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241.
The regional patterns of change of temperature and rainfall that might accompany a global warming due to increased carbon
dioxide can be studied by experiments with theoretical models of the climate system, by reconstructing the climates of past
warm epochs, and by determining the anomalies of temperature and precipitation that prevailed during years or seasons when
the Arctic region was unusually warm. The current study pursues the last course, making use of the northern hemisphere meteorological
data record for the period 1931–1978. Hemispheric maps of anomalies of both temperature and precipitation are presented for
the 10 warmest Arctic seasons and years, and for differences between the 5 warmest and 5 coldest consecutive Arctic winters.
Wintertime anomalies are generally greatest and dominate in determining the annual averages. The hemispheric temperature anomalies
for these data sets are similar to those determined earlier by the first author (Williams, 1980) using 1900–1969 data, but
the precipitation anomalies (for North America alone) show more variation, partly due to the method of computing the anomalies.
Work reported here begun while a visitor to the National Center for Atmospheric Research.
The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
242.
Suzanne B. Bricker Fred T. Mackenzie Jill S. Baron Jason R. Price 《Aquatic Geochemistry》2014,20(2-3):81-86
This special volume of aquatic geochemistry is dedicated to the memory of Owen Peterson Bricker III (1936–2011) and serves as a tribute to his life and career. Owen had a distinguished and productive research career in both academics at Johns Hopkins University (Fig. 1) and as a public servant with the Maryland Geological Survey, the US Environmental Protection Agency, and the US Geological Survey. He was a pioneer and leader in aqueous geochemistry, who applied a study approach that quantified mineral weathering reactions and equilibrium thermodynamic relations to better understand the chemical evolution of stream water in small watersheds. He will be especially remembered for his efforts to establish rigorous field studies in small catchments around the United States as a means of quantifying the sources of acid-neutralizing capacity that affect the chemical status and biological health of natural waters. Fig. 1
Owen in a Johns Hopkins University laboratory in the early years (~1965, note the tie!) 相似文献
243.
Matthew T. Bizjack Susan M. Kidwell Ronald G. Velarde Jill Leonard-Pingel Adam Tomašových 《Marine pollution bulletin》2017,114(1):448-465
Molluscan shell debris is an under-exploited means of detecting, sourcing, and age-dating dredged sediments in open-shelf settings. Backscatter features on the Southern California shelf are suggestive of dredged sediment hauled from San Diego Bay but deposited significantly inshore of the EPA-designated ocean disposal site. We find that 36% of all identifiable bivalve shells > 2 mm (44% of shells > 4 mm) in sediment samples from this 'short dump' area are from species known to live exclusively in the Bay; such shells are absent at reference sites of comparable water depth, indicating that their presence in the short-dump area signals non-compliant disposal rather than natural offshore transport or sea level rise. These sediments lack the shells of species that invaded California bays in the 1970s, suggesting that disposal preceded federal regulations. This inexpensive, low-tech method, with its protocol for rejecting alternative hypotheses, will be easy to adapt in other settings. 相似文献
244.
Scott A. Rush Jill A. Olin Aaron T. Fisk Mark S. Woodrey Robert J. Cooper 《Estuaries and Coasts》2010,33(4):963-970
Much of North America’s tidal marsh habitat has been significantly altered by both natural and man-made processes. Thus, there
is a need to understand the trophic ecology of organisms endemic to these ecosystems. We applied carbon (δ
13C) and nitrogen (δ
15N) stable isotope analysis, along with isotope mixing models, to egg yolk, liver, and muscle tissues of clapper rails (Rallus longirostris) and their likely prey items. This analysis enabled us to explore variation in trophic niche and diet composition in this
important marsh bird in two northern Gulf of Mexico tidal marshes that are river and ocean-dominated. For the river-associated
estuary, δ
13C and δ
15N of egg yolks, liver, and pectoral muscle tissue samples provided evidence that clapper rails maintained a similar diet during
both the winter and the breeding season. A trophic link between C3 primary productivity and the clapper rail’s diet was also indicated as the δ
13C of clapper rail egg yolks related negatively with the aerial cover of C3 macrophytes. Clapper rails from the ocean-dominated estuary had a narrower trophic niche and appeared to be utilizing marine
resources, particularly, based on modeling of liver stable isotope values. Variation in stable isotope values between egg
yolk and liver/muscle in both systems suggests that endogenous resources are important for egg production in clapper rails.
These results demonstrate that diet composition, prey source, and niche width of clapper rails can vary significantly across
different estuaries and appear to be influenced by hydrological conditions. 相似文献
245.
Four diogenites, four howardites and seven eucrites have been analysed for major, minor and a number of trace elements by X-ray fluorescence spectrometry. Inter-element relationships between various elements in howardites, particularly refractory elements, are interpreted in the light of the recently proposed mixing model, whereby howardites are considered to be mixtures of eucritic and diogenitic material. Differences in composition observed between two samples of Frankfort analysed in this work lend strong support to this hypothesis. The nature of the proposed end-member composition in howardites is shown to be variable. 相似文献