustal zones of anomalously low shear wave speed and (2) substantial variations with depth of the pattern of azimuthal anisotropy. Upper crustal azimuthal anisotropy reveals a curvilinear pattern around the eastern Himalayan syntaxis, with fast directions generally parallel to the main strike slip faults. The mantle pattern of azimuthal anisotropy is different from that in the crust and varies from north to south. The tomographically inferred 3‐D variation in azimuthal anisotropy helps constrain the source region of shear wave splitting. South of ∼26°N (off the high plateau) most of the observed splitting can be accounted for by upper mantle anisotropy, but for stations on the plateau proper (with thick crust) crustal anisotropy cannot be ignored. On long wavelengths, the pattern of azimuthal anisotropy in the crust differs from that in the mantle. This is easiest explained if deformation varies with depth. The deep crustal zones of low shear wave speed (and, presumably, mechanical strength) may represent loci of ductile deformation. But their lateral variation suggests that in SE Tibet (localized) crustal channel flow and motion along the major strike slip faults are both important.
The 2007 sea ice minimum: Impacts on the Northern Hemisphere atmosphere in late autumn and early winter
Authors: Strey Sara T. , Chapman William L. , Walsh John E.
Published: December 2010

Over the past several decades, the minimum Northern Hemisphere summer sea ice extent has decreased substantially. We present an analysis of the influence of declining Arctic sea ice cover on the atmosphere, specifically during the autumn/early winter following an extreme summer minimum event. Using ensemble simulations from the Weather Research and Forecast model (v 3.0.1), we compare the atmospheric response for the case of the extreme sea ice minimum of 2007 to the corresponding response for the more typical ice conditions of 1984, the year with median ice extent for the 1979–2008 satellite era. Increased open water enhances heat and moisture flux from the Arctic Ocean to the atmosphere during autumn. We characterize the fluxes both horizontally and vertically and determine the spatial breadth of their influence. The atmospheric response is characterized by a strong increase in 2 m temperature and decrease in sea level pressure locally and by remote responses in the atmospheric circulation throughout the troposphere characterized by a quasi‐barotropic ridge/trough signal in North America. The circulation anomalies drive remote anomalies of temperature and precipitation over eastern North America and the North Atlantic. Advectively driven temperature anomalies, in turn, cause surface flux anomalies over remote regions such as the Great Lakes and the Gulf Stream. The maximum response, as measured by difference in 2 m temperatures over the polar cap from 70°N, occurs between 10 September and approximately 15 November. The persistence of the signal over a 2 month period implies the potential for seasonal predictability of the stronger atmospheric response features. In addition, we determine the significance of prominent features, finding 95% significance in some remote features as far away as the North Atlantic.
Assessing hurricane‐induced tree mortality in U.S. Gulf Coast forest ecosystems
Authors: Negrón‐Juárez Robinson , Baker David B. , Zeng Hongcheng , Henkel Theryn K. , Chambers Jeffrey Q.
Published: December 2010

Tropical cyclones disturb forest ecosystems and have the potential to alter forest structure and species composition as well as ecosystem functions including rates of nutrient cycling and biomass accumulation. Quantifying these forest disturbances is necessary to evaluate the extent and severity of damage for estimating biomass loss, developing regional carbon budgets, and making management decisions following hurricanes. In this study, we quantified forest disturbance (downed and dead and snapped trees) produced by hurricanes using a relationship between field‐measured tree mortality and Landsat data that can be broadly applied to Gulf Coast forest ecosystems impacted by hurricanes. Field‐measured tree mortality data was collected in Gulf Coast forests at 60 inventory plots established to monitor forest disturbance produced by hurricanes Katrina and Rita, which hit the region in 2005, and Hurricane Gustav, which hit the region in 2008. Large‐scale disturbance estimates were obtained by regressing Landsat and Moderate Resolution Imaging Spectroradiometer (MODIS) data that in turn were associated with Forest Inventory and Analysis (FIA) data from the U.S. Forest Service. The use of the general relationship produced a biomass loss from dead trees of 43.9 ± 8.4 Tg C for Hurricane Katrina and 37.9 ± 6.4 Tg C for Hurricane Rita, which are near the upper limit of the expected values reported in our previous studies across a number of different forest types. Our results provide an important contribution for reliable assessments of large‐scale disturbance produced by hurricanes in forest ecosystems. Improving our ability to accurately assess the impacts of hurricanes on forests and on terrestrial carbon cycles is particularly important given that climate projections suggest that hurricane intensity is likely to increase.
Estimating snow sublimation using natural chemical and isotopic tracers across a gradient of solar radiation
Authors: Gustafson Joseph R. , Brooks P. D. , Molotch N. P. , Veatch W. C.
Published: December 2010

Changes in both climate and vegetation may dramatically impact the amount of water stored in seasonal snow cover and the timing of spring snowmelt. This study quantifies how spatial variability in solar radiation affects the spatial and temporal patterns in snow water equivalent (SWE), snow chemistry, and snow water isotopes in the Jemez Mountains, New Mexico. Depth, density, stratigraphy, temperature, and snow samples were collected approximately monthly from five locations between January and April 2007 to quantify the effects of solar forcing on snowpack water and chemical balance. Locations varied in solar forcing due to topography and vegetation, while minimizing variability in precipitation, elevation, aspect, interception, and wind redistribution. Snowfall (340 ± 5 mm) was similar across all sites, but peak SWE at maximum accumulation ranged from 187 to 340 mm. Solute concentrations were highest directly under canopies, intermediate in nonshaded forest openings, and lowest in shaded forest openings. Conservative solute concentrations (SO42−, R2 = 0.80), Cl− (R2 = 0.60), and isotope values (δ18O R2 = 0.96) were inversely related to SWE at maximum accumulation. Mass balance estimates of snowpack water balance using solute concentrations and isotopes indicated that sublimation ranged from <2% to ∼20% of winter precipitation, consistent with previous studies at the site. The strong relationships between solar forcing, SWE, and chemistry suggest that snow chemistry at maximum accumulation can be used to estimate overwinter sublimation. Furthermore, variability in solar forcing also can be used to refine spatial estimates of catchment solute and isotope input at melt.
Soil inorganic carbon stock in the Tibetan alpine grasslands
Authors: Yang Yuanhe , Fang Jingyun , Ji Chengjun , Ma Wenhong , Su Shenshen , Tang Zhiyao
Published: December 2010

As the largest carbon pool in the terrestrial biosphere, soil carbon stock consists of organic and inorganic components. However, previous studies dominantly concentrated on soil organic carbon (SOC) stock, and little is known about the magnitude and patterns of soil inorganic carbon (SIC). In this study, we evaluated the magnitude of SIC stock in the Tibetan alpine grasslands using data from 405 profiles surveyed from 135 sites across the plateau during 2001–2004. Kriging interpolation was conducted to interpolate site‐level observations to the regional level. We also compared spatial and vertical distributions of SIC stock with the corresponding patterns of SOC stock in the Tibetan alpine grasslands. Our results showed that SIC stock in the top 1 meter in the Tibetan alpine grasslands was approximately 15.2 Pg C (1 Pg = 1015g), with an average density (amount per area) of 13.46 kg C m−2. SIC density exhibited different spatial and vertical distributions in comparison with SOC density. Spatially, SIC density in the alpine steppe was larger than that in the alpine meadow, in contrast to SOC distribution. Vertically, SIC stock in the upper 30 and 50 cm accounted for 47.6% and 71.6%, respectively, of that in the upper 1 meter, with lower proportions than that of SOC stock in the same interval (67.8% and 83.3%). In total, SIC stock in the Tibetan alpine grasslands was about 2.1 times the corresponding SOC stock, accounting for 28.5% of the total SIC stock in China. These results highlight that SIC stock in the Tibetan grasslands could make a significant contribution to China's terrestrial carbon balance.
Nitrogen isotope simulations show the importance of atmospheric iron deposition for nitrogen fixation across the Pacific Ocean
Authors: Somes Christopher J. , Schmittner Andreas , Altabet Mark A.
Published: December 2010

Nitrogen (N) fixation by specialized microorganisms (diazotrophs) influences global plankton productivity because it provides the ocean with most of its bio‐available N. However, its global rate and large‐scale spatial distribution is still regarded with considerable uncertainty. Here we use a global ocean nitrogen isotope model, in comparison with δ15NO3− observations, to constrain the pattern of N2 fixation across the Pacific Ocean. N2 fixation introduces isotopically light atmospheric N2 from to the ocean (δ15N = 0‰) relative to the oceanic average near 5‰, which makes nitrogen isotopes suitable to infer patterns of N2 fixation. Including atmospheric iron limitation of diazotrophy in the model shifts the pattern of simulated N2 fixation from the South Pacific to the North Pacific and from the East Pacific westward. These changes considerably improve the agreement with meridional transects of available δ15NO3− observations, as well as excess P (PO43− − NO3−/16), suggesting that atmospheric iron deposition is indeed important for N fixation in the Pacific Ocean. This study highlights the potential for using δ15N observations and model simulations to constrain patterns and rates of N fixation in the ocean.
Formation of highly oxygenated organic aerosol in the atmosphere: Insights from the Finokalia Aerosol Measurement Experiments
Authors: Hildebrandt Lea , Kostenidou Evangelia , Mihalopoulos Nikos , Worsnop Douglas R. , Donahue Neil M. , Pandis Spyros N.
Published: December 2010

Aged organic aerosol (OA) was measured at a remote coastal site on the island of Crete, Greece during the Finokalia Aerosol Measurement Experiments (FAME‐08 and FAME‐09), which were part of the EUCAARI intensive campaigns. Quadrupole aerosol mass spectrometers (Q‐AMSs) were employed to measure the size‐resolved chemical composition of non‐refractory submicron aerosol (NR‐PM1), and to estimate the extent of oxidation of the OA. The experiments provide unique insights into ambient oxidation of aerosol by measuring at the same site but under different photochemical conditions. NR‐PM1 concentrations were about a factor of three lower during FAME‐09 (winter) than during FAME‐08 (summer). The OA sampled was significantly less oxidized and more variable in composition during the winter than during the early summer. Lower OH concentrations in the winter were the main difference between the two campaigns, suggesting that atmospheric formation of highly oxygenated OA is associated with homogeneous photochemical aging.
Dynamic millennial‐scale climate changes in the northwestern Pacific over the past 40,000 years
Authors: Chen M.‐T. , Lin X. P. , Chang Y.‐P. , Chen Y.‐C. , Lo L. , Shen C.‐C. , Yokoyama Y. , Oppo D. W. , Thompson W. G. , Zhang R.
Published: December 2010

Ice core records of polar temperatures and greenhouse gases document abrupt millennial‐scale oscillations that suggest the reduction or shutdown of thermohaline Circulation (THC) in the North Atlantic Ocean may induce the abrupt cooling in the northern hemisphere. It remains unknown, however, whether the sea surface temperature (SST) is cooling or warming in the Kuroshio of the Northwestern Pacific during the cooling event. Here we present an AMS 14C‐dated foraminiferal Mg/Ca SST record from the central Okinawa Trough and document that the SST variations exhibit two steps of warming since 21 ka — at 14.7 ka and 12.8 ka, and a cooling (∼1.5°C) during the interval of the Younger Dryas. By contrast, we observed no SST change or oceanic warming (∼1.5–2°C) during the episodes of Northern Hemisphere cooling between ∼21–40 ka. We therefore suggest that the “Antarctic‐like” timing and amplitude of millennial‐scale SST variations in the subtropical Northwestern Pacific between 20–40 ka may have been determined by rapid ocean adjustment processes in response to abrupt wind stress and meridional temperature gradient changes in the North Pacific.
Aftershocks are well aligned with the background stress field, contradicting the hypothesis of highly heterogeneous crustal stress
Authors: Hardebeck Jeanne
Published: December 2010

It has been proposed that the crustal stress field contains small‐length‐scale heterogeneity of much larger amplitude than the uniform background stress. This model predicts that earthquake focal mechanisms should reflect the loading stress rather than the uniform background stress. So, if the heterogeneous stress hypothesis is correct, focal mechanisms before and after a large earthquake should align with the tectonic loading and the earthquake‐induced static stress perturbation, respectively. However, I show that the off‐fault triggered aftershocks of the 1992 M7.3 Landers, California, earthquake align with the same stress field as the pre‐Landers mechanisms. The aftershocks occurred on faults that were well oriented for failure in the pre‐Landers stress field and then loaded by the Landers‐induced static stress change. Aftershocks in regions experiencing a 0.05 to 5 MPa coseismic differential stress change align with the modeled Landers‐induced static stress change, implying that they were triggered by the stress perturbation. Contrary to the heterogeneous stress hypothesis, these triggered aftershocks are also well aligned with the pre‐Landers stress field obtained from inverting the pre‐Landers focal mechanisms. Therefore, the inverted pre‐Landers stress must represent the persistent background stress field. Earthquake focal mechanisms provide an unbiased sample of the spatially coherent background stress field, which is large relative to any small‐scale stress heterogeneity. The counterexample provided by the Landers earthquake is strong evidence that the heterogeneous stress model is not widely applicable.
Long‐range lightning geolocation using a VLF radio atmospheric waveform bank
Authors: Said R. K. , Inan U. S. , Cummins K. L.
Published: December 2010

Lightning discharges generate broadband electromagnetic pulses with a peak component in the very low frequency (VLF; 3–30 kHz) range. VLF waves propagate through the Earth‐ionosphere waveguide with relatively low attenuation, enabling the detection of these radio atmospherics at great distances from the lightning discharge. A new technique of long‐range (≤6000 km) global lightning geolocation via sferic detection is presented. This new technique catalogs the dominant variation in expected received waveforms in a set of waveform banks, which are then used to estimate the propagation distance and accurately determine the arrival time. Using three sensors in a trial network, this new technique is used to demonstrate a median accuracy of 1–4 km, depending on the time of day. An overall cloud‐to‐ground (CG) stroke detection efficiency between ∼40 and 60% is estimated by correlating individual lightning stroke events to data from the National Lightning Detection Network (NLDN). Additional events reported by the trial network are shown to have a tight spatial clustering to storm clusters identified by NLDN, suggesting that many of the unmatched events correspond to weak cloud‐to‐ground strokes, M components, or cloud pulses. Exploiting an empirical correlation between peak VLF field strength and peak current values reported by NLDN, we also provide unvalidated estimates of the peak current and lightning channel polarity. The trial network does not distinguish between cloud and ground discharges, so these peak current estimates only relate to an Earth‐referenced channel current for the subset of reported events that are return strokes.
A diagnostic study of time variations of regionally averaged background error covariances
Authors: Monteiro Maria , Berre Loïk
Published: December 2010

In variational data assimilation systems, background error covariances are often estimated from a temporal and spatial average. For a limited area model such as the Aire Limited Adaptation Dynamique Developpment International (ALADIN)/France, the spatial average is calculated over the regional computation domain, which covers western Europe. The purpose of this study is to revise the temporal stationarity assumption by diagnosing time variations of such regionally averaged covariances. This is done through examination of covariance changes as a function of season (winter versus summer), day (in connection with the synoptic situation), and hour (related to the diurnal cycle), with the ALADIN/France regional ensemble Three‐Dimensional Variational analysis (3D‐Var) system. In summer, compared to winter, average error variances are larger, and spatial correlation functions are sharper horizontally but broader vertically. Daily changes in covariances are particularly strong during the winter period, with larger variances and smaller‐scale error structures when an unstable low‐pressure system is present in the regional domain. Diurnal variations are also significant in the boundary layer in particular, and, as expected, they tend to be more pronounced in summer. Moreover, the comparison between estimates provided by two independent ensembles indicates that these covariance time variations are estimated in a robust way from a six‐member ensemble. All these results support the idea of representing these time variations by using a real‐time ensemble assimilation system.